JP2005251408A - Solid polymer electrolyte, membrane using it, electrolyte/catalyst electrode assembly, membrane/electrode assembly and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easily manufacturable solid polymer electrolyte, while overcoming a weak point of inferior oxidation resistance of a sulfonated aromatic polymer compound used as a substitute for an expensive fluorine-based solid polymer electrolyte membrane, inexpensive as compared with the fluorine-based solid polymer electrolyte membrane, and having practically sufficient ion conductivity and high durability characteristic, and also to provide: a solid polymer electrolyte membrane formed of the solid polymer electrolyte; an electrolyte/catalyst electrode assembly formed of the solid polymer electrolyte; a membrane/electrode assembly using the electrolyte/catalyst electrode assembly; and a fuel cell using the membrane/electrode assembly. <P>SOLUTION: This solid polymer electrolyte is provided by introducing a proton conductive substituted group in a side chain of a hydrocarbon-based polymer comprising repeating units each having a structure expressed by formula (1) in a principal chain. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a low-cost, high-durability solid polymer electrolyte excellent in oxidation resistance and the like suitable for an electrolyte membrane used in fuel cells and the like, a solid polymer electrolyte membrane using the same, an electrolyte / catalyst electrode assembly, and the The present invention relates to a fuel cell using a solid polymer electrolyte.

  A solid polymer electrolyte is a solid polymer material having an electrolyte group such as a sulfonic acid group or an amino group in a polymer chain, and is firmly bonded to a specific ion and selectively transmits a cation or an anion. Because of its properties, it is formed into particles, fibers, or membranes, and is used for various applications such as electrodialysis, diffusion dialysis, and battery membranes.

  A fuel cell is provided with a pair of electrodes on both sides of a solid polymer electrolyte membrane having a proton-conducting substituent, supplies hydrogen gas, methanol, etc. as fuel to one electrode (fuel electrode), and oxygen gas or air as an oxidant Is supplied to the other electrode (air electrode) to obtain an electromotive force.

  Fluorine-based solid polymer electrolytes with high proton conductivity known under the trade names Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) Since the membrane is excellent in chemical stability, it is widely used as a solid polymer electrolyte membrane for fuel cells and the like.

  By the way, a fluorine-based electrolyte typified by a perfluorosulfonic acid membrane has a C—F bond and thus has a very large chemical stability, and is very suitable as the above-described solid polymer electrolyte for fuel cells. Yes.

  However, the fluorine-based solid polymer electrolyte has a drawback that it is difficult to produce and is very expensive. Therefore, fluorine-based solid polymer electrolyte membranes are used in limited applications such as space or military solid polymer fuel cells, and are used in consumer applications such as solid polymer fuel cells as a low-pollution power source for automobiles. It was difficult to apply to

  Therefore, as an inexpensive solid polymer electrolyte membrane, a solid polymer electrolyte membrane in which an aromatic hydrocarbon polymer typified by engineering plastics is sulfonated has been proposed. These have the advantage of easy manufacture and low cost. (For example, refer to Patent Document 1). Compared with a fluorine-based solid polymer electrolyte membrane represented by Nafion, an aromatic hydrocarbon-based solid polymer electrolyte membrane sulfonated from an engineering plastic has advantages of easy production and low cost. However, it has a drawback that it is very weak in terms of oxidation resistance.

  Patent Document 2 discloses a sulfonic acid compound having at least two sulfonic acid groups in the molecule and an amino compound having at least two amino groups in the molecule as a polymer solid electrolyte having high ion conductivity and extremely excellent toughness. A polysulfonamide polymer solid electrolyte obtained by reacting is described. However, the ionic conductivity of this polymer solid electrolyte membrane is not sufficient as a solid electrolyte membrane for fuel cells.

  According to Non-Patent Document 1, it is reported that, for example, sulfonated polyether ether ketone and polyether sulfone deteriorate from an ether site adjacent to sulfonic acid. From this, it is considered that when an electron donating group is present in the vicinity of the sulfonic acid, the oxidative degradation starts therefrom. Thus, the polymer solid electrolyte having a sulfonic acid group has a problem in terms of oxidation resistance.

