Method for preparing clear polyorganosiloxane elastomers
AssigneeDow Corning Corporation
InventorJary D. Jensen
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Abstract
Compositions yielding optically clear silicone elastomers are obtained by preparing a homogeneous mixture comprising a liquid polydiorganosiloxane containing at least two vinyl or other ethylenically unsaturated radicals per molecule and a finely divided silica filler treated with a hexaorganodisilazane and then adding additional hexaorganodisilazane in an amount equal to at least 5 percent of filler weight. The blending is preferably carried out using a high rate of shear and volatile materials are removed by heating the composition under reduced pressure.
Claims10
A method for preparing an optically clear, curable polyorganosiloxane composition, said method comprising the steps of
- I. blending to homogeniety a first mixture comprising at least one polydiorganosiloxane which contains a least two groups, per molecule, that will react with a curing agent, from 10 to 100 percent by weight, based on the weight of said polydiorganosiloxane, of an untreated reinforcing silica filler, and as a filler treating agent, at least 15 percent by weight, based on the weight of said filler, of a hexaorganodisilazane that is miscible with said polydiorganosiloxane;
- II. subsequently blending said first mixture with an additional quantity of said hexaorganodisilazane equal to at least 5 percent of the weight of said filler to form a second mixture, where the total weight of hexaorganodisilazane used to treat said filler is at least 30 percent of the weight of said filler;
- and
- III. heating said second mixture under reduced pressure to remove volatile materials and form said polyorganosiloxane composition.
Dependencies are inferred from the claim text.