EP4136180A1

EP4136180A1 - Multilayer structure for transporting or storing hydrogen

Info

Publication number: EP4136180A1
Application number: EP21725566.0A
Authority: EP
Inventors: Nicolas Dufaure; Antoine GOUPIL; Olivier Merle
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2020-04-16
Filing date: 2021-04-15
Publication date: 2023-02-22
Also published as: WO2021209718A1; US20230151255A1; JP2023521463A; CA3172593A1; FR3109389A1; CN115413292A; KR20230007381A; MX2022012608A

Abstract

The present invention relates to the use of a sealing layer (1) consisting of a composition comprising at least one polyamide for preparing a multicore structure intended for the transport, distribution or storage of hydrogen, in particular for the distribution or storage of hydrogen, especially for the storage of hydrogen, the sealing layer satisfying a test for contaminants present in the hydrogen and extracted from the sealing layer after contact of the hydrogen with same, the test been carried out as defined in the standard CSA/ANSI CHMC 2: 19, the total proportion of said contaminants extracted in the hydrogen being less than or equal to 3% by weight, in particular less than 2% by weight of the sum of the constituents of the composition.

Description

DESCRIPTION

TITLE: MULTI-LAYER STRUCTURE FOR THE TRANSPORT OR STORAGE OF

HYDROGEN

[Technical area]

The present patent application relates to multilayer structures intended for the transport, distribution or storage of hydrogen, in particular for the distribution or storage of hydrogen, in particular for the storage of hydrogen, comprising a layer of hydrogen. sealant consisting of a polyamide composition and the use of said sealant layer satisfy a test for contaminants present in hydrogen and extracted from said sealant layer by hydrogen, and their manufacturing process.

[Prior art]

Hydrogen tanks are a subject that is currently attracting a lot of interest from many manufacturers, especially in the automotive sector. One of the goals is to offer vehicles that pollute less and less. Thus, electric or hybrid vehicles comprising a battery aim to gradually replace thermal vehicles, such as gasoline or diesel vehicles. However, it turns out that the battery is a relatively complex component of the vehicle. Depending on the location of the battery in the vehicle, it may be necessary to protect it from impact and the external environment, which can be extreme temperatures and varying humidity. It is also necessary to avoid any risk of flames.

In addition, it is important that its operating temperature does not exceed 55 ° C so as not to damage the battery cells and preserve its lifespan. Conversely, for example in winter, it may be necessary to raise the temperature of the battery in order to optimize its operation.

In addition, the electric vehicle still suffers today from several problems, namely the autonomy of the battery, the use in these rare earth batteries whose resources are not inexhaustible, recharging times much longer than the durations. tank filling, as well as a problem of electricity production in the different countries to be able to recharge the batteries.

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

Supplying the fuel cell with hydrogen therefore requires the presence of both a hydrogen storage tank in the vehicle and a pipe for transporting the hydrogen from the tank to the fuel cell.

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

Their basic principle is to separate the two essential functions of sealing and mechanical strength in order to manage them one independently of the other. In this type of tank, a thermoplastic resin liner (or sealing sheath) is associated with a reinforcing structure made up of fibers (glass, aramid, carbon) also called sheath or reinforcing layer which allow working at much higher pressures. while reducing the mass and avoiding the risk of explosive rupture in the event of severe external attacks.

The problem is the same for the transport pipe.

Liners should have some basic characteristics:

The possibility of being transformed by extrusion blow molding, rotational molding, injection, or extrusion Low hydrogen permeability, the permeability of the liner is indeed a key factor in limiting hydrogen losses from the tank;

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

Thermal resistance at 120 ° C.

However, the fuel cell is very sensitive to various contaminants which degrade its performance and durability.

These contaminants can come from several sources: hydrogen itself due to its manufacturing process, the manufacture of the tank and / or the hydrogen transport pipe or different natural constituents such as volatile organic compounds or water is found trapped in particular in the thermoplastic polymer of the sealing layer, and which will subsequently be extracted by hydrogen in contact with said sealing layer, from the presence in the thermoplastic polymer of constituents which are capable of being subsequently extracted by hydrogen in contact with said sealing layer.

According to Chen et al. (A review of PEM hydrogen fuel cell contamination: impact, mechanisms and mitigation, Journal of Power Sources, 165 (2007), 739-756), the hydrogen used as fuel in fuel cells in research, development and demonstrator comes mainly from from commercially available sources. Hydrogen production processes are mainly carried out by reforming from hydrocarbons or oxygenated hydrocarbons, including methane from natural gas and methanol from biomass, but also by electrolysis, partial oxidation of small organic molecules and hydrolysis. sodium borohydride.

Consequently, a tank or a hydrogen transport pipe used with a fuel cell must not only have the basic characteristics listed above but also the hydrogen after contact with the sealing layer of said tank and / or pipe. must contain only a minimum of contaminants extracted from said sealing layer. This double problem is solved by providing a multilayer structure of the present invention intended for the transport, distribution or storage of hydrogen. Throughout this description, the terms “liner” and “sealing sheath” have the meaning same meaning.

The present invention therefore relates to the use of a sealing layer (1) consisting of a composition comprising at least one polyamide for the preparation of a multilayer structure intended for the transport, distribution or storage of hydrogen. , in particular for the distribution or storage of hydrogen, in particular for the storage of hydrogen, said sealing layer satisfying a test for contaminants present in the hydrogen and extracted from said sealing layer after contact with the hydrogen therewith, said test being carried out as defined in the CSA / ANSI CHMC 2: 19 standard, the total proportion of said contaminants extracted in hydrogen, being less than or equal to 3% by weight, in particular less than 2 % by weight of the sum of the constituents of said composition.

