High-pressure container or high-pressure pipe

Abstract

The present invention provides a high-pressure container or high-pressure pipe that is for use in storing or transferring high-pressure hydrogen gas and includes a multilayer structure, wherein the multilayer structure includes a layer (X) containing an ethylene-vinyl alcohol copolymer (A) and a thermoplastic elastomer (B), and a layer (Y) containing a thermoplastic resin (C), the multilayer structure does not include any layers having a hydrogen permeation rate of 5000 cc·20 μm / (m2·day·atm) or more at 20°C and 0% RH inside the layer (X), and when a layer (Y1) positioned inside the layer (X) is included as the layer (Y) in the multilayer structure, the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is less than 5000 cc·20 μm / (m2·day·atm) and the average thickness of the layer (Y1) is 900 μm or less. As a result, it is possible to provide a container or pipe for high-pressure hydrogen gas that offers excellent blister resistance, has high breaking elongation at low temperatures, and thus does not break easily due to deformation.

Description

High-pressure vessels or high-pressure pipes

[0001] The present invention relates to a high-pressure vessel or pipe including a multilayer structure, which is used to store or transport high-pressure hydrogen gas.

[0002] Because hydrogen gas does not produce carbon dioxide when burned, it is a fuel with a low environmental impact, and its use has been widely considered in recent years. In particular, containers and pipes used as fuel for automobiles and other transportation machinery must have not only hydrogen gas barrier properties, but also strength to withstand high pressures and deformation, and light weight to reduce fuel consumption. To date, various resin high-pressure containers and high-pressure pipes have been proposed for storing or transporting high-pressure hydrogen gas.

[0003] Patent Document 1 describes a hydrogen fuel tank and a hydrogen fuel pipe that have a single-layer liner disposed inside, the liner being made of a resin composition comprising 80 to 40% by weight of a saponified ethylene-vinyl acetate copolymer (A) and 20 to 60% by weight of an acid-modified ethylene-α-olefin copolymer rubber (B) and / or an acid-modified thermoplastic elastomer (B'). This is said to enable both hydrogen gas barrier properties and impact resistance at low temperatures to be achieved.

[0004] Patent Document 2 describes a multilayer structure for storing or transporting a gas containing hydrogen, the multilayer structure comprising at least three layers including: a. an inner layer comprising at least one first polymer; b. an intermediate layer comprising an ethylene-vinyl alcohol copolymer; and c. an outer layer comprising at least one second polymer, wherein the water vapor permeability of the inner layer is lower than that of the outer layer. It is said that by making the water vapor permeability of the inner layer lower than that of the outer layer, it is possible to improve hydrogen gas barrier properties.

[0005] JP 2005-68300 A JP 2023-547754 A

[0006] When a resin material comes into contact with high-pressure hydrogen gas, it is inevitable that hydrogen will dissolve in the resin. However, if the pressure is then suddenly reduced, the hydrogen dissolved in the resin will vaporize and expand, which can cause defects called "blisters" in the resin material. In addition to the typical blisters, "blisters" can also include various other types of defects, such as voids, cracks, and delamination. In this specification, "blisters" can also include these various types of defects. Furthermore, since the temperature of the resin drops due to adiabatic expansion during a sudden pressure drop, resin molded products that handle high-pressure hydrogen gas must be able to withstand deformation at low temperatures.

[0007] For example, as described in Patent Document 1, when a single-layer liner containing an ethylene-vinyl alcohol copolymer (hereinafter sometimes referred to as "EVOH") is used, a high-strength tank body or pipe body is placed on the outside, resulting in a heavy total weight. Furthermore, the multilayer structure described in Patent Document 2 fails to achieve both prevention of breakage due to deformation at low temperatures and blister resistance. The present invention has been made to solve the above-mentioned problems, and aims to provide a high-pressure container or high-pressure pipe used for storing or transporting high-pressure hydrogen gas, which includes a multilayer structure that has excellent blister resistance, a large breaking elongation at low temperatures, and is resistant to breakage due to deformation.

[0008] The above-mentioned problems are solved by providing the following invention: [1] A high-pressure container or high-pressure pipe including a multilayer structure used for storing or transporting high-pressure hydrogen gas, wherein the multilayer structure includes a layer (X) containing an ethylene-vinyl alcohol copolymer (A) and a thermoplastic elastomer (B), and a layer (Y) containing a thermoplastic resin (C), and the multilayer structure includes a layer (Y) inside the layer (X) having a hydrogen permeation rate of 5000 cc·20 μm / (m) at 20°C and 0% RH. ２ When the multilayer structure includes, as the layer (Y), a layer (Y1) located inside the layer (X), the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc·20 μm / (m ２1. A high-pressure container or high-pressure pipe having a total average thickness of less than 100 μm / day·atm and an average thickness of layer (Y1) of 900 μm or less. [2] The high-pressure container or high-pressure pipe according to [1], wherein the multilayer structure has a total average thickness of 500 μm or more. [3] The high-pressure container or high-pressure pipe according to [1] or [2], wherein the layer (X) has an average thickness of 30 μm or more. [4] The high-pressure container or high-pressure pipe according to any one of [1] to [3], wherein the mass ratio (B / A) of the thermoplastic elastomer (B) to the ethylene-vinyl alcohol copolymer (A) in layer (X) is 3 / 97 or more and 35 / 65 or less. [5] The high-pressure container or high-pressure pipe according to any one of [1] to [4], wherein the resin components contained in layer (X) consist essentially of the ethylene-vinyl alcohol copolymer (A) and the thermoplastic elastomer (B). [6] The high-pressure container or high-pressure pipe according to any one of [1] to [5], wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer (A) is 15 mol % or more and 35 mol % or less. [7] The high-pressure container or high-pressure pipe according to any one of [1] to [6], wherein the thermoplastic elastomer (B) is an acid-modified thermoplastic elastomer. [8] The high-pressure container or high-pressure pipe according to any one of [1] to [7], wherein the thermoplastic elastomer (B) is at least one selected from the group consisting of an olefin-based thermoplastic elastomer, a styrene-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyamide-based elastomer, and a polyester-based thermoplastic elastomer. [9] The high-pressure container or high-pressure pipe according to any one of [1] to [8], wherein the layer (Y) contains a polyamide as the thermoplastic resin (C).

[10] The high-pressure container or high-pressure pipe according to [9], wherein the layer (Y) contains more than 50% by mass of nylon 6 as the polyamide.

