| 摘要 |
PROBLEM TO BE SOLVED: To easily produce a silica ultrafine powder which is used as an additive for a liquid rubber or resin and has controlled properties affecting stability with time of such a liquid rubber or resin, namely, a controlled specific surface area and a controlled silanol group content. SOLUTION: This production process comprises introducing a siliceous raw material into a vessel placed in an electric furnace, heating the siliceous raw material by passing current through the electric furnace to generate a gas containing silicon suboxide, forming a silica ultrafine powder while supplying an oxidizing gas to the gas containing silicon suboxide and cooling it, and collecting the formed silica ultrafine powder with a collection system, wherein the collection system is connected to a space section of the electric furnace, formed above the upper surface of the vessel, the moisture content of the oxidizing gas is <=40 g/m<3> (including 0), and the specific surface area of the silica ultrafine powder is adjusted by changing the ratio of (the supply volume of the oxidizing gas)/(the volume of the generated gas containing silicon suboxide) within the range of >=200/1.
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