Metallic Pigments in Polymers

243 Pages·2.885 MB·English

by  Wheeler, Ian R.

Metallic Pigments
in Polymers
Ian Wheeler
Rapra Technology Limited
Shawbury, Shrewsbury, Shropshire SY4 4NR, United Kingdom
Telephone: [phone] Fax: [phone]
http://www.rapra.net
1MP Title Page etc 1 27/11/01, 12:08 pm
First Published 1999 by
Rapra Technology Limited
Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK
©1999, Rapra Technology Limited
The right of Ian Wheeler to be recognised as author of this Work
has been asserted by him in accordance with sections 77 and 78 of the
Copyright, Designs and Patents Act 1998.
All rights reserved. Except as permitted under current legislation no part
of this publication may be photocopied, reproduced or distributed in any
form or by any means or stored in a database or retrieval system, without
the prior permission from the copyright holder.
A catalogue record for this book is available from the British Library.
ISBN: 1-85957-166-2
Typeset by Rapra Technology Limited
Printed and bound by Polestar Scientifica, Exeter, UK
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Contents
1 Introduction and History ................................................................................3
1.1 Introduction...........................................................................................3
1.2 Origins and history................................................................................4
2 Metal Pigment Types.......................................................................................7
2.1 Aluminium.............................................................................................7
2.2 Gold bronze...........................................................................................8
2.3 Copper...................................................................................................8
2.4 Nickel ....................................................................................................8
2.5 Stainless steel .........................................................................................9
2.6 Zinc .......................................................................................................9
2.7 Iron........................................................................................................9
2.8 Tin.......................................................................................................10
2.9 Silver....................................................................................................10
2.10 Gold.....................................................................................................10
2.11 Other metals........................................................................................10
3 Manufacture .................................................................................................11
3.1 Dry milling...........................................................................................11
3.1.1 Aluminium...............................................................................12
3.1.2 Gold bronze.............................................................................12
3.2 Continuous dry milling........................................................................13
3.2.1 Aluminium...............................................................................13
3.2.2 Gold bronze.............................................................................13
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3.3 Wet milling ..........................................................................................14
3.3.1 Aluminium...............................................................................14
3.3.2 Gold bronze.............................................................................19
3.3.3 Silver........................................................................................19
3.3.4 Nickel......................................................................................20
3.3.5 Stainless steel ...........................................................................21
3.3.6 Zinc.........................................................................................22
3.4 Continuous wet milling........................................................................22
3.5 Spherical metal pigments .....................................................................22
3.6 Rapidly solidified flakes.......................................................................23
3.7 Vacuum deposition ..............................................................................24
3.8 Cut foil glitters.....................................................................................25
3.9 Flakes with coloured surfaces ..............................................................25
3.9.1 Chemical modification of metal surfaces .................................26
3.9.2 Colour formation in situ..........................................................27
3.9.3 Attachment of pre-formed colorants........................................28
3.10 Metal coatings on non-metallic substrates ...........................................29
3.11 Other methods.....................................................................................30
References.....................................................................................................31
4 Pigment Characteristics.................................................................................35
4.1 Morphology.........................................................................................35
4.1.1 Particle size..............................................................................35
4.1.2 Particle shape...........................................................................38
4.1.3 Aspect ratio .............................................................................39
4.1.4 Surface uniformity ...................................................................41
4.2 Physical properties...............................................................................41
4.2.1 Specific gravity.........................................................................41
4.2.2 Water covering area.................................................................41
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4.2.3 Specific surface area.................................................................42
4.2.4 Heat and lightfastness..............................................................42
4.2.5 Chemical resistance..................................................................43
4.2.6 Magnetism...............................................................................43
4.3 Visual properties..................................................................................43
4.3.1 Colour and brightness..............................................................44
4.3.2 Opacity....................................................................................45
4.3.3 Flop .........................................................................................45
4.3.4 Leafing and non-leafing...........................................................47
4.3.5 Sparkle.....................................................................................50
4.3.6 Distinctiveness of image...........................................................50
4.4 Glitter flakes........................................................................................52
References.....................................................................................................53
5 Delivery Forms..............................................................................................55
5.1 Dry powder..........................................................................................55
5.2 Paste ....................................................................................................55
5.3 Dispersion in resin and solvent ............................................................56
5.4 Plasticiser dispersions...........................................................................56
5.5 Granules ..............................................................................................57
5.6 Dry masterbatch ..................................................................................59
5.7 Liquid masterbatch..............................................................................59
5.8 Compound...........................................................................................60
References.....................................................................................................61
6 Comparison of Mass Pigmentation and Coating...........................................63
6.1 Advantages of coating..........................................................................63
6.1.1 Brightness ................................................................................63
6.1.2 Colour uniformity....................................................................64
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6.1.3 Flop .........................................................................................64
6.1.4 Application temperature..........................................................65
6.1.5 Vacuum metallisation ..............................................................65
6.2 Mass pigmentation advantages............................................................65
6.2.1 Depth of coloration .................................................................65
6.2.2 Single stage versus multistage processing.................................66
6.2.3 Environmental and legislative pressures...................................66
6.2.4 Cost.........................................................................................67
References.....................................................................................................67
7 Mass Pigmentation Application Characteristics ............................................69
7.1 Colour .................................................................................................69
7.2 Dispersibility........................................................................................69
7.3 Opacity and tint strength.....................................................................70
7.4 Orientation..........................................................................................71
7.5 Mechanical properties..........................................................................71
7.6 Cost .....................................................................................................75
7.7 Interrelationships.................................................................................76
7.8 Compatibility.......................................................................................77
7.9 Spherical metal pigments .....................................................................78
7.10 Metal flake pigments with coloured surfaces .......................................78
7.11 ‘Glitter’ flakes......................................................................................79
8 Flow and Weld Lines in Mass Pigmented Applications .................................81
