JP2008031464A - Polyelectrolyte emulsion and use thereof - Google Patents

Abstract

（式中、ｍは５以上の整数を表し、Ａｒ¹は酸性基を有する２価の芳香族基を表す。）
［３］上記いずれかに記載の高分子電解質エマルションと触媒成分とを含む触媒組成物から得られる触媒層、該触媒層を有する膜電極接合体および固体高分子型燃料電池。
【選択図】なしThe present invention provides a polymer electrolyte emulsion suitable for an electrode material, which dramatically improves the power generation performance of a membrane electrode assembly for a fuel cell.
[1] An emulsion in which polymer electrolyte particles are dispersed in a dispersion medium, and the polymer electrolyte contained in the polymer electrolyte particles has substantially a segment having an acidic group and an ion exchange group. A polyelectrolyte emulsion characterized by being a block copolymer composed of non-performing segments.
[2] The polymer electrolyte emulsion of [1] having a segment represented by the following formula (1) as a segment having an acidic group.

(In the formula, m represents an integer of 5 or more, and Ar ¹ represents a divalent aromatic group having an acidic group.)
[3] A catalyst layer obtained from a catalyst composition containing the polymer electrolyte emulsion according to any one of the above and a catalyst component, a membrane electrode assembly having the catalyst layer, and a polymer electrolyte fuel cell.
[Selection figure] None

Description

  The present invention relates to a polymer electrolyte emulsion, and an electrode, a membrane electrode assembly and a polymer electrolyte fuel cell produced using the same.

  In recent years, solid polymer fuel cells are expected to be put to practical use as generators in applications such as residential use and automobile use. In the polymer electrolyte fuel cell, electrodes called catalyst layers containing a catalyst such as platinum that promotes the oxidation-reduction reaction between hydrogen and air are formed on both sides of the polymer electrolyte membrane, and gas is further introduced outside the catalyst layer. It is used as a form having a gas diffusion layer for efficiently supplying the catalyst layer. Here, what formed the catalyst layer on both surfaces of the polymer electrolyte membrane is generally called a membrane electrode assembly (hereinafter also referred to as “MEA”).

  Such MEA is a method of directly forming a catalyst layer on a polymer electrolyte membrane, a method of forming a catalyst layer on a base material to be a gas diffusion layer such as carbon paper, and then bonding this to a polymer electrolyte membrane, A catalyst layer is formed on a flat support substrate, transferred to a polymer electrolyte membrane, and then manufactured using a method of peeling the support substrate. In these methods, a liquid composition in which a catalyst is dispersed or dissolved to form a catalyst layer (hereinafter also referred to as “catalyst ink” which is widely used in the art) is used. . The catalyst ink is usually a catalyst material (catalyst powder) in which a platinum group metal is supported on activated carbon, a polymer electrolyte solution or dispersion containing a polymer electrolyte typified by Nafion, and a solvent, water repellent as necessary. , A pore-forming agent and a thickener are mixed and dispersed. Until now, many techniques for improving the power generation performance of MEA by improving such a catalyst ink have been disclosed.

For example, Patent Document 1 discloses that a sulfonated polymer particle containing polyorganosiloxane as an essential component and an aqueous dispersion (emulsion) containing an aqueous medium are used as an electrode material for a polymer electrolyte fuel cell. It is disclosed that an excellent MEA can be obtained. However, the power generation performance is not always sufficient, and there is room for improvement.
Japanese Patent Laying-Open No. 2005-132996 (Claims)

  An object of the present invention is to provide a polymer electrolyte emulsion suitable for an electrode material capable of dramatically improving the power generation performance of MEA.

The inventors of the present invention have intensively studied an electrode material that can provide an MEA with more excellent power generation performance. As a result, the present invention has been completed.
That is, the present invention provides a polymer electrolyte emulsion shown in the following [1].
[1] A polymer electrolyte emulsion in which polymer electrolyte particles are dispersed in a dispersion medium, and the polymer electrolyte contained in the polymer electrolyte particles substantially has a segment having an acidic group and an ion exchange group. A polyelectrolyte emulsion characterized by being a block copolymer comprising no segments

（式中、ｍは５以上の整数を表し、Ａｒ¹は２価の芳香族基を表し、ここで該２価の芳香族基は、置換基を有していてもよい。なお、ｍ個あるＡｒ¹の一部または全部に酸性基を有する。Ｘは直接結合または２価の基を表す。）
［５］上記高分子電解質が、イオン交換基を実質的に有さないセグメントとして、下記式（３）で表されるセグメントを有する高分子電解質である、［１］〜［４］のいずれかの高分子電解質エマルション

（式中、ａ、ｂ、ｃは互いに独立に０か１を表し、ｎは５以上の整数を表す。Ａｒ²、Ａｒ³、Ａｒ⁴、Ａｒ⁵は互いに独立に２価の芳香族基を表し、ここでこれらの２価の芳香族基は、置換基を有していてもよい炭素数１〜２０のアルキル基、置換基を有していてもよい炭素数１〜２０のアルコキシ基、置換基を有していてもよい炭素数６〜２０のアリール基、置換基を有していてもよい炭素数６〜２０のアリールオキシ基、置換基を有していてもよい炭素数２〜２０のアシル基で、または置換されていてもよいアリールカルボニル基で置換されていてもよい。Ｘ、Ｘ’は、互いに独立に直接結合または２価の基を表す。Ｙ、Ｙ'は、互いに独立に酸素原子または硫黄原子を表す。） Furthermore, the present invention provides the following [2] to [5] as suitable polymer electrolytes applied to [1].
[2] The polymer electrolyte emulsion of [1], wherein the volume average particle size determined by a dynamic light scattering method is 100 nm to 200 μm. [3] The polymer electrolyte is an aromatic hydrocarbon polymer. ] Or [2] polymer electrolyte emulsion [4] The polymer electrolyte is a polymer electrolyte having a segment represented by the following formula (1) as a segment having an acidic group: [1] to [3] ] Any of the polymer electrolyte emulsions

(In the formula, m represents an integer of 5 or more, Ar ¹ represents a divalent aromatic group, and the divalent aromatic group may have a substituent. (A part or all of Ar ¹ has an acidic group. X represents a direct bond or a divalent group.)
[5] Any of [1] to [4], wherein the polymer electrolyte is a polymer electrolyte having a segment represented by the following formula (3) as a segment substantially having no ion exchange group. Polyelectrolyte emulsion

(In the formula, a, b and c each independently represent 0 or 1, and n represents an integer of 5 or more. Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ independently represent a divalent aromatic group. Wherein these divalent aromatic groups are optionally substituted alkyl groups having 1 to 20 carbon atoms, optionally substituted alkoxy groups having 1 to 20 carbon atoms, An aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, and 2 to 2 carbon atoms which may have a substituent. It may be substituted with an acyl group of 20 or an optionally substituted arylcarbonyl group, X and X ′ each independently represent a direct bond or a divalent group, and Y and Y ′ Independently represents an oxygen atom or a sulfur atom.)

The present invention also provides the following [6] to [11] using any of the above polymer electrolyte emulsions.
[6] The polymer electrolyte emulsion of any one of [1] to [5] used for an electrode of a solid polymer fuel cell [7] The content of a good solvent with respect to the polymer electrolyte is 200 ppm or less. [6] A polymer composition comprising the polymer electrolyte emulsion according to any one of the above [8] and a catalyst component.
[9] Membrane of membrane electrode assembly [11] [10] having electrode for polymer electrolyte fuel cell [10] [9] comprising polymer catalyst composition of [8] Solid polymer fuel cell having an electrode assembly

  According to the catalyst ink using the polymer electrolyte emulsion of the present invention, an electrode for producing MEA having excellent power generation performance can be provided. Such an MEA is extremely useful industrially because it can provide a fuel cell with excellent power generation performance.

