GB562617A - Improvements in or relating to the hydrolytic decomposition of titanium salt solutions - Google Patents

Abstract

562,617. Titanium dioxides and oxyhalides.. BRITISH TITAN PRODUCTS CO., Ltd, (Du Pont de Nemours & Co., E. I.). Nov. 11, 1942, No, 15970. [Class 1 (iii)] Titanium dioxide is precipitated by hydrolysiug a titanium salt solution to which has been added a nucleating material containing a titanium oxyhalide, preferably titanium oxychloride. The nucleating material may be prepared by evaporation of a titanium chloride solution containing more than 300 g. TiO2 per litre, and hydrochloric acid equivalent to about 3 or 4 mols HC1 per mol TiO2, by passing a current of air or other inert gas over it at an elevated temperature, e.g. 50-85‹ C. Alternatively, anhydrous TiCl4 may be added to concentrated hydrochloric acid until a substantially dry powder is obtained which is further dried at 50-70‹ C. preferably in a current of air. The preferred dry seeding material has the composition Ti(OH)3Cl.5.H2O although the atomic ratio of Cl : Ti may vary from 0.8- 1.2 : 1. according to the conditions of preparation. Oxybromides and oxyiodides of like composition may also be used, prepared by evaporating or drying the corresponding titanium salt solution. The material is preferably added to 2-5 times its weight of cold or hot water to form a colloidal solution, but may be used dry or in other diluents, for example dilute titanium solutions such as wash waters from the process. The colloidal solution is generally added to the titanium salt solution to be hydrolysed immediately prior to heating and in an amount of about 0.3-5, normally 0.75-2 per cent by weight thereof. Titanium chloride or nitrate solutions containing about 90-120 g/l. TiO2 may be treated to give a rutile pigment but other salts such as the sulphate which gives anatase may be employed at concentrations of about 150-210 g./l. In examples : (1) TiCl4 is dissolved in water until the solution contains 390 g./l. TiO2 and 643 g/l. HC1. This is evaporated to dryness in air at 60‹ C. and dissolved in 3 times its weight of water. The hydrolysis of a TiCl4 solution at 95‹ C. is described. The product is calcined at 800‹ C. to give a pigment; (2) TiCl4 is added to hydrochloric acid and the dry powder obtained heated at 70‹ C. for 1 hour in an air current. It is added to 4 times its weight of water and the solution used for seeding a TiC14 solution which is hydrolysed at above 90‹ C. The titanium oxide is calcined at 975‹ C. to form a pigment.