Multilayer structures for storing hydrogen

Abstract

A multi-layer structure intended for storing hydrogen, comprising, from the inside to the outside, at least one sealing layer (1) and at least one composite reinforcing layer (2), the innermost composite reinforcing layer being wrapped around the adjacent outermost sealing layer (1), and at least the innermost sealing layer comprising, relative to the total weight of the composition: a. 20.5 to 99.845 wt. % of at least one polyamide; b. 0.005 to 0.5 wt. % of at least one catalyst; c. 0.05 to 1 wt. % of at least one heat stabilizer; d. 0.1 to 3 wt. % of at least one thermostabilizer; a multilayer structure made of a composition comprising: one oligo- or poly-carbodiimide; e. 0 to 1.5% by weight of at least one plasticizer; f. 0 to less than 15% by weight, particularly 1 to less than 15% by weight, of at least one polyolefin; g. 0 to 30% by weight of at least one additive, wherein at least one of the composite reinforcing layers is made of a fibrous material in the form of continuous fibers, the continuous fibers being impregnated with a composition comprising mainly at least one polymer P2j (j=1 to m, where m is the number of reinforcing layers), in particular an epoxy resin or an epoxy-based resin.

Description

[Technical Field]

[0001] This patent application relates to a multi-layer composite structure for storing hydrogen and a method for making the same. [Background technology]

[0002] Hydrogen tanks are currently attracting a great deal of attention from numerous manufacturers, particularly in the automotive sector. One of the desired goals is to propose increasingly less polluting vehicles. The aim is therefore for electric or hybrid vehicles containing batteries to gradually replace combustion engine vehicles, e.g., gasoline or diesel vehicles. Batteries have proven to be relatively complex automotive components. Depending on the battery's positioning in the vehicle, it may be necessary to protect it from influences and the external environment, which may have extreme temperatures and variable humidity. It may also be necessary to avoid any fire hazards.

[0003] Furthermore, it is important that the battery's operating temperature does not exceed 55°C, so as not to damage the battery cells and extend their lifespan. Conversely, in winter, for example, it may be necessary to increase the battery temperature to optimize its operation.

[0004] Furthermore, electric vehicles today still suffer from several problems, namely the range of their batteries, the use of rare earth metals in these batteries, which are not an infinite resource, the recharging times which are much longer than the time it takes to fill the tank, as well as the generation of electricity in various countries to allow the batteries to be recharged.

[0005] Hydrogen is therefore a substitute for electric batteries because it can be converted into electricity by a fuel cell, which can then power an electric vehicle.

[0006] Hydrogen tanks usually consist of a metal liner (or sealing layer) that must prevent hydrogen from permeating. One type of tank envisaged is called Type IV, which is based on a thermoplastic liner around which a composite is wrapped.

[0007] Its basic principle is to separate the two essential functions of sealing and mechanical strength and to manage them independently of each other. In this type of tank, a liner (or sealing sheath) made of thermoplastic resin is combined with a reinforcing structure, also known as a reinforcing sheath or layer, made of fibers (glass, aramid, carbon), which allows it to operate at much higher pressures but reduces its weight and avoids the risk of explosion in case of severe external attack.

[0008] The liner must have certain principle characteristics: Possibility of transformation by extrusion blow molding, rotational molding or injection molding. Low hydrogen permeability, indeed the permeability of the liner, is an important factor in limiting hydrogen loss from the tank; Good mechanical properties (fatigue) at low temperatures (-40 to -70°C); Heat resistant up to 120°C.

[0009] In fact, the filling rate of hydrogen tanks needs to be increased, which should be roughly equivalent to that of fuel tanks for internal combustion engines (about 3 to 5 minutes), but this increase in rate causes more significant heating of the tank, which then reaches temperatures of about 100°C.

[0010] The performance and safety assessment of hydrogen tanks can be determined in European reference laboratories (GasTeF: Hydrogen Tank Test Facility), as described by Galassi et al. (World hydrogen energy conference 2012, Onboard compressed hydrogen storage: fast filing experiments and simulations, Energy Procedia 29, (2012) pp. 192-200).

[0011] The first generation of Type IV tanks used a high density polyethylene (HDPE) base liner.

[0012] However, HDPE has the drawback of having a melting point that is too low and a hydrogen permeability that is too high, which presents a problem with new requirements regarding heat resistance and does not allow for an increase in the filling speed of the tank.

[0013] The polyamide PA6 base liner has been under development for many years.

[0014] However, PA6 has the drawback of having low resistance to cold.

[0015] WO2018155491 describes a hydrogen transport component having a three-layer structure, the inner layer of which consists of PA11, 15-50% impact modifier, and 1-3% plasticizer, or a composition lacking plasticizer, and which has hydrogen barrier properties, good flexibility, and durability at low temperatures. However, while this structure is suitable for pipes for transporting hydrogen, it is not suitable for storing hydrogen. Furthermore, the viscosity of this composition is too variable to be stable when deformed by extrusion blow molding, a deformation technique that can produce extremely long melt residence times (up to 20 minutes) at high temperatures within the heat storage block.

[0016] Therefore, there is still a need to optimize, on the one hand, the matrix of the composite in order to optimize its mechanical strength at high temperatures, and, on the other hand, the materials comprising the sealing sheath in order to optimize the operating temperature. Any optional modifications carried out in the composition of the materials comprising the sealing liner must therefore not lead to a significant increase in the manufacturing temperature of this liner compared to what is practiced today (extrusion blow molding, injection molding, rotational molding, etc.).

[0017] These problems are solved by providing the multilayer structure of the present invention, which is intended to store hydrogen. Summary of the Invention

[0018] Throughout this description, the terms "liner" and "sealing sheath" have the same meaning. DETAILED DESCRIPTION OF THE INVENTION

[0019] The invention therefore relates to a multilayer structure intended to store hydrogen, comprising, from the inside to the outside, at least one sealing layer (1) and at least one composite reinforcing layer (2), The innermost composite reinforcing layer is wrapped around the adjacent outermost sealing layer (1), At least the innermost sealing layer comprises, by total weight of the composition: a. 20.5 to 99.845 weight percent of at least one polyamide; b. 0.005 to 0.5 wt. % of at least one catalyst; c. 0.05 to 1 wt. % of at least one heat stabilizer; d. 0.1 to 3 weight percent of at least one oligo- or poly-carbodiimide; e. 0-1.5 wt. % of at least one plasticizer; f. 0 to less than 15 wt. % of at least one polyolefin; g. A composition comprising 0-30% of at least one additive; The total of components a to g is 100% by weight, It relates to a multilayer structure in which at least one of the composite reinforcing layers consists of a fibrous material in the form of continuous fibers that are impregnated with a composition comprising mainly at least one polymer P2j (j=1 to m, m being the number of reinforcing layers), in particular an epoxy resin or an epoxy-based resin.

[0020] Advantageously, the structure is devoid of nucleating agents.