  Hereinafter, preferred embodiments of the present invention will be described.

<Polymer electrolyte>
First, the suitable polymer electrolyte applied to the polymer electrolyte emulsion of this invention is demonstrated. In the polymer electrolyte emulsion of the present invention, a polymer electrolyte having an acidic group as an ion exchange group is used. When such a polymer electrolyte having an acidic group is used, it becomes possible to obtain a fuel cell having further excellent power generation performance as compared with a polymer electrolyte having a basic group.

Examples of the acidic group include a sulfonic acid group (—SO ₃ H), a carboxyl group (—COOH), a phosphonic acid group (—PO (OH) ₂ ), a phosphinic acid group (—POH (OH), and a sulfonimide group. (-SO ₂ NHSO _2- ), phenolic hydroxyl group (-Ph (OH) (Ph represents a phenyl group)), etc. Among them, a sulfonic acid group or a phosphonic acid group is more preferable, and a sulfonic acid group is more preferable. preferable.

The polymer electrolyte applied to the present invention is a block copolymer composed of a segment having an acidic group and a segment having substantially no ion exchange group. This polyelectrolyte may be a block copolymer having one of these segments, or may be a block copolymer having two or more of any one segment, and two of both segments. Any of the above multiblock copolymers may be used.
Although the aqueous dispersion described in Patent Document 1 for producing an electrode material is not specified, a polymer electrolyte obtained from the disclosed production method contains sulfonic acid groups (ion exchange groups) in the molecule. ) Was a random polymer introduced at random.

The present inventors have examined the polymerization sequence of such a polyelectrolyte in detail, and surprisingly, it is surprising that a block copolymer comprising the above-mentioned segment having an acidic group and a segment having substantially no ion-exchange group. It has been found that when an electrode is produced from a polymer electrolyte emulsion using a polymer, the power generation performance can be improved as compared with the aqueous dispersions disclosed so far. The reason for this is not clear, but in the emulsion containing the block copolymer as a polymer electrolyte particle, segments having acidic groups are dense on the surface of each particle, and the inside has substantial ion exchange groups. The electrode obtained from such an emulsion develops a form in which the segments that are not present are dense, and the form in which particles that are dense with the ion exchange groups involved in the electrode reaction are in a continuous form. It is estimated that the power generation performance is excellent.
Such estimation will be described with reference to FIG. FIG. 1 shows polymer electrolyte particles formed in the case of a diblock copolymer comprising a block 1 having an acidic group represented by a solid line and a block 2 having substantially no ion exchange group represented by a one-dot chain line. It is an estimation schematic diagram to represent. If the block 2 aggregates in the center of the particle and the block 1 is directed toward the particle surface, the block 1 related to the electrode reaction of the fuel cell electrode described later is present on the particle surface, which contributes to high power generation performance. Presumed. Heretofore, no polymer electrolyte emulsion based on such an idea has been disclosed.

  The “having an acidic group” segment means that many of the repeating units mainly constituting the segment have an acidic group. Specifically, it is a segment containing 0.5 or more acidic groups calculated on the average per repeating unit constituting such a segment. The segment having such an ion exchange group is more preferably a segment containing 1.0 or more acidic groups per repeating unit constituting the segment.

  The “substantially free of ion exchange groups” segment means that many of the repeating units mainly constituting such segments do not have ion exchange groups (acidic groups and basic groups). Specifically, the ion exchange group is a segment having an average number of 0.1 or less per repeating unit constituting the segment. As the segment substantially free of ion exchange groups, the number of ion exchange groups per repeating unit constituting the segment is preferably 0.05 or less, and the repeating unit constituting the segment It is more preferable that all of these have no ion exchange group.

  Typical examples of the segment having substantially no ion exchange group include, for example, (A) a segment in which the main chain is an aliphatic hydrocarbon chain; (B) all or part of the hydrogen atoms in the aliphatic hydrocarbon chain A segment substituted with a fluorine atom; (C) a segment composed of a polymer chain in which the main chain has an aromatic ring; (D) a polymer chain such as polysiloxane or polyphosphazene substantially free of carbon atoms in the main chain. (E) A segment composed of a polymer chain containing a nitrogen atom in the main chain or side chain.

  On the other hand, typical examples of the segment having an acidic group include, for example, (F) a segment in which an acidic group is introduced into a polymer chain whose main chain is an aliphatic hydrocarbon; and (G) all the hydrogen atoms of the aliphatic hydrocarbon. Or a segment in which an acidic group is introduced into a polymer chain partially substituted with fluorine atoms; (H) a segment in which an acidic group is introduced into a polymer chain in which the main chain has an aromatic ring; A segment consisting of a polymer chain substantially free of carbon atoms such as polysiloxane and polyphosphazene, wherein an acidic group is introduced into the polymer chain; (J) a main chain such as polybenzimidazole containing a nitrogen atom A segment consisting of a polymer chain with an acidic group directly bonded to the main chain or through a side chain, (K) a polymer chain containing a nitrogen atom in the main chain such as polybenzimidazole, sulfuric acid, phosphoric acid, etc. Such as an acidic compound segments introduced by ionic bond.

  In the polymer electrolyte of the present invention, as a segment having substantially no ion exchange group, at least one segment selected from the above (A) to (E) and a segment having an acidic group, Examples are block copolymers each having at least one segment selected from (F) to (K). The combination of these segments is not particularly limited, but in order to further enhance the effects of the present invention, a block copolymer having the above-mentioned segment (C) is preferable as a segment having substantially no ion exchange group. The block copolymer having the segment (H) is preferable as the segment having an acidic group, and the block copolymer having both the segment (C) and the segment (H), that is, An aromatic hydrocarbon polymer electrolyte is more preferable. Here, the “aromatic hydrocarbon-based polymer” is a form in which the main chain constituting such a polymer is mainly formed by connecting aromatic rings directly or by a divalent group, and constituting the polymer. In the composition, it means that the weight fraction of fluorine atoms is 15% by weight or less.

（式中、ｍは５以上の整数を表し、Ａｒ¹は２価の芳香族基を表し、ここで該２価の芳香族基は、置換基を有していてもよい。なお、ｍ個あるＡｒ¹の一部または全部に酸性基を有する。Ｘは直接結合または２価の基を表す。） The block copolymer having both the segment represented by (C) and the segment (H), which is a preferred block copolymer among the above, will be described in detail.
As a segment represented by said (H), the segment represented by following formula (1) is mentioned, for example.

(In the formula, m represents an integer of 5 or more, Ar ¹ represents a divalent aromatic group, and the divalent aromatic group may have a substituent. (A part or all of Ar ¹ has an acidic group. X represents a direct bond or a divalent group.)

  Here, m in Formula (1) represents an integer of 5 or more, preferably in the range of 5 to 1000, more preferably 10 to 1000, and particularly preferably 20 to 500. When the value of m is 5 or more, the ion conductivity expressed by such a segment becomes sufficient, and the power generation performance can be further improved, so that it is preferable as a member for a fuel cell. If the value of m is 1000 or less, it is preferable because production is easier.