The inventors have therefore found that a sealing layer (1) consisting of a composition comprising at least one polyamide made it possible to prepare a multilayer structure intended for the transport, distribution or storage of hydrogen, exhibiting the basic characteristics listed above but that it also made it possible to limit the proportion of contaminants present in the hydrogen and extracted after contact of the hydrogen with said sealing layer.

By "multilayer structure" is meant 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 a backing layer or a waterproofing layer and a backing layer.

The multilayer structure in the present invention also denotes a pipe or a tube intended for transporting hydrogen from the tank to the fuel cell and which comprises or consists of several layers, namely several sealing layers and several outer layers, or a sealing layer and a plurality of outer layers, or a plurality of sealing layers and an outer layer or a sealing layer and an outer layer. The expression "said sealing layer satisfying a test for contaminants present in hydrogen and extracted from said sealing layer by hydrogen" means that the proportion of contaminants present in hydrogen and originating from the layer of leaktightness after contact with hydrogen, whether it is a tank or a pipe, does not exceed the limit values preventing the correct functioning of the fuel cell.

The CSA / ANSI CHMC 2: 19 standard details the procedure used to determine the volatile components in the headspace of a polymer upon exposure to hydrogen in service. The expression "after contact of hydrogen therewith" means as above an exposure to hydrogen during service.

Equipment

The test equipment should include the following: a) cryofocus to preconcentrate gas samples; b) a gas chromatograph using a suitable column, connected in series with a suitable mass selective detector; c) Headspace vials (40 ml), septa, ring closures and vial sealer; d) an analytical balance capable of weighing up to 60,0001 g; and e) a convection oven capable of maintaining a temperature of 70 ± 5 ° C.

Test environment Purity of hydrogen gas

The conditioning hydrogen gas should be of known composition and purity, as described below. The purity of the hydrogen gas used to fill the test chamber should, as a minimum, conform to ISO 14687: 2019, parts 1 to 3, or SAE J2719 (2015). ISO 14687-2 defines the strictest hydrogen quality specification, with the lowest threshold values for each impurity among these ISO standards (see tables 1). SAE J2719 also applies to Proton Exchange Membrane (PEM) fuel cell vehicles and is harmonized with ISO 14687-2.

[Tables 1]

* all values are given in ppm (v / v) unless otherwise specified

^† when the values given in this table 1 differ from the current edition of ISO 14687-2: 2019, the current values apply.

Measurement and Instrumentation The temperature at which measurements of the hydrogen transmission rate are made should be checked to within ± 1 ° C. The test pressure should remain constant within 1% of the test value.

Test procedure

The test procedure is described in ISO 14687: 2019 in section 5.6.

Regarding contaminants

The term contaminant is understood in the broad sense of the term from the moment when said contaminant is extracted from said sealing layer by hydrogen and is not already present in the hydrogen which is introduced into said multilayer structure to make operate the fuel cell of the vehicle, for example due to the process for obtaining hydrogen.

For example, the term contaminant covers metal cations such as K ⁺ , Cu ²⁺ , Ni ²⁺ and Fe ³⁺ which can be produced by stabilizers used in polyamides, organic or metal stabilizers as such, plasticizers , oligomers, in particular caprolactam and its cyclic dimer 1, 8-diazacyclotetradecane-2,7-dione (DCDD), volatile organic compounds such as NH3, NOx, SOx, N2, benzoic compounds, 03, l ' water absorbed by the polyamide after manufacture of the waterproofing layer, fatty substances such as oil.

Volatile organic compounds therefore exclude all the other materials mentioned in the above list. The total proportion of said contaminants extracted in hydrogen is less than or equal to 3% by weight, in particular less than 2% by weight of the sum of the constituents of said composition. Consequently, this total proportion of said extracted contaminants does not take take into account the proportion of contaminants that would come from the hydrogen preparation process or from any other source.

Advantageously, the total proportion of said contaminants extracted in hydrogen is from 0.01% to 3%, in particular from 0.01% to 2%, more particularly from 0.01% to 1%, in particular from 0, 01% to 0.5% by weight.

In a first variant, the contaminants extracted are chosen from plasticizers, stabilizers, oligomers, water, a fatty substance, volatile organic compounds and a mixture of these.

Advantageously, in this first variant, the proportion by weight of each individual contaminant extracted is less than or equal to 1%.

In one embodiment of this first variant, the constitution of the contaminants extracted is as follows: up to 1% plasticizers, up to 0.5% stabilizers, up to 0.5% oligomers, up to 0.5% water, up to 0.5% fatty substance, and up to 0.5% volatile organic compounds, the sum of the contaminants extracted being less than or equal to 3%, in particular less than 2% by weight of the sum of the constituents of said composition.

Advantageously, in this embodiment of this first variant, the total proportion of said contaminants extracted in hydrogen is from 0.01% to 3%, in particular from 0.01% to 2%, more particularly from 0, 01% to 1%, especially from 0.01% to 0.5% by weight.

More advantageously, in this embodiment of this first variant, the proportion by weight of each individual contaminant extracted is less than or equal to 1%.

In a second variant, the extracted contaminants are chosen from stabilizers, water, oil, volatile organic compounds and a mixture thereof.

