Silica powder produced by pyrolysis

Abstract

Pyrogenically produced silicon dioxide powder is in the form of aggregates of primary particles having a BET surface area of 300+-25 m 2> / g. The aggregates display an average surface area of 4800-6000 nm 2>, an average equivalent circle diameter (ECD) of 60-80 nm and an average circumference of 580-750 nm. Independent claims are also included for: (A) production of the silicon dioxide powder, comprising evaporating a mixture of silicon compounds, separately or together, and transferring the vapors by a carrier gas to a mixing chamber, with SiCl 4 as the first component in a proportion of 60-100 wt.% relative to the mixture, and a second component chosen from H 3SiCl, H 2SiCl 2, HSiCl 3, CH 3SiCl 3, (CH 3) 2SiCl 2, (CH3) 3SiCl, (n-C 3H 7)SiCl 3, in a proportion of 0-40 wt.%, relative to the mixture, and a combustion gas and primary air, which can optionally be enriched with oxygen and / or be preheated, are transferred separately to the mixing chamber; igniting in a burner the mixture comprising the vapor of silicon compounds, combustion gas and primary air, and burning the flame into a reaction chamber; introducing secondary air, which surrounds the flame, into the reaction chamber, the ratio of secondary air to primary air being 0.05-4; separating the solid from gaseous substances and steam-treating the solid; where the total amount of oxygen is at least sufficient for the complete combustion of the combustion gas and the silicon compounds, and the amount of feed materials consisting of silicon compounds, combustion gas, primary air and secondary air is chosen such that an adiabatic flame temperature T ad of 1390-1450[deg]C is obtained, where T ad=the temperature of the feed materials+the sum of the reaction enthalpies of the partial reactions / heat capacity of the substances leaving the reaction chamber, comprising silicon dioxide, water, hydrogen chloride, carbon dioxide, oxygen, nitrogen, and optionally the carrier gas if it is not air or nitrogen, taking the specific heat capacity of these substances at 1000[deg]C as a basis; and (B) use of the pyrogenically produced silicon dioxide powder as a filler in rubber, silicone rubber and plastics, to adjust the rheology in paints and coatings, as a polyester, as a support for catalysts, to produce dispersions.

Description

technical field [0001] The present invention relates to a silicon dioxide powder produced by a pyrolysis method, its production method and application. Background technique [0002] The flame hydrolysis process for producing silicon dioxide is a long-known, technically implemented process on a large scale. In this method, vaporized or gaseous hydrolyzable silicon halides are introduced into a flame formed by the combustion of a water-forming hydrogen-containing fuel and an oxygen-containing gas. The combustion flame provides water for the hydrolysis of the silicon halide and sufficient heat for the hydrolysis reaction. Cooling and solid matter separation are usually carried out on the silica powder carried in the remaining reaction gas. Silicon tetrachloride is usually used. However, the use of dichlorosilanes, trichlorosilanes is also known. Oxidation additionally occurs when using carbonaceous ingredients such as methyltrichlorosilane, dimethyldichlorosilane, methyldic...

AI Technical Summary

Problems solved by technology

This shows that for prior art silica powders, although produced in the same type of reaction and with the same or similar parameters such as BET surface area typically set for characterization, the mixing time into the liquid medium is very long

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