EPA-600/R-98-130
October 1998
m
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t „„ TECHNICAL REPORT DATA 4 4
NKMRL—RTP— 120 (Please read Instructions on the reverse before complei PB99_1 ]
B374
mill
1, REPORT NO. 2.
EPA-600 /R- 98-130
3- I II II I
4. TITLE ANO SUBTITLE
Proceedings: Low- and No-VCC Coating Technologies:
2nd Biennial International Conference
S. REPORT DATE
October 1998
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Ella J. Darden and Jesse N. Baskir, Compilers
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
EPA P. O. 5D0852NANX
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Proceedings; 3/13-15/95
14. SPONSORING AGENCY CODE
EPA/600/13
is.supplementary notes ^ppcj) project officer is Michael Kosusko, Mail Drop 61, 919/
541-2734.
i6. ABSTRACTrj-^g repQr|- documents an international conference that provided a forum for
the exchange of technical information on coating technologies. It focused on improved
and emerging technologies that result in fewer volatile organic compound (VGC) and
toxic air emissions than those from traditional coatings. EPA1 s National Risk Man-
agement Research Laboratory and Research Triangle Institure cosponsored the con-
ference, entitled, "Low- and No-VOC Coating Technologies: 2nd Biennial Interna-
tional Conference. " It was held on March 13-15, 1995, in Durham, NC. Approxima-
tely 175 people participated. Plenary presentations provided perspectives from the
coatings industry and from federal and state government representatives. Technical
papers described new coating technologies, coating application equipment, chemical
agents for Coatings removal, and issues associated with measuring the VOC content
of coatings. The technical papers presented at the conference focused on regulations,
radiation-curable coatings, life cycle analysis of coatings, surface preparation, pow-
der coatings, automotive applications, wood furniture technologies, military applica-
tions, architectural and industrial maintenance coatings, and other low- and no™VOC
coating technologies.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. descriptors
b.lOENTIFIERS/OPEN ENDED TERMS
c. COSATI FieM/Gioup
Pollution Emission
Coatings Automotive Industry
Coating Processes Latex
Organic Compounds Powder
Volatility Wood
Toxicity Furniture
Military Research Architecture
Pollution Prevention
Stationary Sources
Wood Furniture
Volatile Organic Com-
pounds (VOCs)
Industrial Coatings
13 B 14 G
UC 05C, 13 F
13 H UJ
07C
20 M 11L
06T 15E
14F 13M.05F
18. distribution statement
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
561
20. SECURITY, CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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NOTICE*
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
PROTECTED UNDER INTERNATIONAL COPYRIGHT
ALL RIGHTS RESERVED.
NATIONAL TECHNICAL INFORMATION SERVICE
U.S. DEPARTMENT OF COMMERCE
Reproduced from
best available copy.
ii
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FOREWORD
The U.S. Environmental Protection Agency is charged by Congress with pro-
tecting the Nation's land, air, and water resources. Under a mandate of national
environmental laws, the Agency strives to formulate and implement actions lead-
ing to a compatible balance between human activities and the ability of natural
systems to support and nurture life. To meet this mandate, EPA's research
program is providing data and technical support for solving environmental pro-
blems today and building a science knowledge base necessary to manage our eco-
logical resources wisely, understand how pollutants affect our health, and pre-
vent or reduce environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks
from threats to human health and the environment. The focus of the Laboratory1 s
research program is on methods for the prevention and control of pollution to air,
land, water, and subsurface resources; protection of water quality in public water
systems; remediation of contaminated sites and groundwater; and prevention and
control of indoor air pollution. The goal of this research effort is to catalyze
development and implementation of innovative, cost-effective environmental
technologies; develop scientific and engineering information needed by EPA to
support regulatory and policy decisions; and provide technical support and infor-
mation transfer to ensure effective implementation of environmental regulations
and strategies.
This publication has been produced as part of the Laboratory's strategic long-
term research plan. It is published and made available by EPA's Office of Re-
search and Development to assist the user community and to link researchers
with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
4 4 4
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Abstract
The report documents an international conference that provided a forum for the exchange of
technical information on coating technologies. It focused on improved and emerging
technologies that result in fewer volatile organic compound (YOC) and toxic air emissions than
those from traditional coatings. Among the new products and improvements discussed were a
100%-solids liquid sprayable coating, solventless architectural coatings, use of effervescent spray
technology to eliminate volatile diluents, and the use of life cycle assessment to develop an
environmental labeling scheme for coatings. It also includes an examination of VOC emissions
to the indoor air environment from latex paints.
XV
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TABLE OF CONTENTS
PAGE
ABSTRACT .. . ™
INTRODUCTION
VIII
SESSION 1 OPENING 1-1
Welcome Frank Princiotta, Director, U.S. Environmental Protection Agency,
National Risk Management Research Laboratory, Air Pollution
Prevention and Control Division (Visuals) 1-3
Keynote Alexander Ramig, Jr., Vice President of Research and Development,
ICFGlidden (Summary) 1-6
State Perspective Gary Hunt, North Carolina Office of Waste Reduction (No Paper)
University Perspective John Massingill, Coatings Research Institute (Visuals).......... 1-8
EPA Coatings Research Michael Kosusko, U.S. Environmental Protection Agency, National
Risk Management Research Laboratory, Air Pollution Prevention
and Control Division 1-30
SESSION 2 REGULATORY UPDATE 2-1
Regulatory Climate (No Paper)
Low VOC Measurements, HAP Measurements in Paints, Questions, Questions, Questions 2-3
Developments in European VOC Emission Regulations 2-61
Coating Alternatives GuidE (CAGE) 2-77
SESSION 3 RADIATION CURABLE COATINGS 3-1
Barriers to the Use of UV and EB Technologies 3-3
Environment and Technology Teamed for Economic Sustainability (Abstract) 3-10
Acrylated Lesquerella Oil in Ultraviolet-Cured Coatings 3-11
Volatile Contents of UV Cationically Curable Epoxide Coatings 3-26
SESSION 4 LIFE-CYCLE ANALYSIS 4-1
The Use of Life Cycle Assessment in an Ecolabeling Scheme: the European Ecolabel on Paints and
Varnishes 4-3
Optimizing Coating Formulations for Total Environmental and Product Performance ........ 4-17
Life Cycle Analysis of an Aqueous Low-VOC Coating 4-33
V
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TABLE OF CONTENTS
(Com.) PAGE
SESSION 5 APPLICATION TECHNOLOGIES/SURFACE PREPARATION .5-1
Advances in Aerospace Coating Technologies: Convergent Spray Technology (Abstract) 5-3
Encapsulant Lead Paint Remover 5-4
Utilization of Effervescent Spray Technology to Eliminate Volatile and Toxic Diluents 5-10
SERDP, USMC Spray Booth Control and P2 Demonstration 5-28
SESSION 6 POWDER COATINGS .6-1
Overview of Powder Coatings Technology and EPA's Powder Coatings Research 6-3
Powder Coatings: Technology of the Future, Here Today 6-7
Chlorinated Malcinized Guayule Rubber in Powder Coatings: No VOC Thermosetting Chlorinated
Rubber Coatings 6-31
Novel Acrylic Cure Polyester Powder Coating Resin Technology 6-40
SESSION 7A AUTOMOTIVE APPLICATIONS 7-1
Reduction of VOC Emissions from Painting of Car Bodies -a Case Study of
Two Swedish Car Plants 7-3
New Low-VOC Fluorinated Coatings 7-13
Supercritical Fluid (SCF) Adhesion Promoters for Automotive Plastic Applications ......... 7-23
SESSION 7B WOOD FURNITURE TECHNOLOGIES ....... 7-35
Demonstration of No-VOC Wood Topcoat 7-37
Evaluation of Supercritical Carbon Dioxide Spray Technology to Reduce Solvents in a Wood
Finishing Process 7-47
Evaluation of Alternative Chemical Strippers on Wood Furniture Coatings 7-57
SESSION 8A MILITARY APPLICATIONS 8-1
Low- and No-VOC Conformal Coatings Over No-clean Flux Residues 8-3
Low-VOC and No-VOC Coating Systems for Aerospace and Its Support 8-17
Low VOC Marine Coatings 8-23
Evaluate Alternative Paint Stripping Technologies Used in Aircraft and Space Vehicles ...... 8-27
vi
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TABLE OF CONTENTS
(Cont.)
PAGE
SESSION 8B ARCHITECTURAL AND INDUSTRIAL
MAINTENANCE COATINGS 8-31
Evaluation of Innovative Low-Volatile Organic Compound Industrial Maintenance Coatings .. 8-33
Solventless and Low-VOC Architectural Coatings Formulated from Novel Latexes with
Low MFT and High Tg 8-46
Evaluation of Emissions from Latex Paint 8-58
New Polyurethane Prepolymers for Ultra-Low VOC Plural Component Coatings 8-70
SESSION 9 LOW- AND NO- VOC COATINGS - PART 1 . 9-1
Organsosilanes in Low VOC Coatings 9-3
Polyester Oligomers of Narrowed Molecular Weight Distribution 9-14
New Epoxy/Anhydride Chemistry for Durable High Solids Coatings 9-30
SESSION 10 LOW- AND NO-VOC COATINGS - PART 2 10-1
100% Solids Liquid Sprayable Coatings 10-3
Alternative Dielectric Coating Medium for Electric Motor Field Coil Manufacture 10-16
Odour and VOC Emissions Reduction on coil-coating Lines by Using Waterbome Paints -
Part II: Full Waterbome System Application 10-26
Closing Remarks 10-37
Appendix A ATTENDEES LIST A-l
v:i i
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INTRODUCTION
In 1992, surface coating operations accounted for approximately 24 percent of all volatile organic
compound (VOCs) released from industrial processes1. While pollution control equipment can reduce
solvent emissions from some coating operations, adoption of pollution prevention techniques such as the use
of lower-emitting coatings, in many cases provides a cost-effective alternative. For many coatings
applications, such as small coating operations or architectural and industrial maintenance applications,
pollution prevention may be the only economically viable approach to reducing emissions. Lower-emitting
coating technologies are being developed rapidly to reduce VOC and hazardous air pollutants (HAP)
emissions from coating operations in a wide variety of industrial and commercial applications. These
technologies include higher solids solventborne coatings, waterborne coatings, coatings containing reactive
diluents. 100 percent solids liquid sprayable coatings, powder coatings, radiation curable coatings, and spray
coatings that employ supercritical carbon dioxide as a solvent. In addition to new coating technologies,
improvements in coating application equipment and application techniques continue to offer opportunities
for substantial reductions in VOC emissions through improved application efficiency.
A conference entitled "Low- and No-VOC Coating Technologies: 2nd Biennial International
Conference" was held on March 13 -15,1995, in Durham, North Carolina. The primary purpose of the
conference was to provide a forum for the exchange of technical information on lower-emitting coating
technologies. Plenary presentations provided perspectives on new technology needs and developments from
the coatings industry and from federal and state government representatives. Papers described some of the
latest developments in new coating technology, coating application equipment, chemical agents for coating
removal, and issues associated with measuring the VOC content of coatings.
Approximately 175 people participated in the conference. Of these attendees, approximately 13
percent were coating users, 12 percent were environmental consultants, 49 percent were government agency
representatives, 9 percent were coating manufacturers, 3 percent were in coating marketing and sales, 3
percent were educators, and 11 percent were in other categories. There were six foreign participants: two
from Canada, two from Belgium, one from Italy, and one from the United Kingdom.
Technical papers presented at the conference focused on regulations, radiation curable coatings, life-cycle
analysis of coatings, surface preparation, powder coatings, automotive applications, wood furniture
technologies, military applications, architectural and industrial maintenance coatings, and other low- and no-
VOC coating technologies. Paper topics included a description of a 100%- solids liquid sprayable coating,
solventless architectural coatings, use of effervescent spray technology to eliminate volatile diluents, the use
of lifecycle assessment to develop an environmental labeling scheme for coatings, and an examination of
VOC emissions to the indoor air environment from latex paints.
'Nizich, Sharon, 1993. National Air Pollutant Emission Trends, 1900-1992. EPA-
454/R-93-032 (NTIS PB94-152097). U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, Research Triangle Park, North Carolina. October.
viii
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SESSION 1
OPiMNO
1-1
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WELCOME ADDRESS
by
Frank Princiotta
Director
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
Research Triangle Park, North Carolina
KEYNOTE
by
Alexander Ramig, Jr.
Vice President of Research and Development
ICFGLIDDEN
Strongsville, Ohio
"State Perspective" (Paper not available for publication.)
by
Gary Hunt
North Carolina Office of Waste Reduction
Raleigh, North Carolina
"University Perspective"
by
John Massingill
Coatings Research Institute
Ypsilanti, Michigan
"EPA Coatings Research"
by
Michael Kosusko
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
Research Triangle Park, North Carolina
1-2
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Wmmmm m Mi M ¦¦¦1
ELCOME
Frank T. Princiotta
Director
Air and Energy Engineering
Research Laboratory*
(*) In mid-1995, redesignated the Air Pollution Prevention and Control
Division of EPA's National Risk Management Research Laboratory.
WELCOME TO
THE RESEARCH TRIANGLE PARK,
DURHAM, and
THE LOW- AND NO-VOC
COATING TECHNOLOGIES:
2ND BIENNIAL INTERNATIONAL
CONFERENCE
1-3
-------
THE AIR AND ENERGY ENGINEERING
RESEARCH LABORATORY (AEERL)
ENVIRONMENTAL MISSION
¦ DEVELOP TECHNOLOGIES TO REDUCE
AIR POLLUTION BY:
- Pollution Prevention
- End-of-Pipe Control
¦ ENHANCE COMPETITIVENESS OF
U.S. BUSINESSES BY IDENTIFYING
TECHNOLOGIES THAT ARE;
- Practical and
- Cost-Effective
CONFERENCE GOALS
¦ EXCHANGE TECHNICAL
INFORMATION ON INNOVATIVE
COATING TECHNOLOGIES
- ESTABLISH AND/OR REINFORCE
COOPERATIVE RELATIONSHIPS
- PRESENT RESULTS OF AEERL
COATINGS RESEARCH
(12 of 46 Topics)
1-4
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THE AIR AND ENERGY ENGINEERING
RESEARCH LABORATORY (AEERL)
RELATIONSHIP TO
REGULATORY DEVELOPMENT
¦ ORGANIZATIONALLY, AEERL IS NOT
RELATED TO THE PROGRAM OFFICES
UNTIL THE ADMINISTRATOR'S LEVEL
¦ AEERL'S FOCUS IS RESEARCH OF
INNOVATIVE TECHNOLOGIES
¦ HOWEVER, REGULATORY SUPPORT IS
PART OF OUR MISSION
THE AIR AND ENERGY ENGINEERING
RESEARCH LABORATORY (AEERL)
POLLUTION PREVENTION RESEARCH
¦ SURFACE COATING AND SOLVENT CLEANING
(Organic Chemicals)
¦ INDOOR AIR QUALITY
(Household and Office Emissions)
¦ STRATOSPHERIC OZONE DEPLETION
(CFC and Halon Replacements)
¦ GLOBAL WARMING
(Energy Issues)
-------
Paints
Bllddan
RESPONSIBLE ENVIRONMENTAL STEWARDSHIP
IMPROVED COATING TECHNOLOGIES
RESULT IN NO OR LESS VOC AND TOXIC AIR EMISSIONS
Summary of Paper presented by Dr. Alexander Ramig, Jr.,
Director-International Research & Development, ICI Paints
Waterborne technology
ICI Paints worldwide has been in the forefront of
waterborne technology for almost half a century. Application
of this technology can be found in each of its core
businesses: decorative paints, coatings for food and
beverage cans and autobody refinishes.
Our main focus of research and development is on low- or
no-VOC product, safety, cost of production and benefits for
end users. In 1948, The Glidden Company, a member of ICI
Paints, developed the first waterborne latex paint, removing
90% of petroleum solvent from consumer interior paint. Two
years later, Glidden introduced the first successful
application of waterborne technology to the industrial
finishing market in automotive primers and in acoustical
tiles.
In 1960, the company introduced electrocoating to
finishers of automotive parts, home appliances and other
metal products, as well as waterborne coatings for industrial
maintenance. In 1970, Glidden developed powder coatings
which are environmentally clean when baked on major metal
parts in the manufacture of home appliances, outdoor
furniture, trucks, vans and many other metal items.
In 1976, the company developed and marketed the first
waterborne can lining to protect flavor and taste of beer and
soft drinks.
In 1992, ICI Paints introduced the first no-VOC consumer
paint by removing the remaining petroleum-based solvent from
latex paint, using new paint technology. ICI's autobody
refinish coatings include a waterborne refinish system for
autobody repair, which was introduced in 1993.
Industry-Government Relationships
Improvement in industry-government relationships is
sought through seeking out true partnerships, recognizing
obstacles and eliminating self-serving objectives both by
government agencies and industries. The purpose of industry
is to service customers and create shareholder value; that of
the government is to serve the people in the national
interest without being burdensome. A bureaucratic structure
/more
1-6
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
-------
in either industry or government leads to duplication, waste,
costly decisions, confusion, self-serving departments and
loss of its founding purpose.
Industry and government can seek out true partnerships
by agreeing on common goals and by conceiving, developing,
monitoring and funding projects jointly. Together they can
create and manage a strategically balanced portfolio of
projects to create value and enhance American industry's
worldwide competitive position and serve the national
interest as well.
VOC Emissions
In the area of Voc emissions across the United States
from cities (about 100) that had higher than acceptable ozone
levels, EPA reports that 47% is generated by highway
vehicles, 15% by organic solvent evaporation, 9% by surface
coatings and 12% split between the petroleum and gas
marketing industries; 5% by treatment, storage and disposal
facilities; 4% by other industry; and chemical manufacturing,
solid waste disposal, fuel combustion, non-residential and
miscellaneous each share 1% in emission measurement.
The author and his company support a national VOC rule
with key issues centered on uniformity and simplicity.
These include:
emphasis on regulation to be acceptable to states so
that they will net be tempted to simplify each in
their own way
application to attainment as well as non-attainment
coatings areas
- Use of a series of VOC Tables as a means to restrict
VOC limits, as opposed to other schemes such as
"Corporate Average - CAVE," etc.
Promotion of specific categories (as opposed to
general) that can be narrowly defined in order to
simplify compliance and ensure strict enforcement -
"button up the loopholes"
Limitation on administrative requirements? such as
labeling, reporting and recordkeeping, using
procedures typified by current state regulations
Support of a fee criteria that is simple and rewards
companies that strive to produce low-voc product
end 9/12/95
1-7
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COATINGS RESEARCH
INSTITUTE
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
JOHN MASSINGILL
DIRECTOR
EASTERN MICHIGAN UNIVERSITY
430 WEST FOREST
YPSILANTI, Ml 48197
-------
NSF COATINGS RESEARCH
CENTER PARTNERS
i "EASTERN MICHIGAN UNIVERSITY
• MICHIGAN MOLECULAR INSTITUTE
-------
NSF COATINGS RESEARCH
CENTER MISSION
~ To be a leading academic organization that
develops relevant scientific knowledge
~ For understanding and expanding the technology of
v paints and coatings
b-»
O
~ For the benefit of its members and
~ To enlarge the cadre of scientists and technologists
capable of working effectively with coatings
-------
Institute Objective
~ PROVIDE SCIENTIFIC KNOWLEDGE
FOR UNDERSTANDING THE
TECHNOLOGY OF PAINTS
~ HELP INDUSTRY MEET
GOVERNMENT MANDATES
~ DEVELOP COATING SCIENTISTS
-------
Meeting the Needs
~ ORGANIZATION
I
h~>
N>
COATINGS RESEARCH INSTITUTE
EASTERN MICHIGAN UNIVERSITY
DR. JOHN MASSINGILL, DIRECTOR
NSF COATINGS
RESEARCH CENTER
DR. FRANK JONES -
DIRECTOR
EMISSIONS EVALUATION
CENTER
DR. TAKI ANAGNOSTAU -
DIRECTOR
CONTRACT
RESEARCH
by
:; FACULTY
-------
NSF COATINGS CENTER
DR. FRANK JONES
t DIRECTOR
U)
-------
NSF COATINGS RESEARCH
CENTER
~ BENEFITS TO MEMBERS
- INFLUENCE CENTER STRATEGY
- INFLUENCE PROJECT SELECTION
- DEVELOP RESEARCH PORTFOLIO
- RAPID INFOMATION TRANSFER
- MEET UNIVIVERSITY RESEARCHERS
- INFORMAL CONSULTING
- PREFERENTIAL ACCESS TO PATENTS
- MEET POTENTIAL EMPLOYEES
-------
NSF COATINGS RESEARCH
CENTER OBJECTIVES
~ BACKGROUND
- Anticipated regulation of voc, hap, odor, safety, and
waste will require revolutionary changes in coatings
s technology
- Coatings industry will be required to change resins,
formulas, and application methods
-------
NSF COATINGS CENTER
OBJECTIVES
~ CORE COMPETENCIES
- NEW CONCEPTS IN POLYMER SYNTHESIS AND
I CROSSLINKING
- PRINCIPLES OF PHYSICAL PHENOMENA
CRITICAL TO COATINGS
- CHARACTERIZATION METHODS FOR COATINGS
-------
NSF COATINGS RESEARCH
CENTER MEMBERS
~ AKZO NOBEL
~ DOW CHEMICAL
~ FLINT INK
r ~ FORD MOTOR
~ ICI-GLIDDEN
~ PPG INDUSTRIES
~ PRA LABS
~ RHONE-POULENC
~ SOUTH COAST AQMD
~ STATE OF MICHIGAN
-------
Cost Analysis
~ $30,000 PER YEAR
~ GET INFORMATION OF VALUE TO
MEMBER
»
5 ~ INTELLECTUAL PROPERTY
~ PATENT RIGHTS
~ POTENTIAL EMPLOYEES
-------
NSF Coatings Research Center
Our Strengths
~ CROSS-LINKING CHEMISTRY
~ CROSS-LINKED FILM PROPERTIES
~ RHEOLOGY CONTROL
~ SCANNING PROBE MICROSCOPY
~ LOW VOC AND NO VOC COATINGS
~ CORROSION PROTECTION
~ SURFACE SCIENCE AND ADHESION
-------
NSF COATINGS RESEARCH CENTER
TANGIBLE ACCOMPLISHMENTS
~ MEMBER COMPANIES STARTED 6
PROJECTS @ $80,000 EACH TO EXPLOIT
CENTER RESULTS
k ~ 26 PUBLICATIONS AND PRESENTATIONS
~ 7 INVENTION DISCLOSURES
~ 3 PATENT APPLICATIONS
~ ONE SMALL BUSINESS SPIN-OFF
~ 20 STUDENTS IN COATINGS RESEARCH
-------
EMISSIONS EVALUATION
CENTER
DR. TAKI ANAGNOSTOU
DIRECTOR
-------
EMISSIONS EVALUATION
CENTER
~ GOAL
- DEVELOPMENT OF RELIABLE ODOR
DETECTION PROCEDURES FOR THE COATINGS
a INDUSTRY
- GUIDE RE-FORMULATION TO MINIMIZE PLANT
ODORS IN COMMUNITY
-------
I
NJ
U)
EMISSIONS EVALUATION
CENTER
~ RESULTS
- THE AUTO INDUSTRY HAS USED THE
EEC RESULTS TO REDUCE ODOR
EMISSIONS FROM PRODUCTION SITES
- ONE MEMBER HAS INCREASED SALES
DRAMATICALLY AS A DIRECT RESULT
OF CENTER WORK
-------
i CONTRACT RESEARCH
-------
CONTRACT RESEARCH BY
FACULTY
~ CURRENT CONTRACT RESEARCH
- WATER-BORNE COATINGS
* - 100% SOLIDS COATINGS
- MAR RESISTANT AUTO COATINGS
- NON-ISOCYANATE TOP COATS
- RESINS FROM RENEWABLE RESOURCES
- REACTIVE DILUENTS FOR LOW VOC ALKYDS
-------
CONTRACT RESEARCH BY
FACULTY
~ RESULTS
- LIQUID CRYSTAL POLYMERS IN COATINGS
» 5 US PATENTS, 4 PENDING
» PILOT SCALE PRODUCTION
- MONSANTO PROJECT
» NEW INSIGHTS INTO MELAMINE RESIN CURE
» DISCOVERY OF LOW TEMPERATURE CURE
MELAMINE CROSSLINKERS
- RESIN DILUENT PROJECT
» REDUCED VOC BY REACTIVE DILUENT
» DEMONSTRATION PROJECT SCHEDULED 1995
-------
REACTIVE DILUENTS FOR
ALKYD COATINGS
STEP 1
IDEA: REACTIVE DILUENTS FOR COATINGS
FINANCIAL SUPPORT:
US AID, USD A, SCAQMD,EPA, SCE
STEP 2
INTERMEDIATE DEVELOPMENT:
PRA LABORATORIES, INC.
FINANCIAL SUPPORT:
EPA, SCAQMD
TECHNICAL ADVISORY TEAM
INDUSTRIAL MEMBER TO TEST
-------
Next Steps
~ JOIN THE NSF CENTER
- TO SHARE IN NEW TECHNOLOGY
~ JOIN THE EEC
- TO CONTROL ODOR IN YOUR PLANTS
~ CONTRACT RESEARCH
- TO SOLVE YOUR PROBLEMS
-------
FOR FURTHER
INFORMATION
JOHN L. MASSINGILL
430 WEST FOREST
YPSILANTI, MI 48197
J—4 '
I
to
~ 313-483-3401
-------
This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved lor
presentation and publication.
EPA Coatings Research
by
Michael Kosusko
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Organies Control Branch, MD-61,
Research Triangle Park, North Carolina 27711
Prepared for.
Low- and No-VOC Coating Technologies:
2nd Biennial International Conference
Durham, North Carolina
March 13, 1995
1-30
-------
I. INTRODUCTION
"For more than two decades, the U.S. Environmental Protection Agency's (EPA's) Air and
Energy Engineering Research Laboratory (AEERL)3, located in Research Triangle Park, North
Carolina, has been exploring control approaches for the pollutants and sources that contribute to air
quality problems. For example, AEERL has successfully developed and demonstrated cost-effective
sulfur dioxide, nitrogen oxides (NOx), and particulate control technologies for fossil fuel combustion
sources. More recently, it has expanded its interest to areas that include organics control, indoor air
quality, radon, stratospheric ozone depletion, and global warming. AEERL also develops inventories
of many types of air emissions. Over the past several years, AEERL has made a substantial effort
to expand pollution prevention as the preferred choice to reduce air emissions. Its goal is to conduct
research that will result in the greatest possible reduction of air pollution for the lowest cost1."
The Organics Control Branch (OCB)b of AEERL is charged with developing and assessing
pollution prevention (P2) techniques for reducing emissions of organic compounds to air, i.e., volatile
organic compounds (VOCs) and hazardous air pollutants (HAPs or air toxics). This presentation
provides a brief overview of OCB's P2 research on surface coating technologies.
In recent years, HAPs and VOCs have been recognized as contributors to human health
problems internationally. EPA's report, Unfinished Business, grouped these pollutants into one
category entitled "hazardous/toxic air pollutants" and identified this category as one of the highest
risks for causing excess cancer deaths2. In addition to direct effects, VOCs react in the atmosphere
to form ozone (and other oxidants) which also affect health, as well as cause damage to materials,
crops, and forests. Even though the EPA has established an ambient ozone standard of 120 parts per
billion (ppb), millions of people live in areas in the U.S. where the ozone standard is routinely
exceeded0. The combination of VOC-produced ozone and human exposures to HAPs makes organic
emissions one of the most pressing environmental problems we face.
II. RESEARCH AND DEVELOPMENT STRATEGY
OCB's overall strategy for answering this question and moving ahead with research and
development (R&D) is as follows:
Step 1. Determine the important organics responsible for:
(1) Tropospheric ozone;
"The Air and Energy Engineering Research Laboratory (AEERL) was renamed during the EPA Office of Research and
Development's (ORD's) reorganization during mid-1995. It is now the Air Pollution Prevention and Control Division
(APPCD) of the National Risk Management Research Laboratory (NRMRL).
^The functions of the Organics Control Branch (OCB) were assumed by the newly formed Emissions Characterization
and Prevention Branch (ECPB) during the mid-1995 ORD reorganization.
cIn November 1996, EPA proposed to change the ambient ozone standard to 80 ppb averaged over an 8 hour period.
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(2) Non-cancer toxicity; and
(3) Cancer.
Step 2. Determine the important sources of these organics.
Step 3. Obtain information on the important sources so that P2 opportunities can be
developed and evaluated.
Step 4, Conduct P2 research,
A. Compounds.
This involved a screening approach which used: (1) the 1985 NAPAP (National Acid
Precipitation Assessment Program)-speciated VOC inventory to identify the most important
compounds contributing to ozone and (2) the 1991 TRIS (Toxics Release Inventory System)
inventory to identify the most important toxic compounds contributing to ozone, non-cancer toxicity,
and cancer3,4. Emissions were weighted according to ozone creation potential, toxic effects potential,
and unit cancer risk to identify the most important compounds and sources. The problem endpoints
and the weighting factors used are indicated in Table I.
Table I. Health Risk Weighting Factors.
PROBLEM ENDPOINT
WEIGHTING FACTOR
Ozone
Incremental ozone reactivity
Non-cancer toxicity
Lowest observable adverse effects level (LOAEL)
Cancer
Cancer inhalation unit risk values
The most important compounds and sources causing ozone, non-cancer toxicity, and cancer
are subdivided by the type of environmental concern as shown in Tables II, IE, and IV.
B. Industries
Research areas (pollutants, processes, and sources) have been identified for which
AEERL/OCB can provide the maximum beneficial environmental impacts, taking into account
technical, resource, regulatory, and political needs. Prevention approaches which are efficient and
cost-effective will be identified, assessed, and demonstrated with the active participation of industry,
small businesses, and other government agencies. Present and near-future strategic directions will
include emphasis on the reduction of the emissions of "high-priority" organic compounds from a few
key manufacturing industries.
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Table II, Key Compounds Contributing to Ozone.
OZONE
Ethylene
Substituted benzenes
Xylenes
C,&> alkanes
C4 - C6 alkanes
C„ - C, olefins
1,3-Butadiene
Table III. Key Compounds Contributing to Non-Cancer Toxicity,
NON-CANCER TOXICITY
Carbon disulfide
Toluene
Formaldehyde
Table IV. Key Compounds Contributing to Cancer.
CANCER
1,3-Butadiene
2-Nitropropane
Chloroform
Methylene chloride (MeClJ
AEERL/OCB will target sources which emit large quantities of "high-priority" VOCs and
HAPs. These industry sources are summarized in Table V. Of the categories in Table ¥,
AEERL/OCB, has selected surface coating technogies as one of its initial focus areas.
C. Types of Research and Evaluation Efforts in Targeted Areas
The types of research and evaluation work that the OCB undertakes in the targeted industry
areas will be tailored to the specific compounds and processes used by these industries.
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Table V. Key Industrial Sources
TARGET INDUSTRY AREAS
INDUSTRY
Plastics
Cellulosie manmade fibers
Plastics materials and resins
Plastic foam products
Synthetic rubber
Synthetic rubber
Petroleum refining
Petroleum refining
Industrial organic chemicals
Industrial organic chemicals
Surface coating
Motor vehicles and car bodies
Wood household furniture
Paper: coated and laminated
Commercial printing, gravure
Reconstituted wood products
Reconstituted wood products
Pulp and paper mills
Pulp and paper mills
Mineral wool
Mineral wool
To the extent possible, knowledge and expertise gained in the earlier target areas will be applied
to solve similar problems in the new target areas. Alternative, lower environmental impact
compounds will be evaluated to replace conventional compounds (e.g., n-methyl-2-pyrrolidone
[NMP] as a potential replacement for MeCl2 for paint stripping). Processes will be scrutinized
and evaluated to identify modifications which may lead to more economical operations while
reducing environmental impacts (e.g., conversion of MeCl2 vats for stripping paint from metal
parts to a silica-based, gas-heated fluidized bed). The OCB's work will include the evaluation of
P2 approaches developed by others, the assessment of existing P2 approaches to determine their
applicability in new areas, the research, development, and demonstration of innovative P2
approaches, and transfer of information about successful approaches to other potential users.
The vision of AEERL's Organics Prevention Research Program is to be the world leader
in providing the techniques, technologies, cost-effective tools, and technical assistance needed to
advance the use of P2 approaches to reduce the emissions of high priority VOCs and HAPs to the
atmosphere. The mechanisms (types of research) used by the OCB to reduce organic emissions
are presented in Figure 1.
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THEME: REDUCTION OF THE MOST IMPORTANT
ORGANIC EMISSIONS CAUSING OZONE,
NON-CANCER TOXICITY, AND CANCER
IDENTIFICATION OF HIGH
PRIORITY
SOURCES AND EMISSIONS
SOURCE MANAGEMENT
• Management Alternatives
• Regulatory Schedules
POLLUTION PREVENTION
• Existing Approaches
• Innovative Approaches
• Cost Analysis
COST COMPARISONS
TECHNOLOGY TRANSFER
• Control Technology Center
• Assessment Tools
• Technical Papers, Meetings
Figure 1. The organics prevention engineering research program
D. Coordination of Research and Evaluation Efforts
The magnitude and importance of the organic emissions problem, coupled with the
OCB's limited fiscal resources and manpower, make coordination and cooperation with others
doing related work absolutely essential. The OCB seeks to be aware of related research and
evaluation efforts and to take these efforts into account in research planning. This is done by
communicating personally with other researchers, participating in technical meetings,
coordinating with trade associations, sponsoring information exchange forums {e.g., this
conference), sponsoring contractor efforts to locate and assess related research being conducted
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elsewhere, and conducting searches of the technical literature related to targeted compounds,
industries, and processes.
E. Technology Transfer
The OCB will continue to place emphasis on the expansion and enhancement of its
technology transfer capabilities. Information developed by the research program is shared in a
variety of ways with clients of the program, including EPA program offices, industries, and small
businesses. To do so, the OCB will:
(1) Issue newsletters, conduct workshops and symposia, and support seminars in Research
Triangle Park by outside experts; and
(2) Participate in the National Pollution Prevention Roundtable, trade association meetings,
and other organizations whose objectives are the advancement of P2 research and P2
technology use by industry.
m. EXISTING SURFACE COATING PROJECTS
A. Introduction
This section briefly describes each of the OCB's surface coating projects that has been
undertaken since 1990. Descriptions are organized first by industrial application, and then, for
those that are more general in nature, by coating technology. Projects that are focused on
technology transfer are presented in a separate section.
Generally, projects in each of the technical areas can be divided into four categories or
types:
(1) Scoping Studies which characterize an industry or process and its emissions and identify
P2 opportunities to reduce those emissions. Scoping projects are ongoing for furniture
restoration and repair, paper and other webs coating, printing, roofing, and
consumer/commercial adhesives.
(2) Technology Assessment and Development Projects which evaluate the technical and
economic feasibility of specific coating technologies or P2 techniques. R&D projects are
included in this category. Technology assessment and development projects are ongoing
to evaluate very-low-VOC coatings for wood furniture manufacturing and auto body
refinishing, to identify technical barriers to the use of radiation-cured and waterbome
coatings, and to assess innovative ink-feed systems for printing, improved degreasing
systems, cleanliness criteria for parts cleaning, and methods for determining the VOC
content of consumer products.
(3) Demonstration Projects which investigate methods of reducing emissions in cooperation
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with industrial partners. Demonstration projects are planned for coated and laminated
substrate manufacturing, for the design of recirculating spray booths incorporating VOC
concentration gradient phenomena, and for precision and non-precision cleaning.
Technology transfer is an important type of project activity in OCB. Through technology
transfer, the results of OCB's research are provided to the people who can use them,
hopefully in a format that they can easily use. Technology transfer also provides OCB an
opportunity to interact with its potential clients (e.g., through workshops and
conferences) to better understand their needs and the status of technology in many
industries.
B. Industries
1. Wood Furniture
a. Status and Future Developments in Verv-Low-VOC Coatings for Wood Furniture
Finishing. The objective of this project is to determine the status of R&D and market
development for very-low-VOC coatings used for wood furniture finishing.
Information has been gathered through contacts with resin suppliers, paint
manufacturers, wood furniture manufacturers, and their trade associations. The
technical barriers and concerns of industry about these coatings have been identified
and explored5. [Bob McCrillis: (919) 541-2733]
b. Accelerated Development and Market Penetration for Verv-Low-VOC/HAP Wood
Furniture Coatings. This project will be initiated during 1994. It will build on the
results described in Section B.l.a. by selecting up to 10 promising coatings for further
evaluation, developing a program to bring each of these to full marketability status,
and testing these coatings in commercial facilities. This work is in progress. [Bob
McCrillis: (919) 541-2733]
c. Field Evaluation of an Innovative Coating Utilizing Reactive Diluents. This project's
objective is to reduce volatile organic emissions from coating operations by
demonstrating the technical and economic feasibility of using reactive diluents in
alkyd and epoxy coating formulations. Organic emissions from coatings which are
formulated with reactive diluents are less than those from traditional, solvent-based
coatings since the reactive diluents react to form part of the coating and are not
flashed off as carrier solvents. The reactive diluent, vernonia oil, has been
successfully tested at the bench-scale at the Coatings Research Institute at Eastern
Michigan University. Since vernonia oil is extracted from a rare African plant which
is not readily cultivated, alternative reactive diluents derived from readily available
soy and linseed oils to mimic the chemical and physical properties of vernonia oil
have been developed. OCB will work with private paint researchers and coating
retailers and users to field- or pilot-test innovative coatings using these diluents. This
project is being performed cooperatively with South Coast Air Quality Management
District (SCAQMD). The final report is available6. [Bob McCrillis: (919) 541-2733]
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d. Furniture Refinishing and Repair, Information on non-process solvent use was
evaluated for 15 industrial and commercial source categories to characterize VOC
emissions and identify P2 opportunities. Non-process solvents are used by industry,
commercial operations, and/or individual consumers; they are not incorporated into a
product or chemically modified as part of the manufacturing process. Project results
will support a Report to Congress, required by § 183(e) of the Clean Air Act
Amendments of 1990 (CAAA), which addresses emissions of VOCs from consumer
or commercial products. The report summarizing the 15 categories is available7.
As a result of the 15-category evaluation, 5 source categories were selected for further
study. One of these categories is Furniture Repair and Refinishing. For each category,
a more detailed evaluation of emissions, emission sources, and P2 opportunities is
being completed. A final report detailing emissions and P2 opportunities for this
category is being prepared. (Mike Kosusko: (919) 541-2734]
e. Alternative Paint Strippers. Chemical paint stripping is a major source of air toxic and
VOC emissions. MeCl2, a halogenated solvent and air toxic compound which is not
regulated as a VOC, is a predominant primary component in chemical strippers used
by the furniture repair and refinishing industry. Researchers have been developing
low-VOC coatings through continuing research, formulation adjustments, and
application testing. The feasibility of using alterative strippers on these low-VOC
coatings has not been documented. This research was conducted to evaluate the
feasibility of using alterative chemical strippers to remove both existing and emerging
low-VOC wood coatings. Performance and emissions associated with each alternative
stripper were determined. The final report is available8.
[Bob McCrillis: (919) 541-2733]
f. Waterborne Two-Component Epoxv Topcoats for Wood Furniture Finishing. A two-
component water-based epoxy resin coating system containing less than 0.08 lb/gal
(10 g/I) VOC has been developed as both clear and white-pigmented topcoats9. The
VOC level, 0.08 lb/gal, is the minimum detection limit of the test procedure for VOC
content. These topcoats have met most performance criteria including: (1) a VOC
content of less than 0.08 lb/gal; (2) high gloss; (3) dry to touch in 10 minutes or less,
dry to handle in 15 minutes or less; and (4) a 2H pencil hardness. A paper describing
this research was presented at the First Low- and No-VOC Coatings Conference10.
This project is cooperatively funded with SCAQMD. Research to develop a complete
coating system (i.e., sealer, stain, and topcoat) which utilizes these resins has been
completed11. [Bob McCrillis: (919) 541-2733]
g. Evaluate P2 Opportunities for Plywood and Particleboard MACT ("Maximum
Achievable Control Technology"!. This Source Reduction Review Project (SRRP)
targets the plywood and particleboard manufacturing industries which were included
in the EPA's initial list of source categories of air toxic chemicals under Section 112
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of the CAAAd. The industry was listed as a potential major source of manganese
compounds and polycyclic organic matter. Emissions of HAPs from this industry
have been associated with, but not limited to, the drying of binders. The objective of
this project is to collect information regarding available and emerging options for P2
in the plywood and particleboard industries. The final report is available12.
[Betsy Howard: (919) 541-7915]
h. Quantification of VOC/HAP Emissions from Conversion Varnish Coatings and
Demonstration of Formaldehvde-Free Alternative Coatings for Kitchen Cabinets.
Wood and wood-veneered kitchen cabinets present a unique finishing challenge
because they must be resistant not only to water, but also to many different detergents
and foods, which may be spilled onto them during their lifetime. This has resulted in
the wide use of conversion varnishes, which are acid-catalyzed reactive coating
systems, that form strong, water resistant, attractive coatings by chemical reaction
after they are applied. However, because these coatings are reactive, they release
reaction byproducts during application and curing, as well as during their use in the
indoor environment. This contributes to chemical emissions from the manufacturing
facilities as well as emissions into the household indoor air.
Although several chemicals may be emitted from these coatings, the chemical of
primary interest is formaldehyde, because it is a HAP, a VOC, a probable carcinogen,
and an irritant. In addition, because the formaldehyde may be formed by the reaction
that occurs after the coating is applied, its emission cannot be estimated from
formulation information.
The objectives of this SRRP project are to: (1) Develop methods to measure cure
emissions from conversion varnishes; (2) Measure cure emissions from several
commonly used conversion varnishes to gain an understanding of their amount and
composition; (3) Investigate alternative, lower-emitting coatings which can provide
the water and chemical resistance and appearance necessary for this application. This
includes coatings currently in use commercially, as well as promising emerging
coatings; and (4) Demonstrate the most promising alternative, and measure emissions
both in the manufacturing plant and in the household indoor environment, to evaluate
their emissions compared to those of the conversion varnishesc. A conference paper
summarizing results is available". [Betsy Howard: (919) 541-7915; Bob McCrillis:
(919) 541-2733]
2. Metal and Plastic Parts and Products Painting for Automotive and Other Applications
a. Small Business Research Focus Group - Metal Parts and Products Coating. In
September 1994, the EPA and Research Triangle Institute (RT1) convened a 1-day
focus group meeting to identify specific research needed to facilitate the adoption of
d The SRRP is described in detail in Section A.9.b. of this paper.
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P2 technologies by small businesses that paint metal parts and products. The minutes
of this focus group are being prepared. [Mike Kosusko: (919) 541-2734]
b. Applied Innovative Coatings Research. The purpose of this research is to identify a
limited number of lower-emitting innovative coatings for metal and plastic
automotive parts applications. These coatings may be either supplied by paint
manufacturers or developed by university researchers, and will be demonstrated at the
Department of Defense's (DoD's) National Defense Center for Environmental
Excellence (NDCEE) in Johnstown, Pennsylvania. To supplement the research
conducted at NDCEE, a technology diffusion plan has been developed for
disseminating information developed during the testing program.
A workgroup of over 40 industry and academic coating technology experts, the
Coatings Research Forum, has been established to identify P2 opportunities, and metal
and plastic part coating formulations for testing. The minutes of the first Forum,
August 1995, and the second Forum, August 1996, are being prepared.
The first Coatings Forum identified four research opportunities: (1) Substitute
Materials or Processes for High-VOC Adhesion Promoters for Coating of
Thermoplastic Olefins; (2) Low- or No-VOC Coatings for Auto Body Refinishing; (3)
Improved Line and Equipment Cleaning for Color Changes; and (4) Enhanced
Coating Transfer Efficiency through Formulation Additives. Testing for the research
area, Transfer Efficiency Additives, was completed June 1996.
[Mike Kosusko: (919) 541-2734]
c. Demonstration of Solvent-Free Precision and Non-Precision Surface Cleaning
Techniques. The purpose of this project is to identify candidate industrial processes in
which conventional cleaning solvents can be replaced by non-organic solvents or by
solventless technology, to demonstrate the alternative techniques, and then to
compare them to conventional cleaning. Two reports detailing these demonstrations
are available1445. [Chuck Darvin: (919) 541-7633]
3. Auto Body Refinishing
a. Reduction of Solvent Emissions from Auto Body Refinishing. The objective of this
1994 project is to demonstrate P2 technology to reduce volatile organic emissions
from auto body refinishing operations. Promising technologies such as high-volume
low pressure spray guns, low VOC paints and primers, waterbome primers, and short
wavelength infrared curing are available for this area. The demonstration will focus
on technologies which can prevent emissions from small, dispersed, stationary area
sources. The results of these tests will be made available to small companies that
previously have not had access to control or prevention technologies. Work is
underway and will be completed during mid-1996. [Geddes Ramsey: (919) 541-7963]
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4. Architectural and Industrial Maintenance (AIM) Coatings
a. Innovative Architectural and Industrial Maintenance fATMl Coatings Assessment.
The goal of this 1994 project is to identify and target AIM coating applications with
high environmental risks, identify potential research partners involved with these
applications, solicit their participation, and evaluate innovative, low-emitting coatings
at their facilities. A report detailing results of this evaluation is being prepared.
[Mike Kosusko: (919) 541-2734]
5. Reinforced Plastics (Gel Coats)
a. Evaluation of Pollution Prevention Techniques to Reduce Stvrene Emissions from
Open Contact Molding Processes. At 21,000 tons (19,050 tonnes) annually, styrene is
the 13th ranked organic compound in the Toxic Release Inventory (TRI) on a mass
emission basis; it is also carcinogenic. Styrene is known to be a significant HAP
emitted from the reinforced plastic composites manufacturing source category.
Limited test data are available to quantify styrene emissions from reinforced plastic
composites fabrication. This is due to the nature of fabrication processes and
facilities, which produce significant fugitive styrene emissions. The goal of this SRRP
is to identify and evaluate testing procedures to quantify styrene emissions from
fabrication processes'1. These testing procedures will be used to quantify the emissions
reduction possible from source reduction techniques. The final report is available16.
[Carlos Nunez: (919) 541-1156]
b. Evaluation of P2 Techniques to Reduce Emissions from Open Contact Molding
Processes. The purpose of this SRRP is to evaluate P2 techniques to reduce stryene
emissions from open contact molding processes4. This process is one of the most
common production processes used by the fiber-reinforced plastics and composites
(FRP/C) industry. It is used to manufacture boats, bathtubs, shower stalls, truck body
parts, swimming pools, storage tanks, etc. The open contact molding process is one of
the FRP/C processes that consumes the most polyester resins. It also has the greatest
potential for emitting styrene due to the spraying equipment used and the openness of
the process. The objective of this test is to use emission measurements and mass
balance calculations to quantify and validate the effects of several P2 techniques,
specifically gel coat/resin formulations and application equipment, on styrene
emissions from the open contact molding process. The project final report is
anticipated for 1997. [Geddes Ramsey: (919) 541-7963]
6. Adhesives
a. Enhancing the Market Penetration of Waterborne and Other Low-Solvent
Consumer/Commercial Adhesives. This project has been funded to identify, develop,
and demonstrate new, innovative waterborne and low-solvent adhesive systems using
recently discovered and other innovative raw materials. Promising adhesive systems
and potential industrial and academic partners will be identified. A research center
may be established at a university or non-profit research institute to develop and/or
evaluate innovative adhesive formulations. [Chet Vogel: (919) 541-2827]
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b. Retrofit of Existing Solvent-based Flexible Substrate Coating Equipment to Use
Water-based Coating Systems. The coated and laminated substrate manufacturing
industry makes a wide variety of pressure sensitive products such as paper (masking),
cloth (duct), and cellophane tapes, tags, and labels, and a number of exotic laminated
products. It was selected for study because of significant air emissions of methyl ethyl
ketone (MEK) and toluene reported in the 1990 Toxics Release Inventory, i.e., it is
the #1 source for MEK (8,050 tons/yr [7,300 Mg/yr]) and the #3 source for toluene
(13,000 tons/yr [11,800 Mg/yr]). A focus group, including members of the Pressure
Sensitive Tape Council (PSTC), the Tag and Label Manufacturers Institute, and
academic and state environmental experts, helped OCB identify opportunities for
significant reductions of volatile HAP emissions in this industry.
The use of solventborne coatings {e.g., adhesives) was identified as the primary
source of the industry's toluene and MEK emissions. The objective of this project is to
evaluate the quality and economic viability of waterborne adhesives when used to
replace solventborne adhesives on flexible substrates by modifying existing coating
equipment. A report documenting background issues for this project is available17.
The high level of industry participation through the PSTC allowed case studies to be
completed and published18,19,20. [Chct Vogel: (919) 541-2827]
c. Small Business Research Focus Groups — Lower-Emitting Adhesives for
Automotive Interior Trim Applications. In August 1995, the EPA and RTI
convened a 1-day focus group meeting to identify P2 research needs associated
with adhesives used in the the automotive interior manufacturing industry.
[Chet Vogel: (919) 541-2827]
d. Textile Screen Printing ~ Alternative Platen Adhesives. As a result of the 15 category
evaluation, 5 categories were selected for further study (see Section B.l.d.). For each
of the five categories (Textile Manufacturing in this case), a more detailed evaluation
of emissions, emission sources, and P2 opportunities was completed. A report
detailing emissions and P2 opportunities for the textile industry is being prepared.
Two evaluations were completed as a result of the textiles report. The feasibility of
substituting waterborne platen adhesives for solvent-based adhesives in aerosol cans
was evaluated, first for automatic and then for manual spraying systems. A paper is
available describing the demonstration of automatic spraying systems.21 Reports
detailing the successful reduction of emissions through the use of waterborne platen
adhesives are being prepared. [Mike Kosusko: (919) 541-2734]
e. Coated and Laminated Paper Equipment Cleaning. The rationale for this project is
similar to that for the "retrofit" project described earlier under in Section B.6.b.
However, the focus of this project is on the second largest source of MEK and toluene
emissions in the industry, equipment cleaning. The objectives of this project are to
identify and evaluate improved methods for cleaning process equipment surfaces,
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recommend candidate demonstration projects, conduct demonstrations, and transfer
technical findings to the small businesses in the industry. A report detailing emissions
characterization and P2 opportunities is available22. A report on demonstrated
alternatives is also available23. [Mike Kosusko: (919) 541-2734]
7. Printing and Publishing
a. Characterization and Modification of Microstructure in Waterborne Inks Stabilized by
Polymeric Surfactants. The objective of this project is to develop the use of polymeric
surfactants to stabilize the microstructure in, and influence the physical properties of,
waterborne inks. The focus will be the enhancement of the performance of traditional
inks, not the reformulation of inks. Specific research will include: 1) characterization
of the microstructure of waterborne ink systems; 2) correlation of the microstructure
with physical properties (e.g., stability, viscosity, ink/substrate compatibility); 3)
identification of the dominant structure-property relationships; and 4) modification of
the microstructure by adjusting the molecular characteristics of polymeric surfactants
to produce a system with the desired properties (e.g., gloss, heat resistance, and
opacity). VOC and air toxic emission reductions will result from this project if it is
successful. [Kaye Whitfield: (919) 541-2509]
b. Innovative Ink Feed Systems. This project is part of the SRRP (see Section B.9,b.
below). It is focused on the flexography and gravure segments of the printing and
publishing industry. Many flexographic and gravure facilities are major sources of
HAPs, especially when compared to offset lithography, letterpress, or screen printing
facilities. The systems (e.g., piping, tanks, and mixers) used to feed ink to printing
presses and their subsequent cleaning requirements are the source of substantial
volatile HAP emissions. Alternative feed systems could substantially reduce these
emissions. A project report is available24. [Carlos Nunez: (919) 541-1156]
8. General
a. Assessment of Pollution Prevention Opportunities in Five Industries. In this small,
cooperative project with the SCAQMD in Los Angeles, California, emissions and P2
opportunities have been assessed for the following five industries, all of which use
surface coatings:
1) Architectural and Industrial Maintenance Coatings;
2) Consumer/Commercial Adhesives;
3) Rotogravure Printing;
4) Flexographic Printing; and
5) Graphic Arts.
The final report for this project is available25. [Mike Kosusko: (919) 541-2734]
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b. Source Reduction Review Program (SRRP) Focus Groups. The purpose of this SRRP
project is to identify P2 opportunities via focus group input for 3 of the 17 SRRP
categories. Of the three, two are surface coating categories (i.e., Paper and Other Webs,
and Reinforced Plastics). The other category is Integrated Iron and Steel Manufacturing.
Focus groups have included the participation of industrial, governmental, and academic
experts to achieve a broad perspective. [Carlos Nunez: (919) 541-1156]
c. Evaluation of Alternative Paint Stripping Technologies Used In Aircraft and Space
Vehicles. Low toxicity and low-VOC paint stripper alternatives for metal reworking were
identified, evaluated, and compiled in this 1994 SRRP project under an Interagency
Agreement with the National Aeronautics and Space Administration (NASA)d.This
project focused on the evaluation and testing of depainting systems which do not use
MeCl2 or any of its sister polluting agents. [Geddes Ramsey: (919) 541-7963]
d. Support to NSF University Cooperative Research Center in Surface Coatings.
This project would provide support to the Industry/University Cooperative Research
Center in Coatings (FUCRCC) established at Eastern Michigan University in 1990 by the
National Science Foundation (NSF). The Michigan Molecular Institute (MMI)
became affiliated with the Center in 1991 and North Dakota State University (NDSU)
became affiliated in 1994. Nine companies and organizations are currently members of
the Center; growth by five to eight new members is planned. The Center's current
scientific and technological program objectives are grouped within principal areas of
expertise:
- To demonstrate new concepts in polymer synthesis and crosslinking
- To leam principles of the physical phenomena that are critical to coatings
technology
- To improve characterization methods for coatings
[Bob McCrillis: (919)541-2733]
C. Technologies
1. Radiation-curable Coatings
a. Technical Barriers to the Use of Radiation-cured and Waterbome Coatings. This project
is part of the SRRP and has focused on wide-web flexography and metal can
manufacturing^ The use of radiation-cured (e.g., ultraviolet [UV]-cured and electron
beam-cured) or waterborne coatings is a P2 option for several SRRP source categories.
However, technical barriers to their broadened usage exist, including concerns about
toxicity and the difficulty of coating complex parts using radiation-cured coatings. The
objective of this project is to identify and characterize these technical barriers and to
identify critical research to overcome them. Results of this project will be available both
as a project report and a journal article26. [Carlos Nunez: (919) 541-1156]
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b. Focus Group Meeting for Metal Can Manufacturers and Flexographic Printing. EPA has
focused significant effort on investigating and evaluating alternative coating formulations
for several industries, specifically focusing on radiation-curable coatings. This work is in
support of the SRRP, which is designed to ensure that source reduction and multimedia
issues are considered during the development of upcoming air, water, and hazardous
waste standards. Two of the 17 SRRP industrial categories were the focus of this meeting.
A report on the research opportunities for both industries will be published. [Carlos
Nunez: (919) 541-1156]
c. Basic R&D on Radiation-cured Coatings. The results of the'Barriers'project (Section
C.l.a.) are being used to target research opportunities for radiation-curable coatings.
[Carlos Nunez: (919) 541-1156]
2. Powder Coatings
a. Application of DoP Powder Coating Expertise to Civilian Applications. The objective of
this 1994 Environmental Technology Initiative (ETI) project is to improve the
competitiveness of small businesses by allowing them to coat their products more
efficiently by using powder coatings whenever they are technically and economically
feasible. Paint powder is electrostatically applied to the substrate. Overspray is collected
and reused. The powder coated parts are then heat-cured in an oven or with infrared
lamps. The process eliminates VOC and many HAP emissions and avoids generation of
paint booth wastewater. The powder coating expertise developed by DoD has been
applied to civilian applications. The project report will become available during 1997.
[Kaye Whitfield: (919) 541-2509]
3. Paint Spray Gun Enhancements
a. Evaluation of Ultra-Low-Volume (TJLV) Spray Gun System. The objective of this project
was to evaluate an ULV spray gun system. Tests have been completed cooperatively with
the U.S. Air Force at Warner-Robins Air Force Base, Georgia. Qualitative results of the
test are promising. An improvement of paint utilization efficiency was attributed to the
enhanced paint lay down provided by the gun. This and the ability to spray high viscosity
paints (which contain fewer solvents) have led to a 50% reduction in VOC emissions.
The project report is available27. [Chuck Darvin: (919) 541-7633]
b. Spray Gun Cleaning. The purpose of this project is to compare emissions from two types
of paint spray gun cleaning equipment (i.e., open- and closed-systems) to each other and
to those of current cleaning practices. This project has been in support of EPA*s Control
Technology Center (CTC). The CTC provides technical support to local, state, and EPA
Regional environmental personnel, small businesses, and international clients. It is co-
sponsored by AEERL and EPA's Office of Air Quality Planning and Standards
(OAQPS). The final report will be available in 1997. [Geddes Ramsey: (919) 541-7963]
4. Partitioned. Recirculating Spray Booth. This project is presented even though it is not P2
since it complements OCB's P2 projects in surface coating. Recirculation in paint spray
1-45
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booths has been recognized for many years as a means of reducing the volume of spray booth
exhaust. This allows the use of a smaller control device, hence reducing air pollution control
costs (i.e., equipment and energy costs). Partitioning of the spray booth exhaust stream takes
advantage of the VOC concentration gradient that exists vertically across the booth exit.
VOCs stratify in the booth and their concentration is greatest closer to the floor. By pulling
the booth exhaust stream from the bottom portion of the booth and the recirculating stream
from the top portion of the booth, the concentration of the exhaust stream can be enhanced,
perhaps removing the same mass of pollutants in a smaller exhaust volume than is possible in
a traditional recirculating booth. Preliminary field tests have shown the feasibility of reducing
controlled air volumes by 50 to 75% below non-recirculating booths.
A demonstration of the stratified recirculation concept at the U.S. Marine Corps
Maintenance Depot near Barstow, California, is complete. During the demonstration, an
existing spray booth was modified to use both recirculation and partitioning. A movable
plenum was used to evaluate the optimum height for flow partitioning. An end-of-pipe
control technology was evaluated in conjunction with the spray booth demonstration. Spray
booth exhaust feeds to a control device which uses UV light to destroy organic compounds
absorbed on a catalytic substrate, scrubbing with ozonated water, and a final activated carbon
polishing step. [Chuck Darvin: (919) 541-7633]
D. Technology Transfer
1. The Surface-Coating-Free Materials Workshop. This workshop was held July 1991 to
explore the potential for development and use of materials that would not need to be coated
during manufacture or recoated during use. If such materials were to come into widespread
use, VOC and air toxic emissions associated with surface preparation (cleaning), coating, and
paint stripping before recoating could be avoided. The proceedings of this workshop are
available28. [Mike Kosusko: (919) 541-2734]
2. The 1st Pollution Prevention Conference on Low- and No-VOC Coating Technologies. This
conference was held in San Diego, California, in May 1993 to provide a forum for
exchanging technical information on innovative coating technology and to allow EPA to
interact with industry, academia, and others interested in surface coating technology.
Conference proceedings are available29. [Mike Kosusko: (919) 541-2734]
3. The 2nd Pollution Prevention Conference on Low- and No-VOC Coating Technologies. This
paper has been prepared for the Proceedings of the 2nd Biennial International Low- and No-
VOC Coating Technologies Conference held March 1995 in Durham, North Carolina,
Proceedings of the Conference will be available. A third conference is tentatively planned.
[Mike Kosusko: (919) 541-2734]
4. Coatings Alternatives Guide fCAGE). In response to environmental regulations, coating
users have been acting to reduce their emissions of HAPs and VOCs from painting
operations. Although coating suppliers are rapidly developing new, low- and no-VOC
coatings, end-users, particularly small business, are frequently unaware of new products and
1-46
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assistance with sorting through hundreds, if not thousands, of available low-emitting products
to determine which products can be of benefit in specific applications .To address this need,
RTI and EPA have cooperatively developed a tool, The Coating Alternatives Guide (CAGE),
for small businesses. CAGE is being developed to assist coating users in identifying and
learning about lower-emitting, technically innovative, cost-effective coatings. It is designed
to provide information on coating equipment and alternatives in a user-friendly, question-
driven format. To date, CAGE has focused on metal substrates. Future modules will include
nonmetallic substrates such as plastics and wood. CAGE is available on the INTERNET and
in a DOS version designed for use on a personal computer. CAGE contains an expert system
and background information. The CAGE program is designed to meet both customer
demands and tough environmental regulations. CAGE has been described in several
conference papers30,31. [Mike Kosusko; (919) 541-2734]
5. Adhesives Alternatives Guide (AAGE1. The purpose of this project is to provide information
on the formulation and use of low- and no-VOC substitutes for conventional, solvent-based
adhesives. AEERL plans to develop a software package call AAGE (The Adhesives
Alternatives Guide) to provide technical assistance to regulators and small businesses. This
software will provide information on the formulation and use of low- and no-VOC substitutes
for conventional solvent-based adhesives. Special emphasis will be placed on the
environmental, health, and safety characteristics and impacts of potential substitutes. These
characteristics and impacts will be compared to those of conventional solvent-based
adhesives. Emission reduction potentials due to the use of alternate processes or products will
also be estimated. Specifying an end product will show the conventional method of
manufacture and several more environmentally friendly means of producing this product.
AAGE has been described in a journal article32. [Chet Vogel: (919) 541-2827]
6. Solvent Alternatives Guide fSAGEI. The objective of this program is to provide a simple
method of identification for cleaning options of low-polluting industrial surface cleaning
alternatives. This software program uses the speed and capability of the computer to
evaluate a large number of operating parameters and conditions to identify the most
viable surface cleaning option for a given situation. The program is available via SAGE
Web Site at http://clean.rti.org/. [Chuck Darvin: (919) 541-7633]
IV. SUMMARY AND CONCLUSIONS
The Organics Control Branch (OCB) has a P2 program which involves industries which
have significant VOC and HAP emissions from surface coating and cleaning operations. These
industries include wood furniture manufacturing, coated and laminated substrate manufacturing,
and printing and publishing. Each of these industries has common concerns, and it is hoped that
the results of our work with one industry will be useful to other industries. This paper
summarizes surface coating research, development, and demonstration activities in OCB. The
input of a broad spectrum of industry, academic, and other experts, such as the attendees at this
symposium, is needed to continue to enhance the focus, quality, and content of OCB's current
and future research activities.
1-47
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V. REFERENCES
1. Shaver, E.M., "Pollution Prevention for Cleaner Air: EPA's Air and Energy Engineering Research
Laboratory," Pollution Prevention Review, Winter 1992-93, 3:1, pp.41-50.
2. U.S. Environmental Protection Agency, 1987. Unfinished Business: A Comparative Assessment of
Environmental Problems, EPA-230/2-87-025a-e (NTIS PB88-127048). Office of Policy, Planning
and Evaluation, Washington, D.C.
3. Saeger, M., et al. The 1985 NAPAP Emissions Inventory (Version 2): Development of the Annual
Data and Modelers' Tapes, U.S. Environmental Protection Agency, Office of Research and
Development, EPA-600/7-89-012a (NTIS PB91-119669), November 1989.
4. Department of Health and Human Services, National Institutes of Health, National Library of
Medicine. 1991. Toxic Chemical Release Inventory Database (TR1S). Bethesda, MD.
5. McMinn, B.W., C.R. Newman, R.C. McCrillis, and M. Kosusko, "VOC Prevention Options for
Surface Coating," Paper Number IU 6B.07, Presented to the 9th World Clean Air Congress, Montreal,
Quebec, Canada, August 30 - September 4,1992.
6. Development of Low Cost Substitutes for Vernonia Oil as Reactive Diluents with Alkyd and Epoxy
Coatings, Final Report prepared for South Coast Air Quality Management District (SCAQMD),
Diamond Bar, California by Coatings Research Institute under SSE93110.
7. Northern, C.M., G.W. Deatherage, and L.A. Hollar, Jr. 1994. Evaluation of Volatile Organic
Emissions Data for Nonprocess Solvent Use in 15 Commercial and Inudstrial Business Categories.
U.S. Environmental Protection Agency, Research Triangle Park, NC.
EPA-600/R-94-019 (NTIS PB 94-152212),
8. Turner, S., C. Martin, R. Hetes, C.M. Northeim. 1996. Sources and Factors Affecting Indoor
Emissions from Engineered Wood Products: Summary and Evaluation of Current Literature. U.S.
Environmental Protection Agency, Research Triangle Park, NC. EPA-600-R-96-067 (NTIS PB96-
183876).
9. Huang, E.W. Research and Product Development of Low-VOC Wood Coatings: Final Report.
1995. U.S. Environmental Protection Agency, Research Triangle Park, NC.
EPA-600/R-95-160 (NTIS PB96-121520).
10. Huang, E.W., L. Watkins, and R.C. McCrillis. "Development of Ultra-low VOC Wood Furniture
Coatings,"1993. Proceedings: Pollution Prevention Conference on Low- and No- VOCCoatin g
Technologies.U.S. Environmental Protection Agency, Research Triangle Park, NC.
EPA-600/R-94-022 (NTIS PB94-152246).
11. Huang, E.W. and R.C.McCrillis. Source Reduction of VOC and Hazardous Organic Emissions from
Wood Furniture Coatings," 1996. Presented at the AWMA Conference: The Emissions Inventory; Key
to Planning, Permits, Compliance, and Reporting, New Orleans, LA.
1 48
-------
12. Martin, C, and C.M. Northeim. 1996. Characterization of Manufacturing Processes and Emissions
and Pollution Prevention Options for the Composite Wood Industry. U.S. Environmental Protection
Agency, Research Triangle Park, NC. EPA-600/R-96-066 (NTIS PB96-183892)..
13. McCrilllis, R.C., et al. "Characterization of Emissions from Conversion Varnishes," 1996. Presented
at the AWMA Conference: The Emissions Inventory; Key to Planning, Permits, Compliance, and
Reporting, New Orleans, LA.
14. Hill, E.A., and K.R. Monroe. 1996. Demonstration of a Liquid Carbon Dioxide Process for Cleaning
Metal Parts, U.S. Environmental Protection Agency, Research Triangle Park, NC.
EP A-600/R-96-131 (NTIS PB97-121149).
15. Hill, E.A., and C.H. Darvin. 1996. Degreasing Metal Parts with Liquid CO? Presented at the National
Pollution Prevention Roundtable Conference, Washington, D.C.
EPA-600/A-96-03 5 (NTIS PB96-169321).
16. Kong, E.J., M.A. Bahner, R.S. Wright, and C.A. Clayton. 1997. Evaluation of Pollution Prevention
Techniques to Reduce Styrene Emissions from Open Contact Molding Processes, U.S. Environmental
Protection Agency, Research Triangle Park, NC. EPA-600/R-97-018a
17. McMinn, B.W., W.S. Snow, and D.T. Bowman. 1995. Solvent-Based to Waterbased Adhesive-Coated
Substrate Retrofit, Vol. II: Process Overview. U.S. Environmental Protection Agency, Research
Triangle Park, NC. EPA-600/R-95-01 lb (NTIS PB96-180443).
18. McMinn, B.W., W.S. Snow, W.S., and D.T. Bowman. 1996. Solvent-Based to Waterbased Adhesive-
Coated Substrate Retrofit, Vol. I: Comparative Analysis. U.S. Environmental Protection Agency,
Research Triangle Park, NC. EPA-600/R-95-01 la (NTIS PB96-180435).
19. McMinn, B.W., W.S.Snow, and D.T. Bowman. 1996. Solvent-Based to Waterbased Adhesive-Coated
Substrate Retrofit, Vol. HI: Label Manufacturing Case Study: Nashua Corporation, U.S.
Environmental Protection Agency, Research Triangle Park, NC.
EPA-600/R-95-011c (NTIS PB96-180450).
20. Snow, W.S., et al. 1996. Solvent-Based to Water-Based Adhesive-Coated Substrate Retrofit, Vol. IV:
Film and Label Manufacturing Case Study: FLEXcon Company, Inc. U.S. Environmental Protection
Agency, Research Triangle Park, NC. EPA-600/R-95-01 Id (NTIS PB96-180468).
21. Deatherrage, G.W., and M. Kosusko. 1994. Demonstration of Waterbased Platen Adhesives
for Garment Screen Printers. Presented at the AWMA Annual Meeting, Cincinnati, OH. U.S.
Environmental Protection Agency, Research Triangle Park, NC. EPA-600/A-94-125 (NTIS
PB94-190931).
22. McMinn, B.W., and J.B. Vitas. 1994. Improved Equipment Cleaning in Coated and Laminated
Substrate Manufacturing Facilities (Phase I). U.S. Environmental Protection Agency, Research
Triangle Park, NC. EPA-600/R-94-007 (NTIS PB94-141157).
23. Vitas J.B., B.W. McMinn, and G.D. McMinn. 1995. Improved Equipment Cleaning in Coated and
Laminated Substrate Manufacturing Facilities (Phase II). U.S. Environmental Protection Agency,
Research Triangle Park, NC. EPA-600/R-95-097 (NTIS PB95-246245).
1-49
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24. Deatherage, O.W., and C.M. Nunez. 1994. Evaluation of Innovative Ink Feed Systems for
the Flexographic and Gravure Printing Industries. U.S. Environmental Protection Agency,
Research Triangle Park, NC. EPA-600/A-94-130 (NTIS PB94-190980).
25. Huang, E.W.1995. Assessment of Pollution Prevention Opportunities for Five Industries.U.S.
Environmental Protection Agency, Research Triangle Park, NC. EPA-600/R-95-001 (NTIS
PB95-167367).
26. Nunez, C.M., B.W McMinn, and J.B. Vitas. 1996. "Barriers to the Use of Radiation-curable
Adhesives in the Coated and Laminated Substrate Manufacturing Industry. Journal of Hazardous
Materials 45: 59-78.
27. Pandalai, K,, and G. Pandalai. 1993. Evaluation of Innovative Painting Processes. U.S. Environmental
Protection Agency, Research Triangle Park, NC. EPA-600/R-93-077 (NTIS ADA 279762).
28. Northeim, C., M. Moore, and M. Kosusko. 1992. Use of Surface-Coating-Free Materials for
Reduction of Volatile Organic Compound Emissions from Coating Operations. Presented
at the AWMA Ninth World Clean Air Congress: Surface-Free-Coating Materials Workshop,
Montreal, Can. EPA-600/A-92-214 (NTIS PB93-106839).
29. Northeim, C.M., and E.J. Darden. 1994. Proceedings of the 1993 Pollution Prevention Conference
on Low-and No-VOC Coating Technologies. U.S. Environmental Protection Agency, Research
Triangle Park, NC. EPA-60G/R-94-022 (NTIS PB94-152246).
30. Comstubble, D., J. Baskir, and M. Kosusko. 1995. An Expert System for Metal Parts and
Products Painting. Presented at the Society of Manufacturing Engineers Conference, Finishing, 95.
Cincinnati, OH.
31. Comstubble, D., J. Baskir, and M. Kosusko. 1996. A Personal Computer Guide for Selecting
Alternative Coatings for Metal Parts and Products Painting. 1996. Presented at the AWMA
Conference, Nashville, TN.
32. Ringler, E., and C.A. Vogel. 1997. "Interactive Software Finds Adhesives That Reduce HAPs."
Adhesive and Sealants Industry, 4:3, 28-31.
1-50
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SESSION 2
REGULATORY UPDATE
2-1
-------
PAPERS PRESENTED:
"Regulatory Climate"
(Paper not available for publication.)
by
Bruce Jordan
Director, U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Durham, North Carolina
"Low VOC Measurements, HAP Measurements in Paints, Questions, Questions, Questions"
by
K. Hiroshi Fujimoto
Advanced Technologies of Michigan
West Bloomfield, Michigan
"Developments in European VOC Emission Regulations"
by
Bob Ollerenshaw
Paint Research Association
Middlesex, United Kingdom
"Coating Alternatives Guide"
by
Jesse Baskir
Research Triangle Institute
Research Triangle Park, North Carolina
2-2
-------
LOW VOC MEASUREMENTS,
HAP MEASUREMENTS IN PAINTS,
QUESTIONS, QUESTIONS, QUESTIONS!
BY
K. HIROSHIFUJIMOTO
ADVANCED TECHNOLOGIES OF MICHIGAN
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
2-3
-------
I WISH TO THANK THE FOLLOWING INDIVIDUALS FOR THEIR HELP
AND CONTRIBUTIONS:
PR, SWAMINATHAN RAMESH. BASF
DR. JOE BENGA. PPG
PR, KEITH OLSON, GENERAL MOTORS
2-4
-------
MY BACKGROUND AND EXPERIENCES
=> TECHNICAL MANAGER, ANALYTICAL SERVICES, BASF
CORPORATION, FOR 35 YEARS
=> INVOLVED IN VOC TEST MEASUREMENTS SINCE 1977 OR
ABOUT 18 YEARS
=> CHAIRMAN, ASTM SUBCOMMITTEE D-1.21 ON ANALYSIS
OF WHOLE PAINT
=> HELPED DEVELOP AND WRITE ASTM TEST METHODS
USED IN US-EPA REFERENCE METHOD 24 FOR VOC
MEASUREMENTS IN PAINTS
=> BI-ANNUALLY, RUN THE "ASTM PAINT VOC MEASURE-
MENT WORKSHOP" THROUGHOUT THE US FOR THE
LAST 10 YEARS
=> RETIRED FOR 2 YEARS
=> PRESIDENT, K. HIRO FUJIMOTO, CONSULTANT, INC.
=> DIRECTOR, ADVANCED TECHNOLOGIES OF MICHIGAN
WHICH SPECIALIZES IN VOC AND HAP MEASUREMENTS
OF PAINTS AND NON-PAINT PRODUCTS.
2-5
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OUTLINE
=> QUICK REVIEW OF THE VOC SITUATION.
=> ASTM TEST METHODS USED IN US-EPA's REFERENCE
METHOD 24 FOR THE MEASUREMENT OF VOCs.
=> CALCULATION OF VOC
=* SHOULD THE "MINUS WATER" CONCEPT BE DROPPED?
=> DIRECT METHOD TO DETERMINE VOCs.
=> MEASUREMENTS OF HAPs IN PAINTS.
=> RULE 311, A GC METHOD TO DETERMINE HAPs.
=> THE USE OF IIS/GC/MS TO DETERMINE HAPs.
=> CONCLUSION
2-6
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BACKGROUND
=> ASTM SUBCOMMITTEE D-1.21 HAS BEEN FORTUNATE IN
BEING ABLE TO TAKE AN ACTIVE PART IN THE DEVEL-
OPMENT OF TEST METHODS NEEDED TO MEASURE
VOCs.
=> BACK IN 1977-1978, WE WERE TRYING TO FIND COMPRO-
MISE TEST METHODS WHICH WOULD COVER 80% OR
90% OF THE PAINTS IN USE AT THE TIME.
=> THANKS TO US-EPA's JIM BERRY's FORESIGHT, AND GARY
McALISTER'S INPUT, WE WERE ABLE TO WORK TO-
GETHER TO DEVELOP REFERENCE METHOD 24.
=> IT HAS BEEN AN EDUCATION AND A SYMBIOTIC RELA-
TIONSHIP FOR ALL OF US.
2-7
-------
REGULATIONS TO LOWER
VOCs AND HAPs
ARE EXCELLENT TOOLS TO CLEAN UP OUR POLLUTED AIR
HOWEVER,
WITHOUT ACCURATE, RELATIVELY EASY TO RUN, TEST
METHODS, ENFORCING THE REGULATIONS BECOMES
DIFFICULT AND/OR IMPOSSIBLE.
THIS IS THE PROBLEM FACING US TODAY.
2-8
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IN 1978. WHEN WE WERE TRYING TO DEVELOP AN ACCEPT-
ABLE TEST TO MEASURE VOCs:
=> 26% NONVOLATILE THERMOPLASTIC ACRYLICS WERE
BEING USED.
=> THE VOCs WERE AROUND 5.0-6.0# / GAL.
=> THERE WERE VERY FEW WATER-REDUCIBLE PAINT
SYSTEMS IN USE.
2-9
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TODAY, THERE HAS BEEN AN 80%-100% IMPROVEMENT OR A
SIGNIFICANT DECREASE IN THE AMOUNT OF VOCs IN
PAINTS THANKS TO THE GENTLE PRODDING OF JIM BERRY
AND HIS STAFF:
=> HIGH SOLIDS PAINT SYSTEMS IN BOTH THE WATER-
AND SOLVENT- REDUCIBLE (60-70% NV) ARE BEING
USED.
=> THE VOCs ARE IN THE NEIGHBORHOOD OF 3.0-2.8# / GAL
OR LESS AND DROPPING
=> THERE IS PRESSURE TO GET LOWER VOCs UNDER;
• AVERAGING
• BUBBLING
• BANKING (VOC CREDITS)
• OFFSETTING
=> POWDER COATINGS WITH NO VOCs
=> MULTI-COMPONENT, LOW OR NO VOC, PAINT SYSTEMS
2-10
-------
IS RM 24 APPLICABLE TO TODAY'S PAINT TECHNOLOGIES?
=> TEST METHODS ARE OK, BUT CALCULATIONS DISTORT
PRECISION SINCE THE SLIGHTEST VARIATIONS IN
EACH OF THE TEST METHODS ARE COMPOUNDED AND
EXAGGERATED.
=> THERE TENDS TO BE GREATER DISCREPANCIES IN THE
DETERMINATION OF HIGH % WATER CONTENT.
=> LOW VOC NUMBERS, I.E. AN 1% VARIATION IN TEST
RESULT FOR A PRODUCT WHICH CONTAINS 10% VOC
IS A DIFFERENCE OF 10%.
zz> AS THE VOCs GO LOWER AND % NONVOLATILES GO UP,
WE ARE SUBTRACTING FROM LARGE NUMBERS TO
OBTAIN SMALL NUMBERS WHICH EXACERBATES THE
SLIGHTEST VARIATION IN TEST RESULTS.
=> FOR LOW VOC CONTAINING PAINTS, WIDE VARIATION IN
REPEATABILITY AND REPRODUCI BILITY ARE SEEN.
--=> COMMON TO SEE NEGATIVE VALUES OBTAINED FOR LOW
VOC CONTAINING PAINTS.
2-11
-------
What VOC is analytically...
A value or number obtained under specified test conditions.
-------
RM 24 is a Compromise Between
• Complexity of test methods
• Use of ASTM test methods which give results
closest to the theoretical values (formula).
• Time required
• Equipment needed
-------
US-EPA's REFERENCE METHOD 24 REFERS TO THE FOLLOW-
ING ASTM TEST METHODS TO DETERMINE PAINT VOCs:
=> ASTM D 1475 "DENSITY OF PAINT, VARNISH,
LACQUER, AND RELATED PRODUCTS'*
=> ASTM D 2369 "VOLATILE CONTENT OF COATINGS
^ ASTM D 3792 "WATER CONTENT OF WATER-REDU-
CIBLE PAINTS BY DIRECT INJECTION INTO A GAS
CHROMATOGRAPH"
=> ASTM D 4017 "WATER IN PAINTS AND PAINT MATER-
IALS BY KARL FISCHER METHOD"
=> ASTM D 4457 "DETERMINATION OF DICHLORO-
METHANE AND 1,1,1-TRICHLOROETHANE IN
PAINTS AND COATINGS BY DIRECT INJECTION
INTO A GAS CHROMATOGRAPH"
• ASTM D 5095 "NONVOLATILE CONTENT IN SILANES,
SILOXANES AND SILANE-SILOXANE BLENDS USED
IN MASORARY WATER REPELLENT TREATMENTS"
• => ASTM D 5403 "VOLATILE CONTENT OF RADIATION
CURABLE MATERIALS"
• RECENTLY APPROVED
2-14
-------
REMEMBER, EACH ONE OF THESE TEST METHODS HAVE A
PRECISION STATEMENT
REPEATABILITY
THE MEASURE OF THE SAME CHEMIST'S ABILITY TO REPEAT
RESULTS ON THE SAME DAY AND ON ANY FOLLOW-
ING DAY.
REPRODUCIBILITY
HOW ONE CHEMIST IN ONE LABORATORY CAN REPRODUCE
THE RESULTS OBTAINED BY ANOTHER CHEMIST IN AN-
OTHER LABORATORY.
IN SUMMARY
THESE ARE PLUS AND MINUS VALUES.
2-15
-------
General Expression
to
i
G\
(weight percent of total volatiles less water
VOC — fess exempt solvents) x (density of coating)
100% - (volume percent of water)
- (volume percent of exempt solvents)
-------
General Expression
K>
j
• VOC = ( ) x ( Dc )
100% - Vw-Vex
(Wv-Ww-Wex)x(Dc)
100% -(Ww)x(Dc/Dw)-( Wex) x(Dc/Dex)
-------
VOCs ARE REPORTED AS:
SOLVENT-REDUCIBLE COATINGS
=> -GRAMS / L
=> POUNDS/GAL
WATER-REDUCIBLE COATINGS
=> GRAMS / L minus WATER
=> POUNDS / GAL minus WATER
FUTURE GOAL-ALL PAINTS & COATINGS
=> MASS OF VOC / MASS APPLIED COATING SOLIDS
2-18
-------
WHY THE "MINUS WATER" CONCEPT?
2-19
-------
Minus Water Calculation
50%
Volatiles
50%
Nonvolatiles
% Volatiles
i
NJ
VOC (with wattr)
VOC (minus water)
50.0%
4.3 lbs./gal.
4.3 lbs./gal.
-------
Minus Water
Calculation
h2o
40%
Volatiles
40%
Nonvolatiles
% Volatiles
VOC (with water)
VOC (minus water)
60.0%
3.4 lbs./gal.
4.3 lbs./gal.
-------
Minus Water
Calculation
20%HjO
30%
Volatiles
50%
Nonvolatiles
% Volatiles
VOC (with water)
VOC (minus water)
50.0%
2.6 lbs./gal.
3.4 lbs./gal.
-------
THEREFORE,
IT IS RECOMMENDED THAT;
FOR LOW VOC PAINTS AND COATINGS, DROP THE
"MINUS WATER" CONCEPT.
THE WIDE VARIATION IN RESULTS ARE DUE TO THE
CALCULATIONS.
HERE ARE MY REASONS!!
2-23
-------
MET24-BLXLS
BETWEEN LABORATORYVOCRANGES@20%NV
s
800.00
600.00 f
400.00
200.00
0.00
-200.00
-400.00
-600.00
-800.00
60.00 65-.00 70.00
79^0—
~—
UCL
—0—
VOC(g/L)
•—
LCL
% WATER
BETWEEN LABORATORY VOC RANGES @30%NV
600.00
400.00
5
n>
200.00
O
o
0.00
>
-200.00
-400.00
50.00
55.00
60.00
69.00
% WATER
BETWEEN LABORATORY VOC RANGES @ 40 % NV
500.00
400.00
300.00
a> 200.00
O
§
100.00
0.00
-100.00
-200.00
§9:09-
50.00
-Q-
% WATER
2-24
-------
MET24-BLXLS
BETWEEN LABORATORY VOC RANGES @ SO % NV
400,00
300.00
5 200.00
® 100.00
§ 0.00
-100.00
-200.00
-_45.Q0
-Q-
% WATER
BETWEEN LABORATORY VOC RANGES @ 60 % NV
400.00
300.00
^ 200.00
O 100.00
>
0.00
-100.00
25.00
30.00
35.00
% WATER
20.00
BETWEEN LABORATORY VOC RANGES @ 70 % NV
300.00
250.00
200.00
«J 150.00
® 100.00
§ 50.00
50.00
100.00
—-to ,00 15.00-
--2QJ0O- .25.00--\^2&00...
% WATER
2-25
-------
PRECISION VOC
TASK GROUP 24, SUBCOMMITTEE DOl.21
mm
JUNE 18, 1990
RESULTS ACCEPTABLE VALUES
D1475-PENS1TY
REPEATABILITY 0.40% 0.6%
REPRODUCIBILITY 3.12% 1.8%
D2369-VOLATILES
REPEATABILITY 1.45% 1.5%
REPRODUCIBILITY 3.43% 4.7%
D3792-WATER BY GC
REPEATABILITY 1.57% 2.9%
REPRODUCIBILITY 7.78% 7.5%
D4017-WATER BY KF
REPEATABILITY 2.39% 4.7%
REPRODUCIBILITY 5.00% 15.0%
2-26
-------
Precision VOC (RR#1)
Task Group 24, Sub D01.21
June 18,1990
Minus Water
Plus Water
Std Dev
Coef Var
Std Dev
Coef Var
Sample 1
Duplicates
0.044
1.42
0.009
0.14
Repeatability
0.044
1.44
0.013
0.20
Reproducibility
0.099
3.23
0.039
0.62
Sample 2
Duplicates
0.131
9.43
0.007
0.09
Repeatability
0.070
5.05
0.008
0.11
Reproducibility
0.328
23.58
0.024
0.34
Sample 3
Duplicates
0.079
3.04
0.007
0.09
Repeatability
0.090
3.45
0.014
0.19
Reproducibility
0.737
28.30
0.122
1.70
Sample 4
Duplicates
0.051
1.23
0.004
0.06
Repeatability
0.140
3.40
0.013
0.18
Reproducibility
0.328
7.98
0.101
1.41
Summary of Precision
Minus Water
Pius Water
Std Dev
Coef Var
Std Dev
Coef Var
Duplicates
14.55
5.11
0.28
0.1
Repeatability
10.65
3.63
0.51
0.18
Reproducibility
54.35
18.36
3.45
1.2
2-27
-------
AS THE VOCs GO LOWER AND LOWER:
ELIMINATE THE "MINUS WATER" CONCEPT FOR THOSE
PAINTS AND COATINGS CONTAINING ONE POUND OR LESS
OF VOCs
REPORT STRAIGHT VOC CONTENT WITHOUT SUBTRACTING
OUT THE WATER
2-28
-------
WHY NOT RUN VOC DIRECTLY?
ELIMINATE ALL THE VOC TESTS IN USE
THIS IS WHAT ASTM SUBCOMMITTEE D-1.21
IS EVALUATING:
2-29
-------
ASTM TASK GROUP D-1.21.27B NEW APPROACH TO DETER-
MINEVOC: CHAIRMAN R, K. M. JAYANTY
=>THIS EPA FINANCED METHOD IS AN ATTEMPT TO
DETERMINE VOCs DIRECTLY.
=>IN SUMMARY, A SEALED GLASS APPARATUS. INTO WHICH
THE PAINT SPECIMEN HAS BEEN PLACED AND
THROUGH WHICH DRY NITROGEN GAS IS PASSED, IS
PUT INTO AN OVEN AND HEATED FOR ONE HOUR AT
100° C. THE EFFLUENTS ARE COLLECTED IN 2 CHAR-
COAL FILLED TUBES IN TANDEM, A 3RD AND 4TH TUBE
CONTAINING INDICATING DRIERITE ARE USED TO
COLLECT THE MOISTURE/WATER.
=*BY DIRECTLY WEIGHING THE GAIN IN WEIGHT OF THE
TUBES AND THE LOSS OF VOLATILES IN THE PAINT
SPECIMEN, THE AMOUNT OF VOC AND WATER PRESENT
CAN BE DETERMINED.
=>IT WAS HOPED THIS DIRECT METHOD WOULD MINIMIZE
THE INHERENT CALCULATION ERRORS IN REPORTING
VOC AS SPECIFIED IN US-EPA's REFERENCE METHOD 24.
2-30
-------
#7 Ace-Threds
with
Teflon O-rings
Size 80
flange joint
with
Viton O-ring
aluminum
foil dish
horseshoe clamp
FIGURE 1. VOLATILIZATION CHAMBER
2-31
-------
vent
2nd Drierit© tube
2 Umin Ng *
1 l/min N,
!
7,
ii
1 st Drierlte tube
2nd charcoal tube
A
1 st charcoal tube
110 C
oven
FIGURE 3. ASSEMBLED APPARATUS
2-32
-------
TG D-1.21.27B (CONTINUED)
=>IHE DIRECT METHOD TO DETERMINE VOCs WAS
SUBMITTED FOR ASTM MAIN COMMITTEE LETTER
BALLOT.
=>THE METHOD WAS WITHDRAWN WHEN IT RECEIVED 9
NEGATIVES AND 6 COMMENTS.
=>MOST NEGATIVES WERE DIRECTED AT THE POOR PRECI-
SION OF 43% REPEATABILITY AND 53% REPRODUCIBILITY
BETWEEN LABORATORIES.
=>IN SUMMARY, OBJECTIONS WERE;
• APPARATUS WAS NOT COMMERCIALLY AVAILABLE
• THE APPARATUS NEEDED IMPROVEMENT,
ESPECIALLY FOR LEAK CHECK PRIOR TO
RUNNING THE TEST
• THE METHOD WAS TOO SLOW AND ONLY ONE
SAMPLE COULD BE RUN AT A TIME
• THE CHARCOAL TUBES USED DID NOT ABSORB METH-
ANOL AND OTHER LOW MOLECULAR WEIGHT
ALCOHOLS
• THE REPRODUOBILIT¥ OF 53% WAS NO IMPROVE-
MENT OVER PRESENT METHODS IN USE
=>THE APPARATUS HAS BEEN IMPROVED. A ROUND ROBIN
IS UNDERWAY WHICH IS BEING SPONSORED BY AND RUN BY
THE EPA
2-33
-------
THE MEASUREMENTS OF HAZARDOUS AIR POLLUTANTS
(HAPs)
UNDER TITLE III (HAPs MAXIMUM CONTROL TECHNOLOGY)
AND TITLE V (OPERATING PERMIT PROGRAM) OF THE
CLEAN AIR ACT AMENDMENTS OF 1990, SECTION 112,
WE HAVE A NATIONWIDE SYSTEM OF OPERATING PERMITS
FOR MAJOR SOURCES OF VOCs AND HAPs.
WE HAVE THE LEGISLATION. HOW ABOUT AN
ACCURATE TEST METHOD TO MEASURE HAPs?
2-34
-------
METHOD XXX - ANALYSIS OF HAZARDOUS AIR POLLUTANT
COMPOUNDS IN PAINTS AND COATINGS BY DIRECT INJEC-
TION INTO A GAS CHROMATOGRAPH (NOW RULE 311)
=> PUBLISHED ON MAY 3, 1994, RECEIVED JUNE 28,1994 FOR
COMMENTS BY US-EPA, GARY McALISTER.
=> THE GAS CHROMATOGRAPHIC (GC) TECHNIQUES USED
ARE OUTDATED-USE OF PACKED COLUMNS AND USE
OF THERMAL DETECTORS.
'EXPERIMENTAL PARAMETERS ARE NOT SPELLED OUT
SUCH AS INJECTION PORT TEMPERATURE, COLUMN
TEMPERATURE.
=> UNDER THESE CONDITIONS, EVERYONE COULD DEVELOP
THEIR OWN TECHNIQUES AND WHICH WOULD BE THE
CORRECT ONE?
=> UNFORTUNATELY, VERY FEW MIXTURES CAN BE COM-
PLETELY SEPARATED BY GC.
=> RECOGNITION OF KNOWNS ARE BASED ONLY ON
RELATIVE ELUTION TIME.
=> THE PURITY OF EACH PEAK AND OVERLAPPING PEAKS
CANNOT BE DETERMINED WITH GC.
=> THE IDENTIFICATION OF BAKING OR CURING BY-PRO-
DUCTS, DEGRADATION COMPOUNDS, VOLATILE
OLIGOMERS, ETC WOULD BE DIFFICULT, IF NOT
IMPOSSIBLE, TO ACCOMPLISH WITH A GC,
2-35
-------
HAP's BY GC (CONTINUED)
CALIBRATION WITH STANDARDS IN THIS METHOD
WOULD TAKE ALL DAY. MIXTURES OF STANDARDS
SHOULD BE USED.
DILUTED PAINT SPECIMENS ARE INJECTED DIRECTLY
INTO THE GC. THE MINIMUM INJECTION PORT TEMP-
ERATURE WHICH CAN BE USED AND WHICH CAN GIVE
ACCEPTABLE SEPARATED PEAKS IS 250° C.
IN RM 24, THE BAKING OR HEATING TEMPERATURE IS
110° C. ARE THE EFFLUENTS THE SAME AT 250° C AS
THOSE GIVEN OFF AT 110° C?
GC WITH A HFID WOULD WORK FOR KNOWNS, BUT IT
COULD NOT IDENTIFY THE CURE BY-PRODUCTS WHICH
COULD CONTAIN HAPs.
2-36
-------
w
TIME, minutes
2-37
-------
Injection Port Temperature Optimization Analysis
Area Percent
Injection Port Temperature
MIAK
Ethyl Benzene
Pentyl Acetate
1,2,4-Trimethyl Benzene
Retention Time
Injection Port Temperature
MIAK
Ethyl Benzene
Pentyl Acetate
1,2,4-Trimethyl Benzene
150
200
250
10.18
9.76
9.46
5.29
4.77
4.48
18.05
18.30
18.36
10,02
9.61
9.05
150
200
250
8.75
8.73
8.74
9.00
8,93
8.98
10.07
10.05
10.05
12.23
12.21
12.21
300
350
400
8.97
8,13
7.53
4.21
3.72
3.43
19.70
16.23
15.33
8.62
7.82
7.27
300
350
400
8.73
8.72
8.72
8.97
8.96
8.96
10.05
10.04
10.04
12.20
12.19
12.19
20,00
c 15.00
0
1 10,00
ra
4>
5.00
0,00
Area Percent Change
150 200 250 300 350
Injection Temperature
400
MIAK
Ethyl Benzene
Pentyl Acetate
1,2,4-Trimethyl
Benzene
<0
.§
I—
c
o
"¦p
c
«
4>
cc
13.00
12.00
11,00
10.00
9.00
8.00
150
Retention Time Change
200 250 300 350
Injection Temperature
400
MIAK
Ethyl Benzene
Pentyl Acetate
1,2,4-Trimethyl
Benzene
2—38
INJPORT.XLS 9/9/93
-------
THE PROBLEMS WITH IDENTIFYING HAPs
GARY McALISTER, US-EPA, STATED HE WANTED ALL OF
THE HAPs PRESENT IN A PAINT TO BE MEASURED AND
REPORTED.
UNLESS HAPs ARE MEASURED UNDER SPECIFIED TEST
CONDITIONS, CHAOS WILL REIGN.
COMPROMISED TEST PARAMETERS SHOULD BE AGREED
UPON SO THAT HAPs IS A NUMBER OBTAINED UNDER
SPECIFIED TEST CONDITIONS.
WHAT CONCENTRATION OF HAPs MUST BE REPORTED,
I.E. 1.0%, 0.10%,0.010% OR 1 PPM?
DO WE MEASURE THE HAPs EMITTED AT 110° C, THE
TEMPERATURE SPECIFIED IN ASTM D 2369 "VOLATILES
IN PAINTS?"
DO WE MEASURE THE HAPs EMITTED AT THE BAKING
TEMPERATURE FOR THE PAINT?
SHOULD SOME COMPROMISE TEMPERATURE SUCH AS
150° C BE USED FOR MEASURING HAPs EMITTED DUR-
ING THE BAKE OR CURE?
SHOULD POWDER COATINGS BE TESTED AT 190° C?
2-39
-------
File
Operator
Acquired
Instrument
Sample Name
Misc Info
Vial Number
C:\HPCKEM\1\DATA\950116\VOASTD09.D
17 Jan 95 12:12 am using AcqMethod RAMESHHS
5972 - In
INSD+ SAMPLE E
5 UL INSD +0.0221 G E
10
Abundance
3200000
3000000
2800000
2600000
2400000
2200000
2000000
TIC: VOASTD09.D
1800000
1600000
1400000
1200000 -
1000000
800000
600000
400000
200000
RUN AT 110° C
Time - - >
5.00
10.00
15 .00
20.00
25 .00
30.00
2-40
-------
File
Operator
Acquired
Instrument
Sample Name
Mise Info
Vial Number
C;\HPCHEM\l\DATA\PPG_E.D
SR
27 Feb 95 5:53 pm using AcqMethod DIRECTSR
5972 - In
paint sample E
Direct injection at 250C, 45 C->300 C @10C/M
1
Abundance
1900000
TIC: PPG E.D
1800000
1700000
1600000
1500000
1400000
1300000
1200000
1100000
1000000
900000
800000
700000
600000
500000
400000
300000
200000
100000
0
Time - - >
10.00
15.00
5 .00
20 . 00
25 . 00
2-41
-------
IF SOPHISTIC HAP RESULTS ARE REQUIRED, WE MUST USE
SOPHISTICATED INSTRUMENTS.
IT IS RECOMMENDED THAT:
=> A METHOD USING HEADSPACE/GAS CHROMATOGRAPHY/
MASS DETECTOR BE DEVELOPED,
=> WHICH USES SPECIFIED TEST CONDITIONS,
=> TO IDENTIFY AND TO OUANTITATE HAPs PRESENT IN
PAINTS AND COATINGS!
2-42
-------
SUMMARY OF THE HS/GC/MS TECHNIQUE
FOR HAPs
A 20 MG PAINT SPECIMEN IS WEIGHED INTO A 20 mL
HEADSPACE VIAL AND SEALED. INTERNAL STDS
CAN BE WEIGHED IN AT THE SAME TIME
THE VIAL IS HEATED AT 110° C IN THE HEADSPACE FOR 20
MINUTES
A 3 mL ALIQUOT OF THE HEAD-SPACE IS INJECTED INTO
A 30 m FUSED DB-5 CAPILLARY COLUMN
CHROMATOGRAPH TEST PARAMETERS:
• INJECTION MODE = SPLITLESS FOR INITIAL 30
SECONDS
• INITIAL OVEN TEMPERATURE = 45° C (FOR 1 MIN.)
• PROGRAM RATE 10° C/MIN.
• FINAL TEMPERATURE = 300° C (HOLD FOR 5 MIN.)
THE SAMPLED MIXTURE OF VOLATILES ARE CHROMA-
TOGRAPHED AND THE ELUTING PEAKS IDENTIFIED BY
THEIR UNIQUE MASS SPECTRA.
RELATIVE RESPONSE RATIOS (RRRs) WITH RESPECT TO
A SPIKED INTERNAL STANDARD ARE USED TO DETER-
MINE THE QUANTITY OF EACH COMPOUND FROM
THEIR PEAK AREAS.
2-43
-------
WITH THE USE OF THE HEADSPACE
=> WATER OR SOLVENT-REDUCIBLE WET PAINTS CAN BE
TESTED
=> POWDER COATINGS CAN BE RUN
=> MULTI-COMPONENT PAINTS, WET OR CURED, CAN BE
RUN
=> VARIOUS HEATING TEMPERATURE PARAMETERS CAN BE
USED WITHOUT DISTORTING THE CHROMATOGRAMS
=> INTERNAL STANDARDS TO QUANTIFY RESULTS CAN BE
USED
=> THE USE OF VERY SMALL SAMPLE SIZE DECREASES THE
EFFECTS OF THE PARTITION COEFFICIENT IN HEAD-
SPACE ANALYSIS
2-44
-------
WITH THE GC/MS
MOST ELUTED PEAKS CAN BE IDENTIFIED QUICKLY
OVERLAPPING PEAKS CAN BE IDENTIFIED
THE PURITY OF THE PEAKS CAN BE CHECKED
ALL THE HAPs PRESENT IN THE CHROMATOGRAM CAN BE
FLAGGED
UNKNOWNS CAN BE RUN AND THE ELUTED PEAKS OF
HAPs CAN BE IDENTIFIED
USE OF INTERNAL STANDARDS HAS THE POTENTIAL TO
GIVE GOOD QUANTITATIVE RESULTS
2-45 ¦
-------
SOME OF THE DRAWBACKS USING HS/GC/MS
COST OF THE INSTRUMENT- -S40K TO S100K
NEED TO DECREASE THE EFFECT OF THE PARTITION CO-
EFFICIENT BY USE OF SMALL SAMPLE SIZE
MATRIX EFFECT
DETERMINATION OF RELATIVE RESPONSE RATIOs(RRRs).
CAN GENERIC STANDARDS BE USED?
NEED FOR MORE RESEARCH
REQUIRES STRONG BACKGROUND IN ORGANIC CHEM-
ISTRY
2-46
-------
SOME OF THE DRAWBACKS USING I1S/GC/MS
COST OF THE INSTRUMENT- -S40K TO S100K
NEED TO DECREASE THE EFFECT OF THE PARTITION CO-
EFFICIENT BY USE OF SMALL SAMPLE SIZE
MATRIX EFFECT
DETERMINATION OF RELATIVE RESPONSE RATIOs(RRRs).
CAN GENERIC STANDARDS BE USED?
NEED FOR MORE RESEARCH
REQUIRES STRONG BACKGROUND IN ORGANIC CHEM-
ISTRY
2-47
-------
File : C:\HPCHEM\1\DATA\941104\JW008 .D
Operator : SR.
Acquired : 5 Nov 94 12:38 am using AeqMethod RAMESHHS
Instrument : 5972 - In
Sample Name: WATER BASED ADHESIVE
Misc Info :
Vial Number: 8
Abundance TIC: AAMA008.D
4000000 -
1
1. 2-Propanol
3500000 -
*
2. Toluene
3000000 -
3-Styrene
2500000 -
4. Propylbenzene/ t
i '
5.BFB, Insd J
2000000 -
3
6.Benzene, propenyl
1500000 -
I
f
7.Hydrocarbon
1000000 -
4,5
9
8 3
8.Butylcellusolve
500000 -
2
7
9.Benzene, 3-cyclohexen-l-y
0 -
4-
, 6
ii
i
I I 1
1 '—"i c=r——I 1 ! 1 r-
1 1 1 1 1 ! 1" 1"' ! 1 1 "I 1 1 —|
u ^ _1 (;r* i i r i | i i i | j t i i ] 1 1 i I' | i i r i— j r
Time--> 5.00 10.00 15.00 20.00 25.00 30.00
-------
Table 19
ESJ
I
TIC:
008.D
|
I
HC-7111 Water Based Adhesive,
Peak#
Time
Area
ID
ppm
1
1.502
2.29E+08
2-propanol
|
21360.52
2
2.961
1527991
2-pentanone, 4-methyl-
14.26125
3
3.301
2329247
Toluene |
21.73964
4
4.173
1456328
Cyclohexene, 4-ethenyl-
13.59239
5
5.024
39172094
Styrene
365.6062
6
5.523
1000000
Propylbenzerie
9.333333
7
5.523
3000000
BFB, insd
27.98769
8
5.738
1161053
cyclohexane, diethyl-
10.83649
9
5.863
306116
Benzene, 1-propenyl-
2.857083
10
5.98
1272977
Benzene, propyl-
11.88112
11
6.123
1121264
benzaldehyde
10.46513
12
6.878
428592
Benzene, 1-methyl-2-propyl-
4.000192
13
8.678
7868964
hydrocarbons j
73.44366
14
9.7
6901277
Ethanol, 2-{2-butoxyethoxy)-
644.1192
15
11.678
1808534
Benzene, 3-cyclohexen-1 -yl-
16.87965
totai=
22559.53
%
2.255953
US EPA R
WI-24
0%
Based on RM-24, we reported no VOC. However, our HS GC/MS shows the presence of
the above.
The compounds flagged (BOLD) are HAPs.
The MSDS sheet mentioned only formaldehyde-melamine polymer @ >60%.
From the compounds detected, there seems to be Styrene. Butadiene latex compounds.
AToM 12/19/94
-------
File
Operator
Acquired
Instrument
Sample Name
Misc Info
Vial Number
C: \HPCHEM\l\DATA\941104\AAMA008 .D
SR
5 Nov 94 12:38 am using AcqMethod RAMESHHS
5972 - In
#18
.#18, 0 . 3573g
Abundance
42 00000
4000000
3800000
3600000
3400000
3200000
3000000
2800000
2600000
2400000
2200000
2000000
1800000
1600000
1400000
1200000
1000000
800000
600000
400000
200000
0
Time-->
TIC: AAMA008.D
/
2-Propanol
Styrene
v
Propylbenzene
I
, v. JJU*..
5,00
10.00
15 .00
20.00
25 . 00
30.00 1
2-50
-------
Pile
Operator
Acquired
Inst rument
Sample Name
Misc Info
Vial Number
C:\HPCHEM\1\DATA\941104\AAMA008.D
SR
5 Nov 94 12:38 am using AcqMethod RAMESHHS
5972 - In
. #18
. .#18, 0 . 3573g
Abundance
220000
200000
180000
160000
140000
120000
100000
80000
60000
TIC: AAMA008.D
40000
20000
\
Toluene
I
BFB
u
HC
V WV1
Butylcellusolve
si
Benzene,3 -cycl
I
/ "NJ
Time-->
4 .00
6.00
.00
10.00
12 .00
2-51
-------
Table 19
TIC;
008.
D
I I
.#18
HC-7111 Water Based Adhesive,
Peak#
Time
Area
ID
ppm
1
1.502
2.29E+08
2-propanol|
21360.52
2
2.961
1527991
2-pentanone, 4-methy
-
14.26125
3
3.301
2329247
Toluene
21.73964
4
4.173
1456328
Cyclohexene, 4-ethenyl-
13.59239
5
5.024
39172094
Styrene | I
365.6062
6
5.523
1000000
Propyl benzene
9.333333
7
5.523
3000000
BFB, insd 27.98769
8
5.738
1161053
cyclohexane, diethyl-j
10.83649
9
5.863
306116
Benzene, 1-propenyl-
2.857083
10
5.98
1272977
Benzene, propyl-
11.88112
11
6.123
1121264
benzaldehyde
10.46513
12
6.878
428592
Benzene, 1 -methyl-2-propyl-
4.000192
13
8.678
7868964
hydrocartwns |
73.44366
14
9.7
6901277
Ethanol, 2-<2-butoxyethoxy>-
644.1192
15
11.678
1808534
Benzene, 3-cyclohexen-1-yl-
16.87965
total=
22559.53
%
2.255953
US EPA RM-24
0%
Based on RM-24, we reported no VOC. However, our HS GC/MS shows the presence of
the above. |
The compounds flagged (BOLD) are HAPs.
The MSDS sheet mentioned only formaldehyde-melamine polymer @ >60%.
From the compounds detected, there seems to be Styrene:Butadiene latex compounds.
AToM 12/12/94
-------
File
Operator
Acquired
Instrument
Sample Name
Misc Info
Vial Number
C:\HPCHEM\1\DATA\TA14614.D
SR
2 Feb 95 11:43 am using AcqMethod RAMESHHS
5972 - In
SAMPLE TA14614.
HS/GC/MS
1
Abundance
4000000 -
3500000
3000000
2500000
2000000
1500000
1000000
500000
0
Time-->
«
H
<
J
P
0
«
Oh
1
rs
H
m
6
J
O
tn
o
hj
CQ
TIC: TA14614.D
w
a
Oh
W
o o
© q
5 .00
10,00
15.00
20 .00
25.00
30 .00
2-53
-------
File : C:\HPCHEM\1\DATA\TA14614.D
Operator : SR
Acquired : 2 Feb 95 11:43 am using AcqMethod RAMESHHS
Instrument : 5972 - In
Sample Name : SAMPLE TA14614.
Misc Info : HS/GC/MS
Vial Number; 1
Abundance
TIC: TA14614.D
4000000 H
3500000
3000000 -
2500000 -
2000000
1500000 -
1000000 -
500000 -
Time-->
2.00
3 . 00
4.00
5,00
6.00
7 .00
.00
1. 00
2-54
-------
CONCLUSION ON ANALYSIS FOR HAPs IN PAINTS
OUR STUDIES HAVE LED US TO CONCLUDE:
=> THE USE OF HS/GC/MS WILL BE A NEEDED SUPPLEMENT
FOR THE VOC DETERMINATION BY US-EPA's REFER-
ENCE METHOD 24.
=> USE OF THESE INSTRUMENTS WILL MEET THE REQl RE-
MENTS STATED IN TITLE III AND TITLE V OF THE 1990
CAAA, THAT IS, IDENTIFICATION OF ALL THE HAPs
CONTAINED IN PAINTS AND COATINGS.
