JP4852828B2 - Electrolyte membrane / electrode structure - Google Patents

Description

  The present invention relates to an electrolyte membrane / electrode structure in which a pair of electrodes are sandwiched between both sides of a hydrocarbon-based solid polymer electrolyte membrane.

  In recent years, new power generation technologies with excellent energy efficiency and environmental friendliness have attracted attention. Among them, polymer electrolyte fuel cells using solid polymer electrolyte membranes have high energy density, and have features such as easy startup and shutdown because of lower operating temperatures than other types of fuel cells. Developments as power supply devices for electric vehicles and distributed power generation are advancing. As such a solid polymer electrolyte membrane, for example, a perfluorocarbon sulfonic acid polymer membrane into which a sulfonic acid group is introduced as represented by Nafion (trade name) manufactured by DuPont, USA is known.

  An electrolyte membrane / electrode structure, which is a basic element of a fuel cell, is configured with a pair of electrodes, that is, a negative electrode catalyst layer film and a positive electrode catalyst layer film, bonded to both sides of a perfluorocarbon sulfonic acid polymer film. For example, the negative electrode catalyst layer film and the positive electrode catalyst layer film are layers prepared by mixing carbon powder in which platinum fine particles or platinum ruthenium fine particles, for example, platinum particles, and proton conductive perfluorocarbon sulfonic acid polymer are mixed. Consists of.

  Here, as a general method for producing an electrolyte membrane / electrode structure, carbon on which platinum is supported on a film-like base material, carbon on which an alloy of platinum and ruthenium is supported, and perfluorocarbon sulfonic acid polymer Is formed by thermal transfer onto a perfluorocarbon sulfonic acid polymer electrolyte membrane.

  In this case, the catalyst layer and the solid polymer electrolyte membrane are bonded under favorable conditions that do not adversely affect the device performance by controlling the temperature, pressure, and time. Specifically, a favorable electrolyte membrane / electrode structure is obtained by pressing for 1 to 5 minutes under the pressure of 4 to 10 MPa at 130 ° C. to 140 ° C. in the vicinity of the glass transition temperature of the perfluorocarbon sulfonic acid polymer membrane, for example, in the case of Nafion. Can be formed.

  The electrolyte membrane in such an electrolyte membrane / electrode structure, that is, a perfluorocarbon sulfonic acid polymer membrane has high acidity of the sulfonic acid group contained in the polymer, and therefore has good battery performance with a relatively small amount of sulfonic acid group. It is the most widely used because of its ability to pull out and the chemical stability that fluorine provides, but the cost of the monomer is high, the control over polymer synthesis is difficult, and the materials used in the equipment are limited As a result, it becomes very expensive and becomes an obstacle to popularization. Further, when applied to a direct methanol fuel cell using liquid fuel, such as methanol, as a fuel, since the affinity between fluorine and methanol is strong, there is a disadvantage that methanol permeability is high and performance cannot be brought out. Accordingly, there is an active movement to produce a hydrocarbon-based solid polymer electrolyte membrane that is cheaper and has low methanol permeability.

  Various hydrocarbon polymer electrolyte membranes in which a sulfonic acid group is introduced into a non-fluorinated aromatic ring-containing polymer have been studied. As a polymer skeleton, considering heat resistance and chemical stability, aromatic polyarylene ether compounds such as aromatic polyarylene ether ketones and aromatic polyarylene ether sulfones can be regarded as promising structures, A sulfonated polyarylethersulfone (for example, see Non-Patent Document 1), a sulfonated polyetheretherketone (for example, see Patent Document 1), sulfonated polystyrene, and the like have been reported. Further, a sulfonated polyarylethersulfone compound having higher thermal stability has been reported by polymerization using a monomer having a sulfonic acid group introduced on an electron-withdrawing aromatic ring (for example, Patent Documents). 2).

However, in aromatic hydrocarbon polymers with improved heat resistance and chemical stability, thermal bonding to the electrode is performed at a temperature near the glass transition temperature generally used in the perfluorocarbon sulfonic acid polymer film described above. This technique is difficult. For example, in the case of a sulfonated polyetheretherketone, the glass transition temperature depends on the amount of sulfonic acid group to be introduced, but is significantly higher than that of a perfluorocarbon sulfonic acid polymer membrane (see Non-Patent Document 2). In such hydrocarbon-based polymers introduced with acidic functional groups such as sulfonic acid groups, the glass transition temperature is high, so the heat resistance is improved, but the adhesiveness of the electrolyte membrane is low, so it is good. It is difficult to produce a simple electrolyte membrane / electrode structure. Further, when bonding is performed at a higher temperature, the deterioration of the polymer is promoted, so that the durability of the electrolyte membrane / electrode structure is lowered. On the other hand, when the amount of sulfonic acid group introduced into the hydrocarbon polymer is increased, the glass transition temperature is lowered, but this is not sufficient, and in addition to the influence of the glass transition temperature itself, the polymer is bonded to the electrode. Therefore, it becomes more difficult to produce a good electrolyte membrane / electrode structure. Furthermore, since the hydrocarbon polymer is essentially inferior in chemical stability compared to the fluorine-based polymer, if the conditions associated with the bonding with the electrode are severe, the deterioration of the membrane characteristics proceeds, and the fuel Reliability and durability when used as a battery are reduced.

