MULTILAYER STRUCTURE FOR THE TRANSPORT OR STORAGE OF HYDROGEN

Abstract

Multilayer structure, intended for the transport, distribution and storage of hydrogen, comprising, from the inside out, at least one sealing layer (1) and at least one composite reinforcement layer (2), said innermost composite reinforcement layer being wound around said outermost adjacent sealing layer (1), said sealing layers being made of a composition comprising predominantly: at least one aliphatic polyamide thermoplastic polymer P1i, i=1 to n, n being the number of sealing layers, semi-crystalline having a Tf, as measured according to ISO 11357-3: 2013, greater than 200°C, excluding a polyether block amide (PEBA), said polyamide thermoplastic polymer being a polyamide having an average number of carbon atoms per nitrogen atom of 7 to 9, up to 30% by weight of shock modifier relative to the total weight of the composition, up to 1,5% by weight of plasticizer relative to the total weight of the composition, said composition being free of nucleating agent, said at least one thermoplastic polyamide polymer of each sealing layer being either identical or different, and at least one of said composite reinforcement layers being made of a fibrous material in the form of continuous fibers impregnated by a composition comprising predominantly at least one P2j polymer, said structure being free of a polyamide polymer layer, said polyamide polymer layer being the outermost layer and adjacent to the outermost composite reinforcement layer.

Description

Title of the invention: MULTILAYER STRUCTURE FOR THE TRANSPORT OR STORAGE OF HYDROGEN technical field

[0001] This patent application relates to composite multilayer structures for the transport, distribution or storage of hydrogen, in particular for the distribution or storage of hydrogen, and their manufacturing process. Prior art

[0002] Hydrogen tanks are a subject that is currently attracting considerable interest from many manufacturers, particularly in the automotive sector. One of the goals is to offer increasingly cleaner vehicles. Thus, electric or hybrid vehicles with batteries aim to gradually replace internal combustion engine vehicles, such as gasoline or diesel vehicles. However, the battery is a relatively complex component of the vehicle. Depending on its location within the vehicle, it may be necessary to protect it from impacts and the external environment, which can involve extreme temperatures and varying humidity. It is also necessary to prevent any risk of flames.

[0003] Furthermore, it is important that its operating temperature does not exceed 55°C to avoid damaging the battery cells and to preserve its lifespan. Conversely, for example in winter, it may be necessary to raise the battery temperature to optimize its operation.

[0004] Moreover, the electric vehicle still suffers today from several problems, namely battery range, the use in these batteries of rare earths whose resources are not inexhaustible, charging times much longer than the times of filling the tank, as well as a problem of electricity production in the different countries to be able to recharge the batteries.

[0005] Hydrogen therefore represents an alternative to the electric battery since hydrogen can be converted into electricity by means of a fuel cell and thus power electric vehicles.

[0006] Hydrogen tanks generally consist of a metallic casing (liner or sealing layer) that must prevent hydrogen permeation. One of the types of tanks envisaged, called Type IV, is based on a thermoplastic liner around which a composite material is wound.

[0007] Their basic principle is to separate the two essential functions of sealing and mechanical strength in order to manage them independently of each other. In This type of tank combines a thermoplastic resin liner (or sealing sleeve) with a reinforcement structure made of fibers (glass, aramid, carbon), also called a sheath or reinforcement layer, which allows it to operate at much higher pressures while reducing mass and avoiding the risk of explosive rupture in the event of severe external aggressions.

[0008] The liners must have certain basic characteristics:

[0009] The possibility of being transformed by extrusion blow molding, rotomolding, injection molding, or extrusion

[0010] Low permeability to hydrogen, the permeability of the liner is indeed a key factor in limiting hydrogen losses from the tank;

[0011] Good mechanical properties (fatigue) at low temperatures (-40 to -70°C);

[0012] Thermal resistance at 120°C.

[0013] Indeed, it is necessary to increase the filling speed of the hydrogen tank which must be approximately equivalent to that of a gasoline tank for a thermal engine (approximately 3 to 5 minutes) but this increase in speed causes a greater heating of the tank which then reaches a temperature of approximately 100°C.

[0014] The performance and safety evaluation of hydrogen tanks can be determined in a European reference laboratory (GasTeF: hydrogen tank testing facility) as described in Galassi et al. (World hydrogen energy conference 2012, Onboard compressed hydrogen storage: fast filing experiments and simulations, Energy Procedia 29, (2012) 192-200).

[0015] The first generation of type IV tanks used a high-density polyethylene (HDPE) based liner.

[0016] However, HDPE has the drawback of having too low a melting point and high hydrogen permeability, which poses a problem with the new thermal resistance requirements and does not allow for an increase in the tank filling rate.

[0017] For several years, liners based on PA6 or PA66 polyamide have been developed.

[0018] However, PA6 and PA66 have the disadvantage of having low cold resistance and high water absorption.

[0019] PA 12 liners have also been developed which have good shock resistance but PA12 has the disadvantage of having too high a permeability to hydrogen.

[0020] Application EP3112421 describes a polyamide resin composition for a molded article intended for high-pressure hydrogen, the composition comprising:

[0021] a polyamide 6 resin (A); and a polyamide resin (B) having a melting point, as determined by DSC, which is not higher than the melting point of the polyamide 6 resin (A) + 20 °C and a cooling crystallization temperature, as determined by DSC, which is higher than the cooling crystallization temperature of the polyamide 6 resin (A).

[0022] French application FR2923575 describes a tank for the storage of fluid under high pressure comprising at each of its ends along its axis a metal end cap, a liner enveloping said end caps and a structural layer of fiber impregnated with thermosetting resin enveloping said liner.

[0023] Application EP3222668 describes a polyamide resin composition for a molded article intended for high-pressure hydrogen, the composition comprising a polyamide resin (A) comprising a motif derived from hexamethylenediamine and a motif derived from an aliphatic dicarboxylic acid of 8 to 12 carbon atoms and an ethylene / α-olefin copolymer (B) modified with an unsaturated carboxylic acid and / or one of its derivatives.

[0024] US patent application US2014 / 008373 describes a lightweight storage cylinder for a high-pressure compressed gas, the cylinder having a liner wrapped with a stress layer, the liner comprising:

[0025] a first inner layer of impact-modified polyamide (PA) in contact with the gas,

[0026] an external thermoplastic layer in contact with the stress layer; and

[0027] an adhesive bonding layer between the first internal impact-modified PA layer and the external thermoplastic layer.

