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US 7,744,972 B2Granted
Stabilized polyethylene material
AssigneeDow Global Technologies LLC
InventorsThoi H. Ho, Detlef Schramm, Pak-Meng Cham, Kalyan Sehanobish
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Abstract
Stabilized polyethylene materials which offer an advantageously balanced combination of thermal, mechanical and processing properties, and which maintain their physical properties in chlorinated water environments are disclosed. The materials include an antioxidant system with components to provide extraction resistance in hot water environments and additionally provides oxidation resistance to both chlorine in the water interior of the pipe and oxygen in contact with the pipe's exterior.
Claims4
A pipe consisting essentially of:
- an ethylene alpha-olefin interpolymer, wherein said ethylene alpha-olefin interpolymer has a density in the range of 0.925 to 0.965 g/cc, a melt index (I2) in the range of 0.05 to 5 g/10 minutes;
- and
- 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;
- optionally one or more metal deactivators;
- 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 830 mV;
- fluid temperature 110° C. (±1);
- air temperature 110° C. (±1);
- pressure 70 psig (±1);
- flow rate 0.1 US gallons/min (±10 percent).
11 more elements
Dependencies are inferred from the claim text.