WO1995015361A1

WO1995015361A1 - Water dispersible metallic pigment

Info

Publication number: WO1995015361A1
Application number: PCT/IE1994/000058
Authority: WO
Inventors: Philip Thornton; David Byrne; Sheila Donegan
Original assignee: Dahlia Ireland Limited
Priority date: 1993-12-01
Filing date: 1994-11-30
Publication date: 1995-06-08
Also published as: AU1118495A; EP0731825A1

Abstract

A water dispersible metallic pigment composition comprises a metallic pigment such as an aluminium pigment incorporated in an associated surfactant structure such as a micelle. The micelle is formed from surfactant concentrations above the critical micelle concentration. The surfactant system may be a binary system comprising surfactant and water or a ternary system including a co-surfactant. The surfactant strucrure is formed prior to the addition of the metallic pigment. The metallic pigment may include a milling aid such as mineral spirits and/or a lubricant such as stearic acid. The metallic pigment composition is easily dispersed and has improved dispersion and gassing stability. Various coating compositions incorporating the metallic pigment composition are described.

Description

"Water Dispersible Metallic Pigment"

In roduc ion

The invention relates to water dispersible compositions of metallic pigments.

Metallic pigments are widely used in coatings, particularly in paints and inks. Aluminium pigments are one of the main metallic pigments and are generally bright flake-like particles. In the presence of water however the pigmentation properties of the aluminium particles are destroyed by reaction between water and aluminium producing aluminium hydroxide and hydrogen gas in accordance with the following equation:

2A1 + 6H_Z0 = 2A1(0H)₃ + 3H₂

The hydrated oxide form of aluminium is not suitable for use as a metallic pigment. In addition, the hydrogen gas generated by the reaction is a fire and explosion hazard.

It is known to passivate the aluminium to prevent the reaction with water by using passivating agents such as phosphates, phosphites, chromates or vanadates. However, in general, these known passivating systems are undesirable and, especially in the case of chromates, may present health and/or environmental problems. In addition, aluminium pigments passivated in this way are generally difficult to disperse.

It is an object of the invention to provide improved water dispersible metallic pigments. Statements of Invention

According to the invention there is provided a water dispersible metallic pigment composition having dispersion and gassing stability comprising a metallic pigment incorporated in an associated surfactant structure formed from surfactant concentrations above the critical micelle concentration.

In a particularly preferred embodiment of the invention the surfactant structure is a micelle.

In one embodiment of the invention the surfactant system is a binary system comprising surfactant and water.

In another embodiment of the invention the surfactant system is a ternary system comprising water, a surfactant and a co-surfactant. In this case preferably the surfactant system has a relatively large micellar region in the water corner of the phase diagram for the surfactant system.

In an especially preferred embodiment of the invention the surfactant structure is formed prior to the addition of the metallic pigment.

In a preferred embodiment of the invention the weight ratio of the metallic pigment to the surfactant structure composition is at least 1:1, most preferably at least 3:1.

In an embodiment of the invention the metallic pigment includes an organic entity.

The organic entity may be a milling aid such as mineral spirits. Alternatively or additionally the organic entity includes a lubricant such as a fatty acid, typically stearic acid or isostearic acid.

In one embodiment of the invention the metallic pigment is in the form of a filter cake.

In another embodiment of the invention the metallic pigment is in the form of a paste.

In a further embodiment of the invention the metallic pigment is in the form of flake.

In one embodiment of the invention the metallic pigment is a leafing metallic pigment.

In another embodiment of the invention the metallic pigment is a non-leafing metallic pigment.

The metallic pigment may be an aluminium pigment or may, for example be a zinc pigment or a gold-bronze pigment.

The term "gold-bronze" as used in this specification refers to copper or copper alloys, especially copper/zinc, with small amounts of other metals to inhibit oxidation.

The surfactant, whether in a binary or ternary system may be an ionic surfactant, a non-ionic surfactant, a cationic surfactant, an anionic surfactant, a zwitteronic surfactant, or an amphoteric surfactant.

There may be a single surfactant or a mixture of compatible surfactants. For ternary surfactant systems the co-surfactant may be any suitable hydrocarbon or mixture of hydrocarbons, typically pentanol or an alcohol higher than pentanol.

The invention also provides a coating composition comprising a metallic pigment of the invention and an appropriate vehicle.

The coating composition may be in the form of an ink, a paint, a water-based acrylic glaze, a water-based alkyd resin, a water-based acrylic melamine, an acrylic latex or the like.

The invention further provides a method for preparing a metallic pigment composition of the invention comprising the steps of :

preparing the surfactant structure; and

adding the metallic pigment to the surfactant structure.

Detailed Description of the Invention

The invention will be more clearly understood from the following description thereof given by way of example only.

This invention is based on the discovery that metallic pigments may be located in a surfactant structure such as the centre of the micelle, thereby preventing interaction with water and the evolution of hydrogen gas.

The invention provides a metallic pigment composition which is easily dispersed, and has improved dispersion and gassing stability. Unlike other passivating treatments, if the metallic particle is damaged during processing of the pigment or composition the surfactant structure will form around the newly exposed surface giving continuing protection of the metal particle.

A surfactant is a chemical species containing a hydrophillic (water loving) and hydrophobic (water hating) moiety. The hydrophobic portion is normally a long chain hydrocarbon in which length, degree of branching and chemical structure differ from one species to another. The hydrophillic region comprises the headgroup of the surfactant and may be ionic or nonionic depending on the surfactant involved.

At a defined concentration of surfactant abrupt changes in the properties of the surfactant solution are observed. This concentration of surfactant is called the critical micelle concentration (CMC). At and above this concentration surfactant monomers exist in equilibrium with organised structures of surfactants called micelles. In these micellar species, the non polar region of the surfactant is substantially located in the interior of the micelle and is thus shielded from the aqueous environment. The polar part is at the exterior of the micelle, thereby allowing favourable interactions with the aqueous bulk phase. The CMC of each surfactant is different and depends on the chemical structure of the surfactant i.e. the number, shape and length of the hydrocarbon chain, the nature of the polar head group and variations in counterion binding for any surfactant system. The CMC can be determined as outlined in Appendix 1.

As the interior of the micelle is composed of hydrocarbon chains, it resembles a hydrocarbon liquid. Thus it is possible to locate material in the interior of the micelle, dispersed in the hydrocarbon liquid and protected from the aqueous phase.

In the invention an associated surfactant structure such as a micelle is used to provide protection to metallic pigments such as aluminium. As a first step a surfactant structure such as a micelle is prepared. The metallic pigment is then added to the micellar solution and, preferably, thoroughly mixed to ensure that the pigment particles are wetted out. It is believed that the micelles wet out on the newly introduced surface of the metallic pigment to give an electrostatic and/or steric barrier.