8.1 Description and origins........................................................................81
8.2 Tool design for injection moulding ......................................................85
8.3 Orientation in multiphase and glass filled polymers ............................87
8.4 Orientation of metal pigments.............................................................89
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8.5 Mould tool design for metal pigments .................................................92
8.6 Gates, sprues and runners....................................................................92
8.7 Tool texturing......................................................................................94
8.8 Additional cavity .................................................................................94
8.9 Dynamic melt techniques.....................................................................94
8.9.1 SCORTEC ...............................................................................94
8.9.2 Other techniques......................................................................97
8.10 Localised mould heating ......................................................................98
8.11 Other techniques..................................................................................99
References.....................................................................................................99
9 Formulation of Mass Pigmented Polymers..................................................105
9.1 General techniques.............................................................................105
9.2 Optimising the formulation ...............................................................105
9.2.1 Flake size ...............................................................................106
9.2.2 Flake concentration ...............................................................106
9.2.3 Polymer transparency ............................................................107
9.2.4 Polymer viscosity ...................................................................107
9.2.5 Metallic/organic pigment combinations.................................108
9.2.6 Deep shades...........................................................................108
9.2.7 Spherical pigments.................................................................108
9.3 Incorporation in polymers .................................................................109
9.3.1 Low shear forces....................................................................109
9.3.2 Improvement of flake orientation ..........................................110
9.4 Increasing pigment quality.................................................................110
9.5 Summary............................................................................................111
References...................................................................................................112
10 Conversion Processes ..................................................................................113
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10.1 Injection moulding.............................................................................114
10.2 Blow moulding ..................................................................................115
10.2.1 Blown film.............................................................................115
10.2.2 Blown containers ...................................................................116
10.3 Extrusion...........................................................................................117
10.4 Co-extrusion......................................................................................117
10.5 Paint-less film moulding.....................................................................117
10.6 In-mould decoration ..........................................................................118
10.7 Vacuum forming and thermoforming.................................................118
10.8 Rotational moulding..........................................................................118
10.9 Glass reinforced plastic......................................................................119
10.10Thermosetting polymers ....................................................................120
References...................................................................................................121
11 Applications of Mass Pigmented Systems....................................................123
11.1 Household goods...............................................................................123
11.2 Sports goods ......................................................................................124
11.3 Agricultural film ................................................................................125
11.4 Sacks and bags...................................................................................125
11.5 Containers .........................................................................................126
11.6 Automotive........................................................................................126
11.7 Pearl simulants...................................................................................127
11.8 Mineral simulants..............................................................................128
11.9 Fibres and textiles..............................................................................128
References...................................................................................................129
12 Metal Pigmented Coatings ..........................................................................131
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12.1 Substrate preparation.........................................................................131
12.2 Coating formulation and properties...................................................132
12.2.1 Pigment particle size ..............................................................132
12.2.2 Concentration........................................................................132
12.2.3 Leafing and non-leafing.........................................................133
12.3 Dispersion and incorporation ............................................................133
12.4 Application to the substrate...............................................................134
12.5 Solvent based systems ........................................................................134
12.6 Water-based systems ..........................................................................135
12.7 UV/EB cured coatings ........................................................................139
References...................................................................................................140
13 Applications of Metal Pigmented Coatings .................................................145
13.1 Painting..............................................................................................145
13.1.1 Solvent-based paints ..............................................................146
13.1.2 Water-based paints.................................................................148
13.1.3 In-mould coating ...................................................................152
13.1.4 Miscellaneous paints..............................................................153
13.2 Printing..............................................................................................153
13.2.1 Solvent-based inks .................................................................154
13.2.2 Paste inks...............................................................................154
13.2.3 Water-based inks....................................................................156
13.2.4 Laminates ..............................................................................157
13.2.5 Security Inks ..........................................................................157
13.2.6 Bronze replacement................................................................158
13.3 UV cured coatings..............................................................................161
13.4 PVC Plastisols....................................................................................162
13.5 Anticorrosive and barrier coatings.....................................................162
13.6 Other applications .............................................................................163
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14 Powder Coatings.........................................................................................167
14.1 Material types and properties ............................................................168
14.2 Manufacture......................................................................................168
14.2.1 Dry blend...............................................................................169
14.2.2 Bonding .................................................................................169
14.2.3 Co-extrusion..........................................................................171
14.2.4 Coated flakes.........................................................................172
14.2.5 Other technologies.................................................................172
14.3 Formulation, application techniques and markets..............................173
14.4 Safety and handling ...........................................................................175
References...................................................................................................176
15 Non-colouristic Applications ......................................................................179
15.1 Mechanical reinforcement..................................................................179
15.2 Microwave heating ............................................................................180
15.3 Electrical conductivity........................................................................183
15.3.1 Product forms........................................................................183
15.4 EMI shielding ....................................................................................184
15.4.1 Origin and measurement........................................................185
15.4.2 Legislative requirements.........................................................185
15.4.3 Shielding principles and techniques........................................185
15.4.4 Shielding of polymers.............................................................186
15.4.5 Coating techniques ................................................................187
15.4.6 Mass pigmentation techniques...............................................191
15.5 Light exclusion ..................................................................................192
15.6 Heat and light reflection....................................................................193
15.7 Thermal conductivity.........................................................................194
15.8 Lubrication and wear reduction.........................................................196
15.9 Gas and moisture barrier ...................................................................196
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