Stabilization of polyethylene during shut-down of molding apparatus

Claim 1

IN A PROCESS WHEREIN A SOLID POLYETHYLENE PRODUCTION COMPOSITION SUBATANIALLY DEVOID OF AN OXIDATIONINHIBITOR IS FED TO A FORMING ZONE AND IS SUBJECTING THEREIN TO A COMBINATION OF OPERATING CONDITIONS INCLUDING AN ELEVATED TEMPERATURE AND PRESSURE TO FORM POLYETHYLENE ARTICLES OF DESIRED FORM WITHOUT SUBATANTIAL CONTAMINATION OD SAID ARTICLE BY RESINIFED PARTICLES OF POLYETHYLENE, AND RESUMPTION OF SAID PROCESS FOLLOWING A SHUT-DOWN RESULTS IN OBJECTIONABLE CONTAMINATION OF THE POLYETHYLENE ARTICLES BY RESINIFIED PARTICLES OF POLYETHYLENE FORMED IN SAID FORMING ZONE DURING SAID SHUT-DOWN WHICH INCLUDES A PERIOD OF TEMPERATURE REDUCTION IN THE FORMING ZONE TO SUBSTANIALLY BELOW OPERATING TEMPERATURE WITH SUBSEQUENT INCREASE OF THE FORMING ZONE TO SUBSTANTIALLY OPERATING, TEMPERATURE, THE IMPROVEMENT WHICH COMPRISES, PRIOR TO SUBSTANTIAL REDUCTION OF SAID FORMING ZONE DURING SAID SHUT-DOWN TO A TEMPERATURE SUBSTANTIALLY BELOW OPERATING TEMPERATURE, REPLACING SAID PRODUCTION FEED TO SAID ZONE WITH A SOLID POLYETHYLENE REPLACEMENT COMPOSITION CONTAINING A PHENOLIC OXIDATION INHIBITOR IN AN AMOUNT OF UP TO ABOUT 2% BY WEIGHT OF THE POLYETHYLENE IN THE REPLACEMENT FEED, SUFFICIENT TO INHIBIT RESINIFICATION OF RESIDUAL POLYETHYLENE IN SAID FORMING ZONE DURING SAID SHUT-DOWN.