Cleaning with Solvents: Science and Technology

High-precision cleaning is required across a wide range of sectors, including aerospace, defense, medical device manufacturing, pharmaceutical processing, semiconductor/electronics, etc.

Cleaning parts and surfaces with solvents is simple, effective and low-cost. Although health and safety and environmental concerns come into play with the use of solvents, this book explores how safe and compliant solvent-based cleaning techniques can be implemented. A key to this is the selection of the right solvent. The author also examines a range of newer "green" solvent cleaning options.

This book supplies scientific fundamentals and practical guidance supported by real-world examples. Durkee explains the three principal methods of solvent selection: matching of solubility parameters, reduction of potential for smog formation, and matching of physical properties. He also provides guidance on the safe use of aerosols, wipe-cleaning techniques, solvent stabilization, economics, and many other topics.

A compendium of blend rules is included, covering the physical, chemical, and environmental properties of solvents.

Preface

Acknowledgments

Disclaimer

What You Can Do with This Book

A Note on Organization

Units Used in This Book

External References Cited in This Book

Chapter 1. Relationship of Solvent Properties to Structure

Abstract

1.1 Background

1.2 The Elements of Cleaning Solvents

1.3 The Incredible Shrinking Periodic Table

1.4 A Solvent can be Elements Arranged in a Structure

1.5 A Solvent can also be a Structure Populated with Additional Elements

1.6 The Future of Solvent Design

1.7 Specific Relationships of Composition and Structure to Solvent Properties

1.8 Solvent Design is Multidimensional

1.9 Solvent Design Goals

1.10 Design of Non-Traditional Solvents

1.11 Solvent Selection

Chapter 2. Solubility Scales (Parameters)

Abstract

2.1 Absolute and Relative Information

2.2 Molecular Soup

2.3 May the Force(s) be With You

2.4 Solubility Parameters

2.5 Kauri Butanol (Kb) Value

2.6 Other Measures of Solvency

2.7 Hildebrand Solubility Parameter

2.8 Hansen Three-Dimensional Solubility Parameters

2.9 Numerical Values of Hansen Solubility Parameters

2.10 The Basic Approach – Comparison to Other Materials

Chapter 3. Solvent Selection for Specific Tasks

Abstract

3.1 Background

3.2 The Nature of Soils

3.3 The Basic Approach to Solvent Selection

3.4 This Author’s Approach

3.5 Autopsy of Some Soils

3.6 Food-Derived Residue

3.7 Lubricants

3.8 Greases

3.9 Coolants or Hydraulic Fluids

3.10 Polymer-Derived Residues

3.11 Biological Residue(s)

3.12 General Observations about Soils

3.13 Use of Hansen Solubility Parameters in Solvent Selection

3.14 Analysis for Specific Soil Components

3.15 General Results from the Use of HSP

3.16 Approach using Mixtures of Identified Soil Components

3.17 Solvent Selection to Clean Collections of Soils

3.18 Food-Derived Residue as a Soil Collection

3.19 Soil Composition Really Doesn’t Matter

3.20 Lubricants as a Soil Collection

3.21 Grease as a Soil Collection

3.22 Coolants or Hydraulic Fluids as a Soil Collection

3.23 Polymer-Derived Residues as a Soil Collection

3.24 Medical Residues as a Soil Collection

3.25 A Summary of Lessons Concerning Cleaning Soil Composites

3.26 Identification of the HSP Values of Industrial Soil Composites

3.27 Working without Numbers—Use of the HSP without Soil Identification

3.28 Limitations of HSP Separation (R_A) for Good Solvent Cleaning Performance

3.29 About Cleaning of All Soils

3.30 The Effect of Normal Boiling Temperature

3.31 Vapor Degreasing vs. Cold Cleaning

3.32 HSP for Vapor Degreasing vs. Cold Cleaning

Chapter 4. SHE Management (Solvent Substitution)

