Polyamide resin composition for molded article in contact with high-pressure hydrogen gas

Abstract

Provided is a polyamide resin composition which has high fluidity and excellent hydrogen barrier properties when formed into a molded article, and which does not impair flexibility in a low-temperature environment. A polyamide resin composition for a molded article that is in contact with high-pressure hydrogen gas, the polyamide resin composition containing (A) an aliphatic homopolymerized polyamide resin, (B) an aliphatic copolymerized polyamide resin, and (C) at least one compound selected from the group consisting of C18-32 fatty acids and derivatives thereof as an optional component, the polyamide resin composition does not substantially contain a polyolefin resin. The relative viscosity of (A) is 1.80-2.70, the relative viscosity of (B) is 2.90-4.20, the relative viscosity of a mixture of (A) and (B) is 2.30-3.60, the total of (A) and (B) is 93.0-100% by mass, (C) is 0-2.0% by mass, and other components are 0-5.0% by mass, and the ratio of (A) to (B) is 50: 50-90: 10 on a mass basis.

Description

Technical Field

[0001] The present invention relates to a polyamide resin composition for use in a molded article that comes into contact with high-pressure hydrogen gas. Background Art

[0002] Polyamide resin has excellent mechanical properties, heat resistance, and chemical resistance, and therefore, is used as an engineering plastic in various applications, and is used by various molding methods. For example, for the purpose of improving heat resistance, mechanical strength, etc., it is known that: an aliphatic copolymer polyamide resin and an aliphatic homopolyamide resin each having a specific relative viscosity are used in combination, and a fibrous reinforcing agent is combined (for example, see Patent Documents 1 and 2). Also known: a flame-retardant polyamide resin composition in which an aliphatic copolymer polyamide resin and an aliphatic homopolyamide resin are used in combination, and a triazine-based compound or the like is combined (for example, see Patent Document 3).

[0003] On the other hand, as a molded product in contact with high-pressure hydrogen, for example, a hydrogen tank used in a hydrogen-powered car is known, and polyamide resin compositions are also used in this field. The hydrogen tank used in a hydrogen-powered car is a high-pressure hydrogen storage container with a barrel-like appearance, which is composed of a metal or resin long inner layer (long inner liner) that directly contacts hydrogen and a fiber-reinforced resin layer stacked on its outer peripheral surface.

[0004] The hydrogen in the hydrogen tank is extremely cold, below -40°C, under high pressure. Therefore, the long inner liner that comes into direct contact with hydrogen is required to have not only gas barrier properties but also flexibility that can withstand high pressure and maintain flexibility even at extremely low temperatures.

[0005] In the past, in the use of molded products in contact with high-pressure hydrogen, molded products formed by polyamide resin compositions whose impact resistance is improved by adding modified polyolefin resins to polyamide resins are used. As such polyamide resin compositions, polyamide resin compositions comprising polyamide and acid-modified polyolefins in a prescribed ratio are disclosed (for example, with reference to patent documentation 4). In addition, a hydrogen tank lining material formed by a polyamide resin composition comprising impact-resistant materials such as polyamide 6, copolyamide and acid-modified ethylene-α-olefin copolymers is proposed, and its gas barrier properties are shown to be excellent, even at low temperatures, it also has excellent impact resistance (for example, with reference to patent documentation 5). Further, a polyamide resin composition is proposed, which comprises polyamide resin and impact-resistant materials, the relative viscosity of the polyamide resin is set to more than 2.7, the terminal amino concentration of the polyamide resin, the content of the acid anhydride group of the impact-resistant agent and the content of the impact-resistant material are set to a prescribed range, and the composition is shown to maintain the good surface appearance of the molded body, and the blow molding property is excellent (for example, with reference to patent documentation 6).

[0006] In addition, it is also known to add an unmodified olefin resin to a polyamide resin composition to improve friction resistance, mold release properties, etc. As such polyamide resin compositions, there are known: a polyamide resin composition comprising a polyamide resin and an olefin elastomer resin having a predetermined weight average particle size in a predetermined ratio (see, for example, Patent Document 7); and a polyamide resin composition comprising a polyamide resin, a modified polypropylene wax, and an unmodified polypropylene resin in a predetermined ratio (see, for example, Patent Document 8).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 4-63863

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 6-299068

[0011] Patent Document 3: International Publication No. 2013 / 099522

[0012] Patent Document 4: Japanese Patent Application Publication No. 2020-122157

[0013] Patent Document 5: Japanese Patent Application Publication No. 2009-191871

[0014] Patent Document 6: Japanese Patent Application Publication No. 2017-206639

[0015] Patent Document 7: Japanese Patent Application Publication No. 2007-119581

[0016] Patent Document 8: Japanese Patent Application Publication No. 2019-1934 Summary of the invention

[0017] Problem that the invention aims to solve

[0018] From the viewpoint of energy saving, lightweight and thin-walled moldings are sought. Especially in moldings in contact with high-pressure hydrogen, gas barrier properties and flexibility under low-temperature environments are reduced due to thin-walling. Therefore, for the polyamide resin composition used in moldings in contact with high-pressure hydrogen, it is sought that even if thin-walling is made, the flexibility under low-temperature environments will not be impaired, and the gas barrier properties are maintained. In addition, since it is a molding, the polyamide resin composition seeks good molding properties achieved by improving fluidity.

[0019] The polyamide resin compositions described in Patent Documents 1 to 3 do not take into account the use of molded products that come into contact with high-pressure hydrogen, and their gas barrier properties and flexibility are insufficient. Although the polyamide resin compositions described in Patent Documents 4 to 6 have high flexibility and impact resistance in low-temperature environments, further improvement in fluidity and moldability is sought. Although the polyamide resin compositions described in Patent Documents 7 and 8 have high friction resistance and mold release properties in the molded products, they do not focus on flexibility and impact resistance in low-temperature environments.

[0020] An object of the present invention is to provide a polyamide resin composition which has high fluidity, is excellent in hydrogen gas barrier properties when formed into a molded article, and does not impair flexibility in a low temperature environment.

[0021] Solutions for solving problems

[0022] The present invention relates to the following [1] to

[12] .

[0023] [1] A polyamide resin composition for a molded article to be in contact with high-pressure hydrogen, comprising an aliphatic homopolyamide resin (A) and an aliphatic copolymer polyamide resin (B), and as an optional component, at least one compound (C) selected from the group consisting of fatty acids having 18 to 32 carbon atoms and derivatives thereof, wherein the polyamide resin composition does not substantially contain a polyolefin resin.

[0024] Regarding the relative viscosity measured at 25° C. by dissolving 1 g of a polyamide resin in 100 ml of 96% sulfuric acid in accordance with JIS K 6920, the relative viscosity of the aliphatic homopolyamide resin (A) is 1.80 to 2.70, the relative viscosity of the aliphatic copolymer polyamide resin (B) is 2.90 to 4.20, and the relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 2.30 to 3.60.

[0025] In 100% by mass of the polyamide resin composition, the total amount of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 93.0 to 100% by mass, the aforementioned compound (C) is 0 to 2.0% by mass, and other components are 0 to 5.0% by mass, and the ratio of the aliphatic homopolyamide resin (A) to the aliphatic copolymer polyamide resin (B) is 50:50 to 90:10 on a mass basis.

[0026] [2] The polyamide resin composition according to [1], wherein the ratio of the aliphatic homopolyamide resin (A) to the aliphatic copolymer polyamide resin (B) is 65:35 to 90:10 on a mass basis.

[0027] [3] The polyamide resin composition according to [1] or [2], wherein the relative viscosity of the aliphatic homopolyamide resin (A) is 1.80 to 2.60.

[0028] [4] The polyamide resin composition according to any one of [1] to [3], wherein the relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 2.40 to 2.80.