[0021] Advantageously, the structure lacks an outermost layer adjacent to the outermost layer of polyamide polymer composite reinforcing.

[0022] Advantageously, the structure lacks a nucleating agent and lacks an outermost layer adjacent the outermost layer of polyamide polymer composite reinforcement.

[0023] The inventors have therefore unexpectedly discovered that the use of long-chain semicrystalline polyamide thermoplastic polymers, comprising limited proportions of impact modifiers and plasticizers, catalysts, heat stabilizers and oligo- or polycarbodiimides, makes it possible to obtain a sealing layer composition with a good viscosity, i.e. a viscosity high enough to be deformed in the molten state, in particular by extrusion blow molding, without increasing the viscosity of the solution, i.e. the intrinsic viscosity, and that this melt viscosity is also sufficiently stable during deformation, in particular by extrusion blow molding. The inventors have also discovered that the combination of the sealing layer with a different polymer for the matrix of the composite, in particular an epoxy resin or epoxy-based resin, in which the composite is wound around the sealing layer, makes it possible to obtain a structure suitable for storing hydrogen and in particular to increase the maximum use temperature, which can reach up to 120°C, and therefore the filling speed of the tank.

[0024] A "multi-layer" tank is to be understood as comprising or consisting of several layers, i.e. several sealing layers and several reinforcing layers, or one sealing layer and several reinforcing layers, or several sealing layers and one reinforcing layer, or one sealing layer and one reinforcing layer.

[0025] The multi-layer structure is therefore understood to exclude pipes or tubes.

[0026] In one embodiment, the multi-layer structure consists of two layers, a sealing layer and a reinforcement layer.

[0027] The sealing layer(s) are the innermost layer relative to the composite reinforcing layer which is the outermost layer.

[0028] The tanks can be tanks for mobile storage of hydrogen on trucks that transport hydrogen, on vehicles that transport hydrogen and supply hydrogen-based fuel cells, for example on trains that supply hydrogen, or on drones that supply hydrogen, but they can also be tanks for fixed storage of hydrogen at stations that distribute hydrogen to vehicles.

[0029] Advantageously, the sealing layer (1) is leak-tight to hydrogen at 23°C, i.e. the hydrogen permeability at 23°C is less than 500 cc.mm / m2.24h.atm at 23°C and 0% relative humidity (RH).

[0030] The composite reinforcing layer(s) are wrapped around the sealing layer by a ribbon (or tape or roving) of polymer-impregnated fibers, which is covered by, for example, filament winding.

[0031] If several layers are present, the polymers are different.

[0032] If the polymer of the reinforcing layer is the same, there can be several layers, but advantageously there is a single reinforcing layer, which then has at least one full wrap around the sealing layer.

[0033] This fully automated process, well known to those skilled in the art, allows for the selection of wrap angles for each layer, which gives the final structure the ability to withstand internal pressure changes.

[0034] If several sealing layers are present, only the innermost sealing layer is in direct contact with hydrogen.

[0035] If only one sealing layer and composite reinforcement layer are present, a multi-layer structure of two layers is thus created, and these two layers can then be adhered to each other, in particular by winding the composite reinforcement layer over the sealing layer, so that they are in direct contact with each other.

[0036] If several sealing layers and / or several composite reinforcement layers are present, the outermost layer of the sealing layer, and thus the one opposite the layer in contact with hydrogen, may or may not be bonded to the innermost layer of the composite reinforcement.

[0037] The other composite reinforcement layers may or may not also be bonded to one another.

[0038] The other sealing layers may or may not also be adhered to each other.

[0039] Advantageously, there is only one sealing layer and one reinforcing layer, which are not adhered to each other.

[0040] Advantageously, there is only one sealing layer and one reinforcing layer, which are not bonded to each other, and the reinforcing layer consists of a fibrous material in the form of continuous fibres, which are impregnated with a composition comprising mainly at least one polymer P2j, in particular an epoxy resin or an epoxy-based resin.

[0041] In one embodiment, there is only one sealing layer and one reinforcing layer, which are not bonded to each other, and the reinforcing layer consists of a fibrous material in the form of continuous fibers, which are impregnated with a composition comprising mainly polymer P2j, which is an epoxy resin or an epoxy-based resin.

[0042] The expression "epoxy-based" means throughout this specification that the epoxy represents at least 50% by weight of the matrix.

[0043] Regarding the sealing layer(s) and composition There may be one or more sealing layers.

[0044] There may be 1 to 10 layers, in particular 1 to 5, in particular 1 to 3, preferentially 1 sealing layer.

[0045] At least the innermost sealing layer comprises: By weight of the total composition: a. 20.5 to 99.845 weight percent of at least one polyamide; b. 0.005 to 0.5 wt. % of at least one catalyst; c. 0.05 to 1 wt. % of at least one heat stabilizer; d. 0.1 to 3 weight percent of at least one oligo- or poly-carbodiimide; e. 0-1.5 wt. % of at least one plasticizer; f. 0 to less than 15 wt. % of at least one polyolefin; g. Contains 0-30% of at least one additive; The composition comprises components a to g totaling 100% by weight.

[0046] In one embodiment, the composition comprises: a. 20.5 to 99.845 weight percent of at least one polyamide; b. 0.005 to 0.5 wt. % of at least one catalyst; c. 0.05 to 1 wt. % of at least one heat stabilizer; d. 0.1 to 3 weight percent of at least one oligo- or poly-carbodiimide; e. 0-1.5 wt. % of at least one plasticizer; f. 0 to less than 15 wt. % of at least one polyolefin; g. 0-30% of at least one additive; The total of components a to g is 100% by weight.

[0047] catalyst: The term "catalyst" refers to a polycondensation catalyst, such as an inorganic or organic acid.

[0048] The proportion by weight of the catalyst is from about 50 ppm to about 5000 ppm, particularly from about 100 to about 3000 ppm, relative to the total weight of the composition.

[0049] Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2) or mixtures thereof.

[0050] Advantageously, the proportion by weight of catalyst is between approximately 50 ppm and approximately 5000 ppm, in particular between approximately 100 and approximately 3000 ppm, relative to the total weight of the composition, said catalyst being chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2) or mixtures thereof.

[0051] Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3) in a proportion of approximately 100 to approximately 3000 ppm.

[0052] Heat stabilizer: This stabilizer may be an organic stabilizer, or more generally a combination of organic stabilizers, such as a first phenolic antioxidant (for example of the type Irganox 245 or 1098 or 1010 from Ciba), a second phosphite antioxidant, and optionally further stabilizers, such as HALS, which stands for hindered amine light stabilizer (for example Tinuvin 770 from Ciba), phenolic phosphite antioxidants, such as ANOX® NDB TL89, UV stabilizers (for example Tinuvin 312 from Ciba), phenolic or phosphorus stabilizers. Amine antioxidants, such as Naugard 445 from Crompton, or even multifunctional stabilizers, such as Nylostab S-EED from Clariant, may also be used.