Abstract

4.1 Background

4.2 Why Substitute Solvents?

4.3 REACH for the Stars

4.4 Becoming Globally Harmonized

4.5 Game Playing

4.6 The Key Element in Successful Solvent Substitution

4.7 What’s Important in Solvent Substitution?

4.8 Examples of Practical Solvent Substitution

4.9 Substitute Solvents for Trichloroethylene

4.10 Enclosed Cleaning Machines

4.11 Solvent Substitution and Use in Non-US Countries

4.12 Summary: Solvent Substitution

4.13 The Right to Know

4.14 Hazardous Air Pollutants (HAPS)

4.15 The Superfund

4.16 Exposure Limits

4.17 Future Impact of SHE Regulation

Chapter 5. Toxicology of Cleaning Solvents

Abstract

5.1 Background

5.2 Sources of Information

5.3 A Prime Substitute for an MSDS

5.4 Specific Hazard Information

5.5 Analysis of Hazard Ratings

5.6 Odor as a Protective Way to Avoid Toxicological Hazards

Chapter 6. The VOC Exemption Game

Abstract

6.1 Background

6.2 The Object of the Game

6.3 US VOC Definition

6.4 History of VOC Regulation in the US

6.5 Estimation(s) of Atmospheric Reactivity

6.6 The Meaning of Atmospheric Reactivity

6.7 Numerical Values of MIR for Cleaning Solvents

6.8 MIR Values within Solvent Types

6.9 Comparison of Ozone Generation by Solvent Type

6.10 Selection of Low VOC Solvents by Structure and Type

6.11 Game Winners! VOC Exempt Solvents

6.12 The Usable Winners

6.13 Those Who Wish to Play: Applicants for VOC Exemption

6.14 Other Countries—Games with Different Rules

6.15 Volatility and Reactivity Don’t Intersect

6.16 An Immodest Proposal

Chapter 7. Economics of Solvent Use

Abstract

7.1 Background

7.2 Transition from Then to Now

7.3 Solvent Price vs. Solvent “Power”

7.4 Prices of Families of Similar Solvents

7.5 Solvent Prices

7.6 Management of Cleaning Solvents

7.7 The US Resource Recovery and Conservation Act (RCRA)

7.8 The Property of Overkill

7.9 Size Does Matter

7.10 Getting There is Not Half the Fun

7.11 Unnatural Selection

7.12 Treatment/Disposal of Cleaning Wastes

7.13 About “My” Solvent

7.14 The Third Requirement of Hazardous Waste Generators (On-Site Treatment)

7.15 Economics of On-Site Waste Treatment

7.16 Chemical Management Services

7.17 Chemical Leasing

7.18 A Case of Need

Chapter 8. Solvent Azeotropes

Abstract

8.1 Background

8.2 About SHE-Driven Change

8.3 Binary Azeotropes

8.4 Methodology for Choosing Replacement Azeotropic Solvent Blends

8.5 Specific Replacements

8.6 Binary Azeotropes Totally VOC Exempt (in US)

8.7 Binary Azeotropes Containing Water

8.8 Binary Azeotropes to Replace Other Solvents: Summary

8.9 Use of Azeotropes vs. Non-Azeotropic Blends in Solvent Cleaning

8.10 Commercial Solvent Blends for Immersion Cleaning

Chapter 9. Wipe Cleaning with Solvents

Abstract

9.1 Background

9.2 Who Does Wipe Cleaning?

9.3 Why Do Wipe Cleaning?

9.4 Roles of the Solvent in Wipe Cleaning

