FR3161008A1 - Flexible subsea pipe comprising an intermediate polymeric layer based on poly(p-phenylene ether) - Google Patents

Abstract

Subsea Flexible Pipe Comprising an Intermediate Polymeric Layer Based on Poly(p-phenylene ether) The present invention relates to a subsea flexible pipe for transportation, comprising, from the inside to the outside: - an inner polymeric sealing sheath, - at least two reinforcing layers, - an outer polymeric sealing sheath, the pipe further comprising, between the inner polymeric sealing sheath and the outer polymeric sealing sheath, at least one layer of polymeric material comprising a PPE, a method for transporting hydrocarbons and/or gases using it, and the use of a layer of polymeric material comprising a PPE as an anti-wear layer or as a thermal insulation layer in a flexible pipe. Figure for abstract: 1

Description

Flexible subsea pipe comprising an intermediate polymeric layer based on poly(p-phenylene ether)

The present invention relates to an underwater pipeline intended for the transport of hydrocarbons in deep water or for the transport of gas, typically methane, hydrogen sulfide, carbon dioxide or a mixture thereof.

These pipes are likely to be used under high pressures, greater than 100 bars, or even up to 1000 bars, and at high temperatures, greater than 110°C, or even 130°C, for long periods of time, i.e. several years, typically 20 years.

Subsea pipelines intended for the transport of hydrocarbons or gas in deep water generally comprise an external sealing polymer sheath, at least two layers of reinforcement around an internal sealing polymer sheath, in which the hydrocarbons and/or gases circulate.

Most flexible pipes used in the offshore oil industry are flexible pipes, generally comprising, from the inside to the outside:

- possibly a metal frame,

- an internal polymeric sealing sheath,

- at least one reinforcing layer made of metal or composite material wires wound helically around the internal sealing sheath (this is typically at least one layer of tensile armor, generally at least two layers of tensile armor),

- an external polymeric sealing sheath.

These pipes are referred to as “usual” pipes below. The structure of these flexible pipes is described in the API RP 17B (2021) and API 17J (2021) standard documents published by the American Petroleum Institute.

They are used particularly in deep water in the oil and gas industry. Typically, they are used for the transport of hydrocarbon fluids, or for the reinjection of carbon dioxide into a subsea reservoir. Flexible oil pipelines generally extend across a body of water between a surface assembly and a bottom assembly. These pipelines can also extend between two surface assemblies.

The body of water is, for example, a sea, a lake or an ocean. The depth of the body of water at the hydrocarbon or gas exploitation installation is, for example, between 500 m and 4000 m.

The installation comprises a surface assembly and a bottom assembly or two surface assemblies which are typically connected together by the flexible conduit.

The bottom assembly is intended to collect the fluid exploited in the bottom of the body of water. The surface assembly is generally floating. It is intended to collect, potentially treat, and distribute the fluid. It is advantageously formed by a floating production, storage and offloading unit called FPSO (Floating Production, Storage and Offloading), a floating unit dedicated to liquefied natural gas called FLNG (Floating Liquified Natural Gas), a semi-submersible platform or an offloading buoy. Alternatively, the surface assembly is a fixed rigid structure of the "jacket" type or an oscillating structure secured to the seabed which may be, for example, a TLP (Tension Leg Platform).

In some cases, for the exploitation of fluids in deep water, the flexible pipe has a length greater than 800 m, or even greater than 1000 m or 2000 m for applications in ultra-deep water.

For great depths, the flexible pipe is sized to withstand very high hydrostatic pressure, for example 200 bar for a pipe submerged at a depth of 2000 m.

In addition, the flexible pipe is generally sized to withstand axial tension greater than the total weight of the flexible pipe suspended from a surface assembly and extending underwater from the surface to the seabed. This is particularly the case when the flexible pipe is used as a riser
("riser" in English) intended to provide a vertical connection between the seabed and the surface assembly in service. The flexible pipe's ability to support its own weight when suspended in the water makes it easier to install at sea from a laying vessel.

However, these flexible pipes are generally heavy, making their installation in deep and ultra-deep water complex and expensive. In addition, risers of this type must generally be equipped with buoys for deep-water applications, which leads to additional expenses and possible storage problems on board laying vessels. Finally, the reinforcing layers, when metallic, are generally sensitive to corrosion, particularly corrosion under the influence of acid gases such as H ₂ S and CO ₂ present in the hydrocarbons of certain deposits.

To overcome these problems, lightweight flexible pipes comprising a tubular reinforcement structure made of composite material comprising a thermoplastic matrix and reinforcing fibers embedded in the matrix have been developed, namely so-called "hybrid" flexible pipes. In these so-called flexible pipes
"hybrids", the metal carcass, the internal polymeric sealing sheath as well as the pressure vault of the flexible pipe described above are replaced by a thermoplastic composite pipe (TCP).

The so-called “hybrid” flexible pipes therefore comprise, from the inside to the outside:

- an internal tubular polymer sheath,

- a tubular reinforcement structure made from a winding of several strips of composite material,

- possibly an intermediate polymer sheath,

- at least one reinforcing layer made of metal or composite material wires wound in a helix around the intermediate polymer sheath (typically at least one layer of tensile armor),

- an external polymeric sealing sheath.

The tubular reinforcement structure generally absorbs most of the radial forces applied to the hybrid flexible pipe. The tubular reinforcement structure also has a barrier function to gases, such as acid gases of the H ₂ S and CO ₂ type contained in the hydrocarbons transported inside the tubular internal polymer sheath. It thus protects the metallic reinforcement elements of the flexible pipe against corrosion phenomena or the composite material of the reinforcement layer from degradation induced by these gases. The tubular reinforcement structure may or may not be bonded to the tubular internal polymer sheath.

The reinforcement layer(s) made of metal wires or composite material are similar to those of unbonded flexible pipes, i.e. they are made of helically wound wires. These are generally tensile armor layers.

Additionally, optionally, these hybrid flexible pipes can include an internal carcass located inside the tubular internal polymer sheath.

These hybrid flexible pipes are notably described in the article “Unbonded Flexible Pipe: Composite Reinforcement for Optimized Hybrid Design” written by N. Dodds, V. Jha, J. Latto and D. Finch, and published under the reference OTC-25753 during the “Offshore Technology Conference” held in Houston from May 4 to 7, 2015, or in applications GB 2 504 065 and WO 2018/091693.

One of the obstacles to the use of hybrid pipes is their poor bending performance, which results in a high minimum bend radius (MBR). Indeed, the bonded structure of the TCPs in hybrid pipes makes them more rigid than pipes made from layers that are not bonded to each other, i.e. in which the layers can move relative to each other. Thus, depending on the requirements for the installation and use of the flexible pipe, either a flexible pipe of the type described in the API RP 17B (2021) and API 17J (2021) standards, or a hybrid pipe, will be preferred.

Whether the pipe has a standard structure or is hybrid, the nature, number, dimensioning and organization of the layers constituting the flexible pipes are essentially linked to their conditions of use and installation.

Pipes may include additional layers to those listed above. In particular, flexible pipes may include additional polymeric layers. The use of thermoplastic materials in unbonded flexible pipes is summarized in the API RP 17B (2021) and API 17J (2021) standards published by the American Petroleum Institute.

The skilled person generally prefers to avoid using an amorphous polymer within a polymer layer of a flexible pipe, because he fears poor resistance to stress cracking. However, the appearance of cracks must be avoided to prevent losses of transported fluid, and therefore for economic and environmental reasons. Since polyphenylene ether (PPE) is amorphous, it is not or is very little used in flexible pipes.

Flexible pipes may include in particular an anti-wear layer and/or a thermal insulation layer.

Whether the flexible pipe is "standard" or hybrid, the different unbonded layers are, to a certain extent, mobile relative to each other, so as to allow the flexible pipe to flex easily. When the pipe comprises several adjacent layers of metal or composite material reinforcement, this mobility induces friction between them and the adjacent layers, and ultimately leads to their premature wear.

Also, in order to prevent at least two of these layers of metallic or composite material reinforcement from being in direct contact with each other, which would cause them to wear, an intermediate layer of polymeric material, called an "anti-wear layer", can be interposed.

Application WO 2006/120320 describes a flexible pipe for the transport of hydrocarbons comprising an anti-wear layer made of amorphous polymer, preferably polysulfone (PSU), polyethersulfone (PES), polyphenylsulfone (PPSU) or polyetherimide (PEI). Application WO 2022/243424 describes a flexible pipe for the transport of hydrocarbons comprising in particular an anti-wear layer made of specific homopolymer polypropylene and an internal or external sealing sheath made of thermoplastic polymer, polyphenylene ether (PPE) being listed among the polymers that can be used.

This intermediate anti-wear layer can, however, deteriorate rapidly when the flexible pipe is subjected to severe stresses, such as those encountered during the exploitation of certain underwater oil fields, located at great depth, and where the hydrocarbon is at a high temperature above 110°C or even 130°C, and/or in the case of severe dynamic conditions (variations in bends of the hose). Under such conditions, this intermediate anti-wear layer can withstand temperatures close to 110°C and contact pressures of around 300 to 400 bars. One of the most common deteriorations is a loss of thickness of the anti-wear layer by creep, which can limit, or even destroy, the protection provided by the anti-wear layer to the reinforcing layers surrounding it.

The development of an anti-wear layer with better creep resistance under the conditions of use of a pipeline, namely at least 100 bar and at least 110°C, is therefore required.

In addition, flexible pipes may include a layer of thermal insulation.

There is a significant temperature difference between the outside of the pipe (usually the temperature of seawater at great depth, i.e. a few degrees) and the inside of the pipe, where the fluid is at a high temperature above 110°C. The aim is to limit the drop in temperature of the transported fluid. In particular, the drop in its temperature leads to an increase in its viscosity, which can impair its flow along the pipe. To achieve this, the pipes are equipped with an intermediate layer of thermal insulation generally located between the external polymeric sealing sheath and the outermost reinforcing layer.

A layer made by winding foamed PVC-c strips is generally used when the pipe is used in medium water depth and/or medium temperature. The foamed PVC-c is first extruded in the form of strips which are then wound with a short pitch to form a layer. This layer is not waterproof. If waterproofing is required, it can be provided with a waterproof sheath under the layer of insulating strips, and/or an external sheath to hold the assembly together. When the pipe is used in deeper water or at higher temperatures, a layer made by winding strips of pure polypropylene or syntactic polypropylene foam is preferred, as polypropylene foam has better hydrostatic resistance than PVC-c foam.

One of the current challenges is that gas or hydrocarbon deposits are dwindling and/or of lower quality. The hydrocarbons present in wells are increasingly viscous and extracting and transporting them requires increasingly high temperatures, now often above 110°C. The polymeric layers of the pipe, particularly the anti-wear layers and the insulating sheaths, are therefore also subjected to increasingly high temperatures, which requires the development of polymeric materials with better thermal resistance, while maintaining acceptable mechanical properties and processability. In addition, with regard to a thermal insulation layer, the material must maintain its thermal insulation performance.

