JP2003197215A - Separator for fuel cell and fuel cell using separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for fuel cells and a fuel cell using the separator for fuel cells which have excellent thickness accuracy by improving conditions, such as density balance of a rib part and a flat part, the forming conditions, and the like. <P>SOLUTION: It is a separator for fuel cells which has the variation of the thickness (difference of the maximum thickness and the minimum thickness in the one sheet) of 0.15 mm or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel cell separator and a fuel cell using the fuel cell separator.

[0002]

2. Description of the Related Art In recent years, fuel cells have received a great deal of attention from the viewpoints of measures to prevent global warming due to the expansion of fossil fuel consumption, energy saving measures, etc., and research and development are being actively conducted by national and university research institutes, major companies, etc. Some have been commercialized.

In particular, the polymer electrolyte fuel cell has an operating temperature of about 80 ° C., which is overwhelmingly lower than that of other fuel cells, and has attracted attention as a generator for automobiles and households. A polymer electrolyte fuel cell is roughly divided into an ion exchange membrane, a platinum catalyst, and a separator. Among them, the function of the separator is to supply hydrogen and oxygen that generate energy to the fuel electrode and the oxygen electrode in a stable manner and to quickly discharge the generated water and cooling water, which is an important member that affects the battery characteristics. .

Further, since several hundred separators are used for one battery (for automobile), downsizing is urgently required. Currently, separator manufacturing companies are improving rib design, thinning and dimensional accuracy, especially plate thickness accuracy. Is required to be improved.

As a method of manufacturing a separator, a molding method (molding) is generally known. When molding a separator consisting of ribs, flats and holes by the molding method, the melt viscosity of the resin used, the amount of conductive filler compounded, the particle size, the shape, etc. are optimized, and the ribs and flats are optimized. Optimum conditions such as density balance and molding conditions of
The current situation is that a separator with the same level of plate thickness accuracy as the machined product has not yet been developed.

A practical fuel cell has an ion exchange membrane, electrodes,
It takes the form of a stack in which hundreds of basic elements called a single cell composed of a platinum catalyst and a separator are laminated. Of these, separators are hundreds of stacked layers, so plate thickness accuracy, especially in-plane plate thickness variation, is a very important characteristic.When using a separator with poor plate thickness accuracy to form a stack, There is a possibility that leakage, cracks during stack assembly, etc. may occur, and the power generation efficiency is significantly reduced.

[0007]

SUMMARY OF THE INVENTION The present invention provides a fuel cell separator and a fuel cell using the same, which has improved plate thickness accuracy by improving conditions such as density balance of ribs and flat parts and molding conditions. To do.

[0008]

The present invention relates to the following. 1. A fuel cell separator having a variation in plate thickness (difference between the maximum thickness and the minimum thickness in one sheet) of 0.15 mm or less. 2. Item 2. The fuel cell separator according to Item 1, wherein the separator has a rib portion and a flat portion. 3. Item 3. The fuel cell separator according to Item 1 or 2, wherein the separator is a molded body containing graphite and a resin. 4. Item 4. The fuel cell separator according to Item 3, wherein the graphite is expanded graphite. 5. Item 5. The fuel cell separator according to Item 4, wherein the expanded graphite is a crushed powder of expanded graphite sheet. 6. Expanded graphite sheet crushed powder has an average particle size of 25 μm to 5 μm.
Item 6. The fuel cell separator according to Item 5, which has a size of 00 μm.

7. 7. The fuel cell separator according to any one of Items 3 to 6, wherein the resin is in the form of powder, is subjected to ring-opening polymerization, and has an average particle size of 1 μm to 100 μm. 8. Item 8. The fuel cell separator according to any one of Items 1 to 7, wherein the separator is obtained by stacking a reinforcing sheet on a flat portion of a molded body and integrating the same. 9. Item 9. The fuel cell separator according to Item 8, wherein the reinforcing sheet is a prepreg. 10. Item 1 whose bulk density is 1.35 g / cm ³ or more
9. The fuel cell separator according to item 9. 11. Item 10. The fuel cell separator according to any one of Items 3 to 10, wherein the molded body is molded by a compression molding method. 12. Item 12. The fuel cell separator according to any one of Items 1 to 11, wherein the separator has a hole portion other than the rib portion and the flat portion. 13. A fuel cell comprising a plurality of fuel cell separators and having an average plate thickness variation (difference between the maximum thickness and the minimum thickness in one sheet) of 0.15 mm or less. 14. The variation in the plate thickness (difference between the maximum thickness and the minimum thickness in one sheet) of all fuel cell separators is 0.15 mm.
14. The fuel cell according to item 13, which is as follows. 15. Item 15. The fuel cell according to Item 13 or 14, which includes the fuel cell separator according to any one of Items 1 to 12. 16. Item 16. The fuel cell according to any one of items 13 to 15, which is a solid polymer type.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The molded product (fuel cell separator) obtained by the present invention has a variation in plate thickness even though it has a rib portion and a flat portion (the maximum thickness and the minimum thickness in one molded product are different). The difference) is 0.15 mm or less, preferably 0.10 mm or less, more preferably 0.05 mm or less, and it is most preferable that there is no difference. The plate thickness referred to in the present invention refers to the thickness of the molded body, specifically, the thickness from the bottom (bottom surface) 7 of the molded body shown in FIGS. 2 and 4 to the apex of the flat portion 3 or the rib portion 1, The variation refers to the difference between the maximum thickness and the minimum thickness in one molded body.

