Silicone release coating compositions
AssigneeDow Corning Corporation
InventorsStephen Cray, Robert Ekeland, Peter Hupfield, Sarah Chare, David Rich, Marc Thibaut
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Abstract
A release coating composition according to the present invention comprises an alkenyl functional polysiloxane (1), a silicon hydride functional polysiloxane (11) and a catalyst (111) comprising a platinum group metal. The alkenyl functional polysiloxane (1) is an alkenylterminated polysiloxane prepared by siloxane polycondensation and/or equilibration using a phosphazene base catalyst followed by neutralisation with an acidic neutralising agent. The level of catalyst (III) in the composition can be as low as 2-40 parts per million platinum group metal by weight.
Claims15
A release coating composition comprising an alkenyl functional polysiloxane (I), a silicon hydride functional polysiloxane (II) and a catalyst (III) comprising a platinum group metal, wherein the alkenyl functional polysiloxane (I) is an alkenyl-terminated polysiloxane prepared by siloxane polycondensation and/or equilibration using a phosphazene base catalyst and that the level of catalyst (III) in the composition is 2-40 parts per million platinum group metal by weight.
A process for the preparation of a branched alkenyl functional polysiloxane (I) capable of reacting with a silicon hydride functional polysiloxane at low levels of platinum group metal catalyst to form a release coating, wherein the process comprises reacting a compound having the empirical formula (SiO4/2)(RaRb2SiO1/2)x wherein each Ra substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 1 to 6 carbon atoms and an alkynyl group having from 1 to 6 carbon atoms, at least three Ra substituents in the branched siloxane being alkenyl or alkynyl units;
- each Rb substituent is selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms, an aryl group, an alkoxy group, an acrylate group and a methacrylate group;
- and the ratio x of (RaRb2SiO1/2) groups to (SiO4/2) units is in the range 2.5 to 4, with a cyclic polydiorganosiloxane and/or a substantially linear hydroxy terminated polydiorganosiloxane in the presence of 2 to 80 parts per million of a phosphazene base catalyst based on the weight of silicon-containing materials and neutralising the reaction mixture.
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Dependencies are inferred from the claim text.