Organopolysiloxane composition

Claim 1

An organopolysiloxane composition which comprises, in admixture: (A) an organopolysiloxane composed of: (i) from 80 to 97.5% by moles of diorganosiloxane units represented by the general unit formula R 2 SiO, in which R is a substituted or unsubstituted monovalent hydrocarbon group free from aliphatic unsaturation, (ii) from 1.2 to 10% by moles of silethylene-containing units expressed by the unit formula OSiMe--CH 2 CH 2 --SiMe 2 O 0 .5, in which Me is a methyl group, (iii) from 1.2 to 10% by moles of trimethyl siloxy units expressed by the unit formula Me 3 SiO 0 .5, in which Me is a methyl group, and (iv) from 0.1 to 4.0% by moles of dimethyl vinyl siloxy units expressed by the unit formula Me 2 ViSiO 0 .5, in which Me is a methyl group and Vi is a vinyl group; (B) an organohydrogenpolysiloxane having, in a molecule, at least one siloxane unit represented by the unit formula R.sub.a H.sub.b SiO.sub.(4-a-b)/2, in which R has the same meaning as defined above, the subscript a is 0, 1 or 2 and the subscript b is 1 or 2 with the proviso that a+b=1, 2 or 3, in an amount sufficient to provide from 0.2 to 4 moles of hydrogen atoms directly bonded to the silicon atoms per mole of the vinyl groups bonded to the silicon atoms in the component (A); (C) a noble metal compound in an amount sufficient to promote the addition reaction between the silicon-bonded vinyl groups in the component (A) and the silicon-bonded hydrogen atoms in the component (B).