Multilayer structure comprising semi-aromatic 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) exhibiting high glass transition temperature and excellent thermomechanical properties as disclosed herein; and 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).

Description

MULTILAYER STRUCTURE COMPRISING SEMI-AROMATIC POLYAMIDE AND ITS USE FOR HYDROGEN STORAGE AND TRANSPORTATIONTECHNICAL FIELD

[0001] 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) exhibiting a high glass transition temperature (Tg) and excellent thermomechanical properties as disclosed herein; and 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).TECHNICAL BACKGROUND

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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 therefore that high temperature peaks can be encountered during rapid filling and / or depressurizing of the tanks. Good mechanical properties such as elongation at break are to be considered in selecting such a material, because such properties are also important to cope with temperature changes, notably low temperature which may occur in depressurizing tanks.

[0006] The material hence should satisfy various properties such as thermal stability / resistance, high barrier against H2, in other words low permeability toH2, easy processability, strong mechanical properties, as well as wide operating temperature range where the material may be used.

[0007] 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.

[0008] 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, among which at least 50 mol% are derived from xylene diamine as disclosed in WO201 6 / 084175A1 (Mitsubishi Electric Corp.).

[0009] 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. There is no disclosure of the polyamide of the present invention.

[0010] WO2023 / 083783A1 (Arkema) discloses a multilayer structure for storing or transporting compressed gas, preferably at high pressure, 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 temperature (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 Tgof 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.

[0011] 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 water absorption values of up to 10% when stored in water. Use of such an aliphatic polyamide hence becomes problematic in applications that require strictaspects on dimensional stability. Water absorption brings about the changes not only in its dimension but also in 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 during the shelf-life.

[0012] Accordingly, semi-aromatic polyamides have been developed to address these problems. For instance, 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 exhibits 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 the presence of water due to a high moisture absorption around 7.5 wt%, as disclosed in US2012 / 0095161 A1 (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.

[0013] US 2023 / 151255 (Arkema SA) discloses the use of a sealing layer of a composition including 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 thehydrogen being less than or equal to 3 percent by weight, in particular less than 2 percent by weight of the sum of the constituents of the composition.

[0014] US 2017 / 02620 (Toray Ind. Inc.) discloses a polyamide resin composition for a molded article exposed to high-pressure hydrogen, which contains a polyamide 6 resin (A) and a polyamide resin (B) having a melting point, as determined by DSC, that is not higher than a melting point of the polyamide 6 resin (A) +20 °C and a cooling crystallization temperature, as determined by DSC, that is higher than a cooling crystallization temperature of the polyamide 6 resin (A), the polyamide resin (B) present in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the polyamide 6 resin (A).

[0015] WO 2023 / 048073 (KURARAY Co. Ltd.) discloses a multilayer structure for storing or transporting a gas comprising hydrogen, wherein the multilayer structure comprises at least three layers comprising an inner layer comprising at least one first polymer, a middle layer comprising ethylene-vinyl alcohol copolymer, and an outer layer comprising at least one second polymer, and wherein the water-vapor transmission rate of the inner layer is lower than that of the outer layer.

[0016] US 2017 / 335999 (Toray Ind. Inc.) discloses a polyamide resin composition for a molded article exposed to high-pressure hydrogen that contains a polyamide resin (A) including a unit derived from hexamethylenediamine and a unit derived from an aliphatic dicarboxylic acid of 8 to 12 carbon atoms and an ethylene / a-olefin copolymer (B) modified with an unsaturated carboxylic acid and / or a derivative thereof.

[0017] EP 3725848 (UBE Corp.) discloses a polyamide resin composition that contains 40-85 parts by mass of a polyamide (A) and 10-20 parts by mass of an impact-resistant material (B) in 100 parts by mass of the polyamide resin composition, which is characterized by a certain parameter relating to the absolute value of the stress change rate obtained via a stress relaxation measurement method.

[0018] The present invention aims to provide 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) that exhibits a high Tgas well as excellent barrier properties against H2. In a preferred embodiment, the Tgof the polyamide (PA) is at least140°C, preferably at least 145°C, and / or at most 200°C, preferably at most 180°C that is significantly higher than Tgof aliphatic polyamides such as PA6 and PA66, corresponding to from about 50°C to about 60°C. The barrier properties against H2 of the polyamide (PA) 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, tensile elongation at break and notched Izod, measured according to ISO527, respectively.

[0019] 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

[0020] 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.

[0021] 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

[0022] 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.

[0023] 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 by weight’ (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.

[0024] 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.

[0025] 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 parentheses can also be omitted.

[0026] A "hydrogen barrier layer" is a layer which prevents or impedes the transport / migration of hydrogen gas (H2) through itself.

[0027] 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: a) the diamine component (A) comprises:- from 38.0 to 54.0 mol% of 1 ,6-diaminohexane;- from 15.0 to 40.0 mol% of a diamine (DA1 ) selected from the group consisting of 1 ,9-diaminononane (C9), 1 ,10-diaminodecane (C10) and mixtures thereof; and- from 15.0 to 40.0 mol% of a diamine (DA2) selected from the group consisting of 1 ,3-b / s(aminomethyl)cyclohexane (1 ,3-BAC), 1 ,4- b / s(aminomethyl)cyclohexane (1 ,4-BAC) and mixtures thereof; the mol% being based on the total moles of diamines in the diamine component (A); and b) the dicarboxylic acid component (B) comprises:- from 95.0 to 100.0 mol% of terephthalic acid; and- from 0 to 5.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA) and mixtures thereof,the mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0028] In the present invention, the barrier layer (Lb) is made of or comprises at least one polyamide (PA) as defined above.

