A tank for storing gas

Abstract

A multi-layer structure for storing compressed gas, preferably at high pressure, more particularly hydrogen, comprising at least three layers, successively from the inside to the outside: at least one sealing layer consisting of a composition comprising as the main component at least one semi-crystalline thermoplastic polyamide having a Tm of less than or equal to 280°C, measured according to the standard ISO 11357-3:2013; at least one intermediate composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition comprising as the main component at least one semi-crystalline thermoplastic polyamide having a Tg of less than 100°C, preferably less than or equal to 80°C, more particularly less than or equal to 60°C, measured according to the standard ISO 11357-3:2013; and at least one outer composite reinforcing layer made of a fibrous material in the form of long fibers impregnated with a composition containing at least one polyphthalamide as the main component, the composition having a Tg of more than 80°C, preferably more than 100°C, as measured according to the standard 11357-3:2013, wherein the outermost sealing layer is welded to the innermost intermediate composite reinforcing layer and the outermost intermediate composite reinforcing layer is welded to the innermost lateral outer composite reinforcing layer.

Description

[Technical field]

[0001] The present invention relates to a tank with a specific multi-layer structure for storing gas, in particular compressed gas at high pressure, and to a method for manufacturing the same. [Background technology]

[0002] One of the aims sought in the field of transport, and in particular in the field of motor vehicles, is to propose less polluting vehicles. For this purpose, the aim is to gradually replace internal combustion engine vehicles, such as gasoline or diesel vehicles, with electric or hybrid vehicles that include batteries. However, batteries turn out to be a relatively complex component of the vehicle. Depending on the location of the battery in the vehicle, it may be necessary to protect the battery from impacts and the external environment, which may be of extreme temperature and variable humidity. Also, any risk of fire must be prevented.

[0003] In addition, to avoid damaging the battery cells and to preserve their lifespan, it is important that the vehicle's operating temperature does not exceed 55°C. Conversely, during winter, for example, it may be necessary to increase the battery temperature to optimize its operation.

[0004] Furthermore, electric vehicles still have several problems, such as battery autonomy, the use of rare earth elements in batteries that are not exhaustible, as well as the problem of producing electricity in different countries to be able to recharge the batteries.

[0005] Hydrogen is therefore an alternative to electric batteries, as it can be converted into electricity by fuel cells, thereby powering electric vehicles.

[0006] Nevertheless, the storage of hydrogen is technically difficult and expensive, especially for mobile storage, due to its very low molecular weight and very low liquefaction temperature. However, to be effective, storage must be done in small quantities, which requires taking into account the temperatures at which the vehicle will be used and keeping the hydrogen under high pressure. This is especially true for fuel cell hybrid road vehicles. In contrast, self-reliance is required for ranges of around 600-700 km, or even less for essentially urban use, as a complement to the battery-powered electric base.

[0007] Hydrogen tanks generally consist of a metal liner, which should prevent the diffusion of hydrogen outside the shell. The first shell should therefore be protected by a second casing (generally made of composite materials) intended to withstand the internal pressure of the tank (e.g. 700 bar) and to withstand possible impacts or heat sources. Furthermore, the tank contains a valve system, which should also be made safe.

[0008] According to the Memorandum on Hydrogen of the French Association for Hydrogen and fuel cell (AFHYPAC (Association Francaise pour l'hydrogen et la pile a combustible)), sheet 4.2, revised in December 2016, the storage and distribution of hydrogen under pressure has been standard practice for many years, using steel cylinders or cylinder assemblies pressurized to 20 or 25 MPa (Type I and II). The drawback of such a storage method is that it has a low hydrogen content of only 14 kg / m3 at bulk-20 MPa and room temperature (21°C). 3 whereas methane has a density of 100 kg / m 3- and especially weight. The weight disadvantage results from the use of steels with a low level of stress to avoid the embrittlement problems caused by hydrogen. The situation has changed radically with the advent of the technology of the so-called types III and IV composite tanks. The basic principle of said tanks is to separate the two essential functions, sealing and mechanical resistance, in order to manage one independently of the other. In said types of tanks, a bladder made of (thermosetting or thermoplastic) resin, called the sealing liner or sheath, is associated with a reinforcing structure made of fibers (glass, aramid, carbon), called the reinforcing sheath or layer. Said types of tanks allow them to operate at much higher pressures while reducing the mass of the tank and preventing the risk of explosive rupture in case of a violent external attack. This makes a pressure of 70 MPa (700 bar) the de facto current standard.

[0009] In type IV tanks, the sealing and reinforcing layers are made of different materials that do not adhere to each other and often cause the collapse of the sealing layer, resulting in both gas accumulation at the interface between the sealing and reinforcing layers and a simultaneous drop in the tank's internal pressure. Moreover, drying of type IV tanks after hydrostatic testing is time-consuming and expensive, since drying can only be performed under vacuum due to the risk of the sealing layer collapsing.

[0010] Such problems have led to the development of Type V tanks, which are based on using the same polymer for the matrix of the sealing layer and the reinforcing layer in order to provide a good and durable weldability between the two layers, thereby obtaining a monolithic tank.

[0011] To manufacture composite shells, tanks with a high glass transition temperature (hereafter Tg), i.e. Tg can exceed 100 ° C, a method is known that uses epoxy resins as the matrix of the composite. A disadvantage of composites with thermosetting resins, especially epoxy resins, is that they generally develop microcracks, which cause large variability or even loss of mechanical strength. Moreover, such a phenomenon is amplified over time by the successive filling / emptying cycles of the tank. It is therefore necessary to increase the carbon fiber content and therefore the weight and cost of the tank.

[0012] Furthermore, for thermosetting resins, especially epoxy resins, microcracks have a negative effect on the impermeability of the composite reinforcement, necessitating the use of thick sealing layers inside the tank (i.e., Type IV tanks).

[0013] Finally, from the point of view of recyclability, current tanks use reinforcing layers made of thermosetting resins, in particular epoxy resins, which are not recyclable.

[0014] However, despite the improvements being made to type IV tanks, they still have drawbacks. In particular, there is a demand to accelerate the filling speed of the tanks. However, the temperature resistance of gas tanks, especially hydrogen tanks, is too low with current solutions. Accelerating the filling speed of the tanks would be advantageous for the consumer and especially would save costs, especially without the additional need to cool the hydrogen to -60 ° C before filling.