2-55
-------
CONCLUSION (CONTINUED)
THE MOST SIGNIFICANT OBSERVATION MADE WITH THE
GC/MS ANALYSES WAS:
=>MANY OF THE PAINTS CONTAINED COMPOUNDS WHICH
WERE ON THE US-EPA's 189 HAPs LIST AND WHICH
WOULD NOT HAVE BEEN FLAGGED BY GC ALONE OR BY
REFERRING TO THEIR MSDS SHEETS.
=> ALL THE COMPOUNDS LISTED ON A MSDS SHEET MAY
NOT EVOLVE AT THE 110° C TEMPERATURE USED IN
ASTM TEST METHOD D 2369.
=> SOME OF THE EFFLUENTS FOUND WERE NOT ON THE
MSDS SHEET.
2-56
-------
File : C:\HPCHEM\1\DATA\950206\POWDER02.D
Operator :
Acquired : 2 Feb 95 2:15 pm using AcqMethod RAMESHHS
Instrument : 5972 - In
Sample Name: SAMPLE G-P
Misc Info : POWDER G-P POLYESTER 0.076.2 MG
Vial Number: 3
Abundance
140000
130000
120000
110000 -
100000 :
90000 :
80000 -
70000
60000
50000
40000
30000
20000
10000
0
Time-~> 2.00
TIC: POWDER02.D
m
M
W
w
an
<
3
p
a
Q
s
a
i
s
o
Vw
4 .00
6 .00
8 .00
10.00 12.00 14.00
2-57
-------
Sheets
% VOC calculations:
Powder Coatings.
@11OC
E-EP
@193C
% Votatiles:
-0,8
1.3
% water:
0
0
Density of specimen, j
j/mL =
1,65
1.65
VOC (straight) =
-13.2
grams/litre
21.45
-0.11
lbs/gallon
0.179
@110C
G-P
@193C
% Voiatiles:
-1.03
3.6
% water:
0
0
Density of specimen, g/mL =
1.56
1.56
1
VOC (straight) =
-16.068
g/litre
56.16
-0.13
lbs/gal
0.47
LBS/GAL
E-EP = Epoxy-polyester hybrid
G-P = Polyester
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CONCLUSIONS
=> PAINT TECHNOLOGY IS IMPROVING DAILY WITH PAINTS
AND COATINGS COMING INTO THE MARKET-PLACE
WITH LOWER AND LOWER VOCs.
=> ALONG WITH THESE INNOVATIONS, THERE MUST BE
CHANGES OR MODIFICATIONS MADE IN TEST METHODS
AND IN CALCULATIONS NEEDED TO MEASURE THESE
LOW VOCs.
=> AS THE VOC NUMBERS GET LOWER, THERE WILL BE,
STATISTICALLY, GREATER VARIATION IN TEST
RESULTS DUE TO THE PRECISION INHERENT IN EACH
TEST METHOD USED TO MEASURE VOCs.
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CONCLUSIONS (CONTINUED)
IT IS RECOMMENDED THAT WE DROP THE "MINUS
WATER" CONCEPT FOR PAINT PRODUCTS W ITH VOCs
LOWER THAN ONE POUND.
HOW LOW A VOCs NUMBERS MUST BE OBTAINED
BEFORE ONE CAN DECLARE A PAINT CONTAINS "ZERO"
VOCs?
SPELL OUT IN DETAIL WHAT TEST PARAMETERS ARE TO
BE USED IN DETERMINING THE HAPs PRESENT IN
PAINTS AND COATINGS.
WE NEED ANSWERS: ARE THE HAPs PRESENT IN WET
PAINT TO BE MEASURED AND/OR HAPs EMITTED
DURING THE BAKING SCHEDULE OR BOTH?
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Developments in European VOC Emission Regulations
(Into or out of a maze?)
Robert J. Ollerenshaw
Paint Research Association
8 Waldegrave Road
Teddington, Middlesex TW11 LD
United Kingdom
Tel, 44 181 977 4427
Fax. 44 181 943 4705
INTRODUCTION
Legislators and industry face the same questions in addressing pollution control:
what substance should be controlled and to what level
where to apply the controls
and how to apply controls
This paper examines how these problems have been addressed in relation to VOC
emission control legislation in what is now the European Union ( EU: pre Maastricht,
the European Community, EC). My aim is to draw out features of the legislation thus
enabling comparison of US and European approaches to the primary international
environmental issue facing the coating industry, that of involvement of VOC
emissions in ground level ozone formation I also aim to steer those of you whose
companies operate or are contemplating operation in Europe through the legislation
maze or towards specialist advice before embarking on your venture.
The European Union is not an homogeneous entity, it is not a federation, though
some may wish it to be. It is a free trade grouping made up of 15 individual member
States each with its own culture, language, economic performance, industrialisation,
climate and indeed air quality. The variation National characteristics is a problem for
European legislators, imagine trying to reach an agreement on a detailed technical
proposal with even like minded individuals when at least ten different languages are
involved It will therefore be no surprise to you to learn that the approach to and
details of VOC emission control legislation varies throughout the Union, Equally,
some 250 EC directives and regulations relating to the environment have been
issued since the first measure was adopted in 1967'.
Against this background, the paper can only be a overview which focuses on
painting processes. There is not time nor space to present complete details of each
piece of legislation or the control of other VOC emission sources, which include
surface cleaning and other coating processes I offer a personal view, drawing upon
my experience in helping companies comply w ith legislation, which I hope will give a
practical, balanced guide since I am a engineer without the potentially partial
interests of a politician, industrialist or legislator The paper considers the legislation
driving forces, the scope of existing and emerging controls in the EU, and offers
some suggestions for future developments
2-61
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily refiect the views of the
Agency and no official endorsement should be inferred.
-------
LEGISLATION DRIVERS
(Into The Maze)
Air Quality, the need for control
Background concentrations of ground level ozone in the Northern Hemisphere
are reported- to have increased 2 fold over the last century and are continuing to
increase at a rate of 1 to 2% per annum. High concentrations are associated with rural
areas, although peaks in urban areas approach these levels (largely due to traffic
emissions): the concentration of YQCs is highest in urban areas. Peak levels of 180
ppb are observed in Central Europe, while in Scandinavia they are rarely above BO
ppb; peaks in the UK are between these values. There is some evidence that ozone
levels in the UK and in Holland are an imported phenomenon, underlining the
transboundary nature of the problem.. However, in spite of several years of co-
ordinated international measurements, there is no comprehensive picture which
includes , seasonal or episodic behaviour of the ozone or VOC distributions over
Europe.
Some coating related VOCs emissions are potentially toxic and odorous air
pollutants. The extent to which VOCs represent a global threat to human health is
unclear, as ambient air monitoring of organic compounds is in its infancy. It is notable
that of the 26 organic compounds now being monitored only heptane, xylene and
toluene are potentially attributable to coating industry use of solvents. While there is
concern about the levels of carcinogens such as benzene and 1.3 butadiene, the VOCs
resulting from solvent use in the coating industry are not seen as representing a
significant health risk. Thus air quality issues related to the toxic and odorous
properties of VOCs emitted from coating operations are invariably local to a specific
facility.
International Protocols
VOC emissions were the subject of the 1991 Geneva Protocol under the UNECE
Convention on Long Range Transboundary Air Pollution Parties to the Protocol
(USA, Canada, EC member states with the exception of Italy and Portugal, and the
European Community) agreed to achieve a 30% reduction (1988 reference) in their
national non- methane VOC emissions by 1999 Additional obligations under the
Protocol include:
- application of emission limits based on best available technologies and
economic feasibility to new mobile and stationary sources and to existing
sources where ozone air quality standards are exceeded or where VOC
fluxes originate.
- application of control measures to products which contain solvents and
promotion of low organic solvent products
- priority action on VOCs with the greatest photochemical ozone creation
potential
- substitution of toxic and ozone depleting VOCs by less harmful
substances
within 5 years of introduction of the Protocol Thus placing reduction of VOC
emissions on the legislation agenda of the European Commission and member state
Governments
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Action under the VOC Protocol is directed towards reducing background ozone
levels and is not expected to eliminate the incidence of severe ozone episodes. The
frequency of episodes in Europe is such that WHO guideline concentration values
are regularly exceeded thus potentially threatening human health, agriculture,
materials and the environment Additional measures to control ozone precursor
emissions are thus likely to be considered in a Protocol review scheduled for 1996.
Assessment of the costs and benefits of action taken to meet the existing VOC
emission reduction target is likely to take some time. In its current review of the NOx
Protocol under the Transboundary Convention the UNECE is considering the
feasibility of producing a "Multi- Media - Multi effect" Protocol to address emissions
of both VOCs and NOx in view their association in ozone formation. Conclusions
on this are also not expected for some time. Thus no international calls for further
curbs on VOC emissions are expected before 2000.
CONTROLS IN MEMBER STATES
(Deep In The Maze)
Strategic Approaches
Several member states have developed or are developing VOC emission reduction
programmes to meet their commitments under the Geneva Protocol. Notable among
these is the KWS 2000 Project conducted in the Netherlands. This project is an
example of interactive policy making in which government and industry examined the
options for reducing VOC emissions in order to establish effective, realistic and
equitable goals. The project involved national and local government (responsible for
issuing permits) and industry representatives. Pressure groups and consumer groups
were consulted but not formally involved in the process The project concluded with
the publication of a control strategy0 based on reduction of both solvent use and
industrial VOC emissions: vehicle and agriculture emissions were not considered. The
plan contains a programme of reduction targets for specific sources and compounds
leading to the prospect of a 58% reduction (from 19S1 levels) in VOC emissions by
2000. Industry involvement in the plan would seem to be beneficial since the
Environment Ministry.were initially seeking 50% reduction. It was envisaged that the
actions to achieve the reductions would include, manufacturer initiatives, education,
and government purchasing policies A feature of the plan is a projected 50-60%
reduction in emissions from painting operations following the introduction of low
VOC coatings, improved application methods and non-organic surface cleaners.
The UK has developed and is implementing a reduction plan"*. The plan, mainly
regulator led with industry involvement, is based on consideration of solvent usage
and the VOC emissions from industry, combustion plant, agriculture and vehicles.
Implementation is largely being effected by the application of emission controls to
industrial solvent users through the permitting of processes under the 1990
Environmental Protection Act. The plan is projected to produce the required 30%
reduction in VOC emissions. However, there is some concern that this will be
insufficient to prevent levels in some UK areas exceeding a proposed ambient air
ozone standard of 50 ppb^
France has also undertaken a strategic review and reached formal agreements with
the solvent using and coating industries in order to effect a 30% reduction in
2-63
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emissions, The Danish government is currently conducting a similar strategic exercise
to KWS 2000 in conjunction with the Industry Council
Sweden achieved a 15-20 % reduction in industrial VOC emissions by 1992 as a
result low cost measures such as process changes, control of fugitive emissions and
the use of low solvent products. These measures are not sufficient to achieve an the
intended reduction of 50% by 2000, Thus the Swedish EPA is planning to apply
stricter controls to those plants already regulated and to extent controls to other
activities^.
Development of strategies has stimulated industry led initiatives to reduce VOC
emissions. European coating manufacturers have developed their own policy7. They
are suggesting % a progressive reduction in the solvent content of decorative,
architectural and some professional ( vehicle reftnish) paints be stimulated through a
compulsory Eco-Labelling scheme They have suggested the solvent levels which
might be used as a label award criterion. Clearly, there is merit in industry participation
in the development and implementation of emission reduction plans
The industry sectors and processes subject to VOC emission control are
commonly selected using emission inventories based solvent input rather than actual
organic compound emissions. Such inventories may intrinsically overestimate source
emissions because paint usually contains a mixture of impure solvents of variable
volatility and solvents enter other waste streams The inventories, nor controls based
on total hydrocarbon emissions, take no account of photochemical ozone creation
potential variations between VOCs (although this distinction only applies if ozone
formation is the only adverse impact). They also create a problem solvent definition for
the purpose of VOC emission control. The UK regulations contain some 4 definitions,
EC regulations another: recent publication of a CEN definition may be helpful. All
VOC definitions encompass the coating degradation product emissions from stoving
plant which are also not accounted in inventories. The problems are only partially
overcome when solvent mass balance data is used to compile inventories. Clearly,
effective focusing controls will only follow from inventories based on measurement.
Ozone formation and organic solvent use have become synonymous to extent that
restriction in paint solvent content is considered the most economic way of reducing
the environmental impact of paint and painting. This is may be so in the case of
architectural / decorative and certain commercial (vehicle refinish) painting . However,
this approach can lead to reductions in coating performance, often neglects creation
of other impacts (such as odour) and the costs associated with re-equipment,
production re-scheduling and energy consumption created by introduction of, say, a
waterborne coating. Recent paint life cycle inventories have shown that significant
environmental impacts can arise from raw material production and paint stoving.
The energy used in waterborne paint stoving is greater than that for an equivalent
organic solvent based system The overall impacts of solvent and water based paints
are comparable and inversely related to coating life. These factors has led to an
industry view that there is too much emphasis on VOC emissions as a separate issue
and that it is time for legislators to focus on "greatest" environmental risks in
controlling paint and painting processes.
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Industrial Emission Controls
Plant permitting is commonly used throughout the Union as a basic method of
applying legal controls to industrial operations. As a result of EC directive 84/360
member states have in place a system of permitting major polluting facilities in the
energy, chemical, mineral metallurgical and waste industries. Coating industry
permitting and associated pollution control may be effected through environmental
protection, planning, public health, worker safety, nuisance or common(case) law.
Although the laws may be international (EU regulations), the current regulations
relating to the coating industry and VOC emissions are national or regional Such
control can, while allowing flexibility in matching emission control requirements to
local economic and environmental circumstances, can lead to a number of problems:
- neglect of emissions to atmosphere (if the local body is primarily
responsible for planning, waste o,r water issues)
- focus on local nuisance issues ( odour, noise, visual impact, amenity)
- focus on specific pollutants (smoke)
- neglect of transboundary effects of emissions
- wide variation in emission control requirements
- variation cost of control for a particular type of operation
Clearly, this last problem is of great concern to the coating plant operators in respect
of their competitiveness when their operation is located in an area with tight emission
controls Thus there is a case for national or international statutory emission limits or
guidance.
Emission Standards
Legislation relating to coating operations and VOC emission control is highly
variable throughout the Union. Only in a few member states has National legislation or
guidance relating to VOC emissions limitation been established. These tend to be the
northern industrialised nations, leading to concerns in these countries about
competitiveness and in the others fears of possible importation of pollution as a result
of industry migration.
In several states VOCs are controlled by applying National emission concentration
standards for particular compounds across the industrial spectrum: coating operations
may be specifically addressed. For example, Germany, Italy and Denmark have a
comprehensive listing of individual organic compounds subject to control. The
emission limit applied is based on substance toxicity categorisation with the lowest
being applied to carcinogenic material The limits become applicable when the
substance mass emission exceeds a given level. The emission standard for a particular
compound and the threshold at which it becomes applicable vary from country to
country.
In other states National VOC emission standards are applied to specific industrial
operations: these can be substance and coating operation specific This the case in
France where the coil and vehicle coating industries are subject to control France is
also probably unique in controlling VOC emissions (in vehicle manufacture) by
applying percentage reduction requirements rather than concentration limits.
The UK probably has the most comprehensive and sophisticated legislation on VOC
emissions from coating processes The Environmental Protection Act of 1990
established a new national pollution control regime based on scheduled processes and
2-65
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substances releases (to all media) which brought coating processes under specific
control for the first time. The list of scheduled coating and printing processes subject
to local control under national guidance includes: coating of metal and plastic, metal
packaging, coil, drums, road vehicles, aircraft, railcars, wood, vehicle respraying and
includes coating manufacture. Both new and existing processes are subject to
permitting and emission limits if the total solvent input exceeds 5 tonnes per annum ( 1
tonne in the case of vehicle refinish and 100 tonne for coating manufacture). The
substances subject to emission limits are specific to the coating operation. The
concentration emission limits applicable to new plant reflect the human and
environmental hazards of the substance emitted (isocyanate, 0.1 mg/mJ; chlorinated
hydrocarbons 20 mg/irH, total hydrocarbon 50 mg/m->) and depend on the mass
emission and the operation (spraying, stoving oven). Exemptions apply if low VOC
coatings are employed. The VOC levels in "compliant coatings" vary with industry
sector, substrate and coating type (primer, base coat, top coat, two pack) but are in the
range 250 to 850 g/1 and are typically about 400 g/1 excluding water. Existing plant
must be upgrade to the new plant standards between 1995 and 2000, depending on
the process. Conditions contained in an operating permit are legally enforceable. As
well as emission limits these include obligations on plant operation and housekeeping,
emission monitoring, dispersion and a general requirement to minimise and render
harmless releases to the environment.
Where a specific coating operation is subject to limits or guidance, the solvent use
or emission threshold bringing the operation into the control regime, the substances
and process elements subject to control and the VOC emission limit applied can vary
between countries.
For all states where national emission standards are in place the concentration limit
values reflect the levels achievable by employing best available techniques. Individual
substances subject to control are selected on the basis of human, rather than
environmental, toxicity. Some chlorinated hydrocarbons are controlled for
environmental reasons, POCP is not used as the basis for ranking organic compounds
for the purposes of applying differential limits The UK's approach of controlling
VOCs by applying a blanket total hydrocarbon emission limit is particularly vulnerable
to criticism for this reason, though it does have the advantage of simplifying emission
measurement.
Other control measures
Emission limits applied to factory based coating don't address significant VOC
releases from decorative, architectural and maintenance paints ( e.g. decorative paints
contribute 4-6% to total VOC emissions) The measures addressed in the following
are more appropriate for control of such releases and may well have a role in industrial
emission control
Product Controls
These may derive from specific regulations relating to the content of preparations
or from product standards. Legislation is in place throughout the community to
control the dangerous substances content of consumer and trade goods ( for example
the legislation following EEC directive 76/769 Restrictions on Marketing and Use of
2-66
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Certain Substances prohibits vinyl chloride monomer and asbestos in paints and
restricts cadmium uses) and to ensure product safety (e.g. toy coatings and
adhesives). Product standards are also used to control the lead and sulphur in fuel for
environmental purposes.
Use of product standards for VOC emission control is limited to a number of
States. Denmark has in place a prohibition of organic solvent in DIY and professional
decorative and maintenance paints. Austria has legislation limiting the solvent content
of decorative paints to 10% from 1996,
Economic Instruments:
Economic instruments include tradable emission permits, taxation (on raw
materials, emissions or on products ) and subsidies (grants, preferential loans).
European legislation provides for use of these measures but subsidies may be
considered to violate the "polluter pays principle". Their use for emission control is
not widespread: there is some limited use of preferential loans for pollution control
projects in Germany. With the possible exception of fuel and liquors, their use in
relation to VOC emission control is minimal: Luxembourg subsidises production of
waterbased paints. Nevertheless their application is being examined in several member
states^ . They are an increasingly favoured measure in the UK and the DOE is
studying their use in relation to solvent use.
Voluntary reductions/ Codes of Practice
Agreements on reducing the solvent content of paint (largely decorative and
architectural) have been reached between industry and government in Denmark,
Netherlands and France. These seem an ideal method of reducing VOC emissions in
the manufacture and use of coatings. However, without legislative back-up there is a
potential problem of equitable enforcement on industry and the achievement of
reductions in time scales to meet environmental and political agendas
Those companies operating to Environmental Management Standards( BS 7750)
and to industry environment management codes of practice (CIA Responsible Care
Programme) or participating in the EU Environmental Management and Audit scheme
(awaiting adoption in member states) have undertaken a commitment to reduce the
environmental impact of their operations and products. These companies include the
larger multi-national decorative and industrial coating manufacturers. This voluntary
action should reflect in reductions in plant VOC emissions and possibly the solvent
content of paint. Larger multi-national coating users also operate to such schemes
again offering the prospect of reduced plant emissions. However, small and medium
size manufacturers and users rarely do.
Public awarenesst consumer pressure)
Eco- labelling is one method of influencing customer choice in an environmentally
positive way. France, Germany, Netherlands, and the Nordic countries have existing
Eco - Labelling schemes each with different VOC content criteria.
A European regulation ( Council Regulation EEC 880/92) is in place establishing a
voluntary consumer goods Eco-Labelling scheme. Criteria, based on Life Cycle
Analysis, have been developed for interior decorative paint. In respect of VOC's the
proposed criteria are:
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class 1: flat (walls/ceilings) <30 g/1: aromatics <0.5 %(w/w) paint.
class2: gloss (trim paints) <250 g/1: aromatics <5% (w/w) paint
where VOC is defined as any organic compound with a boiling point lower than or
equal to 250C at normal pressures. Thus the proposals are expected to be adopted and
a scheme introduced this year.
EUROPEAN (El) LEGISLATION
(The exit or a dead end?)
Framework
EU legislation provides an umbrella framework for legislation in member states.
The legislation process is primarily based on consensus between the EU institutions
and between member states. The Commission, the administrator of EU policy,
initiates legislation by way of a proposal. Consultation with industry usually takes place
at the drafting stage. A formal published proposal is subject to scrutiny and possible
amendment by the Economic and Social Committee and the Parliament before the
Council of Ministers adopt it as legislation This which may establish minimum
standards (e.g. AQ or emission limits) or harmonise existing national laws to
maintain free market ( e.g. machinery and safety), emerges in the form of regulations,
directives, decisions or resolutions. These are implemented, directly in the case of
regulations or with some discretion, through National laws.
The Commission has a mandate through the Treaties of Rome, Paris and Maastricht
to introduce measures which:
- ensure a free market by establishing minimum standards and harmonising
existing regulations in member states.
- protect human health and the environment
-improve standards of living
Framework Action Programmes define Commission environmental policy
(photochemical oxidants were first addressed in the 1973 programme). Specific
objectives in relation to VOC emission control are to.
- ensure co-ordinated air quality and emission measurements across
member states and to secure information dissemination.
- evaluate risks to human health and the environment
- adopt ambient air quality standards for ozone and particular VQCs
- develop effective control programmes to ensure establishment and
maintenance of air quality standards
Air Quality Standards
There are no statutory air quality standards { protection against acute health effects)
or guideline values (defence against long term chronic effects) for VOCs. They are
being considered for known carcinogens such as benzene and 1,3 butadiene, but these
substances are of little direct relevance to coating operations, except so far as they
may be trace contaminants in raw materials.
Ambient air ozone guideline values (table. I) have been established throughout the
Union as a result of the directiveon air pollution by ozone.
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Table 1 Ambient Air Ozone Concentration Guide Values
I h Mean
8 h mean
EU Ozone Directive
health protection threshold
vegetation threshold
Public information threshold
Public warning threshold
90 ppb
85 ppb
20 ppb
50 ppb
WHO
76 -100 ppb ! 50-60 ppb
An air quality standard' ' is in place for NO2 ( annual limit value(98% percentile of
hourly average): 200 (.ig rrf^) which is to be attained by 1997 . Where areas have
ambient levels outside the limit and values can't be met within required time scale,
member states are required to establish plans (by 1994) to bring areas into
compliance by progressive improvement over shortest period of time. The directive
also contains a standstill clause such that there should be no significant deterioration
of air quality outside urban areas.
The proposed framework directive' - on Air Quality Assessment and Management
proposes the introduction of regional air quality zones viz.
poor - member states required to produce improvement plans
improving- no increase in pollution allowed
good - no particular requirement.
and paves the way for further air quality standards to be set (ozone in 1996,
benzene and PAH in 1999) in the Union. Individual member states are to be charged
with meeting air quality standards through National pollution control laws. While
laudable in attempting to focus action on problem areas this proposal would work
against equitable treatment of industry across the Union and neglects the
transboundary nature of the issue.
Pollution Control:
The principles underlying the development of European pollution control measures
include:
- prevention at source and minimising risks to human health and the
environment through a substance and source directed multi-media
approach
- the polluter pays
- resource conservation
- economic feasibility
- economic development (competitiveness)
- international co-operation
There is debate on whether control should be exercised through promulgation of
European wide emission standards or that framework controls should establish air
quality or emission reduction targets with selection of industries for control and
control measures left to individual states This is a difficult judgement to make, since
the first approach leads to commercial equity while the second leads to equitable
environmental quality, both fundamental principles in the Union.
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There is also debate on whether emission standards should be based on the
maximum available control technology irrespective of cost or on best available
techniques taking into account cost impacts The first approach can lead to a
requirement to apply a control particular technology while the second allows control
flexibility. Clearly, the judgement has to be based on evaluation of the economic
(including environmental) and welfare risks associated with particular pollutants.
The EU, recognising the multi-media pollution potential of industrial operations
has recently published a proposal' for integrated pollution prevention and control.
This effectively brings together, and expands to cover land pollution, directive
84/360 EEC on control of air pollution from industrial plants and directive 76/464
EEC on pollution caused by certain dangerous substances discharged into the aquatic
environment. The proposed directive will require member states to introduce a
national permitting procedure for facilities in the chemicals, energy, mineral,
metallurgical, waste and other industries where the potential for pollution is large
Plants producing resins, monomers and other paint raw materials and intermediates
will be subject to the procedure if they produce amino, chloro or organo-metallic
compounds or their capacity exceeds 1 tonne per day. Coating operations come within
the scope of the proposals if their total consumption of organic solvent is greater than
200 kg/h ( approximately 1000 tonnes per year). Recent developments include a
proposal to reduce this solvent use threshold to 100 kg/h (or 100 t.p.a.). Other
coating operations may be covered by daughter directives under this framework.
The permit is to contain conditions for preventing, wherever practicable, or
minimising releases to air, water and land . This is likely to require operators to
carry out a full environmental impact assessment and to consider plant life cycles
While the proposed directive does not include limits for releases to each of the media.
Member States will be required to set these, orequivalent parameters, for a wide
range of polluting, substances including VOCs The limits set are to be based on Best
Available Techniques and should ensure Environmental Quality Standards are not
breached. Where EQSs are being met by less rigorous release controls than
achievable using BAT, greater emissions may be allowed. This provision, in
conjunction with the proposal to designated air quality zones, may pave the way for
tradable permits.
The directive was scheduled to enter into force by 30 June 1995 with new
facilities and existing plant in areas where EQSs are being violated being expected to
comply immediately and other existing plant by 2005. There has been some slippage in
the enactment schedule, but the proposal is expected to take a high priority within
the legislative programme: a directive may adopted in the next 12 months.
The coatings industry is concerned that the recently proposed solvent use threshold
will subject a substantial number of moderately sized operations to more intensive
control than they are currently subjected to. with a consequential increase in pollution
control costs. However, the directive is based on sound pollution control principles
and addresses the problem of harmonisation of control measures across the Union.
A focus for coating industry attention over the last 5 years or so has been
Commission proposals for a directive on the limitation of the emissions of organic
compounds resulting from solvent use in industrial processes. The latest proposal.
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dated July 1994, is ihe 7th unpublished draft released for comment. While the aim of
reducing VOC emissions and features of the proposal have remained through out its
life the scope and detail of the proposal have been subject to considerable debate
with the industry and a consequence of the proposal has been the development of
concerted European industrial action by paint and solvent producers and users (
CEPE, CEFIC, AUGLEME). This debate has resulted in substantial modification of
the proposals from the first draft, notably in the areas of solvent use thresholds,
obtaining exemptions for control action already taken and for the use of low VOC
content coatings. Attempts to accommodate industry's concerns have resulted in a
fairly complex draft of the proposal (it includes 23 annexes detailing the specific
technical requirements). In total 20 (originally only 6) solvent using processes
(responsible for about 34% of total EC emissions) are addressed in the proposal,
those related to coating are listed in table 2.
The proposal will apply to both new and existing plant and contains the following
features:
- process registration: The registration requirement is based on the
mass of solvent used by a facility and this varies with process type and
production throughput It is notable that coating manufacture has been
included in the plants for control as this is estimated to be responsible for
0.7% of the European solvent emission.
- solvent management plans: A solvent mass balance to include releases
to effluent and fugitive emissions.
- integrated pollution control: The air pollution control objectives should
not be met at the expense of discharges to land or water. Recovery and
recycling of solvent is to be encouraged and permit conditions are to
address energy saving.
- emission limits
These are based on health and environmental risks and on BAT.
Organic solvents containing compounds which are classified as
Carcinogens, mutagens or toxic to reproduction [R45, R45, R47, R49,
R60, R61] are to be replaced with less harmful material with minimum
delays and to be reduced to lowest level technically achievable. Emissions
limited to 2 mg/m3 w here the emission of the sum of these compounds
>10 g/h
Chlorinated organic solvents' 20 mg/m3 w here total emission of these
compounds > 100 g/h
Total hydrocarbon (as carbon) the limits proposed vary with type of
process and throughput (table 2).
- exemptions for the use low organic solvent content products.
- compliance deadline deferment: for installations applying abatement
measures before directive comes into force
- exemption from total hydrocarbon emission limits: if National Plans
produce equivalent total reductions 10 years after adoption of the
directive.
- limitation of fugitive emissions: The limitations required depend on the
process.
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-Table 2. Solvent Directive Proposal Processes
Process
Organic Solvent
Use
t per annum
(kg / h)
Emission Limit
nig(C) nr3
Fugitive
Limit
% solvent
input
surface cleaning
1(1) R45 and CI
solvents
2(2) oilier solvents
20 10 50
[00
lo to 15
15 to 20
coating processes of nc« cars
15(15)
Chens: 50
Total 45 to 120
g/m- body area
coating processes of truck
cabins
15(15)
Chens: 50
Total: 55 to 65
i>/m- bodv area
coating processes of s ans and
trucks
15(15)
Ocas: 50
Tola!: 70 to 90
si/'in- bod-v area
coating processes of buses
15(15)
Ovens: 50
Total: 150 10 2 In
g/'m- body area
vehicle refinishing
None
5o
(guide value)
25
coil coating
25(25)
50
5 to 10
coating of metallic and plastic
surfaces
5(5)
15(15)
150
50
25
20
coating processes of wooden
surfaces
5(5)
15(15)
150
Applic. loo
Drv. 50
25
20
coating processes of textile,
fabric, film and paper surfaces
5(5)
15( 15)
150
Applic. 100
Dn. 50
25
20
manufacture of comings,
varnishes, inks and ndhesives
100(100)
150
3 (>lOO<»tpa)
5(< loootpa)
economic instruments: The proposal permits these put is not specific.
- emission monitoring: continuous monitoring if total carbon emission >
10 kg/h: periodic monitoring if total carbon emission > I kg/h.
The need for and genera! aim of the proposed control is accepted by industry, after
all every one benefits from clean air even plant managers The current proposals are
regarded as allowing a flexible approach to pollution control and establishing a
reasonably level commercial playing field across the Union. Key remaining industry
concerns are;
- Solvent use limitation over emphasised: This can compromise product
quality , productivity, process operability and economic performance with
little general environmental benefit H Industry prefers controls on specific
organic compounds.
- a poor perceived balance between costs and environmental benefits
The total cost of implementing the directive has been estimated to be about
S85 billion ( about S2 billion per annum for the painting industry) and lead
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to a 60% reduction ( from I million tonnes) in annual solvent emissions.
However, this has not been translated into anticipated reductions in
ambient ozone concentrations or reductions in adverse health effects.
- unrealistic limits for carcinogenic and chlor inated material.
Emissions from coatings are not regarded as a significant threat to health
or the environment. This criticism may not be valid if longer term chronic
efleets are taken into account.
- focus on coating industry solvents: Undue emphasis when energy,
transportation, agriculture and natural sources can, through release of
VOC, NOx and CO, make a significant contribution to ambient ozone
levels.
- demands for information excessive: Resulting in excessive cost
The scheduled time for introduction of a directive was 1994 with implementation
by member states in 1996. This is clearly unlikely and, despite broad agreement on the
latest draft, it is understood that the proposals are to revised substantially as a result of
a proposed intention to make the "solvent directive" a daughter directive of the IPPC
directive A revised draft proposal is anticipated in the next 3 to 6 months. To
eliminate overlap with an IPPC directive, proposals for a new "solvent directive" are
likely to primarily address those plants falling within scope of IPPC (i.e. those plants
using more than say 100 kg/'h or S00 t/a solvent). For these plants the main features of
the existing directive would be preserved along with a specific requirements for control
of water and land pollution introduced by IPPC. It is understood that general (not
operation specific) emission limits will be proposed. Those plants falling below IPPC
thresholds are likely to be covered by setting a national emission reduction target,
possibly around 50%, which will be specified in the directive, and leaving National
authorities to specify the detail of control measures required to meet the target over
saylO years. Such a proposal, while possibly, simplifying the directive will set
negotiations with industry back The time scale of the Solvent Directive illustrates the
difficulties in obtaining consensus and it is unlikely that a directive will be issued in the
next 12 months, possibly delaying implementation in member states till 1997 or after.
Such delays permit evaluation of the effects of existing VOC emission control
measures and the introduction of ozone air quality standards at a potential cost of
economic disadvantage to those member states where controls are already in place.
CONCLUSIONS: THE FUTURE
(Break out )
There is concern that average ambient air ozone levels are increasing and that
there are European regions where World Health Guidelines for ground level ambient
ozone concentrations are being exceeded and that this will be remain so even if the
current 30% VOC emission reduction target is met. Some are of the opinion that
VOC reductions of the order of 70% are required to redress the problem. The
prospect is therefore for further demands for VOC and other ozone precursor
emission reductions tow ards the end of the millennium, probably as a result of the
1996 review of the Geneva Protocol,
Industry is responsive to need for controls on VOC emissions and are actively
participating in legislation development De\elopment of EU legislation has resulted in
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the emergence of European wide coating industry lobbying groups. To be effective in
legislation formulation and in developing industry led alternatives, these groups have a
wider role in co-ordinating the collection and dissemination of information.
Primary industry concerns are the level of emission control required and the timing
of legislative measures because of the commercial consequences. Clear emission
targets, taking into account cost considerations, accompanied with a reasonable
implementation period mitigate these concerns. The prospect of further controls on
VOC and NOx emissions while still trying to meet existing obligations is
discomforting.
Achieving lower ozone levels may mean extending VOC emission controls to
smaller operations because in many nations large VOC emitters are already subject to
control Also low cost conservation and process efficiency measures will have been
the prime means of achieving a 30 % reduction. Thus further reductions in emissions
is likely to incur greater marginal expenditure.
Emission inventories compiled to prioritise the sources for emission control, should
not be restricted to particular groups of VOC sources or solvent users. Ozone
formation is a complex problem involving several precursors and VOC emissions from
sources other than coating operations. Proposals for emission controls on coating
operations which neglect these factors are unlikely to encourage support from the
industry
Without ambient air pollution measurement, an understanding of the relationship
between pollutant emissions and their ambient air concentrations and air quality
standards based on risks to the human health and environment, it is difficult to
establish effective and economic emission control programmes at international,
national or even facility level. Effective and economic implementation of the principle
of source control also relies on understanding the chemical nature, quantities and
sources of emissions and their fate in the atmosphere. Thus it is the industry's and in
regulator interests to encourage rather than resist emission measurement. If the cost of
such measurements is beyond some enterprises the significant national and
international interests would seem to suggest a case for employing the economic
instrument of a subsidy. Paint manufacturers should consider undertaking their own
research in areas.
Increasing understanding of the nature and toxicology of emissions from coating
plant in addition to environmental impacts during coating life cycle may lead to
rationalisation of VOC emission controls If this is to be done there is a need take
an integrated view of the net environmental impacts of coatings and the coating
industry (as is being done in the revisions of environmental law in Denmark) through
further life cycle analysis. The rationalisation may take the form of greater emphasis
on photochemical reactive and toxic emissions instead of total hydrocarbons, thus
leaving some flexibility in coating formulation to achieve desired coating properties.
Regulators and small to medium size coating users favour coating solvent content
restrictions and the substitution of solvent based coatings with tow or no VOC
coatings to reduce emission levels, because it is perceived as a low cost emission
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control option. However, the costs associated with the substitution and coating
functional performance compromises are often overlooked. Equally, when the life
cycle impacts are considered, net environmental benefits may not be achieved.
Substitution can not therefore be necessarily regarded as a universal economic option
For Eco-Labelling schemes to be effective the criteria for award should be based
on sound and critical life cycle analysis and not on arbitrary targets to reduce solvent
use in the products they are applied to.
VOC emission controls applied to coating operations vary widely throughout the
Union. Harmonisation of industrial pollution controls will follow EU legislation based
on emission standards. Legislation based requiring member states to relate the level of
required pollution control to air quality is unlikely to result in commercially equitable
controls on industry. However, this is probably the best environmental option. Thus, if
environmental protection is the prime aim of the legislation, greater emphasis should be
placed on the promulgation of air quality standards which clearly set pollution
objectives. Attainment and maintenance of these objectives within a specified period
consistent with environmental risk should be the basis of pollution control measures
required of companies, leaving the mechanics of doing this to plant operators.
International issues have tended to shift industry attention from local issues such as
the odour associated coating operat ions. The genuine, but in the majority of cases
unnecessary, fears of health and environmental risks engendered are bad for the
industry image highlighting it as a major polluter and are costly to individual
companies. Eco- labelling should not be regarded as a substitute for objective
information which raises the public knowledge of the environmental risks and benefits
associated with surface coatings. Development and dissemination of such information
might well be considered by the industry groupings which have resulted from
consideration of European directive proposals.
There is rationalisation in the coating market supply side - international leaders are
emerging - and there is internationalisation of manufacturing Such multi-national
companies voluntarily operate to environmental management standards for
commercial reasons. Equally access to finance and insurance for al! companies is
increasingly conditional upon environmental management systems being in place.
Additionally, increased public access to company and environmental information act
to motivate environmental performance improvement. Therefore, as a result of a
consequential company obligation to continually reduce the environmental impacts of
their operations, there is a real prospect of VOC emission reductions through
innovation. In these circumstances, with a strong faith in market mechanisms by
governments and industry, there is a need to examine the effects of these measures in
considering the need for tun her legislation
A compulsory requirement for companies operate to environmental management
standards, along with the application of sector reduction targets, may well provide
the most commercially flexible and economic method of attainment of emission
reductions without the need for the time consuming development of emission
regulations to achieve the same ends
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REFERENCES
OJ = Official Journal of the European (\mummiiy
1. OJ C 233, 30/8/93
2. Ozone in the UK, 3rd report of Photochemical Oxidants Review Group, DOE,
London, 1993
3. Control Strategy for Emissions of Volatile Organic Compounds, Projectbureau
KWS 2000, The Hague , Netherlands. February 1990
4.Reducing Emissions of VOC and Levels of Ground Level Ozone: A UK Strategy.
DOE, London 1993.
5. UK Dept. of Environment Evidence to the House of Commons Select
Committee, London, 1994 (currently examining the issue of VOCs).
6. Froste, H & Forsgren, Sweden Current situation and strategy for the future. VOC
Newsletter, Projectbureau KWS 2000, The Hague , Netherlands, Dec. 1994
7. VOC Policy of the European Paint Industry , CEPE, First International Congress on
VOCs, Maastricht. Netherlands 1991.
8. VOCs in Decorative and Architectural paints: CEPE, Brussels, Begium Dec. 1994
9. Opshoor et al, Management of the Environment the role of Economic Instruments:
OECD Publication 1994: ISBN 92-64-14136-7
10. Council Directive on air pollution by ozone 92/72 EEC: OJ L297 13/10/92
11. Directive on air quality standards for nitrogen dioxide 85/203 EEC, OJ. L087,
31/12/85
12. Council Proposal for Air Quality Assessment and Management COM (94)109 4
July 1994. OJC216, 6/8/94
13 Council Proposal Directive on Integrated Pollution Prevention and Control
COM(93) 423 Final 14 Sept. 1993.
14. Hazel N, LCA of Automotive OEM finishes Coatings Care and the Environment,
PRA London, 1994
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COATING ALTERNATIVES GUIDE (CAGE)
This paper has been reviewed in accordance with the U.S. environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Jesse N. Baskir1
Research Triangle Institute
Pollution Prevention Program
Research Triangle Park, NC 27709-2194
Dean R, Comstubble
Research Triangle Institute
Pollution Prevention Program
Research Triangle Park, NC 27709-2194
Michael Kosusko
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
1.0 INTRODUCTION
Many manufactured items are painted or coated in order to protect the substrate, enhance
the appearance of the product, or both. Conventional liquid paints and coatings contain a
substantial quantity of organic solvent that evaporates during the curing or drying of the coating.
Consequently, surface coating operations are a major source of Hazardous Air Pollutant (HAP)
and Volatile Organic Compound (VOC) emissions. According to recent estimates, air
emissions from industrial surface coating operations in 1992 accounted for nearly 24 percent of
all VOC emissions to air from industrial processes (U.S. EPA 1993). This equaled more than 2.6
million tons (2.4 million metric tons) of VOCs.
As coatings users come under increasing pressure from environmental regulatory
agencies to reduce their emissions of HAPs and VOCs, coatings suppliers are rapidly
developing new lines of low- and no-VOC/HAP coatings. Due to the pace of new product
development, coatings users, particularly small businesses, frequently are not aware of new
products and of the degree to which these products can reduce their process emissions. Even
when businesses are aware of new coatings, they may question whether these products can
meet their operational, aesthetic, and performance requirements.
1 RTI would like to acknowledge the contributions of David Williams of the North
Carolina Office of Waste Reduction, Vic Young of the U.S. EPA's Waste Reduction Resource
Center in Raleigh, North Carolina, Jeffrey Danneman of Reichhold Chemicals, Inc., and Ken
Monroe of Research Triangle Institute, all of whom provided technical review and suggestions
for the development of CAGE.
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To assist the end user with sorting through information about lower-emitting coatings,
Research Triangle Institute (RTI) is working in cooperation with the U.S. Environmental
Protection Agency's Air and Energy Engineering Research Laboratory (AEERL) to develop the
Coating Alternatives Guide (CAGE). The goal of this work is to develop a computer-based tool
that coating users, and those providing technical assistance to them, can use to select technically
appropriate, cost-effective, and low-emitting coatings. CAGE is designed to provide information
on coating equipment and chemistries in a user-friendly, decision-tree format.
The technical effort is focused initially on developing CAGE to provide information
about alternative coatings for metal parts and products painting. CAGE is being developed in
three phases:
1) development of a prototype system using a limited set of coating options,
2) testing the prototype logic system with the help of coating users and state and
local pollution prevention assistance offices, and
3) expansion of CAGE to include additional coatings and detailed information about
coating options.
This paper describes progress in development of the logic framework for the prototype CAGE
system.
2.0 THE CAGE CONCEPT
RTI, in collaboration with EPA, is developing CAGE to address the information needs of
smaller businesses that use coatings. It is expected that the primary audiences for CAGE will be
those at the business responsible for selecting coatings and the staff of technical assistance
programs who conduct pollution prevention assessments for small businesses.
The traditional approach to providing information to smaller businesses generally focuses
on gathering information on a topic and creating a written document which is then made
available through business assistance hotlines, resource centers, and other distribution systems.
Unfortunately, written documents generally have limited utility for meeting the information
needs of a small business for many reasons. These include:
Difficulties Disseminating the Documents. For the information to be used, it must first
get to the intended audience. Many times businesses are not aware of the existence of the
document, do not know where to obtain the document, or find that the copies of the
document they would like are not available.
Information Is Not Complete. Many times resource guides do not have complete
information about all relevant options, so that the information seeker must identify,
locate, and read multiple documents in order to have complete information about relevant
options.
Documents Include Information Irrelevant to the User. For written documents on
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complex subjects, such as coatings, to be of use to a broad audience, they must contain a
tremendous amount of information. However, only a small portion of that information is
likely to be directly relevant to the needs of a particular user. This forces the user to
search through the document to determine which portions may be relevant—a time-
consuming process that may deter small businesses from examining the information.
Information Is Not Current, The "shelf life" for a written document in a rapidly changing
field such as coatings technology may be as short as a year or less. This time frame may
be even shorter if the document contains information such as names and telephone
numbers of product vendors or technical contacts. Most guides are not updated or are
updated infrequently.
The difficulties in gathering and distributing coatings information suggest an information
diffusion approach based on electronic information media. Electronic media provide the ability
to manufacture and distribute essentially unlimited copies of information virtually
instantaneously and at little cost. Diverse sources of information can be collected into a single
information base, to which information can be easily added over time. When information is
updated, it can be made available almost immediately. Electronic media also lend themselves to
user-directed information searches which allow the user to screen out irrelevant information.
The development of CAGE is based on the premise that an electronic information base
available for personal computers can serve as an effective tool to assist coatings users (and the
organizations that provide technical assistance to them). These users need not only information
about the coating chemistries that can reduce emissions from coating operations, but also
expertise to help focus their search on those coating chemistries that can best meet their specific
performance and other requirements. To meet these needs, CAGE will provide 1) information
about a variety of low-emitting coatings and 2) a relative ranking of coatings based on
information provided by the user about a specific application.
The ranking of options is based on the user's answers to a series of questions about
performance requirements, operational limitations of the painting line, appearance requirements,
and cost considerations. CAGE does not rank coatings based on environmental factors. CAGE
includes information only about lower-emitting coatings; conventional low-solids, solvent-borne
coatings are not in the system, and, therefore, are not ranked.
The rationale for developing CAGE is similar to that for the Solvent Alternatives Guide
(SAGE), which RTI developed in collaboration with the EPA, to identify alternative cleaning
chemistries and equipment for small businesses. SAGE has been used successfully to distribute
information about alternative cleaning options to a broad audience. More than 2,000 copies of
SAGE have been distributed to date through EPA electronic bulletin boards and EPA's Control
Technology Center. Many of the users of SAGE are small business assistance providers that take
laptop computers to small businesses and run the SAGE program to identify cleaning chemistry
and equipment options while they are conducting pollution prevention assessments. New
versions of SAGE continue to be developed and distributed through the Internet. It is expected
that CAGE will be as successful as SAGE in helping to disseminate information to small
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businesses.
Because CAGE is primarily aimed at small businesses, the system is currently being
developed using expert system software that runs in a DOS operating system, A DOS-based
system was chosen rather than a Windows system because many small businesses that have
computers are using older AT-based computers operating with DOS systems and may not have
the hardware to adopt Windows.
3.0 TECHNICAL DEVELOPMENT OF CAGE
The remainder of this paper focuses on the development of the logic system in CAGE for
ranking coating options. The development of the logic system for ranking options in CAGE
consists of three main parts;
1) developing the set of coatings to include in CAGE,
2) developing the set of questions that will be used to elicit key applications
information from the user, and
3) developing the logical reasoning and scoring systems that determine how the
user's answers to the questions affect the ranking of coatings.
Each of these items is discussed below.
3.1 Coatings Included in CAGE
The alternative coatings included in CAGE represent "generic" formulations rather than
specific vendor products. This approach was selected for several reasons. Although including
specific coating formulations in CAGE would provide the user with more detailed information
about coatings, doing this would require the use of information from coatings vendors about the
characteristics of their products. It would not be possible to verify all vendor claims about their
products. In addition, including specific product formulations in CAGE would create a situation
in which CAGE would be ranking rival products from vendors for particular applications. This
would not be appropriate because in many cases vendors formulate products specifically to meet
the demands of the customer's application. In addition, a single vendor may offer a large and
diverse product line that changes as new products are introduced. Including all of these in
CAGE and keeping information in the system current would be expensive and extremely
difficult. Finally, CAGE is not intended to be a replacement for the technical representative of
the coatings vendor. Rather, CAGE is intended to narrow the range of formulations that the
coatings user investigates. CAGE also can help the user understand performance issues and
limitations of certain classes of coatings so that the user can be more knowledgeable about
coating options when contacting a vendor.
Several generic coating systems are included in the current prototype for CAGE. Each of
the coating chemistries in the system is currently available with VOC and HAP contents less than
3.5 lb/gal (420 g/1). Current systems are divided into primers and topcoats. The types of
coatings included in these categories are shown in Table 1,
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Table 1. Coating Selections Available in CAGE
Primers
Topcoats
Alkyd (high solids, solvent-borne)
Alkyd (high solids, solvent-borne)
Alkyd (water-reducible)
Alkyd (water-reducible)
Epoxy (2-component, solvent-borne)
Latex
Epoxy (2-component, water-reducible)
Powder (baked finish only)
Latex
Acrylic
Epoxy
Polyester
Urcthane (2-component)
Urethane (1-component, baked finish only)
The expected VOC content range for these formulations will depend on whether the
coating is an air dry, baked, or 2-component coating. Typical VOC content ranges for these
coatings are shown in Table 2.
Table 2. Approximate VOC Content Range for Coating Selections
Coating Type
Approximate VOC Content Range
lb/gal
' g/i
2-Component
2.8
335
Latex
1.5
180
Powder
-0
~0
Solvent-borne air dry
2.5-3.5
300 - 420
Solvent-borne baked finish
2.0-2.8
240 - 335
Water-reducible air dry
2.5-3.0
300 - 360
Water-reducible baked finish
1.5-2.5
180-300
The initial set of coatings included in CAGE has been limited intentionally to simplify
the development of the prototype system. This set of coatings was selected to provide a
representative sample of alternative system chemistries currently available, and will be expanded
as the logic for the system is refined and verified.
3.2 Information Gathered by CAGE to Rank Alternative Coatings
Developing a ranking of potential coating alternatives requires a variety of information
from the coating user regarding the operational, performance, appearance, and other requirements
of the coating system. The system gathers information by asking a series of questions similar to
those a coatings "expert" might ask of a user in order to narrow the list of likely coating
selections.
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CAGE begins by requesting information about the user's current process in order to
determine whether the user is seeking to choose a primer, a topcoat, or both. The program then
gathers information about the current coatings that are being used, the types of cleaning and
pretreatment that are conducted, the application equipment that is currently used, the number of
color changes that typically occur during a day, and the current curing method (air dry, force dry,
or baked). This information helps to establish a "baseline" for the type of coating needed.
Coating selection is also based on the substrate material. CAGE is currently being
developed to address metal parts coating, with a focus initially on steel and aluminum substrates
which are the major metallic substrates used in manufacturing. Future development of CAGE
may include other metal substrates as well as non-metallic substrates such as wood and plastics.
The system then gathers information about the relative importance to the user of coating
appearance, compared to the performance characteristics of the coating. Coating selection in
certain cases is primarily a matter of selecting a coating that looks good (e.g., the metal
components of a stapler); whereas, in other cases, the coating must be able to protect the .
substrate from corrosive environments (e.g., metal components of outboard motors). In some
cases, both properties are important (e.g., certain automotive components). The user's selection
will determine whether high performance coatings will be weighted more strongly.
CAGE then asks questions regarding the types of operational and performance
requirements that the user has. Operational requirements indicate how quickly the coating must
dry or become tack-free in order to ensure that the current rate of production is not compromised.
Performance requirements relate to the level of physical and chemical stress that the final dry
coating must be able to withstand, such as sun exposure, heat, chemical resistance, abrasion
resistance, and impact resistance.
Finally, the system considers a user's willingness to change current equipment, and the
degree to which cost considerations will affect the selection. Users who are unwilling to modify
their current application equipment or who are unable or unwilling to spend more for their
coating will be more constrained in their choice of alternatives than users who may be willing to
consider redesign of their current coating line or a more expensive coating option in order to
reduce their emissions.
3.3 Solution Ranking by CAGE
Information regarding the logic of selecting coatings was gathered primarily through a
series of interviews with coating experts. This information was supplemented with additional
information from the literature regarding coatings properties.
In general, alternatives in CAGE are ranked based on the user's response to questions.
"Scores" for each option are tallied by the system based on the user's response to each question
where scoring occurs. For the prototype, alternatives receive a higher score if the coating will do
a good job of meeting the user's need, a lower score if the coating does not meet the user's need
effectively, and no change in score otherwise. If a coating cannot be used for the user's current
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operation (e.g., if the finish is baked and the user does not have, and will not purchase, the
necessary curing equipment), the coating is eliminated from further consideration,
CAGE keeps track of each coating's score, based on the user's response to questions, and
also maintains a tally of the maximum score possible for a coating. After all questions have been
asked, coatings are ranked based on a score normalized to a top total score of 100 points.
4.0 NEXT STEPS
4.1 Current Plans
CAGE is still in the early stages of development, and much work remains before the
system can realize its full potential. Several items that will be addressed as this research
continues are listed below.
Reports, Development to date on CAGE has focused on the logical process for selecting
coatings based on user-defined needs. However, an equally important aspect of the system will
be the information it provides to the user about the coatings alternatives, their strengths, their
weaknesses, and the specific areas that may be of concern given the user's needs and the
limitations of the coating of interest. The report will provide the user with the information the
user needs to begin discussions with coatings formulators about specific alternative coatings.
Expanded Expert Input, Rankings from CAGE do not represent "right" and "wrong"
answers to the question of coating selection, but rather present a relative preference for certain
coatings in particular applications, based on the expert experience that has been built into the
system. To a certain degree, coating experts may disagree as to the "best" coating selection for a
given application, especially when ranking the "generic" options which are included in CAGE.
As CAGE development continues, additional experts will be consulted regarding the logical
selection process. This will help ensure that the results from CAGE will not be biased by the
preferences of a single coatings expert.
User Testing. The questions used in CAGE will need to be reviewed and refined to
streamline the logical flow and to ensure that the broad range of potential users can understand
the questions that the system asks. RTI expects to test the CAGE system through reviews by
members of small business technical assistance organizations such as the state and local pollution
prevention technical assistance programs that make up the National Pollution Prevention
Roundtable. The system will also be given to coatings users to test and identify problems.
Additional Coating Alternatives. CAGE currently contains a limited set of possible
coating chemistries, RTI will gather further information about coating systems and add them to
CAGE to provide a broader set of possible alternatives for the user to consider.
Providing "Transparent" Logic. While obtaining a ranking of possible alternative
coatings may be useful to the user, of equal interest may be the logical reasoning behind why
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CAGE ranked coatings a particular way for a particular scenario. If CAGE operates as a "black
box," the user will not have access to valuable information regarding coating selection. RTI will
explore ways to ensure that the logical reasoning in CAGE is "transparent" to the user by
providing explanatory notes in the reports provided by CAGE.
4.2 Future Work
Long term development of the CAGE system will seek to expand system capabilities in a
number of areas, as described below.
System Maintenance. New developments in coating technology will require that CAGE
be maintained and updated in order to stay current.
Coating Equipment Selection. CAGE may be developed to look at not only coating
selection, but also coating equipment selection. Coating equipment selection is important not
only because it determines the types of coatings that can be used in specific applications, but also
because low-efficiency equipment can greatly increase VOC emissions. A more comprehensive
CAGE program would consider not only coating selection, but also coating equipment selection.
Additional Substrate Materials. The current focus of CAGE is on aluminum and steel
finishing, which is a major sector of the painting market. Other metal substrates could also be
added to CAGE. In addition, wood and plastic substrates represent a major portion of paint
applications. Future CAGE "modules" could be created to address factors unique to selection of
coatings for these substrates.
Windows-based CAGE. Since computer operating systems continue to move towards
Windows-type operating environments, CAGE could be made available in a Windows-
compatible version. This would offer opportunities to add capabilities to CAGE such as graphics
and a mouse-driven user interface.
REFERENCE
1. U.S. Environmental Protection Agency (U.S. EPA). 1993. National Air Pollutant
Emission Trends, 1900-1992. EPA-454/R-93-032 (NTIS PB94-152097). October.
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SESSION 3
MmTION-CURAlLl COATINGS
3-1
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PAPERS PRESENTED:
"Barriers to the Use of UV and EB Technologies"
by
Jill Vitas
TRC Environmental Corporation
Chapel Hill, North Carolina
"Environment and Technology Teamed for Economic Sustainability"
(Paper not available for publication.)
by
A1 Paskonis
NIST Great Lakes Manufacturing Technology Center
Tucson, Arizona
Arcylate Lesquerella Oil in Ultraviolet Cured Coatings
by
Thomas Schuman
University of Southern Mississippi
Hattiesburg, Mississippi
Volatile Contents of UV Cationically Curable Epoxide Coatings
by
Wells Carter
Union Carbide Corporation
Bound Brook, New Jersey
3-2
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved ior
presentation and publication.
Barriers to the Use of UV and EB Technologies
by
Carlos M. Nunez
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Divison
Research Triangle Park, NC 27711
and
William L. Blake, C. Jeff Harris, W. Scott Snow, and Jill B. Vitas
TRC Environmental Corporation
6340 Quadrangle Drive, Suite 200
Chapel Hill, NC 27514
3-3
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ABSTRACT
Surface coating is the process by which paints, inks, varnishes, adhesives, or other
decorative or functional coatings are applied to a substrate (e.g., paper, metal, plastic, wood) for
decoration and/or protection. This can be accomplished by brushing, rolling, spraying, dipping,
flowcoating, electrocoating, or specialized combinations/variations of these methods. The
substrate and the coating formulation are two important factors that influence the selection of a
coating application process. Once the coating is applied, it is cured or dried using thermal energy
or radiation energy in the form of ultraviolet (UV) and electron beam (EB). This paper briefly
discusses technical, economic, and educational barriers to radiation-curable coatings in each of
the three industries studied.
3-4
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BACKGROUND AND PURPOSE
In support of the Pollution Prevention Act, the Source Reduction Review Project (SRRP),
and Maximum Achievable Control Technology (MACT) standards development, EPA's Air
Pollution Prevention and Control Division (APPCD) is investigating pollution prevention
opportunities for product and material substitutions that help industry to reduce waste,1,2
Radiation-curable coatings have been demonstrated to reduce pollution in several specific
end-use categories.3,4,5 There are two types of radiation curing processes currently in use;
ultraviolet (UV) curing and electron beam (EB) curing. UV-curing equipment consists of a UV
lamp suspended above the coated substrate, a light reflector, a radiation shield, and a cooling
system. The UV-curable coating contains a photoinitiator which initiates the polymerization of
the coating to the substrate when exposed to UV light. In the EB-curing mechanism, an electron
beam excites the electrons in the coating and causes them to crosslink without the aid of
photoinitiators.
ADHESIVE-COATED AND LAMINATED SUBSTRATE MANUFACTURING
This industry is the largest source of methyl ethyl ketone and third largest source of toluene
emissions.6
Technical Barriers3
Raw material availability and the sensitivity of the curing process to the characteristics of
the coating and the substrate are major barriers. UV energy does not penetrate thick, dark, or
colored coatings well, leaving much of the coating uncured. EB electrons cure 100% of solid
adhesives, allowing it to be used on a variety of substrates. Many substrates are sensitive to heat
and chemical elements making it necessary to modify conventional UV lamps. Since heat is not
a concern in EB-curing, it can be successfully used with heat-sensitive substrates.
Economic Barriers3
Capital Costs; Information provided by a supplier of EB-curing and thermal machinery indicates
that solvent-based systems (not including emissions control equipment) have higher investment
costs. For retrofit, a facility would need to add the EB-curing mechanism; however, a German
manufacturer stated that UV-curing mechanisms are more affordable than EB systems.
Operating Costs: Raw material costs are the primary operating cost for any adhesive coating
manufacturer. On an applied-solid basis, the cost of UV adhesives is approximately the same as
the cost of conventional rubber-based adhesives. The cost of EB adhesives, however, is about
33% more. In the case of conventional acrylic-based adhesives, UV and EB adhesives cost 50%
and 88% more, respectively. EB-curable adhesives are best suited for products which require
thick coating weights, where they outperform the other conventional and UV-curing
technologies.
3-5
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Educational Barriers3
The cost of newly installed radiation-curing equipment should approximate that of new
thermal-curing machinery without control equipment. The productivity of the radiation-curing
equipment exceeds that of the thermal system, resulting in lower costs and higher profits.
Employees must be trained to properly handle these coatings. Although non-hazardous,
radiation-curable coatings can cause allergic responses.
METAL CAN MANUFACTURING
This industry emitted over 16,000 tons (14,500 tonnes) of air pollutants in 1992.6
Technical Barriers4
Product Performance: The product performance problems of ink pick off, poor abrasion
resistance, yellowing overvarnish, and off-shade whites were experienced. The UV-curable
coatings used by Coors Brewing Co. achieve a level of abrasion resistance high enough to meet
the standards of other can manufacturers.
Another barrier is the lack of an FDA (Food and Drug Administration)-approved UV-
curable coating for direct contact with food, including beverages. Ball Corporation claimed that
components of the exterior UV-curable coatings migrated to the interior of the cans after the cans
exited the UV-curing oven. However, Coors conducted 3 months of analyses using Fourier
Transform Infrared technology and gas chromatography/infrared detection instruments and found
no volatile components from exterior inks or coatings on the internal coating of its cans. Tests
have shown a loss of coating weight in the internal coating ovens, indicating that waterbased
external coatings also may have a migration problem.
Health and Safety: Through recent advances in monomer chemistry, hazards associated with
radiation-curable coatings have decreased significantly. There are concerns with human skin
becoming sensitized when in direct contact with radiation-curable coatings, and workers are
required to wear appropriate personal protective equipment.
Economic Barriers4
Capital Investment: The most common deterrent, when initially considering a UV-curing system,
is capital cost. However, when adding additional capacity, a plant may consider a UV-curing
oven because the thermal system is a larger capital investment. The can manufacturing business
operates on low margins and high volume. Therefore, line speed is a critical element to be
considered when evaluating new technologies.
Material and Operating Costs: For Coors Brewing Co., the energy savings from its UV-curing
oven compensated for the higher price of UV-curable materials. However, due to increased
material consumption and, therefore, increased costs, the UV-curing alternative was not
economically feasible for Ball Corporation. Another cost barrier is the availability of materials
because ink suppliers consider UV-curable products to be a "specialty" line with a limited
market. Coors believes that, if other can manufacturers used these products, material costs
would fall.
3-6
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Educational Barriers4
One of the most pressing barriers involves the perception of the word "radiation."
Although UV-curing ovens harness radiant energy used to cure the coatings, many people are
still hesitant about using such equipment. Another perceived problem is worker sensitization to
aery late compounds in the inks and coatings, A previous difficulty that has since been overcome
involves oxygen inhibition. Molecular oxygen would react with free radicals in the coating,
forming a peroxide. The reactions would deplete the number of free radicals available for
polymerization during the curing process, leading to incomplete curing, Coors suppliers have
resolved the oxygen inhibition problem through improved coating formulations.
Many industry personnel believe that UV systems are not cost effective; however, the
capital expense for a UV-curing oven is no more than for a new thermal line. Studies indicate
that UV curing oven maintenance and energy costs are less than those for thermal systems.
Increase of raw materials costs may be offset by savings in emissions fees due to fewer releases
of volatile organic compounds and hazardous air pollutants.
COMMERCIAL PRINTING
Commercial printing accounted for over 1,300 tons (1,180 tonnes) of total air releases in 1992/
This paper focuses on wide-web flexographic printing and screen printing
Flexographic Printing
Flexographic printing is the leading printing process in the packaging industry and is
gaining ground in other segments of the printing industry, including newspaper and book
printing. The focus of this section is on wide-web flexography, typically defined as flexographic
printing on substrates that are 36 in. (91 cm) wide or wider.
Technical Barriers
Equipment Suitability. The industry is unsure of the best method to approach conversion: should
the UV-curing equipment be retrofit to the existing press, or should a new press be purchased
that incorporates the UV system? To date, American companies have concentrated on retrofit
solutions, while European companies have focused on designing complete press systems.
Materials Availability. UV-curable flexographic inks have only recently been commercially
produced. One major concern is meeting the FDA criteria for direct contact with food.
Manufacturers are working with FDA to develop UV-curable inks that meet FDA criteria.
Product and Ink Performance. Print quality, the most important property in printing, is
determined by several parameters, such as color density, adhesion to substrate, and dot gain.
Except in glossy printing, UV-curable inks perform as well as or better than solvent-based inks.
Health and Safety. Recent advances in monomer chemistry have significantly reduced the
hazards associated with UV-curable flexographic inks. The monomers have a high molecular
weight which reduces volatility and removes almost any danger associated with vapor inhalation.
3-7
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There are concerns with human skin becoming sensitized when in direct contact with UV-curable
flexographic inks. Also, the potential exists for the ink to be slightly undercured leaving a
residual odor as well as residual unreacted monomers on the printed product. Together, industry
and the EPA are working to develop an acceptable maximum residual monomer level.
Economic Barriers
The primary economic barriers to switching to UV-cured flexographic printing are the
capital cost of new equipment and ink costs. Most UV-curable inks are comparable in price to
solvent-based inks on a cost per unit area covered basis. However, white UV-curable inks are
more expensive than any other UV-curable inks, while white solvent-based inks are the cheapest.
Educational Barriers
The Print Manager at a German firm using UV-curable flexography noted that about 3 to
4 weeks of on-the-job training is required to train a standard solvent-based press operator to
operate a UV-cured press.
Screen Printing
The best known application is printing designs on textiles; however, screen printing is
also used on numerous non-textile substrates; e.g., point-of-purchase advertising material, fleet
graphics, specialty decorations, and fine art.
Use of UV-curable inks offers substantial economic, process, and environmental benefits
including: (1) reduction in required floor space -- large hot-air dryers and drying racks are
unnecessary ; (2) increased throughput - drying is essentially instantaneous; (3) reduction in
health and safety hazards for workers exposed to screen printing inks; and (4) reduced cost per
unit area printed (UV-curable screen printing inks are applied in thinner layers).
Technical Barriers5
Because of curing difficulties, it is necessary to use inks which achieve the proper opacity
with a thin layer of ink. Substrates with deeply textured surfaces may present barriers to screen
printing with UV-curable inks. Ink in the deep recesses of surfaces not exposed to sufficient
light may not cure properly, resulting in poor adhesion of the ink layer to the substrate. UV-
curable inks do not stand up well to finishing procedures after printing, such as die-cutting and
molding. Another barrier is the lack of FDA-approved UV-curable inks for packaging that
contacts food.
Many signs and labels must withstand extended outdoor exposure or harsh industrial
environments. One of the largest markets of this type is fleet graphics, or the large signs that are
placed on the sides of tractor-trailer trucks. UV-curable inks are not capable of meeting the
expected standard of a 6- to 7-year ink life.
Economic Barriers5
Many U.S. screen printers are medium- to small-sized shops, employing less than 50
people and can not afford the capital investment required to convert to UV-curable inks. A shop
3-8
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with only one or two production lines would lose a significant percentage of its production
capacity during conversion. Benefits of larger printers may not be realized in printing small runs
on semi-automatic presses.
Educational Barriers5
Although the Screen Printing Association International provides information on UV-
curable materials, the availability of the information to small shops may be limited.
CONCLUSIONS
Many barriers must be overcome before radiation-curable coatings can penetrate the
industry categories discussed. Many of the barriers are similar across the categories so that the
improvements may be transferred from one industry category to another, EPA is developing the
Adhesives Alternatives Guide (AAGE), which will provide facilities with a computerized system
to assist in the evaluation of alternative adhesives. Working through the Design for the
Environment Program, EPA is investigating alternative inks for flexographie printing
REFERENCES
1. Pollution Prevention Act of 1990, 42 U.S.C. §131011 et seq,
2. U.S. Environmental Protection Agency. Source Reduction Review Project. Office of the
Administrator, Pollution Prevention Policy Staff, Washington, DC. EPA- 100/R-92-002.
March 1992.
3. Vitas, J.B., G.D. McMinn, and W.L. Blake, Jr., Evaluation of Barriers to the Use of
Radiation-Cured and Hot Melt Coatings in Coated and Laminated Substrate
Manufacturing, EPA-600/R-96-Q26 (NTIS PB96-153564), U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1996.
4. McMinn, B.W. and S.R. Church, Evaluation of Barriers to the Use of Radiation-Cured
Coatings in Can Manufacturing, EPA-600/R-95-063 (NTIS PB95-215S10), U.S.
Environmental Protection Agency, Research Triangle Park, NC, April 1995.
5. Harris, C.J,, and J.D. Winkler, Evaluation of Barriers to the Use of Radiation-Cured
Coatings in Screen Printing, EPA-600/R-95-060 (NTIS PB95-208864), U.S.
Environmental Protection Agency, Research Triangle Park, NC, April 1995.
6. U.S. Department of Health and Human Services, Toxic Chemical Release Inventory
Database. National Institutes of Health, National Library of Medicine. Bethesda, MD.
Toxicology Information Program Online Services TOXNET® Files. 1992.
3-9
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ENVIRONMENT AND TECHNOLOGY TEAMED FOR ECONOMIC
SUSTAINABILITY
by
A1 K. Paskonis
NIST Great Lakes Manufacturing Technology Center (GLMTC)
4600 Prospect Avenue
Cleveland, OH 44103
ABSTRACT
Purpose: Emphasis of waste minimization methodologies merged with advanced technologies to
improve both the environment and the bottom line.
Proactive activities in pollution prevention require commitment and vision much like the
commitment to develop and implement new and emerging technology. This is a case of the
linking of both environmental focus and advanced technology to produce not only an
environmentally sound practice but an economically advantageous one.
A waste reduction assessment was conducted at a medium-sized producer of specialized screen
printing products. The company occupies about 40,000 ft2 (3,700 m2) and employs 200 people.
The self-adhesive products are used for identification, decorative trim, and screen printed
circuitry for electronic products. With programs in place to produce products with little or no
solvent content and efforts to reduce production wastes, the company actively began to
implement opportunities identified in the assessment. The aggressive engagement to implement
these opportunities has provided realized savings large enough to improve profits by $188,000
per year. These opportunities were found in changes in cleaning procedures for silk screens, the
deployment of ultraviolet curable inks, and the development and use of waterbased adhesives and
inks.
The work described in this paper was riot funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
3-10
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The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
ACRYLATED LESQUERELLA OIL IN ULTRAVIOLET CURED COATINGS
Shelby F. Thames
Department of Polymer Science
University of Southern Mississippi
Box 10037, Hattiesburg, MS 39406-0037
Min D. Wang
Chemcraft Sadolin, Inc.
3750 New Walkertown Road
Winston-Salem, NC 27105
Haibin Yu
Department of Polymer Science
University of Southern Mississippi
Box 10076, Hattiesburg, MS 39406-0076
Thomas P. Schuman
Department of Polymer Science
University of Southern Mississippi
Box 10076, Hattiesburg, MS 39406-0076
INTRODUCTION
Environmental concerns focusing on the emission of volatile
organic compounds {VOCs) can be ameliorated via the development
and use of very low- to no-VOC coatings. Ultraviolet (UV)
radiation curing is an effective means of incorporating low
molecular weight reactive species into high performance, non-
volatile polymers. The advantages of UV curing include rapid
polymer network formation on heat sensitive substrates, reduced
energy consumption, low emissions, and minimal space
requirements.1 When cost is a consideration, UV curing offers
additional advantages by eliminating the need for high volume air
movement, expensive to operate ventilation systems, solvent
recovery units, or air scrubbers. However, more often than not,
UV curing is accompanied by appreciable volume shrinkage which
can cause loss of adhesion, poor edge coverage, and other film
defects.2
Lesquerella oil (LO) is a vegetable oil of significant
commercial potential and, we believe, can be a valuable raw
material for the design and formulation of UV cured coatings.
Lesquerella oil is obtained from a promising new oilseed crop,
Lesquerella fendleri. This domestic renewable resource offers a
reduction in America's dependence on imported oils of similar
structural features. For instance, LO contains 55-60%
14-hydroxy-cis-11-eicosenoic or lesquerolic acid, a 20-carbon
fatty acid homolog of castor oil's ricinoleic acid.3 The
hydroxy functional fatty acid offers a reactive site for
derivative synthesis such as acrylated LO (ALO). Acrylated
lesquerella oil's synthesis, characterization, formulation into,
and evaluation of UV cured coatings, are the focus of this work.
3-11
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EXPERIMENTAL
Materials
Lesquerella oil was purchased from International Flora
Technology, Ltd. Methacryloyl chloride (MAC), 2 -hydroxysthyl
methacrylate (HEMA), sodium hydride (95%), toluene diisocyanate
(80% 2,4-TDI and 20% 2,6-TDI), triethylamine, tetrahydrofuran
(THF), hydroquinone, dibutyltin dilaurate, sodium hydride, and
dichloromethane were purchased from Aldrich Chemical Company.
All chemicals were used as received except THF, and it was
refluxed over sodium hydride for 1 h and freshly distilled before
use.
Oligomeric reactive diluent photomers 3016, 4061, 4094,
4149, 4770, and 6008 were supplied by Henkel Chemical Company.
Byk 065 and Byk 325 were supplied by BYK Chemie. Silwet 7604 was
obtained from Union Carbide, Irgacure 651 from Ciba-Geigy, and
Benzophenone from Aldrich Chemical Company.
Synthesis of Methacrylated Lesquerella Oil
A solution of 5 0 g (0.092 eq hydroxyl) of LO and 9 g
triethylamine in 100 mL of dichloromethane was added to a three -
neck, 250 mL round bottom flask, equipped with nitrogen inlet,
magnetic stir bar, thermometer, and addition funnel. The flask
was purged with a slow flow of nitrogen while the contents were
stirred at 30oc. Methacryloyl chloride was added dropwise (10/4
g, 0.1 eq) to the reaction flask over 1 h. After addition was
complete, the reaction was continued for 2 h while maintaining a
temperature of 25°C with an ice bath. A 4-4.5 pim glass frit
Buchner funnel was dried at 110°C for 3 h, cooled to room
temperature, and used for salt removal by filtration. The
solvents were rotary evaporated in vacuo.
Synthesis of Acrylated Lesquerella Oil from Hydroxyethyl
Methacrylate
A solution of 16.9 g (0.097 moles) TDI and 0.05 g
hydroquinone in 50 mL THF was added to a three-neck, 250 mL round
bottom flask equipped with magnetic stir bar, heating mantle,
thermometer, condenser, addition funnel, and nitrogen purge
through a vacuum adaptor. The stirred flask contents were heated
to reflux (70oC). 2-hydroxyethyl methacrylate (12 g, 0.092 eq)
dissolved in 100 mL THF was added into the addition funnel and
transferred into the flask dropwise over I h. The stirred flask
contents were maintained at 50oc for 0.5 h. A solution of 0.1 g
dibutyltin dilaurate in 10 mL THF was added in one portion to the
flask and maintained at 5QoC for an additional 0.5 h.
Lesquerella oil (50 g, 0.092 eq) was added to the addition funnel
and transferred dropwise into the reaction mixture over 2 h. The
contents were then maintained at 50oc for 1 h. Finally, 0.65 g
(0.005 eq) HEMA was introduced in one portion to the reaction
3-12
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mixture to end cap any remaining isocyanate. THF was removed
from the final product by rotary evaporation in vacuo.
Characterization Methods
A Bruker AC-200 {200 MHz, W13C dual probe) spectrometer and
a Nicolet IR/42 FTIR spectrophotometer were used for nuclear
magnetic resonance (NMR) and Fourier transform infrared (FTIR)
spectroscopic analysis, respectively. Nuclear magnetic resonance
samples were dissolved in deutero-chloroform spiked with
tetramethy1silane for reference. Fourier transform infrared
samples were analyzed as a film smear on polished NaCl.
Coating Formulations
The raw materials used in the filler and finish coatings are
contained in Table I.
A 100% solids wood sealer formulation containing pigment,
additives, photoinitiators, ALO, and acrylic monomers and
oligomers, was dispersed for 0.5 h to a Hegman 7 grind using a
3.5 in cowles high speed mixer at 150 0 rpm. The UV wood filler
formulations are included in Table II. The sealer was applied on
sanded, poplar with a draw bar at 2 mi Is wet thickness, and
subsequently cured via UV radiation for 7 sec at 11 cm from a 300
W medium pressure mercury UV lamp.
The 100% sol ids wood and metal finish coatings were
formulated with the materials of Table III and prepared in a
manner identical to the filler coatings. The finish coatings
were applied at 2 mils wet film thickness with a draw bar onto a
lightly sanded sealer coating (wood), chromate treated aluminum
(American Society of Testing and Materials Method (ASTM) D-1750,
Type B, Method 2), or cold rolled steel panels. The applied
finishes were irradiated under a 300 W medium pressure mercury UV
lamp for 7 sec at 11 cm distance.
Coating Characterizations
Pencil hardness and cross-hatch adhesion tests were
performed according to ASTM D-3362 and ASTM D-3359, respectively.
Impact resistance .was measured with a BYK-Gardner heavy duty
impact tester, Model IG-1120 with 1.8 kg (4 lb) mass and 1.59 cm
(0.5 in) diameter round peen. Yellowness indexes were measured
by the Applied Color System CS-5 Chroma-Sensor. Specular gloss
was taken with a Gardco Statistical Novogloss as specified by
ASTM D-523. Dry film thicknesses were determined by a Gardco
Minitest 4000 Microprocessor coating thickness gauge. Chemical
resistance was analyzed through a 2 h spot exposure test
according to ASTM D-1308. The tensile strength and percent
elongation we re determined by an MTS Model 810. Thermal analysis
was performed with a Mettler TA4 00 0 system equipped with a DSC 3 0
measuring cell under a nitrogen purge (25 cc/min) and at a
heating rate of IQoC/min.
3-13
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Table I. Raw Material Descriptions
Materials
Molecular
Weight
Acrylate
Functionality
Function
HEMALO
1996
1.6
Monomer
MACLO
1084
1. 8
Moncrr.er
Photomer
3016
452
2
Monomer
Photomer
4061
300
2
Monomer
Photomer
4094
428
3
Monomer
Photomer
4149
428
3
Monomer
Photomer
4770
Oligomer
Photomer
6008
Oligomer
Byk 065
Defoamer
Disperbyk
163
Dispersant
OmeyaCarb
F
Pigment
Byk 3 25
Mar-slip
Irgacure
651
Photoinitiator
Benzophenone
Photoinitiator
Silwet 7604
Surfactant
Table II. Ultraviolet Cured Wood Filler Formulation
Materials
Amount (g)
Photomer 4 061
26
Photomer 4094
20.5
Photomer 414 9
12
Photomer 4770
5
Photomer 6010
5
Disperbyk 163
1
OmeyaCarb F
30
Benzophenone
1.5
Irgacure 651
1
3-14
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Polymer Swelling Experiments
The extent of crosslinking was determined from swelling
experiments of free films. Films were obtained by draw downs
onto polyethylene, and subsequent curing with UV as described.
Free films were removed from polyethylene and fashioned to
approximately 2X0.1 mm dimensions, placed on a microscope
slide, covered with a flat glass cover slip, and viewed
microscopically at 18X magnification. The microscope was
equipped with an ocular scale for millimeter measurements. After
the film dimensions were measured, several drops of methylene
chloride were placed at the slide/cover interface. Swelling
occurred immediately and was complete in less than 1 min after
which 5 individual measurements of the swollen film were taken
and used for determination of the swelling ratio (see Table IV).
The swelling ratio was calculated as the ratio of the length of
the swollen film (Ls) to that of the initial and unswollen (L0)
film.
Table III. Ultraviolet Cured Lesquerella Oil Acrylate High Gloss
Wood Finish Formulation
Materials
1
Amount
(g>
2
Amount
(g)
3
Amount
(g)
HEMALO
--
15 .1
MACLO
15 . 0
Photomer
3016
16 . 1
16.4
16.0
Photomer
4061
20 . 0
20 .1
20.1
Photomer
4094
17. 0
17.2
17. 1
Photomer
4149
4.1
4 . 3
4.2
Photomer
4770
5 . 0
5 .1
5.0
Photomer
6008
10 . 0
10 . 2
10.2
Byk 065
0.4
0.4
0.4
Byk 325
0.5
0 . 5
0 . 5
Irgacure
651
2 .1
2.5
2.5
Benzophenone
1.1
1. 3
1.3
Silwet 7604
0.3
0.4
0.3
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RESULTS AND DISCUSSION
Synthesis
Lesquerella oil methacrylate was synthesized by the reaction
of MAC with LO (Scheme 1). Structural characterization was
performed via FTIR and 13C-NMR spectroscopy.
The FTIR spectrum of LO {Figure 1) offers characteristic
hydroxyl (-0H) absorption centered at 3454 cm'1 and carbon-carbon
double bond (-C=C-) absorption at 1598 cm"1. Ester formation
gives rise to a new absorption in the 1598 cm"1 region
accompanied by the disappearance of the 3454 cm'1 hydroxyl
absorption.
Table IV. Mechanical Properties and Solvent and Chemxcal
Resistance of Lesquerella Oil Aerylate Coatings
Formulation #
1
2
3
Tensile
Strength (psi)
292 8
2220
1894
Percent
Elongation (%)
5.5
6.1
5.4
Tg (oc)
45
51 .4
42 . 3
Linear Swelling
Ratio
1 . Ill
1.108
1.150
MW per X-link
115
106
138
MEK Double Rubs
(on steel
panel)
350
(2 mil)
310
(2 mil)
220
(2 mil)
2 h Spot Test
(ASTM D-1308)
20% H2S04
5
5
4
Soap Solution
5
5
5
D.I. Water
5
5
5
Vinegar
4
4
4
Additional structural confirmation was obtained from 13C-NMR
analysis (Figure 2). The C14 hydroxyl bearing carbon of LO
absorbs at 71.453 ppm, while the adjacent C13 and C15 carbons
absorb at 35.32 ppm and 36.81 ppm, respectively.4 Ester
formation shifts the absorption of the oxygen bearing carbon
3-16
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downfield to 74.0 ppm, while the C13 and C1S absorptions move
upfield to 31.50 and 33.33 ppm, respectively.5
Coatings prepared exclusively with MACLO were soft, and
adhered poorly to metal surfaces. In an effort to improve film
properties, aromaticicy was introduced via reacting TDI with HEMA
and LO to give HEMALO according to Scheme 1.
TDI was initially combined with HEMA in a 1:1 molar ratio to
produce the acrylic-isocyanate intermediate, which was
subsequently reacted with LO to give the desired product, HEMALO.
The synthesis of HEMALO was confirmed by FTIR (Figure 1} and 13C-
NMR (Figure 2) analyses. The FTIR spectrum of HSMALO experienced
a shift of the free hydroxyl absorption from 3454 cm"1 to 3341
cnT1 with derivative formation, and the 1600 cm"1 absorption
CH3—(Q^-NHCOOCHj CH 2 OOC(CH3 )C.=CIfe
p NHCOO
H E MALO-OC(CH2) 9 CH=CHCIi CH (CH2) 5 CH 3
i _
| CH 3—(p^NHCOOCHj CH 2OOC(CH3 )C=CB>
„ N=C=0
O I
LO OC(CH2) 9CH=CHOiCH(CH2) 5 CH3
I OH
i
CH2=C(CF§)C0C1
o *
MACLO OC(Cf I:) gC[ 1 =CIICHCH(CH,) 5CIT3 + HC1
ch2=c(ch,)co6
Scheme 1: Synthesis of MACLO and HEMALO from LO
broadened and intensified signaling the presence of the acrylate
double bond and benzene's aromaticity. The 13C-NMR spectrum of
HEMALO showed decreased absorptions at 71.45, 36.81 and 3 5.32
ppm, and the appearance of absorption frequencies at 76.00,
33.69, and 31.66 ppm, signaling acrylic ester formation.
The amount of acrylic functionality added to LO was
calculated from ^-H-NMR spectral integration (Figure 3) . The
fraction of the acrylic moiety compared to fatty acid was
determined via the ratio of the absorption area corresponding to
3-17
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HEMLO
MACLO
3500
~T—
3000
! | , ¦
2 SOO 2000
Wav enu mt»r (em-1)
—1_
500
4000
1K»
1000
Figure 1: FTIR Spectra of LO, HEMALO, and MACLO
3-18
-------
LO
4-9,1?
HACLO
4-9,17
HEMALO
Gty
¦NH-
m
m
mh
i i i r~ * ( r
70 60 50 40 30 20
Parts Per Million
Figure 2: Carbon-13 NMR Spectra of LO, MACLO, and HEMALO
3-19
-------
LO
Gly
11,12
-CH2-
iGly
•Hi,
20
ui?m a? n
¦Gly
m
mb
20
Hb.11,12
T
i
7 6 5 4 3 2 1
Parts Per Million
FjLtjoirs 3 s Proton NMR Spsctirci of LO/ MACLOf 3ncJ HEMALO
3-20
-------
the trans alkene proton (AHa) to the area corresponding to the
C20 methyl protons (A20) according to Equation 1:
(AHa
[1]
A20
The calculated values of acrylation are enumerated in Table
V. Based on XH-NMR spectrum of LO, the mole fraction of hydroxy
fatty acids of LO is 0.55,6 and if one makes the assumption that
no side reactions occur, the theoretical acrylic/fatty acid ratio
is equal to the hydroxy fatty acid fraction, 0.55, In practice,
MACLO derivation was determined to be 0.54, or a 98% theoretical
conversion. For HEMALO, additional HEMA was addeo to end~cap
unreacted TDI after reaction of the HEMA/TDI intermediate with
LO. Therefore, the acrylate/fatty acid ratio was larger than
theoretical although there remained some unreacted hydroxyls in
HEMALO.
Table V. Fraction of Acrylate Group Relative to Fatty Acid
Derivative
Theoretical
:H-NMR Calculated
Acrylate/Fatty Acid Ratio
Acrylate/Fatty Acid Ratio
MACLO
0 . 55
0.54
HEMALO
0.55
0.61
Swelling Experiments
Swelling of the UV cured films was performed with methylene
chloride. The Flory-Rehner equation (Equation 2) was employed to
calculate the molecular weight between cross-links and the cross-
link density of the films:8,9
- [ In (1 -u2) + v2 + Xi (u2 >2=^in [ (u2)1/3 ~ u2/2 ] (Equation 2 )
where v- is the volume fraction of polymer in the swollen mass,
Xi is the Flory-Huggins polymer-solvent dimensionless interaction
term, Vj, is the molar volume of the swelling solvent, and n is
the number of active chain segments per unit volume. The number
of active chain segments per unit volume (n) equals p/Mc, where p
is the polymer density and Mc is the molecular weight between
crosslinks. The published interaction parameter in chlorinated
solvents indicates a value in the range of 0.4-0.5,10 while our
efforts determined an interaction parameter of 0.5. The molar
volume of methylene chloride is 64.2 mL/mol. The swelling ratio
and the calculated Mc experimental values are given in Table IV.
3-21
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Swelling data provides overall crosslink density and polymer
segment molecular weight between crosslinks. Coating #3 was the
least crosslinked (138 g/crosslink) followed by coatings #1 (115
g/crosslink) and #2 (106 g/crosslink). This is not unexpected as
Coating #3 contained the modified oil and thus two crosslinks per
LO molecule are possible (approx. MW = 982 g/mol), or a
theoretical 540 g/crosslink based solely on MACLQ. Since excess
hydroxyethylmethacrylate was added, TDI-diethoxymethacrylate was
likely formed to some extent and thus reduced the weight per
crosslink.
Coating Physical Properties
Coating properties are shown in Tables IV and VI. All
coatings showed excellent gloss (-80 @ 20o), adhesion (5B), and
pencil hardness on wood panels. When a wood filler was used as a
first down coating, pencil hardness and adhesion was improved.
The gouge pencil hardnesses for coatings #1 and #2 (9H)
outperformed coating #3 (6H). Moreover, coating #3 (MACLO) gave
the lowest tensile strength and glass transition temperature
(T„), which we have attributed to insufficient cure7. This was
% a
confirmed via swelling ratios (see Table IV) which demonstrated
that coating #3 had the highest and coating #2 the lowest
swelling ratio, respectively.
Coatings formulated with ALO were superior to the control
with respect to direct and reverse impact resistance on cold
rolled steel. Cross-hatch adhesion confirmed poorer adhesion to
steel for the control (IB, or 20%) than either coating #2 (4B,
80%) or #3 (5B, 100%). Moreover, coating #2 possessed better
cross-hatch adhesion to aluminum (3B, 60%) than either coating #1
or #3 (0B, 0%).
The UV cured coatings demonstrated excellent chemical
resistance (Table VI), where MEK resistance followed the order of
Coating #1 > coatings #2 > coating #3. A 20% H2S04 solution
treatment did not change the appearance of coatings #1 and #2,
but stained coating #3, a likely result of lower crosslinking
density.
CONCLUSIONS
Acrylated lesquerella oil derivatives were synthesized for
the first time, and formulated into UV cured coatings.
Structural characterization was performed by FTIR, 1H-NMR and 13C-
NMR analyses. The use of .MACLO in UV curing coating formulations
provided for improvements in flexibility11 and adhesion to metal.
Coatings formulated with HEMALO showed significantly improved
adhesion to both steel and aluminum substrates. Lesquerella oil
modification increases flexibility at the expense of Tg and
solvent resistance.
3-22
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Table VI. Physical Properties of Lesquerella Oil Acrylate Coatings
Formulation #
1
2
3
Wood
A1
Steel
Wood
A1
Steel
Wood
A1
Steel
Specular Gloss 20°
(ASTM D-523) 85o
85
99
95
100
93
98
81
98
100
100
72
96
76
97
84
96
79
98
Yellowness Index
1. 3
2 . 3
3.0
Gouge Hardness by
Pencil (ASTM D-
3363)
9H
F
8H
9H
4H
7H
6H
5H
7H
Direct Impact
(ASTM D-2794),(lb-
in)
(J)
40
(4.5)
80
(9.1)
70
(7.9)
Reverse Impact
(ASTM D-2794),(lb-
in)
(J)
(05m
20
(2.3)
20
(2.3)
Cross-Hatch
Adhesion
(ASTM D-3359)
SB
OB
IB
5B
3B
4B
5B
0B
5B
-------
ACKNOWLEDGMENT
This material is based upon work supported by the
Cooperative State Research Service, U.S. Department of
Agriculture, under Grant/Cooperative No. 93-COOP-1-952 9. The
authors wish to express appreciation to Drs. Daniel Kugler and
Harry Parker and Mrs. Carmela Bailey for their support.
3-24
-------
REFERENCES
1. Pappas, S.P. (ed.), In: UV Curing: Science & Technology.
Vol. 2. Technology Marketing Corp., Norwalk, Connecticut,
1980, p. 3.
2. Turner, G.P.A. In: Introduction of Paint Chemistry and
Principles of Films. Chapman and Hall, New York, 1991. p.
225.
3. Smith, C.R., Jr., Wilson, T.K., Miwa, K., Zobel, R . L . ,
Lomar, and Wolff, I.A. Lesquerolic acid. A new hydroxy
acid from lesquerella seed oil. J. Org. Chem, 26: 2903,
1961.
4. Carlson, R.D., Chaudhry, A., Peterson, R.E., and Bagby, M.O.
Preparative chromatographic isolation of hydroxy acids from
lesquerella fendleri and lesquerella gordonil seed oils.
JAOCS. 67: 495, 1990.
5. Levy, G.C. In: Carbon-13 Nuclear Magnetic Resonance
Spectroscopy. 2nd ed. John Wiley and Sens, New York, 1980.
p. 62.
6. Thames, S.F., Yu, H., Wang, M.D., and Schuman, T.P.
Dehydration of lesquerella oil. Accepted JAOCS. 1994,
7. Crompton, T.R. In: Practical Polymer Analysis. Plenum
Press, New York, 1993. p. 585.
8. Sperling, L.H. In: Introduction to Physical Polymer
Science. Wiley-Interscience, New York, 1986. p. 34 3.
9. Tramontano, V.J. Crosslinking of waterborne polyurethane
dispersions. Jin: Proceedings of the Twenty-first
Waterborne, High-Solids, & Powder Coatings Symposium, Part
1. Southern Society for Coatings Technology and University
of Southern Mississippi, New Orleans, Louisiana, 1994. p.
83 .
10. Wolf, B.A, Polymer-solvent interaction parameters. In: J.
Brandrup and E.H, Immergut (eds.), Polymer Handbook, 2nd
ed., John Wiley and Sons, New York, 1975. p. IV 191.
11. Turner, G.P.A. In: Introduction of Paint Chemistry and
Principles of Films. Chapman and Hall, New York, 1991. p.
8 8 .
3-25
-------
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
VOLATILE CONTENTS OF UV CATIONICALLY CURABLE EPOXY COATINGS
J, Wells Carter
Jagdeesh Bandekar
Mark J. Jupina
Linda A. Kosensky
J. W. Perry
Union Carbide Corporation
P.O. Box 670
Bound Brook, NJ 08805
INTRODUCTION
Ultraviolet cationically curable epoxide coatings are used for protecting metal and inks in
rigid packaging applications and as overprint varnishes for plastic tubes. Excellent adhesion to
metal and plastic and toughness during post-forming are benefits of cationic epoxide chemistry
and requirements of these applications. The cycloaliphatic epoxy resins used in these coatings
are low viscosity and low odor. Coatings can be formulated with low application viscosities
without adding solvent; therefore, the coatings have very low volatile organic contents. This
paper reports findings from measurements of the volatile contents of starting-point formulations
using ASTM D 5403-93 and identification of volatiles by analytical techniques.
EXPERIMENTAL DETAILS
Coating volatile contents were measured in triplicate following ASTM D 5403-93 Test
Method A, including Note 3 for UV cationic epoxide coatings. Coating weights ranged 0.2- to
0.4-g and the substrate was 4- X 12-in. aluminum panels for volatile content measurements.
Coatings samples for the FT-IR/TGA, GC/MS and water titration experiments were obtained by
curing the coatings on glass plates and scraping coating samples off the glass. The coated
aluminum panels and coated glass plates were cured using 250 mJ/em2 UV dose supplied by a
LINDE* UV cure unit operated with a 400 W/in. mercury-vapor arc lamp and the conveyor at 90
fpm.
FT-IR/TGA is a hyphenated technique that simultaneously records the thennogravimetrie
(TG) weight loss and the FT-ER spectra of effluent gases without operator intervention.1 The
FT-IR/TGA instrument was from Bio-Rad, Cambridge, MA and consisted of a Bio-Rad FTS60
FT-IR spectrometer and an Omnitherm TG analyzer. The Bio-Rad minicomputer, in addition to
performing its normal FT-IR functions, controlled the operation of the TGA. This enabled the
TG and FT-IR data to be coordinated in time in one computer, and for the spectral data to be
correlated with the observed weight losses. A temperature program was set up which raised the
temperature from 20 to 110 °C at 10 °C/min, held it there for 35 min before continuing at 20
°C/min to 800 °C for 7 min. The ramp to 800 °C was to prepare the equipment for the next
sample.
The samples were analyzed using Headspace Gas Chromatography. The instruments were an
AutoSystem gas ehromatograph interfaced with HS-40 Headspace Sampler, both from Perkin
Elmer. The samples were heated in 22-mL headspace vials in the sampler at 110 °C for 1-h. A
DB-1 (30- X 0.53-mm i.d., 5-|im film) megabore column was used with a split of 5/1 and a
column flow of 8 mL/min helium. The oven program was 60 °C for 4 min, ramp at 10 °C/min to
260 °C. The injection port temperature was 200 °C and the flame ionization detector
temperature was 260 °C. The HS-40 needle and transfer temperatures were 130 °C, and the
pressurization time and injection time was 0.2 min. Gas chromatography/mass spectrometry
3-26
-------
(GC/MS) was conducted using an HP-5890 gas chromatograph interfaced with an HP-5970 mass
Selective Detector, both from Hewlett Packard.
A Mitsubishi Moisture Meter Model CA-05 and Water Vaporizer Model VA-05 were used to
analyze coating volatiles for moisture. Approximately 0.3-g samples were introduced into the
boat and purified and dried nitrogen was passed over the samples with a flow rate of 200 mL/min
for 1-h. The VA-05 was maintained at 110 °C during this time. The water was determined by
coulometric titration. The reagents were Mitsubishi Aquamicron AU and Aquamicron CK.
Replicates were tested. All the water was evolved from the coating samples within the first 30
min.
Two DEFENSOR 3100 humidifiers were used to maintain constant high relative humidity
(RH) when UV curing coatings for volatile content and surface-cure rate measurements requiring
constant high humidity. Sealed chambers containing desiccant or a saturated ZnSCU solution
were used to store coated panels during the 48-h equilibration for volatile content measurements
conducted with the equilibration close to 0% and at 90% RH, respectively.
Surface-cure rates were measured by lightly touching coating surfaces with a cotton ball
immediately after UV curing. The conveyor speeds, measured in feet per minute (fprrj), at which
no cotton fibers adhered to coating surfaces were recorded as the surface-cure rates. Coatings
were applied to aluminum foil-coated paper and cured using a 400 W/in. mercury-vapor arc lamp
for surface-cure rate measurements.
The cycloaliphatic epoxide resins 3,4-epoxy cyclohexylmethyl-3,4-epoxy cyclohexyl
carboxylate (EEC) and bis(3,4-epoxy cyclohexylmethyl) adipate (BEA), polyester diol (hydroxyl
no. 212) and triol (hydroxyl no. 560), epoxidized linseed oil (LOE), and mixed triaryl sulfonium
hexafluorophosphate salts 50 wt% solution in propylene carbonate (PI solution), were obtained
from Union Carbide Corporation. Dipropylene glycol diglycidyl ether (DPGDGE) was obtained
from The Dow Chemical Company. Castor oil was obtained from CasChem, Inc. Indicating
DRIERITE® (anhydrous calcium carbonate) was obtained from W. A. Hammond Drierite
Company and ZnSO4*7H20 from MallinckrodL All materials were used as received.
RESULTS AND DISCUSSION
ASTM 5403-93 Method B Note 3 specifies that cationic epoxide coatings which gain weight
while heating 1-h at 110 °C should equilibrate for 48-h at room temperature after UV curing and
before heating. The coatings presented in Tables I-IV gained weight as a result of UV curing and
two gained weight as a result of heating (coatings G and H in Table II).
The weight gain has been attributed to atmospheric moisture reacting with cationic coatings.2
The superacid (HPFg), which is generated from photolysis of the cationic photoinitiator
(Ar3S+PF6" —> HPFg), is hygroscopic and its appearance greatly increases coating
hygroscopicity.
The FT-IR/TGA method was used to identify the major volatiles from coatings A and C, the
ingredients of which are provided in Table I. Within the first 15 min of each FT-IR/TGA
experiment, an evolved gas was detected whose weight fraction varied between 1 and 3% of the
total weight. Volatile loss was complete within 35 min of heating at 110 °C during the TGA
experiments. Figure 3 shows a representative profile of the evolved gas. The FT-IR spectra of
sample A and C were similar; Figure 4 shows a typical spectrum. The main bands are observed
at 1858 cm"*, due to carbonyl stretch, and near 1107 cm" 1, due to ester type C-0 stretching
band. The FT-IR spectrum corresponds to propylene carbonate (PC) gas, the PI solvent.
3-27
-------
GC/MS identified PC as the major volatile and identified traces of phenyl sulfide, the PI
photolysis product Phenyl sulfide was not detected in the FT-IR spectra probably because its
concentration was too low to be detected. FT-IR/TGA and GC/MS experiments conducted on
coatings A and C found no evidence of epoxy resin or polyol in the volatiles. The titration
method confirmed the presence of water in the volatiles.
In some cases in the results in Tables I and II the amount of potential volatiles was
significantly less (E-H), approximately the same (A, C and D) and significantly more (B) than
the amount of PI solution in the formulations. High coating 7gs and high boiling points of
volatiles would be expected to slow diffusion of volatiles from coatings while heating. Not all of
the PC and phenyl sulfide may evaporate while heating because their boiling points are high (240
and 296 °C, respectively). Water absorbed during UV curing and equilibration which reversibly
hydrated the coating would most likely be evaporated completely while heating because the
boiling point of water (100 °C) is less than the bake temperature (110 °C) and water absorbed
during UV curing and equilibration would reside mostly at the coating surface. Coating 7g
dramatically increases during UV curing and high Tg would limit diffusion of absorbed water
into the lower coating layers. Water at the surface could be volatilized without complications
from diffusion effects. The relative amounts of PC and water in the volatile mix of a cationic
epoxide coating may depend on factors such as the amount of PI solution the coating contains,
coating Tg, hygroscopicity of coating ingredients and the RH during UV curing. The volatiles in
excess of the weight of PI solution in coating B were most likely water. Coating TgS probably
limited the amount of volatiles by limiting diffusion in cases (E-II) where volatile contents were
less than the weight of PI solution.
The process weight gains and potential volatiles of coatings A-E (Table I) were significantly
larger than those of coatings F-H (Table II). The differences between results in Tables I and II
were perhaps due to differences in the amount of PI solution the coatings contained, differences
in the hygroscopicity of ingredients, differences in RH at the time of the measurements or some
combination of these explanations. The RH was not measured when the results in Tables I and II
were obtained.
Comparing the results among Tables I and II suggests volatile contents depend on the amount
of polyol a coating contains. The amount of water absorbed during UV curing was inversely
proportional to polyol concentration in Tables I and II. Coatings A and E contained polyester
diol and castor oil, respectively, and coatings B-D contained no polyol. Coatings A and E gained
about half the weight coatings B-D gained during UV curing. The same trend was demonstrated
by the process weight gains of coatings F-H but the weight gain differences among these
coatings were arguably within experimental error. The potential volatiles of coatings F-H were
proportional to polyol concentration. The potential volatile differences among coatings F-H
were significant PC evaporated (the coatings contained 6% PI solution) and water was absorbed
as a result of heating and the amount of water absorbed increased with decreasing polyol
concentration.
The volatiles of coatings I, which contained 19.2% polyol, and J, which contained no polyol,
were measured using controlled humidity conditions to better understand the effects of RH and
the presence of polyol on volatile content results. Coatings I and J had similar process weight
gains and potential volatiles using low humidity UV cure and equilibration conditions (Table
III), despite the amount of polyol the coatings contained.
Coatings I and J had significantly more process weight gain and significantly more potential
volatiles when high humidity UV cure and equilibration were used compared to when low
humidity conditions were used. The amount of water absorbed during UV cure and equilibration
strongly depended on RH. The amount of potential organic volatiles was probably not affected
3-28
-------
by the humidity during UV cure and equilibration; therefore, the extra potential volatiles
measured under high humidity conditions compared to low humidity conditions was water vapor.
Coating J, which contained no polyol, gained significantly more weight than I during UV curing
and J lost less weight than I during heating using high humidity conditions.
Two mechanisms, which could occur simultaneously, best explain these finding. One
mechanism is that polyol hydroxyls and water compete for epoxides in the presence of superacid
catalyst. According to this mechanism, the rate of the reaction of epoxides with water was higher
in J than in I because polyol hydroxyls were not available in J to compete with water for
epoxide. The epoxides acted like a (irreversible) sponge for hydroxyls from water or polyol or
both (Figure 1). The other mechanism is that polyol hydroxyls associate with cations, such as
superacid (HPFg) and polymerizing cationic centers, and reduce cation hygroscopicity. Cations
act like a (reversible) sponge for hydroxyls and the presence of polyol hydroxyls decreases the
rate of hydration of cations (Figure 2).
H H PF6" H
R—(/ fV PfV R-d+ O-H
vvV\ X '
<_>
PF6- h
R—0+ 0-H R—0 O-H
+ HPF6
Figure 1. Ring-opening Polymerization Initiated By Hydroxyl, Where
R. = H«, R'CH2« (From Polyol), or R"~0
nROH + C+ . * (ROH)„C+
Figure 2. Reaction Of Hydroxyls With Cationic Centers (C+),
Where R» = H» Or Alkyl Radical
Surface-cure rate studies were conducted to better understand the effects of RH and polyol
concentration. The formulations in Table IV were used for the surface-cure rate study. A plot of
surface-cure rate vs. RH is presented in Figure 5. The surface-cure rates passed through maxima
and the positions of the maxima moved to higher RH with decreasing polyol concentration.
Atmospheric moisture enhanced surface-cure rates at low RH as demonstrated by the increased
cure rates with increasing RH up to the maxima for each polyol concentration. This suggests
water absorbed by the coatings acted as initiator for epoxide polymerization. Higher surface-
cure rates of coatings containing higher polyol concentrations at low RH suggest that polyol
3-29
-------
hydroxyl also acted as initiator for epoxide polymerization. Previous reports described polyols
as chain transfer agents for epoxide polymerization. 3 Hydroxyls from water and polyols could
play both roles, initiators and chain transfer agents, As initiators, water and polyol would
increase cure rates. As chain transfer agent, polyol could increase the rate of gellation or become
part of a dangling end. Water could enhance cure rate as an initiator but would produce dangling
ends in the role of chain transfer agent.
At RH values above the maxima in Figure 5 the surface-cure rates decreased probably
because the rate of ring-opening competed effectively with epoxide polymerization. Ring-
opening can lead to dangling ends especially if water participates in the ring-opening reaction
(Figure 1). Cationic epoxide coatings with useful physical properties are generally formulated
with at least a two-fold excess of epoxides relative to polyol equivalents. Excess epoxide is
required to develop high enough crosslink density and Tg via epoxide polymerization to proved
useful physical properties.
The viscosities reported in Tables I and III demonstrate that UY cationic coatings containing
cycloaliphatic epoxides can be formulated to low viscosities required by some application
techniques. The coatings formulations presented also had low odor which is of benefit for plant
environments.
CONCLUSIONS
Cationic epoxide coatings were formulated with low viscosities and were found to have very-
low volatile contents. The major organic volatile was identified as propylene carbonate, the
photoinitiator solvent, by FT-IR/TGA and GC/MS and traces of phenyl sulfide, the photoinitiator
photolysis product, were identified by GC/MS. Water was identified in the volatiles by titration.
The measurement of volatile contents of cationic epoxide coatings was complicated by the
effect of relative humidity. Cationic epoxide coatings absorb atmospheric moisture during UV
curing. Coatings containing less polyol were found to absorb more moisture. Cationic epoxide
coating absorbed more moisture when the volatile content measurements were conducted at
higher relative humidity. Two reactions, reaction with epoxides and hydration of cations, which
could occur simultaneously, were proposed to explain the reactions of atmospheric moisture with
cationic epoxide coatings.
The reaction of water and epoxide was supported by cases where coatings containing no (or
less) polyol absorbed more water as a result of UV curing and had less potential volatiles than
coatings containing (more) polyol, and by surface-cure rate studies. Increasing RH increased
surface-cure rates up to the maxima.
The reversible hydration of cations was supported by the identification of water by titration
as part of the potential volatiles, by findings that the amount of volatiles depended on humidity,
and by cases where the potential volatiles were greater than the amount of PI solution in the
coating.
References
(1) Compton, D. A. C.; Markelov, M.; Mittleman, M. L.; Grasselli, J. G.; Appl. Spectrosc. 1985,
39,909.
(2) Strand, R. C.; Ludwigsen, R. J. SME Technical Paper FC75-328 1975, Society of
Manufacturing Engineers.
(3) Crivello, J. V.; Conlon, D. R.; Webb, K. K. /, Radiation Curing 1986,13(4), 3.
3-30
-------
Table L Volatile Contents Of UV Epoxide Coatings With And Without Polyol
Ingredients
A
B
C
D
E
EEC
62.4
67.2
67.2
67.2
67.2
Polyester Diol
19.2
DPGDGE
14,4
28.8
BEA
28.8
LOE
28.8
Castor Oil
28.8
PI solution
3.8
3.8
3.8
3.8
3.8
Surfactant
0.2
0,2
0.2
0.2
0.2
Viscosity 25 °C (cP)
275
200
580
590
455
VOC fave wt%1
Process
-3.070
-5.655
-7.476
-6.051
-3.268
Potential
3.860
5.378
3.961
3.344
2.856
Total
0.7898
-0.2768
-3.514
-2.706
-0.4117
Standard Deviation
Process
0.2612
0.2232
0.2475
0.1585
0.1207
Potential
0.07911
0.2927
0.1286
0.04040
0.1387
Total
0.3120
0.4660
0.3438
0.1229
0.1422
3-31
-------
Table IL Volatile Contents Of UV Epoxide Coatings Demonstrating Weight Gain As A Result
Of UV Curing And Heating
Ingredients
F
G
H
EEC
68.9
79.3
83.6
Polyester Triol
24.6
14.2
9.9
PI solution
6.0
6.0
6,0
Surfactant
0.5
0.5
0.5
VOC fave wt%)
Process
-0.3422
-0.3691
-0.4797
Potential
2.397
-0.9135
-1.259
Total
2.054
-1.283
-1.738
Standard Deviation
Process
0.07712
0.07526
0.08405
Potential
0.02261
0.1487
0.1471
Total
0.08992
0.1364
0.1871
3-32
-------
Table HI. Volatile Contents Of UV Epoxide Coatings Measured Using Controlled Relative
Humidity
Ingredients I J
19.2 0
14.4 14.4
3.8 3.8
0.2 0.2
EEC
Polyester Diol
DPGDGE
PI solution
Silicone Surfactant
Viscosity 25 °C (cP) 275 305
UV Cure Conditions 28% RH
48-h Equilibration Conditions Desiccated
VOC Cave wt%)
Process -1.719 -1.992
Potential 3.084 4.286
Total 1.365 2.294
Standard Deviation
Process 0.5238 0.3860
Potential 0.9376 0.5642
Total L186 0.9128
UV Cure Conditions 60% RH
48-h Equilibration Conditions 90% RH
VOC (ave wt%)
Process -5.797 -9.432
Potential 6.150 5.732
Total 0.3536 -3.700
Standard Deviation
Process 0.5242 0.1836
Potential 0.4710 0.5563
Total 0.1257 0.4488
3-33
-------
Table IV. UV Epoxide Coatings Used For Surface-Cure Rate Measurements
Ingredients
K
L
M
N
EEC
100
95
90
80
Polyester triol
0
5
10
20
PI Solution
4
4
4
4
Surfactant
0.5
0.5
0.5
0.5
1200
1000
E
JX
OC
-------
0.012-
0.010-
r 0 .008
0.002-
S00
150
200
50
250
300
350
°C
Figure 3. Evolved Gas Profile From FT-IR/TGA Experiment
3-35
-------
0.006
0.005-
b 0.004-
r 0.003-
n 0.002-
0.00!
