Fine dry silica particles

Abstract

Fine dry silica particles are produced by combustion by using a burner of a multiple-pipe structure, feeding a mixed gas of a gas of a siloxane compound without containing halogen in the molecules thereof and an oxygen gas at a ratio of 0.3 to 1.5 into the center pipe of a burner, and feeding a combustible gas into the first annular pipe on the outer side of the center pipe of the burner. The fine dry silica particles has a BET specific surface area of 20 to 55 m2/g, and wherein the water suspension containing the fine silica particles at a concentration of 1.5% by weight has an optical absorbance τ for the light of a wavelength of 700 nm satisfying the following formula (1): τ≦240S−1.4−0.07  (1) wherein S is the BET specific surface area (m2/g) of the fine dry silica particles. The fine dry silica particles do not almost contain coarse particles or aggregated particles, have a sharpe grain size distribution, excellently disperse in the resins, suppress a rise in the viscosity when highly filled, and impart sufficiently large strength to the resin compound.

Dependencies are inferred from the claim text.