GB462998A - Improvements in or relating to the production of titanium dioxide - Google Patents

Abstract

Titanium hydrates are obtained by adding a solid alkali titanate or the product obtained by leaching the latter with water and/or dilute sulphuric acid to a titanium salt solution and heating the solution to promote hydrolysis. Hydrolysis may be effected at atmospheric pressure at or below the boiling point of the solution or by boiling the solution under pressure, and the added titanate &c. is preferably used in a dry state. Solutions of titanium sulphate containing 150 to 250 grms. per litre and having a factor of acidity of 60--90 may be employed. Alkali titanate for use in the process may be obtained by fusing or fritting ilmenite, rutile or titanium oxide with caustic soda or potash; for example, rutile is mixed with a 75 per cent caustic soda solution, the mixture kneaded, soda ash added, and the whole heated to 300 DEG C. and then calcined at 600--650 DEG C. for 30 minutes to yield a fine granular powder. The quantity of titanate added may be 5--20 per cent of the weight of titanium dioxide in the solution, whilst the quantity of leached titanate used may be 1--10 per cent of such weight. Hydrolysis may be effected in the presence of an extender such as barium sulphate, and the products of hydrolysis may be washed and calcined at 800--1000 DEG C. to produce pigments. Calcination may be effected after adding neutralizing agents and in the presence of sintering agents, and the calcined product may be ground wet or dry, and if wet ground, dispersing agents may be present. Specification 451,890 is referred to.