EPA 430/K94/024
MONTREAL PROTOCOL
ON SUBSTANCES THAT DEPLETE
THE OZONE LAYER
UNEP
1994 Report of the
Solvents, Coatings and Adhesives
Technical Options Committee
1995 Assessment
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UNEP
. ' - 1994 Report of the
Solvents, Coatings and Adhesives
Technical Options Committee
1995 Assessment
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Montreal Protocol
On Substances that Deplete the Ozone Layer
UNEP
1994 Report of the
Solvents, Coatings and Adhesives
Technical Options Committee
1995 Assessment
The text of this report is composed in Courier.
Composition and co-ordination: Stephen 0. Andersen (Chair TOC)
Layout: Stephen 0. Andersen
J. Clayton French
Reprinting: UNEP Nairobi, Ozone Secretariat
Date: 30 November 1994
No copyright involved.
Printed in Kenya; 1994.
ISBN 92-807-1456-2
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1994 Report of the
Solvents, Coatings and Adhesives
Technical Options Committee
for the
1995 Assessment
of the
U N-E-.P
MONTREAL PROTOCOL
ON SUBSTANCES THAT DEPLETE
THE OZONE LAYER
pursuant to
Article 6
of the Montreal Protocol;
Decision IV/13 (1993)
by the Parties to the Montreal Protocol
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Disclaimer
*
The United Nations Environment Programme (UNEP), the Technology and Economics
Assessment Panel co-chairs and members, the Technical and Economics Options Committees
chairs and members and the companies and organisations that employ them do not endorse the
performance, worker safety, or environmental acceptability of any of the technical options
discussed. Every industrial operation requires consideration of worker safety and proper disposal
of contaminants and waste products. Moreover, as work continues -including additional toxicity
testing and evaluation- more information on health, environmental and safety effects of
alternatives and replacements will become available for use in selecting among the options
discussed in this document.
UNEP, the Technology and Economics Assessment Panel co-chairs and members, and the
Technical and Economics Options Committees chairs and members, in furnishing or distributing
this information, do not make any warranty or representation, either express or implied, with
respect to the accuracy, completeness or utility; nor do they assume any liability of any kind
whatsoever resulting from the use or reliance upon, any information, material, or procedure
contained herein, including but not limited to any claims regarding health, safety, environmental
effects or fate, efficacy, or performance, made by the source of information.
Mention of any company, association, or product in this document is for information purposes
only and does not constitute a recommendation of any such company, association, or product,
either express or implied.by UNEP, the Technology and Economics Assessment Panel co-chairs
and members, and the Technical and Economics Options Committees chairs and members or the
companies or organisations that employ them.
Acknowledgement
The UNEP Solvents, Coatings and Adhesives Technical Options Committee acknowledges with
thanks, the outstanding contributions from all of the individuals and organisations who provided
technical support to committee members.
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1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES
TECHNICAL OPTIONS REPORT
UNEP SOLVENTS, COATINGS, AND ADHESIVES
TECHNICAL OPTIONS COMMITTEE
Committee member
i
Dr. Husamuddin Ahmadzai
Mr. Lorenzo Alvarez
Dr. Stephen O. Andersen
Dr. David Andrews
Mr. Jay Baker
Mr. Bryan H. Baxter
Mr. Charles Carpenter
Mr. Pakasit Chanvinij
Mr. Mike Clark
Mr. Jorge Corona
Mr. Brian Ellis
Mr. Stephen Evanoff
Mr. Joe R. Felty
Dr. John Fisher
Mr. Art FitzGerald
Ms. Pamela Foster
Mr. Yuichi Fujimoto
Ing. G. Gabelmann
Dr. Leslie Guth
Mr. Don Hunt
Mr. Yoshiyuki Ishii
Mr. Peter Johnson
Dr. William Kenyon
Mr. Sudhakar Kesavan
Mr. Hiroshi Kurita
Dr. Steve Lai
Mr. Leo-Lambert
Mr. Milton Lubraico
Dr. Mohinder Malik
Mr. Shigeo Matsui .
Ms. Annie Maurel-Groleau
Mr. James A. Mertens
Mr. Hank Osterman
Mr. Fritz Powolny
Ms. Cynthia Pruett
Affiliation
Statens Naturvardsverk
SAEO South America Electronics Operation
U.S. EPA
GEC-Marconi Hirst Research Centre
Ford Electronics Technical Center
British Aerospace (Dynamics) Ltd.
Waste Policy Institute
Thai Airways International
Sketchley PLC
Mexican Chamber of Industries
Protonique S.A.
Lockheed Environmental
Texas Instruments Inc.
AT&T Bell Laboratories
IFC
Friends of the Earth
JEMA
ITT Teves GmbH
AT&T Bell Laboratories
U.S. Air Force
Hitachi Ltd.
European Chlorinated Solvents Association
Global Centre for Process Change
ICF Inc.
Japan Assoc. for Hygiene of Chlorinated Solvents
Singapore Institute of Standards and
Industrial Research
Digital Equipment Corp.
Ford Motor Company
Lufthansa German Airlines
Japan Audit and Certification Organisation Ltd.
TELEMECANIQUE
Dow Chemical - Advanced Cleaning Systems
Allied Signal, Inc.
OXITENO
Consultant
Country
Sweden
Brazil
USA (Chairman)
UK
USA
UK
USA
Thailand
UK
Mexico (Vice Chairman)
Switzerland
USA
USA
USA-
Canada
Canada
Japan
Germany
USA
USA
Japan
Belgium
USA
USA
Japan
Singapore
USA
Brazil
Germany
Japan
France
USA
USA
Brazil
USA '
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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UNEP SOLVENTS, COATINGS, AND ADHESIVES
TECHNICAL OPTIONS COMMITTEE (continued)
Committee member Affiliation Country
Mr. Patrice Rollet Promosol France
Mr. Wolf-Eberhard Schiegl Siemens AG Germany
Mr. Hussein Shafa'amri Ministry of Planning Jordan
Lt. Col. John Shirtz U.S. Air Force USA
Mr. Darrel Staley Boeing Company USA
Dr. John Stemniski Charles Stark Draper Laboratory USA
Lt. Col. Doug van Mullem U.S. Air Force USA
Mr. John Wilkinson Vulcan Chemicals USA
Dr. Masaaki Yamabe Asahi Glass Co., Ltd. Japan
Mr. X'Avier Hk Yoong National Semiconductor Malaysia
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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TABLE OP CONTENTS
UNEP SOLVENTS, COATINGS, AND ADHESIVES TECHNICAL OPTIONS REPORT
GLOSSARY . xvi
EXECUTIVE SUMMARY . ES-1
1. INTRODUCTION .'.... 1-1
1.1 BACKGROUND' . . . .- , 1-1.
.1.2 TERMS OF REFERENCE FOR THE COMMITTEE 1-4
1.3 BASIS FOR COMMITTEE RECOMMENDATIONS TO UNEP AND 'COMMITTEE
POSITION ON CFC-113,' 1,1,1-TRICHLOROETHANE AND PARTIALLY
HALO"GENATED FLUOROCARBONS . 1-9
2. ELECTRONICS INDUSTRY APPLICATIONS .' 2-1
2.1 BACKGROUND .[ '. '....',. 2-1
2.2 PRINTED CIRCUIT DESIGN FOR EFFICIENT SOLDERING AND 'CLEANING . 2-4
2.2.1 Low-Solids "No-Clean" Flux Wave Soldering ...... 2-4
2.2.2 Controlled Atmosphere Soldering : . . . 2-5
2.2.3 "Traditional" Flux Soldering and Cleaning 2-7
2.2.4 "Glue-Spots" and Cleaning Quality : 2-10
2.2.5 "No-^Clean" Paste Reflow Soldering 2-10
2.2.6 "Traditional" Paste Reflow Soldering and Cleaning . . 2-10
2.3 CFC-113-USE IN ELECTRONICS ASSEMBLIES . . . . .2-10
2.3.1 Major Assembly Processes 2--10
2.3.2 Flux Types 2-11
2.4 PRODUCTION PROCESSES ' 2-13
2.4.1 "No-Clean" Processes 2-13
2.4.1.1 Low-Solids "No-Clean" Processes . 2-15
2.4.1.2 High-Solids "No-Clean" Processes 2-15
2.4.1.3 Controlled Atmosphere Soldering '. .2-16
2.4.2 Water Soluble Processes . 2-16
2.4.2.1 Traditional Water Soluble Process 2-17
2.4.2.2 "Glycol-Free" Water Soluble Process 2-18
' 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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2.4.3 Saponification Processes . . .' 2-18
2.4.4 Hydrocarbon-Surfactant (HCS or HC/S. Processes .... 2-19
2.4.4.1 Seperable HCS Processes ..... 2-20
2.4.4.2 Miscible Processes 2-21
2.4.5 HC and Derivative Processes 2-21
2.4.5.1 Light HC Solvent Processes 2-21
2.4.5.2 Heavy HC Solvent Processes 2-22
2.4.6 Permitted Halocarbon Processes ............ 2-22
2.4.6.1 Non-Ozone-Depleting Chlorinated Processes . . 2-23
2.4.6.2 HCFC Solvent Processes . ..2-23
2.5 MACHINERY FOR ENVIRONMENTALLY RESPONSIBLE SOLDERING
AND CLEANING 2-24
2.5.1 Conventional Wave Soldering 2-24
2.5.2 Controlled Atmosphere Wave Soldering 2-25
2.5.3 Infra-Red Etc. Solder Paste Reflow . 2-25
2.5.4 Vapour.-Phase Solder Paste Reflow 2-26
2.5.5 Hot Liquid Immersion Solder Paste Reflow 2-26
2.5.6 Aqueous Cleaning (Conventional Water-Soluble Fluxes) . 2-27
2.5.7 Aqueous Cleaning (Glycol-Free Water-Soluble Fluxes) . 2-27
2.5.8 Saponifier Cleaning ' . . 2-28
2.5.9 HCS Solvents : . . 2-28
2.5.10 HC Solvents and Derivatives 2-29
2.5.11.Permitted Halocarbon Solvents 2-30
2.6 PRODUCTION MACHINERY AND MATERIALS . . .'. 2-30x
2.. 6.1 Conventional Wave Soldering Machines . . 2-31
2.6.2 Controlled Atmosphere Wave Soldering Machines . . . .2-34
2.6.3 Vapour Phase Reflow "... 2-36
2.6.4 Infra-Red Reflow Machines 2-36
2.6.5 Other Reflow Methods ..'.. 2-37'
2.7 CLEANING MACHINERY 2-38
2.7.1 "Dishwasher" Types 2-38
2.7.2 "High-Throughput" Types 2-38
2.7.3 "Tank-Line" Batch Types 2-39
2.7.4' Totally Enclosed Types 2-39
2.7.5 Conveyorised "In-Line" Machines . 2-40
2.7.6 Vapour Phase Solvent Machines 2-41
2.8 MACHINE AGITATION 2-41
2.8.1 Sprays for Cleaning 2-41
2.8.2 Sprays for Rinsing 2-42
2.8.3 "Under-Surface" Spraying 2-43
2.8.4 -Ultrasonic Agitation 2-43
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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2.9 DRYING -...!.. 2-45
2.9.1 Mechanical Drying 2-45
2.9.2 Evaporative Drying 2-46
2.9.3 Vapour Phase Drying 2-47
'2.10 CONTAMINATION AND QUALITY CONTROL.' 2-48
2.10.1 Soldei-ability Testers . 2-49
2.10.2.Ionic Contamination Testing '....'...'.. 2-49
2.10.3 Surface Insulation Resistance and ElectromigratioiT
Testing .' 2-50
2.11 PHOTORESIST DEVELOPMENT 2-50
2.12 SUMMARY .2-51
3. ' PRECISION CLEANING APPLICATIONS .3-1
3.1 BACKGROUND 3-1
3.2 CFC-113 AND 1,1,1-TRICHLOROETHANE USE IN PRECISION
CLEANING APPLICATIONS . . 3-3
3.2.1 Precision Cleaning Processes and Equipment ...... 3-3
3.-2.2 Precis'ion Cleaning Applications 3~6,
3.2.2.1 Cleaning Precision Instruments During
Manufacture, Assembly, and Testing .... 3-6
3.2.2.2 Specialised Manufacturing Techniques . . '. . .3-11
3.2.2.3 Maintenance Cleaning and Repair . . . .. . .3-12
3.3 ALTERNATIVES- FOR REDUCING OR REPLACING CFC-113 AND
1,1,1-TRICHLOROETHANE IN PRECISION CLEANING . 3-13
3.3.1 Conservation and Recovery Practices 3-13
3.3.2 Aqueous Cleaning 3-13
3.3.3 Semi-Aqueous Cleaning . 3-19
3.3.4 HCFCs . . . '. 3-23
3.3.5 Alcohols and Ketones 3-28
3.3.6 Perfluorocarbons 3-30
3.3.7 Alcohol Cleaning with Perfluorocarbons 3-32
3.3.8 Aliphatic Hydrocarbons . 3-34
3.3.9 Chlorinated and Other Miscellaneous Organic
Solvents 3-37
3.3.10 Pressurized Gases . 3-37
' 3.3.11 Supercritical Fluids 3-42
3.3.12 Plasma Cleaning ,. 3-47
3.3.13-Ultraviolet Light/Ozone Cleaning Method 3-50
3.4 ENVIRONMENTAL AND ENERGY CONSIDERATION ''-:3-51
3.5 POTENTIAL GLOBAL REDUCTION OF CFC-113 AND
/ ' 1,1,1-TRICHLOROETHANE .IN PRECISION CLEANING APPLICATIONS . . 3-52
1994 UNEP SOLVENTS, COATINGS. AND ADHESIVES REPORT '
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4.- METAL CLEANING APPLICATIONS 4-1
4.1 BACKGROUND 4-1
4.2 CFC-113 AND 1,1,1-TRICHLOROETHANE USE IN METAL CLEANING
APPLICATIONS 4-3
4.2.1 Metal Cleaning Applications 4-3
4.2.2 Metal Cleaning Solvents 4-3
4.2.3 Metal Cleaning Processes 4-4
4.2.3.1 Cold Immersion Cleaning 4-4
4.2.3.2 Vapour/Hot Liquid Cleaning . 4-4
4.2.3.3 Conveyorized Cleaning - 4-7
4.2.3.4 Manual Cleaning . . 4-7
4.2.3.5 Spraying and Flushing Techniques 4-7
4.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND 1,1,1-
TRICHLOROETHANE USE IN METAL CLEANING APPLICATIONS 4-8
4.3.1 Conservation and Recovery Practices 4-8
4.3.2 Alternative Chlorinated Solvents 4-8
4.3.3 Alternative Solvent Blends .... 4-10
4.3.3.1 Vapour Degreasing '. . . .''... .4-10
4.3.3.2 Manual Cleaning . 4-10
4.3.3.3 Cold Immersion Cleaning 4-11
4.3.4 Aqueous Cleaners 4-11
4.3.4.1 Cleaner Formulations 4-11
4.3.4.2 Aqueous Cleaning Processes 4-13
4.3.4.2.1 Immersion Cleaning . . 4-13
4.3.4.2.2' Ultrasonic Cleaning 4-15
4.3.4.2.3 Spray Cleaning ..... 4-16
4.3.5 Hydrocarbon/Surfactant ("Semi-aqueous" and
"Emulsion") Cleaners 4-18
4.3.6 Mechanical Cleaning 4-19
4.3.7 Thermal-Vacuum De-oiling 4-21
4.3.8 No-Clean Alternatives 4-21
4.3.9 CFC-113 and 1,1,1-Trichloroethane Processes
for Which Alternatives are Not Available 4-22
4.4 COST OF ALTERNATIVES 4-22
4.5 ENVIRONMENTAL, HEALTH, AND SAFETY CONSIDERATIONS ...... 4-23
4.6 POTENTIAL GLOBAL REDUCTION OF CFC-113 AND
1,1,1-TRICHLOROETHANE IN METAL CLEANING APPLICATIONS .... 4-23
4.7 SUITABILITY OF ALTERNATIVES FOR DEVELOPING COUNTRIES
AND SMALL QUANTITY USERS ...'.' . . . 4-24
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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5. DRY CLEANING INDUSTRY 5-1
5.1 BACKGROUND 5-1
5.2 CFC-113 AND 1,1,1-TRICHLOROETHANE USE IN THE DRY CLEANING
INDUSTRY . . . : . 5-1'
5.2.1 Dry Cleaning Machines 5-2
5.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND 1,1,1-
TRTCHLOROETHANE USE 5-5
5.3.1 Conservation and Recovery Practices ., 5-5
5.3.2 Alternative Solvents.. 5-7
5.3.2.1 Perchloroethylene 5-7
5.3.2.2 Petroleum Solvents (White Spirit, Stqddard
Solvent, Etc.) 5-9'
5.3.2.3 Hydrofluorocarbons (HCFCs) 5-9
5.3.2.4 Other Alternative Solvents ..... 5-9
5.3.2.5 Centralized Processing Facilities 5-10,
5.4 COST OF ALTERNATIVES ........./ 5-10
5.5 ENVIRONMENTAL AND ENERGY CONSIDERATIONS 5-10
5.6 POTENTIAL GLOBAL REDUCTION OF. CFC-113 USE IN THE
DRYCLEANING INDUSTRY : . . . 5-12
6. ADHESIVE APPLICATIONS -. 6-1
6..1 BACKGROUND 6-1
6.2 1,1,1-TRICHLOROETHANE USE IN ADHESIVE? APPLICATIONS ..... 6-1
6.3 ALTERNATIVES FOR REDUCING OR REPLACING
1,1,1-TRICHLOROETHANE USE 6-4
6.3.1 Other 'Solvent-Based Adhesives 6-4
6.3.2 Water-Based Adhesives 6-6
6.3.3 Hot Melt Adhesives . . . 6-7
6.3.4 Radiation Cured-Adhesives 6-8
6.3.5 High Solids Adhesives,. ' 6-8
6.3.6 Powders 6-9
6.3.7 Non-Volatile Solids and Liquids arid Reactive Liquids . ' 6-9
6.4 COSTS OF ALTERNATIVES . 6-10
6.5 ENVIRONMENTAL AND ENERGY CONSIDERATIONS 6-10
6.6 POTENTIAL GLOBAL REDUCTION OF 1,1,1-TRICHLOROETHANE
USE IN THE ADHESIVES INDUSTRY . .' 6-11-
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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6.7 SUITABILITY OF ALTERNATIVES FOR DEVELOPING COUNTRIES AND
SMALL QUANTITY USERS 6-12
7. COATINGS AND INKS APPLICATIONS 7-1
7.1 BACKGROUND ' 7-1
7.2 CFC-113 AND 1,1;1-YRICHLOROETHANE USE IN COATINGS AND INKS
APPLICATIONS ' '. . 7-1
7.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND L.,1,1-'
TRICHLOROETHANE USE . . . 7-2
7.3.1 Water-based Coatings and Inks . 7-2
7.3.2 High-Solid Coatings : 7-2
7.3.3 Powder Coatings . , 7-3
7.3.4 UV/EB-Cured Coatings and Inks 7-3
7.4' ENVIRONMENTAL AND ENERGY CONSIDERATIONS '..'... 7-3
8. AEROSOLS APPLICATIONS . . , 8-1
8.1 BACKGROUND 8-1
8.2 CFC-113 AND 1,1,1-TRICHLOROETHANE USE IN AEROSOL PRODUCT
APPLICATIONS . ..-' 8-l
8.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND
1,1,1-TRICHLOROETHANE USE IN AEROSOL PRODUCTS '. . 8-2
. 8.3.1 Reformulation Using Petroleum Distillates 8-4
8.3.2 Reformulation to Water-based Systems .... 8-4
8.3.3 Reformulation Using Organic Solvents 8-4
8.3.4 Reformulation Using Nonozone-Depleting Chlorinated
Solvents ,8-5
8.3.5 Reformulation Without a Solvent 8-5
8.3.6 Reformulation Using HGFCs 8-5
8.3.7 Alternative Delivery Systems 8-6
8.4 COSTS OF ALTERNATIVES - 8-6
9. OTHER SOLVENT USES OF CFC-113 AND 1,1,1-TRICHLOROETHANE 9-1
9.1 BACKGROUND - 9-1
9.2 BEARER MEDIA FOR COATING AND IMPREGNATION : 9-1
9.3 VAPOUR SOLDERING TECHNOLOGY '. : . . 9-2
9.4 COMPONENT DRYING , 9-5
9.4.1 Semiconductors . 9-5
9.4.2. Printed Circuit Boards ...'........:.... 9-5
9.4.3 Mechanical Assemblies .'......-... i -...-.... 9-7
9.4.4 Metal Surfaces ..'.-............ 9-7
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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9.5 RIVETING AND MACHINING 9-7
9.6 AIRPLANE HYDRAULIC SYSTEM TESTING , 9-8
9.7 FABRIC PROTECTION AND COATING 9-9
9.8 SEMICONDUCTOR MANUFACTURING 9-10
9.8.1 Plasma Etch Processing .'.9-10
9.8.2 Oxide Growth processing . . '. ' 9-11
9.8.3 Semiconductor Degreasing 9-11
9.8.4 Photolithographic Prcocessing : 9-14
9.9 MISCELLANEOUS TESTING 9-14
9.9.1 Leak Testing 9-14
9.9.2 Laboratory Testing . 9-14
9.10 MOULD RELEASE AGENTS , 9-14
9.11 FILM CLEANING ....'..... 9-1*5
9.12 COMPONENT COOLING ........' 9-16
9.13 MANUFACTURE OF SOLID ROCKET MOTORS . . 9-17
.9.14 OXYGEN SYSTEMS CLEANING . . 9-20
"\
9.15 CORRECTION FLUIDS .9-23
9.16 FABRIC SPOT REMOVER 9-23
9.17 PROCESS SOLVENTS 9-23
10. ALTERNATIVES TO OZONE-DEPLETING SOLVENTS IN DEVELOPING,
COUNTRIES ..." ' 10-1
10.1 INTRODUCTION 10-1
10 ..2 SUBSTITUTES AND ALTERNATIVES 10-1
10.2.1 No-Clean Electronics 10-2
10.2.2 No-Clean Metal Finishing/Fabrication/Assembly . . . . 1.0-2
10.2.3 Aqueous Cleaning .' 10-3
10.2.4 Semi-Aqueous Cleaning . . . 10-4
10.2.5 Organic Solvent Cleaning (alcohols, aliphatics,
ketones, aldehydes, 'and blends or C1-C20,
hydrocarbons and derivatives . 10-5
10.2..6 Chlorinated Aliphatic Solvent Cleaning
(trichloroethylene, perchloroethylene or
dichlorome thane) , . 10-5
10.2.7 Chlorinated Aromatic Solvent Cleaning
(monochlorotoluene/benzotrifluorides) 10-6
10.2.8 Hydrofluorocarbons (HCFC-123, HCFC-141b, HCFC-225) . . 10-6
' 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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10.2.9 Perfluorocarbons 10-7
10.2.10 Hydrofluorocarbons (HFCs) ; 10-8
10.2.11 Dibromethane ' 10-8
10.2.12 Volatile Methyl Siloxanes' (VMSs) . -. . . 10-9
10.2.13 Supercritical Fluid Cleaning .... 10-9
10.2.14 Carbon^Dioxide Snow Cleaning. 10-10
10.2.15 Plasma Cleaning 10-10
10.2.16 Ultraviolet/Ozone Cleaning 10-10
10.3 TECHNOLOGIES FOR DEVELOPING COUNTRIES . . . .... . . . . . 10-12
10.3.1 No-Clean . 10-13
10:3.2 Aqueous/Semi-Aqueous Cleaning 10-13
10.3.3 Organic Solvent Cleaning 10-13
10.3.4 Non-Ozone-Depleting Halogenated Solvents 10-14
10.3.5 HCFC-123, HCFC-225, HCFC-141b, and PFCs 10-14
10.4 RETROFITS : . 10-14
11. CASE STUDIES OF PHASEOUT ACTIVITIES 11-1
ALLIED SIGNAL - An Evaluation of Aqueous Technologies . . . . 11-4
AT&T BELL LABORATORIES - Eliminating Ozone-Depleting
Substances at AT&T . . . 11-6
BECK ELECTRONICS - Semi-Aqueous Equipment Conversion at
Beck Electronics s ' 11-10
FORD MOTOR COMPANY - CFG Solvent Elimination in
Electronics Soldering at Ford Motor Company 11-13
HITACHI - Reduction and Elimination of Ozone-Depleting
Solvents at Hitachi 10-17
HONEYWELL - Replacement of Ozone-Depleting Substances
in Honeywell Space and Aviation Control Products ... 11-20
: IBM CORPORATION - ODS Elimination at IBM Austin, Texas . . 11-23
THE JAPAN INDUSTRIAL CONFERENCE ON CLEANING ......... 11-26
LOCKHEED SANDERS COMPANY - The Elimination of .
1,1,1-Trichloroethane in Electronics Cleaning at
Lockheed Sanders Company 11-29
MILJOMINISTERIET - Hydrocarbon Dry Cleaning at
Miljoministeriet : . 11-33
MINEBEA COMPANY - Phasing Out of Ozone-Depleting Substances
by the Minebea Co. Through the Use of a Water-Based
Cleaning System 11-35
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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NATIONAL SEMICONDUCTOR - Non-ODS Alternatives in the
Cleaning of Integrated Circuits at National
Semiconductor - Malaysia 11-37
NAVAL AVIATION DEPOT - Implementation of ODS Alternatives
at Naval Aviation Depot Cherry Point 11-39
NORTHERN TELECOM - CFC-113 Elimination at Northern
Telecom 11-43
ROBERT BOSCH CORPORATION - Replacing Solvent Cleaning
with Aqueous Cleaning at Robert Bosch Corporation . . 11-47
ROCKWELL INTERNATIONAL - Use of a Low Residue Flux in a
. .Military Electronics Program '. . . . 11-52
SEIKO EPSON CORPORATION - The Cleaning Center System of
Seiko Epson Corporation 11-57
SINGAPORE INSTITUTE OF STANDARDS AND INDUSTRIAL RESEARCH -
The ODS-Free Verification Scheme for Singapore
Industry 11-62
SWEDISH EPA - Eliminating the Use of ODSs in Sweden .... 11-66
TOSHIBA CORPORATION - Non-ODS Substitutes for Wax
Elimination at Toshiba Corporation . . . 11-68
U.S. AIR FORCE AEROSPACE GUIDANCE AND METROLOGY CENTER -
Using New Technologies, to Solve Unique Precision'
Cleaning Operations: The Elimination of Ozone -
Depleting Solvents From the Aerospace and Metrology
. Center Newark Air Force Base, Ohio 11-71
VIBRO-METER SA - Case Study: Vibro-Meter SA, Villars-sur-
Glane, Switzerland - 11-75
REFERENCES ' R-l
APPENDIX A: Members of the UNEP Solvents, .Coatings and Adhesvies
Technical Options Committee for Technical Assessment
for Technical Assessment Under Article 6 of the Montreal
Protocol _ . A-l
APPENDIX B: Expert Advisors to UNEP Solvents, Coatings and
Adhesives Technical Options Committee .' . . . B-l
APPENDIX C: Recommended Guidelines and Control Achievable with Best
Available Technology (BAT) for Volatile Organic
Compound (VOC) Solvent-Based Cleaning C-l
APPENDIX D: CFC-113 and 1,1,1-Trichloroethane Chemical, Trade, and
'. . Company Names .......'.... , . D-l
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES. REPORT
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APPENDIX E: Site Visits E-l
APPENDIX F: German Solvent Use Regulations . F-l
APPENDIX G: Summary of Testing Programs for Alternatives in the
Electronics Industry in Sweden,.United Kingdom, and the
United States ....: '. . : G-l
APPENDIX H: Analysis of Current and Future Production of Carbon
Tetrachloride .H-l
APPENDIX I: Total Equivalent Warming Impact (TEWI) of Solvent
Alternatives .1-1
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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LIST OF FIGURES
Page
Figure 1-1. 1,1,1-Trichloroethane Reduction Schedule
(User Survey Results for Western Europe, North
America, and Japan) 1-7
Figure 1-2 Relative Total Ozone Depleting Potential of Selected
Halogenated Solvents . . 1-15
Figure II-l. Methods of Replacing Ozone-Depleting Solvents in the
Electronics Industry 2-3
Figure II-2. Hypothetical Example of SMD Circuit Designed for
"No-Clean" Wave Soldering Showing Correct Orientation
of Components .....2-6
Figure II-3. Layout Criteria for Effective Cleaning a) Orientation
and .Position . . . 2-8
Figure II-4. Layout Criteria for Effective Cleaning b) Maximum
Ingress of Cleaning Fluids ...... 2-9
Figure III-l. Size Comparison of Computer Disk Drive Head
Clearance with Various Contaminants ..-....'.... 3-2
Figure III-2. ' Metal Cleaning and Precision Cleaning 3-4
Figure III-3. Configuration of a Typical Aqueous Cleaning Process . . 3-16
Figure III-4. Semi-Aqueous Process for Immiscible Hydrocarbon
Solvent .- . , , .' 3-21
Figure III-5. Advanced Design Degreaser for Use With Low Boiling
Point Solvents 3-27'
Figure III-6. Basic Model Design for Carbon Dioxide Supercritical
Cleaning System . . . . : . . 3-46
Figure IV-1. Basic Vapour Degreaser-Batch Cleaning ... ...;.: 4-5
Figure IV-2. Degreasing Performance of HCFC-225 . 4-12
Figure IV-3. Configuration of Aqueous Cleaning Process . . . '. . . .4-14
.Figure IV-4. Semi-Aqueous Process for Immiscible Hydrocarbon
Solvent 4-20
Figure V-l. ' . Basic Drycleaning Machine Principles 5-3
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT '
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Figure V-2. Typical Layout of Basic Components 5-4
Figure XI-1. Annual Use of CFC-113 and 1,1,1-Trichloroethane at
Honeywell Space and Aviation Control Operattions . . 11-.22
Figure XI-2. Lockheed Sanders Company Stencil Cleaning Process . . 11-30
Figure XI-3. Lockheed Sanders Company Cicuit Card Cleaning
Process 11-31
Figure XI-4. Minebea Company's Water-Based Cleaning System .... 11-36
"Figure XI-5. Seiko Epson Cleaning Center System .... 11-58
Figure XI-6. Cleaning Center Layout ... 11-60
Figure C-l. Solvent Lost in a Typical Plant C-2
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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LIST OF'TABLES
Table I-{L.
Table 1-2.
Table 1-3.
Table 1-4.
Table 1-5.
Table 1-6.
Table 1-7.
Table II-l.
Table III-l.
Table III-2.
Table III-3.
Table III-4.
Table III-5.
Table III-6.
Table III-7.
Table III-8.
Table III-9.
Table III-10,
Table III-ll.
Page
Parties to the Montreal Protocol 1-2
Substances Controlled By the Montreal Protocol .... 1-3
Summary of Copenhagen Amendments to the
Montreal Protocol . . . -. 1-5
Comparison of Worldwide Consumption of Controlled
CFCs and Ozone Depleting Potential (OOP) 1-6
Member Countries of the UNEP Solvents, Coatings and
Adhesives Technical Options Committee . , . .1-10
Organizations Whose Employees Serve on the UNEP
Solvents, Coatings, and Adhesives Technical
Options Committee ' 1-11
Corporate and Government Presentations in Meetings
Held By the UNEP Solvents, Coatings, and Adhesives
Technical Options Committee . ............. 1-12
Typical Circuit Board Assembly Contaminants 2-14
Aqueous Cleaning '....... 3-15
Aqueous Cleaning Process Equipment . . . 3-17
Physical Properties of HCFCs and Other Solvents . . . .3-24
Properties of Alcohols ........ 3-29
Properties of Perfluorocarbon Solvents Available
in 1994 . . _. . . 3-31
Perfluorocarbon (PFC) Compatibility with Various
Materials 3-33
Properties of Aliphatic Solvents . ... 3-36
Properties of Halogenated Chlorinated Solvents , 3-38
y
Properties of Ketones ' . . 3-39
Supercritical Carbon Dioxide Applications 3-43
Supercritical Carbon Dioxide Applications 3-45
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table IV-1.
Table V-l.
Table V-2.
Table VI-1.
Table VI-2.
Table VI-3.
Table VIII-1.
Table VIII-2.
Table IX-1.
Table IX-2.
Table IX-3.
Table IX-4.
Table IX-5.
Table XI-1.
Table XI-2.
Table C-.l.
Table C-2.
Table C-3.
Table C-4.
Table C-5.
Table C-6.
Table D-l.
Viable Alternatives to Existing Metal Cleaning
Process Solvents 4-9
General Sources of Solvent Losses From Drycleaning
Machines . 5-6
Chemical Characteristics of Selected Drycleaning
Solvents
5-8
Physical Properties of Common Adhesive Solvents .... 6-3
Uses of 1,1,1-Trichloroethane 6-5
Estimated U.S. and European Adhesive Demand By
Segments - 1988 6-13
Summary of Substitute Solvents for
1,1,1-Trichloroethane in Aerosols 8-3
Costs of Controls for 1,1,1-Trichloroethane in
Aerosols
1-7
Comparison of CFC-113 and a Substitute
Perfluorocarbon as a Secondary Vapour Blanket ..... 9-4
Comparison of Drying Techniques 9-6
Halocarbon Plasma Etchants 9-12
Possible Mixtures for CFC Replacement in Dry
Etching . 9-12
CFC Alternative Etching Compounds . . '. 9-13
Successful ODS Elimination in Singapore . 11-65
Compositions of Vinyl-Copolymer-Type Masking Agents . 11-69
Comparison of Recoverability Between CFC-113
Solvent Grades C-3
Classification of VOCs ,
Comparison of Solvent Recovery Systems
C-4
C-7
A Summary of Available VOG Control Techniques, Their
Efficiencies, and Costs C-8
Typical Emissions From an Optimized Solvents
Cleaning Equipment . . . . .C-ll
Values of Specific Emissions Occurring During
Solvent Degreasing Process (ECE Task Force VOC) .... C-12
CFC Trade Names D-3
" 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table D-2.. CFC-113 Content of Selected Products D-4
Table D-3. Trade Names for 1,1,1-Trichloroethane D-7
Table D-4. 1,1,1-Trichloroethane Content of Selected Products . . D-8
Table F-l. Comparison of US, UK, and TRE Internordic
Cleaning Options Evaluation Programmes . . . F-2
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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GLOSSARY
Acute toxicity
Adsorption
Aerosol Spray
Alcohols
Aqueous cleaning
Azeotrope
Biodegradable
BOD
Carbon.tetrachloride
CFC
CFC-112
CFC-113
The short-term toxicity of a product in a single dose.
Can be divided into oral, cutaneous, and respiratory
toxicities.
Not to be confused with absorption. Adsorption is a
surface phenomenon of some substances that can form a
physicochemical bond with specific materials.
A means of atomizing liquids by propelling them from a
pressurized container through a suitable valve by
either a liquified or pressurized gas.
A series of hydrocarbon derivatives with at least one
hydrogen atom replaced by an -OH group. The simplest
alcohols (methanol, ethanol, n-propanol, and
isopropanol) are good solvents for some organic soils,
notably rosin, but are flammable and can form
explosive mixtures with air. The use of flammable
solvents requires caution and well-designed equipment.
Cleaning with water to which suitable detergents,
saponifiers, or other additives may be added.
A mixture of chemicals is an azeotrope if the vapour
composition is identical to that of-the liquid phase.
This means that the distillate of an azeotrope is
theoretically identical to the solvents from which it
is distilled.. In practice, the presence of
contaminants in the solvent may upset the azeotropy.
Products are classified as biodegradable if they can
be easily broken down or digested by living organisms.
An abbreviation for biochemical oxygen demand, a
measure of the biodegradability of wastewater.
A chlorocarbon solvent with an ODP of approximately
1.1. It is also considered toxic and a probable human
carcinogen (classified as a B2 carcinogen by US EPA).
Its use is strictly regulated in most countries and it
is used primarily as a feedstock material for the
production of other chemicals.
An abbreviation for chlorofluorocarbon.
1,1,2,2-tetrachloro-l,2-difluoroethane.
1,1,2-trichloro-1,2,2-trifluoroethane.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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CFC-113a
Chelation
Chlorocarbon
Chlorofluorocarbon
Chronic toxicity
COD
Conformal coating
Controlled
atmosphere soldering
Defluxing
Detergent
Dichloromethane
Dry cleaning-
Dry film
Fatty acids
An isomer of CFC-113; l,l,l-trichloro-2,2,2-
trifluoroethane.
Chelation is the solubilisation of a metal salt by
forming a chemical complex or sequestering. One way
of doing this is with ethylenediaminetetraacetic acid
(EDTA) salts which have a multidentate spiral ligand
form that can surround metallic and other ions.
An organic substance composed of chlorine and carbon,
e.g., carbon tetrachloride.
An organic substance composed of chlorine, fluorine,
and carbon atoms, usually characterised by high
stability contributing to a high OOP.
The, long-term toxicity of a product in small, repeated
doses. Chronic toxicity can often take many years to
determine'.
An abbreviation for chemical oxygen demand.
A-protective material applied in a thin, uniform layer
to surfaces of an electronic assembly.
A soldering process done in a relatively oxygen-free
atmosphere. The process greatly reduces oxidation of
the solder, so .that less flux is required, thereby
reducing or eliminating the need for cleaning.
The removal of flux residues after a soldering
operation. Defluxing is a part of most high-
reliability electronics production.
A product designed to render -soils (e.g., oils and
greases) soluble in water, usually made from synthetic
surfactants.
A chlorocarbon solvent used extensively for metal
cleaning. Also known as methylene chloride.
A common term for cleaning garments in organic
solvents, as opposed to water.
A photoresist or photoimageable solder mask applied to
printed circuits by lamination.
The principal part of many vegetable and animal oils
and greases. Also known as carboxylic acids, which
embrace a wider definition. These are common
contaminants which use solvents for their removal.
They are also used to activate fluxes.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Flux
Greenhouse effect
Halocarbon
Halons
HCFC
HCS
HFC
Hybrid circuits'
Hydrocarbon
Hydrocarbon derivative
Hydrocarbon/surfactant
solvents
Hydrochlorocarbon
A chemical employed in the soldering process to'
facilitate the production of a solder joint. It is
usually a liquid or solid material, frequently based
on rosin <(colophony).
A thermodynamic effect whereby, energy absorbed at the
earth's surface and normally radiated back out to
space in the form of long-wave infrared radiation, is
retained due to gases in the atmosphere, causing a
rise in global temperature. CFCs that cause ozone
depletion' are "greenhouse gases," with a single CFC-
113 molecule having the same estimated global warming
effect as 14,000 carbon dioxide molecules.
/
Any organic substance where at least one hydrogen atom
in the hydrocarbon molecule has been replaced by a
halogen atom (fluorine, chlorine, bromine, iodine, or
astatine).
Substances used as fire-extinguishing agents and
having high ODPs.
An abbreviation for hydrochlorofluorocarbon.
An abbreviation for hydrocarbon/surfactant (intra).
Ah abbreviation for hydrofluorocarbbn.
/
Electronic circuits, with or without integral passive
components, which are formed by the application of
conductive'and resistive patterns to a vitrous or
ceramic substrate.
An organic substance composed only of hydrogen and
carbon. Gaseous or volatilized hydrocarbons are
flammable.
A hydrocarbon whose molecule has been modified by
adding atoms other.than hydrogen and carbon, e.g.,
alcohols.
A mixture of low-volatility hydrocarbon solvents with
surfactants, allowing the use of a two-phase cleaning
process. The first phase is solvent cleaning in the
blend and the second phase is water washing and
rinsing to remove the residues of the blend and any
.other water-soluble soils. The surfactant ensures the
water-solubility of the otherwise insoluble
hydrocarbon. Sometimes called semi-aqueous solvents.
An organic Substance composed of hydrogen, chlorine,
and carbon, e.g., trichloro.ethylene.
' 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Hydrochloro-
fluorocarbon
IARC
Infra-red soldering
Isopropanol
Leadless surface
mount component
Lifetime
Low-solids flux
MEA '
Metal cleaning
Methyl chloroform
Monoethanolamine
No-clean flux
OOP
An organic substance composed of hydrogen, chlorine,
fluorine, and carbon atoms. These chemicals are less
stable than CFCs, thereby having generally lower ODPs,
usually abbreviated as HCFC.
An abbreviation for International.Agency for Research
.on Cancer.
A method of reflow soldering where the solder and the
parts being joined are heated by the incidence of
infra-red radiation in air, in an inert gas, or in a
reactive atmosphere.
See alcohols.
A surface mount component (SMC) whose exterior
consists of metallized terminations that are an
integral part of the component body.
The folded-e lifetime is the time required for the
quantity of a substance in the atmosphere to be
reduced to 1/e (0.368) of its original quantity. The
folded-e lifetime of CFC-113, for example, is about 80
years.
A flux which contains little solid matter, thereby
reducing or eliminating the need for cleaning. See
no-clean flux.
An abbreviation for monoethanolamine.
General cleaning or degreasing of metallic surfaces or
assemblies generally with unspecified cleanliness
requirements.
See 1,1,1-trichloroethane.
A saponifier capable of reacting with rosin fluxes and
fatty acids. The reaction products are essentially
water-soluble. Usually abbreviated as MEA.
A flux whose residues do not have to be removed from
an electronics assembly; therefore, no cleaning is
necessary. This type of flux is often characterized
by low quantities of residues.
An abbreviation for ozone depletion potential.
Organic acid (OA) flux See water-soluble flux.
Ozone
A gas formed when oxygen is ionised. Ozone partially
filters certain wavelengths .of UV light from the
earth. Ozone is a desirable gas in the stratosphere,
but it is toxic to living organisms at ground level
(see volatile organic compound).
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Ozone depletion
Ozone depletion
potential
Ozone layer
PCB
Pentafluoropropanol
Perchloroethylene
\
Perhalogenation
Photoresist
Precision cleaning
Accelerated chemical destruction of the stratospheric
ozone layer. Chlorine and bromine free radicals
liberated from relatively stable chlorinated,
f luorinated,. and brominated products by ultraviolet
radiation in the ozone layer are the most depleting
species.
A relative index of the ability of a substance to
cause ozone depletion. The reference level of 1 is
assigned as an index to CFC-11 and CFC-12. If a
product has an ozone-depletion potential of 0.5, a
given weight of the product in the atmosphere would,
in time, deplete .half the ozone that the same weight
of CFC-11 or CFC-12-would deplete. Ozone-depletion
potentials are calculated from mathematical models
which take into account factors such as the stability
of the product, the rate of diffusion, the quantity of
depleting atoms per molecule, and the effect of
ultraviolet light and other radiation on the
molecules.
A layer in the stratosphere, at an altitude of
approximately 10-50km, where a relatively .high
concentration of ozone filters harmful ultraviolet
radiation from the earth. . . -
\
An abbreviation for printed .circuit board.
A fluorinated alcohol.
A perhalogenated chlorocarbon solvent used extensively
in industrial degreasing and dry cleaning.
An organic molecule is perhalogenated if all of the
parent hydrogen atoms in a hydrocarbon are replaced
with halogen atoms (astatine, bromine, chlorine,
fluorine, or, iodine). For example, carbon
tetrachloride (CC14) is perchlorinated methane (CH^) .
Chloroform (CHC13)' is an example of a simple
chlorinated methane, where only three of the hydrogen
atoms have been replaced.
A photomechanical product, in the form of a liquid or
a laminated dry film, used in the manufacture o.f
printed circuits. Certain types of these products use
large quantities of ozone-depleting1 hydrochlorocarbon
solvents, usually 1,1,1-trichloroethane.
Dichloromethane is used for stripping some types.
Cleaning of high.-precision mechanical parts and
electronic sensory devices, as opposed to general
metal cleaning. This is usually done in "clean-
rooms," with low particulate contamination, to
specific -standards.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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POTW
Printed circuit
PWA
Reflow soldering
Rosin
Rosin flux
SA Flux
Saponifier
Semi-aqueous solvents
SMC
Solder mask (resist)
Solvent
Solvent containment
Publicly Owned Treatment Works.
A printed circuit is a component for interconnecting
other components. It usually consists of a metallic
conductor pattern on an organic insulating substrate.
After fabrication, it is known as a printed circuit
board (PCB).; after assembly with components .it is
known as a printed wiring assembly (PWA).
[Terminology different in Europe and USA.]
An abbreviation for printed wiring assembly.
A method of electronics soldering commonly used with
surfac'e mount technology, whereby typically7 a paste
formed of solder powder and flux suspended in an
organic vehicle is melted by the application of heat.
A solid resin obtained from pine trees. It is
frequently used as a flux, usually with additives.
A flux whose main constituent is rosin. There are
several categories of rosin flux, often designated by
the codes R (pure rosin), RMA (rosin, mild
activation), RA (rosin, activated usually with free
chloride ions), RSA (rosin, super activated).
Synthetic activated fluxes.
A chemical designed to react with organic fatty acids,
such as rosin, some oils and greases, etc., to form
water-soluble soaps. This is a method for defluxing
and degreasing. Saponifiers are usually alkaline and
may be mineral based (sodium hydroxide or potassium
hydroxide) or organic based (water solutions or
monoethanolamine) . '
Another name for hydrcarbon/surfactant (HCS) solvents.
The UNEP Committee recommends hydrocarbon/surfactant
(HCS) solvents as the more descriptive and accurate
nomenclature.
An abbreviation for surface mount component.
A polymeric coating applied to bare printed circuits
which leaves only the pads or leads, designed to be
subsequently soldered, as bare metal.
An aqueous or organic product designed to clean a
component or assembly by dissolving and/or' displacing
the contaminants present on its surface.
Means of reducing the emission of solvents (e.g.,
CFCs) into the environment. This technique usually
involves improving the design and operation of the
equipment in which the solvent is used.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Surface mount
component (SMC)
Surface mount
technology (SMT)
Surfactant
Terpene
1,1,1-trichloroethane
Ultrasonic cleaning
Vapour-phase cleaning
Vapour-phase (conden-
sation) soldering .
Volatile organic
compound (VOC)
Water-soluble flux
Wave soldering
A component capable of 'being attached to a PCS using
surface mount technology.' The component may be either
leaded or leadless. ' .
A technique for assembling SMCs on the surface of PCBs
and PWAs, as opposed to inserting leads through holes.
A chemical to reduce the surface tension of water.
Also referred to as surface-active agents. Detergents
are made primarily from surfactants.
Any of many homocyclic hydrocarbons with the empirical
formula C10H16. Turpentine is mainly a mixture 'of
terpenes. See hydrocarbon/surfactant solvents.
A hydrochlorocarbon solvent with an estimated ODP of
0.1. Also known as methyl chloroform.
Immersion cleaning where mechanical energy formed by
cavitational implosions close to the.surfaces being
cleaned significantly aids the cleaning operation.
A cleaning process, usually with.CFC-113 solvent or
hydrochlorocarbon solvents, where the final rinse is
achieved by condensing solvent vapours on the parts
being cleaned.
A method of reflow soldering where the solder and the
parts being joined are heated in the vapour of a
perfluorinated substance whose boiling point is <
usually in the range of 215-260°C. In some types of
equipment designed for this process, a less expensive
secondary vapour blanket of CFC-113 is used.
These are constituents tha-t will evaporate at their
temperature of use and which, by a photochemical
reaction under favourable climatic conditions, will
cause atmospheric oxygen to be converted into
potentially smog-promoting tropospheric ozone.*
A flux whose post-soldering residues may be removed by
a water wash. Such fluxes are usually very active, so
adequate defluxing is an essential part of their use.
They are. also known as Organic Acid (OA) fluxes or
inorganic acid fluxes. '
Also known as flow soldering, a method of mass
soldering electronics assemblies by passing them, i
after fluxing, through a wave of molten solder.
Legally, some countries classify all organic substances which evaporate
at ambient temperatures as VOCs, irrespective of their ozone-promoting
properties. .
'' 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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EXECUTIVE SUMMARY: SOLVENTS. COATINGS. AND ADHESIVES TOG
Developed Country Progress in Eliminating Ozone-Depleting Solvents
Most developed country suppliers and consumers of ozone depleting
solvents are halting 'production and use earlier than mandated or expected. A
few enterprises have made unwise first choices of alternatives and substitutes
and are changing to better options.
However, significant problems exist in the European Union (EU), where
many companies began their investments too late and may not be able to halt
their use prior to the 1 January 1995 EU phaseout of production. Furthermore,
some large companies in developed countries may have been over-confident that
their uses would qualify as essential and consequently may not have allowed
enough time for a smooth transition. Varying sizes of enterprises, but
especially small- and medium-sized ones, are identified in many developed
countries as possibly being unaware, unprepared, and financially unable to
make necessary investments ih time to avoid chemical shortages and price
increases that could jeopardize their businesses.
Procrastination in implementing alternatives and substitutes could lead
to significant price increases .for stockpiled and recycled ODSs manufactured
prior to the phaseout. Dramatic price increases could stimulate illegal
markets in imported solvents. In the immediate future, shortages of ozone-
depleting substances (ODSs) for solvent applications could cause companies to
switch to chlorinated solvents and/or HCFCs,> if allowed, because these
solvents can often be used in existing equipment.
Military Progress .
In January 1994 the North Atlantic Treaty Organization (NATO) held its
2nd international conference on "The Role of the Military in Protecting the
Ozone Layer". Participants from Algeria, Belarus, 'Belgium, Brazil, Canada,
Denmark, France, Germany, Hungary,, India, Italy, Japan, Kenya, Latvia,
Lithuania, Norway, Pakistan, Poland, Portugal, Romania, Russia, Spain,
Slovakia, Sweden, Taiwan, Thailand, Netherlands, Turkey, Ukraine, United
Kingdom, United States,,and Uruguay attended the meeting. NATO members
reported that they are meeting or exceeding the production phaseout goals of
the Montreal Protocol and EU members reported that they are meeting their more
stringent goals. Part of the reason for- this progress has been the leadership
of policy makers in some ministries of defence who realized that.global
environmental protection is part of national security'and also recognized that
they cannot continue to depend on chemicals that will be unavailable or
increasingly expensive.
Germany, Norway, and Sweden reported that they have virtually eliminated
the use of ozone-depleting solvents in military applications.
\
German, Swedish, UK, and US participants reported comparable progress in
identifying and documenting alternatives and substitutes for civilian aircraft
maintenance including options that provide equal or improved cleaning, surface
preparation, and bonding. The International Cooperative for Ozone Layer
Protection (ICOLP) announced plans to invite U.S. .Environmental Protection
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
ES-1
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Agency (EPA) and the National Aeronautics and Space Administration (NASA) to
join their global project to phase out ODSs in aerospace operations. NASA and
U.S. EPA are considering the proposal.
The meeting resulted in several recommendations being made to NATO:
Share information on critical uses (e.g. gaseous and liquid oxygen
systems, guidance systems, rocket motors) via electronic data-
bases, publications, workshops and informal working groups.
Foster and support streamlined universal qualification processes
and procedures.
Revise the existing military documentation.
Further investigation, certification, and publication of
alternatives and substitutes for unresolved applications including
critical adhesive bonds in rocket motor manufacturing, cleaning
and verification of gaseous and liquid oxygen systems, and other
specific precision cleaning such as gyroscope bearings in space
systems that must operate for many years without maintenance.
Speed awareness and introduction of proven technologies by
utilizing "tiger teams" of experienced engineers and scientists to
help implement these technologies in military applications.
Developing Country Progress:
In some cases, technology cooperation with developing countries has
already been highly successful or has prepared countries to take prompt action
once incentives and financing are in place. Examples include Mexico,
Thailand, Turkey, and Malaysia. .An important conclusion from investigations
of solvent use in developing countries is that enterprises must be motivated
and prepared to accept new technology. This motivation can result from
government regulation, a clearly articulated industry phaseout strategy, price
increases, product shortages, or supply uncertainty for ozone-depleting
substances. Some technology cooperation efforts have been prematurely
attempted in countries where enterprises and national governments were not
prepared, and as a consequence little actual investment progress has been
made. :
Some regional and national conferences and workshop's have not been as
successful as they could have been because the preconditions for change had
not been met. The Committee recommends that conference planners more
completely involve local industry, industry associations, and chambers.of
commerce in the planning and that they determine whether the preconditions for
change are in place. If it is determined that a conference is useful,
conferences should be organized and announced far in advance. It has. been the
experience of the Committee in developed and developing countries that
representatives of small- and medium-sized solvent-using enterprises do not
travel long-distances for meetings based on general presentations. They are
short of funds and their manufacturing engineers are very busy. This makes
ensuring the presence of a motivational framework all the more important.
One problem common to all countries, but especially'developing
countries, is that domestic small- and medium-sized enterprises that use ODSs
are difficult to identify, may not welcome government officials, and may not
be easy to convince that a change is necessary. .It is likely that many of
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
ES-2
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such users will only make changes when the price increases, when shortages
develop, when domestic regulations are in place, or when multinational
companies require suppliers to phaseout.
Concerns of unannounced changes in speciality products:
The Committee cautions that manufacturers may eliminate ODSs from
products without notifying customers. There is the possibility that the
manufacturer may not appreciate that their product is used in a particular
application where the ODSs provided a necessary performance characteristic
that is not duplicated by the reformulated product. Use of such reformulated
materials and products under these circumstances could be costly or dangerous
to life and health. The solution is for manufacturers of speciality products
to better communicate to end-users, changes in product ingredients and to
cooperate with end-users on performance testing of the new products.
Some Parties may have interpreted process agent use of controlled
substances as subject to phaseout. Other Parties may have interpreted such
use as feedstock not subject to the phaseout. In 1994 the Committee was
unable . to recommend exemptions for process agent use under the Essenti'al Use
Criteria. .
At the October 6-7, 1994 Meeting of the Parties to the Protocol, it was
decided:
"...for an interim period of 1996 only, (Parties may) treat chemical
process agents in a manner similar to feedstock, as recommended by the
Technology and Economic Assessment Panel, and take a final decision on
such treatment-at their. Seventh Meeting;"(Decision VI/10)
The Parties requested the .Technology and Economic Assessment Panel (TEAP)-:
To identify uses of controlled substances as chemical process agents, to
estimate emissions and ultimate fate, and to evaluate control
technologies;
To evaluate alternative process agents or technologies or products
available to replace controlled substances in such uses; and to
To report findings not later than March 1995. The Panel has asked the
government of Sweden to organize and finance a special working group to
complete this work.
1994 Nominations for Essential Uses
The Committee reviewed nominations from Austria, Belgium, Canada,
Denmark, European Commission (EC)', Finland, France, Germany, Greece, Ireland,
Italy, Japan, Netherlands, Norway, Sweden, Switzerland, United Kingdom, and
the United States. In all but laboratory and analytical uses and Space
Shuttle rocket motor manufacturing the Committee was unable to recommend the
nominations because there are technically and economically feasible
alternatives arid substitutes and/or because controlled substances are
available in sufficient quantity and quality from'existing sources. The
* 199A UNEP SOLVENTS. COATINGS, AND ADHESIVES REPORT *
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Committee also found that many requests were insufficiently supported with
technical data.
HCFC
Few large scale current uses of HCFCs have been reported for solvents,
coatings, or adhesives. In the near term HCFCs may be necessary as transition
substances in some limited and unique applications including:
cleaning delicate materials such as cultural heritage and archival
property
cleaning assemblies or components with sensitive materials or
particular soils
« cleaning certain oxygen systems
« cleaning where explosive or flammable conditions are possible
« as a carrier of oil in precision applications.
In6countries where HCFCs are prohibited, enterprises may, in certain
specific cases, select perfluorinated carbons (PFCs) as an adjunct to
specialized cleaning systems. PFCs have extremely long atmospheric lifetimes
and have potent global warming potentials (GWPs) and should therefore be
avoided where ppssible.
The Committee does not recommend the use of HCFC-141b to replace 1,1,1-
trichloroethane as a solvent. A recommendation is not possible because HCFC-
141b has an ozone-depletion potential (ODP) comparable to 1,1,1-
trichloroethane and is not technically suitable for many cleaning
applications. ...
It is estimated that HCFC-lAlb and HCFC-225 together will not replace
more than 1 percent of global.CFC-113 uses unless HCFC-225 becomes a
substitute for CFC-113 in dry cleaning, which could increase use to
approximately 5 percent. In some countries with active HCFC sales efforts,
approximately 5 percent of CFC-113 solv.ent use (excluding dry-cleaning which
may increase use) may be replaced with HCFC-141b. It is estimated that HCFCs
may replace 1-5 percent of 1986 CFC-113 and 1,1,1-trichloroethane use as
transitional substances and where no alternatives or substitutes are currently
available.
The Committee cautions that there may be essential uses of very small
quantities of ozone-depleting solvents that are not yet identified by the
Committee, national governments, product distributors, and possibly the
manufacturers themselves. However, it is expected that these uses will be
identified as the accelerated phaseout in the EU is implemented and as
production is halted. Stockpiled and recycled sources may be adequate to
supply these uses.
PRICE INCREASES AND SHORTAGES OF OZONE-DEPLETING SOLVENTS
CFC-113 is produced primarily as a solvent with certain amounts sold as
a feedstock for production of HFC-134a and some plastics. When CFC-113 sales
in solvent uses are halted in the EU in 1995, and in all developed countries
by 1996, the market may not be sufficient for developed country manufacturers-
to supply developing country markets.
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CFC-113 is currently manufactured in two developing countries -- China
and India -- and production facilities in South Korea and Taiwan are believed
to be currently inactive.
Since 1,1,1-trichloroethane is produced as a feedstock for HCFC-141b and
HCFC-142b, it will be more readily available than CFC-113 after 1996 for
export to developing countries for their domestic needs, subject to Protocol
restrictions.
It is the consensus of the Solvent, Coatings and Adhesives Technical
Options Committee that quality grades of CFC-113 and !,1,1-trichloroethane
will be in uncertain supply after 1996 and that it will be prudent for
enterprises in developing countries to move quickly to reduce and eliminate
dependence on these chemical substances when cost-effective options are
available. European, Japanese, and U.S. chemical manufacturers, distributors,
and customers may have residual chemical supplies produced under national
Protocol quotas or under Basic Domestic Needs quotas that may be marketed to
developing countries if sales are less than expected in their developed
country markets. This oversupply is less likely in the United States where
taxes on stored ozone-depleting substances discourage oversupply.
A variety of alternative substances and technologies are currently in
use or under development to facilitate .the phaseout of CFC-113 and 1,1,1-
trichloroethane. These alternatives include no-clean technologies, aqueous
and semi-aqueous cleaning, other hydrocarbon solvents, non-ozone-depleting
chlorinated solvents, HCFCs, perfluorocarbons, and a growing number of non-
solvent cleaning processes.-
No-clean technologies represent the optimum alternative and have been
applied in an increasingly large number of electronics manufacturing
applications in recent years. Nevertheless, research and testing of no-clean
manufacturing processes is ongoing in the hope of making them viable
alternatives in a wider variety of uses. Second to no-clean with respect to
environmental protection is aqueous or semi-aqueous cleaning. The major
drawbacks of these alternatives may be high energy consumption and wastewater
treatment costs, depending on the process, requirements, and legislation.
HCFCs, though their use is transitional, are important alternatives to
CFC-113 and 1,1,1-trichloroethane solvent use in applications for which no
other viable alternative exists. Because of their lower ozone-depletion
potential (ODP), HCFCs with a short lifetime are preferred tp those with
longer lifetimes. The.ODP of all HCFCs is lower than the ODP of CFC-113.
However, HCFCs should be used as substitutes for 1,1,1-trichloroethane only if
the ODP of.the HCFC substitute is lower than 0.10 and if their emissions are
controlled using the best available technology. In addition, the 1992.
Copenhagen Amendments to the Montreal Protocol require that .production and
consumption of HCFCs, as defined in the Protocol (Annex III G. Article 2F of
UNEP/OzL. Pro. 4/15), must be reduced by 99.5% by 2020 and completely phased
out by 2030. Thus, HCFCs are a valid alternative in certain limited
applications while other, long term alternatives are being developed.
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SECTOR PROGRESS
Electronics Cleaning
The electronics industry, which was heavily dependent on ozone-depleting
solvents until recently, is fortunate to have the widest range of substitute
materials and processes available. There is no technical reason why any
company, large or small, in a developed or developing nation, should not be
able to move away from such solvents immediately. Economic considerations,
reported in previous editions (UNEP 1989, 1991), have shown that most
substitute processes for this industry are less costly to run and, most often,
give improved technical quality. On the other hand, relatively large
investment capital is sometimes required to obtain the required results and
this could be an obstacle, especially for small companies manufacturing "hi-
tech" electronics.
To substitute for CFC-113 in defluxing, there is a large choice of
processes, equipment, and materials commercially available for production
units of all sizes. Where there are no technical specifications that require
post-solder cleaning, "no-clean" techniques are often the most economical.
This technique is recommended where the reliability criteria can be met.
Where cleaning is a requirement, the use of water-soluble chemistry has
generally proved to be preferable to most other processes, although it is not
a universal solution. There is an adequate choice of other techniques where
neither of these can be applied.
The Solvents, Coating and Adhesives Technical Options Committee do not
recommend the following processes in electronics manufacture for funding under
the provisions of the Montreal Protocol Multilateral Fund:
HCFC-141b for defluxing printed circuits
Vapour-phase reflow soldering
Vapour-phase drying of heavy organic solvents using PFCs
Vapour-phase drying of water using MFCs or PFCs.
Precision Cleaning
Precision cleaning applications are characterized by the high level of
cleanliness required to maintain low-clearance or high-reliability components
in working order. They are used in a variety of manufacturing industries,
such as in aerospace, microelectronics, automotive, and medical. Several
factors define' the applications where a precision cleaning process is
required. Some of these factors are:
high standards for the removal of particulates or organic residue
components constructed of chemically-sensitive materials
components with physical limitations, such as geometry or
porosity, which limit the ability to remove entrapped fluids like
water
high-cost components or components requiring high-reliability
»
CFC-113 and 1,1,1 -trichloroe.thane have evolved as the preferred solvent
cleaning method in precision cleaning because of their chemical inertness, low
toxicity, non-flammability, low surface tension, and low water solubility.
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However, to eliminate CFC-113 and 1,1,1-trichloroethane use, a number of
companies have tested and implemented alternative cleaning methods. Possible
alternatives include solvent and non-solvent options. Solvent options include
other organic solvents (such as alcohols and aliphatic hydrocarbons),
perfluorocarbons, HCFCs and their blends, and aqueous and semi-aqueous
cleaners. Non-solvent options include supercritical ^luid cleaning, UV/Ozone
cleaning, pressurized gases, and plasma cleaning. Solvent ,use may also be
reduced by controlled planning of repetitive or multiple cleaning operations.
Metal Cleaning
Metal cleaning is a surface preparation process that removes organic
compounds such as oils and greases, particulate matter, and inorganic soils
from metal surfaces. Metal cleaning prepares parts for subsequent operations
such as further machining and fabrication, electroplating, painting, coating,.
inspection, assembly, or packaging. Parts may be cleaned multiple times
during the manufacturing process.
The control approaches available for metal cleaning operations include
solvent conservation and recovery practices and the use of.alternative
cleaning such as solvent blends, aqueous cleaners, emulsion cleaners,
mechanical cleaning, thermal vacuum de-oiling, and no-clean alternatives.
Alternatives to CFC-113 and 1,1,1-trichloroethane must be selected and
optimized for each application given the varying substrate materials, soils,
cleanliness requirements, process specifications, and end uses encountered in
metal cleaning.
Dry Cleaning
Dry cleaning enables the cleansing and reuse of fabrics that.cannot be
cleaned by alternative methods. The inherent environmental friendliness of
restoring freshness to soiled articles and garments is matched by extreme
efficiency in terms of solvent and energy use in the dry cleaning process
itself. Organic solvents are used to clean fabrics because, unlike water,
they do hot distort some'natural and synthetic fibres. Water cleaning of many
materials can affect the stability of fabric, lining, and interlining and may
cause stretching or shrinkage.
A number of solvents can be used as alternatives to CFC-113 and 1,1,1-
trichloroethane in dry cleaning operations. Perchloroethylene, the most
widely used dry cleaning splvent, has been used in this application for over
30 years, during which, time the systems for its safe use have become highly
developed. The flammability of petroleum solvents effectively precludes their
use in shops, although with proper precautions, they can be a substitute for
CFC-113 on many fabrics. Petroleum solvents include white spirit, Stoddard
solvent, hydrocarbon solvents, isoparaffins, n-paraffin, etc. A number of
HCFCs and HCFC blends are currently available commercially for use in solvent
applications. These include HCFC-123, HCFC-141b, and HCFC-225. These HCFCs
have good stability, appropriate solvency, and non-flammability and some HCFCs
are suitable for cleaning those delicate fabrics that currently depend on CFC-
113. It should be noted, however, that HCFCs are transitional alternatives
subject to a phaseout under the'Montreal Protocol by the year 2030. Other
classes of chemicals such as isoparaffins, solvents derived from sugar cane,
and hydrocarbon/surfactant blends'are theoretically possible alternative dry
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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cleaning solvents. More research, however, is necessary to determine their
feasibility for dry cleaning.
Adhesives
1,1,1-Trichloroethane is used as an adhesive solvent because it is non-
flammable, dries rapidly, does not contribute to local air pollution, and
performs well in many applications, particularly foam bonding. The rubber
binders used in 1,1,1-trichloroethane adhesives are soluble in other solvents,
such as acetone, ethyl acetate, heptane, and toluene. Although there has been
a general trend in the U.S. and Western European adhesives industries to
replace organic solvent-based adhesives with solvent-free types, one
alternative is to return to earlier solvent formulations.
Some adhesives use water, in lieu of organic solvents, as the primary
solvent. Recent literature on water-based adhesives suggests that there is
still much debate about the overall effectiveness of water-based adhesives for
many end uses.
The Committee D-14 of the American Society for Testing and Materials
(ASTM) defines a hot melt adhesive as one that is applied in a molten state
and forms a bond upon cooling to a solid state. Hot melt Pressure-Sensitive
Adhesives (PSAs) now compete with water-based acrylics in outdoor
applications. They have been used on paper labels for indoor applications
since 1978.
Radiation curing is a production technique for drying and curing
adhesives through the use of radiant energy such as ultraviolet (UV), infrared
(IR), electron beam (EB), gamma, and x-rays. Radiation cured adhesives are
especially well adapted for pressure sensitive tapes. One drawback is that
adhesive curing is only possible in the "line of sight" of the radiant energy.
One way to lower volatile organic compound (VOC) emissions when using
solvent-based adhesives is to increase the percent solids in .the formulation.
High solids adhesives have good performance characteristics, including initial
bond strength comparable to that of 30 percent solids adhesives in medium and
high demand applications and can be applied using existing equipment at normal
line speeds with minor modifications. In other application areas, such as
bonding rubber assemblies, high solids adhesives have not been as successful.
One-part epoxies, urethanes, and natural resins are often supplied as
powders that require heat to cure. Powders are only used for non-pressure-
sensitive applications. One advantage of the powder form is that no mixing or
metering is necessary. However, powders must be refrigerated to maximise
shelf life.
Moisture cure adhesives and reactive liquids can be applied as -100
percent non-volatile solid and liquid systems. These adhesives are composed
entirely of binding substances, modifiers, and fillers (i.e., they have no
carrier or solvent). Moisture cure adhesives cure upon exposure to the
humidity in the ambient air; this type of adhesive requires application in a
humid environment and might not work well in dry climates. Some two-component
adhesives use reactive solvents which form part of the cured mass and thus do
not depend on evaporation. In use, one solution consisting of an elastomer
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colloidally dispersed in a monomer is cured by a second solution through a
free radical chemical polymerisation, thereby creating the bond .
Coatings and Inks
1,1,1-Trichloroethane is used by manufacturers, printers, and users of
protective and decorative coatings and inks. CFC-113 use in the production of
coatings or inks is negligible. In coatings, 1,1,1-trichloroethane is used
alone or combined with other solvents to solubilize the binding substance
which is usually composed of resin systems such as alkyd, acrylic, vinyl,
polyurethane, silicone, and nitrocellulose resin. Inks are used to print
items ranging from wallpaper to dog food bags to beverage bottles and.cartons.
Many of these uses involve the application of coloured ink to a film (or
laminate) in the flexible packaging industry.
Some coatings contain water rather than organic solvents. Recent
advances in water-based coating technology have improved the dry-time,
durability, stability, adhesion, and application of water-based coatings.
Primary uses of these coatings include furniture, electronics in automobiles,
aluminum siding, hardboard, metal containers,. appliances, structured steel,
and heavy equipment. Water-based inks for flexographic and rotogravure
laminates have been successfully developed and have overcome technical hurdles
such as substrate wetting, adhesion, colour stability, and productivity.
Although high-solid coatings resemble conventional solvent coatings in
appearance and use, high-solid coatings contain less solvent and a greater
percentage of resin. High-solid coatings are currently used for appliances,
metal furniture, and'a variety of construction equipment. The finish of high-
solid coatings is often superior to that of solvent-based coatings, despite
the fact that high-solid coatings require much less solvent than dp solvent-
based coatings. -
Powder coatings contain the resin only in powder form and thus have no
solvent. While powder coatings were first used only for electrical
transformer covers, they are now used in a large number of applications,
including underground pipes, appliances, and automobiles.
Ultraviolet light/Electron beam (UV/EB)-cured coatings and inks have
been used in very limited applications over the last 20 years, but their use
has seen a dramatic increase in recent years. Several of the markets in which
UV/EB-cured coatings and .inks have been used 'more frequently in recent years
are flexographic inks and coatings, wood furniture and cabinets, and
automotive applications. One major limitation to the use of UV/EB-cured
coatings and inks is outdoor durability. This is an especially important
consideration in automotive applications.
Aerosols Solvent Products
1,1,1-Trichloroethane functions as either an active ingredient (e.g.,
degreaser or cleaner) or as a solvent in aerosol product formulations. Though
most of the aerosol applications traditionally used 1,1,1-trichloroethane as
their solvent, there are a small number of products which made use of CFC-113 .
as well. Most aerosol products currently employing CFC-113. and.1,1,1-
trichloroethane can be reformulated with alternative compounds. Except for
water, some HGFCs, and non-ozone-depleting chlorinated solvents (e.g.,
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *,
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trichloroethylene, perchloroethylene,.methylene chloride), all of the
substitute solvents currently available are more flammable than 1,1,1-
trichloroethane. The flammability is also a function of the propellant;
butane and propane being more flammable than carbon dioxide, nitrous oxide or
the traditional CFC-ll/CFC-12 mixture.
Alternative solvents'currently exist for virtually all aerosol solvent
applications of CFC-113 and 1,1,1-trichloroethane. However, while some of
these alternatives are functional, they are considered to be less than optimal
for a variety of reasons. For example, in applications where a strong solvent
is required, but the use of a flammable solvent would pose serious safety
risks, substitutes may include only HFCs, HCFCs, and chlorinated solvents.
While these solvents would be functional, HCFCs contribute to ozone-depletion,
and chlorinated solvents are toxic and may pose health risks to workers and
users of a product.
CFC-113 and 1,1,1-trichloroethane use in aerosols can also be reduced if
alternative means of delivering the product are developed. Two examples of
these alternative methods are: (1) a manual "wet-brush" (recirculating
liquid) system, as a substitute for aerosol brake cleaners used in repair
shops, and (2) increased use of professional dry cleaning services as a
substitute for the use of aerosol spot removers.
Other Solvent Uses of CFC-113, 1,1,1-Trichloroethane, and Carbon Tetrachloride
Some amount, in most cases relatively small quantities, of CFC-113,
1,1,1-trichloroethane, .and carbon tetrachloride are employed in a number of
industry and laboratory applications. The application areas include drying of
components, film cleaning, fabric protection, manufacture of solid rockets,
laboratory testing and analyses, process solvents, semiconductor
manufacturing, and others.
The Committee 'consensus is that by 1996, in-accordance with the Montreal
Protocol, most of the CFC-113, 1,1,1-trichloroethane, and carbon tetrachloride
used for these applications can be replaced by the alternatives.
In the applications of laboratory analyses and in the manufacture of a
specific large scale solid rocket motor, the Parties have granted an exemption
for continued use of specified ozone-depleting solvents for.1996 and 1997.
The exemptions are subject to review and1alternatives are being investigated.
In the case of use of ozone-depleting substances as process chemicals,
there are also a number of alternatives identified in this report. In
addition, an in-depth review of alternatives is planned for completion and
presentation by the Technical and Economic Assessment Panel' to the Parties by
early 1995.
PROGRESS IN ELIMINATING ODS FROM ROCKET MOTORS
Ozone Depleting Substances (ODSs) have been routinely used globally for
decades in the manufacture of space launch vehicle solid ropket motors (SRMs).
The primarily ozone-depleting solvents used are 1,1,, 1-trichloroethane (TCA or
methyl chloroform) and CFC-113. These substances are used.because of their
excellent cleaning properties, low toxicity, chemical stability and non-
flammability.
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In the United States, large solid rocket motors (SRMs) are used to
launch into space communication, navigational and scientific satellites and
the manned Space Shuttle orbiters. Large SRMs include the existing Titan IV
SRM as well as its upgraded version calle^d the SRMU and the Space Shuttle f
redesigned solid rocket motor (RSRM).
/ __ ,
Despite these technical safety and reliability challenges, the SRM
industry has successfully tested, approved, and implemented significant ODS
elimination. Since 1989, the four US manufacturers of large SRMs have
eliminated over 1.6 million pounds of ODS use per year. Current (1994) ODS
usage is less than 48 percent of the use in 1989. Usage in 1995 is estimated
to be less than 22 percent of 1989, and manufacturers have committed to
complete elimination of ODSs within the next few years.
Update on the Essential Use Applications
NASA/Thiokol was granted an essential use production exemption for 1996
and 1997. NASA/Thiokol have proceeded with their phaseout and are ahead of '
schedule for eliminating non-essential uses and investigating additional
alternatives and substitutes. However, at this time NASA/Thiokol has not
identified any acceptable substitutes that would reduce their essential use
below the previously calculated amounts..
The Solvents, Coatings, and Adhesives TOC reported in the March 1994
Report that it was likely that all manufacturers of solid rocket motors use
ODSs. The Committee has confirmed that other U.S. and European solid rocket
motors use these substances and that these organizations are expected to
nominate additional" essential uses by January 1, 1995 for decision in 1995.
The U.S. Titan program is working to completely eliminate the use of
ODSs and has invested substantial resources in successfully developing
'alternatives to ODS use. The prime contractor and the major manufacturers of
Titan IV vehicle components will reduce all ODS -use by 99 percent, -from 1.33
million kg in 1989 to 9,200 kg in 1996. Four small-quantity ODS .uses are
critical to the success of the Titan SRMU. These are-(1) surface preparation
to ensure effective bonding of the internal insulator-to the composite case,
(2) surface preparation to ensure effective attachment of breather cloth to
the insulator to permit uniform curing, (3) surface preparation to ensure
effective bonding of the propellant to the insulator, and (4) dispersing
propellant cure catalyst during propellant mixing. The quantity of ODS
necessary to complete SRMU.manufacture for the final nine flight sets is 3,660
kg per year or less for 1996 through to 1999.
° Both CFC-113 and TCA are used in the European Ariane Espace Programme.
Efforts to find substitutes for these programmes concern CRYOSPACE for liquid
rocket engines and Societe Europeenne de Propulsion (S.E.P.) for solid motors.
The Japanese space rocket industry currently uses CFC-113 and TCA but
expects to phase out the uses by the end of 1995. Latest achievements include
the solid rocket booster (SRB) for the H-II launch vehicle which is capable of
launching a.2 Ton satellite to Geosynchronous orbit.
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Cleaning of Oxygen Systems
In January 1994 NATO identified the cleaning of oxygen systems as one of
the most difficult challenge facing military and aerospace applications. In
Fall 1994, the International Cooperative for Ozone Layer Protection (ICOLP),
Aerospace Industry Association (AIA), U.S. EPA, 'National Aeronautical and
Space Administration (NASA) and the U.S. Air Force convened a special workshop
on cleaning of oxygen systems without ozone-depleting solvents.
Oxygen systems include: life support systems such as diving, totally
encapsulated suits, emergency breathing devices, fire & rescue backpacks,
submarine, aircraft, manned spacecraft, and medical applications; propulsion
systems such as liquid rocket motors; industrial systems such as chemical
production; and other unique systems and customer products such as welding
equipment.
Oxygen systems must be kept clean because organic compound
contamination, such as hydrocarbon oil, can ignite easily and provide a
kindling chain to ignite surrounding materials. Contamination can also
consist of particles that could ignite or cause ignition when impacting other
parts of the system. Risk is increased by the typical proximity of oxygen
systems to very large quantities of fuel materials, and the common necessity
of locating oxygen systems in confined spaces with difficult or impossible
access and egress (e.g-. space ships, submarines, aircraft, .and. surf ace ships).
. Examples of the challenges presented by these applications include the
cleaning of the space shuttle external fuel tank, cleaning of aircraft carrier
liquid oxygen plants, cleaning of installed submarine and transport aircraft
high pressure oxygen systems, and the gauges and instrumentation associated
with each. Examples of devices typically cleaned in these systems include
tubing, gauges, regulators, valves, and metering devices. It is usually most
effective to clean oxygen equipment at the piece part level in a proper
facility. It is more difficult to clean oxygen equipment in aircraft and ship
equipment in place with difficult accessibility and temperature extremes.
Additional challenges occur in many other industrial oxygen systems such as
those used in production' and transfer of both gaseous and liquid oxygen, in
medical applications, and in welding. Cleaning of equipment used in the
oxygen production industry involves unique challenges such as compatibility
with aluminum heat exchangers.
Solvents such as non-ozone depleting chlorinated solvents and
.hydrocarbons often clean satisfactorily, but all have -environmental or
toxicity concerns, and some have flammability concerns.
Aqueous cleaning options have been successfully developed and .
implemented for many oxygen system cleaning situations. For example-, Lockheed
uses aqueous processes in the manufacturing and maintenance of aircraft and
missile oxygen systems, the Air Force uses aqueous cleaning for some aircraft
oxygen system maintenance, NASA/Kennedy Space Center uses aqueous solutions
for cleaning oxygen bulk storage and transfer systems for rocket motors, and
.the U.S. Navy uses aqueous cleaning processes for cleaning the tubing in
oxygen systems on ships and submarines.
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Isopropyl alcohol (IPA) is being used by Lufthansa German Airlines to
clean the oxygen systems in their commercial aircraft fleet. Sweden has
reported using a solvent blend for oxygen system cleaning consisting of 95%
ethanol. , '
Some parts of oxygen systems can be changed to simplify or avoid the
necessity of cleaning or they can be adapted to' allow aqueous-cleaning.
Some, oxygen system components still depend on CFC or chlorinated solvent
cleaning because current alternatives and substitutes are not technically
suitable. In other cases, rigid specifications and requirements may need to
be changed from prescriptive to performance standards to allow technically
feasible solutions to be used. '
This Report includes case studies of successful elimination of ozone -
depleting solvents which discuss the evaluation and implementation.of
materials, alternative technologies, and processes. The following are
included in Chapter 11: Allied Signal (evaluation of aqueous saponifie.rs) , .
AT&T Bell Labs (non-ODS -alternatives including no-clean soldering), Beck
Electronics (alternative solvents and design of cleaning equipment), Ford
Motor Company (no-clean soldering), Hitachi (non-ODS alternatives), Honeywell
.(non-ODS alternatives), IBM Corporation (no^clean soldering), Japan Industrial
Conference on Cleaning (information dissemination), Lockheed Sanders Company
(company phaseout efforts), Miljoministeriet (hydrocarbon dry cleaning),
Minebea Company (aqueous cleaning of ball bearings), National Semiconductor
(company phaseout efforts), Naval Aviation Depot. Cherry Point (hand-wipe
cleaning). Northern Telecom (company phaseout efforts), Robert Bosch
Corporation (aqueous cleaning), Rockwell International (low-residue flux),
Seiko Epson Corporation (alternatives to ODSs), Singapore Institute of
Standards and Industrial Research (ODS-free certification of businesses),
Swedish EPA (country-wide phaseout efforts), Toshiba Corporation (vinyl-
copolymer masking agent), U.S. Air Force Aerospace Ciuidance and Metrology
Center (aqueous & non-aqueous alternatives), Vibro-Meter, SA (water-based
cleaning). ' . . .
Total Equivalent Warming Impact (TEWI)
Total Equivalent Warming Impact (TEWI) provides an important tool in the
selection procedure for alternative cleaning and drying technologies.
However, TEWI must not be the only criterion when selecting the cleaning.
drying, or other technology for a manufacturing process. The Alternative
Fluorocarbons Environmental Acceptability Study (AFEAS) has provided a
methodology to calculate. TEWI for wide range of available systems.
The selection of the. best technology to displace CFC-113 or 1.1,1-
trichloroethane (methyl chloroform) must be specific to the intended
applications and will represent a trade-off or balancing of several key
parameters: worker safety (toxicity or flammability concerns), investment,
operating costs, energy efficiency and reliability. It must also consider a
series of environmental issues (discharges to water or landfill, local.
environmental air quality (smog) and global impact).
This report has evaluated one of the selection parameters. TEWI. for a
number of systems. A summary of the key findings follows.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Solvent losses from the cleaning equipment are potentially lower than
assumed in the 1991 study., resulting in lower calculated contributions
to TEWI. This reduction in emissions is possible through the adoption
of enhanced vapor recovery and improved/novel approaches to materials
handling (e.g., freeboard dwell). In some cases, the above technologies
can be retrofitted to very modern existing equipment, with results
almost comparable to new equipment. However, such equipment will
require careful operation and maintenance to sustain low emission rates.
The no-clean systems used for the manufacture of printed wire assemblies
have the potential for the lowest TEWI. For metal cleaning,
chlorocarbon-based systems (e.g., PCE, TCE) have the potentially lowest
TEWI. However, these chlorinated solvent systems may be subject to
various national, regional and/or local regulations or emission limits
that may severely limit the use of these chemicals for cleaning
applications.
The PFC system studied has the highest TEWI.
While they use more energy per unit of work (throughput), aqueous, semi-
aqueous and alcohol systems generally have been shown to have a lower
TEWI than HCFC and HFC-based systems because emissions from aqueous,
semi - aqueous, and alcohol systems do not contribute to global warming.
In .the case of HCFC/HFC/PFC-based systems, the direct effect caused by
emission of the chemical, represents from 40 percent to over 90 percent
of the calculated contribution to potential global warming.
Future study should assess, the effects of variations in equipment and
practices'on TEWI and estimate- implementation time for alternative systems in
developing countries.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CHAPTER 1
INTRODUCTION
1.1 BACKGROUND
In response to the growing scientific consensus that chlorofluorocarbons
(CFCs) and halons would ultimately deplete the ozone layer, the United Nations
Environment Programme (UNEP) in 1981 began negotiations to develop
multilateral policies for protecting the ozone layer. These negotiations
resulted' in the Vienna Convention for the Protection of the Ozone Layer in
March -1985. The convention provided a framework for international cooperation
in research, systematic observation, and information exchange. In September
1987, 24 nations including the United States, Japan, the Soviet Union, and
members of the European Community signed the Montreal Protocol on Substances
That Deplete the Ozone Layer (hereafter referred to as "the protocol"). As of
February 1994, 132 nations and the European Community had ratified the
Protocol (see Table 1-1). These countries represent virtually all of the
world's consumption1 of CFCs and halons. The Protocol, which entered into
force on January 1, 1989, limited consumption of specified CFCs to 50 percent
of 1986 levels by.the year 1998 and called for a production freeze of
specified halons at 1986 levels starting in 1992. Table 1-2 lists CFCs,
halons,"and other substances controlled under the Protocol.
Shortly after the 1987 Protocol was negotiated, new scientific evidence
conclusively linked CFCs to depletion of the ozone layer and indicated that
depletion had already occurred. Consequently, many countries called for
further actions to protect the ozone layer by expanding and strengthening the
control measures of the 1987 Montreal Protocol. In June 1990, the Parties to
the Montreal Protocol met in London and agreed to Protocol adjustments
requiring more stringent control measures on the CFCs and halons than those
listed in the original agreement. Amendments'placed further control measures
on other ozone-depleting substances including carbon tetrachloride and 1,1,1-
trichloroethane. In April 1991 the National Aeronautics and Space
Administration (NASA) concluded that depletion of the ozone layer over the
past decade has occurred at a rate faster than previously estimated. The four
to five percent depletion over populated northern latitudes since 1978 led
many countries, to propose' more stringent phase-out schedules than those
proposed at the London meeting of the Parties to the Protocol. As a result,
the Parties to the Protocol met in Copenhagen in November 1992 and agreed to
further amendments and adjustments requiring even more stringent control
measures on all controlled substances. In addition, the Parties added methyl
bromide to the list of controlled substances and agreed to freeze production
of methyl bromide at 1991 levels by January 1, 1995. The reduction schedules
1 .Consumption is equal to production plus imports minus exports.
* 1994 UNEP SOLVENTS, COATINGS,' AND ADHESIVES REPORT *
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Table.I-1. PARTIES TO THE MONTREAL PROTOCOL
Algeria
Antigua and Barbuda
Argentina
Australia
Austria
Bahamas
Bahrain
Bangladesh
Barbados
Belarus
Belgium
Benin
Bosnia/Herzegovina
Botswana
Brazil
Brunei Darussalam
Bulgaria
Burkina Faso
Cameroon
Canada
Central African
Republic
Chile
China
Colombia
Congo
Costa Rica
Cote d'Ivoire
Croatia
Cuba
Cyprus
Czech Republic
Denmark
Dominica
Ecuador
Egypt
El Salvador
EEC
Fiji
Finland
France
Gambia
Germany
Ghana
Greece
Grenada
Date: February 1994
Guatemala
Guinea
Guyana
Honduras
Hungary
Iceland
India
Indonesia
Iran
Ireland
Israel
Italy
Jamaica
Japan
Jordan
Kenya
Kiribati-
Kuwait
Lebanon
Libyan Arab
Jamahiriya
Liechtenstein
Luxembourg
Malawi
Malaysia
Maldives
Malta
Marshall Islands
Mauritius
Mexico
Monaco
Morocco
Myanmar '
Namibia
Netherlands
New Zealand
Nicaragua
Niger
Nigeria
Norway
Pakistan
Panama
Papua New Guinea
Paraguay
Peru
Philippines
Poland
Portugal
Romania
Republic of Korea
Russian Federation
St. Kitts and Nevis
St. Lucia -
Samoa
Saudi Arabia
Senegal
Seychelles
Singapore
Slovakia
Slovenia
Solomon Islands
South Africa
Spain
Sri Lanka
Sudan
Swaziland
Sweden -
Switzerland
Syrian Arab Republic
Tanzania
Thailand
Togo
Trinidad & Tobago
Tunisia
Turkey
Turkmenistan
Tuvalu
Uganda
Ukraine
United Arab
Emirates
United Kingdom
United 'States
Uruguay
Uzbekistan
Venezuela
Viet Nam
Yugoslavia
Zambia
Zimbabwe
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT.
1-2
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Table 1-2. SUBSTANCES CONTROLLED BY THE MONTREAL PROTOCOL
ODP Relative
to CFC-11
Group I:
CFC-11
CFC-12
CFC-113
CFC-114
CFC-115
Group II:
Halon-1211
Halon-1301
Halon-2402
ANNEXE A
Trichlorofluoromethane
Dichlorodifluoromethane
1,1,2-Trichloro-1,2,2-trifluoroethane
1,2-Dichlorotetrafluoroethane
Chloropentafluoroethane.
Bromochlorodifluoromethane
Bromotrifluoromethane
Dibromotetrafluoroethane
0.8
1.0
0.6
3.0
10.0
6.0
Group I:
CFC-13
CFC-111
CFC-112
.CFC-211
CFC-212
CFC-213
CFC-214
CFC-215
CFC-216
CFC-217
Group II:
CC14
Group III:
1,1,1-Trichloro-
ethane
ANNEXE B
Chlorotrifluoromethane 1.0
Pentachlorofluoroethane 1.0
Tetrachlorodifluoroethane 1.0
Heptachlorofluoropropane . . 1.0
Hexachlorodifluoropropane . 1.0
Pentachlorotrifluoropropane 1.0
Tetrachlorotetfafluoropropane ' 1.0
Trichloropentafluoropropane 1.0
Dichlorohexafluoropropane ' 1.0
Chloroheptafluoropropane , 1.0
Carbon Tetrachloride (tetrachlofomethane) -1.1
Methyl Chloroform (1,1,1-Trichloroethane) 0.1
ANNEXE C
Partially halogenated fluorocarbons (including HCFC-22, HCFC-123, HCFC-141,
and HCFC-225), are defined as transitional substances by the Montreal Protocol
under Annexe C.
ANNEXE E
Group I:
CH3Br
Methyl Bromide
0..7
Source: Montreal Protocol on Substances that Deplete the Ozone Layer
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
1-3
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set out in the Montreal Protocol Copenhagen Amendments of 1992 are shown in
Table 1-3.
Table 1-4 compares worldwide consumption and ozone-depletion potentials
.of CFG-11, CFG-12, CFG-113, CFG-114, and CFG-115. Worldwide consumption of
1,1,1-trichloroethane in 1988 and 1990 was 679,000 MT,' and 726,000 MT,
respectively (Midgeley 1991). The 1988 consumption of 1,1,1-trichloroethane
in the U.S, Western Europe, and Japan was estimated at 582,000 MT (Chem
Systems 1989). It has been estimated that of this amount, approximately
100,000 MT of 1,1,1-trichloroethane were used outside W. Europe, Japan, and
the U.S. (Chem Systems 1989). Figure 1-1 presents.the breakdown of 1,1,1,-
trichloroethane consumption in these three regions.
1.2 TERMS OF REFERENCE FOR THE COMMITTEE2
The June 1990 London Meeting of Parties to the Montreal Protocol
reconvened the 1989 UNEP assessment'panels. The 1989 UNEP assessment panels
consisted of the scientific assessment, the environmental effects assessment,
the technology assessment, and the economics assessment panels. The technical
and economics panels were combined for the 1991 Assessment. The three
international assessment panels were requested to report on:
the science of stratospheric ozone-depletion
v
the environmental and public health effects of stratospheric ozone -
depletion
. the technical feasibility, and earliest possible date, -in each of the
major use sectors, for phasing out production of ozone-depleting
substances and the related anticipated economic concerns. The 1991
Technical and Economic Assessment Panel is divided into six
Committees: . .
' -- UNEP Aerosols, Sterilants, Miscellaneous Uses and Carbon
Tetrachloride Technical Options Committee
UNEP Economic Options Committee
UNEP Halons Technical Options Committee
UNEP Refrigeration Options Committee
UNEP Solvents, Coatings and Adhesives Technical Options
Committee.
UNEP Technical Options Committee for Foams
The third meeting of the Parties to the Protocol in Nairobi in June 1991
requested the assessment panels, particularly the Technology Assessment Panels
to:
2 This section addresses Decision 11-13 Assessment Panels of the Second
Meeting of the Parties to the Montreal Protocol, Decision 111-12 Assessment
Panels and Decision III-8 Trade Names of Controlled Substances of the Third
Meeting of the Parties to the Protocol (Kurita 1991b), and Decisions IV-13 and
IV-23 of the Fourth Meeting of the Parties to the Protocol.
* 1994 UNEP SOLVENTS, COATINGS. AND ADHESIVES REPORT *
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Table 1-3: SUMMARY OF COPENHAGEN AMENDMENTS TO THE MONTREAL PROTOCOL
Chlorofluorocarbons (Group I - Annexe A: CFC-11, CFC-12, CPC-113, CFC-
114, CFC-115) : '
Freeze at 1986 levels by July 1989
75 percent reduction from 1986 levels by January 1994
100 percent reduction from 1986 levels by January 1996
Other fully halogenated CFCs (Group I - Annexe B: CFC-13, CFC-lli, CFC-
112, CFC-211, CFC-212, CFC-213, CFC-214, CFC-215, CFC-216, CFC-217)
20 percent .reduction from 1989 levels by January 1993
75 percent reduction from 1989 levels by January 1994
100 percent reduction from 1989 levels by January 1996
Halons (Group II - Annexe A: Halon-1211, Ha Ion 1301,. Halon-2402)
Freeze at 1986 levels by January 1992
100 percent reduction from 1986 levels by January 1994
1,1,1-Trichloroethane (Group III - Annexe B)
Freeze at 1989 levels by January 1993'
. 50 percent reduction from 1989 levels by January 1994
100 percent reduction from 1989 levels by January 1996
Carbon Tetrachloride (Group II - Annexe B)
85 percent reduction from 1989 levels by January 1995
100 percent reduction from 1989 levels by January 1996
Partially Halogenated Fluorocarbons (Group I - Annexe C)
Freeze at specified level by January 1996 (specified level is equal
to 3.1% of 1989 consumption of Group I Annexe A controlled
substances plus 100% of 1989 consumption of Group I Annexe C
controlled substances)
35 percent reduction from level of freeze by January 2004
65 percent reduction from level of freeze by January 2010
90 percent reduction from level of freeze by January 2015
99.5 percent reduction from level of freeze by January 2020
100 percent reduction from level of freeze by January 2030
Methyl Bromide (Group I - Annexe E)
Freeze at 1991 levels by January 1995
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 1-4. COMPARISON OF WORLDWIDE CONSUMPTION OF CONTROLLED CFCS
AND OZONE-DEPLETING POTENTIAL (OOP)
1986 Worldwide
Consumption Percent of Relative Percent ODP
(kilotonnes) , Basket Total ODP of Basket
CFC-11 370 35.0 1.00 36i4 '
CFC-12 480 . ' . 45.4 1.00 47.2 '
CFC-113 178 16.8 0.80 14.0
CFC-114 15 1.4 1.00 1.5
CFC-115 15 . 1.4 0.60 0.9
Atmospheric
Lifetime
(years)
75
111
90
-
-
Source: Montreal Protocol on Substances that Deplete the Ozone Layer
* 199* UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
1-6
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Figure 1-1
BREAKDOWN OF 1,1,1-TRICHLOROETHANE CONSUMPTION IN THE U.S.,
WESTERN EUROPE, AND JAPAN
Metal Cleaning
55%
Adhesives
9%
Metal Cleaning
75%
Other
12%
Aerosols
9%
Electronics
8%
Coating
7%
USA
280,000 metric tons
Metal Cleaning
76%
Other
6%
Electronics
5%
Aerosols
4%
Adhesives
10%
Western Europe
15.1,000 metric tons
Adhesives
5%
Japan
Other
5%
Electronics
13%
Aerosols
1%
151,000 metric tons
Source; Chem Systems 1989
* 1994 UNEP SOLVENTS. COATINGS. AND ADHESIVES REPORT
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"evaluate, without prejudice to Article 5 of the Montreal
Protocol, the implications, in particular for developing
countries, of the possibilities and difficulties of an earlier
phase-out of the controlled substances, for example of the
implications of a 1997 phase-out."
"take into account the London Resolution on transitional
Substances (Annexe VII ''to the report of the Second Meeting of the
Parties to the Montreal Protocol), to identify the specific areas
where transitional substances are required to facilitate the
earliest possible phase-out of controlled substances, taking into
account environmental, technological, and economic factors, where
no other more environmentally suitable alternatives are available.
The quantities likely to be needed for those areas and for those
areas of application currently served by transitional substances
shall both be assessed."
"request the assessment panels to identify the transitional
substances with the lowest potential for ozone-depletion required
for those areas and suggest, if possible, a technically and
economically feasible timetable, indicating associated costs, for
the elimination of transitional substances."
" submit... reports in time for their consideration by the
Open-Ended Working Group with a view to their submission for
consideration by the Fourth Meeting of the Parties."
Most recently, the fourth meeting of the Parties to the Protocol, held
in Copenhagen in November 1992, requested the following activities of the
assessment panels:
"request the Technology and Economic Assessment Panel and its
Technical and Economic Options Committees to' report annually to
the Open-Ended Working Group of the Parties to Montreal Protocol
the technical progress in reducing the use and emissions of
controlled .substances and assess the use of alternatives,
particularly their direct and indirect global-warming effects'."
. "request the three assessment panels to update their reports and
submit them to the Secretariat by 30 November 1994 . . . These
assessments should cover all major facets discussed in the 1991
assessments with enhanced emphasis on methyl bromide. The
scientific assessment should also include an evaluation of the
impact of sub-sonic aircraft on ozone."
"encourage the panels to meet once a year ..."
To assure the widest possible international participation in the review
and the subsequent report, the 1994 Assessment Panels consist of some members
of the 1989 and 1991 UNEP Assessment Panels and additional new experts
nominated by Governments. Not only were experts from industry, government,
academic institutions, and nongovernmental organizations invited to prepare a
comprehensive and technically specific "Control Options Report" for each
sector, but the chairpersons of the.UNEP Technical and Economics Panel and
each of the Technical and Economics Option Committee also contacted countries
* 199H UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
1-8
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to encourage their active participation in this review process. By contacting
producers, manufacturers, and trade associations and by arranging for
additional technical input, the chairpersons of the Technical and Economic
Option Committee further insured widespread participation in preparing the
Technical Options Report on Solvents, Coatings, and Adhesives. As with the
1989 and 1991 reports, the 1994 report has undergone extensive peer review and
will be distributed internationally by UNEP.
The member countries of the Committee included representatives from
North American, Latin American, European, African, and Asian governments and
companies (see Table 1-5). Affiliations of the committee members are listed
in Table 1-6. In addition, the Committee had the benefit of advice from a
distinguished panel of worldwide experts which included representatives of
government agencies, chemical producers, and industry associations (see Table
I--7) . Committee meetings during the preparation of the 1991 report were held
in Germany, Japan, Mexico, Sweden, Switzerland, Thailand, United Kingdom,, and
the United States to facilitate participation by interested organizations.
These meetings enabled Committee members to gather information first hand on
the potential for substitution of CFC-113 and 1,1,1-trichloroethane and on the
progress made to date. The Committee met with a number of companies, trade
associations, and government agencies to understand their position on this
issue.
