Adhesive frame for fuel cell

Abstract

To shorten a manufacturing time and improve the yield.SOLUTION: An adhesive frame 16 for fuel cell is disposed around the periphery of an MEA 14 that constitutes a fuel cell 10, and is a single layer film containing a thermoplastic elastomer and a tackifier.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an adhesive frame for a fuel cell. [Background technology]

[0002] A configuration has been proposed in which a frame-shaped adhesive frame is placed between separators that make up a fuel cell to surround a membrane electrode assembly, which forms the power generation zone. Patent Document 1 discloses a multilayer frame in which both sides of a base sheet such as polyethylene are sandwiched between elastic parts containing at least one of rubber and thermoplastic elastomer resin. Patent Document 2 also discloses a frame in which an adhesive is applied to both sides of a base sheet and the sheets are bonded by a hot press. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-198200 [Patent Document 2] Patent Publication No. 2021-86695 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the prior art, the adhesive frame is a multi-layer sheet in which layers of different materials are laminated, making it difficult to improve yield.

[0005] An object of the present invention is to provide an adhesive frame for a fuel cell that can improve yield. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the objectives, the adhesive frame for a fuel cell of the present invention is an adhesive frame for a fuel cell arranged on the periphery of a membrane electrode assembly that constitutes a fuel cell, and is a single-layer film containing a thermoplastic elastomer and a tackifier. [Effects of the Invention]

[0007] According to the present invention, the yield can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an example of a fuel cell according to an embodiment. [Figure 2] FIG. 2 is an enlarged perspective view of some of the stacked cells in the fuel cell. [Figure 3] FIG. 3 is an exploded perspective view of a single cell. [Figure 4] FIG. 4 is an explanatory diagram of the T-peel test. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an adhesive frame for a fuel cell according to the present invention will be described in detail with reference to the accompanying drawings.

[0010] The adhesive frame for a fuel cell of this embodiment is an adhesive frame for a fuel cell that is arranged on the periphery of a membrane electrode assembly (MEA) that constitutes a fuel cell, and is a single-layer film that contains a thermoplastic elastomer (which makes it reusable) and a tackifier (which is necessary for adhesion since it will be stacked).

[0011] The pressure-sensitive adhesive frame for a fuel cell of this embodiment is a single-layer film containing a thermoplastic elastomer and a tackifier, and therefore can seal between the components that make up the fuel cell by assembling and clamping them at room temperature, thereby shortening the manufacturing time. Furthermore, because the pressure-sensitive adhesive frame for a fuel cell of this embodiment is a single-layer film containing a thermoplastic elastomer and a tackifier, scrap generated during manufacturing can be recycled as a pressure-sensitive adhesive frame for a fuel cell by heating and melting it, thereby improving the yield.

[0012] Therefore, the adhesive frame for a fuel cell of this embodiment can shorten the manufacturing time and improve the yield.

[0013] Furthermore, in the prior art, a heat press step was required when applying an adhesive, but the pressure-sensitive adhesive frame for a fuel cell of this embodiment can eliminate the need for a heat press step.

[0014] In this embodiment, normal temperature means a temperature in the range of 5°C or higher and 35°C or lower.

[0015] The pressure-sensitive adhesive frame for a fuel cell and the fuel cell including the pressure-sensitive adhesive frame for a fuel cell according to this embodiment will be described in detail below.

[0016] Fig. 1 is a schematic diagram showing an example of a fuel cell 10 according to this embodiment. Fig. 1 shows an example of the configuration of a polymer electrolyte fuel cell using an adhesive frame for a fuel cell according to this embodiment. The fuel cell 10 is, for example, a stack of multiple cells C. The stack is clamped in the stacking direction.

[0017] Fig. 2 is an enlarged perspective view of some of the stacked cells C in the fuel cell 10. Fig. 2 shows an enlarged view of three sets of cells C in the fuel cell 10 as an example. Fig. 3 is an example of an exploded perspective view of one set of cells C.