Advantageously, in this second variant, the proportion by weight of each individual contaminant extracted is less than or equal to 0.5%.

In one embodiment of this second variant, the constitution of the contaminants extracted is as follows: up to 0.5% stabilizers, up to 0.5% water, up to 0.5% fatty substance , and up to 0.5% of volatile organic compounds, the sum of the contaminants being less than or equal to 2% by weight of the sum of the constituents of said composition. Advantageously, in this embodiment of this second variant, the total proportion of said contaminants extracted in hydrogen is from 0.01% to 2%, more particularly from 0.01% to 1%, in particular from 0.01 % to 0.5% by weight.

More advantageously, in this embodiment of this second variant, the proportion by weight of each individual contaminant extracted is less than or equal to 0.5%.

Regarding the composition

In a first embodiment, the composition which constitutes said sealing layer (1), in particular in the first variant defined above, comprises by weight: at least 63.5% of polyamide, from 0 to 30% of modifier impact, in particular from 0 to less than 15% of impact modifier, in particular from 0 to 12% of impact modifier, from 0 to 1.5% of plasticizer, and from 0 to 5% by weight of additives, the sum of constituents of the composition being equal to 100%.

Advantageously, said composition of this first embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier.

Advantageously, said composition of this first embodiment comprises from 0.1 to 1.5% of plasticizer.

Advantageously, said composition of this first embodiment comprises from 0.1 to 5% by weight of additives

Advantageously, said composition of this first embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier and from 0.1 to 1, 5% plasticizer.

Advantageously, said composition of this first embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier and from 0.1 to 5% by weight of additives.

Advantageously, said composition of this first embodiment comprises from 0.1 to 1.5% of plasticizer and from 0.1 to 5% by weight of additives

Advantageously, said composition of this first embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier, from 0.1 to 1, 5% plasticizer and 0.1 to 5% by weight additives.

In a second embodiment, the composition which constitutes said sealing layer (1), in particular in the first variant defined above, consists by weight: of at least 63.5% of polyamide, from 0 to 30 % of impact modifier, in particular from 0 to less than 15% of impact modifier, in particular from 0 to 12% of impact 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%.

Advantageously, said composition of this second embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier.

Advantageously, said composition of this second embodiment comprises from 0.1 to 1.5% of plasticizer.

Advantageously, said composition of this second embodiment comprises from 0.1 to 5% by weight of additives.

Advantageously, said composition of this second embodiment comprises from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier and from 0.1 to 1.5% of plasticizer.

Advantageously, said composition of this second embodiment comprises from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier and from 0.1 to 5% by weight of additives.

Advantageously, said composition of this second embodiment comprises from 0.1 to 1.5% of plasticizer and from 0.1 to 5% by weight of additives.

Advantageously, said composition of this second embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier, from 0.1 to 1, 5% plasticizer and 0.1 to 5% by weight additives.

In a third embodiment, the composition which constitutes said sealing layer (1), in particular in the second variant defined above, comprises by weight: at least 63.5% of polyamide, from 0 to 30% of modifier impact, in particular from 0 to less than 15% of impact modifier, in particular from 0 to 12% of impact modifier, and from 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100%.

Advantageously, said composition of this third embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier.

Advantageously, said composition of this third embodiment comprises from 0.1 to 5% by weight of additives.

Advantageously, said composition of this third embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier and from 0.1 to 5% by weight of additives. In a fourth embodiment, the composition which constitutes said sealing layer (1), in particular in the second variant defined above, consists by weight: of at least 63.5% of polyamide, from 0 to 30 % of impact modifier, in particular from 0 to less than 15% of impact modifier, in particular from 0 to 12% of impact modifier, and from 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100%.

Advantageously, said composition of this fourth embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier.

Advantageously, said composition of this fourth embodiment comprises from 0.1 to 5% by weight of additives.

Advantageously, said composition of this fourth embodiment comprises from 1 to 30% of impact modifier, in particular from 1 to less than 15% of impact modifier, in particular from 1 to 12% of impact modifier and from 0.1 to 5% by weight of additives.

Regarding polyamide

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

The polyamide can be a homopolyamide or a copolyamide or a mixture thereof.

Polyamide is a semi-crystalline polyamide, that is to say a material generally solid at room temperature, and which softens during an increase in temperature, in particular after passing its glass transition temperature (Tg), and which may present a clear melting on passing of its so-called melting temperature (Tm), and which becomes solid again when the temperature drops below its crystallization temperature.

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

The number-average molecular mass Mn of said semi-crystalline polyamide 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, even more preferably from 12,000 to 50,000. These Mn values may correspond. at inherent viscosities greater than or equal to 0.8 as determined in m-cresol according to standard ISO 307: 2007 but by changing the solvent (use of m-cresol instead of sulfuric acid and the temperature being 20 ° C).

In one embodiment, the polyamide is chosen from an aliphatic polyamide, a semi-aromatic polyamide and a mixture of the two, advantageously an aliphatic polyamide.

Said aliphatic polyamide can be obtained from the polycondensation: _{at least one C 6} to C 18 amino acid, preferably C 8 to C 18, more preferably C 10 to C 18, even more preferably C 10 to C 12, in particular Cn; or at least one C6 to Cie lactam, preferably C8 to C ₁₈ , more preferably C ₁₀ to Cie, even more preferably C10 to C12, in particular C12; or at least one C4-C36 aliphatic diamine Ca, in particular C6-C36, preferably O _Q - Ci ₈ , preferably C6-C12, more preferably C10-C12 with at least one Cb C4-C36 aliphatic diacid, in particular in C6-C36, preferentially C6-C18, preferentially C10-C18, more preferentially C10-C12.