JP-A-6-93114 (pages 15-17) US Patent Application Publication No. 2002/0091225 (page 1-2) Journal of Membrane Science (Netherlands) 1993, 83, p. 211-220 Journal of Membrane Science 173 (2000) 17-34

  An object of the present invention is to satisfactorily provide an electrolyte membrane / electrode structure using a hydrocarbon-based solid polymer electrolyte membrane and having improved reliability and durability.

  The present invention for solving the above-mentioned problems is an electrolyte membrane / electrode structure comprising a hydrocarbon-based solid polymer electrolyte membrane sandwiched between a pair of electrodes, and the glass transition temperature in the dry state of the electrolyte membrane used is 160 ° C. The electrolyte membrane / electrode structure is characterized in that the electrolyte membrane is made of an electrolyte membrane capable of retaining moisture in the range of 10% to 120% with respect to the weight of the electrolyte membrane.

  The present invention also relates to a method for manufacturing an electrolyte membrane / electrode structure in which a hydrocarbon-based solid polymer electrolyte membrane is sandwiched between a pair of electrodes, in which the hydrocarbon-based solid polymer electrolyte membrane and a pair of electrodes are joined. In the state where the amount of water contained in the hydrocarbon-based solid polymer electrolyte membrane is in the range of 10 to 70% of the maximum amount of water that can be contained in the hydrocarbon-based solid polymer electrolyte membrane, A bonding method of a hydrocarbon-based solid polymer electrolyte membrane and a pair of electrodes, characterized by bonding by pressing, and by this method, an aromatic hydrocarbon-based solid with a high glass transition temperature is essentially obtained. A molecular electrolyte membrane can be bonded to an electrode under relatively mild conditions, and an electrolyte membrane / electrode structure excellent in reliability and durability is provided.

  According to this invention, the water impregnated in the hydrocarbon-based solid polymer electrolyte membrane activates the molecular motion of the polymer and improves the flexibility of the membrane. Since the electrolyte membrane / electrode structure can be produced under conditions where the load on the solid polymer electrolyte is relatively small, the durability of the membrane is improved.

  Further, in the above-described joining method of the hydrocarbon-based solid polymer electrolyte membrane and the pair of hydrocarbon-based solid polymer electrolyte membranes, the hydrocarbon-based solid polymer electrolyte membrane is maintained in an atmosphere in which humidity and / or temperature are controlled. A method for joining a hydrocarbon-based solid polymer electrolyte membrane and a pair of electrodes, characterized in that moisture is imparted to the polymer electrolyte membrane. According to the present invention, since moisture can be evenly introduced into the hydrocarbon-based solid polymer electrolyte membrane, it becomes possible to humidify the membrane in a good state suitable for joining the entire membrane. It becomes possible to obtain an electrode structure with good reproducibility.

  Furthermore, the present invention provides an electrolyte membrane / electrode structure in which the peripheral edge portions of the pair of electrodes are formed of a sealing member, and prevents the fuel from crossing over from the electrode end surface. The durability of the hydrocarbon-based solid polymer electrolyte membrane having essentially low stability can be enhanced.

ただし、Ａｒは２価の芳香族基、Ｙはスルホン基またはケトン基、ＸはＨまたは１価のカチオン種を示す。

ただし、Ａｒ’は２価の芳香族基を示す。 In addition, the present invention includes a polyarylene ether-based compound comprising a constituent represented by the general formula (2) together with the general formula (1) as the organic polymer forming the hydrocarbon-based solid polymer electrolyte membrane The durability of the hydrocarbon-based solid polymer electrolyte membrane can be further enhanced.

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents H or a monovalent cation species.

However, Ar ′ represents a divalent aromatic group.

  The electrolyte membrane / electrode structure of the present invention can provide a fuel cell using a hydrocarbon electrolyte membrane excellent in reliability and durability.

The present invention will be described in detail below.
Hydrocarbon polymer electrolyte membranes with high glass transition temperatures have been studied as candidates for electrolyte membranes with better thermal stability than conventional perfluorosulfonic acid solid polymer electrolyte membranes. Research has been conducted on electrolyte membrane / electrode structures using such hydrocarbon polymer electrolyte membranes. As the hydrocarbon polymer electrolyte here, for example, an aromatic polyarylene ether compound can be considered promising in consideration of heat resistance and chemical stability. In terms of improving heat resistance, the polymer has a glass transition temperature of 160 ° C. or higher in the dry state from the viewpoint that a polymer having a higher glass transition temperature is preferable in order to suppress deformation of the polymer at high temperatures. The temperature is preferably 200 ° C. or higher.

