The Coloration of Wool and Other Keratin Fibres

Keratin fibres, particularly wool fibres, constitute an important natural raw material in textiles due to their comfort and thermal proprieties. Wool coloration demands an understanding of the complex nature of the interplay between wool fibre chemistry, morphology and the coloration processes. The Coloration of Wool and other Keratin Fibres is a comprehensive treatment, written by leading international experts, of the chemistry and chemical processes involved in wool dyeing, printing, preparation and finishing. It covers:  the chemical and physical structure of wool keratin fibres, detailing their complex heterogeneity and the subtle links between fibre structure and dyeability. the coloration of fabrics containing wool, including a variety of wool blends such as wool/silk, wool/polyester and wool/cotton, and luxury keratin fibres such as mohair, cashmere and camel the chemistry of the various types of dyes utilised in wool dyeing and in–depth discussions on the physical properties to optimise these processes practical application of dyes to wool in all its forms, loose stock, combed tops, yarns and piece goods, is covered in the chapter on wool dyeing machinery two chapters, one on bleaching and whitening and one on dyeing human hair, provide a valuable extension to the topic of cosmetic chemistry. This book is essential reading for professionals world–wide working in companies involved in the dyeing and printing of wool, wool blends and other keratin fibres and also for the producers of dyes and auxiliary dyeing agents. It is a valuable resource for teachers and students of universities and technical institutes, as well as for researchers who are focusing their investigations on wool, wool blends, human hair or dyes and auxiliaries.

List of Contributors xv Society of Dyers and Colourists xvii Preface xix 1 The Structure of Wool 1 John A. Rippon 1.1 Introduction 1 1.2 Composition of Wool 2 1.3 Chemical Structure of Wool 5 1.3.1 General Chemical Structure of Proteins 5 1.3.2 Amino Acid Composition of Wool 6 1.3.3 Arrangement of Amino Acids in Wool 8 1.3.3.1 Covalent Crosslinks 10 1.3.3.2 Noncovalent Bonds (Interactions) 10 1.3.4 The Structure of Wool Proteins 11 1.3.5 Wool Lipids 13 1.4 Morphological Structure of Wool 14 1.4.1 The Cuticle and the Fibre Surface 16 1.4.1.1 The Epicuticle and the Allw¨orden Reaction 19 1.4.1.2 The Epicuticle and the Hydrophobic Surface of Wool 21 1.4.1.3 The Exocuticle 22 1.4.1.4 The Endocuticle 22 1.4.2 The Cortex 23 1.4.2.1 Intermediate Filament/Matrix Structure 24 1.4.2.2 Macrofibrils, Nuclear Remnants and Intermacrofibrillar Material 25 1.4.2.3 Ortho/Para Segmentation of the Cortex 26 1.4.3 The Cell Membrane Complex 27 1.4.3.1 Intercellular Cement 29 1.4.3.2 Lipid Component of the Cell Membrane Complex 29 1.4.3.3 Resistant Membranes 29 1.4.3.4 Amount of Cell Membrane Complex in Wool 30 1.4.3.5 Differences Between Cell Membrane Complexes in Cuticle and Cortex 31 