IMPACT RESISTANT POLYOLEFIN COMPOSITIONS

摘要

A heterophasic polyolefin composition comprising (percent by weight): (A) 50-0% of a crystalline propylene polymer having a polydispersity index value from 5.2 to 10 and a content of isotactic pentads (mmmm) higher than 97.5 molar%; said polymer containing at least 95% of recurring units deriving from propylene; (B) 5-20% of a first elastomeric copolymer of ethylene with at least a C3-C8 alpha-olefin comonomer, said copolymer containing from 25 to less than 40% of ethylene, and being soluble in xylene at room temperature in an amount from higher 85 to 95 wt% the intrinsic viscosity [eta] of the xylene soluble fraction ranging from 2.5 to 4.5 dL/g; and (C) 10-45% of a second elastomeric copolymer of ethylene with at least a C3-C8 alpha-olefin comonomer, said copolymer containing from 50 up to 75% of ethylene, and being soluble in xylene at room temperature in an amount from 50 to 85 wt%, the intrinsic viscosity [eta] of the xylene soluble fraction ranging from 1.8 to 4.0 dL/g; wherein the sum of amounts of copolymer (B) and copolymer (C) ranges from 20 to 50% based on the total amount of components (A) to (C), the total amount of ethylene based on the total amount of components (A) to (C) is up to 23% by weight and the ratio between the ethylene content of the fraction insoluble in xylene at room temperature (C2xif) multiplied by the weight percentage of the fraction insoluble in xylene at room temperature (%XIF) and the ethylene content of the fraction soluble in xylene at room temperature (C2xsf) multiplied by the weight percentage of fraction soluble in xylene at room temperature (%SXF), i.e. (C2xif %XIF)/(C2xsf .%SXF), satisfies the following relation (I), wherein x is the total amount of ethylene.