JP2005183061A - Proton conductive high polymer film, and forming method for proton conductive high polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a proton conductive high polymer film which is useful as a polyelectrolytic film for a solid high polymer type fuel cell and a direct methanol type fuel cell, and has an outstanding property, and its stable and inexpensive manufacturing method. <P>SOLUTION: By using the manufacturing method in which a high polymer film is immersed in an organic solvent for reaction comprising a sulfonation agent after the high polymer film is swollen in a swelling organic solvent, proton conductivity in the thickness direction of a sulfonation high polymer film using the swollen high polymer film becomes higher, when compared in the same sulfonation condition. Moreover, a proton conductive high polymer film having proton conductivity equivalent to a conventional one is formed with a smaller amount of a sulfonation agent and by a shorter period of reaction time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a proton conductive polymer membrane useful as a polymer electrolyte membrane for a polymer electrolyte fuel cell and a method for producing the same.

  The proton conductive polymer membrane is useful as a main constituent material of electrochemical devices such as a polymer electrolyte fuel cell, a humidity sensor, a gas sensor, and an electrochromic display device. Among these electrochemical devices, solid polymer fuel cells are expected to be put into practical use in a wide range as one of the pillars of new energy technology. Solid polymer polymer fuel cells (PEFC or PEMFC) that use proton conductive polymer membranes made of polymer compounds as electrolyte membranes can be operated at low temperatures and can be reduced in size and weight. Application to mobile objects, home cogeneration systems, and small portable devices for consumer use is under consideration. In particular, fuel cell vehicles equipped with PEFC have features such as high energy efficiency and low carbon dioxide emission, and social interest is increasing as the ultimate ecological car. In addition, methanol-fueled direct methanol fuel cells (DMFCs) have a simple structure, ease of fuel supply and maintenance, and high energy density. It is expected to be applied to small consumer portable devices such as mobile phones and notebook computers.

  Examples of proton conductive polymer membranes include styrene-based cation exchange membranes developed in the 1950s. However, this styrene-based cation exchange membrane has poor stability under the fuel cell operating environment, and has not been able to produce a fuel cell having a sufficient life.

  As a proton conductive membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark of Nafion, DuPont, the same applies hereinafter) has been developed and applied to many electrochemical devices such as PEFC. The application of is applied. The perfluorocarbon sulfonic acid membrane has high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance. However, the manufacturing process is complicated and expensive. In addition, the permeation amount of methanol, which is considered promising as fuel for fuel cells mounted on consumer portable devices, so-called crossover is large, and the phenomenon that permeated methanol burns at the cathode, that is, a chemical short reaction occurs. There is. When the chemical short reaction occurs, not only the cathode potential is lowered and the cell characteristics are lowered, but also the fuel efficiency is lowered. In addition, proton-conducting polymer membranes of fluorine-containing compounds such as Nafion have a large environmental impact during synthesis and disposal, and are not necessarily a constituent material for fuel cells, which is basically a technology for dealing with environmental problems. Not appropriate.

  For this reason, various non-perfluorocarbon sulfonic acid type proton conductive polymer membranes composed of sulfonated aromatic polymer compounds have been proposed as proton conductive polymer membranes that are easy to manufacture and cheaper. ing. Typical examples thereof include sulfonated polyetheretherketone (see, for example, Patent Document 1), sulfonated polyethersulfone (see, for example, Patent Document 2), and sulfonated polysulfone (for example, Patent Document 1). 3) and sulfonated polyimides of heat-resistant aromatic polymers such as sulfonated polyimide (see, for example, Patent Document 4) have been proposed. In addition, a proton conductive polymer membrane (see Patent Document 5) made of a sulfonated SEBS (styrene- (ethylene-butylene) -styrene) that is inexpensive and mechanically and chemically stable is proposed. Has been. These sulfonated hydrocarbon polymer membranes are said to be easy to manufacture and cost-effective.

  However, the proton conductivity is insufficient for use as a PEFC electrolyte membrane that requires high proton conductivity. In order to improve this, if the amount of proton-conductive substituents such as sulfonic acid groups is increased, the mechanical properties such as tensile and elongation are reduced, and the water absorption becomes higher, increasing the water absorption rate of the membrane. As a result, the handling property is remarkably impaired due to significant swelling. Also, for methanol, which is a promising fuel for fuel cells for small portable devices, proton conductivity and methanol permeability are in a trade-off relationship. Therefore, in order to obtain high proton conductivity, sulfonic acid groups, etc. Increasing the amount of proton-conductive substituent introduced increases the methanol crossover and causes a chemical short reaction. When the chemical short reaction occurs, not only the cathode potential is lowered and the cell characteristics are lowered, but also the fuel efficiency is lowered, and the use thereof may be restricted.

  The polymer electrolyte membrane made of a hydrocarbon polymer compound has many problems in the manufacturing process in addition to the above problems in characteristics.

  Patent Document 6 discloses a method for producing a sulfonated aromatic polymer membrane such as sulfonated polyphenylene sulfide. In this method for producing a sulfonated aromatic polymer membrane, it is described that chlorosulfonic acid is used as a sulfonating agent and dichloromethane is used as a solvent.

