A continuous process for the production of ultra-high molecular weight polyethylene

A continuous process for the production of ultra-high molecular weight polyethylene with an Elongational Stress of at least 0.43 N/mm2 (determined according to DIN 53493) wherein the polymerisation of ethylene takes place in the presence of hydrogen and a Ziegler Natta catalyst comprising:

• I. the solid reaction product obtained by reaction of:
• (a) a hydrocarbon solution comprising
• (1) an organic oxygen containing magnesium compound and
• (2) an organic oxygen containing titanium compound and
• (b) a mixture comprising a metal compound having the formula MeRnX3-n wherein X is a halogenide, Me is a metal of Group III of Mendeleev's Periodic System of Chemical Elements, R is a hydrocarbon radical containing 1-10 carbon atoms and 0≦n≦3 and a silicon compound of formula RmSiCl4-m wherein 0≦m≦2 and R is a hydrocarbon radical containing 1-10 carbon atoms wherein the molar ratio of metal from (b):
• titanium from (a) is lower than 1:1,
• (c) post treatment of the obtained solid reaction product with an aluminium compound having the formula AlRnCl3-n wherein R is a hydrocarbon radical containing 1-10 carbon atoms and 0≦n≦3, and
• combining the reaction product from (I) with
• II. an organo aluminium compound having the formula AlR3 in which R is a hydrocarbon radical containing 1-10 carbon atoms and
• III. an electron donor selected from the group 1,2-dimethoxybenzene, 1,2,4-trimethoxybenzene, 1,2-diethoxybenzene, 2,3-dimethoxytoluene, 1-allyl-3,4-dimethoxybenzene, 1,2-dimethoxyethane, 1,2-dimethoxy cyclohexane, 1,2-dimethoxypropane, 1,2-dimethoxybutane and/or 2,3-dimethoxybutane,
• wherein the polymerisation takes place via a slurry process and wherein the hydrogen to ethylene ratio in the liquid phase of the slurry polymerisation is at least 0.1 mmol hydrogen/mol ethylene.