When the difference between the maximum thickness and the minimum thickness in one separator exceeds 0.15 mm, the adhesion between the separator and the packing becomes poor at the time of stacking the stacks, the gas sealability cannot be obtained, and the stack is fastened. Occasionally, high stress is applied locally, and the separator may be damaged. Further, even when the problem of stack assemblability is small, when the difference between the maximum thickness and the minimum thickness in one separator exceeds 0.15 mm, between the electrode and the separator or between the electrode and the ion exchange membrane, A portion where the force for tightening the stack is hard to be applied is generated, the actual area contributing to power generation is reduced, and the contact resistance is increased, which significantly reduces the power generation efficiency. The separator itself usually has a thickness of 0.3 mm to 5 mm.

In the present invention, the difference between the maximum thickness and the minimum thickness of the molded body (fuel cell separator) is 0.15 m.
In order to make m or less, the density of the rib portion and the flat portion (including the hole portion) at the time of molding may be made substantially equal, and in order to do so, for example, the reinforcing sheet is formed on the portion constituting the flat portion of the molded body. And the spacers, such as SUS and steel plates, of the same area as the ribs are made of gold so that a higher pressure than the flat part is applied only to the part where the ribs are formed during molding, if necessary. This can be achieved by interposing it on at least one of the upper and lower surfaces (the surface in contact with the hot press plate) of the portion of the mold where the rib portion is formed. The thickness of the spacer is preferably in the range of 0.05 mm to 1 mm. By forming by the method described above, not only the plate thickness accuracy is excellent, but also the hot water resistance, electrical characteristics, moldability, gas impermeability, etc. are excellent.

In the fuel cell separator of the present invention, the rib portion is electrically conductive or conductive, and forms a gas flow path when the separators are stacked with the ion exchange membrane and the electrodes interposed therebetween. Further, the flat portion forms a gripping portion of the separator and is configured so that gas does not leak when the gas passes through the flow path. On the other hand, the rib portion is configured so that gas does not leak when the gas passes through the flow path formed when the separators are stacked. The flat portion preferably serves as a gripping portion for fixing the whole when the separators are stacked.

Further, the fuel cell separator according to the present invention may have holes other than the rib and the flat portion, and it is particularly preferable that the flat portion has the holes. The hole portion is configured to form a long hole in the stacking direction when a large number of separators are stacked, and a hole for passing hydrogen gas, oxygen gas, and cooling water is formed. Each hole is configured to be connected to the hydrogen gas flow passage, the oxygen gas flow passage, and the cooling water flow passage formed by the rib portion of the separator. In addition, in the flat part,
It may have a hole for passing a fixing bolt when the separators are stacked.

The molded body having the rib portion and the flat portion is obtained by molding a material containing graphite and a resin into a separator shape, and in particular, one having a structure in which graphite is dispersed in the resin,
It is preferable because it is excellent in electrical properties, moldability, gas impermeability, and inexpensive. There is no particular limitation on the graphite, and natural graphite, artificial graphite or the like is preferably used if cost is important. There is no limitation on the particle size of the graphite used, and it is preferable to mix and use graphite having different particle sizes in consideration of required characteristics and moldability. Further, when weight reduction, mechanical strength (toughness), and plate thickness accuracy are important, it is preferable to use expanded graphite, and it is particularly preferable to use expanded graphite sheet pulverized powder.

It is preferable that the rib portion and the flat portion each have a layer containing expanded graphite and a resin, and these layers are continuous. Thereby, the moldability at the time of molding for obtaining the separator is good, the lightweight property is given to the separator, and the preferable properties such as high toughness and low elasticity are given to the separator.

Expanded graphite preferably used in the present invention includes a step of immersing raw graphite in a solution containing an acidic substance and an oxidizing agent to form a graphite intercalation compound, and heating the graphite intercalation compound to produce graphite. It can be manufactured by a step of expanding the crystal in the C-axis direction to obtain expanded graphite.
As a result, the expanded graphite becomes a bug-like shape and has a entangled complex shape with no directivity.

