Canmaking: The Technology of Metal Protection and Decoration

367 Pages·1998·10.133 MB·English

by  T. A. Turner (auth.)

Canmaking
The Technology of Metal Protection and Decoration
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Canmaking
The Technology of Metal Protection
and Decoration
T.A. TURNER
Crown Cork & Seal
Wantage
UK
SPRINGER SCIENCE+BUSINESS MEDIA, LLC
First edition 1998
© 1998 T.A. Turner
Originally published by Blackie Academic & Professional in 1998
Thomson Science is a division ofInternational Thomson Publishing I(f)P'
Typeset in 10/12 Times by Blackpool Typesetting Services Limited, UK
ISBN 978-1-4419-4743-7 ISBN 978-1-4757-4705-8 (eBook)
DOI 10.1007/978-1-4757-4705-8
AJI rights reserved. No part of this publication may be reproduced, stored in a
retrieval system or transmitted in any form or by any means, electronic,
mechanical photocopying, recording or otherwise, without the prior written
permission of the publishers. Applications for permission should be addressed to
the rights manager at the London address of the publisher.
The publisher makes no representation, express or implied, with regard to the
accuracy of the information contained in this book and cannot accept any legal
responsibility or liability for any errors or omissions that may be made.
A catalogue record for this book is available from the British Library
Library of Congress Catalog Card Number: 97-74422
i§Printed on acid-free text paper, manufactured in accordance with ANSIINISO
Z39.48-1992 (Permanence of Paper)
Contents
Preface xi
1 Metals and methods of manufacture 1
1.1 Introduction I
1.2 Metals used in packaging 3
1.2.1 Steel 3
1.2.2 Aluminium 12
1.2.3 Mechanical properties 12
1.3 Methods of manufacture 13
1.3.1 Welded can manufacture 13
1.3.2 Two-piece can manufacture 16
1.3.3 Beverage cans 20
1.3.4 Easy-open (scored) ends 21
1.3.5 Aerosols 24
1.3.6 Metal c10sures 26
1.3.7 Secondary processes 29
1.3.8 Corrosion 32
Appendix IA: Comparison of methods of gauge and thickness measurements 38
References 38
2 Coating types and their uses 39
2.1 Introduction 39
2.2 Coatings and their resin content 40
2.2.1 OIeo-resinous products 40
2.2.2 Synthetic products 41
2.3 Curing and drying mechanisms 52
2.3.1 Types of curing reaction 52
2.4 Functions of container coatings 58
2.4.1 Corrosion protection 58
2.4.2 Protection of the product 73
2.4.3 Facilitating manufacture 74
2.4.4 Decoration 76
2.4.5 Abrasion resistance 77
2.4.6 Coating systems for processed foods 78
2.4.7 Summary 80
Appendix 2A: Global suppliers of surface coatings 80
References 81
3 Coating technologies and application methods 82
3.1 Introduction 82
3.2 Coating technologies 82
3.2.1 Conventional coatings 83
3.3 Methods of coating application 84
3.3.1 Roller-coating in sheet form 84
3.3.2 Coil-coating 87
3.3.3 Tandem lacquering 88
3.3.4 Anilox coating systems 89
3.3.5 Curtain coating 91
3.3.6 Spraying 91
3.4 Alternative coating systems 107
3.4.1 Electrocoating 107
3.4.2 Autophoresis 115
Vl CONTENTS
3.4.3 UV and electron beam curing 116
3.4.4 Powder coatings 116
3.4.5 Lamination 125
3.4.6 Summary and future development 130
References 130
4 The printing of metal packaging 132
4.1 Introduction 132
4.2 Colour and colour perception 133
4.2.1 Principles of colour science 133
4.2.2 Colour mixtures 133
4.2.3 Colour separation for multi-colour printing 134
4.2.4 Colour measurement 139
4.2.5 Colorants 141
4.3 Colour in metal packaging 142
4.3.1 Pigments in common use 144
4.3.2 Yellow and orange pigments 145
4.3.3 Blue and green pigments 146
4.3.4 Red pigments 147
4.3.5 PMTA pigments 147
4.3.6 White pigments 148
4.3.7 Black pigments 148
4.3.8 Measurement of particle size 148
4.4 Traditional printing processes 149
4.4.1 Lithography 150
4.4.2 Dry-offset 155
4.4.3 Waterless plates (including driography) 156
4.4.4 Gravure 158
4.5 Printing on two-piece cans and other containers 159
4.5.1 Basic design of container printers 161
4.5.2 Two-piece can base coaters 162
4.5.3 Rutherford Process Decorator 162
4.5.4 Developments in flexography 164
4.6 Limitations of traditional printing processes 165
4.6.1 Time to press 165
4.6.2 Cost to run-Iength sensitivity 167
4.6.3 Flexibility 168
4.6.4 The role of digital printing 168
4.7 Alternative and new printing processes 169
4.7.1 Contact processes 169
4.7.2 Non-contact printing 179
4.7.3 Some special applications 181
Appendix 4A: Some major international printing ink companies 185
Appendix 4B: Suppliers of printing machines 186
References 186
5 Curing and drying systems 187
5.1 Introduction 187
5.2 Thermal systems 188
5.2.1 Convected hot air 188
5.2.2 Infrared irradiation 197
5.2.3 Electrical induction heating 201
5.3 Control of VOC emissions 204
5.3.1 Incineration 205
5.3.2 Biodegradation 208
5.3.3 Adsorption 209
CONTENTS vii
5.3.4 Condensation 209
Appendix 5A: Suppliers of oven equipment 210
References 210
6 Curing with ultraviolet irradiation 211
6.1 Introduction 211
6.2 UV-curable systems 212
6.2.1 Free-radical polymerization 212
6.2.2 Cationic curing systems 215
6.2.3 Adhesion 218
6.2.4 Toxicity and handling 218