While we do not wish to be limited by theory it is believed that if the concentration of surfactant in a solution is below the critical micelle concentration the surfactant exists as individual molecules. If a pigment particle is introduced into such a solution of individual surfactant molecules the chance of a pigment particle encountering sufficient individual surfactant molecules to completely cover the surface of the pigment particle prior to any reaction with the water present in the solution is statistically low. In complete contrast, if the concentration of the surfactant is above the critical micelle concentration the surfactant exists as micelles, each of which has a large number of surfactant molecules arranged in a structure. As a statistical event, once a pigment particle comes into contact with a few of the surfactant structures (e.g. micelles) there is sufficient surfactant material to wet out the complete surface of the pigment particle. In this way the pigment particle is very effectively protected prior to any reaction with water taking place. It is for this reason that it is thought necessary to pre¬ form a surfactant structure such as a micelle before the introduction of the metallic pigment.

In the examples given below where aluminium pigments are used these pigments may be in the form of a filter cake. The filter cake is manufactured by milling chopped aluminium foil. The milling is usually carried out in a rotating ball mill using steel balls. Mineral spirits are added to the ball mill as a milling aid. A milling lubricant in the form of stearic acid is also added to the ball mill. After milling, the aluminium slurry is filtered on a filter press to produce filter cake. The filter cake generally comprises 72% to 77% by weight of aluminium, 20% to 25% mineral spirits and 1 to 3% stearic acid.

The filter cake may be modified by the addition of further components to form an aluminium paste. Such components may include fatty acid(s) and/or hydrocarbon liquid(s). For example, the fatty acid may be stearic acid and/or the hydrocarbon liquid may be mineral spirits.

The filter cake may also be dried to substantially remove the mineral spirits to form an aluminium flake.

Preparation of Micelle Shielded Aluminium Paste (MSAP)

EXAMPLE A

A micelle is prepared. The micelle in this case is prepared from an anionic surfactant - AOT (Sodium Dioctyl Sulphosuccinate) supplied by Aldrich Chemicals. The micelle has a micellar composition by weight of 1% AOT and 99% distilled water.

20 g of the micellar composition thus formed is placed in a storage jar and 60 g of aluminium filter cake is added to the micellar composition. The micellar composition and aluminium filter cake are mixed together on a high speed vortex mixer for about 5 minutes to form the micelle shielded -aluminium paste (MSAP) .

EXAMPLE B

Example A was repeated by first preparing a micelle having a micellar composition by weight of 20% SDS and 80% distilled water. Sodium dodecyl sulphate (SDS) is an anionic surfactant which in this case was from Aldrich Chemicals and had a purity of not less than 99%.

A micelle shielded aluminivun paste (MSAP) was then prepared as outlined in Example A using the micellar composition described above.

EXAMPLE C

Example A was repeated by first preparing a micelle having a micellar composition by weight of 25% TRITON X100 and 75% distilled water. TRITON X100 is a non-ionic surfactant available from Union Carbide. EXAMPLE D - (Ink/Paints

50 g of the MSAP prepared in accordance with Example A is placed in a clean beaker and to it is added 10 g of distilled water. This is mixed into a slurry. 40 g of a vehicle is added to the beaker and the slurry is again mixed by hand until a smooth mixture is obtained. A final

100 g of the vehicle is added and the mixture is then stirred on an electric stirrer for 0.5 hours at ~ 200 rpm.

The viscosity of the ink/paint system is measured and if required the ink/paint viscosity is adjusted to 30 - 50 seconds using a Zahn 2 cup using a 50/50 w/w IPA

(Isopropyl Alcohol)/water mixture.

Test 1 - Room temperature Stability Test

Referring to Fig. 1A to 1C which are respectively perspective, side and cross sectional views, a test apparatus 1 used for room temperature stability tests comprises a storage jar 2, typically of 120 mis capacity, closed by a lid 3 having a central hole 4. A plastic film

5 is interposed between the jar 2 and the lid 3. A sample

6 to be tested is placed in the jar 2 to a typical level L. The lid 3 is in this case of 40 mm diameter and the hole 4 is of 10 mm diameter.

A sample of ink is made up using the MSAP of Example A and vehicle for room temperature storage only. 10 g MSAP is placed into the storage jar 2 and to it added 2 g of distilled water which is then mixed into a slurry. 8 g of vehicle is added and mixed in with a spatula to form a smooth mixture. A final 20 g of vehicle is added and stirred in thoroughly by hand to form the ink. The impermeable plastic film 5 is placed over the top of the storage jar 2 and pulled taut. The lid 3 with the hole 4 in it is then placed over the plastic film 5 and screwed on securely. This sample is then weighed and placed on a shelf in the laboratory to be checked weekly for gas production. If gas is produced then a bubble forms in the plastic film 5. The sample is reweighed at the end of each test period to check for weight loss.

Test 2 - 40°C Stability Test

Referring to Fig. 2 a test apparatus 10 for carrying out a gassing stability test comprises a gas washing bottle 11 which is typically filled to a level L with a base coat. An extension 12 is fitted to the bottle 11. The extension 12 includes a lower floor 13 and an upper floor 14. A first pipe 15A communicates between the bottle 11 and the head space above the lower floor 13. A second pipe 15B communicates between a lower chamber CL above the floor 13 and an upper chamber CU above the upper floor 14. A stopper 16 is used to close the extension 12. A side leg 17 projecting from the extension 12 is closed by a screw cap 18.

In order to validate the results of this test, 3 x 50 g samples of the ink/paint from Example D are weighed out into three separate 3-jar glass apparatus 10. The lower chamber CL of the stability apparatus 10 contains 45 mis of coloured water. This is connected to the bottle 11 of the stability apparatus by a quick fit joint J which is smeared with silicon vacuum grease supplied by Dow Corning. All the glass joints are then sealed with parafilm to further reduce any risk of leakage. Each of the test vessels is weighed and then placed into a water bath which is kept at a constant 40°C. The screw cap seal 18 is left open for the first hour of the test and then sealed. The test samples are monitored daily over the test period. Any gas generated in the bottle 11 results in an increased pressure on the liquid in the lower chamber CL and some of the liquid is delivered through the pipe 15B to the upper chamber CU.

Each stability test is allowed to produce < 25 mis of water in the upper chamber CU during the 30 day test period. At the end of the test period the vessel is reweighed to check for weight loss.

EXAMPLE 1

An Aerosol OT (AOT) micelle was prepared by weighing 1 g AOT and adding 99 g distilled water in a suitable container. This was stirred until a completely clear solution was obtained and knowing that the surfactant concentration is above the CMC this clarity confirms the presence of a micelle structure.

20 g of the above micellar solution was placed into a container and to it 60 g of aluminium filter cake was added. This was mixed together on a high speed vortex mixer for approximately 5 minutes. 50 g of the above paste was placed into a clean beaker and to it 10 g of distilled water was added and this was mixed by hand into a slurry. 40 g of Carboset GA 1594 (B F Goodrich) was added to the beaker and the slurry further mixed by hand until a smooth mixture was obtained. A final 100 g of Carboset GA 1594 was added and the mixture was then stirred on an electric stirrer for 0.5 hours at ~ 200 rpm. The viscosity of the system was measured using a Zahn 2 cup and found to be between the required 30 - 50 seconds. If the viscosity is outside the 30 - 50 seconds range it must be adjusted using a 50/50 w/w IPA/water solution.

