Patent ID: 7709585

Claim:
In a process for the solution polymerization of ethylene wherein a single phase solution containing at least ethylene and catalyst dissolved in a solvent is employed to form polyethylene dissolved in said single phase solution, said ethylene polymerization being terminated with at least one deactivator that leaves a decomposition residue, said single phase solution being subjected to a series of process steps to produce an ethylene rich stream containing ethane, hydrogen, CO 2 , C4 and heavier hydrocarbons, and de-activator residue, said ethylene rich stream being suitable for recycling as feed to said ethylene polymerization process, the improvement comprising removing an ethane purge stream downstream of said series of steps from said ethylene rich stream, wherein no purge stream is removed during the series of steps containing ethylene, ethane, hydrogen, CO 2 , C4 and heavier hydrocarbons, and deactivator residue, said ethane purge stream being removed in an amount sufficient to maintain the quantity of ethane in said polymerization process below the level at which polyethylene separates from said single phase solution upstream of said series of steps, cooling said removed ethane purge stream to essentially liquefy it, subjecting said liquefied ethane purge stream to distillation in a high efficiency distillation column that contains the equivalent of at least about 45 trays and produces an overhead stream and a bottoms stream, removing from said high efficiency distillation column a side cut stream that contains a major amount of ethylene, a minor amount of ethane, and essentially no hydrogen, CO 2 , C4 and heavier hydrocarbons, and deactivator residue, recycling said side cut stream as ethylene feed to said polymerization process, and removing said overhead and bottoms streams from said polymerization process, whereby the quantity of said removed overhead and bottoms streams combined is substantially less than if an ethane purge stream was removed from said process during said series of steps in an amount sufficient to maintain the quantity of ethane in said polymerization process below the level at which polyethylene will separate from said single phase solution.