Multilayer structure and article for storing and transporting gas

Abstract

A multi-layer structure suitable for manufacturing a container for storing and transporting gas, in particular a pressure container, is disclosed. The container is particularly adapted to store and transport compressed gas in a vehicle.

Description

[0001] Citation of Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 387,308, filed December 14, 2022, and European Patent Application No. 23158669.4, filed February 27, 2023, the entire contents of each of which are incorporated herein by reference for all purposes. Technical Field

[0003] The present invention relates to a multilayer structure suitable for producing an article suitable for storing and transporting gases, in particular a pressure vessel. The present invention further relates to an article, such as a pressure vessel, comprising the multilayer structure. The present invention further relates to a method for producing a pressure vessel. Background Art

[0004] Pressure vessels characterized by high gas barrier properties have been used to store various gases such as oxygen, carbon dioxide, nitrogen, argon, LPG (liquefied petroleum gas), methane, and hydrogen for long periods of time. Pressure vessels are known that include a non-structural liner surrounded by a structural fiber-reinforced composite material to contain a fluid or gas under pressure. The liner acts as a barrier between the fluid or gas and the fiber-reinforced composite material, thereby preventing leakage and / or other degradation of the structure of the fiber-reinforced composite material. The use of structural fiber-reinforced composite materials comprising a thermoplastic polymer matrix rather than a thermosetting polymer matrix facilitates the reuse of pressure vessels.

[0005] Pressure vessels comprising a polyamide-based liner and an outer layer which is a composite material comprising continuous fibers and a polyamide resin impregnated into the continuous fibers are disclosed in, for example, EP 3225888 A1, EP 3390016 A1, and WO 21152254 A1.

[0006] However, there is still a need to develop articles for transporting and storing hydrogen, like pressure vessels, which combine impermeability to the stored gas and mechanical properties.

[0007] It was therefore an object of the present invention to provide a multilayer structure which combines low permeability to gases such as hydrogen with good mechanical properties. This object is achieved by the multilayer structure of the present invention. Summary of the Invention

[0008] Therefore, a first object of the present invention is a multilayer structure comprising at least one barrier layer [layer (BL)] and at least one composite material layer [layer (CL)] in contact with the at least one barrier layer, wherein:

[0009] - layer (BL) comprises polyamide polymer PA1; and

[0010] - layer (CL) comprising continuous reinforcing fibers and polyamide polymer PA2,

[0011] wherein: the polyamide polymer PA1 is selected from the group consisting of polyamides comprising repeating units derived from the polycondensation of: i) caprolactam; and / or ii) at least one diamine component having 4 to 8 carbon atoms and at least one dicarboxylic acid component having 8 or fewer carbon atoms;

[0012] The polyamide polymer PA2 is selected from the group consisting of polyamides consisting of repeating units derived from the polycondensation of at least one diamine component having at least 9 carbon atoms, at least one aromatic dicarboxylic acid component and optionally one or more components selected from the group consisting of lactams, amino acids and aliphatic dicarboxylic acids.

[0013] A second object of the present invention is an article for storing or transporting gas, comprising the multilayer structure of the first object. Layer (BL) represents the inner layer of the article that comes into contact with the gas to be stored or transported (hereinafter also referred to as "inner layer" or "liner"), while layer (CL) represents the outer layer of the article. The article can be a container, preferably a pressure vessel, i.e., a container for storing gas under pressure.

[0014] A third object of the present invention is a compressed gas in a container comprising the multilayer structure of the first object, wherein layer (BL) is in contact with the compressed gas. Further objects of the present invention are a method for manufacturing the container and the use of the container in a vehicle. DETAILED DESCRIPTION

[0015] In this application:

[0016] - even any description described with respect to a specific embodiment is applicable to other embodiments of the present disclosure and is interchangeable therewith;

[0017] - When an element or component is said to be included in and / or selected from a list of enumerated elements or components, it is understood that in the relevant embodiments expressly contemplated herein, the element or component may also be any one of these enumerated individual elements or components, or may also be selected from a group consisting of any two or more of the explicitly enumerated elements or components; any element or component enumerated in a list of elements or components may be omitted from this list;

[0018] - Any recitation of numerical ranges by endpoints herein includes all numbers subsumed within the recited range as well as the endpoints of that range and equivalents thereof;

[0019] - the indefinite article "a" in expressions like "a (a) polyamide polymer" is intended to mean "one or more", or "at least one", unless otherwise indicated; and

[0020] - The use of parentheses "()" before and after the name, symbol or number of a compound, for example "layer (BL)", "layer (CL)", etc., has the sole purpose of better distinguishing that name, symbol or number from the rest of the text; therefore, said parentheses can also be omitted.

[0021] Unless otherwise expressly indicated, the term "alkyl" as used herein and derivative terms such as "alkoxy," "acyl," and "alkylthio" include within their scope linear, branched, and cyclic moieties. Examples of alkyl groups are methyl, ethyl, 1-methylethyl, propyl, 1,1-dimethylethyl, and cyclopropyl. Unless otherwise expressly indicated, each alkyl and aryl group may be unsubstituted or substituted with one or more substituents selected from, but not limited to, halogen, hydroxy, sulfo, C1-C6 alkoxy, C1-C6 alkylthio, C1-C6 acyl, formyl, cyano, C6-C15 aryloxy, or C6-C15 aryl, provided that these substituents are sterically compatible and meet the rules of chemical bonding and strain energy. The term "halogen" or "halo" includes fluorine, chlorine, bromine, and iodine, with fluorine being preferred.

