Multilayer structure comprising BIO-based polyamide and its use for hydrogen storage and transportation

Abstract

This invention relates to a multilayer structure intended to store and / or transport hydrogen gas (H2) comprising at least one barrier layer (Lb) made of or comprising at least one polyamide (PA) as disclosed herein; and to use of the polyamide (PA) in manufacturing a barrier layer (Lb) in a vessel or a pipe, wherein H2 is in contact with the barrier layer (Lb).

Description

MULTILAYER STRUCTURE COMPRISING BIO-BASED POLYAMIDE AND ITS USE FOR HYDROGEN STORAGE AND TRANSPORTATIONCROSS-REFERENCE TO RELATED PATENT APPLICATION(S)

[0001] This application claims priority filed on 21 December 2023 in the U.S.A, with Nr 63 / 613343, the whole content of this application being incorporated herein by reference for all purposes.TECHNICAL FIELD

[0002] The invention relates to a multilayer structure intended to store and / or transport hydrogen gas (H2) comprising at least one barrier layer (Lb) made of or comprising at least one polyamide (PA); and to use of the polyamide (PA) in manufacturing a barrier layer (Lb) in a vessel or a pipe, wherein H2 is in contact with the barrier layer (Lb).TECHNICAL BACKGROUND

[0003] The natural gas and / or fuel cell vehicles have been continuously desired in the market which keeps asking to find environmentally-friendly solutions. Fuel cell vehicles are powered by fuel cells in which H2 is used as a fuel.

[0004] In parallel, with the requirement to decrease the weight of the vehicles, tanks of H2 based on composite materials are preferred to those made of steel. These tanks need to withstand the internal pressure of H2, while the loss of H2 over time should be minimized.

[0005] Notably, the industry keeps seeking a material that exhibits excellent barrier properties against H2, i.e. low permeability to H2, with a purpose of storing and / or transporting H2, and hence may be used in manufacturing the vessels / tanks to be loaded with pressurized H2.

[0006] Moreover, it is foreseen that the vehicles running with H2, i.e. using H2 as a fuel, will be mainly trucks equipped with large tanks, e.g. tanks for heavy duty applications, such that it should be also considered in selecting a material therefor that high temperature peaks can be encountered during rapid filling and / or depressurizing of the tanks.

[0007] The material hence should satisfy various properties such as thermal stability / resistance, high barrier against H2 (low permeability to H2), easyprocessability, strong mechanical properties, as well as wide temperature range where the material may be used.

[0008] High-pressure gas storage tanks comprising a liner having barrier properties and an outer layer comprising a fiber-reinforced composite material have been developed to address this need. For instance, type IV tanks made of a thermoplastic / non-metallic inner liner encased in an outer layer made up of a composite material have been developed.

[0009] For instance, US2023 / 0142635A1 (Mitsubishi Gas Chemical) discloses a high-pressure gas storage tank having gas barrier properties, e.g. H2 barrier property, wherein the liner is made of a thermoplastic polymer, notably a polyamide that contains a diamine-derived constituent unit and a dicarboxylic acid-derived constituent unit, with at least 50 mol% of the diamine-derived constituent units being derived from xylene diamine as disclosed in WO201 6 / 084175A1 (Mitsubishi Electric Corp.).

[0010] WO2017 / 102385A1 (DSM) discloses a pressure vessel having a hollow body comprising endless fibers embedded in a thermoplastic matrix, where the matrix comprises at least one polyamide containing at least one aliphatic monomeric unit.

[0011] WO2023 / 083783A1 (Arkema) discloses a multilayer structure for storing or transporting compressed gas, preferably at high pressure, more particularly H2. The multilayer structure comprises at least three layers in an order from inside to outside, i.e. at least one sealing layer consisting of a composition comprising at least one semi-crystalline thermoplastic polyamide having a melting point (Tm) of 280°C or less; at least one intermediate composite reinforcing layer consisting of a fibrous material embedded in a composition comprising at least one semi-crystalline thermoplastic polyamide having a glass transition temperature (Tg) of less than 100°C, and at least one outer composite reinforcing layer consisting of a continuous fiber embedded in a composition comprising at least one polyphthalamide having a Tgof greater than 80°C.

[0012] In this regard, known aliphatic polyamides such as PA6 and PA66 are easy to process and generally have high Tm and high heat resistance, in particular when reinforced with fibers or fillers. However, they typically have high waterabsorption values of up to 10% when stored in water. Use of such an aliphatic polyamide hence becomes problematic in applications that require strict requirements on dimensional stability. Water absorption brings about not only the changes in its dimension but also its mechanical properties such as stiffness, modulus, tensile strength, etc., while there are various applications involving mechanical load in contact with water or ambient moisture that require dimensional stability and maintenance of the mechanical properties at the same time.

[0013] Accordingly, semi-aromatic polyamides have been developed to address these problems. Trogamid®T5000, commercially available from Evonik, is an amorphous polyamide composed of terephthalic acid and a mixture of 2,2,4- trimethylhexanediamine (2,2,4-TMD) and 2,4,4-trimethylhexanediamine (2,4,4-TMD), exhibiting a high mechanical strength and a high toughness. However, its bulky diamine component makes the material amorphous and therefore demonstrates limited chemical resistance. Dimensional stability on heating is also restricted by the lack of crystalline content. Although the replacement of linear aliphatic diamines by bulky monomers such as TMD in polyamides generally increases Tg, there is simultaneous drastic reduction of crystallinity. In particular, it loses all of its mechanical integrity when exposed to temperatures higher than its Tgof around 150°C and in presence of water due to a high moisture absorption around 7.5 wt%, as disclosed in US2012 / 0095161A1 (Evonik Degussa). US’161A1 discloses a polyamide molding composition having good processability and Tmof from about 250°C to about 300°C, with sufficiently high crystallinity combined with minimum differences in mechanical properties, heat resistance and dimensional stability in the freshly injection-molded state and also in the moisture-conditioned state.

[0014] EP1795632A1 (Kuraray) relates to a binder fiber suitable for a separator in a battery and discloses a semi-aromatic copolyamide at least having an aromatic ring unit and a C3-7 alkane unit which may have a C1-3 alkyl group as a branched chain, that exhibits high resistance to oxidization / degradation / heat and high electrolyte resistance at high temperature.