JP-A-6-93114, page 1 JP, 2000-331713, A, page 1 Polymer Papers Vol. 59, no. 8, 460-473 pages

  The object of the present invention is to eliminate the disadvantage of inferior oxidation resistance of a sulfonated aromatic polymer compound used as an alternative to an expensive fluorine-based solid polymer electrolyte membrane. Solid polymer electrolyte that has practically sufficient ionic conductivity and high oxidation resistance and is easy to produce using a hydrocarbon-based compound that is less expensive than an electrolyte membrane, and a solid polymer comprising the solid polymer electrolyte To provide an electrolyte membrane, an electrolyte / catalyst electrode assembly comprising the solid polymer electrolyte, a membrane / electrode assembly using the electrolyte / catalyst electrode assembly, and a fuel cell using the membrane / electrode assembly. It is in.

  In order to solve the above-mentioned problem, it is possible to introduce a proton-conducting substituent into a side chain of a hydrocarbon polymer containing a repeating unit having a structure represented by the following formula (1) in the main chain. Became clear.

  Since the hydrocarbon polymer of the present invention contains a sulfonamide group having high oxidation resistance in the main chain of the hydrocarbon polymer and does not contain an electron donating group such as an ether bond that is susceptible to deterioration, The main point is that the polymer is less susceptible to oxidative degradation, and it is possible to obtain a solid polymer electrolyte that has practically sufficient durability and is economical.

  Further, a solid polymer electrolyte membrane comprising the solid polymer electrolyte, or an electrolyte / catalyst electrode assembly comprising the solid polymer electrolyte and a catalyst electrode, and further comprising the electrolyte / catalyst electrode assembly and the solid polymer electrolyte membrane The present invention provides a fuel cell using the membrane / electrode assembly.

  The polysulfonamide-based solid polymer electrolyte according to the present invention is much cheaper than a fluorine-based solid polymer electrolyte membrane, and has a sulfonamide group in the main chain, so that it has excellent durability, particularly oxidation resistance. A polymer electrolyte is obtained. In addition, a membrane, an electrolyte / catalyst electrode assembly, a membrane / electrode assembly, and a fuel cell using the polysulfonamide-based solid polymer electrolyte according to the present invention exhibit practically sufficient performance.

  The solid polymer electrolyte of the present invention has a hydrocarbon polymer composed of a sulfonamide group as a main component in the main chain (hereinafter referred to as a polysulfonamide polymer), and has a proton conductive substituent in the side chain. If it is, there will be no restriction | limiting in particular, A 10% or less copolymerization component may be included in a part of main chain.

  The hydrocarbon portion of the main chain is selected from the group consisting of aromatics and derivatives thereof, alkyl groups and derivatives thereof, alkyl groups having at least one fluorine atom as a substituent and derivatives thereof, aromatic groups and derivatives thereof It is sufficient that it is at least one kind.

  The method for obtaining the polysulfonamide-based polymer is not particularly limited, but specifically, a method of reacting a disulfonyl chloride compound and a diamine compound using a base, a method of polymerizing a dihalogenated sulfonamide compound using a metal catalyst or the like and so on.

  As described in Patent Document 2, only polysulfonamide-based polymers exhibit ionic conductivity, but their ionic conductivity is insufficient for use in fuel cells. Therefore, in order to improve the ionic conductivity of the solid polymer electrolyte, it is necessary to introduce a proton conductive substituent into the side chain. The proton conductive substituent is not particularly limited as long as it can conduct protons. Specifically, the sulfonic acid group, phosphonic acid group, carboxylic acid group, sulfonamide group, sulfonimide group, alkylsulfonic acid group, alkylphosphonic acid group are not limited. Group and alkylcarboxylic acid group. Further, the counter ions of these proton conductive substituents are not necessarily limited to protons, and may contain a small amount of ammonium ions or metal ions.

