Multilayer structure for hydrogen transport or storage

Abstract

The present invention relates to a multilayer structure selected from a reservoir, a pipe or a tube for transporting, distributing or storing hydrogen, comprising, from the inside to the outside, at least one sealing layer and at least one composite reinforcing layer, the innermost composite reinforcing layer being welded to the outermost adjacent sealing layer, the sealing layers consisting of a composition mainly comprising at least one semi-crystalline thermoplastic polymer P1i (i=1 to n, n is the number of sealing layers) having a Tm of less than 280°C, in particular less than 265°C, measured according to ISO 11357-3:2013, and each sealing layer wherein the at least one thermoplastic polymer may be the same or different, and at least one of the composite reinforcing layers consists of a fibrous material in the form of continuous fibers impregnated with a composition mainly comprising at least one, in particular semi-crystalline, thermoplastic polymer P2j (j=1 to m, m is the number of reinforcing layers), the thermoplastic polymer P2j having a Tg, measured according to ISO 11357-3:2013, higher than the maximum use temperature (Tu) of the structure, Tg ≥ Tu + 20°C, with Tu being higher than 50°C, in particular higher than 100°C.

Description

Technical Field

[0001] This patent application relates to multilayer composite structures for the transport, distribution, or storage of hydrogen and methods for making them.

Background Art

[0002] One of the goals sought in the automotive field is to present increasingly less polluting vehicles. Thus, electric vehicles or hybrid vehicles equipped with batteries are gradually aiming to replace internal combustion engine vehicles such as gasoline or diesel vehicles. Batteries have been found to be relatively complex vehicle components. Depending on the positioning of the battery in the vehicle, it may be necessary to protect it from impacts and from the external environment, which can have extreme temperatures and variable humidity. Also, it is necessary to avoid the risk of fire.

[0003] Furthermore, in order to maintain the life of the battery cells without damage, it is important that its operating temperature does not exceed 55°C. Conversely, for example in winter, it may be necessary to raise the battery temperature to optimize its operation.

[0004] Moreover, electric vehicles still have several problems today, namely the driving range of the battery, the use of these batteries of rare earths whose resources are not inexhaustible, and the problems of electricity production in each country where the battery can be recharged.

[0005] Therefore, hydrogen can be converted into electricity by a fuel cell and supply power to an electric vehicle, so it can be an alternative to an electric battery.

[0006] However, hydrogen storage, especially for mobile storage, is technically difficult and costly because of its very low molar mass and very low liquefaction temperature. However, for it to be effective, storage has to be carried out in a small volume, which means that hydrogen has to be maintained under high pressure at the temperature at which the vehicle is used. This is particularly the case for fuel cell hybrid road vehicles with an intended range of approximately 600 - 700 km or less, essentially for urban use, in addition to battery-driven electric base.

[0007] Hydrogen storage tanks are usually made of a metallic liner that must prevent hydrogen leakage. This first liner itself has to be protected by a second liner (usually made of composite material) designed to withstand the internal pressure of the tank (e.g., 700 bar) and any impact or heat source. The valve system also has to be safe.

[0008] According to the Hydrogen Memento Sheet 4.2 of the French Hydrogen Fuel Cell Association (AFHYPAC), revised in December 2016, pressurized hydrogen storage and dispensing using cylindrical steel cylinders or cylinder assemblies inflated to 20 or 25 MPa (type I and type II) have been standard practice for a very long time. The drawback of this storage method is that, compared to 100 kg / m 3 of methane, it is only 14 kg / m 3This is due to the size, and in particular the weight resulting from the use of low-stress steel to avoid the problem of hydrogen embrittlement. This situation has been fundamentally changed by the emergence of composite storage tank technology known as type III or type IV. Their basic principle is to separate two essential functions, sealing and mechanical strength, and manage them independently of each other. In this type of storage tank, a bladder made of a resin (thermosetting or thermoplastic), also known as a liner (or sealing sheath), is combined with a reinforcing structure made of fibers (glass, aramid, carbon), also known as a reinforcing layer or sleeve. As a result, the storage tank can operate at a higher pressure while reducing its mass and avoiding the risk of explosive rupture in the event of a severe external attack. Therefore, 70 MPa (700 bar) has substantially become the current standard.

[0009] In type IV storage tanks, the liner and the reinforcing layer are made of different materials, and they have the drawback of presenting a lack of adhesion between the liner and the reinforcing layer. When there is both gas accumulation and a decrease in the internal pressure of the storage tank on the contact surface between the liner and the composite material, it causes the problem of liner collapse.

[0010] This problem has led to the development of type V storage tanks based on the use of the same polymer for both the liner and the composite matrix to ensure excellent durable adhesion between the liner and the composite material.

[0011] When transporting or distributing hydrogen by means of rigid or flexible pipes, it is also preferable for the hydrogen to be at low volume and thus at high pressure in order to ensure a sufficient flow rate. Thus, with regard to the storage, transport, or distribution of hydrogen, it is interesting to use composite pipes composed of a sealed sheath (ensuring airtightness and chemical resistance) reinforced by an outer layer made of a composite material manufactured by filament winding from unidirectional (UD) tapes deposited in a continuous layer on a liner. If it is desired to make this pipe flexible, one possibility is to wind UD tapes having one or more angular directions with respect to the axis of the pipe so that the composite reinforcement can support the deformation of the composite pipe during use. Thanks to the composite reinforcement, the pipe is able to withstand the internal pressure generated by the fluid being transported.

[0012] Regarding storage tanks, it is necessary for the sealed sheath to resist collapse, especially during production stoppages that lead to a rapid drop in pressure. This risk of collapse exists when the sheath is not adhered to the composite reinforcement and there is a possibility of gas being present between the sealed sheath and the composite reinforcement. To avoid this phenomenon, one solution is to add an internal reinforcement called a carcass to the pressure jacket, which is often metallic and perforated to be flexible and thus not airtight with respect to the fluid being transported. It adds weight, complexity, and cost to the flexible pipe. Also, in order to reduce the weight or remove the internal carcass of the composite pipe, it is necessary to adhere the composite reinforcement to the sealed sheath, as in the case of V-type storage tanks.

[0013] Furthermore, the sealed sheath must, as described above, be able to be continuously extruded, in some cases, onto the support of the internal carcass. This sealed sheath must be sufficiently chemically stable so that its mechanical and sealing properties do not deteriorate in a way that would be fatal during the life of the tank or flexible pipe.