1.3 BASIS FOR COMMITTEE RECOMMENDATIONS TO UNEP AND COMMITTEE POSITION ON
CFC-113. 1.1.1-TRICHLOROETHANE AND PARTIALLY HALOGENATED FLUOROCARBONS
The Committee's recommendations to the UNEP are the consensus of the
Committee. New scientific information suggests that ozone depletion is
occurring at a rapid rate! The levels of future chlorine and bromine
concentrations in the upper atmosphere will depend primarily on future
emissions of CFCs, 1,1,1-trichloroethane, halons, HCFCs, halothanes. and other
ozone-depleting substances. '
In August 1988, the U.S. Environmental Protection Agency (EPA) issued a
study entitled "Future Concentrations of Stratospheric Chlorine arid Bromine"3
which looked at chlorine and bromine levels after the implementation of the
restrictions in the Montreal Protocol. The U.S. EPA predicted that, based on
their growth scenarios, levels of chlorine' in the stratosphere would increase
from 2.7 to 8 parts per billion '(ppb) by 2075, even with the reductions in CFC
production called for in the Protocol. 'This increase would be caused not only'
by the allowed use of CFCs and. halons under the P.rotocol, but also by CFC use
in countries that are not members of the Protocol and by the growth in the
production and use of chemicals such as 1,1,1-trichloroethane and carbon .
tetrachloride. While reduction efforts under the Protocol, coupled-with the
greatly increased number of signatories, is likely to result in increases in
stratospheric chlorine levels closer to the low end of this range, such
increases are still of concern. '
The second and third meetings of Parties to the Protocol in London and
Nairobi called for an examination by the Committee of the technical
3 Clx Report, U.S. EPA. Office of Air and Radiation, 400/1-88/005, August'
1988. ' ' ( .
> '1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 1-5. MEMBER COUNTRIES OF THE UNEP
SOLVENTS, COATINGS AND ADHESIVES TECHNICAL OPTIONS COMMITTEE
Member Countries
Belgium
Brazil
Canada
France
Germany
Japan
Jordan
Germany
Malaysia
Mexico
Singapore
Sweden
Switzerland
Thailand
United Kingdom
United States
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 1-6. ORGANIZATIONS WHOSE EMPLOYEES SERVE ON THE
UNEP SOLVENTS, COATINGS, AND ADHESIVES TECHNICAL OPTIONS COMMITTEE
Member Organizations
Allied Signal Incorporated
Asahi Glass Company Ltd.
AT&T Bell Laboratories
Boeing Company
British Aerospace (Dynamics) Ltd.
Charles Stark Draper Laboratory
Digital Equipment Corporation
Dow Chemical - Advanced Gleaning Systems
European Chlorinated.Solvents Association
Ford Motor Company
Friends of the Earth
GEC -'Marconi
Global Centre for Process Change
Hitachi Ltd!
ICF Incorporated
IFC . .
ITT Teves GmbH
Japan Association for Hygiene of Chlorinated Solvents
Japan Audit and Certification Organisation Ltd.
JEMA
Lockheed
Lufthansa German Airlines
Mexican Chamber of Industries
Ministry of Planning - Jordan
National Semiconductor
OXITENO
Promosol .
Protonique S.A.
SAEO South America Electronics Operation
Siemens AG
Singapore Institute of Standards and Industrial Research
Sketchley PLG
Swedish Environmental Protection Agency
TELEMECANIQUE
Texas Instruments Incorporated
Thai Airways International
U.S. Air Force
U.S. Environmental Protection .Agency
Vulcan Chemicals
Waste Policy Institute
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 1-7. CORPORATE AND GOVERNMENT PRESENTATIONS IN MEETINGS HELD BY THE
UNEP SOLVENTS, COATINGS, AND ADHESIVES TECHNICAL OPTIONS COMMITTEE
1Allied Signal,Inc., U.S.A.
2A11 Japan Laundry and Dry Cleaning Association, Japan
2Alpha Metals, Hong Kong
2Arakawa Chemical Industries, Ltd., Japan
3Asahi Glass Company, Ltd., Japan
2Asea Brown Boveri (ABB)
2Atsugi Unisia Corporation, Japan
2AT&T-Telecommunications Products (Thai) Ltd., Thailand
2Balzers A.G., Principality of Liechtenstein
2Berghof GmbH & Co., Germany
3Boeing Company, U.S.
3British Aerospace (Dynamics) Ltd., U.K.
3Brulin Corporation
2Canon, Inc., Japan
2Chemical Technology Research Co., Ltd., Japan
2Columbia Cement, Co., Inc.
2ConSolve, A.S., Norway
3Daikin Industries, Japan
2Dan Science Co'. , Ltd. , Japan
2Data General, Thailand"
3Deft Corporation
Department of Industrial Works - Ministry of Industry, Thailand
2Digital Equipment Corporation, Singapore
2Dow Chemical, Germany, Switzerland
2Du Pont Electronics, U.K.
3Du Pont, Japan, U.K., and U.S.A.
2Durr GmbH,'Germany
1Ensambles Magneticos, S.A., Mexico
2Ericsson Electronics, Sweden
3Exxon Chemicals, Canada
2Fujitsu Ltd., Japan
2FFV Aerotech, Sweden
2GEC Research, U.K.
2General Dynamics, U.S.A.
1Halogenated Solvents Industry Alliance, U.S.A.
2Hitachi Chemical Techno-Plant Co., Ltd., Japan
2Hitachi, Ltd., Japan
2Hitachi Construction Machinery Co., Ltd., Japan
2IBM, Sweden
3ICI PLC Chemicals and Polymers Ltd., U.K.
International Institute for Energy Conservation, Asia Office, Thailand
2ITT Teves Gmbh, Germany
2Japan Alcohol Association, Japan
2Japan Electrical Manufacturers' Assn., Japan .
2Karl Roll GmbH, Germany
2Koki Company, Ltd., Japan
2Kolb GmbH & Co., Germany
2Leica Heerbrugg, Switzerland
3LPS Laboratories, U.S.
2Matsushita Refrigeration Co., Japan
2Micropolis Corporation, Thailand
2Minebea Group, Thailand
1Ministry of International Trade and Industry, Japan
Mitsubishi Electric Corp., Japan
(continued on next page)
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 1-7. CORPORATE AND GOVERNMENT PRESENTATIONS IN MEETINGS HELD BY THE
UNEP SOLVENTS, COATINGS, AND ADHESIVES TECHNICAL OPTIONS COMMITTEE
(Continued)
33M Corporation
2National Semiconductor, Thailand
2National Research Institute for Pollution and Resources, MITI, Japan
^EC, Japan
2Nippondenso Company, Ltd., Japan
2Nissan Motor Co., Ltd., Japan
2Nissin Electric, Japan
1Northern Telecom, U.S.A. and Canada
2NTN Corporation, Japan - . .'
1Plamex S.A., Mexico
2SAAB Scania, Sweden
4SAGEM, France
^EHO, Germany .
1 Seiko-Epson, Japan
2Semiconductor Ventures International, Thailand
2Senju Metal Industry Co., Ltd, Japan
Reparation Technologists, U.S.A.
1 Sharp Corporation, Japan
2Siam Compressor Industry Co., Ltd., Thailand
3Siemens, Germany
2Siemens-Ele'ma, Sweden .
1Sigma Industries, U.S.A.
2Swedish Institute for Production Engineering Research, Sweden
2Tinker Air Force Base, U.S.A.
3Toshiba Corporation, Japan
2Toshiba Display Devices (Thailand) Co., Ltd., Thailand
4Thiokol Corporation, U.S.A. . .
2ULVAC Ltd., Japan
1United States Air Force Engineering Services Center, Tyndall Air Force Base,
U.S.A.
2VCI, Germany
2VOLVO Aero Support
3W.R. Grace, U.S.
2ZVEI, Germany
1 1989 Presentation. , .
2 1991 Presentation.
3 1989 and 1991 Presentations. .
4 1994 Presentations.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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feasibility of using only alternatives which do not deplete the ozone layer.
In the short-term some might use other low OOP alternatives. Figure 1-2
compares the ODP of CFC-113 and 1,1,1-trichloroethane with that of the new
HCFCs and HFCs currently In use or under development. The Committee believes
that there are a wide variety of alternatives that can completely replace CFC-
113 and 1,1,1-trichloroethane use.
A variety of alternative substances and technologies are currently under
development to facilitate the phaseout of CFC-113 and 1,1,1-trichloroethane.
These alternatives include aqueous and semi-aqueous cleaning, alcohol
mixtures, other hydrocarbon solvents, HCFCs, perfluorocarbons, no-clean
technologies, and a growing number of non-solvent cleaning processes.
No-clean technologies represent the optimum alternative and have been
applied in an increasingly large number of electronics manufacturing
applications in recent years. Nevertheless, research and testing of no-clean
manufacturing processes is ongoing in hopes of making it a viable alternative
in a wider variety of uses. Second to no-clean with respect to ozone layer
protection is aqueous or semi-aqueous cleaning. The major drawbacks of these
alternatives may be high energy consumption and wastewater treatment costs.
HCFCs, though their use is transitional, are important alternatives to
CFC-113 and 1,1,1-trichloroethane solvent use in applications for which no
other viable alternative exists. Because of their lower ozone-depletion
potential, HCFCs with a short lifetime (below 10 years) are preferred to those
with longer lifetimes (over 15 years). However, HCFCs should only be used as
substitutes for 1,1,1-trichloroethane if their ODP is lower than 0.10 and if
their emissions are controlled using the best available technology. As a
result of the 1992 Copenhagen Amendments to the Montreal Protocol, HCFC use is
only a temporary alternative. The amendments state that consumption of HCFCs
must be reduced by 99.5% by 202.0 and completely phased out by 2030. In the
interim, the Protocol recommends that HCFCs only be used in conjunction with
emission control recovery and recycling systems. Thus, HCFCs are a valid
alternative in certain limited applications while other, long-term
alternatives are being developed (Yamabe 1991).4
4 Low ODP alternatives, coupled with recovery systems, could be effective
in protecting the ozone layer. The recovery system would be effective in
reducing the consumption of ozone-depleting chemicals in small factories,
where more than 50 percent of the consumption of these chemicals takes place
(Yamabe 1991).
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
1-14
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0.
a
O
Figure 1-2.
RELATIVE TOTAL OZONE DEPLETING POTENTIAL OF
SELECTED HALOGENATED SOLVENTS*
0.80
0.15
0.00 0.00
0.10
0.06
0.00 0.00
0.04
0.01
125 134a
T
141b 142b
Solvents
143a 152a 1.1.1 225ca 225cb CFC-113
' Relative to CFC-11 which Is set at a value of 1.
llf>077 1
* 1994 UNEP SOLVENTS, COATINGS. AND ADHESIVES REPORT *
1-15
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CHAPTER 2
ELECTRONICS INDUSTRY APPLICATIONS
2.1 BACKGROUND
Since the publication of the 1991 Solvents, Coatings and Adhesives
Technical Option Committee (TOC) report, considerable practical, commercial,
'and technical developments have occurred. Several nations, including Germany,
Sweden and Switzerland, already have legislation in force to phaseout ozone -
depleting solvents. Many other countries, as well as individual users, have
achieved spectacular reductions. ,
Unfortunately, some electronics companies in some nations are unpreparedi
for the 1 January 1996 phaseout. This situation is difficult to understand,
as the electronics industry has found reasonable solutions'for practically all
the problems that have arisen.
This chapter has been rewritten, not merely updated, in an attempt to
keep it a manageable size and due to the significant progress that has
occurred in the electronics industry.
The principal use of CFC-113 and 1,1,1-trichloroethane (methyl
chloroform) solvents in the electronics industry is for defluxing, that is,
the removal of residues from assemblies after soldering.. The flux or solder
paste residues1 are characterised as a mixture of:
raw flux . .
thermally modified flux
flux decomposition products
reaction products between the flux components and metal oxides
from the printed circuit boards, the component leads, and the
molten solder
residues - modified or otherwise - from contaminants previously
left on the boards and components
. residues from soldering oils
paste modifiers.
A further use for 1,1,1-trichloroethane is in printed circuit
fabrication as a developer for photosensitive coatings, mainly dry film
photoresists and dry film solder masks.
The dissemination of information to small production units on
substitutes for ozone-depleting solvents is a problem in many nations. This
may be due to difficulty in assessing substitutes and because companies are
often too small or too remotely located to use consultants effectively.
1 In this chapter, the word flux may be considered as including solder paste,
except where there is a significant distinction specified.
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Language may also play a significant role., as most of the information is
published in English. This has been discussed in the 1994 TEAP report (UNEP
1994).
One other factor which has retarded the phase,-.out of CFC-113 in the
electronics industry has been specifications which discouraged using
substitute cleaning processes for military and similar applications. Much
ordinary electronics production, particularly in the smaller firms, was
cleaned to military approved requirements using CFC-113 arid 1,1,1-
trichloroethane, even though it'was not" strictly necessary. To avoid
duplication of processes and equipment, the military standards were used for
non-military work, which resulted in unnecessarily large CFC emissions. In
February 1991, the U.S. military adopted MIL-STD-,2000 / Revision A (DoD,
1991). This standard conditionally permits the use of non-rosin fluxes and
non-ozone depleting solvents and cleaning processes for most electronics
assembly and retroactively for existing contracts. MIL- STD.- 2000 (Rev A) also
recommends that CFC solvents "be phased out". This revision to -US military.
standards has already had a far-reaching and global effect. Nevertheless,
there is little room for complacency, as was shown by the report to a recent
conference concentrating on these problems (NATO 1994).
In the electronics industry, there are six primary methods that are
suitable for replacing ozone-depleting substances (ODSs) (Figure II-l), each
with a number of important variants. The following list, although .not
exhaustive, is a general review of these as they apply to fluxes and solder
pastes.
"No-Clean" methods, including controlled atmosphere soldering
Water soluble fluxes and water cleaning
Rosin fluxes + saponifier + water cleaning
Rosin & SA fluxes + hydrocarbon/surfactant + water cleaning
Rosin & SA -fluxes + hydrocarbon and derivative (Including alcohol)
solvent cleaning '
Rosin & SA fluxes + permitted halocarbon solvent cleaning.
Due to the numerous financial and environmental considerations, the.
Solvents TOC recommends that the. substitute process be fully tested,
qualified, and found satisfactory under full production conditions before any
capital investment is made. In addition, the process and its supporting
infrastructure should include approval by all the appropriate fire, health,
safety, and environmental authorities.
The following list of questions can help.users decide whether or not to
clean:
is human life, "at stake?*
is the assembly working at high frequency or high impedance?*
are analogue signal levels low?*
2 This standard details requirements for the materials and processes which
may be used in making soldered connections in electronic assemblies. The
soldered connections which must meet this standard's specifications include:
lead and wires inserted in holes, surface-mounted components, and components
attached to terminals.
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Replacement of OD solvents in the military electronics industry
j | OK for all military applications
I OK for some military applications ~ with controls
" Specifically tested and
. . . approved to DEF-STAN 00-10/3
Permitted halocarbon
cleaning????
^^^ &^_M _ I
I Inert atmosphere | (Reactive atmosphere -j
/ I Low-residue flux
Controlled atmosphere
soldering
t3
S
Q>
a
No-clean" processes
("jra3iB6nai wafer" '
;spluble flux. ''
rbon-surfactant
j; cleaning;* water^
Prozone is a registered Trade Mark of British Petroleum Chemicals Limited.
Figure II-l. Methods of replacing ozone-depleting
solvents in the electronics industry. .
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is reliability important?*
are assemblies likely to be subject to high .temperatures3, high
humidity or rapidly changing atmospheric conditions?*
are assemblies to be conformally coated?*
does the customer specify high.reliability standards?*
does the customer exact a long guaranteed lifetime?*
is cost subordinate to other factors?
Is the aspect of the circuit important?
is automatic testing to be done?
is burn-in of the finished assembly done?
The questions with an asterisk (*) are more important in the decision process.
Where cleaning is necessary, there are problems of scale. With CFC-113
vapour defluxing, the equipment price is roughly proportional to the
throughput capacity; this, however, is not always the case with substitute
methods. To achieve a change which produces a satisfactory quality, small
manufacturers in both developing and developed nations may have to pay
disproportionately more for the equipment. In many instances, these "capital
costs may be offset by lower operating costs.
Finally, before assembly is done, the design of the printed circuit is
an all-important factor which is frequently ignored. Successful use of "No-
Clean" fluxes, particularly with wave-soldered SM components, is dependent on
correct PCB design. Similarly, if cleaning is to be carried out, the criteria
are very different and other design factors are required. Often a circuit
which gives excellent results with one process gives very'poor results with
another. Section (2.2) is a new section which addresses this problem.
2.2 PRINTED CIRCUIT DESIGN FOR EFFICIENT SOLDERING AND CLEANING
The use of certain soldering and cleaning processes can be optimised .
only if the PCB is designed correctly for that process (Ellis 1994). The, use
of anything other-than-optimised may seriously compromise the. efficiency.of
the chosen process. This section gives the .designer an introduction to the
subject. A designer must be informed as to which soldering and cleaning
processes are to be used in production before starting work. -It is assumed
that the designer uses a quality electronics CAD system, without it being .
specific to one type. Users of manual draughting, low-cost CAD systems or
those adapted from mechanical. CAD packages may have to make some modifications
and make many manual retouches to comply with the following recommendations.
2.2.1 Low-Solids "No-Clean" flux wave soldering
the use of Low-Solids "No-Clean" fluxes presents the biggest challenge
to the PCB designer, particularly for the SMD circuit. The PCB design is
critical to exploit the operating window, which can b'e quite small.'
Traditional High-Residue fluxes for SMD soldering present a severe
disadvantage when soldering SMD components with a conventional wave soldering
machine. The components themselves create "shadows." which prevent, correct
3 Rosin fluxes start to soften at about 70°C.
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soldering from taking place. This was circumvented by using "double-wave"
soldering machines: the first wave was very turbulent to ensure the solder
penetrated into the "shadows", but left uncontrolled amounts of solder on the
joints and between conductors. The second wave was a smooth, streamline wave
whose function was to remove the excess- solder and to leave sufficient to form
a perfect meniscus at each joint. . -
Without extensive engineering it is generally not possible to use'the
"double-wave" technique with Low-Solids "No-Clean" fluxes because the
turbulent wave offers sufficient agitation so that the quasi-totality of the
flux activator is removed. The second wave has to operate practically without
activator present and the solder joint which results is usually defective. "A
few Low-Solids "No-Clean" fluxes are designed to permit double-wave soldering
but these may present other disadvantages. It is therefore necessary to
ensure, by careful layout, minimum shadowing by the components, so that a
single wave may be used.
Design for Low-Solids "No-Clean" flux soldering of SMD circuits implies
that no solder joint be placed on the last side of the component to '"see" the
solder wave. With components that have connections along .two sides, such as
passive 'Chip components and SMSO ICs, these should present themselves so that
all the solder lands be on either side of the device as "seen" by the wave. A
problem obviously presents itself with components which have soldering lands
along all four sides, such as gull-wing, J-lead PLCCs, or LCCCs. Shadowing
may be minimised by placing this type of device at 45 degrees to the wave
angle. This generally works with the better fluxes. Some of the less
versatile CAD systems do not permit turning components through 45 de,grees or,
if they do, they may not allow the connecting tracks to come out in a very
logical way. This would imply that the component actually be designed
specifically in the library at the required angle, thereby using up four
custom pad (land) sizes, instead of .one. The best method uses a rectangular
pad design with the actual connection offset to the outer edge, if the design
rules' do not allow the connection to be forced at the designed angle. Some
manual retouching may be needed after autorouting. .As cleaning will,not be
carried out, the pad width may be as wide as is necessary to ensure that
bridging does not occur and that the minimum gap width be respected. Via
holes should be spaced away from the pad by an intermediate connection between
them and the hole of a minimum of 1 mm, even if they are tented, filled or
otherwise rendered unsolderable. The major axis of the interconnecting tracks
should be parallel to the axis of the soldering machine, .even if they are
covered with a solder resis-t or mask, in order to ensure minimum solder
t
balling. For double-sided boards with wave-soldered SM components on both
sides, this implies that the boards be soldered in different directions for
eacti side, as most CAD systems force the major routing at 90 degrees; in any
case, this uses the "real'estate" most efficiently. With multilayer circuits,
the problem is not the same as both the outer layers may be forced in the same
direction, according to the flexibility of .the design rules of the system.
Figure II-2 illustrates an example of a hypothetical design for Low-
Solids "No-Clean" soldering. .
2.2.2 Controlled Atmosphere Soldering
. This presents exactly similar problems to that of .the Low-Solids "No-
Clean" flux case and the same criteria apply, as in the preceding section.
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Direction of passage over solder wave
I I I I I I I
llllill MIMIM I IIIMIM I I MM »M I
if. FV? ... [ Tf1 LL« i T: ii. r :₯
-iTiTTiT I rrnTrn rrlrnn mrniT
ii * i i ii * * i i
iliiiii I liiiiiii I Imiiii I ILUJJII I
TT^lF! ' i i I;*1 'I'T'iip ":"j JJF
11. riy -if. T-y-.."iL_T-₯ .11. i ₯
iliiiii ntmTi iTrrmi nriirrr
ii ii « » i i i i
Figure II-2. Hypothetical example of SMD circuit
designed for "No-Clean" wave soldering showing correct
orientation of components.
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2.2.3 "Traditional" flux soldering and cleaning
"Traditional" fluxes may be considered as activated rosin (RMA, RA or F-
SW32 halide free) or water soluble types. The design criteria for soldering
with these fluxes are far less critical and therefore the accent is best
placed on cleaning. For through-hole circuitry, no change is required to the
design rules. The problems arise when cleaning SMDs.
In reality, cleaning with CFC-113 is, in most cases, just as difficult
as with any of the substitute processes, if not more so. This section
therefore applies to all cleaning methods.
The cleaning solvent, be it aqueous or organic, must penetrate as freely
as possible under the components and, having penetrated, must circulate.
Young's law indicates that pure water, with a high surface tension, will
penetrate better, by capillary action, into close spaces than would an organic
solvent or a less pure water, with a lower surface tension. If free
circulation is to take place, then the spaces must be as wide as possible and
the obstructions be minimised. It is therefore important to choose those
components which have the largest stand-off from the printed circuit board.
With plastic moulded components, .it is quite usual to place small stand-off
"blips" in the corners.. Ideally, these "blips" should also have the smallest
surface area, although this criterion is secondary to the height. Smaller
components, such .as 1206 passive chips, have relatively little difficulty, as
far as cleaning is concerned, because of the small area to stand-off ratio.
The placement of wave-soldered SM circuits is therefore the most
critical factor and should, as ideally as possible, be done as a function of
the component height. Some .CAD systems will permit autoplacement where
component height can be a function by limiting tall components to specific ,
parts of the boards, while retaining coupled components (e.g. decoupling
capacitors). The space round tall components should also be greater than
round low ones. This can be done by using a larger rectangular silk profile
than that of the component itself and replacing it after the layout is
completed by an autolibrary function, if there is no .other way possible to
ensure the best conditions within the framework of the CAD system. When
considering component spacing, it must be assumed that worst-case positional
tolerancing will occur: it is therefore a mistake to' force components too
closely together: in fact, the ideal situation is to use the "real estate" of
the PCB to best advantage to maximise component spacing. Orientation is also
critical. This should be arranged to allow the .maximum ingress of cleaning
fluid, so the design is also a function of the way the finished circuit will
pass through the cleaning machine and of the way that the machine operates.
In-line conveyorised spray machines with the jets normal to the surface of the
board are generally less efficient than batch machines where the jets may
attack the boards at an angle as small as 15 degrees. On the other hand, the
former are perhaps much less prone to shadowing problems as the liquid can
penetrate the inter-component space more readily, even if it tends to "puddle"
and stagnate there, rather than circulate.
Figures II-3 and II-4 show a few ideas as to the best,principled to
adopt when designing the placement of boards to be cleaned. Pad width becomes
very critical, in this case, as having a broad solder meniscus' on four-sided
connection components will reduce the ingress of cleaning fluids by as much as
'50 percent, especially if the solvent loses kinetic energy by striking the
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Layout criteria for effective cleaning
Orientation of SOICs and chips: left OK, right poor
§ Taking into account
jl positional tolerances
! and the component
3 height, make sure
there is adequate space
' between them to allow
i
| cleaning fluid to circulate
Fig-2
Do not put large
components in the
line of spray to smaller
ones
Figure 11-3. Layout criteria for effective cleaning
a) orientation and position -
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Layout criteria for effective cleaning
Components placed at an
angle: Solder joints brake the
energetic ingress of cleaning
products.
Minimal sized soldering
lands: maximum ingress
of cleaning products.
Solder lands too wide:
ingress of cleaning
products reduced
by 50%.
Fie.3
Figure II-4. Layout Criteria for Effective Cleaning
b) Maximum ingress, of cleaning fluids
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board surface before being deviated under the components. It is therefore
important, in all cases, to use a pad width which is as narrow as possible,
.but consistent with good soldering quality. Such components must never be
placed at 45 degrees to the axis of the cleaning machine, as the angle will
reduce the "window" between solder joints by 30%: the component must always be
axial.
2.2.4 "Glue-spots" and cleaning quality
The position of the Glue-spots on boards which are not cleaned is not
very critical, within normal parameters. On the other hand, they may be
critical for boards which must be cleaned, as they can restrict the flow of
cleaning fluids. With small components, the Glue-spot is generally placed
centrally. With heavier components, two or more Glue-spots may be required.
If two are used, then the ideal configuration is they should form an axis
which is not in line with the"cleaning machine (as well as being of minimum
size). Either 45 or 90 degrees is generally satisfactory. With three or more
spots, care should' be taken to-avoid shadowing of the space between them.
Most good CAD systems can automatically incorporate the Glue-spot positions in
the component libraries, according to the operator's wishes.
2.2.5 "No-Clean" Paste Reflow soldering
Most "No-Clean" pastes have considerably higher residue levels than many
other "No-Clean" soldering processes as the chemistry must contain sufficient
product to ensure the correct viscosity and .rheological characteristics. As
the paste is reflowed homogeneously by infra-red radiation or by vapour phase
PFC heating, there are few 'orientational problems. As such, there are few
critical design parameters other than those imposed by the'soldering process
itself. Soldering land width and spacing may be critical and the CAD design
rules may need some fine tuning. During component placement, the distance
between components must be sufficient to permit the heating medium to pass.
One of the main difficulties which is sometimes encountered is that of solder
balls. These may cause electrical and/or mechanical problems but they are not
so much a design problem as one of the soldering conditions themselves and the
paste quality and age. Even more important than with wave soldering, via
holes must be well separated from the soldering pads or lands, otherwise the
molten solder may be drained from where i,t is necessary.
f
2.2.6 "Traditional" Paste Reflow Soldering and cleaning
The design rules for rosin or water-soluble paste are similar to those
for "No-Clean" pastes. The components should be selected with maximum stand-
off heights and with other characteristics suitable for re.flow and wave
soldering.
2.3 CFC-113 USE IN ELECTRONICS ASSEMBLIES
2.3.1 Mai or.Assembly Processes
Electronic compo'nents are fluxed and soldered to electronic assemblies
and then cleaned to remove flux residue and other contaminants introduced in
the productionprocess. The electronic components are attached by either
through-hole assembly technology or by surface-mounted assembly technology or
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a combination of the two. The actual techniques are only secondary to the
problems of cleaning, so they will not be discussed here. For further
details, please consult the 1989 and 1991 Solvents TOC reports (UNEP 1989,
1991) or other literature (Ellis 1986).
Boards are soldered in one.of two general ways: (1) a molten Bolder is
used to solder and secure the components onto the board or (2) a solid solder
(normally in the form of wire solder or small solder spheres in a flux paste
matrix) is deposited on the board and later heated. Wave, dip, and drag
soldering are examples of the former; manual, infra-red, condensation reflow,
or hot gas soldering are examples of the latter. Wave soldering is commonly
used in high-throughput electronic assembly operations. Wave-soldered boards
are fluxed and passed over a wave of solder that flows up from the solder
bath. The solder forms an intermetallic bond with the surfaces of the
component leads and tracks and with the plated through-holes of the printed
wiring boards. .
Flux is removed from electronics assemblies to:
remove corrosive flux ingredients
improve adhesion of conformal -coatings
enable easier visual inspection
facilitate automatic testing
minimise leakage currents "
enhance product appearance . .
to. conform to customer specifications
The need for post-solder flux-residue cleaning varies widely and depends
on the final electronics application. For example,.most printed circuit
boards that are. used in toys and home appliances are cleaned perfunctorily, if
at all. In contrast, boards that are manufactured for automotive, military,
space, medical and other critical applications require high levels of
cleanliness. Frequently, boards require cleaning for automatic testing rather
than for reliability (IPC 1986). However, in applications where assemblies
are exposed to elevated temperature and humidity, flux residues can corrode
metallic tracks on-, electronics assemblies and component leads and also create
deleterious effects on the electrical characteristics of the insulation (see
Section 2..1) . '' , .
. 2.3.2 Flux Types
"No-Clean", rosin/resin, synthetically activated, and water-soluble
(also frequently referred to as organic acid) are the major flux types.
There are several variations in so-called "No-Clean" flux types,
containing quantities of resins (some with wood rosin) ranging from zeroup to
about 5% w/w. They all have high degrees of activation, compared to more
traditional rosin or resin fluxes. In extreme cases, the solid matter may be
entirely activators. The activators are most frequently based on non-
halogenated linear carboxylic acids, although some types also use cyclic acids
or organic hydrohalide compounds either alone or in combination. They are
also referred to as "Low-Solids" fluxes. The terminology, in either .case, is
not necessarily precise as,some fluxes with a low solids content may possibly
lend -themselves to cleaning and some fluxes .with a higher solids content may
be perfectly adapted to not being cleaned (DIN-Normen). As a general rule,
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the operating "window" when soldering with "No-Clean" fluxes is narrower than
with many other flux types and they are often more prone to cause solder-
balling (solder balls are.small metallic spheroid particles of typical
diameters within the range of 0..05 to 0.5 mm and which tend to adhere to the
printed circuit substrate.)
When properly prepared, traditional rosin fluxes meet U.S. military
specifications (MIL-F-14256),* have a history of successful use, and do not
always need to be removed after soldering. Rosin is a complex mixture of
isomeric acids and rosin fluxes are classified by the amount of activator
present. Activators, generally halides or carboxylic acids or a combination
of both, increase the wetting ability of the solder by reducing oxides present
on the surfaces to be soldered. While they are the least corrosive and
conductive fluxes, rosin fluxes have limited wetting abilities.
The small amounts of post-soldering board residue can minimise cleaning
problems or eliminate the need for cleaning. Toubin (1989) found that Low-
Solids fluxes can be both efficient and cost effective when run under tight '
process control. A later report (Toubin 1991) has indicated that many of
these fluxes may cause corrosion, and SIR problems. These and other problems
have been corroborated by a small number of users who have reverted to
cleaning after many months of using "No-Clean" techniques for medium-
reliability applications.
Synthetic activated (SA) fluxes (more active than rosin fluxes, but less
active, than many water-soluble fluxes) were initially designed to be removed
specifically with CFC:113. Compared to rosin fluxes, synthetic activated
fluxes, because of their activity, improve the wetting by the solder. SA flux
residues must be removed immediately after, soldering. SA fluxes have never
held more than a small share of the market and, since the reduction of use- of
CFC-113 and 1,1,1-trichloroethane solvents, this share has been reduced even
further. This loss of market share is because SA flux has little specific
advantage except when used.with ozone-depleting solvents.
There are a variety of formulations for water-soluble fluxes which
usually contain relatively large percentages of activators (compared with
rosin fluxes), such as organic acids, hydrochlorides, hydrobromides and amines
dissolved in water or, more usually, alcohol solvents. Water-soluble fluxes,
in general, allow faster soldering rates with fewer rejected boards due to
solder defects and do not.require a saponifier when cleaned with aqueous
cleaning systems. Water-soluble fluxes, as currently formulated, are usually
more corrosive than othe.r fluxes. Subsequent board and component damage can
only.be prevented by thorough and immediate controlled cleaning. It may be
necessary not only to use purified water in aqueous cleaning processes, but
also to treat waste water.
Although aqueous cleaning is used in a number of electronics industry
applications, it 'is not approved for all applications. In the past, U.S.
military electronic assembly specifications did not allow water-soluble.
4 This specification consists of a list .of fluxes, rosin-based liquids, and
pastes-which have been approved for military use. Specifically, they are
intended for use in the assembly of electronic circuitry and electrical
equipment using tin-lead solders'.
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fluxes, but such flux types were acceptable for British military-applications
(DEF-STAN 00/10-3, Baxter 1989). The latest revision to the U.S. military
Tri-Services soldering and assembly standard, MIL-STD-2000,5 Revision A
(issued 14 February 1991), however, allows the use of non-rosin fluxes
provided specific test and quality criteria are met. Some specialised boards
contain materials, such as polyimides and certain glazes in hybrid circuits,
that are incompatible with aqueous cleaning that employs saponifiers. Also,
some water-soluble fluxes with certain polyglycol derivative constituents may
be deleterious to the resin substrate of printed circuit boards particularly
where the base material is of poor quality or has been incorrectly
polymerised. In this case, cleaning leaves a porous surface with flux
residues absorbed into the surface of the printed circuit board. These
hygroscopic residues may cause
-------
Table II-1. TYPICAL CIRCUIT BOARD ASSEMBLY CONTAMINANTS3
Category 1
Category 2
Category 3
Resin and Fibreglass Debris
from Drilling and/or 'Punching
Operations
Metal and Plastic Chips from
Machining and/or Trimming
Operations
Dust
Handling Soils
Lint
Insulation
Hair/Skin
Flux Activators
Activator Residues
Soldering Salts
Handling Soils (Sodium and
Potassium Chlorides)
Residual Plating Salts
Neutralisers
Ethanolamines
Surfactants (ionic)
Flux Resin
Flux Rosin
Oils
Grease
Waxes
Synthetic Polymers
Soldering Oils
Metal Oxides
Handling Soils
Polyglycol Degradation
Byproduct
Hand Creams
Lubricants
Silicones
Surfactants (non-ionic)
3 Contaminants may exhibit characteristics of more than one" category.
*
Category 1 -Particulate ' .
Category 2 -- Polar, ionic,.or inorganic
Category 3 -- Nonpolar, non-ionic, or organic
Source:. ANSI/IPC-SC-.60 1987.
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2.4.1.1 . Low-Solids "No-Clean" processes
These processes use fluxes which may operate according to a number of
different principles. The original types were simply variants of traditional
fluxes of the DIN 8511 F-SW32 (halide-free rosin), which were diluted to
typically one-half to one-third the solids content. The ratio of activator to
rosin was generally much higher. These early fluxes were difficult-to-use.
These were followed by a number of fluxes with greatly reduced rosin or
synthetic resin content and an even higher activator content.- These ones had
a slightly wider operating window. Typical activators were adipic and
succinic acids which were fairly stable at soldering temperatures. The next
generation used flux systems which sublimated at soldering temperatures. This
allowed higher solids content to be used for a reduced volume of residues,
making for considerably easier soldering.
Advantages:
Economical soldering
No cleaning machine or space required'
Environmentally easy to control
. Residues may be cosmetically acceptable ^
Disadvantages:
Restricted operating window
Reliability of assembly needs to be determined
Higher-than-average retouch rate
Some types not suitable for conformal coating
Many types unsuitable for high-reliability applications
Solder-balling may be a problem (not with hand-soldering)
Cleaning not possible with many types
, Double-wave soldering very difficult
Residues may cause corrosion
Residues may deteriorate electrical characteristics
2.4.1.2 High-solids "No-Clean" processes
i-*_^^__ (
These use traditional rosin-based fluxes to R, RMA or RA specifications
or to DIN 8511 F-SW32 standards.
Advantages:
Economical soldering
No cleaning machine or space required
Environmentally easy to control
Easy soldering
Cleaning usually possible, if necessary
Disadvantages:
Reliability of assembly needs to be determined
.Generally unsuitable for conformal coating
Many types unsuitable for high-reliability applications
Automatic testing usually not possible
'Residues unsightly and frequently sticky
Pastes may tend to solder ball . :
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Residues may cause corrosion
Residues may deteriorate electrical characteristics '
2.4.1.3 Controlled atmosphere soldering
Controlled atmosphere soldering can be divided into two types: reducing
and inert atmosphere. Technically, reducing atmospheres are difficult to
maintain and operate at ordinary soldering temperatures but may reduce the
needs of fluxes to extremely small levels, leaving very little flux-related
contamination6. Inert-atmosphere soldering is usually done under pure
nitrogen with strictly-controlled oxygen levels. Inert atmosphere wave
soldering uses a flux which is sometimes called a preparation fluid. Early
types were based on a simple dilute adipic acid solution in isopropanol. The
latest generation sublime' on the solder wave so that the small quantity of
flux almost completely vaporise: the relatively high vapour content may
recondense in a polymerised form on the cooling circuit 'as the PCB leaves the
machine. This leaves a microscopically thin protective coating. Solder
pastes for controlled atmosphere reflow must be formulated to have the right
ratio for the correct rheological characteristics. This makes them leave
residues which are more visible than with wave soldering.
Advantages:
Little dross formation on solder waves
Lowest "No-Clean" residues
Environmentally easy to control
Residues may be cosmetically acceptable
If required, aqueous cleaning is usually easy
Minimum heavy metal salt formation
Disadvantages:
Restricted operating window
Reliability of assembly needs to be determined
Higher-than-average retouch rate
Of doubtful value for conformal coating
Many types unsuitable for high-reliability applications
Solder-balling may be a problem
Residues may cause corrosion
Residues may deteriorate electrical characteristics
, High capital costs
High costs of nitrogen
2.4.2 Water soluble processes
The use of water soluble fluxes and pastes represent the most economical
manner of soldering and cleaning. Many major users have been using them
continuously since the early 1960s. Up to recently, most of the fluxes used
at least some organic hydrochlorides as activators, with some form of glycol
6 It has been stated on a few occasions that it is possible to solder in an
inert atmosphere without any flux, at all. This may be theoretically true
under ideal conditions: in practice, some way of reducing oxides on component
leads and the PCBs must be present.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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derivative as a vehicle. For about fifteen years, .it has been known that a
few of the glycol compounds have caused a deleterious effect on the insulating
characteristics of some organic substrates. This effect has been studied but
little major work was done to characterise the phenomena and to avoid it.
Recently, a number of glycol-free products have appeared on the market,
frequently also halide and VOC-free (or nearly so),. These have generally
shown themselves to be somewhat more difficult to use, but may be useful where
a maximum Surface Insulation Resistance (SIR) is essential.
The aqueous method has proved to be highly popular where the conversion
away from a CFC-113 process has already been made and a cleaning operation has
been deemed essential.
As with all processes, these do require careful quality management.
Less-than-perfect cleaning may produce catastrophic results. Post-soldering
cleaning may be done with just a simple water wash followed by a succession of
water rinses. For best results, at the price of a slightly higher
manufacturing cost,, the final rinses may be achieved with deionised water, .
particularly for high-reliability work or where the tap water quality is poor.
Better results may be obtained by using a chelating solution for the first
wash, to ensure perfect solubilisation of the heavy-metal salts resulting from
the soldering process, again indicated for high-reliability pro.cesses.
Several advantages can also result from the addition of a few percent of
isopropanol to the last rinse water (Protonique 1993).
2.4.2.1 Traditional water soluble process
This process consists of soldering with the help of a water soluble flux
using organic hydrohalide activators, containing little or no water in the
solvent base. The high flux activity, makes this process easy-to-master with
extremely low retouch rates. The cleaning process is easy and the overall
results are suitable for most applications.
One problem common to all pure water processes is that of retouches and
hand soldering. Water soluble flux cored solder wire of all types is
available from many manufacturers, but are not popular because of the fumes
they produce. Good air extraction from the soldering zone is highly
recommended, so that the same cleaning process may be used for mass-soldered
and 'for retouched boards.
Advantages
Lowest cost of all soldering/cleaning processes
Easy soldering
Low retouch rate
Very good residual cleanliness, even under SMDs
Water treatment easy and cheap
Wide range of machines available
30 years of track record
7 All organic fluxes of all families contain volatile organic compounds
(VOCs). Although the solvent system is usually quoted as the main source of
VOCs,- the .activators, surfactants and vehicles also are the sources of
emissions of VOCs at soldering temperatures.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHES1VES REPORT *
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Disadvantages
Good cleaning quality essential - no half measures
Possibility of slightly poorer SIR
Users are afraid to try it \
2.4.2.2 "Glycol-free" water soluble process
This relatively new substitute process has raised some interest in
military circles. The prototype fluxes of this type were developed about
twenty years ago. One German manufacturer marketed a flux using citric acid
as activator, a triol as vehicle, a small amount of a non-ionic surfactant and
alcohol, with a small quantity of added water, as a solvent. Over fifteen
years later, an American company developed a flux consisting of citric acid, a
small amount of non-ionic surfactant and water. This latter development
dispensed with the triol and the alcohol to reduce the VOC content, an added
advantage in regions with rigorous VOC legislation, but-at the cost of
narrowing the soldering "windpw". Another multinational flux manufacturer
announced in 1989 another type of polyglycol-free flux in both low VOC and
"normal" versions, employing completely different vehicle and activator
chemistries. Some of the fluxes in this range may be employed as "No-Clean"
products or for water cleaning, according to the individual circuits being
soldered.
Advantages
Low cost soldering/cleaning processes'
Very good residual cleanliness, even under SMDs
Water treatment easy and cheap
Wide range of machines available
No SIR deterioration
Some products low VOC
Disadvantages
Good cleaning quality essential - no half measures
Some potential users "afraid" of trying it
Reduced operating "window" of soldering operation
2.4.3 Saponification processes
Saponification is a chemical reaction which modifies insoluble rosin
into a water-soluble rosin soap which can then be removed in a similar washing
process (2.4.2) as used for water soluble processes. As it is a chemical
process, it is necessary to use reactive products, generally highly alkaline
mixtures based on monoethanolamine. .These aggressive products require careful
handling. For this reason, this process has not been as popular as the
excellent results may suggest. Cleaning quality has been shown to be
outstanding (Grossmanh 1993) , but this process works best with thin residue
layers. Although slightly more expensive than water soluble flux processes,
the overall cost is acceptable.
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Advantages
Reasonably low cost soldering/cleaning processes
Very good residual cleanliness, even under SMDs
Water treatment reasonably easy and cheap
Wide range of machines available
No need to change flux type in many cases
Over 25 years of good track record
Disadvantages
Good cleaning quality 'essential - no half measures
Users are reluctant to try it
Health and Safety concerns
Thick rosin residues may require long cycle times
Potential incompatibilities with amphoteric metals and polyimide
substrates
. Selection of most suitable saponifier may require much work
2^4.4 Hydrocarbon-Surfactant (HCS or HC/S) Processes.
Also - incorrectly - known as "semi-aqueous" processes, HCS methods have
not seen the commercial success originally forecast. This is due to high
drag-out losses, up to 4 g.dm with densely populated SMD circuits (Scolari
1993) , high equipment cost, VOC concerns, combustibility, difficult recovery
and water treatment etc. Nonetheless, there, remain many niche applications
where HCS processes may be suitable and economical.
The basic principle is simple and effective. Rosin flux based soldering
residues are solubilised in an.organic solvent whose vapour pressure is fairly
low. The contaminated solvent is then removed by a full water wash, usually
very similar as is required for cleaning off water soluble fluxes (2.4.2).
This immediately shows that the cleaning equipment must therefore be designed"
with both the. solvent and aqueous phases in mind. Chemically, the solvents
.may either be natural derivatives, such as terpene'-based substances, or
synthetic hydrocarbons and derivatives. There is no specific advantage in
using the natural products - even though some may be derived from citrus
fruits, for example - from the points of view of health, safety and', the
environment. In fact, many (but not all) synthetic products are considerably
less toxic than those made from citrus fruits.
There are two basic methods used in HCS processes and the equipment for
each is completely or partially incompatible with the other. These can be
considered as ".separable" and "miscible" types. Separable types are based on
light hydrocarbon derivatives with a specific gravity of less than about 0.9
and which do not mix with water. In order to solubilise it in water, it is
blended with a surfactant which allows an unstable emulsion to form. The
water emulsion, if allowed to remain still, will separate out so that the
solvent will float on the surface of the water/surfactant mixture. It can
thus be easily recovered for a partial recycling, but the composition of the
separated product is different from the original solvent. Retaining a' steady
process may therefore be problematic.
The miscible HCS solvents may be subdivided.into those which are blended
with hydrocarbon solvents and more stable surfactants, producing a permanent
* 1994 UNEP SOLVENTS, COATINGS, AND AOHESIVES REPORT *
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emulsion, and those which are hydrocarbons or derivatives which have, within
themselves, a surfactant property, often forming a non-micellar solution.
The cleaning part of the process is the same with both categories of HCS
products. The main difference is with the waste water treatment and recycling
processes.
The cleaning quality or both types of process may be very good, but
tests have shown that both water soluble flux and saponification processes are
even better (Grossmann 1993). It may be possible that the miscible types are
marginally better, although the difference would likely be small.
With separable processes, the initial waste water treatment and/or
recycling is done by the separation. The water then has to be treated to
remove the surfactant, the heavy metal salts and residual solvents. This is
done initially with membrane separation (different membranes -may be required
for each solvent type), followed by active carbon and deionising resin
polishing. The water quality is high enough for recycling up to about 80% of
the total water requirements, but the process is expensive and it does not
include the treatment of the pollutants. The problem is even more difficult
with the miscible types, where the.pollutants are almost impossible to remove
economically from the waste water. A recent development (Treacher 19.93)
attempts to use evaporative separation, but it is a very energy-intensive
method and the recovered solvent has a considerably different composition
compared to the virgin material. It should be stated that most miscible
solvents produce a waste water with high BOD5s, which may'not always meet
water quality standards.
It is possible that some of the less popular types may simply disappear
from the market within the next two or three years. Persons considering these
processes would be well-advised to ensure that back-up products exist should
their original choice be withdrawn from the market (one major manufacturer and
one major distributor have both already dropped the commercialisation of such
products).
2.4.4.1 Separable HCS processes
Separable HCS processes are possibly easier to manage as an overall system
with recycling of the water and the solvent itself. To achieve this
separation requires equipment which is very costly to install, run, and
maintain. As such, this process is easier to amortise f.or very large
production rates where' the equipment is expected to work at near-maximum
capacity 24 hours per day and 7 days per week. Smaller installations without
integral recycling may also be used, but may present other problems, outlined
earlier.
Advantages:
Good cleaning quality
Slightly more forgiving of poor cleaning than many other types
Disadvantages:
Heavy consumption without recycling
High capital costs with recycling
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High maintenance costs
Combustible! .
Separation may be at temperatures above the flash point
Health and Safety concerns
VOC concerns
2.4,4.2 Miscible processes
Other than for industrial cleaning, there is an important niche market
for this type of process: field and service, cleaning. One multinational
soldering product manufacturer offers a cleaning kit consisting of such a
solvent packed in a non-aerosol spray bottle with an adjustable nozzle capable
of a jet or fine sprays. For low. volume industrial cleaning, this type of,
process may be suitable without water treatment, but only on condition of
prior approval of the water authorities: In view of. the high quasi -
irrecoverable drag-but losses, this process is very costly for high-volume
production.
Advantages:
Good cleaning quality
Slightly more forgiving of poor cleaning than many other types
Very adaptable to low-volume cleaning
Some products practically non-toxic
Disadvantages:
Heavy consumption without recycling with water pollution
High capital costs with recycling
High maintenance costs
Combustible
VOC concerns
2.4.5 HC and derivative processes.
Straight HC solvent cleaning use flammable or combustible solvents. The
processes can be divided between those using volatile and flammable solvents
such as light alcohols, and heavier, combustible, substances. Light alcohols,
by themselves, effectively remove rosin residues but many other contaminants,
such as heavy metal salts, may not be correctly eliminated. Some proprietary
blends of heavier solvents are remarkably effective cleaners when correctly
used but their low volatility render them extremely difficult to'dry off.
Drag out losses are very high. As for HCS processes, these may reach as much
as 4 g.dnf2 on densely populated SM circuits, even with.air-knife excess
solvent removal. Energy consumption for drying may be very high with solvents
whose boiling points exceeding about 135°C.
2.4.5.1 Light HC solvent processes
This is occasionally used for very small scale cleaning (i.e. circuits),
using open trays and brushes. They represent distinct fire and toxici.ty
hazards. For full production scale cleaning, machines with, appropriate.
flameproofing, including nitrogen purging, are available. For correct
cleaning quality, many light solvents, including alcohols, saturate at
extremely low levels of heavy metals, particularly lead salts. This means
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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that heavy-duty reflux distilling of the solvent is necessary to ensure enough
pure material is present for the last rinse. This is a very costly process.
Advantages:
Low-cost solvents
Generic solvents readily and universally available .
Easy-to-repurify by reflux distillation
Disadvantages:
High capital cost for machinery
High energy requirements
« Good cleaning quality difficult to ensure consistently
Anti-fire/explosion precautions costly
Solvents are VOCs
2.4.5.2 Heavy HC solvent processes
These are arbitrarily separated from light solvent processes when the
boiling point of the solvent exceeds about 120°C and the flash point is higher
than about 50°C.
Those based on ethylene diglycol type derivatives (also usable as
miscible HCS solvents) are very effective cleaners without much evaporative.
loss. However, they have an extremely low vapour pressure, with flash points
often in excess of 100°C. This renders them very difficult to dry off. Tests
with one type have shown that such solvents may require time and energy
requirements greatly exceeding those of water under the same -conditions by a
factor of five or more (Scolari 19.93) . Drying temperature should be limited
to at least 20°C under the flash point. The drying process may be aided by a
final 'perfluorocarbon vapour phase stage (2.4.6) but this is not recommended
due to the emissions of global warming gases. The process, may consume high
quantities of solvent by drag-out losses.
Advantages:
Good cleaning quality possible
Low fire hazard
Low toxicity (some products) ' .
Easy to handle and use
High rosin loading possible
Disadvantages:
Expensive solvents
Difficult and expensive drying
VOCs
Difficult to repurify and recycle the solvents
2.4.6 Permitted halocarbbn processes
There are three halocarbon processes which may be mentioned, using non-
ozone depleting chlorinated solvents, HCFC and HFC blends and PFC drying
processes.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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All three of these processes demonstrate grave environmental and other
disadvantages. Practical experience in many locations have shown that there
are very few cases where the use of these environmentally disadvantaged.
products present a real benefit over more benign processes for the electronics
industry, either economically, or technically.
At best, they can,offer only a temporary, technically doubtful and
costly alleviation of the problem. Most of those companies in the electronics
industry that have adopted them have chosen HCFCs and they are generally aware.
that this process is temporary and may not be either entirely suitable or
economically viable. However, it may offer them the time necessary to choose
a more suitable process.
2.4.6.1 Non-ozone-depleting .chlorinated processes
Theoretically, all chlorinated solvents are ozone-depleting, although a
number of.them have negligible ozone-depleting potentials. These include
perchloroethylene (tetrachloroethylene) and trichloroethylene. Solvent blends
containing perchloroethylene have been proposed as "cold flux removers". To
date, there is no evidence that these offer any real technical advantage over
other processes. On the other hand, they are known to cause problems with
many synthetic compounds such as a number of plastics and even printed circuit
substrates. As a result, their use is relatively limited. They have
occasionally been employed with "kiss" cleaning machines (bottom-surface.
brushing machines) to remove sufficient flux to allow automatic test machine
probes to contact the metallic surfaces, without truly cleaning the
assemblies, but this is a niche market, possibly better resolved by using
certain qualities of "No-Clean" flux.
Advantages:
Easily obtained, low-cost solvents
Zero-to-low OOP ' .
'. Traditional method
Disadvantages:
Health and safety concerns
Some blends may be VOCs and/or have high GWP
Cleaning quality often mediocre
Plastics and PCB substrates often sensitive to solvent
"Cold" cleaning produces high drag-out losses
"Cold" cleaning blends non-azeotropic
High boi'ling points preclude vapour defluxing in some cases
2.4.6.2 HCFC Solvent processes
Except for the very rare application, HCFC solvents should 'never be used
for cleaning an electronics assembly.
All HCFCs deplete the ozone layer. They are regulated under the .
Montreal Protocol and those controls may become more stringent until a total
phaseout is achieved. Two HCFC solvents are otherwise.suitable for '
electronics cleaning. ,HCFC-141b has a high ODP (comparable with that- of
1,1,1-trichloroethane) and may be' subjected to ..more severe restrictions in the
* 1994 UNEP SOLVENTS, COATJNGS, AND ADHESIVES REPORT *
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short term. It also attacks many plastics materials and has a low boiling
point with a high volatility. This is the least recommended of HCFC solvents
for this work. HCFC-225 is a blend of isomers and has characteristics quite
similar to CFC-113 except for a lower ODP and a higher cost. It is the
nearest solvent we have to a "drop-in" replacement of CFC-113, even to the
extent of blends with similar characteristics.
The equipment, when using HCFCs, must always be suitable to minimise
emissions. This is not only to prevent unnecessary ozone depletion, but also
from a purely economic standpoint as the cost of these solvents is high. Any
unnecessary losses therefore compromise their economic viability. Above all,
they should never be used, in an open-top vapour degreaser, particularly if the
model is more than two years old.
Advantages:
Process similar to the familiar CFC-113 vapour defluxing
Disadvantages: ' '
Ozone depleting
- Some blends may be VOCs and/or have a high GWP
Requires expensive near-zero emission machinery
Forbidden in some nations
Future legislation uncertain in some others
Some solvents expensive
Doubtful economic viability
Cleaning quality doubtful (according, to solvent)
Attacks some plastics (according to solvent)
Transitional substances only
2.5 MACHINERY FOR ENVII "NTALLY RESPONSIBLE SOLDERING AND CLEANING
All electronics solu-^ing and cleaning is detrimental to the
environment. It is important that those selecting equipment choose types
suitable to do the required work, yet cause a minimum amount of environmental
harm. This section will give a brief review of some of the risks that occur
with different process types.
2.5.1 Conventional wave soldering
While wave soldering is generally not a very polluting process, it is
not entirely benign either. The worst pollutants are those derived from the
flux during the preheating and soldering stages. The fluxes generally contain
organic solvents, usually light alcohols. These are evaporated, mostly during
the preheat stage, but residual amounts during the actual soldering. There is
little decomposition of these compounds which are usually almost 100 percent
emitted. They are not very dangerous to the environment, due to their
hydrophilic nature which gives them a very short atmospheric lifetime.
However, a few nations or regions do consider them as VOCs. The cheapest way
of reducing their emissions is to use cold water, in a small.scrubbing tower,
between the machine exhaust and the outside air. The resultant water/alcohol
xixture may then be treated tr. separate the components and thus recover the
ilcohol (this is not necessarily an economical recovery)..
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Also from the flux, activators and vehicles are often volatilised,
sometimes unaltered, sometimes decomposed, as well as the solvent system.
These may be hydrohalide acid gases, amines and amino acids, linear or cyclic
carboxylic acids, oxygenated hydrocarbons or derivates of these substances.
Rosin, for example, may partially decompose into toxic aldehydes. In
particular, Low-Solids "No-Clean" fluxes are often designed to deliberately
volatilise or sublime so as to minimise the quantity of post-soldering
residues. All these products, with the exception of hydrohalide acid gases,
must be considered as VOCs. The quantities emitted per machine may not be
very large, but the global emissions must amount to thousands of tonnes per
year. Some products may even be considered as toxic or otherwise dangerous to
the environment. Again, a water scrubber will reduce 'effectively the quantity
of pollutants emitted, followed, if necessary, with an active carbon filter.
A third class of pollutants derived from wave soldering are metal oxides
and salts. Tin and lead in the solder wave oxidise on the surface. This film
of oxides falls into the solder bath, breaking up as it does so. Turbulence
at the. surface causes a small quantity of these oxides to be projected as an
aerosol- dust into the air. If there are flux activators in the air, as well,,
these oxides may be reduced into metal salts, some of which, finely divided,
may be particularly toxic, even if the quantities are almost infinitesimal.
Again, a water scrubber will remove most of this kind of particle, but the
water may require more rigorous treatment.
Metallic particles, often termed microspheres or microballs, are
frequently produced in relatively,large quantities and may adhere to the
surface of the board. These are mostly removed in subsequent cleaning and may
cause problems in the cleaning product ifxnot carefully mechanically filtered.
2.5.2 Controlled atmosphere wave soldering
The pollution produced from controlled atmosphere wave soldering is
"generally very similar to that from conventional soldering, except that the
oxidation of the solder is much reduced. There is therefore relatively little
metallic salt formation. The quantity is not reduced to zero, because of the
oxides present on the board and component leads before the soldering process
commences. These are not completely reduced to salts before the passage into
the wave, so a finite amount of dross is always present. Microballs are also
more frequently produced with this process but, as the boards are rarely
cleaned, they do not Represent a major hazard in the cleaning process, even if
they may cause electrical problems. A newly .developed-controlled atmosphere
soldering process uses a reducing gas plasma in place of fluxing. It is not
yet sure, to what extent this can reduce organic contaminants on the components
without attacking the organic substrate.
2.5.3 Infra-red etc, solder paste reflow
This section also includes most other types of reflow, with the
exception of vapour phase and liquid immersion types. The pollutants produced
are generally similar to those produced by wave soldering. In addition,
chemical agents in the pastes to establish the right rheplogical
characteristics add to the spectrum of evaporated chemicals. These may take
numerous forms but all such emissions must be considered as VOCs.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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2.5.4 Vapour-phase solder paste reflow
This is possibly one of the worst pollution generators in the
electronics industry, after CFC-113 cleaning. There are several conceptions
of the process, but none are better than the others. Fortunately; it is
losing popularity and few new equipments are being put into service.
The main problem with this process is analogous to that of CFC-113
cleaners. A heavy vapour is used to allow the parts to reach the soldering
temperature. This vapour is not easily contained and the methods used to
contain it often acerbate the problem. The vapour is a perfluorocarbon (PFC)
compound with a boiling point in the range of 215°-260°C. As far as is known,
PFCs have no effect on the ozone layer but -they are among the worst
"greenhouse gases". Furthermore, they have atmospheric lifetimes of 500 to
10,000 years. The breakdown mechanisms are unknown and there is a finite risk
that they may cause unforeseen problems within a few centuries if allowed to
accumulate in the atmosphere. For this reason alone, this process is not
recommended.
There are three major methods used to reduce emissions of the expensive
PFC reflow medium, none of which are completely effective,as the medium is
often entrapped under the components on the assembly. These are the
mechanical machine design, the use of a CFC-113 secondary vapour blanket and
the use of a more volatile, less expensive, PFC secondary vapour blanket. The
latter has only an economical effect, as the PFC used for the blanket is as
bad a "greenhouse gas" as the primary vapour. CFC-113 is, of course, not
acceptable because it is a regulated substance under the Montreal Protocol.
No economical machine design can reduce the emissions of the PFC to an
effective level.
2.5.5 Hot liquid immersion solder paste reflow.
This method uses a glycol derivative heated to the fusion temperature -as
the heating medium. It has a number of advantages, especially for thick film
circuits. A good proportion of the paste residues actually dissolve in the
medium, so that the cleaning process, using a simple water wash, becomes easy.
The medium starts to decompose fairly rapidly, evidenced by a visible
carbonisation, but this does not become serious until the end of the useful
life, of the product, typically 30-40 hours at the reflow temperature. Even
though the vapour pressure of the medium is so low at room temperature that it
may not even be considered a.VOC, the evaporation at fusing temperature is
quite high. This will contribute to tropospheric ozone and smog under the
right weather conditions. The process is quite dirty_as a sticky polymer tends
to condense all around the machine. This makes a good extraction system
essential, designed to minimise cooling at the liquid-air interface. The
extracted air can b'e water-scrubbed: mechanical filters are useless as they
.log very rapidly. The water in the scrubber tower may be contaminated to a
heavy degree but may be used as the first wash water for the reflowed
assemblies. The contaminated water will have a high BODc and some authorities
say not permit its discharge into sewage. The heavy metal content may be
ceptable as much of the metal salts will remain in the fluid. This would .
''quire analysis .before allowing it to discharge.
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The spent fusion fluid must be considered as a hazardous waste and be
disposed of correctly. Apart from the heavy metals, the product-will have
become heavily decomposed and polymerised. It will be largely non-
biodegradable, either in water or soil. It cannot be effectively used as a
fuel unless the metal content is removed and the residues crac.ked to lighter
hydrocarbons. This can be a severe limitation to its use.
The paste type used in this process is usually water-soluble. Rosin will
dissolve reasonably well in most of the commercial fluids, but an accumulation
of rosin residues will reduce the useful life of the product and make it even
more difficult to eliminate.
2.5.6 Aqueous cleaning (conventional water-soluble fluxes)
The first wash water of straight water washing will contain heavy
metals, usually to prohibitive levels. Its pH may also be lower than is
permitted by many authorities. It will also contain glycols and surfactants
which will both increase .the BOD5, but generally not to severe levels with the
levels commonly formed. The water may be treated by any conventional method
to remove the metal content and neutralised with a basic solution. This would
allow the waste water to be discharged, assuming the biodegradability was
acceptable. '
Complete recycling of the waste water is nearly impossible: the maximum
is probably about 75 to 80 percent, in most cases. , The remaining 20 to 25
percent represents drag-out losses, evaporative losses, membrane concentrate
solute, diverse filter replacement losses, deionising column regenerating
solution and rinse waters and other water usage. Any water treatment using
membrane or deionising techniques to remove heavy metals does not really help
the situation: at the best, it displaces the problem to another level, as the
metals are still present either in the concentrated waste water and in the
resins.- On. regenerating the latter, the metal is removed and re-enters into
an aqueous solution. If the resins are mixed bed, this is usually done off-
site and the regenerating station must be warned that heavy metals are
.present. The one advantage in concentrating the heavy metal salts in waste
water is that they become easier to treat than in a highly diluted form.
2.5.7 Aqueous cleaning (glycol-free water-soluble fluxes)
The environmental problems with so-called glycol-free fluxes are
identical to those of conventional, water .soluble fluxes. Despite the term
"glycol-free" some fluxes of this type do contain certain benign glycol
derivates, even if they do not contain the polyglycols suspected of/causing a
reduction of surface insulation.resistance of some substrates. Some of the
surfactants used to allow such fluxes to foam or to improve the wetting of the
flux are very closely.related to some .of the polyglycol derivates.
Some of these fluxes also contain tribasic carboxylic acid activators,
such as citric acid. These are known to have a chelating action on heavy
metal salts. As a result, the latter, may be more difficult to remove until
such time as the acids start to biodegrade, which may take a considerable
amount of time.
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As a general rule, these fluxes are no better environmentally than their
conventional counterparts, as far as the cleaning process is concerned, and
may present greater difficulties.
2.5.8 Saponifier cleaning
Saponifiers based on monoethanolamine operate normally at around 55°C.
At this temperature, there is a certain amount of evaporation of the amine and
the co-solvents. The latter are usually VOCs, but the amines, being basic,
tend to react rapidly with acid gases, such as carbon dioxide, especially in
the presence of humidity. Because of this, their atmospheric lifetime usually
is. very short. The reaction products are generally without effect, being also
very hydrophilic with a very short folded-e lifetime. They may form nuclei
for mist formation if the atmospheric humidity approaches saturation. This
must not be confused with ozone and smog formation due to the' photochemical
reaction between nitrogen oxides and VOCs.
2.5.9 HCS solvents .
HCS solvents may be among the most polluting methods of cleaning.
Practically all the solvents are classed as VOCs at normal operating^
temperatures. Most of the emitted vapours can be collected from all parts of
the machine (including the wash and rinse sections' and the separator, if so
equipped) and economically reduced by a water scrubber.
The most polluting, aspect of the HCS processes is the quality of the
wash and rinse waters. Even if gravitational and/or membrane separation
techniques are used, a considerable quantity of solvent remains either in the
water when the machine is drained and the concentrate contains considerable
proportions of water. Many commercial machines, .including some quite large
and expensive ones, are equipped with no means of separation, meaning that
most of the large quantity of dragged-out solvent ends up in the waste water.
This is especially critical with solvents that actually form a stable mixture
with water, where no economical form of separation can possibly work, except
for the very largest installations. One commercial machine, designed for use
with a high-boiling point solvent, developed in Great Britain, concentrates
the mixture by evaporating off the water. However, this is inefficient and
energy-intensive: as some of the components of the solvents, themselves
zeotropic, form an azeotrope with water, the resultant residue contains water
and has a composition wildly different from that of the original solvent. It
is likely that the recovered solvent is not extensively re-usable and that
considerable quantities of some of the components are emitted.
Solvent drag-out losses can be very high, of the order of 100-500 g/m2
of printed circuit assembly depending essentially on the type and density of
the electronics components. Many'machines are equipped with air knives on
exiting from the solvent phase of the cleaning process. This is insufficient
to significantly reduce the problem: if the energy is sufficient to eliminate
more than a few percent of the solvent residues, most of the solvent will be
atomised or vaporised, thus .displacing the problem from water to ai'r. In
practice, with a machine which air-knives the PCBs without causing undue
losses, only the superficial solvent, representing typically about 50-100
g/m2, will be recovered.
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The solvent in the wash water is usually claimed by the manufacturers to
be "biodegradable". In reality, many HCS solvents have ,a very high BOD5 and
or COD, sometimes exceeding national limits or recommendations even in small
proportions. This aspect should be carefully examined before choosing such a
process or, at least,' a given solvent.
Even if gravitational separation is employed, practically all the
surfactants -- often up to 10% of the solvent volume.-- and dissolved heavy
metals remain in the water. The only way to improve separation is by active
carbon filtration to handle.the large quantities of surfactant followed by
traditional methods of deionisation or precipitation to remove the metals.
Membrane techniques may not be able to separate the two pollutants from' each
other
The most difficult problem is the disposal of the used solvents. These
contain, as well as the original components, heavy metals, rosin residues,
activators and other contaminants resulting from the assembly being cleaned.
They are therefore considered toxic waste. Since about one-third of such
waste is composed of contaminants from the assemblies being cleaned, the
composition is completely unknown and the heavy metal content is-likely to be
quite high. The only safe way to dispose of .these products is to incinerate
them in a kiln designated for the disposal of combustible chemical waste.
There exist a handful.of special purpose-built kilns.for this throughout the '
world, but their use is expensive. More usual is to mix the solvent into
cement kiln fuel with approved installations. Most of the incombustible
residues (heavy metal salts) are incorporated in minute proportions into the
cement. They do not alter the cement properties and they eventually become
encapsulated in a mass of solid cement or concrete where they are harmless.
The remainder of the salts are collected by the fly ash electrostatic
.precipitator whose contents are usually added to the limestone feeding the
kiln. Any acids or other volatiles from decomposition of the activators are
collected in a water scrubber mounted in the flue.
Some manufacturers of HCS solvents try to make light, of the disposal
problem of the used product. For example, it has. been suggested that the
spent solvent may be added to heating fuel oil. The problems that could
result from such advice may be:
clogging of the burner nozzles by burnt rosin, causing poorly
controlled combustion
acid vapours could attack burner parts, boilers and flue linings
if they are of unsuitable materials
all the heavy metal salts would be emitted into the atmosphere
the optimum fuel:air ratio will be upset producing excessive
emissions of NO^ gases and soot
in summer, when~the fuel consumption drops, the problem tends, to
become acerbated by excessive quantities of solvents
This prac'tice, where it is not expressly forbidden by law,, should be
discouraged.
2.5.10 HC solvents and derivatives
As a general rule, all straight solvents are VOCs and their disposal
must be done according to the criteria of common sense. Both these subjects
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form part of the last section (2.5.9) and their treatment is more-or-less
identical. They normally engender no water pollution problems, by definition.
The only exception to this is with the use of light solvents, such as
the lower alcohols. The vapours from these form a distinct fire and explosion
hazard, as well as being VOCs. Appropriate action should be taken, in
conjunction with the local fire protection agency and insurance company, to
prevent any emissions from creating an unforeseen hazard. The best method is
to ensure that the emissions are as low as is humanly possible.
2.5.11 Permitted halocarbon solvents
Wo matter their composition, all halocarbon solvents are dangerous to
the environment, being any combination of ozone-depleting, global-warming,
toxic, VOCs and generally undesirable. It is the responsibility of the user
to reduce their emissions to virtually zero at all times by suitable machine
design and housekeeping practices. There is really no reason why they should
be used for any purpose within the electronics industry, with the possible
exception of a very few minor applications, representing perhaps the
production of one establishment in tens of thousands.
Unfortunately, this is unrealistic. There has been economic pressure to
use HCFC-141b in place of CFC-113. Some vendors claimed that it could be used
in existing machinery without modification of the equipment or the working
practices. The result was that emissions into the atmosphere increased
significantly. Although this solvent has only about one-fifth the ODP of CFC-
113, the net result would be the unnecessary emission of an ozone-depleting
substance. As HCFC-141b mixtures are poor defluxers and can attack some
electronics components,, .there is no reason why it should be used for this
application. If, for any reason, an HCFC solvent must be used for defluxing,
then an HCFC-225 mixture would be more suitable. Also, since it is more
expensive, users will have the incentive to minimise emissions.
The Solvents, Coatings and Adhesives Technical Options-Committee does
not recommend HCFC-141b for defluxing in. the electronics industry under
Multilateral Funding-.
The measures to be taken to minimise emissions of .HCFC-225 and other
halocarbon solvents are described adequately in past editions of these reports
(UNEP 1989, 1991).
2.6 PRODUCTION MACHINERY AND MATERIALS
The choice of machines for assembling and soldering printed circuit
boards is too large to catalogue all that are available. Instead, discussion
8 HCFC-141b has a high ozone depletion potential (ODP) of 0.11 which is
equivalent to the 1,1,1-trichloroethane ODP of 0.12 and it is controlled under
the Montreal Protocol. Future changes may further restrict its use or advance
its phase out dates.. HCFC-141b should therefore 'only be considered as a
replacement for .CFC-113 in specialised application where no other substitute
or alternative exists.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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will focus on the impact they may have on the overall process when
substituting new methods for traditional ones.
2.6.1 Conventional wave soldering machines
When choosing a new wave soldering machine or adapting an existing one,
it is important to look at the means for fluxing. Traditional rosin fluxes
usually foamed very well, so that foam application was the choice of,
predilection. This was simple, effective, and inexpensive. Originally, air
was pumped in through a porous, cylindrically shaped stone. To obtain more
uniform results, this was replaced by synthetic sintered stones. Some of
these were slowly attacked by some fluxes and sintered plastic'"stones" are
now the rule, being cheap and long-lasting. They are,'available in different
pore sizes and the choice may become critical according to the flux
characteristics with modern fluxes.
As a general rule, "No-Clean" Low-Solids fluxes do not foam very well
and are sometimes difficult to use in a foam fluxer. If problems are
experienced, one should try different stone porosities. Having determined the'
best one, if the foam head is still inadequate, it may be necessary to modify
the chimney geometry with either a new chimney or polypropylene .inserts,
fashioned to suit. These should restrict the form to as narrow a chimney as
possible, 6-10 mm internal width at the top and 2-3 mm more than the stone
diameter at the bottom being ideal.
Another approach is to replace a foam fluxer with a fine plastic mesh
drum which turns with the bottom third in the liquid flux. At the top, an
air-knife blows the flux held by capillary action as fine droplets onto the
board. This is possibly more reliable than foam fluxing in difficult cases.
In both of the previous methods, there are considerable changes in the
flux composition with time, as the air used exaggerates the evaporation of
solvents and may add humidity, to the flux. The solvents have to be replaced
to maintain the correct flux characteristics. With conventional fluxes, this
replacement can be calculated and checked easily by simple gravimetric means.
With Low-Solids fluxes, this is not possible as the difference in density
between the flux and the solvent is small and the results can be easily
misinterpreted by the presence of humidity absorbed from the .atmosphere or the
air used in the fluxer. The only reliable low-cost method is by titration and
some flux manufacturers provide simple titration kits for Use with their
fluxes for maintenance.
Another fluxingtmethod is to spray the flux evenly over 'the board using
oscillating or multiple spray heads. These must produce a fine, uniform
deposit without undue quantities of mist which would not only be wasteful but
also present, an explosion hazard. Ultrasonic spraying, for example, is
considered as an excellent means f^or this method. This has the additional
advantage that the flux that is sprayed is always exactly of the "as-
delivered" composition and no maintenance is required.
Fluxer materials must be compatible with the flux being used. In
Europe, the traditional fluxer material is stainless steel. This has proved
to be inadequate for use with some water-soluble fluxes, which can attack it,
especially along, the welds, over a period of time. Early US fluxers were
.frequently made from fabricated PVC sheet. This material resists most fluxes
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very well,.with the exception of those containing esters in their solvent
system. Perhaps polypropylene, which is also cheap and easy to fabricate,
presents the best compromise.
The machine should be fitted with an air-knife immediately after the
fluxer. This serves three purposes:
it removes excess flux and pushes it back into the flux reservoir
or a catch tank
it ensures a more even flux distribution
it helps flash off the excess solvents, easing the load on the
preheater.
Preheating is the next critical point. Some European machines are
inadequate in their preheat temperatures. The preheating is often thought of
as simply to evaporate the solvents in the flux, although this is not true.
It has to bring all the parts of the board and components to be soldered to a
temperature at which the flux can reduce any oxides present before contacting
the wave, so that the molten metal can immediately start forming intermetallic
compounds. This temperature may depend on the flux type and the nature and
quantity of the activators. As .an approximate rule, this critical preheat
temperature is generally in the range of 90°C to 115°C. As it is expected
that the solder should rise in plated-through holes, this should be measured
on the top side of the assembly being soldered at the instant immediately
before entering the wave. Temperature profile recorders are."ideal for
determining this. These are small devices with a number of thermocouples on
flying leads attached at appropriate points to the assembly. The whole device
is passed through the machine and afterwards the results, held in memory, are
analysed and printed out. There are excellent devices of this nature
manufactured in Europe and the USA.
The method of preheating employed is often unique to particular
machines, ranging from convected air to forced hot air and from low-
temperature hot plates to electric light bulbs, or combinations thereof.
There is no ideal method, provided that the required'temperature can be
achieved in the minute or so of preheating. However, particularly when using
Low-Solids fluxes the infra-red absorption characteristics of an assembly can
vary widely according to the peak wavelength of an infra-red generator. Metal
is heated much less efficiently as the wavelength increases so, if the desired
temperature is reached on the top side of the circuit from a very brightly
incandescent source, there is a very real risk that the substrate will become
too hot, causing discoloration, chemical decomposition or an unusual 'set' due
to the glass transition' temperature (T ) being exceeded for too long a time.
Experience has shown that the most usual method employing metallic (Inconel)
Infra-red heaters at temperatures within the range of 400°C to 700°C in a
polished reflector or some hot air types give the best results.
Energy consumption is also a factor where, ideally, all the heat
generated should be converted into a rise of temperature of the PCB. More
important than the actual conversion efficiency is the conservation of energy
in stand-by periods. With incandescent and hot-air preheaters, they can be
switched on as and when needed and switched off when there are no boards being
processed. With metallic or ceramic infra-red heaters, these should be as
thin as possible to minimise thermal inertia. They can then be switched on
.for all the time there is a board present as from the entry of the machine (to
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ensure they are at full working temperature by the time the board reaches the
preheat zone) and switched off again a few seconds before the last board quits
the preheat zone. To .achieve this ultimate performance, sophisticated
temperature controllers using proportional techniques with differentiation and
integration are required, with a sensor wire in the heater itself. These
apply full power to the heater during warm-up to reach the working temperature
very rapidly. About 5°C before reaching the preset heater temperature, the
power is progressively diminished until it reaches optimum at which
temperature the whole system is in perfect equilibrium with no overshoot. The
moment the temperature varies from optimum, the power is adjusted accordingly
to reestablish the perfect conditions. The controller can even anticipate in
advance the conditions needed to perfect the temperature control without any
overshoot or excessive damping.
As well.as "No-Clean" fluxes, low VOC -fluxes are particularly critical
in terms of preheating. They usually .contain a considerable percentage of
water which requires much more energy to evaporate before the board can be
brought.up to the full preheat temperature.
The design of the wave is also particular to many manufacturers and
should be of little consequence in the final results.
One exception to this is that of double waves. , -This technique is
designed to ease soldering of "glue-spotted" surface mount devices. It
consists of having two separate waves or a single ,wave divided into'two zones.
The first wave is purposely highly turbulent, designed to project the molten
solder into the shadows created by the components, allowing initial wetting in
these zones. The second wave is smooth and is designed to ensure that the
wetted areas form a bright, even and smooth meniscus. There is a hie with
this technique. For it to be successful, there must be sufficient flux
available to reduce oxidation at the second wave. With conventional fluxes,
this is no problem. With Low-Solids "No-Clean" fluxes, there is sometimes
insufficient flux remaining after the passage over the first wave to ensure
correct smoothing in the second wave. This implies 'that, at least, medium
solids (about 8-10 percent) fluxes should be used although some engineering
changes ma}' help considerably with lower solids materials. This is not always
compatible with all the "No-Clean" criteria.
Because soldering with modern fluxes is often more critical, with
narrower operating windows, than with conventional fluxes, everything .should
be done to ensure ease of soldering. This means tightening of operating
tolerances. In previous operations, solder alloys with tin contents as low as
40% were successfully used. Only binary or ternary eutectic alloys, such as
63%Sn/37%Pb or 62%Sn/36%Pb'/2%Ag should be considered with Low-Solids "No-
Clean" fluxes. The soldering temperature is also more critical with these
fluxes and should be chosen within the range 230°C to 250°C after practical
trials. _ " .
'Optimisation of the soldering process is tricky, as there are many input.
and output parameters. Some form of scientific evaluation is usually
necessary, especially with "No-Clean" techniques, to bring the trial
procedures within reasonable bounds. One of the easiest ways of doing this i.s
with the Taguchi method whereby eight input variables and any number of output
variables can be analysed with only twelve experiments, followed by a
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thirteenth confirmatory experiment after the analysis. For example, the input
variables could be:
1 Percent flux solids (2-6%)
2 Flux wet weight:area ratio (0.3-0.7 g.dnf2)
3 Conveyor speed (0.9-1.5 m.min"1)
4 Preheat air temperature (180<>C-2200C)
5 Radiant heater temperature (400°C-500°C).
6 Solder temperature (230°C-250«C)
7 Solder resist (dry film or wet film)
8 PCB metal treatment (HAL or IRR)
The output variables could be:
1 Defective solder joints
2 Bridges between joints
3 Other bridging
4 Insufficient rise in PTHs
5 Skipped pads
6 Aesthetically unacceptable or uninspectable joints
7 Solder webbing
8 Visible residues
9 Residues causing AT probe problems
10 Surface insulation resistance etc.
11 Number of less-than-minimal menisci
12 Number of more-than-maximal menisci
Each of these output variables can be weighted in terms of their individual
importance or the list lengthened or shortened at will, without changing the
number of experiments, inasmuch as boards evaluated for one criterion are
suitable for evaluating all the o'ther criteria.
. Commercial software is available for helping in.Taguchi optimisation.
2.6.2 Controlled atmosphere wave soldering machines
These are essentially the same as the machines discussed in section
2.6.1 (q.v.) .
In reality, only inert gas is used in commercial systems, the gas being
generally nitrogen. Reactive gases have been tried, as well as mixtures of
inert and reducing gases. Soft soldering .does not reach temperatures where
reducing gases, such as hydrogen, are really effective. For this reason the
reactive gas technique is not common.
There are three basic techniques used to ensure the soldering zone is
inerted:
a tunnel adaptation of conventional machines , '
purpose-built tunnel machines
purpose-built hermetic machines.
The first is cheap to install and reasonably effective. However, it is
more difficult to. ensure the complete purging of air around the soldering and
preheating zones, an essential element of the technique. Practical tests
\
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indicate that best results are obtained when the oxygen content is reduced to
6-10 ppm, but satisfactory results have been obtained at higher levels of
oxygen. To achieve this under these conditions is very difficult and requires
heavy nitrogen consumption, making it an expensive option in terms of
operating costs.
Purpose built tunnel machines use clever gas.curtaining and other
techniques to reduce the admixture of air into the soldering and preheating
zones without excessive gas consumption. Notwithstanding, the consumption
still remains quite high.
Purpose-built hermetic machines avoid any risk of contamination of the
.nitrogen by air. The assemblies, being processed pass through airlocks at each
end of the machine. The air in them is evacuated twice and replaced by
nitrogen before they are opened to the interior of the machine. This is much
more economical to run, but slightly higher in capital costs.
These machines are typically designed around the use of special fluxes,
sometimes commercially named preparation fluids. Early Inert-atmosphere
fluxes were simply dilute solutions of adipic acid in isopropanol. New Inert-
atmosphere fluxes are appearing on the market which are claimed to have more
benign and/or lesser quantities of residues. One is claimed to leave even a
completely inert polymeric coating over both surfaces, giving additional
protection. When the quantity of residues diminishes, the metal .salts
produced by reaction between the flux activators and oxides present on the
components are more exposed to the effect of atmospheric conditions in
service. Their effect on the reliability of the assembly is still
undetermined.
Some inert-atmosphere machines provide the option of injecting a formic
acid mist in the soldering zone, which may be dangerous. Theoretically,
formic acid volatilises at about the same temperature as water and decomposes
into carbon monoxide (the reducing agent) and water at soldering temperature.
For it to be innocuous, it.would be necessary to ensure complete removal of
the acid from, the assembly. This implies that the whole assembly would need
to be taken to soldering temperature, including the upper surface of the
components, to ensure that any formic.acid was totally, decomposed and that all
parts of it remained at over 100°C during the whole sojourn in the soldering
zone to prevent formic acid from condensing back onto it. Neither of these
conditions can be guaranteed and independent tests with and without formic
acid injection have shown that the residual ionic contamination may be up to
three to four times higher with the .injection than without it.
Various contradictory statements have been published as to whether
Inert-atmosphere soldering is economically viable, compared with traditional
wave soldering. This is not surprising, as individual conditions are so
variable. Unless a machine is used to near-full production capacity,
.preferably 24 hours per day, then it is possible that the cost of amortisation
and keeping it idling (nitrogen consumption) may become prohibitive. The
savings due to lower dross formation are often very small and are offset by
the nitrogen consumption necessary to achieve it. A recent communication even
suggests that hidden costs involved in inert-atmosphere "No-Clean" soldering
may actually make it uneconomical.
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Inert-atmosphere wave soldering has a very narrow operating window and
is very difficult to master during initial set-up. It may require the use of
selected solderable components. Once the process has been optimised, the
retouch rate should not be much higher than that from other processes. The
switch from a traditional machine to an inert-atmosphere machine can be a
lengthy process. An overlap period with both machines in service in parallel
of at least 4-8 weeks is generally necessary. Again, Taguchi optimisation can
be a quick and reliable help to putting such a machine into service.
2.6.3 Vapour phase reflow
Vapour phase reflow will not be discussed due to the decrease in its
use. This method also results in the emission of "greenhouse" or other highly
polluting gases including, in some cases, ozone-depleting blanket gases.
There are no known applications whereby some other means of reflow would
not give equal or better results, usually at lower cost. One critical
application is for reflowing components on certain complex flexible circuits.
The non-directionality of vapour phase reflowing made it technically
attractive for this. Careful jig design is usually sufficient to allow hot
air or infra-red reflow to be equally successful.
The Solvents, Coatings and Adhesives Technical Options Committee- does
not recommend vapour phase reflow in the electronics industry, under the terms
of Multilateral Funding-.
2.6.4 Infra-red reflow machines
There is a wide choice of machines available, from simple "simmerstated"
Infra-red heaters over a moving conveyor to very complex multi-zone machines
with individual inert gas purging of each zone, mixed heating methods and .
sophisticated process control. It is therefore impossible in a few brief
paragraphs to give more than an outline of the process.
The most common process is to stencil or screen solder paste onto the
PCB to be processed, force the components onto the wet paste and then reflow
the paste to achieve good soldered joints.
The paste itself is (usually) an intimate and fairly homogeneous mixture
of minute spheroids of solder, alloy in a chemical mixture. The spheroids are
carefully size-graded and the most popular grades approximate around 50 ^m
diameter. Special purpose pastes may have smaller or larger particles. It is
important to note that smaller particles would appear to approach the ideal,
but they do have more surface area per unit weight of metal, hence any
oxidation becomes greater in proportion to the metal mass and the paste
becomes more difficult to use with a shorter lifetime. The metal to chemical
ratio is typically in therange of 85-95 percent of the total weight, but the
ratio is about only 50 percent by volume. It is important to realise this, as
the quantity of chemicals is much greater with reflow than with wave or hand
soldering (solder wire usually contains only 1-3% flux by weight) and the
9 All.vapour phase reflow processes emit PFC vapours. These may be the
subject in the future to restrictive legislation designed to curtail emissions
of "global warming gases" which may be a cause of climate change. .
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quantity to remove thereafter is also much greater. The chemicals themselves
are a small quantity of flux and, proportionally, much larger quantities of
thixotropic gels and other rheological agents, heavy molecular weight solvents
etc. This mixture of chemicals is very complex and the role that each
component plays during screening/stencilling, holding, component placement,
holding again, preheating, reflowing, holding a third time and cleaning (if
done) must be studied during the formulation. The ideal paste would be a
completely inert mixture that could be screened perfectly without any slump,
with an indefinite open time on the screen, have an indefinite hold time,
would cause instant and perfect adhesion of placed components, could be held
indefinitely without humidity absorption, could be preheated and reflowed
without fault over a wide range of temperature profiles, wetting oxidised
components, and maintaining perfect adhesion of them during the. process, and
then leave no chemical residues or solder balls whatsoever. This fiction does
illustrate that the preheat/reflow process is only a small part of the total
process and cannot be taken in isolation.
The main problem with Infra.-red reflow of pastes that are destined to be
cleaned is the importance of ensuring a perfectly controlled thermal reflow
profile. A recorder of the type mentioned under wave-soldering machines is a
certain asset in ensuring this. The various components of the chemicals used
inter-react with each other as well as with what it contacts on the components
and boards. The result is a mixture whose composition is difficult to
determine. Even a slight change of fusion temperature and/or time may render
the.residues totally impossible to be removed. This is more important with
pastes that leave thick deposits, such as common, general-purpose RMA and RA
pastes. Careful control of the fusion process is therefore very important
when ref lowing this kind of paste., and sophisticated equipment must be used.
Modern "No-Clean" pastes rely on the volatility of their major
components at fusing temperature to minimise the quantity of visible residues.
It is important that at least a thin film of flvix remains until the solder
solidifies, to ensure acceptable menisci. Some require the use of a
controlled atmosphere, either ine.rt or active. For best results,
manufacturer's recommendations should always be closely followed.
As the major part of "No-Clean" pastes does volatilise, the user should
be aware that a large facility could emit significant quantities of VOCs
unless precautions are taken to capture them. This is not commonly realised
and many plants violate VOC emissions laws. The same holds true for some wave
soldering 'fluxes, even low-VOC types, but the quantities of activators which
evaporate involved are relatively small. The term "low-VOC" means that most
of the solvents have been replaced with water and does not .refer to the
activators which are always VOCs at soldering temperature. With pastes, up to
90% of the chemicals, representing typically 45% of the volume of the bought-
in paste, are. organic chemicals which, sooner or later, volatilise during
processing.
2.6.5 Other reflow methods
There are a number of alternative methods of reflow used. These include
thermode, hot gas or air, laser, npn-coherent focused flash radiation, hot
belt (mainly ceramic substrates), liquid immersion,, and the old soldering
iron. These-will not be discussed here, as they are of limited interest and
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their advantages and disadvantages related to cleaning are logical extensions
of the previous sections.
2.7 CLEANING MACHINERY
There are many different types of cleaning machinery and features within
specific types. The following summaries are therefore broad and the user is
warned that they are not comprehensive. Auxiliary features, such as waste
water treatment, are not considered in these lists. The term "drag-through"
is used here to describe liquid that remains in a machine from one operation
to the next, as opposed to drag-out which is liquid that remains on the work-
pieces from one operation to the next.
2.7.1 "Dishwasher" types
"Dishwasher" types of batch machinery are available for use with some
solvents (including some HCS solvents), some emulsion cleaning and most- forms
of aqueous cleaning. It is important to note that unmodified domestic or
industrial dishwashers are unsuitable for cleaning electronics assemblies for
many reasons.
Advantages
Low capital cost
Small floor space "footprint"
Cleaning quality may be excellent
Some may be purged for flammable/combustible solvents
Disadvantages
High energy and pure water requirements per unit area
Very low throughput capacity (typically 1 nr.h"1)
Drying quality may not be perfect
Optimisation of wash and rinse cycles difficult
Machine drag-through high
Saponification may be difficult
Handling of heavy baskets at a low level
2.7.2 "High-Throughput:"' types
"High-Throughput" types of batch machinery are available for use with
some solvents (including some HCS solvents), some emulsion cleaning and most
forms of aqueous cleaning. They are characterised by separate machines or
compartments for cleaning and drying, separate optimised wash and rins.e
circuits for cleaning and rotary high-speed hot-air knives for drying.
Advantages
Will accept output of most soldering machines (20 m2.h"1)
Very efficient cleaning
Very efficient drying
Low pure water and energy requirements
Moderate capital cost
Simple to automatise
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No lifting of heavy baskets
Virtually no machine drag-through
Disadvantages - .
Unless automated, requires some manpower
"Footprint" relatively large (up to 6 m2)
Peak power consumption high (average low)
Combustible solvents need module with different concept
Flammable solvents excluded
2.7.3 "Tank-line" batch types
"Tank-line" types of batch machinery, are available for use with some
solvents, (including some HCS solvents), some emulsion cleaning and most forms
of aqueous cleaning. They are characterised by separate tanks, usually
agitated immersion, for each operation, in line. The baskets are usually
handled by automatic transfer mechanisms ("hoists") which are designed to
perform both the lifting and linear movements.
Advantages
Some will accept output of soldering machine (5-15 m2^"1)
Low pure water requirements . ~ '
Simple to automatise
No lifting of heavy baskets
Virtually no machine drag-through
' Highly flexible modular conception . .
Combustible solvent-compatible
Disadvantages
Unless automated, requires some manpower
"Footprint" large (up to 12 m2) '-.'
Cleaning not always as good as may be required
Drying not always as good as may be required
Energy consumption may be high -
High capital cost
Flammable solvents excluded
2.7.4 Totally enclosed types.
Totally enclosed' types of batch machinery are available for use with all
solvents, emulsion cleaning and all forms of aqueous cleaning. They are
characterised by a sealed cleaning chamber and tanks containing the various
liquids which;.can be pumped in and out the chamber.
Advantages
Lends itself to rotary agitation
Lends itself centrifugal drying
Good cleaning quality possible
Good drying quality possible
Small footprint possible
Excellent flexibility
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Vacuum drying after centrifugation
Easy inert atmosphere purging
Combustible/flammable solvent-compatible
Disadvantages
Assembly size and weight may be limited .
« Very small throughput (typ. 1-2 m2.h"1)
High capital cost
Long cycle times
High machine drag-through
/
2.7.5 Conveyorised "in-line" machines
Conveyorised "in-line" types of machinery are available for use with all
solvents, emulsion cleaning and all forms of aqueous cleaning. They are
characterised by the form of a tunnel divided into compartments for each
function and through which an open mesh conveyor belt transports the
assemblies for cleaning. Warni'ng: there are some smaller Conveyorised
machines available which do not comply with all the criteria listed below and
which are often inefficient in terms of cleaning and/or drying quality.
Advantages
Can be matched to any machine(s) for throughput capacity
Virtually no manual production operations
Modular types flexible
Easy handling of combustible solvents
Inert gas purging possible for flammable solvents
Disadvantages
High to very high capital cost
Large to very large footprint
High production rates impose very long machines' (>15 m)
High energy and pure solvent water demands
Generally poorer cleaning quality than batch machines10
Generally poorer, drying quality than some batch machines10
High drag-out on horizontal assemblies
Angle of spray attack usually less than ideal
10 These generalisations should be qualified by the statement that a few,
costly, state-of-the-art machines may give excellent cleaning and drying
results. They are based on the fact that if a conveyor moves at 1.5 m.min"1
and a cleaning, rinsing or drying phase of the process requires, say, 2-3
minutes to achieve good results, the compartment for that phase should be 3-
4.5 m long and be equipped with the appropriate treatment for the whole of
that length. Few machines offer this possibility. Slowing down the conveyor
may dramatically improve this situation but at the cost of perhaps not being
able to use the other machinery to full capacity.
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2.7.6 Vapour phase solvent machines
These can be used only with solvents whose boiling point is sufficiently
low so that the parts being cleaned are able to support the temperature and
whose vapour is much denser than air. The components must also be compatible
with the solvents and.their vapours (please consult the manufacturers'
literature). Halocarbon solvents were most often used with this technique.
As awareness of environmental problems increased, such machines became
more sophisticated with features to reduce emissions. Nevertheless, few of
the open-top batch machines are able to reduce emissions to acceptable levels
when using CFCs, HCFCs, MFCs or PFCs. On the other hand, some of the fully
enclosed, entirely automatic ones may be acceptable. 'Their use with less
polluting solvents is not so critical but it is still a wise economical and
environmental precaution not to permit any emission that is not strictly
necessary. For this reason alone, .open-top vapour phase solvent machines are
undesirable for use with any solvent used for defluxing or drying printed
circuit assemblies.
There is a problem when using any solvent in.vapour phase in conjunction
with PCB assemblies, especially for tightly packed surface-mounted ones,
regardless of the machine's design.' Vapour becomes trapped under the
components and, as the'assemblies are removed from the vapour zone, it takes
considerable time, for the trapped vapour to,fall back into the machine, .often
counted over several minutes. The machine design and programming must take
this factor into account.
2.8 MACHINE AGITATION
The efficiency of a cleaning operation is often a critical function of
the method and total energy used in agitating the solvent with respect to .the
parts being cleaned. This reaches a peak when cleaning under large surface-
mount devices with small stand-offs from the printed circuit. This section
gives a brief discussion of the most usual types encountered.
2.8.1 Sprays for cleaning
Spray cleaning, correctly applied, is the most efficient way to remove
soils. The function is to ensure a maximum high-energy penetration of the
fluid into all the crevices, over the required time. Many cleaning processes
may require several minutes to. ensure dissolution of the soils, even with
high-energy spraying. .
The form of the sprays should be solid,, coherent jets or linear curtains
applied to the parts at an acute angle. This angle should be as small as
possible to ensure minimum loss of kinetic energy by the fluid "puddling" on
the substrate, but should not be so small that severe shadowing occurs.
Empirical tests reveal that the best compromise, depending on the machine
design, is usually 15° to 45° with respect to the substrate surface. Batch
machines-are generally better than conveyorised machines in this respect. The
geometry of the spraying should be such that all parts of the board are
subjected to direct jet action at least over a part of the cleaning cycle.
This implies that there should generally be relative movement between the
nozzles and the assembly in both axes.
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The efficiency of spray cleaning is dependent on the kinetic energy with
which the cleaning fluid is sprayed onto the assembly. This is a function of
the spray pressure, the spray volume, the fluid velocity, the nozzle design,
the distance between the nozzles and the assembly and some minor factors. It
is perhaps important to note that a given energy may be imparted equally by a
high pressure, low volume or by a low pressure, high volume flow, but the
nozzle design would be different in each case. The energy is given by the
pump and if a pump consumes a given power at the same efficiency, the results
will be similar, no matter what the pressure and volume, assuming correct jet
design. As a rule of thumb, for reasonably efficient cleaning of electronics
assemblies, the minimum practical energy level of a jet bar is approximately
represented by 2 kW (2HP) of pump motor consumption per total metre length of
bar.
v
The high energy levels produced by efficient spray cleaning are
partially dissipated when the jets or curtains hit the assemblies. As a rule,
the higher -the velocity, the more is the energy lost by the rebounding of the
solvent from the topography of a typical assembly. This often produces a fine
mist. Even with combustible liquids with a flash point of 100°C or more, this
mist can be easily ignitable and, if the proportions are right, even
explosive. It is therefore essential to correctly inert-gas purge any
machines where spraying of flammable or combustible fluids occurs and to use
flame-proof and/or inherently safe.electrics and electronics in appropriate
premises.
The removal of~HCS solvents by water is a cleaning operation and not a
rinsing one: it must be followed by a rinsing operation.
2.8.2 Sprays for rinsing
The whole function of rinsing is different from cleaning and efficient
rinsing is best achieved by low-energy spraying. It should be remembered that
at least the last rinse or rinses should be done with pure uncontaminated
solvent or water, so the volume consumed should also be minimised. The
function of rinsing is to replace the contaminated solvent or water by
successive amounts of a cleaner product of the ,same nature. In other words,
it is a series of successive dilutions until the residual contamination level
is acceptable.
The best spray form is a coarse mist with a mean droplet size smaller
than the smallest interstice, so that there is direct penetration with
displacement of the contaminated fluid before much mixing occurs. It is
therefore inefficient to use energy levels which are too high. A typical pump
energy level for_good operation is 200-500 W.m"1 of spray bar and the nozzle
design should be such that the spray, velocity is low with a droplet size of
typically 20-100 ^m. This may be achieved most efficiently with pressures of
about 3 bars.
Again, the angle of attack should be acute at the moment of impact.
This may imply almost horizontal nozzles on conveyorised machines, if the
velocity is fairly low, as recommended above. Batch machines, with the
assemblies held in baskets in a near-vertical position, offer the best and
most economical rinse conditions, but the nozzle design may require to be
different for the top and bottom spray bars, due to the effect of gravity.
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Machines which use the same spray bars for cleaning and rinsing are
essentially a compromise in that neither operation can be done under optimum
conditions. This may be partially compensated for by adjusting the cleaning
and rinsing times and the number of rinses. One severe disadvantage of such
machines is the "drag-through" caused by contaminated liquid from the previous
operation remaining in the pipe-work, so that clean rinse liquid is
contaminated even before it reaches the assemblies being cleaned. This can
severely compromise the throughput and liquid consumption of such machines by
increasing the number of rinses before adequate cleaning quality is achieved.
2.8.3 "Under-surface" spraying
"Under-surface" spraying is not newj but it has regained popularity as a
means of mechanically agitating combustible solvents without forming an
ignitable'mist. It consists of high-energy jet spraying of the parts being
cleaned with the said parts actually immersed in the liquid. The
hydrodynamics of the'spraying is complex 'and the kinetic energy loss is high
over relatively short .distances. As the boards are usually held vertically in
.a basket or jig (batch machine's) or at a 30°-45° angle on conveyorised
machines, the jets are most frequently applied edge-on or close thereto. To
calculate the required pump size, count on at least 5 HP for each square metre
of area being agitated, plus an.extra 10% for each 10 cm of the distance over
which the jets should remain effective (rule of thumb). In this -case, in
order to keep the jets as coherent as possible over a distance, it is
essential that the pressure be,high (>20- bars) and the volume low.
