JP2007335265A - Manufacturing method of polymer electrolyte membrane, as well as polymer electrolyte membrane manufactured by the manufacturing method, and its utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyelectrolyte membrane for expressing high proton conductivity and fuel shut-off property, and having high durability against water and methanol, and its manufacturing method, as well as a membrane electrode assembly utilizing it, and provide a fuel cell. <P>SOLUTION: The polyelectrolyte membrane is manufactured by the manufacturing method including a process in which a polymer film containing a polymer compound having an aromatic unit is brought into contact with a proton conductive functional group-introducing agent, and a process in which the polymer film with which the proton conductive functional group-introducing agent has been brought into contact is heated at 60°C or more and 150°C or less. By this, the polyelectrolyte membrane equipped with the high proton conductivity, the fuel shut-off property, and the high durability can be provided. The polyelectrolyte membrane can be used suitably for the fuel cell such as a solid polymer fuel cell, a direct liquid fuel cell, and a direct methanol fuel cell. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte membrane, a production method thereof, and use thereof. More specifically, a polymer electrolyte membrane that exhibits high proton conductivity and fuel barrier properties and has high durability against water and methanol, a method for producing the same, and a membrane-electrode assembly using the same, and The present invention relates to a fuel cell such as a polymer electrolyte fuel cell, a direct liquid fuel cell, and a direct methanol fuel cell.

  Polymer electrolytes containing proton conductive functional groups such as sulfonic acid groups are used as fuel cells such as solid polymer fuel cells, direct liquid fuel cells, and direct methanol fuel cells. The polymer electrolyte is also used as a raw material for electrochemical elements such as humidity sensors, gas sensors, and electrochromic display elements.

  Among these, fuel cells such as polymer electrolyte fuel cells, direct liquid fuel cells, and direct methanol fuel cells are expected as one of the pillars of new energy technology. For example, a polymer electrolyte fuel cell using an electrolyte membrane made of a polymer compound having a proton-conducting functional group has features such as operation at a low temperature and reduction in size and weight. Application to consumer cogeneration systems and consumer small portable devices is under consideration. Direct liquid fuel cells, especially direct methanol fuel cells that use methanol directly as fuel, have features such as a simple structure, ease of fuel supply and maintenance, and high energy density. As an alternative to lithium-ion secondary batteries, it is expected to be applied to small consumer portable devices such as mobile phones and laptop computers.

  As an electrolyte membrane used in a polymer electrolyte fuel cell, there is a styrene-based cation exchange membrane developed in the 1950s. However, the fuel cell has poor stability under a fuel cell operating environment and has a sufficient lifetime. Has not yet been manufactured.

  On the other hand, as an electrolyte membrane having practical stability, a perfluorocarbon sulfonic acid membrane represented by Nafion (registered trademark) has been widely studied. Perfluorocarbon sulfonic acid membranes are said to have high proton conductivity and excellent chemical stability such as acid resistance and oxidation resistance.

  However, Nafion (registered trademark) is disadvantageous in that it is very expensive because the cost of raw materials used is high and a complicated manufacturing process is required.

  In addition, it has been pointed out that it is deteriorated by hydrogen peroxide generated by the electrode reaction and by-product hydroxy radical. Further, the permeation (also referred to as crossover) of a hydrogen-containing liquid such as methanol which is a raw material of a direct liquid fuel cell is large, and so-called chemical short reaction occurs. As a result, cathode potential, fuel efficiency, cell characteristics and the like are lowered, and it is difficult to use as an electrolyte membrane of a direct liquid fuel cell such as a direct methanol fuel cell. In addition, Nafion (registered trademark), which is a fluorine-based electrolyte membrane, has been pointed out as having the disadvantage that fuel disappears due to crossover even when power is not generated.

  Against this background, various electrolyte membranes such as hydrocarbon electrolyte membranes have been proposed as non-fluorine electrolyte membranes.

  For example, Patent Document 1 proposes a method of improving the stability by forming a triazine ring by applying heat of 200 ° C. or higher to an ion conductive film containing a cyano group.

Patent Document 2 proposes a crosslinked electrolyte membrane using a sulfonic acid group by heat treatment at 150 ° C. or higher.
JP 2005-243492 A (published September 8, 2005) JP 2005-243493 A (published September 8, 2005)

  However, the conventional polymer electrolyte membrane has problems such as insufficient proton conductivity, low fuel barrier property against fuel such as methanol, and poor durability against water and methanol. ing.

  Specifically, in the method for producing an ion conductive film according to Patent Document 1, since the temperature for heat-treating the ion conductive film is high, desorption of ion-exchange functional groups and oxidation of the ion conductive film occur. Therefore, the ion conductive membrane may be deteriorated, and the durability against water, methanol and the like is lowered.

  Moreover, in the manufacturing method of the ion exchange membrane which concerns on patent document 2, a sulfonic acid group is used as an acidic functional group. Sulfonic acid groups are easily compatible with water and cause swelling of the ion exchange membrane. And if an ion exchange membrane swells, it will become easy to permeate (cross-over) fuels, such as methanol. That is, the fuel barrier property of the ion exchange membrane is reduced. Moreover, the ion exchange membrane which concerns on patent document 2 bridge | crosslinks a sulfonic acid group. Since the crosslinked sulfonic acid group cannot carry a proton, the proton conductivity of the ion exchange membrane is lowered. Therefore, this production method cannot provide a polymer electrolyte membrane having sufficient proton conductivity and fuel barrier properties.

  The present invention has been made in view of the above problems, and its object is to provide a polymer electrolyte membrane that exhibits high proton conductivity and fuel cutoff, and has high durability against water, methanol, and the like. An object of the present invention is to provide a membrane-electrode assembly and a fuel cell using the same.

  The present inventor has intensively studied to solve the above problems. In the course of the study, the present inventors accidentally heated a polymer compound having an aromatic unit, a polymer compound having no aromatic unit, and a polymer film containing a proton conductive functional group. Thus, it was found that a polymer electrolyte membrane having high durability against water and methanol can be obtained, and the present invention has been completed.

That is, the method for producing a polymer electrolyte membrane according to the present invention includes the following steps (X) and (Y) in order to solve the above problems:
(X) contacting a polymer film containing a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit with a proton conductive functional group introducing agent;
(Y) The process of heating the polymer film which contacted the said proton conductive functional group introducing agent to 60 degreeC or more and 150 degrees C or less.

  According to said structure, after giving high proton conductivity and fuel blocking | blocking property to a polymer film by said process (X), water resistance and methanol resistance of a polymer electrolyte membrane are obtained by said process (Y). And the polymer electrolyte membrane can be stabilized. Moreover, since it can obtain the effect of durability improvement even if it heats without reducing an ion exchange capacity | capacitance as mentioned later, it turns out that the crosslinking reaction like the cited reference 2 has not occurred. Therefore, the proton conductivity is not lowered while the durability of the polymer electrolyte membrane is improved.

  Therefore, it is possible to provide a polymer electrolyte membrane that exhibits high proton conductivity and fuel barrier properties and has high durability against water and methanol.

  In order to solve the above problems, a method for producing a polymer electrolyte membrane according to the present invention is a polymer in which the polymer compound having an aromatic unit is selected from the following (i) to (iii): Or it is preferable that it is a mixture of these polymers.

(I) at least one polymer selected from the group of polymers consisting of polystyrene, syndiotactic polystyrene, polyphenylene ether, modified polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, and polyphenylene sulfide;
(Ii) a copolymer comprising the polymer described in (i) above;
(Iii) Derivatives of the polymers described in (i) and (ii) above.

