Shin-etsu Chemical Co., Ltd.

Kenichi Kimura

Masatoshi Miyake

Hironao Fujiki

Takeo Yoshida

Manabu Narumi

Nobuhiko Kodana

Masaya Arakawa

Chinami Matsui

Mutsuo Shimizu

Preparation of organoxy-terminated organopolysiloxanes

A hydrolyzable group end-blocked organopolysiloxane is prepared by reacting (A) an organopolysiloxane having a silanol group at each end of its molecular chain with (B) an organosilicon compound having hydrolyzable groups or a partial hydrolyzate thereof in the presence of (C) a condensation catalyst. Use is made of a vibratory mixer comprising a conduit through which a fluid flows in an axial direction and an agitating element disposed in the conduit for reciprocal motion in the flow direction. A reactant mixture of necessary components is introduced into the conduit where the components are vibro-agitated by the agitating element while reaction takes place.

Preparation of hydrolyzable group end-blocked organopolysiloxane

A liquid silicone rubber base including (A) an alkenyl-containing organopolysiloxane, (B) a reinforcing silica filler, (C) a mixing assistant in the form of a silanol-containing compound, (E) an organohydrogen polysiloxane, (f) a platinum catalyst and optionally, (D) a wetting auxiliary catalyst is prepared by previously mixing 10-120 parts of component (A) with 1-35 parts of component (C) and 0-35 parts of component (D) to form a premix liquid, mixing the premix liquid with 100 parts of component (B) to form a premix power, and kneading the premix powder with the remainder of component (A). By adding a curing agent of organohydrogenpolysiloxane/platinum catalyst to the liquid silicone rubber base, there is obtained a liquid silicone rubber composition having improved fatigue endurance.

Preparation of high fatigue endurance liquid silicone rubber composition

A liquid silicone rubber base is prepared by mixing an organopolysiloxane containing at least two alkenyl groups, reinforcing silica having a BET specific surface area of at least 50 m.sup.2 /g, and optionally, a mixing assistant. The mixing step includes a first stage of mixing under a first shear stress of at least 1.times.10.sup.6 N/m.sup.2 for 1-5 minutes and a second stage of mixing under a second shear stress which is up to 1/2 of the first shear stress for at least 2 minutes. The silicone rubber base is sufficiently shelf stable to minimize a viscosity rise with time.

Methods for the preparation of liquid silicone rubber base and liquid

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Annaka, Japan

Kenichi Kimura