Patent ID: 6117946
Filing Date: 2000-09-12
Classification: C08F

Abstract:
A propylene block copolymer consisting of a xylene soluble portion at 20.degree. C. (CXS portion) in an amount of 5 wt % or more and a portion excluding the CXS portion (CXIS portion), wherein:the propylene block copolymer consists essentially of 40 to 85 wt % of a propylene-butene-1, or ethylene-propylene-butene-1 copolymer portion having an ethylene content of 3 wt % or less and a butene-1 content of 6 to 20 wt % produced by copolymerizing propylene, butene-1 and ethylene, or propylene and butene-1 substantially in the absence of an inert solvent in the presence of a Zieglar Natta catalyst in the first step as a component A, and 15 to 60 wt % of a propylene-butene-1, or ethylene-propylene-butene-1 copolymer portion having an ethylene content of 17 wt % or less and a butene-1 content of 3 to 16 wt % produced by subsequently copolymerizing propylene, butene-1 and ethylene, or propylene and butene-1 in the presence of the polymer containing the catalyst, produced in the first step in vapor phase in the second step as a component B, wherein the intrinsic viscosity ({.eta.}B) of the component B is in the range of 1.5 to 5 dl/g, and the ratio of the intrinsic viscosity ({.eta.}A) of the component A ({.eta.}B/{.eta.}A) is 0.5 to 1.8;the melting temperature of the CXIS portion is 130 to 155.degree. C.; andthe difference in transparency in terms of haze between prior to and posterior to the 1-hour treatment at 110.degree. C. of a 150-.mu.m thick film of the propylene block copolymer formed by extrusion is 8% or less, and wherein the propylene block copolymer satisfies the following equations:3.ltoreq.CBE-CAE.ltoreq.15, andCAB-5.ltoreq.CBB.ltoreq.CAB+10,wherein CBE (wt %) and CBB (wt %) represent an ethylene content and a butene-1 content of the component B, respectively, and CAE (wt %) and CAB (wt %) represent an ethylene content and a butene-1 content of the component A, respectively.