In the production method, the polymer film is immersed in an organic solvent containing a sulfonating agent. The reaction rate of introducing the sulfonic acid group into the polymer film is determined by the dissolution of the sulfonating agent into the polymer film. Since the rate and the diffusion rate are considered to be rate-limiting, distribution of the amount of sulfonic acid group introduced occurs in the thickness direction of the sulfonated polymer membrane. That is, there is a problem that the introduction amount of sulfonic acid groups is smaller toward the inside of the polymer film, and as a result, proton conductivity in the thickness direction of the sulfonated polymer membrane is reduced. In addition, when trying to obtain a proton conductive polymer membrane in which sulfonic acid groups are uniformly introduced to the inside, the production efficiency is poor because a large amount of sulfonating agent is required or the reaction time is required to be long. There was a problem.
JP-A-6-93114 Japanese Patent Laid-Open No. 10-45913 JP-A-9-245818 JP 2000-510511 A Japanese National Patent Publication No. 10-503788 International Publication No. 02/062896 Pamphlet

  The present invention has been made in view of the above problems, and is a proton conductive polymer membrane useful as a polymer electrolyte membrane of a solid polymer fuel cell or a direct methanol fuel cell and a method for producing the same, and is excellent It is an object of the present invention to provide a proton conducting polymer membrane having excellent characteristics and a method for producing the membrane stably and inexpensively.

  That is, the method for producing a proton conducting polymer membrane of the present invention relates to immersing a polymer film in a reaction organic solvent containing a sulfonating agent after swelling the polymer film in a swelling organic solvent. Compared with the same sulfonation conditions, the sulfonated polymer membrane using the polymer film after swelling is made by immersing it in a reaction organic solvent containing a sulfonating agent after swelling. The proton conductivity in the film thickness direction is increased, and further, a proton conductive polymer membrane having a proton conductivity equivalent to the conventional one is obtained with a smaller amount of sulfonating agent and with a shorter reaction time.

  When the swelling is carried out in an organic solvent for swelling at a temperature of 50 ° C. or higher and 200 ° C. or lower, it is preferable because the polymer film can be efficiently swollen. Further, the organic solvent for swelling and / or the organic solvent for reaction is preferably a halogen-containing compound from the viewpoint of further efficient swelling. In particular, the organic solvent for swelling and / or the organic solvent for reaction are included in the molecular structure. A compound containing 3 or more carbon atoms and 1 or more halogen atoms is preferred.

  The polymer film used for the production of the proton conducting polymer membrane of the present invention is preferably a hydrocarbon polymer film, and in particular, a hydrocarbon polymer comprising at least one selected from the following group (A). It is preferably made of a hydrocarbon polymer obtained by mixing polymers.

  Group (A): polybenzimidazole (PBI), polybenzoxazole (PBO), polybenzothiazole (PBT), polysulfone (PSU), polyetherethersulfone (PEES), polyarylethersulfone (PAS), polyphenylenesulfone ( PPSU), polyphenylene oxide (PPO), polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO2), polyparaphenylene (PPP), polyether ketone (PEK), polyether ether ketone (PEEK) ), Polyether ketone ketone (PEKK), cyanate ester resin. Furthermore, it is preferable that the hydrocarbon polymer film is made of polyphenylene sulfide (PPS) because a proton conductive polymer membrane having excellent characteristics can be obtained.

  The sulfonating agent used in the method for producing a proton conductive polymer membrane of the present invention is preferably composed of at least one selected from chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, and concentrated sulfuric acid.

  The proton conductive polymer membrane of the present invention is used as a proton conductive membrane for a solid polymer fuel cell, particularly preferably as a proton conductive membrane for a direct methanol fuel cell.

  According to the present invention, when compared with the same sulfonation conditions (same sulfonating agent amount / concentration, same reaction temperature, reaction time), the sulfonated polymer membrane using the polymer film after swelling is more in the thickness direction. Proton conductivity increases. Furthermore, a proton conductive polymer membrane having a proton conductivity equal to or higher than that of the conventional one can be obtained with a smaller amount of sulfonating agent or with a shorter reaction time.

  The method for producing a proton conductive polymer membrane of the present invention is characterized in that a polymer film is immersed in a reaction organic solvent containing a sulfonating agent after swelling with a swelling organic solvent. It is a manufacturing method of a molecular film.

  In the present invention, the swelling of the polymer film means that a swelling organic solvent is contained inside the polymer film, and the weight change before and after the polymer film is immersed in the swelling organic solvent, that is, “swelling organic solvent”. The value obtained by dividing “the weight of the polymer film after being immersed in the solvent” by “the weight of the polymer film before being immersed in the organic solvent for swelling” is greater than 1.

  The polymer film has a weight change of more than 1 and 2 or less. Preferably, it is larger than 1.01 and 1.5 or less. When the weight change is 1 or less, the organic film for swelling is not contained in the polymer film, and the polymer film is not swollen, and the effect in the present invention cannot be expressed. When the weight change is larger than 2, the strength of the proton conductive polymer membrane produced using the swollen polymer film is lowered and cannot be put to practical use.