1.4.3.6 The Cell Membrane Complex and Fabric Properties 31 1.5 Chemical Reactivity of Wool 32 1.6 Damage in Wool Dyeing 32 1.6.1 Nonkeratinous Proteins and Damage in Dyeing 33 1.6.2 Influence of Dyebath pH on Fibre Damage 34 1.7 Conclusion 35 References 35 2 The Chemical and Physical Basis for Wool Dyeing 43 John A. Rippon 2.1 Introduction 43 2.2 The Chemical Basis for Wool Dyeing 43 2.2.1 The Wool–Water System 44 2.2.2 The Amphoteric Nature of Wool and Dyeing Behaviour 44 2.2.3 Classical Theories of Wool Dyeing 46 2.2.3.1 Gilbert–Rideal Theory 47 2.2.3.2 Donnan Theory 48 2.2.4 Modern Theories of Wool Dyeing 49 2.3 Standard Affinity and Heat of Dyeing 50 2.4 Classification of Dyes Used for Wool 52 2.5 Dye Aggregation 55 2.6 The Role of Fibre Structure in Wool Dyeing 60 2.6.1 Diffusion of Dyes 60 2.6.2 Pathways of Dye Diffusion into Wool 61 2.6.2.1 The Fibre Surface as a Barrier to Dyeing 61 2.6.2.2 Diffusion of Dye in the Cortex 64 2.7 Effect of Chemical Modifications on Dyeing 66 2.7.1 Chlorination 66 2.7.2 Plasma Treatment 67 2.7.3 Differential Dyeing 68 2.8 Conclusion 68 References 69 3 The Role of Auxiliaries in the Dyeing of Wool and other Keratin Fibres 75 A.C. Welham 3.1 Introduction 75 3.2 Surface Activity of Wool–Dyeing Auxiliaries 76 3.2.1 Anionic Auxiliaries 76 3.2.2 Cationic Auxiliaries 77 3.2.3 Ethoxylated Nonionic and Cationic Auxiliaries 78 3.2.4 Amphoteric Auxiliaries 80 3.2.5 Other Auxiliaries 81 3.3 Brightening Agents 81 3.4 Levelling Agents 82 3.4.1 Material Faults 83 3.4.2 Dyeing and Processing Faults 83 3.4.2.1 Method 1 84 3.4.2.2 Method 2 84 3.4.2.3 Method 3 84 3.4.2.4 Method 4 85 3.4.3 Testing the Action of Levelling Agents 85 3.4.4 Product Selection 86 3.4.5 Coverage of Skittery or Tippy–Dyeing Wool 86 3.5 Restraining and Reserving Agents in Wool Blend Dyeing 88 3.6 Antiprecipitants 89 3.7 Wool Protective Agents 89 3.8 Low–Temperature Dyeing 90 3.9 Correction of Faulty Dyeings 92 3.10 Aftertreatments to Improve Wet Fastness 93 3.10.1 Effluent Control in Chrome Dyeing 94 3.11 Antifrosting Agents 95 3.12 Antisetting Agents 95 3.13 Sequestering Agents 96 3.14 Conclusion 96 References 97 4 Ancillary Processes in Wool Dyeing 99 D.M. Lewis 4.1 Introduction 99 4.2 Wool Scouring 99 4.3 Wool Carbonising 100 4.4 Shrink–Resist Treatments 102 4.4.1 Top Shrink–Resist Processes 102 4.4.2 Garment Shrink–Resist Treatments 105 4.4.2.1 Chlorine–Resin Processes 105 4.4.2.2 Polymer–Only Systems 106 4.4.3 Fabric Shrink–Resist Treatments 106 4.4.4 Miscellaneous Developments 107 4.4.5 Colour–Fastness Requirements for Machine–Washable Wool 108 4.5 Insect–Resist Treatments 108 4.5.1 Insect Pests 108 4.5.2 Insect–Resist Agents 109 4.5.2.1 Mitin FF High Conc. (CGY) 111 4.5.2.2 Eulan U33, Eulan WA New (BAY) 111 4.5.2.3 Mitin AL (CGY) 112 4.5.3 Application Methods for IR Agents 113 4.5.3.1 Application During Dyeing 113 4.5.3.2 Application During Scouring 113 4.5.3.3 Application by Addition to Spinning Lubricants 114 4.5.3.4 The Current and Future Status