  On the other hand, in order to move the fuel cell satisfactorily, it is preferable to use an electrolyte membrane in which protons easily move in the electrolyte membrane, but protons utilize acidic functional groups present in the electrolyte membrane, Since it moves in a hydrated form with hopping or water, an electrolyte membrane with an increased amount of acidic functional groups can be suitably used. Although details will be described later, for example, when the acidic functional group is a sulfonic acid group, the sulfonic acid group content in the electrolyte membrane is preferably in the range of 0.3 to 3.5 meq / g. When it is less than 0.3 meq / g, there is a tendency that sufficient ion conductivity is not exhibited when used as an ion conductive membrane, and when it is greater than 3.5 meq / g, the ion conductive membrane is not heated and humidified. When the conditions are met, membrane swelling tends to be too large to be suitable for use.

  In such an electrolyte membrane, since the acidic functional group retains water, the electrolyte membrane exhibits water retention. Since water acts effectively when protons move, the property of retaining water along with the presence of the aforementioned acidic functional group is an important property. At this time, the amount of water that can be retained with respect to the weight of the electrolyte membrane is preferably in the range of 10% to 120% as the electrolyte membrane in producing the electrolyte membrane / electrode structure of the present invention. . If it is less than 10%, a sufficient amount of water cannot be maintained when it is used as an electrolyte membrane, so that it tends to show no ionic conductivity. If it is more than 120%, the membrane swells greatly. It becomes too unsuitable for use.

  However, considering the production of the electrolyte membrane / electrode assembly of the present invention using a hydrocarbon-based electrolyte membrane having a glass transition temperature of 160 ° C. or higher, the electrolyte membrane has high heat resistance, but has been conventionally used. It is difficult to form a good bonded body by hot pressing in the vicinity of the glass transition temperature being performed, and when it is simply bonded by heat, durability when used as a fuel cell is low. This tendency becomes particularly difficult when using an electrolyte membrane in which the electrolyte membrane can hold moisture in the range of 10% to 45% and 70% to 120% with respect to the weight of the electrolyte membrane. That is, in an electrolyte membrane in which the amount of water that can be held is in the range of 10% to 45%, the electrolyte membrane is hard and tends not to touch the electrode. There is a problem of peeling, and when it is forcibly adhered at a higher temperature, deterioration such as discoloration of the film or brittleness of the film is observed, resulting in an electrolyte membrane / electrode structure with low durability. On the other hand, in an electrolyte membrane in which the amount of water that can be held is in the range of 50% to 65%, the adhesion with the electrode tends to be slightly relaxed due to the presence of acidic functional groups, and the temperature is raised somewhat. A relatively good electrolyte membrane / electrode structure can be produced, although there is a demerit that it is necessary and the durability slightly decreases. Furthermore, in an electrolyte membrane in which the amount of water that can be held is in the range of 70% to 120%, the presence of more acidic functional groups and a large amount of space that can hold moisture impairs the electrolyte membrane. Therefore, the electrolyte membrane repels the electrode, and it is difficult to simply join the electrode by hot pressing.

  Due to such circumstances, in the electrolyte membrane / electrode structure in which the hydrocarbon-based solid polymer electrolyte membrane excellent in reliability and durability of the present invention is sandwiched between a pair of electrodes, the glass in a dry state of the electrolyte membrane used An electrolyte membrane / electrode structure having a transition temperature of 160 ° C. or higher and an electrolyte membrane comprising an electrolyte membrane capable of retaining moisture in a range of 10% to 120% with respect to the weight of the electrolyte membrane A method for joining a hydrocarbon-based solid polymer electrolyte membrane and a pair of electrodes has also been invented.

  That is, in the state where the amount of water contained in the hydrocarbon-based solid polymer electrolyte membrane is in the range of 10 to 70% of the maximum amount of water that the hydrocarbon-based solid polymer electrolyte membrane can contain, the electrode and hot press It is characterized by joining. More preferably, it is in the range of 10 to 50%. As described above, in the aromatic hydrocarbon solid polymer electrolyte membrane, since the glass transition temperature is high, it is difficult to form a joined body with the electrode by hot pressing when the membrane is in a dry state. In many cases, the electrodes are not joined even by hot pressing, and a phenomenon that the electrodes peel off after joining appears. Therefore, in order to solve this problem, by adding a small amount of moisture to the film and activating the molecular motion of the polymer, it improves the bondability during hot pressing, making it more reliable and durable. An excellent electrolyte membrane / electrode structure was invented.