The method for introducing a proton conductive substituent into a polysulfonamide-based polymer is not particularly limited. As a method for converting X ₁ or X ₃ in the formula (1) into a proton conductive substituent, specifically, a polysulfonamide is used. A method of polymerizing a polysulfonamide polymer after introducing a proton-conductive substituent into a disulfonyl chloride compound, a diamine compound or a dihalogenated sulfonamide compound, which is a raw material for polymer polymerization, or a polysulfonamide polymer and sulfuric acid Or a method of introducing a proton conductive substituent by reacting phosphoric acid or the like.

In addition, as a method for converting X ₂ or X ₄ in the formula (1) into a proton conductive substituent, a polysulfonamide-based polymer is used by using a base such as sodium hydroxide, potassium hydroxide, lithium hydride or sodium hydride. There is a method in which the proton of the sulfonamide group is eliminated and reacted with sultone or the like.

When X ₁ or X _{3 in} the formula (1) is a proton conductive substituent, the proton conductive substituent is hardly detached. When X ₂ or X _{4 in} the formula (1) is a proton conductive substituent, high proton conductivity is obtained, but compared with the case where X ₁ or X ₃ in the formula (1) is a proton conductive substituent. Proton conductive substituents are easily removed. Therefore, from the viewpoint of durability, it is preferable that X ₁ or X _{3 in} the formula (1) is a proton conductive substituent.

  Introducing an aromatic ring into the main chain improves the crystallinity of the main chain and improves the mechanical strength of the film, so it is preferable to include this. The aromatic ring to be introduced has no problem as long as it is a divalent aromatic ring, and preferably has a structure represented by the following formula (2). Furthermore, it is desirable that the carbon number is 6-18. Further, an electron withdrawing group such as a nitro group, a cyano group, or a fluorinated alkyl group may be introduced into the aromatic ring.

  The solid polymer electrolyte of the present invention contains these polysulfonamide polymers as main components. That is, additives such as plasticizers, stabilizers, mold release agents and the like used for ordinary polymers can be used within a range not departing from the object of the present invention. Further, in order to improve the mechanical strength of the solid polymer electrolyte, a polysulfonamide polymer introduced with a proton conductive substituent and another hydrocarbon polymer or fluorine polymer are combined with the polysulfonamide polymer. An amount of 30% or less may be mixed so as not to significantly impair the ionic conductivity.

  The ion exchange group equivalent weight of the solid polymer electrolyte used in the present invention is preferably 200 to 3000 g / mol. Furthermore, the ion exchange group equivalent weight is preferably 300 to 2000 g / mol, and more preferably 500 to 1500 g / mol. When the ion exchange group equivalent weight exceeds 3000 g / mol, the ionic conductivity of the solid polymer electrolyte decreases and the output performance decreases, and when it is lower than 200 g / mol, the water resistance of the solid polymer electrolyte decreases. Absent.

In the present invention, the ion exchange group equivalent weight means the weight corresponding to the molecular weight of the polysulfonamide polymer per mole of the introduced proton conductive substituent unit, and the smaller the value, the more proton conductive groups are introduced. Indicates that The ion exchange group equivalent weight is ¹ H-NMR spectroscopy, elemental analysis, acid-base titration and non-hydroxybase titration described in the specification of JP-T-1-52866 (the specified solution is benzene / methanol of potassium methoxide). Measurement is possible with a solution) or the like.

  As a method for controlling the ion exchange group equivalent weight of the polysulfonamide-based solid polymer electrolyte to 200 to 3000 g / mol, the sulfonation rate, the alkyl sulfonation rate, the sulfonamidation rate, the phosphonation rate, and the like may be controlled.