9.5 Freon (CFC-113)—The Perfect Wipe Solvent

9.6 HCFC-225ca/cb—the Imperfect Wipe Cleaning Solvent

9.7 HFEs/HFCs/OSs—Partially Perfect Wipe Cleaning Solvents

9.8 Wipe Cleaning Solvents Based on Commodity Chemicals

9.9 Wipe Cleaning Solvents Based on Slowly Evaporating Commodity Solvents

9.10 Water-Based Wipe Cleaning Solvents

9.11 Multi-Component Wipe Clean Solvents

9.12 The Option to “Roll Your Own” Wipe Clean Solvent

9.13 The No-Compromise Wipe Cleaning Solvent

9.14 The Joy of Compatibility

9.15 The Plan to Manage Use of Wipe Clean Solvents

9.16 The Necessity for Compromise

9.17 Solvent Selection for Wipe Cleaning

9.18 Paint Stripping by Wipe Cleaning

9.19 Relief from Residues

Chapter 10. Cleaning with Solvent Aerosols

Abstract

10.1 Background

10.2 The Perfect Aerosol-Dispensed Solvent Product

10.3 Any Aerosol—How It’s Produced

10.4 The Aerosol Can Clean, But in a Different Way

10.5 The Aerosol Can

10.6 Marketing 101

10.7 General Applications for Aerosol Cleaning

10.8 The Secret Ingredient (Two Chlorine Atoms)

10.9 Properties of Commercial Aerosol-Delivered Solvent Products

10.10 A Flammable Aerosol—Defined

10.11 The Meaning of Explosive Limits

10.12 Prevention of the Ignition of Aerosols

10.13 Selection of Commercial Blends for Minimum Flammability Risk

10.14 Ignition Safety of Aerosols: Summary

10.15 Hazards Unrelated to Flammability of Aerosols

10.16 Cleaning Potential with Commercial Blends of Aerosol-Delivered Solvents

10.16 Differentiation among Blends

10.17 Summary

Chapter 11. Stabilization of Solvents

Abstract

11.1 Background

11.2 The Nature of Solvent Stabilization

11.3 The Perfect Solvent

11.4 Reaction Pathways of Solvent Degradation

11.5 The Instability of Stabilization

11.6 Illustration of Degradation

11.7 A General Method of Solvent Stabilization

11.8 Removal of Water

11.9 Design of Stabilizer Packages

11.10 Specific Stabilizer Materials

11.11 Formulation of Stabilizer Packages

11.12 Problems with Use of Stabilizer Packages

11.13 Misconceptions about Stabilizer Packages

11.14 Recommended Control Strategies

11.15 A Non-Recommended Control Strategy

11.16 Acid Acceptance Testing

11.17 Stabilizer Booster Packages

11.18 Opinions

11.19 Learn From Others

11.20 Composition of Commercial Stabilizer Packages

11.21 Stabilization of Non-Halogenated Solvents

11.22 In Times of Stress

11.23 Some Simplicity

Chapter 12. Solvent Cleaning: Questions and Answers

Abstract

12.1 Background

12.2 Why is Solvent Cleaning Preferred?

12.3 why isn’t Aqueous Cleaning Technology Preferred?

12.4 Which is More Hazardous, Solvent or Aqueous Technology?

12.5 Is There a Future for Solvent Cleaning in the Us Despite More Restrictive Regulations?

12.6 1,1,1-Trichloroethane (TCA) was the “Right” Solvent Prior to the 1990s; Which One is Now?

