GB734448A - Improvements in or relating to the preparation of titanium dioxide pigment - Google Patents

Abstract

A titanium dioxide pigment which is resistant towards reaction with film-forming vehicles is prepared by reacting titanium tetrachloride vapour, a silicon, halide or oxyhalide (e.g. silicon oxychloride, bromide or oxybromide, but preferably silicon tetrachloride) in the vapour state and free oxygen-containing gases substantially instantaneously at 900-1050 DEG C. and calcining the so-formed oxide at 1100-1300 DEG C. The silicon compound will normally be employed in concentrations by weight less than 10 per cent, and will preferably be between 0.5 and 4 per cent of silicon, based on the titanium. The vapours may be premixed or separately introduced into the reaction zone. Calcination may take about 1/4 -2 hours, depending on the temperature used. In example 1, the starting materials were silicon tetrachloride and titanium tetrachloride, the silicon content being 0.8 per cent by weight of the titanium; a temperature of 1000 DEG C. was used for the oxidation and 1100 DEG C. for calcination. The particles had a diameter of 0.2-0.4 microns. In example 2, the same materials, but with a silicon content as above defined of 4 per cent, were oxidized at 1000 DEG C. and calcined at 1200 DEG C. Specification 567,093 is referred to.