GB585232A - Improvement in recovery of polymerized olefines - Google Patents

Abstract

<PICT:0585232/IV/1> Polyolefines, particularly polyethylene, prepared by gas-phase polymerization under high pressure and temperature, are collected by discharging the reaction mixture directly into a vessel closed to the atmosphere when charged, permitting separation of the gas from the polymer and its expansion to a lower pressure, maintaining a temperature sufficient to keep the polymer plastic and continuously extruding the polymer under the pressure of the unreacted gas. The temperature is maintained by the heat in the unreacted gas and also if necessary by a heated jacket surrounding the vessel. Where the polymerization is carried out at temperatures over 100 DEG C., e.g. 200-300 DEG C., and at pressures over 500 atmospheres, the unreacted gas may be allowed to expand in the vessel to 7-70 atmospheres, preferably 34, and the temperature maintained at 125-300 DEG C. The recovery of solid polyethylene is described using the apparatus illustrated, in which pipe 4 connects the reaction vessel through release valve 5 with the collection vessel. A large perforated pipe 6, surrounded by shield 7 is attached to the end of pipe 4. Valve 8 controls the pressure in the vessel. An expanded end portion perforated with holes 12 at the bottom of the vessel forms an extrusion nozzle from which the polyethylene is obtained in spaghetti-like filaments, unreacted ethylene being discharged through valve 8.