Multilayer structure and pipe for transferring combustible gas

Abstract

To provide a multilayer structure used for storage or transfer of a combustible gas, which exhibits enhanced flexibility without greatly deteriorating the excellent gas barrier properties of a barrier layer containing an ethylene-vinyl alcohol copolymer.SOLUTION: A multilayer structure 1 comprises a first polyamide layer 21 containing a polyamide resin, a barrier layer 10 containing an ethylene-vinyl alcohol copolymer, and a second polyamide layer 22 containing a polyamide resin, and is used for storing or transferring a gas containing a combustible gas. The multilayer structure 1 has a hollow portion surrounding a cavity 5 capable of storing or transferring the gas. In the hollow portion, the first polyamide layer 21, the barrier layer 10, and the second polyamide layer 22 are provided in this order from the cavity 5 side. The thickness t2 of the second polyamide layer 22 is greater than the thickness t1 of the first polyamide layer 21.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a multilayer structure used for storing or transporting gases including combustible gases, and a piping for transporting combustible gases. [Background technology]

[0002] An annular multilayer structure may be used as a pipe for transporting hydrogen from a hydrogen gas generator or a hydrogen gas storage device to a facility that uses hydrogen (e.g., a fuel cell). For example, Patent Document 1 discloses a tube for guiding hydrogen, which includes a support layer, an inner barrier layer, a separation layer, and an outer barrier layer, and the inner and outer barrier layers include vinyl alcohol plastic. Patent Document 2 discloses a multilayer structure for storing or transporting gases including hydrogen, which includes an inner layer, an intermediate layer, and an outer layer, and the inner layer includes high-density polyethylene and the outer layer includes polyamide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-81348 [Patent Document 2] Special Publication No. 2023-547754 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure relates to multi-layer structures for storing or transporting combustible gases that have increased flexibility without significantly compromising the gas barrier properties provided by a barrier layer comprising an ethylene-vinyl alcohol copolymer. [Means for solving the problem]

[0005] The present disclosure includes the following: [1] a first polyamide layer containing a polyamide resin; a barrier layer comprising an ethylene-vinyl alcohol copolymer; a second polyamide layer comprising a polyamide resin; A multilayer structure comprising: the multilayer structure having a hollow portion surrounding a cavity capable of storing or transporting a gas; the first polyamide layer, the barrier layer, and the second polyamide layer are provided in this order from the cavity side in the hollow portion, the thickness of the second polyamide layer is greater than the thickness of the first polyamide layer; A multilayer structure used to store or transport gases, including combustible gases. [2] The multilayer structure according to [1], wherein the barrier layer is in direct contact with the first polyamide layer and the second polyamide layer. [3] The multilayer laminate according to [1] or [2], wherein the flexural modulus of the material forming the second polyamide layer is smaller than the flexural modulus of the material forming the first polyamide layer. [4] the second polyamide layer further comprises a plasticizer and the first polyamide layer does not comprise a plasticizer; or The multilayer structure according to any one of [1] to [3], wherein the second polyamide layer and the first polyamide layer further contain a plasticizer, and the proportion of the plasticizer in the first polyamide layer is smaller than the proportion of the plasticizer in the second polyamide layer. [5] The multilayer structure according to any one of [1] to [4], wherein the polyamide contained in the first polyamide layer and the polyamide contained in the second polyamide layer include polyamide 11. [6] The multilayer structure according to any one of [1] to [5], further comprising a protective layer containing a fluororesin provided on the side of the second polyamide layer opposite to the barrier layer. [7] The multilayer structure according to any one of [1] to [6], wherein the proportion of ethylene units in the ethylene-vinyl alcohol copolymer is 20 mol % or more and 60 mol % or less based on the amount of all monomer units constituting the ethylene-vinyl alcohol copolymer. [8] The multilayer structure according to any one of [1] to [7], wherein the combustible gas contains hydrogen. [9] The multilayer structure according to any one of [1] to [8], wherein the hollow portion is tubular.

[10] [9] A piping for transporting a combustible gas, comprising the multilayer structure according to the present invention. [Effects of the Invention]

[0006] A multilayer structure for storing or transporting combustible gases can be provided that has greater flexibility without significantly impairing the good gas barrier properties provided by the barrier layer containing the ethylene-vinyl alcohol copolymer. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a multilayer structure. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention is not limited to the following examples.