[0015] The use of a polyphthalamide reinforcing layer (hereinafter referred to as PPA) with a high glass transition temperature (hereinafter Tg) represents an important advantage in terms of mechanical resistance at high temperatures. Moreover, said type of resin is thermoplastic, which helps to obtain an easily recyclable tank. The thermoplasticity of the resin reduces the level of microcracks in the composite shell, thereby strengthening the mechanical resistance of the composite shell, reducing the variability of the mechanical resistance and significantly reducing the amount of carbon fiber used and therefore the cost and the carbon footprint of a type V tank compared to a type IV tank. Furthermore, the semi-crystalline nature of the resin increases the sealing against gases, especially hydrogen. The composite shell therefore contributes to the impermeability of the tank, thereby reducing the thickness of the sealing layer and therefore the cost and weight of the inner sealing layer of the tank.

[0016] However, the manufacture of such type of tank by winding a high-temperature composite tape on a thermoplastic polymer sealing layer causes difficulties, during the cooling of the tank, at the end of its manufacture, related to the occurrence of significant residual stresses of thermal origin inherent to the expansion differences of the materials involved, more particularly between the fibers and the polymer that constitute the sealing layer. The above is particularly aggravated in the case of the PPA matrix that constitutes the carbon fiber composite reinforcement. In fact, the high temperatures for using the composite tape containing PPA are the main cause of additional residual stresses in the tank, due to the high melting point of such type of resin as well as its high Tg. If the tank contains a molded insert of a polyamide resin with a low Tg, more particularly polyamide 11 (PA11), typically with a Tg of the order of 50 ° C, said residual stresses can lead to deformation of the insert and hinder the complete manufacture of the tank, in particular the fastening of the base that closes the tank. If the tank is of type V (or 4.5, i.e. the polymer that constitutes the matrix of the composite is of a different nature to that of the sealing layer, but the two polymers remain compatible and weldable with each other) and has a polyamide sealing layer with a low Tg, more specifically of type PA11, the residual stresses can lead to delamination within the composite reinforcement layer itself. Summary of the Invention [Problem to be solved by the invention]

[0017] There is therefore currently a need for a tank that has good mechanical resistance at high temperatures, can be recycled, has a good gas seal and is easy to manufacture, in particular a tank structure that reduces the level of residual mechanical stresses between the composite and the sealing layer and between the composite and the molded insert, related to the thermal differences that the tank is subjected to during its manufacture, so that such a tank is useful for storing hydrogen and any type of gas under pressure, in particular under high pressure.

[0018] Such problems are solved by a tank that includes a specific multi-layer structure. [Means for solving the problem]

[0019] The present invention relates to a multi-layer structure for the storage of compressed gases, preferentially under high pressure, and more particularly hydrogen, which comprises, from the inside to the outside, at least three successive layers: at least one sealing layer consisting essentially of at least one semicrystalline thermoplastic polyamide, preferentially aliphatic, composition, the melting temperature (Tf) of which, measured according to the ISO 11357-3:2013 standard, is less than or equal to 280°C, preferentially less than or equal to 260°C, preferentially less than or equal to 230°C and more particularly less than or equal to 200°C; at least one intermediate composite reinforcing layer made of fibrous material in the form of long fibers impregnated with at least one semicrystalline thermoplastic polyamide, preferentially with an aliphatic-based composition, the Tg of which, measured according to the ISO 11357-3:2013 standard, is less than 100 ° C, preferentially less than or equal to 80 ° C, more particularly less than or equal to 60 ° C, at least one outer composite reinforcing layer made of a fibrous material in the form of long fibers impregnated with a composition comprising, as a main component, at least one polyphthalamide, the Tg of which, measured according to the ISO 11357-3 2013 standard, is higher than 80 ° C, and preferentially higher than 100 ° C, the outermost sealing layer is welded to the innermost intermediate composite reinforcing layer; For a tank comprising a multi-layer structure, an outermost intermediate composite reinforcing layer is welded to an innermost outer composite reinforcing layer.

[0020] The inventors have found that the above problems are solved by inserting a composite reinforcing layer of semi-crystalline thermoplastic polyamide, preferentially aliphatic, with a Tg<100°C between the specific sealing layer and the specific composite reinforcing layer made of PPA.

[0021] Indeed, the tank according to the invention is easy to manufacture, which allows it to be quickly filled and emptied. The tank is characterised by having a high gas seal and being lightweight.

[0022] The invention further relates to a method for manufacturing the tank according to the invention.

[0023] Finally, the invention relates to the use of a tank according to the invention for storing a gas under pressure, more particularly hydrogen, LPG or CNG, compressed air.

[0024] Other features, aspects, objects and advantages of the present invention will become more apparent from the following description.

[0025] It is further provided that, as used herein, the phrases "comprised in" and "of" are to be understood as including each of the referenced boundaries.

[0026] tank The tank according to the invention comprises a multi-layer structure for the storage of compressed gas, more particularly hydrogen, which comprises, from the inside to the outside, at least three successive layers: at least one sealing layer consisting essentially of at least one semicrystalline thermoplastic polyamide, preferentially aliphatic, composition, the Tf of which, measured according to the ISO 11357-3:2013 standard, is less than or equal to 280 ° C, preferentially less than or equal to 260 ° C, preferentially less than or equal to 230 ° C and more particularly less than or equal to 200 ° C, at least one intermediate composite reinforcing layer made of fibrous material in the form of long fibers impregnated with at least one semicrystalline thermoplastic polyamide, preferentially with an aliphatic-based composition, the Tg of which, measured according to the ISO 11357-3:2013 standard, is less than 100 ° C, preferentially less than or equal to 80 ° C, more particularly less than or equal to 60 ° C, at least one outer composite reinforcing layer made of a fibrous material in the form of long fibers impregnated with a composition comprising, as a main component, at least one polyphthalamide, the Tg of which, measured according to the ISO 11357-3 2013 standard, is higher than 80 ° C, and preferentially higher than 100 ° C, the outermost sealing layer is welded to the innermost intermediate composite reinforcing layer; The outermost intermediate composite reinforcing layer is fused to the innermost composite reinforcing layer.

[0027] All layers of the structure according to the invention comprise polyamide as the main component.

[0028] The nomenclature used to define polyamides is described in the ISO 1874-1:2011 "Plastics-Polyamide (PA) molding and extrusion materials-Part 1: Description" standard, especially on page 3 (Tables 1 and 2), and is well known to those skilled in the art. In the notation PAL, PA stands for polyamide and L stands for the number of carbon atoms of the amino acid or lactam. Polyamides are thus obtained by polycondensation of amino acids or lactams containing L carbon atoms. In the notation PAMN, M stands for the number of carbon atoms of the diamine and N stands for the number of carbon atoms of the diacid.

[0029] According to the invention, "semi-crystalline thermoplastic polyamide" means a material which is generally solid at room temperature and which softens with increasing temperature, more specifically after exceeding the glass transition temperature (Tg) and which can exhibit a distinct melt above the so-called melting temperature (Tf), becoming solid again when the temperature falls below the crystallization temperature (TC).

