JP4379130B2 - Proton conducting membrane for direct methanol fuel cell and method for producing the same - Google Patents

Description

  The present invention relates to a proton conductive membrane used in a solid polymer fuel cell, particularly a direct methanol fuel cell in which methanol is directly supplied to a cell without reforming it to hydrogen to generate electric power.

  The direct methanol fuel cell (DMFC), which generates electricity by supplying methanol directly to the cell without reforming it into hydrogen, has features such as power generation performance, ease of handling, and simplicity of the system. As a portable power source for personal computers and the like, it is attracting attention as a power source that replaces the conventional lithium ion battery.

  So far, proton conduction membranes for DMFC include polymers belonging to so-called cation exchange resins, for example, sulfonated products of vinyl polymers such as polystyrene sulfonic acid, perfluoroalkyl sulfonic acid polymers, perfluoroalkyl carboxylic acid polymers, and the like. Among them, a perfluoroalkylsulfonic acid proton conductive membrane represented by Nafion (trade name, manufactured by DuPont) has been widely used.

  However, the perfluoroalkylsulfonic acid proton conductive membrane has high proton conductivity, but has high methanol permeability, so that there is a so-called crossover in which methanol leaks from the anode to the cathode as the water molecules move. There is a problem that the battery performance is remarkably deteriorated. For this reason, it is necessary to use a low-concentration aqueous methanol solution as a fuel, and the power generation efficiency has been greatly reduced. In fact, it has high proton conductivity and improved resistance to methanol solution for use at high methanol concentration, which is expected to be superior to currently used lithium ion batteries. Application of proton conducting membrane is indispensable.

  In addition, perfluoroalkyl sulfonic acid proton conductive membranes are very expensive, and there are problems in physical properties such as use at high temperatures and mechanical strength. From this point of view, a material that is cheaper, is thermally and mechanically stable, and exhibits excellent ion conductivity as a proton conductive membrane has been awaited.

  The proton conducting membrane is supposed to diffuse hydrogen ions through a cluster of water formed in a hydrophilic channel (ion conducting channel). Therefore, from the viewpoint of ionic conductivity, it is considered that the spatial channel structure formed by the ionic conduction component in the film is extremely important. Specifically, the idea of ensuring high ionic conductivity by providing a proton conducting membrane having a membrane structure that continuously forms hydrophilic channels has become common.

  On the other hand, when focusing on the crossover of methanol, there is a problem that methanol permeates and moves together with hydrogen ions and water molecules through the hydrophilic channel as described above. In order to suppress the permeation of methanol, it is necessary to eliminate the continuity of the hydrophilic channel, but if the continuity of the hydrophilic channel is lost, the proton conduction path is cut and the proton conductivity decreases. There are drawbacks.

Using a block copolymer in which two or more kinds of mutually incompatible polymers (block chains) are covalently bonded to form one polymer chain can control the arrangement of chemically different components on the nanometer scale. it can. In block copolymers, short-range interaction resulting from repulsion between chemically different block chains causes phase separation into regions (microdomains) consisting of the respective block chains, but the block chains are covalently bonded to each other. The effect of the long-range interaction that occurs causes each microdomain to be arranged in a specific order. A structure created by the assembly of microdomains made up of block chains is called a microphase separation structure. A block copolymer film is generally produced by spreading a solution of a block copolymer dissolved in an organic solvent on a suitable substrate and then removing the solvent. The microphase-separated structure of the produced membrane is the composition of the constituents as disclosed in Bates, fS; Fredrickson, gH; Annu. Res. Phys. Chem. 1990 (41) 525 (Non-patent Document 1). Shows a crystalline structure such as a spherical micelle structure, a cylinder structure, or a lamellar structure. For example, if a microphase separation structure obtained from a block copolymer consisting of a hydrophilic segment with proton conductivity and a hydrophobic segment with methanol resistance is used, the spatial arrangement of ion conduction sites and methanol permeation suppression sites in the membrane It is expected that can be controlled in more detail.

  A proton conductive polymer solid electrolyte using a block copolymer is disclosed in JP-A-8-20704 (Patent Document 1).

On the other hand, in Japanese Patent Application Laid-Open No. 10-503788 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2003-142125 (Patent Document 3), an example of a solid electrolyte membrane obtained by sulfonating a triblock copolymer using an aliphatic vinyl compound as a raw material Is disclosed.
Bates, FS; Fredrickson, GH; Annu. Res. Phys. Chem. 1990 (41) 525 JP-A-8-20704 Japanese National Patent Publication No. 10-503788 JP 2003-142125 A

  The proton conductive polymer solid electrolyte disclosed in Patent Document 1 discloses a combination of specific chemical structures as a block chain, and the space of ion conduction sites and methanol permeation suppression sites in the membrane targeted by the present invention. The technical idea is different from that which focuses on the improvement of the characteristics by controlling the general arrangement.

  On the other hand, Patent Document 2 and Patent Document 3 focus on spatial arrangement control of ion conduction sites in the membrane, and have high proton conductivity by using a hydrophilic channel (ion conduction channel) as a continuous phase. The purpose is to secure. However, as described above, in these methods, it is difficult to achieve both high proton conductivity and methanol permeation suppression, and an element for suppressing methanol permeation is required separately. In addition, block copolymers having an aliphatic basic skeleton generally have a low glass transition point and thus are thermally unstable, and there is a problem that the phase separation structure changes due to thermal history and the physical properties change. It was.

  The present invention has been made against the background of the prior art as described above. By controlling the spatial arrangement of ion conduction sites and methanol permeation suppression sites in the membrane in more detail, high proton conductivity and The purpose is to achieve both methanol permeation suppression.

  As a result of studying such problems in the prior art, the present inventor has used a microphase separation structure obtained from a block copolymer composed of a hydrophilic segment having proton conductivity and a hydrophobic segment having methanol resistance. It has been found that high proton conductivity and methanol permeation suppression can be achieved by controlling the spatial arrangement of the ion conduction site and the methanol permeation suppression site in more detail, and the present invention has been completed.