  According to said structure, since introduction | transduction of a proton conductive functional group becomes easy, the proton conductivity of the polymer electrolyte membrane obtained, methanol blocking | blocking property, and chemical / thermal stability can further be improved. Therefore, it is possible to provide a polymer electrolyte membrane that exhibits high proton conductivity and has high durability against water and methanol.

  In addition, the use of these polymer compounds is compatible with other polymer compound components contained in the polymer electrolyte membrane, dispersibility, processability when producing polymer films, There is a further effect of improving handling.

  In order to solve the above problems, the method for producing a polymer electrolyte membrane according to the present invention is characterized in that the polymer compound having an aromatic unit is polystyrene, syndiotactic polystyrene, polyphenylene sulfide, and a polyethylene-polystyrene graft copolymer. One polymer selected from the group consisting of these or a mixture of these polymers is preferred.

  According to said structure, introduction | transduction of the said proton conductive functional group becomes easy. In addition, since the polymer compound has an excellent balance between proton conductivity and fuel blocking property, the proton conductivity, methanol blocking property, chemical property of the polymer electrolyte membrane obtained by using these polymer compounds -Thermal stability can be further improved. Therefore, it is possible to provide a polymer electrolyte membrane that exhibits higher proton conductivity and fuel barrier properties and has high durability against water, methanol, and the like.

  In addition, the use of these polymer compounds is compatible with other polymer compound components contained in the polymer electrolyte membrane, dispersibility, processability when producing polymer films, There is a further effect of improving handling.

In order to solve the above-described problems, a method for producing a polymer electrolyte membrane according to the present invention includes a polymer compound having no aromatic unit represented by the following general formula (1):
-(CX ₁ X ₂ -CX ₃ X ₄ )-(1)
_(Wherein, X _{1 to 4 is,} H, based on any one of CH 3, Cl, F, OCOCH 3, CN, COOH, COOCH 3, OC 4 H 9, is selected from the group consisting _{of, X. 1 to 4} are independent of each other and may be the same or different. The polymer is preferably a polymer selected from polymer compounds having a repeating unit of the formula (1) or a mixture thereof.

  According to said structure, the fuel-blocking property with respect to fuels, such as methanol, chemical-thermal stability, etc. in the obtained polymer electrolyte membrane improve. Therefore, a polymer electrolyte membrane excellent in fuel barrier properties can be provided by using these as polymer compounds having no aromatic unit. Moreover, the said structure has the further effect of the compatibility and dispersibility with respect to another polymer compound component, the workability at the time of manufacturing a polymer film, and the improvement of the handleability of the polymer film obtained.

  In order to solve the above problems, the method for producing a polymer electrolyte membrane according to the present invention selects the polymer compound having no aromatic unit from the group consisting of polyethylene, polypropylene, polymethylpentene, and derivatives thereof. It is preferable that it is at least one kind.

  According to said structure, the fuel-blocking property with respect to fuels, such as methanol, chemical-thermal stability, etc. in the obtained polymer electrolyte membrane improve. Therefore, by using these as polymer compounds having no aromatic unit, it is possible to provide a highly durable polymer electrolyte membrane that exhibits higher fuel barrier properties. In addition, the polymer compound is excellent in compatibility and dispersibility with other polymer compound components, processability when producing a polymer film, and handleability of the resulting polymer film, and is also available industrially. Easy. Therefore, the said structure has the further effect that the said polymer electrolyte membrane can be manufactured simply and cheaply.

  In order to solve the above problems, the method for producing a polymer electrolyte membrane according to the present invention preferably performs the step (X) in the presence of an organic solvent.

  According to said structure, it becomes easy to introduce a proton conductive functional group into a polymer electrolyte membrane uniformly. Therefore, a polymer electrolyte membrane that exhibits high proton conductivity can be provided.

  In order to solve the above problems, the method for producing a polymer electrolyte membrane according to the present invention is characterized in that the organic solvent is at least one organic solvent selected from the group consisting of dichloromethane, 1,2-dichloroethane and 1-chlorobutane. It is preferable that

  According to said structure, it becomes easy to introduce a proton conductive functional group into a polymer electrolyte membrane, and the uniformity is also improved. Moreover, the fuel cutoff property of the obtained polymer electrolyte membrane improves by using these. Therefore, a polymer electrolyte membrane having both high proton conductivity and fuel cutoff can be provided. In addition, since the said organic solvent is easy to obtain industrially, there exists the further effect that the said polymer electrolyte membrane can be manufactured cheaply.

  In the method for producing a polymer electrolyte membrane according to the present invention, the proton conductive functional group introducing agent is preferably a sulfonating agent in order to solve the above problems.

  According to said structure, a sulfonic acid group can be introduce | transduced as a proton conductive functional group. The sulfonic acid group is excellent in proton conductivity. Therefore, a polymer electrolyte membrane having high proton conductivity can be provided.

  In the method for producing a polymer electrolyte membrane according to the present invention, the sulfonating agent is preferably chlorosulfonic acid in order to solve the above problems.

  According to said structure, introduction | transduction of a sulfonic acid group becomes easy. Therefore, a polymer electrolyte having high proton conductivity can be provided. In addition, it is possible to improve properties such as proton conductivity, fuel cutoff, and mechanical properties of the obtained polymer electrolyte membrane. Furthermore, since the chlorosulfonic acid is easily industrially available, the polymer electrolyte membrane can be provided at low cost.

  In order to solve the above problems, the method for producing a polymer electrolyte membrane according to the present invention preferably reduces the ion exchange capacity in the step (Y) within a range of 20% or less.

  According to the above configuration, it is possible to provide a highly durable polymer electrolyte membrane while maintaining high proton conductivity.

  In order to solve the above problems, a polymer electrolyte membrane according to the present invention is a polymer electrolyte membrane manufactured by any one of the above-described methods for manufacturing a polymer electrolyte membrane.

  According to said structure, the said polymer electrolyte membrane expresses high proton conductivity and fuel interruption | blocking property, and has high durability with respect to water, methanol property, etc. Therefore, if the polymer electrolyte membrane is used, a membrane-electrode assembly having excellent power generation characteristics and long-term durability, such as a solid polymer fuel cell, a direct liquid fuel cell, a direct methanol fuel cell, etc. Etc. can be provided.

  In order to solve the above problems, the polymer electrolyte membrane according to the present invention is characterized by having a weight retention of 99% or more and 100% or less when immersed in a 64% by weight aqueous methanol solution for 500 hours.

  According to said structure, the said polymer electrolyte membrane has high methanol durability. Moreover, since the polymer electrolyte membrane includes a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit, the polymer electrolyte membrane exhibits high proton conductivity and fuel blocking properties. Therefore, a highly durable polymer electrolyte membrane that exhibits high proton conductivity and fuel barrier properties can be provided.

  In order to solve the above problems, the polymer electrolyte membrane according to the present invention is characterized in that the retention rate of ion exchange capacity when immersed in a 64 wt% methanol aqueous solution for 500 hours is 90% or more and 100% or less. It is said.

  According to said structure, the said polymer electrolyte membrane has high methanol durability. Moreover, since the polymer electrolyte membrane includes a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit, the polymer electrolyte membrane exhibits high proton conductivity and fuel blocking properties. Therefore, a highly durable polymer electrolyte membrane that exhibits high proton conductivity and fuel barrier properties can be provided.

  In order to solve the above problems, a polymer electrolyte membrane according to the present invention comprises a polymer compound having an aromatic unit, a polymer compound not having an aromatic unit, and a proton conductive functional group, and is a 64 wt% aqueous methanol solution. In addition, the weight retention when immersed for 500 hours is 99% or more and 100% or less.

