EPA-600/R-95-01 lc
December 1995
SOLVENT-BASED TO WATERBASED ADHESIVE-COATED SUBSTRATE
RETROFIT - VOLUME IE: LABEL MANUFACTURING CASE STUDY:
NASHUA CORPORATION
By:
Beth W. McMinn
W. Scott Snow
Dan T. Bowman
TRC Environmental Corporation
6340 Quadrangle Drive, Suite 200
Chapel Hill, North Carolina 27514
EPA Contract No. 68-D2-0181
Work Assignment No. 2/017
EPA Project Officer: Chester A. Vogel
Air Pollution Prevention and Control Division
Research Triangle Park, North Carolina 27711
Prepared for:
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
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;foeotord
The U.S. Envir6nmenta£IProtectibri';Agencyl$ chargedfcy CoMresis prbr:^?t5l
tec ting the. Nations,. lanV-V-' •- r«';- • • • ?»»'. fc
blems today and building a science knowledge base necessary to manage,our eco"
logical resources wisely* understand how pollutants affect our ,healthy and pre-u,$
vent or ' reducl^en^onm^^
The National Risk M^agement ftesi^ch* laboratory is the Agency's center for-^Wk
investigation, of. technological md management approaches for reducingrisks ft;
from threats to human health and the environment.- The focus of the Laboratory a-* j
research program is on methods for., the prevention, and control of pollution to air, 7;
land, water/ and^ subsurface ^resources;, protection of water quality in public water,.'
systems; remediation ofcontam^ated^ groundwater; and prevention and-
control of indoor' air poilutionike goal bf ^his' research effort is to catifyzeA'
development and implementation; cw1^oyatiy«^; cost-effective enviroiimerital'-v/ #
technologies; deveiop scientific and %ngineeri^*^ needed by EPA ,
support regulatory and piolicy deciisions; ^^ prbyide technical support andj! infor- k
mation transfer to enBiire effective implementation of environmental regulations ,
This publication, has; been produced asr part of the Laboratory's strategic long-
term research plan. It is" pubUshed and made^ayailable by EPA1 s Office o? He-
search and Developirieht to assistithe user; commiinity and to link researchers
with their clients.V
E.^Timothy.Oppelt;, Director
Natiohal ilisk Management Research Laboratory
EPA^REVIEW NbfiCE,
This report hias been:.pee'f and administratively reviewed by the U.S. Environmentai'
Protection Agency, arid approved for publication. Mention of trade names or
commercial products does hot constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Information
Service, Springfield. Virginia 22161|^
i i
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ABSTRACT
This volume discusses Nashua Corporation's Omaha facility, a label and label stock
manufacturing facility that no longer uses solvent-based adhesives. Information obtained includes
issues related to the technical, economic, and environmental barriers and opportunities associated
with the use of waterbased adhesives. Specific objectives of the visit were to collect information
necessary to characterize Nashua's market profile, manufacturing supplies, manufacturing process
profile, environmental issues, and waterbased adhesive coating experience, as well as the
limitations of waterbased adhesive coatings. The case study report consists of eight chapters.
Chapter 1 give background information related to Nashua's conversion efforts, including market
profile, process description, and a general description of its conversion efforts. Chapter 2
identifies Nashua's motivations for converting its solvent-based operations to waterbased
adhesives. Chapter 3 briefly describes the marketing factors that affected the process conversion.
Chapter 4 identifies the various raw material issues, including costs, involved in the process
conversion. Chapter 5 details the process equipment issues of the conversion, including specific
equipment impacts, costs, vendor selection, and maintenance. Chapter 6 discusses the adhesive
product performance requirements. Chapter 7 describes the effects of conversion on
Nashua's process emissions and waste streams. Chaptee 8 summarizes the
conclusions.
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TABLE OF CONTENTS
Chapter Page
Abstract iii
List of Figures vi
Acronyms vii
Conversion Factors v i i i
1 INTRODUCTION 1-1
1.1 Background 1-1
1.2 Company and Product Description 1-2
1.3 Process Description 1-5
1.4 Comparison of Waterbased and Solvent-based Adhesives 1-8
1.5 Description of the Conversion 1-10
1.6 Unresolved Issues 1-11
2 MOTIVATION FOR CONVERSION TO WATERBASED ADHESIVES 2-1
2.1 Deciding on Waterbased Coatings 2-1
2.2 Regulatory Concerns and Costs Associated with Using Solvent-based
Adhesives 2-1
2.3 Costs Associated with Waterbased Adhesive Use 2-3
2.4 The Decision to Convert 2-4
3 MARKETING FACTORS AFFECTING PROCESS CONVERSION 3-1
3.1 Customer Approval Requirements 3-1
3.2 Nashua's Marketing Techniques 3-1
4 MATERIAL ISSUES INVOLVED IN THE PROCESS CONVERSION 4-1
4.1 Introduction 4-1
4.2 Finding Replacement Waterbased Adhesives 4-2
4.3 Formulation of Solvent-based and Waterbased Adhesives 4-4
4.4 Costs of Alternative Waterbased Adhesives 4-6
4.5 Cleaning Agents 4-6
5 EQUIPMENT ISSUES INVOLVED IN THE PROCESS CONVERSION 5-1
5.1 General 5-1
5.2 Process Design Modifications and Equipment Trials 5-2
5.2.1 Storage Tanks 5-2
5.2.2 Mixing and Holding Tanks 5-3
5.2.3 Resin Heating Oven 5-3
5.2.4 Adhesive Filters 5-3
5.2.5 Piping 5-4
5.2.6 Pumps and Motors 5-4
5.2.7 Heat Exchangers 5-5
5.2.8 Coating Head and Related Equipment 5-5
iv
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TABLE OF CONTENTS (Continued)
5.2.9 Drying/Curing Ovens 5-8
5.2.10 Carbon Adsorber 5-10
5.3 Maintenance and Operational Issues 5-1J
5.4 Vendor Selection and Costs of Modifications 5-12
5.4.1 Storage Tanks 5-12
5.4.2 Mixing and Holding Tanks 5-13
5.4.3 Resin Heating Oven 5-13
5.4.4 Adhesive Filters 5-14
5.4.5 Piping 5-14
5.4.6 Pumps and Motors 5-14
5.4.7 Heat Exchangers 5-15
5.4.8 Coating Head and Related Equipment 5-15
5.4.9 Drying/Curing Ovens 5-15
5.4.10 Carbon Adsorber 5-16
6 ADHESIVE PRODUCT PERFORMANCE REQUIREMENTS 6-1
6.1 Adhesive Performance Criteria 6-1
6.2 Nashua Performance Criteria 6-2
6.3 Ensuring Quality 6-4
7 PROCESS EMISSIONS AND WASTE STREAMS 7-1
7.1 General 7-1
7.2 Changes in Waste Stream Generation and Emissions 7-1
7.2.1 Air Emissions 7-1
7.2.2 Hazardous Waste 7-2
7.2.3 Wastewater 7-2
7.2.4 Solid Waste 7-3
7.3 Waste Disposal Costs and Savings 7-3
8 SUMMARY AND CONCLUSIONS 8-1
8.1 Characterization of Success/failure of Process Conversion 8-1
8.2 Technology Transfer Opportunities 8-3
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LIST OF FIGURES
Number Page
1-1 Nashua Plant Layout 1-4
1-2 Coating Line Operation for Lines 1 and 3 1-6
4-1 Flowchart of Replacement Waterbased Adhesive Selection Process 4-3
5-1 Adhesive Application Equipment 5-6
6-1 Example Application Range of Adhesive-coated Products 6-3
vi"
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ACRONYMS
ASTM
American Society of Testing and Materials
BOD
biological oxygen demand
CAAA
Clean Air Act Amendments of 1990
C/B
cost/benefit
EPA
U.S. Environmental Protection Agency
IR
Infrared
LEL
lower explosive limit
MEK
methyl ethyl ketone
NH,
ammonia
OSHA
Occupational Safety and Health Administration
PM-10
particulate material, nominally 10 jjm and less in diameter
POTW
publicly owned treatment works
PVC
polyvinyl chloride
QA
Quality Assurance
QC
Quality Control
R&D
research and development
TCA
1,1,1-trichloroethane *
USTs
underground storage tanks
voc
volatile organic compound
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CONVERSION FACTORS
To Convert From
To
Multiply by
LENGTH
feet (ft)
meters (m)
inches (in)
MASS OR WEIGHT
pounds (lb)
pounds (lb)
tons
tons
VOLUME
gallons (gal)
gallons (gal)
gallons (gal)
gallons (gal)
PRESSURE
millimeters of mercury
or ton- (mmHg)
TEMPERATURE
Fahrenheit (°F)
Celsius (eC)
meters (m)
feet (ft)
centimeters (cm)
kilograms (kg)
tons
pounds (lb)
kilograms (kg)
liters (1)
cubic inches (in3)
fluid ounces (oz)
cubic meters (mJ)
pounds/inch2 (psia)
Celsius (°C)
Fahrenheit (°F)
0.3048
3.281
2.54
0.454
0.0005
2,000
907.2
3.785
231
128
0.00379
0.1934
subtract 32,
then multiply by 0.5556
multiply by 1.8.
then add 32
viii
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CHAPTER 1
INTRODUCTION
1.1 Background
As part of the overall effort by the U.S. Environmental Protection Agency (EPA) to
identify pollution prevention opportunities associated with manufacturing entities, EPA is
currently assessing the potential for using waterbased adhesive coatings as replacements for
solvent-based adhesive coatings in the adhesives-coated and laminated flexible web substrate
industry. TRC Environmental Corporation (TRC) is supporting EPA in this effort by
investigating the manufacturing barriers and opportunities associated with process conversions
to waterbased adhesives under EPA Contract Number 68-D2-0181, Work Assignment No. 2/017.
For the purposes of this report, the term "solvent" is used to refer to volatile organic
compound (VOC) containing materials used as carriers for adhesive solids and as cleaning agents
in the adhesive coating process. Common examples of solvents used in these ways are methyl
ethyl ketone (MEK), toluene, cyclohexanone, and acetone, although a number of other organic
liquids are used in these capacities as well. Although water is a solvent, for the purposes of
clarity these other VOC-containing liquids are referred to as solvents in this report.
Nashua Corporation's Omaha, Nebraska facility (Nashua), a label and label stock
manufacturing facility, was selected as a case study subject for this assessment. Nashua was
chosen due to its current efforts to convert a solvent-based adhesive coating line to waterbased
adhesives. During the two-day site visit and follow-up telephone interviews, TRC gathered
information on Nashua's process conversion including issues related to the technical, economic,
and environmental barriers and opportunities associated with the use of waterbased adhesives.
Specific objectives of the visit were to collect information necessary to characterize Nashua's
market profile, manufacturing supplies, manufacturing process profile, environmental issues, and
waterbased adhesive coating experience, as well as the limitations of waterbased adhesive
coatings.
This report was written immediately following the completion of the site visit to Nashua.
At the time the report was written at the end of 1993, Nashua had hot yet completed its
conversion to waterbased adhesives. Since this time, according to Nashua personnel, Nashua
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completed its conversion to waterbased adhesives on schedule. All three lines are running with
non-solvent-based formulations, and the facility is no longer producing solvent-based adhesives.
However, the remainder of this report has not been revised to reflect this completion.
This case study report includes eight chapters. Chapter 1 gives background information
related to Nashua's conversion efforts including market profile, process description, and a general
description of its conversion efforts. Chapter 2 identifies Nashua's motivations for converting
its solvent-based operations to waterbased adhesives. Chapter 3 briefly describes the marketing
factors which affected the process conversion. Chapter 4 states the various raw material issues,
including costs, involved in the process conversion. Chapter 5 details the process equipment
issues of the conversion including specific equipment impacts, costs, vendor selection, and
maintenance. Chapter 6 discusses the adhesive product performance requirements and how
Nashua selected replacement waterbased adhesives. Chapter 7 describes the effects of conversion
on Nashua's process emissions and waste streams. Finally, Chapter 8 summarizes the
conclusions of Nashua's conversion effort to waterbased adhesives.
