Multimodal polyethylene compositions and pipe made from same

• US 20070043182A1
• Filed: 11/02/2005
• Published: 02/22/2007
• Est. Priority Date: 08/22/2005
• Status: Active Grant

• Current Assignee: Chevron Phillips Chemical Company LP (Chevron Corp.)
• Original Assignee: Chevron Phillips Chemical Company LP (Chevron Corp.)
• Inventors: Jensen, Michael, Yang, Qing, Martin, Joel, Jayaratne, Kumudini, McDaniel, Max, Krishnaswamy, Rajendra, Thorn, Matthew, DesLauriers, Paul, Lanier, J.
• Granted Patent: US 7,625,982 B2
• Time in Patent Office: Days
• US Class Current: 526/119
• CPC Class Codes: C08F 210/14 Monomers containing five or more carbon atoms
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2500/05 Bimodal or multimodal molecular weight distribution
• CPC Class Codes: C08F 2500/07 High density, i.e. > 0.95 g/cm3
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 23/0807 Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
• CPC Class Codes: C08L 23/0815 Copolymers of ethene with aliphatic 1-olefins
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: Y10T 428/139 Open-ended, self-supporting conduit, cylinder, or tube-type article

Abstract

A multimodal polyethylene composition having at least two polyethylene components, wherein each component has a molecular weight distribution of equal to or less than about 5, one component has a higher molecular weight than the other component, and the higher molecular weight component has an “a” parameter value of equal to or greater than about 0.35 when fitted to the Carreau-Yasuda equation with n=0.

Claims

1. A multimodal polyethylene composition having at least two polyethylene components, wherein:

(a) each component has a molecular weight distribution of equal to or less than about 5;

(b) one component has a higher molecular weight than the other component; and

(c) the higher molecular weight component has an “

a”

parameter value of equal to or greater than about 0.35 when fitted to the Carreau-Yasuda equation with n=0.

2. The composition of claim 1 wherein the higher molecular weight component contains equal to or less than about one long chain branch per about 10,000 carbons.

3. The composition of claim 1 wherein the ratio of short chain branching in the higher molecular weight component to short chain branching in the lower molecular weight component is equal to or greater than about 1.

4. The composition of claim 1 wherein the higher molecular weight component comprises a copolymer of ethylene and 1-olefin and the lower molecular weight component comprises a copolymer of ethylene and 1-olefin, and wherein the 1-olefin in the two components may be the same or different.

5. The composition of claim 4 wherein the 1-olefin is 1-hexene in the two components.

6. The composition of claim 4 wherein the amount of 1-olefin in the higher molecular weight component is equal to or greater than about 1.5 times the amount of 1-olefin in the lower molecular weight component.

7. The composition of claim 1 wherein the higher molecular weight component is catalyzed by a first metallocene catalyst, the lower molecular weight component is catalyzed by a second metallocene catalyst, and the first and second metallocene catalysts are not the same.

8. The composition of claim 1 wherein the weight ratio of higher molecular weight component to lower molecular weight component is equal to or greater than about 0.5.

9. The composition of claim 1 wherein the weight average molecular weight of the higher molecular weight component is equal to or greater than about 9 times the weight average molecular weight of the lower molecular weight component.

10. The composition of claim 1 wherein the multimodal polyethylene composition has a density of from about 0.920 g/cc to about 0.965 g/cc.

11. The composition of claim 1 having a high load melt index of equal to or less than about 30 g/10 min.

12. The composition of claim 1 having a molecular weight distribution of greater than about 6.

13. The composition of claim 1 having a 23°

C. notched Charpy impact energy of greater than about 0.7 Joules per ASTM F 2231.

14. The composition of claim 1 having a Charpy ductile to brittle critical temperature of equal to or less than about −

25°

C. per ASTM F 2231.

15. The composition of claim 1 having a PENT of greater than about 1500 hours per ASTM F 1473.

16. A PE80 or PE100 pipe comprising the multimodal polyethylene composition of claim 1.

17. A pipe comprising the multimodal polyethylene composition of claim 1 and having a rapid crack propagation S4 critical temperature value equal to or less than about −

15°

C. per ISO 13477.

18. A pipe comprising the multimodal polyethylene composition of claim 1 and having a long term hydrostatic strength equal to or greater than 1000 hours per ASTM D 2837.

19. A method of making the pipe of claim 16 comprising extruding the multimodal polyethylene composition to form the pipe.