The high kinetic energy is dissipated thermally within the solvent. It
is.possible that the temperature rise may reach bounds where it approaches the
fluid flash point. In this case, water cooling will be necessary. The
working temperature should always be maintained at 20°C under the flash point
with additional safety devices to shut the machine -down completely 'at 15°C
under the flash point.
There is no advantage to using this technique over 'conventional spraying
with non-flammable substances and its poor energy efficiency is marked.
2.8.4 Ultrasonic agitation
The use of ultrasonics on electronics assemblies is the least understood
and most controversial cleaning technology.
The main classes' of components reported as being potentially damaged by
ultrasonic agitation are non-moulded semiconductors (metal, glass and ceramic
cases), thermionic devices, large multilayer ceramic chip capacitors, liquid
crystal displays and components wound with unencapsulated fine wires. This
list is probably not exhaustive and it certainly does not mean that all
components of the mentioned types will fail after ultrasonic cleaning. It
means that particular prudence is required when judging whether assemblies
with any of these components on may be cleaned or hot.
Most experience with ultrasonic cleaning was with CFC-113. It is of
first importance to note that data obtained with one solvent type should never
be considered as necessarily valid with a different solvent type. The
compressibility and cavitational characteristics of any liquid is unique to
that-liquid alone..
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The first essential criterion to effective ultrasonic cleaning is for
cavitation to occur on the surface to be cleaned. This condition can be
achieved only if there are no dissolved gases and no particles between the
transducers and the parts, otherwise all the ultrasonic energy will be
dissipated away from the cleaning zone, where it will serve no useful purpose.
To achieve adequate cavitation in water or aqueous solutions, for example,
they must be degassed two or three times a day and continually filtered down
to 1 fzm particle size. Degassing is usually done by subjecting the solution
under mechanical agitation to. a moderately high vacuum (<1 mb) at 30-50°C.
Some organic solvents can never be degassed sufficiently to achieve good
cavitation. The quality of emulsions can also vary by the application of
ultrasound.
Frequency is another cause of misunderstanding. Ultrasonic energy is
created by the instantaneous implosion of cavities and the consequent
adiabatic compression of vapour therein. This .causes an astronomic rise of
temperature to thousands of degrees over an extremely short time, measured in
nanoseconds, in turn causing a mechanical shock wave to form in the virtually
incompressible fluid. This shock wave does the work. It is typically
amortised within a millimetre of the point of cavitation, hence the importance
of cavitation on the part being cleaned, preferably on' the contaminant itself.
Cavities do not form at the frequency of the ultrasonic energy but build up
slowly over tens or even hundreds of cycles. This slow rise is a means of
storing energy which is released at the instant of implosion. The high-energy
shock wave is therefore completely aperiodic and cannot be the cause of a
sustained resonance. On the other hand, if there are undamped or poorly
damped mechanically resonant parts, such as-unsupported wires or quartz
crystals, these may be set to oscillate instantaneously at their own natural
frequency, no matter what this is. Repeated oscillation may cause, in the
long term, fatigue which could lead to a loss of reliability. For the
ultrasonic energy to cause direct damage by resonance to a part would seem
highly improbable. The following conditions would have to be united:
the resonant part would have to- have a natural frequency exactly
equal to the excitation frequency
the resonant part .would have to have a high Q to obtain sufficient
amplitude to cause fatigue
the excitation frequency would have to be stable, which is rarely
the case
the excitation would have to be unmodulated to maintain continuous
oscillation, which is rarely the case
the direction of excitation would have to be such that the
amplitude of oscillation was maximised.
It is unlikely that all these conditions would apply. Frequency seems,
therefore, not to play a direct role. On the other hand, it' can play an
indirect role in"that lower frequencies may produce larger but fewer cavities,
so-that the implosion energy per cavity may be greater. Some systems use
sweeping frequencies. Over narrow bands (up to one octave), this technique
would not bring about any significant difference. Another new technique,
developed in Japan, is to use simultaneously three frequencies, such as 35
kHz, 70 kHz and 200 kHz. It is claimed that this is particularly effective,
with correct dosing of each of the three amplitudes, when using degassed water
or aqueous solutions.
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No matter what system is employed, successful use of ultrasonic, cleaning
depends on: . .
cavitation occurring in close proximity to the contaminants
cavitation of sufficient .amplitude/frequency characteristics to
ensure adequate acceleration of the cleaning process
thoroughly degassed solvents or solutions
very tight process control
provably, no deterioration of components
provably, a significant improvement in the residual contamination
levels
If any one of these criteria cannot be met, ultrasonic cleaning should not be
used. In the last condition, "significant" means that if the levels are not
at least 30-50% lower than without ultrasonic cleaning, under otherwise
identical conditions, then the process is not optimised.
2.9 DRYING '
Drying is an important part of the cleaning process and can contribute
to the overall success or otherwise of the operation. The most common methods
of drying organic solvents and wa'ter fall into three categories, mechanical
drying, evaporative drying and vapour phase drying. Each of these has a
number of sub-categories.
Whether an organic solvent or water (or a mixture in some cases) is used
as the final rinse,, it must be realised that drying does involve thermal
considerations by all three categories enumerated above.
2.9.1 Mechanical drying
The two main subcategories of mechanical drying are' effective air-
knifing and centrifugation. In both cases, they are accompanied, to a certain
extent, by a small proportion 'of evaporation. This absorbs sufficient heat
from the ambience to provide the. required latent heat of evaporation. The
result is a drop in temperature. With some organic solvents, this may be
sufficient under some conditions to .take it below the dew point, causing
condensation'Of atmospheric humidity onto the assemblies'and subsequent
further difficulties. The latent heat of condensation of this water will
supply some of the heat required to evaporate the solvent and an equilibrium
will be reached (assuming the solvent is not water soluble). It is sufficient
to ensure that the air in the knife or in the centrifuge, along with the
assemblies, is a few degrees higher than the ambient temperature to avoid
this. In any case, the compression of the air in the air-.knife system should
be sufficient to ensure an adequate heat input.
Mechanical drying is, by far, the most effective means of gross drying.
Ninety.to ninety-five percent of residual water can be eliminated from even
tightly packed surface-mounted assemblies in a matter of thirty seconds. This
will require less than 10 percent of the energy needed to evaporate an
equivalent mass of water. High-boiling point solvents, e.g. diglycol ethers_
with boiling points in excess of 200°C, are much more recalcitrant to
mechanical removal. This is because their evaporation rate is insignificant
below 100°C but, above all, they wet the substrate and components better in
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the interstices, making them more difficult to shift. In some recorded
experiments using hot air-knives at 80°C, on circuits with a medium-high
density of SM components, water was retained at an average of 4.2 g.dm"2 after
immersion in water followed by ordinary handling. Dipping into a solvent with
a boiling point of 210°C, the average weight of retained solvent was 3.9 g.dm"
2. After 20 seconds air-knifing at' 80°C, the figures.were respectively 0.5
and 1.8 g.dm"2. After five minutes, the residues were <0.01 (the limit of
measurement, approximating to total dryness) and 0.55 g.dm"2 respectively.
Even after 30 minutes, the solvent-wetted boards were not dry, even with, the
combination of high-velocity air and moderately high temperature. Repeating
the experiment with water to which 5% of isopropanol was added changed the
mean zero and 20 second weights to 4.05 and 0.35 g.dm"2 respectively, a
distinct improvement over, water alone. (These figures were derived from
experiments conducted in 1993 by a Swiss company which requested anonymity.)
The supreme advantage of mechanical drying is that most of the water or
solvent is eliminated in discrete droplets, typically 100 /jm - 1 mm diameter.
As seen earlier, rinsing is a process of successive dilutions. There dre
therefore always some contaminants in the residual liquid and these are
eliminated along with the droplets. This method therefore produces a
significant improvement of cleaning quality over other methods of drying.
There is no evidence of an increase of fire risk when hot-air knifing
combustible solvents. The droplet size is large and the air velocity is high,
so that the concentration cannot reach dangerous levels, provided that the air
temperature is kept well below the flash point (at'least 20°C less).
It may perhaps be useful to define air-knifing in this context as some
machine manufacturers mistakenly call forced-air circulation air-knifing.
With an air-knife, there are two criteria: the air is forced through a linear
orifice, usually a few millimetres wide, and impinges directly onto the parts
to be dried. The air velocity is generally about 50 m.sec"1 or more. In in-
line machines, two or three air-knives on each side provide the action.
2.9.2 Evaporative drying
This consists of either letting the residual liquid evaporate to dryness
or to force it dry by increasing the temperature and/or reducing the pressure.
The usual means for this are heating by convection, forced air, Infra-red
radiation in ovens or tunnels or vacuum ovens.
The chief disadvantage of evaporative drying is that, as drying
progresses, the volume of liquid diminishes. The remaining liquid tends to
move to where the capillary spaces are smallest, as the contaminants become
gradually more concentrated in it. These spaces are mainly round the solder
joints. Eventually, these contaminants will become dry at the places where
they are deposited, often where they can cause the most electrical or- chemical
harm. It is for this reason that it is stated above that mechanical drying is
preferable for the gross liquid removal. Evaporative drying is used for the
remaining 5 or 10 percent that mechanical drying will not remove.
One of the important aspects of evaporative drying is the large amount
of power required to supply the latent heat of evaporation of the liquid being'
removed. In the case of water, for example, about 6.5 kWh is required to dry
off each litre of water at 80°C, assuming a 10% heat transfer efficiency
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(typical for a forced air oven, convection ovens being even less efficient).
This is typically ten times higher than is required for mechanical removal.
This is another major reason why the latter is preferable for gross drying.
Vacuum drying does not escape this rule, even though it is achieved faster and
at a lower temperature. Any power gained by not heating the solvent to such a
high temperature to obtain a suitable rate of evaporation is more than
compensated for by the power consumed by the vacuum pump itself. The latent
heat of evaporation remains substantially constant over a wide temperature
range and this represents the major part of the power requirements.
x
Vacuum ovens must be fitted with effective vapour traps to prevent water
or solvent vapours from entering the pump, causing a deterioration of the
lubrication and thus damage and to prevent lubricating oil vapours from
refluxing into the oven, where it could condense in the oven and onto the
workpieces.
Infra-red drying efficiency depends on the absorption characteristics at
the wavelength of the radiation s.ource. Black and other dark components tend
to become hotter than the relatively light ones and the substrate. This
temperature differential may become relatively great in some cases.
Forced air drying is the means for the most uniform heating of wet.
assemblies.
2.9.3 Vapour phase drying
This is the familiar way of drying after solvent cleaning using CFC-113
or 1,1.1-trichloroethane. There are three variants, all based on the same
basic idea. These are drying off a solvent in its own vapour, drying off a
solvent in the vapour of another solvent miscible with it and drying, off a
solvent with another one which is not directly miscible with it.
It is important to understand the operating mode of a typical straight
vapour phase cleaning operation. The parts to be cleaned are immersed in the
boiling solvent for gross cleaning. They are then transferred to a clean,
cold solvent bath for rinsing. They should stay there until, at least, the
whole assemblies cool to the solvent temperature. They are then lifted out of
-the liquid into the solvent vapour. Solvent condenses on the parts and gives
a final rinse of relatively clean solvent. The latent heat of condensation
released causes the parts to heat up rapidly and condensation ceases when .they
reach the same temperature as the vapour itself. The parts can then be slowly
withdrawn slowly out of the machine in such a way as to prevent any vapour
from being drawn out with them. This technique is not generally recommended
for defluxing because there are many substitute processes which are less
polluting and .give better results. / .
It is also possible to dry miscible solvents and recover the drag-out by
using vapour phase drying. This is theoretically possible using any solvent
which mixes with the cleaning solvent and satisfies the criteria in the
previous sections. This is perhaps amongst the most efficient ways to dry off
high boiling point solvents (typically BP >170°C and flash point >85°C). This
can be done with many solvent families but with all the disadvantages of
vapour phase cleaning. In effect, the vapour phase solvent cleans off the
contaminated cleaning solvent. In recent years, it has been proposed to use
HFCs and PFCs, which are greenhouse gases, for this application. As the
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emissions of the polluting vapour phase solvents are always more than finite
and there are other ways to achieve similar or better results for electronics
cleaning and drying, it is not a recommended process.
The Solvents, Coatings and Adhesive.s Technical , Opt ions Committee does
.not recommend vapour phase drying of heavier solvents using HFCs and PFCs in
the electronics industry, under the terms of Multilateral Funding.
The use of vapour phase drying of non-miscible solvents is most commonly
applied to water. It is exactly the same as the previous case except that
there is one intermediate step between the cleaning and drying operations.
This involves wetting with some form of third solvent which is miscible or can
be made miscible with both the cleaning and drying solvents or displaces the
cleaning solvent. One way of doing this, with water as the cleaning solvent,
is.to use an oxygenated hydrocarbon solvent such as a light, alcohol or a
heavier diglycol ether. This will dissolve the residual water and the
resultant mixture can be dissolved in the drying solvent. Another method is
to use an intermediate bath of the same solvent as the drying solvent to which
some surfactant is added: To'displace, water from,a part, a light aromatic
hydrocarbon may be used, such as toluene (with flammability and toxicity
problems to be overcome). Drying water using vapour phase techniques is
neither useful nor viable for ordinary electronics, assemblies, although it may
have applications for some complex optical parts. As it is as polluting as
the last process, it is equally not recommended in this context.
The Solvents, Coatings and Adhesives Technical Options Committee does
not recommend vapour phase drying of water using HFCs and PFCs in the
electronics industry, under the terms of Multilateral Funding.
2.10 CONTAMINATION AND QUALITY CONTROL
There are three factors which must be analysed to ensure sufficient
quality in relation to the job to which the .soldered and possibly cleaned
assemblies will be put and to the expected lifetime. These include the
following:
Is the soldering quality sufficient that the rate of retouching is
small and that the risk of breakdowns due to faulty soldering is
negligible? ~
Is there any likelihood of electrical failures due to the presence
of contaminants causing corrosion or leakage during the expected
lifetime of the assembly under the expected worst conditions of
service?
11 All vapour phase drying processes emit CFG, HCFC, HFC or PFC Vapours.
Where these are not already restricted, they may be the subject in the future
to restrictive legislation designed to curtail emissions of "global warming
gases" which may be a cause of climate change.
12 All vapour phase drying processes emit .CFC, HCFC, HFC'or PFC vapours.
Where these are not .already restricted, they may be the subject in the future
to restrictive Legislation designed to Curtail emission's of "global warming
gases'" which may be a cause of climate'change.
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Is the total process arranged so that the production, quality'can
be constantly monitored and, if necessary, corrected and is it
likely to introduce by itself problems which can upset later
quality controls as well as in service?
The first two of these questions relate directly to . the reliability of the
product. The third one is an internal production problem which is not always
evident. One simple example is that if a "No-Clean"'soldering flux with a
high level of residues is used, automatic testing may be upset by contact
problems. .
As a general rule, the third question is answered by a series of
empirical trials. These trials are usually on-going until the whole
production line runs smoothly. The first two questions are answered by three
forms of instrumentation.
2.10.1 Solderability testers
There are several types of solderability tester available on the market.
The. most usual one uses the "wetting balance method". There are two variants,
using a solder bath and a globule. The first-named is most generally useful
for printed circuit boards and wired components whereas the latter type is
certainly indicated for surface-mount chip components, but can also be used on
some other component types. Some instruments have interchangeable solder
sources. All incoming components, .including .PCBs, should be tested to ensure
good solderabil.ity and this is especially important with "No-Clean" processes
where operating windows are often so narrow that a small reduction of
solderability will create catastrophic problems.
2.10.2 . Ionic contamination testing
Ionic contaminants are those that are most likely to cause electrical
problems in an assembly. With "No-Clean" processes, there is a deliberate
introduction of ionic contaminants that is hopefully- controlled by the process
parameters and thus rendered more-or-less relatively harmless. Ionic
.contamination testing after such a soldering process is meaningless. On the
other hand, it is very important to test incoming components and PCBs with an
adequate instrument because any contaminants will pass through the process and
produce any one or more of three effects:
they may upset the soldering process
they may up-set the careful balance of the flux residues, causing
poorer electrical quality and corrosion
they may be the cause of a definitely shorter lifetime of the
assembly under service conditions.
This is therefore an essential element' of "No-Clean" techniques relating to
quality.
Where cleaning is carried out, testing of incoming components may.be
often dispensed with because the soldering processes are usually more tolerant
of .minor solderability problems and any incoming contaminants should be at
least partially removed during the cleaning process.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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When CFC-113 azeotropes were used for cleaning, the process was
relatively "fail-safe". This meant that inadequate cleaning often resulted in
a slight drop in quality. This is not the case with most substitute methods.
Ionic contamination testing is the preferred QC aid to ensure that the quality
is maintained at an acceptable level and is a "must" for most users. Low-cost
process-control instrumentation is therefore becoming available as well as the
very sophisticated testers, which have been available for many years.
2.10.3 Surface insulation resistance and electromigration testing.
SIR testing has been largely ignored as a means of quality control until
recently but is often used as a qualification procedure for methods. New
variants have contributed to its being adopted as a production test with
accelerated test times of about 8 hours'. This is aided by the relatively
recent introduction of new automated test instruments -which take the
difficulties out of the practical measurement.
Such SIR test techniques are an extremely good complement to ionic
contamination testing, but it is emphasised that each gives part of a total
picture with almost no overlap. On occasion, either may indicate dangerous
conditions of residual contamination that the other could never even detect.
They are usable after all types of cleaning process and after "No-Clean"
soldering. They are especially useful after aqueous cleaning methods.
2.. 11 PHOTORESIST DEVELOPMENT
In the. 1991 Solvents TOC Report (UNEP 1991), a detailed section was
published on the problems of developing dry film resists used for etch,
electroplating and solder masks with 1,1,1-trichloroethane. This is a niche
application in the printed circuit manufacturing industry.
Dry film resists were introduced in the late 1960s and they quickly.
found a ready and wide market for some applications. They were initially all
1,1,1-trichloroethane-developed. They supplanted wet resists for most PCB
manufacturing applications. The process caused both considerable OD solvent
emissions, as the solvent was sprayed, and water pollution, as there was
solvent drag-;out into a final water rinse.
By the mid-1970s, aqueous-developed dry-film resists became available.
These were slow to become popular as the process was initially more difficult
to master and the reject rate was higher. These early problems were overcome
and, by 1980, probably over half of the dry film resist .used, of all types,
was aqueous-developed, with an ever-increasing proportion.
By the mid-1980s, aqueous methods were used for over 90% of etch and
plating mask applications and 75% for solder resist applications. The
remaining solvent-developed operations were generally, reserved for state-of-
the-art applications, where the fine-line qualities of aqueous methods were
perhaps at the limit of the technique.
Today, there are substitutes available for 1,1., 1-trichloroethane- .
developed dry-film photoresists for all applications:
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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a. Etch and plating resists:
aqueous-developed dry film photoimaging resists
aromatic solvent-developed wet-film photoimaging resists
aqueous-developed wet-film photoimaging resists
fine-line silk-screening UV-curing resists
fine-line silk-screening thermal-curing resists
b. Solder resists: >
aqueous--dev. dry-film photoimaging (not universal)
curtain-coated HC-developed wet-film photoimaging
curtain-coated aqueous-developed wet-film photoimaging
screen-coated HC-developed wet-film photoimaging
screen-coated aqueous-developed wet-film photoimaging
fine-line silk-screening UV-curing resists
fine-line silk-screening thermal-curing resists
For further details and a more technical discussion on this matter,
please refer to the 1991 Solvents TOG Report (UNEP, 1991). .
There is no technical nor economic reason why 1,1,1-trichloroethane-
developed dry-film photoimageable resists of any nature should continue to be
used:' there is a wide choice of substitutes suitable for all applications. '
2.12 SUMMARY
The electronics industry,, which was heavily dependent on ozone-depleting
solvents until recently, is fortunate to have a wide range of substitute
materials and processes available, there is no technical reason why any
company, large or small, in a developed or developing nation, should not be
able to move away from such solvents immediately. Economical considerations,
reported in previous editions of the Solvents TOC Report (UNEP 1989, 1991),.
have shown that most substitute processes for this industry are'less costly, to
run and, most often, give improved technical quality. On the other hand, a
relatively large capital investment is sometimes required to obtain the
required results. This could be an obstacle, especially for small.companies
manufacturing "hi-tech" electronics. However, even with heavy amortisation
costs, most of these processes can be economically and technically viable.
A number of secondary problems have arisen. One of the most important
is the fact that most information has been published only in English. English
is the most common language in the electronics industry, although it may be
poorly understood, especially in developing nations. This .is a severe
difficulty which can be overcome only by close cooperation between English and
non-English speaking experts. "Hands-on" experience is 'also essential. It
may be useful to publish a series of simple pamphlets (say, up to'16 pages) on
single subjects written in English by experienced engineers. These could be
distributed to developing nations where local engineers could translate them
into the local language. Then they could be published and distributee! free-
6f-charge throughout the local industry. The total cost of this could be less
than that of a single mistake in equipment or process selection.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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To substitute for CFC-113 in defluxing, there is.a large choice of
processes, equipment and materials commercially available for production units
of all sizes. Considerations of economic and technical viabilities under
individual conditions may limit the choices. Where there, are no technical
specifications that require post-solder cleaning, "no-clean" techniques are
often the'most economical. This technique is recommended where the
reliability criteria can be met. Where cleaning is a requirement, the use of
water-soluble chemistry has generally proved to be preferable to most of the
other processes, although it is not a universal solution. There is an
adequate choice of other techniques where neither of these can be applied.
The choice of substitute methods should be subordinate to environmental
considerations. Due to their harmful environmental effects, the following
processes should not be selected for electronics manufacturing without a very
imperative reason, especially as there are usually^ more benign processes
available that will do the same job. The Solvents, Coating and Adhesives
Technical Options Committee does not recommend the following processes in
electronics manufacture for funding under the provisions of the Montreal
Protocol Multilateral Fund:
HCFO-141b for defluxing printed circuits
Vapour-phase reflow soldering
Vapour-phase drying of heavy organic solvents using PFCs
Vapour-phase drying of water using MFCs or PFCs.
Another factor which has become evident only, in recent years is that the
"operating window" of some substitute processes, including "No-Glean" ones, is
considerably narrower than that of traditional ones. If the process is not
perfectly mastered, this^ may result in very significantly increased operating
costs for rework. One of the parameters which can greatly influence the width
of the "operating window" is the design of the assembly being processed. The
design itself should be optimised for the process which will be used in the
subsequent manufacture. Changing from one process to another may require a'
re-design. Fortunately, some of the better CAD systems permit, this switch
very rapidly by simple word processing in text library definitions of the
component "footprints" and in the rules file.
Finally, there are no technical obstacles for a complete and rapid
phaseout of ozone-depleting solvents in the electronics industry in developing
nations, as well as developed ones. In almost every case it is possible to
find substitutive processes that result in significant production cost
savings, although they may require a considerable capital expenditure.
Amortisation of a correctly-chosen investment is typically one to three years
but may require longer periods in exceptional cases. In a few cases, there
may be increased energy requirements, but the cost of this will be more than
offset by other production cost savings.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CHAPTER 3
PRECISION CLEANING APPLICATIONS
3.1. BACKGROUND
Precision cleaning applications are characterized by the high level of
cleanliness required to maintain low-clearance or high-reliability components
in working order. They are used in.a variety of manufacturing industries,
such as in aerospace, microelectronics, automotive, and medical. The primary
factor that defines the applications where a precision cleaning process is
required is high standards for the removal of particulates or organic residue.
There are many types of contaminants that might be required to be
removed in a precision cleaning process. These contaminants are generally
divided into either particulate contamination or npnparticulate contamination.
Particulate contamination is the type of contamination usually resulting from
a preceding manufacturing process,: such as cutting, drilling, grinding, or
buffing of component parts. Nonparticulate contamination is usually composed
of organic residue, such as machining oils, waxes, finger print oil, and so
forth.
As the term suggests, precision cleaning involves the cleaning of
components to a high standard of cleanliness. One example of the cleanliness
required for a precision-cleaned component is provided in Figure III-l, which
shows the dimensional clearance on a computer disk drive.relative to the size
b,f various contaminants. Tight dimensional clearances require the removal of
small particles that become lodged between the two surfaces.
The factor that made CFC-113 the precision cleaning solvent of choice is
its remarkable chemical stability (manifested directly in its compatibility to
structural materials), its low toxicity, and zero flammabil'ity. This has
allowed closed, superclean, white-room assembly areas to be operated safely
and effectively. Probably the most essential example of solvent compatibility
is provided by CFC-113 in cleaning beryllium, particularly in the inertial
sensor industry. As the performance requirements of gyros .increased for both
defence and aerospace applications, the need for a structural material that
combined low density with high dimensional stability also increased. Hot
pressed beryllium has provided that material with a range of properties unique
among materials. It has one distinct disadvantage -v- chemical reactivity,
especially with ionic chlorine. The viability of CFC-113 as a pure, stable
solvent has allowed beryllium to be widely used as a structural material. It
should be noted, however, that mixtures of CFC-113 with methanol will attack
beryllium very vigorously.
\^
1,1,1-Trichloroethane is the solvent of choice in some precision
cleaning applications. Several of its physical properties -- higher
solvency, moderate evaporation rate, and higher boiling point -- make it a
unique product for cleaning some soils, such as heavy grease.
* 1994 UNEP SOLVENTS, COATINGS, AND'ADHESIVES REPORT *
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Figure IU-1
SIZE COMPARISON OF COMPUTER DISK DRIVE HEAD
CLEARANCE WITH VARIOUS CONTAMINANTS
JJJJJJJJJJJJJJJJJJJJ
J-1-JJJJJJJJJJJJJUJJJJ
JJJJJJJJJJJJJJJJJJJJ
JJJ-J-IJJJJJJJJ-IJJJJJJ
J-l-iJJJJJJJJJJJJJJJJJ
i- -; j-i J-l-i j j J JJJ J_i_l _l J,
EDGE OF FLYING HEAD
FLYING HEAD
HEIGHT = 15-45
MICRO IN
HUMAN HAIR
.003 IN. DIA.
L1MT AND DUST
SMOKE PARTICLE
950 MICRO IN. DIA.
FINGER
PRINT
SMUDGE
OXIDE COATING (200 MICRO IN.)
ALUMINUM SUBSTRATE SURFACE
S1I02S-1
Source: Digital Equipment Corporation
S18028-1
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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A number of companies have successfully tested and are currently using
CFC-113 and 1,1,1-trichloroethane alternatives to clean precision instruments.
Companies also are implementing conservation and recovery practices to reduce
solvent use in the short-term. Possible alternatives include solvent and
nonsolvent options. Solvent options include aqueous and semi-aqueous,
alcohols, perfluorocarbons, synthetic aliphatic hydrocarbons,
hydrofluorocarbons (HCFCs) and their blends, and other miscellaneous solvents.
Nonsolvent options include supercritical fluid cleaning, UV/Ozone cleaning,
pressurized gases, and plasma cleaning. Although much testing still needs to
be done for specific applications,1 the Committee consensus is that
alternatives will be substituted for CFC-113 and 1,1,.1-trichloroethane in
virtually all precision cleaning applications by the year 2000.
3.2 CFC-113 AND 1.1.1-TRICHLOROETHANE USE IN PRECISION CLEANING APPLICATIONS
3.2.1 Precision Cleaning Processes and Equipment
To describe "precision cleaning", in a simple succinct way,is difficult.
To overcome this difficulty an integrated manufacturing system is described in
which the differences in "metal cleaning" and "precision cleaning" become
apparent by the nature of the components and the cleaning process.
Figure III-2 shows a diagram containing both metal cleaning (parts
manufacturing) and precision cleaning (clean room assembly) processes. In the
parts manufacturing segment, parts are manufactured, deburred, gauged, cleaned
using 1,1,1 trichloroethane, and stored. In the eleanroom assembly areas,
parts and components are passed through a preliminary "goods inwards" cleaning
process using CFC-113 and then into final assembly and test. In the final
assembly stages, mostly manual, multiple operations are carried out on a given
item and the parts are repeatedly cleaned using CFC-113, during and after each
assembly stage. When complete the finished item is passed through
"acceptance" testing and inspection and then delivered either to detailed
functional testing or directly to the customer. Functional rejects, occurring
during acceptance testing are often torn-down, recleaned, and returned, to the
assembly process.
In the first stage, parts manufacturing, single' parts will be formed by
machining, stamping, pressing, etc. The cleaning requirements include the
removal of burrs and other mechanical residues as well as the removal of gross
residues of machining oils or other processing residues. In this stage,
vapour degreasing with 1,1,1-trichloroethane was a common practice.
Within the clean room assembly area, CFC-113 cleaning would normally
follow. Its particular properties .of nonflammability, low toxicity, and low
odour allow it to be used in small cleaners within laminar flow cabinets or in
bench top units close to the operator's working position. Typical'devices
made in such areas usually contain a wide range of materials. In addition,
many items are fixed using synthetic resins, local soldering operations on
custom-built hybrid devices are required, and many solvent sensitive polymers
1 Testing heeds to be done not only to determine -cleaning effectiveness
but cost and environmental effects as well.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Parts Manufacture
Figure ut-z
Metal Cleaning and Precision Cleaning
Clean Room Assembly
Machine
Room
Degrease
Store
ource: Chem Systems 1989
Currept
1,1,1 TCA
future
Semi-
Aqueous
Deliver
Current
CFC-113
Future
Alcohol or Hydrocarbon
BRITISH AEROSPACE
DEFENCE
SI8028-I
* 1994 UNEF SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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such as polycarbonate and polyether sulphones can be used. The availability
of CFC-113 has obviously been vital in such an operation.
Replacement of currently used solvents is relatively easy in the
"general cleaning" stage of manufacture. Because the basic components are
usually one part-items, they can be cleaned very effectively using
alternatives such as aqueous and semi-aqueous systems. If this system is
incompatible with the parts, due to corrosion sensitivity or shape
limitations, then solvents such as alcohols, HCFCs, and hydrocarbons can be
used, particularly with closed-type cleaning equipment now available to
minimise solvent emissions.
Introducing alternative cleaning materials or processes is particularly
difficult in the final assembly precision cleaning area. This is not due to
the nature of the soils involved, but due to the wide range of materials used
in the manufacture of the assemblies and the small clearances and complexity
found in such devices.
Thus precision cleaning applications might include:
Assembled units with complex shapes and small clearances
A wide range of metallic and nonmetallic components, including
many elastomeric materials
Blind holes with capillary gaps which make evaporation of low
vapour pressure fluids such as water impossible.
Such work pieces are not always small; complete auxiliary power
generators and military aircraft generators can be immersion cleaned using
CFC-113 during maintenance operations, thus avoiding costly and risky
disassembly and reassembly of the units. Alternative cleaning materials or
processes, therefore, are required to have low surface tension, low viscosity,
and relatively high vapour pressure. Alternative processes must be designed
with new cleaning and drying technologies to be used with aqueous and semi-
aqueous cleaning systems.
In the past, standard vapour degreasing equipmentwas used in precision
cleaning processes. The equipment is usually comprised of a boiling sump,
cooling coils, and a clean rinse stage with ultrasonic generators. These
units were often fitted with mechanical handling equipment and installed at
the incoming location adjacent to clean areas so that parts, sub-assemblies,
and proprietary components could be cleaned and rapidly sealed in bags prior
to transfer to the clean room assembly area. Within clean room assembly
areas, smaller CFC-113 and 1,1,1-trichloroethane vapour degreasers with
ultrasonic generators were often installed close to inspection and assembly
areas so that local batch cleaning could be performed.
Bench-top ultrasonic cleaners are used in clean rooms and are often
installed within laminar flow boxes. These ultrasonic units are cold cleaners
in which water is used as the energy coupling medium. Clean glassware
containing a small volume of CFC-113, 1,1,1 trichloroethane, or other
nonflammable solvent is placed in the water such that ultrasonic energy can
agitate and clean the individual components when they are placed in the
solvent. This type of cleaning has a high loss to evaporation; 100 percent of
the evaporated solvent is lost to the atmosphere because there are no cooling
coils -or other- forms of vapour containment or collection. Often this
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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technique is combined with particle counting in which all of the solvent is
microfiltered after cleaning so that the contaminant particles may be counted
under a microscope. , .
Gyroscope flushing tools are dedicated systems designed specifically for
a particular gyroscope. Coupling fixtures attach these tools to the gyroscope
shell. Clean .CFC-113 is forced through the gyroscope via ultra-filters under
pressure in an open-ended process to remove flotation fluid during rework or
to clean an assembly before filling it with oil.
Hydraulic system flush and spray booths are similar to gyroscope
flushing tools but are larger. The flush mechanism pumps CFC-113 through the
hydraulic systems to remove hydraulic fluid. These cleaning machines often
have hand-held spray cleaners for manual cleaning of valve seats. Many are
100 percent evaporative systems in which the solvent evaporates and is removed
from the work areas by extraction fans. Similar techniques are used in the
refrigeration industry to flush out systems before filling.
3.2.2 Precision Cleaning Applications
*
Precision cleaning is discussed in this report in terms of the following
engineering applications: cleaning precision instruments during
manufacturing, testing or assembly; cleaning during specialised manufacturing
techniques; and maintenance and repair cleaning.
3.2.2.1 Cleaning Precision Instruments During Manufacture, Assembly.
and Testing -
Precision cleaning is used to remove contaminants from delicate and
complex instruments such as computer disk drives, inertial guidance systems
(gyroscopes), hydraulic control systems, optical components, and micro-
switches. Traditionally, CFC-113 has been effective in precision cleaning the
following delicate instruments. '
Disk Drives. Disk drives are magnetic storage devices that store
information in computer systems. Disk drives have a very small tolerance for
contamination during assembly. Normally, the record/read head is spaced from
0.813 to 1.143 microns above the recording media surface of the disk
substrate. To place this distance in perspective, smoke particles typically
are on the order of 6.3 microns in diameter. Contaminants must be controlled
at the submicrometer level for the drives to work effectively (Felty 1991).
Possible cleaning alternatives for disk drives include ultrapure water, semi-
aqueous processes, and organic solvents.
Gyroscopes. Precision cleaning is used to clean the mechanical
components of inertial systems, including gyroscopes and accelerometers.2
Parts are repeatedly cleaned at all stages of component assembly to remove
handling contamination and particulate material. Repeated cleaning is
2 Inertial guidance systems or gyroscopes, include rate gyroscopes,
displacement gyroscopes, and rate-integrating gyroscopes. .Displacement
gyroscopes typically are used in autopilots. Rate-integrating gyroscopes are
used in precise inertial navigation systems in missiles, satellite controls,
commercial aircraft, and underwater systems.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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important in gyroscope gimbal assemblies because suspension bearings
lubricated with solid film are sensitive to solid particulate contamination.
Cleanliness helps to assure torque values of a few microgram (mg) centimetres.
To reduce precessional drift, components have often been cleaned in small
ultrasonic cleaners using CFC-113.
In rate-integrating gyroscopes, the flotation fluid surrounding the
inner gimbal is a poly (trifluorochloro) ethylene. When the viscosity of the
fluid must be changed, secondary fluoropolymers are added. Typically this
fluid is poly (l.l-difluoro)ethene. Other fluorinated, high density
materials, such as perfluorotrialkylamines, are also used in the assembly and
testing stages. A related advantage of CFC-113 is its solubility of these
high density polychlororofluoroethylene and polychlorobromoethylene compounds.
These compounds are not soluble in common solvents.
Although the floated gyroscope' technology is being superseded by solid
state, optical systems, commercial and military gyroscope equipment will
remain in service for many years. Because these gyroscopes need to be
serviced and maintained, there is a long-term requirement.for compatible
solvents for manufacturing spare sensors and gyroscopes arid for cleaning
existing units.
Possible cleaning alternatives for gyroscopes include nonozone-depleting
chlorinated solvents, organic solvents, hydrofluorocarbons (HFCs),
hydrochlorofluorocarbons (HCFCs), aqueous processes, supercritical fluids, and
perfluorocarbons (PFCs).
Hydraulic Control Systems. Hydraulic military vehicle control systems
have control valves with extremely small diameter bores as well as parts such
as 0-ring seals and gaskets made of elastomers. These systems are flushed to
remove the working fluid and to remove all particulate contamination during
assembly, after functional testing, and during field maintenance. CFC-113 has
traditionally been the solvent of choice because of its chemical stability and
noncorrosive properties. Smaller tactical weapon systems often use a gas
control system in which a source of high pressure gas, either chemically
generated (e.g., extruded double-based propellent) or a "cold" compressed gas
such as nitrogen at 3.56 x 107 N/M2, controls the actuator systems' valves.
Gas controls require extreme cleanliness as they are sensitive to particulate
contamination. Gas control systems are pressure tested, and water often is
used as the test fluid. Many hot'gas control units have long blind holes from
which it is difficult to remove water by oven evaporation. Water-displacing
mixtures based on CFC-113 effectively dry these systems.
Possible alternatives for hydraulic control system cleaning include
alcohols, supercritical fluids, and gas plasma.
Optical Components. CFC-113 solvent and alcohol azeotrope or surfactant
solvents along with 1,1,1-trichloroethane are widely used in cleaning and
fixturing processes during grinding and polishing operations and prior to
applying vapour deposition coatings in optics fabrication. The surface
cleanliness of glass and metal optical elements are critical to ensure '
adequate adhesion of optical coatings and freedom of movement in low torque
pivots with small clearances.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Solvent cleaning has been an integral part of the manufacturing cycle
for optical components. Solvents used included 1,1,1-trichloroethane,
trichloroethylene, CFC-113, CFC-113 with the azeotropes of methylene chloride,
acetone, methanol, ethanol and CFC-113 dispersions with water and surfactants
as well as individual solvents as methylene chloride,, acetone and methyl,
ethyl, and isopropyl alcohols. Historically solvents have been the preferred
method due to their speed of soil removal, known material compatibility, lack
of residual contamination, ease of use, and low cost. Regulatory changes in
purchase and disposal of these materials is dictating a change to alternative
cl'eaning techniques. These changes will not be without their associated
problems.
Typical part holding (blocking) techniques are used during precision
optical grinding and polishing operations utilizing rosin and paraffin-based
waxes, pitches, and some cyanoacrylate adhesives. In particular, the waxes
and pitches are used for their ability to conform and hold to a variety of
irregular shapes and surface textures. The blocking technique involves
heating the part and tooling, applying a layer of wax to the tool surface,
installing the part, and then allowing the tool to cool before subsequent
processing. The waxes and pitches are also nonreactiye with water-based
coolants and slurries used during the grinding and polishing of optical
elements. Cyanoacrylate adhesives are used during a limited number of
operations where precision tolerances.are required, but are limited by their
ability to withstand the dynamic loading and shocks encountered during some of
the manufacturing procedures.
After processing, part removal is similar to the blocking technique.
The tool is heated, the blocking wax or pitch softens or melts, the part is
removed and both part and tool are cleaned. The use of a solvent vapour
degreaser allows streamlining of the cleaning sequence since all operations
can be performed in a single machine. When the parts/tools are removed from
the degreasing operation, they are clean and ready for additional processing
steps such as vapour deposition of specialized coatings.
The use of cyanoacrylates as blocking agents requires some form of
solvent cleaning to remove all residues prior to additional processing. Much
of this cleaning is performed in soak hoods where the contaminated optical
element is immersed in solvent or where direct manual cleaning is employed
using acetone. Other processing techniques that are dependent on the use of
solvent cleaning are the application of protective coatings used during
fabrication operations to protect finished surfaces. The current selection of
coatings used are solvent based and are resistant to water, again a
requirement due to the use of water-based coolant and processing fluids.
Some water-based cleaning is currently in use for rough cleaning
operations prior to final, fine cleaning operations. Problems have been noted
with residues left after using water-based cleaners prior to vapour deposition
thin film coating operations. The negative impact of these residues on the
adhesive strength of thin film coatings deposited after such operations has
prevented their use in final, fine, or finish cleaning procedures. The .
reduced adhesion and increased propensity for peeling of the coating is
particularly noticeable when completed optical elements are exposed to
elevated temperature and humidity conditions.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Water-based cleaners also suffer from material compatibility problems.
There are well over 100 types of visible glass and infrared materials
(germanium metal, etc.) used in precision optical elements. The need for
precise process control, minimization of staining on optics, difficulties with
rinsing and drying (formerly used chlorofluorocarbons (CFCs)), and equipment
reliability problems associated with utilization 'of aqueous cleaners have
forced manufacturing in'many instances to return to manual final
cleaning/drying operations utilizing acetone and alcohol solvents to replace
CFCs.
The change from solvent cleaning' to alternative methods will require
significant process changes in the future to completely remove CFCs and 1,1,1-
trichloroethane from the precision optics manufacturing process. Blocking
materials, protective coatings, and techniques for final cleaning before
coating will require change. Material compatibility, cleanliness, and process
stability will be critical considerations for any replacement cleaning
solvent. . .
/
HCFCs may provide an alternative for final cleaning operations after wax
and other blocking and grinding/polishing residues have been removed. Testing
(Schaefer and Scott 1991) has indicated that the three-carbon HCFC-225 solvent
is equivalent to CFC-113 in its ability to provide final cleaning before and
after vapour deposition coating operations without introducing stains due to
solvent evaporation. Cleaning equipment used for CFC-113 can also be used for
HCFC-225 because the boiling point is slightly, higher than'CFC-113. It is
important to'operate the equipment, however, with a recovery system to
minimize solvent emissions (Yamabe 1991).3 Newly designed, closed-type
equipment is also available to reduce solvent emissions. Initial testing has
shown the HCFC-225 to exhibit very poor solubility with the typical blocking
waxes and pitches used in the optics manufacturing operation; solvent blends
and new soluble blocking 'materials are being developed to overcome this
"difficulty. In order to use HCFCs throughout the fabrication cycle, new
compatible (soluble) blocking materials will have,to be developed.
Recently, manufacturers of .glass-based optical elements have shifted
away from CFC-113 cleaning solvents.. The use of chemically inert CFC-113
solvents is critical for metal-based optical elements such as highly polished
or diamond turned (machined) aluminum reflective elements. The highly
sensitive metal surfaces are extremely reactive in a fresh, nonoxidised state,
and cleaning with substitute chlorinated' solvents would detrimentally affect
the metal. HCFC-225 has also been evaluated as,replacement for CFC-113 (in
part due to similar boiling points) in this operation and found to be
compatible with the freshly machined surface and capable pf final'cleaning of
such surfaces without generating stains during solvent flash-off.
Other alternatives, known as hydrofluorocarbons (HFCs) and
perfluorocarbons (PFCs), have been developed for use in the precision cleaning
of optics as well. PFCs are currently commercially available., and HFCs are
expected to be available commercially in the next one to two years. Both HFCs
and PFCs exhibit low reactivity, vapour pressures similar to that of CFC-113,
and relative nonflammability. PFCs. have been used for many years as
3 HCFC-225ca and cb have been registered in EINECS, Toxic Substances
Control Act (USA) and in Japan.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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insulating and drying fluids, although the use of PFCs in emissive l
applications such as solvent cleaning is limited. Both HFCs and PFCs, which
do not contribute to stratospheric ozone depletion or to the formation of
tropospheric ozone (smog), have been identified as global warming compounds..
PFCs are more potent global warmers than HFCs because their atmospheric
lifetimes are significantly longer than those for HFCs. Newly designed
equipment is available to aid potential users of either PFCs or HFCs. .The new
equipment is vapour-tight and usually includes options for solvent filtration
and recycling within the unit.
Gas plasma cleaning has become more popular in the mid-1990's for
general precision cleaning of organic contaminants based on the use of the
technology developed in the electronics industry in the 1980's. Gas plasma
cleaning requires the use of oxygen, carbon tetrafluoride/oxygen, or other
gases, to remove trace amounts of organic material. The gas plasma is created
when normal gases are excited above their normal energy levels. The
excitation of the gases results in the creation of excited oxygen molecules,
which then react and oxidize organic molecules to form carbon dioxide and
water vapour. Gas plasma cleaning will damage all amorphous carbon-based
materials and therefore .should not be used with components containing
.plastics. This type of cleaning finds its way into all of the cracks and
crevices of a particular component and is ultimately removed by creating a
vacuum on the cleaning chamber. Waste disposal is generally not a concern
with gas plasma cleaning as the waste components are only the small amounts of
contamination or dirt collected in the gas plasma air filter.
Pressurised CFC-113 is also used for cleaning dust and particles from
high definition cathode ray tube shadow works and electron guns. CFC-113
solvent is very efficient as the high specific gravity allows nonmetallic
particles to be floated off precision parts (Nemoto 1989).
In the past, CFC-113 was used in many drying operations to prevent
streaking and water spot deposition on pre- and post-coat'ed optical element
surfaces. Many of these applications, however, have been replaced with high
vapour pressure organic solvents. In such applications, since these materials
are considered volatile organic compounds (VOCs), vapour retention is critical
to prevent the emission of solvent vapours to the atmosphere 1
Possible alternatives for optical component cleaning include
supercritical fluids, high-purity alcohols, HCFCs, and PFCs.
Electrical Contacts. Micro-switches used for critical switching
functions require extremely clean contacting surfaces. CFC-113 often is used
to clean these surfaces. The switches also can be cleaned using CFC-113 after
assembly to remove particles or oily.material deposited during assembly.
Most electrical contacts in connectors, slip-rings, potentiometers,
microswitches, and relays have precious metal contacts such as gold, gold
alloys, and platinum metals. Precious metal contacts are used in the defence
industry where "single shot" devices require a^long storage life (up to 15
years) and must operate .with greater than 99 percent reliability. High
surface contact resistance is a problem as many of these devices are closed
"cold" (i.e., without an applied voltage) because of safety requirements. In
the past these specifications were met by CFC-113 cleaning. CFC-113 also was
used to clean sliding contacts such as slip rings and potentiometers.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT, *
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Possible alternatives for electrical contact cleaning include
supercritical fluids, gas plasma, HCFCs, high purity organics, and nonozone-
depleting chlorinated solvents.
Medical Equipment Applications. The small blind holes increasingly
found on complex surgical equipment have made it difficult to remove the water
from this equipment.4 A majority of surgical instruments were first dried
using CFC-113 water-displacing materials and then were sterilised.
Orthopaedic prostheses such as hip joints and knee joints are cleaned and
dried using a similar process. CFC-113 was also used to clean pipe-runs,
bedside control systems, and main control panel equipment after installation
and during maintenance cleaning of hospital piped-oxygen systems. HCFCs and t
PFCs can now be used to clean and sterilize these systems. The high
volatility and nonflammability of CFC-113/ HCFCs, and PFCs allows the flushing
solvent to be blown through the oxygen system without risk of explosion.
Vacuum drying can be used to' eliminate any risks of leaving trace amounts of
solvent. The chemical stability of CFC-113, HCFCs, and PFCs and the absence
of stabiliser chemicals helps ensure that organic contaminants can be removed
from the metal parts of the oxygen systems without risk of corrosion.
V . '
Possible alternatives for the cleaning of medical equipment include
supercritical fluids, gas plasma, high-purity alcohols, HCFCs, PFCs, organic
solvents, and vacuum drying. ' ' .
Plastic Assemblies. CFC-113 was'used to remove mould release agents
from a variety of plastic mouldings such as ABS electronic cabinet mouldings,
domestic white goods accessories, medical parts, syringes, spoons, bottles,
and sample vials. The advantage of using CFC-113 in this application is that
there is no risk of surface attack or "crazing," which could occur if other
solvents are used without considering material compatibility issues.
Possible alternatives in this applications include nonozone-depleting
chlorinated solvents and organic solvents where compatible.
3.2.2.2 Specialised Manufacturing Techniques
Precision cleaning also is a component of specialised manufacturing
techniques such as auto-rivetting of commercial aircraft wings and precision
application of special lubricants. .These options are also discussed in
further detail in Chapter 9: Other Uses of CFC-113 and 1,1,1-trichloroethane.
Auto-Rivetting. Commercial aircraft wings often are used as fuel tanks.
These wings, therefore, must be of minimum weight and maximum strength, have a
long corrosion-free life, and be fuel tight. Auto-rive'tting is used to meet
these requirements.5 Traditionally, major aircraft companies have used CFC-
113 for auto-rivetting because the stock being drilled for commercial aircraft
4 In the past, surgical instruments were dried after washing and then
sterilized in hot air ovens.
5 In this process, the wing skins are clamped to the stringers, a double
counter sunk hole is drilled through both components, and an appropriate rivet
slug-is placed, into the bore and the head machined flush with the outer wing
surface.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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wings is much thicker than that on the wings of fighter aircraft. A
proprietary CFC-113 solvent blend is sprayed on the drill tool during cutting
and on the rivet slug as it is placed into the bore. Although the rivet slug
is anodised, the freshly drilled bore surface is not protected. The solvent
spray protects the assembly as it is formed and frees the joint of entrapped
moisture or acidic components that might encourage corrosion. The solvent
rapidly evaporates and helps cool the form.
A possible alternative for this application is the use of rivets with
dry film lubricants.
Application of Special Lubricants. The surface of miniature precision
bearings is coated with a thin oil film. T9 ensure that the film remains
stable over many years of storage life, a lubricant such as a CFC-113 solvent
solution is sometimes applied to the bearings. The low surface tension of
CFC-113 solvent allows the solution, to "wet" the bearing almost instantly.
The rapid solvent evaporation leaves a film of oil on the bearing surface.
Perfluoroether and cyclopentane-based lubricants, which are used in some space-
applications due to their extremely low vapour pressure and flat temperature -
'viscosity curve, use CFC-113 as a carrier for thin film application and to
clean bearings as these lubricants are only soluble in a select few organic
solvents.
3.2.2.3 Maintenance Cleaning and Repair
Maintenance precision cleaning applications include avionics equipment,
glove boxes in the nuclear industry, electronic sensors associated with
offshore oil rigs such as remote cameras and well loggers, and reticles used
to manufacture semiconductors.
In the past, large commercial airline workshops used large amounts of
CFC-113 solvents to clean avionics equipment.6 In the nuclear power
industry, pieces of ancillary equipment that become contaminated with
radioactive dusts are removed in glove boxes using remote handling systems.
With continued use, the boxes themselves become contaminated. Glove boxes can
be decontaminated by spraying with CFC-113 to remove radioactive dusts. The
low surface tension and high volatility of CFC-113 provide good wetting and
penetration for particle removal. The low flammability and low toxicity of
CFC-113 were the main reasons for using CFC-113 on offshore oil rigs where
CFC-113~was used to clean sensors such as remote cameras, drill head attitude
indicators, and well loggers. Pressurised CFC-113 was used for cleaning dust
and particles from reticles used during the manufacture of semiconductors.
The reticle is a patterned glass plate through which light is directed on
wafers to create circuitry. CFC-113 solvent is very efficient as the high
specific gravity allpws nonmetallic particles to be floated off reticles
(Nemoto 1989).
. ' 6 Larger aircraft components are cleaned using other chlorinated solvents
such as trichloroethylene and perchloroethylene in vapour degreasers and
1,1,1-trichloroethane in cold cleaning and vapour degreasing.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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3.3 ALTERNATIVES FOR REDUCING OR REPLACING CFG-113 AND 1.1.1-TRICHLOROETHANE
IN PRECISION CLEANING
CFC-113 and 1,1,1-trichloroethane have evolved as the preferred solvent
cleaning method in precision cleaning because of their chemical inertness; low
toxicity, nonflammability, low surface tension, and low .water solubility.
However, to eliminate CFC-113 and 1,1,1-trichloroethane use, a number of
companies have tested and implemented alternative cleaning methods. Possible
alternatives include solvent and nonsolvent options. Solvent options include
other organic solvents (such as alcohols and aliphatic hydrocarbons),
perfluorocarbons, HCFCs and their blends, and aqueous and semi-aqueous
cleaners. Nonsolvent options include supercritical fluid cleaning, UV/Ozone
cleaning, pressurized gases, and plasma cleaning. Solvent use may also be
reduced by controlled planning of repetitive or multiple cleaning operations.
These alternatives are discussed later in this chapter. ,
Generally, the selection of the most appropriate alternative to either
CFC-113 or 1,1,1 trichloroethane should be made based on a number of factors,
including technical feasibility, environmental, health, and safety impacts,
and cost. Technical feasibility can be predicted by the use of solubility
parameter technology, such as Hildebrand parameters. This process is very
simple and has proven to be accurate in many cases. The basic process
'requires the identification of the solute,^.or contamination, that is to be
removed from a particular surface. Next, the solubility parameter of the
solute is determined and matched to the solubility parameters of hundreds of
common industrial solvents. Several common solvents are selected and the
properties of each should be closely reviewed. Finally, one or two solvents
can be selected for testing on actual hardware. This is a scientific process
on how best to narrow the selection of alternative solvents. For more
information on this process, con'sult "Handbook of Solubility Parameters and
Other Cohesion Parameters",- Allan F.M. Barton, CRC Press.
3.3.1 Conservation and Recovery Practices
Solvent losses are often large in conventional or poorly maintained
plants. In a poorly maintained plant, 20 percent or less of ,the purchased
solvent is generally recovered.
Depending on what measures have already been adopted at a plant,
applications of the guidelines summarized in Appendix C can enable total
emissions to be reduced by up to 90 percent. Solvent losses can be reduced
from 2-5 kg/h-m2 of bath area with conventional practice to 0.2 - 0.5 kg/h-m2
of bath area. For certain alcohol and partially aqueous systems, the overall
base rate of annual loss is around 0.03 - 0.05 kg/h-m2 of bath area.
The recommendations summarized in Appendix C can be implemented to
reduce solvent use in cold cleaning, vapour degreasing, and continuous in-line
cleaning.
3.3.2 Aqueous Cleaning
Aqueous cleaners use water as the primary solvent. Synthetic detergents
and surfactants are combined with special additives such as builders, pH
buffers, inhibitors, saponifiers, emulsifiers, deflocculants, -complexing
agents, antifoaming agents, and others. They provide .multiple options in
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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formulation blending, such as the use of corrosion inhibitors and pH buffers.
Table III-l summarizes the advantages and disadvantages of aqueous cleaning.
The key stages of an aqueous cleaning process are washing, rinsing,
drying, water treatment, and waste recycling/disposal. Although each of these
steps in Figure III-3 is an important and integral part of the aqueous
cleaning system, rinsing and drying may not be necessary in all circumstances
and wastewater disposal may also be integrated into the other steps by
recycling bath contents and the overall water use.
Process Equipment
Aqueous cleaning equipment can be characterized as:
In-line equipment used for high throughput cleaning requirements
Batch equipment used for low throughput such as for maintenance
applications or smaller production processes. The in-line and
batch equipment can be further subdivided into immersion, spray,
and ultrasonic type equipment. Table III-2 summarizes the
advantages and disadvantages of each of these three types of
equipment.
Product design can have a significant influence on cleanability. Choice
of materials and configuration should be reviewed if possible for
opportunities to make changes that can have a major influence on the success
of aqueous cleaning. Care should be exercised to prevent trapping cleaning
fluid in holes and capillary spaces. Low surface tension cleaning solvent
might penetrate spaces and not be easily displaced by the higher surface
tension pure water rinse. Penetration into small spaces is a function of
surface tension, viscosity, and capillary forces.
Water-based cleaning is a more complex process than CFC-113 and 1,1,1-
trichloroethane cleaning. Good engineering and process control are much more
critical to prevent problems. Useful parameters for process control include
bath temperatures, pH, agitation, rinse water quality, and cleaning bath
quality.
Drying presents one of the major challenges to aqueous cleaning for
complex parts and may require considerable engineering and experimentation.
However, there are some aqueous cleaning systems in operation today in
precision cleaning applications that produce spot-free drying. There have
been significant changes in the area of spot-free drying over the last several
years, and there are commercially available systems that will spot-free dry
almost any component.
Aqueous cleaning requires careful consideration of drying.
Thermodynamic or evaporative removal of bulk water is usually not practical
from the perspective of an energy or process time. Mechanical removal of the
water (90 percent or more) can be accomplished in some cases using compact
turbine blowers with filtered output. Design options include variation of
pressure, angle, velocity, and volume. Other sources of air include dedicated
compressors or plant air, but care must be taken to remove oil, particles, and
moisture to the level desired. Economics and.noise reduction are other
considerations in using such options. (Depending on the equipment and plant,
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 7/7-7
AQUEOUS CLEANING
ADVANTAGES
DISADVANTAGES
Aqueous cleaning has several advantages over organic
solvent cleaning.
Safety ' Aqueous systems have few problems with
worker safety compared to many solvents. They
are not flammable or explosive. Toxicity is low for
most formulations, requiring only simple
precautions in handling any chemical. It is
important, however, to consult the material safety
data sheets for information on health, safety, and
environment regulation.
Cleaning -- Aqueous systems can be readily
designed to clean particles and films better than
solvents. '
Multiple Process Options -- Aqueous systems have
multiple process options in process design
formulation arid concentration. This enables
aqueous processes to provide superior cleaning for
a wider variety of contamination.
Inorganic or Polar Soils Aqueous cleaning is
particularly good for cleaning inorganic or polar
materials. For environmental and other reasons.
many machine shops are using or convening to
water-based lubricants and coolants versus oil-
based. These are ideally suited to aqueous
chemistry.
Oil and Grease Removal - Organic films, oils,
and greases can be removed very effectively by
aqueous chemistry.
Multiple Cleaning Mechanism - Aqueous cleaning
functions by several mechanisms rather than just
one (solvency), including saponificatioh (chemical
reaction), displacement, emulsification, dispersion,
and others. Particles are effectively removed by
surface activity coupled with'the applicatipn-t>f
energy.
Ultrasonics Applicability - Ultrasonics are much
more effective in water-based solvents than in
CFC-113 solvents.
Chemical Cost - Low consumption and
inexpensive.
Depending upon the specific cleaning application, however,
there are also some disadvantages.
Cleaning Difficulty -- Pans with blind holes and small
crevices may be difficult to clean and may require
addition of a vacuum dryer.
Process Control - Aqueous processes require careful
engineering and control.
Rinsing --Some aqueous cleaner residues can be
difficult to rinse from surfaces. Nonionic surfactants
are especially difficult to rinse. Trace residues may not
be appropriate for some applications and materials.
Special precautions should be applied for parts
requiring subsequent vacuum deposition, liquid oxygen
contact, etc. Rinsing can be improved using deionized
water or alcohol rinse.
Floor Space - In most instances, aqueous cleaning will
require more floor space..
Drying - For certain part geometries with crevices and
blind holes, drying may be difficult to accomplish. An
additional drying section may be required.
Material Compatibility Corrosion of metals or
delayed environmental stress cracking of certain
polymers may occur.
Water.-- In some applications high purity water is
needed. Depending on purity and volume, high purity
water can be expensive.
Energy Consumption -- Energy consumption may be
higher than solvent cleaning in applications that require
heated rinse and drying stages.
Wastewater Disposal ~ In most instances use of
aqueous cleaning will require wastewater treatment
prior to discharge.
Water Recycling - Wastewater may be recycled. Cost
of equipment and maintenance can be moderately
expensive.
Source: Adapted from ICOLP.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Figure 111-3
CONFIGURATION OF A TYPICAL AQUEOUS
CLEANING PROCESS
Parts from
Manufacturing
Process
Solution
Racirculation:
Filtering, Skimming
Wash
Stage:
Heated Detergent
Solution: Spray.
Immersion
Ultrasonics, etc.
Rinse
Stage:
Water:
Spray. Immersion
Dryer:
Room Temp Air
Heated Air.
or Vacuum
Periodic Removal
Cleaned
Parts Ready
for Continued
Production
Waste Treatment
HMB-2
Source: EPA1989a
* 1994 UNEP SOLVENTS, COATINGS. AND ADHESIVES REPORT *
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Table 7/7-2
AQUEOUS CLEANING PROCESS EQUIPMENT
IMMERSION WITH
ULTRASONIC
AGITATION
IMMERSION
WITH MECHANICAL
AGITATION
SPRAY WASHER
ADVANTAGES
Highest level of
cleaning; cleans complex
parts/configurations
Can be automated
Parts can be welded
Usable with parts on
trays
Low maintenance
Usable with parts on
trays
Will flush out chips
Simple to operate
Cleans complex parts
and configurations
Might use existing
vapour degreasing
equipment with simple
engineering changes
High level of cleanliness
Inexpensive
Will flush out chips
Simple to operate
High volume
Portable
Short lead time
DISADVANTAGES
Highest cost .
Requires rinse water for
some applications
Requires new basket
design
Long lead time
Cannot handle heavy
oils
Limits part size and tank
volumes
Separate dryer may be
required
Requires rinse water for
some applications
Harder to automate
Requires proper part
orientation and/or
changes while in solution
Separate dryer may be
required
Requires rinse water for
some applications to
prevent film residues
Not effective in cleaning
complex parts
Separate dryer may be
required
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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humidity and air-conditioning control as well as associated economics may be
an issue.) Centrifugal drying is another useful option for the mechanical
removal of water from complex, robust parts. Evaporative drying following
mechanical removal can be accomplished using infrared, clean dry air-heated or
ambient temperature, or vacuum-heated drying. Dryers can be designed in-line
or batch. Drying design should always be confirmed with experimentation.
A very effective means of completely removing water from, or drying,
objects with either simple or complex geometries is the use of a vacuum oven.
The amount of vacuum and the temperature together with the length of time an
object is left within the vacuum oven are variables. They should be matched
to the complexity of the object and the nature of its construction (Baxter
1991).
Wastewater minimization and treatment is an important consideration and
is discussed in detail later in this report.
Successful cleaning of both disk-drive parts and gyroscope components
using aqueous detergent processes has been reported. One major company has
switched from a CFC-113 disk drying process to a hot water/air drying system
for some applications (Wolf 1988). Aqueous ultrasonic cleaning also has been
successfully used to clean inertial guidance and navigation systems and
components that are used in some missiles and aircraft in the U.S. Department
of Defense inventory (Patterson 1989).
Alternatives to CFC-113 cleaning of inertial systems, gyroscopes,
accelerometers, and related gaskets, bearings, and housings include
biodegradable aqueous-based systems and nonchlorinated/halogenated
hydrocarbons such as alcohols, ketones (acetone), hydrocarbon/surfactant
blends, and petroleum distillates. The alternatives may be a combination of
systems using ultrasonics, high pressure sprays, surfactants, and ancillary
equipment. The following contaminants have been successfully removed using
aqueous detergents and ultrasonics:
A highly fluorinated, long chain polymer lubricant
Polychlorotrifluoroethylene, a viscous heat transfer
fluid with a low coefficient of expansion
Long chain hydrocarbon oils/grease
Finger prints
Inorganic particulate matter
Rust and other oxides
Some carbonaceous char.
The cleaning equipment used was a self-contained system that cleans
with detergents and water in a cylindrical cleaning tank agitated by
ultrasonics. This aqueous system not only has offset use of CFC-113 and
1,1,1-trichloroethane, but has reduced process time as well. For example,
while manual cleaning of gimbal rings takes approximately 15 minutes per ring,
an aqueous ultrasonic system can clean 24 rings in 25 minutes.
The cleaner provided better cleaning results than those achieved with a
solvent-based system. The self-contained system is a promising spray booth
.media for cleaning parts which cannot be subjected to ultrasonics and also for
bench use where spot cleaning is done as part of the repair process.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Nuclear decontamination may be effectively achieved by an aqueous-based
system and high pressure sand blasting. Also, A1203 and/or glass beads of *
0.1 mm have been used successfully. In this process, the water evaporates and
the residue is cast for disposal (Arvensen 1989).
3.3.3 Semi-Aqueous Cleaning v
Hydrocarbon/surfactant cleaners, one type of emulsion cleaner that can
substitute for CFC-113 and 1,1,1-trichloroethane in precision cleaning
applications, have been included in a number of different cleaners formulated
for different purposes. Hydrocarbon/surfactants are used in cleaning
processes in two ways: They are either emulsified in water solutions and
applied in a manner similar to standard aqueous cleaners or they are applied
in concentrated form and then rinsed with water. Because both methods use
water in the cleaning process, the hydrocarbon/surfactant process is commonly
known as a semi-aqueous process.7
Under certain circumstances, it may be possible to modify an existing single or multi-stage vapour,
degreaser for use with an alternative solvent. For alternative cold dip cleaners such as hydrocarbons, the
vapour degreaser will be used primarily as a containment vessel and the ancillary features such as heaters,
etc., are not required. It may also be possible to adapt a multi-stage degreaser for use with the newly
emerging semi-aqueous cleaning processes. The details of the conversion procedure will depend on the type
of process being'Considered but the following guidelines illustrate the principles.
A. Semi-Aqueous Processes
Halbgenated solvent degreasers are usually fitted with heaters, some form of condensing coils water
cooled or refrigerated, safety cut-out devices and in some cases, ultrasonic agitation and/or pumping and
spraying equipment.
As halogenated solvents are non-flammable, the equipment designed for'their use will have electrical
equipment that will not be certified for use in flammable areas. The semi-aqueous processes use flammable
fluids. Though the fluids are normally used below the flash point, consideration should be given to a
situation where the flash point may be exceeded. In this situation, equipment may have to be modified so
that it shuts down in a safe controlled manner.
Process. Semi-aqueous processes consist of one or two immersion stages in the proprietary
hydrocarbon formulation followed by rinsing in one or two stages of water. Drying is usually required.
The degreaser should have sufficient compartments to accommodate'the chosen semi-aqueous process
commensurate with the level of cleanliness required.
Cleaning Stage. The proprietary semi-aqueous cleaner is contained in the first stage(s). Should
heating be required then it will need to be determined whether there is sufficient heat input with the
existing heating arrangements. Temperatures of 30-50°C are typical, however terpene-based solutions can be
used unheated. -It may be necessary to include some form of cooling in the event that introduced parts are
warm or to counteract excessive heat.input from pumps, ultrasonics, etc.
A control system will need to be installed to control the temperature to 20°C below the flash point
of the semi-aqueous material. .The existing safety cut-out may form part of this system. In addition, a
back up system should be fitted which would shut the system down and sound an alarm should the temperature
reach 10°C below the flash point of the cleaner.
Rinse Stage. Water can be circulated or agitated with ultrasonics in the remaining stages of the
cleaning equipment. It may be necessary to heat the water using the existing heaters to achieve good
rinsing and to assist in dry off. There may be significant drag out of the wash liquid"into the rinse
stages. . Water may be re-circulated or passed to drain depending on the process requirements. If the water
is to be re-circulated, then appropriate ion exchange or membrane technology may need to be installed to
keep the water clean. Similarly, this may be required prior to disposal.
The advice of both the manufacturer of the semi-aqueous cleaning fluid and the degreasing equipment
should be sought before attempting such a conversion (Johnson 1991).
B. Alcohol Process . '
Conversion of standard halogenated solvent degreasing equipment for use with alcohols inerted with
perfludrocarbons is not practicable (Johnson 1991). However, some companies have successfully modified
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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The benefits of semi-aqueous cleaning processes include the following:
Good cleaning ability (especially for heavy grease, tar, waxes,
and hard to remove soils)
Compatibility with most metals and plastics
Suppressed vapour pressure (especially if used in emulsified form)
Nonalkalinity of process prevents etching of metals, thus helping
to keep metals out of wastestrearns
Reduced evaporative loss
Potential decrease in solvent consumption which may lower overall
cost
Ability of some formulas to decant easily from water.
Lower water consumption as compared to aqueous cleaning
The drawbacks include:
Recycling or disposal cost of wastewater could make the process
less economically viable
Flammability concerns if concentrated cleaner is used in spray
cleaners; however, the flammability issue can be solved with
improved equipment design
Objectionable odours with some cleaners such as terpenes
VOCs make up some cleaners
Drying equipment will be required in most applications
Gelling of some cleaners at low water solutions
Difficulty in reducing surfactants used in cleaners
Toxicity considerations not yet established
Auto-oxidization of some cleaners. For example, d-limonene (a
type of terpene) can auto-oxidize. The terpene suffers auto-
oxidation naturally from contact with air. This can in some
instances be reduced using antioxidant additive
Semi-aqueous cleaning systems may require more floor space in some
instances
Energy consumption may be higher than that of solvent cleaning
systems in applications that require heated rinse and drying
stages
In some applications, high purity water which is expensive may be
needed.
The steps in a typical semi-aqueous cleaning process resemble those in
aqueous applications. Most equipment designed for use with semi-aqueous
processes are also similar to aqueous cleaning equipment designs. Figure
III-4 shows the schematic for a typical semi-aqueous cleaning process.
The four major steps used in the cleaning process are washing (with a
hydrocarbon/surfactant), rinsing (with water), drying, and wastewater
disposal. In cases where extreme cleanliness is required, the
hydrocarbon/surfactant cleaning can be followed by a fully aqueous wash step
with an alkaline detergent and a deionized water rinse. As in aqueous
cleaning, it is important to note that both the wash and the rinse stage are
recirculating; these solutions are not continuously discharged.
their vapour degreasers for cold cleaning with isopropanol. The refrigeration system of the units remain
connected but the heaters are disconnected. This maintains the solvent at more than 20°F below its
flashpoint. The equipment is also electrically grounded.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure 111-4
SEMI-AQUEOUS PROCESS FOR
IMMISCIBLE HYDROCARBON SOLVENT
Hydrocarbon/
Surfactant
Wash Stage
Emulsion
Rinse
Rinse
Dryer
Forced Hot Air
Cleaned
Part:'
Hydrocarbon/
Surfactant
Reuse
Dispose or
Recycle
Decanter
(T) Qeaed Loop Water
Treatment
0 Site Water
Treatment or
(T) Direct to Drain
tlMM-11
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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In the wash step, the hydrocarbon/surfactant cleaner is applied to the
part being cleaned with some form of mechanical energy. As a result of the
hydrocarbon/surfactant cleaner's high solvency and low flash points, the
solvent bath is generally not heated; however, some are slightly warmed when
the cleaner is used in a diluted form. Such cleaners are ignitable and should
not be used in vapour or spray cleaning without inert atmosphere or other
protective equipment. Some semi-aqueous cleaners have flash points above
93°C and can be used hot. Application methods that avoid misting such as
spray-under immersion, spin-under immersion, or ultrasonics should be used.
The dilute hydrocarbon emulsion cleaners formulated with water may be
heated. Less mechanical energy is needed when using a hydrocarbon/surfactant
solution as compared to an aqueous solution because of the high solvency of
hydrocarbon/surfactant cleaners.
The clean water rinse step removes the residues left by the wash step.
When concentrated hydrocarbon/surfactant cleaners are used, the rinse step is
necessary because these cleaners have a low volatility which prevents them
from evaporating from the parts cleaned in the wash stage. The rinse step may
not be necessary when dilute hydrocarbon/surfactant emulsion is used if the
level of cleanliness does not require removal of the residue from the wash
stage. In some instances alcohol is used as a final rinse step. The rinse
step may also serve as a finishing process and in some instances is used to
apply rust inhibitors to the parts.
The drying step serves the same function-as it does in aqueous cleaning.
Water is removed from the part to prepare it for further processing or to
prevent rusting. Heated air and high velocity room temperature air are the
principal drying agents. The drying step may not be needed if the parts are
rust inhibited and can air dry.
The wastewater disposal step is always an important part of the cleaning
process. Most of the contaminants in the wastewater are removed by decanters
and filters as the solution is recirculated in the' tank.
Because some hydrocarbon/surfactant cleaners can easily be separated by
decantation from the rinse water. The rinse water may be recycled or reused,
and the waste hydrocarbon/surfactant can be burned as fuel. In such cases,
contaminants like oil and grease, removed from the part being cleaned, are
retained in the hydrocarbon/surfactant phase, thereby greatly reducing the
contaminate loading in the water .effluent.
Equipment for use specifically with concentrated hydrocarbon/surfactants
is available. As with aqueous cleaning, this equipment can be classified as
immersion or spray equipment, and further as batch or In-line equipment.
Although there is a temptation to use existing aqueous equipment for the
hydrocarbon wash unit, this application is potentially dangerous because of
flammability.
Immersion equipment, the simplest design used in hydrocarbon/surfactant
cleaning, works with, but is not limited to, dilute emulsion solutions which
do not present the combustion (flammability) danger of the concentrated
hydrocarbon/surfactants. It can also be used with concentrated
hydrocarbon/surfactant cleaners. This equipment may operate in batch or in-
line configurations. Some old solvent vapour degreasers can be retrofitted to
* 1994 UNE'P SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-22
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immerse the parts into the bath of emulsion cleaner. The parts are simply cold
dipped into the bath, which may or may not be heated. Because of the solvency
of the hydrocarbon/surfactants, very little mechanical energy needs to be
added to achieve adequate cleanliness. Higher cleanliness can be achieved by
adding agitation to the process, either mechanically with ultrasonics or by
heating the wash solution.
\
As with aqueous cleaning, the mechanical spray action improves the
cleaning performance of the solution. When using concentrated hydrocarbon/.
surfactants, the atomized solution is prone to combustion and special care
must be taken to prevent it. Nitrogen blanketing is used to remove oxygen
from the spray chamber and the chamber, both of which are enclosed to prevent
sparks from entering.
In some instances, "spray-under immersion" can be performed. In this.
equipment, high pressure spray nozzles are placed below the surface of liquid.
This prevents the formation of atomized solution and eliminates flammability.
As in any cleaning application, keep in mind that the best process can
be ineffective when used ,on poorly designed parts. Any process can be
improved by a design that reduces the cleaning challenge. This is an
important factor, both economically and functionally, and can often be done
with low cost during product design.
3.3.4 HCFCs
HCFCs are transitional alternatives since their ozone depletion
potential (ODP) values, though small, are not zero. Because of their ODP,
HCFCs were recently added to the list of controlled substances under the
Montreal Protocol. As a result, they are subject to a phaseout by the year
2030, with a 99.5% reduction by the year 2020. Nevertheless, they have the
excellent physical properties of CFCs, such as low surface tension and
nonflammability. It is expected, therefore, that some of them can be used in
certain applications with minimal or no process.changes.
Several HCFCs (e.g., HCFC-225ca/cb, HCFC-141b, and HCFC-123) have been
proposed as possible CFC-113 and 1,1,1-trichlorqethane substitutes. Table
III-3 shows the physical properties of some of these chemicals and compares
them with CFC-113 and 1,1,1-trichloroethane. (Note that HCFC-225 is a mixture
of two isomers, ca and cb, hereafter referenced as HCFC-225.) A typical
composition of HCFC-225 commercially available is a 45/55 percent mixture of
the ca/cb isomers. ODP and toxicity of several of these HCFCs will most
likely greatly limit or completely eliminate their potential for replacing
CFC-113 and 1,1,1-trichloroethane in solvent cleaning applications. Two major
manufacturers have limited or cancelled their production, of HCFC-123: DuPont
will not offer HCFC-123 for cleaning operations, and Allied-Signal has
withdrawn all HCFC-123 formulations from the market. In addition, DuPont has
said that they will not offer any products containing HCFC-141b.
The advantages of HCFCs in the precision cleaning include the following:
they exhibit moderate to good cleaning performance
the CFC-113 cleaning equipment can be used with minor or no
modification
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-23
-------
Table III-3
PHYSICAL PROPERTIES OF HCFCs
AND OTHER OZONE-DEPLETING SOLVENTS
CFC-113
1,1,1-
Trichloro-
ethane
HCFC-225ca HCFC-225cb HCFC-141b
Chemical Formula
Ozone-Depleting
Potential
Boiling Point (°C)
Viscosity (cps)
@25°C
Surface Tension
@ 25° C (dyne/cm)
Kauri-Butanol
Value
Flash Point °C
Toxicity
CCI2FCCIF2
0.8
47.6
0.68
17.3
31
None
Very Low
. CH3CCI3
0.1
73.9
0.79
25.56
124
. None
Low
CF3CF2CHCI2 CCIF2CF2CHCIF CH3CFCI2
-0.01
51.1
0.58.
15.5
34
None
Moderate
-0.04
56.1
0.60
16.6
30
. None
Low
0.11
32.0
0.43
18.4
76
None
Low
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-24
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any assembled units with complex shapes and very small clearances
can be cleaned well
the energy consumption of HCFC cleaning systems may be relatively
small as compared with those of aqueous and semi-aqueous systems
they are compatible with most metals and plastics
HCFC cleaning requires less floor space relative to aqueous and
semi-aqueous cleaning
drying is .easy and the, assembled units leave no cleaning stains
since no water is used during the cleaning process .
The disadvantages of HCFCs include:
they are a transitional solution; the Montreal Protocol has urged
parties to phase-out HCFCs in the period 2020-2040; HCFC-141b has
an'ODP slightly higher than that of 1,1,1-trichloroethane
they are volatile and expensive; therefore they usually require
retrofitting of the existing equipment or new cleaning equipment;
a recovery system will be necessary to minimize the solvent
emissions
they may not be useful in some applications where 1,1,1-
trichloroethane is used ;
they are incompatible with acrylic resins
toxicological testing for HCFC-123, HCFC-141b, and HCFC-225
resulted in moderate controls being recommended for these
solvents.
HCFC-225 is characterized by the equivalence of CFC-11-3 in physical
properties with'ODP values one twentieth that of CFC-113 (Table III-3). It is
expected, therefore, that HCFC-225 can be used in most applications where CFC-
113 is used without any changes of equipments and processes. Equipment
changes would be required, however, to reduce emissions of HCFCs from the
equipment. Applications where HCFC-225 might be used include precision
cleaning of disk drives, gyroscopes, hydraulic control systems,, optical
components, electric contacts, plastic assemblies, and applications of special
lubricants. Evaluations of HCFC-225 in all these applications are currently
in progress.
As mentioned in section 3.2.2.1, recent testing (Schaefer and Scott
1991) has indicated that HCFC-225 is equivalent to CFC-113.in the ability to
provide final cleaning before and after vapour deposition coating operations
without introducing stains due to solvent evaporation. Successful cleaning of
both hard disk drive and hard disk using HCFC-225 has also been reported.
Some companies are intending to switch from CFC-113 to HCFC-225 in those
applications without a process change. So far; HCFC-225 has received good
evaluations as a substitute, for CFC-113 in various applications of precision
.cleaning. There are certain applications in precision cleaning where aqueous
and semi-aqueous systems cannot be applied, and HCFC-225 is emerging as a
promising substitute in those applications.
It-has also been reported that HCFC-225 exhibits poor solvency in some
applications. For example, initial testing has shown the HCFC-225 to exhibit
poor solubility with the typical blocking waxes and .pitches used in the optics
manufacturing operation. HCFC-225 is compatible with most metals and plastics
but may damage acrylic resins. It cannot, therefore, be applied for cleaning
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *. .
3-25 '
-------
assembled units where acrylic resins are used as the essential material.
Compatibility of HCFC-225 with materials which are used in the assembled units
to be cleaned should be tested carefully. It has been confirmed that recovery
systems for CFC-113 can also be applied for HCFC-225. Also, the recovery
system for HCFC-225 has been developed with a 95 percent recovery rate (Yamabe
1991).
The high volatility of some HCFC cleaning solutions require special
equipment design criteria. In addition, the economic and environmentally safe
use of HCFCs may require special emission control features for vapour
degreasers (see Figure III-5). These include:
Automated work transport facilities
Hoods and/or automated covers oh top entry machines
Facilities for work handling that minimize solvent entrapment
Facilities for superheated vapour drying
Freeboard depth to width ratios of 1.2 to 2.0
A main condenser operating at 7.2° to 12.8°C
A secondary condenser operating at -34° to -29°C
A dehumidification condenser operating at -34° to -29°C (optional)
Seals and gaskets of chemically compatible materials
Stainless steel construction
Welded piping containing a minimum of flanged joints
A refrigerated desiccant -dryer for methanol blends
A cool room to work in
Carefully controlled exhaust from the refrigeration unit to
prevent excessive heat from reaching the separator chambers.
Retrofitting or purchasing a new piece of.equipment for use with HCFCs
is recommended in many applications. Material compatibility is another
important consideration. HCFC-141b requires compatibility testing with
magnesium, zinc, and other metals. In addition, the HCFCs have shown some
adverse effects with plastics such as ABS, acrylic, and Hi-Impact Styrene.
Like metals, plastics need to be tested on an individual basis.
The use of HCFCs in cleaning equipment may be viewed in terms of two
distinct equipment categories -- new equipment and retrofitted equipment.
Design changes are much easier to implement in new equipment. For example,
dual sump open top degreasers (batch units) can have the same working area but
different length and width. A degreaser with the lesser width will be more
solvent efficient in terms of diffusion losses. It would be impractical,
obviously, to consider reorienting sumps on an existing machine in order to
take advantage of this design feature. New batch units have the vapour
generation sump offset from the rest of the machine, again to help minimize
solvent losses. Other features on new equipment are: roll-top lids, gasket-
sealed water separator lids, and a P-trap installed in the water drain of the
water separator. These features help economize on the use of solvent. A heat
exchanger can be used to keep the rinse sump of a batch cleaning unit lower
than the boiling point of the solvent by about 10 degrees fahrenheit (24°C).
Some of the features mentioned above (e.g., the roll-top lid, gasket-
sealed water separator lid, and P-trap/water drain of the water separator) are
readily applicable to retrofitted equipment. In-addition, it is relatively
easy to extend the working freeboard. Freeboard height is the distance from
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-26
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Figure 7/7-5
ADVANCED DESIGN DEGREASER FOR
USE WITH LOW BOILING POINT SOLVENTS
Hooded Work Transporter on Open-Top Degreaser
Hood
\
Work Transporter
.Additional
Freeboard
, Diffusion
Control
. Coil -20-F
Freeboard
Depth'
Dehumldlfler
Coll
-20-F
Source: DuPont
Main
Condenser
40"-50»F
Heating
Coll
staooeui-n
|05(»>-U
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-27
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the vapour-air interface line (generally at about the second primary condenser
coil) to the lip of the machine. The freeboard ratio is the freeboard height
divided by the narrowest dimension of the machine, which is normally the
machine width. Freeboard ratio is normally expressed as a percentage.
3.3.5 Alcohols and Ketones
The most common organic solvents are alcohols such as ethanol,
isopropanol, and several glycol ethers (methyl, n-butyl, and diethyl).' Most
of these solvents are chosen for their high polarity and for their very
effective solvent power. The alcohols have a range of flash points and care
must be exercised while using the lower flash point alcohols (see Table
III-4).
Based on material compatibility, alcohols are viable alternatives for
component cleaning. Explosion-proof boiling alcohol cleaners using
isopropanol could.be a practical alternative to CFC-113 and 1,1,1-
trichloroethane in many applications. For bulk cleaning of parts at the
incoming stage, this alternative could be considered; large-scale isopropanol
use may be unacceptable within,clean room areas, however, because of
flammability risks and operator discomfort resulting from alcohol odours as
well as the dehydrating effect of alcohol solvent and vapours on skin
surfaces.
Isopropanol and acetone operating in conjunction with ultrasonics have
been evaluated as alternatives to CFC-113 in precision cleaning (Mobjork
1989). Care must be taken when using flammable solvents in ultrasonic baths
due to the potential for solvent ignition and fires. The following components
and instruments were subjected to overall evaluation in this testing:
Servo component system
Hydraulic series ram screw
Accelerometer cut-out
Horizon indicator
Horizon gyroscope
Gyroscope motor components
Flight position indicator
Turn and bank indicator
Reduction vent valve for oxygen
Oxygen pressure regulator
Parachute swivel connector.
All components and instruments were retrieved from production except for
the oxygen vent and pressure regulator which were manually contaminated. Due
to the flammability of isopropanol and acetone, special explosion-proof batch
vapour-phase cleaners were used in this evaluation.8 A number of precision
components were cleaned in isopropanol or acetone.
8 These ultrasonic vapour-phase cleaners are designed for flammable
liquids. The 'machines are fire- and explosion-proofed according to the DIN-
standards and approved by the Federal Republic of Germany's TUV authority.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-28
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Table IJI-4
PROPERTIES OF ALCOHOLS
Product
Methanol
Ethanol, Prop. Anhydrous
Ethanol, Spec. Industrial Anhydrous
Isopropanol, Anhydrous
n-Propanol
2-Butanol
Isobutanol
n-Butanol
Amyl alcohol (primary)
Methyl Amyl Alcohol
Cyclohexanol
2-Ethylhexanol
Hexanol
LB/GAL
15.6°C
6.60
6.65
6.65
6.55
6.71
6.73
6.68
6 75
6.79
6.72
7.89
6.94
7.90
SP. GR
20°/20°C
0.792
0.799
0.795
' 0.786
0.806
0.809
0.803
0.811
- 0.815
0.808
0.949
0.834 '
0.950
Boiling
Range °C
64-65
74-80
75-81
82-83
96-98
97-102
107-109
116-118
127-139
130-133
160-163
182-186
244-247
FL PT.
"CTCC
12
9
10
12
23
22
29
. 36
. 49
39
61
73
1202
Evap.Rate1
3.5
1.8
1.8
1.7
1.0 .
0.9
0.6
0.5
0.3
0.3
0.05
0.01
0.002
1 N-Butyl Acetate = 1.'
2 C.O.C.
Note: FL. PT. = Flash Pointed Closed Cup Test; SP.GR. =
Source: Southwest Chemical Company, Solvent Properties
Specific Gravity. .
Reference Manual
* 199'f UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-29
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Cleaned with isopropanol:
Swivel connector parts contaminated with low
temperature grease
Gyroscope instruments
Reduction vent valve connections in an oxygen system
contaminated with oils and greases
Oxygen system gas regulators contaminated with soot
and char.
Cleaned with acetone:
Servo-gear piston contaminated with anti-corrosion oil
Series servo contaminated with hydraiulic oils, grease,
and particulates
Accelerometer cut-out contaminated with silicone oil.
Isopropanol proved to be a viable substitute for CFC-113 and generally
is compatible with nonmetallics. However, the use of acetone as a viable
alternative needs to be studied carefully since it is highly aggressive toward
many polymers.
3.3.6 Perfluorocarbons
The perfluorocarbons (PFCs) are a group of fluorine-saturated
hydrocarbons (compounds in which all the hydrogen atoms of the hydrocarbon are
substituted by fluorine). Because of the extreme electronegativity of the'
fluorine atom, this saturation results in high chemical stability in all of
the compounds. Consequently, they are virtually chemically inert, exhibit low
toxicity, are nonflammable, and have zero ozone-depletion potential. As a
result of this very low chemical activity, PFCs can be used in medical
applications and are safe in contact with pure oxygen at high pressures.
Their stability, however, makes PFCs extremely potent global warming
compounds. Due to their high global warming potential (GWP), the use of PFCs
is being restricted in a number of countries.
Choice of base hydrocarbon provides a wide range of molecular weight and
molecular structure resulting in a range of boiling points. Table III-5 shows
some of the basic properties of PFCs that were commercially available in late
1994.
Besides their GWP, another major disadvantage of PFCs is their high cost
which is a result of the complex synthetic production processes. A typical
low- to mid-range boiling PFC, for example, is approximately 326 to $40 US per
kg (late 1994). The high -cost of these compounds -should encourage potential
users to use PFCs only in vapour-tight equipment, reouci ig the amount of PFCs
that are lost to the atmosphere. Another drawback is that PFCs have very low
solvency power for hydrocarbons and are unlikely to be very useful for
removing oils. They have been shown, however, to be excellent solvents for,
perfluoropolyethers and other halogenated compound;..
Where no other substitutes are feasible, PFCs offer possible solutions
to current CFC-113 and 1,1,1-trichloroethane users, particularly in cleaning
parts .for high accuracy gyros. Some current high density flotation fluids are
soluble in certain PFCs, which can therefore be used for flushing filled
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-30
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Table 7/7-5
Properties of Perfluorocarbon Solvents Available in 1 994
Basic Formula
Ozone Depletion Potential
Global Warming Potential1
Boiling Point, °C
Density, g/ml, 25° C
Viscosity, cP, 25°C
Surface Tension,
dynes/cm, 25°C
Silicone Solubility
Fluorocarbon Solubility
Solubility Parameter, H
Flash Point, °C
Approximate Cost, US$/kg
C5F1lN0
Q
6000
50
1.70
0.68
13.0
Very Low
High
6.3
None
23
Vl4
0
5200
56
1.68
0.67
12.0
Very Low
High
5.6
None
23
C7F16
0
49002
80
1.73
0.95
13.0
Very Low
High
5.7
None
23
C8F18
0
47002
101
1.77
1.4
15
Very Low
High
5.7
None
23
CFC-113
0.8
4500
47.6
1.57
0.68
19.0
High
High
7.3 .'
None
22
1,1,1-
Trichloro-
ethane
0.10
100
73.9
1.33
0.79
25.6
Moderate
High
7.7
None
7
1
Based on 100-year time horizon.
Estimated
Source: 3M
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
3-31
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assemblies. In addition, high pressure spraying with PFCs appears to be a
very effective method of particle removal. The excellent chemical stability
^df these fluids makes them compatible with all gyro construction materials
including beryllium. Table III-6 summarizes the compatibility of PFCs with
various materials.
Design of equipment for gyroscope or other precision parts cleaning will
have to.'be specific to each application, whatever type of equipment is
designed, it should be a vapour-tight system to facilitate reclamation and
recycling. The chemical stability of PFCs makes them excellent compounds for
recycling. Currently, suppliers offer reclamation and recycling programs for
these compounds, thus minimizing emissions that could contribute to global
warming.9 If vapour-tight equipment is not utilized, the evaporative loss of
PFC would be prohibitively expensive and would make the use of PFCs very
difficult to rationalize (even considering the high cost and strategic
importance of the products).
3.3.7 Isopropyl Alcohol Cleaning with Perfluorocarbon
Alcohols such as ethyl and isopropyl have been used extensively for
cleaning printed circuit boards and precision components. They are very
effective in removing rosin and polar activators commonly used in flux.
Safety is the primary difficulty in using alcohols because of their high
flammability. In order for alcohols to become viable options, both flame and
explosion proofing are necessary expenditures to prevent- operator injury and
equipment damage. Using a perfluorocarbon (PFC) "blanket" in suitable
equipment renders the alcohol vapour nonflammable, and results in a safer
alcohol vapour degreaser.
The advantages of using this type of process include:
Isopropyl alcohol, being extremely polar, has good solvency and
allows for the removal of differing types of particulate and
organic contamination than CFC-113.
PFCs are nonflammable, have low toxicity and reactivity, and have
zero ozone-depleting potential. v
The nonflammable nature of the alcohol-PFC vapour allows a safe,
-continuous distillation at a lower temperature than isopropyl
alcohol alone with rapid rinsing to give a dry product.
PFC and isopropyl alcohol are virtually non-immiscible; PFC being
more dense forms a layer below the alcohol. If this lower PFC
layer is heated to its boiling point (approximately 50°C), the
vapour generated will entrain the alcohol to form a mixed .vapour
with approximately five percent alcohol at a temperature of 50°C.
This layer is nonflammable.
9 Preliminary studies by one equipment manufacturer have demonstrated
emission reductions of 90 percent for PFCs compared to historical emissions of
CFC-113.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-32
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Table III-61
PERFLUOROCARBON (RFC) COMPATIBILITY
WITH VARIOUS MATERIALS
Class of Material
Rubbers
Polyethylene, polypropylene
Nylons
Polystyrene
"Perspex" ("Plexiglass")
FIFE (unfilled)
PVC (Rigid)
PVC (Rexible)
Electronic circuit boards*
Copper and brass
Other Common metals
Silicone and microcircuit chips
Adhesives
Adhesive tapes
Paper
Enamelled wires
Insulating tapes
Paints
Other surface coatings and sealants
Observation
< 1 percent linear swell, _+ 1 percent change in weight
< 1 percent shrinkage, zero change in weight
Negligible change in dimensions or weight
Variable, generally negligible, shrinkage (e.g., 0.2 percent)
<0.2 percent shrinkage, slight loss in weight
2-3 percent linear swell, up to 10 percent increase in weight
Negligible change
Extraction of plasticizer, loss of flexibility (in hot Flutec)
±_ <0.1 percent dimensional change, zero change in weight
Slight tarnishing (from dissolved oxygen)
No effect detectable
No known effect
1
I No adverse effects detected in any samples tested up to the
\ present time
* Including: SRBP, Epoxy, DAP, Silicone, Melamine, Polyester, with filler materials of all common
types.
Source: Rhone Poulenc, ISC Chemicals Division.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES-REPORT *
3-33
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- Alcohol and PFC are. "clean" agents; i.e., they leave no residue.
They also evaporate readily at,low temperatures.
Additional features of some equipment include a hermetically
sealed lid, under lid basket operation, and a balancing volume to
accommodate volume changes on heat-up and shut-down. Superheated
PFC spray can alsc be used to facilitate removal of isopropyl
alcohol from cleaned parts.
The disadvantages include:
. A properly designed, dedicated piece of equipment consisting of a
conventional two-tank vapour degreaser with a boiling alcohol
(soiled .solvent) tank and a pure hot alcohol rinse tank is
required to operate this process.
Safety systems must be designed to automatically cease operations
should the PFC level drop below the level necessary to prevent
explosion.
Pure alcohols are not effective at removing nonpolar contaminants
like grease and flux residue. However, cleaning effectiveness can
be enhanced by combining the alcohol/PFC cleaner with a precleaner
unit using hydrocarbons or other solvents. - ,
PFCs have a high global warming potential and atmospheric
lifetime.
PFCs are expensive, currently priced from US$26.00/kg.
3.3.8 Aliphatic Hydrocarbons
Aliphatic hydrocarbons, which offer tighter control on composition,
odour, boiling range, evaporation rate, etc., are employed in original
equipment manufacturer (OEM) cleaning processes and will be discussed below.
The advantages of aliphatic hydrocarbon cleaners include.:
Compatible (non-corrosive) with most rubbers, plastics and metals
Employs no water, hence can clean water-sensitive parts
Low odour and low toxicity grades available
Reduced evaporative loss
No wastewater stream
High stability and recovery "~
Recyclable by distillation
Good cleaning ability for wide variety of soils,'especially heavy
grease, tar, waxes, and hard to remove soils. Low surface tension
allows good penetration.
The disadvantages include: ,
Flammability concerns (can be solved with proper, equipment design)
Slower drying times than halogenated solvents
VOC control may be required. However,, equipment,such as carbon
adsorption and condensers can recover solvent from effluent air
* 199
-------
Low occupational exposure limits are associated with some grades.
Waste products are classified as hazardous waste
A wide range of aliphatic hydrocarbon solvents are used in precision
cleaning (see Table III-7)! Petroleum fractions, commonly known as mineral
spirits or naptha, are used extensively in maintenance cleaning. These are
single stage, open top processes using ambient air drying. In most cases such
processes are not suitable for Original Equipment Manufacture (OEM) cleaning.
The major steps in the hydrocarbon cleaning process are washing (1-3
stages depending on degree of cleaning needed) with a hydrocarbon cleaner,
drying using forced air, VOC recovery from solvent-laden air, and waste -
solvent recovery or disposal. The wash steps involve liquid-phase cleaning at
temperatures sufficiently below the flash point of the fluid. Ultrasonics or
other agitation processes such -as immersion spraying, parts rotation, or fluid
pump around can be used to augment cleaning action. (However, note that
ultrasonic equipment manufacturers do not recommended the use of ultrasonics
with flammable solvents.) Spraying or mistingvprocesses, where fine droplets
are formed, should be employed only in an inert environment or with equipment
otherwise protected from ignition conditions, because fine- droplets can be
ignited at temperatures below bulk fluid flash point.
Fluids with flasTi points near 40°C (104°F) or below should be used in
unheated equipment operating at ambient temperatures, although the continued
use of refrigeration coils is preferred. For higher flash points, hot
cleaning can be employed to boost cleaning action. For systems with good
temperature control (independent temperature sensors, cutouts, level
indicators, etc.), a safety margin of 15°C (59°F) between the fluid flashpoint
.and the cleaning temperature, or 90 percent below the lower explosive limit
(LEL), is recommended. For systems with poorer temperature control, a higher
margin should be employed. .
Each wash step should be followed by a drain period, preferably with'
parts rotation, to minimize solvent dragout from stage to stage. ,
In multistage processes, fluid from one bath is periodically transferred
to the preceding bath as its soil level builds up. Fresh solvent is thus
added only to the final bath to ensure the highest parts cleanliness, and
spent solvent is only removed from the first stage.
The drying step normally uses forced air which may be heated. Either
the dryer should operate at 15°C below the flash point of the fluid, or
sufficient air flow should be provided so that the effluent air composition is
well below the.Lower Explosive Limit (LEL) of the system.
'i
The VOC recovery step is an important part of the cleaning process.
Depending on the solvent chosen, either carbon adsorption or condensation are,
the best technologies for recovery of solvent vapours from spent drying air
and lip vent air. There are numerous vendors of such recovery equipment.
In the waste recovery area, the best reclamation technology for these
products is usually filtration and distillation. One of the advantages of the
.low olefin content and narrow distillation range is that the recovery in
distillation is high. Should some disposal of residual solvent be necessary,
fuel substitution or incineration are good routes.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-35
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Table III-7
PROPERTIES OF ALIPHATIC SOLVENTS
Product
Mineral Spirits
Odourless Mineral Spirits
140 Solvent
Kerosene
C10/C11 Isoparaffin
C13 N-Paraffin
C10 Cycloparaffin
LB/GAL
15.6°C
6.37
6.33
6.54
6.60
6.25
6.35
6.75
SP. GR
15.6/15.6
°C
0.764
0.760
0.786
0.790
0.750
0.760
0.810
Boiling
Range °C
152-202
. 177-202
182-210
166-257
160-171
227-238
166-182
FL. PT.
'CTCC
41
53
60
. 54
42
93
41
KB
32
27
30
30
29
22
54
Evap
Rate1
0.1
0.1
0.1
0.19
0.3
0.1
0.2
1 N-Butyl Acetate = 1. .
Note: FL PT. = Flash Point Closed Cup Test; KB = Kauri-Butanol Value; SP.GR = Specific Gravity.
Sources: Southwest Chemical Company, Solvent Properties Reference Manual; Exxon Chemical Company
* 1994 UNEF SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-36
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3.3.9 Chlorinated and Other Miscellaneous Organic Solvents
The precision cleaning industry has always used a very wide range of
miscellaneous solvents. In all applications such solvents are used for manual
operations, usually by means of camel or sable .hair brushes during assembly or
.rework. In addition to those already described, ot'her chlorinated solvents,
ethers, ketones, alcohols, and esters-, are also candidate replacements for
precision applications. Typical uses are local defluxing after solder rework'
operations, defluxing after special solder operations (e.g., strain gauge lead
attachment), and varnish applications (e.g., small scale in-situ coil
impregnations).