0.000-
3000
2500
4000
3500
2000
1500
1000
Wavenurobers
Figure 4. IR Spectrum From FT-IR/TGA Experiment
3-36
-------
SESSION 4
LIFE CYCLE ANALYSIS
4-1
-------
PAPERS PRESENTED:
"The Use of Life Cycle Assessment in an Ecolabeling Scheme:
The European Ecolabel on Paints and Varnishes"
by
James Besnainou
Ecobalance, Inc.
Rockville, Maryland
"Optimizing Coating Formulations for Total Environmental and Product Performance"
by
Jimmy Bassett
Eastman Chemical Company
Kingsport, Tennessee
and
Don Sullivan
Shell Chemical Company
Houston, Texas
"Life Cycle Analysis of an Aqueous Low VOC Coating"
by
Jack Kowal
Coors Brewing Company
Golden, Colorado
4-2
-------
The work described in this paper was not funded by the U.S. Environmental
Protection Agency, The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
The Use of Life Cycle Assessment in an Ecolabeling Scheme:
The European Ecolabel on Paints and Varnishes
Jacques Besnainou and Re mi Coulon
Ecobalance, Inc. 1 Church Street, suite 700, Rockville, MD 20850
Abstract
This article demonstrates how Life Cycle Assessment (LCA) has been used in order to guide and frame the
decision-making processes regarding the selection of "environmentally preferable products" in an ecolabeling
scheme. The case study presented is based on the work made by the Ecobilan Group for the European
Commission on the European Ecolabel of paints and varnishes.
The risks to fail in determining criteria for selecting such environmentally preferable products is obvious, as other
ecolabeling projects have shown. The conflicting interests of the various stakeholders (countries, consumer and
environmental associations, and private companies) are numerous enough to lead to the conclusion that setting
such criteria is impossible. However, a consensus was built among the working group members.
This shows that a reasonable use of LCA, i.e., accounting both for the power and limitations of the tool, can be
crucial in order to:
• rationalize environmental issues, and sometimes challenge generally accepted conventions
* bring confidence to the involved parties (industry, government and associations) in an analytic and transparent
methodology, certified by an independent third-party
1. INTRODUCTION"
1.1. methodology
The methodology to determine ecolabeling criteria can be divided into five steps:
products and market survey: this step aims at proposing a classification of products, with particular reference
to product use, and taking account of the various aspects likely to introduce a variability into the results of the
Life Cycle Inventories (LCI). In particular, it is necessary to define a functional unit to carry out the
inventories.
selection of a certain number of specific products deemed representative of the market and of environmental
issues, for carrying out LCI.
life cycle inventories of the representative selected products: a materials and energy balance is calculated for
the complete life cycle of each selected product from data collected on actual sites.
interpretation of the LCI results in terms of main environmental problems, using the currently available
scientific knowledge.
This step is submitted for consideration to the various interested parties (industrialists, ecologists, consumers,
public authorities, scientists) who may debate interpretation methods and consider the specific aspects of the
ecological problems related to these products.
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definition of ecolabeling criteria and thresholds, based on the results of the life cycle inventories and their
interpretation. These criteria are discussed by various interested parties to obtain a multi-criteria label. At this
stage, technical and economic aspects are also taken into account.
This procedure is iterative, as the different parties concerned may request an extension to other products or a
complementary study on new technologies.
1.2. Ecolabeling Criteria
According to the European council regulation (EEC n° 880/92), articles 4 and 5, three kinds of criteria are
distinguished for the ecolabel:
ecological criteria, which are determined according to a global approach (from the cradle to the grave)
criteria which refer to general principles (toxicity, ...)
- fitness for use criteria, to ensure that the product should have at least a minimum level of quality
2. Definition of the Product Group
According to the European council regulation (EEC n° 880/92, article 3), this definition is based on the function,
i.e., the group to be labelled has to contain products fulfilling the same function.
The definition of the product group was agreed as: "decorative indoor paints and varnishes for professional
and do-it-yourself users".
included in the Field of application:
paint cans bearing the label "for indoors and outdoors use", because they are at least applicable indoors,
undercoats for wood and masonry, because they are applicable indoors,
liquid or paste formulas which have been pre-conditioned or prepared to meet the consumer's needs,
white-base products intended to be tinted with "tinting" machines at the consumer's request.
Excluded from the field of application of the ecolabel:
outdoor paints and varnishes for professional and do-it-yourself users,
paints and varnishes for industrial use,
primary coats for metal, because they are anti-corrosion products.
The chosen functional unit was to cover 20 m2 with an opacity of 98%'.
l Nota: durability has not been included in the functional unit because:
- no standardised test method is representative of the ageing of indoors paints. This type of ageing is very different from
wheathering outdoors and especially it involves neither photodegradation, which is the most severe agression to paint binders,
nor rapid temperature changes.
- Indoors paints generally do not suffer chemical or physical degradation during their normal life span of two to ten years. They
are often changed for a question of fashion or taste. The life time is therfore often shorter than the durability
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3. The Environmental Issues Identified in the Life Cycle of the Indoor
Decorative Paints
3.1. Modest Aim
After the life cycle inventories have been calculated by Ecobilan (with site-specific data provided by European and
American companies) for the eleven representative paints, a lot of detailed figures were available to the ad hoc
working group members. These data encompassed about 150 flows (inventory results) and the contribution of each
stages in the life cycle. The chosen functional unit for the calculation of the inventories was the quantity of paint
needed to cover 20 m2 with an opacity of 98%2.
These inventories have been interpreted in order to identify the main environmental problems raised by the life
cycle of the products.
Because the label is a multi-criteria label, it is not necessary to establish a hierarchy of all the flows. However,
no scientific and objective way exists to prioritize flows corresponding to different environments (C02, CO, NOx>
..., for air, suspended matter, COD, nitrates, for water, ...).
As a consequence, the aim of the interpretation phase is modest: only to distinguish between main problems and
other problems.
The criteria were then determined with relation to each main environmental problem.
3.2. Process to Identify the Main Environmental Problems
The process consists of;
the regrouping of flows which are linked together,
a simple hierarchization of environmental problems:
main problems,
other problems.
The regrouping consists of:
identifying data which are linked together by their common origin.
For instance, in some cases, C02 and CO emissions come mainly from the electricity production.
identifying redundant data.
In the former example, among the C02 emissions, the CO emissions and the electricity consumption, two
information are redundant because they all vary in the same proportions.
retaining data which bring new information.
In the same example, one can keep the C02 emissions (because it contributes to environmental impacts such
as global warming).
2 Nota: durability has not been included in the functional unit because:
- no standardized test method is representative of the aging of indoor paints. This type of aging is very different from
weathering outdoors and especially since it involves neither photodegradation, which is the most severe agression to paint
binders, nor rapid temperature changes.
- Indoor paints generally do not suffer chemical or physical degradation during their normal life span of two to ten years. They
are often changed for a question of fashion or taste. The life time is therfore often shorter than the durability.
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At the same time, the process allows one to:
identify the main contributors (substances, stages) to a given impact, when a relevant index is available. The
use of indices allows one to translate the substances into environmental impacts (non-renewable resources
depletion, global warming, atmospheric acidification, eutrophication, etc.), kid to appreciate the contribution
of each substance to various environmental impacts.
750000
500000
250000 J
^ N20
CO Outputs
In this example, the stage n°7 constitutes the main contribution to the global warming (in C02 equivalent) with
the CO] emissions.
identify the main contributors (stages) to the emission of a given substance or to the consumption of a given
raw material, in the absence of a relevant index3.
Total = 1,373
g
1 2 3 4 5
Stages
6 7 8 9
-200000 9 |
mg -400000 -
-600000 -
-800000 -
r
In this example, the stage n°7 constitutes the main contribution to the particulate matter emissions.
3 Even when index exists and since the available indices rely on the scientific knowledge which is still under discussion, the
interpretation is not limited to the use of these indices.
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3.3.
The Main Environmental Problems and Their Origin in the Life Cycle of the Paints
In the case of the eleven paints which have been studied, regrouping of data yields the results presenting in the
following table and showing the main environmental problems and the stages of the life cycle which constitute the
main origin.
Environmental
problems
Origin in the life cycle of the paints
Non renewable resources
depletion
Mainly coming from: production of the Ti02, the
alkvd resins and the solvents
Mainly due to: petroleum consumption
Global warming
Mainly coming from: production of energy for
Ti02 process, the coke for lithoponc process
Mainly due to: €02 emissions
Atmospheric acidification
Mainly coming from: Ti02 process
Mainly due to: SOx emissions
Tropospheric ozone
creation
Mainly coming from: application of the paint
Mainly due to: VOC emissions
Other air emissions
Mainly coming from: production of energy for
Ti02 process
Water consumption
Mainly coming from: Ti02 process
Eutrophication
Mainly coming from: production of the resins
and their constituents
Mainly due to: COD
Other discharges into water
Mainly coming from: Ti02 process, washing of
the application tools (brushes,...)
Solid waste
Mainly coming from: application of the paint
Mainly due to: can and paint residues
4. The Selectivity of The Ecolabel (Targets)
The thresholds of the criteria must be defined in order to obtain an adequate selection in terms of:
visibility of the label by consumers,
and encouragement for industrialists to improve their products.
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The targets chosen by the ad hoc working group members was that 10 to 15 % (in weight) of paints and
varnishes belonging to the product group meet the thresholds on the European market sewn after the date of
publication of the criteria.
Since the label is a multicriteria label, its selectivity results from the interlacing of its various criteria, and
not solely on one of those (e.g. VOC criterion).
As a consequence, the selectivity of each criterion should be calculated and then the global selectivity of the label,
Within a few months after the criteria and thresholds are published, the competent bodies will be able to observe
the actual selectivity of the thresholds. When selectivity peaks to about 25 %, the European Commission could
then revise the label to make the criteria more severe in order to come back to about 10 to 15% labelled products
(see figure below).
European market
Market share of
labelled products
Time
Revision
Revision
Revision
5. The Ecolabeling Criteria
5.1. The ecological criteria
The ecological criteria are related to the main environmental problems identified in the LCA of the products.
In order to allow private companies to easily check the compliance of their products with the criteria, the
determination of the criteria from the environmental problems was based on the technical and economical
feasibility discussed within the ad hoc working group members.
The ecological criteria presented below are thus not directly expressed in terms of environmental problems to be
reduced but they pave the way to achieving this aim by referring to the key parameters which are at the origin of
these main impacts. For instance, the previous table showed that various environmental problems (nan renewable
resources depletion, global warming, ...) are mainly due to the production of titanium dioxide. Therefore the
proposed criteria are not expressed in terms of reduction of each environmental problem but concerns the
optimization of the use of titanium dioxide (see below) which is the driving parameter in that case.
Each criterion is now presented with some justifications coming from the discussions of the ad hoc working
group.
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5.1.1. Classification of Paints
Community ecolabel requirements on paints and varnishes take into account a classification of paints for criteria
n°3and4.
This classification is based on the function of the paints, and stems from the discussions of the ad hoc working
group members about the volatile organic compounds (VOC) content of the paints which have shown that the
VOC content and various characteristics of the paints (washability, gloss, hiding power, corrosion
resistance, are closely related through the Figment Volumic Concentration (PVC).
This relationship can be roughly represented by the following graph. The purpose of this paragraph is not to give
detailed and technical explanations but only to highlight some general conclusions.
The relation between various characteristics of the paints and the PVC
A
washability
hiding power
corrosion
resistance
gloss;
mat
(low VOC content)
-"VOC content'
mat
CPVC
Vp
The formula which gives the PVC is: PVC = * 100
Vp + Vb
with Vp = Volume of pigments and extenders
Vb = Volume of binder
100 = Volume of the coating
When Vp = 0, i.e. when there is no pigment, PVC = 0.
When Vb - 0, i.e. when the coating is made of solid particles, PVC = 100.
When Vb = 100 - Vp, i.e., when the resin fills the empty areas, PVC reaches the critical PVC; CPVC. Above
this value, the paints have a high hiding power, unwashable and mat with a low VOC content. Below this value,
they have a lower hiding power, washable and the gloss increases with the VOC content.
The CPVC is therefore the limit point for which characteristics change.
PVC should thus have been a relevant way to classify the paints according to the function. But practically
the PVC of a product is difficult to measure.
As a consequence and since gloss is the characteristic of the paints which has the closest relationship to the
VOC content (a low VOC content gives a low gloss as shown on the left side and on the right side of the
graph and a high VOC content gives a high gloss as shown on the left side of the graph), gloss has been
retained to classify the products.
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Then the ad hoc working group members have decided to allow a higher level of VOC for glossy products and a
lower level of VOC for mat products.
Two classes are thus defined:
Class 1: Paints with a specular gloss below or equal to 40 units at a = 60°
Class 2: Paints with a specular gloss above 40 units at a = 60°
Remark; There is no need to distinguish between varnishes with regard to VOC content and aromatics content
because:
there is no particular relationship between gloss and VOC content for varnishes,
additives (and thus not VOC) are used in low quantities in order to obtain mat varnishes (fumed silica and
waxes).
5.1.2. Criterion n" 1: Information to the End User
N
Criterion
Applicable
to
Requirement
Means of
proof
Compliance verification
1
Information
on criteria
relevance
All
Existence of the
recommended wordings
on can
Checking by Competent body
(verification on while basis and
coloured products in the same range}
For instance: "This product complies with the requirements of the European Union ecolabel for indoor paints with
gloss below 40 units". ,
5.1.3. Criteria n° 2 and n 0 3: White pigments
In order to address non-renewable resources depletion, global warming, atmospheric acidification, other air
emissions, water consumption, discharges into water (see table in section 3.3)
Nc
Criterion
Applicable
to
Requirement
Means of
proof
Compliance verification
2
White
pigments
content*
Paints
<40 g/m2
g of white pigment*
m3 of dry film with 98%
opacity**
Producer's
declaration
Checking by competent
body
on white basis only
3
Ti02
production
Paints
To comply with directive
on Ti02 (CEE N°92/112)
Producer's
declaration
Checking by competent
body
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The table in section 3,3 showed that:
titanium dioxide process (either the production of the raw materials or the production of the energy consumed
during the process) is the main contributor to various environmental impacts: non renewable resources
depletion, global warming, atmospheric acidification, other air emissions, water consumption, discharges into
water.
lithopone process is also a main contributor to global warming.
To address these various environmental impacts at the same time, both criteria are related to the key parameters:
the white pigment content and the process.
The criterion n°2 applies to all types of white pigments usually used for the product group: titanium dioxide
(Ti02), lithopone, etc.
One can notice that this criterion is related to the functional unit used in the LCAs.
The criterion n" 3 applies wherever the Ti02 production plant is located, i.e., not only in Europe where the
compliance with the directive is already necessary but also in other countries, and to whatever process is used
(sulfate or chloride).
The selectivity of the Ti02 content requirement (below 40 g/m with 98% opacity) is as follows:
about 50% (in liters) of the water based paints comply with this requirement:
about 80% (in liters) of the solvent based paints comply with this requirement.
5,1.4. Criterion n° 4: Volatile Organic Compounds Content
N°
Criterion
Applicable to
Requirement
Means of proof
Compliance verification
4A
VOC
content
Class 1 paints
<30 minus water
Calculation
and results
provided by
the producer
Checking by competent
body
(verification on the wNte basis and
coloured pioduet in the same
range*
48
VOC
content
Varnishes and
class 2 paints
<250g/l minus water
These volatile organic compounds correspond to the solvents contained in the paints, the resins and the additives.
Due to the lack of a standardized definition, the following definition is proposed;
"any organic compound with, at normal conditions for pressure, a boiling point (or initial boiling point) lower
than or equal to 250°C".
The table in section 3.3 shows that VOC emissions during the application of the paint or the varnishes by the
consumer is the main contributor to the tropospheric ozone formation.
To address this environmental impact, the ad hoc working group members have identified the key parameter being
the VOC content.
As explained above (criterion n°l), the VOC content of a paint increases with the gloss and two classes of paints
have been defined corresponding to two functions characterized by the specular gloss:
the class 1 paints, which are mat, mat-satin or satin and which can have a low VOC content,
the class 2 paints, which are semi-glossy, glossy or high glossy and which have generally a high VOC
content.
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The thresholds have then been determined according to selectivity considerations (see below). The threshold for
class 2 paints has also been chosen in order that the high solid solvent paints could be awarded the label, because
the Life Cycle Inventories have shown that the high solid paints have lesser impacts on the environment than other
technologies when the functional unit is considered,
Calculation of the VOC content:
The VOC content calculation will have to take into account:
solvents voluntarily added by the manufacturer,
coalescing agents and co-solvents falling under VOC definition (see below),
VOC content of resins solutions or emulsions,
solvents known by paint manufacturer (solvents in additives, etc.,.)
solvents recommended for product dilution by the applicant (in accordance with the instructions on the
packaging),
according to the following formulas:
total amount of VOC (in g)
VOC (in g/l minus waterj =
total volume of product (in 1) - total water content (in 1)
or
total amount of VOC (in g)
VOC (in g/l minus water) = 1
total amount of product (in g) _ total water content (in 1)
density
This leaves out minor amounts of VOC coming from additives of unknown composition.
Example of calculation
Solvent based formulation
Solid resin form a polymer emulsion (in % w/w)
32
Pigments (in % w/w)
22
Extenders (in % w/w)
3
Coalescing agent (in % w/w)
7
Water (in % w/w)
36
Total (in % w/w)
100
Density kg/1
1.3
total amount of VOC (in g)
7*1300/100 = 91
total amount of product (in 1)
1.0
total water content (in 1)
36*1300/100/1000 = 0.468
VOC g/l minus water
91/(1.0-0.468) = 171
Today, the varnish technology is mainly solvent based. This explains the fact that the same threshold has been
retained for the varnishes and the class 2 paints.
• Selectivity of the criterion n"4
about 12.9% (in weight) of class 1 European paints comply with the requirement 4A;
about 3.1% (in weight) of class 2 European paints comply with the requirement 4B;
therefore, about 16% (in weight) of European paints comply with the requirement 4.
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5.1.5. Criterion n° 5: Volatile Aromatic Hydrocarbons Content
N°
Criterion
Applicable to
Requirement
Means of prool
Compliance verification
5A
Volatile
aromatic
hydrocarbons
content*
Class 1 paints
<0.5% w/wof
product
Calculation
and results
provided by
the producer
Checking by competent
body
(verification on whits basis and
coloured products in the same
range!
5B
Volatile
aromatic
hydrocarbons
content*
Varnishes and
class 2 paints
<1.6%w/wof
product
This criterion has been defined in order to address the impact on the environment due to the VOC emissions into
the atmosphere.
At first, the members of the working group wanted to use the POCP index (Photochemical Ozone Creation
Potential) to weight the impact of each solvent. But, on the basis of currently accepted scientific knowledge, it
appeared that this index was not reliable enough. The members agreed to determine a specific criterion for the
aromatics content.
The ad hoc working group also decided to have different aromatic thresholds for the two classes in order to allow
high solid solvent paints to be labelled (see above criterion n° 4B),
In fact, the difference one can notice between the two thresholds are not so important when one reasons in terms
of functional unit. This is due to the high performance of the high solid technology: the quantity of paint necessary
to ensure a given opacity is much lower than for a class 1 paint.
Example of calculation
High solid paint
(class 2)
Water borne paint
(class 1)
Average hiding power (ms/l)
20
7
Average density(kg/l)
1.0
1.0
Aromatics content
(% w/w of product)
1.5
0.5
Quantity of aromatics per functional unit
(g/m2)
7.5
7.1
It was not possible to assess the selectivity of this criterion with precision but according to paints manufacturers,
the selectivity is not very important (i.e., this criterion is not very drastic) except that to be awarded the label a
product should not contain traditional white spirit with 17-18% of aromatics.
5.1.6. Criterion n" 6: Water Pollution
N°
Criterion
Applicable
to
Requirement
Means of
proof
Compliance verification
6
Effluents
from
application
tools
cleaning
All
Existence an can of
recommendations
concerning cleaning of
tools'
Checking by competent
body ^verification on whits basis
and coloured product in the same
range)
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The LCAs have shown that the cleaning of the application tools was the main contribution to water impacts.
Due to important variations between the consumer's behaviors (between the different countries in Europe, and
even within the same country), it was irrelevant to define a quantitative criterion.
A qualitative criterion has therefore been defined concerning consumer's information. The recommendation
should be adapted by the manufacturer to the type of product.
Examples of such recommendations are given below:
for solvent based products; 'solvent used for cleaning should be stored and used for later painting operations';
for water based products: 'remove excess product from tools before cleaning them'.
5.1.7. Criterion n° 7: Solid Waste
N°
CritBrion
Applicable
to
Requirement
Means of
proof
Compliance verification
7
Solid waste -
can and
paint
residues
All
Existence of recommendations on
can explaining how to preserve
product in can after opening*
Checking by competent
body {verification on white basis
and coiourtd product in the same
range)
The LCAs have shown that the application of the product by the consumer is the step in the life cycle which
produces the highest quantity of solid waste (paint residues in the can and the can itself).
Waste management differs according to the countries in Europe; this criterion is thus only a qualitative one and
concerns consumer's information. The recommendation is intended to be adapted by the manufacturer to the type
of product and packaging.
5.2. The General Principles Criteria
N»
Criterion
Applicable
to
Requirement
Means of proof
Compliance verification
8
Coloured
pigments and
other
substances
All
No use of substances
based on:
. cadmium
. lead
. chromium VI
. mercury
. arsenic
Producer's
declaration
Checking by competent
body (verification or* whit© basis
ard coloured product in the same
range!
9
Dangerous
substances
All
No use of substances
which are (EEC 67/548):
. very toxic
. toxic
. carcinogenic
. mutagenic
. toxic for reproduction
- Producer's
declaration
- Safety data for
all components
used in the
formulation
provided by the
producer
Checking by competent
body (verification on white basis
and coloured product in the same
range}
10
Dangerous
preparations
All
No hazardous
classification with the
exception of R10
Producer's
declaration
Checking by competent
body ^verification on Mute basis
and coloured product in the same
range)
RLO is the risk sentence associated with flammable preparations having a flash point higher than 21°C (ambient
temperature) and lower or equal to 55 °C and sustaining combustion. Since this sentence does not require the
flame symbol on the label according to directive EEC/67/548, products bearing this sentence on the can comply
with the criterion.
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5.3. The Fitness for Use Criteria
N°
Criterion
Applicable
to
Requirement
Means of proof
Compliance verification
11A
Fitness for
use
Paints
Hiding power >7 m'/l
ISO 6604/1
Test report {test performed
only an white basis product)
11B
Fitness for
use
Varnishes
Satisfactory resistance
to liquid required for
water during one hour
at ambient temperature
ISO 2812/1 -
method 3
Tost report
• Selectivity of criterion n° 11 A:
about 30% (in liters) of the water based paints comply with this requirement,
about 80% (in liters) of the solvent based paints comply with this requirement,
• Selectivity of criteria n° 2 and n°llA taken together:
about 10% (in liters) of the water based paints comply with these two requirements,
about 50% (in liters) of the solvent based paints comply with these two requirements.
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6. The Selectivity of the Ecolabel (Assessment from Criteria)
As shown previously, the ad hoc group has been able to assess the selectivity of various criteria thanks to figures
coming from manufacturers. It was not possible to calculate the selectivity of each criterion due to a lack of
necessary data. This relative lack of information has its source in the industry not being used to work with these
new criteria.
Therefore the following procedure has been used:
the objective of the working group members was that the global selectivity of the label reaches about 10 to 15
% (in weight) soon after the publication of the criteria.
the selectivity has been assessed for three main criteria (white pigment content criterion, VOC criterion and
fitness for use criterion) by the means of specific figures provided by titanium dioxide and paints
manufacturers.
The following table summarizes the selectivity for the criteria:
Criteria
Assessed selectivity
(% of products complying with the requirements at the
European scale)
Criterion n° 2; White pigment content
about 50% (in liters) of the water based paints
about 80% (in liters) of the solvent based paints
Criterion n° 4: VOC content
about 12.9% (in weight) of class 1 paints
about 3.1 % (in weight) of class 2 paints
therefore about 16% (in weight) of paints
Criterion n°l 1 A: Fitness for use for paints
about 30% (in liters) of the water based paints
about 80% (in liters) of the solvent based paints
Criteria n° 2 and n° 11A taken together
about 10% (in liters) of the water based paints
about 50% (in liters) of the solvent based paints
At least, the global selectivity will be lower than the lowest selectivity among the criteria. This lowest selectivity
is 16 % in weight (for VOC criteria).
As a conclusion, the ad hoc working group has estimated that about 10 to 15% of the products may actually
be labelled.
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Low- and No-VOC Coating Technologies
Second Biennial International Conference
Research Triangle Park, North Carolina
March 13 - 15, 1995
OPTIMIZING COATING FORMULATIONS
FOR TOTAL ENVIRONMENTAL AND PRODUCT PERFORMANCE
The work described in this paper was not funded by the U.S. Environmental
Protection Agency, The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
Chemical Manufacturers Association
Oxo Process and Ketones Panels
Air Issues Task Group
2501 M Street, N.W.
Washington, D.C. 20037
Contact: Barbara Francis
Jimmy G. Bassett
Eastman Chemical Company
Robert W. F. Chouffot
Shell Chemical Company
Jeffrey R. Holmstead
Latham & Watkins
James F. Quance
Exxon Chemical Company
David E. Darr
Union Carbide Corporation
Barbara O. Francis
Chemical Manufacturers Association
Donald K. Raff
Hoechst Celanese Corporation
Don A. Sullivan
Shell Oil Company
Roderick D. Gerwe
Eastman Chemical Company
Presented by:
Jimmy G. Bassett
Don A. Sullivan
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EXECUTIVE SUMMARY
Organic solvents have been used for hundreds of years in virtually all types of paints
and coatings. Although waterborne and other alternative coating technologies have begun to
replace solvent-based coatings in certain applications, solvent-based coatings are still used in
the vast majority of coating operations.
Most organic solvents are volatile organic compounds (VOCs) and can react
photochemically in the atmosphere to form ground-level ozone. As a result, policy makers
have encouraged - and in some cases required - the use of low- or no-VOC coatings. This
paper points out that VOC content should be only one of the factors considered by users,
formulators, and regulators when evaluating alternative coating systems.
In some cases, there is no appreciable environmental benefit to be gained from
reducing solvent emissions. Recent reports by the National Academy of Sciences and by the
U.S. Environmental Protection Agency have shown that, in areas where there are relatively
low levels of nitrogen oxides (NOt), reducing VOC emissions will have little or no effect on
reducing ground-level ozone.
In addition, regulatory or voluntary programs to control VOC emissions from coatings
should take seasonal and temperature differences into account. Because of the atmospheric
chemistry of ozone formation, there is little or nothing to be gained from using low-VOC
coatings during the winter months or in the cooler parts of the country. Moreover, the
ozone-formation potential of different VOCs varies depending on their photochemical
reactivity. Therefore, where VOC-control efforts are justified, they should focus on VOCs
with the highest photochemical reactivity.
Coating users and formulators, as well as regulators, should also consider
performance tradeoffs when evaluating low- or no-VOC coating technologies. For technical
reasons, alternative coating technologies are difficult or impossible to use under certain
circumstances. For example, water-based technologies may not be feasible in areas with
high relative humidity or desirable for applications involving frequent touch-up.
The use of low-VOC coatings may also involve significant environmental tradeoffs.
In many cases, for example, water-based coatings generate increased levels of liquid and
solid wastes. In addition, because water has a very high heat of vaporization, water-based
systems often require much more energy usage than solvent-based systems.
Life Cycle Assessment (LCA) is a useful analytical tool for comparing the
environmental tradeoffs associated with the use of alternative coating technologies. Two
recent studies using LCA have shown that water-based systems are not necessarily
environmentally beneficial when compared to traditional solvent-based systems. Because no
coating technology is always environmentally preferable, regulatory programs should be
designed to encourage advances in all coating technologies.
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INTRODUCTION
Organic solvents have been used for hundreds of years in virtually all types of paints
and coatings. In recent years, waterborne and other alternative coating technologies have
begun to replace solvent-based coatings in certain applications. However, with the exception
of architectural coating applications -- where waterborne products are now widely used ~
solvent-based coatings are still used in the vast majority of coating operations.
Most organic solvents are volatile organic compounds (VOCs), which can react
photochemically in the atmosphere to form ground-level ozone. Ground-level ozone is the
main component of "smog," which continues to be a health and environmental concern in
some areas in spite of the progress that has been made in controlling it over the last 20
years. Although VOC emissions from coatings represent a relatively minor portion of total
VOC emissions, industry and regulators have recognized the need to focus on all emissions
that may contribute to ozone formation.
As part of a national effort to reduce ground-level ozone and maintain it within
acceptable levels, the U.S. Environmental Protection Agency (EPA) and other regulatory
agencies have encouraged — and in some cases required — the use of low- or no-VOC
coatings. The use of such products, however, usually involves certain tradeoffs. This paper
points out that the VOC content of a coating should be only one of the factors considered by
users, formulators, and regulators when evaluating low- or no-VOC coating technologies.
In most cases, a switch from a traditional solventborne coating to an alternative
coating technology imposes a direct financial cost (and frequently an indirect performance
penalty) on the user of the coating - a cost that is then passed along, at least in part, to the
ultimate consumer of the coated product. Although these costs can be significant and should
not be overlooked, they are not the focus of this paper. Rather, this paper examines the
other tradeoffs that are associated with alternative coating technologies.
These tradeoffs — whether measured in terms of direct financial costs or otherwise -
should be compared with the benefits of switching to a low- or no-VOC coating.
Historically, these benefits have been measured by the tons of VOC emissions that would be
eliminated by such a switch. As the National Academy of Sciences (NAS) emphasized in a
recent report, however, reducing VOC emissions does not always benefit the environment.
In some cases, VOC emissions have little or no impact on ground-level ozone. Regulatory
efforts should focus on the purpose for which VOC emission are of concern - ground-level
ozone — and not on VOC emissions alone.
Thus, when evaluating low- or no-VOC coating technologies, it is important to
consider the environmental benefits that they will provide and the environmental and
performance tradeoffs that are associated with such technologies. This paper first briefly
reviews the benefit side of this equation, outlining the conditions under which low- or no-
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VOC coatings may be desirable. It then reviews the tradeoffs that companies and regulatory
agencies should consider when evaluating low- and no-VOC coating technologies.
ASSESSING THE ENVIRONMENTAL BENEFITS OF CONTROLLING VOC
EMISSIONS FROM SOLVENTS
Unlike most other regulated pollutants, ozone is not emitted directly into the air from
man-made sources. Rather, it is a so-called "secondary pollutant" that is formed by the
interaction of a broad mixture of natural and man-made emissions (known generally as ozone
precursors) in the presence of sunlight. To the extent possible, regulators and users should
take into account the complexities of the process by which ozone is formed. Otherwise,
significant resources will be spent on coating technologies that have little or no impact on
reducing ozone formation.
The Respective Roles of VOCs and NOx
Although carbon monoxide plays a small role in ozone formation, the most important
ozone precursors are VOCs and oxides of nitrogen (NOx). There are several significant
sources of VOC emissions, including natural or "biogenic" sources such as trees and
vegetation and man-made sources such as vehicle emissions, petroleum refining and
distribution, and combustion sources. As noted above, organic solvents, including solvents
used in coating applications, are also a source of VOC emissions.
For many years, EPA has emphasized reductions in VOC emissions as the primary
approach for controlling ozone. In December 1991, however, the National Academy of
Sciences issued a report entitled Rethinking the Ozone Problem in Urban and Regional Air
Pollution.1 Among other things, the NAS report questioned the regulatory focus on VOC
emissions, noting that ozone is formed only if there is the right atmospheric mixture of
VOCs and NOx. The report concluded that, in many areas, reductions in VOC emissions
would have little or no effect on ozone levels, and that in a few cases, such reductions would
actually be counterproductive and lead to increased ozone levels.
In July 1993, EPA submitted a report to Congress entitled The Role of Ozone
Precursors in Tropospheric Ozone Formation and Control, which responded to the NAS
report.2 This report, which was required under section 185B of the 1990 Amendments to the
Clean Air Act, largely agreed with the conclusions of the NAS study. It noted that, in some
areas, efforts to reduce ozone levels should continue to focus primarily on VOC emissions.
The report acknowledged, however, that in many areas of the country, only NOx reductions
will have a significant effect on reducing ozone levels, and that regional modeling will be
required to identify the type and amount of emissions reductions that will be necessary to
bring specific areas into attainment with national ambient ozone standards.
Low- and no-VOC coatings may be a desirable option in areas that need to reduce
VOC emissions in order to reach attainment with ambient standards. However, in areas that
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are "NOx-limited" -- i.e., where VOC emissions have little or no effect on ozone levels -
regulatory efforts should be focused on reducing NOx emissions. Any program aimed at
reducing solvent emissions in these areas would impose unnecessary costs on businesses and
consumers.
The Role of Sunlight and Temperature
In most parts of the country, high ozone levels are a concern only during the summer,
when higher temperatures increase the rate at which NOx and VOCs react in the atmosphere
to form ozone. The Clean Air Act recognizes this fact by requiring EPA, under certain
programs, to make a distinction between the "high ozone period" (the summertime) and the
rest of the year. For example, during the summer months, gasoline sold in some urban areas
must be reformulated to reduce VOC emissions from vehicles by at least 15 percent.
In addition to making a distinction between summer and winter, EPA has recognized
that hotter areas of the country may require different VOC controls than cooler areas. For
example, EPA has set a more stringent evaporative standard for gasoline sold in certain
southern cities that, on average, experience higher summertime temperatures than the rest of
the country.
Regulatory programs to control VOC emissions from coating operations should also
take seasonal and temperature differences into account. Little or nothing is gained from
using low- or no-VOC coatings during the winter months or in the cooler parts of the
country. EPA already has recognized that it is appropriate to impose different requirements
for coatings depending on the time of year during which they are applied. In the regulatory
negotiation on Architectural and Industrial Maintenance coatings (the so-called "AIM Reg
Neg"), the Agency agreed to propose different VOC limits for traffic paints depending on
whether they are applied during the summer or during the winter. For many solvent users, a
time-of-vear restriction could easily be enforced by including it in their operating permit.
The Importance of Taking Reactivity into Account
Different VOCs (including different solvents) are not equal in their potential to create
ground-level ozone. For many years, EPA has recognized that the potential contribution that
each individual VOC makes to ozone formation depends on its photochemical reactivity.
Assuming that there are sufficient amounts of NOx and sunlight, VOCs with the highest
reactivity cause the most ozone. Therefore, from the standpoint of environmental protection,
reductions of high reactivity VOCs are more valuable than reductions of lower reactivity
compounds.
In recognition of this fact, EPA has developed a list of compounds that have only
"negligible" reactivity. These compounds are exempt from regulation as VOCs, Except for
these exempt compounds, however, federal and state regulations generally treat all VOCs as
though they had the same impact on ozone formation. Unfortunately, this approach does not
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create any incentive for companies to focus on reducing emissions of highly reactive VOCs
that have the greatest impact on ozone formation.
Over the last several years, researchers have begun to develop methods for weighting
the photochemical reactivity of various VOCs, and it is now possible to develop regulatory
programs based on reactivity indices or scales.3 The State of California has already
developed a reactivity-based program for reformulated gasoline that places different weights
on individual VOCs. Because the relative reactivity of different VOCs varies depending on
NOx conditions and other factors, none of these indices is perfect for all conditions. From
an environmental perspective, however, virtually any of them would be preferable to the
current regulatory approach, which treats VOCs as though they were all equal.
Additional data may be needed before a reactivity-based approach can be used for
regulating solvent emissions from coatings. However, both regulators and users should have
a strong incentive for developing and supporting such an approach. A reactivity-based
system would be much more effective at reducing ozone levels than the current approach and
would do so in a more cost-effective manner.
Such an approach would recognize that lowering the VOC content of a coating does
not necessarily reduce its ability to form ozone - even assuming that it is used in an area
that is not NOx-limited. A coating that uses less solvent may not offer an environmental
advantage over a traditional coating if the solvent in the low-VOC coating has higher
photochemical reactivity. Thus, in order to evaluate the benefits of switching to a low-VOC
coating, the reactivity of its solvent must be compared to the reactivity of the solvent it
would replace.
TRADEOFFS ASSOCIATED WITH LOW- AND NO-VOC COATINGS
When considering the total environmental and product performance of a coating, its
VOC content is only one of many factors that should be considered. Some of the factors are
technical, and may appear to be of interest only to formulators and users. Many of these
technical factors, however, have a significant (although sometimes indirect) effect on the
environment and should also be of interest to regulators.
By the same token, users and formulators should be aware of collateral environmental
impacts associated with different low- and no-VOC coatings. These impacts not only affect
the environment, but may also trigger new regulatory requirements of which the user must be
aware.
Technical Considerations
Formulators must balance a number of performance factors in order to develop
acceptable formulations of paints and other coatings. Some of these criteria are relevant
primarily for specific applications. For example, lacquers require careful attention to blush
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resistance, and electrical conductivity is a key factor for electrocoating and electrostatic spray
applications. Most factors, however, are relevant for a wide range of coatings, A
formulator must generally consider the following key criteria when selecting solvents for a
coating formulation: evaporation rate, flash point, resin solubility, surface tension, viscosity,
and miscibility with other solvents and diluents.
The first factor to be considered is the relative evaporation rate of the solvents in the
coating, which in turn can affect each of the other criteria listed above. In particular,
evaporation rate can affect both drying time and resin solubility and must be suitable for the
application method. Spray-applied coatings are formulated with fast evaporating solvent
blends for fast drying and minimal sags and runs, while brush applied coatings use slower
evaporating solvents for longer open time and smooth flowout. Solvent composition changes
as evaporation proceeds, and it is important to manage the changing composition to maintain
solvency and avoid resin precipitation. If the strong active, solvent evaporates too quickly,
the blend becomes richer in diluent and the resin becomes insoluble.
Similarly, changes in solvent composition may affect surface tension, viscosity, blush
resistance, and miscibility and can result in a variety of other performance problems,
including poor leveling, reduced gloss, and other film defects such as "orange peel" and
"fish eyes."
Although it is a challenge to balance these various factors in the formulation of
solvent-based coatings, it is significantly more difficult to strike the proper balance with
lower VOC coatings. Because they have lower solvent content, low- and no-VOC coating
formulations are less forgiving in design, and more demanding of application conditions.
The following sections describe several important issues to consider when evaluating
alternative coating technologies.
Application under Difficult Conditions. For waterborne coatings, one of the most difficult
challenges is application under conditions of high humidity. As noted above, evaporation
rate is a key factor in the performance of virtually all coatings. With solvent-based systems,
the evaporation rate is controlled simply by adjusting the solvent mixture. For waterborne
coatings, however, the evaporation rate is a function of temperature and, in particular,
relative humidity. As relative humidity increases, the evaporation rate slows. Obviously, at
100 percent relative humidity, where the ambient air is fully saturated, there is no
evaporation at all and a water-based coating will not dry.
In order to achieve consistent performance with a waterborne coating, the applicator
must control the heat and humidity in the drying area. Controlling these factors is possible
for enclosed coatings operations, but often requires significant energy usage, which increases
costs and gives rise to collateral environmental impacts associated with energy production
and consumption. For some applications (such as aerospace and ship coating and the coating
of exterior structures), humidity and temperature control is simply not a feasible option.
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The South Coast Basin in southern California has the most severe ozone
nonattainment problem of any area in the United States. Because of its relatively constant
temperatures and low humidity, it also has an ideal climate for the use of waterborne
coatings. Because of the severity of the ozone problem in the South Coast, local regulations
have required many coating operations to switch from solvent-based to water-based coatings.
Due in large part to the Southern California climate, most of these switches have been
successful. Even in the South Coast, however, there continue to be performance and
application problems with waterborne technologies. When considering the potential for
similar technologies to be used elsewhere, solvent users and regulators must take into account
the conditions under which they will be applied. A coating that gives good performance year
around in California or Arizona may simply not work during the summer in Mississippi or
Louisiana or during the winter in New York.
Technical Performance Issues. Solvent-based coatings have other technical advantages
that, in certain applications, make them difficult to replace with alternative coating
technologies. For example, although waterborne coatings can be used in some wood
finishing applications, such coatings generally cannot be used for the initial coat (the base
coat or wash coat) that is applied to the wood. Because wood absorbs water, the application
of a waterborne base coat actually raises small wood particles on the surface of the wood.
This problem - known as "grain raising" — is avoided with solvent-based coatings.
In some cases, the technical advantages of a solvent-based coating also give the
coating an environmental advantage when compared to alternative technologies. Again, the
coating of wood furniture offers an example. Regardless of the type of coating used, the
finish can be damaged during shipping or after the piece of furniture is placed into use.
Traditional nitrocellulose lacquers are easily repaired. The solvent in the touch-up coating
actually dissolves the existing finish coat and allows the new resin to bind with the old. This
makes it simple, for example, to touch up even a very visible spot on the top of a table. In
contrast, when alternative coatings are used, the entire table top must be refinished. This is
not only more costly, but increases waste generation and requires the use of more coating to
cover a greater area. Even if the newer coating has a lower VOC content, the overall
emissions are likely to be higher when touch-up is considered because of the increased
amount of coating that must be used.
A similar issue arises in autobody re finishing. Using a solvent-based system, a small
blemish on a car body can be touched up. With an alternative technology, however, the
whole component (such as the hood or fender) must be refinished. Color-matching is also
much easier with solventborne systems. Where the color match is particularly sensitive, the
use of an alternative coating may require that the entire car be repainted. Such a result is
clearly not desirable either from a cost or an environmental perspective.
"Crab trap" effect. For most businesses with coating operations, a switch to an alternative
coating technology requires a significant up-front capital investment. Because water-based
systems require the use of corrosion resistant components, a company must often replace
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existing tanks and piping with stainless steel at the same time it purchases new spray guns
and baking ovens. Powder coatings require new spray guns and coating handling machinery,
and a company that moves to UV cure or an electron beam curing system must completely
replace its existing equipment.
In many cases, the investment in capital equipment will have the practical effect of
locking companies into new technologies with which they have little or no experience. Thus,
to many solvent users, the alternative technology looks like a crab trap, which lets them in
but will not let them out. Although this may not be a major issue for industries with stable
product lines, it represents a significant concern for industries that need to change the
appearance of their products to respond to customer demands and changes in the
marketplace.
Environmental Tradeoffs
Over the last decade, policy makers have learned that a regulatory strategy designed
to address one environmental problem may inadvertently create other environmental
problems. Often there are cross-media effects, where efforts to reduce pollution in one
media increase pollution in another. For example, treating polluted wastewater may generate
hazardous sludge, and incineration of the sludge may generate hazardous air pollutants.
Even within the same media, efforts to address one problem may give rise to another.
In the early 1970s, for example, regulatory efforts to reduce VOC emissions lead many
companies to replace traditional organic solvents with chlorinated solvents, which were later
determined to play a major role in depleting stratospheric ozone. In light of this history,
regulatory agencies and solvent users should not focus only on VOC emissions. Instead,
they should evaluate the full range of environmental impacts.
Waste Generation. Like most industrial operations, coating operations generate both liquid
and solid waste. In a typical coating operation, waste is generated at various points in the
process. Spray booths or other collection devices for overspray must be cleaned on a regular
basis; piping and spray lines must be drained and flushed whenever color or formulation
changes are made; and empty shipping containers must be cleaned prior to disposal or
reconditioning. In addition, in most operations, some percentage of the coated product must
be stripped and recoated because of flaws in the finish - a process that generates waste in
the form of sludge and spent stripping agent. Thus, among other things, the "reject rate" has
an impact on the generation of both liquid and solid waste.
Solvent-based systems offer significant advantages with respect to the handling of
liquid wastes. The solvent used to clean containers, spray lines, and piping is typically
reused several times before it is disposed of by incineration or used as a supplemental fuel.
Solvent recovery through recycling may also be attractive - for both environmental and
economic reasons. In that case, the solvents are recovered through distillation and then
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reused. Using standard collection procedures, solvent losses are minimal and waste disposal
costs are relatively low.
For water-based systems, disposal of liquid waste is more problematic and costly.
Aqueous wastes consist mostly of water and suspended pigment and resin particles and
soluble organics, with only small amounts of volatile solvents. Liquid waste from the
cleaning of containers, spray lines, and piping cannot be reused. Because of the low energy
content, liquid waste from a water-based system cannot be incinerated or used as
supplemental fuel; and because of the high water content, distillation is usually not a
practical alternative. Instead, it must be disposed of as wastewater. In most cases this
requires pretreatment, which increases costs and often triggers permit requirements.
In many applications, water-based coating systems also generate increased amounts of
solid waste compared to traditional solvent-based systems. Metal coating operations often
use electrocoating or electrostatic spray techniques that minimize overspray and therefore
increase transfer efficiency. It is significantly easier to manage the electrical conductivity for
solvent-based systems than for water-based systems. Therefore, electrocoating and
electrostatic spray techniques are more efficient with solvent-based systems. This not only
has implications for air emissions, but also means that the solvent-based systems will
generate less overspray that must eventually be disposed of as liquid or solid waste.
In addition, water-based coatings have a shorter pot-life than solvent-based coatings.
Although this problem can be managed, it cannot be eliminated entirely. As a result, with
water-based systems, a higher percentage of unused coating must be disposed of as solid
waste.
Finally, as noted above, solvent-based systems are more forgiving than alternative
coating technologies for most applications. Among other things, this means that reject rates
tend to be lower, on average, for solvent-based systems. Because rejected products must
either be disposed of or stripped and recoated, a higher reject rate has several negative
environmental consequences. First, of course, it means that additional energy and materials
are needed either to recoat the rejected product or to manufacture and coat a replacement
product. In addition, an increase in the reject rate increases the generation of liquid and
solid waste.
Energy Consumption. As noted above, the use of waterborne coatings may require special
attention to humidity control, which leads to increases in energy consumption. Even where
humidity is not a major factor, however, many industrial coatings are baked to increase line
speed. Because water has a very high heat of vaporization, water-based systems require
much more energy to bake than do traditional solvent-based systems. In addition, although
water-based systems generate some VOC emissions, the concentrations are usually not high
enough to support efficient combustion in afterburners or incinerators. In contrast, solvent-
based systems produce vapor concentrations that are sufficiently high to serve as a
supplemental fuel source in the baking operation. Therefore, for several reasons, water-
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based coatings are likely to consume more energy than solvent-based systems. Policy makers
should not overlook the environmental consequences of energy consumption when evaluating
the overall impact of different coating technologies.
The Tradeoff Between HAP and VOC Emissions. When evaluating the fall range of
environmental issues related to paints and coatings, it is also important to consider the
tradeoff between VOC emissions and emissions of substances listed as "hazardous air
pollutants" (HAPs) under the federal Clean Air Act. Two of the solvents on the HAPs list,
methyl ethyl ketone (MEK) and methyl isobutyl ketone (M1BK), are very efficient solvents
and, therefore, are especially valuable in the formulation of high solids coatings. Not only
do they dissolve a wide variety of resins, but compared to the available non-ketone
alternatives, they require a smaller amount of solvent to perform the same function. Thus,
the use of MEK and MIBK allows the formulation of coatings with higher solids and lower
solvent emissions. For this reason, the use of MEK and MIBK can reduce VOC emissions
from many coating operations.
In a recent rulemaking to regulate coatings used in the shipbuilding industry, EPA
specifically addressed this issue, noting that a coating reformulated to reduce its HAP content
may have "higher VOC content than the one it replaces." 59 Fed. Reg. 62681, 62688 (Dec.
6, 1994).4 The Agency goes on to state that "the HAP to VOC ratio may even increase
when a company develops a new reformulation with lower VOC." Id. It also notes that,
even where the HAP to VOC ratio in the coating increases, "the absolute HAP emissions are
likely to go down," presumably because higher solids coatings allow more coverage per
gallon of coating. Id. (emphasis added).
In recognition of this tradeoff, the proposed rale for the shipbuilding industry includes
coating content standards that are identical for HAPs and VOCs. This approach encourages
the use of higher solids coatings and eliminates the incentive for formulators to use less
efficient solvents that must be used in greater volumes.
By effectively encouraging the use of certain solvents that are listed as HAPs, the
proposed rule also implicitly recognizes a fact that EPA has explicitly acknowledged in other
rulemakings: that certain solvents listed as IIAPs have relatively low toxicity.
Unfortunately, there are many in the public — and even some solvent users and regulators —
who do not understand that the list of HAPs includes substances with a wide range of hazard
characteristics, including a few such as MEK and MIBK that have low toxicity. Regulators,
chemical users, and the public should understand that, in terms of their potential hazard, all
HAPs are not equal.
In order to understand the relative toxicity of various chemicals, it is helpful to refer
to EPA's recent proposed rule under section 112(g) of the Clean Air Act, which shows that
MEK and MIBK are among the HAPs with the lowest toxicity. 59 Fed. Reg. 15,504 (April
1, 1994).5 More importantly, the proposed rule also contains an EPA model for calculating
the amount of a chemical that may be emitted into the ambient air without posing more than
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a trivial risk to human health or the environment. Even using conservative assumptions, this
model suggests that a typical facility could emit 2000 tons per year of MEK and 1500 tons
per year of MIBK and still pose only a trivial risk.
This analysis is not used to suggest that a facility should be allowed to emit these
quantities without triggering regulatory requirements. It is simply intended to show that
MEK and MIBK pose very little hazard -- even though they are listed as "hazardous air
pollutants." Thus, reformulating a coating to reduce emissions of MEK or MIBK is likely to
increase emissions of VOCs without providing any benefit in terms of risk reduction. This
tradeoff again illustrates the importance of considering all relevant factors instead of focusing
solely on low-VOC or low- HAP content.
The Role of Product Performance. This paper does not attempt to review the data
comparing the performance of various coating technologies in different applications. It must
be noted, however, that product performance is an important factor that cannot be overlooked
when evaluating the overall environmental impact of a coating system.
Long experience in using solvents has allowed product formulators to achieve
important performance attributes across a broad range of coating applications. In some
cases, a switch to low- or no-VOC coatings may reduce product performance and undermine
environmental objectives (in addition to increasing costs). For example, a paint formulator
may be able to reduce the VOC content of an industrial coating by 25 percent, but in the
process might produce a product that lasts only half as long. Because the user would have to
repaint twice as often, the overall VOC emissions would increase, not decrease, over the
long run.
Life-Cycle Assessments
As discussed above, a decision to switch from a traditional solventborne system to a
low-VOC coating technology is likely to involve a number of environmental tradeoffs and
has implications for all environmental media, not simply for ground-level ozone. The
environmental tradeoffs and multi-media effects of different techniques for achieving
environmental goals can be compared through the use of life cycle assessment (LCA), which
allow a rigorous analysis of environmental impacts both upstream and downstream from the
regulated product or process. These consequences can be compared using LCA techniques,
which consider such factors as:
• raw materials input
• energy input
• solid waste generated
• emissions to air
• releases to water
• other environmental releases
• amount of usable product
• product life
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These individual impacts are affected by the respective production-use-disposal chain
for each option considered. The various factors discussed above, including the amount of
coating required per unit of production, refinish and reject rates, and durability of the
finished coating can all influence the overall environmental impact of each option. As with
other analytical tools, LCA does not necessarily provide absolute precision. Nevertheless, it
is a useful tool for comparing the entire range of environmental issues associated with
different approaches for addressing environmental concerns.
Over the past few years, at least two comprehensive life-cycle assessments have been
conducted to compare the overall environmental impact of different coatings technologies. A
1992 study conducted by the Eindhoven University of Technology in The Netherlands used
LCA to compare three types of architectural coatings: a conventional solvent-based alkyd, a
high-solids alkyd, and a water-based acrylic. (Geurink and Bancken, 1992)6 Although the
authors noted that there may be differences in performance or durability among the various
coatings, they assumed for purposes of their analysis that the three coatings provided
equivalent durability - i.e., that a new topcoat would be required every five years, and that
the surface would need to be stripped and recoated at the end of 20 years.
This paper does not attempt a complete review of the methodology and assumptions of
Eindhoven study. The major conclusions of the study were as follows:
• As expected, VOC emissions from waterborne and high-solids coatings were lower
than those from the conventional solvent-based coating.
• However, even the difference in VOC emissions was relatively minor when the
authors accounted for emissions produced by removal of the coatings at the end of
their 20-year useful life. Taking these emissions into account, the VOC emissions
from the conventional solvent-based coating were approximately 10% higher than
those from the water-based coating.
• In terms of environmental impact, the greatest difference between the three coatings
was seen in their contribution to water pollution. Effluents to water during
production-use-disposal chain from the water-based coating were more than double the
effluents from either the conventional or the high-solids coating.
• The authors concluded that "not all levels of environmental criteria are decreased by
the new generation decorative paints. Especially [water-based] acrylics show some
disadvantages (exhaustion [of natural resources], water pollution, acidification)." Id.
at 12.
Whereas the Eindhoven study examined architectural coatings, a second recent study
sponsored by BP Chemicals, Ford Motor Company, and PPG Industries evaluated alternative
coating technologies for an industrial coating operation. (Hazel, 1994)7 In these operations,
low-VOC coatings are not the only option for reducing VOC emissions; rather, various
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forms of VOC abatement technologies such as incineration and absorption may also be used.
These options have different degrees of effectiveness (and cost-effectiveness) in controlling
VOC emissions, and also have other environmental advantages and disadvantages, LCA is a
useful tool for analyzing these various tradeoffs.
This second study used LCA to evaluate the environmental impacts of an automotive
coating operation using a waterborne system compared to the same operation using a solvent-
based system with an incinerator to control VOC emissions. As the author of the study
points out, the three companies that sponsored the study have good credentials for carrying
out such an evaluation. Ford currently operates plants using both technologies; PPG makes
both kinds of paint; and BP Chemicals manufactures chemicals that go into both types of
systems.
In this study, the level of incineration was adjusted to equalize the degree of VOC
control between the two options. By taking advantage of sophisticated computer software
(Chalmers "LCA Tool"), it was possible to study systems that produce either the same level
of VOC emissions from the paint shop itself or the same global VOC emissions, including
manufacture and transportation of raw materials and paint. By holding VOC emissions
constant, the assessment was better able to compare the other environmental impacts of the
two options.
The study then compared a number of upstream and downstream environmental
impacts from the two systems, including emissions to air, water, and land and consumption
of natural resources. Not surprisingly, the study found that "water-based topcoats have some
advantages (principally related to emissions during chemical feedstock manufacture), while
solvent-based systems using VOC abatement have others (principally energy related
emissions). Id. at 8.
For all impacts, the differences were relatively small. The study noted, for example,
that "[consumption of gas and crude oil as feedstocks are lower in the water-based system,
primarily due to a lower organic content in the basecoat," The authors note, however, that
the "amounts involved are small compared to fuel use in the painting process (14%) and
insignificant in relation to the consumption [of fuel] by a car." Id. at 4.
The fundamental conclusion of the study was as follows:
Examination of ... 28 environmental effects (emissions and consumptions)
leads to the conclusion that neither technology has the environmental high
ground. In fact the variability between what is achievable as current good
practice within one technology option can be larger than the difference
between the base cases considered here.
Id. at 8 (emphasis in original). This conclusion may not be satisfying if one is seeking a
single approach for reducing the environmental impacts from coating operations. However,
4-30
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it serves to illustrate the complexity of addressing environmental issues and the need to
evaluate all environmental impacts.
Need to Encourage Advances in AH Coating Technologies
Regulations that require product reformulation are often designed to be "technology
forcing." In the case of regulations based on low- and no-VOC coating technologies, this
means that regulators may expect that future waterbome systems will be able to match the
product performance of current solventborne systems. What this approach overlooks,
however, is the potential for continuing advances in solventborne systems. When mandated
reformulation effectively cuts off further research and development into solventborne
systems, it stands in the way of future developments that could offer both performance and
environmental advantages.
As noted above, a high-VOC coating that lasts for ten years may be environmentally
preferable to a low-VQC coating that lasts for only seven. A technology-forcing regulation
may well lead to a lower-VOC coating that lasts for ten years, but it also may cut off further
research into solvent systems that would have resulted in a 20-year coating.
Thus, for both economic and environmental reasons, regulatory programs should be
designed in a way that allows for advances in all coating technologies, not just in low- and
no-VOC coatings.
CONCLUSION
Regulators, environmental advocates, and industry groups should not focus solely on
VOC emissions when evaluating the environmental and other impacts of coating technologies.
In some cases, reductions in VOC emissions from coating operations offer little or no benefit
to the environment and may impose substantial costs on businesses and consumers. Even
where VOC emission reductions are needed, the fall range of environmental and performance
tradeoffs should be weighed carefully. In many cases, traditional solvent-based coatings will
continue to be the best option for optimizing total environmental and product performance.
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REFERENCES
1. National Academy of Sciences. Rethinking the Ozone Problem in Urban and
Regional Air Pollution. Washington, D C., 1990.
2. U.S. Environmental Protection Agency. The Role of Ozone Precursors in
Tropospheric Ozone Formation and Control. Office of Air Quality Planning and
Standards, Research Triangle Park, N.C., 1993.
3. Carter, W.P.L. Development of Ozone Reactivity Scales for Volatile Organic
Compounds. Air & Waste 44; 881-899, July 1994.
4. U.S. Environmental Protection Agency. National Emission Standards for Hazardous
Air Pollutants; Proposed Standards for Shipbuilding and Ship Repair. 59 Fed. Reg,
62,681, December 6, 1994,
5. U.S. Environmental Protection Agency, Hazardous Air Pollutants: Proposed
Regulations Governing Constructed, Reconstructed or Modified Major Sources;
Proposed Rule. 59 Fed. Reg. 15,504, April 1, 1994.
6. Geurink, P.J.A. and Bancken, E.L.J. Life Cycle Assessments of Decorative Paints.
Paper presented at the 12th International Conference of the International Centre for
Coatings Technology, Paint Research Association, Milan, Italy. November 16-18,
1992.
7. Hazel, N. LCA of Automotive OEM Finishes: Are Water-borne Coatings Really the
Environmental Solution? Paper presented at the 14th International Conference of the
International Centre for Coatings Technology, Paint Research Association, December
1994.
4-32
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The work described in this paper was riot funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
Life Cycle Analysis of an Aqueous Low V.O.C. Coating
Jack Kowal
Coors Brewing Company
Golden, Colorado, USA
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PAGE 2
ABSTRACT:
The accepted method for coating the inside of two piece aluminum cans for beer and
beverage is with a water emulsified polymer that contains 15% to 20% of volatile
solvents. Development of a water based technology that contains less than 2% volatile
solvents has been pursued over the past four years, Coors Brewing Company, Research
and Development group, in conjunction with a major manufacturer of polymer coatings,
has been developing cooperatively an FDA compliant polymer coating. Testing of this
technology in full scale production has been conducted since July of 1994. Once
development is complete, this technology should provide a viable low polluting option to
the conventional materials even when utilizing end of the pipe control devices. Initial,
empirical modeling indicates a 30% reduction in stack and fugitive emissions when
compared to a conventional installation utilizing an incinerator. Comparison of this
technology with accepted standard waterbased technology reveals a reduction in
emissions and/or hazardous waste generation. This reduction is from the point of polymer
manufacturer to final disposition of products and wastes. These factors, when combined
with operation without the energy utilized in end of pipe control, represent significant
pollution prevention gains with resulting benefits of cost savings, energy conservation
and the ability to operate in a practical manner.
INTRODUCTION;
The Coors Can Manufacturing Plant, located in Golden, Colorado, is the largest single
aluminum can manufacturing plant in the world and produces approximately 4 billion
cans a year. The Coors Brewing Company developed the country's first aluminum
beverage can, a two-piece aluminum can, in 1959, and was instrumental in the transfer of
aluminum can production technology throughout the beverage container industry. The
plant currently produces aluminum cans exclusively for the beer beverage market.
Conventional, compliant, aqueous, coating materials used to coat the internal; surfaces of
two piece cans for beer and beverage currently contain a relatively high volume of
solvent. An alternate technology is under development for coating the internal surfaces of
cans that contains a minimal volume of volatiles. The Coors Brewing Company Can
Manufacturing Plant has been developing this technology since 1988 and has achieved
full production scale test success in July of 1994. The Coors plant is currently the only
aluminum can manufacturing plant in the country developing this Ultra Low VOC
technology. A technical comparison of can coating technologies is currently in progress.
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PAGE 3
ALL ESTIMATES ARE BASED ON THEORETICAL CALCULATIONS FROM
FORMULATION DATA AND REPRESENT THE POTENTIAL TO EMIT AND ARE
NOT MEANT TO REPRESENT ACTUAL EMISSIONS FROM A PLANT,
TECHNOLOGY BACKGROUND:
The can manufacturing industry has been investigating lowering the VOC content of these
compliant coatings. Coors also initially investigated lowering VOC content of the coating
with the same basic methods employed by most all of the major suppliers. Coors made an
early determination that the methods being employed would probably not yield the
desired results. A decision was made to investigate the development of a true ZERO
VOC material directly. This is in direct contrast to the popular approach of reducing the
VOC content in steps. It was determined that with a partner we could pool our finances.
We would avoid the costs of the phases involved in the step down approach and apply
these moneys directly to the goal of a ZERO VOC material. It was theorized, with high
probability, that this goal could be achieved with less expenditure than the stepped
approach.
Coors Can Manufacturing has worked in partnerships with several companies with the
purpose of developing a coating for the inside of aluminum cans that contains a minimal
amount of VOC. The initial push for the investigation of a technology of this type was
motivated by a desire to develop a true ZERO VOC coating material The effects of a
technology that was truly ZERO VOC would be to eliminate emissions from the internal
coating process, eliminate the requirement for end of pipe controls, reduce potential
energy consumption, in addition to a desire to provide greater flexibility for production
increases. In 1990, a major coating manufacturer and Coors entered a co-development
agreement for the purpose of developing a coating technology that would minimize the
volatile components while maintaining the required and desired properties necessary to
meet the requirements of beer and beverage packaging.
Currently, the Ultra low VOC coating in use at Coors has sufficient flexibility and
withstands post forming and pack stability suitable for the beer beverage market. Newer,
more flexible, coatings are currently being developed to meet the broader requirements of
the beverage packaging industry.
INTERNAL COATING TECHNOLOGIES:
Potential can coating technologies include the use of conventional solvent based coatings,
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PAGE 4
aqueous co-solvent coatings, powder coatings, and eiectrocoat. Among other factors,
these techniques differ in the content of solvents in the coatings.
Conventional solvent based coatings contain solvents at concentrations of approximately
80 to 90 percent by volume (1). The solvent composition is typically a mixture of
aliphatic hydrocarbons, aromatics, ethers, cellosolves and acetates. As a result, this
method produces significant VOC (volatile organic compound) and HAP (hazardous air
pollutant) emissions. These coatings have good barrier properties and high quality, but
the high VOC emissions have almost eliminated their use for beer and beverage
containers.
Aqueous co-solvent coatings contain less solvent than the conventional solvent based
coatings (1). In water based coatings, the solids content normally ranges from 15 to 30
percent, the water content from 50 to 70 percent, and the solvent content from 10 to 25
percent. The solvent is used to control viscosity, disperse the solids and as an aid in
wetting. Curing is achieved with a thermal oven that requires a high operating
temperature due to the high water content in the coating. Since the coating does contain
solvents, VOC emissions are still present. This coating method is the most widely used in
can manufacturing plants at present time.
Powder coatings are small particles of paint solids that are normally applied to metal by
electrostatic deposition, flame spraying or fluidized bed dipping. The solvent content is
less than 4 percent, therefore VOC emissions are reduced (1). Normal curing
temperatures are also required. This method has not been used in coating beer and
beverage cans due to the limitations of coating a small diameter cylinder.
Ultra Low VOC coating application is currently accomplished with standard airless spray
equipment. While this was not a development limitation, it provides for the most
effortless conversion to this technology as the application equipment does not change.
These coating materials are of polymeric origin and crosslink upon exposure to thermal
energy. Unlike normal coating polymers that are reacted in solvent media, the main
polymer utilized is reacted in water media and amines are added for emulsion stability.
This method allows for an extremely low volume of volatiles that are required to be
added. This coating technology has been developed and is being tested under full
production conditions.
An initial review of feasible technologies and pending air emission regulations indicates
that accepted end of the pipe controls or this Ultra Low VOC technology will be the only
4-36
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PAGE 5
technological methods available at this time capable of reducing emissions to the
proposed levels.
COATING TECHNOLOGY PROCESS DESCRIPTION:
Aluminum cans are made from large coils of aluminum sheet stock by punching
aluminum disks into cups, and sequential drawing and ironing to form the can body. The
can body is trimmed, washed and transferred to a printer, where the decorative ink and
clear protective overvarnish are applied. The ink and overvarnish are then cured. The
cans are then conveyed to the internal coating process. A liquid internal coating is then
spray applied to the interior of the can with airless high pressure equipment. The cans are
then conveyed to a gas fired continuous mat thermal oven where the coating material is
cured. The cans receive further processing where the open ends are reduced in size and
flanged to accept the can end after filling and then checked with light for pin holes and
other deformities.
In the can coating process (Figure 1), individual stations with high pressure spray
equipment are positioned to receive cans to be sprayed. The cans are typically transferred
through the spray operation with an indexing star wheel. The star wheel advances each
can to the spray position where the can stops momentarily but is rotated positively at high
speed (approx. 2,000 rpm). The spray gun is energized and the interior of the can is
sprayed with the liquid coating while the can rotates. This rotation allows the complete
interior of the can to be coated. The coating material that comprises the dried film must
have FDA compliance for this application. The material percentage of solids, normally in
the 20% range, and the viscosity are important factors in successful application of a
continuous film application.
The cans are discharged from the spray application equipment into or onto a conveying
mechanism in route to a thermal curing oven. This mechanism usually provides for an
amount of horizontal rotation that assists in maintaining the distributed coverage and
prevents pooling or sagging of the applied film. In the thin film wet state the material
begins to change and falls out of suspension or emulsion depositing the solid components
onto the substrate.
The thermal curing oven is of multi zone design and allows control over the application of
heat to the items to be cured. The general concept is to raise the temperature slowly in
the first zone. This assists in the release of the solvent present and also pre heats the
water for evaporation. The second and subsequent zones are normally heat zones and can
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PAGE 6
temperatures are raised and held at 4G0»F for 30 to 60 seconds. This time at temperature
is required to affect the crosslinking of the polymer film deposited and to evaporate the
residual water in the coating.
PROCESS EFFICIENCY:
The Coors Can Manufacturing Plant is currently applying both the standard accepted
coating material and testing the Ultra low VOC coating material. We are currently
evaluating the operational parameters of the new materials in comparison to the normally
accepted materials. The Ultra Low VOC material has initially exhibited a greater
application latitude that has allowed process efficiency to be at the high end when
compared to normal materials.
COST EFFICIENCY:
Cost was not a major concern during the early development stages. The' successful
development of a material that could be applied, posses the required film properties and
contain a minimal volume of VOC was the first and foremost goal. It was recognized by
the development team that cost would become a considerable factor to eventual
commercialization. Economics of scale in the coating manufacture have not been
achieved. Data for the application costs is being collected on a continuing basis. Actual
costs can only be estimated at this time. Initial results tend to indicate a definite trend of
lower weight of applied film required to achieve the performance necessary. Another
initial trend indication is that of improved transfer efficiency or a reduction in loss of
material during application.
ENERGY EFFICIENCY:
The total energy consumption requirements have been compared for the Low VOC and
the standard technologies with end of pipe controls (Table 1). Estimates in units of
millions of BTUs per billion cans are provided. The estimates include both BTU values
obtained directly from natural gas (thermal ovens) and BTU values for the electrical
power consumption. Since end of pipe controls would not be necessary with the Ultra
Low VOC material, approximately 17,405 million BTUs are saved per billion cans or a
potential annual industry saving of 1,782,715 million BTUs.
PRODUCT QUALITY:
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PAGE 7
The quality of the coated interior of the can is an important consideration from both
chemical and physical aspects, and as a container for a consumable product. A material
must meet the requirements of FDA. laboratory scale application and final film property
evaluation as a requisite to being considered for any limited scale use in a production
environment. The material currently being tested meets or exceeds the quality
requirements established for the physical can profile utilized by Coors. Additional
development of the properties of the final film will be required to meet the specifications
of other can profiles and individual requirements of other beverage users.
ENVIRONMENTAL IMPACT AND LIFE CYCLE ANALYSIS:
The low VOC internal coating technology offers the opportunity to realize real pollution
prevention and real waste reduction. Wastes are not shifted from one media to another nor
are wastes shifted from being emitted to being stored. Preliminary mass balance
calculations indicate a net reduction in generated pollutants. It is also pertinent to note that
the contaminants are not incorporated into products and volume reductions in pollutants are
not neutralized by increased toxicity. The development of this process yields a product that
reduces pollutants in both emitted and liquid/solid wastes. These savings are realized from
the point of coating manufacture through applied use and final disposition. All the following
estimates include values from the point of manufacture to the final applied disposition.
The real pollution prevention and real waste reductions are accomplished in these ways:
° The low VOC internal coating is manufactured in aqueous media with no solvent
required for manufacture. This fact limits the potential for emission and or end of pipe
controls with their energy consumption and associated emissions.
° The low VOC internal coating contains less VOCs and hazardous air pollutants than any
current commercial thermal-curable coating.
0 A potential for an additive reduction in VOCs and hazardous air pollutants through a
significant increase in transfer efficiency requiring less material being sprayed.
0 A potential for an additive reduction in VOCs and hazardous air pollutants through
superior film properties requiring less material applied.
0 A major reduction in hazardous wastes generated during manufacture and during
application as the low VOC internal coating and the waste are not classified as
hazardous.
° The elimination of the incinerator-generated emissions of CO, NOx SOx, and C02at the
application site.
An initial estimate was made utilizing ASTM method 24 testing of the thermally cured
coating materials. Method 24 is the approved method for determining the volatile content
of coatings. Current materials in general use for internal can coating contain 140.8 tons
4-39
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PAGES
of available VOC per billion cans, which is substantially equivalent to most compliant
internal can coatings available. The Ultra low VOC can coating material, in contrast,
contains 40 tons of available VOC per billion cans produced as measured by EPA Method
24, The same coating material when evaluated by actual formulation data yields only
26,6 tons of available VOC per billion cans produced. This is theorized to be attributed to
the known shortcomings of EPA Method 24 which are magnified as the actual VOC
content becomes lower. When viewed from the respect of volume of VOC purchased in
each coating per billion cans produced, the Ultra low VOC material has an advantage of
an 80% reduction of available emissions.
In addition to VOC emissions, CO. emission estimates were compared for the two
technologies. The CO. estimates were calculated from EPA conversion factors for natural
gas combustion, and also for C02 emission factors for electrical power production. The
CO; estimates for both technologies therefore include the CO, emissions which occur at
the power plant generating the electrical power used for the controls and blowers in the
thermal oven process. When this technology is compared to incineration, the emissions
savings of C02 per billion cans produced is currently estimated at 987.25 tons.
Current accepted technology and the proposed Ultra Low VOC technologies were
compared for waste saving's impact. The first comparison is of the current technology to
the proposed technology, both without incineration. The next comparison is of the
current technology with incineration and the proposed technology without an incinerator.
Table #2 indicates the proposed technology has a potential waste saving of 150.2 tons per
billion cans produced when compared to the current technology without incineration.
Table #3 compares the current technology with incineration to the proposed technology
without incineration and indicates potential waste savings of 1,048.434 tons per billion
cans produced. The Ultra Low VOC technology has the potential to provide a waste
saving over currently accepted materials and, if accepted as a regulatory alternative to
incineration, can provide substantial pollution prevention and energy savings.
A comparison (Table 4) was made for hazardous air pollutants (HAPs). Almost half of
the VOC content in the current compliant internal coatings are glycol ethers, which are
listed hazardous air pollutants in the new Clean Air Act regulations. Therefore, it is
pertinent that with upcoming higher scrutiny and tighter controls for HAPs, a technology
with lower HAP emissions will be highly preferred. Estimated HAP emissions from the
normal compliant internal coating is calculated to be 63 tons/billion cans, and estimates
indicate that the HAP emissions of the Ultra Low VOC technology are approx. 2.3
tons/billion cans. This represents a reduction of 96%.
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PAGE 9
Many operating can facilities do not currently utilize end of pipe controls. When
estimates are evaluated for these facilities, strictly as a pollution prevention technology,
they indicate a potential annual emissions savings per billion cans of 36 tons of hazardous
waste, 114,2 tons of VOCs, 60.7 tons of HAPs, 987.25 tons of CO, and an energy savings
of 17,405 million BTUs.
If acceptance of this technology, as a alternative to thermal destruction, would be
accepted, the impact could generate an estimated annual emission savings per billion cans
when compared to incineration of 36 tons in hazardous waste, 20.568 tons in VOCs, 9.25
tons in HAPs and 987.25 tons in €Oz,
NATIONAL IMPACT:
If the Ultra Low VOC technology was developed for and transferred industry wide, there
would be subsequent notable pollution prevention impacts. The can manufacturing
industry is large, with approximately 130 billion cans produced each year. The vast
majority of these cans are aluminum cans, approximately 103 billion per year (2).
Estimates for the impact of this technology on a national basis have been calculated by
increasing the rate per billion cans to the national production rate.
If recognized as an alternative and adopted across the board, Ulta Low VOC technology
would result in estimated emission savings from can manufacturing of 3,708 tons in
hazardous waste, 2118.5 tons of VOCs, 6,252.1 tons of HAPs, and 101,686.75 tons of
CO,. These impacts can be considered even more substantial taking into account the
regional clustering of can manufacturing plants in several states. The development of a
material that meets the industry requirements and subsequent implementation of this Ultra
Low VOC technology could therefore have a significant impact upon a regional pollution
prevention basis.
INDUSTRY ACCEPTANCE;
Current Ultra low VOC coatings, being tested at Coors, have sufficient flexibility and
withstand post forming and pack stability for the beer beverage market. Newer, more
flexible, coatings are currently being developed to meet the broader beverage packaging
requirements. When the new materials become available there should be an enthusiasm
in the industry to evaluate these coatings. Technically, these materials can be developed
to meet the requirements of the industry.
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PAGE 10
Cost will continue to be a major concern in the competitive environment of the industry
but should improve as the market grows and economies of scale develop. It should be
apparent that industry can and will strive to develop systems, processes and materials that
will eliminate or dramatically improve pollution impacts from manufacturing. A major
consideration will most probably continue to be the impact from Federal, State, and Local
regulatory requirements. With the ability of technologies, such as this one, to have such a
major impact upon energy savings and pollution prevention it would seem highly
advantageous for the regulating agencies to develop specific positive incentive programs.
These incentives would be applicable to concerns that would convert to or engage in the
development of a similar low polluting technology.
The development of a technology such as this can be a lengthy endeavor and industry-
tends to be short term and bottom line driven. These considerations make for a situation
where any definite positive incentive directed toward assisting industry in growing,
remaining competitive and continued operations would prove extremely valuable when
developing a financial case for a development program and budget. A cooperative
approach between industry and government would generate a measurable success for
industry, government, and the environment,
SUMMARY:
The Ultra low VOC coating technology being tested at the Coors Can Manufacturing
Plant has been a developmental success for about one year. Very substantial pollution
prevention benefits are evident with this technology in very low, or zero, VOC and HAP
emissions, and much lower C02 emissions when compared to end of the pipe control
methods. Initial estimates indicate that the Ultra low VOC technology has the potential to
be operationally more cost effective than the alternative technology. This technology is
currently being evaluated in a foil production scale on a limited test basis at the Coors
plant. All production with this technology is currently dedicated to a beer beverage
market, and container product quality is folly acceptable for this market. A coating
material that is more flexible to facilitate post forming is currently desired for many other
beverage markets. New generations of coatings designed around this technology will
have to be developed for the requirements necessary to be acceptable as a universal beer
and beverage material. Now that the technology of producing an Ultra Low VOC can
coating has been developed, future formulations should be capable of being brought to
market in approximately one-half the time or less. The requirements will have to be
investigated and a material developed prior to this technology being considered for use on
a national basis.
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PAGE 1 I
REFERENCES;
1. Randall. P. J. Haz. Materials. 29 (1992) 275-295.
2. Beverage World's Periscope. Vol 112 (1538). p. 17. 1993.
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PAGE 12
TABLE #1
Energy Savings,
Technology
a
Current with
b
Proposed
(c=a - b)
Energy savings
MM/BTU
Billion
18,445
1,040
17,405
MM/BTU
per
Industry
Year
1,889,835
107,120
1,782,715
TABLE #2
Waste Savings.
Comparison of both without incineration.
Waste
generated
(a)
Current
technology
(tons/billion)
(b)
Proposed
technology
(tons/billion)
(c = a - b)
Waste savings
(tons/billion)
Hazardous
Waste Scrap
36.000
0.000
36,000
VOC
140.800
26.600
114.200
CO
0.013
0.013
0.000
NOx .
0.238
0.238
0.000
SO,
0.538
0.538
0.000
co2
67.000
67.000
0.000
Total of waste
(tons/billion)
244.589
94.389
150.200
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PAGE 13
TABLE #3
Comparison with an incinerator on the current technology;
Waste
generated
(tons/billion)
(a)
Current
technology
(tons/billion)
(b)
Proposed
technology
(tons/billion)
(c = a - b)
Waste savings
(tons/billion)
Solid Waste
Hazardous
36.000
0.000
36.000
VOC
47.168
26.600
20.568
CO
0.304
0.013
0.291
NO,
4,313
0.238
4.075
so„
0.788
0.538
0.250
co2
1,054.250
67.000
987.250
Total of
waste
(tons/billion)
1,142.823
94.389
1,048.434
TABLE #4
HAZARDOUS AIRPOLLUTANTS
Technology
HAPs Tons
per Billion
HAPs tons per
Industry Year
Current no
Incinerator
63.0
6,489.0
Current with
9.25
952.75
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PAGE 14
Proposed | 2.3 | 236.9
Low VOC
4-46
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SESSION 5
APPLICATION TECHNOLOGIES/SURFACE PREPARATION
5-1
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PAPERS PRESENTED:
"Advances in Aerospace Coating Technologies: Convergent Spray Technology "
(Paper not available for publication.)
by
Douglas Deason
United Technologies
Huntsville, Alabama
"Encapsulant Lead Paint Remover"
by
Jeffrey Ellermann
Kwick Kleen Industrial Solvents
Vincennes, Indiana
"Utilization of Effervescent Spray Technology to Eliminate Volatile and Toxic Diluents"
by
Michael Smith
Thiokol Corporation
Brigham City, Utah
SERDP, USMC Spray Booth Control and P2 Demonstration"
by
Charles Darvin
U.S. Environmental Protection Agency,
National Risk Management Research Laboratory
Research Triangle Park, North Carolina
5-^
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ADVANCES IN AEROSPACE COATING TECHNOLOGIES:
CONVERGENT SPRAY TECHNOLOGY
by
Douglas M. Deason
and
Jack Scarpa
United Technologies Corporation/USBI
Space Shuttle Operations
New Programs Office
P.O. Box 1900
Huntsville, AL 35807
ABSTRACT
Significant gains in the reduction of volatile organic compound (VOC) emissions from industrial
painting and finishing operations have been achieved in recent years. However, all classes and
types of coatings have not been adequately addressed with best available technology. This is
especially true for high thickness protective coatings requiring significant solvent usage to
deliver and spray-apply these highly filled coating systems. This paper will present a pollution-
preventing technology that uses a solventless spray process to rapidly deposit lightweight highly-
filled coatings. This innovative spray process, Convergent Spray Technology®, produces high
thickness, high performance coatings while eliminating VOCs, significantly reducing hazardous
waste, and using reclaimed or low cost materials as fillers. Convergent spray is so named
because the multi-component solvent-free resin system is mixed within the spray gun, is then
atomized and this stream is converged with the pneumatically delivered powder (filler) stream at
the patented spray gun. Through this method, solvents are no longer required to reduce the
viscosity of the mixture because the filler is separate from the liquid part of the materials supply
system. USBI, the prime contractor on the Space Shuttle Solid Rocket Booster (SRB) program,
is active in broadening the use of the convergent spray process having already demonstrated the
capability of this process to replace thermal protection materials that use methylene chloride and
perchloroethylene and Freon® for launch vehicle applications.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
5-3
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Encapsulant Lead Paint Remover
Jeffrey Ellermann
Kwick Kleen Industrial Solvents
P. O. Box 807
1202 Baraett St.
Vincennes, IN 47591
Jay Bardole
Kwick Kleen Industrial Solvents
P. O. Box 807
1202 Barnett
Vincennes, IN 47591
The purpose of this project is to develop a safe and effective way to remove lead based paint
from structures in need of lead abatement. Lead poisoning occurs in thousands of people every
year, the majority being children. The sole purpose of lead abatement is to remove the lead
hazard. This must be done without creating other hazards. These additional hazards would
include production of harmful lead dust and chemical vapors from volatile organic compounds.
Removing these hazards can also reduce cost. Less ventilation and filter equipment are needed
and a much safer working environment is created for the employee. Until now, the majority of
removal processes created lead dust or VOC vapors. With the Encapsulant Lead Paint Remover
project, a method of removal has been developed which creates no lead dust and emits little or no
VOCs into the environment.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
-------
The risks of children as well as adults being exposed to lead has been well documented in the
past five or six years. Even children with low levels of lead poisoning show decreases in their IQ
scores and other health problems.12 3 4 Occupational lead exposure remains one of the oldest
and most prolific health hazards for working adults.5 The major source of lead exposure is from
paint chips and paint dust. If lead based paint is in or on a home, it can be loosened in several
fashions. Older style homes have windows that slide up and down. Paint that is present where
the window moves will be ground into fine dust and the lead will become a part of the living
environment. It is possible that whatever children touch may contain lead dust and will be
transferred to their mouths, and then, the lead poisoning begins. The paint on the outside of the
house may flake off and easily be tracked into the house becoming part of the living environment
with the same risk. Similar scenarios can be built for doors, walls, and porches that have lead
paint.
The problem of lead poisoning has always been considered greatest in children, however
recently there has been concern for those who are working in lead base paint abatement. The
Occupational Safety and Health Administration has adopted a final standard for occupational
exposures to lead. This standard limits occupational exposure to 50 micrograms per cubic meter
based upon an eight hour time weighted average. The basis for this standard is evidence that
exposure to lead must be maintained below this level to prevent material health impairment and/or
affect the functional capacity of exposed employees.2 In 1992 the Centers for Disease Control
issued an alert that was a "request for Assistance in Preventing Lead Poisoning in Construction
Workers."6 They cited new evidence which associates lead poisoning with abrasive blasting,
sanding, cutting, burning or welding of bridges and other steel structures coated with paints
containing lead. The following year the National Institute for Occupational Safety and Health
created the Adult Blood Lead Epidemiology Surveillance program due to a concern for lead
-j
exposure in workers depainting structures such as bridges and water towers.
Many homes still exist that have bottom layers of paint that were prepared by stirring white
lead, linseed oil and turpentine together until a smooth mixture was attained. After several days
the paint dried, but soon started to flake. Commercial house paints became available and often
contained lead. The use of paints containing lead in private residences was banned in 1978. As
many as 75 percent of homes built before 1980 are reported to have some lead based paint in
them. There are several commercial products on the market that are effective in testing for the
presence of lead in paint.8,9
There have been several approaches to the removal of lead based paint, each having
advantages and disadvantages. Surfaces that are small and can be easily removed from the home
or structure can be taken into a shop and stripped using a solvent based stripper. The risk of the
organic stripper itself aside, this approach is appealing because it contains the lead very well. The
lead is contained in the waste liquid and standard flocculation methods can be used to clean the
waste water to levels that are acceptable for disposal. If the worker elects to use a high pressure
water wash to remove the paint residue and the organic stripper, there is a high risk that the
residue of lead still on the item being stripped will be atomized and enter the breathing zone of the
worker. This risk may be greater than acceptable. Other methods of cleaning the remover and
5-5
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residue from the item are quite safe and effective, but more work intensive. Organic solvent
stripper in a semipastc form may be used on surfaces that cannot be taken into a shop. Clean up
is difficult and work intensive, but reasonably safe if high pressure wash is avoided. Exposure of
the worker to the organic solvents and the release of VOCs to the environment are hazards that
must be considered if this approach is used.
Perhaps the most widely used approach to the removal of lead based paint is mechanical.
Blasting is often used because it is portable and removes the paint. Containment and collection of
the paint chips and the dust is very difficult. The dust generated makes it likely that anyone in the
area will breath the lead containing dust. This is evidenced by the concern for the workers
mentioned earlier who were stripping and repainting bridges. If the stripping is outside of the
house, can the soil be protected from contamination and subsequent "tracking" into the home? If
interior surfaces are sand blasted can all of the dust be removed from environmental surfaces? In
most cases the answer is "No".
Another approach is to encapsulate the lead paint right where it is. The appeal is that there
should be little or no exposure to workers. The fact remains that the lead problem is still present
and will have to be faced sometime even if it is not until the structure is razed. An effort has been
made to use a water based stripper that removes the paint in clumps and stabilizes its lead
content.10 While this is a good approach, the product is usually in place until it is dry, then when
it is removed dust is again generated with all the risks that accompany it. This method of
application is very labor intensive and difficult to use for large projects.
Individuals engaging in lead-based paint activities should be properly trained and certified.
Training should include proper work practices and health and safety protection. In addition to
employee training, engineering and work practice controls which would minimize the level of
airborne lead must be implemented. This includes modifying or substituting established processes,
equipment or products; equipping exhaust ventilation equipment with a dust collection system to
capture lead dust and fumes at the point of generation; and amending general work practices to
reduce the spread of dust. Other work practices and engineering controls such as increasing the
exhaust ventilation system and keeping the worksite as clean as possible should be developed and,
where possible, put into effect.11 In addition to protecting its own employees, the construction
contractor will be expected to conduct its activities in a manner to protect third parties from
exposure to hazardous materials. OSHA is drafting guidelines which would limit the chemicals to
which office workers may be exposed. The contractor will have to be careful that its activities
will not expose those workers to lead dust or chemicals which exceed the OSHA limit.6 These
controls to improve the work and health conditions are costly and time consuming. An abatement
method which would eliminate the lead dust or chemical vapors could drastically reduce cost and
time. The air filters and ventilation equipment are not necessary if little or no air contaminates are
produced.
The alternative seems to combine the advantages of the existing methods and eliminate their
collective risks. Whatever the method, it must remove the lead based paint from the substrate.
Elements of a good approach would contain the lead based paint in a matrix without the
generation of dust. The system needs to be portable enough to be taken to any site and the
5-6
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stripper easily be applied to large surfaces. Simple flocculation methods to clean up small
amounts of wash water can easily be used to reduce waste.
The approach recommended is one that uses a water based stripper that is strongly alkaline.
This has been used to remove paint for some time and is very effective. It may darken the wood,
so if a clear finish is applied after stripping, a wood toner must be used. Along with the aqueous
alkaline solution a polymer that is swelled by the alkaline solution is used. The result is a material
that has a high viscosity and a good coliesiveness. When this is applied to the paint, the aqueous
alkaline solution softens the paint and the paint film is absorbed into the polymer. This stripper
will not work as fast as a methylene chloride solvent stripper, but it will penetrate multiple layers
of paint in an hour. The resident time will be dependent upon the number of layers of paint, the
temperate and other environmental conditions. When the paint is completely absorbed into the
remover matrix, the film can be removed with a putty knife or joint knife. The knife can be used
to get under the film, which can then be peeled off in long rubbery strips. The remover that has
been in contact with the air will become rubbery and form a substantial film. The film will seal the
stripper that is under it and it will stay moist for a longer period of time. Just how long it will stay
moist will depend on the temperature and other environmental conditions. The strips that are
removed can be collected in a plastic bag, sealed, and disposed of by methods normally used for
hazardous waste. The wood remaining will be moist and will have a small amount of residue.
This can be gently washed and the small amount of water collected. Tri sodium phosphate in the
wash water will help to immobilize the lead. The waste water can then be flocculated and the lead
concentration will be reduced to levels that are considered acceptable for wastewater. The total
mass of the remover applied to the paint is small, and as a part of the curing process, there is
evaporation of the water solvent thus the total mass of the stripper is reduced without adding
VOCs to the environment.
A thick semipaste form of the stripper can be applied with a putty knife. This is ideal for small
areas but would be very work intensive for large watts and structural surfaces. The product in a
liquid form can be applied with a wand. The product is designed as a two part system, each is a
water like solution that can easily be pumped. It is recommended that air driven pumps be used
to deliver each of the solutions to a specially designed wand. The solutions mix about two inches
beyond the end of the wand, and react immediately to form a high viscosity material similar to the
semipaste. It can be removed in the same manner as the semipaste form after an appropriate
curing time.
The white lead paint applied directly to bricks is very difficult to remove, and it will be
necessary to remove the layers of more modem coatings, and then apply a second coat of the
stripper to the base coat in order to remove it.
The advantages of this form of lead based paint remover are:
1) There is never any lead laden dust generated.
2) The paint is encapsulated in a moist tough film.
3) The remover itself does not add very much mass to the waste stream
4) The lead in the wastewater from the final cleanup is easily removed and
disposed of.
5-7
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5) Application is easy for either large surfaces or small surfaces.
6) Cost to set up is low.
7) Cost of aqueous strippers is low.
8) Since it is a water based remover there are no VOCs.
Lead poisoning must be reduced. The best way to do this is to eliminate the source of the lead.
As stated before this must be done in the safest manner possible to prevent additional cases of
lead poisoning from occurring during the abatement process or after the abatement is finished.
With dedicated research and new technology, the process described in this paper will enable the
abatement of lead paint from substrates without introducing airborne lead dust or VOC vapors
into the breathing environment.
5-8
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1
2
3
4
5
6
?
8
9
10
11
REFERENCES
Ernliart, Claire, The Scientific Debate is Not Over. Paper presented at Lead Tech '94,
Washington, D C. October 17-19, 1994.
Bornschein, R.L. and Grote, JA. Effects of prenatal lead exposure on infant size at birth,
EPA/EEC Conference on Lead. Edinburg, Scotland, Sept 1986.
Schwartz, J. and Landrigan, P.J. Lead-Induced Anemia: Dose-Response Relationships and
Evidence for a Threshold. AJHP. 80: 165-8, 1990.
Rabinowitz, M.B., Wang, J-D & Soong, W.T. Apparent Threshold of Lead's Effect on Child
Intelligence. Enviromental Contamination and Toxicology. 48: 688-95, 1992.
Gaffrey, Marc. Lead Exposure Presentation. Paper presented at Lead Tech '94, Washington,
D.C, October 17-19, 1994
Request for Assistance in Preventing Lead Poising in Construction Workers Journal of the
American Medical Association, 4/15/92, Vol. 267 Issue 15, p2012, 1/2 p.
Adult Blood Lead Epidemiology and Surveillance, Journal of the American ;Medical
Association, 3/17/93, Vol 269 Issue 11, p 1373, 1/2 p.
Frandon Lead Alert Kit sold by Frandon Enterprises, LeadCheck Swabs sold by Hybrivet
Systems, Inc.
Lewis, W. S., Papamicolopoilos, CD., and Thompson, O. Identification of Lead Based Paint:
Summary of Techniques. Georgia Tech. NAHRO conference. October 27, 1987.
Stripper Makes Paint Removal Less of a Blast. Civil Engineering. April 1992. Vol 62, Issue
4, p. 85.
Rosmarin, Susan. Lead in Construction Industry. Paper presented at Lead Tech '94,
Washington D.C. October 17-19, 1994.
5-9
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The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
Utilization of Effervescent Spray Technology to Eliminate Volatile and Toxic Diluents
Michael W, Smith
Thiokol Corporation
P.O. Box 707 M/S 243
Brigham City, UT 84302-0707
Phone - 801-863-6103
FAX - 801-863-2271
INTRODUCTION
Thiokol Corporation uses several thermal setting urethane and epoxy slurry formulations in the
production of rocket motors and pyrotechnic devices. Some of them are used as liners to bond the
propellant or illuminant to the case wall. Liner formulations typically contain solids which act as
thixotropic agents, thermal resistance and inert fillers. Application of these liners is accomplished by
methods such as spraying or atomizing with centrifugal force (sling lining). The solids loading causes
an increase in the viscosity so that a diluent is required in order to spray them. Typically ozone
depleting, toxic and/or flammable solvents are utilized. The reduction or elimination of these chemicals
is an important focus of this conference.
Two illuminant flares with case diameters of two and five-inches are produced at Thiokol.
Because of the case diameter, spraying has proven to be the most effective method of applying this liner.
The formulation consists of an epoxy binder filled with inert and thixotropic solids. Undiluted this
material has a viscosity which ranges between 300 and 500 poise. Methylene chloride is added to the
mixture to thin the material to a sprayable viscosity. Devilbiss spray equipment is used with a tip that
produces a 45-degree hollow cone pattern. Several passes are required to obtain a liner thickness of
30-40 mils. Multiple passes allows the methylene chloride to evaporate between coats.
Recently OSHA mandated that the current process was unacceptable because worker exposure
to methylene chloride was above the threshold limit value (TLV). Two options were proposed to meet
reduce or eliminate exposure:
1) Identify a method of spraying undiluted liner.
2) Protect workers by isolating the process with either worker protective equipment or by
changes to the facility.
The program decided on the first option based on comparative cost estimates. The following
technologies were considered for evaluation to accomplish this goal:
1) Air assisted
2) Airless
3) Effervescent or two phase flow nozzle
A commercial coatings application company was consulated about the feasibility of using air
assisted and airless spray systems. Samples of the undiluted liner were sent for analysis and evaluation.
The air assisted system was never evaluated because the viscosity of the undiluted liner was outside
equipment parameters.
Airless spray system tests were run and the results were evaluated. Based on these tests, this
option was dropped because the pressures required to atomize the liner were too high to spray small
diameter tubes. This led to the development and evaluation of the effervescent or two phase flow nozzle.
5-10
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DISCUSSION
Background
The effervescent nozzle concept was obtained from Purdue University. Work accomplished to
date on the University level has focused on characterizing nozzle performance with Newtonian fluids with
viscosities up to 100 Cp [1]. The application proposed by Thiokol involved using this technology with
viscous non-Newtonian slurries. Purdue University reviewed the rheological properties data of the liner
and based on their analysis recommended that Thiokol should proceed with feasibility testing.
Approach
The concept of operation for the effervescent nozzle is shown in Figure 1. It is based on
initiating two phase flow under pressure with an aerator chamber which introduces gas into a liquid. This
is accomplished upstream from the orifice. As the mixture leaves the nozzle, atomization is achieved as
a result of the instability of the gas and liquid phases during rapid depressurization when it expands going
through the orifice. This design has been documented by Purdue University in published literature [2],
Theoretical calculations as well as empirical work have shown that atomization is accomplished
independent of fluid viscosity. A prototype unit was designed and fabricated for use in spray testing at
Thiokol.
The flare program initially drove the search for the effervescent nozzle. When the technology
was identified, other programs at Thiokol also expressed interest in conducting feasibility testing. A list
of all the materials that were evaluated in this study is given below:
1) Carbon filled epoxy liner (Flare)
2) Asbestos filled polyester liner
3) Carbon filled polyurethane liner
4) Conoco HD-2 preservative grease
Testing was done with the following objectives in mind:
1) Show atomization occurs.
2) Determine drop size, texture and uniformity of sprayed materials.
3) Determine a pressure range for future quantitative evaluations.
Because this was a feasibility study and not meant to characterize the nozzle, only qualitative
evaluation of the spraying process and substrates was done. Testing for material and bondline strengths
was beyond the scope of this study.
Equipment and Procedure
The spray equipment consisted of the effervescent nozzle connected to liquid and gas manifolds.
The liner material was fed to the manifold from a one gallon fluid reservoir. Nitrogen was used to
pressurize both the gas and liquid sides. The apparatus used is shown in Figure 2. It is the same design
that has been used in documented studies done at Purdue University [2].
The liner was mixed in a Ross mixer using standard Thiokol mix procedures. The end-of-mix
Brookfield viscosity was taken at the spray temperature using a TD spindle. Samples were sprayed over
the given pressure range holding both the substrate and nozzle stationary. The spray action time was
recorded to give an indication of the onset of slumping. Liner thickness was measured using a wet film
5-11
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gauge, A qualitative determination of the texture and coverage was made by a visual examination. High
speed motion pictures as well as real time videos of the spraying process were made. Sprayed samples
were then placed in an oven for curing. Still photographs were taken of all the cured substrates.
Results
The results from these feasibility tests are summarized in the sections below. Each one is
identified by the sprayed material. The parameters used for spraying are given as well as the results.
Carbon Filled Bpoxy Liner (Flare).
The liner was mixed at 75 °F and heated to 150°F for spraying. The Brookfield viscosity at
150°F was 400 poise. Atomization pressure ranged between 300 and 500 psig.
Based on these test results it was concluded that the nozzle was able to atomize and spray the
above formulation. The material was sprayed in a cone shaped pattern resulting in a filled circle on the
substrate. The thickness was uniform across two thirds of the circle but thinned with increasing radius.
The surface texture of the sprayed liner ranged from orange peel to smooth at a thickness of 30-40 mils.
The best results were obtained when spraying at 500 psi.
In order to spray the flare tubes a hollow cone spray pattern is required. With the success of the
feasibility testing, the next challenge was to tailor the spray pattern. First attempts were made with
commercial spray tips used in conjunction with the effervescent nozzle. They proved ineffective. A
nozzle tip was then designed and tested by Thiokol which was successful in spraying the desired pattern.
Asbestos Filled Polv Ester Liner.
The liner was mixed at 150°F and then sprayed. The Brookfield viscosity at 150°F was 850
poise. Two runs were made at 900 psig using this material. Further testing was suspended because the
nozzle clogged.
Based on test results it was concluded that the nozzle was able to atomize and spray the above
formulation. The material was sprayed in a cone shaped pattern. However the nozzle clogged before
a layer of material could be sprayed. A lumpy non-uniform coat was obtained which was attributed to
the fibrous nature of the asbestos.
Carbon Filled Polvurethane liner.
Two batches of liner with this formulation were sprayed. The first batch of liner was mixed at
150°F and then sprayed. The Brookfield viscosity at 150°F was 650 poise. The pressure ranged
between 400 and 800 psig.
Based on test results it was concluded that the nozzle was able to atomize and spray the above
formulation. The material was sprayed in a cone pattern resulting in a filled circle on the substrate. The
thickness was uniform across two thirds of the circle but thinned with increasing radius. The texture
ranged from smooth to orange peel at a thickness of 35-50 mils. The best results were obtained when
spraying at 750 psi.
5-12
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The second batch of liner was mixed and sprayed at 75°F. The Brookfield viscosity at 75°F was
1750 poise. Atomization pressure ranged between 700 and 1200 psig.
Based on test results it was concluded that the nozzle was able to atomize and spray the above
formulation. The material was sprayed in a cone pattern resulting in a filled circle on the
substrate. The thickness was uniform across two thirds of the circle but thinned with increasing radius.
The texture of most samples was orange peel at a thickness of 20-40 mils. The best results were obtained
when spraying at 900 psi.
CONOCO HD-2 preservative grease.
The grease was sprayed at 75'F (ambient) and 150'F onto a plastic surface to determine coverage
and texture. The Brookfield viscosities at 75°F and 150°F were 1400 and 600 poise respectively. The
material was sprayed in a cone pattern resulting in a filled circle on the substrate. The material texture
was semi-smooth with a thickness of 10-20 mils. This material was atomized well at ambient
temperatures at pressures less than 100 psig.
Based on the results of these tests it was concluded that the nozzle was able atomize and spray
the above materials. Heating was not required to reduce the viscosity for atomization.
Table I given below is a tabulation of the important data generated in this study.
TABLE I
Material
Viscosity
(Poise)
Spray
Temperature
(*F)
Optimum
Spray
Pressure
(psig)
Thickness
(mils)
Texture
Carbon Filled Epoxy
400
150
500
30-40
Orange Peel/
Smooth
Asbestos Filled Polyester
850
150
900
NA
Lumpy
Carbon Filled Polyurethane
650
150
750
35-50
Smooth/
Orange Peel/
Lumpy
1750
75
900
20-40
Orange Peel
Conoco HD-2 grease
1400
75
<100
10-20
Semi-Smooth
Summary
In summary, the following observations were made based on the results of feasibility testing. The
effervescent nozzle was capable of atomizing all the materials evaluated in this study. Based on visual
observations it was seen that the drop size distribution varied greatly within a sample run. All samples
were successfully sprayed at pressures less than 1000 psig.
The first priority of this testing was to find a system that would spray undiluted flare liner. The
testing outlined above proved the feasibility of using the effervescent nozzle for that purpose. Further
evaluations were done with flare liner to characterize the specific spray process. The requirement to
5-13
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spray a hollow cone were also met with the design of a spray tip used in conjunction with the effervescent
nozzle. The flare program is currently in the process of incorporating this technology into the production
line.
CONCLUSIONS
Based on the results of these tests, it was concluded that effervescent nozzle is a viable option for
spraying high viscosity liquids and slurries at pressures less than 1000 psig. This allowed for the
spraying of viscous materials without the use of ozone depleting, toxic and/or flammable solvents as
diluents.
5-14
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REFERENCES
Proceedings 1, Bush, S.G, and Sojka, P.E., Entrapment by Effervescent Sprays at Low Mass Flow
Rates. Thermal Sciences and Propulsion Center School of Mechanical Engineering
Purdue University, West Lafayette, IN 47907-1003. In: ILASS-AMERICAS 94, 7th
Annual Conference on Liquid Atomization and Spray Systems Extended Abstracts.
Bellevue, Washington, p. 186
2. Geekler, S.C. and Sojka, P.E., Effervescent Atomization; Limitations due to
Viscoelasticity. Thermal Sciences and Propulsion Center School of Mechanical
Engineering Purdue University, West Lafayette, IN 47907-1003. ]n: ILASS-
AMERICAS 94, 7th Annual Conference on Liquid Atomization and Spray Systems
Extended Abstracts. Bellevue, Washington, p. 181
5-15
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Utilization of Effervescent Spray
Technology to Eliminate Volatile and
Toxic Diluents
ui
i Michael W. Smith
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
CORPORATION
SCIENCE & ENGINEERING
AdhesiVB Materials & Processes
-------
INTRODUCTION
• SOME PROCESSES AT THIOKOL REQUIRE SPRAYING OF URETHANE AND
EPOXY SLURRY FORMULATIONS
• ILLUMINANT FLARE LINER
• CARBON FILLED EPOXY
• 400-700 POISE VISCOSITY @ 75-135T
• DILUTED WITH 1:1 RATIO OF METHYLENE CHLORIDE
• WORKER EXPOSURE ABOVE TLV MANDATED ELIMINATION OF
METHYLENE CHLORIDE
• SPRAYING UNDILUTED LINER CHOSEN TO MEET MANDATE
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
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U1
I
CD
FLARE
CASE
ILLUMINANT
GRAIN
LINER
BULKHEAD
PARACHUTE
COMPARTMENT
D - INSIDE DIAMETER TWO SIZES PRODUCED 2.5- AND 4-INCH CASES
ILLUMINANT FLARE CROSS SECTION
~YM
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
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METHYLENE CHLORIDE ELIMINATION
• SPRAYING OPTIONS IDENTIFIED
• AIR ASSIST
• AIRLESS
• EFFERVESCENT NOZZLE
• CENTIRIFUGAL DISK
• PRELIMINARY EVALUATION RESULTS
• VISCOSITY OF LINER MATERIAL OUTSIDE OF AIR ASSIST EQUIPMENT
PARAMETERS
• AIR} FQQ ATOMI7ATION OPFRATINf^ PRPQQI |Pp ^000
i \i Fi Lai Emm Iwr VpJ f \ I V»/ IVI I mum i \ I I \+J I i Vii ii I 11 \ I MM I I 1 L—• I \ 4— O x« W v I V^r I VJ3
• SAFETY AND PROCESSING CONCERNS
• EFFERVESCENT NOZZLE CHOSEN FOR FURTHER EVALUATION
• CENTRIFUGAL DISK COULD BE USED AS A BACK UP IF REQUIRED
• UNABLE TO LINE SMALL DIAMETER CASES
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
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EFFERVESCENT NOZZLE EVALUATION
• BACKGROUND
• CONCEPT OBTAINED FROM PURDUE UNIVERSITY
• PROVEN WITH NEWTONIAN FLUIDS WITH VISCOSITIES UP TO 100 cP
• THIOKOL APPLICATION FOR NON-NEWTONIAN FLUIDS WITH VISCOSITIES
RANGING BETWEEN 500-2000 POISE
U1
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CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
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ATOMIZING FLUID
(N2, Air, etc)
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LIQUID
AIR INJECTION
MANIFOLD
SINGLE PHASE
FLOW
mmmy/m v///////////m.
/
// \\\,hx^yymsss\'h\vK\fb\sssmss\m^
ORIFICE
GAS EXPANSION/
LIQUID ATOMIZATION
TWO PHASE
FLOW
EFFERVESCENT NOZZLE CONCEPT DRAWING
'€>& CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
-------
TPQTlMfi
I CO I IllM
• MATERIALS EVALUATED AT THIOKOL
* ¦"**¦» IT'S ife. I •*"*< t 1 W r"t 4"%. V > V * / I"""* t A I"""* I I Ik t f — fS. \
• CARBON FILLED EPOXY (FLARE LINER)
ik f% i*** r— /™\
-------
LIQUID FLOW
CONTROL VALVE
LIQUID 1
RESERVOIR
NOZZLE
NITROGEN
FLOW
P-J < P2 CONTROL
VALVE
LIQUID LINE
NITROGEN LINE
SPRAY EQUIPMENT SCHEMATIC
corporation
SCIENCE & ENGINEERING
Adhesive Materials & Processes
-------
PROCESSING
• LINER MATERIALS MIXED IN ROSS MIXER USING STANDARD THIOKOL
PROCEDURES
• END-OF-MIX (EOM) BROOK FIELD VISCOSITY AT MIX TEMPERATURE
• TD SPINDLE @ 5 RPM
• SUBSTRATE AND NOZZLE HELD STATIONARY DURING TESTING
• KRAFT PAPER USED FOR SUBSTRATE
• FILLED CONE SPRAY PATTERN
I
EO
• LINER THICKNESS MEASURED WITH WET FILM THICKNESS GAUGE
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
-------
RESULTS
• OBJECTIVES MET FOR SPRAYING FLARE LINER @ 75°F
• VISCOSITY - 600 POISE
• SPRAY PRESSURE - 500 PSIG
• SPRAYED HOLLOW CONE SPRAY PATTERN
• OTHER MATERIALS
Material
EOM
Viscosity
(Poise)
Spray
Temperature
(°F)
Optimum
Spray
Pressure
(psig)
Thickness
(mils)
Texture
Asbestos Filled Polyester
850
150
900
NA
Lumpy
Carbon Filled Polyurethane
650
150
750
35-50
Orange Peel
1750
75
900
20-40
Orange Peel
Conoco HD-2 grease
1400
75
<100
10-20
Semi-Smooth
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
-------
SUMMARY
• NOZZLE PROVEN FEASIBLE IN SPRAYING A NUMBER OF THIOKOL
MATERIALS
• ALL SPRAYING ACCOMPLISHED AT LESS THAN 1000 PSIG
• FILLED CONE AND HOLLOW CONE SPRAY PATTERNS ACHIEVED
• FLARE PROGRAM CURRENTLY IMPLEMENTING EFFERVESCENT NOZZLE
IN LINER SPRAY PROCESS
U1
i
NJ
ON
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
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CONCLUSIONS
• EFFERVESCENT NOZZLE IS CAPABLE OF SPRAYING NON- NEWTONIAN FLUIDS
• CAN BE USED TO ELIMINATE HAZARDOUS DILUENTS
• VOC
• ODC
• TOXIC
• FLAMMABLE
Ui
t
NJ
CORPORATION
SCIENCE & ENGINEERING
Adhesive Materials & Processes
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SERDP, USMC
SPRAY BOOTH CONTROL AND P2 DEMONSTRATION
By
Charles H. Darvin
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
. Research Triangle Park, NC 27711
This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Prepared for:
TJ.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
5-28
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INTRODUCTION
In 1993, the Strategic Environmental Research and Development Program (SERDP) office
approved a research program to provide a comprehensive pollution prevention (P2) strategy for military
depot facilities. The research and development (R&D) is being conducted by a consortium, consisting of
the U.S. Marine Corps (USMC), Pennsylvania State University's Applied Research Laboratory (ARL),
and the U.S. Environmental Protection Agency (EPA).
