JP2016081717A - Coating composition, separator with coating layer, and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating composition to be used for a separator with a coating layer for a fuel cell, the composition excellent in dispersibility of a carbon material and acid resistance, the separator with a coating layer having long-term durability by using the above coating composition, and the fuel cell excellent in cell characteristics.SOLUTION: The coating composition is to be used for a separator with a coating layer for a fuel cell, in which the coating layer is formed from the coating composition. The coating composition comprises a carbon material (A), a water-soluble resin binder (B), a water-dispersible fine particle binder (C), and an aqueous liquid medium (D).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a coating composition, a separator with a coating layer using the composition, and a fuel cell.

  A fuel cell is a system that can directly convert chemical energy into electrical energy using an electrochemical system, and is expected to be a next-generation energy because of its high efficiency. In particular, solid polymer fuel cells are being actively developed for automobiles, stationary devices, and small mobile devices because of their low operating temperature and high efficiency.

  The basic structure of a fuel cell is that an anode catalyst layer and a cathode catalyst layer are provided so as to face each other with a solid polymer electrolyte membrane interposed therebetween, and a conductive support having gas diffusibility on the surface of the catalyst layer In general, separators are sequentially laminated. An uneven gas flow path is formed on the surface of the separator, and a power generation reaction occurs when a reaction gas (oxygen, hydrogen) is supplied to the catalyst layer through a gas diffusible conductive support. In order to take out the generated electric power, the constituent member preferably has high conductivity, and conventionally, carbon fiber has been used as the conductive support and graphite has been used as the separator.

  The graphite separator is excellent in corrosion resistance and oxidation resistance in high-temperature, high-humidity, acidic atmospheres during power generation, but it is difficult to machine and is mass-productive. There was a problem of being scarce. For this reason, it is preferable to use a metal material that is easier to machine and excellent in mass productivity. However, since it is inferior in oxidation resistance, an oxide film is formed on the surface of the metal material to increase the contact resistance with the conductive support. There was a problem of adversely affecting the characteristics.

  In order to solve the above problems, for example, Patent Document 1 discloses a technique of forming a layer containing a conductive carbon material made of graphite on the surface of a metal separator. Patent Document 2 discloses a method of forming a layer of a coating made of an ionic resin and a conductive powder on the surface of a metal separator by an electrodeposition method. In these inventions, the dispersion of a conductive material is disclosed. The effect of inhibiting oxidation on the surface of the metal separator was insufficient.

On the other hand, Patent Document 3 uses a hydrophilic porous carbon material obtained by molding a graphite powder having a coating layer made of a binder resin formed on its surface and firing it at 600 ° C. or higher. A separator is disclosed. Patent Document 4 discloses a separator having a DLC (diamond-like carbon) film formed on the surface by plasma ion implantation. However, in these inventions, mass productivity is low, and a large separator is inexpensive. It was difficult to manufacture.
For this reason, development of a fuel cell separator having acid resistance, long-term stability, low cost and excellent mass productivity has been desired by further improvement.

JP-A-10-255823 JP 2004-31166 A JP-A-2005-119923 JP 2009-037977 A

  An object of the present invention is a coating composition used for a separator with a coating layer for a fuel cell, which is excellent in dispersibility and acid resistance of a carbon material, and long-term durability can be obtained by using the coating composition of the present invention. And a fuel cell excellent in battery characteristics.

The present invention is a coating composition comprising a carbon material (A) used in a separator with a coating layer for a fuel cell, a water-soluble resin binder (B), and a water-dispersible resin fine particle binder (C). Without impairing the dispersibility of the material (A), the acid resistance of the separator and the cell characteristics of the fuel cell can be improved.
That is, a coating composition used for a separator with a coating layer for a fuel cell, wherein the coating layer is formed from the coating composition,
A fuel comprising a coating composition containing a carbon material (A), a water-soluble resin binder (B), a water-dispersible resin fine particle binder (C), and an aqueous liquid medium (D). The present invention relates to a coating composition used for a battery-coated separator.

  In the present invention, the coating composition is a carbon material (A) in a total of 100% by mass of the solid content of the carbon material (A), the water-soluble resin binder (B) and the water-dispersible resin fine particle binder (C). The coating composition used in the separator with a coating layer for a fuel cell, wherein the content of is 20% by mass or more and 65% by mass or less.

  In the present invention, the coating composition has a water-soluble resin binder (B) content of 100% by mass in total of the solid content of the water-soluble resin binder (B) and the water-dispersible resin fine particle binder (C). The present invention relates to a coating composition used for the separator with a coating layer for a fuel cell, which is 1% by mass or more and less than 40% by mass.

  Moreover, this invention relates to the separator with a coating layer for fuel cells which has a coating layer formed from said coating composition.

  The present invention also relates to a fuel cell using the fuel cell-coated separator.

  By including the carbon material (A), the water-soluble resin binder (B), and the water-dispersible resin fine particle binder (C), the separator can be applied to the separator without impairing the dispersibility of the carbon material in the coating composition. A coating layer having excellent acid resistance can be formed, and a fuel cell having good power generation characteristics can be provided even in an environment where the fuel cell is used. Furthermore, by using a coating composition containing the carbon material (A), the water-soluble resin binder (B), and the water-dispersible resin fine particle binder (C) in a specific ratio, good power generation characteristics can be obtained. A fuel cell can be provided.

<Coating composition>
Here, the coating composition for forming the coating layer used in the present invention will be described. The coating composition contains a carbon material (A), a water-soluble resin binder (B), a water-dispersible resin fine particle binder (C), and an aqueous liquid medium (D).

The proportion of the carbon material (A) in the total solid content of the coating composition is preferably 20% by mass or more and 65% by mass or less, more preferably 25% by mass or more and 60% by mass or less, and further preferably 30% by mass. Above, it is 50 mass% or less.
Further, the proportion of the water-soluble resin binder (B) in the total solid content of the water-soluble resin binder (B) and the water-dispersible resin fine particle binder (C) is 1% by mass or more and less than 40% by mass, preferably Is 3% by mass or more and 20% by mass or less.

  In addition, the appropriate viscosity of the coating composition depends on the method of coating the coating composition, but is generally preferably 10 mPa · s or more and 30,000 mPa · s or less.

Such a coating composition can be obtained by various methods.
The case of a coating composition containing a carbon material (A), an aqueous resin binder (B), a water-dispersible resin fine particle binder (C), and an aqueous liquid medium (D) will be described as an example.
For example,
(X-1) An aqueous dispersion of a carbon material containing a carbon material (A), an aqueous resin binder (B), and an aqueous liquid medium (D) is obtained, and a water-dispersible resin fine particle binder (C And a coating composition can be obtained.
(X-2) An aqueous dispersion of a carbon material containing a carbon material (A), an aqueous resin binder (B), a water-dispersible resin fine particle binder (C), and an aqueous liquid medium (D) is obtained, and a coating composition is obtained. Can be obtained.
(X-3) A solution containing an aqueous resin binder (B), a water-dispersible resin fine particle binder (C), and an aqueous liquid medium (D) is obtained, and a carbon material (A) is further added to form a coating composition. Can be obtained.

  First, the carbon material (A) will be described.

  The carbon material (A) used in the present invention is not particularly limited as long as it is a carbon material having conductivity, but graphite, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber, carbon Fiber), fullerene, etc. can be used alone or in combination of two or more. From the viewpoint of conductivity, availability, and cost, it is preferable to use carbon black.

  Carbon black is a furnace black produced by continuously pyrolyzing a gas or liquid raw material in a reactor, especially ketjen black using ethylene heavy oil as a raw material. Channel black that has been rapidly cooled and precipitated, thermal black obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and particularly various types such as acetylene black using acetylene gas as a raw material, or 2 More than one type can be used in combination. Ordinarily oxidized carbon black, hollow carbon and the like can also be used.

  The oxidation treatment of carbon black is performed by treating the carbon black at a high temperature in the air or by treating it with nitric acid, nitrogen dioxide, ozone, etc., for example, phenol group, quinone group, carboxyl group, carbonyl group. This is a treatment for directly introducing (covalently bonding) such an oxygen-containing polar functional group to the surface of carbon black, and is generally performed to improve the dispersibility of carbon black. However, since carbon conductivity generally decreases as the amount of functional groups introduced increases, it is preferable to use carbon black that has not been oxidized.

As the specific surface area of the carbon black used increases, the number of contact points between the carbon black particles increases, which is advantageous in reducing the internal resistance of the electrode. Specifically, the specific surface area (BET) determined from the amount of nitrogen adsorption is preferably 20 m ² / g or more and 1500 m ² / g or less, more preferably 50 m ² / g or more and 1500 m ² / g or less, and still more preferably. Is preferably 100 m ² / g or more and 1500 m ² / g or less.

  Further, the particle size of the carbon black to be used is preferably 0.005 to 1 μm, particularly preferably 0.01 to 0.2 μm in terms of primary particle size. However, the primary particle diameter here is an average of the particle diameters measured with an electron microscope or the like.

The dispersed particle diameter of the carbon material (A) in the coating composition is desirably refined to 0.03 μm or more and 5 μm or less.
The dispersed particle size referred to here is a particle size (D50) that is 50% when the volume ratio of the particles is integrated from the fine particle size distribution in the volume particle size distribution. A particle size distribution meter such as a dynamic light scattering type particle size distribution meter ("Microtrack UPA" manufactured by Nikkiso Co., Ltd.).