1.2 Company and Product Description
Nashua Corporation began operating its Omaha, Nebraska plant in 1966. The plant was
originally built in 1959 and operated by the International Paper Company. Nashua's Omaha
facility currently employs approximately 90 administrative and management personnel and 200
to 300 production personnel. Since it employs approximately 300 to 400 personnel and annually
produce approximately 200 to 300 million square yards of end-product, Nashua considers itself
a large facility for its industry. The unionized Omaha plant operates 24 hours per day, five to
seven days per week depending on customer demand and produces pressure sensitive labels, roll-
stock, and custom label products. The Omaha facility, a tape plant in Albany, New York, and
a coated products facility at the headquarters in Nashua, New Hampshire, all operate within
Nashua Corporation's Coated Products Group.
Nashua produces 30 to 40 adhesive coating and paper substrate combinations (i.e.,
finished products) for its customers. The Nashua operation can be considered a batch operation,
since it produces different products on its individual coating lines. However, it generally sets up
a coating line to run for many hours (ten or more) before switching to another product. Also,
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while an adhesive's chemical makeup and the paper substrate to which it is applied may differ,
the coating process generally remains the same for each product line, excluding several relatively
easily controlled variables such as line speed, coating thickness, and oven temperature and
configuration. In light of these attributes (e.g., long product runs, similar coating processes for
different products), Nashua believes the term dedicated processor most accurately describes its
operations.
Nashua considers itself a commodity processor. While possessing the capability to
manufacture end-products meeting a wide range of specifications, Nashua generally produces
large amounts of a small number of end-products for application in moderate environmental
conditions (e.g., low humidity, small temperature exposure range). Nashua considers processors
who produce adhesive products for extreme environmental conditions (e.g., high humidity,
corrosive exposure), or who produce small amounts of adhesive products for a specific range of
functions (i.e., batch operations) to be specialized, or specialty processors.
Nashua currently produces approximately 90 percent of its end products using waterbased
adhesive formulations, and is seeking to replace its remaining solvent-based adhesives (ten
percent of end products) with suitable waterbased adhesive formulations by December 31, 1993.
Nashua personnel indicated that it may be necessary to drop one or two product lines in order
to meet this goal, since finding a suitable waterbased adhesive formulation to replace the solvent-
based coating currently used for these product lines has been difficult. However, these products
are a relatively small percentage of the plant's output, and Nashua expects that the loss can be
offset with increased sales of its other products.
Figure 1-1 shows the layout of the Nashua facility. There are three coating lines in the
plant located in the coating room east of the adhesive mixing and filtering rooms. Line 1 is an
adhesive coater/laminator which currently coats with either solvent-based or waterbased
adhesives. Prior to 1989, Line 1 ran full time with solvent-based adhesives, however, it currently
runs approximately 25 percent of the time with solvent-based and 75 percent of the time with
waterbased products. Nashua engineers expect that by the end of 1993, Line 1 will produce only
waterbased products. Line 2 is the release coating line which currently applies either a solvent-
based silicone release coating or a 100 percent solid-catalyzed silicone release coating to paper
stock. Nashua plans to fully convert Line 2 to the solvent-free solid-catalyzed silicone by the
end of 1993. Line 3 is another adhesive coater/laminator and has operated entirely with
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N
BOILER ROOM
SHOP
WASTE TANK
ADHESIVE TANKS
WAREHOUSE
WEST
END
FINISHING ROOM
COATING ROOM
PRESSROOM
SLITTING ROOM
' ' SOLVENT ROOMS
CHEMICAL CLEANING ACRYLIC TANK
AND
OTHER RAW
MATERIAL
STORAGE
Figure 1-1. Nashua's plant layout.
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waterbased coatings since 1982 when it was converted from a waterbased heat sea] coating line.
13 Process Description
Nashua's adhesive storage and transfer operations are quite different for its waterbased
and solvent-based adhesives. Waterbased adhesives are purchased pre-mixed from suppliers and
stored in stirred glass-fiber mixing tanks until being transferred to the process holding tanks for
each coating line. Some additives may be added to the waterbased adhesives in the mixing or
holding tanks to improve its performance and coating properties. Solvent-based adhesives are
formulated on-site in stainless steel mixing/holding tanks. To form a solvent-based adhesive,
adhesive solids (i.e., resins) and additives are first transferred to a tank, and then solvents are
mixed into the tank. These solvents are stored in underground storage tanks (USTs) until transfer
to the mixing/holding tanks.
Both types of adhesive are pumped through piping into mixing/holding tanks before
application to a substrate in the coating head. The piping network used for waterbased adhesives
is made up of polyvinyl chloride (PVC) piping, while the solvent-based adhesives travel through
stainless steel piping. Air pumps are used to transfer the waterbased adhesives, while vane
pumps are used to transfer solvent-based adhesives. Nashua did not reveal any more specifics
about its pump type, as company officials felt this would be revealing potentially beneficial
information to competitors.
Figure 1-2 depicts the coating line operation for Lines 1 and 3. Both types of adhesives
are pumped from holding tanks to the coating head, where they are applied to paper substrate by
a reverse-roll coater. During application of solvent-based adhesive at the coating head, a constant
drip of 1,1,1-trichloroethane (TCA) is used to dissolve buildup of adhesive solids at the edges
of the paper. The spent TCA and dissolved solids are collected for disposal. Scraping blades
are used at the edges of the paper to prevent buildup of waterbased adhesives on the paper edges.
Paper is the only substrate used in products manufactured at Nashua. The facility uses
approximately ten types of face stock papers.
Before the paper substrate is adhesive-coated on Line 1 or 3, a release coating is applied
to the substrate. Nashua uses approximately five types of release liner papers. The 100-percent
solids silicone or a silicone-tolusol mixture is applied to master rolls of raw paper on the Line 2
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To Carbon Adsorber
or Atmosphere
Face
Stock
Adhesive
Evaporated Solvent
or Water Vapor
Substrate
Finished
Product
Lamination
St Rewind
Drying Sc Curing
(Oven)
Adhesive Application
(Coating Head)
Finishing Operations
(Sheeting 4c Die-cutting)
Figure 1-2. Coating line operation for Lines 1 and 3.
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coating machine. The coated release liner is then dried in an oven heated by steam coils for
approximately five to ten seconds. Oven exhaust systems on Line 2 vent directly to the
atmosphere. After drying, the coated release liner is wound onto rolls and transported to either
Line 1 or Line 3 for coating/lamination.
Line 1 can coat either solvent-based or waterbased adhesives. The line typically requires
a downtime of approximately one to two hours to change coating heads and clear the lines when
switching adhesives. Line 1 uses either solvent-based adhesives consisting of natural rubber and
resins dissolved in toluene, which Nashua formulates, or waterbased acrylic adhesives which are
purchased ready-to-use.
After passing through the coating head, the coated paper is conveyed to an oven. The
drying ovens on Line 1 and Line 2 are identical steam-supplied ovens, although the emissions
on Line 1 are vented to a carbon adsorption system when processing solvent-based adhesives.
The Line 3 dryer uses direct-fired natural gas burners and cannot process solvent-based adhesive
products due to fire and explosion hazards. These ovens have five zones, each of which can be
set at a different temperature and air flow. When processing waterbased product, the dried/cured
adhesive and paper is moistened by a water spray mist as it exits the oven. The adhesive-coated
product is then laminated under pressure rollers with the label face stock creating a three-layer
lamination (face stock, adhesive, and release liner).
Once the adhesive-coated paper has been dried and rewound, it is transferred to the
slitting room for cutting and sizing. Nashua has several high-speed slitting machines which cut
the rolls of coated paper into narrow widths for use on its own printing presses or for shipment
as finished product. Excess edge portions of the paper, known as off-cuts, are removed by a trim
system which conveys them to a cyclone separator, and ultimately to a dumpster for transport
to the city landfill. The cut rolls are moved to the pressroom for custom orders or the finish
room for packaging before warehousing and shipment as a finished product. The warehouse
holds custom orders and stock label products awaiting shipment.
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1.4 Comparison of Waterbased and Solvent-based Adhesives
While the production of solvent-based and waterbased products may conceptually be
similar, there are several differences between the processes. Nashua purchases bulk raw materials
for solvent-based adhesives and then mixes all of these components on-site in stainless steel
tanks. When mixing solvent-based adhesives, the solid adhesive products (i.e., the resin and any
additives) arc put into the mixing tank first. These products may be heated in an oven prior to
mixing to reduce their viscosity. Next, toluene (Nashua's primary adhesive solvent) stored in an
UST is piped into the mixing tank, where the ingredients are mixed with stationary dispersers.
Waterbased adhesives are stored in glass-fiber tanks. All of Nashua's waterbased acrylic
adhesives is purchased from suppliers pre-mixed and in bulk quantities. The adhesives are
pumped directly from a supply truck into a glass-fiber storage tank. The adhesives can then be
pumped from the storage tank to a holding tank where additional performance-altering materials
may be blended into the adhesives.
Three to four hours are generally required to make a batch of solvent-based adhesive. For
most waterbased coatings, three to four hours are also needed to blend in all required additives
to a batch. However, some waterbased adhesive formulations require several hours of agitation
between additive additions. During these periods, no labor is expended, but the total time to
manufacture the waterbased batch can extend up to eight hours.
The stainless steel tanks used to mix and store solvent-based adhesives require very little
maintenance. Several tanks installed approximately 20 years ago were thoroughly cleaned for
the first time in 1992. The glass-fiber tanks used to store waterbased adhesives must be
thoroughly cleaned approximately every six months. Cleaning the glass-fiber tanks can take 16
or more man-hours. This lengthy cleanup process is due to the fact that when waterbased
adhesive solids come out of emulsion, either by drying or settling, they do not readily go back
into emulsion. Adhesive solids accumulate over time in the glass-fiber tanks and must be
removed by thorough cleaning of the tank. The cleaning process does not usually interfere with
production on the coating lines, as other tanks can be used while one of the tanks is cleaned.
However, the amount of labor required to clean the waterbased tanks is a significant added
expense not associated with solvent-based adhesives.
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Transfer of solvent-based adhesive to the coating head is accomplished with a vane pump
and a stainless steel piping network. Transfer of waterbased product is performed by air pumps
and PVC piping. The transfer process for waterbased adhesives is complicated by cleanup
difficulties. While the piping for solvent-based adhesives requires minimal maintenance, the
waterbased adhesive piping can become clogged over time. Instead of cleaning, Nashua simply
removes the PVC piping as necessary and replaces it with new piping. Some PVC piping has
required replacement after three years.
Nashua has experienced difficulty with the air pumps used to transfer waterbased acrylic
adhesives. Waterbased adhesives have a tendency to dry in the pumps and cause valves to
become jammed. Nashua first attempted to use diaphragm pumps for waterbased adhesives, but
maintenance problems developed, so these were replaced with the current type of air pump
(Nashua did not wish to reveal the exact type of air pump currently used). Nashua personnel
indicated that the pumping system for waterbased coatings does not approach the reliability of
the solvent-based adhesive coating pumping system. In the future, Nashua hopes to obtain a
more dependable pump system for waterbased adhesives.
The coating head setups used for application of waterbased and solvent-based adhesives
are quite different. The coating thickness, controlled by pressure applied by the coating head
roller system to the paper, is usually greater for waterbased adhesives. While this does not affect
process speed, it does increase the volume of adhesive required for each unit of final product.
Paper speed varies from coating to coating, but the speeds are generally similar for waterbased
and solvent-based coatings and range from 300 to 1,200 feet (91 to 366 meters) per minute. An
additional piece of equipment sometimes employed with waterbased coatings is a heat exchanger,
which is used to ensure a constant adhesive viscosity (via temperature control). The heat
exchanger is not used during a solvent-based coating application.
An important difference in the drying process between solvent-based and waterbased
adhesives is the temperature zoning within the drying ovens. During waterbased coating drying,
the first zone in the drying oven is usually the hottest [up to 250°F (121°C)]. This temperature
is low enough that the adhesive-coated paper is not damaged. The temperature then drops
through the remaining zones to a low ending temperature. For solvent-based coating drying, the
first zone is set to a relatively low temperature. The temperature then increases in the next
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zones, until enough solvent is driven from the adhesive. Usually the last one or two zones are
not heated.
Care must be taken when drying waterbased adhesives to ensure that some water remains
in the adhesive and paper. When the paper is dried below its normal water content it tends to
curl, which is detrimental to the lamination process.