[0053] The stabilizer can also be an inorganic stabilizer, such as a copper-based stabilizer. Examples of such inorganic stabilizers include halides and copper acetate. Secondly, other metals, such as silver, are optionally considered, but are known to be less effective. These copper-based compounds are typically associated with alkali metal halides, especially potassium.

[0054] Advantageously, the heat stabilizer is an organic stabilizer.

[0055] The heat stabilizer is present in a proportion of approximately 0.05% to approximately 1% by weight, in particular approximately 0.05% to approximately 0.3% by weight, relative to the total weight of the composition.

[0056] Advantageously, the proportion by weight of catalyst is between approximately 50 ppm and approximately 5000 ppm, in particular between approximately 100 and approximately 3000 ppm, relative to the total weight of the composition, and the proportion by weight of heat stabilizer is between approximately 0.05% and approximately 1% by weight, in particular between approximately 0.05% and approximately 0.3% by weight, relative to the total weight of the composition, said catalyst being chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2) or mixtures thereof.

[0057] Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3) in proportions of approximately 100 to approximately 3000 ppm.

[0058] Carbodiimide: Carbodiimides represent carbodiimide polymers and oligomers known in the art and can be prepared by polymerization of diisocyanates.

[0059] This reaction can be accelerated by excluding carbon dioxide from the catalyst and product (J. Org. Chem, 28, 2069 (1963); J. Am. Chem. Soc. 84, 3673 (1962); Chem. Rev., 81, 589 (1981); Ange. Chem., 93, 855 (1981)).

[0060] NCO end group reagents may include CH, NH or OH reactive compounds such as esters of malonic acid, caprolactam, alcohols or phenols.

[0061] Alternatively, mixtures of monoisocyanates and diisocyanates can be polymerized to give oligo- or poly-carbodiimides containing substantially non-reactive end groups.

[0062] The carbodiimides used have the general formula: R1-N=C=N(-R2-N=C=N-)n-R3 wherein R1 and R3 represent C1-C20 alkyl, C5-C20 cycloalkyl, aryl having 6-20 carbon atoms or aralkyl having 7-20 carbon atoms, each optionally substituted with an isocyanate group containing a CH, NH or OH reactive compound; R2 represents an alkylene group having 2 to 20 carbon atoms, a cycloalkylene group having 5 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, or an aralkylene group having 7 to 20 carbon atoms; n=1 to 100, preferably 2 to 80, and more preferably 3 to 70.

[0063] The oligo- or poly-carbodiimides may be homopolymers or copolymers, such as copolymers of 2,4-diisocyanato-1,3,5-triisopropylbenzene and 1,3-diisocyanato-3,4-diisopropylbenzene.

[0064] The oligo- or poly-carbodiimides may also be selected from those described in US Pat. No. 5,360,888.

[0065] Suitable oligo- and poly-carbodiimides can be obtained from commercial sources such as Rhein Chemie, Raschig or Ziko.

[0066] Advantageously, the proportion by weight of oligo- or polycarbodiimide used is approximately 0.1 to approximately 3%, in particular 0.5 to 2% and in particular approximately equal to 1% relative to the total weight of the composition.

[0067] Advantageously, the oligo- or poly-carbodiimide is selected from Stabilizer, in particular Stabilizer® 9000, Stabaxol®, in particular Stabaxol® P, in particular Stabaxol® P100 or Stabaxol® P400, or mixtures thereof.

[0068] Advantageously, the invention therefore relates to a structure as defined above, comprising an innermost sealing layer, the innermost sealing layer consisting of a composition comprising at least one catalyst, at least one heat stabilizer and at least one oligo- or poly-carbodiimide in a proportion of approximately 0.1 to approximately 3% by weight, in particular 0.5 to 2% by weight and in particular approximately equal to 1% by weight, relative to the total weight of the composition, and the matrix comprises at least one thermoplastic polymer, in particular a polyamide, said oligo- or poly-carbodiimide being chosen from Stabilizer, in particular Stabilizer® 9000, Stabaxol®, in particular Stabaxol® P, in particular Stabaxol® P100 or Stabaxol® P400, or mixtures thereof, and, where appropriate, up to 1.5% by weight of at least one plasticizer and / or up to 15% by weight of at least one polyolefin.

[0069] Advantageously, the proportion by weight of catalyst is between approximately 50 ppm and approximately 5000 ppm, in particular between approximately 100 and approximately 3000 ppm, relative to the total weight of the composition, the oligo- or poly-carbodiimide is present in a proportion of between approximately 0.1 and approximately 3% by weight, in particular between 0.5 and 2% by weight, in particular approximately equal to 1% by weight, relative to the total weight of the composition, the matrix comprises at least one thermoplastic polymer, in particular a polyamide, and said catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2) or mixtures thereof, and said oligo- or poly-carbodiimide is chosen from Stabilizer, in particular Stabilizer® 9000, Stabaxol®, in particular Stabaxol® P, in particular Stabaxol® P100 or Stabaxol® P400, or mixtures thereof.

[0070] Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3) in proportions of approximately 100 to approximately 3000 ppm.

[0071] Advantageously, the heat stabilizer is present in a proportion of approximately 0.05% to approximately 1% by weight, in particular approximately 0.05% to approximately 0.3% by weight, relative to the total weight of the composition, and the oligo- or poly-carbodiimide is present in a proportion of approximately 0.1 to approximately 3% by weight, in particular 0.5 to 2% by weight, in particular approximately equal to 1% by weight, relative to the total weight of the composition, said oligo- or poly-carbodiimide being chosen from Stabilizer, in particular Stabilizer® 9000, Stabaxol®, in particular Stabaxol® P, in particular Stabaxol® P100 or Stabaxol® P400, or mixtures thereof.

[0072] Advantageously, the proportion by weight of the catalyst is between approximately 50 ppm and approximately 5000 ppm, in particular between approximately 100 and approximately 3000 ppm, relative to the total weight of the composition, the heat stabilizer is present in a proportion of between approximately 0.05% and approximately 1% by weight, in particular between approximately 0.05% and approximately 0.3% by weight, relative to the total weight of the composition, and the oligo- or poly-carbodiimide is present in a proportion of between approximately 0.1% and approximately 3% by weight, in particular between 0.5 and 2% by weight, in particular approximately equal to 1% by weight, relative to the total weight of the composition. In a preferred ratio, the catalyst is selected from phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2) or mixtures thereof, and the oligo- or poly-carbodiimide is selected from Stabilizer, in particular Stabilizer® 9000, Stabaxol®, especially Stabaxol® P, in particular Stabaxol® P100 or Stabaxol® P400, or mixtures thereof.

[0073] Advantageously, the catalyst is chosen from phosphoric acid (H3PO4), phosphorous acid (H3PO3) in proportions of approximately 100 to approximately 3000 ppm.

[0074] Additives: The additives, excluding the nucleating agent, may be selected from another polymer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a pigment, carbon black, and a carbonaceous nanofiller; in particular, the additives, excluding the nucleating agent, are selected from a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a pigment, carbon black, and a carbonaceous nanofiller.