[0029] In one embodiment, the barrier layer (Lb) is in the form of a film.

[0030] In the other embodiment, the barrier layer (Lb) is in the form of a liner.

[0031] 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 in the experimental section.

[0032] The sample in the 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)

[0033] Further normalization is done to standard temperature and pressure, i.e. 273.15 K and 1.013 bar.

[0034] In one embodiment, the barrier layer (Lb) in the form of a film has a thickness of at least 50 pm, or at least 250 pm, or at least 300 pm, or at least 500 pm. In the other embodiment, the barrier layer (Lb) in the form of a film has a thickness of 1 .0 mm or less.

[0035] In a particular embodiment, the barrier layer (Lb) in the form of a film has a thickness of from 100 pm to 1.0 mm.

[0036] In one embodiment, the barrier layer (Lb) in the form of a liner has a thickness of at least 1.0 mm, or at least 2.0 mm. In the other embodiment, the barrier layer (Lb) in the form of a liner has a thickness of 20.0 mm or less, or 15.0 mm or less, or 10.0 mm or less, or 5.0 mm or less.

[0037] In some embodiments, the barrier layer (Lb) in the form of a liner has a thickness of from 1.0 mm to 10 mm, or from 1.0 mm to 5.0 mm, or from 1.0 mm to 3.0 mm.

[0038] In a particular embodiment, the barrier layer (Lb) in the form of a liner has a thickness of from 1 .0 mm to 5.0 mm.

[0039] The film can notably be prepared according to the protocol defined in the experimental section. The conditions provided in the experimental section can be followed for the measurement of permeation coefficient (P).

[0040] The liner can also be processed by various techniques, for instance, injection molding, injection overmolding, extrusion / welding, extrusion blow molding, rotomolding, etc.

[0041] In the present invention, the barrier layer (Lb) in the form of a film typically exhibits a permeability of 150.0 Ncm3mm / m2bar day or less, preferably 120.0 Ncm3mm / m2bar day or less, more preferably 100.0 Ncm3mm / m2bar day or less, even more preferably 90.0 Ncm3mm / m2bar day or less.

[0042] In the present invention, the barrier layer (Lb) in the form of a liner typically exhibits a permeability of 120.0 Ncm3mm / m2bar day or less, preferably 100.0 Ncm3mm / m2bar day or less, more preferably 90.0Ncm3mm / m2bar day or less, even more preferably 80.0Ncm3mm / m2bar day or less.

[0043] Polyamide (PA)

[0044] The polyamide (PA) of the invention is formed from the polycondensation of the diamine component (A) and the dicarboxylic acid component (B). The polyamide (PA) disclosed in the present invention thus comprises in reacted from the diamines of the diamine component (A) and the dicarboxylic acids of the dicarboxylic acid component (B) with the proportions indicated herein.

[0045] 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.

[0046] Diamine component (A)

[0047] The diamine component (A) is based on the following diamines: 1 ,6- diaminohexane (NH2-(CH2)e-NH2); a diamine (DA1 ) selected from the group consisting of 1 ,9-diaminononane (NH2-(CH2)9-NH2), 1 ,10-diaminononane (NH2-(CH2)IO-NH2) and a combination of said two amines; and a b / s(aminomethyl)cyclohexane (DA2).

[0048] The diamine component (A) comprises, consists of, or consists essentially of:- from 38.0 to 54.0 mol% of 1 ,6-diaminohexane;- from 15.0 to 40.0 mol% of a diamine (DA1 ) selected from the group consisting of 1 ,9-diaminononane (C9), 1 ,10-diaminodecane (C10) and mixtures thereof; and- from 15.0 to 40.0 mol% of a diamine (DA2) selected from the group consisting of 1 ,3-b / s(aminomethyl)cyclohexane (1 ,3-BAC), 1 ,4- b / s(aminomethyl)cyclohexane (1 ,4-BAC) and mixtures thereof, the mol% being based on the total moles of diamines in the diamine component (A).

[0049] The proportion of 1 ,6-diaminohexane may be particularly from 38.0 to 52.0 mol%, more particularly from 38.0 to 47.0 mol%. This proportion may also be from 38.0 to 42.0 mol%, or from 43.0 to 47.0 mol%, or from 48.0 to 52.0 mol%.

[0050] In a particular embodiment, the diamine (DA1 ) is 1 ,9-diaminononane (C9).

[0051] In the other particular embodiment, the diamine (DA1 ) is 1 ,10-diaminodecane (C10).

[0052] The proportion of DA1 may be particularly from 18.0 to 40.0 mol%. This proportion may be more particularly from 18.0 to 22.0 mol%, or from 23.0 to 27.0 mol%, or from 28.0 to 32.0 mol%, or from 33.0 to 37.0 mol%.

[0053] The diamine component (A) also comprises a diamine (DA2), selected from the group consisting of 1 ,3-b / s(aminomethyl)cyclohexane (1 ,3-BAC), 1 ,4- b / s(aminomethyl)cyclohexane (1 ,4-BAC) and mixtures thereof.

[0054] In a particular embodiment, the diamine (DA2) is 1 ,3-BAC.

[0055] In the other particular embodiment, the diamine (DA2) is 1 ,4-BAC.

[0056] The proportion of DA2 may be particularly from 18.0 to 40 mol%. This proportion may be more particularly from 18.0 to 22.0 mol%, or from 23.0 to 27.0 mol%, or from 28.0 to 32.0 mol%, or from 33.0 to 37.0 mol%.