[0014] In the case of a flexible pipe having an internal metallic carcass, the sealing liner must be able to withstand the influence of creep of the material from which it is made due to the stresses occurring in the sealing sheath by the internal pressure of the pipe. Creep occurs at the joints (gaps or clearances) between the metallic outer sheaths (e.g., zeta or T-shaped self-clinching) on which the liner rests when the pipe is pressurized by the fluid being transported, creating protrusions of the material and generating stress concentrations, and thus being the preferential failure zone of the sealing sheath. Therefore, the material constituting the sealing sheath must also withstand these stresses.

[0015] For example, Airborne has developed various flexible pipes without an internal carcass and with a sealing sheath adhered to a composite reinforcement, including a PA11 liner with a PA11 FC composite (completed by JIP in 2011), or a PA12 liner with a PA12 FC composite, or a PVDF liner with a PVDF FC composite. However, all of these structures have the drawback that the matrix of the composite reinforcement has a glass transition temperature Tg that is lower than the service temperature Tu of the pipe. That is, in the case of PA11 or PA12-based pipes, the Tg is 50°C in the dry state at 60 - 80°C of the pipe service temperature Tu, and in the case of PVDF, the Tg is -40°C at a service temperature in continuous operation higher than 100°C and close to 130°C. In the specific case of PVDF, the rigidity (modulus) of the matrix remains higher than its Tg until it reaches another transition, the alpha transition is at about 100°C, and above that its behavior becomes purely rubbery. Therefore, in all of the above industrial and commercially available cases of TP matrix composite pipes, the matrix of the composite reinforcement is in a fully rubberized state at the service temperature Tu of the composite pipe.

[0016] To solve this problem and have a composite reinforcement with a Tg higher than the maximum use temperature so that the matrix does not become rubbery at a use temperature of 130°C in this case, Kutting & Total, then Vitrex and Magma, developed a solution consisting of a PEEK sealing sheath (or liner) reinforced with a composite material having a PEEK matrix. The Tg of PEEK is 140°C, and thus this Tg meets the requirement of high rigidity as it is higher than the maximum use temperature. The disadvantage is that as a result, the sealing sheath is also very rigid, which may limit the fatigue life and is thus a major disadvantage for the manufacture of flexible pipes. Furthermore, the processing temperature of this type of sealing sleeve is very high (typically 380 - 400°C), which presents major difficulties in terms of tooling and process control in the case of the normal deformation process of tube extrusion.

[0017] Furthermore, Ticona (Celanese) is offering, in cooperation with Airborne, composite pipes with PPS FC reinforcement and PPS sealing sheaths.

[0018] When Tu > 90°C, this structure presents the same problem of the composite material matrix as the PVDF - based solution (i.e., Tg < Tu), and furthermore shows a problem of the deformation temperature (in the case of PPS and PVDF, typically 350°C vs. 250°C respectively).

[0019] When Tu < 90°C, PPS is suitable for the composite material matrix, but the problems of the extrusion temperature of the sealing liner and its high rigidity remain, limiting the flexibility of the composite pipe.

[0020] When hydrogen is rapidly filled, especially at about 110°C, since the compression of hydrogen causes a temperature rise in the storage tank, if the matrix of the composite material has a Tg lower than this temperature, it is necessary to make the composite material extremely large, so the same technical problems are caused in the case of hydrogen storage tanks.

[0021] Therefore, it still remains necessary, on the one hand, to optimize the matrix of the composite material so as to optimize its mechanical strength at high temperatures and, on the other hand, to optimize the materials constituting the sealing liner so as to optimize its service temperature without reducing the adhesion of the composite reinforcement to the sealing liner. Therefore, possible changes in the composition of the materials constituting the sealing liner, which are made to ensure at least partial miscibility with the matrix of the composite material, should not lead to a significant increase in the manufacturing (extrusion blow, injection, rotational molding, etc.) temperature of this liner compared to what is currently practiced with polyamide and PVDF. Summary of the Invention

[0022] These problems are solved by providing a multilayer structure according to the invention, which is a fully bonded "two-layer material" composite pipe or storage tank, composed of a high-strength composite reinforcement, i.e., including a high-Tg matrix, and in particular deposited by filament winding on a liner extruded previously at a relatively low temperature. The adhesion between the composite material and the liner is very good.

[0023] Throughout this specification, the terms "liner", "sealing sheath" and "pressure jacket" have the same meaning.

[0024] Therefore, the present invention is a multilayer structure selected from storage tanks, pipes or tubes for the purpose of hydrogen transport or storage, comprising, from the inside to the outside, at least one sealing layer and at least one composite reinforcement layer, wherein the innermost composite reinforcement layer is welded to the outermost adjacent sealing layer, the sealing layer is composed of a composition mainly containing at least one semi-crystalline thermoplastic polymer P1i (i = 1 to n, n is the number of sealing layers) whose Tm is less than 280 °C, particularly less than 265 °C, as measured according to ISO11357-3:2013, The at least one thermoplastic polymer of each sealing layer may be the same or different. At least one of the composite reinforcing layers is in the form of a fibrous material of continuous fibers impregnated with a composition mainly containing at least one semi-crystalline thermoplastic polymer P2j (j = 1 to m, where m is the number of reinforcing layers). The thermoplastic polymer P2j has a Tg higher than the maximum use temperature (Tu) of the structure as measured according to ISO 11357-3:2013, with Tg ≧ Tu + 20°C, particularly Tg ≧ Tu + 30°C, and Tu is higher than 50°C, particularly higher than 100°C. Relates to a multilayer structure.

[0025] Therefore, the inventors use different polymers for the composite matrix and the liner, in particular, The matrix of the composite reinforcement remains in its glassy region and has high rigidity, thus enabling the composite to have high mechanical strength. It is composed of a polymer having a Tg significantly higher than the maximum use temperature Tu of the storage tank or pipe (Tg > Tu + 20°C, particularly typically Tg ≧ Tu + 30°C). The semi-crystalline polymer constituting the liner has a low melting point Tm, which unexpectedly enables it to be processed by extrusion, extrusion blow molding, rotational molding, injection, or winding of a pure resin film at a moderate temperature, which is less than 280°C, preferably less than 265°C, in some cases related to the Tm of this polymer. The low-Tm semi-crystalline polymers known to date also have a low Tg and will most likely be below the maximum use temperature. As a result, the polymer constituting the liner acts in the rubbery region and is thus very flexible and highly resistant to fatigue. Its semi-crystallinity ensures good resistance to chemical attack, wear, and creep, and The two aforementioned polymers (the one constituting the matrix of the composite material and the one constituting the liner) are sufficiently miscible with each other in order to ensure the weldability of the composite material to the liner and, as a result, to ensure excellent adhesion between the liner and the composite material. The durability of the adhesion is ensured by the durability of the materials constituting the mixture at the contact surface of the two materials, i.e., the welded joint. The miscibility of the two polymers is preferably represented by a single Tg, or, if not, by the characteristic signature of a partially homogeneous mixture, for example, by the presence of two Tg values intermediate between those of the two pure polymers with respect to the Tg of the two pure polymers.

