Titanium dioxide pigment particles with doped, dense SiO2 skin and methods for their manufacture
AssigneeKronos International, Inc.
InventorsSiegfried Blumel, Lydia Drews-Nicolai
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Abstract
A method of predicting photostability of coatings with various dopants on titanium dioxide pigment particles is disclosed. Calculations of the density of states show that a doped coating which reduces the density of states near the band edge or increases the density of states within the band gap of the pigment particles increases the photostability of the doped pigment.
Claims19
Titanium dioxide (TiO2) pigment particles, comprising:
- a) TiO2 core particles;
- b) a dense silicon dioxide (SiO2) skin covering the core particles, the dense skin produced in a wet-chemical process, the dense skin doped with at least one doping element, wherein the at least one doping element is selected from the group consisting of Sb, In, Ge, Y, Nb, F, Mo, Ce, W and Bi as well as mixtures thereof.
A method for manufacturing TiO2 pigment particles whose surface is coated with a dense SiO2 skin doped with at least one doping element comprising the steps:
- a) providing an aqueous suspension of TiO2 core particles, the aqueous suspension having pH>10;
- b) adding an aqueous solution of an alkaline silicon component and at least one aqueous solution of a component containing at least one doping element, wherein at least one doping element is are selected from the group consisting of Sb, In, Ge, Y, Nb, F, Mo, Ce, W and Bi as well as mixtures thereof,
- c) reducing the pH value of the suspension to a value<9 to produce a dense SiO2 skin doped with at least one doping element deposited on the TiO2 core particles.
Titanium dioxide (TiO2) pigment particles, comprising:
- a) TiO2 core particles;
- b) a dense silicon dioxide (SiO2) skin covering the core, the dense skin produced in a wet-chemical process, the dense skin doped with at least one doping element, wherein the at least one doping element either reduces the density of states near the band edge or creates additional states in the band gap of the material of the dense skin, excluding doping elements selected from the group consisting of Ag, Al, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Mg, Mn, Ni, Pb, Sn, Sr, Ti, Zn, and Zr.
Dependencies are inferred from the claim text.