Process for producing multimodal polyethylene in-situ blends including ultra-high molecular weight fractions

Abstract

The present application relates to a process for producing a multimodal polyethylene composition comprising the steps of polymerizing a polyethylene fraction (A-1) having a weight average molecular weight Mw of equal to or more than 500 kg/mol to equal to or less than 10,000 kg/mol and a density of equal to or more than 915 kg/mto equal to or less than 960 kg/min one reaction step and polymerizing a polyethylene fraction (A-2) having a lower weight average molecular weight Mw as polyethylene fraction (A-1) and a density of equal to or more than 910 kg/mto equal to or less than 975 kg/min a second reaction step of a sequential multistage process wherein one of said polyethylene fractions is polymerized in the presence of the other of said polyethylene fractions to form a first polyethylene resin (A) having a weight average molecular weight Mw of equal to or more than 150 kg/mol to equal to or less than 1,500 kg/mol, and a density of equal to or more than 910 kg/mto equal to or less than 975 kg/m, wherein the weight average molecular weight Mw of the first polyethylene resin (A) is lower than the weight average molecular weight Mw of the polyethylene fraction (A-1), blending the first polyethylene resin (A) with a second polyethylene resin (B) having a weight average molecular weight Mw of equal to or more than 50 kg/mol to less than 500 kg/mol, and a density of equal to or more than 910 kg/mto equal to or less than 970 kg/mto form said multimodal polyethylene composition, wherein the multimodal polyethylene composition a melt flow rate MFR(190° C., 5 kg) of 0.01 to 10 g/10 min and a density of equal to or more than 910 kg/mto equal to or less than 970 kg/ma polyethylene composition obtainable by said process and the polyethylene resin of said first polymerization step.