Shin-etsu Chemical Co., Ltd.

Nissin Chemical Industry Co., Ltd.

Masaharu Takahashi

Minoru Igarashi

Yoshio Inoue

Takeo Yoshida

Jun Hatakeyama

Tsutomu Nakamura

Kunio Itoh

Naoki Omura

Tomiyoshi Tsuchida

Yutaka Hagiwara

Susumu Sekiguchi

Kazuma Momii

Keiji Shibata

Ken-ichi Takita

Motoo Fukushima

Toshio Shinohara

Kenichi Takita

Kenji Tawara

Yoshio Tomizawa

Kipp J Mize

Shinichi Sato

Hirofumi Kishita

Yasushi Yamamoto

Atsushi Yaginuma

Masachika Yoshino

Harukazu Okuda

Hiroyuki Ohata

Masayuki Oyama

Yuji Tokushige

Manabu Narumi

Terukazu Satoh

Kazuo Numata

Hiroshi Matsukawa

Satoshi Terasaki

Yoshio Takeuchi

Keiji Take

Ken-ich Takita

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 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 an alkaline polymerization catalyst, and effecting polymerization at a temperature of 100 to 250&deg; C. and under subatmospheric pressure, (III) continuously adding a neutralizing agent to the reaction mixture of step (II), thereby terminating the polymerization reaction, and (IV) continuously removing the cyclopolysiloxane and volatile components from the reaction mixture.

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.

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.

A silicone rubber is prepared from a silicone rubber compound comprising (A) an organopolysiloxane having an average degree of polymerization of at least 100, (B) a reinforcing silica filler, and (C) an organohydrogenpolysiloxane by mixing component (C) with components (A) and (B) and heating them at a temperature of at least 100.degree. C. to form the silicone rubber compound, adding an organic peroxide or a platinum group metal catalyst to the compound, and crosslinking the compound. The silicone rubber exhibits a minimal difference in physical properties between primary vulcanization and secondary vulcanization.

Method for the preparation of silicone rubber

The process comprises the steps of (A) mixing a base material (A-1), which is obtained by mixing an organopolysiloxane and a reinforcing silica and then heating the resulting mixture, with an aminosilane compound (A-2) represented by the formula:

Process for preparing silicone rubber composition

A silicone rubber composition comprising an organopolysiloxane and a reinforcing silica filler can be improved in crepe hardening and shelf stability by blending a specific compound as a wetter.

Silicone rubber compositions

Hydrolysis of an alkoxysiloxane of the formula: R.sup.1.sub.a (R.sup.2 O).sub.b SiO.sub.(4-a-b)/2 wherein R.sup.1 is a monovalent hydrocarbon group, R.sup.2 is an alkyl group having 1 to 4 carbon atoms, letter a=0 to 2.2, b=0.2 to 3, 2.ltoreq.a+b.ltoreq.3, and the number of silicon atoms in a molecule is 2 to 5, is effected in the presence of a cation exchange resin by adding water therereto in an amount of 1 to 10 mol per mol of the alkoxy group in the alkoxysiloxane and agitating the mixture. Low molecular weight, linear organosiloxanes having a silanol terminal group including dimer diol and trimer diol are produced in high yields.

Process for preparing low molecular weight organosiloxane terminated

The silicone rubber composition of the present invention comprises (A) an organopolysiloxane obtained by mixing and heating an organopolysiloxane having a silanol group at both ends of the molecular chain and a silane or a siloxane having two hydrolyzable groups in the molecule, (B) a finely divided silica, and (C) a curing agent. The composition, wherein the content of low-molecule siloxanes is remarkably constrained, is quite useful in the application wherein low-molecular siloxanes are obnoxious, for example, in the application of electrical contacts and parts used adjacent thereto, roll materials of copying machines, gaskets for construction, etc.

Silicone rubber composition

The present invention provides nonflammable silicone rubber compositions which exhibit a superior non-inflammability and a reduced toxicity due to by-products generated during vulcanization and forming processes.

Nonflammable silicone rubber compositions

An improvement is proposed for an acrylic rubber composition to decrease the stickiness of the rubber composition under processing and shaped and vulcanized articles of the composition to a metallic surface with which the rubber article is kept in contact at an elevated temperature under compression as is the case in packings, gaskets and O-rings as automobile parts. The improvement can be obtained by compounding the rubber composition consisting of an acrylic rubbery polymer, which can be substituted by organosilicon groups, and a reinforcing filler with a limited amount of a specific diorganopolysiloxane, e.g., dimethyl polysiloxane, of which from 5 to 50% in number of the organic groups bonded to the silicon atoms are phenyl groups.

Acrylic rubber composition

A method of producing a silicone rubber composition, comprising heating a mixture of an organopolysiloxane having a silanol group at both the ends of the molecular chain, a end blocking agent, such as a triorganosilanol, a silane or a siloxane having two dialkylaminosilyl groups in the molecule, and a reinforcing filler thereby carrying out chain lengthening and end blocking of said organopolysiloxane. According to this method, a silicone rubber composition whose low-molecular siloxane content is held down remarkably can be produced without consuming a large amount of energy for the mixing.

Method of producing silicone rubber compositions

To a silicone rubber composition including (A) a diorganopolysiloxane having an aliphatic unsaturated hydrocarbon group, (B) an organohydrogenpolysiloxane having at least two SiH groups in a molecule, and (C) a platinum catalyst, is added (D) an organic silicon compound of the following general formula (2): ##STR1## wherein R.sup.2, R.sup.5, and R.sup.6 are independently selected from monovalent hydrocarbon groups free of an aliphatic unsaturated bond, R.sup.3 is a monovalent hydrocarbon group, R.sup.4 is hydrogen or methyl, and n is an integer of 0 to 3. The composition has a long pot life after addition of curing components (B) and (C) and is extrusion moldable into bubble-free transparent parts. The composition is prepared by mixing component (A) with components (B) and (C) while adding component (D) thereto.

Silicone rubber compositions and method for making

A manufacturing method of organosilanes having silanol groups which is characterized by mixing organoalkoxy silanes, having at most a 20 ppm content of chlorine, expressed by the general chemical formula (1) below:

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Annaka, Japan

Masaharu Takahashi