[0015] The present invention aims to provide a multilayer structure intended to store and / or transport hydrogen gas (H2), wherein the multilayer structurecomprises at least one barrier layer (Lb) made of or comprising at least one polyamide (PA) that exhibits a Tgof at least 110°C, preferably at least 115°C, more preferably at least 120°C, as well as excellent barrier properties against H2. The Tgis significantly higher than Tgof aliphatic polyamides such as PA6 and PA66, corresponding to from about 50°C to about 60°C, and the barrier properties against H2 is superior to those of PA6 and PA11. In addition, the polyamide (PA) of the present invention exhibits better mechanical properties, such as chord modulus, ultimate tensile strength and elongation at break, measured according to ISO527. The polyamide (PA) of the present invention also exhibits better IV retention after water ageing, measured according to the protocol defined in the specification.

[0016] An additional benefit of the present invention is the use of more sustainable monomers or polymers in these applications. Accordingly, a polyamide having a significant bio-content may be applied.SUMMARY OF THE INVENTION

[0017] The invention relates to a multilayer structure intended to store and / or transport hydrogen gas (H2) comprising at least one barrier layer (Lb) made of or comprising at least one polyamide (PA) as defined in the specification.

[0018] The invention also relates to use of the polyamide (PA) in manufacturing a barrier layer (Lb) in a vessel or a pipe intended to store and / or transport H2, wherein H2 is in contact with the barrier layer (Lb).DETAILED DESCRIPTION OF THE INVENTION

[0019] In the present application, unless otherwise indicated, any specific embodiment or technical feature relating to a subject-matter is applicable to and interchangeable with another embodiment or technical feature also relating to the same subject-matter and disclosed elsewhere in the application.

[0020] Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. In the context of the present invention, the term ‘percent byweight’ (wt%) indicates the content of a specific component in a mixture, calculated as the ratio between the weight of the component and the total weight of the mixture. As used herein, the concentration of recurring units in ‘percent by mol’ (mol%) refers to the concentration relative to the total number of recurring units in the polymer, unless explicitly stated otherwise.

[0021] It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed. Accordingly, various changes and modifications described herein will be apparent to those skilled in the art. Moreover, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

[0022] For the purpose of the present description and of the following claims: the use of parentheses around symbols or numbers identifying the formulae, for example in expressions like “polyamide (PA)”, etc., has the mere purpose of better distinguishing the symbol or number from the rest of the text and, hence, said parenthesis can also be omitted.

[0023] A "hydrogen barrier layer" is a layer which prevents or impedes the transport of hydrogen gas (H2) through itself.

[0024] The present invention relates to a multilayer structure intended to store and / or transport hydrogen gas (H2), wherein the multilayer structure comprises at least one barrier layer (Lb) made of or comprising at least one polyamide (PA) which comprises recurring units (RPA) formed from the polycondensation of a diamine component (A) and a dicarboxylic acid component (B) wherein:- the diamine component (A) comprises: a) a first diamine (DA1 ) selected from the group consisting of 2,2,4- trimethyl-1 ,6-hexanediamine (2,2,4-TMD), 2,4,4-trimethyl-1 ,6- hexanediamine (2,4,4-TMD) and a mixture thereof; and b) a second diamine (DA2) selected from the group consisting of 1 ,9- nonanediamine (C9), 1 ,10-decanediamine (C10) and a mixture thereof; wherein the molar ratio DA1 / DA2 of the first diamine (DA1 ) to the second diamine (DA2) is between 12 / 88 and 47 / 53, wherein the proportion of the second diamine (DA2) in the diamine component (A) is at least 53mol%, mol% being based on the total moles of diamines in the diamine component (A); and- the dicarboxylic acid component (B) comprises: c) from 70.0 to 95.0 mol% of terephthalic acid; d) from higher than 5.0 mol% to 30.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA), azelaic acid, sebacic acid, dodecanedioic acid, brassylic acid, 1 ,4-cyclohexanedicarboxylic acid (CHDA) and a mixture thereof, mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0025] In the present invention, the barrier layer (Lb) is made of or comprises at least one polyamide (PA) as defined above.

[0026] The permeability (or permeation coefficient (P)) measures susceptibility of a material to be penetrated and crossed by H2. P is obtained by measuring the steady state of transmission using the carrier gas method and a sensor, as defined in the protocol (p2) in the experimental section.

[0027] The sample in a form of a circular film is mounted on a cell so as to form a barrier between two chambers. One chamber contains the test gas (H2) and the other chamber is purged with a sweep gas (synthetic air). The feed side is pressurized with H2 and during the measurement, the concentration of H2 in the sweep gas flow is measured, typically with an electrochemical H2 sensor. Permeation coefficient (P) is calculated according to the equation 1 (Eq. 1 ):P = (C D d / A pP).(T° p / T p°) [Eq. 1 ]P = permeation coefficient (Ncm3mm / m2day bar)C = penetrant concentration (ppm)D = sweep gas flow rate (mL / min) d = sample thickness (mm)A = testing area in contact with the gas (m2) pP= penetrant partial pressure (bar) T = ambient temperature (K) p = ambient pressure (bar)T° = standard temperature (273.15 K) p° = standard pressure (1.013 bar)

[0028] Further normalization is done to standard temperature and pressure, i.e. 273.15 K and 1.013 bar.

[0029] The film can notably be prepared according to protocol (p1 ) in the experimental section. The conditions provided in the experimental section can be followed for the measurement of permeation coefficient (P).

[0030] The barrier layer (Lb) according to the present invention typically exhibits a permeability of 160.0 Ncm3mm / m2bar day or less, preferably 120.0 Ncm3mm / m2bar day or less, more preferably 80.0 Ncm3mm / m2bar day or less, even more preferably 40.0 Ncm3mm / m2bar day or less.

[0031] In one embodiment, the barrier layer (Lb) has a thickness of at least 100 pm, or at least 250 pm. In the other embodiment, the barrier layer (Lb) has a thickness of 10.0 mm or less, or 8.5 mm or less, or 7.5 mm or less.

[0032] In some embodiments, the barrier layer (Lb) has a thickness of from 100 pm to 10.0 mm, or from 250 pm to 10.0 mm, or from 300 pm to 8.5 mm, or from 500 pm to 6.0 mm.

[0033] In a particular embodiment, the barrier layer (Lb) has a thickness of from 100.0 pm to 10.0 mm.