  Specifically, the essential point of the present invention is that the hydrophobic segment forms a lamellar phase and the methanol permeation is suppressed by partially dividing the continuous phase (hydrophilic channel) composed of the hydrophilic segment. It is. At this time, it is necessary that the hydrophilic channel is not completely surrounded by a hydrophobic segment in a spatial network. This is because, from the viewpoint of extending the process of methanol permeating through the hydrophilic channel and suppressing methanol permeation in the membrane, the lamellar structure that partially divides the hydrophilic channel as in the present invention is also capable of completely separating the hydrophilic channel. The aim is the same for the network structure to be enclosed, but if the network structure is formed, the proton conductivity is greatly lowered, and the purpose may not be achieved.

  By limiting the fragmentation of the hydrophilic channel by the lamellar structure composed of the hydrophobic segment to a partial one, it is possible to ensure high proton conductivity without impairing methanol permeation suppression.

That is, the proton conductive membrane for direct methanol fuel cell of the present invention is as follows.
(1) A film comprising a polymer segment (A) having an ion conductive component and a polymer segment (B) having no ion conductive component,
The direct methanol type wherein the morphology of the membrane has a micro phase separation structure, wherein (A) forms a continuous phase and (B) forms a discontinuous lamellar structure. Proton conducting membrane for fuel cells.
(2) In the morphological observation by the electron microscope of the film cross section, the width of the lamellar structure composed of the polymer segment (B) forming the microphase separation structure is
The proton conductive membrane for direct methanol fuel cells according to (1), characterized in that it is in the range of 5 to 200 nm.
(3) The proton conducting membrane for direct methanol fuel cells according to (1) and (2), which is a block copolymer in which polymer segments (A) and (B) are covalently bonded.
(4) The main chain skeleton forming the copolymer having the polymer segments (A) and (B) has a structure in which an aromatic ring is covalently bonded with an appropriate bonding group, and the skeleton of the polymer segment (A) is (1) to (3) a proton conductive membrane for a direct methanol fuel cell, which contains a sulfonic acid group in the side chain.
(5) The solvent used when forming the film composed of the polymer segments (A) and (B) contains 30% by weight or more of an organic solvent that does not interact with the polymer segment (A) having an ion conductive component. (1) to (4) a method for producing a proton conductive membrane for a direct methanol fuel cell.
(6) The organic solvent that does not interact with the polymer segment (A) having the ion conductive component is an organic solvent that does not contain N that is a single or double bond as the bonding mode of the substituent on the nitrogen atom, It contains an organic solvent having at least one group consisting of —O—, —OH, —CO—, —SO ₂ —, —SO ₃ —, —CN, —NO ₂ and —CO ₂ —. (5) A method for producing a proton conductive membrane for a direct methanol fuel cell.

  ADVANTAGE OF THE INVENTION According to this invention, the tolerance to methanol aqueous solution is high, and the proton conductive membrane for direct methanol type fuel cells which has high proton conductivity can be provided. The direct methanol fuel cell using the proton conducting membrane of the present invention can be suitably used even in a high methanol aqueous solution, and high power generation characteristics can be expected.

Hereinafter, the proton conductive membrane according to the present invention will be specifically described.
(Morphology)
The proton conductive membrane according to the present invention comprises a polymer segment (A) having an ion conductive component and a polymer segment (B) having no ion conductive component, and (A) and (B) have a microphase separation structure. It is the formed film. (A) may be considered as a hydrophilic segment, and (B) as a hydrophobic segment. When used in a direct methanol fuel cell, the hydrophilic segment in (A) is proton conducting, and the hydrophobic segment in (B) is methanol permeable. It is mainly responsible for restraint.

  In the film, the hydrophobic segment forms a lamellar phase, and this lamellar structure partially divides the continuous phase composed of the hydrophilic segment. The permeability of methanol to the proton conducting membrane is considered to be defined by the rate of methanol penetration and leaching on the front and back surfaces of the membrane and the diffusion rate of methanol in the membrane. Therefore, due to the partial disruption of the hydrophilic phase due to the lamellar structure that is a feature of the proton conducting membrane of the present invention, the process in which methanol permeates and moves through the hydrophilic channel is extended, and the diffusion rate of methanol in the membrane is reduced. It is considered that methanol permeation in the thickness direction can be suppressed.

  The lamella structure here refers to a hydrophobic structure that is observed in a band or string shape when the morphology of the cross section of the film is observed with, for example, a transmission electron microscope (TEM). At this time, the lamellar structure in the film is a discontinuous phase, and not all are connected to each other. Also, the lamella structure need not be upright but may be winding. The number of hydrophobic lamellae contained per unit volume and the volume fraction of hydrophobic lamellae occupied per unit volume can be changed depending on the structure of the polymer, polymerization conditions, and film forming conditions.

  More specifically, in morphological observation of the cross section of the film using TEM, the width of the lamellar structure consisting of (B) forming a microphase separation structure (corresponding to the thickness of the three-dimensional string-like lamellae, Since it is performed in two dimensions, it is expressed as width here), and the case where it is in the range of 5 to 200 nm is suitable for the present invention.

If the size of the hydrophobic lamella formed from (B) forming the microphase separation structure is outside the above range, the microphase separation becomes unclear when the size is smaller than 5 nm, and the function of methanol permeation suppression by the hydrophobic lamella is manifested. do not do. On the other hand, when it is larger than 200 nm, the hydrophobicity is too strong and the proton conductivity is lowered.
(Block copolymer)
The membrane structure capable of forming a microphase separation structure according to the present invention is a block copolymer in which polymer segments (A) and (B) are covalently bonded, and the main chain skeleton has an aromatic ring with an appropriate bonding group. It has a covalently bonded structure, and the skeleton of the polymer segment (A) contains a sulfonic acid group in the side chain.

  As a means for controlling the microphase-separated structure as described above by defining the structure of the substrate, there is a use of a block copolymer in which incompatible polymers are covalently bonded to each other to form one polymer chain. It is preferable to use a copolymer comprising a polymer segment (A) having an ion conductive component and a polymer segment (B) having no ion conductive component.

  As the structure of the block copolymer, the main chain skeleton forming the copolymer having the polymer segments (A) and (B) has a structure in which an aromatic ring is covalently bonded with a linking group, and the polymer segment (A ) Having a sulfonic acid group in the side chain is preferred.

