Ethylene polymerization process

Claim 1

A PROCESS FOR PREPARATION OF POLYETHYLENE HAVING A DENSITY OF ABOVE ABOUT 0.93 WHICH COMPRISES, IN AN INITIAL POLYMERIZATION ZONE, POLYMERIZING ETHYLENE AT AN ELEVATED PRESSURE AND BELOW ABOUT 150*C. IN THE PRESENCE OF A CHAIN TRANSFER AGENT AND A POLYMERIZATION CATALYST EFFECTIVE FOR POLYMERIZING ETHYLENE AT SAID TEMPERATURE TO PRODUCE IN SAID INITIAL ZONE A SOLID-GAS PHASE COMPRISING UNREACTED ETHYLENE AND SOLID POLYETHYLENE HAVING A DENSITY SUBSTANTIALLY ABOVE 0.93, PASSING SAID GAS-SOLID PHASE FROM SAID INITIAL ZONE INTO A SECOND POLYMERIZATION ZONE MAINTAINED UNDER AGITATION, POLYMERIZING ETHYLENE IN SAID SECOND ZONE AT AN ELEVATED PRESSURE AND ABOVE 150*C. IN THE PRESENCE OF A CHAIN TRANSFER AGENT AND AN ETHYLENE POLYMERIZATION CATALYST EFFECTIVE FOR POLYMERIZING ETHYLENE IN SAID SECOND ZONE TO PRODUCE IN SAID SECOND ZONE A GASEOUS PHASE COMPRISING UNREACTED ETHYLENE AND POLYETHYLENE HAVING A LOWER DENSITY THAN THE POLYETHYLENE PRODUCED IN SAID INITIAL ZONE, AND IN WHICH GASEOUS PHASE THE SOLID POLYETHYLENE FROM SAID INITIAL ZONE DISSOLVES TO PROVIDE AS A PRODUCT OF SAID SECOND ZONE A GASEOUS PHASE COMPRISING UNREACTED ETHYLENE AND POLYETHYLENE HAVING A DENSITY OF ABOVE ABOUT 0.93, SAID CATALYST IN SAID INITIAL ZONE BEING FROM THE GROUP CONSISTING OF ORGANIC HYPONITRITES AND ORGANIC PEROXIDES ACTIVE FOR POLYMERIZING ETHYLENE AT BELOW ABOUT 150*C. AND SAID CATALYST IN SECOND ZONE BEING AN ORGANIC PEROXIDE ACTIVE FOR POLYMERIZING ETHYLENE AT ABOVE 150*C.