Polyolefin treatment process for uniform crosslinking

Abstract

A process produces a block of polyolefin material with uniform crosslinking, which may be uniform between and within polymer chains in the polyolefin material. Steps include: providing an oven; placing the block into the oven; preheating the block to a uniform temperature above the melting point; further heating the block to a temperature at least 30 degrees Centigrade above the melting point; cooling the block to room temperature under an inert gas; and removing oxidized material from surface of the block. Optional steps include: subjecting the block to radiation before placing the block into the oven; removing the gases from the oven on a continuous or stepwise basis; controlling the purge gas flow out of the oven; and determining a heating time period for the block by subjecting control blocks to the same process and analyzing them after various heating times.

1 . A process for producing a polyolefin polymer with uniform crosslinking, the process comprising the steps of:
 providing an oven adapted to control: purge gas flow into and out of the oven; purge gas flow circulation or vacuum conditions within the oven; heating rate; and cooling rate;   placing a block of polyolefin material into the oven, the block comprising an initial shape and a melting point and the polyolefin material comprising a microstructure of carbon-carbon bonds;   preheating the block to a temperature above the melting point and up to about 30 degrees Centigrade above the melting point until such time as the block has a uniform temperature with no significant change in the initial shape;   heating the block to a temperature at least 30 degrees Centigrade above the melting point, said temperature causing carbon-carbon bond breakage within the microstructure;   terminating heating of the block in the oven when a pre-determined crosslinking density level is reached;   cooling the block to room temperature under an inert gas to bring the material back to a solid state; and   removing any oxidized material from surface of the block.   
     
     
         2 . The process of  claim 1 , further comprising the step of removing the gases from the oven on a continuous or stepwise basis. 
     
     
         3 . The process of  claim 1 , further comprising the steps of:
 subjecting the block to radiation before placing the block into the oven; and   removing the gases from the oven on a continuous or stepwise basis.   
     
     
         4 . The process of  claim 1 , further comprising the steps of:
 subjecting the block to radiation before placing the block into the oven; and   minimizing removal of gases from the oven.   
     
     
         5 . The process of  claim 1 , further comprising the step of controlling the purge gas flow out of the oven during the preheating and heating steps to remove gases emitted from the block. 
     
     
         6 . The process of  claim 1 , further comprising the step of determining a heating time period for the block prior to the step of heating the block to a temperature at least 30 degrees Centigrade above the melting point, said temperature causing carbon-carbon bond breakage within the microstructure; wherein determining the heating time period comprises the steps of:
 placing into the oven a plurality of control blocks of the polyolefin material comprising the initial shape;   heating the plurality of control blocks to a temperature at least 30 degrees Centigrade above the melting point, said temperature causing the carbon-carbon bond breakage within the microstructure;   withdrawing from the oven a first control block from within the plurality of control blocks, said withdrawing occurring at a first heating time interval;   cooling the first control block;   analyzing the crosslinking density distribution in the first control block along an axis of diameter or thickness;   removing from the oven a second control block from within the plurality of control blocks, said removing occurring at a second heating time interval after the first heating time interval;   analyzing the crosslinking density distribution in the second control block; and   determining sufficiency of carbon-carbon bond breaking by comparing the crosslinking density distribution between the first control block and the second control block.   
     
     
         7 . The process of  claim 6 , further comprising the step of analyzing a degree of oxidation inward from the surface of the first control block and the second control block. 
     
     
         8 . A polyolefin polymer produced by the process of  claim 1 .