BigPatents India

The precipitated silicic acid having the following parametes: BET surface 80- 180 m2/g CTAB surface 80-139 m2/g BET/CTAB ratio 1.0-1.6 Sears No. (Consumption of 0.1 N NaOH) 5-25 ml DBP No. 200 – 300 ml/100 g Al2O3 content < 5% Wk coefficient < 3.4 Degraded particles < 1.0 µm Non-degradable particles 1.0 – 100 µm is prepared by reacting alkali silicate with mineral acids and aluminium sulfate solution at temperature of 60-95 0C at a pH of 7.0 – 10.0 while stirring constantly, wherein the reaction is continued to a solids concentration of 40-110 g/l, the pH is adjusted to a value between 3 and 5, and the precipitated silicic acid is filtered off, washed and then dried, and optionally ground or granulated . It can be used as filler in rubber mixtures. (FIG. - nil)