Patent ID: 9068028
Filing Date: 2015-06-30
Classification: C08F

Abstract:
1. A process for the preparation of a propylene polymer composition comprising from 50 to 90% by weight of a propylene polymer fraction insoluble in xylene at 25° C., and from 10 to 50% by weight of an ethylene copolymer fraction soluble in xylene at 25° C., said process being carried out in the presence of a catalyst system comprising (a) a solid catalyst component having average particle size ranging from 15 to 80 μm comprising a magnesium halide, a titanium compound having at least a Ti-halogen bond and at least two internal electron donor compounds one of which being present in an amount from 50 to 90% by mol with respect to the total amount of donors and selected from succinates and the other being selected from 1,3 diethers, (b) an aluminum alkyl and optionally (c) an external electron donor compound, the process comprising the following steps: (i) contacting the catalyst components (a), (b) and optionally (c) for a period of time ranging from 0.1 to 120 minutes, at a temperature ranging from 0 to 90° C.; (ii) pre-polymerizing with at least one olefin of formula CH (iii) polymerizing propylene in the optional presence of at least one of ethylene and/or C (iv) in a successive step, carried out in gas-phase, in the presence of the product coming from (iii), polymerizing mixtures of ethylene with α-olefins CH wherein the propylene polymer composition has a ratio between the intrinsic viscosities of the propylene (co)polymer and that of the ethylene copolymer in tetrahydronaphthalene at 135° C. of the portion soluble in xylene and of the portion insoluble in xylene at room temperature from 0.3 to 5; and wherein the propylene polymer composition has an impact strength determined according to ISO 180/1A at −20° C. from