Heterophasic polypropylene with improved balance between stiffness and transparency

摘要

The present invention relates to a heterophasic polypropylene composition with rather high melt flow rate, high stiffness, acceptable impact properties and an advantageous balance between stiffness and transparency. Still further, the present invention is also directed to a process for producing the inventive polypropylene composition, to an article made of the inventive polypropylene composition and to the use of the inventive polypropylene composition for the production of films and molded articles, such as thin-walled plastic containers for packaging. The inventive heterophasic polypropylene composition comprises at least a propylene homopolymer fraction, a propylene random copolymer fraction, two different ethylene-propylene rubber fractions and an ethylene homo- or copolymer fraction.

主权项

1. A heterophasic polypropylene composition comprising
(A) 40-70 wt % of a propylene homopolymer fraction, (B) 10-50 wt % of a propylene random copolymer fraction, (C) 1-20 wt % of a first elastomeric ethylene-propylene copolymer fraction, (D) 1-20 wt % of a second elastomeric ethylene-propylene copolymer fraction, and (E) 5-25 wt % of an ethylene homo- or copolymer fraction having a density between 905 and 925 kg/m3, wherein
the ratio of intrinsic viscosity of fraction (A) to the intrinsic viscosity of combined fractions (A) and (B) is smaller than 0.9,the comonomer content of the propylene random copolymer fraction (B) is up to 5 wt %,the first elastomeric ethylene-propylene copolymer fraction (C) has a different ethylene content than the second elastomeric ethylene-propylene copolymer fraction (D), andthe MFR2 of the heterophasic polypropylene composition is at least 20 g/10 min, the values of MFR2 being measured according to ISO 1133 (230° C., 2.16 kg load).