Patent Application

App. No. 12/380,519

Abstract

Claims (15)

1 . A composition which comprises a polyethylene pipe resin, a primary antioxidant, and an acid.

2 . The composition of claim 1 , wherein the resin has a density within the range of 0.935 to 0.965 g/cm 3 .

3 . The composition of claim 2 , wherein the resin has a density within the range of 0.947 to 0.949 g/cm 3 .

4 . The composition of claim 1 , wherein the resin is a multimodal polyethylene resin.

5 . The composition of claim 4 , wherein the multimodal polyethylene resin is a bimodal resin which comprises from 49 wt % to 60 wt % of a first polyethylene component and from 40 wt % to 51 wt % of a second polyethylene component, wherein the first polyethylene component has a density greater than or equal to 0.965 g/cm 3 and an MI 2 from 50 to 400 g/10 min, and the second polyethylene component has a lower MI 2 and lower density than that of the first polyethylene component.

6 . The composition of claim 4 , wherein the multimodal polyethylene resin is a trimodal polyethylene resin which comprises from 45 wt % to 55 wt % of a first polyethylene component, from 20 wt % to 40 wt % of a second polyethylene component and from 15 wt % to 30 wt % of a third polyethylene component, wherein the first component is an ethylene homopolymer having a density within the range of 0.965 g/cm 3 to 0.973 g/cm 3 and an MI 2 within the range of 100 dg/min to 250 dg/min, the second component is an ethylene-C 3-10 α-olefin copolymer having a density within the range of 0.950 g/cm 3 to 0.962 g/cm 3 and an MI 2 within the range of 0.01 dg/min to 0.1 dg/min, and the third component is an ethylene-C 3-10 α-olefin copolymer having a density within the range of 0.905 g/cm 3 to 0.935 g/cm 3 and an MI 2 less than or equal to 0.005 dg/min.

7 . The composition of claim 1 , wherein the primary antioxidant is a phenolic antioxidant.

8 . The composition of claim 7 , wherein the primary antioxidant is present in an amount within the range of 500 ppm to 5000 ppm based on the weight of the polyethylene pipe resin.

9 . The composition of claim 1 , wherein the acid is benzoic acid.

10 . The composition of claim 1 , wherein the acid is present in an amount within the range of 100 ppm to 3000 ppm.

11 . The composition of claim 10 , wherein the acid is present in an amount within the range of 250 ppm to 2000 ppm.

12 . The composition of claim 11 , wherein the acid is present in an amount within the range of 500 ppm to 1500 ppm.

13 . An extruded pipe comprising the composition of claim 1 .

14 . A multilayer pipe comprising at least one layer of the composition of claim 1 .

15 . The pipe of claim 13 , which is crosslinked.

Assignments (10)