Mode for Carrying Out the Invention

[0026] The immiscibility of the two polymers results in the presence of two Tgs in the mixture of the two polymers corresponding to the respective Tgs of the pure polymers measured separately.

[0027] The “multilayer structure” means, for example, a storage tank, a pipe or a tube provided with or consisting of several layers, in particular two layers.

[0028] The sealing layer(s) is / are the innermost layer(s) as compared with the outermost composite reinforcing layer.

[0029] Even if there is an inner, and thus innermost, unsealed metal layer formed by a helically wound metal strip such as the staple strip (feuillard agrafe) forming the carcass, and the sealing layer(s) is / are coated thereon by extrusion, the sealing layer(s) is / are in contact with hydrogen.

[0030] When there are several sealing layers, only the innermost sealing layer is in direct contact with hydrogen.

[0031] When only one sealing layer and one composite reinforcing layer are present, thus resulting in a two-layer multilayer structure, these two layers are welded and in direct contact with each other and adhered to each other.

[0032] If there are several sealing layers and / or several composite reinforcing layers, the outermost layer of the sealing layer, and thus the layer on the opposite side of the layer in contact with hydrogen, is welded to the innermost layer of the composite reinforcing layer, and thus they are directly in contact with each other and adhered.

[0033] The other composite reinforcing layers are also welded together.

[0034] The other sealing layers are also welded together.

[0035] Regarding the sealing layer and the thermoplastic polymer P1i One or more sealing layers may be present.

[0036] Each of the layers consists of a composition mainly containing at least one thermoplastic polymer P1i corresponding to the number of layers where i exists. i is from 1 to 10, particularly from 1 to 5, particularly from 1 to 3, preferably i = 1.

[0037] The term "mainly" means that the at least one polymer is present in more than 50% by weight based on the total weight of the composition.

[0038] Advantageously, the at least one main polymer is present in more than 60% by weight, particularly more than 70% by weight, particularly more than 80% by weight, and more specifically 90% by weight or more based on the total weight of the composition.

[0039] The composition may further contain an impact modifier and / or an additive.

[0040] The additive can be selected from antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents, plasticizers, dyes, carbon black, and carbonaceous nanofillers.

[0041] Advantageously, the composition mainly consists of the thermoplastic polymer P1i, 0 - 5% by weight of an impact modifier, and 0 - 5% by weight of an additive, and the total of the components of the composition is equal to 100% (for a maximum of 90% of P2i).

[0042] The at least one major polymer in each layer may be the same or different.

[0043] In one embodiment, a single major polymer is present in at least a sealing layer welded to the composite reinforcement layer.

[0044] Thermoplastic polymer P1i A thermoplastic substance, or a thermoplastic polymer, is generally solid at room temperature and softens during a temperature increase, particularly after passing through its glass transition temperature (Tg), and may exhibit a sharp transition when passing through what is called its melting point (Tm), and becomes solid again when the temperature drops below its crystallization temperature, referring to a semi-crystalline material.

[0045] Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) in accordance with standards 11357-2:2013 and 11357-3:2013, respectively.

[0046] The number average molecular weight Mn of the thermoplastic polymer is preferably in the range of 10,000 to 40,000, and preferably in the range of 12,000 to 30,000. These Mn values may correspond to an intrinsic viscosity of 0.8 or more when determined in m-cresol in accordance with standard ISO307:2007, except that the solvent is changed (using m-cresol instead of sulfuric acid and the temperature is 20 °C).

[0047] Examples of suitable semi-crystalline thermoplastic polymers in the present invention include copolymers such as polyamide-polyether copolymers, polyesters, and polyamides including PVDF and PVDF-containing major PVDF / PEI blends.

[0048] Among semi-crystalline polymers, polyamides and their semi-crystalline copolymers are particularly more preferred.

[0049] The nomenclature used to define polyamides is described in ISO standard 1874-1:2011, "Plastiques -- Materiaux polyamides (PA) pour moulage et extrusion - Partie 1: Designation", particularly on page 3 (Tables 1 and 2), and is well-known to those skilled in the art.

[0050] The polyamide may be a homopolyamide, a copolyamide, or a mixture thereof.

[0051] Advantageously, the thermoplastic polymer is a long-chain aliphatic polyamide, i.e., a polyamide having an average number of carbon atoms per nitrogen atom greater than 8.5, preferably greater than 9.

[0052] In particular, the long-chain aliphatic polyamides are selected from polyamide 11 (PA11), polyamide 12 (PA12), polyamide 1010 (PA1010), polyamide 1012 (PA1012), polyamide 1212 (PA1012), or mixtures or copolymers thereof, particularly PA11 and PA12.

[0053] Advantageously, the thermoplastic polymer is a long-chain semi-aromatic polyamide, i.e., a polyamide having an average number of carbon atoms per nitrogen atom greater than 8.5, preferably greater than 9, and having a melting point in the range of 240 °C to less than 280 °C.

[0054] In particular, the long-chain semi-aromatic polyamides are selected from polyamide 11 / 5T, 11 / 6T, or 11 / 10T. In this case, clearly, the ratio of 11 must be selected such that the Tm of the polymer is less than 280 °C, preferably less than 265 °C.

[0055] Advantageously, each sealing layer consists of a composition containing the same type of polymer, particularly polyamide.

[0056] Advantageously, the composition containing the polymer P1i is black and can absorb irradiation suitable for welding.

[0057] There are various methods for welding the thermoplastic polymer part. Thus, contact or non-contact heating blades, ultrasonic, infrared, vibration, rotation or even laser welding of one element to be welded to the other can be used.

[0058] In particular, for the welding of thermoplastic polymer elements by laser welding, it is necessary that the two elements to be welded have different properties with respect to irradiation, in particular laser irradiation, i.e. one of the elements must be transparent to irradiation, in particular laser irradiation, and the other must absorb irradiation, in particular laser irradiation. In particular, the irradiation of the laser irradiation passes through the transparent part and then reaches the absorbing element, where it is converted into heat. Thereby, the contact area between the two elements melts and welding is performed.

[0059] In some applications, it is desirable that both parts to be welded, including the part that is transparent to laser irradiation, be black.

[0060] In order to make them absorbent, it is known to add various additives including, for example, carbon black to impart black color to the polymer and be able to absorb irradiation suitable for welding.

[0061] In one embodiment, the welding is carried out by a system selected from laser, infrared (IR) heating, LED heating, induction or microwave heating or high frequency (HF) heating.

[0062] When the welding is carried out by laser welding, the composition P1i contains a non-massive or non-aggregated carbonaceous filler.