[0034] Polyamide (PA)

[0035] The polyamide (PA) of the invention is formed from the polycondensation of the diamine component (A) and the dicarboxylic acid component (B). The skilled person understands that the proportion of -NH2 from the diamine component (A) and the proportion of -COOH from the dicarboxylic acid component (B) are substantially equimolar. The ratio -NH2 / COOH can be between 0.9 and 1.1 , preferably between 0.95 and 1.05, more preferably between 0.98 and 1.02.

[0036] Diamine component (A)

[0037] The diamine component (A) comprises, consists of or consists essentially of: a first diamine (DA1 ) selected from the group consisting of 2 ,2 ,4-trimethy 1-1 ,6- hexanediamine (2,2,4-TMD), 2,4,4-trimethyl-1 ,6-hexanediamine (2,4,4-TMD) and a mixture thereof; and a second diamine (DA2) selected from the group consisting of 1 ,9-nonanediamine (C9), 1 ,10-decanediamine (C10) and a mixture thereof.

[0038] DA2 is the main or major diamine in the diamine component (A). The proportion of DA2 is 53.0 mol% or more, mol% being based on the total moles of diamines in the diamine component (A). In a particular embodiment, the proportion of DA2 is between 53.0 and 95.0 mol%, mol% being based on the total moles of diamines in the diamine component (A). In a more particular embodiment, this proportion is between 60.0 and 95.0 mol%.

[0039] In one embodiment, the diamine component (A) comprises a first diamine (DA1 ) selected from the group consisting of 2,2,4-TMD, 2,4,4-TMD and a mixture thereof; and a second diamine (DA2) selected from the group consisting of 1 ,9-nonanediamine (C9), 1 ,10-decanediamine (C10) and a mixture thereof. According to this embodiment, the diamine component (A) may additionally comprise 2-methyl-1 ,8-octanediamine (2MeC8) with the proviso that the proportion of 2MeC8 in the diamine component (A) is 10.0 mol% or less, preferably 5.0 mol% or less, mol% being based on the total moles of diamines in the diamine component (A).

[0040] In one embodiment, the diamine component (A) consists essentially of or consists of the first diamine (DA1 ) and the second diamine (DA2).

[0041] In the present invention, the expression "consist essentially" is intended to denote, in relation to the diamine component, that the diamine component (A) consists of DA1 , DA2, and up to 2.0 mol%, preferably up to 1.0 mol%, more preferably up to 0.5 mol% of at least one diamine other than DA1 and DA2, respectively, mol% being based on the total moles of diamines in the diamine component (A).

[0042] DA1 is selected from the group consisting of 2,2,4-TMD, 2,4,4-TMD and a mixture thereof. In one embodiment, DA1 is a mixture of 2,2,4-TMD and 2,4,4- TMD.

[0043] DA2 is selected from the group consisting of 1 ,9-nonanediamine (C9), 1 ,10- decanediamine (C10) and a mixture thereof.

[0044] In a preferred embodiment, the diamine component (A) does not comprise hexamethylene diamine.

[0045] In another preferred embodiment, the diamine component (A) does not comprise a b / s(aminoalkyl)cyclohexane diamine, such as 1 ,3- b / s(aminomethyl)cyclohexane or 1 ,4-b / s(aminomethyl)cyclohexane.

[0046] In the other preferred embodiment, the diamine component (A) does not comprise 2-methyl-1 ,8-octanediamine (2MeC8).

[0047] In a preferred embodiment, DA2 comprises organic carbon of renewable origin, determined according to ASTM D6866-20.

[0048] DA2 is preferably bio-based. In the present invention, the expression "biobased" is intended to denote that a compound is made from substances comprising carbon of renewable origin, derived from living or once-living organisms, excluding materials embedded in geological formations and / or fossilized, for instance petroleum-based.

[0049] In one embodiment, DA2 is 1 ,9-nonanediamine. In a preferred embodiment, the 1 ,9-nonanediamine is bio-based such that the resulting polyamide (PA) exhibits a high bio-based content.

[0050] In another embodiment, DA2 is 1 ,10-decanediamine. In a preferred embodiment, the 1 ,10-decanediamine is bio-based such that the resulting polyamide (PA) exhibits a high bio-based content.

[0051] Molar ratio DA1 / DA2

[0052] In the present invention, the molar ratio DA1 / DA2 of the first diamine (DA1 ) to the second diamine (DA2) is between 12 / 88 and 47 / 53, wherein the proportion of the second diamine (DA2) in the diamine component (A) is at least 53 mol%, mol% being based on the total moles of diamines in the diamine component (A).

[0053] In a particular embodiment, the molar ratio is between 12 / 88 and 37 / 63; or between 12 / 88 and 40 / 60; or between 12 / 88 and 47 / 53; or between 15 / 85 and 37 / 63; or between 15 / 85 and 47 / 53; or between 18 / 82 and 37 / 63; or between 18 / 82 and 47 / 53; or between 25 / 75 and 35 / 65.

[0054] Dicarboxylic acid component (B)

[0055] The dicarboxylic acid component (B) comprises from 70.0 to 95.0 mol% of terephthalic acid and from higher than 5.0 mol% to 30.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA), azelaic acid, sebacic acid, dodecanedioic acid, brassylic acid, 1 ,4-cyclohexanedicarboxylic acid (CHDA) and a mixture thereof, mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0056] In case the other dicarboxylic acid (DI) has more than 8 carbon atoms, the proportion of the other dicarboxylic acid (DI) is preferably lower than 20.0 mol%, more preferably lower than 15.0 mol%, mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0057] In a particular embodiment, the other dicarboxylic acid (DI) is selected from the group consisting of I A, AA, CHDA and combinations of two or more of said dicarboxylic acids.

[0058] In another particular embodiment, the other dicarboxylic acid (DI) is IA, AA or CHDA.

[0059] In a more particular embodiment, the other dicarboxylic acid (DI) is IA.

[0060] The proportion of terephthalic acid in the dicarboxylic acid component (B) may preferably be at least 80.0 mol%, preferably at least 83.0 mol%, more preferably at least 85.0 mol%, even more preferably at least 87.0 mol%, mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0061] In the present invention, the proportion of the other dicarboxylic acid (DI) in the dicarboxylic acid component (B) is higher than 5.0 mol% and 30.0 mol% or less, preferably 20.0 mol% less, more preferably 15.0 mol% less, even more preferably 13.0 mol% or less, mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B). It may be noted that the other dicarboxylic acid (DI) may be a combination of two dicarboxylic acids such that the proportions given herein correspond to the total proportions of dicarboxylic acids (DI).

