Weather resistant titanium dioxide pigment and a process for its production
AssigneeKronos International, Inc.
InventorsLydia Drews-Nicolai, Siegfried Bluemel
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Abstract
The invention relates to a weather resistant titanium dioxide pigment with good optical properties having a SiO2 dense skin doped with metal atoms. Particularly suitable elements for doping are tin, zirconium and titanium. The SiO2 dense skin is composed of multiple layers whereby the innermost layer does not contain any significant quantity of metal atoms. The coating according to the invention is produced by adding the components to the alkaline suspension (pH at least 9) one after the other with a sliding pH. Complete formation of the doped SiO2 dense skin requires that the pH subsequently be lowered to below 9. The pigment is particularly suitable for use in surface coatings and plastics.
Claims23
A material, comprising:
- Titanium dioxide pigment particles, the TiO2 pigment particles having a surface, wherein two or more layers are deposited on the TiO2 pigment surface, and wherein at least one of the two or more layers is a dense SiO2 layer comprising SiO2 containing no significant quantity of metal atoms other than silicon, and wherein at least one of the two or more layers is a dense SiO2 layer comprising SiO2 containing a significant quantity of metal atoms other than silicon, and wherein the specific surface according to BET of the material is greater than the specific surface area of the titanium dioxide particles.
A method comprising:
- a) adding a first material containing silicon to a suspension of titanium dioxide pigment particles, wherein the first material contains no significant quantity of a metal other than silicon;
- then
- b) adding a second material containing a metal other than silicon to the suspension of TiO2 particles, wherein the second material is added after a dense layer of undoped SiO2 has formed on the TiO2 particles, and wherein the addition of the second material results in a dense layer of doped SiO2 deposited upon the dense layer of undoped SiO2;
- wherein after performing step a) and step b) the specific surface according to BET of the particles is increased.
A material, comprising:
- Titanium dioxide pigment particles, the TiO2 pigment particles having a surface, wherein the TiO2 pigment particles have a SiO2 dense skin composed of multiple layers, and wherein the innermost layer of the SiO2 dense skin does not contain any significant quantity of metal atoms other than silicon, and wherein at least one layer of the SiO2 dense skin is doped with a significant quantity of metal atoms other than silicon, and wherein the specific surface according to BET of the material is greater than the specific surface area of the titanium dioxide particles.
Dependencies are inferred from the claim text.