The expansive graphite preferably has a high magnification for securing the strength and sealing property of the separator, and is not particularly limited, but is preferably 150 times or more, and 150 times to 3 times.
It is more preferably 00 times. The expanded graphite can be made into expanded graphite powder by crushing this expanded graphite, but it is preferable to compress the obtained expanded graphite by pressure to obtain a expanded graphite sheet before crushing. Further, the obtained expanded graphite powder is subjected to a treatment (high temperature treatment or the like) for reducing acidic roots contained in the pulverized powder, if necessary.

The above-mentioned raw material graphite is not particularly limited, but a highly crystallized graphite such as natural graphite, quiche graphite, and pyrolytic graphite is preferable. Natural graphite is preferable in consideration of the balance between the obtained properties and economy. The natural graphite used is not particularly limited,
Commercially available products such as F48C (trade name, manufactured by Nippon Graphite Co., Ltd.) and H-50 (trade name, manufactured by Chuetsu Graphite Co., Ltd.) can be used. These are preferably used in the form of scale-like powder.

The acidic substance used for treating the raw graphite is
Generally, a material that can penetrate between layers of graphite such as sulfuric acid to generate an acidic root (anion) having a sufficient expansion ability is used. The amount of the acidic substance used is not particularly limited and is determined by the desired expansion ratio, and for example, it is preferable to use 100 to 1000 parts by weight with respect to 100 parts by weight of graphite.

As the oxidizing agent used together with the acidic substance, peroxides such as hydrogen peroxide, potassium perchlorate, potassium permanganate and potassium dichromate, and acids having an oxidizing action such as nitric acid are used. Hydrogen peroxide is particularly preferable from the viewpoint that it is possible to obtain good expanded graphite easily. When hydrogen peroxide is used as the oxidizing agent, it is preferably used as an aqueous solution. At this time, the concentration of hydrogen peroxide is not particularly limited, but is preferably 20% by weight to 40% by weight. The amount used is also not particularly limited, but it is preferable to add 5 parts by weight to 60 parts by weight as hydrogen peroxide solution to 100 parts by weight of graphite.

The acidic substance and the oxidizing agent are preferably used in the form of an aqueous solution. Sulfuric acid as an acidic substance is used at an appropriate concentration, but a concentration of 95% by weight or more is preferable, and concentrated sulfuric acid is particularly preferable.

In the above, the method for producing the expanded graphite sheet is not particularly limited, but it is generally preferable that the expanded graphite obtained above is formed into a sheet by applying pressure with a press, a roll or the like. There is no particular limitation on the thickness and bulk density of the expanded graphite formed into a sheet, but the thickness is in the range of 0.5 mm to 1.5 mm and the bulk density is 0.2 g /
It is preferably in the range of cm ^{3 to} 1.7 g / cm ³ . If the thickness is less than 0.5 mm, the obtained molded product tends to be brittle, and if it exceeds 1.5 mm, the moldability tends to deteriorate. If the bulk density is less than 0.2 g / cm ³ , the electric resistance tends to deteriorate, and if it exceeds 1.7 g / cm ³ , the expanded graphite is liable to cause cohesive failure during sheet production, Mechanical strength tends to decrease. The size of the density can be adjusted by adjusting the amount of pressurization, the roll gap, and the like. The expanded graphite sheet is preferably crushed by coarse crushing and fine crushing, and then classified as necessary.

In the present invention, the bulk density of the expanded graphite as a raw material is not particularly limited, but it is 0.1 g / cm ³
The range of up to 0.4 g / cm ³ is preferred. If the density of the expanded graphite is too low, the homogeneity of mixing with the resin will decrease, and the gas impermeability of the resulting molded article (fuel cell separator) will tend to decrease. The effect of improving the mechanical strength and conductivity of the molded body (fuel cell separator) is likely to decrease.

The average particle size of the crushed powder of the expanded graphite sheet is not particularly limited, but considering the mixing property with the resin and the moldability, the number average particle size is preferably in the range of 25 μm to 500 μm, and in the range of 50 μm to 400 μm. Is more preferable. If the particle size is less than 25 μm, the effect of entanglement of the expanded graphite powder is reduced, and the strength of the separator tends to decrease easily. On the other hand, if the particle size exceeds 500 μm, the expanded graphite flows to the narrow rib. As a result, it tends to be difficult to form a separator having a thin flat plate and high rib height.

In the present invention, the properties of the resin used are not particularly limited, but safety and shortening of the manufacturing process (low cost)
In consideration of the above, it is preferable to use a thermosetting resin, a high heat resistant resin or a thermoplastic resin which is capable of dry mixing (solventless mixing) and has a stable particle size distribution. The resin is preferably used in the form of powder or particles.

There is no limitation on the chemical structure and type of the resin used, and examples thereof include epoxy resin (which is used in combination with a curing agent), melamine resin, curable acrylic resin, resol type and novolac type powdered phenol resin. The thermosetting resin, the powdery polyamide resin, the powdery polyamideimide resin, the phenoxy resin, the acrylic resin or the like having a high heat resistance or a thermoplastic resin is used. If necessary, a curing agent, a curing accelerator, etc. may be used in combination with the thermosetting resin. The use form of the curing agent and the curing accelerator is preferably powdery or granular. Among these resins, it is preferable to use a phenol resin, which is a thermosetting resin, because it is excellent in economical efficiency, workability, and property balance after curing.