12.7 Solvent Technology Seems to be Widely Opposed as “Toxic.” How can One Get Unbiased Advice?

12.8 Why are Cleaning Solvents Priced so High?

12.9 Why are Cleaning Solvents Produced in China Priced so Cheaply?

12.10 Are Cleaning Solvents Imported from China of Acceptable Quality?

12.11 Why is there so Much Secrecy in Cleaning Technology?

12.12 Why do Prices for Cleaning Solvents Vary so much Among Suppliers?

12.13 Are Offerings from Suppliers of Cleaning Solvents Interchangeable?

12.14 Why are Solvents not Now Recognized as Cleaning Solvents Described Here?

12.15 About odor Thresholds: Some Workers find the odor of Organic Cleaning Solvents Objectionable. What Should be Done?

12.16 Is any Firm Seeking to Develop New Cleaning Solvents?

12.17 Does the Selling Price of Cleaning Solvents Really Matter?

12.18 What is “Fire Point?” How is it Different from Flash Point? should I Care?

12.19 How is One to Select a Supplier of Cleaning Solvents (and Equipment)?

12.20 If I Convert to a Cleaning Solvent Rated “Combustible,” How am I to Dry the Parts?

12.21 High Energy Prices Affect my Costs, How can that Burden be Reduced?

12.22 How is Cleaning Done in Remanufacturing Operations Different from that Done in Manufacturing Operations?

Group A. Basic Information

Introduction

Appendix A1. Basic Data about Cleaning Solvents

Appendix A2. Estimation of Properties of Solvent Blends

A Blend Compositions

B Hansen Solubility Parameters of Blends

C Liquid Density of Blends

D Liquid Viscosity of Blends

E Heat of Vaporization of Blends

F Surface Tension of Blends

G Exposure Limits of Blends

H Molecular Weight of Blends

I Composite Vapor Pressure

J Activity Coefficients of Blends

K Flash Points of Blends

L Lower Explosion (Flammability) Limits of Blend Components

M Maximum Incremental Reactivity (MIR)

N Lower Explosion (Flammability) Limits of Blends

O Relative Evaporation Rate (RER) of Blends

Working Examples

Appendix A3. Derivation of Blend Rule for Solubility Parameters

Appendix A4. Compatibility of Wipe Cleaning Solvents with Surface Materials and Protective Gloves (With Database)

A Harmful Effects of Solvents on Surface Materials

B Differences between Machine and Wipe Cleaning

C Solvent/Surface Compatibility Database

D DESCRIPTION OF THE DATABASE

E Reorganization of the Database to Focus on Specific Surfaces

F Elastomers

G Plastics

H Metals

I Glove Materials

J Use of these Appendices

Appendix A5. Management of Flow of Cleaning Solvents to Wet Surfaces (The Wettability Index and the Dimensionless Ohnesorge Number)

A Flow of Fluids

B Restricted Fluid Flow

C Physical Properties

D Solvents are Fluids

E The Wetting Index

F Limitations of the Wetting Index

G Dimensionless Numbers

H The Ohnesorge Number

I Meanings of the Ohnesorge Number

J Mechanisms Associated with the Ohnesorge Number

K Use of the Ohnesorge Number

L Summary

Group B. Reduction of Ozone Formation by VOCs

Introduction

Appendix B1. Chemistry of Atmospheric Reactions of VOCs Leading to Smog

A Overall Summary

B Combustion-Related Smog (CRS)

C Chemistry of CRS

D Smog Formed with VOCs (Photochemical Smog)

E Distribution of Nitrogen Oxides AffectS Ozone Formation

F Reactions and Removal of Free Radicals

G Reactivity Metrics (MIR)

H Reactivity Metrics (kOH)

I Summary

Appendix B2. Calculation of MIR through Group Contribution Methods

A The Leveling Effect of Maximization

B Prediction of MIR through Group Contribution Analysis

C Results

D The Anomaly!

E Application of Results

F Summary

Group C. Solubility Parameters

Appendix C1. Optimization Method for Determination of Solubility Parameters

A Methodology of an Optimization

A.1 Definition of Correctness

A.2 Mathematical Criteria to Define an Optimum

A.3 Method of Variation of Parameters

Appendix C2. Estimation of Hansen Solubility Parameters (HSP) from Binary Data—PES

A Example Data for Parameter Evaluation

B Estimation of HSP Using Binary Data—Polyethersulfone Polymer (PES)

Appendix C3. Estimation of HSP from Multilevel Data—Bitumen

A Optimization of HSP for Bitumen

B Bitumen is Similar to a Soil

C Hansen Solubility Parameters are Not Legal Tender

Appendix C4. Estimation of HSP from Solvent Mixtures

A Selection of Cleaning Solvents

B Post-Experimental Analysis for Consistency

C Photoresist Materials (Soils)

D Analysis of PR1 Cleaning Tests

E Analysis of Unexpected Solvency Performance

F Local VS. Global Optima

G When a Picture May Not be Worth Any Words

H Evaluation of Cold Cleaning with another Photoresist

I Rate Processes

Appendix C5. Estimation of HSP from Correlations

A Estimation of HSP via Correlations

B Estimation of the Disperse Solubility Parameter

C Estimation of the Polar Solubility Parameter

Appendix C6. Estimation of HSP using the “Pythagorean Theorem”