[0030] The glass transition temperature Tg, the crystallization temperature TC and the melting temperature Tf are determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013, respectively.

[0031] About the sealing layer In the multi-layer structure of the tank according to the invention, one or more sealing layers are or may be present.

[0032] Each of said layers consists of a composition comprising as a main component at least one semi-crystalline thermoplastic polyamide having a Tf, measured according to the ISO 11357-3:2013 standard, of less than or equal to 280°C, preferentially less than or equal to 260°C, preferentially less than or equal to 230°C and more particularly less than or equal to 200°C.

[0033] The term "predominantly" means that said at least one polyamide is present in an amount greater than 50% by weight relative to the total weight of the composition.

[0034] Advantageously, said at least one main polyamide is present in an amount of more than 60% by weight, in particular more than 70% by weight, in particular more than 80% by weight and more particularly in an amount equal to or greater than 90% by weight, relative to the total weight of the composition.

[0035] The composition may also contain impact modifiers and / or additives. However, the barrier layer should not release harmful compounds into the stored gas and should not contain particles that may reduce its permeability. Thus, the skilled person will be careful to select the additives and their content in the composition so as to prevent such release.

[0036] The additives may be selected from among antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents, plasticizers, dyes, carbon black and carbonaceous nanofillers.

[0037] Advantageously, said composition consists essentially of one or more semicrystalline thermoplastic polyamides as defined above, from 0 to 5% by weight of impact modifiers and from 0 to 5% by weight of additives, the sum of the components of the composition being equal to 100% by weight.

[0038] In one embodiment of the tank according to the invention, a single main component, polyamide, is present in the sealing layer.

[0039] Advantageously, the composition forming the sealing layer is black and capable of absorbing radiation suitable for welding.

[0040] To produce the same absorbers, it is known to add various additives, including, for example, carbon black, which impart a black color to the polymer and provide better absorption of radiation suitable for welding.

[0041] Semi-crystalline thermoplastic polyamide The semi-crystalline thermoplastic polyamide may be a homopolyamide or a copolyamide.

[0042] Advantageously, the semicrystalline thermoplastic polyamide contained in the sealing layer has a ratio, indicated by C / N, between the number of carbon atoms and the number of nitrogen atoms of the polyamide of 5 or more, preferentially 8 or more, in particular 9 or more and more particularly 10 or more.

[0043] Preferentially, the semicrystalline thermoplastic polyamides are selected from the group consisting of PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, preferentially PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, 11 / 5T, PA 11 / 6T and PA11 / 10T, very preferentially PA 11 or PA12, and mixtures thereof.

[0044] The content of units 11 in the semi-aromatic copolyamide is adjusted so that the melting point of the copolyamide is less than or equal to 280°C, preferentially less than or equal to 260°C, preferentially less than or equal to 230°C and more particularly less than or equal to 200°C.

[0045] In a preferred embodiment, the semi-crystalline thermoplastic polyamide is an aliphatic semi-crystalline thermoplastic polyamide.

[0046] Preferentially, the semi-crystalline thermoplastic polyamide contained in the sealing layer is an aliphatic semi-crystalline thermoplastic polyamide, more particularly PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, preferentially PA6, PA66, PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA It is selected from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, very preferentially PA 11 or PA12, and mixtures thereof.

[0047] More particularly, the aliphatic semi-crystalline thermoplastic polyamide is chosen from polyamide 11 (PA11), polyamide 12 (PA12), polyamide 1010 (PA1010), polyamide 1012 (PA1012), and more particularly from PA11 and PA12.

[0048] The composition forming the sealing layer comprises a polyamide as defined above as the main component, or a mixture of polyamides as defined above as the main component, such a mixture being present in the composition.

[0049] Intermediate composite reinforcement layer One or more composite reinforcing layers are or can be present as intermediate layers.

[0050] Each of said layers consists of a fibrous material in the form of long fibers impregnated with a composition comprising at least one semicrystalline thermoplastic polyamide, preferentially aliphatic, as the main component, and having a Tg, measured according to standard ISO 11357-3:2013, of less than 100°C, preferentially less than or equal to 80°C and more particularly less than or equal to 60°C.

[0051] The term "as a major component" means that said at least one polymer is present in an amount of more than 50% by weight relative to the total weight of the composition.

[0052] Advantageously, said at least one multipolymer is present in an amount greater than 60% by weight, in particular greater than 70% by weight, in particular greater than 80% by weight and more particularly greater than or equal to 90% by weight, relative to the total weight of the composition.

[0053] The composition may also include impact modifiers and / or additives.

[0054] The additives may be selected from among antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents, plasticizers, dyes, carbon black and carbonaceous nanofillers.

[0055] Advantageously, said composition consists essentially of one or more semicrystalline thermoplastic polyamides as defined above, from 0 to 5% by weight of impact modifiers and from 0 to 5% by weight of additives, the sum of the components of the composition being equal to 100% by weight.

[0056] In one embodiment of the tank according to the invention, a single main component, polyamide, is present in the layer impregnating the fibrous material of the intermediate composite reinforcing layer.

[0057] Advantageously, the composition forming the layer within the layer impregnating the fibrous material of the intermediate composite reinforcing layer is black in color and capable of absorbing radiation suitable for welding.

[0058] To produce the same absorbers, it is known to add various additives, including, for example, carbon black, which impart a black color to the polymer and provide better absorption of the radiation suitable for welding.

[0059] Semi-crystalline thermoplastic polyamide The aliphatic semi-crystalline thermoplastic polyamide may be a homopolyamide or a copolyamide.

[0060] Preferentially, the semicrystalline thermoplastic polyamides are PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, preferentially PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, very preferentially PA 11 or PA12, and mixtures thereof.

[0061] The content of units 11 in the semi-aromatic copolyamide is adjusted so that the glass transition temperature of the copolyamide is less than 100°C, preferentially less than or equal to 80°C and more particularly less than or equal to 60°C.

[0062] In a preferred embodiment, the semi-crystalline thermoplastic polyamide is an aliphatic semi-crystalline thermoplastic polyamide.

[0063] Advantageously, the aliphatic semicrystalline thermoplastic polyamides contained in the composition for impregnating the fibrous material are PA410, PA 56, PA59, PA510, PA512, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, preferentially PA6, PA66, PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA It is selected from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, and mixtures thereof.

[0064] More particularly, the aliphatic semi-crystalline thermoplastic polyamide is chosen from polyamide 11 (PA11), polyamide 12 (PA12), polyamide 1010 (PA1010), polyamide 1012 (PA1012), and more particularly from PA11 and PA12.

