GB426881A - Improvements in and relating to the production of titanium pigments - Google Patents

Abstract

Zinc orthotitanate or pigments containing it are prepared by calcining at temperatures not exceeding 800 DEG C. a mixture of an oxidic or hydratic compound of titanium associated if desired with extenders and a compound of zinc such as the oxide, the titanium and zinc being present in the proportions of 1 : 2 reckoned as TiO2 and ZnO. When hydrated titanium oxide is employed, it may be treated, prior to calcination, to remove sulphuric acid therefrom, such removal being effected before or after admixture with the zinc compound, and in the case of composite pigments, before or after admixture with an extender. In using a hydrated titanium compound, the mixture may be dried, say at 75 DEG C., prior to calcining, and in the calcination step, the presence of a small amount of a halogen compound, for instance, hydrochloric acid promotes the reaction. A relatively small amount of a salt such as sodium or potassium sulphate or sodium carbonate, or of phosphoric acid or a phosphate such as calcium or barium phosphate, may also be added to the mixture. Extenders referred to are barytes, blancfixe, gypsum, whiting, silica, clay, and asbestine, and the use in the process of a composite pigment containing 75 per cent of barium sulphate and 25 per cent of titanium oxide is specified. Specifications 347,129 and 384,473 are referred to. The Specification as open to inspection under Sect. 91 comprises also the following subject - matter:--No limitation as to the relative proportions of titanium and zinc in the reacting mixture is imposed. Temperatures of 650-11000 DEG C. may be used, and the use of zinc sulphide, lithopone, and zinc sulphate is referred to. Examples are also given of the calcination of mixtures of zinc oxide with composite pigments containing titanium oxide and barium or calcium sulphate. This subject-matter does not appear in the Specification as accepted.