Patent ID: 7427649

Claim:
A polyethylene composition with trimodal molecular mass distribution, which comprises: a density in the range from 0.955 to 0.960 g/cm 3 at 23° C.; an MFI 190/5 in the range from 0.8 to 1.6 dg/min; from 45 to 55% by weight of a low-molecular-mass ethylene homopolymer A having a viscosity VN A in the range from 70 to 90 cm 3 /g; from 20 to 35% by weight of a high-molecular-mass copolymer B made from ethylene and a 1-olefin comonomer having from 4 to 8 carbon atoms, wherein a mixture of homopolymer A and copolymer B has a viscosity number VN 2 in the range from 150 to 200 cm 3 /g; and from 20 to 30% by weight of an ultrahigh-molecular-mass ethylene copolymer C containing a 1-olefin comonomer having from 4 to 8 carbon atoms, wherein a mixture of homopolymer A, copolymer B, and copolymer C has a viscosity number VN 3 in the range from 260 to 340 cm 3 /g, and wherein all of the percentage data are based on the total weight of the composition.