[0062] In one embodiment, the dicarboxylic acid component (B) consists essentially of or consists of terephthalic acid and the other dicarboxylic acid (DI).

[0063] In the present invention, the expression "consist essentially" is intended to denote, in relation to the dicarboxylic acid component (B), that the dicarboxylic acid component (B) consists of terephthalic acid, the other dicarboxylic acid (DI) and up to 2.0 mol%, preferably up to 1 .0 mol%, more preferably up to 0.5 mol% of at least one dicarboxylic acid other than terephthalic acid and DI, respectively, mol% being based on the total amount of dicarboxylic acids in the dicarboxylic acid component (B).

[0064] The skilled person in the art understands that the polycondensation of the above-defined monomers results in a polyamide (PA) comprising the recurring units (RPAI ) and (RPA2), represented by the following formulae, respectively,O o— H N — R ■ H N — — 2 - -(RPA2) where R1 is a divalent radical of a diamine corresponding to the combination of a first diamine (DA1 ) and a second diamine (DA2), and R2 is a divalent radical of the other dicarboxylic acid (DI). For instance, if the other dicarboxylic acid (DI) is IA, the recurring unit (RPA2) is represented by the following formula:

[0065] In one embodiment, the polyamide (A) comprises from 70.0 to 95.0 mol% of recurring units (RPAI) and from higher than 5.0 mol% to 30.0 mol% of recurring units (RPA2).

[0066] In a particular embodiment, the total proportion of recurring units (RPAI ) and (RPA2) is at least 95.0 mol%, mol% being based on the total moles of recurring units of the polyamide (PA). This proportion may be preferably at least 99.0 mol%, more preferably at least 99.5 mol%.

[0067] The polyamide (PA) preferably does not comprise recurring units derived from a lactam.

[0068] The polyamide (PA) preferably does not comprise recurring units derived from a hexamethylenediamine.

[0069] The polyamide (PA) of the invention preferably does not comprise recurring units derived from hexamethylene diamine, from b / s(aminoalkyl)cyclohexane diamine such as 1 ,3-b / s(aminomethyl)cyclohexane and 1 ,4- b / s(aminomethyl)cyclohexane), or from 2-methyl-1 ,8-octanediamine (2MeC8).

[0070] In a preferred embodiment, the recurring units (RPA) of polyamide (PA) consist essentially of or consist of the recurring units (RPAI ) and (RPA2).

[0071] In one embodiment, the proportion of recurring units (RPAI ) is from 70.0 to 95.0 mol%, mol% being based on the total moles of recurring units of the polyamide (PA). This proportion may be at least 80.0 mol%, preferably at least 83.0 mol%, more preferably at least 85.0 mol%, even more preferably at least 87.0 mol%.

[0072] In another embodiment, the proportion of recurring units (RPA2) is from higher than 5.0 mol% to 30.0 mol%, mol% being based on the total moles of recurring units of the polyamide (PA). This proportion may be 20.0 mol% or less, preferably 17.0 mol% or less, more preferably 15.0 mol% or less, even more preferably 13.0 mol% or less.

[0073] In case the polyamide (PA) is based on the other dicarboxylic acid (DI) having more than 8 carbon atoms, the proportion of (RPA2) is preferably lower than 20.0 mol%, more preferably lower than 15.0 mol%.

[0074] Inherent viscosity (IV)

[0075] In the present invention, the polyamide (PA) advantageously exhibits an inherent viscosity (IV) between 0.50 and 1.70 dL / g, measured according to ASTM D5336-22 by using a mixture of phenol / tetrachloroethane (60 / 40 weight ratio).

[0076] In particular embodiment, the IV is between 0.70 and 1.00 dL / g; or between 0.80 and 1 .00 dL / g; or between 1 .00 and 1 .50 dL / g; or between 1 .05 and 1 .25 dL / g.

[0077] End-groups

[0078] The end-groups in the polyamide (PA) are selected from the group consisting of -NH2, -COOH and amide end-groups.

[0079] The amide end groups are of formula -NH-C(=O)-R, where R is an alkyl group, an aryl group or a cycloalkyl group and / or of formula -C(=O)-NH-R', where R' is an alkyl group or a cycloalkyl group. More particularly, R is a linear or branched C1-C18 alkyl group or a C5-C10 cycloalkyl group, and / or R' is a linear or branched C2-C18 alkyl group.

[0080] The amide end groups of formula -NH-C(=O)-R result from the reaction of the end-group -NH2 with a monocarboxylic acid of formula R-COOHcorresponding to an end-capping agent, wherein where R is a linear or branched C1-C17 alkyl group and combination of two or more of these acids. Advantageously, said monocarboxylic acid is benzoic acid or cyclohexanoic acid.

[0081] In other particular embodiment, the monocarboxylic acid is selected from the group consisting of acetic acid, propanoic acid, butyric acid, valeric acid, caproic acid, lauric acid, stearic acid, 2-ethylhexanoic acid, cyclohexanoic acid, benzoic acid and combination of two or more of these acids.

[0082] In a particular embodiment, the monocarboxylic acid is of formula CH3-(CH2)n- COOH, where n is an integer from 0 to 16. The amide end groups therefrom are of formula -NH-C(=O)-(CH2)n-CH3.

[0083] The amide end groups of formula -C(=O)-NH-R' result from the reaction of the end-group -COOH with a primary amine of formula R'-NH2, corresponding to an end-capping agent.

[0084] The primary amine may advantageously be selected from the group consisting of the amines of formula R'-NH2, where R' is a linear or branched C2-C18 alkyl group.

[0085] In a particular embodiment, the primary amine is of formula CH3-(CH2)n'-NH2, where n' is an integer from 2 to 18. The amide end groups therefrom are of formula -C(=O)-NH-(CH2)n-CH3.

[0086] In a more particular embodiment, the primary amine is selected from the group consisting of propyl amine, butylamine, pentylamine, hexylamine, 2- ethylhexylamine, n-octylamine, n-dodecylamine, n-tetradecylamine, n- hexadecylamine, stearylamine, cyclohexylamine and combination of two or more of these amines.

[0087] The proportion of the end groups can be quantified by1H NMR or by potentiometric techniques.