  Moreover, the atmospheric temperature which swells a polymer film is more than room temperature. The atmospheric temperature is preferably 50 ° C. to 200 ° C. because the organic solvent can be easily introduced into the polymer film in a shorter time. More preferably, it is 60 degreeC-150 degreeC. When the atmospheric temperature exceeds 200 ° C., the appearance is impaired such as wrinkles in the polymer film or deformation due to distortion. When the ambient temperature is below room temperature, it is necessary to turn on the air to keep the ambient temperature below room temperature, or it is necessary to introduce a cooling device, and when the ambient temperature falls below room temperature, It is thought that the diffusion rate of the organic solvent into the film is lowered, and it is inferior in economic efficiency because it takes a long time for swelling.

  The swelling organic solvent usable in the present invention and (2) can be used as long as they do not practically react with the sulfonating agent and do not deteriorate the polymer film. For example, hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, Acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, 1,1,2,2-tetrachloroethane 1,1,1,2-tetrachloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, dichloromethane, dibromomethane, diiodomethane, 1,2-dichloroethane, 1,2-dibromoethane, 1,2-diiodoethane 1-chloropropane, 1-bromopropane, 1-iodopropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 1-bromobutane, 2-bromobutane, 1-bromo-2-methylpropane, 1 -Iodobutane, 2-iodobutane, 1-iodo-2-methylpropane, 1-chloropentane, 1-bromopentane, 1-iodopentane, 1-chlorohexane, 1-bromohexane, 1-iodohexane, chlorocyclohexane, bromo Examples include cyclohexane and iodocyclohexane.

  Because of the ease of swelling of polymer films, organic solvents for swelling include acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone Pyrrolidone solvents such as 1,1,2,2-tetrachloroethane, 1,1,1,2-tetrachloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, dichloromethane, dibromomethane, diiodomethane, 1,2 -Dichloroethane, 1,2-dibromoethane, 1,2-diiodoethane and the like are preferred. In particular, considering the ease of handling of the solvent used and the properties of the resulting proton conducting polymer membrane, the organic solvent for reaction includes three or more carbon atoms and at least one or more carbon atoms in its molecular structural formula. An organic solvent containing a chlorine atom is preferable, and 1-chloropropane, 1-bromopropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 1-bromobutane, 2-bromobutane, 1-bromo- It is preferably at least one selected from the group consisting of 2-methylpropane, 1-chloropentane, 1-bromopentane, 1-chlorohexane, 1-bromohexane, chlorocyclohexane and bromocyclohexane. Furthermore, at least one selected from 1-chloropropane, 1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane, 1-chloropentane, 1-chlorohexane and chlorocyclohexane because of industrial availability. It is preferable that Among the solvents, 1-chlorobutane is preferable from the viewpoints of industrial availability and the properties of the obtained proton conductive polymer membrane.

  In the present invention, the sulfonic acid group means a substituent containing a sulfonic acid group represented by the following formula (1) or a sulfonic acid group represented by the following general formula (2).

-SO ₃ H (1)
-R-SO ₃ H (2)
[In the formula, R may contain a divalent organic group composed of at least one bond unit selected from the group consisting of alkylene, halogenated alkylene, arylene, and halogenated arylene, or an ether bond.]
The proton conductive polymer compound of the present invention is preferably composed of a hydrocarbon polymer in consideration of methanol blocking properties and the like. Examples of the hydrocarbon polymer compound include polyacrylamide, polyacrylonitrile, polyaryl ether sulfone, poly (allyl phenyl ether), polyethylene oxide, polyether ether sulfone, polyether ketone, polyether ketone ketone, polyvinyl chloride, Poly (diphenylsiloxane), poly (diphenylphosphazene), polysulfone, polyparaphenylene, polyvinyl alcohol, poly (phenylglycidyl ether), poly (phenylmethylsiloxane), poly (phenylmethylphosphazene), polyphenylene ether, polyphenylene Oxide, polyphenylene sulfoxide, polyphenylene sulfide sulfone, polyphenylene sulfone, polybenzimidazole, polybenzoxazole Polybenzothiazole, poly (α-methylstyrene), polystyrene, styrene- (ethylene-butylene) styrene copolymer, styrene- (polyisobutylene) -styrene copolymer, poly1,4-biphenylene ether ether sulfone, polyarylene Examples include ether sulfone, polyether imide, cyanate resin, polyethylene, polypropylene, polyamide, polyacetal, polybutylene terephthalate, polyethylene terephthalate, syndiotactic polystyrene, polyphenylene sulfide, polyether ether ketone, and polyether nitrile.

  Among them, polybenzimidazole is considered when it is easy to introduce a sulfonic acid group and / or a substituent containing a sulfonic acid group, and the properties such as proton conductivity, mechanical properties, and chemical stability of the obtained membrane. , Polybenzoxazole, polybenzothiazole, polysulfone, polyether ether sulfone, polyaryl ether sulfone, polyphenylene sulfone, polyphenylene oxide, polyphenylene sulfoxide, polyphenylene sulfide sulfone, polyparaphenylene, polyether ketone, polyether ketone ketone, cyanate ester It is preferably at least one selected from the group consisting of a resin, syndiotactic polystyrene, polyphenylene sulfide, polyether ether ketone, and polyether nitrile.