[0022] The term "aryl" refers to phenyl, indanyl, or naphthyl. An aryl group may contain one or more alkyl groups and, in this case, is sometimes referred to as an "alkylaryl" group; for example, it may consist of a cyclic aromatic group and two C1-C6 groups (e.g., methyl or ethyl). An aryl group may also contain one or more heteroatoms (e.g., N, O, or S) and is sometimes referred to as a "heteroaryl" group; these heteroaromatic rings may be fused to other aromatic systems.

[0023] A first object of the present invention is a multilayer structure comprising at least one barrier layer [layer (BL)] and at least one layer of composite material [layer (CL)] in contact with the at least one barrier layer, as defined in the accompanying claims.

[0024] Layer (BL)

[0025] Layer (BL) is configured to provide a barrier to gas transmission.

[0026] The layer (BL) comprises at least one polyamide polymer PA1, also referred to below as “polyamide PA1”.

[0027] The polyamide PA1 is chosen from the group consisting of polyamides comprising recurring units derived from the polycondensation of:

[0028] i) caprolactam; and / or alternatively

[0029] ii) at least one diamine component having 4 to 8 carbon atoms and at least one dicarboxylic acid component having 8 or fewer carbon atoms.

[0030] Polyamides comprising repeating units derived from the polycondensation of caprolactam are known and are generally referred to as PA6.

[0031] When polyamide PA1 is formed by polycondensation of a diamine component and a dicarboxylic acid component, the amount of -NH2 groups from the diamine component and the amount of -COOH groups from the dicarboxylic acid component are substantially equimolar. The ratio amine / acid may be from 0.9 to 1.1, preferably from 0.95 to 1.05, even more preferably from 0.98 to 1.02.

[0032] The diamine component may be aliphatic, cycloaliphatic or aromatic. Suitable aliphatic diamines are those having the following formula (I)

[0033] H2N-R 1 -NH2(I)

[0034] where R 1 The alkylene group is a C4-C8 aliphatic or alicyclic alkylene group which may be linear or branched. Among linear or branched alkylene groups, C4-C6 linear alkylene groups are preferred. Among suitable alicyclic alkylene groups, 1,3-bis(aminomethyl)cyclohexane ("1,3-BAC") and 1,4-bis(aminomethyl)cyclohexane ("1,4-BAC") may be mentioned. Preferably, the bis(aminoalkyl)cyclohexane is 1,3-bis(aminomethyl)cyclohexane.

[0035] Bis (aminoalkyl) cyclohexanes can be in cis or trans configuration. Therefore, the diamine component can comprise only cis-bis (aminoalkyl) cyclohexanes, only trans-bis (aminoalkyl) cyclohexanes. Bis (aminoalkyl) cyclohexanes can be a mixture of cis- and trans-bis (aminoalkyl) cyclohexanes. The cis / trans ratio can be between 10 / 90 and 90 / 10, preferably between 20 / 80 and 80 / 20 and even more preferably between 30 / 70 and 70 / 30. In certain embodiments, the cis / trans ratio is between 50 / 50 and 68 / 32.

[0036] The diamine component may be aromatic. Examples of suitable C6-C8 aromatic diamines include, but are not limited to, metaphenylenediamine (MPD), paraphenylenediamine (PPD), paraxylenediamine (PXD), and metaxylenediamine (MXD).

[0037] The dicarboxylic acid component may be aliphatic, cycloaliphatic or aromatic. Notable non-limiting examples of suitable aliphatic dicarboxylic acids are those having formula (II)

[0038] HOOC-R 2 -COOH(II)

[0039] where R 2 The alkylene group may be a linear or branched C1-C6 aliphatic or alicyclic alkylene group. Among the linear or branched alkylene groups, a C4-C6 linear alkylene group is preferred. Among suitable alicyclic alkylene groups, 1,4-cyclohexanedicarboxylic acid and tetrahydrofuran-2,5-dicarboxylic acid may be mentioned.

[0040] Notable non-limiting examples of suitable aromatic dicarboxylic acids are, for example, phthalic acid, in particular terephthalic acid (T) and isophthalic acid (I).

[0041] The polyamide PA1 may be a copolyamide, ie it may be derived from the polycondensation of one or more than one lactam or amino acid and / or one or more diamine components and / or one or more dicarboxylic acid components.

[0042] Typically, polyamide PA1 has a C / NHCO ratio of 6.5 or less, preferably equal to or less than 6.0. The C / NHCO ratio is the average number of carbon atoms between adjacent amide groups per amide group in the polyamide polymer. The average number of carbon atoms between adjacent amide groups is calculated as the average number of carbon atoms per caprolactam, amino acid, diamine, or dicarboxylic acid component in the polymer, weighted by the molar amount of each component in the polymer.

[0043] The polyamide PA1 can conveniently be selected from the group consisting of PA6, PA46, PA56, PA MXD6, PA PXD6, PA MXD6 / MXDI, PA MXD6 / PXD6.

[0044] In an advantageous embodiment, the polyamide PA1 is characterized by a melting temperature of 180 to 300° C. The melting temperature is typically measured by differential scanning calorimetry (DSC) according to ASTM D3418 using a heating and cooling rate of 20° C. / min on the 2nd heat scan.

[0045] Layer (BL) does not contain any continuous reinforcing fibers.