[0088] Number average molecular weight (Mn)

[0089] The polyamide (PA) of the invention generally has a number average molecular weight ("Mn") ranging from 1 ,000 to 40,000 g / mol, e.g. from 2,000 to 35,000 g / mol, from 4,000 to 30,000 g / mol, or from 5,000 to 20,000 g / mol. Mn can be determined using the equation of Mn = 2,000,000 I [EG], wherein [EG] refers to the concentration of end-groups in the polyamide (PA)(mmol / kg). The end-groups in the polyamide (PA) are generally amine and / or acid moieties. Yet, when the polycondensation involves the addition of an endcapping agent, the amine end-groups are converted, partially or totally, into modified end-group(s). For instance, when the end-capping agent is an acid such as benzoic acid or acetic acid, the remaining amine groups may be totally or partially converted into an amide end groups, such as benzamide or acetamide, and these end-groups can easily be quantified by1H NMR.

[0090] Bio-content

[0091] In the present invention, the polyamide (PA) typically exhibits a bio-content of at least 33.0%, preferably at least 40.0 mol%, more preferably at least 45.0%, even more preferably at least 75%, most preferably at least 79%, the biocontent being expressed as the percentage (%) of organic carbon of renewable origin measured according to ASTM D6866-22.

[0092] The bio-content is defined as the % of organic carbon of renewable origin. It corresponds to the amount of C calculated from14C percent as measured in the sample and corrected for isotopic fraction.

[0093] Both 1 ,9-nonanediamine (2HN-(CH2)9-NH2) (C9) and 1 ,10-decanediamine (2HN-(CH2) -NH2) (C10) diamines can be bio-based or derived from petroleum or natural gas.

[0094] C9 is traditionally derived from petroleum or natural gas. For instance, US4510332B (Kuraray) discloses a process for manufacturing 1 ,9-nonanedial starting from 7-octen-1-al which may be prepared by reacting butadiene with water under particular conditions, wherein 1 ,9-nonanedial can be converted to C9 via reductive amination. In the meantime, the bio-based C9 is generally derived from oleic acid, i.e. a fatty acid that occurs naturally in various resources. Such bio-based oleic acid undergoes oxidative cleavage to produce nonanoic acid and azelaic acid, of which the latter is subject to nitrilation and then hydrogenation to obtain C9.

[0095] C10 can be prepared from sebacic acid, which can be produced from adipic acid by electrooxidation process, where adipic acid is traditionally derived from petroleum or natural gas as it is industrially prepared from 1 ,3-butadiene. Biobased C10 may be prepared from sebacic acid derived from castor oil. In the present invention, the polyamide (PA) is prepared from bio-based 1 ,9-nonanediamine (C9) and / or 1 ,10-decanediamine (C10), which makes it possible to obtain a polyamide (PA) with a high bio-content.

[0096] It is also possible to increase the bio-content by additionally using a bio-based terephthalic acid. The bio-content as defined above may then become at least 75.0%, or even at least 79.0 %. A bio-based terephthalic acid may for instance be prepared from a bio-based furfural.

[0097] In a very particular embodiment, the polyamide (PA) is prepared from biobased C9 and / or C10 exhibiting a bio-content of at least 99.0%, preferably at least 99.5%, preferably at least 99.9%, the bio-content being expressed as the % of organic carbon of renewable origin measured according to ASTM D6866- 22.

[0098] Moisture absorption and resistance to water ageing

[0099] The polyamide (PA) of the invention advantageously exhibits a water uptake at 23°C lower than 5.0 wt%. The water uptake at 23°C is determined by preparing a specimen shaped according to ISO527 in its dry state (having moisture content of less than 0.2 wt%); then immersing the same in deionized water at 23°C, until reaching a constant weight; and calculating the water uptake with formula:Water uptake 100wherein Wbefore is the weight of the shaped specimen in its original dry state and Waiter is the weight of the shaped specimen after water uptake.

[0100] The polyamide (PA) of the invention also advantageously exhibits a water uptake of 5.0% or less at 135°C for 200 hours (“resistance to hot water”). The water uptake at 135°C for 200 hours is determined by preparing three samples shaped in the form of ISO527 type IA tensile bars in their dry state (having moisture content of less than 0.2 wt%); immersing three samples in deionized water at 135°C for 200 hours; determining the water uptake for each sample with formula:Water uptake 100wherein Wbefore is the weight of the sample in its original dry state and Wafier isthe weight of the sample at the end of immersion step; and then calculating the water uptake as the arithmetic average of three samples.

[0101] The polyamide (PA) of the invention advantageously exhibits an IV retention of at least 90.0%, preferably at least 95.0%. The IV retention is determined by providing a sample shaped in the form of a ISO527 type IA tensile bar in its dry state (having moisture content of less than 0.2 wt%); immersing the sample in deionized water at 135°C for 200 hours; and then determining the IV retention of the sample with formula:IV retention = (IVafter / IVbefore) x 100 wherein IVbefore and IVafter refer to the inherent viscosity of the samples before and after the test, respectively.

[0102] Thermal properties of the polyamide (PA)

[0103] The polyamide (PA) of the invention exhibits an advantageous combination of thermal properties.

[0104] In one embodiment, the polyamide (PA) exhibits a melting point (Tm) of at least 240°C, preferably at least 250°C, more preferably at least 260°C, measured by Differential Scanning Calorimetry (“DSC”) according to ASTM D3418.

[0105] In the other embodiment, the polyamide (PA) exhibits a Tm of at most 300°C, preferably at most 290°C, more preferably at most 280°C, measured by DSC according to ASTM D3418.

[0106] In some embodiments, Tm is measured by DSC according to ASTM D3418 using a heating and cooling rate of 20°C / min. Three scans are implemented for each DSC test: a first heat up to 350°C, subsequently followed by a first cool down to 0°C and by a second heat up to 360°C. Tm is determined from the second heat up.

[0107] In the present invention, the polyamide (PA) is semi-crystalline

[0108] In one embodiment, the polyamide (PA) exhibits a heat of fusion (Hm) of at least 30.0 J / g, preferably at least 35.0 J / g, measured by DSC according to ASTM D3418.

[0109] In the other embodiment, the polyamide (PA) exhibits Hm of at most 90.0 J / g, preferably at most 80.0 J / mol, measured by DSC according to ASTM D3418.

