JP2007287675A - Membrane electrode assembly and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane electrode assembly having a stable joining state, hardly peeling off the joining part between a membrane and an electrode in cycles of low humidity-high humidity to be especially supposed in the fuel cell, and expected to be long life. <P>SOLUTION: In the membrane electrode assembly formed by heating and/or pressing at least an electrolyte membrane and an electrode membrane, the electrolyte membrane contains a sulfonated aromatic polymer in which at least one sulfonate part is bonded to an aromatic ring of the aromatic polymer, and heating and/or pressing are/or conducted in a state that a solvent, which becomes a good solvent of the sulfonated aromatic polymer, is contained in at least one membrane of the electrolyte membrane and the electrode membrane in a range of 0.1-20 wt.% of each membrane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell that uses pure hydrogen, methanol, ethanol, dimethyl ether, methanol or reformed hydrogen from fossil fuel as a fuel, and uses air or oxygen as an oxidant, and in particular, a solid polymer fuel The present invention relates to a membrane electrode assembly and a fuel cell used in a battery.

  As fuel cell materials, Patent Document 1 and Non-Patent Document 1 disclose sulfonated aromatic polymers containing a sulfonate moiety on a heat-activated non-activated aromatic ring. Patent Document 2 discloses a fuel cell electrode using the fuel cell material as described above. In general, in a fuel cell, electrode membranes (electrode layers) are provided on both surfaces of an electrolyte membrane. Conventionally, in order to integrally form an electrode membrane and an electrolyte membrane, a catalyst paste prepared by previously preparing carbon carrying a catalyst and using the same type of electrolyte as the electrolyte membrane or a different type of electrolyte as a binder is formed on a support. An electrode layer was formed by coating and heat treatment, and the electrolyte membrane was sandwiched between two electrode layers and molded by hot pressing or the like under pressure to perform a three-layer junction of anode electrode / electrolyte layer / cathode electrode.

  However, in such a three-layer joining method, the high heat-resistant electrolyte membrane as described above, which has been increasing in demand in recent years, has insufficient hardness and thermoplasticity, and the joining state is unstable. In the low-humidity-high-humidity cycle assumed in Fig. 1, there is a problem that the membrane-electrode junction is easily peeled off and a long life as a fuel cell cannot be expected.

JP-T-2004-509224 International Publication WO03 / 082956A1 Pamphlet PolymerPreprints (2000), 41 (1), 237

  The present invention aims to solve the above-described problems, and the bonding state is stable, and the membrane-electrode junction is difficult to peel off particularly in a low-humidity-high humidity cycle assumed in a fuel cell. An object of the present invention is to provide a membrane electrode assembly that can be expected to have a long life as a fuel cell. Furthermore, a fuel cell using the membrane electrode assembly is provided.

（式（１）中、ｍおよびｎはそれぞれ正の整数であり、ｎ／ｎ＋ｍは０．００１〜１の範囲であり、Ｙはそれぞれ−Ｓ−、−Ｓ（Ｏ）−、−Ｓ（Ｏ）₂−、−Ｃ（Ｏ）−、−Ｐ（Ｏ）（Ｃ₆Ｈ₅）−およびそれらの組合せからなる群から選択され、Ｚは単結合、−Ｃ（ＣＨ₃）₂−、−Ｃ（ＣＦ₃）₂−、−Ｃ（ＣＦ₃）（Ｃ₆Ｈ₅）−、−Ｃ（Ｏ）−、−Ｓ（Ｏ）₂−および−Ｐ（Ｏ）（Ｃ₆Ｈ₅）−からなる群から選択され、Ａはスルホネート基および式（ＩＩ）で表される基から選択される。）
式（ＩＩ）

（式（ＩＩ）中、Ｂ¹およびＢ²は、それぞれ、連結基を表し、Ｘはイオウ原子を含む基を表し、Ｍはカチオンを表し、ｍ１は１以上の整数を表す。）
（５）前記式（１）において、ｎ／（ｎ＋ｍ）は０．１〜０．８の範囲であり、Ｙは−ＳＯ₂−または−ＣＯ−であり、Ｚは単結合または−Ｃ（ＣＦ₃）₂−である、（４）に記載の膜電極接合体。
（６）前記スルホネート部分が、プロトン型、ナトリウム型またはカリウム型である、（１）〜（５）のいずれか１項に記載の膜電極接合体。
（７）前記電極膜の少なくとも一方が、触媒金属の微粒子を含む炭素材からなる導電材料とバインダーとを含み、かつ、該バインダーが、前記式（１）で表される繰り返し単位を含み、前記バインダーに、体積平均粒子サイズが１ｎｍ〜２００ｎｍであるイオン性ポリマー粒子を含む分散液を用いることを特徴とする、（４）〜（６）のいずれか１項に記載の膜電極接合体。
（８）（１）〜（７）のいずれか１項に記載の膜電極接合体を含む燃料電池。 As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention.
(1) A membrane electrode assembly formed by heating and / or pressurizing at least an electrolyte membrane and an electrode membrane, wherein the electrolyte membrane comprises a sulfonated aromatic polymer to which at least one sulfonate moiety is bonded. In addition, the heating and / or pressurization may be performed on at least one of the electrolyte membrane and the electrode membrane within the range of 0.1 to 20% by weight of the weight of each membrane of the sulfonated aromatic polymer. A membrane electrode assembly, which is performed in a state where a solvent that is a good solvent is contained.
(2) The membrane electrode assembly according to (1), wherein the good solvent is an amide solvent or a sulfoxide solvent.
(3) The sulfonated aromatic polymer is a sulfonated polysulfone, and the sulfonate moiety is provided on a non-activated aromatic ring adjacent to the sulfone functional group of the polysulfone, (1) or (2) 2. The membrane electrode assembly according to 1.
(4) The membrane electrode assembly according to any one of (1) to (3), wherein the sulfonated aromatic polymer includes a repeating unit represented by the following formula (1) or a salt thereof.
Formula (1)

(In the formula (1), m and n are each a positive integer, n / n + m is in the range of 0.001-1, and Y is -S-, -S (O)-, -S (O ) ₂ —, —C (O) —, —P (O) (C ₆ H ₅ ) —, and combinations thereof, Z is a single bond, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —C (CF ₃ ) (C ₆ H ₅ ) —, —C (O) —, —S (O) ₂ — and —P (O) (C ₆ H ₅ ) — Selected from the group, A is selected from a sulfonate group and a group of formula (II).)
Formula (II)

(In formula (II), B ¹ and B ² each represent a linking group, X represents a group containing a sulfur atom, M represents a cation, and m1 represents an integer of 1 or more.)
(5) In the formula (1), n / (n + m) is in the range of 0.1 to 0.8, Y is —SO ₂ — or —CO—, and Z is a single bond or —C (CF ₃ ) The membrane electrode assembly according to (4), which is _2- .
(6) The membrane electrode assembly according to any one of (1) to (5), wherein the sulfonate moiety is a proton type, a sodium type, or a potassium type.
(7) At least one of the electrode films includes a conductive material made of a carbon material containing fine particles of a catalytic metal and a binder, and the binder includes a repeating unit represented by the formula (1), The membrane electrode assembly according to any one of (4) to (6), wherein a dispersion liquid containing ionic polymer particles having a volume average particle size of 1 nm to 200 nm is used as a binder.
(8) A fuel cell comprising the membrane electrode assembly according to any one of (1) to (7).

  The membrane electrode assembly of the present invention is stable in the joined state, and in particular, a membrane electrode assembly in which the membrane-electrode junction is difficult to peel off in a low-humidity-high humidity cycle assumed in a fuel cell can be obtained. Further, such a membrane electrode assembly can be expected to have a long life as a fuel cell.

  Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

The membrane electrode assembly of the present invention has a structure in which an electrolyte membrane having a function of conducting ions, particularly protons, is sandwiched between two electrolyte membranes made of catalyst particles, a carbon material, and a binder having proton conductivity. Specifically, the membrane electrode assembly of the present invention is a membrane electrode assembly formed by heating and / or pressurizing at least an electrolyte membrane and an electrode membrane, and the electrolyte membrane has at least one sulfonate moiety. In addition, the heating and / or pressurization includes a bonded sulfonated aromatic polymer, and a solvent which is a good solvent for the sulfonated aromatic polymer is added to at least one of the electrolyte membrane and the electrode membrane. It is a membrane electrode assembly which is performed in a state where it is contained in a range of 0.1 to 20% by weight.
The membrane / electrode assembly of the present invention can be obtained by laminating an electrode film (electrode layer) on an electrolyte membrane and then joining them. In particular, two electrode films are opposed, laminated, and joined. Is obtained.

(Good solvent)
The good solvent in the present invention may be any solvent that is a good solvent for the sulfonated aromatic polymer, and can be selected from the following:

1) Protic solvent.
A protic solvent is a solvent having a dissociative hydrogen atom. Specifically, methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, 2-butanol, acetamide, and water.
2) Amide solvent.
An amide solvent is a solvent containing an amide structure (—CO—NR—) in the molecule. Here, R represents a hydrogen atom or a substituent. Specifically, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, Hexamethyl phosphorotriamide, tetramethyl urea and the like.
3) Amine-based solvent An amine-based solvent is a solvent containing a basic nitrogen atom in the molecule. Specifically, pyridine, quinoline, isoquinoline, α-picoline, β-picoline, γ-picoline, isophorone, piperidine, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine is there.
4) Ester solvent The ester solvent is a solvent containing an ester structure (—COO—) in the molecule. Specifically, ethyl acetate, propyl acetate, isopropyl acetate, and butyl acetate.
5) Nitrile solvent ester solvent is a solvent containing a cyano group in the molecule. Specific examples include acetonitrile, propionitrile, butyronitrile, and benzonitrile.
6) Sulfoxide solvent The sulfoxide solvent is a solvent containing a sulfoxide structure (—SO—) or a sulfone structure (—SO ₂ —) in the molecule. Specifically, dimethyl sulfoxide, dimethyl sulfone, and sulfolane.
7) Ether solvent The ether solvent is a solvent containing an ether structure (-O-) in the molecule. Specifically, diphenyl ether and anisole.

  Among the above good solvents, the above 2) amide solvents or 6) sulfoxide solvents are preferred, and N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane are preferred. More preferred. Of these, those having a water content of less than 2% are particularly preferred.

  These good solvents may be used as a mixture of two or more. When mixed and used, a combination of solvents that are mutually soluble in an arbitrary ratio is preferable.