[0046] Layer (BL) has a thickness that provides the desired gas permeability value required for the application. Layer (BL) typically has a thickness of at least 100 microns, typically at least 250 microns. Layer (BL) may have a thickness of up to 10.0 mm, even 8.5 mm, 7.5 mm. Layer (BL) may have a thickness of 100 to 10.0 mm, typically 250 to 10.0 mm, even 300 to 8.5 mm, or even 500 to 6.0 mm.

[0047] The layer (BL) may comprise one or more than one polyamide PA1.

[0048] In a first embodiment, the only polymer component in layer (BL) is polyamide PA1.

[0049] In this embodiment, layer (BL) comprises 75.0 wt% or more, even 80.0 wt% or more, or even 85.0 wt% or more of polyamide PA1, relative to the total weight of layer (BL). In this embodiment, layer (BL) may contain 25.0 wt% or less of one or more additives typically employed in the formulation of polyamide polymers. Non-limiting examples of suitable additives include antioxidants (e.g., UV stabilizers and heat stabilizers), impact modifiers, chain extenders, processing aids, nucleating agents, lubricants, flame retardants, smoke suppressants, antistatic agents, anti-blocking agents, colorants, and pigments.

[0050] The total amount of additives may be 20.0 wt% or less, even 10.0 wt% or less, relative to the total weight of layer (BL). When present, one or more additives are at least 0.5 wt%, at least 1.0 wt%, in some cases even at least 2.0 wt% relative to the total weight of the polyamide polymer.

[0051] In a second embodiment, the layer (BL) comprises polyamide PA1 and at least one other thermoplastic polymer different from polyamide PA1.

[0052] In an advantageous aspect of said embodiment, layer (BL) comprises polyamide PA1 and an impact modifier.

[0053] Suitable impact modifiers are, for example, functionalized polyolefins having a glass transition temperature below 25°C.

[0054] The polymer backbone of the impact modifier can be selected from elastomeric backbones, which contain polyethylene and its copolymers, for example, ethylene-butene; ethylene-octene; polypropylene and its copolymers; polybutene; polyisoprene; ethylene-propylene-rubber (EPR); ethylene-propylene-diene monomer rubber (EPDM); ethylene-acrylate rubber; butadiene-acrylonitrile rubber, ethylene-acrylic acid (EAA), ethylene-vinyl acetate (EVA); acrylonitrile-butadiene-styrene rubber (ABS), block copolymer styrene ethylene butadiene styrene (SEBS); block copolymer styrene butadiene styrene (SBS); core-shell elastomers of the methacrylate-butadiene-styrene (MBS) type, or a mixture of one or more of the above.

[0055] When the impact modifier is functionalized, the functionalization of the backbone can result from the copolymerization of monomers containing the functionalization or from grafting another component onto the polymer backbone.

[0056] Specific examples of functionalized impact modifiers are notably terpolymers of ethylene, acrylate and glycidyl methacrylate, copolymers of ethylene and butyl acrylate; copolymers of ethylene, butyl acrylate and glycidyl methacrylate; ethylene-maleic anhydride copolymers; EPR grafted with maleic anhydride; styrene copolymers grafted with maleic anhydride; SEBS copolymers grafted with maleic anhydride; styrene-acrylonitrile copolymers grafted with maleic anhydride; and ABS copolymers grafted with maleic anhydride.

[0057] Functionalized polyolefin impact modifiers are available from commercial sources and include maleated polypropylene and ethylene-propylene copolymers (as PO available) and a maleic anhydride functionalized ethylene-propylene copolymer rubber containing about 0.6 weight percent pendant succinic anhydride groups, such as PO from ExxonMobil Chemical Company. VA 1801; as Available acrylate-modified polyethylenes, such as 9920, an acrylic acid or methacrylic acid modified polyethylene from Dow Inc.; a maleic anhydride modified SEBS block copolymer such as FG1901X, SEBS that has been grafted with about 2 wt% maleic anhydride, available from Kraton Polymers; maleic anhydride functionalized EPDM terpolymer rubber, such as 498, a 1% maleic anhydride functionalized EPDM, available from SI Group.

[0058] Other desirable functionalized impact modifiers include, but are not limited to, ethylene-higher α-olefin polymers and ethylene-higher α-olefin-diene polymers grafted or copolymerized with reactive carboxylic acids or derivatives thereof, such as acrylic acid, methacrylic acid, maleic anhydride or its esters. Suitable higher α-olefins include, but are not limited to, C3 to C8 α-olefins, such as, for example, propylene, 1-butene, 1-hexene and styrene.

[0059] Among the reactive impact modifiers that may be mentioned are those marketed under the trade name

[0060] AX8900 is a random terpolymer of ethylene, acrylic acid ester and glycidyl methacrylate commercially available from Arkema (Bristol, Pennsylvania, USA). Another example of the above-mentioned reactive impact modifier is available under the trade name Paraloid TM EXL 2314, commercially available from Dow (Midland, Michigan, USA), is a core-shell acrylate-based impact modifier comprising a core consisting primarily of crosslinked poly(n-butyl acrylate) rubber and having a shell phase consisting primarily of poly(methyl methacrylate)-poly(glycidyl methacrylate) copolymer.

[0061] In this second embodiment, layer (BL) comprises 1.0 wt % to 25.0 wt % of at least one thermoplastic polymer and / or impact modifier relative to the total weight of layer (BL). The impact modifier may be at least 2.0 wt % or at least 3.0 wt %, or even at least 5.0 wt % of the total weight of layer (BL). The impact modifier typically does not exceed 20.0 wt %, does not exceed 15.0 wt %, does not exceed 12.0 wt %, or even does not exceed 10.0 wt %. Suitable ranges may be, for example, 1.0 to 15.0 wt %, or even 1.0 to 12.0 wt %, or even 2.0 to 10.0 wt %.

