Abstract: In a copolymerization process of propylene, a mixture of unreacted propylene and ethylene is recovered. It is then fed to a distillation system which includes first and second distillation columns. The distillation system is operated in such a way that the temperature and pressure of the top of the second distillation column remain constant and an ethylene-propylene mixture can be recovered at a constant ethylene/propylene ratio from the top of the second distillation column. By using the thus-recovered ethylene-propylene mixture, the copolymerization reaction can be carried out under excellent control so that the ethylene-propylene copolymer can be obtained with uniform quality and properties.

Abstract: A process for purifying a solvent suitable for use in the polymerization of an olefin in the presence of a Ziegler-Natta catalyst, which comprises feeding the polymerization solvent to a stage lower than a chimney tray of a multi-stage distillation column, said chimney tray being provided at a height between the top and bottom of the column, feeding an organoaluminum compound to a stage higher than the chimney tray, drawing out a condensate from the chimney tray, heating the condensate to produce heated vapor, introducing the heated vapor to the chimney tray or to a stage higher than the chimney tray but lower than the stage to which the organoaluminum compound has been fed, and drawing the solvent in a purified state from the top.

Abstract: The method of continuously operating a counter-flow washing column which is supplied with a slurry of solid polymer particles in a diluent from a continuous polymerization zone and with washing liquid for extracting wash slurry and introducing it into a heat tube to separate the vapor of the washing liquid and the solid polymer particles.The improvement involves controlling the extraction amount of the wash slurry from the column by means of:(i) controlling the quantity of heat added to the heat tube, and further(ii) controlling the amount of liquid to be separately introduced into the heat tube,said controls (i) and (ii) being determined by monitoring the amount of the slurry in the last one of reaction cells in the continuous polymerization zone and, on the basis of the monitored amount, determining the amount of extracted slurry.

Abstract: A process is provided herein wherein a solid polymer slurry diluted with a specific diluent is continuously discharged under controlled conditions from a high pressure zone to a low pressure zone substantially maintained at atmospheric pressure and the slurry is then separated into said diluent and dried polymer, the improvement wherein the discharged amount of the solid polymer slurry is strictly controlled by varying the heat in the second zone and simultaneously adding a diluent which is gaseous under normal temperature and pressure so that by the control of these two perimeters a continuous slurry discharge can be maintained at predetermined levels.