| 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 C<SUB>3</SUB>-C<SUB>8 </SUB>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 C<SUB>3</SUB>-C<SUB>8 </SUB>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 (C<SUB>2</SUB>xif) 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 (C<SUB>2</SUB>xsf) multiplied by the weight percentage of fraction soluble in xylene at room temperature (% SXF), i.e. (C<SUB>2</SUB>xif % XIF)/(C<SUB>2</SUB>xsf.% SXF), satisfies the following relation (I), wherein x is the total amount of ethylene.
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