Subgasket manufacturing method and manufacturing system

Abstract

To reduce manufacturing cost of a sub gasket.SOLUTION: A manufacturing method for a sub gasket (5) for a fuel cell (10) includes a step of a manufacturing system (W1) for the sub gasket (5) forming the sub gasket (5) by using a resin composition including a thermoplastic resin, and the resin composition includes a new raw material (M1) that is initially used for formation of the sub gasket (5) and recycled raw materials (M21, M22) that are manufactured from waste of the sub gasket (5).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method and system for manufacturing a subgasket for a fuel cell. [Background technology]

[0002] A fuel cell has a structure in which a membrane electrode assembly, which generates electricity through a chemical reaction of fuel gas, is sandwiched between a pair of separators. A subgasket is attached to the membrane electrode assembly as a support (see, for example, Patent Document 1).

[0003] A subgasket is generally a frame-shaped resin film, and is produced, for example, by forming a thermoplastic resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PN) into a film and then cutting it into a predetermined shape (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-142407 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-159094 Summary of the Invention [Problem to be solved by the invention]

[0005] In the subgasket manufacturing process, unnecessary film is discarded when it is cut into frames. Film with defects such as wrinkles and tears may also be discarded. If these waste materials could be collected and recycled, raw material loss could be reduced.

[0006] The present invention aims to reduce the manufacturing costs of subgaskets. [Means for solving the problem]

[0007] One aspect of the present invention is a method for manufacturing a subgasket (5) for a fuel cell (10), the method comprising: forming the subgasket (5) using a resin composition containing a thermoplastic resin in a subgasket (5) manufacturing system (W1). The resin composition includes a new raw material (M1) used for the first time in forming the subgasket (5) and recycled raw materials (M21, M22) produced from waste materials for the subgasket (5).

[0008] Another aspect of the present invention is a manufacturing system (W1) for manufacturing a subgasket (5) for a fuel cell (10) using a resin composition containing a thermoplastic resin, the system including a control device (65) for controlling the blending of raw materials in the resin composition. The resin composition prepared by controlling the blending includes a new raw material (M1) used for the first time in forming the subgasket (5) and recycled raw materials (M21, M22) produced from waste materials for the subgasket (5). [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce the manufacturing costs of the subgasket. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the configuration of a fuel cell in which a subgasket is used. [Figure 2] FIG. 1 is a schematic diagram showing a configuration of a manufacturing system according to an embodiment of the present invention. [Figure 3] 1 is a graph showing an example of the relationship between the number of times of recycling and the physical properties of a film. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of a manufacturing method and a manufacturing system for a subgasket of the present invention will be described with reference to the drawings. The configuration described below is an example (typical example) of the present invention, and the present invention is not limited to this configuration.

[0012] (fuel cell) First, a fuel cell in which a subgasket is used will be described. FIG. 1 shows the configuration of a fuel cell 10, which is a polymer electrolyte fuel cell (PEFC).

[0013] The fuel cell 10 includes a membrane electrode assembly (MEA) 3, a subgasket 5, and a pair of separators 4 disposed on either side of the MEA 3. The MEA 3 sandwiched between the pair of separators 4 is called a cell. The fuel cell 10 may be a stack of multiple cells. The MEA 3 includes an electrolyte membrane 1 and a pair of electrodes 2 on either side of the electrolyte membrane 1.

[0014] The electrolyte membrane 1 is an ion-conductive polymer electrolyte membrane. Examples of polymer electrolytes that can be used for the electrolyte membrane 1 include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Aquivion (registered trademark), aromatic polymers such as sulfonated polyether ether ketone (SPEEK) and sulfonated polyimide, and aliphatic polymers such as polyvinyl sulfonic acid and polyvinyl phosphoric acid.

[0015] Of the pair of electrodes 2, one electrode 2 is the anode, also called the fuel electrode, and the other electrode 2 is the cathode, also called the air electrode. Hydrogen gas is supplied to the anode as the fuel gas, and air containing oxygen gas is supplied to the cathode.