[0029] [5] The polyamide resin composition according to any one of [1] to [4], wherein the aliphatic copolymer polyamide resin (B) contains 75 mol% or more and less than 95 mol% of structural units derived from ε-caprolactam and structural units derived from 6-aminocaproic acid in 100 mol% of all structural units.

[0030] [6] The polyamide resin composition according to any one of [1] to [5], wherein the compound (C) is at least one selected from the group consisting of fatty acids having 18 to 32 carbon atoms and metal salts, esters and amides thereof.

[0031] [7] The polyamide resin composition according to any one of [1] to [6], wherein the density of the aliphatic homopolyamide resin (A), the aliphatic copolymer polyamide resin (B) and the polyamide resin composition measured in accordance with ISO1183-3 using a Type-A1 test piece molded in accordance with ISO 294-1 using an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C is 1.120 g / cm 3 ~1.150g / cm 3 , 1.100g / cm 3 ~1.130g / cm 3 and 1.120g / cm 3 ~1.140g / cm 3 .

[0032] [8] The polyamide resin composition according to [7], wherein the density of the polyamide resin composition measured in accordance with ISO 1183-3 is 1.126 to 1.129 g / cm using a Type-A1 test piece molded in accordance with ISO 294-1 using an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C. 3 .

[0033] [9] The polyamide resin composition according to any one of [1] to [8], wherein the hydrogen permeability coefficient at 55°C and 1 atm measured by a differential pressure method for a circular molded article having a thickness of 2.0 mm and a diameter of Φ60 mm obtained by molding the polyamide resin composition at a resin temperature of 250°C and a mold temperature of 80°C in accordance with JIS K7126-1 is greater than 0.1×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.8×10 -10 cm 3 cm / (cm 2 ·s·cmHg).

[0034]

[10] A molded article to be brought into contact with high-pressure hydrogen gas, comprising the polyamide resin composition according to any one of [1] to [9].

[0035]

[11] The molded article that comes into contact with high-pressure hydrogen gas according to

[10] , which is one selected from the group consisting of a tank liner for high-pressure hydrogen gas, a hose for high-pressure hydrogen gas, a pipe for high-pressure hydrogen gas, and a joint for high-pressure hydrogen gas.

[0036]

[12] A high-pressure hydrogen tank comprising a high-pressure hydrogen tank liner and a continuous fiber reinforced resin layer, wherein the high-pressure hydrogen tank liner comprises the polyamide resin composition according to any one of [1] to [9].

[0037] Effects of the Invention

[0038] According to the present invention, there can be provided a polyamide resin composition which has high fluidity, is excellent in hydrogen gas barrier properties when formed into a molded article, and does not impair flexibility in a low temperature environment. DETAILED DESCRIPTION

[0039] In this specification, when there are multiple substances corresponding to each component in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition unless otherwise specified. In addition, the relative viscosity specified for the polyamide resin refers to the value measured at 25°C by dissolving 1 g of the polyamide resin in 100 ml of 96% sulfuric acid in accordance with JIS K 6920.

[0040] The polyamide resin composition of the present invention is a polyamide resin composition for a molded article in contact with high-pressure hydrogen, comprising an aliphatic homopolyamide resin (A) and an aliphatic copolymer polyamide resin (B), and as an optional component, at least one compound (C) selected from the group consisting of fatty acids having 18 to 32 carbon atoms and derivatives thereof, wherein the polyamide resin composition does not substantially contain a polyolefin resin. 6920 The relative viscosity of 1 g of a polyamide resin is measured at 25° C. by dissolving the polyamide resin in 100 ml of 96% sulfuric acid. The relative viscosity of the aliphatic homopolyamide resin (A) is 1.80 to 2.70, the relative viscosity of the aliphatic copolymer polyamide resin (B) is 2.90 to 4.20, and the relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 2.30 to 3.60. In 100% by mass of the polyamide resin composition, the total amount of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 93.0 to 100% by mass, the aforementioned compound (C) is 0 to 2.0% by mass, and other components are 0 to 5.0% by mass. The ratio of the aliphatic homopolyamide resin (A) to the aliphatic copolymer polyamide resin (B) is 50:50 to 90:10 on a mass basis.

[0041] By substantially not blending a polyolefin-based resin, setting the relative viscosity of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) within the above range, and setting the ratio of each component within the above range, it is possible to produce a polyamide resin composition that has high fluidity, excellent hydrogen barrier properties when formed into a molded article, and does not impair flexibility in a low-temperature environment.

[0042] The present invention also relates to the use of the polyamide resin composition for manufacturing a molded article in contact with high-pressure hydrogen and a method of using the polyamide resin composition. Furthermore, the present invention is the use of the polyamide resin composition for manufacturing one selected from the group consisting of a high-pressure hydrogen tank liner, a high-pressure hydrogen hose, a high-pressure hydrogen pipe, and a high-pressure hydrogen joint and a method of using the polyamide resin composition. Furthermore, the present invention is the use of the polyamide resin composition for manufacturing one selected from the group consisting of a hydrogen storage tank liner, a hydrogen transfer hose, a hydrogen transfer pipe, and a hydrogen transfer joint and a method of using the polyamide resin composition.

[0043] Here, “substantially free” means that the polyamide resin composition of the present invention and its molded article are not included to such an extent that the functions or characteristics thereof are impaired or changed, and does not exclude inclusion to such an extent that the functions or characteristics are not impaired.

[0044] <Aliphatic Homopolyamide Resin (A)>

[0045] The polyamide resin composition contains an aliphatic homopolyamide resin (A).

[0046] The aliphatic homopolyamide resin (A) refers to a polyamide resin in which the monomer component constituting the aliphatic polyamide resin is a single type. The aliphatic homopolyamide resin (A) may be formed from at least one of a lactam and a hydrolyzate of the lactam, i.e., an aminocarboxylic acid, or may be formed from a combination of an aliphatic diamine and an aliphatic dicarboxylic acid. Here, when the monomer component constituting the aliphatic polyamide resin is a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, the combination of an aliphatic diamine and an aliphatic dicarboxylic acid is regarded as one monomer component.

[0047] Regarding the aliphatic homopolyamide resin (A), according to JIS K 6920, 1 g of the aliphatic homopolyamide resin (A) is dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity measured at 25° C. is 1.80 to 2.70. By setting the relative viscosity of the aliphatic homopolyamide resin (A) to the above range, the fluidity of the polyamide resin composition can be improved, and the moldability of large-sized molded products such as hydrogen tank liners can be improved without impairing the flexibility of the obtained molded products in a low temperature environment. In particular, from the viewpoint of improving the fluidity of the polyamide resin composition and improving the moldability of large-sized molded products such as hydrogen tank liners, the relative viscosity of the aliphatic homopolyamide resin (A) is preferably 1.80 to 2.60, more preferably 2.20 to 2.60, and particularly preferably 2.40 to 2.60.

[0048] When the aliphatic homopolyamide resin (A) contains two or more polyamide resins having different relative viscosities, the relative viscosity of the aliphatic homopolyamide resin (A) is preferably measured as described above.

[0049] From the viewpoint of obtaining better molding processability without impairing the hydrogen barrier properties of the molded article, the density of the aliphatic homopolyamide resin (A) measured in accordance with ISO 1183-3 using a Type-A1 test piece molded in accordance with ISO 294-1 using an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C is preferably 1.120 g / cm 3 ~1.150g / cm 3 , more preferably 1.120 g / cm 3 ~1.140g / cm 3 , more preferably 1.125 g / cm 3 ~1.135g / cm 3 .

[0050] Examples of the aliphatic homopolyamide resin (A) include aliphatic homopolyamide resins formed from aliphatic diamines and aliphatic dicarboxylic acids, and aliphatic homopolyamide resins formed from lactams or aminocarboxylic acids.

[0051] Examples of the monomer component constituting the aliphatic homopolyamide resin (A) include a combination of an aliphatic diamine having 2 to 20 carbon atoms, preferably 4 to 12 carbon atoms, and an aliphatic dicarboxylic acid having 2 to 20 carbon atoms, preferably 6 to 12 carbon atoms, and a lactam or aminocarboxylic acid having 6 to 12 carbon atoms.