  Furthermore, in the present invention, the introduction of a sulfonic acid group and / or a substituent containing a sulfonic acid group, the proton conductivity of the obtained membrane, mechanical properties, chemical stability, fuel such as hydrogen, methanol, etc. In consideration of properties such as blocking properties, blocking properties of oxidants such as oxygen and air, hydrocarbon polymer compounds are crystalline aromatic polymer compounds such as syndiotactic polystyrene, polyphenylene sulfide, and polyether ether ketone. Preferably there is. Furthermore, polyphenylene sulfide is more preferable because it has high proton conductivity, excellent mechanical properties, and high methanol barrier properties.

  Specifically, the polyphenylene sulfide of the present invention is composed of a repeating structural unit represented by the following formula (3).

-[Ar-S] _n- (3)
[Wherein Ar is a divalent aromatic unit represented by the following formulas (4) to (6), and n is an integer of 1 or more]

また前記ポリフェニレンサルファイドのＡｒの一部に、必要に応じて以下の（Ａ）〜（Ｃ）の構造単位を含有してもよい。
（Ａ）芳香族単位の水素原子の一部がアルキル基、フェニル基、アルコキシル基、ニトロ基およびハロゲン基からなる群から選択される少なくとも１つの置換基で置換されたもの。
（Ｂ）３官能フェニルスルフィド単位。
（Ｃ）架橋または分岐単位。

Moreover, you may contain the structural unit of the following (A)-(C) in some Ar of the said polyphenylene sulfide as needed.
(A) A part of hydrogen atoms of an aromatic unit is substituted with at least one substituent selected from the group consisting of an alkyl group, a phenyl group, an alkoxyl group, a nitro group and a halogen group.
(B) Trifunctional phenyl sulfide unit.
(C) Cross-linked or branched unit.

  The thickness of the proton conducting polymer membrane of the present invention can be selected arbitrarily depending on the application. When considering reducing the internal resistance of the membrane, the range has practical mechanical strength, and when used for an electrolyte membrane of a polymer electrolyte fuel cell, the range has a blocking property of fuel and oxidant. And the thinner each, the better. As the characteristics of the electrolyte membrane, as the ion exchange capacity and proton conductivity are equal, the resistance value as the membrane decreases as the thickness decreases. Therefore, the thickness of the film is preferably 5 to 200 μm, more preferably 20 to 150 μm. When this thickness is less than 5 μm, pinholes and film cracking tend to occur during use. Further, when used as an electrolyte membrane of a polymer electrolyte fuel cell, the barrier property of the fuel and the oxidant is insufficient, which tends to cause performance deterioration. Further, when used as an electrolyte membrane of a direct methanol fuel cell, the methanol barrier property is insufficient, and there is a tendency that performance is deteriorated due to methanol permeation. On the other hand, when it exceeds 200 μm, the resistance of the proton-conductive polymer membrane increases, which tends to cause performance degradation.

  As the sulfonating agent, known sulfonating agents such as chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, sulfur trioxide-triethyl phosphate, concentrated sulfuric acid, and trimethylsilyl chlorosulfate can be used. Considering the ease of industrial availability, the ease of introduction of sulfonic acid groups, and the properties of the resulting proton conductive polymer membrane, the use of these sulfonating agents is preferred. In particular, in the present invention, it is more preferable to use chlorosulfonic acid from the viewpoint of easy introduction of a sulfonic acid group, characteristics of the obtained membrane, industrial availability, and the like.

  In addition, by optimizing the reaction system, cyclic sulfur-containing compounds such as propane sultone and 1,4-butane sultone and hydrocarbon polymer compounds in the presence of a catalyst such as aluminum chloride according to the Friedel-Crafts reaction A method of introducing a substituent containing a sulfonic acid group such as a sulfopropyl group or a sulfobutyl group by bringing the aromatic unit inside into contact with each other can also be used.

  As a usage-amount of a sulfonating agent, it is preferable that it is 0.5-30 equivalent with respect to the aromatic unit in a hydrocarbon type polymer compound, Furthermore, it is preferable that it is 0.5-15 equivalent. When the amount of the sulfonating agent used is less than 0.5 equivalent, the amount of sulfonic acid groups introduced is decreased, and the properties of the resulting proton conducting polymer membrane tend to be insufficient. On the other hand, when the amount exceeds 30 equivalents, the polymer film is chemically deteriorated, the mechanical strength of the resulting proton conductive polymer membrane is lowered, and handling becomes difficult. On the other hand, there is a tendency that the practical properties of the proton-conducting polymer membrane are impaired, for example, the methanol blocking property is lowered due to excessive increase.