  Examples of commercially available carbon black include Toka Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furnace Black), Printex L and the like (Degussa Co., Furnace Black), Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, etc., Conductex SC ULTRA, Conductex 975 ULTRA, etc., PUER BLACK100, 115, 205, etc. (manufactured by Colombian, furnace black), # 2350, # 2400B, # 2600B, # 30050B, # 3030B, # 3030B, # 3030B # 3350B, # 3400B, # 5400B etc. (Mitsubishi Chemical Co., Furnace Black), MONARCH1400, 1300, 900, VulcanXC- 2R, BlackPearls2000, etc. (Cabot, Furnace Black), Ensaco 250G, Ensaco 260G, Ensaco 350G, SuperP-Li (manufactured by TIMCAL), Ketjen Black EC-300J, EC-600JD (manufactured by Akzo), Denka Black, Denka Black HS Examples of graphite such as -100, FX-35 (manufactured by Denki Kagaku Kogyo Co., Ltd., acetylene black) include natural graphite such as artificial graphite, flake graphite, massive graphite, and earth graphite, but are not limited thereto. They may be used in combination of two or more.

  As the conductive carbon fibers, those obtained by firing from petroleum-derived raw materials are preferable, but those obtained by firing from plant-derived raw materials can also be used. For example, VGCF manufactured by Showa Denko Co., Ltd. manufactured with petroleum-derived raw materials can be mentioned.

  Next, the water-soluble resin binder (B) will be described.

  The water-soluble resin binder (B) used in the present invention is a mixture of 1 g of water-soluble resin binder (B) in 99 g of water at 25 ° C., stirred, left to stand at 25 ° C. for 24 hours, and then separated and precipitated. In addition, the binder can be completely dissolved in water.

  The water-soluble resin binder (B) is not particularly limited as long as it is a water-soluble resin as described above. For example, acrylic resin, polyurethane resin, polyester resin, polyamide resin, polyimide resin, polyallylamine resin , Polymer compounds including polysaccharide resins such as phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicon resin, fluorine resin, carboxymethyl cellulose. Moreover, if it is water-soluble, the modified substance, mixture, or copolymer of these resin may be sufficient. These binders can be used alone or in combination.

  Although the molecular weight of a water-soluble resin binder (B) is not specifically limited, Preferably a weight average molecular weight is 5,000-2,000,000. A weight average molecular weight (Mw) shows the polystyrene conversion molecular weight in a gel permeation chromatography (GPC).

  Next, the water dispersible resin fine particle binder (C) will be described.

  The water-dispersible resin fine particle binder (C) used in the present invention is generally called an aqueous emulsion, and the binder resin is not dissolved in water but is dispersed in a fine particle state. .

  The emulsion to be used is not particularly limited, and examples thereof include (meth) acrylic emulsions, nitrile emulsions, urethane emulsions, diene emulsions (such as SBR), and fluorine emulsions (such as PVDF and PTFE). Unlike the water-soluble polymer, the emulsion preferably has excellent binding properties between particles and flexibility (film flexibility).

(Particle structure of emulsion)
The particle structure of the water-dispersible resin fine particle binder (C) can be a multi-layer structure, so-called core-shell particles. For example, it is possible to localize a resin in which a monomer having a functional group is mainly polymerized in the core part or the shell part, or to provide a difference in Tg or composition between the core and the shell, thereby improving the curability and drying. Property, film formability, and mechanical strength of the binder can be improved.

(Particle size of emulsion)
The average particle size of the water-dispersible resin fine particle binder (C) is preferably 10 to 500 nm, more preferably 10 to 300 nm, from the viewpoints of binding properties and particle stability. Further, when a large amount of coarse particles exceeding 1 μm are contained, the stability of the particles is impaired, so that the coarse particles exceeding 1 μm are preferably at most 5% or less. In addition, the average particle diameter in this invention represents the volume average particle diameter, and is the value measured by the dynamic light scattering method.

When using a (meth) acrylic-type emulsion, it is preferable to contain the crosslinked resin fine particle demonstrated below. The cross-linked resin fine particles refer to resin fine particles having an internal cross-linked structure (three-dimensional cross-linked structure). When the cross-linked resin fine particles have a cross-linked structure, the electrolytic solution elution resistance can be secured, and the effect can be enhanced by adjusting the cross-linking inside the particles. Moreover, it can contribute to adhesiveness with a separator because bridge | crosslinking-type resin fine particle contains a specific functional group. Furthermore, the coating composition excellent in durability of the fuel cell can be obtained by adjusting the amount of the crosslinked structure and the functional group.
In addition, cross-linking of particles (cross-particle cross-linking) can be used together for cross-linking, but in this case, since a cross-linking agent is added later in many cases, variations in coating layer preparation, high temperature and high fuel cell Leakage of the cross-linking agent component may occur under wet and acidic conditions. For this reason, it is good to use a crosslinking agent to such an extent that water resistance and acid resistance are not impaired.

The crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention are obtained by emulsion polymerization of an ethylenically unsaturated monomer in water in the presence of a surfactant with a radical polymerization initiator. Resin fine particles. The (meth) acrylic emulsion suitably used in the present invention is preferably obtained by emulsion polymerization of an ethylenically unsaturated monomer containing the following monomer groups (C1) and (C2) in the following proportions. .
(C1) From the group consisting of an ethylenically unsaturated monomer (c1) having a monofunctional or polyfunctional alkoxysilyl group and a monomer (c2) having two or more ethylenically unsaturated groups in one molecule At least one monomer selected: 0.1 to 5% by mass
(C2) Ethylenically unsaturated monomers (c3) other than the monomers (c1) to (c2): 95 to 99.9% by mass
(However, the total of the above (c1) to (c3) is 100% by weight)

  Of the ethylenically unsaturated monomers constituting the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention, (c1) and (c3) are in one molecule unless otherwise specified. A monomer having one ethylenically unsaturated group is shown.

<About the monomer group (C1)>
The functional group (alkoxysilyl group, ethylenically unsaturated group) possessed by the monomer contained in the monomer group (C1) is a self-crosslinking reactive functional group, and is mainly used for particle internal crosslinking during particle synthesis. Has the effect of forming. Electrolytic solution resistance can be improved by sufficiently carrying out internal crosslinking of the particles. Therefore, it is possible to obtain crosslinked resin fine particles by using a monomer contained in the monomer group (C1). Moreover, water resistance and acid resistance can be improved by sufficiently carrying out particle crosslinking.

  Examples of the monomer (c1) having one ethylenically unsaturated group and an alkoxysilyl group in one molecule include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ- Methacryloxypropyl tributoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyl Dimethoxysilane, γ-methacryloxymethyltrimethoxysilane, γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, etc. It is.

  Examples of the monomer (c2) having two or more ethylenically unsaturated groups in one molecule include allyl (meth) acrylate, 1-methylallyl (meth) acrylate, and 2-methylallyl (meth) acrylate. 1-butenyl (meth) acrylate, 2-butenyl (meth) acrylate, 3-butenyl (meth) acrylate, 1,3-methyl-3-butenyl (meth) acrylate, 2- (meth) acrylate 2- Chloroallyl, 3-chloroallyl (meth) acrylate, o-allylphenyl (meth) acrylate, 2- (allyloxy) ethyl (meth) acrylate, allyl lactyl (meth) acrylate, citronellyl (meth) acrylate, (meth) Geranyl acrylate, rosinyl (meth) acrylate, cinnamyl (meth) acrylate, diallyl maleate, diallyl itaconic acid (Meth) acrylic acid esters containing ethylenically unsaturated groups such as vinyl (meth) acrylate, vinyl crotonate, vinyl oleate, vinyl linolenate, 2- (2′-vinyloxyethoxy) ethyl (meth) acrylate ; Ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, diacryl Multifunctional (meth) acrylic acid esters such as 1,1,1-trishydroxymethylethane acid, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethylpropanetriacrylic acid Divinylbenzene, divinyl adipate, etc. Vinyls; diallyl isophthalate, diallyl phthalate, etc. diallyl such as diallyl maleate and the like.

  The purpose of the alkoxysilyl group or ethylenically unsaturated group in the monomer (c1) or monomer (c2) is to introduce a cross-linked structure into the particle by self-condensation or polymerization mainly during the polymerization. However, a part of it may remain inside or on the surface after polymerization. The remaining alkoxysilyl group or ethylenically unsaturated group contributes to interparticle crosslinking of the binder composition. In particular, alkoxysilyl groups are preferred because they contribute to improving the adhesion to the separator.

  In this invention, the monomer contained in a monomer group (C1) is used 0.1 to 5 mass% in the whole ethylenically unsaturated monomer (100 mass% in total) used for emulsion polymerization. It is characterized by that. Preferably it is 0.5-3 mass%.

<About monomer group (C2)>
The crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention are the monomer (c1) having one ethylenically unsaturated group and an alkoxysilyl group in one molecule described above, In addition to the monomer (c2) having two or more ethylenically unsaturated groups in one molecule, the monomer group (C2) is ethylenic other than the monomers (c1) and (c2). The monomer (c3) having an unsaturated group can be obtained by emulsion polymerization at the same time.

The monomer (c3) is not particularly limited as long as it is a monomer other than the monomers (c1) and (c2) and has an ethylenically unsaturated group.
Monomer (c4) having one ethylenically unsaturated group and monofunctional or polyfunctional epoxy group in one molecule, one ethylenically unsaturated group and monofunctional or polyfunctional amide group in one molecule And at least one monomer selected from the group consisting of a monomer (c5) having one ethylenically unsaturated group and a monofunctional or polyfunctional hydroxyl group in one molecule (c6) And the monomer (c7) having an ethylenically unsaturated group other than the monomer and the monomers (c1), (c2), and (c4) to (c6) can be used.
By using the monomers (c4) to (c6), an epoxy group, an amide group, or a hydroxyl group can be left in or on the surface of the cross-linked resin fine particles, whereby physical properties such as adhesion of the separator. Can be improved. As for the monomers (c4) to (c6), the functional group tends to remain inside or on the surface even after the synthesis of the particles, and the adhesion effect to the separator is large even in a small amount. Some of them may be used for the crosslinking reaction, and the balance of water resistance, acid resistance and adhesion can be balanced by adjusting the degree of crosslinking of these functional groups.

