Heterophasic propylene copolymers

A polypropylene composition comprising:

• A) from 50 wt % to 90 wt %, based upon the total weight of the polypropylene composition, of a propylene homopolymer having a fraction insoluble in xylene at 25° C., higher than 90%;
• and a MFR L (Melt Flow Rate according to ISO 1133, condition L, at 230° C. and 2.16 kg load) from 0.5 to 200 g/10 min;
• and
• B) from 10 wt % to 50 wt %, based upon the total weight of the polypropylene composition, of a copolymer of propylene and ethylene having from 30.0 wt % to 70.0 wt %, based upon the total weight of the copolymer, of ethylene derived units;
• wherein the sum of the amount of component A) and B) being 100;
• the polypropylene composition having:
• i) an intrinsic viscosity of the fraction soluble in xylene at 25° C. between 2.2 and 4.0 dl/g;
• ii) a MFR L (Melt Flow Rate according to ISO 1133, condition L, at 230° C. and 2.16 kg load) from 0.5 to 100 g/10 min;
• and
• iii) a xylene soluble fraction ranging from 10 wt % to 50 wt %, based upon the total weight of the polypropylene composition;
• and
• the polypropylene composition being obtained by a polymerization process including the steps of:
• step a) polymerizing propylene to obtain component A) in the presence of a catalyst comprising the product of a reaction between:
• a) a solid catalyst component comprising Ti, Mg, Cl, and an internal electron donor compound containing from 0.1 to 50% wt of Bi with respect to the total weight of solid catalyst component;
• b) an alkylaluminum compound and,
• c) an external electron-donor compound having the formula:
• (R1)aSi(OR2)b
• wherein R1 and R2 are independently selected among alkyl radicals with 1-8 carbon atoms, optionally containing heteroatoms, and a is 0 or 1 and a+b=4;
• and
• step b) polymerizing propylene and ethylene to obtain component B) in the presence of the polymerization product of step a).