The chlorinated solvents that do not destroy the ozone layer
trichloroethylene, perchloroethylene, and methylene chloride (dichloro-
methane) also are effective cleaners. Because of their widespread use, they
have been scrutinized for their .safety, health, and environmental impacts.
Many countries have established exposure levels that are considered safe for
workers. In addition, many countries have placed additional controls on
emissions to the atmosphere from processes using these solvents. Local
regulations,. Material Safety Data Sheets, and industrial recommendations such
as those of the American Conference of Governmental Industrial .Hygienists
should be used as guidance in establishing safe handling and usage procedures
for these solvents.
\
The development of extremely low emissions cleaning equipment which
minimizes worker exposure levels, and emissions to the environment, along with
good management practices offers users an alternative that provides for
equivalent or better cleaning with existing technology. The combination of
limits being placed on users will require their use.only in applications where
emissions are very carefully controlled. Table III-8 summarizes the
properties of these other chlorinated solvents.
The ketones (see Table III-9) form a group'of very powerful solvents.
In particular, acetone (dimethyl ketone) and methyl ethyl ketone are very good
solvents for polymers and adhesives. In addition, acetone is an efficient
dewatering agent. However, their extreme flamm'ability' (note that acetone has
a flash point of -18°C) and incompatibility with many structural polymers
(e.g., stress-cracking of polyether sulphone, polyether ketone, and
polycarbonate) means that they should only be used with care and in small
.quantities. Consequently, large-scale use as CFC-113 or 1,1,1-trichloroethane
alternatives would be unlikely.
Esters such as dibasic esters have good solvent properties. Most of
these materials are readily soluble in alcohols, ketones, ethers, and most
hydrocarbons, but are only slightly soluble in water and high paraffinic
hydrocarbons. The materials have high flash points and low vapour pressures.
Dibasic esters, however, are so low in vapour pressure that a residual film
will remain on a surface after application. In addition, they have been found
to be genotoxic and should therefore be used with caution.
3.3.10 Pressurized Gases
Particulate contamination may be removed with pressurized gases, as an
alternative to cleaning with CFC-113 and 1,1,1-trichloroethane. However, the
use of these gases will not generally remove ionic or organic contamination
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
. ' 3-37
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Table III-8
PROPERTIES OF HALOGENATED CHLORINATED
SOLVENTS
Physical Properties CFC-113
1,1,1-
Trichloro-
ethane
Trichloro-
ethylene
Perchloro-
ethylene
Methylene
Chloride
Ozone-Depleting
Potential
0.8
Chemical Formula CCI2FCCIF2
Molecular Weight 187.38
Boiling Point (°C) 47.6
Density (g/cm3) 1.56
Solubility Parameter, 7.7
Hildebrands
Surface Tension
(dyne/cm)
17.3
Kauri Butanol Value 31
Toxicity Low
Carcinogenicity No
Flash Point (°C) None
0.1
CH3CCI3
133.5
72-88
1.34
9.2
25.4
124
Low
No
None
0
CHCICCI2
131.4
86-88
1.46
9.3
29.3
130
Medium
See Note8
None
CCI2CCI2
165.9
120-122
1.62
9.7
31.3
91
Medium
See Noteb
None
-0
CH2CI2
84.9
39.4-40.4
1.33
9.7
N/A
132
Medium .
See Note6
None
a The U.S. EPA has not formally classified trichloroethylene in Category B2 as a "probable human carcinogen,' while the
International Agency for Research on Cancer (IARC) has classified this solvent in Group 3, a substance not classifiable as to
its carcinogenicity in humans.
b The U.S. EPA has not formally classified perchloroethylene in Category B2 as a "probable human carcinogen." IARC has
classified perchloroethylene in Group 2B as a substance considered "possibly carcinogenic to humans.'
c The U.S. EPA has classified methylene chloride in Category 82 as a "probable human carcinogen,1 while IARC has
classified methylene chloride in Group 2B as a substance considered "possibly carcinogenic to humans.'
Source: UNEP (1989).
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table 7/7-9
PROPERTIES OF KETONES
KETONE
Acetone
Methyl Ethyl Ketone (MEK)
Diethyl Ketone
Methyl n-Propyl Ketone .
Cyclohexanone
Methyl Isobutyl Ketone
(MIBK)
Methyl n-Butyl Ketone
Methyl Cyclohexanone
Acetonyl Acetone
Diisopropyl Ketone
Methyl n-Amyl Ketone
Diacetone
Formula
C2H6CO
C3H8CO
C4H10CO
C4H10CO
C5H10CO
C5H,2CO
C7H12CO
C6H12CO
C,H10(CO)2
C6H14CO
C6HUCO
C6H12CO
Mol. Wt.
58.08
72.10
86.13
86.13
98.14
100.16
100.16
112.17
114.14
114.18
114.18
116.16
Ibs
per gal
6.58
6.71
6.80
6.72
7.88
6.68
6.83
7.67
8.10
6.73
6.81
7.82
B.P.
°C
56-57
79-81
100-104
101-107
130-172
112-118
114-137
114-173
185-195
114-127
147-154
130-180
Flash
Point
°C
open cup
-17
-2.2
12.6
7.2
62
17.6
22.5
47.3
78
23.6
48.4
8.8
Evap Rate
CCI4=100
139
97
-
66
12
47
32'
7
-
-
15
4
Solubility
Parameter
- H
9.9
9.3
8.8
8.7
9.9
8.4
8.3
9.3
-
8.0
8.5
- -
Surface
Tension
20°C
Dynes/cm
23.7
24.6
24.8
25.2
-
22.7
25.5
-
39.6
-
-
29.8
Source: DuPont, A.F. Barton, Handbook of Solubility Parameters and Other Cohesion Parameters, CRC Press
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT.*
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(see the section on supercritical fluids). Primary considerations for
choosing pressurized gases depend on the following properties:
Surface chemistry. This factor is ultimately responsible for the nature
of the electrostatic forces between surfaces.
Porosity. Porous (and rough) surfaces possess the potential to
mechanically lock contaminant and substrate and further hinder the
cleaning process.
Roughness of surface. Large.particles on a smooth surface may be
removed more easily than small particles on a rough surface for the same
reason.
Size, shape, and homogeneity of the contaminant. On a microscopic
level, all surfaces possess ridges and valleys that make intimate
contact between surfaces difficult. Adsorbed contamination on particles
and other surfaces also hinders contact and prevents relatively short-
range molecular interactions from occurring.
Sensitivity of the surrounding area to ejected material. Relatively
inert gases and mixtures are most often used with specially designed
equipment to meet the cleanliness requirements of the surrounding area.
Depending upon which pressurized gas is used in the cleaning
application, the advantages of using pressurized gases versus halogenated
solvent cleaning could include the following:
Low viscosity
Low toxicity
High diffusivity
Nonf1ammabi1ity
Low capital cost.
The disadvantages of using pressurized gases could include:
Low density
High pressure (rupturing of seal)
Cleaning of critical components
Often not effective for microscopic particles
Safety considerations.
Possible Gases:
Gases which may be used include.air, rare gases, carbon dioxide,
chlorodifluoromethane (HCFC-22), and nitrogen. These gases are readily
available in bulk and smaller quantities and in numerous grades of purity.
These gases may be stored at room temperature. Dry air is produced from
ordinary air by removing hydrocarbons by oxidation. Carbon dioxide is then
removed and the air is compressed and dried.
Because of its oxygen content, air reacts with many substances, rare
'earth gases, however, are noted for their extreme chemical inactivity. These
monatomic gases are helium, neon, argon, krypton, and xenon and may be
obtained by fractionation of liquid air. Argon, the most abundant of the rare
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-40
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earth gases, is commercially available in cylinders ranging from 1,775 to
6,000 psig at 21.1°C. Argon is not toxic, but is an asphyxiant and is heavier
than air.
Carbon dioxide, which is recovered from a number of processes, is
colourless, odourless, nonflammable, and slightly acidic. .The gas is stable
under most conditions, but it will dissociate into carbon dioxide and carbon
monoxide in the presence of free carbon at high temperatures. For example, at
100°C, the equilibrium ratio of carbon dioxide to carbon monoxide is 0.7
percent to 99.3 percent. Above the critical temperature of 31°C, all solid
carbon dioxide converts to a gas. It may be shipped under its own vapour
pressure of 830 psig at 21.1°C. Caution must be taken in dealing with carbon
dioxide since it acts'as an asphyxiant and cumulative amounts of the gas can
act like a poison. Note that the use of carbon dioxide does not contribute to
global warming because the source of the most carbon dioxide is the air
itself. . .
Colourless and nonflammable, HCFC-22 has an ozone-depletion potential of
0.05. At high temperatures, various metals may catalyze decomposition of the
gas. Silver, brass, bronze, aluminum, ,1340 steel, copper,-nickel, 18-8
stainless steel, and inconel react in descending order, with silver being the
most reactive. Magnesium and aluminum alloys with two percent or more
magnesium are particularly reactive in the presence of water. Natural rubber
may also be swollen and degraded by the solvent. Continued flooding of
localized areas with liquid produces rapid chilling. This feature may be
desirable to remove more tenacious contaminants. It is often shipped as a
liquified gas under its own pressure of 123 psig at 2.1.1°C. The gas is
available in bulk and small disposable cans. Direct contact wi-th liquid
.chlorodifluoromethane may cause frostbite. The gas is considered to be
nontoxic, but high concentrations can produce dizziness, narcosis, and nausea.
Equipment Considerations:
Clean dry air may be economically produced from pressurized air in-
house. Specifically designed diaphragm and other noncontaminating pumps are
available. High efficiency filters, drying agents, arid other equipment can be
used for most of these gases.
A problem inherent in cleaning with high pressure gases is the
development of static charges. Ionizing guns that can alleviate this problem
are available from clean room equipment suppliers.
Typically, clean, dry, inert gas, or air is fed to a pressurized gas gun
at 689.5 kPa. Many models offer 0.3 to 0.5 micron particle filtration with a
maximum outlet pressure of ionized gas at 207 kPa. Different ionizing and
filtration techniques have been designed for specific needs. One model is
reported to remove 3.0 micron size particles with 99 percent efficiency from
bare silicon wafers.
Composition of the contaminant and substrate may determine whether or
not ejected material produced by pressurized gas will damage surrounding
surfaces. Metal dust may be easily removed from an assembly with pressurized
gas. However, if an optical component with a sensitive coating is part of the
assembly, it could be scratched by impinging particles. Particles 'With low
mass may not present a problem. Likewise, harder components may be resistant
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
' , 3-41
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enough to allow this process. Consideration of dislodged particles is not
limited to resistance of the assembly or part because, clean room requirements,
as well as surrounding structure, may not tolerate increased levels of
contamination.
Containment of ejected debris may be accomplished for small parts by
operating the process in a laminar flow work station equipped with a high
efficiency particulate air filter or an ultra-low penetration air filter.
Vacuum may also be used with pressurized gas on some parts to capture
dislodged contamination.
3.3.11 Supercritical Fluids
The use of supercritical fluids (SCF) , especially carbon dioxide, has
escalated in the early 1990' s. SCFs are chemicals that 'are normally liquid or
gaseous at standard temperature and pressure. However, when the pressure and
temperature are increased to specific levels, the chemical reaches a
supercritical state and exhibits very different solvent properties. Table
111-10 lists some of the data for typical supercritical solvents.
In the case of supercritical carbon dioxide (C02) , the fluid has been
used for many years in the food and flavour industry. One example is the use
of supercritical C02 to decaf feinate coffee. The properties of the SCFs are
such that at each temperature and pressure combination within the
supercritical region, the fluid behaves with slightly different solvency
powers. In the coffee -decaf feination example cited above, the coffee beans
are loaded into a very large, high pressure reactor. The C02 is injected into
the reactor and the pressure and temperature are simultaneously increased.
The coffee bean flavour an organic chemical itself is first removed from
the beans by adjusting the pressure and temperature and then releasing the
carbon dioxide to a capture chamber, where the flavour is held. Then, the
reactor is refilled with C02, and adjusted to a different temperature and
pressure and the caffeine is removed and captured' into another holding
.chamber. Finally, the pressure -and temperature combination of the coffee
flavour is readjusted and the flavour is added back to the beans.
The equipment for a supercritical C02 cleaning system can start at
between $60,000 to $120,000 for small reactors of approximately 1 cubic foot
capacity. The cost of the unit depends on the types of soil to be removed and
the size of the high-pressure reactor. It is common for the reactors to be
operated in the 2000 to 5000 psi range with temperatures between 40°C to
Compared to liquid solvents such as CFC-113 and 1 , 1 , 1-trichloroethane ,
SCFs have a higher diffusivity and a much lower density and viscosity. This
combination of characteristics allows for rapid extraction of contaminants and
phase separation. Other chemicals, such as nitrous oxide, ethane, ethylene,
and water, can be used in supercritical cleaning processes, but C02 has proven
to be the safest, the most abundant and economical, and very effective.
Supercritical fluids display the following properties:
wide range of solvent solubilities
gas -like diffusivity
zero surface tension"
* 1994 UHEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-42
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Table 777-70
DATA FOR TYPICAL SUPERCRITICAL SOLVENTS
Solvent
Methane
Ethylene
Chlorotrifluoromethane
Carbon dioxide
Ethane
Nitrous oxide
Sulfur hexafluoride
Propylene
Propane
Ammonia
Trichlorpfluoromethane
n-Hexane
Isopropanol
Ethanol
Toluene
Water
Critical
Temperature
fdee. Q
-83
9
29
31
32
36
45
92
97
132
198
234
235
243
.318
374
Critical
Pressure
fatm)
45.4
49.7
38.7
72.8
48.2
71.5
37.1
45.6
. 41.9
111.3
43.5
29.3
47.0
63.0
40.6
217.7
Density
0.16
0.22
0.58
0.47
0.20
0.45,
- 0.74
0.23
0.22
0.24
0.55
0.23
0.27
0.28
0.29
0.32
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
3-43
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short process times
low energy costs
does not generate waste products (except for the contamination
removed)
gas is completely recoverable
SCFs exhibit many properties of an ideal process, however the high cost
of the equipment and the necessary process development to fine-tune the
cleaning process will require significant funding. Some characteristics of
the SCF process that should be considered include potential material
compatibility problems and the necessary training for operators of the high-
pressure equipment. SCF processes should be targeted to industries where
expensive fluids are to be removed from precision hardware, specifically the
medical, space, and defense industries.
Test results obtained by one company using SCF cleaning for
developmental tests on precision gyroscopes for high-reliability use indicate
the following:
effective removal of oils and polyhalogenated fluids
pressures and temperatures required
-- perfluoropolyether oils ... 1500 psi, 170 °F
-- halogenated and other oils ... 3500 psi, 185 °F
incompatible with hermetically sealed devices
epoxy weight gains detected of greater than 2.5 percent
effective for deep pores (width/diameter of 650 to 10,000)
material compatibilities
-- metals, ceramics, and glass were good.
-- thermoset plastics were good
thermoplastics were fair to good
-- elastomers (rubber) were bad, except for silicones
Supercritical carbon dioxide has been tested by several users as a
potential replacement for precision cleaning with CFC-113 and 1,1,1-
trichloroethane. Table III-11 illustrates the types of applications that have
been successful. It is important to confirm that the cleanliness achieved in
each application matches the precision cleaning requirements.
Process Overview:
Figure III-6 shows a generic supercritical carbon dioxide cleaning
process. Carbon dioxide is pressurized and heated to its supercritical state
and introduced into the 'extraction vessel at the selected extractor operating
conditions. In the extractor, the supercritical fluid selectively extracts
one or more components from the source material. The solute-'rich gas exits the
extractor and undergoes a temperature and/or pressure change. This change
decreases the solubility of the solute in the fluid and, due to the change in
solubility, a solute/fluid separation takes place in the separator vessel.
In order to determine whether SCF is a technically feasible and
economically viable alternative, it is necessary to evaluate, phase equilibrium
properties of the fluids. These include the number of phases present, the
composition and density of each phase, and the equilibrium changes associated
with temperature, pressure, and composition. This is important because of the
often complex behaviour of fluids in high-pressure phase. Phase equilibrium
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table III-ll
SUPERCRITICAL CARBON DIOXIDE APPLICATIONS
Hardware
Spacecraft
Radar
Laser
Gas system
Cleaning aid
Nuclear
Missiles
Materials/Components Cleaned Contaminants Removed
High voltage cables
Bearings
Rivets
Connectors
Transformers
Cables
Optical benches
O-rings
Seals
Cotton ball/wipers
Cotton tipped applicators
Valves
Gyroscopes
Silicone oils
Lubricants
Flux residues
Dielectric oils.
Machine oils
Plasticizers
Plasticizers
Monomers
Organic extractables
Triglycerides
Adhesive residues
Radioactive Oil
Perfluoropolyethers
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure III-6
BASIC MODEL DESIGN FOR CARBON DIOXIDE
SUPERCRITICAL CLEANING SYSTEM
Pressure Regulator
Pumpl
Pump 2
Conditioner
Carbon Dioxide
Gas Supply
High Pressure
Vessel
Gauge
\
Exhaust
Separator
Source: Jackson 1987
I1M06-S1
* 1994 UHEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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and mass transport data is used to size equipment, determine utility
requirements, and estimate costs.
The pressure-dependent dissolving power of C02 is not limited to
polymers and oils of only medium molecular weight and materials of low
polarity. Very highly polar materials such as alcohols and organic acids are
soluble, and among polymeric materials, many polymers and high molecular
weight oils, such as silicones and fluoroethers, commonly associated with
gyroscopes are soluble; silicones of several hundred thousand MW dissolve to
high levels in supercritical C02. For completeness here, SC C02 can dissolve
many hydrocarbons, esters, silicones, perfluorinated oils, halocarbon-
substituted triazines, and polychloro- and bromo-tri'fluoroethylene; these
materials can also be fractionated based on molecular weight which has special
purpose application in lubrication and coating. While there are polymers that
are insoluble in CC>2, some of them depending on the degree of cross-linking
and crystallinity - may exhibit swelling and/or incompatibility in C02.
Unfortunately, there are also many confusing claims which continue to be
perpetuated throughout the literature and patents regarding the ability of SC
C02 to dissolve particulates (e.g., lint, dust, scale, metal, and salts,
etc.), fluxes, and other materials. While it is possible that some dislodging
of particulates can occur due to'velocity forces, they do riot dissolve-in C02.
Based on extensive investigation with rosin-based fluxes, it can be stated
with certainty that these materials are insoluble in carbon dioxide. Some of
the confusion may arise because of incompletely understood phenomena. For
example, abietic acid (the main component of rosin) is soluble in C02 and it
is interesting that a recent international patent application has stated that
abietic acid must be modified/with methanol to impart any reasonable v
solubility in C02. The confusion arises because after exposure t,o high
temperatures required for reflowing solder flux, abietic acid can polymerize
enough to render the flux residue insoluble. Even many low solids and water
soluble fluxes are insoluble in C02", thus SC C02 is not generally applicable
to circuit board cleaning (although in special cases it may show limited
results.)
3.3.12 . Plasma Cleaning .
A plasma is an electrically charged gas containing, ionized atoms,
electrons, highly reactive free radicals, and electrically neutral species.
Plasma, produced by passing an electric current through a process gas, is
characterized by high reactivity and a specific frequency of electromagnetic
radiation, usually in the UV and visual light bands. Common examples of
plasma are fluorescent lighting, neon signs, and the solar corona.
Plasmas can exist in a wide variety of pressure and temperature
conditions, but "cold" plasmas are best for cleaning applications. These
typically have temperatures under 60°C. Normal operating pressures are 1-5
mmHg, under an atmospheric pressure of 760 mmHg. Such operating conditions
are easily produced.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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The cleaning process consists of six steps:
Evacuating the chamber to base vacuum pressure
Introducing process gases and then stabilizing them at operational
pressure
Irradiating the chamber with radio frequency energy to produce the
plasma --a step that causes the process gas to flow through the
chamber removing compounds such as carbon monoxide, carbon
dioxide, and water vapour
Shutting off radio frequency energy and process gases and
returning to base pressure
Purging the chamber with a nonreactive gas such as nitrogen to
remove all traces of volatile compounds
« Returning to atmospheric pressure and then venting to atmosphere.
The third step is the actual cleaning portion of the procedure. The
ipns and electrons in the plasma are energized by the radio frequency
radiation to energy levels of approximately 1 eV. The bonds found in organic
contaminants, C-C,. C-H, and C-0, have energies from 3 to 5 eV. The high
reactivity of the ions, combined with their kinetic energies, is sufficient to
break these organic bonds. The ions then react with the freed atomic
components and form volatile compounds which are then removed by the flow of
the process gas.
The advantages of plasma cleaning include:
Process gases are relatively cheap, nontoxic, and noncaustic.
Example gases are oxygen, argon, helium, silicon tetrafluoride,
and air.
« Only small amounts of process gas are required for each cleaning.
This amount will vary with exposure time and size of enclosure.
Low operating costs compared to solvent cleaning. No disposal
procedures are necessary.
The cleaning time depends greatly on the specific process, but
generally ranges from a few seconds to a few hours.
« Because the plasma is essentially gas-like, all shaped parts are
cleaned simultaneously and evenly. Because the cleaning takes
place, on the molecular level, all features, regardless of size,
are cleaned equally well.
The.disadvantages of plasma cleaning include:
Capital costs are initially high and the equipment is highly
specialized. Reactor costs are typically $20,000 to $130,000.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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For space systems such as satellite optical components that must
be cleaned during use, the plasma gases must be provided at launch
or produced chemically.
. Contaminant layers are not cleaned at an even rate. It may be
-difficult-to determine exactly how long the process should last.
Outer layers are stripped faster, and at lower energies, than
layers close to the original surface. A possible reason for this
could be that the inner layers are exposed to more UV radiation
from the plasma itself, and therefore cross-polymerize and form
stronger bonds with the surface. For space systems, this
uncertainty could lead to overuse of limited process gas supplies.
Plasma is not formed efficiently in hidden areas of complex parts
and diffusion of plasma into these areas is slow.
Using oxygen as a process gas produces a visible film on the
surface of gold mirrors. Such a film may be difficult to remove
and, if left on the mirror, may increase light scattering.
The energy of the process must be limited to avoid sputtering, a
- phenomenon that can damage the elements being cleaned. .
Because cleaning capacity is low, gross contamination should be
removed prior to plasma cleaning.
. Operator training will be required.
A plasma cleaning system usually consists of a reactor, a radio-
frequency generator, and a control system. The reactor, which can be
cylindrical or planar, must hold the components for cleaning. The radio-
frequency generator supplies the energy for creating plasma. The control
equipment governs the composition of the reagent gas, the flow-rate of the
reagent gas, the radio-frequency power, the reactor.'s operating pressure, and,
the processing time.
Several gases possess desirable characteristics for plasma cleaning.
The specific gas would be determined by the application. An important point
to concede is that some surfaces react with some gases directly, a reaction
which could actually cause further contamination.
A readily available, process gas is necessary. Producing such gases in
restricted space may be difficult. Most current cleaning technologies are
batch processes. Further design would be necessary to make plasma cleaning a
viable line procedure. Once-cleaned, precautions must be taken to prevent
recontamination. Slight exposure to plastics or other organic substances may
allow thin layers of organic compounds to adhere to hyperclean surfaces. This
is an important consideration -for precision cleaning operations. '
Plasma has been used in several different applications for removing (1)
organic contamination and residue from substrates, (2) residue from plating
baths and washing solutions, (3) conformal coating to repai'r circuits, and (4)
epoxy markings and light oil on automotive bumpers.
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3.3.13 Ultraviolet Light/Ozone Cleaning Method *
The UV/ozone cleaning process has been used successfully to remove thin
organic films from a number of different surfaces, including glass, quartz,
mica, sapphire, ceramics, metals, silicon, gallium arsenide, and polyamide
cement. .
UV/ozone cleaning is a simple process which is relatively inexpensive to
set up and operate. Under the proper conditions, the process can produce
clean surfaces in less than one minute, and these will remain clean
indefinitely during storage under UV/ozone.
' The basic UV/ozone cleaning process involves the exposure of a
contaminated surface to UV light in the presence of ozone. The cleaning
occurs as a result of various photosensitized oxidation-processes.
Contaminant molecules are excited and/or dissociated by the absorption of
short-length UV light. These molecules, and the free radicals produced by
dissociation, react with atomic oxygen to form simpler, volatile molecules
such as carbon dioxide, water vapour, and nitrogen. This reaction removes the
surface contamination.
There are several variables in the UV/ozone process that determine the
effectiveness of the cleaning. These include the following: contaminants
present, precleaning procedure, UV wavelengths emitted, distance and
atmosphere between the UV source and the surface to be cleaned, contact angle
of the light, and length of time of the exposure..
Testing must be performed to determine optimal orientations for
different contaminants and surfaces to be cleaned. Surfaces that have
multiple contaminants, or thick layers of contaminants, require precleaning in
order for the UV/ozone process to work. UV/ozone will efficiently clean
organic contamination, but particles and inorganic components are more
difficult to remove with this process. To maximize the rate of cleaning, the
part being cleaned should be kept as close as practicable to the UV light
source.
Because the UV/ozone process requires no moving parts, it is easy to
maintain and operate. However, both the use of UV light and the presence of
excessive ozone can be dangerous to humarjs. UV light can cause eye injuries
and ozone causes respiratory damage. The low workplace limits for ozone (0.1
ppm) require special design considerations.
The UV/ozone process may also cause damage to the surface being cleaned.
Staining and discoloration of materials can result from improper wavelengths
and exposure times. Overexposure of materials to UV light can also cause
corrosion. One positive side effect of the UV/ozone process is the
neutralization of static charges on insulator surfaces.
Possible Applications:
The UV/ozone cleaning process has numerous applications. The primary
use is substrate cleaning prior to thin film deposition, such as is necessary
in the production of quartz crystal resonators. The process is also used for
cleaning and storage of metal tools, masks, resonator parts, and storage
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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containers. UV/ozone can be used in a hermetic sealing process that adheres
to clean surfaces in an ultra-high vacuum.
Other applications which have been identified include: photoresist
removal, the cleaning of vacuum chamber walls, photomasks, silicon wafers,
lenses, mirrors, solar panels, complex configured beryllium gyroscope and
accelerometer components, and gallium-arsenide wafers.
Future developments in UV/ozone .cleaning procedures will come from
further testing and experimentation with specific applications. Cleaning
techniques need to be refined considerably before this method of cleaning will
receive widespread acceptance. The technology advances in plasma cleaning and
supercritical fluids may reduce the attention that UV/ozone cleaning will
receive, except for use in special medical applications.
3.4 ENVIRONMENTAL-AND ENERGY CONSIDERATION
Two major factors in determining the feasibility of any proposed
alternative to CFC-113 or 1,1,1-trichloroethane are the environmental impacts
and the energy requirements of the substitute. The wide variety of
alternative processes available carry with them an equally wide variety of
environmental and energy considerations.
Conservation and recovery procedures have proven to be effective in
reducing the environmental impacts of industrial solvent usage. These
procedures are extremely valuable, not~only in cases where acceptable
alternatives to CFC-113 and 1,1,1-trichloroethane have not yet been found, but
also .where organic solvents used in the system vaporize. Currently, though
solvent can be recycled, the recycled solvent is rarely used in precision
cleaning applications due to its perceived impurities. The solution to this
problem is the individual recovery and handling of any solvents in use at a
given location. Careful handling will help prevent the mixing of solvents,
thereby allowing for treatment and potential reuse.. Additionally, companies
may purchase small inexpensive solvent reclamation equipment to,offset the
high costs of solvent disposal.
Several of the alternatives presented in this chapter require wastewater
treatment. These alternatives are the aqueous and semi-aqueous cleaning
processes. In both cases, the treatment of the wastewater can often be
performed in-house so that the water may be recycled.
The ozone-depletion potential (OOP) associated with alternative
processes is an- extremely important environmental consideration. HCFC
solvents have small, but significant, ODPs which may limit their use. ;
Conversely, the ODP of zero associated with alcohols/perfluorocarbons as well
as with perfluoroalkanes make them more attractive alternatives. It should be-
no ted, however, that while these two alternatives have an ODP of zero, they
both have relatively high greenhouse-warming potential.
Manufacturers of chemical solvents and their HCFC alternative financed .a
study of the "Total Equivalent Warming Impacts(TEWI)" of the phase out of
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CFC-113.10 TEWI includes the direct effects of emissions of greenhouse gas
solvents plus the indirect effects of energy required for supply, operation,
and disposal of waste. The analysis aims to include every direct and indirect
effect so that alternatives can be compared for environmental acceptability.
A summary is presented in Appendix I.
Another important consideration of alternatives to CFC-113 and 1,1,1-
trichloroethane in precision cleaning applications is the possible health
effect on workers and the general population. Each alternative has
occupational hazards associated with its use. For example, aliphatic
hydrocarbons are flammable, UV/ozone emits harmful wavelengths of radiation
and produces noxious gas, some gases are asphyxiants, and most chlorinated
solvents are considered potentially carcinogenic.
While energy considerations are also important in the choice of an
alternative precision cleaning method, they usually fall behind environmental
impacts in their importance. One case where energy is of major concern is in
the plasma cleaning process. In this case, it is a necessity that the process
energy be limited to a given level so that the cleaning can be properly
performed,
In many of the other processes, the major energy consideration is the
amount which is consumed in completing the cleaning process. Extremely high
energy utilization will obviously increase the,operating costs.
3.5 POTENTIAL GLOBAL REDUCTION OF CFC-113 AND 1.1.1-TRICHLOROETHANE IN
PRECISION CLEANING APPLICATIONS
In the first release of this document in 1991, this section was written
with the hope that the consortium of academia, industry, and government, could
work together to develop alternatives to ozone depleting solvents in precision
cleaning. .In the 1991 version of this document all of the alternatives that .
are known in late 1994 were known then. However, in 1994 the industries that
were large consumers of ODS have reduced their consumption to approximately
one-third of their 1988 usage.
Several of the technologies that were relatively new in 1991 have become
more sophisticated in recent years. Supercritical fluid cleaning now has its
own society, the Joint Association for .the Advancement of Supercritical fluid
Technology (JAAST), which is developing and promoting the use of supercritical
C02 for high reliability-cleaning in various applications in the space and
defense industry. Semi-aqueous cleaning systems have passed numerous tests
and were first used on satellites in 1992. Gas plasma cleaning applications
have grown significantly. Organic solvents -have progressed from the highly
10 AFEAS member companies include Akzo Chemicals BV (The Netherlands),
Allied-Signal, Inc. (U.S.), Asahi Glass Co., Ltd. (Japan), Atochem (France),
Daikin Industries, Ltd. (Japan), E.I. DuPont De Nemours & Co. (U.S.), Hoechst
(Germany), ICI Chemicals and Polymers, Ltd. (U.K.), Kali-Chemie AG (Germany),
LaRoche Chemicals, Inc. (U.S.), Montefluous S.p.A. (Italy), and Rhone Poulenc
Chemicals/ISC Division (U.K.). The report, produced by Arthur D. Little, is
titled Comparison of Global Warming Implications of Cleaning Technologies
Using a Systems Approach.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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volatile single-component aliphatics (still preferable in some instances) to
blends that offer multiple properties. Finally, the PFCs and continuing
research on hydrofluorocarbons (HFCs) is moving forward, and new equipment has
been manufactured to help reduce the environmental impact of these new
solvents. ,
Conservation and recovery, a common theme in 1991, has become
commonplace in developed countries. Companies in these countries that are
still using ODS solvents have incorporated sliding covers, turn off their
heaters at night, and train their workers in proper vapour degreaser
operation. By January 1, 1996, the majority of companies in the United States
and other industrialised countries, will have met their goal of finding and
implementing more environmentally sound cleaning processes.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CHAPTER 4
METAL CLEANING APPLICATIONS
4.1 BACKGROUND
i
Metal cleaning applications include all applications in which metal
parts are cleaned during manufacturing or maintenance except for those metal
parts that are included in precision cleaning applications.1
Primary Production . .
Metal cleaning can be divided conveniently into 3 main sub-divisions:
Primary production
Periodic maintenance
. Repair and service .
Some of the processes which precede metal cleaning include: guillotining
stock material, numerically controlled machining from solids, multistage deep
drawing, stamping, forging, casting (of all technologies), rolling, extruding,
injection moulding, non-destructive testing, welding, and .vacuum forming from
sheet spinning. The materials which are cleaned in primary procedures
include: ferrous metals and alloys; aluminium, titanium, and other light
metal alloys; zinc based die cast; other nonferrous metals (e.g., copper and
alloys); moulded polypropylene and other thermoplastic materials; carbon fibre
reinforced epoxy, glass fibre reinforced epoxy, and other composite materials;.
and high alumina ceramics. . . .
Finally, the following are examples of processes which follow primary
metal cleaning. These procedures include electrolytic surface treatment,
painting and application of other coatings, chemical vapour deposition, radio
frequency coating, fluid bed coating with polymers, applications of adhesives
prior to bonding, galvanizing, simple surface cleaning prior to rework,
repair, storage or subsequent assembly, and application of temporary
protective materials for storage and delivery protection.
Periodic Maintenance
There are many industrial processes in which plant and machinery are
routinely and regularly disassembled, cleaned, reassembled, and refitted with
functional materials. This can occur at the end of a working interval (end of
1 See Chapter 3. Delicate and intricate metal parts that, must be cleaned
to a degree of. micrometer fineness are considered precision cleaning
applications in this report.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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shift for example) or at fixed intervals. Many of these require the use of
solvents, including CFC-113 and 1,1,1-trichloroethane. Examples include:
Heating, ventilation and air conditioning systems and equipment
Metal working machinery and equipment
Hydraulic equipment and systems
Adhesive spreading machinery (for impact adhesives, adhesives
based on polychloroprene), epoxy resins, hot metal systems, etc.
Silk screen stencils for general printing, solder past printing,
etc.
Instrument pressurized oil filling rigs using Krytox fluorolube
and silicone oils
Polymer forming equipment -- injection moulding, blow moulding --
vacuum moulding, etc.
Conventional hydrocarbon oil-fill rigs -- transformers,
transmission systems -- engines, etc.
Copiers and laser printing machines
Newsprint printing machines
Offset printing machines
Tooling
Repair and Maintenance
This is possibly the most widespread and diverse subdivision of metal
cleaning and covers, for the most part, "cold solvent cleaning" in which
1,1,1-trichloroethane has become the most important'cleaning agent in recent
years. '
To list examples would be to list most mechanical artifacts of the
modern world; however, general areas are:
. Primary power sources
auto engines and power trains
truck diesel engines and transmission
marine diesels, auxiliary deck power sources
-- locomotive diesels and electric motors
aircraft gas turbines and auxiliary power generators
Industrial handling equipment
conveyor systems
cranes and derricks
mobile, overhead hoists
fork lift trucks
Metal working machinery -- machine tools, press-tools, forging --
deep drawing, etc.
Sport and leisure
bicycles
boats
--' outboard motors
cars
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cameras
video recorders
television and radio
1,1,1-Trichloroethane is used extensively in metal cleaning. Worldwide
production in 1990 amounted to about 726,000 metric tonnes with 66 percent of
this total used for metal and precision cleaning. CFC-113 use in metal
cleaning is considerably less than 25 percent of that of 1,1,1-
trichloroethane. This chapter describes a number of alternative materials and
processes that clean metals effectively, including solvent blends, aqueous
cleaners, emulsion cleaners, mechanical cleaning, thermal vacuum deoiling,
and no-clean alternatives.
4.2 CFC-113 and 1.1.1-TRICHLOROETHANE USE IN METAL CLEANING APPLICATIONS
4.2.1 Metal Cleaning Applications
Metal cleaning is a surface preparation process that removes'organic
compounds such as oils and greases, particulate matter, and inorganic soils
from metal surfaces. Metal cleaning prepares parts for subsequent operations
.such as further machining and fabrication, electroplating, painting, coating,
inspection, assembly, or packaging. Parts may be cleaned multiple times
during the manufacturing process..
Metal cleaning usually is done' on flat or formed sheet metal or on
milled and machined metal stock. Tubing, engine-parts, motors, nuts, bolts,
screws, honeycomb structures, and rivets are other common configurations.
Machined parts tend to have complex and curved surfaces with holes and pockets
that can trap both particulate matter and liquids. In large facilities, a *
wide spectrum of metals and alloys may require cleaning using the same
cleaning system. For. example, the U.S. Air Force at one location cleans 15
metal alloys during aircraft maintenance operations (Bellar 1988). Metal
cleaning also involves the cleaning and preparation of moulds used to cast
metal parts, varieties of plastics, and composite, materials.
4.2.2 Metal Cleaning Solvents
Traditionally, chlorinated solvents such as trichloroethylene (TCE),
1,1,1-trichloroethane (TCA), perchloroethylene (PCE), and methylene chloride
(MC) were used for metal degreasing (ICF 1988). 1,1,1-Trichloroethane began
to be substituted for TCE as a metal cleaner in the 1960s; its use, however,
increased dramatically because, of all the chlorinated solvents, 1,1,1-
trichloroethane has relatively low toxicity,.high solvency, low surface
tension, and optimum boiling temperature for vapour degreasing. CFC-113 use
for metal cleaning began in the 1970s as concerns increased about the toxicity
and effects .of long-term, low-concentration exposure to some chlorinated
solvents. In the United States, the use of CFC-113 as a metal cleaner
doubled from 1974 to 1983, from an estimated 26,000 metric tons to 52,000
metric tons. '
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4.2.3 Metal Cleaning Processes
4.2.3.1 Cold Immersion Cleaning
The most common method of cleaning with ambient temperature solvents is
immersion cleaning. Most operations are fairly simple and use halogenated
solvents, organic solvents, or blends near room temperature. The basic
technique involves immersing or dipping a part by manually, mechanically, or
hydraulically lowering the part into a tank containing solvent. While the
simplest immersion cleaning method (application) is soaking the article in
solvent most soils even if solvent- soluble, require agitation for adequate
cleaning. Therefore, immersion/dip cleaning usually is used in conjunction
with other operations such as mechanical agitation or ultrasonic cleaning.
Immersion cleaning also may be used to remove heavy soils prior to manual
cleaning or vapour degreasing. Solvent use in immersion cleaning is
relatively high because of drag-out and because there is frequently no vapour
level control (condenser, cooling coils) on the equipment.
Mechanical- agitation allows nonsoluble particles to be stripped away
from the parts, thus producing cleaner parts than a simple dip tank.
Mechanical agitation is produced by moving the solvent within the bath or the
metal part. The solvent can be agitated mechanically with a motor-driven
propeller or a circulating pump, or can be ultrasonically agita'ted using
transducers and an ultrasonic generator. Parts can be agitated by placing
them on an agitation platform. Air-agitated dip tanks also improve cleaning
efficiency by helping to remove nonsoluble soils, but because this process
greatly increases solvent loss by increasing the evaporation losses and might,
where relevant, increase concern about the evaporation rate of volatile
organic compound (VOC) emissions, it is not a viable option for cleaning
enhancement. ..
Small containers may be used for maintenance cleaning of electronic .
parts; large containers may be used for cleaning .lar^e machined parts or large
volumes of.smaller parts in baskets (ICF 1989). Even if the immersion tanks
are small, there are often many cleaning stations and the solvent may be
changed frequently - - all of which provide additional reasons why cold
immersion cleaning uses a relatively large volume of solvent-. While many
container sizes exist, a typical container (tank) size is about 30 centimetres
by 60 centimetres, containing solvent to a depth of 75 centimetres; the
working volume of solvent ranges from about 50 to 400 litres (ICF 1989).
Tanks are often fitted with recirculation pumps to flush parts. Particulate
filters and stills are integrated in some units to maintain solvent quality.
4.2.3.2 Vapour/Hot Liquid Cleaning
Vapour degreasing is a process that uses the hot vapour of a solvent to
remove soils, oils, greases, and waxes. A basic vapour degreaser .unit is an
open-top steel tank with a heat source at the bottom to boil the solvent and a
cooling zone near the top to condense the solvent vapours. The vapours
displace the lighter air and form a vapour zone above the boiling solvent.
The hot vapour is condensed when it reaches the cooling zone by condensing
coils or a water jacket, thus maintaining a fixed vapour level. Figure IV-1
is a schematic of a traditional open top vapour degreaser.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Figure W-l
BASIC VAPOUR DEGREASER - BATCH CLEANING
SPRAY
TUBE
VAPOUR THERMOSTAT
LIP VENT
CLEAN OUT
DOOR
WATER
SEPARATOR
WATER OUTLET
SOLVENT RETURN
BOILING SUMP
HEATING ELEMENTS
SUMP THERMOSTAT
Source: PPG Industries
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Parts are cleaned by lowering them into the vapour zone. The
temperature differential between the hot vapour and the cool part causes the
vapour to condense on the part and dissolve the contaminants. The condensed
solvent and contaminants then drip into the boiling solvent. Parts dry
quickly upon withdrawal from the vapour zone because they are heated by the
solvent vapours and parts remain immersed in the.vapour until thermal
equilibrium is achieved.
Vapour degreasing is more effective than cold cleaning, where the
solvent bath becomes increasingly contaminated. In vapour degreasing, the
parts are washed with pure solvent because contaminants removed from the part
usually boil at higher temperatures than the solvent and therefore remain in
the boiling solvent. Despite the soils contained in the solvent from
previously cleaned parts, the boiling solvent produces essentially pure
solvent vapours provided that the contaminant level in the boiling sump is
kept low. Heavy contamination will contaminate the vapour by upward
splashing, as a result of the boiling liquid, or by forming an azeotrope with
the solvent.
Metals can be cleaned using one of several batch degreasing methods.
These methods are: vapour-only, vapour-spray-vapour, warm liquid-vapour, or
boiling liquid-warm liquid-vapour. Modifications to the basic vapour
degreaser process are designed to accommodate various cleaning cycles,
requirements, or parts configurations. These modifications include spraying
or immersing the parts in boiling or cool solvent. Immersion vapour
degreasing cycles typically include a warm liquid-vapour cycle and a boiling
liquid-warm liquid-vapour cycle. Immersion vapour degreasing is used to clean
smalL parts packed in baskets, to clean the inside of tubing, or to clean
intricately .patterned parts contaminated with particularly heavy or adherent
soil. ' . ,
Vapour-Only: The simplest degreasing system is the straight vapour
method. With this method, solvent vapour condenses directly on the part,
dissolves the organic contaminant, and removes it and' any particulate residue
from the surface of the part by dripping back into the boiling solvent. When
the part reaches the vapour temperature, vapour condensation ceases and.
cleaning is complete. Parts are dry when removed from the tank. Few
manufacturers currently make vapour-only units because with the simple
addition of a vapour-spray device the effectiveness and applications of the
machine are greatly increased.
Vapour-Spray-Vapour: This cleaning method is similar to the vapour-only
cycle with the addition of a pure distillate rinse step. In this process, the
metal part is lowered into the vapour zone where the condensing solvent cleans
the metal. After condensation, the part is sprayed with warm solvent. The
spray pressure forces the solvent liquid into holes: and helps remove insoluble
soils that cannot be removed by vapour alone.2 The warm spray also .lowers
the temperature of the metal part. After spraying, the cooled metal part
causes further condensation of vapour for the final rinse. This technique
also can remove solvent-insoluble soils such as buffing compounds if the part
2. Spray pressures for standard degreasers should range from 6 psi to 8
psi '(UO KP.a to 55 KPa) (ASM 1982). Excessive pressure disturbs the vapour
zone and causes a high solvent emission rate.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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is sprayed immediately upon entering the vapour before the vapour heat can
affect the compounds and make them difficult to remove. Vapour-solvent
spray-vapour is the most frequently used cleaning cycle (UNEP 1989).
Warm Liquid-Vapour Cycle: During the warm liquid-vapour cycle, the part
is held in the vapour zone until condensation stops and'then lowered into the
warm liquid. Alternatively, parts may be directly lowered into the warm
liquid. Mechanical agitation of the warm liquid removes additional soil. The
part is transferred from the warm liquid to the vapour zone for a final rinse.
Boiling Liquid-Warm Liquid-Vapour Cycle: This cycle cleans small,
intricate parts that are packed closely together in baskets, tubing interiors,
or parts with heavy or adherent soil. A part is first held in the vapour zone
and then lowered into the boiling liquid. In some processes, the part is
lowered directly into the boiling liquid. Once immersed in the boiling
solvent, the violent boiling action scrubs off heavy soil deposits, metal
chips, and insolubles. Prior to the final vapour phase cleaning, the metal
surface temperature of the part is lowered by transferring the part to warm
liquid. This method requires large quantities of solvent and is impractical
.for large parts because of the large volumes of liquid solvent required for
immersion.
4.2.3.3 Conveyorized Cleaning
Conveyorized cleaning equipment using 1,1,1-trichloroethane or CFC-113
is generally configured with a spray, cleaning stage, immersion in one to three
boiling liquid sumps with ultrasonics to enhance cleaning, and in some cases a
superheated drying zcme. Small degreasing machines using 1,1,1-
trichloroethane or CFC-113 may also use ultrasonics to enhance cleaning of
small parts and equipment. Vibratory Conveyorized machines which move small
parts in a screw pattern upward through chlorinated solvent liquid arid vapour
are 'still used.
4.2.,3.4 Manual Cleaning
Metal surfaces can be hand-wiped with a cloth, brush, or sponge that is
moistened with solvent. Solvent containers can be distributed and moved
throughout the shop as needed (ICF 1989). Prior to final assembly, and again
before pairiiting, aircraft and automobile surfaces, for example, are hand-wiped
clean using,solvents. Although widely used in assembly plants; manual
cleaning is an inefficient method of cleaning parts and does not lend itself
to continuous manufacturing operations. It is most appropriate for infrequent
maintenance cleaning.
.4.2.3.5 Spraying and Flushing Techniques
The effectiveness of spraying and flushing cleaning techniques depends
on the solubility of the soil in the selected cleaning media. Spraying and
flushing equipment usually consists of a solvent tank, feeder hose,, spray gun,
overspray containment, and baskets to hold the parts during cleaning. Solvent
is usually supplied by a mechanical pump or a compressed air mechanism. These
methods are most efficient when cleaning outer, metal surfaces. Flushing can'
clean external and internal part surfaces such as metal castings, tubing, heat
exchangers, and assemblies with large cavities.
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4.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND 1.1.1-TRICHLOROETHANE
USE IN METAL CLEANING APPLICATIONS
The control approaches available for metal cleaning operations include
solvent conservation and recovery practices and the use of alternative
cleaning such as solvent.blends, aqueous cleaners, emulsion cleaners,
mechanical cleaning, thermal vacuum de-oiling, and no-clean alternatives.
Alternatives to CFC-113 and 1,1,1-trichloroethane must be selected and
optimized for each application given the varying substrate materials, soils,
cleanliness requirements, process specifications, end uses encountered in
metal cleaning, and the local environmental, safety, and health requirements.
Table IV-1 lists the alternatives that can be used for each process.
4.3.1 Conservation and Recovery Practices
Methods of conserving and recovering CFC-113 and 1,1,1-trichloroethane
solvents range from simple procedures for manually removing large contaminants
prior to degreasing to adding various filtration apparatuses.
In a poorly maintained plant, only about 20 percent of the purchased
solvent quantity is generally recovered. Depending on what measures have
already been adopted at a plant, applications of the guidelines summarized in
Appendix C can enable total emissions to be reduced by 90 percent. Solvent
losses can be reduced from 2-5 kg/h-m2 of bath area'with conventional practice
to 0.2 - 0.5 kg/h-m2 of bath area. For certain alcohol and partially aqueous
systems, the overall base rate of annual loss is around 0.03 - 0.05 kg/h-m2 of
bath area.
The recommendations summarized in Appendix C are concerned with the best
available technology for the following:
cold cleaning
vapour cleaning (including equipment with spray/ultrasound)
continuous "in-line" cleaning..
4.3.2 Alternative Chlorinated Solvents
The chlorinated solvents that do not destroy the ozone layer,
trichloroethylene, perchloroethylene, and methylene chloride (dichloro-
methane)--also are effective cleaners. Because of their widespread use, they
have been extensively scrutinized for their safety, health, and environmental
impacts. Many countries have established exposure levels that are considered
safe for workers. In addition, many countries have placed additional controls
on emissions to the atmosphere from processes using these solvents. Local
regulations, Material-Safety Data Shee.ts, and industrial recommendations such
as those of the American Conference of Governmental Industrial Hygienists
should be used as guidance in establishing safe handling and usage prbcedures
for these solvents.
There are specific metal cleaning operations in which trichloroethylene,
perchloroethylene, and methylene chloride are perceived to be the only
alternatives to CFC-113 and 1,1,1-trichloroethane. Lack of alternatives can
result from concerns abput corrosion of the subs.trate metal (e.g. mild steel),
time restrictions between processes (e.g. degreasing as part of a. metal heat
treating operation), and requirements for removing e-xtremely tenacious soils
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Table IV-1.
VIABLE ALTERNATIVES TO EXISTING METAL CLEANING
PROCESS SOLVENTS
Substitute
Cold Hot . Vapour
Immersion0 Immersion0 Degreasing
High
Pressure
Spray Manual
Alkaline Cleaners X
Emulsion Cleaners X
Low Vapour Pressure
Solvent Blends3 . X
Hydrocarbon/Surfactant
X
X
X
a Nonhalogenated mixtures.
b With appropriate flammability protection.
c Includes agitation such as ultrasonics, mechanical, etc.
Source: Evanoff 1989. . ;
X
Xb
Xb
X
Blends
HCFCs
Naph tha/Hy dr o c arb ons
Naphtha -Terpene Blends
Other Chlorinated Solvents
Steam
Media Blasting
X
X X ' X
X
X
X ' X. X
X
xb
xb
X
X
X
X
X
*
X
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(e.g. asphaltics and waxes) or cleaning intricate parts configurations (e.g.
tubes, metal honeycomb). In these special cases, use of trichloroethylene,
perchloroethylene, or methylene chloride with the incorporation of the
conservation and recovery practices discussed in this report will not only
reduce the use of CFC-113 and 1,1,1-trichloroethane, but will also keep use
within local regulatory units.
Other compounds that recently have emerged as immersion and wipe
cleaning solvents include hydrocarbon/surfactant blends, dibasic acid esters,
n-methyl pyrrolidine, volatile methyl siloxanes, and chlorinated aromatics.
These products are each tested for performance, toxicity, exposure limits,
flammability, carcinogenicity, odour, recyclability, and cost. The.U.S.
Department of Energy (DOE) and the U.S. Air Force are evaluating these
products for toxicity exposure limits, flammability, carcinogenicity, and
costs. These products are also being.tested for cleaning performance,
treatability, recyclability, corrosivity, and VOC emissions. These
alternatives may become increasingly available for commercial use over the
next five years.
4.3.3 Alternative Solvent Blends
4.3.3.1 Vapour Degreasing
The hydrofluorocarbon (HCFC) blends have ozone-depletion factors
associated with them, although these factors are lower than those of CFC-113.
HCFC-123 and HCFC-141b have significantly lower boiling points (27-32°C) than
CFC-113 (48°C) or 1,1,1-trichloroethane (73°C). This raises the possibility
of increased vapour emissions from operating processes, increased fugitive
emissions during material transfer, and increased handling and storage
requirements. The boiling point of HCFC-225 is 51-56°C, which is equivalent .
to that of CFC-113. Blends of HCFC-225 therefore could be an alternative to
CFC-113. HCFCs should be used with a recovery system in order to prevent
solvent emissions, which will minimize worker exposure and-protect the global
environment (Yamabe 1991). '
4.3.3.2 Manual Cleaning
For manual cleaning, a number of commercial solvent blends are
available. These products are mixtures of aliphatic and oxygenated
hydrocarbon solvents (e.g., ketones, ethers, esters, and alcohols). All
degreasing solvents and the organic constituents of blends are volatile and
many are flammable. Such solvents or blends may require control measures in
.accordance with local, regional, or federal regulations or with corporate
policies governing their use. These control measures address concerns over
environmental, health, and safety issues. i
The newer blends being developed are optimised for maximum soil removal,
minimum flammability and toxicity, and low composite vapour pressure/
evaporation rate. These blends are viable substitutes for 1,1,1-
trichloroethane and CFC-113 in situations where volatile organic compounds can
be controlled or are not regulated.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
4-10
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4.3.3.3 Cold Immersion Cleaning
Solvent blends of aliphatic naphtha and certain terpenes and dibasic
esters are commonly used in immersion cleaning of heavy soils and greases in
industrial maintenance operations. These blends are viable substitutes for
1,1,1-trichloroethane and CFC-113 where possible hydrocarbon residue from the
high molecular weight fraction of the naphtha does not ,pose problems and
volatile organic compounds can either be controlled or are not regulated. The
newer blends being marketed have equal cleaning capacity to those that contain
halogenated solvents. These include high flash aliphatic naphthas, blends of
aliphatic naphthas with terpenes or esters, and hydrocarbon/surfactant blends.
HCFC-225 is another alternative that has recently become commercially
available for use ,in cold cleaning applications. Figure IV-2 shows the
degreasing performance of HCFC-225 compared with that of CFC-113 in cold
immersion cleaning. It appears that the degreasing ability of HCFC-225 is
comparable to that of CFC-113, thereby making it a suitable alternative.
4.3.4 Aqueous Cleaners
4.3.4.1 Cleaner Formulations
Aqueous cleaners are a viable, broad substitute for CFC-113 and 1,1,1-
trichloroethane used in degreasing metals. It is estimated that at least 60
percent of the ozone-depleting solvent degreasing operations for metals could
be replaced with aqueous cleaners (Kurita, 1991a). Aqueous cleaners are.
comprised of three major types of components:
builders -- alkaline salts such as sodium tripolyphosphate, sodium
silicate, or sodium hydroxide which make up the largest fraction
of the cleaner.
surfactants -- organic compounds such -as alkyl benzene sulfonates
or polyethoxylated high molecular weight 'alcohols that serve as
wetting and emulsifying agents and thus are the principal source
of the detersive properties of the cleaner...
additives - - organic or inorganic compounds such as the
ethanolamines or sodium citrate that serve as complexing agents
for softening water or binding with undesirable metal ions in
solution. Corrosion inhibitors are also added to minimise the
effect of the aqueous cleaners on the metal surface.3 Numerous
handbooks artd technical references are available and provide a
comprehensive explanation of aqueous cleaner chemistry and
performance (Linford 1950, Spring 1974, U.S. EPA 1991a).
Alkaline cleaners have been applied successfully in detailed bench and
pilot scale testing for metal cleaning applications and,.since 1992, in full-
scale manufacturing of aerospace components at Boeing, Lockheed, McDonnell
3 Silicate salts are typical corrosion inhibitors. Other additives
include anti-oxidants, such as borates, stabilizers, and small amounts of
water-miscible solvents, such as some glycol ethers.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure IV-2
DEGREASING PERFORMANCE OF HCFC-225
(Drawing Oil (Houghton Oil))
100
80
o
0
60
O 40
20
I I I I I III
HCFC-225
O CFC-113
III!
10 20 30 40
Cleaning Time (sec)
50
* 199A UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
4-12
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.Douglas, Northrop, and other aerospace and automobile manufacturing
facilities(Golden, et.al. 1988, Evanoff 1988, 1994, Suciu 1989). These
studies and process changes have demonstrated that alkaline cleaners are
effective in situations where a broad spectrum of soils are present and a
variety of substrate materials are being cleaned. Hundreds of alkaline
cleaning formulations are commercially available and more are currently under
development. These products should be screened for specific applications to
ensure that they meet the soil removal requirements, are compatible with
substrate materials, and do not leave residues harmful to the surface or
downstream surface coating processes.
As an alternative to 1,1,1-trichloroethane and CFC-113 use, the U.S. Air
Force is specifying the use of Mil-C-87937 Cleaning Compound. A corrosion
preventative compound is required if the article is not coated immediately
after cleaning. The Air Force is using aqueous cleaning solutions for
degreasing of landing gear.
Acidic cleaners^ are used to remove .rust and scale which cannot be
removed by organic solvents. They are also used to clean aluminum, a metal
susceptible to etching when cleaned with strong alkaline cleaners. In
general, acidic cleaners cannot be used as substitutes in organic cleaning
applications . '
4.3.4.2 Aqueous Cleaning Processes
The principal stages in aqueous cleaning are washing, rinsing, and
drying (See Figure IV-3). Soil removal is influenced by thermal
(temperature), chemical (concentration), and mechanical (agitation) energies.
These can be optimised for specific cases. Mechanical energy in washing and
rinsing can be provided through ultrasonics, immersion with agitation of the
cleaning solution, or of the parts, and spraying. Aqueous cleaning equipment
can be characterized as either in-line equipment, used for high throughput
cleaning requirements, or batch equipment used for low throughput such as
maintenance applications or smaller production processes, or in areas where
additional, metalworking is required prior to finishing. In-line and batch
equipment can be further subdivided into immersion, spray, and ultrasonic
equipment. Equipment design features and options vary. Options include
solution heater.s, dryers, parts handling automation equipment, in-process
solution filtration, and solution recycle and treatment equipment. .Immersion
cleaning, ultrasonic cleaning, and spray cleaning processes are described
below.
4.3.4.2.1 Immersion Cleaning
Aqueous immersion cleaning combines chemical, thermal, and mechanical
energies. Immersion cleaning consists of four major steps: cleaning, rinsing,
drying, and wastewater treatment (recycling or disposal).
In the cleaning process, the parts are immersed in a solution and some
form of agitation is added to provide the mechanical energy needed to
* Acidic cleaners contain mineral acids (nitric, sulfuric, phosphoric,
and hydrofluoric), chromic acid, or organic acids (acetic and oxalic) plus
detergents, chelating agents, and small amounts of water-miscible solvents.
* 1994 UNEP SOLVENTS, COATINGS, 'AND ADHESIVES REPORT *
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Figure IV-3
CONFIGURATION OF AQUEOUS CLEANING PROCESS
Parts from
Manufacturing
Process
Solution
Racirculation:
Filtering, Skimming
Wash
Stage:
Heated Detergent
Solution: Spray,
Immersion
Ultrasonics, etc.
Rinse
Stage:
Water:
Spray. Immersion
Dryer:
Room Temp Air
or Healed Air
Periodic Removal
Cleaned
Parts Ready
for Continued
Production
Waste Treatment
Source: EPA1989a
flMMII
-------
displace, dissolve, saponify, and emulsify soils. The cleaned parts are
rinsed with deionised or relatively pure water. Additives may be added to
enhance wash solution displacement and decrease the amount of water drag-out
prior to drying. . .
/
Rinsing removes any.remaining contaminants and cleaning solution drag-
out and may serve as a final finishing step. Rinsing is an essential step in
most aqueous cleaning applications. Care should be taken to prevent cleaning
fluids from being trapped in holes and capillary spaces. Low surface tension
cleaners sometimes penetrate spaces and are not easily displaced by the higher
surface tension rinse water. Drying helps prevent surface oxide formation,
eliminates potential corrosion caused by solution penetration between close
tolerance surfaces, and dries parts for further manufacturing activities.5
Drying can be a major challenge in aqueous cleaning. In the case of simple
geometric or flat surfaces, the challenges may be minimal, but for complex
parts, rinsing and drying may require considerable engineering analysis and
experimentation. A combination of mechanical methods and multiple operations
may be required to displace the cleaning solution from the surfaces of. a
geometrically complex part. From the perspective of energy or process time,^
evaporative removal of bulk water is usually not practical. Compact turbine
blowers with filtered output can mechanically remove 90 percent or more of the
water. Care must be taken to assure desired air quality by appropriate
filtration of oil, particulates, and moisture. Noise reduction, humidity, and
air conditioning control are other considerations. Conventional convective
ovens can be used for drying. 'For certain lower temperature drying
requirements, vacuum dryers can be custom designed and fabricated.
The simplest aqueous immersion cleaning machine configuration consists
of a single wash tank. The demands of most cleaning jobs, however, will
likely require more complex equipment configurations. If a part must be
cleaned to a high degree of cleanliness or if the quality of downstream
process solutions is a great concern, several wash 'and. rinse stages would be
required.
4.3.4.2.2 Ultrasonic Cleaning
Ultrasonic cleaning effectively cleans intricate parts and contaminants
such as carbon and buffing compounds that are difficult, to remove (Randall
1988a, Oakite 1988). Ultrasonic machines are appropriate for cleaning small,
parts. ' ' .
Ultrasonic cleaning equipment creates submicron-sized vapour bubbles at
the metal surface by vibrating the cleaning solution at extremely high
frequencies. As the bubbles form and collapse, xthey create a scrubbing action
that cleans the entire surface of the parts, including blind holes -and very
small cracks and recesses (Unique Industries 1988). This cavitation process
creates extremely high temperatures and turbulence on a microscopic scale.
Transducers vibrate the tank (and hence the cleaning solution) at frequencies
from 25kHz to 40kHz (Branson 1988).6.
. 5 Some manufacturing processes require dried parts; others such as many
metal finishing process lines (anodizing or electroplating) do not.
6 1 kHz equals 1,000 vibrations per second.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Gross contamination of parts may reduce the effectiveness of ultrasonic
cleaning. These contaminants are most effectively removed in a heated
immersion tank with agitated cleaning solution or in a spray washer (Randall
1988b). Based on research performed by the U.S. Air Force, it has been
determined that ultrasonic cleaning enhances the corrosivity of the solvents.
Process design requires caution to ensure that the ultrasonics do not cause
any metal surface corrosion or damage to the parts. It also uses relatively
large amounts of electricity compared to agitation immersion cleaners of
similar size (Racquet 1988). Aqueous ultrasonic cleaning equipment can be
configured with other cleaning stages featuring parts and/or fluid agitation,
or it may be used as one step in a spray machine. The ultrasonic/spray
combination is more common for solvent-based equipment than for aqueous
equipment.
As an alternative to 1,1,1-trichloroethane vapour degreasing, the U.S.
Air Force is recommending the use of dip tank and ultrasonic cleaning
procedures utilizing ah aqueous cleaner (Kelly AFB).
4.3.4.2.3 Spray Cleaning
Spray equipment cleans parts with a solution sprayed at pressures from
as low as 14 kPa to 2758 kPa or more. Depending upon the resilience of the
surface to be cleaned, high velocity spray can be used to physically displace
soils. In general, the higher the spray pressure, the more mechanical energy
is provided in removing soil from metal surfaces. Spray cleaners incorporate
low-foaming detergents 'which are not as chemically energetic as those used in
immersion cleaners but are enhanced by the mechanical agitation. Spray
cleaning is. effective on flat surfaces and those made up of simple geometric
parts. Certain configurations such as the interior of an automobile tailpipe,
blind holes in machined parts, and other complex geometries have soiled areas
that are inaccessible to the sprayed cleaning solution; in these instances,
immersion cleaners are more> appropriate.
One difference in spray cleaning equipment is the way in which each
generates mechanical energy to clean parts. While the mechanical action of
spray cleaning equipment is spray action, the mechanical action of an
immersion machine may be created by ultrasonic waves, vertical agitation of
parts, or bath turbulence. A custom spray machine can combine spray action
with the mechanical action used in immersion equipment. Where possible, a
high pressure spray is an effective final rinse step. Optimization of nozzle
design such as spray pattern, drop size and formation, pressure/velocity, and
volume are very important and have a major impact on rinse effectiveness.
Spray rinsing uses less water and can provide cleaner surfaces than an
immersion bath, since the final water which contacts the part can be quite
pure.
The major differences among spray machines, however, relate to the
manner in which the parts are handled. Spray washers are of three general
types: batch, conveyor, and rotary.
Batch Spray Equipment: Batch spray cleaning equipment consists of a
.tank to hold the cleaning solution and a spray chamber with a door. Although
batch spray.machines have a single spray chamber, it is possible to rinse
parts in the same chamber by using a separate set of "plumbing" equipment to
spray water on the parts. The rinse water is then channelled away from the
* 1994 UNEP SOLVENTS, COATINGS, AND'ADHESIVES REPORT *
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tank holding the cleaning solution (Kelly 1988). These chambers can be manual
or automated.
Batch spray machines can be used fo-r maintenance or manufacturing
applications, but generally do not clean as thoroughly as multiple stage
machines. Because maintenance applications tend to have lower throughput
requirements than manufacturing applications, batch spray machines often are
used for maintenance cleaning. For precleaning of heavy soils, large cabinet
wash and rinse chambers with spray nozzles located around the perimeter are
available and have been designed to accommodate objects as large as electric
motors and engines of trains. For removal of heavy greases and tars, high
pressure steam is an excellent medium for precleaning and, for some equipment
maintenance activities, will provide acceptable cleanliness. This approach
has the advantage that the soil and condensate will rapidly separate into
water and oil phases, and in most countries neither phase is considered a .
hazardous waste. Currently Tinker AFB personnel have incorporated an aqueous,
biodegradable solvent into their batch spray system to replace 1,1,1-
trichloroethane solvents. Results to date have been satisfactory.
Conveyorised Spray Equipment: Conveyorised spray cleaning equipment
'consists of a tank to hold the cleaning solution, a spray chamber, and a
conveyor to feed parts through the machine. A more complex Conveyorised
system includes multiple wash and/or rinse stages along the conveyor, each
-stage with its own tank. The rinse water may be recirculated, especially if
it contains a treatment chemical such as a rust inhibitor. The rinse water
may be discharged if throughput is high or if parts drag significant
quantities of cleaning solution out of the wash stages.
Conveyorised equipment is usually used in manufacturing applications
with, high throughput requirements where parts have flat, even, controlled
surfaces. The advantages1of Conveyorised equipment are high throughput and
automated parts handling. If parts are processed before cleaning so that they
may be handled automatically from a process conveyor, it may be unnecessary to
manually handle the par.ts during cleaning. Conveyorised spray washers .can
clean all sizes of parts from a variety of industries.,' The amount of wash and
rinse water required per unit surface area of the part can be as low as 10
percent of that used in batch cleaning. This approach reduces the amount of
wastewater generated as compared to immersion'cleaning and rinsing. For small
parts with uneven and curved.surfaces that may not be readily cleaned with
immersion and agitation, dishwasher-type units with rotating parts holders and
multi-directional spray.nozzles are available.
Rotary Spray Equipment:' Rotary spray equipment is very similar to
Conveyorised spray equipment except-for the manner in which parts are handled..
A rotary machine employs a steel drum with a partition that spirals, along the
inner surface of the drum such that when the drum is rotating, parts will be
transported along the length of the drum. The drum is. perforated so the spray
can impinge on the parts to be cleaned.
Rotary spray washers are designed to clean small parts such as screw
machine parts (e.g., nuts and bolts) and small metal stampings. Rotary
equipment can clean large volumes of parts, but the parts must be able to
withstand the tumbling action of the rotating drum. Parts with delicate outer
diameter threads and polished parts that should not be scratched should be
cleaned in a different type of machine using a.basket with a locking lid that
. " 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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can hold the parts in place during cleaning (Taylor 1988). High throughput
can be achieved with these machines, making them good candidates for high
volume manufacturing operations. One tradeoff, however, is that the rotary
machines.require more energy input than other types,of spray machines.
4.3.5 Hydrocarbon/surfactant ("Semi-aqueous" and "Emulsion") Cleaners
Hydrocarbon/surfactant blends are emulsion cleaners that have been
developed, tested extensively and are beginning to be used as substitutes for
CFC-113 and 1,1,1-trichloroethane in metal cleaning applications which
incorporate high viscosity and high molecular weight soils, semi-solid soils,
and corrosion sensitive substrates. Hydrocarbon/surfactants are included in
many different cleaners and are formulated for different purposes. Examples
of these families of chemicals are the terpene hydrocarbons and glycol ethers.
Hydrocarbon/surfactants are used in cleaning processes in two ways.
They are either emulsified/diluted in water and applied in a manner similar to
standard aqueous cleaners or they are applied in a concentrated form and then
rinsed with water. Because both methods use water in the cleaning process,
the hydrocarbon/surfactant-based process is commonly referred to as a semi-
aqueous process.
The benefits of semi-aqueous cleaning processes include the following:
Good cleaning ability (especially for heavy grease, tar, waxes,
and hard to remove soils)
Compatibility with most metals and plastics
Suppressed vapour pressure (especially if used in emulsified form)
Nonalkalinity of process reduces corrosion potential and reduces
the metal content of wastestreams
Reduced evaporative loss
Potential decrease in solvent consumption which may lower overall
cost
Ability of some formulas to separate easily from water. "
The drawbacks include:
Recycling or disposal cost of wastewater could make the process
less economically viable
Flammability concerns if concentrated cleaner is used in spray
cleaners
Special equipment designs may be needed to account for
flammability
Objectionable odours with some cleaners, such as'terpenes
VOCs are major components of some cleaners
Drying equipment will be required in most applications .
Gelling of some cleaners in low water-content emulsions
Difficulty in reducing surfactants used in cleaners
Toxicity considerations not yet defined for all cleaners
Auto-oxidization of some cleaners. For. example, .d-limonene (a
type of terpene) can auto-oxidize. The terpene suffers auto-
oxidation naturally from contact with air. This can in some
instances be reduced using antioxidant additive .
Semi-aqueous cleaning systems may require more floor space in some
instances '
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Energy consumption may be higher than that of solvent cleaning
systems in applications that require heated rinse and drying
stages
In some applications, high purity water, which is expensive,, may
be needed.
The steps in a typical semi-aqueous cleaning process are analogous to
aqueous cleaning (see Figure IV-4). Equipment for use with semi-aqueous
processes are modifications of aqueous cleaning equipment design. In cases
where extreme cleanliness is required, hydrocarbon/surfactant cleaning can be
followed by a fully aqueous wash step with an alkaline detergent and a
deionized water rinse. Application methods that avoid misting such as spin-
under immersion or ultrasonics should be used.
Dilute hydrocarbon emulsion cleaners formulated with water may be
heated. Less mechanical energy is needed when using a hydrocarbon/surfactant
solution than when using an aqueous solution, because of the high solvency of
hydrocarbon/surfactant cleaners. Rinsing with clean water removes the
residues left by the wash step.
Equipment for use specifically with concentrated hydrocarbon/surfactants
is available. As with aqueous cleaning, this can be classified as immersion
or spray equipment'and as either batch or in-line equipment. Because of the .
solvency of hydrocarbon/surfactants, less mechanical energy is required than
in aqueous cleaning to achieve adequate cleanliness.. Emulsion cleaners also
effectively clean metal parts using ultrasonics.
4.3.6 Mechanical Cleaning
Various mechanical cleaning methods have been used for metal surface
preparation and proposed as possible alternatives for CFC-113 and 1,1,1-
trichloroethane. Brushing, wiping with rags.or sponges, use of sorbent
materials, media blasting, and pressurized gases are being investigated to
various degrees. These methods, however, are generally best suited for lower
grade cleaning requirements or as a precleaning operation.in the removal of
solid and semi-solid soils.
Pressurized gas may be used in some cases for particulate contamination
as an alternative to cleaning with 1,1,1-trichloroethane and CFC-113. Gases
which may be used include air, rare earth gases, carbon dioxide, and nitrogen.
These gases are readily available in bulk and smaller quantities and in
numerous grades of purity. The advantages of cleaning with pressurized .gases
versus 1,1,1-trichloroethane include the following: low viscosity, low
toxicity, high diffusivity, nonflammability, and low capital cost.
Disadvantages of using pressurized gas include: low density, high pressure,
cleaning of critical components, and often ineffectiveness in cleaning
microscopic particles.
Specific technologies under development include wheat starch blasting,
sodium bicarbonate blasting, and carbon dioxide (solid) blasting. These
methods and others being developed will be evaluated by DOE in collaboration
with the U.S. Air Force. Wheat starch can be dissolved in rinse water for
disposal and is not considered a hazardous waste after the oils and greases
are skimmed off. The carbon dioxide evaporates after cleaning leaving the oil
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure IV-4
SEMI-AQUEOUS PROCESS FOR
IMMISCIBLE HYDROCARBON SOLVENT
Hydrocarbon/
Surfactant
Waah Stag*
Emulsion
Rlnaa
Rlnaa
Dryar
Foread Hot Air
Hydrocarbon/
Surfactant
Rauaa
DIspOM or
Racycl*
Ctaanad
Parta
0CloMdLoepWatar
Site Water
TraatmMrt or
Ooirad to Drain
Dacantar
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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and grease contaminates behind, thereby reducing the volume of waste
generated. Carbon dioxide blasting is currently being used for paint
stripping but may be too forceful for less problematic cleaning needs (Kelly
AFB) .
4.3.7 Thermal Vacuum De-oiling
Thermal vacuum de-oiling is a system that uses a heated vacuum chamber
to remove oil from parts by vapourising the oil. The vapours are then pumped
through a cold trap where they are condensed and drained from .the system for
recycle or disposal. Typical cleaning applications for vacuum de-oiling are
parts of either simple or complex design that are soiled with low- to mid-
viscosity oils. This technology can be used to.successfully clean parts
following cutting, machining, quenching, and stamping operations. Vacuum de-
oiling is also used to clean parts in preparation for brazing, coating,
plating, and heat treating operations.
Advantages of vacuum de-oiling include the following: elimination of
cleaning solvents., provision of ultraclean parts, simple operation of
equipment, reclamation of oils, floor space requirements similar to that of
vapour degreaser equipment, and generally no need for environmental permits.
The primary disadvantage of vacuum cleaning is that the system is very soil
specific. Vacuum cleaning is only capable of removing oils that can be
volatilized within certain temperature, time, and pressure ranges. The
equipment settings for these variables depend on the characteristics of the
oil being removed as well as the mass and surface area of the parts being
cleaned. For these reasons vacuum cleaning systems work best in manufacturing
applications that have consistent part size and soil loading.
A number of volatile machining oils and forming lubricants are currently
available to produce metallic parts without vacuum system or cleaning
processes. For example, a heat exchanger of a domestic air-conditioning unit
has been made by aluminum fins and copper tubes with many kinds of machining
oils and forming lubricants. Traditionally, large amounts of 1,1,1-
trichloroethane have been used for removing these oils (Matsui 1991).
4.3.8 No-Clean Alternatives
A number of water-soluble and emulsifiable machining and metal forming
lubricants are available. These products are easier to clean using aqueous or
semi-aqueous cleaners and are less of a concern for worker exposure. Hot
water immersion, spray, or hot water immersion with ultrasonic may be . v
sufficient for removing lubricants that contain emulsifiers. Lubricant spray
applicators which discharge a fine well-controlled mist can decrease lubricant
usage without affecting product quality. Other alternative lubricants under
development include "dry" lubricants and thin polymer sheeting which can be
peeled from the surface after the metal forming operation, or in the case of
tube forming, "empty tube bending" which accomplishes the forming operation
without the use of a lubricant. These products and methods are not standard
industrial practices. They do, however, offer the potential for eliminating
the need for degreasing.
Material flow through production should also be reassessed to minimise
the number of times that a part is degreased and to consolidate the cleaning
operations into a centralised unit or location. In many plants, parts are
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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degreased two and possibly three times before finishing and assembly.
Consolidation of cleaning operations will decrease the amount of solution
treated and waste generated (Evanoff and Weltman 1988).
Segregation and precleaning of heavily soiled parts can extend bath
life. Heavily soiled parts can also be routed separately through a single
precleaning system; this has the effect of decreasing the amount of
contaminated cleaner being generated in the main production area cleaning
systems, because the amount of soil entering these systems is minimised
(Evanoff and Weltman 1988). Sorbent methods (sorbent laden pads or cloths)
can be used to wipe clean parts and surfaces after initial fabrication,
thereby reducing the cleaning requirements.
4.3.9 CFC-113 and 1.1.1-Trichloroethane Processes "for Which Alternatives
are Not Available
Alternatives are currently available for virtually all metal cleaning
processes that previously used CFC-113 and 1,1,1-trichloroethane. Those
applications for which there is no currently available alternative can be put
into two groups. First, there are those applications for which the Parties to
'the Montreal Protocol have granted an Essential Use Exemption (EUE). In
granting these exemptions, the Parties recognize that there are no feasible
alternatives to the use of CFC-113 and 1,1,1-trichloroethane in the short
term. The second group is comprised of some applications for which
stockpiling or recycling of CFC-113 and 1,1,1-trichloroethane is to be used to
satisfy short term demand for.these solvents.
4.4 COST OF ALTERNATIVES
Due to the wide variety of alternatives available to replace CFC-113 and
1,1,1-trichloroethane in metal cleaning applications, a full discussion of the
costs of these alternatives is not practical. However, there are several
universal cost components that should be considered when evaluating
alternative cleaners or cleaning technologies. These cost components can be
split into two groups --one-time costs and recurring costs.
One-time costs are those costs that are -incurred only at the beginning
of a project and are not repeated throughout the project life. The most
significant of these costs is often the capital investment in new equipment or
in the retrofit of existing equipment. Other one-t*Lme costs may include items
.such as laboratory and production testing, environmental, health, and safety
impact studies, equipment installation, personnel training, documentation
revisions, and environmental permitting.
Recurring costs are primarily operating costs. These costs are incurred
throughout the lifetime of the equipment or cleaning process and are often
calculated on an annual basis and compared to the costs of the CFC-113 or
1,1,1-trichloroethane cleaning process. Recurring costs may include costs for
raw materials (cleaning detergents, solvents, water), energy usage, waste
.treatment/disposal, and equipment maintenance. '
* 1994 UNEP SOLVENTS, COATINGS, AND.ADHESIVES REPORT *
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4.5 ENVIRONMENTAL. HEALTH. AND SAFETY CONSIDERATIONS
'»
This document is not a risk assessment and therefore it contains only a
general description of some of the environmental health and safety issues
associated with each alternative-cleaner or cleaning technology. The health
and environmental effects of some of these technical options are still being
investigated. Certain commercial solvents are generally recognised as toxic
while others are suspected but not confirmed as toxic. Other cleaners
including aqueous and emulsion cleaners contain constituents which may be
hazardous or which can have adverse environmental effects if discharged. .
Nonetheless, the use of toxic chemicals is permitted in certain cases by
governmental authorities but usually require strict workplace controls and
effective waste treatment and/or disposal. However, regulations may vary
depending on location. In some circumstances it may be prudent to select
cleaning options that do not depend as heavily on workplace controls and waste
treatment. - ,
The environmental, health, and safety impacts of the alternative
compounds that could be used in cleaning applications must be evaluated prior
'to their use. These impacts may include: acute and chronic health effects,
ozone-depletion potential, flammability., aquatic toxicity, global warming
potential, and volatile organic compound (VOC) classification. Potential
users of alternative cleaners should be; aware of the acceptability of a
particular alternative in their country, region, and locality. Users should
consult local, regional, and federal regulations governing the use, emission,
or disposal of any solvent cleaner. Committee members do not endorse the
worker safety or environmental acceptability of any of the1 technical options
discussed.
4.6 POTENTIAL GLOBAL REDUCTION OF CFC-113 AND 1.1.1-TRICHLOROETHANE IN METAL
CLEANING APPLICATIONS ' . .
The Committee consensus is that mos,t CFC-113 and 1,1,1-trichloroethane
used in metal cleaning applications can be replaced by these alternatives in
accordance with the Montreal Protocol by the year 1996. Some countries,
however, are achieving this phaseout according to their own accelerated
schedule. Approximately seventy-five percent of the short-term reduction of
CFC-113 and 1,1,1-trichloroethane usage is expected to be achieved through
aqueous cleaning substitution.
For general degreasing of metal surfaces and parts, aqueous immersion
cleaners and solvent emulsions can be substituted for most metal cleaning
applications. Many of these substitutions have already taken place in the
developed countries and are underway in developing countries. The remaining
complex cleaning applications can be replaced by sophisticated aqueous
cleaning systems or alternative solvent systems. These complex cleaning
applications will require extensive research-and design efforts. It is
important to allow for the appropriate development time to be sure that
inappropriate choices that might have significant health, safety, or
environmental impacts, are not made. ,
More than 60 percent of 1,1,1-trichloroethane was used by small
manufacturing companies. The technical and economic impacts are critical to
the survival of such companies. They often lack the resources and technical
I
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT "
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capabilities of larger firms, and essentially must rely on the success of the
larger companies to transfer to the smaller firms. This would most likely
mean the smaller companies will be about two years behind the larger firms in
their phaseout. The critical needs for smaller firms to make the changeovers
are: qualification of and transition to new processes, floor space
requirements, capital cost, and in many cases water treatment technology.
4.7 SUITABILITY OF ALTERNATIVES FOR DEVELOPING COUNTRIES AND SMALL QUANTITY
USERS
Developing countries should be able to closely follow the same scenario
as the smaller companies in the developed countries. They may have an
additional lag time in their own smaller industries. Each developing country
will have somewhat different scenarios depending upon their unique industry
basis.
Developing countries which maintain joint ventures with developed
countries, or with a strong multinational company-based manufacturing base
will be able to incorporate new technology fairly rapidly. Most multinational
companies plan to transfer their technology as expediently as possible to
their operations in developing countries. However, there will need to be a
significant time lag in this technology transfer process as well. It is
expected that most multinational companies, including jointly owned affiliate
companies should be able to transition their developing country operations
within two years of their home operations.
Potential alternatives discussed in this chapter, as well as emerging
and developing technologies, will be able to substitute for CFC-113 and 1,1,1-
trichloroethane use in all applications, but especially for 1,1,1-
trichloroethane in metal cleaning applications. Since'more than 60 percent of
annual consumption of 1,1,1-trichlorpethane has been used by sm&ll and medium
enterprises (SMEs), both technological and economical impacts are essential.
Promotion of technology disclosure and even subsidization could be necessary
for average SMEs.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CHAPTER 5
DRY CLEANING INDUSTRY
5,1 .BACKGROUND
Dry cleaning enables the cleansing and reuse of fabrics that cannot be
cleaned by alternative methods. The inherent environmental friendliness of
restoring freshness to soiled articles and garments is matched by extreme
efficiency in terms of solvent and energy use in the dry cleaning process
itself. Organic solvents are used to clean fabrics because, unlike water,
they do not distort some natural and synthetic fibres. Water cleaning of many
materials can affect the stability of fabric, lining, and interlining and may
cause stretching or shrinkage.
In addition to the actual machine cycle, the term "dry cleaning"
includes a large number of operations: customer service, precleaning stain
treatment/heavy soil release, post-cleaning stain treatment, tailoring,
pressing, and ironing'. In such a labour-intensive business, where up to 40
percent of receipts are required for wages alone, dry cleaners have had strong
financial incentive to pay close attention to other operating costs, including
solvent cost/selling price ratio. Even before the ozone-depletion
contribution of solvents became widely known, dry cleaners, for purely
commercial reasons, had been frugal solvent users. This scenario has had two
other effects: low solvent use/high energy efficiency has been an important
factor in the purchase of dry cleaning machines, and manufacturers have
competed to produce and market increasingly efficient and environmentally safe
products.
For many years, dry cleaning machines have been totally enclosed;
incorporating,filtration, distillation, and refrigerated recovery systems
allows solvents to be continuously recycled. The technology developed by some
European dry cleaning machine manufacturers may have applications in the
manufacture of metal cleaning machines which require high solvent efficiency.
5.2 CFC-113 AND 1.1.1-TRICHLOROETHANE USE IN THE DRY, CLEANING INDUSTRY
fc CFC-113 is used as a dry cleaning solvent not only because of its low.
toxicity, stability, nonflammability, and relatively low boiling point, the
latter a factor which minimizes energy requirements during the drying and
distillation, but also because of its low solvency power (31 Kauri Butanol
Value). The low solvency allows the cleaning of fabrics with sensitive dyes
and trimmings which may fade or run if cleaned with other solvents. CFC-113
when used in conjunction with leather oils is ideal for cleaning suede and
leather garments. As CFC-113 is phased out, however, fashion designers and
clothing manufacturers will have less flexibility in their selection and use
of fabrics and trimmings and in the future must construct garments that can be
dry cleaned in other solvents.
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The use of 1,1,1-trichloroethane has been limited as a dry cleaning
solvent for a number of reasons. While its high solvency power (Kauri Butanol
124) removes soiling, easily and thereby reduces the need for prespotting and
recleaning, the solvent damages plastic trimmings, pigment prints, and some
bonded fabrics. In addition, the capital cost of the cleaning equipment is
approximately 60 percent higher than the cost of CFC-113 cleaning equipment.
1,1,1-Trichloroethane not only has a strong odour, but is also heavily
stabilized and, without regular attentions can break down to produce acid
which corrodes the machine and possibly ancillary equipment.
Another major factor limiting the use of 1,1,1-trichloroethane in dry
cleaning relates to care labelling. The solvents to be used for cleaning are
indicated by the marks specified in International Standards Organisation (ISO)
3758. Few garments carry the care label A which indicates the garment may be
safely cleaned in 1,1,1-trichloroethane. The majority of garments are marked
P (clean in perchloroethylene, CFC-113, or.white spirit) or F (clean in CFC-
113 or white spirit). If adhered to, these labels protect the dry cleaner
from liability if the garment is damaged by the dry cleaning process. .
While no more than a few hundred machines in the US and Europe use
1,1,1-trichloroethane as a dry cleaning solvent, a late-1980s study in Japan
by Ethane Research Working Group, a group comprised of solvent producers,
research and trade associations, machinery manufacturers, and detergent
producers, generated interest in machines using 1,1,1-trichloroethane. As a
result, some 2,300 machines were in operation by the beginning of the 1990s.
However, this number still represented only 4.3 percent of the total machine
population.
5.2.1 Dry Cleaning Machines
A modern dry cleaning machine is similar to a combined washing
machine/tumbler dryer. The articles are washed in an organic solvent to which
a liquid detergent is added during the. main wash stage. Following rinsing arid
spinning, the articles are tumble dried in the.same machine. They are only
removed after all of the solvent has been recovered. This system, known as a
totally enclosed machine or dry-to-dry process, prevents the solvent emissions
that previously occurred when clothes were cleaned in one unit and transferred
to a separate dryer (transfer machines).
A dry cleaning machine is required to complete three prime functions:
To thoroughly clean a wixie variety of garments and other articles
To enable complete drying of items before they are taken out of
the machine
I
To purify the solvent for reuse.
To perform its prime functions, three distinct circuits relating to
solvent, air, and distillation operate within the machine. Figure V-l shows
the various flows in a simplified form and Figure V-2 details a typical layout
of basic components.
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Figure V-l
BASIC DRYCLEANING MACHINE PRINCIPLES
Fan
Drum
Solvent
Pump
Distilled
Solvent Tank
Still
Condenser
Solvent Circulation
Filler Circuit
Air Circulation
Drying Circuit
Distillation Circuit
Shown simplified are the three most important stages in drycleaning machine
operation:
Solvent circulation - filter circuit (cage, button trap, pump, filter, and back to cage).
Air circulation - drying circuit (cage, fan, recovery condenser, air heater and back to cage).
Distillation circuit (still, still condenser, water separator, distilled solvent tank).
IIK077-2
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure V-2
TYPICAL LAYOUT OF BASIC COMPONENTS
1 Cage-
2 Button Trap
3 Lint Filter
4 Fan
5 Recovery Condenser
6 Air Heater
7 Solvent Filter
8 Still
9 Still Condenser
10 Water Separator
11 Distilled Solvent Tank
12 Working Tank
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5.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND 1.1.1-TRICHLOROETHANE
USE
5.3.1 Conservation and Recovery Practices
Solvent losses in dry cleaning machines result from poor recovery
(drying), leakage, distillation losses, and incorrect handling during
refilling and servicing. Table V-l lists some of the reasons for losses from
these machines. Improved operator practices and better engineering and
controls could conserve much Of the CFC-113 and 1,1,1-trichloroethane solvent
currently lost. Recycling and recovery technology is already at an advanced
stage in which totally enclosed machines feature refrigerated condensation of
solvent vapour and activated carbon adsorption of any trace emissions of
vapour. Operation and maintenance practices can also ensure that CFC-113
emissions are low. Such practices include activating the drying fan prior to
opening maintenance manholes and daily cleaning of the lint filter.
When a machine has not been operated for a number of hours, solvent
vapours will fill the machine space. By activating the drying fan prior to
opening maintenance manholes, the vapours can be regenerated. Machines can be
equipped with a special timing device that activates the drying fan one to
two minutes prior to opening the machine door, thereby reducing solvent
losses. In general, inspection manholes for the cage (cleaning chamber),
button trap, and lint filter should always remain closed during operation and
should be opened for the shortest possible interval during servicing. In
machines equipped with a button trap that is separate from the regeneration
system, special precautions should be taken when,cleaning the trap -- all
residue from it should be placed .in the lint filter for drying.
Efficient operation of the refrigeration unit in dry. cleaning machines
can reduce CFC-113 losses by up to 25 percent. The large variations in the
size of loads processed by machines result in varying quantities of
uncondensed vapours being left in the distillation units or machines.
Monitoring devices are available to measure the various loads on the
refrigeration unit or heat pump and to be.tter control temperatures. All CFC
machines can be fitted with a low pressure sensor and regulator for the
cooling coils. Such a device monitors the optimal condition for coil
operation and switches off the machine when excessive vapour builds up in the
expansion vent or when the level of refrigerant is inadequate. When a low
pressure device is being installed, the evaporation and condensation
temperatures for the refrigeration cell can be adjusted. The suppliers for
the respective machines can provide the relevant values for optimum drying
efficiency. . ' .
Filter replacement significantly reduces solvent losses. A small
filter, for example, contains approximately 4 to 5 kg of solvent after .
drainage. With proper filter replacement techniques, this solvent can be
recovered in the cleaning drum of machines. : Some machines, however, are
equipped with one large filter or many small filters that do not fit the
machine drum. Machines with more than four filters can be reconstructed so
that filtration takes place only through two filters. Those filters not
operating should be put aside for drainage and subsequent regeneration.
Machines with a single filter that is too large for the drum can be equipped
with sealed drainage vessels that are attached to the machine's 'regeneration
system or stored and transported to a special regeneration facility.
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Table V-l. GENERAL SOURCES OF SOLVENT LOSSES FROM DRY CLEANING MACHINES
Leakage at the still door
Leakage at the button trap hatch
Leakage at the lint filter
Leakage at the loading door
Leakage at the lids for the heating and refrigeration chambers
Leakage at the main drive shaft seals
Leakage at the pipe connections
Spillage during refilling
Clogged air-cooled condensers
Substandard maintenance of the lint filter
Inadequate cooling water flow
.Solvent in the condensed water
Cleaning of the button trap, especially during operations
Excessive build-up of lint between the outer and. inner drums
Negligence during filter replacement or improper machine design
Inadequate final distillation
Overloading
Underloading
Incorrect assembly and installation
Humidity in the cooling system
Incorrect choice of temperatures
Substandard maintenance
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A number of daily operation and maintenance activities also can be
conducted to reduce solvent losses from CFC-113 and 1,1,1-trichloroethane
machines. Because lower air velocity increases drying time, the lint filter
should be cleaned or replaced daily. Prior to system start-up, the cooling
water circulation system should be checked as well as the refrigeration
system, refrigerant, and oil levels. In-addition, all seals and gaskets
should be checked weekly and adjusted if necessary. The machine should not be
overloaded and should be checked to ensure that each load is dried prior to
opening the machine.
Other preventive maintenance practices include cleaning the still only
when it is cold, ensuring that the temperature of the refrigeration cell does
not fall below the freezing point of the solvent, and regularly cleaning the
temperature sensors. In addition, the pressure equalization device should be
checked to ensure that solvent is not allowed to escape, and the activated
carbon filter should be inspected to determine the amount of solvent
recovered. Finally, condensed water from the water separator should be
collected in a transparent container. Before emptying the container, liquid
should be checked'for the presence of any free -solvent. If solvent is
present, it should be separated prior to emptying the container. The contact
water should be disposed of in accordance with the appropriate federal,
regional, and local regulations.
5.3.2 Alternative Solvents
A number of solvents can be used as alternatives to CFC-113 and 1,1,1-
trichloroethane in dry cleaning operations. Table V-2 lists several chemical
characteristics of the alternatives discussed below.
5.3.2.1 Perchloroethylene
Perchloroethylene, the most widely used dry cleaning solvent, has been
used in this application for over 30. years, during which time the systems for
its safe use have become highly developed. For dry cleaners who are seeking
to replace their CFC-113 or 1,1,1-trichlproethane machines, perchloroethylene
is a logical and practical choice. Its higher solvency power than CFC-113
means that it is not suitable to clean a minority of the fabrics, trims, etc.,
that can be cleaned in CFC-113 (Clark, 1991b). It is an adequate replacement
for 1,1,1-trichloroethane. '
Some studies have implicated perchloroethylene as a possible carcinogen
although recent toxicological and epidemiological evidence indicates that this
is either not proven (EPA 1989b) or due to species differences not relevant to
humans (Clark, - 1991a). In addition, it is important to bear in mind that
modern perchloroethylene machines are extremely efficient and usually result
in low solvent emissions. Nonetheless, the use of perchloroethylene in dry
cleaning may be regulated in some countries, regions, or localities. For
example, the U.S. EPA set national emissions standards for perchloroethylene
in September, 1993 that apply to both- new and existing perchloroethylene dry
cleaning facilities. These standards were set in part because
perchloroethylene is listed in the Clean Air Act as a hazardous air pollutant,
and because a recent study in Staten Island, New York and New Jersey .concluded.
that perchloroethylene is "among the toxic air pollutants found at the highest
concentrations in urban air (U.S. EPA, 1993)."
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Table V-2. CHEMICAL CHARACTERISTICS OF SELECTED DRY CLEANING SOLVENTS
Solvents
CFC-113
Perchloroethylene
Petroleum- Based
Solvents
1, 1,1-Tirichloroethane
HCFC-141b
HCFC-123
HCFC-225
Flamm-
ability
NFb
NF
Fc
NF
F
NF
NF
Boiling
Point
(°C)
47.6
121.2
150-210
74.1
32.1
27.6
51-56 .
Heat Required
to Boil
One Litre8
(Real)
64
116
N/A
90
68
62
63-66
Kauri
Butanol
Value
31
90
26-45
124
58
60
30-34
a Heat required to boil one litre of solvent from 20°C.
b NF - Nonflammable.
c F - Flammable.
Sources: TSA 1991, Rodgers 1989, Kirk-Othmer 1983, Basu 1989.
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5.3.2.2 Petroleum Solvents (White Spirit. Stoddard Solvent. Etc.)
The flammabili'ty of petroleum solvents effectively precludes their use
in shops, although with proper precautions, they can be a substitute for CFC-
113 on many fabrics. In Australia, for example, a fabric labelling convention
has been introduced that designates white spirit as a substitute for CFC-113
in the dry cleaning of specific fabrics (Standards Association of Australia,
1987).
Petroleum solvents include white spirit, Stoddard solvent, hydrocarbon
solvents, isoparrafins, n-parrafin, etc. Depending on the solvent,
characteristics such as flash point, solvency (Kauri Butanol value),
distillation temperature, etc. will vary. White spirit and stoddard solvent
were developed for dry cleaning applications 40-50 years ago, and have been
used to some extent in the U.S., Europe, Japan, and Australia. However, their
use has been gradually decreasing over time because of substitutions made to
nonflammable solvents and because of regulations restricting emissions of
volatile organic compounds. In addition, despite epidemiological studies
there are unresolved issues concerning the toxicity of some petroleum
solvents.
Recent improvements in dry cleaning equipment to maximize recovery of
cleaning solvents while minimizing emissions has resulted in increases in the
use of flammable solvents. In addition, new petroleum solvents are being
marketed that have lower odour and toxicity.
5.3.2.3 Hydrochlorofluorocarbons (HCFCs)
i
A number of HCFCs and HCFC 'blends are currently available commercially
for use in solvent applications. These include HCFC-123, HCFC-141b, and HCFC-
225. These HCFCs have good stability, excellent solvency, and nonflammability
and some HCFCs are suitable for cleaning those delicate fabrics that currently
depend on CFC-113. Due to its status as a suspected, carcinogen, HCFC-123 is
not being marketed for use in solvent applications and is therefore not a
possible alternative to CFC-113 and 1,1,1-trichloroethane. In addition, HCFC-
141b is not a recommended alternative, especially for 1,1,1-trichloroethane,
because it has an ozone depletion potential (ODP) comparable to that of 1,1,1-
trichloroethane. HCFC-225, which is a blend of the ca and cb isomers, has a
similar boiling point to CFC-113 and is proving suitable for cleaning many
sensitive fabrics. Because of dry cleaners' concerns for the solvent
cost/selling price ratio, the cost of the blend will determine how readily it
is used. It should be noted, however, that HCFCs are transitional
alternatives subject to a phaseout under the Montreal Protocol by the year
2030. . .
5.3.2.4 Other Alternative Solvents
Other classes of chemicals such as iso-paraffins, solvents derived from
sugar cane, and hydrocarbon/surfactant blends arev theoretically possible
alternative dry cleaning solvents. More research, however, is necessary to
determine their feasibility for dry cleaning.
Recently; a large chemical manufacturer introduced a synthetic, high-
purity hydrocarbon solvent. Some of the properties' which may make it a good
dry cleaning solvent include good cleaning power, low odour, long service
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life, high flash point, and low toxicity. A relatively high flash point of
64°C (147°F) provides a greater margin of safety over most other hydrocarbon
solvents, thereby reducing building fire suppression requirements in some
areas. This solvent is currently in use at dry cleaning facilities and the
following properties have been observed (Exxon, 1994):
compatible with closed-loop, dry-to-dry machines traditionally
used with perchloroethylene (PERC) and petroleum solvents
compatible with common additives
requires virtually no deodorants since it is virtually odourless
cycle time comparable to that of a Stoddard solvent, and slightly
longer than PERC
little or no plant/building modifications except for the approval
from the Fire Marshal
releases dirt to carbon/clay filters improving cleanliness and
prolonging solvent life -
Potential users of this or any other flammable solvent should determine their
acceptability given local fire regulations.
5.3.2.5 Centralized Processing Facilities
The establishment of centralized cleaning facilities could augment the
controls on solvent losses that can be achieved at small, individual dry
cleaning establishments. At centralized facilities, additional investments in
control devices and standardized operation and maintenance practices can lead
to more efficient solvent use.
5.4 COST OF ALTERNATIVES
A dry cleaning machine is the most expensive single item of capital
expenditure incurred when establishing a dry cleaning operation. Dry cleaning
machines are usually designed to last for 12 to 15 years. Most CFC-113 and
1,1,1-trichloroethane machines can only function using the original solvent.