  According to said structure, the said polymer electrolyte membrane has high methanol durability. Moreover, since the polymer electrolyte membrane includes a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit, the polymer electrolyte membrane exhibits high proton conductivity and fuel blocking properties. Therefore, a highly durable polymer electrolyte membrane that exhibits high proton conductivity and fuel barrier properties can be provided.

  In order to solve the above problems, a polymer electrolyte membrane according to the present invention comprises a polymer compound having an aromatic unit, a polymer compound not having an aromatic unit, and a proton conductive functional group, and is a 64 wt% aqueous methanol solution. Further, the retention rate of the ion exchange capacity when immersed for 500 hours is from 90% to 100%.

  According to said structure, the said polymer electrolyte membrane has high methanol durability. Moreover, since the polymer electrolyte membrane includes a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit, the polymer electrolyte membrane exhibits high proton conductivity and fuel blocking properties. Therefore, a highly durable polymer electrolyte membrane that exhibits high proton conductivity and fuel barrier properties can be provided.

  The membrane-electrode assembly according to the present invention is characterized by using the above polymer electrolyte membrane in order to solve the above-mentioned problems.

  According to said structure, since the polymer electrolyte membrane which has high proton conductivity and fuel cutoff property is used, the membrane-electrode assembly provided with the outstanding power generation characteristic and long-term durability can be provided.

  In order to solve the above problems, a fuel cell according to the present invention is characterized by using the polymer electrolyte membrane.

  According to the above configuration, since the polymer electrolyte membrane having high proton conductivity and fuel cutoff is used, it has excellent power generation characteristics and long-term durability, for example, solid polymer fuel cell, direct liquid Fuel cells such as a fuel cell and a direct methanol fuel cell can be provided.

  As described above, the method for producing a polymer electrolyte membrane according to the present invention comprises (X) a polymer compound containing an aromatic unit and a polymer film containing a polymer compound not having an aromatic unit as a proton conductive functional group. A step of bringing the polymer film into contact with the group-introducing agent and (Y) the proton-conductive functional group-introducing agent into contact with the group-introducing agent.

  Therefore, it is possible to provide a highly durable polymer electrolyte membrane having high proton conductivity and fuel blocking properties and high water resistance and methanol resistance.

  Furthermore, by using the polymer electrolyte membrane, a membrane-electrode assembly having excellent power generation characteristics and long-term durability, for example, a solid polymer fuel cell, a direct liquid fuel cell, a direct methanol fuel cell Etc. can be provided.

  An embodiment of the present invention will be described as follows.

  In the present embodiment, a polymer film containing a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit is brought into contact with the proton conductive functional group introducing agent in the presence of an organic solvent. Thereafter, the polymer electrolyte membrane is obtained by heating to 60 ° C. or more and 150 ° C. or less, and then used for a fuel cell. However, the scope of the present invention is not limited to these explanations, and other than the following examples, the scope of the present invention can be appropriately changed and implemented without departing from the spirit of the present invention.

<1. Composition of polymer electrolyte membrane>
The polymer film in the present embodiment is not limited as long as it includes a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit.

  By including the polymer compound having an aromatic unit, the aromatic unit can be substituted with a proton conductive functional group such as a sulfonic acid group. Therefore, by including the polymer compound having the aromatic unit, the polymer electrolyte membrane can exhibit proton conductivity. On the other hand, since a polymer compound having no aromatic unit does not have an aromatic unit in its structure, a proton conductive functional group such as a sulfonic acid group is not introduced. That is, in the polymer electrolyte membrane containing the polymer compound having no aromatic unit, a hydrophilic proton conductive functional group such as a sulfonic acid group is introduced into the aromatic unit contained in the polymer electrolyte membrane. Even in this case, swelling due to hydrogen-containing liquid such as water or methanol contained in the fuel can be suppressed. Therefore, the use of the polymer compound having no aromatic unit can maintain high blocking performance of fuel and oxidant.

  The polymer compound having an aromatic unit is not limited as long as it is a polymer compound having an aromatic ring. For example, polystyrene, syndiotactic polystyrene, polyarylethersulfone, polyetherethersulfone, Polyether ketone, polyether ketone ketone, polysulfone, polyparaphenylene, polyphenylene sulfide, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfoxide, polyphenylene sulfide sulfone, polyphenylene sulfone, polybenzimidazole, polybenzoxazole, polybenzothiazole, polyether sulfone , Poly 1,4-biphenylene ether ether sulfone, polyarylene ether sulfone, polyimide, polyether Imide, cyanate ester resin, polyetheretherketone, derivatives and copolymers thereof, polyethylene-polystyrene graft copolymer, polyethylene-polystyrene block copolymer, polypropylene-polystyrene graft copolymer, (ethylene-glycidyl methacrylate) ) -Polystyrene graft copolymer, (ethylene-ethyl acrylate) -polystyrene graft copolymer, polypropylene- (acrylonitrile-styrene) graft copolymer, polycarbonate-polystyrene graft copolymer, polycarbonate- (acrylonitrile-styrene) graft copolymer Polymer, vinyl acetate resin-polystyrene block copolymer, acrylic resin-polystyrene block copolymer, Modiper series (manufactured by NOF Corporation) Registered trademark), Epofriend series (manufactured by Daicel Chemical Co., Ltd.) and the like. These may use only 1 type and may use 2 or more types together.

  Here, in the present specification, the “derivative” may be any derivative known to those skilled in the art and is not particularly limited.

  In the present specification, the “copolymer” is not particularly limited as long as it is a copolymer conventionally known to those skilled in the art. For example, a copolymer such as a block copolymer, a graft copolymer, or a random copolymer obtained by polymerizing two or more monomers including each monomer unit constituting the various polymers described above can be exemplified. .

  Examples of the polymer compound having the aromatic unit include polystyrene, syndiotactic polystyrene, polyphenylene ether, modified polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone and polyphenylene sulfide, derivatives and copolymers thereof, In addition, a polyethylene-polystyrene graft copolymer is preferable. By using these, compatibility and dispersibility with respect to other polymer compound components contained in the polymer electrolyte membrane can be improved, and introduction of a proton conductive functional group is facilitated. Furthermore, processability when manufacturing polymer films, handling properties of the resulting polymer films, proton conductivity and methanol blocking properties of polymer electrolyte membranes obtained from the polymer films, chemical and thermal stability Can be improved.

  Furthermore, the polymer compound having an aromatic unit is preferably polystyrene, syndiotactic polystyrene, polyphenylene sulfide, or polyethylene-polystyrene graft copolymer. If it is said structure, it is excellent in the balance of proton conductivity and fuel interruption | blocking property.

  In the present invention, the polymer compound having no aromatic unit refers to a polymer compound having no aromatic ring in the molecule, and whether or not it has an aromatic ring is, for example, known techniques such as NMR You can check with the equipment. The polymer compound having no aromatic unit used in the present invention is not limited as long as it is a polymer compound having the above structure. For example, ethylene, propylene, 1-butene, 1-pentene, Polyolefin resins such as homopolymers or copolymers of α-olefins such as 1-hexene, 3-methyl-1-butene, 4-methyl-1-pentene, 5-methyl-1-heptene, polyvinyl chloride, chloride Vinyl chloride resins such as vinyl-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-olefin copolymer, polyamide resins such as nylon 6 and nylon 66, polytetrafluoroethylene, tetrafluoroethylene- Perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-exafluoropropylene Emissions copolymer, tetrafluoroethylene - ethylene copolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, and fluorine-based resins such as polyvinyl fluoride can be exemplified.

