Process for producing polyethylene having a broad molecular weight distribution

Claim 1

In a process for polymerizing ethylene with at most 20 mole % of one or more alpha-alkenes of 3 to 10 carbon atoms, in two liquid full loop reactors comprising a first and second reactor connected in a series by one or more settling legs of the first reactor connected for discharge of slurry from the first reactor to the second reactor, said process being carried out at a temperature of 50° to 120° C. under an absolute pressure of 1 to 100 bar in the presence of a catalyst, the average molecular weight being regulated, which process comprises carrying out the polymerization such that the introduction of a co-monomer is carried out essentially in the first reactor, that the molecular weight is regulated in the first reactor to form polymers having HLMI between 0.01 and 10 g/10 min., that the residence time in the first reactor is adjusted to produce 30 to 70 wt % of the total polymer and that the molecular weight is regulated in the second reactor to form polymers such that the final polymers have a HLMI higher than 1 g/10 min., the improvement which comprises using one or more settling legs of the first reactor for the transfer to the second reactor wherein the solids content of the slurry in said settling leg is concentrated by gravity settling to a solids concentration that is at least 5 wt % higher than the solids concentration in the first reactor and then discharged from said settling leg to the second reactor.