As the main chain skeleton, a structure in which an aromatic ring is covalently bonded with a linking group in consideration of mechanical strength and heat resistance is preferable. The formation of a microphase separation structure is greatly affected by thermodynamic control, and it is known that the composition of the substrate and the thermal history during film formation are important for the phase separation structure. In addition, considering the stabilization of film properties after film formation, it is necessary to select a material that is not easily affected by thermal history, that is, a material having a high glass transition temperature. The selection of the block copolymer (polyarylene) contained in is preferable.

  As for the ion conductive component, a sulfonic acid group is preferable from the standpoint of substrate stability and proton conduction efficiency. Further, the introduction position is preferably introduced through a specific bonding group or atomic group as a side chain rather than directly introduced into the main chain from the viewpoint of formation of a microphase-separated structure and mechanical strength. . A polymer in which a sulfonic acid is directly introduced into the main chain has several disadvantages regarding required basic characteristics of a proton conductive membrane for a fuel cell, in addition to low ability to form a microphase separation structure and low mechanical strength.

  Hereinafter, the polyarylene copolymer containing a sulfonic acid group according to the present invention and a film obtained therefrom will be described in detail.

  The polyarylene having a sulfonic acid group used in the present invention includes a repeating structural unit represented by the following general formula (A) and a repeating structural unit represented by the following general formula (B). It is a polymer represented by general formula (C).

In the formula, A represents a divalent electron-withdrawing group. Specifically, —CO—, —SO ₂ —, —SO—,
—CONH—, —COO—, — (CF ₂ ) ₁ — (wherein 1 is an integer of 1 to 10), —C (CF ₃ ) ₂ — and the like can be mentioned.

B represents a divalent electron donating group or a direct bond. Specific examples of the electron donating group include — (CH ₂ ) —, —C (CH ₃ ) ₂ —, —O—, —S—, —CH═CH—, —C≡C— and

Etc. The electron-withdrawing group means a group having a Hammett substituent constant of 0.06 or more when the phenyl group is in the m-position and 0.01 or more when the p-position is p-position.

Ar represents an aromatic group having a substituent represented by —SO ₃ H, and specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group. Of these groups, a phenyl group and a naphthyl group are preferable.
m represents an integer of 0 to 10, preferably 0 to 2, n represents an integer of 0 to 10, preferably 0 to 2, and k represents an integer of 1 to 4.

In formula (B), R ^{1 to} R ⁸ may be the same as or different from each other, and are selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group. At least one atom or group is shown.

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.

  Examples of the fluorine-substituted alkyl group include trifluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, trifluoromethyl group, pentafluoroethyl group, and the like. Etc. are preferable.

Examples of allyl groups include propenyl groups,
Examples of the aryl group include a phenyl group and a pentafluorophenyl group.

  W represents a single bond or a divalent electron-withdrawing group, and T represents a single bond or a divalent organic group.

  In the formula (B), p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

  The block copolymer is represented below.

(In the formula (C), W, T, A, B, Ar, m, n, k, p and R ^{1 to} R ⁸ are W, T, A in the general formulas (A) and (B), respectively. , B, Ar, m, n, k, p, and R ^{1 to} R ⁸ , x and y are molar ratios when x + y = 100 mol%.)
The polyarylene having a sulfonic acid group used in the present invention has a repeating structural unit represented by the formula (A) in a proportion of 0.05 to 99.95 mol%, preferably 10 to 99.5 mol%. The repeating structural unit represented by (B) is 0.05 to 99.95 mol%, preferably 0.8.
It is desirable to contain in the ratio of 5-90 mol%.

(Method for producing block copolymer having sulfonic acid group)
The copolymer of the present invention comprises a monomer that forms the repeating unit (a) of the block represented by the general formula (A) and a monomer that forms the repeating unit (b) of the block represented by the general formula (B). Alternatively, it can be synthesized by copolymerizing with an oligomer.

  Further, a polymer having a block of the general formula (A) not containing a sulfonic acid group and a block represented by the general formula (B) can be synthesized in advance, and the polymer can be synthesized by sulfonation. .

  The reaction conditions for synthesizing the copolymer of the present invention, the monomer forming the repeating unit (a), and the functional group of the monomer forming the repeating unit (b), the repeating unit (a) is repeated from these monomers. Known reaction conditions and functional groups used for synthesizing the structural unit (polymer) and the structural unit (polymer) in which the repeating unit (b) is repeated are selected.

  The copolymer of the present invention is prepared by previously polymerizing at least one of the monomer that forms the repeating unit (a) and the monomer that forms the repeating unit (b) to produce a precursor. It can be produced by reacting other copolymer components.

  As the monomer that can be the structural unit of the general formula (A), for example, a compound represented by the following general formula (D) is used.

In the formula (D), X represents a halogen atom other than fluorine (chlorine, bromine, iodine), —OSO ₂ Z (
Here, Z represents an alkyl group, a fluorine-substituted alkyl group or an aryl group. A, B, m, n and k have the same meanings as A, B, m, n and k in the general formula (A), respectively.

Ar ′ represents an aromatic group having a —SO ₃ H or —SO ₃ R group when not sulfonated, and a substituent represented by —SO ₃ H or —SO ₃ R group when sulfonated. An aromatic group having no group is exemplified, and specific examples of the aromatic group include a phenyl group, a naphthyl group, an anthracenyl group, and a phenanthyl group. Of these groups, a phenyl group and a naphthyl group are preferable. R represents a hydrocarbon group having 1 to 20 carbon atoms, preferably 4 to 20 carbon atoms.

  m represents an integer of 0 to 10, preferably 0 to 2, n represents an integer of 0 to 10, preferably 0 to 2, and k represents an integer of 0 to 4 (when sulfonating, k may be 0) ).

  As the oligomer (E), for example, a compound represented by the following general formula (E) is used.

