Polypropylene composition and process for producing the same

A process for producing a polypropylene composition comprising the steps of:

• (co)polymerizing, ethylene or a mixture of ethylene and at least one other olefin to form 0.01-5 parts by weight of an olefin (co)polymer having an intrinsic viscosity as measured in tetralin at 135° C. and represented by [η]E of 15-100 dl/g (a);
• polymerizing propylene to form 100 parts of a propylene homopolymer having an intrinsic viscosity as measured in tetralin at 135° C. and represented by [η]PP of 0.2-15 dl/g, (b);
• and
• copolymerizing a mixture of ethylene and propylene to form 28-300 parts by weight of an ethylene-propylene copolymer having an intrinsic viscosity as measured in tetralin at 135° C. and represented by [η]RC of 0.2-10 dl/g, (c), and to thereby form the composition, ([η]RC/[η]PP)×(WPP/WRC), of the ratio of the intrinsic viscosity of the ethylene-proplyene copolymer (c) to that of the propylene homopolymer (b) represented by [η]RC/[η]PP and the ratio of the weight of propylene homopolymer (b) to that of the ethylene-propylene copolymer (c) represented by WPP/WRC falls within the range of 0.2-3.0, wherein the above steps are performed in the presence of a catalyst for producing polyolefin comprising a transition metal compound catalyst component containing at least a titanium compound, an organometallic compound of a metal selected from the group consisting of metals belonging to Group I, Group 2, Group 12, and Group 13, and an optional electron donor.