[0018] 2 and 3, for example, a cell C includes an MEA (membrane electrode assembly) 14, separators 12 and 13, and an adhesive frame for a fuel cell 16. FIG. 3 shows, as an example, a configuration in which one cell C includes a pair of separators 12 and 13 and an MEA 14 disposed between the pair of separators 12 and 13. However, one cell C may also be configured to include one separator 12 or 13 and an MEA 14, and the separators 12 and 13 may be previously combined by welding or the like.

[0019] The separators 12 and 13 are substantially rectangular members with manifold holes 12A and 13A formed near their outer peripheries. Furthermore, the separators 12 and 13 have grooves formed thereon by molding or the like, and these grooves form flow paths within the fuel cell 10, such as an oxidizing gas flow path, a fuel gas flow path, and a refrigerant flow path.

[0020] Examples of materials for the separators 12 and 13 include stainless steel, titanium, and carbon composite materials.

[0021] The MEA 14 functions as a power generating body and is a rectangular thin plate assembly in which an electrolyte membrane is sandwiched between a pair of electrodes.

[0022] The adhesive frame 16 for the fuel cell is disposed on the periphery of the MEA 14. More specifically, the adhesive frame 16 for the fuel cell is disposed between a pair of separators 12 and 13 that are disposed adjacent to each other in the stacking direction. As shown in Fig. 3, the adhesive frame 16 for the fuel cell is a rectangular frame-shaped, film-like insulating sheet that is disposed so as to surround the periphery of the MEA 14, which has a substantially rectangular shape.

[0023] The adhesive frame 16 for the fuel cell is adhered to the periphery of the MEA 14 and the separator 12. The adhesive frame 16 for the fuel cell also seals the periphery of the MEA 14.

[0024] The adhesive frame 16 for the fuel cell is sandwiched between the opposing separators 12, 13 of the cells C adjacent in the stacking direction. A seal is maintained between the separators and the fuel cell frame. The adhesive frame 16 for the fuel cell is provided with a manifold hole 16A.

[0025] There are no limitations on the thickness of the adhesive frame for a fuel cell 16. For example, the thickness of the adhesive frame for a fuel cell 16 can be selected from an appropriate range of about 25 μm to 300 μm.

[0026] The adhesive frame 16 for a fuel cell disposed between the separators 12 may be used in one layer or in multiple layers of two or more layers.

[0027] During operation of the fuel cell 10, fuel gas and oxidant gas are supplied through the gas flow paths. A coolant also flows through the coolant flow paths to mitigate heat generation during power generation. The peripheral edge of the MEA 14 is sealed by the fuel cell adhesive frame 16. This prevents gas mixing and leakage. The electrolyte membrane 14A is also kept moist. Furthermore, as described above, the fuel cell adhesive frame 16 can be assembled at room temperature in a short time. Therefore, there is little risk of the electrolyte membrane 14A deteriorating during assembly. Furthermore, the sealing properties of the fuel cell adhesive frame 16 are not likely to deteriorate even in the operating environment of the fuel cell 10. Therefore, the fuel cell 10 can operate stably for a long period of time.

[0028] (Adhesive frame for fuel cells) Next, the composition of the adhesive frame 16 for a fuel cell will be described in detail.

[0029] The adhesive frame 16 for a fuel cell includes a thermoplastic elastomer and a tackifier.

[0030] (thermoplastic elastomer) The type of thermoplastic elastomer contained in the adhesive frame for a fuel cell 16 is not particularly limited.

[0031] For example, it is desirable to use one or more types of thermoplastic elastomer selected from an olefin-based thermoplastic elastomer and a styrene-based thermoplastic elastomer. Olefin-based and styrene-based thermoplastic elastomers are preferred because they are highly durable against water and acids such as hydrofluoric acid, and also because they extract less impurities that may affect the fuel cell 10.

[0032] Examples of olefin-based thermoplastic elastomers include those obtained by dynamically crosslinking an olefin-based copolymer rubber such as ethylene-propylene copolymer rubber or ethylene-propylene-diene copolymer rubber (EPDM) with an olefin-based resin such as a propylene-based resin or an ethylene-based resin.

