Abstract: Process for preventing build-up in the reactors used in the free radical polymerization of ethylenically unsaturated monomers, and more particularly of vinyl chloride, in which the reactor walls are subjected to heat treatment before the reactors are charged in preparation for the polymerization process.

Abstract: The constituents of an exhausted toluene-dimethylformamide solvent mixture used for removing polyvinyl chloride deposits from polymerization reactors, are separated by adding water to said mixture and distilling off toluene, thereby to obtain a distillation residue having a water content of at least 2 wt.% and a toluene content not exceeding 10 wt.%, precipitating the polymer by cooling the distillation residue, adding a further amount of water, distilling off any toluene present, recovering the precipitate and distilling the residual aqueous solution to recover the dimethylformamide.

Abstract: In the aqueous polymerization of vinyl chloride and vinylidene chloride polymers and copolymers in reactors having exposed metal surfaces, undesirable thin polymer build up is noted on the metal surface exposed to the polymerization media. Such polymer build up is substantially reduced if before the polymerization the reactor is first mechanically cleaned to remove visible polymer deposits and then cleaned of organic materials adsorbed on the metal surfaces; and thereafter between polymerization charges as required, by treatment with a hot-alkali detergent mixture to remove organic residues from the surface of said metal surfaces.

Abstract: An improvement in a process for the copolymerization of ethylene and an .alpha.-olefin having 3 to 18 carbon atoms and optionally also a nonconjugated diene having only one readily polymerizable double bond in the presence of a catalyst and a liquid organic medium to an elastomeric copolymer insoluble in the liquid polymerization medium, having a portion of said medium occluded therein, and tending to agglomerate on solid surfaces, wherein simultaneously and continuouslyA. the agglomerated copolymer adhering to the interior surfaces of the polymerization vessel is removed with a wall scraper which is being cleaned by a cleaning member associated therewith;B. the agglomerated copolymer is collected; andC. the collected agglomerated copolymer is concurrently sheared and extruded, whereby the occluded liquid polymerization medium is separated from the copolymer and remains in the polymerization vessel, while the copolymer is discharged from said vessel.