One of the objectives of the present invention is to provide a subsea pipeline for the transport of hydrocarbons and/or gas (in particular methane, hydrogen sulfide, carbon dioxide or a mixture thereof) comprising an intermediate polymeric sheath, typically an anti-wear layer or a thermal insulation layer, which has a good compromise between thermal resistance, in particular at temperatures above 110°C, mechanical strength, in particular creep resistance at such temperatures and at pressures of at least 100 bar, and processability, and furthermore, when this layer is a thermal insulation layer, low thermal conductivity, and this over the entire service life of the pipeline, typically 20 years.

One of the objectives is to provide a pipe comprising an intermediate polymeric sheath and for this pipe to be suitable for the underwater transport of hydrocarbons and/or gases (in particular methane, hydrogen sulfide, carbon dioxide or a mixture thereof) at high temperatures, typically at least 110°C.

To these ends, according to a first object, the invention relates to a flexible underwater pipe intended for the transport of hydrocarbons and/or gas comprising from the inside to the outside:

- an internal polymeric sealing sheath,

- at least two layers of reinforcement,

- an external polymeric sealing sheath,

the pipe further comprising, between the internal polymeric sealing sheath and the external polymeric sealing sheath, at least one layer of polymeric material,

characterized in that said polymeric material:

- comprises at least 50% by weight of poly(p-phenylene ether) (PPE), and

- has a flexural modulus measured at 20°C according to ASTM D 638-14 greater than 2000 MPa.

The invention is based on the discovery that such a polymeric material presents a good compromise between its ability to be transformed and mechanical characteristics, in particular good creep resistance at pressures of more than 100 bar and a temperature of 110°C, and low thermal conductivity.

Moreover, such a polymeric material is resistant to the pressure and temperature conditions mentioned above.

In addition, it has a chemical resistance compatible with its use as a polymeric material of a layer of a flexible pipe for the transport of hydrocarbons. The annular space (space between the internal polymeric sheath and the external polymeric sheath for sealing the pipe) in which the polymeric sheath is located comprises gases and/or acids (CO ₂ and H ₂ S in particular). Advantageously, the polymeric material is not sensitive to hydrolysis, unlike a polyamide-based layer. In addition, the polymeric material is little, if at all, sensitive to plasticization induced by CO ₂ .

The polymeric material has a creep resistance that allows the layer formed from it to maintain a sufficient thickness so that the reinforcing layers surrounding it do not come into contact, and therefore do not wear against each other, which is advantageous for its use as an anti-wear layer. The use of such a material makes it possible to reduce the loss of thickness of the anti-wear layer, which is advantageous because the more the thickness of the anti-wear layer is maintained, the better it protects the reinforcing layers surrounding it.

The polymeric material has low thermal conductivity which makes the layer formed from it useful as a thermal insulation sheath.

Despite the high proportion of PPE within the polymeric material, the polymeric material as defined above has good resistance to stress cracking.

Definitions

"Transport of hydrocarbons and/or gas" means the transport of hydrocarbons, gas or a mixture thereof. The gas is preferably methane (CH ₄ ), hydrogen sulfide (H ₂ S), carbon dioxide (CO ₂ ) or a mixture thereof.

The term "thermoplastic polymer" refers to a polymer that becomes less viscous, or more liquid, or liquid when heated sufficiently and that reversibly retains its thermoplasticity. Thermoplastic polymers are generally contrasted with thermosetting polymers, which irreversibly transform into an insoluble, non-formable polymer network when heated.

The term "homopolymer" means a polymer consisting of a single repeating unit.

A copolymer is a polymer resulting from the copolymerization of at least two types of chemically different monomers, called comonomers. A copolymer is therefore formed from at least two repeating units derived from different monomers. It can also be formed from three or more repeating units derived from different monomers.

The copolymer may have a homogeneous structure, in particular of the statistical, alternating or random type, or a heterogeneous structure, in particular of the sequenced or block type. In particular, the term "block copolymer" or "block copolymer" is understood to denote copolymers in the aforementioned sense, in which at least two distinct homopolymer blocks are covalently linked. The length of the blocks may be variable. The blocks may be composed of 1 to 1000, preferably 1 to 500, more preferably 1 to 100, and in particular 1 to 50 repeating units, respectively. The link between the two homopolymer blocks may be: a simple covalent bond or an intermediate non-repeating unit called a junction block.

By polymers “of the same nature”, it is meant, within the meaning of the present invention, that the polymers are capable of melting and forming an intimate mixture, without phase separation, after cooling.

“Consisting essentially of unit(s)” means that the unit(s) represent(s) a molar proportion of 95% to 99.9% of the total number of moles of repeating units in the polymer.

“Consisting of unit(s)” means that the unit(s) represent(s) a molar proportion of at least 99.9%, in particular 100%, in the polymer relative to the total number of moles of repeating units in the polymer.

The term "glass transition temperature", denoted T _g , is understood to mean the temperature at which an at least partially amorphous polymer passes from a rubbery state to a glassy state, or vice versa, as measured by differential scanning calorimetry (DSC) according to standard NF ISO 11357-2:2020, in second heating, using temperature ramps in heating and cooling at 20°C/min. In the present application, when reference is made to a glass transition temperature, it is more particularly, unless otherwise indicated, the glass transition temperature at half-step height as defined in this standard.

The term "Charpy impact strength", or more simply "impact strength", refers to the impact strength of bars of size 80*10*4 mm ³ notched type A, as measured according to ISO 179:2010. The actual measurement corresponds to the average of 10 tests carried out consecutively. A notch (V-shaped with a notch bottom radius of 0.25 +/- 0.05 mm) can be implemented on a device specially designed for this purpose (Automatic Notchvis Plus), marketed by the company Ceast). The bars are then left to rest for 24 hours. The impact strength measurement can be carried out on a Zwick 5102 impact testing machine.

The singular forms “un” and “le” applied to the constituents of the polymeric material, such as PEE, mean by default “at least one” and respectively “said at least one”. The singular forms nevertheless include, without it being necessary to repeat it each time, the embodiments where “un” means “a single one” and “le” means “the only one”.

In all that follows, the terms "outer" or "external" and "inner" or "inner" are understood respectively as being radially farthest from the axis of the flexible pipe, and as being radially closer to the axis of the flexible pipe. The expressions "outermost layer" or "innermost layer" are understood respectively as being the layer radially farthest from the axis of the flexible pipe, and as being the layer radially closest to the axis of the flexible pipe. The flexible pipe according to the invention comprises at least two reinforcing layers. Among these reinforcing layers, there is one which is the outermost reinforcing layer and which is therefore the reinforcing layer radially farthest from the axis of the flexible pipe, and there is another which is the innermost reinforcing layer and which is therefore the reinforcing layer radially closest to the axis of the flexible pipe.

By "layer adjacent to a layer" is meant that the two layers follow each other in the structure of the pipe and that no other layer (whatever its nature) is located between them.

By "two consecutive reinforcement layers" is meant two reinforcement layers that follow one another in the structure of the flexible pipe, without any other reinforcement layer being located between these two reinforcement layers. For example, in a structure (reinforcement layer A / reinforcement layer B / reinforcement layer C), reinforcement layers A and B are consecutive to each other and reinforcement layers B and C are consecutive to each other, but reinforcement layers A and C are not consecutive to each other, because there is a reinforcement layer B located between them. Two consecutive reinforcement layers may be adjacent (no other layer between them) or non-adjacent, because there may be one or more other layers between them, provided that this/these other layer(s) is/are not a reinforcement layer(s). Typically, this/these other layer(s) may be a polymeric layer(s). For example, in a structure (reinforcing layer A / polymeric layer B / reinforcing layer C), reinforcing layers A and C are consecutive.

In the present application, the concept of long pitch winding covers any helical winding with a helix angle less than or equal to 60°, in particular less than or equal to 55°, typically between 20° and 60°, for example between 25° and 45°, the angle being relative to the axis of the flexible pipe.

The concept of short pitch winding refers to any helical winding with a helix angle close to 90°, typically 75° to 90°.

Layer of polymeric material comprising a PPE

The pipe according to the invention comprises at least one intermediate layer (i.e. between the internal polymeric sealing sheath and the external polymeric sealing sheath) made of polymeric material comprising at least 50% by weight, in particular at least 60% by weight, preferably at least 65% by weight, of poly(p-phenylene ether) (PPE). The layer of polymeric material generally comprises less than 99% by weight, sometimes less than 95% by weight of PPE.

Advantageously, using at least 50% by weight of PPE within the polymeric material allows the polymeric material to have a high glass transition temperature (Tg), which allows it to withstand the high temperatures encountered when the pipe is put into operation, and in particular to have good creep resistance at at least 100 bar and at least 110°C. This glass transition temperature also depends on the nature and proportion of any other components of the polymeric material.

Preferably, the polymeric material has a glass transition temperature (Tg) greater than or equal to 130°C, it being understood that when the polymeric material has several glass transition temperatures, at least one of them (and preferably the one corresponding to the PPE) is greater than or equal to 130°C. For example, the polymeric material may comprise one or more additives which induce the appearance of secondary peaks of low Tg in calorimetry but this (these) peak(s) must not be taken into account.

Poly(p-phenylene ether) (PPE), also called polyphenylene ether (PPE), or poly(phenylene oxide) (PPO) is a thermoplastic polymer which has the advantage of being suitable for high temperatures.

PPE can be a homopolymer or a copolymer. When it is a copolymer, the PPE may be a (p-phenylene ether A) / (p-phenylene ether B) copolymer, said (p-phenylene ether B) being different from (p-phenylene ether A), or a (p-phenylene ether) A / polymer B copolymer, said polymer B not being a poly(p-phenylene ether). Preferably, the polymer B is a thermoplastic polymer, in particular a polystyrene (PS), a polyolefin such as polyethylene or polypropylene, a polyamide (PA) or a poly(phenylene sulfide (PPS). For example, the PPE may be a poly(p-phenylene ether) / polyolefin copolymer, for example obtained by grafting a poly(p-phenylene ether) with a polyolefin functionalized with maleic anhydride, typically during the kneading phase in the melted, using a binder such as phenylenediamine.

Preferably, the p-phenylene ether units of PPE have the following formula (I):

(I)

in which:

- n is an integer greater than 2 representing the number of units in the PPE (and is typically from 10 to 1,000,000, especially from 20 to 10,000),

- independently in each unit, R ¹ and R ² independently represent a hydrogen, a halogen or an Alk or –X-Alk group where:

- Alk represents a linear or branched C ₁ -C ₁₂ alkyl, in particular C ₁ -C ₆ , preferably C ₁ -C ₃ , said alkyl being optionally substituted by one or more groups chosen from a hydroxyl and a halogen and

- X represents O, SH, (CO) or –(C=O)-O.

When the ^R1 and ^R2 groups are the same from one unit to another, PPE is a homopolymer.

Preferably, in each unit, one of the groups R ¹ and R ² is H and the other is chosen from H and a linear or branched C ₁ -C ₁₂ alkyl, in particular C ₁ -C ₆ , preferably C ₁ -C ₃ . Mention may for example be made of poly(2,6-dimethyl-1,4-phenylene oxide) (R ¹ represents H and R ² methyl).

A preferred PPE is that of formula (I) in which R ¹ and R ² represent H. This is poly(1,4-phenylene oxide).