  These good solvents are heated and / or pressurized in a state where they are contained in at least one of the electrolyte membrane and the electrode membrane in a range of 0.1 to 20% by weight of the total weight of each membrane. However, the good solvent is preferably contained in the range of 0.5 to 10% by weight, and more preferably in the range of 1 to 5% by weight. The good solvent contents of the electrolyte membrane and the electrode membrane may be different from each other, and it is preferable to include them in only one of them from the viewpoint of productivity.

  The method of including a good solvent in the electrolyte membrane and / or electrode membrane may be performed by adjusting the degree of drying in the manufacturing process of the electrolyte membrane and / or electrode membrane, and may be performed later by a method such as spraying or coating. It may be included. The range of the solvent content when it is included later is as described above.

(Electrolyte membrane)
The electrolyte membrane used in the present invention includes a sulfonated aromatic polymer having at least one sulfonate moiety. Here, the sulfonated aromatic polymer is preferably a sulfonated polysulfone. Furthermore, it is preferable that the sulfonate part is provided on the non-activated aromatic ring adjacent to the sulfone functional group, which is an aromatic ring of the sulfonated polysulfone.
In the present specification, polysulfone means an aromatic compound (phenylene, naphthylene, heterylene, etc.) is a divalent electron-withdrawing group (—SO ₂ —, —SO—, —CO—, —PO (C ₆ H ₅ )-And the like) and a divalent electron-donating group (—O—, —S—, etc.), and is a polymer having at least one —SO ₂ — and at least one —O in the repeating unit. Those containing-are preferred. The sulfonate moiety may be either proton type (sulfonic acid) or salt type (alkali metal salt, alkaline earth metal salt, etc.).
The non-activated aromatic ring in the present invention is an aromatic ring having a substituent that is an electron-withdrawing group.
Here, the electron-withdrawing group is not particularly defined, but a halogen atom (fluorine, chlorine, bromine, iodine), nitro group, sulfone (—SO ₂ —) group, sulfoxide group (—SO—), keto Group and phosphono group, and a sulfone group is particularly preferable. In addition to these electron-withdrawing groups, an electron-donating group (alkyl group, oxygen atom, sulfur atom) may be substituted. As the aromatic ring, a phenylene group, a naphthylene group, and a heterylene group are preferable, and a 1,3-phenylene group and a 1,4-phenylene group are particularly preferable.

As used herein, “sulfonate” or “sulfonated” means a sulfonate group, or a sulfo group, ie, SO ₃ ^— , which is in the acid form (—SO ₃ H, sulfonic acid) or salt form ( is either -SO ₃ Na, etc.). The salt form cation is preferably a monovalent or divalent cation, more preferably a monovalent cation. Examples include alkali metals (lithium, sodium, potassium, cesium), alkaline earth metals (calcium, magnesium, etc.) or other metals, inorganic cations or organic cations (ammonium, etc.). In particular, lithium, sodium, and potassium salts are preferable, and sodium salts and potassium salts are particularly preferable. You may employ | adopt a several thing from the group of these cations and protons.
In addition, anions (bromide ions, chloride ions, sulfate ions, nitrate ions, etc.) mixed in the raw material or in the process of synthesis and film formation may be included.

  Further, the term “polymer”, when used, is used broadly and includes homopolymers, random copolymers and block copolymers.

  The sulfonated aromatic polymer used in the present invention preferably contains a repeating unit represented by the formula (1) or a salt thereof:

（式（１）中、ｍおよびｎはそれぞれ正の整数であり、ｎ／ｎ＋ｍは０．００１〜１の範囲であり、Ｙはそれぞれ−Ｓ−、−Ｓ（Ｏ）−、−Ｓ（Ｏ）₂−、−Ｃ（Ｏ）−、−Ｐ（Ｏ）（Ｃ₆Ｈ₅）−およびそれらの組合せからなる群から選択され、Ｚは単結合、−Ｃ（ＣＨ₃）₂−、−Ｃ（ＣＦ₃）₂−、−Ｃ（ＣＦ₃）（Ｃ₆Ｈ₅）−、−Ｃ（Ｏ）−、−Ｓ（Ｏ）₂−および−Ｐ（Ｏ）（Ｃ₆Ｈ₅）−からなる群から選択され、Ａはスルホネート基および式（ＩＩ）で表される基から選択される。）
式（ＩＩ）

（式（ＩＩ）中、Ｂ¹およびＢ²は、それぞれ、連結基を表し、Ｘはイオウ原子を含む基を表し、Ｍはカチオンを表し、ｍ１は１以上の整数を表す。） Formula (1)

(In the formula (1), m and n are each a positive integer, n / n + m is in the range of 0.001-1, and Y is -S-, -S (O)-, -S (O ) ₂ —, —C (O) —, —P (O) (C ₆ H ₅ ) —, and combinations thereof, Z is a single bond, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —C (CF ₃ ) (C ₆ H ₅ ) —, —C (O) —, —S (O) ₂ — and —P (O) (C ₆ H ₅ ) — Selected from the group, A is selected from a sulfonate group and a group of formula (II).)
Formula (II)

(In formula (II), B ¹ and B ² each represent a linking group, X represents a group containing a sulfur atom, M represents a cation, and m1 represents an integer of 1 or more.)

n / (n + m) is preferably from 0.1 to 0.8, and more preferably from 0.3 to 0.7. Y is preferably —SO ₂ — or —CO—, and more preferably —SO ₂ —.
Z is preferably a single bond, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —CO—, or —SO ₂ —, and more preferably a single bond or —C (CF ₃ ) ₂ —.

  The sulfonated aromatic polymer used in the present invention may be a copolymer of a sulfonated polysulfone and another polymer. Examples of such a polymer include polyethersulfone, polyimide, polyetherketone and Examples include poly (arylene ether phosphine oxide) and polyphenylene.

In this invention, it is preferable that group represented by general formula (II) has couple | bonded.
Formula (II)

（一般式（ＩＩ）中、Ｂ¹およびＢ²は、それぞれ、連結基を表し、Ｘはイオウ原子を含む基を表し、Ｍはカチオンを表し、ｍ１は１以上の整数を表す。）
一般式（ＩＩ）中、Ｂ¹およびＢ²はそれぞれ連結基を表す。
連結基としては、好ましくはアルキレン基（好ましくは炭素原子数（以下Ｃ数ということがある）１〜２０のアルキレン基、例えば、メチレン基、エチレン基、メチルエチレン基、プロピレン基、メチルプロピレン基、ブチレン基、ペンチレン基、ヘキシレン基、オクチレン基）、アリーレン基（好ましくはＣ数６〜２６のアリーレン基、例えば１，２−フェニレン基、１，３−フェニレン基、１，４−フェニレン基、４−フェニレンメチレン基、１，４−ナフチレン基）、アルケニレン基（好ましくはＣ数２〜２０のアルケニレン基、例えば、エテニレン基、プロペニレン基、ブタジエニレン基）、アルキニレン基（好ましくはＣ数２〜２０のアルキニレン基、例えば、エチニレン基、プロピニレン基）、アミド基、エステル基、スルホン酸アミド基、スルホン酸エステル基、ウレイド基、スルホニル基、スルフィニル基、チオエーテル基、エーテル基、カルボニル基、ヘテリレン基（好ましくはＣ数１〜２６のヘテリレン基、例えば、６−クロロ−１，３，５−トリアジル−２，４−ジイル基、ピリミジン−２，４−ジイル基、キノキサリン−２，３−ジイル基）、または、これらの２以上組み合わせて構成されるＣ数０〜１００（より好ましくはＣ数１〜２０）の連結基を表す。これらの基は、本発明の趣旨を逸脱しない範囲内において置換基を有していてもよいが、置換基を有さない方が好ましい。これらの中でもより好ましくは、アルキレン基、アルキニレン基、アリーレン基、チオエーテル基、エーテル基を含む基であり、さらに好ましくは、アルキレン基、アリーレン基、チオエーテル基、エーテル基を含む基である。

(In general formula (II), B ¹ and B ² each represent a linking group, X represents a group containing a sulfur atom, M represents a cation, and m1 represents an integer of 1 or more.)
In general formula (II), B ¹ and B ² each represent a linking group.
The linking group is preferably an alkylene group (preferably an alkylene group having 1 to 20 carbon atoms (hereinafter sometimes referred to as C number), such as a methylene group, an ethylene group, a methylethylene group, a propylene group, a methylpropylene group, Butylene group, pentylene group, hexylene group, octylene group), arylene group (preferably an arylene group having 6 to 26 carbon atoms, such as 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group, 4 -Phenylenemethylene group, 1,4-naphthylene group), alkenylene group (preferably an alkenylene group having 2 to 20 carbon atoms, for example, ethenylene group, propenylene group, butadienylene group), alkynylene group (preferably having 2 to 20 carbon atoms). Alkynylene group, for example, ethynylene group, propynylene group), amide group, ester group, sulfone Amide group, sulfonate group, ureido group, sulfonyl group, sulfinyl group, thioether group, ether group, carbonyl group, heterylene group (preferably a C1-C26 heterylene group such as 6-chloro-1,3, 5-triazyl-2,4-diyl group, pyrimidine-2,4-diyl group, quinoxaline-2,3-diyl group), or a combination of two or more thereof having 0 to 100 carbon atoms (more preferably Represents a linking group having 1 to 20 carbon atoms. These groups may have a substituent within a range not departing from the gist of the present invention, but it is preferable that these groups have no substituent. Among these, a group containing an alkylene group, an alkynylene group, an arylene group, a thioether group or an ether group is more preferred, and a group containing an alkylene group, an arylene group, a thioether group or an ether group is more preferred.

In general formula (II), X contains one or two or more sulfur atoms, may be composed of only sulfur atoms, or may be composed of sulfur atoms and other atoms. Preferably, -S -, - SO- and -SO ₂ - is a group containing at least one of.

In the general formula (II), M represents a cation, preferably a proton, an alkali metal (lithium, sodium, potassium) cation, an alkaline earth metal (potassium, strontium, barium) cation, a quaternary ammonium (trimethylammonium, Selected from the group consisting of protonated forms of triethylammonium, tributylammonium, benzyltrimethylammonium) cation, organic base (triethylamine, pyridine, methylimidazole, morpholine, tributylammonium, tris (2-hydroxyethyl) amine), more preferably Proton.
In general formula (II), m1 is preferably an integer of 1 to 6, and more preferably an integer of 1 to 3.