[0009] Fig. 1 is a cross-sectional view showing an example of a multilayer structure. The multilayer structure 1 shown in Fig. 1 is a tubular body having a tubular hollow portion surrounding a cavity 5. Fig. 1 shows a cross section perpendicular to the longitudinal direction of the multilayer structure 1. The multilayer structure 1 is configured to allow gas to flow through the cavity 5.

[0010] The multilayer structure 1 is composed of a first polyamide layer 21 containing a polyamide resin, a barrier layer 10 containing an ethylene-vinyl alcohol copolymer, a second polyamide layer 22 containing a polyamide resin, and a protective layer 30 containing a fluororesin. In a hollow portion of the multilayer structure 1 that surrounds the cavity 5, the first polyamide layer 21, the barrier layer 10, and the second polyamide layer 22 are provided in this order from the cavity 5 side.

[0011] The barrier layer 10 containing ethylene-vinyl alcohol copolymer (EVOH) is a layer that mainly inhibits the permeation of combustible gases (e.g., hydrogen) from the cavity 5 side to the outside of the multilayer structure 1. Ethylene-vinyl alcohol copolymer is a relatively brittle material, but when a first polyamide layer 21 and a second polyamide layer 22 are provided on both sides of the barrier layer 10 and the thickness of the second polyamide layer is greater than the thickness of the first polyamide layer, the multilayer structure 1 can have appropriate flexibility.

[0012] The thickness of the barrier layer 10 may be 100 μm or more and 800 μm or less from the viewpoint of barrier properties against combustible gases, etc. The thickness of the barrier layer 10 may be 200 μm or more, or 300 μm or more. Even when the barrier layer 10 is relatively thick, the multilayer structure 1 can have appropriate flexibility.

[0013] The proportion of ethylene units in the ethylene-vinyl alcohol copolymer contained in the barrier layer 10 may be 20 mol % or more and 60 mol % or less, or 20 mol % or more and 30 mol % or less, based on the amount of all monomer units constituting the ethylene-vinyl alcohol copolymer. The proportion of the ethylene-vinyl alcohol copolymer in the barrier layer 10 may be 60 mass % or more, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 95 mass % or more, or may be 100 mass % or less, based on the mass of the barrier layer 10.

[0014] The first polyamide layer 21 and the second polyamide layer 22 each contain a polyamide resin. The first polyamide layer 21 and the second polyamide layer 22 may contain the same or different types of polyamide resin.

[0015] When the thickness of the first polyamide layer 21 is t1 and the thickness of the second polyamide layer 22 is t2, t2 is greater than t1. When t2 is greater than t1, the multilayer structure 1 is likely to have appropriate flexibility. t1 and t2 refer to the maximum thickness of each layer in the stacking direction of the multilayer structure 1. The stacking direction of the multilayer structure 1 is usually the direction along the shortest line connecting the inner surface of the multilayer structure 1 on the cavity side to the outermost surface of the multilayer structure 1. The ratio t2 / t1 of the thickness t2 of the second polyamide layer 22 to the thickness t1 of the first polyamide layer 21 may be, for example, 1.5 or greater and 8.0 or less. The ratio t2 / t1 may be 2.0 or greater, 2.5 or greater, 3.0 or greater, or 3.5 or greater, or 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, 5.0 or less, or 4.5 or less.

[0016] The thickness t1 of the first polyamide layer 21 may be 100 μm or more and 600 μm or less. The thickness t1 of the first polyamide layer 21 may be 150 μm or more, or 550 μm or less, 500 μm or less, 450 μm or less, 400 μm or less, 350 μm or less, 300 μm or less, or 250 μm or less.

[0017] The thickness t2 of the second polyamide layer 22 may be 500 μm or more and 1500 μm or less. The thickness t2 of the second polyamide layer 22 may be 550 μm or more, 600 μm or more, 650 μm or more, 700 μm or more, or 750 μm or more, and may be 1400 μm or less, 1300 μm or less, 1200 μm or less, 1100 μm or less, 1000 μm or less, 950 μm or less, 900 μm or less, or 850 μm or less.

[0018] The polyamide resin contained in the first polyamide layer 21 or the second polyamide layer 22 may be, for example, polyamide 11, polyamide 12, polyamide P9T, or a combination of two or more selected from these. The polyamide resin contained in the first polyamide layer 21 or the second polyamide layer 22 may be polyamide 11, polyamide 12, or a combination thereof, or may be polyamide 11.