A significant portion of the cost of eliminating CFC-113 or 1,1,1-
trichloroethane use can be attributed to the need to replace an otherwise
satisfactory dry cleaning machine. The majority of dry cleaning businesses
are small and the high capital cost involved in 'early replacement may result
in the businesses being forced to close. For certain CFC-113 machines, one of
the HCFCs (e.g., HCFC-225) or HCFC blends discussed in section 5.3.2.3 may
prove to be a "drop-in" alternative, thereby saving the cost of early machine
replacement. In other CFC-113 machines, extensive and costly (approximately
50 percent of replacement cost) modifications to accommodate an HCFC or HCFC
blend may be possible. For machines using 1,1,1-trichloroethane, a
modification of the energy balance may allow a change to perchloroethylene. A
switch to flammable petroleum or hydrocarbon solvents will require-extensive
modifications or the purchase of new equipment to provide adequate safety
precautions needed because of the flammability of the solvents.
5.5 ENVIRONMENTAL AND ENERGY CONSIDERATIONS
The solvent efficiency of the current generation of hermetically sealed
perchloroethylene dry cleaning machines not only reduces emissions but also
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enables the solvent to be continuously recycled. The machines have introduced
a number of features which reduce the amount of solvent being used and which
achieve solvent losses of less than one percent of load weight (equivalent to
0.2 to 0.5 kg/g-m2 of basket cross-sectional area of dry cleaning). Such
technology, however, has a significant impact on machine cost, although the
initial capital outlay'is offset by savings in perchloroethylene, energy, and
consumption of cooling water (Clark, 1991a).
These new features include the following systems:
carbon adsorption
disc filtration
heat pump technology
HCFCs.
Carbon Adsorption
For many years, carbon adsorption systems which adsorb solvent vapour
from air prior to discharge into the atmosphere have been available. They
have usually been free standing and used in connection with the larger
industrial machines. This technology has now been modified to enable
adsorption'units to be built into smaller,machines. Air from the cage at the
end of the drying cycle is passed through the adsorption unit prior to opening
the cage door for unloading. The cage door can be interlocked to prevent '
opening until solvent concentration has been reduced to a pre-determined
level.
Disc Filtration
This method of removing the insoluble soil from cleaning solvent is
gaining much support. When a series of fine (less than 30 micron mesh)
polyester disc filters are used, still residues are greatly reduced and the
need for filter cartridges is eliminated. This-method of filtration,
therefore, reduces the amount and cost of waste disposal, eliminates solvent
losses associated with the changing of cartridges, and saves the cost of
cartridges or other filtration media such as powder.' .
Heat Pump Technology
With heat pump technology, the heat generated by the warm side of
refrigeration units is used to reduce the energy levels required for garment
drying and/or to preheat .solvent awaiting distillation.
HCFCs .
If proven dry cleaning systems for HCFCs or HCFC blends become
available, the lower boiling points of these solvents may further reduce
energy use. Although the ODPs of HCFCs are lower than those of
chlorofluorocarbons (CFCs), they are not zero, and special recovery systems
will be needed to minimize solvent emissions.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT * .
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5.6 POTENTIAL GLOBAL REDUCTION OF CFG-113 AND 1.1.1-TRICHLOROETHANE USE IN
THE DRY CLEANING INDUSTRY
Reductions in CFC-113 and 1,1,1-trichloroethane solvent losses from dry
cleaning uses are possible to achieve using currently commercially available
equipment and cleaners. .
Long-term reductions in 1,1,1-trichloroethane and CFC-113 use will occur
as the capital stock of machines turns over to new machines that do not use
these solvents. Perchloroethylene, in most cases, is the logical replacement,
although it is not suitable for cleaning about 5 percent of the fabrics and
trims that now can be cleaned with CFC-113.
Proven HCFC systems may emerge in which specialized cleaning
requirements can be met. In addition, as the concern over the human health
effects of perchloroethylene becomes of greater concern and is addressed by
increasingly stringent emissions reduction requirements, other alternatives
are likely to gain larger market shares in the dry cleaning industry.
Reductions arising from relocation of 1,1,1-trichloroethane or CFC-113
machines to centralized facilities are unlikely to be significant as it is
difficult to justify the large investment required for such a move when viewed
against a phaseout schedule. The solvent reduction benefits from centralized
facilities may be more fully realized with perchloroethylene or the other
alternatives described as companies replace machines using CFC-113 arid 1,1,1-
trichloroethane.
The Committee consensus is that no CFC-113 or 1,1,1-trichloroethane
should be necessary in the dry cleaning industry in developed countries.by the
year 1996. CFC-113 and 1,1,1-trichloroethane use can be largely eliminated
through the use of currently available alternative solvents, such as
perchloroethylene. Furthermore, the Committee warns garment manufacturers
that clothing or other textile products that can only be cleaned in CFC-113
may, at some future date, no longer be able to be cleaned. As a precaution,
in the event that HCFC substitutes do not become available, garment
manufacturers are advised to ensure that fabrics, trimmings, and interlinings
are suitable for dry cleaning in perchloroethylene.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CHAPTER 6
ADHESIVES APPLICATIONS
6.1 BACKGROUND . '
1,1,1-Trichloroethane is used as an adhesive solvent because it is non-
flammable, dries rapidly, does not contribute to local air pollution, and
performs well in many applications, particularly foam bonding. The use of
1,1,1-trichloroethane in these applications has diminished due to the
implementation of the Montreal Protocol. However, in 1989 40-50 thousand
tonnes of the chemical were used in adhesive applications in the U.S., Western
Europe, and Japan (Chem Systems, 1989). As CFC-113 is not used in adhesives
it is not discussed further in this section.
A partial list of applications where 1,1,1-trichloroethane adhesives are
used includes:
packaging;
non-rigid bonding;
construction;
.tapes;
rigid bonding;
transportation; and
consumer adhesives.
This section provides a summary of 1,1,1-trichloroethane use in
adhesives. Section 6.2 discusses the physical properties of 1,1,1-
trichloroethane that make it attractive for adhesives use and gives examples
of its use. Section 6.3 discusses a number of alternatives for reducing or
replacing 1,1,1-trichloroethane in adhesives, and Section 6.4 compares the
costs of these alternatives. Section 6.5 discusses the environmental and
energy considerations of alternatives. Section 6.6 presents potential global
reduction of 1,1,I-trichloroethane in the adhesives industry. Finally,
Section 6.7 discusses the suitability of alternatives-for developing countries
and small quantity users.
6.2 1.1.1-TRICHLOROETHANE USE IN ADHESIVES APPLICATIONS
1,1,1-trichloroethane has several physical characteristics that provide
desirable performance properties, for adhesive applications. It has been used
for many years in contact bond adhesives because it offers similar performance
characteristics to the flammable solvent-based adhesives it replaced and.yet
is not flammable. In particular, it has found wide use in bonding decorative
laminates to substrates such as particle board and plywood (Dawnkaski 1991).
In general, 1,1,1-trichloroethane has been used when:
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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a solvent-based adhesive is desired for rapid drying time and high
film strength, and either flammability is a consideration or the
use of volatile organic compounds (VOCs) is restricted; and
bonding certain substrates, such as foam, plastic, or wood.
Table VI-1 presents physical properties of 1,1,1-trichloroethane and
selected conventional solvents used in adhesives. Of particular note is that
1,1,1-trichloroethane (and methylene chloride) has no flash point.1 The
other conventional solvents listed in the table have low flash points, low
explosion limits, and are considered to be flammable solvents.
1,1,1-trichloroethane also displays low water affinity. Only 0.05 grams
of 1,1,1-trichloroethane can be dissolved in 100 grams of- water at 25°C. It
is, therefore, used as a coalesceht in some water-based adhesive systems.
1,1,1-trichloroethane evaporates faster than other solvents used in adhesive
formulations, which allows increased throughput in applications where drying
time contributes to the overall process yield (e.g., in pressure-sensitive
tape manufacturing). The density of chlorinated solvents, such as 1,1,1-
trichloroethane, is greater than that of conventional solvents used in
adhesives, and the solids/viscosity relationship of adhesives diluted with
chlorinated solvents is different from those diluted with conventional
solvents. When selecting solvent alternatives, these differences are taken
into account with regard to application cylinders, machine speeds, and so on.
1,1,1-trichloroethane has a mid-range solvency when compared to
conventional .adhesive solvents. .The chemical is an active solvent for alkyl,
acrylic, chlorinated rubbers and many phenolic resins and a diluent for
nitrocellulose, vinyl, and epoxy resins (Dow 1984). 1,1,l-.Trichloroethane can
be mixed with other solvents to adapt its solubility strength to the needs of
a specific resin system. This task is usually performed by the adhesive
formulator who customises solvent blends to meet specific solubility needs.
In the U.S., 1,1,1-trichloroethane is exempt from volatile organic
compound (VOC) regulations in most states, which provided an incentive for
some adhesive manufacturers and their customers to use the solvent in place of
VOC solvents (Dawnkaski 1991). As an example, 1,1,1-trichloroethane has been
used as a replacement for organic solvents in the following applications (UNEP
1989):
manufacture 'of styrene-butadiene latex adhesives;
formulation of polyurethane-adhesives;
replacing extremely flammable solvents in pressure-sensitive tapes
and labels, and in industrial and consumer adhesives;
'Substituting flammable solvents in PVC flooring adhesives; and
replacing ethyl acetate solvents in laminating adhesives used in
packaging.
In general, 1,1,1-trichloroethane is used as active solvent in solvent-
borne adhesives and as a diluent in water-borne adhesives. Solvent borne
adhesives containing 1,1,1-trichloroethane are primarily contact adhesives and
1 Flash point temperature is the lowest temperature at which vapours
above a volatile combustible substance ignite in air when exposed to flame.
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Table VI-1. PHYSICAL PROPERTIES OF COMMON ADHESIVE SOLVENTS
Solvent
Flash Point.
Open Cup
Flammable Limit
in Air
25°C (Volume %)
Upper Lower
Water
Soluble in Kg/
lOOg Solvent Liter
(g) 20°C
1,1,1-Trichloroethane NFa
Methylene Chloride NF
Toluene 7.22
n-Hexane -27.8
Methyl Ethyl Ketone -5.6
Ethyl Acetate -2.2.
12.5
22.0 .
7.0 .
6.9
11.5
11.0
7.5
14.0
1.3
1.25
1.81
2.25
0.05
0.17
0.05
0.01
11.80
3.3
1.314
1.316
0.870
0.678
0..804
0.900
a NF = No Flash Point.
Source: Dow 1984.
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spray adhesives used where good "green bond," or initial bond, is desired, as
in the manufacture of foam cushioned furniture or plastic laminated
countertops. The primary binders in these adhesives are rubbers of various
kinds, including natural rubber, neoprene, chloroprene, and styrene-butadiene
rubber. Acrylic binders are also used. Adhesive grades applied by extrusion
or spraying have dry solids contents of less than 15 percent, while other
grades are between 15 and 30 percent. Table VI-2 shows specific binding
substances (i.e., adhesive type) where 1,1,1-trichloroethane is used.
In assembling foam padded furniture, for example, a thin film of
adhesive is applied to the two surfaces being joined. When the foam padding
is applied to the frame, the adhesive bonds immediately. The adhesive joint
must then hold without adhesive or solvent migrating into the foam material
and ruining it. In other words, the tack, or "stickiness", of the adhesive
must decline quickly. The 'time between application and the last moment for
assembly (when the tack disappears) is called the "open assembly time". The
solvent-based rubber adhesives'have good properties in these respects, with
good green bond and a short open assembly time.
Two paths are available for solvent reduction in adhesives; established
technologies and emerging technologies. Established technologies include
other solvent-based adhesives, water-based adhesives, hot melt systems, and
solvent recovery systems in continuous operations. Emerging technologies
include radiation cured adhesives, "high solids" adhesives, powders, and
reactive liquids. These technologies are discussed .in further detail below.
6.3 ALTERNATIVES FOR REDUCING OR REPLACING 1.1.1-TRICHLOROETHANE USE
6.3.1 Other Solvent-Based Adhesives
The rubber binders used in 1,1,1-trichloroethane adhesives are soluble
in other solvents, such as acetone, ethyl acetate, -heptane, and toluene.
Although there has been a general trend in the U.S. arid Western European
adhesives industries to replace organic solvent-based adhesives with solvent-
free types, one alternative is to return to earlier solvent formulations.
According to one market survey conducted in the U.S., volatile organic
compound (VOC) regulations provided the initial impetus for moving away from
solvent-based technologies. However, for some industry sectors, such as
tapes, this shift would continue in the absence of regulations because
alternative technologies are more competitive on a cost and performance basis
(Ellerhorst 1982). The use of solvent-diluted (as opposed to solvent-based)
adhesives has also been declining for economic reasons (Kimel 1988).
The use of solvent-based adhesives is costly because they require flame
proof equipment and extraction systems (6'Driscoll 1988, Johnson -1991). The
premises and apparatus must be designed fire-safe in terms of both sparking
and static electricity. In many cases it is necessary to use robots in closed
booths, which means large-scale use is required for cost effectiveness.
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Table VI-2. USES OF 1,1,1-TRICHLOROETHANE
Use Sector
Binding Substance
As Active Solvent in Solvent-Borne
Adhesives
Styrene-Butadiene Rubber (SBR)
Neoprene
Natural Rubber
Rubber Cement
Other
As a Diluent or Coalescent in Water-
Bo rne Adhesives3
a No data is currently available on the specific binding systems that employ
1,1,1-trichloroethane as a diluent and or coalescent.
Source: Based on Skeist 1987.
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6.3.2 Water-Based Adhesives
Some adhesives use water, in lieu of organic solvents, as the primary
solvent. A water-based adhesive can be a solution, a latex, or an emulsion.
Solutions are made from materials that are soluble in neutral or alkaline
water; most natural adhesives are water solutions. Latexes are stable
dispersions of solid polymeric material in an essentially aqueous medium
(Landrock 1985), while emulsions are stable dispersions of immiscible liquids.
Emulsions usually appear milky white in the liquid state but dry to a clear
film. In industry, the terms latex and emulsion are generally synonymous.
Latex adhesives are more likely to replace solvent-based adhesives than
solution adhesives because their synthetic binders provide more versatility
and higher performance (Landrock 1985). Latexes, however, require more
extensive formulation because they are produced from polymers not originally
designed for use as adhesives.
The binding substances that are candidates for water-borne adhesives
include:, natural substances, including natural rubber; synthetic elastomers
such as styrene butadiene rubber, neoprene, and isoprene; vinyl resins such as
polyvinyl acetate (PVAc) and polyvinyl chloride (PVC); acrylics; and epoxies
(Landrock 1985). Some of these binding substances require additional
formulation and additives like emulsifiers, surfactants, or additional resins.
Water-based binding substances use the traditional methods for adhesive
application. These include brush, .spray, roll coat, curtain, flow, and knife
coat (Landrock 1985).
Recent literature on water-based adhesives suggests that there is still
much debate about the overall effectiveness of water-based, adhesives for many.
end uses. In general, water-based adhesives show good durability, water
resistance, and adhesion to a wide variety of substrates, especially in the
area of nonporous to porous bonding (Chao and Hernisch 1986). Problems still
exist in the bonding of non-porous to non-porous substrates because water is
difficult to evaporate from such substrates. In addition water-based
adhesives are not suitable for non-structural bonding of rubbers and many
plastics.
Water-based adhesives can bond moist surfaces better than solvent-based
adhesives. One inherent advantage of water emulsions is that viscosity is
independent of molecular weight of the resin (Fries 1984). The higher initial
molecular weight polymer provides greater internal cohesive strength to the
freshly made bond. This initial, green bond is important to avoid uneven bond
stress and blisters in laminating applications (Fries 1981 and Fries 1984).
Poor initial bond strength has been a criticism of low molecular weight water-
borne adhesives. Unlike solvent-borne and hot melt adhesives, there are no
restrictions on the initial molecular weight of the resin for water emulsions'.
The direct replacement of solvents.by water is not feasible in all
sectors. Selecting water as the vehicle in adhesives demands totally new
concepts in raw materials and formulation as discussed above. Water-based
adhesives often require special handling in manufacturing, storage, and
application. They must be kept from freezing during shipment and storage
(Landrock 1985, Dawnkaski 1991). Problems with corrosion require that all
storage and transfer pipes be corrosion-resistant. Some manufacturers,
however, maintain that corrosion is-not a factor if additives which prevent
corrosion are included in the formulation, and one set of laboratory tests
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found water-borne adhesives not to be more prone to corrosion than solvent-
borne adhesives (Manino 1981). The problem has not been resolved
conclusively; more research and development is needed in this area (Johnson
1991). Another problem with storing water-based adhesives is that agitation
is needed to maintain consistency of the dispersed materials in the adhesive
solution. Yet.agitation can cause foaming, and anti-foaming agents compromise
adhesive bond performance.
Water-based adhesives reportedly have other performance disadvantages
when compared with solvent-based adhesives. During application, water-based
adhesives do not "wet" surfaces as well as their solvent-based counterparts
due to water's inherent polarity and high surface tension (Dawnkaski 1991).
Minor contamination of the surface (e.g., oil, mould release, fingerprints)
can lead to bonding problems.2 Water-based adhesives do not have the
versatility of application provided by solvent-based adhesives (Johnson 1991).
Although polar substrates, such as natural rubber, bond well with water-borne
adhesives, nonpolar elastomer substrates, such as ethylene propylene
copolymers, are difficult to'bond (Manino 1981). Silicones and
fluoroelastomers provide a greater challenge, and water-borne adhesives still
cannot compete with solvent-borne systems in these areas (Manino 1981).
Finally, spray application of water-based adhesives can be especially
difficult due to the ease with which water- carried adhesives are atomized.
Spray application results in a fine mist that can travel to all areas of a
shop, coating persons and objects with a thin coating of adhesive (Dawnkaski
1991). . .
6.3.3 Hot Melt Adhesives
The Committee D-14 of the American Society for Testing and Materials
(ASTM) defines a hot melt adhesive as one that is applied in a molten state
and forms a bond upon cooling to a solid state (Fullhart and Mottershead
1980). Hot melts are primarily 100 percent solids thermoplastic bonding
materials that achieve a solid state and resultant strength upon cooling. The
major applications of hot melt adhesives are bookbinding, packaging, textiles,
and product assembly, including construction glazing and automotive door panel
and carpet installation (Fullhart and Mottershead 1980). Application methods
include melt-reservoir and pressure-feed systems (Landrock 1985). The binding
substances that provide the foundation for hot melt adhesives are ethylene
vinyl acetate (EVAc) and other polyolefin resins; polyamide (or nylon) and
polyester resins; polyester/amide resin alloys; and thermoplastic elastomers
(Landrock 1985). Foamable hot melts (e.g., polyethylene) form a superior bond
with metals, plastics and paper (Landrock 1985).
Although earlier hot melt pressure sensitive adhesives (PSAs) had
unacceptable colour retention and UV resistance, present hot melt PSAs are
clear and UV resistant (Maletsky and Villa 1984). Hot melt PSAs now compete
with water-based acrylics in outdoor applications (Maletsky and Villa 1984).
They have been used on 'paper labels for indoor applications since 1978.
2 A solvent-based primer can boost performance by ensuring a clean
substrate for the water-based adhesive. A primer uses less than half as much
solvent as solvent-borne adhesives. 1,1,1-Trichloroethane has been used as a
primer to degrease many substrates (Landrock 1985).
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Hot melts are, however, limited in several key performance
characteristics. They have poor specific adhesion to a number of substrates,
creep under load over time and at high temperatures, have limited strength,
and limited heat resistance (Landrock 1985). A specific hot melt acrylic used
for pressure-sensitive applications has poor tack for many applications
(Lipiec 1982). . Room temperature shear resistance and elevated temperature
shear resistance are also, deficient in hot melt acrylic PSAs (Lipiec 1982).
6.3.4 Radiation Cured Adhesives
/ ( N
Radiation curing is a production technique for drying and curing
adhesives through the use of radiant energy such as ultraviolet (UV), infrared
(IR), electron beam (EB), gamma, arid x-rays. In essence, radiant energy
becomes chemical energy in the forming of the adhesive bond. The binding
agents that can be cured with radiant energy are acrylics, epoxies, urethanes,
anaerobic adhesives, and polyester resins (Adhesives Age 1988). Pressure-
sensitive or 100 percent non-volatile formulations of adhesives are applied by
conventional techniques betwe'en one or two plastic films and then cured by
exposure to radiant energy (Chemical Week 1987). Application areas include
electronics, communications, consumer products, transportation, packaging, and
medical and dental uses (Bluestein 1982). Radiation cured adhesives are
especially well adapted for pressure sensitive tapes. One drawback is that
adhesive curing is only possible in the "line of sight" of the radiant energy.
Pressure-sensitive tapes are another major application of radiation cured
adhesives. High growth is anticipated for UV and EB cured adhesives. It is
not evident whether UV methods are particularly suited to bonding opaque
substrates.
,6.3.5 High Solids Adhesives
One way to lower volatile organic compound (VOC) emissions when using
solvent-based adhesives is to increase the percent solids in the formulation.
In the specific example of polyester urethane laminating adhesives, high
solids/low solvent adhesives are an alternative to' solvent-borne adhesive
systems. Using the existing technology for polyesters and polyester urethane
systems, high solids have been very successful in laminating uses (Bentley
1983.). One manufacturer supplies a 68.5 percent solids polyester urethane
laminating adhesive which meets VOC regulations by lowering the amount of
solvent used (Wood 1984). High solids adhesives have good performance
characteristics, including initial bond strength, comparable to that of 30
percent solids adhesives in medium and high demand applications and can be
applied using existing equipment at normal line speeds with minor
modifications.(Wood 1984).
In other application areas, such as bonding rubber assemblies, high
solids adhesives have not been as successful. For bonding rubber assemblies,
high solids adhesive films are too thick, which results in limited versatility
and generally poor performance (Manino 1981). In general, high solids
adhesives cost more per pound since they do not contain the nonreactive
solvent as a diluent. However, advanced products consisting of a 100 percent
solid adhesive and a liquid primer are now commonly used in critical
structural bonding applications, such as aircraft wings. The 100 percent
solids structural adhesives generally require refrigeration, shelf life
control, and training or practice in application.
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6.3.6 Powders
One-part epoxies, urethanes, and natural resins are often supplied as
powders that require heat to cure (Frisch and Xiao 1988). Powders are only
-used for non-pressure-sensitive applications. They are generally applied in
three ways:, by sifting the powder onto pre-heated substrates, by dipping a
preheated substrate into the powder, and by melting the powder into a paste or
liquid and applying it by conventional means (Landrock 1985). One advantage
of the powder form is that no mixing or metering is necessary. However,
powders must be refrigerated to maximise shelf life (Landrock 1985). No data
are currently available comparing performance and cost with solvent-borne
adhesives.
6.3.7 Non-Volatile Solids and Liquids and Reactive Liquids .
Moisture cure adhesives and reactive liquids can be applied as 100
percent non-volatile solid and liquid systems. These adhesives are composed
entirely of binding substances, modifiers, and fillers (i.e., they have no .
carrier or solvent). Moisture cure adhesives cure upon exposure to the
humidity in the ambient air; this type of adhesive requires application in a
humid environment and might not work well in dry climates. Moisture cure
adhesives are available in 100 percent non-volatile liquids and solids, hot'
melts, solvent-borne formulations, and other technologies (Frisch and Xiao
1988) . Moisture-cured silicone-based adhesives include at least two specific
types, methoxy-cured and acetoxy-cured. These systems use water in the
atmosphere to react in the adhesive reaction. The by-products are small
quantities of either methanol or acetic acid.
The 100 percent non-volatile moisture cure systems are of interest
because they offer another alternative to the solvent-based systems; The two
primary binding substances used in moisture cure adhesives are isocyanates and
polyurethanes (D'Autilio 1983). They are available as single and multiple
component adhesives. The two-part system physically separates the binding
agent from the curing agent during storage. Although the adhesive requires
metering and mixing to cure, the two-part system has a longer shelf life. The
two-component system also achieves higher performance. A two-component
solvent-free" isocyanate adhesive that does not require moisture to cure nor
precise metering has appeared on the market. A thin coat of one component is .
applied to one part and a thin coat of the other to the second part. The two
are brought together and form a rapid and strong bond in a few seconds. As
the bond does not require oxygen.to form (i.e., is anaerobic), isocyanate
adhesives are useful.for joining metallic and other non-porous parts. Tests
have shown, however, .that the electrical properties of the adhesive exclude it
from electronics applications, such as bonding surface mounted components to
substrates prior to wave soldering.
Some two-component adhesives use reactive solvents which form part of
.the cured mass and thus do not depend on evaporation. In use, one solution
consisting of an elastomer colloidally dispersed in a monomer is cured by a
second solution through a free radical chemical polymerisation, thereby
creating the bond (Prane 1980). The binding substances for reactive liquid
adhesive systems include epoxies, urethanes, polyesters, silicones,
polysulphides, acrylics, modified phenolics,' and resin compounds (Prane 1980).
Reactive liquids are used for high performance structural applications.
Application methods are similar to those used in contact adhesives, namely,
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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brush, roller, or spray (Prane 1980). No information is currently available
on the relative performance attributes of this emerging technology.
6.4 COSTS OF ALTERNATIVES
Substitution costs for the established alternative technologies are in
most cases driven by the raw material costs and capital investments required
to implement these technologies. Research and development resources are also
required to develop, and test alternative technologies - 'water-based adhesives,
hot melt adhesives, and solvent recovery - for specific adhesive systems. The
cost of switching to an alternative solvent is highly dependent on whether or
not the solvent is a VOC since VOC emission and worker safety regulations may
require installing expensive ventilation and vapour recovery equipment.
Converting to water-based solvents allows adhesives users to reduce
their inventory of solvents. Water-based adhesives require stainless steel
application equipment, hoses, stirrers, etc., and there may be significant
conversion costs. Water-based adhesives clean easily during application, but
the rinse water should be properly disposed of or recycled.
Although hot melt adhesives are more expensive per unit of formulated
weight, in many applications their use leads to reduced overall costs. The
conversion to a hot melt system requires installing new, moderately expensive
equipment. The capital costs of conversions are offset by saving space and
energy from the use of automated equipment, lowered raw material costs, and
increased productivity (Lipiec 1982). Hot melts can be applied faster and
more efficiently than .water-based adhesives because there is no delay for
evaporation (Kimel 1988). Since hot melt formulations contain 100 percent
solids, they can be slightly more expensive when shipment in refrigerated
trucks is required.
Prior to curing, radiation cured adhesives have a longer shelf life than
most adhesives (Bluestein 1982). Their use leads to production of a more
reliable product, lower rejection rates and labour costs, and reduced cleanup
and inspection times (Moreau 1988). Radiation cured adhesives are an option
for new production facilities due to the simpler, .space-'saving equipment
(Bluestein 1982). Among the radiation curable technologies, UV and EB curing
have separate applications. UV curing is more cost effective for smaller
applications, whereas EB curing is better adapted for large scale operations.
Radiation cured adhesives have some disadvantages. Existing equipment
cannot be used for this type of adhesive without the addition of a cure unit
(Bluestein 1982).. In addition, the applications are limited to "line of
sight" for radiation cured adhesives.
As mentioned above, high solids adhesives typically cost more but
outperform their solvent-borne counterparts at lower solids levels. This
technology development is ongoing. .
6.5 ENVIRONMENTAL AND ENERGY CONSIDERATIONS
There are a number of environmental and energy implications to replacing
1,1,1-trichloroethane-based adhesives with alternatives. Returning to the use
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of other solvent-based adhesives will affect local air pollution and worker
safety unless precautions are taken. VOC solvents contribute to the formation
of tropospheric ozone and their use is restricted in many localities; their
flammability requires the installation of special equipment to minimize the
danger from fire or explosion. These concerns were the incentive to move to
the use of 1,1,1-trichloroethane initially.
Water-based adhesives have a number of characteristics that make them
attractive substitutes. As they contain no volatile organic solvents, water-
based adhesives do not. contribute to local smog problems and are nonflammable.
They can, however, emit small quantities of hydrocarbons, ammonia, and
emulsion-stabilising substances. In ideal situations, these pollutants can be
removed to some extent using, for example, wet scrubbers.
From the energy perspective, drying ovens used for solvent-based systems
generally are adequate to handle water-based adhesives. Increased air flow
rates and longer oven bake cycle times are required to evaporate water,
however, so process flow can be affected and energy usage may increase.
Hot melt adhesives also have several environmental and energy
advantages. As no solvents are used in hot melts, they do not contribute to
smog formation. In part because no drying oven is needed, hot melt pressure
sensitive adhesives require far less energy to process than most other
adhesive types (Maletsky and Villa 1981). The percent solids in the
formulation directly influences the amount of energy saved; this percentage
varies depending on the application. One drawback .of hot melts is that the
presence of hot equipment may be a danger to workers (Fullhart and Mottershead
1980).
The advantages of radiation cured adhesives are low energy costs and
reduced emission of waste effluents and polluting gases and liquids.
Both moisture cure adhesives and reactive liquids achieve compliance
with VOC regulations because they contain no solvents. Moisture cure systems
also need no driers, and thus save energy (D'Autilio 1983). The application
equipment is more compact than that of solvent-based systems, but moisture
cure adhesives cannot use existing solvent application equipment (Morphy et
al. 1987). Moisture-cured adhesives and sealants, especially silicones,
evolve small amounts of methanol, acetic acid, or other products of the
moisture reaction. There is some concern that the catalysts used with
reactive liquid systems are,, in some cases, hazardous or toxic substances
(Dawnkaski 1991). . '
6.6 POTENTIAL GLOBAL REDUCTION OF 1.1.1-TRICHLOROETHANE-USE IN THE ADHESIVES
INDUSTRY
There is limited data, on the worldwide market for adhesives; however,
information is available on the U.S., European, and Japanese markets. The
1983 adhesive demand in the U.S. and Europe was 4,900 million dry formulated
pounds and it grew at an annual rate of 3.9 percent to approximately 5,900
.million pounds in 1988 (Broxterman 1988). The U.S. portion of this demand is
significantly larger than the European portion, representing about 4,600
million pounds, or 75 to 80 percent of the estimated demand in 1988. The
Japanese market is considered roughly equivalent to the European market,
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together consuming 1,300 million dry pounds of adhesives in 1987 (O'Driscoll
1988). Approximately 40-50 thousand tonnes of 1,1,1-trichloroethane was used
in adhesives in these countries in 1985 (ICF 1989). Table VI-3 shows the U.S.
and European adhesive demand by segment. ~
As mentioned above, there has been a worldwide trend away from the use
of solvent-based adhesives. The cost savings associated with water-borne and
hot melt systems are such that this trend would continue even in the absence
of the Montreal Protocol's provisions.
6.7 SUITABILITY OF ALTERNATIVES FOR DEVELOPING COUNTRIES AND SMALL QUANTITY
USERS
Most established alternatives to 1,1,1-trichloroethane solvent adhesives
can be used in developing countries and by small quantity users. Some
systems, hot melts for example, require a larger capital investment for
equipment, although the cost per application compares favourably. The cost of
converting to an alternative adhesive system may be a hurdle in some
situations.
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Table VI-3. ESTIMATED U.S. AND EUROPEAN ADHESIVE DEMAND BY SEGMENTS -- 1988
Market Segment
Packaging
Non-Rigid Bonding
Construction
Tapes
Rigid Bonding
Transportation
Consumer
TOTAL
Estimated 1988
U.S. and Western
Millions of
Dry Formulated Pounds
2,500
1,100
1,000
500
400
300
" IPO
5,900
Demand
Europe
Percent
42.4%
18,6 .
16.9
8.5
i '
6.8
5.1
1.7
100.0
Source: Based on Broxterman 1985.
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CHAPTER 7
COATINGS AND INKS APPLICATIONS
7.1 BACKGROUND
It is estimated that 48 percent of the U.S. coatings market in 1986 was
based on solvent-based formulations. This represents solvent use in coatings
in 1989 of 1.7 million metric tons, of which only 1.2 percent or 21,800 tonnes
(for Europe, North America, and Japan in 1989) (ECSA, HSIA, JAHCS) was 1,1,1-
trichloroethane (Chem Systems, 1989). Water-based coatings accounted for 12
percent of the market; high solids, 11.5 percent; two part-systems, 12
percent; emulsions, 10 percent; powder coatings, 6 percent; and ultraviolet
light/electron beam (UV/EB) cured coatings, 1.5 percent of the market. In
addition, there are solvent-recovery and low-emissions coating application
methods, such as dipping, flow, and curtain coating that are alternatives to
the use of spray coating. . , . > '
7.2 CFC-113 .AND 1.1.1-TRICHLOROETHANE USE IN COATINGS AND INKS APPLICATIONS
1,1,1-Trichloroethane is used by manufacturers, printers, and users of
protective and decorative coatings and inks. CFC-113 use in the production of
coatings or inks is negligible. Therefore, this chapter will focus, on the use
of 1,1,1-trichloroethane in coatings and inks applications. In coatings,
1,1,1-trichloroethane is used alone or combined with other solvents to
solubilize the binding substance which is usually composed of resin systems
such as alkyd, acrylic, vinyl, polyurethane, silicone, and nitrocellulose
resin. In addition to its good solvency, 1,1,1 -trich'loroethane is also used
because of its nonflammability and fast evaporation rate,. These properties
also make 1,1,1-trichloroethane a suitable thinner for spray coating
applications as well as an excellent solvent for ink applications. Inks are
used to print items ranging from wallpaper to dog food bags to beverage
bottles and cartons. Many of these uses involve the application of coloured
ink to a film (or laminate) in the flexible packaging industry.
Although the overall market for coatings and inks in the U.S. showed
relatively slow growth in the 1980s (approximately 1 percent according to U.S.
Industrial Outlook 1989) , the trend in the late 1980s to replace volatile
organic compound (VOC) solvents in coatings and inks formulations with 1,1,1-
trichloroethane resulted in a significant increase in 1,1,1-trichloroethane
demand. However, this growth in usage of 1,1,1-trichloroethane has reversed
in recent years because of the addition of 1,1,1-trichloroethane to the list
of substances controlled under the Montreal Protocol.
1 In the .U.S. 1,1,1-trichloroethane is also -used frequently because of
its non-volatile-organic compound (VOC) status.
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7.3 ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND 1.1.1-TRICHLOROETHANE
USE
The use of 1,1,1-trichloroethane in the production of coatings and inks
has been reduced in the early 1990s through more extensive use of several o.f
the aforementioned formulations, specifically water-based coatings and inks,
high-solids coatings, and powder coatings. Because these alternative
formulations function as well as 1,1,1-trichloroethane-based formulations in
most applications, the use of these alternative coatings and inks results only
in a difference in handling procedures. These differences should manifest
themselves predominantly in storage and distribution as many of these
alternatives will be more flammable than their 1,1,1-trichloroethane-based
counterparts (SNV 1990a).
7.3.1 Water-based Coatings and Inks
Some coatings contain water rather than conventional solvents. They can
be applied using a variety of methods, including: dipping, flow coating,
conventional air and airless atomizing, air and airless electrostatic
spraying, rotating disks and bells, rolling, continuous coating, centrifugal
coating, and tumbling. Recent advances in water-based coating technology have
improved the dry-time, durability, stability, adhesion, and application of
water-based coatings. Primary uses of these coatings include furniture,
electronics in automobiles, aluminum siding, hardboard, metal containers,
appliances, structured steel, and heavy equipment. In some water-based
coatings, standard solvents are added for ease of application, but even these
contain much less solvent than conventional coatings and meet VOC limits since
the primary solvent is water. A typical formulation blending water with
conventional solvents might contain 80 parts water to 20 parts solvent by
volume (UNEP 1992).
Water-based inks for flexographic and rotogravure laminates have been
successfully developed and have overcome technical hurdles such as substrate
wetting, adhesion, colour stability, and-productivity. Solvent-based inks
have good wetting properties because of the low surface tension of most
solvents. However, water has a relatively high surface tension as compared
with most solvents and it requires the use of co-solvents to lower the surface
tension to enable the wetting of treated surfaces. A mixture that is 80 parts
water and 20 parts alcohol and ethyl acetate by volume will achieve an
effective surface tension. The ability of the. water-based ink to adhere to
the film can be enhanced by treating the film by means of accepted methods
such as use of primers or heat. About 55 percent of the flexographic inks and
15 percent of the gravure inks used in the U.S. in 1987 were water-based.
Continued growth of aqueous inks has been projected by various industry
sources.
7.3.2 High-Solid Coatings
Although high-solid coatings resemble conventional solvent coatings in
appearance and use, high-solid coatings contain less solvent and a greater
percentage of resin. They are applied u'sing methods similar to those used for
water-based coatings. High-solid coatings are currently used for appliances,
metal furniture, and a variety of construction equipment. The finish of high-
solid coatings is often superior to that of solvent-based coatings, despite
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the fact that high-solid coatings require much less solvent than do solvent-
based coatings.
7.3.3 Powder Coatings
Powder coatings contain the resin only in powder form and thus have no
solvent. They are applied using fluidized beds, electrostatic spray, and
electrostatic fluidized beds. The object to be coated is heated above the.
powder's melting point, so that when the object is removed from the presence
of heat, the resin fuses into a continuous film. The resin then hardens to
form a finish that has excellent durability and corrosion resistance. While
powder coatings were first used only for electrical transformer covers, they
are now used in a large number of applications, including:
underground pipes;
electrical components;
concrete reinforcing bars;
. appliances;
automobiles; '
farm and lawn equipment;
lighting fixtures;
aluminum extrusions;
steel shelving; and,
some furniture. .
7.3.4 UV/EB-Cured Coatings and Inks. .
UV/EB-cured coatings arid inks have been used in very limited
applications over the last 20 years, but their use has seen a dramatic
increase in recent years. Several of the markets in which UV/EB-cured
coatings and inks have been used more frequently in recent years are
flexographic inks and coatings, wood furniture and cabinets, and automotive
applications. It is estimated that the usage of UV/EB-cured products has
grown by 11 percent annually in North America between the years 1988 and 1993,
and this growth is expected to continue for another five years. Annual growth
in Europe is estimated at 5-6 percent. Although this growth is expected to
slow in the future, UV/EB-curing is likely to remain popular in niche
applications (MFC 1994b). One business manager for a supplier of these
coatings has estimated that UV/EB coatings' share of the worldwide paint and
coatings market will double over the next 5 to 7 years (MFC 1994a).
There are several factors which contribute to the growing popularity of
UV/EB-cured coatings and inks. These include: high quality, rapid cure
times, low energy use, small space requirements, elimination of some handling
problems, and reduction in emissions of ozone-depleting substances and VOCs..
One major limitation to the use of UV/EB-cured coatings and inks is outdoor
durability (MFC 1994b). This is an especially important consideration in
automotive applications.
7.4 ENVIRONMENTAL AND ENERGY CONSIDERATIONS
Goods are printed or coated with solvent-based coatings and inks in a
continuous process. Once the coating or ink has been applied, the product
passes through a drying step where the solvent is emitted through evaporation.
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Solvent recovery syr.tems such as carbon adsorption can be used to capture
these solvent emissions. As discussed earlier, technological innovation is
overcoming the stabilization problems which sometimes occur.
The types of coatings and inks described in this chapter as alternatives
to formulations containing 1,1 ,"l-trichloroethane reduce solvent emissions by
reducing or eliminating the use of conventional solvents. Therefore, the
environmental impacts associated with such solvent emissions are also reduced.
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CHAPTER 8
AEROSOLS APPLICATIONS
8.1 BACKGROUND
Aerosol packaging is a popular method for storing and dispensing
consumer and industrial products ranging from insecticides to hair sprays. In
1986, the worldwide aerosol industry produced an estimated 6.8 billion units.
Western Europe was the largest producer, followed by the United States and
Asia. 1,1,1-Trichloroethane consumption in aerosol applications in the U.S.
was approximately 18,590 metric tonnes (ICF 1989a). It is estimated that
Western Europe and Japan consumed 12,425 and 10,790 metric tonnes of 1,1,1-
trichloroethane in 1984, respectively (ICF 1989a). The Aerosol Industry of
Japan estimates that consumption of 1,1,1-trichloroethane in the Japanese
aerosol industry had dropped to 5,000 metric tonnes in 1990 (Kurita 1991b).
No data are available for the rest of the world. No information is currently
available on current chlorinated solvent consumption trends in Western Europe,
Japan, and the rest of the world, therefore, the discussion that follows
focuses on the U.S. market for aerosols. The major aerosol product end-uses
where 1,1,1-trichloroethane is used includes automotive and industrial
products, pesticides, and household products (ICF 1989a).
8.2' CFC-113 AND 1.1.1-TRICHLOROETHANE USE IN AEROSOL PRODUCT APPLICATIONS
In an aerosol package, the contents are stored under pressure in a metal
container and dispensed in a controlled manner by activating a valve. The
continued effect of the type of propellent used, the shape of the opening from
which the contents are expelled from the can, and the composition of the
product determine the form in which the product is delivered. This form can
range from a fine mist (the most common) to a liquid stream to a foamy lather.
In general, the components of an aerosol are the'active ingredient, the
solvent or carrier, and the propellant. The active ingredient is responsible
for the effectiveness of the product (i.e., the ingredient that allows a
cleaner to clean); the solvent or carrier solubilizes all ingredients in the
formulation to allow for uniform dispensing of the product; and the propellant
expels the contents from the can.
1,1,1-Trichloroethane functions as either an active ingredient (e.g.,
degreaser or cleaner) or as a solvent in aerosol product formulations. 1,1,!-
Trichloroethane's high density adds to container weight while its high
stability translates to a long shelf li-fe. Other properties that make 1,1,1-
trichloroethane especially well-suited for aerosol applications are its
nonflammability, excellent solvent properties, high evaporation rate, and
ability to generate a spray of small particle size. Quick evaporation allows
1,1,1-trichloroethane to deliver .the active ingredient efficiently and a small
particle size results in a good spray pattern.
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Though most of the aerosol applications traditionally used 1,1,1-
trichloroethane as their solvent, there are a small number of products which
made use of CFC-113 as well. Probably a few tens of tonnes per year of CFC-
113 were used annually in the late 1980s. The application where CFC-113 was
most often used as a solvent is in the removal of flux from electronic
components such as printed circuit boards (PCBs). In these products, CFC-113
was often mixed with another chemical such as isopropyl or ethyl alcohol.
These product mixtures were often used due to the fact that they act as both
degreasers and cleaners, and leave very little residue on evaporation.
Conformal coatings also make use of CFC-113. These products are sprayed
on printed circuit boards and other electronic components to serve as a
sealant. Over a wide range of temperatures, these coatings protect equipment
from environmental conditions which would normally damage the equipment.
Depending on the resin used in the coating, 1,1,1-trichloroethane is sometimes
included as well.
Finally, CFC-113 is often used in aerosol application for contact
cleaners. The cleaners are used as part of the routine maintenance of
electrical equipment in order to prevent malfunctions which might occur from
everyday pollutants. Because this equipment is often cleaned while energized,
it is important that the aerosol cleaner be nonflammable, thus making CFC-113
an attractive ingredient. Use of these cleaners helps to maintain continuity
within electrical circuits (Chemtronics 1989).
8.3. ALTERNATIVES FOR REDUCING OR REPLACING CFC-113 AND 1.1.1-TRICHLOROETHANE
USE IN AEROSOL PRODUCTS
Most aerosol products currently employing CFC-113 and 1,1,1-
trichloroethane can be reformulated with alternative compounds. Table VIII-1
lists substitute solvents and the major product application areas. From a-
number of properties determining product performance, two performance factors
are considered of most importance: flammabili.ty and density. These factors
are also listed across the top of the table. Except for water, some
hydrochlorofluorocarbons (HCFCs), and non-ozone-depleting chlorinated solvents
(e.g., trichloroethylene, perchloroethylene, methylene chloride), all of the
substitute solvents currently available are more flammable than 1,1,1-
trichloroethane. The flammability is also a function of the propellant;
butane and propane being more flammable than carbon dioxide, nitrous oxide or
the traditional CFC-ll/CFC-12 mixture.
Alternative solvents currently exist for virtually all aerosol solvent
applications of CFC-113 and 1,1,1-trichloroethane. However, while some of
these alternatives are functional, they are considered to be"less than optimal
for a variety of reasons. For example, in applications where a strong solvent
is required, but the use of a flammable solvent would pose serious safety
risks, substitutes may include only hydrofluorocarbons (HFCs), HCFCs and
chlorinated solvents. While these .solvents would be functional, HCFCs
contribute to ozone-depletion, and chlorinated solvents are toxic and may pose
health risks to workers and users of a product.
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Table VIII-1. SUMMARY OF SUBSTITUTE SOLVENTS FOR
1,1,1-TRICHLOROETHANE AND CFC-113 IN AEROSOLS
Major Product Applications Performance Factors
1
, 1 , 1-Trichloroethane
CFC-113
A&I Pest HH
* * *
*
Flammability
None
None
Density
1.32
1.57
Substitute Solvents:
Petroleum Distillates
Aromatic Hydrocarbons
Alcohols
Ketones
Water Systems
Dimethyl Ether
Chlorinated Solvents
HCFCs
High
High
High
High
Low to None
High
None
0.75
0.87
0.80
0.81
1.00
0.66
1.31-
1.62
None
1-1.21
* Denotes that the substitute solvent can be used in the product application
indicated.
A&I
Pest
HH
Automotive and Industrial Products.
Pesticides.
Household Products.
Source: Based on ICF 1989a.
* 199* UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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8.3,1 Reformulation Using Petroleum Distillates
One alternative for the replacement of CFC-113 and 1,1,1-trichloroethane
in aerosol products is reformulation using petroleum distillates. Due to the
high flammability of the petroleum products, reformulation from CFC-113 and
1,1,1-trichloroethane to petroleum distillates can only be performed in select
applications and with proper explosion proof equipment. Commercially
available products reformulated with petroleum distillates and other
hydrocarbon solvents exist for various automotive products such as tire
cleaners, lubricants, spray undercoatings, and in household products such as
water repellents/shoe waterproofers, glass frostings, and insecticides.
Extreme care must be exercised in both the manufacture and use of these
products to reduce the risk of explosion.
8.3.2 Reformulation to Water-based Systems
Reformulation from 1,1', 1-trichloroethane or CFC-113 to water-based
systems can be performed in a number of applications, including shoe polishes,
foggers (partial or total release insecticides used to control infested
rooms), mould release agents, and fabric protectants. The major
disadvantage/concern of reformulation of 1,1,1-trichloroethane or CFC-113 to
water-based systems is the effectiveness of the final product. These concerns
arise from several fundamental differences in the systems. For example, it is
generally agreed that water-based foggers are less effective because they do
not disperse well and they result in large particle sizes (Ortho 1989,
McLaughlin Gormley King Company 1989, Sprayon 1989). These factors make the
foggers less effective than foggers which utilize 1,1,1-trichloroethane since
the water tends to be ineffective at penetrating the exoskeleton of insects.
Tests are currently underway to produce water-based solvent mixtures which
will be able to overcome this problem.
Other drawbacks associated with water-based aerosol products include
long drying time and inability to sufficiently wet 'the surface being sprayed.
The relatively slow evaporation rate of water .as compared to that of CFC-113
or 1,1,1-trichloroethane results in a slow drying time. While the drying time
can be accelerated with the application of heat, it is still likely to be
significantly longer than the drying times associated with CFC-113 and 1,1,1-
trichloroethane. Also of concern in some applications is the reduced
wettability of a formulation that has been reformulated to use water as the
primary solvent. The high surface tension of water often results in less
efficient wetting of surfaces being sprayed. This is an especially important
consideration in applications such as mould release agents (UNEP 1994b).
Despite these drawbacks, water-based aerosol formulations are becoming
more common in a wide variety of industries, especially among those wanting to
avoid the use of flammable solvents, HCFCs, and chlorinated solvents.
8.3.3 Reformulation Using Organic Solvents
There are a number of alternative organic solvents that can be used to
replace CFC-113 or 1,1,1-trichloroethane in many aerosol applications. These
alternative solvents include petroleum distillates, alcohols, ketones, and
terpenes. . These solvents are capable of removing a wide variety of
contaminants, and all are currently used in commercially available aerosol
products. This strong cleaning power, coupled with the ability to solubilize
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other active ingredients, makes these alternative solvents attractive
substitutes for CFC-113 and, 1, 1',1-trichloroethane.
There are two primary drawbacks associated with the reformulation of
aerosol products using organic solvents -- flammability and environmental
impact. All of the aforementioned organic solvents are flammable and must
therefore be used with extreme caution to reduce the risk of explosion and
fire. While many users are able to safely implement flammable formulations
with only minor process and handling changes, others may not be able to
overcome the risks associated with the flammability qf the solvents. For
example, flammable solvents are not a viable alternative for the in-situ
cleaning of energized equipment. The major environmental concern associated
with these organic solvents is their impact on the formation of smog and other
ground-level pollution. In the United States, virtually all of these-solvents
are classification as volatile organic compounds (VOCs) and their use is
severely restricted in some geographic areas. Nonetheless, where flammable
solvents are acceptable, reformulation using organic solvents is an attractive
option.
8.3.4 Reformulation Using Nonozone-Depleting Chlorinated Solvents
Reformulating aerosol products to use nonozone-depleting chlorinated
solvents in place of'CFC-113 or 1,1,1-trichloroethane is an option in limited
applications. The chlorinated solvents that might be used are
trichloroethylene, perchloroethylene, and methylene chloride. The primary
benefit associated with these alternatives is their nonflammability. This
property makes them"one of the few viable alternatives for aerosol cleaners
used on energized equipment.
Potential formulators and users of aerosols containing these solvents
must be aware of their associated human health risks. All three of these.
alternatives are potentially carcinogenic to humans and have accordingly low
occupational exposure limits (UNEP 1994a).
8.3.5 Reformulation Without a Solvent
In some cases where CFC-113 or 1,1,1-trichloroethane is used only -as a
solvent or carrier, and not as an active ingredient, it may be possible to
reformulate the aerosol product to function without the use of a solvent. In
these nonsolvent systems', the active ingredient of the product is dispersed
solely by the force of the propellant. Such a formulation is currently being
marketed by several manufacturers of aerosol .mould release agents, who have
observed increased performance in some applications because there is no longer
any possibility of the solvent attacking plastics or metals with which it
comes into contact. However, it is also possible to obtain inferior
performance, primarily because of the uneven dispersion of the active
ingredient which may occur in the absence of a solvent carrier (UNEP 1994b).
8.3.6 Reformulation Using HCFCs
Another-alternative for replacing CFC-113 and 1,1,1-trichloroethane in
limited aerosol applications is reformulation with HCFCs. At the present
time, HCFC-141b is the only commercially available alternative, although it is
expected that HCFC-225 will become available for aerosol applications in the
near future. HCFC solvents have much the same properties as CFC-113 and
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1,1,1-trichloroethane, making them ideal replacements from a technical
standpoint. However, HCFCs are ozone-depleting substances and will therefore
add further to depletion of the ozone layer. HCFC-141b has an ozone-depletion
potential (ODP) comparable to that of 1,1,1-trichloroethane, and should
therefore not be used as a substitute for 1,1,1-trichloroethane. It is
important to note that HCFCs are a transitional substitute at best because
they are scheduled for a complete phaseout under the Montreal Protocol by the
year 2030. In addition, certain countries have restricted the use of HCFCs in
some applications. Given these considerations, HCFCs should only be
considered in applications where a nonflammable formulation must be used, and
even then, when no other alternative is satisfactory.
8.3.7 Alternative Delivery Systems
CFC-113 and 1,1,1-trichloroethane use in aerosols can also be reduced if
alternative means of delivering the product are developed. Two examples of
these alternative methods .are: . (1) a manual "wet-brush" (recirculating
liquid) system, as a substitute for aerosol brake cleaners used in repair
shops, and (2) increased use of professional dry cleaning, services as a
substitute for the use of aerosol spot removers. Although more examples of
alternative non-aerosol methods can be found for the other aerosol products
that currently use CFC-113 and 1,1,1-trichloroethane, the cost data presented
in this chapter uses these two applications as examples.
8.4 COSTS OF ALTERNATIVES
Table VIII-2 presents the costs for the two groups of control
technologies for reducing 1,1,1-trichloroethane use in aerosol products: (1)
the reformulation of aerosol products, and .(2) a switch to an alternative
method to deliver the product other than by means of an aerosol. The
methodology used to estimate the costs associated-with the reformulation of
aerosol products currently using l.l.l-'trichlbroethane is based on a previous
analysis (ICF 1989b) and includes the/estimation of reformulation costs per
plant (i.e., R&D, marketing, and capital costs), the number of aerosol plants
that would incur these costs (based/on the production volume of an average
"model" plant), and the calculation of total annualized cost.
Using reformulation with petroleum distillates as an example, it is easy
to see the effects of such a change on the production cost of aerosol
products. Looking first at the cost of the product itself, the use of this
new solvent will most likely increase the cost of the container in which it is
distributed. Due to the fact that the petroleum-based solvents have a density
of about 0.75, as compared to 1.32 for 1,1,1-trichloroethane, a larger
container will be needed in order to hold a similar weight of the product.
This is a significant consideration since the cost of the packaging accounts
for almost 36 percent of the product cost to the manufacturer (ICF 1989).
For the case of petroleum distillates, the change from 1,1,1-
trichloroethane use will necessitate expenditures in research and development,
labelling, and public education. Due to the flammable nature the new solvent,
a public education program might be needed to inform potential users of the
proper precautions which should be taken when using the product. In addition,
increased research and development will be needed to search for ways by which
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TABLE VIII-2. COSTS OF CONTROLS FOR 1,1,1-TRICHLOROETHANE IN AEROSOLS
Control Option
Alternate Delivery Systems
Occupational Uses
Consumer Uses
Incremental Costs? (thousand dollars)
1 Total
R&D and Annualized
Capital Marketing6 Costsc
Reformulation to:
Petroleum Distillate
Water-based Systems
5 , 594
92.3 . ~ 2,244
. 622.7
260.2
170,700d
19,000.0
a Raw material costs are not considered in this analysis primarily because
the replacement chemicals in both, the reformulated products and the alternate
delivery systems are as expensive as 1,1,1-trichloroethane '.
b Includes R&D and marketing costs associated with the reformulation of
various automotive and industrial products, household products, and aerosol
pesticides currently using methyl chloroform.
c Costs are discounted at the social rate of discount (2 percent) over the
equipment lifetime (10 years).
d These costs represent the capital investment required if all users of
1,1,1-trichloroethane-based brake cleaners purchased alternative equipment.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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the reformulated solvent might be made safer and more efficient. Finally,
retrofitting of assembly line equipment will most likely be needed in order to
provide adequate measures for fire-prevention as well as firefighting (ICF
1989a).
The example just presented is perhaps the most extreme case. Though the
cost impacts of other alternative solvents may not be as extensive as those
for petroletun distillates, they may be significant.
The costs of the two options considered in the alternative delivery
system category include the costs incurred by the current users of aerosol
products (e.g., brake shop owners and consumers) and do not include costs to
the aerosol industry. It is estimated that aerosol manufacturing facilities
could either reformulate these products or produce other, aerosol products
without incurring major financial losses.
An example of an alternative to consumer use of 1,1,1-trichloroethane-
based spot-removing aerosols is the use of professional cleaning services.
Aerosol spot removers are designed to reduce consumers' dry-cleaning costs by
providing consumers an easy way'to remove spots from dry-cleanable garments.
Most of the industry for aerosol spot removers has reformulated products to
use HCFCs in place of 1,1,1-trichloroethane. In the event that aerosol spot
removers were no longer available, consumers would be forced to resort to
additional dry cleaning services. These costs are based on the increase in
the number of times that consumers will have dry-cleaners remove spots from
garments that the consumer could have treated him or herself with aerosol spot
removers (ICF 1989b).
The data used in this analysis includes experimental data on the number
of spot treatments obtainable from a can of aerosol spot removers, the likely
interval between dry cleaning events, the size of the spot remover market, and
current dry cleaning fees. Spot removers used 1.1 million kilograms of 1,1,1-.
trichloroethane in. 1987. The results of this analysis indicate that
additional dry cleaning costs to consumers are approximately $20 per kilogram
of 1,1,1-trichloroethane used. These are upperbound costs, because a portion
of current users of aerosol spot removers might decide to "live with the spot"
a little longer, taking the garment to a dry cleaning service only when it
became time for general cleaning of the garment. In this case, additional dry
cleaning expense would be avoided. Even in this case, however, costs would
probably be higher, compared to other 1,1,1-trichloroethane controls, since
consumers pay more to have a spot treated by a professional dry cleaning
service than they do if they use aerosol spot removers.
Aerosol brake cleaners are used by brake mechanics to-(l) remove oil,
grease and brake fluid from the brake drum system, (2) remove the excess .dust
accumulated inside the brake housings, and_(3) remove glaze from brake pad
surfaces. To remove oil, grease, and brake.fluid, the best alternative to an
aerosol is to degrease manually, using a petroleum-naphtha-based solvent and
an ordinary scrub brush. To remove excess dust and glaze, there are several
alternatives, to cleaner application by aerosol, including vacuum enclosures,
recirculating liquid systems, and wet brush systems. The liquid applied
generally contains water and a surfactant (PEI 1983). The wet-brush is the
lowest-cost option. It is estimated that there are 297,416 brake repair shops
that employ aerosol brake cleaners (PEI 1983). The cost of substituting with
the wet-brush system is $574 per shop, so the investment for all shops would
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amount to $170.7 million. Operating costs are assumed to be approximately the
same as the current costs of aerosol brake cleaners; thus, the cost of the
equipment is believed to be indicative of the additional costs incurred.
Using 10-year and 2 percent discount rates, annual costs amount to
approximately $19 million.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CHAPTER' 9
OTHER SOLVENT USES OF OZONE DEPLETING SUBSTANCES (CFC-113, 1,1,1-
TRICHLOROETHANE AND CARBON TETRACHLORIDE)
9.1 BACKGROUND '
Some amount, in most cases relatively small quantities, of CFC-113,
1,1,1-trichloroethane, and carbon tetrachloride are employed in a number of
industry and laboratory applications. These include:
bearer media for coating and impregnation
vapour soldering technology
component drying
riveting and machining ,
airplane hydraulic system testing
fabric protection and coating
semiconductor manufacturing
miscellaneous testing (including leak detection)
mould release agents
film cleaning
component cooling
manufacture of solid .rocket motors
oxygen systems cleaning
correction fluids
fabric spot remover
process solvents
The Committee consensus is that by 1996, in accordance with the Montreal
Protocol, most of the CFC-113, 1,1,1-trichloroethane, and carbon tetrachloride
used for these applications .could be replaced by the alternatives discussed in
this chapter.
In the applications of laboratory analyses and in the manufacture of a
specific large scale solid rocket motor, the Parties have granted an exemptio,n
for continued use of specified ozone-depleting solvents for 1996 and 1997.
The exemptions are subject to review and alternatives are being investigated.
In the case of use of ozone-depleting substances as process chemicals,
there are also a number of alternatives identified in this report. In
addition, an, in-depth review of alternatives is planned for completion and
presentation by the Technical and Economic Assessment Panel to the Parties by
early 1995. . ^
9.2 BEARER MEDIA FOR COATING AND IMPREGNATION
In some applications, CFC-113 is used as a carrier of lubricants that
reduce frictional damage. In a typical process, gold-plated contacts .are
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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dipped into a bath of CFC-113 containing two percent of a lubricant such as
perfluorinated polyether. The CFC-113 acts both as a cleaner and a lubricant
bearer. The following alternatives have been identified for this application
(Nordin 1988, Owens 1990):
Use of mechanical methods, such as spraying or rolling, to
dispense the lubricant. (The problem of excessive application of
the lubricant must be solved as the lubricant must not exceed four
micrograms per contact.
Application of the lubricant via emulsions. (These should be
water-based emulsions if possible.)
Use of an alternative non-halogenated solvent compatible with
fluorinated lubricants.
Use of an alternative lubricant. (The lubricants should be
compatible with the materials in use.)
Use of a perfluorinated solvent has been demonstrated with
perfluoropolyether lubricants and is in commercial use in several
countries. However, because of the high global warming potential
of perfluorinated solvent's, they should only.be used in
applications where emissions.can be kept at or near zero.
Hydrochlorofluorocarbons (HCFCs) might be considered despite their
small contributions to ozone-depletion. It is important that
HCFCs only be used where other alternatives are considered
unacceptable, and that recovery systems be used in conjunction
with HCFCs!
HFCs might be considered despite their contributions to global-
warming. It is important that HFCs only be used where other
alternatives are considered unacceptable, and that recovery
systems be used in conjunction with HFCs.
i
9.3 VAPOUR SOLDERING TECHNOLOGY ^
Vapour-phase soldering, also known as condensation soldering, is a
reflow method that involves boiling a liquid and putting the cool electronic
assembly along with unmelted solder into the hot vapour. The vapour raises
the temperature of the cool electronic assembly and the solder until the
solder melts. Because of its all-around heat application, vapour-phase
soldering is one of a limited number of soldering processes that, in
principle, enables both sides of a substrate to be soldered simultaneously!
It cannot, however, be used as the only soldering process in mixed assemblies
because the process can damage temperature-sensitive bodies on some leaded
components (Pawling 1987).
. The primary liquids used in vapour-phase soldering -- nonflammable
perfluorinated organic compounds -- are nonozone-depleting but costly. In
addition, they have a'very high global warming potential. To minimise, primary
vapour losses, a less expensive secondary, vapour blanket .using a chemical with
a lower boiling point, such as CFC-113 (boiling point 47.6°C), is often used.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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With standard top loading batch equipment, this cuts losses of the primary
vapour by a factor of ten (Seidinger 1989). CFC-113 also serves as a conduit
for the release of toxic hydrofluoric acid and perfluoroisobutylene (PFIB)
that may be generated if the primary vapour overheats. To minimise vapour
losses and reduce emissions of toxic compounds, the blanket should be operated
at a low temperature. The interface of the two vapours forms a zone where the
secondary vapour can also break down, releasing hydrochloric and hydrofluoric
acids, phosgene, and carbonyl fluoride. Treating the condensate will not only
eliminate most of these dangerous by-products but will also reduce corrosion
of the machine itself.
Two possible alternatives to using CFC-113 to form a secondary vapour
blanket in reflow soldering include:
Eliminating the use of a secondary vapour blanket. Although joint
quality would not suffer, eliminating the secondary blanket could
increase production costs for the reflow soldering operation by a
factor of 10. A primary vapour recovery unit that claims to
recover up to 80 percent of any primary vapour entering the
extraction system is now available. With this-unit, net fluid
costs could be reduced from approximately U.S. $10-14/hour to U.S.
$3-4/hour.
Using a secondary vapour blanket that does not deplete the ozone
layer. Recently a perfluorocarbon liquid has been introduced as a
possible substitute for the secondary blanket. The compound has a
half life of approximately 1,000 years and does not contain
chlorine, bromine, or hydrogen atoms. (Niemi 1991) However, the
extremely long atmospheric^lifetime of perfluorocarbons give them
high global-warming potentials. Therefore, they should only be
used in equipment that is specially designed to minimise
emissions. To replace perfluorocarbons in this and other
applications, an alternative known as hydroflubrocarbons (HFCs)
are currently being developed.
Where specifications and throughput allow, IR spidering is also an
alternative process. Table IX-1 summarises a recent evaluation comparing the.
use of CFC-113 and,a perfluorocarbon as the secondary blanket in vapour-phase
soldering equipment. The results of this test show:
CFC-113 and the perfluorocarbon are consumed in similar
quantities.
The rate of corrosion is somewhat lower for the perfluorocarbon,
as measured by the copper wire method.
An equivalent amount of PFIB is generated for both
chemicals. '
The amount of total hydrohalic acids generated is much lower for
the perfluorocarbon.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Table IX-1. COMPARISON OF CFC-113 AND A SUBSTITUTE
PERFLUOROCARBON AS A SECONDARY VAPOUR BLANKET
Characteristic CFC-113 Perfluorocarbon
Rate of Consumption (m3/hr) 1.14-1.51 x 1CT4 1.14-1.51 x 10'4
Vapour Temperature (°C)
Secondary vapour 55-60 58-61
Primary vapour 216-218 217-218
Rate of Corrosion (mm/yr) 5.59 x 10'2 2.03 x 10'2
Perfluoroisobutylene Generation
(Mgm/m3/hr) <0.227 <0..227
Hydrofluoric Acid Generation
(/igm/m'/hr)
150°C 682 (8 HC1) 1140
215°C 9,090 (240 HC1) 4420
Source: Seidinger 1989
* 1994 UHEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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9.4 COMPONENT DRYING
Many precision devices, such as electrical and electronic parts,
mechanical assemblies, optical equipment, and delicate instruments, come into
contact with water during manufacturing and assembly. Such parts must be
dried promptly after cleaning to prevent rusting, water staining, and general
deterioration in quality that can lower product reliability. A dedicated
drying or dewatering process is often used to remove moisture. Typical
techniques include:
centrifugal processing followed by hot air drying
absorbent drying using alcohols, such as ethanol, isopropanol, and
acetone
vapour drying with non-CFC solvents, such as chlorocarbon
displacement or solubilisation drying using CFC-113-based drying
formulations (Johnson 1991).
The trade-offs among these drying techniques are compared in Table IX-2.
Process recovery and conservation methods for CFC-113 in drying are
similar to those in typical solvent cleaning systems. The use of CFC-113, for
drying represents, perhaps, less than 10 percent o.f the CFC-113 used for
cleaning, but many of the applications are critical (Johnson 1991).
9.4.1 Semiconductors1
\
. ' Integrated circuits, the major product of the semiconductor industry,
are a combination of electronic devices including transistors, diodes,
resistors, and capacitors which are placed in a-single, semiconductor crystal.
During the fabrication of integrated circuits, CFC-113 is used for'
displacement drying of semiconductor materials, such as wafers. Depending on
the integrated circuit being made (e.g., metal oxide semiconductors (MOS) or
bipolar), different process steps, which can include wafer preparation,
oxidation, doping, and layering, are repeated so that drying may occur many
times during the fabrication process.
9.4.2 Printed Circuit Boards . .
Of the four processes commonly used for critical drying of printed
circuit boards during manufacturing, two processes use CFC-113. These
processes involve: .
Dipping the wet boards in a .circulating bath of pure CFC-113. The
water is displaced, floats on the solvent surface, and is pumped
off the surface into a separator so that the boards are not re-
wetted when removed. Following this bath, the board is usually
passed through a vapour degreaser containing a CFC-113/ethanol
azeotrope to remove residual water traces. .
1 Semiconductors are materials having an electrical conductivity between
that of a conductor and an insulator. They are either discrete devices such
as transistors or thyristors, or integrated circuits that contain two or more
devices in a single semiconductor crystal.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table IX-2. COMPARISON OF DRYING TECHNIQUES
Dewatering
Technique
Advantages
Disadvantages
Centrifugal
processing and
hot air drying
Low equipment cost,
handling.
Can be used for simple
shape products. High
energy costs, spots.
Absorbent
drying using
alcohols
Drying at room temperature.
Large solvent
consumption. Needs
fire protection
measures.
Displacement
drying with
PFCs and HCFCs
Satisfactory drying at 50°C
or below.
High cost of solvents.
Bear in mind OOP and
GWP.
Displacement
drying with
chlorinated
solvents
Displacement
drying using
CFC-113
Proven, available, possible
to retrofit equipment
Energy efficient, rapid
drying.
Possible compatibility
with materials.
Requires careful
management and
handling.
Higher equipment costs.
Increasing operating
costs. May leave a
residual film.
Depletes stratospheric
ozone layer.
Source: Johnson 1991.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Dipping the wet boards into a surfactant/CFC-113 mixture to
emulsify the water, then using a vapour degreaser to remove the
surfactant.
The other two critical drying processes, use alternative solvents. The
circuits can "be dried by:
Dipping the wet boards into two successive isopropanol tanks
fitted with dryers
Dipping the wet boards into a water-displacement product based on
toluol. The water drains through a grid in the bottom of the
tank.
CFC-113 use could be eliminated by switching to these two alternative drying
processes.
Another method for eliminating CFC-113 in this application is to
eliminate the use of water in the manufacturing process, thereby eliminating
the need for drying. Alternatives to the use of water-based processes are
discussed in detail in the chapter on Electronics Cleaning. For manufacturers
using small quantities or operating in developing countries, alcohols and
alcohol/perfluorocarbon mixtures are suitable alternatives to CFC-113 and
1,1,1-trichloroethane, for unlike aqueous and semi-aqueous processes, water
treatment systems are not required (Matsui 1991).
9.4.3 Mechanical Assemblies
For further information, refer to the chapter on Precision Cleaning.
9.4.4 Metal Surfaces
For further information, refer to the chapter on Precision Cleaning.
9.5 RIVETING AND MACHINING
CFC-113 is used as a 'lubricant and coolant in certain drilling and
riveting operations during the manufacture of aircraft frames, particularly
wing assemblies. In this operation, an automatic drill/riveting machine
clamps the aircraft skin and stringer together, drills -and countersinks a
close tolerance hole through the two pieces, inserts and compresses a rivet,
and shaves the rivet flush to provide an aerodynamically smooth surface. The
entire operation takes approximately seven seconds. CFC-113 is used primarily
to carry away heat generated during the drilling and shaving processes, which
extends the bit life of the dr.ill and improves the finish of the hole. .For
one company, CFC-113 also lubricates the rivet as it is inserted and prevents
corrosion in the riveted area after assembly. For some applications,
lubrication of the rivet is critical to ensure that the rivet completely
expands into the drilled hole. Incomplete "fill" leads to fatigue stress and
the possibility of leakage from fuel tanks located in the wings of the
aircraft.
Manufacturers agree that non-evaporative lubricants are adequate for
holes less than two or three hole diameters in depth. For deeper holes,
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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lubricants combined with cold air is considered more promising. Possible
substitutes for CFG-113 in shallow holes include long chain fatty alcohols and
emulsified water/oil mixtures. Manufacturers agree that the ideal substitute
must:
have appropriate coolant/lubricity characteristics
be nontoxic and nonflammable for worker safety
leave no residue that could prevent good bonding of paints and
sealants
be noncorrosive
Additional research is needed to determine whether non-CFC alternatives
will meet these requirements. In recent years, the International Cooperative
for Ozone Layer Protection (ICOLP) has promoted intercompany research between
McDonnell-Douglas, Boeing, and British Aerospace on alternative methods of
riveting (British Aerospace 1990; Grumman Aircraft 1990).
9.6 AIRPLANE HYDRAULIC SYSTEM TESTING
New airplane hydraulic systems are routinely tested for leaks by adding
hydraulic fluid through existing airplane ground service connections,
pressurizing a portion of the system, and then visually inspecting for leaks.
Discovered leaks are stopped and spilled hydraulic fluid is cleaned up. This
process is repeated at higher pressures for each portion until the entire
hydraulic system is pressurized to 3000 psi (210 kg/cm2) without leaks.
CFG-113 is used to clean up the spilled hydraulic fluid. This solvent is
necessary because it can be used inside the airplane fuselage without
flammability or toxicity problems. Also, because CFC-113 is more dense than
hydraulic fluid and completely evaporates, it is possible to flush
inaccessible areas without concern for corrosion.
A new process that significantly reduces the use of CFC-113 has recently
been used for hydraulic systems testing. The .process uses inert gas and audio
inspection. Pressurized nitrogen is introduced into the hydraulic system
through a hydraulic pump filter module. As the gas enters the system, it
bypasses component valves that are designed to operate under hydraulic fluid
pressure. Bypassing these valves allows the entire system to be filled at
once, including the fluid reservoir which has a 75 psi (5.3 km/cm2) relief
valve. Although this relief valve limits the maximum pressure that can be
applied to the system, it is still great enough to force gas through system
leaks that would require much higher pressure if hydraulic fluid were used.
By using an ultrasonic sound detector tuned to the frequency of the escaping
gas, a 95% or better leak detection rate is achievable. The new process is
very capable of finding major leaks that previously required large quantities
of CFC-113 for clean up after testing with hydraulic fluid. The few leaks
that show up when the system is finally fully charged with hydraulic fluid are
relatively small and require much smaller quantities of CFC-11'3 for clean up.
However, an alternative is still being sought for this reduced, but necessary
solvent use.
The new gas leak detection system has reduced CFC-113 consumption for
hydraulic spill .clean up, on average from 25 to 3 gallons (95 to 11 litres)
per plane (Boeing 1991).
* 1994 UHEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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9.7 FABRIC PROTECTION AND COATING
1,1,1-Trichloroethane is used as a solvent in fabric protection agents
sold for both industrial and consumer use. Like other chlorinated solvents,
1,1,1-trichloroethane "dissolves" the polymeric fluorinated compounds that
protect the fabric (teflon, for example), causing them to swell so that a more
homogeneous mixture or dispersion can be applied.
There are three general classifications of fabric protection products
which use 1,1,1-trichloroethane. The most common is the aerosol can which is
widely used by consumers to treat fabrics, in their home. The second is for
Retailer Applied Fabric Treatment (RAFT), where a retailer provides the
application of a fabric treatment, usually for soil or stain protection, as an
after sale service. The third application method is mill application. Mill
application has a long history and is either done at the mill, where the
fabric is manufactured, or by a special contractor who performs the
application either for the manufacturer or for a user of the fabric (Mertens
1991a). ,
The aerosol application is perhaps the largest and most diversified
segment as there are many formulators and packagers of aerosol fabric
protection products. They are usually based on a fluorocarbon or a silicone
resin and use a solvent carrier. The solvent most commonly used is 1,1,1-
trichloroethane, primarily due to its excellent solvency, fast evaporation
rate, low flammability, low toxicity, and nonphotochemical reactivity (Mertens
1991a). .
The Retailer Applied Fabric Treatment is usually found in the retail
furniture business and in automotive dealerships. The seller of a piece of
upholstered furniture or a fabric automobile interior often offers the
application of soil and stain preventative spray after the sale of the product
itself. This application uses predominately fluorocarbon resin with some
silicone. The fluorocarbon resins are often formulated with 1,1,1-
trichloroethane. There is a wide variation in the quality of the application
methods in this' area. Some of the retailers have large warehouse operations
where they can install ventilation booths and have well trained operators
performing the application. Others are small operations and may spray on the
fabric protection at the loading dock door. Because of these varied
application procedures, the properties of 1,1,1-trichl'oroethane are well
suited to this application (Mertens 1991a).
There is also an-extension of the RAFT application where fabric
protectants are applied in the home. In this application, a service company
comes to the consumer's home and applies fabric protection to furniture,
drapes, and/or carpeting. The toxicity, flammability, and odour are major
factors in the choice of solvents used in these applications. The consumer '
does not want any lingering odours in the home after the application, of the
fabric protector, and the applicator needs to be concerned about the
flammability and toxicity of the product during the. application (Mertens
1991a).
Mill application of fabric protectors is usually performed on an :
automatic processing machine custom designed for the operation. The
advantages of mill application are the ability to cover the cloth completely
with the fabric protector and to automate the process. These systems usually
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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incorporate some form of vapour recovery, and because of this, 1,1,1-
trichloroethane has not been the solvent of choice for the larger mill
treatment operations. Trichloroethylene has often been used where vapour
recovery is incorporated into the process (Mertens 1991a).
Replacement of !,!, 1-trichloroethane in fabric protection applications
will vary significantly in each of these applications. For example, 3M has
developed a hydrocarbon solvent version of its Scotchguard fabric protection
products. This product is flammable and contains volatile organic compounds
(VOCs), and therefore may contribute to the formation of tropospheric ozone
(smog). In many areas there are stringent regulations controlling the use of
VOCs in aerosol cans, and the use of these alternatives may be restricted in
those areas that have high tropospheric ozone levels. In addition, there will
be a need for consumer education to illustrate the risks associated with the
flammability of such replacement products (Mertens 1991a).
Replacement in RAFT applications will be difficult for those areas that
have tropospheric ozone problems. The most likely replacement solvent for
this application will be mineral spirits or hydrocarbon solvents. With both
types of solvents, the dry time will be extended and the flammability may be
of concern to users. Additional capital expense may be required to handle and
use these solvents safely (Mertens 1991a).
DuPont has just introduced a water-based fluorocarbon resin system which
will- replace solvent-based fluorocarbon products that are currently used in
this application. The system will require the purchase of special equipment
for the application of. the water-based product.
Mill applications appear to have the greatest opportunity to change to
alternative systems as they can substitute solvents and use add-on controls to
minimize emissions of solvents that are VOCs, Hazardous Air"Pollutants, toxic,
or otherwise pose a threat. Trichloroethylene with carbon adsorption has been
successfully used in this application for many years, and can easily be
extended to replace any use of 1,1,1-trichloroethane (Mertens 1991a).
Although it is possible to obtain solutions or dispersions of polymeric
fluorinated compounds using other solvents such as hydrocarbons and esters,
there is still some loss of the solvent effect. In addition to its "swelling"
capacity, 1,1,1-trichloroethane also possesses an unusually high density
(nearly twice that of other solvents) --a characteristic which reduces the
tendency of the solids to settle. Alternative formulations will require more
frequent and thorough agitation to keep the solids suspended.
9.8 SEMICONDUCTOR MANUFACTURING
9.8.1 Plasma Etch Processing
x
As shown in Table IX-3 (Mocella 1991), several CFC and fluorocarbon
compounds are used in plasma etching of silicon wafers. Of these materials,
FC-14 (CF^), CHF3 and C2F6 do not contain chlorine or bromine and are not
ozone -depleters, but some (e.g. C2F6) have high'global-warming potentials.
The remaining materials deplete ozone and will be phased out by the year 1996
in developed countries under the Montreal Protocol. ' Several alternatives are
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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now available while others require further testing and development (Felty
1991).
Mixtures of various fluorocarbons (PCs) and hydrofluorocarbons (MFCs)
with nonozone-depleting chlorine sources may be an alternative used in the
etching process (see Table IX-4). Some of these (e.g., SF6, CF4, C2F6, HFCs)
may have high global-warming potentials. Many of these alternatives are in
the development stages and transition to high volume production with data on
cost and impact on production yields have not yet been determined. Adopting
any of the other alternatives will require modifying processes to account for
variances in reaction kinetics and materials and insuring equipment
compatibility. Another factor limiting the attractiveness of these
alternatives (Felty 1991) is conversion costs or loss in yields.
One possible option is the use of chlorofluorocarbon (CFC) alternative
compounds. Several of the fluorocarbon compounds listed in Table IX-5 are
potential replacements for existing CFCs. Many of these compounds have been
evaluated as etchants, with some reported success (Mocella 1991). Like the
substitutes, some of the materials have no ozone-depleting potential while
others, primarily the HCFCs, have low ozone-depletion potentials and may, for
a limited time, find uses in critical applications. However, potential users
of HCFCs should be aware that these chemicals were recently added to the list
of substances controlled under the Montreal Protocol and are currently
scheduled to be completely phased out by the year 2030, with a 99.5% reduction
required by the year 2020.
9.8.2 Oxide Growth Processing
1,1,1-Trichloroethane is used for silicone oxidation in diffusion
furnaces during semiconductor wafer fabrication processing. 1,1,1-
Trichloroethane is delivered through a leak tested system to the silicon
oxidation furnaces where the following reaction takes place:
CH3CC13 + 2 02 -- 2 C02 + 3 HC1
4 HC1 + 02 -- 2 C12 + 2 H20
It should be noted, however, that none of the 1,1,1-trichloroethane is emitted
to the atmosphere. This use is a transformation process and should be treated
in the same way as feedstock applications. The combustion reaction is
quantitative, whenever sufficient oxygen is present. Even in an oxygen
deficient environment, 1,1,1-trichloroethane quantitatively decomposes at the
furnace temperature forming carbon, carbon monoxide and HC1. The chlorine
species produced as by-products of the diffusion reactions,chlorine and
hydrogen chloride gases, are scrubbed to prevent emission to the troposphere.
9.8.3 Semiconductor Degreasing .
CFC-113 and 1,1,1-trichloroethane are used in the electronics industry
to degrease semiconductors as part of the silicon wafer fabrication process.
In.the late 1980s, two companies jointly announced the introduction of a new
technology for cleaning semiconductor wafers. The technology, called "water-
ice cleaning," does not require CFC-113 or 1,1,1-trichloroethane. It relies
instead on a spray of ice particles 30 to 300 microns in diameter. The
particles, are delivered at close to the speed of sound and,at temperatures
below -50°C. The hardness and size of the particles as well as the pressure
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table IX-3. HALOCARBON PLASMA ETCHANTS
Designation
CFG -11
CFC-12
CFG -13
CFC-13Br
FC-14
HFC-23
CFC-li5
FC-116
Carbon Tetrachloride
Formula
CFC13
CF2C12
CF3C1
CF3Br
CF4
CHF3
C2F5C1
C2F6
CC14
OOP
1.0
1.0
1.0
10.0
0.0
0.0
0.6
0.0
1.1
Source: Adapted from Mocella 1991.
Table IX-4. POSSIBLE MIXTURES FOR CFG REPLACEMENT IN PRY ETCHING
Alternative 1 : Fluorocarbon +
CF4
C2F6
CHF.3
Alternative 2 : . Fluorine Source +
NF3
SF6
SiF4
Chlorine Source
C12
HC1
SiCl4
BC13
Chlorocarbon
CCl4a
CHC13
8 CC14 is an ozone-depleting substance (ODS) and scheduled for a phaseoUt
under the Montreal Protocol.
Source: Mocella 1991
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table IX-5. CFC ALTERNATIVE ETCHING COMPOUNDS
Designation
HCFC-22
HCFC-123
HCFC-124
HFC-125
HFC-134a
HCFC-141b
HCFC-142b
HFC-152a
Formula
CHF2C1
. CF3CHC12
CF3CHFC1
C2HF5
CF3CH2F
CFC12CH31 . 5
CF2C1CH3
CH3CHF2
- , ODP
0.055
0.02-0,
0.02-0.
0.0
0.0
0.11
0.065
0.0
.06
.04
Source: Adapted from Lerner, Mocella 1991.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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and angle of the spray can be controlled as needed. This process is designed
for use in place of the vapour degreasing stage of wafer processing (Nikkei
Sangyo Shinbun 1989, Denpa Shinbun 1989).
9.8.4 Photolithographic Processing
The photolithographic process for semiconductor wafer fabrication uses
CFCs in various cleaning and drying processes. In semiconductor
manufacturing, processes and equipment are designed around various solvents
and specific application needs (e.g., chlorine source for etching silicone as
part of the photoresist process). The use of lasers and dry photoresist
methods or the implementation of aqueous chemistry photoresists can reduce
solvent dependency (Karash 1991).
9.9 MISCELLANEOUS TESTING /
9.9.1 Leak Testing
Both helium and CFC-113 are being used as an alternative to detect leaks
in aircraft fuel tanks. Any solvent compatible with tank materials can be
used as a substitute for CFC-113. Helium is being used successfully for leak
detection. In detecting leaks in metal gyro housings, for example; CFC-113 is
also used as a medium. The integrity of the seal in certain metal gyro
housings containing an inert gas atmosphere is tested during repair operations
by immersing the housing which contains pressurized gas into a bath of CFC-
113. This method quickly locates any "gross" leaks that may exist. Possible
alternatives for gyros include replacing the CFC-113 with a blend of cyclic
fluorocarbon ether and aliphatic fluorocarbon or with a solution made from
pure water and a surfactant. There are also systems available which detect ,
leaks of this type using infrared techniques (Hunt 1991). Perfluorocarbons
(PFCs) have associated global warming issues.
\ .
9.9.2 Laboratory Testing
CFC-113, 1,1,1-trichloroethane, and carbon tetrachloride are also used
for analyses in laboratories or investigations (e.g., quality testing and
analyzing oils and greases). Use of ozone-depleting solvents in laboratory
applications has been granted a global exemption to the phaseout by the
Parties to the Protocol for a period of two years beginning in 1996. Refer to
the global exemption and ongoing activity in this area for more information.
9.10 MOULD RELEASE AGENTS
In order to prevent adhesion, release agents form a barrier between a
moulding compound and the mould. Sometimes release agents also function as a
lubricant and are used in the moulding of graphite epoxy thermoplastic,
thermosetting plastic, and rubber parts.
The active component in a release agent may be.mixed with the moulding
compound (an internal release agent) or sprayed onto the mould prior to
moulding (an external release agent). Only,external release agents contain
.solvents. Waxes, fatty acids, silicone oils, or fluoropolymers are normally
used as the active component in external release agents. To insure an even
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application of the release agent, the active component is diluted with solvent
to produce a formulation of one to five percent active ingredient and the
remainder a mixture of solvents.
Commonly used in the solvent mixture to control both the flashpoint of
the release agent and the evaporation rate of the main solvent, 1,1,1-
trichloroethane's high density prevents sedimentation of the active
ingredients. It is rarely used for its solvent capabilities. Other
components of solvent mixtures include xylene, mineral spirits, methyl ethyl
ketone, .and ethanol. With fluorinated polymer release agents, 1,1,1-
trichloroethane swells the fluoropolymer and makes it "fluffy," which
counteracts sedimentation and improves the agent's release properties. In
release agents with other active ingredients, 1,1,1-trichloroethane does not
serve the same function and reformulation should prove simpler.
The recent trend in industry is toward the use of internal release
agents or water-based external release agents. Internal release agents,
however, are not good for foamed products since the structure of the foam is
partially controlled by surface-active foam stabilizers whose function is
disturbed by the internal release agent. The plastic foam- industry,
therefore, is pushing the development of water-based external release agents.
The general'objection to water-based release agents is that they evaporate too
slowly and reduce the temperature of the .mould (which then lowers the
production rate). Internal release agents are a possible alternative for
moulded rubber products.
Several manufacturers of aerosol mould release agents have developed
"nonsolvent" formulations in which the active ingredient is dispensed without
the aid of a solvent. This type of formulation has proven effective in some
applications. A potential problem with nonsolvent mould releases is the
uneven dispersion and wetting that can occur because the active ingredient is
not- solubilized.
9.11 FILM CLEANING
Prior to the introduction of the Lipsner Smith Motion Picture Film
Cleaning Machine, film was most often hand-cleaned. A typical cleaning .
operation would include a solvent-wetted wiping cloth and a set of rewinds.
The solvent of choice was carbon tetrachloride (Mertens 1991a, Tisch 1991).
When Lipsner Smith designed the first automatic film cleaning machine,
carbon tetrachloride's excellent solvent action, its rapid rate of
evaporation, non-flammability, and its lack of any softening action on the
film were recognized. Because of known toxic effects, Lipsner Smith
investigated alternative solvents and liquids that would provide the same
characteristics without the toxicity problem. Some of the solvents evaluated
included cyclohexane, hexane, methylene chloride, perchloroethylene, 1,1,2-
trichloroethylene, 1,1,2-trichloro-1,2,2-trifluoroethane, and 1,1,1-
trichloroethane (Mertens 1991a, Tisch 1991).
1,1,1-Trichloroethane, because of its desirable solvent characteristics,
its low cost and low toxicity, was chosen to be used with the mechanized
Lipsner Smith system. From that point on, 1,1,1-trichloroethane has been the
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world's most commonly used film cleaning solvent and is used exclusively with
Lipsner Smith machines (Mertens 1991a, Tisch 1991).
With the exception of limited competition in France and Japan, Lipsner
Smith machines dominate the world's market for film cleaning. There are
approximately 600 users worldwide who use approximately 1,500 units. These
users make up an estimated 90 percent of the total units used in the world for
film cleaning. The typical L_psner Smith user is a film laboratory or film-
to-videotape transfer facility which operates two units with an annual solvent
usage of about 15 drums (55 U.S. gallons/drum) (Mertens 1991a, Tisch 1991).
The film cleaning industry is now rather steady as the film-to-videotape
revolution of the 1970s and 1980s appears to have run its course. As a
result, the need for film cleaning will continue for the next several years as
its only foreseeable replacement technology is coming from high-definition
video as an origination medium and/or as a theatrical distribution medium.
However, this technology is unlikely to have any significant impact for at
least ten years (Mertens 1991a, Tisch 1991).
Since the addition of 1,1,1-trichloroethane to the Montreal Protocol,
Lipsner Smith has reviewed their needs and the choice of 1,1,1-trichloroethane
as the cleaning solvent. They have tested several alternative cleaning
solvents with varying levels of success.
Perchloroethylene is a viable substitute for 1,1,1-trichloroethane in
virtually all film cleaning applications. As a result specially designed
cleaning equipment has been developed that limits emissions of
perchloroethylene during the cleaning process. This special equipment helps
to reduce the risks to workers associated with the toxicity of this
substitute. Besides the health risks associated with the use of
perchloroethylene, users must consider the slower drying time as compared to
1,1', 1-trichloroethane. However, while perchloroethylene's lower volatility
increases drying time, it decreases solvent consumption because less solvent
is lost through evaporation. . . .
Another alternative that has proven effective in select applications is
water-based film cleaning. These systems clean film using a spray system and
a water/surfactant cleaner formulation. The major concerns with water-based
spray cleaning are the potential for damage to the film caused by the spray
and the need for a special drying stage in the process.
Two other alternative solvents are currently being evaluated for use in
the film cleaning industry -- perfluorocarbons (PFCs) and hydrofluorocarbons
(HFCs). Lipsner-Smith has been testing HFC 43-10 and hopes that it can be
marketed in the film cleaning sector as a replacement for 1,1,1-
trichloroethane in the next one to'two years. PFCs and HFCs have global-
warming issues which should be taken into consideration during evaluation.
9.12 COMPONENT COOLING .
CFC-11 and CFC-12 in aerosol cans are used to cool, or thermally shock,
electrical components during certain diagnostic procedures in the fault
isolation of defective circuits and circuit components on printed circuit
boards. HCFC-22 is an alternative with a much lower ozone-depletion potential
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(ODP) which provides essentially the same degree of cooling. Howeyer, because
HCFC-22 still contributes to ozone-depletion, other alternatives have recently
been developed. These include HFC-134a or liquid, nitrogen in aerosol cans, as
well as mechanical cooling devices using a vortex principle and compressed air
(Hunt 1991).
There are other uses of CFC-113 and 1,1,1-trichloroethane such as pre-
surgical skin cleaning and as a cooling media in controlled fusion experiments
(Stemniski, 1991a). The Committee believes that the quantity used in such
uses is small. These uses were not discussed in detail by the Committee.
9.13 MANUFACTURE OF SOLID ROCKET MOTORS'
Ozone Depleting Substances (ODSs) have, been routinely used globally for
decades in the manufacture of space launch vehicle solid rocket motors (SRMs).
The primary ODS solvents used are 1,1,1-trichloroethane (TCA or methyl
chloroform) and CFC-113.. These substances are used because^ of their excellent
cleaning properties,' low toxicity, chemical stability and non-flammability.
Non-flammability is of critical importance to the safety of operations
involving highly energetic propellant materials.
In the United States, large solid rocket motors (SRMs) are used to
launch into space .communication, navigational and scientific satellites and
the manned Space Shuttle orbiters. Large SRMs include the existing Titan IV
SRM as well as its upgraded version called the SRMU and the Space Shuttli
redesigned solid rocket motor (RSRM). ^
a. The SRM manufacturing industry is unique in that there is no method
to test the performance of an individual SRM prior to use. The only way an
SRM can be tested is for it to be static fired. In this way, it is consumed
and cannot be used again (although various components may be re-used, as is
done in the Shuttle program.) Accordingly, SRM success can only be assured
through rigorous manufacturing including detailed material specifications and
continuous quality control.
b. SRM manufacturing is also unique in that the physics and chemistry
of SRM functioning is currently only partially understood. For example,
burning of SRM propellant has not been completely physically modeled or
.described due to the extremely hi-gh temperatures and gas velocities involved.
Therefore, the knowledge .of rocket manufacturing gained in the past is
critically important to safety and reliability. SRM manufacturers can change
current methods of manufacturing only after long-term testing and extensive
evaluation. Even after such evaluations, it is not certain that the change in
methodology will be successful on the SRM. Accordingly, the end users
(customers) of SRMs require SRM manufacturers to follow a rigorous system of
change control whose objective is to ensure that no changes in the SRM
'manufacturing process be made without explicit advance approval based upon the
results of the extensive testing. Such testing and evaluation can involve
numerous steps up to and including full scale ground-level static firing of an
SRM.
. -
c. Despite these technical safety and reliability challenges, the SRM
industry has successfully tested, approved, arid implemented significant ODS
elimination. Since 1989, the four US manufacturers of large SRMs. have
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eliminated over 1.6 million pounds of ODS use per year. Current (1994) ODS
usage is less than 48 percent of the use in 1989. Usage in 1995 is estimated
to be less than 22 percent of 1989, and manufacturers have committed to
complete elimination of ODSs within the next few years.
Update on the NASA/Thiokol Applications
The National Aeronautics and Space Administration (NASA) and Thiokol was
granted an essential use production exemption for 1996 and 1997. NASA/Thiokol
have proceeded with their phaseout and are ahead of schedule for eliminating
non-essential uses and investigating additional alternatives and substitutes.
However, at this time NASA/Thiokol has not identified any acceptable
substitutes that would reduce their essential use below the previously
calculated amounts. It is expected that they will request the government of
the United States to nominate an extension of essential use for the years
1998, 1999, 2000, and 2001.
Other U.S. Rocket Applications
The Solvents, Coatings, and Adhesives Technical Options Committee (TOC)
reported in the March 1994 Report that it was likely that all manufacturers of
solid rocket motors use ODSs. The Committee has confirmed that other U.S. and
European solid rocket motors use these substances and that these organizations
are expected to nominate additional essential uses by January 1, 1995 for
decision in 1995.
a. The U.S. Air Force Titan Program may prepare an Essential Use
Exemption request for Continued Use of TCA for Critical Titan SRMU
Manufacture. A nomination by January 1, 1995 could be considered for Decision
by the Parties in November 1995.
b. The Titan launch system offers assured access to space for payloads
requiring heavy-lift capabilities. Titan payloads have historically been
among the most important .and valuable in space exploration, e.g., the Gemini
manned space program, Helios solar observers, Viking Mars landers, and Voyager
deep space probes. In the near future, Titan will launch Cassini, a fully
integrated international exploration spacecraft. Communications,
environmental, scientific, and international security satellites are expected
to be among the payloads carried into space on Titan in the next decade.
c. The U.S. Titan program is working to completely eliminate the use of
ODSs and has invested substantial resources in successfully developing
alternatives to ODS use. The original production schedule of the Titan solid
rocket motor upgrade (SRMU) required completion of hardware delivery in 1995.
At the same time that the amendments to the Montreal Protocol accelerated ODS
phase-out requirements, the Titan Program slowed down production to complete
hardware delivery in 1999. The combined effect of these two events has made
it impossible for the Titan Program to qualify alternatives for all ODS uses
by the ODS projection ban of 1 January 1996. It is therefore necessary that
small-quantity critical uses of 1,1,1-trichloroethane continue, to allow
completion of the currently authorized compliment of Titan SRMUs. These uses
cannot be modified without full qualification testing, which would disrupt the
launch schedule for years, cost hundreds of millions of dollars, and
effectively halt the contributions of the Titan program to global access to
space.
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d. The Titan manufacturing team has undertaken an intensive program to
identify and evaluate alternatives to ODS throughout the rocket motor
production process. The program includes eliminating non-critical uses and
minimizing the quantities of ODS in essential uses. The prime contractor and
the major manufacturers of Titan IV vehicle components will reduce all ODS use
by 99 percent, from 1.33 million kg in 1989 to 9,200 kg in 1996. Four small-
quantity ODS uses are critical to the success of the Titan SRMU. These are
(1) surface preparation to ensure effective bonding of the internal insulator
to the composite case, (2) surface preparation to ensure effective attachment
of breather cloth to the insulator to permit uniform curing, (3) surface
preparation to ensure effective bonding of the propellant to the insulator,
and (4) dispersing propellant cure catalyst during propellant mixing. The
quantity of ODS necessary to complete SRMU manufacture for the final nine
flight sets is 3,660 kg per year or less for 1996 through to .1999.
e. As in the case of the Shuttle Program, substitutes for certain
critical uses with severe safety and reliability concerns have not yet been
identified or have not yet been qualified. Given this critical need for
safety and reliability, the Request for Exemption for continued TCA production
to support these essential needs may be submitted. The request, if submitted,
will need to contain detailed discussions of the critical needs for continued
use, search for alternatives, and future plans to minimize the TCA quantities
needed. . ' '
European Rocket Applications
The TOC has learned that ODS are currently used in European liquid and
solid rocket motors.
a. .Both CFC-113 and TCA are used in the European Ariane Espace Program.
Efforts to find substitutes for these programs concern CRYOSPACE for liquid
rocket engines and Societe Europeenne de Propulsion (S.E.P.) for solid motors.
b. CRYOSPACE will not apply for an essential'use exemption this year.
Stockpiling and substitution are expected to address their present concerns.
S.E.P. is expected to apply for an exemption before 1 January 1995. The
processes involved might be slightly different from those of the Shuttle or
Titan IV Programs but are also similar because the Ariane rockets carry
comparable large payloads. However, given the similar need for safety and
reliability it is likely that their exemption will also contain detailed
discussions of the critical needs, search for alternatives, and future plans
to minimize the OD.S quantities needed.
Japanese Rocket Applications
The TOC has learned that ODSS are currently used in Japanese solid
rocket motprs but an essential use exemption is not expected.
a. Development of Japanese SRM technologies began in 1953. Over 40
years of research as well as trial and'error resulted in the development and
manufacture of vehicles ranging from sounding rockets and satellite launch
vehicles to defense related systems. The Japanese space rocket industry
Currently uses CFC-1-13 and TCA but expects to phase out the uses by the end of
1995. Latest achievements include the solid rocket booster (SRB).for the H-II
launch -vehicle, which is capable of launching a 2 Ton satellite to
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Geosynchronous orbit. The SRB is 1.8 meter in diameter, 23 meters long and
weighs 70 Tons. Two SRfis are attached to the first stage of the two stage H-
II vehicle which is 50 meters long and weighs 260 tons.
b. The three stage MV rocket with a 2.5 meter diameter SRM is on
schedule in design and construction. The Japanese scientists independently
developed specialized materials and manufacturing processes utilizing both
metallic and nonmetallic materials. These materials require surface
activation of each layer by an advanced shot blasting technique rather that
the use of JCA. Phase out of TCA is on schedule for the end of 1995.
c. It is recognized that the Space Shuttle and the Titan IV are
significantly larger vehicles relying on previously qualified technologies.
Due to their size, design and operational differences and unique performance
requirements, the Shuttle and Titan programs have critical uses not required
on Japanese launch vehicles. Japanese industry has recommended that Space
Shuttle and Titan programs continue to use TCA for critical uses until the
schedule allows complete testing of alternatives.