The PPE may be the only thermoplastic polymer in the polymeric material. The polymeric material is, for example, made up of PPE and one or more additives, in particular those defined below.

The polymeric material may alternatively comprise at least one other thermoplastic polymer which is not a PPE, at least one thermoplastic elastomer or a mixture thereof. This(these) other thermoplastic polymer(s) and/or this(these) thermoplastic elastomer(s) advantageously make it possible to improve the processability and/or the mechanical properties of the polymeric material, in particular the heat deflection temperature (HDT). However, they may cause a reduction in the glass transition temperature of the polymeric material and therefore its creep resistance. This is why the maximum proportion of thermoplastic polymer other than PPE, thermoplastic elastomer or mixture thereof is less than or equal to 50% by weight relative to the weight of the polymeric material.

Said at least one thermoplastic polymer is typically chosen from a polystyrene (PS), a polyolefin such as polyethylene or polypropylene, a polyamide (PA) and a polyphenylene sulfide (PPS), preferably from a polystyrene (PS), a polyolefin, and a polyphenylene sulfide (PPS), particularly preferably from a polypropylene and a polystyrene.

One of the disadvantages of polyamide is that it tends to hydrolyze in the presence of water, often contained in raw materials (chemical aging). Hydrolysis is rapid when subjected to temperatures (around 110°C and above) and low pH values (pH less than 7). Therefore, preferably, the polymeric material is free of polyamide.

The polymeric material may be free of any thermoplastic polymer other than those specifically mentioned above.

The thermoplastic elastomer generally comprises a polyolefin, such as polyethylene or polypropylene, combined with an elastomer, and is for example chosen from SBS (styrene butadiene styrene), SEBS (styrene ethylene butadiene styrene) and EPDM (ethylene propylene diene monomer).

The polymeric material may comprise one or more additives, preferably non-polymeric ones.

Advantageously, the polymeric material comprises from 0% to 30%, typically from 0% to 25%, in particular from 1% to 20%, or even from 2% to 10% by weight of additives, relative to the total weight of polymeric material.

Among the additives, one or more fillers may be mentioned. Among the possible fillers, one may mention in particular silica and alumina, nucleating fillers such as mineral fillers, in particular talc, carbon fillers, in particular carbon nanotubes or carbon blacks, ceramic fillers, in particular boron nitride (BN), or metal oxides, in particular ZnO or MgO, or reinforcing fillers such as glass fibers or carbon fibers.

Among the additives, one or more functional additives may be mentioned. Examples that may be mentioned as such are antistatic agents, antioxidant agents, anti-UV agents, stabilizers in the melt state, conductive agents, impact modifiers, compatibilizing agents, flame retardants, blowing agents, agents capable of reducing the coefficient of friction such as PTFE, nucleating agents, crosslinking agents, coupling agents, colorants as well as reactive agents such as alkali carbonates. In particular, when the polymeric material comprises, in addition to PPE, at least one other thermoplastic polymer, the polymeric material generally comprises a compatibilizing agent which makes it possible to facilitate and improve their mixing. Furthermore, when the polymeric material is foamed, it may comprise one or more blowing agents and optionally a nucleating agent.

Among the additives, one or more plasticizers may be mentioned. The plasticizer may, for example, be chosen from the compounds defined in the book Handbook of Plasticizers edited by Georges Wypych. For example, the polymeric material comprises from 0% to 5% by weight of plasticizer.

According to one embodiment, the polymeric material comprises, or even consists of:

- from 50 to 100%, in particular from 60 to 99%, typically from 65 to 95%, preferably from 70 to 85% of PPE,

- from 0 to 50%, in particular from 1 to 40%, typically from 5 to 35%, preferably from 15 to 30% of one or more thermoplastic polymers, in particular as defined above, and

- from 0 to 30%, in particular from 0 to 20%, typically from 0 to 10%, preferably from 1 to 5% of one or more additives, in particular as defined above.

The polymeric material of the layer preferably has a melt flow index measured according to ISO 1133 revised in 2011 at 230°C under a mass of 2.16 kg of less than or equal to 4.0 g/10 minutes. Such melt flow indices facilitate the preparation of a strip or tubular sheath by extrusion. The use of polymeric material with a higher melt flow index can lead to strips or layers whose thickness is not sufficiently uniform, which is detrimental to its performance. The melt flow index is generally greater than 0.1 g/10 minutes, in particular greater than 0.3 g/10 minutes, preferably greater than or equal to 2.0 g/10 minutes.

The polymeric material of the polymeric material layer may have one, more, or all of the properties listed below.

The polymeric material of the polymeric material layer of the pipe has a flexural modulus measured at 20°C according to the ASTM D 638-14 standard greater than 2000 MPa, in particular greater than or equal to 2100 MPa, preferably greater than or equal to 2250 MPa, particularly preferably greater than or equal to 2500 MPa. These flexural moduli are particularly suitable for the polymeric material layer to have good creep resistance at at least 100 bar and at least 110°C. The flexural modulus of the polymeric material is generally less than 4.0 GPa, typically less than 3.5 GPa, in particular less than 3.2 GPa, preferably less than 3.0 GPa. For the purposes of the present application, when the polymeric material is foamed, the flexural modulus is that of the polymeric material of the foam, and not that of the polymeric material foam. Thus, the flexural modulus is not measured on the foam, but on the polymeric material in unfoamed form, typically on a sample of extruded unfoamed polymeric material.

Preferably, the polymeric material of the polymeric material layer of the pipe has an HDT, measured according to ASTM D 648-18 and under 1.8 MPa, greater than 70 °C and ideally greater than 80 °C, or even greater than 80 °C. Such HDTs also allow good creep resistance, and are thus advantageously higher than the HDT of polypropylene (around 40/50 °C) which is sometimes used as an anti-wear layer material.

Preferably, the polymeric material of the polymeric material layer of the pipe has a nominal strain at break as measured according to ISO 527-1A:2019 at 20°C greater than 8%, typically greater than 10%, in particular greater than 15%, preferably greater than 20%.

Preferably, the polymeric material of the polymeric material layer of the pipe has a Charpy impact strength according to ISO 179-1:2010/1eA greater than 5 KJ/m², preferably greater than 6 KJ/m², more preferably greater than 7 KJ/m², and more preferably greater than 8 KJ/m².

Preferably, and in particular when the layer is used as a thermal insulation layer, the polymeric material of the polymeric material layer of the pipe has a thermal conductivity at 20°C of less than 0.25 W/(m.K), preferably less than 0.20 W/(m.K) and particularly preferably less than 0.17 W/(m.K) as measured according to ISO 22007-4:2024.

In one embodiment, the polymeric material of the polymeric material layer has a flexural modulus greater than 2500 MPa at 20°C according to ASTM D 638-14, a thermal conductivity less than 0.17 W/(m.K) according to ISO 22007-4:2024 and an HDT, measured according to ASTM D 648-18 and under 1.8 MPa, greater than 100°C.

The polymeric material as defined above may be foamed or unfoamed.

When the polymeric material is foamed, the flexural modulus described above is that of the polymeric material of the foam, not that of the polymeric material foam.

Preferably, when the polymeric material is foamed, it contains at least 70%, preferably at least 80% by weight of PPE. These high proportions of PPE allow the resulting layer to have a sufficient flexural modulus to be used as an intermediate layer in a flexible pipe.

The embodiment in which the polymeric material is foamed is particularly advantageous when the layer of polymeric material is used as a thermal insulation layer. On the other hand, for use as an anti-wear layer, it will generally be preferred that the polymeric material is not foamed.

Whether the polymeric material is foamed or unfoamed, the polymeric material layer can:

- either be produced by helical winding, generally with a short pitch, of at least one strip of said polymeric material,

- either be a tubular sheath obtained by extrusion.

In general, the strip of said polymeric material has a rectangular cross-section, or close to it. Preferably, the strip has a thickness of 0.1 to 10.0 mm, preferably 0.5 to 5.0 mm and/or a width of 30 to 200 mm, preferably 40 to 150 mm. The length of the strip is variable and can be up to 5 km long.

When the layer is produced by helical winding of at least one strip of said foamed polymeric material, the pipe may comprise one or more additional polymeric layer(s) on the internal and/or external side of the layer of polymeric material, in order to improve the sealing and/or cohesion of the layer of polymeric material.

• Le fait d’utiliser des bandes enroulées à pas court fait qu’il peut exister entre chaque bande un espace (typiquement rempli d’un fluide tel qu’un gaz et/ou de l’eau), qui est néfaste en ce qu’il augmente la conductivité thermique globale de la couche.
• Il n’est généralement pas nécessaire d’insérer une couche polymérique supplémentaire du côté interne de la couche en matériau polymérique, et l’absence de cette couche améliore l’isolation thermique car la couche en matériau polymérique est plus proche du fluide transporté. En effet, plus la couche en matériau polymérique est du côté externe de la conduite, moins elle est efficace pour isoler thermiquement, et réciproquement plus elle est du côté interne (donc plus proche du fluide transporté), plus elle est efficace pour isoler thermiquement. Ainsi, plus il y a de couches du côté interne de la couche en matériau polymérique, plus cela l’éloigne du fluide transporté, et moins elle est efficace pour isoler thermiquement.
• L’épaisseur d’une gaine d’isolation obtenue par extrusion peut être plus facilement optimisée que celle d’une couche obtenue à partir d’enroulement de bandes, l’épaisseur de la couche étant alors un multiple de l’épaisseur unitaire des bandes.

When the polymeric material is foamed, the embodiment in which the layer is a tubular sheath obtained by extrusion is however preferred. Indeed, the fact of being able to directly extrude a foamed sheath has many advantages compared to the use of a layer produced by winding a strip of foamed material:

• Using short-pitch wound strips means that there may be a gap between each strip (typically filled with a fluid such as gas and/or water), which is detrimental in that it increases the overall thermal conductivity of the layer.
• It is generally not necessary to insert an additional polymeric layer on the inner side of the polymeric material layer, and the absence of this layer improves thermal insulation because the polymeric material layer is closer to the transported fluid. Indeed, the more the polymeric material layer is on the outer side of the pipe, the less effective it is at thermal insulation, and conversely, the more it is on the inner side (therefore closer to the transported fluid), the more effective it is at thermal insulation. Thus, the more layers there are on the inner side of the polymeric material layer, the further it is from the transported fluid, and the less effective it is at thermal insulation.
• The thickness of an insulating sheath obtained by extrusion can be more easily optimized than that of a layer obtained from winding strips, the thickness of the layer then being a multiple of the unit thickness of the strips.

When the layer is made of foamed polymeric material (whether it is a tubular sheath obtained by extrusion or made by helical winding of at least one strip), the foamed polymeric material preferably has closed-cell porosity, which prevents any interconnection between cells and therefore the passage of seawater and flooding of the annulus of the flexible pipe (i.e. the space between the layer of foamed polymeric material and the internal polymeric sheath of the pipe).