  Here, when the amount of water present in the electrolyte membrane is less than 10%, the molecular motion of the polymer is not sufficiently activated, so that the bonding state is insufficient and the amount of moisture added to the electrolyte membrane When the electrolyte membrane contracts due to vaporization, distortion occurs due to the stress generated at the joint between the electrolyte membrane and the electrode, so the electrode is often not joined by hot pressing, and the electrolyte membrane works well immediately after hot pressing. -Even if it seems that an electrode structure is formed, in this case as well, a phenomenon occurs in which the electrode peels off from the electrolyte membrane over time. On the other hand, when hot pressing is performed from a state where 70% or more of the maximum amount of water that can be contained in the electrolyte membrane is applied to the electrolyte membrane, the electrolyte membrane is joined from a state where it is considerably swollen with water. Since it is bonded to the electrode in a swelled state, the load on the electrolyte membrane is large, the durability of the fuel cell is lowered, and an electrolyte membrane / electrode structure that easily causes gas leakage is produced. Here, even when it is in the range of 50% to 70%, it is possible to produce an electrolyte membrane / electrode structure with good characteristics. However, since the electrolyte membrane partially deforms, there is a possibility that the electrolyte membrane / electrode structure is somewhat inferior in quality. Compared with the electrolyte membrane / electrode structure produced by simply joining by increasing the temperature and pressure during hot pressing, the electrolyte membrane produced by the hot pressing method after impregnating moisture according to the present invention -The electrode structure has excellent performance and durability.

  In the method for producing an electrolyte membrane / electrode structure according to the present invention, a method for adding a specific amount of moisture to the solid polymer electrolyte membrane is not particularly limited, and a method for spraying moisture using a spray or the like, humidity or temperature. For example, a method of holding and moistening the solid polymer electrolyte membrane in an atmosphere in which the above is controlled is preferably used. Among them, the method of holding the solid polymer electrolyte membrane in an atmosphere in which humidity and temperature are controlled is a particularly preferable method because it is possible to impart moisture uniformly and quantitatively. The reproducibility of an excellent electrolyte membrane / electrode structure that can reduce the reproducibility that becomes a problem when applying a high degree of water and the distribution of moisture in the surface direction and the thickness direction is uniform and the bonding state with the electrode is uniform. It can be manufactured well. The atmosphere for humidifying the film is not particularly limited, and can be arbitrarily selected according to the type and characteristics of the film.

  In addition, in a fuel cell, a catalyst layer sheet in which a catalyst layer composed of carbon particles supporting platinum fine particles or platinum-ruthenium fine particles and an ion exchange polymer is formed on a film-like substrate with a uniform film thickness is superimposed on the electrolyte membrane. After that, in order to perform thermal transfer, it is necessary to move only the catalyst layer to the electrolyte membrane while giving a certain degree of adhesion so that the catalyst layer does not peel off even if handled somewhat. At this time, it is difficult to control the balance between the catalyst layer and the film-like substrate material. In particular, when an electrolyte membrane / electrode structure is produced simply by raising the temperature, the adhesive force between the catalyst layer sheet and the catalyst layer becomes stronger, so when the film is peeled off, a part of the catalyst layer remains on the film surface. The problem of being peeled off also occurs, and a homogeneous electrolyte membrane / electrode structure cannot be produced. The temperature at the time of thermal transfer is preferably 150 ° C. or lower, more preferably 140 ° C. or lower.

  The form of the electrode in the present invention is not particularly limited. For example, the type of catalyst and the type and amount of ion exchange polymer contained in the electrode are not limited. For example, the ion exchange polymer may be a perfluorosulfonic acid polymer, a hydrocarbon polymer, or a partially fluorinated hydrocarbon polymer.

  Further, the present invention provides an electrolyte membrane / electrode structure in which peripheral portions of a pair of electrodes of the electrolyte membrane / electrode structure are formed of a sealing member, and a hydrocarbon solid polymer electrolyte having essentially low stability. The durability of the membrane can be increased. That is, since the electrolyte membrane is exposed at the periphery of the electrode, fuel crossover due to gas or liquid permeation through the electrolyte membrane is likely to occur. For example, in a hydrogen / air type fuel cell, the cathode reaction When oxygen gas, which is a gas, flows into the anode through the hydrocarbon-based solid polymer electrolyte membrane present in the periphery of the electrode, hydrogen peroxide is generated, which promotes deterioration of the electrolyte membrane. Since resistance to side reactions in such fuel cells is lower than that of fluoropolymers in the case of hydrocarbon polymers, the reliability and durability of the fuel cell can be improved by covering the periphery of the electrode with a seal member. It can be improved.

  The material of the sealant is not particularly limited, and those that exhibit an effect by being cured after being applied to the electrolyte membrane / electrode structure, such as an adhesive, can be suitably used. It may be a sealing agent that can be sealed so as to prevent the gas flow path so that the reaction gas does not easily reach the periphery of the electrode.

  In addition, the electrolyte membrane / electrode structure of the present invention is characterized by using a hydrocarbon-based electrolyte membrane. In particular, the polyarylene ether-based compound in which a sulfonic acid is introduced onto an aromatic ring, heat resistance, workability Thus, it is possible to provide an electrolyte membrane / electrode structure using a hydrocarbon-based solid polymer electrolyte membrane, which is useful as an ion conductive membrane excellent in ion conductivity. The polyarylene ether compound according to the present invention will be described in detail below.

