Flexible tube and method for producing the same

DESCRIPTIVE MEMORY

The object of the present invention is a flexible multilayer construction tube with unbound layers, as well as a manufacturing process. A tube of this type, for the purpose of simplification and according to the use in English, will be called Unbonded Flexible Pipe. A high resistance to the diffusion of gases from a transported liquid is placed and, therefore, can be used very advantageously for the transport of crude oil, natural gas, methanol, CO₂ and the like

Unbonded Flexible Pipes are like the state of the art. These tubes contain an inner lining, usually in the form of a plastic tube, as a barrier against the exit of the transported liquid, as well as one or more layers of reinforcement on the outer side of this inner liner. The Unbonded Flexible Pipe may contain additional layers, for example, one or more reinforcing layers on the inner side of the inner liner, to prevent the inner lining from being heated with great external pressure. An internal reinforcement of this type is usually called a housing. Beyond it, an outer cover may be contained, to provide a barrier against the penetration of liquid from the outside environment into the reinforcing layers or other polymeric or metallic functional layers that are inside. In many cases, a thermoplastic layer is introduced between the outer reinforcing layers, for example in the form of rolled "antiwear tapes", in order to avoid wear in the metal construction by friction.

Typical Unbonded Flexible Pipes are described, for example, in WO 01/61232, US 6 123 114 and US 6 085 799; beyond that, they are characterized in greater detail in API Recommended Practice 17B, “Recommended Practice for Flexible Pipe”, 3.® edition, March 2002, as well as in API Spécification 17J, “Spécification for Unbonded Flexible Pipe” 2.® edition, November 1999.

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The term "unbonded" means, in this context, that at least two of the layers, including the reinforcing layers and the plastic layers, are not joined together in a constructive manner. In practice, the tube contains at least two reinforcing layers, which are not directly or indirectly connected to each other along the length of the tube, that is, through other layers. In this way, the tube is ductile and flexible enough to roll it for transport purposes.

Taies Unbonded Flexible Pipes are used in different executions in offshore applications, as well as in different onshore applications for the transport of liquids, gases and suspensions. For example, they can be used for the transport of fluids in a place where there is a very large or very different water pressure throughout the length of the tube, approximately in the form of ascent pipes that go from the bottom of the sea to an installation in or near the surface of the sea, in addition, as tubes for the transport of liquids or gases between different facilities, such as tubes that are lying deep at the bottom of the sea, or as tubes between facilities near the sea surface.

In conventional flexible tubes, the reinforcement layer or reinforcement layers are most often made of steel wires, steel profiles or steel bands arranged in a spiral, where each of the layers can be formed with different winding angles with respect to the tubular axis. In addition, there are also embodiments in which at least one reinforcement layer or all reinforcement layers are composed of fibers, for example, of glass fibers, approximately in the form of fiber bundles or fibers of fibers which, by In general, they are embedded in a polymer matrix.

The inner lining is composed in the state of the art usually of a polyolefin like polyethylene which can also be crosslinked, of a polyamide like PA11 or PA12 or of polyvinylidene fluoride (PVDF).

Polyethylene has the disadvantage of swelling a lot in contact with crude or natural oil and then sliding. In addition, the transported non-polar medium passes through the polyethylene wall outward. For this reason, polyethylene is not generally used for pipes in direct contact with product streams, but especially for so-called water injection pipes.

PA11 ο PA12 polyamide polyamides are very suitable for their very good mechanical properties, excellent hydrocarbon resistance and low swelling as material for the inner lining. The particular suitability of polyamides was described in detail in OTC publication 5231 "Improved Thermoplastic Materials for Offshore Flexible Pipes". However, they can only be used up to approx. 70 ° C as maximum, since at higher temperatures there is a greater hydrolysis by the process water contained in crude oil or natural gas. By this hydrolysis, the molecular weight of the polyamide is reduced to such an extent that the mechanical properties get considerably worse and the tube eventually fails. In API 17TR2 for PA11 a detailed test procedure for the determination of hydrolysis properties is described and can be applied in the same way for PA12.

PVDF is used up to 130 ° C as maximum. According to the modification, it is also rigid with less compression deformability at higher temperatures up to approximately 130 ° C. However, at temperatures above 130 ° C, there must be a decrease in internal pressure with blistering and microfoaming. PVDF swells especially in CO₂ supercritical up to approx. 25%; The blistering that occurs with the reduction of pressure results from the good permeation barrier that is also poorly diffused. In this case, a locaor desorption of the gas occurs within the layer, where the cohesion resistance of the material is exceeded.

