Shin-etsu Chemical Co., Ltd.

Isao Watanuki

Nobuhiko Kodana

Hiroshi Tsumura

Kazushi Satoh

Makoto Sato

Masaaki Furuya

Masao Maruyama

Masanori Fukuhira

Akihito Tsukuno

Hidehiko Aonuma

Masaru Suzuki

Siloxanes are purified by contacting siloxanes containing ionic crystals as an impurity with a polar solvent, evaporating the solvent, thereby increasing the mean particle size of the ion crystals, and removing the ion crystals from the siloxanes by filtration. The method enables brief, efficient purification of siloxanes in high yields, offering siloxanes having a minimal content of ionic crystals.

Siloxane purification

An efficient and safe method is proposed for the preparation of an oximesilane compound having a group of the general formula --O--N.dbd.CR.sup.2 R.sup.3, in which R.sup.2 and R.sup.3 are each a hydrogen atom or a monovalent hydrocarbon group, bonded to the silicon atom. The method consists of successive steps of which the first is for the reaction of a chlorosilane compound with ammonia and the second is for the reaction of the reaction mixture coming from the first step with an oxime compound to introduce the oxime groups as bonded to the silicon atom. Different from conventional methods in which formation of an explosive compound such as hydrochloride of an organic base or oxime compound is unavoidable, the inventive method does not involve formation of such an explosive by-product so that the desired oximesilane compound can be obtained without the danger of explosion.

Method for the preparation of an oximesilane compound

A simple but very effective and reliable method is proposed for the decolorizing purification of a halogenated silane compound, e.g., methyl trichlorosilane, colored by containing a very small amount of heavy metal impurities such as iron. The method comprises: contacting the halogenated silane compound with a small amount of a cationic surface active agent which is solid and insoluble in the silane such as a quaternary ammonium salt, e.g., trimethyl octadecyl ammonium chloride, for 2 to 240 minutes; and then separating the silane compound from the cationic surface active agent.

Method for decolorizing purification of halogenated silane

An improvement is proposed for minimizing coloration of an oximesilane synthesized by the reaction of a chlorosilane such as vinyl trichlorosilane and an oxime compound such as methyl ethyl ketone oxime in the presence of a nitrogen-containing basic compound as an acceptor of the hydrogen chloride followed by the removal of the precipitates of the hydrogen chloride salt of the base and distillation. The improvement comprises conducting the distillation of the filtrate after removal of the precipitates of salt is performed in the presence of a nitrogen-containing basic compound such as ammonia in the filtrate, for example, by blowing ammonia gas into the liquid under distillation. An already colored oximesilane product also can be decolorized by blowing ammonia gas thereinto.

Method for the preparation of an oximesilane without coloration

The process of producing a catalyst for polymerization of organosiloxanes comprises heat-treating a mixture of an aqueous solution of a tetraalkylphosphonium hydroxide, such as tetramethylphosphonium hydroxide, and a cyclic or noncyclic siloxane component, thereby controlling the water content of the system so that the molar ratio of the amount of water in the system to the amount of the quaternary phosphonium hydroxide component in the system will be from 3.0 to 4.0. The process ensures that the crystallization of the tetraalkylphosphonium hydroxide component in the catalyst is obviated effectively.

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Gunma, Japan

Isao Watanuki