Abstract: Process for producing a multimodal polyethylene in at least two loop reactors connected in series. In the process 20-80 wt % of a high molecular weight (HMW) polymer is made in suspension in a first reactor and 20-80 wt % of a low molecular weight (LMW) polymer is made in suspension in a second reactor, one polymer being made in the presence of the other in either order. The ratio of the average activity in the LMW reactor to the average activity in the HMW reactor is from 0.25 and 1.5, where average activity in each reactor is defined as the rate of polyethylene produced in the reactor (kgPE/hr)/[ethylene concentration in the reactor (mol %)×residence time in the reactor (hours)×feed rate of catalyst into the reactor (g/hr)], residence time being defined as the mass of the polymer in the reactor (kg)/the output rate of polymer from the reactor (kg/hr), and the volumes of the two reactors differ by less than 10%.

Abstract: A polyethylene composition is disclosed having an unpigmented density of at least 946 kg/m3 and a melt index MI5 of 0.05 to 2 g/10 min, and comprising from 48 to 49.5% by weight based on the total weight of the composition of an ethylene polymer fraction (A) having a density of at least 969 kg/m3, and from 50.5 to 52% by weight with based on the total weight of the composition of a copolymer fraction (B) of ethylene and 1-hexene having a melt index MI5 of 0.001 to 0.5 g/10 min and a density of no more than 930 kg/m3.

Abstract: Process for producing a multimodal polyethylene in at least two reactors connected in series, in which 20-80 wt % of a high molecular weight (HMW) polymer is made in suspension in a first reactor and 20-80 wt % of a low molecular weight (LMW) polymer is made in suspension in a second reactor in the presence of the HMW polymer, wherein the solids concentration in the second LMW reactor, defined as the mass of polymer divided by the total mass of slurry, is at least 35 wt %, most preferably between 45 wt % and 60 wt %, and/or the ratio of solids concentration in the first reactor to that in the second reactor is maintained at less than 1.0, preferably between 0.6 and 0.8, and further wherein the volume of the second reactor is at least 10%, preferably at least 30% and more preferably at least 50% greater than the volume of the first reactor.

Abstract: Polymerisation process in which polyethylene is produced in slurry in a polymerisation reactor in the presence of a Ziegler Natta catalyst and an activator, and a stream or slurry containing the polymer is withdrawn from the reactor and transferred to a flash tank operating at a pressure and temperature such that at least 50 mol % of the liquid or non-polymer component of the stream entering the flash tank or slurry is withdrawn from the flash tank as a vapour and at least 98 mol % of the vapour withdrawn from the flash tank is capable of being condensed at a temperature of between 15 and 50° C., without compression. A by-product suppressor, which reduces the amount of by-product formed per unit of polyethylene produced by at least 10%, compared with an identical polymerisation process where the by-product suppressor is not present, is used in the reactor. The molar ratio of the by-product suppressor added to the reactor to titanium added to the reactor is between 0.2 and 1.

Abstract: Process for producing a multimodal polyethylene in at least two reactors connected in series, in which 20-80 wt % of a high molecular weight (HMW) polymer is made in suspension in a first reactor and 20-80 wt % of a low molecular weight (LMW) polymer is made in suspension in a second reactor. The ratio of the average activity in the LMW reactor to the average activity in the HMW reactor is from 0.25 and 1.5, where average activity in each reactor is defined as the rate of polyethylene produced in the reactor (kgPE/hr)/[ethylene concentration in the reactor (mol %)×residence time in the reactor (hours)×feed rate of catalyst into the reactor (g/hr)], residence time being defined as the mass of the polymer in the reactor (kg)/the output rate of polymer from the reactor (kg/hr). The volume of the second reactor is at least 10% greater than the volume of the first reactor, and the ratio of length to diameter of the first reactor, L/D(1), is greater than that of the second reactor, L/D(2).

Abstract: An uncompounded polyolefin powder is disclosed, having a particle size distribution such that D95 is less than 355 ?m and (D90?D10)/D50 is less than 1,2, where D95, D90, D50 and D10 are defined such that 95 vol %, 90 vol %, 50 vol % or 10 vol % of the polymer particles have a diameter of less than D95, D90, D50 and D10 respectively, A process for making the powder is also disclosed.