[0057] In a particular embodiment, the proportions in the diamine component (A) are:- from 42.0 to 47.0 mol% of 1 ,6-diaminohexane;- from 33.0 to 37.0 mol% of a diamine (DA1 ); and- from 18.0 to 22.0 mol% of a diamine (DA2), the mol% being based on the total moles of diamines in the diamine component (A).

[0058] In another particular embodiment, the proportions in the diamine component (A) are:- from 48.0 to 52.0 mol% of 1 ,6-diaminohexane;- from 18.0 to 22.0 mol% of a diamine (DA1 ); and- from 28.0 to 32.0 mol% of a diamine (DA2), the mol% being based on the total moles of diamines in the diamine component (A).

[0059] In another particular embodiment, the proportions in the diamine component (A) are:- from 38.0 to 42.0 mol% of 1 ,6-diaminohexane;- from 23.0 to 27.0 mol% of a diamine (DA1 ); and- from 33.0 to 37.0 mol% of a diamine (DA2), the mol% being based on the total moles of diamines in the diamine component (A).

[0060] In another particular embodiment, the proportions in the diamine component (A) are:- from 48.0 to 52.0 mol% of 1 ,6-diaminohexane;- from 28.0 to 32.0 mol% of a diamine (DA1 ); and- from 18.0 to 22.0 mol% of a diamine (DA2), the mol% being based on the total moles of diamines in the diamine component (A).

[0061] In another particular embodiment, the proportions in the diamine component (A) are:- from 48.0 to 52.0 mol% of 1 ,6-diaminohexane;- from 18.0 to 22.0 mol% of a diamine (DA1 ); and- from 28.0 to 32.0 mol% of a diamine (DA2), the mol% being based on the total moles of diamines in the diamine component (A).

[0062] In another particular embodiment, the proportions in the diamine component(A) are:- from 43.0 to 47.0 mol% of 1 ,6-diaminohexane;- from 33.0 to 37.0 mol% of a diamine (DA1 ); and- from 18.0 to 22.0 mol% of a diamine (DA2), the mol% being based on the total moles of diamines in the diamine component (A).

[0063] In the present invention, the term “consist essentially” is intended to denote, in relation to the diamine component (A), that the diamine component (A) comprises the indicated diamines and may also comprise up to 2.0 mol%, preferably up to 1.0 mol%, more preferably up to 0.5 mol% of at least one additional diamine other than the indicated ones, the mol% being based on the total moles of diamines in the diamine component (A).

[0064] In a particular embodiment, the diamine component (A) consists of 1 ,6- diaminohexane; a diamine (DA1 ) selected from the group consisting of 1 ,9- diaminononane (C9), 1 ,10-diaminodecane (C10) and mixtures thereof; a diamine (DA2) selected from the group consisting of 1 ,3-BAC, 1 ,4-BAC and mixtures thereof; and up to 2.0 mol%, preferably up to 1.0 mol%, more preferably up to 0.5 mol% of at least one additional diamine other than 1 ,6- diaminohexane, DA1 and DA2, the mol% being based on the total moles of diamines in the diamine component (A).

[0065] Dicarboxylic acid component (B)

[0066] In the present invention, the dicarboxylic acid component (B) comprises terephthalic acid as the major component. The dicarboxylic acid component(B) may also comprise another diacid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA) and mixtures thereof.

[0067] The dicarboxylic acid component (B) comprises, consists of, or consists essentially of:- from 95.0 to 100.0 mol% of terephthalic acid; and- from 0 to 5.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of IA, AA and mixtures thereof, the mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0068] In one embodiment, the dicarboxylic acid component (B) comprises:- from 98.0 to 100.0 mol% of terephthalic acid; and- from 0 to 2.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of IA, AA and mixtures thereof, the mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0069] In a particular embodiment, the dicarboxylic acid component (B) comprises from 95.0 to 99.9 mol% of terephthalic acid and from 0.1 to 5.0 mol% of the other dicarboxylic acid (DI).

[0070] In another particular embodiment, the dicarboxylic acid component (B) comprises from 98.0 to 99.9 mol% of terephthalic acid and from 0.1 to 2.0 mol% of the other dicarboxylic acid (DI).

[0071] In a more particular embodiment, the other dicarboxylic acid (DI) is isophthalic acid (IA).

[0072] In another more particular embodiment, the other dicarboxylic acid (DI) is adipic acid (AA).

[0073] In the present invention, the term “consist essentially of” is intended to denote, in relation to the dicarboxylic acid component (B), that the dicarboxylic acid component (B) comprises the indicated dicarboxylic acids and may also comprise up to 2.0 mol%, preferably up to 1.0 mol%, more preferably up to 0.5 mol% of at least one additional dicarboxylic acid other than terephthalic acid and DI, the mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

[0074] Preferably, the polyamide (PA) of the present invention does not comprise recurring units derived from an aminoacid and / or a lactam.

[0075] In one embodiment, the diamine component (A) does not comprise isophoronediamine.

[0076] In one embodiment, the polyamide (PA) comprises the recurring units (RPAI), (RPA2), (RPA3-I ) and / or (RPA3-2):(RPA3-2). where Ri is hexamethylene -(CH2)e- and R2 is a divalent radical of a diamine selected from the group consisting of 1 ,9-diaminononane (C9), 1 ,10- diaminodecane (C10) and mixtures thereof.

[0077] RPAI corresponds to the recurring unit obtained from the reaction of 1 ,6- diaminohexane and terephthalic acid, and RPA2 corresponds to the recurring unit obtained from the reaction of C9 and / or C10 with terephthalic acid.Likewise, RPA3-I corresponds to the recurring unit obtained from the reaction of 1 ,3-BAC with terephthalic acid, and RPA3-2 corresponds to the recurring unit obtained from the reaction of 1 ,4-BAC with terephthalic acid.

