| 摘要 |
1281728 Coating metal oxides BRITISH TITAN Ltd 14 Sept 1970 [25 Sept 1969] 47214/69 Headings C1A and C1N Metal oxide particles are coated by forming an aqueous solution of a hydrolysable metal salt, raising the pH by adding alkali, redissolving any p.p.t. formed with acid, heating the solution, mixing with the metal oxide particles, and precipitating hydrous metal oxide from the solution on to the particles. Preferably, TiO 2 is coated with Al 2 O 3 from solutions of AlCl 3 , Al(NO 3 ) 3 or Al 2 (SO 4 ) 3 . The alkali may be alkali metal hydroxide or carbonate or NH 4 OH and the temp. during addition should be at most 40‹ C. The acid if used may be HCl, H 2 SO 4 or HNO 3 . The solution may be heated to 40-90‹ C. and then diluted. Precipitation may be effected by adding alkali to raise the pH to at least 5, at a temp. of at least 35‹ C., e.g. 40- 65‹ C. The pH may subsequently be raised to 6-9. The particles may also be coated, before or after precipitation, with hydrous oxides of Al, Ti, Ge, Zn, Zr or Si, silicates of Al or Mn, or phosphates of Ti, Zr, Al or Mn, by conventional methods. They may also be post-treated with a polyol, alkanolamine or polyamine. |