[0016] At the anode, electrons (e - ) and protons (H + ) occurs. The electrons move to the cathode via an external circuit (not shown). This electron movement generates a current in the external circuit. The protons move to the cathode via the electrolyte membrane 1.

[0017] At the cathode, electrons transferred from the external circuit convert oxygen gas (O2) into oxygen ions (O2 -) is generated. The oxygen ions are transferred to the protons (2H + ) to form water (H2O).

[0018] The electrode 2 includes a catalyst layer 21. In this embodiment, the electrode 2 includes a gas diffusion layer 22 to improve the diffusibility of the fuel gas. The gas diffusion layer 22 is disposed on the separator 4 side of the catalyst layer 21.

[0019] The catalyst layer 21 promotes the reaction between hydrogen gas and oxygen gas by the catalyst. The catalyst layer 21 includes a catalyst, a carrier that supports the catalyst, and an ionomer that coats these. Examples of the catalyst include metals such as platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh), palladium (Pd), and tungsten (W), as well as mixtures and alloys of these metals. Among these, platinum, and mixtures and alloys containing platinum are preferred from the viewpoints of catalytic activity, resistance to carbon monoxide poisoning, heat resistance, and the like.

[0020] Examples of the carrier include conductive porous metal compounds having pores such as mesoporous carbon and Pt black. Mesoporous carbon is preferred from the viewpoints of good dispersibility, large surface area, and little particle growth at high temperatures even when a large amount of catalyst is supported. As the ionomer, an ion-conductive polymer electrolyte similar to that of the electrolyte membrane 1 can be used.

[0021] The gas diffusion layer 22 can diffuse the fuel gas supplied to the fuel cell 10 uniformly over the entire surface of the catalyst layer 21 . The gas diffusion layer 22 can be formed by disposing a gas diffusion layer sheet as the outermost layer of the MEA 3. Examples of the gas diffusion layer sheet include porous fiber sheets such as carbon fibers that have electrical conductivity, gas permeability, and gas diffusivity, as well as metal sheet materials such as foam metal and expanded metal.

[0022] The separator 4 is also called a bipolar plate. The separator 4 has a concave-convex structure. This concave-convex structure can be formed by press-molding a metal substrate such as titanium, a titanium alloy, or stainless steel. The concave-convex structure can also be formed by molding a composition containing carbon.

[0023] The recesses 4a of the separator 4 form fluid flow paths between the separator 4 and the MEA 3. The flow paths are not only a supply path for fuel gas but also a discharge path for water produced by chemical reactions during power generation. When cooling water is used to cool the fuel cell 100, the flow paths are also used as a passage for the cooling water.

[0024] (subgasket) The subgasket 5 is attached to the electrolyte membrane 1. For example, the subgasket 5 is a frame body that surrounds the outer periphery of the MEA 3 and functions as a support for the MEA 3. The subgasket 5 also seals the inside of the fuel cell 10 by abutting against the separator 4 at the outer periphery.

[0025] A resin with low electrical conductivity can be used as the material for the subgasket 5. From the viewpoint of processability, a thermoplastic resin is preferable. The subgasket 5 can contain additives as needed.

[0026] The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and glass-filled polypropylene (PP-G), polyphenylene sulfide (PPS), polystyrene (PS), silicone resins, fluorine-based resins, etc. These may be used alone or in combination of two or more.

[0027] (Subgasket manufacturing method) FIG. 2 shows the configuration of a manufacturing system W1 for the subgasket 5. As shown in FIG. 2, the manufacturing system W1 includes a weighing device 61, an extruder 62, a stretching device 63, a processing device 64, and a control device 65.

[0028] In the manufacturing system W1, various raw materials for the subgasket 5, such as thermoplastic resin, are weighed by a weighing device 61. The weighed raw materials are fed into a hopper (not shown) and mixed to prepare a resin composition containing a thermoplastic resin. The resin composition is supplied from the hopper to an extruder 62.