  The concentration of the sulfonating agent in the solvent may be appropriately set in consideration of the target introduction amount of sulfonic acid groups and reaction conditions (temperature / time). Specifically, it is preferably 0.1 to 10% by weight, and a more preferable range is 0.2 to 5% by weight. If it is lower than 0.1% by weight, the sulfonating agent and the aromatic unit in the polymer compound are difficult to contact, and the desired sulfonic acid group cannot be introduced or it takes a long time to introduce. is there. On the other hand, if it exceeds 10% by weight, the introduction of sulfonic acid groups tends to be uneven, and the mechanical properties of the resulting proton conducting polymer membrane tend to be impaired.

  The reaction temperature and reaction time for contacting are not particularly limited, but are set in the range of 0 to 100 ° C., more preferably 10 to 30 ° C., 0.1 hour or more, more preferably 2 to 100 hours. Is good. When the reaction temperature is lower than 0 ° C., cooling equipment and the like are required, and the reaction tends to take more time than necessary, which is not preferable, and when it exceeds 100 ° C., the reaction proceeds excessively, It is not preferable because it tends to cause side reactions and deteriorate the characteristics of the film. In addition, when the reaction time is shorter than 0.1 hour, the contact between the sulfonating agent and the aromatic unit in the polymer compound becomes insufficient, and it is difficult to introduce a desired sulfonic acid group. When the time exceeds 100 hours, productivity tends to be remarkably lowered, and a great improvement in film properties tends not to be expected. Actually, it is set so that a proton conductive polymer membrane having desired characteristics can be efficiently produced in consideration of a reaction system such as a sulfonating agent and a solvent to be used and a target production amount. do it.

  The method for producing a sulfonated polymer membrane of the present invention may be carried out continuously. That is, after a film made of a polymer compound to be treated is immersed in a swelling solvent and swollen, it is supplied to a reaction tank with a sulfonating agent, and a washing process and a drying process are continued as necessary. May be implemented. This method further improves the productivity of the sulfonated polymer membrane.

  Moreover, a sulfonic acid group can be introduce | transduced with a film (film | membrane) shape by making a polymer film contact with a sulfonating agent within a reaction tank. Therefore, compared to the conventional method of synthesizing a sulfonated polymer in a homogeneous reaction system and then processing it into a membrane shape, steps such as recovery / purification / drying of reactants, dissolution of the sulfonated polymer in a solvent It is preferable because steps such as coating on a support and solvent removal can be omitted. Furthermore, since the film is continuously supplied, the productivity is remarkably improved.

  In addition, by continuously removing and washing the sulfonating agent attached to and / or contained in the film immersed in the reaction vessel, it is possible to prevent peripheral devices from being corroded by the sulfonating agent and to handle the film. Improve. The conditions for removal / washing may be appropriately set in consideration of the type of sulfonating agent and polymer compound to be used, but the remaining sulfonating agent is inactivated by washing with water or neutralized using alkali. It may be processed.

  Furthermore, by continuously drying the obtained sulfonated polymer membrane, the sulfonated polymer membrane can be recovered in a practically usable form. The drying conditions may be appropriately set in consideration of the type of polymer film used and the characteristics of the sulfonated polymer membrane to be obtained. Since the sulfonic acid group has strong hydrophilicity, it may be swelled with water during the washing process. Therefore, it shrinks during drying, and there is a risk that irregularities such as wrinkles and swelling occur. Therefore, it is preferable to dry by applying an appropriate tension in the surface direction of the sulfonated polymer membrane during drying. Moreover, in order to suppress rapid drying, you may dry gradually under adjustment of humidity.

Depending on the sulfonating agent used and the reaction conditions for sulfonation, for example, when polyphenylene sulfide is used as the polymer compound, the sulfide unit (—S—) in the polymer film is replaced with the sulfoxide unit (—SO—) or sulfone. Oxidized to unit (—SO ₂ —), sulfoxide unit (—SO—) oxidized to sulfone unit (—SO ₂ —), and hydrogen of phenylene unit substituted with substituent such as —Cl Side reactions may occur. However, as long as the properties of the obtained sulfonated polymer membrane are not significantly deteriorated, a structural unit resulting from the side reaction may be included.

  In order to further improve the characteristics of the sulfonated polymer membrane produced by the above method, it is preferable to irradiate radiation such as electron beam, γ-ray, ion beam and the like.

  Next, a solid polymer fuel cell (direct methanol fuel cell) using the sulfonated polymer membrane of the present invention will be described with reference to the drawings as an example.

  FIG. 1 is a cross-sectional view of an essential part of a solid polymer fuel cell (direct methanol fuel cell) using a sulfonated polymer membrane of the present invention.

  This comprises a sulfonated polymer membrane 1, a catalyst-carrying gas diffusion electrode 2 in contact with one membrane, a fuel gas or liquid formed in the separator 4, and a flow path 3 for feeding an oxidant. It is.

  Methods for joining the catalyst-supported gas diffusion electrode 2 to the sulfonated polymer membrane 1 have been studied in the past, such as sulfonated polymer membranes made of perfluorocarbon sulfonic acid membranes and sulfonated polymer membranes made of polymer compounds ( For example, a known method performed with sulfonated polyether ether ketone, sulfonated polyether sulfone, sulfonated polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide, or the like is applicable.

