Process for polymerising an olefin monomer in at least one continuous tubular loop reactor of a multiple reactor system, optionally together with an olefin comonomer, in the presence of a polymerisation catalyst in a diluent, to produce a slurry containing solid particulate olefin polymer and diluen
Process for polymerising an olefin monomer in at least one continuous tubular loop reactor of a multiple reactor system, optionally together with an olefin comonomer, in the presence of a polymerisation catalyst in a diluent, to produce a slurry containing solid particulate olefin polymer and diluent. The average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 700 mm. A high molecular weight (HMW) polymer is made in a first reactor and a low molecular weight (LMW) polymer is made in a second reactor, the first (HMW) reactor having a space time yield (defined as production of polymer in kg/h per unit volume of reactor) greater than 100 kg/m3/h, and the ratio of space time yield in the first (HMW) reactor to the second (LMW) reactor is greater than 1.
대표청구항▼
The invention claimed is: 1. Process which comprises polymerising an olefin monomer in at least one continuous tubular loop reactor of a multiple reactor system, optionally together with an olefin comonomer, in the presence of a polymerisation catalyst in a diluent, to produce a slurry comprising s
The invention claimed is: 1. Process which comprises polymerising an olefin monomer in at least one continuous tubular loop reactor of a multiple reactor system, 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 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, and a high molecular weight (HMW) polymer is made in a first reactor and a low molecular weight (LMW) polymer is made in a second reactor, the first (HMW) reactor having a space time yield (defined as production of polymer in kg/h per unit volume of reactor) greater than 100 kg/m3/h, and the ratio of space time yield in the first (HMW) reactor to the second (LMW) reactor being greater than 1. 2. Process according to claim 1, wherein the solids concentration in the continuous tubular loop reactor is at least 20 volume %. 3. Process according to claim 1, wherein the average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 750 mm. 4. Process according to claim 1, wherein greater than 70%, of the total length of the continuous tubular loop reactor has an internal diameter at least 700 mm. 5. Process according to claim 4, wherein greater than 70%, of the total length of the continuous tubular loop reactor has an internal diameter at least 750 mm. 6. Process according to claim 1, wherein the Froude number is maintained in at least one reactor of the multiple reactor system at or below 30. 7. Process according to claim 1, wherein the total pressure drop in the loop of the reactor is less than 1.3 bar and the polymer production rate is greater than 25 tonnes per hour. 8. Process according to claim 1, wherein at least 30 wt % of the total polymer produced in the multiple reactor system is made in said continuous tubular loop reactor. 9. Process according to claim 1, wherein 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) is below 0.005, in which D10 and D90 are the diameters under which 10% and 90% by weight respectively of the particles are collected. 10. Process according to claim 1, wherein the particle size distribution of the polymer particles is such that (D90-D10)/D50 is less than 2, in which D10, D50 and D90 are the diameters under which 10%, 50% and 90% by weight respectively of the particles are collected. 11. Process according to claim 1, wherein D95 is less than 2000 μm in which D95 is the diameter under which 95% by weight of the particles are collected. 12. Process according to claim 1, which comprises making a multimodal ethylene polymer in which a low molecular weight (LMW) polymer is made in one reactor, and a high molecular weight (HMW) polymer is made in another reactor, the polymers being made in either order and the second polymer being made in the presence of the first. 13. Process according to claim 12, wherein either: the multimodal ethylene polymer has a density greater than 940 kg/m3 and a melt flow index MI5 of 0.05 to 50 g/10 min, said ethylene polymer comprising— from 30 to 70 wt %, based on the total weight of the ethylene polymer, of a first polyethylene fraction having a density of at least 950 kg/m3 and a melt flow index MI2 of at least 10 g/10 min, and from 70 to 30 wt %, based on the total weight of the multimodal ethylene polymer, of a second polyethylene fraction comprising units of ethylene and optionally up to 5 mol % of at least one other alpha-olefin containing from 3 to 12 carbon atoms, and a melt flow index MI2 of less than 10 g/10 mm; or the multimodal ethylene polymer has a density between 900 and 930 kg/m3 and a melt flow index MI2 of 0.1 to 20 g/10 mm, said ethylene polymer comprising: from 30 to 70 wt %, based on the total weight of the ethylene polymer, of a first polyethylene fraction having a density of less than 950 kg/m3 and a melt flow index MI2 of at least 10 g/10 mm, and from 70 to 30 wt %, based on the total weight of the multimodal ethylene polymer, of a second polyethylene fraction comprising units of ethylene, from 0.1 to 20 mol % of an alpha-olefin containing from 3 to 12 carbon atoms, and a melt flow index MI2 of less than 10 g/10 mm. 14. Process according to claim 2, wherein the solids concentration in the continuous tubular loop reactor is at least 25 volume %. 15. Process according to claim 14, wherein the solids concentration in the continuous tubular loop reactor is at least 30 volume %. 16. Process according to claim 3, wherein the average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 850 mm. 17. Process according to claim 4, wherein greater than 85% of the total length of the continuous tubular loop reactor has an internal diameter at least 700 mm. 18. Process according to claim 5, wherein greater than 85% of the total length of the continuous tubular loop reactor has an internal diameter at least 850 mm. 19. Process according to claim 6, wherein the Froude number is maintained in at least one reactor of the multiple reactor system between 1 and 20. 20. Process according to claim 19, wherein the Froude number is maintained in at least one reactor of the multiple reactor system between 2 and 15. 21. Process according to claim 7, wherein the total pressure drop in the loop of the reactor is less than 1 bar, and the polymer production rate is greater than 45 tonnes per hour. 22. Process according to claim 8, wherein more than 40 wt % of the total polymer produced in the multiple reactor system is made in said continuous tubular loop reactor. 23. Process according to claim 9, wherein the density span of the polymer powder particles is below 0.003. 24. Process according to claim 23, wherein the density span of the polymer powder particles is below 0.0026. 25. Process according to claim 24, wherein the density span of the polymer powder particles is below 0.0023. 26. Process according to claim 10, wherein the particle size distribution of the polymer particles is such that (D90-D10)/D50 is less than 1.5. 27. Process according to claim 26, wherein the particle size distribution of the polymer particles is such that (D90-D10)/D50 is less than 1.2. 28. Process according to claim 11, wherein D95 is less than 1500 μm. 29. Process according to claim 28, wherein D95 is less than 1000 μm. 30. Process according to claim 29, wherein D95 is less than 355 μm. 31. Process according to claim 1, wherein the continuous tubular loop reactor whose average internal diameter along at least 50% of its total length is at least 700 mm is the second (LMW) reactor, and the first (HMW) reactor has an average internal diameter along at least 50% of its total length of less than 700 mm. 32. Process according to claim 1, wherein the ratio of the average internal diameter of the first (HMW) reactor to the average internal diameter of the second (LMW) reactor is between 0.8 and 1.4.
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