A C to C 12 amino acid is in particular 6-aminohexanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid as well as its derivatives, in particular N-heptyl-11-aminoundecanoic acid.

When said at least one semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one amino acid, it can therefore comprise a single amino acid or several amino acids.

Advantageously, said semi-crystalline aliphatic polyamide is obtained from the polycondensation of a single amino acid and said amino acid is chosen from 11-aminoundecanoic acid and 12-aminododecanoic acid, advantageously 11-aminoundecanoic acid.

The lactam in O _Q to C12 is in particular caprolactam, decanolactam, undecanolactam, and lauryllactam.

When said at least one semi-crystalline aliphatic polyamide is obtained from the polycondensation of at least one lactam, it can therefore comprise a single lactam or several lactams.

Advantageously, said at least one semi-crystalline aliphatic polyamide is obtained from the polycondensation of a single lactam and said lactam is chosen from lauryllactam and unecanolactam, advantageously lauryllactam.

The Ca diamine can be linear or branched. Advantageously, it is linear.

Said at least one C4-C36 diamine Ca can in particular be chosen from butanemethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9 -nonamethylenediamine, 1,10- decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1, 13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,16-hexadecamethylenediamine and 1,18-hexadecamethylenediamine and 1,18-hexadecamethylenediamine , octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids. Advantageously, said at least one Ca diamine is C6-C36 and chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9- nonamethylenediamine, 1, 10-decamethylenediamine, 1, 11-undecamethylenediamine, 1, 12-dodecamethylenediamine, 1, 13-tridecamethylenediamine, 1, 14-tetradecamethylenediamine, 1, 16-hexadecamethylenediamine, 1, 16-hexadecamethylenediamine, 18ediamine and 1 roctadecenediamine, reicosanediamine, docosanediamine and diamines obtained from fatty acids.

Said at least one Cb C4 to C36 dicarboxylic acid can be chosen from butanedioic acid, pentanedioic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and diacids obtained from fatty acids.

The diacid can be linear or branched. Advantageously, it is linear.

Advantageously, the aliphatic polyamide is chosen from PA6, PA66, PA11, PA12, PA610, PA612, PA1010, PA1012 and PA1212.

Said semi-aromatic polyamide can be, in particular, a semi-aromatic polyamide of formula X / YAr, as described in EP1505099, in particular a semi-aromatic polyamide of formula A / XT in which A is chosen from a unit obtained from an amino acid as defined above, a unit obtained from a lactam as defined above and a unit corresponding to the formula (Ce diamine). (Cd diacid), with c representing the number of carbon atoms of the diamine and d representing the number of carbon atoms of the diacid, c and d each being between 4 and 36, advantageously between 9 and 18, the unit (diamine in Ce) being chosen from aliphatic diamines, linear or branched, as defined above, cycloaliphatic diamines and alkylaromatic diamines and the unit (diacid in Cd) being chosen from aliphatic, linear or branched diacids, as defined above, cycloaliphatic diacids and aromatic diacids;

XT denotes a unit 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 / 11 T, A being as defined above, in particular a polyamide chosen from a PA MPMDT / 6T, one PA11 / 10T, one PA 5T / 10T, one PA 11 / BACT, one PA 11 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one 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.

T is terephthalic acid, MXD is m-xylylenediamine, MPMD is methylpentamethylene diamine, and BAC is bis (aminomethyl) cyclohexane.

Said semi-aromatic polyamide can also be a polyamide of formula ZAr in which Z is a unit resulting from the polycondensation of at least one aliphatic diamine in Ca as defined above and Ar is an aromatic dicarboxylic acid, in particular the terepthalic acid, isophthalic acid and naphthalenic acid. In one embodiment, the polyamide is aliphatic and selected from PA6, PA66, PA11, PA12, PA610, PA612, PA1010, PA1012 and PA1212.

In another embodiment, the polyamide is semi-aromatic and chosen from polyamide 11 / 5T, 11 / 6T, 11/1 OT, MXDT / 10T, MPMDT / 10T and BACT / 10T.

In one embodiment, said polyamide of said composition is washed beforehand at least once with a system chosen from a polar solvent, in particular methanol, water or water vapor, or a mixture of these. this.

Regarding the impact modifier

The impact modifier can be any impact modifier from the moment when a polymer of lower modulus than that of the resin, exhibiting good adhesion with the matrix, so as to dissipate the cracking energy.

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

In one embodiment, PEBAs are excluded from the definition of impact modifiers.

The polyolefin of the impact modifier can be functionalized or non-functionalized or be a mixture of at least one functionalized and / or at least one non-functionalized. For simplicity, the polyolefin has been designated by (B) and functionalized polyolefins (B1) and unfunctionalized polyolefins (B2) have been described below.

An unfunctionalized polyolefin (B2) is conventionally a homopolymer or copolymer of alpha olefins or diolefins, such as, for example, ethylene, propylene, butene-1, octene-1, butadiene. By way of example, we can cite:

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

the homopolymers or copolymers of propylene.

- ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of 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) acrylate (for example methyl acrylate), or vinyl esters of carboxylic acids saturated such as vinyl acetate (EVA), the proportion of comonomer being up to 40% by weight.