9.14 OXYGEN SYSTEMS CLEANING
In January 199,4 NATO identified the cleaning of oxygen systems as one of
the most difficult challenges facing military and aerospace applications. In
Fall 1994, the International Cooperative for Ozone Layer Protection (ICOLP),
Aerospace Industry Association (AIA), U.S. Environmental Protection Agency,
National Aeronautical and Space Administration (NASA) and the U.S. Air Force
convened a special workshop on cleaning of oxygen systems without ozone -
depleting solvents. This section of this report is based on their conclusions
and recommendations. .
Oxygen systems include:- life support systems such as diving, totally
encapsulated suits, emergency breathing devices, fire & rescue backpacks,
submarine, aircraft, manned spacecraft, and medical applications; propulsion
systems such as liquid rocket motors; industrial systems such as chemical
production; and other unique,systems and customer products such as welding
equipment.
Oxygen itself is chemically stable, is not shock-sensitive, will not
decompose, and is not.flammable. However, use of oxygen involves a degree of
risk because oxygen is a strong oxidizer that vigorously supports combustion.
Oxygen is reactive at ambient conditions and its reactivity increases with
pressure, temperature, and concentration. Most materials, both metals and
nonmetals, are flammable in high-pressure oxygen.. Therefore, systems must be
designed to reduce or eliminate ignition hazards.
The successful design, development, and operation of oxygen systems
requires special knowledge and understanding of material properties, design
practices, ignition mechanisms, test data, and manufacturing and operational
techniques. Oxygen systems must be kept clean because .organic compound
contamination, such as hydrocarbon oil, can ignite easily and provide a
kindling chain to ignite surrounding materials. Contamination can also
consist of particles that could ignite or .cause ignition when impacting other
parts of the system. Risk is increased by the. typical proximity of oxygen
systems to very large quantities of fuel materials, and the common necessity
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of locating oxygen systems in confined spaces with difficult or impossible
access and egress (e.g. space ships, submarines, aircraft, and surface ships).
Despite safety engineering efforts, formal safety requirements and procedures,
and cleaning with CFC solvents--CFCs are not the only solvents used--; serious
accidents have occurred. These accidents have resulted from a variety of
situations including human error, poor design and material selection,
hydrocarbon and particulate. contamination, and unanticipated circumstances
including collisions and acts,of war.
The oxygen system cleaning challenge is' directly affected by the
system's materials, system geometry, location and access, operational
parameters, and the type and extent of contamination including cleaning and
verification fluid residue. For example, the increased atmospheric pressure
in deep diving drastically lowers acceptable human exposure limits for solvent
residue. '
Examples of the challenges presented by these applications include the
cleaning of the space shuttle -external fuel tank, cleaning of aircraft carrier
liquid oxygen plants,, cleaning of installed submarine and transport aircraft
high pressure oxygen systems, and the gauges and instrumentation associated
with each. Examples of devices typically cleaned in these systems include
tubing, gauges, regulators, valves, and metering devices. It is usually most
effective to clean oxygen equipment at the piece part level in a proper
facility. It is more difficult to cleari oxygen equipment in aircraft and ship
equipment in place with difficult accessibility and temperature extremes.
Additional challenges occur in many other industrial oxygen systems such as
those used in production and transfer of both gaseous and liquid oxygen, in
medical applications, and in welding. Cleaning of equipment used in the
oxygen production industry involves unique challenges such as compatibility
with aluminum heat exchangers.
For oxygen systems are expressed in mg per unit area of total
contamination (measured as non-volatile residue). These standards are
empirically developed and operationally justified, for specific applications.
They vary from country to country and application to application. In the
United States the generally accepted standards of cleanliness for military,
aircraft, and hospital applications is 3.0 mg/sq. ft.; for NASA space
applications the standard is 1.0 mg/sq. ft.; and for industrial applications
it is 10-50 mg/sq.ft. Standards and test methods are specified in American
Standard Testing Methods (ASTM-G63 for evaluating nonmetallic materials, -G88
for designing systems, and -G94 for evaluating metal materials), Compressed
Gas Association (CGA), Department of Defense (DOD), NASA (SN-C-0005), Society
of Automotive Engineers (SAE), and other documents. These standards are
empirically developed, operationally justified for specific applications.
However, they may be too low or too high for unique applications with atypical
conditions such as rapid changes in temperature or pressure or unusual
electrostatic potential.
Solvents such as non-ozone depleting chlorinated solvents and
hydrocarbons often clean satisfactorily, but all have* environmental or
toxicity concerns, and some have flammability concerns. Environmental, worker
safety, and flammability concerns are addressed when cleaning choices are made
for specific systems.
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Traditional cleaning with CFC-113 and 1,1,1-trichloroethane (scheduled
for production phase-out under the Montreal Protocol) is only sustainable
using stockpiles or new production under terms of the Montreal Protocol's
Essential Use Process. Historically verified cleaning with chlorinated
solvents is possible in some circumstances where worker exposure can be
mitigated, but not for applications in confined spaces and for certain life
support systems. New solvents such as HCFCs and HFCs may be appropriate for
some of these situations, but the problem of performance and safety has not
yet been verified for all applications and HCFCs are scheduled for phaseout
after 2000.
Aqueous cleaning options have been successfully developed and
implemented for many oxygen system cleaning situations. For example, Lockheed
uses aqueous processes in the manufacturing and maintenance of aircraft and
missile oxygen systems, the Air Force uses aqueous cleaning for some aircraft
oxygen system maintenance, NASA/Kennedy Space Center uses aqueous solutions
for cleaning oxygen bulk storage and transfer systems for rocket motors, and
the U.S. Navy uses aqueous cleaning processes for cleaning the tubing in
oxygen systems on ships and submarines.
Aqueous cleaning of oxygen systems often requires enhancement for
cleaning efficiency thrpugh means such as ultrasonics, increased temperature,
spray, or aggressive flushing. The performance of each option must be
verified to the particular application. It is also important to verify
supplier claims and monitor quality assurance.
Isopropyl alcohol (IPA) is being used by Lufthansa German Airlines to
clean the oxygen systems in.their commercial aircraft fleet. Sweden has
reported using a solvent blend for oxygen system cleaning consisting of 95%
ethanol. . .
Some parts of oxygen systems can be changed to simplify or avoid the
necessity of cleaning or they can be adapted to allow aqueous cleaning.
Some oxygen system components still depend on CFC or chlorinated solvent
cleaning because current alternatives and substitutes are not technically
suitable. In other cases, rigid specifications and requirements may need to
be changed from prescriptive to performance standards to allow technically
feasible solutions to be used. For example, anodized parts that are dyed for
visual identification may fade with certain aqueous cleaning processes.
Anodized surfaces have also been attacked by heated aqueous solutions.
Components and systems with complex geometries may trap fluid or have voids
and spaces where high surface tension cleaners cannot remove soils. Thus, a
particular aqueous process will not be appropriate for all situations, but it
is possible to select an aqueous system to clean many oxygen systems and sub-
systems .
Some parts of oxygen systems can be changed to simplify or avoid the
necessity of cleaning or they can be adapted to allow aqueous cleaning. For
example:
Option 1: By-pass service ports can be added to equipment to allow
pressure gauges to be calibrated in-place rather than through removal
.and subsequent calibration which increases the chance of gage
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contamination and system contamination through opening which thus often
leads to cleaning.
' Option 2: Replace pressure gauges with new gauges at frequent intervals
to avoid the current practice of cleaning and calibrating at fixed
intervals, thereby eliminating the need for maintenance cleaning.
Option 3: Send the gauges to central cleaning facilities that can use
alternative cleaning processes.
Option 4: Replace the difficult-to-clean blind 'tube bourdon tube gauges
with- transducer or liquid filled, sealed-tube gauges which are both much
simpler to clean. Other changes such as eliminating or changing paint
and dyes that are incompatible with aqueous cleaning may also help
facilitate cleaning without CFCs. ' .
The selection of any cleaning process requires careful evaluation of
toxicity and the possibility of exposure controls, of the new residue that may
be introduced by the cleaning fluids, of the suitability of test procedures
for quantifying-the allowable concentrations of new residues, and of the new
challenges of a new cleaning process such as rinsing, removing the bulk
chemical or water from the surface of components, and drying.
Screening of substitutes and alternatives also involves cleaning and
drying performance, ,cost, materials compatibility of the cleaner and
residues, consideration of worker health and safety, and evaluation of proper
disposal of waste so.ils and cleaners.
Implementation may require re-qualification in the operational
environment, careful training of cleaning personnel, effective testing for.
quality and continuous vigilance to confirm that suppliers meet strict product
requirements. '
9.15 CORRECTION FLUIDS
Traditionally, 1,1,1-trichloroethane has been.used as a carrier for
whitener in correction fluids. Currently, formulations are available that use
water or petroleum distillates as an alternative.
9.16 FABRIC SPOT REMOVER
In some areas, ODSs such as 1,1,1-trichloroethane and carbon
tetrachloride are used as a spot remover for the treatment of fabrics.
Alternatives include hydrocarbons and perchloroethylene.
9.17 PROCESS SOLVENTS
Ozone-depleting solvents such as 1,1,1-trichloroethane and carbon
tetrachloride are used in the process industries (e.g., pharmaceutical,
chlorinated rubber, silicone manufacturing, chlorine production). Some
alternatives are available as identified in Appendix I. The sector, however.
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requires further in-depth review which is planned under the auspices of the
United Nations Environment Programme (UNEP) Technical Options Panel.
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CHAPTER 10
ALTERNATIVES TO OZONE-DEPLETING SOLVENTS IN DEVELOPING COUNTRIES
10.1 INTRODUCTION
Solvents account for approximately 15% of the ozone depletion.potential
of chemicals targeted for phaseout under the Montreal Protocol. This category
includes CFC-113 (chlorofluorocarbon-113), TCA (1,1,1-trichloroethane; methyl
chloroform), carbon tetrachloride, and some HCFCs (hydrochlorofluorocarbons).
Most of these solvents are used in the manufacture of electronics products;
for precision cleaning; to clean metal .parts before further processing; and as
carriers for solvating agents,' lubricants, adhesives, and specialty coatings.
Progress in achieving the phaseout has been excellent in this sector,
given the widespread use of ozone-depleting solvents and the variety and
complexity of their applications. Of the various uses, the electronics
industry has progressed furthest towards a complete phaseout. Full phaseout
for metal cleaning applications is hampered by the large number of small
users, many of whom are undercapitalized. In precision cleaning applications,
users have been aggressively implementing alternatives. Yet, in some cases-,
they are still searching for solutions for cleaning precision parts that are
especially vulnerable, to residues or reactivities, or that have, unusually
stringent cleanliness criteria.
10.2 . SUBSTITUTES AND ALTERNATIVES
Substitutes for CFC-113 and TCA of commercial interest include:
No-clean electronics.
No-clean metal finishing/fabrication/assembly
Aqueous cleaning
Semi-aqueous cleaning
Hydrocarbons and derivatives or oxygenated organic solvents
Trichloroethylene, perchloroethylene, and dichloromethane
cleaning
Halogenated aromatics (monochlorotoluene/benzotrifluorides)
Cleaning with hydrochlorofluorocarbons (HCFC-141b, HCFC-225)
Cleaning with perfluorocarbons (PFCs) or hydrofluorocarbons
(HFCs) ' '
Cleaning with dibromomethane
Cleaning with volatile methyl siloxanes
Supercritical fluid cleaning
Carbon dioxide snow cleaning .
Plasma cleaning
Ultraviolet/ozone cleaning
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10.2.1 No-Clean Electronics
Eliminating cleaning (no-clean) is.the preferred choice of all the
options that -are available. Its current use is extensive in electronics
applications. Moreover it is now becoming available in metals preparation -
better lubricants (e.g. ones that can be re-used and re-captured; dry film
lubricants) and more efficient processes that permit elimination of, or
reduction in, cleaning.
In electronics manufacturing, the adoption of no-clean technology often
requires upstream investment to ensure cleanliness. For example, board
suppliers to the assembly house, whether captive or contract, must often
(depending on board complexity) improve their pre-packaging cleanliness and
packaging quality in order to assure that no packaging particulates are
dropped on the surface of the board during shipping and handling. This step
is necessary because the board will not be cleaned after unpacking. Since the
packaging material is normally conductive, contamination on the boards from
conductive particles can be deleterious.
Often, there is a need for the installation of precise flux application,
along with a need for a corresponding means to measure and control this part
of the process. There exists relatively low cost, effective technology for
this part of the soldering process, which the International Cooperative for
Ozone Layer Protection (ICOLP) has available through Northern Telecom's fluxer
and tester design.
Advantages: _ This process change eliminates the need for cleaning
chemicals - a pollution prevention approach that can lower
chemical use and waste production. It is a very simple
process that has particular application in the manufacture
of consumer electronics. It saves costs and/or is cost
competitive.
Disadvantages: More sophisticated industrial and military products may
require stricter adherence to cleanliness standards for
board fabrication. Sophisticated products require
significant technical expertise. So far, it is mostly used
during printed circuit board assembly. In metal working,
processing and handling procedures can be improved, which
can reduce or eliminate the need for cleaning. Very often,
however, either the primary or the secondary soil to be
removed is particulate matter. If particulates are one of
the soils, no-clean is not an effective technology option.
Also, use of the "bare minimum" to maximize effectiveness of
vanishing oil causes major risk to tool lifp. Some tools
are very costly. For example, connector tools can run as
high as $100,000. Some vanishing oils may have associated
volatility or Global Warming Potential (GWP) issues.
10.2.2 No-Clean Metal Finishing/Fabrication/Assembly
Elimination of cleaning steps from the finishing fabrication and
assembly areas is a preferred option if applicable. There are several
possible opportunities to consider no-clean technologies. In some instances
it may be practical to just eliminate one or mare'of the cleaning steps. This
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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step is practical if a part is cleaned more than once during manufacture or is
cleaned again after it is assembled. ' Another possibility is to utilize
alternative processing fluids for cutting, drawing, or machining metal parts.
Vanishing oils are one of these methods. A vanishing oil is a very
light weight oil, usually with a very low molecular weight. It evaporates from
the part after the cutting or machining operation and before an operation that
it might interfere with. An example of this process would be where a part is
stamped out and then held in inventory for several hours or even days before
it is used in the next operation. The next operation may even enhance the
evaporation of the lubricant, such as annealing ovens, or other heated
operation. Many of the vanishing oils evaporate quite rapidly (within a few
hours), and will therefore not interfere with subsequent machining operations.
In some cases, it might be possible to utilize a lubricant that is beneficial
for the downstream application, or one that does not require removal. Many
ferrous metal working operations clean parts then apply a rust preventative
material to the part to inhibit rusting during storage or transportation. It
is very possible to eliminate the cleaning operation and use the machining
lubricant as the corrosion preventative, or apply the corrosion preventative
without cleaning off the lubricant. Usually the part is cleaned again when it
is ready to be used in the final assembly. Although cleaning is not always
completely eliminated, one or more cleaning operations are eliminated.
Advantages: This process change can eliminate the need for cleaning
chemicals - a pollution prevention approach that can lower
chemical use and waste production.. It is a very simple
process that has particular application in many metal
finishing applications.
/
Disadvantages: There may be many hidden costs associated with the use of
no-clean technologies. Increased tool wear often occurs
with the use of vanishing oils, as they are not very
viscous. Also, in many operations, there is a need for
clean parts for quality control measurements. If a cleaning
operation is eliminated for production, a method of cleaning
for testing needs to be implemented.
A second disadvantage is that many manufacturers are
required to clean parts to a specification set by the
customer. The customer will need to change the acceptance
specifications that .they are currently utilizing. This can
be very difficult in today's environment of quality
suppliers and just-in-time manufacturing.
10.2.3 Aqueous Cleaning
Aqueous cleaning uses water as the primary cleaning medium, but often
detergents (saponifiers) and other chemicals.are added to enhance cleaning
performance. .
Advantages: Aqueous solvent and added chemicals generally have low
toxicity and the cleaning power is good for most soil's.
Chemical costs are low, and there are lower materials losses
compared with other cleaning processes.
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Disadvantages:
10.2.4
Effluent treatment or recycling may be necessary, and drying
needs may require new capital intensive equipment and result
in higher energy costs. It is not always possible to use
aqueous cleaning on water sensitive substrates or on complex
geometries. Aqueous cleaning solvents are more time
consuming than other methods. Moreover aqueous cleaning may
require-more floor space, and' it m'ay not be effective on
high viscosity linear hydrocarbons, asphaltic, micellar or
carbonaceous oils.. Strongly corrosive (acidic or basic)
aqueous cleaning chemicals can require the use of protective
gear to reduce exposure due to acute toxic potential.or.
chronic effects. Also, water consumption can be high - up
to 10 gallons per minute (gpm), unless water is recycled,
which can be a factor in limited water supply or
environmentally sensitive situations.
Semi-Aqueous Cleaning
Semi-aqueous cleaning is also a water-based cleaning process that uses
relatively low molecular weight organic chemicals to enhance cleaning
performance. Semi-aqueous processes include the addition of chemicals such as
terpenes.
Advantages:
Disadvantages:
Semi-aqueous solvent cleaners are generally stronger in
solvency 'than aqueous cleaners because their organic portion
aids in dissolving organic contamination. The chemicals
used in semi-aqueous processes have low toxicity, although
their toxicity can be higher than that of the chemicals used
in aqueous cleaning processes. Semi-aqueous processes offer
good cleaning power for most soils; waste minimization is
possible through water reuse, and residual concentrated
wastes can be used as cement kiln fuel. Semi-aqueous
solvents exhibit a low vapour pressure, so only small
quantities are lost to evaporation.
All degreasing solvents and the organic constituents of
blends are volatile, and may requirecontrol measures in
accordance with national, regional, and local regulations,
as well as corporate policy. These control measures address
concerns over environmental, health, and safety issues.
Effluent treatment is likely since soluble solvents
generally have very high biological oxygen demands (BODs),
requiring solvent disposal. Flammability and emulsion
stability may be an issue in some cases. The drying
requirement are similar to those of aqueous cleaning,
possibly requiring new, capital intensive equipment and
incurring higher energy costs compared with some other
options. . It is not always possible to use aqueous or semi-
aqueous processes on water sensitive substrates or on
complex geometries. Moreover this process may require more
floor space, as well as high capital expenditure. Water
consumption can range up to 2-3 gpm, which, can be a factor
in limited water supply or environmentally sensitive
situations.
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10.2.5 Organic Solvent Cleaning (alcohols, aliphatics. ketones.
aldehydes, .and blends or C1-C20. hydrocarbons and
derivatives)
Organic solvent cleaning provides another alternative to ozone-depleting
solvents. Alcohols, aliphatics, ke'tones, aldehydes, and mixtures of these
chemicals can be used. As with other options, they have advantages and
disadvantages.
Advantages:
Disadvantages:
10.2.6
Organic solvents have good cleaning power and are
comparatively simple to use. Process cleaning times are
shorter than aqueous or semi-aqueous cleaning. Most
contaminated solvent can be easily filtered and distilled,
with proper equipment, for reuse. They are also cost
competitive.
All degreasing solvents and the organic constituents of
blends are-volatile and may require control measures in
accordance with national, regional, and local regulations,
as well as corporate policy. These control measures address
concerns over environmental, health, and safety issues.
Most organic solvents are also flammable and/or combustible.'
For these reasons, special equipment and facilities may be
required to ensure protection of worker health and safety.
In these cases, capital intensive expenditures will arise.
In addition, precautions for waste disposal are necessary.
Some organic solvents are unsuitable for use on plastic
parts, and low-volatility solvents are difficult -to dry,
especially on complex, geometries.
Chlorinated Aliphatic Solvent Cleaning (trichloroethylene.
perchloroethylene or dichloromethane1)
Trichloroethylene, perchloroethylene, and dichloromethane do not deplete
the ozone layer and can be used as alternatives for cleaning.
Advantages:
Disadvantages:
These non-ozone-depleting halo'genated solvents have
potentially high cleaning properties for oils, greases and
some other organic soils; they are nonflammable and non-
corrosive to most materials; and they are'simple to use.
They offer low operating costs, and it is sometimes possible
to retrofit existing equipment at low cost.
All'degreasing solvents and the organic constituents of
blends are volatile, and may require control measures in
accordance with national, regional, and local regulations as
well as corporate policy. These control measures address
concerns over,environmental, health, and safety issues. In
addition, special materials and waste handling practices are
necessary. Moreover, good waste management practices should
be implemented in order to prevent accidental releases to
soils and groundwater, which may result in expensive long-
term clean-up costs. Newer vapour-tight machines or
equipment with vapour-emission controls offer more
assurances of worker safety, but at a significantly higher
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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10.2.7
cost. Chlorinated solvents may be unsuitable for use on
some plastics. High boiling point solvents (e.g.
perchloroethylene) may be uneconomic in vapour degreasing
operations due to energy costs.
Chlorinated Aromatic Solvent Cleaning
(monochlorotoluene/benzotrifluorides)
Monochlorotoluenes/benzotrifluorides are a new option. They have good
solvency properties, but they have a low suggested occupational exposure limit
(30 ppm).
Advantages:
Disadvantages:
10.2.8
Monochlorotoluenes/benzotrifluorides have the advantage of
good cleaning potential. These chemicals also form miscible
solvent blends, and some are nonflammable.
All degreasing solvents and the organic constituents of
blends are volatile and may require control measures in
accordance with national, regional, and local regulations,
as well as corporate policy. These control measures address
concerns over environmental, health, and safety issues. As
with.the other non-ozone-depleting solvents, there is the
possibility of contamination of soils and groundwater from
spills and accidental discharges which can result in
expensive long-term clean-up costs. Some products,
especially if contaminated with soils, may emit highly toxic
by-products in the event of accidental fire or incineration.
This group of chemicals is not yet authorized in the United
States for use as replacements for ozone-depleting solvents.
Hvdrochlorofluorocarbons (HCFC-123. HCFC-141b. HCFC-225)
HCFC-123 and HCFC-141b are now sold in most markets. HCFC-225,
available in some markets now, will be fully available in 1995, except where
expressly forbidden by ozone layer protection legislation. These HCFCs are
good cleaners for certain specialized applications and can be blended with
other solvents such as alcohol for suitable cleaning performance. The U.S.
Environmental Protection Agency (EPA) has banned the use of HCFC-141b as a
solvent in all cases effective January 1, 1996. Limited exemptions may be
granted for replacement of CFC-113 where no other alternative exists. In
Sweden all uses of HCFCs in solvent operations were banned as of 1 January
1994.
Advantages:
Disadvantages:
These HCFCs have cleaning power comparable to CFC-113 and
they are nonflammable (in most applications). HCFC-225
shows good compatibility with plastics, elastomers and
metals, and has a low ozone-depleting potential'(ODP)
relative to HCFC-141b (.025-.033 ODP depending on the blend
of the ca and cb isomers). HCFC-225 can be used in existing
retrofitted cleaning equipment. HCFC;141b also has a low
toxicity.
All HCFCs have the disadvantage of being ozone-depleting
substances, albeit with lower ODPs than CFC-113, and thus
are transitional substances in some uses. HCFC-141b has a
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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low boiling point, a relatively high OOP (.11) and damages
plastics and elastomers. HCFC-225 is more expensive than
HCFC-141b. All of the toxicblogical testings of HCFC-225ca
and HCFC-225cb planned under the Programme for Alternative
Fluorocarbon Testing (PAFT)-IV were completed by early-1994.
Based on these. PAFT results, the.acceptable exposure limit
(AEL) of the commercially available HCFC-225 blend has been
set at 50 ppm (8hr-Time Weighted Average) by a manufacturer.
All degreasing solvents and organic constituents of blends
are volatile, and may require cpntrol measures in accordance
with national, regional, and local regulations, as well as
corporate policy. These control measures address concerns
over environmental, health, and safety issues. Special low-
emissions equipment, which is now commercially available, is
essential for environmental protection and solvent usage
cost reasons. Retrofitting of existing equipment to utilize
HCFC-225 may require additional freeboard, automated lid and
hoist emission controls, and replacement of pump seals to .
prevent excessive emissions. Because HCFCs are transitional
in nature, a second shift from HCFCs to'a non-ODS
alternative wiLl ultimately be required. It may.be more
cost effective to move immediately to the non-ODS technology
to avoid the costs of changing the cleaning process twice,
if possible. Good management of wastes is also recommended!
Important note: HCFC-lAlb has a high ozone depletion
potential (OOP) of 0.11, which is equivalent to the TCA OOP
of 0.12, and is controlled under the Montreal Protocol.
Future changes may further restrict its use or advance its
phaseout dates. HGFC-141b should therefore only be
considered as a replacement for CFC-113 in specialized
applications where no other alternative exists. It should
never be considered as a replacement for TCA.
10.2.9 Perfluorocarbons (PFCs) .
Perfluorocarbons (PFCs) are a subject of increased interest over the
last year, especially for cleaning precision-engineered parts. An atmospheric
lifetime of greater than 500 years means that PFCs have a significant direct
global.warming potential. The US EPA Significant New Alternatives Program
(SNAP) allows the use of PFCs in electronics and precision cleaning
applications only where users can prove that, due to performance or safety
requirements, no other technically feasible alternative exists. Sweden is
reviewing the use of PFCs, as an alternative to ODSs, to be permitted only
with waivers after January -1,, 1996.
Advantages: , PFCs are not ozone-depleting substances and should be
allowed for special precision cleaning applications, such as
oxygen systems, nuclear triggers, and electromechanical
gyroscopes. PFCs are non-flammable and of low toxicity.
They are good rinsing and drying agents. Furthermore, they
are very stable molecules and will not attack non-fluorine
containing substrates.
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Disadvantages:
10.2.10
On the other hand, PFCs are a poor solvent, thus they must
be used with other more effective solvent cleaners. All
degreasing solvents and the organic constituents of blends
are volatile and may require control measures in accordance
with national, regional,and local regulations, as well as
corporate policy. These control measures address concerns
over environmental, health, and safety issues. PFCs are
expensive to purchase and they have an extremely high global
warming potential. PFCs should only be used as a
transitional substance in special applications. The World
Bank may request that project applications using PFCs
demonstrate adequate emission reduction capabilities in
their equipment. New equipment will usually be required.
Important note: PFCs may be controlled internationally or
nationally to protect against climate change. They are not
recommended for financing under the Montreal Protocol.
Hydrofluorocarbons (HFCs)
HFC solvents are likely to be commercially available within two years.
The key environmental characteristic of concern is their long atmospheric
lifetime.
Advantages:
Disadvantages:
10.2.11
HFC solvents are non-flammable and of low toxicity. They
are better solvents than PFCs, and their behaviour is
analogous to CFC-113 in a manufacturing setting, due to
similar physical properties. HFCs are the probable drop-in
replacement for. the use of PFCs. The availability of HFCs
is limited now, but several companies have plans for
commercial production soon.
HFC solvents are likely to be expensive and toxicity testing
is not complete. Toxicity of HFCs is expected to vary
depending on their chemical structure. Due to low solvency,
they may need co-solvents to be used in solvent blends or in
solvent/solvent systems. These systems are non-ODS, low-
GWP, and of low toxicity. They have moderately long
atmospheric lifetimes (approximately 20 to 30 years), thus
they have moderately high global warming potentials. All
degreasing solvents and the organic constituents of blends
are volatile and may require control measures in accordance
with national, regional, and local regulations as well as
corporate policy. These control measures address concerns
over environmental, health, and safety issues.
Important note: May be controlled internationally or
nationally to protect against climate change. Not
recommended for financing under the Montreal Protocol.
Dibromomethane
Dibromomethane (a component of a proprietary product) is a new
substitute that entered the market in 1993. Its cleaning power is yet
unproveri.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Advantages: Dibromomethane is being offered as a drop-in replacement for
CFC-113, which would be an advantage where expensive
cleaning equipment is in place.
Disadvantages: Dibromomethane has a relatively high ozone depleting
potential (ODP) and its cleaning power is unproven. It is
likely to be more toxic than methylene chloride
(dichloromethane), have a high probability of forming
hydrogen bromide and other toxic substances if near a heat
source, and its high boiling point (97°C) renders is an
unlikely candidate for use with non-metallic parts. Also,
it contributes to photochemical smog. All degreasing
solvents and the organic constituents of blends are volatile
( and may require control measures in accordance with
national, regional, and local regulations, as well as
corporate policy. These control measures address concerns
over environmental, health, and safety issues. Since
dibromomethane is an ODS, it should not be listed as an
alternative. It is considered unacceptable by the U.S. EPA.
Important note: Dibromomethane is not recommended for
financing under the Montreal Protocol.
10.2.12 Volatile Methyl Siloxanes (VMSs)
This is another new substitute that entered the market in 1993. I. has
been used in the past in cosmetics. It use is of particular interest
especially for cleaning silicone-based fill fluids in guidance
.instrumentation. VMSs should be allowed for special cleaning applications,
however their use is expected to be infrequent.
Advantages: VMSs have low toxicity. VMSs are one of the few solven-ts
that are chemically compatible-with silicone fluids.
Disadvantages: VMSs are expensive. Controls for flammability may be
necessary and some formulations have.low suggested
occupational exposure limits. All degreasing solvents and
the organic constituents of blends are volatile, and may
require control measures in accordance with national,
regional, and local regulations, as well as corporate
policy. These control measures address concerns over
environmental, health, and safety issues. They have limited
applicability.
Important note: VMSs are not yet -proven suitable for
financing under the Montreal Protocol.
10.2.13 Supercritical Fluid Cleaning (SCF)
Supercritical fluids, especially carbon dioxide, have been used for more
than a decade to selectively remove, chemical components from processed foods,
coffee, hops, and tobacco. Two of the most common uses are to de-caffeinate
coffee beans, and remove cholesterol from eggs. .
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Advantages: This alternative is environmentally benign. SCFs have
liquid-like densities combined with the beneficial transport
properties of gases, such as low viscosity and high
diffusivity. Also, without surface tension limitations,
SCFs can penetrate small spaces and are therefore very
useful for cleaning complex geometries. Carbon dioxide is
additionally advantageous because it is non-flammable,
environmentally acceptable, inert, non-toxic, recyclable,
and low in cost.
Disadvantages: Only limited applications have been proven so far. In
general, hydrophobic contaminants, such as oils, dissolve
well in supercritical C02. Hydrophillic contaminants, such
as inorganic salts, have little solubility. There are high
start-up costs that require extra operator training.
Equipment to be used with supercritical fluids is capital
intensive because of the high gas pressure required to
operate the process.
10.2.14 Carbon Dioxide Snow Cleaning
, CO, snow is a relatively new cleaning technique that can be used to
replace CFC-113 and TCA in a variety of cleaning applications. During
cleaning, C02 snow is directed toward the contaminated surface. Cleaning
occurs as a result of the momentum transfer between the solid C02 particles
and particulate contamination. The collisions loosen the particulates from
the surface, and the gaseous C02 sweeps them away.
Advantages: Carbon dioxide snow cleaning is an inexpensive method of
removing particulates from surfaces. This is a good
replacement for the use of CFC-113 as a dusting agent on
optical surfaces.
Disadvantages: Carbon dioxide at ambient pressure does not exhibit good
. solubility properties and it is unlikely that it could be
used as a solvent cleaner. Another disadvantage of carbon
dioxide snow is that it is much colder than CFC-113 and may
cause moisture to condense from the air onto the part being
cleaned. Carbon dioxide has a global warming potential and
its use would be a net contribution to climate change unless
it has a source that would otherwise be an immediate
emission. However, most carbon dioxide is scavenged from
emissions and thus makes no net contribution to climate
change.
10.2.15 Plasma Cleaning
Plasma cleaning may have benefits in the metal cleaning industry equal
to the benefits of "no-clean" processes in the electronics industry. Plasma
cleaning, especially oxygen, has been used for many years in the electronics
industry for the removal of oxides from electronic components prior to
adhesive bonding. In recent years, larger pieces of equipment have been used
to remove organic contamination from aircraft wings and mechanical devices.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Advantages:
Disadvantages:
10.2.16
The low pressure process is environmentally sound because
the waste products are combustion by-products of the organic
contamination, usually of very small quantity. Since the
plasma acts like a gas, the cleaning ability is independent
of the geometry of the part to be cleaned. Plasma cleaning
could be the primary method of .cleaning metallic parts in
the future. Plasma cleaning is more environmentally sound
than the use of aqueous or organic solvents.
Plasma cleaning cannot be used on components that are
plastic, rubber, or contain other carbon-based materials.
Also, it is often used with many potentially harmful gases
and mixtures which could ionize and recombine to form by-
products even more detrimental than the original plasma.
Ultraviolet/Ozone Cleaning:
The ability of ultraviolet (UV) light to decompose organic molecules has
been known for a long time, but it is only during the past decade that UV
cleaning of surfaces has been explored for commercial applications. UV/ozone
cleaning is primarily the result of photosensitized oxidation processes. The
contaminant molecules.are excited and/or'dissociated by absorption of short-
wavelength UV light. Atomic oxygen and ozone are produced simultaneously when
02 is dissociated by the absorption of UV with wavelengths less than 245.4 nm.
Atomic oxygen is also produced when ozone is dissociated by the use of the UV
and longer wavelengths of radiation. The- excited contaminant molecules, and
the free radicals produced by the dissociation of the contaminant molecules,
react with atomic oxygen to form simpler, volatile molecules such as C02, H20,
and Np. The UV/ozone cleaning procedure is widely used in cleaning prior to
thin film deposition in the crystal industry.
Advantages:
Disadvantages:
The process is environmentally safe, yielding non-ozone -
depleting products and, of course, not involving any ozone-
depleting substances in the process. The UV/ozone cleaning
procedure has been shown to be highly effective in removing
a variety of contaminants from surfaces. Examples of
contaminant effectively removed from surfaces include human
skin oils, cutting oil, rosin mixtures, lapping compound,
vacuum pump oil, DC-704 and DC-705 silicone diffusion pump
oil, and rosin flux from rosin-core lead-tin solder.
Another advantage is that the process is inexpensive, not
requiring elaborate apparatus construction or waste product
disposal. Depending on the size of the cleaning
requirement, few safety features need to be considered.
Commercial equipment is available for smaller applications.
The UV/ozone chamber also acts as an excellent storage
facility for cleaned substrates, preventing any subsequent
organic surface contamination. The procedure produces clean
surfaces at room temperature.
The primary disadvantage to UV/ozone cleaning is that thick
contamination cannot be effectively removed from substrates.
The optimum result is obtained when thin film contamination
is present. This requires pre-cleaning before final
* 1994' UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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cleaning. UV/ozone does not remove particles from surfaces
unless these particles are organic in composition. The
generation of ozone in the procedure may be a safety
consideration, and the apparatus, depending on size, needs
to be placed in an exhaust hood or other similar exhausting
system.
10.3 TECHNOLOGIES FOR DEVELOPING COUNTRIES '
. The alternatives to ozone-depleting solvents used by. the electronics,
precision cleaning, and metal degreasing industries have been ranked in order
of greatest commercial interest based on environmental effects and on the
possibility of their use in developing countries.
The selection of the alternative should be based on five primary
factors. The alternative: 1. should not be an ozone-depleting substance, 2.
should enable the enterprise to maintain a product reliability level at lea'st
equal to the past methods, 3. should be economical, 4. should not create
significant environmental problems, and 5. should not compromise worker or
consumer health and safety.
Emerging technologies such as HFCs and VMSs are not. recommended for
implementation and financing until their toxicity, technical, and economic
performances are established. Super critical fluid cleaning (SCF), plasma
cleaning, and ultraviolet ozone cleaning are recommended for use and financing
under the condition that they can be shown to be cost effective, even though
they have low environmental impact, because they are mostly used for specialty
applications, and because of specialized engineering and training
requirements.' Other emerging technology, such as dibromomethane solvents, are
not recommended for implementation and financing until they are developed
further. Chlorinated solvents should only be used where exposure to workers
can be controlled within allowed limits.
In order of preference, then, the alternatives that should be considered
for developing countries are:
Tier 1: No-clean, keep-clean
Tier 2: .Aqueous/semi-aqueous cleaning
Tier 3a: Organic solvent cleaning (with solvents having toxicities
less than non-ozone-depleting halogenated.solvents)
Tier 3b: Non-.ozone-depleting halogenated solvents
Tier 3c: Organic solvent cleaning (with solvents having toxicities
greater than non-ozone-depleting halogenated solvents)
Tier 4a: HCFC-225 and HCFC-123
Tier 4b: HCFC-141b
Tier 5: PFCs '
Some comments on each of these alternatives should be considered in
deciding which is more appropriate for each cleaning application.
All applications to the Fund that propose the use of aqueous or semi-
aqueous cleaning should include funding for recycling, waste water treatment,
and drying equipment. Applications that involve the use of organic and
hydrogenated solvents should include containment equipment, adequate
* 1994- UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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ventilation control, and/or low emission equipment. The guidelines should
include requirements for personnel safety, for example, the use of eye guards
by workers who perform the cleaning operation.
10.3.1 No-Clean
No-clean is the recommended option for the manufacture of consumer
electronics, and it is a preferred option for the manufacture of more
sophisticated printed wiring assemblies. To ensure success however, no-clean
processes require skilled operators, increased control of incoming part
quality, and superior machinery due to narrow operating windows and time to
prove its reliability of hardware produced with the .technology.
10.3.2 Aqueous/Semi-Aqueous Cleaning
Aqueous and semi-aqueous cleaning technologies, with proper controls and
monitoring, are generally considered to have low environmental impact due to
the low toxicity of the constituents. However, poor housekeeping practices,
such as unnecessary dumping of the cleaning tanks, can cause these cleaners to
have worse effects than would ordinarily be expected. In addition, if
effluent is untreated, cleaning solution discharges as well as any hazardous
soils could cause environmental problems. In an area with water management or
water supply problems, aqueous cleaners may be a poor choice unless efficient
water recycling is possible. Aqueous/semi-aqueous formulations should be
carefully screened to avoid additives that are toxic to human health or may
cause synergistic. toxicity in the environment. The use of aqueous or semi-
aquepus cleaning should include funding for drying, recycling, and waste
treatment equipment.
10.3.3 . Organic Solvent Cleaning
° i
Although toxicity can be a concern for some formulations, the principal
risk is derived from the high flammability of the more volatile compounds.
Such solvents are not appropriate for use in settings with sources of ignition
unless appropriate precautions are taken, and proper ventilation and
individual protective equipment is used. Similarly, the possibility of soil
or groundwater contamination is of concern if proper materials handling
practices are not followed. Caution should be used when these solvents are
used with sprays, heaters, or ultrasonic equipment.
10.3.4 Non-Ozone-Depleting' Halogenated Solvents
Where emission issues are of concern, emission control equipment should
be included-to meet domestic regulations. Strict adherence to proper
industrial hygiene practices is essential where these solvents are used
because their worker exposure limits are similar to organic solvents. These
chemicals have intrinsic properties that point to the possibility of human
health and environmental impacts. However, new equipment, although expensive,
is available that can control emissions and therefore significantly lower
risks. These chemicals should generally be avoided if poor attention to
chemical handling and waste disposal procedures is predicted, since
inadvertent spills can lead to unacceptable worker exposure and soil or
groundwater contamination. All of these chemicals are associated with high .
start-up costs due to expensive equipment. On the other hand, non-ozone-
depleting halogenated solvents may offer the lowest operating costs since they
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are the least costly chemicals in the group. However, there is a high 'risk of
contaminating soil and/or groundwater in spite of well engineered and
maintained systems. The costs of cleaning up contaminated soil and/or
groundwater can be substantial. The Implementing Agencies of the Multilateral
Fund (United Nations Development Programme, United Nations Environment
Programme, United Nations Industrial Development Organisation, World Bank)
should consider the cost of monitoring these projects and the cost of
insurance that could pay for cleanup.
10.3.5 HCFC-123. HCFC-225. HCFC-141b. and PFCs
HCFC-225 is very similar to CFC-113 in physical and chemical properties,
and can form azeotropes with alcohols. They exhibit good materials
compatibility and can therefore be used to replace CFC-113 with few changes in
the process. HCFCs-225 has been used in applications where other alternative
technologies cannot be applied.
Because of a high ozone depletion potential (OOP), HCFC-141b is never
suitable as a substitute for 1,1,1-trichloroethane. It is suitable as a
substitute for CFC-113 only when lower OOP alternatives, including HCFC-225,
are not feasible. Because HCFCs are transitional in nature, a second shift to
,a non-ODS alternative will ultimately be required. It may be more cost
effective to move immediately to a non-ODS technology to avoid the costs
associated.with qualifying and changing the cleaning process twice, if
possible.
PFCs should only be used in electronics and precision cleaning
applications where no other alternative will provide the needed performance.
Low loss equipment is available for PFCs and HCFC-141b, and if either must be
usedj this equipment should be used, PFCs are not likely to be an acceptable
substitute for manufacturing processes used in developing countries.
Use practices and local environmental considerations, can move a
particular chemical either up or down in the selection hierarchy.
10.4 RETROFITS
Retrofits for solvent, cleaning applications are not as common as for
refrigeration or for foam-blowing.. Retrofits' should not be allowed except in
extraordinary circumstances for adapting solvent cleaning equipment to HCFCs.
HCFCs are ozone-depleting substances and should not be recommended for use in
retrofits, unless the equipment is very new aiad is designed to have very low
emissions through the incorporation of advanced freeboard designs, chiller
systems, and adsorption/recycle/destruetion systems. For current users of
CFC-113 or TCA solvents as cleaners, the most likely retrofits are to:
Chlorinated Solvents
Retrofit of existing .cleaning equipment to chlorinated solvents is
generally low cost.- The chemical properties are similar to TCA
and CFC-113 and chemical costs are significantly lower. Most
equipment can be modified to use any of the other chlorinated
solvents and meet U.S. Occupational Safety and Health
Administration (OSHA) or other worker exposure requirements.
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However, it is expensive and more difficult to meet the volatile
organic compound (VOC) and Air Toxic requirements. The U.S.
Maximum Achievable Control Technology (MACT) standards will
require more investment in equipment retrofit than the OSHA
standards and possible periodic monitoring, record keeping, and
reporting. The cost of the retrofit should include a period of
monitoring the vapour emissions of the replacement chemical from
the machine, and take into account the costs associated with
cleaning up contaminated soil and/or groundwater. In addition,.
monitoring on a basis which is possible in industrialized
countries may be difficult to put into practice in some developing
countries.
HCFC-225
Since the physical arid chemical properties of HCFC-225 are similar
to CFC-113, it can be used in a retrofit application, but is
recommended only for applications where other, more
environmentally acceptable alternatives are not feasible.
However, low loss equipment, which Is now commercially available,
is recommended due to the relatively high cost of HCFC-225.
HCFC-lAlb .
Due to a lower boiling point and high ozone depletion potential, a
retrofit can be expensive. Significant degreaser modifications
must be made, such as adding freeboard, chillers, programmable
hoists, automatic sliding access ports, and molecular sieves, in
order to reduce emissions. Moderately high retrofit costs,
combined with higher chemical costs, make HCFC-141b a poor
candidate for retrofits. Retrofit to HCFC-141b is not recommended
for investment.
Retrofits to aqueous and semi-aqueous cleaning is also possible.
Degreaser tanks are sometimes retrofitted for water based cleaners, but this
requires extensive engineering redesign and should not be attempted without
direct consultation with a qualified equipment supplier. For semi-aqueous
processes, the chemical manufacturer.must also be consulted.
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CHAPTER 11
CASE STUDIES OF PHASEOUT'ACTIVITIES
This chapter includes company case studies providing examples of
successful programmes to eliminate the use of ozone-depleting solvents in
industry. The case studies discuss the evaluation and implementation of
materials, alternative technologies, and processes to eliminate the use of
CFC-113 and 1,1,1-trichloroethane in cleaning operations. The following 22
case studies are presented in this chapter:
1) Allied Signal -- "An Evaluation of Aqueous Technologies at Allied Signal
Aerospace Canada (ASAC)" -- A description of the evaluation of various aqueous
saponifiers. .
2) AT&T Bell Laboratories -- "AT&T and the Elimination of Ozone-Depleting
Substances" -- A description of the alternative cleaning and manufacturing .
technologies, as' well as no-clean techniques.
3) Beck Electronics -- "Semi-Aqueous Equipment Conversion at Beck
Electronics" -- A description of the evaluation of more than 20 alternative
solvents and the design and construction of custom cleaning equipment.
Obsolete vapour degreasers were converted to use the new terpene-based
solvent.
4) Ford Motor Company -- "CFC Elimination in Electronics Soldering at Ford
Motor Company" -- A description of the use of no-clean soldering and nitrogen
inertion in electronics manufacturing. ...
5) Hitachi -- "Reduction and Elimination of ODS Solvents at Hitachi" --,A
general overview of the different types of alternatives evaluated by Hitachi.
6) Honeywell -- "Replacement of Ozone-Depleting Substances in Honeywell
Space and Aviation Control Products" -- A description of,the use of various
alternatives to ODSs including supercritical fluid cleaning, C02 snow,
perfluorocarbon sprays, water-based sprays, and the use of semi-aqueous
processes.
7) IBM Corporation -- "ODS Elimination at IBM Austin, Texas" -- A
description of the aqueous and no-clean processes implemented in the printed
circuit board manufacturing process. . <
8) Japan Industrial Conference on Cleaning (JICC) -- "The Japan Industrial
Conference on Cleaning" -- A description and history of the JICC, an
information clearinghouse formed to assist Japanese industry in identifying
and evaluating non-ODS solvents. .
9) . Lockheed Sanders Company -- "The Elimination 6'f 1,1,1-trichloroethane in
Electronics Cleaning at Lockheed Sanders Company" -- A description of the
alternative cleaning systems employed to replace 1,1,1-trichloroethane use in
electronic component cleaning.
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10) Miljoministeriet -- "Hydrocarbon Dry Cleaning at Miljoministeriet" -- A
description submitted by the Danish EPA of the use of an alternative
hydrocarbon dry cleaning system to replace ODS use in dry cleaning.
11) Minebea Company -- "Phasing Out of Ozone-Depleting Substances by the
Minebea Co." -- A description of implementing an aqueous cleaning system for
the cleaning of ball bearings.
12) National Semiconductor -- "Elimination of ODSs at National
Semiconductor, Malaysia" -- A description of management and technical process
from team development through implementation.
13) Naval Aviation Depot -- "Elimination of Ozone Depleting Solvents at
Naval Aviation Depot Cherry Point" -- A general discussion of the program
including a special discussion of hand-wipe cleaning.
14) Northern Telecom -- "Northern Telecom and CFC-113 Elimination" -- A
summary of the steps to eliminate CFC-113 from the program's inception in 1987
and'including a discussion of the company's efforts to assist developing
countries through cooperation with ICOLP and UNEP.
15) Robert Bosch Corporation -- "Replacing Solvent Cleaning with Aqueous
Cleaning" -- A case study prepared by the Centre for Aerosol Technology
detailing elimination of CFC-113 and trichloroethylene at Robert Bosch
Corporation.
16) Rockwell International -- "Use of a Low-Residue Flux in a Military
Electronics Program" -- Qualification of a low-residue flux on the Hellfire
Missile assembly line.
17) Seiko Epson Corporation -- "The Cleaning Center System of Seiko Epson
Corporation" -- A description of an information clearinghouse and a central
cleaning facility to assist small and medium-sized facilities in identifying
and evaluating alternatives to ODSs. .
18) Singapore Institute of Standards and Industrial Research (SISIR) -- "The
ODS-Free Verification Scheme for Singapore Industry" -- A description of the
SISIR certification of businesses as "ODS-Free."
19) Swedish EPA -- "Eliminating the use of ODSs in Sweden" -- A discussion
of the programmes sponsored by the Swedish EPA (SNV) to phaseout ODSs in
Sweden.
20) Toshiba Corporation -- "Non-ODS Substitutes for Wax Elimination at
Toshiba Corporation" -- A description of the qualification and implementation
of a vinyl-copolymer-type masking agent to replace wax masking in plating
applications at aircraft maintenance facilities. Unlike wax, the new masking
agent can be removed without the use of solvents.
21) U.S. Air Force Aerospace Guidance and Metrology Center -- "Using New
Technologies to Solve Unique Precision Cleaning Operations: The Elimination
of Ozone-Depleting Solvents at the Aerospace Guidance and Metrology Center at
Newark Air Force Base" -- A description of the non-aqueous alternatives used
to eliminate the use of ODSs in precision cleaning applications. Alternatives
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addressed include alcohols, volatile methyl siloxanes, supercritical fluids,
and perfluorocarbons.
22) Vibro-Meter SA -- "The implementation of Water-Based Cleaning at Vib.ro-
Meter SA, Switzerland" -- A description o'f the implementation of a water-based
cleaning system to remove flux residues from printed circuit assemblies used
in vibration detectors. Includes a brief evaluation of other alternatives
considered.
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ALLIED SIGNAL - AN EVALUATION OF AQUEOUS TECHNOLOGIES
I. INTRODUCTION .
In response to the Allied Signal corporate mandate to eliminate the use
of all Class I ODSs from its cleaning operations,' Allied Signal Aerospace
Canada (ASAC) chose to develop a saponified aqueous replacement process. The
project was undertaken in conjunction with recommendations made by the
Electronics Defluxing Alternative Team (EDAT), comprised of scientists and
engineers from various Allied Signal Aerospace divisions throughout the United
States and Canada.
II. EVALUATING METHODS
A total quality leadership-style (TQL) approach was used, whereby a team
of manufacturing engineers representing all facilities were responsible for
the evaluation of various alternatives. The EDAT classified potential
alternatives into three categories:, those available for immediate
incorporation, those not as readily available and those that would not be
considered. The team evaluated three cleaning technologies for immediate use:
semi - aqueous, saponified aqueous, and fully aqueous. EDAT used the Index of
Technical Feasibility as an analytical measure ranking all weighted technical
factors against the relative net present value including life cycle costs to
evaluate each alternative. The final selections were based on tests performed
on 28 cleaner technology/equipment combinations. Of these combinations, 8
semi-aqueous, 14 saponified, aqueous and six fully aqueous combinations of
batch and in-line equipment were considered. The controls were CFC-113 and
methyl chloroform solvent baseline'processes.
A standard and controlled evaluation protocol was developed for all
phases of testing. The standard test protocol was based on IPC-CP-61. The
amount of ionic contamination on 331 test specimens was determined in
accordance with IPC-TM-650, Method 2.3.26.1. In addition to the commonly used
visual and ionic testing, EDAT evaluated numerous samples using high-
performance liquid chromatography (HPLC), surface insulation resistance (SIR)
and ion chromatography tests. The SIR test was performed on 306 of the
standard test specimens in accordance with IPC-TM-650, Method 2.6.3.3, Class
III. A total of 10,710 SIR readings were taken from seven SIR test patterns
on each board, with five readings per pattern. The specific 'attributes EDAT
required for the SIR tests included:
the -results should be as good as or better than the baseline
controls
resistance readings not less than 108 ohms
the difference between initial resistance readings and the first
readings at temperature and humidity should be less than LOG 3.
The SIR and HPLC tests were used to identify residual organic residue.
The ion chromatography test measured residual ionic contamination and
classified them as a chloride, bromide, nitrate or a weak organic acid.
Adhesion testing was carried out with acrylic and urethane coatings on 108 of
the test boards. Extensive wash and rinse water analyses were conducted and
testing was completed for a minimum number of parameters, including lead, BOD
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(biological oxygen demand) and pH. The EDAT also completed cost analyses for
all of the candidate processes. The cost analyses considered capital outlay,
installation costs, and operation and maintenance costs.
III. EVALUATION RESULTS
\ The evaluation of the test results was performed in three phases. Phase
I included candidates available for immediate use, Phase II involved detailed
tests using various equipment alternatives and the best chemistries identified
in Phase I, and Phase III addressed additional chemistries using the equipment
selected in Phase II. , The SIR data was given the most weight in test
evaluations primarily because EDAT believed that SIR tests were the most
"realistic indicator of long-term reliability. Final test results revealed .
that two aqueous saponifiers .best satisfied the test criteria: an inorganic -
based aqueous saponifier with a moderate pH and an organic-based monoethanol-
amine (MEA)/glycol ether-based aqueous saponifier. The inorganic-based
aqueous saponifier performed effectively and had human and environmental
safety advantages. -These advantages were the primary reasons for its
implementation at the Commercial Avionics System Division.- Although the
inorganic-based aqueous saponifier.is used in a 10% concentration versus a 4%
concentration for the organic-based cleaner, its extended bath life makes it a
more economical cleaner. In addition, the inorganic saponifier is less
aggressive on solder masks than other saponifiers that have a tendency to
remove dry-film solder masks. Finally wastewater analysis confirms that the
use of inorganic-based saponifiers reduces wastewater contamination, thereby
reducing water treatment costs.
Overall, testing of the aqueous saponifiers reveal that both perform
better than the benchmark used in the EPA/DoD/IPC Ad Hoc Phase II testing.
IV. FOR FURTHER INFORMATION, PLEASE CONTACT:
Michael Weidman
Sector Programme Coordinator
Allied Signal Aerospace
400 N. Rogers Road
Olathe, KS 66062-1212
USA
Tel: 1-913-768-2294
Fax: 1-913-791-1341 .
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ELIMINATING OZONE-DEPLETING SUBSTANCES AT AT&T
I. SUMMARY
AT&T became a corporate leader in the research and development of
alternatives to ozone-depleting solvents. At AT&T, ODSs were used as solvents
in a variety of processes ranging from metal degreasing to circuit board
fabrication, circuit board assembly, multi-chip module assembly, and
semiconductor manufacture. This product variety made AT&T's ODS elimination
efforts more difficult than at a less vertically- integrated company. AT&T
was able to eliminate ODSs by using its research and development strengths and
manufacturing expertise at Bell Laboratories to develop alternative
technologies. Also critical to the success of the company's efforts were
factory teaming and management support and commitment.
Since developing its alternative technologies, AT&T has expended
significant effort sharing its technology with other companies. AT&T,
Northern Telecom, and U.S. EPA formed with six other founding companies to
support these goals, the International Cooperative for Ozone Layer Protection
(ICOLP).
II. INTRODUCTION
AT&T began developing and testing water-soluble fluxes in the early
1980s with good success. In 1988, the company astounded the world when they
organized a press conference with U.S. EPA to announce they had co-developed a
.terpene-based solvent to replace CFC-113 in some processes. Until then, it
was argued that CFC was essential to electronics manufacturing. The following
year, AT&T developed a precision spray fluxer for use with low-solids (no-
clean) fluxes. The same year AT&T announced its goals for aggressively
eliminating ODSs as part of a comprehensive pollution prevention plan.
In 1990, AT&T reaffirmed its commitment to the environment by
eliminating the use of CFCs in its packaging materials. This and prior
actions led to public recognition, including two awards': The American's
Corporate Conscience Award from the Council on Economic Priorities, and a U.S.
Environmental Protection Agency (EPA) Stratospheric Ozone Protection Award.
The following year, additional public recognition for the company's
environmental efforts included the-New Jersey Governor's Award for Outstanding
Achievement in Pollution Prevention, the National Association for
Environmental Management's Environmental Excellence Award, a citation in the
first President's Environment & Conservation Challenge Award, and another EPA
Stratospheric Ozone Protection Award. AT&T also completed development of a
water-soluble flux suitable for military applications in 1991.
AT&T has continued to aggressively research and develop alternatives to
ODS from 1992 to present. Some of the recent developments include:
a technique for manufacturing integrated circuits using a non-
ozone-depleting solvent;
a water-soluble solder paste comprised of common food ingredients;
and
a low-residue soldering iron technology.
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AT&T eliminated about 1.1 million kg of CFC emissions from its
manufacturing operations worldwide by year-end 1992. This action resulted in
millions of dollars in manufacturing cost savings. Also during 1992, AT&T was
awarded its third U.S. EPA Stratospheric Ozone Protection Award and shipped
its 100th low-solids spray fluxer. In 1993, AT&T announced that it had
virtually eliminated ODS emissions from its manufacturing operations.
III. ODS ALTERNATIVES
AT&T investigated many types of options to re'place ODS use, including:
alternative cleaning technologies;
no-clean technologies; and
alternative manufacturing technologies.
The implementation of all of these options was needed in order to
successfully eliminate its use of ODSs because of the great variety of
applications in which ODSs were used.
Alternative cleaning technologies
AT&T found that it could change the flux or the solvent used and still
obtain acceptable product quality for many of its processes. Technologies
implemented included water-soluble fluxes and terpene-based solvents.
Water-soluble flux. AT&T was one of. the first companies to implement water-
soluble fluxes and aqueous cleaning processes. First initiated in 1981, AT&T
continues to use this method in.the manufacture of some circuit boards. In
1993, AT&T developed a new family of solder pastes using common U.S. Food and
Drug Administration-approved food ingredients to create a water-washable
solder paste that is more benign and easier to use than previous water-soluble
formulations.
Terpene-based solvents. AT&T worked with Petroferm, Inc. to develop a solvent
to replace CFC-113.for circuit boards that could not be cleaned with water
alone. The companies completed development and testing of a cleaning solution
called BIOACT(R)-EC7 in early 1988. Since this solvent was derived from
oranges, it was biodegradable and could be safely handled by a conventional
sanitary waste treatment facility.
No-clean technologies
AT&T, working cooperatively with ICOLP and other companies, also
investigated the option of using low-residue, low-solids fluxes to eliminate
the need for post-solder cleaning altogether.
Low-solids spray fluxer. In 1989, AT&T already had implemented its patented
system in its factories, and thus eliminated the need to clean electronics
circuitry after soldering. This system'controls the application of low-solids
flux coatings on circuit boards through precision spraying. As a result,
little post-solder flux residue remains and cleaning is unnecessary. In 1994,
this technology is being used by AT&T and more than 40 other companies
worldwide. ' .
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Low-residue hand soldering. AT&T developed a hand soldering iron that greatly
reduces the residue from cored-solder wire. It then licensed the technology
to Hexacon Electric Company so that others could use this no-clean technique.
Alternative manufacturing technologies
AT&T investigated whether certain products could be manufactured using a
different process altogether in order to avoid cleaning methods using ODSs.
The company developed alternative manufacturing methods for two of its
products -- printed circuit boards and integrated circuits.
Printed circuit board fabrication. During the manufacture of printed circuit
boards, a photoresist technique has been used to develop the pattern of
conductors on the board. This process originally used chlorinated solvents
but now uses an aqueous solution developed .by AT&T, eliminating usage of
millions of kilogrammes of ozone-depleting and non-ozone-depleting chlorinated
solvents.
Integrated circuit fabrication. In early 1993, AT&T scientists and engineers
announced that they had developed a new technique for the manufacture of
densely packaged integrated circuits .(multi-chip modules). The new process
used n-butyl butyrate (a common non-toxic chemical) instead of 1,1,1-
trichloroethane. N-butyl butyrate is a chemical that occurs naturally in
cantaloupes and other fruits.
IV. . RESULTS
AT&T applied each of these technologies as early as feasible to achieve
its ODS elimination goals. AT&T's ODS emissions had been reduced 86 percent
by year-end 1992, with 100 percent elimination at 20 of 44 majority-owned AT&T
plants. AT&T had virtually eliminated ODS emissions from all manufacturing by
April 1993. Not only did this have environmental benefits, but it resulted in
cost savings and yield improvements in many manufacturing processes.
V. TECHNOLOGY SHARING
AT&T's technologies to replace ODS use are available for use by
electronics manufacturers worldwide. In addition to developing unique
alternative technologies, AT&T has participated in a number of industry
cooperatives, several of which have successfully formed partnerships with
government to further the dissemination of information on alternative
technologies.
To help others address the ODS issue, AT&T founded or participated in
the following initiatives:
ICOLP. A cross-industry organization, the International
Cooperative for Ozone Layer Protection (ICOLP) is dedicated to
sharing knowledge about ODS substitutes with manufacturers
worldwide, especially in developing countries that lack resources
to research arid develop their own alternatives. ICOLP created
OZONET, a database of technical options to replace ODSs that is
accessible from more than 750 cities in 35 countries.
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GEMI. The Global Environmental Management Initiative (GEMI)
fosters environmental excellence by businesses worldwide. It
coordinates initiatives with academia, government, and non-
governmental organizations.
UNEP. AT&T scientists have participated in the first, second and
third Solvents, Coatings, and Adhesives Technical Options
Committees for the United Nations Environmental Programme (UNEP).
The committees evaluate the alternatives to ODSs for cleaning
applications and forward recommendations to the signatories to. the
Montreal Protocol.
Environmental Management Roundtable. This forum for senior
environmental officers of major U.S. companies meets regularly to
transfer technologies and information.
Ad Hoc Solvents Working Group. This group is a U.S. EPA, U.S.
Department of Defense, and industry partnership to qualify ODS
alternatives for military applications. AT&T chaired the Testing,
Monitoring and Validation Committee.
VI. FOR FURTHER INFORMATION, PLEASE CONTACT:
Dr. Leslie Guth
AT&T Bell Laboratories
P.O. Box 900
Princeton, NJ 08542-0900
USA
Tel: 1-609-639-3040
Fax: 1-609-639-2343
Tricia Geoghegan
AT&T Public Relations
Room B1338 ,
131 Morristown Rd. /
Basking Ridge, NJ 07922
USA
Tel: 1-908-204-8264
Fax: 1-908-204-8549
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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SEMI-AQUEOUS EQUIPMENT CONVERSION AT BECK ELECTRONICS
I. SUMMARY
Beck Electronics manufactures electronic products including professional
telecommunications and avionic systems. Many of its production lines shared a
central CFC-113 cleaning facility. As a result, Beck engineers sought a
solvent-type technology which would minimize disruption of production. After
evaluating many types of technologies, Beck decided on terpene-based solvents
in conjunction with water rinsing. Since terpene-type degreasers were not yet
commercially available, Beck retrofitted two vapour degreasers to use terpene-
based solvents.
II. INTRODUCTION
Beck's product line includes Electro-Magnetic Interference (EMI) filters
for use in Electro-Magnetic Compatibility (EMC) applications, whose typical
end uses include telecommunications and avionic systems. Since the central
CFC-113 degreasing facility serviced over 1,500 different types of products,
Beck preferred to find a technology as close as possible in operation to CFC-
using cleaning equipment in order not to interfere with the many manufacturing
processes dependent on solvent cleaning. "No-clean" technologies were ruled
out.
The general-purpose nature of the facility also meant that the new
solvent had to be compatible with the polymer resins and lacquers used in some
products, yet aggressive enough to clean even "baked-on" flux residues. Beck
also strove to avoid any new process that would have a significant
environmental impact, "such as technologies resulting, in the generation of
wastewater.
Beck's first step was to test twenty different alternative solvents.
Those solvents formulated around citrus- or pine-derived terpenes had the best
results in terms of both compatibility and effectiveness. Unfortunately,
equipment specifically built for these solvents was not commercially available
at the time.
Time was critical due to the impending deadline set by the Montreal
Protocol. Beck's solution to this dilemma was to build its own equipment by
converting old vapour degreasers already in its possession.
III. DESIGN CRITERIA
Beck chose to use terpene-based solvents with a water rinse because of
the large amounts of soil to be removed and the need to remove ionic
contamination. However, since terpenes are insoluble in water, the first
stage of rinsing required emulsification of the solvent to allow rinsing by
successive water stages. . Ultrasonic agitation assisted in forming the
emulsion. Beck also found that the terpene-based solvents were most effective
when heated to about 40° C, and that overheating would lead to early
deterioration of the solvent and would pose a fire hazard. To avoid the
generation of wastewater, Beck also required a method to separate the emulsion
' - * 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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so that the soil and spent solvent could be isolated for removal and disposal
or recycling.
IV. PRACTICAL SOLUTION
Beck had two older two-stage vapour degreasers, one of which had an
ultrasonic compartment that was ideal for the emulsification process.
However, simply filling the other (sump) side with the terpene-based solvent
was not practical because direct heating meant that the solvent in contact
with the heating element would become too hot. Beck decided to try an
indirect heating approach. «
To heat the solvent, A stainless steel tank purchased from a local
catering equipment store was suspended in the sump, which also contains
emulsified solvent. A pump was connected between the sump and the ultrasonic
side of the degreaser so that the hot emulsion could be circulated over the
weir between them. In this way, the sump containing the solvent was heated by
contact with the emulsion.
A stainless steel solvent tank, purchased from a local catering
equipment store was suspended in the sump, which also contains emulsified
solvent. A pump was connected between the sump and the ultrasonic side of the
degreaser 'so that the hot emulsion could be circulated over the weir between
them. In this way, the solvent in the new stainless steel tank was heated by
contact with the emulsion.
The second vapour degreaser was used to perform the final water rinses.
Initially, tap water was used. However, Beck soon converted to deionized
water to control ionic contamination. The deionized (DI) water is circulated
through a carbon filter and resin filter. A later refinement was to circulate
the solvent and emulsion through particulate filters to prolong their
usefulness.
V. PROJECT SUMMARY
Solvent: Terpene-based.
Solvent compartment: Inner compartment suspended in
existing sump tank of vapour degreaser. Indirectly heated
to about 35° C. Circulated through particle filter.
Emulsion compartment: Directly heated to about 40° C using
existing heaters. Ultrasonic capability of vapour degreaser
aids in emulsification. Emulsion circulated over weir,
around solvent tank, and returned through particle filter.
Rinsing method: Deionized (DI) water at ambient
temperature.
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VI. FOR FURTHER INFORMATION, PLEASE CONTACT:
M. A. Hazell
Beck Electronics Limited
Main Cross Road South Denes
Gt Yarmouth Norfolk
United Kingdom NR30 3PX
Tel: 44-493-856282 or 330332
Fax: 44-493-850169 or 859025
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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CFC SOLVENT ELIMINATION IN ELECTRONICS SOLDERING AT FORD MOTOR COMPANY
I. INTRODUCTION
The strategy to eliminate chlorofluorocarbon (CFC) solvent cleaning from
Ford Motor Company's electronics printed circuit-board manufacturing processes
was based on the international recognition of CFC environmental concerns. The
successful implementation of CFC-free soldering technologies was the result of,
developing and applying innovative manufacturing processes. Ford Motor
Company became a leader in inert gas wave soldering and eliminated CFC
cleaning processes ahead of the schedule mandated by the Montreal Protocol.
With the cooperation of the United States Environmental Protection Agency and
members of the International Cooperative for Ozone Layer Protection, worldwide
technology sharing was accomplished to expedite the CFC/ozone depleting
solvent elimination program. This case study will,highlight the technical,
environmental, and managerial success Ford achieved as a result of
accelerating the implementation of .the Montreal Protocol.
/
II. CLEANING OPTIONS
The first steps taken to eliminate CFC/ozone depleting solvent cleaning
were to research potential technologies, develop the most viable options, and
test these alternatives for reduction/elimination potential. The
possibilities were numerous, with each technology providing advantages rnd
disadvantages. The field was narrowed to five possible solutions:. No Clean
Flux, Inert Nitrogen Soldering, Aqueous Cleaning, Semi-Aqueous Cleaning, and
Hydrochlorofluorocarbon Solvent Cleaning. A study was conducted to identify
key elements of each technology for feasibility to existing Ford manufacturing
plants worldwide. This study highlighted each technology for its
effectiveness in eliminating CFC solvent cleaning. Some key areas considered
were printed circuit board cleanliness, product reliability, equipment
reliability, environmental impact, and cost competitiveness. The selection
was narrowed to two technologies that rated highest in these categories: No
Clean Flux and Inert Nitrogen Soldering. The implementation of these two
technologies provided the best solution for CFC/ozone depleting solvent
elimination, but required significant development and testing.
The following list highlights the advantages and disadvantages each
technology presented for worldwide implementation:
No Clean Fluxes
Pros:
Uses existing solder systems
Lowest cost
Eliminates CFC emissions
Reduces volatile organic compound emissions
Eliminates cleaning machines
Shortest implementation lead time
Reduces' material usage
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Cons:
Requires new application/control equipment
Need to determine solder quality
Need to determine probe test capability
Need to determine conformal coat compatibility
Need to determine product long term reliability
Need to determine component solderability
Inert Nitrogen Soldering
Pros:
Flux with low solids used '
Best printed circuit board cleanliness
Probe test easily
Conformal coats easily
Eliminates CFC emissions
Reduces volatile organic compound emissions «
Eliminates cleaning machines
Reasonable implementation lead time
Improves product quality
Reduces material usage - - flux and solder
Requires less floor space
Cons:
Additional costs for cryogenic nitrogen and equipment
Replace existing solder equipment
New handling procedures for chemicals
Need to determine equipment emissions
Need to determine product long term reliability
Need to determine component solderability
Need to determine.solder quality
With the completion of extensive field, laboratory, and manufacturing
plant testing, the new process merged both technologies with superior results.
Solder quality was enhanced with cooperation of component suppliers providing
improved solderable components to meet the new requirements of the lower
activity fluxes used for inert nitrogen soldering. Flux formulations were
developed using low activity organic acid without rosins or resins added.
Product long term reliability was proven in fleet vehicles and extensive
'laboratory life tests with 100 percent compliance. Equipment emissions were
eliminated for CFCs (100 percent), and formic acid (100 percent), and reduced
for volatile organic compounds (70 percent) and lead (40 percent). Printed
circuit board probe testing without cleaning was tested and implemented.
Conformal coatings without volatile organic compound content were developed
with suppliers to eliminate process emissions. CFC cleaning machines were
removed from the production floor, which resulted in extra floorspace. Flux
material usage was reduced to 80 percent with flux-thinner purchases
completely eliminated. Flux density test/control equipment was removed from
the process with new spray technology and handling procedures. End-of-line
ionic contamination equipment was removed from the process with new cleaner
solder process stability. New inert wave solder equipment innovations were
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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developed with suppliers to reduce solder joint defects to less than 10 ppm.
Finally, capital equipment expenditures were recovered and resulted in
additional long term savings in materials consumption, quality products, and
equipment reliability.
III. BENEFITS
The elimination of all CFC cleaning on May 1, 1993, for Ford Electronics
facilities, exceeded the timing of the Montreal Protocol. In addition to
realizing the benefits of CFC emission elimination programs, Ford Electronics
embarked on a policy of waste minimization for all sources. This internal
requirement to minimize emissions to the fullest extent technically possible
resulted in lower emissions in areas not covered by the Montreal Protocol.
Volatile organic compound reductions resulted from new equipment developments,
material developments, and process parameters that reduce solvent emissions at
the source. The ultrasonic fluxer technology eliminated the need to use
containment equipment to capture flux volatiles. The 100 percent solids
conformal coatings eliminated the emissions of solvents during cure time. The
use of inert gas in soldering reduced the content of lead .oxides being formed
as waste in emissions. Finally, process enhancements eliminated the use of
formic acids in the solder process.
IV. CONCLUSION
Ford has shared the knowledge gained from its successful program.
Ford's involvement with the International Cooperative for Ozone Layer
Protection has resulted in supporting and presenting technical papers at
international conferences. This commitment increases the technical knowledge
of the electronics industry in CFC elimination strategies. Ford has supported
government/industry publications that benchmarked prior cleaning effectiveness
and set the path for emerging replacement technologies. This global
responsibility, with the help of the United States Environmental Protection
Agency, has produced outstanding results and achievements for Ford Motor
Company and others. . '
The success of this program was highlighted by awards presented to
Ford's electronics operations and its employees from various sources. The
United States Environmental Protection Agency and the International
Cooperative for Ozone Layer Protection recognized Ford's contributions, as did
the State of Pennsylvania. Various employees have won awards from Ford for
their contributions.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Jay Baker
Ford Electronics Technical Center
Room C130
17000 Rotunda Drive
Dearborn, MI 48121
USA
Tel: -1-313-845-3597
. Fax: 1-313-323-.8295
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
.11-15
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Peter J. Sinkunas
Ford Electronics Technical Center
Room C130
17000 Rotunda Drive
Dearborn, Ml 48121
USA
Tel: 1-313-845-^643
Fax: 1-313-323-8295
* 1994 UNEP SOLVENTS. COATINGS, AND ADHES1VES REPORT *
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REDUCTION AND ELIMINATION OF OZONE-DEPLETING SOLVENTS AT HITACHI
I. INTRODUCTION
Industries in Japan were requested to switch the usage of
trichloroethylene and tetrachloroethylene to 1,1,l-trichl(oroethane in the late
1980s. Hitachi adopted this policy and changed its systems to 1,1,1-
trichloroethane in 1989. Hitachi began to reduce usage of CFC-113 iti 1988 by
introducing recovery and recycling systems. The company has been steadily
reducing its consumption of ozone-depleting solventssince 1989, Hitachi
completed its phaseout of CFC-113 in 1993, and 1,1,1-trichloroethane will be
phased out in 1994. '
The company became a member of the International Cooperative for Ozone
Layer Protection (ICOLP) to support this belief. It also sent experts to many
ODS phaseout strategy meetings and seminars, with a special focus on those
held in developing countries.
Hitachi produces several kinds of products, including electric power
generators, electricity transmitting equipment, computers and peripherals,
communication equipment, trains, semiconductor devices, and domestic
appliances. Alternative cleaning technologies considered to replace ODS
solvents for each of these products are described in this case study;
II. ALTERNATIVE TECHNOLOGIES
Hitachi was accustomed to using solvents in cleaning applications and
initially focused on solvent-type alternatives, including:
Hydrochlorofluorocarbons (HCFCs); '
Perfluorocarbons; .
Alcohols;
. Aliphatic Hydrocarbons
Ketones;
. Ethers; and ,
? Aromatic Hydrocarbons.
CFC-113 and 1,1,1-trichloroethane are very effective solvents for which
Hitachi found no equivalent solvent-type replacements to meet its cleanliness
and material compatibility needs. HCFC-225 was initially considered by
Hitachi to be similar enough to ODS solvents be a drop-in replacement.
However, the Montreal Protocol was amended in 1992 to include the phaseout of
HCFCs by the end of 2030, so Hitachi considered this chemical a temporary
solution at best and did not actively pursue its use.
Subsequently, many types, of non-solvent cleaning and no-clean
substitutes were investigated in an attempt to match the cleaning ability of
the ODS solvents. Hitachi considered the available alternatives including:
No-clean technologies, e.g., evaporating oil, lubricant coated
steel sheets, thin polymer peeling sheets,, and ultrasonic plastic
deformation; ' . '
Mechanical cleaning, e.g., blasting and pressurized gas;
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Aqueous cleaning, e.g., alkaline cleaners, hydrocarbon/surfactant
cleaners, and steam distillation under vacuum; and
Miscellaneous options, e.g., ultraviolet light/ozone cleaning,
supercritical cleaning.
Based on its investigation, Hitachi established internal guidelines for
the selection of alternative chemicals and technologies. These guidelines
are:
No-clean technologies are recommended.
Chlorinated solvents are generally prohibited,' including HCFCs.
However, HCFC-225 may be appropriate at times, but only for
transitional use.
Low-boiling point PFCs are restricted.
Energy consumption of alternative technology is a prime
consideration.
The remainder of this case study presents some of the options considered
which were eventually adopted by Hitachi.
No-Clean Technologies
Hitachi considered the following no-clean alternatives to reduce its use
of ODS solvents:
lubricant coated steel sheets;
drying press oil; and
ultrasonic plastic deformation in pipe working.
The use of lubricant-coated steel sheets was one of the no-clean options
considered. In conventional metal pressing applications, lubricating oil is
applied and the oil is cleaned off after-working the metal. The drawing
characteristics of lubricant-coated steel sheets are the same as non-coated
steel sheets. .
Drying press oil was a second no-clean alternative evaluated.
Conventional lubricating oil for punch working is not volatile and the oil
must be cleaned off after working the metal. Recently, volatile lubrication
oil has been developed which generally leaves minimal residual oil film
thicknesses after only one hour drying time at room temperature. Film
thicknesses can be reduced even faster at higher temperatures, but a drying
furnace is recommended for the fastest drying. It is important to note that
some of these drying oils contain chlorinated solvents and require that
special attention be paid to occupational health and safety.
Ultrasonic plastic deformation in pipe working was the final no-clean
option considered. When ultrasonics are used in plastic deformation
processes, it is known that changes occur, including:
%
reduction of deformation resistance
reduction of friction between tool and work piece
physical and mechanical property changes in metal
temperature increase in metal.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Since the deformation resistance and friction between tool and work can
be reduced, some pipe working can be accomplished without lubricating oil. In
the case where the thickness of the pipe wall is not large, the pipe wall will
be bent or expanded without lubricating oil
Blasting technology
Some types of residue can be cleaned from work pieces by blasting solid
particles at the work surface. When flammable solid particles are used,
careful attention must be paid to avoid combustion.
Aqueous cleaning and wastewater treatment
In aqueous cleaning at Hitachi, typically, work pieces are cleaned in
the first stage, removed and subjected to two rinse stages, and then dried.
It is important to monitor the concentration of cleaning agents which are
dragged from the cleaning tank to the rinse tanks since the cleanliness of the
work piece depends on the purity of the final rinse water.
Each type of cleaning agent may require a different -type of wastewater
treatment for the effluent generated. It is very important to investigate the
types and amounts of materials that may be dissolved in the wastewater since
some aqueous cleaning agents remove larger amounts of metals, e.g. lead, than
CFC-113 or 1,1,1-trichloroethane. .
Ultraviolet light/ozone cleaning
By applying large doses of ultraviolet light to the surface to be
cleaned, ozone is created from the surrounding atmosphere. Ozone is a very
reactive substance and oxidizes organic compounds to create carbon oxides and
hydrogen oxides. These products are volatile and evaporate from the surface
of the part being cleaned.
This type of cleaning technology is effective in removing organic
residues from the surface of the part, but is ineffective on non-organic
residue since the oxides formed are nonvolatile and remain on the surface of
the part.
III. FOR'FURTHER INFORMATION CONTACT, PLEASE CONTACT:
Mr. Yoshiyuki Ishii .
Senior Engineer
Environment Policy Office , :
Hitachi, Ltd.
New Marunouchi Building .
5-1, Marunouchi 1-chome, Chiyoda-ku
Tokyo 100
Japan
Tel: 81-3-3212-1111 x2722
Fax: 81-3-3214-3545
* 1994 UNEP SOLVENTS. COATINGS, AND^ADHESIVES REPORT *
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REPLACEMENT OF OZONE-DEPLETING SUBSTANCES IN HONEYWELL
SPACE AND AVIATION CONTROL PRODUCTS
I. INTRODUCTION '
This case study focuses on the alternatives examined for implementation
in Space and Aviation Control products. Honeywell Space and Aviation Control
offers: systems integration capabilities, automatic flight control systems,
electronic cockpit displays, flight management systems, precision components
for strategic missiles, and other control technology for space and aviation
applications. The combined usage of CFC-113 and 1,1,1-trichloroethane in 1988
for these facilities was approx. 590,000 kg.
II. PRINTED WIRING BOARD CLEANING
Space and Aviation Control assembles plated through-hole boards, mixed
technology boards, and surface mount-only boards. The primary solvent used
for cleaning in this application is Freon-TMS, an azeotrope of CFC-113 with
methanol. The primary challenge for cleaning is in surface mount technology
applications, which have tight clearances to the board and a high packing
density of components on the board. A test board was designed with surface
mount technology and a range of components from 50 mil to 20 mil pitch.
Cleanliness was determined using surface insulation resistance testing,
ionograph testing, and residual rosin testing. Material compatibility tests
were also performed on the various materials found in the assembly of printed
wiring boards.
Semi-aqueous solvents.were selected as an interim step for the
replacement of CFC-113 and 1,1,1-trichloroethane because of the high
reliability and performance requirements of space and aviation products and
because of the time-frame required for substitution. The implementation of
semi-aqueous solvents required .only a change in the cleaning material and no
change of the flux since the semi-aqueous solvents were formulated to remove
the traditional rosin residue. Six semi-aqueous solvents were tested and two
were selected for implementation -- a terpene hydrocarbon and an aliphatic
hydrocarbon. In-line and batch equipment purchased and installed in 1993
worked extremely well at the facilities. For .example, a Minneapolis facility
realized a US$400,000 savings in raw material costs in a single year because
of the implementation of these alternative solvents. The semi-aqueous
technology implemented also proved to be a viable alternative for high-
reliability applications.
III. GYROSCOPES AND PRECISION GUIDANCE INSTRUMENTS
Momentum control gyroscopes and precision guidance instruments are used
to control and detect movement in satellites, space probes and platforms, and
missiles. Contamination-free- surfaces are required during fabrication in
order for these devices to operate reliably for extended periods of time in
harsh military and space environments. The cleaning processes used must be
compatible with a variety of materials, including: metals, thermoset
polymers, thermoplastics, elastomers, lubricants, -organic and inorganic
coatings, and optical components. In addition, cleaning processes must be
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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effective in removing contaminants such as hydrocarbon, ester, and
fluorocarbon lubricants, handling debris, damping fluids, and process
residuals.
For particle removal in critical cleaning operations, C02 "Snow",
perfluorocarbon sprays, and water-based sprays were selected as alternatives
to ozone-depleting solvents. Equipment has also been specially designed to
use perfluorocarbon solvents for the removal of fluorocarbon oils and greases,
while limiting solvent emissions to the atmosphere. Carbon dioxide is also
being used in another cleaning process -- supercritical fluid cleaning -- for
the removal of a wide variety of oils. Flammable and combustible solvents
have also been employed for processes that are not compatible with other
alternative cleaning solutions.
IV. CONCLUSIONS
The varied nature of the substrates being cleaned and the contaminants
present, coupled with the required high reliability of military and space
hardware, led to the. development and implementation of a wide variety of
cleaning processes and materials that use no ozone-depleting substances.
Figure XI-1 shows the annual use of CFC-113 and 1,1,1-trichloroethane at the
Honeywell Space and Aviation Control Operations. In 1988 the combined usage
of these ozone-depleting solvents was 590,000 kg. By the end of 1993, the
usage had decreased by 73% to 160,000 kg and the company saved millions of
dollars in raw material costs. Many of the alternative processes implemented
are new, while others like aqueous cleaning were already in use in cleaning
applications but''required further development and refinement for use on high-
re.liability hardware. The result of implementing alternative cleaning
techniques for Honeywell Space and Aviation Control products was not less
dependable equipment, but rather higher quality hardware whose cleaning
processes have been thoroughly evaluated and qualified.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Mr. Lee Tischler
Corporate Environment, Health ft Safety
Honeywell Inc.
Honeywell Plaza
P.O. Box 524
Minneapolis, MN 55440-0524
USA
Tel: 1-612-951-2517
Fax: 1-612-951-2525
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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FigureXI-1
ANNUAL USE OF CFC-113 AND 1,1,1-
TRICHLOROETHANE AT HONEYWELL SPACE AND
AVIATION CONTROL OPERATIONS
73% decrease 1988-1993
1988 1989 1990 1991 1992 1993
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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QDS ELIMINATION AT IBM AUSTIN, TEXAS
I. SUMMARY
IBM was among the first companies to assess alternative cleaning
technologies in order to take a proactive stance on the CFC Phaseout. After
ruling out several options for its pilot project, the company successfully
implemented aqueous cleaning. However, after no-clean technologies were
further developed, the company adapted new, superior alternative.
II. INTRODUCTION
,IBM Austin began a program to eliminate chlorofluorocarbons (CFCs) and
1,1,1-trichloroethane (TCA) from its manufacturing processes prior to the U.S.
ratification of the Montreal Protocol. In 1987, IBM set goals to drastically
reduce CFCs by 1991 and TCA by 1992. IBM finalized the company goals in 1990,
setting the date for completion of CFC phaseout at 1993 and TCA phaseout at
1995.
IBM Austin concluded in 1987 that options that could be implemented
immediately included HCFCs, semi-aqueous cleaning, and aqueous cleaning.
HCFCs were viewed by IBM to be a short-term solution. No-clean technology was
available but had been neither fully developed nor tested to meet IBM Austin's
rigorous manufacturing requirements. Semi-aqueous technology, a new
development at the time, required sophisticated fire protection systems to
protect against flammability risks. Therefore, aqueous cleaning was chosen
in 1987 as the best available solution to eliminate CFC and TCA usage.
Aqueous cleaning would be only ah interim solution until a no-clean technology
that met IBM's manufacturing requirements was fully developed and qualified.
IBM Austin met its goals and completed the elimination of the use of
CFCs during the first half of 1991 and the use of TCA by year-end 1992. Over
one year after implementation of water-soluble materials, no-clean had become
the least expensive of all non-ODS cleaning options, reinforcing IBM's
original long-term goal to move to this technology.
The no-clean process reduces cost in several ways. First, it eliminates
the cleaning stream as well as the waste stream. Other important cost-
reducing elements are the elimination of floor space requirements for cleaning
apparatus and the reduction in overall cycle time. With the elimination of
cleaning operations, the number of required operators on the manufacturing
floor can be reduced. The low cost of this option, in conjunction with recent
progress made in developing advanced flux materials and the understanding of
the remaining residues has made no-clean a viable alternative.
III. THE AQUEOUS CLEANING PROCESS
IBM examine several important elements in implementing the aqueous
cleaning process. These included:
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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equipment design; .
process parameter setup; and
process control.
The cleaner selected was tailored to the needs of IBM's cleaning process
and the type of flux selected. When specifying the materials of construction,
IBM had to consider the flux activity and the corrosive nature of the
residues.
Due to their low vaporization temperatures, typical solvents generally
are dried with forced air only. Water, on the other hand, does not evaporate
as easily and the design of the drying system for the aqueous cleaning system
required a combination o,f forced air and heat. The introduction of high-
velocity/high-volume blowers greatly improved the drying of many designs, but
this method was not considered adequate for connectors with openings
perpendicular to the air flow. Therefore, IBM selected a system with an
optimal heating profile to ensure success.
Process parameter setup was critical to the successful implementation of
aqueous systems. Therefore, in order to select an overall set of process
parameters, IBM established a procedure was established to identify and
evaluate the process interactions.
Process control was another key element in the implementation of aqueous
cleaning processes. Process control is the ability to produce a product with
consistent quality in mass production. Good controls ensure that the product
is properly cleaned and that no corrosive residues are present that would have
an adverse effect on the reliability of the final product. Methods for the
measurement and control of the cleaning process included:
. equipment controls/statistical process control (SPC); and
random temperature,, humidity, and bias stress testing.
Random temperature, humidity and bias stress testing stimulates the
durability and reliability of a product in the field.
IV. THE NO-CLEAN PROCESS
Implementation of no-clean technologies differed significantly from
implementation of aqueous cleaning technologies. The elements of a program to
implement no-clean materials included:
probe testing/residue thickness;
» flux interactions/reliability;
solderability on a copper surface;
ease of manufacturing; and
use of nitrogen as a controlled atmosphere.
Probe testing was the chief method used to detect assembly-process and
electrical defects on printed circuit boards. Some no-clean fluxes leave non-
corrosive residues on assemblies which inhibit this form of testing. In order
to minimize this impact, no-clean methods had to be compatible with probe
testing by leaving little to no residue on the probe surface.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Flux interaction with materials of construction was another critical
factor. In all cases, whenever a new flux is to be implemented, compatibility
with existing materials must be established. Although a rigorous chemical
composition analysis also might have been effective, this was accomplished
through reliability testing at IBM.
Initially, it was expected that solderability of the components and the
carrier would pose a problem to the implementation of a no-clean process. It
was thought that hot air solder level (HASL) cards would be required. Due to
the added cost of solder levelling and the adverse effects on fine pitch
processing, it was decided that any no-clean implementation would use bare
copper boards with an organic protective coating.
The ease of manufacturing using solder pastes and fluxes was another
prerequisite. . IBM's minimum requirement for no-clean solder pastes was the
ability to screen 0.41 mil pitch components. In fact, the robustness of the
screen printing process was greatly improved as a result of switching to no-
clean materials. Because flux chemistry turned out to be much more resistant
to.changes.in the temperature and especially the humidity, resulting in better
rheological performance. .
Another important consideration during the implementation of no-clean
processes was the use of inert gas. Nitrogen is used to control oxidation on
bare copper surfaces, but its use added to the overall cost of soldering. The
company's ultimate goal was to use nitrogen only over the wave solder pot,
where .dross reduction/elimination would provide an additional benefit.
Solder balls have long been considered a problem with the use of no-
clean materials in that the solder balls are no longer removed during a .
subsequent cleaning process. The formation of solder balls attached to
discrete chip components was a problem in one of IBM's processes. An analysis
suggested that the pad size and dimensions contributed significantly to the
problem. These problems where solved through a combination of design and
processing controls.
From 1989 to 1993, IBM Austin eliminated the use of CFCs and TCA, and-.
reduced water consumption through the implementation of no-clean technology
processes:
approx. 196,000 kg of CFC-113 phased out from peak 1988
usage
approx. 140,000 kg of TCA phased out from peak 1988 usage
Nearly .378.5 litres per minute water use eliminated.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
/ John J. Prusak
IBM Corporation
11400 Burnet 'Road
Austin, TX 78758
USA
Tel: 1-512-838-6895
: Fax: 1-512-838-6953
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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THE JAPAN INDUSTRIAL CONFERENCE ON CLEANING
I. SUMMARY
In response to the Montreal Protocol, the government of Japan enacted
legislation phasing out the use of ozone-depleting substances, including the
solvents 1,1,1-trichloroethane and CFC-113. However, users of these chemicals
required assistance, in implementing alternatives to these solvents because of
the great diversity in applications, enterprises, and substitute chemicals and
technologies. To provide this assistance, a new organization -- the Japan
Industrial Conference on Cleaning (JICC) -- was formed. JICC will accomplish
its mission through promoting mutual friendship and cooperation between
members, disseminating and exchanging information, standardizing technologies,
and providing a central point of contact with regulatory authorities.
II. INTRODUCTION '
1,1,1-Trichloroethane and CFC-113 are scheduled to be phased out by the
end of 1995 in developed countries. Total elimination of these substances
entails developing and testing the most appropriate alternative chemicals or
technologies for each application. To accomplish this task, each of the
.issues listed below must be considered:
1. Diversity of application
Solvent applications are diversified, involving cleaning many
.different types of'contaminants from a wide variety of parts. In
addition, some.applications involve additional processes before
and after cleaning. Hence, the individual requirements of each
process 'must be considered in order to select the most appropriate
alternative.
2. Diversity of enterprises
Many different sizes of manufacturers have been using ozone-
depleting solvents, with medium and small enterprises accounting
for more than 50 percent of total consumption in Japan. As a
result of these circumstances, it is important to ensure good
contact between users of solvents and manufacturers of alternative
technologies.
3. Diversity of alternatives and substitutes
An investigation of the wide array of alternatives and related
technologies is essential to selecting the best option' for each
application. In addition, users should conduct comprehensive
testing to ensure the success of the new chemical or technology.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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III. ESTABLISHMENT OF A NEW INDUSTRIAL ORGANIZATION
The Japan Industrial Conference on Cleaning was established in April 13,
1994\to assist in phasing out ODS solvents. Members of JICC are enterprises
involved in supplying equipment and chemicals for various cleaning
technologies, including ultrasonic cleaning, spray cleaning, vacuum cleaning,
and high-pressure cleaning.
IV. " JICC OBJECTIVES .
JICC furthers the development of non-ODS cleaning technologies,
contribute to environmental protection, and promote the expansion ,of business
in related fields by working toward a number of objectives.
Mutual friendship and information exchange between members, especially in
different industrial fields. JICC aims to aid in the exchange of information
to support business activities not only for suppliers of cleaning
technologies, but also for users of such technologies.
Dissemination of information on cleaning technologies through educational
materials and outreach efforts. JICC facilitates the understanding of new
cleaning technologies. Educational materials will stress a "total system"
approach, focusing on the strong interdependencies between each segment of
industrial processes and the cleaning process.
Mutual cooperation to further the development of new technologies. In
particular, JICC will increase and enhance cooperation between different
fields of technologies.
Standardization of related technologies in order to ease the decision process
faced by owners of existing cleaning equipment. Equipment owners are now
faced with a wide array of options in considering their conversion to
alternative technologies and are in need of some way to reduce their
selections to the best technology for their application. To meet each user's
requirements, JICC intends to investigate which features can be standardized
on each technology, such as safe'ty and environmental protection features to
meet legal requirements. :
Contact with administrative authorities to deal with special issues which
would be difficult to handle by independent associations. JICC ,will be become
industry's central point of contact with administrative authorities in the
government and to effectively voice industry's concerns in preparation for'
legislation on present and future global environmental issues.
V. JICC MEMBERS . .
JICC is comprised of four types of members. Regular members are
enterprises which manufacture cleaning equipment, cleaning agents, and
auxiliary equipment. Supporting members are enterprises t;hat support JICC's
activities and assist in achieving JICC's objectives. Group members are
groups that support JICC's activities and assist in achieving JICC's
objectives. Finally, special members are groups that support JICC's
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
. 11-27
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activities and assist in achieving JICC's objectives and are also endorsed by
JICC's board of directors.
VI. FOR FURTHER INFORMATION, PLEASE CONTACT:
Secretariat of JI-3C
c/o The Japan Society of Industrial
Machinery Manufacturers (JSIM)
Kikaishinko Building, 4F
3-5-8, Shiba-Koen, Minato-Ku
Tokyo, 105
Japan
Tel: 81-3-3431-6517
Fax: 81-3-3431-6518
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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THE ELIMINATION OF 1,1,1-TRICHLOROETHANE IN ELECTRONICS CLEANING
AT LOCKHEED SANDERS COMPANY
I. INTRODUCTION
An important part of the manufacturing process for printed circuit
boards and other electronic components is the removal of residues during the
post-assembly cleaning process. In recent years, the Lockheed Sanders Company
used 1,1,1-trichloroethane (TCA) for cleaning electronic components. However,
in an effort to protect the environment and reduce operating costs, Sanders is
eliminating the use of TCA from its cleaning operations. This effort has been
implemented through a Sanders Process Action Team.
II. PROCESS DESCRIPTION
/
The two standard processes for electronic component cleaning at Sanders
were vapour degreasing and immersion cleaning with TCA. Due to concern for
ozone layer protection and rising costs associated with TGA-based cleaning as
the production phaseout date approaches, Sanders tested several alternative
cleaning processes. Sanders chose two spray cleaning systems to replace TCA
for cleaning in surface mount technology (SMT) applications.
Stencil Cleaning
Sanders selected the EMC Global Technologies Model IPA-30 batch cleaner
for stencil cleaning. The batch cleaner is a closed-loop, explosion proof
machine incorporating a wash and a dry cycle. Figure XI-2 shows a simplified
version of the stencil cleaning process. Isopropyl alcohol (IPA) is sprayed
onto circuit boards via rotating spray arms at high-volume and low-pressure
during the wash cycle. Excess alcohol evaporates in the dry cycle when air is
pumped through the rotating arms. .
Printed Circuit Board (PCB)
A Hollis/Electrovert HS-332 cleaning machine with Alpha 3555 saponifier
is now used to clean assembled SMT circuit cards. The cleaning solution is a
concentrated alkaline liquid designed to remove flux residues from soldered
electronic assemblies. Its characteristic low foaming and high surface
insulation resistance (SIR) satisfy the performance requirements of the
cleaning process. Figure XI-3 details the cleaning process flow for the
circuit card cleaning system. In the wash cycle the cleaning solution is
heated and sprayed onto the circuit cards with high volume, high pressure jet
nozzles. A recirculating pump returns the solution to a holding reservoir for
reuse. Once the PCBs have been washed with the cleaning solution they are
spray rinsed with deionized water to remove excess cleaner and residues. The
parts are dried using "air knives" to remove all moisture that may be trapped
in crevices and are passed through a convection heating station to ensure that
all parts are completely dry. Finally, the cleaning solution is transferred
to an external ultrafiltration unit where it is recycled and stored for the
next cleaning cycle. However, due to the build up of dissolved metals and
gradual degradation of the saponifier over time, the cleaning solution must be
changed periodically. Rinsewaters are being treated using activated carbon
and ion exchange resin beds to form a "closed-loop" rinsewater system.
1
* 1994 UNEP SOLVENTS, COATINGS, AND AOHESIVES REPORT *
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Figure XI-2
LOCKHEED SANDERS COMPANY STENCIL
CLEANING PROCESS
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
11-30
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Figure XI-3
LOCKHEED SANDERS COMPANY CIRCUIT CARD
CLEANING PROCESS
CIRCUIT
CARDS IS
CONVEYOR
TO ATMOSPHERE
WASH
STATION
PROCESS ADt
AD)
KMFE
RJNSE
STATION
FILTER
OLTTSIDE
AIR
HEATER SLOWER
AD)
KNIFE.
HOT AOt
DRYING
STATION
CARDS OUT
AOITIMIS
C1EANER
AIR
KMFE
FILTER
RINSE
WATER '
FILTEIt
fi
>
AW '
KMFE
/ i
DEIOMZEDWATKR
SYSTEM
HI/MI-
HOCUS A«
FILTER
OUTSIDE
AIM
KEATKR (LOWER
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
11-31
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III. BENEFITS & LIMITATIONS
Some of the benefits of using both aqueous and IPA cleaning processes in
place of TCA cleaning include:
elimination of the use of ozone-depleting chemicals
effective removal of ionic compounds
components cleaned maintain high surface insulation resistance
(SIR)
« enclosed equipment reduces vapours in the workplace
« lower operating costs
Limitations of the aqueous and IPA cleaning processes include:
« _ IPA is flammable and must be used with extreme care
« Alpha 3555 is combustible and corrosive
« Alpha 3555 is comprised of several constituents with low Threshold
Limit Values .(TLVs) (two constituents each accounting for 40% of
the formulation have TLVs of 3 ppm and 50 ppm)
« space required for alternative cleaning systems is typically
larger than for the TCA system
IV. PLANNED PROCESS IMPROVEMENTS
Lockheed Sanders Company is also evaluating a water soluble flux to
further enhance the soldering process and minimize waste generation. The flux
under consideration, Alpha WS-360, is a halide-free organic flux which leaves
a negligible amount of residue after the soldering process. Implementation of
the water soluble flux would eliminate the use of IPA in stencil cleaning.
V/ FOR FURTHER INFORMATION, PLEASE CONTACT:
Mr. Stephen Evanoff
Lockheed
980 Kelly Johnson Dr.
Las Vegas, NV 89119
USA
Tel: 1-702-897-3228
Fax: 1-702-897-6645
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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HYDROCARBON DRY CLEANING AT MILJOMINISTERIET
I. INTRODUCTION
The Center Rens in Helsinge, Denmark has demonstrated that Satec's
reloading hydrocarbon dry cleaning system can replace CFC-113 as a dry
cleaning solvent for cleaning fabrics and leather. It has also been
determined that a large portion of perchloroethylene cleaning can be replaced
with hydrocarbon cleaning.