[0078] All the proportions and embodiments provided herein for the proportions of the diamines of 1 ,6-diaminohexane, DA1 and DA2 in the diamine component (A) can be translated into the proportions of (RPAI ), (RPA2), (RPA3-I ), and (RPA3-2), respectively.

[0079] In one embodiment, the total proportion of recurring units (RPAI ), (RPA2), (RPAS- 1) and (RPA3-2) in the polyamide (PA) is at least 95.0 mol%, particularly at least 99.0 mol%.

[0080] In another embodiment, the recurring units of the polyamide (PA) consist essentially of or consist of the recurring units (RPAI ), (RPA2), (RPA3-I ) and / or (RPA3-2). In the present invention, the term “consist essentially of” is intended to denote, in relation to the recurring units of the polyamide (PA), that the recurring units comprise the indicated recurring units and may also comprise up to 2.0 mol%, preferably up to 1.5 mol%, more preferably up to 1.0 mol%, even more preferably up to 0.5 mol% of at least one additional recurring unit other than the recurring units (RPAI), (RPA2), (RPA3-I) and (RPA3-2).

[0081] End-groups

[0082] 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 fully, 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 partially or fully converted into benzamide or acetamide end-groups.

[0083] The end-groups in the polyamide (PA) are selected from the group consisting of - NH2, -COOH and amide end-groups. Indeed, the end-groups in the polyamide (PA) may be -NH2 or -COOH. Yet, when the polycondensation involves the addition of an end-capping agent, these end-groups may be converted, partially or fully, into amide end-groups.

[0084] 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. R is more particularly a linear or branched C1-C17 alkyl group or a C5-C10 cycloalkyl group. R' is more particularly a linear or branched C2-C18 alkyl group.

[0085] The amide end-groups of formula -NH-C(=O)-R result from the reaction of the end-groups -NH2 with a monocarboxylic acid (as an end-capping agent) of formula R-COOH.

[0086] The monocarboxylic acid may advantageously be selected from the group consisting of benzoic acid; cyclohexanoic acid; R”-COOH (R” is a linear or branched C1-C17 alkyl group), and combinations thereof.

[0087] In a 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 combinations thereof.

[0088] In another particular embodiment, the monocarboxylic acid is of formula CH3- (CH2)n-COOH, where n is an integer between 0 and 16. The amide end group to be formed with said monocarboxylic acid is then of formula -NH-C(=O)- (CH2)n-CH3.

[0089] In case a primary amine of formula R'”-NH2(where R'” is a linear or branched C2-Ci8 alkyl group) is used as an end-capping agent, the amide end group to be formed with said primary amine is then of formula -C(=O)-NH-R'”.

[0090] The primary amine may advantageously be of formula CH3-(CH2)n'-NH2where n' is an integer between 2 and 18. The amide end group to be formed with said primary amine is then of formula -C(=O)-NH-(CH2)n'-CH3.

[0091] In a 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 combinations thereof.

[0092] The proportion of the end-groups in the polyamide (PA) can be quantified by 1 H NMR spectroscopy or by potentiometric techniques.

[0093] Inherent viscosity (IV)

[0094] In the present invention, the polyamide (PA) advantageously exhibits an inherent viscosity ("IV") of between 0.5 and 1.5 dL / g, more particularly between 0.7 and 1.3 dL / g, more particularly between 0.75 and 1.20 dL / g, measured according to ASTM D5336-22 by using a mixture of phenol / tetrachloroethane (60 / 40 in weight ratio).

[0095] In a particular embodiment, the IV is between 0.80 and 1 .00 dL / g; or between 0.90 and 1.20 dL / g; or between 0.95 and 1.20 dL / g.

[0096] The polyamide (PA) of the present 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 bar (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 IVafier refer to the inherent viscosity of the samples before and after the test, respectively.

[0097] Number average molecular weight (Mn)

[0098] The polyamide (PA) of the present invention generally has a number average molecular weight (Mn) ranging from 1 ,000 g / mol to 40,000 g / mol, for example from 2,000 g / mol to 35,000 g / mol, from 4,000 to 30,000 g / mol, or from 5,000 g / mol to 20,000 g / mol. Mn may also be between 8,000 and 20,000 g / mol. Mn is preferably strictly higher than 8,000 g / mol. Mncan be determined by size exclusion chromatography (SEC) with polystyrene as a standard or by using the equation of Mn = 2,000,000 / [EG], wherein [EG] is the proportion of end- groups in the polyamide (PA) expressed in mmol / kg.

[0099] 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 spectroscopy.

[0100] Bio-content

[0101] In the present invention, the polyamide (PA) typically exhibits a bio-content of at least 20.0%, the bio-content being expressed as the percentage (%) of organic carbon of renewable origin measured according to ASTM D6866-22.

[0102] 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.

[0103] Both 1 ,9-nonanediamine (2HN-(CH2)9-NH2) (C9) and 1 ,10-decanediamine (2HN-(CH2) -NH2) (C10) that are used for the preparation of the polyamide (PA) can be bio-based or derived from petroleum or natural gas.

[0104] 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 toC9 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.

[0105] 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. In this regard, bio-based C10 may be prepared from sebacic acid derived from castor oil.

[0106] 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.