[0063] When the welding is carried out by induction, the composition P1i contains metal particles.

[0064] Advantageously, the welding is carried out by a laser system.

[0065] Regarding the composite reinforcement layer and the thermoplastic polymer P2j One or more composite reinforcing layers may be present.

[0066] Each of said layers consists of a composition mainly comprising at least one thermoplastic polymer P2j, where j corresponds to the number of layers present.

[0067] j is included in the range of 1 to 10, particularly 1 to 5, especially 1 to 3, and preferably j = 1.

[0068] The term "mainly" means that said at least one polymer is present in more than 50% by weight relative to the total weight of the composition.

[0069] Advantageously, said at least one main polymer is present in more than 60% by weight, particularly more than 70% by weight, especially more than 80% by weight, and more specifically 90% by weight or more relative to the total weight of the composition.

[0070] Said composition may further comprise an impact modifier and / or additives.

[0071] The additives can be selected from antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents, plasticizers, and dyes.

[0072] Advantageously, said composition mainly consists of said thermoplastic polymer P2j, 0 to 5% by weight of an impact modifier, 0 to 5% by weight of additives, and the total of the components of the composition is equal to 100% (for a maximum of 90% of P2j).

[0073] Said at least one main polymer in each layer may be the same or different.

[0074] In one embodiment, a single main polymer is present in at least the composite reinforcing layer welded to the sealing layer.

[0075] In one embodiment, each reinforcing layer comprises the same type of polymer, particularly polyamide.

[0076] Thermoplastic polymer P2j A thermoplastic substance, or a thermoplastic polymer, is generally solid at room temperature, and can be semi-crystalline or amorphous, especially semi-crystalline. During a temperature increase, especially after passing through its glass transition temperature (Tg), it softens and, when amorphous, flows at a higher temperature, or, when semi-crystalline, may show a sharp transition when passing through the so-called melting temperature (Tm). When the temperature drops below its crystallization temperature Tc (in the case of semi-crystalline) or below its glass transition temperature (in the case of amorphous), it becomes solid again, referring to a material.

[0077] Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) in accordance with Standards 11357-2:2013 and 11357-3:2013 respectively.

[0078] The polymer P2j of at least one composition of the composite reinforcing layer has a Tg higher than the maximum service temperature (Tu) of the structure, especially such that Tg≧Tu + 20°C, especially Tg≧Tu + 30°C.

[0079] In one embodiment, the polymer P2j has Tg≧Tu + 20°C, especially Tg≧Tu + 30°C regardless of the position of the reinforcing layer.

[0080] In another embodiment, the reinforcing layer made of a composition containing the polymer P2j having Tg≧Tu + 20°C, especially Tg≧Tu + 30°C, is a layer welded to the sealing layer.

[0081] In one embodiment, the polymer P2j of at least one composition of the composite reinforcing layer has a Tg higher than the maximum service temperature (Tu) of the structure by Tg≧Tu + 20°C, and the reinforcing layer made of a composition containing the polymer P2j is a layer welded to the sealing layer.

[0082] In one embodiment, the polymer P2j of at least one composition of the composite reinforcing layer has a Tg that is Tg≧Tu + 30°C higher than the maximum service temperature (Tu) of the structure, and the reinforcing layer made of the composition containing the polymer P2j is a layer welded to the sealing layer.

[0083] In another embodiment, the reinforcing layer made of a composition containing a polymer P2j having Tg≧Tu + 20°C, particularly Tg≧Tu + 30°C, is the outermost reinforcing layer of the structure. The number average molecular weight Mn of the thermoplastic polymer is preferably in the range of 10,000 to 40,000, and preferably in the range of 12,000 to 30,000. These Mn values may correspond to an intrinsic viscosity of 0.8 or more when determined in m-cresol according to standard ISO307:2007, provided that the solvent is changed (using m-cresol instead of sulfuric acid, and the temperature is 20°C).

[0084] Examples of suitable semi-crystalline thermoplastic polymers in the present invention include polyamides, particularly those containing aromatic and / or alicyclic structures, including copolymers such as polyamide-polyether copolymers, polyesters, polyaryl ether ketone (PAEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ketone ether ketone ketone (PEKEKK), polyimides, particularly polyether imide (PEI) or polyamide-imide, polysulfones (PSU), particularly polyaryl sulfones such as polyphenyl sulfone (PPSU), polyether sulfone (PES) may be mentioned. Semi-crystalline polymers are particularly preferred, and polyamides and their semi-crystalline copolymers are particularly preferred.

[0085] The nomenclature used to define polyamides is described in ISO standard 1874-1:2011, "Plastiques - Materiaux polyamides (PA) pour moulage et extrusion - Partie 1: Designation", particularly on page 3 (Tables 1 and 2), and is well-known to those skilled in the art.

[0086] The polyamide may be a homopolyamide, a copolyamide, or a mixture thereof.

[0087] Advantageously, the semi-crystalline polyamide is a semi-aromatic polyamide, particularly the semi-aromatic polyamide of formula X / YAr described in EP1505099, and particularly the semi-aromatic polyamide of formula A / XT, wherein A is a unit derived from an amino acid, a unit derived from a lactam, and a represents the number of carbon atoms of a diamine, b represents the number of carbon atoms of a diacid, a and b are each between 4 and 36, preferably between 9 and 18, the unit (Ca diamine) is selected from linear or branched aliphatic diamines, cycloaliphatic diamines, and alkyl aromatic diamines, and the unit (Cb diacid) is selected from units corresponding to the formula (Ca diamine).(Cb diacid) selected from linear or branched aliphatic diacids, cycloaliphatic diacids, and aromatic diacids, X.T represents that x represents the number of carbon atoms of Cx diamine, x is between 5 and 36, preferably between 9 and 18, and particularly a polyamide having the formula A / 5T, A / 6T, A / 9T, A / 10T, or A / 11T, where A is as defined above, and particularly PA MPMDT / 6T, PA11 / 10T, PA5T / 10T, PA11 / BACT, PA11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA11 / BACT / 6T, PA11 / MPMDT / 6T, PA11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXDT / 10T, 11 / 5T / 10T, which represents a unit obtained from the polycondensation of Cx diamine and terephthalic acid.

[0088] T corresponds to terephthalic acid, MXD corresponds to m-xylenediamine, MPMD corresponds to methylpentamethylenediamine, and BAC corresponds to bis(aminomethyl)cyclohexane. The semi-aromatic polyamide defined above has a Tg of particularly 80 °C or higher.

[0089] Advantageously, each composite reinforcing layer consists of a composition containing the same type of polymer, particularly a polyamide.

[0090] Advantageously, the composition containing the polymer P2j is permeable to irradiation suitable for welding.