  Specifically, a method using a commercially available gas diffusion electrode (manufactured by E-TEK, USA) can be exemplified, but the method is not limited thereto.

  As an actual method, an alcohol solution of a perfluorocarbon sulfonic acid polymer (such as a Nafion solution manufactured by Aldrich), a sulfonated polymer compound constituting the sulfonated polymer membrane of the present invention, or a known sulfonated polymer compound Both surfaces of the sulfonated polymer membrane 1 of the present invention using an organic solvent solution (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide) as a binder. The surface of the catalyst-carrying gas diffusion electrode 2 on the catalyst layer side is aligned, and bonding can be generally performed at a press temperature of about 120 to 250 ° C. using a press machine such as a hot press machine or a roll press machine. Moreover, it is not necessary to use a binder as needed. Further, the catalyst-carrying gas diffusion electrode 2 may be prepared using the following materials and bonded to the sulfonated polymer membrane 1 for use.

  Here, the material used to prepare the catalyst-carrying gas diffusion electrode 2 includes, as a catalyst, a metal such as platinum or ruthenium or an alloy thereof that promotes a fuel oxidation reaction and oxygen reduction reaction, a catalyst carrier, Conductive materials such as fine-particle carbon materials (for example, carbon nanohorns, fullerenes, activated carbon, carbon nanotubes, etc.) as conductive materials, fluorine-containing resins having water repellency as binders, etc., if necessary Examples of the support include carbon cloth and carbon paper, and examples of the impregnation / coating material include perfluorocarbon sulfonic acid polymers, but the present invention is not limited thereto.

  A joined body of the sulfonated polymer membrane 1 obtained by the above method and the catalyst-carrying gas diffusion electrode 2 is made of a pair of graphite in which a flow path 3 for feeding fuel gas or liquid and oxidant is formed. Is inserted between the gas separators 4 and the like to obtain a solid polymer fuel cell (direct methanol fuel cell) comprising the sulfonated polymer membrane of the present invention. A gas containing hydrogen as a main component, a gas or liquid containing methanol as a main component as a fuel gas or liquid, and a gas containing oxygen (oxygen or air) as an oxidant are supplied from separate flow paths 3 respectively. By supplying the catalyst-supported gas diffusion electrode 2, the polymer electrolyte fuel cell operates. At this time, when methanol is used as the fuel, a direct methanol fuel cell is obtained.

  The polymer electrolyte fuel cell of the present invention can be used alone or in a stack to form a stack, or a fuel cell system incorporating them can be used.

  Further, a direct methanol fuel cell using the sulfonated polymer membrane of the present invention will be described with reference to the drawings as an example.

  FIG. 2 is a cross-sectional view of the main part of a direct methanol fuel cell comprising the sulfonated polymer membrane of the present invention. This is a sulfonated polymer membrane 6 and a catalyst-carrying electrode 7 bonded to both sides of the membrane 6 to form a membrane-electrode assembly. The required number of membrane-electrode assemblies are arranged in a plane on both sides of a fuel (methanol or methanol aqueous solution) tank 8 having a fuel (methanol or methanol aqueous solution) filling section 9 and a supply section 9. Further, a support body 10 in which an oxidant flow path 11 is formed is disposed on the outside, and a cell and a stack of a direct methanol fuel cell are configured by being sandwiched between them.

  Besides the above examples, the sulfonated polymer membrane of the present invention is disclosed in JP 2001-313046, JP 2001-313047, JP 2001-93551, JP 2001-93558, JP 2001-93561, JP 2001-102069, JP 2001-102070, JP 2001-283888, JP 2000-268835, JP 2000-268836, JP 2001. It can be used as an electrolyte membrane of a direct methanol fuel cell, which is publicly known in Japanese Patent No. -283892.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by these Examples, In the range which does not change the summary, it can change suitably.

(Example 1)
Polyphenylene sulfide was used as the hydrocarbon polymer compound. Polyphenylene sulfide (trade name: DIC-PPS FZ-2200-A5, manufactured by Dainippon Ink Industries, Ltd.) was melt-extruded with an extruder having a screw temperature of 290 ° C. and a T die temperature of 320 ° C. to obtain a film having a thickness of 50 μm. The polyphenylene sulfide film thus obtained was left to stand in a hot air oven set at 150 ° C. for 30 minutes for recrystallization.

  1-chlorobutane was used as the organic solvent for swelling and the organic solvent for reaction.

  The swelling treatment was performed as follows. After weighing 2.09 g of the polyphenylene sulfide film into a 900 mL mayonnaise bottle filled with 1-chlorobutane, the mayonnaise bottle is left in a 100 ° C. hot air oven for 4 hours and cooled to room temperature. Thereafter, the polyphenylene sulfide film was taken out. When the weight of the polyphenylene sulfide after the swelling treatment was measured, it was 8% by weight.

  671 g of 1-chlorobutane and 11.26 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. The swollen polyphenylene sulfide film was immersed in a chlorosulfonic acid solution and allowed to stand at room temperature for 20 hours (chlorosulfonic acid is 5 equivalents relative to the aromatic units of polyphenylene sulfide). After standing at room temperature for 20 hours, the polyphenylene sulfide film was recovered and washed with ion exchange water until neutral.