In particular, as the polymer compound having no aromatic unit, the following general formula (1)
-(CX ₁ X ₂ -CX ₃ X ₄ )-(1)
_(Wherein, X _{1 to 4 is,} H, based on any one of CH 3, Cl, F, OCOCH 3, CN, COOH, COOCH 3, OC 4 H 9, is selected from the group consisting _{of, X. 1 to 4} are mutually independent and may be the same or different.)
It is preferable that it is one polymer selected from the high molecular compound which has these repeating units, or these mixtures. By using these, compatibility and dispersibility with other polymer compound components, processability when producing polymer films, handling properties of the resulting polymer films, and methanol blocking of the polymer electrolyte obtained therefrom , Chemical and thermal stability can be improved.

  Furthermore, in consideration of industrial availability, mechanical properties and handling properties of the resulting polymer film, proton conductivity, fuel blocking property, chemical stability, etc. of the obtained polymer electrolyte membrane, polyethylene, polypropylene, Polymethylpentene or a derivative thereof is preferable.

  In the polymer film, the mixing ratio of the polymer compound having the aromatic unit and the polymer compound not having the aromatic unit is not particularly limited, but the aromatic unit in the polymer film is not limited. It is preferable that the content of the polymer compound that does not contain is 30% by weight or more and 90% by weight or less. If it is in the said range, the swelling effect with respect to the water and methanol aqueous solution of a polymer electrolyte membrane can fully be acquired, and desired fuel cutoff property can be expressed. Moreover, since a proton conductive functional group can be sufficiently introduced, desired proton conductivity can be exhibited. In the case where a copolymer of a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit is used as the polymer compound having an aromatic unit, the aromatic unit in the polymer film is used. It is preferable that the total amount of the polymer compound not having an aromatic group and the polymer compound having no aromatic unit in the copolymer is 30% by weight or more and 90% by weight or less. If it is in the said range, the swelling effect with respect to the water and methanol aqueous solution of a polymer electrolyte membrane can fully be acquired, and desired fuel cutoff property can be expressed. Moreover, since a proton conductive functional group can be sufficiently introduced, desired proton conductivity can be exhibited.

  The proton conductive functional group contained in the polymer electrolyte membrane of the present invention is not limited as long as it dissociates protons in a water-containing state. For example, sulfonic acid group, phosphoric acid group, carboxylic acid group Examples thereof include phenolic hydroxyl groups. Of these, sulfonic acid groups are preferred. This is because the sulfonic acid group can be easily introduced into the polymer film, and the resulting polymer electrolyte has excellent proton conductivity.

  That is, the proton conductive functional group introducing agent is not limited as long as the proton conductive functional group can be introduced, but is preferably a sulfonating agent.

  The sulfonating agent is not limited as long as a sulfonic acid group can be introduced into the polymer film. For example, chlorosulfonic acid, a compound containing chlorosulfonic acid, fuming sulfuric acid Known sulfonating agents such as sulfur trioxide, sulfur trioxide-triethyl phosphate, concentrated sulfuric acid, and trimethylsilyl chlorosulfate are preferable. Of these, compounds containing chlorosulfonic acid and chlorosulfonic acid are more preferable. Chlorosulfonic acid and compounds containing chlorosulfonic acid are industrially available and easy to introduce sulfonic acid groups, and further improve the proton conductivity, fuel barrier properties, mechanical properties, etc. of the resulting polymer electrolyte membrane. be able to.

  The amount of the sulfonating agent may be appropriately set according to the target introduction amount of the sulfonic acid group, reaction conditions (temperature / time), etc., but is 0.1 to 100 times that of the polymer film. The amount (weight ratio) is preferable, and more preferably 0.5 to 50 times (weight ratio). Within the above range, sulfonic acid groups can be sufficiently introduced, and characteristics such as proton conductivity of the obtained polymer electrolyte membrane can be sufficiently obtained. In addition, the resulting polymer film is chemically stable, mechanical strength is improved, and handling is easy. In addition, the fuel barrier properties are sufficiently exhibited, and practical characteristics of the polymer electrolyte membrane such as durability against water-soluble liquids and methanol aqueous solutions can be sufficiently obtained.

  In addition, when using the organic solvent described later, the concentration of the sulfonating agent in the organic solvent may be appropriately set according to the target introduction amount of the sulfonic acid group, reaction conditions (temperature / time), etc. Specifically, it is preferably 0.05 to 20% by weight, more preferably 0.2 to 10% by weight. Within the above range, the sulfonating agent and the aromatic unit in the polymer film can be easily contacted with each other, so that a desired amount of sulfonic acid group can be introduced. Further, the time required for introduction can be shortened. The introduction of the sulfonic acid group can be made uniform, and the mechanical properties of the obtained polymer electrolyte membrane are not impaired.

<2. Production Method of Polymer Electrolyte Membrane According to the Present Invention>
A known method can be used as a method for producing the polymer film. Examples thereof include melt extrusion molding such as inflation method and T-die method, calendar method, cast method, cutting method, emulsion method, hot press method, and the like. A production method by melt extrusion is preferred. Melt extrusion molding is excellent in productivity, mechanical properties of the resulting polymer film, ease of control of film thickness, applicability to various resins, environmental load, and the like.

  Specifically, for example, a polymer copolymer having an aromatic unit, which is a main raw material of the polymer film, and a pellet or powder of a polymer compound not having an aromatic unit are mixed in advance at a predetermined blending ratio, A method in which a film is formed while being melt-kneaded is introduced into an extruder in which a T-die is set. At this time, if the extruder used is a twin screw extruder, a polymer film in which these components are melted and uniformly dispersed can be obtained. Further, the film may be formed using pellets melt-kneaded with a twin-screw extruder so as to have a predetermined blending ratio in advance, or a masterbatch pellet may be used to achieve a predetermined blending ratio. Thus, the film may be formed while melt-kneading. Moreover, when there is no problem in the dispersibility of the components to be combined, the film may be formed with a single screw extruder in which a T die is set.

  As the thickness of the polymer film, any thickness can be selected according to the application. For example, when reducing the internal resistance of the obtained polymer electrolyte membrane, the thinner the polymer film, the better. On the other hand, in view of methanol blocking property and handling property of the obtained polymer electrolyte membrane, it is not preferable that the thickness of the polymer film is too thin. Considering these, the thickness of the polymer film is preferably 1.2 μm to 350 μm. When the polymer film is thicker than 1.2 μm, it can be easily formed into a film, and can prevent wrinkles and breakage during processing and drying when introducing a proton conductive functional group. Can be improved. Moreover, the proton conductivity of the obtained polymer electrolyte membrane can be sufficiently expressed.

  Furthermore, after obtaining the polymer film, a treatment such as biaxial stretching may be performed to control the molecular orientation or the like, or a heat treatment may be performed to control the crystallinity.

  Further, if necessary, a crosslinking agent or an initiator is added to introduce a crosslinked structure into the polymer film, various fillers are added to increase the mechanical strength of the polymer film, glass nonwoven fabric, etc. It is also within the scope of the present invention to form a composite by pressing with a reinforcing agent.

  In addition, as long as the processing and performance of the polymer electrolyte membrane are not affected, various commonly used additives may be appropriately used. For example, the compatibility of the reaction system according to the present invention is originally good, but a compatibilizing agent may be added in order to further improve the compatibility. Moreover, you may add the antioxidant for preventing resin degradation, the antistatic agent for improving the handling in the shaping | molding process of the said polymer film, a lubricant, etc.

