The present invention relates to a process for producing a multimodal polyethylene composition in the reactor system according to the invention, 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 or a medium molecular weight polyethylene; (b) removing in the hydrogen removal unit 98.0 to 99.8% by weight of the hydrogen comprised in a slurry mixture obtained from the first reactor at a pressure in the range of 103-145 kPa (abs) and transferring the obtained residual mixture to the second reactor; (c) polymerizing ethylene and optionally C.sub.4 to C.sub.12 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 or a first ultra high molecular weight polyethylene in the form of a homopolymer or a copolymer 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 1-70% by mol, preferably 1-60% 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 or a second ultra high molecular weight polyethylene homopolymer or copolymer; and a multimodal polyethylene composition obtainable this way.

A process for the preparation of an ultra-high molecular weight ethylene homopolymer having a MFR.sub.21 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.

The present application relates to a process for producing a multimodal polyethylene composition comprising the steps of blending a polyethylene fraction (A-1) having a weight average molecular weight Mw of equal to or more than 700 kg/mol to equal to or less than 10,000 kg/mol and a density of equal to or more than 920 kg/m.sup.3 to equal to or less than 960 kg/m.sup.3 and a polyethylene fraction (A-2) having a lower Mw as polyethylene fraction (A-1) and a density of equal to or more than 910 kg/m.sup.3 to equal to or less than 960 kg/m.sup.3 with a weight ratio of (A-1) to (A-2) of 45:55 to 80:20 to form a first polyethylene resin (A) having a Mw of equal to or more than 200 kg/mol to equal to or less than 1500 kg/mol, a melt flow rate MFR.sub.5 (190° C., 5 kg) of 0.001 to 10 g/10 min and a density of equal to or more than 910 kg/m.sup.3 to equal to or less than 960 kg/m.sup.3, blending the first polyethylene resin (A) with a second polyethylene resin (B) having a Mw of equal to or more than 50 kg/mol to less than 700 kg/mol, and a density of equal to or more than 910 kg/m.sup.3 to equal to or less than 960 kg/m.sup.3 to form the multimodal polyethylene composition, wherein the multimodal polyethylene composition a melt flow rate MFR.sub.5 (190° C., 5 kg) of 0.01 to 10 g/10 min and a density of equal to or more than 910 kg/m3 to equal to or less than 970 kg/m.sup.3, a polyethylene composition obtainable by said process and the polyethylene resin of said first blending step.

The present invention relates to a multimodal polyethylene composition comprising: (A) 40 to 65 parts by weight, preferably 43 to 52 parts by weight, most preferred 44 to 50 parts by′ weight, of the low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g/mol, wherein the low molecular weight polyethylene has a MI2 of 500 to 1,000 g/10 min according to ASTM D 1238; (B) 5 to 17 parts by weight, preferably 10 to 17 parts by weight, most preferred 10 to 15 parts by weight, of the first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or the first ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol; and (C) 30 to 50 parts by weight, preferably 37 to 47 party by weight, most preferably 39 to 45 parts by weight, of the second high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g/mol or the second ultra high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g/mol, wherein the density of the first high molecular weight polyethylene or the first ultra high molecular weight polyethylene and the second high molecular weight polyethylene or the second ultra high molecular weight polyethylene is in the same range and both densities are in the range from 0.910 to 0.940 g/cm3; and the molecular weight distribution of the multimodal polyethylene composition is from 18 to 30, preferably 20 to 28, measured by gel permeation chromatography, film comprising the multimodal polyethylene composition and the use thereof.

Embodiments of a polyethylene polymer blend having a melt index (I.sub.2)<2 g/10 min are provided, wherein the polyethylene polymer blend comprises at least about 50% by wt. of at least one high density polyethylene resin (HDPE) having a density ≧0.950 g/cm3, a melt index (I.sub.2)<4 g/10 min; a melt flow ratio (I.sub.10/I.sub.2)≦9, and a molecular weight distribution (MWD) of about 2 to about 5; and further comprises about 1% to about 20% by wt. of at least one low density polyethylene resin (LDPE) having a density ≦0.930 g/cm3, a melt index (I.sub.2) of about 0.1 to about 10 g/min, and an MWD>3.

The present invention provides a polyamide resin composition (nylon composition) and a sliding member using this, which have excellent moldability and sliding properties. The polyamide resin composition contains, as additives, polyethylene resin of 5 to 20% by mass, polytetrafluoroethylene resin of 5 to 30% by mass, modified polyolefin resin of 0.5 to 5% by mass, and phosphate of 1 to 5% by mass, in addition to polyamide resin that is a main component. The sliding member is produced by molding this polyamide resin composition.

The present invention generally provides implantable articles and methods of forming implantable articles from a crosslinked ultrahigh molecular weight polyethylene (“UHMWPE”) blend stabilized with Vitamin E. The crosslinked UHMWPE blend may be prepared by combining the UHMWPE material and vitamin E prior to irradiating the UHMWPE blend with electron beam radiation at a sufficient radiation dose rate to induce crosslinking. The crosslinked UHMWPE blend may be incorporated into a variety of implants, and in particular, into endoprosthetic joint replacements

Embodiments of the present disclosure include composites and flexible multilayer pipe liners comprising a fibrous layer; and a polyolefin backing layer comprising a blend of: (a) an ultra-high molecular weight ethylene-based polymer having an intrinsic viscosity from 5 to 50 deciliters/gram, (b) a polyethylene resin comprising a first molecular weight ethylene-based polymer component and a second molecular weight ethylene-based polymer component, wherein the polyethylene resin has a density from 0.930 to 0.960 g/cc; (c) a thermoplastic polyolefin elastomer having a density of from 0.850 to 0.910 g/cc; and (d) optionally, a fluoropolymer.

Methods of making crosslinked polymeric materials and crosslinked interlocked hybrid polymeric materials using photoinitiator, antioxidant, additive, and photoirradiation of polymeric blend and/or interlocked hybrid materials are provided. Methods of spatially controlling macroscopic properties and morphology of polymeric materials, and products made by the methods also are provided.

High density polyethylene blend, comprising (A) 55 to 99 wt % of a high density multimodal polyethylene component having a density of at least 930 kg/m3, and (B) 1 to 45 wt % of an ultra-high molecular weight polyethylene homo- or copolymer component having (i) an intrinsic viscosity of at least 15.0 dl/g (ii) an a nominal viscosity molecular weight (Mv) of at least 2.0*10.sup.6 g/mol and (iii) a molecular weight of (M.sub.w) of at least 0.7*10.sup.6 g/mol, and wherein said blend has an MFR.sub.21 of 0.05 to 10.0 g/10 min and a density of at least 925 kg/m.sup.3.