One hazard associated with solvent-based adhesive drying not associated with waterbased
adhesive drying is the risk of buildup of explosive concentrations of solvent. Monitoring of the
oven air is necessary to ensure concentrations stay well below the lower explosive limit (LEL)
of the solvent. The LEL is the minimum airborne concentration at which the solvent will
combust with a sufficient ignition source (i.e., a spark). Solvent air concentration monitoring is
an additional cost associated with solvent-based coating that is not required for waterbased
coating. LEL meters can cost several thousands of dollars, are relatively expensive to maintain,
and require monitoring by properly trained personnel. There is an additional hazard insurance
cost as well.
The wind-up operation after adhesive drying is the same for both waterbased and solvent-
based adhesives. The cured web is wound in concert with a non-stick backing into a roll, which
is either finished and shipped, or cut, printed, and made into labels. Finishing and printing
operations were generally unaffected by the changeover from solvent-based to waterbased
adhesives.
1.5 Description of the Conversion
Nashua began coating waterbased pressure-sensitive products in 1982. At that time,
Nashua converted what was a waterbased heat seal coating line to the waterbased adhesive
pressure-sensitive label line. Nashua made this change to waterbased adhesives because
management executives felt that waterbased products would have a strong future in the label
manufacturing industry. To effect the changeover, Nashua purchased several new adhesive
holding tanks, made of glass-fiber, in which adhesive could be stored and agitated before use.
PVC piping and new pumps were installed to transfer the product to the coating heads. Nashua
experimented with coating speeds, thicknesses, and drying oven temperatures to determine the
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optimum conditions. Within one week, Nashua was able to produce a viable waterbased
adhesive-coated product.
Nashua began a complete facility conversion from solvent-based adhesives to waterbased
adhesives in the Omaha plant in 1987. The decision to convert was made by Nashua's President
at that time. The time frame for the changeover apparently was not specified. The main factors
driving the conversion were the economic and environmental advantages of waterbased adhesives.
Nashua adopted a policy to replace its solvent-based products with waterbased products which
had qualitative improvements, such as lower production cost and increased temperature range
before adhesive failure. The company's research and development (R&D) department was
charged with seeking out and testing new waterbased formulations. Where product improvements
were feasible, Nashua incorporated new waterbased adhesives into its products and offered the
improved products to its customers.
Nashua's new waterbased products were offered to its clients as product improvements.
The products were not marketed as replacement products for its solvent-based adhesive-coated
products. Nashua has been able to successfully replace most of its solvent-based adhesives with
improved waterbased adhesives, has lost few clients, and has remained profitable during the
changeover to waterbased coatings.
With the passage of the Clean Air Act Amendments of 1990 (CAAA), Nashua decided
to expedite its conversion to waterbased coatings, and to eliminate all solvent use. At that time,
Nashua decided to attempt to be solvent-free by December 31, 1993. Despite some setbacks,
they have managed to remain on schedule, and still believed it was possible to meet their goal.
1.6 Unresolved Issues
Two issues must be resolved before Nashua can complete the transition to solvent-free
operations. First, Nashua has one or two remaining solvent-based adhesive-coated product lines.
To complete conversion, Nashua will either have to find satisfactory waterbased adhesive
replacements or eliminate those product lines. Second, equipment cleaning solvents will have
to be eliminated. Nashua uses toluene and TCA to dissolve adhesive buildup on coating
equipment during cleaning operations for both solvent-based and waterbased adhesive coating
equipment. Cleaning solvent replacement is particularly difficult because of the chemistry of
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acrylic waterbased adhesives. Waterbased adhesives arc in an emulsion form. Once the acrylic
solids have left the waterbased suspension (i.e., once the water has evaporated, or the adhesives
have accumulated on the bottom of the tank), they will not readily reenter the suspended state.
However, the acrylics are low-polarity or non-polar substances which easily dissolve in non-polar
solvents like toluene and TCA. One potential alternative cleaner being considered by Nashua is
mineral spirits. Whatever alternative cleaning method is chosen, Nashua expects that machine
operators will have to perform much more manual scraping and peeling of dried adhesive.
Nashua was optimistic that both of these issues could be resolved to allow solvent elimination by
their self-imposed deadline of December 31, 1993. Nashua met its major goal by changing
its remaining solvent-based adhesive-coated product lines to waterbased products in January
1994. However, as of November 30, 1995, alternate cleaners have not been found.
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CHAPTER 2
MOTIVATION FOR CONVERSION TO WATERBASED ADHESIVES
2.1 Deciding on Waterbased Coatings
When Nashua made the corporate decision to phase out the use of solvent-based adhesives
in 1987, it did not seriously consider any adhesive coating technologies other than waterbased
coatings. There were two reasons why waterbased adhesives were the sole alternative: (1)
Nashua had considerable experience with waterbased coatings, as it already operated one coating
line dedicated to waterbased adhesives, and prepared the company for a complete conversion to
waterbased adhesives; and (2) waterbased adhesives have proven effective at Nashua and
throughout the industry. At the time of Nashua's decision, other technologies such as hot melt,
two-part reactive, and radiation-curable coatings had not been proven effective in the marketplace
to the same degree as waterbased adhesive coating technology. These two considerations made
the decision to convert to waterbased adhesives Nashua's only logical choice.
In the future, Nashua personnel believe that other technologies like those mentioned
above, or combinations of those technologies, will be researched and possibly employed by
Nashua, especially when the limitations of waterbased adhesive coatings appear to be reached.
In the near term, Nashua will only employ and develop waterbased adhesive coating technology.
2.2 Regulatory Concerns and Costs Associated with Using Solvent-based Adhesives
As previously discussed, Nashua's commitment and conversion to waterbased adhesive
coatings began well before the advent of the CAAA. There were a number of regulatory and
monetary influences in making the decision to convert. At the time of the corporate decision to
convert to waterbased adhesives, Nashua had three main regulatory costs associated with solvent
use. These were the costs for maintaining the solvent recovery system, monitoring costs, and
cleaning solvent disposal costs.
The solvent recovery system is used to collect vapors produced in the drying oven on
Line 1 after coating solvent-based adhesives. The system employs a carbon adsorption system
which uses a charcoal bed to adsorb solvent vapors. The system is approximately 85 to
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90 percent efficient (i.e., 10 to 15 percent of the captured solvent vapor escapes into the
atmosphere).
The solvent recovery system has been very expensive to maintain and has been unreliable
at times. The charcoal bed used to adsorb solvent vapors must be replaced about every five years
at a cost of approximately $75,000. Some industries replace their charcoal every two to three
years (for maximum control efficiency) depending on economic feasibility. However, many
companies capture solvents not only for environmental reasons, but also for reuse as a solvent.
Therefore, some facilities located in attainment areas where solvent emissions requirements are
relatively less stringent may not replace their charcoal until it is required or economically
feasible.
Additional costs associated with the carbon adsorption system are monitoring and repair
of the system. Nashua personnel stated that maintenance problem with the system occurred
weekly. While most problems are minor, the cost of the maintenance crew's time to repair the
solvent recovery system becomes significant when viewed as an added cost of using solvent-
based adhesives. Nashua representatives could not quantify the time spent monitoring,
maintaining, and repairing the solvent recovery system. However, a simple calculation shows
that if three maintenance personnel each spend ten hours per week on the solvent recovery
system, and their average pay is $25 per hour with benefits, the labor costs to Nashua would be
approximately $39,000 on an annual basis. While this a rough estimate, it is likely that the
additional annual cost to Nashua for operating the solvent recovery system is in the tens of
thousands of dollars.
Once the conversion to waterbased adhesives is complete, Nashua will sell the solvent
recovery system. Nashua officials believe that the system will sell for approximately $50,000,
although Nashua will have to pay to remove the system and dispose of the charcoal. Since these
costs could approach the selling price of the system, Nashua does not expect to make a profit
from the sale.
The second major cost associated with the use of solvent-based adhesives has been the
cost of monitonng. Nashua has several LEL meters which it uses to ensure that solvents are not
venting into the plant. These instruments cost approximately $8,000 to $10,000 each, and must
be calibrated and repaired every few years.
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The third major cost associated with the solvent-based adhesive use is disposal of waste
adhesive and solvents used for cleaning. Nashua must pay between $100 to $600 to dispose of
a 55-gallon drum of waste solvent. In addition, shipping costs average $25 to $50 per drum.
The solvents, primarily TCA and toluene, are disposed of by an incineration company who uses
the liquid wastes for fuel blending.
An additional cost factor associated with the use of solvent-based adhesives is regulatory
fees for air emissions. Nashua has been exempt from paying air emission regulatory costs (i.e.,
air discharge permit fees), as its emissions have been grandfathered from current regulations.
However, future permitting requirements (i.e., Title V operating permits) would likely impact
Nashua's emissions. If Nashua continued to use solvent-based adhesives in the future, it would
probably have to pay permitting fees for its emissions.
2.3 Costs Associated with Waterbased Adhesive Use
While there are significant costs associated with solvent-based adhesives, the conversion
to waterbased adhesives required a much greater investment of time and capital. Since 1987,
Nashua has purchased 13 glass-fiber tanks for blending and storage of waterbased adhesives.
These tanks range in cost from $5,000 to $75,000, excluding installation costs which are
approximately two to three times the purchase cost of each tank. Nashua has purchased new
piping and air pumps for transfer of the waterbased adhesive to the coating heads on an as-
needed basis as their capacity to coat waterbased adhesives has increased. Piping is relatively
inexpensive while air pumps range from $500 to $2,000 each. Nashua also installed three heat
exchangers to ensure that the waterbased adhesive remains at a constant temperature during
coating. These cost under $5,000 each plus installation costs of $2,000 to $3,000 each.
Nashua has incurred additional cleaning costs associated with waterbased coatings. While
the stainless steel tanks and piping of the solvent-based system rarely need cleaning, the glass-
fiber tanks must be cleaned every six months. Cleaning the tanks requires approximately
16 man-hours and a labor cost per tank of about $1,000 per year. Also, waterbased adhesives
are more difficult to clean from equipment resulting in an increased labor effort.
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Nashua also stated that increased output of wastewater has resulted from the conversion.
Wastewater disposal costs are approximately $350 per week higher than before conversion. This
cost includes increased wastewater generated and shipping costs.
In addition to these relatively quantifiable costs above, Nashua has incurred some costs
associated with learning to use waterbased coatings. The amount of time spent by Nashua
personnel learning to mix, transfer, coat, and dry waterbased adhesives is significant, although
it is not easily quantified. Nashua's largest learning costs have revolved around the pumping
system for transferring waterbased adhesives to the coating head. Nashua has found that
waterbased acrylics have a strong tendency to dry in the valves of the pumps, causing them to
stick. Cleaning the pumps is costly, time consuming, and can interfere with the production
process. Nashua could not quantify the labor hours that have been spent on pumping problems,
however, the company considers it a significant cost of using waterbased adhesives.
2.4 The Decision to Convert
Nashua has invested significant capital to effect the conversion to waterbased adhesives.
While initial savings are obviously not the reason Nashua decided to convert, costs did play a
central role in its decision. Nashua personnel indicate that there were three motives behind the
corporate executive decision to switch to waterbased adhesives: regulatory costs, research and
growth, and environmental benefits.
The first motive in the decision was to avoid future regulatory costs. While its coating
lines are not currently regulated for air emissions, Nashua felt that future regulations might
become stringent enough to make solvent-based adhesive use unprofitable. Nashua believed that
since the trend towards higher-priced permits would continue, solvent-free waterbased adhesives
seemed an appealing alternative to solvent-based adhesives.
A second motive for converting to waterbased adhesives was to become involved in a
developing field of adhesive technology. Nashua plays an active role in professional
organizations and in development work with adhesive formulators and equipment suppliers.
According to Nashua personnel, there was essentially no continuing research aimed towards
improving current solvent-based adhesives. Nashua personnel believed that adhesive formulators
realized that solvent usage would be phased out and were concentrating their research and
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development efforts on other adhesive technologies, such as waterbased, hot melt, and two-part
reactive adhesives. Nashua found that, for its purposes, waterbased adhesives possessed the
performance levels (e.g., tack, adhesion, temperature sensitivity) required by its customers.
Currently, the costs of formulating solvent-based adhesives and purchasing waterbased adhesives
are approximately the same for Nashua ($1 to $2 per dry pound). With continuing research,
Nashua feels that future waterbased adhesive prices may drop as performance levels increase.