[0052] Examples of the aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,8-octanediamine, 2,2,4 / 2,4,4-trimethylhexamethylenediamine, etc. Examples of the aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanediic acid, eicosanedioic acid, and derivatives thereof.

[0053] Examples of the combination of an aliphatic diamine and an aliphatic dicarboxylic acid include a combination of hexamethylenediamine and adipic acid, a combination of hexamethylenediamine and sebacic acid, and a combination of hexamethylenediamine and dodecanedioic acid. It is preferred to use equimolar salts of these combinations.

[0054] As lactam, α-pyrrolidone, δ-valerolactam, ε-caprolactam, ω-enantholactam, ω-capryllactam, ω-undecanoic acid, ω-laurolactam etc. can be listed. From the viewpoint of productivity, lactam is preferably ε-caprolactam, ω-undecanoic acid or ω-laurolactam. In addition, as aminocarboxylic acid, γ-aminobutyric acid, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid can be listed.

[0055] Specific examples of the aliphatic homopolyamide resin (A) include polyamide 4, polyamide 6, polyamide 7, polyamide 8, polyamide 9, polyamide 11, polyamide 12, polyamide 66, polyamide 412, polyamide 59, polyamide 510, polyamide 512, polyamide 69, polyamide 610, polyamide 612, polyamide 96, polyamide 99, polyamide 910, polyamide 912, polyamide 106, polyamide 109, polyamide 1010, polyamide 1012, polyamide 126, polyamide 129, polyamide 1210, polyamide 1212, and polyamide 122.

[0056] From the viewpoint of productivity, the aliphatic homopolyamide resin (A) is preferably at least one selected from the group consisting of polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11 and polyamide 12, and polyamide 6 and / or polyamide 66 are particularly preferred.

[0057] The aliphatic homopolyamide resin (A) may be one kind or a combination of two or more kinds.

[0058] <Aliphatic Copolyamide Resin (B)>

[0059] The polyamide resin composition contains an aliphatic copolymerized polyamide resin (B).

[0060] The aliphatic copolymer polyamide resin (B) refers to a polyamide resin in which the monomer components constituting the aliphatic polyamide resin are a combination of two or more. The aliphatic copolymer polyamide resin (B) is a copolymer of two or more selected from the group consisting of a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, and an aminocarboxylic acid. Here, regarding the combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a combination of one aliphatic diamine and one aliphatic dicarboxylic acid is regarded as one monomer component.

[0061] Regarding the aliphatic copolymer polyamide resin (B), according to JIS K 6920, 1 g of the aliphatic copolymer polyamide resin (B) is dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity measured at 25° C. is 2.90 to 4.20. By setting the relative viscosity of the aliphatic copolymer polyamide resin (B) to the above range, the moldability of the polyamide resin composition is not impaired, and the flexibility of the obtained molded product in a low temperature environment can be improved. The relative viscosity of the aliphatic copolymer polyamide resin (B) is preferably 2.90 to 3.50, and more preferably 2.90 to 3.20.

[0062] When the aliphatic copolymer polyamide resin (B) contains two or more polyamide resins having different relative viscosities, the relative viscosity of the aliphatic copolymer polyamide resin (B) is preferably measured as described above.

[0063] From the viewpoint of obtaining good hydrogen barrier properties without impairing moldability, the density of the aliphatic copolymer polyamide resin (B) measured in accordance with ISO 1183-3 using a Type-A1 test piece molded by an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C in accordance with ISO 294-1 is preferably 1.100 g / cm 3 ~1.130g / cm 3 , more preferably 1.100 g / cm 3 ~1.125g / cm 3 , more preferably 1.110 g / cm 3 ~1.120g / cm3 .

[0064] Examples of the aliphatic diamine include the same diamines as those exemplified as the raw materials of the aliphatic homopolyamide resin (A).

[0065] Examples of the aliphatic dicarboxylic acid include the same dicarboxylic acids as exemplified as the raw material of the aliphatic homopolyamide resin (A).

[0066] Examples of the lactam include the same lactams as those exemplified as the raw material of the aliphatic homopolyamide resin (A). Examples of the aminocarboxylic acid include the same aminocarboxylic acids as those exemplified as the raw material of the aliphatic homopolyamide resin (A).

[0067] These aliphatic diamines, aliphatic dicarboxylic acids, lactams, and aminocarboxylic acids may be used alone or in combination of two or more.

[0068] Specific examples of the aliphatic copolymer polyamide resin (B) include polyamide 6 / 66, polyamide 6 / 69, polyamide 6 / 610, polyamide 6 / 611, polyamide 6 / 612, polyamide 6 / 11, polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 6 / 66 / 610, and polyamide 6 / 66 / 612.

[0069] Among these, at least one selected from the group consisting of polyamide 6 / 66, polyamide 6 / 12, and polyamide 6 / 66 / 12 is preferred, and at least one selected from the group consisting of polyamide 6 / 66 and polyamide 6 / 66 / 12 is more preferred.

[0070] From the viewpoint of flexibility in a low temperature environment, the aliphatic copolymer polyamide resin (B) preferably contains 30 mol% or more and less than 95 mol% of structural units derived from ε-caprolactam and structural units derived from 6-aminocaproic acid in 100 mol% of all structural units, more preferably 75 mol% or more and less than 95 mol%, and particularly preferably 85 mol% or more and 93 mol% or less.

[0071] The aliphatic copolymer polyamide resin (B) may be one kind or a combination of two or more kinds.

[0072] (Mixture of aliphatic homopolyamide resin (A) and aliphatic copolymer polyamide resin (B))

[0073] The relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 2.30 to 3.60. Here, the aforementioned mixture refers to a mixture consisting only of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) mixed in the same ratio as in the polyamide resin composition.

[0074] By setting the relative viscosity of the aliphatic homopolyamide resin (A) to 1.80 to 2.70, the relative viscosity of the aliphatic copolymer polyamide resin (B) to 2.90 to 4.20, and the relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) to 2.30 to 3.60, the fluidity of the polyamide resin composition can be improved, the flexibility in a low temperature environment when the molded article is made is not impaired, and the hydrogen barrier property can be improved. The relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is preferably 2.30 to 3.00, more preferably 2.40 to 2.80, and particularly preferably 2.50 to 2.80.

[0075] The relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is preferably measured in accordance with JIS K 6920 at 25°C by dissolving 1 g of the mixture in 100 ml of 96% sulfuric acid.

[0076] From the viewpoint of the fluidity of the composition and the hydrogen barrier property of the molded product and the flexibility in a low temperature environment, the total content of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) in 100% by mass of the polyamide resin composition is 93.0 to 100% by mass, and more preferably 98.0 to 100% by mass. The polyamide resin contained in the polyamide resin composition is particularly preferably composed of only the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B). Among them, from the viewpoint of the crystallinity of the polyamide resin, a mixture of polyamide 6 and polyamide 6 / 66 or a mixture of polyamide 6 and polyamide 6 / 66 / 12 is particularly preferred.

[0077] From the viewpoint of the fluidity of the composition and the hydrogen barrier properties and flexibility of the molded article under low temperature environment, the ratio of the aliphatic homopolyamide resin (A) to the aliphatic copolymer polyamide resin (B) is 50:50 to 90:10, preferably 65:35 to 90:10 on a mass basis.

[0078] (Other polyamide resins)

[0079] The polyamide resin composition may contain other polyamide resins in addition to the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) within the scope that does not hinder the purpose of the present invention. As other polyamide resins, the following polyamide resins can be listed, which are copolymers having alicyclic, aromatic, etc. structures in the main chain or side chain. For example, other polyamide resins are preferably copolymer polyamide resins containing at least two aromatic monomer components.