The goal of this research program is to develop and evaluate innovative manufacturing and
emission control technologies that manifest a F2 philosophy to reduce total emissions from manufacturing
and maintenance processes. The focus of the program is on painting and surface cleaning operations
which represent over 75 percent of the total pollutant emissions from typical Department of Defense (DoD)
facilities.
The program is divided into two parts. First, innovative P2 technologies for painting and surface
cleaning processes will be identified. Full scale demonstration of acceptable alternatives will follow.
Anticipated technologies to be studied and demonstrated include ultra low volume (ULV) paint
technology, which is predicted to reduce paint use and emissions by 25 percent; and the use of n-
methylpyrrolidone (NMP), as a surface cleaning solvent substitute alternative for methylene chloride.
Second, R&D studies will be conducted on the use of ultraviolet/ozone (UV/ozone)
radiation destruction of volatile organic compound (VOC) emissions integrated into a novel spray booth
flow management design concept. Fundamental and applied research on the UV/ozone technology will be
conducted at the ARL, utilizing a 2000 cfm (56.6 mVmin) pilot scale laboratory system. The results will
be transferred to and implemented in a foil scale 45,000 cfm (1274 mVmin) demonstration system. An
integral part of this demonstration is the full scale validation of the exhaust flow management concept
called recirculation and partitioning. This concept will reduce the control system treatment volume from
120,000 to 45,000 cfm (3398 to 1274 m3/min). This booth design concept will significantly reduce the
cost of operating emission control technologies for paint spray booths.
PAINTING AND SURFACE CLEANING PROCESSES
ULV Paint Delivery System
An initial objective of the evaluation of an innovative paint pumping device (the ULV system) was
to prove its feasibility for the Marine Corps Logistics Base (MCLB) Chemical Agent Resistant Coating
(CARC). The ULV system tested, manufactured by Air Compliance Technology, Greensboro, GA, is a
paint delivery system designed to improve the performance of airless guns. It is different from
conventional high-pressure paint systems in that, rather than using a piston pump to pump the paint to high
pressure, it uses a nitrogen-pressurized floating piston to pressurize paint in a high-pressure-capacity
container. Improved performance Is obtained primarily because the ULV system allows airless spraying at
a lower paint pressure than conventional airless (500-800 psi [3447-5516 kPa] for ULV vs. 1500-2000 psi
[10,342-13,790 kPA] for conventional airless).
During preliminary trials by the manufacturer, it was found inappropriate for this type of
application. Higher pressures (700-800 psi) caused compaction of the material in the lines and on strainer
and filter screens. This clogging effect can be eliminated if pressures lower than 500 psi are used. The
materials sprayed with the ULV system included one- and two-component CARCs and a primer. The
spray pattern was found unacceptable, having heavy "crows feet" or heavy edges.
5-29
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N-methylpyrrolidone (NMP)
The objective of this task was to demonstrate the effectiveness of P2 technologies or processes in
reducing hazardous air pollutant (HAP) emissions resulting from paint stripping by immersion in
methylene chloride. Methylene chloride is a HAP, a suspected carcinogen, and one of 17 chemicals on the
EPA's 33/50 list of priority pollutants. NMP, a non-HAP and less volatile solvent, was identified and
tested as a paint stripping alternative to methylene chloride and is currently being used at the MCLB in
Albany, GA,
FLOW MANAGEMENT AND CONTROL TECHNOLOGY
Air Recirculation and Partitioning
The dominant factor in controlling spray booth emissions is the cost resulting from the need to
process large volumes of contaminated air. Therefore, the main objective of this task was to reduce the
amount of contaminated air to be treated by an end-of-pipe control technology while maintaining safe
working conditions. This objective was achieved by modifying a spray booth using the recirculation and
exhaust flow partitioning concepts.
Recirculation reduces the flowrate volume to the booth that would be discharged to an end-of-pipe
control system on a spray booth. The technique recirculates a portion of the exhaust air back to the spray
booth thus decreasing the flow volume passing to the atmosphere which requires treatment. During
recirculation, a portion of the exhaust stream must be removed from the recirculating stream and vented to
a control device. Before reentering the booth, the recirculated air is mixed with fresh air equal in volume
to the exhaust air and sufficient to guarantee that the booth atmosphere remains at an acceptable level to
ensure fire and worker safety. Coupled with recirculation is the benefit caused by a concentration gradient
formed in the booth during painting. Tests of this concentration gradient revealed that higher average
vertical concentration tended to be segregated in the lower level of the booth downstream from the painting
operation. This results in VOC-lean and -rich zones in the booth. Exhaust from the rich zone can be
directed to a control device, and the lean zone atmosphere can be recirculated to the booth carrying only a
fraction of the generated pollutant.
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SESSION 6
POWDER COATINGS
6-1
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PAPERS PRESENTED;
"Overview of Powder Coatings Technology"
by
Kaye Whitfield
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Research Triangle Park, North Carolina
'Powder Coatings: Technology of the Future, Here Today'
by
Gregory Bocchi
Powder Coatings Institute
Alexandria, Virginia
'ChJorinated-Maleinized Guayule Rubber in Powder Coatings:
No VOC Thermosetting Chlorinated Rubber Coatings"
by
Thomas Schuman
University of Southern Mississippi
Hattiesburg, Mississippi
'Novel Aciylic Cure Polyester Powder Coating Resin Technology''
by
Eric Dumain
Reichhold Chemicals, Inc.
Research Triangle Park, North Carolina
6-2
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Overview of Powder Coatings Technology and
EPA's Powder Coatings Research
by
J. Kaye Whitfield
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Presented at the Low-/No- VOC Coating Technologies 2nd Biennial International Conference
Durham, NC
March 14, 1995
The purpose of this paper is to provide a brief overview of powder coatings technology and then
to highlight the powder coating research currently in progress in U.S. Environmental Protection
Agency's (EPA) Organics Control Branch (OCB).
Introduction and Background
Powder coating is an organic finishing technology that offers users the potential to reduce
volatile organic compound (VOC) emissions near zero. Due to ever-increasing VOC emission
restrictions placed on manufacturers, powder coatings production and use has been growing
dramatically over the past few years at an estimated rate of 15%.' The technology has been
accepted by such manufacturing communities as automotive, appliance, furniture, and
equipment. However, small business manufacturers have difficulty investigating innovative
technologies such as powder coatings due to size and budget restrictions.
Powder coatings are of interest to EPA and industry because of what is generally referred to as
the five Es:23,4
Environmental benefits
The well known environmental benefits are that powder coatings emit very little to
no VOCs and hazardous air pollutants (HAPs). These coatings also are compliant with
federal government regulations for waste disposal.
Energy savings/conservation
Powder coating systems consume, on average, 50% less energy than conventional
systems.
6-3
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Efficiency
Less application of powder, typically one coat, is required for an acceptable finish as
compared to conventional solvent-borne coatings; therefore, powder coating is more
efficient. Since rejection rates per part are usually lower, an increase in production occurs,
which also increases efficiency.
Economic benefits
According to representatives at Reichold Chemical Company's Coatings Division,3
businesses that convert to powder technology usually experience a payback period of I
year or less.
Excellence of finish
The finish on substrates coated with powder is excellent, and the appearance of the end
product is greatly improved, especially when compared to solvent-borne coatings.
Current EPA Research in Powder Coatings
The strategic focus of EPA's OCB is VOC/HAP elimination and reduction; therefore, powder
coatings technology is a logical area to focus our research efforts. One of the greatest advantages
of powder coatings technology is that it is environmentally acceptable because of its potential to
replace HAP and VOC emitting solvent-borne coatings. Some other advantages of powder
coatings are that they are :2,4
• 100% solids;
• recyclable (the over spray from the powders is 99% reusable);
• durable and exhibit superior quality in appearance and protection;
• simple to use;
• relatively safe; and,
• environmentally acceptable.
Some of the disadvantages of powder coatings technology are that they are:2,4
• restricted to mostly metal substrates;
• not flexible (color changes are limitations); and
• difficult to coat if the part is a complex geometry.
EPA and the National Defense Center for Environmental Excellence (NDCEE). with funding
6-4
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from EPA's Environmental Technology Initiative, are conducting a study to demonstrate the
applicability of powder coatings technology for small businesses. The objectives are to 1) gain a
more widespread use of powder coating application technology in order for small businesses to
have an alternative to conventional solvent-borne coating use, 2) demonstrate the viability of
these systems, and 3) provide an economic analysis as an incentive for small businesses to
convert.
Summary
Powder coatings technology has the potential to reduce and/or eliminate many sources of HAPs
and VOCs. For that reason, EPA has chosen to focus research efforts on helping a group that, in
aggregate, is a major emitter of VOCs and HAPs, small businesses. Since small businesses may
not have the resources to explore alternative technologies, this study will allow for conversion to
a more environmentally acceptable technology without making any financial expenditures.
Although a demonstration of powder technology has been conducted for EPA, the data from the
study are in review; therefore, no results are available. However, initial findings show that
powder coatings technology may be a viable alternative for small businesses, and that the
technology may prove economical as well.
6-5
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References
1)Bocchi, G„ "Powder Coatings - Markets and Applications," Powder Coatings Institute,
Alexandria, VA, 1993, p.41
2)Dawson, Samuel, "State of Worldwide Powder Coating Industry," Nordson Corporation,
presented by Ken Kreeger, Coatings Science of Powder Coatings Short Course, University of
Southern Mississippi, May 16,1994, Hattiesburg, MS.
3)Private Communication, Reichold Chemicals, Inc., Coatings Division, Presentation to U.S.
Environmental Protection Agency, March 30, 1994, Research Triangle Park, NC.
4)FouIk, Roy and Moore, Dave, "Advances in Powder Coating Technology," Evtech, Coatings
Science of Powder Coatings Short Course, University of Southern Mississippi, May 17, 1994,
Hattiesburg, MS.
6-6
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THE POWDER COATING INSTITUTE
584-1770 \
2121 Eisenhower Avenue • Suite 401 • Alexandria, VA 22314 • (703) 684-1770
1-800-988-COAT FAX (703) 684-1771
POWDER COATINGS:
Technology of the Future, Here Today
An Overview of Powder Coating Materials,
Equipment and Applications
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
6-7
"First At The Finish Line"
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POWDER COATINGS:
Technology of the Future, Here Today
1.0 INTRODUCTION
This report provides an overview on the current status of powder coating technology in 1993.
The use of powder coating in North America is increasing at a remarkable rate of 12 percent
per year in pounds of powder sold;1 a consequence of recent improvements in the technology
to manufacture and apply powder coatings, coupled with environmental considerations. There
are currently about 3,000 powder coating operations in the United States and the number is
increasing rapidly.2
From an environmental standpoint, the increased use of powder coatings as an alternative to
liquid, solvent-based coatings results in significantly less emissions of volatile organic
compounds (VOC's) and hazardous air pollutants (HAP's) as defined by Section 112 of the
Clean Air Act Amendments of 1990. (Most of the HAP's released by the coatings industry are
solvents that are volatile organic compounds although other air toxics may also be a constituent
of some coatings.) Furthermore, powder processes can also reduce energy consumption and
hazardous waste generation. Because powder coatings are applied as dry, finely divided
particles, no VOC's are released during application and only minute quantities are released
during the curing process. Further, in contrast to most liquid painting processes, powder
overspray can be recovered and reused, rather than discarded as waste or hazardous waste.
Use of powder coatings is seen by many air and other pollution control agencies as a means of
reducing VOC's, HAP emissions, and hazardous waste from industrial finishing operations.
This report provides technical information on powder coatings as well as examples of the types
of commercial products being powder coated. It is anticipated that this will assist state and
local agencies evaluate the relationship between powder and air pollution control and
hazardous waste reduction technology by answering questions concerning performance,
applicability, costs, and availability.
The information presented in this report is based on data obtained from literature searches,
contacts with several state and local air pollution control agencies, written survey
questionnaires, and industry experts.
The remainder of this report is divided into six sections. The first section provides a brief history
of powder coatings from the 1950's into the 1990's. The next describes the different classes of
powder coatings that are currently available, including those very recently developed. The
types of equipment required for a powder coating line are described in Section 4. The types of
products that are typically powder coated are listed in Section 5. Section 6 discusses the
economic advantages of using powder coatings and presents a cost comparison between
powder and liquid coatings. Section 7 presents conclusions drawn from the study and Section
8 provides a list of references for the reader who wishes to explore the subject in greater detail.
6-8
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2.0 BACKGROUND
The technology for finishing metal products with dry powder coatings rather than with
conventional liquid paints has been available in this country since the mid-1950's. By the late
'50's, powder was being used to coat pipe for corrosion protection and electric motor parts for
insulation. These early powder coatings were applied using a fluidized bed process in which
heated parts were dipped into a vat where the powder is fluidized by air. The particles of
powder that contact the heated metal parts would adhere and soften and flow into a smooth
even layer. Most coatings applied in these fluidized beds were vinyl or epoxy powders. Typical
coating thicknesses ranged from 150 to 1,000 jim (6 to 40 mils) and the applied coatings were
functional (e.g. for corrosion resistance) rather than decorative.3
During the evolution of powder coating technology, several disadvantages or potential problems
were identified. Most have since been resolved or minimized. The following are some of the
problematic issues of the past:
1. Any process that required frequent color changes would entail extensive
downtime. The ability to apply a wide range of colors was restricted by
equipment limitations and changeover times. Rapid color changes typically
required multiple booths, with each booth dedicated to specific colors. Also,
special equipment was required to isolate and recover different colors in order to
gain the economic advantages of recycling the powder.
2. Storage and handling of powder was sensitive to temperature and humidity;
powder would not fluidize well if exposed to excessive moisture.
3. Accurate feeding of powder to the spray gun was often difficult. The result was
uneven flow and variations in film thickness.
4. Color matching and color uniformity was potentially more difficult to achieve than
with liquid coatings.
5. Uniformity of coating thickness was sometimes difficult to maintain and thin films
25 to 51 jxm (1 to 2 mils) were sometimes difficult to achieve.
6. Cure temperatures required for some powders were so high that their use would
risk damage to solder joints or temperature-sensitive parts of items being coated.
7. Powder coatings were especially susceptible to "Faraday cage" effects which
prevented charged particles from adhering to internal corners and recessed
areas.
8. Airflow in the booth and the area prior to the oven had to be carefully controlled
to avoid dislodging spray-applied powder that is held in place primarily through
electrostatic attraction.
9. Because of the extra equipment requirements (multiple booths, powder handling,
application and recovery systems), conversion of an existing liquid line to powder
was often expensive.
Technological advances that have addressed and minimized or eliminated most of these issues
are discussed in this report.
The primary development that opened the way for powder coatings to become a major factor in
the metal finishing industry was the introduction of the electrostatic spray process in the early
1960's. Electrostatic spraying allowed 1) the application of relatively thin layers of powder
coatings and 2) powder to be used on parts that could not be heated or dipped in a fluidized
bed. Powder coatings, for the first time, became an economically viable alternative for
decorative as well as functional coatings.
6-9
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The emergence of powder coatings as an alternative to liquid decorative coatings led to the
development of a variety of resin systems specifically designed to meet the needs of the
diverse user industries. Epoxy resins were used almost exclusively during the early years of
powder coatings. Polyesters, polyester/urethanes, epoxy-polyester hybrids, acrylics, and
polyvinylidene fluoride have now become equally accepted resin systems, each having its own
market share depending on the performance characteristics needed for the product. Powder
coatings are currently available in clear and virtually any color, gloss level, or texture.
Recent advances in application technology also have allowed powder coatings to be used by an
increasing number of industries. Automated finishing systems that allow rapid and frequent
color changes and high powder utilization efficiencies resulting in minimal waste have made
powder an economical coating in many high-volume industries. (Powder utilization is a term
used to reflect the waste per unit of coating sprayed. It credits overspray that is captured and
recycled when expressing efficiency as the percentage of total powder sprayed that is
deposited on the work piece.)
3.0 POWDER COATING MATERIALS
As recently as the early 1970's, the powder coating industry had a limited number of solid resin
systems on which to base powder formulations. Consequently, the ability of the powder coating
industry to meet the diverse needs of the finishing industry was also limited. For several
reasons, including increased concerns over VOC emissions, worker safety, and energy costs
during the 1970's, the popularity of powder coatings grew until powder coatings represented
almost 11 percent of all industrial coatings used in the finishing industry by 1992.4 As interest
in powder coatings has continued to grow, the industry has simultaneously responded with
technological improvements. These include:
1. New, more efficient application and recovery equipment.
2. The ability to match virtually any color or texture with powder coatings. While
there have been limitations in producing certain metallic effects with powder
coatings, technology is continuing to perfect the metallic look.
3. Improved powder resin systems that provide a wide range of properties including
performance, gloss, film thickness, and texture, that can coat not only metal, but
also glass and ceramics.
4. The addition of infrared curing equipment to replace or supplement conventional
gas, oil, and electric convection ovens.
5. The availability of powder in virtually any quantity, to suit the needs of every
customer. (Minimum orders vary with the powder manufacturer.)
3.1 THERMOPLASTIC POWDERS
A thermoplastic powder coating is one that melts and flows when heat is applied, but continues
to have the same chemical composition once it cools and solidifies. Thermoplastic powders are
based on high molecular weight polymers that exhibit excellent chemical resistance, toughness,
and flexibility. These resins tend to be difficult to grind to the consistent fine particles needed
for spray application, and when heated, have a high viscosity. Consequently, they are applied
mainly by the fluidized bed application technique, and used mostly in thick film applications.
Typical thermoplastic powder coatings include: polyethylene, polypropylene, nylon, polyvinyl
chloride, thermoplastic polyamides. and thermoplastic polyesters.
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Polyethylene powders were the first thermoplastic powder coatings to be offered. They provide
excellent chemical resistance and outstanding electrical insulation properties. Polyethylene
coatings are smooth, have a medium gloss, and good release properties that allow sticky
materials to be cleaned from their surfaces, and are often used as coatings for laboratory
equipment.
Polypropylene produces a surface that is very inert and is often used in applications where the
powder coated part may be exposed to chemicals. Nylon offers excellent abrasion, wear and
impact resistance, and a low coefficient of friction. They are commonly used as mechanical
coatings for sliding and rotating bearing applications in appliances, farm equipment, and textile
machinery. Polyvinyl chloride provides good durability as well as flexibility. An example of a
product coated with polyvinyl chloride is dishwasher racks. Thermoplastic polyamides provide
excellent resistance to detergents, impact, and high temperatures. Thermoplastic polyesters
offer good exterior durability and weatherability, and do not usually require a primer for good
adhesion to most metals. They are often used on outdoor metal furniture.
Thermoplastic powders are especially well suited for a thick coating capable of extreme
performance requirements. Because of the inherent thickness of these coatings, they do not
generally compete in the same market as liquid paints.
3.2 THERMOSETTING POWDERS
Thermosetting powder coatings are based on lower molecular weight solid resins. These
powders also melt when exposed to heat. After they flow into a uniform thin layer, however,
they chemically cross-link within themselves or with other reactive components to form a
reaction product of much higher molecular weight. The final coating has a much different
chemical structure than the basic resin. These newly formed materials are heat stable and,
unlike the thermoplastic products after curing, will not soften back to the liquid phase when
heated. Resins used in thermosetting powders can be ground into very fine particles necessary
for spray application and thin, paint-like coatings. Because these systems produce a finish that
offers properties comparable to liquid coatings, most of the technological advancements in
recent years have been with thermosetting powders.
Thermosetting powders are derived from three generic types of resins: epoxy, polyester, and
acrylic. From these three basic resin types, five coating systems are derived. Epoxy resin-
based systems are the most common and are available in a wide range of formulations. They
are used for both functional and decorative coatings. Their functional properties include
outstanding corrosion resistance and electrical insulation. Decorative epoxies offer attractive
finishes that are flexible, tough, have excellent corrosion resistance, and high impact strength.
Epoxies lack ultraviolet resistance and therefore, are not recommended for outdoor use
because in prolonged sunlight exposure, they tend to chalk and discolor. Various types of
hardeners are used with epoxy powder to optimize appearance and properties for use in a wide
range of applications. Recent developments allow epoxies to be cured at temperatures as low
as 121°C (250°F) for 20 to 30 minutes, or even shorter times at higher temperatures.®
Epoxy-polyester hybrid coatings are used mainly for decorative applications. They are more
resistant to chalking and over-bake yellowing than pure epoxies but have a lower surface hard-
ness and are less resistant to solvents. Hybrids also exhibit better transfer efficiency and a
greater degree of penetration into recessed areas of a part.
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Polyester-TGIC coatings contain a polyester resin cross-linked with trigiycicsyl isocyanurate
(TGSC) as a curing agent. These powders offer very good mechanical properties, impact
strength, and weather resistance. They are resistant to chalking and are often used for such
outdoor applications as patio furniture, lawn mowers, and aluminum extrusions and panels for
large commercial buildings.
Acrylic-urethane coatings are formulated with acrylic resins cross-linked with blocked
isocyanates. They have excellent color, gloss, hardness, weatherability, and chemical
resistance. They have an excellent thin film appearance but are less flexible than polyesters.
Polyester-urethane coatings are formulated with polyester hydroxyl resin combined with
blocked isocyanate hardeners. Polyurethane powders exhibit outstanding thin film appearance
and toughness as well as good weathering properties.
Table 1 provides a summary of the key physical properties of these thermosetting powder
coatings.
3.3 NEWLY DEVELOPED POWDERS
Advancements in powder coating formulations are occurring at a rapid pace. Powders are
being developed to compete with almost every market that has traditionally been held by liquid
coatings. Factory-applied architectural coatings (based on fluoropolymers), heat resistant
coatings, metallic and textured coatings, low-temperature-cure powders, transparent and clear
powders, and powders that can be used to color plastic parts by introducing the powder into the
mold used for compression-molded plastic are in production use at this time. Most of these
developments have occurred during the last several years and most powder coating
manufacturers believe that the potential of powder coatings is only beginning to be realized.
In addition to the coating types discussed above, new developments are occurring in the area
of enamel powders. Conventional porcelain enamel, the glassy coating traditionally found on
metal surfaces such as bathtubs and washing machines, is a vitreous inorganic coating bonded
to metal by fusion. The powder coating process for porcelain enamel involves the re-fusing of
powdered glass on the metal surface at a cure temperature of 1200°F. The powdered glass is
formed by melting oxide components and then quenching to form enamel frits. The frits can be
converted to wet sprayabie suspensions or to dry enamel powders through ball-milling. The
resultant enamel coating is heat stable to over 450°C (842°F), color fast, and scratch resistant.?
Enamei powders, a potential replacement for porcelain, are now available in a range of colors.
Continued development will make these coatings even more competitive.
Polyvinylidene fluoride coatings have recently become available in powder form.® These
fluoropolymer powder coatings have been available in Europe for about 4 years and are now
sold in the United States. Their cure temperature is in the range of 475°-525°F. Because of
their high resistance to weathering, industrial pollution, and corrosion, they are factory-applied
for use on exterior aluminum extrusions and paneis for architectural purposes.
4.0 POWDER COATING EQUIPMENT
The process of applying powder coatings to the surface of a product is, in general terms, similar
to the traditional painting line used to apply liquid coatings. For powder coating (or traditional
painting), parts to be coated first are exposed to a pretreatment operation to ensure that the
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TABLE I. TYPICAL PROPERTIES OF THERMOSETTING POWDER COATINGS4
PROPERTIES
Epoxy
Epoxy/polyester
hybrid
TGIC polyester
Polyester
urethane
Acrylic 1
urethane
Application Thickness
0.5-20 milsa
0.5-10 mils
0.5-10 mils
0.5-10 mils
0.5-10 mils
Cure Cycle (metal temperatures)'1
450°F - 3 min
250°F - 30 min
450°F - 3 min
325°F - 25 min
400°F - 7 min
310°F - 20 min
400°F - 7 min
350°F - 17 min
400°F - 7 min
360°F - 25 min
Outdoor weatherability
Poor
Poor
Very Good
Very Good
Excellent
Pencil Hardness
HB-5H
HB-2H
HB-2H
HB-3H
H-3H
Direct Impact Resistance, in-lbc
80-160
80-160
B0-160
80-160
20-60
Adhesion
Excellent
Excellent
Excellent
Excellent
Excellent
Chemical Resistance
Excellent
Very Good
Good
Good
Very Good
" Thickness of up to 150 mils can be applied via multiple coats in a fluidized bed,
b Time and temperature can be reduced, by utilizing accelerated curing mechanisms, while maintaining the same general properties.
c Tested at a coating thickness of 2.0 mil.
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surface to be coated is clean and free of grease, dust, rust, etc. In most cases, the parts are
also subjected to treatments such as phosphating and chromatizing to improve the adhesion of
the surface coating. After pretreatment and drying, the parts enter the spray booth. After the
spray coating is applied, parts enter the curing oven to melt and cure the coating.
The following sections present information about the types of equipment that are available for
each step in the process outlined above. Numerous manufacturers of powder coating
equipment compete in today's market. Each has products that perform the same basic task.
The discussions here are generic, in that manufacturers' brand names are not used, and will
focus on the spray application of powder to a metal substrate. (Curing ovens used with powder
coating systems are similar to those used for liquid coating lines.)
4 1 PRETREATMENT
Although the substrate pretreatment process is critical to achieving an acceptable powder
coated finish, the need for good pretreatment is not unique to powder finishes. All industrial
surface coatings require a substrate that is clean and dry. A wide range of pretreatment
requirements is available for both powder and liquid coatings. The pretreatment process
selected is a function of the characteristics of the coating, the substrate, and the end use of the
product being coated. The pretreatment process is normally conducted in a series of spray
chambers where alkali cleaners, iron or zinc conversion coatings, and rinses are applied. Parts
of various size or shape may be cleaned with pressurized and/or heated sprays. Dip tanks may
be used instead of spray for some applications. Powder coating lines usually incorporate a
phosphate application step that adds corrosion protection and improves the adhesion of the
coating to the substrate.
Pretreatments most often used in powder coating are iron phosphate for steel, zinc phosphate
for galvanized or steel substrates, and chrome phosphate for aluminum substrates. After the
parts have passed through all of the pretreatment steps, they are normally dried in a low
temperature dry-off oven. After drying, the parts are ready to be powder coated.
4.2 POWDER APPLICATION
The powder coating application process makes use of four basic types of equipment; the
powder delivery system, the electrostatic spray gun system, the spray booth, and the powder
recovery system. The flow schematic is shown in Figure 1.
4.2.1 Powder Delivery System
Powder is supplied to the spray gun by the powder delivery system. This system consists of a
powder storage container or feed hopper, and a pumping device that transports a mixture of
powder and air into hoses or feed tubes. Pneumatic pumps driven by clean, dry compressed
air are most often used because they aid in separating the powder into individual particles for
easier transport. Each powder pump supplies powder to one gun, typically many feet from the
powder supply. Delivery systems are available in many sizes. Proper selection depends on the
application, number of guns to be supplied, and volume of powder to be sprayed in a given time
period. Recent improvements in powder delivery systems, coupled with better powder chemi-
stries that reduce clumping of the powder, have made possible the delivery of a very consistent
flow of particles to the gun. Some feed hoppers vibrate to help prevent dogging or clumping of
powders difficult to fluidize prior to entry into the transport lines.
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WORKPIECE
CARTRIDGE FILTER
POWDER
SPRAY GUN
HIGH-VOLTAGE
POWER SUPPLY
COLLECTOR WITH
COLOR MODULE
ROTARY SIEVE
FINAL
FILTER
FEED HOPPER
SPRAY BOOTH
\
/
OVERSPRAY
RECYCLE LINE
Flow Chart of a Cartridge
Booth System
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4.2.2 Electrostatic Sprav Guns
Electrostatic powder spray guns direct the flow of powder; control the pattern size, shape, and
density of the spray as it is released from the gun; impart the electrostatic charge to the powder
being sprayed; and control the deposition rate and location of powder on the target. All spray
guns can be classified as either manual (hand-held) or automatic (mounted to a fixed stand or
gun mover). Both manual and automatic guns are manufactured by many companies.
Although their basic principles of operation are similar, there is an almost limitless variety in
style, size, and shape. The type of gun chosen for a given coating line can, thus, be matched
to the coating characteristics needed for the products being coated.
Most common is for the electrostatic charge to be imparted to the powder particles after they
exit the spray nozzle by a charging electrode located at the front of the gun. These "corona
charging" guns generate a high-voltage, low-amperage electrostatic field between the electrode
and the product being coated. The charge on the electrode is usually negative. Its strength
can be controlled by the operator. Powder particles that pass through the ionized electrostatic
field at the tip of the electrode become charged. Their flight to the substrate is influenced by
the electrostatic field. The particles follow the field lines and air currents to the target workpiece
and are deposited on the electrically grounded surface of the workpiece. One drawback to this
type of gun is the relative difficulty of coating irregularly shaped parts that have recessed areas
or cavities (that may be affected by the Faraday cage effect) into which the electrostatic field
lines cannot reach. Because the powder particles are influenced by the presence of the field
lines, deposition into recesses and cavities is more difficult, but can be overcome.
Another approach in electrostatic spray guns is the "tribo" electric gun. The powder particles in
a tribo electric gun receive an electrostatic charge as a result of friction which occurs when
powder particles rub a solid insulator or conductor inside the gun. The resulting charge is
accomplished by stripping electrons from the powder, producing positively charged powder.
Because there is no actual electrostatic field, the charged particles of powder migrate toward
the grounded workpiece and are free to deposit in an even layer over the entire surface of the
workpiece. Since there is no electrostatic field, the Faraday cage effect is minimized and
deposition into recesses improved. However, each charging technology should be tested to
determine the practical application for each unique situation.
Other improvements made to spray guns involve variations in the spray patterns to improve the
efficiency with which they deposit powder on the substrate. Nozzles that are more resistant to
clogging have also been introduced, along with ways to continuously clean charging electrodes.
Spray guns with variable spray patterns are also available to allow the use of one gun on
different parts and configurations, innovations in spray gun design have also resulted in
versatile and efficient guns with increased ease of operation. The spray equipment used for
manual spraying is simple to control and use. Only a brief period of training is required before
the painter can meet quality objectives.
4.2.3 Powder Spray Booths
The primary function of the powder spray booth is to safely contain the powder so that
overspray cannot migrate into other areas. Several criteria must be met in selecting the
appropriate spray booth for a given coating line. The entrance and exit openings must be
properly sized to allow clearance of the largest product part. The airflows through the booth
must be sufficient to channel all overspray to the recovery system, but not so forceful that it
disrupts the powder deposition and retention on the part. This is usually accomplished by
maintaining a minimum average face velocity of 100 ft/min across all end openings. If one
6-16
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booth is to be used for multiple colors, the booth interior should be free of narrow crevices,
seams, and irregular surfaces that would be difficult to clean. This is especially important if
collected overspray is to be recycled.
Because there is no solvent loading of the air exhausted from a powder coating booth, the air
can be circulated back into the plant. This saves considerable energy during winter months,
compared with the energy required to heat makeup air to replace the solvent-laden air flow from
a liquid paint booth.9
4.2.4 Powder Recovery and Recycle Systems
The powder recovery and recycle systems may or may not be an integral part of the spray
booth. The economic efficiencies arid environmental benefits associated with reuse of
oversprayed powders has led equipment manufacturers to develop systems designed
especially to accommodate powder recovery. Traditional spray booths for liquid coatings have
either dry or wet filter systems to remove overspray from the exhaust air stream. The collected
paint is typically of no value and is therefore discarded, usually at considerable expense since
most solvent-based paint overspray meets the RCRA definition of Hazardous Waste.
Recovered powder is of greatest value if free of color contamination. When a single particle of a
different color is cured on a part, it will not blend in but remains visible. Numerous systems are
now available that segregate colors within the same booth. The systems make use of either
cyclones or cartridge fitter modules that are dedicated to each color and can be easily removed
and replaced when a color change is needed. Color changes can be accomplished by
disconnecting the powder delivery system, purging the powder lines, cleaning the booth,
exchanging the cyclone canister or filter module used for the previous color with the cyclone
canister or filter module for the next color, and connecting the powder delivery system for the
new color. Equipment manufacturers have made significant design improvements in powder
spray booths that both allow color changes to be made with a minimal downtime and allow the
recovery of a high percentage of the overspray. As with spray guns, there are a large number
of spray booth and powder recovery designs from which to choose, depending upon the exact
requirements of a given finishing system.
4.2.5 Curing Ovens
There are three basic oven types normally used in the curing of powder coated parts;
Convection, infrared, or a combination of the two. Convection ovens can be either gas or
electric. Air is heated and circulated inside the oven around the powder coated parts. The
parts attain the temperature within the oven.
Infrared (1R) ovens using either gas or electricity as their energy source emit radiation in the IR
wavelength band. This radiated energy is absorbed by the powder and the substrate
immediately below the powder but the entire part need not be heated to cure temperature. This
allows a relatively rapid heat rise causing the powder to flow and cure when exposed for a
sufficient time.
Combination ovens generally use IR as the first zone to melt the powder quickly. The following
convection zone can then utilize rather high velocity currents since there is no danger of dis-
turbing the powder. These higher velocities permit faster heat transfer and a shorter cure time.
6-17
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4 3 COLOR CHANGEOVERS
Color change in a powder coating system can be accomplished in a relatively short period of
time, about one minute when independent booths are moved on and off line. The off-line booth
is cleaned while the on-line booth is in production. Adequate time must be allowed to clean an
off-line booth before the next color change can occur.
As a result, equipment manufacturers have developed their own approaches to minimizing color
change downtime. Color change in an automatic single booth system (eight automatic guns
and two manual guns) will generally range from 15 minutes to one hour utilizing two people.
Larger systems would require a proportionately longer time.
4.4 TRANSFER EFFICIENCY
Transfer efficiency is generally defined as the ratio of powder deposited on the part or parts to
the total amount of powder sprayed. (This fraction is normally multiplied by 100 to express it in
percent.) Recovered powder is not considered in this calculation. Many factors can affect
transfer efficiency, including proficiency of the operator, shape of the part, booth design,
condition of the spray equipment, part grounding, powder condition, and application techniques.
Powder's big economical advantage over liquid paints is that transfer efficiency is not also a
measure of paint efficiency. The powder overspray can, with properly designed equipment, be
captured and resprayed thereby raising powder utilization to almost 100 percent.
4.5 FILM THICKNESS
Powder coatings can be applied in a wide range of film thicknesses. Continuous films as low as
0.5 mils (0.005") can be applied, as can specialized applications that require as much as 10
mils or more. The very thin films will require special powder grinds. Extremely heavy films are
generally achieved by coating the part while it is hot.
The normal range of the vast majority of applications would be 1,0-3.0 mils with an average
target value of 1.5 mils. The part's function and its expected environmental exposure will
usually dictate the type of coating material to be used and the desired film thickness.
4.6 PROCESS CONTROL IN POWDER APPLICATION SYSTEMS
Process control in powder application systems can be broadly classified into four major
categories: gun movement, gun triggering, booth/recovery system monitoring, and flame
detection.
The use of oscillators, reciprocators, and robots to control spray equipment reduces labor costs
and provides more consistent coverage.
Gun triggering, or triggering the gun on and off using a device that can sense when the target is
properly positioned, will reduce overspray material, which translates into lower material and
maintenance costs. Automatic gun triggering can also have other benefits such as improved
quality of the finish and reduced film build at edges.
In addition to controlling the gun functions, other booth and recovery system variables such as
moisture in the air supply, powder level in the feed hopper, and routine diagnostic variables can
be monitored using either a microprocessor or programmable logic controllers (PLC's).
6-18
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Finally, it is mandatory in the U.S. that automatic systems include a flame detection device
interlocked with the high-voltage power supply, conveyor, and application and recovery
equipment. These devices cut off all electrical and pneumatic supplies within one-haif second
after detecting an ignition,
4.7 POWDER STORAGE AND HANDLING
Coating manufacturers recommend that powders be stored at temperatures below 80°F and for
a maximum of six months.
5.0 END USES OF POWDER COATINGS
As can be-seen in Table 21® , the list of products currently being powder coated is extensive.
There are certain market sectors where powder coatings have shown particularly strong growth
rates. For example, powder coatings are being used extensively to produce linings on the
inside of oil drilling pipe where severe pressures, high temperatures, and corrosive materials
are too aggressive for all but a few types of coatings. The automotive industry is increasing its
use of powder coatings for economic, quality, and ecological reasons. Powder is being used by
some manufacturers for the exterior body intermediate coat - the primer-surfacer - as well as for
finishing of underhood components. Parts that require extra protection as well as a decorative
finish are increasingly being powder coated. Wheels, bumpers, shock absorbers, mirror
frames, oil filters, engine blocks, battery trays, and coil springs are some of the many
automotive products being powder coated. Clear powder coatings, for use over automotive
exterior basecoats, are now being developed for commercial application as an alternative to
solvent-borne clear coats.
The appliance industry is the largest single market sector for thermosetting powders,
accounting for about 21 percent of powder sales.11 As porcelain-replacement powders
become further developed, the appliance market will continue to grow. Current uses include
range housings, freezer cabinets, dryer drums, and washer tops and lids.
Outdoor furniture, farm implements, and lawn and garden equipment are also major markets for
powder coatings. The general metal finishing industry accounts for about 53 percent of
thermoset powder sales.11 (The general metal finishing industry is defined here as including all
metal finishing industries except for the automotive, appliance, architectural, and lawn and
garden finishing industries.)
Potential large market areas for powders are the aluminum extrusion and architectural products
markets. The recent advances in polyester-TGIC and fluoro-polymer powders have enabled
powder coatings to compete with liquid architectural coatings in durability, weatherability, and
resistance to fading. Some of these coatings applied to building panels have been out in the
field in Europe since 1976 with good results.
The custom coating sector is one of the fastest growing segments of powder coating, meeting
the need for most of the sectors mentioned above. Of the estimated 3,000 powder coating
systems in use in North America, 900 are custom coaters.
The Powder Coating Institute estimates that powder coating use in North America will grow
from 74,560 tons in 1992 to about 117,946 tons in 1996. During this period, the projected
6-19
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TABLE 2
END USES FOR THERMOPLASTIC AND THERMOSET POWDERS
METAL SUBSTRATES
AUTOMOTIVE
EXTERIO R;
Wheels
Luggage racks
Window trim
Track tool boxes
Windshield wipers
Bumpers
Rally (roll) bars
Mirror brackets
Primer surfaeer
Anti-chip primers
Radio antennas
Door handles
Air louvers
AUTOMOTIVE
INTERIOR:
Ash trays
Speaker covers
Defroster vents
Steering wheels
Seat pedestals
Seat belt latches/mounts
Jacks/lug wrenches
Truck seat frames
AUTOMOTIVE
UNDERBODY:
Engine blocks
Radiators
Suspension systems
Coil springs
Shock absorbers
Oil/air filters
Motor mounts
intake manifolds
Valve covers
Brake assemblies
Battery trays
Pulleys
Fuel injector tubes
A/C components
Small motor components
METAL SUBSTRATES
AUTOMOBILE MISC.:
Boat trailers
Trailer hitches
Mobile home doors/windows
Motorcycles
MAJOR APPLIANCES:
Gas & electric ranges
Range hoods
Refrigerator doors, shelving,
liners, & skins
Washer tops & lids
Dryer drums
Freezer cabinets
Water heaters
FURNITURE-HOME'
Bunk beds
Patio furniture
Kitchen tables/chairs
Chair frames & bases
Baby strollers/swings/
playpens, etc.
Folding chairs/tables
Barbecue grills
Metal cabinets
Bookends
Wire baskets
FURNITURE-COMMER-
CIAL/INSTITUTIONAL:
Chair bases/frames
Office partitions
Filing/storage cabinets
Lockers
Wastebaskets
Dentist chairs
Hospital beds
Examination tables
Copier cabinets
Stadium seating
SHELVING & RACKING:
Retail store shelving
Retail store racks
Point-of-display racks
Warehouse rack systems
METAL SUBSTRATES
HEATING/VENTILA-
TION/AIR COND.;
Central A/C cabinets
Window A/C cabinets
Gas/electric furnace cabinets
Swimming pool heaters
Evaporation coolers
Space heaters
Air cleaners
INDUSTRIAL EQUIP-
MENT/MACHINERY:
Industrial mixers
Grain storage systems
Animal feeding units
Thickness gauges
Friction disk binders
Vending machines
Ice making machines
Irrigation pipes
Pay phones/booths
Electrostatic spray equipment
Escalator steps
Battery chargers
Air compressors
Pressure reserve tanks
Fans, shutters, louvers
Gas & electric meters
Drum rings
Food processing carts
Lobster traps
Hand trucks
Gasoline pumps
Sonar equipment
LAWN & GARDEN:
Riding mowers
Walk-behind mowers
Edgers
Fertilizer spreaders
Snowblowers
Garden tillers
Chain saws
Tractors
(continued on next page)
6-20
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TABLE 2 (Continued)
END USES FOR THERMOPLASTIC AND THERMOSET POWDERS
METAL SUBSTRATES
HARDWARE:
Brass & metal door hardware
Brass bathroom fixtures
Closet organizers
Wire & metal shelving
Drapery hardware
Shower curtain hardware
Safe deposit boxes
Wine racks
Christmas tree stands
Notebook spiral wires
Luggage frames
Desk accessories
Mechanical pens/pencils
Thumbtacks
Wire cloth/screens
Water pumps
Water tanks
Steel drums
Scaffolding
Military hardware
Door thresholds
Alarm system bells
Propane tanks
Draw slides/suspension units
Camp stoves
Grapevine support poles
VCR cases
Water cans
Mailboxes
Screen doors
Aluminum doors/windows
Metal doors
Antennas
Gas cans
Pool hardware
Highway & other signs
Fence wire & poles
Guard rails
Building facade panels
Satellite dishes
Fire extinguishers
Parking meters
Aluminum extrusions
Post-formable tubing
Ornamental iron security
doors
METAL SUBSTRATES
TOOLS;
Tool boxes & chests
Hand tools
Snowplow blades
Power tools
Steel carts
Hand trucks
LIGHTING FIXTURES:
Fluorescent lighting fixtures
Decorative lighting fixtures
Desk lamps
Yard lights
Light poles
Outdoor lighting Fixtures
SMALL APPLIANCES:
Kitchen blinds
Kitchen, mixers
Crock pots
Vacuum cleaners
Can openers
Floor care machines
Cigarette lighters
Microwave oven cavities
Fans
Speaker frames
Microphones
Tape player doors
Computer frames/cabinets
Bathroom scales
Automatic timers
SPORTS/RECREATION:
Playground equipment
Recreation vehicle hardware
Bicycle frames/wheels
Gas/electric golf carts
Golf clubs
Snowmobiles
Ski poles & ski parts
Metal toys
Wagons
Marine motors & drives
Archery bows
Exercise equipment
METAL SUBSTRATES
ELECTRIC
COMPONENTS:
Motor windings & housings
Magnet wire
Electrical motor -
stators/'rotors
Computer room floor sys.
ELECTRICAL EQUIP.:
Transformers
Switch gear
Electric junction boxes
Electric connectors
Buss bars
Electrical instrument
housings/cabinets
OTHER FUNCTIONAL
COATINGS:
Petroleum transmission pipes
Oil well drilling pipes
Reinforcing bar for concrete
Rebar saddles
Cable for p res tressed
concrete
Structural steel
Conduit
Truck splines
Dishwasher baskets
Military projectiles
NON-METAL
SUBSTRATES
CERAMICS:
Decorative glass bottles
Flash bulbs
Instrument bulbs
Roofing tile
WOOD:
Toilet seats
PLASTIC:
Sinks/shower stalls
Automotive fascias
Automotive dashboards
6-21
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annual growth rate for selected market areas is: automotive-9%. appliance-11%, architectural-
9.5%, tawn arid garden products-8%, and general metal finishing-12 %
6.0 ECONOMIC ADVANTAGES OF POWDER COATING VS. LIQUID COATINGS
When comparing powder coating systems with liquid coating systems, several significant
advantages are readily apparent. There are also other, seemingly less significant advantages
that, when viewed collectively, contribute substantial cost savings. This section discusses the
economic advantages of powder vs. liquid coating systems in the following areas: energy
savings, labor savings, greater operating efficiencies, and environmental benefits. A detailed
cost comparison of powder vs. liquid coating systems also is provided at the end of this section.
fi.1 ENERGY SAVINGS
There are two significant advantages of powder coating which contribute to lower energy costs
as compared to liquid coating. The first is that the air used to exhaust the powder spray booth
can be recirculated directly to the plant since the powder does not contain volatile compounds
at room temperature. This eliminates the cost of heating or cooling the makeup air that occurs
when air is exhausted from the plant with liquid spray painting operations, a particular
advantage where seasonal weather conditions are extreme. The second advantage is the
lower cost of heating the curing oven. Ovens that cure solvent-based coatings must heat and
exhaust huge volumes of air to ensure that the solvent fumes do not approach the lower
explosive limit. Because powder coatings have no solvent content, the required exhaust flow in
the curing ovens is considerably lower resulting in energy savings even when higher cure
temperatures are involved.
6.2 LABOR SAVINGS
The required operator skills and training for operation of a powder coating system are less than
those needed for a liquid system and considerably less than those required for an electrocoat
system. Powder is "ready to use" when purchased and does not require labor for mixing with
solvents or catalysts as is necessary with liquid coatings. Also, there are no critical operating
parameters to monitor such as viscosity and pH (which are monitored in many liquid coating
systems) or percent solids, specific resistance, and binder to pigment ratio, (which all must be
monitored in electrocoating systems). Additionally, powder systems lend themselves well to
automation. Since powder coatings do not run, drip, sag, or have solvent pops, a wider variety
of parts can be coated automatically.
6.3 GREATER OPERATING EFFICIENCY
Because no drying or flash-off time is required, and the powder application system allows parts
to be racked closer together on a conveyor, more parts can pass through the production line
resulting in greater operating efficiency and lower unit costs. Despite the greater line speeds,
powder coating systems generally have significantly lower reject rates than do liquid coating
systems. One reason for this lower reject rate is that it is virtually impossible to have drips,
runs, or sags when applying powder coatings. Additionally, because booth air exhaust may be
returned to the spray room, it is practical to reduce rejects caused by airborne contamination by
enclosing the spray room and keeping it under slightly positive pressure while air conditioning
and filtering the air. If, prior to entering the cure oven, a powder coated part is found to be
improperly sprayed, the powder can be blown off with an air gun and the bare part recoated.
Another factor which contributes to a greater operating efficiency is the fact that oversprayed
powder can be reclaimed and reused, and material usage is minimized.
6-22
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6.4 ENVIRONMENTAL BENEFITS
As regulatory agencies further limit the amount of solvent and hazardous air pollutants (HAP's)
that can be emitted, many plants that use liquid coating systems are finding it necessary to
purchase VOC control equipment, such as afterburners, to incinerate the emitted solvents and
HAP's. Another environmental problem faced by liquid coating users is the increased difficulty
and cost of disposing of hazardous waste generated by liquid coating overspray. With a dry
powder coating system, there is no liquid paint sludge to send to a disposal site.
6.5 COST COMPARISON: POWDER VS. LIQUIDS
A detailed cost comparison between powder and liquid coating systems is provided below. The
three types of liquid coating systems included in the comparison are: conventional solvent,
water-borne, and high solids. Total capital and annual operating costs are provided for each of
the four coating systems. Material costs represent two-thirds or more of the total annual
operating costs, and therefore, detailed material costs are also provided.
6.5.1 Total Capital Costs
Capital costs for four different coating systems (i.e. conventional solvent, water-borne, high
solids, and powder) are presented in Table 3. The source of these costs is a reprint from
Products Finishing entitled "Powder Coating Advantages" (1991), generated by The Powder
Coating Institute ^2 "Powder Coating Advantages" is an updated version of the 1987
publication "Powder Coating Today." These cost estimates are consistent with estimates
provided by powder coating equipment suppliers in response to questionnaires submitted by
the EPA.
Powder coating equipment that cost $150,000 in 198313 could be purchased for $145,000 in
1990. The "Powder Coating Advantages" article includes a carbon absorber in the cost of the
conventional solvent-borne liquid coating system.
The capital costs presented in Table 3 are based on the following assumptions:
1. The parts to be coated are formed sheet steel parts that are of average
complexity;
2. Both sides of each part are automatically coated and touched up manually;
3. Two colors are used;
4. There is a production rate of one million square feet of surface coated per
month based upon a five-day week, one-shift operation;
5. Conveyor speed is 15 ft/min;
6. The installation is new and has automatic equipment to efficiently apply
either a conventional solvent, water-borne, high solids, or powder coating;
7. A carbon absorber for emission compliance (cost $96,000) is added to the
system applying conventional solvent-borne coatings to satisfy emission
regulations; and
8. The same pretreatment systems and ovens can be used with each system
with little or no modification.
6.5.2 Material Costs
Materials costs for the four coating systems are presented in Table 4; these costs are based on
two different sources of information. Both sources calculated the material costs in a similar
manner with the higher solids system generally having a lower unit volume material cost. The
most complete and up-to-date source of cost information is the aforementioned "Powder
Coating Advantages" article (Reference Nos. 15 and 17 in Tables 4 and 5). Costs obtained
6-23
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Type of Coating
TABLE 3. TOTAL CAPITAL COSTS12
Equipment
Capital Cost
Conventional Solvent
2 Waterwash Booths
$115,000
I Dry Filter Booth
8 Automatic Guns
2 Manual Guns
2 Reciprocators
Paint Heating Equipment
Carbon Absorber for Emission
$ 96,000
Compliance
$211,000
Total
Water-borne
2 Waterwash Booths
$120,000
1 Dry Filter Booth
8 Automatic Electrostatic Guns
2 Manual Electrostatic Guns
2 Reciprocators
Safety Interlocks and Standoffs
High Solids
2 Waterwash Booths
$115,000
1 Dry Filter Booth
8 Automatic Electrostatic Guns
2 Manual Electrostatic Guns
2 Reciprocators
Paint Heating Equipment
Powder
1 Booth with 50 sq. ft. opening
$145,000
8 Automatic Guns
2 Manual Guns
2 Reciprocators
2 Reclaim Stands with Automatic Reclaim
2 Collectors
Fire Detection
6-24
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TABLE 4. MATERIAL COSTS, DOLLARS
Item
Ret#
Conventional
Solvent
Water-borne
Higher
Solids
Powder*
Coating cost, S/gal
(14)
—
—
21.00
2.40
(15)
11.00
12.40
17.25
2.35
Volume solids, %
(14)
—
...
54
98
(15)
43
35
63
98
Reducing agent cost,
(14)
N/A
N/A
N/A
$/gal
(15)
2.00
N/A
N/A
N/A
Mix ratio (coating:
(14)
....
N/A
N/A
N/A
reducing agent)
(15)
4:1
N/A
N/A
N/A
Mixed coating costs,
(14)
...
—
21.00
2.40
S/gal
(15)
9.20
12.40
17.25
2.35
Volume solids at
(14)
54
98
spray viscosity, %
(15)
34,4
35
63
98
Specific gravity
(14)
...
...
...
1.6
(15)
...
—
...
1.6
Theoretical coverage,
(14)
...
866
118
ft2/gal/mil
(15)
552
561
1,011
118
Dry film thickness.
(14)
...
...
1.2
1.5
milsb
(15)
1.0
1.0
1.0
1.5
Transfer efficiency,
(14)
...
...
80
95
%e
(15)
45
55
60
96
Actual coverage,
(14)
—
...
577
75
ft2/gal
(15)
248
309
607
76
Applied cost, S/fi2
(14)
...
...
0.0364
0.0320
(15)
0.0371
0.0401
0.0284
0.0309
Annual cost to coat
(14)
HllMM
...
436,800
384,000
12x10s ft2, $
(15)
445,200
481,200
340,800
370,800
a Substitute pounds for gallons in all calculations,
b Coating thicknesses were normalized to put costs on a common basis.
c Transfer efficiency is the ratio of coating that adheres to the part and the coating that is sprayed through
the gun. In the case of powder coating, where powder is recovered and recycled, the term "utilization
efficiency" is used.
6-25
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from the User's Guide To Powder Coating (1987) (Reference No. 14) were included in Tables 4
and 5 for comparison purposes. (Note that in Table 4, the columns for powder costs are in
terms of lb. rather than gal.)
The material costs presented in Reference Nos. 15 and 17 are based on 1990 data and the
following assumptions:
1. The conventional solvent-borne baking enamel price represents a material
with 43 percent (by volume) solids applied at an average thickness of 25
um (1.0 mils};
2. The water-borne acrylic price is based upon a 35 percent (by volume)
solids material applied at an average thickness of 25 fim (1.0 mils);
3. The higher solids coating is a general purpose polyester at 63 percent
solids applied at an average thickness of 25 p.m (1.0 mils); and
4. The powder coating is a general-purpose polyester powder applied at an
average thickness of 30 p.m (1.2 mils).
These dry film thicknesses were set at levels that are believed to be representative of current
industry practices.
6.5.3 Total Annual Operating Costs
The total annual operating costs for the four coating systems are presented in Table 5. All
literature references used to create Table 5 identified powder coating as having the lowest
annual operating costs. The highest operating costs were associated with the conventional
solvent or water-borne coating systems. Labor, cleanup, maintenance, energy, and waste
disposal costs were lowest for the powder coating system, which contributed to overall lower
annual operating costs. The "Powder Coating Advantages" article (Reference No. 17) again
provided the most complete and up-to-date information on annual operating costs. The
operating costs presented in that brochure are based on 1990 data and the following
assumptions:
1. Labor costs $14.55 per hour and supervision costs $18.45 per hour;
2. Cost of electricity = $0,085 per kWh;
3. Cost of natural gas = $3.23 per thousand ft3; and
4. Removal of nonhazardous paint sludge was estimated to cost $300 per
55-gal drum.
The material costs for any of'the four coating systems could be less than those shown if either
the volume solids and/or transfer efficiency is increased and/or the film thickness lowered. For
example, if the transfer efficiency for the higher solids case (Reference 15, Table 4) is
increased from 60 to 70 percent, the annual materials cost to coat will drop from $340,800 to
$292,500. The annual cost to coat = [(coating thickness) (mixed coating cost) (surface area
coated per year)] / [(theoretical coverage) (utilization efficiency)]. Likewise, if the powder
coating thickness in Reference 15 (Tables 4) were decreased from 25 to 20 fim (1.0 to 0.8
mils), the material cost would drop from $340,800 to $272,970.
It should be noted that, currently, the minimum consistent powder coating film thickness is in
the range of 10-15 fim (.5 mil). If the product can perform satisfactorily with a thinner film, the
extra cost of applying more powder than necessary should be considered when comparing
alternative coatings.
6-26
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TABLE 5. TOTAL ANNUAL OPERATING COSTS, DOLLARS-
Conventional Higher
Item
Ref. #
Solvent
Water-borne Solids
Powder
Material, $/yr
(16)
—
—
436,800
384,000
(1?)
445,200
481,200
340,800
370,800
Labor and clean-up,
(16)
...
111,400
85,200
S/yr
(17)
160,200
160,200
160,200
98,600
Maintenance, $/yr
(16)
...
11,840
5,060
(17)
29,300
29,300
29,300
17,000
Energy, $/yr
(16)
—
—
38,474
34,905
(17)
21,400
22,800
19,900
11,525
Sludge disposal, $/hr
(16)
8,460
N/A
(17)
50,100
33,300
27,300
975
Filter replacement,
(16)
—
1,920
N/A
$/hr
(17)
—
—
—
•—
Amortization, 10-yr
(16)
—
—
...
straight line, $
(17)
21,100
12,000
11,500
14,500
Total annual cost, $b
(16)
...
...
594,670
497,310
(17)
727,300
738,800
589,900
513,400
Applied cost, S/ft2
(16)
...
0.0508
0.0425
(17)
0.0606
0.0616
0.0491
0.0428
a Assumed 2,000 operating hours per year.
b Numbers have been rounded.
6-27
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7.0 CONCLUSIONS
The use of powder coatings as functional and decorative industrial finishes is increasing at a
dramatic rate. At an annual rate of 12 percent, powder coating is the fastest growing finishing
technology on the market.'' (Sales volumes of powder coatings are much smaller than liquid
coatings, so a direct comparison of growth rates is not meaningful.) Significant improvements
in powder coating materials and application, and powder recovery systems have made powder
one of the most cost effective finishing systems available. In addition, because powder
coatings contain no solvents and overspray can be recovered and recycled, air and water
pollution problems are eliminated in well-operated facilities. Energy costs attributable to heating
and ventilation are significantly reduced.
The use of powder coatings as an alternative to liquid, solvent-based coatings results in a
significant decrease in VOC and HAP emissions. Powder coatings can be characterized as the
lowest VOC-content coating among the compliance options available to industrial finishers.
Table 6 presents a VOC reduction comparison of the four coating systems reviewed in Section
6. The values in this table were based on the average of the values presented in Table 4. As
shown in Table 6, VOC emissions for powder coating systems are 98.4 percent lower than
those for conventional solvent coating systems, 98.1 percent Sower than those shown for higher
solids systems, and 97.7 percent lower than for water-borne systems.
Most of the drawbacks to the use of powders that existed a few years ago (see Section 2) have
been eliminated. New resin systems allow powders to meet the coating specifications for
almost any application. Thin films (from less than 25 um [1 mil] to about 76 um [3 mils]) in a
very wide range of colors, glosses, and textures can be applied at powder utilization rates of 95
percent or higher.^ Many of these coatings can be cured at temperatures of 121°C to 177QC
(250°F to 350°F) in 15 to 30 minutes.6 Powder manufacturers are continuing to work toward
perfecting resin and curing agent designs that will allow lower cost coatings and low
temperature cure coatings. Low temperature curing powders allow for higher line speeds, and
expand the list of potential substrates to plastics, wood, and heat sensitive products like
automobile shock absorbers.
Significant advancements are also being made in the weatherability of powders for use in
automotive and architectural applications. Clear powder coatings are used for a wide range of
applications in a number of markets, including the automotive industry, where clear polyester
and acrylic powders are being used to finish wheels. Powder resin systems are now available
that provide the exterior durability properties required of an automotive exterior body topcoat.
Recent and ongoing developments in the equipment used for powder application have
significantly reduced the time, effort, and capital cost required for color changes. Properly
designed powder systems can change colors in minutes. Currently, high-production powder
systems apply more than 20 different colors, with several color changes per day.^
Coil coating technology for powder continues to be developed. Coil coating is the coating of flat
metal sheet or strip that comes in rolls or coils. The metal is coated on one or both sides on a
continuous production line basis.
An in-mold powder coating process has been developed in which powder coating material is
sprayed onto a heated mold cavity before the molding cycle begins. When the molding
operations are performed, the powder coating chemically bonds to the molding compound and
6-23
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produces a product with a coating that is chip and impact resistant.
The powder coating of pre-cut metal blanks which are then post-formed prior to final assembly
remains a strong growth area for powder, with high transfer efficiency and uniform film
thickness. 20
Advances in microprocessors, robotics, and infrared curing technology are allowing increased
production in powder coating facilities. All of these advances, plus the inherent advantages of
working with powder, ensure that powder coatings will have a permanent and ever-increasing
share of the finishing market.
TABLE 6. VOC REDUCTION COMPARISON8
Convention-
Water-
Higher
Powder
al Solvent
borne
Solids
Coating
Volume solids at spray viscosity, percentb
34.4
35
58.5
98
Volume VOC content, percentc d
67
16
40
1
Actual coverage, ft3/gal (fP/Ib for powder)'
248
309
592
75.5
VOC emissions, tons/yrf
38
26
31
0.6
a Assumed !2xl06 ft2 of parts coated per year.
b Average of values presented in Table 4b.
c Assumed density of solvent equals 7.36 lb/gal.
d Water-borne coating VOC content assumed to be 25 percent of the nonsolids portion.
e Average of values presented in Table 4b. Based on transfer efficiencies presented in Table 4b.
f Control device assumed for conventional solvent with overall efficiency of about 70 percent (based on capture
efficiency of about 75 percent and destruction efficiency of about 95 percent). All other systems assumed to have
no control device.
Issued 2/94
6-29
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8.0 REFERENCES
1. Bocchi, G.J, "Powder Coatings - Markets and Applications," Prepared for presentation
at the European Coatings '93 Conference and Trade Show. 1993. p.1
2. Reference 1, p. 26.
3. Miller, E.P. and Taft, D.D. Fundamentals of Powder Coating. Society of Manufacturing
Engineers, Dearborn, Michigan. 1974. p. 13.
4. Reference 1, p. 25.
5. User's Guide to Powder Coating, Second Edition. Society of Manufacturing Engineers,
Dearborn, Michigan. 1987. p. 12.
6. The Powder Coating Institute 'Technical Brief No. 1," January 1986. (Revised 1994.)
7. "Electrostatic Powder Coating." Dow Chemical Europe. Undated brochure, p, 7.
8. "Sigma Coatings, The Specialist in Exterior Paint Systems, Introduces Sigma PVDF, a
New Generation of Powder Coatings." Sigma Coatings, Industrial Coatings Division,
NL-37QQ AC Zeist Undated brochure.
9. Montenaro, D. "Economics of Powder Coating." In: Conference Proceedings. Powder
Coating '38. Sponsored by The Powder Coating Institute. November 1-3, 1988. p. 9-7.
10. Gill, D.E. "Powder Coatings and Their Uses." Metal Finishing. August 1988. p. 41.
(Revised 1993 by The Powder Coating Institute.)
11. Reference 1, p. 1 -17.
12. Bocchi, G.J. "Powder Coating Advantages." Reprint from Products Finishing. 1991.
p. 5.
13. Cole, G., Jr. "VOC Emission Reductions and Other Benefits Achieved by Major Powder
Coating Operations." The Powder Coating Institute. (Presented at the Air Pollution
Control Association Meeting, San Francisco, June 24-29, 1984). p. 13.
14. Reference 5, p. 25.
15. Reference 12, p. 6.
16. Reference 5, pp. 27-28.
17. Reference 12, p. 8.
18. Reference 5, p. 3.
19. "Why Powder Coat? A Practical Guide to Powder Coating." Volstatic, Inc., Florence,
Kentucky. Undated brochure, p. 1.
20. Reference 1, pp. 33-35.
6-30
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The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
CHLORINATED-MALEINIZED GUAYULE RUBBER IN POWDER COATINGS:
NO VOC THERMOSETTING CHLORINATED RUBBER COATINGS
Speaker: Thomas Schuman
Shelby F. Thames
Department of Polymer Science
University of Southern Mississippi
Box 10037, Hattiesburg, MS 39406-0037
William A, Purvis
Department of Polymer Science
University of Southern Mississippi
Box 10076, Hattiesburg, MS 39406-0076
INTRODUCTION
Chlorinated rubber, the addition and substitution reaction product of
natural rubber and chlorine gas, is known for its low water vapor
permeability, good chemical resistance, abrasion resistance, corrosion
resistance, and flame retardant properties.1 Consequently, it is used as a
coating component in a variety of coating applications including marine
coatings, swimming pool coatings, and corrosion resistant coatings.2 However,
the use of chlorinated rubber in coating compositions has declined in recent
years primarily because chlorinated rubber coatings must be cast from volatile
organic compounds (VOCs), and the films formed possess poor solvent
resistance. Therefore, we have created a novel, multi-functional derivative
of chlorinated rubber for use in low VOC formulations. Specifically, this
investigation describes the synthesis of anhydride functionalized chlorinated
rubber and its utilization in powder coatings and contributes to other recent
work in this area.3"6
The powder coatings industry has experienced significant growth since
its inception, and by all accounts this trend is expected to continue. Growth
in powders is due in large measure to its environmental advantages of low to
no "VOC emissions. Thus, by 1988, the .annual growth rate was 23% in the United
States alone.1 Accordingly, as powder coatings reach toward new technological
heights and thus new applications, there is need for additional polymer
systems to meet specific performance requirements.
Powder coatings formulated from chlorinated rubber (CR) have received
little or no attention in the literature. Presumably, this is due to poor
thermal properties. For instance, CR has high glass transition temperatures
(>100°C) and undergoes decomposition prior to melting.8 When used alone, it
performs poorly as a powder coating resin. Polymers with a low melt viscosity
are desirable as powder coating.resins in order to obtain adequate film
coalescence, good flow, and adhesion. Thus, melt temperatures of 50 to 100°C
are attractive as they are easily processed at low costs. Thus, we have
investigated polymer blends as an approach to partially stabilize an otherwise
thermally unstable CR.
Chlorinated rubber blends of alkyd resins, acrylics, epoxy esters, epoxy
resins, hydrocarbon resins, rosins, and tars have been used successfully in
solvent cast coatings and give desirable film properties representing an
amalgamation of resin types.8 Thus, blending novel crosslinkable CR with
functionalized powder coating resins was an attractive concept to the design
and synthesis of no VOC, CR, powder coatings.
We have previously reported the synthesis of chlorinated-maleinized
guayule rubber (CMGR), a thermosetting CR derived from guayule natural rubber.
The synthesis was accomplished by grafting maleic anhydride (MA) onto
unsaturated sites with the subsequent chlorination of residual double bonds.®
(See Figure 1.)
6-31
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Figure 1: Synthesis of Chlorinated-Maleinized Guayule Rubber
CI CI
CH-
Variations in the stoichiometric quantities of maleic anhydride grafts
have been affected to produce a myriad of chlorinated-maleinized rubber
crosslinkable agents. Chlorine, as a part of the rubber composition,
dramatically improves water resistance, chemical resistance, and flame
resistance. On the other hand, the anhydride moiety effectuates crosslinking
via covalent bond formation and thereby improves a number of polymer
properties, not the least of which is solvent resistance. Thus, this novel
material shows unusual promise as a CR additive in thermosetting powder
coatings, and it is to this end that this research was focused.
EXPERIMENTAL PROCEDURES
Materials
Crude low molecular weight guayule rubber (LMWGR) and resinous byproduct
was obtained from Bridgestone/Firestone, and the LMWGR was separated from
plant resin by continuous acetone-extraction. The rubber was further purified
by the addition of a 10% (w/w) toluene solution of rubber to an equal or
greater volume of methanol. Reagent grade MA, benzoyl peroxide, chlorine, and
1,2-dichloroethane were purchased from Aldrich and used as received. Primid
XL-552, a hydroxy alkyl amide supplied by Rohm & Haas, functioned as the
powder coating curative. Modaflow Powder III obtained from Monsanto Company
was added to the powder formulations to improve flow. Schweizerhall, Inc.
supplied benzoin, a degas agent, and McWhorter Technologies supplied 30-3070,
an acid-functional polyester resin. For the analysis of CR, samples of
Alloprene R-20 provided by ICI Resins, Inc., were utilized.
Synthesis of Chlorinated-Maleinized Guayule Rubber
A 50 gram sample of purified rubber was dissolved in 1,2-dichloroethane
to a 2% (w/w) concentration, and placed in a 3000 ml three-neck round bottom
flask equipped with a mechanical stirrer, addition funnel, thermometer, gas
dispersion tube with a scintered glass end, and condenser. The amount of MA
for the desired degree of maleinization was added to the flask as a solid.
Nitrogen was bubbled through the solution for 10 min to sparge the remaining
oxygen. The contents of the flask were heated to reflux (83°C) , during which
time a 250 ml 1,2-dichloroethane solution of benzoyl peroxide was added
dropwise with caution over a 30 min period. Reflux continued throughout the
grafting and chlorination reactions. After 3 h, chlorine gas was introduced
into the reactor at a rate of 0.2-0,3 g/min until a total of 90 g of chlorine
was added. Chlorination was affected via a lecture bottle equipped with
6-32
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teflon tubing, and the weight loss of the bottle was monitored with a Mettler
PM3 000 balance. The solution was cooled, concentrated in vacuo, and the
product isolated by the addition to 2000 ml of stirring methanol followed by
vacuum filtration. The product, a coarse yellow powder, was further purified
by dissolution in toluene followed by precipitation into methanol. After
drying overnight in vacuo, a fine light-yellow product is obtained.
Equivalent Weight Analysis
Samples were weighed to four significant figures and dissolved in a
blend of 100 ml of toluene and 25 ml of isopropanol. Titration with
phenolphthalein indicator was affected against a 0.1040 M solution of
potassium hydroxide in methanol and the equivalent weight per carboxylate
(EWC> was determined using Equation 1:
EWC = W/(2VK) [13
where W = weight of specimen, V = ml of KOH to neutralize, and K = moles
KOH/ml of solution. In the denominator, the two accounts for only % of the
carboxylate of the anhydride is measured via this method. The percent
grafting efficiency was determined on samples prior to chlorination by
comparing the calculated equivalent weight to the theoretical equivalent
weight assuming stoichiometric conversion as represented by Equation 2.
GE = (Theoretical EWC/Calculated EWC) * 100 [23
Characterization of CMGR and CMGR Powder Coatings
For infrared analysis, samples were cast onto sodium chloride discs from
tetrahydrofuran and dried in vacuo for 30 min. Fourier transform infrared
(FTIR) spectroscopic analysis was performed on a Nicolet IR/42
Spectrophotometer. Thermal properties were monitored via a Mettler DSC 3 0
equipped with liquid nitrogen subatnbient cooling. The temperature profile of
analysis included heating the samples from room temperature to 100°C at
10°C/min cooling to 0°C at 10°C/min and finally heating to 300°C at 10aC/min to
complete the cycle. TGA weight loss analysis was recorded on a Mettler TGA 50
under an air atmosphere. Samples were heated from 30°C to 500°C at 20°C/min.
Environmental scanning electron microscopy (ESEM) was obtained from an
Electroscan Type II ESEM. The coatings were evaluated according to ASTM
standards as listed in Table I.
Table I: CMGR Coating Tests
Test
ASTM
Impact Resistance
D-2794
Conical Mandrel
D- 552
Crosshatch Adhesion
D-3359
Pencil Hardness
D-3363
MEK Double Rubs
D-4752
8 Hour Spot Tests
D-13 08
Film Thickness
D-1186
Gloss
D- 523
Salt Fog Exposure
B-117
6-33
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Gel time analysis was performed on a Thermoelectric Company cure plate at
188°C. Samples weighing 1 g were added to the cure plate and the time
required for sample gelation was recorded.
Formulation of Chlorinated-Maleinized Guayule Rubber Powder Coatings
Chlorinated-maleinized guayule rubber of 5% MA content was blended with
a commercially available polyester-polyamide powder coating at 4, 6, and 10%
(w/w). To affect good mixing, CMGR and the reactive polyester (30-3070) were
dissolved in THF at room temperature, the solvent was removed in vacuo at
40°C, and the residual powder was dried overnight before mix extrusion.
A stoichiometric balance of 1:1.01 of the CMGR/polyester blend and the
curative (primid xl-552), respectively, was confirmed by titration of each of
the reactants.
All formulations (Table II) were mix processed and extruded according to
parameters listed in Table III.
Table II: Powder Coating Formulations
Material {g}
Control
4% CMGR
6% CMGR
10% CMGR
30-3070
282.21
260
251.01
228 .5
CMGR
20
30
50
Primid XL-552
11.8
12.27
13
13 .45
Benzoin
2 . 59
2.59
2 .59
2.59
Modaflow III
3 .75
3.75
3 .75
3 .75
Dupont R-960
199.S5
199.65
199.65
199.65
Total
500
500
500
500
Table III: Processing Parameters
Premix
Henschel FM-10 C
120 sec at 2000 RPM
Extrusion
Werner & Pfleiderer ZSK 3 0
Screw Temperature
113°C
Die Temperature
113°C
Load on ZSK 3 0
30%
Speed
300 RPM
Chill Rolls
Temperature
55°C
Roll Speed
45 Hz
6-34
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The final particle size was obtained by grinding on a Micron Powder
Systems Model SH Bantam Mill and sifting through 110 micron mesh on a Kem-U-
Tech Laboratory Sifter. The powders were sprayed onto cold rolled steel
panels with a Nordson Corona Model NVC 4 Spray System, and cured in a Despatch
Gas Oven at 325°C for 20 rain.
RESULTS AND DISCUSSION
Chlorinated-Maleinized Guayule Rubber
Chlorinated-maleinized guayule rubber containing 5, 10, 15, and 25 mol%
MA was synthesized according to the synthetic scheme of Thames and He (Figure
1). Titration prior to chlorination confirms a grafting efficiency greater
than 85% with averages of 90%. The products, fine light-yellow powders, were
analyzed by thermal, titriometric, and infrared analysis.
The products were titrated to determine the acid value or equivalent
weight with varying MA content. Accordingly, the results of Table IV confirm
increasing acid value and decreasing equivalent weight as the MA content
increases.
Table IV: Selected Properties of Chlorinated-Maleinized Guayule Rubber
% MA
Acid Value
EWC
T
Ag
0%
115°C
5%
42
1,352g/COOH
16S°C
10%
65
866g/COOH
148°C
15%
91
614g/CG0K
158°C
25%
113
495g/COOH
159°C
The glass transition temperatures (Tg) of the CMGR compositions of Table
IV ranged from 158°C to 166°C. While maleinization increases the Tg of CR, no
consistent relationship between MA content and Tg was apparent. The variation
in thermal characteristics with maleinization is illustrated in Figure 2.
The gradually increasing exotherm beyond 210°C is presumably due to slow
decomposition of CMGR.
Infrared analysis corroborates the structural similarity of CMGR and CR,
yet with the addition of the anhydrxde functionality. For instance, the FTIR
spectrum for CMGR and CR shown in Figure 3 suggests structural likeness
through conparable IR absorption frequencies. While for the most part the
spectra are similar, variations occur via absorptions in the 1650 cm 1 - 1850
cm"1 and approximately 700 cm"1 regions. In the latter instance, the
absorption is consistent with carbonyl stretching of the anhydride moiety.
The split absorption is indicative of atmospheric hydrolysis of the anhydride
to acid moieties. This feature is further noted with the broadening of the
aliphatic C-H absorption of CMGR at 3500 - 2500 cm"1. The absorption at
approximately 700 cm"1 in the CR spectrum is indicative of C-Cl stretching.
Other minor spectral differences can be attributed to the anhydride
functionale of CMGR. Hence, titriometric, thermal, and infrared analysis
confirm the successful synthesis of chlorinated-maleinized rubber.
6-35
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Figure 2: DSC Thermograms for Chlorinated-Maleinized
Guayule Rubber and Chlorinated Rubber
CHLORINATED RUBBER
CMSR
~i f—i 1 1 1 J 1—"i i—r—j—r—r—i i | i i > i {
so. 100. 150. 200. 250.
Figure 3: PTIR Spectrum of Chlorinated-Maleinized
Guayule Rubber and Chlorinated Rubber
4-
2500
2000
1500
1000
3000
Waven umber
CR - CMGR
6-36
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Chlorinated-Maleinized Guayule Rubber Powder Coatings
Having confirmed the synthesis of CMGR and its similarity to CR, we
turned our attention to the use of these materials in powder coatings, their
application, and coatings evaluation. Powder coatings containing 4, 6, and 10
wt% CMGR were formulated, applied, cured, and evaluated.
The data of Table V is instructive in confirming film property
variations attributable to CMGR. For instance, with increasing anhydride
functionality gel time diminished as expected, coating hardness increased and
MEK resistance increased up to a 6% use level of CMGR. However, MEK double
rubs, and NaOH resistance suggest strongly that coatings formulated with 10%
CMGR contain unreacted acid functionality. For instance, the reduction in MEK
resistance from 140 to 135, the dramatic gloss reductions, and the diminished
NaOH resistance suggest an excess of carboxylate functionality.
Table ¥: Powder Coating Properties
Test
Control
4% CMGR
6% CMGR
10% CMGR
Thermal Properties
T
59°C
54°C
56°C
54°C
Gel Times at 188°C
141 sec
104 sec
69 sec
63 sec
Average Film Thickness
2 mils
2 mils
2 mils
2 mils
Impact Resistance
Forward (in-lb)
160
160
160
160
Reverse (in-lb)
140
140
160
160
Conical Mandrel
Pass
Pass
Pass
Pass
Crosshatch Adhesion
5B
5B
5B
5B
Pencil Hardness
2H
5H
6H
8H
MEK Double Rubs
SO
110
140
135
Gloss (20/60)
55/85
33/72
20/55
1/5
8 Hour Spot Tests3
2 0% Sulfuric Acid
5
5
5
5
10% NaOH
5
5
5
4
Cone. NH4OHb
5
5
5
5
Water
5
5
5
5
150 Hour Salt Fog
Pass
Fail
Fail
Fail
a - 5= no effect 4= stain only 3= blistering 2= lifted film 1= failure
b - 30% HH3 by weight
Coatings containing CMGR are light tan in color while the control was
white. This color variation is suggestive of thermal decomposition or
oxidation of the CMGR, yet TGA analysis showed essentially no weight change at
the curing temperature (Figure 45 . Thus, the slight discoloration is
6- 37
-------
consistent with the off-white color of CMGR. The TGA profiles for the control
and the CMGR coatings {Figure 4) are quite similar with only slight variations
in the thermal decomposition as the CMGR content is increased. TGA analysis
confirms the beginning of thermal decomposition near the 250°C region. Gloss
reduction was progressive with the addition of CMGR and at 10% (w/w) CMGR
coatings took on a low gloss, textured finish. The dramatic gloss loss with
increasing amounts of CMGR is indicative of high melt viscosities and/or a
heterogeneous medium produced by excessive, and thus unreacted, functionality.
The textured appearance of coatings formulated with 10% CMGR, whether due to
changes in melt viscosity or phase separation, gives them a unique, attractive
appearance.
Figure 4: TGA Analysis of Powder Coatings
Control
4% CMGR
Cure Temperature
6% CMGR
10% CMGR
T
, r
, r
T
T
T
T
T
T
T
T
100. 200. 300. 400. "C
While gel time, pencil hardness, solvent resistance, and reverse impact
improved with the addition of CMGR, corrosion resistance declined. This is
suggestive of diminished flow and wetting associated with the addition of
CMGR. Indeed, the ESEM corroborated a crack-marred surface, and thus porous
films that allow moisture penetration and consequently corrosion.
CONCLUSIONS
Chlorinated-maleinized guayule rubber, a novel chlorinated rubber
bearing acid anhydride functional sites, has been synthesized and employed in
a number of powder coating formulations. The incorporation of the acid
anhydride functionality to CR was confirmed by infrared analysis and
titration.
Powder coatings blended with CMGR showed improvements in cure rate,
solvent resistance, pencil hardness, and reverse impact while adhesion,
6-38
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flexibility, and chemical resistance were retained. Formulations of powder
coatings containing alloprene, a commercially produced CR, gave similar
results, but lacked the solvent resistance of the CMGR coatings. However, the
CMGR led to gloss reductions and at a 10% level, an attractive, low gloss,
textured finish was obtained. Of more concern, however, is the observed poor
corrosion resistance believed to be a function of film porosity. Thus, the
overall utility of CMGR as a powder coating reagent requires additional
formulation variations and perhaps CMGR structural variations in order to
enhance flow and wetting characteristics.
This work has confirmed for the first time the utility and shortcomings
of CMGR as a reactive polymer in powder coating formulations. We will
continue this investigation in pursuit of high performance and durable CMGR
powder coatings.
ACKNOWLEDGMENTS
The authors are grateful to Dr. Thomas P. Schuman, Payton Poole, Kyle
Copeland, Michael Blanton, Samuel Pace, Kamlesh Panjnani, and Paula Partrige
for their assistance and helpful advice. This research is supported by the
Cooperative State Research Service, U.S. Department of Agriculture, under the
Cooperative Agreement No. 93-COOP-1-9531.
REFERENCES
1. Baker, C.L. Modified natural rubber. In: Bhowmick and Stephens
(eds.j, Handbook of Elastomers. Ch. 2. Marcel Dekker, Inc., New York,
New York. 1988. p. 33.
2. Paul, S. Chlorinated rubber. Iri: Surface Coatings. Ch. 4. John Wiley
& Sons, New York, New York. 1985. pp. 248-300.
3. Thames, S.F. and He, Z.A. Chlorinated, hydroxylated low molecular
weight guayule rubber as a convertible binder in thermoset coatings.
Industrial Crops and Products. 2(2): 75, 1993.
4. Thames, S.F. and He, Z.A. Synthesis of chlorinated rubber with acrylate
and carboxylic acid functionalities. Industrial Crops and Products.
2(2): 83, 1993.
5. Anbazhagan, K., Reddy, C.R., and Joseph, K.J. Thermal properties of
polyurethanes crosslinked with chlorinated rubber graft copolymers.
Polymer Degradation and Stability. 15: 109, 198S.
6. Deb, P.C. and Sankholkar, S.c. Grafting IV. graft tercopolymers as
antifouling resins. Journal of Applied Polymer Science. 43: 1007,
1991.
7. Misev, T.A. Introduction. In: Powder Coatings Chemistry and
Technology. Ch. 2. John Wiley & Sons, New York, New York. 1991. p. 3.
8. Alloprene. A technical bulletin distributed by Imperial Chemical
Industries PLC. Imperial Chemical Industries PLC, Runcorn Cheshire,
England. 1986. pp. 3-5.
9. Thames, S.F., Rahman, A., and Poole, P. W. Synthes is and
characterization of chlorinated maleinized rubber from low molecular
weight guayule rubber. Industrial Crops and Crops. 2(2): 69, 1993.
6-39
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The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
NOVEL ACRYLIC CURE POLYESTER POWDER COATING RESIN TECHNOLOGY
Eric Dumain
Reichhold Chemicals, Inc.
2400 Ellis Road
Research Triangle Park, North Carolina 27709-3582
INTRODUCTION
Increasingly stringent environmental regulations within the industrial finishing industry have
caused coatings formulators to focus on the development of technologies that meet the dual requirements
of environmental compliance and high performance. Powder coatings, as a result, are enjoying double
digit growth as industrial finishers look for ways to meet these challenges.
Powder coatings have been projected to account for 15 % of the overall North American
industrial finishing market by the end of the decade.1 As powder replaces traditional liquid paint
technologies on an ever-increasing basis, tougher performance standards for powder coatings are being
demanded. These new conditions have led to the development of novel powder coating resin technology
that offers the formulator an excellent approach to meeting the needs of today's challenging coatings
environment.
POWDER COATINGS BACKGROUND
Powder coatings, unlike conventional liquid paint technologies, contain no solvents (100 %
solids), and are virtually 100 % VOC free. A major benefit is its' high materia! utilization rate.
Oversprayed powder can be reclaimed and, after mixing with virgin powder, can be reused. Other
economic advantages of powder are the reduced costs of waste disposal and pollution control. (There is
no liquid paint sludge, and spray booth air can be recycled to the plant facility.) Additionally, the choice
of color is as varied as in liquid coatings, and special effect finishes are also possible through the use of
various additives.
A typical powder coating consists of a thermosetting resin, crosslinker, flow and levelling
agents, pigmentation, and inorganic fillers. These solid materials are premixed either in low or high
intensity mixing equipment prior to being melt-mixed in a compounding extruder. During the extrusion
process, the resinous mixture is heated above its' melting point and made homogeneous through
mechanical shear. Therefore, proper temperature/shear relationiship is key to obtaining optimum
dispersion of the coating's components. The molten extrudate is usually cooled by the use of chill rolls,
or a cooling belt, whereby it is converted into a crushable ribbon. This ribbon is then pulverized and
classified to the desired particle size for application. For general metal applications, a 40 micron average
particle size powder coating is common. Figure 1 shows a schematic representation of a continuous
powder coating production process.
6-40
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FIGURE 1
Resin
Curative
premixer
Powder Manufacturing Process
Additives
Figment
' MELT-llIX EXTRUDER
ji
¦J.i"
WmSMrnm
F^=l
Classifying screen
Filling & Pack iging
t Km? W>
The powder can subsequently be applied to a grounded metal substrate with an electrostatic (corona
charging) spray gun. Other application methods are also possible: tribocharging, whereby the powder
particles receive a frictional charge as they pass through the spray apparatus, and fluidized bed dipping,
Tribocharging is suitable for metal fabrications that have unusual geometries, and would therefore be
vulnerable to Faraday cage effect.2 Fluidized bed dipping is utilized in applications such as pipe coatings
that require film thicknesses in excess of 10 mils. The final step in the process is the curing of the
powder coating. This can be accomplished by gas or electric convection ovens, infrared cure, or a
combination of both convection and radiation. During the cure cycle, the powder fuses, melts, and flows
to form a continuous film. After a suitable cure cycle, the coating will have developed a highly
crosslinked system, with the resultant physical properties.
Powder coating technologies can be broadly classified as either thermosetting or thermoplastic.
Thermoplastic powders, the oldest powder coatings technology, include materials such as nylon and
polyvinyl chloride. Unlike the particle size mentioned above, the thermoplastics have a much larger
average particle size (> 100 microns), as it takes much more energy to grind them.3 After the initial cure
cycle they can be remelted if desired, and will solidify upon cooling. Thermosetting powders,
conversely, cannot be remelted once they have undergone cure. The materials that are used for these
powder coating vehicles (resin and cross linker) are usually high molecular weight, crystalline polymers.
They must have a careful balance of rheological and reactive properties. Additionally, they must be low
enough in Tg to have suitable flow properties, but at the same time, be stable under long-term storage
conditions. The thermosetting variety are more widely used, comprising approximately 91 % of current
U.S. powder consumption. 4
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The thermosetting chemistries can be grouped as epoxies, polyesters, epoxy-polyester hybrids,
and acrylics. As is the case with other coatings technologies, each powder chemistry has its' inherent
advantages and disadvantages. The oldest thermosetting powder technology involves the use of epoxy
resins which are diglycidyl ethers of bisphenol A (DGEBA), crosslinked with amines, anhydrides,
dicyandiamide, or linear phenoic curatives. While this system has excellent corrosion and chemical
resistance, its' exterior durability and overbake resistance is poor.
Saturated polyester resins followed, and a host of curing agents are commercially available for
these polymers. These polyesters are generally classified as carboxyl fuctional or hydroxyl functional.
The carboxy polyesters can be cured with epoxy functional resins. These systems are referred to
as polyester-epoxy hybrids, and are characterized by very good film smoothness and mechanical
properties. They also exhibit the problems associated with straight epoxy systems, that is, fair to poor
exterior durability. One system that does offer excellent exterior durability features a trifunctional
curative- triglycidylisoeyanurate, or TGIC. However, recently published toxicity data has raised some
health concerns for personnel using this material.4 Generally, an overall advantage of the epoxy/carboxy
crosslinking mechanism is that it proceeds by addition, hence no volatiles are evolved during the cure
cycle.
Hydroxyl functional polyester resins can be crosslinked with several different hardeners, the
most widely used being blocked isophoronediisocyanate (IPDI). Epsilom caprolactam is typically the
blocking agent used in the IPDI prepolymers. Coatings made with these materials are referred to as
polyurethanes and exhibit good film smoothness, exterior durability, storage stability, and mechanical
properties. Disadvantages of polyurethanes include elevated bake temperature requirements (> 350 0 F),
and the evolution of small amounts of volatiles during cure. A portion of the blocking agent sublimes
during the cure process. In inadequately vented ovens, it appears as a bluish haze, and is perceived to be
a health hazard. The effectiveness of infrared curing lamps can also be decreased as the V -caprolactam
accumulates on the heating surfaces. As more powder coatings end-users utilize IR curing, solutions to
this problem will need to be developed. Possibly as a proactive measure, a growing number of urethane
users are requesting " £ -caprolactam-free" coatings, without sacrificing the performance benefits of
smoothness and flexibility normally associated with this technology. One such alternative will be
discussed in this paper.
Another major class of powder coatings are the acrylics. They can be hydroxy, carboxy, or
glycidyl functional. The crosslinking of these resins occurs much in the same fashion as their polyester
analogues. The OH and COOH acrylics can be cured with the same materials as the polyesters. However,
they have not seen the same acceptance as the polyesters due to poorer mechanical properties and high
cost vs. the polyesters.
The glycidyl functional acrylics have seen recent growth because of their excellent exterior
durability, relatively low cure temperatures (300 0 F), and film smoothness. Acrylics based upon glycidyl
methacrylate (GMA) crosslinked with linear dibasic acids such as dodecanedioic acid (DDDA) have
been found to be the highest performing thermoset powder coating in terms of exterior durability and
acid rain resistance. This technology does have a few disadvantages, however. GMA acrylics usually
have lower mechanical properties such as flexibility and impact resistance than polyesters. Additionally,
formulated GMA acrylic/DDDA powder coatings (or "pure" acrylics) typically exhibit incompatibility
with other powder coating chemistries. A polyester coating contaminated with less than i % of a GMA
acrylic coating will cause massive film defects (i.e. cratering). It is not the acrylic component that
6-42
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induces the incompatibility, but rather the use of siloxane flow modifiers within the acrylic powder
coating that give the undesired result. The observed cratering is the end result of the large surface tension
gradient between the polyester and acrylic films.
Researchers at Reichhold Chemicals, Inc. and its' parent company, Dainippon Ink and
Chemicals (DIC) of Japan, have sought to develop unique resins for the powder coatings industry that
would help overcome some of the above mentioned problems and disadvantages, while advancing the
state-of-the-art in powder coating technology.
Two examples of our progress here include the development of high performance coatings for
precoated metal (PCM) and development of powders with extremely low gloss that are highly-
reproducible. The new resins should also find utility in general metals applications that require a high
level of performance,
DEVELOPMENT OF NOVEL CURING MECHANISMS
A novel acrylic cure technology has been developed that features the crosslinking of carboxyl
functional sites on polyester resins with glycidyl methacrylate (GMA) acrylic curing agents. This
addition chemistry, referred to as an acrylic/polyester hybrid, has inherent advantages over the
conventional carboxy/glycidyl powder technologies described previously in that it combines good
exterior durability with lower associated health risks. This curing mechanism produces uniform, high-
gloss finishes with film smoothness comparable to that of a standard TGIC-cured coating. At the same
time, it can be considered an alternative to £ -caprolactam-containing urethane powder coatings. The
curing mechanism is shown in Figure 2.
ACRYLIC CURE POLYESTER
FIGURE 2
Carboxyl Polyester
COOH
GMA ACRYLIC
U.S. Patent 4,499,239
6-43
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A second curing mechanism similarly involves the utilization of GMA acrylic curing agents with
a polyester resin that has bifunctionality, that is, there are both carboxy! and hydroxy I groups available
for crosslinking. An isocyanate is used here to react with the OH groups of the polyester. However, the
required amount is much less than the standard polyurethane, so the associated volatile level is lower.
Figure 3 shows the curing mechanism for this system. Again, coatings based on this approach show
good film smoothness, mechanical properties, and very good exterior durability.
MULTI-CURE ACRYLIC/POLYESTER
Patent Pending FIGURE 3
COOH
OH
NCO
BLOCKED NCO
GMA ACRYLIC
Bifunctional Polyester
A third approach also uses the bifunctional polyester. As before the carboxyl groups of the
polyester react with the oxirane groups of the acrylic curing agent, and the hydroxyl/isocyanate reaction
takes place. However, the GMA acrylic hardener in this case also has OH groups, and these can also
react with the NCO curative. This curing mechanism is referred to as a multi-crosslinking system. It has
a high crosslink density and exhibits the benefits of urethane and acrylic chemistries. Although slightly
more blocked isocyanate is used in this system, it is still less than would be found in a conventional
polyurethane powder coating. Formulated coatings based on these materials exhibit excellent
smoothness, flexibility, chemical and stain resistance, as well as good exterior durability. With this
balance of properties, the bifunctional polyester/acrylic has the attributes necessary to satisfy most
coating service environments. The reaction diagram for this system is shown in Figure 4. Formulations
for the three acrylic/polyester systems are listed in Table 1, with their corresponding cured physical
properties listed in Table 2. It should also be noted that these acrylic/polyester curing mechanisms do not
cause the contamination problems associated with "pure" GMA acrylic powder coatings.
6-44
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MULTI-CROSSLINKING ACRYLIC CURE POLYESTER
FIGURE 4
Bifunctional Polyester
U.S. Patent 4,818,791
COOH
OH
<
NCO
GMA ACRYLIC
BLOCKED NCO
OH
NCO
PRE-COATED METAL FINISHING
Pre-coated metal (PCM), or blank, finishing technology has been established commercially in
Southeast Asia and Europe for several years, and is now being developed in North America. The concept
is similar to liquid coil coating, in that it involves the coating of flat steel stock. However, powder
coating of blanks gives edge coverage usually not associated with liquid coil coating.
Blanks are cut to size, holes punched in the blanks, and then the piece is powder coated. After
the coating has cured, the blank is formed into the shape of a refrigerator, laundry machine, or file
cabinet, for example. Since the blanks are subjected to large amounts of bending, (also called post-
forming) excellent flexibilty is a prerequisite for the applied powder coating. Additionally, the appliances
will ultimately be exposed to severe operating conditions, (washing machines, for instance) and the
powder coatings applied to these products must have superior resistance to detergents and other
chemicals that can stain or damage the finished product. For these reasons, the above mentioned multi-
crosslinking technology (Figure 4) is an excellent approach to this new coating process,
A unique feature of blank lines is that they typically use infrared cure technology. Gas
convection curing dominates the general metal finishing markets, but infrared cure is preferred for the
PCM process because of its' efficient mode of heat transfer. Unlike convection curing, which cures the
coating by transferring heat from the substrate to the film, infrared energy is absorbed directly by the
coating. Also, the IR energy must "see" the material that it is targeted for. Therefore, the simple
geometry of a PCM application line is well-suited for IR cure. With this arrangement, it has been found
that the blocking agent in urethane coatings is not suitable for IR ovens, and hence a new challenge for
the PCM market has occurred. That is, PCM-grade coatings are most desirable when they are £ -
6-45
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caprolactam-free. The commercially available internally-blocked (£ -caprolactam-free) IPDI
crosslinker, because of its' higher melt viscosity and slower reactivity, generally gives powder coatings
with poorer film appearance and lower mechanical flexibility, Multi-crosslinking powder coatings
formulated with this £ -caprolactam-free isocyanate exhibit only minor decreases in film appearance
while still retaining their post-formability. Table 3 shows a physical property comparison of multi-
crosslinking power coatings with J] -caprolactam blocked IPDI and £ -caprolactam-free IPDI.
LOW-GLOSS POWDER COATINGS
Interest in low-gloss powder coatings continues to increase, particularly in the area of exterior
durable coatings. Reproducible low-gloss coatings are well-established in the epoxy and epoxy-polyester
hybrid coating technology segments. 5 However, for exterior applications, these chemistries are not
suitable because of their tendency to easily chalk and yellow.
Previously, methods for producing exterior durable powders relied upon the use of flattening
agents such as silica, or by dry-blending polyester powders of differing reactivities together. Such
techniques have frequently resulted in an inconsistent matte appearance, or have been dependent upon
carefully controlled extrusion and curing conditions. The dry-blending method has also been shown to be
quite labor intensive and impractical when carried out in a production environment.
The novel acrylic cure powder coating resin technology is well-suited for this coatings challenge.
Both the carboxy polyester/GMA acrylic and bifiinctional polyester/GMA acrylic/NCO (multi-cure)
systems can be produced in a full range of gloss, from matte to high gloss, with excellent smoothness and
mechanical properties. In addition, these systems have excellent gloss stability over a wide range of cure
cycles. By varying the ratio of the GMA acrylic hardeners- Fine-Clad® A-249-A and A-229-30-A for the
bifunctional polyester type, Fine-Clad®A-244-A and A-229-30-A for the carboxy polyester type- a
consistent and predictable gloss level is achieved. Tables 4 and 5 display powder coating formulations
and physical property test data for the multi-cure systems in a full range of gloss. Table 6 illustrates the
linear relationship between GMA acrylic hardener ratios and 60° gloss in these prepared powder
coatings. Table 7 displays the gloss stability of a formulated matte finish (Formulation I -Table 4) for a
time/temperature cure matrix. This gloss stability is especially critical for end-users that paint substrates
of varying mass on the same finishing line, where actual metal temperatures may widely fluctuate.
CONCLUSION
Industrial finishing is changing rapidly. Today's strict environmental laws pose significant
challenges for coatings end-users. Powder coatings have demonstrated their capabilities as
environmentally sound alternatives to the traditional solvent-borne coatings technology. The novel
acrylic cure polyester approach presented here allows the industrial finisher to apply superior coatings,
while significantly reducing waste and VOC-type pollution. The acrylic/polyester approach provides
state-of-the-art performance in the new pre-coated metal/blank, low-gloss, and exterior durable polyester
arenas.
ACKNOWLEDGEMENTS
The author wishes to thank his co-workers who contributed to this paper: Richard Kittle, Richard
Hong, Andrew Woo, and Dr. Hirofumi Takeda.
6-46-
i
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REFERENCES
1. Bocehi, G. Powder Coatings- Markets and Applications, Powder Coatings Institute, Alexandria, Virginia,
1993. 41 pp.
2. Glossary of Powder Coating Terms. Powder Coating. 5:7, 1994.
3. O'Donnell, G. Recent Developments in Thermoplastic Powder Coatings. Paper presented at 1993 13th
International Conference, International Centre for Coatings Technology, Brussels, Belgium. November 15-17, 1993.
4. Skeist, Incorporated, POWDER COATINGS II A Multiple-Client Study. Skeist, Incorporated, Whippanv,
New Jersey, September 1990.
5. Bate, D.A. Low Gloss Curing Derivatives. In : The Science of Powder Coatings Chemistry, Formulation and
Application. Vol. 1. London, United Kingdom, 1991. p.75.
6-47
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TABLE 1: ACRYLIC/POLYESTER FORMULATIONS
nPQPRIPTinM "ACRYLIC "MULTI- "MULTI-X-
Ut CURE" CURE" LINKING"
Formula No. 12 3
FINE-CLAD® M-8400 Carboxy Polyester (1) 80.0
FINE-CLAD® A-239-J Bifunct.Polyester (1) - 76.0
FINE-CLAD® A-239-X Bifunct.Polyester (1) - - 72.5
FINE-CLAD® A-229-30-A GMA Acrylic (1) 20.0 15.0
FINE-CLAD® A-244-AGMA Acrylic (1) - - 11.0
Huls B-1530IPDI (E-caprolactam blocked) - 9.0 13.5
Actiron DBT (2)
-
0.6
0.3
Modaflow 2000 (3)
1.5
1.5
1.5
Benzoin
0.5
0.5
0.5
Ti02
43.0
43.0
43.0
(1) Reichhold Chemicals, Inc.
(2) Dibutyl Tin Dilaurate- Synthron, Inc.
(3) Monsanto, Inc.
6-48 '
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TABLE 2 : PHYSICAL PROPERTIES FOR ACRYLIC/CURE POLYESTERS
DESCRIPTION
FORMULA NO.
Baking Schedule, min./°F
Film Thickness,mils
Gloss, 60°/20°
"b" value
PC! Flow Rating (1-10) 10=Best
Pencil Hardness
Gardner Impact:F/R (5/8"), IN.-LBS.
Mar Resistance
Crosshatch Adhesion
Solvent Cure Test-PCI # 8 B- (1)
Inclined Plate Flow (PCI # 7), mm
Gel time (PCI #6), seconds
100 % Overbake Resist., Gloss 60°/20°
100 % Overbake Resist., "b" value
Delta b
Xenon Arc Weather-o-meter Exposure;
% Gloss Retention after 500 hours
"ACRYLIC CURE"
I
10/400 °F
2.5
91/66
0.35
3
H
40/20
Excellent
100%
part./full cure
50 mm
30-35 sec.
90/63
0.65
0.3
65%
"MULTI-CURE"
10/400 °F
2.1
91/62
-0.14
4
H
60/60
Good
100%
part/full cure
85 mm
65-70 sec.
88/58
0.16
0.3
75%
(1) Powder Coating Institute Test # 8B: 100 Double Rubs with MEK
6-49
"MULTI-X-LINKiNG
3
10/400 °F
2.4
93/82
0.7
6
2H
120/120
Excellent
100%
Full cure
. 100 mm
45-50 sec.
92/75
1.4
0.7
50%
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TABLE 3: MULTI-CROSSLIN KING POWDER COATINGS:
COMPARISON OF £ -CAPROLACTAM-containing and £ - CAPROLACTAM-free coatings
A
B
FINE-CLAD ®A-239-X Bifunct.Polyester (1)
72.5
72.5
FINE-CLAD ® A-244-A GMA Acrylic (1)
11.0
11.0
Hiils B-1530 IPDI (E-caprolactam blocked)
13.5
-
Hiils BF-1540 (E-caprolactam-free)
-
14.4
Actiron DBT (2)
0.3
1.5
Modaflow 2000 (3)
1.0
1.5
Benzoin
0.5
0.5
Ti02
43.0
43.0
(1) Reichhold Chemicals, Inc.
(2) Dibutyl Tin Dilaurate- Synthron, Inc.
(3) Monsanto, Inc.
Baking Schedule, min./°F
10/400 °F
10/400° F
Film Thickness,mils
2.4
2.3
Gloss,60°/20°
93/82
91/58
"b" value
0.7
0.3
PCI Flow Rating (1-10)
6
5-6
Pencil Hardness
2H
2H
Gardner lmpact:F/R (5/8"), IN,-LBS.
120/120
60/60
Mar Resistance
Excellent
Fair
Crosshatch Adhesion
100%
100%
Solvent Cure Test-PCI # 8 A- (4)
Full cure
partial cure
Inclined Plate Flow (PCI # 7), mm
100 mm
99 mm
Gel time (PCI #6), seconds
45-50 sec.
95-100 sec.
100 % Overbake Resist., Gloss 60°/20°
92/75
88/49
100 % Overbake Resist., "b" value
1.4
1.4
Delta b
0.7
1.1
Flexibility: T-Bend
2T
5-6T
(4) Powder Coating Institute Test # 8B: 100 double rubs with mek
6-50
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TABLE 4: POWDER COATING FORMULATIONS FROM MATTE TO HIGH GLOSS
Formulas I-VI: Bifunctional Polyester/GMA Acrylic/ IPDI;
i
ii
Hi
JV
V
VI
Parts by weight
FINE-CLAD ® A-239-X Bifunct.Polyester (1)
64.5
64.5
64.5
64.5
64.5
64.5
FINE-CLAD® A-229-30-A GMA Acrylic (1)
0.0
8.0
10.0
12.0
14.0
16.0
FINE-CLAD® A-249-A GMA Acrylic (1)
24.0
12.0
10.0
8.0
6.0
4.0
FINE-CLAD® M-8400 Carboxy Polyester (1)
-
-
-
-
-
-
FINE-CLAD® A-244-A GMA Acrylic (1)
-
-
-
-
-
-
Huls B-1530 IPDI
12.0
16.0
16.0
16.0
16.0
16.0
Dodecanedioic Acid (2)
1.5
1.5
1.5
1.5
1.5
1.5
Actiron DBT (3)
0.2
0.4
0.4
0.4
0.4
0.4
C i7 Z imidazole (4)
0.2
0.2
0.2
0.2
0.2
0.2
Modaflow 2000 (5)
0.5
0.5
0.5
0.5
0,5
0.5
Benzoin
0.5
0.5
0.5
0.5
0,5
0.5
Ti02
43.0
43.0
43.0
43.0
43.0
43.0
(1) Reichhold Chemicals, Inc.
(2) DuPont Plastics
(3) Dibutyl Tin Dilaurate- Synthron, Inc.
(4) Air Products, Inc.
(5) Monsanto, Inc.
PROCESSING NOTES
PREMIX: Each batch blended in Henschel mixer for 30 seconds @ 2000 RPM.
EXTRUSION: Werner & Pfleiderer ZSK-30 twin-screw extruder;
250 RPM screw speed
Feed rate = 60 Ibs,/hr., Barrel temperatures: Zone 1 = 90 0 C, Zone 2 = 80 0 C,
Extrudate passed through Strand chill rolls and ground using a Brinkmann ZM-1 centrifugal mill @ 15,000 RPM.
Powder classified through a U.S. 200 mesh screen (75 microns) and sprayed onto cold rolled steel with a Nordson
Versa-Spray electrostatic spray gun.
6-51
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TABLE 5 :Acrv1ic/Polvester Powder Coating Evaluations: MATTE TO HIGH GLOSS
Formula No,
Baking Schedule, min./°F
Film Thickness,mils
Gloss,60°/20°
"b" value
PCI Flow Rating (1-10)
Pencil Hardness
Gardner impact:F/R (5/8"), IN.-LBS.
Mar Resistance
Crosshatch Adhesion
Solvent Cure Test (PCI # 8 B)
Inclined Plate Flow (PCI # 7), mm
Gel time (PCI #6), seconds
100 % Overbake Resist., Gloss 60°/20°
100 % Overbake Resist, "b" value
Delta b
Formulas l-Vf: Bifunctional Polyester/GMA Acrylic/ IPDI
i
11
ill
JM
V
VI
10/400°F
10/400°F
10/400°F
10/400°F
10/400°F
10/400°F
2.5 mils
2.3 mils
2.0 mils
2,6 mils
2.0 mils
2.0 mils
10/2
25/3
40/8
55/13
70/22
86/42
0.7
2.3
1.7
3.0
1.0
2.9
6
4
4
4
5
5
H
H
H
H
H
H
160/160
160/160
160/160
160/160
100/100
100/40
good
good
good
good
good
good
100%
100%
100%
100%
100%
100%
full cure
full cure
part, cure
part, cure
partcure
part, cure
40 mm
51 mm
56 mm
54 mm
59 mm
59 mm
30-40 sec.
35-40 sec.
35-40 sec.
45-50 sec. 45-50 sec.
45-50 sec.
10/2
24/4
40/5
56/12
67/22
85/46
0,9
2.75
2.1
3.5
1.9
3.3
0.2
0.45
0.4
0.5
0.9
0.4
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TABLE 6:Matte to High Gloss Acrylic/Polyester
Powder Coatings
60 Degree Gioss
70
O) 40
o
30 .
20 ..
Formula No,
6-53
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TABLE 7
TIMF/TEMPERATURE CURE MATRIX FOR MATTE FINISH:
(FORMULATION I.TABLE 4)
60 0 GLOSS
10 MINUTES @ 180 °C 9.1
20 MINUTES @ 180 0 C 8.0
30 MINUTES @ 180 °C 7.5
10 MINUTES @ 200 °C 8.6
20 MINUTES @ 200° C 8.1
30 MINUTES (® 200 °C 9.5
6-54
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SESSION 7A
AUTOMOTIVE APPLICATIONS
7-1
-------
PAPERS PRESENTED;
"Reduction of VOC Emissions from Painting of Car Bodies - a Case Study of Two Swedish
Car Plants"
by
Peter Adler
Swedish Environmental Protection Agency
Stockholm, Sweden
"New Low VOC Fluorinated Coatings"
by
Massimo Scicchitano
Ausimont S.p.A.
Milano, Italy
"Supercritical Fluid (SCF) Adhesion Promoters for Automotive Plastic Applications"
by
Rick Copeland
Union Carbide Corporation
South Charleston, West Virginia
7-2
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Reductions of VOC emissions from paint-
ing of car bodies - a case study of two
Swedish car plants
Peter Adler,
Sector specialist, car manufacturing and foundries,
Swedish Environmental Protection Agency
(Address from 1st July 1995:}
S-106 48 Stockholm
SWEDEN
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessariiy reflect the views of the
Agency and no official endorsement should be inferred.