A third motive expressed by Nashua personnel for the conversion to waterbased adhesives
was the company executives' belief that moving toward waterbased adhesives was
environmentally correct. Nashua personnel indicated that the company had other compelling
reasons to convert to waterbased adhesives, as mentioned in the previous paragraphs. However,
they believed that the executive decision to convert to waterbased adhesives was an attempt to
move into a more environmentally sound means of production, above and beyond monetary
considerations.
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CHAPTER 3
MARKETING FACTORS AFFECTING PROCESS CONVERSION
3.1 Customer Approval Requirements
For Nashua's clients, performance characteristics and price are currently, and likely to
remain, the two most important factors in their decision to buy adhesive-coated products. Nashua
marketing personnel indicated that only very recently has a third factor, environmental impact
of the product, become important to some clients.
In order to retain its client base during the conversion to waterbased adhesives, Nashua
must cover the same range of applications achieved with solvent-based adhesives at competitive
prices. It has taken Nashua several years to acquire a range of waterbased adhesives that covers
its application needs while providing competitive prices. Nashua began the conversion to
waterbased adhesives in 1987 and has been replacing products incrementally since. Nashua's
technique of incremental replacement is described in Chapter 4.
3.2 Nashua's Marketing Techniques
When the executive decision to convert to waterbased adhesives was made in 1987, the
timetable for the conversion was not definitively set. To keep Nashua profitable during the
conversion process, it was decided that the conversion would be performed incrementally over
time. Nashua's laboratory was charged with locating waterbased adhesives that were less
expensive and had improved performance over Nashua's solvent-based adhesives. When a
suitable waterbased adhesive was obtained, it was introduced as a new and improved product to
their customers.
Nashua's clients have responded positively to the new adhesives. Nashua's incremental
replacement technique has allowed the company to find high quality adhesives, satisfy is clients
performance and pricing requirements, and reduce its use of solvent-based adhesives. Nashua
planned to be solvent-free by the end of 1993.
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CHAPTER 4
MATERIAL ISSUES INVOLVED IN THE PROCESS CONVERSION
4.1 Introduction
Nashua uses three primary raw materials for label stock manufacturing: adhesive (and
its components), release coat, and paper substrate. Although all three materials are affected,
adhesive formulations have undergone the most change during the conversion to a waterbased
process, and are the focus of this chapter. To formulate solvent-based adhesives, Nashua
purchases raw chemicals, baled rubber, and toluene, and mixes them on-site. Formulating
solvent-based adhesive from raw materials is less expensive for Nashua than buying them coater-
ready from a supplier. The Omaha facility does not yet formulate its own waterbased adhesives,
but hopes to in the future.
During the adhesive conversion, Nashua has also been converting its release coating from
a solvent-diluted silicone to a 100 percent solids silicone. This release coat conversion was
prompted by Nashua's corporate decision to eliminate all solvent usage in its processes. Nashua
has experienced some difficulties with the new solids silicone release coating. Nashua attributes
these difficulties to limited time spent on development, not to inherent problems with the solids
silicone coating.
To be compatible with the higher pH of the waterbased adhesives, Nashua had to purchase
slightly different types of paper stock. The costs and performance quality of this new paper are
very close to the old paper and Nashua uses the same vendors as before the conversion.
Untreated paper has a relatively high surface energy on which waterbased adhesives can generally
be coated effectively. For this reason, coating modifications needed to process waterbased
adhesives may be very different at a facility that coats lower surface energy materials, such as
plastic films. Another material issue relevant to the conversion is the cleaning agents used for
coating equipment. This issue is discussed briefly in this chapter.
Nashua has experience with coating waterbased pressure-sensitive products since 1982
when Line 3 was converted from a waterbased heat seal to a waterbased label stock coating line.
In 1987, a corporate mandate put the entire company on a six year plan to convert its
solvent-based adhesives to waterbased adhesives. Since then, the Omaha facility has been
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gradually converting Line 1 to solvent-free waterbased adhesives. These efforts were accelerated
in the last six months of 1993 to reach the corporate goal of complete conversion by December
31, 1993. For this reason, many of the facets of conversion discussed in this chapter are
currently being reviewed and may change depending on Nashua's needs.
4.2 Finding Replacement Waterbased Adhesives
Although conversion of each adhesive-coated product line was different, Nashua was able
to follow general guidelines while choosing replacement waterbased adhesives. Figure 4-1 is a
flowchart of the general steps Nashua has used to replace solvent-based adhesives. The first step
in finding an alternative waterbased adhesive is to define the customer performance specifications
required of the end-product. This task was relatively simple for Nashua since it already knew
most of its customer requirements. In some cases, tests were performed to determine customer
specifications, which allowed Nashua to improve its adhesives' properties before introducing
them to customers.
Depending on the end-use application, customer specifications can require varying
amounts of adhesion and tack. Customer specifications depend on the application environment,
expected adherents (substrates the end-product will be applied to, such as frozen food packages),
and required bond strength. Variables in the application environment include temperature,
humidity, and chemical or water exposure. The nature of the adherend for which the adhesive
is intended is critical to adhesive performance, because it must be compatible with the adhesive.
Also, the bond strength must be adequate for the application, whether it be a permanent vertical
label (e.g., 55-gallon drum label), or an easily removable/reusable label.
After determining a profile environment for which a solvent-based adhesive will be used,
Nashua can determine whether one of its current waterbased adhesives will meet the performance
specifications of the end-product it wants to change. If a potentially suitable adhesive is found
in-house, research and development (R&D) and cost/benefit (C/B) analyses are performed to
determine the feasibility of using that adhesive for the new application. Nashua can attempt to
modify the adhesive's properties by addition of tackifiers, plasticizers, other performance
enhancers, and/or fillers (as stated previously, Nashua does not formulate its own waterbased
adhesives, however, it does have the capability to slightly modify its purchased adhesives by
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Perform R&D and
Cost/Benefit Analysis
to Determine Feasibility
Determine Required Product
Performance Specifications
Yea
f Is Adhesive Cost A
I Effective and Meeting |-
l Specifications? J
No
WHI Any Current Waterbased
Adhesives Meet or Exceed
Specifications?
No
Can Any Current Waterbased Adhesive
be Modified to Meet or Exceed
Specifications?
Determine Required
Modifications
)
Yes
No
Yes
Yes
C
Can Re-Formulation
Occur In-House?
Does Current Vendor Have Similar
Adhesive to Meet or Exceed
Specifications?
Yes
Yes
No
Is the Cost Similar to ^ No
Call Vendors Requesting
Current Solvent-Based I—
Waterbased Adheeives to
Adhesive? J
Meet Specifications
Adhesive be
Found that Meets
Specifications and
Is Cost Effective?
Can
No
Yes
Begin Bench-Scale
and Full—Scale
Production of
New Adheelve
Consider Dropping
Product Line if
New Waterbased
Adhesives are
Unfeasible
Choose Top 4 or 5
Adhesives to Perform
R&D and Cost/Benefit
Analysis to Determine
Feasibility
Figure 4-1. Flowchart of replacement waterbased adhesive selection process.
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blending additives into the formulation). If its current adhesive does not meet the required
specifications, Nashua may consult with its adhesive vendor to determine if different formulations
of the adhesive are available. If so, Nashua will perform R&D and C/B analyses on a more
suitable version of the adhesive to determine its application feasibility.
If Nashua is unable to locate a suitable waterbased replacement or improvement (from the
current vendor), various adhesive vendors are contacted with requests for product samples of their
waterbased adhesives that meet the proper specifications. Nashua may receive 10 to 20 new
adhesive formulations as a result of these requests, and tests each of the samples. Measurements
taken may include shear strength, viscosity, tack, and adhesion using a bench-scale coating
apparatus. This testing narrows the field to a few candidates. At this point, all other factors such
as cost, compatibility, marketability, and ease of application enter the decision-making process.
The adhesives are ranked to determine which will undergo extensive R&D and pilot-scale testing.
If a suitable replacement adhesive is not found for a particular product, Nashua may
consider dropping that product line based on C/B analyses. If the incremental cost of searching
for or using a particular waterbased adhesive does not appear to be cost-effective or technically
feasible (i.e., if the customer would not benefit from the conversion), Nashua may consider
dropping that product line, especially if it is a low volume product.
4.3 Formulation of Solvent-based and Waterbased Adhesives
Nashua formulates its solvent-based adhesives on-site. Before conversion efforts began,
the company used six solvent-based and four waterbased adhesive formulations. It currently uses
only two solvent formulations which constitute less than ten percent of its product volume.
When conversion is complete, Nashua expects to have eight to ten solvent-free waterbased acrylic
formulations. The adhesive technology effects of Nashua's conversion to waterbased adhesives
are discussed here.
To formulate a solvent-based adhesive, Nashua takes baled natural rubber and mills it into
strands a few inches (centimeters) in length. The milled rubber is then added with resins and
additives into a mixing tank. Prior to their addition, the resins are heated in an oven to between
140° and 160°F for approximately two to eight hours. The purpose of heating is to reduce the
naturally high viscosity of the resins for better mixing. The final ingredient is the carrier
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(toluene), which Nashua stores in USTs outside the facility. Toluene is the final ingredient added
because of the explosion potential caused by static electricity that can be generated when stirring
the solvent.
Nashua is not currently formulating its own waterbased adhesives. These adhesives are
purchased as pre-mixed emulsions and stored in glass-fiber tanks until use. These tanks are
located inside the facility and provide constant/intermittent agitation to reduce the amount of
settling solids. The pre-mixed adhesives include most of the ingredients that Nashua will use in
its waterbased formulations, although some materials are generally added to the emulsion before
being sent to the coating head. Nashua may add fillers or tackifying agents to the adhesives in
a holding tank located next to the coating room. The amount and type of additives are product-
specific.
Nashua's waterbased adhesive formulations include a concentration of less than
0.5 percent ammonia (NH3). The purpose of this ammonia is to keep the adhesive slightly basic
(pH of approximately 8.0 to 9.0), which Nashua has determined to be the best for its coating
operations. Nashua engineers stated that most adhesive coaters in the industry operate their
waterbased adhesives either slightly acidic or slightly basic depending on each facilities' substrate
characteristics.
One of the major problems with waterbased adhesives at Nashua is maintaining consistent
waterbased coating viscosities. Waterbased coating viscosity varies with temperature and
humidity and is constantly monitored in the storage tanks. Ingredients may be added periodically
for viscosity adjustment. Nashua strives to maintain coating viscosities of waterbased adhesives
between 500 and 2,000 centipoise, although for any waterbased adhesive application, the coating
viscosity will vary considerably depending on the coating method used. Solvent-based adhesives
tend to be somewhat higher in viscosity.
Nashua uses a heat exchanger located at each coating head pumping station to help ensure
constant coating viscosity. This heat exchanger is not used for every waterbased adhesive and
its temperature varies between waterbased formulations. Viscosity control is one of the primary
reasons that waterbased adhesives are more difficult to coat than solvent-based adhesives. On
rare occasions, entire batches of waterbased adhesive have been rejected and sent to waste tanks
or recycled back to storage tanks where the viscosity can be adjusted and monitored. Solvent-
based adhesives do not experience such wide variations in viscosity. Through trial and error,
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Nashua determined that its solvent-based adhesives coat test at a temperature of approximately
90°F, which is the normal ambient temperature in the plant year-round.
Nashua indicated that the solids content of its previous solvent-based and current
waterbased adhesives vary over the same range. Solids content of its solvent-based adhesives
range from 30 to 70 percent while that of waterbased adhesives range from 30 to 60 percent.
For this reason, coating thicknesses and weights have not varied considerably between the two
types of adhesives. Coating thicknesses range from one to three thousandths of an inch and
coating weights range from 11 to 17 pounds of adhesive per ream of paper. For both adhesive
types, the actual coating thickness is product and adhesive specific.
4.4 Costs of Alternative Waterbased Adhesives
In general, the cost of Nashua's waterbased adhesives is approximately the same (within
ten percent) as the cost of formulating its solvent-based adhesives. Nashua estimated that the
costs for its solvent-based adhesives range from $1 to $4 per pound of wet adhesive {i.e., mixed
adhesive, which is ready to apply to a substrate). This cost varies with the price of oil and is
higher for some specialty types of adhesives. Although the average cost of waterbased adhesives
also ranges from $1 to $4 per wet pound, some formulations are more expensive than solvent-
based, resulting in increased costs to customers. This increase in costs has not changed Nashua's
profit margin.