When the layer is made of foamed polymeric material (whether it is a tubular sheath obtained by extrusion or made by helical winding of at least one strip), it may also comprise two polymeric layers, one which covers the external surface of the layer of foamed polymeric material, and the other which covers the internal surface of the layer of foamed polymeric material. This polymeric layer can be considered as a skin of the layer of foamed polymeric material. This polymeric layer typically has a thickness of 10 microns to 1 mm. It makes it possible to limit, or even prevent, the diffusion of seawater and/or to protect the foamed polymeric material in the event of accidental tearing of the external sealing polymeric sheath and flooding of the annular space of the flexible pipe. The polymeric layers are generally created during the foaming process by adapting the process parameters. Alternatively, each polymeric layer(s) may be obtained by extrusion onto the layer of foamed polymeric material (this may be carried out in 2 passes, by coextrusion, in tandem) or by winding, preferably with a short pitch, strips of polymer and then welding them. The material of the polymeric layer useful as a protective sheath may be identical to or different from that of the foamed polymeric material (but the material of the polymeric layer useful as a protective sheath is not foamed). The layer of foamed polymeric material and the layer covering it may be unbonded, or bonded, whether or not by means of an adhesive.

In order to achieve thermal insulation efficiency and the ability to withstand high pressures and temperatures, it is necessary to have a compromise between the density of the foamed polymeric material and its compressive strength. For this purpose, a porosity rate of 10% to 80% is preferred, and 20% to 70%, and preferably 30% to 60%. The porosity rate can be determined by density measurement.

The diameter of the pores is preferably less than 200 microns, preferably less than 100 microns and even better less than 50 microns, as measured by microscopy, preferably scanning electron microscopy (SEM). In the case where the pores are of the ovoid type (stretched in the direction of extrusion), the above size is understood as the smallest diameter.

Each layer of polymeric material can be single-layer or multi-layer, for example two- or three-layer.

When the layer comprises several polymeric layers, the polymeric materials of the layers may be identical or different (for example, it may be two distinct polymeric materials in each layer of polymeric material, provided of course that at least one of the layers is of polymeric material as defined below). Typically, the other polymeric layer(s) is(are) free of PPE. Preferably, the polymeric material of this at least one other layer is chosen from polyolefins, fluoropolymers, in particular PVDF and PVC, advantageously superchlorinated PVC or PVCc.

In the embodiment described above in which the foamed polymeric material is coated on the inner side and the outer side with a polymeric layer useful as a protective sheath, the layer is three-layer (polymeric layer useful as a protective sheath / layer of foamed polymeric material / polymeric layer useful as a protective sheath).

Preferably, the layer of polymeric material is single-layer, which excludes multi-layer layers, whether the layers are not bonded together or bonded together, in particular by an adhesive or because they have been formed by coextrusion. A single layer rather than two or more makes it possible to avoid the accumulation of gas between the layers.

The polymeric material layer of the flexible pipe is typically tubular, generally has a diameter of 50 mm to 600 mm, preferably 50 to 400 mm, and/or a length of 1 m to 10 km.

According to a first alternative, the layer of polymeric material is an anti-wear layer.

Preferably, the polymeric material layer of the flexible pipe then has a thickness greater than 0.2 to 2 mm. The term "thickness" refers to the average thickness over the entire layer. Generally, the thickness of the layer is the same within ±5%, typically ±2%, at any point in the layer. This thickness can be measured with a caliper.

Particularly when the polymeric material layer is an anti-wear layer, the polymeric material layer can be located between two consecutive reinforcement layers. The polymeric material layer is then surrounded by two reinforcement layers. The polymeric material layer can be:

- not adjacent to the reinforcing layers surrounding it (there are then one or more layers between the polymeric material layer and each reinforcing layer),

- adjacent to one of the reinforcement layers or not adjacent to the other reinforcement layer,

- adjacent to each of the reinforcing layers. This is the preferred embodiment. In this case, the layer of polymeric material is the only layer between the two reinforcing layers.

When the layer of polymeric material is not adjacent to one of the reinforcing layers surrounding it, there may, for example, be a retaining layer between said reinforcing layer and the layer of polymeric material.

The polymeric material of the anti-wear layer is preferably non-foamed, which allows better mechanical resistance, particularly against creep.

The anti-wear layer can:

- either be a tubular sheath obtained by extrusion, typically on a reinforcing layer,

- or be made by helical winding, generally with a short pitch, of at least one strip of said polymeric material. The turns of the strip(s) are not necessarily welded together. Such an anti-wear layer is therefore generally not waterproof.

According to a second alternative, the layer of polymeric material is a thermal insulation layer.

Preferably, the layer of polymeric material of the flexible pipe then has a thickness greater than 3 mm, in particular greater than 4 mm, preferably greater than 5 mm, particularly preferably greater than 6 mm. The term “thickness” refers to the average thickness over the entire layer. Generally, the thickness of the layer is the same within ±5%, typically within ±2%, at any point in the layer. This thickness can be measured with a caliper.

Particularly when the polymeric material layer is a thermal insulation layer, the polymeric material layer is located between the outermost reinforcing layer and the outer polymeric sealing sheath.

Pipe structure and different layers

The pipe includes an internal sealing polymer sheath.

The material constituting the internal sealing polymer sheath must be chemically stable and capable of mechanically resisting the transported fluid and its characteristics (composition, temperature and pressure). The material must combine characteristics of ductility, resistance to time (generally, the pipe must have a lifespan of at least 20 years), mechanical resistance, heat and pressure. In particular, the material must be chemically inert with respect to the chemical compounds constituting the transported fluid or have aging kinetics compatible with the application.

Various polymer materials can be used in the internal polymeric sealing sheath of the subsea flexible pipeline, usually thermoplastic materials. The internal polymeric sealing sheath is, for example, made of polyolefin such as polyethylene, in particular medium or high density polyethylene, or polypropylene, polyamide, in particular polyamide 11 or 12, polyvinylidene fluoride (PVDF), copolymers of polyvinylidene fluoride and polyhexafluoropropylene (PVDF-HFP), poly(phenylene sulfide) (PPS), PAI (polyamide-imide), PEI (polyether-imide), PSU (polysulfone), PPSU (polyphenylsulfone), PES (polyethersulfone), PAS (polyarylsulfone), PPE (polyphenylene ether), PPS (polyphenylene sulfide), LCP (liquid crystal polymers), PPA (polyphthalamide), polyetheretherketone (PEEK), PEK (polyetherketone), PEEKK (polyetheretherketoneketone), PEKK (polyetherketoneketone), PEKEKK (polyetherketoneetherketoneketone), copolymers thereof, and/or mixtures thereof.

The internal polymeric sealing sheath generally has a diameter of 50 mm to 600 mm, preferably 50 to 400 mm, and/or a thickness of 1 mm to 150 mm, preferably 4 to 20 mm and/or a length of 1 m to 10 km.

The pipe includes at least two layers of reinforcement.

Typically, each reinforcing layer consists of a helical winding of at least one wire with non-contiguous turns. The wire is usually metallic or made of a composite material, particularly a composite based on a thermoplastic or thermosetting polymer, generally reinforced with fibers.

Typically, the pipe comprises at least one tensile armor ply as a reinforcing layer, preferably at least two tensile armor plies, generally an even number of tensile armor plies. The tensile armor plies are made of wires wound in long pitches. The wire is metallic or made of a composite material, in particular a composite based on a thermoplastic or thermosetting polymer, generally reinforced with fibers. The armor plies made of composite material are typically obtained by a pultrusion process.

The armor elements of a first layer are generally wound at an opposite angle to the armor elements of a second layer. Thus, if the winding angle relative to the pipe axis of the armor elements of the first layer is equal to + α, α being a helix angle less than or equal to 60° relative to the axis of the flexible pipe, the winding angle relative to the pipe axis of the armor elements of the second layer following the first layer is typically - α.

Generally, each of the tensile armor plies is unbonded to the adjacent polymeric layers. By “unbonded” is meant that the tensile armor plies are free to move relative to the adjacent polymeric layers (in particular relative to the polymeric material layer if it is adjacent). Typically, the tensile armor plies of the flexible pipe are not embedded in a polymeric or elastomeric sheath (in particular in the polymeric material layer). Similarly, there is preferably no adhesive between the reinforcement layers and the adjacent polymeric layer(s) (in particular the adjacent polymeric material layer).

Typically, in the case where the flexible pipe in service is required to withstand high pressures, the main function of the tensile armor layers is to absorb the axial forces linked on the one hand to the internal pressure prevailing inside the flexible pipe and on the other hand to the weight of the flexible pipe, particularly when it is suspended.

In one embodiment, the pipe comprises at least two tensile armor plies and the layer of polymeric material is located between two consecutive armor plies, and is preferably adjacent to each of these consecutive armor plies. The layer of polymeric material then generally provides the function of an anti-wear layer.

In another embodiment, the layer of polymeric material is located between the outermost armor ply and the outer polymeric sealing sheath. The layer of polymeric material then generally provides the function of a thermal insulation layer.

The flexible pipe may include, as a reinforcing layer, a reinforcing tape or retaining layer between the outer polymeric sealing sheath and the armor ply (the outermost ply when there are several armor plies). This reinforcing tape is formed, for example, of a high mechanical strength anti-buckling layer in order to limit the buckling of the tensile armor ply(ies) in the event that the pipe is subject to the reverse bottom effect phenomenon. This anti-buckling layer is, for example, made of aramid. The reinforcing tape is wrapped around the outermost armor ply, advantageously as indicated in API Standard 17J of 2021.

In one embodiment, the layer of polymeric material is located between the reinforcing tape and the outermost armor ply, and is preferably adjacent to the reinforcing tape and the outermost armor ply. The layer of polymeric material then generally provides the function of an anti-wear layer.

In another embodiment, the layer of polymeric material is located between the reinforcing tape and the external polymeric sealing sheath. The layer of polymeric material then generally provides the function of a thermal insulation layer.

The flexible pipe includes an external polymeric sealing sheath to prevent seawater from penetrating into the flexible pipe. This protects the reinforcement layers from seawater and therefore prevents the phenomenon of corrosion by seawater.

The external polymeric sealing sheath is advantageously made from a polyolefin, such as polyethylene, from a polyamide, such as PA11 or PA12, from a fluorinated polymer such as polyvinylidene fluoride (PVDF), or from a thermoplastic elastomer comprising a polyolefin, such as polyethylene or polypropylene, combined with an elastomer of the SBS (styrene butadiene styrene), SEBS (styrene ethylene butadiene styrene), EPDM (ethylene propylene diene monomer), polybutadiene, polyisoprene or polyethylene-butylene type.

The thickness of the external polymeric sealing sheath is, for example, between 5 mm and 15 mm.

The outer polymeric sealing sheath is generally the outermost layer of the flexible pipe (it is therefore not coated by any other layer).

Preferably, the inner polymeric sealing sheath and/or the outer polymeric sealing sheath (is) are free of PPE.

The pipe may also include a metal casing. If the pipe includes a metal casing, it is said to have a rough-bore. If the pipe does not have a metal casing, it is said to have a smooth-bore.

The main function of the metal casing is to absorb radial forces directed from the outside to the inside of the pipe in order to prevent the collapse of all or part of the pipe under the effect of these forces. These forces are notably linked to the hydrostatic pressure exerted by seawater when the flexible pipe is submerged. Thus, the hydrostatic pressure can reach a very high level when the pipe is submerged at great depth, for example 200 bar when the pipe is submerged at a depth of 2000 m, so it is often essential to provide the flexible pipe with a metal casing.

