Dow Corning Corporation

James R Falender

John C Saam

Angelika H McHale

Jonathan Lipowitz

Andrew H Ward

Thomas C Kendrick

Sheryl A Bowman

Sarah E Lindsey

Claudia M Mettler

Hydroxyl-endblocked polydiorganosiloxane oligomer is polymerized through the use of a catalyst mixture of quaternary ammonium carboxylate and carboxylic acid. The method heats the mixture of oligomer and catalyst to a temperature in the range of from 90.degree. C. to 150.degree. C., removing water from the mixture, until the desired degree of condensation is achieved. When cooled, the product is a stable polydiorganosiloxane of increased molecular weight. The catalyst can be inactivated by heating and removing volatile byproducts. One embodiment of the method adds an acidic or neutral reinforcing filler to the mixture before polymerization to yield a storage stable silicone polymer-filler mixture which is useful in a manner similar to conventionally produced silicone polymer-filler mixtures.

Method of polymerizing hydroxyl endblocked polydiorganosiloxane using

A composition containing a chelated titanium compound and an additive selected from the group consisting of (1) esters of thioalkanoic acids, (2) di-tertiary-butyl phenol containing compounds, (3) organic phosphites, and (4) mixtures of (2) and (3), retards the color change of the composition on storage. When this composition is used as the catalyst for one package, room temperature curing silicone elastomeric compositions of the type comprising a hydroxyl endblocked polydiorganosiloxane and a silane having an average of from 2.01 to 4 inclusive alkoxy radicals, the silicone elastomeric composition can be stored without substantial color formation. The improvement in reduced color change is useful in silicone elastomeric compositions which are clear or light colored.

Color stable chelated titanate compositions

A method of polymerizing an oligomer comprising a polydiorganosiloxane, polydiorganocyclosiloxane, or mixture thereof in the presence of reinforcing filler using a catalytic amount of sulfuric or sulfonic acid is described. The sulfonic acid is of the formula XSO.sub.3 H wherein X is selected from the group consisting of halogen, alkyl, aryl, alkoxy, and alkaryl radicals. The dispersion of reinforcing filler in polydiorganosiloxane is produced using less energy, with fewer manufacturing steps than current commerical processes. The silicone polymer-filler mixture produced by this method is useful as electrical insulation compounds, in greases, and in producing curable compositions useful as sealants, caulking compounds, and heat curable silicone elastomeric compositions.

Method of polymerizing polydiorganosiloxane fluid-filler mixture using

Oligomers of low molecular weight polydiorganosiloxanes, polydiorganocyclosiloxanes, or mixtures are polymerized in the presence of acidic or neutral reinforcing fillers. Trifluoromethane sulfonic acid is used as the polymerization catalyst. The method can also include endblocked polydiorganosiloxane to control the molecular weight of the silicone polymer in the silicone polymer-filler produced. The method combines the oligomer and filler, heats to from about 70.degree. to 150.degree. C., adds catalyst, adjusts temperature, and polymerizes the mixture, then inactivates with a Lewis base such as calcined magnesium oxide. The non-crepeing silicone polymer-filler mixture which is the product of the method is usable as electrical insulation grease, or as a reinforced polymer mixture useful in producing silicone elastomers. The mixture can be mixed with curing agents to produce heat curable and moisture curable elastomeric compositions.

Method of polymerizing oligomers of polydiorganosiloxane in the presence

A method of producing a silicone polymer-filler mixture in powder form has been developed. The method combines an oligomer consisting of a polydiorganosiloxane, sufficient acidic or neutral reinforcing filler to yield a powder, and a catalytic amount of a catalyst consisting of (a) sulfuric acid or a sulfonic acid of the formula XSO.sub.3 H wherein X is selected from the group consisting of halogen, alkyl, aryl, alkoxy and alkaryl radicals, (b) perfluorinated alkane sulfonic acid, and (c) a combination of quaternary ammonium carboxylate and carboxylic acid, to give a powdery mixture. The powdery mixture is polymerized, then the catalyst is inactivated while maintaining a powdery state. The method requires a minimum of energy for mixing.

Polymerization of silicone polymer-filler mixtures as powders

The impact strength of certain thermoplastic vinylic polymers is improved by polymerizing the corresponding monomers in an emulsion of a diorganosiloxane containing units of the formula HSR'SiR.sub.n O.sub.3-n/2. For example a styrene acrylonitrile copolymer containing 20 percent by weight of a dimethylsiloxane-3-mercaptopropylsiloxane copolymer having 1 mol percent mercaptosiloxane has an Izod notched impact strength of 10.8 foot pounds per inch.

Toughened mercaptosiloxane modified emulsion polymerized vinylic polymers

Improvement in impact strength of certain vinylic polymers is obtained by dissolving a mercaptosiloxane-dimethylsiloxane copolymer in a vinylic monomer and converting the monomer to a polymer by bulk or suspension polymerization in the presence of a free radical generator. For example, a copolymer of mercaptopropylmethylsiloxane and dimethylsiloxane is dissolved in styrene and the styrene is copolymerized with acrylonitrile in bulk and/or in water suspension using benzoyl peroxide as a catalyst.

Toughened mercaptosiloxane modified bulk polymerized vinylic polymers

The gas permeability of a polymeric material is altered by irreversibly mechanically stressing in at least one direction a polymeric material which is a mixture of two phases where one phase is evenly distributed throughout a second phase and one phase is present in an amount of at least 10 weight percent. The phases are polymeric materials which each have an elastic shear modulus of less than 10.sup.9 dynes per square centimeter at processing temperature, are chemically dissimilar materials and have oxygen gas permeabilities which differ by a factor of at least 10. At least one phase is a thermoplastic which is solid at ambient temperature and the mixture retains its physical state on standing at ambient temperature over extended periods of time. An example would be cold rolling a sheet of a polyblend of polyethylene and polydimethylsiloxane. Mechanically stressing film in at least one direction by cold rolling, drawing or blowing polymeric materials as defined above alters the gas permeability from unstressed film. An extruded tube of polymeric material mechanically stressed in at least one direction has altered gas permeability compared to an unstressed tube.

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Sanford, MI, United States of America

James R Falender