A PROCESS FOR THE PRODUCTION OF BIMODAL POLYETHYLENE IN THE PRESENCE OF THIS CATALYST SYSTEM

摘要

The invention relates to a process for the production of bimodal polyethylene in a two-step polymerisation process in the presence of a catalyst system comprising: (I) the solid reaction product obtained by reacting of: a) a hydrocarbon solution containing 1) an organic oxygen containing magnesium compound or a halogen containing magnesium compound and 2) an organic oxygen containing titanium compound and b) an aluminium halogenide having the formula AIRnX3-n in which R is a hydrocarbon radical containing 1 - 10 carbon atoms, X is halogen and 0 < n < 3 (II) an aluminium compound having the formula AIR3 in which R is a hydrocarbon radical containing 1 - 10 carbon atom and (III) an electron donor selected from the group of 1,2-dialkoxyalkanes and 1,2- dialkoxyalkenes wherein in the first step a low molecular weight polyethylene is produced which has a MFI190/1,2 is between 1 and 200 dg/min, and in the second step a high molecular weight ethylene copolymer is produced in which the MFI190/5 of the total product is between 0.1 and 5 dg/min, and the weight fraction of the material produced in the first step is between 40 wt% and 60 wt% of the total product.