  When the solid polymer electrolyte used in the present invention is used as a fuel cell, it is usually used in a membrane state. There are no particular restrictions on the method of converting the polysulfonamide polymer into a membrane, but a method of forming a film from a solution state (solution casting method), a method of forming a film from a molten state (melt press method or melt extrusion method), etc. are possible. It is. Specifically, with respect to the solution cast method, for example, a polymer solution is cast-coated on a glass plate, and the film is formed by removing the solvent. The solvent used for film formation is not particularly limited as long as it can dissolve and then remove the polysulfonamide compound, and N, N′-dimethylformamide, N, N-dimethylacetamide, N-methyl-2 -Aprotic polar solvents such as pyrrolidone, dimethyl sulfoxide, tetrahydrofuran, etc., or alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dichloromethane, trichloroethane, etc. Alcohols such as halogen solvents, methanol, ethanol, i-propyl alcohol, and t-butyl alcohol are preferably used.

  Although there is no restriction | limiting in particular in the thickness of this solid polymer electrolyte membrane, 10-200 micrometers is preferable. 30-100 micrometers is especially preferable. A thickness of more than 10 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 200 μm is preferable in order to reduce membrane resistance, that is, improve power generation performance. However, even if the film thickness is less than 10 μm, this does not apply as long as the film has a strength that can withstand practical use. In the case of the solution casting method, the film thickness can be controlled by the solution concentration or the coating thickness on the substrate. When the film is formed from a molten state, the film thickness can be controlled by stretching a film having a predetermined thickness obtained by a melt press method or a melt extrusion method at a predetermined magnification.

  The electrolyte / catalyst electrode assembly is prepared by dissolving a polysulfonamide-based solid polymer electrolyte in the solvent used for preparing the solid polymer electrolyte membrane and bonding the catalyst electrode using this.

The catalyst electrode here can be prepared by supporting fine particles of catalyst metal on a conductive material. The catalyst metal used for the catalyst electrode may be any metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen. For example, platinum, gold, silver, palladium, iridium, rhodium, ruthenium, iron , Cobalt, nickel, chromium, tungsten, manganese, vanadium, or alloys thereof. In particular, platinum is often used. The particle size of the metal serving as a catalyst is usually 10 to 300 angstroms. When these catalysts are attached to a carrier such as carbon, the amount of the catalyst used is small and advantageous in terms of cost. The amount of the catalyst supported is preferably 0.01 to 10 mg / cm ² with the electrode formed.

  As the conductive material, any material can be used as long as it is an electron conductive material, and examples thereof include various metals and carbon materials. Examples of the carbon material include carbon black such as furnace black, channel black, and acetylene black, activated carbon, graphite, and the like, and these are used alone or in combination.

  As a method for supporting the catalyst metal on these conductive materials, the catalyst metal is deposited on the surface of the conductive material (mainly used in the case of carbon materials) by a reduction method, or the catalyst metal is suspended in a solvent. There is a method of applying to the surface of a conductive material.

  The membrane / electrode assembly is formed by applying a solution prepared by dissolving a polysulfonamide-based solid polymer electrolyte in the solvent used for the preparation of the solid polymer electrolyte membrane to the electrolyte / catalyst electrode assembly and bonding it to the solid polymer electrolyte membrane. Create with. Here, the electrolyte / catalyst electrode assembly used does not necessarily have to be an electrolyte / catalyst electrode assembly using a polysulfonamide-based solid polymer electrolyte. However, since the solid polymer electrolyte swells with respect to water, joining different solid polymer electrolytes may cause the solid polymer electrolyte and the electrolyte / catalyst electrode assembly to be separated. It is preferable to join with the electrolyte / catalyst electrode assembly using the polysulfonamide-based solid polymer electrolyte used.

  In the fuel cell, a single cell is formed by arranging a current collector with a groove forming a fuel flow path or an oxidant flow path called a separator on the outside of the membrane / electrode assembly formed as described above. A plurality of single cells are stacked through a cooling plate or the like. It is desirable to operate the fuel cell at a high temperature because the catalytic activity of the electrode increases and the electrode overvoltage decreases. However, since the electrolyte membrane does not function without moisture, it needs to be operated at a temperature at which moisture management is possible. The preferable range of the operating temperature of the fuel cell is from room temperature to 100 ° C.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In addition, the measurement conditions of each physical property are as follows.