[0033] Examples of styrene-based thermoplastic elastomers include styrene-based block copolymers such as styrene-butadiene block copolymer (SBS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), styrene-isobutylene-styrene copolymer (SIBS), styrene-isobutylene copolymer (SIB), polybutadiene (PB), and styrene-(ethylene-ethylene / propylene)-styrene block copolymer (SEEPS).

[0034] The thermoplastic elastomer contained in the adhesive frame for a fuel cell 16 may be at least one selected from the group of thermoplastic elastomers listed above.

[0035] Among these, it is preferable to use a styrene-based thermoplastic elastomer as the thermoplastic elastomer contained in the adhesive frame 16 for a fuel cell, from the viewpoint (reason) of elasticity and gas barrier properties.

[0036] Furthermore, from the viewpoints of heat aging resistance and gas barrier properties, it is preferable to use at least one of a styrene-isoprene-styrene block copolymer (SIS) and a styrene-isobutylene-styrene copolymer (SIBS) as the styrene-based thermoplastic elastomer, and it is particularly preferable to use a styrene-isobutylene-styrene copolymer (SIBS).

[0037] The mass average molecular weight, styrene content, and softening point of each of the styrene-isoprene-styrene block copolymer (SIS) and styrene-isobutylene-styrene copolymer (SIBS) contained in the adhesive frame for fuel cells 16 are not limited.

[0038] Specific examples of commercially available styrene-isoprene-styrene block copolymers (SIS) include QTC3290 (manufactured by Nippon Zeon Co., Ltd.) and SIS5229P (manufactured by ENEOS Material Trading Co., Ltd.).

[0039] Specific examples of commercially available styrene-isobutylene-styrene copolymers (SIBS) include SIBSTAR103T (manufactured by Kaneka Corporation).

[0040] The thermoplastic elastomer may be acid-modified. Here, "acid" refers to an acid component such as acid, acid anhydride, acid ester, or metallocene. The acid-modified portion of the thermoplastic elastomer contributes to adhesive strength (peel strength).

[0041] (tackifier) As the tackifier contained in the adhesive frame 16 for a fuel cell, any appropriate tackifier can be used.

[0042] Examples of tackifiers include tackifier resins. Specific examples of tackifier resins include rosin-based tackifier resins (e.g., unmodified rosin, modified rosin, rosin phenolic resins, and rosin ester resins), terpene-based tackifier resins (e.g., terpene resins, terpene phenolic resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins), hydrocarbon-based tackifier resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene-based resins and xylene-based resins), aliphatic and aromatic petroleum resins, aliphatic and alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins), phenol-based tackifier resins (e.g., alkylphenol resins, xylene-formaldehyde resins, resols, and novolacs), ketone-based tackifier resins, polyamide-based tackifier resins, epoxy-based tackifier resins, and elastomer-based tackifier resins. Among these, rosin-based tackifying resins, terpene-based tackifying resins, and hydrocarbon-based tackifying resins (such as styrene-based resins) are preferred.The tackifiers may be used alone or in combination of two or more.

[0043] Specific examples of commercially available tackifiers contained in the adhesive frame 16 for fuel cells include Quintone (registered trademark) 2940 (manufactured by Nippon Zeon Co., Ltd.), Quintone G115 (manufactured by Nippon Zeon Co., Ltd.), Quintone 1340 (manufactured by Nippon Zeon Co., Ltd.), and T-REZ HA125 (manufactured by ENEOS Corporation).

[0044] The content of tackifier in the adhesive frame 16 for the fuel cell is preferably 0% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and particularly preferably 20% by mass or more and 40% by mass or less, relative to 100% by mass of the entire adhesive frame 16 for the fuel cell.

[0045] By containing a tackifier within the above range relative to 100% by mass of the adhesive frame 16 for fuel cells contained in the adhesive frame 16 for fuel cells, adhesive strength (peeling strength) and elasticity are obtained, resulting in the effect of improving sealing properties.