  Examples of the monomer (c4) having one ethylenically unsaturated group and a monofunctional or polyfunctional epoxy group in one molecule include glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate. Etc.

  Examples of the monomer (c5) having one ethylenically unsaturated group and a monofunctional or polyfunctional amide group in one molecule include, for example, a primary amide group-containing ethylenically unsaturated monomer such as (meth) acrylamide. N-methylol acrylamide, N, N-di (methylol) acrylamide, alkylol (meth) acrylamides such as N-methylol-N-methoxymethyl (meth) acrylamide; N-methoxymethyl- (meth) acrylamide, Monoalkoxy (meth) acrylamides such as N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meth) acrylamide, N-pentoxymethyl- (meth) acrylamide; N, N-di (methoxymethyl) acrylamide, N-ethoxy Methyl-N-methoxymethylmethacrylamide, N, N-di (ethoxymethyl) acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N, N-di (propoxymethyl) acrylamide, N-butoxymethyl-N- (Propoxymethyl) methacrylamide, N, N-di (butoxymethyl) acrylamide, N-butoxymethyl-N- (methoxymethyl) methacrylamide, N, N-di (pentoxymethyl) acrylamide, N-methoxymethyl-N Dialkoxy (meth) acrylamides such as (pentoxymethyl) methacrylamide; dialkylamino (meth) acrylamides such as N, N-dimethylaminopropylacrylamide and N, N-diethylaminopropylacrylamide; N, N- Methyl acrylamide, N, N-dialkyl such as diethyl acrylamide (meth) acrylamides; and diacetone (meth) keto group, such as acrylamide-containing (meth) acrylamides and the like.

  Examples of the monomer (c6) having one ethylenically unsaturated group and a monofunctional or polyfunctional hydroxyl group in one molecule include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. 4-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl-2-hydroxyethylphthalic acid, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl Examples include alcohol.

  Some of the functional groups of the monomers contained in the monomers (c4) to (c6) may react during particle polymerization and be used for intraparticle crosslinking. In this invention, the monomer contained in monomer (c4)-(c6) is 0.1-20 mass% in the whole ethylenically unsaturated monomer (100 mass% in total) used for emulsion polymerization. It is preferably used, more preferably 1 to 15% by weight, and particularly preferably 2 to 10% by weight.

  The monomer (c7) is not particularly limited as long as it is a monomer having an ethylenically unsaturated group other than the monomers (c1), (c2), and (c4) to (c6). For example, a monomer (c8) having one ethylenically unsaturated group and an alkyl group having 8 to 18 carbon atoms in one molecule, one ethylenically unsaturated group in one molecule, and a cyclic structure And the monomer (c9). When the monomer (c8) and / or the monomer (c9) is used for the emulsion polymerization as the monomer (c7) (including other monomers as the monomer (c7)) The monomers (c8) and (c9) are all monomers having an ethylenically unsaturated group ((c1), (c2), (c4) to (c6) and (c7)). It is preferable that 30-95 mass% is contained in total. It is preferable to use the monomer (c8) or the monomer (c9) because it is excellent in particle stability, water resistance and acid resistance during particle synthesis.

  Examples of the monomer (c8) having one ethylenically unsaturated group and an alkyl group having 8 to 18 carbon atoms in one molecule include 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and myristyl. (Meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate and the like can be mentioned.

  Examples of the monomer (c9) having one ethylenically unsaturated group and a cyclic structure in one molecule include alicyclic ethylenically unsaturated monomers and aromatic ethylenically unsaturated monomers. It is done. Examples of the alicyclic ethylenically unsaturated monomer include cyclohexyl (meth) acrylate and isobornyl (meth) acrylate, and examples of the aromatic ethylenically unsaturated monomer include benzyl (meth) acrylate. Phenoxyethyl (meth) acrylate, styrene, α-methylstyrene, 2-methylstyrene, chlorostyrene, allylbenzene, ethynylbenzene and the like.

  Examples of the monomer (c7) other than the monomer (c8) and the monomer (c9) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n-butyl (meth). ) Alkyl group-containing ethylenically unsaturated monomers such as acrylate, pentyl (meth) acrylate, heptyl (meth) acrylate; nitrile group-containing ethylenically unsaturated monomers such as (meth) acrylonitrile; perfluoromethylmethyl (meta ) Acrylate, perfluoroethylmethyl (meth) acrylate, 2-perfluorobutylethyl (meth) acrylate, 2-perfluorohexylethyl (meth) acrylate, 2-perfluorooctylethyl (meth) acrylate, 2-perfluoroiso Nonylethyl (meth) acrylate, 2-par Fluorononylethyl (meth) acrylate, 2-perfluorodecylethyl (meth) acrylate, perfluoropropylpropyl (meth) acrylate, perfluorooctylpropyl (meth) acrylate, perfluorooctyl amyl (meth) acrylate, perfluorooctylun Perfluoroalkyl group-containing ethylenically unsaturated monomer having 1 to 20 carbon atoms such as decyl (meth) acrylate; perfluorobutylethylene, perfluorohexylethylene, perfluorooctylethylene, perfluorodecyl Perfluoroalkyl such as ethylene, perfluoroalkyl group-containing ethylenically unsaturated compounds such as alkylene; polyethylene glycol (meth) acrylate, methoxypolyethylene Glycol (meth) acrylate, ethoxypolyethyleneglycol (meth) acrylate, propoxypolyethyleneglycol (meth) acrylate, n-butoxypolyethyleneglycol (meth) acrylate, n-pentoxypolyethyleneglycol (meth) acrylate, phenoxypolyethyleneglycol (meth) acrylate , Polypropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxypolypropylene glycol (meth) acrylate, propoxypolypropylene glycol (meth) acrylate, n-butoxypolypropylene glycol (meth) acrylate, n-pentoxypolypropylene glycol (meta ) Acrylate, phenoxy polypropylene glycol (Meth) acrylate, polytetramethylene glycol (meth) acrylate, methoxypolytetramethylene glycol (meth) acrylate, phenoxytetraethylene glycol (meth) acrylate, hexaethylene glycol (meth) acrylate, methoxyhexaethylene glycol (meth) acrylate Ethylenically unsaturated compounds having a polyether chain such as: ethylenically unsaturated compounds having a polyester chain such as a lactone-modified (meth) acrylate; (meth) acrylic acid dimethylaminoethyl methyl chloride salt, trimethyl-3- (1- (Meth) acrylamide-1,1-dimethylpropyl) ammonium chloride, trimethyl-3- (1- (meth) acrylamidopropyl) ammonium chloride, and trime Quaternary ammonium base-containing ethylenically unsaturated compounds such as ru-3- (1- (meth) acrylamide-1,1-dimethylethyl) ammonium chloride; vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, caprylic acid Fatty acid vinyl compounds such as vinyl, vinyl laurate, vinyl palmitate and vinyl stearate; Vinyl ether ethylenically unsaturated monomers such as butyl vinyl ether and ethyl vinyl ether; 1-hexene, 1-octene, 1-decene, 1 Α-olefinic ethylenically unsaturated monomers such as dodecene, 1-tetradecene and 1-hexadecene; allyl monomers such as allyl acetate and allyl cyanide; vinyl such as vinyl cyanide, vinylcyclohexane and vinylmethylketone Monomer; acetylene, ethynyl Examples include ethynyl monomers such as toluene.

  Examples of the monomer (c7) other than the monomer (c8) and monomer (c9) include maleic acid, fumaric acid, itaconic acid, citraconic acid, and alkyl or alkenyl monoesters thereof. , Phthalic acid β- (meth) acryloxyethyl monoester, isophthalic acid β- (meth) acryloxyethyl monoester, terephthalic acid β- (meth) acryloxyethyl monoester, succinic acid β- (meth) acryloxyethyl Carboxyl group-containing ethylenically unsaturated monomers such as monoesters, acrylic acid, methacrylic acid, crotonic acid and cinnamic acid; Tertiary butyl group-containing ethylenically unsaturated monomers such as tertiary butyl (meth) acrylate; Sulfo group-containing ethylenically unsaturated monomers such as vinyl sulfonic acid and styrene sulfonic acid; (2- Phosphoric acid group-containing ethylenically unsaturated monomers such as droxyethyl) methacrylate acid phosphate; diacetone (meth) acrylamide, acrolein, N-vinylformamide, vinyl methyl ketone, vinyl ethyl ketone, acetoacetoxyethyl (meth) acrylate, Keto group-containing ethylenically unsaturated monomers such as acetoacetoxypropyl (meth) acrylate and acetoacetoxybutyl (meth) acrylate (monomers having one ethylenically unsaturated group and a keto group in one molecule) Etc.

  When a keto group-containing ethylenically unsaturated monomer is used as the monomer (c7), a polyfunctional hydrazide compound having two or more hydrazide groups capable of reacting with a keto group as a crosslinking agent is mixed with the binder composition. A tough coating film can be obtained by crosslinking between a keto group and a hydrazide group. This has excellent water resistance, acid resistance, and binding properties. Furthermore, since both resistance in a high temperature environment and flexibility can be achieved, a fuel cell excellent in long-term durability can be obtained.

  Further, among the monomers (c7), an ethylenically unsaturated monomer having a carboxyl group, a tertiary butyl group (tertiary butanol is removed by heat to form a carboxyl group), a sulfo group, and a phosphate group. The resin fine particles obtained by copolymerization of the above functional groups remain in the particles and on the surface even after polymerization, and have the effect of improving the physical properties such as the adhesion of the separator, and at the same time prevent aggregation during synthesis. In some cases, the stability of the particles after synthesis may be maintained, so that they can be preferably used.

  A part of the carboxyl group, tertiary butyl group, sulfo group, and phosphoric acid group may react during polymerization and be used for intraparticle crosslinking. When a monomer containing a carboxyl group, a tertiary butyl group, a sulfo group, and a phosphoric acid group is used, 0.1% is added to the whole ethylenically unsaturated monomer (100% by mass in total) used for emulsion polymerization. The content is preferably 10 to 10% by mass, and more preferably 1 to 5% by mass. Furthermore, these functional groups may react during drying and be used for cross-linking within or between particles.