In the formula (E), R ′ and R ″ may be the same as or different from each other, and a halogen atom or —OSO ₂ Z excluding a fluorine atom (where Z is an alkyl group, a fluorine-substituted alkyl group or an aryl group) The group represented by this is shown. Examples of the alkyl group represented by Z include a methyl group and an ethyl group, examples of the fluorine-substituted alkyl group include a trifluoromethyl group, and examples of the aryl group include a phenyl group and a p-tolyl group.

R ^{1 to} R ⁸ may be the same or different from each other, and are at least one atom selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group, or Indicates a group.

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, and a hexyl group, and a methyl group and an ethyl group are preferable.

  Examples of the fluorine-substituted alkyl group include trifluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, perfluorohexyl group, trifluoromethyl group, pentafluoroethyl group, and the like. Etc. are preferable.

Examples of allyl groups include propenyl groups,
Examples of the aryl group include a phenyl group and a pentafluorophenyl group.

W represents a single bond or a divalent electron-withdrawing group, and examples of the electron-withdrawing group include those described above.
T is a single bond or a divalent organic group, and may be an electron-withdrawing group or an electron-donating group. Examples of the electron-withdrawing group and the electron-donating group include the same groups as described above.

  p is 0 or a positive integer, and the upper limit is usually 100, preferably 10-80.

Specifically, as the compound represented by the general formula (E), when p = 0, for example, 4,4′-dichlorobenzophenone, 4,4′-dichlorobenzanilide, bis (chlorophenyl) difluoromethane, 2, 2-bis (4-chlorophenyl) hexafluoropropane, 4-chlorobenzoic acid-4-chlorophenyl, bis (4-chlorophenyl) sulfoxide, bis (4-chlorophenyl) sulfone, 2,6-dichlorobenzonitrile, 9,9- Bis (4-hydroxyphenyl) fluorene is mentioned. In these compounds, compounds in which a chlorine atom is replaced with a bromine atom or an iodine atom, and compounds in which at least one of halogen atoms substituted in the 4-position in these compounds are substituted in the 3-position are exemplified.

When p = 1, the specific compound represented by the general formula (E) is, for example, 4,
4′-bis (4-chlorobenzoyl) diphenyl ether, 4,4′-bis (4-chlorobenzoylamino) diphenyl ether, 4,4′-bis (4-chlorophenylsulfonyl) diphenyl ether, 4,4′-bis (4- Chlorophenyl) diphenyl ether dicarboxylate, 4,4′-bis [(4-chlorophenyl) -1,1,1,3,3,3-hexafluoropropyl] diphenyl ether, 4,4′-bis [(4-chlorophenyl) Tetrafluoroethyl] diphenyl ether, compounds in which the chlorine atom is replaced with a bromine atom or iodine atom in these compounds, compounds in which the halogen atom substituted in the 4-position in these compounds is substituted in the 3-position, and further in these compounds, the diphenyl ether At least one of the groups substituted in the 4-position is in the 3-position And the like.

Examples of the polymerization solvent that can be used when the monomer (D) and the oligomer (E) are reacted include tetrahydrofuran, cyclohexanone, dimethyl sulfoxide, N,
N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N′-dimethylimidazolidinone and the like can be mentioned. Of these, tetrahydrofuran, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and N, N′-dimethylimidazolidinone are preferable. These polymerization solvents are preferably used after sufficiently dried.

  The total concentration of the monomers in the polymerization solvent is usually 1 to 90% by weight, preferably 5 to 40% by weight.

  Moreover, the superposition | polymerization temperature at the time of superposing | polymerizing is 0-200 degreeC normally, Preferably it is 50-120 degreeC. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 40 hours.

  When a sulfonic acid group is introduced into the resulting polyarylene, which is a block copolymer, a sulfonating agent is used. At this time, it may be in the absence of a solvent or in the presence of a solvent. Examples of the solvent include hydrocarbon solvents such as n-hexane, ether solvents such as tetrahydrofuran and dioxane, aprotic polar solvents such as dimethylacetamide, dimethylformamide, and dimethylsulfoxide, tetrachloroethane, dichloroethane, chloroform, and chloride. And halogenated hydrocarbons such as methylene.

  As a method for introducing a sulfonic acid group, for example, the obtained polyarylene is sulfonated under known conditions using a known sulfonating agent such as sulfuric anhydride, fuming sulfuric acid, chlorosulfonic acid, sulfuric acid, sodium hydrogen sulfite and the like. (Polymer Preprints, Japan, Vol. 42, No. 3, p. 730 (1993); Polymer Preprints, Japan, Vol. 43, No. 3, p. 736 (1994); Polymer Preprints, Japan , Vol. 42, No. 7, p. 2490-2492 (1993)].

  Specifically, the reaction conditions for the sulfonation are not particularly limited, but the temperature is not particularly limited, but is usually −50 to 200 ° C., preferably −10 to 100 ° C. The time is usually 0.5 to 1,000 hours, preferably 1 to 200 hours.

  For example, by reacting 4,4′-dihydroxybenzophenone and 4,4′-dichlorodiphenylsulfone at high temperature in the presence of a base, an oligomer having both ends of a chlorine atom is synthesized, and a block of the general formula (B) is synthesized. A polyether ketone sulfone precursor is obtained. Next, coupling polymerization with 2,5-dichloro-4 ′-(4-phenoxy) phenoxybenzophenone is performed to synthesize a polyether ketone sulfone copolymer, and then the sulfone is synthesized to synthesize the copolymer of the present invention. can do.

  The amount of sulfonic acid group in the copolymer of the present invention is 0.3 to 5 meq / g, preferably 0.5 to 3 meq / g, more preferably 0.8 to 2.8 meq / g. If it is less than 0.3 meq / g, the proton conductivity is low. On the other hand, if it exceeds 5 meq / g, the hydrophilicity may increase and the solvent resistance may be greatly reduced.

  The amount of the sulfonic acid group can be adjusted by changing the use ratio of the monomer that forms the repeating unit (a) and the monomer that forms the repeating unit (b), and the type and combination of the monomers.

