Polypropylene Compositions

A polypropylene composition comprising:

• (A) a first polypropylene which is a metallocene-catalyzed homopolymer, or a metallocene-catalyzed random copolymer of propylene and of a co-monomer having at most 0.5% by weight of co-monomer content, relative to the total weight of the random copolymer, as determined by 13C NMR analysis;
• and
• (B) a second polypropylene which is a metallocene-catalyzed random copolymer of propylene and of a co-monomer;
• wherein the polypropylene composition has:
• a total co-monomer content of at least 1.1% by weight relative to the total weight of the polypropylene composition, as determined by 13C NMR analysis, the co-monomer being an alpha-olefin different from propylene;
• a melting temperature Tm of at least 140° C., measured by DSC;
• a crystallization temperature Tc of at least 95° C., measured by DSC;
• a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) [Mw/Mn] of at least 3.5;
• a ratio of z-average molecular weight (Mz) to weight average molecular weight (Mw) [Mz/Mw] of at least 2.2;
• and
• a co-monomer distribution ratio R(Mz)/R(Mn) of at most 0.995, wherein R(Mz) is the ratio at Mz of the IR signal measured at 2959 cm−1 on the signal at 2928 cm−1, and R(Mn) is the ratio at Mn of the IR signal measured at 2959 cm−1 on the signal at 2928 cm−1, as determined by IR-detected gel permeation chromatography.

A process for the preparation of the polypropylene composition comprising:

• (i) providing a first polypropylene which is a metallocene-catalyzed homopolymer or a metallocene-catalyzed random copolymer of propylene and of a co-monomer having at most 0.5% by weight of co-monomer content, relative to the total weight of the random copolymer, as determined by 13C NMR analysis,
• (ii) providing a second polypropylene which is a metallocene-catalyzed random copolymer of propylene and of a co-monomer,
• (iii) and obtaining a polypropylene composition comprising the first and second polypropylene, wherein steps (i) and (ii) are carried out by polymerizing propylene and, if any, the co-monomer in the presence of a metallocene catalyst;
• the polypropylene composition having:
• a total co-monomer content of at least 1.1% by weight relative to the total weight of the polypropylene composition, as determined by 13C NMR analysis, the co-monomer being an alpha-olefin different from propylene;
• a melting temperature Tm of at least 140° C., measured by DSC;
• a crystallization temperature Tc of at least 95° C., measured by DSC;
• a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) [Mw/Mn] of at least 3.5;
• a ratio of z-average molecular weight (Mz) to weight average molecular weight (Mw) [Mz/Mw] of at least 2.2;
• and
• a co-monomer distribution ratio R(Mz)/R(Mn) of at most 0.995, wherein R(Mz) is the ratio at Mz of the IR signal measured at 2959 cm−1 on the signal at 2928 cm−1, and R(Mn) is the ratio at Mn of the IR signal measured at 2959 cm−1 on the signal at 2928 cm−1, as determined by IR-detected gel permeation chromatography.