  The washed polyphenylene sulfide film was allowed to stand for 30 minutes in a constant temperature and humidity chamber adjusted to 23 ° C. and controlled to a relative humidity of 98%, 80%, 60% and 50%, respectively, and dried. As a proton conductive polymer membrane, a polyphenylene sulfide membrane into which a sulfonic acid group was introduced (hereinafter referred to as a sulfonated polyphenylene sulfide membrane) (80 mm × 80 mm, thickness: 105 μm) was obtained.

Various characteristics of this proton conductive polymer membrane were measured by the following methods.
(Measurement method of ion exchange capacity)
A proton conductive polymer membrane (about 10 mm × 40 mm, thickness: arbitrary) is immersed in a saturated aqueous sodium chloride solution and reacted at 60 ° C. for 3 hours in a water bath. After cooling to room temperature, the sample was thoroughly washed with ion-exchanged water, titrated with 0.01N aqueous sodium hydroxide solution using a phenolphthalein solution as an indicator, and the ion-exchange capacity was calculated.
(Thickness direction proton conductivity)
The sulfonated polyphenylene sulfide membrane was cut into a circular shape with a diameter of 16 mm, left in pure water for 3 hours or more, then taken out and wiped off with excess filter paper before being used for measurement. After attaching platinum electrodes to the front and back surfaces of the test specimen and installing them in a two-pole sealed metal cell, under the condition of a voltage of 0.5 V at room temperature, the AC impedance method (frequency: 42 Hz to 5 MHz), Membrane resistance was measured and the film thickness proton conductivity was calculated.
(Methanol barrier)
Using a membrane test apparatus manufactured by Beadrex, ion-exchanged water and a methanol aqueous solution with a predetermined concentration are separated by a proton-conducting polymer membrane, and the amount of methanol that has permeated to the ion-exchanged water after a predetermined time has passed. Quantified. After calculating the methanol permeation rate from this, the methanol permeation coefficient was determined. The methanol permeability coefficient was calculated according to the following formula. A methanol aqueous solution having a methanol concentration of 64% by weight was used.

Methanol permeability coefficient (μmol / (cm · day))
= Methanol permeation amount (μmol) × film thickness (cm) / (membrane area (cm ² ) × permeation time (days))
The smaller the methanol permeability coefficient, the better the methanol barrier property.

  Table 1 shows the results of the characteristics evaluation of this film.

（実施例２）
炭化水素系高分子化合物として、ポリフェニレンサルファイドを使用した。ポリフェニレンサルファイドフィルムに東レ（株）製ポリフェニレンサルファイドフィルム（商品名：トレリナ（登録商標）、膜厚：５０μｍ）を使用した。

(Example 2)
Polyphenylene sulfide was used as the hydrocarbon polymer compound. A polyphenylene sulfide film (trade name: Torelina (registered trademark), film thickness: 50 μm) manufactured by Toray Industries, Inc. was used as the polyphenylene sulfide film.

  Methylene chloride was used as the organic solvent for swelling. The swelling treatment was performed as follows. In a 900 mL capacity mayonnaise bottle filled with methylene chloride, 2.09 g of polyphenylene sulfide film was weighed and allowed to stand at room temperature for 2 hours, and then the polyphenylene sulfide film was taken out. When the weight of the polyphenylene sulfide after the swelling treatment was measured, it was increased by 10% by weight.

  1-Chlorobutane was used as the organic solvent for the reaction. 671 g of 1-chlorobutane and 4.50 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. The swollen polyphenylene sulfide film was immersed in a chlorosulfonic acid solution and allowed to stand at room temperature for 20 hours (chlorosulfonic acid is 2 equivalents relative to the aromatic units of polyphenylene sulfide). Thereafter, the polyphenylene sulfide film was recovered and washed with ion-exchanged water until neutral.

  The polyphenylene sulfide film after washing was dried in the same manner as in Example 1.

  Table 1 shows the results of the characteristics evaluation of this film.

(Example 3)
The same procedure as in Example 2 was performed except that the sample was immersed in a chlorosulfonic acid solution and allowed to stand at room temperature for 4 hours.

  Table 1 shows the results of the characteristics evaluation of this film.

(Comparative Example 1)
In the same manner as in Example 1, a polyphenylene sulfide film before the swelling treatment was obtained. 1-Chlorobutane was used as the organic solvent for the reaction.

  671 g of 1-chlorobutane and 11.26 g of chlorosulfonic acid were weighed to prepare a chlorosulfonic acid solution. The polyphenylene sulfide film was immersed in a chlorosulfonic acid solution and left at room temperature for 20 hours (chlorosulfonic acid is 5 equivalents relative to the aromatic unit of polyphenylene sulfide). After standing at room temperature for 20 hours, the polyphenylene sulfide film was recovered and washed with ion exchange water until neutral.

  The polyphenylene sulfide film after washing was dried in the same manner as in Example 1.