  When the general formula (II) forms a salt, the acid residue proton is preferably substituted with the following cation, and the substitution ratio (cation / acid residue ratio) is 0 to 1, Although there is no particular limitation in the process of synthesizing the electrolyte, it is preferably 0.1 or less when used as a solid electrolyte for a fuel cell. Cations that form salts include alkali metal (lithium, sodium, potassium) cation, alkaline earth metal (potassium, strontium, barium) cation, quaternary ammonium (trimethylammonium, triethylammonium, tributylammonium, benzyltrimethylammonium) Protonates of cations and organic bases (triethylamine, pyridine, methylimidazole, morpholine, tributylammonium, tris (2-hydroxyethyl) amine) are preferred, alkali metal cations or ammonium cations are more preferred, and alkali metal cations are particularly preferred.

Although the example of general formula (II) is shown below, this invention is not limited to these.

An example of a method for synthesizing the sulfonated polysulfone used in the present invention will be given. A sulfonated activated aromatic monomer that is a monomer having at least one sulfonate group and at least two leaving groups, and a non-sulfonated monomer that has at least two leaving groups that do not have a sulfonate group It includes a step of reacting an activated aromatic monomer with a comonomer having at least two leaving groups and removing them by condensation of these leaving groups.
Sulfonated activated aromatic monomers include 3,3′-disulfonated 4,4′-dichlorodiphenyl sulfone. The monomer may also be a mixture of two or more, for example, 3,3′-disulfonated 4,4′-dichlorodiphenylsulfone and non-sulfonated activated at a molar ratio in the range of 0.001 to 0.999. A mixture of aromatic monomers 4,4′-dichlorodiphenyl sulfone may be used.
The comonomer having two leaving groups is preferably one selected from the group consisting of 4,4′-biphenol, hydroquinone, 4,4 ′-(hexafluoroisopropylidene) diphenol and phenylphosphine oxide bisphenol, More preferred are 4,4′-biphenol and 4,4 ′-(hexafluoroisopropylidene) diphenol. The sulfonate group may be a sulfonic acid group or a salt form thereof.

The sulfonated aromatic polymer used in the present invention forms a sulfonated aromatic polymer by directly polymerizing a sulfonated activated aromatic monomer, a non-sulfonated activated aromatic monomer and a comonomer (eg, bisphenol). It is preferable to do. Activating groups for these monomers can include —S—, —SO—, —SO ₂ —, —CO— and —PO (C ₆ H ₅ ) —. These monomers are exemplified by the dihalide form or the dinitro form. Halides include, but are not limited to, Cl, F and Br.

  This sulfonated activated aromatic dihalide is prepared by sulfonating the corresponding activated aromatic dihalide by sulfonation methods known to those skilled in the art. The sulfonated activated aromatic dihalide can then be used in the formation of the sulfonated copolysulfone. The general reaction scheme for forming this sulfonated polysulfone is shown in Scheme 1 below.

Scheme 1

In Scheme 1, Y is a group that activates the leaving group X, and is —S—, SO—, —SO ₂ —, —CO—, —PO (C ₆ H ₅ ) —, or a combination thereof. . The activating group of the sulfonated activated aromatic monomer may be the same as or different from the activating group of the non-sulfonated activated aromatic monomer.
X is preferably any activated leaving group (for example, dihalide group or dinitro group), and more preferably a dihalide group (Cl, F, Br, etc.).
Z is a single bond, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —C (CF ₃ ) (C ₆ H ₅ ) —, —CO—, —SO ₂ — or —PO ( C ₆ H ₅₎ - a.
k is the number of repeating units.

  The molar ratio of the sulfonated activated aromatic monomer to the activated aromatic monomer, m and n are each a positive number, n / (n + m) is in the range of 0.001-1, 0.1-0. 8 is preferable, and 0.3 to 0.7 is more preferable.

  In the present invention, the sulfonated polysulfone is formed by selecting or synthesizing the desired sulfonated monomer (preferably dihalide) and then condensing with an appropriate comonomer (eg, bisphenol). The sulfonated monomer can be added alone or with non-sulfonated monomers. A particularly preferred sulfonated monomer is 3,3′-disulfonated-4,4′-dichlorodiphenylsulfone (SDCDPS), which is shown in Structure 3. The chlorine atom substituted at the 4,4′-position may be a fluorine atom or a bromine atom, but a chlorine atom or a fluorine atom is particularly preferred.

Structure 3

  The non-sulfonated monomer is preferably one that forms a sulfonated polysulfone with the sulfonated monomer, and the non-sulfonated monomer can be selected depending on the desired properties of the resulting polymer or membrane. A particularly preferred non-sulfonated monomer is 4,4′-dichlorodiphenyl sulfone (DCDPS). The relative molar ratio of the sulfonated monomer to the non-sulfonated monomer varies depending on the desired properties of the material and is, for example, in the range of 0.001-1, preferably 0.3-0.6.

  The comonomer used to form the sulfonated polysulfone can also be selected depending on the desired properties and application of the resulting membrane. As preferred comonomers, 4,4′-biphenol, hydroquinone, 4,4 ′-(hexafluoroisopropylidene) diphenol, phenylphosphine oxide bisphenol or other aromatic bisphenols can be used. Further, the bisphenol may contain an aliphatic substituent or an aromatic substituent. In particular, 4,4′-biphenol and 4,4 ′-(hexafluoroisopropylidene) diphenol are preferable.

In addition to the above, the sulfonated aromatic polymer used in the present invention can be synthesized according to a known method (for example, Polymer Preprints (2000), 41 (1), 237). And a method in which polycondensation of each and one or more compounds selected from aromatic nucleophilic compounds under basic conditions is preferably used.
In the present invention, for example, as shown in Scheme 2, 3,3′-disulfonated 4,4′-dichlorodiphenylsulfone and dichlorodiphenylsulfone and 4,4′-biphenol are directly condensed to form sulfonated poly ( Arylene ether sulfone) can be synthesized.

Scheme 2
Synthesis of sulfonated poly (arylene ether sulfone)

In the present invention, as an example of a method for synthesizing a polymer compound before introduction of a sulfonic acid group, a compound represented by the following formula (III) and a compound represented by the following formula (IV) are polymerized (preferably, And polycondensation).
Formula (III)

式（ＩＩＩ）中、Ｘ¹は、ハロゲン原子（例えば、フッ素原子、塩素原子）またはニトロ基を表す。２つのＸ¹はそれぞれ同一でも異なっていてもよい。

In formula (III), X ¹ represents a halogen atom (for example, a fluorine atom or a chlorine atom) or a nitro group. Two X ^{1 s} may be the same or different.

式（ＩＶ）中、Ａは、上記式（１）におけるＹと同義であり、好ましい範囲も同義である。ｍは０、１または２である。ＲおよびＲⁱは、それぞれ、Ｃ数１〜１０のアルキル基であり、メチル基あるいはエチル基が好ましい。ｓおよびｓⁱは０〜４の整数であり、０または１が好ましい。 Formula (IV)

In formula (IV), A has the same meaning as Y in formula (1), and the preferred range is also the same. m is 0, 1 or 2. R and ^Ri are each an alkyl group having 1 to 10 carbon atoms, preferably a methyl group or an ethyl group. s and s ⁱ are integers of 0 to 4, and 0 or 1 is preferable.

  Specific examples of the compound represented by the formula (III) include the compounds represented below.

  These compounds can be used alone or in admixture of two or more.

  Specific examples of the compound represented by the formula (IV) include hydroquinone, resorcin, 2-methylhydroquinone, 2-ethylhydroquinone, 2-propylhydroquinone, 2-butylhydroquinone, 2-hexylhydroquinone, and 2-octylhydroquinone. 2-decanyl hydroquinone, 2,3-dimethyl hydroquinone, 2,3-diethyl hydroquinone, 2,5-dimethyl hydroquinone, 2,5-diethyl hydroquinone, 2,6-dimethyl hydroquinone, 2,3,5-trimethyl hydroquinone 2,3,5,6-tetramethylhydroquinone, 4,4′-dihydroxybiphenyl, 2,2′-dihydroxybiphenyl, 3,3′-dimethyl-4,4′-dihydroxybiphenyl, 3,3 ′, 5 , 5'-Tetramethyl-4,4 ' -Dihydroxybiphenyl, 3,3'-dichloro-4,4'-dihydroxybiphenyl, 3,3 ', 5,5'-tetrachloro-4,4'-dihydroxybiphenyl, 3,3'-dibromo-4,4 '-Dihydroxybiphenyl, 3,3', 5,5'-tetrabromo-4,4'-dihydroxybiphenyl, 3,3'-difluoro-4,4'-dihydroxybiphenyl, 3,3 ', 5,5'- Tetrafluoro-4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenylmethane, 2,2'-dihydroxydiphenylmethane, 3,3'-dimethyl-4,4'-dihydroxydiphenylmethane, 3,3 ', 5,5 '-Tetramethyl-4,4'-dihydroxydiphenylmethane, 3,3'-dichloro-4,4'-dihydroxydiphenylmethane, 3,3', 5,5'-tetrachloro -4,4'-dihydroxydiphenylmethane, 3,3'-dibromo-4,4'-dihydroxydiphenylmethane, 3,3 ', 5,5'-tetrabromo-4,4'-dihydroxydiphenylmethane, 3,3'-difluoro -4,4'-dihydroxydiphenylmethane, 3,3'5,5'-tetrafluoro-4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 2,2'-dihydroxydiphenyl ether, 3,3'- Dimethyl-4,4′-dihydroxydiphenyl ether, 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenyl ether, 3,3′-dichloro-4,4′-dihydroxydiphenyl ether, 3,3 ′ , 5,5'-tetrachloro-4,4'-dihydroxydiphenyl ether, 3,3'-dibromo-4,4 '-Dihydroxydiphenyl ether, 3,3', 5,5'-tetrabromo-4,4'-dihydroxydiphenyl ether, 3,3'-difluoro-4,4'-dihydroxydiphenyl ether, 3,3 ', 5,5'- Tetrafluoro-4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfide, 2,2′-dihydroxydiphenyl sulfide, 3,3′-dimethyl-4,4′-dihydroxydiphenyl sulfide, 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxydiphenyl sulfide, 3,3′-dichloro-4,4′-dihydroxydiphenyl sulfide, 3,3 ′, 5,5′-tetrachloro-4,4 ′ -Dihydroxydiphenyl sulfide, 3,3'-dibromo-4,4'-dihydroxydiphenyl sulfide, 3,3 ' 5,5′-tetrabromo-4,4′-dihydroxydiphenyl sulfide, 3,3′-difluoro-4,4′-dihydroxydiphenyl sulfide, 3,3 ′, 5,5′-tetrafluoro-4,4′- Dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenylsulfone, 2,2′-dihydroxydiphenylsulfone, 3,3′-dimethyl-4,4′-dihydroxydiphenylsulfone, 3,3 ′, 5,5′-tetramethyl -4,4'-dihydroxydiphenylsulfone, 3,3'-dichloro-4,4'-dihydroxydiphenylsulfone, 3,3 ', 5,5'-tetrachloro-4,4'-dihydroxydiphenylsulfone, 3, 3'-dibromo-4,4'-dihydroxydiphenyl sulfone, 3,3 ', 5,5'-tetrabromo-4,4'-dihydroxydiph Nyl sulfone, 3,3′-difluoro-4,4′-dihydroxydiphenyl sulfone, 3,3 ′, 5,5′-tetrafluoro-4,4′-dihydroxydiphenyl sulfone, 2,2-bis (4-hydroxyphenyl) ) Propane, 2,2-bis (2-hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3-chloro-4-hydroxyphenyl) propane, 2,2-bis (3,5-dichloro-4-hydroxyphenyl) propane, 2,2-bis (3-bromo-4-hydroxyphenyl) propane, 2,2-bis (3,5-didibromo-4- Hydroxyphenyl) propane, 2,2-bis (3-fluoro-4-hydroxyphenyl) propane, 2,2-bis (3,5-difluoro-4-hydro) Cyphenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, α, α′-bis (4-hydroxyphenyl) -1,4-diisopropylbenzene, α, α′-bis ( 2-hydroxyphenyl) -1,4-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -1,3-diisopropylbenzene, α, α′-bis (2-hydroxyphenyl) -1,3- Diisopropylbenzene, α, α′-bis (3-methyl-4-hydroxyphenyl) -1,4-diisopropylbenzene, α, α′-bis (3,5-dimethyl-4-hydroxyphenyl) -1,4- Diisopropylbenzene, α, α'-bis (3-methyl-4-hydroxyphenyl) -1,3-diisopropylbenzene, α, α'-bis (3,5-dimethyl-4- Hydroxyphenyl) -1,3-diisopropylbenzene and the like. These aromatic diols can be used alone or in admixture of two or more.