6.3 UV-curing equipment 220
6.3.1 Mercury vapour lamps 220
6.3.2 Other lamps and configurations 224
6.4 The application of UV curing in metal packaging 227
6.4.1 Sheet-fed operations 229
6.4.2 Thermal bump 235
6.4.3 Applications in two-piece can decoration 235
6.5 Factor limiting the use of UV curing 236
6.5.1 Changes in canmaking technology 236
6.5.2 Alternative materials technology 237
6.5.3 Concerns about toxicity 238
6.5.4 Initial technical short-comings of UV-curable materials 239
6.5.5 Cost of materials 239
6.6 Electron beam (electron curtain) curing 241
6.7 Conclusions 243
Appendix 6A: Suppliers and producers of UV-curing equipment 243
References 244
7 Practical rheology 245
7.1 Introduction 245
7.2 Theory of rheology 246
7.3 Rheological properties of paste inks 246
7.3.1 Pseudo-plastic behaviour 247
7.3.2 Thixotropy and dilatancy 248
7.3.3 Tack 250
7.3.4 The effect of temperature 250
7.4 Viscosity measurement 252
7.4.1 Types of viscometer 252
7.4.2 Flow cups 253
7.4.3 Falling bar viscometer 254
7.5 Rheology and press behaviour 256
7.5.1 Wet-on-wet trapping 256
7.5.2 Press temperature 262
7.5.3 Other aspects of press performance 262
7.5.4 Impact on the lithographic process 263
7.6 Application of roJler-coatings 263
7.6.1 Lacquer application at elevated temperature 263
7.6.2 Automatic viscosity contro1 263
References 266
8 Colour reproduction and pre-press technologies 267
8.1 Introduction 267
8.2 Half-tone images 269
8.2.1 Screen angles 271
8.2.2 Stochastic screens 272
viii CONTENTS
8.3 Colour separation 273
8.3.1 Colour correction 275
8.3.2 Markolor 276
8.3.3 Dot area and dot gain 277
8.4 Distortion printing 278
8.5 Modem graphics systems 280
8.5.1 The scanner 282
8.5.2 Raster Image Processor (RIP) 284
8.5.3 Image-setter 285
8.5.4 Proofing machines 285
8.6 Pixels, dots, etc. 286
8.7 Printing plates 288
8.7.1 Metal plates for lithography 288
8.7.2 Recent developments in plate-making 290
8.7.3 Examples of alternative imaging processes 291
8.8 Offset blankets 293
8.8.1 Selection of blanket type 295
8.8.2 Special blankets 296
8.9 Make-ready and change-over 296
8.9.1 Plate change 297
8.9.2 Wash-up ofthe blankets and/or roller system 297
8.9.3 Colour setting and control 297
Appendix 8A: Examples of proofing machines 299
References 299
9 Test methods 300
9.1 Introduction 300
9.2 Materials, application and curing 301
9.2.1 Rheology 301
9.2.2 Printability testing 304
9.2.3 Colour and colour strength 307
9.2.4 Film thickness 310
9.2.5 Solids content 311
9.2.6 Drying and curing 312
9.3 Performance testing 314
9.3.1 Adhesion 314
9.3.2 Hardness and abrasion resistance 316
9.3.3 Degree of cure 317
9.3.4 Solvent and chemical resistance 318
9.3.5 Light fastness 381
9.4 Product testing 319
9.4.1 Pack testing 319
9.4.2 Mobility (coefficient of friction and slip testers) 326
9.4.3 Extraction testing 328
Appendix 9A: Suppliers of tack measuring equipment 331
Appendix 9B: Suppliers of viscometers and rheometers 331
Appendix 9C: Suppliers of laboratory proofers and printability testers 331
Appendix 9D: Makers and suppliers of spectrophotometers and colorimeters 331
Appendix 9E: Suppliers of abrasion and rub testers 332
References 332
10 Factors driving future development 333
10.1 Introduction 333
10.2 Environmentallegislation 334
10.3 Current legis1ation 337
10.3.1 USA 337
10.3.2 Legis1ation in Europe and the rest of the world 340
CONTENTS IX
10.4 Ozone depletion 343
10.5 Other hazardous wastes 343
10.5.1 Hexavalent chromiurn 344
10.6 Environmental strategies 344
10.7 Trends in surface coatings development 345
10.7.1 Powders 345
10.7.2 Laminates 346
10.7.3 100% water-borne 346
10.7.4 Radiation curable 346
10.8 Recycling 347
10.8.1 Technical factors 347
10.8.2 Economics 347
10.9 Food contact issues 348
10.9.1 Elimination of potentially toxic materials 348
10.9.2 Functional barrier concept 349
10.10 Commercial factors 349
10.10.1 Performance and quality 349
10.10.2 Faster response times to customer needs 350
References 351
Index 353
Preface
This book describes the materials and processes used in the protection and
decoration of meta! packaging. It is intended to give the reader a familiarity with
the technology and terminology used in the industry and an insight into the
reasons why certain technologies are used and why others have been discarded.
It deals with the basic substrates, steel and aluminium, the demands of the
markets served, briefly with the basic metal-forming processes used in the
production of metal packaging and the specific needs of different packaging
types in terms of decoration and metal protection.
Whilst most relevant technologies are covered to some extent, the greatest
emphasis is placed on those used or likely to be used extensively, such as
ultraviolet curing, and less attention is given to those used less widely.
This book will be a useful reference to existing producers of packaging
seeking opportunities for change and for those newly entering the industry
whether as packaging manufacturers or as packaging users.
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