Phenolic resin has powder characteristics such as a uniform particle size, less blocking (aggregation of powder), less gas generated during the reaction, easier molding, and heat treatment completed in a short time. Phenolic resins having the characteristics are preferable, and among them, it is preferable to use a phenol resin containing a dihydrobenzoxazine ring which is polymerized by ring-opening polymerization [having a chemical structural unit represented by the general formulas (A) and (B)].

[0029]

[Chemical 1] (In the formula, hydrogen bonded to the aromatic ring is substituted with an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group, a phenyl group, or an alkyl group having 1 to 3 carbon atoms or an alkoxyl group, except for one of the ortho positions of the hydroxyl group. Optionally substituted with a hydrocarbon group such as a phenyl group).

[0030]

[Chemical 2] (In the formula, R ¹ is a hydrocarbon group such as an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group, a phenyl group, or a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms or an alkoxyl group; Hydrogen attached to may be substituted with similar hydrocarbon groups).

When a powdery phenolic resin is used as the resin, its particle size distribution is not particularly limited, but it is possible to mix it uniformly with the crushed powder of expanded graphite sheet in a short time by a dry method, and the resin flow during molding. In consideration of the above, the number average particle size is preferably in the range of 1 μm to 100 μm, and 5 μm to 50 μm.
The range of μm is more preferable.

The mixing ratio of the expanded graphite and the resin used in the present invention is determined by taking into consideration the values of various characteristics of the fuel cell separator which is the final molded product to be targeted. / Resin = 95/5 to 30/70 (weight ratio)
Is preferable, and 90/10 to 50/50 (weight ratio)
Is more preferable, and the range of 85/15 to 60/40 (weight ratio) is further preferable. Here, when the mixing ratio of the expanded graphite and the resin exceeds 95/5, the mechanical strength tends to decrease sharply, while when it is less than 30/70, the amount of the expanded graphite as a conductive substance added is small. , Electrical characteristics tend to deteriorate.

There is no particular limitation on the method of mixing the expanded graphite and the resin, and a dry mixing method using a shaker, a V blender or the like that does not apply a large shearing force to the expanded graphite at the time of mixing in order to prevent the expanded graphite from being pulverized. It is preferable. When the expanded graphite is pulverized during mixing, the mechanical strength of the obtained fuel cell separator tends to be sharply reduced.

The above-mentioned mixed powder can be directly used as a molding material powder, but in the present invention, in order to further improve the mixing property and the workability at the time of molding, the mixed powder is pressure-molded to form a sheet. What was made (hereinafter, "molding sheet")
Is used).

There are no particular restrictions on the method of manufacturing the forming sheet, but for example, a mixture charging tank, a gate adjusting machine for adjusting the material to a constant thickness, a slitter for finishing to a constant width, a transfer device for transferring the processing material, and sheet formation. A forming sheet manufacturing apparatus or the like configured from a rolling roll or the like can be used. When the flat portion has a hole, it is preferable that the sheet is formed with the hole.

In order to improve the strength of the molding sheet, the curing reaction of the resin contained in the molding sheet is partially promoted, or the molding sheet is partially (not completely) heat-melted before the production of the separator. Can be offered. There is no limitation on the curing reaction or the method of heat-melting, for example, a method of heating the obtained forming sheet, more specifically, the above-mentioned rolling roll shall be equipped with a heating device and passed through this rolling roll. There are a method of occasionally heating and a method of passing the obtained molding sheet through a heating oven.

The type of the reinforcing sheet to be laminated and integrated on the flat part of the molded body (fuel cell separator) includes the amount of resin contained in the molded body containing expanded graphite and resin, the type of resin (molecular weight, melting point, reaction). Although it is arbitrarily determined depending on the time, etc., it is preferable to use, for example, a prepreg obtained by impregnating a glass cloth (glass woven cloth or glass non-woven cloth) with a resin and drying it (curing degree of the resin is in B stage state). .

As the resin of the prepreg, for example, an epoxy resin is preferable in terms of plate thickness accuracy, cost, workability, characteristics of the obtained separator and the like. Regarding the molecular weight and melting point of the above-mentioned epoxy resin, it is preferable to use the same resin as the resin contained in the molding sheet in terms of plate thickness accuracy, appearance of the separator obtained by molding, characteristics, and the like.

The above-mentioned epoxy resin is preferably an epoxy resin having two or more epoxy groups which are crosslinking points in terms of heat resistance, mechanical strength and the like. Furthermore, the curing time of the epoxy resin is preferably shorter than that of the resin contained in the molding sheet. When the curing time of the epoxy resin is longer than that of the resin contained in the molding sheet, it tends to flow into the ribs formed by the molding sheet during molding and harden, resulting in poor plate thickness accuracy and a defective product. is there.