The functionalized polyolefin (B1) can be a polymer of alpha olefins having reactive units (the functionalities); such reactive units are the acid, anhydride, or epoxy. By way of example, mention may be made of the preceding polyolefins (B2) grafted or co- or ter polymerized with unsaturated epoxides such as glycidyl (meth) acrylate, or with 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 alternatively by carboxylic acid anhydrides 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 degree of grafting, for example from 0.01 to 5% by weight.

The functionalized polyolefin (B1) can be chosen from the following (co) polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the degree of grafting is for example from 0.01 to 5% by weight:

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

- ethylene and vinyl acetate (EVA) copolymers, 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;

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

The functionalized polyolefin (B1) can also be chosen from ethylene / propylene copolymers predominantly in propylene grafted with maleic anhydride and then condensed with mono-amine polyamide (or a polyamide oligomer) (products described in EP-A-0342066) .

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

By way of example of functionalized polyolefins of the latter type, mention may be made of the following copolymers, 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:

- ethylene / (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 (meth) acrylate / (meth) acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

In the above copolymers, (meth) acrylic acid can be salified with Zn or Li.

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

Furthermore, the aforementioned polyolefins (B1) can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the abovementioned polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, and the like. capable of reacting with these or mixtures of at least two functionalized polyolefins capable of reacting with each other.

The copolymers mentioned above, (B1) and (B2), can be copolymerized in a random or block fashion and have a linear or branched structure.

The molecular weight, the MFI number, the density of these polyolefins can also vary to a large extent, which will be appreciated by those skilled in the art. MFI, short for Melt Flow Index, is the melt flow index. It is measured according to the ASTM 1238 standard.

Advantageously, the unfunctionalized polyolefins (B2) are chosen from homopolymers or copolymers of polypropylene and any homopolymer of ethylene or copolymer of ethylene and of a comonomer of higher alpha olefinic type such as butene, hexene, octene or 4-methyl 1-Pentene. Mention may be made, for example, of PPs, high density PE, medium density PE, linear low density PE, low density PE, very low density PE. These polyethylenes are known to those skilled in the art as being produced according to a "radical" process, according to a "Ziegler" type catalysis or, more recently, according to a so-called "metallocene" catalysis.

Advantageously, the functionalized polyolefins (B1) are chosen from any polymer comprising alpha olefinic units and units bearing polar reactive functions such as epoxy, carboxylic acid or carboxylic acid anhydride functions. As examples of such polymers, mention may be made of the ter polymers of ethylene, of alkyl acrylate and of maleic anhydride or of glycidyl methacrylate, such as Lotader® from the Applicant or polyolefins grafted with l. maleic anhydride such as Orevac® from the Applicant as well as ter polymers of ethylene, of alkyl acrylate and of (meth) acrylic acid. Mention may also be made of homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or mono-amino polyamide oligomers. Advantageously, said constituent composition of said sealant layer or layers is devoid of polyether block amide (PEBA). In this embodiment, the PEBAs are therefore excluded from the impact modifiers.

Advantageously, said transparent composition is devoid of core-shell particles or “core-shell” core-shell polymers.

By core-shell particle, it is necessary to understand a particle of which the first layer forms the core and the second or all of the following layers form the respective shell.

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

In one embodiment, when the polyamide of the composition is a semi-aromatic polyamide, the proportion of impact modifier is then from 0 to less than 10% by weight, in particular from 0 to 8% by weight, in particular from 1 to less than 10% by weight, especially 1 to 8% by weight. Advantageously, in this last embodiment, said composition also comprises from 0.1 to 5% by weight of additives.

Regarding the plasticizer

The plasticizer can be a plasticizer commonly used in compositions based on polyamide (s).

Advantageously, a plasticizer is used which has good thermal stability so that no fumes are formed during the stages of mixing the various polymers and of processing the composition obtained.

In particular, this plasticizer can be chosen from: benzene sulfonamide derivatives such as n-butyl benzene sulfonamide (BBSA), ortho and para isomers of ethyl toluene sulfonamide (ETSA), N-cyclohexyl toluene sulfonamide and N- (2-hydroxypropyl) benzenesulfonamide (HP-BSA), esters of hydroxybenzoic acids such as 2-ethylhexyl para-hydroxybenzoate (EHPB) and 2-decylhexyl para-hydroxybenzoate (HDPB), esters or ethers of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfurylalcohol, and esters of citric acid or of hydroxymalonic acid, such as oligoethyleneoxymalonate.

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

Another more particularly preferred plasticizer is N- (2-hydroxy-propyl) benzene sulfonamide (HP-BSA). The latter in fact has the advantage of avoiding the formation of deposits at the level of the screw and / or of the extrusion die (“die tears”), during a step of transformation by extrusion.

It is of course possible to use a mixture of plasticizers. Regarding additives

The additives can be selected from an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a nucleating agent and a colorant.

Regarding the structure

According to another aspect, the present invention relates to a multilayer structure comprising at least one sealing layer (1) as defined above.

During the contact of hydrogen with said sealing layer, the total proportion of said contaminants extracted and present in the hydrogen is less than or equal to 3% by weight, in particular less than 2% by weight of the sum of the constituents of the composition constituting said waterproofing layer, determined according to the test defined in the CSA / ANSI CHMC 2: 19 standard.

In a first embodiment, said multilayer structure corresponds to a reservoir and further comprises at least one composite reinforcing layer (2), said sealing layer being in contact with hydrogen.