of Wool Moth–Proofing 114 4.6 Flame–Retardant Treatments 115 4.7 Antisetting Agents 116 4.7.1 The Role of Oxidants in Preventing Setting in Dyeing 118 4.7.2 The Role of Electrophilic Reagents in Controlling Setting in Dyeing 119 4.8 Fibre Arylating Agents 120 References 126 5 Bleaching and Whitening of Wool: Photostability of Whites 131 Keith R. Millington 5.1 Introduction 131 5.2 Wool Colour 132 5.2.1 Measuring Wool Colour 132 5.2.2 Improving Wool Colour by Selection 134 5.2.3 Improving Colour in the Scour 134 5.2.4 Nonscourable Yellowing 135 5.2.5 Wool Colour Compared with Cotton and Synthetics 135 5.3 Wool Bleaching 138 5.3.1 Oxidative Bleaching 138 5.3.2 Reductive Bleaching 139 5.3.3 Double (or Full) Bleaching 140 5.3.4 Bleaching of Pigmented Wools 140 5.3.5 Bleaching in the Dyebath 140 5.3.6 Biobleaching of Wool Using Enzymes 142 5.3.7 Activated Peroxide Bleaching 143 5.3.8 Catalytic Peroxide Bleaching 144 5.3.9 Novel Bleaching Methods for Wool 144 5.4 Fluorescent Whitening of Wool 144 5.5 Photostability of Wool 145 5.5.1 Mechanism of Wool Photoyellowing 148 5.5.2 Mechanism of Photoyellowing of Fluorescent Whitened Wool 149 5.5.3 Methods for Improving Photostability 151 References 153 6 Wool–dyeing Machinery 157 Jamie A. Hawkes and Paul Hamilton 6.1 Introduction 157 6.2 Top Dyeing 158 6.2.1 Longclose (UK) Large Bump Tops 160 6.2.2 Obem Big Form 161 6.2.3 Vigoreux Printing 161 6.3 Loose Stock Dyeing 162 6.3.1 Continuous Dyeing of Loose Stock 165 6.4 Hank–Dyeing Yarn 166 6.4.1 Carpet Yarn 166 6.4.2 Hand–Knitting and Machine–Knitting Yarn 167 6.4.3 Robotic Handling 169 6.4.4 Space Dyeing of Yarn 169 6.5 Yarn Package Dyeing 171 6.5.1 Package Preparation 172 6.5.2 Machinery 175 6.6 Piece Dyeing 178 6.6.1 Jet and Overflow Dyeing 178 6.6.2 Beam Dyeing 179 6.7 Garment Dyeing 179 6.8 Carpet Piece Dyeing 182 6.9 Drying 183 6.9.1 Mechanical Moisture Removal 183 6.9.2 Thermal Moisture Removal 184 6.10 Dyehouse Automation 186 6.10.1 Dyehouse Control Systems 186 6.10.2 Factory Management Systems 188 6.10.3 Process Control 188 6.10.4 Effluent Control Systems 190 6.10.5 Colour Measurement 191 6.11 Laboratory Dyeing 192 6.11.1 Tops, Loose Stock, Hanks and Package Yarn 193 6.11.1.1 Moving Fabric and Moving Liquor 193 6.11.1.2 Stationary Beaker and Moving Liquor 196 6.11.1.3 Stationary Beaker and Moving Liquor 196 6.11.1.4 Stationary Liquor and Moving Fabric 198 6.11.2 Piece Dyeing 198 6.11.3 Garment Dyeing 201 6.11.4 Laboratory Machine Control Systems 202 References 203 7 Dyeing Wool with Acid and Mordant Dyes 205 P.A. Duffield 7.1 Introduction 205 7.2 Acid Dyes 208 7.2.1 Acid Dye Subclassification 208 7.2.1.1 Level–Dyeing or Equalising Acid Dyes 209 7.2.1.2 Fast Acid or Half–Milling Dyes 211 7.2.1.3 Milling and Super–Milling Dyes 212 7.2.2 Optimised Dye Ranges 213 7.3 Natural Dyes 213 7.4 Mordant Dyes 214 7.4.1 Chrome Dyeing Processes 216 7.4.1.1 Prechrome Dyeing 217 7.4.1.2 Metachrome Dyeing 217 7.4.1.3 Afterchrome Dyeing 218 7.4.2 Theoretical Aspects 219 