| 摘要 |
<p>The chalking tendency of titanium dioxide pigments is reduced by the presence of particulate insoluble hydrous titanic phosphate on the particles of titanium dioxide. There may be from 0,1 to 5% of weight of hydrous titanic phosphate present; hydrous titania and hydrous alumina also may be present. The pigment is prepared by adding a phosphatic compound, e.g. orthophosphoric acid or trisodium phosphate, to an aqueous slurry of titanium dioxide containing a dissolved titanic salt, e.g. titanic sulphate, titanyl sulphate, titanic nitrate or titanium tetrachloride, to precipitate the hydrous titanic phosphate, and then neutralizing the slurry. Calcium, sodium and aluminium, and sulphate, chloride and nitrate ions may also be present in the coating on the particles. Examples are given.</p> |
