Slurry phase polymerisation process

A process comprising polymerizing in a loop reactor 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 Froude number is in the range 2 to 15, wherein the loop reactor has an internal diameter of over 500 millimeters, wherein the solids concentration of the slurry in the loop reactor is above 20 vol % and the average particle size is between 100 and 1500 microns, and wherein the loop reactor is one of two or more reactors connected in series and being used to produce a multimodal polymer, and at least one of the following applies:

• i) hydrogen is maintained at a low (or zero) concentration of 0-0.1 vol % in the reactor(s) manufacturing the high molecular weight components and hydrogen is maintained at a high concentration of 0.5-2.4 vol % in the reactor(s) manufacturing the low molecular weight components,
• ii) there is being produced a polymer with molecular weight less than 50 kDaltons,
• iii) there is being produced a polymer with molecular weight greater than 200 kDaltons,
• iv) there is being produced a polymer with a melt index below 0.1,
• v) there is being produced a polymer with a melt index above 50.