The molecular weight of the block copolymer precursor containing the sulfonic acid group of the present invention, that is, the base polymer before sulfonic acid induction or introduction, is 10,000 to 1,000,000, preferably 20,000 to 80 in terms of polystyrene-converted weight average molecular weight. Ten thousand. If it is less than 10,000, the coating film properties are insufficient, such as cracks occurring in the molded film, and there are also problems with the strength properties. On the other hand, when it exceeds 1,000,000, the solubility becomes insufficient, the solution viscosity is high, and the smoothness of the surface may be deteriorated after drying.
(Proton conducting membrane)
The proton conducting membrane of the present invention can be obtained, for example, by dissolving the above-described polyarylene copolymer having a sulfonic acid group of the present invention (hereinafter simply referred to as “polyarylene having a sulfonic acid group”) in a solvent. It is produced by being cast into a film by a method (solvent casting method) or the like, which is cast on a substrate and molded into a film. The substrate is not particularly limited as long as it is a substrate used in an ordinary solution casting method. For example, a substrate made of plastic or metal is used, and preferably a thermoplastic such as a polyethylene terephthalate (PET) film. A base material made of resin is used. At the time of casting, the thickness of the cast liquid can be adjusted by using a metal plate or a metal bar called a bar coater having a predetermined thickness cut (bar coating method).

  In preparing the proton conducting membrane, in addition to polyarylene having a sulfonic acid group, an inorganic acid such as sulfuric acid or phosphoric acid, an organic acid containing a carboxylic acid, an appropriate amount of water, or the like may be used in combination.

Specifically, the method for producing a proton conducting membrane for a direct methanol fuel cell according to the present invention, when producing a membrane comprising polymer segments (A) and (B),
An organic solvent that does not interact with the polymer segment (A) is contained in an amount of 30% by weight or more in the solvent in which the polymer segments (A) and (B) are dissolved in the casting solvent.

In the present invention, the organic solvent that does not interact with the polymer segment (A) having an ion conducting component used as a casting solvent for the proton conducting membrane includes a single or double bond as the bonding mode of the substituent on the nitrogen atom. Some N-free organic solvents can be used. (Ie, not amino, imino, amide, imide compounds)
For example, methanol, ethanol, 1-propanol, 2-propanol, n-butyl alcohol, 2-methyl-1-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol, cyclohexanol, dicyclohexanol, 1-hexanol, 2-methyl-1 -Pentanol, 2-methyl-2-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4- Methylcyclohexanol, 1-octanol, 2-octanol, 2-ethyl -1-hexanol, ethylene glycol, propylene glycol, 1.3-butanediol, glycerol, m-cresol, diethylene glycol, dipropylene glycol, diacetone alcohol, dioxane, butyl ether, phenyl ether, isopentyl ether, dimethoxyethane, diethoxy Ethane, bis (2-methoxyethyl) ether, bis (2-ethoxyethyl) ether, cineol, benzylethyl ether, furan, tetrahydrofuran, anisole, phenetole, acetal, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, cyclopenta Non, cyclohexanone, 2-hexanone, 4-methyl-2-pentanone, 2-heptanone, 2,4-dimethyl-3-pentanone, 2-octanone Acetophenone, mesityl oxide, benzaldehyde, ethyl acetate, n-butyl acetate, isobutyl acetate, sec-butyl acetate, isoamyl acetate, pentyl acetate), isopentyl acetate, 3-methoxybutyl acetate, methyl butyrate, ethyl butyrate, lactic acid Methyl, ethyl lactate, butyl lactate, γ-butyrolactone, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2- Propanol, dimethyldiethylene glycol, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfide, acetonitrile, butyronitrile, nitromethane, nitroethane, 2-nitropropane, nitrobenzene, benzene, toluene, xyle , It may be mentioned hexane, cyclohexane and the like. These may be used in combination of two or more, and one or more of them may be —O—, —OH, —CO—, —SO ₂ —, —SO ₃ —, —CN, —NO ₂ and —CO _2. An organic solvent having at least one group consisting of — is preferred.

  Examples of the organic solvent that interacts with the polymer segment (A) having an ion conductive component with respect to the organic solvent include pyridine, n-methyl-2-pyrrolidone, 2-pyrrolidone, dimethylacetamide, tetramethylurea, dimethylformamide, and the like. Of the basic organic solvent. In the present invention, such a solvent may be included as long as the object is not impaired.

  The organic solvent that does not interact with the polymer segment (A) having the ion conductive component needs to be contained in an amount of 30% by weight or more in the total solvent. Furthermore, it is preferable to contain 60 weight% or more, More preferably, it is 90 weight% or more.

  If it is less than the above range, the influence of the organic solvent interacting with the polymer segment (A) having the ion conductive component becomes large, and the solvent coordinates to the polymer segment (A) having the ion conductive component and locally aggregates. In some cases, a structure is formed, and the hydrophobic segments (B) are gathered around the structure, and a network structure in which (B) surrounds the result (A) may be formed.

  On the other hand, when the organic solvent as described above is within the above range, the interaction between the hydrophilic segment (A) and the solvent is small, and (A) tends to take a continuous phase. The reason why (B) forms a lamellar structure cannot be determined, but when considering the agglomeration due to the hydrophobic interaction between (B) and the affinity with (A), it is finally thermodynamically stable. It is thought to have a lamellar structure.

  The polymer concentration of the solution in which the polyarylene having a sulfonic acid group is dissolved is usually 5 to 40% by mass, preferably 7 to 25% by mass, although it depends on the molecular weight of the polyarylene having a sulfonic acid group. If it is less than 5% by mass, it is difficult to form a thick film, and pinholes are easily generated. On the other hand, if it exceeds 40% by weight, the solution viscosity is so high that it is difficult to form a film, and surface smoothness may be lacking.

The solution viscosity is usually 2,000 to 100,000 mPa · s, preferably 3,000 to 50,000 mPa · s, although it depends on the molecular weight of the polyarylene having a sulfonic acid group and the polymer concentration. If it is less than 2,000 mPa · s, the retention of the solution during film formation is poor,
May flow from the substrate. On the other hand, if it exceeds 100,000 mPa · s, the viscosity is too high to be extruded from the die and it may be difficult to form a film by the casting method.

  After forming the film as described above, by immersing the obtained undried film in water, the organic solvent in the undried film is replaced with water, and the residual solvent amount of the resulting proton conducting membrane is reduced. Can do.

