Abstract: Polymer powder is separated from a carrier gas by separating the polymer powder from the carrier gas in a cyclone separator, drawing the thus-separated polymer powder through a bottom part of the separator into a hopper, feeding out the polymer powder by a rotary feeder from the hopper while controlling the revolution speed of the rotary feeder in accordance with the powder level in the hopper, and controlling the volume of a purge gas, which is introduced into a polymer powder guide extending between the separator and the hopper for the prevention of plugging thereof, in accordance with the revolution speed of the rotary feeder. The height of the top of the powder in the hopper is maintained at a predetermined constant level.

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.

Abstract: Stereospecific polymerization of .alpha.-olefins is carried out with use of a catalyst comprising an activated titanium component obtained by treating copulverized products of magnesium halide, an organosilicon compound having at least one alkoxyl group and a halogenated hydrocarbon with titanium halide, an organoaluminum compound and an electron donative compound.

Abstract: Method of adding water and a hydroxide of an alkali metal or alkaline earth metal to a washing solvent such as an alkylamide and/or alkylsulfoxide when washing and removing high molecular substances stuck on the interior of a production apparatus or molding machine for an aromatic vinyl-acrylonitrile copolymer. A method for regenerating and recovering the washing solvent used for the above-mentioned washing and removal by means of an evaporator and distillation tower.

Abstract: Stereospecific polymerization of .alpha.-olefins is carried out with use of a catalyst system comprising an activated titanium compound, an organoaluminum compound and an electron donative compound. The activated titanium compound is obtained by copulverizing magnesium halide, a halongenated hydrocarbon and an orthocarboxylic acid ester and then treating the copulverized product with titanium halide.

Abstract: Stereospecific polymerization of .alpha.-olefins is carried out with use of a catalyst comprising an activated titanium component obtained by treating products of copulverization of magnesium halides and aromatic orthocarboxylic acid esters with titanium halides, an organoaluminum compound and an electron donative compound. .alpha.-Olefin polymers of high stereospecificity are thus obtained with a high polymerization activity.