[0029] The resin composition is melt-kneaded by the extruder 62 and extruded into a sheet through a T-die to form a film. The film is cooled by a cooling roll or the like (not shown) and then transported to the stretching device 63. In the stretching device 63, the film is stretched in at least one axial direction. Note that stretching may be performed as needed.

[0030] The film is then cut in processing device 64. For example, a long film transported by a roll-to-roll method is cut into rectangular shapes at regular intervals to form openings in the subgasket 5. The film is then cut into rectangular shapes of a predetermined size larger than the opening around the opening, thereby forming a subgasket 5 with an opening in the center.

[0031] The fuel cell 10 is manufactured using the subgasket 5 described above. First, an ink for forming a catalyst layer 21 is coated on the electrolyte membrane 1, and an electrolyte membrane 1 (CCM: Catalyst Coated Membrane) is formed with the catalyst layer 21 laminated thereon. This CCM is placed in the central opening of the subgasket 5, and the edge of the opening of the subgasket 5 and the outer edge of the CCM are bonded by thermocompression or with an adhesive or the like. Next, gas diffusion layers 22 and separators 4 are placed on both sides of the CCM in this order, and the fuel cell 10 is manufactured.

[0032] The manufacturing system W1 can use only the new raw material M1 as the raw material for the subgasket 5, but can also use recycled raw materials M21 and M22 in combination. The use of recycled raw materials M21 and M22 reduces raw material loss and cuts manufacturing costs.

[0033] The new raw material M1 is a single type of raw material used for the first time in manufacturing the subgasket 5. The recycled raw materials M21 and M22 are manufactured from waste materials of the subgasket 5. That is, the recycled raw materials M21 and M22 are resin compositions containing a thermoplastic resin, and may be mixtures of multiple types of raw materials.

[0034] The recycled raw material M21 is a first recycled raw material produced from waste v1 of subgaskets 5 collected before use in the fuel cell 10. For example, films that have defects such as wrinkles or tears during the manufacturing process of the subgasket 5, or films that do not meet certain quality requirements, such as films manufactured under unstable temperature conditions, are discharged as waste v1. Unnecessary portions of films cut in the processing device 64 are also discharged as waste v1. Furthermore, subgaskets 5 that have defects such as tears during the manufacturing process of the fuel cell 10 are also discharged as waste v1. Such waste v1 is collected and regenerated as recycled raw material M21.

[0035] The recycled material M22 is a second recycled material produced from waste v2 of the subgasket 5 recovered after use in the fuel cell 10. For example, when the fuel cell 10 incorporating the subgasket 5 deteriorates with use and is discarded, the subgasket 5 is recovered from the fuel cell 10 and regenerated as the recycled material M22.

[0036] By using not only the recycled material M21 obtained from the film waste v1 but also the recycled material M22 obtained from the fuel cell 10 waste v2, the manufacturing cost can be reduced more than when only the recycled material M21 is used.

[0037] In the manufacturing system W1, a control device 65 controls a weighing device 61 that weighs each raw material, thereby preparing a resin composition containing new raw material M1 and recycled raw material M21, recycled raw material M22, or both.

[0038] (Recycled material blend ratio) In the manufacturing system W1, the blending ratio of the recycled raw materials M21 and M22 in the resin composition used to manufacture the subgasket 5 is preferably 50% by mass or less, and more preferably 25% by mass or less.

[0039] The more recycled materials M21 and M22 are used, the more reductions in manufacturing costs become possible. However, recycled materials M21 and M22 have different thermal histories than virgin material M1. Shearing and stretching during melt-kneading can lead to differences in the molecular weight distribution of the thermoplastic resin in the raw materials. Due to these differences, the physical properties of films made with both recycled materials M21 and M22 tend to vary more than films made with virgin material M1 alone, making quality control more difficult.

[0040] As an example, FIG. 3 shows the relationship between the tensile strength K (MPa) of a polyphthalamide film and the number of times of recycling n. As shown in FIG. 3, the tensile strength K of the film decreases as the number of times of recycling n increases.