[0019] The flexural modulus of the material forming the second polyamide layer 22 may be smaller than the flexural modulus of the material forming the first polyamide layer 21. This allows the multilayer structure 1 to more easily have appropriate flexibility. The flexural modulus here may be the modulus measured by a three-point bending test on a rectangular test piece cut out from a sheet-like molded product made of the same material (polyamide composition) as the material forming the first polyamide layer 21 or the second polyamide layer. When the flexural modulus of the material forming the first polyamide layer 21 is E1 and the flexural modulus of the material forming the second polyamide layer 22 is E2, the ratio E2 / E1 may be 0.10 or more and 0.80 or less. The ratio E2 / E1 may be 0.15 or more, 0.20 or more, or 0.25 or more, or may be 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, or 0.40 or less.

[0020] The flexural modulus E1 of the material forming first polyamide layer 21 may be 400 MPa or more and 2000 MPa or less. The flexural modulus E1 of the material forming first polyamide layer 21 may be 450 MPa or more, 500 MPa or more, 550 MPa or more, 600 MPa or more, 650 MPa or more, 700 MPa or more, 750 MPa or more, or 800 MPa or more, or may be 1500 MPa or less, 1400 MPa or less, 1300 MPa or less, 1200 MPa or less, 1100 MPa or less, 1000 MPa or less, 950 MPa or less, or 900 MPa or less.

[0021] The flexural modulus E2 of the material forming the second polyamide layer 22 may be 200 MPa or more and 1800 MPa or less. The flexural modulus E2 of the material forming the second polyamide layer 22 may be 250 MPa or more, 300 MPa or more, 350 MPa or more, 400 MPa or more, 450 MPa or more, or 500 MPa or more, or may be 1000 MPa or less, 900 MPa or less, 850 MPa or less, 800 MPa or less, 750 MPa or less, 700 MPa or less, 650 MPa or less, or 600 MPa or less.

[0022] The elastic modulus of the first polyamide layer 21 and the second polyamide layer 22 can be adjusted, for example, by introducing a plasticizer. From the viewpoint of adjusting the elastic modulus, the second polyamide layer 22 may further contain a plasticizer, and the first polyamide layer 21 may not contain a plasticizer. Alternatively, the second polyamide layer 22 and the first polyamide layer 21 may further contain a plasticizer, and the proportion of the plasticizer in the first polyamide layer 21 may be smaller than the proportion of the plasticizer in the second polyamide layer 22. The proportion of the plasticizer here may be a proportion based on the total mass of the first polyamide layer 21 or the second polyamide layer 22.

[0023] When the second polyamide layer 22 and the first polyamide layer 21 contain a plasticizer, the plasticizer contained in the first polyamide layer 21 may be the same as or different from the plasticizer contained in the second polyamide layer 22. The plasticizer can be arbitrarily selected from those commonly used as plasticizers for polyamide resins.

[0024] 1 , the barrier layer 10 is in direct contact with the first polyamide layer 21 and the second polyamide layer 22 without an adhesive layer or the like. Even if no adhesive layer is provided, sufficient adhesion can be ensured between the barrier layer 10 and the first polyamide layer 21 or the second polyamide layer 22. However, an adhesive layer may be provided between the barrier layer 10 and the first polyamide layer 21 and / or the second polyamide layer 22, if necessary.

[0025] The protective layer 30 is provided on the opposite side of the second polyamide layer 22 to the barrier layer 10, and is positioned as the outermost layer of the multilayer structure 1. The protective layer 30 containing a fluororesin can further improve the weather resistance of the multilayer structure 1. The protective layer 30 can also contribute to maintaining the gas barrier performance of the barrier layer 20 by suppressing the penetration of water into the barrier layer 10. The fluororesin contained in the protective layer 30 may be, for example, ethylene-tetrafluoroethylene copolymer (ETFE). The thickness of the protective layer 30 may be, for example, 100 μm or more and 1000 μm or less.

[0026] The multilayer structure 1 having a tubular hollow portion can be used, for example, as a piping for transporting a combustible gas for transporting a gas containing a combustible gas. In particular, the multilayer structure 1 may be a piping for transporting a hydrogen gas for transporting a gas containing hydrogen. A piping provided with the multilayer structure 1 may be installed outdoors.

[0027] The hollow portion of the multilayer structure 1 has a substantially circular cross section. The outer diameter D of the multilayer structure 1 may be, for example, 8 mm or more and 200 mm or less. The inner diameter d of the multilayer structure 1 may be, for example, 6 mm or more and 190 mm or less. The thickness of the multilayer structure 1 may be, for example, 1 mm or more and 15 mm or less.

