Flexible tube having high temperature resistance

1. A flexible pipe having a multilayer structure with unbonded layers, where the pipe comprises an interior lining comprising unbonded layers (a) and (b):

a) at least one layer comprising a molding composition, wherein the molding composition comprises a polymer selected from the group consisting of:

a polyarylene ether ketone,

polyphenyl sulfone,

polyphenylene sulfide,

a blend of a polyarylene ether ketone and polyphenylene sulfide, and semiaromatic polyamide, where from 5 to 100 mol% of a dicarboxylic acid content thereof derives from an aromatic dicarboxylic acid having from 8 to 22 carbon atoms, and which has a crystallite melting point Tm of at least 260° C., determined according to ISO 11357;

b) at least one layer comprising a fluoropolymer molding composition;

wherein the flexible pipe is operable at 200° C. to convey a fluid selected from the group consisting of crude oil, natural gas, methanol, and super critical carbon dioxide and resistant to the diffusion of gases from the conveying fluid;

wherein the flexibility of the pipe when subjected to a temperature of 130° C. is retained when the pipe is subjected to a temperature of 200° C.;

wherein the flexible pipe does not form stress cracks in deformed regions when the pipe is subjected to a temperature of 200° C.; and

wherein the interior lining is an unbonded three-layer lining having a layer sequence a/b/a and all of the a and b layers in the unbonded three-layer sequence a/b/a are unbonded to each other.

2. The flexible pipe of claim 1 , wherein the interior lining is a tube.

3. The flexible pipe of claim 1 , further comprising, alongside the interior lining, one or more unbonded layers selected from the group consisting of

an internal carcass,

one or more external reinforcing layers, and

an exterior sheath.

4. The flexible pipe of claim 1 , wherein the crystalline melting point Tm is at least 270° C.

5. The flexible pipe of claim 1 , wherein the crystalline melting point Tm is at least 280° C.

6. The flexible pipe of claim 1 , wherein an exterior layer (a) comprises polyphenylene sulfide.

7. The flexible pipe of claim 1 , wherein an interior layer (a) comprises the polyarylene ether ketone, polyphenylene sulfide, or a blend of the polyarylene ether ketone and polyphenylene sulfide.

8. The flexible pipe of claim 1 , wherein an exterior layer (a) comprises polyphenylene sulfide, and an interior layer (a) comprises the polyarylene ether ketone, polyphenylene sulfide, or a blend of the polyarylene ether ketone and polyphenylene sulfide.

9. The flexible pipe of claim 1 , wherein the molding composition comprises the polyarylene ether ketone.

10. The flexible pipe of claim 9 , wherein the polyarylene ether ketone comprises units of the formulae

(—Ar—X—) and (—Ar′—Y—),

wherein

Ar and Ar′ are each independently a divalent aromatic moiety selected from the group consisting of 1,4-phenylene, 4,4′-biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene;

X is carbonyl or sulfonyl; and

Y is selected from the group consisting of O, S, CH 2 , and isopropylidene.

11. The flexible pipe of claim 10 , wherein at least 50% of the units of the formula (—Ar—X—) have X groups which are carbonyl groups, and at least 50% of the units of the formula (—Ar—Y—) have Y groups which are O groups.

12. The flexible pipe of claim 10 , wherein at least 70% of the units of the formula (—Ar—X—) have X groups which are carbonyl groups, and at least 70% of the units of the formula (—Ar—Y—) have Y groups which are O groups.

13. The flexible pipe of claim 10 , wherein at least 80% of the units of the formula (—Ar—X—) have X groups which are carbonyl groups, and at least 80% of the units of the formula (—Ar—Y—) have Y groups which are O groups.

14. The flexible pipe of claim 9 , wherein the polyarylene ether ketone has a formula selected from the group consisting of formulae I-IV:

15. The flexible pipe of claim 1 , wherein the interior lining has a total wall thickness of 2 to 50 mm.

16. The flexible pipe of claim 1 , wherein the interior lining has a total wall thickness of 5 to 16 mm.

17. The flexible pipe of claim 1 , wherein each layer (a) has a thickness of 0.1 to 10 mm.

18. The flexible pipe of claim 1 , wherein each layer (a) has a thickness of 0.2 to 8 mm.