  For example, a carboxyl group can react with an epoxy group during polymerization and drying to introduce a crosslinked structure into the resin fine particles. Similarly, a tertiary butyl group can react with an epoxy group in the same manner as described above since tertiary butyl alcohol is generated and a carboxyl group is formed when heat of a certain temperature or higher is applied.

  These monomers (c7) are used in combination of two or more of the above-mentioned monomers in order to adjust the polymerization stability and glass transition temperature of the particles, as well as the film formability and film properties. Can be used. Further, for example, by using (meth) acrylonitrile in combination, there is an effect that rubber elasticity is exhibited.

<Method for Producing Crosslinked Resin Fine Particles in (Meth) Acrylic Emulsion Suitable for Use in the Present Invention>
The crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention are synthesized by a conventionally known emulsion polymerization method.

<Emulsifier used in emulsion polymerization>
As the emulsifier used in the emulsion polymerization in the present invention, a conventionally known one such as a reactive emulsifier having an ethylenically unsaturated group or a non-reactive emulsifier having no ethylenically unsaturated group may be arbitrarily used. it can.

  Reactive emulsifiers having an ethylenically unsaturated group can be further roughly classified into anionic and nonionic nonionic ones. Especially when an anionic reactive emulsifier or nonionic reactive emulsifier having an ethylenically unsaturated group is used, the dispersed particle size of the copolymer becomes fine and the particle size distribution becomes narrow. In this case, water resistance and acid resistance can be improved. These anionic reactive emulsifiers or nonionic reactive emulsifiers having an ethylenically unsaturated group may be used singly or in combination.

  Specific examples of the anionic reactive emulsifier having an ethylenically unsaturated group are illustrated below, but the emulsifiers that can be used in the present invention are not limited to those described below.

  As an emulsifier, an alkyl ether type (as commercial products, for example, Aqualon KH-05, KH-10, KH-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap SR-10N, SR-20N manufactured by ADEKA Co., Ltd., Laterum PD-104 manufactured by Kao Corporation); sulfosuccinic acid ester system (for example, LATEMUL S-120, S-120A, S-180P, S-180A manufactured by Kao Corporation, Elemiol manufactured by Sanyo Chemical Co., Ltd.) JS-2 etc.); alkylphenyl ether type or alkylphenyl ester type (commercially available products include, for example, Aqualon H-2855A, H-3855B, H-3855C, H-3856, HS-05 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) , HS-10, HS-20, HS-30, ADEKA Corporation ADEKA rear SDX-222, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, SE-20N, etc.) (meth) acrylate sulfate ester (commercially available products include, for example, Japanese emulsifiers) Antox MS-60, MS-2N, Sanyo Kasei Kogyo Co., Ltd., Eleminol RS-30, etc.); Phosphate ester (for example, H-3330PL, Daiichi Kogyo Seiyaku Co., Ltd., stock) Adeka Soap PP-70 manufactured by the company ADEKA).

  Nonionic reactive emulsifiers that can be used in the present invention include, for example, alkyl ether-based (commercially available products such as Adeka Soap ER-10, ER-20, ER-30, ER-40, manufactured by ADEKA Corporation, Laterum PD-420, PD-430, PD-450, etc. manufactured by Kao Corporation; alkyl phenyl ethers or alkyl phenyl esters (for example, Aqualon RN-10, RN- manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 20, RN-30, RN-50, ADEKA Corporation ADEKA rear soap NE-10, NE-20, NE-30, NE-40, etc.); (meth) acrylate sulfate ester system (commercially available products include, for example, RMA-564, RMA-568, RMA-1114, etc. manufactured by Nippon Emulsifier Co., Ltd.) .

  When the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention are obtained by emulsion polymerization, together with the above-described reactive emulsifier having an ethylenically unsaturated group, an ethylenically unsaturated group may be used. Non-reactive emulsifiers that do not have any can be used in combination. Non-reactive emulsifiers can be broadly classified into non-reactive anionic emulsifiers and non-reactive nonionic emulsifiers.

  Examples of non-reactive nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether Sorbitan monolaurate, sorbitan monostearate, sorbitan higher fatty acid esters such as sorbitan trioleate; polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate; polyoxyethylene monolaurate, Polyoxyethylene higher fatty acid esters such as polyoxyethylene monostearate; oleic acid monoglyceride, stearic acid monoglyceride Glycerine higher fatty acid esters such as chloride, polyoxyethylene-polyoxypropylene block copolymers, and the like can be exemplified polyoxyethylene distyrenated phenyl ether.

  Examples of non-reactive anionic emulsifiers include higher fatty acid salts such as sodium oleate; alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate; alkyl sulfate esters such as sodium lauryl sulfate; polyoxyethylene lauryl ether Polyoxyethylene alkyl ether sulfates such as sodium sulfate; polyoxyethylene alkylaryl ether sulfates such as polyoxyethylene nonylphenyl ether sodium sulfate; sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, polyoxyethylene lauryl sulfosuccinic acid Alkylsulfosuccinic acid ester salts such as sodium and derivatives thereof; polyoxyethylene distyrenated phenyl ether And the like can be exemplified sulfuric ester salts.

  The usage-amount of the emulsifier used in this invention is not necessarily limited, It can select suitably according to the physical property calculated | required when crosslinked type resin microparticles are used as a final binder. For example, the emulsifier is usually preferably 0.1 to 30 parts by mass, more preferably 0.3 to 20 parts by mass with respect to a total of 100 parts by mass of the ethylenically unsaturated monomers. More preferably, it is in the range of 5 to 10 parts by mass.

  In emulsion polymerization of the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention, a water-soluble protective colloid can be used in combination. Examples of water-soluble protective colloids include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salt; Examples thereof include saccharides, and these can be used alone or in a combination of plural kinds. The amount of the water-soluble protective colloid used is 0.1 to 5 parts by mass, more preferably 0.5 to 2 parts by mass per 100 parts by mass in total of the ethylenically unsaturated monomers.

<Aqueous medium used in emulsion polymerization>
Examples of the aqueous medium used in the emulsion polymerization of the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention include water, and a hydrophilic organic solvent does not impair the object of the present invention. Can be used in

<Polymerization initiator used in emulsion polymerization>
The polymerization initiator used for obtaining the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention is not particularly limited as long as it has the ability to initiate radical polymerization, and is known in the art. Oil-soluble polymerization initiators and water-soluble polymerization initiators can be used.

  The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), and tert-butyl peroxide. Organic peroxides such as oxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide; 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4- Examples thereof include azobis compounds such as dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1′-azobiscyclohexane-1-carbonitrile. These can be used alone or in combination of two or more. These polymerization initiators are preferably used in an amount of 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the ethylenically unsaturated monomer.

  In the present invention, it is preferable to use a water-soluble polymerization initiator. For example, ammonium persulfate, potassium persulfate, hydrogen peroxide, 2,2′-azobis (2-methylpropionamidine) dihydrochloride and the like are conventionally known. A thing can be used conveniently. Moreover, when performing emulsion polymerization, a reducing agent can be used together with a polymerization initiator if desired. Thereby, it becomes easy to accelerate the emulsion polymerization rate or to perform the emulsion polymerization at a low temperature. Examples of such a reducing agent include reducing organic compounds such as metal salts such as ascorbic acid, ersorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, Examples include reducing inorganic compounds such as sodium bisulfite, ferrous chloride, Rongalite, thiourea dioxide, and the like. These reducing agents are preferably used in an amount of 0.05 to 5.0 parts by mass with respect to 100 parts by mass of the total ethylenically unsaturated monomer.

<Conditions for emulsion polymerization>
In addition, it can superpose | polymerize by a photochemical reaction, radiation irradiation, etc. irrespective of an above described polymerization initiator. The polymerization temperature is not less than the polymerization start temperature of each polymerization initiator. For example, in the case of a peroxide-based polymerization initiator, it may be usually about 70 ° C. The polymerization time is not particularly limited, but is usually 2 to 24 hours.

<Other materials used for reaction>
Further, if necessary, sodium acetate, sodium citrate, sodium bicarbonate, etc. as a buffering agent, and octyl mercaptan, 2-ethylhexyl thioglycolate, octyl thioglycolate, stearyl mercaptan, lauryl mercaptan as a chain transfer agent A suitable amount of mercaptans such as t-dodecyl mercaptan can be used.

  When a monomer having an acidic functional group such as a carboxyl group-containing ethylenically unsaturated monomer is used for polymerization of the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention, Or can be neutralized with a basic compound after polymerization. When neutralizing, it can be neutralized with ammonia or alkylamines such as trimethylamine, triethylamine and butylamine; alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine and aminomethylpropanol; and a base such as morpholine. . However, it is a highly volatile base that is highly effective in drying, and preferred bases are aminomethylpropanol and ammonia.

<Characteristics of cross-linked resin fine particles in (meth) acrylic emulsion preferably used in the present invention>
(Glass-transition temperature)
Further, the glass transition temperature (hereinafter also referred to as Tg) of the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention is preferably −50 to 70 ° C., more preferably −30 to 30 ° C. preferable. The glass transition temperature is a value obtained using a DSC (differential scanning calorimeter).

(Particle structure)
Moreover, the particle structure of the cross-linked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention can be a multi-layer structure, so-called core-shell particles. For example, it is possible to localize a resin in which a monomer having a functional group is mainly polymerized in the core part or the shell part, or to provide a difference in Tg or composition between the core and the shell, thereby improving the curability and drying. Property, film formability, and mechanical strength of the binder can be improved.