[0110] In some embodiments, Hm is measured by DSC according to ASTM D3418, using a heating and cooling rate of 20°C / min. Three scans are implementedfor each DSC test: a first heat up to 350°C, subsequently followed by a first cool down to 0°C and by a second heat up to 360°C.

[0111] In one embodiment, the polyamide (PA) exhibits a glass transition temperature (Tg) of at least 110°C, measured by DSC according to ASTM D3418.

[0112] In a preferred embodiment, the polyamide (PA) exhibits a Tgof at least 115°C, measured by DSC according to ASTM D3418.

[0113] In a particularly preferred embodiment, the polyamide (PA) exhibits a Tgof at least 120°C, measured by DSC according to ASTM D3418.

[0114] In the other embodiment, the polyamide (PA) exhibits a Tgof at most 140°C, measured by DSC according to ASTM D3418.

[0115] In some embodiments, Tgis measured by DSC according to ASTM D3418, using a heating and cooling rate of 20°C / min. Three scans are implemented for each DSC test: a first heat up to 350°C, subsequently followed by a first cool down to 0°C and by a second heat up to 360°C. Tg is determined from the second heat up.

[0116] The polyamide (PA) of the invention may exhibit an optimal combination of such thermal properties.

[0117] In a particular embodiment, the polyamide (PA) exhibits the following combination of properties:- a Tm of from 240°C to 300°C, preferably from 240°C to 290°C;- a Tgof at least 115°C, preferably at least 120°C;- a bio-content of at least 33.0%, preferably at least 40.0 mol%, more preferably at least 45.0%, even more preferably at least 75.0%, most preferably at least 79.0%.

[0118] Process of preparation of polyamides (PA)

[0119] The polyamides (PA) described herein can be prepared by any conventional method adapted to the synthesis of polyamides. The polyamide (PA) is generally produced via the polycondensation in the melt. The polyamide (PA) can be prepared by heating a reaction mixture (RM) comprising or consisting of all the monomers (i.e. DA1 , DA2, terephthalic acid and DI), preferably in the presence of less than 60 wt% of water, preferably less than 30 wt%, more preferably less than 20 wt%, even more preferably less than 10 wt%, mostpreferably without water. The proportion of water is provided based on the total weight of the reaction mixture (RM).

[0120] The reaction mixture (RM) generally comprises the above-referenced diamines and dicarboxylic acids in a quantity such that the proportion of - COOH groups from the dicarboxylic acids and the proportion of -NH2 groups from the diamines are substantially equimolar.

[0121] In some embodiments, the reaction mixture (RM) comprises a catalyst. The catalyst may be selected from the group consisting of phosphorous acid, orf / io-phosphoric acid, mefa-phosphoric acid, alkali-metal hypophosphite such as sodium hypophosphite and phenylphosphinic acid, frequently phosphorous acid.

[0122] To control the molar mass, the reaction mixture (RM) may also further comprise at least one end-capping agent as disclosed above.

[0123] The temperature at which the reaction mixture (RM) is heated must be high enough to induce the reaction between the amine groups of the diamine component (A) and the carboxylic groups of the dicarboxylic acid component (B) and to decrease the viscosity of the mixture. This temperature is generally at least 150°C, preferably at least 200°C, and can be increased during the polycondensation in a step-wise manner. The polycondensation results in the formation of the amide bonds, while releasing water as a by-product.

[0124] In the present invention, the polyamide (PA) may further comprise at least one inorganic filler and / or at least one plastic additive to produce a polymer composition (PC), wherein the plastic additive is different from the inorganic filler.

[0125] In one embodiment, the polymer composition (PC) comprises at least 50.0 wt% of at least one polyamide (PA) and at most 20.0 wt% of at least one inorganic filler and / or at least one plastic additive, wt% being based one the total weight of the polymer composition (PC).

[0126] The inorganic filler is typically selected in the group consisting of talc, clay, mica, kaolin, calcium carbonate, calcium silicate, magnesium carbonate, glass fibers, carbon fibers and combinations thereof.

[0127] The inorganic filler may more particularly be a clay. The clay may be selected in the group consisting of montmorillonite, hectorite, saponite, vermiculite and combination of two or more of said clays.

[0128] The plastic additive other than inorganic filler is typically selected in the group consisting of tougheners, plasticizers, colorants, pigments, antistatic agents, dyes, lubricants, thermal stabilizers, light stabilizers, flame retardants, nucleating agents, antioxidants, UV absorbers, acid scavengers and combinations thereof.

[0129] The polymer composition (PC) may further comprise at least one aliphatic polyamide. The proportion of the aliphatic polyamide in the polymer composition (PC) is typically at least 10.0 wt%, the wt% being based on the total weight of the polymer composition (PC).

[0130] The total proportion of the inorganic filler(s) and the plastic additive(s) in the polymer composition (PC) may be at most 25.0 wt%, at most 20.0 wt%, or at most 15.0 wt%, or at most 10.0 wt%, relative to the total weight of polymer composition (PC). When present, the total proportion of the inorganic filler(s) and / or the plastic additive(s) is at least 0.1 wt%, even at least 0.5 wt%, relative to the total weight of polymer composition (PC).

[0131] The proportion of the polyamide (PA) in the polymer composition (PC) is preferably at least 95.0 wt%, preferably at least 97.0 wt%, preferably at least 99.0 wt%, wt% being based on the total weight of the polymer composition (PC).

[0132] In one embodiment, the present invention relates to a multilayer structure intended to store and / or transport hydrogen gas (H2), comprising- at least one barrier layer (Lb) as defined in the present invention; and- at least one structural layer (Ls).

[0133] In a particular embodiment, the multilayer structure is a vessel or a pipe.

[0134] In the present invention, the expression “vessel” is intended to denote a hollow container, in particular a hollow container for containing a gas, preferably a pressurized gas.

[0135] The vessel typically has a cylindrical shape, while its dimension, such as length, internal volume, shape, etc. are defined depending on its end use.

[0136] Advantageously, the barrier layer (Lb) or one of the barrier layers (Lb) is in contact with or is intended to be in contact with the contained gas. (H2).

[0137] In one embodiment, the multilayer structure comprises a film having only one barrier layer (Lb). The multilayer structure may comprise a film having another barrier layer (Lb ) made of or comprising a polymer different from a polyamide (PA) as defined in the present invention.

[0138] The function of the structural layer (Ls) is to provide the structural rigidity and integrity to the multilayer structure and to protect the film comprising the barrier layer (Lb).