[0065] Outer composite reinforcement layer One or more composite reinforcing layers may be present as outer layers.

[0066] Each of said layers consists of a composition comprising, as a main component, at least one polyphthalamide having a Tg greater than 80° C., preferentially greater than or equal to 100° C., measured according to standard ISO 11357-3:2013.

[0067] The term "as a major component" means that said at least one polymer is present in an amount of more than 50% by weight relative to the total weight of the composition.

[0068] Advantageously, said at least one multipolymer is present in an amount of more than 60% by weight, in particular in an amount of more than 70% by weight, in particular in an amount of more than 80% by weight and more particularly in an amount equal to or greater than 90% by weight, relative to the total weight of the composition.

[0069] The composition may also include impact modifiers and / or additives.

[0070] The additives may be selected from among antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents, plasticizers, dyes, carbon black and carbonaceous nanofillers.

[0071] Advantageously, said composition consists essentially of one or more semicrystalline thermoplastic polyamides as defined above, from 0 to 5% by weight of impact modifiers and from 0 to 5% by weight of additives, the sum of the components of the composition being equal to 100% by weight.

[0072] In one embodiment of the tank according to the invention, a single main component, polyamide, is present in the layer within the layer impregnating the fibrous material of the outer composite reinforcing layer.

[0073] Advantageously, the composition is black and capable of absorbing radiation suitable for welding.

[0074] To produce the same absorbers, it is known to add various additives, including, for example, carbon black, which impart a black color to the polymer and provide a better absorption of the radiation suitable for welding.

[0075] Polyphthalamide The polyamide may be a homopolyamide or a copolyamide.

[0076] Advantageously, the semicrystalline polyamide is a semiaromatic polyamide, in particular a semiaromatic polyamide having the formula X / YAr as described in EP 1505099, in particular a semiaromatic polyamide having the formula A / XT, in which A is selected from units resulting from amino acids, units resulting from lactams and units having the formula (Ca diamine) (Cb diacid), a is the number of carbon atoms of the diamine and b is the number of carbon atoms of the diacid, a and b are each comprised between 4 and 36, advantageously between 9 and 18, the units (Ca diamine) being selected from linear or branched aliphatic diamines, cycloaliphatic diamines and alkylaromatic diamines and the units (Cb diacid) being selected from linear or branched aliphatic diacids, cycloaliphatic diacids and aromatic diacids.

[0077] XT represents a unit resulting from the polycondensation of a Cx diamine with terephthalic acid, where x represents the number of carbon atoms of the Cx diamine, x being comprised between 5 and 36, advantageously between 9 and 18.

[0078] Preferentially, the polyamide contained in the layer impregnating the fibrous material of the outer composite reinforcing layer has the formula A / 5T, A / 6T, A / 9T, A / 10T, A / 11T, a / BACT, A / MPMDT or A / MXDT, A being as defined herein, more particularly PA MPMDT / 6T, PA 11 / 10T, PA 5T / 10T, PA 11 / 6T / 10T, PA MXDT / 4T, PA MXDT / 6T PA, MXDT / 10T PA, MPMDT / 4T PA, MPMDT / 6T PA, MPMDT / 10T PA, PA 11 / MXDT / 4T, PA 11 / MXDT / 6T, PA 11 / MXDT / 10T, PA 11 / MPMDT / 4T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA and mixtures thereof.

[0079] T represents terephthalic acid, MXD represents m-xylylenediamine, MPMD represents 2-methylpentamethylenediamine, and BAC represents bis(aminomethyl)cyclohexane.

[0080] The composition may also include impact modifiers and / or additives.

[0081] The additives may be selected from among antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents, plasticizers and colorants.

[0082] Advantageously, said composition consists of one or more polyphthalamides having a Tg greater than 80° C., measured according to standard ISO 11357-3:2013, between 0 and 5% by weight of impact modifiers and between 0 and 5% by weight of additives, the sum of the components of the composition being equal to 100%.

[0083] The at least one major polymer of each layer may be the same or different.

[0084] In one embodiment, a single polyphthalamide is present as the major component of an outer composite reinforcing layer that is welded to the intermediate layer.

[0085] Advantageously, the carbonaceous nanofillers are non-agglomerated or non-aggregated.

[0086] Advantageously, the carbonaceous nanofillers are incorporated in the composition in an amount ranging from 100 ppm to 500 ppm, preferentially from 100 ppm to 250 ppm.

[0087] Advantageously, the carbonaceous nanofillers are chosen from carbon nanotubes (CNTs), carbon nanofibers, graphene, nanometric carbon black and mixtures thereof.

[0088] Advantageously, the carbonaceous nanofiller does not include nanometric carbon black.

[0089] About fiber materials As regards the fibres forming said fibrous material present in the intermediate and outer layers, these are in particular fibres of mineral, organic or vegetable origin.

[0090] Advantageously, said fibre material may be sized or unsized.

[0091] The textile material may therefore contain up to 0.1% by weight of organic material (thermosetting or thermoplastic resins) and is called sizing.

[0092] Fibres of mineral origin include, for example, carbon fibres, glass fibres, basalt or basalt-based fibres, silica fibres or silicon carbide fibres.

[0093] Fibers of organic origin include, for example, fibers based on thermoplastic or thermosetting polymers, such as semi-aromatic polyamide fibers, aramid fibers or polyolefin fibers. Preferentially, it contains an amorphous thermoplastic polymer, which has a glass transition temperature Tg higher than the Tg of the constituent thermoplastic polymer or polymer mixture of the pre-impregnated matrix, if the pre-impregnated matrix is ​​amorphous, or higher than the Tf of the constituent thermoplastic polymer or polymer mixture of the pre-impregnated matrix, if the pre-impregnated matrix is ​​semi-crystalline. Advantageously, it contains a semi-crystalline thermoplastic polymer, which has a melting temperature Tf higher than the Tg of the constituent thermoplastic polymer or polymer mixture of the pre-impregnated matrix, if the pre-impregnated matrix is ​​amorphous, or higher than the Tf of the constituent thermoplastic polymer or polymer mixture of the pre-impregnated matrix, if the pre-impregnated matrix is ​​semi-crystalline. Thus, there is no risk of the organic fibers of the fibrous material melting when the final composite is impregnated by the thermoplastic matrix.

[0094] Fibres of vegetable origin include natural fibres including flax, hemp, lignin, bamboo, silk, especially spider silk, sisal and other cellulosic fibres, more particularly viscose. The fibres of vegetable origin can be used pure, treated or coated with a coating layer to facilitate adhesion and impregnation of the thermoplastic polymer matrix.