[0028] WO1855491 describes a hydrogen transport component having a three-layer structure, the inner layer of which is composed of PAU, 15 to 50% of a shock modifier, and 1 to 3% of a plasticizer, or is plasticizer-free, and exhibits hydrogen barrier properties, good flexibility, and durability at low temperatures. However, this structure is suitable for pipes for hydrogen transport but not for hydrogen storage.

[0029] Thus, it remains to optimize, on the one hand, the composite matrix to maximize its high-temperature mechanical resistance, and on the other hand, the material composing the sealing liner to optimize its processing temperature. Therefore, any modification to the composition of the sealing liner material must not result in a significant increase in the manufacturing temperature (extrusion blow molding, injection molding, rotomolding, etc.) of this liner, compared to current practices.

[0030] Furthermore, the shock resistance, water absorption and hydrogen permeability of the material composing the sealing sheath must also be optimized.

[0031] These various problems are solved by providing a multilayer structure of the present invention intended for the transport, distribution or storage of hydrogen.

[0032] Throughout this description, the terms “liner” and “sealing sleeve” have the same meaning.

[0033] The present invention therefore relates to a multilayer structure for the transport, distribution and storage of hydrogen, comprising, from the inside out, at least one sealing layer (1) and at least one composite reinforcement layer (2),

[0034] said innermost composite reinforcement layer being wrapped around said outermost adjacent sealing layer (1),

[0035] said sealing layers being made of a composition comprising mainly:

[0036] at least one aliphatic polyamide thermoplastic polymer Pli, i=l to n, n being the number of sealing layers, semi-crystalline whose Tf, as measured according to ISO 11357-3: 2013, is greater than 200°C, excluding a polyether block amide (PEBA),

[0037] said thermoplastic polyamide polymer being a polyamide having an average number of carbon atoms per nitrogen atom of 7 to 9,

[0038] up to 30% by weight of shock modifier, in particular up to less than 15% by weight of shock modifier, in particular up to 9% by weight of shock modifier relative to the total weight of the composition,

[0039] up to 1.5% by weight of plasticizer relative to the total weight of the composition,

[0040] said composition being devoid of a nucleating agent,

[0041] said at least one thermoplastic polyamide polymer of each sealing layer, which may be identical or different,

[0042] and at least one of said composite reinforcement layers being made of a fibrous material in the form of continuous fibers impregnated by a composition comprising predominantly at least one polymer P2j, (j=1 to m, m being the number of reinforcement layers), in particular an epoxy or epoxy-based resin, or a polyisocyanate-based resin, in particular polyisocyanurates,

[0043] said structure being devoid of a polyamide polymer layer, said polyamide polymer layer being the outermost and adjacent to the outermost layer of composite reinforcement.

[0044] The Inventors therefore unexpectedly found that the use of a thermoplastic polyamide polymer having an average number of carbon atoms per nitrogen atom of 7 to 9, comprising a limited proportion of shock modifier and plasticizer, for the sealing layer, with a different polymer for the composite matrix and in particular an epoxy or epoxy-based resin, or a polyisocyanate-based resin, in particular polyisocyanurates, said composite being wound on the sealing layer, made it possible to obtain a compromise in particular on shock resistance, hydrogen permeability and water absorption compared to thermoplastic polyamide polymers having an average number of carbon atoms per nitrogen atom less than 7 and greater than 9, and thus made it possible to obtain a structure suitable for the transport, distribution or storage of hydrogen and in particular an increase in the maximum operating temperature of up to 120°C, thus making it possible to increase the filling speed of the tanks.

[0045] By "multilayer structure" means a tank comprising or consisting of several layers, namely 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.

[0046] The multilayer structure is therefore understood to exclude a pipe or tube.

[0047] In one embodiment, said multilayer structure consists of two layers, a sealing layer and a reinforcing layer.

[0048] The sealing layer or layers are the innermost layers in relation to the composite reinforcement layers which are the outermost layers.

[0049] The tank can be a tank for mobile hydrogen storage, i.e. on a truck for transporting hydrogen, on a car for transporting hydrogen and supplying hydrogen to a fuel cell for example, on a train for supplying hydrogen or on a drone for supplying hydrogen, but it can also be a stationary hydrogen storage tank at a station for distributing hydrogen to vehicles.

[0050] Advantageously, the sealing layer (1) is hydrogen-tight at 23°C, i.e. the hydrogen permeability at 23°C is less than 100 cc.mm / m2.24h.atm at 23°C under 0% relative humidity (RH).

[0051] Permeability can also be expressed in (cc.mm / m2.24h.Pa).

[0052] The permeability must then be multiplied by 101325.

[0053] In one embodiment, ethylene and alpha-olefin copolymers are excluded from the shock modifying composition of said sealing layer(s).

[0054] In another embodiment, the said sealing layer(s) are made of a composition comprising mainly:

[0055] at least one aliphatic polyamide thermoplastic polymer, i=l to n, n being the number of sealing layers, semi-crystalline, whose Tf, as measured according ISO 11357-3: 2013, is greater than 200°C, excluding a polyether block amide (PEBA),

[0056] said thermoplastic polyamide polymer being a polyamide having an average number of carbon atoms per nitrogen atom of 7 to 9, excluding PA610.

[0057] In yet another embodiment, the said sealing layer(s) are made of a composition comprising mainly:

[0058] at least one aliphatic polyamide thermoplastic polymer Pli, i=l to n, n being the number of sealing layers, semi-crystalline whose Tf, as measured according to ISO 11357-3: 2013, is greater than 200°C, excluding a polyether block amide (PEBA),

[0059] said thermoplastic polyamide polymer being a polyamide having an average number of carbon atoms per nitrogen atom of 7 to 9, excluding PA610,

[0060] ethylene and alpha-olefin copolymers being excluded from the shock modifier.

[0061] The composite reinforcement layer(s) is / are wrapped around the sealing layer by means of polymer-impregnated fiber tapes (or tapes or rovings) which are deposited, for example, by filament winding.

[0062] When several layers are present, the polymers are different.

[0063] When the polymers of the reinforcing layers are identical, there may be several layers but advantageously, only one reinforcing layer is present and which then has at least one complete wrap around the sealing layer.