[0091] Thermoplastic polymers are generally permeable for welding purposes, particularly for laser welding. The carbonaceous nanofiller makes it possible to impart black color to the layer of the composition containing the thermoplastic polymer while maintaining the permeability of the layer to laser irradiation.

[0092] Advantageously, the carbonaceous nanofiller is non-lumpy or non-aggregated.

[0093] Advantageously, the carbonaceous nanofiller is incorporated into the composition in an amount of 100 ppm to 500 ppm, preferably 100 ppm to 250 ppm.

[0094] Advantageously, the carbonaceous nanofiller is selected from carbon nanotubes (CNT), carbon nanofibers, graphene, nanoscale carbon black, and mixtures thereof.

[0095] Advantageously, the carbonaceous nanofiller does not contain nanometer carbon black.

[0096] In one embodiment, the welding is performed by a system selected from laser, IR heating, or induction heating.

[0097] Advantageously, the welding is performed by a laser system.

[0098] Advantageously, the laser irradiation is infrared laser irradiation and preferably has a wavelength between 700 nm and 1200 nm, and preferably between 800 nm and 1100 nm.

[0099] Regarding the structure The multilayer structure thus includes at least one sealing layer that is welded together and at least one composite reinforcing layer.

[0100] In one embodiment, in the multilayer structure, each polymer P1i of each sealing layer is partially or completely miscible with each polymer P1i of the adjacent layer, and each polymer P2j of each reinforcing layer is partially or completely miscible with each polymer P2j of the adjacent layer. When adjacent, each polymer P2j is partially or completely miscible with each polymer P1i, and polymer P21 is partially or completely miscible with the adjacent polymer P11. The complete or partial miscibility of the polymers is defined by the difference in the glass transition temperatures of the two resins in the mixture relative to the difference in the glass transition temperatures of the two resins before the mixture. When the difference is equal to 0, the miscibility is complete. When the difference is different from 0, the miscibility is partial, and the immiscibility of polymer P2j with polymer P1i is excluded.

[0101] When the miscibility of the polymers is partial, the difference is such that the greater the miscibility, the smaller the difference.

[0102] Advantageously, when the miscibility of the polymers is partial, the difference is less than 30% in absolute value, preferably less than 20%.

[0103] In one embodiment, the glass transition temperature of the mixture depends on whether the miscibility is complete or partial and is between the glass transition temperatures of the polymers before blending and must be at least 5 °C, preferably at least 10 °C, and different therefrom.

[0104] The expression "fully miscible" means, for example, that when two polymers P11 and P12 having Tg11 and Tg12 respectively are present in two adjacent sealing layers or two adjacent reinforcing layers, the mixture of the two polymers has only one Tg1112, the value of which is between Tg11 and Tg12.

[0105] This Tg1112 value is thus at least 5 °C, especially at least 10 °C higher than Tg11 and at least 5 °C, especially at least 10 °C lower than Tg12.

[0106] The expression "partially miscible" means, for example, that when two polymers P11 and P12 having Tg11 and Tg12 respectively are present in two adjacent sealing layers or two adjacent reinforcing layers, the mixture of the two polymers has two Tgs, Tg’11 and Tg’12, such that Tg11 < Tg’11 < Tg’12 < Tg12.

[0107] These Tg’11 and Tg’12 values are at least 5 °C, especially at least 10 °C higher than Tg11 and at least 5 °C, especially at least 10 °C lower than Tg12.

[0108] The immiscibility of the two polymers results in the presence of two Tgs, Tg11 and Tg12, corresponding to the respective Tgs of the pure polymers measured separately, in the mixture of the two polymers.

[0109] Advantageously, the welded sealing layer and reinforcing layer are each made of a composition containing different polymers.

[0110] Nevertheless, the different polymers may be of the same type.

[0111] Thus, when one of the two welded composite reinforcement layers and the sealing layer is made of a composition containing an aliphatic polyamide, the other layer is made of a composition containing a polyamide that is not aliphatic, for example a semi-aromatic polyamide, such that it has a high Tg polymer as the matrix of the composite reinforcement.

[0112] The multilayer structure may include up to 10 sealing layers and up to 10 composite reinforcement layers.

[0113] It is clear that the multilayer structure is not necessarily symmetric, and thus may include more sealing layers than composite layers, and vice versa.

[0114] Advantageously, the multilayer structure includes 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 sealing layers and 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 composite reinforcement layers.

[0115] Advantageously, the multilayer structure includes 1, 2, 3, 4, or 5 sealing layers and 1, 2, 3, 4, or 5 composite reinforcement layers.

[0116] Advantageously, the multilayer structure includes 1, 2, or 3 sealing layers and 1, 2, or 3 composite reinforcement layers.

[0117] Advantageously, these are each made of a composition containing a different polymer.

[0118] Advantageously, these are each made of a composition containing a polyamide corresponding to polyamides P1i and P2j, respectively.

[0119] Advantageously, these are each made of a composition containing a different polyamide.

[0120] In one embodiment, the multilayer structure includes a single sealing layer and several reinforcement layers, and the sealing layer is welded to the adjacent reinforcement layer.

[0121] In another embodiment, the multilayer structure includes a single reinforcing layer and several sealing layers, and the reinforcing layer is welded to the adjacent sealing layer.

[0122] In one advantageous embodiment, the multilayer structure includes a single sealing layer and a single composite reinforcing layer that are both welded together.

[0123] Therefore, all combinations of these two layers are within the scope of the present invention as long as at least the innermost composite reinforcing layer is welded to the outermost adjacent sealing layer, whether or not the other layers are welded together.

[0124] Advantageously, in the multilayer structure, each sealing layer is made of a composition containing the same type of polymer P1i, particularly a polyamide.

[0125] The expression "the same type of polymer" means, for example, a polyamide that may be the same or different depending on the layer.

[0126] Advantageously, the polymer P1i is a polyamide, and the polymer P2j is a polyamide.

[0127] Advantageously, the polyamide P1i is the same for all sealing layers.

[0128] Advantageously, the polymer P1i is a long-chain aliphatic polyamide, particularly PA1010, PA1012, PA1212, PA11, PA12, particularly PA11 or PA12.

[0129] Advantageously, the polyamide P1i is a long-chain semi-aromatic polyamide, particularly PA11 / 5T, PA11 / 6T or PA11 / 10T. In this case, clearly, the ratio of 11 must be carefully selected so that the Tm of the polymer is less than 280°C, preferably less than 265°C.

[0130] Advantageously, in the multilayer structure, each reinforcing layer is made of a composition containing the same type of polymer P2j, particularly polyamide.

[0131] Advantageously, the polyamide P2j is the same for all reinforcing layers.

