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Abstract

A process for the improvement of titanium dioxide pigments by a post-treatment, wherein the titanium dioxide pigment produced by any process, in the form of an aqueous suspension and in any order, is treated with an aqueous titanium oxide chloride solution resulting from the scrubbing of off-gases derived from the production of titanium tetrachloride and, optionally, with one or more other water-soluble metal salts which when neutralized form difficult-to-dissolve oxide hydrates and/or other difficult-to-dissolve compounds, and/or optionally with a water-soluble silicate, and where difficult-to-dissolve oxide hydrates and/or other difficult-to-dissolve compounds are precipitated onto the titanium dioxide pigment from the titanium oxide chloride solution and, if present, from the other metal salts and/or the silicate, and where the titanium dioxide pigment thus treated is recovered such as by being separated from the suspension, washed, dried and milled. It is found that such a post-treatment can improve titanium dioxide pigments in various properties such as weather resistance and optical properties.

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First Claim