[0041] In Figure 3, the tensile strength K when n = 0 is the tensile strength of a film made of 100% polyphthalamide by mass produced using only the new polyphthalamide material M1. The tensile strength K when n = 1 is the tensile strength of a film produced by blending 25% by mass of recycled material M21 produced from waste film when n = 1 and 75% by mass of new material M1. From n = 2 onwards, the recycled material M21 is produced from waste film when the recycling count n is n-1 in the same way, and the tensile strength K of the film produced by using 25% by mass of recycled material M21 in combination with new material M1 is measured.

[0042] The subgasket 5 also tends to have similar variations in physical properties. However, if the blending ratio of recycled materials M21 and M22 is 50% by mass or less, the new material M1, which has stable physical properties, accounts for the majority, and it is possible to maintain a consistent quality of the subgasket 5. Furthermore, if the blending ratio is 25% by mass or less, it is easier to maintain high quality.

[0043] In particular, the blending ratio of the recycled raw material M22 in the resin composition is preferably 25% by mass or less. The recycled raw material M22 has a history of use in the fuel cell 10 and has a thermal history of being exposed to high temperatures during power generation. Furthermore, because the recycled raw material M22 is exposed to the presence of water, hydrogen gas, or oxygen gas, it is more susceptible to deterioration than the recycled raw material M21, which has no history of use. Therefore, by setting the blending ratio to 25% by mass or less, it becomes easier to maintain a consistent quality of the subgasket 5. From the viewpoint of maintaining high quality, the blending ratio of the recycled raw material M22 is more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0044] The control device 65 calculates the amounts of new raw material M1 and recycled raw materials M21 and M22 to be added so as to achieve the above-mentioned blending ratio. The control device 65 controls the weighing device 61 to measure the calculated amounts of each raw material to prepare the resin composition.

[0045] The control device 65 may be a computer equipped with a CPU (Central Processing Unit), a control unit such as a microcomputer, a storage unit such as a hard disk, an operation unit, a display unit, a communication unit, and the like.

[0046] The amount of new raw material M1 input is calculated according to the blending ratio of each raw material in recycled raw materials M21 and M22. When waste materials v1 and v2 are subgaskets 5 manufactured in manufacturing system W1, the blending ratio of each raw material in recycled raw materials M21 and M22 is the same as the composition of subgasket 5.

[0047] When the waste materials v1 and v2 are subgaskets 5 of unknown composition, the composition of the recycled materials M21 and M22 can be analyzed using an infrared spectrometer or the like to determine the blending ratio of each material in the recycled materials M21 and M22.

[0048] An example calculation will be described for a subgasket 5 manufactured using a resin composition consisting of 95% by mass of PEN and 5% by mass of additives. When preparing 100 parts by mass of a resin composition using recycled raw material M21 so that the blending ratio in the resin composition is 30% by mass, the control device 65 calculates the input amounts as follows. The composition of recycled raw material M21 is the same as that of subgasket 5, with a blending ratio of PEN of 95% by mass and an blending ratio of additives of 5% by mass. Amount of recycled raw material M21 added: 30 parts by mass Amount of new PEN raw material M1 added: 57 parts by mass Amount of new additive raw material M1 added: 3 parts by mass

[0049] As described above, recycled materials M21 and M22 containing additives can be used in the same way as recycled materials M21 and M22 containing no additives. Since the effect of additives may decrease with repeated recycling, it is preferable to use recycled materials M21 and M22 containing no additives rather than those containing additives.

[0050] (Recycling System) The production system W1 may include a recycling system W2 that produces recycled materials M21 and M22 from the waste materials v1 and v2. The recycling system W2 includes an extruder 71 and a pelletizer 72.

[0051] The recycling system W2 collects waste material v1 of the subgasket 5 that is discarded before use in the fuel cell 10. The waste material v1 is unnecessary subgasket 5 that is discarded during the manufacturing process of the subgasket 5 or when the subgasket 5 is incorporated into the fuel cell 10, as described above.

