Patent ID: 8759448

Claim:
A high density polyethylene moulding composition having a multimodal molecular weight distribution, having a density according to ISO 1183 at 23° C. in the range of 945 to 965 kg/m 3 and an MFR 190/2 according to ISO 1133 in the range of 0.05 to 25 g/10 min, said polyethylene moulding composition comprising at least three ethylene polymer fractions having distinct molecular weights: A) 15 to 50 wt % of a low molecular weight ethylene homopolymer fraction with a weight average molecular weight Mw in the range of 15 to 40 kg/mol; B) 15 to 50 wt % of a medium molecular weight ethylene homopolymer fraction with a weight average molecular weight Mw in the range of 70 to 180 kg/mol; and C) 15 to 50 wt % of a high molecular weight ethylene copolymer fraction with a weight average molecular weight Mw in the range of 200 to 400 kg/mol; and wherein the composition has: a tensile modulus according to ISO 527-2:1993 measured on compression moulded samples of at least 800 MPa; a Charpy impact strength CIS (23° C.) according to ISO 179:2000 measured on V-notched samples produced by compression moulding of at least 30 kJ/m 2 ; and an environmental stress crack resistance ESCR measured as FNCT full notch creep test according to ISO/DIS 16770.3 at 50° C. and 6 MPa of at least 20 h.