Polyolefin pipe resin with very good sagging and slow crack growth resistance

Abstract

The invention relates to a polyethylene (PE) composition comprising a base resin which comprises (A) a first ethylene homo- or copolymer fraction, wherein fraction (A) has melt flow rate, MFR2, from 100 to 600 g/10 min; and (B) a second ethylene-1-hexene copolymer fraction, wherein fraction (A) has a lower molecular weight than fraction (B) and wherein fraction (B) is present in an amount of from 50.0 to 58.0 wt. % based on the total weight of the base resin; wherein the base resin has a content of units derived from 1-hexene from 0.44 to 0.79 mol % based on the total amount of base resin; wherein the base resin has a molecular weight distribution, being the ratio of Mw/Mn, from 32 to 40 and the base resin has a Z average molecular weight, Mz, of more than 1,500 kg/mol; wherein the polyethylene composition has a melt flow rate MFR5 from 0.10 to 0.25 g/10 min; and a melt flow rate ratio, FRR21/5, from 30 to 42; and wherein the polyethylene composition has a critical temperature, Tc, in the rapid crack propagation test of −10° C. or lower and not less than −25° C. The invention also relates to a PE composition obtainable by a multistage process, an article comprising a PE composition, a pipe and use of a PE composition comprising a base resin for producing an article.

Dependencies are inferred from the claim text.