Manufacture of particulate olefin polymers

A process for the manufacture of particulate olefin polymers consisting of the catalytic polymerization of C.sub.2 - to C.sub.8 -.alpha.-monoolefins at temperatures of from 20.degree. to 110.degree. C and olefin pressures of from 0.01 to 40 bars in an auxiliary liquid containing the monomers to be polymerized in dissolved form and the particulate polymer formed in suspended form, the reaction mixture being circulated in a loop to which the starting materials are fed and from which the particulate polymer formed is removed, wherein

• a. a side stream is branched off from said loop to remove from 0.01 to 30% of the material present in the loop at the branching point,
• b. the side stream is caused to pass through a separating zone wherein from 1 to 90% of the particulate olefin polymer suspended in the side stream is separated solely by centrifugal acceleration into a solid phase of particulate polymer and a liquid phase which is a suspension of residual polymer particles at temperatures and pressures in the same range as in the loop and
• c. the separated particulate olefin polymer is discharged through a flashing means and the liquid phase is returned to said loop.