[11] The high-pressure container or high-pressure pipe according to [9] or

[10] , wherein the layer (Y) contains 10 to 30% by mass of nylon 6 / 66 as the polyamide.

[12] The high-pressure container or high-pressure pipe according to any one of [1] to

[11] , wherein the layer (Y) contains 10 to 30 mass% of a thermoplastic elastomer (B').

[13] The high-pressure container or high-pressure pipe according to

[12] , wherein the thermoplastic elastomer (B) contained in the layer (X) and the thermoplastic elastomer (B') contained in the layer (Y) are the same type of thermoplastic elastomer.

[14] The high-pressure container or high-pressure pipe according to any one of [1] to [8], wherein the layer (Y) contains a polyolefin as the thermoplastic resin (C).

[15] The multilayer structure has, as the layer (Y), a layer (Y1) located inside the layer (X), and the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc·20 μm / (m. ２

[16] The high-pressure container or high-pressure pipe according to any one of [1] to

[14] , wherein the thermal expansion coefficient (Tc) of the layer (Y1) is less than 1 / 2 day atm and the average thickness of the layer (Y1) is 900 μm or less.

[16] The high-pressure container or high-pressure pipe according to

[15] , wherein the layer (Y1) comprises a polyamide.

[17] The high-pressure container or high-pressure pipe according to

[15] or

[16] , wherein the layer (Y1) has an average thickness of 50 to 500 μm.

[18] The high-pressure container or high-pressure pipe according to any one of [1] to

[17] , wherein the layer (Y2) is located outside the layer (X) as the layer (Y).

[19] The high-pressure container or high-pressure pipe according to

[18] , wherein the layer (Y2) comprises a polyamide.

[20] The high-pressure container or high-pressure pipe according to

[18] , wherein the layer (Y2) comprises a polyolefin.

[21] The high-pressure container or high-pressure pipe according to any one of

[18] to

[20] , wherein the average thickness of the layer (Y2) is 100 to 1500 μm.

[22] The multilayer structure has, as the layer (Y), a layer (Y1) located inside the layer (X) and a layer (Y2) located outside the layer (X), and the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc 20 μm / (m ２

[23] The high-pressure container or high-pressure pipe according to any one of [1] to

[22] , further comprising a reinforcing layer on the outside of the multilayer structure.

[0009] The high-pressure container and high-pressure pipe of the present invention, which are used for storing or transporting high-pressure hydrogen gas, have excellent hydrogen gas barrier properties and excellent blister resistance. The high-pressure container and high-pressure pipe contain a resin multilayer structure, which is lightweight and has a high breaking elongation at low temperatures, making it less likely to be broken by deformation.

[0010] The present invention relates to a high-pressure container or high-pressure pipe containing a multilayer structure, which is used for storing or transporting high-pressure hydrogen gas. The multilayer structure includes a layer (X) containing an ethylene-vinyl alcohol copolymer (A) (hereinafter sometimes referred to as "EVOH (A)") and a thermoplastic elastomer (B), and a layer (Y) containing a thermoplastic resin (C). The multilayer structure further includes a layer (Y) on the inside of the layer (X) that has a hydrogen permeation rate of 5000 cc·20 μm / (m) at 20°C and 0% RH. ２ Furthermore, when the multilayer structure includes a layer (Y1) located inside the layer (X) as the layer (Y), the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc·20 μm / (m ２ The hydrogen permeation rate is measured in accordance with the method described in ISO 15105-2:2003. The present invention will be described in detail below.

[0011] The multilayer structure contained in the high-pressure vessel or high-pressure pipe of the present invention comprises a layer (X) and a layer (Y). The layer (X) comprises EVOH (A) and a thermoplastic elastomer (B), and the layer (Y) comprises a thermoplastic resin (C).

[0012] The EVOH (A) contained in the layer (X) contains ethylene units, vinyl ester units, and vinyl alcohol units as main structural units. EVOH is usually obtained by copolymerizing ethylene and a vinyl ester to obtain an ethylene-vinyl ester copolymer, and subsequently saponifying the copolymer. Vinyl acetate is preferably used as the vinyl ester.

[0013] The ethylene unit content of EVOH (A), i.e., the ratio of the number of ethylene units to the total number of monomer units in EVOH, is preferably 15 to 60 mol%. An ethylene unit content of 15 mol% or more facilitates melt molding, and the higher the ethylene content, the better the melt moldability. The ethylene unit content is more preferably 20 mol% or more, and even more preferably 23 mol% or more. On the other hand, an ethylene unit content of 60 mol% or less improves hydrogen gas barrier properties. The ethylene unit content is more preferably 50 mol% or less, and even more preferably 40 mol% or less. When particularly high hydrogen gas barrier properties are required, the ethylene unit content is preferably 35 mol% or less, and more preferably 30 mol% or less.

[0014] The saponification degree of EVOH (A), i.e., the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl acetate units in EVOH, is preferably 80 mol% or more. A saponification degree of 80 mol% or more improves hydrogen gas barrier properties. The saponification degree is more preferably 98 mol% or more, and even more preferably 99 mol% or more. The saponification degree may be 100 mol% or less.

[0015] EVOH (A) may contain other monomer units in addition to ethylene units, vinyl acetate units, and vinyl alcohol units. The inclusion of other monomer units may increase the breaking elongation of layer (X) at low temperatures. From the viewpoint of hydrogen permeation rate, the content of such other monomer units is preferably 10 mol % or less, more preferably 5 mol % or less, even more preferably 2 mol % or less, and most preferably contains substantially no other structural units. Examples of other monomers include alkenes such as propylene, butylene, pentene, and hexene; 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3 ... -butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methylene Examples of the alkylene compound include alkenes having an ester group such as propane or saponified products thereof; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, or the like, or anhydrides, salts, or mono- or dialkyl esters thereof; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallylsulfonic acid, or salts thereof; vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, and γ-methacryloxypropylmethoxysilane; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, and vinylidene chloride.

[0016] The layer (X) contains a thermoplastic elastomer (B) in addition to the EVOH (A). By containing the thermoplastic elastomer (B), the breaking elongation of the layer (X) at low temperatures increases, making the multilayer structure less susceptible to destruction by deformation due to pressure changes or external forces.