The above epoxy resin is also used in combination with a curing agent, a curing accelerator, etc., if necessary. The types of the above epoxy resins, curing agents, types of curing accelerators, etc. and their blending amounts are determined with reference to the molecular weight, melting point, flowability, curing time, etc. of the resin used in the mixture constituting the molded body. It Considering the above-mentioned properties, features, cost, storability, etc., the epoxy resin is preferably a bisphenol A / epichlorohydrin type epoxy resin,
Epoxy resins having a number average molecular weight of 900 or more are particularly preferable.

A dicyandiamide, which is latent in consideration of storability, is preferably used as the curing agent used in combination with the above epoxy resin, and benzyldimethylamine (BDMA) is used as the curing accelerator. The mixing ratio is preferably in the range of epoxy resin / dicyandiamide / benzyldimethylamine (BDMA) = 100/2 to 8 / 0.1 to 0.4 (weight ratio).

The glass composition of the above glass cloth is not particularly limited, but C glass or E glass can be used. The fiber diameter of glass is also not particularly limited, but 0.03 mm to 0.45 m in consideration of plate thickness accuracy, mechanical strength, etc.
The range of m is preferable, and the range of 0.06 mm to 0.35 mm is more preferable. It is preferable that the glass cloth (glass woven cloth or glass non-woven cloth) or the glass fiber of the raw material thereof is subjected to a silane-based surface treatment in order to secure the adhesiveness (sealing property) with the resin.

In the above prepreg, the resin is impregnated by, for example, glass cloth (glass woven cloth or glass non-woven cloth).
Can be performed by applying a resin varnish in which an epoxy resin, a curing agent, a curing accelerator and the like are uniformly dissolved in an organic solvent. The amount of resin (solid content) applied to the glass cloth is preferably 30 parts by weight to 60 parts by weight with respect to the glass cloth, and 3
More preferably 5 to 55 parts by weight. Resin amount is 30
If it is less than part by weight, the adhesive force with the flat part forming sheet at the time of molding tends to decrease, and if it exceeds 60 parts by weight, the resin component increases and the resin component flows out to the ribs and the like and the plate thickness accuracy decreases conversely. There is.

The amount of the prepreg, that is, the reinforcing sheet, to be replenished in the flat portion is calculated from the sheet density, the plate thickness of the molded product, and the rib design (rib thickness, height, etc.). It may be replenished to suit.

Obtained molded product (fuel cell separator)
There is no particular limitation on the density of, but for example, the bulk density of the flat part is preferably 1.35 g / cm ³ or more, and 1.35 g
The range of / cm ^{3 to} 1.75 g / cm ³ is more preferable.
The bulk density of the rib portion is preferably 1.35 g / cm ³ or more, more preferably in the range of ^{1.45g / cm 3 ~1.75g / cm 3} . It is preferable to have the above density because sufficient airtightness can be maintained and the plate thickness accuracy is excellent.

There is no particular limitation on the molding method for obtaining the above-mentioned molded product (fuel cell separator), but the cost of the molding machine, the plate thickness accuracy of the resulting molded product, the resin that can determine the electrical properties and mechanical properties The compression molding method is preferable in consideration of the optimum orientation of the expanded graphite powder therein.

The fuel cell has a structure in which the separator of the present invention is used to stack an electrolyte layer made of a solid polymer electrolyte membrane or the like and a required number of cells sandwiching the electrolyte layer. The separator in the present invention can be used as a separator for fuel cells of alkaline type, solid polymer type, phosphoric acid type, molten carbon salt type, solid acid type, etc., which are classified according to the type of electrolyte, and particularly solid polymer type fuel cells It is preferable to use

The fuel cell of the present invention comprises a plurality of fuel cell separators by stacking a required number of cells as described above, that is, by assembling a stack. As a separator for a fuel cell, variation in plate thickness (difference between maximum thickness and minimum thickness in one sheet) is 0.
The average value of the variation in the plate thickness of the fuel cell separator is 0.15 mm, although the thickness may exceed 15 mm.
The following is preferable. Thereby, the output of the battery can be secured. Also, ensure sufficient battery output,
In addition, in order to ensure sufficient stack assembleability, the variation in the plate thickness (difference between the maximum thickness and the minimum thickness in one sheet) of all the fuel cell separators included in the fuel cell is 0.1.
It is preferably 5 mm or less.

With the structure as shown above,
It is possible to obtain a fuel cell separator and a fuel cell which are excellent in plate thickness accuracy and have no problems in gas impermeability, electrical characteristics, mechanical strength and the like.