  Moreover, the preferable compounding ratio of the compound represented by the formula (III) and the compound represented by the formula (IV) is represented by the formula (III) with respect to 1 mol of the compound represented by the formula (IV). The compound to be used is preferably 0.7 to 1.3 mol, more preferably 0.9 to 1.1 mol, and even more preferably 0.95 to 1.05 mol.

  When the compound represented by the formula (III) and the compound represented by the formula (IV) are polycondensed to synthesize the proton acid group-containing polysulfone (solid electrolyte) of the present invention, in the presence of a basic compound. A polycondensation method is preferably used.

  The type of reaction agent, reaction conditions, and the like are not particularly defined, and known reaction agents, reaction conditions, and the like can be applied. Reactants include alkali metals (lithium, sodium, potassium), alkaline earth metals (potassium, strontium, barium), basic metal compounds such as zinc oxide, various metal carbonates (sodium carbonate, lithium carbonate, potassium carbonate, Cesium carbonate), acetate (sodium acetate, lithium acetate, potassium acetate, cesium acetate), hydroxide (lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide), quaternary ammonium salt (Trimethylammonium hydroxide, triethylammonium hydroxide, tributylammonium hydroxide, benzyltrimethylammonium hydroxide), organic bases (triethylamine, pyridine, methylimidazole, morpholine, tributylammonium, (2-hydroxyethyl) amine) and the like.

  The amount of these reactants used is preferably 0.05 to 10.0 moles, more preferably 0.1 to 4.0 moles, and more preferably 0.5 to 2 moles with respect to 1 mole of the sum of moles of monomers to be condensed. .5 mol is particularly preferred.

  The reaction for producing the electrolyte membrane used in the present invention is usually carried out in a solvent. The following are mentioned as a preferable solvent.

1) ether solvent 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxyethoxy) ethane, tetrahydrofuran, bis [2- (2-methoxyethoxy) ethyl] ether, 1,4-dioxane and the like.
2) Aprotic amide solvents N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N -Methylcaprolactam, hexamethylphosphorotriamide and the like.
3) Amine solvents pyridine, quinoline, isoquinoline, α-picoline, β-picoline, γ-picoline, isophorone, piperidine, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine etc.
4) Other solvents: dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, sulfolane, diphenyl sulfone, tetramethyl urea, anisole and the like.

  Among the above-mentioned solvents, particularly preferred solvents include the aprotic amide solvent described in the above item 2) and the dimethyl sulfoxide and sulfolane described in the item 4). N, N-dimethylacetamide, N, N-diethylacetamide, N -Methyl-2-pyrrolidone, dimethyl sulfoxide and sulfolane are more preferred.

  These solvents may be used alone or in combination of two or more. Moreover, it can also be used by further mixing these 1 type (s) or 2 or more types using the solvent shown to the following 5) term | claim. When mixed and used, it is not always necessary to select a combination of solvents that dissolve in each other at an arbitrary ratio, and a non-mixed and non-uniform state may be used. Further, the solvent may be distilled off and added during the reaction in order to adjust the reaction concentration and the reaction solution viscosity. The concentration profile is preferably a low concentration for dissolution at the time of charging, a high concentration for promoting the reaction in the middle period, and a low concentration again for fluidization in the final period.

  The concentration of the reaction performed in these solvents (hereinafter referred to as polymerization concentration) is not limited, but the reaction rate decreases at low concentrations, and the viscosity becomes too high at high concentrations, making stirring difficult. The appropriate concentration is, for example, 1% to 100% (no solvent) as the solid content concentration, preferably 5% to 70%, and particularly preferably 10% to 50%.

The atmosphere is air, nitrogen, helium, neon, or argon, and is not particularly limited, but is preferably an inert gas such as nitrogen or argon.
Furthermore, in order to remove moisture contained in the raw material out of the system as a pretreatment for the reaction, it is preferable that another solvent coexists. Examples of the solvent used here include the following 5).
5) benzene, toluene, o-xylene, m-xylene, p-xylene, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, bromobenzene, o-dibromobenzene, m-dibromobenzene, p- And dibromobenzene, o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, o-bromotoluene, m-bromotoluene, and p-bromotoluene. These solvents may be used alone or in combination of two or more.

  There are no particular limitations on the temperature, time and pressure of the reaction for producing the electrolyte membrane used in the present invention, and known conditions can be applied. That is, the reaction temperature is preferably 50 ° C to 300 ° C, more preferably 100 to 270 ° C, and further preferably 130 to 250 ° C. Moreover, although reaction time changes with kinds of monomer to be used, the kind of solvent, and reaction temperature, 1 to 72 hours are preferable. More preferably, it is 3 hours to 48 hours, More preferably, it is 5 to 24 hours. The reaction pressure may be under pressure or under reduced pressure, but may be normal pressure.

The electrolyte membrane used in the present invention may be formed by solution casting a mixture of a sulfonated aromatic polymer (particularly a sulfonated polysulfone) and an inorganic heteropolyacid. The inorganic heteropolyacid is preferably selected from the group consisting of phosphotungstic acid, phosphomolybdic acid, and zirconium hydrogen phosphate, but is not limited thereto.

In the present invention, the following introduction method can be used as a method for introducing a sulfonic acid group into the polymer compound before introduction of the sulfonic acid group. In addition to the method of directly introducing a sulfonic acid group into the polymer compound, the polymer compound may be polymerized after introduction into the monomer.
For example, when B ¹ is a methyl group, a halogenomethylated polysulfone using a halogenomethylating agent such as chloromethyl methyl ether described later, and then a compound containing a thioether bond in the alkyl chain, such as 3-mercapto described below Examples thereof include a method of reacting sodium -1-propanesulfonate and sodium 2-mercaptoethanesulfonate.

  In the present invention, the halogenoalkyl group includes a chloromethyl group, bromomethyl group, iodomethyl group, chloroethyl group, bromoethyl group, iodoethyl group, chloropropyl group, bromopropyl group, iodopropyl group, chlorobutyl group, bromobutyl group, iodobutyl group, Examples include halogeno (C 1-6) alkyl groups such as chloropentyl group, bromopentyl group, iodopentyl group, chlorohexyl group, bromohexyl group, iodohexyl group, and the like, and halogenomethyl group is preferred.

  In order to introduce a preferred halogenomethyl group in the present invention into an aromatic ring (halogenomethylation reaction of an aromatic ring), known reactions can be widely used. For example, chloromethyl methyl ether, 1,4-bis (chloromethoxy) butane, 1-chloromethoxy-4-chlorobutane, etc. are used as chloromethylating agents, and tin chloride, zinc chloride, aluminum chloride, titanium chloride, etc. are used as catalysts. A chloromethyl group can be introduced into an aromatic ring by carrying out a chloromethylation reaction using a Lewis acid or hydrofluoric acid. The solvent is preferably dichloroethane, trichloroethane, tetrachloroethane, chlorobenzene, dichlorobenzene, nitrobenzene, etc., and the reaction is preferably carried out in a homogeneous system. Alternatively, a halogenomethylation reaction can be performed using paraformaldehyde and hydrogen chloride, hydrogen bromide, or the like.

  As used herein, “heteropolyacid”, “inorganic heteropolyacid” and “HPA” have meanings known to those skilled in the art and are described in particular in Katsoulis, D. et al. E. "A Survey of Applications of Polyoxometalates", Chemical Reviews, Vol. 1, pages 359-387 (1998). Further, the present specification can be understood in consideration of the contents described in these documents.

  The weight ratio of the heteropolyacid to the sulfonated aromatic polymer (particularly the sulfonated polysulfone) is preferably in the range of 10% to 60%. This ratio can be appropriately determined depending on the type of sulfonated aromatic polymer used and the type of heteropolyacid.

  The amount of the sulfonic acid group in the sulfonated aromatic polymer in the present invention is usually 0.05 to 2, preferably 0.3 to 1.5, with respect to 1 unit of the repeating unit constituting the polymer. It is a piece. By setting the number to 0.05 or more, proton conductivity is further improved. On the other hand, by setting the number to 1.5 or less, the hydrophilicity is improved to become a water-soluble polymer, or the durability is lowered due to water solubility. Can be more effectively deterred.