[0075] The other polymer may be another semi-crystalline thermoplastic polymer or a different polymer, especially EVOH (ethylene vinyl alcohol).

[0076] In one embodiment, the single polyamide is present in at least the sealing layer that does not adhere to the composite reinforcing layer.

[0077] polyamide The polyamide is in particular a semicrystalline, especially an aliphatic or semi-aromatic polyamide, in particular an aliphatic polyamide.

[0078] Semicrystalline polyamides generally refer to materials that are solid at room temperature and that soften during an increase in temperature, in particular after passing through the glass transition temperature (Tg), and that can exhibit a sharp transition as they pass through what is called the melting point (Tm), becoming solid again when the temperature is reduced below their crystallization temperature.

[0079] Tg, Tc and Tm are determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013, respectively.

[0080] The number-average molecular weight Mn of said semicrystalline polyamides preferably ranges from 10,000 to 85,000, in particular from 10,000 to 60,000, preferentially from 10,000 to 50,000, and even more preferentially from 12,000 to 50,000. These Mn values ​​can correspond to an intrinsic viscosity of 0.8 or more, determined in m-cresol according to standard ISO 307:2007, but by changing the solvent (m-cresol is used instead of sulfuric acid, and the temperature is 20° C.).

[0081] The nomenclature used to define polyamides is set out in ISO Standard 1874-1:2011 "Plastiques -- Materiaux polyamides (PA) pour moulage et extrusion -- Partie 1: Designation", in particular page 3 (Tables 1 and 2), and is well known to those skilled in the art.

[0082] The polyamide may be a homopolyamide or a copolyamide, or a mixture thereof.

[0083] In one embodiment, the polyamide is an aliphatic polyamide, in particular a long-chain aliphatic polyamide, i.e. a polyamide having an average number of more than 8.5, preferably more than 9, in particular more than 10 carbon atoms per nitrogen atom.

[0084] In detail, the long chain aliphatic polyamides are: It is selected from polyamide 10 (PA10), polyamide 11 (PA11), polyamide 12 (PA12), polyamide 1010 (PA1010), polyamide 1012 (PA1012), polyamide 1212 (PA1012) or mixtures thereof, or copolyamides thereof, in particular PA11 and PA12.

[0085] More particularly, polyamide 11 (PA11), polyamide 12 (PA12), polyamide 1012 (PA1012), polyamide 1212 (PA1012) or mixtures thereof, or copolyamides thereof, in particular PA11 and PA12.

[0086] In one embodiment, the long chain aliphatic polyamide is: It is selected from polyamide 12 (PA12), polyamide 1010 (PA1010), polyamide 1012 (PA1012), polyamide 1212 (PA1012) or mixtures thereof, or copolyamides thereof, in particular PA12.

[0087] In another embodiment, the long chain aliphatic polyamide is: It is selected from polyamide 12 (PA12), polyamide 1012 (PA1012), polyamide 1212 (PA1012) or a mixture thereof, or a copolyamide thereof, in particular PA12.

[0088] In another embodiment, the semi-crystalline polyamide thermoplastic resin polymer is a semi-aromatic semi-crystalline polyamide, particularly a long-chain semi-aromatic semi-crystalline polyamide, that is, a polyamide having an average number of carbon atoms of more than 8.5, preferably more than 9, and particularly more than 10 per nitrogen atom, and a melting point of 240 °C to less than 280 °C.

[0089] In particular, the long-chain semi-aromatic semi-crystalline polyamide is selected from polyamide 11 / 5T or 11 / 6T or 11 / 10T, MXDT / 10T. <PMDT / 10T and BACT / 10T.

[0090] Advantageously, each sealing layer consists of a composition containing the same polyamide.

[0091] When welding is essential, there are various methods available to weld elements made of polyamide thermoplastic resin polymers. Therefore, contact or non-contact heating blades, ultrasonic, infrared, vibration, rotation, or even laser welding can be used to weld one element to another.

[0092] Regarding polyolefins In one embodiment, PEBA is excluded from the definition of polyolefins.

[0093] Polyolefins can be functionalized or non-functionalized, or can be a mixture of at least one functionalized and / or at least one non-functionalized polyolefin. For the sake of brevity, polyolefins are represented as (B), functionalized polyolefins as (B1), and non-functionalized polyolefins as (B2) as described below.

[0094] Non-functionalized polyolefins (B2) are traditionally homopolymers or copolymers of alpha-olefins or diolefins, such as ethylene, propylene, 1-butene, 1-octene, butadiene. Examples that may be mentioned include: - Polyethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene. - Propylene homopolymers or copolymers. - Ethylene / alpha-olefin copolymers, such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM). - Styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers. - copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids, such as alkyl (meth)acrylates (for example methyl acrylate), or vinyl esters of saturated carboxylic acids, such as vinyl acetate (EVA), the proportion of comonomers being able to reach 40% by weight.

[0095] The functionalized polyolefin (B1) can be a polymer of alpha-olefins having reactive units (functional groups); such reactive units can be acid, anhydride, or epoxy functional groups. Examples include the aforementioned polyolefins (B2) grafted, copolymerized, or terpolymerized with unsaturated epoxides, such as glycidyl (meth)acrylate, or with carboxylic acids or their corresponding salts or esters, such as (meth)acrylic acid (which can be fully or partially neutralized with a metal, such as Zn), or with carboxylic anhydrides, such as maleic anhydride. The functionalized polyolefin can be, for example, a PE / EPR mixture, the weight ratio of which can vary widely, for example, between 40 / 60 and 90 / 10, and which is cografted with an anhydride, in particular maleic anhydride, at a grafting rate of, for example, 0.01 to 5% by weight.

[0096] The functionalized polyolefin (B1) may be chosen from the following (co)polymers grafted with maleic anhydride or glycidyl methacrylate, the grafting rate being, for example, between 0.01 and 5% by weight: - of PE, of PP, of copolymers of ethylene and propylene, butene, hexene or octene, containing, for example, 35 to 80% by weight of ethylene; - Ethylene / alpha-olefin copolymers, such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM). - Styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers. - ethylene and vinyl acetate copolymers (EVA) containing up to 40% by weight of vinyl acetate; - ethylene and alkyl (meth)acrylate copolymers containing up to 40% by weight of alkyl (meth)acrylate; - Ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers containing up to 40% by weight of comonomer.

[0097] The functionalized polyolefins (B1) can also be selected from ethylene / propylene copolymers condensed primarily with propylene grafted with maleic anhydride and then with monoamine polyamides (or polyamide oligomers) (products described in EP-A-0,342,066).

[0098] The functionalized polyolefin (B1) can also be a copolymer or terpolymer of at least the following units: (1) ethylene, (2) alkyl (meth)acrylate or vinyl ester of a saturated carboxylic acid, and (3) anhydride, such as maleic anhydride or (meth)acrylic acid, or an epoxy, such as glycidyl (meth)acrylate.

