Resin compositions and heat-sealable composite biaxially-stretched films

Claim 1

A biaxially-stretched polypropylene composite film comprising a biaxially-stretched film of a crystalline polypropylene and a monoaxially-stretched or biaxially-stretched film of a resin composition bonded in laminated state to at least one surface of the crystalline polypropylene film, the resin composition comprising: from 96 to 50 percent of a propylene copolymer (a), which is a member selected from the group consisting of (a 1 ) ethylene-propylene random copolymers each of an ethylene component content of 1.5 to 10 percent, (a 2 ) ethylene-propylene-butene-1 random copolymers each of an ethylene component content of 0 to 5 percent, a butene-1 component content of 8 to 30 percent, and a propylene component content of 92 to 65 percent, and from 3 to 30 percent of a polybutene-1- (b); and from 1 to 20 percent of an ethylene-propylene-butene-1 random random copolymer (c) of a propylene component content of 0.5 to 3 percent and a butene-1-component content of 2 to 10 percent, of a density of 0.915 to 0.935 g./cm. 3 , and of a melting point of 115° to 125° C., all quantities expressed in percent being by weight, and in which the melt flow rate of said propylene copolymer (a) is about 1 to 30 g./10 min., the melt flow rate of said polybutene-1 (b) is about 5 to 50 g./10 min. and the melt flow rate of said ethylene-propylene-butene-1 copolymer (c) is about 2 to 50 g./10 min., with the proviso that at 180°-300° C. the melt flow rate of propylene copolymer (a) is equal to or less than those of polybutene-1 (b) and ethylene copolymer (c).