  In addition, you may pre-dry an undried film before immersing an undried film in water after film-forming. The preliminary drying is performed by holding the undried film at a temperature of usually 50 to 150 ° C. for 0.1 to 10 hours.

  When immersing an undried film in water, for example, a batch method in which a sheet is immersed in water is employed. Alternatively, a continuous method is adopted in which the laminated film is immersed in water in a state where the film is formed on a substrate film such as PET, or the film separated from the substrate is immersed in water and wound.

  In the case of the batch method, a method of fitting the treated film to the frame is preferable in that wrinkle formation on the surface of the treated film is suppressed.

  When immersing an undried film in water, it is preferable that water has a contact ratio of 10 parts by mass or more, preferably 30 parts by mass or more with respect to 1 part by mass of the undried film. In order to minimize the amount of residual solvent in the resulting proton conducting membrane, it is preferable to maintain a contact ratio as large as possible. In addition, it is effective in reducing the amount of residual solvent in the resulting proton conducting membrane by changing the water used for immersion or allowing it to overflow so that the organic solvent concentration in the water is always kept below a certain level. is there. In order to suppress the in-plane distribution of the amount of the organic solvent remaining in the proton conductive membrane, it is preferable to homogenize the concentration of the organic solvent in water by stirring or the like.

  The temperature of water when the undried film is immersed in water is preferably 5 to 80 ° C. The higher the temperature, the higher the rate of substitution between the organic solvent and water, but the greater the amount of water absorbed by the film, so the surface of the proton conducting membrane obtained after drying may become rough. Considering the replacement speed and ease of handling, a temperature range of 10 to 60 ° C. is more preferable.

  The immersion time is usually 10 minutes to 240 hours, preferably 30 minutes to 100 hours, although depending on the initial residual solvent amount, contact ratio, and treatment temperature.

  Thus, when an undried film is immersed in water and then dried, a proton conductive membrane with a reduced amount of residual solvent is obtained, and the residual solvent amount in the proton conductive membrane is usually 5% by mass or less.

  Further, for example, the contact ratio between the undried film and water is 50 parts by mass or more of water with respect to 1 part by mass of the undried film, the temperature of water at the time of immersion is 10 to 60 ° C., and the immersion time is 10 minutes. By setting it to 10 hours, the residual solvent amount of the proton conductive membrane obtained can be made 1 mass% or less.

  As described above, after immersing the undried film in water, the film is dried at 30 to 100 ° C., preferably 50 to 80 ° C., for 10 to 180 minutes, preferably 15 to 60 minutes, and then 50 to 150 ° C. Thus, a proton conducting membrane is obtained by drying for 0.5 to 24 hours.

  The proton conductive membrane thus obtained has a dry film thickness of usually 10 to 300 μm, preferably 20 to 200 μm.

  The proton conducting membrane of the present invention may contain an anti-aging agent, preferably a hindered phenol compound having a molecular weight of 500 or more. By containing an anti-aging agent, the durability of the proton conducting membrane is further improved. Can do.

As such a hindered phenol compound having a molecular weight of 500 or more, specifically, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) proonate] (trade name: IRGANOX 245) 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 259), 2,4-bis- (n- Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -3,5-triazine (trade name: IRGANOX 565), pentaerythrityl-tetrakis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX 1010), 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade) Product name: IRGANOX 1035), octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) (trade name: IRGANOX 1076), N, N-hexamethylenebis (3,5-di-) t-butyl-4-hydroxy-hydrocinnamamide) (IRGAONOX 1098), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene ( Trade name: IRGANOX 1330), tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate (trade name: IRGANOX 3114), 3,9-bis [2- [3- (3 -T-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane (trade name: Sumilizer GA- 80).

  These hindered phenol compounds are preferably used in an amount of 0.01 to 10 parts by mass with respect to 100 parts by mass of the polyarylene having a sulfonic acid group.

  These hindered phenol compounds may be added to a solution in which polyarylene having a sulfonic acid group is dissolved.

  The proton conducting membrane of the present invention exhibits excellent methanol permeability, heat resistance, oxidation resistance, and toughness while maintaining high proton conductivity, so that it is used for fuel cells for household power sources, fuel cell vehicles, and mobile phones. Fuel cell, fuel cell for personal computer, fuel cell for portable terminal, fuel cell for digital camera, portable CD, MD fuel cell, fuel cell for headphone stereo, fuel cell for pet robot, fuel cell for electric assist bicycle, electric scooter It can be suitably used for applications such as fuel cells.

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

  In the examples, sulfonic acid equivalent, molecular weight, proton conductivity, methanol aqueous solution resistance (film area change rate), and methanol permeability were determined as follows.

1. Sulfonic acid equivalent The polymer having the sulfonic acid group was washed with water until the water was neutral, thoroughly washed with water except for free remaining acid, dried, weighed a predetermined amount, THF / Phenolphthalein dissolved in a mixed solvent of water was used as an indicator, titration was performed using a standard solution of NaOH, and the sulfonic acid equivalent was determined from the neutralization point.

2. Measurement of molecular weight The polyarylene weight-average molecular weight containing no sulfonic acid was determined by GPC using polystyrene (THF) as a solvent and the molecular weight in terms of polystyrene. The molecular weight of the polyarylene having a sulfonic acid group was determined by GPC using N-methyl-2-pyrrolidone (NMP) to which lithium bromide and phosphoric acid were added as a solvent as an eluent.