  What is necessary is just to set suitably the reaction temperature and reaction time when making the said polymer film and the said proton conductive functional group introduction | transduction agent contact according to the introduction amount, reaction conditions, etc. of the target proton conductive functional group.

  For example, the reaction temperature is preferably 0 to 100 ° C, more preferably 10 to 30 ° C. When the reaction temperature is higher than 0 ° C., the reaction time can be further shortened without requiring equipment for cooling or the like. Further, excessive progress of reaction and occurrence of side reactions can be prevented, and the characteristics of the film can be improved. Moreover, it is preferable that the said reaction temperature is below the boiling point of the organic solvent to be used, when using an organic solvent. This is because it is not necessary to use a pressure vessel when the reaction temperature is not higher than the boiling point of the organic solvent.

  The reaction time is preferably 0.5 hours or longer, more preferably 2 to 100 hours. When the time is 0.5 hours or longer, the proton conductive functional group introducing agent can be sufficiently brought into contact with the aromatic unit in the polymer film, and the intended proton conductive functional group can be easily introduced. Moreover, when reaction time is 100 hours or less, while being able to ensure efficient productivity, the characteristic of a polymer electrolyte membrane improves. Actually, it is possible to efficiently produce a polymer electrolyte membrane having desired characteristics in consideration of a reaction atmosphere such as a proton conductive functional group introducing agent and an organic solvent to be used, and a target production amount. It should be set as follows.

  The ion exchange capacity of the polymer electrolyte membrane obtained by the above steps is preferably 0.2 to 5.0 meq / g, and more preferably 0.5 to 3.0 meq / g. When the ion exchange capacity is 0.2 meq / g or more, the desired proton conductivity can be sufficiently exhibited. In addition, when the ion exchange capacity is 5.0 meq / g or less, swelling with respect to water, methanol, or the like can be sufficiently suppressed, so that deterioration or dissolution of the obtained polymer electrolyte membrane can be prevented.

  The method for bringing the polymer film into contact with the proton conductive functional group introducing agent is not limited, but is preferably performed in the presence of an organic solvent.

  By bringing the polymer film into contact with the proton conductive functional group introducing agent in the presence of an organic solvent, the polymer film is prevented from being directly contacted with the proton conductive functional group introducing agent, while maintaining the target amount. It becomes possible to introduce a proton conductive functional group.

  The organic solvent does not decompose the proton conductive functional group introducing agent, does not inhibit the introduction of the proton conductive functional group into the aromatic unit, and does not inhibit the thermoplastic polymer or the antioxidant in the polymer film. Anything that does not cause degradation such as decomposition can be used. By using an organic solvent, the polymer film can easily swell, and the proton conductive functional group introducing agent can be diffused into the polymer film. In addition, it is possible to suppress degradation of the polymer film due to an excessive reaction caused by direct contact between the proton conductive functional group introducing agent and the polymer film.

  The organic solvent according to the present invention is preferably a halogenated hydrocarbon in view of the ease of introduction of proton conductive functional groups and the properties of the obtained polymer electrolyte membrane, such as dichloromethane, 1,2-dichloroethane, Examples include chloroform, 1-chloropropane, 1-chlorobutane, 2-chlorobutane, 1,4-dichlorobutane, 1-chloro-2-methylpropane, 1-chloropentane, 1-chlorohexane, chlorocyclohexane and the like. In particular, the halogenated hydrocarbons are preferably dichloromethane, 1,2-dichloroethane and 1-chlorobutane in view of industrial availability, ease of introduction of proton conductive functional groups, and characteristics of the obtained electrolyte membrane. . In addition, these organic solvents may be used independently and may mix and use 2 or more types suitably.

  The temperature of the heat treatment for the polymer film brought into contact with the proton conductive functional group introducing agent is not limited as long as it is 60 ° C. or higher and 150 ° C. or lower, but preferably 80 ° C. or higher and 150 ° C. or lower. It is. By performing the heat treatment, the polymer electrolyte membrane is stabilized, and an electrolyte membrane excellent in durability such as water resistance and methanol resistance can be obtained. In addition, when the temperature of the said heat processing is 60 degreeC or more, the effect of this invention can be acquired and efficient productivity can be ensured. In addition, by heating at a heat treatment temperature of 150 ° C. or lower, the polymer skeleton can be prevented from being deteriorated or melted. Further, elimination of sulfonic acid groups and crosslinking reaction can be suppressed. Therefore, the ion exchange capacity is prevented from being lowered and there is no possibility of adversely affecting proton conductivity.

  The heating time may be appropriately set depending on the characteristics of the polymer electrolyte membrane to be obtained, but is preferably 1 minute to 30 hours, more preferably 10 minutes to 10 hours. When the heating time is 1 minute or longer, an electrolyte membrane having excellent durability such as water resistance and methanol resistance can be obtained. By performing the heating in 30 hours or less, efficient productivity can be ensured and the obtained high The molecular electrolyte membrane can prevent deterioration.

  The heat treatment conditions are preferably set such that the decrease in ion exchange capacity before and after the heat treatment is 20% or less. The heat treatment conditions for reducing the ion exchange capacity to 20% or less are not limited as long as this can be achieved. For example, the heat treatment conditions can be achieved by the preferred heating temperature and heating time described above. In addition, although the reduction | decrease of the said ion exchange capacity is so good that it is small, if it is 20% or less, the high proton conductivity by this invention can be maintained.

<3. Use of Polymer Electrolyte Membrane According to the Present Invention>
Next, an embodiment of a polymer electrolyte fuel cell using the polymer electrolyte membrane of the present invention will be described with reference to the drawings. In the present embodiment, a solid polymer fuel cell will be described as an example, but the present invention can be similarly applied to a direct liquid fuel cell and a direct methanol fuel cell.

  FIG. 1 is a diagram schematically showing a cross-sectional structure of a main part of a polymer electrolyte fuel cell using a polymer electrolyte membrane according to the present embodiment.

  As shown in FIG. 1, a polymer electrolyte fuel cell 10 according to the present embodiment includes a polymer electrolyte membrane 1, catalyst layers 2 and 2, diffusion layers 3 and 3, and separators 4 and 4.

  The catalyst layer 2 is in contact with the polymer electrolyte membrane 1. The diffusion layer 3 is in contact with the back surface of the contact surface between the catalyst layer 2 and the polymer electrolyte membrane 1 in the catalyst layer 2. The separator 4 is in contact with the back surface of the contact surface between the catalyst layer 2 and the diffusion layer 3 in the diffusion layer 3. The separator 4 is formed with a flow path 5 for sending fuel gas or liquid (such as aqueous methanol solution) and an oxidant. In other words, the cells of the polymer electrolyte fuel cell 10 are constituted by these members.

  Generally, a polymer electrolyte membrane 1 joined with a catalyst layer 2 or a polymer electrolyte membrane 1 joined with a catalyst layer 2 and a diffusion layer 3 is a membrane-electrode assembly (hereinafter referred to as “MEA”). And is used as a basic member of a polymer electrolyte fuel cell (direct liquid fuel cell, direct methanol fuel cell).

  The MEA is produced by a polymer electrolyte membrane made of perfluorocarbon sulfonic acid and other hydrocarbon polymer electrolyte membranes (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated) that have been studied in the past. Polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide, etc.) can be used.

  An example of a specific method for producing MEA is shown below, but the present invention is not limited to this.

  The catalyst layer 2 is formed on the release film by applying the dispersion solution for forming the catalyst layer on a release film such as polytetrafluoroethylene by spraying and drying and removing the solvent in the dispersion solution. To do. The dispersion for forming the catalyst layer is prepared by dispersing a metal-supported catalyst in a polymer electrolyte solution or dispersion.