[Ion exchange group equivalent weight measurement]
Ion exchange group equivalent weight measurement The polysulfonamide polymer of the present invention to be measured is precisely weighed (a (gram)) in a glass container that can be sealed, and an excess amount of calcium chloride aqueous solution is added thereto and stirred overnight. . Hydrogen chloride generated in the system was titrated (b (ml)) with 0.1N sodium hydroxide standard aqueous solution (titer f) using phenolphthalein as an indicator. The ion exchange group equivalent weight (g / mol) was determined from the following formula.
Ion exchange group equivalent weight = (1000 × a) / (0.1 × b × f)

[Ion conductivity measurement]
The solid polymer electrolyte membrane of the present invention was subjected to two-terminal impedance measurement using an electrochemical impedance measurement device (manufactured by Solartron, SI1287) in a frequency range of 0.1 Hz to 65 kHz, and ion conductivity was measured. In addition, the said measurement was implemented at 75 degreeC by water vapor | steam atmosphere.

[Oxidation resistance test]
The solid polymer electrolyte membrane of the present invention was immersed in a Fenton reagent (containing 40 ppm of iron) heated to 60 ° C. consisting of adding 0.63 mg of iron sulfate heptahydrate to 20 ml of 10% aqueous hydrogen peroxide, The time required for the polymer electrolyte membrane to dissolve in the Fenton reagent was determined.

[Fuel cell single cell performance evaluation]
The membrane / electrode assembly was incorporated into an evaluation cell, and the fuel cell output performance was evaluated. Hydrogen / oxygen was used as a reaction gas, and both were humidified through a water bubbler at 70 ° C. at a pressure of 1 atm, and then supplied to the evaluation cell. The gas flow rate was 60 ml / min for hydrogen, 40 ml / min for oxygen, and the cell temperature was 75 ° C. The battery output performance was evaluated by an H201B charge / discharge device (made by Hokuto Denko).

[Example 1]
(1) Synthesis of sulfonated benzene-hexamethylene polysulfonamide While stirring an amine solution consisting of 11.6 g of hexamethylenediamine, 21.2 g of sodium carbonate, 8.0 g of sodium lauryl sulfate, and 800 ml of water, m-benzenedisulfonyl chloride A disulfonyl chloride solution consisting of 27.5 g and 800 ml of methylene chloride was added dropwise. After stirring for 15 minutes, 400 ml of methanol was added, resulting in a white precipitate. The resulting precipitate was washed with ethanol by a mixer, washed with deionized water and suction filtration three times, and then dried under reduced pressure at 120 ° C. overnight.

  The inside of the 500 ml four-necked round bottom flask was purged with nitrogen, and then 200 ml of chlorosulfuric acid was added. While maintaining the temperature at 5 ° C., 31.2 g of the above benzene-hexamethylene polysulfonamide was dissolved. After stirring for 30 minutes, the reaction solution was slowly added dropwise to 10 l of deionized water to precipitate sulfonyl chloride benzene-hexamethylene polysulfonamide, which was collected by filtration. The resulting precipitate was repeatedly washed with deionized water using a mixer and collected by suction filtration until the filtrate became neutral.

The obtained sulfonyl chloride benzene-hexamethylene polysulfonamide is hydrolyzed by immersing it in an excess aqueous sodium hydroxide solution, boiled with a hydrochloric acid solution, and then dried under reduced pressure at 120 ° C. overnight, thereby sulfonated benzene-hexamethylene polysulfone. The amide was obtained.
The resulting sulfonated benzene-hexamethylene polysulfonamide had an ion exchange group equivalent weight of 1000 g / mol.

(2) Production of solid polymer electrolyte membrane The product obtained in the above (1) was dissolved in methanol to a concentration of 10% by weight. This solution was spread on glass with a doctor knife and dried to prepare a solid polymer electrolyte membrane having a thickness of 40 μm.

(3) Preparation of catalyst electrode layer, membrane / electrode assembly, and fuel cell 40% by weight of platinum-supported carbon was mixed with the 10% by weight methanol solution of (2) above with platinum-supported carbon and solid polymer electrolyte. The mixture was added so that the weight ratio was 2: 1 and dispersed uniformly to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to both sides of the solid polymer electrolyte membrane obtained in (2) above, and dried to prepare a membrane / electrode assembly having a platinum loading of 0.25 mg / cm ² . When this was used to evaluate the performance of a single fuel cell, an output of 40 mW / cm ² was shown.