In many cases, crude oil or natural gas appears with temperatures clearly above 130 ° C from the source. In order to exploit these sources through flexible pipes, a pre-connected process stage is necessary for cooling the medium. Therefore, it would be desirable to have available a Unbonded Flexible Pipe that can also be used at higher temperatures, in order to save this process stage.

A flexible tube for the transport, for example, of hot methanol in an Umbilical, containing an inner layer of PEEK or polyphenylene sulfide is described in document 2008/125807. The inner diameter of this tube is in the range of 4 to 500 mm, while the PEEK layer thickness is 0.7 to 5 mm. However, as in the case of Unbonded Flexible Pipes a layer thickness of at least 2 mm and typically 3 to 20 mm is required, in order to guarantee the mechanical stability of the layer necessary for assembly and handling, it will result here , in the case of the known stiffness of PEEK, a tube that is not flexible enough to be wound in a drum with a justifiable radius.

Another embodiment of a flexible multilayer tube with an inner PEEK tube is described in WO 99/67561. The tube is composed of polymeric and textile layers that are constructively bonded together along the tube; The typical layer thickness of the inner tube is 6 to 12 mm.

Document 2006/047774 describes a multilayer tube with a layer that is composed of a semi-aromatic polyamide.

US 5 876 ​​548 describes a flexible metal tube in which an elastomeric layer is placed on a housing and a contraile polymer layer is above; In addition to a number of other possibilities, PEEK is also mentioned for him.

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In document 2005/028198 a Unbonded Flexible Pipe is described in which the inner lining is composed of a thicker polymeric layer and a thinner film with barrier properties. For the materials of the thicker polymeric layer and the film, two identical comprehensive lists are indicated; the film can be composed, beyond elio, of metal, in both lists PEEK, PEKK and polyphenylene sulphide (PPS) are mentioned.

The tube of US 5 934 335 contains a layer that may be composed of PFA. The PFA drains a lot, however, at higher temperatures and fills, depending on the direction of compression, the intermediate spaces between the articulated areas of the housing or the reinforcing layer that is connected outwards, which considerably reduces the flexibility of the tube. In the deformed areas, beyond the elio, fissures due to the tension that can cause destruction of the inner lining are formed. Therefore, US 5 934 335 recommends filling the intermediate spaces of the housing with an elastomer.

In the extrusion of the corresponding polymeric layers, the specialist faces a series of problems. On the one hand, the extrusion of a tube with a large internal diameter is problematic in the case of high melting point polymers or in the case of polymer-based molded masses that, by nature, possess only a low melt strength. On the other hand, in the extrusion the molded mass penetrates into the housing or a reinforcement layer in the intermediate spaces of the steel construction, which leads to the loss of flexibility and, due to different local cooling speeds, to internal stresses which can cause the polymer layer to fail. Therefore, it has long been the state of the art to apply functional layers by winding tapes.

The winding of tapes in an inner tube is described in WO

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2004/048833. The tapes are composed, for example, of a molded mass of polyolefin; they can be coated with an adhesive to fix them in an overlapping area.

In US 2007/0125438, a flexible tube is described which contains a rolled layer of tapes that are composed of polytetrafluoroethylene (PTFE). With it, operating temperatures of more than 130 ° C are possible.

Document US 2004/0060610 describes a Unbonded Flexible Pipe containing from inside out a housing, a spirally wound layer of plastic tapes, a solid layer of pressure-proof solid plastic extruded on it, at least one reinforcing layer, So as an exterior lining.

These rolled tapes have the disadvantage that they can be displaced, which could cause that the layer that is above is no longer covered in certain places, so that the material of the next layer of the inner lining slides by the external pressure in the intermediate spaces of the housing or, in the case of an AntiWear Tapes, friction from metal to metal. Another disadvantage is justified by the fact that a rolled belt does not have a sufficient barrier action against the permeation of components of the transported medium, just when the tension applied in the winding was lost over time by relaxation.

The object of the invention is to avoid these disadvantages.

This object is solved by forming in the manufacture of a flexible multilayer construction tube with unbound layers a layer of a molded plastic mass that is spirally wound in another inner layer, after which they are welded in overlapping areas at the same time or then the upper layer and the lower layer of the tape together.