  That is, by synthesizing a polyarylene ether using a 3,3′-disulfo-4,4′-dichlorodiphenylsulfone derivative as a monomer having a sulfonic acid group introduced on an electron-withdrawing aromatic ring, sulfone can be obtained even at high temperatures. It is a polymer in which the acid group is not easily released, and by using 2,6-dichlorobenzonitrile together with the 3,3′-disulfo-4,4′-dichlorodiphenylsulfone derivative, the polymerizability is low. It is a polyarylene ether having a feature that a polyarylene ether compound having a high degree of polymerization can be obtained even when a '-disulfo-4,4'-dichlorodiphenylsulfone derivative is used.

  That is, the sulfonic acid group-containing polyarylene ether-based compound of the present invention is characterized in that it contains a structural component represented by the general formula (2) together with the following general formula (1).

ただし、Ａｒは２価の芳香族基、Ｙはスルホン基またはケトン基、ＸはＨまたは１価のカチオン種を示す。

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents H or a monovalent cation species.

ただし、Ａｒ’は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  In addition, the sulfonic acid group-containing polyarylene ether-based compound part of the present invention may contain structural units other than those represented by the above general formula (1) and general formula (2). At this time, the structural units other than those represented by the general formula (2) or the general formula (3) are preferably 50% by weight or less of the polyarylene ether introduced with the sulfonic acid of the present invention.

  The sulfonic acid group-containing polyarylene ether compound of the present invention preferably has a sulfonic acid group content in the range of 0.3 to 3.5 meq / g. When it is less than 0.3 meq / g, there is a tendency that sufficient ion conductivity is not exhibited when used as an ion conductive membrane, and when it is greater than 3.5 meq / g, the ion conductive membrane is not heated and humidified. When the conditions are met, membrane swelling tends to be too large to be suitable for use.

  As the sulfonic acid group-containing polyarylene ether-based compound of the present invention, a compound containing the structural component represented by the general formula (4) together with the following general formula (3) is particularly preferable. By having a biphenylene structure, the film has excellent dimensional stability under high-temperature and high-humidity conditions, and also has high film toughness.

ただし、ＸはＨまたは１価のカチオン種を示す。

X represents H or a monovalent cation species.

  The sulfonic acid group-containing polyarylene ether compound of the present invention can be polymerized by an aromatic nucleophilic substitution reaction containing compounds represented by the following general formulas (5) and (6) as monomers. Specific examples of the compound represented by the general formula (5) include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3, 3'-disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl sulfone, and those in which their sulfonic acid group is converted to a salt with a monovalent cationic species. It is done. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. Examples of the compound represented by the general formula (6) include 2,6-dichlorobenzonitrile and 2,6-difluorobenzonitrile.

ただし、Ｙはスルホン基またはケトン基、Ｘは１価のカチオン種、Ｚは塩素またはフッ素を示す。

Y represents a sulfone group or a ketone group, X represents a monovalent cation species, and Z represents chlorine or fluorine.

  In the above aromatic nucleophilic substitution reaction, various activated difluoroaromatic compounds and dichloroaromatic compounds can be used in combination with the compounds represented by the general formulas (5) and (6) as monomers. Examples of these compounds include, but are not limited to, 4,4′-dichlorodiphenylsulfone, 4,4′-difluorodiphenylsulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, and the like. Without limitation, other aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like that are active in aromatic nucleophilic substitution can also be used.

  In addition, Ar in the structural component represented by the general formula (1) and Ar ′ in the structural component represented by the general formula (2) are generally the same as those described above in the aromatic nucleophilic substitution polymerization. It is a structure introduced from an aromatic diol component monomer used together with the compounds represented by formulas (5) and (6). Examples of such aromatic diol monomers include 4,4′-biphenol, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy). Phenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxy-3) , 5-dimethylphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, bis ( 4-hydroxyphenyl) diphenylmethane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9- (3-methyl-4-hydroxyphenyl) fluorene, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, hydroquinone, resorcin, and the like. In addition, polyarylene by aromatic nucleophilic substitution reaction Various aromatic diols that can be used for the polymerization of ether compounds can also be used. These aromatic diols can be used alone, but a plurality of aromatic diols can be used in combination.

  When the sulfonic acid group-containing polyarylene ether compound of the present invention is polymerized by an aromatic nucleophilic substitution reaction, an activated difluoroaromatic compound containing the compounds represented by the general formula (5) and the general formula (6) and / or A polymer can be obtained by reacting a dichloroaromatic compound and an aromatic diol in the presence of a basic compound. The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more. Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like, and those that can convert an aromatic diol into an active phenoxide structure may be used. It can use without being limited to. In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by weight. When the amount is less than 5% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high and the post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration.

