| 摘要 |
There are disclosed precipitated silicas which are characterized by the following physical-chemical data: -A B C -BET-surface area m2/g 400-600 400-600 400-600 -according to DIN 66131 -DBP-Number % 340-380 320-360 310-360 -Bulk density according g/l 180-220 75-120 35-70 -to DIN 53194 -"ALPINE-Sieve Wt. % 25-60 <0.1 <0.01 -Residue" >63 m mu - Depending on the particle distribution curve, these precipitated silicas can be employed as silica carriers for active materials of all types, as antiblocking agents for polypropylene and polyethylene films, as thickening silica in specific polar systems in which pyrogenic silicas show little thickening capacity, as highly active matting agents for varnishes and as catalyst carriers as well as insulating materials. The precipitated silicas are produced by establishing a silica final concentration of 46 grams/l in a receiver having water present heated to a temperature of 40 DEG -42 DEG C. while holding the pH constant in the range of 6-7 by simultaneously running in a water glass solution and sulfuric acid while maintaining shearing with an Ekato Turbine over the entire precipitation time, interrupting the precipitation for 90 minutes from the 13th to 103rd minute according to a total precipitation of 146 minutes, aging the suspension of precipitated silica for 12-17 hours, separating the precipitated silica from the suspension with the help of a filter press, washing, liquifying the filter cake with water and/or acid to a suspension having 10-16 weight % solids, finally spray drying and either not grinding or grinding with a cross flow mill or jet mill. |
