Polyethylene pipe resin with improved long term hydrostatic strength

Abstract

The present invention relates to a polyethylene composition comprising a base resin which comprises (A) a first ethylene homo- or copolymer fraction, and (B) a second ethylene copolymer fraction, wherein fraction (A) has a lower molecular weight than fraction (B), fraction (A) is present in an amount of 45.0 to 55.0 wt. %, preferably 46.0 to 53.0 wt. %, more preferably 46.5 to 52.0 wt. %, based on the total weight of the base resin, fraction (B) is present in an amount of 55.0 to 45.0 wt. %, preferably 54.0 to 47.0 wt. %, more preferably 53.5 to 48.0 wt. %, based on the total weight of the base resin, the base resin has a density of 945 kg/m3 to 958 kg/m3, more preferably of 947 to 956 kg/m3, and most preferably of 948 kg/m3 to 954 kg/m3, the polyethylene composition has a melt flow rate MFR5 of 0.15 to 0.30 g/10 min, preferably of 0.20 to 0.29 g/10 min, and still more preferably of 0.22 to 0.28 g/10 min, the polyethylene composition has a flow rate ratio FRR21/5 of 25 to 35, more preferably of 28 to 34, the polyethylene composition has a molecular weight distribution MWD of 20 to 30, more preferably from 21 to 29, and the polymer composition has an average chain length of 900 carbons or higher, to a process for producing the polyethylene composition, to an article, especially a pipe comprising the polyethylene composition and to the use of the polyethylene composition for the production of an article, especially a pipe.

Dependencies are inferred from the claim text.