Organopolysiloxane compositions

Claim 1

A composition suitable for conferring release properties on substrates comprising 100 parts by weight of a curable linear diorganopolysiloxane, a cross-linking agent therefore and/or a catalyst therefore and 0.1 to 50 parts by weight of a copolymer of the average general formula A.sub.3 SiO(Me.sub.2 SiO).sub.x (MeRSiO).sub.y (MeHSiO).sub.z SiA.sub.3 where R is selected from (a) alkyl groups having at least four carbon atoms, alkaryl, aralkyl and cycloalkyl groups; (b) groups -R 1 -QR 2 where R 1 is a divalent group containing at least two carbon atoms and joined to silicon by a C-Si linkage, R 2 is a monovalent hydrocarbon group and W is either oxygen or sulphur; and (c) hydrocarbonoxy groups having at least four carbon atoms and joined to silicon by a C-Si linkage, A is selected from the groups R, lower alkyl groups, phenyl groups, alkenyl groups, alkoxy groups, hydroxy groups and hydrogen, x and z, which will not normally be the same, are O or a number not greater than 950, y is a number from 1 to 1000, x + y + z is not less than 20 and not greater than 1000, y/(x + y + z) is not less than 0.05 and the total ratio of R:Si in the composition is not less than 1:2000.