Dow Corning Corporation

William Herron

Phillip Joseph Griffith

Richard G Taylor

John S Currie

Brian Robert Harkness

Rosemary M Taylor

David J Wilson

Remy Bischoff

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 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 process for the ring-opening polymerisation of cyclosiloxanes, which comprises contacting a cyclosiloxane with 1-500 ppm by weight of a phosphazene base, based on the weight of cyclosiloxane, in the presence of water, preferably 0.5-10 mols per mol of phospazene base. Also claimed is a process in which the cyclosiloxane is present together with an agent which inhibits catalyst activity of the phosphazene base, e.g. carbon dioxide or water, in which the polymerisation is initiated by reducing the effect of the inhibiting agent e.g. by heating.

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Cowbridge, United Kingdom

William Herron