Nashua stated that the largest contributing cost in its end-product is the raw paper used
to manufacture its label stock. Paper costs range from $0.50 to $0.75 per pound depending on
grade and specification. The cost of the adhesives is a distant second or third largest expense
behind energy. Raw paper costs have increased minimally due to the change in paper type.
4.5 Cleaning Agents
The final raw material issue at Nashua concerns the cleaning agents used to remove
adhesive from storage tanks, adhesive filters, coating equipment, and spills. Nashua personnel
indicated that cleaning requirements have increased as a result of converting from solvent-based
to waterbased adhesives. This is due to the chemical properties of acrylic adhesives. Once an
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acrylic adhesive has dried (i.e., the water has evaporated) it forms a hard, polymer layer.
Solvents can penetrate this layer, and Nashua currently uses toluene and TCA to clean equipment.
Nashua is attempting to replace its traditional cleaning solvents with less volatile (and hazardous)
substances. Nashua engineers indicated that waterbased acrylic adhesives can be cleaned with
a mixture of soap, water, and low volatility solvents (e.g., mineral spirits) when wet; however,
more frequent and labor-intensive cleaning activities such as scraping and peeling will be
required to clean dried adhesive residue. Nashua expects that with increased experience, the
cleaning duties should become less cumbersome.
Storage tank cleaning has become somewhat less problematic with the addition of glass-
fiber lined storage tanks for waterbased adhesives. These glass-fiber tanks are cleaned with
high-pressure water and scraping tools approximately once every six months. In contrast, the
stainless steel storage tanks used for solvent-based adhesives require virtually no cleaning, since
toluene provides continuous cleaning during the mixing stage. Cleaning of other waterbased
coating equipment (i.e., coating heads, drip trays, etc.) is performed using water spray and
scraping. The solvent-based coating equipment rarely requires cleaning but TCA or toluene is
used to clean the equipment when necessary. Nashua uses PVC piping for waterbased adhesive
transfer which, instead of routine cleaning, is replaced when clogged with adhesive. Some pipe
replacement was required after three years of use.
Nashua indicated that its largest daily cleaning problem is the metal filters used to filter
adhesive when transferring from mixing tank to coating head. Currently, these filters are
removed from the lines every three to four hours for cleaning in a toluene bath with a scrub
brush. Since Nashua is phasing out its use of toluene, a new method for cleaning the filters will
need to be developed. Nashua has yet to find an equally effective replacement for toluene
cleaning of waterbased adhesive filters.
Nashua uses a TCA drip while coating solvent-based adhesives to remove adhesive from
the paper's edges during coating. This prevents "oozing" of adhesive during roll wind-up by
removing one-quarter to one-half inch of adhesive from both edges of the paper. This "oozing"
can potentially cause major handling problems. Nashua is currently using a "wiping blade" setup
to remove waterbased adhesive from the edge of the paper. This is a more labor-intensive
method than the TCA drip. Nashua personnel hope to find a more effective solventless method
of removing adhesive from the edges of the product.
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CHAPTERS
EQUIPMENT ISSUES INVOLVED IN THE PROCESS CONVERSION
5.1 General
Nashua personnel indicated that nearly every aspect of its label stock manufacturing
process had been affected by the conversion to waterbased adhesives. However, all of these
changes have proven feasible and have been implemented over time. Nashua believed that any
problem arising from the conversion could be solved with a concerted effort in R&D,
engineering, and redesign. Since Nashua has been gradually converting its process for about
seven years, it has been able to spread its efforts out over a much longer time frame than is
normally available to plants attempting to meet permitting deadlines.
This chapter details the process equipment changes that were accomplished for the
conversion. The following list contains the equipment and machinery which required
modification during the conversion.
• Storage tanks
• Mixing and holding tanks
• Resin heating oven
• Adhesive filters
Piping
• Pumps and motors
• Heat exchangers
• Coating head and related equipment
• Drying/curing ovens
• Carbon adsorber
Section 5.2 discusses specific equipment changes and equipment performance requirements.
Section 5.3 presents maintenance issues related to the conversion. Finally, Section 5.4 outlines
the costs and vendor selection process associated with implementing the changes.
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5.2 Process Design Modifications and Equipment Trials
During the conversion to waterbased adhesives, much of the equipment and machinery
used in the adhesive coated product manufacturing process had to be replaced, added, retrofitted,
or decommissioned. These modifications and equipment trials are addressed in this section.
5.2.1 Storage Tanks
Nashua currently uses USTs located outside the facility to store toluene for solvent-based
adhesives. These underground tanks reduce the fire and explosion hazards of toluene and rarely
require cleaning or maintenance. Other raw materials for its solvent-based adhesives are stored
in boxes or drums inside the facility until use.
For waterbased adhesive storage, Nashua has installed glass-fiber lined tanks inside the
plant near the mixing rooms. Since Nashua has been gradually converting to waterbased
adhesives, replacement tanks have been added as necessary to meet the increased waterbased
capacity. Their location is more convenient than the USTs for cleanup (performed approximately
twice per year) and maintenance. Nashua decided that using the original stainless steel USTs
would not be feasible for waterbased acrylic adhesives due to the cleaning frequency and
difficulty in removing acrylic from the steel walls.
Since the solids in waterbased adhesives tend to settle and stick to the interior walls of
the tanks, two blades (one located near the top, and the other near the bottom) are included to
provide continuous/intermittent agitation. This agitation is required to stabilize the emulsion and
thus maintain a coatable viscosity for the waterbased adhesives. However, over-agitation of
waterbased adhesives may result in foaming either in the tank or at the coating head. Agitation
is not required for solvent-based adhesives since they are formulated on-site using just-in-time
manufacturing methods.
Continuous viscosity measurement is required when preparing and coating waterbased
adhesives. Nashua uses a viscometer located next to the storage tanks, where an operator keeps
a log of waterbased adhesives' viscosity. If the viscosity varies outside an acceptable range for
an application, the chemists are immediately notified. Viscosity-altering chemicals may be added
as necessary. This monitoring was not required when mixing solvent-based adhesives.
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Finally, a new glass-fiber waste storage tank has been purchased, which is larger than any
of Nashua's waterbased adhesive storage tanks. This tank stores waste or rejected adhesive until
ready for transport to the local publicly-owned treatment works (POTW).
5.2.2 Mixing and Holding Tanks
Nashua uses stainless steel mixing tanks to formulate its solvent-based adhesives.
Waterbased adhesives are held in tanks located beside the coating room. Nashua pumps the
premixed waterbased adhesives from its storage tanks to the holding tanks where an operator may
add some materials to slightly alter the adhesives' properties or coating weight. As with storage
tanks, these holding tanks have been replaced on an as-needed basis over the last seven years.
In addition, most of the pumps, valves, and pipes were changed by Nashua personnel while the
tanks were installed by outside support. Also, the mixing and holding tank rooms will no longer
require explosion-proof walls when conversion to waterbased adhesives is complete.
5.2.3 Resin Heating Oven
The oven Nashua uses to heat resins for solvent-based adhesives will no longer be needed
when conversion to waterbased adhesives is complete. However, this oven will be kept on-site
should Nashua have a future need for it.
5.2.4 Adhesive Filters
Nashua currently uses similar stainless steel canister filters to filter both its solvent-based
and waterbased adhesives. The company will continue to use these filters when conversion is
complete. The major difference between adhesive filters is that the mesh or screen size is
slightly larger for waterbased adhesives. This is due to the emulsion state of the waterbased
adhesives which have slightly larger particle sizes.
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5.2.5 Piping
Nashua uses stainless steel pipes for piping solvent-based adhesives. These are in the
process of being replaced with PVC pipes for the waterbased adhesives. The primary reasons
for using PVC are low cost and ease of replacement. PVC piping is considerably cheaper than
stainless steel and, as with tanks, has been replaced on an as-needed basis. Also, the PVC piping
will not be cleaned when clogged, but will be replaced as necessary. This replacement has been
accomplished in-house. PVC pipes have not been used for solvent-based adhesives due to the
explosion potential of toluene.
5.2.6 Pumps and Motors
Nashua's pumping requirements for solvent-based and waterbased adhesives differ
significantly. Nashua uses a simple high-shearing (agitation) vane pump with solvent-based
adhesives. For its waterbased adhesives, Nashua experimented with a lobe pump and an air
(diaphragm) pump, and determined that the air pump worked better. Air pumps are low-shearing
pumps because the adhesive is not agitated by pump blades such as those used in vane pumps.
However, maintenance personnel stated that the air pumps require extensive maintenance.
Acrylic adhesives tend to stick in the pump valves causing them to be taken off-line for a four-
hour cleaning approximately every three to four months. As with tanks and pipes, Nashua has
purchased replacement pumps on an as-needed basis.
Pump motors required replacement due to the different air coupling mechanisms of the
new air pumps. Nashua personnel did note that there was no increase in motor capacity or
energy required for the waterbased conversion. A bonus for Nashua is that the new motors do
not need to be explosion-proof. Explosion-proof motors were required to run solvent-based
adhesives to provide protection of the volatile toluene used in the mixture. Nashua's waterbased
adhesives contain no solvents and thus have no explosion potential.
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5.2.7 Heat Exchangers
An additional piece of equipment that Nashua sometimes uses for waterbased adhesives
is a heat exchanger located at the supply pump to the coating head. This heat exchanger is used
when necessary to ensure a consistent coating viscosity (via temperature control). Viscosity is
a primary control variable of Nashua's waterbased adhesives and requires constant monitoring
to ensure proper coating thicknesses and uniformity. Nashua's heat exchangers are of the plate-
frame type and are primarily used for cooling rather than heating purposes. Solvent-based
adhesives do not require a heat exchanger.
5.2.8 Coating Head and Related Equipment
One of the major modifications for Nashua's conversion involved the redesign of the
coating head and related equipment on Line 1. For solvent-based adhesives, Nashua used various
coating methods including direct gravure and direct reverse gravure. However, in order to coat
waterbased adhesives, Nashua altered its coating head to include a reverse rolling mechanism for
adhesive metering. Figure 5-1 illustrates the waterbased coating head used at Nashua. The
metering roll is used to pick up adhesive from the trough and transfer it to the application
(reverse) roll. This reverse roll application is used to even out the waterbased adhesive before
it contacts the paper substrate. This type of coating is termed three roll reverse gravure or offset
gravure.
In order to coat waterbased adhesives faster, Nashua changed the type of coating rollers
it used. Traditional steel rollers were not the best suited for waterbased application. Nashua uses
a combination of steel and rubber rollers to apply its waterbased adhesives. In addition to the
coating head configuration change, Nashua changed the gravure coating head density. Since
waterbased adhesives have higher surface tension and thus do not wet the paper substrate as well
as solvent-based adhesives, a smaller gravure density was designed to provide more coating
points on the substrate. Specific details of coating head configuration and gravure density are
considered proprietary by Nashua Corporation and therefore are not discussed here. Nashua
engineers did indicate that waterbased coatings could have been coated with its solvent-based
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Wiping Blades
Metering Roll
Adhesive
Dams
Paper Substrate
Coating
Pan
Application
. Roll
Rod
To Waste Collection Tank
From Holding/
Mixing Tank
Exchanger
Figure 5-1. Adhesive application equipment.
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coating heads at a much slower speed. To increase line speed, the coating head was changed to
include rubber rollers and the gravure density was increased.
In the recent past, Nashua had used only one coating head system on Line 1. This caused
switchover delays of approximately eight hours to convert from a solvent-based to a waterbased
coating head. To combat this problem, Nashua redesigned its Line 1 coating machine to have
two easily interchangeable coating heads (since Line 3 is dedicated to waterbased product, no
changes were made to it). This reduced changeover downtime from eight hours to one to two
hours. The coating head can be changed in approximately fifteen minutes, however, to change
the supply and flush the adhesive dispensing equipment, another hour or so is required.
Nashua has found that the coating process is less robust (i.e., requires more maintenance
and downtime) for waterbased adhesives. Increased cleaning requirements and more frequent
machine adjustments for coating thickness and smoothness are required for waterbased adhesives.