The tape is wound under tension, so that it is joined by adhesion by the compression pressure with the lower layer.

In one possible embodiment, a housing is located on the inner side of the inner liner of the Unbonded Flexible Pipe. These housings and their design are state of the art. In another possible embodiment, the Unbonded Flexible Pipe does not contain a housing, especially when it must not be operated at high outside pressures.

Beyond it, the Unbonded Flexible Pipe contains on the outer side of the inner lining one or more reinforcing layers, which are usually composed of steel cables, steel profiles or steel bands arranged in a spiral. The execution of these layers of reinforcement is state of the art. Preferably, at least one of these reinforcing layers is constructed in such a way that it resists internal pressure, and at least one of these reinforcing layers is constructed in such a way that it resists tensile forces. An outer lining can be added to the reinforcement layer or to the reinforcement layers, usually in the form of a tube or hose of a thermoplastic molded mass or an elastomer.

In a first embodiment, the tape is wound in the housing and then released. Then other layers of the inner liner can be extruded on the tape. The primary functions of the belt are here the slip protection and / or the permeation barrier.

In a second embodiment, the tape is wound on the inner liner in tubular form and then welded. Such a construction is convenient when in operation the internal pressure of the tube is higher than the external pressure; With the tape, sliding of the inner lining in the empty spaces of the steel construction of the next reinforcing layer can be avoided.

In a third embodiment, the tape is wound on a reinforcing layer and then welded. Then two layers of metal reinforcement are separated and et ύ an · '&lt;*' · 's. '&gt;

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horn Anti-Wear Tape.

In the same tube, the first, second and third embodiments can be combined with each other, where the materials of the tapes can be different. For example, a tube may contain a first tape of a molded PEEK mass on the housing that acts as a barrier layer and as a slip protection. An extruded layer of a fluoropolymer follows, for example, PFA, which, in turn, is covered by a tape of, for example, a molded mass of polyphenylene sulfide (PPS), a molded mass of PEEK or a molded PPA dough. Among the following reinforcement layers, Anti-Wear Tapes are then disposed of a molded mass with low slip friction coefficient, for example, a PEEK molded mass.

Suitable materials for the tape are preferably molded masses based on partially crystalline polymers, for example, olympic polymers, polyamides, fluoropolymers, polyphenylsulfone, polyarylene ether ketones, polyphenylene sulfide or a mixture of polyarylene ether ketone / polyphenylene sulfide. In this case, the tape can have one layer or several layers, for example, two layers or three layers.

The olefinic polymer used for the belt can be, first of all, a polyethylene, especially a high density polyethylene (HDPE), or an isotatic or syndiotactic polypropylene. The polypropylene can be a homo- or a copolymer, for example, with ethylene or 1-butene as a comonomer, and random block copolymers can be used. Beyond elio, polypropylene can also be modified on impact, for example, according to the state of the art, by means of ethylene-propylene rubber (EPM) or EPDM. The syndiotic polystyrene which can also be used according to the invention can be prepared in a known manner by polymerization of metallocene-catalyzed styrene.

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The polyamide used for the tape can be prepared from a combination of diamine and dicarboxylic acid, of a amino-aminocarboxylic acid or the corresponding lactam. Basically any polyamide can be used, for example, PA6 or PA66. In a preferred embodiment, the monomer units of the polyamide contain on average at least 8, at least 9 or at least 10 atoms of C. In lactam mixtures, the arithmetic mean is considered here. In the case of a combination of diamine and dicarboxylic acid, the arithmetic mean of the diatoms of C of diamine and dicarboxylic acid in this preferred embodiment may be at least 8, at least 9 or at least 10. Appropriate polyamides are, for example: PA610 (prepare from hexamethylenediamine [6 atoms of CJ and sebacic acid [10 atoms of C), the average of C atoms in the monomer units is here of 8), PA88 (prepare from octamethylenediamine and 1,8-octanoic acid), PA8 (preparable from goat-lactam), PA612, PA810, PA108, PA9, PA613, PA614, PA812, PA128, PA1010, PAIO, PA814, PA148, PA1012, PA11, PA1014, PA1212 and PA12. The preparation of polyamides is state of the art. In fact, copolyamides can also be used on this basis, where eventually monomers such as caprolactam can also be used.

