| abstract |
This invention concerns a post-treatment of TiO 2 having pigmentary morphological and granulometric characteristics, with the purpose of conferring to it a compact, uniform and adhering coating with a controllable specific surface area. n The process comprises three stages: firstly, activating the surface of the TiO 2 particles in a moving bed by treatment with an anhydrous gas at a temperature from 400° to 600°, secondly, reacting the particles in a moving bed with one or more chlorides selected from AlCl 3 , SiCl 4 and ZrCl., in the presence of a carrier gas, at a temperature from 400° to 700°C, and thirdly, treating the particles with a gas containing water vapour at a temperature from 200° to 400°C. n During the second stage, the chlorides may be allowed to react with oxygen with the consequential deposition on the particles of the corresponding oxides. |