[0046] (anti-aging agent) The pressure-sensitive adhesive frame for a fuel cell 16 may further contain an antioxidant. It is believed that the effect of the pressure-sensitive adhesive frame for a fuel cell 16 further containing an antioxidant is that the weather resistance and heat resistance are improved.

[0047] As the antioxidant contained in the adhesive frame 16 for a fuel cell, any appropriate antioxidant can be used.

[0048] Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.

[0049] Commercially available antioxidants include Nonflex Alba QS (manufactured by Seiko Chemical Co., Ltd.).

[0050] (Other ingredients) The fuel cell adhesive frame 16 may contain any appropriate additives as needed, such as plasticizers, softeners, antioxidants, processing aids, waxes, and the like.

[0051] (Application to fuel cells) The adhesive frame 16 for a fuel cell is suitably used for sealing between steel members of a fuel cell 10. The fuel cell 10 to which the adhesive frame 16 for a fuel cell is applied may be any fuel cell that operates at a temperature at which the organic component (thermoplastic elastomer) that forms the framework of the adhesive frame 16 for a fuel cell can be used. A suitable example of the fuel cell 10 is a polymer electrolyte fuel cell (PEFC) (including a direct methanol fuel cell (DMFC)).

[0052] The areas between the components sealed by the adhesive frame for fuel cells 16 vary depending on the type, structure, etc. of the fuel cell 10. That is, the adhesive frame for fuel cells 16 of this embodiment can be used in any area where airtightness and liquid tightness are required and where a sealing member has conventionally been used. Furthermore, the adhesive frame for fuel cells 16 of this embodiment may be used in all areas of the fuel cell 10 that require sealing, or may be used in some of the areas that require sealing.

[0053] 2 and 3, the area sealed by the adhesive frame 16 for a fuel cell may be between the frame supporting the MEA 14 and the separator 12 and the separator 13. Other areas sealed by the adhesive frame 16 for a fuel cell include the area between the separators 12 and 13 that face each other across the MEA 14, and the area between the separators 12 and 13 that constitute adjacent cells C.

[0054] The adhesive frame 16 for a fuel cell of this embodiment is a single layer film containing a thermoplastic elastomer and a tackifier, and therefore can seal between the components that make up the fuel cell by applying a load at room temperature, thereby shortening the manufacturing time. Furthermore, because the adhesive frame 16 for a fuel cell of this embodiment is a single layer film containing a thermoplastic elastomer and a tackifier, sheet scraps 23 generated during manufacturing can be reused as adhesive frames 16 for fuel cells by heating and melting them, thereby improving the yield. [Example]

[0055] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0056] Test pieces having the following adhesive frame 16 for a fuel cell and a comparative adhesive frame for a fuel cell were prepared, and the adhesive strength (peel strength) of these test pieces was evaluated.

[0057] -Preparation of test specimens- For the pressure-sensitive adhesive frame 16 for fuel cells and the comparative pressure-sensitive adhesive frame for fuel cells, raw materials were prepared with the compositions shown in Table 1. In Table 1, for compositions other than the SIS-based or SIBS-based thermoplastic elastomer, the content is shown relative to 100% by mass of the SIS-based or SIBS-based thermoplastic elastomer.

[0058] The raw materials having the composition shown in Table 1 were mixed for 1 minute in a Henschel mixer. Next, the resulting mixture was fed into the feed port of a co-rotating twin-screw kneading extruder (cylinder diameter 32 mm, L / D=56) having a raw material feed port, dynamically heat-treated by melt-kneading at 180°C, and extrusion-molded into a sheet having a thickness of 200 μm, thereby obtaining pressure-sensitive adhesive frames for fuel cells 16 of Examples 1 to 7 and comparative pressure-sensitive adhesive frames for fuel cells of Comparative Examples 1 and 2.