[0095] The textile material may also be a textile made by knitting or weaving the fibers.

[0096] This may also correspond to a fiber having a holding thread.

[0097] Such constituent fibers can be used alone or in a mixture, whereby organic fibers can be mixed with mineral fibers and pre-impregnated with thermoplastic polymer powder to form a pre-impregnated fibrous material.

[0098] The organic fiber yarn can have multiple weave weights. Moreover, it can also have multiple geometric shapes. The constituent fibers of the fiber material can be in the form of a mixture of reinforcing fibers with different geometric shapes. The fibers are long fibers.

[0099] Preferentially, the fibre material consists of long fibres chosen from glass fibres, carbon fibres, basalt fibres or fibres containing basalt, more particularly carbon fibres, used in the form of a thread or multiple threads.

[0100] Multilayer structure Thus, the multi-layer structure comprises at least one sealing layer, at least one intermediate composite reinforcing layer, and at least one outer composite reinforcing layer, with all adjacent layers being welded together.

[0101] In one embodiment, in said multi-layer structure, each polyamide contained in the composition forming each sealing layer is partially or fully miscible with each polyamide contained in the composition forming each adjacent sealing layer.

[0102] The same applies to intermediate composite reinforcing layers if the structure includes multiple layers.

[0103] The same is true for the outer composite reinforcement layers if the structure includes multiple layers.

[0104] Additionally, the outermost sealing layer is welded to the innermost intermediate composite reinforcement layer, and the outermost intermediate composite reinforcement layer is welded to the innermost outer composite reinforcement layer.

[0105] Such welding of the various layers results in total or partial miscibility of the compositions and / or matrices contained in the layers.

[0106] The total or partial miscibility of the compositions is determined by the ratio of compounds between the difference in glass transition temperatures of the two compositions of two adjacent layers and the difference in glass transition temperatures of the two compositions before mixing by fusing the two compositions.

[0107] The miscibility is, in absolute value, total when the ratio is equal to 0, and partial when the ratio is different from 0 and less than 1. The immiscibility between the polyamide contained in the composition for forming the sealing layer and the polyamide contained in the composition for impregnating the fiber material of the intermediate layer is excluded. Similarly, the immiscibility between the polyamide contained in the composition for impregnating the fiber material of the intermediate layer and the polyamide of the composition for impregnating the fiber material of the outer layer is excluded.

[0108] Advantageously, when the miscibility of the composition is partial, the ratio is less than 30% in absolute value, preferably less than 20%.

[0109] In one embodiment, the glass transition temperature of the one or more mixtures should be included between the glass transition temperatures of the polyamides before mixing, depending on whether the miscibility is total or partial, and differ by at least 5°C, preferably at least 10°C.

[0110] The expression "completely miscible" means, for example, that two polyamides designated as PAa and PAb, each having Tga and Tgb respectively, are present in two adjacent sealing layers or reinforcing layers, and when Tga is lower than Tgb, the mixture of the two polyamides has only one Tgab, the value of which is included between Tga and one of the Tgbs.

[0111] In that case, the value of the Tgab value is at least 5°C, more particularly at least 10°C greater than Tga and at least 5°C, more particularly at least 10°C less than Tgb.

[0112] The expression "partially miscible" means, for example, that when two polyamides PAa and PAb, each having Tga and Tgb respectively, are present in two adjacent sealing layers or reinforcing layers, the mixture of the two polyamides has two Tgs, Tg’a and Tg’b, and Tga < Tg’a < Tg’b < Tgb.

[0113] In that case, the values ​​of Tg'a and Tg'b are at least 5°C, more particularly at least 10°C, greater than Tga and at least 5°C, more particularly at least 10°C, less than Tgb.

[0114] The immiscibility of the two polyamides results in the presence of two Tg, Tga and Tgb in the mixture of the two polyamides which correspond to the respective Tg, Tga and Tgb of the pure polymers obtained separately.

[0115] It is not outside the scope of the present invention if the glass transition temperatures of a mixture of two polyamides are the same or different at the temperature before mixing, but the two polyamides are reactive with each other.

[0116] Advantageously, the welded sealing layer and the intermediate reinforcing layer each consist of a composition comprising a different polyamide, and the intermediate reinforcing layer and the outer reinforcing layer each consist of a composition comprising a different polyamide.

[0117] The multi-layer structure may include up to 300 sealing layers, up to 10 intermediate composite reinforcement layers, and up to 300 outer composite reinforcement layers.

[0118] It will be quite clear that the multi-layer structure is not necessarily symmetrical and may therefore include more sealing layers than composite layers, or vice versa.

[0119] Advantageously, said multi-layer structure comprises 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 sealing layers, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 intermediate composite reinforcement layers and 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 outer composite reinforcement layers.

[0120] Advantageously, the multilayer structure comprises 1, 2, 3, 4 or 5 sealing layers, 1, 2, 3, 4 or 5 intermediate composite reinforcement layers and 1, 2, 3, 4 or 5 outer composite reinforcement layers.

[0121] Advantageously, said multilayer structure comprises one, two or three sealing layers and one or three composite reinforcing layers, each of which is made of a composition comprising a different polyamide.

[0122] In a preferred embodiment, the tank according to the invention comprises a multi-layer structure comprising only one sealing layer, only one intermediate composite reinforcement layer and only one outer composite reinforcement layer, said sealing layer being welded to said adjacent intermediate composite reinforcement layer and said intermediate composite reinforcement layer being welded to said adjacent outer composite reinforcement layer, said intermediate composite reinforcement layer having preferentially a thickness of 1 to 30%, more particularly a thickness of 1 to 10%, even more preferentially a thickness of 1 to 5% with respect to the thickness of all composite reinforcement layers of the multi-layer structure, i.e. the intermediate composite reinforcement layer and the outer composite reinforcement layer.

[0123] In another embodiment, the tank according to the invention comprises a multi-layer structure comprising only one sealing layer, only one intermediate composite reinforcement layer and only one outer composite reinforcement layer, said sealing layer being welded to said adjacent intermediate composite reinforcement layer and said intermediate composite reinforcement layer being welded to said adjacent outer composite reinforcement layer, said sealing layer having the same composition as said intermediate composite reinforcement layer and said intermediate composite reinforcement layer, and having preferentially a thickness of 1 to 30%, more particularly a thickness of 1 to 10%, even more preferentially a thickness of 1 to 5% relative to the thickness of all composite reinforcement layers of the multi-layer structure.