The metal casing also serves to prevent the internal polymeric sealing sheath from collapsing during rapid decompression of a flexible pipe that has transported hydrocarbons. Indeed, the gases contained in the hydrocarbons diffuse slowly through the internal polymeric sealing sheath and become partly trapped in the annular space between the internal polymeric sealing sheath and the external polymeric sealing sheath. Consequently, during a production shutdown causing rapid decompression of the interior of the flexible pipe, the pressure in this annular space may temporarily become significantly higher than the pressure inside the pipe, which in the absence of a metal casing would lead to the collapse of the internal polymeric sealing sheath.

The metal carcass is made up of longitudinal elements wound helically with a short pitch. These longitudinal elements are stainless steel strips or wires arranged in turns stapled to each other. Advantageously, the metal carcass is made by profiling a strip into an S shape and then winding it helically so as to staple the adjacent turns together.

Therefore, generally, for the transport of hydrocarbons, a pipe with a metal casing is preferred. Furthermore, when the pipe is intended both to transport hydrocarbons and to be submerged at great depth, then the metal casing becomes essential in most applications.

The metal carcass is generally adjacent to the internal polymeric sealing sheath. Since the metal carcass is not adjacent to another reinforcing layer, it is not subject to frictional wear and is therefore preferably not coated with an anti-wear layer.

Two preferred variants are described below for the structure of the pipe, depending on whether it is a usual flexible pipe, typically whose structure is as described in the standard documents API RP 17B (2021) and API 17J (2021), or a hybrid pipe.

“Usual” flexible pipe

According to a first variant, the flexible pipe comprises (or is made up of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- possibly a pressure vault as a reinforcing layer,

- at least one tensile armor layer as a reinforcing layer, preferably at least two tensile armor layers,

- possibly a reinforcing tape as a reinforcing layer,

- the external polymeric sealing sheath,

the pipe further comprising, between the internal polymeric sealing sheath and the external polymeric sealing sheath, at least one layer of polymeric material as defined above.

The pressure vault is an additional reinforcing layer intended to absorb the radial forces linked to the internal pressure and directed from the inside to the outside of the pipe, in order to prevent the internal polymer sheath from bursting under the effect of the pressure prevailing inside the pipe.

Usually, the pressure vault is located towards the inside of the pipe. It is a more internal layer than the tensile armor layer(s). The pressure vault is made up of longitudinal elements wound with a short pitch, for example metal wires of shape Z (zeta), C, T (theta), U, K, X or I, and/or at least one aramid strip, and/or at least one composite strip comprising a polymer matrix in which reinforcing fibers are embedded, for example glass, carbon, aramid, and/or basalt fibers.

Its presence is not essential, particularly when the helix angles of the wires constituting the tensile armor plies are close to 55°. Indeed, this particular helix angle gives the tensile armor plies the capacity to absorb, in addition to axial forces, the radial forces exerted on the flexible pipe and directed from the inside to the outside of the pipe.

Furthermore, for high internal pressures, it is known to add a hoop made by winding at least one metal wire, advantageously of rectangular cross-section, with a short pitch around the pressure vault to increase the burst resistance of the pipe.

Preferably and in particular for deep-sea applications, in addition to the tensile armor layers, the flexible pipe according to the first variant comprises a pressure vault and, possibly, a hoop, inserted between the internal polymeric sealing sheath and the tensile armor layers.

The flexible pipe may further comprise, as a reinforcing layer or retaining layer, a reinforcing tape between the outer polymeric sealing sheath and the armor ply (the outermost ply when there are several armor plies). This reinforcing tape is formed, for example, of an anti-buckling layer of high mechanical strength in order to limit the buckling of the tensile armor ply(ies) in the event that the pipe is subject to the reverse bottom effect phenomenon. This anti-buckling layer is, for example, made of aramid. The reinforcing tape is wrapped around the outermost armor ply, advantageously as indicated in API Standard 17J of 2021.

The flexible pipe is preferably of the unbonded type, that is to say that its reinforcing layers, such as the tensile armor ply(ies) and/or the pressure vault, are unbonded to the adjacent polymeric layer(s), such as the inner polymeric sealing sheath and/or the outer polymeric sealing sheath and/or the layer of tubular polymeric material as defined above. By “unbonded” is meant that the reinforcing layers are free to move relative to the polymeric layers. Typically, the reinforcing layers of the flexible pipe are not embedded in a polymeric or elastomeric sheath. Similarly, there is preferably no adhesive between the reinforcing layers and the adjacent polymeric layer(s).

Alternatively, the flexible pipe is of the bonded type, that is to say that at least one of the reinforcing layers, often metallic or made of composite material, is bonded to an adjacent polymeric layer. If the reinforcing layer is sandwiched between two polymeric layers, one or both faces of the reinforcing layer may be bonded to the adjacent polymeric layer(s). Each of the reinforcing layers may be bonded to an adjacent polymeric layer, by one face of the reinforcing layer, or by both faces when the reinforcing layer is sandwiched between two polymeric layers. For example, the internal polymeric sealing sheath may be bonded to the innermost reinforcing layer. This bond may be obtained through the use of an adhesive or an elastomer between two adjacent layers, or by embedding at least one face of the reinforcing layer in the adjacent polymeric or elastomeric sheath.

The layer comprising a polymeric material as defined is typically:

- between the pressure vault and the hoop (this is generally an anti-wear layer),

- between the hoop and the innermost tensile armor layer (this is generally an anti-wear layer),

- between the pressure vault and the innermost tensile armor layer (this is generally an anti-wear layer), and/or

- between two consecutive layers of tensile armor (this is generally an anti-wear layer) and/or

- between the outermost tensile armor layer and the reinforcing tape (this is generally an anti-wear layer), and/or

- if the reinforcing tape is present, between the reinforcing tape and the external polymeric sealing sheath (this is then generally a thermal insulation layer), or, if the reinforcing tape is absent, between the outermost tensile armor layer and the external polymeric sealing sheath (this is then generally a thermal insulation layer).

In a first embodiment of this first variant, the pipe comprises at least two tensile armor plies and the layer of polymeric material as defined above is located between two consecutive armor plies, and is preferably adjacent to each of these two consecutive armor plies. The flexible pipe then comprises (or even consists of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- possibly a pressure vault as a reinforcing layer,

- at least two tensile armor plies as reinforcing layers, the layer of polymeric material as defined above being located between two consecutive armor plies and preferably being adjacent to each of these consecutive armor plies,

- possibly a reinforcing tape as a reinforcing layer, and

- the external polymeric sealing sheath.

Typically, when the flexible pipe comprises two layers of tensile armor, the flexible pipe comprises (or is made up of) from the inside towards
the exterior:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- possibly a pressure vault as a reinforcing layer,

- an internal tensile armor layer as a reinforcing layer,

- the layer of polymeric material as defined above, preferably adjacent to the internal tensile armor layer,

- an external tensile armor layer as reinforcing layers, preferably adjacent to the polymeric material layer,

- possibly a reinforcing tape as a reinforcing layer, and

- the external polymeric sealing sheath.

When the pipe comprises more than two tensile armor plies, it comprises a layer of polymeric material as defined above located between two consecutive armor plies. Preferably, it then comprises several layers of polymeric material as defined above, typically a layer of polymeric material as defined between all the consecutive armor plies. If “m” is the number of armor plies, then there are “m-1” layers of polymeric material.

In a second embodiment of this first variant, the pipe comprises a pressure vault and the layer of polymeric material is located between the pressure vault and the tensile armor ply (or the innermost tensile armor ply when there are several tensile armor plies).

The flexible pipe then includes (or is made up of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a pressure vault as a reinforcing layer,

- a layer of polymeric material as defined above, preferably adjacent to the pressure vault,

- at least one internal tensile armor ply as a reinforcing layer, preferably adjacent to the polymeric material layer,

- an external tensile armor layer as a reinforcing layer,

- possibly a reinforcing tape as a reinforcing layer, and

- the external polymeric sealing sheath.

The first embodiment and the second embodiment of the first variant can be combined with each other. Thus, in a third embodiment, the pipe comprises a pressure vault and at least two tensile armor plies, and at least two layers of polymeric material as defined above, where a first layer of polymeric material is located between the pressure vault and the innermost tensile armor ply and is preferably adjacent to them, and a second layer of polymeric material is located between two consecutive armor plies and is preferably adjacent to each of these two consecutive armor plies. When the pipe comprises two armor plies, it then comprises (or is made up of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a pressure vault as a reinforcing layer,

- a first layer of polymeric material as defined above, preferably adjacent to the pressure vault,

- an internal tensile armor ply as a reinforcing layer, wherein the internal tensile armor ply is preferably adjacent to the first layer of polymeric material,

- a second layer of polymeric material as defined above, preferably adjacent to the internal tensile armor layer,

- an external tensile armor ply as a reinforcing layer, wherein the external tensile armor ply is preferably adjacent to the second layer of polymeric material,

- possibly a reinforcing tape as a reinforcing layer, and

- the external polymeric sealing sheath.

These first, second and third embodiments of the first variant are particularly suitable when the layer of polymeric material is useful as an anti-wear layer. Thus, generally, the layer(s) of polymeric material defined in the first, second and third embodiments is (are) one or more anti-wear layers.

In a fourth embodiment of this first variant, the pipe comprises a layer of polymeric material as defined above between the outermost reinforcing layer and the outer polymeric sealing sheath.

The flexible pipe then typically includes (or is made up of), from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- possibly a pressure vault as a reinforcing layer,

- at least one tensile armor layer as a reinforcing layer, preferably at least two tensile armor layers,

- possibly a reinforcing tape as a reinforcing layer,

- the layer of polymeric material as defined above,

- the external polymeric sealing sheath.

This fourth embodiment is particularly suitable when the layer of polymeric material is useful as a thermal insulation layer. Thus, generally, the layer(s) of polymeric material defined in the fourth embodiment is(are) an insulating sheath(s).

This fourth embodiment of the first variant may be combined with each of the first, second and third embodiments of the first variant defined above. Such a combination is particularly preferred when it is desired that the pipe comprises both a thermal insulation layer and one or more wear layers. For example, the flexible pipe may comprise (or even consist of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- possibly a pressure vault as a reinforcing layer,

- a first layer of polymeric material as defined above,

- at least two tensile armor plies as reinforcing layers, a second layer of polymeric material as defined above being located between two consecutive armor plies and preferably being adjacent to these consecutive armor plies,

- possibly a reinforcing tape as a reinforcing layer,

- a third layer of polymeric material as defined above,

- the external polymeric sealing sheath.

Hybrid flexible driving

In a second variant, the conduct includes from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a composite reinforcing structure as a reinforcing layer, the composite reinforcing structure comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix reinforced with fibers,

- possibly a sealing layer made of a thermoplastic material,

- at least one tensile armor layer as a reinforcing layer,

- possibly a reinforcing tape,

- the external polymeric sealing sheath,

the pipe further comprising, between the internal polymeric sealing sheath and the external polymeric sealing sheath, at least one layer of polymeric material as defined above.