[0059] <Adhesion strength evaluation> A T-peel test was carried out to evaluate the adhesive strength (peel strength) of the pressure-sensitive adhesive frames for fuel cells 16 of Examples 1 to 7 and the comparative pressure-sensitive adhesive frames for fuel cells of Comparative Examples 1 and 2.

[0060] 4 is an explanatory diagram of the T-peel test. Each of the adhesive frames for fuel cells 16 of Examples 1 to 7 and the comparative adhesive frames for fuel cells of Comparative Examples 1 and 2 was cut into a strip shape with a width of 1 cm to prepare a test piece TPE.

[0061] Next, the following was performed on each of the test pieces TPE of the fuel cell adhesive frames 16 of Examples 1 to 7 and the comparative fuel cell adhesive frames of Comparative Examples 1 and 2. Specifically, the test piece TPE was sandwiched between SUS plates bent into an L shape, and a designated load (50 N) was applied for 1 second at room temperature (35°C), thereby crimping the test piece TPE and the SUS plates (T / P). The SUS plates (T / P) were prepared as an example of a separator 12.

[0062] Next, the test pieces TPE prepared for each of the fuel cell adhesive frames 16 of Examples 1 to 7 and the comparative fuel cell adhesive frames of Comparative Examples 1 and 2 were attached to a tensile tester, and a T-peel test was performed. As shown in FIG. 4, the ends of the SUS plates not holding the test piece TPE were clamped by a clamp and bent at an angle of approximately 90° relative to the adhesive surface of the TPE along the peel direction (indicated by the upward arrow in the figure). The clamp then pulled the ends of the pair of SUS plates not holding the test piece TPE in opposite directions at an angle of approximately 180° to each other, thereby peeling the test piece TPE from the SUS plate prepared as separator 12. This test was performed at 23°C (room temperature), and the clamp movement speed was 10 mm / min. The peel force (N / mm) when the test piece TPE was peeled from the SUS plate was determined.

[0063] The evaluation criteria for the peel strength were as follows: Judgment result 0: Peel force less than 0.03 N / mm Judgment result 1: Peel force 0.03N / mm or more and less than 0.15N / mm Judgment result 2: Peel force 0.15N / mm or more and less than 0.5N / mm Judgment result 3: Peel force 0.5N / mm or more and less than 1.0N / mm Judgment result 4: Peeling force 1.0 N / mm or more

[0064] The evaluation results are shown in Table 1.

[0065] [Table 1]

[0066] As shown in Table 1, the adhesive frames 16 for fuel cells of Examples 1 to 7 had better evaluation results for adhesive strength (peel strength) than the comparative adhesive frames for fuel cells of the comparative examples. Also, as shown in Table 1, the adhesive frames 16 for fuel cells of Examples 4 to 7, which used a SIBS-based thermoplastic elastomer, often had evaluation results for stronger adhesive strength (peel strength) than the adhesive frames 16 for fuel cells of Examples 1 to 3, which used a SIS-based thermoplastic elastomer.

[0067] The various materials and compositions used in the above examples are merely examples, and the present invention is not limited to these. Furthermore, the specific structure of the fuel cell 10 is not limited to those exemplified in Figures 1 to 3. [Explanation of symbols]

[0068] 10 fuel cell 14 MEA (membrane electrode assembly) 16 Adhesive frame for fuel cells

Claims

1. An adhesive frame for a fuel cell, which is disposed on the periphery of a membrane electrode assembly constituting the fuel cell, and which is a single layer film containing a thermoplastic elastomer and a tackifier. Adhesive frame for fuel cells.

2. The thermoplastic elastomer is a styrene-based block copolymer. The adhesive frame for a fuel cell according to claim 1 .

3. The styrene-based block copolymer is at least one of a styrene-isoprene-styrene block copolymer (SIS) and a styrene-isobutylene-styrene block copolymer (SIBS). The pressure-sensitive adhesive frame for a fuel cell according to claim 2 .

4. Further comprising a tackifier, The adhesive frame for a fuel cell according to claim 1 .

5. Further comprising an antioxidant, The adhesive frame for a fuel cell according to claim 1 .

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