[0132] Advantageously, the polymer P2j is a semi-aromatic polyamide selected from PA MXDT / 6T, PA11 / 10T, PA11 / BACT, PA5T / 10T, PA11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA11 / BACT / 6T, PA11 / MPMDT / 6T, PA11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXDT / 10T, and PA5T / 10T.

[0133] Advantageously, in the multilayer structure, when polyamides P1i and P2j are different, i.e., when the sealing layer is made of a composition containing a long-chain aliphatic polyamide, as long as the sealing layer is made of a composition containing a semi-aromatic polyamide, each sealing layer is made of a composition containing the same type of polymer P1i, particularly polyamide, and each reinforcing layer is made of a composition containing the same type of polymer P2j, particularly polyamide.

[0134] Advantageously, the polymer P1i is a long-chain aliphatic polyamide, particularly PA1010, PA1012, PA1212, PA11, PA12, particularly PA11 or PA12, and the polymer P2j is a semi-aromatic polyamide particularly selected from PA MPMDT / 6T, PA PA11 / 10T, PA11 / BACT, PA5T / 10T, PA11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA11 / BACT / 6T, PA11 / MPMDT / 6T, PA11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXDT / 10T, and PA5T / 10T.

[0135] Advantageously, the multilayer structure consists of a single reinforcing layer and a single sealing layer, wherein the polymer P1i is a long-chain aliphatic polyamide, particularly PA1010, PA1012, PA1212, PA11, PA12, particularly PA11 or PA12, and the polymer P2j is a semi-aromatic polyamide particularly selected from PA MPMDT / 6T, PA PA11 / 10T, PA11 / BACT, PA11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA11 / BACT / 6T, PA11 / MPMDT / 6T, PA11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXDT / 10T.

[0136] According to one embodiment, the multilayer structure is a storage tank.

[0137] According to another embodiment, the multilayer structure is a flexible pipe.

[0138] The maximum use temperature Tu of the multilayer structure is above 50°C, particularly above 100°C.

[0139] In one embodiment, the multilayer structure defined above has pressure resistance to vacuum and drying ability.

[0140] In fact, when storing or transporting hydrogen, due to the permeability of the sealing layer to the hydrogen being transported or stored, hydrogen may diffuse through the sealing layer from the inside of the tube or storage tank to the contact surface between the outermost sealing layer and the first composite reinforcement layer. The accumulation of hydrogen at this location can generate a pressure that may lead to the collapse of the sealing layer if the internal pressure of the tube or storage tank is lower than the pressure at the contact surface with the composite reinforcement. In particular, this can occur when the pumping or transportation of hydrogen stops during production shutdown when the pressure drops by several hundred bar to atmospheric pressure, or when the storage tank is empty. The same applies to the internal hydraulic test of the storage tank, where this water is likely to move by infiltration at the contact surface between the composite reinforcement and the outermost layer of the sealing layer, and then it becomes very difficult to remove, especially leading to a long and costly drying cycle of the storage tank under reduced pressure.

[0141] In another embodiment, the multilayer structure defined above further includes a metal carcass located within the sealing layer.

[0142] This metal carcass is not for leak prevention and is the innermost layer.

[0143] Advantageously, the multilayer structure further includes at least one outer layer, in particular a metal layer, which is the outermost layer of the multilayer structure.

[0144] The outer layer is a second reinforcement layer but is made of metal and not a composite material.

[0145] Also, there may be a polymeric protective layer (outermost layer) on the structure, which has a role in preventing wear or enables the placement of an inscription on the structure.

[0146] Regarding the fiber material Regarding the fibers constituting the fiber material, these are in particular inorganic, organic or vegetable fibers.

[0147] Advantageously, the fiber material may or may not be sized.

[0148] The fibrous material can thus contain up to 0.1% by weight of an organic material (thermosetting or thermoplastic resin type), called a sizing agent.

[0149] Examples of inorganic fibers include carbon fibers, glass fibers, basalt or basalt-based fibers, silica fibers or silicon carbide fibers. Examples of organic fibers include thermoplastic or thermosetting polymer-based fibers such as semi-aromatic polyamide fibers, aramid fibers or polyolefin fibers. Preferably, these are based on amorphous thermoplastic polymers, and when the polymer or thermoplastic polymer mixture is amorphous, have a glass transition temperature Tg higher than that of the polymer or thermoplastic polymer mixture constituting the prepreg matrix, or when the polymer or thermoplastic polymer mixture is semi-crystalline, have a Tg higher than the Tm of the polymer or thermoplastic polymer matrix constituting the prepreg matrix. Advantageously, these are based on semi-crystalline thermoplastic polymers, and when the polymer or thermoplastic polymer mixture is amorphous, have a melting temperature Tm higher than the Tg of the polymer or thermoplastic polymer mixture constituting the prepreg matrix, or when the polymer or thermoplastic polymer mixture is semi-crystalline, have a Tm higher than the Tm of the polymer or thermoplastic polymer matrix mixture constituting the prepreg matrix. Thus, during impregnation of the final composite with the thermoplastic matrix, there is no risk of melting of the organic fibers constituting the fibrous material. Examples of plant fibers include natural linen, hemp, lignin, bamboo, silk, especially spider silk, sisal, and other cellulose fibers, especially viscose. These plant fibers can be used as pure, treated or coated with a coating layer to facilitate adhesion and impregnation of the thermoplastic polymer matrix.

[0150] The fibrous material can also be a fabric woven from fibers, a braided cord.

[0151] Moreover, it can correspond to fibers having a support thread (fils de maintien).

[0152] These constituent fibers may be used alone or as a mixture. Thus, organic fibers can be mixed with the thermoplastic polymer powder to be pre-impregnated to form a pre-impregnated fiber material.

[0153] The organic fiber strands can have some basis weight. Furthermore, they can have some geometric shapes. The constituent fibers of the fiber material can further assume the form of a mixture of these reinforcing fibers having different geometric shapes. The fibers are continuous fibers.

[0154] Preferably, the fiber material consists of continuous carbon fibers or glass fibers or a mixture thereof, especially carbon fibers. It is used in the form of one roving or several rovings.

[0155] According to another aspect, the present invention relates to a method for manufacturing a multilayer structure defined above, characterized in that it comprises a step of welding the reinforcing layer defined above to the sealing layer defined above.

[0156] Advantageously, the welding step is carried out by a system selected from laser, infrared (IR) heating, LED heating, induction or microwave heating or high frequency (HF) heating.

[0157] Advantageously, the method comprises a step of extruding the sealing layer onto a metal carcass and a step of welding the reinforcing layer to the sealing layer.

