Film-forming organopolysiloxane composition

Claim 1

A film-forming organopolysiloxane composition comprising an organic solvent dispersion of (a) 50 to 90 weight percent of a block organopolysiloxane copolymer composed of (i) 10 to 80 weight percent of an organopolysiloxane resin composed of R x SiO( 4 -x)/2 units, wherein R is a monovalent hydrocarbon group and x has an average value of 1.0 to 1.3, (ii) 2 to 30 weight percent of end-blocking siloxane unit composed of R 1 y R 2 SiO (3-y)/2 units, wherein R 1 is a silicon-bonded hydrolyzable group, R 2 is a monovalent hydrocarbon group and y has an average value of 1.8 to 2.0, and (iii) 10 to 80 weight percent of a straight-chain organopolysiloxane composed of R32SiO units, wherein R 3 is a monovalent hydrocarbon group, at least 80 mole percent of said R 3 group being methyl; (b) 2 to 50 weight percent of a compound selected from the group consisting of an organosilane having the general formula wherein R 4 , R 5 , R 6 and R 7 are monovalent hydrocarbon groups, a is zero, 1, 2, 3 or 4, b is zero, 1, 2, 3 or 4, a + b is 3 or 4, c is zero or 1 and a + b + c + d is 4, and a partial hydrolyzate of said organosilane; (c) 4 to 40 weight percent of a component selected from the group consisting of a mixture of an epoxy group-containing organoalkoxysilane and an alkenyl group-containing organoacetoxysilane in a weight ratio of 1:9 to 9:1 and a condensation-reaction product of said mixture; (d) 0.1 to 10 weight percent of a diorganopolysiloxane which is terminated with a group selected from the group consisting of an hydroxyl group and an alkoxy group; and (e) 0.1 to 10 weight percent of a condensation-reaction catalyst.