[0062] In a second embodiment, the layer (BL) may additionally comprise additives as described above in detail. The total amount of additives may be 20.0 wt % or less, even 10.0 wt % or less, relative to the total weight of the layer (BL) and / or at least 1.0 wt %, even at least 2.0 wt % relative to the total weight of the layer (BL).

[0063] Layer (BL) can be prepared using common techniques for making films or sheets of polyamide polymers, as known to those skilled in the art. For example, layer (BL) can be produced by rotational molding, injection molding, and optionally welding, pipe extrusion, and extrusion blow molding. These films can optionally be uniaxially or biaxially oriented. Biaxial orientation can be carried out on a tenter frame biaxial orientation apparatus as known in the art.

[0064] When more than one layer (BL) is present in the multilayer structure of the invention, each layer (BL) may comprise the same or different polyamide PA1, preferably the same polyamide PA1.

[0065] Layer (CL)

[0066] The multilayer structure of the present invention comprises at least one layer (CL).The layer (CL) comprises continuous reinforcing fibers and a polyamide polymer PA2 (hereinafter also referred to as "polyamide PA2").

[0067] The polyamide PA2 is selected from the group consisting of polyamides consisting of repeating units derived from the polycondensation of at least one diamine component having at least 9 carbon atoms, at least one aromatic dicarboxylic acid component and optionally one or more components selected from the group consisting of lactams, amino acids and aliphatic dicarboxylic acids.

[0068] The diamine component can be aliphatic, cycloaliphatic or aromatic. Notable non-limiting examples of suitable aliphatic or cycloaliphatic diamines are those of formula (III):

[0069] H2N-R 3 -NH2(III)

[0070] where R 3 It is a C9-C20 aliphatic or alicyclic alkylene group that can be straight or branched. Among straight or branched alkylene groups, straight or branched C9-C16 alkylene groups are preferred, and straight or branched C9-C12 alkylene groups are even more preferred. Notable non-limiting examples include 1,9-nonanediamine, 2-methyl-1,8-octanediamine (Me8), 1,10-decanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 2,2,4-trimethyl-1,6-hexanediamine or 2,4,4-trimethyl-1,6-hexanediamine (TMD isomers), 5-methyl-1,9-nonanediamine. Among suitable alicyclic alkylene groups, isophorone diamine, 4,4'-methylene-bis(2-methylcyclohexylamine) (MACM), 4,4'-methylene-bis-cyclohexylamine (PACM) and mixtures thereof can be mentioned.

[0071] In certain embodiments, the aliphatic diamine can be derived from renewable materials.Notable non-limiting examples of such diamines are, for example, 1,9-nonanediamine, 1,10-decanediamine, which can be derived from castor oil, and 1,12-dodecanediamine.

[0072] The dicarboxylic acid component is an aromatic dicarboxylic acid. Suitable aromatic dicarboxylic acids include, but are not limited to, terephthalic acid, isophthalic acid; naphthalene dicarboxylic acid (e.g., naphthalene-2,6-dicarboxylic acid); 4,4'-biphenylcarboxylic acid; 2,5-pyridinedicarboxylic acid; 2,4-pyridinedicarboxylic acid; 3,5-pyridinedicarboxylic acid; 2,2-bis(4-carboxyphenyl)propane; 2,2-bis(4-carboxyphenyl)hexafluoropropane; 2,2-bis(4-carboxyphenyl)ketone; 4,4'-bis(4-carboxyphenyl)sulfone; 2,2-bis(3-carboxyphenyl)propane; 2,2-bis(3-carboxyphenyl)hexafluoropropane; 2,2-bis(3-carboxyphenyl)ketone, and bis(3-carboxyphenoxy)benzene.

[0073] Polyamide PA2 is formed by the polycondensation of a diamine component and a dicarboxylic acid component as defined above. The amount of -NH2 from the diamine component and the amount of -COOH from the dicarboxylic acid component are substantially equimolar. The amine / acid ratio is 0.9 to 1.1, preferably 0.95 to 1.05, and even more preferably 0.98 to 1.02.

[0074] The polyamide PA2 may be a copolyamide, i.e. it may be derived from the polycondensation reaction of one or more lactams or amino acids and / or one or more diamine components and / or one or more dicarboxylic acid components, with the proviso that the diamine component is a diamine having 9 or more carbon atoms and the dicarboxylic acid component comprises at least one aromatic dicarboxylic acid.

[0075] Typically, when polyamide PA2 is formed from the polycondensation of a diamine component and a dicarboxylic acid component, it has a C / NHCO ratio of 7.5 or more. The C / NHCO ratio can be calculated as detailed above for polyamide PA1.

[0076] The polyamide PA2 can conveniently be selected from the group consisting of PA9T, PA9T / 8MeT, PA10T, PA9T / TMDT, PA10 / TMDT, PA 10T / 10I, PA9T / 9I, PA 11T, PA 12T, PA 9T / 11T, PA 9T / 12T, PA 10T / 11T, PA10T / 12T, PA 11T / 12T.

[0077] Polyamide PA2 may have a melting temperature of 200-320° C., preferably 220-300° C. The melting temperature is typically measured by differential scanning calorimetry (DSC) in the 2nd heat scan according to ASTM D3418 using a heating and cooling rate of 20° C. / min.

[0078] The layer (CL) may comprise one or more than one polyamide PA2.

