GB566499A - Improvements in or relating to the manufacture of titanium pigments - Google Patents

Abstract

566,499. Titanium pigments. NATIONAL TITANIUM PIGMENTS, Ltd., and BENNETT, A. N. C. Feb. 11, 1943, No. 2286. [Class 1 (iii)] In the production of a rutile titanium dioxide pigment, (1) a titanium dioxide precipitate is obtained by hydrolysing a titanium sulphate solution in the presence of a " nucleating liquid "prepared by adjusting a titanium sulphate solution to a pH value of 2-7 at a temperature between 45‹ and 70‹ C. by means of alkali, the " nucleating liquid " being mixed at a concentration of 10-40 grms. TiO2 per litre with the solution to be hydrolysed in such quantity that at least 1 per cent of TiO2 based on the TiO2 content of the solution is introduced; (2) the precipitate so obtained is peptised or dispersed, as by addition of hydrochloric acid, and added to the titanium sulphate solution to be hydrolysed at a concentration of 10-15 grms. per litre in such amount as to introduce at least 8.5 per cent TiO2 based on the TiO2 content of the solution, the initial concentration of the latter being such that after addition of the peptised precipitate, the solution contains 55-75 grms. TiO2 per litre. In step (1) the amount of "nucleating liquid " added for hydrolysis should preferably not exceed that necessary to introduce 7 per cent TiO2 based on the TiO2 content of the sulphate solution and the TiO2 content of the resulting solution should be 100-150 grms. per litre. In step (2), the precipitate, prior to being peptised may be washed, suspended in water and brought to a pH value of 6-7 by addition of alkali and then washed to remove soluble salts., Enough may be introduced into the solution to be hydrolysed to correspond to 10 per cent of the initial Tio2 content of the solution, and the introduction may be effected gradually in the form of an extenuated stream or film flowing down a surface dipping into the solution and with agitation of the latter, which is preferably hot. The final precipitate may be calcined with addition of a small proportion of magnesium or lithium or compounds thereof as described in Specification 553,135. Specifications 405,669, 533,227 and 542,579 also are referred to.