| 摘要 |
PURPOSE:To produce an ultramarine compsn. which does not cause fading, by bringing active silica gel into contact with ultramarine particles to deposit silica on the surfaces of the ultramarine particles. CONSTITUTION:One equivalent of an alkali metal silicate (e.g. sodium silicate) and 0.2-0.4 equivalents of a 1-10% aq. soln. of an acid (e.g. sulfuric acid) are fed through feeding means 9, 10 to a subreactor 5. The pH of the mixture is adjusted to 7-10 and the mixture is reacted at 60-100 deg.C to form active silica sol The active silica sol is fed to a main reactor 1 which contains a slurry having a pH of 9-11 and contg. 5-30wt% ultramarine particles having an average particle size of 0.2-20mu suspended therein, in such as proportion as to give 5-25pts.wt. silica sol per 100pts.wt. ultramarine, and ultramarine is brought into contact with silica sol at 90-95 deg.C for 20sec or shorter to deposit silica on the surfaces of ultramarine particles. The reaction mixture is neutralized, and the product is recovered by filtration, washed with water and dried by heating at 100 deg.C or above.
|
