DE2634661

1481151 Treating titanium dioxide pigment TIOXIDE GROUP Ltd 11 June 1976 [14 Aug 1975] 33826/75 Heading ClN TiO 2 pigment is treated by forming an aqueous dispersion of the pigment containing as a dispersant 0À1-0À3% by weight monoisopropanolamine, 0À05-0À5% water soluble phosphate or a mixture thereof, or a water soluble silicate in amounts of 0À1-0À5% used alone or together with the monoisopropanolamine and/or the phosphate, adding to the aqueous dispersion 0À05-1% water soluble phosphate (when the dispersing agent is not solely a phosphate), 0À2-2À5% water soluble hydrolysable acidic compound of Zr, 0À2-2À5% water soluble hydrolysable acidic compound of Al, 0-1% water soluble compound Si and finally a water soluble hydrolysable alkaline compound of Al in amounts 0À5-2À5%, adjusting pH if necessary to 6À5-8À5 and recovering the treated pigment (all percentages are by weight expresssed as the oxide based on weight of TiO 2 ). The pigment preferably contains 0À1-0À5% Al 2 O 3 and at least 95% rutile and may be derived from either the chloride or sulphate process. Suitable phosphates are NaH 2 PO 4 or sodium hexametaphosphate. The preferred silicate is sodium silicate. Suitable zirconium compounds are zirconium sulphates and zirconium chloride. The preferred acidic compounds of aluminium are the sulphate, chloride and nitrate. The alkaline aluminium compound is typically sodium aluminate. After recovery the pigment may be treated with trimethylolpropane.