[0124] In another preferred embodiment, the tank according to the invention is a multi-layer structure, a single sealing layer consisting essentially of at least one semi-crystalline thermoplastic polyamide, preferentially aliphatic, composition, the melting temperature (Tf) of which, measured according to the ISO 11357-3:2013 standard, is less than or equal to 230°C; only one intermediate composite reinforcing layer consisting of a fibrous material in the form of long fibres impregnated with a composition containing at least one semicrystalline thermoplastic polyamide, preferentially aliphatic, predominantly, component, the composition having a Tg of less than 60°C, measured according to the ISO 11357-3:2013 standard; and a single outer composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition comprising, as a main component, at least one polyphthalamide, the Tg of which, measured according to the ISO 11357-3:2013 standard, is greater than 100°C, The sealing layer includes a multi-layer structure, the intermediate composite reinforcement layer being fused to an intermediate composite reinforcement layer, the intermediate composite reinforcement layer being fused to an outer composite reinforcement layer.

[0125] According to a preferred embodiment, all composite reinforcing layers comprise carbon fiber.

[0126] According to a preferred embodiment, the tank according to the invention is a multi-layer structure for the storage of compressed gases, preferentially under high pressure, more particularly hydrogen, which comprises, from the inside to the outside, at least three successive layers: PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11, PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, preferentially PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA at least one sealing layer consisting of a composition comprising as a main component at least one semicrystalline thermoplastic polyamide selected from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, preferentially PA 11 and PA12, and mixtures thereof; - Tg, measured according to the standard ISO 11357-3:2013, is less than 100 ° C, preferentially less than or equal to 80 ° C, more particularly less than or equal to 60 ° C, such as PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, 25 PA1218, PA11, PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, preferentially PA6, PA66, PA410, PA510, PA 69, PA610, PA at least one intermediate composite reinforcing layer consisting of a fibrous material in the form of long fibres impregnated with a composition comprising as a main component at least one semicrystalline thermoplastic polyamide selected from the group consisting of PA 512, PA612, PA 514, PA614, PA618, PA PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, preferentially PA 11 or PA12 and mixtures thereof; - Tg measured according to the ISO 11357-3 2013 standard is higher than 80°C, preferentially higher than 100°C, for PA MPMDT / 6T, PA 11 / 10T, PA 11 / BACT, PA 5T / 10T, PA 11 / 6T / 10T, MXDT / 4T PA, MXDT / 6T PA, MXDT / 10T PA, PAMPMDT / 4T PA, MPMDT / 6T PA, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 4T, PA BACT / 10T / 6T, PA 11 / BACT / 4T, PA 11 / BACT / 6T, PA 11 / BACT / 10T, PA 11 / MXDT / 4T, PA 11 / MXDT / 6T, PA at least one outer composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition comprising as a main component at least one polyphthalamide selected from the group consisting of PA 11 / MXDT / 10T, PA11 / MPMDT / 4T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / MXDT / 10T, PA11 / 5T / 10T and mixtures thereof, the outermost sealing layer is welded to the innermost intermediate composite reinforcing layer; The outermost intermediate composite reinforcing layer comprises a multi-layer structure that is fused to the innermost outer composite reinforcing layer.

[0127] According to a preferred embodiment, the tank according to the invention is a multi-layer structure for the storage of compressed gases, preferentially under high pressure, more particularly hydrogen, which comprises, from the inside to the outside, at least three successive layers: - PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11, PA12, preferentially PA 6, PA66, PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA at least one sealing layer consisting of a composition comprising as a main component at least one semi-crystalline thermoplastic aliphatic polyamide selected from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, preferentially PA 11 and PA12, and mixtures thereof; - Tg, measured according to the standard ISO 11357-3:2013, is less than 100 ° C, preferentially less than or equal to 80 ° C, more particularly less than or equal to 60 ° C, such as PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11, PA12, preferentially PA 6, PA66, PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA at least one intermediate composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition comprising as a main component at least one semicrystalline thermoplastic aliphatic polyamide selected from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, preferentially PA 11 or PA12 and mixtures thereof; - Tg measured according to standard ISO 11357-3 2013 is higher than 80°C, preferentially higher than 100°C, for PA MPMDT / 6T, PA 11 / 10T, PA 11 / BACT, PA 5T / 10T, PA 11 / 6T / 10T, PA MXDT / 4T, PA MXDT / 6T, PA MXDT / 10T, PA MPMDT / 4T, PA MPMDT / 6T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 4T, PA BACT / 10T / 6T, PA 11 / BACT / 4T, PA 11 / BACT / 6T, PA 11 / BACT / 10T, PA 11 / MXDT / 4T, PA 11 / MXDT / 6T, PA at least one outer composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition comprising as a main component at least one polyphthalamide selected from the group consisting of PA 11 / MXDT / 10T, PA11 / MPMDT / 4T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / MXDT / 10T, PA11 / 5T / 10T and mixtures thereof, the outermost sealing layer is welded to the innermost intermediate composite reinforcing layer; The outermost intermediate composite reinforcing layer comprises a multi-layer structure that is fused to the innermost outer composite reinforcing layer.

[0128] In another preferred embodiment, the tank according to the invention is a multi-layer structure, - only one sealing layer of polyamide 6, - only one intermediate composite tough layer, the matrix of which is polyamide 6, and a single outer composite reinforcing layer, the matrix of which is a copolyamide containing BACT units, i.e. having the formula A / BACT; The sealing layer includes a multi-layer structure, the intermediate composite reinforcement layer being fused to an intermediate composite reinforcement layer, the intermediate composite reinforcement layer being fused to an outer composite reinforcement layer.

[0129] In another preferred embodiment, the tank according to the invention is a multi-layer structure, - only one sealing layer of polyamide 66, - only one intermediate composite tough layer, the matrix of which is polyamide 66, and comprising only one outer composite reinforcing layer, the matrix of which comprises BACT units, i.e. is a copolyamide having the formula A / BACT, where A is as defined above, The sealing layer includes a multi-layer structure, the intermediate composite reinforcement layer being fused to an intermediate composite reinforcement layer, the intermediate composite reinforcement layer being fused to an outer composite reinforcement layer.

[0130] In another preferred embodiment, the tank according to the invention is a multi-layer structure, - Only one sealing layer of polyamide 11 / 10T, - only one intermediate composite tough layer, the matrix of which is polyamide 11 / 10T, and a single outer composite reinforcing layer, the matrix of which comprises 10T units, i.e. is a copolyamide having the formula A / 10T, where A is as defined above; The sealing layer includes a multi-layer structure, the intermediate composite reinforcement layer being fused to an intermediate composite reinforcement layer, the intermediate composite reinforcement layer being fused to an outer composite reinforcement layer.