  Moreover, the polymer logarithmic viscosity of the sulfonic acid group-containing polyarylene ether compound of the present invention is dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, and is measured using an Ubbelohde viscometer in a constant temperature bath at 30 ° C. It is preferably 0.1 or more when measured. When the logarithmic viscosity is less than 0.1, the membrane is likely to be brittle when formed as an ion conductive membrane. The reduced specific viscosity is more preferably 0.3 or more. On the other hand, if the reduced specific viscosity exceeds 5, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

  The sulfonic acid group-containing polyarylene ether compound of the present invention can be used as a simple substance, but can also be used as a resin composition in combination with other polymers. Examples of these polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyamides such as nylon 6, nylon 6,6, nylon 6,10 and nylon 12, polymethyl methacrylate and polymethacrylate. Acrylate resins such as polymethyl acrylate, polyacrylic acid esters, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, Cellulosic resins such as ethyl cellulose, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyether Heat curing of aromatic polymers such as sulfone, polyether ether ketone, polyether imide, polyimide, polyamide imide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin There are no particular restrictions on the conductive resin. A resin composition with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferred combination for improving polymer dimensionality. It is more preferable to introduce a sulfonic acid group into these basic polymers. When these resin compositions are used as an electrolyte membrane, the sulfonic acid group-containing polyarylene ether-based compound of the present invention is preferably contained in an amount of 50% by mass or more and less than 100% by mass of the entire resin composition. More preferably, it is 70 mass% or more and less than 100 mass%. When the content of the sulfonic acid group-containing polyarylene ether compound of the present invention is less than 50% by weight of the entire resin composition, the sulfonic acid group concentration of the ion conductive membrane containing this resin composition is lowered and good ions are obtained. There is a tendency that the conductivity cannot be obtained, and the unit containing the sulfonic acid group becomes a discontinuous phase and the mobility of ions to be conducted tends to be lowered. In addition, the composition of the present invention, if necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, It may contain various additives such as dispersants, polymerization inhibitors, radical inhibitors, inorganic compounds and inorganic-organic hybrid compounds for controlling the characteristics of the electrolyte membrane, and further in the electrolyte membrane. It may contain catalyst particles and the like.

  The sulfonic acid group-containing polyarylene ether compound and the resin composition thereof of the present invention can be processed into an electrolyte membrane by any method such as extrusion, rolling, or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. Examples of the solvent include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and hexamethylphosphonamide, and alcohols such as methanol and ethanol. An appropriate one can be selected, but is not limited thereto. A plurality of these solvents may be used as a mixture within a possible range. The compound concentration in the solution is preferably in the range of 0.1 to 50% by weight. If the concentration of the compound in the solution is less than 0.1% by weight, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by weight, the workability tends to deteriorate. A method of obtaining a molded body from a solution can be performed using a conventionally known method. For example, the molded product can be obtained by removing the solvent by heating, drying under reduced pressure, immersion in a compound non-solvent that can be mixed with a solvent that dissolves the compound, or the like. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure. At this time, if necessary, it can be molded in a form combined with other compounds. When combined with a compound having a similar dissolution behavior, it is preferable in that good molding can be achieved. The sulfonic acid group in the molded article thus obtained may contain a salt form with a cationic species, but it can be converted to a free sulfonic acid group by acid treatment as necessary. You can also.

Moreover, when producing an electrolyte membrane from the sulfonic acid group-containing polyarylene ether compound of the present invention and its resin composition, the most preferable is casting from a solution, and the solvent is removed from the cast solution as described above. Thus, an ion conductive membrane can be obtained. The removal of the solvent is preferably by drying from the uniformity of the ion conductive membrane. Moreover, in order to avoid decomposition | disassembly and alteration of a compound or a solvent, it can also dry at the lowest temperature possible under reduced pressure. Further, when the viscosity of the solution is high, when the substrate or the solution is heated and cast at a high temperature, the viscosity of the solution is lowered and the casting can be easily performed. The thickness of the solution at the time of casting is not particularly limited, but is preferably 10 to 1000 μm. More preferably, it is 50-500 micrometers. If the thickness of the solution is less than 10 μm, it tends to be unable to maintain the form as an ion conductive membrane, and if it is thicker than 1000 μm, a non-uniform polymer electrolyte membrane tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, the thickness can be controlled with the amount and concentration of the solution with a constant thickness using an applicator, a doctor blade, or the like, and with a cast area constant using a glass petri dish or the like. The cast solution can obtain a more uniform film by adjusting the solvent removal rate. For example, in the case of heating, the evaporation rate can be reduced by lowering the temperature in the first stage. In addition, when immersed in a non-solvent such as water, the coagulation rate of the compound can be adjusted by leaving the solution in air or an inert gas for an appropriate time. The ion conductive film of the present invention can have any film thickness depending on the purpose, but it is preferably as thin as possible from the viewpoint of ion conductivity. Specifically, it is preferably 5 to 200 μm, more preferably 5 to 50 μm, and most preferably 5 to 20 μm. If the thickness of the ion conductive membrane is less than 5 μm, handling of the ion conductive membrane is difficult and a short circuit or the like tends to occur when a fuel cell is manufactured. The power generation performance tends to decrease. When used as an ion conductive membrane, the sulfonic acid group in the membrane may contain a metal salt, but it can be converted to free sulfonic acid by an appropriate acid treatment. In this case, it is also effective to immerse the membrane obtained in an aqueous solution of sulfuric acid, hydrochloric acid, etc. with or without heating. The ion conductivity of the ion conductive film is preferably 1.0 × 10 ⁻³ S / cm or more. When the ionic conductivity is 1.0 × 10 ⁻³ S / cm or more, a good output tends to be obtained in a fuel cell using the ion conductive membrane, and is less than 1.0 × 10 ⁻³ S / cm. In some cases, the output of the fuel cell tends to decrease.