[Example 2]
(1) Synthesis of sulfobutylated benzene-hexamethylene polysulfonamide 31.2 g of benzene-hexamethylene polysulfonamide described in Example 1 was dissolved in 200 ml of 1N aqueous sodium hydroxide solution. While stirring this, a butane sultone solution consisting of 6.7 g of 1,4-butane sultone and 20 ml of ethanol was added dropwise. After stirring at 70 ° C. for 3 hours, 1N hydrochloric acid solution was added dropwise to the reaction solution to precipitate sulfobutylated polysulfonamide, which was collected by filtration. The resulting precipitate was repeatedly washed with deionized water using a mixer and collected by suction filtration until the filtrate became neutral. The resulting sulfobutylated polysulfonamide had an ion exchange group equivalent weight of 1300 g / mol.

(2) Production of Solid Polymer Electrolyte Membrane A solid polymer electrolyte membrane with a thickness of 40 μm was produced in the same manner as in Example 1.

(3) Production of catalyst electrode layer, membrane / electrode assembly and fuel cell A membrane / electrode assembly having a platinum loading of 0.25 mg / cm ² was produced in the same manner as in Example 1. When this was used to evaluate the performance of a single fuel cell, an output of 40 mW / cm ² was shown.

[Example 3]
(1) Synthesis of sulfobutylated benzene-benzenepolysulfonamide While stirring an amine solution consisting of 12.7 g of p-aminochlorobenzene and 100 ml of water, 21.1 g of p-chlorobenzenesulfonyl chloride was added. When 8 g of sodium hydroxide was added thereto, p-chlorobenzenesulfonyl chloride was dissolved. When this was neutralized with hydrochloric acid, a white precipitate was formed. The resulting precipitate was repeatedly washed three times with deionized water washing using a mixer and suction filtration, and then dried under reduced pressure at 60 ° C. overnight.

  30.2 g of the above sulfonamide was dissolved in 50 ml of dimethylacetamide (dehydrated), 50 mg of nickel chloride (anhydrous), 70 mg of bipyridine, 3.8 g of triphenylphosphine, and 8.7 g of zinc were added, and the mixture was stirred at 80 ° C. for 8 hours. After removing the metal salt with hydrochloric acid, the collection operation by deionized water washing with a mixer and suction filtration was repeated, followed by drying under reduced pressure at 120 ° C. overnight.

31.0 g of the above benzene-benzenepolysulfonamide was dissolved in 200 ml of 1N aqueous sodium hydroxide solution. While stirring this, a butane sultone solution consisting of 6.7 g of 1,4-butane sultone and 20 ml of ethanol was added dropwise. After stirring at 70 ° C. for 3 hours, 1N hydrochloric acid solution was added dropwise to the reaction solution to precipitate sulfobutylated benzene-benzenepolysulfonamide, which was collected by filtration. The resulting precipitate was repeatedly washed with deionized water using a mixer and collected by suction filtration until the filtrate became neutral.
The obtained sulfobutylated benzene-benzenepolysulfonamide had an ion exchange group equivalent weight of 1000 g / mol.

(2) Production of solid polymer electrolyte membrane The product obtained in (1) was dissolved in dimethyl sulfoxide so as to have a concentration of 10% by weight. This solution was spread on glass with a doctor knife and dried to prepare a solid polymer electrolyte membrane having a thickness of 40 μm.

(3) Preparation of catalyst electrode layer, membrane / electrode assembly and fuel cell 40% by weight of platinum-supported carbon was mixed with 10% by weight dimethyl sulfoxide solution of (2), platinum-supported carbon and solid polymer electrolyte. Was added so that the weight ratio was 2: 1 and dispersed uniformly to prepare a paste (electrode catalyst coating solution). This electrode catalyst coating solution was applied to both sides of the solid polymer electrolyte membrane obtained in the above (2) and then dried to prepare a membrane / electrode assembly having a platinum loading of 0.25 mg / cm ² . When this was used to evaluate the performance of a single fuel cell, an output of 40 mW / cm ² was shown.

