Manufacture of pigmentary titanium dioxide

Abstract

Abstract The process comprises hydrolysing a solution of titanium sulphate, washing the titanium dioxide hydrolysate, and then calcining the hydrolysate at a temperature from 750 to 1000*C. to yield titanium dioxide pigment having desirable properties in terms of brightness, opacity, and/or texture. A rutile-promoting seed is incorporated with the titanium sulphate solution and/or with the hydrolysate. In the process, the pH of the wet hydrolysate is in the range of from 6 to 10 immediately before calcination, and there is present in the hydrolysate immediately before calcination an ammonium compound that will be expelled, together with any decomposition products thereof, during calcination; a treating agent or agents selected from beryllium, aluminium, magnesium, zinc and compounds thereof, and a treating agent or agents selected from sodium potassium, rubidium, caesium, and compounds thereof, with the proviso that lithium and/or a lithium compound may be substituted for any or all of the agent or agents selected from the first-mentioned and/or second-mentioned group. The total quantity of the ammonium compound is at least 0.7 percent (calculated as ammonium sulphate); the total quantity of agents from the first-mentioned group is from 0.02 to 0.50 percent (calculated as the metal oxide or oxides); and the total quantity of agents from the secondmentioned group is from 0.05 to 1.0 percent (calculated as the alkali metal oxide or oxides). All the percentages are by weight and are based on the weight of titanium dioxide. The ammonium compound and the treating agent or agents may be incorporated with the hydrolysate in any order. Conveniently, any necessary pH adjustment is effected at least in part by using an alkaline ammonium compound.

Inventors

• 👤 Maurice Arthur Claridge
• 👤 Richard Vyvian Pearse

Bibliographic Details