[0052] The collected waste v1 is crushed into chips, melted and kneaded by an extruder 71, and extruded into strands. The strands are cut by a pelletizer 72 to produce pellets of the recycled material M21.

[0053] In the pellet manufacturing process of the recycled raw material M21, pellets manufactured under unstable temperature conditions or discolored pellets may be discharged. These discharged pellets are also waste v1 of the subgasket 5 and can be recycled. The pellet waste v1 is recovered and fed into the extruder 71 together with the film waste v1.

[0054] Meanwhile, the subgasket 5 is removed from the discarded used fuel cell 10 and collected as waste v2. Like the waste v1, the waste v2 is also pulverized into chips, melted and kneaded by an extruder 71, and then extruded into strands. The strands are cut by a pelletizer 72 to produce pellets of the recycled material M22.

[0055] In the pellet manufacturing process of recycled raw material M22, pellets manufactured under unstable temperature conditions, discolored pellets, etc. may be discharged. The discharged pellets are collected as waste v2 of subgasket 5 and fed back into extruder 71 together with waste v2 of film.

[0056] As described above, according to this embodiment, the waste materials v1 and v2 of the subgasket 5 can be recycled for the manufacture of the subgasket 5. This reduces the loss of raw materials and the costs required for processing the waste materials v1 and v2, thereby enabling a reduction in manufacturing costs. Because not only the waste material v1 of the subgasket 5 collected before use in the fuel cell 10 but also the waste material v2 of the subgasket collected after use in the fuel cell 10 are recycled for the manufacture of the subgasket 5, it is possible to further reduce manufacturing costs compared to recycling only the waste material v1.

[0057] Furthermore, the blending ratio of recycled raw materials M21 and M22 in the resin composition from which the subgasket 5 is manufactured is controlled to 25% or less. Because the virgin new raw material M1 accounts for the majority, a certain level of quality can be maintained in the subgasket 5, making quality control easy.

[0058] The greater the blending ratio of the recycled raw materials M21 and M22, the more the manufacturing cost can be reduced, but the physical properties of the subgasket 5 tend to vary, making quality control difficult. However, in this embodiment, by limiting the blending ratio of the recycled raw materials M21 and M22 to a specific ratio, it is possible to achieve both reduced manufacturing costs and quality control. This is particularly useful when PEN or PET, which are more functional and expensive than general-purpose resins such as polyolefin resins, are used as raw materials, as this significantly reduces manufacturing costs while maintaining high functional quality.

[0059] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

[0060] In the above-described manufacturing system W1, the extruder 62 and the stretching device 63 are given as examples of molding devices for forming the film of the subgasket 5. However, the film molding method is not limited to extrusion molding, and molding devices that employ other film molding methods such as calendar molding or inflation molding may also be used.

[0061] Furthermore, waste materials discharged upstream in the manufacturing process of the subgasket 5 undergo less change due to thermal history, stretching, and the like than waste materials discharged downstream. Therefore, the waste materials v1 may be separated for each process step to produce recycled materials M21, and the blending ratio of recycled materials M21 produced from upstream waste materials v1 may be higher than that of recycled materials M21 produced from downstream waste materials v1. This makes it easier to maintain a certain level of quality while reducing manufacturing costs.

[0062] For example, the recycled material M21 may be produced by separating it into recycled material M211 and recycled material M212 as follows: The recycled material M211 is produced from film waste v1 discharged up to the stretching process. The recycled material M212 is produced from film waste v1 discharged after the stretching process. [Table 1] [Example]

[0063] A PEN subgasket (a) was manufactured by controlling the blending ratio of new PEN raw material M1 to 75 mass% and recycled raw materials M21 and M22 to 25 mass%. There was almost no difference in physical properties such as tensile modulus or tensile strength between subgasket (b), manufactured using only new raw material M1, and subgasket (a), and they were of similar quality.

