Polyethylene composition for pipe applications with improved sagging and extrusion properties

Abstract

The present invention relates to a polyethylene composition comprising, a base resin (A) comprising a copolymer of ethylene and at least one comonomer selected from alpha-olefins having from three to twelve carbon atoms, wherein the ethylene copolymer comprises a low molecular weight component (A-1) and a high molecular weight component (A-2) with the low molecular weight component (A-1) having a lower weight average molecular weight than the high molecular weight component (A-2), (B) carbon black in an amount of 1.0 to 10 wt % based on the total amount of the polyethylene composition, and (C) optional further additives other than carbon black; wherein the low molecular weight component (A-1) has a melt flow rate MFR(190° C., 2.16 kg) of equal to or more than 150 g/10 min to equal to or less than 400 g/10 min, determined according to ISO 1133, the base resin (A) has a density of equal to or more than 943 kg/mto equal to or less than 957 kg/m, determined according to ISO 1183, and the composition has a melt flow rate MFR(190° C., 5 kg) of equal to or more than 0.14 g/10 min to equal to or less than 0.30 g/10 min, determined according to ISO 1133, a viscosity at a constant shear stress of 747 Pa, eta, of equal to or more than 800 kPa*s to equal to or less than 1300 kPa*s, and complies with the in-equation (I) eta>−1800×MFR+1200 (I), a process for producing said polyethylene composition and an article comprising said polyethylene composition.