[0131] In another preferred embodiment, the tank according to the invention is a multi-layer structure, - only one sealing layer of polyamide 11, - only one intermediate composite tough layer, the matrix of which is polyamide 11, and a single outer composite reinforcing layer, the matrix of which comprises 10T units, i.e. is a copolyamide having the formula A / 10T, where A is as defined above; The sealing layer includes a multi-layer structure, the intermediate composite reinforcement layer being fused to an intermediate composite reinforcement layer, the intermediate composite reinforcement layer being fused to an outer composite reinforcement layer.

[0132] In another preferred embodiment, the tank according to the invention is a multi-layer structure, - only one sealing layer of polyamide 11, - only one intermediate composite tough layer, the matrix of which is polyamide 11, and a single outer composite reinforcing layer, the matrix of which comprises 10T units, i.e. is a copolyamide having the formula A / 10T, where A is as defined above; The sealing layer includes a multi-layer structure, the intermediate composite reinforcement layer being fused to an intermediate composite reinforcement layer, the intermediate composite reinforcement layer being fused to an outer composite reinforcement layer.

[0133] Preferentially, said intermediate composite reinforcing layer has a thickness of between 1 and 10%, and even more preferentially between 1 and 5%, relative to the thickness of all the composite reinforcing layers of the multilayer structure.

[0134] Advantageously, the multi-layer structure of the tank of the invention consists of three layers as defined in the different embodiments above.

[0135] About Tanks According to one embodiment, the tank according to the invention may comprise a multi-layer structure as defined above and one or more inserts.

[0136] According to another embodiment, the tank according to the invention may comprise a multi-layer structure as defined above and one or more bases.

[0137] According to yet another embodiment, the tank according to the invention may comprise a multi-layer structure as defined above, one or more inserts and one or more bases.

[0138] An "insert" as defined by the present invention refers to a part that is inserted before or during the deposition of the composite reinforcing layer.

[0139] The insert is intended to be used in the assembly of the tank and the base.

[0140] The insert can be inserted at the beginning of the tank manufacturing step. In such a case, the insert is a component of the sealing layer. The inset can, for example, then support a connection element of the tank in the vehicle. This allows such a component to be directly connected to the initial sealing layer.

[0141] Preferentially, the tank comprises one or more injection molded inserts made of a semi-crystalline, preferentially aliphatic, thermoplastic polymer.

[0142] Preferentially, the insert comprises, as a main component, at least one semi-crystalline thermoplastic polyamide, preferentially aliphatic, with a Tf<280° C.

[0143] Preferentially, the inserts are PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11, PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, preferentially PA6, PA66, PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA It comprises at least one polyamide chosen from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, preferentially PA 11 or PA12 and mixtures thereof.

[0144] Depending on the position of the insert in the structure, the insert is an injection part made of the same semi-crystalline thermoplastic polyamide as the sealing layer, or of an aliphatic semi-crystalline thermoplastic polyamide contained in the intermediate composite reinforcing layer.

[0145] According to one embodiment of the tank according to the invention, the tank comprises a multilayer structure as defined above, one or more inserts and one or two bases, more particularly made of metal and overmolded with a semi-crystalline thermoplastic polyamide, preferentially aliphatic, with a Tf<280°C.

[0146] If the tank comprises a base, the base may be overmolded with a semi-crystalline thermoplastic polyamide, preferentially an aliphatic polyamide.

[0147] Preferentially, the polyamide for overmolding the base or bases is PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11, PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, preferentially PA6, PA66, PA410, PA510, PA 69, PA610, PA 512, PA612, PA 514, PA614, PA618, PA It is selected from PA1010, PA1012, PA1014, PA1018, PA1214, PA1218, PA11 and PA12, preferentially PA 11 or PA12 and mixtures thereof.

[0148] Preferentially, the material of the insert, the material of the layer overmolding the base and the material comprised in the sealing layer are the same.

[0149] When the welding between the base of the tank and the insert or sealing layer is performed by induction, the composition used to overmold the metal part of the base and / or the composition used to mold the insert comprises ferromagnetic metal particles.

[0150] method A further subject of the invention is a method for manufacturing a tank as defined above, comprising the following successive steps: - at least one step of depositing an intermediate composite reinforcing layer onto the sealing layer; and - at least one step of welding an outer composite reinforcement layer onto an intermediate composite reinforcement layer, Includes.

[0151] In one embodiment, the heating of the composite tape before it is deposited on the tank is carried out by a system selected from infrared (IR) heating, LED heating, induction or microwave heating or radio frequency (HF) heating. The system for placing said composite tape or tapes in contact with the tank is sufficiently rapid so that the temperature of said tape or tapes remains above the crystallization temperature of the resin forming the matrix of said composite of which said tape or tapes are composed, preferentially 20° C. above the crystallization temperature.

[0152] Advantageously, the method comprises depositing an intermediate composite reinforcement layer, followed or not by depositing a portion of an outer composite reinforcement layer on top of the assembly consisting of the insert and the sealing layer, then welding the base to the insert and then completing the deposition of the outer composite reinforcement [layer].

[0153] In another embodiment, the base may be welded directly to the sealing layer. Then, all the composite layers: middle and outer are deposited.

[0154] use Finally, the invention relates to the use of a tank as described above for the storage of gases under pressure, in particular hydrogen, LPG, CNG, compressed air, for example for energy storage.

[0155] The following examples illustrate the present invention without, however, limiting it. EXAMPLES

[0156] In the following examples, a tank according to the invention and a comparative tank were manufactured: the tank according to the invention comprises a multi-layer structure including an intermediate composite reinforcing layer, and the comparative tank comprises a multi-layer structure without any intermediate composite reinforcing layer.

[0157] In all examples the tanks are manufactured by winding a thermoplastic tape, which is heated by IR heating, which is deposited by a robot at a speed of 12 m / min.

[0158] For the tank according to the invention, the method consists in wrapping a tape around the sealing layer, the tape being pre-impregnated beforehand with the composition of the intermediate composite reinforcing layer.

[0159] The thermoplastic tape wrapping step is then performed again, but this time the tape is pre-impregnated with the composition of the outer composite reinforcement layers and wrapped around the intermediate composite reinforcement.

[0160] [Examples 1 and 2] Tank manufacturing The sealing layer for tanks 1 and 2 was obtained by wrapping a PA11 film with melting temperature Tf=190°C around a metal mandrel. Melting the PA11 film produces the sealing layer in situ. An injection molded PA11 insert was also placed on the mandrel before depositing the composite tape. The base is overmolded with PA11.