[0079] In an advantageous embodiment, polyamide PA2 is the only polymer in layer (CL).

[0080] Layer (CL) comprises continuous reinforcing fibers impregnated with poly(arylene sulfide) polymer as described in detail below. As used herein, the expression "continuous reinforcing fibers" refers to fibers having a length of at least 5 mm. The length of the fibers corresponds to the longest dimension of the fibers.

[0081] In some embodiments, the continuous reinforcement fibers have a length in their longest dimension of at least 1 cm, at least 25 cm, or at least 50 cm. The length of the continuous reinforcement fibers depends on the shape and size of the finished part.

[0082] The continuous reinforcing fibers are selected from the group consisting of glass fibers, carbon fibers, aluminum fibers, metal fibers, ceramic fibers, titanium fibers, magnesium fibers, boron carbide fibers, rock wool fibers, steel fibers, aromatic polyamide fibers, and natural fibers (e.g., cotton, flax, and wood). Preferably, the continuous reinforcing fibers are selected from the group consisting of glass fibers, carbon fibers, aromatic polyamide fibers, and ceramic fibers. Advantageously, the continuous reinforcing fibers are carbon fibers.

[0083] In some embodiments, layer (CL) may include one or more additional continuous reinforcement fibers, each compositionally different and as described above.

[0084] In general, continuous reinforcing fibers account for at least 5.0% of the total volume of layer (CL). Typically, continuous reinforcing fibers constitute at least 10.0%, at least 15.0%, at least 20.0%, at least 25.0%, even at least 30.0% of the total volume of layer (CL). Continuous reinforcing fibers are no more than 80.0%, no more than 75.0%, even no more than 70.0% of the total volume of layer (CL). Continuous reinforcing fibers can conveniently account for 20.0% to 75.0%, 25.0% to 70.0%, 25.0% to 65.0% and even 30.0% to 60.0% of the total volume of layer (CL). Polymer matrix represents the remainder of the volume of layer (CL).

[0085] The continuous reinforcing fibers in the layer (CL) are typically aligned in a single direction. The fibers are typically aligned so that at least 70%, at least 80%, at least 90%, or at least 95% of the fibers have a direction within 30 degrees, within 25 degrees, within 20 degrees, within 15 degrees, or within 10 degrees of the direction of the other fibers.

[0086] In certain embodiments, the continuous reinforcement fibers in layer (CL) may be arranged at an angle to each other.The continuous reinforcement fibers may be arranged as a woven fabric or a layered fabric or any combination of one or more.

[0087] The layer (CL) can be manufactured by methods well known in the art. Typically, the manufacturing method comprises the steps of impregnating the continuous reinforcing fibers with polyamide PA2, and subsequently cooling or drying to form the layer (CL).

[0088] Impregnation of the continuous reinforcing fibers with polyamide PA2 can be carried out by a melt impregnation process comprising contacting the continuous reinforcing fibers with a melt of the polyamide polymer. After melt impregnation, the impregnated continuous reinforcing fibers are cooled to form a solid composite material.

[0089] Alternatively, impregnation can be performed by a solution or slurry process. In a solution process, a solution is formed by dissolving the polyamide polymer in a liquid medium. The solution is applied to the surface of the continuous reinforcement fibers, for example, by passing the continuous reinforcement fibers through a bath of the solution. The coated fibers are then heated and consolidated. In a slurry process, the continuous fibers are impregnated with polymer particles, for example, by passing the fibers through a suspension of particles in a liquid or a fluidized bed of particles. The fibers containing the polymer particles are then heated and consolidated.

[0090] When more than one layer (CL) is present, each layer (CL) may comprise the same or a different polyamide PA2, typically the same polyamide PA2.

[0091] The layer (CL) has a thickness typically between 100 and 500 microns. This thickness is adapted to provide a multilayer structure that can be easily shaped to provide an article, such as a container.

[0092] Multi-layer structure

[0093] The multilayer structure comprises at least one layer (BL) and at least one layer (CL) in contact with the at least one layer (BL), as defined above.

[0094] The multilayer structure may comprise up to ten layers (BL) and up to ten or even more than ten layers (CL).

[0095] The multilayer structure does not comprise an adhesive or cohesive layer between layer (BL) and layer (CL).

[0096] The multilayer structure may comprise more layers (BL) than layers (CL), or vice versa. Typically, the multilayer structure does not comprise alternating layers (BL) and layers (CL).

[0097] Advantageously, the multilayer structure comprises one, two, three, four, five, six, seven, eight, nine or ten layers (BL) and one, two, three, four, five, ten, 50, 100 or even more (such as 200 or 300) layers (CL).

[0098] In one embodiment, the multi-layer structure includes a single layer (BL) and a plurality of layers (CL).

[0099] In one aspect of this embodiment, when multiple layers (CL) are present, they have the same composition. There can be 2, 3, 5, 10, 50 and even 100, 200 or 300 layers (CL).

[0100] In an embodiment of the present invention, layer (BL) comprises polyamide PA1 having a C / NHCO ratio of 6.5 or less, and layer (CL) comprises polyamide PA2 having a C / NHCO ratio that is at least 20% greater than the C / NHCO ratio of polyamide PA1. Preferably, layer (BL) comprises polyamide PA1 having a C / NHCO ratio of 6.0 or less, and layer (CL) comprises polyamide PA2 having a C / NHCO ratio that is at least 20% greater than the C / NHCO ratio of polyamide PA1.

