Manufacturing method of multi-layer separator

Abstract

[Problem] To provide a multilayer separator which is capable of stabilizing the gas barrier characteristics at high levels.　[Solution] The present invention relates to a multilayer separator 1 which is provided with: a plate 2 which contains graphite and a resin, and has a surface that is provided with grooves 30, 32 serving as flow channels; and an internal barrier layer 3c for gas barrier, the internal barrier layer 3c being positioned inside the plate 2 in the thickness direction so as to divide the plate 2 into two regions in the thickness direction. The present invention also relates to a method for producing this multilayer separator 1.

Description

Cross References

[0001] The entire disclosures of the patents, patent applications and publications cited in this application are hereby incorporated by reference. [Technical field]

[0002] The present invention relates to a multi-layer separator. Ta's It relates to a manufacturing method. [Background technology]

[0003] A fuel cell is a battery that extracts energy by utilizing the reaction between hydrogen and oxygen. Since the reaction produces only water, fuel cells are known as environmentally friendly batteries. In particular, solid polymer fuel cells are considered promising as batteries for automobiles, communication devices, electronic devices, etc., because they enable high power density and are small and lightweight, and some of them have been put to practical use. A fuel cell is a cell stack composed of multiple cells stacked on top of each other. A wall member called a separator is placed between the cells. The separator is a partition plate that separates the passages of hydrogen and oxygen that are adjacent to each other, and plays a role in allowing hydrogen and oxygen to flow in contact with each other uniformly over the entire surface of the ion exchange membrane. For this reason, grooves that serve as the flow paths are formed in the separator.

[0004] Separators are broadly classified into metallic and carbon-based separators based on the material of which they are made. Stainless steel, aluminum or its alloy, or titanium or its alloy are generally used for metallic separators. Metallic separators have excellent workability and can be thinned due to the strength and ductility inherent to metals. However, metallic separators have a higher specific gravity than carbon separators described below, which is contrary to the weight reduction of fuel cells. Furthermore, metallic separators have the disadvantage of low corrosion resistance and forming a passivation film depending on the material. Corrosion of metallic materials or a passivation film is undesirable because it leads to an increase in the electrical resistance of the separator. Coating metallic separators with precious metals by plating or sputtering, etc., leads to high costs, but in order to prevent such high costs, a method is known in which the convex parts of the flow paths formed on the surface of the separator are formed with a photoresist film (see Patent Document 1).

[0005] On the other hand, carbon material-based separators have the advantage of being smaller in specific gravity and more corrosion resistant than metal material-based separators. However, carbon material-based separators are inferior in processability and mechanical strength. There is also a demand for further lower electrical resistance (i.e., further higher electrical conductivity). As a method for improving mechanical strength, for example, a separator in which graphite particles are dispersed in a thermoplastic resin is known (see Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-090937 A [Patent Document 2] JP 2006-294407 A Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors belonging to the present applicant have previously developed a separator having a resin (particularly preferably polyphenylene sulfide) film on both sides of the thickness direction of a carbon material-based separator (Patent Application No. 2020-072036). By providing the resin film, the separator has higher strength than conventional separators and also has high gas barrier performance. However, separators arranged between cells of batteries including fuel cells are desired to have higher and more stable gas barrier properties.

[0008] An object of the present invention is to provide a multilayer separator that can highly stabilize gas barrier properties. [Means for solving the problem]

[0009] (1) In order to achieve the above object, a multilayer separator according to one embodiment includes a plate containing graphite and a resin, the plate having grooves on a surface thereof as flow paths; an inner barrier layer for gas barrier, which is disposed inside the thickness direction of the plate and divides the thickness direction into at least two regions; Equipped with. (2) In the multilayer separator according to another embodiment, the inner barrier layer may preferably be a film-like layer different from the plate. (3) In the multilayer separator according to another embodiment, the inner barrier layer may preferably be a filled layer in which resin or rubber fills spaces between particles or fibers that make up the plate. (4) In the multilayer separator according to another embodiment, the inner barrier layer may preferably include the filling layer and a film-like layer different from the plate. (5) The multilayer separator according to another embodiment may preferably include two or more of the inner barrier layers. (6) In the multilayer separator according to another embodiment, the inner barrier layer may preferably contain at least one of polyether ether ketone and polyphenylene sulfide. (7) In the multi-layer separator according to another embodiment, the inner barrier layer may preferably include at least one of stainless steel and graphite. (8) The multilayer separator according to another embodiment may further include a surface barrier layer for gas barrier, preferably on at least one surface of the plate in the thickness direction. (9) In the multilayer separator according to another embodiment, the surface barrier layer may preferably contain at least one of polyether ether ketone and polyphenylene sulfide. (10) The multilayer separator according to another embodiment preferably includes the internal barrier layer and the surface barrier layer, and the thickness of the internal barrier layer may be greater than the thickness of the surface barrier layer. (11) The multilayer separator according to another embodiment may preferably be a fuel cell separator used between cells of a fuel cell. (12) In order to achieve the above object, a method for producing a multilayer separator according to one embodiment is a method for producing any of the multilayer separators described above, comprising the steps of: A first mixture supplying step of supplying a mixture containing graphite and a resin into a die; an intermediate layer film positioning step of positioning an intermediate layer film for forming the inner barrier layer on the mixture in the mold; a second mixture supplying step of supplying the mixture onto the middle layer film; a molding step of curing a laminate including at least the mixture, the intermediate layer film, and the mixture to form a molded body; Including, Before the molding step, the middle layer film arrangement step and the second mixture supply step are each repeated once or twice or more. (13) A method for producing a multilayer separator according to another embodiment is preferably a method for producing a multilayer separator including the internal barrier layer and a surface barrier layer for gas barrier on at least one surface of the plate in the thickness direction, the method comprising the steps of: A surface film arranging step of arranging a surface film for forming the surface barrier layer in a mold, The first mixture supplying step, the middle layer film arranging step, and the second mixture supplying step may be carried out after, before, or both before and after the surface layer film arranging step. (14) In another embodiment of the method for producing a multilayer separator, a pre-molding step of obtaining the laminate in a semi-cured state may be preferably carried out prior to the molding step. (15) In the method for producing a multilayer separator according to another embodiment, the surface film arrangement step may be preferably carried out between the pre-molding step and the molding step. (16) In the method for producing a multilayer separator according to another embodiment, the multilayer separator may preferably be a fuel cell separator used between cells of a fuel cell. Effect of the Invention