First embodiment: reservoir

Said multilayer structure can therefore comprise at least one waterproofing layer and at least one composite reinforcing layer which is wrapped around the waterproofing layer and which may or may not adhere to each other.

In one embodiment, at least one of said composite reinforcing layers (2) consists of a fibrous material in the form of continuous fibers impregnated with a composition mainly comprising at least one polymer P2j, (j = 1 to m , m being the number of reinforcing layers), in particular an epoxy or epoxy-based resin, said structure being devoid of an outermost layer and adjacent to the outermost layer of composite reinforcement made of polyamide polymer.

Advantageously, said sealing and reinforcing layers do not adhere to each other and consist of compositions which respectively comprise different polymers. However, said different polymers can be of the same type.

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

Said multilayer structure can comprise up to 10 waterproofing layers and up to 10 composite reinforcement layers of different types. It is obvious that said multilayer structure is not necessarily symmetrical and that it can therefore comprise more sealing layers than composite layers or vice versa, but there cannot be alternation of layers and of reinforcing layer.

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 layers composite reinforcement.

Advantageously, said multilayer structure comprises one, two, three, four or five waterproofing layers and one, two, three, four or five composite reinforcement layers. Advantageously, said multilayer structure comprises one, two or three waterproofing layers and one two or three composite reinforcement layers.

In one embodiment, said multilayer structure comprises a single waterproofing layer and several reinforcing layers, said adjacent reinforcing layer being wrapped around said waterproofing layer and the other reinforcing layers being wrapped around the reinforcing layer. directly adjacent.

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.

In an advantageous embodiment, said multilayer structure comprises a single sealing layer and a single composite reinforcing layer, said reinforcing layer being wrapped around said sealing layer.

All combinations of these two layers are therefore within the scope of the invention, provided that at least said innermost composite reinforcing layer is wrapped around said outermost adjacent sealing layer, the other layers adhering or not between them or not.

Advantageously, in said multilayer structure, each sealing layer consists of a composition comprising the same type of polyamide.

By the same type of polymer is meant, for example, a polyamide which can be an identical or different polyamide depending on the layers.

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

Advantageously, in said multilayer structure, each sealing layer comprises the same type of polyamide and each reinforcing layer comprises the same type of polymer P2j, in particular an epoxy or epoxy-based resin.

Advantageously, the P2j polyamide is identical for all the reinforcing layers. Advantageously, said polymer P2j is an epoxy resin or an epoxy-based resin. Advantageously, the polyamide is identical for all the sealing layers. Advantageously, said polyamide of the waterproofing layer is an aliphatic polyamide, in particular PA6, PA66, PA610, PA612, PA1010, PA 1012, PA 1212, PA11, PA12, in particular PA 11 or PA12 and said polymer P2j is a semi polyamide. -aromatic, in particular chosen from a PA MPMDT / 6T, a PA11 / 10T, a PA 11 / BACT, a PA 5T / 10T, a PA 11 / 6T / 10T, a PA MXDT / 10T, a PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, one PA and 11 / MXDT / 10T. In one embodiment, said multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polyamide of the sealing layer is a long chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, in particular PA 11 or PA12 and said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, a PA11 / 10T, a PA 11 / BACT, a PA 5T / 10T, one PA 11 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T and a PA 11 / MXDT / 10T.

A long chain polyamide is a polyamide with an average number of carbon atoms per nitrogen atom greater than 8.

In another embodiment, said multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polyamide of the sealing layer (1) is a long chain aliphatic polyamide, in in particular PA1010, PA 1012, PA 1212, PA12, in particular PA12 and said polymer P2j is a semi-aromatic polyamide, in particular chosen from a PA MPMDT / 6T, a PA PA11 / 10T, a PA 11 / BACT, a PA 5T / 10T one PA 11 / 6T / 10T, one PA MXDT / 10T, one PA MPMDT / 10T, one PA BACT / 10T, one PA BACT / 6T, PA BACT / 10T / 6T, one PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T and a PA 11 / MXDT / 10T.

In yet another embodiment, the multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polyamide of the sealing layer (1) is a long chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA11, PA12, or semi-aromatic, in particular chosen from polyamide 11 / 5T or 11 / 6T or 11 / 10T, MXDT / 10T, MPMDT / 10T and BACT / 10T, in particular PA 11 or PA12 and said polymer P2j is an epoxy resin or an epoxy-based resin.

In another embodiment, the multilayer structure consists of a single reinforcing layer and a single sealing layer in which said polyamide of the sealing layer (1) is a long chain aliphatic polyamide, in particular PA1010, PA 1012, PA 1212, PA12, or semi-aromatic, in particular chosen from polyamide 11 / 5T or 11 / 6T or 11 / 10T, MXDT / 10T, MPMDT / 10T and BACT / 10T , in particular PA12 and said polymer P2j is an epoxy resin or an epoxy-based resin. Advantageously, said multilayer structure further 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.

Said outer layer is a second but transparent reinforcing layer which makes it possible to put an inscription on the structure.

In a second embodiment, said multilayer structure corresponds to a pipe and further comprises at least one outer metal braid (2 ’), said sealing layer being in contact with hydrogen.

There is therefore no composite reinforcing layer in this latter embodiment.

This pipe is intended in particular to connect the reservoir defined above to the fuel cell.

The characteristics of the waterproofing layer are the same as above.

