Shin-etsu Chemical Co., Ltd.

Kenji Tawara

Masaharu Takahashi

Minoru Igarashi

Yutaka Hagiwara

Keiji Shibata

Yoshio Tomizawa

An organopolysiloxane gum is prepared by polymerizing a cyclic organopolysiloxane with a low molecular weight linear organopolysiloxane end-blocked with a triorganosilyl group in the presence of a thermally decomposable catalyst. After the polymerization reaction, the catalyst is deactivated by heating the reaction product under a subatmospheric pressure of typically up to 500 mmHg.

Preparation of organopolysiloxane gum

An organopolysiloxane gum is prepared by polymerizing a cyclic organosiloxane with a low molecular weight, linear organopolysiloxane end-blocked with a triorganosilyl group in the presence of an alkaline catalyst. The polymerization reaction is effected under a reduced pressure, typically of 500 mmHg or lower.

Preparation of organoplysiloxane gum

An organopolysiloxane gum is continuously prepared by (I) mixing at least one cyclopolysiloxane with an end capping agent, (II) feeding the mixture to a self-cleaning reactor along with a polymerization catalyst of thermal decomposition type, and effecting polymerization at a temperature of 80-130&deg; C., (III) heating the reaction mixture of step (II) at a temperature of 130-200&deg; C. under subatmospheric pressure for deactivating the catalyst, thereby terminating the polymerization reaction, and (IV) continuously removing the cyclopolysiloxane and volatile components from the reaction product.

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Annaka, Japan

Kenji Tawara