Embodiments of the present invention will be described below with reference to the drawings. 1 is a plan view showing an example of the shape of a fuel cell separator according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG. 3 is another embodiment of the present invention. And FIG. 4 showing an example of the shape of the fuel cell separator that becomes
3 is a cross-sectional view taken along line YY of FIG. 3, 1 is a rib portion having ribs (grooves) for securing gas and cooling water supply passages, 2 is a hole portion for supplying gas and cooling water, 3 Is a flat portion, 4 is a glass cloth prepreg for improving dimensional accuracy, 5 is a protrusion, and 6 is a groove.

[0051]

EXAMPLES The present invention will be described below with reference to examples. Example 1 (1) Production of mixed powder for molding Expanded graphite sheet having a plate thickness of 1.0 mm and a bulk density of 1.0 g / cm ³ (manufactured by Hitachi Chemical Co., Ltd., trade name Carbofit HGP-105) was used. Crush with a coarse crusher and a fine crusher,
Expanded graphite sheet pulverized powder with a number average particle size of 100 μm 0.7
I got kg. Next, there is little volatile gas at the time of molding, and a powdery phenolic resin having a number average particle diameter of 20 μm, which has the chemical structural units shown in the general formulas (A) and (B) (manufactured by Hitachi Chemical Co., Ltd., trade name HR1060). 0.3 kg was added and dry mixed with a small V blender to obtain 1.0 kg of mixed powder.

(2) Glass cloth prepreg manufacturing dimensions Glass cloth cut into 200 mm × 200 mm (manufactured by Nitto Boseki Co., Ltd., trade name WF230 100BS6,
Plain weave, weight per unit area 203 g / m ² , thickness 0.
25 mm, silane treatment) was prepared. On the other hand, powdered epoxy resin (Shell Chemical Co., Ltd., trade name Epicoat 10
04) 100 g, dicyandiamide (reagent) 3 g and benzyldimethylamine (reagent) 0.15 g were slowly added to 150 g of methyl oxitol (organic solvent) and mixed uniformly to obtain a resin composition.

Thereafter, a glass cloth impregnated with the resin composition so as to have a ratio of 40 parts by weight of the resin composition and 60 parts by weight of the glass cloth per one glass cloth was prepared, and the glass cloth was prepared at 160 ° C. Heat treatment was performed for 5 minutes to obtain a glass cloth prepreg having a thickness of 0.26 mm.

(3) Production of Fuel Cell Separator Next, a mold was used to obtain a fuel cell separator having the shape shown in FIGS. 1, 2, 3 and 4. Among them, the lower mold for obtaining the separator having the shape shown in FIGS. 1 and 2 [the part which becomes the B surface (rear surface) of FIG. 1 after molding] is a female mold whose molding surface (vertical, horizontal 200 mm) is flat, The upper mold [the part to be the A surface (surface) of FIG. 1 after molding] was used as a male mold having a protrusion. However, the upper mold has rib height of 0.5 after molding.
mm, rib pitch 4 mm, rib width 2 mm, and rib taper 10 degrees.

On the other hand, for obtaining a separator having the shape shown in FIGS. 3 and 4, a lower mold [a part which becomes B surface (rear surface) of FIG. 3 after molding] and an upper mold [A surface (front surface) of FIG. 3 after molding] Both molds were made into male molds having protrusions. Of these, the lower mold has a rib height of 0.5 mm and a rib pitch of 8 after molding.
mm, the rib width is 4 mm, and the rib taper is 10 degrees. The upper mold had the same shape as the upper mold for obtaining the separator having the shape shown in FIGS. 1 and 2.

The mixed powder obtained in (1) was molded using a sheet molding machine having a rolling roll, the weight per unit area was 0.19 g / cm ² , and the dimensions were 200 mm × 200 mm.
A molding sheet having a thickness of 5 mm was obtained.

Thereafter, the lower mold for obtaining the separator having the shape shown in FIGS. 1 and 2 is heated to 180 ° C., one molding sheet obtained above is placed on the lower mold, and One piece of the glass cloth prepreg 4 obtained in (2) was cut out in the central portion thereof to form a molding sheet, and the glass sheet was placed thereon. After that, the part having the protrusion of the upper mold is set downward on the upper part of the mold, and the plate thickness of the obtained molded product is 1.5 mm.
Under such conditions, that is, 180 ° C, surface pressure 19.6 MPa
(2 × 10 ⁶ kg / m ² ) was molded for 10 minutes, and then the holes 2 were punched in 6 places of the flat portion 3 with a simple punching machine to form a fuel cell separator having the shape shown in FIGS. 1 and 2. 100 sheets of (a) were obtained. In addition, in FIG. 1 and FIG.
Reference numeral 5 is a protrusion, 6 is a groove, and 7 is a bottom (bottom surface).