[0158] According to another aspect, the present invention relates to the use of a multilayer structure selected from a storage tank, a pipe or a tube, comprising at least one sealing layer defined above and at least one composite reinforcing layer defined above, from the inside to the outside, To fabricate a storage tank or a pipe or a tube for transporting, distributing, and storing hydrogen, the innermost composite reinforcing layer is welded to the outermost adjacent sealing layer. The sealing layer consists of a composition mainly containing at least one semi-crystalline thermoplastic polymer P1i (i = 1 to n, where n is the number of sealing layers) with a Tm of less than 280 °C, particularly less than 265 °C, as measured according to ISO 11357-3:2013. The at least one thermoplastic polymer of each sealing layer may be the same or different. At least one of the composite reinforcing layers consists of a fibrous material in the form of continuous fibers impregnated with a composition mainly containing at least one, particularly semi-crystalline, thermoplastic polymer P2j (j = 1 to m, where m is the number of reinforcing layers). The thermoplastic polymer P2j has a Tg higher than the maximum use temperature (Tu) of the structure, Tg ≥ Tu + 20 °C, particularly Tg ≥ Tu + 30 °C, as measured according to ISO 11357-3:2013, and Tu is higher than 50 °C, particularly higher than 100 °C. Regarding use.

Examples

[0159] In all examples, a storage tank is obtained by rotational molding of the liner at a temperature compatible with the properties of the thermoplastic resin used, but in all cases it is less than 280 °C.

[0160] In the case of epoxy, a wet filament winding method is used, which consists of winding fibers around the liner, and the fibers are pre-impregnated in a liquid epoxy bath. The storage tank is then polymerized in an oven for 2 hours.

[0161] In all other cases, a fibrous material pre-impregnated with a thermoplastic resin (tape) is used. This tape is deposited by filament winding using a robot equipped with a 1500 W laser heater at a speed of 12 m / min, and there is no polymerization step.

[0162] Example 1 (counterexample) Type IV hydrogen storage tank composed of T700SC31E (manufactured by Toray Industries, Inc.) carbon fiber epoxy composite reinforcement (Tg 80°C) and PA6 sealing layer. There is no miscibility between the two resins (see Table 1), which hinders the welding between the fibrous reinforcement and the sealing layer.

[0163] Example 2 (counterexample) Type IV hydrogen storage tank composed of T700SC31E (manufactured by Toray Industries, Inc.) carbon fiber epoxy composite reinforcement (Tg 80°C) and HDPE sealing layer. There is no miscibility between the two resins (see Table 1), which hinders the welding between the fibrous reinforcement and the sealing layer.

[0164] Example 3 Type IV or V hydrogen storage tank composed of T700SC31E (manufactured by Toray Industries, Inc.) BACT / 10T carbon fiber composite reinforcement and PA6 sealing layer. There is good partial miscibility between the two resins, enabling good welding between the fibrous reinforcement and the sealing layer (see Table I).

[0165] The selected BACT / 10T composition has a melting temperature Tm of 283°C, a crystallization temperature Tc of 250°C, and a glass transition temperature of 164°C.

[0166] Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) according to Standards 11357-2:2013 and 11357-3:2013, respectively.

[0167] Example 4 Type IV or V hydrogen storage tank composed of T700SC31E (manufactured by Toray Industries, Inc.) BACT / 10T carbon fiber composite reinforcement and PA66 sealing layer. There is good partial miscibility between the two resins, enabling good welding between the fibrous reinforcement and the sealing layer (see Table I). The selected BACT / 10T composition has a melting temperature Tm of 283°C, a crystallization temperature Tc of 250°C, and a glass transition temperature of 164°C. Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013, respectively.

[0168] The melting point of the PA66 liner (268.8 °C) is higher compared to the PA6 liner of Example 3 (220 °C), facilitating the taping and manufacture of the storage tank.

[0169] Example 5 Type IV or V hydrogen storage tank composed of CT24-5.0 / 270-T140 (manufactured by SGL Carbon) 11 / BACT / 10T carbon fiber composite reinforcement and PA11 sealing layer. There is good partial miscibility between the two resins (see Table 1), leading to good welding between the fibrous reinforcement and the sealing layer. The selected 11 / BACT / 10T composition has a melting temperature Tm of 280 °C, a crystallization temperature Tc of 220 °C, and a glass transition temperature of 160 °C. Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013, respectively.

[0170] Example 6 Type IV or V hydrogen storage tank composed of CT24-5.0 / 270-T140 (manufactured by SGL Carbon) 11 / BACT / 10T carbon fiber composite reinforcement and PA11 / 10T sealing layer. There is good partial miscibility between the two resins (see Table 1), leading to good welding between the fibrous reinforcement and the sealing layer.

[0171] The selected 11 / BACT / 10T composition has a melting temperature Tm of 280 °C, a crystallization temperature Tc of 220 °C, and a glass transition temperature of 160 °C. Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013, respectively.

[0172] The 11 / 10T composition used for the liner results in a Tm of 255 °C.

[0173] The use of an 11 / 10T liner with a melting point of 255 °C is close to that of the 11 / BACT / 10T resin used as the matrix of the composite material, facilitating the processing of the storage tank.

[0174] Example 7 Type IV or V hydrogen storage tank composed of CT24-5.0 / 270-T140 (made by SGL Carbon) 11 / BACT carbon fiber composite reinforcement and PA11 sealing layer. There is good partial miscibility between the two resins (see Table 1), which leads to good welding between the fibrous reinforcement and the sealing layer. The selected 11 / BACT composition has a melting temperature Tm of 278 °C, a crystallization temperature Tc of 210 °C, and a glass transition temperature of 157 °C. Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013 respectively.

[0175] The use of a low crystallization rate 11 / BACT polymer allows for a lower taping temperature than 11 / BACT / 10T in the previous example and facilitates the use of a PA11 liner.

[0176] Example 8 Type IV or V hydrogen storage tank composed of CT24-5.0 / 270-T140 (made by SGL Carbon) 11 / BACT carbon fiber composite reinforcement and PA11 / 10T sealing layer. There is good partial miscibility between the two resins (see Table 1), which leads to good welding between the fibrous reinforcement and the sealing layer.

[0177] The selected 11 / BACT composition has a melting temperature Tm of 278 °C, a crystallization temperature Tc of 210 °C, and a glass transition temperature of 157 °C. Tg, Tc, and Tm are determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013 respectively.

[0178] The 11 / 10T composition used for the liner results in a Tm of 255 °C.

[0179] The use of an 11 / 10T liner with a melting point of 255 °C is close to 11 / BACT, which is the reinforcing resin of the composite material, and facilitates the installation of the storage tank.

[0180] In all of the examples in Table 1 below, to evaluate the miscibility of the resins, the mixtures were made from powders having a particle size of about 150 μm in a micro DSM with a recycle time of 1 minute after melting. All mixtures were made at 300 °C, except for the epoxy - polyethylene mixture made at 220 °C.

