GB1013471A - Process for treating recycle streams - Google Patents

Abstract

Purified ethylenically unsaturated polymers are made by (1) polymerizing in bulk, or in a hydrocarbon solvent, one or more monomers in the presence of a Ziegler-Natta type catalyst, (2) removing the polymer slurry from the polymerization zone to a flashing zone wherein monomer and/or solvent is removed, (3) removing catalyst residues from the polymer by treatment with an alcohol and acid, (4) contacting the stream of monomer and/or dispersing medium with water to remove any alcoholic or acidic impurities, (5) contacting stream (4) with a water absorbing medium, and (6) recycling the stream from (5) to (1). In a modification (2) may be omitted and the recycle stream of monomer and/or dispersing medium is removed at step (3). The recycle stream separated from the polymer is step (2) or (3) may be split into a liquid and vapour phase which may each be treated separately as in (4) and (5), or it may be split after treatment (4) and each phase treated separately as under (5). Monomers mentioned are ethylene, propylene, butene-1, and mixtures thereof, 3-methyl-1-butene, 4-methyl-1-pentene, and styrene. The alcohol is preferably isopropyl alcohol and the acid HCl. The absorbing medium may be a bed of molecular sieves. The Specification contains flow diagrams of suitable methods for carrying out the process. Hydrogen may be present during the polymerization as a molecular weight controller. Specification 789,791, 799,392, 810,023 and 828,791 are referred to.