Heterophasic polypropylene with improved balance of impact resistance / toughness, improved powder flow, lower emissions and lower shrinkage

摘要

A heterophasic polypropylene composition comprising (A) from 48 to 78% by weight of a crystalline isotactic propylene homopolymer matrix having a penta concentration as determined by means of 13C NMR spectroscopy of more than 96 mole% and a matrix flow rate (MFRM) as determined at 230 ° C and a load of 2.16 kg according to ISO 1133 within the range of 15 to 200 g / 10 min, (B) from 22 to 52% by weight of a predominantly amorphous propylene copolymer, 25 to 48% by weight of ethylene and / or an α-olefin having 4-10 carbon atoms being present in the composition as dispersed particles, and (C) from 0.0 to 5.0% by weight of a crystalline ethylene copolymer, an α-olefin with 3-10 carbon atoms being present in the composition as inclusions of the dispersed particles of (B) and (D) from 0 to 1.0% by weight of an alpha nucleating agent for the α and / or γ phase of poly isotactic propylene, said composition being further characterized by (i) a total fluidity index (MFRT) as determined at 230 ° C and a load of 2.16 kg according to ISO 1133 within the range of 2.0 to 50 g / 10 min, (ii) a xylene soluble fraction (XCS) determined at 25 ° C in accordance with ISO 16152 within the range of 22 to 52% by weight, (iii) an intrinsic viscosity of the XCS fraction such and as measured in accordance with DIN ISO 1628/1 in decalin at 135 ° C which is within the range of 2.5 to 9.0 dl / g (iv) a relative content of isolated sequences with respect to ethylene sequences in the form of blocks (I (E)) of the XCS fraction that meets the inequality (I) I (E) 78 - 1.97xC + 0.015x (C) 2 in which C is the comonomer content [% by weight] of the XCS fraction and in which the content of I (E) is defined by equation (II) ** Formula ** where I (E) is the relative content of isolated sequences with respect to eti sequences leno in the form of blocks [in%]; fPEP is the mole fraction of propylene / ethylene / propylene (PEP) sequences in the sample; fPEP is the mole fraction of propylene / ethylene / ethylene (PEE) sequences and ethylene / ethylene / propylene (EEP) sequences in the sample; fEEE is the mole fraction of ethylene / ethylene / ethylene (EEE) sequences in the sample in which all sequence concentrations are based on the statistical triad analysis of 13C NMR data.