[0064] This fully automated process, well known to those skilled in the art, allows, layer by layer, the selection of the winding angles that will give the final structure its ability to resist internal pressure loading.

[0065] When several sealing layers are present, only the innermost layer of the sealing layers is in direct contact with hydrogen.

[0066] When only a sealing layer and a composite reinforcement layer are present, thus leading to a two-layer multilayer structure, then these two layers can adhere to each other, in direct contact with each other, in particular due to the wrapping of the composite reinforcement layer on the sealing layer.

[0067] When several sealing layers are present and / or several composite reinforcement layers, then the outermost layer of said sealing layers, and therefore opposite the layer in contact with hydrogen, may or may not adhere to the innermost layer of said composite reinforcement.

[0068] The other composite reinforcement layers may also adhere or not to each other.

[0069] The other sealing layers may also adhere or not to each other.

[0070] Advantageously, only a sealing layer and a reinforcing layer are present and do not adhere to each other.

[0071] Advantageously, only a sealing layer and a reinforcing layer are present and do not adhere to each other and the reinforcing layer consists of a fibrous material in the form of continuous fibers impregnated by a composition comprising predominantly at least one P2j polymer, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0072] In one embodiment, only a sealing layer and a reinforcing layer are present and do not adhere to each other and the reinforcing layer consists of a fibrous material in the form of continuous fibers impregnated by a composition comprising mainly a P2j polymer which is an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0073] The expression based on epoxy throughout the description means that the epoxy represents at least 50% by weight of the matrix.

[0074] Regarding the sealing layer(s) and the thermoplastic polymer Pli

[0075] One or more sealing layers may be present.

[0076] Each of said layers is made up of a composition comprising predominantly at least one thermoplastic polymer Ply, i corresponding to the number of layers present, i is between 1 and 10, in particular from 1 to 5, especially from 1 to 3, preferably i = 1.

[0077] The term "majority" means that said at least one polymer is present at more than 50% by weight relative to the total weight of the composition.

[0078] Advantageously, said at least one major polymer is present at more than 60% by weight, in particular at more than 70% by weight, particularly at more than 80% by weight, more particularly greater than or equal to 90% by weight, relative to the total weight of the composition.

[0079] Said composition may also include up to 30% by weight relative to the total weight of the composition of shock modifiers and / or a plasticizer and / or additives.

[0080] The additives may be selected from another polymer, an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a colorant, carbon black, and carbon nanofillers, with the exception of a nucleating agent; in particular, the additives may be selected from an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, lubricant, inorganic filler, flame retardant, dye, carbon black and carbon nanofillers, with the exception of a nucleating agent.

[0081] Said other polymer may be another semi-crystalline thermoplastic polymer or a different polymer and in particular an EVOH (Ethylene vinyl alcohol).

[0082] Advantageously, said composition comprises said thermoplastic polymer Pli predominantly, from 0 to 30% by weight of shock modifier, in particular from 0 to less than 15% of shock modifier, in particular from 0 to 9% of shock modifier, from 0 to 1.5% of plasticizer and from 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100%.

[0083] Advantageously, said composition consists mainly of said thermoplastic polymer Pli, 0 to 30% by weight of impact modifier, in particular 0 to less than 15% of impact modifier, in particular 0 to 9% of impact modifier, 0 to 1.5% of plasticizer and 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100%.

[0084] Said at least one major polymer of each layer may be identical or different.

[0085] In one embodiment, at least one major polymer is present in the sealing layer which does not adhere to the composite reinforcement layer.

[0086] In one embodiment, said composition comprises a shock modifier of 0.1 to 30% by weight, in particular from 0.1 to less than 15% by weight, in particular from 0.1 to 9% by weight of shock modifier relative to the total weight of the composition.

[0087] In one embodiment, said composition is free of plasticizer.

[0088] In another embodiment, said composition comprises a shock modifier of 0.1 to 30% by weight, in particular from 0.1 to less than 15% by weight, in particular from 0.1 to 9% by weight of shock modifier and said composition is free of plasticizer relative to the total weight of the composition.

[0089] In yet another embodiment, said composition comprises a shock modifier of 0.1 to 30% by weight, in particular from 0.1 to less than 15% by weight, in particular from 0.1 to 9% by weight of shock modifier and from 0.1 to 1.5% by weight of plasticizer relative to the total weight of the composition. Thermoplastic Polymer Ply

[0090] Thermoplastic, or semi-crystalline thermoplastic polymer, is understood to be a material that is generally solid at room temperature, and which softens when the temperature increases, in particular after passing its glass transition temperature (Tg), and which may exhibit a clear melting when passing its so-called melting temperature (Tf), and which becomes solid again when the temperature decreases below its crystallization temperature.

[0091] Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2:2013 and 11357-3:2013 respectively.

[0092] The number-average molecular weight Mn of said semi-crystalline polyamide thermoplastic polymer is preferably in a range from 10,000 to 85,000, in particular from 10,000 to 60,000, preferably from 10,000 to 50,000, and even more preferably from 12,000 to 50,000. These Mn values ​​can correspond to inherent viscosities greater than or equal to 0.8 as determined in m-cresol according to ISO 307:2007 but by changing the solvent (using m-cresol instead of sulfuric acid and the temperature being 20°C).

[0093] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0094] The polyamide can be a homopolyamide or a copolyamide or a mixture of these.

[0095] Advantageously, said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612.

[0096] In one embodiment, said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512 and PA612.

[0097] Advantageously, each sealing layer is made of a composition comprising the same type of polyamide.

[0098] In cases where welding is required, there are various methods for welding thermoplastic polyamide polymer elements. These include contact or non-contact heating blades, ultrasound, infrared, vibration, rotation of one element to be welded against the other, or laser welding. Regarding the shock modifier

[0099] The shock modifier can be any shock modifier as long as it is a polymer with a modulus lower than that of the resin, exhibiting good adhesion with the matrix, so as to dissipate the cracking energy.

[0100] The shock modifier is advantageously made up of a polymer having a flexural modulus of less than 100 MPa measured according to ISO 178 and a Tg of less than 0°C (measured according to standard 11357-2 at the inflection point of the DSC thermogram), in particular a polyolefin.

[0101] In one embodiment, PEBAs are excluded from the definition of shock modifiers.

[0102] The shock modifier polyolefin may be functionalized or non-functionalized or be a mixture of at least one functionalized and / or at least one non-functionalized functionalized. For simplicity, we have designated the polyolefin by (B) and we have described below functionalized polyolefins (B1) and non-functionalized polyolefins (B2).