Introduction
The two major Swedish car plants constitute significant
point sources of VOC emissions in a part of the country which
is subject to high total VOC emission levels. The plants have
received conditions according to the Environmental Protection
Act stipulating that their emissions of volatile organic
compounds should be gradually reduced until they reach a
level of approximately 2 kg of VOC per car body. According to
the conditions, this final goal should be reached by 1998 or
2000.
Emissions have already decreased significantly. The
companies' efforts to reduce emissions are carried out with
insight from, and in consultation with, the environmental
authorities at local, regional and national level.
In this paper, the conditions in the two factories per-
mits are presented, followed by information on past and
present VOC-emissions. After this a general technical de-
scription of implemented and planned abatement measures for
different processes is given, with emission factors (kg
VOC/car) for each process.
Volvo, Torslanda1
Conditions in the permit
Emissions of VOCs may not exceed the following values:
1992 - 1995 1 100 tons per year
1996 - 1997 700 tons per year
from 1998 inclusive 450 tons per year
The emission limits include all emissions from the whole
factory, but they are not related to the degree of capacity
utilization. The permit allows for the production of 260 000
7-3
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car bodies per year and the assembly of 170 000 cars per
year. However, the actual highest production of car bodies is
not likely to exceed approximately 200 000 per year.
The paint shop for small parts may paint 235 000 detail
racks per year, and the spare parts paint shop (electrodip)
may paint 1 500 000 m2 per year. Emissions from certain acti-
vities which cannot be directly related to the production of
cars, such as painting of trucks, and laboratory and develop-
ment center, are also included in the emission limit,
VOC emissions past and present
VOC emissions were approximately 23 kg/car body before
work was started during the 70'ies m order to reduce them.
In 1989, when the old paintshop was still in full use,
VOC emissions from the whole plant were 1794 tons, of which
1750 tons can be more or less related to the production of
cars; that year 178 000 car bodies were painted and 134 000
cars assembled. In 1994, with the old paintshop virtually
discontinued, emissions related to the production of cars
were according to preliminary figures 350 tons (approx
105 000 car bodies painted, 94 000 cars assembled). Emissions
were thus an average of 3.3 kg/produced car, or 2.7 kg/car
body if the 71 tons from the small parts paint shop are ex-
cluded.
Electrodip
The consiarption of solvents in the electrodip paint shop
is approximately 0,82 kg/car body. Of this, about 20% is
incinerated in the afterburners on the drying ovens, and
about 50% leaves the paint shop in waste water. The solvents
in question are biodegradable, and calculations have shown
that they will mostly not evaporate before reaching the
public wastewater treatment plant.
Lead-free electrodip that has been introduced in the
spare parts paint shop contains a third as much solvent as
the ordinary electrodip. Volvo plans to introduce the lead-
free paint for electrodipping of car bodies as well, but
there are still technical problems left to solve.
The new paint shop for surfacer and topcoat
The new paint shop, with far-reaching abatement measures,
started production in the autumn of 1990 and has, after a
fairly long period for starting up, since the middle of 1993
painted virtually all the car bodies which are painted at
Torslanda.
7-4
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Ill 1994 the emissions from the new paint shop were
(104 000 car bodies painted);
Source Emission Emission
(tons) (kg/car body)
Abrasive resistant 8.7 0.08
paint etc
Surfacer 12.4 0.12
Basecoat 87 0.84
Clearcoat 22.4 0.22
Cleaning of painting 31 0.30
equipment and booths
TOTAL 161 1.55
Waterborne paints. Virtually all basecoats are waterborne,
typically with 13 - 15% solvents. The metallic basecoats have
a rather low content of paint solids, generally 15 - 25%.
Destruction of solvents. Air from the application of abra-
sive resistant paint, surfacer and clearcoat is concentrated
with respect to solvents. Air from automated spray booths is
recirculated over the booths, whereas air from manual appli-
cation of surfacer and clearcoat is concentrated in active
carbon filters. The concentrated air flows are incinerated in
regenerative sand beds. Air from the storage tanks for paint
booth scrubber water is ducted back to the paint booth, so
this air is also cleaned.
Solvents in ventilated air from paint-mixing rooms, and
air from sedimentation tanks for scrubber water from solvent-
borne booths, are concentrated in a zeolite rotor and then
ducted to the same incineration equipment as the solvents
from painting.
Flue gases from all drying ovens are treated by incinera-
tion.
Cleaning of equipment and booths. Booth walls and some
equipment are coated with a substance that enables paint to
be removed using high pressure water. Booth windows and other
equipment are coated with a plastic film, so that paint can
easily be removed by removing the film.
Non-fixed spraying equipment from both solventborne and
waterborne booths is cleaned in special rooms. The air from
7-5
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these rooms is ducted to the same abatement equipment as air
from the paint-mixing rooms.
Such solvents that still need to be used for cleaning of
booths and equipment {eg equipment that cannot be treated
with protective layers as described above) in solvent-borne
booths are collected and sent to be distilled at an external
plant, for reuse at Volvo.
The remaining emissions of VOCs from cleaning come mostly
from in-booth cleaning of equipment for waterborne paint. The
solvents used for this consist mostly of butyl glycol.
Emission figures for solvents from cleaning are calcula-
ted as 10% of the net consumption tie excluding solvents
recollected for redistillation) in booths connected to abate-
ment equipment, and total net consunption in booths that are
not connected to abatement equipment.
In the "bad old days" there was much less check of how
much solvents were used, but consunption is estimated by
Volvo to have been up to 1 500 tons per year. Collection of
solvents for redistillation was started m 1986/1987; before
then all cleaning solvents were emitted. Nowadays, much
greater care is placed on not using more cleaning solvents
than necessary. The economizing on solvents for cleaning has
been good for the external environment, for the workplace
environment, and for finances.
Efficient application of paint. The amount of overspray is
reduced by using electrostatic equipment. Virtually all
layers covering the corplete outer surface are applied using
electrostatic bells, with only 10 - 15% overspray. Handguns
have also been improved in order to reduce overspray frcxn
manual application. However, Volvo is gradually going over to
automated application on the inside of bodies as well. This
should increase transfer efficiency, perhaps from about 30%
to 40%, thereby decreasing paint consunption in proportion.
Underbody coating
Volvo has gone over to underbody coating that is of the
hot-melt kind, with no solvents, using heat instead to get
sufficiently low viscosity for application. This is applied
after topcoat. Before, VOC emissions from underbody coating
were 4.7 kg/car. The 0.23_kg/ear that_are still emitted come
from the coating of chassi details which are fitted during
assembly.
7-6
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Cavity protection material
The dry content in cavity protection material has been
increased to 64%, and the quantity that is applied has been
optimized, so that resulting emissions (=consumption) of
solvents are down to an average of 0.16 kg/car.
The aim is to go over to 100% solids material. (This has
already been achieved at Volvo's equivalent plant in Flan-
ders .)
Assembly and final adjustment
Emissions of solvents from assembly and final adjustment
are approximately 0.25 kg/car. Use of solvents for cleaning
equipment and workplaces has been dramatically reduced by
introducing formalized routines for the issuing of solvents
to personnel. Water-based cleaners have largely been able to
replace solvents.
Repair painting of originally waterborne coats is done
with waterbased paint.
Volvo has started to use "wrap-guard", a plastic paint-
protection film, that is put on already after the car-body
paint shop and stays on throughout assembly. This has meant
that the amount of repair painting has decreased. This also
serves as paint protection for delivery, thereby more or less
eliminating the use of other paint protection.
Nowadays, the only fluid paint protection that needs to
be applied is in the engine compartment, and waterborne
material is used as long as there is no risk for frost.
Small parts paint shop
Measures against VOC-emissions from the small parts paint
shop, which paints small parts for cars produced both at the
Torslanda plant and at Volvo's plant in Flanders, can basi-
cally be the same as from the main car body paint shop.
However, due to the fact that the present small parts paint
shop is not designed for waterborne paints, and to some other
technical problems, abatement has not come as far. Qnissions
from this paint shop thus were as much as 71 tons in 1994,
but measures to decrease emissions are planned.
Conclusions
Leaving aside the small parts paint shop, results already
reached or expected in the near future at the Torslanda plant
should give the following emissions from activities related
to the production of cars: electrodip 0.1; abrasive resistant
7-7
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paint to clearcoat 1.3 - 1.5/ underbody coating 0.23; cavity
protection material -0; assembly arid final adjustment 0.25;
paint protection -0; altogether approximately 2 kg/car.
SAAB Automobile AB, Trollhattan2
Conditions in the permit
Bnissions of VOCs to air are not allowed to exceed the
higher of following values A or B for each year; nor are
emissions allowed to exceed the values C:
A BC
tecs per year kg/car, tons per year
yearly average
1995 - 1996 550 7.0 840
1997 275 6.0 700
1998 275 4.5 525
1999 275 4.5 460
from 2000 inclusive 275
The permit allows for the production of 120 000 cars per
year.
VOC emissions past and present
VOC emissions were approximately 20 kg/car body up to the
beginning of the 801ies, when work was started in order to
reduce them.
Below, emissions expressed in kg/car are compared for 1990
(when 57 000 cars were produced) with planned emissions for
1994 and 2000.
Source emission in kg/car
1990 1994 2000
Primer 0.93
Electrodeposition 1.2 0.0631 0.063)
Surfacer and un- 2.4 0.85 0.18
der-body coating
Topcoat 4.82! 4.4 0.92
Cavity protection
material
2.025 0.05 0.05
Assembly, final 0.70 0.10 0.10
adjustment and
paint protection
7-8
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Cleaning1' and 1.52i 1.7 1.0
miscellaneous
TOTAL 13.4 .7.1 2.3
11 Emissions from cleaning do not include solvents that are
collected and redistilled.
2iQnissions that in 1990 were reported from the major
paint shops probably include certain emissions from
cleaning, that in later years have been reported as such
in order to get a better grip of how large emissions from
cleaning are. This does not change the figure for total
emissions.
31 Emissions from the new electrodip might be 0 to 0.2
kg/car higher if emissions of solvents to water are
emitted to air at a later stage.
Electrodip and primer
The anodic electrodeposition (on the inside of the body)
and the primer {on the outside), which together emitted
approximately 2 kg VOC per car, were replaced in spring 1993
with a cathoaic electrodip. The flue gases from the drying
oven are. incinerated in an afterburner. The ventilation from
the application of the paint is ducted to the drying oven and
thence to the afterburner; the energy cost for the further
emission reduction thus achieved is approximately 1 USD per
kg VOC.
Uhderbody coating
The dry content in underbody coating has been increased
to 83 % dry content by weight; suitable viscosity for appli-
cation is achieved by heating to 50°C. Including the effect
of the drying oven's afterburner, which is estimated to
incinerate 90% of VOCs in the underbody coating, resulting
emissions from underbody coating are estimated to be 0.12
kg/car. (Measurements at SAAB have shown that virtually no
solvents are emitted from the underbody coating during appli-
cation. )
Surfacer and topcoat
Continuous inprovement. Emissions have already been reduced
through increased concentration of dry substance in metallic
paint and other paints, electrostatic application with rota-
ting bells, and optimization of surface thickness and of
application area.
7-9
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Overspray. "The VOC emissions resulting from overspray are
significant - despite improvements they are still about l
kcj/car body from solid topcoat and 2 kg/car body from metal-
lic basecoat with clearcoat. Overspray is approximately 25 -
30% from automated spraying, but a lot higher from hand-
spraying. Hand-spraying is used for the inside of car bodies
and for the final coat on the outside of metallic paints.
Planned new paint shops in the 90's. The present surfacer
is planned to be replaced by a waterborne surfacer. Water-
borne surfacers with a solvent content of 3-4% are available
on the market. Powder-coat surfacer might also be a possi-
bility, with interesting developments m that area going on
in the USA.
The present system for topcoat - a single paint layer for
solid colors and a basecoat layer and a clearcoat layer for
metallic colors - will be replaced with a system with both
basecoat and clearcoat irrespective of color type. The base-
coat is planned to be be waterborne. Either the clearcoat
will be waterborne or the flue gases will be cleaned from
solvents. The intermediate drying zone between basecoat and
clearcoat is planned to be ducted to a drying oven's after-
burner. Altogether, VOC emissions from topcoat will be re-
duced to about 1 kg/car, compared with about 6 kg/car (me-
tallic) and about 3 kg/car (solid) in 1992.
Cleaning of equipment and booths
Protective polyethylene films are applied on paint-spray-
ing equipment and on paint booth windows. The films can be
removed by hand when paint has built up on them, and deposi-
ted as fairly harmless waste. A water-soluble resin is appli-
ed to paint booth walls, so that they can be cleaned using
high-pressure water. In these ways, cleaning solvents are
avoided.
Use of water/butylglycol mixtures replace organic sol-
vents for the cleaning of equipment where waterborne paint is
used.
Use of teflon-coated gratings in the spraybooths in order
to decrease the building up of paint on these surfaces is
being discussed.
A number of. different measures, such as reducing the
number of locations where cleaning with solvents can be
carried out, and adding lids to cleaning trays, have improved
housekeeping of solvents.
Thinners used for cleaning the paint distribution system
is collected (and distilled in-house' for reuse).
7-10
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Cleaning is still a significant source of VOC emissions, but
they come from many small-scale sources, rather than from a
large easily identified process, and are thus easily over-
looked. -The size of the emissions is also very much the
result of how careful individuals are when cleaning equip-
ment. SAAB has for these reasons striven to increase aware-
ness on the shop floor of how important carefulness in clean-
ing is for reducing the factory's environmental impact.
Cavity protection
The dry content in cavity protection material has gradu-
ally been increased. Many years ago, VOC emissions from such
material ran to many hundreds of tons per year. In 1991,
emissions had been reduced to approximately 1.3 kg/car.
Cavity protection material consisting of >99% solids has now-
been introduced, giving emissions of approximately 0.02 kg/
car, and lower costs. This also irrproves the working environ-
ment, through decreased evaporation of VOCs from car bodies
on production lines after the cavity protection treatment.
Furthermore, spillage of cavity protection material on car
bodies and equipment can now be removed using detergents •
instead of solvents.
Assembly
Solvent-based corrosion protection materials applied
during assembly are gradually being substituted by other
protection on parts, eg hot dip galvanizing.
Parts of car bodies that are easily damaged are covered
with protective plastic shields during assembly, thus de-
creasing the need for repair painting.
Afterburners
Installation of afterburners after drying ovens for
surfacer and underbody coating, for metallic and for corro-
sion protection have decreased emissions by 1.9 kg/car.
With the planned new paint shops, all drying ovens will
have afterburners.
Paint protection
Previously, solventborne material was used for temporary
paint protection treatment, but SAAB has now switched over to
waterborne material. This has decreased emissions from about
0.6 kg per treated car to virtually nil (0,01 kg/car} . This
also leads to reduced VOC emissions when the paint protection
is removed: solventborne material will generally be removed
7-11
-------
using petroleum spirits, wheras waterborne material can be
removed by aqueos cleaners (that do, however, contain EDTA).
Paint sludge
Analyses carried out on SAAB's paint sludge from topcoat
(solventborne) showed that the VOC content is 3 - 7%, How-
ever, most of the VOC that was in the sludge consisted of
butanol, which was shown in another experiment to evaporate
from the sludge more slowly than the water did.
Sludge from topcoat (approximately 150 - 200 tons in
1993) is at present incinerated in a municipal solid waste
incinerator; this seems to be working well, but a final
decision on whether to continue with this arrangement on a
regular basis has not yet been taken. The solvents that are
destroyed in this way have not been deducted from the emis-
sion figures quoted above.
Conclusion
The sum of VOC emissions from electrodeposition, under-
body coating, surfacer, basecoat and clearcoat will thus be
approximately 1.2 kg/car. amissions from cavity protection
material and assembly etc are now less than 0.2 kg/car.
Together with planned decreases in emissions from cleaning,
total emissions should be down to 2.3 kg/car by the year
2000. With the possible exception of end-of-pipe abatement
after clearcoat if solvent-borne is chosen, this decrease
will have been achieved solely by good housekeeping and using
low-solvent materials.
References
1. Annual Environmental reports and public documents from
licensing procedures, from Volvo Car Corporation, Tors-
landa plant; and personal corrmunication with Mihkel Laks,
Stanley Johansson and Rosemarie Andersson, Volvo
2. Annual Environmental reports and public_documents from
' licensing procedures, from SAAB Automobile Corporation,
Trollhattan plant; and personal corrmunication with Everth
Andersson, Tomas Stalfors, Sten-Olof Gothberg and Arne
Wolgast, SAAB.
7-12
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NEW LOW V.O.C. FLUORINATED COATINGS
Massimo Scicchitano , Stefano Turri , Claudio Tonelli
Angelo Locaspi
AUSIMONT S.p.A., Centro Ricerche & Sviluppo
Viale Lombardia 20,
20021 Bollate (Milano), ITALY
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
7-13
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INTRODUCTION
A well known problem in the manifacturing industry is
the aspect related to the coating operations on finished
or semi-finished articles. Coatings are applied to protect
the' substrate and improve the aspect. The process
frequently involves the use of solvents as film forming
coadiuvant and diluent; the solvent release into the
atmosphere is the source of one the major concerns of the
manifacturing industry. The future regulations and laws
claim for the reduction of Volatile Organic Compounds (VOC) to
obtain environmental friendly coatings. According to this
view, paint producers are working' in two directions: the former
towards formulations having a lower solvent amount, the latter
to develop technologies characterized "per se" by low V.O.C.
Thus, water based and powder coatings are increasingly used,
although this approach hardly meets the requirement of the
market in terms of quality and durability of the final
material.
A really innovative system should present the following
profile:
• to match the most restrictive coming laws concerning the
problem of solvent emission into the atmosphere
• to be applicable with the existing apparatus
• to be a high performance material: durability, protection,
appearance.
Fluoropolymers as starting materials for high
performance coatings are well known expecially for their
superior durability, weatherability and chemical resistance^.
Polyvinylidene fluoride^ (PVDF} is widely used in the
architectural field; it is a high molecular weight
thermoplastic fluoropolymer which is usually formulated with
acrylic resins in a latent solvent paint to improve the
rheological behaviour and adhesion, PVDF coatings are
considered as particularly suitable for long term outdoor
expositions.
More recently, thermocurable fluoropolymers^ were
developed consisting of
chlorotrifluoroethylene/vinylethers or vinylesters
alternated copolymers with free OH pendant groups. In
any case, the relatively high molecular weight of these
polymers (>10000) and the intrinsic stiffness of the main
chain cause a high viscosity and, consequently, a large
amount ¦ of solvents is required for a correct
application. Therefore, these formulations have a solid
content around 10 - 40 %, and that fact appears as a serious
drawback and limitation in a future wider use of these
coatings.
Perfluoropolyethers (PFPE) and their functionalized
derivatives present , on the contrary, an exceptionally high
7-14
-------
chain flexibility and a molecular weight easily available in
the oligomeric ranged. Their resistance to aggressive
environments (chemical, thermal, photooxidative) is
excellent^, and their bulk viscosity is generally low enough to
require a very reduced amount of solvent in formulation: in
principle, fluoropolyether derivatives offer the
possibility to join a low V.O.C with high performances
characteristic of fluorinated coatings.
THE RESINS
In this work, hydroxy bearing resins will be described
as useful for one-pack coating formulations. The .table 1
reports the main features of this new class of
fluoropolyether based resins, named FLUOROBASE 2 (FBZ).
They consist of a random perfluoropolyether chain
(CF2CF2O)p(CF2O)q- having primary and secondary hydroxy
functions; a minor number of -CCOH groups can be optionally
present. The molecular weight is tipically comprised
between 1000 and 2000. The composition of the PFPE chain
determines a p/q ratio generally close to 1: the quite
random distribution of the -CF2CF2O- and -CF2O- units
prevents any possibility of crystallization and the
fluoroetheric nature imparts the characteristic flexibility,
evidenced by the low Tg value. The whole macromolecule
consists of C-C, C-0 and C-F simple bonds and the hydroxylic
functionality (that is the number of reactive groups per
molecule) is 2-4.
Table 1: Main features of new FLUOROBASE Z resins
Resins type FBZ 1010
OH functionality 2.8-3.0
Acid Number
Viscosity(cP,20°C) 300-600
Glass Transition(°C) -90/-100
FBZ 1020 FBZ 1030 FBZ 1040
3.8-4.0 1.9-2.2 3.3-3.6
10-25
2500-3000 80-150 5000-6000
-80/-90 -100/-110 -60/-70
The viscosity (data given at 20° in table 1) ranges
from 100 to 6000 cP mainly depending on functionality, with
a minor effect of the flexible chain.
Viscosity of these resins is strongly influenced
by addition of few percents of solvent; the figure 1 shows the
viscosity-concentration dependence of FBZ 1030 in
three different solvents (a fluoroalkane, a ketone, an
alcohol), whereas the figure 2 shows the viscosity-
7-15
-------
concentration curves (on a semilogarithmic plot) of FBZ
1010, 1020 and 1030 in methyl isobutylketone (MIBK) . It
appears that fluoroalkanes ("good" solvents of PFPE chain6)
have a much lower effect on the resin viscosity with respect
to ketones and alcohols which are "poor" solvents of PFPE.
Furthermore, the viscosity reducing power of polar
solvents is more marked for higher functionality resins
(FBZ 1020). All these experimental evidences suggest that
viscosity of these PFPE based polyols is dominated by polar
interactions (as hydrogen bonds) among the ends which create
intermolecular associations.
A very limited amount of a polar solvent enables to
reduce steeply viscosity of the mixture disrupting
these associations, while fluorinated non-polar solvents
cannot compete with hydrogen bonds, so showing a lower
10000
100 K
« 20 30
X**
Figure 1: Viscosity of FBZ
1030 in various solvents at I
25'C.
0 « 10 18 20
icJvent % w/w
~71030 121010 AZ1020
Figure 2: Viscosity of FBZ
resins in MIBK at T= 25°C.
viscosity reducing power. Similar effects were
described7 also concerning other polyolic "hydrogenated"
resins (acrylics), but the viscosity reduction caused by
polar solvents on FLUOROBASE Z resins is more marked due to
7-16
-------
the high selectivity of the end group solvatation and high
molecular mobility of the PFPE chain.
It should be noticed that alcohols, esters, ketones are
very useful solvents for one-pack coating formulations;
these fluoropolyether based resins can be considered
as structurally suitable for the preparation , of new
high-performance low VOC coatings, in that generally few
percents of a proper solvent are enough to control the
rheology of the system to the specific applicative need.
THE FORMULATIONS
FLUOROBASE Z resins can be formulated with a variety
of common melaminic and isocyanic hardeners; typical examples
are monomeric and oligomeric methylated melamines
(commercial CYMEL 303 and 325) and ketoxime-blocked IPDI and
HDI isocyanurates (VESTANA? B1358 and DESMODUR BL3175
respectively). Solvents suitable are butanol, butyl
acetate, PMA, MIBK and others belonging to the same
classes. At the ¦ same time, curing conditions are
conventional: 140-150 °C./30 min with p-toluensulfonic acid
catalysis for melamines, 150-180 °C./30-10 min with dibutyl tin
dilaurate catalysis for blocked isocyanates. The resin FBZ
1040 is preferred in melamine based formulations because its
higher acid number makes easier compatibilization (even
without solvent) and catalyzes the crosslinking reaction.
Compatibility (meant as the possibility to obtain clear
formulations of FBZ resins), is generally good with ketoxime
blocked polyisocyanates and it seems easier for the lower
functionality resins (FBZ 1010 and 1030). Due to its high OH
functionality,it is advisable using alcohols as butanol in
formulations based on FBZ 1020; in any case , aliphatic or
aromatic hydrocarbons should be eliminated previously if
present in the commercial hardener (for ex. BL3175).
The solid content achievable is 100 - 80% for
melamine formulations and 85 - 70 % for the higher viscosity
blocked isocyanurates. Also taking into account the
evaporation of the blocking agent (methanol and methyl ethyl
ketoxime), interestingly low VOC coatings are obtained.
It should be noticed that solvent is used exclusively
for reducing the viscosity of the formulation, while
good coating appearance and correct film formation are assured
by the flexibility and the newtonian behaviour of the PFPE
chain also without solvent.
The knowledge of viscosity - temperature dependence of
these formulations can be of concern in view of
particular technologies (as hot spraying, for example)
allowing to reach the best results in terms of low VOC.
Thus, the figure 3 shows the viscosity-temperature relation
for some formulations according to an Arrhenius type plot. It
seems that an approximated straight line dependence is
7-17
-------
followed, likely thanks the low Tg value7 and the good
compatibility of the fluoropolyether resins with the
hardeners. That fact assures the possibility to foresee
easily the effect of temperature on viscosity which is,
around 50°C, generally comprised between 50 and 500 cP.
10000
1000 -¦
cf>«
100
;<
k
X
A
~
X
X
A
~
X
X
A
~
X
A
~
X
10 1 1 1 1 ) 1 1 1 1
0.003 0.00306 0.0031 0.00316 0.0032 0.00326 0.0033 0.0033S 0.0034 0.00345
VT(*K)
~21020/B13S8 ¦Z101WBL317S AZ1040/C32S X21
-------
THE COATINGS
As a general rule, the polyurethanic materials
previously described always show two distinct Tg values. The
former glass transition temperature is generally located
around -100°C and corresponds to the fluoroetheric
segregated phase. The Cp variation at the transition is
rather low {about 0.01 cal/g) and the Tg is sometimes
difficult to evaluate, especially for FBZ 1020 cured films
where the weight fraction of fluorinated moiety is lower.
The latter thermal transition should be attributed to the
urethanic "hydrogenated" phase; significant differences
may be observed moving from the HDI cured films to the
IPDI ones and, within each class, changing the hydroxy
functionality of the resin. In fact, the degree of
crosslinking appears as a factor regularly influencing the
upper Tg value, which varies from about -10° to +30 °C. {HDI
cured) and from +65° to +145 °C. (IPDI cured), in both cases
changing the OH functionality of the resin from 2 to 4.
The melamine cured films show, on the contrary, a only
Tg value at about 160 °C. without other detectable transitions
at lower temperatures. The lack of the "fluorinated Tg" may be
partially due to a relatively low sensitivity of the DSC
method and partially to a real constraint effect exerted on
the PFPE chain by the highly crosslinked polymeric network
which strongly lowers its degrees of freedom.
The typical two-phases morphology of the
fluorcpolyether polyurethanes finds a close correspondence
also in their mechanical properties. Stress-strain curves8
were carried out at +23°C on self-supported films peeled off
PTFE or PFA plates after curing. As an example, the figure 4
shows the comparison between the tensile curves of FBZ 1030
films cured with BL3175 and B1358.
The presence of a glassy phase (Tg +65") in the latter
material determines a tough-plastic behaviour with , yielding
occurring around 30-35 MPa {yield stress) and 6-7% (yield
strain) . The HDI cured film is, by contrast, tested at a
temperature above any thermal transition and it shows a
rubberlike behaviour with no yielding phenomena and much
lower tensile strenght than in the former case. The rupture
strain (about 80%), noticeable for a coating, is practically
the same for both cases in that it is determined mainly by
the chair, lenght of the soft segment {the PFPE chain) among
the chemical junctions of the polymeric network . Analogous
considerations could be done also for the FBZ 1010 and FBZ
1020 coatings taking into account a progressive increase in
tensile strenght and decrease of rupture strain regularly
increasing the OH functionality of the resin.
For all these evidences it can be argued that IPDI based
hardeners are surely more appropriate in order to obtain
coatings characteri zed by mechanical propert ies (i.e.
7-19
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hardness) of interest for the high temperature
applications. In any case, the presence of a relevant
rubbery segregated phase imparts a noticeable flexibility to
these, polyurethanic coatings (the T-bend test performed on
coated aluminum panels is tipically 0-1 T) , which could be
very useful especially for the coil-coating technology .
An important consideration
should be done about the
appearance of these new
materials. In spite of the
presence of generally well
segregated phases, all these
coatings appear as quite
transparent without any
haze effect (transmitted
light through coated glass
panels is always 100%). This
may be explained invoking
the presence of microdomains
sized exclusively well below
the wavelenght of light. That
fact is very important because
it allows the use of these
materials as clear coats
without loosing some relevant
properties inferred by the
multiphasicity, like the good
flexibility and formability,
Melamine cured films are
also characterized by a
complete transparency: the
application conditions, the good adhesion on various primed
substrates and the high fluorine content make these coatings
as promising high protection topcoats in the automotive
technology. . Solvent-less coatings can be reached using
these new fluoropolyether based resins. An example is given
by FBZ 1G40/CYMEL 303 coating (hardener 20-25% w/w), which
components are completely miscible even without solvent; the
viscosity (around 5000-6000 cP at ambient temperature) can
be furtherly reduced by hot applications or, eventually,
studying C02 based systems. The leveling of such a
coating is very high notwthstanding the absence of a
solvent.
The table 2 summarizes some relevant properties of
melamine cured FBZ coatings. The values of hardness and
gloss are acceptable notwithstanding the high content of
"soft" and low refraction index perfluoropolyether. On the
other hand, the very high fluorine content determines a high
inertness to chemicals as acids and organic solvents, and an
exceptionally high abrasion resistance {evaluated as gloss
retention after a standard mar test used in the automotive
30 -¦
20 ••
Figure 4: Stress-strain curves
of the crosslinked films
7-20
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industry). These outstanding . performances are surely
related to the low coefficient of friction and reduced
contact area typical of highly fluorinated materials.
Accelerated weathering tests on the films are in progress,
even if previous experiences carried out on fluorinated resins
have stressed out an exceptionally inertness even in very
drastic conditions (U.V. radiation, chemicals, humidity); this
is a fundamental starting point to obtain coatings showing
very high weatherability.
Table 2; Properties of melamine cured FBZ 1040 films
VOC (ASTM D 3960-81)
Fluorine Content
Hardness (Persoz)
Gloss (60°C)
D.O.I.
Conic Mandrel
Abrasion Resistence
(Gloss retention)
Acid Resistance
(Spot Test, H2S04 381, 25°C)
Solvent Resistence
(Spot Test, MEK, Xylene, 25°C)
Adhesion
(Cross cut test, on primed panels)
180-400 g/L (1.
32-36% w/w
230-250
78-85
excellent
< 3.17
95-98 %
no effect
no effect
100 I
5-3.3 Lb/Gal)
CONCLUSIONS
Fluoropolyetheric polyols can be considered as the
most suitable resins in order to obtain low VOC and high
performance coatings. In fact, the hydroxy .functionality
imparts crosslinkability and promotes compatibility with
solvents and hardeners through polar interactions. On the
other hand,' the oligomeric PFPE chain gives a very limited
contribution to viscosity and, furtherly, assists the
correct film formation during the curing process thanks its
high flowability. The bulk viscosity of the resin may be
tuned to the desired value by hot application or addition of
limited amounts of solvent, which selectively interacts with
polar end groups. Low VOC coatings are therefore
available for the high temperature technology (coil-coating,
automotive, architectural) characterized by good resistance
towards abrasion and chemicals. Further studies are
developing in order to set up also low temperature curing
low VOC fluoropolyether based coatings.
7-21
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REFERENCES
1- K.Johns, Proceedings of the 2nd PRA International Conference
Fluorine in Coatings", Sept. 28-30 Salford {England),
(1994)
2- L.A,Wall, "Fluoropolymers, High Polymers XXV", Wiley ed.,
New York (1972)
3- S.Munekata, "Prog.Org,Coat." 16, 113 {1988)
4- D.Sianesi,G.Caporiceio,D.Mensi U.S.Patent 3.847,978 ,
MONTEDISON •
5- D.Sianesi, A.Pasetti, R.Fontanelli, M.Binaghi "Wear" 18, 85
(1971)
6- P.Cotts, "Macromolecules" 27, 6487 (1994)
7- L.W.Hill, Z.W.Wicks "Prog.Org.Coat." 10, 55 (1982)
8- ASTM D1708
7-22
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SUPERCRITICAL FLUID (SCF) ADHESION PROMOTERS
for Automotive Plastic Applications
E. Rick Copeland
Union Carbide Corporation
3200-3300 Kanawha Tpk.
S. Charleston, WV 25303
INTRODUCTION
The growth of thermoplastic polyolefins (TPO) for the automotive plastics market
is pushing industry to better understand issues regarding the application of coatings to
TPO substrates. Some of the issues relate to federal, state and county environmental
regulations; adhesion and penetration of the coating into the substrate as well as the
intercoat adhesion between layers of coatings. One method of resolving some of these
issues is using chlorinated polyolefins (CPO) tie-coats to assist in the adhesion of
topcoats to untreated TPO.
An alternative spray process, the supercritical fluid {SCF) process was
developed for applying solvent borne (CPO) adhesion promoters to TPO. This paper
will discuss how during plant trials, the SCF process dramatically reduced solvent
emissions, improved application efficiency, and enhanced product performance.
ADHESION PROMOTERS
Adhesion promoters are coatings specifically designed to promote adhesion
to hard-to-adhere-to substrates like thermoplastic olefins (TPO). Adhesion
promoters are typically non-reactive, one component (1K) solvent-borne polymers,
averaging less than 10% volume solids. The products are normally HVLP applied at
0.2 to 0.4 mils dry film thickness. Adhesion promoters use chlorinated polyolefin
resins (CPO) to obtain adhesion to TPO and modifying resins to acquire adhesion of
a polyurethane topcoat to the primer. Optimization of these resins is key to assuring
peak performance. Adhesion promoters are primarily composed of aromatic
solvents because CPO resins are best solubilized and most stable with aromatics.
Because TPO consists primarily of polypropylene, and is a difficult substrate for
standard polyurethane coatings to adhere to, it is necessary to use an adhesion
promoter.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
7-23
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There are also other pretreatments available for TPO which eliminate the
need for an adhesion promoter; such as vapor degreasing, UV light irradiation
(utilizing Benzophenone), flame treatment, gas plasma, and corona discharge. But
due to environmental regulations and cost, these methods have not been widely
used in North America,
By far, the easiest method for reducing VOC of the adhesion promoter would
presumably be reducing its solvent content and increasing its solids content. This,
however, is much more difficult then it appears. The key component in adhesion
promoters, the CPO resin, requires a substantial amount of solvent to bring it to a
sprayable viscosity. Solvent contents of 6.5 to 7.0 lbs. per gallon are normally
required for proper spraying and leveling of the wet film.{1) Reductions in solvent
content give high viscosities and poor atomization which causes spotty application
with significant orange peel. The film does not sufficiently wet the substrate surface
and also causes minimal adhesion. The high degree of orange peel can profile
through the topcoat, resulting in an unsatisfactory painted surface with lower DOI.
For these reasons an alternative spray process, the supercritical fluid (SCF)
spray process was tested because it could spray a higher viscosity product, and
reduce the VOCs. The process could also produce a satisfactory film with good
atomization, flow, and leveling properties.
SUPERCRITICAL FLUID (SCF) SPRAY PROCESS APPROACH
The supercritical fluid spray process for the application of coatings was first
proposed in 1990 as a new pollution prevention technology. (2) The process uses
carbon dioxide to replace the volatile organic solvents used in conventional and high
solids coating formulations. The technical developments of the process were
described in 1993. (3-4) Early results showed that the process could actually
improve coating appearance, improve corrosion resistance and performance when
removing most of the solvent from solvent-borne formulations. (5) The polymer
chemistry and phase relationships of coating concentrates with carbon dioxide were
described in 1994. These studies demonstrated that carbon dioxide has favorable
properties for spraying coatings at very high polymer levels. The design of polymers
with a relatively high carbon dioxide solubility, allows very-low-solvent and solvent-
free coatings to be developed and sprayed. (6)
SPRAY GENERATION AND CONDITIONS
The supercritical fluid spray process uses specifically designed spray
equipment which meters and pressurizes the coating and carbon dioxide gas
respectfully. The supercritical pressures are well within the standard regime of
current spray application systems; allowing the use of airless spray guns, hoses,
7-24
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spray nozzles, and pumps. The supercritical temperatures are well within the coating
parameters of conventional heated paint systems. Because there is no need for
exotic spray equipment, a wide selection of previously developed accessories for
other paint systems and lines can be utilized.
In order for carbon dioxide (which is a gas under normal conditions) to be
dissolved in the coating formulation, it is necessary to pressurize the mixture to
maintain the supercritical conditions (1200 - 1600 psig). These conditions are well
within the standard regime of current spray application systems. For carbon dioxide
to be supercritical and offset the cooling which occurs as carbon dioxide diffuses
from the solution as a free gas in the spray, the solution is heated. The typical range
is from 40 to 70 degrees Celsius {100 to 160 degrees Fahrenheit). The carbon
dioxide is used at a level which gives a decompressive spray with the desired
atomization and film properties. The dissolved carbon dioxide usually reduces the
spray viscosity to less that 50 centipoise. The coating material usually has a
formulated viscosity from 800 to 3000 centipoise, but materials as high as 100,000
centipoise have been successfully sprayed. As for the adhesion promoter, the
material was sprayed at 20,000 centipoise
The amount of viscosity reduction is a function of the polymer system,
temperature, pressure, carbon dioxide concentration, and solubility. The viscosity
reduction is important because it allows the spray solution to be readily atomized
into fine droplets necessary to deposit a high quality, uniform coating film. The
supercritical carbon dioxide is used at a level that gives a decompressive spray with
the desired atomization and film deposition characteristics. This can vary from 10 to
50% by weight of the spray mixture, depending on the solubility, solvent level,
pigment level, spray temperature, and spray pressure.
Another unique feature of the supercritical fluid spray process is the carbon
dioxide level in the spray mixture can be used to regulate the film build and to some
extent, its dry time. When spraying at constant pressure through any given nozzle of
fixed flow, increasing the concentration of carbon dioxide reduces the deposited film
thickness. As the film thickness decreases, so does its dry time. When a constant
film thickness is required, the dry time can be reduced by increasing the
concentration of carbon dioxide in the spray mixture. This has the same effect as
increasing the overall relative evaporation rate (RER) of the total solvent blend. This
effect of increased carbon dioxide on reduced dry time is most noticeable in lacquer
coating systems. Conversely, the dry time can be extended by simply reducing the
carbon dioxide concentration in the spray mixture. Thus allowing a single coating
formulation to be successfully spray applied across a broad range of ambient
conditions without the need for solvent additions or extending the production line for
longer dry times.
7-25
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SPRAY CHARACTERISTICS
Supercritical carbon dioxide functions both as a viscosity reducer and a
generator of vigorous atomization. This vigorous atomization is produced by a new
decompressive mechanism that remedies the defects of airless spraying. This new
decompressive spray produces a high quality, uniform film. Conventional airless
spray techniques are often characterized by coarse atomization and defective spray
fans that limit their usefulness to the application of low - quality films. The
conventional atomization mechanism employs a high pressure drop across the spray
orifice to generate a high-velocity liquid film.
The film becomes unstable when the shear between the high velocity film and
the surrounding air exceeds the surface tension and cohesive forces in the film.
When the shear is high enough, the film disintegrates into a series of droplets.
Because the surface tension and cohesive forces in the film are not completely
overcome, the spray consists of nonuniform size droplets. The spray fan tends to
contain jets which limit the ability to deposit a high quality, uniform film.
Even though the spray produced using carbon dioxide is airless in nature, it
has all of the desirable traits of air spray, without high air volumes. A feathered
spray, with the spatial uniformity of fine droplet sizes necessary for obtaining high
quality films and high transfer efficiencies, is produced from the vigorous
decompressive atomization provided by carbon dioxide. Due to the finer atomization
produced by the supercritical spray than conventional airless sprays, a carefully
controlled experiment was conducted comparing the airless supercritical spray fluid
to air spray. (7)
The vigorous decompressive atomization is believed to be produced when the
dissolved supercritical carbon dioxide in the spray solution suddenly becomes
exceedingly supersaturated as the spray exits the nozzle and undergoes a rapid and
large pressure drop. The dissolved carbon dioxide is driven forcefully to the
gaseous state. The rapid gasification of the carbon dioxide overwhelms the surface
tension and cohesive forces of the spray solution before a liquid film can form at the
nozzle. By disrupting the formation of the liquid film, the defects of the airless film
are avoided. Because the fan is no longer constrained by the surface tension and
cohesive forces of the airless fan, a wider fan is generated at the nozzle exit. This
permits the formation of a rounded parabolic - shaped spray fan with high uniformity
of droplet sizes.
The fan is characterized by tapered edges similar to those of conventional air
spray fans. The tapered edges permit the coating material to be deposited uniformly
in a wide central region, with progressively less coating deposited towards the
edges of the fan. This is particularly desirable when there is a need to overlap
7-26
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adjacent layers of sprayed coating to produce a uniform film thickness. More
importantly, by further optimizing the adhesion promoter, it could also be applied
electrostatically to fully utilize the parabolic spray and wrap the part for a more
tailored application. The fan widths of the spray are regulated by nozzle selection, as
is done with conventional airless spray.
Decompressive atomization can produce fine sprays that are in the same size
range as air spray systems and rotary atomizers. Laser light scattering
measurements show that average droplet sizes are typically in the 20 to 50 micron
range, although much smaller and larger sizes can be produced if desired.
Furthermore, the droplet size distributions can be quite narrow, which is highly
desirable to obtain both high quality coatings and high transfer efficiency.
The most significant difference between SCF and air spray is the widths of the
droplet size distributions, as compared in Figures 1-3. The droplet size of 35
microns (sauter mean diameter) and a narrow distribution in Figure 1 having by
volume only 1% large droplets and 11% small droplets is characteristic of the SCF
spray. For comparison, the air spray was adjusted to the same average size in
Figure 2. This, however, produced a very broad distribution having relatively large
fractions of large droplets (22%) and smalt droplets (19%).
Whereas the decompressive spray would produce an excellent appearance,
the corresponding air spray would produce an unacceptably poor appearance
because of the many large droplets. In order to reduce the fraction of large droplets
to an acceptable level (3%), atomizing air flow was increased. Even though this did
reduce the larger particles, it also produced much smaller spray particles. These
smaller particles of about 20 microns (35%) would significantly lower the transfer
efficiency as in Figure 3. In order for air spray to achieve equal appearance to SCF
spray, air spray could have a substantially smaller average droplet size than
decompressive sprays.
Conversely, by overatomizing the coating to reduce the larger droplets, this
creates smaller droplets that became overspray and reduces transfer efficiency. In
contrast to the decompressive spray, the narrow droplet size distribution produces
both good appearance and high transfer efficiency. Coating quality deteriorates
significantly as the number and size of the largest droplets in the spray increase
above a low level. The acceptable level depends on coating thickness. Generally, it
is desirable to minimize the population of droplets above about 70 microns in size.
Transfer efficiency decreases rapidly when the droplet size is below about 10
microns. When droplets become too small for inertial and electrostatic forces to
transport droplets to the substrate, they are lost as overspray. The decompressive
sprays often have 90 to 96% of the droplets between 12 and 65 microns in size.
7-27
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Droplet Size Distribution Comparison
Between SCF Spray and Air Spray
Figure 1
A. C02 DECOMPRESSIVE SPRAY
35 MICRON AVERAGE SIZE
Figure 2
B. AIR SPRAY HAVING SAME
AVERAGE DROPLET SIZE
35 MICRON AVERAGE SIZE
20
cr-
UU
O
>
10
0
^n%Jj
~ < I i
1%
4 10 20 40 100 400
20
o
UU
D 10
_i
O
>
0
• 19% J
W-
4 10 20 40 100 400
Figure 3
c. AIR SPRAY HAVING HIGH
atomizing air flow to
ELIMINATE LARGE DROPLETS
LOW AVERAGE DROPLET SIZE
20
cr-
UJ
D 10
o
>
3%
0 I—r—r- r 1 r
4 10 20 40 100 400
DROPLET SIZE, MICRONS
7-28
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Furthermore, the decompressive atomization produces a spray that is highly
spatially uniform in droplet size, whereby the droplet size varies very little with
position in the spray. The measured droplet sizes are constant along the major and
minor axes of the spray and they do not change with distance from the spray tip.
Spatial uniformity in droplet size is highly desirable for obtaining high quality
coatings and higher transfer efficiency, because it gives a narrower overall droplet
size distribution for the entire spray. Thus eliminating portions of the spray that have
too coarse or too fine atomization.
SCF ADHESION PROMOTER OPTIMIZATION
The coating used in the supercritical fluid (SCF) process was designed from a
commercially used adhesion promoter. The SCF adhesion promoter is at higher solids
and contains a different solvent composition than the conventional formulation. The
volume solids for the conventional formulation are 7.5%, whereas the volume solids for
the SCF formulation are substantially higher at 20.6%. Because of the dramatic
reduction in the solvent content of the SCF adhesion promoter, solvent reformulation
was necessary to obtain a high quality coating with good flow and leveling properties.
A comparison of the physical properties of the solvent blends for the conventional and
SCF formulated coatings is shown in Table 1.
Table 1
Solvent Blend
Properties
Conventional
Adhesion Promoter
SCF
Adhesion Promoter
Density
7.23 Ib/cjal
7.27 lb/gal
Relative
Evaporation Rate
(RER)
56.4
26.6
Non-Polar
Solubility
Parameter
8.02
7.94
Polar
Solubility
Parameter
3.74
3.40
Hydrogen Bonding
Solubility
Parameter
0.41
0.66
The solvents used for the SCF formulation have similar solubility parameters to
those used in the conventional formulation. The major difference between the two
formulations is the relative evaporation rates (RER). The conventional solvent blend
has a much faster evaporation rate (RER=56.4) than the SCF solvent blend
(RER=26.6).
7-29
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APPLICATION RESULTS
The SCF application of adhesion promoter on TPO bumpers was initially
trialed at the Ford Milan plant in Michigan in 1994. The objectives were to determine
product performance; VOC reduction; and application effectiveness. The SCF
adhesion promoter was applied to TPO bumpers at a dry film thickness of 0.3 mils.
The applied film is smoother and also exhibits less orange peel than the
conventional film applied with HVLP spray guns. The material utilization of the SCF
applied adhesion promoter was found to be much better than the conventionally
applied HVLP adhesion promoter. The transfer efficiency improved from
approximately 28% for the conventional process to about 38% for the SCF process.
This dramatic improvement allows applicators to spray substantially higher solids
paint using the SCF process and greater latitude for achieving the desired film build.
The transfer efficiency improvement coupled with the higher solids formulation
for the SCF process also results in significant VOC reduction. The pounds of
solvent emitted per gallon of solids applied (GSA) is calculated at approximately
323 for the conventional process and 77 for the SCF process. This represents a
76% reduction in emissions. By combining the SCF process with oven incineration,
an even greater reduction in the VOC of the coating formulation can be achieved.
The solvent emissions in the spray booth and oven can be estimated for each
coating formulation by using a proprietary state-of-the-art computer program.
The computer program takes into account room temperature evaporation of
solvent (spray booth), elevated temperature evaporation of solvent (oven), polymer-
solvent interactions, solvent-solvent interactions, diffusion of solvent through a film,
and film thickness. Based on this modeling, approximately 98% of the solvent in the
conventional formulation is emitted in the spray booth, while for the SCF formulation,
only 64% of the solvent is emitted in the spray booth. Specifically, the SCF process
shifts the solvent emission from the spray booth to the oven. If the solvent emitted in
the oven is incinerated, the SCF process leads to an even higher reduction in
solvent emissions. The solvent emissions for the conventional and SCF
formulations are summarized in Table 2.
7-30
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Table 2
Conventional
Adhesion Promoter
SCF
Adhesion Promoter
% Volume Solids
7.5
20.6
% Transfer Efficiency
28
38
VOC (LBS/Gallon)
6.8
6.1
VOC (LBS/Gallon of Solids
Applied)
323.8
77.9
Solvent Split
% Booth
98
64
% Oven
2
36
Booth Overspray
(LBS/GSA)
233.1
48.3
Booth Solvent Split
(LBS/GSA)
84.8
18.9
Oven Solvent Split
(LBS/GSA)
1.9
10.7
Total Emissions, LBS/GSA
(Without Oven Incineration)
323.8
77.9
Total Emissions, LBS/GSA
(With Oven Incineration)
321.9
67.2
PERFORMANCE TEST RESULTS
Several tests were performed on both compounded and reactor grade TPO
plaques prepared as illustrated in Figure 4. The polyurethane basecoats and
clearcoats were applied using standard conventional air atomized spray. Painted
plaques were tested after a 72 hour ambient air postcure. All testing passed as
illustrated in Figure 5.
7-31
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FIGURE 4
STEPS UTILIZED FOR TPO PLAQUE PREPARATION
AND COATINGS APPLICATION
1)
No pretreatment or powerwash, air blow off only
2)
Application of adhesion promoter
3)
2 to 3 minute ambient air flash
4)
30 minute bake @ 250°F
5)
10 minute cooldown
6)
Application of polyurethane basecoat
7)
5 minute ambient air flash
8)
Application of polyurethane clearcoat
9)
10 minute ambient air flash
10)
30 minute bake @ 1B0°F
FIGURE 5
TEST RESULTS USING THE SUPERCRITICAL FLUID SPRAY PROCESS
FOR ADHESION PROMOTER
TEST COMPOUNDED TPO REACTOR TPO
Adhesion PASS PASS
Water Immersion (240 Hrs.) PASS PASS
Gas Drip Resistance PASS PASS
Flexibility @ 23°C PASS PASS
(21, Mandrel)
Flexibility @ -20°C PASS PASS
(31, Mandrel)
Thermal Shock PASS PASS
H20 Spot PASS PASS
Soap Spot PASS PASS
UBC Spot PASS PASS
Acid Spotting PASS PASS
Chemical Resistance
Motor Oil PASS PASS
Tar & Road Oil Remover PASS PASS
WWF PASS PASS
Chip Resistance PASS PASS
Heat Resistance PASS PASS
Resistance to Scuffing PASS PASS
(5000 cycles)
7-32
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CONCLUSION
Thus far, test results show that the supercritical fluid spray (SCF) process can
be used to reduce the VOC of a solvent borne adhesion promoter without affecting
adhesion performance on TPO bumpers and plaques in both laboratory and
production settings. The supercritical fluid process meets performance criteria;
surpasses regulatory standards for automotive plastic component adhesion
promoters; and is proving to be a very effective approach for achieving these goals.
ACKNOWLEDGMENTS
I acknowledge the valuable contributions of M. Austin, J. McGowan,
R. Ryntz, M. Strehle, T. Wilkins of Ford Motor Company; J. Clifford, J. Lockhart,
R. Pierce, J. Schenk, K. Steed, P. Walther of Red Spot Paint and Varnish Company,
Inc; R. Milovich, J. Penick, H. Turner of Nordson Corporation; M. Kendig of Rockwell
International; D. Senser of the University of Wyoming; J. Argyropoulos, R. Bailey,
C. Lee, K. Nielsen and D. Ross of Union Carbide Corporation.
7-33
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REFERENCES
1. Pierce, R. S., et al. "VOC Compliant Approaches to TPO Adhesion Promoters
for Exterior Coatings Applications." Paper No. 940860, Proceedings of the
Society of Automotive Engineers (SAE) 1994 International Congress, Detroit;
SAE Technical Paper Series, Warrendale, PA (February 1994).
2. Nielsen, K. A., et al. "Supercritical Fluid Spray Application Technology: A
Pollution Prevention Technology for the Future." Journal of Oil & Color
Chemists Association 74 (10): 362-368 (October 1991).
3. Nielsen, K. A,, et al. "Spray Application of Low-VOC Coatings Using
Supercritical Fluids." Society of Automotive Engineers 1991 Transactions,
Journal of Materials & Manufacturing 100 (5): 9-16 (1992).
4. Nielsen, K. A., et al. "Supercritical Fluid Spray Coating: Technical Development
of a New Pollution Prevention Technology." Pages 173-193 in Storey, R. F.
and Thames, S. F. Proceedings of the Twentieth Water-Borne, Higher-Solids,
and Powder Coatings Symposium, New Orleans (February 1993).
5. Kendig, M., et al. "Corrosion Induced Adhesion Loss - Low Volatile Organic
Content (VOC) Coatings." Final Report to the Materials Interfaces Division of
the Office of Naval Research, Arlington, VA by Rockwell International (March
1993).
6. Argyropoulos, J. N., et al. "Polymer Chemistry and Phase Relationships of
Supercritical Fluid Sprayed Coatings." Pages 765-785 in Storey, R. F. and
Thames, S. F. Proceedings of the Twenty-First Waterbome, Higher-Solids, and
Powder Coatings Symposium, New Orleans (February 1994).
7. Senser, D. W., et al. "A Comparison Between the Structure of Supercritical
Fluid and Conventional Air Paint Sprays." Proceedings of the Seventh Annual
Conference on Liquid Atomization and Spray Systems, Bellevue, WA, (May
1994).
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SESSION 7B
WOOD FURNITURE TECHNOLOGIES
7-35
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PAPERS PRESENTED:
"Demonstration of No-VOC Wood Topcoat''
by
Eddy Huang
AeroVironment
Monrovia, California
"Evaluation of Supercritical Carbon Dioxide Spray Technology to Reduce Solvents in a
Finishing Process"
by
Paul Randall
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Cincinnati, Ohio
"Evaluation of Alternative Chemical Strippers on Wood Furniture Coatings'
by
Sonji Turner
Research Triangle Institute
Research Triangle Park, North Carolina
7-36
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DEMONSTRATION OF NO-VOC WOOD TOPCOAT
Eddy W. Huang
AeroVironment Inc.
222 East Huntington Drive
Monrovia, California 91016
Robert C. McCrillis
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
INTRODUCTION
The worldwide coatings market is estimated to be in excess of $34 billion annually. The
U.S. market is about $14 billion segmented in three main categories: (1) Architectural Coatings
(AC); (2) Product Coatings used by original equipment manufacturers (PC-OEM); and (3)
Special Purpose Coatings (SPC). In most markets, customers' needs are being satisfied by a
relatively small number of coatings companies, many with sales approaching $1 billion. A
significant number of coatings operations are part of large chemical groups such as AKZO,
Ashahi, BASF, DuPont, ICI, Mitsubishi, and PPG Industries. The industry also includes a
number of very large independents, like Beckers, Jotun, Kansai, Lilly, Nippon Oil & Fats,
Nippon Paint, Reliance, Sadolin, Sherwin Williams, and Valspar. The profile of the coatings
industry and the markets it serves has undergone dramatic change in the last decade. The
strongest thrusts have been forced by such things as huge business realignments, consolidations
and reductions in the number of coatings companies, and the impact of environmental
compliance.
The U.S. Environmental Protection Agency (EPA) has implemented regulations to
minimize or eliminate the emissions of volatile organic compounds (VOCs). It is estimated that
the annual U.S. market for wood coatings is approximately 240,000 m3 (63 million gallons).1 On
this basis, between 57 and 91 million kilograms (125 and 200 million pounds) of VOCs are
emitted into the air each year from the use of presently used waterbome and solvent-borne
systems.
The objective of this project was to develop a new low-/no-VOC wood topcoat through
continuing research, formulation adjustments, and application testing. Efforts were dedicated to
conduct joint research into new promising technologies that are sufficiently mature for
demonstration to wood product manufacturers. The high value-added coating products were
developed utilizing existing technical know-how, data, and patents related to the new technology.
This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
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DISCUSSION
Background
EPA and state environmental agency actions to lower VOC emissions have had an effect
on the marketing of coatings, and the organic and inorganic binders which are widely used in the
industry. Some companies seek to qualify coatings thinned with "conforming" solvents
(solvents not photochemically reactive) such as chlorinated hydrocarbons. One of these solvents,
1,1,1 trichloroethane, is no longer a feasible compliance option since it has been found to be a
hazardous air pollutant (HAP) and to contribute to global warming. Other companies have
pursued latex-based, water-dispersed coatings even though they do not currently meet chemical
resistance, during those critical first days after application, and drying rate specifications . Many
waterborne coatings rely on coalescing agents to achieve a smooth cured film (eliminate "orange
peel"). (Ethylene glycol ethers, often used as coalescing agents, are HAPs.) As research
continues, there are an increasing number of durable waterborne and water- reducible coatings
which are free of coalescing agents. Finally, there is a resurgence of interest in solvent-free
coatings (e.g., powder and radiation cured coatings), which would probably not have reached
such research intensity were it not for the air, water, and toxicity legislation on state and federal
levels.
The wood coating industry can be separated into two categories having different
requirements with respect to application technique.2 These are flat stock coating, and the coating
of three dimensional objects. Flat stock is usually coated on a continuous coating line of some
type, and more complicated three dimensional objects, such as furniture, usually require spray
application and batch drying. The kitchen cabinet industry uses nitrocellulose (N/C) for the high
end or conversion varnish/conversion lacquer (also called acid catalyzed) coatings for the bulk of
its finishing needs. Conversion varnishes and lacquers contain up to 50% of urea or melamine
formaldehyde resins which are only partially cured at the low temperatures allowable for wood
surfaces. In addition, formaldehyde may be formed as a reaction product during curing. Thus
formaldehyde emanates from the coating throughout its use life as well as during the coating
process. Formaldehyde has been designated by the EPA and California Air Resources Board as a
probable carcinogen. The N/C must be replaced to meet VOC regulations and the uncured
urea/melamine formaldehyde containing coatings replaced due to the formaldehyde emissions.
Water-based products have been introduced to much of the lumber industry to replace the
high VOC materials previously used on plywood, hardboard, particle board, and regenerated
wood-finger jointed wood products. These products, however, are a full step down in
performance properties such as hardness, toughness, adhesion, and solvent and stain resistance.
Their second weakness is in energy consumption; i.e., they require long time/temperature
exposure for cure. They may or may not result in formaldehyde emissions.
The South Coast Air Quality Management District (SCAQMD) "Rule 1136 - Wood
Products Coatings" regulates the allowable VOC concentration of wood coating products. It is
estimated that compliance throughout the SCAQMD jurisdiction with these rules would reduce
VOC emissions by about 18 Mg (20 tons) per day. By phasing in low-VOC coatings, instead of
requiring installation of add-on controls, SCAQMD believes that furniture manufacturers will be
7-38
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i
able to comply with SCAQMD's rules without increased costs. Rule 1136 currently limits the
VOC content to 680 gfi of clear topcoat and 600 g/l of pigmented coating, less water and less
exempt compounds. (Unless otherwise stated, all VOC content data in this paper are less water
and exempt compounds.) A final compliance limit of 275 g/f for both clear topcoats and
pigmented coatings is currently set to take effect by July 1,1995.3
A new zero-VOC wood topcoat which consists of an epoxy component and an amine
curing component was patented by Adhesive Coatings Co. (ADCO), San Mateo, California. The
complete absence of organic solvents means that this new topcoat not only less hazardous to use
but emits practically no VOCs and therefore does not significantly contribute to air pollution.
A new two-component water-based epoxy wood coating system, based on the new,
ADCO topcoat chemistry developed in this project, has the potential to replace a very significant
share of current organic solvent systems in use. As will be discussed later, the new zero-VOC
topcoat's high gloss and excellent chemical resistance properties are ideal for the wood
manufacturing industry for flat stock, for particle, chip, and wood flower products; spray primers
for door skins; and finishing systems for interior wood products such as furniture and kitchen
cabinets. This material can be manufactured using readily available raw materials and standard
resin manufacturing equipment without polluting the atmosphere.
To date, substantial progress has been made in identifying market opportunities for new
environmentally sound products. In addition to the research and development of a new zero-
VOC wood topcoat, a marketing plan of the developed product was included as part of this
development project. This included working with the manufacturers and suppliers to develop a
marketing plan to get the products into use by the public.
Coating Characteristics
The most important properties for low-VOC coating technologies are:
* "Dial-a-Cure" (control cure speed through selection/matching of curing agent)
ultra-fast cure (air cure in minutes)
high speed application (forced cure in seconds)
* Friendly to adverse application conditions
cures under broad temperature range
cures on wet or dry surfaces
* Liquid
water emulsions with water as the continuous phase, no solvents, no keying
agents, no film coalescing aids present or required
high solids
* Environmentally sound
water reducible & water cleanup of materials
no solvent (low-VOC)
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no or very low formaldehyde emissions
no free isocyanate
The new two component water-based epoxy topcoat developed in this project has the
potential to meet the performance of the solvent-based system and can replace current solvent
systems. The attractive coatings properties which make them promising can also be applied in
the wood products area. These properties include:
* low or no formaldehyde
* extreme water and chemical resistance
* very fast cure
* liquid at high solids
* low temperature cure
* no solvents and thus low-/no-VOC.
The new ADCO wood topcoat is a two-part, chemically cured, water reducible, air dry
epoxy coating for use as a durable coating for wood surfaces and wood products. It can be used
as a sealant and as a high gloss, durable topcoat that gives a lacquer like, clear finish. The
complete absence of organic solvents in the formulation or their formation during curing, results
in zero emission of VOCs and HAPs. The self-contained manufacturing process also emits no
significant air pollutants. The polymer/curing agent screening matrix, performance
characteristics, and chemical/stain resistance of this no-VOC topcoat are discussed in the
following section.
Polymer Formulation Testing
Polymer variations of ADCO's basic EnviroPolymer (A) in combination with each of
several proprietary curing agents (B) were conducted. All combinations contained low or no
VOCs. Up to eight different ratios were evaluated for each combination, and the best ratio
observed was then selected for further evaluation by applying this coating on solid oak.
Four variations of EnviroPolymer A-l (EP 180-60), A-2 (EP 200-60), A-3 (EP 510-60),
and A-4 (EP H-60) were used in this project. Four proprietary curing agents B-l (80-70), B-2
(65-71), B-3 (65-99), and B-4 (81-93) were identified as being the most likely to yield promising
results. The initial ratings used to identify the most promising ratios for further evaluation were
(1) excellent/very promising, (2) good/somewhat promising, (3) fair/possible, and (4)
poor/unlikely (see Table 1).
Formulations A-l/B-2 and A-2/B-1 were judged to be the most likely to yield promising
test results when applied to a substrate for further determination of the coatings performance
characteristics (dry time, gloss, parallel groove adhesion, scrape/mar, and chemical and stain
resistance). Dry time was measured as the amount of time that was taken for the coating to
harden before it could be sanded and re-coated. To be objective, a gloss meter was used to put a
measured value on the degree of gloss. The method described in ASTM D 5234 was followed.
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TABLE L POLYMER/CURING AGENT SCREENING MATRIX
A-l
A-2
A-3
A-4
B-l
Good
Excellent
Poor
Poor
B-2
Excellent
Good
Fair
Poor
B-3
Good
Good
Good
Good
B-4
Good
Good
Good
Fair
Evaluation of adhesion to different surface treatments, or different coatings to the same
treatment is extremely important to the furniture manufacturing industry. The method described
by ASTM D 3359s was followed. After parallel grooves were cut into the coating, tape was
applied over the grooves and removed. The cross-hatch pattern was inspected through a
magnifying glass and rated against the standards. Gt 0/5B was the best rating followed by Gt
1/4B, Gt 2/3B» Gt 3/2B, Gt 4/1B, and Gt 5/OB.
A modified ASTM D 2197 method5 was followed to differentiate the degree of coating
hardness. After complete curing, the scrape/mar resistance was determined by pushing the
panels beneath a round stylus or loop that was loaded in increasing amounts until marring of the
coatings was detected.
Resistance to various household chemicals is an important characteristic of wood
furniture finishes. The methods described by ASTM D 13087 were followed. This evaluation
covers the effects household chemicals have on organic finishes such as discoloration, change in
gloss, blistering, softening, swelling, and loss of adhesion.
A cooperative study on the evaluation of low-VOC coatings for wood furniture showed
that several water-based clear topcoats meet the VOC content requirement 275 g/f.8 The
performance characteristics of this new zero-VOC coating were compared with those of other
low-VOC waterborne coatings in Tables 2 and 3. From Table 2, this new zero-VOC coatings
showed excellent performance characteristics in terms of adhesion, dry time, gloss, and
scrape/mar resistance. The scrape/mar resistance was especially remarkable (twice as good as
the average of other waterborne coatings).
SCAQMD method 304-91 (Determination of Volatile Organic Compounds (VOC) in
Various Materials) was used to conduct VOC analysis.9 ASTM D 147510 was used to determine
the density of coatings. Total volatile content was measured by ASTM D 2369" and water
content was determined by ASTM D 3792.12
Market Analysis
The wood coating market is segmented by the industry into wood-furniture, fixtures, and
wood-factory finishing. These segments in turn are sub-segmented into wood furniture, kitchen
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TABLE 2. PERFORMANCE CHARACTERISTICS OF
LOW-/NO-VOC COATINGS
Manufacturer/
Topcoat
Adhesion
Dry Time
(minutes)
Gloss
60° Sheen
Scrape/Mar
(grams)
ADCO Topcoat
GT 0/5B
20-25
80.0
1050
AKZO 680-60C018-115
W/B
GT 0/5B
30-35
34.3
300
AMT 01TC-0090-50 W/B
GT 0/5B
30-35
62.0
500
GUARDSMAN 45-1065-
40 W/B
GT 0/5B
30-35
46.8
800
LILLY 787W43 W/B
GT0/5B
30-35
23.9
300
PINNACLE 137-CL-l
GT 0/5B
30-35
79.4
500
SHERWIN-WILLIAMS
T70C510 W/R
GT 0/5B
30-35
44.0
500
SINCLAIR WL 14-9
GT 0/5B
30-35
38.6
400
WATERCOLOR Topcoat
GT 0/5B
30-35
37.1
600
TABLE 3. CHEMICAL AND STAIN RESISTANCE OF
LOW /NO-VOC COATINGS
Manufacturer/
Acetone3
Coffee
Mustard
Hot Tap
Nail Polish
Topcoat
Water
Remover
ADCO Topcoat
1
1
2
1
2
AKZO 680-60C018-115 W/B
3
1
2
1
2
AMT 01TC-0090-50 W/B
2
1
2
1
2-
GUARDSMAN 45-1065-40 W/B
2
1
2
1
3
LILLY 787W43 W/B
2
1
2
2
3
PINNACLE 137-CL-l
2
1
2
1
I
SHERWIN-WILLIAMS
2
1
2
1
2
T70C510 W/R
SINCLAIR WL 14-9
2
1
2
1
2
WATERCOLOR Topcoat
1
1
1
1
2
a. 1 = no effect, 2 = slight effect, 3 = medium effect
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cabinet, new case goods, plywood/hardboard/regenerated wood products, flat stock finishes, and
specialty product finishes. The furniture industry is faced with a dilemma. Other than special
small segments of the paper coating industry, wood furniture coatings consume almost 100% of
the nitrocellulose coatings produced. The coatings, by the very nature of the high intrinsic
viscosity of nitrocellulose, are very low in solids and thus are very high in solvent and high
VOCs.
The high emission rate has caused the loss of all operating permits in some states and
some permits in every state; and wood furniture manufacturers are either moving off-shore or
concentrating in the Southeastern U.S. Radiation-cure techniques and coatings have made some
penetration, although small, because the shape of the item produced does not lend itself as
readily to use of existing technology such as ultraviolet (UV) or electron beam (EB) equipment.
One approach used by the furniture industry to "stay-in business" has been introduced in Europe.
This is a modified case goods approach where most of the pieces are prefinished in flat stock.
The piece of furniture is then assembled and given a final finish and touch-up. The coating used
for the flat stock pieces is a low-VOC content radiation-cured product. The final finish,
however, is likely to be high VOC content N/C. The new zero-VOC topcoat developed in this
project meets the same cure rate without the radiation equipment investment cost, hazard to the
eyes of the employees, and skin sensitivities. In addition the complete finish can be applied after
assembly, if desired.
In the zero-VOC wood coating market research, the needs for new products were
discussed with the leaders in the manufacture of regenerated wood products; i.e., particle board,
chip board, and wood flake products. There are many product opportunities for application of
this new technology. Efforts were focused on such promising possibilities as binders for particle,
chip, and wood flower products; spray primers for door skins; surfaeers for concrete form boards
to replace paper laminate; and finishing systems for interior wood products such as furniture and
kitchen cabinets.
It is anticipated that the zero-VOC wood topcoat developed in this project will set new
industry standards by addressing the following manufacturers' problems:
* The formaldehyde problem. All manufacturers seek low or no formaldehyde
exposure to their employees; the atmosphere surrounding the manufacturing site;
and the customer or user.
* Lower moisture transmission problem. All manufacturers seek to reduce the
degradation caused by swelling and warping from changes in product dimension
from water penetration.
* Exterior market problem. All manufacturers seek to upgrade their product line to
achieve penetration in the exterior product market.
* The down-time cleanup problem. All manufacturers of regenerated board must
shut down periodically for cleanup to reduce the unacceptable green board
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rejection rate and fire hazard.
* The energy problem. All of the products used by the mills require extensive
time/temperature cure or drying cycles. Low temperature or fast air dry would
lend improved economics to the industry and/or provide a large competitive
advantage over the competitors.
* The toxic air emissions problem. Some facilities in the furniture industry may use water-
based formulations which contain toxic compounds, most notably, ethylene glycol
ethers,13 Most waterborne wood coatings used glycol ethers in their formulations to stay-
in compliance.
Most wood furniture is finished with nitrocellulose resin-based coatings averaging 750
g/d VOC and 375 g/{hazardous air pollutants (HAPs). In the finishing of an average dining room
table (4 ft X 6 ft), about 9 kilograms of VOCs and 4.5 kilograms of HAPs are emitted. While
progress has been made to formulate low-VOC coating systems, many of these use ethylene
glycol ethers, which are more toxic than most of the solvents used with nitrocellulose systems.
Based on the South Coast Air Quality Management District/Southern California
Edison/California Furniture Manufacturers Association Cooperative study of low-VOC coatings
for wood furniture, the VOC/air toxic compounds contained in the commercially available water-
based clear topcoat were evaluated. In Table 4, the VOC/air toxic contents of ADCO's new
zero-VOC coating were compared with commercial coatings which met the VOC content
requirement of 275 g/t.
Many resin and coatings manufacturers have done research on very low-VOC coatings
for the wood furniture industry. Penetration into the market place has been slow. Without
regulatory pressure, there is no incentive to switch from traditional high-VOC nitrocellulose
coating systems.
Several wood furniture manufacturers and coating suppliers were contacted to identify wood
coating concerns, current application methods, costs, and critical areas for product improvements.
Marketing information related to the wood coatings market was collected. This information was
reviewed to establish what specific data still need to be collected and how they should be used in
structuring the planned market survey of wood coating suppliers. The product marketing discussions
have centered on how to commercialize specific low-/no-VOC finished coating applications resulting
from this wood coating project.
CONCLUSIONS AND RECOMMENDATIONS
The resulting topcoat showed excellent performance characteristics in terms of adhesion,
gloss value, dry time, hardness, level of solvents, and chemical/stain resistance in laboratory
development tests. The VOC contents of both the clear topcoat and the white pigmented topcoat
were less than 10 g/f, the detection limit of the test method. This coating's performance and
properties in finished material were compared favorably with other low-VOC waterborne wood
coatings.
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TABLE 4. VOC/TOXIC COMPOUNDS CONTAINED
IN WATERBORNE COATINGS
Manufacturer/
VOC
HAPs
Topcoat
W
Name
Weight
(%)
ADCO Topcoat
<10a
None
0
AKZO 680-60C018-115
W/B
210
Ethylene Glycol Monobutyl Ether
Diethylene Glycol Monobutyl Ether
6.2
3.9
AMT 01TC-0090-50 W/B
240
Propylene Glycol N-Butyl Ether
1-10
GUARDSMAN 45-1065-
40 W/B
270
Diethylene Glycol Monobutyl Ether
Propylene Glycol N-Butyl Ether
6.0
3.0
LILLY 787W43 W/B
240
Propylene Glycol N-Butyl Ether
3.4
PINNACLE 137-CL-l
270
Triethylamine
Ethylene Glycol Monobutyl Ether
Diethylene Glycol Monobutyl Ether
<5.0
3.0
3.0
SHERWIN-WILLIAMS
T70C510 W/R
270
Ethylene Glycol Monobutyl Ether
Diethylene Glycol Monobutyl Ether
4.8
9.2
SINCLAIR WL 14-9
200
Diethylene Glycol Monobutyl Ether
3.0
WATERCOLOR Topcoat
100
Propylene Glycol N-Butyl Ether
1-10
a. Detection limit of test method.
Demonstration of the new topcoat at one or more furniture manufacturing facilities would be
the next step in commercializing this technology. Further development work may be required in
parallel with each demonstration to tailor rheology, dry time, etc. to the host's furniture finishing line.
The identification and/or development of compatible low-/no-VOC "stain" and "sealer" wood
coatings would provide a complete low-/no-VOC wood coating system.
REFERENCES
1. Huang, E.W., L. Watkins, and R.C. McCrillis. "Development of Ultra-Low VOC Wood
Furniture Coatings," in Proceedings: Pollution Prevention Conference on Low- and No-
VOC Coating Technologies. EPA-600/R-94/Q22 (NTIS PB94-152246), San Diego, CA,
February 1994.
2. Kinzer, K.E. Dual Cure Low-VOC Coating Process, DOE/ID/12692-6, December 1993.
3. Proposed Amended Rule 1136 - Wood Products Coatings, June 23, 1994. South Coast
Air Quality Management District, Diamond Bar, CA.
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4. D 523-89, "Standard Test Method for Specular Gloss," American Society for Testing and
Materials, 1916 Race St., Philadelphia, PA.
5. D 3359-93, "Standard Test Method for Measuring Adhesion by Tape Test," American
Society for Testing and Materials, 1916 Race St., Philadelphia, PA.
6. D 2197-86, "Standard Test Method for Adhesion of Organic Coatings by Scrape
Adhesion," American Society for Testing and Materials, 1916 Race St., Philadelphia, PA.
7. D 1308-87, "Standard Test Method for Effect of Household Chemicals on Clear and
Pigmented Organic Finishes," American Society for Testing and Materials, 1916 Race
St., Philadelphia, PA,
8. A Cooperative Study - Evaluation of Low VOC Coatings for Wood Furniture. South
Coast Air Quality Management District, Southern California Edison Company Customer
Technology Application Center, and California Furniture Manufacturers Association
(released in June 1994).
9. Choa, C.B. and S. Horn. Laboratory Methods of Analysis for Enforcement Samples.
"Method 304-91, Determination of Volatile Organic Compounds (VOC) in Various
Materials," South Coast Air Quality Management District, Diamond Bar, CA, June 1991.
10. D 1475-90, "Standard Test Method for Density of Paint, Varnish, Lacquer, and Related
Products," American Society for Testing and Materials, 1916 Race St., Philadelphia, PA.
11. D 2369-93, "Standard Test Method for Volatile Content of Coatings," American Society
for Testing and Materials, 1916 Race St., Philadelphia, PA.
12. D 3792-91, "Standard Test Method for Water Content of Water-Reducible Paints by
Direct Injection into a Gas Chromatography' American Society for Testing and Materials,
1916 Race St., Philadelphia, PA.
13. Supplemental Environmental Assessment for: Proposed Amended Rule 1136 - Wood
Products Coatings, June 1994. South Coast Air Quality Management District, Diamond
Bar, CA.
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EVALUATION OF SUPERCRITICAL CARBON
DIOXIDE SPRAY TECHNOLOGY TO REDtJCE SOLVENTS
IN A WOOD FINISHING PROCESS
This paper has been reviewed In accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Paul M. Randall
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
INTRODUCTION
This project was conducted by the Pollution Prevention Research Branch(PPRB) of the U.S.
Environmental Protection Agency(EPA) with the cooperation of Union Carbide Corporation, Nordson
Corporation , and the Pennsylvania House Furniture Company. The PPRB is evaluating and
demonstrating new technologies for pollution prevention through the Pollution Prevention Clean
Technology Demonstration (CTD) Program. (1)
This paper reviews the use of supercritical C02 technology for paint spray application.
Pennsylvania House Furniture Co. has used supercritical C02 coating technology to apply a
nitrocellulose lacquer finish to oak and cherry furniture on a chair-finishing line. At current Pennsylvania
House production rates, more than 250 furniture units per day are coated with nitrocellulose lacquer by
this process.
During the evaluation, three issues of this technology were examined:
• Product Quality: to show that coating applied by this spray technology meets company
standards for a quality finish.
• Pollution Prevention Potential: to demonstrate that use of this spray application technology for
solvent replacement in coatings reduces volatile organic compounds (VOCs) released during
finishing operations.
• Economics: to document the cost to install and operate this technology on an existing spray
coating finish line.
Although the research described in this article has been funded wholly or in part by the EPA, it
has not been subjected to Agency review and therefore does not necessarily reflect the views of the
Agency. No official endorsement should be inferred. Also, mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
PROCESS DESCRIPTION
Supercritical fluids are gases that exist at temperatures and pressures near or above the critical
point of the fluid as depicted on a phase diagram (Figure 1). At the critical point, the properties of the
liquid and the gas are similar or identical. The resulting single-phase fluid exhibits solvent-like
properties that can be altered by adjusting temperature and pressure. A number of gases have been
examined for use as supercritical fluids in applications such as industrial and analytical separation
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processes, cleaning, chromatography, arid coaling. The UNICARB™ process for coating uses
nontoxic, nonflammable carbon dioxide as the supercritical fluid for coating dilution. Carbon dioxide,
readily available as a by-product of a variety of industrial processes, has a critical temperature of
31,3*C (88'F) and a critical pressure of 72.9 atm (1070 psi), falling within the ranges already used for
heated paint systems and airless spray equipment.
Union Carbide Corporation developed the use of supercritical C02 for spray coating applications,
introducing this technology commercially in 1988 under the UNICARB™ tradename^ 2,3) In the
UNICARB™ process, the solvent-like properties of supercritical C02 are exploited to replace a portion
of the organic solvent in the conventional solvent-borne coating formulation. The supercritical CO? acts
as a diluent solvent to thin the viscous coating just prior to application, so that the coating can be
atomized and applied with a modified spray gun. According to Union Carbide, 30 to 80% of the organic
solvent in a coating formulation can be replaced with supercritical fluid. Typically, most of the volatile,
fast-drying solvents and some of the medium-drying solvents are eliminated, retaining enough medium-
and slow-evaporating solvents to obtain proper leveling and film coalescence. The solvent blends may
need to be adjusted to optimize performance with the supercritical C02 spray technology. This usually
can be done without changing the resin chemistry or pigment-loading levels. The solvent level of even
conventional high-solids coatings can be reduced further when applied by this process. The actual
reduction in solvent content that can be achieved is dictated by a number of factors. These include the
type of coating being applied and its exact formulation, the desired film thickness and properties of the
applied coating, and the environment in which the coating is being applied.
Thermosetting, thermoplastic, air-dry, and two-component formulations, in clear, pigmented, and
metallic coating systems, have been developed successfully for application by supercritical C02 spray
technology. Limitations exist with pigmented systems because some of the pigments, (e.g., carbon
black), may be soluble in the supercritical C02. However, other pigments, including aluminum flake,
titanium dioxide, and calcium carbonate, have been included successfully in formulations applied using
this process. Nitrocellulose, silicone alkyds, acrylics, and a two-part urethane formulation have been
developed for supercritical C02 application. Union Carbide is currently working on a two-part epoxy
system and a phenolic resin formulation.
The supercritical temperature and pressure of C02 are within the ranges already used for heated
paint systems and airless spray equipment, but special equipment is needed to introduce the C02 into
the reduced solvent formulations and then heat and pressurize the resultant mixture prior to spraying.
Typically, 10 to 50% carbon dioxide by weight may be introduced depending on the solubility in the
coating, the solids level, the pigment loading, and the ambient conditions in the spray booth. Heating
iowers the coating viscosity for easier pumping but decreases the solubility of the C02 in the coating
concentrate. Therefore, optimum operating temperature and pressure must be determined and
maintained to achieve the best results in each application.
Usually, the coating is heated to 40° to 70'C with spray pressures of 1200 to 1600 psi. The
specialty formulated coatings are applied with spray guns similar to those used for airless applications.
However, because the decompression of supercritical C02 results in finer atomization of the sprayed
coating and smaller particles than is common with use of airless spray equipment, slight modification of
the spray gun nozzle design was required to optimize the spray pattern. The result is a more finely
dispersed and more uniform pattern than typically is achieved with conventional air spray equipment.
Nordson Corporation designed the spray guns used by Pennsylvania House. A supply unit
mixes coating concentrate and carbon dioxide to a desired ratio, pressure, and temperature, and
delivers the solution to specially designed spray guns. The size of the supply unit is dictated by
production requirements. A microprocessor-based controller continuously monitors the system and
allows the operator to adjust the ratio of coating concentrate to carbon dioxide for best results. The
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supply unit and controller are placed adjacent to, but outside of, the spray booth. The system
equipment is available for either manual or automatic operation. Manual and automatic spray guns for
electrostatic and non-electrostatic applications can be used with minor modifications to the nozzle.
Because the reduced solvent coating is more viscous, a special pumping station is required.
Pennsylvania House uses the UNICARB™ process on the chair-finishing line at its plant in White
Deer, Pennsylvania, to apply nitrocellulose lacquer finishes. This supercritical COz spray technology
has allowed Pennsylvania House to continue using the solvent-borne nitrocellulose lacquer coating that
is used widely in the U.S. wood-finishing industry, while reducing VOC emissions from their finishing
operation. To bring this technology to production-line use, Pennsylvania House worked closely with
Union Carbide to optimize the basic process, Nordson for equipment-related issues, and with
Guardsman and Lilly to optimize the formulations of reduced solvent coatings.
The chair-finishing line at the White Deer facility carries chairs, stools, and mirrors from assembly
through the finishing process and to packaging. The finishing process is labor intensive, with manned
stations for staining, wiping, rubbing, sanding, polishing, and inspection. The overhead conveyor
system runs through the various work stations at 6 to 7 ft per minute; 6 ft per minute is approximately
60-70% of capacity. At this speed, 250-300 units per day are produced. Total time on the line from
start to finish is about 4 hours.
Two color stains usually are used to highlight the natural grain and provide color to the wood.
Toner stain is sprayed on first, followed by a sprayed mineral-spirit wiping stain, which then is wiped off
by hand. Some pieces get a spatter stain for special effects before entering the oven for the first
drying step. Oven temperature is maintained at 110'F for all heating steps.The next step is spray
application of a 20%-solids nitrocellulose sealer followed by a second pass through the oven. Light
hand sanding is performed if needed before or after application of the sealer.
The nitrocellulose lacquer is spray applied next. In the conventional finishing process,
nitrocellulose lacquer (21-23%-solids) is applied manually using airless spray equipment in two coats,
with a pass through the oven between the coats. Flash-off time between spraying the coating and
entering the oven is 10 to 12 minutes. Oven residence time is 7 minutes. The same flash-off and
oven-time intervals are used after the second coat of lacquer. Furniture units remain on the line at
ambient temperatures for one hour and forty-five minutes after the last oven pass before they are
packaged. When the supercritical C02 finishing process is used, only one coat of nitrocellulose lacquer
is needed to achieve the desired film build and finish quality. The nitrocellulose lacquer formulation
optimized for the Pennsylvania House production line has approximately a 41%-solids content. This
coating is applied using the UNICARB™ equipment in spray booth #1, followed by a 10- to 12-minute
flash-off period, and a 7-minute pass through the oven. Because Pennsylvania House has not
reconfigured the chair conveyor line, the UNICARB™ line follows the existing conveyor line through the
unused spray booth #2 and the final stage of the oven before reaching inspection and packaging for
shipment. The second oven pass is not required for this process but has no negative effect on the
cured finish coat.
Conventional and reformulated nitrocellulose lacquer coatings used by Pennsylvania House are
supplied to the spray guns directly from the shipping drums. The drums of coating are equilibrated and
mixed in the Pennsylvania House paint room before being pumped through lines to the spray booths.
Temperature and humidity changes in the plant sometimes require adjustments in the solvent blend of
the formulations for optimal spray results. With conventional lacquer, solvent is added to the drum of
coating, which then takes about 1 hour to reach the spray booth. This adjustment process sometimes
must be repeated to get the desired results. Once extra solvent has been added to a drum of coating,
the contents of the drum have a higher volatile content. With the supercritical COz spray system, the
-------
operator simply adjusts the ratio of C02 to coating concentrate at the control unit located just outside
the spray booth. No additional solvents are introduced into the process, and adjustments are
immediately evident.
PRODUCT QUALITY EVALUATION
The specific objective of the product quality evaluation was to determine whether nitrocellulose
lacquer applied by the supercritical CO., process provides a wood finish of equal or better quality than
does the conventional nitrocellulose formulation and spray technique previously used by Pennsylvania
House Furniture Company. At Pennsylvania House, the appearance and quality of the final finish are
judged through visual examination by inspectors on the coating line. Special attention is given to gloss,
smoothness, and the lack of surface defects such as blisters or pinholes.
Product quality was evaluated through subjective evaluations performed by Pennsylvania House
staff members and a panel of Battelle coatings personnel. Test substrates were finished on the
production lines during an on-site visit. A set of samples was finished using the one-coat UNICARB™
process, and two other sets were finished using one and two coats of the "standard" nitrocellulose
formulation and the airless spray equipment still in place on the chair-finishing line. All panels were
finished by the same production methods that typically are used on the chair line at Pennsylvania
House.
The subjective product quality evaluations demonstrated that a coating applied by the
supercritical C02 spray process yielded a product with a finish quality equal to or better than the finish
quality obtained by conventional materials and methods. Samples finished by the supercritical C02
process and by the two-coat conventional process were rated as "acceptable." Samples sprayed with
one coat of the nitrocellulose by the conventional process were not acceptable.
In addition to the subjective visual inspections of the test samples, Battelle staff made
measurements of gloss(Table 1) using ASTM D529. These measurements provide some quantitative
insight into the physical attributes of the finish line of each of the coating processes. The test
procedure outlined in ASTM D529 recommends averaging six gloss measurements for a 3-inch x 6-inch
sample area, which correlates to 49 measurements on the 7-inch x 21 -inch test substance used here.
The mean and standard deviation of the 49 data points represent the overall gloss appearance of each
sample, alleviating subjective biases of the person performing the measurements while still
incorporating the assessment of any nonuniformity in the gloss across the sample surface. The breadth
in standard deviation of the data can be used as a gauge of the uniformity of the sample finish across
the complex geometry of the test panels. Gloss test results for each of the nine panels are reported
as the mean of 49 determinations and then averaged for each of the sample sets for easy comparison
among each of the finishing processes in Table 1. The averaged gloss data for the UNICARB™
samples are statistically the same as those for the conventional two-coat process. The gloss data of
both of these sets show that they are substantially glossier than the one-coat conventional finish
sample set.
These results are supported by Pennsylvania House records for consumer acceptance. Internal
quality control audits on chair-line products show a decrease in finish defects using the supercritical
COs system. Based on the number of furniture units requiring rework because of finish defects, product
efficiency has improved since the UNICARB™ process was implemented.
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POLLUTION PREVENTION POTENTIAL
The pollution prevention potential of this technology is based on reducing the emissions of
organic solvents without adding to other wastestreams. The nitrocellulose lacquer finishing process
used on the chair line can contribute to pollution in two ways: VOC emissions from the coating
formulation, and spray booth wastes, including solvent-laden filters and nitrocellulose "dust". In
conventional spray coatings, a blend of fast-evaporating solvents, medium-evaporating solvents, and
slow-evaporating solvents are used. In the supercritical C02 spray process, most of the fast- and
medium-drying solvents are replaced by supercritical C02 and the slow-drying solvents are adjusted
slightly for better film formation. Although reducing VOC emissions is important, it is equally important
to demonstrate the supercritical C02 process does not add pollutants to other wastestreams.
Pennsylvania House has been able to reduce the number of coats of nitrocellulose lacquer from
two to one. The volume of nitrocellulose lacquer used in each finishing operation was determined
during the initial phases of implementing the supercritical CO? process at Pennsylvania House.
Metering devices were placed in-line on the airless spray guns used to apply the conventional
nitrocellulose formulation, and on the coating inlet line to the supercritical fluid supply unit used to feed
the coating mixture concentrate and the supercritical C02 to the modified spray guns used with the
UNICARB™ process.
Pennsylvania House records indicate that it takes approximately 473 ml of the conventional
formulation to apply the two coats needed to achieve the desired quality in the finished product. The
UNICARB™ process required about 207 ml of the reduced solvent formulation per furniture unit to
achieve the same quality. There are two reasons that a smaller volume of coating is required when the
supercritical C02 process is used; 1. the higher solids content of the UNICARB™ formulation means
that more resin is transferred to the substrate per volume of formulation sprayed and 2. the increased
viscosity of the film deposited by the process inhibits film buildup by soaking into the wood substrate.
Table 2 compares the volatile solvent content( % by weight) of the two formulations used by
Pennsylvania House. The UNICARB™ coating is formulated using 17.5% less solvents {on an
absolute basis) than the conventional formulation. Only 9.67% of the UNICARB™ formulation is
comprised of Hazardous Air Pollutant (HAP) materials compared to 35.78% for the conventional
formulation. On a per-gallon-of-coating-sprayed basis, this difference would result in a relative
decrease in VOC emissions of 22.81%, with a 72.97% decrease in HAPs using the UNICARB™
formulation. VOC contents are reported as 563 gms/l for the UNICARB™ formulation and 707 gms/l for
the conventional system.
Assuming an average yearly production of 50,000 units and the use of 207 ml for the one-coat
UNICARB™ process and 474 ml for the two-coat conventional formulation, the UNICARB™ formulation
uses 10,220 liters and the conventional formulation uses 24,604 liters to finish the units. Based on the
reported VOC contents, this system change corresponds to an annual reduction in VOC emissions of
67.5% when the newer process is used.
Coating overspray at Pennsylvania House is collected on dry filters that are compressed and
stored in 55-gal drums for disposal by landfill. One drum, at a disposal cost of $150/55 gal drum, can
hold about 200 compacted filters and solid debris. Waste products generated will include dry and
solvent-laden filters and nitrocellulose dust, both loose and trapped in the filters. No liquid waste was
generated. Because Pennsylvania House does not separate waste by production lines, no physical
data were available for the solid wastestream analysis. However, discussions with Pennsylvania House
management and staff consistently indicated that the solid and liquid wastestreams were unaffected by
the conversion to the supercritical C02 technology.
7-51
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The chair-finishing process is the same except for the application of the nitrocellulose lacquer
finish. Using the old process, two booths were in operation which required cleaning and maintenance.
With the UNICARB™ process, only one booth is needed. The transfer efficiency of the modified
UNICARB™ spray gun and the air-assisted spray gun are both approximately 50% based on Union
Carbide records. However, due to the increased solids content of the UNICARB™ formulation, more
solid waste is generated from the overspray by the UNICARB™ process. The 28 dry filters In each of
the two spray booths needed for the conventional two-coat finishing process were changed once per
week for a total disposal rate of 56 filters/week. The 28 dry filters in the one spray booth required for
UNICARB™ finishing are changed twice per week for a total of 56 filters/week. Dry paint and dust from
the booths is packed in the disposal drums with the filters, but no increase or decrease in the total
volume of these products was noted. Thus, no change was observed by Pennsylvania House in the
volume of solid waste generated by converting to the supercritical C02 spray process on the chair line.
ECONOMIC ANALYSIS
The objective of the economic analysis was to determine the payback period for the switch to the
supercritical C02 spray process from the previously used conventional process. The initial investment
in capital equipment and installation costs were consider along with the operating costs(materials,
waste disposal, labor and utilities). The return-on-investment (ROI) was calculated based on the costs
associated with capital expenditures, including equipment and installation, and the return on this invest-
ment generated through lower personnel, operating, and materials costs. Details on the ROI calculation
are included in the full report.(1)
Implementing the UNICARB™ finishing process on the chair line at Pennsylvania House resulted
in substantial annual savings in both utilities and labor as show in Table 3. The annual operating costs
were based on the production of 50,000 chairs per year. The UNICARB™ process costs of $ 46,000
include $ 37,000 for the coatings formulation and C02 concentrate and $ 9,000 for the C02 equipment
rental. The conventional formulation costs for the same number of furniture units would be $ 47,000.
By converting from a two-coat process to the one-coat process, Pennsylvania House was able to
decrease its utility costs by $ 11,000 because there was one less booth to operate. Labor costs were
reduced by $ 46,000 because one less finisher and one less sander were needed. Waste handling and
disposal costs and finishing line maintenance remained the same for both processes.
Cost savings, realized from a decreased in raw materials costs, were offset by the leasing fees
for the C02 tank and pump at Pennsylvania House. Additional savings could be realized by decreasing
the size of the existing ovens to reflect the change to a one-coat system. Pennyslvania House did not
downsize the production ovens to gain gas utility savings.
The annual operating costs of the supercritical C02 finish line is approximately $ 58,000 less per
year than that of the conventional line. The initial capital investment for the UNICARB™ process was $
58,000 of which $ 46,000 was for equipment purchase and $ 12,000 for installation of the equipment.
The more detailed economic evaluation found in the full report demonstrates a positive return on
investment after the first year with a total payback period with three years if gas utility savings are
included, and five years if gas utilities are not included.
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CONCLUSIONS
This technology evaluation shows that supercritical C02 spray technology has potential as a
pollution prevention option in the application of solvent-borne coatings. This technology is not limited to
one coating type, but could be used to reduce the solvent level required to spray apply a variety of
solvent-borne coatings. The wood furniture facility where this evaluation was conducted maintained
product quality with a nitrocellulose lacquer finish and reduced VOC emissions from the coating
process. No additional wastes entered the wastestream. Immediate operating savings of $ 58,000/yr
were realized. A 100% ROI should be achieved within five years after implementation.
Although the research described in this article has been funded wholly or in part by the EPA, it
has not been subjected to Agency review and therefore does not necessarily reflect the views of the
Agency. No official endorsement should be inferred.
Also, mention of trade names or commercial products does not constitute endorsement or
recommendation for use.
REFERENCES
1. Heater, K.J., Parsons, A.B., Olfenbuttel, F.F., Randall, P.M., Evaluation of Supercritical Carbon
Dioxide Technology to Reduce Solvents in Spray Coating Applications. EPA/60Q/R-94/043, U.S.
Environmental Protection Agency, Cincinnati, Ohio, 1994.
2. "Carbide Licenses Coatings Technology." Chemical Engineering News, July 30, 1990. p.9.
3. Hoy, K. Unicarb System for Spray Coatings- A Contribution to Pollution Prevention. European
Polymer Paint Colour Journal. 181:438, 440-2, 1991.
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TABLE 1. Gloss data on sample panels
Finishing Process
Sample
Number
Average
Gloss Data/Panel
Average Gloss
Data/Set
46482-9-1
20,3
±4.3
Conventional
One Coat
46482-9-2
20,4
±3.1
20.3
46482-9-3
20.3
±3.1
46482-10-1
33.2
± 1.6
Conventional
Two Coat
46482-10-2
35.0
±2.2
32.3
46482-10-3
28.7
+ 2.8
46482-11-1
3S.3
±3.2
UNICARB™
46482-11-2
30.5
±3.1
31.5
46482-11-3
28.7
± 2.9
TABLE 2. Comparison of volatile solvent content of conventional and
UNICARB™ coating formulations as percent weight.
Materials Description
HAP (Y/N)
Conventional
(% by weight)
UNICARB™
(% by weight)
MEK-heptanone
No
37.25
methoxypropylacetate
No
7.36
xylene
Yes
16.80
isopropanol
No
11.20
6.55
toluene
Yes
10.39
N-buty! acetate
No
11.83
isobutyl acetate
No
6.89
2-butoxyethanol
Yes
3.27
9.67
MIBK
Yes
5.32
isopropyl acetate
No
1.46
Other
2.37
5.87
Total VOC (% by weight)
76.88
59.34
7-55
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Table 3. Summary of Annual Operating Cost Comparing Conventional
Finish Line with Supercritical C02 Finish Line
Conventional
Supercritical C02
Item
(S/year)
(S/year)
Coating Materials
47,000
37,000
C02 Storage Equipment
...
9,000
Spray Booth #2
Finish Labor
23,000
...
Sanding Labor
23,000
...
Electricity
11,000
...
TOTAL
104,000
46,000
7-56
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Evaluation of Alternative Chemical
Strippers on Wood Furniture Coatings
Sonii L. Turner
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709
Robert C. McCrillis
U.S. Environmental Protection Agency,
Air and Energy Engineering Research Laboratory, (MD-61)
Research Triangle Park, NC 27711
Abstract: Alternative chemical strippers have been evaluated to determine the potential effects
on air emissions resulting from solvent changes in the furniture repair and refinishing industry.
Alternative chemical strippers used to remove both traditional and emerging low-VOC (volatile
organic compound) wood coatings were evaluated. Phase 1 was a laboratory evaluation of five
chemical stripper combinations on three types of coatings. Phase 2 was the assessment of the best
performing alternative stripper from the laboratory evaluation in a furniture repair and refinishing
facility. This paper discusses both phases of research. Screening and assessment results will be
presented at this conference.
Introduction
Chemical strippers employ a variety of chemical mechanisms and may be designed for
specific functions. Solvents that cause physical and chemical reactions are often involved in
chemical stripping applications. Chemical stripper removal processes encompass cold solvent
(acid or alkaline activated), hot alkaline removal, and molten salt baths. These stripping
solvents are designed to degrade coating films or destroy adhesion of the film from the
substrate to which it is attached (Hahn). In the original equipment and furniture manufacturing
markets, chemical strippers are used to remove defective coatings from items that do not pass
inspection. They are also used to clean spray booths and coating application equipment. In
this study, five alternative cold solvent chemical strippers were used to remove three coating
types of wood furniture coatings from wooden surfaces. Following coating removal, the
effectiveness of each chemical stripper to remove the coatings from the wooden surfaces was
evaluated.
Methylene chloride (CH2C12) is a halogenated solvent and a suspected carcinogen;
however, it is not defined as a volatile organic compound (VOC) by the Environmental
Protection Agency's (EPA's) definition. CH2C12 has been a primary component formulated in
chemical strippers. The effectiveness of CH2C12 is due to its small molecular size, which
promotes rapid penetration into the coating film, and to its intermediated solvency for various
7-57
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polymer coatings. As CH2C12 penetrates to the substrate, the coating film swells to several
times its original volume. The swelling causes an increase in internal pressure at the interface
with the coating relieved in a direction away from the substrate. Thus the film wrinkles,
blisters, buckles, and bubbles, resulting in its release from the substrate. CH2C12 has been
used in nearly all chemical stripping applications because it can effectively strip a broad range
of cured coatings from a substantial variety of substrates (Sizelove, Wollbrinck). Annual
estimates for CH2C12 usage in paint stripping have ranged from approximately 50 million
kilograms to 70 million kilograms.
Other solvents and chemicals that are often found in chemical stripper formulations
may include: alcohols, xylene, toluene, amines, glycol ethers, mineral spirits, methyl ethyl
ketone, acetone, phenol, and benzene (Sizelove, Wollbrinck). These additional components,
several of which are VOCs and some of which are hazardous air pollutants (llAPs), are often
used to enhance the properties and performance of primary components. In some cases,
solvent blends that dissolve the coating film are favored over other types of chemical strippers.
Some solvent chemical strippers that employ ketones and aromatic hydrocarbon blends are
used primarily where other chemical strippers fail such as on low intrinsic strength films or
sharply angled surfaces (Sizelove, Wollbrinck). Annual VOC emission estimates for all U.S.
furniture stripping firms have been reported to be as high as 1.1 million kilograms.
Alternative chemical strippers have been evaluated to determine the potential effects on air
emissions resulting from solvent changes in the furniture repair and refinishing industry.
Project Description
The purpose of this research was to evaluate the feasibility of using alternatives to high
VOC/HAP solvent-based chemical strippers that are currently used in the furniture repair and
refinishing industry to remove both traditional high VOC lacquer and emerging, low-VOC,
wood furniture coatings. Research Triangle Institute (RTI), under a cooperative agreement
with the U.S. EPA's Air and Energy Engineering Research Laboratory, screened five
alternative chemical strippers, consisting of one industrial and four retail chemical strippers.
Alternative chemical strippers were evaluated based on their stripping effectiveness compared
to a CH2Cl2-based stripper. A panel of individuals experienced in the area of chemical
stripping evaluated the samples and selected the most effective chemical stripper for further
evaluation. An on-site assessment of the best performing alternative chemical stripper from
the screening evaluation took place at a local furniture refinishing facility. The EPA, RTI,
several coating suppliers, one chemical stripper supplier, and two local furniture refinishing
facilities participated in this project.
Project Objectives
This project was undertaken to identify chemical strippers that could serve as
alternatives to CH2Cl2-based chemical strippers and to evaluate their effectiveness for the
removal of furniture coatings typically used on wooden substrates encountered in furniture
refinishing industries. The specific objectives of this research were to:
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1. Conduct a laboratory evaluation of the performance of five alternative chemical
stripper formulations and compare their performance to the performance of a traditional
solvent-based chemical stripper formulation on three coating types found on wood furniture
substrates.
2. Assess, in a furniture refinishing facility, the use of the best performing alternative
stripper on traditional furniture coatings and new emerging low-VOC furniture coatings.
This project was limited to conducting a screening study and assessing of one industrial
and four retail chemical strippers following the recommendations of the manufacturer or
supplier of the material. No provisions were made for extending the experiments to cover the
modifications of the five chemical strippers, or for the formulations of the chemical strippers.
Refinement in the formulation of effective chemical strippers, and a thorough evaluation of the
health and environmental effects, were beyond the scope of work for this project.
Project Activities
The laboratory evaluation, the first objective, involved cold, solvent strippers; no
thermal methods were used. Solvent strippers work solely by dissolving the coating film.
Their dissolving mechanism causes them to become rapidly saturated with dissolved coating.
Care must be taken to prevent redeposition of the film on the substrate. Cold strippers act best
when they are not true solvents of the film, but are absorbed by the film. This action is
similar to the actions of CH2Cl2-based strippers. Five chemical strippers and three coating
types were selected cooperatively by the EPA and RTI. The selected strippers consist of a
combination of one or more of the following constituents: CH2C12» dibasic ester (DBE),
n-methylpyrrolidone (NMP), and d-limonene. A CH2Cl2-based chemical stripper was used as
the standard. The other chemical strippers did not contain CH2C12. DBE is a mixture
consisting of refined dimethyl esters of adipic, glutaric, and succinic acids. The chemical
strippers are identified as a number with at least one formulation constituent in parentheses.
Individual constituents of each chemical stripper are listed in Table 1.
Coating types included traditional furniture coatings, which are often solvent-based
nitrocellulose coatings, and new emerging coating types, which included waterborne and high
solids coating types from four major wood furniture coating suppliers. Screening was
performed in a laboratory hood at RTI by RTFs laboratory staff. Selected strippers were
applied to remove the cured coatings from a 30 cm x 30 cm area of oak, pine, and maple
wood substrates. The manufacturers' directions for the strippers were observed. Coating
removal quality achieved by each of the alternative strippers was compared to the removal
quality using a CH2Cl2-based stripper.
A panel of three non-RTI reviewers qualitatively evaluated the performance of the
alternative chemical strippers. Each panelist ranked the quality of coating removal from zero
to 10 based upon the percentage of coating removed. A score of 10 represented 100 percent
removal while a score of zero represented no activity by the stripper on the coating. The final
ranking represented the consensus of the panel. Ranking results are presented in Table 2.
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The second objective was to assess the best performing chemical stripper, as found
from the laboratory phase, in a furniture repair and refinishing facility. A facility
representative applied the stripper and evaluated the quality and ease of coating removal for the
alternative stripper selected for on-site assessments. The representative then compared the
removal quality and ease of the alternative stripper to the removal quality and ease of the
stripper routinely used at the evaluation facility.
RTI personnel estimated the emissions that result from the use of each stripper based
upon the quantity of chemical stripper used. Using the information provided by material
safety data sheets (MSDSs), RTI personnel estimated VOC and CH,C12 emissions of the
investigated chemical strippers. Emission estimates for the alternative strippers were
compared with emission estimates for the currently used products to learn the potential for
emission reduction and pollution prevention.
Performance and Materials
The stripping performance of five chemical stripper formulations versus the
performance of a CII2Cl2-based formulation was measured on furniture quality finished
30 cm x 30 cm solid wood coupons. Wood coupons were prepared according to methods
typically used by coating manufacturers to market their coatings to the furniture industry.
Three coating types (clear topcoats) from four unnamed coating suppliers were applied to oak,
maple, and poplar wood coupons. Of the three wood types, the emphasis of this study was
placed on oak. Wood types representation in this study were: porous hardwood, oak;
nonporous hardwood, maple; and softwood, poplar. The clear topcoat types were; traditional
nitrocellulose lacquer, high-solids, and waterborne coatings. Each of the clear topcoats was
applied to the wood substrate using spray and oven curing applications similar to those
typically used in a furniture manufacturing facility.
Each wood coupon was treated using a process of three coating steps that consisted of
at least a stain, sealer, and clear topcoat. Once received from the coating suppliers the
coupons were allowed to cure further for 10 days under ambient conditions. Individual
constituents of each chemical stripper used for this test are listed in Table 1.
Application and Removal
All laboratory chemical stripper application and removal tests were conducted under a
laboratory hood at approximately 22.4°C (72.3°F). For four cases, the chemical strippers
were applied using 2-inch natural bristle brushes following the manufacturer's directions. For
the single case where the chemical stripper was not applied using a brush, a heavy paper towel
was saturated with the less viscous chemical stripper and applied to the wooden substrate, as
the manufacturer suggested.
The area covered by each coating application was approximately 930 cm2 (1 ft2). The
total coverage area for each of the five chemical strippers was approximately 6.1 m2 (20 ft2).
The total volume of each chemical stripper used for the total area is presented in Table 3.
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Treated coatings were removed with a disposable putty knife that had a blade about 1.3 cm
(0.5 in.) wide. Table 4 lists the general ease of removal for the three coating types during the
actual removal. Chemical strippers are identified above each column, and the coating types
are listed beside each row in Table 4. Once the coatings were removed from the wooden
coupons with the putty knife, the surface was wiped with a cloth and received no further
treatment.
Stripper Evaluation
Laboratory Evaluation. Following stripper application and removal, a panel of
individuals experienced in the area of chemical stripping visually evaluated the performance
effectiveness of each chemical stripper on each coating type. Each chemical stripper test was
ranked on a scale from zero to 10 (where, zero represented no activity by the stripper to
remove the coating, and 10 represented 100 percent coating removal). The ranking results of
the visual evaluation are presented in Table 2.
Figures 1 and 2 are photos of the test coupons with coatings removed using Chemical
Stripper 4 (d-Limonene) and Chemical Stripper 5 (H20), respectively. Below each photo is
the chemical stripper used in the screening evaluation. The chemical strippers ranked in order
of best to worst are: Chemical Stripper 4 (d-Limonene), Chemical Stripper 5 (H20),
Chemical Stripper 3 (NMP, DBE), Chemical Stripper 1 (Standard), and Chemical Stripper
2 (NMP, DBE). The top three performing chemical strippers from this study were closely
ranked, Chemical Stripper 4 (d-Limonene) at 7.9, Chemical Stripper 5 (H20) at 7.5, and
Chemical Stripper 3 (NMP, DBE) at 7.3. According to the panel, Chemical Stripper
4 (d-Limonene) was the most effective chemical stripper in the group. Figures 3 and 4 are
photos of test coupons with coatings removed using Chemical Stripper 4 (d-Limonene).
Because of its low vapor pressure, chemical stripper 5 (H20) can be left on the paint for
extended periods without loss of solvents, allowing more flexibility in working time.
However, this DBE chemical stripper is waterborne and can raise the grain of wooden
substrates. Material cost for chemical strippers at the time of this study is presented in
Table 5. The relative cost of the chemical strippers for the area treated in this study is listed in
Table 6.
Furniture Repair and Refinishing Facility Evaluation. A local refinisher
demonstrated the stripping effectiveness of Chemical Stripper 4 (d-Limonene) in his facility on
a chair seat, a square table top, and circular table top. The participating refinisher was not
aware of the specific coating types on the substrates; however, he took the liberty to speculate
on the general coating type based on appearance, removal ease, and his experience. The
coatings removed from the square table surface consisted of several layers of paint covering
the original varnished surface with a removal time of approximately 45 minutes. Coatings
removed from the chair seat were layers of lacquer-type finishes with a removal time of
approximately 10 minutes. Removal time for coatings removed from the circular table top was
approximately 6 minutes, and the coatings removed consisted of a traditional lacquer furniture
coating system. All furniture pieces were presumed to have been solid wood. The area of
coating removed was roughly 930 cm2 (1 ft2) from each surface.