II. PROCESS CHARACTERISTICS
The higher initial cost .of the Satec hydrocarbon dry cleaning system is
a significant factor discouraging Danish dry cleaners from investing in the
new equipment. However, the price of a comparable perchloroethylene machine
is expected to increase as future European Community regulations restrict the
use of chlorinated solvents. At Center Rens, the operating costs for
hydrocarbon cleaning systems are the same as for CFC-cleaning systems.
Hydrocarbon cleaning may also be less expensive for dry cleaning
establishments situated in municipalities which impose high taxes for waste
disposal.
With the implementation of the hydrocarbon dry cleaning process,
cleaning solvent consumption was reduced by approximately 60 percent. The use
of hydrocarbons is estimated to be slightly more than one percent per kg of
clothes cleaned. Other significant characteristics of the hydrocarbon
technology include:
The consumption of energy which might be increased with
hydrocarbon cleaning, however, energy use has not been compared.
Water consumption is independent of the technology because cooling
water is recirculated.
The emission of ozone depleting substances will end.
There will be an increase in the emissions of hydrocarbons which
contribute to the formation of "smog".
Waste quantity (distillation residue, sludge of textile fibres,
fluid-containing filters) will remain unchanged, but the character
of the waste will be changed to flammable oil waste, which is more
economic to dispose.
' Wastewater consists of water with a very low hydrocarbon content
(< 20 ppm). Cooling units without water recovery also produce
some wastewater .(80 litres per charge).
Hydrocarbon vapours in the dry cleaning room appear in
low concentrations (< 5% of the threshold limit value).
Air change requirements will vary between 3 and 10 times per hour
most of the year, because of the need to keep the shop doors open
to allow heat from the process to escape.
Risk to unprotected skin is considered low, but the use of
protective1 gloves is highly recommended.
The Danish EPA does not consider that flammability is a major
risk. However, it is recommended that normal precautions for
handling flammable substances be taken.
* 1994 UNEP SOLVENTS. COATINGS, AND ADHESIVES REPORT *
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III. CONCLUSIONS
The Danish EPA supported the Hydrocarbon Dry Cleaning project where
hydrocarbons replaced CFC-113 and perchloroethylene in dry cleaning
operations. The project was carried out successfully without increasing risk
for the workers in the facility.
IV. FOR FURTHER INFORMATION, PLEASE CONTACT:
Per Henrik Pedersen
Danish Environmental Protection Agency
Strandgade 29
DK-1401 Copenhagen K
Denmark
Tel: 45-32-66-01-00
Fax: 45-32-66-04-79
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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PHASING OUT OF OZONE-DEPLETING SUBSTANCES BY THE MINEBEA CO.
THROUGH THE USE OF A WATER-BASED CLEANING SYSTEM
I. INTRODUCTION
The Minebea Co. in Thailand and Japan has developed and implemented a
water-based cleaning system to clean miniature ball bearings and other parts.
The water-based cleaning system eliminates the use of ozone-depleting
substances such as CFC-113 and 1,1,1-trichloroethane. The cleaning .system
utilizes ultrasound arid deoxidized water and reduces the load on wastewater
treatment systems by eliminating the need for anticorrosive agents in the
rinsing process.
II. OPERATION OF THE WATER-BASED SYSTEM'
.The water-based cleaning system operates through the use of ultrasonic .
energy and deionized water. Ultrasonic energy in water causes the pitting or
wearing away of debris from metal' surfaces (a process known as cavitation).
Use of deoxidized water in this cleaning process acts both to enhance
'cavitation, and thus cleaning, and curbs rusting of steel surfaces because the
rate of rusting is proportional to the concentration of dissolved oxygen in
the water.
Figure XI-4 is a diagram of a water-based cleaning system. The par's
enter the detergent bath, followed by the rinse bath where deoxidized water is
added, and continue on to the dryer. The water from the rinse bath is sent to
the waste water treatment system'.
III. CONCLUSIONS
The water-based cleaning system which uses deoxidized water provides
several advantages over other 'cleaning methods. Deoxidized water enhances the
effect of ultrasonic energy in washing and curbs rusting of steel. In
addition, the use of a deoxidized system eliminates the need for anticorrosive
agents in rinsing and thereby reduces the load on wastewater treatment
systems.
The Minebea Co. believes that a water-based washing system must be
designed to realize maximum washing effect with minimum water consumption.
IV. FOR FURTHER INFORMATION, PLEASE CONTACT:
Morio Higashino
Minebea Co., Ltd.
4106, Miyota, Miyota-cho
Kitasuku-gun Nagano-ken
Japan
Tel: 81-.(0)267-31-1312
Fax: 81-(0)267-31-1330
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure XI-4
MINEBEA COMPANY'S WATER-BASED
CLEANING SYSTEM
FILTER ©PUMP ©FAN
bath no.
1
2
3
4
solvent
detergent
purified and deoxydized water
others
filtering
filtering
hot air
hot air
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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NON-ODS ALTERNATIVES IN THE CLEANING OF
INTEGRATED CIRCUITS AT NATIONAL SEMICONDUCTOR - MALAYSIA
I. INTRODUCTION . ,
As part of a partnership between the Malaysian Government and industry
to eliminate the use of ozone-depleting solvents in cleaning operations,
National Semiconductor in Penang, Malaysia worked closely with, the government
on efforts to find alternatives to the use of ODS in industry. This effort
lead National Semiconductor to implement changes in its cleaning operations
for Integrated Circuits (ICs).
II.' SELECTION OF AN ALTERNATIVE PROCESS
The ODS elimination efforts at National Semiconductor were a result of
active employee involvement in environmental programs, lead by company
management. The environmental efforts were coordinated by a Task Force
leader. The Task Force was comprised of representatives from a number of the
company's divisions, including, Process Engineering, Plant Engineering,
Maintenance, Material- Control, and Purchasing.
The criteria for selecting ODS alternatives included:
quality and reliability of the finished products
workplace health and safety, and environmental impact,
capital investment/Return on Investment (ROI)
Ozone Depletion Potential (ODP)/Global Warming Potential (GWP)
process flexibility, including transition to new equipment, and
worker training.
III. PROCESS IMPLEMENTATION . ' .
In the implementation stage an alternative cleaning process was
identified based on the criteria described above. In the new "Green" process,
pre-solder M-Pyrol cleaning step was replaced with a citric acid wash. In
addition, wave soldering was replaced with solder plating in the new process.
The ODS cleaning in the old process was replaced with a hot deionized (DI)
water rinse, and ambient air drying was replaced with hot air drying.
Overall, the "Green" process resulted in an increase in output from
18,300 units/hour to 84,500 units/hour. The new process resulted in very
consistent product quality, while reducing the chemical cost per unit to 1/3
of the original cost. In addition, the new process equipment was easy to
clean and maintain while the original equipment required significant effort to
clean.
IV. CONCLUSIONS
'Implementing the new cleaning system required a total capital
expenditure of $250,000/as well as special training for workers on the new
equipment. The new cleaning system not only resulted in improved cleaning at
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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National Semiconductor, but was also a positive step towards the elimination
of ODS use in all industry in Malaysia.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
X'avier HK Yoong
National Semiconductor Sdn Bhd
Bayan Lepas
Free Industrial Zone
11900 Penang
Malaysia
Tel: 60-4-837211
Fax: 60-4-833894
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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IMPLEMENTATION OF ODS ALTERNATIVES AT NAVAL AVIATION DEPOT CHERRY POINT
I. SUMMARY
The Naval Aviation Depot (NADEP) at Cherry Point, North Carolina is
responsible for a variety of aircraft maintenance activities that originally
required extensive use of ozone-depleting solvents. Since that.time, cabinet-
style aqueous parts washers, aqueous ultrasonic processing, and non-ODS
methods of cleaning parts by hand have all been significant steps towards
NADEP's goal of eliminating ODS use. While phaseout .efforts have depended
upon equipment procurement and technology development, the attitudes of the
work force and cooperation between departments within the facility have been
the most important factors in the success of the program.
II. INTRODUCTION
NADEP performs repair, overhaul, maintenance and engineering support
functions on a variety of weapons systems including the C-130 aircraft, the H-
46 helicopter, the AV-8B vertical/short take-off and'landing (V/STOL), and the
V-22 tilt-rotor aircraft.
Repair and maintenance requirements frequently required the use of a
wide variety of hazardous or environmentally harmful materials, including
ODSs. Cleaning prior to inspection, repair, testing or reassembly all r?.lied
on the performance of these types of materials. The primary substances used
in these cleaning tasks until 1990 were 1,1,1-trichloroethane and CFC-113.
Large-batch vapour degreasing with 1,1,1-trichloroethane was the
preferred method of cleaning aircraft and engine components. Fourteen
degreasers, were in use in 1990 and accounted for the bulk.of ODS usage in.the
facility. The two degreasers located in the engine cleaning shop and plating
facility alone consumed 75 percent of the 1,1,1-trichloroethane used in 1990.
Cleaning parts by hand in bench-top applications-was another activity
requiring large amounts of ODSs.
NADEP identified the largest factor affecting its overall consumption of
ODSs as being the non-critical use of ODSs in solvent cleaning. Seventy five
percent of total ODS consumption was for applications for which alternatives
were already available at the depot. For this reason, NADEP decided that its
goal should be ODS elimination, not just reduction.
III. INITIATING CHANGE
Once NADEP had finished its survey of ODS consumption in its maintenance
procedures, it developed an action plan. The plan initially focused on
training the entire workforce that NADEP's goal was to eliminate ODS use.
First, all of the product support engineers were briefed on their new .
responsibilities --to stop specifying ODSs in new engineering directives and
to review existing directives to identify ODS requirements. Production
artisans also had to be aware of the new mission since personnel in the
production shops had to be strong allies during this process. Depot
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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management also took the initiative to include pollution prevention briefings
during regularly scheduled shop safety meetings, focusing the discussion on
specific materials and processes within that shop that would be affected by
the ODS elimination.
Engineering personnel targeted the largest critical use for its initial
ODS elimination efforts -- the vapour degreasers in the plating facility and
in the cleaning shop. They required that engineering and shop personnel
accept responsibility to ensure maximum results from any expended efforts.
Engineering personnel first had to identify all uses of the vapour degreasers,
and then investigate and approve alternative cleaning processes. They also
had to be available during the implementation phase to troubleshoot any
problems that arose. Shop personnel had to be willing to try new products or
procedures and also had to be committed to working with engineering personnel
to develop alternative processes.
Management also recognized that while engineering and shop personnel
carried responsibility for.process changes, individuals from throughout the
facility would need to lend support in order to successfully implement change.
A depot-wide effort was undertaken involving personnel in facilities and
equipment engineering, capital procurement and budgeting, environmental
engineering, safety, and.maintenance.
IV. EXAMINING ALTERNATIVES
The first alternative investigated to replace vapour degreasing was
aqueous immersion using alkaline detergent. A variety of cleaning products
were tested using various temperatures, exposure times, parts orientation, and
agitation methods. After completion of testing, NADEP concluded that this
option would not satisfactorily replace vapour degreasing for its
applications.
The second alternative investigated was .a cabinet-style parts washer.
The unit applied a hot solution of aqueous detergent at pressures from 40 to
220 psi. After the initial engineering evaluation, production personnel
visited the manufacturer of the parts washer to evaluate cleaning performance
on actual parts. After they witnessed the performance of the parts washer,
they became convinced that this technology would perform adequately for their
needs and subsequently procured three units for initial implementation.
However, NADEP found during implementation that the parts washers were
not effective on all types of soil, and thus did not totally eliminate the
need for the vapour degreasers. Other technologies were investigated and
NADEP found that for the removal of carbon, wet sodium bicarbonate blast units
were more effective than the parts washers. Both open-blast and glovebox wet-
type units were procured for this application'.
Since the technologies had been so successful at supplanting the vapour
degreasers, a date was set to "lock-out"the vapour degreasers in these shops.
Engineering and shop personnel then worked to have the alternate processes
operational in time to meet this goal.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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During commissioning of the parts washers, NADEP found that, while shop
personnel were pleased with the performance of the washers, it was difficult
to handle the existing work load without .improving the design of the loading
baskets. Through trial and error, facility personnel developed round,
covered, compartmentalized baskets that greatly improved the shop's
satisfaction with the production of the new process.
While struggling to eliminate the largest uses of 1,1,1-trichloroethane,
NADEP was also evaluating the largest uses of CFC-113. The electric motor
shop was using a large CFC-113 ultrasonic unit that consumed 6,800 kilograms
per year in a relatively inefficient manner. A new ultrasonic unit, suitable
for use with aqueous cleaning solutions was implemented, which performs
equally well.
To continue its evaluation, NADEP tried cleaning parts previously
cleaned ultrasonically with CFC-113, in one of the new cabinet style parts
washers. Test results indicated that these parts were cleaned just as
thoroughly by the new aqueous parts washer but with significantly higher
throughput. The change resulted in a significant reduction in turnaround time
for the parts originally cleaned with CFC-113.
V. ALTERNATIVES FOR HAND CLEANING
Non-ODS substitutes for cleaning parts by hand have proven more
difficult to locate than substitutes for batch processes because of NADEP's
many requirements of solvents used in this application. These requirements
include: ' . /
. good performance at room temperature;
good performance without rinsing;
a flashpoint above 140° F; and
the solvent cannot contain any products from the EPA's list
of 17 high-priority toxic substances.
NADEP found some petroleum/terpene products and aqueous products meeting
MlL-C-85570 Type II to be suitable for many applications. However., these two
types of materials did not satisfy the requirements of all the depot's clean-
by-hand applications, especially some precision cleaning tasks. Processes and
materials are still being evaluated for these applications.
NADEP's current philosophy for clean-by-hand applications has been
summarized on videotape and is being used as a training supplement. The
depot's philosophy dictates the use of batch cleaning methods whenever
possible, with use of the least objectionable chemicals when cleaning by hand.
VI. REMAINING ODS REQUIREMENTS . . . ,
Oxygen system cleaning has proven to be the most difficult challenge for
ODS elimination. NADEP is working together with the Naval Sea Systems Command
and others within the Naval Air Systems Team, in the evaluation of alternative
materials and processes for this application. NADEP is optimistic that
alternatives will be identified by the end of 1994. At the request of the
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
11-41. ,
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North Atlantic Treaty Organization (NATO), the U.S. Air Force and the U.S. EPA
are organizing a global effort to solve these problems.
VII. SUMMARY
The ODS elimination effort at NADEP has been largely successful because
of the dedication of personnel throughout the facility toward meeting this
common goal. The benefits have also been shared by the entire workforce
through reduced costs, reduced turnaround time, and pride in protecting
health, safety and the environment.
VIII. FOR FURTHER INFORMATION, PLEASE CONTACT:
Ms. Mary Beth Fennell
Naval Aviation Depot Code 345
PSC Box 8021
Cherry Point, NC 28533
USA
Tel: 1-919-466-8142
Fax: 1-919-466-8108
* 1994 UNEP SOLVENTS. COATINGS, AND ADHESIVES REPORT *
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CFC-113 ELIMINATION AT NORTHERN TELECOM
.I. INTRODUCTION .
Over a period of three years beginning in 1988, Northern Telecom
invested approximately $1 million in a CFC-113 phaseout program. The
immediate payoff from this investment was $4 million. The savings came first
from conservation measures that reduced purchases of CFC-113 cleaning
solvents, and ultimately from the implementation of an innovative "no clean"
technology that eliminated the need for cleaning altogether.
When the project 'started, Northern Telecom was using 1,000 tons of CFC-
113 each year. The corporation succeeded in eliminating CFC-113 use from its
manufacturing operations worldwide in 1992, which at that time was nine years
ahead of the date set by the Montreal Protocol (The Protocol has since been
revised.). '
The business case for CFC elimination was not the initial impetus for
the project, but instead emerged gradually as the project progressed. The
decision to undertake such an aggressive environmental challenge to the
corporation came from a group, of seventy Northern Telecom engineers, who came
together at an internal CFC Workshop in 1988 to 'consider the impact of the
Montreal Protocol on the corporation's activities.
At the time, Northern Telecom, like other manufacturers in the industry,
relied heavily on the- use of CFC-113 to remove flux residue from printed
circuit boards. CFC-113 was considered the most effective cleaner available
and was relatively safe to use, with low toxicity and flammability levels.
The challenge was to find a safe alternative that would satisfy customer
requirements for high-quality, reliable products at an affordable price.
II. THE PHASEOUT PROCESS
The CFC Workshop set the ambitious goal of meeting this challenge within
three years, and a Task Force was set up to accomplish this goal. Management
commitment to the project, both from the corporate environment function and
from the operational side, played an important role in the project's eventual
success. The Task Force had access-to the most senior levels of management in
the corporation, as well as close working relationships with contacts in each
of Northern Telecom's forty-two manufacturing plants.
In order to "fast-track" the process, the Task Force was organized into
three teams, each of which took on a different assignment. One team was
responsible for finding ways to reduce CFC consumption through conservation.
Initial results from one test location were impressive, and technological
changes had succeeded in controlling loss and unnecessary evaporation of the
solvent into the atmosphere. An improved CFC-113 distribution system included
a software package, designed by Northern Telecom engineers, that monitored and
managed metering devices and leak detectors connected to the piping system.
Within months, CFC-113 requirements had been reduced by 50 percent. The
addition of activated charcoal absorption reduced the needs still further. It
was'estimated that the savings from the decrease in CFC-113 purchases would
pay for the new technology in under two years.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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A second team was responsible for finding effective and safe cleaning
alternatives. A number of options were considered, including water and
alcohol cleaning processes, and alternative solvents such as terpenes. The
feasibility assessment for each option took into account a number of variables
including: process compatibility, flexibility and performance, capital costs,
operating costs, and safety and environmental issues. In order to assess the
technical feasibility of each option, the team developed a "difficulty index"
that compared the degree of difficulty of using a non-CFC process with that of
the CFC-113 process. The economic feasibility was evaluated using the net
present value of the two processes.
The interest of this group was soon caught by the possibility of
eliminating the need for cleaning altogether. The long-term solution selected
by the team was the "no clean" process, which involves the controlled
application of a low-solids flux containing only alcohol and 1-3 percent
solids. If properly managed, the residue remaining on the boards after the
soldering process does not detract from product reliability. A board duster
can test the cleanliness of the circuit board by applying a fine spray of
powder to the surface of the board and measuring weight gain. When no weight
gain occurs, the board has met the cleanliness standards.
The crucial factor in implementing the "no-clean" process was ensuring
that customers had confidence in the new process. The third Task Force team
had been interacting with outside stakeholders in the project. They had been
sharing project progress with governments, media,. customers, suppliers,
environmental groups, and the general public. Northern Telecom manufacturing
plants had been working closely with suppliers who were developing new
chemical formulations and fluxes. In one project, Northern Telecom engineers
collaborated with chemical producers, flux and equipment manufacturers,
government agencies, industry associations, and the U.S. military on .a project
to set cleanliness standards .for circuit boards used by the military.
Customers were involved in shaping and monitoring the testing of the new
technology, and found that the resulting circuit boards were as clean as those
manufactured using CFC-113 cleaning. In fact, improvements in quality had
actually been obtained.
By December 1991, all of the locations originally involved in the
project had met the company's CFC-113 elimination target. Eight of the
fifteen new plants involved due to Northern Telecom's 1991 acquisition of STC
Pic in the United Kingdom had also become CFC-113 free. The other seven had
committed to eliminating CFC-113 use by early 1992, complying with Northern
Telecom's policy that any new acquisitions would have up to fifteen months to
meet the corporate standard.
III. TECHNOLOGY COOPERATION
Cooperation with outside groups had been a key element in the Northern
Telecom project's success. In 1989, Northern Telecom joined with o'ne of its
competitors, AT&T, and with the U.S. Environmental Protection Agency (U.S..EPA)
to form the Industry Cooperation for Ozone Layer Protection (ICOLP -- now
known as the International Cooperative for Ozone Layer Protection). ICOLP's
continuing mandate is to promote the worldwide exchange of non-proprietary
information on ozone-depleting solvent alternatives. It now has 12
multinational member companies, and has, as affiliated members, research and
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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development institutes, environment ministries, military, and noh-governmental
organizations from Canada, China, France, Japan, Korea, Mexico, Russia,
Sweden, Taiwan, Turkey, United Kingdom and United States.
ICOLP members provide experts to participate in conferences and
workshops, write technical manuals, undertake special projects, and
participate in technology cooperation projects. One of Northern Telecom's
contributions to ICOLP was the creation of OZONET, an electronic information
system on ozone-depleting solvent alternatives. The database, now part of the
United Nations Environmental Programme OzonAction database, is available via
modem from many parts of the world.
Under the auspices of ICOLP, Northern Telecom participated in a 1991
technology cooperation project, working in partnership with the Government of
Mexico, the Mexican association of industries, and the U.S. EPA. The project
was designed to help the Mexican electronics industry eliminate the use of
ozone-depleting substances through workshops and on-site technical assistance.
The collective efforts of the partners in the program have achieved
substantial success -- a 70 percent reduction in ozone-depleting solvent use
in Mexico. The program has also introduced Mexican manufacturers to the
latest and best alternative technologies, thereby improving their competitive
advantage in the global economy.
In 1993, the World Bank agreed to provide ICOLP with money from the
Multilateral Fund set up under the Montreal Protocol, to help ICOLP launch a
"global solvents" project. This money has paid for part of the cost of
technology cooperation initiatives that have since been launched in seven
countries. On each project, one or more ICOLP companies have taken the lead
in managing activities in cooperation with a designated host country agency.
Motorola led an initiative in Malaysia, and IBM took the lead in Korea and
Taiwan. Other ICOLP companies have partnered with the Japan Electric
Manufacturing Association and the Japanese Ministry of International Trade and
Industry to lead a cooperative effort with industry and the government of
Thailand. This year, the Ministry of the Electronics Industry in China agreed
to work in partnership with Northern Telecom on a program to help the Chinese
electronics industry eliminate the use of ozone-depleting substances.
Northern Telecom served as project manager for an initiative' in Turkey, will
lead workshops in India, and is starting to plan projects in Brazil and
Vietnam. . .
Northern Telecom's leadership in CFC-113 elimination and its willingness
to share its experience have brought it international recognition, including
three prestigious awards: the U.S. Environmental Protection Agency's
Stratospheric Ozone Protection Award, the United Nations Environment
Programme's North American Leadership Award, and the U.S. President's
Environmental and Conservation Challenge Award for Innovation.
IV. CONCLUSION '
While the environmental challenge set by the Montreal Protocol was the
spark for this ambitious project, Northern Telecom has seen direct business
benefits. These include direct cash savings, a heightened international
reputation for environmental leadership, and improved relationships with
customers, suppliers, government agencies and other stakeholders. This
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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experience has created an atmosphere of management support for environmental
projects, and opened the door for new initiatives in such areas as product
life cycle management and environmental management systems.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Elizabeth H. Rose
Northern Telecom
3 Robert Speck Parkway
Mississauga, Ontario L4Z 3C8
Canada
Tel: 1-905-566-3270
Fax: 1-905-566-3348
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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REPLACING SOLVENT CLEANING WITH AQUEOUS CLEANING AT
ROBERT BOSCH CORPORATION
I. SUMMARY
/
Robert Bosch Corporation's Charleston, South Carolina plant has been
successful in replacing ODS cleaning solvents with non-chlorinated solvents.
The technologies implemented have all cleaned as well or better than the
original chlorinated solvents and have done so with reduced capital costs and
similar or reduced labour costs. This result is due in part to the fact that
ODS usage has been eliminated at a time when ODS prices have more than
tripled. In addition, by using this opportunity to implement more energy
efficient technologies in the phaseout process, the electric costs for its
cleaning processes have been cut in half. Bosch is convinced that the time
and resources already spent in converting from chlorinated solvents have been
a good investment, and the company will continue to pursue these activities
until all trichloroethylene (TCE) and hydrocarbon solvents have been replaced.
To date, Bosch has eliminated all CFC-113 usage and .two thirds of its
trichloroethylene (TCE) usage. The company's goal is to be completely free of
chlorinated solvent usage by the end of 1995. These changes in cleaning
processes have not only responded to the environmental goals of the Montreal
Protocol and EPA's 33/50 Program, but 'have also resulted in improved cleaning
at significantly reduced costs.
II. INTRODUCTION
The Robert Bosch Corporation is a U.S. subsidiary of Robert Bosch GmbH
of Stuttgart, Germany. Bosch's Charleston plant manufactures automotive
products and is the largest plant in the U.S. subsidiary, with about 1,700-
people working in 600,000 square feet of manufacturing space. The plant has a
heavy engineering emphasis in support of its assembly and test functions.
The primary products produced in the plant are gasoline fuel injectors,
anti-lock brake systems, and diesel fuel pumps. The metal parts manufactured
in the plant were cleaned with CFC-113 and TCE. The company plans to
eliminate the use of TCE in support of the EPA's 33/50 Program and in response
to the availability of improved cleaning efficiency and product performance
associated with new replacement cleaning technologies. Eliminating
chlorinated solvents on'the production floor required a large team effort.
Team participants included the plant manager, planners and users of the
solvent replacements, and other support personnel.
The implementation of non-chlorinated solvents began in early 1990. By
the end of 1992, all CFC-113 use had been eliminated by'adopting alternative
technologies. These processes are continually being reevaluated and improved;
certain types of replacement processes described have been superseded by newer
measures, and additional upgrades will continue to be introduced.
A key decision made early in the process was to replace the Company's
large aging central degreasing stations with a number of small cleaning units,
each designed and dedicated for cleaning just one type-of part at one step in
the product assembly process. This strategy required reassessment of each
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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cleaning step and the identification of equipment and chemistry for optimizing
each aqueous replacement.
As a result of this decision, annual use of approx. 247,000 kg of CFC-
113 use has been eliminated at the Charleston plant, along with the approx.
41,000 kg of TCE. In addition, major cost savings have been realized by
implementing more energy efficient aqueous cleaning technologies. The
Company's records indicate that the combined costs of chemicals and
electricity have been significantly reduced, reflecting both the elimination
of all CFC solvent cleaning as well as the switch from a few large central
cleaning stations to many small dedicated cleaning units.
III. DESCRIPTION OF PARTS CLEANED AT THE CHARLESTON PLANT
Most of the parts cleaned in the plant are for two assemblies: a fuel
injector and an anti-lock brake system. Some parts are cleaned more than once
during the assembly process, resulting in over 30 separate cleaning
operations. The parts to be cleaned generally consist of mild steel,
stainless steel, plastic, and rubber, and contamination to be removed
typically incudes metal chips and fibres, grinding coolants, shop dirt,
chemical residues, and fingerprints.
Cleaning operations at Bosch include both gross cleaning and precision
cleaning. Gross cleaning is carried out on the open production floor, and
precision cleaning is performed in the Class 10,000 clean room where final
assembly takes place. Inadequate cleaning can compromise product performance
and may result in failures. While the cleaning requirements are less than
those of the semiconductor or disk drive industries, part cleanliness at Bosch
means more than simple washing or scrubbing in soap and water. Particles
larger than about 25 /tm are of concern and are targets for removal by the
cleaning process.
IV. PREVIOUS SOLVENT CLEANING TECHNOLOGY AT THE CHARLESTON PLANT
In 1988, all cleaning operations for manufacturing were performed using
either CFC-113 or TCE. Typically these cleaning steps were carried out in
large centrally located degreasers. Eight units used TCE and seven used CFC-
113. These degreasers were off-the-shelf, commercially available units, and
all included some form of solvent recovery. The units used combinations of
spray and ultrasonic agitation in addition to vapour degreasing to dislodge
the contaminants.
Both the TCE and the CFC-113 units served as general purpose cleaning
stations for the various cleaning steps required in manufacturing. Parts
passed through the cleaning station in their order of arrival, and .the
throughput time for baskets containing a total of 27 to 45 kg of parts was
typically about 40 minutes. In this operating mode, solvent consumption in
1988 was 247,000 kg of CFC-113 and 60,000 kg of TCE.
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V. OPTIONS FOR REPLACING CHLORINATED SOLVENTS
Options considered for replacing chlorinated solvents included "no-
clean" , other organic solvents, aqueous cleaning, and supercritical carbon
dioxide. The most desirable option considered was the no-clean option. In
evaluating no-clean manufacturing, the cleaning step was first examined to
determine if cleaning was absolutely necessary. Sometimes the cleaning step
can be eliminated with minor or no changes to the rest of the manufacturing
process. Successful replacement of a chlorinated solvent with a no-clean
process is a relatively rare event, but has large benefits in reduced costs
and cycle time.
An example of this type of process change at Bosch was the replacement
of solvent cleaning of a part between two machining steps. In the no-clean
process, the oil-based lubricant is centrifuged off the parts, eliminating the
wash and rinse cycles formerly used to clean the part. This eliminated a
waste stream and, reduced the cycle time, chemical usage, and floor space
required. The implementation of this no-clean technology was the result of an
idea originated by shop floor manufacturing personnel.
For those operations for which no-clean technologies were not feasible,
Bosch chose to bypass interim alternatives such as hydrbchlorofluorocarbon
(HCFC) solvents. It 'also was decided not to revert to the hydrocarbon
cleaners used in earlier years. The Company's decision was to immediately
address the long-term environmental issues associated with cleaning and to
develop cleaning methods that would be as permanent as could be conceived
under current knowledge and regulations.
The next option considered was aqueous cleaning. Aqueous cleaning with
deionized water has proven very effective, especially when customized for a
specific cleaning step on a specific part. The costs of deionized water
cleaning become affordable when used in the limited quantities required by
small, dedicated cleaning stations that incorporate reuse of the water before
discharge. Bosch team members decided that parts cleaning could best be done
with small custom cleaners dedicated to one or a few cleaning steps, which was
a major change from the large central cleaners of 1988. This change
eliminated any possibility of cross contamination, shdrtened cycle times, and
allowed better matching of each cleaning process to the specific part and
contaminants. The switch from large central cleaners to small custom units
has improved part cleaning efficiency and reduced solvent losses. The
introduction of single function washers for critical cleaning tasks was made
easier by the fact that much of the existing cleaning equipment was 10 years
old and in need of replacement. Particles larger than 500 /im were not being .
removed from parts in some of these units, and the Company felt that
retrofitting or modifying the existing equipment would have been both
expensive and short-sighted. Selecting new, customized equipment, however,
required careful analysis of many cleaning steps..
^ ' ,
The team reviewed other options for replacing chlorinated solvents, but
did not select them for testing. Some, like supercritical carbon dioxide
cleaning, were expensive and not production-ready. The primary reason for
dismissing other options, however, was that aqueous replacement technology .had
more advantages and fewer potential drawbacks.
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VI. CLEANING PROCESS SELECTION
Bosch uses two tests to evaluate the cleanliness of parts and the
effectiveness of cleaning techniques. The first is a visual inspection.
Parts are inspected for contaminants including fibres, dust, and machining
debris. In a second test, lots are periodically audited by a five minute
ultrasonic extraction of one basket of parts from the lot in petroleum
distillate. The particles released during the extraction are collected on a
filter with a 5 /urn pore rating and weighed to assess cleanliness. Control
charts plotting reject rates from both the visual inspection and the
extraction test monitor the efficiency of the cleaning process.
Supporting tests may be carried out in a vendor's facility but vendor
data have generally played a minor role in the replacement team's decisions.
Time lapses between vendor cleaning and evaluation at Bosch hinder the use of
this approach. New process evaluation at Bosch is typically performed on
production equipment made available for tests during off-peak hours. Either
an existing production unit is modified or adapted to a new process, or a
prototype production unit is ordered from a vendor. Modifications and fine
tuning are then carried out on the production scale units before the new
process is incorporated into an ongoing production line.
VII. HARDWARE SELECTION
Solvent replacement selection at Bosch has always started with the
selection of the cleaning process and associated hardware, such as
ultrasonics, high-pressure spray, or turbo washing, rather than the selection
of a cleaning solvent or fluid. .The argument for this approach is that there
are hundreds of chemicals to choose from but only a handful of cleaning
processes.
To rapidly identify suitable aqueous cleaning hardware, Bosch first
investigated off-the-shelf washing equipment. If off-the-shelf units proved
ineffective or were not available, Bosch retrofitted existing equipment or
engineered custom units of its own design. In one application, it converted a
low-pressure spray washer to high pressure; in another, a high pressure unit
was modified to use water instead of CFC-113. A turbo washer has also proven
successful in aqueous cleaning of certain parts, but no single piece of
hardware has been suitable for all cleaning applications.
Drying following wash and rinse was a sensitive issue for Bosch.
Functional requirements typically require that all water be removed before the
next operation. Removal of water by heating the parts often produced
unacceptable spotting. Centrifuging at,room temperature aftep aqueous
cleaning has now become the drying technique adopted almost universally by
Bosch. The centrifuges used provided the option of warm air circulation
during the spinning, but this drying assistance has often not been necessary.
VIII. CHEMISTRY SELECTION
Compatibility of a chemistry with a part is determined by the Bosch
chemical and metallurgical laboratories. These tests for chemical
compatibility and absence of part degradation take 24 to 96 hours and are
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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conducted before introducing any chemical into production. Safety
considerations (flammability or toxicity) caused some solvents to be
eliminated from consideration. The production floor itself then became the
laboratory for final acceptance tests. Reasons for rejection included poor
cleaning in production and objections from production personnel concerning
solvent odour or part appearance after cleaning.
All but one replacement solution adopted to date has consisted of
deionized water alone or deionized water with an alkaline cleaner. The
specific additives and surfactants used in the cleaning steps were selected to
be compatible with the part being cleaned, the soil being removed, and the
cleaning equipment used. These decisions involved experimenting with various
proprietary products to confirm rust protection and satisfactory soil removal.
For example, oil-based lubricants are used for machining the parts. The parts
are cleaned in aqueous systems with chemistries that allow the oil removed to
separate from the water. Oil is then removed from the tanks in most
operations by skimming or gravity separation in holding tanks, and is
subsequently shipped off-site in sealed containers for disposal.
Parts cleaned by an aqueous.replacement method typically had a different
feel and appearance than those cleaned with a chlorinated solvent. They
appeared dull and often had a different colour and some visible water spots.
These obvious differences worried production personnel who were slow to accept
the new cleaning process until they adjusted to the new acceptance tests and
received assurances from the Quality Gauging Department that the new cleaning
process was adequate. Only after a transition period, which varied frop part
to part and was as long as six months, did production personnel accept
ownership of the new cleaning apparatus. Until this confidence was built, all
breakdowns, equipment, and performance problems were immediately passed back
to the replacement team. Once transfer of ownership was completed on one
part, acceptance for other parts developed more easily and quickly.
IX.. FOR FURTHER INFORMATION, PLEASE CONTACT:
Mr. Charles H. Darvin
U.S. EPA
Air & Energy Engineering Research Lab, MD-61
Research Triangle Park, North Carolina 2771V
USA
Tel: 1-919-541-7633
Fax: 1-919-541-0361
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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USE OF A LOW RESIDUE FLUX IN A MILITARY ELECTRONICS PROGRAM
I. SUMMARY
Rockwell Tactical Systems Division (TSD) and the U.S. Army Missile
Command collaborated in a fifteen-month long evaluation of low-residue fluxes.
The evaluation was specific to the options for the AGM-114 Hellfire Missile
assembly line, and two of the new fluxes tested were eventually qualified for
use. In July 1993, 'Hellfire became the first U.S. Army production program to
implement low-residue flux technology. Today this technology is used in all
of the assembly line's processes: wave soldering, lead tinning and hand
soldering.
II. INTRODUCTION
In developing its ODS elimination program, Rockwell TSD first conducted
an ODS usage survey. The survey revealed that its greatest use of ODSs
involved rosin-based flux removal. 1,1,1-Trichloroethane was being used in
batch degreasers, in-line solvent .cleaners, and for manual brush cleaning,
with consumption levels at 32,000 kg per year.
The objectives of the program were to:
minimize the number of new chemicals brought into the
division; <
keep capital expenditures for new equipment low;
maintain weapon system performance and reliability; and
minimize the impact of implementing a new cleaning
technology on a production line that consistently produced
defect-free circuit cards (CCAs).
Rockwell TSD produces several products for the Army and the Air Force,
so in selecting a candidate production line for its first alternative
technology trial, the company had many products to choose from. Since its
highest volume product was the Hellfire Missile, this choice offered the most
hardware for testing. Although all the Hellfire circuit cards are strictly
through-hole (no surface-mount) ,. some contain high density areas of moisture-
sensitive circuitry. It was felt that Hellfire hardware would provide "worst-
case" 'testing, and data collected during testing could be applicable to the
other programs.
In formulating the ODS elimination program, a number of strategies were
considered. The company first considered solvent-based technologies as a
replacement for 1,1,1-trichloroethane. However, this proposition had several
problems. For example, many alternate solvents:
are hazardous to some degree;
are expensive to produce;
require special handling;
require special storage conditions;
require costly disposal techniques;
. are relatively new with, little usage history;
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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are undesirable for global warming, toxicity, or other
reasons; or
require expensive equipment for use.
Rather than focus on finding and testing solvent replacements for 1,1,1-
trichloroethane, Rockwell decided that a preferable'approach would be simply
to eliminate use of rosin flux. Preliminary lab tests were performed with
both no-clean (low-residue) and water soluble fluxes. Five non-rosin no-clean
fluxes and six water-soluble organic acid fluxes were selected for the initial
test. These preliminary tests evaluated:
capability to solder plated-through-holes;
effectiveness in tinning aged component leads;
ionic cleanliness following a warm deionized water rinse;
and
solder mask effects..
The soldering performance for most of the flux samples was found to be
adequate with two of the no-clean fluxes having outstanding results. While
not expected to match the performance of the organic acid -(water soluble)
formulations, the no-clean fluxes surpassed the RMA-type flux used as a
control. With this finding, Rockwell decided to only continue testing the top
two no-clean fluxes, thereby avoiding the problems associated with removing
organic acid residues caused by their corrosive characteristics.
One early finding was that the no-clean residues interfered slightly
with the adhesion of some conformal coatings. This problem was resolved by
washing the residues off with a saponified water cleaner prior to coating.
Based oh this favourable preliminary data, a straw-man qualification
plan was presented to the Army's Missile Command, Hellfire Project Office,
and Product Assurance Directorate. The Army agreed to partner with Rockwell
TSD and co-sponsor the qualification effort. * .
III. FLUX QUALIFICATION
A solder lab was established exclusively for the purpose of evaluating
flux performance on coupons and circuit cards, providing the ability to
conduct the study without exposing deliverable hardware to non-compliant
chemicals. This lab was equipped with an Electrovert 400SV wave solder
machine, a Branson precision batch cleaner, and a Zero Ion cleanliness tester.
Manual soldering stations were set up to allow assemblers to try the new low
residue cored-wire fluxes in simulated touch-up practices.
A test scenario was developed from available information. At the time
of this evaluation design, no documentation existed with definitive DoD flux
qualification requirements (although Bellcore had a TSY document that was
available, and a draft of MIL-STD-2000B offered a test plan). Criteria was
established and agreed upon by all Army and Rockwell team members. Following
is a brief description of the tests that were performed in the qualification
effort.
Surface Insulation Resistance (SIR) Testing. Pre-cleaned IPC B-24 Test Boards
were prepared-by fluxing and wave soldering with the comb patterns in the
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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bottom-side and top-side configurations. Some test boards were cleaned using
a saponified water wash; the rest were not cleaned. Hand soldering was also
performed on test boards using the equivalent flux formulations in cored
solder wire. RMA fluxed and soldered test boards were tested along with the
new flux boards. Pre-cleaned non-soldered test boards were used as controls.
The test consisted of subjecting the boards to 85°C and 85% relative
humidity conditions for 28 days with a 50-volt DC bias applied. A reverse
bias of 100 volts was placed across the comb pattern and resistance
measurements taken every 24 hours. All patterns were continuously monitored
for any resistance breakdown caused by dendritic growth across conductor
patterns. Boards successfully maintained SIR values well above the IxlO8 ohm
requirement.
Corrosion testing. This test was performed using the standard copper mirror
method described in IPC-TM-650. Both fluxes were certified to be halide-free
by their respective manufacturers.
Production hardware testing (CCA). Hellfire circuit cards with known
sensitivities to moisture were assembled using the new fluxes. They were then
subjected to the maximum expected.system temperature (63°C) and 85% relative
humidity for seven days, while under the 12 volt potential normally used in
operation. No flux related anomalies were observed.
System Qualification Testing. As a final test for the Hellfire system, all
CCAs were soldered with the new fluxes and assembled into the respective upper
level modules using the no-clean wire'solder. Modules were powered (18 VDC
and 28 VDC) and subjected to 63°C and 85% relative humidity conditions for
seven days. Following this treatment all modules were inspected and found to
be functionally sound.
IV. FACTORY IMPLEMENTATION
On July 28, 1993, Rockwell converted the Hellfire production line to no-
clean or low-residue flux. All rosin fluxes and rosin-cored solders were
removed from the work stations. Several months prior to this activity, a task
group from Operations had generated a comprehensive checklist of all items
that would be affected by the flux change as part of an implementation plan.
Rockwell addressed those processes affected by the flux and processes that
relied on the use of 1,1,1-trichloroethane, which was to be eliminated after
the new flux was introduced. The company's plan detailed each activity and
listed its priority, the person(s) responsible for the'activity, and a
schedule for completing the activity.
Examples of items affected by the plan were:
process sheets;
training manuals;
new chemical forecasts;
waste disposal; and
new process control procedures/equipment.
During the testing phase, it was determinedthat spraying was the
optimum method to apply flux. Therefore, the receipt and installation of a
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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spray fluxer was a major item on the list to be completed. Because low-
residue flux is contained in a sealed reservoir, no significant evaporation
occurs, reducing the need to monitor flux consistency. In addition, no flux
need ever be discarded due to contamination or oxidation. Solder defects on
the evaluation assemblies were .very low (one. to two defects per card), but
higher than those with the RMA process (normally averaging 0.7 defects per
card, or-99.9% defect free). Initially, the number of defects using the no-
clean flux averaged around 6 per card. However, by fine-tuning the process
over a four month period, defect levels were reduced to below the best results
achieved with RMA-type fluxes.
The fumes from the new flux were found to be irritating to some
employees. Fume extractors were installed on the soldering irons to rectify
this problem. Many operators have found that in most cases, the new solder
wire performed better than the RMA-cored wire, with the exception of tinning
stranded wires. None of the low-residue' fluxes have been found to adequately
tin the inner strands and prevent "birdcaging."
V. OBSERVATIONS AFTER EIGHT MONTHS . .
The decision to-use low-residue flux has proven to be the best option
for Rockwell TSD. Defect levels have generally remained at or below those
experienced with RMA fluxes. It is important to note the low-residue flux is
less "forgiving" than rosin-cored flux. When, parts were highly solderable,
few problems with the low-residue flux were encountered; however, when parts
were marginally solderable, low-residue flux performance was not so good.
Problems with solderability typically have been traceable to isolated lots of
boards or components. . ' t
As mentioned previously, solder-plated stranded wire is very difficult
to tin with the new flux. The use of higher levels of flux solids and
ultrasonic solder pots have failed to solve the problem.. However, silver- ,
plated stranded wires appear to tin very well.
Wave solder processes established for the rosin fluxes tend to evaporate
the low-residue fluxes too quickly, resulting in a very dry board and poor
through-hole wetting. In addition, the low-residue fluxes to increase the
amount of solder dross generated. Dross reducers are being used to alleviate
this problem. An inert atmosphere may also help, but has not yet been tested.
The anticipated change in solder joint shape and brightness did not appear, so
a recalibration of inspectors was not required. Finally, since the' fumes were
more irritating than those of the RMA-type flux, ventilation was increased,
especially around the spray fluxer areas, and hand solder work stations.
In addition to being a technical success, this project has demonstrated
the achievements possible by a cooperative effort between government agencies
and industry.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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VI. FOR FURTHER INFORMATION, PLEASE CONTACT:
Ralph Vaughan
Rockwell International Corporation
Tactical Systems Division
1800 Satellite Boulevard
Duluth, GA 30136
USA
Tel: 1-404-497-5222
Fax: 1-404-497-5555
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THE CLEANING CENTER SYSTEM OF SEIKO EPSON CORPORATION
I. SUMMARY
Almost all manufacturers share production responsibilities with
suppliers. This allows them to "borrow" individuals with technical
experience, maximizing the efficiency of their own human resources. Under
this co-production arrangement, manufacturers can make high-quality products
faster and at. lower cost than otherwise possible. This arrangement also lends
itself to solving shared problems, including environmental problems such as
ozone depletion.
Without such cooperation, small- and medium-sized companies may have
difficulty in finding ways to establish alternative technologies and introduce
new equipment without interfering with production. In addition, they may be
hampered by:
poor investment payback;
limited floor space; ., . '
lack of technical expertise regarding cleaning machinery and
solvents, making them overly reliant on equipment/solvent
manufacturers for technical assistance; and
a small labour pool with few,engineers.
Given these limitations, small- and medium-sized companies may not be
able to eliminate use of ODS on their own. Moving to alternative cleaning
processes is not simply a matter of transferring technology from larger
companies. The Cleaning Center System of Seiko Epson is designed to address
these problems.
II. INTRODUCTION
Like many other small- to medium-sized companies, Seiko Epson has opened
a cleaning center equipped with non-ODS cleaning equipment. Seiko Epson has
invited many of its parts suppliers to share the use and expenses of this
cleaning center. The center is designed to eliminate ozone-depleting
substances from production processes.
III. THE CLEANING CENTER SYSTEM
The Cleaning Center is a way to share ODS-free cleaning equipment with
suppliers of Seiko Epson. The primary benefit of a common cleaning center is
an opportunity to share costs while preventing pollution. The system is.
described in. Figure XI-5 using the printed circuit board manufacturing process
as an example.
First, Seiko Epson supplies the subcontractor (supplier) with printed
circuit board (PCB) parts. The subcontractor then mounts these parts oh PCBs.
Next, the mounted PCBs are transported to Seiko Epson to be cleaned by Seiko
Epson's ODS-free cleaning process. After the boards have been cleaned, the
subcontractor transports them back to its own plant, inspects them and makes
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT * ,
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FigureXI-5
SEIKO EPSON CLEANING CENTER SYSTEM
SEIKO EPSON CORP.
PARTS CONTROL
MANUFACTURING LINE
THE CLEANING CENTER
/ MO\
MOVEMENT OF
VPARTS TO BE CLEANED/
MANUAL
INSERTION
SOLDERING
INSPECTION/
REPAIR
SUPPLIERS
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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any necessary repairs. Finally, the finished products are delivered to Seiko
Epson. ' ;
In the present arrangement, the CDS-free cleaning equipment is used 24
hours a day. From 8:30 AM to 5:00 PM, products entirely manufactured by Seiko
Epson are cleaned. The remainder of the day is scheduled for supplier use,
with employees of Seiko Epson running the cleaning operation. Suppliers can
deliver dirty parts and pick up clean parts 24 hours a day.
The layout of the cleaning operation is shown in Figure XI-6. Some
general technical information about the cleaning equipment is given below:
System size: 1.6 m X 5.86 m.
Conveyor speed: 0.8 m/min.
Cleaning capacity: 1.6 to 1.7 million parts/month.
USQ restricted to glass epoxy circuit boards with maximum
width of 400 mm constructed using lead wires or SMT.
Parts can extend up to 80 mm from the surface of the
conveyor belt. . ' .
Pure water feeding device: 30 litre ion replacement tower.
Pure water control ration resistance value:, 1 us/cm.
Two-tiered float switch used to monitor water levels in each
bath. . . . -
The bath configuration is in-line and uses- a conveyor belt. It has
showers that simultaneously clean the top and bottom surface of printed
circuit boards. The system has three zones - saponifica.tion, rinsing, and
drying. It uses a closed system so wastewater treatment is not required, and
the cleaning machine works for more than one specification1of circuit board.
The speed of the cleaning machine can be adjusted such that only one person is
required for normal operation of the system.
IV. ISSUES
Each supplier is responsible for controlling its produces. A cleaning
order is attached to each lot of products and all work is carried out on the
basis of the order.
Some advantages of the system and equipment-sharing arrangement include:
high equipment investment efficiency;
better cleaning results than old system;
.consistent cleaning quality;
lower cleaning costs; and
lower expenditures for energy and solvents.
Disadvantages include longer lead times and higher transportation costs
since suppliers are required to transport their products to the cleaning
center. Prior to their use of the Seiko Epson Cleaning Center System, the
cleaning process was integrated into their own manufacturing system. The
Cleaning Center was designed for 24-hour-a-day operation to help alleviate
these higher costs.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Figure XI-6
CLEANING CENTER LAYOUT
BARKING TERMINAL
I HADING DUCK
KIR SUI'Pl.lbRS
PRODUCTS
STOCK AREA FOR
CLEANING PRODUCTS
Conveyor belt -
transporting
cleaned products
I
Cleaning Machine
I.UADINli IXK.K
KOR SlilKOKI'SON
I'RODl'CTs
SEIKO EPSON
MANUFACTURING
PROCESSES
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Prior to the Cleaning Center opening, suppliers picked up Epson-supplied
parts and delivered finished products. Under the common cleaning center
arrangement, however, they were initially required to make an extra trip in
the middle of the production process to have their products cleaned. This
factor increased their transportation costs. To maintain transportation costs
at the previous level,t Seiko Epson adjusted its delivery schedules' so that a
truck runs a regular route that covers all suppliers twice a day. In the
first round, Seiko Epson delivers cleaned parts to the suppliers and picks up
finished products. In the second round, Seiko Epson delivers parts to be
packaged and picks up boards to be cleaned.
V. CONCLUSION
Smaller enterprises may sometimes need the cooperation of larger
companies if they are to achieve a total phaseout of ODS before the January 1,
1996 deadline. Seiko Epson believes the common cleaning center arrangement is
an effective way to help small- and medium-size companies eliminate ODS.
Seiko Epson also believes that the Cleaning Center System can be easily
applied to many industries in many countries. The company recommends
retaining technical experts in the various relevant fields during the
transition period to efficiently manage any problems that may arise.
VI. FOR FURTHER INFORMATION, PLEASE CONTACT:
Kaichi Hasegawa
General Administrative Manager
Environmental Affairs Manager
Seiko Epson Corporation
3-5, Owa 3-Chome, Suwa-Shi
Nagano-Ken, 392 Japan
Tel: 81-266-52-3131
Tel: 81-255-58-0416 (direct)
Fax: 81-266-58-9584
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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THE ODS-FREE VERIFICATION SCHEME FOR SINGAPORE INDUSTRY
I. INTRODUCTION
The project to develop an ODS-Free Verification Scheme was begun in June
1993 by the Singapore Institute of Standards and Industrial Research (SISIR)
as a means for companies to demonstrate (via third-party proof) that they are
not using ozone-depleting substances in their manufacturing processes. The
Scheme is open to local manufacturers in Singapore and has t le support of the
Singapore Economic Development Board (EDB) and multinational companies (MNC)
through the Local Industry Upgrading Program (LIUP). MNCs and large local
companies contribute program managers to LIUP in the planning and
implementation of programs for upgrading the technology and business of local
vendors.
The SISIR Scheme provides several services to companies.
It provides public recognition for companies who have phased out
ODS in their manufacturing processes.
It provides MNCs and international purchasing offices (IPO) in
Singapore with a source of independent verification and eliminates
the potential for multiple audits.
It makes it easier for participating companies to export products
to countries such as the U.S., since the U.S. Clviau Air Act
requires the labelling of imports that are manufactured using
substances which are harmful to the ozone layer.
It provides technical assistance from SISIR to companies who are
switching to ODS-free alternatives as well as corr"ltation on the
means to obtain verification.
SISIR's Chief Executive, Mr. Khoo Lee Meng, believes that no other
signatory to the Montreal Protocol has a national verification scheme similar
to that established in Singapore.
II. REASONS FOR THE ODS-FREE VERIFICATION SCHEME
The industry's need for an independent, third-party verification scheme
was identified through the LIUP's network of MNC-partners. The necessity for
this type of verification scheme arose as a result of the following issues:
The current worldwide 'green' movement.
The imposition of the ODS phaseout schedule under the Montreal
Protocol.
Many of Singapore's trading partners require imports to be
ODS- free.
III. VERIFICATION PROCEDURE
Companies participating in the verification scheme follow an established
procedure:
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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The applicant company submits flow charts, discloses the chemicals
used in th .aufactu: _ process . nd indi if th< .-any
has obtained or is seeking.ISO 9000 certification.
SISIR conducts audits of the company. SISIR examines supporting
documents and doc'nnentation ~-ocedures, -nd tests sap^is of
chemicals employed in manufacturing to verify that .no ODSs are
being used.
Following initial certification, the company is periodically
surveyed to ensure compliance with the terms and conditions of the
Verification Scheme.
The verification procedure costs local companies between U.S.$4,000 and
U.S.$8,000. To help local companies defray the cost of verification, the EDB
offers financial assistance under the Local Enterprise Technical Assistance
Scheme (LETAS). Grants of up to-70% of the cost are -Carded to companies who
seek verification before December 1994: After December 1994, grants of up ^to
50% of the cost will be available to companies.
IV. SUCCESS OF THE VERIFICATION PROGRAM
Companies cited a variety of reasons why they participated in the
verification program. For example, New Electronic Technology joined the
Scheme because several of its customers ship their products to the United
States and these products need to be labelled. Micro-Team Industries, which
used solvents to chemically coat electronic parts and other objects with
metal, stopped using these solvents in order to protect the health of their
workers. SEA Trading Co. said they participated to demonstrate to the public
their belief that environmental protectioti .is important.
Since the verification program began, more than 40 companies have
expressed interest in seeking verification. As of March 1994, eight companies
had received verification. As of August 1994, Leica Instruments, a
multinational company which produces precision optical components, had been
successfully audited. Another multinational company, SONY Display Device,
which produces colour television tubes, is ready for the pre-award audit. In
addition, thirty companies are currently in various stages of application for
verification.
The eight companies which have received certification for having stopped
using ODS in their manufacturing processes are primarily plastics moulding and
electronics components manufacturers. Six of these eight companies are in the
EDB's LIUP: . .
Hi-P Tool & Die
Next Electronic Technology
Mould Technic
Micro-Team Industries .
Joetsu Engineering Plastic
Chartered Electronics Co.
The remaining two companies which received certification are:
Singapore Asahi Chemical & Solder Industries
SEA Trading Co. '
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table XI-1 presents more detailed information on each of these eight
businesses.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Dr. Stephen Lai
Singapore Institute of Standards and Industrial Research.
1 Science Park Drive
Singapore, 0511
Tel: 65-772-9548
Fax: 65-777-1765
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table XI-1
SUCCESSFUL ODS ELIMINATION IN SINGAPORE
Name of Company
No. of Employees
Type of Business
HI-P Tool & Die Ltd.
75
Mould design &
fabrication for
injection moulded
plastic parts for
electrical industries.
Next Electronic
Technology Pte Ltd.
303
Contract manufacturing
of PCBs, flexible
circuits, & ceramic
hybrid modules.
Mould Technic Pte Ltd.
56
Design & fabrication of
precision moulds and
plastic injection .
moulded parts primarily
for medical industry.
Micro-Team Industries
Pte Ltd.
33
Electrolysis nickel
plating of metals and
plastics, chemical
conversion of metals, &
passivation of steels.
Jpetsu Engineering
Plastic Pte Ltd.
15
Mould design and
'fabrication, 'precision
engineering plastic,
injection moulded parts
for audio, computer,
electrical, &
electronic component
manufacturers.
Chartered ^Electronics
Co. Pte Ltd.
110
Wire harnessing and
electronic parts
assembly.
Singapore Asahi
Chemical & Solder
Industries Pte Ltd.
40
Manufacturing solder
paste, bars, wires,
anodes, soldering
fluxes, and chemicals
for electronics
industry.
SEA Trading Company Pte
Ltd.
38
Manufacturing
polystyrene disposable
products.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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ELIMINATING THE USE OF ODSs IN SWEDEN
I. INTRODUCTION
In 1988 the Swedish Government, after consultation with industry,
industrial and trade associations, and concerned agencies, passed a law
mandating a complete phaseout of ozone-depleting solvents (ODS) in all end-
uses by the end of 1995. This was the first complete phaseout schedule
proposed worldwide.
The task of implementing the overall phaseout of ODSs in Sweden was
delegated to the Government to the Swedish EPA (SNV). In light of the global
nature of the hazardous impact of ODSs, a vital component of the Swedish
strategy was to transfer experiences from the Swedish phaseout to other
countries and thus strive for an early global phase out of ODS substances.
II. EVALUATING ODS USE
It was believed that although the amount of ODS used and emitted in
Sweden was small, and the direct impact on improvement of the ozone layer
would also be small, the diversity of the Swedish industrial structure and
application areas for the CFCs was as complex as any of the larger users of
ODS. Consequently the experience gained by Sweden from the phaseout would be
valuable to other major users.
Of the various ODS-use areas, the solvents sector is generally
considered to be among the most sophisticated and complex. The major users of
ODS-solvents are the electronics, telecommunications, aerospace, defense and
general engineering sub-sectors. Consequently, ODS solvents were believed to
be difficult to replace. The Swedish Legislation called for the solvent
sector to be addressed first and mandated a 100 percent phaseout by January 1,
1991 -- four years ahead of the national phaseout.
III. PHASEOUT PROGRAMMES
The SNV developed the solvent phaseout implementation programme by
cooperating with the concerned Nordic industries in a number of R&D
programmes. These programmes called for the assessment of alternatives and
investments in some new technologies. Two major programmes were the TRE
(Teknik f6s Ren Elektronik) and AMY (Avfetlning av Metallytor) projects.
These projects addressed alternatives and reliability issues. The US$3.5
million programmes were co-financed by industry (e.g., electronics,
telecommunications, aerospace companies -- Ericsson, ABB, FFV, SAAB,
Electrolux, NFT, Norsk Hydro); governmental authorities (e.g., SNV (Sweden),
The Norwegian State Pollution Control Agency, The 'Danish Ministry of
Environment, The Swedish Defence Procurement Authority); research and
development institutes (IVF (Sweden), YKI (Sweden), MRI (Sweden), EC
(Denmark), VTT (Finland); industry associations (MF (Sweden); and a financial
institution (The Nordic Investment Fund).
The programmes were carried out with active participation of all
involved parties and began with a number of awareness workshops and
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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conferences. A hallmark of the programmes was to exclude chemical and.
equipment supplier financing and rely only on industrial user and agency
financing.. It' was the opinion of industry that this approach would maintain
the integrity of the programme and its undertaking.
The programme was initiated in 1988 and terminated in 1993. The
activity helped contribute in a significant manner to the Swedish industry's
virtual 100 percent phaseout of CFC and 1,1,1-trichloroethane use as solvent
as mandated by 1991 and 1995, respectively. In the case of Sweden, only SNV
has had the authority to issue exemptions for the use of CFC'as a solvent
after the phaseout date. As .of January 1, 1991, exemptions had been granted
for only a few hundred kilogrammes of CFC usage. These exemptions have not
required renewal. In the case of 1,1,1-trichloroethane,, exemptions for a few
hundred kilogrammes have' been submitted to date and are under review. These '
exemptions, if granted are expected to be valid only for 1995.
IV. INFORMATION DISSEMINATION
A vital component of the phaseout strategy was to disseminate the
results of the Swedish phaseout experience to outside parties and to work for
a more rapid global phaseout than that agreed upon by the initial Montreal
Protocol. This effort was executed by participation in the UNEP technical
assessment committees, e.g., the Solvents, Coatings, and Adhesives Committee.
The 1989 committee included industry and government participants from the
Canada, Japan, Sweden, Switzerland, U.K., and U.S. The approach adopted for
the assessment.was to assess all alternatives and, on site, examine the
alternatives in operations to assess the feasibility .of a complete phaseout
worldwide by the year 2000 in the solvent sector.
The second committee was convened in 1991 and included representatives
from major chemical companies. The mandate for the second committee called
for a close examination of the .possibility of a more rapid phaseout despite
the inclusion of 1,1,1-trichloroethane which at one stage was considered as an
alternative to the use of CFC as a solvent. The replacement of 1,1,1-
trichloroethane was considered especially difficult due to its large and
diverse use. The committee examined.alternative operations on site for a
variety of applications and the conclusion drawn by the committee was that,
provided sufficient funds and resources were available, a complete phaseout
was possible by the year 1996 with a ten-year grace period for the developing
countries. .
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Dr. Husamuddin Ahmadzai
Naturvardsverket
Smidesvagen 5
S-171 85 Solna
Sweden
Tel: 46-8-799-11-45
Fax: 46-8-98-99-02
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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NON-ODS SUBSTITUTES FOR WAX ELIMINATION AT TOSHIBA CORPORATION
I. SUMMARY
Manufacturers have developed vinyl-copolymer type masking materials that
can be removed by hand-wiping with dry rags or rags dipped in .organic solvents
such as methyl ethyl ketone (MEK). The use of these materials can be a
practical "and easily-implemented alternative to the use of wax masking
materials and ozone-depleting solvents (ODSs) at aircraft maintenance
facilities.
II. INTRODUCTION
Aircraft parts and electric equipment parts are typically covered with a
protective mask prior to chrome plating to restrict electroplating to the
unmasked locations on the parts. .At Warner Robins Air Logistic Center's
Plating Shop, microcrystalline beeswax was used in combination with
electroplating tape to mask parts prior to chrome plating. Before converting
to non-ODS technology, Warner Robins removed this wax by placing the parts in
a vapour degreaser after plating. After several hours, the heated 1,1,1-
trichloroethane vapour dissolved the wax. The facility's two vapour
degreasers were able to dewax approximately 500 chrome-plated parts per month.
During the process, wax would accumulate on the bottom of the degreasers and
form a thick sludge. The degreasers required weekly cleaning to maintain
their efficiency and to prevent accumulation of the wax sludge. This cleaning
used approximately 1,514 litres of 1,1,1-trichloroethane per week to remove
approximately 1,136 litres of sludge that was recycled at another location on-
site. The use of 1,1,1-trichloroethane has been discontinued in this
application and wax is now removed from aircraft parts using steam cabinets
equipped with numerous high pressure nozzles.
III. THE ALTERNATIVE SELECTION PROCESS
Electric companies have been using vinyl-copolymer type masking
materials for years in the same application as Warner Robins. This type of
material can be removed by hand easily without the use of solvents. Some
aircraft maintenance engineers previously considered vinyl-copolymer type
materials to be less effective than wax in terms .of productivity and
reliability, especially on narrow areas or complicated surfaces. However,
vinyl-copolymer type masking agents have been developed recently that
alleviate these concerns.
Table XI-2 shows an example of the composition of vinyl-copolymer type
masking agents. Many electrical engineers consider vinyl-copolymer type
materials to be better than wax in operating characteristics, since vinyl-
copolymer type materials can be applied with a brush or a spray and dried at
room temperature. Narrow areas can be coated carefully and with precision,
whereas parts must be dipped when using wax as a masking agent. One problem
involved in using vinyl-copolymer type materials, however, is its lower
adhesive strength.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Table Xl-2
COMPOSITIONS OF VINYL-COPOLYMER-TYPE
MASKING AGENTS
Compounds
Resin
Softener
Plasticizer
Stabilizer
Colouring Dye
Surface Lubricant
Antifoaming Agent
Solvents
Red
(Precoat: Sticky)
Vinyl chloride/
Vinyl Acetate Copolymer
DOA
(Dioctyl Adipate)
Epoxytriglycerol
Dibutylbis
.(Lauroyloxy)
stannate
Oil Red
Silicone
Silicone Type
Acetone 14-15%
MEK (Methyl Ethyl
Ketone) 30%
Methyl Isobutyl Ketone
17%
Toluene 5% .
Green (Maincoat: Normal)
Phtalocyanine Green
* 1994 UNEP SOLVENTS. COATINGS, AND ADHESIVES REPORT *
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Occasionally, vinyl-copolymer type films peel off because of bubbles
generated by electrolysis, indicating that it may be necessary to reinforce
some areas with electroplating tape. Another method to prevent peeling is by
.double-coating the part. In this process, a sticky precoat containing toluene
as a solvent is applied first, and then the main coat is applied.
IV. CONCLUSION
Vinyl-copolymer type materials should be a convenient material to use in
masking parts prior to chrome plating activities. The use of these materials
is expected to increase as more aircraft maintenance facilities are convinced
that vinyl-copolymer type materials will perform as well as wax in terms of
workpiece productivity and masking reliability. It is. important to establish
evaluation methods and also conduct additional field testing of these masking
agents to determine their effectiveness.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
/
Mr. Shigeo Matsui
Manager ; '
Environmental Protection Group .-
Toshiba Corporation
Research and Development Center
1, Komukai Toshiba-Cho, Saiwai-Ku
Kawasaki, 210, Japan
Tel: 81-44-549-2293
Fax: 81-44-555-2074
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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USING NEW TECHNOLOGIES TO SOLVE UNIQUE PRECISION CLEANING OPERATIONS: THE
ELIMINATION OF OZONE-DEPLETING SOLVENTS
FROM THE AEROSPACE GUIDANCE AND METROLOGY CENTER
NEWARK AIR FORCE BASE, OHIO
I. INTRODUCTION
The Aerospace Guidance and Metrology Center (the Center) operates a
major repair facility at Ohio's Newark Air Force Base. The Center's primary
purpose is to repair inertial guidance and navigation systems used by U.S. Air
Force aircraft and missiles. These sophisticated systems contain complex
electromechanical components that are extremely susceptible to contamination.
As a result, the Center operates a variety of general and precision cleaning
systems, all of which are located in strictly controlled environments.
Prior to 1988, the Center consumed approximately 1,250 metric tons (MT)
of CFC-113 and smaller quantities of 1,1,1-trichloroethane (TCA) annually
during the precision cleaning of various electromechanical components. Both
ozone-depleting solvents were used, to remove oil, dirt, fingerprints, and
other contaminants deposited on electromechanical components during their
operation and repair.
II. AQUEOUS ALTERNATIVES
Following the .signing of the Montreal Protocol in 1987, the Center began
its search for CFC-113 and TCA alternatives. In order to avoid possible
future regulatory constraints, the Center sought the most environmentally
benign solution to its cleaning problem., The Center, which had access to an
inexpensive water supply and a local municipal wastewater treatment plant,
began to investigate aqueous cleaning technologies. Aqueous detergents were
known to be environmentally friendly and are usually nontoxic or low in
toxicity. An independent consultant hired by the Center to conduct a study of
the impacts of aqueous cleaning concluded that there would be no need for
wastewater pretreatment if the Center converted to aqueous cleaning processes.
In addition, aqueous products do not contribute to ozone-depletion or global
warming, and are not classified as volatile organic compounds (VOCs).
Since process development began in 1987, the Center has replaced 43
percent of its ODS-based cleaning with aqueous cleaning technologies, and has
installed 17 aqueous cleaning stations, most of which include a variety of
aqueous cleaning devices. Many of the cleaning stations contain ultrasonic
equipment, and each has access to a heated water supply and compressed-air
drying system. To ensure consistent precision cleaning and spot-free drying,
the Center uses only high quality deionized water that is filtered and
recirculated through the deionizing system to prevent the build up of
particulate and biological film. The water supply can be heated and delivered
to the appropriate cleaning station at.temperatures ranging from .16°C to 68°C.
The compressed air is filtered and delivered through a hand-held blowing
device at a gage pressure of 414 kPa and a flow rate of 0.0084 m3/sec. This
method of drying parts removes moisture in a consistent and spot-free manner
at least as rapidly as CFC-113 evaporates from the same.parts when dried in
still air. Using this system, the Center is confident that at least 95
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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percent of its ODS-based cleaning methods will be replaced by aqueous
technologies by 1995.
The Center scrutinizes every aspect of its existing cleaning me'thods to
ensure that aqueous alternatives are tailored perfectly to the application.
Because components repaired and cleaned by the Center are constructed from a
variety of different materials including jewels, adhesives, plastic, copper,
iron, beryllium, and aluminum, personnel must adjust the parameters of each
alternative cleaning process so that the process satisfactorily cleans the
specific part without damage. Consequently, the aqueous detergent, the length
of the drying and rinsing cycles, the temperature of the water, and the design
of the cleaning machine are all subject to change from.one process to the
next. For this reason, the Center develops:,each new cleaning process.
individually. Developing an aqueous method of cleaning gyroscope components,
for example, required testing various water temperatures to ensure that the
epoxy used to bind the gyroscope components was not damaged during the
cleaning process.
The Center will not convert to aqueous alternatives unless it is
convinced that the new process will provide a final product at least of a
quality equal to that of the ODS-based process it replaces. Remarkably, the
Center has found that product quality usually increases after converting to
aqueous cleaning. Aqueous methods of cleaning precision bearings, for
example, increased their acceptable product yield by 25 to 65 percent compared
to bearings cleaned with CFC-113. Another remarkable trend that has occurred
at the Center following conversion to aqueous cleaning methods is an overall
decrease in product processing times. For example, the total processing time
required to clean one of the gyroscopes,repaired at the Center was reduced by
7.1 percent after switching from CFC-113 to aqueous cleaning, a reduction
equivalent to 16 hours of labour. The Center also found that aqueous cleaning
processes are much less expensive than equivalent ODS cleaning processes. The
reduction in CFC-113 use that has occurred at the Center as a result of its
current 43 percent conversion.to aqueous cleaning is equivalent to an annual
reduction of $1.8 million in operating costs. .The investment cost for a 100
percent conversion to aqueous cleaning is not expected to exceed $1.5 million.
Complete conversion to aqueous cleaning will also reduce' energy consumption
and hazardous waste disposal at the Center.
III. NONAQUEOUS ALTERNATIVES
Converting ODS-based cleaning processes,to aqueous-based cleaning
processes has numerous advantages. Unfortunately, it is not possible to use
aqueous processes for certain cleaning applications. For these processes, .the
Center evaluated and selected nonaqueous alternatives on the basis of cleaning
performance, environmental impact, cost effectiveness, and employee health and
safety. Using these criteria, the Center identified alcohol, volatile methyl
s'iloxanes, perfluorocarbons, and supercritical fluids as potential nonaqueous
technoloeies that can be used to replace ODS-based cleaning processes. These
four tec rologies have no ozone-depleting potential (OOP) and are either
nontoxic or have very low toxicity. Each nonaqueous technology, however, has
one or m re major drawbacks.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Alcohol technologies can be used by the Center to remove mildly
activated rosin flux residues (a by-product of soldering) deposited on fragile
gyroscope wires. Aqueous cleaning is not possible because the wires are so
fragile that the surface tension of water will deform them. The primary
concern with using isopropyl alcohol (IPA) is its flanunability. For this
reason, the Center has selected a cleaning system designed with safety
features that allow its use with pure IPA in normal production areas without
special precautions. IPA, however, is a VOC whose emissions are subject to
control in many localities. .
The Center is investigating .the use of volatile methyl siloxanes for
removing a variety of contaminants, including difficult-to-remove phenylmethyl
silicone which is used as a damping fluid in some gyroscopes. Like IPA,
methyl siloxanes are flammable materials that require special handling and
disposal. Unlike IPA, however, methyl siloxanes are quite expensive.
Repairing inertial navigation systems requires extremely critical
precision cleaning, and the Center obtained assistance from the Small Business
Innovative Research Program (SBIRP) to develop solutions to this problem.
SBIRP funding is available to the Department of Defense (DqD) as a means of
encouraging small U.S. businesses to apply their innovative concepts to solve '
DoD problems. The Phasex Corporation was selected to assist in a project
which involved the removal of a heavy phenylm'ethyl silicone oil from a complex
accelerometer assembly. The assembly must be cleaned in one piece, which is
difficult to achieve with CFC-113 and impossible to achieve with an aqueous
proce3s. Phasex considered both carbon dioxide and ethane as part of a
supercritical fluid (SCF) cleaning process to remove silicone oil from the
assembly. After,thorough research and testing, ethane was found to be
superior to carbon dioxide as a supercritical solvent for removing the oil.
Although ethane is flammable, it, unlike carbon dioxide, has no global warming
potential. In general, SCF technology is effective at removing oil and grease
from components or assemblies whose parts are not harmed by temperature and
pressure applied during the process. Phasex, working with process experts at
the Center, designed and constructed a SCF cleaning station which can operate
with either carbon dioxide or ethane. The cleaning delivers a superb product,
but will not be used for applications which can be performed with cheaper or
more environmentally benign technologies.
A second SBIRP project was aimed at developing a perfluorocarbon
technology for the removal of fluorinated oil and particulate from inertial
components. Entropic Systems was selected to lead the project;, and developed
an ultrasonic process that uses a perfluorocarbon with a fluorinated
surfactant for cleaning. The process removes particulates better than CFC-
113, and has been incorporated into a low-emission cleaning station that began
operation in 1994. Because of the high cost and high global warming potential
of perfluorocarbons, the Center plans to use the new technology only when
other alternatives are not capable of achieving the desired level of
cleanliness.
* 1994 UNEP SOLVENTS. COATINGS, AND ADHESIVES REPORT *
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IV. CONCLUSION
Through the extensive research, development, and implementation of
alternative manufacturing and cleaning methods, the Aerospace Guidance and
Metrology Center has dramatically reduced its use of CFC-113 and TCA in the
last five years. The Center plans to continue reducing its use of ozone-
depleting solvents to achieve a complete phaseout in early 1995.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Don E. Hunt
Chief Scientist
AGMC/CN
813 Irving-Wick Drive., W
Newark Air Force Base
Newark, OH 43057-Q013
USA
Tel: 1-614-522-7712
Fax: 1-614-522-7449
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Case Study: Vibro-Meter SA, Villars-sur-Glgne, Switzerland
I. INTRODUCTION . .
Vibro-Meter SA is a manufacturer of vibration detectors for gas turbines
and similar applications, as well as sensors for pressure, flow etc. They
also design and manufacture the associated electronics for these sensors.
Because its products are used extensively in the aerospace industry, high-
reliability is a requirement for all finished products.
The electronics assemblies use conventional, surface-mount, and mixed
technologies with small physical dimensions and high component densities on
multi-layer boards. Prior to 1992, wave-soldering was performed exclusively
with a medium-solids RA flux and reflow soldering used an RMA solder-paste.
The cleaning process used a CFC-113/alcohol azeotrope in an open-top manual
vapour phase degreaser with water-cooling and two solvent tanks. Initially,
no specific precautions were taken to minimise solvent vapour emissions.
Therefore, the solvent consumption per unit area of cleaned boards was
relatively high, especially considering that the production rate was moderate
and inc ons i s tent.
In early 1992, it was realised that the Swiss Federal Ordinance on
Substances Dangerous to the Environment was legislating a phase out of the use
of CFC-113 and 1,1,1-trichloroethane for industrial purposes by December 31,
1992. .
II. THE SEARCH FOR A SUBSTITUTE
A study of substitute processes (materials.and equipment) was undertaken
and it became apparent that all the technically and economically viable
cleaning methods used water, at least in the final-phase of cleaning. 'Given
the stringent regulations on heavy metals, ( 0.1 mg/1 for lead, 1 mg/1 for
copper, and 2 mg/1 for tin ) in water quality in the Swiss Federal Ordinance
on the Discharge of Waste Waters, the prospect of using water in the cleaning
process was not initially attractive. In addition, the Cantonal (State)
authorities wished to apply Federal recommendations for pH and BOD5 to the
wastewater. As the production level at the Vibro-Meter facility was fairly
small, a capital-intensive or consumable-intensive wastewater treatment plant
could not be justified.
After a quick examination of the possible alternatives, the list was
narrowed to the following:
"No-clean" soldering . .
Water-soluble flux with aqueous-cleaning
Sappnification-removal of rosin fluxes, plus aqueous cleaning
Hydrocarbon/surfactant removal of rosin fluxes, plus aqueous
cleaning
"No-clean" techniques were rejected because of worries about consistency
in process control and materials.. An examination of available machinery for
aqueous cleaning revealed that there were three types readily available: a
modified 'dishwasher', type which could have limited throughput and relatively
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
11-75
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high water and energy consumption; a 'high-throughput' batch machine; and a
number of conveyorised "in-line" machines.
Ill. AQUEOUS CLEANING OF PRINTED CIRCUIT BOARDS .
One 'high-throughput' batch machine vendor offered a solution which
satisfied all of the company's requirements in terms of capacity, technical
feasibility, and water and energy consumption. With the assistance of
information from the vendor, this system was accepted by the authorities on
condition that analyses taken at the outfall showed acceptable pollutant
levels according to Federal and Cantonal regulations. The only exception
allowed by the authorities was for the stainless steel machine to be cleaned
periodically with a short-chain linear carboxylic acid product whose working
solution could have a pH lower than the permitted limit of 6. This cleaning
process involved a maximum of 50 litres of solution once per month.
The system has a "hold tank" after soldering with a water-soluble flux
or paste. All the assemblies coming out of the wave-soldering machine or the
reflow oven were immediately placed in a polyethylene tank containing a weak
aqueous chelating solution. This room-temperature solution removed most of
the residues from the warm assembly while they .were still liquid and took them
into solution. The slight alkalinity of the solution (pH about 9) also,
prevented the highly acidic flux residues from attacking the solder surface,
ensuring an easily inspectable solder joint. In addition, the chelating
action solubilised the heavy metal salts resulting from the reaction between
the flux and the metal oxides on the solder surface or the component leads.
Foam reduction was yet another advantage of the process. The result of the
"hold tank" was that less than 5-10% of the normal amount of contaminants were
present after the solution left the tank. The water in the "hold tank" is
tested by a dye which changes colour if the pH drops excessively and by a
visible precipitation if the heavy metal content exceeds the chelating power
of the solution. '
The cleaning machine has a 50 litre tank which is .initially filled with
tap or deionised water. A high-power pump sprays the water onto the
assemblies, which are held near-vertically in baskets, via jets from linearly
oscillating spray bars held above and below the parts. After the wash cycle,
the boards are sprayed in open circuit with deionised water. This water may
have 3-5% isopropanol added. The rinse spray bars are separate from the wash
spray bars. The oscillation of the spray bars ensures approximately eight to
ten separate spray rinses at any given point on an assembly during the 30-45
second rinse period. The rinse water is uncontaminated when it initially
reaches the assemblies. After the rinse cycle, the lightly contaminated rinse
water falls into the wash-water tank a'nd dilutes the contents. Wash water is
normally only.'drained at the end of each week.
Once rinsed, the baskets are transferred into an separate drying
machine. The drying machine utilizes very-high-speed rotary air knives which
mechanically blow off the excess water and contaminants (approximately 90-95%
of the quantity at the cleaning machine exit) within a few seconds. The
resi'dual moisture is then evaporated, requiring comparatively little energy.
It is possible to clean and dry a basket with 1-2 nr of assemblies every 6-8
minutes.
1994 UNEP SOLVENTS, COATINGS, AND ADHES1VES REPORT *
11-76
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The residues from the new cleaning system have been shown by
Contaminometer tests to be better than /s-1/io °f t^e residue levels from the
previously used CFC-113 cleaning system, and well under the limits specified
by military standards. The only negative aspect that has arisen is the need
to be more careful about selecting components with the cleaning process in
mind. Although an adaptation period was needed to achieve optimum
performance, the use of water-soluble chemicals has made the soldering process
marginally better, resulting in a small reduction in the amount of rework
required.
No significant problems have arisen as a result of wastewater
generation. The contents of the hold-tank are drummed disposed of as a
special hazardous waste after the tank is emptied periodically. The .costs -of
treating a lightly basic aqueous solution with heavy metals are relatively
small.
The company has found that the equipment selected is particularly
economical in terms of both deionised water and energy use with no overall
cost increase compared to CFC-113. Typical consumption is 5 litres and
700 kWh per square metre of assemblies, respectively.
IV. CONCLUSIONS
This case study provides an example of the defluxing of high-reliability
assemblies in a small-to-medium sized enterprise, respecting all the
environmental criteria in a.country noted for severe restrictions. The same
techniques may be applied in both developing and developed nations. The
capital cost required for the conversion is approximately US$40,000.
V. FOR FURTHER INFORMATION, PLEASE CONTACT:
Monsieur A. Blanc
Vibro-Meter S.A,
route de Moncor
CH-1701 Fribourg
Switzerland
Tel: 41-37-87-11-11
Fax: 41-37-87-16-59
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
11-77
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APPENDIX A
Members of the UNEP Solvents, Coatings and Adhesives
Technical Options Committee for Technical. Assessment
Under Article 6 of the Montreal Protocol
Dr. Husamuddin Ahmadzai
Swedish Environmental
Protection Agency
STATENS NATURVARDSVERK
S-171 85 SOLNA
Sweden
Phone: 46 8 799 1145
Fax: 46 8 989 902
Mr. Lorenzo Alvarez
SAEO South America Electronics
Operation
Av. Orlanda Bergamo, 1000
Bairro Industrial de Cumbica-
Guarulhos
Sao 'Paulo
Brazil
Phone: 55 11 945 9367
Fax: 55 11 945 9160
Dr. Stephen 0. Andersen
Deputy Director
Stratospheric Protection
Division . ,
U.S. Environmental Protection
Agency
Mail Code 6205J
401 M Street, SW '
Washington, DC 20009
Phone: 1 202 233 9069
Fax: 1 202 233 9576
Dr. David Andrews
GEC-Marconi
Hirst Research Centre
Elstree Way
Borehamwood
Herts WD6^1RX
United Kingdom
Phone: 44 81 953 2030
Fax: 44 81 732 0340
Chapter Committees
Electronics Cleaning;
Precision Cleaning; Metal
Cleaning; Dry Cleaning;
Adhesives; Aerosol Products;
Other Uses
TOC Committee Chair
Precision Cleaning
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Mr. Jay Baker
Ford Electronics Technical
Center
Room C290
17000 Rotunda Drive
Dearborn, MI 48121
Phone: 1 313 845 3597
Fax: 1. 313 323 8295 .
Mr. Bryan Baxter
#30 '
The Avenue
Hitchin
Hertfordshire SG4 9RJ
United Kingdom
Phone: 44 462 455 379
Fax: 44 462 456 775
Mr. Charles Carpenter
Waste -Policy Institute
PO Box 35399
Brooks AFB, TX 78235-5399
Phone: 1 210 534 8012
Fax: 1 210 536 2069
Mr. Pakasit Chanvinij
Thai Airways International
Ltd.
Bangkok Airport
Don Muang
Thailand
Phone: 662 531 1955 64 ext.
1185
Fax: 662 533 6288
Mr. Mike Clark
Sketchley Dry Cleaners
PO Box 7
Hinckley
Leicestershire LE10 2NE
United Kingdom
Phone: ' 44 455 238 133
Fax: 44 455 619 056
Mr. Jorge Corona
Environmental Commission
Cto. Misioneros G-8, dep. 501
Cd. Satelite
53100, Edo de Mex.
Mexico
Phone: 52 5 393 3649 / 399
9130
Fax: 52 5 572 9346
Electronics Cleaning
Chair - Precision Cleaning;
Other Uses
Metal Cleaning; Adhesives;
Coatings and Inks
Metal Cleaning; Precision
Cleaning
Chair - Dry Cleaning
TOC Committee Vice Chair,
Chair - Aerosol Products
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Mr. Brian Ellis
Protonique S.A.
PO Box 78
CH-1032 Romanel-sur-Lausarine
Switzerland
Phone: 41 21 648 2334
Fax: 41 21 648' 2411
Mr. Stephen Evanoff
Lockheed Environmental
980. Kelly Johnson Dr.
Las Vegas, NV 89119
Phone: 1 702 897 3228
Fax: 1 702 897 6645 '
Mr. Joe R. Felty
Texas Instruments Incorporated
MS 8013
2501 W. University
McKinney, TX 75070
Phone: 1 214 952 5318
Fax: 1 214.952 2568
Dr. John Fisher
AT&T Bell Laboratories
PO Box 900
Princeton, NJ 08542-0900
Phone: 1 609 639 2219
Fax: 1 609 639 2835
Mr. Art FitzGerald
IFC
3187 Barwell Rd.
Mississauga, Ontario L5L 3Z6
Canada
Phone: 1 905 569 2733
Fax: 1 905 569 2733
Chair - Electronics Cleaning
Chair - Metal Cleaning;
Adhesives; ;Coatings and Inks
Electronics Cleaning; . '
Precision Cleaning; Othe.r JJses
Alternate for Dr. Leslie Guth
.Chair - Coatings and Inks
Ms. Pamela Foster
Friends of the Earth
701-251 Laurier Avenue West
Ottawa, Ontario KIP 5J6
Canada
Phone: 1 613 230 3352
Fax: 1 613 232 4354
Mr. Yuichi Fujimoto
JEMA
4-15, Nagata-cho 2-chome
Chiyoda-Ku
Tokyo 100
Japan
Phone: 81 3 3581 4845
Fax: 81 3 3506 0475
Electronics Cleaning;
Precision Cleaning; also
Senior Advisor TEAP
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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Ing. G. Gabelmann
ITT Teves GmbH
Guerickestr. 7
6000 Frankfurt/M. 90
Federal Republic of Germany.
Phone: 49 69 76 03 2878
Fax: 49 69 76 10 61
Dr. Leslie Guth
AT&T Bell Laboratories
PO Box 900
Princeton, NJ .08542-0900
Phone: 1 609 639 3040
Fax: 1 609 639 2851
Mr. Don E. Hunt
United States Air Force
AGMC/CN
813,Irvingwick Dr. West
Newark AFB, OH 43057-0013
Phone: 1 614 522 7712
Fax: 1 614 522 7449
Mr. Yoshiyuki Ishii
Senior Engineer
Environment Policy Office
Hitachi Ltd.
New Marunouchi Bldg.
5 -1, Marunouchi 1-chome,
Chiyoda-ku
Tokyo 100
Japan
Phone: 81
2722
Fax: 81 3 3214 3545
Electronics Cleaning;
Precision Cleaning
Electronics Cleaning
Precision Cleaning
Metal Cleaning; Precision
Cleaning
3 3212 llll ext.
Mr. Peter G. Johnson
European Chlorinated Solvent
Assoc.
Avenue E. Van Nieuwenhuyse 4,
box 2
B-1160 Brussels
Belgium
Phone: 32 2 676 72 63
Fax: 32 2 676 72 41
Dr. William'G. Kenyon
Global Centre for Process
Change
PO Box 553
Montchanin, DE 19710-0553
Phone: 1 302 652 5597
Fax: 1 302 652 5701
Metai; Other Uses
Electronics Cleaning; Metal
Cleaning; Other Uses
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Mr. Sudhakar Kesavan
ICF Incorporated
Suite 1000
1850 K Street, NW
Washington, DC 20006 . -
Phone: 1 202 862 1140
Fax: 1 202 862 1144
Mr. Hiroshi Kurita
Japan Association for Hygiene
of Chlorinated Solvents
(JAHCS)
Hongoh-wakai Building
40-17 Hongoh 2-Chome
Bunkyo-ku, Tokyo 113
Japan
.Phone: 81 3 3814 3411/3412
Fax: 81 3 3814 3413
Dr. Steve Lai
Singapore Institute of
Standards and Industrial
Research (SISIR)
l Science Park Drive .
Singapore.0511
Phone: 65 772 9548
Fax: 65 777 1765
Mr. Leo Lambert
Digital Equipment Corporation
200 .Forest Street
Marlboro, MA 01752
Phone: 1 508 467 3647
Fax: 1 508 467 1300
Mr. Milton E. Lubraico
Ford Industria e Caomercio
Av. Orlanda Bergamo, 1000
Bairro Industrial .de Cumbica -
Guarulhos
Sao Paulo
Brazil 07200
Phone: 55 11 753 4665
Fax: 55 11 945 9110 4671
Dr. Mohinder P. Malik
Manager, Materials and Process
Technology
Lufthansa German Airlines
Postfach 630300
D-22313 Hamburg
Germany
Phone: 49 40 50 70 2139
Fax: 49 40 50 70 1397
Chair - Other Uses; Dry
Cleaning; Adhesives; Aerosol
Products
Chair - Laboratory Uses;
Precision Cleaning; Metal
Cleaning
Electronics Cleaning;
Precision Cleaning
Electronics Cleaning
Metal Cleaning; Precision
Cleaning
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Mr. Shigeo Matsui
Manager
Japan Audit and Certification
Organization Ltd.
Hoshigaoka Building 2F
2-11-2 Nagata-cho Chiyoda-ku
Tokyo
100 Japan
Phone: 81 3 3503 8021
Fax: 81 3 3506 0475
Ms. Annie Maurel-Groleau
TELEMECANIQUE '
43-45 Boulevard Franklin
Roosevelt
B.BP. 236
92*504 Rubil-Malmaison
Cedex
France
Phone: 33 1 45 69 22 22
Fax: 33 1 45 69 20 76
Mr. James A. Mertens
Dow Chemical
Advanced Cleaning Systems
2020 Dow Center
Midland, MI 48674
Phone: 1 517 63 8325
Fax: 1 517 636 8933
Mr. Hank Osterman
Allied Signal, Inc.
Fluorocarbons
Nichols 5
PO Box 1139
101 Columbia Rd.
Morristown, NJ 07962-1053
Phone: 1 201 455 4551-
Fax: 1 201 455 2745/2615
Mr. Fritz Powolny
OXITENO
Av. Brig Luis Antonio
1343 10 Ampar
Sao Paul SP
Brazil
Phone: 55 11 283 6106/6044
Fax: 55 11 284 2501
Ms. Cynthia Pruett
12592 Daffodil Drive
Mariassas, VA 22111-4644
Phone: 1 703 367 1019
Fax: 1 703 .367 2319
Electronics Cleaning;
Precision Cleaning; Metal
Cleaning
Electronics Cleaning; Metal
Cleaning; Dry Cleaning;
Adhesives; Aerosol Products,-
Other Uses
Chair - TEWI; Metal Cleaning
Metal Cleaning; Drecision
Cleaning
Electronics Cleaning
1994 UNEP SOLVENTS,-COATINGS, AND ADHESIVES REPORT
A-6
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Mr. Patrice Rollet
Promosol
26, Avenue de Petit Pare
94683 Vincennes Cedex
France
Phone: l 33 1 43 98 75 00
Fax: 33 1 43 98 21 51
/
Ing. Wolf-Eberhard Schiegl
Siemens AG '
ZPL r ZUWS
Otto-Hahn-.Ring 6
8-1730 Munchen
Federal Republic of Germany
Phone: 49 89 636 40165
Fax: 49 89 636 40162
* - v
Mr. Hussein Shafa'amri
PO Box 555
Amman
Jordan
Phone: 962 66 444 66
Fax: 962 66 493 41
»
.Lt. Col. John Shirtz
Space and Missile Systems
Center/SDZ
2435 Vela. Way
Suite 2218
Los Angeles AFB, CA 90245-5500
Phone: 1 301 363 0010
Fax: 1 301 363 6439
Mr. Barrel A. Staley
Boeing Defense & Space Group
MS 89-18
PO Box 3999
Seattle, WA 98124-2499
Phone:. 1 206 773 0046
Fax: 1 206 773 2432
Dr. John R. Stemniski
Charles Stark Draper
Laboratory
555 Technology Square
Cambridge, MA 02139-3563
Phone: I 617 258 4265
Fax: 1 617 258 1131
Metal Cleaning; Other Uses
Electronics Cleaning;
Precision Cleaning
.Chair - Rocket Applications;;
Precision Cleaning; Other Uses
Metal Cleaning; Precision
Cleaning
Precision Cleaning; Metal
Cleaning; Adhesives; Coatings
and Inks ""
1994 UHEP SOLVENTS, COATINGS. AND ADHESIVES REPORT
A - 7
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Lt. Col. Doug van Mullem
United States Air Force
Space and Missile Systems
Center/CV
2430 E. El Segundo Blvd.,
Suite 6037
Los Angeles AFB, CA 90245-4689
Phone: 1 310 363 0013 '
Fax: 1 310 363 1256
Mr. John Wilkinson
Vulcan .Materials Co.
Chemicals.Division
1899 L Street, NW
Suite 500
Washington, DC 20036
Phone: 1 202 293 0635
Fax: 1 202 659 3119
Mr. Masaaki Yamabe
Asahi Glass Co., Ltd.
1150 Hazawa-cho, Kanagawa-ku
Yokohama 221
Japan
Phone: 81 45 334 6111
Fax: 81 45 334 6023
Mr. X'Avier Hk Yoong
National Semiconductor Sdn Bhd
Bayan Lepas Free Trade Zone
11900 Penang
Malaysia
Phone: 60 483 7211
Fax: 60 483 3894
Alternate for Lt.
Shirtz
Col. John
Metal Cleaning; Adhesives;
Coatings and 'Inks >
Electronics Cleaning;
Precision Cleaning; Metal
Cleaning
* 1994 UNEP SOLVENTS, COATINGS. AND ADHESIVES REPORT *
A-8
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APPENDIX B
Expert Advisors to the UNEP Solvents. Coatings and Adhesives
Technical Options Committee
Mr. Wayne Bishop
MR&D Engineer
Boeing Commercial Airplane Group
PO Box 3707 .
MS: 97-39
Seattle, WA 98124-2207
Tel: 206-237-8168
Mr. Bill Brox
IVF
Molndalsvagen 85, S-412 85
Goteborg, Sweden
Mr. Shigeru Dejima
Deputy Division Manager, Fabricare Research Center
All Japan Laundry & Drycleaning Association
472 Akiba-cho, Totsuka-ku, Yokohama-shi
Kanagawa-ken 245
Japan ... .
Tel: 81-45-811-3639
Fax: 81-45-812-5176
Mr. Joseph M. Fletcher
MR&D Engineer . , -
Boeing Commercial Airplane Group
PO Box 3707
MS: 97-29
Seattle, WA 98124-2207
Tel: 206-237-5992
Fax: 206-237-1465
Mr. Rick Freeman
Chemical Engineer
Boeing Commercial Airplane Group
PO Box 3707
M.S. 5H-23
Seattle, WA 98124-2207
Tel: 206-931-5098 -
Fax: 206-931-2815
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
B-l
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Dr. Johnny L. Golden
Senior Specialist Engineer
Boeing Defense and Space Group
PO Box 3707
MS: 82-32
Seattle, WA 98124-2207
Tel: 206-773-2055
Fax: 206-773-4946
Mr. Gene Green
MR&D Factory Support Lead
Boeing Commercial Airplane Group
PO Box 3707
MS: 99-39
Seattle, WA 98124-2207
Tel: 206-237-3310
Fax: 206-237-4509
Mr. Michael Hall
Environmental Unit IB
Desk 3/043
Department of Trade and Industry
151 Buckingham Palace Road
London SW1W 9SS
United Kingdom
Dr. Kevin Joback
Molecular Knowledge Systems
26-452 Kessler Farm Dr.
Nashua, NH 03063
Tel: 603-881-9821
Mr. Thomas Jones,
Research Engineer
Boeing Commercial Airplane Group
PO Box 3707
M.S. 5H-23
Seattle, WA 98124-2207
Tel: 206-931-5914 -.
Fax: 206-931-2815
Dr. Karla Karash
EG&G Dynatrend
21 Cabot Rd.
Woburn, MA 01801
Tel: 617-935-3960
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
B-2
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Mr. Robert A. Kisch, P.E.
Specialist Engineer
Boeing Commercial Airplane Group
PO Box 3707
MS: 5H-23
Seattle, WA 98124-2207
Tel: 206-931-2106
Fax: 206-931-2815
Mr. Toshihide Kita
General Manager, Technical Department
Japan Association for Hygiene of Chlorinated Solvents
40-17, Hongo 2-chome, Bunkyo-ku
Tokyo 113
Japan
Tel:. 81-3-3814-3412
Fax: 81-3-3814-3413
Mr. Kenroh Kitamura
Research Center
Asahi Glass Co., Ltd.
1150 Hazawa-Cho Kanagawa-Ku
Yokohama City
221 Japan
Tel: +81 45 334 6137
Fax: +81 45 334 6187
Mr. Ronald Kuse
MR&D Engineer
Boeing Commercial Airplane Group
P.O. Box 3707
M.S. 97-29
Seattle, WA 98124-2207
Tel: 206-237-1505
Fax: 206-237-1465
Mr. Bud Levine
Vice President
Deft, Chemical Coatings
17451 Von Karman St.
Irvine, CA 92714
Tel: 714-474-0400
Fax:
Mr. Bjorn Lindstrom
Ericsson Radar Electronics AB
Bergfotsgatan 2, S-431 84
Molndal, Sweden
Tel:.46-31-67-1000
'Fax: 46-31-87-6639
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Mr. Nigel S. Lo
Senior Specialist Engineer
Boeing Commercial Airplane Group
PO Box 3707
MS: 5H-23
Seattle, WA 98124-2207
Tel: 206-931-5090
Fax: 206-931-2815
Dr. Peter G. Miasek
Market Development Account Executive
Performance Products Group
Exxon Chemical Canada
P.O. Box 4029, Station 'A'
Toronto, Ontario M5W 1K3
Canada
Tel: 416-733-5310
Fax:
Mr. Shinsuke Morikawa
Research Center
Asahi Glass Co., Ltd.
1150 Hazawa-Cho Kanagawa-Ku
Yokohama City
221 Japan
Tel: +81 45 334 '6137
Fax: +81 45 334 6187
Mr. Robert H. Norris
Technology Transfer Manager, Adhesive Systems
3M Industrial Specialties Division
3M Center Bldg. 209-IN-18
St. Paul, MN 55144-1000
Tel: 612-736-8236
Fax: 612-733-4457
Mr. Michael C. Oborny
Cleaning and Contamination Control Division 1834
Sandia National Laboratories
Albuquerque, NM 87185-5800
Tel: 505-845-8040
Fax: 505-844-1543
Mr. Donald Peterson
Lead Engineer Wing Line Support
Boeing Commercial Airplane Group
PO Box 3707
MS: 92-07
Seattle, WA 98124-2207
Tel: 206-237-7015
Fax: 206-237-4604
* 1994 UNEP SOLVENTS-, COATINGS, AND ADHESIVES REPORT
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Dr. Hans K. Pulker
Director - Central Research Laboratory
Balzers Ltd.
FL-9496 Balzers, Liechtenstein
Tel: 075 .4 41-11/4.4396
Fax: 075 4 27 61
Ms. JoAnn A. Quitmeyer
Research Associate, Metalworking Fluids
Dewey and Almy Chemical Division
W.R. Grace & Co. - Conn.
55 Hayden Ave.
Lexington, MA 02173
Tel: 617-861-6600
Fax:
Mr. Alan Robinson
Lead MR&D Engineer, Retired
Boeing Commercial Airplane Group
c/o Mr. Ronald Kuse
The Boeing Co.
P.O. Box 3707
M.S. 97-29
Seattle, WA 98124-2207
Tel: 206-237^1505
Fax: 206-237-1465
Mr. Joel E; Rodgers
Vice President
Genesolv/Baron-Blakeslee
Allied-Signal, Inc.