[0099] As examples of functionalized polyolefins of the latter type, the following copolymers may be mentioned, in which ethylene preferably represents at least 60% by weight and the terpolymer (functional group) represents, for example, 0.1 to 10% by weight of the copolymer: - ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers; - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers; - Ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

[0100] In the aforementioned copolymers, the (meth)acrylic acid may be salified with Zn or Li.

[0101] The term "alkyl (meth)acrylate" in (B1) or (B2) represents C1 to C8 alkyl methacrylates and acrylates, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethyl-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0102] Furthermore, the previously mentioned polyolefins (B1) may also be crosslinked by any suitable method or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the previously mentioned polyolefins with difunctional agents capable of reacting with them, such as diacids, dianhydrides, diepoxy, etc., or mixtures of at least two functionalized polyolefins capable of reacting together.

[0103] The copolymers (B1) and (B2) mentioned above may be copolymerized in a statistical or sequential manner and have a linear or branched structure.

[0104] The molecular weight, MFI index, and density of these polyolefins can also vary widely, as will be known to those skilled in the art. MFI, short for Melt Flow Index, is a measure of fluidity in the molten state. It is measured according to standard ASTM 1238.

[0105] Advantageously, the non-functionalized polyolefin (B2) is selected from polypropylene homopolymers or copolymers, and any ethylene homopolymer or copolymer, and higher alpha-olefin comonomers, such as butene, hexene, octene, or 4-methyl-1-pentene. Mention may be made, for example, of PP, high-density PE, medium-density PE, linear low-density PE, low-density PE, and very low-density PE. These polyethylenes are known to those skilled in the art to be produced according to the "free radical" process, according to the "Ziegler" catalysis process, or, more recently, by so-called "metallocene" catalysis.

[0106] Advantageously, the functionalized polyolefin (B1) is selected from any polymer containing alpha-olefin units and units bearing polar reactive functional groups, such as epoxy, carboxylic acid, or carboxylic acid anhydride functional groups. Examples of such polymers include terpolymers of ethylene, alkyl acrylate, and maleic anhydride or glycidyl methacrylate, such as Lotader® from the applicant, or maleic anhydride-grafted polyolefins, such as Orevac® from SK Chemicals, as well as terpolymers of ethylene, alkyl acrylate, and (meth)acrylic acid. Mention may also be made of homopolymers or copolymers of polypropylene grafted with carboxylic acid anhydrides and then condensed with polyamide or monoamine polyamide oligomers.

[0107] Advantageously, the composition constituting the sealing layer(s) is devoid of polyether block amide (PEBA), which in this embodiment is therefore excluded from the polyolefin.

[0108] Regarding plasticizers: The plasticizer may be one typically used in polyamide(s) based compositions.

[0109] Advantageously, plasticizers with good thermal stability are used so as not to form fumes during the process of mixing the different polymers and deforming the resulting composition.

[0110] In detail, this plasticizer: benzenesulfonamide derivatives, such as the ortho and para isomers of n-butylbenzenesulfonamide (BBSA), ethyltoluenesulfonamide (ETSA), N-cyclohexyltoluenesulfonamide and N-(2-hydroxypropyl)benzenesulfonamide (HP-BSA); Esters of hydroxybenzoic acid, such as 2-ethylhexyl para-hydroxybenzoate (EHPB) and 2-decylhexyl para-hydroxybenzoate (HDPB), Esters or ethers of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfuryl alcohol, and It may be selected from esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxymalonate.

[0111] A preferred plasticizer is n-butylbenzenesulfonamide (BBSA).

[0112] Another, more particularly preferred, plasticizer is N-(2-hydroxypropyl)benzenesulfonamide (HP-BSA). Indeed, the latter has the advantage of preventing the formation of deposits ("eye gunk") in the extrusion screw and / or die during the deformation process by extrusion.

[0113] Of course, it is possible to use mixtures of plasticizers.

[0114] In one embodiment, the composition of at least one innermost sealing layer comprises at least one polyolefin in a proportion of from 1% to less than 15% by weight, in particular from 1% to 12% by weight, in particular from 1% to 10% by weight, relative to the total weight of the composition.

[0115] In one embodiment, the composition lacks a plasticizer.

[0116] In one embodiment, the composition of at least one innermost sealing layer comprises at least one polyolefin in a proportion of from 1% to less than 15% by weight, in particular from 1% to 12% by weight, in particular from 1% to 10% by weight, relative to the total weight of the composition, and the composition is devoid of plasticizers.

[0117] In yet another embodiment, the composition of at least one innermost sealing layer comprises at least one polyolefin in a proportion of from 1% to less than 15% by weight, in particular from 1% to 12% by weight, in particular from 1% to 10% by weight, relative to the total weight of the composition, and 0.1 to 1.5% by weight of a plasticizer relative to the total weight of the composition.

[0118] Regarding composite reinforcement layers and polymer P2j The polymer P2j can be a thermoplastic polymer or a thermosetting polymer.

[0119] There may be one or more layers of composite reinforcement.

[0120] Each of said layers consists mainly of fibrous material in the form of continuous fibers impregnated with a composition comprising at least one thermoplastic polymer P2j, where j corresponds to the number of layers present.

[0121] j includes 1 to 10, in particular 1 to 5, especially 1 to 3, with j=1 being preferred.

[0122] The term "predominantly" means that at least one of said polymers is present in an amount of more than 50% by weight, based on the total weight of the composition and matrix of the composite.

[0123] Advantageously, said at least one main polymer 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.

[0124] The composition may further comprise impact modifiers and / or additives.

[0125] Impact modifier The impact modifier advantageously consists of a polymer, in particular a polyolefin, having a flexural modulus of less than 100 MPa, measured according to standard ISO 178, and a Tg (measured at the inflection point of the DSC thermogram according to standard 11357-2) of less than 0°C.

[0126] Polyolefin is as defined above.

[0127] The additives of the composition of the composite reinforcing layer, excluding the nucleating agent, may be selected from antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, plasticizers and pigments.

[0128] Advantageously, said composition consists mainly of said thermoplastic polymer P2j, 0-15% by weight of impact modifier, in particular 0-12% by weight of impact modifier, 0-5% by weight of additives, the sum of the constituents of the composition being equal to 100% by weight.

[0129] The at least one predominant polymer in each layer may be the same or different.

[0130] In one embodiment, a single predominant polymer is present in at least the composite reinforcement layer and does not adhere to the sealing layer.

[0131] In one embodiment, each reinforcement layer comprises the same type of polymer, in particular an epoxy resin or epoxy-based resin.

[0132] Polymer P2j Thermoplastic polymer P2j Thermoplastics or thermoplastic polymers generally refer to materials that at room temperature are solids that may be semi-crystalline or amorphous, in particular semi-crystalline, and that soften during an increase in temperature, in particular after passing through a glass transition temperature (Tg), and flow at higher temperatures if amorphous, or that may exhibit a sharp transition when passing through the so-called melting point (Tm), if semi-crystalline, and become solid again when the temperature is reduced below its crystallization temperature Tc (in semi-crystalline) and below its glass transition temperature (in amorphous).