[0080] Examples of the aliphatic diamine and aliphatic dicarboxylic acid as raw materials of other polyamide resins include those exemplified in the aliphatic homopolyamide resin (A). Examples of the lactam and aminocarboxylic acid as raw materials of other polyamide resins include those exemplified in the aliphatic homopolyamide resin (A).

[0081] Examples of alicyclic diamines constituting other polyamide resins include cyclohexanediamine, methylcyclohexanediamine, isophoronediamine, bis(3-methyl-4-aminocyclohexyl)methane, etc. Examples of aromatic diamines constituting other polyamide resins include p-phenylenediamine, m-phenylenediamine, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, and 4,4'-diaminodiphenylether, etc.

[0082] Examples of alicyclic dicarboxylic acids constituting other polyamide resins include 1,3-cyclopentane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, etc. Examples of aromatic dicarboxylic acids constituting other polyamide resins include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,4-phenylenedioxy diacetic acid, 1,3-phenylenedioxy diacetic acid, dibenzoic acid, 4,4'-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, and 4,4'-biphenyl dicarboxylic acid.

[0083] Specific examples of other polyamide resins include polycondensates of isophthalic acid / terephthalic acid / hexamethylenediamine / bis(3-methyl-4-aminocyclohexyl)methane, polycondensates of terephthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine, polycondensates of isophthalic acid / bis(3-methyl-4-aminocyclohexyl)methane / ω-laurolactam, and polycondensates of isophthalic acid / terephthalic acid / bis(3-methyl-4-aminocyclohexyl)methane. / condensation product of hexamethylenediamine (polyamide 6T / 6I), condensation product of isophthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine, condensation product of isophthalic acid / terephthalic acid / 2,2,4-trimethylhexamethylenediamine / 2,4,4-trimethylhexamethylenediamine, condensation product of isophthalic acid / bis(3-methyl-4-aminocyclohexyl)methane / ω-laurolactam, etc.

[0084] Specifically, the other polyamide resin is preferably formed from 40 to 95 mol% of terephthalic acid component units, 5 to 60 mol% of isophthalic acid component units, and an aliphatic diamine. Preferred combinations of monomer components constituting the other polyamide resin include an equimolar salt of hexamethylenediamine and terephthalic acid and an equimolar salt of hexamethylenediamine and isophthalic acid.

[0085] The other polyamide resin is preferably a copolymer containing 60% by mass or more and 99% by mass or less of units derived from a monomer component consisting of an aliphatic diamine, isophthalic acid, and terephthalic acid, and containing 1% by mass or more and 40% by mass or less of units of an aliphatic polyamide component.

[0086] (Manufacture of polyamide resin)

[0087] As the manufacturing apparatus of the polyamide resin, there can be cited known polyamide manufacturing apparatuses such as batch reactors, single-tank to multi-tank continuous reaction apparatuses, tubular continuous reaction apparatuses, single-screw type mixing extruders, twin-screw type mixing extruders and other mixing reaction extruders. As the polymerization method, known methods such as melt polymerization, solution polymerization, and solid phase polymerization can be used, and polymerization can be performed by repeatedly performing normal pressure, reduced pressure, and pressurized operations. These polymerization methods can be used alone or in appropriate combinations.

[0088] <At least one compound (C) selected from the group consisting of fatty acids having 18 to 32 carbon atoms and derivatives thereof>

[0089] The polyamide resin composition preferably further comprises at least one compound (C) selected from the group consisting of fatty acids having 18 to 32 carbon atoms and derivatives thereof (hereinafter also referred to as compound (C)). Compound (C) is more preferably at least one selected from the group consisting of fatty acids having 18 to 32 carbon atoms and metal salts, esters and amides thereof. By making the polyamide resin composition contain compound (C), the flexibility in a low temperature environment when the molded article is made will not be impaired, and the demolding property when the molded article is manufactured by injection molding or the like can be improved. Compound (C) can be a combination of one or more, and from the viewpoint of demolding property, a mixture of two or more is preferred.

[0090] Examples of the fatty acid having 18 to 32 carbon atoms include saturated fatty acids such as stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, and docosanoic acid; unsaturated fatty acids such as oleic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, eicosenoic acid, erucic acid, and nervonic acid; and compounds in which a part of the hydrogen atoms of the alkyl or alkenyl groups of the above fatty acids such as ricinoleic acid are substituted by hydroxyl groups or the like.

[0091] Examples of the derivatives of fatty acids having 18 to 32 carbon atoms include metal salts of the aforementioned fatty acids, ester compounds formed from the aforementioned fatty acids or halides of the aforementioned fatty acids and compounds having a hydroxyl group, and amide compounds formed from the aforementioned fatty acids and compounds having an amino group. Examples of the metal of the metal salt of the aforementioned fatty acid include lithium, magnesium, calcium, aluminum, cadmium, barium, zinc, and lead.

[0092] Examples of the ester compounds include monoester compounds such as butyl stearate, stearyl stearate, arachidyl arachidate, behenyl behenate, lignoceryl cerate, behenyl cerate, dioctadecyl cerate, myricyl melissin, tridodecyl tridecanoate, oleyl oleate, ethylene glycol monostearate, glyceryl monostearate, and pentaerythritol monostearate; and polyester compounds of fatty acids and polyols such as ethylene glycol distearate, ethylene glycol dimontanate, glyceryl (di- or tri-)stearate, glyceryl (di- or tri-)montanate, pentaerythritol (di-, tri- or tetra-)stearate, and pentaerythritol (di-, tri- or tetra-)montanate.

[0093] From the viewpoint of availability and moldability, stearyl stearate, behenyl behenate, ethylene glycol monostearate, ethylene glycol dimontanate, or (di- or tri-) montanic acid glyceryl is preferred.

[0094] Examples of the metal salt of the fatty acid include calcium stearate, magnesium stearate, zinc stearate, barium stearate, aluminum stearate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, magnesium 12-hydroxystearate, aluminum 12-hydroxystearate, barium 12-hydroxystearate, lithium 12-hydroxystearate, sodium 12-hydroxystearate, lithium behenate, calcium behenate, zinc behenate, magnesium behenate, sodium behenate, potassium behenate, calcium montanate, zinc montanate, magnesium montanate, aluminum montanate, sodium montanate, and potassium montanate.

[0095] From the viewpoint of moldability, calcium stearate, zinc stearate, lithium behenate, calcium 12-hydroxystearate, or calcium montanate is preferred.

[0096] Examples of the amide compound include stearic acid amide, arachidic acid amide, behenic acid amide, wood wax amide, wax amide, montanic acid amide, melissic acid amide, tris-dodecanoic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, and 12-hydroxystearic acid amide; methylene bis-stearic acid amide, methylene bis-12-hydroxystearic acid amide, methylene bis-arachidic acid amide, methylene bis-behenic acid amide, methylene bis-wood wax amide, methylene bis-waxylic acid amide, methylene bis-montanic acid amide, methylene bis-melissic acid amide, methylene bis-triacontanoic acid amide, ethylene bis-stearic acid amide, ethylene bis-12-hydroxystearic acid amide, ethylene bis-arachidic acid amide, ethylene bis-behenic acid amide, methylene bis-wood wax amide, methylene bis-waxylic acid amide, methylene bis-montanic acid amide, methylene bis-melissic acid amide, methylene bis-triacontanoic acid amide, ethylene bis-stearic acid amide, ethylene bis-12-hydroxystearic acid amide, ethylene bis-arachidic acid amide, ethylene bis-behenic acid amide aliphatic carboxylic acid bisamides such as amine, ethylenebislignoceric acid amide, ethylenebisceric acid amide, ethylenebismontanic acid amide, ethylenebismelly flower acid amide, ethylenebistriacontanoic acid amide, butylenebisstearic acid amide, hexamethylenebisoleic acid amide, hexamethylenebisstearic acid amide, hexamethylenebis-12-hydroxystearic acid amide, hexamethylenebisarachidic acid amide, hexamethylenebisbehenic acid amide, hexamethylenebislignoceric acid amide, hexamethylenebisceric acid amide, hexamethylenebismontanic acid amide, hexamethylenebismelly flower acid amide, hexamethylenebistriacontanoic acid amide, etc.; N-substituted compounds of the above amide compounds such as N-stearyl stearic acid amide, N-hydroxymethyl stearic acid amide, N-dioctadecylmontanic acid amide, etc.