  The molecular weight of the precursor polymer before sulfonation of the sulfonated aromatic polymer used in the present invention is a polystyrene-equivalent weight average molecular weight, preferably 1,000 to 1,000,000, more preferably 1, 500 to 400,000. By setting it to 1,000 or more, it tends to be able to suppress the occurrence of cracks in the molded film, tends to improve the coating properties, and tends to improve the strength properties, which is preferable. On the other hand, by setting it as 1,000,000 or less, the solubility tends to be good, the solution viscosity tends to be low, and the workability tends to be good.

In addition, the structure of the sulfonated aromatic polymer used in the present invention has S = O absorption of 1,030 to 1,045 cm ⁻¹ , 1,160 to 1,190 cm ⁻¹ , 1,130 according to infrared absorption spectrum. ˜1,250 cm ⁻¹ C—O—C absorption, 1,640 to 1,660 cm ⁻¹ C═O absorption, etc., and these composition ratios can be determined by neutralization titration of sulfonic acid or elemental analysis. I can know. Moreover, the structure can be confirmed from the peak of aromatic protons at 6.8 to 8.0 ppm by nuclear magnetic resonance spectrum ( ¹ H-NMR).

  In the membrane formation process of the electrolyte membrane used in the present invention, the membrane is formed by extrusion molding using a liquid in which the sulfonated aromatic polymer compound and the filler are maintained at a temperature higher than the melting point or a liquid dissolved using a solvent. Alternatively, these liquids may be cast or coated to form a film. These operations can be performed with a film forming machine using a roll such as a calendar roll or a cast roll or a T-die, and can also be a press forming using a press machine. Further, a stretching process may be added to control film thickness and improve film characteristics.

  Furthermore, surface treatment may be performed after the film forming step. As the surface treatment, rough surface treatment, surface cutting, removal, and coating treatment may be performed, which may improve the adhesion with the electrode.

  10-500 micrometers is preferable and, as for the thickness of the electrolyte membrane used by this invention, 25-150 micrometers is especially preferable. It may be in the form of a film at the time of molding, or may be cut into a film after being formed into a bulk body.

  The electrolyte membrane used in the present invention can be impregnated into the pores of the porous substrate to form a membrane. The reaction solution after completion of the second step of the present invention may be applied and impregnated on a substrate having pores, or the substrate may be immersed in the reaction solution to fill the electrolyte membrane in the pores to form a membrane. . Preferable examples of the substrate having pores include porous polypropylene, porous polytetrafluoroethylene, porous cross-linked heat-resistant polyethylene, and porous polyimide.

Other Components of Electrolyte Membrane Used in the Present Invention The electrolyte membrane used in the present invention may be added with an antioxidant, a water absorbing agent, a plasticizer, a compatibilizer or the like as necessary in order to improve the membrane characteristics. The content of these additives is preferably in the range of 1 to 30% by mass with respect to the total amount of the electrolyte membrane.

  Antioxidants include (hindered) phenol, mono- or divalent sulfur, trivalent and pentavalent phosphorus, benzophenone, benzotriazole, hindered amine, cyanoacrylate, salicylate, oxalic Acid anilide compounds are preferred examples. Specific examples thereof include compounds described in JP-A-8-53614, JP-A-10-101873, JP-A-11-114430, and JP-A-2003-151346.

  Water-absorbing agents (hydrophilic substances) include cross-linked polyacrylate, starch-acrylate, poval, polyacrylonitrile, carboxymethylcellulose, polyvinylpyrrolidone, polyglycol dialkyl ether, polyglycol dialkyl ester, silica gel, synthetic zeolite, alumina gel , Titania gel, zirconia gel, and yttria gel are preferable examples. Specific examples include water absorbing agents described in JP-A Nos. 7-13003, 8-20716, and 9-251857. .

  Plasticizers include phosphoric acid ester compounds, phthalic acid ester compounds, aliphatic monobasic acid ester compounds, aliphatic dibasic acid ester compounds, dihydric alcohol ester compounds, oxyacid ester compounds, and chlorination. Paraffin, alkylnaphthalene compounds, sulfonalkylamide compounds, oligoethers, carbonates, and aromatic nitriles are preferable examples. Specifically, JP2003-197030A and JP2003-288916A. And plasticizers described in JP-A No. 2003-317539.

Furthermore, the electrolyte membrane used in the present invention may contain various polymer compounds for the purpose of (1) increasing the mechanical strength of the membrane and (2) increasing the acid concentration in the membrane.
(1) For the purpose of increasing mechanical strength, a polymer compound having a molecular weight of about 10,000 to 1,000,000 and having good compatibility with the electrolyte membrane of the present invention is suitable. For example, perfluorinated polymer, polystyrene, polyethylene glycol, polyoxetane, poly (meth) acrylate, polyether ketone, polyether sulfone, and two or more polymers thereof are preferable, and the content is 1 to 30 based on the total. A range of mass% is preferred.
The compatibilizer preferably has a boiling point or sublimation point of 250 ° C. or higher, more preferably 300 ° C. or higher.
(2) For the purpose of increasing the acid concentration, a perfluorocarbon sulfonic acid polymer typified by Nafion, a polymer compound having a ptronic acid moiety such as poly (meth) acrylate having a phosphate group in the side chain, and the like are preferable. As a quantity, the range of 1-30 mass% is preferable with respect to the whole.

As the characteristics of the electrolyte membrane used in the present invention, those having the following various performances are preferable.
The ionic conductivity is preferably 0.005 S / cm, particularly preferably 0.01 S / cm or more at 25 ° C. and 95% RH, for example.
For example, the tensile strength is preferably 10 MPa or more, particularly preferably 20 MPa or more.

The electrolyte membrane used in the present invention preferably has a stable water absorption and moisture content. Moreover, the thing whose solubility is a grade which can be disregarded substantially with respect to alcohol, water, and these mixed solvents is preferable. Moreover, the thing which is a grade which can be substantially disregarded in the weight reduction and shape change when immersed in the said solvent is preferable.
The ion conduction direction when the film is formed is preferably higher in the direction from the front surface to the rear surface than in other directions, but may be random.

The heat resistant temperature of the electrolyte membrane used in the present invention is preferably 200 ° C. or higher, more preferably 250 ° C. or higher, and particularly preferably 300 ° C. or higher. The heat resistant temperature can be defined as, for example, the time when the weight loss reaches 5% when heated at a rate of 1 ° C./min. This weight loss is calculated excluding evaporation such as moisture.

  Furthermore, when the electrolyte membrane used in the present invention is used in a fuel cell, an active metal catalyst that promotes the redox reaction between the anode fuel and the cathode fuel may be added. Thereby, the fuel which has permeated into the electrolyte membrane is consumed in the electrolyte membrane without reaching the other electrode, and crossover can be prevented. The active metal species used is not limited as long as it functions as an electrode catalyst, but platinum or an alloy based on platinum is suitable.

The membrane and electrode assembly (hereinafter referred to as “MEA”) of the present invention can be used in a fuel cell.
FIG. 1 shows an example of a schematic cross-sectional view of the membrane electrode assembly of the present invention. The MEA 10 includes an electrolyte membrane 11 and an anode electrode 12 and a cathode electrode 13 that are opposed to each other with the electrolyte membrane 11 interposed therebetween.
The anode electrode 12 and the cathode electrode 13 are composed of, for example, porous conductive sheets (for example, carbon paper) 12a, 13a and catalyst layers 12b, 13b (in the case of this embodiment, the electrode film referred to in the present invention is a porous conductive sheet) And a catalyst layer). The catalyst layers 12b and 13b are made of a dispersion in which carbon particles (for example, ketjen black, acetylene black, carbon nanotubes, etc.) carrying a catalyst metal such as platinum particles are dispersed in a proton conductive material (eg, Nafion). . In order to bring the catalyst layers 12b and 13b into close contact with the electrolyte membrane 11, the porous conductive sheets 12a and 13a coated with the catalyst layers 12b and 13b may be pressure-bonded to the electrolyte membrane 11 by a hot press method or appropriately supported. Generally, a method in which the catalyst layers 12b and 13b coated on the body are pressure-bonded while being transferred to the electrolyte membrane 11, and then sandwiched between the porous conductive sheets 12a and 13a is generally used.

  FIG. 2 shows an example of a fuel cell structure. The fuel cell includes an MEA 10, a current collector 17 including a pair of separators 17 that sandwich the MEA 10, and a gasket 14. The anode electrode side current collector 17 is provided with an anode electrode side air supply / exhaust port 15, and the cathode electrode side current collector 17 is provided with a cathode electrode air supply / exhaust port 16. Gas fuel such as hydrogen and alcohols (such as methanol) or liquid fuel such as an aqueous alcohol solution is supplied from the anode electrode side supply / exhaust port 15, and oxygen gas, air, etc. are oxidized from the cathode electrode side supply / exhaust port 16. An agent gas is supplied.

  For the anode electrode and the cathode electrode, a catalyst in which active metal particles such as platinum are supported on a carbon material is used. The particle size of the active metal that is usually used is in the range of 2 to 10 nm. The smaller the particle size, the greater the surface area per unit mass and the greater the activity, which is advantageous. It is said that the limit is about 2 nm.

  The active polarization in the hydrogen-oxygen fuel cell is larger in the cathode electrode (air electrode) than in the anode electrode (hydrogen electrode). This is because the cathode electrode reaction (oxygen reduction) is slower than the anode electrode. For the purpose of improving the activity of the oxygen electrode, various platinum-based binary metals such as Pt—Cr, Pt—Ni, Pt—Co, Pt—Cu, and Pt—Fe can be used. In a fuel cell using a fossil fuel reformed gas containing carbon monoxide as an anode fuel, it is important to suppress catalyst poisoning by CO. For this purpose, platinum-based binary metals such as Pt—Ru, Pt—Fe, Pt—Ni, Pt—Co, Pt—Mo, Pt—Ru—Mo, Pt—Ru—W, Pt—Ru—Co. Platinum-based ternary metals such as Pt—Ru—Fe, Pt—Ru—Ni, Pt—Ru—Cu, Pt—Ru—Sn, and Pt—Ru—Au can be used.

  As the carbon material for supporting the active metal, acetylene black, Vulcan XC-72, ketjen black, carbon nanohorn (CNH), and carbon nanotube (CNT) are preferably used.