(Particle size)
The average particle diameter of the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention is preferably 10 to 500 nm from the viewpoint of the binding property of the carbon material and the stability of the particles, More preferably, it is 30 to 300 nm. In addition, the average particle diameter in the present invention represents a volume average particle diameter and can be measured by a dynamic light scattering method.

<Uncrosslinked compound (E) added to polymerized resin fine particles>
The (meth) acrylic emulsion suitably used in the present invention, in addition to the crosslinked resin fine particles, further includes an uncrosslinked epoxy group-containing compound, an uncrosslinked amide group-containing compound, an uncrosslinked hydroxyl group-containing compound, and It is preferable to include at least one uncrosslinked compound (E) selected from the group consisting of uncrosslinked oxazoline group-containing compounds [hereinafter sometimes referred to as compound (E)]. The compound (E) is a compound that does not dissolve in the aqueous liquid medium and is dispersed.

  The “uncrosslinked functional group-containing compound” which is the compound (E) is the inside of the (meth) acrylic emulsion suitably used in the present invention like the monomer contained in the monomer group (C1). Unlike a compound that forms a cross-linked structure (three-dimensional cross-linked structure), it refers to a compound that is added after emulsion polymerization (polymer formation) of resin fine particles (does not participate in internal cross-linking of resin fine particles). That is, “uncrosslinked” means that it is not involved in the formation of an internal crosslinked structure (three-dimensional crosslinked structure) of the (meth) acrylic emulsion suitably used in the present invention.

  The (meth) acrylic emulsion suitably used in the present invention has a cross-linked structure to ensure the resistance to electrolyte, and by using the compound (E), an epoxy group in the compound (E), At least one functional group selected from an amide group, a hydroxyl group, and an oxazoline group can contribute to adhesion to the separator. Furthermore, the composition for coating excellent in durability of the separator with a coating layer can be obtained by adjusting the amount of the crosslinked structure and the functional group.

  The crosslinked resin fine particles in the (meth) acrylic emulsion preferably used in the present invention must be crosslinked inside the particles. Water resistance and acid resistance can be ensured by appropriately adjusting the crosslinking inside the particles. Furthermore, the functional group-containing crosslinked resin fine particles are at least one selected from the group consisting of an uncrosslinked epoxy group-containing compound, an uncrosslinked amide group-containing compound, an uncrosslinked hydroxyl group-containing compound, and an uncrosslinked oxazoline group-containing compound. By adding the uncrosslinked compound (E), an epoxy group, an amide group, a hydroxyl group or an oxazoline group acts on the separator, and the adhesion can be effectively improved. Since the functional group contained in the compound (E) is stable by heat during long-term storage or coating film preparation, the effect of adhesion to the separator is great even when used in a small amount. Furthermore, it is excellent in storage stability. Compound (E) may react with the functional group in the cross-linked resin fine particles for the purpose of adjusting the flexibility, water resistance, and acid resistance of the binder. If the functional group in the compound (E) is excessively used for the reaction of (2), the functional group capable of interacting with the separator is reduced. For this reason, the reaction between the crosslinked resin fine particles in the (meth) acrylic emulsion suitably used in the present invention and the compound (E) needs to be at a level that does not impair the adhesion to the separator. Further, when a part of the functional group contained in the compound (E) is used for the crosslinking reaction [when the compound (E) is a polyfunctional compound], by adjusting the degree of crosslinking of these functional groups, It is possible to balance water resistance, acid resistance and adhesion.

<Uncrosslinked epoxy group-containing compound>
Examples of the uncrosslinked epoxy group-containing compound include epoxy group-containing ethylenically unsaturated monomers such as glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate; Radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers containing monomers; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol Diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) Cyclohexane Polyfunctional epoxy compounds; bisphenol A- epichlorohydrin epoxy resins, and epoxy resins such as bisphenol F- epichlorohydrin type epoxy resin.

  Among epoxy group-containing compounds, in particular, epoxy resins such as bisphenol A-epichlorohydrin type epoxy resins and bisphenol F-epichlorohydrin type epoxy resins, and ethylenically unsaturated monomers containing epoxy group-containing ethylenically unsaturated monomers. A radical polymerization resin obtained by polymerizing a saturated monomer is preferred. The epoxy resin can be expected to have a synergistic effect of improving water resistance and acid resistance by having a bisphenol skeleton, and improving separator adhesion by a hydroxyl group contained in the skeleton. In addition, radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers including epoxy group-containing ethylenically unsaturated monomers improve separator adhesion by having more epoxy groups in the resin skeleton. Moreover, the effect of improving water resistance and acid resistance compared with a monomer can be expected by using a resin.

<Uncrosslinked amide group-containing compound>
As an uncrosslinked amide group-containing compound, for example, a primary amide group-containing compound such as (meth) acrylamide; N-methylolacrylamide, N, N-di (methylol) acrylamide, N-methylol-N-methoxymethyl (meta) ) Alkylol (meth) acrylamide compounds such as acrylamide; N-methoxymethyl- (meth) acrylamide, N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meta ) Monoalkoxy (meth) acrylamide compounds such as acrylamide and N-pentoxymethyl- (meth) acrylamide; N, N-di (methoxymethyl) acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N, N -Di (Etoki Methyl) acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N, N-di (propoxymethyl) acrylamide, N-butoxymethyl-N- (propoxymethyl) methacrylamide, N, N-di (butoxymethyl) Dialkoxy (meth) acrylamides such as acrylamide, N-butoxymethyl-N- (methoxymethyl) methacrylamide, N, N-di (pentoxymethyl) acrylamide, N-methoxymethyl-N- (pentoxymethyl) methacrylamide Compounds; dialkylamino (meth) acrylamide compounds such as N, N-dimethylaminopropylacrylamide and N, N-diethylaminopropylacrylamide; N, N-dimethylacrylamide and N, N-diethylacrylamide Any dialkyl (meth) acrylamide compound; keto group-containing (meth) acrylamide compound such as diacetone (meth) acrylamide or the like, and the above amide group-containing ethylenically unsaturated monomers; Examples thereof include a radical polymerization resin obtained by polymerizing an ethylenically unsaturated monomer containing a monomer.

  Among the amide group-containing compounds, radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers including amide group-containing ethylenically unsaturated monomers such as acrylamide are particularly preferable. By having more amide groups in the resin skeleton, the separator adhesion can be improved, and by using the resin, an effect of improving water resistance and acid resistance compared to the monomer can be expected.

<Uncrosslinked hydroxyl group-containing compound>
Examples of the uncrosslinked hydroxyl group-containing compound include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate 4-hydroxyvinylbenzene, Hydroxyl group-containing ethylenically unsaturated monomers such as 1-ethynyl-1-cyclohexanol and allyl alcohol; radical polymerization obtained by polymerizing ethylenically unsaturated monomers containing the hydroxyl group-containing ethylenically unsaturated monomers Resins: linear aliphatic diols such as ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol; propylene glycol, neopentyl glycol 3-methyl-1,5 Pentanediol, 2,2-branched aliphatic diols such as diethyl-1,3-propanediol; and 1,4-bis cyclic diol such as (hydroxymethyl) cyclohexane.

  Among the hydroxyl group-containing compounds, radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers including a hydroxyl group-containing ethylenically unsaturated monomer or cyclic diols are particularly preferable. A radical polymerization resin obtained by polymerizing an ethylenically unsaturated monomer containing a hydroxyl group-containing ethylenically unsaturated monomer improves separator adhesion by having more hydroxyl groups in the resin skeleton, Moreover, since it is resin, the effect which improves water resistance and acid resistance compared with a monomer can be anticipated. Cyclic diols can be expected to have an effect of improving water resistance and acid resistance by having a cyclic structure in the skeleton.

<Uncrosslinked oxazoline group-containing compound>
Examples of the uncrosslinked oxazoline group-containing compound include 2′-methylenebis (2-oxazoline), 2,2′-ethylenebis (2-oxazoline), and 2,2′-ethylenebis (4-methyl-2-oxazoline). ), 2,2′-propylenebis (2-oxazoline), 2,2′-tetramethylenebis (2-oxazoline), 2,2′-hexamethylenebis (2-oxazoline), 2,2′-octamethylene Bis (2-oxazoline), 2,2′-p-phenylenebis (2-oxazoline), 2,2′-p-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-p -Phenylenebis (4-methyl-2-oxazoline), 2,2'-p-phenylenebis (4-phenyl-2-oxazoline), 2,2'-m-phenylenebis (2-oxazoline), 2 , 2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-m-phenylenebis ( 4-phenylenebis-2-oxazoline), 2,2′-o-phenylenebis (2-oxazoline), 2,2′-o-phenylenebis (4-methyl-2-oxazoline), 2,2′-bis (2-oxazoline), 2,2′-bis (4-methyl-2-oxazoline), 2,2′-bis (4-ethyl-2-oxazoline), 2,2′-bis (4-phenyl-2) -Oxazoline), and further an oxazoline group-containing radical polymerization resin.

  Among oxazoline group-containing compounds, in particular, phenylene bis-type oxazoline compounds such as 2′-p-phenylenebis (2-oxazoline), or ethylenically unsaturated monomers containing an oxazoline group-containing ethylenically unsaturated monomer A radical polymerization resin obtained by polymerizing is preferred. The phenylenebis type oxazoline compound has an effect of improving water resistance and acid resistance by having a phenyl group in the skeleton. In addition, radical polymerization resins obtained by polymerizing ethylenically unsaturated monomers including oxazoline group-containing ethylenically unsaturated monomers improve separator adhesion by having more oxazoline groups in the resin skeleton. In addition, the resin can improve water resistance and acid resistance compared to the monomer.

<Addition amount of compound (E), molecular weight>
Compound (E) is preferably added in an amount of 0.1 to 50 parts by weight, more preferably 5 to 40 parts by weight, based on 100 parts by weight of the solid content of the cross-linked resin fine particles. Furthermore, two or more types of compounds (E) can be used in combination.