Ar ¹ in the general formula (1) represents a divalent aromatic group. Examples of the divalent aromatic group include divalent monocyclic aromatic groups such as 1,3-phenylene group and 1,4-phenylene group, 1,3-naphthalenediyl group, and 1,4-naphthalene. Divalent condensed ring system such as diyl group, 1,5-naphthalenediyl group, 1,6-naphthalenediyl group, 1,7-naphthalenediyl group, 2,6-naphthalenediyl group, 2,7-naphthalenediyl group And divalent aromatic heterocyclic groups such as aromatic groups, pyridinediyl groups, quinoxalinediyl groups, and thiophenediyl groups. A divalent monocyclic aromatic group is preferred. In addition, the segment represented by the general formula (1) has an acidic group in part or all of Ar ¹ , and the acidic group may be directly bonded to the aromatic ring in Ar ¹ . The form which couple | bonded the bivalent group as a spacer may be sufficient, and the combination may be sufficient.

Ar ¹ may have an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkoxy group having 1 to 20 carbon atoms, or a substituent. It is substituted with an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, or an acyl group having 2 to 20 carbon atoms which may have a substituent. May be.

  Here, as the alkyl group having 1 to 20 carbon atoms which may have a substituent, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, isobutyl group N-pentyl group, 2,2-dimethylpropyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, 2-methylpentyl group, 2-ethylhexyl group, nonyl group, dodecyl group, hexadecyl group, octadecyl group, icosyl group Alkyl groups having 1 to 20 carbon atoms such as fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group And an alkyl group having a total carbon number of 20 or less.

  Examples of the optionally substituted alkoxy group having 1 to 20 carbon atoms include methoxy group, ethoxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, sec-butyloxy group, tert. -Butyloxy group, isobutyloxy group, n-pentyloxy group, 2,2-dimethylpropyloxy group, cyclopentyloxy group, n-hexyloxy group, cyclohexyloxy group, 2-methylpentyloxy group, 2-ethylhexyloxy group, Alkoxy groups having 1 to 20 carbon atoms such as dodecyloxy group, hexadecyloxy group, icosyloxy group and the like, fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl Group, naphthyl group, phenoxy group, naphthyl group Such as carboxymethyl groups are substituted, the total carbon number and an alkoxy group having 20 or less.

  Examples of the aryl group having 6 to 20 carbon atoms that may have a substituent include aryl groups such as a phenyl group, a naphthyl group, a phenanthrenyl group, and an anthracenyl group, and these groups include a fluorine atom, a hydroxyl group, and a nitrile group. An amino group, a methoxy group, an ethoxy group, an isopropyloxy group, a phenyl group, a naphthyl group, a phenoxy group, a naphthyloxy group, and the like are substituted, and an aryl group having a total carbon number of 20 or less is exemplified.

  Examples of the aryloxy group having 6 to 20 carbon atoms that may have a substituent include aryloxy groups such as a phenoxy group, a naphthyloxy group, a phenanthrenyloxy group, and an anthracenyloxy group, and these The group is substituted with fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group, etc., and the total number of carbon atoms is 20 or less An aryloxy group is mentioned.

  Examples of the acyl group having 2 to 20 carbon atoms which may have a substituent include 2 carbon atoms such as acetyl group, propionyl group, butyryl group, isobutyryl group, benzoyl group, 1-naphthoyl group and 2-naphthoyl group. ~ 20 acyl groups, and these groups are substituted with fluorine atom, hydroxyl group, nitrile group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group, etc. The acyl group whose total carbon number is 20 or less is mentioned.

Specific examples of the segment represented by the above formula (1) are given below. X is a direct bond (A-1) to (A-14), X is an oxygen atom (B-1) to (B-13), X is an oxygen atom, Ar ¹ is two aromatic rings Is an aromatic group bonded with a sulfonyl group, a carbonyl group or a hydrocarbon group (C-1) to (C-11), and X is a sulfur atom (D-1) to (D-6) And a segment having m bonded segments, and a segment having at least 0.5 × m or more acidic groups. In the following examples, -Ph represents a phenyl group.

（上式中、Ｚは酸性基であり、ｒ、ｓは、それぞれ独立に、０〜１２の整数であり、Ｔは、酸素原子、硫黄原子、カルボニル基、スルホニル基のいずれかを表す。＊は結合手を表す。） In the structural unit exemplified above, the structural unit having an acidic group is a group having an acidic group selected from the group consisting of an acidic group and those exemplified in the following formula (2) on the aromatic ring in the structural unit. Means that at least one is bonded.

(In the above formula, Z is an acidic group, r and s are each independently an integer of 0 to 12, and T represents any of an oxygen atom, a sulfur atom, a carbonyl group, and a sulfonyl group. Represents a bond.)

  The structural units constituting the segment having an acidic group exemplified above are (A-1), (A-2), (A-5), (A-9), (A-13), (B -1), (B-12), (C-1), (C-4), (C-7), (C-10), and (C-11), preferably (A-1), (A-2) (A-5), (A-10), (C-1) and (C-11) are more preferred, and (A-1), (A-2) or (A-10). ) Is particularly preferred. Among these segments, m of these structural units are linked, and among these segments, (0.5 × m) or more structural units are preferably segments having an acidic group, and all m structural units It is particularly preferable that has an acidic group.

（式中、ａ、ｂ、ｃは互いに独立に０か１を表し、ｎは５以上の整数を表す。Ａｒ²、Ａｒ³、Ａｒ⁴、Ａｒ⁵は互いに独立に２価の芳香族基を表し、ここでこれらの２価の芳香族基は、置換基を有していてもよい炭素数１〜２０のアルキル基、置換基を有していてもよい炭素数１〜２０のアルコキシ基、置換基を有していてもよい炭素数６〜２０のアリール基、置換基を有していてもよい炭素数６〜２０のアリールオキシ基、置換基を有していてもよい炭素数２〜２０のアシル基で、または置換されていてもよいアリールカルボニル基で置換されていてもよい。Ｘ、Ｘ’は、互いに独立に直接結合または２価の基を表す。Ｙ、Ｙ’は、互いに独立に酸素原子または硫黄原子を表す。） On the other hand, the segment having substantially no suitable ion exchange group is a segment represented by the following formula (3).

(In the formula, a, b and c each independently represent 0 or 1, and n represents an integer of 5 or more. Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ independently represent a divalent aromatic group. Wherein these divalent aromatic groups are optionally substituted alkyl groups having 1 to 20 carbon atoms, optionally substituted alkoxy groups having 1 to 20 carbon atoms, An aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, and 2 to 2 carbon atoms which may have a substituent. It may be substituted with an acyl group of 20 or an optionally substituted arylcarbonyl group, X and X ′ each independently represent a direct bond or a divalent group, and Y and Y ′ Independently represents an oxygen atom or a sulfur atom.)

Here, a, b, and c in Formula (3) each independently represent 0 or 1. n represents an integer of 5 or more, and is preferably 5 to 200. If the value of n is too small, problems such as insufficient water resistance and durability are likely to occur. Therefore, n is particularly preferably 10 or more.
Further, Ar ^2, Ar ³ in the formula ^{(3), Ar 4, Ar} 5 represents a divalent aromatic group independently of each other. Examples of the divalent aromatic group include the same groups as those exemplified for Ar ¹ .