[0139] In one embodiment, the structural layer (Ls) comprises a polymer matrix and fibers, i.e. a composite.

[0140] In a particular embodiment, the fibers are selected from the group consisting of glass fibers, carbon fibers, aramid fibers, stainless steel fibers, potassium titanate whiskers, and combination of two or more said fibers.

[0141] In a preferred embodiment, the fibers are continuous fibers.

[0142] In the other embodiment, the structural layer (Ls) is selected from the group consisting of metallic layers.

[0143] The multilayer structure may comprise two or more reinforcing layers. For instance, the multilayer structure may comprise from the inside to the outside of the structure: a film comprising at least one barrier layer (Lb) as disclosed herein; at least one structural layer (Lsi) made of a polymer matrix and fibers; and at least one metallic structural layer (LS2).

[0144] In one embodiment, the multilayer structure is a vessel having a inner volume from 5.0 to 500.0 liters.

[0145] In the other embodiment, the multilayer structure is a vessel having an operating temperature range from -70.0 to 150.0°C.

[0146] Use of Polyamide (PA)

[0147] The present invention also relates to use of the polyamide (PA) as disclosed herein in manufacturing a barrier layer (Lb) in a vessel or a pipe intended to store and / or transport H2, wherein H2 is in contact with the barrier layer (Lb).

[0148] In one embodiment, the vessel disclosed herein is comprised in a vehicle.

[0149] In a particular embodiment, the vehicle is a car, a truck, a train, a ship, an urban mobility vehicle, an airplane, a helicopter or any other vehicle that could be powered by converting a gas into energy by any means.

[0150] Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0151] The invention will be now explained in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention.EXPERIMENTAL SECTION

[0152] Raw Materials1 .9-diaminononane (C9): synthesized within Solvay (derived from bio-based oleic acid);1 .10-diaminodecane (C10): commercially available from Hangzhou;- terephthalic acid (TA), isophthalic acid (IA) & phosphorous acid: commercially available from Sigma Aldrich;- 2,2,4-trimethyl-1 ,6-hexanediamine (2,2,4-TMD) and 2,4,4-trimethyl-1 ,6- hexanediamine (2,4,4-TMD): commercially available from Evonik Industries; sebacic acid (SA): commercially available from Sigma-Aldrich, octadecanedioic acid (C18): commercially available from Wilmar Oleo North America LLC, adipic acid (AA): commercially available from Invista.

[0153] Synthesis of the polyamides

[0154] All of the (co)polyamides disclosed in Table I were prepared according to a similar process in an autoclave reactor equipped with a distillate line fitted with a pressure control valve.

[0155] Example 1 (E1)

[0156] The polyamide (E1 ) was prepared by charging into the reactor 4.23 g of C9, 1.81 g of a mixture of 2,2,4-TMD and 2,4,4-TMD (“TMD”), 5.38 g of terephthalic acid, 0.60 g of isophthalic acid, 5.92 g of deionized water, and 0.004 g of phosphorous acid. The reactor was then sealed and purged withN2 gas. The reactor was heated to 175°C and held for 25 min, followed by heating to 235°C and holding for 30 min, followed by heating to 288°C and holding for 25 min, followed by heating to 315°C and holding for 50 min in an order. The steam generated was slowly released to keep the internal pressure under 200 psig. Once the temperature was at 315°C for 15 min, the reactor pressure was slowly reduced to atmospheric pressure within 45 min, while maintaining the temperature at 315°C. After holding for an additional 20 min with N2 gas purging, the reactor was cooled to room temperature and the polymer was retrieved from the reactor.

[0157] E2-E7 and CE1 -CE11 were prepared similar to the procedure detailed above for E1.

[0158] Thermal Performance

[0159] Tg, Tm and Hmwere measured by DSC according to ASTM D3418 using a heating and cooling rate of 20°C / min. Three scans were used for each DSC test: a first heat up to 350°C, followed by a first cool down to 30°C, and by a second heat up to 360°C. Tg, Tm and Hm were determined from the second heat up and were indicated in Table I.

[0160] Bio-content

[0161] The bio-content was measured according to ASTM D6866-22 and indicated in Table I.

[0162] Permeability

[0163] The polyamides were processed by injection molding using a Fanuc S 2000 i injection molding machine to produce samples. The temperature profile of the barrel was from 295 to 300°C and the hopper was set at 60°C. The mold temperature was set at 100°C. Screw speed for dosing was 150 rpm and injection speed was 20 mm / s. Dosing time was approximately 5.5 seconds, injection time 3 seconds and cooling time 40 seconds. Backpressure was 55 bars, commute pressure 829 bars and maintain pressure 600 bars during 12 seconds.

[0164] The samples in the form of a square sheet were mounted on a cell to form a barrier between two chambers. One chamber contained the test gas (H2) and the other chamber was purged with a sweep gas (synthetic air). The feed side was pressurized with H2 and during the measurement, the concentration of H2in the sweep gas flow was measured, typically with an electrochemical H2 sensor.

[0165] The samples were then annealed for 2 hours at 160°C in dry air; were mounted in a sealed chamber; and a check was made to ensure that the chamber is leak tight by applying hydrogen at 1.0 MPa on the feed side. Subsequently, the chamber was conditioned at the temperature of testing (23°C). On the feed side, H2 was fed at 1 .0 MPa. On the permeate side, synthetic air was fed at a controlled throughput and H2 was measured using a calibrated leak detector (e.g. Sentrac® from Inficon), until a stable value for H2 was obtained to assure a stationary regime.

[0166] The permeation coefficient (P) is calculated according to equation (Eq. 1 ) as defined above in the specification.

[0167] As demonstrated by the data indicated in Table I & Table II below, the polyamide (PA) according to the present invention exhibits an advantageous combination of Tg, Tmand Hm, while ensuring a substantial portion of biocontent.

[0168] This optimal combination of properties ensure that the polyamide (PA) can be processed into a barrier layer having high barrier against H2, i.e. low permeability to H2, comprised in a film, that was demonstrated by the permeability (permeation coefficient (P)) in Table II (E6).

[0169] Additionally, in comparison to the comparative ones, the polyamides (PA) of the present invention exhibited excellent mechanical properties in terms of chord modulus, ultimate tensile strength and elongation at break (E4 vs. CE8), measured according to ISO527. The ultimate tensile strength refers to the maximum stress that a material can withstand while being stretched or pulled before breaking, and the elongation at break refers to the ratio of the initial and final lengths of a material before it breaks.