[0097] From the viewpoint of moldability, stearic acid amide, behenic acid amide, montanic acid amide, oleic acid amide, erucic acid amide or ethylene bisstearic acid amide is preferred, and ethylene bisstearic acid amide is more preferred.

[0098] From the viewpoint of the balance between the hydrogen barrier properties of the molded article, the flexibility in a low temperature environment, and the releasability, the content of the compound (C) in 100% by mass of the polyamide resin composition is 0 to 2.0% by mass, preferably 0.01 to 2.0% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.2 to 1.0% by mass.

[0099] <Other ingredients>

[0100] The polyamide resin composition may contain other components within the range that does not impair the effects of the present invention. Other components include antioxidants, crystal nucleating agents, crystallization accelerators, heat-resistant agents, plasticizers, foaming agents, weathering agents, antistatic agents, flame retardants, flame retardant aids, pigments, dyes and other functional agents; resins other than the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B); lubricants other than the compound (C); and the like.

[0101] The content of other components is 0 to 5.0% by mass, preferably 0.01 to 2.0% by mass, and more preferably 0.05 to 1.5% by mass in 100% by mass of the polyamide resin composition.

[0102] The polyamide resin composition does not substantially contain polyolefin resins. By substantially not containing polyolefin resins, the fluidity of the composition can be improved, and the moldability can be improved. Furthermore, the hydrogen barrier properties of the molded product can be improved, and the linear expansion coefficient can also be reduced. Here, "substantially free of" means: not included to the extent that the functions or characteristics of the polyamide resin composition of the present invention and its molded product are damaged or not included to the extent that changes are caused, and inclusion to the extent that the functions or characteristics are not damaged is not excluded. Specifically, "substantially free of" means that the content ratio of polyolefin resins in 100% by mass of the polyamide resin composition is less than 0.1% by mass, preferably less than 0.05% by mass, and more preferably less than 0.01% by mass.

[0103] Examples of such polyolefin resins include unmodified polyolefin resins and modified polyolefin resins. Examples of unmodified polyolefin resins include homopolymers of α-olefins such as ethylene and propylene; (ethylene and / or propylene) / α-olefin copolymers, etc. Examples of modified polyolefin resins include polyethylene, polypropylene, (ethylene and / or propylene) / α-olefin copolymers, etc., which have functional groups such as carboxyl groups, anhydride groups, carboxylic acid ester groups, carboxylic acid metal salts, carboxylic acid imide groups, carboxylic acid amide groups, and epoxy groups; copolymerized polyolefin resins such as (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers; and olefin ionomers such as salts of (ethylene and / or propylene) / (α,β-unsaturated carboxylic acid and / or α,β-unsaturated carboxylic acid ester) copolymers.

[0104] The polyamide resin composition preferably contains an antioxidant as another component. Examples of the antioxidant include organic antioxidants and inorganic antioxidants.

[0105] (Organic antioxidant)

[0106] Examples of the organic antioxidant include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. From the viewpoint of improving the antioxidant properties of the molded article, the organic antioxidant is preferably at least one selected from the group consisting of phenolic antioxidants, phosphorus antioxidants, and sulfur antioxidants, and more preferably contains both phenolic antioxidants and phosphorus antioxidants.

[0107] Specific examples of the phenolic antioxidant include N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamic acid amide (Irganox (registered trademark) 1098; manufactured by BASF Japan Co., Ltd.), pentaerythritol-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox (registered trademark) 1010; manufactured by BASF Japan Co., Ltd.), ethylenebis(oxyethylene)bis[3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate] (Irganox (registered trademark) 245; manufactured by BASF Japan Co., Ltd.). JAPAN Co., Ltd.), 3,9-bis[2-〔3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy〕-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (SUMILIZER (registered trademark) GA-80; Sumitomo Chemical Co., Ltd.), preferably at least one selected from the group consisting of these. The phenolic antioxidant may be used alone or in combination of two or more.

[0108] As the phosphorus antioxidant, specifically, tris(2,4-di-tert-butylphenyl)phosphite (Irgafos (registered trademark) 168; manufactured by BASF JAPAN), bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite (ADEKASTAB (registered trademark) PEP-36; manufactured by ADEKA), and a reaction product of biphenyl, phosphorus trichloride and 2,4-di-tert-butylphenol with tetrakis(2,4-di-tert-butylphenoxy)-4,4-biphenyl diphosphine as the main component (Hostanox (registered trademark) P-EPQ (registered trademark) P; manufactured by Clariant Japan) can be cited, and at least one selected from the group consisting of these is preferred. The phosphorus antioxidant may be used alone or in combination of two or more.

[0109] As the sulfur-based antioxidant, thioether-based antioxidants can be cited, specifically, distearyl-3,3-thiodipropionate (Irganox (registered trademark) PS802; manufactured by BASF Japan), pentaerythritol tetrakis (3-laurylthiopropionate) (SUMILIZER (registered trademark) TP-D; manufactured by Sumitomo Chemical Co., Ltd.), didodecyl (3,3'-thiodipropionate) (Irganox (registered trademark) PS800; manufactured by BASF Japan), preferably at least one selected from the group consisting of these. The sulfur-based antioxidant may be used alone or in combination of two or more.

[0110] The content of the organic antioxidant is preferably 0.01 to 5.0% by mass, more preferably 0.01 to 2.0% by mass, and particularly preferably 0.05 to 1.5% by mass, based on 100% by mass of the polyamide resin composition.

[0111] (Inorganic antioxidant)

[0112] As inorganic antioxidants, halogenated metal antioxidants can be cited. Halogenated metal antioxidants are components that mainly impart long-term heat resistance. Halogenated metal antioxidants are compounds of halogens and metals. As halogens, fluorine, chlorine, bromine, iodine, etc. can be cited. As metals, Group 1 elements (alkali metals), Group 2 elements (alkaline earth metals), Group 3 elements to Group 12 elements (such as transition metals), etc. can be cited. The metal in the halogenated metal is preferably a metal of Group 1 elements (alkali metals) or Group 11 elements (copper group).

[0113] As the halogenated metal when the metal is a Group 1 element (alkali metal), potassium iodide, potassium bromide, potassium chloride, sodium iodide, sodium chloride, etc. can be listed. In addition, as the halogenated metal when the metal is a Group 11 element (copper family), cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide, cupric iodide, etc. can be listed. The halogenated metal antioxidant is more preferably a mixture of cuprous iodide and potassium halide or a mixture of cuprous bromide and potassium halide, and is particularly preferably a mixture of cuprous iodide and potassium iodide or a mixture of cuprous bromide and potassium bromide. In the mixture of cuprous iodide and potassium iodide or the mixture of cuprous bromide and potassium bromide, the mixing amount (mass %) of potassium iodide or potassium bromide is preferably more than the mixing amount (mass %) of cuprous iodide or cuprous bromide.

[0114] Furthermore, it is more effective to use a nitrogen-containing compound such as melamine, benzoguanamine, dimethylol urea, or cyanuric acid in combination.

[0115] The inorganic antioxidant may be used alone or in combination of two or more.

[0116] The content of the inorganic antioxidant is preferably 0.01 to 5.0% by mass, more preferably 0.01 to 2.0% by mass, and particularly preferably 0.05 to 1.0% by mass, based on 100% by mass of the polyamide resin composition.

[0117] [Method for producing polyamide resin composition]

[0118] The method for producing the polyamide resin composition is not particularly limited, and for example, the following method can be applied.

