GB1087697A - Production of titanium dioxide pigments - Google Patents

Abstract

Rutile TiO2 is prepared by oxidizing TiCl4 in a closed reactor with a gas containing molecular oxygen at a temperature between 900 DEG and 1700 DEG C. and a pressure throughout the reaction of at least 20 p.s.i.g. The product has improved chalk-fading properties. AlCl3 in an amount equivalent to 0.1-10% by weight of the TiCl4 may be present during the reaction preferably by being introduced into a vaporized TiCl4 stream. The TiCl4 may be introduced as a vapour into a pressure-resisting corrosion-resistant reaction vessel such as disclosed in Specification 764,082, and as disclosed in that Specification, build-up on the walls may be prevented by passage of cool chlorine or nitrogen into the chamber to maintain the walls at approximately 300 DEG C. The cooled chlorine containing gases may be recycled to a chlorination plant. The pigment suspension produced is rapidly cooled to below 600 DEG C. to prevent particle size growth, if desired as disclosed in U.S. Patent 2,833,627. The gas containing molecular oxygen (air, oxygen, oxygen-enriched air) may be humidified by addition of up to 10% by weight of water vapour. In Example 1 trace amounts of KCl dissolved in water are added to the TiCl4 stream as a metal ion nucleant to aid in particle size as disclosed in Specification 922,671.