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US 10,501,613 B2Granted
Low-sag polyethylene pipes and methods thereof
AssigneeEquistar Chemicals, LP
InventorsHarilaos Mavridis, Chun D. Lee, Steven W. Horwatt, Sameer D. Mehta
Life of this patent
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Abstract
The present disclosure relates to pipes comprising bimodal high molecular weight high density polyethylene which has been extruded in the presence of one or more organic peroxides that are present in an amount ranging from 30 ppm to 200 ppm. The pipe has an improved long-term hydrostatic strength. Also provided are methods for preparing pipes having these characteristics.
Claims10
An extruded pipe comprising:
- (1) a bimodal high molecular weight high density polyethylene having a density ranging from about 0.9460 g/cm3 to about 0.9520 g/cm3, and (2) a polypropylene random copolymer containing one or more organic peroxides,
- wherein the pipe was extruded in the presence of about 30 ppm to about 200 ppm of one or more organic peroxides,
- wherein the one or more organic peroxides has a half-life of 1 hour at a temperature in the range of about 125° C. to about 145° C., and
- the extruded pipe has a long-term hydrostatic strength tF/tR ratio of about 1.5 or greater when determined at 23° C. and 12 MPa and/or at 23° C. and 11.5 MPa, where tF is the time-to-failure of the pipe and tR is the time-to-failure of a comparative pipe which has not been extruded with organic peroxide.
1 more element
Dependencies are inferred from the claim text.