[0133] Tg, Tc and Tm are determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013, respectively.

[0134] The number average molecular weight Mn of the thermoplastic polymer, when it corresponds to a polyamide, preferably ranges from 10,000 to 40,000, preferably from 10,000 to 30,000. These Mn values, determined in m-cresol according to standard ISO 307:2007 but by changing the solvent (m-cresol is used instead of sulfuric acid, the temperature is 20°C), can correspond to an intrinsic viscosity of 0.8 or more.

[0135] Examples of suitable semi-crystalline thermoplastic polymers in the present invention include: copolymers, including polyamide-polyether copolymers, particularly polyamides containing aromatic and / or alicyclic structures; polyester, Polyaryletherketone (PAEK), Polyetheretherketone (PEEK), Polyetherketoneketone (PEKK), Polyetherketoneetherketoneketone (PEKEKK), polyimides, in particular polyetherimides (PEI) or polyamide-imides, Polyarylsulfone (PSU), in particular polyarylsulfone, for example polyphenylsulfone (PPSU), Polyethersulfone (PES).

[0136] Semicrystalline polymers, particularly polyamides and their semicrystalline copolymers, are more particularly preferred.

[0137] 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", especially page 3 (Tables 1 and 2), and is well known to those skilled in the art.

[0138] The polyamide may be a homopolyamide or a copolyamide, or a mixture thereof.

[0139] Advantageously, the semicrystalline polyamide is a semi-aromatic polyamide, in particular of formula X / YAr as described in EP 1 505 099, in particular of formula A / XT, where A is chosen from units resulting from amino acids, units resulting from lactams and units corresponding to formula (Ca diamine) (Cb diacid), a represents the number of carbon atoms of the diamine and b represents the number of carbon atoms of the diacid, a and b are each between 4 and 36, advantageously between 9 and 18, and the units (Ca diamine) are chosen from linear or branched aliphatic diamines, cycloaliphatic diamines and alkylaromatic diamines, and the units (Cb diacid) are chosen from linear or branched aliphatic diacids, cycloaliphatic diacids and aromatic diacids; XT represents units resulting from the polycondensation of Cx diamines and terephthalic acid, x represents the number of carbon atoms in the Cx diamine, x is between 5 and 36, advantageously between 9 and 18, especially polyamides of the formula A / 5T, A / 6T, A / 9T, A / 10T or A / 11T, where A is as defined above, in particular PA MPMDT / 6T, PA11 / 10T, PA 5T / 10T, PA 11 / BACT, PA 11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, PA The polyamide is selected from 11 / MXDT / 10T and 11 / 5T / 10T.

[0140] T corresponds to terephthalic acid, MXD corresponds to m-xylylenediamine, MPMD corresponds to methylpentamethylenediamine and BAC corresponds to bis(aminomethyl)cyclohexane. The semi-aromatic polyamides defined above have in particular a Tg of greater than or equal to 80° C.

[0141] The expression "stable upon deformation" means that the melt viscosity does not change by more than 70% over time, in particular from 1 minute (the time required to melt the product) to at least 30 minutes, particularly from 1 minute to 30 minutes.

[0142] Advantageously, the melt viscosity of the composition of the innermost sealing layer remains substantially constant for up to 20 minutes.

[0143] "Substantially constant" should be understood to mean that the melt viscosity does not change by more than 20% up to 20 minutes, between 1 minute and at least 5 minutes, in particular between 1 minute and 5 minutes.

[0144] Advantageously, the composition is also resistant to thermal oxidation.

[0145] The expression "resistance to thermo-oxidation" is characterized by the half-life (in hours) of the material, which corresponds to the time after which an ISO 527-2 1BA specimen aged in air at 140°C has lost half of its initial elongation at break, measured according to standard ISO 527-2 (2012).

[0146] Advantageously, the resistance to thermo-oxidation is at least 80 days, in particular 100 days.

[0147] Advantageously, the composition has a melt viscosity at 270° C., as determined by oscillatory rheology as defined above, of from about 13,000 to about 23,000 Pa·s.

[0148] The melt viscosity is determined by oscillatory rheology in a Physica MCR301 apparatus at 270°C, under a nitrogen flush at 10 rad / s, 5% deformation, and 10 s-1 shear between two parallel plates of 25 mm diameter.

[0149] The intrinsic viscosity is measured according to standard ISO 307:2007, except that in m-cresol instead of sulfuric acid and at a temperature of 20°C.

[0150] Thermosetting polymer P2j The thermosetting polymer is selected from epoxy or epoxy-based resins, polyesters, vinyl esters and polyurethanes, or mixtures thereof, in particular epoxy or epoxy-based resins.

[0151] Advantageously, each composite reinforcement layer consists of a composition comprising the same type of polymer, in particular an epoxy resin or an epoxy-based resin.

[0152] The composition comprising the polymer P2j may be transparent to radiation suitable for welding.

[0153] In another embodiment, the composite reinforcement layer is wrapped around the sealing layer without any subsequent welding.

[0154] Regarding the structure The multi-layer structure thus comprises a sealing layer and at least one composite reinforcement layer wrapped around the sealing layer, which may or may not be adhered to each other.

[0155] Advantageously, the sealing layer and the reinforcing layer do not adhere to each other and are made of compositions each comprising a different polymer.

[0156] However, the different polymers may also be of the same type.

[0157] Thus, if one of the two composite reinforcement and sealing layers consists of a composition comprising an aliphatic polyamide, then the other layer consists of a composition comprising a polyamide that is not aliphatic, for example a semi-aromatic polyamide, so as to have a high Tg polymer as the matrix of the composite reinforcement.

[0158] The multi-layer structure may include up to 10 sealing layers and up to 10 composite reinforcing layers of different properties.

[0159] It is clear that the multi-layer structure is not necessarily symmetrical, and therefore it may contain more sealing layers than composite layers, or vice versa, but there cannot be an alternation of layers and reinforcement layers.

[0160] Advantageously, said multi-layer structure comprises 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 reinforcing layers.

[0161] Advantageously, said multi-layer structure comprises 1, 2, 3, 4 or 5 sealing layers and 1, 2, 3, 4 or 5 composite reinforcing layers.

[0162] Advantageously, said multi-layer structure comprises one, two or three sealing layers and one, two or three composite reinforcing layers.

[0163] Advantageously, they each consist of a composition comprising a different polymer.

[0164] Advantageously, these consist of a composition comprising a polyamide, in particular a semicrystalline polyamide, in particular an aliphatic or aromatic polyamide, and an epoxy or epoxy-based resin P2j, respectively.

[0165] In one embodiment, the multi-layer structure includes a single sealing layer and several reinforcement layers, with adjacent reinforcement layers wrapped around the sealing layer and other reinforcement layers wrapped around immediately adjacent reinforcement layers.