  Table 1 shows the results of the characteristics evaluation of this film.

(Comparative Example 2)
A polyphenylene sulfide film (trade name: Torelina, film thickness: 50 μm) manufactured by Toray Industries, Inc. was used as the polyphenylene sulfide film.

  A chlorosulfonic acid solution was prepared by weighing 671 g of methylene chloride and 4.50 g of chlorosulfonic acid. 2.09 g of a polyphenylene sulfide film was immersed in a chlorosulfonic acid solution and allowed to stand at room temperature for 20 hours (chlorosulfonic acid is 2 equivalents relative to the aromatic unit of polyphenylene sulfide). Thereafter, the polyphenylene sulfide film was recovered and washed with ion-exchanged water until neutral. The polyphenylene sulfide film after washing was dried in the same manner as in Example 1.

  Table 1 shows the results of the characteristics evaluation of this film.

(Comparative Example 3)
A 130 μm thick Nafion (registered trademark) (grade name: Nafion 115, DuPont) was used as the proton conductive membrane, and the film thickness proton conductivity and methanol permeability coefficient were measured. Table 1 shows the results of the characteristics evaluation of this film.

  From the comparison between Examples 1 to 3 and Comparative Examples 1 to 3 in the proton conductivity of Table 1, the sulfonated membrane obtained by the production method of the present invention has a proton conductivity equal to or higher than that of the conventional proton conductive membrane. It was revealed that it is useful as a proton conductive membrane for membranes for solid polymer fuel cells and direct methanol fuel cells.

  Further, from comparison between Examples 1 to 3 and Comparative Examples 1 to 3 in the methanol permeability coefficient of Table 1, the proton conducting polymer membrane of the present invention is equivalent to or more than the conventional proton conducting polymer membrane. It has been found that it has a cutoff coefficient and is useful as a proton conductive polymer membrane for direct methanol fuel cells.

  Furthermore, in the comparison between Example 1 and Comparative Example 1, the proton conductivity in the thickness direction is increased by 3 to 4 digits even when the amount of the sulfonating agent used and the reaction time are the same. Also, in the comparison between Example 3 and Comparative Example 2, it can be seen that the reaction time can be greatly shortened by swelling. The present invention is also excellent in terms of productivity and economy. That is, according to the production method of the present invention, the reaction time can be greatly shortened, and a proton conductive polymer membrane having higher proton conductivity can be obtained under the same reaction conditions.

It is principal part sectional drawing of the polymer electrolyte fuel cell (direct methanol fuel cell) of this invention. It is principal part sectional drawing of the direct methanol type fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Proton conductive polymer membrane 2 Catalyst carrying | support gas diffusion electrode 3 Flow path 4 Separator 5 Gasket 6 Proton conductive polymer film 7 Catalyst carrying | support gas diffusion electrode 8 Fuel tank 9 Fuel filling part 10 Support body 11 Oxidant flow path from here Describe the code

Claims (10)

  A method for producing a proton conductive polymer membrane, comprising swelling a polymer film in an organic solvent for swelling and then immersing the polymer film in an organic solvent for reaction containing a sulfonating agent.   The method for producing a proton-conductive polymer membrane according to claim 1, wherein the swelling is performed in an organic solvent for swelling at a temperature of 50 ° C or higher and 200 ° C or lower.   3. The method for producing a proton conductive polymer membrane according to claim 1, wherein the organic solvent for swelling and / or the organic solvent for reaction is a halogen-containing compound.   The organic solvent for swelling and / or the organic solvent for reaction is a compound containing 3 or more carbon atoms and 1 or more halogen atoms in its molecular structure. A method for producing the proton conductive polymer membrane according to the description.   The method for producing a proton-conductive polymer membrane according to any one of claims 1 to 4, wherein the polymer film is a hydrocarbon polymer film. The hydrocarbon polymer film is made of a hydrocarbon polymer obtained by mixing at least one hydrocarbon polymer selected from the following group (A). A method for producing a proton conductive polymer membrane according to any one of the above.
Group (A): polybenzimidazole (PBI), polybenzoxazole (PBO), polybenzothiazole (PBT), polysulfone (PSU), polyetherethersulfone (PEES), polyarylethersulfone (PAS), polyphenylenesulfone ( PPSU), polyphenylene oxide (PPO), polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO2), polyparaphenylene (PPP), polyether ketone (PEK), polyether ether ketone (PEEK) ), Polyether ketone ketone (PEKK), cyanate ester resin.   The method for producing a proton conductive polymer membrane according to claim 6, wherein the hydrocarbon polymer film is made of polyphenylene sulfide (PPS).   The method for producing a proton conductive polymer membrane according to claim 1, wherein the sulfonating agent is at least one selected from chlorosulfonic acid, fuming sulfuric acid, sulfur trioxide, and concentrated sulfuric acid.   A proton conductive polymer membrane produced by the production method according to claim 1, which is used as a proton conductive membrane for a polymer electrolyte fuel cell.   A proton conductive polymer membrane produced by the production method according to claim 1, which is used as a proton conductive membrane for a direct methanol fuel cell.

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