[0017] The thermoplastic elastomer (B) contained in layer (X) is not particularly limited as long as it is a melt-moldable elastomer. In order to increase the breaking elongation of the multilayer structure at low temperatures, it is preferable that the breaking elongation at 23°C and 0% RH measured in accordance with ASTM D638 is 100% or more, that is, the sample breaks at a length at least twice its original length in a tensile test. The tensile breaking elongation of the thermoplastic elastomer (B) is more preferably 200% or more, and even more preferably 500% or more.

[0018] Examples of the thermoplastic elastomer (B) include an olefin-based thermoplastic elastomer, a styrene-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, and a polyester-based thermoplastic elastomer, and a combination of these may be used.

[0019] Olefin-based thermoplastic elastomers are thermoplastic elastomers whose main component is polyolefin. Typically, they are elastomers having a microphase-separated structure of crystalline hard segments such as polyethylene or polypropylene and soft segments such as ethylene-α-olefin random copolymers. Suitable examples of olefin-based thermoplastic elastomers include thermoplastic elastomers made of ethylene-α-olefin copolymers and propylene-ethylene copolymers, with ethylene-α-olefin copolymers being particularly suitable. The carbon number of the α-olefin constituting the ethylene-α-olefin copolymer is preferably 3 or more and 8 or less, more preferably 3 or more and 6 or less, and even more preferably 3 or 4.

[0020] Styrenic thermoplastic elastomers are thermoplastic elastomers whose hard segments are mainly composed of polystyrene. Typical examples include block copolymers containing high-Tg hard segments made of styrene polymers and low-Tg soft segments made of polymers such as butadiene, isoprene, and isobutylene.

[0021] Polyurethane thermoplastic elastomers are block copolymers consisting of hard segments containing urethane bonds and soft segments. A typical hard segment consists of a polyurethane block formed by the reaction of a short-chain glycol such as 1,4-butanediol with a diisocyanate. A typical soft segment consists of a block derived from a long-chain glycol such as a polyether diol or polyester diol.

[0022] Thermoplastic polyamide elastomers are block copolymers consisting of hard segments containing amide bonds and soft segments. Typical hard segments consist of blocks of polyamides such as nylon 6 and nylon 12, while soft segments consist of blocks derived from long-chain glycols such as polyether diols and polyester diols.

[0023] Thermoplastic polyester elastomers are block copolymers consisting of hard and soft segments containing ester bonds. The hard segments typically consist of blocks of polyester such as polybutylene terephthalate, while the soft segments consist of blocks derived from long-chain glycols such as polytetramethylene glycol.

[0024] The thermoplastic elastomer (B) is preferably an acid-modified thermoplastic elastomer. By acid-modifying the thermoplastic elastomer (B), compatibility with EVOH is improved, and the breaking elongation at low temperatures of the layer (X) and the multilayer structure is increased, thereby making it possible to obtain a high-pressure container and a high-pressure pipe that are resistant to breakage due to deformation.

[0025] In this case, the acid value of the acid-modified thermoplastic elastomer (B) is preferably 8.5 mgKOH / g to 15 mgKOH / g. The acid value is more preferably 9 mgKOH / g or more, even more preferably 10 mgKOH / g or more, and particularly preferably 11 mgKOH / g or more. The acid value is more preferably 14 mgKOH / g or less, and even more preferably 13 mgKOH / g or less. When multiple types of thermoplastic elastomers (B) are used, for example, when an unmodified thermoplastic elastomer and an acid-modified thermoplastic elastomer are used in combination, the weighted average of the acid values ​​of those thermoplastic elastomers is taken as the acid value of the thermoplastic elastomer (B).

[0026] In the case of olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers, acid modification can be achieved by copolymerizing an olefin having a carboxyl group or its anhydride. For example, acid-modified elastomers can be obtained by copolymerizing unsaturated monomers such as maleic acid, maleic anhydride, fumaric acid, itaconic acid, and acrylic acid. Among these unsaturated monomers, maleic anhydride is particularly preferred. The unsaturated monomer may be copolymerized when producing the hard segment or soft segment, or may be introduced by graft modification into an unmodified thermoplastic elastomer. Among acid-modified thermoplastic elastomers, acid-modified ethylene-α-olefin copolymers are particularly preferred. The ethylene-α-olefin copolymers to be acid-modified are as described above.

[0027] In the case of polyurethane-based thermoplastic elastomers, polyamide-based elastomers, and polyester-based thermoplastic elastomers, the thermoplastic elastomers can be acid-modified by using those having a carboxyl group or its anhydride in the monomer units constituting the hard or soft segments. However, polyurethane-based thermoplastic elastomers and polyamide-based elastomers have good compatibility with EVOH even without acid modification, so there is not much benefit to acid modification.

[0028] The mass ratio (B / A) of the thermoplastic elastomer (B) to the EVOH (A) in the layer (X) is preferably 3 / 97 or more and 35 / 65 or less. By setting the mass ratio (B / A) within this range, a sea-island structure in which island phases of the thermoplastic elastomer (B) are dispersed in a sea phase of the EVOH (A) is easily formed in the layer (X), resulting in improved hydrogen gas barrier properties. A mass ratio (B / A) of 3 / 97 or more effectively increases the breaking elongation at low temperatures of the layer (X) and the multilayer structure. The mass ratio (B / A) is more preferably 5 / 95 or more, and even more preferably 7 / 93 or more. On the other hand, a mass ratio (B / A) of 35 / 65 or less effectively prevents deterioration of the hydrogen gas barrier properties of the layer (X) and the multilayer structure. The mass ratio (B / A) is more preferably 25 / 75 or less, even more preferably 15 / 85 or less, and particularly preferably 13 / 87 or less. The proportion of EVOH (A) and thermoplastic elastomer (B) in the resin components contained in layer (X) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Furthermore, the resin components contained in layer (X) preferably consist essentially of EVOH (A) and thermoplastic elastomer (B), and may consist essentially of EVOH (A) and thermoplastic elastomer (B). Here, "consisting essentially of" allows for the inclusion of optional components to the extent that they do not affect the effects of the present invention. In this specification, "consisting only of" means excluding optional components other than impurities that are inevitably contained. This also applies to the following explanations in this specification.

[0029] In the layer (X), it is preferable to form a sea-island structure in which island phases of thermoplastic elastomer (B) are dispersed in a sea phase of EVOH (A). This allows for a multilayer structure with a low hydrogen permeation rate to be obtained. In the examples of the present specification, even when a certain amount (5 to 35 mass%) of thermoplastic elastomer (B) with an extremely high hydrogen permeation rate is blended with EVOH (A), the hydrogen permeation rate is not significantly higher than when EVOH (A) is used alone (Comparative Example 1), and it is believed that the above-mentioned sea-island structure is formed in these examples. In such a sea-island structure, finer particles of EVOH (A) may be dispersed among the particles of thermoplastic elastomer (B) that constitute the island phases.