[0119] When mixing the aliphatic homopolyamide resin (A), the aliphatic copolymer polyamide resin (B), and the optional compound (C) and / or other components, a single-screw or twin-screw extruder, a Banbury mixer, a kneader, an open roll or other commonly known melt-kneading machine can be used. In addition, a blender that does not perform melt-kneading can also be used. In the case of melt-kneading, any of the following methods can be used, for example: a method of using a twin-screw extruder to blend all the raw materials and then melt-kneading; a method of blending a portion of the raw materials, then blending, further blending the remaining raw materials, and then melt-kneading; or a method of blending a portion of the raw materials and then mixing the remaining raw materials during melt-kneading using a side feeder. The polyamide resin composition can be in the form of pellets, for example, or in the form of powder.

[0120] [Density of polyamide resin composition]

[0121] From the viewpoint of rigidity and low temperature properties of the molded article, the density of the polyamide resin composition measured in accordance with ISO 1183-3 using a Type-A1 test piece molded in accordance with ISO 294-1 using an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C is preferably 1.120 g / cm 3 ~1.140g / cm 3 , more preferably 1.121 g / cm 3 ~1.135g / cm 3 , more preferably 1.125 g / cm 3 ~1.135g / cm 3 , particularly preferably 1.126 to 1.129 g / cm 3 The density of the polyamide resin composition can be determined from the density of each raw material of the polyamide resin composition and its composition ratio.

[0122] [Application of polyamide resin composition]

[0123] The polyamide resin composition has high fluidity, excellent hydrogen barrier properties and flexibility in low temperature environments when formed into molded articles, and can be used for molded articles that come into contact with high-pressure hydrogen. The polyamide resin composition is not particularly limited and can be used to produce molded articles obtained by known methods.

[0124] A molded article in contact with high-pressure hydrogen refers to a molded article in contact with hydrogen at a pressure above normal pressure. The molded article of the present invention has excellent hydrogen barrier properties, and therefore, it can be expected to exert an effect of suppressing the generation of defects when the filling and pressure release of high-pressure hydrogen are repeated. Therefore, it is preferably used for molded articles in contact with hydrogen at a pressure of 20MPa or more, and more preferably for molded articles in contact with hydrogen at a pressure of 30MPa or more. On the other hand, it is preferably used for molded articles in contact with hydrogen at a pressure of less than 200MPa, more preferably for molded articles in contact with hydrogen at a pressure of less than 150MPa, and further preferably for molded articles in contact with hydrogen at a pressure of less than 100MPa.

[0125] Examples of molded products that come into contact with high-pressure hydrogen include high-pressure hydrogen containers and parts thereof, preferably one selected from the group consisting of a high-pressure hydrogen tank liner, a high-pressure hydrogen hose, a high-pressure hydrogen pipe, and a high-pressure hydrogen joint.

[0126] Another embodiment of the present invention is one selected from the group consisting of a hydrogen storage tank liner, a hydrogen transfer hose, a hydrogen transfer pipe, and a hydrogen transfer joint comprising a polyamide resin composition. The hydrogen may be high-pressure hydrogen.

[0127] The high-pressure hydrogen tank liner comprising a polyamide resin composition can be combined with a continuous fiber reinforced resin layer and suitably used as a high-pressure hydrogen tank. That is, another embodiment of the present invention is a high-pressure hydrogen tank, which comprises a high-pressure hydrogen tank liner and a continuous fiber reinforced resin layer, and the high-pressure hydrogen tank liner comprises a polyamide resin composition. In the high-pressure hydrogen tank, it is preferably a form in which a continuous fiber reinforced resin layer is stacked on the outside of the high-pressure hydrogen tank liner comprising a polyamide resin composition. In the present invention, continuous fiber refers to a fiber having a fiber length of 100 mm or more.

[0128] Still another embodiment of the present invention is a hydrogen storage tank including a hydrogen storage tank liner and a continuous fiber reinforced resin layer, wherein the hydrogen storage tank liner includes a polyamide resin composition.

[0129] As the continuous fiber constituting the continuous fiber reinforced resin layer, carbon fiber, glass fiber, aramid fiber, etc. can be listed, among which carbon fiber is preferred from the viewpoint of specific strength and lightness. The continuous fiber can be used alone or in combination of two or more.

[0130] From the viewpoint of handling ease and weight reduction, the fiber diameter of the continuous fibers is preferably 5 to 30 μm, more preferably 5 to 20 μm, and even more preferably 5 to 10 μm.

[0131] The resin constituting the continuous fiber reinforced resin layer can be a thermosetting resin or a thermoplastic resin. As a thermosetting resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, phenolic resin, polyurethane resin, silicone resin, etc. can be exemplified, wherein, from the viewpoint of processability, epoxy resin is particularly preferred. As epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, isocyanate modified bisphenol A type epoxy resin, etc. can be listed. These thermosetting resins can be used alone or in combination of two or more. When using a thermosetting resin, a curing agent, a reaction accelerator, etc. can be used in combination.

[0132] Examples of thermoplastic resins include polyethylene resins, polypropylene resins, polyvinyl chloride resins, ABS resins, polystyrene resins, AS resins, polyamide resins, polyacetal resins, polycarbonate resins, thermoplastic polyester resins, PPS resins, fluororesins, polyetherimide resins, polyetherketone resins, polyimide resins, copolymers of these resins, and the like. These thermoplastic resins may be used alone or in combination of two or more. When using a thermoplastic resin, a compatibilizer, a flame retardant, and the like may be used in combination.

[0133] Another aspect of the present invention is a method for producing a high-pressure hydrogen tank, including the step of forming a high-pressure hydrogen tank liner from a polyamide resin composition.

[0134] There is no particular limitation on the method for manufacturing a high-pressure hydrogen tank, and the following methods may be used, for example: a method of winding continuous fibers around a high-pressure hydrogen tank liner formed into a tank shape, coating the continuous fibers with a thermosetting resin and heat-curing the continuous fibers; a method of winding continuous fibers around the aforementioned high-pressure hydrogen tank liner, and then coating the continuous fibers with a heat-melted thermoplastic resin; a method of winding continuous fibers in a state of being coated or impregnated with an uncured thermosetting resin around the aforementioned high-pressure hydrogen tank liner, and then heat-curing the uncured thermosetting resin; a method of winding continuous fibers in a state of being coated or impregnated with a thermoplastic resin around the high-pressure hydrogen tank liner, and then heat-melting the uncured thermoplastic resin; a method of molding a high-pressure hydrogen tank liner on the inner side of a continuous fiber-reinforced resin layer pre-molded into a tank shape; a method of separately molding a continuous fiber-reinforced resin layer and a high-pressure hydrogen tank liner, and then inserting a liner molded product into the continuous fiber-reinforced resin layer, etc.

[0135] Still another aspect of the present invention is a method for producing a hydrogen storage tank, comprising the step of forming a liner of the hydrogen storage tank from a polyamide resin composition.

[0136] [Method for producing molded articles in contact with high-pressure hydrogen gas]

[0137] Examples of methods for producing a molded article that comes into contact with high-pressure hydrogen include blow molding, extrusion molding, injection molding, and rotational molding, and injection molding and rotational molding are more preferably used.

[0138] There is no particular limitation on the method for producing an injection molded product from a polyamide resin composition by injection molding, and a known method can be used. For example, a method based on ISO 294-1 can be referred to. The molding conditions during injection molding are not particularly limited, and for example, the resin temperature of the polyamide resin composition can be set to 250 to 270° C., and the mold temperature can be set to 60 to 80° C.

[0139] The method for producing a rotationally molded product from a polyamide resin composition by rotational molding is not particularly limited, and a known method can be used. For example, reference is made to the method described in International Publication No. 2019 / 054109.