Ar ² , Ar ³ , and Ar ⁴ are each an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkoxy group having 1 to 20 carbon atoms, and a substituent. An aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, and an aryl group having 2 to 20 carbon atoms which may have a substituent. It may be substituted with an acylcarbonyl group or an arylcarbonyl group having 2 to 20 carbon atoms which may have a substituent, and examples thereof include those exemplified for Ar ¹ above.
Y and Y ′ in the formula (3) each independently represent an oxygen atom or a sulfur atom. X and X ′ in the formula (3) each independently represent a direct bond or a divalent group. Among them, a carbonyl group, a sulfonyl group, a 2,2-isopropylidene group, or 9,9 -A fluorenediyl group is preferred.

Preferable representative examples of the structural unit represented by the formula (3) include the following. In addition, n is synonymous with the said General formula (3).

  Specifically, (H-1) to (H-50) shown in the following Table 1, Table 2, and Table 3 are exemplified as suitable block copolymers to be applied to the present invention.

が挙げられる。 In particular, preferred block copolymers include

Is mentioned.

  The abundance ratio of the block having an acidic group that forms the block copolymer and the block having substantially no ion exchange group can be optimized depending on the type of each block. The block having an acidic group is in the range of 30% by weight to 60% by weight with respect to the total weight of the polymer electrolyte.

<Average particle size>
The average particle diameter of the particles contained in the polymer electrolyte emulsion of the present invention is represented by a volume average particle diameter determined by measurement based on a dynamic light scattering method, and is preferably in the range of 100 nm to 200 μm. The average particle size is preferably in the range of 150 nm to 10 μm, and more preferably in the range of 200 nm to 1 μm. When the average particle diameter of the polymer electrolyte particles is in the above range, the obtained polymer electrolyte emulsion has practical storage stability, and when the film is formed, the uniformity of the film is relatively good. There is an advantage to become. The above-mentioned particles are not only polymer electrolyte particles made of a polymer electrolyte but also particles containing a polymer electrolyte and an additive, particles made of an additive, etc. It is a concept that includes all particles dispersed in a molecular electrolyte emulsion.

<Polymer electrolyte emulsion>
The method for producing the polymer electrolyte emulsion of the present invention is not particularly limited as long as the polymer electrolyte particles comprising the polymer electrolyte can be dispersed in the dispersion medium. As one example, a polymer electrolyte is dissolved in a good solvent of the polymer electrolyte to obtain a polymer electrolyte solution, and then this polymer electrolyte solution is added to another solvent (the high solvent of the emulsion). An example is a production method in which a polymer electrolyte dispersion is obtained by dropping the polymer electrolyte particles into a poor solvent of the molecular electrolyte and precipitating and dispersing the polymer electrolyte particles in the poor solvent. Further, the step of removing the good solvent contained in the obtained polymer electrolyte dispersion using membrane separation such as dialysis membrane, and further, the polymer electrolyte dispersion is concentrated by distillation etc. It can be shown as a preferable manufacturing method to adjust. By this method, a polymer electrolyte emulsion can be produced from any polymer electrolyte. In the exemplified production method, the definitions of “good solvent” and “poor solvent” are defined by the weight of the polymer electrolyte that can be dissolved in 100 g of the solvent at 25 ° C. The solvent in which 1 g or more of the polymer electrolyte is soluble is a poor solvent, and the poor solvent is a solvent in which the polymer electrolyte can dissolve only 0.05 g or less. The residual amount of the good solvent in the polymer electrolyte emulsion is preferably 200 ppm or less, more preferably 100 ppm or less, more preferably 50 ppm or less, in the polymer electrolyte emulsion obtained through such membrane separation. It is particularly preferable that the good solvent used in the step of preparing the polymer electrolyte solution is removed to such an extent that the good solvent is not substantially contained.

<Dispersion medium>
The poor solvent for dispersing the polymer electrolyte particles is not particularly limited as long as it does not interfere with the dispersion stability of the applied polymer electrolyte. Water, alcohol solvents such as methanol and ethanol, and nonpolar organic solvents such as hexane and toluene Or a mixture thereof. However, from the viewpoint of reducing environmental burden when used industrially, water or a solvent containing water as a main component is preferably used.

<Polymer electrolyte concentration>
The polymer electrolyte concentration of the polymer electrolyte emulsion of the present invention is 0.1 to 10% by weight. Here, the polymer electrolyte concentration is defined as a value obtained by dividing the total weight of the applied polymer electrolyte by the total weight of the obtained polymer electrolyte emulsion. The concentration of the polymer electrolyte is preferably 0.5 to 5% by weight, more preferably 1 to 2% by weight. If the polymer electrolyte concentration is in the above range, it is preferable because a large amount of solvent is not required to form a coating film, and it is excellent in coating properties.

<Emulsifier>
In order to give better dispersion stability to the polymer electrolyte emulsion of the present invention, an emulsifier may be added as long as the effect intended by the present invention is not impaired. Examples of surfactants used as emulsifiers include anionic surfactants such as alkyl sulfates (salts), alkylaryl sulfates (salts), alkyl phosphates (salts), and fatty acids (salts); alkylamine salts, Cationic surfactants such as alkyl quaternary amine salts; Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers and block polyethers; Carboxylic acid types (for example, amino acid types, betaine acid types) ), Amphoteric surfactants such as sulfonic acid type, and trade names of Latmul S-180A (manufactured by Kao Corporation), Eleminol JS-2 (manufactured by Sanyo Kasei Co., Ltd.), Aqualon HS-10, KH-10 (Daiichi Kogyo) Manufactured by Pharmaceutical Co., Ltd.], Adekari Soap SE-10N, SR-10 [Asahi Denka Kogyo Co., Ltd.], An ox MS-60 [manufactured by Nippon Emulsifier Co., Ltd.], it is possible to use any of such reactive emulsifier such as.

  Among polymers having a hydrophilic group, those which are soluble in a dispersion medium and have a dispersion function can also be used as an emulsifier. Examples of such polymers include styrene / maleic acid copolymer, styrene / acrylic acid copolymer, polyvinyl alcohol, polyalkylene glycol, sulfonated polyisoprene, sulfonated hydrogenated styrene / butadiene copolymer, styrene / Examples thereof include a sulfonated product of a maleic acid copolymer and a sulfonated product of a styrene / acrylic acid copolymer. In particular, the volume resistance can be reduced by using a polymer having a sulfonic acid group in an acid form. Examples of such a polymer include a sulfonated product of polyisoprene, a sulfonated product of hydrogenated styrene / butadiene copolymer, a sulfonated product of styrene / maleic acid copolymer, and a sulfonated product of styrene / acrylic acid copolymer. Can do.

  These emulsifiers can be used alone or in combination of two or more. When an emulsifier is used, 0.1 to 50 parts by weight of the emulsifier is usually used with respect to 100 parts by weight of the emulsion. The amount of the emulsifier used is preferably 0.2 to 20 parts by weight, more preferably 0.5 to 5 parts by weight. When the amount of the emulsifier used is within this range, it is preferable because the dispersion stability of the polymer electrolyte particles is improved and the operability such as suppression of foaming is improved.

<Other additives>
Thus, the polyelectrolyte emulsion of the present invention can be prepared. However, the polyelectrolyte emulsion of the present invention contains other additives such as inorganic or organic particles, adhesion assistants, sensitizers, leveling agents, and colorants. May be contained. In addition, such an additive may be contained in the polymer electrolyte particles constituting the polymer electrolyte emulsion as described above, or may be dissolved in the dispersion medium, or the polymer electrolyte. Apart from the particles, they may be present as fine particles comprising other components.