  The catalyst layer 2 formed on the release film is disposed on both surfaces of the polymer electrolyte membrane 1, and hot-pressed under predetermined heating and pressurizing conditions to join the polymer electrolyte membrane 1 and the catalyst layer 2 and release them. By peeling the mold film, an MEA in which the catalyst layers 2 are formed on both surfaces of the polymer electrolyte membrane 1 can be produced.

  Further, the catalyst-supported gas in which the catalyst layer 2 is formed on the diffusion layer 3 by applying the dispersion solution onto the diffusion layer 3 using a coater or the like, and drying and removing the solvent in the dispersion solution. A diffusion electrode is produced, the catalyst layer 2 side of the catalyst-carrying gas diffusion electrode is disposed on both sides of the polymer electrolyte membrane 1, and hot pressing is performed under predetermined heating and pressurizing conditions. An MEA having the catalyst layer 2 and the diffusion layer 3 formed on both sides can be manufactured. In addition, you may use a commercially available gas diffusion electrode (made by USA E-TEK company etc.) for the said catalyst carrying | support gas diffusion electrode.

  Examples of the polymer electrolyte solution include an alcohol solution of a perfluorocarbon sulfonic acid polymer compound (such as Nafion (registered trademark) solution manufactured by Aldrich) or a sulfonated aromatic polymer compound (eg, sulfonated polyether ether ketone). , Sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polyimide, sulfonated polyphenylene sulfide, and the like) can be used.

  As the carrier in the metal-supported catalyst, conductive particles having a high specific surface area can be used as the carrier, and examples thereof include carbon materials such as activated carbon, carbon black, ketjen black, vulcan, carbon nanohorn, fullerene, and carbon nanotube. . In addition, as the metal catalyst in the metal-supported catalyst, any metal catalyst that promotes the oxidation reaction of the fuel and the reduction reaction of oxygen can be used, and the fuel electrode and the oxidant electrode may be the same or different. I do not care. For example, noble metals such as platinum and ruthenium or alloys thereof can be exemplified, and a promoter for promoting their catalytic activity or suppressing poisoning by reaction by-products may be added.

  The dispersion solution for forming the catalyst layer may be applied by spraying or may be appropriately diluted with water or an organic solvent in order to adjust the viscosity to be easily applied with a coater. Moreover, you may mix fluorine-type compounds, such as tetrafluoroethylene, in order to provide water repellency to the catalyst layer 2 as needed.

  As the diffusion layer 3, a porous conductive material such as carbon cloth or carbon paper can be used. In order to promote the diffusibility of fuel and oxidant and the discharge of reaction by-products and unreacted substances, it is preferable to use those that are coated with tetrafluoroethylene or the like to impart water repellency. Further, an adhesive layer made of the polymer electrolyte or the like may be provided between the polymer electrolyte membrane 1 and the catalyst layer 2 as necessary.

  The conditions for hot pressing the polymer electrolyte membrane 1 and the catalyst layer 2 under heating and pressurizing conditions may be appropriately set according to the type of polymer electrolyte contained in the polymer electrolyte membrane 1 or the catalyst layer 2 to be used. Good.

  Generally, the heating temperature is equal to or lower than the thermal degradation or thermal decomposition temperature of the polymer electrolyte membrane or the polymer electrolyte, and is a temperature higher than the glass transition point or the softening point of the polymer electrolyte membrane 1 or the polymer electrolyte. Is preferably carried out under temperature conditions above the glass transition point and softening point of the polymer electrolyte membrane 1 and the polymer electrolyte.

  Moreover, it is preferable that pressurization conditions are the range of 0.1MPa-20MPa. As a result, the polymer electrolyte membrane 1 and the catalyst layer 2 are sufficiently in contact with each other, and there is no deterioration in characteristics due to significant deformation of the material used. In particular, when the MEA is formed only from the polymer electrolyte membrane 1 and the catalyst layer 2, the diffusion layer 3 may be disposed outside the catalyst layer 2 and used only by contacting without being particularly bonded. I do not care.

  The MEA obtained by the method as described above is inserted between a pair of separators 4 in which a flow path 5 for feeding fuel gas or liquid and an oxidant is formed, and the like according to the present embodiment. A polymer electrolyte fuel cell comprising a molecular electrolyte membrane can be obtained.

  As the separator 4, a conductive material such as carbon graphite or stainless steel can be used. In particular, when a metal material such as stainless steel is used, it is preferable to perform a corrosion resistance treatment.

  A gas or liquid mainly containing hydrogen or a gas or liquid mainly containing methanol or a gas containing oxygen as an oxidant (oxygen or air) is diffused as a fuel gas or liquid from separate flow paths 5. By supplying the catalyst layer 2 via the layer 3, the polymer electrolyte fuel cell generates power. At this time, when a hydrogen-containing liquid is used as a fuel, a direct liquid fuel cell is obtained, and when methanol is used, a direct methanol fuel cell is obtained. That is, in the present embodiment, the polymer electrolyte fuel cell has been described. However, the present embodiment can be applied to a direct liquid fuel cell and a direct methanol fuel cell as they are.

  In addition, 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.

  Next, an embodiment of a direct methanol fuel cell using the polymer electrolyte membrane of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram schematically showing a cross-sectional structure of a main part of a direct methanol fuel cell made of the polymer electrolyte membrane according to the present embodiment.

  As shown in FIG. 2, the direct methanol fuel cell 20 according to the present embodiment includes an MEA 16, a fuel (methanol or methanol aqueous solution) tank 17, a fuel filling unit (supply unit) 18, and a support 19.

  A required number of MEAs 16 are arranged on both sides of the fuel tank 17 in a planar shape. The MEA 16 may be obtained by the method described above. Further, a support body 19 is disposed outside the MEA 16. An oxidant flow path 15 is formed in the support 19. By sandwiching the support 19, a direct methanol fuel cell cell and stack are formed.

  In addition to the above examples, the polymer electrolyte membrane of the present invention is disclosed in JP 2001-313046, JP 2001-313047, JP 2001-93551, JP 2001-93558, JP 2001-93561 A, JP 2001-102069 A, JP 2001-102070 A, JP 2001-283888 A, JP 2000-268835 A, JP 2000-268836 A, JP It can be used as an electrolyte membrane of a polymer electrolyte fuel cell or a direct methanol fuel cell, which is publicly known in JP-A-2838992. Based on these known documents, those skilled in the art can easily construct a polymer electrolyte fuel cell or a direct methanol fuel cell using the polymer electrolyte membrane of the present invention.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, A various change is possible in the range shown to the claim. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  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)
<Preparation of polymer film>
Polyphenylene sulfide (manufactured by Dainippon Ink and Chemicals, LD10p11) as a polymer compound having an aromatic unit, and high-density polyethylene (HI-ZEX 3300F, manufactured by Mitsui Chemicals, Inc.) as a polymer compound having no aromatic unit. used.

  First, 30 parts by weight of polyphenylene sulfide pellets and 70 parts by weight of high density polyethylene pellets were dry blended.

  Next, the dry blended pellet mixture was melt-extruded using a twin-screw extruder with a T-die set to obtain a polymer film (containing 70% by weight of high-density polyethylene in the polymer film). . The melt extrusion molding was performed under the conditions of a screw temperature of 290 ° C. and a T die temperature of 290 ° C.