[0161] The metal mandrel was removed after deposition of about 1-30% of the total thickness of the composite reinforcement. PA11 with a glass transition temperature Tg=50°C was used to impregnate the carbon fibers of the intermediate composite reinforcement layer. The base was then welded to the tank blank and the wrapping of the composite tape was continued until the final tank was manufactured. Table 1 below shows the materials of the tank's multilayer structure.

[0162] [Table 1]

[0163] Other materials for the outer layer were tested to manufacture a tank according to the invention. Table 2 below shows the materials tested for the composition impregnating the carbon fibers of the outer composite reinforcing layer.

[0164] [Table 2]

[0165] Several thicknesses of intermediate composite reinforcement layers were tested: 1, 3, 5, 10, 15 and 30% of the total composite reinforcement layers in the structure.

[0166] Tank Rating The tank was visually evaluated to see if the insert had been deformed, especially the sealing surface and any deviations in roundness of the insert.

[0167] The quality of the weld between the base and the insert was also observed. If after visual inspection the quality seems to be sufficiently good, the quality of the weld of the base on the insert is tested by pressurizing the tank blank at 4 bar for 12 hours. If the weld leaks before the end of such period, the quality of the weld is poor; otherwise the weld is considered to be good.

[0168] The results are shown in Table 1.

[0169] [Examples 3 to 4] According to the manufacturing methods of Examples 1 and 2, Examples 3 and 4 were carried out.

[0170] [Table 3]

[0171] To manufacture the tank according to the invention, different materials for the outer layer were tested. Table 4 below shows the materials tested for the composition impregnating the carbon fibers of the outer composite reinforcing layer.

[0172] [Table 4]

[0173] Several thicknesses of intermediate composite reinforcement layers were tested: 1, 3, 5, 10, 15 and 30% of the total composite reinforcement layers in the structure.

[0174] [Examples 5 and 6] According to the manufacturing methods of Examples 1 and 2, Examples 5 and 6 were carried out.

[0175] [Table 5]

[0176] To manufacture the tank according to the invention, different materials for the outer layer were tested. Table 6 below shows the materials tested for the composition impregnating the carbon fibers of the outer composite reinforcing layer.

[0177] [Table 6]

[0178] Several thicknesses of intermediate composite reinforcement layers were tested: 1, 3, 5, 10, 15 and 30% of the total composite reinforcement layers in the structure.

[0179] [Example 7] The sealing layer in the tank of Example 7 was obtained by rotational molding. The tank of Example 7 does not have an insert.

[0180] After cutting into two parts, the tank was visually evaluated. The quality of the welding of the intermediate composite layer on the sealing layer was evaluated as well as the quality of the welding of the composite layers to each other by observing the cross-section of the tank. If the visual inspection leads to finding delamination in the thickness of the tank, it is concluded that the welding of the tapes on the sealing layer or to each other is insufficient.

[0181] [Table 7]

[0182] The results of all these examples show the advantages associated with the presence of an intermediate layer in the tank structure.

Claims

1. A multi-layer structure for the storage of compressed gas, comprising, from the inside to the outside, at least three successive layers: at least one sealing layer consisting of a composition comprising, as a base, at least one semi-crystalline thermoplastic polyamide having a melting temperature (Tf) of less than or equal to 280°C, measured according to the ISO 11357-3:2013 standard; at least one intermediate composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition comprising, as a base, at least one semi-crystalline thermoplastic polyamide having a glass transition temperature (Tg) of less than 100 ° C., measured according to the ISO 11357-3:2013 standard; at least one outer composite reinforcing layer consisting of a fibrous material in the form of long fibers impregnated with a composition containing, as a main component, at least one polyphthalamide, the composition having a glass transition temperature (Tg) measured according to the ISO 11357-3 2013 standard of greater than 80°C, the outermost sealing layer is welded to the innermost intermediate composite reinforcing layer; A tank comprising a multi-layer structure in which an outermost intermediate composite reinforcement layer is welded to an innermost outer composite reinforcement layer.

2. 2. The tank according to claim 1, wherein the semi-crystalline thermoplastic polyamide contained in the sealing layer has a C / N ratio of 5 or more.

3. 2. Tank according to claim 1, characterized in that the semi-crystalline thermoplastic polyamide contained in the sealing layer is selected from PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAII, PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, and mixtures thereof.

4. 2. The tank according to claim 1, wherein the semi-crystalline thermoplastic polyamide contained in the sealing layer is an aliphatic polyamide.

5. 2. Tank according to claim 1, characterized in that the semi-crystalline thermoplastic polyamide impregnating the long fibres of the intermediate composite reinforcing layer is selected from PA410, PA 56, PA59, PA510, PA512, PA513, PA 514, PA6, PA 66, PA 69, PA610, PA612, PA614, PA618, PA1010, PA1012, PApip10, PApip12, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11, PA12, PA 11 / 5T, PA 11 / 6T and PA11 / 10T, and mixtures thereof.

6. 2. The tank according to claim 1, wherein the semi-crystalline thermoplastic polyamide impregnating the long fibers of the intermediate composite reinforcing layer is an aliphatic polyamide.

7. The semi-crystalline thermoplastic polyamide impregnating the long fibers of the composite outer reinforcing layer is selected from the group consisting of PA MPMDT / 6T, PA 11 / 10T, PA 11 / BACT, PA 5T / 10T, PA 11 / 6T / 10T, PA MXDT / 4T PA, MXDT / 6T PA, MXDT / 10T PA, MPMDT / 4T PA, MPMDT / 6T PA, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 4T, PA BACT / 10T / 6T, PA 11 / BACT / 4T, PA 11 / BACT / 6T, PA 11 / BACT / 10T, PA 11 / MXDT / 4T, PA 11 / MXDT / 6T, PA 11 / MXDT / 10T, PA 11 / MPMDT / 4T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / MXDT / 10T, PA11 / 5T / 10T, and mixtures thereof.

8. 2. The tank according to claim 1, wherein the intermediate composite reinforcing layer has a thickness of 1 to 30% of the total thickness of the composite reinforcing layers of the structure.

9. 2. The tank according to claim 1, characterized in that the fibrous material present in the intermediate composite reinforcement layer and the outer composite reinforcement layer is selected from glass fiber, carbon fiber, basalt fiber, or basalt-containing.

10. 10. The tank of claim 1, comprising one or more injection-molded inserts of semi-crystalline thermoplastic polymer.

11. The following successive steps: - at least one step of welding said intermediate composite reinforcing layer onto said sealing layer, and - at least one step of welding said outer composite reinforcement layer onto said intermediate composite reinforcement layer, A method for manufacturing a tank as defined in any one of claims 1 to 10, characterized in that it comprises:

12. Use of a tank as defined in any one of claims 1 to 10 for storing a gas under pressure.