Patent ID: 8163226

Claim:
A process for making a pipe consisting essentially the steps of: selecting an ethylene alpha-olefin interpolymer composition, wherein said ethylene alpha-olefin interpolymer composition has a density in the range of 0.925 to 0.965 g/cc, a melt index (I 2 ) in the range of 0.05 to 5 g/10 minutes; and selecting an antioxidant system, wherein said antioxidant system consist essentially of; from 500 to 5000 ppm of 3,3′,3″,5,5′,5″-hexa-tert-butyl-α, α′, α″-(mesitylene-2,4,6-triyl)tri-p-cresol; from at least 300 to 5000 ppm of Pentaerythritol Tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), Octadecyl-3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate, or combinations thereof; from 500 to 5000 ppm of Tris(2,4-ditert-butylphenyl) phosphate; optionally one or more metal deactivators; forming said alpha-olefin interpolymer composition and said antioxidant system into a pipe; wherein said pipe has an F time in Jana Laboratories Procedure APTF-2 of at least 1000 hours, under the following conditions: pH 6.8 (±0.1); Chlorine 4.1 mg/L (±0.1); Nominal ORP 830mV; fluid temperature 110° C. (±1); air temperature 110° C. (±1); pressure 70 psig (±1); flow rate 0.1 US gallons/min (±10 percent).