[0140] (Density of molded product)

[0141] The density of the molded product in contact with high-pressure hydrogen can be measured according to ISO 1183-3. Alternatively, the density of the molded product can be obtained based on the density and composition of each raw material of the molded product. For example, the density of the molded product can be calculated by the following formula (1).

[0142] Density of molded product = Σ(ρ i ×W i )------Formula (1)

[0143] In the formula, ρ i is the density of each raw material (g / cm 3 ), W i is the composition ratio of each raw material.

[0144] From the viewpoint of rigidity and low-temperature properties of the molded article, the density of the molded article in contact with high-pressure hydrogen is preferably 1.120 g / cm 3 ~1.140g / cm 3 , more preferably 1.121 g / cm 3 ~1.135g / cm 3 , more preferably 1.125 g / cm 3 ~1.135g / cm 3 , particularly preferably 1.126 to 1.129 g / cm 3 .

[0145] (Hydrogen permeability coefficient of molded products)

[0146] Regarding molded articles that come into contact with high-pressure hydrogen, in accordance with JIS K 7126-1, the polyamide resin composition is used and an injection molding machine is used to mold a plate-shaped test piece of 80 mm×80 mm and 2.0 mm in thickness at a resin temperature of 250°C and a mold temperature of 80°C. For a circular molded article of Φ60 mm in diameter cut out from the test piece, the hydrogen permeability coefficient at 55°C and 1 atm measured by a differential pressure method is preferably greater than 0.1×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.8×10 - 10 cm 3 cm / (cm 2 ·s·cmHg), more preferably more than 0.1×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.7×10 -10 cm 3 cm / (cm 2 ·s·cmHg), more preferably more than 0.1×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.5×10 -10 cm 3 cm / (cm 2 When the hydrogen permeability coefficient is within the above range, the hydrogen barrier property is excellent and the molded article can be suitably used for a molded article that comes into contact with high-pressure hydrogen.

[0147] (Low-temperature flexibility of molded products)

[0148] Regarding molded articles in contact with high-pressure hydrogen, for a Type-A1 test piece obtained by molding the polyamide resin composition according to ISO 294-1 at a resin temperature of 250°C and a mold temperature of 80°C using an injection molding machine, the test piece is stored at -60°C for 1 hour, and the tensile modulus is preferably greater than 1,600 MPa and less than 2,800 MPa, more preferably greater than 1,600 MPa and less than 2,750 MPa, and further preferably greater than 1,600 MPa and less than 2,700 MPa. If the tensile modulus at -60°C is within the above range, the molded article has an excellent balance between flexibility and mechanical strength in a low-temperature environment, and can be suitably used for molded articles in contact with high-pressure hydrogen. If the tensile modulus is 1,600 MPa or less, the molded article is easily deformed. When the tensile elastic modulus is 2,800 MPa or more, the molded product is easily broken.

[0149] Example

[0150] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0151] [Evaluation method]

[0152] 1. Relative viscosity

[0153] For an aliphatic homopolyamide resin, an aliphatic copolymer polyamide resin, and a mixture thereof, 1 g of the polyamide resin was dissolved in 100 ml of 96% sulfuric acid, and the relative viscosity at 25° C. was measured in accordance with JIS K6920.

[0154] 2. Density

[0155] The density of the aliphatic homopolyamide resin, aliphatic copolymer polyamide resin and polyamide resin composition was measured in accordance with ISO 1183-3 using a Type-A1 test piece molded by an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C in accordance with ISO 294-1.

[0156] 3. Injection flow length

[0157] Using an injection molding machine (manufactured by Nissin Resin Industry Co., Ltd., trade name: PS40E) equipped with a bar flow mold with a cavity thickness of 1 mm, a width of 15 mm, and a length of 360 mm, the pellets of the embodiment and the comparative example were injection molded under the molding conditions of an injection pressure of 50 MPa, a barrel temperature of 265°C, a mold temperature of 65°C, an injection speed of 38 mm / sec, an injection time of 4 seconds, and a cooling time of 15 seconds. The total length of the molded product obtained by injection molding from the gate outlet was measured as the L / T flow length. The fluidity of the polyamide resin composition was evaluated according to the following criteria.

[0158] ◎: L / T flow length is 120 mm or more

[0159] ○: L / T flow length is 105 mm or more and less than 120 mm

[0160] ×: L / T flow length is less than 105mm

[0161] 4. Hydrogen permeability coefficient

[0162] According to JIS K7126-1, the pellets of the examples and comparative examples were respectively used to form a plate-shaped test piece of 80 mm × 80 mm and a thickness of 2.0 mm at a resin temperature of 250 ° C and a mold temperature of 80 ° C using an injection molding machine. For the circular molded product with a diameter of Φ60 mm cut from the test piece, a hydrogen permeation test was performed at 55 ° C, 0% RH and 1 atm using the differential pressure method. The measuring device used a differential pressure gas / vapor permeability measuring device (GTR-30XAD, serial number: G2700T·F (manufactured by GTR TEC Co., Ltd.)). The hydrogen barrier properties were evaluated according to the following criteria.

[0163] ◎: Hydrogen permeability coefficient exceeds 0.1×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.5×10 -10 cm 3 cm / (cm 2 ·s·cmHg)

[0164] ○: Hydrogen permeability coefficient is 1.5×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.8×10 - 10 cm 3 cm / (cm 2 ·s·cmHg)

[0165] ×: Hydrogen permeability coefficient is 1.8×10 -10 cm 3 cm / (cm 2 ·s·cmHg) or more

[0166] 5. Tensile elastic modulus at -60°C

[0167] According to ISO 294-1, the pellets of the embodiment and the comparative example were respectively used, and the injection molding machine was used to mold them at a resin temperature of 250°C and a mold temperature of 80°C to produce Type-A1 test pieces. After the test piece was stored at -60°C for 1 hour, the tensile modulus was measured at a test speed of 50 mm / min at a tensile nominal deformation between 0.3% and 0.5% in accordance with ISO 527-2. In addition, the presence or absence of brittle failure during the tensile test was evaluated. The testing machine used was a tensile testing machine manufactured by INSTRON: Model 5567. Based on the value of the tensile modulus, the softness was evaluated according to the following criteria.

[0168] ◎: Tensile modulus at -60°C is more than 1,600 MPa and less than 2,700 MPa

[0169] ○: The tensile modulus at -60°C is 2,700 MPa or more and less than 2,800 MPa

[0170] ×: Tensile modulus at -60°C is 2,800 MPa or more

[0171] [Materials used]

[0172] 1. Polyamide resin

[0173] (1) Aliphatic homopolymer polyamide resin

[0174] PA6-1: Polyamide 6 (manufactured by UBE: relative viscosity = 1.93, density = 1.129 g / cm 3 )

[0175] PA6-2: Polyamide 6 (manufactured by UBE: relative viscosity = 2.24, density = 1.129 g / cm 3 )

[0176] PA6-3: Polyamide 6 (manufactured by UBE: relative viscosity = 2.45, density = 1.129 g / cm 3 )

[0177] PA6-4: Polyamide 6 (manufactured by UBE: relative viscosity = 2.64, density = 1.129 g / cm 3 )

[0178] PA6-5: Polyamide 6 (manufactured by UBE: relative viscosity = 2.78, density = 1.129 g / cm 3 )

[0179] (2) Aliphatic copolymer polyamide resin

[0180] PA6 / 66-1: Polyamide 6 / 66 (manufactured by UBE: relative viscosity = 3.04; copolymer of polyamide 6 component = 92 mol% and polyamide 66 component = 8 mol%, density = 1.117 g / cm 3 )

[0181] PA6 / 66-2: Polyamide 6 / 66 (manufactured by UBE: relative viscosity = 4.05; copolymer of polyamide 6 component = 90 mol% and polyamide 66 component = 10 mol%, density = 1.117 g / cm 3 )

