Process for expanding polyethylene

Claim 1

A PROCESS WHICH COMPRISES SUBJECTING POLYETHYLENE HAVING NOT MORE THAN ABOUT 90% CRYSTALLINE MATERIAL AND CONTAINING (1) A SOLID RUBBER BLOWING AGENT DECOMPOSES WITH LIBERATION OF GAS AT A TEMPERATURE OF ABOUT 300* TO 700*F. AND (2) AN EFFECTIVE AMOUNT OF AN ORGANIC PEROXIDE HAVING A HALF-LINE OF MORE THAN 5 MINUTES AT 2750*F. AND LESS THAN ONE HOUR AT 375*F., WHILE OCCUPYING THE ENTIRE SPACE IN A CONFINED ZONE WHERE EXPANSION IS NOT POSSIBLE TO A TEMPERATURE AT WHICH THE POLYETHYLENE BECOMES STRUCTUALLY TRANSFORMED SO THAT AT LEAST 10% OF THE POLYETHYLENE IS INSOLUBLE WHEN MAINTAINED IN TOLUENE AT 100* C. FOR 24 HOURS AND AT WHICH THE BLOWING AGENT DECOMPOSES WITH LIBERATION OF GASEOUS MATERIALM COOLING THE CONFINED POLYETHYLENE CONTAINING THE GASEOUS MATERIAL TRAPPED THEREIN, REMOVING THE COOLED POLYETHYLENE FROM THE CONFINED ZONE AND HEATING THE COOLED POLYETHYLENE TO A TEMPERATURE AT WHICH THE ENTRAPPED GASEOUS MATERIAL CAUSES EXPANSION OF THE POLYETHYLENE.