Underwater pipe comprising a sheath comprising a polypropylene block copolymer

Abstract

An underwater pipe including a metal reinforcing layer around an inner polymeric sealing sheath which may be in contact with hydrocarbons. The inner polymeric sealing sheath includes a polypropylene block copolymer or a mixture of polypropylene block copolymers, wherein the polypropylene block copolymer or the mixture has a density greater than 0.900 g/cm3, and a melt index measured at 230 C. under a mass of 2.16 kg of less than 10 g/10 minutes, its preparation method and its use for the transport of hydrocarbons. Such a sheath may be used in contact with hydrocarbons at high temperature.

Claims

1. An underwater pipe for the transport of hydrocarbons comprising a metal reinforcing layer around an inner polymeric sealing sheath capable of being in contact with the hydrocarbons, wherein the inner polymeric sealing sheath comprises a polypropylene block copolymer or a mixture of polypropylene block copolymers, wherein the polypropylene block copolymer or the mixture has: a density greater than 0.900 g/cm.sup.3, and a melt index measured at 230 C. under a mass of 2.16 kg of less than 10 g/10 minutes.

2. The underwater pipe according to claim 1, wherein the polypropylene block copolymer or the polypropylene block copolymer mixture has: a density greater than 0.902 g/cm.sup.3, and/or a melt index measured at 230 C. under a mass of 2.16 kg of less than 5 g/10 min.

3. The underwater pipe according to claim 1, wherein the polypropylene block copolymer or polypropylene block copolymer mixture has a melting temperature of at least 145 C.

4. The underwater pipe according to claim 1, wherein the polypropylene block copolymer has a degree of crystallinity of at least 40%, or the polypropylene block copolymer mixture comprises at least one polypropylene block copolymer having a degree of crystallinity of at least 40%.

5. The underwater pipe according to claim 1, wherein the polypropylene block copolymer or the polypropylene block copolymer mixture has a swelling rate of less than 30% by weight when it is brought into contact with Biofree EN 590 diesel at 110 C. for 6 hours.

6. The underwater pipe according to claim 1, wherein the polypropylene block copolymer, or the at least one polypropylene block copolymer of the polypropylene block copolymer mixture, has a crystalline morphology of more than 50% of the beta and/or alpha type.

7. The underwater pipe according to claim 1, wherein the polypropylene block copolymer, or the at least one polypropylene block copolymer of the polypropylene block copolymer mixture, is obtained by polymerization in the presence a betagenic or alphagenic nucleating agent.

8. The underwater pipe according to claim 1, wherein the weight proportion of the polypropylene block copolymer, or polypropylene block copolymer mixture, in the inner polymeric sealing sheath is greater than 50% by weight, relative to the inner polymeric sealing sheath.

9. The underwater pipe according to claim 1, wherein the polypropylene block copolymer is crosslinked, or the polypropylene block copolymer mixture comprises at least one crosslinked polypropylene block copolymer.

10. The underwater pipe according to claim 1, wherein the inner polymeric sealing sheath comprises: from 0 to 20% by weight of plasticizer, and/or from 0 to 20% by weight of impact modifier.

11. The underwater pipe according to claim 1, which is a rigid pipe, and wherein the metal reinforcing layer consists of a metal tube.

12. A method for transporting hydrocarbons wherein hydrocarbons are transported in the underwater pipe according to claim 1.

13. The underwater pipe according to claim 1, which is a flexible pipe, and wherein the reinforcing layer consists of a long pitch winding of at least one wire with non-contiguous turns.

14. The underwater pipe according to claim 13, comprising, from the outside to the inside: at least one layer of tensile armor as reinforcing layer, the inner polymeric sealing sheath, and a metal carcass.

15. A method for preparing the underwater pipe according to claim 1, comprising the following steps: a) extrusion to form the inner polymeric scaling sheath comprising the polypropylene block copolymer or the polypropylene block copolymer mixture, wherein the extrusion is possibly carried out on another layer, b) assembling the inner polymeric sealing sheath obtained in step a) with the metal reinforcing layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a partial schematic perspective view of a flexible pipe according to the invention. It illustrates a pipe according to the invention comprising, from the outside to the inside: an outer polymeric sheath 10, an outer ply of tensile armor 12, an inner ply of tensile armor 14 wound in the opposite direction to the outer ply 12, a pressure vault 18 to take up the radial forces generated by the pressure of the hydrocarbons transported, an inner polymeric sheath 20, and an inner carcass 22 to take up radial crushing forces,
wherein the inner polymeric sealing sheath 20 comprises a polypropylene block copolymer or a polypropylene block copolymer mixture with a density and melt index as defined above.

(2) Due to the presence of the inner carcass 22, this pipe is said to be rough bore. The invention could also be applied to a so-called smooth-bore pipe, which does not include an inner carcass.