3. Measurement of proton conductivity AC resistance was measured by pressing a platinum wire (f = 0.5 mm) against the surface of a 5 mm wide strip-shaped proton conducting membrane sample, holding the sample in a constant temperature and humidity device, and between the platinum wires It was obtained from AC impedance measurement. That is, the impedance at an alternating current of 10 kHz was measured in an environment of 25 ° C., 60 ° C., and a relative humidity of 80%. A chemical impedance measurement system manufactured by NF Circuit Design Block Co., Ltd. was used as the resistance measurement device, and JW241 manufactured by Yamato Scientific Co., Ltd. was used as the constant temperature and humidity device. 5 platinum wires are pressed at 5mm intervals, and the distance between the wires is 5-20mm.
The AC resistance was measured. The specific resistance of the membrane was calculated from the line-to-line distance and the resistance gradient, and the proton conductivity was calculated from the reciprocal of the specific resistance.
Specific resistance R (Ω · cm) = 0.5 (cm) × film thickness (cm) × resistance-to-resistance gradient (Ω / cm)
4). Resistance to aqueous methanol (solubility and swelling in aqueous methanol)
Resistance evaluation with respect to the methanol aqueous solution was performed by immersing the proton conductive membrane in a methanol aqueous solution having a predetermined concentration (10% by weight) at room temperature for 20 hours and measuring the area before and after immersion. The evaluation film was formed by casting from an 18% by weight solution, dried at 150 ° C., and then the solvent removed by washing with water was cut into a 40 × 30 mm sample.

Area change rate (%) = (Area after immersion) / (Area before immersion) × 100
In consideration of practicality as a DMFC, the area change rate of the film measured under the above conditions is preferably 120% or less.
(Methanol permeability)
For evaluation of methanol permeability, a proton conducting membrane sample cut into a predetermined cell with a diameter of 60 mm is set, a 10% by weight methanol aqueous solution is supplied from the front side, the pressure is reduced from the back side, and the permeate is trapped with liquid nitrogen. The permeation vaporization measurement method (pervaporation method) was used. The temperature was set to 25 ° C., and the characteristics were evaluated from the methanol permeation amount (methanol flux) under reduced pressure conditions and the separation coefficient showing the selective permeability between methanol and water. The methanol flux and the separation factor were determined by the following formula. The smaller the values of both the methanol flux and the separation factor, the better the characteristics. The permeate refers to the permeate collected with a liquid nitrogen trap, and the permeate concentration refers to the weight concentration of methanol in the permeate.

Methanol Flux (g / (m ² · h)) = (permeate weight (g) / recovery time (h) / sample area (m ² )) × permeate concentration (%)
Separation factor = (permeate concentration (%) / (100-permeate concentration (%))) / (feed solution concentration (%) / (100-feed solution concentration (%)))
When considering practicality as DMFC, the methanol flux measured under the above conditions needs to be 240 or less, and preferably 220 or less. The separation factor is required to be 2.0 or less as a minimum condition.

Synthesis example 1
Preparation of oligomer 4,4′-dihydroxybenzophenone (4,4′-DHBP) was added to a 2 L three-necked flask equipped with a stirrer, thermometer, condenser, Dean-Stark tube, and nitrogen-introduced three-way cock. 99.4 g (0.46 mol), 4,4′-dichlorodiphenyl sulfone (4,4′-D
CDS) 148.2 g (0.52 mol), potassium carbonate 86.9 g (0.63 mol)
1,3-Dimethyl-2-imidazolidinone (DMI) 500 mL and toluene 200 mL were added, heated in an oil bath, and reacted at 150 ° C. with stirring under a nitrogen atmosphere. When water produced by the reaction was azeotroped with toluene and reacted while being removed from the system with a Dean-Stark tube, almost no water was observed in about 3 hours. Subsequently, most of the toluene was removed while gradually raising the reaction temperature to 180 ° C., and the reaction was continued at 180 ° C. for 8 hours. Then, 9.2 g (0.032 mol) of 4,4′-DCDS was added, and another 2 hours. Reacted. After allowing the resulting reaction solution to cool, precipitates of inorganic compounds produced as a by-product were removed by filtration, and the filtrate was put into 4 L of methanol. The precipitated product was collected by filtration, dried, and then dissolved in 500 mL of DMI. This solution was added to 4 L of methanol and reprecipitated to obtain 175 g (yield 77%) of the target compound.

The number average molecular weight in terms of polystyrene determined by GPC (THF solvent) of the obtained polymer is 3
4000. Further, the obtained polymer was soluble in NMP, DMAc, DMI and the like, Tg was 157 ° C., and thermal decomposition temperature was 500 ° C.

  The resulting polymer has the following formula (I):

It was presumed to have a structure represented by

Synthesis example 2
(Synthesis of polyarylene copolymer)
17.6 g (1.8 mmol) of the oligomer obtained in Synthesis Example 1, 25.4 g (58.4 mmol) of 2,5-dichloro-4 ′-(4-phenoxy) phenoxybenzophenone (DCPPB), bis (triphenylphosphine) ) 1.18 g (1.8 mmol) of nickel dichloride, 1.17 g (7.8 mmol) of sodium iodide, 6.30 g (24.0 mmol) of triphenylphosphine, and 9.41 g (144 mmol) of zinc dust are added to the flask. Replaced with dry nitrogen. Next, 100 ml of N-methyl-2-pyrrolidone was added to the flask, heated to 80 ° C., and polymerized for 4 hours with stirring. After the obtained polymerization solution was diluted with NMP, it was filtered using Celite as a filter aid, and the filtrate was poured into 1000 mL of a large excess of methanol to coagulate and precipitate. The coagulated product was collected by filtration, air-dried, redissolved in 200 mL of NMP, poured into 1500 mL of a large excess of methanol, and coagulated and precipitated. The coagulated product was collected by filtration and dried in vacuo to obtain 35.7 g (92%) of the desired copolymer. The number average molecular weight in terms of polystyrene determined by GPC (NMP) was 57000, and the weight average molecular weight was 165000.

Synthesis example 3
(Synthesis of polyarylene copolymer containing sulfonic acid group-1)
16 g of the copolymer obtained in Synthesis Example 2 was added to a 500 ml separable flask equipped with a stirrer and a thermometer, and then 160 ml of sulfuric acid having a concentration of 98% was added, and the temperature in the flask was kept at 25 ° C. under a nitrogen stream. For 24 hours. The obtained solution was poured into a large amount of ion exchange water to precipitate a polymer. Next, the polymer was repeatedly washed until the pH of the washing water reached 5, and then dried to obtain 18 g (yield 91%) of a sulfonic acid group-containing polymer. The polystyrene-equivalent number average molecular weight determined by GPC (NMP) of this sulfonic acid group-containing polymer was 56000, the weight average molecular weight was 171,000, and the actually measured sulfonic acid equivalent was 2.1 meq / g.

