Molding process using curable silicone release compositions

Claim 1

In a process for forming molded articles, said process comprising placing a molding composition in a mold, converting the molding composition to a solid molded article and thereafter separating the solid molded article from the mold, the improvement comprising applying to at least one shape-determining surface of the mold, and thereafter curing, before the molding composition is placed in contact therewith, a curable silicone release composition obtained by mixing components consisting essentially of (I) a polydiorganosiloxane having the general formula ViR.sub.2 SiO(R.sub.2 SiO).sub.x (RViSiO).sub.y SiR.sub.2 Vi wherein x and y are integers whose sum has an average value sufficient to provide the polydiorganosiloxane with a viscosity at 25° C. of at least 1.0 pascal-seconds, Vi denotes a vinyl radical and each R denotes, independently, a monovalent radical selected from the group consisting of methyl, phenyl and saturated hydrogen radicals having from 2 to 6 carbon atoms, the total number of organic radicals in the polydiorganosiloxane consisting of at least 95 percent methyl radicals and no more than 1 percent vinyl radicals, (II) a xylene-soluble copolymer of (CH 3 ) 3 SiO 1/2 , (CH 3 ) 2 (CH 2 ═CH)SiO 1/2 and SiO 4/2 siloxane units, said copolymer having from 1 to 5 percent by weight of vinyl radicals, based on the weight of the copolymer, and a total of from 0.6 to 1.1 of said (CH 3 ) 3 SiO 1/2 plus (CH 3 ) 2 (CH 2 ═CH)SiO 1/2 siloxane units for every said SiO 4/2 siloxane unit, (III) a methylhydrogenpolysiloxane, soluble in the mixture of (I) plus (II), and having an average of at least three silicon-bonded hydrogen radicals per molecule, said hydrogen radicals being bonded to separate silicon atoms, and (IV) a catalytic amount of a hydrosilylation catalyst, said components being mixed in sufficient amounts to provide, in the curable silicone release composition, from 10 to 70 parts by weight of (II) for every 100 parts by weight of (I) plus (II) and from 2 to 10 silicon-bonded hydrogen radicals for every silicon-bonded vinyl radical.