Shin-etsu Chemical Co., Ltd.

Yasuaki Nozawa

Kiyoshi Shirasuna

Susumu Ueno

Keiji Shibata

Takayuki Matsuzawa

Hidekazu Uehara

Masanori Akiyama

Hydrophobic silica fine powder is produced by pyrolyzing a silane compound to form a silica fine powder and hydrophobizing the silica fine powder with an organohalosilane in a fluidization vessel. Hydrophobized silica fine powder which flies out of the fluidization vessel is collected with a cyclone and bag filter which are held at a temperature of 100-500&deg; C. An apparatus for carrying out the process is also provided. Under simple controlled conditions that involve holding the cyclone and bag filter for recovering fugitive silica from the fluidization vessel to temperatures of 100-500&deg; C., the method and apparatus are able to recover essentially 100% of fugitive silica, thus increasing yield of the product and alleviating the burden on waste gas treatment.

Method for producing hydrophobic silica fine powder

Hydrophobic silica fine powder is produced by pyrolyzing a silane compound to form a silica fine powder and hydrophobizing the silica fine powder with an organohalosilane as hydrophobizing agent in a fluidization vessel. A portion of the silica fine powder is bypassed to a waste gas line from the fluidization vessel and collected with a cyclone and bag filter, and the collected powder is fed to the fluidization vessel where it is hydrophobized. The amount of unreacted organohalosilane in the waste gases is reduced, alleviating the burden on waste gas treatment. The silica having the unreacted organohalosilane borne thereon is fed back to the fluidization vessel, increasing the reaction efficiency of organohalosilane.

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Annaka, Japan

Yasuaki Nozawa