[0181] At the end of the mixing process, the mixture is injected into a mold to produce test specimens characterized by DMA. TIFF0007713133000001.tif148170 Miscibility test results - Column 4: Glass transition temperature of each resin before mixing - Column 5: Glass transition temperature of the resins in the mixture - Column 6: Ratio of the difference in the glass transition temperature of the resins in the mixture to the difference in the glass transition temperature of the resins before mixing. 100% indicates immiscibility of the resins, <80% indicates low miscibility, <30% indicates good but partial miscibility, 0 indicates complete miscibility.

Claims

1. A multilayer structure selected from a storage tank, a pipe, or a tube for the purpose of hydrogen transport, distribution, or storage, wherein the multilayer structure includes, from the inside to the outside, at least one sealing layer and at least one composite reinforcing layer, The innermost composite reinforcing layer is welded to the outermost adjacent sealing layer, The sealing layer is composed of a composition mainly containing at least one semi-crystalline thermoplastic polymer P1i (i = 1 to n, n is the number of sealing layers) whose Tm is less than 280 °C as measured according to ISO 11357-3:2013, The at least one thermoplastic polymer of each sealing layer may be the same or different. At least one of the composite reinforcing layers is composed of a fiber material in the form of continuous fibers impregnated with a composition mainly containing at least one thermoplastic polymer P2j (j = 1 to m, m is the number of reinforcing layers). The thermoplastic polymer P2j has a Tg > 70 °C as measured according to ISO 11357-3:2013, Each polymer P1i of each sealing layer is partially or completely miscible with each polymer P1i of the adjacent layer, each polymer P2j of each reinforcing layer is partially or completely miscible with each polymer P2j of the adjacent layer, and polymer P21 is partially or completely miscible with the adjacent polymer P11, The complete or partial miscibility of the polymers is defined by the difference in the glass transition temperatures of the two resins in the mixture measured by DMTA according to ISO 4664-1 with respect to the difference in the glass transition temperatures of the two resins before the mixture. When the difference is equal to 0, the miscibility is complete. When the difference is different from 0, the miscibility is partial. The multilayer structure is characterized in that the polymer P1i and the polymer P2j are polyamides.

2. The multilayer structure according to claim 1, wherein Tm is less than 265 °C.

3. The multilayer structure according to claim 1 or 2, wherein the thermoplastic polymer P2j is semi-crystalline.

4. The multilayer structure according to any one of claims 1 to 3, wherein Tg > 80 °C.

5. The multilayer structure according to any one of claims 1 to 4, wherein Tg > 120 °C.

6. The multilayer structure according to any one of claims 1 to 5, characterized in that each sealing layer contains the same type of polymer.

7. The multilayer structure according to any one of claims 1 to 5, wherein each reinforcing layer contains the same type of polymer.

8. The multilayer structure according to claim 6 or 7, wherein each sealing layer contains the same type of polymer and each reinforcing layer contains the same type of polymer.

9. The multilayer structure according to any one of claims 1 to 8, characterized by having a single sealing layer and a single reinforcing layer.

10. The multilayer structure according to any one of claims 1 to 9, wherein the structure is a storage tank or a flexible pipe.

11. The multilayer structure according to any one of claims 1 to 10, wherein the composition containing the polymers P1i and P2j also contains an additive.

12. The multilayer structure according to claim 11, wherein the additive is carbon black, carbon nanotube (CNT) or graphene.

13. The multilayer structure according to any one of claims 1 to 12, wherein the composition containing the polymer P2j is permeable to irradiation for welding.

14. The multilayer structure according to claim 13, wherein the welding is performed by a system selected from laser, infrared (IR) heating, LED heating, induction or microwave heating or high frequency (HF) heating.

15. The multilayer structure according to claim 1, wherein the polymer P1i is a long-chain aliphatic polyamide or semi-aromatic.

16. The multilayer structure according to claim 15, wherein the polymer P1i is PA1010, PA1012, PA1212, PA11, PA12.

17. The multilayer structure according to claim 16, wherein the polymer P1i is PA11 or PA12.

18. The multilayer structure according to any one of claims 15 to 17, wherein the polymer P1i is PA11 / 5T, PA11 / 6T and PA11 / 10T.

19. The multilayer structure according to claim 1, wherein the polymer P2j is a semi-aromatic polyamide.

20. The multilayer structure according to claim 19, wherein the polymer P2j is a semi-aromatic polyamide selected from PA MPMDT / 6T, PA11 / 10T, PA11 / BACT, PA5T / 10T, PA11 / 6T / 10T, PA MXD T / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA11 / BACT / 6T, PA11 / MPMDT / 6T, PA11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXD T / 10T, PA11 / 5T / 10T.

21. The multilayer structure according to any one of claims 1 to 20, wherein the polymer P1i is a long-chain aliphatic polyamide or semi-aromatic, and the polymer P2j is a semi-aromatic polyamide.

22. The multilayer structure according to claim 21, wherein the polymer P1i is PA1010, PA1012, PA1212, PA11, or PA12.

23. The multilayer structure according to claim 21 or 22, wherein the polymer P1i is PA11 / 5T, or PA11 / 6T or PA11 / 10T.

24. The multilayer structure according to any one of claims 21 to 23, wherein the polymer P1i is PA11 or PA12.

25. The multilayer structure according to any one of claims 21 to 24, wherein the polymer P2j is a semi-aromatic polyamide selected from PA MPMDT / 6T, PA PA11 / 10T, PA11 / BACT, PA5T / 10T, PA11 / 6T / 10T, PA MXD T / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA11 / BACT / 6T, PA11 / MPMDT / 6T, PA11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXD T / 10T, PA11 / 5T / 10T.

26. The multilayer structure according to any one of claims 1 to 25, further comprising a metallic carcass located within the sealing layer.

27. The multilayer structure according to any one of claims 1 to 26, further comprising at least one outer layer, the layer being the outermost layer of the multilayer structure.

28. The multilayer structure according to claim 27, wherein the at least one outer layer is a metal layer.

29. The multilayer structure according to any one of claims 1 to 28, wherein the fiber material is selected from glass fiber and carbon or basalt or basalt-based fiber.

30. A method for manufacturing the multilayer structure defined in any one of claims 1 to 29, the method comprising the step of welding the reinforcing layer according to claim 1 to the sealing layer according to claim 1.

31. The method according to claim 30, wherein the welding step is performed by a system selected from laser, infrared (IR) heating, LED heating, induction or microwave heating or high frequency (HF) heating.

32. The method according to claim 30 or 31, comprising the step of extruding the sealing layer onto a metal carcass and the step of welding the reinforcing layer to the sealing layer.

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