GB944216A - Improvements in and relating to titanium and aluminium salt solutions - Google Patents

Abstract

An aqueous solution of aluminium and titanium sulphates is prepared by filtering an aqueous suspension of a titanium dioxide hydrolysate using an organic filter aid, incorporating hydrogen peroxide, or an inorganic peracid, or a sodium, potassium or ammonium salt of an inorganic peracid, with the filtered titanium dioxide in an amount such that the final solution is substantially free from carbonaceous colouring matter, dissolving the titanium dioxide in sulphuric acid, and forming a solution containing aluminium sulphate in admixture with the titanium sulphate. The filter-aid may be wood flour. The titanium dioxide may be washed after filtering. The aluminium sulphate may be prepared by reacting aluminium, aluminium hydroxide, or hydrated alumina with sulphuric acid, and may be formed either apart from, or in the presence of the hydrolysate. Alternatively, aluminium hydrate may be dissolved in an excess of sulphuric acid and the hydrolysate added to the resulting solution. The sulphuric acid may have a concentration of from 93 to 20% oleum. The mixed solution obtained will normally be hot and viscous and may be cast in moulds in which it solidifies on cooling, or it may be diluted to prevent solidification. The solution may be employed for the surface treatments of pigments and fillers, such as titanium dioxide, blanc fixe, or calcium sulphate by depositing hydrated titanium dioxide on the surface of the pigment or filler.ALSO:The surfaces of pigments, such as titanium dioxide, mixed pigments containing titanium dioxide, and coloured pigments, may be treated by depositing on their surfaces mixed hydrated titanium dioxide and alumina from an aqueous solution of titanium and aluminium sulphate substantially free of carbonaceous colouring matter (see Division C1). In an example, a yellow titanium pigment was prepared by forming an aqueous suspension containing 100 parts titanium dioxide, 16.5 parts hydrated nickel sulphate, and 18 parts antimony oxide, drying, calcining, and grinding. The resultant pigment was dispersed in water with the addition of sodium silicate solution, and the titanium and aluminium sulphate solution was then added. The pH of the resultant mixture was brought to 7 by the addition of sodium hydroxide solution, with the resultant deposition of the hydrous oxides of silicon, aluminium, and titanium. The suspension was then filtered, washed, dried, and disintegrated to give an improved pigment.