Dow Corning Corporation

Dow Corning Taiwan, Inc.

Phillip Joseph Griffith

William Herron

Richard G Taylor

Jary David Jensen

John S Currie

Brian Robert Harkness

Diane Marie Kosal

Rosemary M Taylor

David J Wilson

Chu Yat Ho

Lori Jean Conway

William James Schulz, Jr

Herschel Henry Reese

Peter Lamont

Thomas E Gray

Steven Fred Dopp

A continuous process for producing a silicone polymer comprises the sequential steps of (i) polymerisation of a linear silanol group containing siloxane by condensation polymerisation, or of a cyclosiloxane by ring opening polymerisation, or of a mixture of said linear and cyclosiloxanes with a phosphazene base in the presence of water and the presence or absence of a filler in an extruder, (ii) neutralising the reaction mixture in an extruder, and (iii) stripping the neutralised reaction mixture to remove volatile materials. Preferably, step (iii) is performed in an extruder, more preferably steps (i), (ii) and (iii) are all performed in the same extruder.

Continuous process for producing a silicone polymer

A continuous process for producing a silicone polymer comprises the sequential steps of (i) polymerisation of a linear silanol group containing siloxane by condensation polymerisation, or of a cyclosiloxane by ring opening polymerisation, or of a mixture of said linear and cyclosiloxanes with a phosphazene base in the presence of water and the presence or absence of a filler in a static mixer, (ii) neutralising the reaction mixture in a static mixer, an in-line mixer or an extruder, and (iii) stripping the neutralised reaction mixture to remove volatile materials. Preferably step (ii) is performed in a static mixer and step (iii) is performed in a thin film stripper, extruder or co-rotating processor.

A process for making a flowable powdered base suitable for use in the formulation of liquid silicone rubber compositions that can be cured to form silicone elastomers. The process comprises (A) fluidizing a reinforcing silica filler in a high-shear mixer, (B) maintaining the content of the mixer at a temperature below about 60.degree. C. while adding to the mixer a silylating agent, a nitrogen containing compound to facilitate the silylation reaction, and water thereby forming an essentially homogeneous mixture comprising a treated reinforcing silica filler; (C) adding a polydiorganosiloxane having a viscosity of about 0.03 to 300 Pa.s at 25.degree. C. to the mixer and forming a flowable powdered base having an average particle size of from about 1 to 1000 microns, and (D) heating the flowable powdered base under conditions sufficient to remove volatiles.

Process for making powdered base for formulating curable liquid silicone

A process for producing a silicone polymer having a volatile material content of less than 1% by weight, preferably less than 0.1% by weight, comprises the sequential steps of (i) producing an unstripped silicone polymer by polymerisation of a linear silanol group containing siloxane by condensation polymerisation, or of a cyclosiloxane by ring-opening polymerisation, or of a mixture of said linear and cyclosiloxanes, with a phosphazene base in the presence of water and the presence or absence of a filler, (ii) neutralising the catalyst, and (iii) stripping the unstripped silicone polymer, preferably at temperatures of 200.degree. C. and above.

Process for producing a silicone polymer

A method for the preparation of hydrophobic fumed silicas which are useful, for example, as reinforcing fillers in rubber compositions. The method comprises two steps, where in the first step an aqueous suspension of fumed silica is contacted with an organosilicon compound in the presence of a catalytic amount of an acid to effect hydrophobing of the fumed silica. In the preferred method the first step is conducted in the presence of a water miscible organic solvent which facilitates hydrophobing of the fumed silica with the organosilicon compound and the fumed silica has a BET surface area greater than 50 m.sup.2 /g. In the second step the aqueous suspension of the fumed silica is contacted with a water-immiscible organic solvent at a solvent to silica weight ratio greater than 0.1:1 to effect separation of the hydrophobic fumed silica from the aqueous phase. In a preferred process the hydrophobic fumed silica has a surface area within a range of about 100 m.sup.2 /g to 750 m.sup.2 /g.

