| 摘要 |
In preparing titanium oxide with or without an extender by a process involving the hydrolysis of an acid titanium solution in the presence of suspended calcium sulphate, fine particles of hydrated titanium oxide, produced by precipitation with a "neutralizing agent"--from a mineral acid solution of a titanium salt, are introduced into the solution before hydrolysis. The "neutralizing agent" is one which binds the free or combined acid in the solution. The hydrated titanium oxide may be introduced into the hydrolysis solution by precipitation in situ, or by adding a pre-formed precipitate. The calcium sulphate may be formed by adding an aqueous slurry of calcium carbonate or slaked lime to concentrated sulphuric acid and it may be present when the neutralizing agent is added, or it may be added afterwards. The precipitate obtained by hydrolysis is washed, to remove all or part of the calcium sulphate, dried, and calcined at 700-1200 DEG C. The washing may be effected with a salt solution, e.g. with ammonium chloride for the removal of calcium sulphate. Neutralizing agents specified are sodium carbonate, potassium hydroxide, ammonium hydroxide, calcium carbonate, and barium hydroxide. Extenders specified are precipitated blanc fixe and milled natural barytes or silica. The examples describe the preparation from ilmenite of pigments containing (a) 99,1 per cent titanium oxide, (b) 74,7 per cent titanium oxide and 25,2 per cent calcium sulphate, and (c) 25,1 per cent titanium oxide and 74,8 per cent barium sulphate. Specification 364,562 is referred to.
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