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Chemical Stripper 4 (d-Limonene) successfully removed the topcoats from the
lacquer-type surfaces of the chair and circular table top without disturbing the appearance of
the stain. However, it left a film on the lacquer-type surface that was removed by wiping the
surface with an unsoiled cloth moistened with Chemical Stripper 4 (d-Limonene). Roughly
three layers of paint and one layer of varnish were removed from the square table top leaving a
raw wood surface. The refinisher said that the product was reliable. However, he was
concerned with the cost.
Conclusions
Results from this evaluation included: (1) the subjective determination of a viable
substitute for solvent-based chemical strippers based upon the effectiveness of the evaluated
alternative chemical strippers, (2) the potential effect of the alternative chemical stripper on air
emissions, and (3) the cost associated with the use of the alternative chemical stripper.
Implementing the use of the alternative chemical stripper as a viable substitute was at the
discretion of the host facility.
The VOC and CH2C12 emission estimates resulting from the use of alternative chemical
strippers and currently used solvent-based chemical strippers were calculated using the
available information provided from the MSDSs of each chemical and the amount of chemical
stripper used. A cost assessment was generated from usage information provided by the host
facility and cost information provided by the vendor for chemical strippers only. Relative
costs and emission estimates are presented in Tables 6 and 7, respectively. Waste
management, other cost associated with using the alternative chemical stripper, and handling
and safety were not directly related to the objectives of this study and should be included in
future work.
References
Halm, W. J., and P. O. Werschulz. Evaluation of Alternatives to Toxic Organic Paint
Strippers. Prepared for the U.S. Environmental Protection Agency, EPA/600/2-86/063 (NTIS
PB86-219177). July 1986.
Sizelove, Robert. Paint Stripping Updated. Industrial Finishing. October 1972.
Wollbrinck, Thomas. The Composition of Proprietary Paint Strippers. JAIC 32(1993):43-57.
7-62
-------
FIGURE 1. PHOTO OF TEST COUPONS FINISHED WITH VARIOUS FURNITURE COATINGS
AND THEN STRIPPED USING CHEMICAL STRIPPER 4 (D-LIMONENE).1
FIGURE 2. Photo of test coupons finished with various furniture coatings
AND STRIPPED USING CHEMICAL STRIPPER 5 (HjO).1
1 Coatings and wood types from top-to-bottom and left-to-right in figure are: waterborne on oak, high-solids on oak,
and nitrocellulose lacquer on oak, poplar, and maple.
7-63
-------
FIGURE 3. PHOTO OF TEST COUPONS FINISHED WITH A LACQUER SYSTEM ON MAPLE
BEFORE AMD AFTER TREATMEMT USING CHEMICAL STRIPPER 4 (D-LIMONENE).
FIGURE 4. PHOTO OF TEST COUPONS FINISHED WITH A HIGH-SOLIDS SYSTEM ON OAK
BEFORE AND AFTER TREATMENT USING CHEMICAL STRIPPER 4 (D-LIMONENE).
7-64
-------
Table 1. Constituents of Chemical Strippers
Chemical Stripper
Constituent Weight %
1 (Standard)
Methylene Chloride * >10
Methanol * <25
Toluene * >35
Acetone < 25
Paraffin Wax < 5
2 {NMP, DBE)
N Methyl-2-Pyrrolidone f
Dimethyl Glutarate f
Dimethyl Adipate +
Dimethyl Succinate f
3 (NMP, DBE)
l-Methyl-2-Pyrrolidone f
Dimethyl Glutarate f
Dimethyl Adipate f
Dimethyl Succinate f
4 (d-Limonenc)
n-Methyl Pyrrolidone 50-75
d-Limonene 25 - 50
5 (H20)
Water 65-75
Dimethyl Adipate 20 - 30
Dimethyl Glutarate 1-5
Hydrated Magnesium
Aluminum Silicate 0 - 2
Hydrated Aluminosilicate 0 - 2
* Hazardous Air Pollutants
1 Constituent weight percent undisclosed on Material Safety Data Sheets (MSDSs); therefore, primary
constituent can not be identified.
Table 2. Average Ranking from Stripping Evaluations *
1
(Standard)
2
(NMP, DBE)
' 3 .
(NMP, DBE)
4
(d-Limonene)
5
-------
Table 3. Usage Estimates
Chemical Stripper
Volume/Coverage Area, (m3/m2)
1 (Standard)
1.22 X 10 4
2 (NMP, DBE)
1.74 x 1Q-4
3 (NMP, DBE)
2.67 x 10"4
4 (d-Limonene)
3.23 x 10-4
5 (H20)
6.47 x iO"4
Table 4. Removal Ease for Coatings
Coating Types
1
(Standard)
' '2 ' .
(NMP, DBE)
3
(NMP, DBE)
4
(d-Limonene)
5: •
(H2o)
NitroceEuIose
VE
VE
VE
VE
VE
Waterborne
RE
RE
RE
D
RE
High Solids
RE
RE
RE
D
VE
ve = Very Easy RE = Relatively Easy D = Difficult
Tables. Material Cost
(U.S. Dollars)
Chemical Stripper
Quart
Gallon
1 (Standard)
4.03
10,17
2 (NMP, DBE)
7.95
21.94
3 (NMP, DBE)
9.22
25.16
5 (H20)
6.79
16.37
4 (d-Limonene)
11.73*
46.93*
9.73'
38.93f
* 4 (d-Limonene) is only available for purchase in 5- and 55-gallon quantities, this is an estimate using the
5-gallon quantity.
1 4 (d-Limonene) is only available for purchase in 5- and 55-gallon quantities, this is an estimate using the
55-gallon quantity.
7-66
-------
Table 6. Relative Material Cost for Stripping a Fixed Area * *
(U.S. Dollars)
Chemical Stripper
Cost/Area, ($/m2)
Relative Cost
1 (Standard)
0.52
1.0
2 (NMP, DBE)
1.46
2.8
3 (NMP, DBE)
2.61
5.0
5 (H20)
4.65
9.0
4 (d-Limonene)
3.401
6.6t
2.82*
5.4"
All significant figures are not shown. Numbers are rounded to the nearest one hundredth,
4 (d-Limonene) is only available for purchase in 5- and 55-gallon quantities, this is an estimate using
the 5-gallon quantity.
* 4 (d-Limonene) is only available for purchase in 5- and 55-gallon quantities, this is an estimate using
the 55-gallon quantity .
7-67
-------
Table 1, Emission Estimates
Chemical Stripper
voc
fU /^I
mass/area, (g/nr)
1 (Standard)
85,85
9.54
2 (NMP, DBE)
160.90
-
3 (NMP, DBE)
263.74
-
4 (d-Limonene)
158.94
-
5 (H,0)
139.86
-
7-68
-------
SESSION 8A
MILITARY APFUC4TI0NS
8-1
-------
PAPERS PRESENTED:
"Low- and NoVOC Conformal Coatings Over No-clean Flux Residues"
by
Edward Shearls
SAIC
Indianapolis, Indiana
"Low-VOC and No-VOC Coating Systems for Aerospace and Its Support"
by
Dan Bernard
DEFT, Inc.
Irvine, California
"Low VOC Marine Coatings"
by
Charles Ayers
Jotun/Valspar
Baltimore, Maryland
"Evaluate Alternative Paint Stripping Technologies Used in Aircraft and Space Vehicles"
by
Geddes Ramsey
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Research Triangle Park, North Carolina
8-2
-------
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
LOW- AND NO-VOC CONFORMAL COATINGS OVER NO-CLEAN FLUX RESIDUES
Edward A. Shearls
SAIC
714 N. Senate Avenue
Indianapolis, IN 46202-3112
Timothy Crawford
EMPF
714 N. Senate Avenue
Indianapolis, IN 46202-3112
Julie Kukelhan
SAIC
714 N. Senate Avenue •
Indianapolis, IN 46202-3112
INTRODUCTION
The use of conformal coatings over Printed Wiring Assemblies (PWAs) today presents three
manufacturing challenges. First, in response to the impending phaseout of chlorofhiorocarbon-based
solvents, low residue or no-clean fluxes have been developed. These fluxes are advertized as leaving no,
or very little benign residue after the soldering process, but the main concern is whether these benign
residues interfere with conformal coating adhesion to PWAs, Second, most conformal coatings in use
release significant amounts of volatile organic compounds (VOCs) during coating application. The use of
new conformal coatings with lower VOC content and less environmental impact is rapidly becoming an
important issue. The Clean Air Act of 1990 drives the eventual use of no- or low-VOC conformal
coatings with negligible environmental impact. The third challenge is to determine whether it is feasible
and practical to apply a low-VOC coating over a no-clean flux.
This paper describes results of a three phase effort that addresses these challenges completed at
the Electronics Manufacturing Productivity Facility (EMPF). Phase 1 evaluated the adhesion and
performance of current (not low-VOC) acrylic, polyurethane, silicone, and parylene conformal coatings
applied over test pallets manufactured with no-clean (low residue) fluxes and pastes. Phase 2 evaluated
the use of currently available low-VOC conformal coatings applied over commonly used RMA and water
soluble fluxes and pastes. Environmental stress screening (ESS) tests were performed in both phases to
down select no-clean materials and low-VOC coatings for further testing in Phase 3, the application of
low-VOC coatings over no-clean fluxes and pastes on functional boards (PWAs).
METHODOLOGY
Preliminary Compatibility Testing
Preliminary compatibility testing was performed to ensure test pallet (Phase 1 and 2) and
functional test board (Phase 3) base materials (fluxes, pastes, base metals, laminate, and solder mask
combinations) were compatible. Five RMA fluxes, four water-soluble fluxes, seven RMA pastes, and six
water-soluble pastes comprised the matrix of representative common fluxes and pastes tested. A popular
liquid photoimageable (LP1) and a popular dry film solder mask were tested.
Fluxes were applied to test pallets using individual spray bottles. Pastes were printed using an
80-mesh, 10-mil-thick screen. Pallets were wave soldered or IR reflowed according to manufacturers'
technical literature. Those made with RMA materials were cleaned with 10% Armakleen E-2001
detergent. Those made with water-soluble materials were cleaned with DI water only. The flux and
8-3
-------
paste producing the best soldered pallets were used to make Phase 2 test pallets and Phase 3 PWAs.
Test Pallets and Coupons
The test pallets used in the Phase 1 and Phase 2 efforts were 4-00 inches by 5.00 inches (10.20 x
12.75 cm) and had four test coupons to a pallet, with break-away tabs between the coupons (see Figure
1). Each test coupon contained a 1.00 inch by 1.50 inch (2.54 x 3.80 cm) copper rectangle with a 0.50
inch by 1.00 inch (1.27 x 2.54 cm) solder
mask strip down the center. One half of the
test pallets had coupons with LPI film solder
mask, the other half had dry film solder mask.
The majority of the coupons had bare copper
on the areas adjacent to the solder mask. The
remainder had hot air solder leveled (HASL)
on the areas adjacent to the solder mask. The
laminate was FR4 material.
The masks and the metal surfaces
allowed the base metal/mask test coupon
combinations:
° Copper/Photoimageable Liquid
° Copper/Dry Film
° HASL/Photoimageable Liquid
° HASL/Dry Film Figure 1 Test Coupon
Including the FR4, this arrangement allowed evaluation of conformal coating adhesion to five
different substrates and interfaces after application of the various flux residues.
Phase 1. No-Clean Flux Evaluation
It was impossible to evaluate every standard (not low-VOC) conformal coating and no-clean flux.
One acrylic, one polyurethane, one silicone and one parylene were randomly selected to represent their
respective coating families. The coatings were applied at Specialty Coating Services of Indianapolis,
Indiana. Flux and paste selection were more complicated because of the broadness of the no-clean
definition. The materials available were grouped into resin, rosin, or rosin/resin free categories, and
further divided by solids content, activator and carrier. Twelve pastes and eleven fluxes were chosen to
represent the no-clean industry.
Liquid fluxes were applied to the test pallets with a high pressure spray system designed for no-
clean fluxes. Precision Dispensing Equipment of Bay Village, Ohio brought the system to the EMPF and
operated it. The fluxes were processed on a nitrogen inerted wave soldering machine using a profile
recommended by material vendors. No-clean solder pastes were printed to the test pallets and reflowed
in a nitrogen environment using forced convective air reflow and a profile recommended by the material
vendor.
In Phases 1 and 2, representative pieces of the conformal coated coupons were visually examined
and tested for adhesion. Additional samples were subjected to ESS tests which included either
temperature/humidity, thermal cycle, thermal shock, salt fog, a sequence of all tests, or no test. The
stress tests and conditions used are listed in Table 1.
L
.
8-4
-------
TABLE 1 ENVIRONMENTAL SCREENING TEST SUMMARY
Stress Test
Specification
Conditions
T emperature/Humidity
MIL-STD-S10D
Method 507.2
168 hours, 30 to 60° C; 85-95%
relative humidity
Thermal Cycling
IPC-TM-650
Method 2.6.6
24 hours, -55 to +125° C; 30 min per
temp and 15 min dwell at 25° C
between each ramp
Thermal Shock
MIL-STD-202F
Method 107D
24 hours, -55 to +125" C; 15 min per
temp.
Salt/Fog
MIL-STD-810D
Method 509.2
48 hours, 35° C
ASTM D3359 was used to measure conformal coating adhesion, modified to eliminate as much
of the subjectivity as possible. Instead of a hand-held cutting tool, an IBM robot was fitted to hold the
cutting tool and the test coupon and programmed to perform the actual cutting. The coupon was cut
and then rotated 90 degrees and cut again to form a lattice pattern. A specified tape was pressed over
the area and then removed. Use of the robot gave uniform depth, pressure and lattice formations. The
same technician performed all tape applications and ratings. Adhesion was rated for each substrate on a
5 to 0 point system, with 5 best and 0 worst as shown in Table 2.
TABLE 2 ADHESION GRADING SCHEME
GRADE
CRITERIA
5
The edges of the cuts are completely smooth; none of the squares of the lattice is
detached.
4
Small flakes of the coating are detached at intersections; less than 5% of the area is
affected.
3
Small flakes of the coating are detached along the edges and at intersections of cuts. The
area is 5-15% of the lattice.
2
Coating has flaked along the edges and on parts of the squares. The area affected is 15-
35% of the lattice.
1
Coating has flaked along the edges of cuts in large ribbons and whole squares have
detached. The area affected is 35-65% of the lattice.
0
Flaking and detachment worse than grade 1.
8-5
-------
Phase 2. Low-VOC Conformal Coating Evaluation
The most compatible RMA and water soluble fluxes and pastes, determined by preliminary
compatibility testing, were used to make test pallets as described in that section for low-VOC conformal
coating evaluation. Fourteen different conformal coatings representing the generic coating groups were
applied to test pallet replicates (ten of each type shown in Table 3).
TABLE 3. TEST PALLET MATRIX
Solder Mask
Flux
Paste
RMA
Water Soluble
RMA
Water Soluble
Liquid Film
X
X
X
X
Dry Film
X
X
X
X
After a literature review, it was decided that LP I solder mask pallet results were the primary
criteria for flux, paste, and conformal coating selections in this project, as LPI solder mask would be used
on the pallets for the Phase 3 (no-clean materials with low-VOC conformal coatings) effort. LPI solder
mask has been shown the most compatible with no-clean fluxes1 and more compatible with conformal
coats than other types2. A solder mask comparison3 reports LPI masks reduce tombstoning and solder
balls, withstand multiple refiow cycles, and are easily cleaned. Several papers describe favorable solder
ball dynamics with LPI masks4A6,7.
The coatings were evaluated using the environmental screening tests described earlier to
determine the most promising one from each generic group to use in the Phase 3 effort.
Phase 3. Low-VOC Conformal Coating Over No-Clean Flux Evaluation
Populated boards (PWAs) were manufactured for the Phase 3 evaluation using the liquid film
photoimageable solder mask and the laminate from earlier testing. The no-clean fluxes and pastes that
graded best in the Phase 1 effort was used for one set of these boards. The RMA fluxes and pastes and
the water soluble fluxes and pastes selected in the compatibility pretesting were used to manufacture
two additional sets of populated boards. A set of not-populated boards served as a final control set.
The RMA and water soluble paste and flux combinations representing current industry
conditions and the no-clean fluxes and pastes used in the Phase 3 effort are shown in Table 4. These
fluxes and pastes demonstrated the best adhesion with the traditional conformal coatings on the test
coupons.
The low-VOC conformal coatings chosen for Phase 3 are shown in Table 5. These conformal
coatings demonstrated the best adhesion when used with traditionally fluxed and cleaned test coupons.
Table 6 shows the ESS test fate for each board in a 12 replicate set. One board in each group
was not ESS tested.
8-6
-------
TABLE 4 FLUX & PASTE SELECTION
PASTE
FLUX
RMA
Alpha RMA 209
Alpha 615 RMA
WS
Am tech WS-465XT
Lonco Organo Flux 3355 W
No-Clean
AIM LR5
AIM Base I
Alpha 970S Kester 970S
Hi-Grade 3570-T Alpha NR200
TABLE 5 CONFORMAL COATING SELECTED
Conforaial Coating Type
Conformal Coating Selected
Acrylic
Quick Cure 576
Urethane
Dymax 986
Epoxy
Envibar 1244T
Silicone
Loctite 5290
Parylene
Parylene C
TABLE 6 BOARD TESTING SCHEME
BOARD NUMBER
ESS TEST
1-3
SIR
4-6
Sequential ESS
7
No ESS
8
Humidity Only
9
Thermal Cycle Only
10
Thermal Shock Only
11
Salt Fog Only
12
Spare PWA
8-7
-------
PWAs were visually examined and tested for adhesion in four different locations, (two on the
top-side and two on the bottom-side). The slightly modified version of ASTM D3359 described earlier
was used to measure conformal coating adhesion. Adhesion was rated using the grading system shown
in Table 2.
RESULTS
Visual Inspection of Conformal Coatings
Visual Inspection Of Acrvlic Coating
Control PWAs (non-populated PWAs) had minor dewetting on both sides and some coating
discoloration. Major dewetting occurred on the component side of all processed (fluxed) assemblies, and
the Plastic Leaded Chip Carriers (PLCCs) and other chips. PWAs manufactured with RMA and no-clean
paste and flux also showed poor adhesion of the conformal coating on the PLCCs after being
environmentally stressed. Lighter colored PLCC areas could be flaked easily using a probe or a
fingernail. Acrylic coatings on the no-clean assemblies were discolored and were "bubbled" on the
bottom side. PWAs made with water soluble flux and paste had good, uniform coating coverage on their
bottom sides.
Visual Inspection Of Polvurethane Coating
Minor dewetting on the PLCCs and chips occurred on the boards made with RMA and no-clean
paste and flux. The no-clean paste and flux displayed dewetting around the component pad areas.
Control PWAs and PWAs manufactured with water soluble paste and flux displayed coatings with good,
uniform coverage.
Visual Inspection Of Parvlene Coating
All PWAs displayed good, uniform Paiylene coatings.
Visual Inspection Of Epoxv Coating
The coating on all PWAs displayed major dewetting on the component side and the PLCCs and
chips. The PLCCs exhibited adhesion problems after environmentally stressing. PWAs manufactured
with RMA or water soluble paste and flux displayed good, uniform Epoxy coatings on their bottom sides.
PWAs manufactured with no-clean paste had slight dewetting on their bottom sides.
Visual Inspection Of Silicone Coating
Control PWAs and all PWAs manufactured with RMA or water soluble paste and flux produced
Silicone coatings with good, uniform coverage. PWAs manufactured with no-clean paste and flux
displayed slight dewetting around component pad areas.
Adhesion of Conformal Coatings After Environmental Stress Testing
The top and bottom board adhesions for each PWA were rated on a 0-5 scale, then converted to
a percent (100 percent maximum). Table 7 shows the overall average adhesion by coating for each ESS
test. Table 8 shows the average percent adhesion for each coating as a function of the paste/flux type
for each ESS test.
8-8
-------
Adhesion of Acrylic Coating after ESS
The PWAs that went through only Humidity and only Salt Fog tests had average adhesions of 25
percent (see Table 7). No paste/flux material did well but values for boards made with no-clean
materials were exceptionally poor (see Table 8). PWAs that went through all environmental stresses
had an average adhesion of 55 percent, again because of poor adhesion for no-clean material boards.
PWAs that saw no environmental stresses had an average adhesion of 61 percent. Thermal shock and
thermal cycling tests, with resultant average adhesions of 86 and 90 percent respectively, had the least
effects on PWA adhesion.
Analyzed in overall terms of paste/flux materials (see Table 8), the acrylic coated PWAs made
with RMA and the water soluble paste and flux had adhesion averages of 64 and 62 percent,
respectively. The control PWAs had an average adhesion of 65 percent. The no-clean paste and flux had
the lowest adhesion average (37 percent).
TABLE 7 AVERAGE ADHESION BY ESS TEST vs COATING TYPE
ESS TEST
COATING
HUMID
T. CYCLE
T.SHOCK
SALT FOG
ALL
NONE
ACRYLIC
25
90
86
25
55
61
URETHANE
69
78
79
78
71
75
PARYLENE
99
90
85
80
96
98
EPOXY
91
89
86
50
80
86
SILICONE
69
64
61
65
74
80
average
71
82
81
61
81
80
Adhesion of Urethane Coating after ESS
Urethane coatings produced boards with average adhesions from 69 to 79 percent (Table 7).
The PWAs that went through humidity stress only had an average adhesion of 69 percent. PWAs that
went through all environmental stresses had an average adhesion of 71 percent. PWAs that saw no
environmental stresses had an average adhesion of 75 percent. PWAs that went through only thermal
cycling, or thermal shock, or salt fog, had average adhesions of 78 or 79 percent.
In terms of paste/flux materials (Table 8), average adhesions ranged from 69 to 80 percent. The
control PWAs had an average adhesion of 69 percent. The PWAs manufactured with RMA paste and flux
had an average adhesion of 80 percent. The PWAs manufactured with water soluble paste and flux had
an average adhesion of 77 percent. The PWAs manufactured with no-clean paste and flux had an
average adhesion of 73 percent.
Adhesion of Parvlene Coating after ESS
The average salt fog adhesion value of 80 percent (Table 7) for PWAs coated with Parylene is a
reflection of the poor adhesion (30 percent average) on PWAs made with RMA (Table 8). Parylene
coated PWAs that went through only thermal shock testing "had an average adhesion of 85 percent.
8-9
-------
PWAs that went through only thermal cycling had ail average adhesion of 90 percent. PWAs that saw
no environmental stresses had an average adhesion of 98 percent. PWAs that went through humidity
and PWAs that saw all environmental stresses had average adhesions of 99 and 96 percent, respectively.
In terms of paste/flux materials (Table 8), the control PWAs had the best adhesion (99 percent),
followed by PWAs manufactured with water soluble paste and flux (93 percent average adhesion). PWAs
manufactured with RMA paste and flux had average adhesion of 87 percent. The PWAs manufactured
with low-residue paste and flux had a comparable adhesion of 84 percent.
Adhesion of Epoxv Coating after ESS
The epoxy coated PWAs that went through only salt fog testing had an average adhesion of 50
percent (Table 7), again because of the poor adhesion of the boards made with no-clean materials (Table
8). PWAs that went through all environmental stresses had an average adhesion of 80 percent. The
remaining ESS tests produced adhesion values that were essentially equivalent. PWAs that saw no
environmental stresses and the PWAs that went through only thermal shock had average adhesions of 86
percent. PWAs that went through only thermal cycling had an average adhesion of 89 percent.
Individual humidity testing produced an average adhesion of 91 percent.
In overall terms of paste/flux materials (Table 8), the control PWAs had the best average
adhesion value (95 percent). The RMA paste and flux PWAs had an average adhesion of 86 percent.
The water soluble paste and flux had an average adhesion of 82 percent. The no-clean paste and flux
had average adhesion of 58 percent.
Adhesion of Silicone Coating after ESS
The silicone coated PWAs generally did poorly in the various individual ESS tests, with average
adhesion values in the 61 to 69 percent range (Table 7). PWAs that saw all environmental stresses had
an average adhesion of 74 percent. The PWAs that saw no environmental stresses had average adhesion
of 80 percent.
In terms of paste/flux materials (Table 8), the PWAs manufactured with water soluble paste and
flux had an average adhesion of 74 percent. Those manufactured with RMA paste and flux and the
control PWAs had average adhesions of 71 and 70 percent, respectively. The PWAs manufactured with
no-clean paste and flux had an average adhesion of 60 percent.
Overview Of Conformal Coating Adhesion
In terms of severity for the conformal coatings tested (Table 7), the salt fog test is most severe
with an average adhesion of 61 percent. Humidity testing produces an average adhesion of 71 percent.
The remaining ESS tests are equivalent in severity, with average adhesions of 81 or 82 percent. Control
PWA adhesion is 80 percent.
When all environmental stresses are averaged for the various paste and flux combinations (Table
9), the PWAs coated with Parylene C had the highest average adhesion (91 percent). PWAs coated with
epoxy were next with an average of 80 percent adhesion. The urethane coated boards had 75 percent
average adhesion, followed by silicone-coated PWAs with 69 percent average adhesion and acrylic-coated
PWAs with 57 percent average adhesion.
8-10
-------
TABLES ADHESION MATRIX
COATING & TEST
PASTE/FLUX TYPE
ACRYLIC
RMA
WATER SOLUBLE
NO-CLEAN
CONTROL
ESS AVE
HUMIDITY
35
40
0
25
25
THERMAL CYCLE
85
100
75
100
90
THERMAL SHOCK
90
70
85
100
86
SALT FOG
25
SO
0
25
25
ALL
72
60
15
72
55
NONE
80
50
45
70
61
paste/flux ave
64
62
37
65
57
URETHANE
HUMIDITY
80
60
75
60
69
THERMAL CYCLE
80
80
70
80
78
THERMAL SHOCK
80
80
75
80
79
SALT FOG
80
80
75
80
78
ALL
78
90
69
46
71
NONE
80
75
75
70
75
paste/flux ave
80
78
73
69
75
EPOXY
HUMIDITY
100
100
65
100
91
THERMAL CYCLE
90
90
75
100
89
THERMAL SHOCK
80
90
75
100
86
SALT FOG
70
45
5
80
50
ALL
89
92
40
88
77
NONE
85
75
85
100
86
paste/flux ave
86
82
58
95
80
SILICONE
HUMIDITY
70
80
65
60
69
THERMAL CYCLE
60
70
65
60
64
THERMAL SHOCK
60
60
65
60
61
SALT FOG
75
75
30
80
65
ALL
80
77
58
80
74
NONE
80
80
80
80
80
paste/flux ave
71
74
60
70
69
PARYLENE
HUMIDITY
100
100
95
100
99
THERMAL CYCLE
100
80
80
100
90
THERMAL SHOCK
95
80
65
100
85
SALT FOG
30
100
90
100
80
ALL
98
O
O
84
100
96
NONE
100
100
95
95
98
paste/flux ave
87
93
84 | 99 | 91
8-11
-------
TABLE 9 ADHESION MATRIX AVERAGES
COATING & TEST
PASTE/FLUX TYPE
COATING
RMA
WATER SOLUBLE
NO-CLEAN
CONTROL
ESS AVE
ACRYLIC
64
62
37
65
57
URETHANE
80
78
73
69
75
EPOXY
86
82
58
95
80
SILICONE
71
74
60
70
69
PARYLENE
87
93
84
99
91
SIR Testing
SIR values are shown in Table 10 and Figures 2-6, None of the SIR value changes shown are
significant value changes and none would be classed a failure. Average SIR values improved after SIR
testing for the epoxy, silicone, and urethane coatings. Average SIR values decreased slightly (0,44 log
ohm; less than one order of magnitude) for the acrylic coating and decreased even more (1.19 log ohm;
slightly over one order of magnitude) for the Parylene coating. The average SIR value for the parylene
group is almost 2 log ohms less than that of the closest group (the acrylic coating). Note that for all but
the silicone group, the No-clean boards had the lowest SIR values in each group (Figures 2-6). The No-
clean boards had a higher SIR value than the RMA and Control Boards in the silicone coating group.
Figure 7 shows average adhesion values for the five conformal coatings evaluated in the Phase 3
effort plotted for the RMA, Water-soluble, and No-clean fluxes and pastes used to manufacture the PWAs.
The flux/paste graph lines are relatively close together over the urethane, silicone, and parylene
conformal coatings, indicating all have equivalent adhesion for the materials tested.
CONCLUSIONS
A viable test vehicle (pallet) and methodology for assessing interactions between no-clean
materials and low-VOC conformal coatings have been developed.
The results of this effort indicate that it is practical to use low-VOC coatings over no-clean fluxes
and pastes in some circumstances. When materials are graphed against adhesion (Figure 7), it is
apparent that the urethane, silicone, and parylene conformal coatings used in this study have as good
adhesion over no-clean materials as over RMA and water-soluble materials.
It is important to remember these results apply only to the specific coatings tested and the
specific fluxes, pastes, and solder mask over which they were applied. Coatings that did not perform
well in these tests will perform very well with different PWA materials. Coating performance is related
to material compatibility. It is extremely important that all materials be carefully screened for
compatibility before selecting a no-clean flux/paste and low-VOC conformal coating combination. It is
also important to fine tune manufacturing processes employed and then keep them constant. Small
process changes can have large effects on surface conditions, which in turn effect conformal coating
adhesion.
All reports and data analysis for each phase effort and the initial compatibility testing are
available from the EMPF library.
8-12
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TABLE 10 SIR VALUES (LOG OHMS)
ACRYLIC COATING
INITIAL
24HRS
96 HRS
168 HRS
FINAL
RMA
11.71
8.50
8.38
8.46
12.01
WATER SOLUBLE
11.57
8.39
8.31
8.38
11.55
NO-CLEAN
12.61
7.69
7.93
8.12
10.90
CONTROL BOARD
12.19
8.17
8.34
8.46
11.87
average
12.02
11.58
EPOXY COATING
INITIAL
24 HRS
96 HRS
168 HRS
FINAL
RMA
10.77
8.35
8.43
7.89
12.40
WATER SOLUBLE
10.65
**
8.33
7.81
12.23
NO-CLEAN
10.82
**
8.11
8.69
11.58
CONTROL BOARD
10.82
**
8.35
8.03
12.06
average
10.76
12.07
PARYLENE COATING
INITIAL
24 HRS
96 HRS
168 HRS
FINAL
RMA
10.80
8.56
8.19
8.11
9.76
WATER SOLUBLE
10.84
8.51
8.28
8.16
10.21
NO-CLEAN
10.41
7.83
7.66
7.59
8.88
CONTROL BOARD
11.07
8.28
8.11
8.01
9.50
average
10.78
9.59
SILICONE COATING
INITIAL
24 HRS
96 HRS
168 HRS
FINAL
RMA
11.50
8.51
8.35
8.26
12.03
WATER SOLUBLE
11.34
**
8.51
8.45
12.53
NO-CLEAN
11.90
**
8.42
8.32
12.27
CONTROL BOARD
11.27
**
8.23
8.07
11.86
average
11.50
12.17
URETHANE COATING
INITIAL
24 HRS
96 HRS
168 HRS
FINAL
RMA
11.04
8.00
8.14
7.82
12.34
WATER SOLUBLE
10.98
7.87
7.94
7.82
12.39
NO-CLEAN
10.84
7.72
7.94
8.11
11.38
CONTROL BOARD
10.80
7.58
7.82
7.93
11.95
average
10.91
12.01
** Data lost through equipment malfunction
8-13
-------
14.00
12.00
10.00
e.oo
RMA
6.00
WATER SOLUBLE
NO-CLEAN
^-"CONTROL BOARD
2 00
0.00
INITiA
FIGURE 2 ACRYLIC COATING SIR VALUES
14.00
12 DO
10.00
S.0C
6.00
4 00
2 00
0.00
IN IT! A
-fr—
-?++«-
'"90 HR6-
108 UBS
-fWftti
RMA
WATER SOLUBLE
NO-CLEAN
'CONTROL BOARD
FIGURE 3 EPOXY COATING SIR VALUES
12.00
10.00
8.00
6,00
4.00
2.00
0.00
INiTiAc
24 HR5 -96 HRB WttSS- FttWtl
RMA
"WATER SOLUBLE
TW-CLEAN
' 'CONTROL BOARD
¦O-
FIGURE 4 PARYLENE COATING SIR VALUES
8-14
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14.00
12.00
10.00
8.00
6.00
4.00
2 00
O.OO
INUIAl
-55-HR6 168+tHS-
—F+NAti
RMA
^"WATER soluble
NO-CLEAN
" "CONTROL BOARD
FIGURE 5 SILICONE COATING SIR VALUES
"WATER SOLUBLE
—NO CLEAN
¦CONTROL BOARD
FIGURE 6 URETHANE COATING SIR VALUES
RMA ^ —
WATER SOLUBL;
NO-CLEAN
SILICONE PARYLENE
ACRYLIC URETHANE EPOXY
FIGURE 7 MATERIAL COMPARISON
8-15
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REFERENCES
1. Hemens-Davis, C., and Sunstrum, R, No-Clean: Material Compatibility Issues. Circuits Assembly
4(3): 47, 1993.
2. Vazirani, G., Krevor, D., Chavez, M,, Muley, S., Provancher, R., Ransier, D. and McNelly, D. Conformal
Coats and Their Compatibility with Solder Masks. Kaiser Electronics, San Jose, California. (R). 1992,
3. Tennant, T. Solder Mask Options for the '90s. Electronic Packaging and Production 34(21: 99. 1994.
4. Crum, S. Advances in Liquid Photoimageable Solder Mask Technology. Electronic Packaging and
Production 33(9): 78, 1993.
5. Feiyance, D., and Shubert, F. Matte-Surface solder Masks Reduce Solder Ball Defects. Electronic
Packaging and Production 33(9): 58, 1993.
6. Freitag, B. Reducing Solder Microballs in Inert Wave Soldering. Electronic Packaging and Production
34(2): 79, 1994.
7. Tuck, J. Low End Does Not Equal Low Tech. Circuits Assembly 4(10): 24, 1993.
8-16
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Low VOC and No-VOC Coating Systems For Aerospace and Its Support
Dan Bernard
Deft, Inc.
17451 Von Karman Avenue
Irvine, CA 92714
Research and development was required to lower the VOC of two component urethanes while
avoiding problems created by high solids systems on aircraft. Without such research, there was
very little hope to lower VOC content in this industrial segment
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
8-17
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A discussion of newer technologies for aerospace to reduce or remove VOC and
hazardous air pollutants requires a short history as a prelude. Prior to 1988, most finish coats on
aircraft and pound support equipment were coated with a two component urethane. Military
equipment was coated with a specification, Mil-C-83286, which had a VOC of 600 g/l (5 lbs. per
gal.) as a normal figure. Commercial aircraft operated under different specification, but the VOC
was at a similar value. In 1988, the specification, Mil-C-85285B, was issued which required
VOC maximums of 420 g/1 (3.5 lbs. per gallon) for aircraft and 340 g/1 (2.8 lbs. per gallons) for
ground support. These coatings began their inroads into the military market in late 1988. The
savings in VOC were significant and even more than some realized when the square foot
coverage was considered.
The following shows the calculations for actual VOC reductions on a typical camouflage
product.
Mil-C-83285, color 36375
32.3% solids volume
577 g/1 (4.82 lbs.) VOC
618 sq. ft/gal. at 1 mil dry
Mil-C-85285B Type I, color 36375
52.3% solids volume
420 g/1 (3.5 lbs.) VOC
840 sq. ft/ gal. at 1 mil dry
1000 gallons of Mil-C-83286 covers 518,000 sq. ft.
1000 gallons of Mil-C-83286 contains 4,820 lbs. of solvent
617 gallons of Mil-C-85285 Type I covers 518,000 sq. ft.
617 gallons of Mil-C-85285 Type I contains 2160 lbs. of solvent
Savings of 2660 lbs. of solvent
With these types of savings, great strides had been made and research continued to lower
the VOC's, but the high solids had created some situations that meant higher solids may not be
the most desirable resultant materials.
These main situations presented by the higher solids urethanes were:
1. Difficulty in controlling film thickness
a. higher weight
b. reduction in VOC savings
c. outgassing
2. Shorter pot life
3. Higher viscosities giving rise to more orange peel, and exaggerated by newer
high transfer efficiency guns.
4. Slow cure response at lower temperatures.
8-18
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It was evident that higher and higher solids would only compound these problems. The
logical approach was to use water to be able to lower application solids and still use high
performance systems for aerospace systems. The use of exempt solvents such as 1,1,1
trichloroethane were not considered as a logical solution for long term research. Water was the
only logical approach to lower VOC and still apply thin films.
The question became how low can we go? Two systems have been developed and tested
to a proposal specification of Mil-C-83286 low VOC version. One material has a VOC of less
than 250 g/1 and its prototype have had limited applications on aircraft. The other material has
approximately zero VOC, and is just in the final research phases with no large scale applications
as of January 1995. The term "zero VOC' or approximately zero is based on theoretical
calculations. The test methods involved in water determinations at this time have high enough
percentage errors to yield fluctuating values. Some of these can even be negative values which
would be wonderful, but not real.
The following graphs show how these results can vary. This is only presented to justify
the use of theoretical VOC values in this presentation.
The following charts show the general characteristics and performance results to the
proposed Mil-C-83286 low VOC draft specification. It must be noted that this is not a
specification for use and has only been drafted as a guide to follow for development purposes,
however, the majority of requirements exceed those of Mil-C-83286 and Mil-C-85285.
Specification
Two Component Urethane
Water Based at 210 g/l VOC
Drying Time
Set to Touch 2 hours
2 hours
8 hours
Dry hard 8 hours
Viscosity 15 to 30 seconds #4FC
Pot Life 4 hours minimum
25-30 seconds
4 hours
VOC 210 g/1 max
Gloss Camouflage 85°/5 max
210 g/1
2
60° 85
.98
Uniform
No Effect
10% to 15%
10% impact
Passes 2 inch
Gloss 20785 min
Hiding Power .94 minimum
Surface smooth and uniform
Wet Tape 24 hours
Impact Flexibility 20%
Heat Resistance 4 hours @ 300°F
Low Temperature Flexibility-2 inch mandrel
Fluid Immersion
Lube Oil Mil-L-23699 24 hours @ 150°F
Hydrocarbon TT-S-735 Type III 14 days
Hydraulic Fluid Mil-H-83282 14 days
Hydraulic Fluid Mil-H-5606 14 days
Skydrol 500B 14 days
Distilled water 4 days @ 100°F
F hardness, Tr blisters
H hardness
AE less than 1
H
H hardness
F hardness
H hardness
H hardness
F hardness
Jet Fuels 14 days
Accelerated Weathering No Significant Changes
Pencil Hardness (no requirement)
8-19
-------
% Application Solids by Volume (no requirement)
39%
Specification
Two Component Urethane
Water Based at Zero VOC
Set to Touch 2 hours
2-3 hours
Dry hard 8 hours
10 hours
Viscosity 15 to 30 seconds #4FC
20 seconds
Pot Life 4 hours minimum
4 hours
VOC 210 g/1 max
0
Gloss Camouflage 8575 max
3 @ 60° 3 @ 85
Gloss 20785 min
88
Hiding Power .94 minimum
.98
Surface smooth and uniform
Smooth
Wet Tape 24 hours
No Effect
Impact Flexibility 20%
40%
Heat Resistance 4 hours @ 300°F
Passes 20%
Low Temperature Flexibility-2 inch mandrel
Passes 2 inch
Fluid Immersion
Lube Oil Mil-L-23699 24 hours @ 150°F
H hardness
Hydrocarbon TT-S-735 Type III 14 days
H hardness
Hydraulic Fluid Mil-H-83282 14 days
2H hardness
Hydraulic Fluid Mil-H-5606 14 days
2H hardness
Skydrol 500B 14 days
F hardness, 30 d
Distilled water 4 days @ 100°F
3H hardness
Jet Fuels 14 days
2H hardness
Accelerated Weathering No Significant Changes
AE less than 1
Pencil Hardness (no requirement)
2H-3H
% Application Solids by Volume (no requirement)
50%
The information in the testing data shows these two separate two component urethane
systems can perform to the majority of the desired requirements. Some fluctuation may occur as
the products are commercialized and total field condition impacts are seen.
Areas of future work will concentrate on pot life and dry time controls at various
humidities.
8-20
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Frequency
of Occurrence
1-
0.0 +
0' L J'*™ I
L J
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.
|i*^J | | | | |LX^I| | | | I |
Proposed Limit
2.9 lbs/gal
.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
VOC (lbs/gal)
Figure 1 - Illustration of Method 24's lack of repeatability
within a single laboratory for water-reducible
primer. Note that some values are negative.
Source: Boeing- Commercial Airplane Group
-------
Frequency 7
of Occurrence
6 +
5 +
QO
I
PO
CO
4
3
2
1
-------
LOW VOC MARINE COATINGS
CHARLES F. AYRES
JOTUN/VALSPAR MARINE COATINGS
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
The marine environment contains many ot the most corrosive
atmospheric elements to be found anywhere on this planet. Ultra
violet rays both direct and reflected from the surface of the
water. Constant salt spray, high condensing humidities and even
acid rain. These extreme conditions make the protection of metal
a severe problem. Add to this intermittent immersion and total
immersion in sea water for 24 - 36 months.
Fouling below the water by animal and plant organisms and
extreme variations in climatic conditions round out this assault.
Marine coatings are formulated to handle these varying degrees of
assault.
Marine coatings are either applied in a shipyard where all
necessary equipment is available to handle any situation, or
applied by the crew of the ship where a roller and brush are the
only tools available. Shipyards were able to apply so called
'exotic' coatings such as epoxies and urethanes. Full systems
are shipyard applied from the primer to the topcoat. Ships crews
on the other hand are mainly limited to maintenance and light
repair work. The coatings are one pack and very user friendly.
The basic coatings in this category were usually pure or modified
alkyds. All of these coatings were historically high VOC because
the technology or the need wasn't there to do anything
differently.
8-23
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California was the leader in reducing pollution. Rule 3 &
Regulation 66 were the precursors of things yet to come.
Louisiana was the next state to establish VOC regulations. Then
came the Clean Air Act of 1990 which established the fact that
the paint industry was part of the problem and we would have to
reduce VOC's. The list of Hazardous Air Pollutants (HAP) was
also out and many of the solvents used were on this list as well.
At this time many paint companies already had paints that
met California rules and a separate line of coatings for the rest
of the country. The California paints were harder to use and did
not perform as well as the other paints. As stated before the
technology was not always available. Raw material suppliers did
not see the profitability in formulating products for one state.
What happened? With the Clean Air Act the industry had no
choice but to change. A great deal of research has been done by
raw material suppliers and paint manufacturers to develop low VOC
products as good as or better than the high VOC coatings. Some
technology has fallen by the wayside.
Lacquer dry coatings such as chlorinated rubber and vinyl
may be a thing of the past. To get to the required VOC of 2.8
and still have a usable viscosity creates a challenge for the
resin and coating formulator which is extremely difficult.
Alkyds have been developed to 2.8 #/gal. VOC. These
products are generally higher in viscosity but are able to be
applied with a brush, roller, or spray equipment. A little
slower dry than the traditional'alkyd coatings in most cases. As
8-24
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with most of the low VOC coatings care must be taken to only get
the required film build for proper dry.
Water base inorganic zinc primers have been around for-quite
a few years. Low VOC solvent based inorganic zinc primers have
been developed. These can be used in the same applications as
their predecessors.
Water borne coatings have come a long way also. Resins have
been developed to give more durable coatings with good gloss
retention. Single pack water borne acrylics can be formulated
which are just as good as their solvent base counter parts.
Early water resistance is being improved. Water borne epoxies
have been developed that even have resistance to immersion.
Basic drawback with using water is that it cannot be applied
below 40°F.
Solvent borne and 100% solid epoxies. Resins have been
developed with lower viscosities but equal performance to high
VOC coatings. Generally these coatings either have no pot life
or a very short pot life and must be used with plural component
spray equipment.
Equipment has been developed to handle low VOC coatings that
have high viscosities. Airless spray pumps have high ratios so
that the paint is pumped at higher pressures. High Volume.Low
Pressure (HVLP) conventional equipment has been developed. It is
good for spraying small areas with high viscosity coatings but is
not fast enough for large areas such as ships hulls.
Two other areas of coatings are powder coatings and flame
spray. Powder coatings in their present form are suitable for
8-25
-------
small items that can be removed from the ship and painted in a
shop. They require electrostatic application and curing at high
temperatures. Flame spray can be done in situ. It is slow but
very expensive.
The marine paint industry has met the challenge to make low
VOC coatings that are able to protect marine structures. We are
still making improvements in coatings and are always on the look
out for new technologies to make better coatings that are
environmentally friendly.
8-26
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved lor
presentation and publication.
Evaluate Alternative Paint Stripping Technologies Used in Aircraft and Space Vehicles
Geddes H. Ramsey
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
Abstract
Solvent strippers have been widely used to remove industrial coatings for many years. Normally
used at room temperature, strippers can remove a wide range of organic coatings without attacking underlying
metal substrates. Maintaining the integrity of metallic and nonmetallic substrates is a crucial requirement for
the aerospace industry. The minimum acceptable control technology standard will target methylene chloride
which is the main ingredient of the chemical paint strippers used presently. To meet the new regulations, an
agreement to study alternative depainting techniques was signed by EPA and the National Aeronautics and
Space Administration (NASA) in 1993. Other partners include the Air Force, commercial airlines, and
aircraft manufacturers, A technical advisory committee was formed to recommend the testing protocol for the
technologies to be evaluated. Seven non-hazardous air pollutant alternative stripping techniques have been
identified and will be evaluated at NASA on either real aircraft panels or on accelerated aged panels. The
alternative techniques are biodegradable or water-based chemical strippers, a carbon dioxide (C02) pulsed
laser, the Flashjet system, high-pressure water stripping, plastic media blasting, sodium bicarbonate wet
stripping, and wheat starch blasting. Elimination of methylene chloride can result in better technical
performance, cost savings in materials and hazardous waste treatment, reduction of overall emissions, and
fewer reporting requirements.
Evaluate Alternative Paint Stripping Technologies Used in Aircraft and Space Vehicles
Charged by Congress to protect the Nation's land, air, and water resources, the Environmental
Protection Agency (EPA) strives to formulate and implement actions leading to a compatible balance between
human activities and continuing viability of natural systems. To minimize continuing threats to public health
and the environment from the use of paint removal products containing hazardous air pollutants, an
interagency agreement to study alternative depainting technologies was signed between EPA and the National
Aeronautics and Space Administration (NASA), Marshal! Space Flight Center (MSFC). A similar agreement
was also reached with the U.S. Air Force (USAF). Each agreement focuses on the evaluation and testing of
depainting systems which do not use methylene chloride or any of its sister polluting agents.
Solvent strippers have been w idely used to remove industrial coatings for many years. Normally
used at room temperature, solvents can remove a wide range of organic coatings without attacking underlying
metal substrates. Maintaining the integrity of metallic and nonmetallic substrates is a crucial requirement for
industries which maintain coated metal structures (e. g., aircraft, defense materiel, shipbuilding, automotive,
and home appliance).
8-27
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Paint removal techniques fall within the following categories:
ABRASIVE
IMPACT
CRYOGENIC
THERMAL
Using brute force to weaken and remove the coating solely through sanding
or scouring action
Relying on particle impact to crack the coating for removal
Using extreme cold to make the coating more friable and induce differential
contraction, resulting in debonding
Using heat to oxidize, pyrolyze, and/or vaporize the coating through attack
of its weaker constituents
MOLECULAR BONDING/
DISASSOCIA TION
Using non-hazardous chemicals to weaken or break molecular bonds in
protective coatings
The selection of techniques for study and evaluation is driven by such factors as the characteristics of
the structures to be cleaned (e. g., size, substrate hardness, heat tolerance), paint/coating compositions,
desired substrate texture after coating removal (e.g., rough, smooth), cleaning rates (i.e., throughput needed
for production volume), facility space, compatibility with other existing systems, tolerance for any waste
products produced, initial capital outlay, and operating costs. The processes which were the main focus of
initial literature searches were primarily focused on aircraft/spacecraft needs, where relatively soft, thin
aluminum substrates make up the bulk of the finished surfaces to be cleaned. All parties concurred that it
was not the intent of either interim or final reports to recommend one product or process over another, but
rather to evaluate each depainting system to whatever depth was practicable and present a factual account of
the strengths and limitations of each. End users must make their own decisions concerning implementation.
Alternatives
Replacement of hazardous materials (rather than monitoring and controlling their release) is an
avoidance activity. The team is investigating replacements for depainting methods which use methylene
chloride. Several alternatives have been identified, which strip paint in various ways:
CO2 pulsed laser systems remove organic coatings via pyrolysis or vaporization.
The advantages of the laser stripper are:
Reduces solid waste to a fine ash
Effective on composites
Precision control
Reliable and repeatable stripping
Minimal temperature increase
The disadvantages are:
Large initial capital investment
High technical skills required
Air emissions must be treated
FLASHJET™ systems are similar, but they use thermal energy produced by xenon flash lamps to
8-28
-------
soften the coating and a low pressure CO, particle stream to sweep away the softened coating.
The advantages are: The disadvantages are:
High degree of control Applicable only to large aircraft
Small volume of waste Requires offgas and particulate collection
Potential for products of incomplete combustion
High-pressure water stripping completely eliminates the need for hazardous materials by using the
impact energy of a water spray at 10,000 psi (68,948 kPa) or higher.
The advantages are: The disadvantages are:
High stripping rate Ultrahigh pressures require automation
Water can be recycled Improper operation can damage substrate
Compatible with most treatment systems Water can damage joints and seals
Automated fairly easily
• Plastic media blasting chips away paint by optimizing blast particle hardness, geometry, and impact
energy, eliminating paint flakes in a wastewater stream.
The advantages are: The disadvantages are:
Produces no volatile organic compounds Disposal of spent media
Has a high stripping rate Contaminants may damage substrate
Eliminates water usage Media may close cracks
Can selectively remove individual layers Media are flammable
Recyclable Produces airborne particulate
No size limitations
Fully developed systems available
• Sodium bicarbonate wet stripping sprays baking soda (an environmentally benign substance)
suspended in water at medium to low pressures.
The advantages are: The disadvantages are:
Process can selectively remove layers Nonrecyclable
Inexpensive stripping media Wet sludge may be hazardous waste
Liquid waste easily treated Potential substrate damage
Water dissipates heat on substrate
• Wheat starch blasting uses a controlled hardness of wheat starch applied via low-pressure air, which
eliminates the handling of wastewater.
The advantages are: The disadvantages are:
Media are nontoxic and biodegradable Low stripping rates
Inexpensive media Media can collect in cracks
Eliminates water usage Media are moisture sensitive
Can remove layers selectively Contaminated media could be harmful
Safe for clad aluminum and composites Particles in media could damage substrate
Reusable media
Media become more effective after use
No volatile organic compounds generated
Chemical stripping products are available which are water-based and/or biodegradable, which means
that they can be recycled and disposed of with minimal waste handling. Evaluations were conducted
8-29
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on 31 products, focusing on spray-on, rinse-off chemicals at various dwell times.
Test Products for Chemical Stripping
Product
Vendor
3M Safest Stripper
3M Corporation
Heavy Duty Paint Stripper #539
AMAX Industrial Products Group
ARCQSOLV PM ACETATE and DPM ACETATE
ARCO Chemical Company
NMP and NMP-T
BASF Corporation, Chemical Division
Wright Way Stripper
BEX Processing Systems
Safety Strip 4000
Brulin Corporation
Back to Nature AP40, AP41, VI, \U. and VIH
Dynacraft Industries
Dynasolve 711 and 750
Dynaloy, Inc.
Prep Rite
Ecolink, Inc.
EZE 540 and 542
EZE Products
F.0.2115A
Fine Organics Corporation
Ship Shape
International Specialty Products
Cee-Bee Stripper EI004B, El 092A, and E2000
McGean-Rohco, Inc.
Ultra Safe Stripper
National Solvent Corporation
Orehem LPI779BC
Orcherrt, Inc.
Parks Pro Stripper D
Parks Corporation
EG 566
PYROCK Chemical
Strypeeze Green Label Remover
Savogran Company
Turco 6776 and 6813
Turco Products
PSL-230
U.S. Polychem Corporation
The advantages arc:
Strippers are nontoxic
¦ Safe for clad aluminum and composites
No volatile organic compounds generated
Ambient temperature process
Low initial capital investment
The disadvantages are:
Slow stripping rates
Waste could be hazardous
Nonrecyclable
Labor intensive
Elimination of depainting materials and processes based on methylene chloride can result in better
technical performance, cost savings in materials and hazardous waste treatment, reduction of overall
emissions, and fewer reporting requirements.
8-30
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SESSION 8B
ARCHITECTURAL AND INDUSTRIAL MAINTENANCE
COATINGS
8-31
-------
PAPERS PRESENTED;
"Evaluation of Innovative Low-Volatile Organic Compound Industrial Maintenance Coatings"
by
Dean Cornstubble
Research Triangle Institute
Research Triangle Park, North Carolina
"Solventless and Low-VOC Architectural Coatings Formulated from Novel Latexes
with Low MFT and High Tg"
by
Thomas Schuman
University of Southern Mississippi
Hattiesburg, Mississippi
"Evaluation of Emissions from Latex Paint"
by
Bruce Tichenor
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Research Triangle Park, North Carolina
"New Polyurethane Prepolymers for Ultra-low VOC
Plural Component Coatings"
by
Thomas Santosusso
Air Products & Chemicals, Inc.
Allentown, Pennsylvania
8-32
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
Evaluation of Innovative Low-Volatile Organic Compound Industrial Maintenance
Coatings
Dean R. Cornstubble. Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North
Carolina 27709; and Michael Kosusko, U.S. Environmental Protection Agency, Air and Energy
Engineering Research Laboratory, Research Triangle Park, North Carolina 27711.
INTRODUCTION
End users of industrial maintenance coatings in today's marketplace are becoming more critical of the
coatings they select. Coatings must meet not only their performance expectations but also implemented State
and, most recently, proposed Federal regulations for volatile organic compounds (VOCs). Users are concerned
whether innovative coating technologies that are designed to meet VOC regulations will retain the quality and
longevity performance characteristics of current, noncompliant coatings that are well respected in the field.
Thus, end users, particularly small businesses, are looking for information from independent research studies
such as this one that test and evaluate new industrial maintenance coating technologies.
To address these concerns, this research project identified and evaluated emerging low-VOC industrial
maintenance coating technologies as pollution prevention alternatives to high-VOC solvent-borne coatings.
In addition, this project provides end users with an independent evaluation of some new low-VOC coatings.
Industrial maintenance coatings are defined as heavy-duty coatings, including primers, sealers, undercoats, and
intermediate and top coats that are formulated to protect metal substrates from degradation when exposed to
aggressive environments. Metal substrates include bridges, military equipment, ships, septic tanks, and all
exterior steel structures. Aggressive environments to which these protected substrates are exposed include
coastal, industrial, commercial, and institutional sites. Exposure includes frequent scrubbing or abrading,
immersion in water or wastewater, and exposure to steam.
This paper presents the results of an evaluation of five industrial maintenance coating system
alternatives compared to a standard high-VOC coating. Procedures used in this research study included
determining each coating's physical properties, having three operators apply each coating system to a set of
test panels consisting of two different substrates, and conducting four durability tests and a 3-month outdoor
exposure test on the coated test panels. The results of this evaluation are intended to promote the use of low-
VOC coatings in the marketplace, thereby reducing VOC emissions.
BACKGROUND
Research Triangle Institute (RTI), in collaboration with the U.S. Environmental Protection Agency's
(EPA's) Air and Energy Engineering Research Laboratory (AEERL), contacted coating formulators, resin
manufacturers, industrial users, and trade organizations to help identify and target research needs and
opportunities within a specific category of the architectural and industrial maintenance (AIM) coatings
industry. The emphasis in these contacts was to identify low hazardous air pollutant (HAP) and low-VOC
coatings. Representatives from AIM coating manufacturers, resin manufacturers, users, representative
associations, and other associations affected by AIM coating regulations were contacted. The majority of these
contacts were AIM regulatory negotiation committee members. Industrial maintenance coatings were
identified as the highest priority for evaluating new low-VOC coatings.
8-33
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A survey conducted by SRI International in 1990 for the National Paint and Coatings Association
(NPCA) indicated that approximately 90.8 million liters (24 million gallons) of industrial maintenance coatings
were sold in the United States in that year.1 VOC content ranges for these coatings were 351 to 500 g/f (2.9
to 4.2 lb/gal), with an average of 425 g/C (3.5 lb/gal). Based on this average, the estimated national VOC
emissions in the year 1990 were 38,590 Mg (42,538 tons). For every 50-g/i (0.4-Ib/gal) reduction in VOC
content, the estimated national VOC emissions from manufacturers converting to low-VOC coating
formulations would be reduced by 4,540 Mg (5,004 tons). Thus, this project was initiated to evaluate the
technical feasibility of innovative low-VOC industrial maintenance coatings.
EXPERIMENTAL METHODS
Evaluation testing was designed on the basis of six discrete areas: coating systems, substrates, physical
property testing, VOC emissions determination, and performance and outdoor exposure testing. Each section
is discussed below.
Coating Systems
Coating systems evaluated are described genetically in Table 1.
Table 1. Coating Systems Tested
Coating system
System coatings
Generic description
1
primer
solvent-borne, moisture-cured polyurethane
intermediate
solvent-bome, zinc-rich, moisture-cured polyurethane
topcoat
solvent-borne polyurethane
2
primer
waterborne epoxy ester
topcoat
waterborne latex
3
primer
solvent-bome alkyd resin
topcoat
waterborne acrylic
4
topcoat
solvent-bome, two-component polysiloxane epoxy
5
primer
water-reducible alkyd
topcoat
waterborne acrylic
6 (standard)
primer
solvent-borne alkyd resin
topcoat
solvent-borne alkyd enamel
8-34
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Selection of these coatings was based on communications with coating suppliers who had new low-
VOC products that were either just entering the market or had been on the market less than one year. The
standard was randomly selected based on its high VOC content with respect to the EPA-proposed regulation
and its applicability to most industrial maintenance settings.
Substrates
The use of test panels is common practice for evaluating paints and related coatings (see American
Society for Testing and Materials [ASTMJ Standard D 609 and ASTM Standard D 2201).2 The most widely
used substrates in industrial maintenance applications are ASTM A36 and ASTM A588 steels. ASTM A36
steel is an all-purpose carbon-grade steel used in building and bridge construction. ASTM A588 steel is a
corrosion-resistant, high-strength, low-alloy steel that is suitable for use in the bare or uncoated condition
where exposure to a normal atmosphere causes a tightly adherent oxide to form on the surface of the substrate
protecting it from further oxidation. The A588 steel, when used as a coated substrate, is claimed to provide
a longer coating life than other structural steels, such as A36.
A total of 216 test panels were ordered from the Jay Allen Steel Company in Pittsburgh, Pennsylvania:
108 of the A36 panels and 108 of the A588 panels. The dimensions of each test panel were 152.4 mm x 304.8
mm x 6.35 mm (thickness) (6 in x 12 in x 1/4 in). In the design of the experiment, six panels were assigned
per substrate per coating system, with four of the panels sent to KTA-Tator in Pittsburgh, Pennsylvania, for
durability testing and two sent to the LaQue Center in Kure Beach, North Carolina, for outdoor exposure
testing.
Surface Preparation of Substrates
Surface contaminants that could reduce adhesion, such as grease, oil, dirt, or mill scale, were removed
prior to painting. Upon arrival at the painting contractor's facility, each test panel was inspected by an
operator. Inspection revealed little or no mill scale on each panel surface but did reveal the presence of grease
and dirt. Mechanical cleaning was not necessary. For cleaning, operators cleaned each panel with rags soaked
with lacquer thinner to remove surface contaminants.
Six panels of each substrate were then attached to a 1.2 m x 0.9 m x 0.013 m (4 ft x 3 ft x lk in)
wooden board by Velcro hook and loop strips. Each test panel was labeled with an identification number for
data quality control. This configuration provided a total panel surface area of 0.54 m\ 0.9 m x 0.6 m (6 ft2,
3 ft x 2 ft) for each operator to apply each coating, giving an adequate amount of coating coverage for
calculating each coating system's VOC emissions as applied.
Physical Properties of Each Coating
Before application, an operator thoroughly mixed each container of coating, then poured 7.6 to 11.4
{(2 to 3 gal) of the coating into a standard 18.9 f (5 gal) container. Three grab samples were taken from the
center of the container. Each 500-mf (17-fl.oz) sample was delivered to RTI's analytical laboratory and
analyzed, in triplicate, to determine the percent VOC content by volume percent water content (if the coating
was waterborne), density, percent volume solids, and percent weight solids of each coating. The analysis
method used was EPA Reference Method 24.3 Volume solids and weight solids of each coating were derived
from ASTM Standard D 2369.2
8-35
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VOC Emissions Determination
VOC emissions, as applied, per operator per coating were determined from weight loss data of the
standard 5-gal paint container and each coating's percent solids, by weight. Weight loss was determined by
weighing the standard 5-gal container before and after each coating application using a Sartorius F32000S
floor scale, with a capacity of 32 kg (71 lb) and a readability of 0.1 g (0.0002 lb).
Prior to coating application, each test panel, with Velcro strips and label attached, was weighed. The
technique used to determine the weight of each test panel was to place a standard clean and empty 5-gal
container on the center of the pan of the floor scale used to determine coating usage during application. The
weight of the container was tared out. A test panel was then placed on top of the container in a centered
position. Each test panel from each set of 12 panels (each set equals 12 test panels on each support board for
each operator) was placed on top of the container in the same position. After weighing, the container was
removed, the scale re-zeroed, and the container placed back on top of the scale for the next set of readings.
After the coating application phase of the test was complete, test panels were removed from their
wooden supports and laid horizontally side by side on plywood panels away from the test area. They were
allowed to air-cure in this position for a minimum of 7 days. After air curing, each test panel was reweighed
to determine the amount of coating solids remaining on each panel. The same floor scale was used to
determine these weights.
Performance Testing
Four test panels from each coating, substrate, and operator combination were shipped to KTA-Tator
in Pittsburgh, Pennsylvania, for durability testing. Each test panel was subjected to four performance tests:
impact resistance (ASTM D 2794); adhesion (ASTM D 3359); methyl ethyl ketone (MEK) rub (ASTM D
4752); and pencil hardness (ASTM D 3363).2 A test matrix representing the number and type of panels per
coating system tested was designed: three panels per test per substrate (for three operators each) per coating
system for each test panel, resulting in a total number of 72 panels tested for five coating systems and the
standard.
Outdoor Exposure Testing
The LaQue Center in Wrightsville Beach, North Carolina, conducted a 3-month exposure test of the
remaining 72 panels. This test site is one of four outdoor exposure testing facilities in the United States. The
test site is classified as a severe marine atmospheric environment.
LaQue Center personnel arranged each test panel on exposure racks in a testing area, 25 m (82 ft) from
the Atlantic Ocean, at their Kure Beach, North Carolina, facility. In addition, they performed and documented,
as necessary, the following tests: dry film thickness (DFT) of the coating on each pane; gloss measurements
of each panel prior to exposure on the racks per ASTM Standard D 523; scribed each panel per ASTM
Standard D 1654; exposed each panel at 30° to the horizontal facing the Atlantic Ocean for 3 months; and
photographed all coated panels together.
After exposure, each panel was inspected for: gloss, before and after washing, per ASTM Standard
D 523; chalking per ASTM Standard D 4214 (Test Method C); blisters per ASTM Standard D 714; creepage
at the scribe per ASTM Standard D 1654; and rust per ASTM Standard D 610. A photograph was taken of
each panel while on the exposure racks; a group photo of each set of six panels (per substrate per coating
system) and one photograph of the most severely affected panel in the set were taken.
8-36
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RESULTS
The results from this evaluation include analyses of each coating's physical properties, calculations
of VOC emissions as applied, and results from performance and outdoor exposure testing. Performance and
outdoor exposure results were used to provide end users with a qualitative assessment of each coating's
applicability to field service. The following sections describe each evaluation and its results.
Coating Analysis
The underlying purpose for analyzing each coating was to determine VOC content, density, solids
weight percent, and water content in weight percent. VOC content values were used to provide a comparison
against the proposed EPA VOC content limits for the years 1996 and 2000 and for the year 2004. Density and
solids weight percent were used to calculate VOC emissions. Water content in weight percent was analyzed
to show the amount of water in each waterbome coating. Table 2 summarizes the analytical results.
Table 2. Results of Coating Analyses *
Coating
system
Sample
VOC
contentbAd
(g/P)
Density
(g/cm3)*
Solids
content
(wt. %)
Water
content
(wt. %)
1
primer
360
2.4
85
_ r
intermediate
360
1.6
78
-
topcoat
372
1.3
71
-
2
primer
283
1.2
44
46
topcoat
284
1.2
49
38
3
primer
394
1.4
72
-
topcoat
190
1.1
45
47
4
topcoat
84(mixed)g
1.3 8
NAh
NA
5
primer
237
1.2
37
56
topcoat
284
1.2
40
49
6 (standard)
primer
394
1.4
72
-
topcoat
424
1.0
57
-
" Values shown are the mean of six samples per coating.
b VOC content as applied, minus water, of each sample
analyzed.
c 1 g/( = 0.008345 lb/gal.
4 No bias was determined for VOC content measurements
although they tended to run 3 to 7 percent higher than
values provided by the manufacturers.
e 1 g/cm' = 62.43 lb/ft5.
1 No water detected,
8 Manufacturer's numbers were used.
* NA = Not available since EPA Method 24 could not
be used.
8-37
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VOC Content
Figure 1 compares analyzed VOC content versus the EPA-proposed VOC content limits for the years
1996 and 2000 and for the year 2004. Of the six coating systems evaluated, systems 2, 3, 4, and 5 met the
EPA-proposed VOC content limits. Coating system 4, which was the two-component polysiloxane, could not
be analyzed by the testing laboratory using EPA Method 24. The manufacturer's value for VOC content was
used.
450
^ 400 ••
§ 350
300
| 250
o 2oo
y 150
© 100
50
"5=
o-
:Q:
III!
IP
|jj
—
irx
—o
—o
Coating
Ell!! Analyzed
—0~~ Proposed 2004 limit
—O— Proposed 1996 & 2000 limit
[NOTE: 1 g/d = 0.008345 lb/gal]
Figure 1. Average VOC Content for Each Coating System
VOC Emissions
Figure 2 shows that the average VOC emissions of coating systems 3,4, and 5 were lower than those
of system 6 (the standard). Over time, the lowest-VOC content coating system would prove to be a better
system than the standard with respect to VOC emissions if the durability (i.e., service life) and cost of that
system were equivalent.
Performance Testing
Table 3 ranks each coating system by performance test. The purpose of this ranking is to provide a
representative idea of how each coating system performed overall and how each system compared to the
standard with respect to performance testing. Each test was assigned a point value on a scale of 1 to 5, each
unit depending on the scale for each test. This rating system was selected because each of the test results could
be conveniently divided into five sections. Refer to each test separately described below for definitions related
to each test's rating definition.
All coating systems outperformed the standard. Coating system 4 outperformed all other coatings and
was shown to be the best performing in durability. The following sections describe the results of each
performance test as they related to the ASTM standard test methods employed.
8-38
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7001-
¦ Operator A ~ Operator B ~ Operator C
Coating System (by Operator)
* Weight data for coating system 2 not available. [NOTE: 1 g/mz = 0.295 lb/in2]
Figure 2. VOC Emissions as Applied per Unit Area
Table 3. Ranking of Each Coating System
(Performance Testing)
Sub-
Coating
Impact
Adhesion
MEK resistance
Hardness
strate
system
resistance Method A Method B
To winter To metal
Scratch Gouge
Total
Rank
1
3
5
5 5
5 3
26
2
2
5
4
1 5
3 3
21
3
3
3
3
2 5
2 2
17
6
4
5
5
5 5
5 4
29
1
5
5
5
1 2
5 2
20
4
6
2
1
5 5
3 2
18
5
(standard)
A588
1
4
5
5 5
4 3
26
2
2
5
5
1 5
3 3
22
3
3
4
3
2 5
5 2
21
4
4
5
5
5 5
5 3
28
1
5
5
5
1 2
5 2
20
6
6
3
2
5 5
4 2
21
4
(standard)
(continued)
8-39
-------
Table 3. Ranking of Each Coating System (continued)
Rating Definitions (mean of three operators):
MEK resistance
Rating Impact resistance Adhesion (Double rubs to Hardness
surface)
- — — —
2 31-60 2 11-20 4-7
3 61-90 3 21-30 8-11
4 91-120 4 31-40 12-13
5 121 + 5 41 + 14
Impact Resistance: ASTM Standard D 2794. According to ASTM, the impact resistance test method
has been found to be useful over many years in predicting the performance of organic coatings for their ability
to resist cracking caused by impacts. This test measures the indentation that results when a painted panel is
struck with a hard object such as a steel ball. Results of impact testing are illustrated in Figure 3 for A36 and
A588 substrates. Clearly, coating systems 2,4, and 5 performed best, having an end failure point of 8.96 m-kg
(160 in-lb). The standard, along with systems 1 and 3, showed poor performance in comparison to systems
2,4, and 5. Their end failure point was 5.60 m-kg (100 in-lb) or less. All coating systems proved to be equal
to or better than the standard's 3.36 m-kg (60 in-lb). Results are also summarized in Table 3.
Adhesion: ASTM Standard D 3359. Because the substrate and degree of surface preparation have a
drastic effect on coating adhesion, this method of evaluating a coating's adhesion to different substrates or
surface treatments, or of different coatings to the same substrate and treatment, is of considerable usefulness
I Operator A ~ Operator B ~ Operator C
e
1
i
PM
*5
b
Coating System
[NOTE: 1 in-lb = 0.056 m-kg]
Figure 3. Impact Resistance (Average of Substrates A36 and A588)
8-40
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to die coatings industry. In this test, a strip of tape is used to measure the amount of coating removal from a
scribed 'X' on the painted surface. As shown in Table 3, coating systems 1,2,4, and 5 performed the best,
with adhesion ratings of 4 and 5. System 3 and the standard showed poor performance with adhesion ratings
of 3 and 2, For systems 1 and 4, both adhesion methods (A and B) were used because of differences in DFTs
on each of their panels. For system 1, the DFT on each test panel was an average of 0.030 cm (11 mils [0.011
in]), whereas for coating system 4, some panels measured more than 0.013 cm (5 mils [0.005 in]) DFT. This
variation was due primarily to operator skill level and, in the case of coating system 4, mishandling of several
panels during application, which resulted in reapplied coating. For all coating systems, adhesion performance
on A588 substrates was consistently better than on A36 substrates. This showed that adhesion between the
coating system and the substrate was markedly improved by the thin oxide layer on the A588 panels.
MEK Rub: ASTM Standard D 4752. The MEK rub test method is used primarily for assessing the
MEK resistance of ethyl silicate (inorganic) zinc-rich primers. However, this test method was chosen as a good
indication of how each coating system would stand up to a strong and commonly used chemical solvent such
as MEK. In this test, an MEK-saturated cloth was continually rubbed over each coated panel until either the
metal substrate was exposed or 50 double rubs was reached, A double rub is defined as a back-and-forth
motion of approximately 2 in (50 mm) in length over a specified test area on the panel. For this test, double
rubbing was evaluated on both the topcoat and the primer (by scraping away topcoat). Table 3 shows that
MEK performance was consistently superior for coating systems 1,4, and the standard. The results for coating
systems 2 and 3 showed poor performance of their topcoats on both substrates, whereas their primers showed
excellent performance on both substrates. Coating system 5 showed poor performance in all cases. Coating
systems 1 and 4 had equivalent results. Both coating systems showed high tolerance for the MEK rub test.
Pencil Hardness: ASTM Standard D 3363. Film hardness of a coating can be rapidly and
inexpensively determined by drawing pencil leads of known hardness across a test area. The procedure called
for a technician to draw pencils of decreasing hardness across a specified test area until a pencil was found that
would neither cut through nor scratch the surface of the film. Any defacement of the film other than a cut
(gouge) was considered a scratch.
Interpretation of the data from this test is best illustrated in Table 4. The resulting pencil hardness of
each coating system by substrate and by each endpoint test (either scratch or gouge) was assigned a number
for clarity of data presentation. For example, a pencil hardness of 6B was equated to a 1, a pencil hardness
of 5B was equated to a 2, and so on up to 6H which was equated to a 14. Based on these numerical
assignments, a generic rating of excellent, very good, good, fair, and poor was given to each test for each
substrate and coating system.
Tables 3 and 4 show that coating systems 1,4, and 5 had the greatest hardness resistance of 12 to 14
(4H to 6H) on both substrates in the scratch test, but proved to be fair to good, 4 to 11 (3B to 3H), in the gouge
tests. Coating system 2 showed a hardness range of 8 to 11 (H to 2H) on both substrates. System 3 proved
to perform best only on the A588 substrate in the scratch test The standard, coating system 6, showed
moderate performance in both tests on both substrates. Coating system 4, however, outperformed all other
coating systems in the pencil hardness tests with an 8 to 14 rating (F to 6H pencil hardness).
Outdoor Exposure Testing
Outdoor exposure testing of each coating system was evaluated at the LaQue Center's marine
atmospheric testing area located 25 m from the Atlantic Ocean. The exposure date was August 18,1994,
8-41
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Table 4. Pencil Hardness Rating for Each Coating System
Coating system
Test result
1
2
3
4
5
6
A36-Scratch
E
G
F
E
E
G
A588-Scratch
VG
G
E
E
E
VG
A36-Gouge
G
G
F
VG
F
F
A588-Gouge
G
G
F
G
F
F
E = Excellent (14); VG = Very Good (12-13); G = Good (8-11); F = Fair (4-7); P = Poor (1-3). Values in
parentheses are mean values of operators A, B, and C.
and the inspection date was December 1, 1994, for a total exposure period of 15 weeks. Orientation of the
exposed panels was 30° facing the ocean (east). Table 5 ranks each coating system by exposure test. Each
test was assigned a point value on a scale of 0 to 10.
Table 5. Ranking of Each Coating System a
(Outdoor Exposure Testing)
Sub-
Coating
strate
system
Gloss
Creepage
Rust
Blisters
Chalk
Total
Rank
A36
1
8
10
10
10
10
48
I
2
0
7
10
10
10
37
6
3
5
7
10
10
10
42
3
4
10
4
10
10
10
44
2
5
8
6
8
10
10
42
3
6 (standard)
6
7
10
10
8
41
5
A588
1
8
10
10
10 .
10
48
1
2
0
7
10
10
10
37
6
3
5
8
10
10
10
43
3
4
10
4
10
10
10
44
2
5
8
7
7
10
10
42
4
6 (standard)
6
8
10
10
8
42
4
' Mean of three operators.
Only coating systems 1,3, and 4 outperformed the standard. Coating system 1 outperformed all other
coatings and was shown to be the best performing in weathering durability. The following sections describe
each test performed on each panel at the conclusion of exposure testing.
Creepage: ASTM Standard D 1654. A 5-cm (2-in) scribe was made on the lower half of each test
panel according to the procedures in ASTM Standard D 1654 prior to exposure. The representative mean,
maximum, and minimum of creepage, corrosion, or loss of paint extending from the scribe mark, was recorded.
8-42
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As illustrated in Table 5, coating systems 2, 3, 5, and 6 showed creepage between 0.5 and 3.0 mm
(1/64 to 1/8 in) over the 3-month exposure period. Coating system 4 performed the worst with creepage
between 3.0 and 7.0 mm (1/8 to 1/4 in). Interestingly, coating system 1 outperformed all other systems with
zero creepage from the scribe. This could be due to the larger film thickness of a three-coating system versus
the smaller film thicknesses of the other coating systems. In comparison to the standard, only coating system
1 showed superiority in paint retention at the scribe over the other coating systems.
Rust: ASTM Standard D 610. The degree of rusting on each test panel was determined by the percent
of the area rusted. These percentages were converted into a rust grade scale ranging from 0 to 10 as shown
in Table 5. Only coating system 5 showed significant rusting. All other systems, including the standard,
showed very little rusting.
Blistering: ASTM Standard D 714. The degree of blistering of each test panel, according to ASTM
Standard D 714, was evaluated by comparing each exposed surface to a photographic reference standard.
Reference standards were selected by ASTM in four steps corresponding to size on a numerical scale from 10
to 0, in which No. 10 represents no blistering. Blistering standard No. 8 represents the smallest size blister
easily seen by the unaided eye. However, as illustrated in Table 5, no blistering occurred (10) on any of the
six coating systems evaluated for either substrate.
Chalking: ASTM Standard P 4214 (Test Method C). By definition, chalking is the formation on a
pigmented coating of a friable powder evolved from the paint film itself at, or just beneath, the surface.
Method C was used for evaluating the degree of chalking on each test panel. Table 5 shows the results of
chalking on substrates A36 and A588 by coating system and by operator. A 10 indicates no film formation
on the surface of the test panel. An 8 indicates a slight film formation. As shown, coating systems 1 through
5 outperformed system 6 with a 10 rating as compared to an 8 rating. No distinction can be made between
each of coating systems 1 through 5.
Gloss: ASTM Standard D 523. Gloss measurements were taken with a Minolta Multi, Gloss 268, at
a 60° orientation. Gloss measurements of each test panel were taken at three separate intervals: after the initial
setup, before washing with water and a mild detergent solution, and after washing.
Table 6 reveals the same pattern for either substrate where the initial gloss for coating systems 1, 4,
and 6 were consistently higher than for systems 2, 3, and 5. With respect to gloss retention from initial setup
to post-washing of the panels, coating systems 4 and 5 were the best, having relatively the same gloss for both
substrates. However, coating system 2 was the only coating system to have an increase in gloss from initial
setup to post-washing for both substrates. This was possibly due to additional curing and/or loss of VOCs or
to the sloughing off during exposure of pigmentation within the paint system, which is typically added to
achieve gloss specifications. Gloss for coating systems 3 and 6 decreased the most out of all systems. In
comparison to the standard, coating systems 1 and 4 had the highest degree of gloss and the most gloss
retention after exposure.
8-43
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Table 6. Gloss Reduction
Coating system
Initial gloss
Final gloss
Percent reduction
A36
1
86
71
17
2
40
56
-40
3
25
12
52
4
85
82
4
5
54
46
15
6 (standard)
75
42
44
A588
1
85
70
18
2
33
45
-36
3
23
11
52
4
74
70
5
5
29
24
17
6 (standard)
66
38
42
SUMMARY
Table 7 summarizes ranking results of each coating system evaluated for VOC emissions and
durability and outdoor exposure testing. For both substrates A36 and A588, coating system 4 performed the
best while outperforming the standard. Coating system 1 performed well but had high VOC emissions.
Table 7, Summary of Overall Coating System Performance
Ranking
Sub-
Coating
Sum of
Overall
strate
system
Emissions
Durability
Outdoor exposure
ranks*
rank
A36
1
5
2
1
8
2
2
NA"
3
6
?
9
3
3
6
3
12
4
4
1
1
2
4
1
5
2
4
3
9
3
6 (standard)
4
5
5
14
5
A588
1
5
2
1
8
2
2
NA
3
6
?
?
3
3
4
3
10
3
4
1
1
2
4
1
5
2
6
4
12
4
6 (standard)
4
4
4
12
4
a Emissions, durability, and outdoor exposure ranks were summed to give overall ranking.
b Not available
8-44
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CONCLUSIONS
The objective of the evaluation was to compare VOC emissions, as applied, of alternative low-VOC
industrial maintenance coating systems to a standard. The results of performance testing in conjunction with
the 3-month outdoor exposure test were inconclusive as to a coating system's service life. However, some
conclusions can be made from this evaluation as to the degree of VOC emissions reduction of the coating
systems tested versus the standard.
• The tables and figures presented in this paper show that VOC emissions were dependent on several
factors, including the VOC content of each coating layer of each coating system, the number of
coating layers per system, and the amount of coating applied (as recommended by the manufacturer).
However, these tests have shown that the solvent-borne, two-component polysiloxane epoxy and the
multi-layer, solvent-borne polyurethane coating systems were better than the standard, a solvent-borne
alkyd.
• The solvent-borne, two-component polysiloxane epoxy coating system achieved excellent ratings in
most categories of testing and was the lowest VOC content coating (by a factor of 4 versus the
standard).
• Although the multi-layer, solvent-borne polyurethane coating system had higher VOC emissions than
the standard, it is apparent from the emissions data that number of coatings and film thickness played
a major role in producing such high emissions. Thus, a low VOC content for a coating does not
necessarily mean lower emissions for the system as applied. It did, however, perform as well as or
better than the standard in almost all cases.
• Thus, as a result of the severity of this evaluation test, not only would implementation of all of these
alternative coating systems, over time, reduce emissions but these systems would also excel in the field
under light or moderate conditions as compared to the standard coating system.
REFERENCES
1. Reisch, Marc S., "Paints and Coatings," Chemical & Engineering News, pages 34-61, October 18,
1993.
2 . American Society for Testing and Materials. 1994, Annual Book of American Society for Testing
and Materials. Volumes 6.01,6.02,6.03, and 6.04, Philadelphia, Pennsylvania.
3 . Emission Measurement Technical Information Center. May 1993. NSPS Test Method, Method
24 - Determination of Volatile Matter Content, Water Content, Density, Volume Solids, and
Weight Solids of Surface Coatings. Research Triangle Park, North Carolina.
8-45
-------
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
SOLVENTLESS AND LOW-VOC ARCHITECTURAL COATINGS FORMULATED
FROM NOVEL LATEXES WITH LOW MFT AND HIGH TG
Speaker: Thomas Schuman
Shelby F. Thames
Department of Polymer Science
University of Southern Mississippi
Box 10037, Hattiesburg, MS 39406-0037
Zhiyu Wang
Department of Polymer Science
University of Southern Mississippi
Box 10076, Hattiesburg, MS 39406-0076
INTRODUCTION
In order to meet requirements of the Clean Air Act
Amendments of 19 9 0 and subsequent government legislation,
coatings manufacturers must develop technologies allowing the
formulation of low volatile organic compounds (VOCs)/low odor
products that possess desirable end-use properties. The demands
for change are both a challenge, and an opportunity for coating
industries1"7.
A common ideology of the coatings industry is that
performance of solventless architectural coatings must be poor
since they lack conventional coalescing agents. Indeed, it is
well established that useful protective coatings must possess
below ambient minimum film formation temperatures (MFT or MFFT)
for flow, leveling, and substrate adhesion, and reach a glass
transition temperature (Tg) well above ambient for a useful
lifetime. While the synthesis of low MFT polymers alone is a
relatively simple matter, the combination of low MFT and high Tg
has been elusive for some time. The common problem associated
with low MFT latexes is low film Tg and therefore poor
performance properties. To overcome this dilemma, most
contemporary water-based coatings are formulated from latexes
with high MFT, and consequently require co-solvents and
coalescing agents to facilitate film formation such that
significant VOCs are present.
The focus of this work has concentrated on the design,
synthesis, characterization, and formulation of novel low
temperature MFT latexes that cured to above ambient Tg polymers.
Consequently, emulsion polymers with Tg-MFT differentials
approaching 20 ± 3°C have been synthesized and coating film
properties formulated from the novel latexes are compared with
those derived from a well-known commercial latex requiring
coalescing agents.
EXPERIMENTAL DETAILS
Chemicals
Butyl carbitol (99+%) and propylene glycol (99%) were
purchased from Aldrich, sodium bicarbonate (A.C.S. grade) from
Fisher Scientific, potassium tripolyphosphate (KTPP, 94%) from
8-46
-------
Pfaltz & Bauer, and Tronox CR-800 {rutile titanium dioxide
pigment) from Kerr-McGee. Ti-Pure R900 {rutile titanium dioxide
pigment) was obtained from DuPont., Huber 70C {Kaolin clay) from
JM Huber, Beavewhite 325 (TALC) and Duramite {calcium carbonate)
from ECC, Natrosol Plus (grade 330, an associative cellulosic
thickener) from Aqualon, Kathon LX {1.5%, solventless
microbicide), Tamol 731 (25%, polyacrylic acid dispersant),
Hopaque OP-62 LO (36.5%, polymeric pigment), and QR-7Q8 (35%,
rheology modifier) from Rohm & Haas, UCAR Polyphobe 102 and 107
(25%, associative thickeners), and commercial latex (CL, 55%
vinyl acrylic latex), Surfynol 465 (65%, nonionic surfactant, VOC
content < 0.01%) from Air Products, and Byk 034 (defoamer, VOC
content <2%) and Byk 035 (defoamer, VOC content <3%) from Byk.
All ingredients were used as received.
Emulsion Polymerization
Starve-fed emulsion copolymenzations were used to
synthesize solventless latexes of 40-50% solids content. The
latexes have remained stable at room temperature for 10 months
from this writing.
Emulsion Polymer Characterization
Latex properties have been determined and are listed in
Table 1, together with those of a well-known vinyl acrylic latex.
The solids contents were determined gravimetrically, while
particle sizes were measured by a Coulter N4 MD Sub-micron
Particle Analyzer. A Mettler DSC-30 measuring cell was used to
determine Tg of the latex films (mid-point value). In a typical
measurement, the temperature range for DSC analysis was from
-50°C to 250°C at a heating rate of 10°C/min. Minimum film
forming temperature of latexes was determined by a MFFT Bar 90.
Table 1. General Properties of Latex Paint Formulations
Latex Code USM Latex USM Latex Commercial
A B Latex (CL)a
Solids content {%) 45 42.5 55
pH 4.9 5.1 5.0
Dn (ntnl 180 190 330
Tg (°C) 16.9 21.8 12
MFT (°C) -12 8
^Technical data obtained from manufacturing specifications.
Latex Paint Formulations
A mill base for each latex of Table 1 was prepared according
to the formulations in Table 2. The formulation recipes for
8-47
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vinyl-acrylic paints at 55% PVC derived from the mill base a are
listed in Table 3, while the formulation recipes for 20% PVC
acrylic paints from mill base b are itemized in Table 4. Table 5
contains formulations from mill base c and QR-708 or Natrosol
Plus thickeners formulated to 55% PVC.
Coating Film Characterization
Tensile strength and percent elongation of films were
determined with an 810 Material Test System. The coatings were
cast onto polyethylene sheets which allowed easy film removal.
The test specimen were approximately 13 mm wide, 0.06-0.12 mm
thick with a gauge length of 15 mm. Film dry times were
determined from a 7-mil wet film on standard Leneta charts via a
Gardner Circular Dry Time Recorder. Pencil hardness was measured
according to American Society of Testing and Materials method
(ASTM) standard D-3363, while the conical mandrel flexibility was
determined via ASTM method D-52 2. Crosshatch adhesion tests were
performed according to ASTM standard D-3359 on chromate
pretreated aluminum plates and phosphatized steel plates. Scrub
resistance was conducted on coated panels (PC P121-10N, black
plastic) after one and four weeks dry time, respectively, to
obtain the number of cycles to initial break or to film failure
with a 10-mil brass shim, according to ASTM standard D-2486 .
Specular gloss at 20°, 60°, and 85° was determined with a
Byk-Gardner Micro Triglossmeter, while contrast ratios were
measured with a Chroma-QC quality control system. Film thickness
was determined by
a Gardner Minitest 4000 Coating Thickness
Gauge.
Table 2.
Formulations
for Mill
Bases a
, b and ca
Ingredients
Base a
Base b
base c
Suppliers
Tronox CR-800 (g)
455
1200
0
Kerr-McGee
Ti-Pure R9 0C (g)
0
0
1200
DuPont
Huber 70C (g)
292 . 5
0
0
JM Huber
Beavewhite 325 (g)
260
0
0
ECC
Duramite (g)
325
0
0
ECC
Natrosol Plus (g)
12
5
0
Aqualon
Kathon LX 1,5% (g)
5
4
4
Rohm & Haas
KTPP (g)
6.5
5
5
Pfaltz & Bauer
Byk 034 (g)
12
9
9
Byk
Tamol 731 25% (g)
39
30
30
Rohm & Haas
Surfynol 465
-------
RESULTS AND DISCUSSION
While the synthesis and composition of the solventless vinyl
acrylic latexes cannot be disclosed at this time, it is
instructive to examine the properties of formulated coatings.
The Tg-MFT differential (Table 1) of the commercial latex is 4°C,
while the differential for USM latex A and USM latex B is 18°C»
and 20°C, respectively. Tg values were determined from clear
films that had air-dried for two weeks. These data are
suggestive of ambient temperature crosslinking. For instance,
the films were immersed in THF and have remained intact, clear,
and non-cloudy after 3 months as of this writing.
Table 3. Formulations of Vinyl Acrylic Paints
of 55% PVC from Mill Base a
USM
USM
Commercial
Paint Code®
A-a
B-a
CL-a
Suppliers
Mill Base a (g)
180
180
180
This work
Deionized Water (g)
29.5
22
36
Na2C03 (20%) (g)
6.0
7.0
6.0
Fisher
Byk 035 (g)
0.4
0.4
0.4
Byk
Surfynol 465 (g)
1.0
1.0
1.0
Air Products
USM Latex A (45%) (g)
86. 7
0
0
This Work
USM Latex B (42.5%) (g)
0
91.8
0
This work
Commercial Latex (55%) (g)
0
0
71.0
Ropaque OP-62 LO (36.5%) (g)
20
20
20
Rohm & Haas
Polyphobe 107 (25%) (g)
0.8
1.2
1.3
Union Carbide
Polyphobe 102 (25%) (g)
5.0
6.0
6.4
Union Carbide
Butyl Carbitol (g)
0
0
3.0
Aldrich
Propylene Glycol (g)
0
0
7.0
Aldrich
Total
329.4
329.4
332.1
Paint Properties
PVC (%)
55
55
55
Volume Solids (%)
33.6
33.0
33.5
Weight Solids (%)
49. 9
50.0
49.6
Stormer Viscosity (KU)
99
100
105
ICI (poise)
1.6
2.0
2.0
pH, Initial
9.1
9.4
8.6
VOC (g/L)
<0.4
<0.4
122
aLatex name - mill base code.
8-49
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Table 4. Formulations of Vinyl Acrylic Paints
of 20% PVC from Mill Base b
USM
USM
Commercial
Paint Code3
A-b
B-b
CL-b
Suppliers
Mill Base b (g)
100
100
100
This work
Deionized Water (g)
35.3
25.3
58.0
Na2C03 (20%) (g)
8,4
8 . 0
8.0
Fisher
Byk 035 (g)
0.4
0,4
0.4
Byk
Surfynol 465 (g)
1.6
1.6
1.6
Air Products
USM Latex A (45%) (g)
170
0
0
This work
USM Latex B (42.5%) (g)
0
179
0
This work
Commercial Latex (55%) (g)
0
0
138
Polyphobe 107 (25%) (g)
1.0
1.0
1.3
Union Carbide
Polyphobe 102 (25%) (g)
7.0
7.0
11.0
Union Carbide
Butyl Carbitol (g)
0
0
3.0
Aldrich
Propylene Glycol (g)
0
0
7.0
Aldrich
Total
323.7
322.3
328.3
Paint Properties
PVC (%)
20
20
20
Volume Solids (%)
33,0
33 . 0
32.6
Weight Solids (%)
46 .3
46 .4
45.6
Stormer Viscosity (KU)
83
78
81
ICI (poise)
1.3
1.0
1.3
pH, Initial
8.8
9.3
8.1
VOC (g/L)
<0.3
<0.3
118
aLatex name-mill base code.
8-50
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Table 5. Formulations of Vinyl Acrylic Paints
of 55% PVC from Mill Base c
USM
USM
USM
Paint Code3
A-c-1
A-c-2
B-c
Suppliers
Mill Base c (g)
200
200
200
This work
Natrosol Plusb (3.5%) (g)
30.1
0
0
Aqualon
QR-708C (7%) (g)
0
17. 8
17.6
Rohm & Haas
Na2C03 (20 %) (g)
4.2
3 . 8
3.8
Fisher
Surfynol 465 (g)
0.9
0.9
0 . 9
Air Products
Byk 035 (g)
0.4
0.4
0.4
Byk
USM Latex A (45%) (g)
72.3
72.5
0
This work
USM Latex B (42.5%) (g)
0
0
76.6
This work
Total
307. 9
295.4
299.3
Paint Properties
PVC (%)
55
55
55
Volume Solids (%)
33
34.0
33.3
Weight Solids (%)
56.0
58.3
57.6
Stormer Viscosity (KU)
76
83
80
ICI (poise)
0.8
1.1
1.0
pH, Initial
8.4
8.6
8.8
VOC (g/L)
<0.51
22.5
22.3
aLatex name-mill base code - numerical number if applicable.
bpre-mixed at 500 rpm to obtain 3,5% Natrosol Plus (grade 330)
water solution.
c140 g of QR-708 (35%) was diluted in 560 g of water and
pre-mixed, containing 7.8% of propylene glycol.
USM vinyl acrylic latexes and the commercial latex were
formulated into paints at 55 and 20% PVC according to the
formulations of Table 3 (mill base a) and Table 4 (mill base b),
respectively. A formulation above the critical pigment volume
concentration (CPVC) was chosen, even though some suggest
formulating below CPVC for solventless coatings8. The CPVC was
approximated by determining an oil absorption of 24.3 g/L for
mill base a according to ASTM D-281. Although an approximate
CPVC of 54.8 was calculated, the true CPVC is less since the oil
absorption technique gives values greater than those for latex
paints, a result of lower binder efficiencies of the lattices9,10.
USM vinyl acrylic lattices were formulated at 55% PVC using
Natrosol Plus or QR-708 as thickener rather than UCAR Polyphobes
as noted in Table 5. This approach was undertaken since the
rheology modifier QR-70 8 contains 7.8% propylene glycol and
contributes to VOC. Small amounts of propylene glycol were added
to the formulation to study, and thus better appreciate, the
8-^1
-------
performance of solventless USM latexes in low VOC coatings as
well as solventless coatings.
Paints produced according to Tables 3, 4, and 5 formulations
were made into films for film property determinations. All film
properties of Tables 6-8 were determined after 7 days air dry.
Films used for tensile and elongation tests were of 16-mil wet
film thickness, while the remaining films were of a 7-wet mil
thickness.
Paint film coalescence is crucial to developing film
properties, and the efficacy of film formation was estimated from
tensile property measurements. As shown in Tables 6 and 7, all
films prepared from solventless paints were much stronger than
their counterparts, the films derived from paints of CL.
Table 6. Film Properties "Vinyl Acrylic Paints
Formulated from Mill Base a
USM
USM
Commercial
ASTM
Paint Code
A-a
B — si
CL-a
Method
Tensile Strength (psi)
853
884
596
D-2370
Elongation at Break (%)
8.4
8.6
26.1
D-2370
Wet Thickness (mil)
7
7
7
Volume Solids (%)
33.6
33 .0
33 .5
Dry Time (min)
50
40
55
D-1640
MFT (°C)
0
0.5
1
D-2354
Pencil Hardness
4H
4H
2H
D-3363
Conical Mandrel (1/8")
pass
pass
pass
D-522
Adhesion on Aluminum
5B
5B
4B
D-3359
Adhesion on Steel
5B
5B
4B
D-3359
Scrub
Initial Break
170
160
170
D-2486
Film Failure
240
230
250
D-2486
Sheen, 85°
1.9
1.9
1.7
D-523
Contrast Ratio
94.8
94 . 9
94.1
D-3022
The dry time for solventless paints was consistently shorter
than for conventional paints. Also, films from the solventless
coatings were typically harder after 7 days dry (Tables 6, 7 and
8). All paint films changed little after the 7 days air dry
period as noted by pencil hardness determinations (Table 9).
A determination of MFTs for all paints, solventless and
low-VOC systems were similar and in the 0-2°C range.
8-52
-------
Table 7. Film Properties Vinyl Acrylics Coatings
Formulated from Mill Base b
USM USM Commercial ASTM
Faint Code A-b B-b CL-b Method #
Tensile Strength (psi)
468
821
245
D-2370
Elongation at Break (%)
717
403
1130
D-2370
Wet Thickness (mil)
7
7
7
Volume Solids (%)
33.0
33 . 0
32.6
Dry Time (min)
45
55
60
D-1640
MFT (°C)
2
2
2
D-2354
Pencil Hardness
F
H
HB
D-3363
Conical Mandrel (1/8")
pass
t** a a cs
UabD
pass
D-522
Adhesion on Aluminum
5B
5B
4B
D-3359
Adhesion on Steel
5B
5B
4B
D-3359
Scrub
Initial Break
700
600
400
D-2486
Film Failure
860
720
530
D-2486
85° Gloss
82.8
79.5
85.3
D-523
60° Gloss
70.4
66.6
73.0
D-523
20° Gloss
31.9
22.9
28.8
D-523
Contrast Ratio
97.2
97.2
95.7
D-3022
Wet and dry adhesion values for USM lattices derived
coatings applied to aluminum and steel panels were superior to
coatings formulated with commercial lattices. Conventional latex
paints have long suffered from wet adhesion limitations by virtue
of being stabilized in, and delivered from water11. Thus,
techniques to evaluate the hydrophobieity of paint films are
significant to paint performance, and scrub resistance tests are
therefore a common practice. In the present circumstance, scrub
resistance values (Tables 6, 7, and 8} of the solventless,
coalescent-free, paints are comparable with conventional
formulations.
8-53
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Table 8. Film Properties Vinyl Acrylic Coatings
Formulated from Mill Base c
USM
USM
USM
ASTM
Paint Code
A-c-1
A-c-2
B-c
Method
Wet Thickness (mil)
7
7
7
Volume Solids (%)
33.0
34.0
33.3
Dry Time (min)
30
35
40
D-1640
MFT (°C)
2
2
2
D-2354
Pencil Hardness
F
F
F
D-3363
Conical Mandre1(1/8")
pass
pass
pass
D-522
Adhesion on Aluminum
4B
4B
4B
D-3359
Adhesion on Steel
4B
4B
4B
D-3359
Scrub
Initial Break
200
240
190
D-24 86
Film Failure
280
300
260
D-24 86
85° Gloss
58.2
57.1
48 .4
D-523
60° Gloss
13 .5
13 . 3
14.3
D-523
20° Gloss
1.9
1 . 9
1.9
D-523
Contrast Ratio
98 .5
98 . 6
98.0
D-3022
It has been suggested that the analytical methods for
evaluating solventless coatings should be reviewed since no- and
low-VOC coatings are new technology2'3. For instance, while
conventional latex coating formulations possess added coalescing
agents, it is reasonable to conclude that full coalescence, and
thus film properties, would occur quickly. However, solventless
latex coatings contain no added coalescing agents, and it is
likewise reasonable that film property development would be
delayed to some extent. Thus, scrub resistance of the lattices
were evaluated at 7 and 28 day dry times, the latter being
consistent with the DIN 53.778 standard scrub test used in
Germany3. The results are plotted in Figures 1 and 2.
Flat paints (55% PVC5 (Figure 1) are heavily pigmented and
are not expected to equal the performance of the less pigmented
semi-gloss coatings (20% PVC) (Figure 2). Indeed, this is
confirmed for all coatings of Figures 1 and 2, i.e., all 20% PVC
coatings are superior in scrub resistance to the best 55% PVC
formulation whether dried 7 or 28 days. The addition of small
amounts of coalescing aids in formulas USM A-c-2 and USM B-c
provide slight improvement in coalescence as reflected in
improved scrub resistance after 7 days dry time. However,
greatest improvement in scrub resistance was developed in the
solventless coatings USM A-a, USM B-a and USM A-c-1 by simply
extending the drying period from 7 to 28 days. This latter
effect is clearly a result of the unique coalescence and curing
mechanism of the USM lattices.
8-54
-------
Table 9. Pencil Hardness as a Function of Dry Time
Paint MFT Thickness Pencil Hardness (Scratch)
Code °C mils 1 day 7 days 17 days
USM A-a
0
1.37
HB
4H
4H
USM B-a
0.5
1.51
F
4H
4H
CL-a
1
1.22
H
2H
2H
USM A-b
2
1.05
B
F
F
USM B-b
2
1.16
B
H
H
CL-b
2
1.13
B
HB
HB
USM A-c-1
2
1»2 B
HB
F
F
USM A-c-2
2
1.28
HB
F
F
USM B-c
2
1.39
HB
F
F
Gloss values demonstrate that the solventless coatings of
Table 7 are effectively coalesced and are gloss competitive with
the conventionally formulated coating. The lower gloss values
are noted when Ti-Pure R900 is the lone pigment (Table 8}.
CONCLUSIONS
Vinyl acrylic lattices have been synthesized that require no
coalescing aids, and possess Tg-MFT differentials of 20 + 3°C.
The low MFT allows formulation of waterborne coatings that will
film form near 0°C. Film properties have been evaluated and
found to be equal or better than coatings formulated with VOC
contributing coalescing aids.
ACKNOWLEDGMENTS
This research was supported by the Cooperative State
Research Service, U.S. Department of Agriculture, under Agreement
No. 91-38202-592 8. We extend our thanks to Drs, Daniel E.
Kugler, Harry Parker, and Mrs. Carmela Bailey.
8-55
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REFERENCES
1. Klein, R.J. Formulating low-odor, low-VOC interior paints.
Modern Paint and Coatings. 83:3, 37, 1993.
2. Leraan, A. Solvent-free architectural coatings. Paper
presented at 47th Annual Spring Symposium, Pacific Northwest
Society for Coatings Technology, Victoria, Canada. April
28-30, 1994.
3. Currie, B. EVA maintains paint properties, lowers VOC.
Modern Paint and Coatings. 83:9, 34, 1993.
4. Huang, H., Watkins, L., and McCrillis, R.C. Formulating
ultra-low-VOC wood furniture coatings. Modern Paint and
Coatings. 83:12, 41, 1993.
5. Ulyatt, J.A. Solvent-free wall paints for interior use.
Polymers Paint Colour J. 183, 412, 1993,
6. Broek, A.D. Environment-friendly paints,- their technical
(im)possibilities. Progress in Organic Coatings. 2, 55,
1993 .
7. Kohlhammer, H.Z. and Krell, M. VOC-emission from latex
paints and plasters during application. Surface Coatings
International. 4, 142, 1994.
8. Buttrick, G.W. Formulating water-borne trade sales coatings.
In: The University of Southern Mississippi (ed.) Coatings
Science for Coatings Formulators, Short Course, Hattiesburg,
Mississippi, 1993. p.73.
9. Stieg, F.B., Jr. Pigment/binder geometry, in: T.C. Patton
(ed.}, Pigment Handbook. Vol. 3. John Wiley & Sons, New
York, 1973 . pp. 203-217.
10. Patton, T.C. Paint Flow and Pigment Dispersion, 2nd Ed.
Chapter 8. John Wiley & Sons, New York, 1979. p. 192.
11. Kreis, R.W. and Sherman, A.M. Development of a ureido
functional monomer for promoting wet adhesion in latex
paints. Paper presented at the Fifteenth Water-Borne &
Higher-Solids Coatings Symposium, New Orleans, Louisiana.
February 3-5, 1988.
8-56
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Figure 1. Scrub Resistance For Fiat Wail Paints
fpTbavs ¦2BDavsl
USM A-a USM B-a CL-a USM A-c-1 USM A-c-2 USMB-c
Figure 2. Scrub Resistance For Semigloss Paints
~ 7 Days
¦ 2SDays
USM A-b
USM B-b
8-57
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This paper has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
presentation and publication.
EVALUATION OF EMISSIONS FROM LATEX PAINT
Brace A. Tichenor
Indoor Air Branch
Air and Energy Engineering Research Laboratory
US EPA
Research Triangle Park, NC 27711
INTRODUCTION
Traditional methods of assessing latex paint emissions have been developed to
determine cumulative mass emissions of volatile organic compounds (VOCs) for purposes
of determining their impact on the ambient air, specifically for their contributions to
photochemical smog. In indoor environments, the concern is directed to determining the
time varying exposure of occupants to total VOCs, as well as individual organic
compounds. The Indoor Air Branch of EPA's Air and Energy Engineering Research
Laboratory, Research Triangle Park, NC, has developed a three phase approach (i.e.,
small chamber source characterization - indoor air quality (IAQ) modeling - test house
validation) for developing emissions data for indoor sources (see Fipre I)1. This
approach provides information on the temporal distribution of indoor emissions and
allows occupant exposures to these emissions to be determined2. Over the past year,
this approach has been used to evaluate indoor emissions from latex paint.
CHAMBERS
IAQ MODEL
a a
TEST HOUSE
- Controlled Experiments
- Evaluate Environmental
Variables
- Develop Source Emission
Factors
- Air Exchange
- HVAC Operation
- Sources and Sinks
- Predict Indoor
Concentration
- Full Scale Testing
- Room-to-Room
Transport
- Model Validation
Figure 1. Three-phase IAQ research approach
For presentation at Low- and No-VOC Coating Technologies 2nd Biennial
International Conference, March 13-15, 1995, Durham, NC.
8-58
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RESEARCH PLAN
A three-part latex paint emissions study is underway: 1) Initial Assessment; 2)
Chamber Testing; 3) Test House Validation Studies, The Initial Assessment was
designed to determine the most appropriate techniques for conducting the overall latex
paint assessment program, including: a) selection and purchase of test paint; b) analysis
of volatile organic compounds (VOC) and water content using American Society for
Testing and Materials (ASTM) methods; c) determination of major organic compounds;
d) development of optimal sampling and analysis methods for organic paint emissions;
and e) evaluation of paint application methods. The purposes of the Chamber Testing
are to: a) select the test substrate; b) develop data for determining VOC emission rates;
and c) develop and evaluate source emission models, including mass transfer models.
The Test House Validation Studies will develop data for evaluating and validating source
emission models, including mass transfer models. In addition, the studies should
provide data for assessing scale-up of small chamber source emissions data. The
following information is expected to result from this assessment of latex paint: a)
Emission rate data for VOCs from latex paint on gypsumboard for specific test
parameters; b) Validated source emissions models for latex paint, including mass transfer
models; and c) Test house data showing the concentrations of VOCs from latex paint.
Ultimately, the effort should result in a test method proposal for ASTM.
The three part evaluation program was initiated in 1994. Part 1 (Initial
Assessment) has been completed; Part 2 (Chamber Testing) is scheduled for completion
early in 1995; and Part 3 (Test House Studies) will be completed by the end of 1995.
INITIAL ASSESSMENT
The purpose of the initial assessment was to determine the most appropriate
techniques for conducting the overall latex paint assessment program, including: a)
selection and purchase of test paint; b) compilation of information on paint composition
based on product label and MSDS (Manufacturer's Safety Data Sheet); c) analysis of
VOCs and water content using ASTM methods; d) determination of major organic
compounds; e) development of optimal sampling and analysis methods for organic paint
emissions; and f) evaluation of paint application methods.
Paint Composition
The paint selected for evaluation is a white interior flat latex wall paint (with
vinyl acetate monomer) produced by a major US manufacturer. Based on ASTM
methods3 for paint analysis, the paint has the following composition by weight: non-
volatiles = 57% and volatiles = 43% (water = 40% and VOC = 3%). Analysis of
the paint by liquid injection to a gas chromatograph gave a total VOC (TVOC)
content = 45 mg/g, with the following composition (in mg/g): ethylene glycol = 24;
Texanol® = 13; butoxyethoxyethanol = 5; propylene glycol = 2; and diethylene
glycol = 1.
8-59
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Sampling and Analysis Methods
Evaluation of available methods resulted in the selection of the following
sampling and analysis techniques for VOC emissions from latex paint; a) sampling on
Tenax®TA sorbent; b) thermal desorption and concentration; and c) analysis by gas
chromatograph (with a DB™-Wax column) using a flame ionization detector (FID).
Paint Application Methods
Three application methods were evaluated: slit applicator (a laboratory "standard"
method), brush, and roller. The roller method was selected for use in the remainder of
the study.
CHAMBER TESTING
Environmental test chamber methods have been developed for evaluating emissions
from indoor materials and products4. Flow-through, dynamic chambers are used when
emission rates are to be determined. The chambers used in this study have a volume
of 53 liters and are constructed with electropolished stainless steel interior surfaces to
minimize adsorption of VOCs. Small fans are used to enhance mixing and provide a
velocity near the test surface of 5 - 10 cm/s, which is typical of indoor environments.