  The function of the catalyst layer was caused by (1) transporting the fuel to the active metal, (2) providing a field for the oxidation (anode electrode) and reduction (cathode electrode) reaction of the fuel, and (3) redox. (4) transporting protons generated by the reaction to the electrolyte membrane. For (1), the catalyst layer needs to be porous so that liquid and gaseous fuel can permeate deeply. (2) is the active metal catalyst described above, and (3) is the same carbon material as described above. In order to fulfill the function (4), a proton conductive material is mixed in the catalyst layer.

  The proton conductive material of the catalyst layer is not limited as long as it is a solid having a proton donating group, but is a polymer compound having an acid residue used for an electrolyte membrane, perfluorocarbon sulfone represented by Nafion (registered trademark). Heat resistant aromatics such as acid polymers, poly (meth) acrylates having phosphate groups in the side chain, sulfonated polyetheretherketone, sulfonated polyetherketone, sulfonated polyethersulfone, sulfonated polysulfone, and sulfonated polybenzimidazole Examples include polymers, sulfonated polystyrene, sulfonated polyoxetane, sulfonated polyimide, sulfonated polyphenylene sulfide, sulfonated polyphenylene oxide, and sulfonated polyphenylene. Specifically, JP 2002-110174 A, JP 20 No. 2-105200, JP-A No. 2004-10777, JP-A No. 2003-132908, JP-A No. 2004-179154, JP-A No. 2004-175997, JP-A No. 2004-247182 and JP-A No. 2003-2003. No. 147074, Japanese Patent Application Laid-Open No. 2004-234931, Japanese Patent Application Laid-Open No. 2002-289222, and Japanese Patent Application Laid-Open No. 2003-208816. When the electrolyte membrane used in the present invention is used for the catalyst layer, the same kind of material as that of the electrolyte membrane is obtained, so that the electrochemical adhesion between the electrolyte membrane and the catalyst layer is increased, which is more advantageous.

Moreover, when a binder contains polysulfonated sulfone, such as a repeating unit represented by Formula (1), for example, it is preferable to use a dispersion liquid containing ionic polymer particles having a volume average particle size of 1 nm to 200 nm.
Below, an example of the adjustment method of an ionic polymer particle dispersion liquid is demonstrated. The ionic polymer particle dispersion is an ion obtained by dissolving an ionic polymer in a poor solvent in which the ionic polymer is hardly soluble, and in a good solvent that is miscible with the poor solvent and in which the ionic polymer is easily soluble. The ionic polymer particles can be produced by continuously mixing the ionic polymer solution. Here, the continuous mixing means a state in which the poor solvent and the ionic polymer liquid are mixed in a flowing state, and new mixing continues to occur over time.

Here, the poor solvent in which the ionic polymer in the present invention is hardly soluble means, for example, a solvent having a solubility of the ionic polymer of 10 mg / mL or less.
One kind or two or more kinds of poor solvents may be mixed. The poor solvent used in the present invention is preferably water.

The good solvent is not particularly limited as long as it dissolves the ionic polymer and is miscible with the poor solvent, and may be a mixed solvent of two or more good solvents.
The good solvent used in the present invention is preferably an organic solvent that can be easily removed from the ionic polymer particle dispersion. Examples of such solvents include methanol, ethanol, isopropyl alcohol, 1-butanol, n-methylpyrrolidone, acetone, tetrahydrofuran, dimethylformamide, ethylenediamine, acetonitrile, methyl ethyl ketone, dimethyl sulfoxide, dichloromethane, and dimethylacetamide.

For example, in order to contain ionic polymer particles of submicron order of 1 to 200 nm, when mixing the poor solvent and the ionic polymer solution, the volume flow ratio of the poor solvent to the good solvent is 1: 1 to 100. Is preferably set to 1: 1, more preferably 5: 1 to 100: 1, and still more preferably 10: 1 to 100: 1. Furthermore, in order to obtain an ionic polymer particle dispersion having a smaller particle size and excellent dispersion stability by mixing the poor solvent and the ionic polymer solution, a dispersion stabilizer is added to the poor solvent or the ionic polymer solution. It is preferable to contain.

The catalyst layer preferably further contains a water repellent. The water repellent is preferably a fluorine-containing resin having water repellency, and more preferably has excellent heat resistance and oxidation resistance. Examples thereof include polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

The amount of active metal used is suitably in the range of 0.03 to 10 mg / cm ² from the viewpoint of battery output and economy. The mass of the carbon material supporting the active metal is suitably 0.5 to 10 times the mass of the active metal. The mass of the proton conductive material is suitably 0.1 to 0.7 times the mass of the active metal-carrying carbon.

  It is also called an electrode base material, a permeable layer, or a backing material, and plays a role of collecting current and preventing water from accumulating and deteriorating gas permeation. Usually, carbon paper or carbon cloth can be used, and polytetrafluoroethylene (PTFE) treated for water repellency can be used.

Examples of the method for supporting the catalytic metal include a thermal reduction method, a sputtering method, a pulse laser deposition method, a vacuum deposition method, and the like (for example, International Publication WO2002 / 05451).
No. 4 pamphlet).

A method for manufacturing the electrode film will be described.
An electrolyte membrane typified by Nafion is dissolved in a solvent, and a dispersion mixed with a catalyst material supporting a catalyst metal is dispersed. Solvents of the dispersion are heterocyclic compounds (3-methyl-2-oxazolidinone, N-methylpyrrolidone, etc.), cyclic ethers (dioxane, tetrahydrofuran, etc.), chain ethers (diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl) Ether, polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether, etc.), alcohols (methanol, ethanol, isopropanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, etc.), many Polyhydric alcohols (ethylene glycol, propylene glycol, polyethylene glycol, poly Pyrene glycol, glycerin, etc.), nitrile compounds (acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, benzonitrile, etc.), nonpolar solvents (toluene, xylene, etc.), chlorinated solvents (methylene chloride, ethylene chloride, etc.), Amides (N, N-dimethylformamide, N, N-dimethylacetamide, acetamide and the like), water and the like are preferably used, and among these, heterocyclic compounds, alcohols, polyhydric alcohols and amides are preferably used.

  The dispersion method may be a method using stirring, but ultrasonic dispersion, ball mill, or the like can also be used.

  Application of the dispersion will be described. In the coating step, the dispersion may be used to form a film by extrusion molding, or these dispersions may be cast or applied to form a film. The support in this case is not particularly limited, but preferred examples include a glass substrate, a metal substrate, a polymer film, a reflector and the like. Examples of polymer films include cellulose polymer films such as triacetylcellulose (TAC), ester polymer films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and fluorine such as polytrifluoroethylene (PTFE). Examples thereof include a polymer film and a polyimide film. The coating method may be a known method, for example, using curtain coating method, extrusion coating method, roll coating method, spin coating method, dip coating method, bar coating method, spray coating method, slide coating method, print coating method, etc. Can do. In particular, when a conductive porous body (carbon paper, carbon cloth) is used as a support, a catalyst electrode membrane can be directly produced.

These operations can be performed by a film forming machine using a roll such as a calendar roll or a cast roll or a T die, or can be a press forming using a press machine. Further, a stretching process may be added to control film thickness and improve film characteristics. As another method, a method of forming a catalyst layer by directly spraying the electrode catalyst made into a paste as described above onto a polymer electrolyte membrane using a normal spray or the like can be used. A uniform electrode catalyst layer can be formed by adjusting the spraying time and the spraying amount.

  The drying temperature of the coating process is related to the drying speed and can be selected according to the properties of the material. Preferably it is -20 degreeC-150 degreeC, More preferably, it is 20 degreeC-120 degreeC, More preferably, it is 50 degreeC-100 degreeC. A short drying time is preferable from the viewpoint of productivity. However, if the drying time is too short, defects such as bubbles, surface irregularities, and film cracks may be caused. For this reason, the drying time is preferably 1 minute to 48 hours, more preferably 5 minutes to 10 hours, and further preferably 10 minutes to 5 hours. Control of humidity is also important, and is preferably 25 to 100% RH, more preferably 50 to 95% RH.

  A coating liquid (dispersion) in the coating step preferably has a low content of metal ions, and particularly preferably has a low transition metal ion content, especially iron ions, nickel ions, and cobalt ions. The content of transition metal ions is preferably 500 ppm or less, and more preferably 100 ppm or less. Therefore, the solvent used in the above-mentioned process is also preferably a solvent having a low content of these ions.

  Further, the surface treatment may be performed after the coating process. As the surface treatment, rough surface treatment, surface cutting treatment, removal treatment, and coating treatment may be performed, which may improve the adhesion with the electrolyte membrane or the porous conductor.

  The thickness of the catalyst layer in the electrode film in the present invention is preferably from 5 to 200 μm, particularly preferably from 10 to 100 μm.

The following four methods are preferable for the production of MEA.
(1) Proton conductive material coating method: A catalyst paste (ink) based on active metal-supported carbon, proton conductive material, and solvent is directly applied to both sides of the electrolyte membrane, and a porous conductive sheet is thermocompression-bonded (hot press). Thus, a MEA having a five-layer structure is manufactured.
(2) Porous conductive sheet coating method: After a catalyst paste is coated on the surface of the porous conductive sheet to form a catalyst layer, it is thermocompression-bonded (hot pressed) with the electrolyte membrane to produce a MEA having a five-layer structure. The same as (1) above except that the coating support is different.
(3) Decal method: After a catalyst paste is applied on a support (polytetrafluoroethylene (PTFE) sheet or the like) to form a catalyst layer, only the catalyst layer is transferred to the electrolyte membrane by thermocompression bonding (hot pressing). A three-layer MEA is formed, and a porous conductive sheet is pressure-bonded to produce a five-layer MEA.
(4) Post-catalyst support method: After applying and forming an ink obtained by mixing a platinum-unsupported carbon material together with a proton conductive material on an electrolyte membrane, a porous conductive sheet or PTFE, platinum ions are impregnated in the electrolyte membrane, Platinum particles are reduced and deposited in the film to form a catalyst layer. After forming the catalyst layer, the MEA is produced by the above methods (1) to (3).