[0030] The layer (X) may contain various additives in addition to the resin component. For example, carboxylic acid compounds, phosphoric acid compounds, boron compounds, metal salts, antioxidants, ultraviolet absorbers, plasticizers, lubricants, stabilizers, surfactants, colorants, antistatic agents, desiccants, crosslinking agents, fillers, various fibers, etc. may be appropriately blended. Furthermore, the layer (Y) may contain similar additives.

[0031] The carboxylic acid compound may be a monocarboxylic acid, a polycarboxylic acid, or a combination thereof. The carboxylic acid compound may be an ion, and the carboxylic acid ion may form a salt with a metal ion. The content of the carboxylic acid and the carboxylic acid ion is preferably 50 to 400 ppm. Suitable examples of the carboxylic acid compound include aliphatic carboxylic acids such as acetic acid and stearic acid.

[0032] The phosphate compound is not particularly limited, and various acids such as phosphoric acid and phosphorous acid, and salts thereof, can be used. The phosphate may be contained in the form of primary phosphate, secondary phosphate, or tertiary phosphate, with primary phosphate being preferred. The cation species is also not particularly limited, but alkali metal salts are preferred. Of these, sodium dihydrogen phosphate and potassium dihydrogen phosphate are preferred. When layer (X) contains a phosphate compound, the content of the phosphate compound is preferably 5 to 100 ppm in terms of phosphate radical.

[0033] The boron compound is not particularly limited, and examples thereof include boric acids, borate esters, borate salts, boron hydrides, and the like. Specifically, examples of boric acids include orthoboric acid, metaboric acid, and tetraboric acid. Examples of borate esters include triethyl borate and trimethyl borate. Examples of borates include alkali metal salts, alkaline earth metal salts, and borax of the various boric acids listed above. Among these compounds, orthoboric acid (hereinafter sometimes simply referred to as boric acid) is preferred. When layer (X) contains a boron compound, the content of the boron compound is preferably 50 to 400 ppm in terms of elemental boron. A boron compound content of 50 ppm or more tends to suppress torque fluctuations during heat melting. On the other hand, a boron compound content of 400 ppm or less tends to maintain good moldability.

[0034] The cation species of the alkali metal salt is not particularly limited, but sodium salt or potassium salt is preferred. The anion species of the alkali metal salt is also not particularly limited. It can be added as a carboxylate, carbonate, hydrogencarbonate, phosphate, hydrogenphosphate, borate, hydroxide, etc. When layer (X) contains an alkali metal salt, the content of the alkali metal salt is preferably 40 to 500 ppm in terms of metal element. When the content of the alkali metal salt is 40 ppm or more, interlayer adhesion tends to be good. On the other hand, when the content of the alkali metal salt is 500 ppm or less, melt stability tends to be excellent.

[0035] The cation species of the alkaline earth metal salt is not particularly limited, but magnesium salt or calcium salt is preferred. The anion species of the alkaline earth metal salt is also not particularly limited. It can be added as a carboxylate, carbonate, hydrogencarbonate, phosphate, hydrogenphosphate, borate, hydroxide, etc. The content of the alkaline earth metal salt is preferably 10 to 300 ppm. When layer (X) contains an alkaline earth metal salt, the generation of deteriorated products such as gels during repeated melt molding of the molded body tends to be suppressed. It is also preferable to use a polyvalent metal salt such as a zinc salt instead of the alkaline earth metal salt.

[0036] In the layer (X), the proportion of the EVOH (A) and the thermoplastic elastomer (B) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more.

[0037] The method for mixing EVOH (A) and thermoplastic elastomer (B) is not particularly limited, but a method in which they are melt-kneaded in an extruder is preferred. When molding the multilayer structure, EVOH (A) and thermoplastic elastomer (B) may be melt-kneaded, but a preferred method is to thoroughly melt-knead EVOH (A) and thermoplastic elastomer (B) in a twin-screw extruder or the like, cut them, and prepare pellets in advance, which are then introduced into a molding machine for molding the multilayer structure.

[0038] The hydrogen permeation rate of the layer (X) per unit thickness (20 μm) at 20° C. and 0% RH is 200 cc·20 μm / (m ２ The hydrogen permeation rate is preferably 100 cc·20 μm / (m·day·atm) or less. ２ ·day·atm) or less, and more preferably 80cc·20μm / (m ２ ・day・atm) or less.

[0039] The multilayer structure contained in the high-pressure container or high-pressure pipe of the present invention includes, in addition to the layer (X) containing EVOH (A) and thermoplastic elastomer (B), a layer (Y) containing a thermoplastic resin (C). By including layer (Y) in addition to layer (X) having excellent hydrogen gas barrier properties, the thickness of the multilayer structure can be increased, thereby increasing its rigidity. Furthermore, EVOH is generally a hard resin that is difficult to stretch, and even when a thermoplastic elastomer (B) is mixed with it, its breaking elongation at low temperatures is still insufficient. In contrast, by laminating layer (Y) containing another thermoplastic resin (C), the breaking elongation of the multilayer structure at low temperatures can be sufficiently increased.

[0040] The multilayer structure included in the high-pressure container and high-pressure pipe of the present invention is integrally melt-molded. For example, a multilayer structure including layer (X) and layer (Y) can be integrally molded by co-extrusion molding or coinjection molding. Therefore, even if the exterior of the integrally molded multilayer structure is covered with reinforcing layers made of metal, FRP, or the like to form a laminated structure, these reinforcing layers do not constitute the multilayer structure of the present invention.

[0041] The thermoplastic resin (C) used in the layer (Y) is a resin having a higher hydrogen permeation rate than the layer (X). The hydrogen permeation rate of the thermoplastic resin (C) at 20°C and 0% RH is 200 cc·20 μm / (m ２ The thermoplastic resin (C) is appropriately selected depending on the application, and polyamide, polyolefin, polyester, styrene-based resin, polyurethane, acrylic resin, etc. can be used.

