Removal of oligomers from substantially crystalline, .alpha.-olefin polymers

A method for stripping oligomers from finely divided, substantially crystalline, .alpha.-olefin polymer particles containing oligomers at a concentration of at least 250 parts by weight per million parts by weight of the polymer, which method comprises:

• establishing a bed comprising said particles at a temperature sufficient to evaporate oligomers from said particles, but insufficient to cause said particles to become sticky to the extent they tend to substantially agglomerate and to adhere to walls and the like,
• fluidizing said bed by passing through said bed at a bed fluidizing velocity a stream of gas inert to said particles and oligomers under prevailing conditions, whereby evaporated oligomers are removed from the bed, and
• maintaining said particles at a temperature of 100.degree. to about 140.degree. C. for a period of about 1 hour to about 3 hours, sufficient for a substantial portion of said oligomers in said particles to evaporate therefrom,
• the temperature and period of time being selected according to the proportion and maximum chain length of the oligomers to be stripped from the particles.