Emissions testing is conducted by placing a freshly painted (2-3 min.) substrate (16.3
x 16.3 cm) in the chamber, painted side up. The chamber is then closed, and clean
air (< 5 jig/m3 TVOC) flow is started through the chamber. A flow rate of 0.44
1/min, equivalent to 0.5 air changes per hour, is used. Samples of the chamber outlet
are taken using the techniques described above. Sufficient samples are collected to
describe the change in emissions over time. Testing is conducted at 23°C with an inlet
relative humidity of 50%.
The purpose of the chamber testing is to: a) Select the test substrate; b)
Determine emission rates for total VOC as well as for individual compounds; c)
Determine the effect of previous coats on emissions; d) Determine short- and long-term
emission rates; and e) Evaluate and develop source emission models, including mass
transfer models.
Selection of Test Substrate
VOC emissions from painted gypsumboard and stainless steel were evaluated
using dynamic chamber tests. While stainless steel is routinely used as a test substrate
in emissions testing due to its non-adsorbent properties, gypsumboard is a more realistic
choice for latex paint. As shown in Figure 2, VOC emissions from painted
gypsumboard are quite different than those from stainless steel. Significant amounts of
VOCs are adsorbed by the gypsumboard, thus reducing the short term emissions to the
indoor air. Thus, gypsumboard was selected at the test substrate.
8-60
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140
New Gypsumboard Stainless Steel
120
80
60
40
20
0
150
0
100
Time (h)
Figure 2. Emissions of TVOC from painted gypsumboard and stainless steel
(Dynamic chamber tests)
Emissions of Individual Latex Paint VOCs
The chamber samples were also analyzed to determine the emissions of individual
latex paint components, namely: ethylene glycol, propylene glycol, diethylene glycol,
butoxyethoxyethanol, and Texanol® [2,2,4-Trimethyl-l,3-pentanediol Mono(2-
methylpropanoate); mixture of two isomers]. As shown in Figure 3, emissions of
Texanol® and ethylene glycol are the highest, with Texanol® emissions predominating for
the first 50 hours and ethylene glycol emissions being the primary VOC emitted
thereafter.
The Effect of Previous Coats on Emissions
Testing was conducted to determine if paint applied to previously painted
gypsumboard affects the emission profile. Two previously coated boards were used: 1)
a piece of gypsumboard cut from a wall of EPA's IAQ test house that had not been
repainted for over 8 years and 2) a gypsumboard sample painted 5 weeks previously.
As shown in Figure 4, the two previously painted gypsumboards had emission profiles
essentially the same as for the first coat on new gypsumboard.
8-61
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P. Glycol E. Glycol BEE Texanol
100
Time (h)
P. Glycol = Propylene Glycol
E. Glycol = Ethylene Glycol
BEE= Butoxyethoxyethanol
Figure 3. Emissions of latex paint VOCs from painted gypsumboard (Dynamic
chamber test)
50
New Gypsumboard 2nd Coat (New Board) House Board
40
CD 30
20
10
0
100
150
0
Time (h)
Figure 4. Emissions of TVOC from first and second coats of latex paint on
gypsumboard (Dynamic chamber tests)
8-62
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Long and Short Term Emissions
Many wet, evaporative sources of indoor air pollution emit for only a short time
(e.g., several days). Most of the testing done in this evaluation program occurred over
a 7 day (168 hour) period, as shown in Figures 2, 3, and 4, One test has been
continued in order to observe the emissions from latex paint over the long term.
Figure 5 shows the emissions of VOCs over a period of almost 6 months (4200 hours
or 175 days). Note that the emissions of ethylene glycol are much higher than the
other compounds. Also note that at the last sampling period, the concentrations of
butoxyethoxyethanol and Texanol® were near the quantification limit of the sampling and
analysis system.
£
O)
g
c
o
+3
nj
43
c
-------
For sources with decaying emissions, a common approach is to assume a first
order decay:
EF = EF0e'to (1)
where EF0 = initial emission factor (mg/m2h); k = first order rate constant (h'1); and
t = time (h). Some decaying sources, usually long lasting emitters, can be described
by a second order decay equation:
EF = (EFJ/d + k2EFct) (2)
where k2 = second order decay constant.
Source models have also been developed that are based on fundamental mass
transfer processes. For sources with gas-phase limited mass transfer (e.g., evaporation
from wet sources), the emission factor can be described as:
EF = kg(C„ - C) (3)
where, kg = mass transfer coefficient (m/h); C, = concentration of vapor in the air
just above the emitting surface (mg/m3); and C = concentration of vapor in the room
air (mg/m3). C, is the vapor pressure, expressed as concentration, in equilibrium with
the source. Previous work5 has shown a linear relationship between C, and the mass of
VOC in the source (M):
C4 = CV(M/M0) (4)
where Cv = concentration of VOC over fresh source (i.e., at time = 0); M = mass in
source (mg/m2) at time t; M0 = initial mass in source (mg/m2). The mass transfer
coefficient (kg) is determined by the vapor diffusivity of the emissions in air, the
velocity above the source, and the geometry (size and shape) of the source.
Data from the dynamic chamber testing of painted gypsumboard have been fit
with several source emissions models. As shown in Figure 6, the first order decay
model (Equation 1) does not apply to latex paint TVOC emissions, while the gas-phase
mass transfer model (Equations 3 & 4) does a good job of predicting short term
emissions. Long term emissions are mainly controlled by diffusion within the
gypsumboard, so a gas-phase limited model will not provide adequate predictions.
Figure 7 illustrates the use of a second order decay model (Equation 2) for predicting
long term emissions. A mass transfer model embodying both gas- and solid-phase mass
transfer controls is under development.
8-64
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Data 1 st Order Model Mass Transfer Mode
^30
w- 20
40 60
Time (h)
100
Figure 6. Short term emissions models - TVOC from painted gypsumboard (Dynamic
chaniTjer test)
100
30
n
s
10
B
3
o
1
o
>
H
0.3
0.1
Data 2nd Order Model
1,000 1,500
Time (h)
2,000
2,500
Figure 7. Long term emission model - TVOC from painted gypsumboard (Dynamic
chamber test)
8-65
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TEST HOUSE VALIDATION STUDIES
The purpose of the test house validation studies is to develop data for evaluating
and validating source emission models, including mass transfer models. In addition, the
studies should provide date for assessing seale-up of small chamber source emissions
data. Test house studies will include: a) Anemometer traverses of test house walls to
determine velocity distributions; b) Experiments to validate source emission mass transfer
models; and c) Development of mass transfer coefficients for typical painting scenarios.
APPLICATION OF RESEARCH RESULTS
Emission rates developed from source testing are used in indoor air quality
models6 to predict indoor concentrations over space and time. The second order
emission model (Equation 2 and Figure 7) was used to predict the concentrations of
TVOCs in a hypothetical three-room apartment (see Figure 8) when latex paint is
applied to interior walls.
Bedroom
(3x4x2.5 m)
(4x7x2.5m)
Hall (1x2x2.5m)
Bath
(2x3x2.5m)
Figure 8. Floor plan for one-bedroom apartment
8-66
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The model used an outdoor air exchange rate of 0.5 per hour and assumed a
forced air heating/cooling system. The painting schedule was: Living area, 8AM -
Noon; Hall, 1 - 2PM; Bedroom, 2 - 3PM; and Bath, 3 - 4PM. Figures 9 and 10
show the concentrations in each room for TVOC and Texanol®, respectively, for the
first 100 hours. After that time, the concentration in all rooms was equal and the
decay was much slower. Figure 11 shows the concentration of TVOC in the living
area out to 700 hours.
60
50
n
E 40
E
<£. 30
O
^ 20
10
0
0 20 40 60 80 100
Time (h)
Figure 9. Predicted concentrations of TVOC from interior painting
FINAL PRODUCTS
The following information is expected to result from this assessment of a latex
paint; a) Emission rate data for VOCs from latex paint on gypsumboard for specific test
parameters; b) Validated source emissions models for latex paint, including mass transfer
models; c) Test house data showing the concentrations of VOCs from latex paint; and
d) A draft ASTM "Standard Practice for Determining Emissions from Interior Latex
Paints." If a mass transfer model can be used to successfully predict emissions, a test
method based on ASTM VOC content and equilibrium data from static headspace should
be possible. Thus, the dynamic chamber test method would be replaced by a simpler
and less expensive technique. Other latex paints need to be evaluated to provide data
for generalizing these test methods.
Living Area Bedroom Bath
8-67
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20
Living Area Bedroom Bath
10
5
0
100
0
Time (h)
Figure 10. Predicted concentrations of Texanol® from interior painting
50
40
*0) 30
O 20
10
0
500
100
200
300
400
Time (h)
600
700
0
Figure 11. Predicted TVOC concentrations in living area from interior painting
8-68
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REFERENCES
1) Tichenor, B., Sparks, L., White, J., and Jackson, M. Evaluating sources of
indoor air pollution. Journal of the Air and Waste Management Association.
40: 487, 1990.
2) Sparks, L., Tichenor, B., and White, J. Modeling individual exposure from
indoor sources. In: N. L. Nagda (ed.), Modeling of Indoor Air Quality and
Exposure. ASTM Publication STP 1205, American Society for Testing and
Materials, Philadelphia, PA, 1993. p. 245.
3) Brezinski, J. Manual on determination of volatile organic compounds in paints,
inks, and related coating products. ASTM Manual Series, MNL 4, American
Society for Testing and Materials, Philadelphia, PA, 1989.
4) ASTM. Standard guide for small-scale environmental chamber determinations of
organic emissions from indoor materials/products. ASTM D5116-90. American
Society for Testing and Materials, Philadelphia, PA, 1990.
5) Tichenor, B., Guo, Z., and Sparks, L. Fundamental mass transfer model for
indoor air emissions from surface coatings. Indoor Air. 3: 263, 1993.
6) Sparks, L., Tichenor, B., White, J., and Jackson, M. Comparison of data
from an IAQ test house with predictions of an IAQ computer model. Indoor
Air. 4: 577, 1991.
8-69
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New Polyurethane Prepolymers for Ultra-Low VOC Plural Component Coatings
Sherri. L. Bassner
Air Products and Chemicals, Inc.
7201 Hamilton Boulevard
Allentown, PA 18195
USA
E-mail: bassnesl@ttown.apci.com
Jeffrey Kramer
Air Products and Chemicals, Inc.
7201 Hamilton Boulevard
Allentown, PA 18195
USA
E-mail: kramerj@ttown.apci.com
Thomas M. Santosusso
Air Products and Chemicals, Inc.
7201 Hamilton Boulevard
Allentown, PA 18195
USA
E-mail: santostm@ttown.apci.com
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
©1995 Air Products and Chemicals, Inc.
(Reproduced with permission)
8-70
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SUMMARY
The drive toward lower and lower VOC coatings has led to a resurgent interest in plural
component spray application technology. With this equipment, the reactive components are
mixed just before or at the spray gun. Separating the components in this way before spraying
allows the use of elevated temperatures to reduce formulation viscosity without concerns over
the working life of the formulation, reducing or eliminating the need for solvent. The
development of a new technology for producing very narrow molecular weight distribution
isocyanate-terminated prepolymers with very low residual diisocyanate monomer has improved
the viability of this process. These prepolymers decrease rapidly in viscosity with increasing
temperature, and the low monomer content reduces worker exposure potential. This paper will
introduce this prepolymer technology and illustrate the use of these prepolymers in formulating
very low or near zero VOC polyurethane topcoats for high performance applications.
INTRODUCTION
Two part solvent-based coatings systems utilizing aliphatic isocyanates and polyester or
acrylic polyols have become the industry standard for weatherable topcoats. These coatings
systems combine exceptional resistance to chemical and physical damage with high gloss levels
and long term retention of gloss, color and mechanical properties. Traditionally, these coatings
systems have been formulated with a liquid polyisocyanate as one component and a high
molecular weight, high functionality polyol and associated pigments and additives as the second
component.1
A major driving force in the reformulation of coatings the world over is the need to
reduce solvent emissions on application. One disadvantage of these traditional polyurethane
formulations is the high solvent demand of the polyol component. This factor has limited the
volatile organic content (VOC) reduction available with traditional polyol systems. One route to
lowering VOC is to employ lower molecular weight polyols. As formuiators incorporate more
and more lower molecular weight (lower viscosity) polyols or reactive diluents into their
systems, there has been an inevitable trade-off in physical properties of the resulting coatings
and/or handling of the reactive mixture. Many low VOC polyurethane coatings today suffer
from poor solvent resistance, poor flexibility, and an extreme sensitivity to catalyst level as it
affects cure profile. In addition, with less solvent in the formulation and fewer ingredients to
manipulate, maintaining convenient mixing ratios has also been a struggle.
Isocyanate producers have done an excellent job in educating their customers on the safe
use of isocyanates in coatings and are constantly working to lessen any potential problems
associated with these materials. One approach toward further improving isocyanate handling,
described here, is to utilize higher molecular weight, isocyanate-terminated prepolymers as a
source of isocyanate.
Concurrent with the drive toward lower and lower VOC for conventionally applied
coatings, formuiators and applicators have also increased the use of more specialized application
equipment. Plural component application equipment has been used for many years to apply
100% reactive, fast reacting polyurethane coatings for thick film linings and for adhesives and
8-71
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sealants. With this equipment, the reactive components are metered into a chamber designed to
rapidly mix the components. The reactive mixture is then pumped to a traditional airless or air-
assisted airless spray gun.
This process has a number of advantages over conventional application equipment.
Since material is used only on demand, little product is wasted, and start-up and shut-down times
are reduced. In fact, for reasons of the productivity enhancement alone seen with this
equipment, product finishers have sharply increased their use of plural component polyurethane
coatings on industrial finishing lines. Often traditional solvent-borne, lower VOC coatings are
used with increased catalyst levels to speed cure times and lower oven temperatures. Since the
reactive components are mixed only seconds before application, short potlives can easily be
tolerated. In fact, for extremely fast systems, equipment exists which mixes the components in
the spray gun itself a fraction of a second before application.
Perhaps more important for low VOC formulations, since short potlives can be tolerated,
elevated temperatures can be used to lower the viscosity of the components instead of solvent.
Using this approach, extremely high non-volatile material (NVM) coatings—approaching 100%
NVM—may be possible using raw materials currently employed in conventional higher NVM
formulations. Protective coating applicators and formulators are beginning to take advantage of
these attributes to apply high quality primers and weatherable topcoats. This type of system
works well in a controlled environment with stationery equipment., such as shop-applied rail car
coatings or shop-coated structural steel. As equipment and formulations are refined, the
potential also exists to take this type of equipment into the field.
This paper presents the use of newly developed isocyanate prepolymers—defined here as
isocyanate/polyol adducts-as one alternative to formulating two component polyurethane
topcoats. These prepolymers offer the advantages of a narrow molecular weight distribution,
rapid viscosity reduction with increasing temperature or solvent level, very low diisocyanate
monomer content, equivalent or improved film properties and weatherability characteristics
compared to conventional coatings of this type, less sensitivity to catalyst level variability, and
the ability to be formulated at a 1:1 volume ratio. While these prepolymers also are being used
to formulate conventionally applied primers and topcoats2, this paper will focus on the
development of formulations specifically for plural component applied coatings where the
unique characteristics of these prepolymers are used to overcome a number of formulating
difficulties.
New Polyurethane Prepolymer Technology
Polyurethane prepolymers have been employed in certain segments of the coatings,
adhesives, sealants, and elastomer industries for many years.3 By forming a "pre"-poIymer (see
Fig. 1), diisocyanate monomer content is reduced and the reactivity of this partially reacted
system is simpler to control. These prepolymers, however, have seen limited use in higher NVM
coatings formulations. An examination of the synthesis process sheds some light on why this is
so.
8-72
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Figure 1: Comparison of Prepolymer Synthesis Technologies
POLYOL D11SOCYANATE
AIRTHANE X \ CONVENTIONAL
PREPOLYMERS / \ PREPOLVMERS
>90% 55-65%
30-40%
2-4%
The traditional synthesis process, depicted on the right side of Figure 1, typically
involves the exothermic reaction of one equivalent of polyol with two equivalents of
diisocyanate monomer. The desired end product, the isocyanate-capped polyol, makes up only
around half of the weight of the final product mixture. Using this process, many of the
diisocyanate monomer molecules react through both isocyanate groups, creating high molecular
weight oligomers. These oligomeric species, which can be much larger than the simple 3:2
diisocyanatetpolyol adduct shown in Figure 1, lead to the high solvent demand, relatively short
pot lives, and poor sprayability of many prepolymer-based coatings formulations.
New technology, described in detail elsewhere,4'5'6 has made available polyurethane
prepolymers, tradenamed AIRTHANE® prepolymers, with half the viscosity of their
conventional counterparts and extremely low diisocyanate monomer levels (<0.1% for aromatic
isocyanates, <1.0% for aliphatic isocyanates). These materials, made by a process that keeps
oligomer content very low, have the lower solvent demand and favorable pot life/dry time
balance needed for high NVM formulating (see Figures 2 and 3 and Table 1).
8-73
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Figure 2: Comparison of Prepolymer Viscosities
in Xylene
_ 6000
CO
o_ 5000
O
~ 4000
b 3000 •
CO
O 2000
m 1000 •
> 0
/
/
/
65 70 75 80 85 90
WEIGHT PERCENT PREPOLYMER
PC-500
CONV. ANALOG
95
Figure 3: Comparison of Viscosity Build of
Typical Prepolymer-based 2K Formulations
_ 2500
w
o 2000
> 1500
9? 1000
0
5 10 15 20 25
REACTION TIME (MIN)
30
AIRTHANE - ¦ - ANALOG 1 -A-ANALOG 2
8-74
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Table 1: Comparison of pot life (doubling of initial viscosity) and thin film cure times for a
conventional prepolymer and its analog prepared by the Airthane prepolymer process.
Prepolymer Wt. Solids (%) Pot life Cure time
Conventional 80 40 min 4.5 h
Prepolymer
Airthane 85 2 h 6 h
Prepolymer
Formulating for Plural Component Equipment
A typical plural component spray system contains the units described below in Figure 4.
The reacting components are either pumped directly from their drums or from heated pots. The
pumping mechanisms are typically reciprocating piston pumps that can deliver the two fluids at a
set or variable volume ratio. The more common equipment will deliver a set ratio of 1:1, 2:1, or
4:1. Many set ups include in-line heaters and filters and may include a recirculation capability
prior to the integrator. The integrator is a static mixer, often a proprietary design of the
manufacturer. Following the integrator, the material is pumped through a "whip" section of hose
to a standard airless or air-assisted airless spray gun.
Figure 4: Typical Plural Component Spray Equipment
INTEGRATOR
HEATERS
AND
FILTERS
PUMP
GUN
The most critical event in the application of a successful system is the mixing of the
components in the integrator. While different integrator designs affect how well the components
mix, there are certain characteristics of the liquids that will lead to good mixing. It is generally
believed7 that in situations of laminar flow, it is easier to mix materials of more equal viscosity.
If viscosities are unequal, it is easier to mix a small amount of a low viscosity material into a
higher viscosity material than vice versa. Most plural component polyurethane formulations fall
8-75
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into the latter catagory, where a relatively small low viscosity isocyanate component is mixed
into a larger pigmented polyol component. However, it would be better yet if nearly equal
amounts of materials with matching viscosities could be used.
Problems also arise when, as frequently happens, the delivered ratio of the proportioning
equipment varies slightly from the nominal. While equipment technology is improving at a
rapid rate, mechanical proportioners such as those described above can often vary by up to 5%.
Equipment that is not very carefully maintained can vary even further. For consistent
application of high quality coatings, the formulation needs to be somewhat forgiving of ratio
variations. These fluctuations are much more detrimental to a high ratio formulation (4:1 and
up) than to a 1:1 ratio formulation since changes in the volume of the small volume component
will have a more significant effect on the stoichiometry of the reacting system. Our goal, then,
in formulating two part polyurethane coatings for plural component application was to develop
systems at a 1:1 volume mix ratio wherein in the two components would have similar viscosities
at application temperature.
Formulation Details and Coating Performance
Two types of formulations were developed. The first, for more weatherable applications,
is based on acrylic polyol s and is considered a high NVM system. A typical formulation is
detailed in Table 2. The isocyanate component of this formulation is a prepolymer based
isophorone diisocyanate (IPDI) and a mixture of neopentyl glycol adipates. It has a nominal
equivalent weight of 540 g/eq (on solids) and an average functionality of about 2.5. It is used in
this formulation as an 85% NVM solution in methyl amyl ketone (MAK). This formulation is
delivered at a 1:1 volume mix ratio with an NCO/OH of 1.1. The viscosity profiles versus
temperature for the isocyanate and polyol components are shown in Figures S and 6,
respectively. Note that the two components have very similar viscosities at the application
temperature of 50°C.
Table 2: Typical formulation for high NVM weatherable topcoat.
Material
Weieht fib)
Volume (gal)
Supplier
Comments
Component I
Chempol 17-
242.19
27.84
CCP
acrylic polyol
3855
Zoldine. RD4
21.53
2.84
Angus
reactive diluent
Ti-Pure R960
384,49
11.58
DuPont
pigment
Disperbyk 110
18.20
2.14
Byk-Chemie
dispersant
Dislon NS-30
1.58
0.21
King Industries
thixotrope
Tinuvin 292
8.87
1.06
Ciba-Geigy
HALS
Tinuvin 400
10.44
1.26
Ciba-Geigy
UVA
Tego 980
4.14
0.52
Tego Chemie
air release
DABCO 120
0.59
0.07
Air Products
catalyst
18% Zn-Oct
3.52
0,40
OMG
catalyst
MAK
13.96
2.05
solvent
Subtotal
709.51
49.97
8-76
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Table 2: (continued)
Material Weight (lb) Volume (gal) Supplier Comments
Component II
Airthane 442.64 50.03 Air Products isocyanate
ASN-540M prepolymer
Totals 1152.15 100.00
Weight percent NVM = 87.76%; Volume percent NVM a 79.94%; PVC = 15.27%;
VOC = 1.41 Ib/gal (169 g/L); Mix Ratio: 1:1
Figure 5: Thermal Profla for ASN-540M
6COO
4000
3000
2000
1000
0
25
30
35
6C
SO
70
BO
Temperature (C)
Figure 6: Thermal Profie for Pigment Grind of High NVM Formulation
5000
3000
I
I
* 2000
>
1000
25
40
50
60
Temperature (C)
8-77
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The second type of formulation developed is based on polyester polyols and can be
formulated at less than 0.20 lb/gal (24 g/L). A typical formulation is detailed in Table 3. The
isocyanate component of this formulation is a mixture of the prepolymer used above with
polyisocyanates based on hexamethylene diisoeyanate (HDI). This unique combination of
isocyanates provides low viscosity, high crosslink density, and sufficient molecular weight to
formulate at a 1:1 mix ratio with an NCO/OH of 1.1. The use of the low oligomer prepolymer is
critical to the success of this mixture. A conventional prepolymer would have too high a
viscosity and most likely impart poor sprayability to the formulation. The viscosity profiles
versus temperature for the isocyanate and polyol components are shown in Figures 7 and 8,
respectively. Note, again, that the two components have very similar viscosities at the
application temperature of 50°C.
Table 3; Typical formulation for very low VOC topcoat.
Material
Weisht (lb)
Volume (sal)
SuDolier
Comments
Component I
Chempol 18-
192.10
20.11
CCP
polyester
2244
polyol
Tone 0301
82.33
9.10
Union Carbide
poly-
caprolactone
Ti-Pure R960
483.85
14.57
DuPont
pigment
Disperbyk 110
21.47
2.52
Byk-Chemie
dispersant
Dislon NS-30
1.99
0.27
King Industries
thixotrope
Tinuvin 292
7.44
0.89
Ciba-Geigy
HALS
Tinuvin 400
8.76
1.06
Ciba-Geigy
UVA
Tego 980
3.72
0.47
Tego Chemie
air release
Byk 320
4.29
0.61
Byk-Chemie
flow aid
DABCQ 120
0.37
0.04
Air Products
catalyst
18% Zn-Oct
4.43
0.51
OMG
catalyst
Subtotal
810.75
50.15
Component II
Airthane
234.98
25.38
Air Products
isocyanate
ASN-540M
prepolymer
Desmodur
117.49
12.12
Miles/Bayer
HDI
N3300
isocyanurate
Luxate HD-
117.49
12.35
Olin
HDI uretdione
100
Subtotal
469.96
49.85
Totals
1280.71
100.00
Weight percent NVM = 98.74%; Volume percent NVM = 97.94%; PVC = 15,57%;
VOC = 0.16 lb/gal (19 g/L); Mix Ratio: 1:1
8-78
-------
Flgur* 7: Thermal Prod# for 100% NYM Isocyanate Bf*nd
Iemp«faturt (C)
Figur# 8: Thermal Profl# for Vary Low VOC Pigment Grind
14000
12000
10000
8000
6000
4000
2000
0
25
The properties of these coatings are representative of traditional solvent bome urethanes
and compare well with those of an HDI isocyanurate control. Physical and mechanical property
comparisons are shown in Table 4. It is important to note that handling the isocyanurate control
was much more difficult than the prepolymer based formulations. The control formulation
required a 4:1 mix ratio (non-integer mix ratios were needed with other control formulations
tried) and showed an extreme sensitivity to catalyst level. This was demonstrated by measuring
the pot life of each of the formulations. The prepolymer formulations described above did not
gel for several hours when mixed at ambient temperatures. The control formulations with no
catalyst also had a pot life of several hours. The control formulations with the same modest
catalyst levels used with the prepolymers, however, gelled in less than 15 minutes. Current work
8-79
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is aimed at better quantifying the relative catalysis {attitude of the prepolymer and control
formulations, but it is apparent that the prepolymer approach is much less sensitive to variations
in catalyst level.
Table4: Representative Coating Film Property Comparison
Property
Prepolymer
Isocvanurate
Prepolymer
Acrylic
Acrvlic Control
Polyester
Set time (hours)
3
3
2
Dry hard (hours)
16
15.5
3
Pencil Hardness
HB
HB
HB
Dry Adhesion
5A
4A
4A
(ASTM D3359)
Wet Adhesion
4A
4A
4A
(24 h, D3359)
Impact (D/R in-lb)
160/160
160/160
160/160
MEK rubs
100+
100+
100+
60° Gloss
92.6
94.7
95.3
Gloss Retention
92%
88%
97%
(1000 h, UV-B313)
Plural Component Application
Application trials of the two sample formulations were conducted at Graco, Inc.
Engineering Labs in Franklin Park, IL. The pump used was a Graco Bulldog 206-740 fixed at a
1:1 volume mix ratio with a 32:1 air/fluid pump ratio. This set-up utilizes equivalent volume
dual pistons which fill on the up-stroke and empty on the down stroke. The reacting materials
were pumped directly from 5 gallon pails, through in-line heaters and 60 mesh filters, and could
be recirculated through this cycle to heat the material fully. The fluid lines to the mixing
manifold were resistively heated. The mixing element was a 3/8" diameter static mixer with 30
elements. Both formulations were easily pumped at temperatures from 120°F to 150°F. The
appearance and properties of the applied material also indicated excellent mixing of the reactive
components. Applied films were smooth and uniform, and coating film performance was as
expected. The coatings were applied by airless (517, 617, and 619 tips) and high pressure air-
assisted airless (608 cap, 100 psi atomizing pressure) methods. Applications characteristics were
fair. The near-zero VOC, polyester-based formulation atomized better than the higher solids
acrylic formulation; however, both formulations showed some tailing. Larger tips and slightly
higher application temperatures may have improved the spray pattern, but the trial was limited in
the amount of available formulated paint at this writing.
CONCLUSIONS
The development of low oligomer content isocyanate terminated prepolymers
(diisocyanate/polyol adducts) has introduced a new option in formulating very high NVM two
component urethane coatings. The low solvent demand of these prepolymers and their rapid
viscosity decrease with increasing temperature has allowed the use of this type of material for
8-80
-------
the first time in high performance, plural component applied coatings. The higher equivalent
weight of these prepolymers allows the formulator to develop paints at a 1:1 volume mix ratio.
These formulations showed good handling and excellent mixing properties. Coatings applied by
airless and air-assisted airless methods showed fair atomization and excellent flow out. The
performance of these coatings is as good as, or better than, high mix ratio polyisocyanate-based
control formulations.
8-81
-------
REFERENCES
1. See, for example: Surface Coatings. Ed, by J. M. Waldie, TAFE Educational Books, Mcarthur Press, Australia,
1983.
2. J. Kramer and S. L. Bassner, Modern Paint and Coatings, June, 1994; J. Kramer and S. L. Bassner, Paint and
Coatings Industry, August, 1994.
3.G. Oertel, Polvurethane Handbook. Hanser Publishers, New York, 1985.
4.S. L. Bassner, American Paint and Coatings Journal, August 17 and August 24,1992.
5.W, E. Starner, I. P. Casey, and S. M, Clift, Rubber and Plastic News, October 19, (28), 1987,
6. J. R. Quay, S. L. Bassner, and T. M. Santosusso, U.S. 5,115,071, issued May 19, 1992.
7. See, for example: Tadmor and Gogos, Principles of Polymer Processing. Wiley, 1979; Middleman,
Fundamentals of Polymer Processing. McGraw Hill, 1977; and Oldshue, Fluid Mixing Technology. McGraw
Hill, 1983.
NTIS is authorized to reproduce and sell this
report. Permission for further reproduction
must tie obtained Irora the copyright owner.
©1995 Air Products and Chemicals, Inc.
(Reproduced with permission)
8-82
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SESSION 9
LOW- AMD NO-VOC COATINGS-PART I
9-1
-------
PAPERS PRESENTED:
"Organsosilanes in Low VOC Coatings"
by
Kamlesh Panjnani
University of Southern Mississippi
Hattiesburg, Mississippi
"Polyester Oligomers of Narrowed Molecular Weight Distribution"
by
Robert DeRuiter
Reichhold Chemicals
Research Triangle Park, North Carolina
"New Epoxy/Anhydride Chemistry for Durable, High Solids Coatings"
by
Michael Gould
The Dow Chemical Company
Freeport, Texas
9-2
-------
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
ORGMFSOSILANES IN LOW VOC COATINGS
Shelby F. Thames
University of Southern Mississippi
Department of Polymer Science
Box 10037, Hattiesburg, MS 39406-0037
TCamlpHh a. Pan
University of Southern Mississippi
Department of Polymer Science.
Box 10076, Hattiesburg, MS 39406-0076
INTRODUCTION
The genus, Lesquerella., is a new domestic crop with
potential industrial significance, and is native to the Southwest
United States. Three hydroxy fatty acids (Figure 15,
lesquerolic, densipolic, and auricolic acids, are the primary
fatty acids in lesquerella oil (LO) and make up approximately 60%
of the oil composition.1"7 Lesquerella is particularly attractive
as a raw material since, unlike other domestic vegetable oils,
the three major fatty acids in lesquerella are structurally
similar to ricinoleic acid (Figure 1), the principal fatty acid
of castor oil (CO). Currently, CO and its derivatives are the
sole commercial source of hydroxyl fatty acid.8'9 However, since
the early 1970's, all CO consumed by the United States has been
imported. Price instability and inconsistent supply have
handicapped end-users, making corporate planning difficult.
Consequently, a domestic, economically-attractive, and high
performance CO substitute is desirable. However, lesquerella is
a semi-drying oil with an iodine value of 102-116, and therefore,
must be modified if used in air dry coatings.10"13
Silicon-containing polymers have widely been used in
industry to improve flow, leveling, exterior durability,
electrical resistance, corrosion resistance, and weather
resistance. Structurally, most silicon-containing materials have
one or more Si-0 bonds and are therefore classified as silicones.
Organosi1ane polymers, on the other hand, contain a
hydrolytically stable Si-C bond which confers property
enhancements normally associated with silicone modification,
i.e., increased thermal stability, improved solubility, enhanced
processibility, and better weatherability. 14"is Thames, et al
reported the synthesis, characterization, and evaluation of
powder coatings containing organosilane diacids and anhydrides as
crosslinking agents. These coatings display improved gloss,
gloss retention, flow, and leveling.17 ls Furthermore, Thames, et
al have confirmed that silane incorporation lowers glass
transition temperatures, enhances thermal stability, and improves
solubility in organic solvents. Thus, this investigation
focused on the combined influence of pendent organosilane
dicarboxylic acids in LO based coatings.
9-3
-------
O OH
HO—1—(CH2) y-CH—CH—CHt-^H—(CH2) 5-CH3
Ricinoleic acid
O
OH
HO—
2) 9-CH=CH—CH2-'
:h—(ch2> 5-CH3
Lesquerolic acid
0
OH
HO—-C—(CH2) 9-CH=CH—CH2-CH—(CH2) 2 CH=CH—CH2—CH3 Auricolic acid
0
OH
Figure 1
EXPERIMENTAL
Materials
Lesquerella oil (refined from Lesquerella fendleri) was
purchased from International Flora Technology Ltd. Phthalic
anhydride, terephthalic acid, and trimethylol ethane were
obtained from Aldrich Chemical Company, Inc. Lithium ricinoleate
was purchased from Pfaltz & Bauer, Inc. Cobalt, zirconium, and
manganese driers were provided by Nuodex, Inc. as 6% metal
solutions. Exkin No. 2, an antiskinning agent (methyl ethyl
ketoxime), was obtained from Huls America, Inc. Activ 8, a drier
accelerator, and Nacure 155 (dinonyl naphthalene disulfonic acid)
were provided by R. T. Vanderbilt Co., Inc. and King Industries,
respectively. Cargill 23-2317, a highly methylated me1amine
resin, was supplied by Cargill, Inc. All additives, solvents,
catalyst, and raw materials with the exception of the
organosilane dicarboxylic acids were used as received.
The monosubstituted pendent organosilane dicarboxylic acids,
2-trimethylsilyl terephthalic acid, 2-dimethylphenylsi iyi
terephthalic acid, 2-diphenylmethylsilyl terephthalic acid, and
2-triphenylsilyl terephthalic acid, were synthesized according to
Scheme 1. The disubstituted pendent organosilane dicarboxylic
acids, 2,5-di(trimethylsilyl) terephthalic acid and 2,5-
di(dimethylphenylsilyl) terephthalic acid, were synthesized
according to Scheme 2.
9-4
-------
Synthesis of Monosubstituted Organosilane Dicarboxylic Acids -
Scheme 1
n-Butyl lithium (10 M) in hexanes (10% molar excess) was
added to a solution of 2-bromo-p-xylene in anhydrous ether at 0°C
under nitrogen. After one hour, the desired chlorosilane (10%
molar excess) was added dropwise, lithium chloride was
subsequently removed by filtration, and the solvents were removed
in vacuo. The intermediates formed were purified by vacuum
distillation or recrystallization followed by oxidation with
KMn04 in a water/pyridine mixture to give the respective
monosubstituted organosilane dicarboxylic acids. All
monosubstituted organosilane intermediates and dicarboxylic acids
were characterized via Fourier transform infra red (FTIR),
nuclear magnetic resonance (NMR) spectroscopy, and elemental
analysis.
Synthesis of Disubstituted Organosilane Dicarboxylic Acids -
Scheme 2
n-Butyl lithium (10 M) in hexanes (10% molar excess) was
added to a solution of 2,5-dibromo-p-xylene in anhydrous ether at
15-20°C under nitrogen. After one hour, the desired chlorosilane
(10% molar excess) was added dropwise. The process of metalation
and addition of chlorosilane was completed again in order to
obtain the disubstituted product. The intermediates formed were
purified by recrystallization and subsequently oxidized with
KMn04 in a water/pyridine mixture to the respective disubstituted
organosilane dicarboxylic acids. All disubstituted organosilane
intermediates and dicarboxylic acids were characterized via FTIR,
NMR spectroscopy, and elemental analysis.
S1R3 SiR.3
H:-C"~C/ ~CH3 (Fyr idine/Water )*" HOOC^pC-COOH
BuLi
R3Siel
(Ether/o°C)'
Reflux
Scheme 1
Br
'CH3 (Ether/15 - 20°C)'
2BuLi
2R3SXC1
SiR.3
HOOC <(3 COOH
KME1O4
(Pyxidine/Water)
Reflux
Scheme 2
9-5
-------
Alkyd Resin Synthesis - Scheme 3
O OH
ch2—o—I!—(ch2) 9—ch=ch—ch2—in—(ch2) 5-ch3
o
O——(CH;;) 7-CII=CH—(CH2) 7-CH3 +
0 OH
ch2—o—h—(ch2) 9—ch=ch—ch2—(!:k—(ch2} 5-ch3
OH
Stj
-tl2
ch3—ch2—c—ch2
~h2
!)h
1) Monoglyceride process;
ISO 2 2 0°C; lithium ricinoleate
2) Add phthalic anhydride, terephthalic acid/
organosilane diacid; 220°C
P' = H (terephthalic acid)
= SiR.3 (organosilane diacid)
O
OH
ch3—ch2—d:—ch2-o—c—(ch2) 9-ch==ch—CH2—6h (CH2) 5-CH3
it
-H2
c=o
c=o
h2
O
OH
CH3—CH2—CH —CH2—0—C—(CH2) 9-CH=CH—CH2—CH—(CH2) 5—CH3
~h2
Tn
Scheme 3
9-6
-------
Medium oil length polyester resins (55% oil length), were
synthesized via the monoglyceride process.22 The control
formulation was synthesized with LO, trimethylol ethane, phthalic
anhydride, and terephthalic acid. In the experimental
formulations, terephthalic acid was replaced with organosilane
dicarboxylic acid. All alkyd resins were synthesized at an alkyd
constant of 1.04 and 10% excess hydroxy1. The polyesterification
reaction was monitored by titrating the reaction mixture with
alcoholic potassium hydroxide (KOH) and terminated at an acid
value of 8±2 mg KOH/g of sample. The percent non-volatiles of
each alkyd was determined from the weight loss on heating samples
at 150°C until constant weight was attained (ASTM D-1644).
Air Drying Coating Formulation
A control and six experimental air drying coatings were
formulated by adding cobalt, manganese, and zirconium driers,
Activ 8, and Exkin No. 2, to each of the polyester resins. All
formulation components (Table 1) were mixed with a high speed
stirrer at 500 rpm for 15 minutes, and allowed to stabilize for
24 hours prior to application. With a draw-down bar, 4 mils
thick coatings were applied onto a 3" x 6" x 0.2" low-carbon,
mild steel, QD-36 untreated panels previously wiped with methyl
ethyl ketone (MEK). The films were air dried for one week before
testing.
Table 1 - Air Drying Coating Formulation
Ingredient % by Weight
Polyester (80% non-volatiles)
92.50
Cobalt drier (6% metal)
1.10
Manganese drier (6% metal)
0 .70
Zirconium drier (6% metal)
1. 90
Act iv 8
1. 90
Exkin No. 2
1.90
Total
100.00
Alkyd-Melamine Coating Formulation
The control and six experimental polyester resins were
crosslinked with Cargill 23-2317. All coatings were formulated
at 70:30 alkyd-melamine ratio by weight. Nacure 155 was added to
catayze the crosslinking reaction. All the components in the
formulation (Table 2) were mixed with a high speed stirrer at 500
rpm for 15 minutes and then allowed to stabilize for 24 hours
prior to coating application. With a draw-down bar, 4 mils thick
coatings were applied onto a 3" x 6" x 0.2" low-carbon, mild
9-7
-------
steel, QD-36 untreated panels previously wiped with MEK. The
films were heat cured at 120°C for 30 minutes. The cured films
were equilibrated for seven days before testing.
Table 2 - Thermosetting Alkyd-Melamine Coating Formulation
Ingredient % by Weight
Polyester {80% non volatiles) 68.70
Cargill 2 3-2317 (84% non volatiles) 28.00
Nacure 155 3.30
Total 100.00
Alkyd.-Kelamine ratio 'by weight) 70:30
Testing Equipment
Polyester molecular weights were determined with a Perkin
Elmer model 250 binary LC pump, equipped with model 13 ultra-
violet detector. Three gel permeation chromatography (GPC)
columns of pore size 50, 500, and 104 angstroms were placed in
series and calibrated using polystyrene standards. The GPC
results were analyzed with GPC data analysis software from
Polymer Labs (PL Caliber version 5.11). Polyester viscosity was
measured at 80% solids in xylene, on a Brookfield viscometer
model DV-II (ASTM D-2196).
Dry film thicknesses were measured by a Gardco Minitest 4000
Microprocessor coating thickness gauge (ASTM D-1186). Impact
resistance was determined with a BYK Gardner impact tester model
IG-1120, using a 1.82 Kg., 1.27 cm. diameter steel pin (ASTM D-
2794) , Pencil hardness was expressed in terms of pencil leads of
known hardness (ASTM D-3363). Adhesion was assessed by applying
and removing a pressure-sensitive tape over a Crosshatch
constructed by eleven cutting blades (ASTM D-3359). Flexibility
was measured by bending coated panels on a Paul N. Gardner, Model
MN-CM conical mandrel (ASTM D-522).
RESULTS AND DISCUSSION
Gel permeation chromatography data (Table 3), indicate that
the molecular weight of the polyesters ranged from 3500-4100
g/mol based on polystyrene standards. However, the.acid values
for all fell in the 8±2 range thus approximating a molecular
weight of 5500-6500 g/mol.23
9-8
-------
HOOC— C00K
Terephthalic acid
(Control)
COOH
HOOC
2-Trimethylsilyl
terephthalic acid
{Formulation #2)
HOOC
CH3
COOH
2-Dimethylphenylsilyl
terephthalic acid
(Formulation #3)
COOH
HOOC
2-Diphenylmethylsilyl
terephthalic acid
(Formulation #4)
HOOC
COOH
2-Triphenylsilyl
terephthalic acid
(Formulation #5)
HOOC
COOH
2, 5-Di(trimethylsilyl)
terephthalic acid
(Formulation #6)
CH3
HOOC —(^y)—COOH
CH3,
^Si'
XCH3
2,5-Di(dimethylphenylsilyl)
terephthalic acid
(Formulation #7}
Figure 2
Viscosity and appearance measurements are listed in Table 3,
The control, and formulations 2, 3, and 6 were cloudy. On the
other hand, formulations 4, 5, and 7 were clear and lower in
viscosity. The clarity"and reduced viscosity is attributable to
the high reactivity and increased acidity of carboxyl m 2~
diphenylmethylsilyl terephthalic acid, 2-triphenylsilyl
9-9
-------
terephthalic acid, and 2,5-di(dimethylphenylsilyl) terephthalic
acid as a result of (p-d) w bonding.19 The increased reactivity
reduces synthesis time, therefore limiting viscosity increases
due to thermal polymerization. The enhanced acidity of the
carboxyl group and the existence of silane moieties bestows
improved solubility in organic media and thus a clear polyester.
The structure and designation of the dicarboxylic acids used in
the polyester syntheses are included in Figure 2.
Table 3 - Polyester Properties
Formulation
Appearance
Viscosity
Molecular
Acid
Weight
Number
£cps)
(MJ
mg KOH/g
Control
Cloudy
1750
3589
9.6
Formulation
#2
Cloudy
1840
4006
8.5
Formulation
#3
Cloudy
2290
3556
9.4
Formulation
#4
Clear
1140
4079
9.2
Formulation
#5
Clear
830
3812
• 9.5
Formulation
#6
Cloudy
1690
3876
9.4
Formulation
#7
Clear
1040
3913
9.2
The physical properties of the air drying coating
formulations are included in Table 4. All coating formulations
showed excellent impact resistance, flexibility, and adhesion.
However, the control formulation was tacky even after one week
dry time, indicating incomplete curing .via oxidative
polymerization. Pencil hardness data corroborated incomplete
curing of the control polyester. Dry times for the experimental
polymers decreased with increasing aromatic content of
organosilane diacids.
Table 4 - Air Drying Coating Properties
Formulation
Drying
Pencil
Impact
Flexi-
Adhesion
Time
Hardness
Resistance
bility
(hr)
(inch-lbs)
(inch)
Control
>168
-------
The thermosetting polyester-melamine crosslinked film
properties are listed in Table 5. All formulations gave
excellent flexibility, impact resistance, and adhesion.
Crosslink density (MEK rub resistance) and pencil hardness of the
experimental formulations were better than the control, and
improved with increasing aromatic content in the silane diacids;
a feature of increased fp-d) ir bonding.
Table 5 - Polyester-Melamine Coating Properties
Formulation
Pencil
Impact
Flexibility
Adhesion
MEK
Hardness
Resistance
Rubs
(inch-lbs)
(inch)
Control
2H
160+/160+
0 .125
5B
25
Formulation
#2
2H
160+/160+
0.125
5B
25
Formulation
#3
4H
160+/160+
0.125
5B
40
Formulation
#4
4H
160+/160+
0.125
5B
60
Formulation
#5
4H
160+/160+
0.125
5B
75
Formulation
#6
2H
160+/160+
0 ,125
5B
35
Formulation
#7
4H
160+/160+
0. 125
5B
65
CONCLUSIONS
The use of organosilane dicarboxylic acids in LO based
polyesters provided a polyester of lower viscosity than a
corresponding, non-silane modified control polymer synthesized
and formulated to the same molecular weight and non-volatiles,
respectively. In air drying formulations, the organosilane
modified coatings dried faster to harder films. Furthermore,
organosilane, thermosetting polyester-melamine polymers exhibited
improved pencil hardness and MEK resistance, properties accruing
from high crosslink density. The improvements were obtained
without losses in adhesion, flexibility, or impact resistance.
ACKNOWLEDGMENT
This material is based upon work supported by the
Cooperative State Research Service, U.S. Department of
Agriculture, under Cooperative Agreement Number 91-38202-5928.
Our thanks to Dr. Daniel E. Kugler and Mrs. Carmela Bailey for
their time and support.
9-11
-------
REFERENCES
1. Smith Jr., C.R., Wilson, T.L., Miwa, T.K., Zcbel, H.,
Lohmar, R.L., and Wolff, I.A. Lesquerolic acid. A new
hydroxy acid from lesquerella sed oil. J. Org. Che it.. 26:
2903, 1961.
2. Smith Jr., C.R., Wilson, T.L., Bates, R.B., and Scholfield,
C.R. Densipolic acid: A unique hydroxydienoid acid from
Lesquerella densipila seed oil. J. Org. Chem. 27: 3112,
1962.
3. Barclay, A.S., Gentry, H.S., and Jones, Q. The search for
new industrial crops II: Lesquerella cruciferae as a source
of new oilseeds. Economic Botany. 16: 95, 1962.
4. Gentry, H.S. and Barclay, A.S. The search for new
industrial crops III: Prospectus of lesquerella fendleri.
Economic Botany. 16; 2 06, 1962,
5. Mikolajczak, K.L., Earle, F.R., and Wolff, I.A. Search for
new industrial oils - VI. Seed oils of the genus
Lesquerella. J. Am. Oil Chem. Soc. 39: 78, 1962.
6. Carlson, K.D., Chaudhry, A., and Bagby, M.O. Analysis of
oil and meal from Lesquerella fendleri seed. J. Am. Oil
Chem. Soc. 67: 438, 1990.
7. Carlson, K.D., Chaudhry, A., Peterson, R.E., and Bagby, M.O.
Preparative chromatography isolation of hydroxy acids from
Lesquerella fendleri and L. gordonii seed oils, J. Am. Oil
Chem. Soc. 67495, 1990.
8. Achaya, K.T. Chemical derivatives of castor oil. J. Am.
Oil Chem Soc. 48: 758, 1971.
9. Naughton, F.C. Production, chemistry, and commercial
applications of various chemicals from castor oil. J. Am.
Oil Chem. Soc. 51; 65, 1973.
10. Thames, S.F., Bautista, M.O., Watson, M.D., and Wang, M.D.
Application of lesquerella oil in industrial coatings. In:
Polymers from Agricultural Coproducts. ACS Symposium Series
575, 1994. p. 213.
11. Thames, S.F., Wang, M.D., and Yu, H. Dehydrated lesquerella
oil in me1amine¦a1kyd coatings. Submitted for publication
to Industrial Crops and Products, August 1994.
12. Thames, S.F., Edwards, L.H., Wang, M.D., and Yu, H,
Dehydration of lesquerella oil. Accepted for publication in
Journal of Applied Polymer Science, December IS94.
9-12
-------
13. Thames, S.F. and Yu, H. Synthesis, characterization, and
lesquerella oil product in water reducible coatings, in:
Proceedings of the Twenty-Second Annual Waterborne, High-
Solids, and Powder Coatings. Louisiana, 1995, p. 362.
14. Kovacs, H.N., Delman, A.D., and Simms, B.B. Silicon
containing amide, benzimidazole, hydrazide, and oxadiazole
polymers. J. Poly. Sci. A-l, 6; 2103, 1968.
15. Ghatge, N.D. and Jadhav, J.Y. Preparation of silicon-
containing polymers - I. Polyimides from dianhydrides and
organosilicon diisocyanates. J. Poly. Sci.: Chem. Ed.
22 (1) ; 3055, 1983.
16. Mohite, S.S., Maldar, N.N., and Marvel, C.S. Synthesis and
characterization of silicon-containing phenylated soluble
aramids. J. Poly. Sci., Chem. Ed, 26: 2777, 1988.
17. Thames, S.F. and Patel, N. The effects of silicon
incorporation on the performance of epoxy derived powder
coatings. Journal of Coatings Technology. 61(772): 532,
1989 .
18. Pace, S.D., Malone, K.G., and Thames, S.F. Arylsilane
polyarylates: Novel high temperature thermoplastic solvent
cast coatings. Journal of Coatings Technology. 62 {780) :
101, 1990.
19. Thames, S.F., Panjnani, K.G., Pace, S.D., and Blanton, M.D.
Optimizing organosilanes in powder coatings. European
Coatings Journal. 10/94; 705, 1994.
20. Thames, S.F., Panjnani, K.G., Pace, S.D., Blanton, M.D., and
Cumberland, 3.R. Accepted for publication in the Journal of
Coatings Technology, February 1995.
21. Tregre, G.J., Reed, J.S., Malone, K.G., and Thames, S.F.
Novel alternative in high performance clear coats:
Molecular composites utilizing arylsilane aramids, Journal
of Coatings Technology. 63(792): 79, 1991.
22. Oil and Colour Chemists' Association. Manufacture of alkyd
resins. In: Surface Coatings, Vol. I. Tafe Educational
Books, New South Wales, Australia, 1983. p. 65.
23. Oil and Colour Chemists' Association. Vegetable oils. In:
Surface Coatings, Vol. I. Tafe Educational Books, New South
Wales, Australia, 1983. p. 36.
9-13
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POLYESTER OLIGOMERS OF NARROWED MOLECULAR WEIGHT DISTRIBUTION
Roy C. Williams
Richard M. Benton
Robert S. DeRuiter
Reichhold Chemicals
P.O. Box 13582
Research Triangle Park, NC 27709-3582
ABSTRACT
Attempts to reduce the VOCs in thermosetting solvent borne enamels have led to the use
of very low molecular weight polyester oligomers. Unfortunately, traditional polyester
preparation techniques leave relatively large amounts of unreacted polyo Is or polyacids that
contribute to VOC, and still produce molecular weight fractions larger than desired. This leads
to diminishing returns in VOC reductions. A technique is described to narrow this molecular
weight distribution and eliminate low molecular weight residual reactants by a series of
alternating stepwise reactions using oxirane and anhydride reactants. The oligomers produced are
described and characterized, and their performance in high solids baking enamels reviewed.
Difficulties in pigmentation stability in regard to acid catalyst adsorption, gloss and film
performance are described as well as corrective techniques for use with these oligomers.
Lack of high molecular weight fractions and possible ionic content from catalyst-polymer
bonding cause problems in obtaining high resistivity. Synthetic approaches giving higher
aliphatic content in the polyesters which counter this and lead to high resistivity paints are
described.
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
9-14
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BACKGROUND
Polyester oligomers crosslinked with hexamethoxymethyl-melamine(HMMM) type
resins have become increasingly popular as a high solids answer to regulatory demands for
lowered volatile organic compound (VOC) coatings. They offer economical baking enamels of
low VOCs with an excellent combination of hardness, flexibility and resistance properties. The
formula below illustrates such a simple white high gloss baking enamel for spray application.
ILLUSTRATION I
White High Gloss Spray Enamel
Polyester A
Gal.
Material
430.80
13.06
Rutile Titanium Dioxide
172,32
19.02
90% Isophthalic Polyester A
21.54
3.19
n-Butanol
64.62
8.91
Xylene
6.46
0.89
Viscosity Suspension and Sag Control Additive
695.74
45.07
Disperse to 7+ N.S.
278.58
30.75
90% Isophthalic Polyester A
161,55
16.16
Hexamehoxymethyl melamine
4.06
0.51
p-TSA (40% solution)
0.72
0.09
Anti-Crater Additive
53.85
7.43
Xylene
1194.50
100.01
ANALYSIS:
Pigment/Binder Ratio
Percent Solids, Weight
Percent Solids, Volume
Viscosity at 25°C (approx. Seconds, #4 Ford Cup)
Theoretical VOC:
Pounds/Gallon
Grams/Liter
Determined VOC, via ASTM Method D3960
Pounds/Gallon
Grams/Liter
Typical Baking Schedule, Min/°F
0.8/1.0
81.4
69.2
50
1.85
222
2.57
308
15-20/300-350
9-15
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More recently there has been pressure for further VOC reductions; for example, the 2.3
lb/gal or 275 g/1 requirements in California. As the above formula illustrates, there is not really a
lot (15% by weight) of solvent left which can be removed from these paints. This is especially
significant when one considers that a substantial portion of the VOC is alcohols (methanol)
evolved from the crosslinking resin, and some low molecular weight esters. This is illustrated by
a comparison of the theoretical VOC (solvent evolved) with the determined VOC as measured by
ASTM 3960. These crosslinker-derived emissions would represent about 28% of the total from
the paint.
To achieve the solvent reduction needed to meet the newer VOC guidelines, one sees one
has to remove approximately all of the solvent from the Polyester Oligomer A of the above paint
example. This corresponds to approximately an 85% NV white paint as per the above formula. If
one further reduces the molecular weight (MW) of the polyester oligomer in an attempt to
maintain the same viscosity at the reduced solvent level, the determined NV of the polyester does
not rise much above the original 90%. This is due to increased amounts of unreaeted and volatile
glycols and simple esters. Those function at best as weak solvents. Even anticipating that these
would not volatilize from the film because of reaction with the hexamethoxy-methylmelamine
(HMMM) resins, they still lead to diminishing returns in terms of emissions. One must consider
the reaction of propylene or neopentyl glycol with HMMM and the attendant methanol
evolution.
ILLUSTRATION II
H H
I I
HO-C C—OH + HMMM » 2CH3OH
ii A
ch3 h
(76 MW) Volatile •» (64 MW) Volatile
Actually, the diminishing VOC returns seen on molecular weight reduction of these oligomers
has been long recognized as per the 1981 Journal of Coatings Technology article by Belote and
Blount.1
As they discussed in their study of a series of neopentyl-adipic-phthalic polyesters of
varying molecular weights, little VOC reduction was obtained in going below 1000 MW, as is
roughly illustrated below:
9-16
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TABLE I
Mn
Theoretical
VOC
Determined VOC
@ 325°F
Determined VOC
@ 250°F
1400
3.2
3.5
3.2
1200
2.6
3.0
2.8
1000
2.5
2.9
2.7
800
2.4
2.9
2.7
600
2.2
2.9
2.7
Generally this type of phenomenon is noted with the wide variety of polyester oligomers used in
these coatings.
CONSIDERATION OF THE MOLECULAR WEIGHT DISTRIBUTION
Since the molecular weight of these oligomers is low and little is gained by any further
molecular weight reduction, one is led to consider viscosity improvements by manipulation of
the molecular weight distribution. A technique for doing this is discussed below.
NARROWED MOLECULAR WEIGHT DISTRIBUTION TECHNIQUES
The use of certain polyols such as 2.2,4-trimethyl-l,3-pentanediol. having hydroxyl
functionalities of unequal reactivity, can provide self limiting polyester chain growth if carefully
balanced with other polyols.
ALTERNATING STEPWISE REACTION APPROACH
A recognized approach to controlling the molecular weight distribution of such polyester
oligomers is to prepare them in a stepwise fashion at temperatures below those resulting in
transesterification reactions which could broaden the distribution. Ordinarily, one would not do
this in polyesterification reactions due to the time involved in the many steps. The low
molecular weights desired in the oligomers, however, makes the approach feasible. One would
employ a reactant in each step capable of rapidly reacting to completion at lower temperatures.
Thus, one would alternate the different reactants in each subsequent step such that the new
reactant is only reactive with the resultant functionality derived in the prior step, but not with
functionality derived from its own reaction. Thus it theoretically becomes possible to force the
reaction of every initial molecule one time. This is done by balancing the number of moles of
reactant with the equivalents of reactive functionality on the molecule derived in the prior step
and carrying the reaction to completion. The alternation of steps insures that all the molecules are
increased in size only by the increment derived from the reactant and thus remain theoretically
identical
9-17
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Fortunately, two common reaction types offer possibilities for carrying out this approach.
These are the half ester reaction of an anhydride with hydroxyl yielding a carboxyl group, and
the oxirane reaction with carboxyls liberating a hydroxyl. Both can be carried out at 120°C in
one to four hours depending on catalysts chosen.
Since it is desired to build oligomers with functionalities of two or greater, the reaction
would be initiated with a multifunctional molecule. The reaction sequence could thus be seen in
Illustration III with suitable abbreviations.
ILLUSTRATION III
M.W.
HO-R-OH 76
HOOC - Anh-R-Anh - COOII 372
HO - Ox-Anh-R-Anh-Ox - OH 488
HOOC - Anh- Ox - Anh- R-Anh -Ox- Anh - COOII 784
HO - Ox-Anh-Ox-Anh-R-Anh Ox-Anh-Ox - OH 900
Since the number of steps is relatively small to build oligomers of the molecular weight
desired for these low VOC coatings, and the time of each step relatively short, the economics is
not disturbed by lengthy reaction times. The reaction sequence described above would entail
about twelve hours, comparable to conventional polyesterification reaction times.
The immediate question is, whether such a scheme can indeed give oligomers free of side
reactions and of very narrow molecular weight distribution. To investigate this, we prepared an
oligomer from succinic anhydride and cyclohexene oxide (CHOx) using an adipic acid initiator
in five steps (Illustration IV). The results are listed in Tables II and III.
Initiator
+2 Anhydrides
(Anh)
+2 Oxiranes
(Ox)
+2 Anhydries
+2 Oxiranes
9-18
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ILLUSTRATION IV
Step 1: 2 moles of cyclohexane oxide (CHOx) reacted with 1 mole of adipic acid (AdA),
yielding
HO-CHOx-AdA-CHOx-OH (342 MW)
Step 2: 2 moles of succinic anhydride (SU) added yielding
HOOC-SU-CHOx-AdA-CHOx-SU-COOH (542 MW)
Step 3: 2 moles of cyclohexane oxide added, yielding
HO-CHOx-SU-CIlOx-AdA-CHOx-SU-CHOx-OH (738 MW)
Step 4: 2 moles of succinic anhydride added, yielding
HOOC-SU-CHOx-SU-CHOx-AdA-CHOx-SU-CHOx-SU-COOH (938 MW)
Step 5 2 moles of cyclohexane oxide, yielding
HO-CHOx-SU-CHOx-SU-CHOx-AdA-CHOx-SU-CHOx-SU-CHO-OH (1134 MW)
TABLE II
GPC Results
Cyclohexane Oxide-Succinic Anhydride Oligomerization (Against Polystyrene Standards)
Step
Theo. Mn
Mn
Mw
Pd
1
342
325
344
1.06
2
542
500
554
1.11
3
738
691
803
1.16
4
938
845
943
1.12
5
1134
1067
1175
1.10
Conventional
1134
1163
2445
2.10
Indeed, the results indicate very narrow molecular weight distributions are possible.
9-19
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TABLE III
90% Oligomer in Ethoxyethyl Propionate
Step 1 (342 MW)
Step 3 (738 MW)
Step 5 (1134 MW)
80% Solution
Oxirane Anhydride
26 Stokes
649 Stokes
7300 Stokes
49 Stokes
>150 Stokes
USE OF THE TECHNIQUE
Fortunately, there are a good number of economical oxiranes and anhydrides which can
be used to custom design a wide variety of oligomers of different molecular weights and
compositions. Oligomer compositions can be prepared while varying the potential film hardness
from aromatic content, potential flexibility from aliphatic content, reactivity from end group
functionality (hvdroxyl-carboxyl), etc. While higher molecular weight materials can be
prepared, those most suitable for coatings VOC reduction generally consist of three to five steps.
When different anhydrides or oxiranes are used in preparing oligomers, they can be used
in separated steps to keep molecular uniformity. Thus, different reaetants can be kept at the same
position on the oligomer chains, and in the same molar ratio in each chain. For convenience,
they may also be mixed in the same step, which can yield several similar species differing in
composition but relatively close in molecular weight and average viscosity. For example, one
might use an equimolar mixture of phthalic and succinic anhydrides in the second step of a three
step procedure.
PROPYLENE PHTHALATE ADIPATE OLIGOMERS
The GPC data below represents an economical propylene phthalate adipate oligomer
synthesized by a similar route. It is an oligomer with a molar ratio of 4 polyols to 3 poly acids.
A polyester oligomer of essentially the same molar composition was prepared in a
simple, one-step polyesterification process by replacing the propylene oxide with propylene
glycol. Water was removed via a packed-column condenser at 410°F. Viscosity, nonvolatile and
GPC comparisons were run on the two oligomers (Table IV).
9-20
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TABLE IV
Propylene Oxide One-Step
3-Step Oligomer Oligomer
Nonvolatile 94% 92%
95% Viscosity in EEP 227 404
GPC Results
Mn (PS) 863 959
Mw (PS) 1136 1686
Pd (PS) 1.31 1.76
ENAMEL FORMULATION
The reduced molecular weight, narrowed polydispersity, and subsequent reduced
viscosity of these resins, allow enamels to be formulated with significantly lower VQC. For
example, a simple white high gloss baking enamel with the 90% isophthalic Polyester A yields a
determined enamel VOC of 2,6 lbs/gal. In the same formula, two of the reduced polydispersity,
propylene adipate phthalate type polyesters, AR2 and AR3, are used. Their respective enamel
determined VOCs are 2,4 and 2.1 lbs/gal, at the same viscosity. Table V shows the physical
properties of the white enamel films for Polyester A, Polyester AR2 and Polyester AR3.
TABLE V
Comparison of Conventional and Stepwise Polyesters
Enamel Properties
Viscosity, #4 Ford cup (sec.)
det VOC, lbs/gal
Film Properties
(Baked 20 min. @ 350°F)
Pencil Hardness
Impact (direct/reverse)
60°/20° Gloss
Crosshatch Adhesion, 0-5, 5=best
"b" Value Color
The properties are quite similar except for the gloss values. The lower values observed
for the AR2 and AR3 films forced a closer examination as to how these polyesters respond to
common polyester formulating techniques.
Isophthalic
Polyester A
40-50
2.6
Polyester AR2
40-50
2.4
40-50
2.1
4H
4H
3H
60/20
60/20
60/20
94/80
78/38
70/24
5
5
5
-0.2
-0.4
0.0
9-21
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It was realized that lowering both the molecular weight and the polydispersity of these
resins caused them to behave differently, compared to the 90% isophthalic Polyester A,
Specifically, the resins showed differences in both the grinding and the letdown phases of
preparation. Consequently, differences were observed in the appearances of the films that were
formed. By measuring film properties, both physically and analytically, much was learned about
the nature and extent of the differences that these resins showed in response to simple
formulating techniques versus Polyester A. As these phenomena were understood, changes in
the formulation were made, and these are reviewed in the following sections.
SPECULAR GLOSS
As indicated in the previous section, it was immediately observed that substituting the
lower molecular weight polyesters AR2 and AR3, into the simple gloss white formula, produced
films with a lower 60°/20° gloss reading than Polyester A. There are several possible reasons for
this. First, overeatalysis - which could cause some areas of the film to cure faster than others
("hot spots"). This, in turn, could cause uneven film formation yielding surface defects. Second
- catalyst incompatibility - which could cause pigment flocculation, which reduces gloss.2 Third,
poor pigment dispersion - perhaps the result of poor wetting ability of the resins. Fourth,
pigment de-wetting during baking - leading to flocculation during cure.
Experimental testing to the conclusion that the initiator was the main problem. The
addition of 0.1% of dimethyl ethanol amine (DMEA) improved the gloss.
Scanning electron micrographs were taken of films both with and without DMEA. The
high gloss, DMEA containing film was smooth. The low gloss, non-DMEA containing film
appeared rough, with definite signs of Benard cell formation. Both of these observations indicate
an unstable pigment dispersion and possible flocculation, which lower gloss3
Hence, this small amount of DMEA yields high gloss films by either blocking the
catalyst, and/or stabilizing the pigment dispersion. Yet, even though DMEA addition increases
gloss, the flow and leveling of the enamel are not as good as Polyester A. Various slower
evaporating solvents were also tested to improve gloss and low, but the same low gloss and
marginal flow were observed.
CURE STABILITY
As the molecular weight of the polyester was further lowered, from Polyester AR2 to
Polyester AR3, the importance of the pigment dispersion phase became more significant.
Evidence for this came from the cure stability data. Immediately after preparation, a film of the
Polyester A4 enamel cured to an F pencil hardness when baked 15' at 3G0°F. However, after 24
hours, the same enamel would only cure to a 3B hardness. As time went on, the enamel cured to
lower and lower hardnesses, until only a tacky wet film resulted after baking. This indicated that
perhaps the curing catalyst was becoming deactivated. The polyester/Ti02 dispersion was not
9-22
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sufficiently stable, leading to catalyst adsorption and rendering the enamel incapable of
producing a cured, hard film. Such pigment-catalyst interactions have been previously reported.4
To remedy this, many pigment dispersants were tested to attempt to eliminate the
pigment-catalyst interactions. Of the 30 dispersants tested, only dioctyl sodium sulfosuecinate
(DOSS) provided a system with good cure stability, as demonstrated in Table VI.
TABLE VI
Cure Stability on Aging of AR3 White Enamels
Baked 15 min @ 300°F
Film Hardness
Catalyst System
Det. VOC
Initial
24-Hour
7-Day
(lb/gal)
Bake Out
Bake Out
Bake Out
p-TSA
2.00
<5B
<5B
Tacky Film
p-TSA/DOSS
2.15
H
H
H
p-TSA/DDBSA
2.20
H
H
H
The reason that only DOSS is effective at stabilizing the cure is complex. At first it was
felt that it improved and stabilized the pigment dispersion. The DOSS could preferentially wet
the pigment surface and remain there to prevent catalyst adsorption in the can. Also, it may
remain on the pigment surface to prevent any de-wetting and subsequent catalyst adsorption that
may occur during baking. Although this may be partially true, the gloss values remained low,
and the flow and leveling properties still gave indications of partial flocculation. The
improvement in cure properties was related to the strong acid group contained in the surfactant.
DISPERSION STABILITY
Although DOSS, DNNSA, DDBSA and the amine blocked catalysts impart cure stability
to the enamel, they may not aid in pigment dispersion stability. Initially the dispersions show a
7.5 + N.S. Hegman reading and appear glossy, which indicate a good dispersion. However, the
cured films have low gloss, marginal flow and leveling, and very noticeable orange peeling.
These are all signs of poor dispersion stability. This instability can occur either in the can (room
temperature storage), during the shear of spraying, or during the baking process. Yet, it must be
remembered that both the higher and lower molecular weight fractions that are characteristic of
conventional high solids polyesters have been removed. Evidently the absence of these fractions
detracts from the ability of the resin to produce a stable dispersion. Since the commercially
available dispersants proved ineffective, it was thought that replacing some of the polyester
oligomer with a small percentage of a higher molecular weight, better dispersing resin, would
help stabilize the dispersion.
9-23
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Many types of resins that were known to give excellent dispersions were tested. Two of
these, an acrylic (AC1) and a coconut alkyd (ALi) were found to give excellent dispersions.
Table VII shows the properties of each of these resins.
TABLE VII
Resin Properties of Coconut Alkyd - AL1 and Acrylic AC 1
ALI
AC1
Resin NV - Percent Solids, Wt.
60
69-71
Resin Vise. Stokes
36-64
98 -148
Color
3 max.
5 max.
Specific Gravity 25°C/25°C
—
1.04-1.06
Pounds/Gallon, solution
8.7
8.7
Acid Value, on solids
6-10
60-70
Hydroxyl Value
90-110
33
Solvent
xylene
2-butoxy-ethanol
MW
17,391
15,882
MN
2,346
4,815
PD
7.41
3.30
In addition to stable dispersions, these resins also imparted cure stability, excellent flow
and leveling, high gloss, minimal orange peel and high depth of image (DOI). Also, scanning
electron micrographs (SEM) of films with the coconut alkyd versus ones without it show a
smooth film versus a bumpy one. X-ray analysis of these same surfaces show well dispersed
titanium in the coconut alkyd containing film, whereas the film without it shows that the bumps
contain flocculates of titanium. Tables VIII and IX show the cure stability and gloss
improvements over the system without these.
TABLE VIII
Cure Stability of AR3 versus AR3 + ALI, and AR3 + AC1
15 Min @ 300°F Pencil Hardness
20 Min @ 350°F Pencil Hardness
Resin
Initial
Bakeout
24-Hour
Bakeout
4-Weeks
Bakeout
Initial
Bakeout
24-Hour
Bakeout
4-Weeks
Bakeout
AR3
SB
<5B
<5B
4H
4H
4H
AR3 + AL1
H
H
H
4H
4H
4H
AR3 +AC1
H
H
H
4H
4H
4H
9-24
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TABLE IX
Film Properties of AR3 versus AR3 + AL1 and AR3 + AC1
15 Min @ 300°F
20 Min @ 350°F
"b"
"b"
Det.
Pencil
60/20
Value
Impact
Pencil
60/20
Value
Impact
VOC
Reason
Hard.
Gloss
Color
Resist.
Hard.
Gloss
Color
(D/R)
(lb/gal)
AR3
<5B
—
—
—
4H
82/45
+0.1
80/20
2.1
AR3+AL1
H
95/88
-0.8
120/80
4H
96/89
+ 1.0
80/20
2.3
AR3+AC1
H
94/85
-0.7
100/60
4H
94/81
-0.4
80/20
2.3
Note that even though these higher molecular resins are used as dispersing aids, the VOC
of the enamels is still only 2.3 lb/gal, versus the 2.6 value observed for Polyester A.
The high molecular weight of grinding resins can be directly contrasted to the effect of
the high molecular weight fractions of Polyester A (2.6 lb/gal). By examining the molecular
weight values for all of these resins, a reason for the above observation becomes apparent
In Polyester A, the MW and MN are 1584 and 824, respectively. Thirty percent of the
chains range between 2649 and 5715 molecular weight (21% on total resin solids), and the white
enamel VOC is 2.6 lb/gal. For AR3, MW and MN are reduced to 755 and 567, respectively,
with 30% of the chains being 1000-2100 molecular weight, which is less than half the value of
the high molecular weight fraction in Polyester A, This difference allows the reduction of the
VOC from 2.6 lb/gal to 2.1 lb/gal.
In the coconut alkyd, MW is 17,391 and MN is 2346, with 30% of the alkyd ranging
26,000 to 238,000 molecular weight. When used with AR3, only 5-10% on total resin solids is
necessary to give the desired enamel properties. This is much less than the 21% of the higher
molecular weight, viscosity contributing material that is present in Polyester A. Hence, although
the alkyd improves the enamel properties, it only increases the VOC from 2.1 to 2.3 lb/gal,
which is less than the 2.6 lb/gal value for Polyester A. The effect with the acrylic is similar. Its
MW is 16,000 and MN is 4815, with 30% of the chains ranging 20,000-71,000 molecular
weight.
WEATHERING RESISTANCE
While it has been shown that the enamel physical properties of a conventional high solids
polyester (isophthalic Polyester A) are not sacrificed when reducing both the molecular weight
and the molecular weight distribution, the weathering properties must also be tested.
9-25
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It is interesting to compare the QUV performance of the lower molecular weight
Polyesters AR2 and AR3 with Polyester A. It is believed that poor pigment dispersion stability
is responsible for cure and flow deficiencies in AR3 enamels. However, co-grinding with the
alkyd (AL1) or acrylic (AC1) improved the flow and cure stability properties significantly.
Based on these results, one might also expect the alkyd and the acrylic to improve AR3 QUV
resistance. Yet, Table X shows that this is not the case for the alkyd. Contrarily, the acrylic does
give noted improvement. This suggests that there may be a difference between how well these
resins protect the pigment surface when exposed to QUV. It has been previously shown that the
formation of free radicals from the exposed pigment can be one of the most effective catalysts for
resin degradation and poor QUV resistance. *6 Coconut alkyds, in general, do not perform as well
as acrylics in the QUV. This difference is manifested here when they are co-ground into the
AR3 enamels.
TABLE X
QUV Yellowing/Gloss Loss Resistance of Gloss White Enamels
Baked 20 Min @ 350°F
Initial
112 Hours
240 Hours
544 Hours
"b"
"b"
"b"
"b!5
Gloss
Value
Gloss
Value
Gloss
Value
Gloss
Value
Resin
60/20
Color
60/20
Color
60/20
Color
60/20
Color
AR1
93/78
+0.9
76/63
+1.5
75/32
+2.1
54/12
+1.2
AR2
92/68
+0.5
81/46
+2.4
20/3
+2.9
4/2
+2.7
AR3+DOSS
94/75
+0.8
73/35
+4.3
26/4
+4.6
13/2
+4.3
AR3+AL1
92/72
+1.8
77/40
+2.1
49/12
+2.7
8/2
+2.9
AR3+5% AC1
95/89
+0.7
88/65
+0.9
59/21
+1.1
31/4
+2.0
AR3+10% AC1
94/84
+0.7
88/64
+1.9
63/20
+0.7
27/3
+2.0
RESISTIVITY
The conductivity of a polymer and its solutions is generally described as being directly
related to concentration and to mobility of ions passing through it under a charge potential. To
minimize conductivity of a polymer solution and maximize its inverse or resistivity, it is desired
to decrease the concentration or solubility of ions in it. Also increasing the intrinsic viscosity and
thus resistance to ion transport raises the resistivity. The latter, of course, is the opposite of what
is needed lower the VOC in paints. Thus, removing the high molecular weight fractions as is the
case with the stepwise polymers removes that which contributes most to chain entanglement and
intrinsic viscosity.
Thus as is the case with high solids polymers and their paints in general, it was desired to
raise resistivity by use of non-polar solvents such as xylene, and to thus minimize the solubility
of ions such as those of the acidic catalysts within the paints. These approaches were insufficient
in the case of the stepwise polymers such as AR2 and AR3. Resistivity in paints such as the
9-26
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white gloss enamel were still below 0.1 megaohm. The resistivity was considerably lower than
would be expected, and this lead to the suspicion that ionic contribution was being made by
catalyst residues still bonded to the polyester and thus soluble and conductive in the organic
medium.
It was thus desired to raise the resistivity of the stepwise oligomers by use of polyester
components which would raise the aliphatic content and provide branching and molecular
structure favorable for resistivity. These would also hopefully provide a less favorable media for
the solubility of ionic polymeric species.
With the use of branched components inserted into the stepwise oligomers structure, it
was possible to prepare paints of high resistivity. In the gloss white enamel formula of the prior
illustrations, VOCs below 2.3 lb/gal at 45 sec". #4 Ford Cup were obtained with the oligomers
designated AR90 and AR93. Resistivities are on the order of one to three megohms. The paints
showed stable cure rates and the resultant films showed high gloss with an excellent combination
of hardness and flexibility as well as resistance to accelerated weathering as per Table XI below;
TABLE XI
Oligomers for High Resistivity
NV
Viscosity
OHV
AR90
97 (1% solvent)
450 Stokes
145
250 Stokes
130
95 (5%)
AR93
White Gloss Formula
VOCs lb/gal
Mega Ohms
Viscosity #4 Ford
2.2
2.1
45 Sec
2.3
1.5
45 Sec,
Films 20 Min @ 350°F
Pencil Hardness
Impact in/lb
Gloss 60°/20°
After 400 Mrs QUV
4H
60/10
93/83
67/27
2H
80/20
93/87
54/18
9-27
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CONCLUSIONS
The stepwise molecular weight Polyester AR90 is capable of providing an oligomer
which will produce films with the same high quality properties as higher molecular weight, lower
solids polyesters, at a much lower determined VOC. These low VOCs cannot be achieved by
lowering the molecular weights of conventionally produced polyesters. Variations in the
properties can be made by the use of pigment dispersants and co-grinding resins. These studies
indicate the need for substituting some of the polymer with a better dispersion resin, to obtain the
best pigment dispersion, cure stability, flow and leveling, gloss and DOI. This suggests that
when removing the low and high molecular weight fractions that are present in conventional high
solids polyesters, the resin becomes less capable of giving a stable pigment dispersion.
The regulations are also reported to be changing downward in VOC allowances and it is
not clear where they will stop. Table XII below which shows VOC versus paint reduction
viscosity indicates that the narrowed molecular weight distribution polyesters maintain or
improve their VOC advantage at the higher viscosities.7,8 The VOC range of 1.3 to 1.5 lb/gal is
therefore possible using application equipment designed to spray these higher viscosities. With
crosslinkers which would not have emissions by-products VOCs below 1.0 lb/gal might be
possible with such equipment,
TABLE XII
VOC vs. Viscosity of Application
VOC
VOC
Polyester
Trade Name
50 sec. #4 Ford
250 sec. #4 Ford
A
Aroplaz 6768
2.6 lb/gal
1.9 lb/gal
Aroplaz 6755
2.8 lb/gal
2.1 lb/gal
AR2
2.3 lb/gal
1.4 lb/gal
AR90
Aroplaz 6820
2.2 lb/gal
1.3 lb/gal
AR93
2.3 lb/gal
1.4 lb/gal
9
-28
-------
1 Belote, S.P., and Blount, W.W.. "Optimizaing Resins for Low VOC", Journal nf
Coatings Technology. 51, (681), 33, 81.
2 Calbo, L.J., "Catalyst Selection for High Solids Coatings",
September, 1982, p. 18
Hansen, C.M., "Organic Solvents in High Solids and Water-Reducible Coatings",
Progress in Organic Coatings, 1Q, 331,82.
4 Kaluza, U., "Flocculation of Pigments in Paints - Effects and Causes", Progress in
Organic Coatings. 1£L 289, 82.
5 Morrison, W.J., Jr., 'Adsorption of Acid Catalyst onto Ti02 Pigments", Polymeric
6 Volz, H.G,, Gunther, K., Fitzky, H.G., "Surface Reactions on Titanium Dioxide
Pigments in Paint Films During Weathering", Progress in Organic Coatings. 2,223, 73/74.
7 J.O.A.P.S.. 22,1989, pp. 1753-1776.
8 L. Matejka et al„ J. Polvm. Sci. Polvm. Chem. Fit. 21,1983, p. 2873.
9-29
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New Epoxy/Anhydride Chemistry for
Durable, High Solids Coatings
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
Michael L, Gould
The Dow Chemical Company
Resin Products R&D, B-1603
2301 N. Brazosport Blvd.
Freeport, TX 77541-3257
Marvin L. Dettloff
The Dow Chemical Company
Resin Products R&D, B-1S11
2301 N, Brazosport Blvd.
Freeport, TX 77541-3257
INTRODUCTION
Heightened concern for the environment across many segments of America has led to
increasingly stringent regulations regarding the use of volatile organic compounds (VOC) in
coatings, cleaning solutions, adhesives and sealants, refrigerants and fuels1. Embodiment of this
concern has taken forms as diverse as comprehensive governmental regulations and increased
consumer demand for products produced by "green" technologies. Probably the most pervasive
of regulations are the Clean Air Act Amendments of 1990 which have brought about major
changes in approaches to formulation and application of coatings, among other things.
A survey of trade literature and technical journals in recent years suggests that changes
in technology to accommodate lower VOC coating formulations have been rapid and effective.
However, in the manufacturing and service sectors of US industry the high cost of capital, high
potential product liability and general concern for customer satisfaction comprise a formidable
inertia to change coating systems unless there is absolutely no choice in a given situation.
Today's regulatory climate provides a powerful economic stimulus to implement new, compliant
technologies.
OEM Automotive Coatings
Automotive manufacturing in North America is a microcosm of the general coatings
industry. Auto OEMs have their own particular material and capital cost constraints to work
within, but in terms of performance, they have the strictest requirements of any segment of the
weatherable/durable coatings industry. Coatings which will satisfy automobile manufacturers
will likely meet or exceed the performance expectations of all other segments provided that the
coating chemistry is applicable to those other segments.
9-30
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Automotive coatings technologies have undergone substantial change in the last twenty
years and will likely see even further change shortly before the turn of the century, A significant
shift in performance focus has occurred in the last decade due to increasing liability concerns
associated with "environmental etch" — the physical erosion of coating material on vehicles
exposed to acid rain. While acrylic melamine chemistry continues to enjoy favored status in
terms of overall material volume applied on North American automobiles, it has become the
target chemistry for improvement or replacement by new, "etch-resistant" coating systems in
topcoat applications. These new systems present opportunities for suppliers to participate in
providing coating systems, raw materials and equipment to manufacturers for future generations
of vehicles.
The most prominent recent trend, considering both performance and regulatory factors, is
to utilize "high solids" (3.5 lbs VOC/gallon or less) coating systems. For instance, a low VOC
electrocoat primer might be followed by a waterborne or powder primer surfaeer. Basecoat may
be either waterborne or solventborne. The clearcoat, which provides the smoothness, depth and
luster to the vehicle can then be applied as a medium to high solids solventborne system with
traditional equipment. With this integrated systems approach, total VOCs in pounds per
manufacturing site can be controlled by careful production scheduling.
Increasingly strict regulatory requirements will stimulate the evolution of automotive
coatings technology in the near future2. Technical strategies to meet the demands of lower site
emissions include:
1) abatement of emissions "at the stack" after application on the paint line3
2) wider implementation of novel application technologies like supercritical C02 spray4
3) increasing use of non-volatile reactive solvents
4) increasing use of waterborne coatings
5) increasing use of powder coatings
6) reduction in molecular weight/viscosity of coating resins to afford higher solids
Implicit in these strategies are advantages and limitations that will ultimately drive one
approach further than the rest as the "best available technology". Strategy one is probably the
least attractive due to high capital equipment costs and tax considerations, and general preference
for source reduction strategies upstream of the abatement option5'6. Strategies two through five
will likely produce one dominant driver at some point in the future.
For the present, that leaves strategy six as the most likely area in which immediate
coatings system improvements will be made. These improvements will necessarily comprise
more than just incremental performance enhancements; cost and product stewardship concerns
will be critical factors which must be considered during the research and development phases of
new materials.
DURABLE, HIGH-SOLIDS SOLVENTBORNE COATINGS
The following discussion focuses on the application of novel technology to category
six -- higher solids solventborne systems via reduced molecular weight/viscosity of system
components.
9-31
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High solids solventborne epoxy/acid and epoxy/anhydride systems for automotive
clearcoats began to appear in the literature in the mid to late 80s7,8. While there was some
established history for the use of "epoxy/carboxy" chemistries in durable coatings applications,
this was nonetheless an unexpected challenge to the perceived preeminence of polyurethane
chemistry and was especially significant in light of the common perception that epoxy resins
(i.e., aromatic glycidyl ethers) don't "weather" well.
Traditional applications of epoxy/acid chemistry in durable coatings include systems as
diverse as multifunctional epoxies reacted with dicarboxylic acids, multifunctional (alkyl) acrylic
acids reacted with difunctional epoxies and multifunctional (alkyl) acrylic epoxies reacted with
multifunctional carboxylic acids9. Principal advantages of epoxy/acid chemistry include low raw
material cost, excellent film appearance, durability and environmental etch resistance10. In
addition, the chemistry is versatile enough to produce ambient or elevated temperature cure with
common catalysts. Epoxy/acid systems can be applied as solventborne, powder or waterborne
coatings.
Traditional applications of epoxy/anhydride chemistry are somewhat more limited.
Typical anhydride resins used in durable coatings are comprised of polymers based on maleic
or itaconic anhydrides11. These are commonly crosslinked by difunctional epoxy resins,
multifunctional (alkyl) acrylic epoxies or both. Some references are made to lower molecular
weight compounds such as methyl hexahydrophthalic anhydride (MHHPA) being used to
crosslink multifunctional epoxies9-12, but concerns about the pulmonary toxicity of these
materials limits their efficacy in spray applications.
In each of the above cases, the anhydride moiety is a five-membered cyclic structure:
o
Figure 1. Five-membered cyclic anhydride
However, other permutations of the anhydride linkage are possible; poly alkyl poly anhydrides
(e.g., poly adipic poly anhydride) are anhydride-"bridged" linear polymers which can react in the
presence of strong nucleophiles to produce polyesters and/or polyamides, for instance.
Another distinct example of the anhydride functional group is a linear linkage as
described above, but with one end pendant to a larger structure such as a polymer or oligomer
"backbone". Such structures, insofar as their utilization in coatings, were unreported until
recently13'14. This paper deals with some of the features of materials which contain linear
pendant anhydride (LPA) moieties.
9-32
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Linear Pendant Anhydrides (LPA)
The simplest representation of this class of materials is seen in Figure 2: the anhydride
linkage is terminated by a simple alkyl group (R') on one side, and attached to a central moiety
or backbone (R) on the other.
The nature of LPA resins is substantially affected by the structures of R and R' and can be
specifically tailored to meet desired performance criteria. For instance, where R is a polymeric
backbone, high Tg, high-melting friable solids are easily isolated from process solvents. By
contrast, where R is a multifunctional polyester oligomer, lower Tg, low-melting solids can be
isolated.
Where R' is methyl, cure with epoxy resins and suitable catalysts can be realized at
ambient to bake temperatures; where R' is a higher order residue, such as an isobutyl or t-butyl
group, cure is difficult even during extended bake times at high temperatures. LPA resins
terminated with substituted alkyl groups can be formulated to stable one-package coatings;
partially aeylated LPA resins have very high reactivity and relatively short pot lives when
formulated as single-package coatings.
The following examples comprise actual formulations with spray viscosities, application
parameters and coatings evaluation data. A thorough description of each system is included for
purposes of illustrating the wide range of binders/crosslinkers which can be utilized.
Additives to the fully formulated systems were based on weight percentages of total resin
solids (TRS). Equivalent weights are expressed on a solution basis. All formulations included
Tinuvin® 292 hindered amine light stabilizer (HALS) at 1%, Tinuvin® 384 ultraviolet absorber
(UVA) at 1.5%, BYK 358 flow control agent at roughly 0. 1% and phosphonium catalyst at 2%.
Each formulation was "let down" to spray viscosity (35 +/- 1 Zahn #2 seconds) with DowanoKD
PMA.
Formulations were spay-applied through a standard siphon-feed pneumatic spray gun
to bare polished steel or waterborne basecoat on electrocoated steel. Typical spray parameters
were 70 psi line pressure, 6 psi cup pressure. Panels were "flash dried" for 5-10 minutes and
then baked at 265-285 deg. F in a forced-air oven for 30 minutes. Physical properties were
typically measured within twenty-four hours after bake.
Tinuvin® is a trademark of Ciba-Geigy Corporation
Dowanol® is a trademark of The Dow Chemical Company
O o
n
Figure 2. Generic linear pendant anhydride (LPA)
FORMULATION AND APPLICATION OF LPA-BASED COATINGS
9-33
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Each formulation was measured for actual solids (ASTM D-2369) and contrasted with
theory. Discussion of that particular measurement follows the formulation and performance
inventory for systems I-VI. Other performance parameters of interest included 20 degree gloss
over basecoat, DOI (distinctness of image), Knoop Hardness and Gardner Impact resistance. A
brief discussion of durability performance also follows the next section.
Formulation I: LPA Copolymer and Difunetional Glycidyl Ester
The LPA binder was the acetylated product of a 25% (w/w) methacrylic acid copolymer, with
a balance of acrylic co-monomers and styrene, Diglycidyl-1, 2-cyclohexane dicarboxylate, a
low viscosity liquid epoxy resin, was utilized at 100% solids as the crosslinker.
Component
Anhydride Binder Resin (66.3% solids; 867 FEW*, solution)
Diglycidyl-1,2-cyclohexane dicarboxylate (159 EEW*)
Tetraphenyl phosphonium bromide (30% solution)
Tinuvin 292
Tinuvin 384
BYK 358
Dowanol PMA
i Weight (g) |
sdo 1
| 5.25
0.79 |
. 1.18
" 0l6™ ™ |
38.6
Theoretical system solids = 54.3%
Measured system solids = 52.8% +/- 1.2
Zahn #2 time = 353*secoiHiT™Bake30*mmHesW^M1degrF™™
Film Thickness
2.69 +/- 0.09 mils
MEK Resistance (# double rubs to failure)
Gloss (20 degree over basecoat)
Distinctness of Image
Knoop Hardness
200+
84 +/- 1
"90+/-2 |
2.9+/-0.10
5% NaOH (24 hour spot test)
10% H2SQ4 (24 hour spot test)
Gardner Impact (steel only)
Pass (no staining or spotting)
Pass
80 in-lb forward
20 in-lb reverse
*FEW = Functional Equivalent Weight; EEW = Epoxide Equivalent Weight
9-34
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Formulation II: Tetrafunetional LPA Oligomer and GMA Copolymer
The GMA copolymer binder was based on 40% (w/w) glycidyl methacrylate "loading" in the
monomer feed with a balance of acrylic co-monomers and styrene. The theoretical Tg of the
GMA copolymer [Fox method15] was calculated to be 34 deg. C. The measured Tg [DSC
method] was 36.6 deg. C. The LPA oligomer was the acetylated product of pentaeiythritol
reacted with a 50/50 weight blend of MHHPA/HHPA.
Component
Weight (g
GMA Copolymer Binder Resin (63.9% solids; 534 EEW)
85.3
Tetrafunetional LPA Oligomer (81.0% solids; 340 FEW)
b solution
etrapnen
Tinuvin 292
Tinuvin 384
BYK 358
Dowanol PMA
on mm
romi
easure
stem son
Zahn #2 time = 34.9 seconds. Bake 30 minutes at 265 de
Film Thickness
2.86 +/- 0.17 mils
MEK Resistance (# double rubs to failure)
I 200+
Gloss (20 decree over basecoat
lstmcmess oi image
noop Hardness
5% NaQH (24 hour spot test)
10% H2SQ4 (24 hour spot test)
Gardner Impact (steel only)
Pass
60 in-lb forward
10 in-lb reverse
9
-35
-------
Formulation III: Trifunctional / Tetrafunctional LPA Oligomer and GMA Copolymer
The GMA copolymer binder used was as described in Formulation II. The LPA oligomer was
the acetylated product of a 50/50 weight blend of trimethylolpropane and pentaerythritol reacted
with a 50/50 weight blend of MHHPA/HHPA.
Weight (gj
Component
GMA Copolymer Binder (63,9% solids; 534 EEW)
LPA Oligomer Blend (71.9% solids; 413 FEW)
Tetraphenyl phosphomum bromide (30% solution)
Tinuvin 292
Tinuvin 384
BYK 358
Dowanol PMA
Theoretical system solids = 59.7%
Measured system solids = 57.9% +/- 0.4
Zahn #2 time = 34.7 seconds. Bake 30 minutes at 265 deg. F
Film Thickness
2.88 +/- 0.13 mils
MEK Resistance (# double rubs)
Gloss (20 degree over basecoat)
200+
84+/-1
92 +/- 2
103+^0.36
60 in-Ib forward
10 in-lb reverse
distinctness or ima;
Knoop Hardness
5% NaOH (24 hour spot test)
10% H2SQ4 (24 hour spot test)
Gardner Impact (steel only)
9-36
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Formulation IV: Difunctional LPA Oligomer and GMA Copolymer
The GMA copolymer binder used was as described in Formulation II. The LPA oligomer was
the acetylated product of neopentyl glycol reacted with a 50/50 weight blend of MHHPA/HHPA.
Component
GMA Copolymer Binder (63.9% solids; 534 EEW)
"Afunctional LPA Oligomer (81.6% solids; 412 FEW, solution)
Tetraphenyl phosphonium bromide (30% solution)
Tmuvin 292
Tinuvin 384
BYK 358
Dowanol PMA
Theoretical system solids
66.5%
Measured system solids = 62.5% +/- 0.3
Zahn#
seconds
Bake 30 minutes at
time
).29 mils
Film Thickness
MEK Resistance (# double rubs to failure)
Gloss (20 degree over basecoat)
83 +/- 1
Distinctness of Imag
6.49 +/- 0.26
Pass
Pass
40 in-lb forward
Knoop Hardness
5% NaOH (24 hour spot test)
10% H2SQ4 (24 hour spot test)
Gardner Impact (steel only)
<5 in-lb reverse
9-37
-------
Formulation V: Tetrafunctional LPA Oligomer and Difunctional Glycidyl Ester
The glycidyl ester crosslinker was defined in experimental formulation I. The LPA oligomer
was the acetylated product of pentaerythritol reacted with a 50/50 weight blend of
MHHPA/HHPA.
"Component
Weight (g)
TetiifunHional^LPA 'T)fligom^
Digjycidyl-1,2-cyctohexane"^dicaito^yfate (159 EEW)
70.0
Tetranhenvl
hosphonium bromide (30% solution
Tinuvin 292
T** * O
Tinuvm 3
BYK 358
Dowanol PMA
Theoretical system solids
Measured system solids = 63.9% +/- 0.5
Zahn #2 time = 34.6 seconds. Bake 30 minutes at 285 dee. F
Film Thickness
2M+/- 0.23 mils
+
82 +7-1
MEK Resistance
# double rubs to failure
Gloss (20 degree over basecoat)
Distinctness of Ima
Knoop Hardness
8.13+/-0.70
NaOH (24
ur spot test)
H2S04(24
tour spot test)
dner Impact
steel only)
40 m-lb forward
<5 m-lb reverse
9-38
-------
Formulation VI:
Glyeidyl Ester
Trifunctional / Tetrafunctional LPA Oligomer and Difunctional
The glyeidyl ester crosslinker was defined in experimental formulation I, The LPA oligomer
was the acetylated product of a 50/50 weight blend of trimethylolpropane and pentaerythritol
reacted with a 50/50 weight blend of MHHPA/HHPA.
T^ponent
"Weight (g)"
LPA Qligomerllend(71.9%'solldi
413 FEW)
Diglycidyl-l,2-cycIohexane dicarboxylate (1:59 £EW)
Tetraphenyl phosphonium bromide (30% solution)
Tinuvin 292
70.0
Dowanol PMA
Theoretical system solids = 710%
Measured system solids = 69.9% +/- 0.2
Zahn #2 time = 35.2 si^
Film Thickness
MEK Resistance (# double rubs to failure) ~ 1200+
Gloss(20deCT^ "" [83 +7-T
Dxstinrtnessof Image "
Knoop Hardness " '' ' ~ ' j 6^59 H7-TT76"
?%rNa"OH (24 hoTir spot test) ~ """" - "Tpa~Ss'L
10% H2SQ4 (24 hourlpot test) [ Pass
Gardner ImpET(S^^
<5 in-lb reverse
RESULTS AND DISCUSSION
The principal objective of contrasting the previous six experimental formulations was to
demonstrate the versatility in enhancing theoretical system solids by making subtle changes in
the architecture of the constituent binder and crosslinker resins. LPA resins are inherently simple
to design; the ultimate performance goal of a coating system should be achievable by simple
experimentation with different LPA structures. Where very high solids (<2.6 lbs VOC/gal) are
desired, and where high crosslink density can be tolerated, a system such as experimental
formulation #6 is feasible. Where a softer, more flexible coating formulation is desired, and
where higher VOC levels can be tolerated, a system such as experimental formulation #1 is
indicated.
9-39
-------
Table I summarizes the six experimental systems, and a "standard" polyester polyol / HDI
trimer polyurethane system from the perspective of formulation solids at roughly comparable
viscosity. The systems are rank-ordered from lowest solids to highest solids, with no other
performance parameters considered. Numbers in parentheses under System / Description
indicate the theoretical functionality of the LPA oligomers).
Table I. Rank-Order of Experimental Formulated Systems by Theoretical Solids
System / Description Zahn #2 Theoretical Solids Measured Solids
Viscosity (sec,) (% w/w) (% w/w)
#1 - LPA Polymer/diglycidyl 35.3 54.3 52.8+/- 1.2
ester
"Standard" - Polyester polyol / 34.3 54.9 54.8 +/- 0.0
HDI Trimer Polyurethane
#2-LPAOligomer(4)/40% 34.9 56.6 54.8+/-0.2
GMA Copolymer
#3 - LPA Oligomer (3 + 4) / 34.7 59.7 57.9+/-0.4 '
40% GMA Copolymer
#5 - LPA Oligomer (4) / 34.6 64.2 63.9+/-0.5
diglycidyl ester
#4-LPA Oligomer(2)/40% 33.8 66.5 62.5+/-0.3
GMA Copolymer
#6-LPA Oligomer (3+ 4)/ 35.2 71.0 69.9+/-0.2
diglycidyl ester
With concern for VOCs in coating formulations being a primary driver for new
technology development, the delta between theoretical and actual (measured) solids in the
experimental systems deserves some attention. In effect, there are two primary forces at work
which lead to a loss of some of the system "solids": 1) volatility of the constituents and 2) self-
condensation of LPA functional groups to form an intermolecular linkage and liberate a volatile
symmetrical anhydride. Both phenomena lead to an undesirable increase in measured VOC and
are related to the degree that each exacerbates the other.
In formulations such as #1, #2, #3 and #4 where one of the constituents is a polymer, fast
vitrification of the film leads to a higher probability of unreacted low molecular weight material
vaporizing from the matrix. This is nicely contrasted in formulations #1 and #4 where each
system has a two-functional component. System #4 in particular loses 4% of its theoretical
solids due to the loss of the volatile two-functional LPA molecule. System #1 utilizes a less
volatile two-functional diglycidyl ester, which nonetheless will volatilize when tested alone by
ASTM D-2369.
9-40
-------
In the second situation described previously, the LPA functional group can condense with
itself to liberate a volatile symmetrical anhydride, acetic anhydride (III) in the cases of the resins
formulated for this study:
Rl
i? St QO GO r*n
f
-------
In the present study, durability testing requiring extensive investment of time was not
possible. However, Figure 2 represents accelerated durability testing by QUV® 313b conducted
in this laboratory for analogous formulations. The curves depicted in the graph represent average
20 degree gloss readings for six panels distributed randomly in two QUV cabinets. Error bars
are not included, nor are the ordinate values expressed as percent retention of initial gloss,
because the time to failure of these systems is substantially different from one another.
90-
50 1
30
Polyurethane "Standard**
LPA/rjon-acrylic glycidyl ester
LPA/GMA-40 Copol
Epoxy / Pciyester-Acid System
10-
1 1 I' I t »
2000 4000 6000
Hours in QUV @ 313b Exposure (With Moisture)
8000
Figure 4. Gloss Retention of Epoxy / LPA Systems Versus "Standards" in QUV Testing
For the purposes of this study, four systems have been represented: 1) polyester polyol/
HDI trimer polyurethane "standard" [experimental system #7)], 2) LPA oligomer / glycidyl ester
system [similar to experimental systems #5 and #6], 3) LPA oligomer / 40% GMA copolymer
[experimental system #2] and 4) 40% GMA copolymer with saturated acid-functional polyester
crosslinker. Each system was stabilized as reported for the experimental formulations in this
study: 1% HALS and 1.5% UVA by weight based on total resin solids. The testing cycle was
4 h UV/60 deg. C,4h CON/50 deg. C as per ASTM D-4587.
QUV® is a trademark of The Q-Panel Company, Cleveland, OH
9-42
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A cursory analysis of Figure 2 suggests that while "standard" polyester urethane and
epoxy / acid clearcoat systems have excellent durability in this test to about 5000 hours exposure,
the two LPA-based systems have even greater durability. System #2 was removed from the test
condition after 9600 hours with over 70% retention of initial gloss. None of these test systems
was optimized, although previous extensive experience with the polyurethane system led to its
adoption as the "standard" for comparative purposes in this ongoing testing program.
CONCLUSIONS
In an effort to address the major driving forces for new technology development in
durable coatings applications, a new epoxy-based chemistry was introduced. Performance
standards for automotive coatings were chosen as a target in an evaluation of typical coating
performance parameters including appearance, flexibility, solvent resistance and durability in
accelerated laboratory testing. Perhaps the most important picture this study paints for the
research community is that epoxy-based coatings, traditionally thought of as non-weatherable,
are very durable while meeting all other requisite performance criteria.
Driving forces to lower VOC levels in paint systems while improving appearance,
durability and reducing or minimizing cost will continue to force the evolution of new
technologies. "Epoxy / car boxy" chemistry, one of the newest challengers in the marketplace,
is substantially qualified to address these driving forces. In particular, linear pendant anhydride
(LPA) / glycidyl ester technology offers tremendous latitude in binder / crosslinker architecture
to address solids, flexibility and durability.
Very high solids formulations (< 2.6 lbs. VOC / gal) applicable to traditional application
equipment are possible with this chemistry. Future work will explore alternative application
methods for LPA-based systems. Exploration of system improvements will focus on laboratory
evaluations of etch resistance and scratch / mar performance relative to standard paint systems.
ACKNOWLEDGMENTS
The authors would like to acknowledge the valuable contributions of W. C. Cunningham, S. K.
Falcone, R. A. Hickner, R. R. Moore, D. L. Parker, J. A. Rabon and M. Tran in the creation and
testing of materials for this study.
9-43
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13. Isozaki, Osamu, et. al., JP 05,295, 236 (1993). Chem. Abstracts 120: 273208s.
14. Gould, M. L., et. al., WO 94/11415 (1994).
15. Fox, T. G„ Bull. Am. Phys. Soc., i (3), 123 (1956).
9-44
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SESSION 10
LOW- AND NO--YOC COATiNO-S-FART 1
10-1
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PAPERS PRESENTED:
"100% Solids Liquid Sprayable Coatings"
by
David Grafflin
Tioga Coatings Corporation
Calumet City, Illinois
"Alternative Dielectric Coating Medium for Electric Motor Field Coil Manfacturc"
by
William Herz
University of Alabama
Tuscaloosa, Alabama
"Odour and VOC Emissions Reduction on Coil-coating Lines by Using Waterborne Paints- Part
II: Full Waterborne System Application"
by
Serge Vigneron
Soeiete Beige de Filtration
Louvain-la-Neuve, Belgium
Closing Remarks
by
Michael Kosusko
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
Research Triangle Park, North Carolina
10-2
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- 100% Solids Liquid Sprayable Coatings
David M. Grafflin
Tioga Coalings Corporation
Subsidiary of Tioga International, Inc.
1440 Huntington Drive
Calumet City, Illinois 60409
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
Introduction:
This paper covers a series of environmentally compliant liquid coatings, with a primary
emphasis on the first commercially available 100% solids liquid sprayable baking coating. The
application and performance characteristics of this technology, along with companion compliant
coatings materials developed to fulfill other coatings technology niches will be discussed. Given
the focus of this conference, the availability of these materials provides significant economic
advantages for the liquid coatings end-user who is facing regulatory pressures and needs to
consider alternatives for compliance which provide required levels of performance while
addressing existing and proposed regulations on VOC's, HAPs content, and SARA 313 reportable
constituent issues, while at the same time not requiring full-scale equipment conversions.
Virtually the entire industrial coatings-related community [raw material suppliers,
chemicals and coatings manufacturers, and end users] have watched with great interest the
development of (and the lack of uniform enforcement of) the Clean Air Act of 1990 and its
Amendments, While there once appeared that there would be wide-spread general enforcement
of these regulations across industry segments and geographies, certainly the record to date has
been one of localized limited activity, most typically the result of specific incidents or local (state
level) interest. The initial implications of the regulations, however, have prompted re-alignments
in technology development by suppliers to the coatings industry, and the ensuing years have seen
some distinctly different formulation approaches taken to providing the end users of paints and
coatings with environmentally friendly alternatives. This conference has been organized to focus
on those liquid compliance coatings technologies which are commercially available or under
advanced development, and to identify which can provide end users the technology they need to
maintain their requirements for product performance while addressing current or proposed
environmental regulations without the necessity for add-on control equipment (incinerators,
thermal oxidizers, etc.) or wholesale conversion of existing application equipment.
Several years ago, certainly before a significant pretense of regulatory pressure began to
emerge, one of the first major compliance alternatives to conventional solvent-borne liquid
coatings came in the introduction of powder coatings. While capable of providing an option in
many situations, a conversion to powder from liquid always requires rather considerable
equipment expense, often in the range of hundreds of thousands of dollars. While it provides an
escape from the VOC issue, the use of powder coatings leaves the end user to
10-3
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CHART ONE: Comparative Features And Benefits Summary Chart
Product Features
TioTech 20
TioTech 21
Powder
Solv. Hi Solids
Water Hi Solids
Differentials In Solids As Supplied
100%
67-94%solids
100% solids
60-65%solids
50-55% solids
Differentials In First Pass Transfer Efficiency
Specific Product Attributes
Low cost/AccCpplied Film Build (0.5-1,0 mils DFT)
Potential 75% Reduction In Heated Make-Up Air Requirements
No Additional Application Or Cure Equipment Investment
Faster Line Speed (No "Flash Off Zone Needed)
Minimal Waste Disposal Cost
No Product Capacity Limits Due To Current VOC Allowables
Color Changes In Less Than Two Minutes
Reduced Need For Explosion-Proof Equipment
Reduced Need For Extensive Fire Sprinkler Systems
Multiple Color Overspray Is Recyclable
No Need For Separate Paint Room/Reduced Manpower Costs
Lower Shipping Costs With No Solvent Or Water Shipped
No Need For Special Weather Formulas/Solvent Purchases
Lower Scrap Rates Due To Accurate Wet Film Measurement
No Need For Refrigerated/Humidity Controlled Storage Area
Excellent Film Control Due To Lack Of "Fines"
No Solvent Or Co-Solvent, Eliminates LEL/LFL Concerns
Overspray/Plant Contaminated Material Is Filterable
Meets All Existing/Proposed Environmental Rules On Emissions
Number of "Yes* Issues
yes
¦
yes
¦
yes
m
yes
no
no
[ no
18
11
11
3
deal with the issues of difficult control of thin films, lack of quick or easy color changing without
extensive dedicated equipment, the unavailability of blending systems which can make short runs
10-4
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of custom colore effective, the tendency to build thick films on cut edges, and all of the other
characteristics which are typical of powder coatings technologies. As environmental pressures
increased, on the liquid side, the initial compliance alternative was water-borne coatings. The
technical definition of water-borne materials does not equate to a lack of solvent, and in many
cases, while solvent levels are lowered in water-borne formulations, they may not be lowered to a
point that they will not be the subject of the first round of serious control requirements. Utilizing a
partial introduction of water as a diluent in these materials, resulting in a VOC level which is still in
the vicinity of 3.0 pounds per gallon, does not provide a meaningful alternative. Keep in mind,
there are many excellent conventional high solids solvent-borne materials available today which
routinely are capable of providing VOC levels in the 2.5 pounds per gallon range. In all fairness,
however, there are a number of water-borne materials available in a variety of resin technologies
for application on metals and plastics which are both water-borne and zero VOC. A drawback
shared by all of these water-borne materials is the requirement for equipment modifications
including grounding and isolation of equipment for electrostatic application, the use of stainless
steel fittings to avoid premature corrosion and system failure, and a tendency for the overspray of
these materials to be somewhat more difficult to clean up due to a tendency to remain tacky for an
extended period of time on booth walls, conveyor hooks, filter sections, etc. As a result, in many
regions, the disposal of waste materials including water-borne coatings residue is becoming
increasingly expensive and difficult to arrange.
An alternative approach to the concept of compliance in liquid coatings was taken,
however, in considering looking at systems for which the vehicle could be the basic resin itself,
rather than either solvent or water. This novel approach, which at first blush might appear to be
almost a chemical oxymoron, was intended to develop materials which could be described as
100% solids, liquid, sprayable coatings. While many may have considered the potential for
creating materials of this sort, the technical persistence and innovation which have made this
possible are the result of an extensive evaluation of formulation alternatives, the willingness to
consider unique combinations of materials and their processing, and an essential understanding of
the breakthroughs necessary to make this successful. Significant re-engineering of existing
technologies on this level is not accomplished by attempting to "tweak" conventional high solids
coatings. Those materials, while very competent in their current state, rely on the presence of a
level of solvents in order to maintain their stability, and do not lend themselves to this kind of
modification.