[0042] The layer (Y) may be a layer (Y1) located inside the layer (X), or a layer (Y2) located outside the layer (X). That is, the multilayer structure included in the high-pressure container or high-pressure pipe of the present invention has at least one of a layer (Y1) and a layer (Y2). Therefore, the multilayer structure of the present invention may have any of a Y1 / X, X / Y2, or Y1 / X / Y2 configuration. Furthermore, the layer (Y1) or the layer (Y2) may be composed of a plurality of layers, and the plurality of layers may be made of the same type of resin or different resins.

[0043] The total average thickness of the multilayer structure contained in the high-pressure container or high-pressure pipe of the present invention is preferably 500 μm or more. The thicker the total average thickness, the more rigid the multilayer structure, making it less susceptible to destruction due to pressure changes in the hydrogen gas contained therein or deformation due to external forces. The total average thickness is more preferably 650 μm or more, and even more preferably 750 μm or more. On the other hand, if the total average thickness is too thick, the weight of the multilayer structure becomes too large. The total average thickness is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 2 mm or less. Note that, unless otherwise specified, the "total average thickness" of the multilayer structure refers to the average value of thicknesses measured at any five locations. Furthermore, the "average thickness" of each layer described below also refers to the average value of thicknesses measured at any five locations, unless otherwise specified.

[0044] In the multilayer structure, it is also preferable that the average thickness of the layer (X) is 30 μm or more. If the average thickness of the layer (X) is too thin, the hydrogen gas barrier property will decrease. The average thickness is more preferably 50 μm or more, and even more preferably 70 μm or more. On the other hand, if the average thickness of the layer (X) is too thick, the production cost will increase. The average thickness is usually 500 μm or less, and preferably 200 μm or less.

[0045] The multilayer structure contained in the high-pressure vessel or high-pressure pipe of the present invention has a hydrogen permeation rate of 5000 cc·20 μm / (m ２ That is, the layer (Y1) is not included and the layer (X) is the innermost layer, or the layer (Y1) located inside the layer (X) does not include a layer having a hydrogen permeation rate of 5000 cc·20 μm / (m) at 20° C. and 0% RH. ２ Furthermore, when the layer (Y1) is included, the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH must be less than 5000 cc·20 μm / (m ２ The average thickness of the layer (Y1) must be 900 μm or less. By satisfying these conditions, a multilayer structure having good blister resistance can be obtained.

[0046] The material of the layer (Y1) is not particularly limited as long as it is a thermoplastic resin that satisfies the above-mentioned hydrogen permeation rate. In particular, it is preferable that the layer (Y1) contains polyamide. The polyamide layer can be bonded to the EVOH layer without an adhesive, and polyamide also has excellent strength and toughness. Examples of polyamide that can be used include nylon 6, nylon 66, nylon 12, and copolymers thereof, such as nylon 6 / 66. Blends of multiple polyamides can also be used. It is preferable that the layer (Y1) contains more than 50% by mass of nylon 6 as the polyamide. It is also preferable that the layer (Y1) contains 10 to 30% by mass of nylon 6 / 66 as the polyamide.

[0047] Although the layer (Y) may be composed of multiple layers, it is preferable that the layer (Y1) does not include an adhesive resin layer. This is because adhesive resin layers generally have poor hydrogen gas barrier properties and are more likely to cause blistering. From this perspective, a polyamide that can be directly bonded to the layer (X) is suitable as the material for the layer (Y).

[0048] It is also preferred that layer (Y) contains 10 to 30 mass % of thermoplastic elastomer (B'). This allows for a multilayer structure having a high elongation at break at low temperatures and being less susceptible to fracture due to deformation. The thermoplastic elastomer (B') used here can be any of the thermoplastic elastomers described above as the thermoplastic elastomer (B) contained in layer (X).

[0049] It is preferable that the thermoplastic elastomer (B) contained in layer (X) and the thermoplastic elastomer (B') contained in layer (Y) are made of the same type of thermoplastic elastomer. This improves the interlayer adhesion between layer (X) and layer (Y). Here, "same type" means, for example, an olefin-based thermoplastic elastomer and an olefin-based thermoplastic elastomer, or a styrene-based thermoplastic elastomer and a styrene-based thermoplastic elastomer. Furthermore, it is more preferable that both the thermoplastic elastomer (B) and the thermoplastic elastomer (B') are ethylene-α-olefin copolymers, and it is even more preferable that the α-olefins are the same. It is also preferable that both the thermoplastic elastomer (B) and the thermoplastic elastomer (B') are acid-modified ethylene-α-olefin copolymers, and it is even more preferable that the α-olefins are the same.

[0050] The average thickness of layer (Y1) is preferably 50 to 500 μm. If layer (Y1) is too thick, blister resistance may decrease. The average thickness of layer (Y1) is more preferably 400 μm or less. On the other hand, if layer (Y1) is too thin, layer (Y2) often becomes thick in order to obtain rigidity. In such cases, the difference in thickness between layer (Y1) and layer (Y2) becomes too large, which may make it difficult to melt-mold the multilayer structure. The average thickness of layer (Y1) is more preferably 100 μm or more, and even more preferably 200 μm or more.

[0051] The multilayer structure contained in the high-pressure container or high-pressure pipe of the present invention preferably has, as layer (Y), a layer (Y2) located outside layer (X). In this case, layer (Y2) preferably contains a polyamide. As the polyamide, the same polyamide as that described for layer (Y1) can be used. As mentioned above, it is also preferable that the thermoplastic elastomer (B') is contained.

[0052] It is also preferred that layer (Y2) contains a polyolefin. Since layer (Y2) is disposed outside layer (X) containing EVOH, it does not dissolve large amounts of hydrogen and does not require blister resistance, so polyolefins can be used. The use of polyolefins may be advantageous when used in environments requiring water resistance. Polyethylene, polypropylene, etc. can be used as polyolefins. Polyethylene, particularly high-density polyethylene, is preferred because of its high elongation at break at low temperatures. Depending on the application, the layer may be crosslinked by electron beams or the like. When layer (Y2) contains a polyolefin, adhesion to layer (X) is often insufficient. Therefore, it is preferred that layer (Y2) have a multilayer structure and an adhesive resin layer be disposed on the surface in contact with layer (X).

[0053] The average thickness of layer (Y2) is preferably 100 to 1500 μm. Since layer (Y2) is not required to be blister-resistant, it may be thick. A large thickness allows the total average thickness of the entire multilayer structure to be large, making it suitable for applications requiring rigidity. The average thickness of layer (Y2) is more preferably 200 μm or more, and even more preferably 400 μm or more. On the other hand, from the viewpoint of ease of melt molding, it is more preferably 1000 μm or less, and even more preferably 800 μm or less.

