Shin-etsu Chemical Co., Ltd.

Ken-ichi Isobe

Hiroshi Tsumura

Kazushi Satoh

Kiyoyuki Mutoh

A novel and efficient method is disclosed for decreasing the content of residual alkoxy groups in an organopolysiloxane such as so-called MQ resins, usually and unavoidably, having a considerable amount of residual alkoxy groups bonded to the silicon atoms to be very detrimental against practical application of the organopolysiloxane. The method comprises admixing the alkoxy-containing organopolysiloxane with a strongly alkaline compound such as alkali metal hydroxides as a catalyst, an aprotic polar solvent such as N,N-dimethyl formamide, dimethyl sulfoxide and the like and water each in a specified amount and heating the mixture, for example, under reflux so that the alkoxy groups are rapidly hydrolyzed and can be removed in the form of an alcohol.

Method for decreasing content of alkoxy groups in alkoxy containing

An efficient and economically advantageous method is proposed for the preparation of an organopolysiloxane comprising tetrafunctional siloxane units, i.e. Q units, and, typically, monofunctional siloxy units, i.e. M units, and useful as a reinforcing agent in silicone rubbers. The method comprises the steps of: mixing the reactants for providing the Q and M units, such as ethyl orthosilicate and trimethyl methoxy silane, in a desired molar ratio; and heating the mixture at a temperature higher by at least 10.degree. C. than the boiling point of the mixture under normal pressure in a closed vessel in the presence of water and a catalyst such as a sulfonic acid group-containing compound. In addition to the greatly shortened reaction time and remarkably decreased contents of residual alkoxy groups and gelled matter in the product, the method is advantageous also in respect of the absence of the problems caused by the disposal of the waste water as well as the corrosiveness of hydrogen chloride unavoidably produced in the conventional prior art methods.

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Gunma, Japan

Ken-ichi Isobe