Process for separation of the solvents from polyethylene formed in highpressure polymerization of ethylene in the presence of solvents and from low-pressure circulating gas

Claim 1

A TWO STAGE PROCESS FOR REMOVING SOLVENT FROM POLYETHYLENE FORMED IN THE CONTINUOUS HIGH-PRESSURE POLYMERIZATION OF ETHYLENE AT A TEMPERATURE OF BETWEEN 150 AND 400*C. AND PRESSURES OF BETWEEN 500 AND 4000 ATMOSPHERES WHICH COMPRISES: PASSING THE REACTION MIXTURE FROM THE REACTION VESSEL TO A HIGH-PRESSURE SEPARATOR HELD AT A PRESSURE OF MORE THAN 150 ATMOSPHERES, SAID REACTION MIXTURE CONTAINING POLYETHYLENE, ETHYLENE, AND SOLVENT MAINTAINING A PREDETERMINED LEVEL OF POLYETHYLENE IN SAID HIGH-PRESSURE SEPARATOR, REMOVING THE BULK OF THE ETHYLENE AND SOLVENT FROM THE REACTION MIXTURE IN SAID HIGHPRESSSURE SEPARATOR AND PASSING SAID ETHYLENE AND SAID SOLVENT INTO A HIGH-PRESSURE GAS CYCLE HELD AT A PRESSURE GREATER THAN 100 ATMOSPHERES; EXPANDING SAID POLYETHYLENE FROM SAID HIGH-PRESSURE SEPARATOR INTO A LOW-PRESSURE SEPARATOR, REMOVING ETHYLENE ENTRAINED BY THE POLYETHYLENE IN DISSOLVED FORM FROM THE POLYETHYLENE TOGETHER WITH SOLVENT AND PASSING SAID ETHYLENE AND SAID SOLVENT INTO A LOW-PRESSURE GAS CYCLE, SAID POLYETHYLENE THEREAFTER BEING REMOVED IN PURIFIED FORM FROM SAID LOW-PRESSURE SEPARATOR, SAID ETHYLENE AND SAID SOLVENT IN SAID LOW-PRESSURE CYCLE PASSING TO A GAS COOLER AND INTO AN ATMOSPHERIC SEPARATOR; SEPARATING THE BULK OF THE SOLVENT FROM SAID ETHYLENE IN SAID ATMOSPHERIC SEPARATOR, AND COOLING THE RESIDUAL GAS CONSISTING OF ETHYLENE AND RESIDUAL SOLVENT IN A COUNTERCURRENT HEAT EXCHANGER; PASSING SAID BULK OF