[0054] It is preferable that the multilayer structure has both a layer (Y1) and a layer (Y2) because of good melt moldability. Thus, when the multilayer structure has a layer structure of Y1 / X / Y2, it is preferable that the outer layer (Y2) is thicker than the inner layer (Y1). More specifically, the thickness ratio (Y1 / Y2), which is the ratio of the average thicknesses of the layer (Y1) and the layer (Y2), is preferably 1 / 99 or more and 45 / 55 or less. That is, if Y1 is too thick, blisters are likely to occur, but the overall thickness is large and rigidity can be increased.

[0055] The high-pressure container or high-pressure pipe of the present invention may have a reinforcing layer on the outside of the multilayer structure. This improves safety against high-pressure hydrogen gas. The reinforcing layer on the outside of the multilayer structure may be formed by wrapping around the integrally molded multilayer structure, or the multilayer structure may be inserted into the reinforced container or reinforcing pipe. Examples of materials for the reinforcing layer include metal and fiber-reinforced plastic.

[0056] The high-pressure container or high-pressure pipe of the present invention is used for storing or transporting high-pressure hydrogen gas. The purity of the hydrogen gas handled in the present invention is preferably 80% by volume or more, more preferably 90% by volume or more, even more preferably 95% by volume or more, and particularly preferably 99% by volume or more, and may consist essentially of hydrogen gas. Other components that may be contained in hydrogen gas include, but are not limited to, methane, ethane, ethylene, acetylene, propane, propene, butane, nitrogen, oxygen, argon, carbon dioxide, carbon monoxide, water, ammonia, and hydrogen sulfide. The pressure of the hydrogen gas stored in the high-pressure container or high-pressure pipe may be 10 MPa or more, 20 MPa or more, or 50 MPa or more, taking into consideration the balance between storage efficiency and safety. The pressure of the hydrogen gas is usually 150 MPa or less. Here, the above pressure is the highest pressure during use. The present invention provides a method for storing or transporting such high-pressure hydrogen gas using the high-pressure container or high-pressure pipe of the present invention.

[0057] The uses of the high-pressure container or high-pressure pipe of the present invention are not particularly limited, but they can be used for various hydrogen gas storage containers and hydrogen gas transfer pipes. Because they are lightweight and resistant to deformation, they are preferably suitable for use in transportation machinery using hydrogen gas as fuel. Suitable transportation machinery includes automobiles, more preferably fuel cell electric vehicles (FCEVs) and hydrogen engine automobiles. These automobiles are clean vehicles whose only exhaust gas is water, but how to handle high-pressure hydrogen gas presents a challenge. Although the high-pressure container or high-pressure pipe of the present invention is made of resin, it has excellent hydrogen gas barrier properties and is also highly resistant to high pressures and deformation. Therefore, from the perspective of emphasizing the balance between environmental performance and safety, it is suitable as a hydrogen gas storage container or hydrogen gas transfer pipe to be installed in fuel cell electric vehicles and hydrogen engine automobiles.

[0058] (Materials used in the examples and comparative examples) EVOH (A) A-1: ​​"EVAL (registered trademark) L171B" (EVOH, manufactured by Kuraray Co., Ltd., ethylene unit content 27 mol%, MFR 4.0 g / 10 min (210°C, 2160 g load)) Thermoplastic elastomer (B) B-1: "TAFMER (trademark) MH7020" (maleic anhydride modified ethylene-1-butene copolymer, manufactured by Mitsui Chemicals, Inc., acid value 12 mg KOH / g) B-2: "TAFMER (trademark) MP0620" (maleic anhydride modified ethylene-propylene copolymer, manufactured by Mitsui Chemicals, Inc., acid value 12 mg KOH / g) B-3: "TAFMER (trademark) A4050" (ethylene-1-butene copolymer, manufactured by Mitsui Chemicals, Inc.) The acid value was measured using xylene as a solvent according to the method described in JIS K 2501:2003. The thermoplastic elastomer (B) was used to mold 1A dumbbells using an injection molding machine manufactured by The Japan Steel Works, Ltd., and the breaking elongation was measured at 23°C and 0% RH according to ASTM D638. The results were greater than 500% for all of B-1, B-2, and B-3. Thermoplastic resin (C) PA6: "UBE Nylon (trademark) 1030B" (nylon 6, manufactured by Ube Industries, Ltd.) PA6 / 66: "UBE Nylon (trademark) 5034B" (nylon 6 / 66, manufactured by Ube Industries, Ltd.) PA11: "Rilsan (trademark) PA11" (nylon 11, manufactured by Arkema) HDPE: "Novatec HD (trademark) HB111R" (high-density polyethylene, manufactured by Japan Polyethylene Corporation) Ad (adhesive resin): "Admer (trademark) GT6" (maleic anhydride-modified polyethylene, manufactured by Mitsui Chemicals, Inc.)

[0059] (Evaluation Method) (1) Hydrogen Permeation Rate (H ２ For the single layer films and multilayer structures of layer (X) obtained in the examples and comparative examples, the hydrogen permeation rate (cc / (m)) at 20°C and 0% RH was measured using a gas permeability measuring device (GTR-21) manufactured by GTR Tech Co., Ltd. in accordance with the method described in ISO 15105-2:2003. ２ The hydrogen permeation rate of the polyamide compositions used in the layer (Y) of Examples 1 to 18, 20, and 21 and Comparative Examples 1 to 3 was 200 cc·20 μm / (m ２· day · atm), and 5000cc · 20 μm / (m ２ The hydrogen permeation rates of the HDPE and adhesive resin (Ad) used in the layer (Y) of Example 19 and Comparative Examples 3 and 4 were all less than 5000 cc·20 μm / (m ２ ・day・atm) or more.

[0060] (2) Breaking Elongation The monolayer films of layer (X), monolayer films of layer (Y), and multilayer structures obtained in the Examples and Comparative Examples were cut into 15 mm wide strips to prepare measurement samples, and the tensile breaking elongation of the obtained measurement samples was measured using a universal testing machine 3367 (manufactured by Instron Japan Company Limited) under the conditions of −60° C., a chuck distance of 50 mm, and a pulling rate of 50 mm / min.

