Continuous removal of residual hydrocarbons from polyolefins

In a process for freeing polyolefins, selected from the group consisting of polyethylene and polypropylene made by catalytic polymerization of alpha-olefins in a hydrocarbon solvent having 6-11 carbon atoms and containing about 10 to 50 weight % residual hydrocarbons, from said residual hydrocarbons by mixing the hydrocarbon-containing polyolefin with water, agitating the mixture so as to convert it into a homogeneous dispersion containing 10 to 40 weight % of the polyolefin, contacting said dispersion countercourrently with steam, removing an aqueous polyolefin dispersion free from said hydrocarbons and separating the polyolefin from the water, the improvement which comprises:

• (a) using surfactant-containing water having a surface tension of 50 to 68 dynes/cm., with respect to air, measured at 20.degree. C. with said surfactant being ethoxylated stearic acid;
• (b) subsequently introducing the homogeneous dispersion into the upper portion of a column with at least 5 sieve plates therein for contacting it with the steam, said sieve plates having a free cross-sectional area increasing continuously from the lowermost to uppermost plate by about 3% up to 90% of the plate surface area and being arranged so as to be spaced from each other as intervals increasing from the lowermost to the uppermost plate, the interval between the two uppermost plates being 10 times the interval between the two lowermost plates;
• and
• (c) removing the aqueous polyolefin dispersion free from said hydrocarbons through said column's base portion.