TiO2-Pigmente

1,202,540. Coated TiO 2 . AMERICAN CYANAMID CO. 30 Nov., 1967 [24 March, 1967], No. 54653/67. Heading ClN. Pigmentary TiO 2 is coated with the hydrous oxides of Si and Al in the weight ratio SiO 2 / Al 2 O 3 of at least 5, using at least 0À5 pts. by wt. of the oxides per 100 pts. TiO 2 . Coating may be effected by adding aqueous Al 2 (SO 4 ) 3 or AlCl 3 and Na silicate to a slurry of TiO 2 and adjusting the pH if necessary with NaOH or HCl, ageing at 5-100‹ C., washing, optionally treating with triethanolamine or ethylhexoic acid, drying, and fluid energy milling with air or steam at above 450‹ F. under 100-175 p.s.i.g. pressure. The SiO 2 /Al 2 O 3 ratio may be 5-7 and the amount of SiO 2 0À5-1À7%. The TiO 2 may be anatase or rutile obtained from the sulphate process or by combustion or hydrolysis of TiCl 4 . The intial slurry may contain 15-30% solids by weight and may be treated with a dispersing agent, e.g. 0À05% NaOH and hydroclassified to remove particles larger than 4Á.