The appropriate amounts of the above were then tested according to Test 1 and Test 2 above.

This is Example No. 1 from Table. 1. The ink/paint systems described below were all prepared in a similar manner.

TABLE 1

Aluminium ink/paint systems based on micelle A (1% AOT / 99% H_zO) - Example A which demonstrated gassing stability over a three month period at room temperature.

Example No. System

1. Al ink with an MSAP containing micelle A and Carboset GA 1594¹.

2. Al ink with an MSAP containing micelle A and Joncryl 1536².

3. Al ink with an MSAP containing micelle A and pH adjusted water.

4. Al ink with an MSAP containing micelle A and Zinchem 146³.

5. Al ink with an MSAP containing micelle A and Zinpol 146⁴.

6. Al ink with an MSAP containing 1:10 micelle A : aluminium pigment and pH adjusted water.

7. Al paint with an MSAP containing micelle A and Worleecryl 8410.⁵

8. Al paint with an MSAP containing micelle A and Neocryl BT-20.⁶

9. Al paint with an MSAP containing micelle A and Neocryl BT-44.⁷

10. Al paint with an MSAP containing micelle A and Morcryl 1503".

11. Al paint with an MSAP containing micelle A and Alkyd resin.⁹

12. Al paint with an MSAP containing micelle A and Zinpol 132 ^l0.

13. Al paint with an MSAP containing micelle A and Croda Acrylic¹¹.

14. Al paint with an MSAP containing micelle A and Silres MP42E¹².

The main variant in this table is the type of resin used in the systems. All the above MSAPs are based on aluminium pigment 210NA - refer to Table 11. Explanatory Notes

1. Carboset GA 1594 is a commercial vehicle supplied by BF Goodrich.

2. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

3. Zinchem 146 is a commercial vehicle supplied by E.H. Worlee & Co. (UK) Ltd.

4. Zinpol 146 is a commercial vehicle supplied by E.H. Worlee & Co. (UK) Ltd.

5. Worleecryl 8410 is a commercial vehicle supplied by E.H. Worlee & Co (UK) Ltd.

6. Neocryl BT-20 is a commercial vehicle supplied by Zeneca Resins.

7. Neocryl BT-44 is a commercial vehicle supplied by Zeneca Resins.

8. Morcryl 1503 is a commercial vehicle supplied by Morton International Ltd.

9. Uradil XP 516 AZ supplied by DSM Resins (UK) Ltd.

10. Zinpol 132 is a commercial vehicle supplied by E.H. Worleέ & Co. (UK) Ltd.

11. An acrylic ink supplied by Croda.

12. Silres MP42E is a commercial vehicle supplied by Wacker Chemicals. TABLE 2

Aluminium ink/paint systems based on micelle A (1% AOT / 99% H-,0) - Example A & different aluminium pigments, which demonstrated gassing stability over a three month period at room temperature.

Example No. System

15. Al ink with an MSAP containing micelle A and 803 AP¹ & Joncryl 1536².

16. Al ink with an MSAP containing micelle A and 803 AP & pH adjusted water³.

17. Al ink with an MSAP containing micelle A and 9535A AP & Joncryl 1536².

18. Al ink with an MSAP containing micelle A and 720-AR AP & pH adjusted water.

19. Al ink with an MSAP containing micelle A and 720-AR AP & Joncryl 1536².

20. Al ink with an MSAP containing micelle A and N735A AP & Joncryl 1536².

21. Al ink with an MSAP containing micelle A and 9535A AP & pH adjusted water.

22. Al ink with an MSAP containing 1:2 micelle A : foilflake AP & pH adjusted water.

1

23. Al ink with an MSAP containing micelle A and 7125 AP & pH adjusted water.

24. Al ink with an MSAP containing micelle A and 7125 AP & Joncryl 1536².

25. Al ink with an MSAP containing micelle A and 911 NL AP & pH adjusted water.

26. Al ink with an MSAP containing micelle A and 911 NL AP & Joncryl- 1536².

27. Al ink with an MSAP containing micelle A and AP & pH adjusted water.

28. Al ink with an MSAP containing micelle A and 7016 AP & Joncryl 1536².

29. Al ink with an MSAP containing micelle A and LA1337 AP & pH adjusted water.

30. Al ink with an MSAP containing micelle A and LA1337 AP & Joncryl 1536.

The main variant in this table is the type of aluminium pigment used in the systems. Details of the various aluminium pigments are given in Table 11. Explanatory Notes :

1. A.P. - aluminium pigment.

2. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

3. pH adjusted water is adjusted to a pH of ~8.00. TABLE 3

Aluminium ink/paint systems based on micelle B (20% SDS / 80% H₂0) - Example B above which demonstrated gassing stability over a three month period at room temperature.

Example No. System

31. Al paint with an MSAP containing micelle B & Silres MP42E¹.

32. Al ink with an MSAP containing micelle B & Carboset GA 1594².

33. Al ink with an MSAP containing micelle B & pH adjusted water.

34. Al ink with an MSAP containing micelle B & Zinchem 146³.

35. Al paint with an MSAP containing micelle B & Morcryl 1503⁴.

36. Al ink with an MSAP containing 1:10 micelle B : 210NA A.P. & pH adjusted water.

The main variant in the above table is the type of resin used in the systems. All the above MSAPs are based on aluminium pigment 210NA - see Table 11.

Explanatory Notes.

l. Silres MP42E is a commercial vehicle supplied by Wacker Chemicals.

2. Carboset GA 1594 is a commercial vehicle supplied by BF Goodrich.

3. Zinchem 146 is a commercial vehicle supplied by E.H. Worlee & Co. (UK) Ltd.

4. Morcryl 1503 is a commercial vehicle by Morton International Ltd.

TABLE 4

Aluminium ink paint systems based on micelle B (20% SDS / 80% HgO) - Example B above & different aluminium pigments, which demonstrated gassing stability over a three month period at room temperature.