[0061] (3) Blister Resistance The monolayer films and multilayer structures of layer (X) prepared in the Examples and Comparative Examples were cut into 80 mm x 10 mm squares. For multilayer structures having layer (Y2), the outer layer side (layer (Y2)) and the cut surface were covered with aluminum foil using an adhesive to prepare test specimens. The test specimens were placed in an autoclave, and high-pressure hydrogen gas was introduced to a pressure of 2 MPa. High-pressure hydrogen gas was then introduced over 30 minutes to increase the pressure from 2 MPa to 90 MPa, and the specimen was maintained at 85°C for 10 minutes, after which the pressure was reduced to 2 MPa in 0.5 minutes. This cycle was repeated 10 times, and the test specimens were then removed from the autoclave. The vertical cross sections of the test specimens were observed, and the presence or absence of blisters (defects such as blisters, voids, cracks, and delamination) was visually determined. Judgment: Standard (single layer film of layer (X)) A: No blisters were observed B: No blisters were observed on the surface, but some were observed inside C: Blisters were observed on the surface and inside Judgment: Standard (multilayer structure) A: No blisters were observed B: Blisters with a length of less than 50 μm in the longitudinal direction were observed C: Blisters with a length of 50 μm or more in the longitudinal direction were observed

[0062] Example 1 90 parts by mass of (A-1) as the EVOH (A) and 10 parts by mass of a maleic anhydride-modified ethylene-1-butene copolymer (B-1) as the thermoplastic elastomer (B) were dry-blended, and the mixture was extruded using a 30 mmφ twin-screw extruder ("TEX-30SS-30CRW-2V" manufactured by The Japan Steel Works, Ltd.) at 220°C, a screw rotation speed of 200 rpm, and an extrusion rate of 25 kg / hour. The mixture was pelletized and then dried at 30°C for 16 hours under reduced pressure to obtain EVOH resin composition pellets.

[0063] The obtained EVOH resin composition pellets were used to form a monolayer film having a layer (X) with an average thickness of 20 μm using a single-screw extruder ("D2020" manufactured by Toyo Seiki Seisaku-sho, Ltd., D (mm) = 20, L / D = 20, compression ratio = 3.0, screw: full flight). The extrusion conditions were as follows: Extrusion temperature: 220°C Die width: 30 cm Take-up roll temperature: 80°C Screw rotation speed: 40 rpm Take-up roll speed: 3 m / min The obtained monolayer film was evaluated according to the methods described in the above evaluation methods (1) to (3). The results are shown in Table 2.

[0064] 60 parts by mass of PA6 and 20 parts by mass of PA6 / 66 as the thermoplastic resin (C), and 20 parts by mass of maleic anhydride-modified ethylene-1-butene copolymer (B-1) as the thermoplastic elastomer (B) were dry-blended, and the mixture was extruded using a 30 mmφ twin-screw extruder ("TEX-30SS-30CRW-2V" manufactured by The Japan Steel Works, Ltd.) under conditions of 220°C, a screw rotation speed of 200 rpm, and an extrusion resin rate of 25 kg / hour. The mixture was pelletized and then dried at 30°C for 16 hours under reduced pressure to obtain PA resin composition pellets.

[0065] The obtained PA resin composition pellets were used to produce a monolayer film having a layer (Y) with a thickness of 20 μm using a single-screw extruder ("D2020" manufactured by Toyo Seiki Seisaku-sho, Ltd., D (mm) = 20, L / D = 20, compression ratio = 3.0, screw: full flight). The extrusion conditions were as follows: Extrusion temperature: 220°C Die width: 30 cm Take-up roll temperature: 80°C Screw rotation speed: 40 rpm Take-up roll speed: 3 m / min The obtained monolayer film was evaluated using the method described in the above evaluation method (2). The results are shown in Table 2.

[0066] Using the above EVOH resin composition pellets and PA resin composition pellets, a two-kind, three-layer multilayer structure (Layer (Y1) / Layer (X) / Layer (Y2)=PA / EVOH / PA=thicknesses of 300 μm / 100 μm / 500 μm: total thickness of all layers of 900 μm) was obtained under the following conditions.

[0049] Extruder: Layer (X): 20 mmφ extruder, laboratory machine ME type CO-EXT (manufactured by Toyo Seiki Seisaku-sho, Ltd.) Layer (Y): 32 mmφ extruder GT-32-A (manufactured by Plastics Technology Research Institute Co., Ltd.) Layer (X) extrusion temperature: feeding section / compression section / metering section / die = 170 / 210 / 220 / 220°C Layer (Y) extrusion temperature: feeding section / compression section / metering section / die = 170 / 220 / 230 / 230°C Die: 300 mm wide coat hanger die (manufactured by Plastics Technology Research Institute Co., Ltd.) The obtained multilayer structure was evaluated according to the methods described in the above evaluation methods (1) to (3). The results are shown in Table 2.

[0067] (Examples 2 to 18, 20, 21 and Comparative Examples 1 and 2) Resin composition pellets, single-layer films, and multilayer structures were prepared and evaluated in the same manner as in the examples, except that the content and type of each component in Layer (X), the content and type of each component in Layer (Y), and the thickness of each layer in the multilayer structure were changed as shown in Table 1. The results are shown in Table 2.

[0068] (Example 19) Using the EVOH resin composition pellets obtained in Example 1 as the material for Layer (X), and HDPE and Ad (adhesive resin) as the materials for Layer (Y), a three-kind, three-layer multilayer structure (Layer (X) / Layer (Y2) = EVOH / Ad / HDPE = 100 μm / 50 μm / 800 μm: total thickness of all layers 950 μm) was produced by coextrusion under the following extrusion conditions. Evaluation was performed in the same manner as in Example 1, except that the obtained multilayer structure was used. The results are shown in Table 2. [Extruder] For layer (X): 20 mm φ extruder, Lab machine ME type CO-EXT (manufactured by Toyo Seiki Seisakusho Co., Ltd.) For Ad: 20 mm φ extruder SZW20GT-20MG-STD (manufactured by Technovel Co., Ltd.) For HDPE: 32 mm φ extruder GT-32-A (manufactured by Plastics Technology Research Institute Co., Ltd.) [Layer (X) extrusion temperature] Feeding section / compression section / metering section / die = 180 / 210 / 220 / 220°C [Ad extrusion temperature] Feeding section / compression section / metering section / die = 170 / 210 / 220 / 220°C [HDPE extrusion temperature] Feeding section / compression section / metering section / die = 170 / 210 / 220 / 220°C

[0069] Furthermore, a monolayer film of layer (X) and a monolayer film of HDPE were prepared for evaluation. The monolayer film of layer (X) was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2. The monolayer film of HDPE was prepared and evaluated in the same manner as in Example 1, except that HDPE was used instead of the PA resin composition. The results are shown in Table 2.