[0010] According to the present invention, the gas barrier properties can be highly stabilized. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 shows a plan view of a multilayer separator according to a first embodiment of the present invention. [Figure 2A] FIG. 2A shows a cross-sectional view of the multi-layer separator taken along line AA of FIG. 1 and an enlarged view of a portion B thereof. [Figure 2B] FIG. 2B shows enlarged views of variations a, b, c, and d of part C in part B of FIG. 2A. [Figure 2C] FIG. 2C shows enlarged views of variations a, b, and c of part D in part B of FIG. 2A. [Diagram 3] FIG. 3 shows an example of a flow of main steps of the manufacturing method according to the first embodiment. [Figure 4] FIG. 4 shows cross-sectional views of the respective steps of the manufacturing method shown in FIG. [Diagram 5] FIG. 5 shows cross-sectional views of the process steps subsequent to FIG. [Figure 6]FIG. 6 shows an example of a flow of main steps of the manufacturing method according to the second embodiment. [Figure 7] FIG. 7 shows in cross section the status of each step of the manufacturing method shown in FIG. [Figure 8] FIG. 8 shows in cross section the state of each process subsequent to FIG. [Figure 9] FIG. 9 is a cross-sectional view showing a state in which grooves are formed in a semi-cured preform in a manufacturing method for a multilayer separator according to a modified example. [Figure 10] FIG. 10 shows a cross-sectional view of the multilayer separator according to the second embodiment taken along line AA similar to FIG. 2A, and an enlarged view of a portion B thereof. [Figure 11] FIG. 11 shows an example of a flow of main steps in the method for producing a separator according to the second embodiment. [Figure 12] FIG. 12 shows an example of a flow of main steps of a manufacturing method different from that shown in FIG. [Explanation of symbols]

[0012] Reference Signs List 1,1a...separator (multilayer separator, fuel cell separator), 2...plate, 2a...mixture, 3a...surface barrier layer, 3b...surface barrier layer, 3c...inner barrier layer, 4...surface film, 5...surface film, 6...middle film, 30,32...groove, 31...surface, 40,45...lower mold (a component of the mold), 41,51...recess, 42,52...irregularities, 50,55...upper mold (a component of the mold), 60,65...mold, 70,70a...preformed body (laminate in a semi-cured state), F1...layer, F2...coating layer, M...filling layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, each embodiment of the present invention will be described with reference to the drawings. Note that each embodiment described below does not limit the invention according to the claims, and all of the elements and combinations thereof described in each embodiment are not necessarily essential to the solution of the present invention.

[0014] First Embodiment 1. Multi-layer separator Fig. 1 shows a plan view of a multilayer separator according to a first embodiment of the present invention, Fig. 2A shows a cross-sectional view of the multilayer separator shown in Fig. 1 taken along line AA and an enlarged view of a part B thereof.

[0015] The multilayer separator (hereinafter, simply referred to as "separator") 1 according to this embodiment is a plate-like body having a substantially rectangular shape in a plan view. The separator 1 is a plate-like body sandwiched from both sides of a membrane electrode assembly (MEA) in which both sides of an electrolyte membrane are sandwiched between an air electrode and a hydrogen electrode in, for example, a fuel cell. In this embodiment, the separator 1 is broadly interpreted to include an anode-side separator arranged on the hydrogen electrode (also referred to as "anode electrode") side, and a cathode-side separator arranged on the air electrode (also referred to as "cathode electrode") side. In this embodiment, the separator 1 is a carbon material-based separator. Moreover, the separator 1 is not limited to use in fuel cells, and can also be used as a plate-like member arranged between cells of other batteries (preferably storage batteries).

[0016] The separator 1 has through holes 11, 12, 21, and 22 penetrating in the thickness direction. The through holes 11 and 21 are arranged on one end side of the separator 1. The through hole 12 is arranged on the other end side opposite the one end side of the separator 1, facing the through hole 21 when the separator 1 is viewed in plan. The through hole 22 is arranged on the other end side opposite the one end side of the separator 1 so as to face the through hole 11 when the separator 1 is viewed in plan. A groove 30 is formed as a flow path on one surface side (front surface side) of the separator 1. The surface 31 other than the groove 30 is convex with respect to the groove 30. In addition, a groove 32 is formed as a flow path on the surface (rear surface side) opposite the one surface side of the separator 1. The surface 31 other than the groove 32 is convex with respect to the groove 32.

[0017] When the separator 1 is a cathode separator, the through hole 11 is an oxidizing gas supply port. The through hole 12 is an oxidizing gas exhaust port. The through hole 21 is a hydrogen gas exhaust port. The through hole 22 is a hydrogen gas supply port. The oxidizing gas is, for example, air, but may be oxygen. The groove 30 on the front side of the separator 1 is a flow path for the oxidizing gas to flow. The groove 32 on the back side of the separator 1 is a flow path for the cooling water to flow. In FIG. 1, the flow of the oxidizing gas is indicated by white arrows.

[0018] When separator 1 is an anode separator, through-hole 11 is a hydrogen gas supply port. Through-hole 12 is a hydrogen gas exhaust port. Through-hole 21 is an oxidizing gas exhaust port. Through-hole 22 is an oxidizing gas supply port. Groove 30 on the front side of separator 1 is a flow path for hydrogen gas to flow. Groove 32 on the back side of separator 1 is a flow path for cooling water to flow.

[0019] The separator 1 includes at least a plate 2 and an inner barrier layer 3c disposed inside the plate 2. In this embodiment, the separator 1 preferably includes surface barrier layers 3a and 3b on both surfaces of the plate 2 in the thickness direction.

[0020] (plate) The plate 2 is a plate containing graphite and resin, and has grooves 30, 32 as flow paths on the surface of the plate. The plate 2 is a molded body containing graphite and resin, and has a microstructure in which graphite is dispersed in the resin that has solidified after melting. The plate 2 may have fibers in addition to the graphite and resin. The fibers may be any type of fiber such as resin fiber, carbon fiber, ceramic fiber, etc., but are preferably resin fiber, and more preferably aramid fiber. By providing the plate 2 with fibers, the strength of the plate 2 can be further increased. The plate 2 has grooves corresponding to the grooves 30, 32 of the separator 1. The area of ​​the plate 2 in a plan view is preferably 10 to 1000 cm. 2 , more preferably 100 to 750 cm 2The thickness of the plate 2 is preferably 0.1 to 20 mm, and more preferably 0.2 to 10 mm.