[0103] A non-functionalized polyolefin (B2) is classically a homopolymer or copolymer of alpha olefins or diolefins, such as, for example, ethylene, propylene, 1-butene, 1-octene, butadiene. Examples include:

[0104] - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene.

[0105] -homopolymers or copolymers of propylene.

[0106] - ethylene / alpha-olefin copolymers such as ethylene / propylene, the EPR (abbreviation for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM).

[0107] - the styrene / ethylene-butene / styrene (SEBS) block copolymers, styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS).

[0108] - copolymers of ethylene with at least one product selected from the salts or the esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (e.g. methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer can reach 40% by weight.

[0109] The functionalized polyolefin (B1) can be a polymer of alpha olefins having reactive motifs (the functionalities); such reactive motifs are acid, anhydride, or epoxy functions. By way of example, one can cite the preceding polyolefins (B2) grafted or co- or ter polymerized by unsaturated epoxides such as glycidyl (meth)acrylate, or by carboxylic acids or the corresponding salts or esters such as (meth)acrylic acid (the latter being able to be totally or partially neutralized by metals such as Zn, etc.) or even by anhydrides of carboxylic acids such as maleic anhydride. A functionalized polyolefin is for example a PE / EPR mixture, the weight ratio of which can vary widely, for example between 40 / 60 and 90 / 10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate for example of 0.01 to 5% by weight.

[0110] The functionalized polyolefin (Bl) can be selected from the following (co)polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the grafting ratio is, for example, from 0.01 to 5% by weight:

[0111] - PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing, for example, 35 to 80% by weight of ethylene;

[0112] - ethylene / alpha-olefin copolymers such as ethylene / propylene, the EPR (abbreviation for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM).

[0113] - styrene / ethylene-butene / styrene block copolymers (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS).

[0114] - ethylene and vinyl acetate (EVA) copolymers, containing up to 40% in weight of vinyl acetate;

[0115] - ethylene and alkyl (meth)acrylate copolymers, containing up to 40% in weight of alkyl (meth)acrylate;

[0116] - ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0117] The functionalized polyolefin (Bl) can also be selected from ethylene / propylene copolymers major in propylene grafted with maleic anhydride and then condensed with mono-amino polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

[0118] The functionalized polyolefin (Bl) may also be a co- or ter polymer of at least the following motifs: (1) ethylene, (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

[0119] By way of example of functionalized polyolefins of this latter type, the following copolymers may be cited, where ethylene preferably represents at least 60% by weight and where the ter monomer (the function) represents, for example, from 0.1 to 10% by weight of the copolymer:

[0120] - ethylene / alkyl (meth)acrylate / (meth)acrylic acid copolymers or maleic anhydride or glycidyl methacrylate;

[0121] - ethylene / vinyl acetate / maleic anhydride or methacrylate copolymers glycidyl;

[0122] - ethylene / vinyl acetate or alkyl (meth)acrylate / acid copolymers (meth)acrylic or maleic anhydride or glycidyl methacrylate.

[0123] In the preceding copolymers, (meth)acrylic acid can be salified with Zn or Li.

[0124] The term "alkyl (meth)acrylate" in (B1) or (B2) refers to methyl acrylates and alkyl acrylates in Cl to C8, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0125] Furthermore, the aforementioned polyolefins (B 1) can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the aforementioned polyolefins with a reagent difunctional such as diacid, dianhydride, diepoxy, etc. capable of reacting with these or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0126] The copolymers mentioned above, (Bl) and (B2), can be copolymerized statistically or sequentially and exhibit a linear or branched structure.

[0127] The molecular weight, MFI, and density of these polyolefins can also vary considerably, a fact that those skilled in the art will appreciate. MFI, short for Melt Flow Index, is the melt flow index. It is measured according to ASTM 1238.

[0128] Advantageously, unfunctionalized polyolefins (B2) are selected from homopolymers or copolymers of polypropylene and any homopolymer of ethylene or copolymer of ethylene and a higher alpha-olefin comonomer such as butene, hexene, octene, or 4-methyl-1-pentene. Examples include PP, high-density PE, medium-density PE, linear low-density PE, low-density PE, and ultra-low-density PE. These polyethylenes are known to those skilled in the art to be produced by a "radical" process, by Ziegler-type catalysis, or, more recently, by so-called "metallocene" catalysis.

[0129] Advantageously, functionalized polyolefins (Bl) are selected from any polymer comprising alpha olefin motifs and motifs bearing polar reactive functions such as epoxy, carboxylic acid, or carboxylic acid anhydride groups. Examples of such polymers include terpolymers of ethylene, alkyl acrylate, and maleic anhydride or glycidyl methacrylate, such as the Applicant's Lotader®, or polyolefins grafted with maleic anhydride, such as the Applicant's Orevac®, as well as terpolymers of ethylene, alkyl acrylate, and (meth)acrylic acid. Also included are homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamine oligomers of polyamide.

[0130] Advantageously, the composition of the sealing layer(s) is free of polyether block amide (PEBA). In this embodiment, PEBA is therefore excluded from the impact modifiers.

[0131] Advantageously, said transparent composition is devoid of core-shell particles or core-shell polymers.

[0132] By core-shell particle, it is to be understood that a particle whose first layer forms the core and the second or all subsequent layers form the respective shells.

[0133] The core-shell particle can be obtained by a multi-step process comprising at least two steps. Such a process is described, for example, in documents US2009 / 0149600 or EP0722961.

[0134] In one embodiment, ethylene / alpha-olefin copolymers are excluded from shock modifiers. Regarding the plasticizer

[0135] The plasticizer may be a plasticizer commonly used in polyamide(s)-based compositions.

[0136] Advantageously, a plasticizer is used which has good thermal stability so that no fumes are formed during the mixing steps of the different polymers and the transformation of the composition obtained.

[0137] In particular, this plasticizer may be selected from:

[0138] Benzene sulfonamide derivatives such as n-butyl benzene sulfonamide (BBSA), the ortho and para isomers of ethyl toluene sulfonamide (ETSA), N-cyclohexyl toluene sulfonamide and N-(2-hydroxypropyl) benzene sulfonamide (HP-BSA),

[0139] hydroxybenzoic acid esters such as ethyl-2-hexyl para-hydroxybenzoate (EHPB) and decyl-2-hexyl para-hydroxybenzoate (HDPB),

[0140] the esters or ethers of tetrahydrofurfuryl alcohol such as oligoethyleneoxy-tetrahydrofurfuryl alcohol, and

[0141] esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxymalonate.

