GB1156575A - Pigmented Material - Google Patents

Abstract

1,156,575. Coated TiO 2 . BRITISH TITAN PRODUCTS CO. Ltd. 7 May, 1968 [17 June, 1967], No. 28051/67. Heading C1N. [Also in Division D2] A TiO 2 pigment is coated with hydrous A1 2 0 3 , an inorganic phosphate, and an organic polyol. The amounts used may be 0À5-10% Al 2 0 3 , 0À2-5% P 2 O 5 , and 0À1-1% polyol, by wt. of TiO 2 . The coating may also contain hydrous 5i0 2 (0À2-5%) and hydrous Ti, Zr, and Ce oxides (each 0À35-7À5%). The polyol may be pentaerythritol, trimethylol propane, triethanolamine, or triisopropanolamine. The TiO 2 may be coated by adding to an aqueous slurry of TiO 2 at 35-60‹ C. a solution of the metal salts (e.g. Al sulphate, Na aluminate, Na silicate) followed by a phosphate solution (e.g. NH 4 H 2 PO 4 , H 3 PO 4 , or alkali metal phosphate). The solution is then neutralized with alkali, e.g. NaOH or acid, e.g. H 2 SO 4 , to a pH of 4-8, and 'the pigment is filtered, washed, dried, and fluid energy milled in steam. The polyol may be added during milling, or may be dissolved in water and stirred with the pigment before drying. When Al 2 (SO 4 ) 3 and H 3 P0 4 are used the coating is Al phosphate. When the pigment is coated with Al and Ti oxides, the coating solution may be obtained by dissolving hydrous TiO 2 in H 2 50 4 at 150‹ C., then dissolving hydrous A1 2 0 3 at 135‹ C. The coated pigment may be treated with anionic or polyacrylate dispersants. The TiO 2 may be anatase or rutile and may be obtained by the sulphate or halide process.