The metal frame is typically as described above.

The tubular reinforcement structure may be unbonded to the tubular internal polymer sheath, or may be bonded to the tubular internal polymer sheath, whether by means of an adhesive or not.

The composite reinforcement structure comprises at least one, preferably a plurality of laminated reinforcement layers, and optionally, an anti-delamination layer interposed between at least two reinforcement layers.

Each laminated reinforcement layer consists of a superposition of composite reinforcement layers. Each reinforcement layer consists of a polymer matrix and reinforcing fibers embedded in the polymer matrix.

Preferably, each reinforcing layer of the composite reinforcing structure is formed from a winding of at least one composite strip having several layers of fibers embedded in a thermoplastic matrix, each strip having a length greater than at least 10 times its width and at least 10 times its thickness.

For example, the length of each composite strip is greater than 100 m and is between 100 m and 4500 m and/or the width of each composite strip is between 6 mm and 50 mm and/or the thickness of each composite strip is between 0.1 mm and 1 mm.

The number of composite layers within the reinforcing composite structure is typically from 2 to 300, in particular from 10 to 200, preferably from 20 to 100. Generally, this number is always even to ensure the balance of the reinforcing composite structure.

The thickness of each laminated composite layer is generally between 1 mm and 30 mm.

Preferably, each composite strip has at 23°C, a tensile modulus greater than 10 GPa, in particular between 30 GPa and 170 GPa, as measured by Standard NF EN 2561, January 1996, an elongation at break greater than 1%, in particular between 1% and 5%, as measured by Standard NF EN 2561, January 1996, and/or a maximum tensile strength greater than 100 MPa, and in particular between 350 MPa and 3500 MPa as measured by Standard NF EN 2561, January 1996.

The absolute value of the winding helix angle of each composite strip relative to the axis of the flexible pipe is generally between 20° and 85°, typically between 50° and 85°, preferably between 55° and 70°. This ensures elongation of the composite under the effect of internal pressure. Such a helix angle also allows adequate cooperation with the armor plies.

The matrix polymer of each reinforcement layer is thermoplastic. For example, the polymer forming the matrix is selected from a polyolefin such as polyethylene, a polyamide such as PA11 or PA12, a fluoropolymer such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride and polyhexafluoropropylene copolymers (PVDF-HFP), PEK (polyetherketone), PEEK (polyetheretherketone), PEEKK (polyetheretherketoneketone), PEKK (polyetherketoneketone), PEKEKK (polyetherketoneetherketoneketone), PAI (polyamide-imide), PEI (polyether-imide), PSU (polysulfone), PPSU (polyphenylsulfone), PES (polyethersulfone), PAS (polyarylsulfone), PPE (polyphenylene ether), PPS (polyphenylene sulfide), LCP (liquid crystal polymers), PPA (polyphthalamide), copolymers thereof and/or mixtures thereof or a mixture of one or more of these with a polysiloxane, PTFE (polytetrafluoroethylene) or PFPE (perfluoropolyether).

The polymer of the matrix is advantageously of the same nature as that of the internal polymeric sealing sheath. By "of the same nature" is meant the polymer of the internal polymeric sealing sheath and the polymer of the thermoplastic matrix are capable of melting and forming an intimate mixture, without phase separation, after cooling.

The fibers of each reinforcing layer of the composite reinforcement structure are generally made of glass, carbon, aramid, and/or basalt, and preferably carbon.

The fibers are preferably arranged, for each reinforcing layer, unidirectionally in the thermoplastic matrix. They are then parallel to each other. Alternatively, the reinforcing fibers are crossed in two orthogonal directions, or are arranged randomly in the matrix.

The length of the reinforcing fibers in each reinforcing layer is greater than 100 m, and is in particular between 100 m and 4500 m.

As explained above, the composite reinforcement structure provides radial resistance to the flexible pipe that contains it. The composite reinforcement structure prevents the internal polymer sealing sheath from being crushed during rapid decompression of the pipe carrying the fluid.

The flexible pipe may be free of a sealing layer of thermoplastic material around the reinforcing structure. Preferably, the innermost tensile armor layer of the pipe is then not bonded to the composite reinforcing structure.

Alternatively, the flexible pipe may comprise a sealing layer made of a thermoplastic material around the composite reinforcement structure. The presence of the sealing layer makes it possible in particular to protect the composite reinforcement structure against the harmful effects of the components present in the annulus, in particular by avoiding the formation of discontinuities. Preferably, the innermost tensile armor layer of the pipe is then not bonded to the sealing layer made of a thermoplastic material.

The sealing layer is formed from a thermoplastic material. For example, the polymer forming the sealing layer is selected from a polyolefin, optionally crosslinked, such as polyethylene or polypropylene; a thermoplastic elastomer (TPE) such as thermoplastic polyurethane (TPE-U or TPU) or styrenic copolymers (TPE-S or TPS) or vulcanized polypropylene and ethylene-propylene-diene copolymers (PP-EPDM) (TPE-V or TPV); a polyamide such as PA11 or PA12; or a fluoropolymer such as polyvinylidene fluoride (PVDF) or copolymers of polyvinylidene fluoride and polyhexafluoropropylene (PVDF-HFP). Alternatively, the sealing layer comprises a polymer selected from PEK (polyetherketone), PEEK (polyetheretherketone), PEEKK (polyetheretherketoneketone), PEKK (polyetherketoneketone), PEKEKK (polyetherketoneetherketoneketone), PAI (polyamide-imide), PEI (polyether-imide), PSU (polysulfone), PPSU (polyphenylsulfone), PES (polyethersulfone), PAS (polyarylsulfone), PPE (polyphenylene ether), PPS (polyphenylene sulfide), LCP (liquid crystal polymers), PPA (polyphthalamide) and/or mixtures thereof or a mixture of one or more of these with a polysiloxane, PTFE (polytetrafluoroethylene) or PFPE (perfluoropolyether).

The polymer of the sealing layer is advantageously of the same nature as that of the thermoplastic matrix of the reinforcing layer, more advantageously of the same nature as that of the thermoplastic matrix of the reinforcing layer and that of the internal polymeric sealing sheath.

The thickness of the sealing layer is for example between 1 mm and 20 mm, preferably it is less than or equal to 15 mm, preferably from 3 mm to 10 mm.

The sealing layer may be formed from a single piece of polymeric tubular sheath. The sealing layer is then typically formed from an extruded thermoplastic polymer tubular sheath.

Alternatively, the sealing layer may be made from a discontinuous structure, for example from an assembled polymeric strip. For example, it is formed by winding at least two strips of a thermoplastic material and welding the at least two strips together.

When the sealing layer is formed from a tubular sheath, it is advantageously obtained by extruding a thermoplastic material around the composite reinforcement structure. In this first case, the thickness of the sealing layer is typically 3 to 15 mm, preferably 4 mm to 10 mm.

When the sealing layer is formed from an assembled polymeric strip, it is advantageously produced by winding thermoplastic strips of a polymer as described above, followed by a step of welding the thermoplastic strips. Preferably, the turns of a first layer are joined (edge to edge without overlap) and the turns of an upper layer are arranged so as to have an overlap of two adjacent, lower strips ensuring the sealing of the sealing layer. In this second case, the thickness of the sealing layer is typically less than 3 mm, advantageously less than 2 mm, even more advantageously less than 1 mm.

The sealing layer may or may not be bonded to the reinforcing composite structure.

The composite reinforcement structure may have low tensile strength and may tend to elongate under the effect of axial forces. By absorbing axial forces, the pipe's armor plies advantageously prevent the composite reinforcement structure from elongating.

The layer comprising a polymeric material as defined is typically:

- between the composite reinforcement structure and the innermost tensile armor layer (this is generally an anti-wear layer), and/or

- between two consecutive tensile armor layers (the layer comprising a polymeric material is then generally an anti-wear layer) and/or

- between the outermost tensile armor layer and the reinforcing tape if the latter is present (the layer is then generally an anti-wear layer), and/or

- if the reinforcing tape is present, between the reinforcing tape and the external polymeric sealing sheath (this is then generally a thermal insulation layer), or, if the reinforcing tape is absent, between the outermost tensile armor layer and the external polymeric sealing sheath (this is then generally a thermal insulation layer).

In a first embodiment of this second variant, the pipe comprises at least two tensile armor plies and the layer of polymeric material as defined above is located between two consecutive armor plies and is preferably adjacent to each of these two consecutive armor plies.

The flexible pipe then includes (or is made up of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a composite reinforcing structure as a reinforcing layer, the composite reinforcing structure comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix reinforced with fibers,

- possibly a sealing layer made of a thermoplastic material,

- at least two tensile armor plies as reinforcing layers, the layer of polymeric material as defined above being located between two consecutive armor plies and preferably being adjacent to each of these consecutive armor plies,

- possibly a reinforcing tape,

- the external polymeric sealing sheath.

Typically, when the flexible pipe comprises two layers of tensile armor, the flexible pipe comprises (or is made up of) from the inside towards
the exterior:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a composite reinforcing structure as a reinforcing layer, the composite reinforcing structure comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix reinforced with fibers,

- possibly a sealing layer made of a thermoplastic material,

- an internal tensile armor layer as a reinforcing layer,

- the layer of polymeric material as defined above, preferably adjacent to the internal tensile armor layer,

- an external tensile armor layer as reinforcing layers, preferably adjacent to the polymeric material layer,

- possibly a reinforcing tape,

- the external polymeric sealing sheath.

When the pipe comprises more than two tensile armor plies, it comprises a layer of polymeric material as defined above located between two consecutive armor plies. Preferably, it then comprises several layers of polymeric material as defined above, typically a layer of polymeric material as defined between all the consecutive armor plies. If “m” is the number of armor plies, then there are “m-1” layers of polymeric material.

This first embodiment of the second variant is particularly suitable when the layer of polymeric material is useful as an anti-wear layer. Thus, generally, the layer(s) of polymeric material defined in the first embodiment is (are) one or more anti-wear layers.

In a second embodiment of this second variant, the pipe comprises a layer of polymeric material as defined above between the reinforcing structure and the tensile armor ply (the innermost tensile armor ply when there are several).

The flexible pipe then typically includes (or is made up of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a composite reinforcing structure as a reinforcing layer, the composite reinforcing structure comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix reinforced with fibers,

- possibly a sealing layer made of a thermoplastic material,

- the layer of polymeric material as defined above,

- at least one tensile armor layer as a reinforcing layer, preferably at least two tensile armor layers,

- possibly a reinforcing tape,

- the external polymeric sealing sheath.

This second embodiment of the second variant is particularly suitable for the first alternative defined above, that is to say when the layer of polymeric material is useful as an anti-wear layer. Thus, generally, the layer(s) of polymeric material defined in the first embodiment is(are) one(s) of the anti-wear layers.

In a third embodiment of this second variant, the pipe comprises a layer of polymeric material as defined above between the outermost reinforcing layer and the outer polymeric sealing sheath.