[0107] It is also possible to increase the bio-content by additionally using a bio-based terephthalic acid. The bio-content of the polyamide (PA) as defined above may then become at least 65.0%. A bio-based terephthalic acid may for instance be prepared from a bio-based furfural, as disclosed in Tachibana, Y., Kimura, S. & Kasuya, K.-i. “Synthesis and Verification of Biobased Terephthalic Acid from Furfural” Sci. Rep. 5, 8249; DOI: 10.1038 / srep08249 (2015).

[0108] 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%, more preferably at least 99.9%, the bio-content being expressed as the % of organic carbon of renewable origin measured according to ASTM D6866-22.

[0109] Moisture absorption

[0110] The polyamide (PA) advantageously exhibits a water uptake at 23°C lower than 5.0 wt%.

[0111] The water uptake at 23°C is determined by (i) providing a specimen shaped according to ISO527 in its dry state (moisture content of less than 0.2 wt%); (ii) immersing the same in deionized water at 23°C, until reaching a constant weight; and (iii) calculating the water uptake with the formula:W „ -Wh fWater u ptake =x1 ooWbeforewherein 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.

[0112] Thermal properties of the polyamide (PA)

[0113] The polyamide (PA) of the present invention exhibits an advantageous combination of thermal properties. Any feature of the thermal properties disclosed below can be used to characterize the polyamide (PA).

[0114] In one embodiment, the polyamide (PA) exhibits a melting temperature (Tm) of at least 250°C, preferably at least 260°C, measured by Differential Scanning Calorimetry (“DSC”) according to ASTM D3418.

[0115] In the other embodiment, the polyamide (PA) exhibits a Tm of less than 300°C, preferably at most 290°C, measured by DSC according to ASTM D3418.

[0116] In some embodiments, Tm is measured by DSC according to ASTM D3418 with 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.

[0117] In one embodiment, the polyamide (PA) exhibits a glass transition temperature (Tg) of at least 140°C, preferably at least 145°C, measured by DSC according to ASTM D3418.

[0118] In the other embodiment, the polyamide (PA) exhibits a glass transition temperature (Tg) of at most 200°C, preferably at most 180°C, measured by DSC according to ASTM D3418.

[0119] 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. Tgis determined from the second heat up.

[0120] In a particular embodiment, the difference between Tm and Tgof the polyamide (PA), i.e. Tm-Tgis less than 130°C, preferably less than 125°C, the Tm and Tgbeing measured by DSC according to ASTM D3418.

[0121] In a more particular embodiment, the Tm-Tgis less than 120°C, the Tmand Tgbeing measured by DSC according to ASTM D3418.

[0122] In the present invention, the polyamide (PA) is semi-crystalline.

[0123] In one embodiment, the polyamide (PA) exhibits a heat of fusion (Hm) of at least 15.0 J / g, preferably at least 20.0 J / g, more preferably at least 25.0 J / g, even more preferably at least 27.0 J / g, measured by DSC according to ASTM D3418.

[0124] Hm may be at most 40.0 J / g or at most 39.0 J / g.

[0125] In a particular embodiment, Hm is between 15.0 and 40.0 J / g.

[0126] 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 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.

[0127] The polyamide (PA) of the present invention exhibits an optimal combination of such thermal properties.

[0128] In a particular embodiment, the polyamide (PA) exhibits the following combination of properties:- a Tm of from 250°C to less than 300°C, preferably from 260°C to 290°C;- a Tgof from 140°C to 200°C, preferably from 145°C to 180°C; and- a bio-content of at least 20.0%.

[0129] Process of preparation of polyamides (PA)

[0130] The polyamides (PA) described herein can be prepared by any conventional method adapted to the synthesis of polyamides and polyphthalamides. The polyamide (PA) is generally produced via polycondensation in the melt. The polyamide (PA) can be prepared by heating a reaction mixture (RM) comprising all the monomers that constitute the polyamide (PA), e.g. 1 ,6- hexanediamine, DA1 , DA2, terephthalic acid and optionally 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%, most preferably without water. This proportion is given based on the total weight of the reaction mixture (RM).

[0131] In some embodiments, the reaction mixture (RM) comprises a catalyst, which may be selected from the group consisting of phosphorous acid, orthophosphoric acid, mefa-phosphoric acid, alkali-metal hypophosphite such assodium hypophosphite and phenylphosphinic acid, frequently phosphorous acid.

[0132] The proportion of the catalyst in the reaction mixture (RM) is preferably between 0.005 and 2.5 wt% based on the weight of the monomers in the reaction mixture (RM).

[0133] To control the molar mass, the reaction mixture (RM) may also further comprise at least one end-capping agent as disclosed above.

[0134] The temperature at which the reaction mixture (RM) is heated must be high enough to induce the reaction between the amine groups and the carboxylic groups and to decrease the viscosity of the reaction mixture. This temperature is generally at least 150°C, preferably at least 200°C that can be increased during the polycondensation in a step-wise manner. The reaction mixture (RM) is preferably heated at a temperature > Tm + 25°C. The polycondensation results in the formation of the amide bonds and the release of water as a byproduct.

[0135] The reaction mixture (RM) comprises the diamines of the diamine component (A) and the diacid(s) of the dicarboxylic acid component (B). As detailed above, the proportions of the two components is such that the reaction mixture comprises the monomers in a quantity that the proportion of -COOH groups from the dicarboxylic acids and the proportion of -NH2 groups from the diamines are substantially equimolar. The molar ratio -NH2 from the diamines of the diamine component (A) / -COOH from the dicarboxylic acids of the dicarboxylic acid component (B) is preferably between 0.9 and 1.1 , preferentially between 0.95 and 1.05, even more preferentially between 0.98 and 1.02.