[0021] The resin constituting the plate 2 is not particularly limited, but is preferably a thermoplastic resin. A resin more suitable for the plate 2 is a resin having excellent heat resistance, and specific examples thereof include polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyamide (PA), polyether ketone ether ketone ketone (PEKEKK), polyether ketone (PEK), liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), polyimide (PI), polyamide imide (PAI), polyether sulfone (PES), polyphenyl sulfone (PPSU), polyether imide (PEI) and polysulfone (PSU). Among these, PPS or PEEK is particularly suitable. Examples of PPS include M2888 and E2180 manufactured by Toray Industries, Inc., and FZ-2140 and FZ-6600 manufactured by Dainippon Ink and Chemicals, Inc.

[0022] The average particle size of the resin used before molding the plate 2 is preferably 1 μm or more and 300 μm or less, more preferably 5 μm or more and 150 μm or less, and even more preferably 10 μm or more and 100 μm or less. Here, the average particle size refers to a particle size measured by a laser diffraction / scattering type particle size distribution measurement method. The measurement method of the average particle size hereinafter is the same.

[0023] The graphite constituting the plate 2 may be any of artificial graphite, expanded graphite, natural graphite, etc. Here, expanded graphite refers to graphite or a graphite intercalation compound in which the graphite layers are expanded by inserting a layer of another material (=intercalation) into a specific surface of a structure in which regular hexagonal planes of graphite (graphite) are stacked. Examples of the expanded graphite include BSP-60A (average particle size 60 μm) or EXP-50SM manufactured by Fuji Graphite Industries Co., Ltd. Examples of the artificial graphite include 1707SJ (average particle size 125 μm), AT-No.5S (average particle size 52 μm), AT-No.10S (average particle size 26 μm), and AT-No.20S (average particle size 10 μm) manufactured by Oriental Sangyo Co., Ltd., or PAG and HAG manufactured by Nippon Graphite Industries Co., Ltd. Examples of the natural graphite include CNG-75N (average particle size 43 μm) manufactured by Fuji Graphite Industries Co., Ltd., or CPB (scale graphite powder, average particle size 19 μm) manufactured by Nippon Graphite Industries Co., Ltd. There are no particular restrictions on the shape of the graphite particles, and they can be appropriately selected from flaky, scaly, spherical, and the like. Furthermore, the graphite may partially contain non-crystalline carbon (amorphous carbon).

[0024] The average particle size of the graphite used before forming the plate 2 is preferably 1 μm to 500 μm, more preferably 3 μm to 300 μm, and even more preferably 10 μm to 150 μm.

[0025] The graphite and the resin may be mixed together after adjusting the particle size separately and then used to form the plate 2, or may be kneaded together first, pulverized, and the particle size adjusted before being used to form the plate 2. When the graphite and the resin are kneaded together and then pulverized to adjust the particle size, the average particle size of the mixed powder is preferably 1 μm or more and 500 μm or less, more preferably 3 μm or more and 300 μm or less, and even more preferably 10 μm or more and 150 μm or less.

[0026] The mass ratio of graphite and resin constituting the plate 2 is graphite:resin=70-95 parts by mass:30-5 parts by mass. For example, 5 parts by mass of resin can be mixed with 70 parts by mass or more and 95 parts by mass or less of graphite to form the material for the plate 2. Similarly, for example, 30 parts by mass of resin can be mixed with 70 parts by mass or more and 95 parts by mass or less of graphite to form the material for the plate 2. The plate 2 preferably contains more graphite than resin in terms of mass ratio. A more suitable mass ratio of graphite to resin is 10 parts by mass of graphite or 10.1 parts by mass or more and 20 parts by mass or less of graphite to 1 part by mass of resin. As described above, when the parts by mass of graphite are more than the parts by mass of resin, the number of contact points between the graphite particles is more than that of conventional separators, and thus the electrical resistance of the separator 1 can be lowered (i.e., the electrical conductivity can be increased). A representative sample of the separator 1 has a volume resistivity of 5 mΩcm or less.

[0027] (Inner barrier layer) The internal barrier layer 3c is a gas barrier layer located inside the thickness direction of the plate 2 and dividing the thickness direction into at least two regions. In this embodiment, only one internal barrier layer 3c is provided in the plate 2. Therefore, the thickness direction of the plate 2 is divided into two regions by the single internal barrier layer 3c. However, the plate 2 may include two or more internal barrier layers 3c. In that case, the thickness direction of the plate 2 is divided into three or more regions by two or more internal barrier layers 3c.

[0028] FIG. 2B shows enlarged views of variations a, b, c, and d of part C in part B of FIG. 2A.

[0029] In the form a, an internal barrier layer 3c is provided inside the thickness direction of the plate 2. In the form a, the internal barrier layer 3c is a film-like layer F1 different from the plate 2. In the form b, the internal barrier layer 3c is provided inside the thickness direction of the plate 2, impregnated with resin or rubber. In the form b, the internal barrier layer 3c is a filling layer M in which the resin or rubber fills the spaces between the particles or fibers that constitute the plate 2. In the forms c and d, the internal barrier layer 3c includes the filling layer M and the layer F1. Thus, the internal barrier layer 3c preferably takes the forms a, b, c, and d. However, the internal barrier layer 3c may take a form other than the forms a, b, c, and d as long as it has a gas barrier property superior to the plate 2. In the present application, "gas barrier" means a property that prevents gas permeation. Hereinafter, the internal barrier layer 3c of the form a will be mainly described.

[0030] The inner barrier layer 3c is preferably a layer containing a resin or rubber. The inner barrier layer 3c may or may not have excellent electrical conductivity. The inner barrier layer 3c is mainly made of one or more of the above-mentioned suitable resins constituting the plate 2, and more preferably, is mainly made of at least one of PEEK and PPS. Here, the "main material" means a material that occupies more than 50% by mass of the film 3. The main material may be, for example, 51%, 60%, 70%, 80%, 90%, 95% or 100% by mass, as long as it exceeds 50% by mass with respect to the mass of the film 3. The inner barrier layer 3c may contain at least one of PEEK and PPS, but may not contain it as the main material. The inner barrier layer 3c may also be a layer using a graphite film obtained by carbonizing and crystallizing a resin such as polyimide, polyamideimide, polybenzimidazole, polyamide, or polyoxazole by high-temperature heat treatment. Examples of such graphite films include Graphinity manufactured by Kaneka Corporation and PGS graphite sheet manufactured by Panasonic Corporation. Furthermore, the inner barrier layer 3c may be a layer using a metal. In this case, suitable metals include stainless steel (SUS301, SUS304, SUS316L, SUS430, SUS630, etc.), copper C1020, titanium TP270, etc.

[0031] The thickness of the inner barrier layer 3c is preferably 2 μm or more and 100 μm or less, more preferably 2 μm or more and 75 μm or less, and even more preferably 5 μm or more and 50 μm or less. When the thickness of the inner barrier layer 3c is 2 μm or more, or even 5 μm or more, the separator 1 can have higher gas barrier performance, higher strength (bending strength), and easier handling. On the other hand, when the thickness of the inner barrier layer 3c is 100 μm or less, or even 75 μm or less, or even 50 μm or less, the volume resistivity can be lowered. In this embodiment, the strength means the bending strength measured by JIS K7171.

[0032] The main resin material constituting the plate 2 and the main resin material constituting the inner barrier layer 3c may be the same type of thermoplastic resin. In this case, the resin near the inner barrier layer 3c of the plate 2 and the resin constituting the inner barrier layer 3c can be partially integrated, which can further improve the strength of the separator 1. The thermoplastic resin is preferably PEEK or PPS.

[0033] By providing the internal barrier layer 3c inside the plate 2, the gas barrier properties can be improved even if the thicknesses of the surface barrier layers 3a, 3b are made smaller when the surface barrier layers 3a, 3b are disposed on the front and / or back sides of the plate 2 in the thickness direction. In addition, although there is a risk that the surface barrier layers 3a, 3b will break at the locations of the grooves 30, 32, the presence of the internal barrier layer 3c can maintain the gas barrier properties favorably even in such a case. Furthermore, even if at least one of the surface barrier layers 3a, 3b is not provided, the presence of the internal barrier layer 3c can maintain the gas barrier properties favorably.

[0034] (Surface barrier layer) As described above, this embodiment further includes surface barrier layers 3a and 3b for gas barrier on both surfaces in the thickness direction of the plate 2. Note that only the surface barrier layer 3a or the surface barrier layer 3b may be provided on one surface of the plate 2 in the thickness direction.

[0035] The surface barrier layers 3a and 3b include the grooves 30 and 32 and the surface 31 of the plate 2 other than the grooves 30 and 32, and cover the front and back surfaces of the plate 2. That is, the surface barrier layers 3a and 3b cover both the front and back surfaces of the plate 2, including the inner surfaces of the grooves 30 and 32. In this embodiment, the surface barrier layer 3a covers one side surface in the thickness direction of the plate 2, and the surface barrier layer 3b covers the other side surface in the thickness direction. However, the surface barrier layer may be in a bag shape that envelops the outer surface of the plate 2 with the surface barrier layer 3a and the surface barrier layer 3b joined together.

[0036] FIG. 2C shows enlarged views of variations a, b, and c of part D in part B of FIG. 2A.

[0037] In the form a, the surface of the plate 2 is provided with a film mainly made of resin or rubber. In the form a, the surface barrier layer 3b is a film-like covering layer F2 different from the plate 2. In the form b, the surface barrier layer 3b is impregnated with resin or rubber near the surface of the plate 2. In the form b, the surface barrier layer 3b is a filling layer M in which the resin or rubber fills the spaces between the particles or fibers that constitute the plate 2. In the form c, the surface barrier layer 3b includes the filling layer M and the covering layer F2. Thus, the surface barrier layer 3b (as well as 3a) preferably takes the form a, b, or c. However, the surface barrier layers 3a and 3b may take forms other than the forms a, b, and c as long as they have better gas barrier properties than the plate 2. In the present application, "gas barrier" means a property that prevents gas from passing through. Hereinafter, the surface barrier layers 3a and 3b of the form a will be mainly described.

[0038] The surface barrier layers 3a, 3b are preferably layers containing resin or rubber. The surface barrier layers 3a, 3b may or may not have excellent electrical conductivity. The surface barrier layers 3a, 3b contain one or more of the above-mentioned preferred resin choices constituting the plate 2 as the main material, and more preferably contain at least one of PEEK and PPS as the main material. Here, the "main material" means a material that occupies more than 50% by mass of the surface barrier layers 3a, 3b. The main material may be, for example, 51%, 60%, 70%, 80%, 90%, 95% or 100% by mass, as long as it exceeds 50% by mass with respect to the mass of the surface barrier layers 3a, 3b. Note that the inner barrier layers 3a, 3b may contain at least one of PEEK and PPS but may not contain it as the main material.

[0039] The preferred thickness range of the surface barrier layers 3a, 3b and the advantages of having the surface barrier layers in this thickness range are similar to those of the internal barrier layer 3c. The thickness of the surface barrier layers 3a, 3b is preferably smaller than that of the internal barrier layer 3c. This is because the surface barrier layers 3a, 3b are more easily attached to the outer surface of the plate 2, including the grooves 30, 32. In addition, when forming a cell and a cell stack, if the thickness of the surface barrier layers 3a, 3b of the separator 1 is reduced, the surface barrier layers 3a, 3b are less likely to act as insulating layers, and the contact resistance can be reduced.

[0040] The main resin material constituting the plate 2 and the main resin material constituting the surface barrier layers 3a, 3b may be the same type of thermoplastic resin. In this case, the resin near the surface of the plate 2 and the surface barrier layers 3a, 3b covering the plate 2 can be integrated, thereby further improving the strength of the separator 1. The thermoplastic resin is preferably PEEK or PPS.

[0041] 2. Manufacturing method of multi-layer separator Next, a method for producing the multilayer separator according to the first embodiment of the present invention will be described.

[0042] The separator 1 includes a first mixture supplying step of supplying a mixture containing graphite and a resin into a mold, a middle layer film arranging step of arranging a middle layer film 6 for forming an inner barrier layer 3c on the mixture in the mold, a second mixture supplying step of supplying the mixture onto the middle layer film 6, and a molding step of curing a laminate containing at least the mixture, the middle layer film 6, and the mixture to form a molded body. In addition, before the molding step, the middle layer film arranging step and the second mixture supplying step are each repeated once or twice or more. In addition, the manufacturing method of the separator 1 (hereinafter, also simply referred to as the "manufacturing method") includes a surface layer film arranging step of arranging the surface layer films 4, 5 in the mold, and the first mixture supplying step, the middle layer film arranging step, and the second mixture supplying step are performed after, before, or both before and after the surface layer film arranging step. In the following embodiment, the manufacturing method of the multilayer separator is preferably a method of manufacturing a fuel cell separator used between cells of the fuel cell. In addition, the separator 1 is preferably a carbon material-based separator. However, the separator 1 is not limited to use in fuel cells, and can also be used as a plate-like member disposed between cells of other batteries (preferably storage batteries).

[0043] Fig. 3 shows an example of a flow of main steps of the manufacturing method according to the first embodiment. Fig. 4 shows, in cross-section, the status of each step of the manufacturing method shown in Fig. 3. Fig. 5 shows, in cross-section, the status of each step subsequent to Fig. 4.

[0044] The separator 1 can be manufactured through a surface film arrangement step (S100), a first mixture supply step (S110), a middle film arrangement step (S120), a second mixture supply step (S130), a surface film arrangement step (S140), and a molding step (S150). Steps S100 to S150 will be described in detail below with reference to FIGS. 3 to 5.

[0045] (1) Surface film placement process (S100) This step is a step of placing the surface film 4 inside the mold 60. Specifically, a lower mold 40 constituting the mold 60 is prepared, and the surface film 4 is placed in the recess 41 of the lower mold 40 (see FIGS. 4(a) and 4(b)). The lower mold 40 has projections and recesses 42 on the inner bottom surface of the recess 41 that can transfer and form the grooves 32.

[0046] (2) First mixture supply step (S110) This step is a step of supplying a mixture 2a containing graphite and resin into a mold 60. Specifically, the mixture 2a is supplied onto a surface film 4 placed on a lower mold 40 (see FIG. 4(c)).

[0047] (3) Middle layer film placement process (S120) This step is a step of placing the middle layer film 6 on the mixture 2a in the mold 60. Specifically, the middle layer film 6 is laid on the mixture 2a on the surface film 4 placed in the recess 41 of the lower mold 40 (see FIG. 4(d)).

[0048] (4) Second mixture supply step (S130) This step is a step of supplying a mixture 2a containing graphite and resin into a mold 60. Specifically, the mixture 2a is supplied onto the middle layer film 6 in the lower mold 40 (see FIG. 4(e)).

[0049] (5) Surface film placement process (S140) This step is a step of placing a surface film 5 on the mixture 2a in the mold 60 after the second mixture supply step (S130). Specifically, the surface film 5 is laid on the mixture 2a on the middle layer film 6 placed in the recess 41 of the lower mold 40 (see FIG. 4(f)).

[0050] (6) Molding process (S150) This step is a step of hardening a laminate including the surface film 4, the mixture 2a, the middle layer film 6, the mixture 2a, and the surface film 5 to produce a molded body. Specifically, an upper mold 50 constituting a mold 60 is prepared, and placed on the recessed portion 41 side of the lower mold 40, and the lower mold 40 and the upper mold 50 are closed (see Figs. 5(g) and (h)). The upper mold 50 has a recess 51 on the surface facing the recessed portion 41 of the lower mold 40. The recessed portion 51 has an unevenness 52 on its inner bottom surface that can transfer and form the groove 30. After the mold 60 is clamped, it is heated to mold the laminate. As a result, the mixture 2a hardens to form the plate 2. In addition, the grooves 30 and 32 covered with the surface barrier layers 3a and 3b are formed by the transfer of the unevenness 41 and 51. In addition, an inner barrier layer 3c is formed inside the plate 2 (see Fig. 5(i)).

[0051] After the molding step (S150), the mold 60 is opened, and the separator 1 is completed. It is not necessary to perform either the surface film arranging step (S100) or the surface film arranging step (S140). In addition, after the second mixture supplying step (S130), a set of the middle film arranging step (S120) and the second mixture supplying step (S130) may be repeated one or more times.

[0052] Fig. 6 shows an example of a flow of main steps of a manufacturing method according to the second embodiment. Fig. 7 shows, in cross-section, the status of each step of the manufacturing method shown in Fig. 6. Fig. 8 shows, in cross-section, the status of each step subsequent to Fig. 7.

[0053] 6 is a method in which a semi-cured laminate of mixture 2a, middle layer film 6, and mixture 2a is prepared, and then the laminate is sandwiched between surface layer films 4 and 5 and molded to produce separator 1. That is, in this manufacturing method, a pre-molding step is performed before the molding step to obtain a laminate in a semi-cured state.

[0054] The separator 1 can be manufactured through a first mixture supplying step (S200), a middle layer film arranging step (S210), a second mixture supplying step (S220), a pre-molding step (S230), a surface layer film arranging step (S300), a pre-molded body arranging step (S310), a surface layer film arranging step (S320), and a molding step (S330). S200 to S230 and S300 to S330 will be described in detail below with reference to Figs. 6 to 8.

[0055] (1) First mixture supply step (S200) This step is a step of supplying a mixture 2a containing graphite and resin into a mold 65. Specifically, the mixture 2a is supplied into the recess 46 of the lower mold 45 (see FIG. 7(a)).

[0056] (2) Middle layer film placement process (S210) This step is a step of placing the intermediate layer film 6 on the mixture 2a in the mold 65. Specifically, the intermediate layer film 6 is laid on the mixture 2a supplied to the recess 46 of the lower mold 45 (see FIG. 7(b)).

[0057] (3) Second mixture supply step (S220) This step is a step of supplying a mixture 2a containing graphite and resin into a mold 65. Specifically, the mixture 2a is supplied onto the middle layer film 6 in the lower mold 45 (see FIG. 7(c)).

[0058] (4) Preforming process (S230) This step is a step of semi-curing a laminate containing the mixture 2a, the middle layer film 6, and the mixture 2a to produce a preform. Specifically, an upper mold 55 constituting a mold 65 is prepared and placed on the recessed portion 46 side of the lower mold 45, and the lower mold 45 and the upper mold 55 are closed (see Figs. 7(d), (e), and (f)). The upper mold 55 has a recess 56 on the surface facing the recessed portion 46 of the lower mold 45. After the mold 65 is clamped, the laminate is heated to semi-cure. The temperature at this time is lower than the temperature in the molding step. As a result, a preform (semi-cured laminate) 70 having an inner barrier layer 3c is completed.

[0059] (5) Surface film placement process (S300) This step is a step of placing the surface film 4 in the mold 60 (FIG. 8(g)). The specific content is the same as the surface film placing step (S100) in the manufacturing method according to the first embodiment.

[0060] (6) Preform Arrangement Step (S310) This step is a step of placing the preform 70 on the surface film 4 placed in the recess 41 (FIG. 8(h)).

[0061] (7) Surface film placement process (S320) This step is a step of arranging a surface film 5 on the mixture 2a constituting the preform 70 in the mold 60 after the preform arranging step (S310) (see FIG. 8(i)).

[0062] (8) Molding process (S330) This step is a step of hardening a laminate including the surface film 4, the preform 70 (mixture 2a, middle film 6, and semi-hardened mixture 2a), and the surface film 5 to produce a molded body. Specifically, an upper mold 50 constituting a mold 60 is prepared, and placed on the recessed portion 41 side of the lower mold 40, and the lower mold 40 and the upper mold 50 are closed (see FIG. 8(j)). After clamping the mold 60, the mold is heated to mold the laminate. As a result, the mixture 2a hardens to form the plate 2. Also, the grooves 30, 32 covered with the surface barrier layers 3a, 3b are formed by the transfer of the irregularities 41, 51 (see FIG. 8(k), (l)).

[0063] After the molding step (S330), the mold 60 is opened, and the separator 1 is completed. It is not necessary to perform either the surface film arranging step (S300) or the surface film arranging step (S320). In addition, after the second mixture supplying step (S220), a set of the middle film arranging step (S210) and the second mixture supplying step (S220) may be repeated one or more times.

[0064] FIG. 9 is a cross-sectional view showing a state in which grooves are formed in a semi-cured preform in a manufacturing method for a multilayer separator according to a modified example.

[0065] In this modification, unevenness is formed on the inner bottom surfaces of the lower mold 45 and the upper mold 55, and a pre-molded body 70a with grooves 30, 32 is manufactured by the pre-molded body arrangement step (S310). In the pre-molded body arrangement step (S310), the pre-molded body 70a is arranged on the surface film 4 so that the grooves of the pre-molded body 70a match the unevenness 42 (see FIG. 9(h2)). After that, the unevenness 52 of the upper mold 50 is aligned with the grooves of the pre-molded body 70a, and the upper mold 50 and the lower mold 40 are closed, and the mold 60 is clamped. Thereafter, the molding step (S330) of the manufacturing method according to the second embodiment is carried out, and the separator 1 is completed (FIGS. 8(k), (l)).

[0066] <Second embodiment> Next, a second embodiment of the present invention will be described. In the multilayer separator and the manufacturing method thereof according to the second embodiment, the overlapping descriptions of the portions common to the first embodiment will be omitted and the descriptions in the first embodiment will be used instead.

[0067] 1. Multi-layer separator FIG. 10 shows a cross-sectional view of the multilayer separator according to the second embodiment taken along line AA similar to FIG. 2A, and an enlarged view of a portion B thereof.

[0068] The separator 1a according to this embodiment includes a plate 2 and an inner barrier layer 3c disposed inside the plate 2. This embodiment differs from the separator 1 according to the first embodiment in that it does not include the surface barrier layers 3a, 3b. The separator 1a is the same as the separator 1 except that it does not include the surface barrier layers 3a, 3b.

[0069] 2. Manufacturing method of multi-layer separator FIG. 11 shows an example of a flow of main steps in the method for producing a separator according to the second embodiment.

[0070] The separator 1a includes a first mixture supplying step (S400) of supplying a mixture containing graphite and a resin into a mold, a middle layer film arranging step (S410) of arranging a middle layer film 6 for forming an inner barrier layer 3c on the mixture in the mold, a second mixture supplying step (S420) of supplying the mixture onto the middle layer film 6, and a molding step (S430) of curing a laminate containing at least the mixture, the middle layer film 6, and the mixture to form a molded body. In addition, after the second mixture supplying step (S420), a set of the middle layer film arranging step (S410) and the second mixture supplying step (S420) may be repeated one or more times. The first mixture supplying step (S400) is common to the first mixture supplying step (S110) except that the first mixture supplying step (S400) is performed without arranging the surface layer film 4 in the mold 60. The middle layer film arranging step (S410) is common to the middle layer film arranging step (S120). The second mixture supplying step (S420) is the same as the second mixture supplying step (S130). The molding step (S430) is the same as the molding step (S150) except that it is performed without disposing the surface films 4, 5. Therefore, a description overlapping with the manufacturing method of the separator 1 according to the first embodiment will be omitted here.

[0071] FIG. 12 shows an example of a flow of main steps of a manufacturing method different from that shown in FIG.

[0072] The separator 1a can be manufactured through a first mixture supplying step (S500), a middle layer film arranging step (S510), a second mixture supplying step (S520), a pre-molding step (S530), a pre-molded body arranging step (S600), and a molding step (S610).

[0073] The first mixture supplying step (S500) is the same as the first mixture supplying step (S200). The middle layer film arranging step (S510) is the same as the middle layer film arranging step (S210). The second mixture supplying step (S520) is the same as the second mixture supplying step (S220). The pre-molding step (S530) is the same as the pre-molding step (S230). In addition, after the second mixture supplying step (S520), a set of the middle layer film arranging step (S510) and the second mixture supplying step (S520) may be repeated one or more times. The pre-molded body arranging step (S600) is the same as the pre-molded body arranging step (S310) except that it is performed without going through the surface film arranging step (S300). The molding step (S610) is the same as the molding step (S330) except that it is performed without the surface films 4, 5. Therefore, a description overlapping with the manufacturing method of the separator 1 according to the first embodiment shown in FIG. 6 will be omitted here.

[0074] <Other embodiments> As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these and can be practiced in various modifications.

[0075] The grooves 30 of the separators 1 and 1a may be grooves that form flow paths other than the flow paths that allow gas to flow in the direction indicated by the white arrows in Fig. 1. The grooves 32 may be grooves that form any type of flow path. For example, the grooves 30 may be grooves that form linear flow paths from one end of the separator 1 to the other end, and the grooves 32 may be grooves that form linear flow paths in a direction approximately perpendicular to the grooves 30. The separators 1 and 1a may not have at least one of the grooves 30 and 32.

[0076] In the above embodiment, the preform 70 does not have any grooves corresponding to the grooves 30, 32, but may have grooves shallower than the grooves 30, 32. In that case, when the mold 60 is closed for molding, the previously formed shallow grooves can be deepened to change into the grooves 30, 32.

[0077] After the molding step, a trimming step may be performed in which excess areas of the surface films 4, 5 or the intermediate film 6 are trimmed off.

[0078] The separator 1 includes surface barrier layers 3a and 3b, but may include only the surface barrier layer 3a or only the surface barrier layer 3b. When the surface barrier layer 3a or the surface barrier layer 3b is provided only on one surface in the thickness direction of the plate 2, the first mixture supplying step, the middle layer film supplying step, and the second mixture supplying step may be performed after or before the surface layer film arranging step. In addition, a pre-molded body arranging step may be performed after or before the surface layer film arranging step, in which a pre-molded body 70 obtained by performing pre-molding via the first mixture supplying step, the middle layer film supplying step, and the second mixture supplying step is arranged. A surface layer film arranging step may be performed between the pre-molding step and the molding step.

[0079] The manufacturing methods of each of the above-described embodiments are methods for manufacturing fuel cell separators in which the inner barrier layer 3c (and the surface barrier layers 3a, 3b) are layers of resin or rubber, but the methods may also be methods for manufacturing fuel cell separators in which these barrier layers 3a, 3b, 3c have layers including a filling layer M such as in forms b, c, and d of FIG. 2B and forms b and c of FIG. 2C. EXAMPLES

[0080] Next, examples of the present invention will be described in comparison with comparative examples. Note that the present invention is not limited to the following examples.

[0081] 1. Main ingredients of the plate (1) Graphite For the graphite powder used as the constituent material of the plates of the multilayer separator (hereinafter also referred to as "separator"), two types of graphite powder were used: Oriental Kogyo Co., Ltd. product number: 1707SJ (artificial graphite, average particle size 125 μm) and Oriental Kogyo Co., Ltd. product number: AT-No.5S (artificial graphite, average particle size 52 μm). (2) Resin Polyphenylene sulfide (PPS) powder was used as the resin that constitutes the separator plates. The PPS used was a fine powder of flake-shaped PPS powder manufactured by Toray Industries, Inc., product number: Torelina M2888 (MFR600), which was freeze-ground and adjusted to an average particle size of 50 μm. (3) Aramid fiber As the aramid fibers forming the separator plates, two types of para-aramid fibers were used: Technora T32PNW 3-12 (average fiber length 3.2 mm, average fiber diameter 18 μm) manufactured by Teijin Limited, and Twaron (registered trademark) D8016 (average fiber length 0.8 mm) manufactured by Teijin Limited.

[0082] 2. Pretreatment of raw materials before molding The graphite powder and the resin powder were mixed and pulverized in a ball mill using zirconia balls. The ball mill pulverization was terminated when it was confirmed through particle size distribution measurement (measurement by a laser diffraction / scattering particle size distribution measurement method) that the particle size of the mixed powder was 90±10 μm on average.

[0083] 3. Surface film A PPS film was used as the surface film. The PPS film used was a 9 μm-thick film (product number: Torelina 9-3071) manufactured by Toray Industries, Inc.

[0084] 4. Middle layer film Four types of films were used for the middle layer: PPS, PEEK, SUS304, and graphite. For the PPS film, a 25 μm thick film (product number: Torelina 25-3030) manufactured by Toray Industries, Inc. was used. For the PEEK film, a 6 μm thick film manufactured by Shin-Etsu Polymer Co., Ltd., using raw materials manufactured by Solvay Specialty Polymers, Inc. (product number: KT-851NL SP), was used. For the SUS304 film, a 20 μm thick film (product number: SUS304 H-TA) manufactured by Nippon Kinzoku Co., Ltd. was used. For the graphite film, a 32 μm thick film (product number: Graphinity 32 μm) manufactured by Kaneka Corporation was used.

[0085] 5.Mold The mold used for molding was a top-bottom split mold made of prehardened steel NAK80 manufactured by Daido Steel Co., Ltd. When closed, there was a space (approximately 63 cm2) inside the mold in which the separator could be molded. 3 In addition, the bottom of the inside of each of the upper and lower dies has projections and recesses for forming the grooves of the separator.

[0086] 6. Evaluation Methodology (1) Volume resistivity The volume resistivity of the separator was measured in accordance with JIS K7194 using an apparatus (Loresta-GX T-700) manufactured by Nitto Seiko Analytech Co., Ltd. A volume resistivity of less than 2.5 mΩcm was evaluated as passing. (2) Bending test The bending test of the separator was performed based on JIS K7171 using an apparatus manufactured by Shimadzu Corporation (Autograph AG-100kNG). Bending strength A bending strength of more than 40 MPa was rated as acceptable. Bending strain A bending strain of 0.7% or more was rated as pass. (3) He gas permeability coefficient at 23℃ The gas permeability coefficient of the separator was measured using He gas in accordance with JIS K7126-1 using a gas permeability measuring device (K-315-N-03) manufactured by Rika Seiki Kogyo Co., Ltd. The permeability coefficient was 1.0×10 -15 mol m / m 2 When the resistance was less than 1.5 sec·Pa, the evaluation was passed.

