POLYPROPYLENE BLOCK COPOLYMER AND THE FILM THEREOF

摘要

A polypropylene block copolymer comprising a meltkneaded block copolymer obtained, using a Ziegler-Natta catalyst, by polymerizing monomer comprising propylene to form a polymer comprising polypropylene (component A) in an amount of from 60 to 80% by weight to the total polymer amount in substantially the absence of an inert solvent in a 1st step and then polymerizing a mixture of ethylene and propylene having an ethylene content of from 20 to 50% by weight in a vapor phase to form an ethylene propylene copolymer (component B) in amount of from 20 to 40% by weight to the total polymer amount in a vapor phase in a 2nd step, said block copolymer being such that the intrinsic viscosity of the component B (¢?!B) is at least 2.0 dl/g and the ratio (¢?!B/¢?!A) of the intrinsic viscosity of the component B (¢?!B) to the intrinsic viscosity of the component A (¢?!A) is 1.8 or less.