  Although the molecular weight of a compound (E) is not specifically limited, It is preferable that a weight average molecular weight is 1,000-1,000,000, Furthermore, 5,000-500,000 are more preferable. In addition, the said weight average molecular weight is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

Next, the aqueous liquid medium (D) will be described.
As the aqueous liquid medium (D) used in the present invention, it is preferable to use water, but if necessary, for example, an organic solvent compatible with water is used to improve the coating property to the separator. You may do it.
Examples of organic solvents that are compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters. , Ethers, nitriles and the like, and may be used as long as they are compatible with water.

  Furthermore, a film-forming auxiliary, an antifoaming agent, a leveling agent, a preservative, a pH adjusting agent, a viscosity adjusting agent and the like can be blended in the coating composition as necessary.

(Disperser / Mixer)
As an apparatus used when obtaining the coating composition of the present invention or the catalyst ink composition for a fuel cell described later, a disperser or a mixer that is usually used for pigment dispersion or the like can be used.

  For example, mixers such as dispersers, homomixers, or planetary mixers; homogenizers such as “Clearmix” manufactured by M Technique, or “fillmix” manufactured by PRIMIX; paint conditioner (manufactured by Red Devil), ball mill, sand mill (Shinmaru Enterprises "Dynomill", etc.), Attritor, Pearl Mill (Eirich "DCP Mill", etc.), or Coball Mill, etc .; Media type dispersers; Wet Jet Mill (Genus, "Genus PY", Sugino Media-less dispersers such as “Starburst” manufactured by Machine, “Nanomizer” manufactured by Nanomizer, etc., “Claire SS-5” manufactured by M Technique, or “MICROS” manufactured by Nara Machinery; or other roll mills, etc. Although The present invention is not limited to these. Moreover, as the disperser, it is preferable to use a disperser that has been subjected to a metal contamination prevention treatment from the disperser.

  For example, when using a media-type disperser, a disperser in which the agitator and vessel are made of a ceramic or resin disperser, or the surface of the metal agitator and vessel is treated with tungsten carbide spraying or resin coating. Is preferably used. As the media, it is preferable to use glass beads, ceramic beads such as zirconia beads or alumina beads. Moreover, also when using a roll mill, it is preferable to use a ceramic roll. Only one type of dispersion device may be used, or a plurality of types of devices may be used in combination. In the case of a carbon material or a fuel cell catalyst material that easily breaks or crushes particles due to a strong impact, a medialess disperser such as a roll mill or a homogenizer is preferable to a media disperser.

<Separator with coat layer>
The separator with a coating layer of the present invention comprises a separator and a coating layer formed from the coating composition.

(Separator)
The separator for a fuel cell is usually in the form of a sheet or a plate, and concave and convex grooves are formed on one or both sides thereof. The groove portion of the separator for a fuel cell is in close contact with a conductive support of an electrode membrane assembly for a fuel cell, which will be described later, so that the groove portion serves as a gas flow path, and fuel gas (hydrogen) or oxidant gas (oxygen) The reaction gas such as is supplied. Usually, the depth of the groove is 0.05 mm to 2.0 mm, and the groove width and the rib width are the same. The thickness of the separator is not particularly limited depending on the size and application of the fuel cell, but is usually about 0.1 mm to 3.0 mm.

  The material of the fuel cell separator is not particularly limited, but carbon, aluminum, titanium, stainless steel, iron, steel, copper, zinc, tin, magnesium, manganese, silicon, nickel, lead, bismuth, lithium, vanadium, molybdenum, Zirconium, palladium, and alloys thereof can be used. Moreover, surface treatment, a primer, etc. can be given to the material surface as needed.

  The gas flow path shape of the fuel cell separator is generally a serpentine flow path that connects the gas supply port to the gas discharge port of the fuel cell with a single serpentine flow path, but is not limited to this. is not.

(Method of applying the coating composition to the separator)
There is no restriction | limiting in particular as a method of apply | coating the coating composition on a separator, A well-known method can be used.
Specific examples include a gravure coating method, a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a screen printing method, or an electrostatic coating method.
As the drying method, standing drying, blow dryer, hot air dryer, infrared heater, far infrared heater and the like can be used, but not particularly limited thereto.
Moreover, you may perform the rolling process by a lithographic press, a calender roll, etc. after application | coating.

<Fuel cell>
The fuel cell can be classified into several types depending on the electrolyte used. However, as the fuel cell of the present invention, a polymer electrolyte fuel cell is more preferable, and the separator with a coat layer is also preferably used. Can do.

(Solid polymer fuel cell)
In the polymer electrolyte fuel cell, the separator 1, the gas diffusion layer 2, the anode catalyst layer (fuel electrode) 3, the cathode catalyst layer (air electrode) 5, and the gas diffusion are arranged so as to sandwich the polymer electrolyte 4. It is composed of a layer 6 and a separator 7.
The separators 1 and 7 supply and discharge reaction gases such as fuel gas (hydrogen) and oxidant gas (oxygen). When the reaction gas is uniformly supplied to the anode and cathode catalyst layers 3 and 5 through the gas diffusion layers 2 and 6, a gas phase is formed at the boundary between the catalyst provided on both electrodes and the solid polymer electrolyte 4. A three-phase interface of (reactive gas), liquid phase (solid polymer electrolyte membrane), and solid phase (catalyst possessed by both electrodes) is formed. A direct current is generated by causing an electrochemical reaction.

In the above electrochemical reaction,
Cathode side: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
Anode side: H ₂ → 2H ⁺ + 2e ⁻
H ⁺ ions (protons) generated on the anode side move toward the cathode side in the solid polymer electrolyte 4, and e ⁻ (electrons) move to the cathode side through an external load. .

On the other hand, on the cathode side, oxygen contained in the oxidant gas reacts with H ⁺ ions and e ⁻ that have moved from the anode side to generate water. As a result, the above-described fuel cell generates direct-current power from hydrogen and oxygen to generate water.

(Catalyst material for fuel cells)
A known or commercially available catalyst material for the fuel cell can be used. For example, the catalyst particles may be those supported on carbon particles, oxide particles, or nitride particles as a catalyst support.

Examples of the catalyst particles include platinum, gold, silver, palladium, iridium, rhodium, ruthenium, and alloys thereof.
Examples of the catalyst carrier include the following.
Examples of the carbon particles include those similar to the carbon material (A).
Examples of the oxide particles include indium oxide, tin oxide, zinc oxide, titanium oxide, silica, and alumina.
Examples of the nitride particles include titanium nitride, zirconium nitride, niobium nitride, tantalum nitride, chromium nitride, vanadium nitride, and the like.
For these catalyst supports, an optimum material can be selected according to the required performance.

  The loading rate of the catalyst particles on the catalyst carrier is not particularly limited. When platinum is used as the catalyst particles and carbon particles are used as the catalyst carrier, the catalyst particles can normally be loaded up to about 1 to 70% by mass with respect to 100% by mass of the catalyst particles.

Examples of commercially available fuel cell catalyst materials include:
Platinum-supported carbon particles such as TEC10E50E, TEC10E70TPM, TEC10V30E, TEC10V50E, TEC66E50;
Platinum-ruthenium alloy-supported carbon particles such as TEC66E50 and TEC62E58;
Can be purchased from Tanaka Kikinzoku Kogyo Co., Ltd., but is not limited thereto.

(Fuel cell binder)
As the binder for the fuel cell, a proton conductive polymer is preferable. The proton conductive polymer refers to a binder having a hydrophilic functional group, and preferably has a proton conductivity of 100% RH and 10 ⁻³ Scm ⁻¹ or more at 25 ° C.
Here, examples of the hydrophilic functional group include acidic functional groups such as sulfo group, carboxyl group, and phosphoric acid group, and basic functional groups such as hydroxyl group and amino group. From the viewpoint of proton dissociation, sulfo group, A carboxyl group, a phosphate group, and a hydroxyl group are more preferable.
Polymers exhibiting proton conductivity include sulfo group-introduced olefin resins (polystyrene sulfonic acid, polyvinyl sulfonic acid, etc.), polyimide resins, phenol resins, polyether ketone resins, polybenzimidazole resins, and polystyrene. Resin having sulfonic acid such as sulfonic acid doped product of styrene resin, styrene / ethylene / butylene / styrene copolymer, perfluorosulfonic acid resin;
A resin having a carboxylic acid such as polyacrylic acid or carboxymethylcellulose;
A resin having a hydroxyl group such as polyvinyl alcohol;
A resin having an amino group such as polyallylamine, polydiallylamine, polydiallyldimethylammonium salt, polybenzimidazole resin formed into a salt with an acid at an imidazole moiety;
Examples thereof include resins having other hydrophilic functional groups such as polyacrylamide, polyvinyl pyrrolidone, and polyvinyl imidazole. In particular, a perfluorosulfonic acid resin is chemically very stable by introducing a fluorine atom having a high electronegativity, has a high degree of dissociation of a sulfo group, and can realize high proton conductivity. Specific examples of such proton conductive polymers include “Nafion” manufactured by DuPont. Usually, the proton conductive polymer is used as an alcohol aqueous solution containing about 5 to 30% by mass of the polymer. As the alcohol, for example, methanol, propanol, ethanol diethyl ether and the like are used.

(solvent)
As the solvent used in the catalyst ink composition for fuel cells, the same solvent as the above-mentioned aqueous liquid medium (D) is used, but is not limited thereto.

(Catalyst ink composition for fuel cells)
The fuel cell catalyst ink composition is a composition for forming a fuel cell catalyst layer, and is a composition containing a fuel cell catalyst material, a fuel cell binder and a solvent.
The types and ratios of the catalyst material, the proton conductive polymer, and the solvent contained in the catalyst ink composition are not limited and can be appropriately selected within a wide range. As a preferable range, for example, the proton conductive polymer is 10 to 300 parts by mass, preferably 20 to 250 parts by mass with respect to 100 parts by mass of the catalyst material.