On the other hand, the fuel cell having the shape shown in FIGS. 3 and 4.
100 sheets of separator (a) for molded products have a thickness of 1.6 m
m, that is, obtained through the same steps as above.
It was Also, the ribs of the obtained fuel cell separator (a)
Part bulk density is 1.52 g / cm^ThreeAnd the bulk density of the flat part is
1.52 g / cm^Three, The fuel cell separator (a)
The bulk density of the bump is 1.61 g / cm^ThreeAnd bulk density of flat part
Is 1.41 g / cm ^ThreeMet.

Example 2 Using the same mold as in Example 1, a spacer having the same dimension as the outermost length and width of the rib portion and having a thickness of 0.05 mm was placed at the center of the upper die. After being inserted between the upper die and the hot press plate, the molded body was subjected to the following conditions such that the plate thickness was the same as in Example 1, that is, the same steps as in Example 1 were followed, and the fuel cell separator (A ) And a fuel cell separator (a)
100 sheets of each were obtained. The bulk densities of the obtained fuel cell separator (a) and fuel cell separator (a) were the same values as in Example 1, respectively.

Example 3 Using the same mold as in Example 1, a spacer having the same area as the rib and having a thickness of 0.05 mm was pressed with the upper mold so as to be positioned in the center of the upper mold and the lower mold. Inserted between the hot plate and between the lower mold and the press hot plate respectively, and under the following conditions, the plate thickness of the molded body is the same as that of Example 1, that is, the same process as in Example 1. Thus, 100 sheets of the fuel cell separator (A) and 100 sheets of the fuel cell separator (A) were obtained. The bulk densities of the obtained fuel cell separator (a) and fuel cell separator (a) were the same values as in Example 1, respectively.

Comparative Example 1 Through the same steps as in Example 1, the weight per unit area was 0.26 g / cm ² , and the dimensions were 200 mm × 200 mm.
A molding sheet having a thickness of 7 mm was obtained. Then, except that the glass cloth prepreg is not placed on the upper surface of the molding sheet, the plate thickness of the molded body is 1.8 mm (which becomes the fuel cell separator (a)) and 2.0 mm (fuel cell separator). (A)), that is, the fuel cell separator (A) and the fuel cell separator (A) are each subjected to 100 steps through the same steps as in Example 3.
Got one by one. The bulk density of the rib portion of the obtained fuel cell separator (a) was 1.67 g / cm ^3, and the bulk density of the flat portion was 1.44 g / cm ³ . Further, the bulk density of the rib portion of the fuel cell separator (a) was 1.64 g / cm ³ and the bulk density of the flat portion was 1.30 g / cm ³ .

COMPARATIVE EXAMPLE 2 Except that the glass cloth prepreg was not placed on the upper surface of the molding sheet, the conditions were such that the plate thickness of the molded body was the same as in Comparative Example 1, that is, the same process as in Example 1. Through the fuel cell separator (a) and the fuel cell separator (a)
Of 100 sheets were obtained. The bulk densities of the obtained fuel cell separator (a) and fuel cell separator (a) were the same values as in Example 1, respectively.

Next, with respect to the total number of the fuel cell separators (a) and the fuel cell separators (a) obtained in the respective Examples and Comparative Examples, as shown in FIG. 1 and FIG.
For each 16 points in total (4 points in the figure) (marked with ● in the figure), measure the plate thickness from the bottom (bottom surface) to the tops of the flat part 3 and the rib part 1 using a micrometer, and measure one separator surface. The variation of the plate thickness (difference between the maximum thickness and the minimum thickness) was calculated. Table 1 shows the average value, the maximum value, and the minimum value of the variations of these 200 separators.

Further, a fuel cell was assembled by using the fuel cell separator (a) and the fuel cell separator (a) obtained in the respective examples and comparative examples, and the cell characteristics were confirmed. First, a carbon powder carrying a platinum catalyst and a perfluorosulfonic acid powder were dispersed in ethanol to prepare a paste, which was uniformly applied to carbon paper to form an electrode catalyst layer. Two pieces of carbon paper coated with this paste are cut into 150 mm square pieces, and a 50 μm-thick perfluorosulfonic acid film (DuPont, trade name Nafion) is sandwiched so that the paste surface faces inside,
A membrane electrode assembly (MEK) was manufactured by pressure bonding while heating.

Next, the fuel cell separators (a) having the shapes shown in FIGS. 1 and 2 and the fuel cell separators (b) having the shapes shown in FIGS. 3 and 4 obtained in the respective examples and comparative examples.
100 sheets each, and the MEK is sandwiched between the A surface (front surface) of the fuel cell separator (a) shown in FIG. 1 and the A surface (front surface) of the fuel cell separator (a) shown in FIG.
The periphery of the rib portion 1 and the hole portion 2 of both separators were sealed with a liquid packing (silicone rubber), and 100 sets of single cells were produced.