[0101] Despite the difference in C / NHCO ratio between PA1 and PA2, the multilayer structure of the present invention unexpectedly exhibited an excellent phase interface between PA1 and PA2, with no defects observed in RX chromatography.

[0102] The multilayer structure of the present invention may, for example, comprise the following:

[0103] a layer (BL) comprising a polyamide PA1 chosen from the group consisting of PA6, PA46, PA56, PA MXD6, PA PXD6, PA MXD6 / MXDI, PAMXD6 / PXD6, copolymers thereof and blends thereof; and a layer (CL) comprising a polyamide PA2 chosen from the group consisting of PA9T, PA9T / 8MeT, PA10T, PA10 / TMDT, PA 10T / 10I, PA9T / 9I, PA 11T, PA 12T, PA 9T / 10T, PA9T / 11T, PA 9T / 12T, PA 10T / 11T, PA 10T / 12T, PA 11T / 12T, copolymers thereof and blends thereof; or alternatively

[0104] a layer (BL) comprising a polyamide PA1 chosen from the group consisting of PA6, PA46, PA56, PA MXD6, PA PXD6, PA MXD6 / MXDI, PAMXD6 / PXD6, copolymers thereof and blends thereof; and a layer (CL) comprising a polyamide PA2 chosen from the group consisting of PA9T, PA9T / 8MeT, PA10T, PA10 / TMDT, PA 10T / 10I, PA9T / 9I, copolymers thereof and blends thereof.

[0105] The multilayer structure of the present invention may alternatively comprise the following:

[0106] a layer (BL) comprising a polyamide PA1 having a melting temperature of 180 to 300° C. and a layer (CL) comprising a polyamide PA2 having a melting temperature of 200 to 320° C.; or

[0107] a layer (BL) comprising a polyamide PA1 having a C / NHCO ratio of 6.5 or less, preferably from 6.5 to 5.0, and a layer (CL) comprising a polyamide PA2 having a C / NHCO ratio of at least 7.5.

[0108] In some embodiments, the multilayer structure may include an additional layer in contact with layer (CL) on the opposite side of layer (BL). The additional layer may or may not contain reinforcing fibers. The additional layer may or may not contain a polyamide polymer.

[0109] The multilayer structure of the present invention can be manufactured according to any method known in the art.

[0110] In an embodiment of the invention, layer (BL) and layer (CL) are manufactured separately and subsequently laminated together. Heat is typically applied to bond layer (BL) and layer (CL) together.

[0111] Products

[0112] Another object of the invention is an article for storing and / or transporting gases, comprising the multilayer structure as defined above.Notable non-limiting examples of articles are hoses, pipes, tubes, joints, tanks, reservoirs or generally containers.

[0113] Among these, the multilayer structure of the present invention is suitable for use as a hose for compressed gas, particularly hydrogen. Hoses for compressed hydrogen are used to load hydrogen from hydrogen stations into fuel cell vehicles and the like. Because hoses for compressed hydrogen are subjected to repeated temperature fluctuations (thermal cycling) from -40°C or lower to 90°C or higher during loading and unloading of high-pressure hydrogen, they are required to have high resistance to heat and pressure cycling, as well as hydrogen gas barrier properties.

[0114] A hose for high-pressure hydrogen is a hose comprising a multi-layer structure of the first object, wherein a layer (BL) contacts the compressed gas and a layer (CL) represents the outside of the hose.

[0115] The multilayer structure of the present invention is characterized by high heat resistance and good hydrogen barrier properties. These characteristics make the multilayer structure particularly well-suited for use in containers for storing gases under pressure, such as hydrogen.

[0116] Another object of the present invention is a container for storing or transporting gases, comprising a multilayer structure as defined above.

[0117] The term "vessel" is used herein to refer to a hollow container. The container of the present invention is in particular a hollow container for containing a gas, preferably a pressurized or compressed gas.

[0118] Layer (BL) denotes the inner layer of the container which is in contact with the gas to be transported or stored, also referred to below as the “liner.” Layer (CL) denotes the outer layer of the container.

[0119] The container is preferably a pressure vessel, ie a container suitable for storing and transporting gas under pressure.

[0120] The container, or preferably a pressure vessel, comprises a hollow body and at least one boss. A boss is known to those skilled in the art and refers to an opening to which a seal is attached, which allows gas or fluid to flow into and out of the container. The boss is typically made of metal.

[0121] The hollow body can have any shape that is suitable for storing a gas, in particular a gas under pressure.

[0122] In some conventional embodiments, the container has a cylindrical shape and bosses are placed at the ends. Frequently, the container has two bosses at each end of the cylindrical shape.

[0123] The shape of the hollow body is determined by the desired use. It is usually, but not exclusively, cylindrical, with a diameter between 10.0 cm and 1.0 m. The diameter may be at least 15.0 cm or larger.

[0124] The length of the hollow body also depends on the end use and can be, for example, between 50.0 cm and up to a length of 10.0 m. These larger lengths are typically used for gas transport. As an example, for containers in trucks, the length is typically between 1.0 m and 3.0 m.

[0125] The container of the present invention may have a 3 and 5.0m 3 Between, even 5.0dm 3 Up to 1.0m 3 The internal volume of the container may be at least 10.0 dm 3 , or even at least 15.0dm 3 The internal volume can be up to 1.0m 3 , even up to 0.5m 3 .

[0126] The container comprises a hollow body comprising, from the interior to the exterior of the container, at least one layer (BL), or liner, as defined above, and at least one layer of structural composite material in contact with the at least one layer (BL), the structural composite material being a layer (CL) as defined above. The layer (BL) is in contact with the gas contained in the container.

