Patent ID: 7595103

Claim:
Polypropylene pipes having at least one layer made of a propylene polymer composition having a melt flow rate value of at most 2 g/10 min, the composition comprising (parts by weight): (1) 100 parts of a crystalline random propylene-ethylene-butene-1 copolymer having an ethylene content of 2-5% by weight and a butene-1 content of 2.5-10% by weight prepared by polymerising the monomers in a single polymerisation stage or in two or more sequential polymerisation stages or by blending polymer products of two or more separate polymerisation stages; (2) 0 to 70 parts of an elastomeric polyolefin selected from the group consisting of: (a) a copolymer of ethylene with propylene and, optionally a diene, having an ethylene content of from 17 to 45 wt % and an propylene content from 55 to 83 wt %; and (b) a copolymer of ethylene with a C 3 -C 10 α-olefin having an ethylene/C 3 -C 10 α-olefin weight ratio of from 29 to 86 wt % ( 13 C-NMR analysis) and having a Mw/Mn ratio of less than 3.5; and (3) 0-30 parts of a polymer of ethylene having a melting temperature over 120° C. and intrinsic viscosity of from 2 to 6 dL/g; with the proviso that when the elastomeric polyolefin is present, the polymer of ethylene is at least 12 parts based on 100 parts off the crystalline random propylene copolymer (1) and that at least one of the layer of the polypropylene pipes, made of the propylene polymer composition, is substantially free from random copolymers of propylene with at most 15 wt % of ethylene as the sole comonomer.