EXAMPLE NO. SYSTEM

37. Al ink with an MSAP containing micelle B and 803 AP' & pH adjusted water³.

38. Al ink with an MSAP containing micelle B and 803 AP¹ & Joncryl 1536².

39. Al ink with an MSAP containing micelle B and 9535 A AP' & pH adjusted water³.

40. Al ink with an MSAP containing micelle B and 9535 A AP' & Joncryl 1536².

41. Al ink with an MSAP containing micelle B and 180C AP' & Joncryl 1536².

42. Al ink with an MSAP containing micelle B and 720-AR AP' & pH adjusted water³.

43. Al ink with an MSAP containing micelle B and N735A AP' & Joncryl 1536².

44. Al ink with an MSAP containing micelle B and N735A AP' & Joncrvl 1536².

45. Al ink with an MSAP containing micelle B and 911NL AP' & Joncryl 1536².

46. Al ink with an MSAP containing micelle B and 911NL AP¹ & pH adjusted water³.

47. Al ink with an MSAP containing micelle B and 7016 AP' & pH adjusted water³.

48. Al ink with an MSAP containing micelle B and 7016 AP' & Joncryl 1536².

49. Al ink with an MSAP containing micelle B and LA1337 AP¹ & Joncryl 1536².

50. Al ink with an MSAP containing micelle B and LA1337 AP' & pH adjusted water³.

The main variant is the type of aluminium pigment used in the systems. Details of the various aluminium pigments are given in Table 11.

Explanatory Notes.

1. AP - Aluminium Pigment.

2. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

3. pH adjusted water is adjusted to a pH of ~8.00. TABLE 5

Aluminium ink/paint systems based on micelle C (25% TX-100 / 75% H₂0) - Example C above which demonstrated gassing stability over a 3 month period at room temperature.

EXAMPLE NO. SYSTEM

51. Al ink with an MSAP containing micelle C & pH adjusted water.

52. Al ink with an MSAP containing micelle C & Silres MP42E¹.

53. Al ink with an MSAP containing micelle C & Zinchem 146².

54. Al ink with ^n MSAP containing micelle C & Zinpol 146^β.

55. Al paint with an MSAP containing micelle C & Morcryl 1503³.

56. Al paint with an MSAP containing micelle C & Neocryl W-1200⁴.

57. Al paint with an MSAP containing micelle C & Neocryl BT-20⁵.

The main variant in the above table is the type of resin used in the systems. All the above MSAPs are based on aluminium pigment 210NA - Table 11.

Explanatory Notes.

1. Silres MP42E is a commercial vehicle supplied by Wacker Chemicals.

2. Zinchem 146 is a commercial vehicle supplied by E.H. Worlee & Co. (UK) Limited.

3. Morcryl 1503 is a commercial vehicle supplied by Morton International Limited.

4. Neocryl W-1200 is a commercial vehicle supplied by Zeneca Resins.

5. Neocryl BT-20 is a commercial vehicle supplied by Zeneca Resins. 6. Zinpol 146 is a commercial vehicle supplied by E. H. Worlee & Co. (UK) Limited.

TABLE 6

Aluminium ink paint systems based on micelle C (25% TX-100 / 75% H₂0) - Example C above - with different aluminium pigments which demonstrated gassing stability over a three

EXAMPLE NO. 1 SYSTEM

58. Al ink with an MSAP containing micelle C and 803 AP' & pH adjusted water ³.

59. Al ink with an MSAP containing micelle C and 803 AP' & Joncryl 1536².

60. ; Al ink with an MSAP containing micelle C and 9535A AP¹ & pH adjusted water³.

!

61. Al ink with an MSAP containing micelle C and 720-AR AP¹ & pH water.

62. Al ink with an MSAP containing micelle C and 720-AR AP¹ & Joncryl 1536².

63. Al ink with an MSAP containing micelle C and N735A AP¹ & Joncryl 1536².

64. Al ink with an MSAP containing micelle C and 7125 AP¹ & pH adjusted water³.

65. Al ink with an MSAP containing micelle C and 911NL AP¹ & pH adjusted water³.

66. Al ink with an MSAP containing micelle C and 911NL AP' & Joncryl 1536².

67. Al ink with an MSAP containing micelle C and 7016 AP' & Joncryl 1536².

68. Al ink with an MSAP containing micelle C and 7016 AP¹ & pH adjusted water³.

The main variant in the above table is the filter cake used in the systems. Details of the various aluminium pigments are given in Table 11. Explanatory notes.

1. AP - aluminium pigment.

2. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

3. pH adjusted water is adjusted to a pH of ~ 8.00. Aluminium ink/paint systems with different micelles which demonstrated gassing stability over a 6 month period at room temperature.

TABLE 7

EXAMPLE NO. SYSTEM

69. Aluminium ink with an MSAP containing micelle A & pH adjusted water¹.

70. Aluminium paint with an MSAP containing micelle A & Zinchem 146².

71. Aluminium paint with an MSAP containing micelle A & Zinpol 146³.

72. Aluminium ink with an MSAP containing micelle A & Joncryl 1536".

73. Aluminium ink with an MSAP containing micelle A & Carboset GA 1594⁵.

74. Aluminium ink with an MSAP containing micelle A & Silres MP42E⁶

TABLE 8

EXAMPLE NO. SYSTEM

75. Aluminium ink with an MSAP containing 1:2 micelle B : aluminium pigment & pH adjusted water¹.

76. Aluminium paint with an MSAP containing micelle B and Zinchem 146^z.

77. Aluminium paint with an MSAP containing micelle B & Silres MP42E⁶

TABLE 9

The main variant in the above 3 tables is the type of resin used in the systems. All the above MSAPs are based on filter cake 210NA.

Explanatory notes.

1. pH adjusted water is adjusted to a pH of ~8.00. 2. Zinchem 146 is a commercial vehicle supplied by E.H. Worleέ & Co. (UK) Ltd.

3. Zinpol 146 is a commercial surfactant supplied by E.H. Worlee & Co. (UK) Ltd.

4. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

5. Carboset GA 1594 is a commercial vehicle supplied by BF Goodrich.

6. Silres MP42E is a commercial vehicle supplied by Wacker Chemicals. TABLE 10

Alumimum paint/ink systems containing micelles based on commercial surfactants other than those of Examples A, B or C above, which demonstrated gassing stability over a 6 month period at room temperature.

EXAMPLE NO. SYSTEM

82. Aluminium ink with an MSAP containing 20% Sellogen DFL' & 80% water and Joncryl 1536².

83. Aluminium ink with an MSAP containing 10% Sellogen DFL¹ & 90% water and pH adjusted water³.

84. j Aluminium ink with an MSAP containing 20% SDS^b % 80% water and j Lucidene 202".

85. j Aluminium ink with an MSAP containing 1% CTAB⁸ & 99% water and pH adjusted water³.

86. Aluminium ink with an MSAP containing 5% CTAB⁶ & 95% water and pH adjusted water³.

87. j Alumimum ink with an MSAP containing 20% CTAB⁶ & 80% water i | and Joncryl 1536².

88. _| Aluminium ink with an MSAP containing 10% Sellogen DFL¹ & 90% I water and Joncryl 1536¹.

89. i Aluminium ink with an MSAP containing 10% Tego Betain HS⁷ & pH j adjusted water³.

90. | Aluminium ink with an MSAP containing 20% Phospholan PNP9" and 1 Joncryl 1536².