[0166] In another embodiment, the multi-layer structure includes a single reinforcing layer and several sealing layers, the reinforcing layers would around adjacent the sealing layers.

[0167] In one advantageous embodiment, the multi-layer structure comprises a single sealing layer and a single composite reinforcement layer, the reinforcement layer being wrapped around the sealing layer.

[0168] All combinations of these two layers are therefore within the scope of the present invention, provided that at least the innermost composite reinforcement layer is wrapped around the adjacent outermost sealing layer, and the other layers may or may not be adhered to each other.

[0169] Advantageously, in said multilayer structure, each sealing layer consists of a composition comprising the same type of polyamide, in particular a semi-crystalline, especially an aliphatic polyamide, in particular a long-chain or semi-aromatic polyamide, in particular a long-chain polyamide.

[0170] The expression "homogeneous polyamide" means a polyamide which may be the same or different depending on the layer, for example.

[0171] Advantageously, the polyamide is a semi-crystalline, especially an aliphatic polyamide, in particular a long-chain or semi-aromatic polyamide, especially a long-chain polyamide, and the polymer P2j is an epoxy or epoxy-based resin.

[0172] In a first variant, the polyamide is a semi-crystalline, especially an aliphatic polyamide, in particular a long-chain polyamide, and the polymer P2j is an epoxy or epoxy-based resin.

[0173] In a second variant, the polyamide is a semi-aromatic, in particular a long-chain, polyamide and the polymer P2j is an epoxy or epoxy-based resin.

[0174] Advantageously, the polyamide is the same in all sealing layers.

[0175] Advantageously, the semi-crystalline polyamide is a long-chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, especially PA 11 or PA12.

[0176] Advantageously, the polyamide is a long-chain semi-aromatic polyamide, in particular PA 11 / 5T, PA 11 / 6T or PA 11 / 10T. Obviously, in this case the amino 11 content in the copolyamide must be carefully selected so that the Tm of the polymer is lower than 280°C, preferably 265°C.

[0177] Advantageously, in said multilayer structure, each reinforcement layer consists of a composition comprising the same type of polymer P2j, in particular an epoxy resin or an epoxy-based resin.

[0178] Advantageously, the polyamide P2j is the same in all reinforcement layers.

[0179] Advantageously, in said multilayer structure, each sealing layer consists of a composition comprising the same type of polyamide, in particular a semicrystalline polyamide, and each reinforcing layer consists of a composition comprising the same type of polymer P2j, in particular an epoxy or epoxy-based resin.

[0180] Advantageously, the polyamide is a long-chain aliphatic semi-crystalline polyamide, in particular PA1010, PA 1012, PA 1212, PA 11, PA12, in particular PA11 or PA12, and the polymer P2j is a semi-aromatic semi-crystalline polyamide, in particular selected from PA MPMDT / 6T, PA11 / 10T, PA 11 / BACT, PA 5T / 10T, PA 11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, PA and 11 / MXDT / 10T.

[0181] In one embodiment, the multilayer structure consists of a single reinforcing layer and a single sealing layer, the polyamide is a long-chain aliphatic semi-crystalline polyamide, in particular PA1010, PA 1012, PA 1212, PA 11, PA12, in particular PA11 or PA12, and the polymer P2j is a semi-aromatic polyamide, in particular selected from PA MPMDT / 6T, PA11 / 10T, PA 11 / BACT, PA 5T / 10T, PA 11 / 6T / 10T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 10T, PA BACT / 6T, PA BACT / 10T / 6T, PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, and PA 11 / MXDT / 10T.

[0182] In yet another embodiment, the multilayer structure consists of a single reinforcing layer and a single sealing layer, said polymer P1i is a long-chain aliphatic semi-crystalline polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, or semi-aromatic semi-crystalline, in particular selected from polyamides 11 / 5T or 11 / 6T or 11 / 10T, MXDT / 10T, MPMDT / 10T and BACT / 10T, especially PA 11 or PA12, and said polymer P2j is an epoxy or epoxy-based resin.

[0183] Advantageously, said multilayer structure further comprises at least one outer layer of fibrous material made of continuous glass fibers impregnated with a transparent amorphous polymer, said layer being the outermost layer of said multilayer structure.

[0184] The outer layer is a second stiffener layer but is transparent, allowing text to be placed on the structure.

[0185] Regarding fibrous materials As regards the fibres that make up said fibrous material, these are in particular inorganic, organic or vegetable fibres.

[0186] Advantageously, said fibrous material may or may not be sized.

[0187] The fibrous material may therefore contain up to 3.5% by weight of organic material (thermoset or thermoplastic type) referred to as sizing.

[0188] Inorganic fibers include, for example, carbon fibers, glass fibers, basalt or basalt-based fibers, silica fibers, or silicon carbide fibers. Organic fibers include thermoplastic or thermosetting polymer fibers, such as semi-aromatic polyamide fibers, aramid fibers, or polyolefin fibers. Preferably, these fibers are amorphous thermoplastic polymers, having a glass transition temperature (Tg) higher than that of the polymer or thermoplastic polymer blend constituting the pre-impregnated matrix when the thermoplastic polymer blend is amorphous, or a Tg higher than that of the polymer or thermoplastic polymer blend constituting the pre-impregnated matrix when the thermoplastic polymer blend is semi-crystalline. Advantageously, these fibers are semi-crystalline thermoplastic polymers, having a melting temperature (Tm) higher than that of the polymer or thermoplastic polymer blend constituting the pre-impregnated matrix when the thermoplastic polymer blend is amorphous, or a Tm higher than that of the polymer or thermoplastic polymer blend constituting the pre-impregnated matrix when the thermoplastic polymer blend is semi-crystalline. Therefore, there is no risk of melting the organic fibers that make up the fibrous material during the impregnation of the final composite with the thermoplastic resin matrix. Among the plant fibers of natural origin, mention may be made of natural fiber-based linen, hemp, lignin, bamboo, silk, and other cellulosic fibers, in particular viscose fibers. These plant fibers may be used pure, treated with a coating layer, or coated to promote adhesion and impregnation of the thermoplastic polymer matrix.

[0189] The fibrous material can also be a cloth, braided or woven fabric using fibers.

[0190] This may also correspond to a fiber with supporting threads.

[0191] These component fibers can be used alone or in mixtures. Thus, organic fibers can be mixed with inorganic fibers and pre-impregnated with thermoplastic polymer powder to form a pre-impregnated fibrous material.

[0192] The organic fiber strands may have several basis weights. They may also have several shapes. The component fibers of the fibrous material may also take the form of a mixture of these reinforcing fibers having different shapes. The fibers are continuous.

[0193] Preferably, the fibrous material is selected from glass fibers, carbon fibers, basalt fibers or basalt-based fibers, or mixtures thereof, in particular carbon fibers.

[0194] It is used in the form of a strand or several strands.

[0195] According to another aspect, the invention relates to a method for producing a multilayer structure as defined above, characterized in that it comprises a step of preparing the sealing layer by extrusion blow molding, rotational molding or half-shell injection molding.