[0028] The multilayer structure 1 can be manufactured by a conventional molding method, for example, by extrusion molding, in which multiple layers of material are extruded.

[0029] The present invention is not limited to the above examples and can be modified as appropriate. For example, the multilayer structure 1 may have only one barrier layer as in the example of FIG. 1, or may have two or more barrier layers. The protective layer 30 containing a fluororesin does not have to be provided. The hollow portion of the multilayer structure does not have to be tubular, and may have any shape that forms a cavity capable of storing a gas.

[0030] Below, an example in which the flexibility of the multilayer structure according to the present disclosure was verified will be described.

[0031] The flexural modulus and deflection were calculated for an analytical model of a three-layer tubular body consisting of a first polyamide layer, a barrier layer, and a second polyamide layer. The dimensions of the tubular body were as follows: Outer diameter D: 31.4mm Inner diameter d:28.4mm

[0032] Calculations were performed on a multilayer structure formed from materials having the flexural modulus shown in Table 1. In the ethylene-vinyl alcohol copolymer (EVOH) contained in the EVOH composition, the proportion of ethylene units was 29 mol% based on the amount of all monomer units constituting the EVOH.

[0033] [Table 1]

[0034] The flexural modulus and deflection were calculated for each of levels #1 to #5, in which the types of materials constituting the first polyamide layer, barrier layer, and second polyamide layer and the thicknesses of each layer were set as shown in Table 2. The deflection shown in the table is the deflection when a load of 0.00013 kg / mm ​​is applied to the center of a 3000 mm long tubular body in the longitudinal direction with both ends fixed.

[0035] [Table 2]

[0036] The tubular structures of levels 1 to 5 have the same gas barrier properties because they have barrier layers of the same thickness. As shown in Table 2, the tubular structures of levels 1 to 3, in which t2 is greater than t1, exhibited smaller flexural moduli and larger deflections than the tubular structures of levels 4 and 5. This suggests that the multilayer structures according to the present disclosure have higher flexibility without significantly compromising the excellent gas barrier properties provided by the barrier layer. [Explanation of symbols]

[0037] 1...multilayer structure, 5...cavity, 10...barrier layer, 21...first polyamide layer, 22...second polyamide layer, 30...protective layer, t1...thickness of first polyamide layer, t2...thickness of second polyamide layer.

Claims

1. a first polyamide layer containing a polyamide resin; a barrier layer comprising an ethylene-vinyl alcohol copolymer; a second polyamide layer containing a polyamide resin; A multilayer structure comprising: the multilayer structure having a hollow portion surrounding a cavity capable of storing or transporting a gas; the first polyamide layer, the barrier layer, and the second polyamide layer are provided in this order from the cavity side in the hollow portion, the thickness of the second polyamide layer is greater than the thickness of the first polyamide layer; A multilayer structure used to store or transport gases, including combustible gases.

2. 10. The multilayer structure of claim 1, wherein the barrier layer is in direct contact with the first polyamide layer and the second polyamide layer.

3. 10. The multilayer structure of claim 1, wherein the flexural modulus of the material forming the second polyamide layer is less than the flexural modulus of the material forming the first polyamide layer.

4. the second polyamide layer further comprises a plasticizer and the first polyamide layer does not comprise a plasticizer; or 10. The multilayer structure of claim 1, wherein the second polyamide layer and the first polyamide layer further comprise a plasticizer, and the percentage amount of the plasticizer in the first polyamide layer is less than the percentage amount of the plasticizer in the second polyamide layer.

5. 2. The multilayer structure of claim 1, wherein the polyamide contained in the first polyamide layer and the polyamide contained in the second polyamide layer comprise polyamide 11.

6. 2. The multilayer structure of claim 1, further comprising a protective layer comprising a fluororesin provided on the side of the second polyamide layer opposite the barrier layer.

7. 2. The multilayer structure according to claim 1, wherein the proportion of ethylene units in the ethylene-vinyl alcohol copolymer is 20 mol % or more and 60 mol % or less based on the amount of all monomer units constituting the ethylene-vinyl alcohol copolymer.

8. The multi-layer structure of claim 1 , wherein the combustible gas comprises hydrogen.

9. 10. The multi-layer structure of claim 1, wherein the hollow portion is tubular.

10. A piping for transporting a combustible gas, comprising the multilayer structure according to claim 9.

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