Method for preparing hydrophobic fumed silica

A method for the preparation of hydrophobic precipitated silicas which are useful, for example, as reinforcing fillers in rubber compositions. The method comprises two steps, where in the first step an aqueous suspension of precipitated silica is contacted with an organosilicon compound in the presence of a catalytic amount of an acid to effect hydrophobing of the precipitated silica. In the second step the aqueous suspension of the hydrophobic precipitated silica is contacted with a water-immiscible organic solvent at a solvent to silica weight ratio greater than 5:1 to effect separation of the hydrophobic precipitated silica from the aqueous phase.

Method of preparing hydrophobic precipitated silica

A platinum curing organosiloxane composition having improved hysteresis characteristics when cured. The composition requires the presence of a diorganovinylsiloxy terminated polydiorganosiloxane having a viscosity within a range of about 20 Pa.multidot.s to 200 Pa.multidot.s at 25.degree. C. and containing essentially no ethylenically unsaturated hydrocarbon radicals bonded to non-terminal silicon atoms and a diorganovinylsiloxy terminated polydiorganosiloxane having a viscosity within a range of about 0.1 Pa.multidot.s to 200 Pa.multidot.s at 25.degree. C., where from 1 to 5 percent of the non-terminal repeating units of the siloxane comprise a vinyl radical. In addition, the present composition comprises 10 to 30 weight percent of a reinforcing silica filler that has been treated with hexamethyldisilazane and 1,1,3,3-tetramethyl-1,3-divinyldisilazane, and an organohydrogensiloxane resin crosslinker comprising greater than 5 silicon-bonded hydrogen atoms per molecule.

Organohydrogensiloxane resin crosslinker curable organosiloxane

A platinum group-metal curing liquid silicone rubber compositions having improved physical properties such as tear and heat-aging, especially at durometers below about 35 and above about 65. The present inventors have unexpectedly discovered that the addition of diorganohydrogensiloxy end-blocked polydiorganosiloxanes and triorganosiloxy end-blocked polydiorganosiloxanes having a viscosity greater than about 10 Pa.cndot.s at 25.degree. C. to liquid silicone rubber compositions can provide for the described improved properties.

Use of high molecular weight organopolysiloxanes to improve physical

A method for preparing organopolysiloxane bases with high levels of fillers. The present inventors have found that by mixing the components of the base at a temperature below about 60.degree. C. for a period of time sufficient to effect essentially a homogeneous blend, a base composition is formed which can be further blended with a platinum group metal-containing catalyst, an organohydrogensiloxane, and optionally an inhibitor to form a curable liquid silicone rubber (LSR) composition. The curable LSR composition has improved flow characteristics and improved shelf life when compared to similar materials where the base is prepared at temperatures above about 60.degree. C. The improved flow characteristics allows larger quantities of fillers to be incorporated into the curable LSR composition while still maintaining acceptable flow characteristics. Silicone elastomers prepared using the curable LSR compositions can have improved swell and degradation resistance to oils, lower compression set values, and improved tear, elongation, and tensile values and require no post cure. The present organopolysiloxane bases are particularly useful as a common base for forming a group of cured silicone elastomers with a range of durometers.

Method for preparing organopolysiloxane bases and compositions therefrom

A platinum curing organosiloxane composition having improved hysteresis characteristics when cured. The composition requires the presence of a diorganovinylsiloxy terminated polydiorganosiloxane having a viscosity within a range of about 20 Pa.multidot.s to 200 Pa.multidot.s at 25.degree. C. and containing essentially no ethylenically unsaturated hydrocarbon radicals bonded to non-terminal silicon atoms and a diorganovinylsiloxy terminated polydiorganosiloxane having a viscosity within a range of about 0.1 Pa.multidot.s to 200 Pa.multidot.s at 25.degree. C., where from 1 to 5 percent of the non-terminal repeating units of the siloxane comprise a vinyl radical. In addition, the present composition comprises 10 to 30 weight percent of a reinforcing silica filler that has been treated with hexamethyldisilazane and 1,1,3,3-tetramethyl-1,3-divinyldisilazane, and an organohydrogen siloxane crosslinker comprising at least ten silicon-bonded hydrogen atoms per molecule.

Growing community of inventors

Llandough, United Kingdom

Phillip Joseph Griffith