As a polyamide, a semi-aromatic polyamide can also be used advantageously, whose proportion of dicarboxylic acid is 5 to 100 mol% of an aromatic dicarboxylic acid with 8 to 22 C atoms and which has a melting point of crystallite T_m, determined according to ISO 11357 in the second heating, at least 260 ° C, preferably at least 270 ° C and with special preference, at least 280 ° C. These polyamides are usually called PPA. They can be prepared from a combination of diamine and dicarboxylic acid, optionally with the addition of a ω-aminocarboxylic acid or the corresponding lactam. The appropriate types

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they are, for example, PA66 / 6T, PA6 / 6T, PA6T / MPMDT (MPMD represents 2-methylpentamethylenediamine), PA9T, PA10T, PA11T, PA12T, PA14T, as well as copolycondensates of these latter types with an aliphatic diamine and an aliphatic dicarboxylic acid a ω-aminocarboxylic acid or a lactam.

* In addition to polyamide, the molded mass may also contain other components such as high impact impact modifiers, other thermoplastics, plasticizers and other customary additives. It is only necessary for the polyamide to form the matrix of the molded mass.

The fluoropolymer used for the tape can be, for example, a polyvinylidene fluoride (PVDF), an ethylene-tetrafluoroethylene (ETFE) copolymer, a modified ETFE with the aid of a horn tercomponent, for example, propene, hexafluoropropene, vinyl fluoride or vinylidene fluoride (eg, EFEP), an ethylene-chlorotrifluoroethylene (E-CTFE) copolymer, a polychlorotrifluoroethylene (PCTFE), a copolymer of chlorotrifluoroethylene-perfluoroalkyl vinyl ether-tetrafluoroethylene (CPT) copolymer, a tetrafluoroethylene-hexafluoropropene copolymer (FEP) or a perfluoroalkylvinyl tetrafluoroethylene ether copolymer (PFA) copolymer. Copolymers based on vinylidene fluoride, which have up to 40% by weight of other tais corno monomers, for example, trifluoroethylene, chlorotrifluoroethylene, ethylene, propene and hexafluoropropene are also taken into account.

Polyphenylenesulfone (PPSU) is produced, for example, under the brand name Radel® of Solvay Advanced Polymers. It can be prepared from 4,4'diihydroxybiphenyl and 4,4'-dihydroxydiphenylsulfone by nucleophilic substitution. For use as an Anti-Wear Tape, a mixture of PPSU / fluoropolymer, for example a mixture of PPSU / PTFE, is also especially suitable.

The polyarylene ether ketone that can also be used contains units of the

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formulas (-Ar-X-) and (-Ar'-Y-), wherein Ar and Ar 'represent a divalent aromatic radical, preferably 1,4- phenylene, 4,4'-biphenylene, as well as 1.4 -, 1,5- or 2,6-naphthylene. X is an electron extraction group, preferably carbonyl or sulfonyl, while Y is another group like O, S, CH₂, isopropylidene or the like. In this case, at least 50%, preferably at least 70% and with special preference, at least 80% of the X groups represents a carbonyl group, while at least 50%, preferably at least 70 % and with special preference, at least 80% of the Y groups are composed of oxygen.

In the preferred embodiment, 100% of the X groups are composed of carbonyl groups and 100% of the Y groups, of oxygen. In this embodiment, the polyarylene ether ketone may be, for example, a polyether ketone (PEEK; formula I), a polyether ketone (PEK; formula II), a polyether ketone ketone (PEKK; formula III) or a polyether ketone ketone (PEEKK; formula IV), but of course other arrangements of the carbonyl and oxygen groups are also possible.

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c-III

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Ο Ο

IV

The polyarylene ether ketone is partially crystalline, which is manifested, for example, in the DSC analysis by finding a melting point of the crystallite T_m which, according to the magnitude, in most cases is 300 ° C or more.

The polyphenylene sulfide used for the tape contains units of the formula (-C₆H₄-S-);

Preferably, it is composed of at least 50% by weight, at least 70% by weight or at least 90% by weight of these units. The other units may be those indicated above in the case of polyaryletherketone, or tri- or tetrafunctional branched units resulting from the joint use of, for example, trichlorobenzene or tetrachlorobenzene in the synthesis. Polyphenylene sulfide is commercially available in a number of types or molded masses.

