BigPatents India

Precipitated silica, characterized by the following physico-chemical parameters: BET surface area 120-300 m2/g CTAB surface area 100-300 m2/g BET/CTAB ratio 0.8 – 1.3 Sears index (Consumption of 0.1 N NaOH) 6-25 ml DBP index 150 – 300 g/100g Wk coefficient < 3.4 Particle size of the degraded particles < 1.0 µm Particles size of the non-degradable particles. 1.0 -100 µm It in prepared by a process in which an alkali metal silicate (preferably soda water-glass) is reacted with mineral acids (preferably sulfuric acid) at temperatures of 60 – 95 0C at a pH of 7.0 - 11.0 with continuous stirring, the reaction is continued up to a solids concentration of 40 g - 110 g, the pH is adjusted to a value between 3 and 5, and the precipitated silica is filtered off, washed and then dried, and if appropriate ground or granulated. It is employed as a filler in vulcanizable mixtures for the production of tyres. (FIG.1).