<Preparation of polymer electrolyte membrane>
In a glass container, 868 g of dichloromethane and 8.7 g of chlorosulfonic acid were weighed to prepare a 1% by weight chlorosulfonic acid solution. 2.0 g of the polymer film was weighed, immersed in the chlorosulfonic acid solution, and allowed to stand at 25 ° C. for 20 hours (the amount of chlorosulfonic acid added was 4.3 times the weight of the polymer film). . After the standing, the polymer film was collected and washed with ion exchange water until neutral.

  The polymer film after washing is left in a thermo-hygrostat whose temperature is adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, respectively. The polymer electrolyte membrane was obtained by drying.

<Polymer electrolyte membrane heat treatment>
Next, the obtained polymer electrolyte membrane was heat-treated in a vacuum oven at 80 ° C. for 3 hours to obtain a polymer electrolyte membrane subjected to the heat treatment. The decrease in ion exchange capacity before and after the heat treatment was 3.6%.

<Measurement method of ion exchange capacity>
A polymer electrolyte membrane sample (about 10 mm × 40 mm) was immersed in 20 mL of a saturated aqueous solution of sodium chloride at 25 ° C., and then subjected to an ion exchange reaction at 60 ° C. for 3 hours in a water bath.

  It cooled to 25 degreeC after the said ion exchange reaction. Next, the polymer electrolyte membrane sample was sufficiently washed with ion-exchanged water, and all of the saturated aqueous sodium chloride solution and the washing water were collected. To this recovered solution, a phenolphthalein solution was added as an indicator, and neutralization titration was performed with a 0.01N sodium hydroxide aqueous solution to calculate the ion exchange capacity. Table 1 shows the results of applying the polymer electrolyte membrane before and after the heat treatment to this ion exchange capacity measurement method.

<Measurement method of proton conductivity>
A polymer electrolyte membrane sample (about 10 mm × 40 mm) stored in ion-exchanged water was taken out, and water on the surface of the polymer electrolyte membrane was wiped off with a filter paper. Next, a polymer electrolyte membrane sample is placed in a bipolar non-sealed polytetrafluoroethylene cell, and the platinum electrode is placed on the surface of the polymer electrolyte membrane sample (on the same side) so that the distance between the electrodes is 30 mm. installed. Membrane resistance at 23 ° C. was measured by an alternating current impedance method (frequency: 42 Hz to 5 MHz, applied voltage: 0.2 V, Hioki LCR meter 3531Z HITESTER), and proton conductivity was calculated. Table 1 shows the results of applying the polymer electrolyte membrane after the heat treatment to this proton conductivity measurement method.

<Measurement method of methanol barrier properties>
In an environment of 25 ° C., ion exchange water and a 64 wt% aqueous methanol solution were isolated by an electrolyte membrane using a membrane permeation experiment apparatus (KH-5PS manufactured by Beadrex). A solution containing methanol permeated to the ion-exchanged water after a predetermined time (2 hours) was collected, and the amount of methanol permeated with a gas chromatograph (Gas Chromatography GC-2010, manufactured by Shimadzu Corporation) was quantified. From this quantitative result, the methanol permeation rate was determined, and the methanol permeation coefficient was calculated. The methanol permeability coefficient was calculated according to the following formula 1.

[Formula 1]
Methanol permeability coefficient (μmol / (cm ・ day))
= Methanol permeation amount (μmol) × film thickness (cm) / (membrane area (cm ² ) × permeation time (days))
Table 1 shows the methanol permeability coefficient of the polymer electrolyte membrane after the heat treatment.

<Methanol resistance test>
The polymer electrolyte membrane was immersed in a 64 wt% aqueous methanol solution and allowed to stand in an oven at 60 ° C. After a predetermined time, the electrolyte membrane was collected and washed with ion exchange water.

  The polymer electrolyte membrane after washing is dried in a constant temperature and humidity chamber adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity of 98%, 80%, 60% and 50%, respectively. The weight and ion exchange capacity were measured.

  FIG. 3 shows the relationship between the immersion time and the weight retention rate as a result of the methanol resistance test.

  FIG. 4 shows the relationship between the immersion time and the ion exchange capacity as a result of the methanol durability test.

  In the present invention, the weight retention is a value calculated by the following mathematical formula 2.

[Formula 2]
Weight retention (%)
= Polymer electrolyte membrane (g) after immersing in 64% by weight methanol aqueous solution and elapse of a predetermined time × Polymer electrolyte membrane (g) immediately before immersing in 100/64% by weight methanol aqueous solution
In the present invention, the retention rate of the ion exchange capacity is a value calculated by the following mathematical formula 3.

[Formula 3]
Retention rate of ion exchange capacity (%)
= Ion exchange capacity (milli equivalent / g) after immersing in a 64% by weight methanol aqueous solution after elapse of a predetermined time × Ion exchange capacity (milli equivalent / g) immediately before being immersed in a 100/64% by weight methanol aqueous solution
The results obtained by subjecting the polymer electrolyte membrane after the heat treatment obtained in this example to the methanol durability test are indicated by white square symbols in FIGS. 3 and 4. The weight retention rate of the polymer electrolyte membrane according to the present example after 99 hours of the methanol resistance test was 99%, and the retention rate of the ion exchange capacity was 100%.

(Example 2)
<Preparation of polymer film>
Polyphenylene sulfide (manufactured by Dainippon Ink and Chemicals, LD10p11) as a polymer compound having an aromatic unit, and high-density polyethylene (HI-ZEX 3300F, manufactured by Mitsui Chemicals, Inc.) as a polymer compound having no aromatic unit. used.

  50 parts by weight of polyphenylene sulfide pellets and 50 parts by weight of high density polyethylene pellets were dry blended. Next, using a twin-screw extruder with a T-die set, the dry blended pellet mixture was melt-extruded to obtain a polymer film (containing 50% by weight of high-density polyethylene in the polymer film). . The melt extrusion molding was performed under the conditions of a screw temperature of 290 ° C. and a T die temperature of 290 ° C.

<Preparation of polymer electrolyte membrane>
In a glass container, 856 g of dichloromethane and 4.3 g of chlorosulfonic acid were weighed to prepare a 0.5 wt% chlorosulfonic acid solution. 2.0 g of the polymer film was weighed, immersed in the chlorosulfonic acid solution and allowed to stand at 25 ° C. for 20 hours (the amount of chlorosulfonic acid added was 2.1 times the weight of the polymer film). After the standing, the polymer film was collected and washed with ion exchange water until neutral.

  The polymer film after washing is left in a thermo-hygrostat whose temperature is adjusted to 23 ° C. for 30 minutes under humidity control of relative humidity 98%, 80%, 60% and 50%, respectively. The polymer electrolyte membrane was obtained by drying.

  Next, heat treatment was performed under the same conditions as in Example 1. The decrease in ion exchange capacity before and after the heat treatment was 0.8%.

  Table 1 shows the results of measuring the ion exchange capacity, proton conductivity, and methanol permeability coefficient of the polymer electrolyte membrane after heating in the present example.

  In addition, the results of the methanol resistance test on the heated polymer electrolyte membrane in this example are indicated by black square symbols in FIGS. 3 and 4. The weight retention rate of the polymer electrolyte membrane according to the present example after 99 hours of the methanol resistance test was 99%, and the retention rate of the ion exchange capacity was 100%.

(Comparative Example 1)
Nafion (registered trademark) 115 (manufactured by DuPont) was used as the polymer electrolyte membrane.

  The heat treatment described in Examples 1 and 2 was not performed.

  Table 1 shows the results of measuring the ion exchange capacity, proton conductivity, and methanol permeability coefficient of the polymer electrolyte membrane according to this comparative example, as in Example 1.