(3) Likewise, the scope of the present invention is not exceeded by eliminating the pressure vault 18, insofar as the helix angles of the threads constituting the armor plies 12, 14 are close to 55 and in the opposite direction.

(4) The armor plies 12, 14 are obtained by long-pitch winding of a set of metal or composite material wires, generally of substantially rectangular section. The invention also applies if these wires have a section of circular or complex geometry, for example of the auto-stapled T type. FIG. 1 shows only two armor plies 12 and 14, but the pipe could also include one or more additional armor pairs. The armor ply 12 is said to be external because it is here the outermost, starting from the inside of the pipe, before reaching the outer sealing sheath 10.

(5) The flexible pipe may also comprise layers not shown in FIG. 1, such as: a holding layer between the outer polymeric sheath 10 and the tensile armor plies 12 and 14, or between two tensile armor plies, one or more anti-wear layers of polymeric material in contact either with the inner face of the aforementioned holding layer, or with its outer face, or with both faces, wherein this anti-wear layer prevents the holding layer from wear through contact with metal armor. Anti-wear layers, which are well known to those skilled in the art, are generally made by helical winding of one or more ribbons obtained by extrusion of a polymeric material based on polyamide, polyolefins, or PVDF (polyvinylidene fluoride). Reference may also be made to the document WO 2006/120320 which describes anti-wear layers consisting of polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU), polyetherimide (PEI), polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) or phenylene polysulfide (PPS) ribbons.

(6) FIG. 2 shows a partial schematic perspective view of a rigid pipe according to the invention. It illustrates a pipe according to the invention comprising, from the outside to the inside: a metal reinforcing layer 8, an inner polymer polymeric sheath 9 comprising a polypropylene block copolymer or a mixture of polypropylene block copolymers of density and melt index as defined above.

EXAMPLE

Example 1: Swelling Rate of Polypropylenes in the Presence of a Petroleum Fluid at Elevated Temperature

(7) Samples of different families of polypropylene were weighed and then contacted with a petroleum fluid: the Biofree EN 590 diesel, and then weighed after contact for a certain time in this fluid. The difference in mass before and after contacting makes it possible to determine the degree of swelling.

(8) The swelling rate (mass percentage) of various families of polypropylene in the presence of a petroleum fluid: the Biofree EN 590 diesel, were compared and are provided in Table 1.

(9) TABLE-US-00001 TABLE 1 Swelling rate of various polypropylenes in the presence of Biofree EN 590 diesel swelling rate in presence density of Biofree EN 590 diesel fluid index according at at at according to to ISO 1183 110 C. 110 C. 120 C. ASTM D1238 revised in after after after polypropylene (g/10 min) 2012 6 h 188 h 115 h syndiotactic FINAPLAST 2.0 0.88 31% x x homopolymer 1251 from Total random PPC 3221 1.8 0.902 110% x x copolymer from Total block PPH3666 1.5 0.905 17% 48% 53% copolymer from Total block PPC 1640 0.3 0.905 23% 45% 56% copolymer from Total block PPC 1645 0.3 0.905 15% 28% 37% copolymer from Total metallocene Lumicene 10 0.902 88% x x random MR10MX0 copolymer from Total

(10) These results show that the polypropylene block copolymers used in the sheath of the pipe according to the invention have a low swelling rate in the presence of hydrocarbons at high temperatures.

Example 2: Resistance of Polypropylenes Upon Violent Decompressions

(11) Several polypropylenes were saturated with gas at high temperatures and pressures, and then the pressure was lowered to atmospheric pressure (1 bar) at a decompression rate of 70 bar/min similar to the operation of a flexible pipe. The appearance of blisters on the surface of the polypropylenes after this treatment was followed (Table 2).

(12) TABLE-US-00002 TABLE 2 appearance of blisters on the surface of various polypropylenes after violent decompressions density fluid index according conditions of according to to ISO 1183 pressurization ASTM D1238 revised in temperature polypropylene (g/10 min) 2012 gas and pressure blistering block PPC 3645 1.3 0.905 mixture 200 bar and no copolymer from Total 85% 120 C. CH.sub.4/15% CO.sub.2 block PPC 1645 0.3 0.905 mixture: 200 bar and no copolymer from Total 85% 110 C. CH.sub.4/15% CO.sub.2 random PPR 3221 1.8 0.902 mixture 200 bar and yes copolymer from Total 85% 110 C. CH.sub.4/15% CO.sub.2 syndiotactic FINAPLAS 2 0.88 mixture 200 bar and yes copolymer 1251 from 85% 110 C. Total CH.sub.4/15% CO.sub.2

(13) These results show that the polypropylene block copolymers used in the pipe according to the invention are capable of withstanding violent decompressions simulating production shut-downs.