100. Aluminium ink with an MSAP containing 1% Sellogen HR⁹ and pH adjusted water³.

101. Aluminium ink with an MSAP containing 20% Sellogen DFL¹ & 80% water and pH adjusted water³.

102. Alumimum ink with an MSAP containing 20% Tego Betain HS⁷ & 80% water and pH adjusted water³.

103. _| Aluminium ink with an MSAP containing 10% Phospholan PNP9⁸ & | 90% water and pH adjusted water³.

104. j Aluminium ink with an MSAP containing 10% Tego Betain HS⁷ & 90% ! water and Joncryl 1536².

105. Alumimum ink with an MSAP containing 20% Tego Betain F^1U & 80% j water and pH adjusted water³.

106. j Alumimum ink with an MSAP containing 10% Tego Betain F¹⁰ & 90% water and pH adjusted water³. j

107. Aluminium ink with an MSAP containing 5% CTAB⁶ & 1% Hexanol & 94% water & Joncryl 1536².

The main variant in the above table is the micellar composition used in the systems. All the above MSAPs are based on aluminium pigment 210NA. Explanatory notes.

1. Sellogen DFL is an anionic surfactant supplied by Henkel Performance Chemicals.

2. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

3. pH adjusted water is adjusted to a pH of ~ 8.00.

4. Lucidene 202 is a commercial vehicle supplied by Morton International Ltd.

5. SDS (at least 99% pure) is an anionic surfactant supplied by Aldrich Chemical Co.

6. CTAB is a cationic surfactant supplied by Aldrich Chemical Co.

7. Tego Betain HS is a zwitterionic surfactant supplied by T.H. Goldscbmidt A.G..

8. Phospholan PNP9 is an anionic surfactant supplied by Harcross Chemicals (UK) Ltd.

9. Sellogen HR is an anionic surfactant supplied by Henkel Performance Chemicals.

10. Tego Betain F is a zwitterionic surfactant supplied by T.H. Goldschmidt AG.

TABLE 11

Composition of the various aluminium pigments : filter cakes; pastes; and flakes

* As measured on Microtrac by Leeds and Northrup. ** Includes lubricant 1. Filter Cake manufactured by Shamrock Alumimum Ltd.

2. Aluminium Flake manufactured by U.S. Aluminum Inc

3. Aluminium Flake manufactured by U.S. Aluminum Inc

4. Automotive, high purity, acid resistant, Aluminium paste manufactured by Canbro Inc.

5. Aluminium Paste, Non-Leafing in Isopropyl Alcohol manufactured by U.S. Aluminum Inc. 6. Alumimum Flake manufactured by U.S. Aluminum Inc.

7. Aluminium Paste manufactured by U.S. Aluminum Inc.

8. Aluminium Flake, Non-Leafing manufactured by U.S. Aluminum Inc.

9. Alumimum Paste manufactured by U.S. Aluminum Inc.

10. Aluminium Paste manufactured by U.S. Aluminum Inc. 11- Aluminium Paste, in Isopropyl Acetate manufactured by U.S. Aluminum Inc. Example 108

The following mixed surfactant system has been prepared :

Aluminium ink with an MSAP containing 3% *Atlox 5320 & 97% Water and Joncryl 1536.

This system is on test at room temperature for almost three months and is passing the test.

*Atlox 5320 is a commercial surfactant mix supplied by I.C.I. Surfactants.

40°C STABILITY TESTS ON COMMERCIAL VEHICLES

The following examples show results for some commercial vehicles evaluated as per the 40°C stability test (Test 2 above) . Each example is cross indexed to the corresponding room temperature result shown in Tables 1 to 10.

Example 109 (See also Tahlg 1 Example 7 for room t-f»mpf»τature result)

System: MSAP based on 1% AOT/99% water with Worleecryl 8410 vehicle (1:10 w/w)

Worleecryl 8410 (Worlee Chemicals).

This is an alkaline soluble acrylic anionically stabilised emulsion. The solids content is 40% in water. It has excellent wetting properties, dries fast, excellent gloss, a low minimum film forming temperature (MFFT) and is thus highly flexible. It has excellent adhesion on various substrates. It has FDA approval, which makes it highly appropriate for use. It is claimed to be stable for a minimum of 30 days at 50°C and is designed for use in aqueous flexographic and gravure inks and overlay or overprint varnishes. It is also claimed to have been designed for use with metallic systems. For use, it must be reduced to 20-25% solids with water and must also be neutralised with ammonia to obtain a clear solution of medium viscosity with a pH of 7.5-8.0.

Average number of mis of hydrogen produced over the 30 day test period: 11.7 mis. Example 110 (see also Tab1p> 1 _f F.xample 10 for room temperature result)

System : MSAP based on 1% AOT/99% water with Morcryl 1503 vehicle (l:10w/w)

Morcryl 1503 (Morton Chemicals)

This is a styrene acrylic resin solution. It is 30% solids, with a pH of 7.5-7.8. It is a solution polymer designed for stability with metal pigments. It can be used as the sole binder or in combination with other resins.

Average number of mis of hydrogen produced over the 30 day test period : 5.6 mis.

Ryam lp Hi (see alsn Tahle 5 Ryam JLe 56 for room temperature result)

System: MSAP based on 25% Triton X100/75% water with Neocryl W1200 vehicle (1:10 w/w)

Neocryl W-1200 (Zeneca Resins)

This is an acrylic colloidal printing ink resin solution which is supplied in a neutralised form. It is free of emulsifiers and contains some water and isopropanol. The main properties of this resin are as follows :

a) excellent pigment wetting and gloss b) stability with low cost organic pigments c) easy to clean off the press d) excellent transfer and printability e) low foaming tendency

This resin has 40% solids. Its solvent content is 18% IPA and 42% water. Neocryl W1200 has been developed for flexo printing inks on paper and cartons. It may also be used in temporary coatings and screen printing inks.

Average number of mis of hydrogen produced over the 30 day test period : 7.3 mis.

Example 112 (see also Table 1 Example 12 for room temperature result)

System : MSAP based on 1% AOT/99% water with Zinpol 132 vehicle (1:10 w/w)

Zinpol 132 (Worlee Chemicals) This resin is a styrene acrylic emulsion, supplied at 40% solids in water. It is designed specifically for use with aluminiu and bronze powders. Due to this, it gives excellent metallic ink brilliance, with excellent ink stability on storage and shipping. It can be used for both flexo and gravure printing. It is reportedly stable at 40°C for 30 days. It has FDA approval from the following chapters : 175.105, 175.300, 175.320, 176,1700 and 176.180.

Average number of mis of hydrogen produced over the 30 day test period : 12.5 mis.

Ryample 113 (see also Table R Example 77 and Table 7 Ex m le 74 for room temperature result)

Formulation of a heat resistant paint.

A heat resistant water dilutable aluminium coating according to the following formulation was produced.

All parts are by weight. 75 parts Wacker Silicon resin emulsion MP42E

0.5 parts Wacker HDK N20

24 parts Micelle Shielded Aluminium Paste.

