| 摘要 |
Precipitated silicas which have the following physicochemical characteristics, depending on the manner in which they are milled: -Pendulum -roller mill Jet mill -BET m2/g 15-110 15-110 -surface -area -Tamped g/l 150-750 90-650 -den- -sity -Cu abrasion in 10% mg 5-30 5-30 -strength glycerol -dispersion -Lightness % 86-96 90-96 -value -A -Particle size dis- as in FIG. 1 as in FIG. 2 -tribution curve -determined by a -Coulter Counter -"ALPINE screen retain- % by <1.5 <0.1 -ings" >63 mu m weight -Viscosity of a 30% mPa.s 30,000 to 60,000 -strength dispersion in -a 1:1 glycerol/water -mixture (Brookfield -RTV, Sp5) - are prepared by diluting a precipitated silica original suspension obtained according to German Published Application DAS 1,467,019 and simultaneously adding alkali metal silicate solution, sulfuric acid and water while keeping the pH constant between 7 and 9. The precipitated silica is then filtered off, washed, dried and milled using a pendulum roller mill or a jet mill. Because of their abrasiveness, the precipitated silicas can be employed as cleansing and abrasive agents and, in the case of the jet-milled product, also as a polishing agent, abrasive and thickener in toothpastes.
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