High performances multimodal ultra high molecular weight polyethylene

A process for producing a multimodal polyethylene composition in a reactor system comprising:

• (a) a first reactor,
• (b) a hydrogen removal unit arranged between the first reactor and a second reactor comprising at least one vessel connected with depressurization equipment;
• (c) the second reactor;
• and
• (d) a third reactor,
• the process comprising:
• (a) polymerizing ethylene in an inert hydrocarbon medium in the first reactor in the presence of a catalyst system, selected from Ziegler-Natta catalyst or metallocene, and hydrogen in an amount of 0.1-95% by mol with respect to the total gas present in the vapor phase in the first reactor to obtain a low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol or medium molecular weight polyethylene having a weight average molecular weight (Mw) of more than 90,000 to 150,000 g/mol wherein the low molecular weight polyethylene, respectively the medium molecular weight polyethylene, has a density at least 0.965 g/cm3, and the low molecular weight polyethylene has MI2 in the range from 10 to 1,000 g/10 min and the medium molecular weight polyethylene has MI2 in the range from 0.1 to 10 g/10 min;
• (b) removing in the hydrogen removal unit 98.0 to 99.8% by weight of the hydrogen in a slurry mixture obtained from the first reactor at an operation pressure in the range of 103-145 kPa (abs) and transferring the obtained residual mixture to the second reactor;
• (c) polymerizing ethylene and optionally α-olefin comonomer in the second reactor in the presence of a catalyst system, selected from Ziegler-Natta catalyst or metallocene, and in the presence of hydrogen in an amount obtained in step (b) to obtain a first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or a first ultra high molecular weight polyethylene in the form of a homopolymer or a copolymer having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol and transferring a resultant mixture to the third reactor;
• and
• (d) polymerizing ethylene, and optionally α-olefin comonomer in the third reactor in the presence of a catalyst system, selected from Ziegler-Natta catalyst or metallocene, and hydrogen, wherein the amount of hydrogen in the third reactor is in a range of 0.1-70% by mol, with respect to the total gas present in the vapor phase in the third reactor or optionally substantial absence of hydrogen to obtain a second high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or a second ultra high molecular weight polyethylene copolymer having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol.