WO2019176995A1

WO2019176995A1 - Separator for fuel cell and method for manufacturing same

Info

Publication number: WO2019176995A1
Application number: PCT/JP2019/010190
Authority: WO
Inventors: 昭紘小泉; 勝米山; 岡田　晃; 鈴木　勤
Original assignee: 信越ポリマー株式会社
Priority date: 2018-03-13
Filing date: 2019-03-13
Publication date: 2019-09-19

Abstract

Provided are: a separator which is for a fuel cell and can improve conductivity or mechanical strength for fluid of about 80°Cand also achieve slimness or miniaturization; and a method for manufacturing the same. Provided is a separator 1 for a fuel cell that uses a polymer film having ion-conductivity as an electrolyte, the separator 1 including 15-40 parts by mass of a fiber resin, and 85-60 parts by mass of a conductive material having higher conductivity than the fiber resin 4, wherein the fiber resin 4 contains a polypropylene fiber system 5 having an average fiber length of at least 1-80 mm, and the conductive material 7 contains at least one among particulate conductive materials 8 and a fibrous conductive material 9. The fiber resin 4 and the fibrous conductive material 9 are introduced into three-dimensional network gaps formed between the particulate conductive materials 8 of the conductive material 7, filling the gaps. Since the fiber resin 4, the particulate conductive materials 8, and the fibrous conductive material 9 are complexly interwound and integrated, multiple particulate conductive materials 8 can be strongly connected, thereby improving conductivity.

Description

Fuel cell separator and method for producing the same

The present invention relates to a fuel cell separator for a fuel cell using a polymer membrane having ion conductivity as an electrolyte and a method for producing the same.

The polymer electrolyte fuel cell has a short start-up time and a low operating temperature, and therefore has been vigorously developed in various fields as a promising candidate for the next-generation energy technology (see

Patent Documents

1, 2, and 3). . This solid polymer type fuel cell is used by laminating a large number of separators, and this separator is an important part because it exhibits gas separation and current collecting functions.
Although not shown, a conventional fuel cell separator is formed into a flat rectangular plate with a predetermined composite conductive material. The predetermined composite conductive material is made of, for example, a carbonaceous material selected from thermoplastic resin, graphite, and ketjen black, and carbon nanotubes in order to obtain excellent mechanical strength and conductivity, and these are melted during molding. And mixed.

Japanese Patent Laid-Open No. 2005-200620 JP 2003-082247 A JP 2003-109622 A

Conventional fuel cell separators are formed as described above and provide a predetermined effect. However, since graphite and carbon nanotubes are merely dispersed in the thermoplastic resin, the connection between the graphite is poor and the conductivity is low. It is difficult to improve. This makes it difficult to meet recent market demands for even higher electrical conductivity.

In addition, in recent years, separators for fuel cells have high conductivity for reducing the internal resistance of the fuel cells, as well as mechanical strength, thinness, and small size that do not deteriorate against hot water at about 80 ° C. during operation. Thinness of 1 mm or less is required to contribute to the process. However, it is very difficult to improve the electrical conductivity, the mechanical strength against hot water of about 80 ° C., and the reduction in thickness and size.

The present invention has been made in view of the above, and can improve the electrical conductivity and mechanical strength against a fluid of about 80 ° C., and can achieve a reduction in thickness and size, and its manufacture. It aims to provide a method.

In order to solve the above-mentioned problems, the present invention includes 15 to 40 parts by mass of a fiber resin and 85 to 60 parts by mass of a conductive material that is more conductive than the fiber resin.
The fiber resin includes a polypropylene fiber system having an average fiber length of 1 to 80 mm, and the conductive material includes at least one of a particulate conductive material and a fibrous conductive material.

The fiber resin can contain aramid fibers.
The polypropylene fiber system of the fiber resin is preferably a polypropylene fiber.
Further, it is preferable that the particulate conductive material of the conductive material is graphite particles having an average particle diameter of 3 to 500 μm, and the fibrous conductive material of the conductive material is carbon fiber.
Further, the particulate conductive material of the conductive material is preferably expanded graphite particles having an average particle diameter of 3 to 500 μm.
The particulate conductive material of the conductive material is preferably artificial graphite particles having an average particle diameter of 3 to 500 μm.

Moreover, in order to solve the said subject in this invention, it is a manufacturing method of the separator for fuel cells in any one of Claim 1 thru | or 6,
Part of the conductive material is dispersed in the fiber resin to form a composite sheet, the composite sheet is set in the decompression tool, and the exposed portion is filled with the remainder of the conductive material, and the decompression tool is closed and decompressed. By forming a conductive molded body, and then laminating a composite sheet on the exposed portion of the molded conductive molded body and compressing it by heating, a fuel cell separator is formed.

The composite sheet is prepared by mixing and dispersing the fiber resin and a part of the conductive material to form a slurry, forming the slurry into a sheet, pressurizing and drying the sheet, and then heating the dried sheet. It may be formed by applying pressure.

Here, the conductive material in the claims includes at least various carbon-based materials and a metal filler made of metal particles, metal fibers, or the like having excellent conductivity. Part of this conductive material does not particularly ask for the particulate conductive material, the fibrous conductive material, the particulate conductive material, and the fibrous conductive material. The remainder of the conductive material is not particularly limited to the particulate conductive material, the fibrous conductive material, the particulate conductive material, and the fibrous conductive material. The expanded graphite particles include both expanded graphite particles and expanded graphite particles that have been expanded. The separator for a fuel cell may be a plate having a plurality of fluid flow paths arranged on both front and back surfaces, a bent plate having a continuous wavy cross section, or the like.

According to the present invention, it contains 15 to 40 parts by mass of a fiber resin and 85 to 60 parts by mass of a conductive material that is more conductive than the fiber resin. Flexibility, flexibility, durability to a fluid of about 80 ° C., and the like can be imparted. Further, since the average fiber length of the fiber resin is in the range of 1 to 80 mm, the dispersibility is improved, the composition of the fuel cell separator is made uniform, and the difference in the partial physical properties and conductivity of the fuel cell separator is reduced. be able to.

According to the present invention, there is an effect that the fuel cell separator can be provided with high conductivity and mechanical strength against a fluid of about 80 ° C. In addition, the fuel cell separator can be reduced in thickness and size.

According to the invention described in claim 2, since the aramid fibers are included in the fiber resin, the fiber resins can be appropriately entangled to reinforce the fiber resin. Further, heat resistance, strength, chemical resistance and the like can be imparted to the fiber resin to improve the quality of the fuel cell separator, and the material composition of the fuel cell separator can be made substantially uniform.

According to the invention described in claim 3, since the polypropylene fiber system is polypropylene fiber, the adhesiveness of the conductive material is improved, and the mechanical properties can be improved. In particular, when the polypropylene fiber system is acid-modified polypropylene fiber, the adhesiveness of the conductive material is remarkably improved, and the mechanical characteristics can be improved. In addition, due to the improved adhesiveness, even if the fuel cell separator is immersed in a liquid at about 80 ° C. for a long time, dropping of the conductive material from the fuel cell separator is reduced.

According to the fourth aspect of the present invention, since the particulate conductive material of the conductive material is graphite particles, the composition and shape of the conductive material can be controlled. Further, since the fibrous conductive material of the conductive material is carbon fiber, the risk of a decrease in durability of the fuel cell separator is reduced. In addition, excellent heat resistance and mechanical strength can be obtained, and the weight can be reduced.

According to the invention described in claim 5, since the graphite particles are expanded graphite particles that expand with heating, excellent conductivity can be obtained, and furthermore, the gap between the expanded graphite particles can be blocked to prevent liquid leakage. Can do.
According to the sixth aspect of the present invention, since the graphite particles are not natural graphite particles but artificial graphite particles, there are few impurities such as metals and the crystallinity is uniform, which is suitable for manufacturing a fuel cell separator.

It is a plane explanatory view showing typically an embodiment of a separator for fuel cells concerning the present invention. It is a section explanatory view showing typically an embodiment of a separator for fuel cells concerning the present invention. It is an expansion explanatory view showing typically the state where the fiber resin, particulate conductive material, and fibrous conductive material in the embodiment of the separator for a fuel cell according to the present invention are intertwined and integrated. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically embodiment of the manufacturing method of the separator for fuel cells which concerns on this invention, (a) A figure is explanatory drawing which shows the state which set the composite sheet to the inner bottom face of a suction jig, (b) figure Is an explanatory view showing a state in which a conductive conductive material is supplied onto the surface of the composite sheet, and (c) is a diagram in which a scraper is brought into contact with the particulate conductive material on the suction jig, and the scraper is moved horizontally. FIG. 4D is an explanatory view showing a state in which a conductive molded body is formed by compressing the particulate conductive material of the suction jig upside down. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional explanatory view schematically showing an embodiment of a method for producing a fuel cell separator according to the present invention, wherein (a) shows another composite on the exposed surface by inserting a conductive molded body into the lower mold of the mold. An explanatory view exaggeratingly showing a state in which sheets are stacked, and FIG. 5B is an explanatory view exaggeratingly showing a state where an upper mold of a mold is brought into contact with another composite sheet.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. A fuel cell separator 1 according to this embodiment includes a fiber resin 4 and a fiber resin 4 as shown in FIGS. Among the aramid fibers 6 having at least a polypropylene fiber system 5 and an aromatic skeleton, the fiber resin 4 includes a polypropylene fiber system 5, and the conductive material 7 has a particulate conductive property. This is a planar rectangular separator containing at least one of the material 8 and the fibrous conductive material 9.

As shown in FIG. 1 and FIG. 2, the fuel cell separator 1 is formed into a substantially cross-sectional waveform with a continuous rectangular wave and has a thickness of 1 mm or less, specifically 0.2 to 0, from the viewpoint of thinning. .9 mm, preferably 0.5 to 0.7 mm, and a plurality of connection ports 2 for connection with other components of the fuel cell are perforated at the peripheral edge. The fuel cell separator 1 is formed into a substantially corrugated cross section so that a plurality of flow paths 3 for circulating a predetermined liquid or gas are disposed on both the front and back surfaces, and the plurality of flow paths 3 have a flow path structure. From the viewpoint of contributing to the composite, the serpentine shape is bent and arranged at the substantially central portion excluding the peripheral portion, and each flow path 3 is formed in a concave shape with a continuous U-shaped cross section.

As shown in FIGS. 4 and 5, such a fuel cell separator 1 is formed by dispersing a part of a conductive material 7 in a fiber resin 4 to form a composite sheet 10, and forming the composite sheet 10 in a suction jig 11. Is set, and the exposed surface is filled with the remainder of the conductive material 7, the suction jig 11 is closed and the pressure is reduced to form the conductive molded body 13, and then the composite is formed on the exposed portion of the molded conductive molded body 13. It is preferable that the sheet 10 is laminated and heated and compressed to produce a thin plate having a substantially corrugated cross section.

The fiber resin 4 and the conductive material 7 contain more conductive material 7 in a mass ratio than the fiber resin 4. That is, the mass ratio between the fiber resin 4 and the conductive material 7 is to improve the conductivity, thinning, flexibility, flexibility, durability against hot water at about 80 ° C. during operation, and the like of the fuel cell separator 1. , 15-40: 85-60.

The reason why the fiber resin 4 is 15 to 40 parts by mass is that when the fiber resin 4 is less than 15 parts by mass, the fusion with the conductive material 7 becomes insufficient, and the conductive material 7 falls off from the fuel cell separator 1, This is because the mechanical strength of the fuel cell separator 1 is insufficient, and breakage easily occurs. On the other hand, when the fiber resin 4 exceeds 40 parts by mass, the blending amount of the conductive material 7 is insufficient, and the conductivity of the fuel cell separator 1 is lowered.

The fiber resin 4 is easy to mold at a relatively low temperature (160 to 170 ° C.), and contains a polypropylene fiber system 5 such as a polypropylene (PP) fiber that is inexpensive and easily available. A resin may be contained as necessary, and when other fibrous resin is contained, the aramid fiber 6 is optimal. The average fiber length of the fiber resin 4 is 1 to 80 mm, preferably 2 to 40 mm, more preferably 2 to 10 mm.

This is because if the average fiber length of the fiber resin 4 is in the range of 1 to 80 mm, the dispersibility is improved, and the composition of the entire conductive molded body 13 is made uniform during the production of the fuel cell separator 1, resulting in partial physical properties. This is because the difference in electrical conductivity can be reduced. In addition, it is possible to prevent the fiber resin 4 from dropping from the conductive molded body 13 during the manufacture of the fuel cell separator 1.

Examples of the polypropylene fiber system 5 include unmodified polypropylene fibers having an average fiber length of 1 to 80 mm or acid-modified polypropylene fibers, and acid-modified polypropylene fibers having an average fiber length of 1 to 80 mm are particularly suitable. This is because, in the case of acid-modified polypropylene fibers, the adhesiveness of the conductive material 7 is remarkably improved, and mechanical properties (for example, bending strength and tensile strength) are also greatly improved. Further, due to the improved adhesiveness, even if the conductive material 7 is exposed to hot water at about 80 ° C. for a long time, dropping of the conductive material 7 from the fuel cell separator 1 is reduced, which is effective for maintaining the form of the fuel cell separator 1. It is.

The acid-modified polypropylene is not particularly limited, but has a carboxyl group such as maleic anhydride, itaconic anhydride, citraconic anhydride, maleic acid, itaconic acid, citraconic acid, fumaric acid, acrylic acid, crotonic acid and the like. It is a polypropylene copolymerized with the monomer it has. Moreover, although an acid-modified polypropylene may be used independently, you may use it in combination of 2 or more type. Furthermore, it is also possible to combine unmodified polypropylene and acid-modified polypropylene.

The aramid fiber 6 is composed of fibers having an average fiber length of 1 to 10 mm, preferably an average fiber length of 2 to 5 mm, each of which is a para-based material or a meta-based material, or a mixture thereof in an arbitrary composition ratio. The fiber resin 4, the conductive material 7, and the fiber resin 4 are appropriately entangled at the time of manufacture to function to reinforce the fiber resin 4. The aramid fiber 6 may have any shape such as a pulp shape or a cut fiber shape, but a pulp shape with a fluffy surface is preferable from the viewpoint of appropriately entwining and twisting the fiber resin 4 and the conductive material 7.

The aramid fiber 6 reinforces the other fiber resin 4, but does not stop at the reinforcing function, and by providing the other fiber resin 4 with heat resistance, strength, chemical resistance, etc. It functions to contribute to quality. Since this aramid fiber 6 does not particularly contribute to the improvement of conductivity, when it is added, it is preferable to add about 1 to 5 parts by mass. As the aramid fiber 6, a Kevlar cut fiber [manufactured by Toray DuPont Co., Ltd .: Kevlar (registered trademark)] having a length of 3 mm can be used.

As shown in FIG. 3, the conductive material 7 is optimal to contain both the particulate conductive material 8 and the fibrous conductive material 9, but other than the particulate conductive material 8 and the fibrous conductive material 9. Other kinds of conductive materials may be contained, only the particulate conductive material 8 or only the fibrous conductive material 9 may be used. When the conductive material 7 contains both the particulate conductive material 8 and the fibrous conductive material 9, the fibrous conductive material 9 tends to be oriented in the plane direction, so that the conductivity in the plane direction of the fuel cell separator 1 is improved. Can be made.

On the other hand, since the particulate conductive material 8 is oriented regardless of the surface direction or the thickness direction, the electrical conductivity in the thickness direction of the fuel cell separator 1 is insufficient with the fibrous conductive material 9 alone. be able to. Further, when the particulate conductive material 8 is temporarily formed to form a three-dimensional network of conductive paths, the resistance value in the thickness direction of the fuel cell separator 1, which is difficult to achieve with only the fibrous conductive material 9, is reduced. be able to.

Thus, when the conductive material 7 contains both the particulate conductive material 8 and the fibrous conductive material 9, the conductivity in both the thickness direction and the surface direction of the fuel cell separator 1 is improved. Can do. It is preferable that the particulate conductive material 8 and the fibrous conductive material 9 contain more particulate conductive material 8 than the fibrous conductive material 9 from the viewpoint of improving conductivity. The specific mass ratio is in the range of about 40 to 82:20 to 3.

The particulate conductive material 8 may be metal particles having excellent electrical conductivity, but graphite particles 8a capable of controlling the composition and shape are preferable because the durability of the fuel cell separator 1 may be reduced. If the graphite particles 8a are selected, excellent electrical conductivity can be expected since the electric resistance value is 1 to 3 × 10 ⁻³ Ω · cm. As shown in FIG. 3, the graphite particles 8a form a three-dimensional network that is a conductive path, and at least the fiber resin 4 and the fibrous conductive material 9 are filled in the gaps of the three-dimensional network.

The shape of the graphite particles 8a includes a flake shape, a spherical shape, a scale shape, and the like, but is not particularly limited. The average particle size of the graphite particles 8a is 3 to 500 μm, preferably 3 to 400 μm, more preferably 3 to 300 μm, as measured by a laser diffraction / scattering particle size distribution measurement method. This is because, if the average particle diameter is in the range of 3 to 500 μm, it is easy to form the composite sheet 10 that is a component when manufacturing the fuel cell separator 1.

The graphite particles 8a include types such as expanded graphite particles 8b, expanded graphite particles, artificial graphite particles, and natural graphite particles. Preferably, the expanded graphite particles 8b, expanded graphite particles, and artificial graphite particles expand by heating. Is preferred. Expanded graphite refers to graphite or a graphite intercalation compound in which graphite layers are expanded by intercalation of another material layer on a specific surface of a structure in which regular hexagonal planes of graphite are stacked. The reason why the expanded graphite particles 8b are suitable is based on the reason that excellent conductivity can be obtained and the gap between the expanded graphite particles 8b can be closed to prevent the leakage of hot water.

In terms of this point, if the expanded graphite particles 8b are employed, they expand by heating, so that the voids in the fuel cell separator 1 can be filled with the graphite particles 8a. This is because the electrical resistance value can be reduced. Further, it is possible to suppress swelling due to the hot water soaking into the voids in the fuel cell separator 1.

On the other hand, artificial graphite is formed by adding a binder such as pitch to raw coke and heating it to around 1300 ° C., followed by primary firing, then impregnating the primary fired product into pitch resin, and further approaching 3000 ° C. It is graphite produced by secondary firing at a high temperature. This artificial graphite is generally characterized by high quality and stable quality with ash content of 0.5%, volatile content of 0.5%, fixed carbon of 99% and total sulfur of about 0.02%. Artificial graphite is suitable because it is suitable for industrial products because it has few impurities such as metals and has uniform crystallinity.

As expanded graphite particles 8b, EXP-50SS (manufactured by Fuji Graphite Industry Co., Ltd .: product name) having an average particle size of 300 μm, EXP-80S [manufactured by Fuji Graphite Industry Co., Ltd .: product name] having an average particle size of 200 μm Etc. Examples of the expanded graphite particles include BSP-60A (manufactured by Fuji Graphite Industry Co., Ltd .: product name) having an average particle diameter of 60 μm. Examples of the artificial graphite particles include JSG-75S [manufactured by Fuji Graphite Industry Co., Ltd .: product name] having an average particle diameter of 45 μm and AT-No. 5S [made by Oriental Sangyo Co., Ltd .: product name]. Further, as the natural graphite particles, scaly graphite powder CB-100 [manufactured by Nippon Graphite Industry Co., Ltd .: product name] having an average particle diameter of 80 μm corresponds.

The fibrous conductive material 9 may be a metal fiber that can be expected to have a low electrical resistance value. However, since the durability of the fuel cell separator 1 may be lowered, the carbon fiber 9a is excellent in heat resistance and is light and strong. Is preferred. Among the carbon fibers 9a, light graphite (graphite) fibers that are excellent in conductivity, heat resistance, chemical resistance, and the like are optimal. If a graphite fiber is selected, the electric resistance value is 1 to 3 × 10 ⁻³ Ω · cm, and the electric resistance value is lower than that of the fiber resin 4, so that high conductivity can be obtained.

The average fiber length of the carbon fiber 9a is 1 to 60 mm, preferably 2 to 20 mm, more preferably 2 to 5 mm. This is because, if the average fiber length is in the range of 1 to 60 mm, the carbon fibers 9a are arranged in the plane direction that contributes to the flexibility of the fuel cell separator 1 by using fibers larger than the thickness of the composite sheet 10. This is based on the reason that a thin fuel cell separator 1 that can be easily bent and does not break even when bent can be obtained.

As the carbon fiber 9a, PAN-based fibers and pitch-based fibers can be used alone or in combination. Examples of the PAN-based carbon fiber 9a include TORAYCA [Toray Industries, Inc .: registered trademark] cut fiber T008-003 (fiber diameter φ7 μm, cut length 3 mm). On the other hand, the pitch-based carbon fiber 9a corresponds to YSH-60A-30S [manufactured by Toray Industries, Inc .: product name] (fiber diameter φ7 μm, cut length 3 mm).

In the above, when the fuel cell separator 1 is manufactured, first, in order to obtain the required number (two in this embodiment) of the composite sheet 10, the fiber resin 4 containing the aramid fiber 6 and the carbon of the conductive material 7 are used. A fibrous conductive material 9 composed of fibers 9a and the like is mixed and dispersed in water to prepare a slurry having a solid content of 0.5 to 10 wt%, and a flocculant is added to the slurry, and these mixtures are similar to papermaking. By forming into a sheet in the manner, a sheet for the composite sheet 10 is formed. When the sheet is formed in this manner, the sheet is pressurized and dried to remove moisture, and the dried sheet is set in a dedicated mold and heated and pressed to apply the fibrous conductive material of the conductive material 7 to the fiber resin 4. The required number of felt-like composite sheets 10 in which 9 is dispersed substantially uniformly are formed.

When this composite sheet 10 is molded, carbon particles are used in place of the carbon fibers 9a of the conductive material 7, and a felt shape in which the carbon particles of the conductive material 7 are dispersed substantially uniformly in the fiber resin 4 by the same operation as described above. The composite sheet 10 can be formed. Further, the carbon fiber 9a and the carbon particles are used as the conductive material 7, and the felt-like composite sheet 10 in which the carbon fibers 9a and the carbon particles are substantially uniformly dispersed in the fiber resin 4 is formed by the same operation as described above. You can also Further, when the fuel cell separator 1 having a thickness of less than 1 mm is manufactured, the composite sheet 10 may be formed to have a thickness of less than 1 to 7 mm, preferably less than 1 to 5 mm.

Next, a female suction jig 11 shown in FIG. 4 is prepared, and a single composite sheet 10 formed on the inner bottom surface of the suction jig 11 is set (see FIG. 4A), and the exposed surface thereof. A particulate conductive material 8 made of expanded graphite particles 8b of the conductive material 7 is filled on the top (see FIG. 4 (b)), and the space between the inside of the suction jig 11 and the surface of the composite sheet 10 is many. It is filled with the particulate conductive material 8.

In this case, the filling amount of the particulate conductive material 8 is 0.5 to 1.8 g, preferably 0.8 to 1.2 g per unit area of the composite sheet 10. When the particulate conductive material 8 is packed on the surface of the composite sheet 10, the scraper 12 or the like is brought into contact with the particulate conductive material 8 on the suction jig 11, and the scraper 12 or the like is moved horizontally (FIG. 4 ( c), the excess particulate conductive material 8 on the suction jig 11 is removed and leveled, and the upper surface of the opening of the suction jig 11 and the particulate conductive material 8 are aligned and aligned.

Next, the upper opening of the suction jig 11 is closed and turned upside down, and the bottom of the upside down suction jig 11 is connected to a vacuum pump or the like to perform suction and pressure reduction, and the particulate conductive material 8 is compressed to become conductive. After molding the molded body 13 (see FIG. 4D), the conductive molded body 13 molded from the suction jig 11 is removed. When the conductive molded body 13 is molded, the aramid fibers 6 function to make the material composition of the fuel cell separator 1 uniform.

To explain the homogenizing function, when the conductive molded body 13 is molded, the polypropylene fiber system 5 of the fiber resin 4 melts and flows in the conductive molded body 13, but a part of the conductive material 7 is the polypropylene fiber system 5. In some cases, the composition of the conductive molded body 13 may flow and cause a partial variation. However, when the aramid fiber 6 is blended, the fluffy surface of the aramid fiber 6 becomes a resistance of a part of the conductive material 7, and as a result, the material composition of the fuel cell separator 1 can be made uniform.

Next, a dedicated mold 20 for compression molding the fuel cell separator 1 was prepared, and a conductive molded body 13 was inserted into the opened lower mold 21 of the mold 20 and molded on the exposed surface. Another composite sheet 10 is laminated (see FIG. 5A), and the upper mold 22 of the mold 20 is brought into contact with the composite sheet 10 (see FIG. 5B). The mold 20 includes a lower mold 21 and an upper mold 22 that face each other, and concave and convex portions for forming the flow path 3 are formed on the cavity surfaces of the lower mold 21 and the upper mold 22, respectively.

When the conductive molded body 13 is inserted into the lower mold 21 of the mold 20, the exposed surface of the conductive molded body 13 is a composite from the viewpoint of improving the strength by sandwiching the particulate conductive material 8 between the composite sheet 10. It is preferable not on the sheet 10 side but on the particulate conductive material 8 side.

When the upper mold 22 of the mold 20 is brought into contact with the composite sheet 10, the mold 20 is strongly clamped and heated under pressure to compress the fuel cell separator 1 having a corrugated cross section into a thin plate having a thickness of 1 mm or less. To do. In this case, the mold clamping pressure of the mold 20 is about 400 to 900 kg / cm ² (about 40 to 90 MPa), preferably about 50 to 70 MPa, more preferably about 55 to 65 MPa. The heating temperature is 170 to 300 ° C., preferably 175 to 220 ° C., since the melting point of the polypropylene fiber system 5 of the fiber resin 4 is 165 ° C. and the thermal decomposition starting temperature is about 300 ° C.

When the fuel cell separator 1 is molded by heat compression, a three-dimensional network is formed between a large number of particulate conductive materials 8, and the fiber resin 4 of the composite sheet 10, the aramid fiber 6, The fibrous conductive material 9 flows in intricately and closes, and these are intricately wound together, thereby improving the mechanical strength. Further, the polypropylene fiber system 5 of the fiber resin 4 is melted to become a binder resin for fixing the particulate conductive material 8 and the fibrous conductive material 9, and the fiber shape of the polypropylene fiber system 5 disappears.

Once the fuel cell separator 1 is compression molded, the complete fuel cell separator 1 can be manufactured by opening the mold 20 and removing the fuel cell separator 1. A typical sample of the fuel cell separator 1 has a surface / thickness resistance value of 20 mΩ · cm / 20 mΩ or less.

According to the above, the fiber resin 4, the aramid fiber 6, and the fibrous conductive material 9 flow into the gaps of the three-dimensional network formed between the many particulate conductive materials 8 in a complicated manner, and are blocked. Since the aramid fiber 6, the particulate conductive material 8, and the fibrous conductive material 9 are intricately wound and integrated, a large number of the particulate conductive materials 8 can be firmly connected and the conductivity can be significantly improved. Further, the fiber resin 4 and the conductive material 7 are not simply blended, but the fiber resin 15 to 40 parts by mass and the conductive material 85 to 60 parts by mass are blended, so that the fuel cell separator 1 has high conductivity, 1 mm. The following thinning, flexibility, flexibility, durability against hot water of about 80 ° C., etc. can all be imparted.

In addition, in the said embodiment, although the several flow path 3 was shape | molded in the serpentine shape, you may shape | mold in a straight shape etc. Further, the aramid fiber 6 may be omitted if it is not necessary to reinforce the fiber resin 4 in particular. Moreover, although the example in which the conductive material 7 is mainly composed of the graphite particles 8a and the carbon fibers 9a has been shown in the above-described embodiment, the present invention is not limited to this. For example, carbon particles instead of the carbon fibers 9a (for example, carbon nanotubes) Or carbon black) and graphite particles 8a. In this case, the carbon particles are preferably contained in a smaller mass ratio than the graphite particles 8a. Specifically, the carbon particles are preferably mixed with the graphite particles 8a in the range of 20 to 3 parts by mass or less with respect to 40 to 82 parts by mass of the graphite particles 8a.

Embodiments of a fuel cell separator and a method for producing the same according to the present invention will be described below together with comparative examples.
[Example 1]
First, in order to obtain a composite sheet for a fuel cell separator, as shown in Table 1, 15 parts by mass of polypropylene fiber as a fiber resin, 72 parts by mass of expanded graphite particles as a conductive material, 10 parts by mass of carbon fiber, and aramid A slurry was prepared by mixing and dispersing 3 parts by mass of fibers in water.

As the polypropylene fiber, a short fiber obtained by cutting an acid-modified polypropylene fiber [manufactured by Daiwabo Polytech Co., Ltd .: product name PZ-AD] into a length of 3 mm was used. Further, BSP-60A [manufactured by Fuji Graphite Industry Co., Ltd .: product name] having an average particle diameter of 60 μm was used as the expanded graphite particles of the conductive material. As the carbon fiber, a cut fiber T008-003 (fiber diameter φ7 μm, cut length 3 mm) of carbon fiber trading card [manufactured by Toray Industries, Inc .: registered trademark] was used. Further, as the aramid fiber, a 3 mm long Kevlar cut fiber [manufactured by Toray DuPont: Kevlar (registered trademark)] was used.

Once the slurry was made, a flocculant was added to the slurry. As this aggregating agent, an additive composed of 0.001 part by mass of cationic polyacrylic acid soda and 0.00001 part by mass of anionic polysodium soda was used. When the flocculant is added to the slurry, a mixture of the slurry and the flocculant is formed into a paper sheet by a 25 cm square sheet machine having a mesh structure, and the paper sheet is set in a press machine heated to 110 ° C. Heating and pressing at a pressure of about 200 kg / cm ² for about 5 minutes, drying the papermaking sheet to remove moisture, and having a thickness of 1.7 mm in which expanded graphite particles and carbon fibers are uniformly dispersed and entangled in polypropylene fibers A composite sheet was formed.

Next, a female suction jig having the same outer dimensions as the fuel cell separator is prepared, a composite sheet cut on the inner bottom surface of the suction jig is set, and the expanded graphite of the conductive material is formed on the exposed surface. 10 parts by mass of the particles were filled, and the space between the inside of the suction jig and the surface of the composite sheet was completely filled with expanded graphite particles. As the expanded graphite particles, the above BSP-60A [manufactured by Fuji Graphite Industry Co., Ltd .: product name] was selected.

Once the expanded graphite particles are packed on the surface of the composite sheet, excess expansion on the suction jig can be achieved by bringing the scraper into contact with the expanded graphite particles on the suction jig and moving the scraper horizontally. The graphitized graphite particles were removed and leveled, and the upper surface of the opening of the suction jig and the surface of the expanded graphite particles were aligned and aligned.

Next, the top of the suction jig is closed and turned upside down, and the bottom of the upside down suction jig is connected to a vacuum pump for suction and pressure reduction, and the expanded graphite particles are compressed to form a conductive molded body. Then, the conductive molded body molded from the suction jig was removed.
Next, a dedicated mold for molding the fuel cell separator is prepared, a release agent is uniformly applied to the cavity surface of the mold, and a conductive molded body is inserted into the lower mold of the mold and the mold is opened. Another composite sheet was laminated on the exposed surface, and the upper mold of the mold was brought into contact with this composite sheet. As a mold release agent, Die Free GA7500 [manufactured by Daikin Industries, Ltd .: product name] was selected. The mold was previously heated to 200 ° C.

Once the upper die of the mold is brought into contact with the composite sheet, the die is strongly clamped at 60 MPa and heated under pressure, and immediately transferred to a compression molding machine for cooling with the temperature of the upper and lower hot plates being 30 ° C., The separator for fuel cells was compression molded by pressurizing and cooling until the temperature of the mold reached about 80 ° C. After the fuel cell separator was compression molded, the mold was opened and the fuel cell separator was removed to obtain a fuel cell separator having a size of 25 cm × 25 cm and a thickness of 0.6 mm.

When the fuel cell separator was manufactured, a hot water immersion test at 80 ° C. was performed. In this hot water immersion test at 80 ° C., the tensile strength, the volume resistance value in the surface direction, the resistance value in the thickness direction, and the thickness of the fuel cell separator before and after the test are measured, and whether or not the fuel cell separator is cracked. The results are summarized in Table 2.

The initial tensile strength of the fuel cell separator before the hot water immersion test is based on JIS K6251. Three manufactured fuel cell separators are punched into No. 1 dumbbell test pieces, and RTC-1310A [manufactured by Orientec Co., Ltd .: product Name] was used, a tensile test was carried out under the condition of a tensile speed of 10 mm / min, and the average value of the measured values was defined as the initial tensile strength.

On the other hand, the tensile strength after the hot water immersion test of the fuel cell separator is based on JIS K6251 and the manufactured fuel cell separator is punched into No. 1 dumbbell test pieces, and the total mass of these three test pieces is Prepare pure water equivalent to 4 times the volume of the sample, put the test piece and pure water into a pressure-resistant container [Product name: TAF-SR300, manufactured by Pressure-resistant Glass Industry Co., Ltd.], and seal it at 80 ° C. Set. After setting in a constant temperature bath at 80 ° C. in this way, 100 hours after setting, RTC-1310A [manufactured by Orientec Co., Ltd .: product name] was used, and a tensile test was performed at a tensile speed of 10 mm / min. The average value of the measured values was taken as the tensile strength.

The volume resistance value in the plane direction before the hot water immersion test of the fuel cell separator was measured by punching out seven manufactured fuel cell separators into a No. 1 dumbbell test piece and measuring by a four-terminal four-probe method. Specifically, seven test pieces having a size of 5 cm × 5 cm were cut out from the manufactured fuel cell separator, and a low resistivity meter [Mitsubishi Chemical Corporation: The product name was measured by Loresta GP MCP-T610], and the average value of the measured values was defined as the volume resistance value in the surface direction.

On the other hand, as for the volume resistance value in the surface direction after the hot water immersion test of the fuel cell separator, the manufactured fuel cell separator was punched into No. 1 dumbbell test pieces, and the total of these seven test pieces was Prepare pure water equivalent to 4 times the mass, and put the test piece and pure water into a pressure-resistant container [product name: TAF-SR300 type manufactured by Pressure Glass Industry Co., Ltd.] and seal it, and keep it at 80 ° C. Set in the tank. After setting in a constant temperature bath at 80 ° C. in this way, 100 hours after setting, measurement was performed by the four-terminal four-probe method as described above.

Regarding the resistance value in the thickness direction of the fuel cell separator before the hot water immersion test, first, seven test pieces having a size of 5 cm × 2.5 cm were cut out from the manufactured fuel cell separator, and the test pieces were cut into glass tubes. Between them. The glass tube was a type in which a bent bottom portion of a φ10 mm glass U-shaped tube was cut and a holder with a screw hole was bonded to the cut bottom portion.

Once the test piece is sandwiched between the glass tubes, fix it with a screw so that mercury does not leak from between the test piece and both sides of the glass tube, inject a certain amount of mercury into both sides of the glass tube, and prepare with mercury The resistance value [manufactured by Hioki Electric Co., Ltd.] was connected with a lead wire, the resistance value was measured so as to be conductive, and the average value of the measured values was measured.

Regarding the resistance value in the thickness direction after the hot water immersion test of the fuel cell separator, 7 sheets of the manufactured fuel cell separator were punched into a No. 1 dumbbell test piece, and 4 times the total mass of these 7 test pieces. Pure water corresponding to the above was prepared, a test piece and pure water were put into a pressure vessel [product name: TAF-SR300 type manufactured by Pressure Glass Industry Co., Ltd.], sealed, and set in a constant temperature bath at 80 ° C. After setting in an 80 ° C. constant temperature bath in this way, 100 hours after setting, the resistance value in the thickness direction before the hot water immersion test was measured.

Regarding the thickness of the fuel cell separator before the hot water immersion test, seven test pieces having a size of 5 cm × 2.5 cm were cut out from the fuel cell separator, and the thickness of each test piece was measured before and after the hot water immersion test. Measured with a vessel [Mitutoyo Co., Ltd .: product name ID-CX] was used as the average value of the measured values.

On the other hand, regarding the thickness of the fuel cell separator after the hot water immersion test, seven of the manufactured fuel cell separators were punched into No. 1 dumbbell test pieces, and four times the total mass of the seven test pieces. Pure water corresponding to the above was prepared, a test piece and pure water were put into a pressure vessel [product name: TAF-SR300 type manufactured by Pressure Glass Industry Co., Ltd.], sealed, and set in a constant temperature bath at 80 ° C. When set in a constant temperature bath at 80 ° C. in this way, 100 hours after setting, the thickness was measured in the same manner as before the hot water immersion test.

Regarding cracking of the fuel cell separator, the fuel cell separator before the hot water immersion test and the fuel cell separator after the hot water immersion test are bent at both ends on the diagonal line, and the fuel cell is in contact until both ends come into contact with each other. It was visually evaluated whether or not cracking occurred in the separator.

[Example 2]
A slurry was prepared by mixing and dispersing 25 parts by mass of polypropylene resin as a fiber resin, 60 parts by mass of expanded graphite particles of a conductive material, 10 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber in water. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are summarized in Table 2.

Example 3
30 parts by mass of polypropylene resin as a fiber resin, 55 parts by mass of expanded graphite particles of a conductive material, 10 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber were mixed and dispersed in water to prepare a slurry. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are summarized in Table 2.

Example 4
30 parts by mass of polypropylene resin as a fiber resin, 60 parts by mass of expanded graphite particles of conductive material, and 10 parts by mass of carbon fiber were mixed and dispersed in water to prepare a slurry, and aramid fibers were omitted. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are summarized in Table 2.

Example 5
A slurry was prepared by mixing and dispersing 35 parts by mass of polypropylene resin as a fiber resin, 50 parts by mass of expanded graphite particles of conductive material, 10 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber in water. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are shown in Table 2.

Example 6
A slurry was prepared by mixing and dispersing 25 parts by mass of polypropylene resin as a fiber resin, 60 parts by mass of expanded graphite particles of a conductive material, 10 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber in water. The polypropylene fiber was a short fiber cut into a fiber having an average fiber length of 5 mm after fiberizing an unmodified polypropylene fiber [manufactured by Prime Polymer Co., Ltd .: product name J105H] having an average fiber diameter of 20 μm by a melt spinning method. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells.

Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are shown in Table 2.