[0127] The liner is intended to provide a barrier between the fluid or gas and the layer (CL), thereby preventing leakage. Typically, the layer (CL) is positioned around the liner to provide mechanical properties, such as resistance to burst pressure.

[0128] The container may be manufactured according to any method known in the art.

[0129] For example, the liner can be prepared by blow molding, tube extrusion, injection molding and welding and / or rotational molding.The layer (CL) can then be applied to the outer surface of the liner by winding a tape comprising continuous reinforcing fibers and polyamide polymer PA2 around the hollow body made of the liner.

[0130] Other manufacturing methods known in the art for making pressure vessels may be used to make the vessels of the present invention.

[0131] Therefore, the present invention also relates to a method for producing a container, comprising the following steps:

[0132] a. Providing a layer (BL) in the form of a hollow body;

[0133] b. Providing a layer (CL) in the form of a continuous strip;

[0134] c. Wrapping the tape around the liner while consolidating the tape with heat;

[0135] d. Cooling the object obtained at the end of step c. to make it solid.

[0136] The term "tape" is understood herein to mean an elongated object having a longitudinal direction, a width, a thickness, and a cross-sectional aspect ratio, i.e., the ratio of thickness to width. The cross-section is defined as being substantially perpendicular to the longitudinal direction of the tape. The longitudinal, or machine, direction of the tape generally corresponds to the orientation of the endless fibers. The length of the tape is not particularly limited. The length can exceed 10 km and depends primarily on the continuous fibers and the method used to produce the tape. However, for convenience, the tape can be manufactured in smaller sizes, depending on the requirements of the intended application.

[0137] Consolidation is preferably performed by means of heat, such as heat provided by a laser (eg an infrared laser), or a heating element such as an oven.

[0138] Containers according to the present invention exhibit a nominal pressure of at least 2.5 MPa, typically at least 20.0 MPa, or even at least 30.0 MPa. The nominal pressure may be up to 70.0 MPa, 100 MPa, or even 150.00 MPa and greater. Advantageously, the container of the present invention has a nominal pressure of 20.0 to 70.0 MPa.

[0139] For hydrogen gas storage using containers according to the present invention, a burst pressure of at least 157.5 MPa can be achieved. Containers for compressed hydrogen storage typically require a nominal pressure of 35.0 MPa or 70.0 MPa. The burst pressures measured according to ECE R134 are typically up to 78.8 MPa and 157.5 MPa, respectively.

[0140] The multilayer structure of the present invention is characterized by good hydrogen barrier properties and mechanical properties both at high and low temperatures.The multilayer structure of the present invention further exhibits limited water absorption.

[0141] Another object of the present invention is a compressed gas contained in a container, comprising the multilayer structure of the first object, wherein the layer (BL) 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.

[0142] 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.

[0143] Another object of the invention is a vehicle comprising a container or a compressed gas contained in a container.

[0144] The vehicle may be a car, truck, train, boat, city mover, airplane, helicopter, or any other vehicle that can be powered using conversion of gas to energy by any means.

[0145] The above embodiments are intended to be illustrative rather than restrictive. Other embodiments are within the scope of the invention. In addition, although the present invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that changes may be made in form and detail without departing from the spirit and scope of the present invention.

[0146] Examples

[0147] Material

[0148] PA1-1: MX Nylon S6007, a PA MXD6 nylon polymer commercially available from Mitsubishi Gas Chemical Co.

[0149] PA1-2: BXT 2000, an impact-modified PA MXD6 / MXDI copolymer, commercially available from Solvay Specialty Polymer USA, LLC

[0150] PA1-3: 1004, namely PA 6T / 6I / 66 copolymer, which is commercially available from Solvay Specialty Polymers LLC, USA

[0151] PA1-4: ET 1000HS NT, an impact-modified PA 6T / 6I / 66 copolymer, is commercially available from Solvay Specialty Polymers LLC, USA

[0152] PA2-1: GC98018, PA 9T / 8MeT copolymer, commercially available from Kuraray

[0153] PA12 is L25NZ, an impact-modified PA12, is commercially available from EMSChemie

[0154] Tensile testing

[0155] Tensile properties are measured according to ISO 527-2 using samples meeting the requirements of ISO 1BA at a test speed of 5 mm / min and the specified temperature. The ISO 1BA samples are annealed at a temperature 20°C above their glass transition temperature for a period of 2 hours to ensure complete crystallization before tensile testing.

[0156] Determination of H2 permeability coefficient

[0157] Samples for hydrogen permeation testing were prepared as follows. The polymer was dried overnight at 107°C in a desiccant drying oven with a dew point of -40°C to ensure that the material was dry before injection molding into plaques. Following the polymer supplier's recommended injection molding process guidelines, the material was injection molded into 10 cm × 10 cm × 0.32 cm plaques using a 250 ton Sumitomo SE 250EV-A HD all-electric injection molding machine. The molding machine was equipped with a 45 mm screw size with a maximum screw speed of 250 rpm and a maximum shot capacity of 0.34 dm 3 The machine had a maximum shot size of 21 cm and a maximum injection pressure of 215 MPa. The plates were annealed at a temperature 20° C. above their glass transition temperature for a period of 2 h to ensure complete crystallization prior to hydrogen permeation testing.

[0158] The sample was placed in a sealed chamber and checked for airtightness by applying hydrogen at 1 MPa on the feed side. The chamber was then adjusted to the test temperature. H₂ was fed to the feed side at 1 MPa. On the permeate side, synthetic air was fed at a controlled flow rate, and H₂ was measured using a calibrated Inficon Sentrac H₂ leak detector until a stable H₂ value was achieved to confirm stationary conditions.