Abstract: Process for transferring a slurry stream containing polymer through a transfer line from a polymerisation reactor to a downstream vessel by, prior to entry into the downstream vessel, separating the slurry stream into two flows, the first flow being recycled upstream of the flow separation and the second flow being passed into the downstream vessel. The flow separation is located more than halfway along the transfer line between the reactor and the downstream vessel.

Abstract: Uncompounded polyolefin powder which is multimodal and has a particle size distribution such that D95 is less than 355 ?m, D5 is at least 60 ?m, and (D90?D10)/D50 is less than 1.2, where D95, D90, D50 and D10 are defined such that 95 wt %, 90 wt %, 50 wt % and 10 wt % of the polymer particles have a diameter of less than D95, D90, D50 and D10 respectively.

Abstract: Continuous process for manufacturing a polyolefin resin in at least two reactors in which in a first polymerization reactor, an olefin is polymerized continuously in the presence of a catalyst and a diluent to produce a first suspension comprising the diluent and polyolefin particles. At least a portion of the first suspension is transferred from the first polymerisation reactor to a second polymerisation reactor where further polymerisation takes place. A further suspension containing diluent and polymer particles is withdrawn from the second reactor and transferred to two separators, in each of which separators a diluent-rich flow and a concentrated suspension of polyolefin particles are formed and separated. The diluent-rich flow from one separator is recycled to a reactor preceding the second reactor, and the diluent-rich flow from the other separator is recycled to the second reactor. The invention enables higher separator efficiencies to be achieved.

Abstract: A process comprising polymerising in a loop reactor of continuous tubular construction an olefin monomer optionally together with an olefin comonomer in the presence of a polymerisation catalyst in a diluent to produce a slurry comprising solid particulate olefin polymer and the diluent wherein the internal diameter of at least 50% of the total length of the reactor is at least 700 millimeters and the solids concentration in the reactor is at least 20 volume % is disclosed.

Abstract: Olefin polymerisation process in which a slurry of olefin polymer is produced within a polymerisation zone, followed by withdrawing a polymer slurry stream from the polymerisation zone, and passing the polymer slurry stream through a transfer line to a centrifugal concentrating device which separates the polymer slurry stream into a solids-lean stream or streams each having a solids concentration less than that of the polymer slurry stream entering the concentrating device and a solids-rich stream or streams each having a solids concentration greater than that of the polymer slurry stream entering the concentrating device. At least part of the solids-rich stream or streams is recycled back into the polymer slurry stream upstream of the concentrating device and downstream of the polymerisation zone, and 2-60 vol % of the solids-rich slurry stream is recycled back into the polymer slurry stream upstream of the concentrating device.

Abstract: Process comprising polymerizing in a loop reactor of a continuous tubular construction an olefin monomer optionally together with an olefin comonomer in the presence of a polymerization catalyst in a diluent to produce a slurry comprising solid particulate olefin polymer and the diluent, wherein the average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 700 mm wherein the HMW polymer is produced in a reactor upstream of the LMW polymer reactor and the ratio of the average internal diameter of the HMW reactor to the average internal diameter of the LMW reactor is between 0.8 and 1.4.

Abstract: A process comprising polymerising in a loop reactor of a continuous tubular construction an olefin monomer optionally together with an olefin comonomer in the presence of a polymerisation catalyst in a diluent to produce a slurry comprising solid particulate olefin polymer and the diluent wherein the average internal diameter of at least 50% of the total length of the reactor is at least 650 millimeters, the solids concentration in the reactor is at least 15 volume % and having a particle size distribution such that (D90?D10)/D50 is less than 2.

Abstract: A process for controlling a slurry phase (co-) polymerisation process in the presence of a polymerisation catalyst, which comprises maintaining the density SPAN of the polymer powder particles (defined as the absolute value of the density difference in g/cm3 between the average density of the polymer particles exiting the reactor with particle size above D90 and the average density of the material with particle size below D10) below 0.005, preferably below 0.003, more preferably below 0.0026, most preferably below 0.0023.