[Comparative Example 1]
(1) Synthesis of sulfonated polyethersulfone After the inside of a 500 ml four-necked round bottom flask equipped with a reflux condenser connected with a stirrer, thermometer and calcium chloride tube was purged with nitrogen, 25 g of polyethersulfone ( PES) (Amoco Engineering Polymer, Radel) and 125 ml of concentrated sulfuric acid were added. The mixture was stirred overnight at room temperature under a nitrogen stream to obtain a uniform solution. To this solution, 48 ml of chlorosulfuric acid was added dropwise from a dropping funnel while stirring under a nitrogen stream. Since the chlorosulfuric acid reacted vigorously with the water in the concentrated sulfuric acid and foamed for a while after the start of the dripping, it was dropped slowly, and after the foaming became mild, the dropping was finished within 5 minutes. After completion of the dropwise addition, the reaction solution was sulfonated by stirring at 25 ° C. for 3.5 hours. The reaction solution was then slowly added dropwise to 15 l of deionized water to precipitate sulfonated polyethersulfone, which was collected by filtration. The deposited precipitate was repeatedly washed with deionized water by a mixer and collected by suction filtration until the filtrate became neutral, and then dried under reduced pressure at 80 ° C. overnight.
The resulting sulfonated polyethersulfone electrolyte had an ion exchange group equivalent weight of 960 g / mol.

(2) Production of Solid Polymer Electrolyte Membrane A solid polymer electrolyte membrane having a thickness of 40 μm was produced in the same manner as in Example 3.

[Comparative Example 2]
(1) Synthesis of benzene-hexamethylene polysulfonamide Benzene-hexamethylene polysulfonamide was synthesized in the same manner as in Example 1.
(2) Production of Solid Polymer Electrolyte Membrane A solid polymer electrolyte membrane having a thickness of 40 μm was produced in the same manner as in Example 3.

  For Examples 1 to 3 and Comparative Examples 1 and 2 above, an oxidation resistance test and ion conductivity measurement were performed. The evaluation results are shown in Table 1.

Claims (8)

A solid polymer electrolyte having a hydrocarbon compound containing a repeating unit having a structure represented by the following formula (1) as a main chain and having a proton-conductive substituent in a side chain.

(R ₁ and R ₂ are groups selected from the group consisting of aromatics and derivatives thereof, alkyl groups and derivatives thereof, alkyl groups having at least one fluorine atom as a substituent, and derivatives thereof, wherein X ₁ , X ₂ , X ₃ and X ₄ are arbitrary groups, and any one is a proton-conductive substituent.)   The proton conductive substituent is at least one selected from the group consisting of a sulfonic acid group, a phosphonic acid group, a carboxylic acid group, a sulfonamide group, a sulfonimide group, an alkylsulfonic acid group, an alkylphosphonic acid group, and an alkylcarboxylic acid group. The solid polymer electrolyte according to claim 1, which is a seed. _3. The solid polymer electrolyte according to claim 1, wherein R ₁ or R ₂ is a group containing one or more aromatic groups represented by the following formula (2).

  A solid polymer electrolyte membrane comprising the solid polymer electrolyte according to any one of claims 1 to 3.   An electrolyte / catalyst electrode assembly comprising a catalyst electrode in which fine particles of a catalytic metal are supported on the surface of a conductive material made of a carbon material, and the solid polymer electrolyte according to any one of claims 1 to 3.   A membrane / electrode assembly comprising the solid polymer electrolyte membrane according to claim 4 and an electrolyte / catalyst electrode assembly.   A membrane / electrode assembly comprising the solid polymer electrolyte membrane according to claim 4 and the electrolyte / catalyst electrode assembly according to claim 5.   A fuel cell using the membrane / electrode assembly according to claim 6 or 7.