Finely divided precipitated silicas with a high structure, process for their preparation and their use

The finely divided precipitated silica with a high structure with a It can be prepared by heating a mixture of water and sodium silicate with stirring to a temperature of 70 to 80 C, to this template concentrated sulfuric acid until half of the alkali present is neutralized, dosed, treated the reaction mixture by means of a shear unit and optionally simultaneously increasing the temperature to 86 ± 5 ° C, after a period of 30 to 120 minutes, adding concentrated sulfuric acid at a higher rate until the pH of the resulting silica suspension is 3.0 to 3.5, optionally the silica suspension with water diluted, optionally by means of a centrifugal pump and a hydrocyclone separates the coarse fraction, the silica filtered off by means of a known filter device, the silicic acid filter cake washes sulfate-free,the silica filter cake is redispersed with the addition of water by means of a stirrer to a suspension having a solids content of 80 ± 10 g II, optionally added to this suspension Alkyldimethylbenzyl ammonium chloride, spray-drying the suspension thus obtained and optionally grinding the dried product. The precipitated silica can be used both uncoated and coated as a matting agent in paints.