The paint was prepared using the following Micelle Shielded Aluminium Pastes (MSAP) :

(a) 20% SDS/80% water

(b) 1% AOT/99% water

The aluminium paste was stirred slowly with the HDK N20 into the emulsion MP42E. The Silicon resin MP 42E was a shear stable, non ionically stabilised, storage stable aqueous emulsion of a medium-hard methylphenyl silicone resin, which dries tack free at room temperature. It has a low solvent content (7% xylene) which gives environmentally friendly coatings. Depending on pigmentation, temperature resistant and temperature shock- resistant coatings up to 650°C can be produced. It can be used in a wide variety of applications including the automotive industry for exhaust coatings and in industrial and chemical plants .

The paint prepared using the above formulation was subjected to the 40°C stability test as described in Test 2.

Both paints based on (a) and (b) passed the 40°C stability test:

Paint based on (a) : Average number of mis of hydrogen produced over the 30 day test period : 10 mis. Paint based on (b) : Average number of mis of hydrogen produced over the 30 day test period : 21.6 mis.

Both paints based on (a) and (b) are stable at room temperature for more than 6 months.

The following are examples of ternary systems. One of the main criteria used in the selection of the surfactant system was the presence of a relatively large micellar region in the water corner of the phase diagram for the surfactant system. The following phase diagrams are included for illustrative purposes.

Fig. 3 is the phase diagram for the surfactant system sodium dodecyl sulphate (SDS)/water/pentanol (after Prof. S.E. Freiberg, Clarkson University, Potsdam, New York, U.S.A.)

Fig. 4 is the phase diagram for the surfactant system TRITON XlOO/water/pentanol.

In all of the examples below a micelle was prepared as described in Example A except that a co-surfactant was also added. A micelle shielded aluminium paste was prepared as described in Example B and an Ink/Paint was prepared as described in Example D.

The following ternary micellar systems were subjected to the 40°C stability test described in Test 2 above and remained stable after 30 days - see Table 12. For room temperature stability test results - see Table 13. Table 12 - Ternary micellar systems which remained stable after being subjected to the 40°C stability test for 30 days.

Table 13 • Ternary micellar systems which remained stable after 3 months at room temperature.

EXAMPLE System Conclusions

117 Al ink with an MSAP based on a micelle of 17% SDS/13% Pentanol/ Stable. 70% water with 210NA filter cake and Joncryl 1536 as vehicle.

118 Al ink with an MSAP based on a micelle of 20% Triton X-100/2% Stable. Decanol/ 78% water with 210NA filter cake and Joncryl 1536 as vehicle.

119 Al ink with an MSAP based on a micelle of 15% Brij 96/3% Stable. Hexanol/82% water with 210NA filter cake and Joncryl 1536 as vehicle.

120 Al ink with an MSAP based on a micelle of 10% SDS/5% Pentanol/ Stable. 85% water with 210 NA filter cake and pH adjusted water as vehicle.

121 Al ink with an MSAP based on a micelle of 5% CTAB³/1% Hexanol/ Stable. 94% water with 210NA filter cake and Joncryl 1536 as vehicle.

1. Joncryl 1536 is a commercial vehicle supplied by S.C. Jonson Polymer.

2. Brij 96 is a non-ionic commercial surfactant supplied by ICI Surfactants.

3. CTAB - Cetyltrimethylammomumbromide, a cationic surfactant supplied by Aldrich Chemical Co. Alkyd Resin

The alkyd resin chosen was Uradil XP 516 AZ (DSM Resins). It is composed of a long oil alkyd emulsion with an oil length of 63%. It is 60% solids in water and is amine free. It has a pH of 4.0, which was adjusted to pH 8 before use. Its main properties are good air drying, good gloss and excellent penetration/adhesion.

Samples were prepared as described in Example D using the above alkyd resin as vehicle and tested according to Test 1 and Test 2 described above.

Test 1 Results

Samples which demonstrated gassing stability over a 3 month period at room temperature are shown in Example 11 above.

Test 2 Results

Example No. System and Result.

122 MSAP based on 1% AOT / 99% Water : Uradil XP 516 AZ (1:10 w/w) Average mis of hydrogen produced over the 30 day test period : 13.5 mis

; 123 MSAP based on 10% Tego Betain HS / 90% Water : Uradil XP 516 AZ

3 j (1:10 w/w)

Average mis of hydrogen produced over the 30 day test period : 12.3 mis

1

124 MSAP based on 10% Tego Betain F / 90% Water : Uradil XP 516 A2 ; (1:10 w/w)

Average mis of hydrogen produced over the 30 day test period : 5.7 mis

All the above MSAPs are based on alumimum pigments 210NA - See Table 11. - 29a.-

The exact amount of associated surfactant structure required to impart gassing stability to the aluminium pigment is difficult to calculate for the following reasons. The packing and packing density of each surfactant is particular to that surfactant. The packing efficiency of the surfactant will depend upon a number of factors including the size of the headgroup, the presence of multiple tail groups, aromatic structures in the tail group, the presence of unsaturation in the tail group, electrostatic interaction between the headgroups, the nature of the metallic surface to be covered and the formation of duplex layers.

In practical terms the ideal would be to have as little surfactant as possible in the micelle shielded paste in order to keep the final concentration of surfactant in the end use coating to a minimum. High concentrations of surfactant in a coating generally give rise to poor performance and relatively weak films.

Systems with micellar solution : aluminium pigment content of 2:1 w/w using an SDS/Pentanol/Water (17%/13%/70%) micelle in both Joncryl 1536 and pH water have passed the three month room temperature stability test. However, other surfactants may give stable systems at even lower aluminium pigment concentration.

- 30 -

It will be appreciated that while the invention has been specifically described with reference to aluminium pigments it is expected that the invention may be applied to any other suitable metallic pigments including gold/bronze, zinc, stainless steel and the like.

Example 125 - Zinc

The possibility of stabilising zinc pigment in the same manner as the micelle shielded aluminium pastes described above was investigated. If this method of protecting the zinc is successful, it could lead to the development of a passivated water borne zinc rich primer with cathodic protection. This cathodic protection would result due to the collapse of the micellar structure on drying of the paint film in contrast to protection provided by chromates, in which the passivation offered by the chromates leads to suppression of the cathodic protection in the paint film on drying.

Using the method of Example 1 above, two zinc paints were prepared using Micelle A - 1% AOT, 99% H₂0 and Micelle B - 20% SDS 80% H_z0. In place of the aluminium paste used in this formulation, a micellar system in which zinc pigment was vortexed with the micelle to give a zinc paste. A zinc pigment was used, namely : Larvik Zinc dust. Brand STD 7, sample no. 203. Using this pigment, a blank zinc paint was also prepared in which there was no micelle present. The samples were thickened by the addition of 1.5% Hydroxy ethyl cellulose (w/w based on the final formulation) . Using Test 2 above the following results were obtained. - 31 -

TABLE 14 i I

Sample No. of mis of Days hydrogen produced

Zinc STD 7 + 1% AOT micellar solution , 4.4 30

Zinc STD 7 + 20% SDS micellar solution 18 30

The blank failed the test.