<Application>
The polymer electrolyte emulsion of the present invention is suitable as a binder resin for producing a polymer electrolyte fuel cell, but can also be applied to various uses such as a polymer electrolyte membrane, other coating materials, and a binder resin. It is. Moreover, when using for such a use, another polymer can also be used together from a viewpoint of designing a physical property etc. Examples of other polymers include known resins such as urethane resins, acrylic resins, polyester resins, polyamide resins, polyethers, polystyrenes, polyester amides, polycarbonates, polyvinyl chloride, and diene polymers such as SBR and NBR.

<Film forming method>
The polymer electrolyte emulsion of the present invention can obtain a highly accurate film by various film forming methods. Examples of the film forming method include cast film forming, spray coating, brush coating, roll coater, flow coater, bar coater, dip coater, and the like. Using these film forming methods, the polymer electrolyte emulsion is used as a base material. The film can be formed by coating the film and applying a drying treatment as necessary. The coating film thickness varies depending on the use, but is usually a dry film thickness of 0.01 to 1,000 μm, preferably 0.05 to 500 μm.

Moreover, there is no restriction | limiting in particular in the base material used for film shaping | molding, For example, non-ferrous materials, such as high molecular materials, such as polycarbonate resin, an acrylic resin, ABS resin, polyester resin, polyethylene, a polypropylene, nylon, aluminum, copper, duralumin Examples thereof include steel plates such as metals, stainless steel and iron, carbon, glass, wood, paper, gypsum, alumina, and hardened inorganic materials. There is no restriction | limiting in particular in the shape of a base material, Porous materials, such as a nonwoven fabric etc. from a planar thing, can be used.
Furthermore, when producing a catalyst layer of a polymer electrolyte fuel cell, which is a suitable application of a polymer electrolyte emulsion, the polymer electrolyte emulsion or the polymer electrolyte emulsion and a catalyst component are mixed in an ion conductive membrane. By directly applying the catalyst ink thus formed, it is possible to produce a form in which the ion conductive membrane and the catalyst layer are joined. Details of such use will be described later.

<Description of MEA>
Next, the MEA produced using the polymer electrolyte emulsion of the present invention will be described. The MEA of the present invention comprises an ion conductive (polymer electrolyte) membrane and a catalyst layer. The catalyst layer is formed by applying a catalyst ink to the ion conductive membrane. In addition, if a catalyst ink is applied to a substrate that can be a gas diffusion layer to obtain a laminate in which the gas diffusion layer and the catalyst layer are laminated and integrated, and the laminate is bonded to an ion conductive membrane, The MEA of the invention can also be obtained as a form having a gas diffusion layer, that is, a so-called membrane electrode gas diffusion layer laminate (MEGA).

  First, the ion conductive film will be described. The ion conductive membrane includes a polymer electrolyte of a block copolymer similar to that exemplified as the polymer electrolyte constituting the polymer emulsion, and a polymer electrolyte selected from the following examples, It has a form. As described above, both the ion conductive membrane constituting the MEA and the catalyst layer contain the polymer electrolyte, but the polymer electrolytes may be the same or different.

  In the polymer electrolyte constituting the ion conductive membrane, specific examples of the block copolymer other than the polymer electrolyte include, for example, (A ′) a hydrocarbon polymer having a main chain made of an aliphatic hydrocarbon and a sulfone. A polymer electrolyte having an acid group and / or a phosphonic acid group introduced; (B ′) a polymer in which all or part of the hydrogen atoms of the aliphatic hydrocarbon are replaced by fluorine atoms; (C ′) a main chain having an aromatic ring Hydrocarbon polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group are introduced into a polymer having a hydrogen atom; (D ′) The main chain is composed of an aliphatic unit and an inorganic unit structure such as a siloxane group or a phosphazene group. Hydrocarbon polymer electrolyte in which a sulfonic acid group and / or phosphonic acid group is introduced into the polymer; (E ′) before introduction of the sulfonic acid group and / or phosphonic acid group in (A ′) to (D ′) above. A hydrocarbon-based polymer electrolyte in which a sulfonic acid group and / or a phosphonic acid group is introduced into a copolymer composed of any two or more kinds of repeating units selected from repeating units constituting the polymer; (F ′) main chain or A hydrocarbon polymer electrolyte in which an acidic compound such as sulfuric acid or phosphoric acid is introduced into a hydrocarbon polymer containing a nitrogen atom in the side chain by an ionic bond is exemplified.

Among the polymer electrolytes exemplified above, the polymer electrolytes (C ′) and (E ′) are preferable from the viewpoint of achieving both high power generation performance and durability, and in particular, the high polymer constituting the ion conductive membrane. The molecular electrolyte is preferably a block copolymer, and the polymer main chain preferably has an aromatic ring and has a sulfonic acid group as an ion exchange group (ion conductive group). Particularly preferred is a block copolymer comprising a block having a sulfonic acid group and a block having substantially no ion exchange group.
Examples of such a block copolymer include a block copolymer having a sulfonated aromatic polymer block described in JP-A-2001-250567, JP-A-2003-32322, and JP-A-2004-359925. Examples thereof include block copolymers having a main chain structure of polyether ketone and polyether sulfone described in patent documents such as JP-A-2005-232439 and JP-A-2003-113136.

Furthermore, in addition to the polymer electrolyte exemplified above, the ion conductive membrane may contain other components in a range that does not significantly reduce proton conductivity according to desired characteristics. Examples of such other components include additives such as plasticizers, stabilizers, mold release agents, and water retention agents that are used in ordinary polymers.
In particular, it is preferable to include the stabilizer described above in the polymer electrolyte membrane during the operation of the fuel cell, because it is possible to suppress deterioration due to peroxide generated in the adjacent catalyst layer.

  For the purpose of improving the mechanical strength of the ion conductive membrane, a composite membrane in which a polymer electrolyte and a predetermined support are combined can also be used. Examples of the support include substrates such as a fibril shape and a porous membrane shape.

A catalyst layer is formed on the ion conductive film using a catalyst ink made of the polymer electrolyte emulsion of the present invention.
Here, the catalyst ink contains a catalyst substance as an essential component in addition to the polymer electrolyte emulsion of the present invention. As the catalyst material, those used in conventional fuel cells can be used as they are, for example, noble metals such as platinum and platinum-ruthenium alloys, complex-based electrode catalysts (for example, polymer society fuel cells). Materials Research Group, “Fuel Cell and Polymer”, pages 103-112, Kyoritsu Shuppan, published on Nov. 10, 2005). Furthermore, from the viewpoint that hydrogen ions and electrons can be easily transported in the catalyst layer, it is preferable to use a conductive material carrying the catalyst substance on the surface. Examples of the conductive material include conductive carbon materials such as carbon black and carbon nanotubes, and ceramic materials such as titanium oxide.

  The other components constituting the catalyst ink are optional and are not particularly limited, but a solvent may be added for the purpose of adjusting the viscosity of the catalyst ink. Further, for the purpose of increasing the water repellency of the catalyst layer, a water repellent material such as PTFE, and for the purpose of increasing the gas diffusibility of the catalyst layer, a pore former such as calcium carbonate further enhances the durability of the obtained MEA. For the purpose, a stabilizer such as a metal oxide may be included.