[0142] A preferred plasticizer is n-butyl benzene sulfonamide (BBSA).

[0143] Another particularly preferred plasticizer is N-(2-hydroxy-propyl)benzenesulfonamide (HP-BSA). The latter has the advantage of preventing the formation of deposits at the screw and / or the extrusion die ("die tears") during an extrusion processing step.

[0144] A mixture of plasticizers can obviously be used.

[0145] Regarding the composite reinforcement layer and the P2j polymer

[0146] The P2j polymer can be a thermoplastic polymer or a thermoset sand polymer.

[0147] One or more layers of composite reinforcement may be present.

[0148] Each of said layers is made of a fibrous material in the form of fibers continuous impregnated by a composition comprising predominantly at least one thermoplastic or thermosetting polymer P2j, j corresponding to the number of layers present.

[0149] j is from 1 to 10, in particular from 1 to 5, especially from 1 to 3, preferably j = 1.

[0150] The term “majority” means that said at least one polymer is present at more than 50% by weight relative to the total weight of the composition and matrix of the composite.

[0151] Advantageously, said at least one major polymer is present at more than 60% by weight, in particular more than 70% by weight, particularly more than 80% by weight, more particularly greater than or equal to 90% by weight, relative to the total weight of the composition,

[0152] Said composition may also include shock modifiers and / or additives.

[0153] The additives may be selected from an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a plasticizer and a colorant, with the exception of a nucleating agent.

[0154] Advantageously, said composition consists mainly of said thermoplastic polymer P2j, 0 to 15% by weight of impact modifier, in particular 0 to 12% by weight of impact modifier, 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100% by weight.

[0155] Said at least one major polymer of each layer may be identical or different.

[0156] In one embodiment, only one major polymer is present at least in the composite reinforcement layer and which does not adhere to the sealing layer.

[0157] In one embodiment, each reinforcing layer comprises the same type of polymer, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates. P2j Polymer P2j thermoplastic polymer

[0158] Thermoplastic, or thermoplastic polymer, is understood to be a material which is generally solid at room temperature, which may be semi-crystalline or amorphous, in particular semi-crystalline and which softens upon an increase in temperature, in particular after passing its glass transition temperature (Tg) and flows at a higher temperature when it is amorphous, or which may exhibit a clear melting upon passing its so-called melting temperature (Tf) when it is semi-crystalline, and which becomes solid again upon a decrease in temperature below its crystallization temperature, Te, (for a semi-crystalline) and below its glass transition temperature (for an amorphous).

[0159] Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to standard 11357-2:2013 and 11357-3:2013 respectively.

[0160] The number-average molecular weight Mn of said thermoplastic polymer is preferably in the range of 10,000 to 40,000, preferably from 10,000 to 30,000. These Mn values ​​can correspond to inherent viscosities greater than or equal to 0.8 as determined in m-cresol according to ISO 307:2007 but by changing the solvent (using m-cresol instead of sulfuric acid and the temperature being 20°C).

[0161] Examples of suitable semi-crystalline thermoplastic polymers in the present invention include:

[0162] polyamides, in particular comprising an aromatic and / or cycloaliphatic structure, including copolymers for example polyamide-polyether copolymers, polyesters,

[0163] polyaryletherketones (PAEK),

[0164] polyetherether ketones (PEEK),

[0165] polyetherketone ketones (PEKK),

[0166] polyetherketone ketones (PEKEKK),

[0167] polyimides, in particular polyetherimides (PEI) or polyamide-imides,

[0168] polylsulfones (PSU), in particular polyarylsulfones such as polyphenyl sulfones (PPSU),

[0169] polyethersulfones (PES).

[0170] Semi-crystalline polymers are particularly preferred, and in particular polyamides and their semi-crystalline copolymers.

[0171] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0172] The polyamide may be a homopolyamide or a copolyamide or a mixture of these.

[0173] Advantageously, the semi-crystalline polyamides are semi-aromatic polyamides, in particular a semi-aromatic polyamide of formula X / YAr, as described in EPI505099, in particular a semi-aromatic polyamide of formula A / XT in which A is selected from a motif obtained from an amino acid, a motif obtained from a lactam, and a motif corresponding to the formula (Ca diamine) (Cb diacid), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b each being between 4 and 36, advantageously between 9 and 18, the (Ca diamine) motif being selected from aliphatic diamines, linear or branched, cycloaliphatic diamines, and alkylaromatic diamines, and the (Cb diacid) motif being selected from aliphatic diacids, linear or branched, cycloaliphatic diacids and aromatic diacids;

[0174] XT designates a motif obtained from the polycondensation of a Cx diamine and terephthalic acid, with x representing the number of carbon atoms of the Cx diamine, x being between 5 and 36, advantageously between 9 and 18, in particular a polyamide of formula A / 5T, A / 6T, A / 9T, A / 10T or A / 1T, A being as defined above, in particular a polyamide selected from 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, one PA 11 / MXDT / 10T, one 11 / 5T / 10T.

[0175] T corresponds to terephthalic acid, MXD to m-xylylene diamine, MPMD to methylpentamethylene diamine, and BAC to bis(aminomethyl)cyclohexane. The aforementioned semi-aromatic polyamides defined above have, in particular, a Tg greater than or equal to 80°C. P2j thermosetting polymer

[0176] Thermosetting polymers are selected from epoxy or epoxy-based resins, polyesters, vinyl esters, polyisocyanate-based resins, in particular polyisocyanurates,

[0177] and polyurethanes, or a mixture thereof, in particular epoxy or epoxy-based resins or a polyisocyanate-based resin, in particular polyisocyanurates.

[0178] Advantageously, each composite reinforcement layer is made of a composition comprising the same type of polymer, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0179] Said composition comprising said polymer P2j may be transparent to radiation suitable for welding.

[0180] In another embodiment, the wrapping of the composite reinforcement layer around the sealing layer is carried out without any subsequent welding. Regarding the structure

[0181] Said multilayer structure therefore comprises at least one sealing layer and at least one composite reinforcement layer which is wrapped around the sealing layer and which may or may not adhere to each other.