Here, the hot press method is a method in which an electrolyte membrane is sandwiched between electrode membranes and temperature and pressure are applied. Further, before performing hot pressing, it is preferable that the electrolyte membrane and electrode film containing a good solvent are bonded together and allowed to stand for a while at a temperature lower than the temperature during hot pressing (bonding operation). Regarding the conditions of the bonding operation, the temperature is preferably in the range of 10 to 80 ° C, more preferably in the range of 20 to 40 ° C. The time is preferably from 0.1 to 10 minutes, more preferably from 0.5 to 5 minutes.
Regarding hot press conditions, the hot press temperature is preferably 100 ° C. or higher, more preferably 130 ° C. or higher, and further preferably 150 ° C. or higher. The upper limit of the press temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower.

When the above salt is used, the following steps are further required.
For use as a fuel cell application, the sulfonated aromatic polymer used as the raw material for the electrolyte membrane in the present invention needs to have proton conductivity. For this purpose, the salt substitution rate of the electrolyte membrane is reduced to 99% or less before the contact by contacting with an acid. By joining the electrode catalyst and the polymer electrolyte membrane and then bringing them into contact with the acid, it is possible to recover the reduction in the moisture content and ion conductivity of the membrane due to the thermal history received during electrode joining.

As a method of contacting with an acid, a known method of dipping or spraying an acidic aqueous solution such as hydrochloric acid, sulfuric acid, nitric acid, or organic sulfonic acid can be used, but the dipping method is simple and preferable. Further, a method using hydrochloric acid, sulfuric acid or nitric acid which are mineral acids is preferable, and sulfuric acid is particularly preferable. Although the density | concentration of the acidic aqueous solution to be used is dependent also on the ionic conductivity fall state, immersion temperature, immersion time, etc., 0.0001-5 normal acidic aqueous solution can be used suitably, for example, 0.1-0.1 A range of 2N is more preferable. In many cases, the immersion temperature can be sufficiently converted at room temperature, and when the immersion time is shortened, the acidic aqueous solution may be heated. In this case, the range of 30 to 100 ° C is preferable, and the range of 50 to 95 ° C is more preferable. Although the immersion time depends on the concentration of the acidic aqueous solution and the immersion temperature, it can be preferably carried out in the range of approximately 10 minutes to 24 hours, and is preferably 6 hours or less in the above range from the viewpoint of productivity, and preferably 4 hours. The following is more preferable. The impurity contained in the acidic solution is preferably 1% by weight or less, and more preferably 0.1% or less.

  When the fuel cell is operated, a method in which the proton moving inside the electrolyte membrane functions as an acid to wash away the substituted cation and develop higher ion conductivity can be used. A method for producing a fuel cell using the membrane electrode assembly produced in this manner will be described.

  The solid polymer electrolyte fuel cell includes an MEA, a current collector, a fuel cell frame, a gas supply device, and the like. Of these, the current collector (bipolar plate) is a graphite or metal flow path forming material and current collector having a gas flow path on the surface or the like. By inserting a plurality of MEAs between such current collectors and stacking them, a fuel cell stack can be produced.

  The higher the operating temperature of the fuel cell is, the higher the catalyst activity is. However, the fuel cell is usually operated at 50 to 120 ° C. where water management is easy. The higher the supply pressure of oxygen and hydrogen, the higher the output of the fuel cell, which is preferable. However, since the probability of contact between the two due to damage to the electrolyte membrane also increases, the pressure should be adjusted to an appropriate pressure range, for example, 1 to 3 atmospheres. Is preferred.

  The anode fuel that can be used as the fuel of the fuel cell of the present invention includes hydrogen, alcohols (methanol, isopropanol, ethylene glycol, etc.), ethers (dimethyl ether, dimethoxymethane, trimethoxymethane, etc.), formic acid, Examples thereof include borohydride complexes and ascorbic acid. Examples of the cathode fuel include oxygen (including oxygen in the atmosphere) and hydrogen peroxide.

  The methods for supplying the anode fuel and the cathode fuel to the respective catalyst layers include (1) a method of forced circulation using an auxiliary device such as a pump (active type), and (2) a method not using an auxiliary device ( For example, in the case of a liquid, there are two types, ie, a passive type in which a catalyst layer is exposed to the atmosphere and supplied to the atmosphere in the case of a gas due to capillary action or natural fall, and these can be combined. The former is advantageous in that the pressure and humidity of the reaction gas can be adjusted to increase the output, but there is a drawback that it is difficult to reduce the size. The latter is advantageous in that it can be miniaturized, but has a drawback that high output is difficult to obtain.

Since the single cell voltage of the fuel cell is generally 1.2 V or less, the single cells are used in series stacking according to the required voltage of the load. As the stacking method, “planar stacking” in which the single cells are arranged on a plane and “bipolar stacking” in which the single cells are stacked via separators having fuel flow paths formed on both sides are used. The former is suitable for a small fuel cell because the cathode electrode (air electrode) comes out on the surface, so that air can be easily taken in and can be made thin. In addition to this, a method of applying MEMS technology, performing fine processing on a silicon wafer, and stacking has been proposed.

  Fuel cells are considered to be used in various applications such as automobiles, homes, and portable devices. In particular, hydrogen fuel cells take advantage of the high output and make use of various types of hot water generators for home use and transportation. It is expected to be used as a power source for devices and as an energy source for portable electronic devices. For example, hot water generators that can be preferably applied include homes, apartment houses, hospitals, transportation equipment such as automobiles, ships, and portable equipment such as mobile phones, mobile notebook computers, and electronic still cameras. Examples of portable devices that can be preferably applied include portable generators and outdoor lighting devices. It can also be preferably used as a power source for industrial or household robots or other toys. Furthermore, it is also useful as a power source for charging secondary batteries mounted on these devices. In addition, the use of an emergency power supply has been proposed.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Average molecular weight]
The average molecular weight of the polymer was determined as a molecular weight in terms of polystyrene by gel permeation chromatography (GPC) using N, N-dimethylformamide (DMF) as a solvent.

[Ion exchange capacity]
A predetermined amount of the polymer was weighed and immersed in a 1N NaOH aqueous solution for 12 hours, and an excess amount of NaOH was neutralized and titrated with 1N hydrochloric acid using a pH meter. From the difference between the initial molar amount of NaOH and the molar amount of HCl required for neutralization, the amount of sulfonic acid in the polymer was calculated. By dividing this by the predetermined amount (polymer amount), the ion exchange capacity per unit weight was calculated.

[Durability test]
As a simulation test of a fuel cell in which high humidity operation and low humidity operation are repeated, MEA was sandwiched between PTFE meshes, boiled in water for 2 hours, and a room temperature blow drying 2 hour cycle was repeated 10 times.

[Synthesis Example 1]
(Sulfonated polysulfone 1)
A sulfonated monomer was prepared with reference to PolymerPreprints (2000), 41 (1), 237. 4,4′-Dichlorodiphenylsulfone (DCDPS) was reacted with fuming sulfuric acid followed by neutralization with sodium chloride and sodium hydroxide. This electrophilic aromatic substitution process resulted in a derivative with the sulfonyl group in the meta position and the chlorine group in the ortho position. This chemical structure was confirmed by H-NMR, C-NMR, mass spectrometry, infrared spectrum and elemental analysis. The expected structure was obtained with a yield of close to 80%. This compound is referred to as SDCDPS.

Sulfonated poly (arylene ether sulfone) 1 was synthesized by reacting with biphenol at 40% SDCDPS relative to the total concentration of dihalide (DCDPS + SDCDPS). This polymer synthesis (Scheme 1) condenses a controlled amount of sulfonated activated halide (SDCDPS), 4,4′-dichlorodiphenylsulfone and biphenol in NMP (containing toluene as an azeotropic agent). The process of carrying out is included. The substituted activated halide was clearly less reactive and less soluble. Therefore, the temperature required for polymerization was somewhat higher than usual (up to about 190 ° C.). These polymerizations were performed in the sodium salt form of SDCDPS and utilized the very high stability of the sulfonate. The sulfonated polysulfone 1 was obtained by the above operation. From the NMR spectrum, it was found that a copolymer having almost the same charge ratio was obtained. When the molecular weight distribution was measured using GPC in a DMF solvent, the number average molecular weight was 76,000, and the weight average molecular weight was 211,000. The introduction of these sodium sulfonate groups was also confirmed in the FT-IR spectrum, where the strong and characteristic peaks at 1030 cm ⁻¹ and 1098 cm ⁻¹ were attributed to symmetric and asymmetric stretches of SO ₃ Na.

[Synthesis Example 2]
(Sulfonated polysulfone 2)
The bisphenol in the sulfonated polysulfone 1 was replaced with 4,4 ′-(hexafluoroisopropylidene) diphenol in equimolar conversion, and the same operation was performed to obtain a sulfonated polysulfone 2. From the NMR spectrum, it was found that a copolymer having almost the same charge ratio was obtained. When molecular weight distribution was measured using GPC in a DMF solvent, the number average molecular weight was 68,000, and the weight average molecular weight was 200,000. The introduction of the sodium sulfonate group was confirmed by FT-IR.

[Synthesis Example 3]
(Synthesis of sulfonated polysulfone 3)
As a monomer, 2,2-bis (4-hydroxyphenyl) propane and bis (4-chlorophenylphenyl) sulfone were used. Maruzen: 4th edition, Experimental Chemistry Course, Vol. 28, Polymer Synthesis, p. According to the general polymerization method described in 357, polysulfone was synthesized.
Thereafter, chloromethyl methyl ether (ClCH ₂ OCH ₃ ) to which SnCl ₄ was added was added to a solution in which the polysulfone was dissolved in 1,1,2,2-tetrachloroethane.
Put potassium chromatography tert- butoxide _{((CH 3) 3 COK)} ) and 3-mercapto-1-propane sulfonate _{(HS- (CH 2) 3 -SO} 3 Na), was added dehydrated dimethylformamide (DMF). A solution of the chloromethylated polysulfone synthesized above in dehydrated DMF was added to the three-necked flask containing the solution prepared above using a dropping funnel and allowed to react. Thereafter, suction filtration was performed to separate the precipitate portion and the filtrate, and the precipitate portion was dried to obtain a sulfonated polysulfone 3 compound.
The sulfonated polysulfone 3 was dispersed in N, N-dimethylacetamide and dissolved by stirring to obtain a 20% by weight dope. This was filtered through a PTFE microfilter having an average pore diameter of 0.45 μm, cast on a glass plate, and developed using an applicator. This was gradually heated from room temperature and dried. By peeling from the glass plate, a sodium salt-type membrane of sulfonated polysulfone 1 was obtained. This was immersed in dilute hydrochloric acid, converted into a proton type, washed with water, and dried to obtain an ion exchange membrane of proton type sulfonated polysulfone 3. The ion exchange capacity after film formation and proton exchange was 1.29 meq / g.