As the effort for commercialization of a material of this sort came toward success, certain
characteristics of this emerging technology became better defined. In the absence of conventional
diluents, it is not surprising that these materials are typically higher in viscosity than their
traditional counterparts. As compared to a traditional material which might exhibit a viscosity of
500 centipoises, the first iterations of this new technology emerged at levels above 10,000
centipoises. Overtime, subsequent revisions of this basic chemistry have lowered package
viscosity to levels below 6,000 centipoises at room temperature, still somewhat thicker than
traditional materials. For purposes of comparison, this approaches the room temperature viscosity
of pure maple syrup.
Material viscosities at this level can generate some understandable concerns in fluid
handling. In a traditional material with this sort of consistency, it would be virtually impossible to
move the material through fluid lines or application equipment with any realistic level of control. In
these formulations, however, an inherent understanding of their thixotropy (the property of highly
viscous materials to become more fluid as they are heated, shaken, stirred, etc.) is necessary.
The unique response of these materials to the mechanical influences of agitation, shear and
temperature translate to the development of excellent fluid management and spray application
characteristics. On high speed rotary atomizers (disks, bells, etc.) typically operating at 35,000
rpm or higher, application at either room temperature or very slightly elevated temperatures (less
than 11 OF.) results in an ability to apply controllable thin films with excellent coverage,
10-5
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electrostatic wrap, flow and levelling. The advantage of utilizing heat in the range of 100-11 OF. is
the assurance of uniform fluid flow rates year-round due to uniform material temperature
regardless of changes in ambient plant environment. As heat is introduced to the coating, the
addition of every twenty degrees Fahrenheit sees an associated reduction In viscosity of fifty
percent. Keep in mind that conventional solvent-borne materials, which are much lower in initial
application viscosity, undergo evaporation of the solvent as they travel through the air from the
application equipment to the part being painted, resulting in a material which arrives at the part
fairly high in viscosity, and one which (therefore) does not exhibit sags or runs. The materials
which are the focus of this presentation react to the shear created by the rotary atomizers by
lowering their viscosity in flight, but then regain their viscosity on the part, similarly preventing
sags or runs. These coatings, given their solvent-free make-up, maintain essentially all of the
electrostatic charge to which they are introduced, resulting in outstanding first pass transfer
efficiencies (routinely measured at numbers above ninety percent when applied on high-speed
rotary atomizers) and associated excellent wrap properties as they are applied. This combination
of characteristics provides a material which typically requires significantly less reinforcement or
touch-up than more conventional solids materials. In addition, if there is a desire to apply these
materials to embossed metal surfaces, the rheology of the coatings can be modified to provide a
coating which will coat the coined or embossed surface uniformly, with excellent sag control on the
flat surfaces of the pattern and "hang* on the edges of the valleys, without material flowing away
from the edges and/or filling the pattern. The cosmetic results of this sort of application rival any
of the more conventional solids liquid materials which have been used for some time, and exceed
the capabilities of powder coatings in applications on embossed surfaces.
CHART TWO; First Pass Transfer Efficiency Numbers By Application Method
Transfer Efficiency
Transfer Efficiency
Definitions:
Application Equipment
On Small Targets
On Large Targets
Conventional Air
15%
40%
Large Targets:
Conventional Air Assisted Airless
30%
60%
Doors, partitions,
Conventional Airless
20%
50%
desks shelving, etc.
Conventional HVLP
30%
45%
Electrostatic Air
40%
65%
Small Targets:
Electrostatic Air Assisted Airless
45%
75%
Wire goods, tubular
Electrostatic Airless
45%
75%
furniture, hardware,
Rotary Atomizers-H. S, Disks
85%
95%
etc.
Rotary Atomizers-H S Bells
80%
90%
The coatings developed in this work truly represent a unique chemistry. In performance,
they resemble most closely the properties and characteristics of a modified polyester film. These
are one-pack materials which cross-link with heat to form a film. In line with the commitment to
provide materials with optimum environmental responsibility, these formulations contain no heavy
metals, do not contain materials on the HAPs inventory, have no SARA 313 reportables and have
no VOC's as supplied.
On the subject of VOC's, however, some clarification of this issue is required. While the
individual components of these coatings when compiled into the finished material are of a nature
that no VOC's are reportable in the initial package, if one runs either ASTM method D-2369 or
EPA Test Method 24 on these products, some volatiles are given off. In these test methods, about
0.3 grams of coating is placed in an analytical testing pan and weighed. It is then heated to 110C.
for one hour, and re-weighed to determine the degree of weight loss. The weight loss represents
10-6
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what are identified as voiatiies. The 100% solids version of this chemistry, when evaluated with
these test methods, shows a material loss which calculates to approximately 0.8 pounds per gallon
VOC's. What has volatilized during the test are low molecular weight organic materials. These
are not conventional solvents being removed from the formulation, these are formulated materials
whose components in the lowest molecular weight region are being given off. It should be noted,
this same phenomenon with a measurable loss of volatile contents occurs in the cure of powder
coatings, again despite the complete lack of conventional solvents in their formulation.
Other characteristics of these materials deserve attention as well:
Gloss; typical formulations can be provided at gloss levels between 20% and 90% when
read on a 60 degree gloss meter. If one attempts to formulate materials much below 20%, the
additions of the necessary flattener to achieve a true matte finish can have a dramatic effect on
increasing the viscosity and render the material very difficult to manage.
Pencil Hardness: Depending on the length of the cure cycle at a stated temperature,
significant differences in pencil hardness can be observed. For instance, in conventional
convection cure ovens at a 325F. cure temperature, a pencil hardness of "F° is measured after 6
minutes of exposure, while a pencil hardness of *4H" is measured after 14 minutes at the same
temperature. At a 350F. cure temperature, a four minute cure cycle will provide an "F" pencil
hardness, while a nine minute exposure will provide a "4H" pencil hardness. In the high heat
conditions present in a coil coating oven (30 seconds or so at a peak metal temperature of 435-
450 F.), H-2H pencil hardness is accomplished within these typical cure parameters. Keep in
mind, cure can begin very quickly as no solvent has to be removed from the film prior to beginning
the cross-linking process. The attached graph summarizes this relationship between time,
temperature and pencil hardness in a conventional convection oven.
CHART THREE: Cure Characteristics (Time Versus Temperature)
T 350 F.
IMI
E
\ \ \ \
M
i \ \ \ \
P
\ \ \ \
E
\ \ \ \ N.
R 325 F,
\ F \ \ N.
A
\ \H \. \ N.
T
\ \ \
U
\ N. NH 3H 4H
R
E 300 F,
\
5 10 15 20 25 30 35 40
TIME (mlns
Exterior Weathering: when these coatings are placed on traditional exterior exposure
without the use of a primer, the films do not yellow, crack, craze, blister, pit or delaminate.
However, the films do exhibit some loss of gloss and develop a level of chalking. Currently, in
order to pass more stringent exterior exposure requirements, materials that meet these needs
require the application of a companion environmentally compliant primer. A conversion of this
product to a single-coat technology is in its final stages of development, but all work to date
indicates that as a two-coat system, these chemistries will provide excellent weathering
characteristics for a wide range of applications. This is not to indicate that in this current state they
10-7
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will be able to match the exterior exposure performance of traditional PVDF films with ceramic
pigmentation, which remain the benchmark of high-performance exterior exposure. It is the
intention of the research effort underway to be able to provide this weatherable material in a single
package, single-coat material.
Corrosion Resistance: in typical salt spray and humidity testing, these materials
demonstrate the range of performance one would typically associate with their more conventional
counterparts (1/8" maximum creep from scribe at 500 hours over Bonderite 1000,'Parcolene 60
treated cold rolled steel). As with more conventional solids materials, this performance can be
dramatically affected by the selection of pretreatment processes which are utilized prior to their
application. As indicated previously, the use of an associated primer, or the use of two coats of
this material, will also enhance properties related to corrosion resistance.
Hiding Properties: these materials will provide excellent hiding at and below 0.5 mils dry
film thicknesses, depending on the color being applied and the shape and contour of the parts
being painted. In addition, the combination of hiding properties and electrostatic wrap discussed
earlier typically allows the end user to enjoy a significant improvement in overall film requirements
versus appearance when compared either to more conventional solids liquid materials or to
powder coatings, it is very difficult to control powder coatings consistently at films under 2.5 mils,
while this material can be easily maintained at less than 0.5 mils if desired. It should be noted that
in order to obtain optimum performance from the liquid materials, typical dry film thicknesses are
in the range of 0.8-1.0 mils.
Flammability: this material, in its 100% solids version, does not have a measurable flash
point. As you start to heat it much past 200F., the coating begins to cure. As a result, it is rated
as a Class lll-B combustible for purposes of transportation and storage, the same classification as
powder coatings.
Settling: Referring back to the discussion of thixotropy, these materials do not settle in
the traditional fashion. Therefore, continuous agitation is not required as it would be with a more
traditional material. As a result, the normal paint kitchen set-up with timed agitation, etc., is not
required, and this material can, in fact, be stored immediately next to the spray booth, shortening
supply lines and reducing the necessary circulation equipment.
Required Minimum Air-Flow: the application of any coatings requires some level of air
to be moved past the operators and through the spray area. These materials, like powder
coatings, do not require the same levels of air make-up or flow as more conventional materials,
which can generate a variety of process benefits. Not only does the lesser use of air reduce the
cost of heating air and controlling the paint room environment, the physical reduction in air-flow
through the spray area can lessen the potential for dust and dirt contamination to be blown onto
the applied but uncured film. In addition, the sizing of new equipment to comply with insurance
regulations on operator safety becomes less complex when this material is utilized exclusively.
Reclaim of Overspray: in a clean room environment, overspray can be captured and
recycled with no loss of properties as there is no solvent being lost which needs to be
reconstituted. If dust or other contaminants are a problem, the material may need to be filtered
prior to re-use. In addition, if there is a suitable application for a blended color, all of the
overspray can be collected in a single holding tank, blended together under simple agitation to
create a single color, with complete compatibility, and re-applied as needed. The capability to
collect overspray and to re-use it either by itself or in conjunction with companion materials in a
blend is not shared with powder coatings, where the only reclaim option is to isolate all materials
individually, and to assure that there has been no cross-contamination of either the equipment or
the coating in order for it to be re-used.
10-8
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Shelf Life: there are no particular differences in the storage of this materia! as compared
to a high-quality conventional coating. It is warranted for storage in unopened containers for
twelve months from the date of manufacture, and only requires normal cautions in its handling.
After the twelve month period, we do reserve the right to evaluate the material to assure that
nothing unusual has been done with the coating in the interim.
With this information as a background, what about those end users who face a desire to
find a compromise between remaining with conventional high solids materials and current
application equipment and going to 100% solids material, and the potential for having to install
equipment modifications (which may range from merely the installation of line heaters to the use
of larger feed lines and fluid handling equipment to adapt to the higher viscosity of the full-strength
materials or the transition to state of the art application equipment)? In these cases, there is a
product option available which provides a significant reduction in VOC's while allowing the
continued use of existing application equipment.
CHART FOUR; Comparative VOC's Chart
Category of Comparison
Conv.
Solids
Conv,
High Solids
Ultra-High
Solids-No. 1
Ultra-High
Solids-No. 2
Ultra-High
Solids-No. 3
VOC Levels/Gallon
4.0 lbs
2.8 lbs
1.5 lbs.
1.0 lbs.
0.5 lbs.
Approximate Volume Solids
40%
60%
77.50%
85%
92.50%
Sq. Ft /Gal. (g 1.0 mil (theoretical)
640
960
1240
1360
1480
Sq. Ft./Gal 50% First Pass Tr. Eff,
320
480
620
680
740
Gallons To Cover 1 .OMM Sq. Ft. © 1.0 Mil
3,125
2,083
1,613
1,470
1,351
VOC's On 1 OMM Sq. Ft @ 1.0 Mil
12,500 lbs.
5,832 lbs.
2,419 lbs.
1,470 lbs.
676 lbs.
% VOC's Vs. 40% Vol Solids Coating
100%
46%
19%
12%
5%
Based on 1 ,OMM sq. It. at 1.0 mil dry film
This second family of materials is created by taking the 100% solids coating and
introducing a small amount of non-HAPs solvents to create a significantly less viscous material
(the impact on viscosity of low levels of diluent is remarkable). As summarized on Chart Two, the
resulting coating has all of the properties of its 100% solids counterpart, but in a package which
allows easier application on existing manual or automatic spray equipment. The amount of
dilution can be monitored, depending upon equipment requirements, to provide a material which
ranges in calculated VOC's from just over 1.0 pound per gallon to approximately 2.5 pounds per
gallon (including cure by-products), or 0.5 to 1.5 pounds per gallon as supplied,. An option this
material provides, in addition to being essentially a "plug-in" process change, is a mechanism
whereby a significant reduction in VOC's can be implemented almost immediately, as a
demonstration of a significant commitment to environmental compliance without having to make a
large initial capital investment in advance. While many of the issues relating to equipment
changes can be eliminated by the choice of the super high solids materials, keep in mind that this
option with its use of solvent brings back into play the need to store this material like its more
conventional counterparts and to maintain a higher level of booth air make-up and exhaust than
the more compliant material.
10-9
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CHART FIVE: Typical Physical Properties
TioTech 20
TioTech 21
Weight Per Gallon:
9.4 to 14,0 pounds
9,0 to 13.5 pounds
Weight Solids:
100%
84% to 96%
Volume Solids:
100%
80% to 93%
Theoretical Coverage At One Mil Dry Film Thickness:
1600 square feet
1280-1488 square feet
Color/Gloss:
Matched To Standard
Matched To Standard
Flash Point:
Greater than 200F.
Greater than 1Q0F.
Shelf Life:
Twelve Months
Twelve Months
Pencil Hardness:
H-4H
H-4H
Stain Resistant To:
All Standard Stains
AH Standard Stains
Adhesion to Cold-Rolled Steel:
100% cross-hatch
100% cross-hatch
Mar Resistance:
Excellent
Excellent
Flexibility:
Pass 1 /8" mandrel
Pass 1/8" mandrel
Direct Impact:
Pass 120 inch-pounds
Pass 120 inch-pounds
Salt Spray {500 Hours):
1/8" creep
11B" creep
Solvent Resistance: 200 MEK Double Rubs
Solvent Resistance: 200 Xylene Double Rubs
no apparent effect
no apparent effect
no apparent effect
no apparent effect
Automotive Fluid Resistance:
(after 16 hours immersion):
no apparent effect
no apparent effect
no apparent effect
no apparent effect
no apparent effect
no apparent effect
no apparent effect
no apparent effect
Taber Abrasion: 500 eydes/500 grams/CS10 wheels
0.02 grams
0,02 grams
Tested On Bonderlte 1000/Parcolene M Substrate
As an example of the levels of impact this technology can have, in a typical industrial high
volume facility, utilizing a conventional (40%) solids material, it would not be unusual to generate
750 tons per year of VOC's. In a transition to high (60%) solids material, this number would drop
to approximately 345 tons per year of emissions. However, in a transition to the super high (85%)
solids, this number moves down to a level approaching 100 tons per year, and a move to the
100% solids material can lower the number to less than 60 tons per year, with all of these volatiles
coming from the resin component, not from any solvents or other traditional organic constituents.
10-10.
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From almost any perspective, the availability of these levels of VOC reduction can allow riot only
the resolution of virtually any environmental concern tied to emissions, but in this age of regulatory
balancing, can provide the opportunity for emission offsets (where these are available) to support
the installation of other processes within the manufacturing operation which while not paint-related,
may generate measurable VOC's of their own, and thus impact some of the issues related to air
permits.
CHART SIX: Comparative Systems Costs - Liquid Vs. Powder Coatings
| CONVERSION JUSTIFICATION EXAMPLE
| Powder Coatings |
TioTech 20
Volume Solids
100%
100%
.¦.•.¦.".'••••.v.'.v.'.v.v v.v.v.v.v.*.v.\\.v.v.v.v.v.v.v '.I
Potential Material Utilization (with overspray recovery)
95%
95%
Typical Solid Density (both with same "light" color)
14 lbs ./gallon
14 lbs (gallon
Typical Quoted Price (Computed Equivalent Price)
$2.50/ib. OR $35.00/gal.
$35.00/gal OR $2.50/ib.
Dry Film Thickness Applied
1 _5 mite
0.T5 mils
First Pass Transfer Efficiency
55%
90%
Cost/Square Foot At First Pass Transfer Efficiency
0.0595
0.0182
Cost/Square Foot At Potential Utilization
0.0344
0.0172
Cost Savings Versus Powder;
Based on first pass efficiency:
69%
Based on potential utilization:
50%
v-XvivXX-v-VM-'1
cost per square foot = $/gal. x mils/16.04 x % efficiency
~
Example of potential payback justification:
IF powder purchases equal:
$1,000,000 per year
TioTech 20 usage @ 50% savings level would be:
$500,000 per year
Gallons purchased @ $35.00/gallon would be:
14,286 gallons per year
Daily usage @ 52 May weeks would be:
55 gallons per day
If the equipment cost to convert to a one dam per day
100% solids liquid spray application is less than
$500,000 - the payback would be less than one year.
Therefore:
Converting to a 100% solids liquid would then result in a
net operating profit of $500,000 below the line for
every future year following the year of installation.
10-11
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An additional topic which should be mentioned at this point of the conversation is
economics. For too long, a myth has surrounded powder coatings that they represent not only the
environmental alternative for those confronting some of these issues, but are also the low-cost
choice - in reality, once liquid coatings move up to ultra-high solids levels, the economics begin a
dramatic shift.
Not surprisingly, when development work of this sort is undertaken, avenues of technology
are uncovered which can lead to a variety of additional compliant materials. Among the other
variants of the super high/100% solids materials is a companion 100% solids material which can
have application as a primer-surfacer in the automotive industry. The automotive exterior
coatings market, as you know, typically utilizes a high-build cathodic electrodeposition primer as a
foundation over pretreatment and ends up with a color coat or color coat/clear coat combination on
top of it. In-between, while the trend had been away from the use of a primer-surfacer to act as a
higher dry-film buffer between the primer and color coat, for a variety of reasons ranging from
levelling to corrosion resistance to control of color development, greater attention is being given to
the use of a barrier coat. In many cases, air permits have been re-written to reflect the absence of
this layer, so the availability of a low or no VOC material for this application can be evaluated
without having to re-open an air permit modification caused by the consideration of a low solids
material of the sort previously utilized. It should be noted that there is currently no intention to
consider these materials as automotive exterior body color materials, both due to the issues of
cost and of weathering data versus the current chemistries being utilized, and due to the historical
dominance and support data tied to the existing suppliers and their materials.
Remaining in the general industrial coatings arena, a material has been developed which
is a zero VOC water-borne air dried material for applications on metals, etc. This material
formulates at approximately 40% volume solids, has no measurable flash point, and if thinning is
required, it can be done with tap water. This material is very forgiving of reasonable levels of
surface contaminants, and will demonstrate excellent adhesion over various clean surfaces, with
or without subsequent pretreatment. After 24 hours of air drying, or a short period of force drying
(30 minutes at 150F or so), this material exhibits reasonable hardness and excellent film flexibility,
impact resistance, and other physical properties.
Automotive exterior color coats notwithstanding, there are other applications of great
interest in the automotive industry for compliant materials which have resulted from this extensive
evaluation of technology. Remaining for the moment on applications for metal substrates, a
compliance material has been developed in a zero VOC water-borne material for use as a transit
coating for protecting the exterior of the automotive or light truck surface during storage and
shipment. Applied as a water-borne solution coating, the material dries to a water-resistant film
which while in place is equally resistant to acids (acid rain, airborne contaminants, etc.), and upon
arrival at the dealer, is removed in conjunction with the use of an alkaline cleaner solution which is
sprayed onto the surface, allowed to remain in contact with the surface for a couple of minutes,
and then removed with a pressurized water rinse. Use of a material of this sort is a consideration
both as an additional protection for high-end models where every measure of surface
enhancement is being taken, and in replacement of the contact film laminates currently in vogue
for this sort of protection. The films, while functionally effective, are relatively expensive (typically
above $10.00 per vehicle), can be difficult to remove, and create a disposal issue for the dealer
which is an additional hurdle. The water-borne solution, while essentially clear, can be dyed
slightly (if desired) to be more evident once in use.
Staying with the automotive market, but moving into the growing arena in the use of
plastics, an application which has generated extensive VOC levels (and in so doing has limited its
development despite considerable customer interest) has been the painting of polypropylene and
other olefinic substrates. These materials are of great interest in the automotive market in that
they are relatively inexpensive, are completely recyclable into themselves (primary surface uses
10-12
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can be ground up and re-used as a primary surface, not relegated to backers and other non-critical
uses due to an inability to provide a smooth surface), and they exhibit good weathering
characteristics in their own tight. The weakness of these materials relates to the difficulty of
obtaining the required adhesion of paints and adhesives on these surfaces. As a result, these
materials have typically required an adhesion promoter prior to the application of the color coat.
These coatings, typically applied in very thin (0.1-0.2 mils DFT) films, have traditionally been very
low solids products (5-6% volume solids is not unusual) containing an associated high level of
aggressive coalescent solvents, designed to penetrate the surface of the plastic and to set up
adhesion sites for the subsequently applied color coats. It is not unusual for the solvent-borne
materials of this type to generate 6.0-7.0 pounds per gallon of VOC's,
CHART SEVEN: Zero VOC TPO Finishing Process
\ Comparative Sotverrt Volumes
Solvent Clear Coat 60% Volume Solids
Solvent Color Coat 50% Volume Solids
Solvent TPO Primer 10% Volume Solids
Clear Coat
1.0 Mil DFT
Color Coat
1.0 Mil DFT
TPO Primer
0.25 Mil DFT
Clear Coat
Solvents
Color Coat
Solvents
TPO Primer
Solvents
No Primer
Solvents
With
Zero VOC
TPO Primer
which can effectively offset any compliance of the subsequent topcoats because of the very high
volume of VOC's released in their application. This impact is demonstrated on the attached chart.
As you can see, in an operation coating 100,000 square feet of material at 0.2 mils dry film
thickness with equipment providing 70% transfer efficiency, more than a ton of VOC's could
eliminated per year in the use of a zero VOC adhesion promoter versus a more traditional
material. Development work undertaken to provide a material of this sort has resulted in a
patented zero VOC waterbome emulsion-type material. This product is applied in equally thin
films from a much higher solids material (13% volume solids).
Optimum film formation with this material occurs in the presence of heat, as it requires an
exposure to 180F. at some point during the process cycle. Interestingly, this exposure to heat can
come during the curing of the subsequently applied topcoat, aliowing the adhesion promoter and
topcoat to be handled in a wet-on-wet application process if there is no existing provision for
curing the adhesion promoter by itself. This in no way reduces the properties of the adhesion
promoter or the subsequently topcoated material. Once the adhesion promoter and topcoat are in
place, they perform very well in the most aggressive automotive evaluations, including thermal
shock and other deployment analysis, which are sufficiently destructive to expose a film weakness
10-13
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very quickly. In those applications which are not topcoated, but rather are intended for the
bonding of an adhered companion surface (typically the double-sided tape used to bond body-side
moldings, etc.), this material serves as an excellent foundation for the existing adhesives to allow
the olefins to compete for these applications which have previously been dominated by the use of
PVC. The strength of PVC has been in its superior adhesion, while the weaknesses of PVC have
CHART EIGHT: Zero VOC TPO Primer Description
Weight Per Gallon
8.55 Pounds
Weight Solids
15%
Volume Solids
13%
Recommended Film Thickness
0 2-04 Mils DFT
Theoretical Coverage @ 0.2 Mils DFT
1043 Sq. Ft/Gallon
Package Viscosity
200 - 400 cps (Brookfleld)
Thinner (If Desired)
Tap Water
pH
8.5-9.S
Flash Point
None Measurable
VOC's (Pounds Per Gallon)
Zero
been in exterior weathering (to the point of requiring a clear coat) and in its non-recyclability into
an equivalent use. Once the issues relating to the adhesion of the tape to an olefin are resolved,
however, with a material of this sort many other design options open up for the end user. In
addition to this material being provided in a standard clear formulation, it is also available in a
pigmented conductive version, intended to enhance the electrostatic properties of the substrate for
subsequent application of color coats. This can be a significant benefit for first pass transfer
efficiency on molded or intricately shaped parts, and as such, can provide additional economic
incentives to consider a material of this sort.
[It should be stated once again that the chemistry of the adhesion promoter is completely
different from any of the other low and no VOC materials discussed in this paper.]
Summary
The issues related to the implementation of these various technologies will vary by region,
by industry and by facility. It is becoming clear that the Clean Air Act will be enforced with varying
emphasis from region to region, and it is too early to tell whether the tenets of the regulations
which call for uniform enforcement across similar industries wilt materialize. Eventually, however,
there can be little doubt that the intentions of the Clean Air Act and its Amendments will be
10-14
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enforced, and that there will be little forgiveness for having ignored its requirements. It is
unrealistic to imagine that the conventional high solids (60% or so volume solids) materials in
wide-spread use today will meet the requirements of the regulators without the installation of
extensive control equipment. For this reason, it is equally unlikely that the liquid coatings
manufacturers will spend any measurable portion of their development budgets in the future on
making a "better" 60% solids material. Selective development investments In water-borne
systems will certainly continue, particularly in the zero VOC water-containing materials where a
real contribution can be made to lowering emissions. It will be unlikely that similar levels of
investment in product development will be undertaken on a wide-spread basis in powder coatings
for some fundamental reasons. There is sizable over-capacity in the North American powder
coatings market currently, with over 60 manufacturers of most chemistries. The result of this
combination, not surprisingly, is an ongoing commoditization of the powder coatings market as
prices are driven down to a level which makes it difficult to justify true product development
activities. In addition, there are so few powder coatings manufacturers who are basic in resin
manufacture that the bulk of the market is left to pick materials from a common raw material base
in which differentiation is almost impossible. There will always be a market for powder coatings,
certainly, but the "easy" improvements in this technology have already been realized. The more
difficult hurdles confronting powder coatings (mentioned previously) will not readily disappear, and
the availability of a viable liquid material which effectively removes these hurdles changes the
issues when an end user confronts his options for equipment conversion and process compliance.
The core message of this presentation is quite simply this: for the broad-based
requirements of the general industrial coatings marketplace (office fumiture-files-partitions,
appliances, shelving, tool boxes, commercial and residential metal furniture, electrical component
enclosures, and other general metals end uses), liquid materials are available TODAY which
provide the optimum blend of performance and compliance, coupled with value economics which
allow the end user to achieve all of his needs.
10-15
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ALTERNATIVE DIELECTRIC COATING MEDIUM FOR ELECTRIC MOTOR FIELD
COIL MANUFACTURE
William J. Hen, Mohammed Imanuddin, I. Atty Jefcoat, and Robert A. Griffin
Department of Chemical Engineering, The University of Alabama, Tuscaloosa, AL 35487-0203
The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
INTRODUCTION
A combination of company policy to reduce use of 33/50 chemicals, increasing
production rates and implementation of the Clean Air Act Amendments (CAAA) with
regard to emission limits of hazardous air pollutants (HAP) led General Electric (GE)
Small Motors-Dothan to initiate a project with The University of Alabama to find a
satisfactory solution to the potential problem of excess xylene air emissions from
varnish curing operations. The process of interest was the coating and curing of small
motor field coils with a polyester varnish using xylene as the carrier. Replacement of
the current varnish with a waterborne varnish would help the plant meet environmental
regulations while still expanding to take advantage of higher productivity potential in the
plant. An additional benefit expected was a potential energy savings. The project was
funded by the Alabama Universities-Tennessee Valley Authority Research Consortium
(AUTRC) and GE, with cost-sharing by the University. GE and the University of
Alabama had worked together previously on a waste reduction project in an epoxy
armature-coating operation with satisfactory results.
BACKGROUND
The General Electric Company's Dothan Motor Plant produces 20,000 motors
per year in a size range of 1-60 HP. The plant began production in 1975, and employs
300. In order to improve productivity and competitiveness, all manufacturing processes
are being reviewed with a view towards minimizing or eliminating hazardous or other
wastes and by-products while reducing costs and processing time.
Field coils are a component of motors, and the coating process for this item is
under study by GE as a target for improvement. A polyester varnish coating is applied
to the formed wires to stabilize the configuration and to protect the current-carrying
wires in the field coil. Characteristics required in a good varnish in this application are
dielectric strength, bond strength, and good thermal stability. The coating process
includes coating application, forming, and convection oven curing for a total of 1.5
hours, after which the field coil enters the next manufacturing step.
Problems with the current process include energy usage, process time, safety
and environmental concerns from the solvents contained in the varnish, varnish
residue, and waste disposal.
10-16
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ORGANIZATION
The GE plant is organized around a total quality management concept, the
organization is essentially one-tiered, and the contact for the project was the quality
business team leader. This organization allowed for excellent communication and
action, and GE personnel reflected an open-mindedness and cooperation which helped
the project move ahead. In addition, there was experience from an earlier project
which eased orientation and personnel relationships. The University effort was
accomplished by a research engineer and a graduate student, with oversight by
Chemical Engineering faculty. The waterborne varnish supplier provided ample
samples, field test equipment, extensive laboratory testing facilities, and personnel for
field trials.
METHODS
A review was made of the existing production processes for coating and curing
field coils using a xylene solvent polyester varnish at 50% solids. The main focus was
on one of three lines used to produce field coils in the plant. Coils in this process are
wound, pre-formed, dipped and cured, cooled, taped, re-dipped and cured, partially
cooled, formed, and cooled. A family of waterborne varnishes was selected after
discussion with GE's technical support staff, who had been reviewing candidate
varnishes. These varnishes feature no or low VOC content, and a possibly shorter time
and lower temperature cure cycle. Facilities were prepared for batch dipping and
curing of coils. Tests were done with these varnishes in the laboratory for physical
characteristics and in batch coating of coils for cure optimums, and in side-dip plant
trials to determine efficacy. Final recommendations were made to GE Small Motors
Management.
Existing Production Processes
Three areas of field coil production were identified, the Lanly oven/industrial
main coil area, the Michigan oven/BT coil area, and the Dispatch oven/SMR field
wound area. GE personnel suggested that the Lanly /industrial main coil area is the
prime process area for this project, since the process can be easily duplicated in
laboratory-scale tests, as the coils are separate and easy to manipulate. In this
process, the prepared wound and preformed coils are hung on a conveyor which
passes the coil through a bath, containing the current varnish and into an oven cure at
350°F for 90 minutes. Xylene is added to the varnish to control viscosity. Natural gas
is the energy source for all three ovens. The coil then receives a nylon and fiberglass
tape cover and is treated again in the same way, partially cooled, re-formed, cooled
and installed in the motor frame after testing for insulation integrity. Chemical
components are provided from the storeroom in five gallon pails. A waste drum,
labelled hazardous, contained drippings obtained during routine cleaning and oven
clean-out, which is done every week. The bath is kept at ambient temperature and the
viscosity and level are checked on a routine basis. Venting of fumes to roof or side-wall
10-17
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is accomplished with vacuum hoods and fans.
Evaluation of Alternative Coatings
Two alternative coating materials were already selected by GE for testing.
Evaluation of the varnish physical properties were critical for the success of this project.
Dielectric strength is more important with this coating than the bond strength and
adhesion in the armature/epoxy system studied last year, since the coil is relatively
static. However, vibration can be a problem, so the final cure must be such that the
coating retains integrity under thermal stress found in DC motors. Testing for physical
properties and comparison to the existing varnish was carried out at the supplier's
laboratory in the presence of the University project team members. This laboratory was
well equipped with specialized equipment for complete testing of varnish coatings using
accepted ASTM methods.
Routine physical property measurements of the varnish such as solids content
and viscosity was carried out in the University's laboratory using standard procedures
recommended by the supplier for solids content and GE's preferred viscosity testing
using a Zahn viscometer. Bulk curing tests were attempted in aluminum cups.
Measuring the hardness of the varnish cure was attempted using a penetrometer.
Batch coating and curing of test coils with the new varnishes was accomplished at the
University's Chemical Engineering facilities with equipment specially built for this
project. Un-coated coils were supplied by GE, and varnish by the supplier. Trials were
made to establish the level of coating retention, and to determine time and temperature
parameters for an acceptable cure of the coil. Visual determination of coating
thickness, uniformity, and completeness within the coil was attempted by electronic
microscope techniques. Also, the hardness of the coil coating was estimated from
penetrometer data.
Side-Dip Plant Trials
Successful laboratory tests were confirmed in side-dip plant trials. Using
approximations to existing processing conditions on the Lanly Oven line, for example,
coils were treated with the proposed varnish by dipping into a pail of the varnish and
then putting the coils into the production line just after the normal varnish dip. In
several tests, a DATAPAQ recorder (DATAPAQ, Inc., Wilmington, MA) was attached to
a treatment coil allowing temperature measurement of air, coil surface, and coil interior
throughout the curing cycle. Trials were also attempted on the Michigan Oven line. A
DATAPAQ recorder was again utilized, but testing of the coils subsequent to curing was
limited to electrical integrity only, which was acceptable, due to the fact that the coils
are already mounted in housings.
10-18
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RESULTS
Physical Properly Tests
The initial proposed water-borne varnish selected was designated as P.D.
George (PDG) 1000-Low VOC Waterborne Insulating Varnish (P.D. George Company,
St. Louis, MO). Limited physical property testing for solids content (specified at 30%)
and viscosity indicated variations from specification. P.D. George indicated that these
problems were due to weather-related manufacturing situations, which were
subsequently cleared up. Later in the project, this product was offered and tested at
34% solids, in an attempt to improve film build characteristics. Lastly, a product with
slightly higher VOC content, designated as 1000-70B, with 70% solids was tested in
dilutions down to 35%.
Major physical property testing of 1000-Low VOC in comparison with GE's
existing xylene-based varnish was done at the supplier's laboratory facilities in St. Louis
on June 13,1994. Basically, the waterborne varnish was as good or better in tests
such as dielectric strength, helical coil bond strength, pencil hardness, flexibility, and
surface and volume resistivity. Film build was significantly less for the proposed
varnish, which was of concern to GE.
Tests were done in the University's laboratory on the xylene-based varnish
currently used by GE and the new water-based formulations for viscosity. Results are
given in Table 1. Bulk testing for optimum cure cycles was attempted with poor results
due to bubbling. However, samples of the current xylene-containing varnish were
cured at different temperatures and subjected to a modified penetrometer test to
measure degree of hardness. Conventional hardness testing equipment such as
Rockwell, Brinell, and Vicker could not be used as the samples were too soft. Samples
cured at 130° & 150°C were too soft to achieve results, but the data obtained for 170°
and 190°C confirm an increase in hardness at higher temperatures.
The wire from a field coil was coated with both varnishes and cured and
thickness measured with a micrometer. The xylene-based coating was thicker on
average (two thousandths vs one thousandth). The coated wire was bent at a sharp
angle and viewed under an optical microscope with polarized light at magnifications
from X50 to X200. No distortion or fracture of the coating wall was observed.
Coated coils from both treatments were cross-sectioned for microscopic
analysis. It was observed that the xylene-based varnish-treated coil was more compact
than the water-based varnish-treated coil. Also, the xylene-base coating showed more
uniformity of coating between the individual wires than did the water-base coating.
Laboratory Coating and Curing Trials
Table 2 summarizes significant results from coating and curing trials in our
laboratory during the project. Parameters for varnish treatment of the field coils under
10-19
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Table 1
Viscosity of Current and Proposed Varnishes
Zahn Viscometer seconds at 24°C
XYLENE BASE
1000 - 70B
1000-LOW VOG
1000 - LOW VOC
WATEH
% SOLIDS
50
35
34
30
0
ZAHN CUP#1
188-191
133-135
50-51
32-33
30-31
ZAHN CUP #2
94-96
65-67
23-25
16-17
15-16
ZAHN CUP #3
46-48
32-34
11-12
7-8
7-8
10-20
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Table 2
Summary of Coil Curing Laboratory Trials
VARNISH: (Ml 9637, XYLENE BASED
SOLIDS CONTENT; 50%
SOLIDS,%
CURING
TEMP., C
CURING
TIME, MIN.
VARNISH
USED, g
REMARKS
50
177
90
20.3
Currently in use in GE Dothan Plant
VARNISH: 1000 LOW VOC WATER30RNE
SOLIDS CONTENT; 30%
SOLIDS, %
CURING
TEMP., C
CURING
TIME, MIN.
VARNISH
USED, g
REMARKS
30
150
60
8.2
a. First cure: very hard
b. Second cure after wrapping: hard
c. Film buildup: poor
30
140
60
9.0
a. First cure: medium hard
b. Second cure; hard: B staging: not good
c. Film buildup: poor
VARNISH: 1000 LOW VOC WATERBORNE
SOLIDS CONTENT; 34%
SOLIDS, %
CURING
TEMP., C
CURING
TIME, MIN.
VARNISH
USED, g
REMARKS
34
121
60
13.8
a. First cure: very soft
b. Not done
c. Film buildup: poor
34
140
60
12.7
a. First cure: medium hard
b. Second cure: very soft, pressing not effective
c. Film buildup: poor
34
140
90
13.3
a. First cure: hard
b. Second cure; good
c. Film buildup: poor
10-21
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Table 2 (Continued)
Summary of Coil Curing Laboratory Trials
VARNISH: P ED 1000 - 70B WATERBORNE
SOLIDS CONTENTS: 70% DILUTED TO DIFFERENT PERCENTAGES
SOLIDS,%
CURING
TEMP., oC
CURING
TIME, WIN.
VARNISH
USED, g
REMARKS
50
150
70
20.1
a. First cure; very hard
b. B-staging: no
c. Film buildup: thick, as good as xylene varnish
40
150
75
19.2
a. First cure: very hard
b. B-staging: no
c. Film buildup: excellent
40
150
70
19.0
. a. First cure: very hard
b. B-staging: no
c. Film buildup: excellent
40
150
60
18.3
a. First cure: medium hard
b. B-staging: not satisfactory
c. Film buildup: good
40
150
45
19.1
a. First cure: soft
b. B-staging: very soft
c. Film buildup: excellent
35
160
60
17.3
a. First cure: hard
b. Second cure after wrapping: soft
c. Film buildup: good
35
150
60
17.0
a. First cure: soft
b. B-staging: no
c. Film buildup: good
' 35
135
50
18.8
a. First cure: soft
b. B-staging: no
c. Film buildup: good
35
121
40
20.0
a. First cure: very soft
b. B-staging: no
c. Film buildup: excellent
35
110
90
17.2
a. First cure: very soft
b. Second cure: very soft
c. Film buildup: good
35
125
90
19.2
a. First cure: medium hard
b. Second cure: soft
c. Film buildup: excellent
35
140
90
19.0
a. First cure: hard
b. Second cure: fair
c. Film buildup:excellent
' 35
150
90
18.9
a. First cure: hard
b. Second cure: good
c. Film buildup: excellent
10-22
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the current operating conditions in the GE plant are given. Coils are dipped in a 50%
solids varnish containing xylene as the solvent, and are cured at 177°C for 90 minutes.
Varnish retention on the coils was 20.3 grams.
Data is also given on the tests done using the PDG 1000-Low VOC waterborne
varnish at 30% solids. Using the reduced curing temperature of 150°C and reduced
curing time of 60 minutes as recommended by PDG, the cure was very hard, but it was
found that the cure softened on reheating. Also, the varnish retention of only 8.2 grams
is significantly less than the current standard, indicating insufficient film build. A rerun
of this materia! using a curing temperature of 140°C gave a slightly softer cure. Again,
the varnish retention is only 9 grams.
Tests with the 1000-Low VOC material with the solids content raised to 34% are
also presented. This material was supplied by PDG after the low retention results in
our lab trials and in a side-dip plant test. The results of the laboratory tests are slightly
better than the 30% solids data, but still are short of the targeted retention of about 20
grams found in the control, currently used product.
Lastly, tests with PDG's 1000-70B, a 70% solids material with somewhat higher,
but still acceptable, VOC content are also given. The material was diluted to a range of
35-50% solids. Curing temperatures tested ranged from 110°C to 150°C with curing
times from 40 to 90 minutes, the latter time being the current standard operating time in
the plant. From the results of these trials, it appears that this material, diluted for
economy sake to 35% solids, retains enough viscosity to give a retention similar to that
of the control xylene varnish (Table 1), and cures well at a lower temperature of 140-
150°C.
Side-Dip Plant Trials
Side-dip plant trials were done on June 6 and November 30, 1994, with
University and supplier personnel present.
On June 6, trials were done on both the Lanley and Michigan Oven lines, using
1000-Low VOC material at 30% solids. Six coils were treated in the Lanley Oven with
the test material and were subsequently distributed three each to the University and to
PDG. The DATAPAQ data collector was utilized to collect temperature and time
through the oven. Lanley coils were checked for cure visually and appeared almost
overcured when reformed. When cut in cross section, the lack of film build was
apparent and the wires were not firmly bound in a cohesive matrix. A test was also
done on the Michigan Oven line with two coils, and the DATAPAQ was again utilized,
but no results could be drawn from the test due to the difficulty in evaluating the
Michigan coils which are already mounted in motor housings.
Trials in November were accomplished on both lines using both 1000-Low VOC
at 34% solids and 1000-70B High Solids diluted to 35% solids. The Lanley coils were
10-23
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deemed satisfactory using 1000-70B High Solids material diluted to 35% solids and
cured at 163°C for 90 minutes. The Michigan coils are still being evaluated at the time
of preparation of this report by GE and PDG, using a humidity test procedure to confirm
proper coating of the NOMEX paper in the motor mount.
DISCUSSION
Tests with proposed waterborne varnishes indicate that they perform well
compared to existing xylene-containing varnishes. However, in this project, problems
were encountered with quality control of solids content. Apparently, supplying
companies are not experienced in the problems relating to storage and shipping of
water-containing formulations during winter months. Care must be exercised in
acceptance of these materials in cold weather periods.
Viscosity variations from solvent-based materials to waterborne materials will
also require attention. In this case, the recommended varnish at 30% solids was close
to the viscosity of water, and retention of the material on a multi-wire coil of up to 1.5
inches diameter after a short ambient temperature dip was not sufficient. These results
led to the supplier offering a variation up to 34% solids, but the increase was not
enough to significantly improve the retention rate, as the viscosity was still significantly
lower than the current varnish mix.
The supplier indicates that the solids content of 1000-Low VOC cannot be further
increased. This material contains no co-solvent, only a pH adjusting chemical,
dimethylethanol amine (DMEA), and has less than one pound of VOC's per gallon.
Alternatively, 1000-70B High Solids Water Borne Insulating Varnish at 70%
solids and 2.63 pounds of VOC's per gallon was diluted to 35% solids and gave a
satisfactory viscosity and coating retention. Use of this product would result in
significantly less VOC's (2.63/2) than the existing xylene-based varnish (about 3.85
pounds per gallon VOC's), a reduction of 65%.
Potential energy savings also exist with the waterborne coatings. The supplier
has indicated a curing temperature as low as 121°C for 60 minutes would give a
satisfactory cure, while our tests indicate that 140-150°C are required. This is still
significantly below the existing 177°C - 90 minutes condition in the Lanly Oven line.
Considering the current state of xylene emissions at the plant and anticipated
production increases, a move to the 1000-70B High Solids waterborne material diluted
to 35% solids appears to be a viable alternative for the GE plant for the Lanley Oven
line. The data collected should also apply to the Michigan Oven and Dispatch Oven
operations, but no concrete data has been collected in this study for confirmation.
10-24
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CONCLUSION AND RECOMMENDATIONS
Based on the results of laboratory physical properties testing, laboratory coating
and curing trials on prototype coils, and side-dip plant testing, carried out in the
University's laboratories, the supplier's laboratories, and at the GE plant, replacement
waterborne low VOC varnishes represent a viable alternative to xylene and other high
VOC-containing insulating varnishes in field coil coating operations. Replacement of
these varnishes will meet a corporate goal at GE for VOC reduction, will help the plant
minimize adverse effects of the Clean Air Act Amendments (CAAA), reduce emissions
reported on SARA Title III Section 313, reduce hazardous wastes, improve worker
health and safety, and reduce energy consumption. GE management at the Dothari
Motor Plant agree with this conclusion and expect to replace the xylene-containing
varnish with the waterborne varnish as soon as practically possible, probably by mid-
1995.
The results from this study can most probably be applied to other similar varnish
coating manufacturing, including motor rebuilding shops.
ACKNOWLEDGEMENTS
The authors acknowledge the support of the Alabama Universities/Tennessee
Valley Authority Research Consortium, GE Small Motors - Dothan, and The University
of Alabama for financial and in-kind support of this research effort.
10-25
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The work described in this paper was not funded by the U.S. Environmental
Protection Agency. The contents do not necessarily reflect the views of the
Agency and no official endorsement should be inferred.
Odour and VOC emissions reduction on coil-coating lines
by using waterborne paints - part. II:
full waterborne system application
S. Vigneron8, P. Deprelle^ J. Henniac
a Research Engineer, Head of the Laboratory for Waste Effluent Treatment and Olfactometry
(LTEG), Society Beige de Filtration/UCL, Louvain-La-Neuve, Belgium,
k Engineer in charge of the analytical support, LTEG, UCL
c Professor at the Universite Catholique de Louvain, SBF Chairman
Adress: Laboratoire de Trailement des Effluents Gazeux et d'Oifactomtirie, UCL, Unite des Procidts,
Vok Minckelers, 1 - B-1348 LOUVAIN-LA-NEUVE (Belgium), tel. +32 10 47 23 19 ¦ Fax +32 10
47 24 69 - email lteg@ucl.ac.be
1. Foreword
It is more and more admitted that the use of abatement techniques in order to
reduce Volatile Organic Compounds emissions will not allow to achieve in the future
the planned rejection objectives. This fact is especially admitted; indeed the
abatement techniques located at "end of line" will always have a limited efficiency
while their investment costs, possibly operating costs, can penalize products
competitiveness.
Therefore, chemical industry agreed to make particular efforts for the elaboration
of substitution products in order to eliminate as much as possible the organic phase.
By suppressing the emission source, nuisances, which can affect workers as well as
the environment, are eliminated.
In particular, in the paints field, new types of systems have appeared : paints
formulations, coating application mode, etc...
Unfortunately, the originality of the proposed systems usually requires a deep
process readjustment since the required application or curing mode is totally
different. Finally, these systems are not yet adapted to all materials, for instance the
application processes based on U-V or electron beam curing for steel [1], For the
chosen example, i.e. coil-coating where paint is applied on a steel sheet running
continuously through roll coaters, homogeneity and layer thicknesses are typical
characteristics of the delivered product. In this industry, only a few paints, which can
be considered as high solids, are used (e.g. PVC), as well as waterborne paints chosen
as primer or backer.
The present paper presents the advancement of an E.G. research [2] studying the
feasibility of waterborne systems for coil-coating applications. Nowadays in Europe
almost coil-coaters are using exclusively Organic Based Solvent (OBS-) paints. The
SQLLAC steelmaker group, especially on its industrial plant localized at Onnaing
(France), is an exception: great interest is accorded to Waterborne (W-) systems
because their use allows to increase the rate of production without explosive
problems. So, W-paints are used as backer.
After some generalities giving informations about the coil-coating process and the
analytical methods which were used, the paper will be divided into three parts:
10-26
-------
- comparison of two epoxies (OBS- and W-) used in a semi-classic paint system
(OBS-primer and OBS-top coat + W-backer);
- presentation of the test results from a full waterborne system at industrial scale;
- comparison of the W-system with a full OBS-system.
All results are presented on the basis of equivalent ESP's*.
2. Generalities
2.1. Description of the coil-coating line
The concept of a coil-coating line is shown in figure 1.
Steel and galvanized steel coils 600 to 1500 mm wide and 1,25 to 1,5 mm thick are
alternatively unrolled on two drive machines; a stitching machine realizes the junction
between rolls and ensures a continuous steel sheet at the inlet of the installation. The
accumulator allows to feed the "process" section during these stitching operations.
A surface treatment is carried out in order to provide, in addition to the anti-corrosion
properties, an excellent adhesion of paints on the metal.
The sheet arrives then in the paint cabin (more or less 300 m^ volume). A first
machine, equipped with rolls, allows to apply :
- on the upper side: a 5 Jim thickness dry primer;
- on the lower side: a 7 jiin thickness dry backer.
After passing in the primer oven (20 s to 1 min according to the speed), a second layer
is deposited by a second painting machine (10-19 |im top coat giving the color and the
organic coating characteristics) before entering in a second oven (finish oven) and
undergoing a cooling under water before rewinding of the coil after the checking post.
Each oven is followed by a dedicated thermal incinerator. The incinerators are
supplied by extractors which keep the ovens depressurized.
Thanks to a gas input, the combustion of organic solvents contained in the paints
takes place at about 700°C and allows for cracking these solvents.
I
i 1 i
5 i I
PfVUCXAftCA
pJsI
TO# COAT AftEA
WEI SECTION
ssmTf
Fig. 1 - Diagram of a coil-coating line
2.2. Analytical methods
The given results in this paper concern odour levels measurements coupled with
high sensitive chemical analysis; the odorous power (pOU) is a tool used as
intermediate result to link chemical compounds concentration with odours
concentration.
ESP: dry content of the paint, % volume
10-27
-------
Odours are measured by means of an
dynamic olfactometer (ODILE from Soci6t6
Beige de Filtration) in reference to the
latest works of the European Committee of
Standardisation (CEN) [3]. Z is the dilution
factor expressed as and r/p is the
ratio of perception positive responses of the
panel (r) on the full number of
presentations of a dilution (p) (number of
panellist x number of individual
presentation) (see figure 2). The odour
concentration (Z50) is determined as
occuring to the more probable dilution by
the PROBIT [4] statistic at the level (1- a)
matching 0,95. Q and Qod are respectively
the inodor air and the odorous sampling
flow-rates delivered by the olfactometer.
This measure is independent of the odour
quality.
1,0.
0,8
0,6
r/p
0,4
0,2
0,0.
Zst
4
V.
1,5
i,o
J,5
1",0 3,5
LOG Z
Fig. 2 - Example of an odour curve plotting
and odour concentration determination:
(A) Experimental response of the panel
(positive perception); (-) Statistic fitting for
Zso determination
(PROBIT): Z50 a 274 u.oJm®
The above procedure is useful to determine the odours annoyance and allows for
comparing levels of odours concentrations. It is important to determine which
compound or group of compounds is responsible for the odour annoyance. This
information can only be obtained by means of high sensitive chemical analysis like
chromatography coupled with mass spectrometry (GC-MS).
Correlations can be made in such a way between the air sample analyzed and the
applyed paint. So, paint analysis are made in order to determine which compounds
are emitted during application by means of dynamic headspaces through the paint.
The pOU illustrates the individual contribution of each volatile compounds
identified in the perceived odour. Following its definition it is expressed in term of odour
decibel (dBo) as
X pOUi = X log(|) [dBo]
where Cj and dj are respectively the detected concentration of the volatile compound
and its individual odour perception threshold (pOU = 0 when C £ d).
1 TEDLAR BAG
TEFLON TUBE
TEFLON VALVE
METALDRUM
PUMPING SYSTEM
(pump, battery, flexible tube, flowmeter)
Sampling is made via
TEDLAR bags which give,
with a minimum of
precautions, accurate
results. Bags are filled as
much as possible by a
direct vacuum system
shown at figure 3.
Fig. 3 • Vacuum sampler
10-28
-------
Both samples for olfactometry or for chemical analysis are made this way. For
chemical analysis, several milliliters of gas are passed through an adsorbent cartridge
before to be put into a Thermal Cryogenic Trap (TCT) system as injection device into
the GC-MS. Quantification is made in reference to standards. Detection limit of the
system is in the range of 0,01 - 0,1 ppb (or |ig/m3).
2.3. Paint composition
Solvent phase compo-
sitions for equivalent
organic/water paint sys-
tems are given in the
table I (from PPG [5]).
Table I • Comparison of
paint compositions for
equivalent organic/water
systems
Paint
PRIMERS
OBS-Epcxy
W-A-Epoxy
SOLVENT COMPOSITION (%
ESP Coverage
% aroma tics alcohols esters ketones water
51
43
TOP COATS
OBS-P E
W-Acrylic
63
60
BACKERS
OBS-Epoxy
W-A-£poxy
50
49
310
310
350
350
320
310
64
30
29
59
24
27
52
29
32
64
17
73
10
59
Compounds
Sulk %
1
Isobutanol
0,36
2
n-Butanol
2,67
3
Benzene
8.55E-04
4
2-Butanona
0,4
5
Ethyl glycd acetate
0,01
6
1 -Methoxy 2-Propanot
3.86
7
Toluene
7,65
8
3-Hexene-2-one
0,4
9
Cydohexanone
0,76
10
4-Methyl 2-Pentanone
0,12
11
X C7 alkanes (Heptane Incl.)
1.75E-03
12
Ethyl benzene
3.67
13
m+p-Xylenes
5,97
14
o-Xylene
2,37
15
S-Methyi 2-Hexanone
1,19
16
X C8 alkanes
2.18E-03
17
Indene
0,02
18
19
4-Methyl 4-Hydroxy 2-Pentanone
Isobutyt acetate
4,7
0,03
20
Butyl acetate
0,5
21
Methyl styrene
0,67
22
23
2-Butoxy ethanol
Methyl Cetlosofve acetate
0,1
2,12
24 X CSAIkyl benzenes {=)
0,48
25
£C3 Alky! benzenes
31,11
26
Naphtalene
X C3 alkanes
0,3
27
0,09
28
1 -Methyl 2,3-Dihydroinderte
4,51 E-03
29
Cello solve acetate
•
30 X C4Alky1 benzenes {=)
0,54
31
XC4Alkyl benzenes
21,36
32
33
Isophorone
XC10 alkanes (Decane incl.)
0,73
0,39
34
Ethylene Glycol diacetate
0,47
3S
XC5Alkyfben2enes
1,46
36
X C11 alkanes
0,07
37
2-<2-8utoxyethoxy) elhanol
0,09
36
Butyt diglycd acetate
0,3
39
Ring etfier
3,8
SOLVESSO/SHELLSOL
65,27
As illustrated by tables II and III, the
composition of OBS-paints can be complex
because of the great use of petroleum cuts
(Solvesso/Shellsol) as solvent. The choice of the
organic solvents is more functional for W-
paint.
COMPOUNDS
Bulk (%)
Butyl Glycol
25
n-Butarsol
23
Toluene
16
Methyl PirroBdinone
14
Butoxyethoxy ethanol
14
Amines and surfactants
9
Table II - Typical organic solvent content
of a W-paint
Table III - Compilation of solvent phase content for
based organic solvent paints [6]
3. Comparison of paint cabin ambiences
This section compares the emissions
occuring during the primer (or backer) coat
application of an OBS-epoxy and a waterborne
one. Analysis for the W-epoxy was made
during the application of a "semi-classic" paint
system (primer and top coats being OBS and
backer being a W-paint).
10-29
-------
2-Butanono Cyclohexanone
n-8utanol Styrene
Toluene o-Xylene
Butyl acc latje
Dlacetoie alcohol
Ettjl'ltoluerie
\ ¥ 11 Xylenes
Naphtalene
WORKPLACE
RUNT
SPECIES
[pg/scm]
fjOU
*
I £Aromati«
29793
4,17
78,88
11 £ Polyaromatics
465
0,97
0,06
ID £ Alcohols
3142
0,89
1,90
IV X Aldehydes
-
-
-
V I Ketones
4581
0,29
9,99
VI £ Acetates
1704
0,89
9,16
VD £ Carboxylic acids
34
0,14
0,02
VTO £ Nitro-compounds
-
-
-
IX £Alkanes
-
-
-
X £ Cycloalkanes
-
-
-
TOTAL
397 IS
7,36
100,00
Odour dilution factor
382
C3 Alkylbenzenes
C4 Alkylbenzenes
EPOXY
Scanurn
Fig. 4 * Chromatogram
coat
of a work ambience during the application of a OBS-EPOXY as primer
(recapitulative table of quantitative results in locket)
100
2-Butanone To,uene
Isobutanol m Butyl acetate
%FS
n-Butanol
1-Methoxy
4*Meth
m
662
Ethylbenzene
2-p opan »l
t\ 2- penta lone
Dl^cetonf alcohol
m+p Xylene#
(Cyclohexanone
Nonane
492
956
l.U<<
WORKPLACE
BUNT
SPECIES
pOU
[flg/scmj
1
I £Atomatics
17031,5
3,41
672
II £ Polyaromatics
0
0,00
0,9
III £ Alcohols
10036
2,04
20
IV £ Aldehydes
0
0,00
0
V £ Ketones
3502,5
0,87
9,2
VI £ Acetates
2067
1,79
2,5
VII £ CaxboxySic acids
0
0,00
0
VIII £ Nitrocompounds
0
0,00
0
DC £ Alkanes
33
0,00
0,2
X £ CycloaJkanes
0
0,00
0
TOTAL
32670
8,11
100
Odour dilution factor
318
tfthpnol 2-butoxy
Methyl styrene
WATERBORNE EPOXY
03 Alkylbenzenes
C4 Alkylbenzenes
iiitiiittiimtitui
Fig. 5 - Chromatogram of a work ambience during the application of a W-EPOXY as primer cost
(recapitulative table of quantitative results In locket)
Measurements were lead into two different coating plants; the air dilution flow-rate
around the paint machine corresponding to the figure 1 (OBS-epoxy) was exactly the
double of the flow-rate value corresponding to figure 2 (W-epoxy). So it can be seen
10-30
-------
that the same levels of concentration and odours are reached when using the
waterbome paint although the air dilution flow-rate was reduced by a factor 2,
The chromatograms reflect very well the differences between the two systems. It can
be pointed out that the overall composition of W-paints is in accordance with the
formulation given by the manufacturer only from a qualitative point of view.
On the basis of those results it was decided to begin an ECSC research to study
[2] the application of a full waterbone system.
4. Full waterbome system
4.1. Results of measurements
Trials were led on the site of Ormaing (France) with a system constituted of three
coats (primer, backer and top coat). Primer and backer are waterbome epoxies
whereas top coat was an acrylic one. Table IV summarizes the obtained results on
the three work place areas whereas the Table V summarizes the obtained results on
both sides of the two incinerators (inlet and outlet).
The chromatogram at figure 6 shows the GC-MS analysis on the inlet effluent of
the incinerator treating emissions from ovens drying and curing backer and top coats
(respectively, chromatograms shown at fig. 7 and 8).
The chromatogram (figure 8) obtained for the analysis of the top coat paint
(waterbome acrylic) can be compared with the chromatogram (figure 9) obtained for
the analysis of a based organic solvent paint (polyester).
H«xyn 3 oi Butoxyethand
dlmathyl 34*6
1-Methyl 2~Pyrro!ldlnon«
*6.96
6000000
Butoxyethoxy sthanol
5963
3000600
3068
18.(0
39-19
m
10.Od
50.06
60.00'
TOM
Tim*
Fig. 6 - Chromatogram of the incinerator inlet: loaded gas effluent
by backer and top coat* »olvent» from curing oven
10-31
-------
BACKER
TOP COAT
PRIMER
SPECIES
Woifc place
Paint
Work place
Paint
Wortc place
Paint
fug/m3]
XpOL
%
fwM
XpOU
%
(na/m3)
XpOU
%
%
X Aromatic*
4017,4
2,36
86,6
10,2
17854,6
5,7
45,8
5.8
7280,6
1.8
66,8
11.1
X Alcohol#
64,0
0.00
1.4
57,5
14868,6
1,7
38,2
68,2
3200,4
1,2
29,4
82,5
X Aldehydes
0.0
0.00
0,0
0,0
21,1
1.4
0,1
0,0
2.1
0,4
0,0
0,0
X Ketones
312,7
0,00
6,7
0.4
4659,7
0.2
11,7
2,4
334,4
0,0
3,1
0,8
X Acetates
163,9
0,00
3,5
0,2
1068,1
3,4
2,7
23,6
59,6
0,8
0,5
5,5
X Nltro compounds
0,0
0,00
0,0
30,3
0,0
0,0
0,0
0,0
0,0
Ofl
0,0
0,0
X Alkanes
70,4
0,00
1.7
0,0
532,0
0
1.4
0,0
16,0
0
0,1
0,0
I Ethers
0,0
0,00
0,0
1,5
54,9
0,0
0,1
0,0
7,5
0,0
0,1
0,0
Sums
4636,3
2,36
1.7
1,5
38960,0
12,5
1,5
6,0"
10900,7
-TS-
"' 0,2
6,0
u.oJm 3
70
293,0
379
Table IV - Amblences analyses at work places
compared with headspace paint analyses
SPECIES
PRIMER INCINERATOR
TOP AND BA«
2KER INCINERATOR
INLET
Paint
OUTLET
e
INLET
Paint
OUTLET
£
[jigftnS]
XpOL
%
%
XpOL
%
XpOL
%
%
XpOL
%
X Aromatics
49527,9
7,86
13,4
11.1
1068,6
0,05
97,9
70894,3
8,21
11,3
7,9
2026,6
0,44
99.2
X Alcohols
248522,7
6,37
67,4
62,5
0,0
0,00
100,0
333699,0
7,05
52,9
63,1
296,9
0,00
99,9
X Aldehydes
22169,6
6,23
6,0
0,0
240,8
0,54
98,9
14390,0
8,65
2,3
0,0
120,3
1,40
992
X Ketones
21680,0
2,53
5,9
0,8
1113,7
0,00
94,8
13338,9
1,91
2,1
1,4
187,5
0,00
98,6
X Acetates
20754,6
5,07
5,6
5,5
0,0
0,00
100,0
8777,5
4,90
1.4
12,5
21,7
0,00
99,8
X Nitro compounds
2830,2
0,00
0,8
0,0
782,6
0,00
-
177580.0
0,00
28,2
14,4
150,1
0,00
80,5
X Alkanes
294,8
0,00
0,1
0.0
5508,5
0,00
-
11515,1
0,00
1,8
0,0
31,3
0,00
99,7
X Ethers
2948,1
0,00
0,8
0.0
0.0
0,00
100,0
0,0
0,00
0,0
0,7
0,0
0,00
-
Sums
368627.9
28,06
0,9
0,0
8714,3
0,60
97,6
630094,7
30,72
1,8
0,7
2834,4
1,84
99,6
u.oim 3
8444
884
89,5
19612,5
1252
93,6
Table V - Incinerator* effluents analyses ~ abatement efficiencies
compared with headspace paint analyses
-------
"SmSXSSaF"
lc+$ 7
900C
-------
m
l-Methoxy 2-propanol
41* Toluene
%P$-
2-Buta lone
rv 3utanol
Diacetone alcohol/ 695
4£thylbenzene
nt^none
1.931
mip Xylenes
U2
252
'1t r^i t
m
591
m
Scti
4.2. Discussion
l.M
|2-Butoxy thar
Nonan<
1227
1311
15T2
im
1129
SPECIES
WORKPLACE MINT
pOU x
I £ Aromatic#
D I Poly*rom»tlci
BI E Alcohols
IV £ Aldehyde*
V Z Ketones
VI £ Acetates
VIII C*rboxylk *d
-------
two systems are equivalent from a toxicity point of view. To a same level of
concentration as measured in this study, W-system does not allow to reduce
significantly odours concentrations.
At incinerator inlet (corresponding to the ovens outlet) and outlet, the difference
consists in the presence of a greatest quantity of by-products (by partial oxidation or
recombination) than for using a OBS-system. Furthermore, some by-products like
nitro-compounds are not found with OBS-systems.
The first category of identified by-products are aldehydes. Aldehydes are mainly
the product of the partial oxidation of the alcohols and their content into ovens and
incinerators effluent outlet is obviously increased since the greatest percentage of
alcohols involved in the W-paint formulation: from traces detected for OBS-system
(bulk percentage <0,1 %), aldehydes concentration can reach several %. They are
100 time more odorous than alcohols and it implies greater values in dBo (odour
power) but the VOC's blending effect limits very well the increasing of the odour
concentration.
The second category of by-products are nitro-compounds: 2-Methyl Pyrrolidinone
can be a major component of solvent phase of a W-paint. This compound is used as a
reaction susceptor during curing and fully participates as a linking agent. Some
quantities of this compound can however be retrieved at the incinerator inlet (0,1 % of
the bulk concentration to be compared with the 30 % of the bulk composition of the
organic solvents of the backer W-paint, see tables IV-VI). The thermal degradation of
this component is easy but susceptible to give by-products like alkyl nitrates, nitriles
and nitroalkanes. Formation of HCN is not impossible and precautions must be
especially observed to maintain the incinerator temperature at a sufficient level (>
700 °C). No traces of nitro-compounds were found at work place ambiences.
5. Implication on the abatement techniques
They are no major disturbances to use W-system with conventional thermal
incinerators but because of the presence of greater quantity of by-products
precautions must be taken to keep a sufficient high temperature. Investigations led
on a pilot catalytic incinerator show that no problem occurs when W-system is used.
Use of W-paints allows a deep reorientation of abatement technologies because a
lot of parameters is significantly modified. Techniques such as biofiltration,
adsorption, scrubbing and condensation, membrane separation can be investigated.
As a matter of fact, the major identified compounds at the inlet of incinerators are
ethanol (1,5-3%), n-butanal (1,3-5,1%), 1-Butanol (14,1-22,8%), toluene (6-8%) hexyn-
ol-dimethyl (11 %), 2-butoxyethanol (22-29%) and 2-Pyrrolidinone 1-Methyl (0,6-
28,1%). From one paint to another, the ranges of percentage (except for the latest
compounds) are close. Global percentage in aroma tics is included in the range 11,3-
13,4%. The limited number of VOC compounds allows for recovery of solvent by
adsorption or condensation. The more xenobiotic compounds for a biofiltration system
are constituted by aromatics (10%); otherwise the level of concentration is not too
high and a higher water content is present.
The main subsisting problem to allow such techniques is the oven temperature
level. Almost all the recovery techniques needs an inlet effluent temperature reaching
no more than 40 °C to be efficient. Condensation and membrane separation are the
two opposite exceptions: condensation needs cryogenic temperature whereas
membrane technology is promising to be used at temperature in the range of 200-250
°C.
10-35
-------
The response at this problem is coming from new development of electrical heated
ovens using magnetic induction properties [8] from which outlet effluent
temperatures are Mwer than 80 °C.
6, Availability
Waterborne paints are used as primer, backer and topcoat but only for building
end uses, i.e. cladding, siding and roofing of industrial, commercial and residential
buildings. These coatings are available only in low or semi-gloss finishes on various
substrata: aluminium, hot dip galvanized steel,...
The durability of waterborne topcoats is excellent; waterborne finishes can be
classified as veiy high durable coatings second only to fluorocarbons.
Building market represents about the third of the coil-coating activity so W-
systems can be used in large quantities.
For the full scale test done at Sollac plant, some problems about viscosity and
pigments decantation into the paint barrels, emulsion at rolls application (craters
formation on the surface of the coating) and vaporization rate must be solved.
7. Conclusions
The advantages and the limitations of a waterborne system in comparison with a
classical based organic solvent one are well shown in this study. Full W-system
allows for reducing by two the needed flow-rate both for paint cabin or area ventilation
and for air dilution through the ovens and subsequently through the incinerators.
Indeed, the level of odours and VOC's concentrations is lower. In such conditions it
was demonstrated in a previous paper [5] that energy consumption can be kept
constant or only lightly increased.
Waterborne systems are waiting for the industrial request which can spread their
availability for a large range of coating. They offer new possibilities for a more
environment-friendly coating operation by example by using recovery techniques for
solvent reuse.
References
[1] MOLENAAR F,, Electron beam curing of coating on metal substrates ¦ Perspectives for coil coating,
TNO Centre for Polymeric Materials, Report n° 957E/"89, December 1989, Delft, The
Netherlands
[2] VIGNERON S., Reduction of VOC's emissions and Odour annoyances from coil-coating works:
comparative study of based organic solvent with low solvent systems, especially waterborne, CECA
research n° 7261-01/509/02, SBF/UCL, Louvain-La-Neuve, Belgique (end of work: October 1995).
[3] Co mite Europeen de Normalisation, Odour concentration measurement by dynamic olfactometry,
Document 064/e, CEN TC264/WG20D0URS', Final WG2 Draft prEN, 91-11-17
[41 FINNEY D.J., Probit analysis, Third edition, Cambridge University Press, 1971, Great Britain
[5] TOULEMONDE G., CLAUSEN G„ VIGNERON S., Odour and VOC emissions reduction on coil-
coating Urns by using waterborne paints, Studies in Environmental Science 61, (1994), 239-250
[6] VIGNERON S., TERMON1A M., HERMIA J., VOC's measurement in paint workshops, Studies in
Environmental Science 61, (1994), pp. 177-188
[7] VIGNERON S., Olfactive annoyances in the steel industry: study of preventive and abatement
techniques, CECA research n° 7261-04/441/02, final report, SBF/UCL, Louvain-La-Neuve, April
1992, Belgium
[81 R. WANG and T. DERIAUD, Chauffage induct if dans le traitement en continu des bandes d'acier,
Congrfes europeen "L'induction et ses applications industrielles", mars 1991, Strasbourg, France
10-36
-------
CLOSING REMARKS
FOR LOW- AND NO-VOC COATING TECHNOLOGIES:
SECOND BIENNIAL INTERNATIONAL CONFERENCE
Michael Kosusko
First of all, I would like to thank the speakers and session chairs for contributing their time
to prepare for, and/or to present their research at, what I feel has been a very productive conference.
Second, I would like to thank the audience, for staying on to the very end of a long, 2Vi days of
exceptional presentations and for asking many excellent questions. Most of all, I would like to thank
our co-sponsors at Research Triangle Institute (RTI) for their hard work and constant attention to
details. RTFs Ella Darden, Coleen Northeim, and Jesse Baskir, have helped put together an
excellent program and brought us all together. Finally, I wish to thank Reichhold Chemicals for
sponsoring refreshments for several of our breaks.
This has been the 2nd Biennial International Conference on Low- and No-VOC Coating
Technologies, The Conference had over 185 participants with 45 speakers. Overall, we have had
a very diverse and exciting program featuring information on everything from powder coatings to
the use of life cycle assessment for eeolabelling. The conference has provided us with the
opportunity to interact with a broad range of coating researchers, suppliers, and users, with
environmental advocates, and with government and trade association officials.
The overall goals of the technology development process include reduced environmental
impacts, lowered process costs, and enhanced U.S. competitiveness in worldwide markets. The
process of getting new, lower-emitting coating technologies developed and delivered to the user
involves many players, each of whom faces unique challenges.
(1) Coating developers in industry and universities must integrate new materials and concepts
from the very fundamental to the somewhat applied. Their challenge is to
develop lower-emitting technologies that not only perform as well as current
technologies, but perform better and at lower cost.
(2) For coatings evaluators, such as private organizations and the U.S. Environmental Protection
Agency's research laboratories, the challenge is to complete thorough and
objective evaluations of new technologies in terms of emissions reduction
potential, performance, and cost of implementation.
(3) For technical assistance agents, such as those from state and local governments, the challenge
is to keep on top of the latest technical developments, digest the information, and
convey the relevant details to the user.
All of these players have been in the audience during this conference. I hope that you have had a
chance to exchange information and network.
10-37
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Finally, I'd like to point out that this has been an international conference and I'd like to
recognize the efforts that our international colleagues have made to get here, I hope that you have
enjoyed the conference and have found it to be useful and informative.
10-38
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APPENDIX A
ATTEN DEES LIST
A-l
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees •
Adams, Carl L.
Logistics Management Specialist
Joint Depot Maintenance Analysis Group
1080 Hamilton Street
Dayton, OH 4544-5370
Ph: 513-296- 8295
Fax: 513-296-8257
Adler, Peter
Principal Technical Officer
Swedish Environmental Agency
2-106 48 Stockholm, Sweden
Ph:468799 1171
Fax: 46 B 799 1602
Albrecht, Terry L.
Environmental Engineer
NC Office of Waste Reduction
3825 Barrett Drive
Raleigh, NC 27609
Ph: 919-571-4100
Fax:919-571-4135
Albright, Bill
Environmental Engineer
NC DEHNR
3825 Barrett Drive
Raleigh, NC 27626
Ph: 919-541-4100
Fax:919-571-4135
Allen, Thomas
Environmental Engineer Supervisor
EHNR, DEM, Air Quality Section
P.O. Box 29535
Raleigh, NC 27626
Ph: 919-733-1489
Fax: 919-733-1812
A-2
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Low- and No-VOC Coating Technolog les: 2nd Biennial International Conference
March 13-15,1995
Attendees
Almodovar, Paul
Environmental Engineer
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
(MD-13)
Research Triangle Park, NC 27711
Ph: 919-541-0283
Fax: 919-541-5689
Amos, Kenna
Pacific Environmental Services, Inc.
5001 South Miami Boulevard Suite 300
P. O. Box 12077
Research Triangle Park, NC 27709-2077
Ph: 919-941-0333
Fax: 919-941-0234
Annis, Phillip
Pollution Prevention Specialist
University of Wisconsin-Extension
1304 South 70th Street
West Allis, W1 53214
Ph: 414-475-2845
Fax: 414-475-3777
Arnold, Anne
Environmental Engineer
U.S. EPA Region 1
JFK Federal Building
Boston, MA 08803
Ph: 617-565-3166
Fax: 617-565-4939
Avers, Charles
Marine Paint Chemist
Jotun/Valspar Corp.
1401 Severn Street
Baltimore, MD 21220
Ph: 410-625-7307
Fax: 410-625-7302
A-3
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Barlow, Melvin
Methods Engineering Specialist
United Technologies-Pratt & Whitney
400 Main Street
East Hartford, CT 06108
Ph: 203-565-6592
Fax: 203-565-8249
Barsotti, Robert
Senior Research Associate
E.I. Dupont Co., Inc.
3401 Grays Ferry Avenue
Philadelphia, PA 19146
Ph: 215-339-6575
Fax: 215-339-6008
Baskir, Jesse
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709-2194
Ph: 919-541-5882
Fax:919-541-7155
Bassett, Susan
Editor, The Air Pollution Consultant
8773 S. Ridgeline Blvd.
Highlands Ranch, CO 80126-2329
Ph: 303-470-1900, Ext. 18
Fax: 303-470-5119
Bassett, Jimmy G.
Principal Technical Representative
Eastman Chemical Co.
Lincoln Street
P.O. Box 1974
Kingsport, TN 37663-5230
Ph: 615-229-2644
Fax; 615-224-0414
Berry, Jim
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
(MD-13)
Research Triangle Park, NC 27711
Ph: 919-541-5605
Fax: 919-541-5600
Best, Kurt
Development Chemist
Miles, Inc.
Moray Road, Building 8
Pittsburgh, PA 15205-9741
Ph: 412-777-2932
Fax: 412-777-2802
Bishop, Gene
Materials Engineer
U.S. Air Force
WR-ALC/TIE
Robins AFB, GA 31098
Ph: 912-926-3284/3553
Fax: 912-926-6619/7468
Biundo, Vito
Materials Scientist
Anheuser-Busch Companies, Inc.
1 Busch Place (156-1)
St. Louis, MO 63118
Ph: 314-577-2962
Fax: 314-577-7062
Bocchi, Greogory J.
Director
The Powder Coating Institute
2121 Eisenhower Avenue
Suite 401
Alexandria, VA 22314
Ph: 703-684-1770/ 1-800-988-COAT
Fax: 703-684-1771
A-4
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Bromfield, David
Engineer
Dade County D.E.R.M.
33 SW 2nd Ave,, Suite 1200
Miami, FL 33130-1540
Ph: 305-372-6B27
Fax: 305-372-6760
Brown, Angela
Engineer
Boeing Defense & Space Group
P.O. Box 3707, MS-82-32
Seattle, WA 98124-2499
Ph: 206-773-2647
Fax: 206-773-4946
Bush, Bonnie
Engineer
U.S. EPA Region 5
AE-17J
77W. Jackson
Chicago, IL 60604
Ph: 312-353-6689
Fax: 312-353-8289
Carter, Wells
Project Scientist
Union Carbide
P.O. Box 670
Bound Brook, NJ 08876
Ph; 908-563-5704
Fax: 908-563-6083
Carter, Bob
Senior Staff Engineer
Waste Reduction Resource Center
3825 Barrett Drive
Raleigh, NC 27609
Ph: 919-571-4100 or 800-476-8686
Fax: 919-571-4135
Chastain, Bruce
Certified Industrial Hygienist
Life Cycle Engineering, Inc.
1 Poston Road, Suite 300
Charleston, SC 29417
Ph: 803-556-7110, Ext. 301
Fax: 803-556-2621
Combes, James
Postdoctoral Research Associate
University of North Carolina
CB 3290
Dept. of Chemistry
Chapel Ilill, NC 27595
Ph: 919-962-1346
Fax: 919-962-2388
Copeland, E. Rick
Marketing Manager
Union Carbide Corporation
3200-3300 Kanawha Turnpike
Building 740/5th Floor, Room 5126
South Charleston, WV 25303
Ph: 304-747-5296
Fax: 304-747-4886
Corastubble, Dean
Research Chemical Engineer
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709-2194
Ph: 919-541-6813
Fax: 919-541-7155
Coulon, Remi B.
Ecobalance, Inc.
1 Church Street
Suite 700
Rockville. MD 20850
Ph: 310-309-0800
Fax: 310-309-1579
A-5
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Cox, Lyndon
Mechanical Engineer
Cox Consulting
8 N, Poston Court
Durham, NC 27705
Ph: 919-541-4005
Fax:919-541-0361
Craig, Todd
Vice President of Technology
Dennis Chemical Co.
2700 Papin Street
St. Louis, MO 63103
Ph: 314-771-1800
Fax: 314-771-8399
Grumpier, Paul
Pollution Prevention Engineer
Georgia - Pollution Prevention Assistance
Division
7 MLK Jr. Drive, Suite 450
Atlanta, GA 30334
Ph: 404-651-5120
Fax: 404-651-5130
Cuilla. Mark
Environmental- Engineer
NC DEHNR- DEM- Air Quality
16 N. West Street
Raleigh, NC 27603
Ph: 919-733-1499
Fax: 919-733-1812
Darden, Ella
Project Administration Specialist
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709-2194
Ph: 919-541-7026
Fax: 919-541-7155
Darr, David
Development Scientist
Union Carbide
P.O. Box 8361
So. Charleston, WV 25303
Ph: 304-747-3649
Fax: 304-747-7225
Darvin, Charles
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
(MD-91)
Research Triangle Park, NC 27711
Ph: 919-541-7633
Fax: 919-541-0361
Deason, Douglas M.
Chief, Technology Development
United Technologies Corporation/IJSBI
P.O. Box 1900
Huntsville, AL 35807
Ph: 205-721-2931
Fax: 205-721-2254
Delaney, Paul
Manager, Clean Air Technologies
Southern California Edison
6090 Irwindale Avenue
Irwindale, CA 91702
Ph: 818-812-7549
Fax: 818-812-7381
Denman, William
Environmental Engineer
U.S. EPA Region 4
345 Courtland Street, NE
Atlanta, GA 30365
Ph; 404-347-3555, Ext. 4208
Fax: 404-347-2130
A-6
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
DeRuiter, Robert S.
Senior Applications Chemist
Reichhold Chemicals, Inc.
240 Ellis Road
P.O. Box 13582
Research Triangle Park, NC 27709-3583
Ph: 919-990-8220
Fax:919-990-7711
DeVries, Douglas
Environmental Manager
Hyde Manufacturing Company, Inc.
54 Eastford Road
Southbridge, MA 01550-1875
Ph: 508-764-4344, ext. 228
Fax: 508-765-5250
Dion, Jim
Manager-Environmental & Safety
Kawneer Co., Inc.
555 Guth ridge Court
Norcross, GA 30092
Ph; 404-840-6458
Fax: 404-734-1560
Docherty, Mike
Assoc. Project Engineer
Concurrent Technologies Corporation
1450 Scalp Avenue
Johnstown, PA 15904
Ph: 814-269-6462
FAX: 814-269-2798
Drewke, Kimberly
Airframe Engineer
U.S. Air Force
3001 Staff Drive, Suite 2AC497E
OC-ALC/LAKRA
Tinker AFB, OK 73145
Ph: 405-736-3660
Fax: 405-736-54412
Ducey, Ellen
Environmental Engineer
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
(MD-13)
Research Triangle Park, NC 27711
Ph: 919-541-5408
Fax: 919-541-5689
Dumain, Eric D.
Senior Applications Chemist
Reichhold Chemicals, Inc.
240 Ellis Road
P.O. Box 13582
Research Triangle Park, NC 27709-3583
Ph: 919-990-8264
Fax: 919-990-8218
Ellermann, Jeff
Chemist
Kwick Kleen Industrial Solvents
1202 Barnett Street
P.O. Box 807
Vincennes, IN 47501
Ph: 812-992-3987
Fax: 812-882-4037
Emerson, Mike
President
Huntington Steel
P.O. Box 1178
Huntington, WV 25714-1178
Ph: 304-522-8218
Fax: 304-525-4282
Fairer, Clarence
Environmental Engineer
ADEM
P.O.Box 301463
Montgomery, AL 36130-1463
Ph: 334-271-7861
Fax: 334- 270-5612
A-7
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Low- and No-VOC Coating Technologies; 2nd Biennial International Conference
March 13-15,1995
Attendees
Feenstra, Michele
Director
Pollution Prevention Institute
Kansas State University
133 Ward Hall
Manhattan, KS 66506
Ph: 913-532-6501
Fax: 913-532-6952
Ferman, Martin
Staff Research Engineer
General Motors
Research and Development Center
30500 Mound Road, 1-6
Warren, MI 48090-4055
Ph; 810-986-1622
Fax: 810-986-1910
Fitzpatrick, Michele
Project Manager
U.S. Coast Guard R&D Center
1082 Shennecossett Road
Groton, CT 06340-6096
Ph; 203-441-2859
Fax: 203-441-2792
Frances, Barbara
Associate Director
Chemical Manufacturers Association
2501 M Street NW
Washington, DC 20037
Ph: 202-887-1314
Fax: 202-887-5427
Freeman, Chuck
Lab Technician
Eastman Chemical Co.
P.O. Box 1974
Lincoln Street
Kingsport, TN 37662
Ph: 615 224-0250
Fax: 625-229-3928
Freeman, Richonia
Environmental Engineer
Missouri Department of Natural Resources
Air Pollution Program
205 Jefferson Street
P. O. Box 176
Jefferson City, MO 65101
Ph: 314-751-4817
Fax: 314-751-2706
Fujimoto, K. Hiroshi
K. Hiroshi Fujimoto Consultants
5171 Rock Run
West Bloomfield, MI 48322
Ph; 810-788-9707
Fax: 810-788-9707
Garland, Charles
President
MMC Compliance Engineering, Inc.
200 Ligon Street
Norfolk, VA 23501
Ph: 804-494-0710
Fax: 804-494-0742
Gilbert, Monique
Communuate-Urbaine de Montreal
827 Cremazie E.
Montreal (Quebec) CANADA
Ph: 514-280-4433
Fax: 514-280-4285
Goode, Herbert
Specialist Engineer
Boeing
P. O. Box 3707/NYS 8J-74
Seattle, WA 98124-2207
Ph: 206-773-0830
Fax: 206-773-6288
A-8
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Low- and No-VOC Coating Technologies; 2nd Biennial International Conference
March 13-15,1995
Attendees
Goon, Steven
Engineer
McDonnell Douglas
5000 McDowell Road
Mesa, AZ 85205
Ph: 602-891-5913
Fax: 602-891-5280
Gould, Michael
Project Leader
The Dow Chemical Company
2301 N. Brazosport Blvd., B-1603
Freeport, TX 77566-3257
Ph: 409-238-5827
Fax; 409-238-4530
Grafflin, David M.
Director of Sales & Marketing
Tioga Coatings Corporation
Administrative and Research Center
1440 Huntington Drive
Calumet City, IL 60409
Ph: 708-862-2929
Fax: 708-862-3313
Greenkom, Robert
Research Coordinator
Purdue University
School of Chemical Engineering
West Lafayette, IN 47907
Ph; 317-494-4051
Fax: 317-494-0805
Grovenstein, Jim
Staff Engineer
Waste Reduction Resource Center
3825 Barrett Drive
Raleigh, NC 27609
Ph: 919-571-4100
Fax: 919-571-4135
Gupta, Ravi la
Environmental Engineer
NC Office of Waste Reduction
3825 Barrett Drive
Raleigh, NC 27609
Ph: 919-571-4100
Fax: 919-571-4135
Hagler, Diane
Environmental Protection Specialist
U.S. Army Missile Command
ATTN: AMSMI-Rd St. CM
Redstone Arsenal, AL 35898
Ph: 205-876-1074
Fax: 205-84201359
H anion, James
Sr. Environmental Engineer
EIS Environmental Engineers
1701 N. Ironwood Drive
South Bend, IN 46635
Ph: 219-277-5715
Fax: 219-273-5693
Harding, Madelyn
Administrator, Product Compliance &
Registrations
The Sherwin-Williams Co.
101 Prospect Avenue, NW
Cleveland, OH 44115
Ph: 216-566-2630
Fax; 216-566-2730
Harrington, Jon
Southeastern Regional Sales Manger
Deft, Incorporated
17451 Von Karman Avenue
Irvine, CA 92714
Ph: 800-544-3338
Fax: 714-474-7269
A-9
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Hathaway, Donna J,
ECS III
Louisiana Dept. of Envir, Quality
P. O. Box 82135
Baton Rouge, LA 70884-2135
Ph: 504-765-0132
Fax; 504-765-0222
Hayes, Deborah
Development Associate - Chemist
PPG Industries, Inc.
4325 Rosanna Drive
Allison Park, PA 15101
Ph: 412-492-5429
Fax: 412-492-5221
Herz, William J.
Research Engineer
The University of Alabama
Department of Chemical Engineering
275 II.M. Comer Hall
Tuscaloosa, AL 35487-0203
Ph; 205-348-1102
Fax: 205-348-9659
Holzinger, David
Development Chemist
PPG Industries
10800 S 13th Street
Oak Creek, WI 53154
Ph: 414-764-6000, ext. 375
Fax: 414-764-9452
Horvath, Stan K.
Sr. Product Manager
Dupont
950 Stephenson Highway
Troy, MI 4800707
Ph: 810-583-8037
Fax: 810-583-4555
Howard, Elizabeth
U.S. Environmental Protection
National Risk Managment Research Laboratory
(MD-54)
Research Triangle Park, NC 27711
Ph: 919-541-7915
Fax:919-541-2157
Huang, Eddy W.
Principal Air Quality Engineer
AeroVironment, Inc.
222 East Huntington Drive
Monrovia, CA 91016
Ph: 818-357-9983, ext. 397
Fax: 818-357-0989
Hudson, Jerry
NDCEE Program Manager
Concurrent Technologies Corporation
1450 Scalp Ave
Johnstown, PA 15904
Ph: 814-269-2804
Fax: 814-269-2798
Hume, Andrea
Environmental Engineer
State of Delaware, DNREC
715 Grantham Lane
New Castle, DE 19720
Ph. 302-323-4542
Fax: 302-323-4561
Hunt, Gary
North Carolina DEHNR
Office of Waste Reduction
3825 Barrett Drive
P.O. Box 27687
Raleigh, NC 27611
Ph: 919-571-4100
Fax: 919-571-4135
A-10
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Ibarra, Olga
Engineer
Dept. of Natural Resources Protection
Board of County Commissioners
Broward County
Fort Lauderdale, FL 33301
Ph: 305-519-1275
Fax; 305-519-1495
Irvine, Robert
Senior Environmental Engineer
State of Michigan Air Quality Division
Box 30260
Lansing, MI 48909
Ph: 517-373-7042
Fax: 517-373-1265
Johnson, Bill
Environmental Engineer
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
(MD-15)
Research Triangle Park, NC 27711
Ph: 919-541-5245
Fax: 919-541-0824
Jones, Jerry
Technical Director
Pratt & Lambert United, Inc.
P. O. Box 160
Fulton Street
Sumter, SC 29150
Ph: 803-775-6351
Fax: 803-778-1627
Jordan, Bruce C.
Director
U.S. Environmental Protection Agency
Emissions Standards Division
Office of Air Quality Planning and Standards
(MD-13)
Research Triangle Park, NC 27711
Ph: 919-541-5572
Fax: 919-541-0072
Kittle, Rick
Senior Applications Chemist
Reichhold Chemicals, Inc.
240 Ellis Road
P.O. Box 13582
Research Triangle Park, NC 27709-3583
Ph: 919-990-7595
Fax:919-990-7711
Klute, Brian J.
U.S. Air Force
8 WL/MLSE
2179 12th Street, Suite 1
Wright Patterson AFB, OH 45433
Ph: 513-255-3929
Fax: 513-476-4378
Kobak, Seana
Chemical Engineer
Boeing
P.O. Box 3707, MS 97-29
Seattle, WA 98124-2207
Ph: 206-234-1720
Fax: 206-237-1465
Koerschner, Michael
Environmental Engineer
NC DEHNR-DEM
59 Wood Fin Place
Asheville, NC 28801
Ph: 704-251-6208
Fax: 704-251-6452
A-l 1
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Low- and No-VOC Coating Technologies; 2nd Biennial International Conference
March 13-15,1995
Attendees
Kosusko, Michael
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory
(MD-61)
Research Triangle Park, NC 27711
Ph: 919-541-2734
Fax: 919 541-0359/2157
Kowal, Jack
R&D Project Manager
Coors Brewing Company
MS#CC290
17555 W. 32nd Avenue
Golden, CO 80401
Ph: 303-277-2038
Fax: 303-277-6670
Kukier, Stan
Chemical Engineer
U.S. EPA-Region 4, Air Enforcement Branch
345 Courtland St., N.E.
Atlanta, GA 30365
Ph; 404-347-3555
Fax: 404-347-3059
Lashley, Morgan
Research and Development Chemist
UCB Chemicals
2000 Lake Park Dr.
Smyrna, GA 50080
Ph: 404-801-3280
Fax: 404-801-3234
Lassalle, Eric
Environmental Compliance Manger
Metro Machine Corporation
P.O. Box 1860
Norfolk, VA 23501
Ph: 804-494-0714
Fax: 804-494-0268
Ledbetter, Floyd
U.S. EPA Region 4
345 Courtland Street, NE
Atlanta, GA 30365
Ph; 404-347-2904
Fax: 404-347-5207
Lee, Harold
Engineer I
NC DEHNR/DEM
15 N. West Street
Raleigh, NC 27603
Ph: 919-733-1477
Fax; 919-733-1812
Leovic, Kelly
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory
(MD-54)
Research Triangle Park, NC 27711
Ph: 919-541-7717
Fax: 919-541-2157
Lettice, Fred
Senior Manager
South Coast Air Quality Management District
21865 E. Copley Drive
Diamond Bar, CA 91765
Ph: 909-396-2576
Fax: 909-396-3341
Lilly, Thomas
Environmental Engineer
State of Delaware, DNREC
715 Grantham Lane
New Castle, DE 19720
Ph: 302-323-4542
FAX; 302-323-4561
A-12
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Lindsay, Rosanne
Environmental Scientist
U.S. EPA Region 5
77 W. Jackson Boulevard
Chicago, IL 60604
Ph: 312-353-1151
Fax: 312-886-5824
Massingill, John L., Jr.
Director, Coating Research Institute
Eastern Michigan University
430 W. Forest
Ypsilanti, MI 48187
Ph: 313-487-2203
Fax: 313-483-0085
McCrillis, Bob
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
(MD-61)
Research Triangle Park, NC 27711
Ph: 919-541-2733
Fax: 919-541-0359
McMinn, Beth W.
Environmental Engineer
TRC Environmental Corp.
6340 Quadrangle Drive, Suite 200
Chapel Hill, NC 27514
Ph.(919)419-7564
Fax: (919)419-7501
Mefrakis, Refaat
Environmental Engineer
Missouri Department of Natural Resources - Air
Pollution Control
P. O. Box 176
Jefferson City, MO 65201
Ph: 314-751-4817
Fax: 314-751-2706
Miller, Bonnie
Air Quality Permit Program Manager
Hill AFB
OO-ALC/EME
7274 Wardleigh Road
Hill AFB, UT 84056-5137
Ph: 801-777-1449
Fax: 801-777-4306
Moehrbach, Rudy
Staff Engineer
Waste Reduction Resource Center
3825 Barrett Drive.
Raleigh, NC 27609
Ph: 800-476-8686
Fax: 919-571-4135
Morgan, Roger E,
Sr. Tech Manager
Valspar Corp
1401 Severn St.
Baltimore, MD 21230
Ph: 410- 625-7308
Fax: 410-625-7302
Morse, C. Philip
Staff Engineer
Waste Reduction Resource Center
3825 Barrett Drive
Raleigh, NC 27609
Ph: 800-476-8686
Fax: 919-571-4135
Murphy, Norma
Environmental Chemist
NC Office of Waste Reduction
3825 Barrett Drive
Raleigh, NC 27609
Ph: 919-571-4100
Fax; 919-571-4135
A-13
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Myers, Marion
Group Leader
Rust-Oleum Corporation
8105 Gergussion Drive
Pleasant Prairie, WI 53158
Ph: 414-947-6859
Fax: 414-947-6855
Naas, Jamal
Environmental Engineer
Wayne County Dept. of Environment
Air Quality Management Division
640 Temple, 7th Floor
P.O.Box 851271
Westland, MI 48185
Ph: 313-832-5006
Fax: 313-832-5066
Nagarajan, Rajarnami
Senior Chemist
First Chemical Corporation
1001 Industrial Boulevard
Pascaguola, MS 39564
Ph: 601-938-2742
Fax: None Given
Nelson, Wendy
Materials Engineer
Allied Signal Inc.
Aerospace Equipment Systems
2525 W. 190th (TOR-36-93273)
Torrance, CA 90504-6099
Ph: 310-512-3722
Fax: 310-512-2477
Noonan, James
Assistant Director of Technical Assistance
Purdue University
Pollution Prevention Institute
1291 Cumberland Ave., Suite C-l
W. Lafayette, IN 47906
Ph: 317-494-5036
Fax: 317-494-6422
Nordberg, Dave
Ozone Maintenance Specialist
Oregon DEQ
Air Quality Division 11th Floor
811 SW 6th Avenue
Portland, OR 97204
Ph: 503-229-5519
Fax: 503-229-5675
Nunez, Carlos
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory (MD-61)
Research Triangle Park, NC 27711
Ph:919-541-1156
Fax: 919-541-0359
Ollerenshaw, Bob
Head, Process & Environment Group
Paint Research Association
8 Waldegrave Road
Teddington
Middlesex TW11 8LD
United Kingdom
Ph: 44 181 977 4427
Fax: 44 181 943 4705
Osborne, Michael C.
Chief, Indoor Enviroment Management Branch
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
(MD-54)
Research Triangle Park, NC 27711
Ph: 919-541-4113
Fax: 919-541-2157
A-14
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Ozumba, Charles
Environmental Engineer
Missouri Dept. of Natural Resources
Air Pollution Control Program
P. O. Box 176
Jefferson City, MO 65102-0176
Ph.314-751-4817
Fax; 314-751-2706
Palchak, Greg
Manager, Environmental Affairs
PPG Industries, Inc.
4375 Rosanna Drive, Building C
Allison Park, PA 15101
Ph: 412-492-5436
Fax: 412-492-5377
Paluzzi, Joseph
Program Manager
Massachusetts OTA
100 Cambridge Street
Boston, MA 02202
Ph; 617-727-3260, Ext. 695
Fax: 617-727-3827
Panjnani, Kamlesh
University of Southern Mississippi
Department of Polymer Science
Box 10076
Hattiesburg, MS 39406-0076
Ph: 601-266-5683
Fax: 601-266-5880
Papke, Sharon
Marketing Specialist
Miles, Inc.
Moray Road
Pittsburgh, PA 15205
Ph: 412-777-4984
Fax: 412-777-2940
Parker, Amy
Environmental Engineer
Midwest Research Institute
401 Harrison Oaks Blvd, Suite 350
Cary, NC 27513
Ph: 919-677-0249 ext. 5135
Fax: 919-677-0065
Parks, Albert Richard
Director, Materials Corrosion Control
U.S. Navy - NAVAL SEA Systems
Washington, DC 20362
Ph; (703J-602 0213
Fax: (703) 602 0247
Paskonis, A1
Technical Program Manager
NIST/GLMTC
4600 Prospect Avenue
Cleveland, OH 44103
Ph: 216-432-5352
Fax: 216-432-5314
Patlis, Paul
Environmental Scientist
United Technologies Corp.
1 Financial Plaza
Hartford, CT 06101
Ph: 203-728-6511
Fax: 203-728-6569
Pavliscak, Barbara
Air Management Engineer
Wisconsin Dept. of Natural Resources
101 S. Webster - AM/7
Madison, WI 53703
Ph: 608-264-8880
Fax: 608-267-0560
A-15
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Low- and No-YOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Perz, John
Technology Manager
Lubrizol Corp.
29400 Lakeland, Boulevard
Wickliffe, OH 44092
Ph: 216-943-1200, Ext, 6217
Fax: 216-943-9094
Petroviek, Bruce P.
Sales Development Specialist
Dupont Nylon
Chestnut Run Plaza- LR3N47
P.O. Box 80705
Wellington, DE 19880-0705
Ph: 302-999-3326
Fax: 302-999-3441
Pino, Maria
Environmental Engineer
U.S. EPA Region 3
MC 3H721
Ozone/CO & Mobile Sources Section
841 Chestnut Street
Philadelphia, PA 19107
Ph: 215-597-9337
Fax: 215-597-1129
Ponder, Wade
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory
(MD-61)
Research Triangle Park, NC 27711
Ph: 919-541-2818
Fax:919-541-0359
Praschan, Eugene
Regulatory Liaison Manager
American Automobile Manufacturers Assoc.
1000 Park Forty Plaza, Suite 300
Durham, NC 27713
Ph: 919-361-0210
Fax:919-361-0212
Pridgeon, Ron
Environmental Engineer
N.C. Office of Waste Reduction
3825 Barrett Drive
Raleigh, NC 27609
Ph: 919-571-4160
Fax: 919-571-4135
Princiotta, Frank
Director, Air Pollution Prevention and Control
Division
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
(MD-60)
Research Triangle Park, NC 27711
Ph: 919 541-2821
Fax: 919-541-5227
Pulley, David
Chemical Engineer
Naval Air Warfare Center
Box 5152, MS 08
Warminster, PA 18974
Ph: 215-441-1904
Fax: 215-441-1925
Ramig, Alex
Vice President of Research and Development
ICI/Glidden
16651 Sprague Road
Strongsville, OH 44136
Ph: 216-826-5287
Fax: 216-826-5220
Ramsey, Geddes H.
Chemical Engineer
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
(MD-61)
Research Triangle Park, NC 27711
Ph: 919-541-7963
Fax: 919-541-0359
A-16
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Randall, Paul M.
Chemical Engineer
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
Mail Stop 466
26 W. Martin Luther King Drive
Cincinnati, OH 45268
Ph: 513-569-7673
Fax: 513-569-7111
Reeves, Tom
Environmental Manager
Naval Surface Warfare Center
Port Hueneme Division
4363 Missile Way
Code 1600
Port Hueneme, CA 93043-4307
Ph: 805-982-0812
Fax: 805-932-6253
Reeves, David
Manager
Midwest Research Institute
401 Harrison Oaks Boulevard
Gary, NC 27513
Ph: 919-677-0249, Ext. 5190
Fax: 919-677-0065
Richoux, Michelle
Environmental Engineer
Fairchild AFB
92 CES/CEVP
100 W. Ent. Street, Suite 155
Fairchild AFB, WA 99011-9404
Ph: 509-247-2313
Fax: 509-247-2878
Ries, Frank
Sales & Marketing Representative - Auto
Union Gas Limited
50 Keil Drive, North
Chatham, Ontario, CANADA
N7M571
Ph; 519-436-4638
Fax: 519-436-4645
Roberts, Omer
Environmental Engineer
MO Dept of Natural Resources
P.O. Box 176
Jefferson City, MO 65102
Ph: 314-526-6627
Fax: None Given
Rocky,Joseph
Marketing Manager
Union Carbide Corp.
39 Old Ridgebury RD J2
Danbury, CT 06817
Ph: 203-794-2967
Fax: 203-794-3016
Rodriguez, Dan
General Engineer
Operational Technologies
4100 NW Loop 410, Suite 230
San Antonio. TX 70229
Ph: 210-731-0000
Fax: 210-731-0008
Romanchuk, Richard
NSWC PHD
CODE 4C13
4363 Missile Way
Port Hueneme, CA 93043
Ph: 805-982-7385
Fax: 805-982-7326
A-17
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Rosenkranz, Francis.
Iowa Waste Reduction Assistance Program
1720 Springdale Drive
Clinton, IA 52732
Ph: 319-243-7757
Fax: None Given
Ross, Alexander
Government Affairs Director
Rad Tech International
400 N, Cherry Street
Falls Church, VA 22046
Ph: 703-534-9313
Fax: 703-533-1910
Santobianco, John
Market Development Specialist
First Chemical Corporation
1001 Industrial Road
Pascagoula, MS 39581-3237
Ph: 601-762-0870
Fax: 601-762-5213
Santossuso, Thomas M.
R&D Manager
Air Products and Chemicals Division
7201 Hamilton Boulevard
Allentown, PA 18195
Ph: 610-481-7408
Fax: 610-481-2963
Schultz, Karl R,
Environmental Consultant
E.I. Dupont Co.
1007 Market, B5227
Wilmington, DE 19898
Ph: 302-773-4394
Fax: 302-773-4494
Schuman, Thomas P.
University of Southern Mississippi
Department of Polymer Science
Box 10076
Hattiesburg, MS 39406-0076
Ph: 601-266-5683
Fax: 601-266-5880
Scicchitano, Massimo
Ausimont, Italy
Viale Lombardia, 20
20021 Boullate (Milano)
Italy
Ph: 02 3835 6237
Fax: 02 3835 6355
Sellers, David
Environmental Engineer, Senior
Virginia Dept. of Environmental Quality
2010 Old Greenbriar Road, Suite A
Chesapeake, VA 23320-2168
Ph: 804-424-6707
Fax: 804-424-6841
Serageldin, Mohamed
U.S. Enviromental Protection Agency
Office of Air Quality Planning and Standards
(MD-13)
Research Triangle Park, NC 27711
Ph: 919-541-2370
Fax: 919-541-0072
Shearls, Edward A.
Senior Environmental Scientist
SAIC
714 N. Senate Avenue
Indianapolis, IN 46202
Ph: 317-231-2010
Fax: 317-231-2010
A-18
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Smith. Michael
Senior Engineer
Thiokol Corporation
P.O. Box 707, M/S 243
Brigham City, UT 84302-0707
Ph: 801-863-6103
Fax: 801-863-2271
Soltys, Kenneth
Environmental Analyst
Massachusetts Office of Technical Assistance
Commonwealth of Massachusetts
100 Cambridge Street, Room 2109
Boston, MA 02043
Ph: 617-727-3260, Ext. 687
Fax: 617-727-3827
Sproule, Michael
Technical Manager
PPG Industries, Inc.
760 Pittsburgh Drive
Delaware, OH 43015
Ph: 614-363-6700
Fax: 614-362-6802
Stein, Dennis
Regulatory Affairs Specialist
3M
3M Center 225-3N-02
St. Paul, MN 55144
Ph: 612-736-1596
Fax: 612-736-9278
Stout, Ronnie
Technical Representee
Eastman Chemical Co.
P. O. Box 1974
Kingsport, TN 37662
Ph: 615-229-3373
Fax: 615-229-3328
Strum, Madeleine
Environmental Engineer
U.S. Environmental Protection
Office of Air Quality Planning and Standards
(MD-13)
Research Triangle Park, NC 27711
Ph: 919-541-2383
Fax: 919-541-5689
Sullivan, Don A.
Senior Research Chemist
Shell Chemical Company
Westhollow Technology Center
P.O.Box 1380
Houston, TX 77251-1380
Ph: 713-544-7296
Fax:713-544-8118
Swanson, Thomas
Product Manager-Pfeiffer Systems
Balzers
7 Sagamore Park Road
Hudson, NH 03051
Ph: 603-889-6888
Fax: 603-889-8573
Swarup, Vijay
Staff Engineer
Exxon Chemical
5200 Bayway Drive
Baytown, TX 77522
Ph: 713-425-1681
Fax: 713-425-2747
Swoboda, Scott
Paint Shop Process Engineer
Texas Instruments
6000 Lcmnion Avenue
Dallas, TX 75209
Ph: (214)956-6711
Fax: (214) 956-6424
A-19
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Tichenor, Bruce
Senior Research Engineer
U.S. Environmental Protection Agency
National Risk Managment Research Laboratory
(MD-54)
Research Triangle Park, NC 27711
Ph: 919-541-2991
Fax: 919-541-2157
Turner, Sonji
Chemical Engineer
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, NC 27709-2194
Ph: 919-541-7162
Fax:919-541-7155
Verstraete, Stephen
Beige de Filtration
Voie Minckelers, 1
B-1348
Louvain-la-Neuve
Belgium
Ph: 32-10-47-2499
Fax: 32-10-47-2451
Yigneron, Serge
Engineer
Universite Catholique de Louvain
Societe Beige de Filtration
Voie Minckelers, 1
B-1348
Louvain-la-Neuve
Belgium
Ph: 32 10 47 23 19
Fax: 32 1047 24 69
Vogel, Chester
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory (MD-61)
Research Triangle Park, NC 27711
Ph: 919-541-2827
Fax:919-541-2157
Wain, Jonathan
Technology Manager
Lubrizol
29400 Lakeland Boulevard
Wickliffe, OH 44092
Ph: 216-943-1200, Ext. 7935
Fax: 216-943-9019
Webb, Jennifer
Environmental Engineer
Missouri Department of Natural Resources
Air Pollution Control Program
P.O. Box 176
205 Jefferson Street
Jefferson City, MO 65102
Ph: 314-751-4817
Fax: 314-751-2706
White, James
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory
(MD-54)
Research Triangle Park, NC 27711
Ph: 919-541-1189
Fax: 919-541-2157
A-20
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Low- and No-VOC Coating Technologies: 2nd Biennial International Conference
March 13-15,1995
Attendees
Whitfield, Kaye
Environmental Engineer
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory
(MD-61)
Research Triangle Park, NC 27711
Ph; 919-541-2509
Fax; 919-541-0359
Williams, Derrick
Program Engineer
Industrial Eleetrotechnology Laboratory
2401 Research Drive, Box 8301
Raleigh, NC 27695
Ph: 919-515-6676
Fax: 919-515-4709
Wolfe, Randy S.
Environmental Chemist, VI
MS Office of Pollution Control
P.O. Box 10385
Jackson, MS 39289-0385
Ph: 601-961-5171
Fax: 601-961-5742
Wong, Robert
Manager, Air Compliance Section
Broward County DN RP - Air Quality Division
218 SW 1 Avenue
Ft. Lauderdale, FL 33301
Ph: 305-519-1248
Fax: 305-519-1495
Wooten, Robert
NC DEHNR
15 N. West Street
Raleigh, NC 27603
Ph: 919-733-1815
Fax: 919-733-1812
Wu, Fonda B.
Project/Systems Engineer
Hughes Aircraft Company
Radon Communications Systems
RE/R7/P513,
P.O. Box 902
2000 El Segundo Boulevard
ElSegundo, CA 90245
Ph: 310-334-3636
Fax: 310-334-2578
Zekom. Andreas
Mechanical Engineer
Hill AFB
00-ALC/EME
7274 Wardleigh Road
Hill AFB, UT 840556-5137
Ph: 801-777-0359
Fax: 801-777-4306
Zlotin, Natalie
County of San Diego Air Pollution Control
District
9150 Chesapeake Drive
San Diego, CA 92123
Ph: 619-694-3307
Fax: 619-694-2730
Zook, Lee
Sr. Materials Engineer
USBI
M/C USB-OE
P. O. Box 21212
Kennedy Space Center, FL 32815
Ph: 407-867-9771
Fax: 407-867-9829
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