Tioxide Group Services Limited

Sergio Pieri

Piergiorgio Nencini

David L Foulger

A process for preparing anatase titanium dioxide by precipitating hydrous titanium oxide in the absence of added nuclei from a solution of titanium sulphate containing the equivalent of 200 to 300 grams TiO.sub.2 per liter and having an acid to titanium ratio in the range 1.6:1 to 2.2:1, the precipitation being induced by the addition of 5 to 35 parts water per 100 parts titanium sulphate solution. The hydrous titanium oxide is calcined in the presence of an amount of potassium compound equivalent to between 0.20 and 0.60 weight percent calculated as K.sub.2 O based on TiO.sub.2 and between 0.15 and 0.55 weight percent phosphorus calculated as P.sub.2 O.sub.5 based on TiO.sub.2. The hydrous titanium oxide is subjected to calcination in a process having a specified thermal profile. The product of the process is anatase titanium dioxide having an average crystal size larger than conventionally prepared anatase. Said product is easily milled to form a product with a high single crystal fraction.

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Follonica, Italy

Sergio Pieri