Shin-etsu Chemical Co., Ltd.

Keiji Shibata

Minoru Igarashi

Masaharu Takahashi

Yutaka Hagiwara

Kenji Tawara

Susumu Ueno

Kiyoshi Shirasuna

Yoshio Tomizawa

Yasuaki Nozawa

Hidekazu Uehara

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.

Method for producing hydrophobic silica fine powder

Silanol group-containing organosilicon compounds having a low average degree of polymerization are prepared in an efficient and inexpensive manner by adding water at pH 1-5 to an organooxysilane, mixing them, thus forming a hydrolyzed organooxysilane mixture, and adding a mono- and/or di-alkali metal salt of phosphoric acid to the mixture so as to give pH 5-9.

Preparation of silanol-containing organosilicon compounds

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.

Preparation of organopolysiloxane gum

In a first step, basic components including (A) 100 parts by weight of an organopolysiloxane gum, (B) 5-100 parts by weight of a reinforcing silica filler, and (C) 0.1-30 parts by weight of a processing aid are fed batchwise to a closed mixer for mixing them until uniform. In a second step, the mixture is continuously fed into a kneader/extruder for heat treating. The first step achieves quick dispersion and cooperates with the second step for the efficient production of a heat-curable silicone rubber compound.

Method for preparing heat-curable silicone rubber compounds

In a first step, basic components including (A) 100 parts by weight of an organopolysiloxane gum, (B) 5-100 parts by weight of a reinforcing silica filler, and (C) 0.1-30 parts by weight of a processing aid are fed batchwise to a closed mixer for mixing them at a temperature of room temperature to 150.degree. C. In a second step, the mixture is fed into a kneader/mixer for heat treating at a temperature of 150-250.degree. C. The first step achieves quick dispersion and cooperates with the second step to form a heat-curable silicone rubber compound in an efficient manner.

Growing community of inventors

Annaka, Japan

Keiji Shibata