[0136] The polycondensation is advantageously performed in a well-stirred vessel equipped with means to remove the volatile products of the reaction. As the viscosity of the reaction mixture increases over time, the stirrer is adapted to provide sufficient stirring to the reaction mixture (RM) at the beginning of the polymerization and when the conversion of the polycondensation is nearly complete.

[0137] The conditions disclosed in the experimental section may conveniently be used for the preparation of the polyamide (PA).

[0138] 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.

[0139] 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, the wt% being based one the total weight of the polymer composition (PC).

[0140] The inorganic filler is typically selected from the group consisting of talc, clay, mica, kaolin, calcium carbonate, calcium silicate, magnesium carbonate, glass fibers, carbon fibers and combinations thereof.

[0141] The inorganic filler may more particularly be a clay. The clay may be selected from the group consisting of montmorillonite, hectorite, saponite, vermiculite and combinations thereof.

[0142] The plastic additive other than inorganic filler is typically selected from 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.

[0143] 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).

[0144] 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%, 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% or even at least 0.5 wt%, relative to the total weight of polymer composition (PC).

[0145] The proportion of the polyamide (PA) according to the present invention in the polymer composition (PC) is preferably at least 95.0 wt%, preferably at least 97.0 wt%, more preferably at least 99.0 wt%, the wt% being based on the total weight of the polymer composition (PC).

[0146] 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).

[0147] In a particular embodiment, the multilayer structure is a vessel or a pipe.

[0148] 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.

[0149] The vessel typically has a cylindrical shape, while its dimension, such as length, internal volume, shape, etc. are defined depending on its end use.

[0150] 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).

[0151] 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.

[0152] 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).

[0153] In one embodiment, the structural layer (Ls) comprises a polymer matrix and fibers, i.e. a composite.

[0154] 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 combinations thereof.

[0155] In a preferred embodiment, the fibers are continuous fibers.

[0156] In the other embodiment, the structural layer (Ls) is selected from the group consisting of metallic layers.

[0157] 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 in an order: a film or a liner comprising at least one barrier layer (Lb) as disclosed herein; at least one structural layer (Lsi) made of a polymer matrix and fibers; andat least one metallic structural layer (LS2).

[0158] Use of Polyamide (PA)

[0159] 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).

[0160] The Applicant also believes that in addition to H2, the present invention can be potentially used to store and / or transport other gas such as natural gas, CO2, etc.

[0161] The article

[0162] A further object of the invention is an article for the storage and / or transportation of a gas, comprising the multilayer structure as defined above. Notable non-limiting examples of articles are hoses, pipes, tubes, joints, tanks, reservoirs or, in general, vessels.

[0163] Of these, the multilayer structure of the present invention is suitable for use as a hose for compressed gas, in particular hydrogen. The hose for compressed hydrogen is used as a hose for charging a fuel-cell vehicle or the like with hydrogen from a hydrogen station. Since the hose for compressed hydrogen is subject to repeated temperature changes (heat cycles) from -40°C or lower to 90°C or higher due to charging and discharging of high-pressure hydrogen, it is required to have high heat cycle resistance as well as hydrogen barrier.

[0164] The hose for high-pressure hydrogen is a hose comprising the multilayer structure of the first object, wherein barrier layer (Lb) is in contact with the compressed gas.

[0165] The inventive multilayer structure is characterized by high thermal resistance and a good hydrogen barrier. These features make the multilayer structure particularly well adapted for the use in vessels for storing gasses such as hydrogen under pressure.

[0166] A further object of the invention is a vessel for the storage or transport of a gas, comprising the multilayer structure as defined above.

[0167] The term “vessel” is used herein to refer to a hollow container. The vessel of the invention is in particular a hollow container for containing a gas, preferably a pressurized or compressed gas.

[0168] Layer (BL) represents the internal layer of the vessel which is in contact with the gas to be transported or stored, hereinafter referred to as “liner”. Layer (CL) represents the external layer of the vessel.

[0169] The vessel is preferably a pressure vessel, that is a vessel suitable for the storage and transport of a gas under pressure.

[0170] The vessel, or preferably the pressure vessel, comprises a hollow body and at least one boss. A boss is known by a person skilled in the art and it refers to the opening in which a closure is attached which allows flow of gas or fluid in and out the vessel. A boss is usually made of metal.

[0171] The hollow body may have any shape suitable for the storage of a gas, in particular of a gas under pressure.

[0172] In certain conventional embodiments, the vessel has a cylindrical shape and a boss is placed at the end. Often, a vessel has two bosses at each end of the cylindrical shape.

[0173] The shape of the hollow body is determined by the desired use. It is usually but not exclusively cylindrical with a diameter of between 10.0 cm and 1.0 m. The diameter may be at least 15.0 cm or more.

[0174] The length of the hollow body also depends on the end use and may for example be between 50.0 cm and up to lengths as large as 10.0 m. These higher lengths are usually employed for gas transport. As an example, for vessels in trucks the length is usually between 1 .0 m and 3.0 m.

[0175] The vessel may have an inner volume from 5.0 to 1000.0 liters, or from 10.0 to 500.0 liters.

[0176] The vessel has an operating temperature range of at least -70.0°C, or at least -60.0°C, or at least -40.0°C and / or 250°C or less, or 150°C or less, or 120°C or less, or 85°C or less.

[0177] In particular embodiments, the vessel has an operating temperature range of from -70.0°C to 250.0°C, or from -70.0°C to 150.0°C, or from -60.0 to 120°C, or from -40.0°C to 85°C..

[0178] The vessel may be prepared according to any method known in the art.