Example 7
A slurry was prepared by mixing and dispersing 25 parts by mass of polypropylene resin as a fiber resin, 60 parts by mass of artificial graphite particles of conductive material, 10 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber in water. As the artificial graphite particles, JSG-75S [manufactured by Fuji Graphite Industry Co., Ltd .: product name] having an average particle size of 45 μm was used. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells.

Example 8
20 parts by mass of polypropylene fiber as a fiber resin, 70 parts by mass of artificial graphite particles of conductive material, 5 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber were mixed and dispersed in water to prepare a slurry. About the other part, it carried out similarly to Example 7, and manufactured the separator for fuel cells.

Example 9
20 parts by mass of polypropylene fiber as a fiber resin, 70 parts by mass of artificial graphite particles of conductive material, 5 parts by mass of carbon fiber, and 5 parts by mass of aramid fiber were mixed and dispersed in water to prepare a slurry. The polypropylene fiber was changed to a short fiber obtained by cutting acid-modified polypropylene fiber [manufactured by Daiwabo Polytech Co., Ltd .: product name PZ-AD] into a length of 3 mm. About the other part, it carried out similarly to Example 7, and manufactured the separator for fuel cells.

[Comparative Example 1]
As shown in Table 3, the polypropylene fiber as the fiber resin is changed to 8 parts by mass, the expanded graphite particles of the conductive material are changed to 80 parts by mass, the carbon fiber is 10 parts by mass, and the aramid fiber is changed to 2 parts by mass. About the part, it carried out similarly to Example 1, and manufactured the separator for fuel cells. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are shown in Table 4.

[Comparative Example 2]
8 parts by mass of polypropylene resin as a fiber resin, 80 parts by mass of expanded graphite particles as a conductive material, 10 parts by mass of carbon fiber, and 2 parts by mass of aramid fiber were used. As the polypropylene fiber, an unmodified polypropylene fiber [manufactured by Prime Polymer Co., Ltd .: product name J105H] having an average fiber diameter of 20 μm was fibrillated by a melt spinning method, and then a short fiber cut to an average fiber length of 5 mm was used. .

For other parts, a fuel cell separator was produced in the same manner as in Example 1. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are shown in Table 4.

[Comparative Example 3]
Polypropylene fiber, which is a fiber resin, was 8 parts by mass, conductive graphite particles of 80 parts by mass, carbon fiber 10 parts by mass, and aramid fiber 2 parts by mass. As the artificial graphite particles, JSG-75S (manufactured by Fuji Graphite Industry Co., Ltd .: product name) having an average particle diameter of 45 μm was used. About the other part, it carried out similarly to Example 1, and manufactured the separator for fuel cells. Once the fuel cell separator is manufactured, a hot water immersion test at 80 ° C. is performed, and the tensile strength, volume resistance value in the plane direction, resistance value in the thickness direction, and thickness of the fuel cell separator before and after the test are measured, The presence or absence of cracks in the fuel cell separator was examined, and the results are shown in Table 4.

The fuel cell separator of each example was confirmed to have excellent values for tensile strength, volume resistance in the surface direction, resistance in the thickness direction, and thickness before and after the 80 ° C. hot water immersion test. Moreover, although the separator for fuel cells of each Example was observed, it confirmed that there was no crack and the effect excellent about a softness | flexibility and intensity | strength was acquired.

On the other hand, the fuel cell separator of each comparative example has few polypropylene fibers and more conductive material than necessary, so the tensile strength before and after the 80 ° C. hot water immersion test, and the volume resistance value in the plane direction. The value of became low, and a satisfactory effect could not be obtained. Furthermore, although the fuel cell separator could be made thin, when it was bent at both ends on the diagonal, the fuel cell separator was cracked before both ends contacted, and there was doubt about practicality. occured.

The fuel cell separator and the manufacturing method thereof according to the present invention are used in the field of manufacturing fuel cells.

DESCRIPTION OF SYMBOLS 1 Fuel cell separator 3 Flow path 4 Fiber resin 5 Polypropylene fiber system 6 Aramid fiber 7 Conductive material 8 Particulate conductive material 8a Graphite particle 8b Expanded graphite particle 9 Fibrous conductive material 9a Carbon fiber 10 Composite sheet 11 Suction jig (reduced pressure) Ingredients)
13 Conductive molding 20 Mold 21 Lower mold 22 Upper mold

Claims

15 to 40 parts by mass of a fiber resin and 85 to 60 parts by mass of a conductive material having better conductivity than the fiber resin,
A fuel cell separator, wherein the fiber resin includes a polypropylene fiber system having an average fiber length of 1 to 80 mm and the conductive material includes at least one of a particulate conductive material and a fibrous conductive material.
The fuel cell separator according to claim 1, wherein the fiber resin comprises an aramid fiber.
The fuel cell separator according to claim 1 or 2, wherein the polypropylene fiber system of the fiber resin is polypropylene fiber.
4. The fuel cell separator according to claim 1, wherein the particulate conductive material of the conductive material is graphite particles having an average particle diameter of 3 to 500 μm, and the fibrous conductive material of the conductive material is carbon fiber.
The fuel cell separator according to claim 4, wherein the conductive conductive material is expanded graphite particles.
The fuel cell separator according to claim 4, wherein the conductive conductive material is artificial graphite particles.
A method for manufacturing a fuel cell separator according to any one of claims 1 to 6, wherein a composite sheet is formed by dispersing a part of a conductive material in a fiber resin, and the composite sheet is set in a decompression tool. The exposed portion is filled with the remainder of the conductive material, and the pressure reducing tool is closed and decompressed to form a conductive molded body. Thereafter, the composite sheet is laminated on the exposed portion of the formed conductive molded body and heated and compressed. A method for producing a fuel cell separator, comprising forming a fuel cell separator.