Importance

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Abstract

Improved coated inorganic pigments having a first coating of Al.sub.2 O.sub.3, SiO.sub.2, or optionally other oxide such as a source of P.sub.2 O.sub.5, or mixtures thereof, an optional coating of ZrO.sub.2, SnO.sub.2, TiO.sub.2, SiO.sub.2, CeO.sub.2 or mixtures thereof, and a final coating of Al.sub.2 O.sub.3 which exhibit good durability, dispersibility, and optical properties in plastic or paint compositions are disclosed. Also disclosed is a process whereby an aqueous slurry of an inorganic pigment is milled to achieve a particular particle size distribution, a first coating of Al.sub.2 O.sub.3, SiO.sub.2, or optionally other oxide such as a source of P.sub.2 O.sub.5, or mixtures thereof is precipitated onto the pigment material within a first pH range, an optional amount of ZrO.sub.2, SnO.sub.2, SiO.sub.2, TiO.sub.2, CeO.sub.2 or mixtures thereof is added to the aqueous slurry within a second pH range to obtain an optional coating over the first coating, and a final coating of Al.sub.2 O.sub.3 is added over the prior coating(s).

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First Claim