Engineered Solvent Systems
P.O. Box 1139R
101 Columbia Road
Solvay-5
Morristown, NJ 07962
Mr. Dave Smukowski
Senior Manager of Environmental Operations
The Boeing Co.
P.O. Box 3707
M.S. 7E-EH
Seattle,. WA 98124-2207
Tel: 206-393-4782
Fax: 206-393-4718
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Dr. Donald R. Theissen
Director
3M Corporate Product Responsibility
3M Center Bldg. 225-3N-09
St. Paul, MN 55144-1000
Tel: 612-733-6050
Fax:
Mr. John Vakiner
Optics Process Engineer
Texas Instruments Incorporated
Box 660246, M/S 3189
Dallas, TX 75243
Tel: 214-480-4552
Mr. Pei Wang
Semiconductor Group
Texas Instruments Incorporated
Box 665012, M/S 944
Dallas, TX 75265
Tel: 214-997-3268
Mr. Raymond Watkins
Functional Test Electrician
Boeing Commercial Airplane Group
P.O. Box 3707
M.S. 00-56
Seattle, WA 98124-2207
Tel:' 206 342 4839
Dr. Jorg Wullschleger
President, CEO
Leica Heerbrugg Ltd.
CH-9435
Heerbrugg, Switzerland
Tel: 071 703 857/703 131
Fax: 071 703 018
Mr. Shun-ichi Yamashita
Chiefr Technical Department
Kanto Denka Kogyo Co., Ltd.
Tokio Kaijo Bldg. Shinkan llth Floor
1-2-1, Marunouchi, Chiyoda-ku, Tokyo 100,
Japan
Tel: 81-3-3216-4562
Fax: 81-3-3216-4581
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
B-6
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Mr. Dennis Zupan
Technical Supervisor
Brulin & Company, Inc.
P.O. Box 270-B
2920 Dr. Andrew J. Brown Ave.
Indianapolis, IN 46206
Tel: Inside Indiana 1-800-423-0962
Toll Free 1-800-428-7149
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
B-7
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APPENDIX C1
RECOMMENDED GUIDELINES AND CONTROL ACHIEVABLE WITH
BEST AVAILABLE TECHNOLOGY (BAT) FOR
VOLATILE ORGANIC COMPOUND (VOC) SOLVENT-BASED CLEANING
I. GENERAL
Solvent losses are often very great in, a conventional or poorly
maintained plant. In a(poorly maintained plant, only about 20 percent of the
purchased solvent quantity is generally recovered (Figure C-l).
Numerous solvent blends are used in the industry and accordingly, not
all are equally recoverable. Table C-l compares some CFC-113 based solvents
for conventional recovery.
Depending on what measures have already been adopted at,a facility,
application of the guidelines summarized below can enable total emissions to
be reduced by 90 percent. Solvent losses can be reduced from 2-5 kg/h-m2 of
bath area with conventional practice to 0.2 - 0.5 kg/h-m2 of bath area.. For
certain alcohol based and partially aqueous systems, the overall base rate of
annual losses is around 0.03 - 0.05 kg/h,m2 of bath area (Ahmadzai, 1991a).
The guidelines are concerned with the best available technology for the
following: ' .
cold cleaning
. vapour cleaning (including equipment with spray/ultrasound)
continuous "in-line" cleaning.
Table C-2 lists several VOCs and classifies them according to their
importance in episodic ozone formation.
II. DESIGN OF THE CLEANING EQUIPMENT
1. Cover
For processes where:
the solvent has a vapour pressure > 2 kPa (15 mm Hg) at 38°C
(e.g:, all halogenated solvents), or
the solvent is heated, or .
the solvent is agitated mechanically, or
where the equipment's opening is > 1.0 m2,
1 The information presented in this appendix was provided by Dr.
Husamuddin Ahmadzai.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-l
-------
Figure C-l
SOLVENT LOST IN A TYPICAL PLANT
Solvent
Evaporative Losses,
Seals, etc. 12%
Drag Out Evaporative Losses,
40% Seals, etc. 2%
Evaporative Losses
1%
Holding
Tanks
3%
Spills, Leaks
18%
Recycle
Hand
Cleaning
15% Evaporative Losses
*
H
UJ
I'
o
Source: Northern Telecom. 1989 CFC Program.
-------
Table C-l. COMPARISON OF RECOVERABILITY BETWEEN
CFC-113 SOLVENT GRADES
Grade
Major Use
Recoverability
In-House (Yield)
.Straight CFC-113
Azeotropes
CFC-113/alcohols
CFC-113/acetone
CFC-113/MC
Non-Azeotropes
CFC-113/high'bp alcohols
CFC-113/low bp alcohols
CFC-113/water emulsions
CFC-113/displacement
surfactants
CFC-113/lubricant
Vapour cleaning of, plastic/ High
metals/glass
Flux removal High
Vapour cleaning of plastics High
Vapour cleaning of metals High
Flux removal High
Flux removal ' Low
Precision cleaning and Low
drying
Drying High
Metal working (e.g., riveting) Zero
Source: Adapted from Clementson 1988c.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-3
-------
Table C-2. CLASSIFICATION OF VOCs
More important
Alkenes
Aromatics
Alkanes
Aldehydes
Biogenics
Less important
Alkanes
Ketones
ketone
Alcohols
Esters
Least important
Alkanes
Alkynes
Aromatics
Aldehydes
Ketones
Alcohols
Esters
Chlorinated hydrocarbons
> C6 alkanes except 2,3 dimethylpentane
All aldehydes and benzaldehyde "
Isoprene
C3 - C5 alkanes and 2,3 dimethylpentane
Methyl ethyl ketone and methyl t-butyl
Ethanol
All esters except methyl acetate
Methane and ethane
Acetylene
Benzene
Benzaldehyde
Acetone
Methanol
Methyl acetate
Methyl chloroform,
Methylene chloride,
Trichloroethylene and tetrachloroethylene
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT.*
C-4
-------
it should be possible to operate the cover automatically or with minimal
effort. Cover design (e.g., horizontally sliding action) should permit
operation that does not create turbulence in the vapour zone (e.g., avoid
flip-open type design). The equipment should be designed so that the cover(s)
opens and closes only during charging or discharging of the workload (e.g.,
air lock).
2. Arrangement for Drainage of Cleaned Components
For solvents with a vapour pressure > 2 kPa (at 30 mm Hg, 38°C),
drainage 'should take place inside the machine with the cover closed.
3. Safety Devices
To prevent solvent evaporation during equipment stoppages, the following
safety devices should be 'installed:
Monitors and thermostats to check the flow of liquid to the
condenser and heating element (< 18°C) and an equipment shut
off'in the event of a circulation stoppage or overheating.
t
- Spray monitor that shuts off the spray device, if the vapour
level drops 10 cm.
4. Operating Instructions Should be Posed Visibly and Should
Summarize All Operating Steps
5. Design of -Solvent Spray
To cpnserve solvent, the spray should be of the continuous type (not
atomizing). The nozzle pressure should be regulated so it does not give rise
to excessive splatter, _and where applicable, be applied under the vapour
level.
6. Design of Work Load Carrier
Components should be fed in automatically. The design of the work load
carrier should facilitate drainage and not cause a "piston effect." A hook
arrangement is preferable.
/
7. For solvents with a vapour pressure > 2 kPa (30 mm Hg. 38°C) or
solvents that- work at temperatures > 50°C. the following features
should be incorporated where technically feasible:
Freeboard zone ratio2 should be 0.75 - 2.00, preferably >
1.0 (ratio B/A in figure A-2).
Water cover (the solvent should not be water-soluble and
should be heavier than water) should be ensured. Water
2 The freeboard zone ratio is the ratio between the distance from the
vapour level to the rim of the tank (the free-board height) and the width of
the equipment.
* .199* UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-5
-------
cover counteracts evaporation of solvent (to the
atmosphere).
Refrigeration coil (mandatory with vapour cleaners) should
have a working temperature of about -25°C. A defroster
should be included. The following capacities can be
adequate for this purpose:
Bath Width (m) Cooling Capacity (Watts/m perimeter)
<1.0 190
>1.0 290
>1.8 385
>2.4 480
>3.0 580
Adsorption filter shall be rated to ensure good function (at
least 95% efficiency), so that outgoing solvent
concentrations do not exceed 25 ppm2 toward the end of an
adsorption cycle. The ventilation air flow should be 15-20
m3/minute and m3 bath area.
Other technology (e.g., thermal destruction) that can ensure
a better or more efficient control of emissions than that
described above.
Table C-3 depicts, a comparison of some solvent recovery systems and
Table C-4 summarizes available VOC control techniques, their efficiencies,' and
costs.
.8. Design of devices for transport, filling and emptying of solvent.
Devices for transport, storage, and discharge'of volatile solvents
should be built as closed-loop systems.
III. OPERATION OF THE CLEANING EQUIPMENT
1. Prevent solvent losses from exceeding 10-20 WT percent of
purchased quantity. Spent solvent should be transported and.
stored in closed vessels only.
2. Close the cover after each concluded work operation in the
cleaning bath.
3. Place the components in a manner that permits complete drainage of
solvent. The speed of component feed should not exceed 3 m/min
vertically, 3-6 m/min horizontally. A slower feed speed is
preferable (modern equipment permits horizontal speeds of 0.5 -
2.0 m/min and 0.3-0.8 m/min vertically). Hold in the vapour zone
for at least 30 seconds or until condensation on the components
3 Concentration in mg/m3 = (molar weight in g>/22.414) (concentration in
ppm). NOTE: 22.414 = molar volume expressed in litres at 0°C and 101.3 kPa.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-6
-------
Table C-3 COMPARISON OF SOLVENT RECOVERY SYSTEMS
. TYPE OF SYSTEM
Adsorption or
absorption
Desorption
Liquefaction
Water separation
Gas concentration
Boiler
Blended solvents
Treatment of
wastewater
PRESSURE SWING
ADSORPTION
Activated carbon
granule
Pressure swing
(warm air)
Predemoisture cool
under pressure
Unnecessary
Applicable in a
wide range
Unnecessary
Applicable
Unnecessary
FIXED BED
Activated carbon
granule or
activated carbon
fibre
Temperature swing
(steam)
Cool
Necessary
Applicable in a
wide range
Necessary
Not applicable
Necessary
FLUIDIZED BED
Activated carbon
bead
Temperature swing
(hot. air)
Cool
Necessary in some
cases
LIQUID ABSORBENT
Fluorinated inert
liquid
Temperature swing
(distillation) -
Cool
(Not clear)
Inadequate for low concentration (needs
preconcentration)
Necessary in some cases
Applicable in some
cases
Unnecessary
(Not clear)
Unnecessary
Source: Yamabe 1991.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-7
-------
Table C-4. A Summary of Available VOC Control Techniques, Their Efficiencies and Costs
Technique
Lower Concentration
in Air Flow
Efficiency Cost
Higher Concentration
in Air Flow
Efficiency Cost
Application
Thermal incineration **/.
Catalytic incineration **/
Adsorption */
(activated carbon filters)
Absorption
(waste gas washing)
Condensation */
Biofiltration
High
High
High
High
Medium
High
High
Medium
Medium
High
Medium
Medium
Medium
.Medium
Medium
Low
Medium to
high
Low
Low ***/ Low
Wide, for high concentration flows
More specialized for lower
concentration flows
Wide for low concentration flows
Wide for high concentration flows
Special cases of high
concentration flows only
Mainly in low concentration flows,
including odour control
Concentration: Lower < 3 g/m3 (in many cases < 1 g/m3) , Higher > 5 g/m3
Efficiency: High > 95%
Medium 80-95%
Low < 80%
Total cost-:
High > 500 ECU/t VOC abated
Medium 150-500 ECU/t VOC abated
Low < 150 ECU/t VOC abated
*/ These processes can be combined with solvent recovery systems. Cost savings then ensue.
**/ Savings due to energy recovery are not included, these can reduce the costs considerably.
***/ With buffering filters to dampen emission peaks, medium to high efficiencies are achieved at medium to low
costs.
' 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-8
-------
ceases. Allow clean components to drain for at least 15 -
30 seconds or until they stop dripping. During vapour
cleaning, components should drain until they are visibly
dry.
4. Never clean porous materials (e.g., cloth, leather, rope) or
absorbent materials in the vapour zone.
5. Keep the horizontal area of the workload to one-half the
bath area.
6. Maintain between the workload and the edges of the opening
at entry and exit a distance of < 10 cm or < 10% of the
width of the opening (calculated on the basis of the
workload silhouette).
-7. Do not allow the vapour level to drop more than 10 cm when
the workload is introduced into the vapour zone.
8. Never spray above the vapour level. Avoid spraying with
cold solvent.
.9. Check for leaks regularly throughout the entire system. The
system includes cleaning and peripheral equipment (filters,
storage, and filling/emptying devices, etc.). In the event
of leakage, the equipment must be shut off and repaired
immediately. A floor sump should be provided for collection
of spillage.
10. Keep air flow ventilation below or at 15-20 m3/min,m2 of
bath area unless a higher rate is required to meet mandatory
work hygiene limits. Ventilation fans shall not be
positioned near the bath opening.
11. Check to ensure that water is not visible in the solvent
leaving the condensate separator (vapour cleaning system).
Water forms a low-boiling azeotrope, increases solvent
consumption, and causes corrosion damage. Water content
should be maintained under 50-100 mg/1.
12. Shut off the equipment (vapour cleaning) if it is expected-
to remain idle for more than 2 hours.
13: Use a solvent filter to extend solvent life and reduce the
amount of solvent waste. In general, solvent should be
changed when the contamination level reaches about 10
percent by volume.'Solvent should be added via closed-loop
systems with entry below the liquid surface.
14. 'Check the acid acceptance of the solvent regularly., adjust
as necessary. Typically, if acid acceptance values go below
0.08 weight percent as sodium hydroxide, monitoring should
be frequent. Corrective action should be taken if the value
reaches 0.04.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
C-9'
-------
IV. WASTE TREATMENT AND DISPOSAL
Waste from degreasing processes are primarily hydrocarbons and solid
residues and, depending on the pretreatment, can contain anywhere from 20 to
70 percent solvent and water condensate.
In some cases, single-plate distillation can be used to concentrate
soils and recover solvent for reuse. Distillation combined with product
filtration (e.g., ultra filtration) and desiccation can produce virgin quality
solvent product assuming no other solvent may have been introduced as a
contaminant. The oil can be concentrated for reuse. i
Wastewater can be treated using activated carbon to remove trace solvent
or can be sent to a waste disposal company for treatment. Still bottoms and
unrecoverable solvent wastes can be disposed of by thermal destruction in
commercial hazardous waste incineration or industrial furnaces equipped with
appropriate scrubbing and particulate control technology.
Other treatment methods currently being researched are ozonation,
hydrogen peroxide oxidation, carbon adsorption, and resin adsorption. These
four processes may be used to treat wastewater generated during cleaning and
degreasing operations by removing organics from the wastewater. Wastewater
having undergone one or more of these processes successfully will have low
enough concentrations of organics so that industrial wastewater treatment
plants (IWTPs) can properly complete the regeneration of such water. The goal
of using these treatments is to bring the final concentration of organics in
wastewater below the regulatory agency's allowable limits.
Table C-5 illustrates emissions achievable with optimization of solvent-
cleaning equipment. In addition, values of specific emissions occurring in
the process of solvent cleaning are depicted in Table C-6.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-10
-------
Table C-5
TYPICAL EMISSIONS FROM OPTIMIZED SOLVENT
CLEANING EQUIPMENT
Optimization No.
1 2
Version 1 1
Version 2 2
3
4
Version 3' 5
6
7
8
Solvent
3
Chl-s*
Chl-
CFC-
Chl-
Chl-
Chl-
Chl-
s*
113
s*
s*.
s*
s*
Chl-s*
Losses
Stand-by
kg/h-m2
4
0
0
0
.0
' 0
0
0
! 0
.12
.0,2
.01
,03
.02
.02
.02
.01
0% load
kg/h
5
0
0
0.
0
0,
0,
0.
. o.
.3
.05
.02
.08
.05
,05
.05
,03
0
0
0-,
0
0,
0.
0,
P.
100% load
kg/h
6
.7-0.
.35
.15-0
.27-0
.15
.15-0
.1-0.
,06
8
.17
.6
;
.7
3
*Chl-s = Chlorinated solvent
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-ll
-------
Table C-6 ^
VALUES OF SPECIFIC EMISSIONS OCCURRING DURING
SOLVENT DECREASING PROCESS (ECE TASK FORCE VOC)
SUBSTANCE '
Petrol
Kerosene
White spirit
Benzene ' .
Trichloroethylene
Trichloroe thane
CFC-113
AMOUNT
(kg/h-m2)
4.53
1.56
5.80
2.97
3. -94
. 4.20
14.91
t
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
C-12
-------
APPENDIX D
CFC-113 AND 1,1,1-TRICHLOROETHANE CHEMICAL, TRADE, AND COMPANY NAMES
In order to maintain clarity in naming the solvents used in modern
industry, chemical manufacturers and consumers have developed an "industry
code" for naming chemical compounds. Compounds such as chlorofluorocarbons
(CFCs) are followed by a three number code which identifies the composition of
the compound. The code is defined as follows:
CFC-xyz.
where: x is the number of carbon atoms in the compound minus 1 (if
x=0, "then it is omitted from the code);
y is the number of hydrogen atoms in the compound plus 1; and,
z is the number of fluorine atoms.
For example, the formula for trichlorotrifluoroethane is CC12FCC1F2.
Applying the naming convention to the formula, the code becomes:
X = 2 - 1 = 1 No. of carbon atoms = 2
Y = 0 + 1 = 1 No. of hydrogen atoms = 0
Z = 3 No. of fluorine atoms <- 3
Thus, the code is 113 (this compound is CFC-113).
There are currently ten manufacturers of CFC-113'in the U.S., Europe and
Asia, plus an unknown number of manufacturers in the former Soviet Union,
People's Republic of China, and Eastern Europe. As each has a different name
for their product, Tables D-l and D-2 list the product names, producers, and
CFC content for CFC-113. .
Different suppliers use Trade names in various ways: all of Id's
Arklone products are 113-based, the suffix referring to the composition,
Arklone P and P-SM are pure 113, Arklone E, L, A, F, etc. are blended with
other solvents, such as methylene chloride, isopropanol, ethanol, etc.
However, Dupont's Freon products cover a wider range, including the
refrigerants (for example Freon 11 and Freon 12). The Dupont 113-based
systems have a prefix T (e.g. Freon TF, TMC, TP, TE, etc.).
1,1,1-Trichloroethane is also known by several other names. The most
common of these alternatives is methyl chloroform. This name is often felt to
.be unacceptable because it implies that the product contains chloroform, which
is not the case. Another name which is becoming more popular in the U.S. is
"trike."' The usefulness of this name is often discounted as well since this
name has previously been used for trichloroethylene. Tables D-3 and D-4 list
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-l
-------
the producers of 1,1,1-trichloroethane, their Trade names, and the 1,1,1-
trichloroethane content of the products.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-2
-------
TABLE D-l. CFC TRADE NAMES
Company
ICI
Dupont
AtoChem
Hoechst
Kali Chem
ISC Chemicals
Allied
Montefluos
Asahi Glass
Daikin
Central Glass
Showa Denko
Country
UK
US
France
Germany
Germany
UK
US
Italy
Japan
Japan
Japan
Japan
Trade Name
Arklone
Freon
Flugene
Frigen
Kaltron
Fluorisol
Genesolve
Delifrene
.Fronsolve
Daiflon
CG Triflon
Flon Showa Solvent
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
D-3
-------
TABLE D-2. CFC-113 CONTENT OF SELECTED PRODUCTS
Company
Dupont
Product
% CFC-113
Asahi Glass Co., Ltd.
Central Glass Co.,
Ltd.
Freon TMS
Freon TES
Freon SMT
Freon MCA
Freon TA
Freori TDF
Freon TWD 602
Freon TP35
Freon TE35
Freon TMC
Freon TF
Freon PCA
94.05
95.2
69
62.8
88.9
9,9.9
91.5
65
65
50.5
100
100
Fronsolve 100
Fronsolve AE 96
Fronsolve AP 65
Fronsolve AM 50.5
Fronsolve AES 96
Fronsolve AMS 94
Fronsolve AD-7 99.5
Fronsolve AD-9 99.5
Fronsolve AD-17 83
Fronsolve AD-19 82
Fronsolve UF-1 80
Fronsolve UF-4 86
Fronsolve UF-5 90
Fronsolve AC 87.5
Fronsolve AW 97
Nanofron E . 96
Nanofron A 75
Nanofron B 65
CG Triflon 100
CG Triflon E 96
CG Triflon P 65
CG Triflon M 50.5
CG Triflon ES 95.5
CG Triflon EE 92
CG Triflon E35 65
CG Triflon MES 93.3
CG Triflon Cl 98.7
CG Triflon Dl 99.5
CG Triflon D3 99.4
CG Triflon Wl 91.2
CG Triflon A 87.5
CG Triflon FD . 78
CG Triflon CP 90
CG Triflon EC 85.5
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-4
-------
TABLE D-2.. CFC-113 CONTENT OF SELECTED PRODUCTS
(Continued)
Company
'Daikin Industries,
Ltd.
Du Pont-Mitsui'
Fluorochemicals Co.
Ltd.
ICI PLC
Product
DAIFLON S3
DAIFLON S3-E
DAIFLON S3-P35
DAIFLON S3-MC
DAIFLON S3-ES
DAIFLON S3-W6
DAIFLON S3-EN
DAIFLON S3-HN
DAIFLON S3-A
MAGICDRY MD-E6 .
MAGICDRY MD-E35
MAGICDRY MD 201
MAGICDRY MD 202
MAGICDRY MD 203
% CFC-113
100
96
65
50.
95.
91.
86
90
87.
94
65
99.
99.
99.5
Freon TF
Freon TE
Freon T-P35
Freon TMC
Freon TES.
.Freon T-E6
Freon T-E35
Freon T-DEC
Freon T-DECR
Freon TMS
Freon SMT
Freon T-B1 .
Freon T-DA35
Freon T-DA35X
Freon T-DFC
Freon T-DFCX
Freon T-WD602
Freon TA
Freon MCA
100
95.5
64.7
50.5
95.2
94
65
93.5
64.5
94.0
69.1
. 98.6
' 99.7
99.6
99.9
99.9
91.5
88.9
63-
ARKLONE
ARKLONE
ARKLONE
ARKLONE
ARKLONE
ARKLONE
ARKLONE
ARKLONE
ARKLONE
P
PSM
L
AS
AM
K
W
EXT
AMD
100
100
97.1
96
94.2
75
91.5
64.7
94.1
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-5
-------
TABLE D-2, CFC-113 CONTENT OF SELECTED PRODUCTS
(Continued)
Company Product % CFC-113
Showa Denko K. K. Flon Showa FS-3 100
Flon Showa FS-3E 96
Flon Showa FS-3P 65
Flon Showa FS-3M 50.5
Flon Showa FS-3ES 96
Flon Showa FS-3MS 50.5
Flon Showa FS-3D 99.9
Flon Showa FS-3W 91.5
Flon Showa FS-3A 87.5
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-6
-------
TABLE D-3. TRADE NAMES FOR 1,1,1-TRICHLOROETHANE
Manufacturer
Trade Name
ICI
Dow
AtoChem
Solvay
PPG
Vulcan
Asahi Glass
Toagosei
Kanto Denka Kogyo
Central
Tosoh
Genklene
Propaklone
Chlorothene* (R) Industrial Solvent
Chlorothene* (R) NU
Chlorothene* (R) SM
Chlorothene* (R) VG
Chlorothene* (R) XL
Chlorothene* (R) SL Solvent
Dowclene (R) EC-CS
Dowclene* (R) LS
1Dowclene* (R) EC
Prelete* (R) Defluxer Solvent
Proact* (R) Solvent
2Aerothene* (R) TT Solvent
Aerothene* (R) TA Solvent
Film Cleaning Grade
S.E.M.I. Grade
3Methyl Chloroform, Low Stabilized - PW
3Methyl Chloroform, Low Stabilized
3Methyl Chloroform, Technical
Baltane
Solvethane
Triethane
1,1,1, Tri
Asahitriethane
1,1,1, Tri
Kanden Triethane
1,1,1, Tri
Toyoclean
Trademark of The Dow Chemical Company.
1 75 percent 1,1,1-Trichloroethane and 25 percent perchloroethane.
2 Aerosol Grade.
3 Non-trademark product names.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-7
-------
TABLE D-4. 1,1,1-TRICHLOROETHANE CONTENT OF SELECTED PRODUCTS
Manufacturer
Asahi Chemical Industry,
Co., Ltd.
Asahi Glass Co,. , Ltd.
Central Glass Co., Ltd.
Trade Name
1,1,1-Trichloroethane
Content %
ETHANA NU 94
ETHANA VG 94
ETHANA AL 94
ETHANA HT 94
ETHANA RD 94
ETHANA IRN 90
ETHANA FXN 90
ETHANA SL '94
ETHANA TS 94
ETHANA RS 84
TAFCLEN 90
(Dry cleaning solvent)
AQUADRY 50 94
ASAHITRIETHANE 96
ASAHITRIETHANE ALS 93
ASAHITRIETHANE UT 96
ASAHITRIETHANE LS 9.6
ASAHITRIETHANE BS 92
ASAHITRIETHANE V5 91
ASAHITRIETHANE EC Grade 96
SUNLOVELY 95
(Dry Cleaning Solvent)
CG TRIETHANE N 97
CG TRIETHANE NN 96
CG TRIETHANE NNA- 94
CG TRIETHANE F 97
ICI PLC
GENKLENE LV
GENKLENE N
GENKLENE A
GENKLENE P
PROPAKLONE
GENKLENE LVS
GENKLENE LVX
GENKLENE LVJ
GENKLENE PT
95.2
95.4
96,
99.
89,
95.
90.
95
.5
,7
,6
.7
.7
,2
99.9
Kanto Denka Kogyo Co.,
Ltd.
KANDEN TRIETHANE R
KANDEN TRIETHANE H
KANDEN TRIETHANE HA
KANDEN TRIETHANE HAK
KANDEN TRIETHANE E
KANDEN TRIETHANE EP
KANDEN TRIETHANE HB
KANDEN TRIETHANE HC
KANDEN TRIETHANE HF
97
97
94
93
98
97
94
94
94
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
D-8
-------
TABLE D-4. 1,1,1-TRICHLOROETHANE CONTENT OF SELECTED PRODUCTS
(Continued)
Manufacturer
Kanto Denka Kogyo Co.,
Ltd. (continued)
Toagosei Chemical
Industry Co., Ltd.
Tosoh Corporation
Trade Name
1,1,1-Triehloroethane'
Content %
KANDEN TRI ETHANE HG
KANDEN TRIETHANE HS
KANDEN TRIETHANE HT
KANDEN TRIETHANE N
KANDEN TRIETHANE ND
KANDEN TRIETHANE SR
KANDEN TRIETHANE SRA
KANDEN TRIETHANE EL
KANDEN TRIETHANE ELV
94'
99
97
100
97
90 ,
, 91
97
97
Three One-R 96
Three One-S 95
Three One-A 95
Three One-AH 95
Three One-S(M) 95
Three One-F 95
Three One-TH 95
Three One-HS ' 95
Three One-EX 90
Shine Pearl 94
(Dry Cleaning Solvent)
Toyoclean EE 97
Toyoclean T 97
Toyoclean SE ,. 84
Toyoclean 0 ' 100
Toyoclean HS 96
Toyoclean 1C 91
Toyoclean NH 96
Toyoclean AL 95
Toyoclean ALS 91
Toyoclean EM 96
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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APPENDIX E
SITE VISITS
The following is a summary of the site visits conducted by committee
members to aid in the preparation of the 1991 United Nations Environment
Programme (UNEP) Solvents, Coatings, and Adhesives Technical Options Report.
Site Visit
IBM Jarfalla
The IBM Jarfalla plant was built in 1970 and specializes in building
printers for all IBM markets. Control units for disk storage and bank
terminal supports are also bviilt at the plant which employs about 900 people.
This facility now has a strict environmental policy after having been
self-admittedly one of the worst users of chlorofluorocarbons (CFCs) in
Sweden, using 16 tonnes of CFC in 1986. They effectively now use no CFCs.
They also have a complete.control inventory of all chemicals under very strict
regulation and an environmental policy which began in 1971.
IBM Jarfalla began an energetic program of elimination of CFCs by
altering/changing the final steps of the initial sequence as well as changing
the cutting oil. Stage I, which consisted mainly of "housekeeping" measures
resulted in CFC use dropping to 4.7 tonnes in 1988, a 64% reduction. Stage II
involved a CFC phase-out by either a cessation of oil use or a switch to oils
which are water soluble or which form emulsions. In Stage III, the drying
process was phased out. This was replaced by deionized (DI) .water rinse with.
and without ultrasonics. The final stage is a dip in an inhibitor. Finally,
a hot air dry is applied. All of these processes'occur with no notable change
in cleaning time.
The oily water is passed through an ultrafilter which costs 600.00 SEK.
The total cost for CFC phase-out at Jarfalla was 300.00 SEK.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Siemens-Elema
Siemens-Eleina specializes in the production of medical apparatus.
Specifically, it specializes in medical applications such as X-ray technology,
electromechanical devices (such as pacemakers), EKG equipment, and
respirators, as well as dental and hearing aid devices. The firm employs
about 2,000 people and is considered to be an extremely small CFC user.
1,1,1-Trichloroethane is used primarily to clean the pacemaker circuit boards.
1,1,1-Trichloroethane usage is estimated to be 4.2 Tonnes/year as a cold spray
in an enclosed chamber.
The alternatives to CFC and 1,1,1-trichloroethane .(TCA) cleaning are
described below. '
Alternatives to CFC as Cleaning Agents at Siemens-Elema
Electronic circuits for pacemakers:
Old Method Present Method
Serial cleaning with '82-83 Spray cleaning with 1,1,1-
Arklone F Trichloroethane*
Vapour zone soldering . IR-soldering
Freon 113 as fluid '89
Other electronic equipment: ' ,
Old Method Present Method
Semi-manual cleaning with perchloro- Rinsing with deionized water; hot
ethylene '89 air
* To be changed 92-93
Plans are to phase out CFCs and TCA with either isopropyl alcohol (IPA)
or Ethanol sprays preferably by the end of 1991, but no later than 1993.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
BALZERS AG
. The Balzers Group is a division of Oerlikon-Buhrle, the latter employing
30,000 persons worldwide with sales of almost $3 billion. Balzers, with 3,900
employees and $300 M sales, are world leaders in high vacuum and thin film
techniques. Both Balzers and Oerlikon-Buhrle are actively pursuing a CFC-113
policy, based initially on usage audits. Most usage within Balzers has
already been eliminated. .
Amongst their strictly defined product lines, Balzers also produces
accessory equipment. This equipment includes aqueous cleaning machines for
substrates and lenses prior to vacuum coating. A typical cleaner may clean
ultraspnically about 500 ophthalmic lenses per hour. Drying was originally
performed using alcohol followed by CFC-113. A demonstration was made of a .
modified machine which successfully dried the components by partially
recirculating hot air. This machine will be marketed in the future.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Leica Heerbrugg AG
Leica Heerbrugg AG is a multinational organization which manufactures
precision optical instruments, often with complex components. Total world
sales reach approximately US$850 M.
Sensitive optical glasses have to be perfectly cleaned before coating.
Leica Heerbrugg AG has adopted mixed aqueous/solvent techniques for cleaning.
Previously, the final stages were in alcohol followed'by CFC-113. Their
active corporate environmental policy dictates as rapid a phase-out as
possible and experiments have been made involving the following processes:
drying in alcohol vapour
drying in warm air
drying by infra-red
drying in warm air followed by evacuation
drying in 'low pressure microwave plasma
None of these processes have shown a distinct lead over the others and all
have considerable disadvantages. The Committee suggested that Leica might
want to examine alcohol/perfluorocarbon drying as another approach, in the
meantime taking care to limit CFC-113 emissions.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
FFV Aerotech AB
FFV Aerotech is a member of the large industrial group Celsius
Industries. The Celsius Group employs 13,000 people internationally and had
1991 sales projected at 9000 MSEK. The products manufactured focus on the
marine, aviation, and electronics sectors. FFV Aerotech AB employs 970 people
and markets maintenance and technical consultant services to the Swedish
Defense Forces. It also develops advanced systems for the Swedish Air Force
and carries out modification. The functions performed using ozone depleting
solvents include the repair of airborne instruments and the development and
manufacture of modifications. This FFV plant is one of the four industrial
concerns in Sweden to receive an exemption (500 kg for 1991) to the phase-out
of CFC-113. They have evaluated alternatives for their precision cleaning
requirements and have approved a cleaning concept using ethanol and a KLN
Ultraschell GmbH machine. Three of the machines will be in operation in mid-
August and a fourth is in the process of procurement.
With the fourth machine, they will be completely free'of the use of CFC-
113 in their precision cleaning operation. The exemption granted them for the
use of CFC-113 past January 1991, expires in August 1991. They are satisfied
that the alcohol cleaning process they are installing will meet all Swedish
requirements for explosion-proof, safe, clean effluent operation. One problem
area that remains to be solved is the identification of a satisfactory solvent
for removing a fluorinated grease of the "Krytox" type.' For low temperature
testing, the Company has successfully applied carbon dioxide impingement.
* 1994 UNEP SOLVENTS,-COATINGS, AND ADHESIVES REPORT *
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Site Visit
Plamex S.A.
Plamex S.A. manufactures telephone and other communication headsets. It
is a subsidiary of Plantronics Inc., a company based in California, U.S.A. '
The company uses a CFC-113 blend to clean printed circuit boards. The
facility consumes around 36 drums annually (1 drum contains 55 gallons of
solvent). Of this amount, 6 drums of material is recovered and sent to a
recycling facility. Each drum of virgin material costs about US$950.
After observing the operations, the committee members offered a number
of suggestions on ways to reduce solvent use in the facility. These include
the following:
modification of vapour degreasers being currently used to replace
lift lids with roll-back type lids; increased freeboard height,
and a recommendation that the spray wand be used sparingly and
properly;
use of milder flux for rework to make it easier to clean;
specification of solderability requirements of components before
acquisition so as to minimize rework;
careful storage of components in inert atmospheres so as to
minimize any contamination; and
% rationalize the use of vapour degreasers in the facility so as to
reduce the number.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Ensambles Magneticos. S.A.
Ensambles Magneticos, S.A. is a manufacturer of magnetic recording heads
for rigid disc drives. It is a subsidiary of Sunward Technologies Inc., a
firm with headquarters in California, U.S.A. The company uses CFC-113 for
precision cleaning and defluxing of printed circuit board assemblies.
Ensambles engineers implemented a simple system that .allows workers to
slowly remove parts to reduce dragout. The technique uses a fixed rod mounted
below the degreaser lid and a basket handle with hooks that allows the
operator to raise the basket several inches at a time allowing the parts to
drain.
The committee members gave a number of suggestions to the facility
managers on ways to reduce the use of ozone-depleting substances (ODSs).
These included the following: '
the use of an alcohol based wire cleaning solvent instead of CFC-
113 based solvent. This would involve investigation of the type
of drawing'oils used in the manufacture of the wire and its
solubility with alcohol
change in the method of storing solvent drums to ensure minimal
storage and handling loss; the working drum should be stored in a
cool enclosed space
improvement in the solvent transfer procedure from the drum to the
degreaser. The use of manual or electric drill powered pumps to
pump the material from the drum to the degreaser was recommended
replacement of a lift lid with a roll-back type lid on the
degreaser
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Saab/Scandia
Saab Combitech Electronics produces electronics for each of the
Saab/Scandia business groups and sells contract board assembly services to
outside clients. They had 1990 sales of 1.9 billion with 204 MSEK profit.
One-third of their solvent using production is for automobiles; one-third for
space, automation, transportation control, and military; and one-third for
contract assembly.
Their products range from simple, consumer grade products to
-sophisticated products for high reliability applications (automobile safety
systems, missile control modules, space technology).
In 1986, one year prior to the Montreal Protocol, Saab made a corporate
decision to.reduce dependence on chemicals that deplete the ozone layer.
Literally overnight, the electronics division was instructed to cancel plans
to purchase new CFC vapour degreasers and to freeze annual use of CFC-113.
This policy change occurred during a period of rapid sales increase.
Saab had been using a combination of in-line vapour degreasers, aqueous,
and had cleaning processes. They used CFC-113 but no other chlorinated
solvents because the federal environmental agency would not grant them a
chlorinated solvent emission permit. The sequence of CFC elimination was:
1986 Corporate.decision to freeze CFC. use
1987 Vapour-phase CFC processes eliminated
1988 Carbon adsorption system installed
1989 Low-solid flux implemented
Controlled atmosphere soldering machine purchased
1990 Controlled atmosphere/low solids implemented
1991 Process simplified; new flux investigations
Saab is now manufacturing without the use of CFC-113 or methyl
chloroform solvents and is satisfied with the quality of its final products.
They use Lonco 25 in a SEHO controlled atmosphere wave soldering machine;
water soluble flux in an in-line aqueous/saponifier process; and alcohol
cleaning (90% ethanol, 10% IPA) for rework and for touch-up prior to conformal
coating (if used). Alcohol is also used for final cleaning of products for
military customers. Boards are now cleaner than when they were using CFC-113.
The sequence of changes was more expensive than would be necessary today
because the controlled atmosphere machine was an early generation model and
there were difficulties of optimization resulting from oxygen contamination of
the nitrogen supply and an inaccurate oxygen sensor. The investment costs are
being repaid from savings in operating costs.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT «
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Atsugi Unisia Corporation
Atsugi-Unisia is a manufacturer of a wide range of car components
including hydraulic tappets (valve lifters), pistons, clutch plates, 4-wheel
steering systems, dampers, and air conditioning systems.
During 1990, their total use of ozone-depleting materials was:
CFC-12 96 tonnes
CFC-113 126 tonnes
1,1,1-Trichloroethane ' 864 tonnes
The CFC-12 was used for air conditioner compression testing. The CFC-
113 was used for cleaning parts .after machining and before heat treatment.
1,1,1-Trichlbroethane was also used for this purpose and. for electronics .
cleaning and had a very important use as a cleaner for pistons before the
application of a PTFC/phenolic resin low friction coating. This is used as a
long-life, low-friction coating on pistons for high performance turbo blown
engines. ' . i
Atsugi plans to introduce aqueous alkali cleaning of the hydraulic valve
lifter parts, and the piston precleaning and both aqueous cleaning and burn
off degreasing for pre-heat treatment cleaning.
Currently aqueous cleaning of pistons is causing some loss of adhesion
of the low friction coating and some adjustments to heat treatment will be
required after both aqueous and.burn off degreasing. The company plans to be
out of CFC-113 and CFC-12 use by 1993 and out of 1,1,1-trichloroethane by
2000.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Minebea Group
Minebea Co. Ltd. heads a group of 52 subsidiaries and 14 affiliates with
more than 25,000 employees and a sales turnover of almost Y230 billion.
The Company originated in 1951 as a maker of miniature ball bearings and
is now the world leader in this field. The Company has pursued a course of
expansion and diversification action, derived from both internal growth and
strategic acquisitions. Precision technology and production expertise have
been central to Minebea's development.
The visit was hosted by Mr. Mizugami, the Japan based Managing Director
of Minebea. The plant at Bang-Pa-In, north of Bangkok, is the largest
miniature precision bearing plant in the world.
The Group operation in Thailand comprises:
Pelmec Thai Ltd.
NMB Hi-Tec Bearings Ltd.
NMB Precision Ball's Ltd. at Bang-Pa-In
Minebea Thai Ltd.
Thai Ferrite Ltd.
Taal Products (Thailand) Ltd. at Navanakoru
NMB Thai Ltd.
Minebea Thai Ltd. (Ayuthlaya Plant) at Ayuthlaya
Minebea Electronics (Thailand) Co. Ltd.
Minebea Thai Ltd. Lopburi Plant at Lopburi
Minebea Thai Agroindustry Co. Ltd. at Pathumthani
The company first came to Thailand in 1972 with a small plant
manufacturing finished bearings from parts made in Japan. Currently they
employ 17,000 people at Bang Pa-In and make 55 million pieces (i.e., finished
bearings) per month.
Their current use of CFC-113 and 1,1,1-trichloroethane are:
CFC-113 90 tons per month
1,1,1-Trichloroethane 260 tons per month
Bearings are made from 440C (stainless) and 52100 carbon steel
(corrodible). They also have a material similar to 440C, known as NMB alloy
DD, which has quieter running characteristics.
They plan to phase out CFC-113 use by the end of 1995, and 1,1,1-
trichloroethane use by the end of 1997.
The current method for cleaning bearing parts (rings, balls, retainers
etc.) is:
1,1,1-Trichloroethane degrease
Detergent water clean
Wash in deionised water
Dewater in Freon TDFC
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Rinse in Freon TF
The CFG-113 replacement process will be:
Water detergent clean
Water rinse
Dewatering oil
It should be emphasized that the cleaning process described above for
bearing parts was demonstrated. However, this process cannot be used for
assembled bearings because there is the possibility of chemical reactions
occurring when dewatering oil is mixed with lubricant oil from bearings.
Therefore, their main concern was to find a method for cleaning assembled
bearings to remove particulate contamination.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
ABB Automation
.Circuit Pack Assembly:
Chronology
Pre-1974 TH Rosin Flux Perchloroethylene clean
1974-1985 TH WSF Water clean
1985-1987 TH WSF Water clean
SM Rosin CDC clean*
1987-1989 TH WSF Water clean
SM LSF Water clean for solder balls**
* ABB determined that they could not use WSF for SM due to component
compatibility issues.
** Water is used to clean LSF soldered boards only for the purpose of avoiding
BSD problems during brushing to remove solder balls. A dry brushing technique
is desirable.
Policy Deployment:
Local pressures from authorities and public.
Required elimination of 1,1,1-trichloroethane and methyl chloride by end
of 1987 for PCB fabrication
Permit denial for use of CFC for printed wire assembly (PWA) forced
changes to occur
Internal pricing of materials is used to force individual product lines
to seek alternatives
Obstacles: . .
Alkaline PC board processing has improved quality, but finer features
will require improved technology
LSF narrows process window, produces solders balls, causes
crosses/icicles
Additional Information:
*
ABB Automation was using a small amount of CFC-113 to clean artwork
films. Changed over to alcohol (IPA) earlier in 1991,
Produces 300,000 boards/yr (15,000-17,000 m2/yr).
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Siam Compressor Industry Co. Ltd.
This company is a joint Nippon-Thai venture, the main owners being
Mitsubishi Electric Co. Ltd. and the Siam Cement Co. Ltd. The product line is
exclusively small unit air-conditioner rolling piston type rotary compressors
(approx. 2,250-11,000 kCal/h) which are used in equal parts for the domestic
and export markets. The production capacity is 300,000 compressors per year.
The only solvent use is for cleaning diverse castings after machining.
For this process., trichloroethylene is used in a conveyorized "hanging part"
'machine at 1 m/min. The key point is that the machine was constructed under
license in Thailand to a Japanese custom design. As the parts being cleaned
were soiled with, essentially, non-soluble and soluble cutting oils and
grinding grit, with blind holes and intricate topography, ultrasonics were
liberally applied in immersion tanks.
Internal distillation was sufficient to maintain adequate solvent purity
as well as a vapour phase final rinse. The machine height-was sufficient to
ensure that the entry and exit slots were well over the freeboard.
.Typical trichloroethylene (TCE) losses were very small, evidenced by the
fact that the average measured exposure level is 2 ppm at any place. The
average net and consumption must have been small with two 250 kg drums of new
solvent used per month less the solvent content of three,to four similar drums
produced for solvent reclamation (percentage of solvent unspecified). Only
new solvent was used. The used solvent was sent to a government reclamation
facility^ ;
Although not relevant to the solvents committee, a small quantity of
HCFC-22 were used for Quality Control/Quality Analysis purposes. Currently
this is all vented, but it is planned to reclaim it..shortly, budgetary.
approval being currently in the process. Very tight wastewater control is
also applied, an order of magnitude better than Thai regulations for suspended
solids, dissolved metals and biological oxygen demand (BOD). The wastewater
is used for irrigating the factory lawns. This example is evidence that tight
environmental control is possible and economical in a developing nation and
the Solvents, Coatings and Adhesives Committee and the Economics Committee
were unanimous in congratulating SCI on keeping such an exemplary "tight
ship".
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Nissan - Japan
Nissan Motor Co. will phase out its use of CFC-113, -11, and -12 by the
end of 1994, the fastest schedule for a motor company worldwide. By March,
1991, CFC-12 recovery and recycling equipment was installed in 3,000 Nissan
service factories throughout Japan. By 1994, HFC-134a will be phased in as an
alternative refrigerant for production models. CFC-11 blowing agent for foam
has already been replaced with an air based foaming system. CFC-113 will be
replaced with aqueous, semi-aqueous systems, and other alternatives by March,
1992.
Nissan Motor Co. cleans plastic car bumpers with methyl chloroform
before painting. These uses will be replaced with an aqueous cleaning
process.
* 1994 UHEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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'Site Visit -
AT&T - Thailand
'
AT&T has a consumer products factory in Bangkok, Thailand. It opened in
Spring, 1990 CFC-free' due' to the upfront planning prior to opening. This
factory, along with several other A&T operations, is furthering AT&T towards
it's corporate goal to eliminate emissions of CFCs from manufacturing by the
end of 1994.
Mr. Ken Lannin, Managing Director of the factory welcomed the committee
and made opening remarks.
Dr. Stephen Andersen, the committee chairman, listed AT&T's leadership
in environmentally-sound manufacturing including: aqueous cleaning work,
terpene technology announcement in 1988, leadership in Ad Hoc Solvent Work
Group CFC benchmarking and alternative testing since 1988, UNEP committee
membership in 1989, International Cooperative for Ozone Layer Protection
(ICOLP) inception in 1990, and United Nations Environment Programme (UNEP)
committee membership in 1991. Dr. Andersen asked for AT&T's help in his
proposed partnership between U.S. Environmental Protection Agency (EPA), Thai
government, and Japan's Ministry of International Trade and Industry (MITI)
which will work to eliminate CFC usage in Thailand.
Mr. Greg German, Director, Engineering,'gave an overview of the factory
in preparation for the tour. There are four assembly lines that make 10-12
corded telephone products. Low solids flux applied with AT&T spray fluxers is
used to wave solder bare copper circuit boards coated with either a rosin-
based or imidazole-based solderability preservative. By carefully selecting
the right low solids flux and controlling the quantity with the patented AT&T-
developed fluxer, postrsolder cleaning is not necessary and therefore not
done. The first generation AT&T spray fluxers are used in this factory.
These, and second generation AT&T spray fluxers, have been, implemented on many
AT&T lines. Also, this technology is being offered commercially and has been
implemented by other companies in the'U.S.
The Moving Coil Receiver (MCR) line uses a hot-melt glue that does not
contain 1,1,1-trichloroethane. Soldering is done manually with a .low solids
flux cored solder. . '
Plastic moulding is accomplished using a mould release compound with
isopropyl alcohol (IPA)., not CFCs.
Recycling in the factory is performed wherever possible including
plastic,-wood, paper, and moulding re-grind.
The director of purchasing and transportation, Visan Palattanavit, has
started receiving surveys back from vendors regarding their CFC usage, fo do
this, he obviously has' good knowledge of all suppliers. He stated that, other
than IPA, very few chemicals are used.
(Guth)
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Nissin Electric Co.. Ltd.
.Nissin Electric Company, Ltd. produces electrical substation equipment,
reactive power compensation equipment, control systems, charged particle beam
for semiconductor manufacturing, and engineering services to outside clients.
The company had sales of 80,188 million Yen (US$507 million) in 1990 with a
profit of 2,726 million yen (US$17 million).
Nissin has reduced its consumption of CFC-113 from 11 tons per year in
1986 to 4 tons in 1990. Over 40 percent of the 1990 consumption was used for
defluxing of printed wiring assemblies (PWAs) as a result of the electronics .
soldering operation. The greatest part of the consumption (46.7 percent), was
used for degreasing of oils from high vacuum equipment and 13.3 percent for
degreasing of oils prior to thin film coating. The company has a. goal of
eliminating CFC-113 use by the end of 1995. Alternatives for replacing CFC-
113 include the use of alkali washing processes to clean metal parts and the
use of no-clean fluxes for PWA operations.
Nissin also consumes significant quantities of 1,1,1-trichloroethane.
Reductions have been made from a 1986 .high of 81 tons per year to 76 tons per
year in 1990. The greatest use of 1,1,1-trichloroethane (55.8 percent) is in
the degreasing of metal parts after machining operations and prior to chemical
finishing processes. The next largest consumption of 1,1,1-trichloroethane
(35.2 percent) is for dissolving of epoxy resin during cleaning/maintenance of
equipment which mixes the resins for use in encapsulation processes as
electrical insulating materials. Finally, 9 percent of the total 1,1,1-
tr.ichloroetharie consumption is used for miscellaneous degreasing of other
products. Alternatives for replacing 1,1,1-trichloroethane include alkali
cleaning, isopropyl alcohol cleaning and the development of other alternative
cleaning agents currently under development.
Although the minimization of 1,1,1-trichloroethane has been strongly
pursued, a net decrease of 5 percent has been realized to date. Nissin feels
that the elimination of 1,1,1-trichloroethane may be more difficult than CFC-
113 because of the difficulty in finding a safe (worker exposure),
nonflammable solvent with the solvency power for mixed epoxy resin that is
provided by methyl chloroform. Nissin.is also 'requiring their subcontractors
to reduce and eliminate the use of CFC-113 and 1,1,1-trichloroethane on
products supplied to Nissin.
(Felty)
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Hitachi Construction Machinery Co.. Ltd.
Hitachi Construction Machinery employs 4,500 people and manufactures a
variety of construction machines including excavators, crawler cranes, shield
machines, etc. Net sales were approximately US$ 1870 million in 1990.
In 1988, this plant consumed 15 metric tones of CFC-113. The
consumption was reduced to 0.6 metric tonnes in 1990 by introduction of liquid
petroleum gas (LPG) spray and water based cleaning: CFCs will be eliminated
in 1995.
In 1990, 212 metric tons of 1,1,1-trichloroethane were consumed at this
location. 1,1,1-Trichloroethane will be eliminated in 1998. Recent
developments and observations aiding in the phaseout of these materials
include the following:
A water based alternative has already been introduced for
components cleaning. '
1,1,1-Trichloroethane is used as a cleaning agent in the process .
of heat treatment. Alternative technologies are now being
investigated in several kinds of agents. These alternative
technologies are rather difficult than those technologies
> currently being used. ,
Operating costs, of water-based cleaning is lower than previous
solvent cleaning costs. But, operating costs for alternative
cleaning in heat treatment processes is estimated to be higher
than that, of 1,1,1-trichloroethane.
Waste water is separately treated in three systems for different
. kinds of wastes.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
National Research Institute for Pollution and Resources - Japan
National Research Institute for Pollution and Resources is concerned
with a wide range of research fields related to exploitation, processing and
utilization of. mineral resources and energy, mine and industrial safety and
environmental protection. Research subjects include mineral resources
development and utilization, energy development and utilization, environmental
protection, and mine and industrial safety.
The visit to NRIPR at Tsukuba focused primarily on the research directed
at the destruction of CFCs. Presentations were made on catalytic
decomposition, recovery by adsorption, decomposition by thermal plasma, and
thermal decomposition.
Catalytic decomposition is accomplished in a reactor at relatively low
reaction temperatures of about 300°C using a fine powder catalyst. The
catalyst basis is HY-Zeolite with Ti02/ZrQ2. The residence time is 1-2
seconds and, at flow rates of 50 I/minute, is 100 percent efficient. The
apparatus is laboratory scale. H-mordenite and Ti02/Zr02 have the highest
activity and selectivity. .
Recovery by adsorption is based on adsorption on zeolite. Adsorption is
effected by the zeolite pore size rather than chemical surface interaction.
The process is based on size exclusion as the adsorption preference is in the
order of CsY>KY>NaY where the large cation influences adsorption. Microwave
radiation processes can be used for selective adsorption of CFC in water
vapour.
CFC decomposition by thermal plasma reactor was achieved using a JEOL RF
generator. Inductively coupled, radio frequency, plasma reaction at 10,000°C
using Argon gas were the conditions employed... The product distribution in.
CC13F decomposition by R.F. plasma was not encouraging where at least six
different CFC decomposition products were identified.
Thermal decomposition of CFCs and industrial chlorinated organics
studies were conducted in the presence of methane in which oxygen was. in
excess. The examination of thermal decomposition products revealed that the
99 percent destruction temperature (760°C) was almost the same with hexane as
methane. The 99 percent destruction temperature for CFC-12 was 820°C.
Optimum conditions involving dilution with hydrocarbons and sufficiently
high temperatures must be determined for complete incineration.
While these procedures operating at laboratory scale are encouraging in
destruction efficiency and cost, the scale-up to industrial concentration
destruction requirements needs to be explored on both an efficiency, and costs
basis. NRIPR researchers feel that "commercial" feasibility may take about 1-
2 years and the strong candidate will be incineration.
* 199* UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Site Visit
Digital Equipment Corporation. Republic of Singapore
Digital Equipment Corporation is one of the world's largest suppliers of
networked computer systems, software, and services. Digital leads the
industry in open, multi-.vendor systems integration. An international company,
Digital does more than half of its business outside the United States,
developing and manufacturing products and providing customer services in the
Americas, Europe and the Pacific Rim.
f
The purpose of the visit was-'to observe the surface mount module ,
manufacturing process which utilizes aqueous cleaning 'for removing process
flux chemicals. The aqueous cleaner being utilized in Singapore is the High
Performance Aqueous Microdroplet Module Cleaning system introduced by Digital
Equipment Corp. in Washington, D.C. on April 5, 1990. ;
The Singapore plant converted from being a CFC user for cleaning surface
mount products to an aqueous process during 1991. .The plant tour exhibited
how the system was being utilized, including showing its operational
performance with the particular products being manufactured in the plant.
Questions by the participants ranged from defining the total
installation time, understanding the energy usage of the equipment to the
amount of CFC's eliminated by changing to an aqueous cleaning process. During
the discussions it was mentioned that the advantages outweighed the
disadvantages and the process is successful and is meeting all the
manufacturing expectations. It was also demonstrated that aqueous cleaning is
a viable reliable alternative, capable of successfully replacing CFC's as a
cleaning methodology.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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UNEP SOLVENTS COMMITTEE -- DUSSELDORF, GERMANY - 2 JULY 1991
Attending this meeting were several speakers and guests representing
different associations and trade groups.
Dr. Heinrich Kraus Ministry of the Environment
(Speaker)
Dipl.-Ing. Christian Hering Duerr (Speaker)
Mr. Peter Gunther Machining-Association
Dipl.-Ing. Rupert Rompel Environmental Affairs ZVEI (German
Electric and'Electronics
Manufacturers Association)
Dipl.-Ing! Robert Auer von Brunkau VCI
Dr. John Place European Chemical Industry
Federation
Dr. Hiemke Environmental Ministry - Germany
Prof. Nader . VCI ^
Mr. G. Gabelmann ITT Teves
Ing.-Dr. W. Schiegl -Siemens AG
Dr. Anne Janssen Mannesmann
Mr. Karl-Heinz Pieper Ministry of Finance
Mr. H. Schwenzer IBM Germany
The meeting was hosted by the German representatives of the Solvents
Adhesives and Coatings Committee, Gunter Gabelmann ITT - Teves, and Dr.
Wolf-Eberhard Schiegl, Siemens.
Dr. Schiegl started the meeting off with a short description of the
German situation, which is that they are faced with a phase out of ozone
depleting solvents by the end of 1992 and they have a difficult job ahead of
them. The industry was working with the Environmental ministry on a proposed
date of 1993 when, at the last minute, the date was moved up to 1992 by the
Burndersrat (Upper House). This will make things very difficult for German
industry. Dr. Schiegl mentioned that it would be especially hard on the small
printed circuit board manufacturers. Mr: Schiegl then introduced Dr. Kraus of
the Ministry of Environment.
Dr. Kraus gave a very detailed review of the laws which are affecting
the use of solvents and, in particular, those solvents that are ozone
depleting substances. There are two different regulations facing Methyl
Chloroform users in Germany; one is a prohibition on ozone depleting
substances which was to go into effect on August 1, 1991, and the other is the
revision of the Emission Control Act (2 BImSch V), in effect March 1, 1991.
Article 5 of the CFC Prohibition Ordinance deals with cleaning agents
and solvents. This covers the manufacture of products and formulations
containing ozone depleting substances to an extent greater than 1 percent by
weight. There are exceptions to this part, such as use as a chemical cleaning
agent in closed systems under 2 BImSch V, or to manufacture other less
hazardous substances. The competent local (Laender) authorities may give
temporary exemptions if the use is perceived to be absolutely necessary.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Article 2 of the Emission Control Ordinance (2 Bimsch V) limits volatile
halogenated solvents for operating closed cleaning facilities to
perchloroethylene, trichloroethylene, and dichloromethane, in a technical pure
form.
CFC-113 and CFC-11 can be used until December 31, 1991 in already
constructed facilities. By January 1,,1993, methyl chloroform will no longer
be allowed unless by exemption.
2 Bimsch V defines the competent authority that may allow for exemptions
as the Laender authorities, as well as the circumstances and individual
requirements (such as economic hardship) for obtaining, exemptions. The local
authorities will have this authority.
The German regulatory action was thought by the Bundersrat to be -
necessary since so much TCA is used, and its "long" lifetime allows it to
easily reach the stratosphere.
Dr. Anderson summarized Dr. Kraus' talk as follows:
Phase-out-was reviewed as technically feasible by 1994, with special
needs being met by exemptions. The implication is that Germany can accomplish
this phase-out by 1992 with heroic -efforts and can do it economically by 1994.
Germany is a sophisticated, developed country, and as such, should be able to
help other less developed countries, especially those dominated by. multi-
nationals such as South Korea and Singapore.
Dr. Anderson strongly urged that the German government and industry
should contribute their experience to the on-going panel work and participate
in the coming working meetings (August/September). Dr. Anderson mentioned the
example of Mexico and their partnership program with the USA; they are ready
to receive from the World Bank Fund and the Multi-Lateral funds .to start the
program.
Discussion of Dr. Kraus' presentation was as follows:
There was some concern that German industry, with this early phase-out
date, might make an alternative choice that appears to be environmentally
acceptable, then need to change again, thus undergoing the cost of the change
twice.
Mr. Rumple pointed out that both the Environmental Ministry and Industry
had been negotiating for a 1994 date, and were surprised at the last minute
change to 1992.
Dr. Kraus is concerned that this law was passed too quickly and without
enough deliberation and planning regarding the scope of its potential impacts.
It would be possible to amend the law, but this would take two years, which is
beyond the cut-off date.
Next, Mr. Gabelmann gave a description of the experience of ITT-Teves.
Teves began to look at alternatives after the 1986 BiMSch laws were passed.
Mr. Gabelmann traced the timeline for replacement of methyl chloroform in the
ABS manufacturing system. It took from January 1987 until April 1991 to
evaluate, test, select, install, start up, and de-bug the alternative system.
*' 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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The ABS system involves a high priority for safety, multiple substrates and
complex geometry.
Mr. Gabelmann pointed out the availability of parallel cleaning lines
which allowed them the flexibility to be testing the new line without
interfering with production; a luxury smaller companies .will not have
available. They estimated the cost to be 1.7 MM DM. A total of 12 cleaning
lines need to be replaced in this one factory.
The problem areas they ran into were compatibility with other materials,
adhesion of parts, and compatibility with other process, such as
electroplating. There were problems with the equipment, such as chain drives,
and electrical control filters. They also had new quality demands to deal
with, such as new parts and materials to clean, that were not part of the
original plans.
Small companies have special concerns, inadequate knowledge of the law,
difficulty getting information, lack of trained employees, production demands
on existing equipment which limits testing opportunity, and the unavailability
of complete alternative systems.
Other issues that need to be addressed-are the Water Act, and the
requirements on waste water treatment plants. There is not enough experience
in these areas -to sufficiently handle all the requirements..
Dr. Schiegl then gave a summary of experiences of Siemens. He discussed
a comparison of the environmental impacts of chlorinated solvents and aqueous
cleaning.
Chlorinated . Aqueous
- Volume of water is small - Water waste treatment
- Safe handling required tech. - Batch treatment
knowledge - Concentration by ultra
filtration
- Sludge handling - Sludge handling
' He compared the operating costs for the solvent process with those for
the new aqueous process in a printed circuit board operation.
Actual Normal
Maintenance 71 59
Electrical 8 12
Product 205 135
Waste Disposal 128 46
Total 412 252
DM/sq.m. of PCB 3.15 2.52
Mr. Herring of Duerr Equipment Company:
Mr. Herring summarized the availability of equipment that will use the
solvents that are allowed under the new emission laws with their very tight
limits. First, he discussed the availability of very tight, degreasers that
will use solvents, allowed under the new emission limits. He explained how
* 1994 UNEP SOLVENTS. COATINGS, AND ADHESIVES REPORT-*
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the equipment works and minimizes any emissions to the environment and
protects the worker from exposure to the solvent vapours. Since 1985, they
have sold 500 degreaser units.
Mr. Herring also detailed the aqueous equipment which his company makes,
50 of which have been sold since 1988. Today, 75 percent of the cleaner
machines he makes are aqueous and 25 percent are solvent-based.
"\
Mr. Herring said that it was not possible to replace all the equipment
in two years. He does not think hydrocarbons are ready yet and there is
currently no hydrocarbon equipment. It takes approximately one year to
deliver the equipment after the,order is received.
A discussion period followed the presentations.
Prof. Nader pointed out that the German law did not undergo any
technical review, and was a political action. German companies will have to
deal with the two laws, the CFC/Halon regulation and the 2 BImSch V
regulation. Industry will either need to seek local exemptions under these
laws, or use the materials allowed under the BiMSch requirements (i.e., using
other chlorinated solvents with extremely,low emission levels).
Other alternatives that the German industry can use are to search 'for
and implement alternative materials, although the short time frame will not
allow for much of this. Importation of products containing or manufactured
with ozone depleting substances is not restricted in any way so that adhesives
and glues can be formulated outside of Germany, then imported for use in
Germany. Also, manufacturers can have parts shipped out of the country for,
processing such as cleaning and then shipped back for installation.
Summary comments.
Steve Anderson - Chairman,Solvents Committee: Equipment manufacturers
need to work hard to make the changes in Germany. They should expand
manufacturing capability to meet the short term needs of the German situation,
then be positioned to help the rest of the world. The German industry should
organize into expert teams and make their expertise available to the rest of
the world after they complete the German phase-out.
Dr. Schiegl: A 1994 phase-out would have been hard to meet, but
industry would have pushed hard to meet it. The 1992 date is out of range
since it will take about five years to make the required changes. Germany is.
further ahead than most countries because they have had, for some years,
aggressive regulations on solvents and companies have programs in place to try
to eliminate their use.
»
Mr. Gabelmann: Four to five years is needed to convert a challenging
and difficult application. Smaller companies are not sure if they can meet
even that schedule. German industry may need to send products to foreign
countries and will need to seek exemptions under local regulations.
Mr. Romple: A lot of information needs to get out to the smaller
companies. They need time to think about and react to the regulations. What
will happen at this time is unknown.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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EEC laws give standard requirements for the community and member
countries and can be very stringent on environmental matters. Sweden,
although not a member of the EEC, did not have an equipment shortage during
their phase, but the product split in Sweden is different to Germany and other
European countries. Trichloroethylene dominates the metal cleaning sector
with 1,1,1-trichloroethane having a very small share, due mainly to the strong
position of the indigenous trichloroethylene producer. Ninety percent of
telecommunications allowed for relatively easy substitutions by "no clean"
fluxes. In Germany, much of the CFC-113 in use is for precision and
mechanical cleaning which is more difficult to substitute.
General summary comments of the session:
Adhesives and fine line space circuit boards and other specialized
uses will be problem areas.
Aggressive German phase out will shift some production to other
countries and/or lead to exemptions.
Notification of the large numbers of users is critical,
information on know-how and engineering is needed for smaller
users.
There may be a shortage of experts to deal with the problems.
There may be a shortage of supply in new equipment. Dr. Anderson
expressed confidence that equipment supplies will be able to meet
the challenge.
Evening Session:
A brief special evening meeting was held to accommodate a last minute
request of the Japan Alcohol Association. This association has been
conducting tests for the comparison of cleaning with ethanol and.ethanol/water
mixtures as alternatives to CFC cleaning. The special delegation was
represented by association members, producers, and an equipment supplier.
They presented preliminary data showing effective cleaning using alcohols,
chiefly ethanol. The study so far indicates that alcohols and blends are
effective cleaners; one must have the proper equipment and deal with water
contamination. They have additional work underway to help further define
their process and applications areas.
* 1994 UNEP SOLVENTS, COATINGS. AND ADHESIVES REPORT *
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APPENDIX F
SUMMARY OF TESTING PROGRAMS FOR ALTERNATIVES
IN THE ELECTRONICS INDUSTRY IN
SWEDEN, UNITED KINGDOM, AND THE UNITED STATES
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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TABLE F-l. COMPARISON OF US, UK, AND TRE INTERNORDIC CLEANING OPTIONS
EVALUATION PROGRAMMES
Collaboration
Timescale Monitor
TEST VEHICLE
Substrate
Components
Max I/O
Min Pitch
Min Stand-off
Height
Flux
Soldering
Method
ASSEMBLY
CLEANING
OPTIONS DATA >
CFC
Semi-Aqueous
HCFC
Aqueous
Low Solids Flux
Com. Atmosphere
Alcohol
IPC/DOD/EPA
Voluntary
1988-1992/3
IPC, etc.
FR4
LCC
68
0.050"
0.005" (fixed)
RA
VPS; Wave
Multi-site
Multi-line
(1989) Phase 1
(1991) Phase 2
(1991) Phase 2
(1993) Phase 3
(1993) Phase 3
(1993) Phase 3
i.
\
UK
Contractual
1990-1992
DTI/MOD
SMT:FR4
Mixed Tech : FR4
SMT : Ceramic
PLCC; QFP; SOIC
chip capacitors
160
0.025"
.
RA;RMA;No
clean
IR; Wave
Central
Single Line
1992
1992
1992
1992
1992
1992
1992
, ' .
UK
Contractual
1990-91
NPL
FR4
QFP; PLCC
100
0.025"
0.003"
RMA; Water
soluble
IR; Wave
Multi-site
Single Line
1990
1990
1990
1990
1991
-
1990
. »
TRE
Internordic
Contractual
1988-92
IVF Sweden
FR4
LCC, PLCC, DIL,
SOT,. chip capacitor
68
0.025"
= 0.003"
RMA, No clean,
OA
VPS, IR, Wave
Multi-site
Complete
Complete
-
-
Complete
Complete
Complete
1992: Off-shelf
commercial
products, water
cleaning micro-
emulsion storage,
handling, white
residues
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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APPENDIX G
LIST OF MEMBERS OF ICOLP AND JICOP
INTERNATIONAL COOPERATIVE FOR OZONE LAYER PROTECTION
MEMBERS LIST OF ICOLP
AT&T
British Aerospace .
Ford Motor Company
Hitachi Limited
Honeywell
IBM Corporation
Mitsubishi Electric Corporation
Motorola Corporation
Ontario Hydro
Northern Telecom
Texas Instruments
Toshiba Corporation
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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MEMBER'S LIST OF JICOP
(as of Sept 1994, in alphabetical order)
Aerosol Industry Association of Japan
All Japan Laundry and Drycleaning Association
Association of Methyl Bromide Industry Japan
Association of Polyurethane Foam Industry
Chemicals Inspection & Testing Institute, Japan
Communications Industry Association of Japan
Electronic Industries Association of Japan (EIAJ)
Electronic Materials Manufacturers Association of Japan
Extruded Polystyrene Foam Industry Association
The Federation of Electric Power Companies
Federation of Electroplating Industry Association, Japan
The Federation of Pharmaceutical Manufacturers' Associations of Japan
The Glass Manufacturers Association of Japan
Heat Treatment Trade Association of Japan
High Expanded Polyethylene Foam Industry Association
Industrial Pollution Control Association Japan
Japan Adhesive Industry Association
Japan Air Soft Gun Association .
Japan Alcohol Association (JAA)
Japan Aluminium Federation
Japan Association for Hygiene of Chlorinated Solvents (JAHCS) \
Japan Association of Refrigeration & Air-Conditioning Contractors
Japan Association of Wholesales for Laundry and Drycleaning
Japan Auto Parts Industries Association (JAPIA)
Japan Automobile Manufacturers Association, Inc. (JAMA)
* 199* UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Japan Automobile Service Promotion Association (JASPA)
The Japan Bearing-Industrial Association (JBIA)
Japan Business Machine Makers Association (JBMA)
Japan Camera Industry Association
s '
Japan Chemical Importer's Association (JCIA)
Japan Chemical Industry Association
Japan Chemical Industry Ecology-Toxicology & Information Center (JETOC)
Japan Clock & Watch Association (JCWA)
Japan Container Association
Japan Cosmetic Industry Association
Japan Dyestuff & Chemical Industry Association
Japan Electric Measuring Instruments Manufacturers' Association (JEMIMA)
The Japan Electrical Manufacturers' Association (JEMA)
I
Japan Electronic Industry Development Association (JEIDA)
The Japan Fire Extinguishing System Manufacturers' Association
Japan Flon Gas Association
Japan Industrial Conference on Cleaning (JICG)
Japan Information Service Industry Association (JISA)
The Japan Iron and Steel Federation (JISF)
Japan Laundry and Drycleaning Conference (JLDC)
Japan Metal Sash Institute
Japan Metal Siding Industry Association
Japan Metal Stamping Association
Japan Petrochemical Industry Association (JPCA)
Japan Prefabricated Freezer and Refrigerator Industrial Association
Japan Printed Circuit Association
The Japan Refrigeration and Air Conditioning Industry Association (JRAIA)
Ja'pan Semiconductor Parts Industrial Association
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
G-3
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Japan Soap and Detergent Association
The Japan Society of Industrial Machinery Manufacturers (JSIM)
Japan Surfactant Industry Association
The Japan Valve Manufacturers' Association
Japan Wood Preservers Industry Association (JWPIA)
Japanese Association of Refrigeration
Japanese Consumers' Co-Operative union (JCCU)
The Japanese Electric Wire & Cable Makers' Association
National Federation of Petroleum Commercial Association
Research Institute of Innovative Technology for the Earth, Department
for the New Generation Refrigerant Research
The Society of Japanese Aerospace 'Co., Inc.
Ultrasonic Manufacturers Association
* 1994 UNEF SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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APPENDIX H
ANALYSIS OF CURRENT AND FUTURE PRODUCTION OF CARBON TETRACHLORIDE
(Reproduced from the 1994 Report of the UNEP Aerosols, Sterilants,
Miscellaneous Uses, and Carbon Tetrachloride Technical Options Committee)
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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VI. CARBON TETRACHLORIDE (CTC)
6.1 Introduction
Carbon tetrachloride (CTC) is a heavy, colourless liquid at normal temperatures and
pressures (boiling point 77"C). It is non flammable, miscible with most organic liquids
and is a powerful solvent. In the past CTC has been used for charging fire extinguishers,
as grain insecticide fumigants, as an antihelminthic agent (especially for the treatment of
liver fluke in sheep) as a solvent in the rubber industry and most commonly as a dry
cleaning solvent and metal degreasing solvent. It has been almost completely supplanted
in the developed countries by less toxic and often more effective materials for all these
uses but it is believed to still be used, for example as a grain fumigant in some
developing countries.
CTC is the most toxic of the chloromethanes (10 ppm by volume in air threshold limit as
a maximum safe concentration for daily 8hr exposure [26]). It is harmful if swallowed,
inhaled or absorbed through the skin and -its vapour decomposes on contact with flame
or very hot surfaces to give off phosgene and other toxic products. CTC vapour or mist
is irritating to the skin, eyes, mucous membranes and upper respiratory tract. Exposure
can cause stomach pains, vomiting, diarrhoea, nausea, dizziness and headaches, and
damage to the eyes, liver and kidneys.
CTC is produced primarily as a feedstock tor CFC 11/12 production in which it is
converted to the respective CFC by replacement of either one or two chlorine atoms by
fluorine atoms, normally in a process where CTC is reacted with hydrogen fluoride (HF)
in the presence of a catalyst.
There are a number of other minor feedstock uses of CTC, in which the CTC is entirely
transformed during the process, which are permitted under the Montreal Protocol.
These feedstock uses include the production of key pharmaceutical and agricultural
chemicals and use as a catalyst promoter in oil refineries.
It is important to distinguish between dispersive and non-dispersive uses of CTC. There
are a number of possible ways of interpreting what is and what is not a dispersive use of
CTC (and other controlled substances). For the purposes of this report' the following
definitions have been applied:
A dispersive use is any use of CTC in which all or some part of the CTC is emitted to
the environment, for example laboratory use (eg. spectroscopy), inert reaction solvent
(eg. pharmaceutical manufacture). , .
A non-dispersive use is any use in which the CTC takes part in the reaction and is,
thereby transformed into another chemical, for example CFC manufacture, catalyst
reforming, reagent use.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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There is a grey area where the CTC may react partially in the process. This is claimed
to occur during the manufacture of chlorinated rubber.
A very small percentage of CTC production is used for dispersive uses. The main
dispersive use, is as a solvent for materials undergoing chlorination, the majority being
used in the production of chlorinated rubber and small quantities are used as a process
solvent in the pharmaceutical industry. In certain circumstances, it is possible to make
such uses virtually non-dispersive by the application of modern technology and thermal
oxidation processes.
A small but important dispersive use of CTC is the laboratory use of CTC for example, a
solvent for infra-red analysis of oil.. Dispersive uses are described in more detail below.
Inadvertent production of CTC also arises in some important industrial processes. For
example, in the production of chlorinated solvents, chloromethane and vinyl chloride. In
most cases the CTC is either recycled and destroyed within the production unit or is used
as a feedstock for production of another chlorinated derivative. For example, CTC
produced in vinyl chloride monomer plants is often used as a feedstock in the production
of either trichloro- or tetrachloroethylene. Alternatively, CTC may be thermally oxidised
to produce either hydrogen chloride(HCl) or chlorine which is then recycled for use in
chlorination or oxychlorination processes. Small trace levels of CTC will remain in the
final chlorinated derivative. It is estimated that these levels do not exceed 100 ppm and
are generally 10 ppm. This issue is under review by the United Nations Environment
Program (UNEP) Technology and Economic Assessment Panel.
6.2 CTC Production and Consumption
CTC is normally produced by the high temperature chlorination of propylene or
methanes, usually known as chlorinolysis. Other starting materials include vinyl chloride
(VC) by-products, ethylene dichloride, propylene dichloride, chloromethane by-products
and propylene oxide by-products. CTC can also be produced by chlorination of carbon
disulphide. Production facilities for CTC usually produce CTC alone or CTC and ^
perchlorethylene as joint products - these latter facilities can usually be tuned to produce
either 100% perchlorethylene or 100% CTC by recycling within the plant.
The global production data for CTC has not been reported. It is anticipated the data
collected under the Montreal Protocol will provide information on production for non-
feedstock uses and consumption in the future. It is possible to estimate total CTC
production for CFC production by using the following formula:
CFC 11 produced x 1.14* = CTC consumed
CFC 12 produced x 1.30* = CTC consumed .
( (*): These figures are average values and for guidance only)
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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By using data provided by the Alternative Environmental Acceptability Study (AFEAS)
[Production, Sales and Atmospheric Release of Fluorocarbons through 1992, Alternative
Fluorocarbons Environmental Acceptability Study 1993 [3], it is possible to make the
following estimates (in tonnes).
Year
1990
1991
1992
CFC11
232,916
213,486
186,373
CTC*
265,524
243,374
212,465
CFC 12
230,950
224,805
216,262
CTC*
300,235
292,247
281,141
Total CTC
565,759
535,621
493,606
AFEAS estimate that between 18-31% of 1991 production of CFC 11/12 is unreported in
the above data. Data are not included in the above Table for the following countries,
Argentina (in part), States of the former Commonwealth of Independent States, the
Czech Republic, the Slovak Republic, India, China, Romania and South Korea.
The most comprehensive data worldwide on CTC production and consumption is that
published by the Japanese Association for the Hygiene of Chlorinated Solvents (JAHCS).
These are summarised below.
Production and Consumption of CTC in Japan (tonnes)
Year
Production
Import
Export
Consumption
CFC
Feedstock
Miscellaneous
1988
60,790
47,996
16
108,770
101,692
X
7,078
1989
57,530
44,219
37
101,712
93,135
8,577
1990
52,039
19,868
516
71,391
63,305
8,086
1991
51,475
17,013
2,200
66,288
58,595
7,693
1992
49,539 ,
2,481
2,648
49,372
44,449
4,239
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Miscellaneous uses described in the Table include other feedstock uses of CTC.
Miscellaneous Use of CTC in Japan is estimated to be about 6000 tonnes. Dispersive
uses in Japan in 1989 was approximately 7600 tonnes. The largest portion of this volume
was consumed by the chlorination of rubber and poly-olefin which accounted for some
3000 tonnes in 1989. Producers are still working on a feasible substitute with phase out
of CTC expected by the end of 1994.
Inadvertent CTC production is not reported. This topic is dealt with separately by the
Technology and Economic Assessment Panel. It is anticipated that this material will
continue to be produced. The majority will be recycled or destroyed with small
quantities being isolated and purified to be used as feedstocks for other chlorinated
hydrocarbon processes or as feedstock for the production of Pharmaceuticals and
agrochemicals, as permitted under the Protocol.
6.3 Non-Dispersive Uses of GTC
The main use of CTC is as a feedstock for CFC 11 and 12 production. It can be
estimated that 95 to 97% of CTC production is used in this manner. Reported world
wide production [3] of CFC 11 and 12 has declined from 748,511 metric tonnes in 1986
to 402,635 in 1992 with a corresponding decline in CTC production. This will decline
further as CFC phase out is approached.
It is possible to hydrogenate CTC to chloroform and this may become a way of disposing
of involuntary CTC production. No operating full-scale processes are known.
CTC is also used as a feedstock in the manufacture of a number of important fine
chemicals, agrochemicals and pharmaceuticals. Products manufactured include the
pesticides chloranthil, DCPA, picloram, permethrin and cypermethrin, the drugs AZT
and dalacin and the production of the important intermediate trityl chloride.
CTC is used as a 'catalyst sweetener' in the petrochemical industry where its role is to
maintain the presence of chloride ions on the catalyst surface. The CTC is destroyed
within this process but it is likely that non-ozone depleting substances such as
tetrachloroethylene or ethylene dichloride could be, and are used to provide this a similar
effect. . ; .
Another small volume application is in the stabilisation of liquid sulphur trioxide for
transport and storage. It is claimed that the CTC reacts with the SO3 in situ to form the
stabilising agent as shown in the reaction below:
2SO3 + CC14 > COC12 + S2O5C15
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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Reagent
CTC is an important reagent in several reactions. When used as a reagent CTC is
consumed or chemically altered so this can be considered a non dispersive use.
Supercritical CTC reacts with metals such as niobium and tantalum to form chloride
salts. This reaction can be used to purify the valuable metals from their oxides.
CTC is used in free radical reactions and will add across double bonds to functionalise
olefins [27]. For example, CTC adds across the double bond in ethyl vinyl ether to give
.the functionalised ether.
Alcohols can be converted into chlorides using triphenyl phosphine and CTC under mild
conditions [28]. A similar procedure can be used to open epoxides to give cw-vicinal
dichlorides [29], and to chlorinate enolisable ketones and ureas [30]. In general there
are many other chlorinating agents for these purposes but in some cases this reaction
cannot be substituted.
Aldehydes, ketones and some esters react with CTC in the presence of
triphenylphosphine, tris(dimethylamino)phosphine, and other reagents, to give the
dichloromethylene derivative [31]. CTC is often used as the solvent as well as the
reagent in this reaction.
The radical degradative chlorination of carboxylic acids and acid chlorides using CTC
and 2 - mercaptopyridine - N - oxide has been used to prepare, otherwise difficult chlorp
compounds from the corresponding carboxylic acids [32].
Other useful reactions using CTC as a reagent include its -use as a trichloromethylating
agent in Friedel-Crafts type reactions. [33] and as a chlorine source in the palladium
catalysed chlorination of trialkylsilanes to give trialkylsilyl chlorides [34].
In all cases, at the research level, the world consumption of CTC as a reagent is very
small compared with other uses.
6.4 Dispersive Uses of CTC
CTC is classified by most regulatory authorities as a 'possible' human carcinogen, and as
such its use in dispersive applications is small in countries with strict occupational health
and safety legislation. These regulations require that most applications of CTC are
totally enclosed with recovery and recycling equipment.
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6.4.1 Chlorination Reactions
The largest use of CTC outside CFC production is as an inert solvent in chlorination
reactions. Other non-ozone depleting chlorocarbons are not suitable for this application
as they are either not inert or do not have the required solvency properties. Indeed, in
some cases, for example the manufacture of chlorinated rubber, there is evidence that
CTC plays an essential role as a reagent in chlorination reactions with a small percentage
reacting, and thereby being destroyed in the process. Considerable work is being carried
out to identify alternatives , and in a number of cases to minimise CTC emissions. In
general, CTC is recycled and losses are low. The average recovery efficiency is about
98%. In new-plants recovery rates exceeding 99.9% can be realised. With modern
technology and the incineration of CTC containing process residues, it is possible to
reduce emissions to a practicable minimum. In such circumstances such applications
could be considered as 'non-dispersive' and with appropriate monitoring could be
permitted to be continued after the CTC phase-out.
The major products where CTC is used as a solvent are chlorinated ethylene vinyl
.acetate copolymers, chlorinated polyethylene and chlorinated polypropylene, which are '
used principally in marine and weatherproof paints (EEC use of CTC in chlorinated
rubber manufacture in 1989 was approximately 2300 tonnes, but is anticipated will have
reduced significantly since 1989).
There is a trend away from chlorinated rubber paints with aqueous and other polymer
based systems becoming available although for some applications it is extremely difficult
to find alternatives as no other paint system offers all the superior properties which are
combined in chlorinated rubber. In many countries, specifications and standards demand
the use of chlorinated rubber systems which have been subjected to rigorous and long
term testing procedures to guarantee their efficacy in use.
In these areas the alternatives will have to be subjected to similar testing regimes prior to
their adoption. By the end of 1995, Japanese chlorinated rubber producers will have
moved to alternatives.
CTC is used as an inert solvent in chlorination reactions for the manufacture of a
number of pharmaceutical products or intermediates, such as the drug, Ibuprofen. In
certain circumstances other inert solvents such as chlorobenzenes may be appropriate but
these will require pharmaceutical approval which can take up to 5 years.
l '
It is believed that CTC is still used as a cleaning solvent in parts of Eastern Europe,
India, South East Asia and USSR and this view is supported by measurements of
atmospheric CTC concentrations. However, no data on CTC use in this region have
been obtained. .
Another application is the use of CTC in the palm oil industry in South East Asia as an
extractant. Consumption data are not available.
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6.4.2 Laboratory Uses
The unique physical and chemical characteristics of CTC have led to its adoption
worldwide as a laboratory solvent for many different applications. CTC is used for
routine chemical analysis for the operation and environmental control of many chemical
manufacturing plants. It is also used for the research and development of technologies
and products in most laboratories throughout the developed and developing world. As a
result of its unique characteristics there are few alternatives which are available.
Some examples of CTC laboratory use include:
extraction solvent
reaction solvent
eluent for chromatography
spectroscopy
analysis standard
Current consumption rate worldwide is estimated to be less than 1000 tonnes per annum.
The majority of analytical methods using CTC are documented standards which will
require changing through individual national and international standards organisations.
CTC used for laboratory uses is distributed to laboratories worldwide through a totally
different route than the majority of applications discussed in this chapter.
In most circumstances it is marketed as ultra pure grade or as spectroscopic standards in
containers which vary in volume from a few hundred millilitres to a size of five litres. In
most analytical techniques only a few millilitres is used per analysis.
Extraction Solvent
CTC is a powerful non polar solvent for many organic compounds and its use is specified
in many national and international standard procedures. With the range of solvents
available for extractions, its use for this purpose could cease immediately in the majority
of cases with little disruption to normal laboratory procedure, were it not for these
standards. Because of the known toxicity of CTC it is generally used as an extraction
solvent only as a last resort.
One example of the use of CTC as an- extraction solvent used in an analysis standard is
the Wijs method for determining the "iodine value", a common parameter measured in
edible oils. The test involves dissolving the oil or fat in CTC, adding standardised Wijs
solution, then after the reaction is complete adding potassium iodide solution and
titrating the free iodine with sodium thiosulphaie. CTC is used as the solvent because it
is inert to Wijs solution. Alternative methods to the Wijs procedure will need to be
developed in order to cease this dispersive use of CTC.
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Inert Reaction Solvent
CTC is used as a inert reaction solvent in several useful chemical procedures.
Regioselective bromination reactions using yV-bromosuccinimide (NBS) and regioselective
chloririations using TV-chlorosuccinimide (NCS), are usually carried out in Ci'C. Although
other solvents have been used for this type of reaction it has been shown that the
regioselectivity of NBS and NCS reactions can be significantly altered by changing the
solvent.[35].
CTC and the chlorofluorocarbons (CFCs) are common solvents for fluorination reactions
using molecular fluorine or fluoroxytrifluoromethane (CF^OF). Fluorine is a highly
reactive gas that often breaks carbon chains into smaller units, a side reaction that
sometimes becomes troublesome in chlorinations as well. Substitution of other solvents
in these reactions would be difficult. Carbon tetrafluoride may be too low boiling in
some cases and higher perfluorinated hydrocarbons would probably suffer attack by
molecular fluorine. Some such reactions can be carried out using nitrogen as solvent at
low temperatures.
Eiuent for Chromatography
CTC has found use as an eluent for gas chromatography because it is relatively volatile
and is a good solvent. Again these physical features are found in many other common
laboratory solvents and therefore, CTC use could cease in the majority of cases for this
purpose. In some cases, its use as a eluent may be stipulated for analytical procedures
and substitutes will require regulatory approval. :
Spectroscopy
Samples for infra-red (ir) spectroscopy analysis can be prepared in various ways.
Gaseous samples can be introduced directly into a cell containing ir transparent windows.
Liquid samples are often run as thin films between two ir transparent plates, of which
sodium chloride and potassium bromide plates are the most common. Spectra of solids
may be obtained by grinding the solid in a drop of liquid paraffin (Nujol) and then
pressing the sample between two plates as for liquids. Nujol absorbs ir in the C-H region
so alternative methods must be used if this region is important. Solid samples may also
be ground with potassium bromide and pressed into thin, disks and this method often
gives the most satisfactory ir spectra for both solids and liquids.
Molecular interactions of interest may change markedly from the solid state or neat
liquids to those found in solution, and ir spectra taken in dilute solutions of non polar
solvents are normally .better resolved. For these reasons, ir spectra are sometimes
recorded in a sample cell where the analyte is dissolved in a suitable solvent. Obviously,
the solvent must not significantly absorb ir radiation in the region of interest. CTC is one
of the best solvents for this purpose because it only absorbs ir radiation in narrow bands
and in areas that are usually of little interest. Other'solvents which may be used include
alcohol free chloroform and carbon disulfide. .
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CTC is used in certain applications as a transparent spectroscopic medium in ultra-violet
spectroscopy, which is usually effective for the identification of substances that have an
absorption band in the ultra-violet range, for instance, nitrogen or aromatic compounds.
Trace components which have fluorescence or substances which have an affinity with
appropriate fluorescent agents can be identified in low concentrations by fluorescence
spectroscopy. CTC is used as a non-fluorescent carrier solvent.
Nuclear magnetic resonance (n.m.r.) spectroscopy is used extensively for' the
identification of substances which have complex molecular structures. CTC is used as the
most appropriate solvent in many cases due to its solvency characteristics and unique
chemical structure. In some circumstances deuterochloroform is an effective substitute.
f-
The quantities of CTC used for these purposes are small; usually requiring 1 ml or less
for each sample. CTC is very useful for this purpose and for specialist applications in
most cases it would be difficult to substitute.
Analysis Standard
Carbon tetrachloride is-also used as an analysis standard in various analytical procedures
[36]. One such example is as a component of the Karl Fisher reagent, which is used to
determine the water content of a variety of substances. In this case a number of
alternative reagents and techniques are currently under development.
CTC is used as a calibration standard for the monitoring of atmospheric concentrations
of CTC and similarly for the monitoring of CTC concentrations in water. There is
obviously little space for alternatives tovCTC in these applications.
6.4.3 Agricultural and Veterinary Uses
CTC is known to have been used in two main areas: as an insecticide fumigant,
especially in stored grain and cereal products; and as a veterinary antihelmintic agent,
especially for the treatment of liver fluke in sheep.
There seems to be no documented evidence of either use currently, although there are
suspicions that CTC is still used in certain countries because it is cheap. Amounts are
likely to be small and declining.
CTC was used as a bulk grain fumigant in Africa up to 10 years ago. Currently its use
would be very limited at the individual farmer level.
CTC is possibly still used as an anti-fluke agent in Nepal and Sudan, but generally there
is worldwide distribution of much better drugs that are not expensive.
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6.4.4 Chlorine Production
CTC is used in chlorine production to prevent the build up of potentially explosive
concentrations of nitrogen trichloride
The NC1? is formed by reaction between chlorine and traces of nitrogen in the original
raw material, brine (NaCl), during the electrolytic process which produces chlorine and
caustic soda (NaOH).
A number of companies pass the chlorine which contains the1 trace levels of NCl^ through
CTC which dissolves out the potentially explosive , product. The CTC is then destroyed. by
incineration. Because of the strict guidelines pertaining to the handling of chlorine this
process is totally enclosed.
There are a number of alternatives which can be adopted to prevent the build up of .
NC1V These vary depending upon the source of the nitrogen in the brine and include:
a) Removal of nitrogen from the brine prior to chlorine production
if in the form of ammonia, acidify and strip to remove
if ferrocyanide-based destroy with chlorine
. removal by raising temperature of brine to >100°C.
b) Destroy NC13
use UV-light reactor to destroy NCl-^.
A number of alternatives exist for the destruction or prevention of formation of NCl^ in
chlorine production that could be adopted over the next few years, although probably not
within the current CTC phase out schedule. In many circumstances where the CTC
containing residues are incinerated, the use may be considered as non-dispersive.
6.5 Options for Replacement
In some applications, no replacement for CTC will be required because either the
application is being phased out, or the CTC is chemically transformed during the process
or is completely destroyed or recycled. These applications are described in Section 6.3
above.
No general substitute has been identified for CTC, although progress in certain specific
cases has been made. In its application as an inert solvent in chlorination reactions no
substitute has yet been identified. It should be possible by application of containment
technology to minimize CTC emissions. It should be noted that where CTC is used as a
inert reaction solvent for chemical production any change may require time for regulatory
approval. With reduced CTC production as a result of CFC phase out, there may be
problems in obtaining CTC of sufficient purity for these applications.
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6.6 Recovery anu Recycling
In tVie majority "f c?ses CTC "seH as an r^rt "eaction "oh'^nt is recrve-~d in the
production process and re-cycled in-house. When recycling is inappropriate, for example,
when the CTC becomes unsuitable for continued use, it is available for reclamation or
destruction. -
Where destruction follows use of CTC in a totally enclosed systems, emissions of CTC to
the environment can be considered as insignificant.
6.7 Emission Minimization
It is essential that all emissions of CTC are minimised during manufacture and use. To
provide additional guidance to facility operators, a "Code of Good Housekeeping" has
been prepared, based on a similar code prepared by the UNEP Destruction Technical
Advisory Committee. This code is also intended to provide a framework of practices and
measures that should be adopted at facilities undertaking the use of CTC.
Not all measure-s will be appropriate to all sifuations and circumstance" and as with any
Code, nothing specified should be regarded as a barrier to the adoption of better or s
more effective measures if these can be identified. The suggested Code of Good
Housekeeping is described in Appendix 6.
6.8 Developing Country Perspective
Some developing countries have small chlorinated rubber manufacturing facilities. It is
believed that at present, one or two other facilities using outdated technologies are being
re-installed or are in the planning stages.
The dispersive use of CTC in developing countries is small and is principally for-cleaning
applications. Alternatives already exist and are widely available as discussed in the
UNEP Solvents, Coatings and Adhesives Technical Options Report. In those countries
that continue to produce CFCs it is likely that CTC will still be used for this and other
applications.
6.9 Summary and Conclusions
World production and consumption of CTC will reduce substantially as manufacture of
CFC 11 and CFC 12 is reduced and phased out. Some inadvertent production will
continue as a result of other chlorinated processes. Control technology will keep
emissions of this material to a minimum.
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A number of important chemical processes will continue to use CTC as a feedstock in
which the CTC is either destroyed or chemically transformed. These processes will
include chemical feedstock for pharmaceutical-and agrochemical production, 'catalyst
sweetening' and sulphur trioxide stabilisation. Total use in.these areas is estimated to be
less than 5000 tonnes per annum.
A number of alternatives, such as other chlorinated or inert solvents, have been identified
for certain uses of CTC as an inert solvent for chlorination reactions. Alternatives can
only be identified on a case by case basis. In principle, by -the application of containment
technology and the use of thermal oxidation to destroy CTC-containing process residues,
CTC emissions can be virtually eliminated from these applications. As a result total
usage should reduce rapidly.
In these circumstances, the CTC use as chemical process agents is effectively non-
dispersive except for insignificant emissions. A decision will be required by the Parties to
define and consider what control measures are appropriate for these applications.
There has currently been little effort in the development of alternatives to CTC for
analytical and laboratory applications. Further, many users of CTC are unaware of its
role in ozone depletion, contributing to the lack of development of alternatives. A
number of national and international laboratory standards specify the use of CTC as a
solvent, these will require amendment by the relevant authorities.
At this time the committee supports 'the concept of a global exemption for laboratory
uses of CTC with appropriate controls as described in the March 1994 report of the
UNEP Technology and Economic Assessment Panel. A decision will be required by the
Parties on whether these analytical and laboratory uses should be controlled and, if so, by
what mechanism.
REFERENCES
[3] Grant Thornton Report 1993, Alternative Fluorocarbons Environmental
Acceptability Study, August 1993.
[26] Lewis, R. J., Sax's Dangerous Properties of Industrial Materials, Vol. II, 8th Ed.,
Van Nostraand Reinhold, New York 1992.
[27] Friedlina, R. Kh., Velichko, F. K., Synthesis, 145, 1977.
[28] Appel, R.,Angew. Chem. Int. Ed. EngL, 14, 801, 1975.
[29] Isaacs, N.S., Kirkpatrick, D., Tetrahedron Lett., 3869, 1972.
[30] Appel, R., Warning, K., Ziehn, K. D., Ber Deutsch-Chem. Ges., 107, 698, 1974.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT
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[31] Rabinowitz, R., Marcus, R., . J Am. Chem Soc., 84, 1312, 1962; Chapleur, Y., J
Chem. Soc. Chem. Commun., 7, 449, 1984; Suda, M., Fukushima, A,. Tetrahedron
Lett., 22, 759, 1981; Tanaka, H., Yamashita,.S., Yamanoue, M., Torii, S., J. Org.
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[32] Barton, D.H. R, Crich, D, iMotherwell, W.B., Tetrahedron Lett., 24, 4979, 1983.
[33] Newman, M. S., Pinkus, A. G., J. Org Chem., 19, 978, 1954.
[34] Citron, J. D., Lyons, J.E., Sommer, L.H., / Org Chem., 34, 638, 1969.
[35] Offerman, ,W. and Vogtle F., Angew Chem. Int. Ed Engi, 19, 464 1980.
[36] "Annual Book of ASTM standards", American Society for Testing and Materials,
1991
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APPENDIX .1
TOTAL EQUIVALENT WARMING IMPACT (TEWI) OF SOLVENT ALTERNATIVES
Total Equivalent Warming Impact (TEWI) provides an important tool in the
selection procedure for alternative cleaning and drying technologies.
However, TEWI must not be the only criterion when selecting the cleaning,
drying, or other technology for a manufacturing proces's. The Alternative
Fluorocarbons Environmental Acceptability Study (AFEAS) has provided a
methodology to calculate TEWI for wide range of available systems.
The selection of the best technology to displace CFC-113 or 1,1,1-
trichloroethane (methyl chloroform) must be specific to the intended
applications and will represent a .trade-off or balancing of several key
parameters: worker safety (toxicity or flammability concerns), investment,
operating costs, energy efficiency and reliability. It must also consider a
series of environmental issues (discharges to water or landfill, local
environmental air quality (smog) and global impact).
This report has evaluated one of the selection parameters, TEWI, for a
number of systems. A" summary of the key findings follows.
Solvent losses from the cleaning equipment are potentially lower than
assumed in the 1991 study, resulting in lower calculated contributions
to TEWI. This reduction in emissions is possible through the adoption
of enhanced vapour recovery and improved/novel approaches to materials
handling (e.g., freeboard dwell). In some cases, the above technologies
can be retrofitted to very modern existing equipment, with results
almost comparable to new equipment. However, such equipment will
require careful operation.and maintenance to sustain low emission rates.
The no-clean systems used for the manufacture of printed wire assemblies
have the potential for the lowest TEWI. For metal cleaning,
chlorocarbon-based systems (e.-g., perchlorpethylene, 1,1,1-
trichloroethane) have the potentially lowest TEWI. However, these
chlorinated solvent systems may be subject to various national, regional
and/or local regulations or emission limits that may severely limit the
use of these chemicals for cleaning applications.
The perfluorocarbon (PFC) system studied has the highest TEWI.
While.they use more energy per unit of work (throughput), aqueous, semi-
aqueous and alcohol systems generally have been shown to have a lower
TEWI than hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC)-
based systems because emissions from aqueous, semi-aqueous, and alcohol-
systems do not contribut'e to global warming.
1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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In the case of HCFC/HFC/PFC-based systems, the direct effect caused by
emission of the chemical, represents from 40 percent to over 90 percent
of the calculated contribution to potential global warming.
Future study should assess the effects of variations in equipment and
practices on TEWI and estimate implementation time for alternative systems in
developing countries.
* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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x *
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1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES-REPORT *
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* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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* 1994 UNEP SOLVENTS, COATINGS, AND ADHESIVES REPORT *
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