  Further, the results of the methanol durability test on the polymer electrolyte membrane according to this comparative example are indicated by white triangle symbols in FIGS. 3 and 4.

(Comparative Example 2)
<Production of polymer electrolyte membrane>
In a reaction vessel equipped with a mechanical stirrer, a nitrogen introduction tube, and a dropping funnel, 3.7 g of PEEK450P (manufactured by Victorex MC Ltd., molecular weight of about 100,000) was put. In the reactor, 92 g of concentrated sulfuric acid was added using a dropping funnel and stirred at room temperature for 3 days.

  After the completion of the stirring, the obtained reaction solution was poured into 3 liters of pure water, and washed with 3 liters of pure water 10 times until the filtrate became neutral. The obtained reaction product was dried at 90 ° C. for 10 hours under a vacuum of 1 Torr (1.3332 hPa) to obtain 4.5 g of a yellow solid. 2.14 g of this yellow solid was dissolved in 26.4 g of N, N-dimethylformamide (DMF) and placed in a petri dish having an inner diameter of 60 mm. Furthermore, it was dried at 110 ° C. for 3 hours under a vacuum of 1 Torr (1.3332 hPa) in a vacuum oven.

  The dried film obtained by the above drying was swollen with water and then peeled off from the petri dish and dried at 110 ° C. for 5 hours under a vacuum of 1 Torr (1.3332 hPa). Thereby, a polymer electrolyte membrane was obtained.

<Polymer electrolyte membrane heat treatment>
Next, the obtained polymer electrolyte membrane was heat-treated in a vacuum oven at 170 ° C. for 3 hours to obtain a heat-treated polymer electrolyte membrane.

  Table 1 shows the results of measuring the ion exchange capacity of the polymer electrolyte membrane according to this comparative example in the same manner as in Example 1.

  In Table 1, the comparison between Examples 1 and 2 and Comparative Example 1 reveals that the electrolyte membrane of the present invention exhibits proton conductivity in the same order as known electrolyte membranes for fuel cells and is useful as an electrolyte membrane for fuel cells. It was shown that. Furthermore, since the methanol permeability coefficient of Examples 1 and 2 is lower than that of Comparative Example 1, the polymer electrolyte membrane according to the present invention has a high methanol barrier property and is particularly suitable as an electrolyte membrane for a direct methanol fuel cell. It has been shown to be useful. Furthermore, the comparison between Examples 1 and 2 and Comparative Example 2 showed that the polymer electrolyte membrane according to the present invention maintained proton conductivity within a 20% decrease in ion exchange capacity before and after heat treatment. From this, it was shown that the polymer electrolyte membrane according to the present invention is useful as a polymer electrolyte membrane for a fuel cell.

  As a result of comparison between Examples 1 and 2 and Comparative Example 1 in FIG. 3, the polymer electrolyte membrane according to the present invention exhibited high weight retention under immersion in a 64 wt% methanol aqueous solution. From this, it was shown that the polymer electrolyte membrane according to the present invention is excellent in methanol resistance and is particularly useful as an electrolyte membrane for a direct methanol fuel cell.

  A comparison between Examples 1 and 2 and Comparative Example 1 in FIG. 4 showed that the polymer electrolyte membrane according to the present invention was not reduced in ion exchange capacity when immersed in a 64 wt% methanol aqueous solution. From this, it was shown that the polymer electrolyte membrane according to the present invention has excellent durability against methanol and is particularly useful as an electrolyte membrane for a direct methanol fuel cell.

  The polymer electrolyte membrane according to the present invention has various industrial applicability including fuel cells such as solid polymer fuel cells, direct liquid fuel cells, and direct methanol fuel cells.

FIG. 1 is a diagram schematically showing a cross-sectional structure of a main part of a polymer electrolyte fuel cell using a polymer electrolyte membrane according to the present embodiment. FIG. 2 is a diagram schematically showing a cross-sectional structure of a main part of a direct methanol fuel cell made of the polymer electrolyte membrane according to the present embodiment. FIG. 3 is a graph showing the relationship between the immersion time and the weight retention rate as a result of the methanol durability test. FIG. 4 shows the relationship between the immersion time and the ion exchange capacity as a result of the methanol durability test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2 Catalyst layer 3 Diffusion layer 4 Separator 5 Channel 10 Solid molecular fuel cell 15 Oxidant channel 16 Membrane-electrode assembly (MEA)
17 Fuel tank 18 Fuel filling part 19 Support body 20 Direct methanol fuel cell

Claims (13)

A method for producing a polymer electrolyte membrane comprising the following steps (X) and (Y):
(X) A proton conductive functional group introducing agent for introducing a proton conductive functional group into a polymer film containing a polymer compound having an aromatic unit and a polymer compound not having an aromatic unit into the polymer film Contacting with
(Y) The process of heating the polymer film which contacted the said proton conductive functional group introducing agent to 60 degreeC or more and 150 degrees C or less. 2. The polymer electrolyte according to claim 1, wherein the polymer compound having an aromatic unit is one polymer selected from the following (i) to (iii), or a mixture of these polymers: Membrane manufacturing method:
(I) at least one polymer selected from the group of polymers consisting of polystyrene, syndiotactic polystyrene, polyphenylene ether, modified polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, and polyphenylene sulfide;
(Ii) a copolymer comprising the polymer described in (i) above;
(Iii) Derivatives of the polymers described in (i) and (ii) above.   The polymer compound having an aromatic unit is one polymer selected from the group consisting of polystyrene, syndiotactic polystyrene, polyphenylene sulfide, and polyethylene-polystyrene graft copolymer, or a mixture of these polymers. The method for producing a polymer electrolyte membrane according to claim 1 or 2. The polymer compound having no aromatic unit is represented by the following general formula (1):
-(CX ₁ X ₂ -CX ₃ X ₄ )-(1)
_(Wherein, X _{1 to 4 is,} H, based on any one of CH 3, Cl, F, OCOCH 3, CN, COOH, COOCH 3, OC 4 H 9, is selected from the group consisting _{of, X. 1 to 4} are independent of each other and may be the same or different from each other.) The polymer according to claim 1, which is a polymer selected from polymer compounds having a repeating unit, or a mixture thereof. The manufacturing method of the polymer electrolyte membrane of any one of Claims 1.   The polymer compound having no aromatic unit is at least one selected from the group consisting of polyethylene, polypropylene, polymethylpentene, and derivatives thereof. 2. A method for producing a polymer electrolyte membrane according to item 1.   The method for producing a polymer electrolyte membrane according to any one of claims 1 to 5, wherein the step (X) is performed in the presence of an organic solvent.   The method for producing a polymer electrolyte membrane according to claim 6, wherein the organic solvent is at least one organic solvent selected from the group consisting of dichloromethane, 1,2-dichloroethane and 1-chlorobutane.   The method for producing a polymer electrolyte membrane according to any one of claims 1 to 7, wherein the proton conductive functional group introducing agent is a sulfonating agent.   The method for producing a polymer electrolyte membrane according to claim 8, wherein the sulfonating agent is chlorosulfonic acid.   The method for producing a polymer electrolyte membrane according to any one of claims 1 to 9, wherein the ion exchange capacity in the step (Y) is reduced within a range of 20% or less.   The polymer electrolyte membrane manufactured by the manufacturing method of the polymer electrolyte membrane of any one of Claims 1-10.   A membrane-electrode assembly comprising the polymer electrolyte membrane according to claim 11.   A fuel cell comprising the polymer electrolyte membrane according to claim 11.

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