From the results above, it is evident that the presence of the micelle protects the zinc pigment from attack by water as seen by the reduction of hydrogen evolution in the presence of the micelle. In the case of the STD 7 pigment, the protection offered by the micelle is sufficient to indicate a positive result, based on the limit of hydrogen evolution of 25 mis at 40°C for 30 days.

- 32 -

Example 126 - Gold Bronze

Gold bronze pigments are typically copper or copper alloys, usually copper/zinc, with small amounts of other metals to inhibit oxidation. They are produced by the attrition of finely divided, usually atomised, metal particles by mechanical means, usually ball milling, into platelet type structures. A lubricant, usually a saturated fatty acid, is added to assist the attrition, prevent cold welding of the particles and provide leafing.

Procedure

Samples were prepared as follows :-

The following micellar solutions were prepared :-

(a) 20% SDS¹ / 80% Water

(b) 1% AOT n-^z / 99% Water

Two micelle shielded pastes were made using the above micelles as follows :

17.5 g micellar solution

52.5 g gold bronze pigment

This was mixed on a vortex mixer for approximately 5 minutes to ensure thorough mixing.

Each of the above pastes was made up into an ink as follows :

5g micelle shielded paste lg distilled water 4g Joncryl 1536³

These were mixed, and then a further lOg Joncryl 1536³ was added and mixed thoroughly - 33 -

The above inks were tested according to Test 3 below.

Test 3

A sample of ink is made up of using the above micelle shielded paste and vehicle for room temperature storage only. 5g micelle shielded paste is placed into a storage jar and to it is added lg of distilled water which is then mixed into a slurry. 4g of vehicle is added and mixed in with a spatula to form a smooth mixture. A final lOg of vehicle is added and stirred in thoroughly by hand to form the ink. A piece of impermeable film is placed over the top of the storage jar and pulled taut. A lid is then placed over the film and screwed on securely. This sample is then weighed and placed on a shelf in the laboratory to be checked weekly for discoloration, this usually appears as a blue/green discoloration. If there is no discoloration the sample is kept on test for a further period. The sample is reweighed at the end of each test period to check for weight loss.

The above procedure was repeated using the vehicles Zinchem 146 and Lucidene 202.

Explanatory Notes.

1. SDS (at least 99% pure) is sodium dodecyl sulphate supplied by Aldrich Chemical. 5. AOT is sodium dioctyl sulphosuccinate supplied by Aldrich Chemical Co.

3. Joncryl 1536 is a commercial vehicle supplied by S.C.

Johnson Polymer.

Gold bronze ink systems based on pastes made using micelle (a) and (b) above which exhibited no discoloration over a 3 month period at room temperature. - 34 -

Table 15

Example No. Sample

126 Ink made using paste based on micelle (a) + Joncryl 1536'

127 Ink made using paste based on micelle (a) + Zinchem 146²

128 Ink made using paste based on micelle (a) + Lucidene 202³

129 Ink made using paste based on micelle (a) + pH adjusted water

130 Ink made using paste based on micelle (b) + Joncryl 1536

131 Ink made using paste based on micelle (b) + pH adjusted water

All the above pastes are based on Bronze pigment RPG 9520 manufactured by U.S. Bronze Powders Inc.

Explanatory notes for Table 15.

1. Joncryl 1536 is a commercial vehicle supplied by S.C. Johnson Polymer.

2. Zinchem 146 is a commercial vehicle supplied by E.H. Worlee & Co. (UK) Ltd.

3. Lucidene 202 is a commercial vehicle supplied by Morton International Limited.

4. pH adjusted water is adjusted to a pH of ~ 8.00.

- 35 -

While various micelle surfactant systems have been described above it is envisaged that the surfactant structure may be a lyotropic liquid crystal structure.

Such a structure is formed by the addition of solvent to concentrated surfactant systems.

Fig. 5 is a phase diagram illustrating where different phases are normally found. The examples described above are within the L_! and D phases which are single phase associated surfactant systems.

In Fig. 5 :

Lj = micelle L₂ = microemulsion D =- lamellar liquid crystal E = hexagonal liquid crystal F = reversed hexagonal liquid crystal I - cubic liquid crystal

Liquid crystals or mesophases are states of matter in between liquids and crystalline solids. In these systems there is long range order but not short range order.

There are three main classes of lyotropic liquid crystals:

(a) Lamellar (or neat)

(b) Hexagonal (or middle)

(c) Cubic or viscous isotropic

(a) Lamellar

This is the most common type of mesophase. It consists of surfactant bilayers separated by water layers. The surfactant head groups are restricted to the chain/water interface. These layers can extend over large distances - 36 -

often to the order of microns or more. Due to the hydrocarbon tail of the surfactant reaching into the interior of the lamellar liquid crystal, it is possible to locate materials in the interior of the liquid crystal thereby preventing interaction with water. Thus both water sensitive and water insoluble materials may be dispersed in an aqueous environment without any detrimental effects.

The lamellar liquid crystal has a semi liquid and mucous consistency. They are optically anisotropic, when viewed between cross polars, they shine. Microscopic examination shows both planar and mosaic (Maltese crosses) pattern.

(b) Hexagonal

Hexagonal structures are the second most common type of liquid crystals. There are two types - normal and reverse. Low angle X-ray diffraction patterns have shown these structures to be composed of long cylindrical micelles packed in a hexagonal array, where the polar groups occupy the cylinder surfaces. The cylinders are separated by a continuous water environment. In the reverse hexagonal phase, the hydrocarbon tails occupy the spaces between the hexagonally packed water molecules.

This liquid crystal is very stiff. It is fairly transparent and is anisotropic. Microscopy studies between polaroid plates have shown a very angular structure.

(c) Cubic

There are two main classes of cubic phases - normal and reverse. The first group l or I₂ consists of close packed spherical micelles. Both body centred and face centred - 37 -

structures are found. These structures have similar dimensions to those of micellar solutions, micelle-micelle separations being similar to those in hexagonal liquid crystal phases.

The second group of cubic phases (Vj and V₂) consists of interdispersed 3-D networks of water and surfactants. They are bicontinuous, in that both water and surfactant form separate continuous regions.

In general the cubic phase is very stiff gel, which is transparent and shows no birefringence.

The invention is not limited to the embodiments hereinbefore described which may be varied in detail.

- 38 -

APPENDIX 1

Determination of CMC

The surface tension of the surfactant solutions was measured by the du Nouy tensiometer ring method using a torsion balance from Whites Electrical Co.