[0087] 7. Manufacturing of multi-layer separators <Example> (1) Example 1 977.8 parts by mass of artificial graphite particles (product number: 1707SJ), 244.4 parts by mass of artificial graphite particles (product number: AT-No.5S), 100 parts by mass of PPS powder, 62.5 parts by mass of para-aramid fiber (Technora T32PNW 3-12), and 4.2 parts by mass of para-aramid fiber (Twaron (registered trademark) D8016) were prepared, and these were mixed and dispersed in water to prepare a slurry with a solid content of 1%. This mixture was put into a filter equipped with a 25 cm square inlet, and a sheet-like wet sheet, which is the residue obtained by filtration, was formed. The wet sheet was set in a press machine heated to 150°C and pressurized and heated at a surface pressure of 8 MPa for about 20 minutes, and the wet sheet was dried to remove moisture, resulting in a 1 mm thick sheet with a basis weight of 1100 g / m2 in which artificial graphite particles, PPS particles, and aramid fibers were dispersed. 2 A preplate of 1 μm was produced. Another preplate was produced by the same procedure as above, and a total of two preplates were prepared. A 9 μm thick PPS film was laid as a surface film in the inner recess of the lower die constituting the split type die, and one of the preplates was provided on the film. Next, a 25 μm thick PPS film was placed on top of that as a middle layer film. Next, another preplate was provided on the PPS film as the middle layer film. Next, a 9 μm thick PPS film was laid on the preplate as a surface film. Next, the upper die constituting the split type die and the lower die were closed to perform molding. The molding was performed by heating the die at a surface pressure of 4 MPa until the temperature of the die rose to 340° C., increasing the pressure to 90 MPa and holding for 1 minute. After that, the die was pressurized and cooled to 30° C. while maintaining the pressure. After molding was completed, the die was opened, the molded body was removed, and the production of the separator was completed. The separator was evaluated by the above evaluation method. (2) Example 2 A separator was produced and evaluated under the same conditions as in Example 1, except that a SUS304 film was used as the middle layer film. (3) Example 3 A separator was produced and evaluated under the same conditions as in Example 1, except that a graphite film was used as the middle layer film. (4) Example 4 A separator was produced and evaluated under the same conditions as in Example 1, except that a PEEK film was used as the middle layer film.

[0088] <Comparative Example> (1) Comparative Example 1 The raw materials, mass parts of the raw materials, and manufacturing method of the preplate were the same as those in Example 1, with a thickness of 2 mm and a basis weight of 2200 g / m 2 The preplate was produced. The preplate was provided in the recess on the inside of the lower die constituting the split die. Next, the upper die and the lower die constituting the split die were closed to perform molding. The molding was performed by heating the die at a surface pressure of 4 MPa until the temperature rose to 340°C, and then increasing the surface pressure to 90 MPa and holding for 1 minute. Thereafter, the die was pressurized and cooled to 30°C while maintaining the pressure. After molding was completed, the die was opened, the molded body was removed, and the production of a separator without a middle layer film and a surface layer film was completed. The separator was evaluated in the same manner as in Example 1. (2) Comparative Example 2 A preplate similar to that of Comparative Example 1 was manufactured. A 9 μm thick PPS film was laid as a surface film on the inner recess of the lower die constituting the split type die, and the preplate was provided on the film. Next, a 9 μm thick PPS film was laid as a surface film on the preplate. Next, the upper die constituting the split type die and the lower die were closed to perform molding. The molding was performed by heating the die at a surface pressure of 4 MPa until the temperature of the die rose to 340° C., and then increasing the surface pressure to 90 MPa and holding for 1 minute. Thereafter, the die was pressurized and cooled to 30° C. while maintaining the pressure. After molding was completed, the die was opened, the molded body was removed, and the production of a separator without a middle layer film was completed. The separator was evaluated in the same manner as in Example 1.

[0089] 8.Results Table 1 shows the production conditions and evaluation results of each of the examples and comparative examples.

[0090] [Table 1]

[0091] In Comparative Examples 1 and 2, the volume resistivity, bending strength, and bending strain passed the test, but the He gas permeability coefficient failed the test, whereas in Examples 1 to 4, all properties passed the test. [Industrial Applicability]

[0092] The multi-layer separator according to the present invention can be used as a separator between cells in a battery, particularly a storage battery.

Claims

1. A plate including graphite and resin, the plate having grooves on a surface thereof as flow paths; an inner barrier layer for gas barrier, which is disposed inside the thickness direction of the plate and divides the thickness direction into at least two regions; a surface barrier layer for gas barrier provided on at least one surface of the plate in the thickness direction; A method for manufacturing a multi-layer separator comprising: a first mixture supplying step of supplying a mixture containing graphite and a resin into a die; an intermediate layer film positioning step of positioning an intermediate layer film for forming the inner barrier layer on the mixture in the mold; a second mixture supplying step of supplying the mixture onto the middle layer film; a surface film placement step of placing a surface film for forming the surface barrier layer in a mold; a molding step of curing a laminate including at least the mixture, the intermediate layer film, and the mixture to form a molded body; Including, Before the molding step, the middle layer film arrangement step and the second mixture supply step are each repeated once or twice or more; A method for manufacturing a multilayer separator, characterized in that the first mixture supplying step, the middle layer film arrangement step, and the second mixture supplying step are carried out after, before, or both before and after the surface film arrangement step.

2. 2. The method for producing a multi-layer separator according to claim 1, wherein the inner barrier layer is a film-like layer different from the plate.

3. 2. The method for producing a multilayer separator according to claim 1, wherein the inner barrier layer is a filled layer in which resin or rubber fills spaces between particles or fibers constituting the plate.

4. 4. The method for producing a multi-layer separator according to claim 3, wherein the inner barrier layer includes the filling layer and a film-like layer different from the plate.

5. The method for producing a multilayer separator according to any one of claims 1 to 4, characterized in that the multilayer separator has two or more inner barrier layers.

6. 6. The method of claim 1, wherein the inner barrier layer comprises at least one of polyether ether ketone and polyphenylene sulfide.

7. 7. The method of claim 1, wherein the inner barrier layer comprises at least one of stainless steel and graphite.

8. A method for manufacturing a multilayer separator described in any one of claims 1 to 7, characterized in that the surface barrier layer includes at least one of polyether ether ketone and polyphenylene sulfide.

9. A method for manufacturing a multilayer separator described in any one of claims 1 to 8, characterized in that the thickness of the internal barrier layer is greater than the thickness of the surface barrier layer.

10. 10. The method for producing a multilayer separator according to claim 1, further comprising the step of: conducting a pre-molding step to obtain the laminate in a semi-cured state prior to the molding step.

11. The method for producing a multilayer separator according to claim 10, wherein the surface film arrangement step is carried out between the pre-molding step and the molding step.

12. 12. The method for producing a multilayer separator according to claim 1, wherein the multilayer separator is a separator for a fuel cell used between cells of a fuel cell.

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