[0182] Advantageously, said sealing and reinforcing layers do not adhere to each other and are made up of compositions which respectively comprise different polymers.

[0183] Nevertheless, said different polymers may be of the same type.

[0184] Said multilayer structure may comprise up to 10 sealing layers and up to 10 composite reinforcement layers of different natures.

[0185] It is quite clear that the said multilayer structure is not necessarily symmetrical and that it can therefore include more sealing layers than composite layers or vice versa, but there cannot be an alternation of layers and reinforcing layer.

[0186] Advantageously, said multilayer structure comprises one, two, three, four, five, six, seven, eight, nine or ten sealing layers and one, two, three, four, five, six, seven, eight, nine or ten composite reinforcement layers.

[0187] Advantageously, said multilayer structure comprises one, two, three, four or five sealing layers and one, two, three, four or five composite reinforcement layers.

[0188] Advantageously, said multilayer structure comprises one, two or three sealing layers and one, two or three composite reinforcement layers.

[0189] Advantageously, they are made up of compositions which respectively comprise different polymers.

[0190] Advantageously, they are made up of compositions which respectively comprise polyamides corresponding to Pli polyamides and an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular P2j polyisocyanurates

[0191] .

[0192] In one embodiment, said multilayer structure comprises a single sealing layer and several reinforcement layers, said adjacent reinforcement layer being wrapped around said sealing layer and the other reinforcement layers being wrapped around the directly adjacent reinforcement layer.

[0193] In another embodiment, said multilayer structure comprises a single reinforcing layer and several sealing layers, said reinforcing layer being wrapped around said adjacent sealing layer.

[0194] In an advantageous embodiment, said multilayer structure comprises a single sealing layer and a single composite reinforcement layer, said reinforcement layer being wrapped around said sealing layer.

[0195] All combinations of these two layers are therefore within the scope of the invention, provided that at least the innermost composite reinforcement layer is wrapped around the outermost adjacent sealing layer, the other layers adhering to each other or not.

[0196] Advantageously, in said multilayer structure, each sealing layer is made up of a composition comprising the same type of Pli polymer, in particular a polyamide.

[0197] By the expression same type of polymer, it is necessary to understand for example a polyamide which can be an identical or different polyamide depending on the layers.

[0198] Advantageously, said Pli polymer is a polyamide and said P2j polymer is an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0199] Advantageously, the Pli polyamide is identical for all sealing layers.

[0200] Advantageously, said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612.

[0201] In one embodiment, said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512 and PA612.

[0202] Advantageously, in said multilayer structure, each reinforcing layer is made of a composition comprising the same type of polymer P2j, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0203] Advantageously, the P2j polyamide is identical for all reinforcing layers.

[0204] Advantageously, in said multilayer structure, each sealing layer is made of a composition comprising the same type of polymer Pli, in particular a polyamide and each reinforcing layer is made of a composition comprising the same type of polymer P2j, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0205] Advantageously, said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612 and said P2j polymer 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, PA and 11 / MXDT / 10T.

[0206] In one embodiment, said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512 and PA612 and said P2j polymer 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, one PA and 11 / MXDT / 10T.

[0207] In one embodiment, said multilayer structure consists of a single reinforcing layer and a single sealing layer in which said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612 and said P2j polymer 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 a PA 11 / MXDT / 10T.

[0208] In one embodiment, said multilayer structure consists of a single reinforcing layer and a single sealing layer, wherein said polymer Pli is an aliphatic polyamide selected from PA410, PA412, PA510, PA512 and PA612 and said 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.

[0209] In yet another embodiment, the multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polymer Pli is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612 and said polymer P2j is an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0210] In another embodiment, the multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polymer Pli is an aliphatic polyamide selected from PA410, PA412, PA510, PA512 and PA612 and said polymer P2j is an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

[0211] Advantageously, said multilayer structure further comprises at least an outer layer made of a continuous glass fiber fibrous material impregnated with a transparent amorphous polymer, said layer being the outermost layer of said multilayer structure.

[0212] Said outer layer is a second reinforcing layer but transparent which allows an inscription to be placed on the structure.

[0213] In one embodiment, said sealing layer comprises, from the inside out:

[0214] a layer (a) made of a composition as defined above,

[0215] optionally a binder layer;

[0216] a hydrogen barrier layer, in particular made of fluoropolymer, especially PVDF, or EVOH, preferably EVOH;

[0217] optionally a binder layer;

[0218] a layer (b) made up of a composition as defined above. Regarding the barrier layer

[0219] The term “barrier layer” refers to a layer with low permeability and good resistance to hydrogen; that is, the barrier layer slows the passage of hydrogen into other layers of the structure or even outside the structure. The barrier layer is therefore primarily a layer that prevents excessive hydrogen loss into the atmosphere through diffusion, thus avoiding explosion and ignition problems.

[0220] These barrier materials can be low-carbon polyamides, i.e., those in which the average number of carbon atoms (C) relative to the nitrogen atom (N) is less than 9, preferably semi-crystalline and with a high melting point, polyphthalamides and / or also non-polyamide barrier materials such as highly crystalline polymers such as ethylene vinyl alcohol copolymer (hereinafter referred to as EVOH), or even functionalized fluorinated materials such as functionalized polyvinylidene fluoride (PVDF), functionalized ethylene tetrafluoroethylene (ETFE) copolymer, functionalized ethylene tetrafluoroethylene hexafluoropropylene (EFEP) copolymer, functionalized polyphenylene sulfide (PPS), functionalized polybutylene naphthalate (PBN). If these polymers are not functionalized, then an intermediate binder layer can be added to ensure good adhesion within the MLT structure.

[0221] Among these barrier materials, EVOHs are particularly interesting, especially those richest in vivnyl alcohol comonomer and those modified with shocks because they allow for the creation of less fragile structures.

[0222] The expression "barrier layer" means in other words that said barrier layer is very low permeability to hydrogen, in particular the permeability to hydrogen at 23°C is less than 100, in particular less than 75 cc.mm / m2.24h.atm at 23°C under 0% relative humidity (RH).

[0223] Permeability can also be expressed in (cc.mm / m2.24h.Pa).

[0224] The permeability must then be multiplied by 101325. Regarding fibrous material

[0225] Regarding the constituent fibers of said fibrous material, these are in particular fibers of mineral, organic or vegetable origin.