Regarding the fibrous material

Regarding the constituent fibers of said fibrous material, they are in particular fibers of mineral, organic or plant origin.

Advantageously, said fibrous material can be sized or not sized.

Said fibrous material can therefore comprise up to 3.5% by weight of an organic material (thermosetting or thermoplastic resin type) called sizing.

Among the fibers of mineral origin, mention may be made of carbon fibers, glass fibers, basalt or basalt-based fibers, silica fibers, or silicon carbide fibers, for example. Among the fibers of organic origin, mention may be made of fibers based on a thermoplastic or thermosetting polymer, such as semi-aromatic polyamide fibers, aramid fibers or polyolefin fibers, for example. Preferably, they are based on an amorphous thermoplastic polymer and have a glass transition temperature Tg greater than the Tg of the polymer or mixture of thermoplastic polymer constituting the pre-impregnation matrix when the latter is amorphous, or greater than the Tm of the polymer or mixture of thermoplastic polymer constituting the prepreg matrix when the latter is semi-crystalline. Advantageously, they are based on semi-crystalline thermoplastic polymer and have a melting temperature Tm greater than the Tg of the polymer or mixture of thermoplastic polymer constituting the prepreg matrix when the latter is amorphous, or greater than the Tm of the thermoplastic polymer. polymer or mixture of thermoplastic polymer constituting the prepreg matrix when the latter is semi-crystalline. Thus, there is no risk of fusion for the organic fibers constituting the fibrous material during impregnation with the thermoplastic matrix of the final composite.

Among the fibers of plant origin, mention may be made of natural fibers based on flax, hemp, lignin, bamboo, silk, in particular spider silk, sisal, and other cellulose fibers, in particular viscose. These fibers of plant origin can be used pure, processed or else coated with a coating layer, in order to facilitate the adhesion and impregnation of the thermoplastic polymer matrix.

The fibrous material can also be fabric, braided or woven with fibers.

It can also correspond to fibers with retaining threads.

These constitution 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 to form the pre-impregnated fibrous material.

The rovings of organic fibers can have several grammages. They can also have several geometries. The fibers constituting the fibrous material can also be in the form of a mixture of these reinforcing fibers of different geometries. Fibers are continuous fibers.

Preferably, the fibrous material is chosen from glass fibers, carbon fibers, basalt or basalt-based fibers, or a mixture of these, in particular carbon fibers.

It is used as a wick or several wicks.

According to another aspect, the present invention relates to a method of manufacturing a multilayer structure as defined above, characterized in that it comprises a step of manufacturing a sealing layer (1) as defined in one of claims 1 to 12, by injection, extrusion, extrusion blow molding or rotational molding.

In one embodiment, said method comprises a preliminary step of washing the polyamide of the composition at least once with a system chosen from a polar solvent, in particular methanol, water or water vapor, or a mixture of these.

Advantageously, said method of manufacturing a multilayer structure which corresponds to a reservoir and as defined above, is characterized in that it comprises a step of filament winding of a reinforcing layer (2), such as defined above, around the waterproofing layer (1).

Advantageously, said multilayer structure can be washed after manufacture at least once with a system chosen from a polar solvent, in particular methanol, water or water vapor, or a mixture thereof.

In the case of washing after manufacture with a polar solvent, in particular methanol or with a water-polar solvent mixture, it is necessary to rinse the structure to remove all traces of methanol.

Advantageously, the structure is dried for 2 days under a stream of dry air, in particular at a temperature of 40 ° C to 80 ° C, in particular from 50 ° C to 70 ° C, in particular at 60 ° C after manufacture or after manufacturing and washing.

All the characteristics detailed above also apply to the process. Examples:

The following compositions were prepared according to techniques well known to those skilled in the art for the constitution of the sealing layer (1) of the structures of the invention (Table 2). [Tables 2]

C1 to C2: comparative compositions

PA11: PA11 is a polyamide 11 of Mn (number molecular mass) 45,000. The melting point is 190 ° C, its enthalpy of fusion is 56 J / g.

PA11 / 10T: Rilsan HT (Arkema)

Plasticizer: BBSA (n-butyl benzene sulfonamide)

Impact modifier: lotader® 4700 (50%) + lotader® AX8900 (25%) + lucalene® 3110 (25%) Additives: stabilizers

The sealing layers (liner) of the invention comprising a sealing layer (1) are obtained by rotational molding of the sealing layer (liner) with the various compositions above at a temperature suited to the nature of the material. thermoplastic resin used.

The multilayer structures comprising a composite reinforcement of epoxy resin or epoxy-based resin are obtained by a wet filament winding process which consists in winding carbon fibers around the liner, which fibers being pre-impregnated in a bath of liquid epoxy or a liquid epoxy based bath. The reservoir is then polymerized in an oven for 2 hours.

The contaminants extracted in the hydrogen from the various waterproofing layers of the multilayer structures made from the above compositions were quantified according to the CSA / ANSI CHMC 2: 19 standard:

Multilayer structure with waterproofing layer based on composition-11: <0.5%

Multilayer structure with waterproofing layer based on composition-12: <0.5%

Multilayer structure with waterproofing layer based on composition-13: <0.5%

Multilayer structure with waterproofing layer based on composition-14: <0.5%

Multilayer structure with waterproofing layer based on composition-15: <0.5%

Multilayer structure with a waterproofing layer based on CI composition:> 3%

Multilayer structure with waterproofing layer based on composition-C2:> 3%

Claims

1. Use of a waterproofing layer (1) consisting of a composition comprising at least one polyamide for the preparation of a multilayer structure intended for the transport, distribution or storage of hydrogen, in particular for the production. distribution or storage of hydrogen, in particular storage of hydrogen, said sealing layer satisfying a test for contaminants present in hydrogen and extracted from said sealing layer after contact of hydrogen with the latter , said test being carried out as defined in the CSA / ANSI CHMC 2: 19 standard, the total proportion of said contaminants extracted in hydrogen, being less than or equal to 3% by weight, in particular less than 2% by weight of the sum of the constituents of said composition.

