Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1996-02-15
1998-12-15
Bell, Mark L.
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106404, 428407, C09C 162
Patent
active
058490728
DESCRIPTION:
BRIEF SUMMARY
The invention concerns metal pigment dispersions, a process for the production thereof and the use of those metal pigment dispersions for the production of paints or lacquers and inks, in particular printing inks.
Paints or lacquers and inks which contains flake-form metal pigments have a very wide range of uses. They are used in the paint industry as so-called metallic paints for painting motor vehicles, machines and the like. In the printing ink industry they are used for the production of printing inks for metallic and effect printing, but also for the surface coating of packaging materials using printing procedures in order thereby to replace the procedure of using metal foil for lining purposes, which is expensive in terms of This applies in particular for the packaging for foodstuffs and semi-luxury foods and tobacco.
Irrespective of the purpose of use thereof, the production of metal pigments is effected by coarse gravel-like powder, flakes or coarse pigments being ground in a plurality of steps until they are of the desired fineness or particle size. Thus for example aluminium, gold bronze, copper or zinc are reduced in size by crushing in a ball mill in the presence of hard round crushing bodies or by stamping. The crushing operation can be carried out wet, as for example when dealing with aluminium in the presence of white spirit, or dry, as for example when dealing with gold bronze or copper.
In the case of the wet crushing process the suspension which is obtained from the ball mill is pressed out on a filter press, giving a filter cake, for example in the case of aluminium, with a solvent content of about 20%. This filter cake must be dried to powder for use in many paints and printing inks, and frequently has to be made into a paste again with other solvents.
Metal pigments have a flake structure with a shape factor (ratio of diameter to thickness) of 10-500. It is only that particle shape that permits a metallic silver or gold effect, by virtue of the reflection characteristics. When crushing coarse powder, flakes or coarse pigments as the starting material, fresh surfaces are constantly produced. Accordingly in the crushing operation there is a need to add so-called crushing aids (`lubricants`). By virtue of the surface of the metal pigments being coated with lubricant and as a result of a reaction between the metal pigment surface and the lubricant, for example in the form of metal soap formation, that avoids cold welding or bonding and thus serious impairment of the optical effect of the metal particles. The crushing aids used are usually fatty acids or derivatives thereof, in the case of aluminium preferably stearic acid and oleic acid and, in the case of gold bronze and copper, preferably stearic acid. Those crushing aids also provide for control of the `leafing` and `non-leafing` properties of the pigments, which are again crucial in regard to the optical aspect and the adhesion of the pigments.
When crushing metal pigments when using fatty acids or derivatives thereof, undesirable fatty acid decomposition products also occur in the presence of oxygen from the air, besides the metal salts, in particular organic aldehydes and acids which adhere to the surface of the metal pigments and which cannot be removed with conventional processes. Furthermore, due to the above-mentioned decomposition products, for example butyric acid can also be formed, the metal pigments produced in that way have a typical unpleasant smell which is also present on the end product. It is precisely when those metal pigments are to be used in the foodstuffs area that this is not acceptable for sensory reasons.
In addition, when aluminium is subjected to wet crushing in the presence of white spirit as the crushing medium and a crushing aid such as for example oleic acid, the need to remove the white spirit also gives rise to further disadvantages. They are in particular that condensation and distillation wastes occur, as well as the fact that it is necessary to ensure that the waste slurries which are produced when t
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Appleyard Colin
Sommer Gunter
Bell Mark L.
Eckart-Werke Standard-Bronzepulver-Werke
Hertzog Scott L.
Lucas James A.
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