Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1998-01-09
1999-11-16
Bell, Mark L.
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106415, 106437, 106438, 106439, 106441, 106442, 106446, 428402, C09C 136
Patent
active
059850205
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to very thin, plateletlike titanium dioxide reduction pigments.
Plateletlike titanium dioxide reduction pigments are known. However, they are based on the use of mica as substrate. The titanium dioxide is precipitated onto the mica and is subsequently subjected to partial reduction to titanium suboxides. Reducing agents used are gaseous reducing agents, such as hydrogen and ammonia, or solid reducing agents, such as silicon or titanium. Some of these pigments also possess an additional top layer comprising silicon dioxide.
U.S. Pat. No. 4,948,631 describes a process for preparing particularly bluish pearl luster pigments by reducing titanium dioxide-coated mica pigments with ammonia at temperatures from 750 to 850.degree. C.
JP H4-20 031 describes a process for producing a colored mica pigment by mixing a titanium dioxide-mica pigment with titanium and reducing the resulting mixture under reduced pressure at from 500 to 1000.degree. C.
U.S. Pat. No. 4,623,396 describes a titanium dioxide-mica pigment consisting of mica, a first layer of titanium dioxide, titanium suboxides and titanium oxynitrides and a second layer of titanium dioxide.
Mica pigments are used widely in the printing and coating industries, in cosmetics and in polymer processing. They are distinguished by interference colors and a high luster. For the formation of extremely thin layers, however, mica pigments are not suitable, since the mica itself, as substrate for the metal oxide layers of the pigment, has a thickness of from 200 to 1200 nm. A further disadvantage is that the thickness of the mica platelets within a certain fraction defined by the platelet size in some cases varies markedly about a mean value. Moreover, mica is a naturally occurring mineral which is contaminated by foreign ions. Moreover, technically highly complex and time-consuming processing steps are required, including, in particular, grinding and classifying.
Pearl luster pigments based on thick mica platelets and coated with metal oxides have, owing to the thickness of the edge, a marked scatter fraction, especially in the case of relatively fine particle-size distributions below 20 .mu.m.
As a substitute for mica it has been proposed to use thin glass flakes which are obtained by rolling of a glass melt with subsequent grinding. Indeed, interference pigments based on such materials exhibit color effects superior to those of conventional, mica-based pigments. Disadvantages, however, are that the glass flakes have a very large average thickness of about 10-15 .mu.m and a very broad thickness distribution (typically between 4 and 20 .mu.m), whereas the thickness of interference pigments is typically not more than 3 .mu.m.
EP 0 384 596 describes a process in which hydrated alkali metal silicate is subjected at temperatures of 480-500.degree. C. to the action of an air jet, forming bubbles with thin walls; the bubbles are subsequently comminuted to give plateletlike alkali metal silicate substrates with a thickness of less than 3 .mu.m. However, the process is complex and the thickness distribution of the resulting platelets is relatively broad.
DE 11 36 042 describes a continuous belt method of preparing plateletlike or glitterlike oxides or oxide hydrates of metals of groups IV and V and of the iron group of the Periodic Table. In this method, a release layer comprising, for example, a silicone coating is first of all applied, if desired, to a continuous belt in order to facilitate the subsequent detachment of the metal oxide layer. Then a liquid film is applied which comprises a solution of a hydrolyzable compound of the metal which is to be converted into the desired oxide, and the film is dried and subsequently detached using a vibration device. The layer thickness of the platelets obtained is given as being 0.2 to 2 .mu.m, although no concrete examples of this are cited.
EP 0 240 952 and EP 0 236 952 propose a continuous belt method of preparing different plateletlike materials, including silicon dioxide, aluminiu
REFERENCES:
patent: 3395203 (1968-07-01), Morita et al.
patent: 3767443 (1973-10-01), Clark et al.
patent: 3861946 (1975-01-01), Waitkins et al.
patent: 4978394 (1990-12-01), Ostertag et al.
Derwent abstract 87-039671 of JP 61 295 234 A, Dec. 1986.
Derwent abstract 70-18273R of JP 45-6424 B, Nov. 1970.
Andes Stefanie
Brenner Gunter
Bruckner Dieter
Heyland Andrea
Hock Sabine
Bell Mark L.
Hertzog Scott L.
Merck Patent Gesellschaft mit beschrankter Haftung
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