2. Use according to claim 1, wherein the extracted contaminants are selected from plasticizers, stabilizers, oligomers, water, a fatty substance, volatile organic compounds and a mixture thereof.

3. Use according to claim 2, wherein the proportion by weight of each individual contaminant extracted is less than or equal to 1%.

4. Use according to claim 2 or 3, wherein the constitution of the extracted contaminants is as follows: up to 1% plasticizers, up to 0.5% stabilizers, up to 0.5% oligomers, up to 0.5% water, up to 0.5% fatty substance, and up to 0.5% volatile organic compounds, the sum of the contaminants extracted being less than or equal to 3%, in particular less than 2% by weight of the sum of the constituents of said composition.

5. Use according to one of claims 1 to 4, wherein said composition comprises by weight: at least 63.5% of polyamide, from 0 to less than 30% of impact modifier, in particular from 0 to less than 15% of impact modifier, in particular from 0 to 12% of impact 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%.

6. Use according to claim 1, wherein the extracted contaminants are selected from stabilizers, water, oil, volatile organic compounds and a mixture thereof.

7. Use according to claim 6, wherein the proportion by weight of each individual contaminant extracted is less than or equal to 0.5%.

8. Use according to claim 6 or 7, wherein the constitution of the extracted contaminants is as follows: up to 0.5% stabilizers, up to 0.5% water, up to 0.5% of fatty substances, and up to 0.5% of volatile organic compounds, the sum of the contaminants being less than or equal to 2% by weight of the sum of the constituents of said composition.

9. Use according to one of claims 6 to 8, wherein said composition comprises by weight: at least 63.5% of polyamide, from 0 to less than 30% of impact modifier, in particular from 0 to less than 15% of impact modifier, in particular from 0 to 12% of impact modifier, and from 0 to 5% by weight of additives, the sum of the constituents of the composition being equal to 100%.

10. Use according to one of claims 1 to 9, wherein the polyamide is selected from an aliphatic polyamide, a semi-aromatic polyamide and a mixture of the two.

11. Use according to claim 10, wherein the polyamide is aliphatic and selected from PA6, PA66, PA11, PA12, PA610, PA612, PA1010, PA1012 and PA1212.

12. Use according to claim 10, in which the polyamide is semi-aromatic and chosen from polyamide 11 / 5T, 11 / 6T, 11 / 10T, MXDT / 10T, MPMDT / 10T and BACT / 10T.

13. Multilayer structure comprising at least one sealing layer (1) as defined in one of claims 1 to 12.

14. Multilayer structure according to claim 13, characterized in that it corresponds to a reservoir and further comprises at least one composite reinforcing layer (2), said sealing layer being in contact with hydrogen.

15. Multilayer structure according to claim 13 or 14, characterized in that at least one of said composite reinforcing layers (2) consists of a fibrous material in the form of continuous fibers impregnated with a composition mainly comprising at least a polymer P2j, (j = 1 to m, m being the number of reinforcing layers), in particular an epoxy or epoxy-based resin, said structure being devoid of an outermost layer and adjacent to the most outer layer more exterior composite reinforcement in polyamide polymer.

16. Multilayer structure according to one of claims 13 to 15, characterized in that each sealing layer comprises the same type of polyamide.

17. Multilayer structure according to one of claims 13 to 16, characterized in that each reinforcing layer comprises the same type of polymer, in particular an epoxy resin or an epoxy-based resin.

18. Multilayer structure according to one of claims 13 to 17, characterized in that each sealing layer comprises the same type of polyamide and each reinforcing layer comprises the same type of polymer, in particular an epoxy resin or based on epoxy.

19. Multilayer structure according to one of claims 13 to 18, characterized in that it has a single sealing layer and a single reinforcing layer.

20. Multilayer structure according to one of claims 13 to 19, characterized in that said structure further comprises at least one outer layer (3) made of a continuous fiberglass fibrous material impregnated with a transparent amorphous polymer, said layer being the outermost layer of said multilayer structure.

21. Multilayer structure according to claim 13, characterized in that it corresponds to a pipe and further comprises at least one outer metal braid (2 '), said sealing layer being in contact with hydrogen.

22. A method of manufacturing a multilayer structure as defined in one of claims 13 to 20, characterized in that it comprises a step of manufacturing a sealing layer (1) as defined in one of claims 1 to 12, by injection, extrusion, extrusion blow molding or rotational molding.

23. A method of manufacturing a multilayer structure according to claim 22, characterized in that it comprises a preliminary step of washing the polyamide of the composition at least once with a system chosen from a polar solvent, in particular methanol, water or water vapor, or a mixture thereof, before the step of manufacturing said sealing layer (1) by injection, extrusion or rotational molding.

24. A method of manufacturing a multilayer structure according to claim 22 or 23, characterized in that it comprises a step of filament winding of a reinforcing layer (2), as defined in one of claims 14. at 20, around the sealing layer (1).