[0159] The permeability coefficient is calculated taking into account the sample thickness, exposed surface, carrier gas flow rate, and pressure.

[0160] The results are shown in Table 1.

[0161] Table 1

[0162]

[0163] The data in Table 1 show a good compromise between hydrogen permeability and mechanical properties. The combination of the above properties allows the design of thinner liners without compromising the mechanical properties of the article.

[0164] Preparation of multilayer structures

[0165] Starting from unidirectional PA 2-1 / carbon fiber tapes using polymer PA 2-1 and a 60% volume fraction of carbon fibers Hyosung 2550,12k (hereinafter CF), composite samples with a thickness of 4 mm were prepared in a press at 320° C. with an applied pressure of 0.5 MPa for 5 minutes and 2 MPa for 1 minute.

[0166] Samples of PA 1-1 sheet and PA 1-2 sheet (as described above) as layer (BL) were co-consolidated with a PA 2-1 / CF composite sample (as layer (CL)) in a press with limited contact time under the following operating conditions (to simulate the conditions of the winding process): preheating of the mold at 285°C; contact time of 3 minutes, contact pressure of 0.7 MPa.

[0167] At the end of the consolidation step, the samples were analyzed by X-ray tomography using a 150 kV source and a focus of 20 μ. The results are reported in Table 2.

[0168] Table 2

[0169]

[0170] The interface between layer (BL) and layer (CL) in the multilayer structure defined above shows no defects, regardless of the different nature of the polyamide polymers in the layers.

Claims

1. A multilayer structure comprising at least one barrier layer [layer (BL)] and at least one composite material layer [layer (CL)] in contact with the at least one barrier layer, wherein: - layer (BL) comprises polyamide polymer PA1; and - layer (CL) comprising continuous reinforcing fibers and polyamide polymer PA2, wherein: the polyamide polymer PA1 is selected from the group consisting of polyamides comprising repeating units derived from the polycondensation of: i) caprolactam; and / or ii) at least one diamine component having 4 to 8 carbon atoms and at least one dicarboxylic acid component having 8 or fewer carbon atoms; The polyamide polymer PA2 is selected from the group consisting of polyamides consisting of repeating units derived from the polycondensation of at least one diamine component having at least 9 carbon atoms, at least one aromatic dicarboxylic acid component and optionally one or more components selected from the group consisting of lactams, amino acids and aliphatic dicarboxylic acids.

2. The multilayer structure according to claim 1, wherein Polyamide PA1 has a C / NHCO ratio of 6.5 or less, preferably 5.0 to 6.

5.

3. The multilayer structure according to claim 1 or 2, wherein Polyamide PA2 has a C / NHCO ratio which is at least 20% greater than this C / NHCO ratio of polyamide PA1.

4. The multilayer structure according to any one of claims 1 to 3, wherein The polyamide PA1 is selected from the group consisting of PA6, PA46, PA56, PA MXD6, PA PXD6, PA MXD6 / MXDI, PA MXD6 / PXD6, copolymers thereof and blends thereof.

5. The multilayer structure according to any one of claims 1 to 4, wherein The polyamide PA2 is selected from the group consisting of PA9T, PA9T / 8MeT, PA10T, PA10 / TMDT, PA 10T / 10I, PA9T / 9I, PA 11T, PA 12T, PA 9T / 10T, PA9T / 11T, PA 9T / 12T, PA 10T / 11T, PA 10T / 12T, PA 11T / 12T, copolymers thereof and blends thereof.

6. The multilayer structure according to any one of claims 1 to 5, wherein Polyamide PA1 has a melting temperature of 180 to 300°C, and polyamide PA2 has a melting temperature of 200 to 320°C.

7. A multilayer structure as claimed in any one of the preceding claims, wherein The continuous reinforcing fibers have a length of at least 5 mm.

8. The multilayer structure according to any one of the preceding claims, wherein The continuous reinforcing fibers are selected from the group consisting of glass fibers, carbon fibers, aromatic polyamide fibers, and ceramic fibers.

9. The multilayer structure according to any one of the preceding claims, wherein The amount of these continuous reinforcing fibers ranges from 15.0% to 80.0% relative to the total volume of the layer (CL).

10. The multilayer structure as claimed in any one of the preceding claims, consisting of one or more layers (BL) and one or more layers (CL).

11. An article for storing and / or transporting gases, comprising the multilayer structure according to any one of the preceding claims.

12. The article of claim 11 in the form of a container or a hose.

13. The container according to claim 12, which is in the shape of a hollow body, wherein the hollow body has one or more of the following: -10.0 to 1.0 m diameter; - 50.0 cm to 10.0 m in length; and -3.5dm 3 Up to 5.0m 3 internal volume.

14. A compressed gas contained in a container as claimed in any one of claims 12 or 13, wherein the compressed gas is in contact with the layer (BL).

15. The compressed gas of claim 14, wherein the compressed gas is selected from the group consisting of hydrogen, oxygen, nitrogen, argon, helium, methane, propane, compressed natural gas, CO2, and ammonia.

16. A vehicle comprising a container as claimed in any one of claims 12 or 13 or a compressed gas as claimed in claim 14 or 15.

17. Use of the hose according to claim 12 for transporting compressed gas.

18. Use of the container according to any one of claims 12 or 13 for storing or transporting compressed gas.

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