Abstract: A process for heating a polymer-containing stream being transferred from a polymerization reactor to a separation zone or device is described, comprising passing the stream through a heater comprising at least one transfer line for the stream and means for heating the transfer line, wherein the average particle size of the solid polymer is less than 3 mm, the mass flowrate of the polymer-containing stream exiting the heater is no more than 15% greater than the mass flowrate exiting the reactor, and the average velocity of the polymer-containing stream at 80% along the length of the heated part of the transfer line measured from the transfer line inlet is at least 6 m/s, preferably at least 8 m/s and more preferably at least 10 m/s and the pressure drop across the transfer line is between 0.01 bar/m and 0.2 bar/m.

Abstract: Process for heating a polymer-containing stream being transferred from a polymerization reactor to a degassing vessel operating at a pressure between 6 bara and 12 bara. The process includes passing the stream through a heater having a transfer line for the stream and a device for heating the transfer line. The pressure drop in the heater is between 5% and 50% of the total pressure drop between the polymerization reactor and the entry to the degassing vessel. The pressure drop across the length of the heater is less than 0.5 barh per tonne of polymer, and the average Reynolds number across the cross-section of the stream at any point along the length of the transfer line of the heater is greater than 500,000, such that at least 90 mol% of the hydrocarbon fluids withdrawn from the polymerization reactor operation are vaporized before entry into the degassing vessel.

Abstract: Process for heating a polymer-containing stream being transferred from a polymerization reactor to a degassing vessel operating at a pressure between 6 bara and 12 bara. The process includes passing the stream through a heater comprising a transfer line for the stream and a device for heating the transfer line. The ratio of the stream velocity at the outlet of the heater to that at the inlet, Vo/Vi, is at least 1.1, typically between 1.2 and 4, and the total specific heat transfer area of the transfer line is at least 0.5 m2 per tonne/h of production of polymer. The pressure drop across the length of the heater is less than 0.5 bar per tonne/h of polymer, such that at least 90 mol % of the hydrocarbon fluids withdrawn from the polymerization reactor operation are vaporized before entry into the degassing vessel.

Abstract: Novel copolymers are described comprising ethylene and alpha-olefins having (a) a density (D) in the range 930-960/g/m3 (b) a melt index (MI2) in the range 0.1-3.5 g/10 min (c) a melt elastic modulus G? (G?=500 Pa) in the range 40 to 150 Pa, and (d) a ratio of complex dynamic shear viscosities ?*(0.1)/?*(100) in the range 1.5 to 5.5. The novel copolymers are particularly suitable for use as Polyethylenes of Raised Temperature Resistance (PE-RT) for use in hot water piping systems. The novel copolymers may be prepared by use of meltallocene catalyst systems. Pipes having a time to failure of ?500 hrs measured according to ISO 1167 at 110° C. and 2.6 MPa prepared in a single reactor are also disclosed.

Abstract: Film formed from a polyethylene resin composition which obeys a dynamic rheological relationship at 190° C. between melt storage modulus G?, measured in Pa and at a dynamic frequency where the loss modulus G?=3000 Pa, and dynamic complex viscosity ?*100, measured in Pa·s at 100 rad/s, such that (a) G?(G?=3000)>?0.86?*100+z where z=3800, and at the same time (b) G?(G?=3000)>0.875?*100?y where y=650, and having an impact strength (DDT) of at least 250 g, measured on 15 ?m thick film (blown under conditions with BUR=5:1 and Neck Height=8×D) conditioned for 48 hours at 20°-25° C., according to ASTM D1709.

Abstract: Oxygen barrier compositions are described comprising 70-95 wt % of a polyolefin, and incorporated in said polyolefin ?0.1-10 wt % of an ethylene-vinyl alcohol polymer containing between 27 mol % and 44 mol % of ethylene units; 0.1-5 wt % of an active oxygen scavenger; 0.1-10 wt % of either a clay having an aspect ratio of at least 10, preferably at least 20, more preferably at least 50, or a nucleating agent, or a polyamide optionally containing such a clay or nucleating agent; and 0.1-5 wt % of a compatibiliser.