| 摘要 |
Pptd. silica is prepared by reacting an alkali metal silicate with an acidifying agent, then adding further alkali metal silicate to give a suspension, separating and drying. An initial starter is formed in which the silicate concn., based on SiO2, is below 20 g/l, the amount of acidifying agent added is such that /-5% of the amt. of M2O in the initial starter is neutralised, and the remaining metal silicate is added simultaneously such that the ratio of silicate added, based on SiO2, to the silicate in the initial starter is 4-100. Also claimed are: (i) pptd. silica (I) having a specific ctab surface Sctab of 140-240 m<2>/g, a median dia., after disaggregation by ultra-sound, of below 2.5 mu and a disaggregation factor after ultra-sound of more than 11 ml; and (ii) pptd. silica (II) having a specific CTAB surface (SCTAB) of 140-240 m<2>/, a median dia., after disaggregation by ultra-sound, of below 5 mu , a disaggregation factor after ultra-sound of more than 5.5 ml as well as a porous distribution such that the proportion of pores of dia. 175-275 A is less than 50% of the porous vol. of pores of dia. at most 400 A. |