[Film preparation]
Sulfonated polysulfone 1, sulfonated polysulfone 2 or sulfonated polysulfone 3 was dispersed in N, N-dimethylacetamide and dissolved by stirring to obtain a 20 wt% dope. This was filtered through a PTFE microfilter having an average pore diameter of 0.45 μm, cast on a glass plate, and developed using an applicator. This was gradually heated from room temperature and dried. By peeling from the glass plate, a sulfonated polysulfone salt-type membrane was obtained. This was immersed in dilute hydrochloric acid, converted into a proton type, washed with water and dried to obtain a proton-type sulfonated polysulfone membrane (acid type). The ion exchange capacity of the sulfonated polysulfone membrane (acid type) was 1.28 meq / g for sulfonated polysulfone 1, 1.25 meq / g for sulfonated polysulfone 2, and 1.29 meq / g for sulfonated polysulfone 3.

(Comparative Example 1)
(1) Production of electrode membrane (1-1) Production of electrode membrane A solution of 2 g of platinum-supported carbon (48 mass% of platinum supported on Vulcan XC72 (manufactured by Tanaka Kikinzoku Co., Ltd.)) and sulfonated polysulfone 1 (5% N- 15 g of methyl-2-pyrrolidone solution) was mixed and dispersed with an ultrasonic disperser for 45 minutes. The obtained dispersion was coated on a polytetrafluoroethylene film (made by Saint-Gobain) containing a reinforcing material using a bar coater, and heated and dried at 40 ° C. under normal pressure, followed by further drying under reduced pressure (temperature: 60 ° C., Time: 8 hours). An electrode film having a platinum loading of 0.2 mg / cm ² was produced by punching to a predetermined size.

(2) Production of MEA The electrode membrane obtained above was bonded to both sides of the produced polysulfone 1 electrolyte membrane (salt type) so that the coated surface was in contact with the proton conducting membrane, and after aging, 180 ° C., 3 MPa, 2 minutes Then, the temperature was lowered while applying pressure, and then the base used for the production of the electrode film was peeled off to produce an MEA. Here, the thermocompression bonding was performed without using a good solvent. Then, it was immersed in 0.5 mol / L dilute sulfuric acid, heated at 90 ° C. for 2 hours, washed with water, immersed in water for 2 hours, and dried.

(3) A gas diffusion electrode made of E-TEK cut to the same size as the electrode is laminated on the MEA obtained in the fuel cell characteristics (2), set in a standard fuel cell test cell manufactured by Electrochem, and the test cell as fuel The battery was connected to a battery evaluation system (manufactured by NF Circuit Design Block, As-510). A humidified hydrogen gas was supplied to the anode side and a simulated atmosphere was supplied to the cathode side, and the operation was continued until the voltage was stabilized. Thereafter, a load was applied between the anode electrode 12 and the cathode electrode 13, and the maximum output and the average cell area resistance value by the current interruption method were recorded from the current-voltage characteristics.

(Comparative Example 2)
The same operation was performed except that polysulfone 1 was replaced with polysulfone 2 in Comparative Example 1 above.

(Comparative Example 3)
The same operation was performed except that polysulfone 1 was replaced with polysulfone 3 in Comparative Example 1 above.

(Comparative Example 4)
The same operation was performed except that the production of the electrode film in Comparative Example 3 was changed as follows.
(1-2) Production of Electrode Film The proton sulfonated polysulfone 3 compound was dissolved in N-methylpyrrolidone, which is a good solvent, to obtain a 3% ionic polymer solution. The poor solvent and the ionic polymer solution were continuously mixed to obtain an ionic polymer particle dispersion. Water was used as the poor solvent. The supply flow rates of the ionic polymer solution and the poor solvent were 20 ml / min and 50 ml / min, respectively. Here, the temperature of the ionic polymer liquid was 45 ° C., and the poor solvent was supplied at 25 ° C. The volume average particle size of the ionic polymer particles dispersed in this ionic polymer particle was 170 nm. The ionic polymer solution was concentrated, and the solvent was replaced with n-propyl alcohol to prepare a binder solution as a 5 wt% solution.
2 g of platinum-supporting carbon (50 mass% of platinum supported on Vulcan XC72) and 15 g of the ionic polymer particle dispersion were mixed and dispersed with an ultrasonic disperser for 30 minutes. The obtained dispersion was coated on a reinforcing polytetrafluoroethylene film (manufactured by Saint-Gobain), heat-dried at 40 ° C under normal pressure, and further heat-dried under reduced pressure (temperature: 60 ° C, time: 8). time). An electrode film having a platinum loading of 0.2 mg / cm ² was produced by punching to a predetermined size.

Example 1
In the electrode film production process of Comparative Example 1, the electrode film was dried until the loss on drying of the electrode film reached 2%. In the MEA production process, the time after bonding was 1 minute, and the following operations were performed in the same manner.
The loss on drying is measured by subtracting the weight of the electrode film excluding the base weight for drying under vacuum heating from the electrode film excluding the base weight after drying. Obtained by dividing. Therefore, the loss on drying corresponds to the solvent content of the electrode film.

(Example 2)
In Example 1, the sulfonated polysulfone 1 was replaced with the sulfonated polysulfone 2, and the operation was performed in the same manner except that the elapsed time after bonding was 3 minutes in the MEA preparation process.

Example 3
The operation was performed in the same manner as in Example 2 except that the electrode film was dried until the loss on drying of the electrode film reached 4%, and the elapsed time after bonding was 1 minute in the MEA preparation process.

Example 4
In the MEA preparation process of Comparative Example 2 above, N-methylpyrrolidone was sprayed on both sides so as to be 0.14 mg / cm ² with respect to the electrolyte membrane, and the same operation was performed except that the elapsed time after bonding was 5 minutes. I did it.

(Example 5)
The same operation as in Example 2 was conducted except that dimethyl sulfoxide was used as the solvent for the sulfonated polysulfone 2 solution.

(Example 6)
The same operation was performed except that a sulfonated polysulfone electrolyte membrane having a loss on drying of 3% was used in Comparative Example 2 above.

(Example 7)
The same operation was performed except that a sulfonated polysulfone electrolyte membrane having a loss on drying of 3% was used in Comparative Example 3 above.

(Example 8)
The same operation as in Comparative Example 4 was conducted except that a sulfonated polysulfone electrolyte membrane having a loss on drying of 3% was used.

  FIG. 3 is an enlarged schematic cross-sectional view of the electrolyte membrane / catalyst membrane junction in the present invention and comparative examples. In the comparative example, a clear interface is formed because the catalyst membrane (18) and the electrolyte membrane (19) are laminated, but in the present invention, a mixed layer is formed between the two due to the effect of a good solvent. The

The membrane electrode assembly of the present invention was found to have a low resistance as a battery and a high maximum output, and no change in the durability simulation test. These were considered to be because the film-electrode adhesion was good and the damage to the film was small.

It is a schematic sectional drawing which shows the structure of the catalyst electrode joining film | membrane using the polymer electrolyte membrane of this invention. It is a schematic sectional drawing which shows an example of the structure of the fuel cell of this invention. It is an expansion schematic sectional drawing of the membrane electrode assembly in this invention and a comparative example.

Explanation of symbols

10 ... Membrane electrode assembly (MEA)
DESCRIPTION OF SYMBOLS 11 ... Electrolyte membrane 12 ... Anode electrode 12a ... Anode electrode porous conductive sheet 12b ... Anode electrode catalyst film 13 ... Cathode electrode 13a ... Cathode electrode porous conductive sheet 13b ... Cathode electrode catalyst membrane 14 ... Gasket 15 ... Anode electrode gas supply / exhaust port 16 ... Cathode electrode gas supply / exhaust port 17 ... Current collector 18 ... Catalyst layer 19 ... Electrolyte membrane 20 ..Catalyst layer and electrolyte membrane mixed layer

Claims (8)

A membrane electrode assembly formed by heating and / or pressurizing at least an electrolyte membrane and an electrode membrane, wherein the electrolyte membrane includes a sulfonated aromatic polymer to which at least one sulfonate moiety is bonded; and The heating and / or pressurization is performed by applying a good solvent for the sulfonated aromatic polymer to at least one of the electrolyte membrane and the electrode membrane in the range of 0.1 to 20% by weight of the weight of each membrane. A membrane electrode assembly which is performed in a state in which a solvent is contained. The membrane electrode assembly according to claim 1, wherein the good solvent is an amide solvent or a sulfoxide solvent. The membrane electrode according to claim 1 or 2, wherein the sulfonated aromatic polymer is a sulfonated polysulfone, and the sulfonate moiety is provided on a non-activated aromatic ring adjacent to a sulfone functional group of the polysulfone. Joined body. The membrane electrode assembly according to any one of claims 1 to 3, wherein the sulfonated aromatic polymer includes a repeating unit represented by the following formula (1) or a salt thereof.
Formula (1)

(In the formula (1), m and n are each a positive integer, n / n + m is in the range of 0.001-1, and Y is -S-, -S (O)-, -S (O ) ₂ —, —C (O) —, —P (O) (C ₆ H ₅ ) —, and combinations thereof, Z is a single bond, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —C (CF ₃ ) (C ₆ H ₅ ) —, —C (O) —, —S (O) ₂ — and —P (O) (C ₆ H ₅ ) — Selected from the group, A is selected from a sulfonate group and a group of formula (II).)
Formula (II)

(In formula (II), B ¹ and B ² each represent a linking group, X represents a group containing a sulfur atom, M represents a cation, and m1 represents an integer of 1 or more.) In the formula (1), n / (n + m) is in the range of 0.1 to 0.8, Y is —SO ₂ — or —CO—, and Z is a single bond or —C (CF ₃ ) _2. The membrane electrode assembly according to claim 4, which is −. The membrane electrode assembly according to any one of claims 1 to 5, wherein the sulfonate moiety is proton type, sodium type or potassium type. At least one of the electrode films includes a conductive material composed of a carbon material containing fine particles of a catalytic metal and a binder, and the binder includes a repeating unit represented by the formula (1), and the binder includes: The membrane electrode assembly according to any one of claims 4 to 6, wherein a dispersion liquid containing ionic polymer particles having a volume average particle size of 1 nm to 200 nm is used. A fuel cell comprising the membrane electrode assembly according to claim 1.

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