[0179] The vessel according to the invention exhibits a nominal pressure of at least 2.5 MPa, typically at least 20.0 MPa, even at least 30.0 MPa. The nominal pressure may be up to 70.0 MPa, 100 MPa, even 150.00 MPa and more.Advantageously, the vessel of the invention has a nominal pressure of 20.0 to 70.0 MPa.

[0180] A burst pressure of at least 157.5 MPa may be reached for the storage of hydrogen gas with a vessel according to the invention. Vessels for the storage of compressed hydrogen typically require nominal pressures of 35.0 MPa or 70.0 MPa. Burst pressures, measured according to ECE R134, are typically up to 78.8 MPa and 157.5 MPa, respectively.

[0181] The inventive multilayer structure is characterized by a good hydrogen barrier and mechanical properties both at high and low temperatures. The inventive multilayer structure further exhibits limited water pick-up.

[0182] A further object of the invention is a compressed gas contained in a vessel comprising the multilayer structure of the first object, wherein barrier layer (Lb) is in contact with the compressed gas. The gas is advantageously selected from the group consisting of hydrogen, oxygen, nitrogen, argon, helium, methane, propane, compressed natural gas, CO2 and ammonia.

[0183] The gas is typically at a pressure of at least 5.0 MPa, preferably at least 10.0 MPa. Depending on the gas, the pressure may be up to 150.0 MPa.

[0184] A further object of the invention is a vehicle comprising the vessel or the compressed gas contained in the vessel.

[0185] The vehicle may be a car, a truck, a train, a ship, an urban mobility vehicle, an airplane, a helicopter or any other vehicle that could be powered using the conversion of a gas into energy by any means.

[0186] 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.

[0187] 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

[0188] Raw Materials1 ,9-diaminononane (C9): synthesized within Syensqo (derived from bio-based oleic acid);1 ,10-diaminodecane (C10): synthesized within Syensqo (derived from biobased castor oil);1 ,6-diaminohexane (HMD): commercially available from Solatia, Inc.;1 ,3-bis(aminomethyl)cyclohexane (1 ,3-BAC): commercially available from TCI America;- terephthalic acid (TA): commercially available from Flint Hills Resources; phosphorous acid: commercially available from Sigma Aldrich.

[0189] Synthesis of the polyamides

[0190] All polyamides disclosed in Table I were prepared in an autoclave reactor equipped with a distillate line fitted with a pressure control valve. More particularly, all polyamides were prepared by charging into the reactor the monomers with the proportions targeted, water and phosphorous acid, according to the procedure given below in Example 1 .

[0191] Example 1 (E1): the polyamide E1 was prepared by charging into the reactor 1.77 g of HMD, 2.05 g of C10, 0.96 g of 1 ,3-BAC, 5.32 g of TA, 4.98 g of deionized water, and 0.0033 g of phosphorous acid. The reactor was sealed, purged with N2 gas three times. The reactor was heated to 177°C and held for 30 min, subsequently followed by heating to 232°C and holding for 30 min, followed by heating to 288°C and holding for 30 min, followed by heating to 343°C and holding for 35 min. The steam generated was slowly released to keep the internal pressure under 200 psig. Once the temperature was at 343°C for 35 min, the reactor pressure was slowly reduced to atmospheric pressure over 25 min. After finishing the depressurization, N2 gas was used to continuously purge the reactor over 25 min. Afterwards, the reactor was cooled to room temperature and the polyamide was retrieved from the reactor.

[0192] Bio-content of the polyamide was measured according to ASTM D6866-22 and indicated in Table I.

[0193] Thermal Properties (Tg, Tm & Hm)

[0194] The Tg, Tm and Hm were measured by Differential Scanning Calorimetry (“DSC”) according to ASTM D3418 using a heating and cooling rate of 20°C / min. Three scans were made for each DSC test: a first heat up to 350°C, followed by a first cool down to 0°C, followed by a second heat up to 360°C. The Tg, Tm and Hm were determined from the second heat up.

[0195] Mechanical Properties

[0196] Tensile elongation at break (%), Chord Modulus (MPa) and Notched Izod (kJ / rri2) were measured according to ISO527 (using ISO 1A bars), ISO527 (using ISO 1A bars), and ISO180, respectively. The elongation at break refers to the ratio of the initial and final lengths of a material before it breaks.

[0197] Permeability

[0198] The polyamide (E1 ) was processed by extrusion to produce a sample in the form of a film having thickness of 166 pm.

[0199] The sample was 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 H2 in the sweep gas flow was measured, typically with an electrochemical H2 sensor.

[0200] The sample was then annealed for 2 hours at 180°C in dry air; was mounted in a sealed chamber; and a check was made to ensure that the chamber is leak tight by applying hydrogen at 0.14 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.

[0201] The permeation coefficient (P) is calculated according to equation (Eq. 1 ) as defined above in the specification.

[0202] The comparative polyamide (CE1 ) was processed according to the same procedure as E1 by extrusion to produce a sample in the form of a film having thickness of 545 pm, except that the annealing was made for 2 hours at 200°C. Depending on the thickness of the film, the annealing was implemented for 2 to 16 hours.

[0203] In brief, the bars prepared for the measurement of mechanical properties and the films prepared for the measurement of permeability were annealed at a temperature of between 20~40°C and Tgof each polyamide for 2~16 hours, so as to ensure the crystallinity of each sample.