Line operators stated that the most often adjusted coating parameters are nip gap size (i.e.,
distance between application roll and reverse roll) and reverse roll speed. These are also
important control elements in solvent-based coating, however, the frequency of required
adjustments is greater for waterbased coating. Nashua has also experienced foaming with
waterbased adhesives due to their emulsion state. Excessive agitation can cause waterbased
formulations to foam, creating additional coating problems.
In addition to changing the coating head, other related equipment required retrofit or
replacement. Traditionally, Nashua has used a TCA drip to remove excess adhesive from the
paper's edges to prevent runout of the adhesive during windup. However, Nashua plans to phase
out TCA and is currently using a stationary wiper blade on either end of the coating head to wipe
the adhesive from the paper's edges and return it to the adhesive reservoir. Nashua personnel
indicate that this is a short-term solution and alternative methods are currently under
consideration.
Nashua also has made available a smoothing bar for its waterbased adhesives, although
it is not always used for every application. The purpose of this smoothing bar is to provide a
smooth, even coat of adhesive across the entire paper length. The bar is located immediately
after the coating head and is not required for solvent-based adhesives.
Nashua believes that its current waterbased coating heads have reached their maximum
production volume capacity (i.e., they cannot generate product any faster). The company is
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currently looking to replace the Line 3 coating head with a new, higher-volume head. Nashua
would not disclose the design of the new coating head.
52.9 Drying/Curing Ovens
The final major modification for the Nashua involved the drying/curing ovens. Solvent-
based adhesives require an oven temperature configuration in which the temperature in the initial
zone is relatively low and gradually increases in subsequent zones. At the final zone, the
temperature is at its highest to evaporate any remaining solvent in the adhesive. At Nashua, this
solvent-based temperature profile involves oven temperatures of approximately 100°F at the low
end and 200°F at the high end. This configuration is necessary because solvent-based adhesives
may dry improperly if introduced to high temperatures during the initial curing stages, and
excessive solvent removal may lead to explosion hazards.
Waterbased adhesives exhibit the opposite response. They are exposed to high
temperatures (approximately 250°F) in the initial zone(s) of the drying oven to evaporate the
water as quickly as possible and cure the adhesive. The temperature is then reduced during
subsequent zones until it approaches 55°F at the oven exit. Heat exchangers are used to supply
the cool air during final oven zones for waterbased adhesives. Nashua engineers stated that the
oven temperatures are set permanently for drying/curing of all its waterbased formulations.
Operators are not required to change these settings when coating different adhesives. Nashua
also indicated that its oven energy requirements have not increased during the conversion.
Although the temperature profiles have changed, the overall energy requirements have remained
approximately the same.
Nashua's ovens employ a roller system to keep the coated web moving through the oven.
The ovens for Lines 1 and 2 are heated by forced steam generated from an on-site boiler. The
same oven on Line 1 is used to dry/cure both waterbased and solvent-based adhesive coatings.
Line 3 is heated by natural gas burners within the drying line. The steam or natural gas heats
the air in the oven to a maximum of approximately 250°F. Each oven is approximately 200 feet
long and has up to five temperature zones. Within each zone, the temperature can be controlled
independently of the other zones in the oven. When coating waterbased adhesives, all the ovens
use an air recirculation system. Only a portion of the air passing over the coated web is vented
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to the atmosphere, while the remainder is again passed over the web. This lowers the energy
requirements, especially for the on-site boiler during the winter months. Nashua engineers noted
that the energy cost on a dollars per BTU basis is approximately the same for steam and direct-
fired ovens.
Total air flow through the ovens remains approximately the same as before conversion,
although some reconfiguration has occurred to accommodate temperature differences. Air flow
per temperature zone was changed, but exact air flow per zone is considered proprietary
information by Nashua. Typically, solvent-based products begin with a high airflow in the initial
zone to evaporate the large amount of solvent and keep the solvent concentration below the LEL.
The air flow drops during subsequent oven zones. Waterbased products experience the opposite
treatment to solvent-based products; low air flows are predominant in the initial oven zones while
higher air flows are typical in the last oven zone.
A significant drying problem associated with waterbased adhesives is curling. At Nashua,
these adhesives are subjected to high temperatures in the early stages of drying which not only
evaporate water from the adhesive, but also evaporate the natural water content of the paper
substrate. In simple terms, dry paper tends to curl. Curling can lead to major laminating
problems. Since the face stock used for lamination has its natural water content intact, over-dry
adhesive-coated paper tends to draw water from the face stock, resulting in curling. For the
waterbased adhesives, Nashua strives to keep a final water content after drying of about two to
three percent. Even with this water content in the adhesive, the paper tends to curl. Nashua has
diminished this problem somewhat with the addition of a water misting system located at the exit
of the drying oven. Upon exiting the oven, the cured coating and paper are sprayed with an even
water mist to replenish the natural water content of the paper. Nashua sets the final oven zone
temperature at approximately 55°F because the paper exhibits the best water absorption properties
at that temperature.
Curl is much less of a problem with solvent-based adhesives since high temperatures are
not introduced until the final drying stages, thus reducing the residence time for the water in the
paper to evaporate. Also, toluene has a low flash point (40°F) and high vapor pressure
(20 mmHg abs); therefore, the oven temperatures are not quite as high for the solvent-based
adhesives, allowing the paper's natural water content to remain in the paper.
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Nashua personnel indicated that Line 1 oven capacity was not an issue in the conversion
to waterbased adhesives. The company's original ovens had enough capacity to run waterbased
adhesives at approximately the same line speeds as its solvent-based counterparts. The addition
of infrared (IR) heaters to some oven zones has increased drying capability. These IR heaters
provide additional heating capacity by pre-heating the adhesive-coated paper using less energy
than would otherwise be required by the oven. This allows a lower residence time in the oven,
which is important for faster line speeds in waterbased formulations. Nashua uses one to five
IR heater(s) per set of ovens. Since Line 3 ovens have been configured to run waterbased
adhesives, no changes were necessary in its configuration.
Most of the oven changes were accomplished using in-house knowledge except for
IR heater installment. These heaters were installed by the vendor but are maintained in-house.
A benefit of converting to waterborne adhesives has been the reduced fire and explosion
hazards in the ovens caused by the solvent-based adhesives. Prior to conversion, Nashua used
monitors to constantly record the LEL of solvent present in the ovens. These monitors will be
removed when conversion is completed. Also, by removing the explosion hazard, Nashua will
not have to continually measure dilution air flow in the ovens and may reduce air dilution costs.
Nashua has plans to fit new ovens on its Line 3 coating machine. These ovens will
replace the current ovens, which are approximately 25 years old. Nashua is doing this to help
accomplish its goal of enabling Line 3 to apply both release and adhesive coats and also laminate
coated paper. Nashua personnel specifically stated that the new ovens are not a result of process
changeover, rather, they are simply upgrading to state-of-the-art ovens.
5.2.10 Carbon Adsorber
When using solvent-based adhesives on Line 1, Nashua sends the oven exhaust to a
carbon adsorption system located on the roof of the facility. With the conversion to waterbased
adhesives, Nashua will no longer need this solvent recovery system. They already have made
plans to sell the adsorption system for approximately $50,000; however, it will cost
approximately this much to remove the system and dispose of the fouled charcoal. Removal of
this system will reduce operational costs including charcoal replacement, steam production for
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stripping the charcoal of its organics, and a recovery system to extract the organics from the
steam.
5.3 Maintenance and Operational Issues
Nashua's conversion to waterbased adhesives has involved various equipment maintenance
issues. Maintenance has increased in some instances and decreased in others depending on the
type of equipment. Overall, however, Nashua personnel indicate that maintenance requirements
have balanced and remain approximately the same as they were before conversion. They also
expect that some of the new problems will disappear with time as they gain experience in the
coating with waterbased adhesives. This section briefly discusses the maintenance issues
involved with each equipment item pertinent to the conversion process.
Nashua indicated that while maintenance activities associated with storage, mixing, and
holding tanks have changed, there has been no net increase in maintenance in this area. New
maintenance activities include more frequent cleaning and some increased clogging. These
requirements absorb maintenance capacity previously associated with solvent-based adhesives,
including monitoring for leaks and accessing USTs for repair.
Maintenance requirements for the new PVC piping have remained the same or are
somewhat lower than for the stainless steel pipes used for solvent-based adhesives. Clogging
problems are readily solved by replacing the inexpensive PVC pipes with new ones.
Pump maintenance has increased due to the tendency of waterbased acrylic adhesives to
stick in the pump valves. This results in taking the pumps off-line for approximately four hours
every three to four months for cleaning.
The heat exchangers are relatively low maintenance items. They require only periodic
preventative maintenance to clean or repair.
Nashua expects no change in maintenance for the coating head and related equipment.
In fact, since creating the dual coating head for Line 1, maintenance problems associated with
switching the coating head have been eliminated. Although the waterbased coating head has
more parts (e.g., metering roll, and smoothing bar), maintenance has not been a major deterrent
to changeover.
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Maintenance requirements for the drying/curing ovens have evolved during the conversion.
Maintenance costs for the LEL meters have dropped since solvent-based use has diminished,
however, the IR heaters for waterbased adhesives require periodic maintenance. Nashua expects
that some additional maintenance may be required in the future if the drying of waterbased
adhesives begins to affect the interior of the ovens via solids entrapment.
The conversion has reduced maintenance on the carbon adsorber. Under full-time solvent-
based operation, the carbon adsorber required maintenance approximately five to ten times per
year. This level has been reduced as the percentage of solvent-based adhesive use has declined.
Since the adsorber will no longer be used at the Nashua facility after complete conversion, this
maintenance requirement will be eliminated.
5.4 Vendor Selection and Costs of Modifications
Nashua used several methods to locate and install new equipment during the conversion
to waterbased adhesives. The particular path chosen varied depending on the equipment sought.
Nashua also verified equipment costs using several different routes. This section examines
Nashua's process for finding equipment for conversion and investigating capital and installation
costs of this equipment.
5.4.1 Storage Tanks
In choosing new tanks, Nashua consulted an outside agent that it uses on a continual basis
for purchasing much of its auxiliary (i.e., non-process) equipment. This agent deals with many
tank vendors and was entrusted to choose the best (and most cost-effective) tanks for Nashua's
application. Nashua indicated that the agent receives a small fee (percentage of the purchase
price) as part of the agreement.
Nashua's internal group of maintenance and engineering personnel installed auxiliary
components (e.g., pipes, pumps, valves, and switches) before the tanks were installed. However,
actual tank installation was performed by the tank vendor. The new tanks required four to eight
hours of installation time each, depending on size. The tanks range in size from 700 to 15,(XX)
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gallons and range in cost from $5 per gallon for small tanks ($3,500) to $1.33 per gallon for
large tanks ($20,000). Installation costs run two to three times the purchase cost of each tank.
Nashua stated that a total of ten storage tanks have been installed as capacity for
waterbased adhesives has grown. Nashua noted that annual incremental costs for continuous
mixing of waterbased adhesives are minimal. Cleaning costs for storage tanks will increase.
Solvent-based storage tanks rarely required cleaning, but waterbased tanks will require cleaning
approximately twice per year. Cleaning involves two one-man shifts (16 man-hours) and
generates $600 in wastewater disposal costs. The wastewater is stored in waste tanks on-site
until being transferred to the local POTW.
5.4.2 Mixing and Holding Tanks
The rooms which house mixing and holding tanks have undergone a complete retrofit with
equipment compatible with waterbased formulations. After complete conversion, these rooms
will no longer need to be explosion proof due to the removal of solvent materials. Nashua
estimated that the necessary retrofit was accomplished in approximately one day per room, by
internal labor, and cost approximately $5,000. The scrap steel was sold for a minimal return of
$2 per 100 pounds.
Nashua used the same purchasing agent for retrofitted holding tanks as for storage tanks.
The tanks range in size from 700 to 3,000 gallons and range in cost from $3,500 for small tanks
to $15,000 for large tanks. Installation costs run two to three times the purchase cost of each
tank. Annual costs for operating the new holding tanks should remain the same as for
solvent-based materials.
5.43 Resin Heating Oven
The only cost difference associated with the resin heating oven may be reduced energy
requirements due to the phasing out of in-house formulated solvent-based adhesives.