[0196] In one embodiment, the method for producing a multi-layer structure comprises filament winding a reinforcement layer, as defined above, around a sealing layer, as defined above.

[0197] All the features detailed above also apply to the method. [Example]

[0198] In all the examples, the tank is obtained by rotational moulding of a sealing layer (liner) at a temperature adapted to the properties of the thermoplastic resin used.

[0199] Working Example: Products used The polyamide used is Rilsan® PA11 (BESNO, sold by Arkema), The heat stabilizer is ANOX® NDB TL89: a phenol phosphite organic stabilizer sold by Chemtura. The carbodiimide used is Stabiliser® 9000 (poly-(1,3,5-triisopropylphenylene-2,4-carbodiimide) sold by Raschig. The catalyst used is H3PO3 or H3PO4. BBSA: n-butylbenzenesulfonamide sold by PROVIRON EXXELOR VA 1801: Polyolefin (maleic anhydride-functionalized ethylene-propylene copolymer) sold by Exxon.

[0200] Example 1: Evaluation of compositions of the present invention: melt viscosity and heat resistance at 140°C. The indicated ratios are percentages by weight based on the total weight of the composition.

[0201] Tested in a twin-screw extruder (Coperion ZSK40, with two screws of 40 mm diameter and a length equal to 40 times the diameter) at 280°C, 300 rpm, and 60 kg / h under a vacuum of 600 mmHg. Allow the PA base to dry (<0.1% humidity)

[0202] The compositions of the present invention and comparative compositions are presented in Table 1. TIFF0007809105000001.tif59170

[0203] Example 2: Comparison of properties of a composition according to the present invention with comparative composition 1 Liners made of PA11, comparative compositions 1 and 2, and inventive compositions 1 and 2 were prepared by rotational molding.

[0204] The hydrogen permeability was determined according to the following protocol: it consisted in flushing the upper surface of the film with a test gas (hydrogen) and measuring by gas chromatography the flux diffusing through the lower film, which was further flushed with the carrier gas: nitrogen.

[0205] The experimental conditions are presented in Table 2 and the results are presented in Table 3: TIFF0007809105000002.tif92170TIFF0007809105000003.tif54170

[0206] The results in Table 3 show that the liners prepared from the compositions of the present invention (Inv1 and Inv2) have lower hydrogen permeability.

[0207] Example 3: Notched Charpy impact strength at -30°C according to ISO 179-1:2010 A liner identical to Example 2 was prepared by rotational molding.

[0208] These liners were tested for notched Charpy impact strength at -30°C.

[0209] The notched Charpy impact strength results are shown in Table 4. TIFF0007809105000004.tif46170

[0210] The cold resistance of PA11 liners with no plasticizer or 1.5% plasticizer is higher than that of PA11 liners with 6% plasticizer or 12% plasticizer.

Claims

1. A multilayer structure intended to store hydrogen, comprising, from the inside to the outside, at least one sealing layer (1) and at least one composite reinforcing layer (2), the innermost composite reinforcing layer is wrapped around the adjacent outermost sealing layer (1); At least the innermost sealing layer comprises, by total weight of the composition: a. 49 to 99.845 wt. % of at least one polyamide; b. 0.005 to 0.5 wt. % of at least one catalyst; c. 0.05 to 1 wt. % of at least one heat stabilizer; d. 0.1 to 3 weight percent of at least one oligo- or poly-carbodiimide; e. 0 to 1.5 wt. % of at least one plasticizer; f. 0 to less than 15 weight percent of at least one polyolefin; g. 0-30% of at least one additive and a composition comprising: A multilayer structure, wherein at least one of the composite reinforcing layers consists of a fibrous material in the form of continuous fibers, the fibrous material being impregnated with a composition comprising mainly at least one polymer P2j, j=1 to m, where m is the number of reinforcing layers.

2. 10. The multi-layer structure of claim 1, wherein each sealing layer comprises the same polyamide.

3. 3. A multilayer structure according to claim 1, wherein each reinforcement layer comprises the same polymer.

4. 4. A multilayer structure according to claim 2 or 3, characterized in that each sealing layer comprises the same polyamide and each reinforcing layer comprises the same polymer.

5. 5. A multilayer structure according to any one of claims 1 to 4, characterized in that it has a single sealing layer and a single reinforcing layer.

6. 6. A multilayer structure according to any one of claims 1 to 5, characterized in that the polyamide of the innermost sealing layer is a long chain aliphatic polyamide or a semi-aromatic polyamide.

7. The multilayer structure described in claim 6, characterized in that the long-chain aliphatic polyamide is selected from the group consisting of PA1010, PA1012, PA1212, PA11, or PA12, and the semi-aromatic polyamide is selected from the group consisting of 11 / 5T, 11 / 6T, 11 / 10T, MXDT / 10T, MPMDT / 10T, and BACT / 10T.

8. 8. A multilayer structure according to claim 1, characterized in that the polymer P2j is an epoxy resin or an epoxy-based resin.

9. 7. The multilayer structure according to claim 6, characterized in that the multilayer structure consists of a single reinforcing layer and a single sealing layer, the long-chain aliphatic polyamide is selected from PA1010, PA1012, PA1212, PA11, PA12, or the semi-aromatic polyamide is selected from polyamide 11 / 5T or 11 / 6T or 11 / 10T, MXDT / 10T, MPMDT / 10T and BACT / 10T, and the polymer P2j is an epoxy resin or an epoxy-based resin.

10. 10. The multilayer structure of claim 1, wherein the melt viscosity of the composition of the innermost sealing layer is substantially constant for up to 20 minutes.

11. 11. The multilayer structure of claim 1, wherein the composition of the innermost sealing layer is further resistant to thermal oxidation.

12. 12. The multilayer structure of any one of claims 1 to 11, characterized in that the composition of the innermost sealing layer has a melt viscosity of 13,000 to 23,000 Pa s as determined by oscillatory rheology at 270°C, under a nitrogen flush at 10 rad / s, 5% deformation, and 10 sec-1 shear between two parallel plates of 25 mm diameter.

13. 13. A multilayer structure according to any one of claims 1 to 12, characterized in that the fibrous material of the composite reinforcing layer is selected from glass fibres, carbon fibres, basalt fibres or basalt-based fibres, or mixtures thereof.

14. 14. The multilayer structure of claim 1, further comprising at least one outer layer of a fibrous material made of continuous glass fibers and impregnated with a transparent amorphous polymer, said outer layer being the outermost layer of the multilayer structure.

15. 15. A method for producing a multilayer structure according to any one of claims 1 to 14, characterized in that it comprises the step of preparing a sealing layer by extrusion blow molding, by reactive extrusion, by rotational molding, injection molding or extrusion.

16. 16. A method for producing a multi-layer structure according to claim 15, comprising the step of filament winding a reinforcing layer according to claim 1 around a sealing layer according to claim 1.

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