Patent ID: 8142753
Filing Date: 2012-03-27
Classification: C01B,C03C,C08K,C09D,C09G,C09K

Abstract:
1. A process for preparing fumed silica in a reactor having a combustion zone, the fumed silica having a specific surface area from 30 to 500 m 2 /g, a mean aggregate particle size of from 100 to 500 nm, a relative thickening action of greater than 2.0 based on an amount of 2% by weight of silica in a silicone oil with optimal dispersion, and a proportion of coarse particles less than 0.03% by weight based on the weight of the fumed silica and fewer than 100,000 coarse particles per 1 milliliter of a 10% by weight aqueous dispersion of the silica, comprising introducing reaction gases into the reactor through a reactor nozzle and reacting the reaction gases in a flame in an amount of minimally 100 kg/h of at least one silicon compound, an amount of combustion gas of at least 100 m 3 (STP)/h and an amount of air with more than 20% by volume of oxygen of at least 300 m 3 (STP)/h, an exit velocity of the gases at the reactor nozzle being between 10 and 200 m/s, and the gas velocity and the temperature at the reactor nozzle and in the reactor having a radially homogeneous distribution.