Pipes
Pipe with an outer diameter of from 90 to 630 mm and a minimum wall thickness of higher than 3.6 mm, having (a) an extrapolated time-to-failure (ASTM F2023 and ASTM F2769-10, performed on 16 mm SDR 7.4 pipe) of at least 50 years (for classification code CL5), (b) a time to failure (ISO 1167, performed on 32 mm SDR 11 pipe) of at least 10000 hours (110° C. under hoop stress of 2.6 MPa), and (c) a resistance to slow crack growth (ISO 13479 (80° C., 9.2 bar, performed on 110 mm SDR 11 pipe)) of at least 5000 hrs. The pipe contains a copolymer of ethylene and an a-olefin, and has (a) a density (D) in the range 933-948 kg/m 3 , (b) a melt index (MI 2 ) in the range 0.15-2.0 g/10 min, and (c) a melt elastic modulus G′ (G″=500 Pa) in the range 40 to 150 Pa.
1. A pipe having an outer diameter of from 90 to 630 mm and a minimum wall thickness of higher than 3.6 mm, said pipe having
(a) an extrapolated time-to-failure according to ASTM F2023 and ASTM F2769-10 (performed on 16 mm SDR 7.4 pipe) of at least 50 years (for classification code CL5),
(b) a time to failure according to ISO 1167 (performed on 32 mm SDR 11 pipe) of at least 10000 hours (110° C. under hoop stress of 2.6 MPa),
(c) a resistance to slow crack growth according to ISO 13479 (80° C., 9.2 bar, performed on 110 mm SDR 11 pipe) of at least 5000 hrs, and
(d) a MRS classification according to ISO 9080 of at least 8.0 MPa,
said pipe comprising a copolymer of ethylene and an α-olefin, said copolymer having
(a) a density (D) in the range 933-948 kg/m 3
(b) a melt index (MI 2 ) in the range 0.15-2.0 g/10 min, and
(c) a melt elastic modulus G′ (G″=500 Pa) in the range 40 to 150 Pa.
2. A pipe according to claim 1 having an extrapolated time-to-failure according to ASTM F2023 and ASTM F2769-10 of at least 60 years (for classification code CL5).
3. A pipe according to claim 1 exhibiting a halting of crack propagation at an internal pressure equal to at least 10 bars, as measured at 0° C. on a pipe of diameter 110 mm and thickness 10 mm according to method S4 described in ISO 13477:2008.
4. A pipe according to claim 1 wherein the copolymer has a density (D) in the range 933-940 kg/cm 3 .
5. A pipe according to claim 1 wherein the copolymer has a melt index (MI 2 ) in the range 0.8-1.5 g/10 min.
6. A pipe according to claim 1 wherein the copolymer has a melt index (MI 5 ) in the range 0.5 to 6.0.
7. A pipe according to claim 1 wherein the copolymer has a melt elastic modulus G′ (G″=500 Pa) in the range 40 to 100 Pa.
8. A pipe according to claim 1 wherein the copolymers have a Composition Distribution Branch Index (CDBI) in the range 55-75%.
9. A pipe according to claim 1 wherein the copolymer has a molecular weight distribution in the range 3.5 to 10.
10. A pipe according to claim 1 wherein the copolymer has a ratio of complex dynamic shear viscosities η*(0.1)/η*(100) in the range 1.5 to 5.5.
11. A pipe according to claim 1 wherein the copolymer has a unimodal molecular weight distribution.
12. A pipe according to claim 1 wherein the copolymer is prepared by use of a single site catalyst system.
13. A pipe according to claim 12 wherein the single site catalyst system comprises a metallocene.
14. A pipe according to claim 1 wherein the α-olefin has C4 to C12 carbon atoms.
15. A pipe according to claim 14 wherein the α-olefin is 1-hexene.
16. A pipe according to claim 1 further comprising an antioxidant system comprising
(a) a first antioxidant,
(b) a second antioxidant,
(c) at least one metal deactivator, and optionally
(d) an acid scavenger.
17. A pipe according to claim 16 wherein the antioxidant system comprises
(a) 0.01-0.3 parts, (b) 0.05-1 parts and (c) 0.01-0.3 parts and (d) <0.25 parts per 100 parts of the polymer composition.
18. A pipe according to claim 16 comprising 0.1 parts of (a), 0.25 parts of (b) 0.1 part of (c) and 0.05 parts of (d).
19. A pipe according to claim 16 wherein (a) is a phosphite, (b) is a hindered phenol and (c) is a hydrazine.
20. A pipe according to claim 16 wherein the acid scavenger is zinc oxide.
21. A pipe according to claim 4 wherein the copolymer has a density (D) in the range 935-940 kg/cm 3 .
22. A pipe according to claim 5 wherein the copolymer has a melt index (MI 2 ) in the range 1.0-1.3 g/10 min.
23. A pipe according to claim 6 wherein the copolymer has a melt index (MI 5 ) in the range 1.0 to 5.0.
24. A pipe according to claim 23 wherein the copolymer has a melt index (MI 5 ) in the range 2.0 to 4.0.
25. A pipe according to claim 7 wherein the copolymer has a melt elastic modulus G′ (G″=500 Pa) in the range 40 to 70 MPa.
26. A pipe according to claim 8 wherein the copolymers have a Composition Distribution Branch Index (CDBI) in the range 58-72%.
27. A pipe according to claim 9 wherein the copolymer has a molecular weight distribution in the range 3.5 to 8.0.
28. A pipe according to claim 1 wherein the copolymer has a ratio of complex dynamic shear viscosities η*(0.1)/η*(100) in the range 2.0-5.0.
29. A pipe according to claim 28 wherein the copolymer has a ratio of complex dynamic shear viscosities η*(0.1)/η*(100) in the range 2.5-4.5.