Quantification of these savings, as well as savings in reduced maintenance and operator labor,
was not possible. Nashua personnel believe that these costs are minimal.
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5.4.4 Adhesive Filters
Nashua has purchased some new stainless steel filters for its waterbased adhesives;
however, these have been purchased over the last eight years on an as-needed basis. For this
reason, the total capital cost for filters has been dispersed over a number of years. Some of
these filters were already in use because of the waterbased capacity of Line 3. Nashua uses
approximately 10 to 15 stainless steel filters which cost about $2,000 each and are purchased
from two vendors.
5.4.5 Piping
When retrofit of its mixing and holding tank rooms is complete, Nashua will have
replaced all its stainless steel pipes with relatively inexpensive PVC piping. The stainless steel
piping has been replaced with PVC as waterbased capacity has grown or when older pipes were
clogged or worn out. PVC piping costs approximately $0.50 per foot and is purchased at a local
supply house. New pipes are installed by Nashua personnel.
5.4.6 Pumps and Motors
Pump and motor replacement has been accomplished by trial and error at Nashua. Pump
vendors were contacted with pump specifications and trials of air and lobe pumps were
performed to determine which was best suited for Nashua's application. Changeout of pumps
involved replacement of the pump and connection to a new motor. The replacement and hookup
of these pumps was accomplished with in-house personnel.
Currently, Nashua is using an air pump which costs approximately $500 to $2,000. The
vane pumps that Nashua used for solvent-based adhesives have been replaced with waterbased
compatible pumps as waterbased coating capacity has grown. Testing and trial runs of new
pumps have been conducted during the last seven years as old pumps have required replacement.
The energy costs for the motors have remained approximately the same. Maintenance of the air
pumps has increased relative to the vane pumps used for solvent-based adhesives; however, some
of these pumps are replaced rather than repaired due to economic feasibility. ,
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5.4.7 Heat Exchangers
The heat exchangers used to maintain constant coating viscosity were purchased through
the same agent Nashua uses to purchase storage and holding tanks. The purchase cost of one of
these heat exchangers was under $5,000 with an additional $2,000 to $3,000 for installation. The
additional energy costs associated with operating these heat exchangers was unknown.
Maintenance of the heat exchangers is minimal and therefore maintenance costs are not
quantified.
5.4.8 Coating Head and Related Equipment
Nashua personnel stated that in the past they have designed and modified the coating
heads for waterbased adhesives in-house at a cost of approximately $200,000. However, Nashua
is currently contacting vendors about new waterbased coating head designs. Nashua is talking
to various coating head vendors who specialize in coating waterbased adhesives and discussing
specific needs. Nashua intends to increase its line speeds in the near future; the factor limiting
line speed is the coating head (oven capacity is currently not a limitation at Nashua). From
experience, Nashua expects a newly designed coating head purchased from an outside vendor to
cost in the range of $300,000 to $600,000. Annual maintenance and operational costs for the
new coating heads are not expected to change.
5.4.9 Drying/Curing Ovens
Nashua did not increase its oven capacity to incorporate waterbased adhesives. Its oven
length was adequate to operate at approximately the same line speeds as solvent-based materials
with changes in zone configuration and temperatures only. The only capital costs Nashua
incurred were the result of adding one to five IR heaters to its ovens to increase drying/curing
speeds. These IR heaters cost approximately $10,000 each with an additional $10,000 for
installation. The highest expense associated with IR heaters is the control panel, which cost
$40,000 each. Since up to three or four IR heaters can be operated by one control panel, Nashua
needed several panels for its IR heaters.
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Nashua expects its energy requirements to remain approximately the same for drying
waterbased adhesives as it is for solvent-based adhesives. The only increased energy requirement
may result from the use of IR heaters, however, Nashua believes that the energy required to
operate this equipment is much less than that required to heat the oven air to higher temperatures.
Nashua expects that maintenance costs for its LEL meters should diminish as solvent-based
adhesives are replaced. However, future maintenance costs may increase should Nashua
experience acrylic buildup from use of waterbased adhesives.
Nashua's new state-of-the-art oven that will be installed on Line 3 will cost approximately
$1,000,(XX). This figure is given only as a reference for new oven costs (since the ovens are not
a requirement for conversion) and is not relevant to costs associated with Nashua's changeover
process. In fact, no capital costs for Nashua's current oven were incurred as a result of the
changeover (for the purposes of this report, IR heaters are treated as a separate expense from
ovens).
5.4.10 Carbon Adsorber
Nashua expects maintenance and operation costs for its carbon adsorption system to be
eliminated when conversion is complete. This system is slated for removal, saving approximately
$75,000 every five years in carbon replacement costs and approximately $60,000 per year in
electrical energy costs. Steam production and maintenance costs will also disappear. Nashua
will sell the recovery system equipment for a modest price of $50,000 when the conversion is
complete. This is approximately the cost of system removal and fouled carbon disposal.
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CHAPTER 6
ADHESIVE PRODUCT PERFORMANCE REQUIREMENTS
6.1 Adhesive Performance Criteria
Although Nashua produces label products aimed at the commodity sector of the adhesive
market, product performance requirements are still critical to its product lines' success. There
are two factors which must be considered to determine if an adhesive formulation will perform
its function correctly: the adhesive performance levels required in the application and the
environmental conditions to which the adhesive will be subjected.
There are three important adhesive properties by which adhesive performance may be
judged: tack, peel adhesion, and creep while experiencing shearing forces. Tack is defined by
the American Society of Testing and Materials (ASTM) as the property of a material which
enables it to form a bond of measurable strength immediately on contact with another surface.
Tack is quantified by measuring the force necessary to break such a bond. Peel adhesion is the
force required to break the bond between the adherend and adherent (the backing for the
adhesive) after a specified dwell time. It is quantified by measuring the force required to remove
an adhesive and its backing from a specified adherend surface at a specified rate of peel. Creep
results when the cohesive strength of the adhesive is not sufficient to withstand a shearing force.
When the adhesive experiences creep, the end result is that the adherent moves in relative
position to the adherend.
There are seven important environmental constraints on the performance of adhesives.
These constraints are temperature, humidity, solvent exposure, exposure to corrosive agents,
ultraviolet light exposure, exposure to air pollutants, and adherend surface conditions. Each
adhesive formulation will respond to these environmental influences differently. Exposure to
these environmental factors is strongly dependent on the end use of the product. For example,
bumper stickers for automobiles are exposed to extreme temperatures and humidity, as well as
air pollutants. Labels for frozen foods (which Nashua manufactures) are exposed to very low
temperatures.
The surface condition of the adherend for which the adhesive-coated product is intended
plays a strong role in resultant adhesive bond strength. If the surface condition is very rough,
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the adhesive may not develop enough surface contact with the adherend to form a strong
adhesive bond. If the adherend surface is too smooth, weak chemical interactions between the
adhesive and the adherend may compromise the strength of the adhesive bond. Dirt, loose paint,
or other surface contaminants can compromise adhesive bond strength dramatically.
6.2 Nashua Performance Criteria
For Nashua's niche in the marketplace, the two most important environmental exposures
are temperature and surface condition of the adherend. Since each adhesive formulation generally
has limited environmental conditions in which it functions well, Nashua has designed its entire
adhesive product line to cover a broad range of temperatures and surface conditions. Nashua's
product lines attempt to cover application temperatures from -30° to 150DF, on surfaces ranging
from corrugated cardboard to smooth plastics. This range of applications can be envisioned as
a two dimensional box, as depicted in Figure 6-1.
Nashua was able to cover the spectrum depicted in Figure 6-1 by using solvent-based
adhesives. In its move to waterbased adhesives, it has been necessary for them to retain coverage
of this spectrum of applications, or risk losing market segments. For the most part, Nashua has
had success finding waterbased adhesive formulations which met or exceeded the spectrum of
applications of the solvent-based adhesive formulations they replaced.
Nashua described a recent successful waterbased adhesive replacement of a solvent-based
adhesive. Nashua has one client who formerly purchased two label products manufactured with
solvent-based adhesives. One product was used by the client for room temperature applications,
while the other was used at low temperatures. The room temperature solvent-based adhesive cost
Nashua approximately $1.00 per pound of wet adhesive. The low temperature solvent-based
adhesive cost Nashua approximately $1.50 per pound of wet adhesive. Nashua was able to obtain
a waterbased adhesive which, at a cost of approximately $1.15 a pound, performs in both the
room temperature and low temperature environments.
Nashua has found that some inherent qualities possessed by waterbased adhesives are
superior to solvent-based adhesives for some of Nashua's end-product applications. For instance,
the tack of waterbased adhesives is generally somewhat lower than for solvent-based adhesives.
For the application of some labels, lower tack can be beneficial. If a label is improperly placed,
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Low-Smooth
Plastics
Surf oca
Energy
On
I
OJ
High-Corrogated
Cardboard
Sotvent-based
Adhesive 14
r
Waterbased
Adhesive #~
t
Waterbased
Adhesive #2
r
.1.
Solvent-based
Adhesive
ised I
" L
Solvent—based
Adhesive #3
Waterbased
Adhesive |1
n
H
J
J
Solvent—based
Adhesive |5
Waterbased
Adhesive §3
Solvent-based
Adhesive |2
-30*
Temperature *F
150T
Figure 6-1. Example application range of adhesive-coated products.
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it can be removed and reapplied without destroying the label. This property leads to additional
applications for waterbased adhesives, including removable/reusable labels. Nashua has found
that final adhesive bond strength is generally greater with waterbased formulations, so permanent
bonding can be stronger than with solvent-based adhesives.
While Nashua has had success replacing most of its solvent-based adhesives with
waterbased adhesives, duplicating the performance of every product has not yet been possible.
Nashua personnel believe that it may have to cease production of one product for which a
suitable waterbased adhesive alternative has not been found. Nashua personnel are not
particularly concerned about the loss of this product, as it represents a small portion of their
production volume (approximately ten percent of current sales).
In general, Nashua has found that the end product manufactured with waterbased
adhesives can be more robust for Nashua's applications than that manufactured with solvent-
based adhesives. While the end product may be superior with waterbased adhesives, the process
of coating those adhesives is much more cumbersome. Nashua personnel are convinced that the
increases in end product quality justify the more troublesome production process associated with
waterbased adhesives.
6.3 Ensuring Quality
Since the conversion to waterbased adhesives began, Nashua has been improving its
methods of ensuring the quality of its products. Until the late 1980s, when Nashua used
primarily solvent-based adhesives, the company employed a Quality Control (QC) method of
ensuring product quality. With this method, Nashua often tested a wet adhesive in its laboratory
before its use in production. Nashua's current on-site laboratory has assumed more of a Quality
Assurance (QA) function. Nashua's waterbased adhesives are, for the most part, already
formulated when they arrive from the adhesive manufacturer. Nashua takes samples from the
adhesive supply to determine if the adhesives perform according to the manufacturer's claims and
within Nashua's limits. This is accomplished by applying the adhesive to a substrate in the
laboratory on a bench scale coater and testing various adhesive parameters, such as peel adhesion
and tack. A sample of adhesive is run through an infrared spectrometer, which is capable of
determining if the adhesive has the correct chemical structure. This is an important test, because
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in the past, Nashua has received bulk shipments which were discovered to be the wrong adhesive.
According to Nashua personnel, Nashua's revised methods of laboratory QA have been highly
successful in ensuring adhesive quality.
With the shift towards QA, Nashua has enabled its laboratory to become more involved
with research and development of waterbased adhesives. Nashua stays abreast of new
developments in waterbased coating technology and is continually searching for potential product
improvements. Nashua is also conducting research that would allow the facility to formulate its
own adhesives in the future. According to Nashua personnel, when solvent-based adhesives were
prevalent at Nashua, the laboratory was viewed as an added expense in the business. Nashua
now considers its laboratory an important tool in the continuing success of its waterbased
adhesive-coated products.
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CHAPTER 7
PROCESS EMISSIONS AND WASTE STREAMS
7.1 General
Nashua personnel have stated that the primary purpose of the company's conversion to
waterbased adhesives was to ensure compliance with future federal and state regulations. The
conversion has caused changes in Nashua's waste streams and other emissions. This chapter
discusses environmental issues related to the conversion.
