Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1994-09-23
1996-07-30
Group, Karl
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106436, 106442, 106DIG3, 428363, 428402, C04B 1404, C04B 1420, C04B 1410, C04B 1422
Patent
active
055407692
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This is a 371 of PCT/EP93/00617, filed Mar. 16, 1993.
The present invention relates to a platelet-shaped colored pigment comprising titanium dioxide, one or more suboxides of titanium, and an oxide or oxides of one or more different metals and/or non metals.
BACKGROUND OF THE INVENTION
There is a continuously increasing demand for pigments with intense pearlescent color and/or metallic luster in the field of paints, coatings, inks, plastics, cosmetics and especially for exterior coatings. Therefore, the development in the field of pigments aims at lustrous and hiding pigments which can be new effect pigments or replace the metallic pigments such as aluminum flakes with their known disadvantages. It is known that coatings of TiO.sub.2 -layers on platelet-shaped substrates produce the so-called pearlescent effect. For this kind of pigments it is possible to control the interference color by changing the thickness of the TiO.sub.2 -layer. It is known from DE 3433657, U.S. Pat. No. 4,623,396 and EP 0332071 to use suboxides, e.g. suboxides of titanium, for the coating of platelet-shaped substrates whereby for the reduction of the TiO.sub.2 ammonia gas is used.
However, the reduction of solid particles by a reducing gas is not suitable for an industrial production, because the color of the product as a function of the degree of reduction is difficult to control. It is dependent on the size of the particles, the temperature, the gas flow and the time of treatment. Furthermore special facilities for dangerous or toxic gas are necessary. It is also known that such suboxides provide functional properties such as electric conductivity.
JP-A-1-158077 discloses a pigment consisting of a titanium oxide layer containing a dark color region on a mica core and a color tone adjusting layer as covering layer comprising at least one of silicon oxide, aluminum oxide and zinc oxide or a composite oxide thereof. The dark color region is composed of a dark color metal oxide, such as titanium oxide or iron oxide of lower order, of titanium nitride, titanium oxide or carbon black.
The pigment is manufactured in a first step by heating and reducing titanium dioxide-coated mica flakes at a temperature of from 500.degree. C. to 1000.degree. C. in a reducing gas; or by blending titanium dioxide-coated mica flakes with titanium metal and heating the resulting blend in a vacuum at a temperature of from 500.degree. to 1000.degree. C. for a long time of more than 6 hours. The covering layer is deposited in a second step in an aqueous medium by precipitating of silicon dioxide hydrate on the first layer containing the titanium suboxides and drying or firing the pigment. This additional coating improves heat stability of the suboxide containing layer. However, the functional properties such as electric conductivity of the first layer is shielded by this second layer. The pigment has the disadvantage that it is manufactured in a complicated two-step process which raises the price. The reduction in vacuum requires expensive facilities and complicated operation and high temperature and longer reaction time causes low production efficiency. Furthermore the used titanium metal is expensive.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide platelet-shaped colored pigments having improved heat stability without losing the functional properties of colored layers which are producible in a simple one-step process.
This object is solved according to the present invention by a platelet-shaped colored pigment on the basis of a platelet-shaped substrate which is covered by a coating layer containing TiO.sub.2, one or more suboxides of titanium and an oxide or oxides of one or more different metals and/or non metals. The concentration of said titanium oxides in the coating layer is maximum in the proximity of the substrate surface and gradually decreases towards the pigment surface and the concentration of said oxide or oxides of one or more different metals and/or non metals i
REFERENCES:
patent: 4450012 (1984-05-01), Messer et al.
patent: 4623396 (1986-11-01), Kimura et al.
patent: 4828623 (1989-05-01), Nitta et al.
patent: 4948631 (1990-08-01), Ostertag et al.
patent: 5118352 (1992-06-01), Noguchi
Abstract of JP 58 164 653 Sep. 29, 1983.
Abstract of JP 3,079,673. Mar. 31, 1992.
Abstract of JP 59 126 468. Jul. 21, 1984.
Database WPIL, Section Ch, Week 8345, Derwent Publications Ltd., London, GB; Class E32, AN 83-810901 (abstract of JP-A-58 164 653). Sep. 29, 1983.
Ambrosius Klaus
Franz Klaus-Dieter
Nitta Katsuhisa
Wilhelm Stefan
Group Karl
Marcheschi Michael
Merck Patent Gesellschaft mit beschrankter Haftung
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