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|1. (WO2018002617) POLYETHYLENE FOR PIPES|
|Applicants:||NORNER VERDANDI AS
|Title:||POLYETHYLENE FOR PIPES|
The present invention provides a process for the preparation of a multimodal polyethylene, said multimodal polyethylene preferably having a bimodal or trimodal molecular weight distribution, comprising: (i) polymerising ethylene and optionally an α-olefin comonomer in a first polymerisation stage to produce a first ethylene polymer; and (ii) polymerising ethylene and optionally an α-olefin comonomer, in the presence of said first ethylene polymer, in a second polymerisation stage, wherein said first and second polymerisation stages are carried out in the presence of an unsupported metallocene catalyst, which is a complex of a group 4 to 10 metal having at least two ligands, wherein at least one of the ligands is persubstituted and comprises a delocalised pi system of electrons, each polymerisation stage produces at least 5 %wt of said multimodal polyethylene, and said multimodal polyethylene has a multimodal molecular weight distribution, a molecular weight of at least 50,000 g/mol and a bulk density of at least 250 g/dm3.