Method of improving the oxidative thermal stability of ethylene polymers

A method of improving the taste and odor properties and the oxidative thermal stability of a first thermoplastic ethylene polymer, comprising removing residual unreacted monomer or monomers, solvent and thermally unstable species from said ethylene polymer, thereby forming a second more oxidatively thermally stable ethylene polymer having an oxidative exotherm of not more than about 50 percent of the oxidative exotherm of the first polymer, as measured by differential scanning calorimetry, the method comprising:

• (a) feeding the thermoplastic ethylene polymer into a devolatilization extrusion system having at least two vacuum zones and at least one barrel, the at least one barrel having
• i. a first vacuum zone,
• ii. at least one stripping agent injection port,
• iii. at least one confined mixing zone, and
• iv. a second vacuum zone,
• wherein the at least one confined mixing zone is situated immediately downstream of the at least one stripping agent injection port the second vacuum zone is situated downstream of the first vacuum zone, and the first vacuum zone is designed to operate partially-filled with polymer;
• (b) conveying the polymer through the extrusion system;
• (c) applying vacuum to the first vacuum zone:
• (d) concurrently injecting at least about 0.1 percent by weight based on total thermoplastic ethylene polymer feed of at least one inert stripping agent to at least one stripping agent port;
• (e) mixing the polymer and the inert stripping agent in the at least one confined mixing zone:
• (f) applying vacuum to the second vacuum zone;
• and
• (g) recovering the extruded ethylene polymer.