[0064] Subgaskets were manufactured by gradually reducing the blending ratio of new raw material M1 in subgasket (a) and increasing the blending ratio of recycled raw materials M21 and M22 accordingly. As the blending ratio of recycled raw materials M21 and M22 increased, the variation in physical properties became greater compared to subgasket (b). [Explanation of symbols]

[0065] 10···Fuel cell, 3···MEA, 1···Electrolyte membrane, 2···Electrode, 4···Separator, 5···Subgasket, W1···Subgasket manufacturing system, 61···Weighing machine, 62···Extruder, 64···Processing equipment, W2···Recycling system, 71···Extruder, 72···Pelletizer

Claims

1. A method for manufacturing a subgasket (5) for a fuel cell (10), comprising the steps of: The manufacturing system (W1) for the subgasket (5) includes a step of forming the subgasket (5) using a resin composition containing a thermoplastic resin, The resin composition includes a new raw material (M1) used for the first time in forming the subgasket (5) and recycled raw materials (M21, M22) produced from waste materials of the subgasket (5), The recycled materials (M21, M22) include a first recycled material (M21) and a second recycled material (M22), The first recycled material (M21) is produced from the first waste, which is the waste collected before use in the fuel cell (10), The second recycled material (M22) is produced from the second waste, which is the waste recovered after use of the fuel cell (10), The total blending ratio of the recycled raw materials (M21, M22) in the resin composition is 50 mass% or less, The blending ratio of the second recycled material (M22) in the resin composition is 25% by mass or less, A method for manufacturing a subgasket (5).

2. The total blending ratio of the recycled raw materials (M21, M22) in the resin composition is 25 mass% or less. A method for manufacturing a subgasket (5) according to claim 1.

3. The blending ratio of the second recycled material (M22) in the resin composition is 5 mass% or less. A method for manufacturing a subgasket (5) according to claim 1 or 2.

4. The recycled raw materials (M21, M22) are Pellets made from the waste material of the subgasket (5); Secondary waste, which is waste of the pellets, discharged in the process of producing the pellets; Including, The secondary waste includes the pellets produced under unstable temperature conditions. A method for manufacturing a subgasket (5) according to any one of claims 1 to 3.

5. A manufacturing system (W1) for manufacturing a subgasket (5) for a fuel cell (10) using a resin composition containing a thermoplastic resin, comprising: A control device (65) for controlling the blending of each raw material in the resin composition; a recycling system (W2) for producing recycled raw materials (M21, M22) from waste of the subgasket (5); Equipped with The resin composition prepared by controlling the blending contains a new raw material (M1) used for the first time in forming the subgasket (5) and the recycled raw materials (M21, M22), The recycled materials (M21, M22) include a first recycled material (M21) and a second recycled material (M22), The recycling system (W2) comprises: producing the first recycled raw material (M21) from the first waste, which is the waste of the subgasket (5) collected before use of the fuel cell (10); producing the second recycled raw material (M22) from second waste, which is the waste of the subgasket (5) recovered after use of the fuel cell (10); The control device (65) The total blending ratio of the recycled raw materials (M21, M22) in the resin composition is controlled to 50 mass% or less, The blending ratio of the second recycled material (M22) in the resin composition is controlled to 25 mass% or less. A manufacturing system (W1) for a subgasket (5).

6. The control device (65) controls the blending ratio of the entire recycled raw materials (M21, M22) in the resin composition to 25 mass% or less. A manufacturing system (W1) for a subgasket (5) according to claim 5.

7. The control device (65) controls the blending ratio of the second recycled raw material (M22) in the resin composition to 5 mass% or less. A system (W1) for manufacturing a subgasket (5) according to claim 5 or 6.

8. The recycling system (W2) comprises: producing pellets from the waste of said subgasket (5); Collecting secondary waste, which is waste from the pellets, discharged in the process of producing the pellets; obtaining the recycled raw materials (M21, M22) from the pellets and the secondary waste; The secondary waste includes the pellets produced under unstable temperature conditions. A manufacturing system (W1) for a subgasket (5) according to any one of claims 5 to 7.

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