  By producing an electrolyte membrane / electrode structure with respect to the above-described electrolyte membrane composed of an ion conductive membrane, a hydrocarbon-based solid polymer fuel cell with particularly improved reliability and durability can be provided.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.

<Method for Measuring Dry Weight of Electrolyte Membrane> An electrolyte membrane having a size of 5 × 5 cm was vacuum-dried in a vacuum dryer at 50 ° C. for 6 hours, then cooled to room temperature in a desiccator, and then immediately measured. The dry weight (Wd) of the film.

<Moisture content of electrolyte membrane> The moisture content (Ws) of the electrolyte membrane in a specific moisture state is measured immediately after removing the water adhering to the membrane surface by lightly wiping the surface of the electrolyte membrane with a Kim pipe. When the weight obtained was set to Wi, it was calculated from the following formula.
Ws = (Wi−Wd) / Wd × 100 (%)

<Maximum Moisture Content of Electrolyte Membrane> First, a sample after dry weight (Wd) measurement was taken out after being immersed in ultrapure water at 25 ° C. for 8 hours with occasional stirring, and water droplets adhering to the membrane surface were removed with Kimwipe. Wiped off. From the weight (Ww) measured immediately thereafter, the maximum water content (Wm) of the membrane was calculated from the following formula.
Wm = (Ww−Wd) / Wd × 100 (%)

<Glass Transition Temperature> The glass transition temperature of the ion exchange membrane was measured as follows. A strip-shaped sample with a width of 5 mm was set on a dynamic viscoelasticity measuring apparatus (model name: Rheogel-E4000) manufactured by UBM Co., Ltd. so that the distance between chucks was 14 mm, and the sample was dried for 4 hours under a dry nitrogen stream. After that, the turn obtained when measuring in the measurement step at a frequency of 10 Hz, a strain of 0.7%, a nitrogen stream, a measurement temperature range of 25 ° C. to 200 ° C., a temperature increase rate of 2 ° C./min, and 2 ° C. in tension mode. Delta peak temperature.

<Proton conductivity> A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped membrane sample on a probe for self-made measurement (manufactured by Teflon (R)), and a constant temperature / humidity oven at 80 ° C. and 95% RH ( The sample was held in Nagano Scientific Machinery Co., Ltd., LH-20-01), and the impedance between the platinum wires was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. The measurement was performed while changing the distance between the electrodes, and the conductivity obtained by canceling the contact resistance between the film and the platinum wire was calculated from the gradient obtained by plotting the distance measured between the electrodes and the resistance measurement value estimated from the CC plot.
Conductivity [S / cm] = 1 / film width [cm] × film thickness [cm] × resistance interelectrode gradient [Ω / cm]

<Power generation test> The electrolyte membrane / electrode structure is incorporated into an evaluation fuel cell FC25-02SP manufactured by Electrochem, and supplied with hydrogen and air humidified with ultrapure water at 75 ° C. to the anode and cathode at a cell temperature of 80 ° C. Then, a discharge test with a current density of 0.5 A / cm ² was performed. The measurement was performed by reading the voltage after continuous operation for 8 hours.

<Durability Evaluation> The durability test of the electrolyte membrane / electrode structure was determined from the time when the power generation test was continued as it was after the power generation test described above, and the performance deteriorated (voltage drop due to gas leak, etc.).

Example 1
The electrolyte membrane in the electrolyte membrane / electrode structure of Example 1 was produced by the following method. That is, 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) 5.2335 g (0.0106 mole), 2,6-dichlorobenzonitrile (abbreviation: DCBN) 2. 3323 g (0.035559 mole), 4,4′-biphenol 4.5086 g (0.02421 mole), potassium carbonate 3.8484 g (0.02784 mole) and molecular sieve 2.61 g were weighed into a 100 ml four-necked flask and nitrogen was added. Shed. After adding 35 ml of NMP and stirring at 148 ° C. for 1 hour, the reaction was continued by raising the reaction temperature to 195-200 ° C. and sufficiently increasing the viscosity of the system (about 5 hours). After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand. The obtained polymer was washed in boiling ultrapure water for 1 hour and then dried. The logarithmic viscosity of the polymer was 1.25. 1 g of the polymer was dissolved in 5 ml of NMP, cast on a glass plate on a hot plate to a thickness of about 200 μm, NMP was distilled off until it became a film, and then immersed in water overnight. The obtained film was treated with boiling water in 2 liters of a 1 mol / l sulfuric acid aqueous solution for 1 hour to remove the salt, and then boiled with ultrapure water 3 times for 1 hour to remove the acid component. Then, it dried at room temperature in the state which fixed the film. On the other hand, the electrode used for the electrolyte membrane / electrode structure of Example 1 was produced by the following method. First, in a 20% Nafion (trade name) solution (product number: SE-20192) manufactured by DuPont, catalyst-supported carbon (carbon: Valcan XC-72 manufactured by Cabot, platinum catalyst-supported amount: 40% by weight) A Nafion weight ratio of 2.7: 1 was added and stirred to prepare a catalyst paste. This catalyst paste was applied to Toray carbon paper TGPH-060 that had been subjected to water-repellent finishing so that the amount of platinum deposited was 0.4 mg / cm ² , and dried to provide an electrode (gas diffusion layer with catalyst layer). Produced. As an adhesion method of the electrolyte membrane and the electrode produced as described above, after applying moisture to the electrolyte membrane by spraying ultrapure water uniformly and lightly using an air brush, the electrode with the catalyst layer facing the electrolyte membrane side And was hot-pressed at 130 ° C. and 8 MPa for 3 minutes.