Then, 100 sets of the obtained single cells are adjacent to the B side (rear surface) of the fuel cell separator (a) shown in FIG. 1 which is the outer side, and the fuel cell separator (a) shown in FIG. Rib portion 1 and hole portion 2 on the B side (back surface) of
Laminate while sealing the periphery with liquid packing (silicone rubber), and sandwich the top and bottom of the laminate with rigid plates.
The stack was fixed by applying a surface pressure of 00 KPa to obtain a stack for checking battery characteristics.

Hydrogen gas was passed through the hole (manifold) part 2 in the stack for battery characteristic confirmation obtained in this way,
Supply air and cooling water, keep at 80 ℃, 0.4mA
The operation was performed at a current density of / cm ² for 100 hours, and the output voltage of each single cell was measured. Table 1 shows the maximum voltage and the minimum voltage in 100 cells after 100 hours have passed. The voltage of 40 hours was measured for the stack of Comparative Example 1 in which leakage of hydrogen gas occurred within 100 hours of operation, and the voltage was not measured for Comparative Example 2 in which cracking occurred during stack assembly. It was

[0068]

[Table 1]

As shown in Table 1, the separators of Examples 1 to 3 according to the present invention have less variation in plate thickness than the separators of Comparative Example 1 and Comparative Example 2 and have good plate thickness accuracy and stack assemblability. It is clear that the battery stack can be supplied with a high output even after 100 hours of operation, and that there is no problem with the soundness of the battery stack. Comparative Example 1
In the variation of the plate thickness of the separator obtained in step 1, the minimum value and the average value are 0.15 mm or less, but the maximum value is 0.15 mm.
It was 6 mm. As described above, when even one sheet contained more than 0.15 mm, the stack assemblability was poor, and a high output could not be obtained after 100 hours of operation.

[0070]

The fuel cell separator of the present invention is a fuel cell separator having excellent plate thickness accuracy. Further, the fuel cell of the present invention is a high-performance fuel cell having a fuel cell separator with excellent plate thickness accuracy.

[Brief description of drawings]

FIG. 1 shows an example of the shape of a fuel cell separator according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 shows an example of the shape of a fuel cell separator according to another embodiment of the present invention.

FIG. 4 is a sectional view taken along line YY of FIG.

[Explanation of symbols]

1 rib part 2 holes 3 Flat part 4 glass cloth prepreg 5 protrusions 6 groove 7 Bottom (bottom)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 8/10 H01M 8/10 (72) Inventor Jun Fujita 3-3-1, Ayukawa-cho, Hitachi-shi, Ibaraki Hitachi Chemical Co., Ltd. Yamazaki Plant F-term (reference) 4F071 AA01 AA41 AB03 AD02 AD06 AH15 BB03 BC02 BC07 BC12 4J002 AA021 CC181 CD001 CH081 CL001 CM041 DA036 FD016 GD00 GQ00 5H026 AA06 BB02 CC03 CX04 H05 H03 H18H03

Claims (16)

[Claims] 1. A fuel cell separator having a variation in plate thickness (difference between maximum thickness and minimum thickness in one sheet) of 0.15 mm or less. 2. The fuel cell separator according to claim 1, wherein the separator has a rib portion and a flat portion. 3. The fuel cell separator according to claim 1, wherein the separator is a molded body containing graphite and a resin. 4. The fuel cell separator according to claim 3, wherein the graphite is expanded graphite. 5. The fuel cell separator according to claim 4, wherein the expanded graphite is a crushed powder of expanded graphite sheet. 6. The crushed powder of expanded graphite sheet has an average particle size of 25.
The fuel cell separator according to claim 5, which has a thickness of from μm to 500 μm. 7. The fuel cell separator according to claim 3, wherein the resin is in the form of powder, is subjected to ring-opening polymerization, and has an average particle size of 1 μm to 100 μm. 8. The fuel cell separator according to claim 1, wherein the separator is formed by superposing a reinforcing sheet on a flat portion of the molded body and integrating the reinforcing sheet. 9. The fuel cell separator according to claim 8, wherein the reinforcing sheet is a prepreg. 10. The fuel cell separator according to claim 1, which has a bulk density of 1.35 g / cm ³ or more. 11. The fuel cell separator according to claim 3, wherein the molded body is molded by a compression molding method. 12. The fuel cell separator according to claim 1, wherein the separator has a hole portion other than the rib portion and the flat portion. 13. A fuel cell comprising a plurality of separators for a fuel cell, wherein the average value of the variation in the plate thickness (difference between the maximum thickness and the minimum thickness in one sheet) is 0.15 mm or less. 14. Any of the fuel cell separators has a plate thickness variation (difference between the maximum thickness and the minimum thickness in one sheet) of 0.
The fuel cell according to claim 13, which has a diameter of 15 mm or less. 15. A fuel cell according to claim 13 or 14, which comprises the fuel cell separator according to any one of claims 1 to 12. 16. A solid polymer type product according to claims 13 to 15.
The fuel cell according to any one of 1.