  The method for preparing the catalyst ink composition is not particularly limited. In the preparation, each component may be dispersed at the same time, or the catalyst material may be dispersed in advance in the solvent, and then the proton conductive polymer component may be added. Can be optimized.

(Fuel cell electrode membrane assembly)
An electrode membrane assembly for a fuel cell is formed by adhering a fuel cell catalyst layer to one or both sides of a proton-conducting solid polymer electrolyte membrane, and further, a gas diffusing conductive material on one or both sides. The support is closely attached.

  As a method for producing a fuel cell electrode membrane assembly, a fuel cell catalyst layer previously formed on a transfer substrate is transferred onto one or both sides of a solid polymer electrolyte membrane, and then a conductive support is thermocompression bonded. The method of producing the electrode membrane assembly for fuel cells by this is mentioned. Alternatively, a fuel cell electrode membrane assembly may be produced by thermocompression bonding a fuel cell catalyst layer previously formed on a conductive support on one or both sides of a solid polymer electrolyte membrane.

(Solid polymer electrolyte membrane)
Examples of the solid polymer electrolyte membrane include perfluorosulfonic acid-based fluorine ion exchange resins. By introducing a fluorine atom with high electronegativity, it is chemically very stable, the dissociation degree of sulfo group is high, and high ionic conductivity can be realized. Specific examples include “Nafion” manufactured by DuPont, “Flemion” manufactured by Asahi Glass, “Aciplex” manufactured by Asahi Kasei, “Gore Select” manufactured by Gore, and the like. The thickness of the electrolyte membrane is usually about 20 μm to 250 μm, preferably about 10 μm to 80 μm.

  The water repellent layer for a fuel cell is a microporous layer formed on a conductive support. This layer is also referred to as a water repellent layer or MPL (micro porous layer). In addition to uniform gas supply to the catalyst layer and improved electrical conductivity, drainage of water generated during power generation on the cathode side. It has the role of improving sex. Moreover, since it is located between the conductive support and the catalyst layer due to the structure of the fuel cell, it may be handled as a part of the catalyst layer.

  The water repellent layer or MPL can be formed by, for example, applying a carbon material and an ink composition containing a water repellent material on a carbon paper substrate and baking at about 300 ° C.

(Transfer substrate)
The transfer substrate is a film substrate for applying a catalyst ink composition to form a fuel cell catalyst layer and transferring the catalyst layer on the transfer substrate to a solid polymer electrolyte membrane such as Nafion. As the transfer substrate, a polymer film that is inexpensive and easily available is preferable, and polytetrafluoroethylene, polyimide, polyethylene terephthalate, and the like are more preferable. Specific examples include Teflon (registered trademark) sheets. The thickness of the transfer substrate is usually about 6 μm to 100 μm, preferably about 10 μm to 50 μm, more preferably about 15 μm to 30 μm, from the viewpoints of handleability and economy.

(Conductive support)
As the conductive support, various conductive supports constituting the anode or the cathode can be used. However, in many fuel cells represented by the polymer electrolyte fuel cell, oxygen in the air is taken in on the cathode side, and the anode On the side, a porous or fibrous support is preferred so that gas can pass and diffuse so that hydrogen can be taken up. Furthermore, since it is necessary to take in and out electrons, a conductive material must be used. Carbon paper made of carbon material, carbon felt, carbon cloth, etc. are preferable. Specific examples include “TGP-H-090” manufactured by Toray Industries, Inc. These conductive supports are also called gas diffusion layers or GDLs in fuel cells.

  EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples and comparative examples, “part” represents “part by mass” and “%” represents “% by mass”.

<Preparation of water dispersion of water dispersible resin fine particle binder (C)>
[Synthesis Example 1]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser was charged with 40 parts of ion-exchanged water and 0.2 part of Adeka Soap SR-10 (manufactured by ADEKA) as a surfactant. 48.5 parts of methyl methacrylate, 50 parts of butyl acrylate, 1 part of acrylic acid, 0.5 part of 3-methacryloxypropyltrimethoxysilane, 53 parts of ion-exchanged water, and ADEKA rear soap SR-10 (ADEKA Corporation as a surfactant) 1% of the pre-emulsion prepared by mixing 2 parts in advance was further added. After raising the internal temperature to 70 ° C. and sufficiently substituting with nitrogen, 10% of 10 parts of a 5% aqueous solution of potassium persulfate was added to initiate polymerization. After maintaining the inside of the reaction system at 70 ° C. for 5 minutes, the remaining pre-emulsion and the remaining 5% aqueous solution of potassium persulfate were added dropwise over 3 hours while maintaining the temperature at 70 ° C., and stirring was further continued for 2 hours. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. 25% aqueous ammonia was added to adjust the pH to 8.5, and the solid content was adjusted to 40% with ion-exchanged water to obtain an aqueous dispersion of the water-dispersible resin fine particle binder (C). In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

<Production of Compound (E) [Production of Epoxy Group-Containing Compound]>
[Production Example 1]
Into a reaction vessel equipped with a stirrer, thermometer, dropping funnel, and refluxing apparatus, 20 parts of isopropyl alcohol and 20 parts of water were charged. Moreover, 2 parts of potassium persulfate was dissolved in 30 parts of isopropyl alcohol and 30 parts of water, and charged into the dropping tank 2. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropwise addition, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. and an epoxy having a solid content of 40%. A group-containing compound (methyl methacrylate / methyl acrylate / glycidyl methacrylate copolymer) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

<Production of Compound (E) [Production of Amide Group-Containing Compound]>
[Production Example 2]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a refluxing vessel was charged with 90 parts of water. Separately, 20 parts of acrylamide was dissolved in the dropping tank 1 and 2 parts of potassium persulfate was dissolved in 90 parts of water. The dropping tank 2 was charged. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropping, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and the amide having a solid content of 40% was obtained. A group-containing compound (polyacrylamide) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

[Production Example 3]
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a refluxing vessel was charged with 40 parts of water. Separately, 40 parts of 2-ethylhexyl acrylate, 40 parts of styrene, and 20 parts of dimethylacrylamide were added to the dropping tank 1, and 2 parts of potassium sulfate was dissolved in 60 parts of water and charged into the dropping tank 2. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropping, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and the amide having a solid content of 40% was obtained. A group-containing compound (2-ethylhexyl acrylate / styrene / dimethylacrylamide copolymer) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

<Production of Compound (E) [Production of Hydroxyl-Containing Compound]>
[Production Example 4]
Into a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a refluxing vessel, 20 parts of isopropyl alcohol and 20 parts of water are charged, and 40 parts of methyl methacrylate, 40 parts of butyl acrylate, and 20 parts of 2-hydroxyethyl methacrylate are separately added dropwise. In the tank 1, 2 parts of potassium persulfate was dissolved in 30 parts of isopropyl alcohol and 30 parts of water and charged into the dropping tank 2. After the internal temperature was raised to 80 ° C. and sufficiently substituted with nitrogen, the dropping tanks 1 and 2 were dropped over 2 hours to carry out polymerization. After completion of the dropping, stirring was continued for 1 hour while maintaining the internal temperature at 80 ° C. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C., and the hydroxyl group having a solid content of 40% A containing compound (methyl methacrylate / butyl acrylate / 2-hydroxyethyl methacrylate copolymer) solution was obtained. In addition, solid content was calculated | required by 150 degreeC 20 minute baking residue.

[Synthesis Examples 2 to 21]
Except having changed into the material and composition shown to Table 1, 3, the aqueous dispersion of the water-dispersible resin fine particle binder (C) of the synthesis examples 2-10 and 18-21 is obtained by the method similar to the synthesis example 1, respectively. It was.
In addition, the water dispersions of the water-dispersible resin fine particle binders (C) in Synthesis Examples 11 to 17 in Table 2 were prepared in advance by the same method as in Synthesis Example 1, and the water-dispersible resins in Synthesis Examples 1 to 10 obtained in advance. It was synthesized by using any one of aqueous dispersions of fine particle binder (C) as a base and mixing with compound (E). In addition, the numerical value in Tables 1-3 represents a mass part. However, in Synthesis Examples 20 and 21, the resin aggregated during the emulsion polymerization, and the desired aqueous dispersion of the water-dispersible resin fine particle binder (C) could not be obtained.

In addition, description of the product name in Table 1 and Table 3 is as follows.
Adekaria soap SR-10: alkyl ether anionic surfactant (manufactured by ADEKA Corporation)
ADEKA rear soap ER-20: alkyl ether nonionic surfactant (manufactured by ADEKA Corporation)
Epoxy resin: Product name Adeka Resin EM-1-60L, manufactured by ADEKA Corporation, epoxy equivalent 320, bisphenol A-epichlorohydrin type epoxy resin, oxazoline-containing acrylic / styrene resin: product name Epocross K-2020E, manufactured by Nippon Shokubai Co., Ltd. , Oxazoline equivalent 550

<Coating composition>
Example 1
Acetylene black (A-1: Denka Black HS-100) as a conductive carbon material
10 parts, 5 parts of polyallylamine 20% aqueous solution (B-1) as a water-soluble resin binder (1 part as a solid content), polytetrafluoroethylene 30-J as a water-dispersible resin fine particle binder (Mitsui / Dupont Fluorochemical Co., Ltd.) (Manufactured) 31 parts of a 60% aqueous dispersion (C-1) (18.6 parts as a solid content) and 104 parts of water are mixed in a mixer, and further dispersed in a sand mill to form a coating composition ( 1) was obtained. The degree of dispersion of the obtained coating composition was determined by determination with a grind gauge (according to JISK5600-2-5). The evaluation results are shown in Table 4. The numbers in the table indicate the size of the coarse particles, and the smaller the value, the better the dispersibility, and the more uniform and good state.