[0226] Advantageously, said fibrous material may be coated or uncoated.

[0227] Said fibrous material may therefore comprise up to 3.5% by weight of a material of an organic nature (such as thermosetting resin or thermoplastic) called ensimage.

[0228] Examples of mineral-based fibers include carbon fibers, glass fibers, basalt or basalt-based fibers, silica fibers, and silicon carbide fibers. Examples of organic-based fibers include thermoplastic or thermosetting polymer-based fibers, such as semi-aromatic polyamide fibers, aramid fibers, polyester fibers, and polyolefin fibers. Preferably, these fibers are based on an amorphous thermoplastic polymer and have a glass transition temperature (Tg) higher than the Tg of the thermoplastic polymer or polymer blend constituting the pre-impregnation matrix when the latter is amorphous, or higher than the Tf of the thermoplastic polymer or polymer blend constituting the pre-impregnation matrix when the latter is semi-crystalline.Advantageously, these fibers are based on semi-crystalline thermoplastic polymers and have a melting point (Tf) higher than the melting point (Tg) of the amorphous polymer or thermoplastic polymer blend used in the pre-impregnation matrix, or higher than the Tf of the semi-crystalline polymer or thermoplastic polymer blend used in the pre-impregnation matrix. Therefore, there is no risk of melting of the organic fibers that make up the fibrous material during impregnation by the thermoplastic matrix of the final composite. Examples of plant-based fibers include natural fibers made from flax, hemp, lignin, bamboo, silk (particularly spider silk), sisal, and other cellulosic fibers, especially viscose.These plant-based fibers can be used pure, treated, or coated with a layer of coating to facilitate adhesion and impregnation of the thermoplastic polymer matrix.

[0229] The fibrous material may also be a fabric, braided or woven with fibers.

[0230] It may also consist of fibers with holding threads.

[0231] These constituent fibers can be used alone or in mixtures. Thus, organic fibers can be mixed with mineral fibers to be pre-impregnated with thermoplastic polymer powder and form the pre-impregnated fibrous material.

[0232] Organic fiber strands can have various basis weights. They can also have various geometries. The constituent fibers of the fibrous material can also be in the form of a mixture of these reinforcing fibers of different geometries. The fibers are continuous fibers.

[0233] Preferably the fibrous material is chosen from glass fibers, carbon fibers, basalt or basalt-based fibers, or a mixture thereof, in particular carbon fibers.

[0234] It is used in the form of one wick or several wicks.

[0235] According to another aspect, the present invention relates to a method for manufacturing a multilayer structure as defined above, characterized in that it includes a step of preparing the sealing layer by extrusion blow molding, rotomolding, injection or extrusion.

[0236] In one embodiment, said method of manufacturing a multilayer structure includes a step of filament winding the reinforcing layer as defined above around the sealing layer as defined above.

[0237] All the detailed characteristics above also apply to the process.

[0238] Brief description of the figures.

[0239] [Fig-1] shows the Charpy impact notched at 23 and -40°C according to ISO 179-1:2010 of five Liners in KJ / m2: from left to right PA 12, PA612, PA610, PA6 and PA66 (for each liner: left histogram: 23 °C and right histogram: - 40°C)

[0240] [Fig.2] shows the hydrogen permeability at 23°C in cc.mm / m2.j.atm of liners of Left to right: PA12, PA6, PA610 and PA612.

[0241] [Fig.3] shows the hydrogen permeability at 23°C in cc.mm / m2.j.atm of liners of PA610 with different proportions of shock modifier (mixture Lotader® 4700 (50%) + Lotader® AX8900 (25%) + Lucalène® 3110 (25%)): from left to right: PA610 without shock modifier, PA610 with 8% shock modifier, PA610 with 12% shock modifier, and PA610 with 15% shock modifier.

[0242] [Fig.4] shows the water reabsorption as a percentage at 23°C and 100% relative humidity.

[0243] EXAMPLES

[0244] In all examples, the tanks are obtained by rotomolding the sealing layer (liner) at a temperature adapted to the nature of the thermoplastic resin used.

[0245] In the case of composite reinforcement made of epoxy resin or epoxy-based resin, or a polyisocyanate-based resin, particularly polyisocyanurates, a wet filament winding process is then used, which consists of winding fibers around the liner. These fibers are pre-impregnated in a liquid epoxy bath or a liquid epoxy-based bath. The tank is then cured in an oven for 2 hours.

[0246] In all other cases, a fibrous material pre-impregnated with thermoplastic resin (tape) is then used. This tape is deposited by winding filamentary by means of a robot with a 1500W power laser heater at a speed of 12m / min and there is no polymerization step.

[0247] Example 1: Charpy impact notched at -40°C according to ISO 179-1:2010

[0248] A liner having a carbon number per nitrogen atom greater than 9 (PA12), Two liners with a carbon-to-nitrogen ratio of less than 7 (PA6 and PA66), and two with a carbon-to-nitrogen ratio of 7 to 9 (PA610 and PA612) were prepared by rotomolding as above.

[0249] These five liners were tested in notched Charpy shock at -40°C and the results are presented in [Fig.1].

[0250] The shock resistance of the PA610 and PA612 liners is better compared to that of the PA6 and PA66.

[0251] Example 2:

[0252] Permeability of PA12, PA612, PA610 and PA6 liners without shock modifier.

[0253] A liner with a carbon number per nitrogen atom greater than 9 (PA12), a liner with a carbon number per nitrogen atom less than 7 (PA6), and two with a carbon number per nitrogen atom between 7 and 9 (PA610 and PA612) were prepared by rotomolding and the hydrogen permeability at 23°C was tested.

[0254] This involves scanning the upper surface of the film with the test gas (Hydrogen) and measuring, by gas chromatography, the flux that diffuses through the film in the lower part, which is scanned by the carrier gas: Nitrogen.

[0255] The experimental conditions are presented in Table 1:

[0256] [Tables 1] LYSSY GPM500 Coupling Apparatus / GC Chromatographic Detection (TCD) Poraplot Q Column (L=27.5m, Dint=0.530mm, Film Thickness=20 P) Carrier Gas: NITROGEN Diffusing Gas: HYDROGEN U (H2) Test Area: 50cm2 Calibration: Absolute by direct injection through a septum Column Head Pressure: 18psi Isothermal Oven Temperature: 30°C Detector Temperature: 200°C Detector: TCD [-] Injector Temperature: Lyssy Injection Loop Temperature: 23°C / 0%RH

[0257] The results are presented in [Fig.2] and show that the PA610 and PA612 liners both exhibit a much lower hydrogen permeability than a PA12 liner.