Example 1
5.0 g of the sulfonic acid group-containing polymer obtained in Synthesis Example 3 was added to a 50 cc screw tube containing 18.3 g of γ-butyrolactone and 12.3 g of tetrahydrofuran, and the mixture was stirred for 24 hours with a wafer blower, and the viscosity was 5000 cp. A homogeneous polymer solution was obtained.

The above solution was cast on a PET film by a bar coating method, and dried at 80 ° C. for 30 minutes and 150 ° C. for 60 minutes to obtain a uniform and transparent film having a thickness of 100 μm. The cross-sectional morphology of the film was determined by immersing the film in an aqueous lead nitrate solution having a concentration of 1 M / L for 3 nights, and then cutting out an ultrathin section using a microtome method. Transmission electron microscope (TEM, HF-100FA manufactured by Hitachi, Ltd.) ).

  In the TEM observation, it was observed that the domain consisting of the hydrophilic segment (A) containing sulfonic acid and the domain consisting of the hydrophobic segment (B) not containing sulfonic acid were microphase-separated. The domain consisting of (B) formed a twisted string-like lamella structure, and the width of the lamella was 30-34 nm. Although (A) is partially divided by (B), it is considered that a continuous phase is formed when viewed in the whole film.

The produced film (film thickness: 100 μm) had a methanol flux of 80 (g / h / m ² ). The area change rate was 115% (10% by weight aqueous methanol solution), and the conductivity was 0.141 S / cm (60 ° C./80% RH) and 0.067 S / cm (25 ° C./80% RH).

Comparative Example 1
The methanol flux of the cast film (film thickness: 180 μm) of perfluoroalkylsulfonic acid (trade name: Nafion 117 (registered trademark), manufactured by DuPont) was 228 (g / h / m ² ). The area change rate was 125% (10% by weight aqueous methanol solution). The conductivities were 0.090 S / cm (60 ° C./80% RH) and 0.047 S / cm (25 ° C./80% RH). Nafion 117 is a spherical hydrophilic domain of several nanometers in a hydrophobic continuous phase, as introduced in many literatures (for example, “Practical application of fuel cell for portable devices” Technical Information Association, 2002). The continuous phase of the hydrophilic part and the lamellar structure of the hydrophobic part as in the present invention are not observed.

  The results are also shown in Table 1.

Claims (4)

A film comprising a block copolymer in which a polymer segment (A) having a sulfonic acid group and a polymer segment (B) having no sulfonic acid group are covalently bonded ;
The polymer segment (A) is composed of repeating structural units represented by the following general formula (A),
The polymer segment (B) is composed of repeating structural units represented by the following general formula (B),
The direct methanol type wherein the morphology of the membrane has a micro phase separation structure, wherein (A) forms a continuous phase and (B) forms a discontinuous lamellar structure. Proton conducting membrane for fuel cells.
(In the formula, A represents a divalent electron-withdrawing group. B represents a divalent electron-donating group or a direct bond. Ar represents an aromatic group having a substituent represented by —SO ₃ H; m shows the integer of 0-10, n shows the integer of 0-10, k shows the integer of 1-4.
(In Formula (B), R ^{1 to} R ⁸ may be the same or different from each other, and are selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group, a fluorine-substituted alkyl group, an allyl group, an aryl group, and a cyano group. And at least one atom or group, W represents a single bond or a divalent electron-withdrawing group, T represents a single bond or a divalent organic group, and p is 0 or a positive integer.   In the morphological observation of the cross section of the film by the electron microscope, the width of the lamellar structure corresponding to the thickness of the three-dimensional string-like lamella is in the range of 5 to 200 nm. The proton conductive membrane for a direct methanol fuel cell according to claim 1, wherein When forming a film composed of polymer segments (A) and (B),
In a solvent in which the polymer segments (A) and (B) are dissolved in a casting solvent,
An organic solvent that does not interact with the polymer segment (A) and is methanol, ethanol, 1-propanol, 2-propanol, n-butyl alcohol, 2-methyl-1-propanol, 1-pentanol, 2-pentanol 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol, cyclohexanol Dicyclohexanol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol 1-octanol, 2-octanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, 1.3-butanediol, glycerol, m-cresol, diethylene glycol, dipropylene glycol, diacetone alcohol, dioxane, butyl ether , Phenyl ether, isopentyl ether, dimethoxyethane, diethoxyethane, bis (2-methoxyethyl) ether, bis (2-ethoxyethyl) ether, cineol, benzylethyl ether, furan, tetrahydrofuran, anisole, phenetole, acetal, acetone , Methyl ethyl ketone, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone, 2-hexanone, 4-methyl-2-pentanone, 2-heptano 2,4-dimethyl-3-pentanone, 2-octanone, acetophenone, mesityl oxide, benzaldehyde, ethyl acetate, acetic acid-n-butyl, acetic acid isobutyl, sec-butyl acetate, isoamyl acetate, pentyl acetate), isopentyl acetate, 3-methoxybutyl acetate, methyl butyrate, ethyl butyrate, methyl lactate, ethyl lactate, butyl lactate, γ-butyrolactone, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-isopropoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dimethyl diethylene glycol, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfide, acetonitrile, butyronitrile, nitromethane, nitroethane, 2-nitrop 3. The direct methanol fuel cell according to claim 1, comprising at least 30 wt% of one or more organic solvents selected from the group consisting of pan, nitrobenzene, benzene, toluene, xylene, hexane, and cyclohexane. For Proton Proton Conductive Membrane.   The organic solvent is dioxane, butyl ether, phenyl ether, isopentyl ether, dimethoxyethane, diethoxyethane, bis (2-methoxyethyl) ether, bis (2-ethoxyethyl) ether, cineol, benzylethyl ether, furan, tetrahydrofuran. , Anisole, phenetole, acetal, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone, 2-hexanone, 4-methyl-2-pentanone, 2-heptanone, 2,4-dimethyl-3-pentanone The method for producing a proton conductive membrane for a direct methanol fuel cell according to claim 3, wherein the proton conductive membrane is one or more selected from the group consisting of 2-octanone and acetophenone.