7.2 Changes in Waste Stream Generation and Emissions
Most of Nashua's waste streams and emissions are expected to decline to negligible levels
when conversion to waterbased adhesives is completed, replacement of current cleaning solvents
(i.e., toluene and TCA) is effected, and elimination of the solvent-diluted silicone release coat
is achieved. Wastewater discharges are the only waste stream expected to increase. Process air
emissions from the solvent-based adhesives through the oven on Line 1 will be completely
eliminated in this conversion process. Non-process air emissions such as cleaning and fugitive
leaks from toluene and TCA storage and handling are also expected to be eliminated. This
section discusses the quantifiable impact of conversion on air emissions, hazardous waste
generation, wastewater discharges, and solid waste.
7.2.1 Air Emissions
To quantify the air emissions differential at Nashua, stack and fugitive emissions of
toluene and TCA were compared from pre-conversion to expected levels after conversion.
Nashua strives to leave less than one percent solvent in its final coated product; however, this
amount will be neglected for the following crude analysis of Nashua's annual toluene emissions.
Before conversion, Nashua estimated its stack and fugitive emissions of toluene at
1,500,000 pounds per year after control. After conversion, Nashua expects that toluene emissions
will be zero from the adhesive coating process and minimal from cleanup operations. (Toluene
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used in cleanup operations will be replaced as soon as a viable alternative is found.) Before
conversion, stack and fugitive TCA emissions were approximately 60,000 pounds per year. After
conversion (when TCA cleaning requirements are reduced), Nashua expects that TCA air
emissions will be negligible. Some TCA may be used as a final wipe on the coating head after
cleaning until a suitable replacement is found.
The less than 0.5 percent concentration of ammonia present in waterbased adhesives has
caused increased concern because of the Occupational Safety and Health Administration (OSHA)
regulations concerning worker exposure to ammonia. Testing and personnel monitoring will be
continued to ensure worker safety.
Nashua personnel stated that the particulate material (PM-10) emissions from their boiler
operations should remain about the same after conversion. Demand on its boiler output should
not change significantly. However, personnel indicated that if PM-10 emissions became a
problem, control equipment may be added.
122 Hazardous Waste
Before conversion, Nashua recovered toluene emissions from the oven via a carbon
adsorber. This recovered toluene was then sent to an incineration company who used the solvent
for fuel blending. Nashua estimated that it sent 30 55-gallon drums per month to the incinerator
before conversion. After conversion, it expects to send about one 55-gallon drum of toluene
waste monthly to the incinerator, if no replacement is found.
TCA hazardous waste shipments should remain about the same after conversion as before,
approximately one to two 55-gallon drums per month. The reason for this is that before
conversion Nashua recycled approximately 90 percent of the TCA they used for cleaning
purposes. Due to the reduction in TCA usage, Nashua will no longer recycle TCA and all spent
TCA will be disposed.
7.23 Wastewater
Nashua's wastewater disposal methods have changed as a result of the conversion.
Nashua generates wastewater from cleaning operations and waste waterbased adhesive.
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Originally, only Line 3 operations (which have always been waterbased) resulted in process
wastewater. Solvent-rich effluent from Lines 1 and 2 were collected via a drainage system and
stored in waste tanks until shipment off-site as hazardous waste. Wastewater shipments have
increased as Nashua has brought more waterbased products on-line. Nashua officials were unable
to quantify wastewater discharge differences before and after conversion although they stated that
the amount generated has increased.
Nashua engineers stated that officials at the local POTW are very receptive to its
wastewater because it has a high in biological oxygen demand (BOD) and provides excellent
organics to break down sewage from other city wastes. However, in the future, Nashua expects
that the POTW will not as readily accept its high-BOD wastewater as stricter environmental
regulations lower the amount of organics that can be released to the sewer. Nashua personnel
noted that a minuscule amount of organics will always be present in its waste adhesive resulting
from the concentration of broken down chains of acrylate polymers produced during
polymerization of the waterbased acrylic formulation.
7.2.4 Solid Waste
Nashua engineers indicated that they do not expect the amount of solid waste to increase
due to the conversion. Most of the company's solid waste consists of waste coated paper which
is currently not recyclable. Nashua's total hazardous waste shipment volume has been reduced,
since the paper originally coated with solvent was sent off-site as hazardous waste, but as a result
of the conversion, can now be landfilled. Other wastes, like solid waste generated during
cleaning operations (e.g., brushes, rags) can be landfilled when contaminated with waterbased
adhesives, whereas solvent-based adhesive cleaning waste must be disposed of as hazardous
waste.
73 Waste Disposal Costs and Savings
Nashua expects to decrease its emissions and disposal costs by decreasing permitting
requirements, lowering insurance costs, and reducing hazardous waste disposal costs. Future air
permit expenses will be reduced after the changeover. Beginning in November of 1993, the State
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of Nebraska will begin charging industrial facilities $25 per ton of hazardous emissions. This
change is in conjunction with requirements set forth in the CAAA. Nashua will avoid this cost
due to their process conversion to waterbased adhesives. The paperwork and man-hours required
to develop an operating permit will also be significantly reduced for its coating operations.
Additional savings will result from a reduction in hazardous waste disposal paperwork and
associated man-hours. Also, the reduction in volume of hazardous waste generated (especially
toluene) by Nashua will result in significant savings. A 55-gallon drum typically costs
$25 to $50 per drum to ship off-site and a minimum of $100 to $600 to dispose of, depending
on its contents. Assuming a typical shipping and disposal cost of $180 per drum, a total of
approximately $62,000 could be saved per year in toluene disposal.
Some of the savings in hazardous waste shipments would be offset by the increased
volume and cost of wastewater piped off-site. Nashua stated that sewage disposal costs are much
higher in the Omaha area than the cost of city water. Nashua estimated wastewater disposal costs
at about $350 per week greater than pre-conversion costs. Assuming a 50 week work year,
additional wastewater disposal costs amount to $17,500.
Concern over leaking USTs is another potential environmental problem that is eliminated
by the conversion to waterbased adhesives. The conversion to waterbased adhesives will ensure
that no potentially expensive underground solvent leaks occur and contaminate groundwater.
Nashua does not expect its solid waste disposal costs to change significantly after the
conversion. Some incremental costs may decrease since adhesive-coated solid waste will no
longer be considered hazardous and can be landfilled. By decreasing the volume of hazardous
waste generated, Nashua has been able to redistribute its waste disposal costs from hazardous to
nonhazardous solid and liquid wastes. After Nashua has found new cleaning agents for its
waterbased adhesives, the disposal costs of their current cleaning solutions (toluene and TCA)
will decline further or be eliminated. Depending on the volatility and hazard of its new cleaning
agents, a further reduction of hazardous wastes such as cleaning tool washing and cleaning rags
may be possible.
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CHAPTER 8
SUMMARY AND CONCLUSIONS
8.1 Characterization of Success/failure of Process Conversion
Nashua's conversion to waterbased adhesives can generally be characterized as highly
successful, as the company is very close to achieving its goals of sol vent-free operations while
maintaining profitability. There are several attributes of Nashua's operations, all previously
discussed in this report, which have facilitated conversion to waterbased adhesives:
• Nashua's production lines generally operate in a dedicated mode.
• Nashua manufactures products aimed at commodity market sectors.
• Nashua has allowed a relatively long time (approximately six to seven years) to fully
effect the conversion.
• Nashua had significant experience using waterbased adhesive coatings before the
conversion began (approximately five years).
• Nashua management planned and initiated the conversion, and have continued to provide
their full support.
In Nashua's experience conducting the waterbased conversion, it has also identified numerous
impediments to solvent-based adhesive product manufacturing including:
• There will be future regulatory costs of stack and fugitive emissions of solvents.
• There is a potential for solvent leaks or spills and associated costs.
• There are inherent dangers of solvents (e.g., explosivity, combustibility, noxious fumes)
and resulting monitoring and precautionary costs.
• Expensive maintenance of its solvent-recovery system is required for solvent-based
manufacturing.
• There is a lack of current research into improvement of solvent-based adhesives.
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Nashua aJso noted numerous advantageous qualities possessed by waterbased adhesives:
• Waterbased adhesives are similar in price or cheaper than solvent-based adhesives.
• The performance levels of waterbased adhesives are fully satisfactory for Nashua's
products.
• Waterbased adhesives do not contain high levels of hazardous materials (e.g., solvents).
• Research and development into waterbased adhesives is significant and continuing.
• There is potential for expansion into new markets with waterbased adhesive-coated
products.
Prior to implementing the conversion to waterbased adhesives, Nashua understood that there
would be associated negatives, including:
« There is an increased capital cost of new equipment for waterbased adhesive storage,
transfer, and coating application.
• There are associated personnel training costs.
• Finding and testing waterbased adhesive coatings that meet internal and external
performance criteria is time-consuming and costly.
• There are potential difficulties in the implementation of the conversion of a product line
(i.e., marketing considerations).
• There is the potential for the loss of some product lines and market niches.
• The costs of removal of equipment used for storage, transfer and coating of solvent-based
adhesives are significant.
Nashua personnel indicate that the conversion to waterbased adhesives has been successful
on several levels. First, Nashua has found waterbased adhesives that can successfully compete
with solvent-based adhesives for its applications. Second, Nashua has converted most of its
operations already, and has remained profitable during the conversion period. Third, Nashua is
removing itself from future hazards and costs associated with solvent-based adhesive use.
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Finally, Nashua personnel strongly feel that their company has moved towards a more
environmentally sound means of production, above and beyond monetary considerations.
8.2 Technology Transfer Opportunities
While Nashua's conversion to waterbased adhesives has been successful, the keys to the
success of the conversion, which were delineated in the first series of bullets in this chapter,
apply specifically to Nashua. Other plants and manufacturers may find uses for waterbased
adhesives if they have similar operations. Other manufacturing processes, such as batch
operations or specialty product manufacturing, might be less amenable to conversion. Conversion
opportunities for different companies and plants must be considered individually. However,
Nashua's successful conversion certainly demonstrates that waterbased adhesives have market
potential.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before compi
1. REPORT NO. 2.
EPA-600/R-95-011c
4. TITLE AND SUBTITLE
Solvent-Based to Waterbased Adhesive-Coated
Substrate Retrofit, Volume III: Label Manufacturing
Case Study: Nashua Corporation
5. REPORT DATE
December 1995
6. PERFORMING ORGANIZATION CODE
7. AUTHORtS)
Beth W. McMinn, W. Scott Snow, and Dan T. Bowman
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
TRC Environmental Corporation
6340 Quadrangle Drive. Suite 200
Chapel Hill, North Carolina 27514
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D2-0181, Task 2/017
liz. 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 PERIOO COVERED
Final: 11/92-6/93
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes project officer is Chester A. Vogel, Mail Drop 61, 919/
541-2827. This series includes five volumes.
i«.abstract volume discusses Nashua Corporation's Omaha facility, a label and
label stock manufacturing facility that no longer uses solvent-based adhesives. Infor-
mation obtained includes issues related to the technical, economic, and environmen-
tal barriers and opportunities associated with the use of waterbased adhesives. Spe-
cific objectives of the visit were to collect information necessary to characterize
Nashua's market profile, manufacturing supplies, manufacturing process profile,
environmental issues, and waterbased adhesive coating experience, as well as the
limitations of waterbased adhesive coatings. The case study report consists of eight
chapters. Chapter 1 gives background information related to Nashua's conversion
efforts, including market profile, process description, and a general description of
its conversaion efforts. Chapter 2 identifies Nashua's motivations for converting its
solvent-based operations to waterbased adhesives. Chapter 3 briefly describes the
marketing factors that affected the process conversion. Chapter 4 identifies the var-
ious raw material issues, including costs, involved in the process conversion. Chap-
ter 5 details the process equipment issues of the conversion, including specific equip-
ment impacts, costs, vendor selection, and maintenance. Chapter 6 discusses the
adhesive product performance requirements. Chapter 8 summaries the conclusions.
t7. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS .
c. COSATI Field/Group
Pollution Adhesives
Labels Coatings
Solvents
Substrates
Equipment
Cleaning
Pollution Prevention
Stationary Sources
Water-based Adhesives
13 B 11A
13 D 11C
1IK
11D
14G
13H
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report/
Unclassified
21. NO. OF PAGES
62
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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