[0258] Fig. 3 shows the influence of the shock modifier on the hydrogen permeability of a PA610 liner.

[0259] Example 3: Water replenishment

[0260] Test tubes of PA6, PA66, PA610, PA612, and PA12 are immersed in demineralized water at 23°C. Daily (excluding weekends), the samples are removed from the water, dried, weighed, and returned to the water. Once the mass stabilizes (reaches a plateau), the value is recorded on the graph. This value corresponds to the maximum mass of water that these products can absorb at 23°C.

[0261] Fig. 4 shows that the water uptake of PA612 and PA610 is much lower than that of PA6 and PA66.

[0262] Liners made of PA6, PA6.10, PA6.12, and PA12 were covered with a composite shell made by winding T700SC31E carbon fibers (produced by Toray) impregnated with an epoxy resin. The assembly was heated for 5 hours at 110°C to cure the epoxy resin. The tanks were then cut and analyzed. The PA6 liner showed bubbles on its outer surface (the surface in contact with the composite structure). The PA6.10, PA6.12, and PA12 liners showed no defects.

[0263] Example 4

[0264] Type IV hydrogen storage tank, composed of an epoxy composite reinforcement (Tg 120°C) carbon fibers T700SC31E (produced by Toray) and a PA612 sealing layer.

[0265] Cycled pressure tests at -40°C are carried out on the tanks. The pressure is applied via glycol or silicone oil, cycles between 20 and 875 bar are applied according to Regulation (EC) No 79 / 2009, until 100 cycles are reached or the tank breaks (deviation from EC79 regulation which requires 45000 cycles).

[0266] Following these cycles, the tank is emptied, and a hydrogen pressure test is performed on the submerged tank. No leaks are observed. An examination of the inside of the tank reveals no cracks.

[0267] Example 5 (counter-example):

[0268] Type IV hydrogen storage tank, composed of an epoxy composite reinforcement (Tg 120°C) carbon fibers T700SC31E (produced by Toray) and a PA 12 sealing layer.

[0269] The same test is carried out with the same result: absence of crack

[0270] Example 6: Type IV hydrogen storage tank, composed of a reinforcement in epoxy composite (Tg 120°C) T700SC31E carbon fibers (produced by Toray) and a PA6 sealing layer.

[0271] The same cyclic pressure test is performed, but over only 2 cycles. After 2 cycles, the tank is emptied, and a hydrogen pressure test is performed on the submerged tank. A stream of bubbles is observed, indicating that the tank has ruptured. An examination of the inside of the tank confirms this rupture.

[0272] These tests show us that a PA6 liner is much less resistant than a PA612 or PA 12 liner.

[0273] Figures 1 to 4 show that PA610 and PA612 offer the best compromise for shock resistance, permeability and water absorption compared to PA12, PA6 and PA66.

[0274] A PA610 or PA612 liner therefore offers a good compromise between mechanical resistance and hydrogen barrier properties while ensuring less moisture absorption.

Claims

1. Demands A multilayer structure for the transport, distribution and storage of hydrogen, comprising, from the inside out, at least one sealing layer (1) and at least one composite reinforcement layer (2), said innermost composite reinforcement layer being wrapped around said outermost adjacent sealing layer (1), said sealing layers being made of a composition comprising predominantly: at least one aliphatic polyamide thermoplastic polymer, i=l to n, n being the number of sealing layers, semi-crystalline with a Tf, as measured according to ISO 11357-3: 2013, greater than 200°C, excluding a polyether block amide (PEBA), said thermoplastic polymer polyamide being a polyamide having an average number of carbon atoms per nitrogen atom of between 7 and 9, up to 30% by weight of shock modifier, in particular up to less than 15% by weight of shock modifier, in particular up to 9% by weight of shock modifier relative to the total weight of the composition, up to 1.5% by weight of plasticizer relative to the total weight of the composition, said composition being devoid of a nucleating agent, said at least one thermoplastic polyamide polymer in each sealing layer being either identical or different, and at least one of said composite reinforcement layers being made of a fibrous material in the form of continuous fibers impregnated by a composition comprising predominantly at least one P2j polymer, (j = 1 to m, m being the number of reinforcement layers), in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates, said structure being devoid of a polyamide polymer layer, said polyamide polymer layer being the outermost layer and adjacent to the outermost composite reinforcement layer; and said structure comprises at least one outer layer made of a continuous fiberglass fibrous material impregnated with a transparent amorphous polymer, said layer being the outermost layer of said multilayer structure.

2. Multilayer structure according to claim 1, characterized in that the ethylene and alpha-olefin copolymers are excluded from the shock modifier.

3. Multilayer structure according to any one of claims 1 to 2, characterized in that each reinforcing layer comprises the same type of polymer, in particular an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

4. Multilayer structure according to any one of claims 1 to 3, characterized in that it has a single sealing layer and a single reinforcing layer.

5. Multilayer structure according to any one of claims 1 to 4, characterized in that said Pli polymer is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612, in particular from PA410, PA412, PA510, PA512 and PA612.

6. Multilayer structure according to any one of claims 1 to 5, characterized in that said polymer P2j is an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

7. Multilayer structure according to any one of claims 5 or 6, characterized in that said multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polymer Pli is an aliphatic polyamide selected from PA410, PA412, PA510, PA512, PA610 and PA612, in particular from PA410, PA412, PA510, PA512 and PA612. and said polymer P2j is an epoxy or epoxy-based resin or a polyisocyanate-based resin, in particular polyisocyanurates.

8. Multilayer structure according to any one of claims 1 to 7, characterized in that the fibrous material of the composite reinforcement layer is selected from glass fibers, carbon fibers, basalt or basalt-based fibers, or a mixture thereof, in particular carbon fibers.

9. A method for manufacturing a multilayer structure as defined in any one of claims 1 to 8, characterized in that it comprises a step of preparing the sealing layer by extrusion blow molding, rotomolding, injection or extrusion.

10. A method for manufacturing a multilayer structure according to claim 9, characterized in that it comprises a filament winding step of the reinforcing layer as defined in claim 1 around the sealing layer as defined in claim 1.

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