High density polyethylene for pipe applications with improved pressure performance and mechanical properties

Abstract

The present invention concerns a multimodal polyethylene composition comprising a base resin comprising a copolymer of ethylene and at least one comonomer selected from alpha-olefins having from 3 to 10 carbon atoms, wherein the base resin has (a) a density of at least 945.0 kg/m3 and not more than 955.0 kg/m3, determined according to ISO 1183-1:2004, (b) a melt flow rate MFR5 (190° C., 5 kg), determined according to ISO 1133, of from 0.15 to 0.25 g/10 min., and wherein the polyethylene composition has (c) a molecular chain length, determined according to Quantitative 13C{1H} NMR analysis, of at least 850 and not more than 1200, and (d) a tensile modulus of at least 900 MPa and not more than 1200 MPa, determined according to ISO 527-3, a method for its production, a pipe or fitting comprising it and its use for increasing the pressure resistance and/or the slow crack growth resistance of a pipe or fitting. The multimodal polyethylene composition provides improved balance of pressure resistance and slow crack growth resistance with improved mechanical properties, such as tensile properties, strain hardening modulus, and impact performance.

Dependencies are inferred from the claim text.