In the case of polyarylene ether ketone / polyphenylene sulfide mixtures, both components can be present in any imaginable mixing ratio, so that the composition range from pure polyaryletherketone to polyphenylene sulfide can be covered without problems. In general, the mixture contains at least 0.01% by weight of polyarylene ether ketone or at least 0.01% by weight of polyphenylene sulfide. In a preferred embodiment, the mixture contains at least 50% by weight of polyarylene ether ketone.

η

The molded mass of the tape may contain the usual excipients and additives, as well as possibly other polymers, in the case of polyarylene ether ketone, for example, fluoropolymers taies such as PFA (a tetrafluoroethene copolymer) and perfluorovinylmethyl ether, polyimide, polyetherimide, LCP taies as, for example, liquid crystalline polyester, polysulfone, polyethersulfone, polyphenylsulfone, polybenzimidazole (PBI) or other high temperature resistant polymers, in the case of polyphenylene sulfide, for example, copolymers or terpolymers of ethylene with polar comonomers and, in the case of partially aromatic polyamide, an aliphatic polyamide. The molded polyamide mass may contain, for example, also a hydrolysis stabilizer, a plasticizer or modifier of high impact resistance. When using Anti-Wear Tape, the molded mass of the tape may contain, beyond it, a lubricant such as graphite, molybdenum disulfide, hexagonal boron nitride or PTFE. The proportion of olefinic polymer, polyamide, fluoropolymer, polyphenylsulfone, polyarylene ether ketone, polyphenylene sulfide or polyarylene ether ketone / polyphenylene sulfide mixture in the molded mass is at least 50% by weight, preferably at least 60% by weight, with special preference, of at least 70% by weight, especially at least 80% by weight and with very special preference, at least 90% by weight. The tape may be reinforced, beyond elio, by long fibers, for example, with fiberglass fabric or wicks. In this case, it can also contain another layer of the non-reinforced molded dough and / or serve to reduce or replace a metal reinforcement.

The width of the tape depends on the diameter of the tube. The usual widths are in the range of about 20 mm to about 700 mm and preferably in the range of about 30 mm to about 500 mm. The thickness of the tape is limited because, on the one hand, it must be mechanically stable enough and, on the other hand, it must be flexible enough to be able to continue rolling.

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In practice, the tape usually has a thickness in the range of 0.05 mm to 3 mm and preferably in the range of 0.1 mm to 2 mm.

The cross section of the tape can be rectangular. But notches can also be found on the sides, so that the overlapping areas fit and give an essentially smooth surface of the winding.

Usually, a layer of tape is wound overlapping; for the overlapping area, approximately 10% of the width of the tape is sufficient in magnitude. However, a first layer of butt tape can also be wound and a second layer of butt tape over it, but displaced approximately half a width of tape.

After winding, the tape is welded at the overlapping sites. This can occur either by welding with hot gas, by contacting a heating element, with the help of a flame or advantageously with irradiation of electromagnetic rays in the UV, visible or IR spectral range. Especially preferred are laser welding or infrared ray welding. When using slip protection tapes or Anti-Wear-Tape horn, it achieves in principle a punctual welding to fix the tape; however, it is preferred to generate a continuous unbroken seam. In fact, the tapes can also be welded in overlapping areas over their entire surface.

In the case of welding with laser beam or two-component infrared ray, the radiated upper component for the radiation used is essentially transparent, while the lower component is absorbent. In order to achieve an optimal welding result, it is therefore advantageous when the belt has different absorption properties throughout its width. This can be produced by coextrusion of an essentially transparent molded mass with a corresponding but absorbent molded mass, so that the tape has on one side an absorbent band having,

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AV for example, a width of about 3 to about 90% of the entire width of the tape. When winding the tape, it should be taken into account that the absorbent side is down and covered by the transparent side. Alternatively, when two layers of tape are wound on top of one another, for example, butt, the material of the lower tape layer may contain an absorbent additive, while the material of the upper layer of the tape is widely transparent. By using very thin tapes, all the tape material can also be made absorbent.

Laser beam welding, infrared beam welding, as well as appropriate absorbent additives are well known to the expert. The most common absorbent addition is hollin, but any other known additive in the usual amounts can also be used.

By fixing the form according to the invention for assembly and operation, as well as the gas tightness achieved, greater freedom of design can be obtained from the Unbonded Flexible Pipe.

The claims in sheet number sixteen follow.