(Examples 2 to 13, Comparative Examples 1 and 2)
Coating compositions (2) to (15) were obtained in the same manner as in Example 1 except that the materials and composition ratios shown in Table 4 were changed. Further, as in Example 1, the degree of dispersion by a grind gauge is shown in Table 4.

The materials used in the examples are shown below.
<Conductive carbon material (A)>
A-1: Denka Black HS-100 (manufactured by Denki Kagaku Kogyo)
A-2: Mitsubishi Carbon # 3050B (Mitsubishi Chemical Corporation)
A-3: Denka black granular product (manufactured by Denki Kagaku Kogyo)
<Water-soluble resin binder (B)>
B-1: polyallylamine PAA-05 (20% aqueous solution) (manufactured by Nitto Boseki)
B-2: Carboxymethyl cellulose (Wako Pure Chemical Industries, Ltd.)
B-3: polyacrylic acid (Wako Pure Chemical Industries, average molecular weight 5000)
B-4: Styrene acrylic copolymer (20% aqueous solution of copolymer of 25% styrene 75% acrylic acid)
<Water-dispersible resin fine particle binder (C)>
C-1: Polytetrafluoroethylene 30-J (solid dispersion 60% aqueous dispersion) (Mitsui / Dupont Fluorochemicals)
-C-2: Urethane emulsion Disco Pearl U-53 (30% solids aqueous dispersion) (manufactured by Sumika Bayer Urethane Co., Ltd.)
C-3: Styrene butadiene emulsion TRD-2001 (48% solid content aqueous dispersion) (manufactured by JSR)

  As shown in Table 4, it was clarified that the coating compositions (1) to (13) of the present invention are excellent in dispersibility of the carbon material and are uniform coating compositions.

<Preparation of separator with coat layer>
[Example A-1: Separator with coat layer (1)]
The fuel cell separator coating composition (1) was added to the container, and the separator was immersed in the container for a certain period of time and then pulled up, and then dried at 120 ° C. for 30 minutes to obtain a separator with a coating layer (1). The thickness of the coat layer was 1.5 μm. The acid resistance of the coating layer of the obtained separator with a coating layer was evaluated by the method described below. The evaluation results are shown in Table 5. The separator used was a serpentine-type single flow path (flow path width 1.0 mm, rib width 1.0 mm, flow path depth) in the center of an 8 cm square material made of SUS304 and in the range of 5 cm square. 0.6 mm) formed on one side was used.

[Examples A-2 to A-13, Comparative example B-1 and 2: Separator with coat layer (2) to (15)]
Except having changed into the composition for fuel cell separator coating of Table 5, the separator (2)-(15) with a coating layer was obtained by the method similar to Example A-1, respectively. Table 5 shows the evaluation results of acid resistance.

(Acid resistance evaluation of separator with coat layer)
The separators with a coating layer (1) to (15) prepared above were immersed in a sulfuric acid aqueous solution at 100 ° C. and pH = 1 for 72 hours, washed sufficiently with ion-exchanged water, and dried at 100 ° C. for 1 hour.
Thereafter, using a knife, incisions from the surface of the coat layer to the depth reaching the separator were made at 6 mm in length and width at intervals of 2 mm. Adhesive tape was applied to the cut and peeled off immediately, and the degree of coating layer dropping was visually determined. The evaluation criteria are shown below.

○: “No peeling (good)”
○ △: “Slightly peelable (can be used)”
Δ: “About half peel (defect)”
×: “Peeling at most parts (very bad)”

  As shown in Table 5, it was clear that the separators with coat layer (1) to (13) of the present invention had good adhesion and excellent acid resistance even after immersion in an acidic aqueous solution. A separator for a fuel cell is a flow path of a gas containing water vapor. In particular, in a polymer electrolyte fuel cell, it is assumed to be used under high temperature and acidic conditions. It is very important to be.

(Preparation of catalyst ink composition for fuel cell)
4 parts by weight of platinum catalyst-supporting carbon (manufactured by Tanaka Kikinzoku Co., Ltd., 46% platinum, TEC10E50E) as catalyst material, 56 parts by weight of 2-propanol as solvent, and 20 parts by weight of ion-exchanged water are mixed by stirring with a disper. After preparing a paste composition (solid content concentration 4% by mass), 20 parts by mass of 20% by mass Nafion dispersion solution (manufactured by DuPont, CTypeDE2020) is added as a proton conductive polymer, and the mixture is stirred and mixed with a disper. Thus, a catalyst ink composition for fuel cells (solid content concentration of 8% by mass, catalyst ink composition and 100% by mass of the catalyst material and the total ratio of the proton conductive polymer) was produced.

(Preparation of fuel cell electrode membrane assembly)
The above fuel cell catalyst ink composition is applied onto a Teflon (registered trademark) film so that the basis weight of the platinum catalyst is 0.1 mg / cm ² , and is heated and vacuum-dried. As a result, a Teflon (registered trademark) film was obtained.
Subsequently, two 5 cm square punched pieces were produced from a Teflon (registered trademark) film on which a fuel cell catalyst layer was formed, and an 8 cm square solid polymer electrolyte membrane (Nafion NR-212, manufactured by DuPont, film thickness) The catalyst layer was transferred onto the solid polymer electrolyte membrane by peeling off the Teflon (registered trademark) film after closely adhering to the center of 51 μm from both sides and holding at 150 ° C. and 5 MPa. Further, by adhering a carbon paper substrate (SGL24-BCH, manufactured by SGL Carbon Co., Ltd.) made of 5 cm square carbon fiber to the surface of the catalyst layer, a fuel cell electrode membrane assembly having an electrode area of 5 cm square is produced. did.

<Production of evaluation cell for fuel cell>
[Example 14]
The electrode part of the fuel cell electrode membrane assembly described above was surrounded by a gasket, and then sandwiched from both sides so that the gas flow path part of the separator with coat layer (1) overlapped the electrode area. Finally, two current collector plates were mounted on both sides to produce a fuel cell evaluation cell.
[Comparative Example 3]
An evaluation cell for a fuel cell was produced in the same manner as in Example 14 except that a separator that was not coated with the coating composition was used.

[Examples 15 to 26, Comparative Examples 4 and 5]
An evaluation cell for a fuel cell was produced in the same manner as in Example 14 except that the separators with the coat layer (2) to (15) were changed.

(Fuel cell characteristic evaluation: resistance value change rate)
Using the obtained evaluation cell for a fuel cell, the cell temperature was set to 80 ° C., air humidified at a temperature of 60 ° C. and a relative humidity of 42% was supplied from the cathode side at a flow rate of 800 mL / min, and the temperature from the anode side was 77 ° C. Supply the hydrogen gas humidified at a relative humidity of 88% at a flow rate of 550 mL / min, record the resistance value after holding for 3 hours at a current density of 500 mA / cm ² and the resistance value after holding for 72 hours, and change the resistance value The ratio (percentage of the ratio of the resistance value after 3 hours / the resistance value after 72 hours) was calculated (the smaller the value, the better). All measurements were carried out using an AutoPEM series “PEFC evaluation system” (manufactured by Toyo Technica). The evaluation results are shown in Table 6.

○: “Change rate is 102% or less. Very good.”
○ △: “Change rate is higher than 102% and 106% or less. Good”
Δ: “Change rate is higher than 106% and 130% or less. Usable.”
X: “Change rate is 130% or more.

  As shown in Table 6, it was found that the fuel cell using the coated layer separator of the present invention has an excellent resistance value change rate. Content of water-dispersible resin fine particle binder occupying the total solid content of water-soluble resin binder and water-dispersible resin fine particle binder constituting the coat layer because there is no perfect correlation between the adhesion of the coat layer and the rate of change in resistance value Is within a specific range of the present invention, it is conceivable that the conductive state throughout the fuel cell device is good.

  Further, as shown in Table 6, in the case of the fuel cell using the separator with a coating layer of the present invention, the resistance value change rate is better than the evaluation result of Comparative Example 3 in which the coating layer is not used. I understand that. This is because in Comparative Example 3 in which no coating layer was used, an oxide film was formed on the separator surface under the high temperature, high humidity, and acidic conditions that are the operating conditions of the fuel cell, and the conductivity was extremely deteriorated. Moreover, in Comparative Examples 4 and 5, when the separator with a coat layer of the comparative example is used, it can be seen that the resistance value change rate is poor. This is considered that the dispersibility of the coating composition was insufficient, so that the internal structure of the coat layer became sparse and the separator surface could not be protected.

FIG. 1 is a schematic diagram of the structure of a fuel cell.

1 Separator 2 Gas diffusion layer 3 Anode electrode catalyst (fuel electrode)
4 Solid polymer electrolyte 5 Cathode electrode catalyst (Air electrode)
6 Gas diffusion layer 7 Separator

Claims (5)

A coating composition used for a separator with a coating layer for a fuel cell, wherein the coating layer is formed from the coating composition,
A fuel comprising a coating composition containing a carbon material (A), a water-soluble resin binder (B), a water-dispersible resin fine particle binder (C), and an aqueous liquid medium (D). The coating composition used for the separator with a coating layer for batteries.   Content of carbon material (A) in coating composition is 100 mass% in total of solid content of carbon material (A), solid content of water-soluble resin binder (B), and solid content of water-dispersible resin fine particle binder (C). The coating composition used for the separator with a coating layer for a fuel cell according to claim 1, wherein is 20% by mass or more and 65% by mass or less.   The coating composition has a water-soluble resin binder (B) content of 1% in a total of 100% by mass of the solid content of the water-soluble resin binder (B) and the solid content of the water-dispersible resin fine particle binder (C). The coating composition used for the separator with a coating layer for a fuel cell according to claim 2, wherein the coating composition is at least% and less than 40% by mass.   The separator with a coating layer for fuel cells which has a coating layer formed from the composition for coating of Claims 1-3.   A fuel cell using the separator with a coating layer for a fuel cell according to claim 4.

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