US Patent 7264672 Titanium dioxide pigment composite and method of making same

A process for producing an improved titanium dioxide pigment composite is provided, as are particles produced thereby. The process comprises producing a slurry comprising titanium dioxide particles, leaching alumina from the surface of the titanium dioxide particles in the presence of a soluble phosphate and precipitating aluminum phosphate from the slurry onto the surface of the titanium dioxide particles thereby forming a uniform coating of aluminum phosphate on the surfaces of the titanium dioxide particles. An anionic poly-electrolyte can be added to the resulting slurry. The slurry can then be treated such that the anionic poly-electrolyte forms an additional coating on the aluminum phosphate-coated titanium dioxide particles.