[0070] Comparative Example 3 A multilayer structure was produced and evaluated in the same manner as in Example 19, except that the material of layer (Y) and the average thickness of each layer were changed as shown in Table 1, and the extrusion temperature of the polyamide composition (PA) was changed as follows to produce a three-kind, five-layer multilayer structure (layer (Y1) / layer (X) / layer (Y2) = PA / Ad / EVOH / Ad / PA = 300 μm / 50 μm / 100 μm / 50 μm / 500 μm: total thickness of all layers 1000 μm). The results are shown in Table 2. Furthermore, for evaluation, a monolayer film of layer (X) and a monolayer film of the polyamide composition were produced and evaluated in the same manner as in Example 1. The results are shown in Table 2. [Polyamide composition extrusion temperature] Feed section / compression section / metering section / die = 170 / 220 / 230 / 230°C

[0071] Comparative Example 4 A multilayer structure was produced and evaluated in the same manner as in Example 19, except that the material of layer (Y) was changed as shown in Table 1 and a three-kind, five-layer multilayer structure (layer (Y1) / layer (X) / layer (Y2) = HDPE / Ad / EVOH / Ad / HDPE = 350 μm / 50 μm / 100 μm / 50 μm / 350 μm: total thickness of all layers 900 μm) was produced by coextrusion. The results are shown in Table 2. In addition, a monolayer film of layer (X) and a monolayer film of HDPE were produced for evaluation in the same manner as in Example 1 and evaluated. The results are shown in Table 2.

[0072]

[0073]

Claims

1. A high-pressure container or high-pressure pipe containing a multilayer structure used for storing or transporting high-pressure hydrogen gas, wherein the multilayer structure comprises a layer (X) containing an ethylene-vinyl alcohol copolymer (A) and a thermoplastic elastomer (B), and a layer (Y) containing a thermoplastic resin (C), and the multilayer structure has, on the inside of layer (X), a hydrogen permeation rate of 5000 cc·20 μm / (m ２ When the multilayer structure includes, as the layer (Y), a layer (Y1) located inside the layer (X), the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc·20 μm / (m ２ A high-pressure vessel or a high-pressure pipe, wherein the average thickness of the layer (Y1) is less than 900 μm.

2. A high-pressure vessel or high-pressure pipe according to claim 1, wherein the multilayer structure has a total average thickness of 500 μm or more.

3. The high-pressure vessel or high-pressure pipe according to claim 1 or 2, wherein the average thickness of layer (X) is 30 μm or more.

4. The high-pressure container or high-pressure pipe according to claim 1 or 2, wherein the mass ratio (B / A) of the thermoplastic elastomer (B) to the ethylene-vinyl alcohol copolymer (A) in the layer (X) is 3 / 97 or more and 35 / 65 or less.

5. The high-pressure container or high-pressure pipe according to claim 1 or 2, wherein the resin component contained in layer (X) consists essentially of ethylene-vinyl alcohol copolymer (A) and thermoplastic elastomer (B).

6. The high-pressure vessel or high-pressure pipe according to claim 1 or 2, wherein the ethylene unit content of the ethylene-vinyl alcohol copolymer (A) is 15 mol % or more and 35 mol % or less.

7. A high-pressure container or high-pressure pipe according to claim 1 or 2, wherein the thermoplastic elastomer (B) is an acid-modified thermoplastic elastomer.

8. A high-pressure container or high-pressure pipe according to claim 1 or 2, wherein the thermoplastic elastomer (B) is at least one selected from the group consisting of olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, polyamide-based elastomers, and polyester-based thermoplastic elastomers.

9. A high-pressure vessel or high-pressure pipe according to claim 1 or 2, wherein the layer (Y) contains a polyamide as the thermoplastic resin (C).

10. The high-pressure vessel or high-pressure pipe according to claim 9, wherein layer (Y) contains more than 50% by mass of nylon 6 as the polyamide.

11. The high-pressure vessel or high-pressure pipe according to claim 9, wherein the layer (Y) contains 10 to 30 mass % of nylon 6 / 66 as the polyamide.

12. The high-pressure container or high-pressure pipe according to claim 1 or 2, wherein the layer (Y) contains 10 to 30 mass % of the thermoplastic elastomer (B').

13. The high-pressure container or high-pressure pipe according to claim 12, wherein the thermoplastic elastomer (B) contained in the layer (X) and the thermoplastic elastomer (B') contained in the layer (Y) are made of the same type of thermoplastic elastomer.

14. A high-pressure vessel or high-pressure pipe according to claim 1 or 2, wherein the layer (Y) contains a polyolefin as the thermoplastic resin (C).

15. The multilayer structure has, as the layer (Y), a layer (Y1) located inside the layer (X), and the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc·20 μm / (m ２ 3. The high-pressure vessel or high-pressure pipe according to claim 1 or 2, wherein the average thickness of the layer (Y1) is less than 900 μm (day·atm).

16. A high-pressure vessel or pipe according to claim 15, wherein the layer (Y1) comprises a polyamide.

17. The high-pressure vessel or high-pressure pipe according to claim 15, wherein the average thickness of the layer (Y1) is 50 to 500 μm.

18. A high-pressure vessel or high-pressure pipe according to claim 1 or 2, which has as layer (Y) a layer (Y2) located outside layer (X).

19. A high-pressure vessel or pipe according to claim 18, wherein the layer (Y2) comprises a polyamide.

20. A high-pressure vessel or pipe according to claim 18, wherein layer (Y2) comprises a polyolefin.

21. The high-pressure vessel or high-pressure pipe according to claim 18, wherein the average thickness of the layer (Y2) is 100 to 1500 μm.

22. The multilayer structure has, as the layer (Y), a layer (Y1) located inside the layer (X) and a layer (Y2) located outside the layer (X), and the hydrogen permeation rate of the layer (Y1) at 20°C and 0% RH is 5000 cc·20 μm / (m ２ 3. The high-pressure vessel or high-pressure pipe according to claim 1 or 2, wherein the average thickness of the layer (Y1) is 900 μm or less and is thinner than the average thickness of the layer (Y2).

23. A high-pressure vessel or high-pressure pipe according to claim 1 or 2, further comprising a reinforcing layer on the outside of the multilayer structure.

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