  The catalyst ink is obtained by mixing the above components by a known method. Examples of the mixing method include an ultrasonic dispersion device, a homogenizer, a ball mill, a planetary ball mill, and a sand mill.

A catalyst layer is formed on the ion conductive membrane using the catalyst ink prepared as described above. A known technique can be applied to such a forming method. However, the catalyst ink containing the polymer electrolyte emulsion of the present invention can be directly applied to the ion conductive film, followed by a drying treatment, etc. On the other hand, it is possible to form a catalyst layer having high bondability.
The method for applying the catalyst ink is not particularly limited, and existing methods such as a die coater, screen printing, a spray method, and an ink jet method can be used.

  Next, a fuel cell provided with MEA obtained by the manufacturing method of the present invention will be described.

FIG. 2 is a diagram schematically showing a cross-sectional configuration of a fuel cell according to a preferred embodiment. As shown in FIG. 2, the fuel cell 10 includes catalyst layers 14 a and 14 b on both sides of an ion conductive membrane 12 so as to sandwich the membrane, which is an MEA 20 obtained by the manufacturing method of the present invention. Furthermore, the catalyst layers on both sides are provided with gas diffusion layers 16a and 16b, respectively, and separators 18a and 18b are formed in the gas diffusion layers.
Here, the MEGA described above includes the MEA 20 and the gas diffusion layers 16a and 16b.

  Here, the catalyst layers 14a and 14b are layers that function as electrodes in the fuel cell, and either one of them serves as an anode catalyst layer and the other serves as a cathode catalyst layer.

  The gas diffusion layers 16a and 16b are provided so as to sandwich both sides of the MEA 20, and promote the diffusion of the raw material gas into the catalyst layers 14a and 14b. The gas diffusion layers 16a and 16b are preferably made of a porous material having electron conductivity. For example, a porous carbon non-woven fabric or carbon paper is preferable because the raw material gas can be efficiently transported to the catalyst layers 14a and 14b.

  Separator 18a, 18b is formed with the material which has electronic conductivity, As this material, carbon, resin mold carbon, titanium, stainless steel etc. are mentioned, for example. Although not shown, the separators 18a and 18b are preferably provided with a groove serving as a flow path for fuel gas or the like on the catalyst layers 14a and 14b side.

  The fuel cell 10 can be obtained by sandwiching MEGA as described above between a pair of separators 18a and 18b and joining them together.

  The fuel cell of the present invention is not necessarily limited to the above-described configuration, and may have a different configuration as long as it does not depart from the spirit of the fuel cell.

  The fuel cell 10 may be one having the above-described structure sealed with a gas seal body or the like. Furthermore, a plurality of the fuel cells 10 having the above structure can be connected in series to be put to practical use as a fuel cell stack. The fuel cell having such a configuration can operate as a solid polymer fuel cell when the fuel is hydrogen, and as a direct methanol fuel cell when the fuel is an aqueous methanol solution.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Measurement method of weight average molecular weight)
The weight average molecular weight of the polymer electrolyte was calculated by performing measurement by gel permeation chromatography (GPC) and performing polystyrene conversion. The measurement conditions of GPC are as follows.
GPC conditions and GPC measurement device HLC-8220 manufactured by TOSOH
・ Two columns AT-80M made by Shodex are connected in series ・ Column temperature 40 ℃
Mobile phase solvent Dimethylacetamide (LiBr added to 10 mmol / dm ³ )
・ Solvent flow rate 0.5mL / min

(Measurement method of ion exchange capacity)
The dry weight of the polymer electrolyte to be measured was determined using a halogen moisture meter set at a heating temperature of 105 ° C. Next, this polymer electrolyte membrane was immersed in 5 mL of a 0.1 mol / L sodium hydroxide aqueous solution, and then 50 mL of ion-exchanged water was further added and left for 2 hours. Thereafter, titration was performed by gradually adding 0.1 mol / L hydrochloric acid to the solution in which the polymer electrolyte membrane was immersed, and the neutralization point was determined. Then, the ion exchange capacity (unit: meq / g) of the polymer electrolyte membrane was calculated from the dry weight of the polymer electrolyte membrane and the amount of hydrochloric acid required for the neutralization.

(Average particle size measurement method)
The average particle size of the particles present in each emulsion was measured using a concentrated particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics). The measurement temperature is 30 ° C., the integration time is 30 minutes, and the wavelength of the laser used for the measurement is 660 nm. The obtained data is analyzed by the CONTIN method by using the analysis software (FPAR system VERSION 5.1.7.2) attached to the above apparatus, and the scattering intensity distribution is obtained. did.

(Power generation performance evaluation method)
A fuel cell was manufactured using a commercially available JARI standard cell. That is, an effective membrane area is obtained by arranging carbon separators in which gas passage grooves are cut on both outer sides of the MEGA, and further arranging a current collector and an end plate in order on the outer sides and fastening them with bolts. A 25 cm ² fuel cell was assembled. While maintaining the obtained fuel cell at 80 ° C., humidified hydrogen was supplied to the anode and humidified air was supplied to the cathode. At this time, the back pressure at the gas outlet of the cell was set to 0.1 MPaG. Each source gas was humidified by passing the gas through a bubbler. The water temperature of the hydrogen bubbler was 80 ° C., and the water temperature of the air bubbler was 80 ° C. Here, the hydrogen gas flow rate was 529 mL / min, and the air gas flow rate was 1665 mL / min.

Production Example 1 [Synthesis of polymer electrolyte A]
In an argon atmosphere, a flask equipped with an azeotropic distillation apparatus was charged with 600 ml of dimethyl sulfoxide (hereinafter referred to as “DMSO”), 200 mL of toluene, 26.5 g (106.3 mmol) of sodium 2,5-dichlorobenzenesulfonate, The following polyether sulfone (Sumitomo Chemical's Sumika Excel PES5200P, Mn = 5.4 × 10 ⁴ , Mw = 1.2 × 10 ⁵ ) 10.0 g, 2,2′-bipyridyl 43.8 g (280.2 mmol) ) Was added and stirred. Thereafter, the bath temperature was raised to 150 ° C., and water in the system was azeotropically dehydrated by distilling off toluene, followed by cooling to 60 ° C. Next, 73.4 g (266.9 mmol) of bis (1,5-cyclooctadiene) nickel (0) was added thereto, the temperature was raised to 80 ° C., and the mixture was stirred at the same temperature for 5 hours. After allowing to cool, the reaction solution is poured into a large amount of 6 mol / L hydrochloric acid to precipitate a polymer, which is filtered off. Thereafter, washing and filtration operations with 6 mol / L hydrochloric acid were repeated several times, followed by washing with water until the filtrate became neutral and drying under reduced pressure to obtain 16.3 g of the intended polymer electrolyte A. The weight average molecular weight was 270000, and the ion exchange capacity was 2.3 meq / g. Here, m and n represent the average degree of polymerization of the repeating units in parentheses constituting each block.