[0170] The polyamide (PA) of the present invention also exhibited good IV retention after water ageing, measured according to the protocol defined in the specification.Table I* proportions of the monomers: in mol% based on the total moles of diamines in the diamine component (A) and to the total moles of dicarboxylic acids in the dicarboxylic acid component (B)** TA: terephthalic acid; IA: isophthalic acid; AA: adipic acid; CHDA: 1 ,4-cyclohexanedicarboxylic acid; SA: sebacic acid; C18: octadecanedioic acid*** amorphousTable II* measured according to ISO527** measured according to protocol defined in the specification (see § "Moisture absorption and resistance to water ageing")*** measured according to protocol (p2) as above defined

Claims

CLAIMS1. A multilayer structure intended to store and / or transport hydrogen gas (H2), wherein the multilayer structure comprises at least one barrier layer (Lb) made of or comprising at least one polyamide (PA) which comprises recurring units (RPA) formed from the polycondensation of a diamine component (A) and a dicarboxylic acid component (B) wherein:- the diamine component (A) comprises: a) a first diamine (DA1 ) selected from the group consisting of 2,2,4- trimethyl-1 ,6-hexanediamine (2,2,4-TMD), 2,4,4-trimethyl-1 ,6- hexanediamine (2,4,4-TMD) and a mixture thereof; and b) a second diamine (DA2) selected from the group consisting of 1 ,9- nonanediamine (C9), 1 ,10-decanediamine (C10) and a mixture thereof; wherein the molar ratio DA1 / DA2 of the first diamine (DA1 ) to the second diamine (DA2) is between 12 / 88 and 47 / 53, wherein the proportion of the second diamine (DA2) in the diamine component (A) is at least 53 mol%, mol% being based on the total moles of diamines in the diamine component (A); and- the dicarboxylic acid component (B) comprises: c) from 70.0 to 95.0 mol% of terephthalic acid; and d) from higher than 5.0 to 30.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA), azelaic acid, sebacic acid, dodecanedioic acid, brassylic acid, 1 ,4- cyclohexanedicarboxylic acid (CHDA) and a mixture thereof, mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

2. The multilayer structure according to claim 1 , wherein the polyamide (A) comprises from 70.0 to 95.0 mol% of recurring units (RPAI ) and from higher than 5.0 to 30.0 mol% of recurring units (RPA2) represented by the following formulae, respectively,wherein Ri a divalent radical of a diamine corresponding to the combination of a first diamine (DA1 ) and a second diamine (DA2), and R2 a divalent radical of a dicarboxylic acid selected from the group consisting of isophthalic acid (IA), adipic acid (AA), azelaic acid, sebacic acid, dodecanedioic acid, brassylic acid, 1 ,4-cyclohexanedicarboxylic acid (CHDA) and a mixture thereof3. The multilayer structure according to claim 1 or 2, wherein the total proportion of recurring units (RPAI ) and (RPA2) is at least 95.0 mol%, preferably at least 99.0 mol%, more preferably at least 99.5 mol%, based on the total moles of the polyamide (PA).

4. The multilayer structure according to any one of the preceding claims, wherein the proportion of terephthalic acid in the dicarboxylic acid component (B) or the proportion of recurring units (RPAI ) in the polyamide (PA) is at least 80.0 mol%, preferably at least 85.0 mol%, more preferably 87.0 mol%, based on the total moles of the dicarboxylic acid component (B) or the polyamide (PA).

5. The multilayer structure according to any one of the preceding claims, wherein the proportion of the other dicarboxylic acid (DI) in the dicarboxylic acid component (B) or the proportion of recurring units (RPA2) in the polyamide (PA) is at most 20.0 mol%, preferably at most 15.0 mol%, more preferably 13.0 mol%, based on the total moles of the dicarboxylic acid component (B) or the polyamide (PA).

6. The multilayer structure according to any one of the preceding claims, wherein the polyamide (PA) exhibits a bio-content of at least 33.0%, preferably at least 40.0%, more preferably at least 45.0%, even more preferably at least 75.0%, most preferably at least 79.0%, the bio-content being expressed inpercentage (%) of organic carbon of renewable origin measured according to ASTM D6866-22.

7. The multilayer structure according to any one of the preceding claims, wherein the polyamide (PA) exhibits a melting point (Tm) of at least 240°C, preferably at least 250°C, more preferably at least 260°C, and / or at most 300°C, preferably at most 290°C, more preferably at most 280°C, Tm being measured by Differential Scanning Calorimetry (“DSC”) according to ASTM D3418, notably using a heating and cooling rate of 20°C / min.

8. The multilayer structure according to any one of the preceding claims, wherein the polyamide (PA) exhibits a glass transition temperature (Tg) of at least 110°C, preferably at least 115°C, more preferably at least 120°C, Tgbeing measured by DSC according to ASTM D3418, using a heating and cooling rate of 20°C / min.

9. The multilayer structure according to any one of preceding claims, wherein the barrier layer (Lb) exhibits a permeability of 160 Ncm3mm / m2bar day or less, preferably 120.0 Ncm3mm / m2bar day or less, more preferably 80.0 Ncm3mm / m2bar day or less, even more preferably 40.0 Ncm3mm / m2bar day or less, measured according to the protocol (p2) defined in the experimental section.

10. The multilayer structure according to any one of the preceding claims, wherein barrier layer (Lb) has a thickness of from 100.0 pm to 10.0 mm.11 . The multilayer structure according to any one of the preceding claims, further comprising at least one structural layer (Ls).

12. The multilayer structure according to any one of the preceding claims, which is a vessel or a pipe.

13. The multilayer structure according to any one of the preceding claims, wherein the barrier layer (Lb) is in contact with H2.

14. The multilayer structure according to any one of the preceding claims, wherein the structural layer (Ls) comprises a polymer matrix and fibers, preferably continuous fibers.

15. The multilayer structure according to claim 14, wherein the fibers are selected from the group consisting of glass fibers, carbon fibers, aramid fibers, stainless steel fibers, potassium titanate whiskers, and combination of two or more of said fibers.

16. Use of the polyamide (PA) as defined in any one of claims 1 to 8 in manufacturing a barrier layer (Lb) in a vessel or a pipe intended to store and / or transport H2, wherein H2 is in contact with the barrier layer (Lb).

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