The flexible pipe then typically includes (or is made up of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a composite reinforcing structure as a reinforcing layer, the composite reinforcing structure comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix reinforced with fibers,

- possibly a sealing layer made of a thermoplastic material,

- at least one tensile armor layer as a reinforcing layer, preferably at least two tensile armor layers,

- possibly a reinforcing tape,

- the layer of polymeric material as defined above,

- the external polymeric sealing sheath.

This third embodiment of the second variant is particularly suitable when the layer of polymeric material is useful as a thermal insulation layer. Thus, generally, the layer(s) of polymeric material defined in the second embodiment of the second variant is(are) an insulating sheath(s).

This third embodiment of the second variant may be combined with the first embodiment and/or the second embodiment of the second variant defined above. Such a combination is particularly preferred when it is desired that the pipe comprises both a thermal insulation layer and one or more wear layers. For example, the flexible pipe may comprise (or even consist of) from the inside to the outside:

- possibly a metal frame,

- the internal polymeric sealing sheath,

- a composite reinforcing structure as a reinforcing layer, the composite reinforcing structure comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix reinforced with fibers,

- possibly a sealing layer made of a thermoplastic material,

- the layer of polymeric material as defined above,

- at least two tensile armor plies as reinforcing layers, a first layer of polymeric material as defined above as an anti-wear layer, the first layer of polymeric material being located between two consecutive armor plies and preferably being adjacent to each of these consecutive armor plies,

- possibly a reinforcing tape,

- a second layer of polymeric material as defined above as a thermal insulation layer,

- the external polymeric sealing sheath.

Whatever the structure of the pipe and in particular whatever the variant and the embodiment of the variant considered, the pipe may also comprise one or more additional polymeric layers between two consecutive layers.

For example, the pipe may include a retaining layer either between the outer polymer sheath and the tensile armor ply (the outermost tensile armor ply when there are several tensile armor plies), or between two consecutive tensile armor plies.

According to a second subject, the invention relates to the method for preparing the pipe defined above comprising the association of at least one layer of polymeric material as defined above with an internal polymeric sealing sheath, at least two reinforcing layers, an external polymeric sealing sheath and optionally with the other additional layer(s), in particular those defined above.

The embodiments/alternatives/variants defined above for the other objects are applicable.

The method may comprise preparing the at least one layer of polymeric material as defined above.

When the layer of polymeric material as defined above is a tubular sheath, it is typically obtained by extrusion. The extrusion is typically carried out on the layer adjacent to the inner side of the layer of polymeric material.

Alternatively, the layer of polymeric material as defined above is formed by helical winding of at least one strip of polymeric material as defined above, this winding being typically carried out on the layer of the pipe which is adjacent on the internal side to the layer of polymeric material, then possibly abutting the strips together. The strips can be joined, typically by welding, in particular by ultrasound, by laser, or by covering then heating, for example in contact with a heating plate until melting, or by bonding (with glue, tape or adhesive).

The method may comprise a prior or simultaneous step of preparing the at least one strip of polymeric material as defined above, generally by extrusion. The polymeric material as defined above has the advantage of being easy to extrude. Generally, the polymeric material as defined above is extruded in the form of thin, long sheets, then these are slit to obtain the strips of the desired width (from 30 to 200 mm, preferably from 40 to 150 mm, typically 40, 75, 100 or 126 mm). Alternatively, the polymeric material as defined above is extruded directly in the form of a strip having the desired width. The strips are then packaged for installation on a pipe production device.

When the polymeric material of the layer is foamed, the method may comprise a step of foaming the polymeric material.

The polymeric material can be foamed chemically, physically, or by combining both techniques.

Reference can be made to the state of the art on chemical foaming (e.g. Handbook of Foaming and Blowing Agents, 1st Edition - January 13, 2017, George Wypych).

Physical foaming is commonly referred to as "direct gassing" and generally involves the solubilization of gases, usually _CO2 and/or _N2, in the molten polymeric material. An example is the MuCell ^® process, which uses a supercritical fluid to produce a microcellular foamed material by extrusion. The gas dissolves in the polymeric material under the action of heat and pressure. Additives are optionally introduced, such as blowing agents, which can either influence the size of the cells (also called pores) and the quantity of open or closed cells, or provide specific properties (flame retardancy, liquid absorption capacity, etc.). Several extruder variants are developed for this "direct gassing" process: very long single-screw extruders (minimum length L equal to 30 times the diameter D (L/D=30), tandem extruders, twin-screw extruders for example. These extruders are capable not only of melting and mixing the components of the polymeric material (PPE, possibly other thermoplastic polymer and/or thermoplastic elastomer, additive), but also of dispersing the physical blowing agent, cooling the polymeric material containing the blowing agent and maintaining sufficient pressure until the mixture is extruded.

In the chemical foaming process, gas is generated in the polymeric material by the decomposition of at least one chemical foaming agent (CFA) dispersed in the polymeric material. The CFAs decompose into gas (diffusing in the polymeric material) and solid particles. The latter serve as nucleation sites during foaming. A nucleating agent can also be used to create sites from which pores can grow. Standard extruders can be used for this process (length generally around 24 times the diameter). However, the screw must have sufficient mixing capacity so that the chemical foaming agents are well distributed throughout the mass. Accurate and stable temperature control is necessary to maintain a constant expansion rate.

Whether foaming is physical or chemical, it can lead to a collapse of the polymeric material's melt strength (reduction in viscosity), which can sometimes make it difficult to obtain homogeneous porosity. In order to increase the viscosity of the polymeric material in the molten state, a chemical agent that is a precursor to crosslinking (e.g. peroxide) and/or grafting (coupling agent) of the polymer chains can be added to the polymeric material in order to chemically modify its structure and thus adjust its elongational viscosity during foaming.

According to a third object, the invention relates to an underwater pipe capable of being obtained by the aforementioned method.

According to a fourth object, the invention relates to the use of the aforementioned underwater pipeline for the transport of hydrocarbons and/or gas. The invention also relates to a method for transporting hydrocarbons and/or gas, typically methane, hydrogen sulfide, carbon dioxide or a mixture thereof, comprising the transport of hydrocarbons and/or gas within a pipeline as defined above.

The embodiments/alternatives/variants defined above for the other objects are applicable.

The subsea pipeline according to the invention is suitable for the transport of gas, typically methane, hydrogen sulfide, carbon dioxide or a mixture thereof, in particular carbon dioxide for reinjection into the subsea reservoir from which the hydrocarbons are extracted.

Advantageously, and in particular thanks to the PPE-based polymeric material of the polymeric material layer defined above, the pipe defined above is capable of withstanding temperatures greater than or equal to 110°C, preferably greater than or equal to 130°C, in particular greater than or equal to 150°C, or even greater than or equal to 170°C. Thus, the hydrocarbons and/or gases transported may have a temperature greater than or equal to 130°C, in particular greater than or equal to 150°C, or even greater than or equal to 170°C.

Flexible pipes can be used at great depths, typically up to 3000 meters deep.

According to a fifth subject, the invention relates to the use of a layer of polymeric material comprising at least 50% by weight, in particular at least 60%, preferably at least 65% by weight, of poly(p-phenylene ether) (PPE), and having a flexural modulus measured at 20°C according to standard ASTM D 638-14 greater than 2000 MPa as a thermal insulation layer and/or as an anti-wear layer in a flexible underwater pipe intended for the transport of hydrocarbons and/or gas comprising from the inside to the outside:

- an internal polymeric sealing sheath,

- at least two layers of reinforcement,

- an external polymeric sealing sheath.

The embodiments/alternatives/variants defined above for the other objects are applicable.

Other features and advantages of the invention will emerge from reading the description given below of particular embodiments of the invention, given for informational but non-limiting purposes, with reference to the figures and examples which follow.

FIG. 1 There FIG. 1 is a partial schematic perspective view of a “usual” flexible pipe.

The flexible pipe 8 has a central section illustrated in part on the FIG. 1 It delimits an internal passage for the circulation of hydrocarbons or gas which extends along an axis A-A', between the upstream end and the downstream end of the flexible pipe 8. It opens out through the end pieces (not shown).

There FIG. 1 illustrates a pipe in accordance with the invention comprising (or even consisting of), from the outside to the inside:

- an external polymeric sealing sheath 10,

- a thermal insulation layer 11 comprising a polymeric material as defined above,

- an external layer of tensile armor 12 produced by helical winding with a long pitch of a longitudinal metallic or composite material element,

- a first anti-wear layer 14 comprising a polymeric material as defined above,

- an internal layer of tensile armor 16 produced by helical winding with a long pitch of a longitudinal metal or composite material element (in the opposite direction to the helical winding of the longitudinal element of the external layer of tensile armor 12),

- a second anti-wear layer 18 comprising a polymeric material as defined above,

- a pressure vault 20 produced by helical winding with a short pitch of a longitudinal element,

- an internal polymeric sealing sheath 22, and

- an internal carcass 24 for absorbing radial crushing forces.

The conduct represented in the FIG. 1 understand :

- a first layer comprising a polymeric material as defined above to form a first anti-wear layer 14 between the two tensile armor plies 12, 16,

- a second layer of polymeric material as defined above to form a second anti-wear layer 18 between the pressure vault 20 and the internal tensile armor layer 16,

- a third layer of polymeric material as defined above to form a thermal insulation layer 11 between the external polymeric sealing sheath 10 and the external tensile armor layer 12.

The first anti-wear layer 14, the second anti-wear layer 18 and the thermal insulation layer 11 may independently be a sheath of polymeric material as defined above, typically obtained by extrusion, or a layer produced by helical winding of at least one strip of a polymeric material as defined above.

Thanks to these two anti-wear layers 14, 18, the tensile armor plies 12, 16 and the pressure vault 20 are not in contact with each other, so that, when the flexible pipe bends, there is no wear due to friction of the reinforcement layers against each other.

Thanks to the thermal insulation layer 11, the flexible pipe is thermally insulated and there is less heat loss between the inside and outside of the pipe.

Due to the presence of the internal carcass 24, this pipe is said to have a rough bore. The invention could also be applied to a so-called smooth-bore pipe, not having an internal carcass.

The invention could be applied to a pipe comprising only one of the three layers comprising a polymeric material as defined above, or only two of these three layers.

Likewise, it would not be outside the scope of the present invention to remove the pressure vault 20 and the anti-wear layer 18, and to maintain the anti-wear layer 14 and/or the thermal insulation layer 11.

On the FIG. 1 , only two tensile armor plies 12 and 16 are shown, but the pipe could also comprise one or more additional pairs of tensile armor. The anti-wear layer may then be present between two successive armor plies. There may also be an anti-wear layer between each of the armor plies. For example, if there are four armor plies, the pipe may comprise, from the outside to the inside, an outermost armor ply, a first anti-wear layer of polymeric material as defined above, an outer intermediate armor ply, a second anti-wear layer of polymeric material as defined above, an inner intermediate armor ply, a third anti-wear layer of polymeric material as defined above, an innermost armor ply, the first, second and third anti-wear layers being identical to each other or different.

The flexible conduit may also include layers not shown in the FIG. 1 , such as a retaining layer, for example between the external polymeric sheath 10 and the external tensile armor ply 12, or between two tensile armor plies 12 and 16, or in contact either with the internal face of the anti-wear layer 14, or with its external face.

