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AssigneeBorealis AG
InventorsIrfan SAEED, Esa KOKKO, Mika SALO, Sanjay RASTOGI, Dario ROMANO, Sara RONCA
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A process for the preparation of an ultra-high molecular weight ethylene homopolymer having a MFR21 of 0.01 g/10 min or less, said process comprising: (I) prepolymerising at least ethylene at a temperature of 0 to 90° C. in the presence of a heterogeneous Ziegler Natta catalyst to prepare an ethylene prepolymer having an Mw of 40,000 to 600,000 g/mol; and thereafter in the presence of the prepolymer and said catalyst; (II) polymerising ethylene at a temperature of 55° C. or less, such as 20 to 55° C., to prepare said UHMW ethylene homopolymer; wherein the UHMW ethylene homopolymer comprises up to 8 wt. % of said prepolymer.
A process for the preparation of an ultra-high molecular weight ethylene homopolymer having a MFR21 of 0.01 g/10 min or less, said process comprising:
A process as claimed in any preceding claim wherein the prepolymer is an ethylene homopolymer.
A process as claimed in any preceding claim wherein the heterogeneous ZN catalyst comprises a support, such as a silica support, preferably having a particle size in the range of 5 to 30 microns.
A process as claimed in any preceding claim wherein the pre-polymerisation step (I) is carried out in the presence of hydrogen.
A process as claimed in any preceding claim wherein the pressure of the pre-polymerisation step (I) is 20 to 40 bars and/or wherein the pressure of the polymerisation step (II) is 10 to 30 bars.
A process as claimed in any preceding claim wherein the pre-polymerisation step (I) is carried out at a temperature of 20 to 80° C. and/or wherein the polymerisation step (II) is effected at a temperature of 25 to 50° C.
A process as claimed in any preceding claim wherein the prepolymer has a Mw of 100,000 to 600,000, preferably 150,000 to 550,000 g/mol.
A process as claimed in any preceding claim wherein hydrogen is removed from the product of the pre-polymerisation step (I) before the subsequent polymerisation step (II).
A process as claimed in any preceding claim wherein the partial pressure of ethylene in the polymerisation step (II) is 5 to 7 bars.
A process as claimed in any preceding claim wherein the polymerisation step (II) is carried out at 30° C. and with an ethylene pressure of 6 bar.
A process as claimed in any preceding claim wherein the polymerisation step (II) is effected in the absence of hydrogen.
A process as claimed in any preceding claim wherein the UHMWPE comprises 1.0 to 8.0 wt. % of the prepolymer.
A process as claimed in any preceding claim wherein the polymerisation step (II) is carried out in a slurry loop reactor.
An ultra-high molecular weight ethylene homopolymer having an MFR21 of 0.01 g/10 min or less having:
Dependencies are inferred from the claim text.