7.4.3 Low–Chrome Dyeing 223 7.5 Specific Dyeing Methods 226 References 227 8 Dyeing Wool with Metal–complex Dyes 229 Stephen M. Burkinshaw 8.1 Introduction 229 8.2 Dye Structure 230 8.2.1 Electronic Structure 232 8.2.2 Colour and Light Fastness 235 8.2.3 Stereochemistry and Isomerism 236 8.2.4 1 : 1 Metal–Complex Dyes 237 8.2.5 1 : 2 Metal–Complex Dyes 239 8.2.5.1 Weakly Polar 1 : 2 Dyes 239 8.2.5.2 Strongly Polar 1 : 2 Dyes 240 8.3 Dye Application 242 8.3.1 1 : 1 Metal–Complex Dyes 242 8.3.1.1 Dye–Fibre Interaction 244 8.3.2 1 : 2 Metal–Complex Dyes 246 8.3.2.1 Weakly Polar 1 : 2 Dyes 246 8.3.2.2 Strongly Polar 1 : 2 Dyes 246 8.3.2.3 Dye–Fibre Interaction 247 8.4 Environmental Aspects 248 References 248 9 Dyeing Wool with Reactive Dyes 251 D.M. Lewis 9.1 Introduction 251 9.2 Commercial Reactive Dyes for Wool 252 9.3 The Chemistry of Reactive Dyes 253 9.3.1 Nucleophilic Substitution Reactions 253 9.3.2 Michael Addition Reaction 253 9.3.3 Specific Reactive Dyes for Wool 254 9.3.3.1 Lanasol (CGY, now Huntsman) Dyes 254 9.3.3.2 Drimalan F (S, now Clariant) Dyes 256 9.3.3.3 Realan (DyStar) Dyes 257 9.4 Application Procedures 260 9.4.1 Auxiliary Agents 260 9.4.2 Dyeing Processes used with Reactive Dyes 261 9.4.2.1 Untreated Wool 261 9.4.2.2 Machine–Washable Wool 262 9.4.2.3 Aftertreatment of Dyeings 263 9.4.2.4 Measurement of Dye Fixation 267 9.4.2.5 Novel Processes for use with Reactive Dyes 269 9.4.3 Effect of Reactive Dyes on Fibre Properties 276 9.5 Novel Reactive Dye Systems for Wool 281 9.5.1 Maleinimides 281 9.5.2 Isocyanate and Isothiocyanate Bisulphite Adducts 281 9.5.3 Carboxymethyl Carbodithioate Dyes 282 9.5.4 Trifunctional Reactive Dyes Prepared from bis–(chloroethyl–sulphonylethyl)amine [P–3] Reaction with a DCT Dye 282 9.5.5 Crosslinking Agents to Covalently Fix Acid Dyes to Wool 283 9.6 Identification of the Reaction Sites in the Fibre 285 9.7 Conclusion 287 References 287 10 Dyeing Wool Blends 291 D.M. Lewis 10.1 Introduction 291 10.2 Wool/Cotton 293 10.2.1 Dyeing of Cotton 293 10.2.2 Exhaustion Dyeing of Wool/Cotton Blends 296 10.2.2.1 Direct Dyes 297 10.2.2.2 Reactive (Cotton) Dyes 297 10.2.2.3 Vat Dyes 298 10.2.2.4 General Comments 299 10.2.3 Pad Dyeing of Wool/Cotton Blends 300 10.2.4 Wool Damage During Dyeing 301 10.3 Amination of Cellulosic Fibres 303 10.4 Wool/Silk 305 10.4.1 Dyeing of Silk 306 10.4.2 Dyeing of Wool/Silk Blends 308 10.4.2.1 Milling and 1 : 2 Metal–Complex Dyes 309 10.4.2.2 Reactive Dyes 309 10.5 Wool/Nylon 310 10.5.1 Dyeing of Nylon 310 10.5.1.1 Fibre Structure 310 10.5.1.2 Acid Dyes 312 10.5.1.3 Factors Influencing the Dyeing Behaviour of Nylon 314 10.5.1.4 Practical Considerations 317 10.5.2 Dyeing of Wool/Nylon Blends 319 10.5.2.1 Acid Levelling Dyes 319 10.5.2.2 Milling and 1 : 2 Metal–Complex Dyes 321 10.5.2.3 Afterchrome Dyes 322 10.5.2.4 Reactive Dyes 323 10.6 Wool/Polyester 323 10.6.1 Dyeing of Polyester 323 10.6.1.1 Fibre Structure 323 10.6.1.2 Adsorption of Disperse Dyes 325 10.6.1.3 Dispersing Agents 