FIG. 2 There FIG. 2 is a partially cutaway perspective view of a hybrid-type flexible pipe according to the invention.

The flexible pipe 28 has a central section illustrated in part on the FIG. 2 It delimits an internal passage for the circulation of hydrocarbons or gas which extends along an axis A-A', between the upstream end and the downstream end of the flexible pipe 28. It opens out through the end pieces (not shown).

The flexible pipe 28 comprises, from the inside to the outside:

- an internal polymeric sealing sheath 30,

- a tubular composite reinforcement structure 31, covering the tubular sheath 30 and being linked to it,

- a sealing layer 32,

- a first anti-wear layer 33 comprising a polymeric material as defined above,

- an internal armor layer 34 (not bonded to the sealing layer 32 and not bonded to the first anti-wear layer 33) produced by helical winding with a long pitch of a longitudinal metal or composite material element,

- a second anti-wear layer 35 comprising a polymeric material as defined above,

- an external armor layer 36 produced by helical winding with a long pitch of a longitudinal element 50 made of metal or composite material (in the opposite direction to the helical winding of the longitudinal element of the internal tensile armor layer 34),

- a thermal insulation layer 37 comprising a polymeric material as defined above,

- an external polymeric sealing sheath 38.

The conduct represented in the FIG. 2 understand :

- a first layer comprising a polymeric material as defined above to form a first anti-wear layer 33 between the composite reinforcement structure 31 and the internal tensile armor ply 34,

- a second layer comprising a polymeric material as defined above to form a second anti-wear layer 35 between the two tensile armor plies 34, 36,

- a third layer of polymeric material as defined above to form a thermal insulation layer 37 between the external tensile armor layer 36 and the external polymeric sealing sheath 38.

The first anti-wear layer 33, the second anti-wear layer 35 and the thermal insulation layer 37 may independently be a sheath of polymeric material as defined above, typically obtained by extrusion, or a layer produced by helical winding of at least one strip of a polymeric material as defined above.

Thanks to these two anti-wear layers 33, 35, the tensile armor plies 34, 36 and the reinforcement structure 31 are not in contact with each other, so that, when the flexible pipe bends, there is no wear due to friction of the reinforcement layers against each other.

Thanks to the thermal insulation layer 37, the flexible pipe is thermally insulated and there is less heat loss between the inside and outside of the pipe.

The flexible pipe 28 is devoid of a metal casing; it is designated by the English term “smooth bore”. The internal surface of the internal polymeric sealing sheath 30 directly delimits the internal passage for the flow and transport of fluids. It would not be outside the scope of the invention if a metal casing were present. This casing would then be coated with the internal polymeric sealing sheath 30.

There FIG. 2 illustrates an alternative in which the thermoplastic composite pipe of the conduit comprises a sealing layer 32 made of a thermoplastic material. It would not be outside the scope of the invention if this layer 32 were absent.

The composite reinforcement structure 31 comprises a winding of at least two laminated reinforcement layers. Each laminated reinforcement layer comprises a superposition of composite reinforcement layers. Each composite reinforcement layer comprises a thermoplastic matrix 40 and fibers 42 embedded in the thermoplastic matrix 40.

Preferably, each composite layer of the reinforcing structure 31 is formed from a winding of at least one composite strip 44 having several layers of carbon fibers 42 embedded in a thermoplastic matrix 40, each strip typically having a length greater than at least 10 times its width and at least 10 times its thickness.

Typically, when producing each composite reinforcing layer 21, the or each composite strip 44 is wound helically around the internal polymeric sealing sheath 30, and is heated to cause partial melting of the thermoplastic matrix 40, and bonding with the successive turns of the composite strip 44 and the internal polymeric sealing sheath 40, and possibly with the sealing layer 32 made of a thermoplastic material. Advantageously, the composite strips 44 are wound helically around the external surface defined by the internal polymeric sealing sheath 30, generally with an absolute value of the winding helix angle as defined above of each composite strip 44 relative to the axis A-A' of the internal polymeric sealing sheath 30.

Advantageously, the operations are repeated with several concentric layers to form the composite reinforcement structure 31 with other composite strips 44, as described previously. The composite reinforcement structure 31 is thus manufactured layer by layer, each new outer layer having a thickness substantially equal to that of a composite strip 44.

If present, the sealing layer 32 of thermoplastic material is then formed around the composite reinforcement structure 31, typically either by extruding a thermoplastic material onto the composite reinforcement structure 31, or by winding at least two strips of a thermoplastic material around the composite reinforcement structure 31, then welding the at least two strips together, for example by laser, thermal, electromagnetic or flash radiation. Preferably, the turns of a first layer are contiguous (edge to edge without overlap) and the turns of an upper layer are arranged so as to have an overlap of two lower adjacent strips ensuring the sealing of the sealing layer of thermoplastic material. The thermoplastic strips used are typically prepared by extrusion of the thermoplastic material.

Example

The strips (unfoamed) were obtained by extrusion on a Mélaine 65 type extruder. The granules were previously dried for 3 hours at 100°C.

- Formulation No. 1 PPE+TPE (Thermoplastic elastomer) (comparative): reference FLEX NORYL ^TM RESIN WCV072

Thickness: 1.5 mm

Modulus: 1750 MPa

Supplier: Sabic

- Formulation No. 2 PPE+PP (comparative): reference PPE Xyron T0703

Thickness: 1.5 mm

Modulus: 1900 MPa

Supplier AsahiKasei

- Formulation No. 3 PPE (according to the invention): reference Xyron 1002 H

Thickness: 0.47mm

Modulus: 2650 MPa

Supplier: AsahiKasei

A first series of creep tests was carried out at 110°C under 150 bar and between joints representative of the arrangement in a pipe. After 20 hours of testing, formulation No. 1 had lost almost 20% of its thickness, while formulation 2 had only lost 11% of its thickness. Formulation No. 1 was therefore discarded because the loss of thickness implies too low creep resistance.

A second series of creep tests was carried out over a longer period, namely around 100 hours, still at 110°C under 150 bar. It was observed that formulation 2 showed a thickness reduction of 17%, while formulation 3 only showed a thickness reduction of 10%. Formulation 3 therefore showed much better creep resistance at 110°C under 150 bar.

Claims (13)

Flexible underwater pipeline intended for the transport of hydrocarbons and/or gas comprising from the inside to the outside:
- an internal polymeric sealing sheath (22;30),
- at least two reinforcing layers (12,16,20;31,34,36),
- an external polymeric sealing sheath (10;38),
the pipe further comprising, between the internal polymeric sealing sheath and the external polymeric sealing sheath, at least one layer (11, 14, 18; 33, 35, 37) of polymeric material,
characterized in that said polymeric material:
- comprises at least 50% by weight, in particular at least 60%, preferably at least 65% by weight, of poly( p -phenylene ether) (PPE), and
- has a flexural modulus measured at 20°C according to ASTM D 638-14 greater than 2000 MPa. Pipe according to claim 1, in which the polymeric material has a glass transition temperature (Tg) greater than or equal to 130°C, it being understood that when the polymeric material has several glass transition temperatures, at least one of them is greater than or equal to 130°C. A pipe according to claim 1 or 2, wherein the polymeric material further comprises at least one thermoplastic elastomer, or at least one other thermoplastic polymer which is not a PPE, or a mixture thereof. Pipe according to claim 3, in which the polymeric material comprises at least one other thermoplastic polymer chosen from a polystyrene (PS), a polyolefin such as polyethylene or polypropylene, a polyamide (PA) and a polyphenylene sulfide (PPS), preferably from a polystyrene (PS), a polyolefin, and a polyphenylene sulfide (PPS), particularly preferably from a polypropylene and a polystyrene. A pipe according to any one of claims 1 to 4, wherein the polymeric material has:
- a melt flow index (measured according to ISO 1133-1:2022 at 230°C under a mass of 2.16 kg) less than or equal to 4.0 g/10 minutes, and/or
- an HDT, measured according to ASTM D 648-18 and under 1.8 MPa, greater than 70°C and ideally greater than 80°C, or even greater than 80°C, and/or
- an elongation at break determined at 20°C according to ASTM D 685-22 of at least 20%, and/or
- a thermal conductivity at 20°C of less than 0.25 W/(mK), preferably less than 0.20 W/(mK) and particularly preferably less than 0.17 W/(mK) as measured according to ISO 22007-4:2024. A pipe according to any one of claims 1 to 5, wherein the polymeric material is foamed, or is not foamed. Pipe according to any one of claims 1 to 6, in which the at least one layer (11, 14, 18; 33, 35, 37) of polymeric material is:
- either produced by helical winding of at least one strip of the polymeric material as defined in claim 1,
- either a tubular sheath obtained by extrusion of the polymeric material as defined in claim 1. Pipe according to any one of claims 1 to 7, in which the at least one layer (14,18;33,35) of polymeric material is located between at least two consecutive reinforcing layers (12,16,20;31,34,36), and is preferably adjacent to each of said consecutive reinforcing layers (12,16,20;31,34,36). Pipe according to any one of claims 1 to 8, in which the at least one layer of polymeric material (11;37) is located between the outermost reinforcing layer (12;36) of the pipe and the outer polymeric sealing sheath (10;38). Pipe according to any one of claims 1 to 9, comprising from the inside to the outside:
- possibly a metal frame (24),
- the internal polymeric sealing sheath (22),
- possibly a pressure vault (20) as a reinforcing layer,
- at least one tensile armor ply (12, 16) as a reinforcing layer, preferably at least two tensile armor ply (12, 16),
- the external polymeric sealing sheath (10),
the pipe further comprising, between the internal polymeric sealing sheath and the external polymeric sealing sheath, at least one layer (11, 14, 18) of polymeric material as defined in claim 1. Pipe according to any one of claims 1 to 10, comprising from the inside to the outside:
- possibly a metal frame,
- the internal polymeric sealing sheath (30),
- a composite reinforcing structure (31) as a reinforcing layer, the composite reinforcing structure (31) comprising a winding of at least two laminated reinforcing layers, each reinforcing layer being made from a thermoplastic matrix (40) reinforced with fibers (42),
- possibly a sealing layer (32) made of thermoplastic material,
- at least one tensile armor layer (34,36) as a reinforcing layer,
- the external polymeric sealing sheath (38),
the pipe further comprising, between the internal polymeric sealing sheath (30) and the external polymeric sealing sheath (38), at least one layer of polymeric material (33, 35, 37) as defined in claim 1. Method of transporting hydrocarbons and/or gas comprising the transport, preferably at a temperature greater than or equal to 110°C, of hydrocarbons and/or gas within a pipe as defined in any one of claims 1 to 11. Use of a layer (11,14,18;33,35,37) of polymeric material comprising at least 50% by weight, in particular at least 60%, preferably at least 65% by weight, of poly(p-phenylene ether) (PPE), and having a flexural modulus measured at 20°C according to standard ASTM D 638-14 greater than 2000 MPa as a thermal insulation layer and/or as an anti-wear layer in a flexible underwater pipe intended for the transport of hydrocarbons and/or gas comprising from the inside to the outside:
- an internal polymeric sealing sheath (22;30),
- at least two reinforcing layers (12,16,20;31,34,36),
- an external polymeric sealing sheath (10;38).