Production Example 2 [Synthesis of polymer electrolyte B]
The polymerization was carried out in a 2 L separable flask equipped with a Dean-Stark tube, 13.04 g (56.95 mmol) of potassium hydroquinonesulfonate, 34.71 g of dipotassium 4,4′-difluorodiphenylsulfone-3,3′-disulfonate. (68.34 mmol), 4,4′-difluorodiphenylsulfone 29.35 g (114.00 mmol), 4,4′-dihydroxydiphenyl ether 23.50 g (125.39 mmol), potassium carbonate 27.72 g (200.58 mmol) Then, azeotropic dehydration was performed in DMSO (395 mL) and toluene (70 mL) under an argon atmosphere at a bath temperature of 170 ° C. (internal temperature: 140 ± 5 ° C.) for 3 hours. After 3 hours, toluene was removed from the system, and the reaction was further performed at an internal temperature of 150 ° C. for 3 hours. The reaction was followed by GPC measurement. After completion of the reaction, the reaction solution was allowed to cool to 80 ° C. and added dropwise to 3 L of 2M aqueous hydrochloric acid. The precipitated white polymer was washed with water until pH 7 and then treated with water at 80 ° C. for 2 hours for 2 times. By drying in an oven (80 ° C.), 81.60 g (yield 97%) of polymer electrolyte B, which is a random polymer, was obtained. The weight average molecular weight was 340000, and the ion exchange capacity was 2.0 meq / g. In addition, what is shown below shows that the structural unit which comprises the polymer electrolyte B is connecting at random. Note that a, b, c, and d represent the average degree of polymerization of the repeating units in parentheses, and the expression “ran” represents random copolymerization in which the repeating units in parentheses are randomly copolymerized.

Production Example 3 [Synthesis of Stabilizer Polymer d]
Synthesis of Polymer a A 2 L separable flask equipped with a reduced-pressure azeotropic distillation apparatus was purged with nitrogen, and 63.40 g of bis-4-hydroxydiphenylsulfone, 70.81 g of 4,4′-dihydroxybiphenyl, N-methyl-2-pyrrolidone ( (Hereinafter referred to as “NMP”) 955 g was added to obtain a uniform solution. Thereafter, 92.80 g of potassium carbonate was added, and dehydrated under reduced pressure at 135 ° C. to 150 ° C. for 4.5 hours while distilling off NMP. Thereafter, 200.10 g of dichlorodiphenylsulfone was added and the reaction was carried out at 180 ° C. for 21 hours.
After completion of the reaction, the reaction solution was added dropwise to methanol, and the precipitated solid was filtered and collected. The recovered solid was further washed with methanol, washed with water, and washed with hot methanol and dried to obtain 275.55 g of polymer a. The structure of polymer a is shown below. The polymer a had a polystyrene equivalent weight average molecular weight of 18000 as measured by GPC, and the ratio of q and p determined from the integral value of NMR measurement was q: p = 7: 3. In addition, the following "random" description shows that the structural unit which forms the following polymer a is copolymerized at random.

Synthesis of Polymer b The 2 L separable flask was purged with nitrogen, and 101.12 g of nitrobenzene and 80.00 g of polymer a were added to obtain a uniform solution. Thereafter, 50.25 g of N-bromosuccinimide was added and cooled to 15 ° C. Subsequently, 106.42 g of 95% concentrated sulfuric acid was added dropwise over 40 minutes, and the reaction was carried out at 15 ° C. for 6 hours. Six hours later, 450.63 g of a 10 w% aqueous sodium hydroxide solution and 18.36 g of sodium thiosulfate were added while cooling to 15 ° C. Thereafter, this solution was added dropwise to methanol, and the precipitated solid was collected by filtration. The recovered solid was washed with methanol, washed with water, washed again with methanol and dried to obtain 86.38 g of polymer b.

Synthesis of Polymer c A 2 L separable flask equipped with a reduced-pressure azeotropic distillation apparatus was purged with nitrogen, and 116.99 g of dimethylformamide and 80.07 g of polymer b were added to obtain a uniform solution. Thereafter, dehydration under reduced pressure was performed for 5 hours while distilling off dimethylformamide. After 5 hours, the mixture was cooled to 50 ° C., 41.87 g of nickel chloride was added, the temperature was raised to 130 ° C., and 69.67 g of triethyl phosphite was added dropwise, and the reaction was carried out at 140 ° C. to 145 ° C. for 2 hours. After 2 hours, an additional 17.30 g of triethyl phosphite was added, and the reaction was carried out at 145 ° C. to 150 ° C. for 3 hours. After 3 hours, the mixture was cooled to room temperature, a mixed solution of 1161 g of water and 929 g of ethanol was added dropwise, and the precipitated solid was filtered and collected. Water was added to the collected solid and sufficiently pulverized, washed with a 5% by weight aqueous hydrochloric acid solution and washed with water to obtain 86.83 g of polymer c.

Synthesis of Polymer d A 5 L separable flask was purged with nitrogen, 35 wt% hydrochloric acid 1200 g, water 550 g, and polymer c 75.00 g were added, and the mixture was stirred at 105 ° C. to 110 ° C. for 15 hours. After 15 hours, the mixture was cooled to room temperature and 1500 g of water was added dropwise. Thereafter, the solid in the system was filtered and collected, and the obtained solid was washed with water and hot water. After drying, 72.51 g of the target polymer d was obtained. The phosphorus content determined from elemental analysis of polymer d was 5.91%, and the value of x (number of phosphonic acid groups per biphenylyleneoxy group) calculated from the elemental analysis value was 1.6.

Production Example 4 [Synthesis of dipotassium 4,4′-difluorodiphenylsulfone-3,3′-disulfonate]
To a reactor equipped with a stirrer, 467 g of 4,4′-difluorodiphenylsulfone and 3500 g of 30% fuming sulfuric acid were added and reacted at 100 ° C. for 5 hours. The obtained reaction mixture was cooled and then added to a large amount of ice water, and 470 mL of a 50% aqueous potassium hydroxide solution was further added dropwise thereto.
Next, the precipitated solid was collected by filtration, washed with ethanol, and dried. The obtained solid was dissolved in 6.0 L of deionized water, 50% aqueous potassium hydroxide solution was added to adjust the pH to 7.5, and then 460 g of potassium chloride was added. The precipitated solid was collected by filtration, washed with ethanol, and dried.
Thereafter, the obtained solid was dissolved in 2.9 L of DMSO, insoluble inorganic salts were removed by filtration, and the residue was further washed with 300 mL of DMSO. To the obtained filtrate, 6.0 L of a solution of ethyl acetate / ethanol = 24/1 was added dropwise, and the precipitated solid was washed with methanol, dried at 100 ° C., and 4,4′-difluorodiphenylsulfone-3,3. 482 g of dipotassium dipotassium disulfonate was obtained.

Production Example 5 [Production of polymer electrolyte C]
(Synthesis of polymer compound having sulfonic acid group)
In a flask equipped with an azeotropic distillation apparatus, 9.32 parts by weight of dipotassium 4,4′-difluorodiphenylsulfone-3,3′-disulfonate obtained in Production Example 1 in an argon atmosphere, 2,5-dihydroxybenzene 4.20 parts by weight of potassium sulfonate, 59.6 parts by weight of DMSO, and 9.00 parts by weight of toluene were added, and argon gas was bubbled for 1 hour while stirring these at room temperature.
Thereafter, 2.67 parts by weight of potassium carbonate was added to the obtained mixture, and azeotropic dehydration was performed by heating and stirring at 140 ° C. Thereafter, heating was continued while distilling off toluene, and a DMSO solution of a polymer compound having a sulfonic acid group was obtained. Total heating time was 14 hours. The resulting solution was allowed to cool at room temperature.