327 10.6.1.4 Levelling Agents 328 10.6.1.5 Carriers 328 10.6.1.6 Machinery 330 10.6.1.7 Continuous Dyeing 330 10.6.1.8 Heat Setting 331 10.6.1.9 Practical Considerations 331 10.6.2 Dyeing of Wool/Polyester Blends 333 10.6.2.1 Dyeing Procedures 333 10.6.2.2 Dyeing Conditions 334 10.6.2.3 The Role of Oxidants in Preventing Setting in Dyeing 335 10.6.2.4 Dye Selection 336 10.6.2.5 Carrier Selection 337 10.6.2.6 Reactive Disperse Dyes for Wool/Polyester Blend Dyeing 339 10.6.2.7 Novel Arylating Agents for Facilitation of the Dyeing of Wool and Polyester Fibres with Disperse Dyes 341 10.7 Wool/Acrylic 341 10.7.1 Dyeing of Acrylic Fibres 342 10.7.1.1 Fibre Structure 342 10.7.1.2 Cationic Dyes 344 10.7.2 Dyeing of Wool/Acrylic Blends 348 10.7.2.1 Preparation 348 10.7.2.2 Dyeing Procedures 348 10.7.2.3 Novel Dyeing Techniques for Wool/Acrylic Blends 351 10.8 Conclusion 351 References 352 11 The Coloration of Human Hair 357 Robert M. Christie and Olivier J.X. Morel 11.1 Introduction 357 11.2 Structure and Morphology of Human Hair 359 11.3 Natural Colour of Hair 360 11.4 Physical Chemistry of Hair Dyeing 364 11.5 Toxicology of Hair Dyes 365 11.6 Oxidative Hair Coloration 366 11.7 Alternative Approaches to Permanent Hair Dyeing 369 11.8 Nonoxidative Hair Dyeing 375 11.9 Conclusion 386 References 387 12 Wool Printing 393 P.J. Broadbent and M.L.A. Rigout 12.1 Introduction 393 12.2 Preparation for Printing 394 12.2.1 Oxidative Processes 394 12.2.1.1 Chlorination with Dichloroisocyanuric Acid 395 12.2.1.2 Kroy Technology 396 12.2.2 Polymer Treatments 396 12.2.2.1 Top Treatment: Chlorination–Hercosett 396 12.2.2.2 Fabric Treatments 397 12.2.3 Plasma Treatments 397 12.2.4 Other Methods of Preparation for Printing 398 12.3 Direct Printing 399 12.3.1 Machinery 399 12.3.2 Dye Selection and Print Recipes 399 12.3.2.1 Nonreactive Dyes 400 12.3.2.2 Reactive Dyes 400 12.3.2.3 Pigments 401 12.3.2.4 Recipes 401 12.3.3 Steaming 402 12.3.4 Washing and Aftertreatment 404 12.4 Discharge Printing 405 12.4.1 Ground Shades 405 12.4.2 Discharge Agents 405 12.4.3 Illuminating Dyes 407 12.4.4 Printing and Fixation 407 12.5 Resist Printing 408 12.5.1 Chemical Resist Processes 409 12.5.1.1 Sulphamic Acid Resist Printing 409 12.5.2 Mechanical/Chemical Resist Processes 411 12.5.2.1 Thiotan WS 412 12.5.3 Reactive–Under–Reactive Resist 412 12.6 Digital Printing 412 12.6.1 Machinery 413 12.6.2 Ink Formulation 413 12.6.2.1 Nonreactive Dye–Based Inks 414 12.6.2.2 Reactive Dye–Based Inks 414 12.6.3 Fabric Pretreatment 415 12.6.4 Fixation 417 12.6.4.1 Steaming 417 12.6.4.2 Print–Batch 417 12.6.5 Wash–Off 417 12.7 Wool Blends 418 12.7.1 Wool/Polyester 419 12.7.2 Wool/Cotton 419 12.7.3 Wool/Acrylic 420 12.8 Cold Print Batch 420 12.9 Transfer Printing 421 12.9.1 Wet or ‘Migration’ Transfer Printing 421 12.9.2 Sublimation Transfer Printing 422 12.9.3 Benzoylated Wool 424 12.10 Novel Effects 425 12.10.1 Burn–Out ( devor´ee ) Printing 425 12.10.2 Sculptured Effects 425 References 426 Index Color plate