Reference example 1
An electrolyte membrane / electrode structure was produced using the same method as in Example 1 except that only the amount of water contained in the electrolyte membrane was changed.

Example 3
An electrolyte membrane / electrode structure was produced using the same procedure as in Example 1 using the electrolyte membrane synthesized in Example 1 with a ratio of S-DCDPS and DCBN of 23:77.

Example 4
An electrolyte membrane / electrode structure was produced using the same method as in Example 1 using the electrolyte membrane synthesized in Example 1 with a ratio of S-DCDPS and DCBN of 62:38.

Example 5
After an electrolyte membrane / electrode structure was produced in the same manner as in Example 1, the periphery of the electrode was sealed using a sealant (Threebond TB1152).

Example 6
When humidifying the electrolyte membrane in the examples, instead of directly applying moisture by air spray, by exposing the electrolyte membrane to an environment of 20 ° C. and 90 RH% for 20 hours, except that the electrolyte membrane was uniformly humidified, An electrolyte membrane / electrode structure was produced using the same method as in Example 1. When eight sets of electrolyte membrane / electrode assemblies were prepared and compared, it was confirmed that the water content could be controlled with good reproducibility. In the humidification by the air spray performed in Examples 1 to 5, the amount of water cannot be controlled with good reproducibility. Moreover, according to the present Example, it showed favorable durability compared with the electrolyte membrane / electrode structure to which moisture was given by air spray. This is probably because the electrolyte membrane is uniformly humidified, so that the bonding state is also uniform.

Comparative Example 1
An attempt was made to produce an electrolyte membrane / electrode structure using the same method as in Example 1 except that no moisture was included in the electrolyte membrane using an air brush. Unfortunately, an electrolyte membrane / electrode structure could not be produced.

Comparative Example 2
An electrolyte membrane / electrode structure was prepared by the method of Comparative Example 1 except that hot pressing was performed at 185 ° C. and 8 MPa for 3 minutes. Although the electrolyte membrane / electrode structure could be produced, discoloration of the membrane was confirmed. The performance of the power generation test was lower than those of Example 1, Reference Example 1 and Example 5 , and the durability was poor. A method of hot pressing at 170 ° C. was also tried, but in that case, an electrolyte membrane / electrode structure could not be produced.

Comparative Example 3
An electrolyte membrane / electrode structure was produced by the method of Example 4 except that the electrolyte membrane was immersed in ultrapure water. The deformation of the electrolyte membrane was large. When the power generation test was carried out, gas leak occurred at the time when 1 hour passed, and the evaluation was not possible.

Table 1 shows the composition of the electrolyte membrane, the characteristics of the electrolyte membrane, the bonding conditions with the electrodes, and the characteristics of the electrolyte membrane / electrode structure in Examples 1, 3 to 6, Reference Example 1 and Comparative Examples 1 to 3. Show.

  The electrolyte membrane / electrode structure of the present invention can provide a fuel cell using a hydrocarbon electrolyte membrane excellent in reliability and durability.

  The electrolyte membrane / electrode structure of the present invention can provide a hydrocarbon-based electrolyte membrane / electrode structure excellent in reliability and durability, and the reliability and durability of the fuel cell can be improved.

Claims (2)

A hydrocarbon using a polyarylene ether compound characterized by containing a constituent represented by the general formula (2) as well as the general formula (1) as the organic polymer forming the hydrocarbon solid polymer electrolyte membrane In an electrolyte membrane / electrode structure in which a solid polymer electrolyte membrane is sandwiched between a pair of electrodes, the glass transition temperature in the dry state of the hydrocarbon solid polymer electrolyte membrane is 160 ° C. or higher, and the hydrocarbon type In the solid polymer electrolyte membrane, the maximum moisture content with respect to the weight of the electrolyte membrane is in the range of 10% to 120%, the lower limit value of the moisture content is 10% , and the upper limit value is less than 70% with respect to the maximum moisture content. Alternatively , an electrolyte membrane / electrode structure characterized by being joined to the electrode by hot pressing in a water-containing state, which is a larger value of 10% .

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents H or a monovalent cation species.

However, Ar ′ represents a divalent aromatic group. The electrolyte membrane / electrode structure according to claim 1, wherein peripheral edges of the pair of electrodes are formed of a seal member.