Patent ID: 6225414
Filing Date: 2001-05-01
Classification: C08F

Abstract:
A polypropylene block copolymer comprising components A and B which is obtained by:producing an ethylene-propylene copolymer moiety as a component A having an ethylene content of 1.5 to 6.0% by weight in the absence of an inert solvent in a first step, with a Ziegler-Natta catalyst, andthen producing an ethylene-propylene copolymer moiety as the component B having an ethylene content of 7 to 17% by weight in a gas phase in a second step,wherein component A is present in the copolymer in an amount of 40 to 85% by weight and component B present in the copolymer in an amount of 15 to 60% by weight based on the total of components A and B; the intrinsic viscosity ((.eta.)B) of the component B is from 2.0 to 5.0 dl/g and the ratio ((.eta.)B/(.eta.)A) of the intrinsic viscosity ((.eta.)B) of the component B to the intrinsic viscosity ((.eta.)A) of the component A is within the range of 0.5 to 1.8, the intrinsic viscosity being measured in tetralin at 135.degree. C.; and wherein the difference (EB-EA) between the ethylene content of the component B in percent by weight (EB) and the ethylene content of the component A in percent by weight (EA) is 3 to 15% by weight.