[0182] PA6 / 66 / 12-1: Polyamide 6 / 66 / 12 (manufactured by UBE: relative viscosity = 4.05; copolymer of polyamide 6 component = 88 mol %, polyamide 66 component = 5 mol %, and polyamide 12 component = 7 mol %, density = 1.117 g / cm 3 )

[0183] 2. Polyolefin resin

[0184] Maleic anhydride-modified ethylene-butene copolymer (manufactured by Mitsui Chemicals, Inc., Tafmer (registered trademark) MH5020, density = 0.866 g / cm 3 (Product Catalog Data)

[0185] 3. Compound (C)

[0186] A mixture of long-chain fatty acid esters with carbon atoms of 18 to 32 and long-chain fatty acid calcium

[0187] 4. Antioxidants

[0188] Halogenated metal antioxidant: a mixture of cuprous iodide and potassium iodide, with a mass ratio of 1:6

[0189] Examples 1 to 9 and Comparative Examples 1 to 7

[0190] For each component described in Table 1 and Table 2, a ZSK32mc twin-screw extruder (manufactured by Coperion, with a barrel diameter of 32 mm and an L / D of 48) was used as a twin-screw kneading machine, and melt-kneading was performed under the conditions of a barrel temperature of 250° C., a screw speed of 200 rpm, and a discharge rate of 50 kg / hrs to produce pellets of the target polyamide resin composition. It should be noted that the unit of the composition in the table is mass %, and the entire resin composition is set to 100 mass %.

[0191] The pellets obtained in this manner were subjected to the above-mentioned evaluations. The evaluation results of the polyamide resin compositions of Examples 1 to 9 and Comparative Examples 1 to 7 are shown in Tables 1 and 2, respectively.

[0192] [Table 1]

[0193]

[0194] [Table 2]

[0195]

[0196] As shown in Table 1, the polyamide resin compositions of Examples 1 to 9, which contain an aliphatic homopolyamide resin (A) having a relative viscosity of 1.80 to 2.70 and an aliphatic copolymer polyamide resin (B) having a relative viscosity of 2.90 to 4.20, and a relative viscosity of the mixture of the components (A) and (B) of 2.30 to 3.60, and do not contain a polyolefin resin, have high fluidity, excellent hydrogen barrier properties of molded articles, no brittle fracture in a tensile test at -60°C, and excellent flexibility in a low temperature environment. The polyamide resin compositions of Examples 3, 4, and 7, in which the relative viscosity of the aliphatic homopolyamide resin (A) is 2.20 to 2.60, the relative viscosity of the aliphatic copolymer polyamide resin (B) is 2.90 to 4.20, and the relative viscosity of the mixture of the components (A) and (B) is 2.40 to 2.80, are excellent in fluidity, hydrogen barrier properties of molded articles, and flexibility in a low temperature environment, and are preferred.

[0197] Comparative Example 1, which used only an aliphatic homopolyamide resin having a relative viscosity outside the range of the present application as the polyamide resin, had poor fluidity. Comparative Examples 2 to 4, which used an aliphatic homopolyamide resin having a relative viscosity within the range of the present application but did not mix an aliphatic copolymer polyamide resin (B), had poor flexibility in a low temperature environment. Comparative Example 5, which used an aliphatic homopolyamide resin (A) having a relative viscosity within the range of the present application and an aliphatic copolymer polyamide resin (B) but whose mixture had a relative viscosity outside the range of the present application, suffered brittle failure during a tensile test at -60°C.

[0198] Comparative Example 6 obtained by using only the aliphatic copolymer polyamide resin (B) was inferior in fluidity. Comparative Example 7 obtained by using aliphatic homopolyamide resin and modified polyolefin resin in combination was inferior in fluidity and hydrogen barrier properties of the molded article.

[0199] Industrial Applicability

[0200] The polyamide resin composition of the present invention can be suitably used to produce various molded products by injection molding, rotational molding, and the like.

Claims

1. A polyamide resin composition for a molded article in contact with high-pressure hydrogen, comprising an aliphatic homopolyamide resin (A) and an aliphatic copolymer polyamide resin (B), and at least one compound (C) selected from the group consisting of fatty acids having 18 to 32 carbon atoms and derivatives thereof as an optional component, wherein the polyamide resin composition does not substantially contain a polyolefin resin. Regarding the relative viscosity measured at 25°C by dissolving 1 g of a polyamide resin in 100 ml of 96% sulfuric acid in accordance with JIS K 6920, The relative viscosity of the aliphatic homopolyamide resin (A) is 1.80 to 2.70, The relative viscosity of the aliphatic copolymer polyamide resin (B) is 2.90 to 4.20, The relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 2.30 to 3.60, The polyamide resin composition contains 93.0 to 100 mass % of the total of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B), 0 to 2.0 mass % of the compound (C), and 0 to 5.0 mass % of other components in 100 mass % of the polyamide resin composition. The ratio of the aliphatic homopolyamide resin (A) to the aliphatic copolymer polyamide resin (B) is 50:50 to 90:10 on a mass basis.

2. The polyamide resin composition according to claim 1, wherein The ratio of the aliphatic homopolyamide resin (A) to the aliphatic copolymer polyamide resin (B) is 65:35 to 90:10 on a mass basis.

3. The polyamide resin composition according to claim 1 or 2, wherein The relative viscosity of the aliphatic homopolyamide resin (A) is 1.80 to 2.

60.

4. The polyamide resin composition according to claim 1 or 2, wherein The relative viscosity of the mixture of the aliphatic homopolyamide resin (A) and the aliphatic copolymer polyamide resin (B) is 2.40 to 2.

80.

5. The polyamide resin composition according to claim 1 or 2, wherein The aliphatic copolymer polyamide resin (B) contains 75 mol% or more and less than 95 mol% of a structural unit derived from ε-caprolactam and a structural unit derived from 6-aminocaproic acid in 100 mol% of all structural units.

6. The polyamide resin composition according to claim 1 or 2, wherein The compound (C) is at least one selected from the group consisting of fatty acids having 18 to 32 carbon atoms and metal salts, esters and amides thereof.

7. The polyamide resin composition according to claim 1 or 2, wherein The density of the aliphatic homopolyamide resin (A), the aliphatic copolymer polyamide resin (B) and the polyamide resin composition measured in accordance with ISO 1183-3 using a Type-A1 test piece molded by an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C in accordance with ISO 294-1 was 1.120 g / cm 3 ~1.150g / cm 3 , 1.100g / cm 3 ~1.130g / cm 3 and 1.120g / cm 3 ~1.140g / cm 3 .

8. The polyamide resin composition according to claim 7, wherein The density of the polyamide resin composition measured in accordance with ISO 1183-3 was 1.126 to 1.129 g / cm2 using a Type-A1 test piece molded by an injection molding machine at a resin temperature of 250°C and a mold temperature of 80°C in accordance with ISO 294-1. 3 .

9. The polyamide resin composition according to claim 1 or 2, wherein The hydrogen permeability coefficient at 55°C and 1 atm measured by the differential pressure method for a circular molded article having a thickness of 2.0 mm and a diameter of Φ60 mm obtained by molding the polyamide resin composition at a resin temperature of 250°C and a mold temperature of 80°C using an injection molding machine in accordance with JIS K7126-1 is greater than 0.1×10 -10 cm 3 cm / (cm 2 ·s·cmHg) and less than 1.8×10 -10 cm 3 cm / (cm 2 ·s·cmHg).

10. A molded article in contact with high-pressure hydrogen, comprising the polyamide resin composition according to claim 1 or 2.

11. The molded article in contact with high-pressure hydrogen according to claim 10, which is one selected from the group consisting of a tank liner for high-pressure hydrogen, a hose for high-pressure hydrogen, a pipe for high-pressure hydrogen, and a joint for high-pressure hydrogen. 12 . A high-pressure hydrogen tank, comprising a high-pressure hydrogen tank liner and a continuous fiber reinforced resin layer, wherein the high-pressure hydrogen tank liner comprises the polyamide resin composition according to claim 1 or 2.

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