[0204] As demonstrated by the results indicated in Table I, the specific proportions of the monomers make it possible to have balanced properties, i.e. an advantageous combination of Tg, Tmand Hm, while ensuring a substantial portion of bio-content, notably a high Tgand a low Tm. In addition, the polyamide according to the present invention (E1 ) exhibits significantly high tensile elongation at break and notched Izod as indicated in Table II below, notably in comparison to the comparative ones (CE1 & CE8). It also exhibits improved chord modulus.

[0205] Moreover, this optimal combination of thermomechanical properties and permeability ensure that the polyamide (PA) of the present invention 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 data indicated in Table II [permeation coefficient (P) of E1 vs. CE1],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)Table 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 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: a) the diamine component (A) comprises:- from 38.0 to 54.0 mol% of 1 ,6-diaminohexane;- from 15.0 to 40.0 mol% of a diamine (DA1 ) selected from the group consisting of 1 ,9-diaminononane (C9), 1 ,10-diaminodecane (C10) and mixtures thereof; and- from 15.0 to 40.0 mol% of a diamine (DA2) selected from the group consisting of 1 ,3-bis(aminomethyl)cyclohexane (1 ,3-BAC), 1 ,4- bis(aminomethyl)cyclohexane (1 ,4-BAC) and mixtures thereof; the mol% being based on the total moles of diamines in the diamine component (A); and b) the dicarboxylic acid component (B) comprises:- from 95.0 to 100.0 mol% of terephthalic acid; and- from 0 to 5.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA) and mixtures thereof, the 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 melting temperature (Tm) of the polyamide (PA) is: at least 250°C, preferably at least 260°C; and / or less than 300°C, preferably at most 290°C, the Tm being measured by Differential Scanning Calorimetry (DSC) with a heating and cooling rate of 20°C / min pursuant to ASTM D3418.

3. The multilayer structure according to claim 1 or 2, wherein the glass transition temperature (Tg) of the polyamide (PA) is: at least 140°C, preferably at least 145°C; and / or at most 200°C, preferably at most 180°C, the Tgbeing measured by Differential Scanning Calorimetry (DSC) with a heating and cooling rate of 20°C / min pursuant to ASTM D3418.

4. The multilayer structure according to any one of the preceding claims, wherein the difference between Tmand Tgof the polyamide (PA) is less than 130°C, preferably less than 125°C.

5. The multilayer structure according to any one of the preceding claims, wherein the diamine component (A) comprises 2.0 mol% or less of at least one additional diamine other than 1 ,6-diaminohexane, DA1 and DA2, the mol% being based on the total moles of diamines in the diamine component (A).

6. The multilayer structure according to any one of the preceding claims, wherein the dicarboxylic acid component (B) comprises 2.0 mol% or less of at least one additional dicarboxylic acid other than terephthalic acid and DI, the mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B).

7. The multilayer structure according to any one of the preceding claims, wherein the polyamide (PA) comprises the recurring units (RPAI ), (RPA2), (RPAS- 1) and / or (RPA3-2):(RPA3-2). where Ri is -(CH2)e- and R2 is the divalent radical of a diamine selected from the group consisting of 1 ,9-diaminononane (C9), 1 ,10-diaminodecane (C10) and mixtures thereof.

8. The multilayer structure according to any one of the preceding claims, wherein the total proportion of the recurring units (RPAI ) , (RPA2) , (RPA3-I) and (RPA3-2) in the polyamide (PA) is at least 95.0 mol%, preferably at least 98.0 mol%, more preferably at least 99.0 mol%, the mol% being based on the total moles of the recurring units (RPA) of the polyamide (PA).

9. The multilayer structure according to any one of the preceding claims, wherein the polyamide (PA) is prepared from 1 ,9-diaminononane (C9) and / or 1 ,10-diaminodecane (C10) exhibiting a bio-content of at least 99.0%, preferably at least 99.5%, more preferably at least 99.9%, the bio-content being expressed in percentage (%) of organic carbon of renewable origin measured according to ASTM D6866-22.

10. The multilayer structure according to any one of preceding claims, wherein the barrier layer (Lb) in the form of a film exhibits a permeability of 150.0 Ncm3mm / m2bar day or less, preferably 120.0 Ncm3mm / m2bar day orless, more preferably 100.0 Ncm3mm / m2bar day or less, measured according to the protocol defined in the experimental section.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 structural layer (Ls) comprises a polymer matrix and fibers, preferably continuous fibers.

14. The multilayer structure according to claim 13, 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.

15. Use of a polyamide (PA) comprising recurring units (RPA) formed from the polycondensation of a diamine component (A) and a dicarboxylic acid component (B) wherein: a) the diamine component (A) comprises:- from 38.0 to 54.0 mol% of 1 ,6-diaminohexane;- from 15.0 to 40.0 mol% of a diamine (DA1 ) selected from the group consisting of 1 ,9-diaminononane (C9), 1 ,10-diaminodecane (C10) and mixtures thereof; and- from 15.0 to 40.0 mol% of a diamine (DA2) selected from the group consisting of 1 ,3-bis(aminomethyl)cyclohexane (1 ,3-BAC), 1 ,4- bis(aminomethyl)cyclohexane (1 ,4-BAC) and mixtures thereof; the mol% being based on the total moles of diamines in the diamine component (A); and b) the dicarboxylic acid component (B) comprises: from 95.0 to 100.0 mol% of terephthalic acid; and- from 0 to 5.0 mol% of the other dicarboxylic acid (DI) selected from the group consisting of isophthalic acid (IA), adipic acid (AA) and mixtures thereof, the mol% being based on the total moles of dicarboxylic acids in the dicarboxylic acid component (B), 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).

16. The use according to Claim 15, wherein said polyamide (PA) is as defined in any one of Claims 2 to 9.

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