In this method the force needed to detach a ring from an interface is measured by suspending the ring using a torsion wire arrangement. The detachment force is related to the surface tension by the following equation :

where F is the pull on the ring, R is the mean radius for the ring and β is a correction factor. The correction factor allows for the non vertical direction of the tension forces and for the complex shape of the liquid supported by the ring at the point of detachment. Thus the correction factor depends on the dimensions of the ring and the nature of the interface. Values of β have been calculated by Harkins and Jordan (J. Amer. Chem. Soc. 52, 1751 (1930)).

Procedure

The measurement of surface tension was carried out to ASTM D1590-60. The balance used had a graduated scale which allowed readings in dynes.

All glassware to be used was soaked overnight in a chromic acid solution to ensure minimum contamination of the solutions with material which may alter the surface tension. The apparatus was then calibrated using HPLC grade water. The platinum-iridium wire was cleaned by - 39 -

passing it through a flame. The sample to be tested was then placed in the measurement vessel on the sample platform. The platform was then raised to completely submerge the ring. The platform was lowered slowly by means of the adjusting screw and at the same time the torque of the ring system was increased by means of the dial adjustment. These two simultaneous adjustments must be made very carefully so the ring system remains constantly in the zero position. The dial reading was noted when the ring broke free of the water surface. Three measurements were made on each solution and the results were averaged. All measurements were made at 23°C.

The corrected surface tension was then calculated from the following equation :

surface tension, dynes/cm = PF where P is the scale reading in dynes per cm when the film breaks, and F is the correction factor.

A worked example for the determination of the CMC of Atlox 5320 (ICI SURFACTANTS) is shown below

Surfactant : Atlox 5320

Concentrate Lon of Surfai

Surfactant (*) (dyne;

0.025 44.75

0.05 39.75

0.1 33.58

0.25 34.00

0.4 35.17

0.5 35.33

0.8 35.17 - 40

These values were plotted - see Fig. 6 - and the point corresponding to the CMC was formed to be 0.1%.

Claims

- 41 -CLAIMS

1. A water dispersible metallic pigment composition having dispersion and gassing stability comprising a metallic pigment incorporated in an associated surfactant structure formed from surfactant concentrations above the critical micelle concentration.

2. A metallic pigment composition as claimed in claim 1 wherein the surfactant structure is a micelle.

3. A metallic pigment composition as claimed in claim 1 or 2 wherein the surfactant system is a binary system comprising surfactant and water.

4. A metallic pigment composition as claimed in claim 1 or 2 wherein the surfactant is a ternary system comprising water, a surfactant and a co-surfactant.

5. A metallic pigment composition as claimed in claim 4 wherein the surfactant system has a relatively large micellar region in the water corner of the phase diagram for the surfactant system.

6. A metallic pigment composition as claimed in any preceding claim wherein the surfactant structure is formed prior to the addition of the metallic pigment.

7. A metallic pigment composition as claimed in any preceding claim wherein the weight ratio of the metallic pigment to the surfactant structure composition is at least 1:1. - 42 -

8. A metallic pigment composition as claimed in a preceding claim wherein the weight ratio of the metallic pigment to the surfactant structure composition is at least 3:1.

9. A metallic pigment composition as claimed in any preceding claim wherein the metallic pigment includes an organic entity.

10. A metallic pigment composition as claimed in claim

9 wherein the organic entity includes a milling aid.

11. A metallic pigment composition as claimed in claim

10 wherein the milling aid is mineral spirits.

12. A metallic pigment composition as claimed in claim 9 or 10 wherein the organic entity includes a lubricant.

13. A metallic pigment composition as claimed in claim 12 wherein the lubricant is a fatty acid.

14. A metallic pigment composition as claimed in claim 12 or 13 wherein the lubricant is stearic acid.

15. A metallic pigment composition as claimed in claim 12 or 13 wherein the lubricant is isostearic acid.

16. A metallic pigment composition as claimed in any preceding claim wherein the metallic pigment is in the form of a filter cake.

17. A metallic pigment composition as claimed in any of claims 1 to 15 wherein the metallic pigment is in the form of a paste. - 43 -

18. A metallic pigment composition as claimed in any of claims 1 to 15 wherein the metallic pigment is in the form of flake.

19. A metallic pigment composition as claimed in any preceding claim wherein the metallic pigment is a leafing metallic pigment.

20. A metallic pigment composition as claimed in any of claims 1 to 18 wherein the metallic pigment is a non-leafing metallic pigment.

21. A metallic pigment composition as claimed in any preceding claim wherein the metallic pigment is an aluminium pigment.

22. A metallic pigment composition as claimed in any of claims 1 to 20 wherein the metallic pigment is a zinc pigment.

23. A metallic pigment composition as claimed in any of claims 1 to 20 wherein the metallic pigment is a gold-bronze pigment.

24. A metallic pigment composition as claimed in any preceding claim wherein the surfactant is an ionic surfactant.

25. A metallic pigment composition as claimed in any of claims 1 to 23 wherein the surfactant is a non-ionic surfactant.

26. A metallic pigment composition as claimed in any of claims 1 to 24 wherein the surfactant is a cationic surfactant. - 44 -

27. A metallic pigment composition as claimed in any of claims 1 to 24 wherein the surfactant is an anionic surfactant.

28. A metallic pigment composition as claimed in any of claims 1 to 24 wherein the surfactant is a zwitterionic surfactant.

29. A metallic pigment composition as claimed in any of claims 1 to 24 wherein the surfactant is an amphoteric surfactant.

30. A metallic pigment composition as claimed in any preceding claim wherein the surfactant is a single surfactant.

31. A metallic pigment composition as claimed in any of claims 1 to 29 wherein the surfactant is a mixture of compatible surfactants.

32. A metallic pigment composition as claimed in any of claims 5 to 31 wherein the co-surfactant is a suitable hydrocarbon or a mixture of hydrocarbons.

33. A metallic pigment composition as claimed in claim 32 wherein the hydrocarbon is an alcohol.

34. A metallic pigment composition as claimed in claim 33 wherein the alcohol is pentanol or an alcohol higher than pentanol.

35. A metallic pigment composition substantially as hereinbefore described with reference to the drawings and examples. - 45 -

36. A coating composition comprising a metallic pigment composition as claimed in any preceding claims and an appropriate vehicle.

37. A coating composition as claimed in claim 36 in the form of an ink.

38. A coating composition as claimed in claim 36 in the form of a paint.

39. A coating composition as claimed in claim 36 wherein the vehicle is a water based acrylic glaze.

40. A coating composition as claimed in claim 36 wherein the vehicle is a water based alkyd resin.

41. A coating composition as claimed in claim 36 wherein the vehicle is a water based acrylic melamine.

42. A coating composition as claimed in claim 36 wherein the vehicle is an acrylic latex.

43. A method for preparing a metallic pigment composition as claimed in any of claims 1 to 35 comprising the steps of :

preparing the surfactant structure; and

adding the metallic pigment to the surfactant structure.

44. A method for preparing a metallic pigment composition substantially as hereinbefore described with reference to the drawings and examples.