A Estimation of All HSP using The “Pythagorean Theorem”

Appendix C7. Estimation of HSP from an Equation of State

A Two Fundamental Building Blocks

B Implementation of the Fundamentals

C Calculated Outcomes vs. Accepted HSP Values

D Analysis of Outcomes

E Summary

Appendix C8. Estimation of HSP from Group Contribution Methods

A Relationship to Other Methods

B About Group Contribution Methods

C Group Contribution Methods for Hansen Solubility Parameters

D The Method of Stefanis and Panayiotou

E Application of the Stefanis Panayiotou Method

F A Specific Example

G Use of Group Contribution Methods for HSP via Neural Networks

H Comparison of Estimation Methods for HSP

I The Critical Flaw in All Group Contribution Systems for Solubility Parameters: Group Identification

Appendix C9. Estimation of HSP for Soil Mixtures

A Reasons for Determination of HSP by Solubility Experiments

B Methods for Solvent Selection with HSP via Solubility Experiments

C Methods of Determining Solubility/Insolubility

D Determination of HSP for Soil Materials: Summary

Appendix C10. Hoy Solubility Parameters

A Other Solubility Parameters

B Hoy Solubility Parameters

C Calculation of the Hoy Total Solubility Parameter

D Fractionation by Hoy of His Total Solubility Parameter

E The Aggregation Number

F Calculation of the Polar Attraction Constant (F_P)

G Calculation of Hoy's Hydrogen Bonding Solubility Parameter

H Calculation of Hoy's Polar Solubility Parameter

I Calculation of Hoy's Disperse Solubility Parameter

J Calculated Results of Hoy Solubility Parameters

K Group Contribution Constants Used to Produce Hoy Solubility Parameters

L Unique Advantages of the Hoy Solubility Parameters

M Hoy Solubility Parameters from Functional Group Analysis

N Non-Interchangeability of Functional Groups

O Hoy Solubility Parameters of Polymers

P Equivalence of Hoy and Hansen Solubility Parameters

Q Hoy Solubility Parameters for Non-Polymeric Soils

R Choice of Systems of Solubility Parameters

Appendix C11. Values of Hansen Solubility Parameters for Solvents, Soils, and Polymers

A Hansen Solubility Parameter Data About Cleaning Solvents

B Hansen Solubility Parameter Data About Soil Components

C Hansen Solubility Parameter Data About Polymeric Materials

Appendix C12. The Teas Graph

A Fractional Solubility Parameters (the Teas Graph)

B How to Use the Teas Graph

C A Limitation of the Teas Graph

D A Crucial Flaw of the Teas Graph

Group D. Solvent Substitution

Introduction

Appendix D1. Examples and Methodology of Solvent Substitution

A VOC Exemption in Aerospace Wipe Cleaning

B No Change in Time to Complete Dryness

C Improved Flammability Ratings

D Substitution for Trichloroethylene

E Substitution for Benzene

F Substitution for Methylene Chloride

G Substitution for Perchloroethylene

H Substitution for Methyl Ethyl Ketone (MEK)

I Substitution for CFC-113 as a Wipe Clean Solvent

J Selection Based on Evaporation Rate

K Selection Based on Surface Tension

L The Missing Unit Operation

M Solvent Substitution Examples: Summary

Appendix D2. Examples of Solvent Substitution to Achieve VOC Reduction

A Background

B Approaches for Solvent Substitution Based on Minimization of MIR Values

C Substitution for Trichloroethylene

Index

Engineers and scientists involved in precision cleaning across sectors including aerospace, defense, medical device manufacturing, pharmaceutical processing, semiconductor / electronics, etc.

• Three methods explained in detail for substitution of suitable solvents for those unsuitable for any reason: toxic solvents don't have to be tolerated; this volume explains how to do better
• Enables users to make informed judgments about their selection of cleaning solvents for specific applications, including solvent replacement decisions
• Explains how to plan and implement solvent cleaning systems that are effective, economical and compliant with regulations