(Synthesis of polymer compounds substantially free of ion exchange groups)
A flask equipped with an azeotropic distillation apparatus was charged with 8.32 parts by weight of 4,4′-difluorodiphenylsulfone, 5.36 parts by weight of 2,6-dihydroxynaphthalene, 30.2 parts by weight of DMSO, and 30.2 parts by weight of NMP in an argon atmosphere. And 9.81 parts by weight of toluene were added, and argon gas was bubbled for 1 hour while stirring at room temperature.
Thereafter, 5.09 parts by weight of potassium carbonate was added to the obtained mixture, and azeotropic dehydration was performed by heating and stirring at 140 ° C. Thereafter, heating was continued while toluene was distilled off. Total heating time was 5 hours. The resulting solution was allowed to cool at room temperature to obtain a NMP / DMSO mixed solution of a polymer compound substantially free of ion exchange groups.

得られた高分子電解質Ｃのイオン交換容量は１．９ｍｅｑ／ｇであり、重量平均分子量は、４．２×１０⁵であった。なお、ｓ、ｒは各ブロックを構成する括弧内の繰返し単位の平均重合度を表すものである。 (Synthesis of block copolymer)
While stirring the obtained NMP / DMSO mixed solution of the polymer compound having substantially no ion exchange group, the total amount of the DMSO solution of the polymer compound having the sulfonic acid group and 80.4 parts by weight of NMP were added thereto. DMSO (45.3 parts by weight) was added, and a block copolymerization reaction was carried out at 150 ° C. for 40 hours.
The obtained reaction solution was dropped into a large amount of 2N hydrochloric acid and immersed for 1 hour. Thereafter, the produced precipitate was filtered off and then immersed again in 2N hydrochloric acid for 1 hour. The obtained precipitate was filtered and washed with water, and then immersed in a large amount of hot water at 95 ° C. for 1 hour. And this solution was dried at 80 degreeC for 12 hours, and the polymer electrolyte C which is a block copolymer was obtained. The structure of this polymer electrolyte C is shown below.

The obtained polymer electrolyte C had an ion exchange capacity of 1.9 meq / g and a weight average molecular weight of 4.2 × 10 ⁵ . In addition, s and r represent the average degree of polymerization of the repeating units in parentheses constituting each block.

Production Example 6 [Preparation of ion conductive membrane]
The polymer electrolyte C obtained in Production Example 5 was dissolved in NMP to a concentration of 13.5 wt% to prepare a polymer electrolyte solution. Next, this polymer electrolyte solution was dropped on a glass plate. Then, the polymer electrolyte solution was uniformly spread on the glass plate using a wire coater. At this time, the coating thickness was controlled using a wire coater having a 0.25 mm clearance. After application, the polymer electrolyte solution was dried at 80 ° C. under normal pressure. Then, the obtained membrane was immersed in 1 mol / L hydrochloric acid, washed with ion-exchanged water, and dried at room temperature to obtain an ion conductive membrane C having a thickness of 30 μm.

Example 1 [Preparation of polymer electrolyte emulsion]
The polymer electrolyte A 0.9 g obtained in Production Example 1 and the polymer d 0.1 g obtained in Production Example 3 were dissolved in NMP so as to be 1.0 wt%, thereby producing 100 g of a polymer electrolyte solution. . Next, 100 g of this polymer electrolyte solution was dropped into 900 g of distilled water at a dropping rate of 3 to 5 g / min using a burette to dilute the polymer electrolyte solution. The diluted polymer electrolyte solution was subjected to dispersion medium replacement with running water for 72 hours using a cellulose tube for dialysis membrane dialysis (UC36-32-100, manufactured by Sanko Junyaku Co., Ltd .: molecular weight cut off 14,000). The polymer electrolyte solution subjected to the dispersion medium replacement was concentrated to a concentration of 1.5% by weight using an evaporator to prepare a polymer electrolyte emulsion. The average particle size of the polymer electrolyte emulsion A was 101 μm. Further, the amount of NMP in the polymer electrolyte emulsion A was 4 ppm.

(Create MEA)
1 g of platinum-supporting carbon (SA50BK, manufactured by N.E. Chemcat) on which 50% by weight of platinum was supported on 5.3 g of the polymer electrolyte emulsion A was added, and 28.8 g of ethanol was further added. The obtained mixture was subjected to ultrasonic treatment for 1 hour and then stirred for 5 hours with a stirrer to obtain a catalyst ink. Subsequently, in accordance with the method described in Japanese Patent Application Laid-Open No. 2004-089976, a catalyst ink was applied to a 5.2 cm square region at the center of one surface of the ion conductive film C. The distance from the discharge port to the film was set to 6 cm, and the stage temperature was set to 75 ° C. After eight times of overcoating, the mixture was left on the stage for 15 minutes to remove the solvent and form a catalyst layer. Similarly, the catalyst ink was applied to the other surface to form a catalyst layer. From the composition of the catalyst layer and the applied weight, an MEA in which 0.6 mg / cm ² of platinum was disposed on one side was obtained. Table 1 shows the current density at 0.2 V obtained as a result of the power generation test.

Comparative Example 1
(Preparation of polymer electrolyte emulsion)
The polymer electrolyte A used in Production Example 1 was replaced with the polymer electrolyte B obtained in Production Example 2, and the same experiment as in Example 1 was performed, except that an emulsion concentrated to 2% by weight was obtained. Emulsion B was obtained. The average particle diameter of this polymer electrolyte emulsion B was 437 nm. Further, the amount of NMP in the polymer electrolyte emulsion B was 8 ppm.

(Create MEA)
1.4 g of platinum-supporting carbon (SA50BK, manufactured by N.E. Chemcat), in which 50 wt% platinum was supported, was added to 5.3 g of the polymer electrolyte emulsion B, and 12.5 g of ethanol was further added. The obtained mixture was subjected to ultrasonic treatment for 1 hour and then stirred for 5 hours with a stirrer to obtain a catalyst ink. Subsequently, in accordance with the method described in Japanese Patent Application Laid-Open No. 2004-089976, a catalyst ink was applied to a 5.2 cm square region at the center of one surface of the ion conductive film C. The distance from the discharge port to the film was set to 6 cm, and the stage temperature was set to 75 ° C. After eight times of overcoating, the mixture was left on the stage for 15 minutes to remove the solvent and form a catalyst layer. Similarly, the catalyst ink was applied to the other surface to form a catalyst layer. From the composition of the catalyst layer and the applied weight, an MEA in which 0.6 mg / cm ² of platinum was disposed on one side was obtained. Table 4 shows the current density at 0.2 V obtained as a result of the power generation test.

  From Table 1, it was found that the power generation performance is improved when the polymer electrolyte emulsion 1 that is a block copolymer is used compared to the case where the polymer electrolyte 2 that is a random copolymer is used.

It is a figure which shows typically the presumed structure of a polymer electrolyte particle. It is a figure which shows typically the cross-sectional structure of the fuel cell which concerns on suitable embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Segment which has an acidic group 2 ... Segment which does not have an ion exchange group substantially 10 ... Fuel cell, 12 ... Ion conduction membrane, 14a, 14b ... Catalyst layer, 16a, 16b ... Gas diffusion layer, 18a, 18b ... Separator, 20 ... MEA

Claims (11)

  A polymer electrolyte emulsion in which polymer electrolyte particles are dispersed in a dispersion medium, and the polymer electrolyte contained in the polymer electrolyte particles includes a segment having an acidic group and a segment having substantially no ion exchange group. A polyelectrolyte emulsion characterized by being a block copolymer.   The polymer electrolyte emulsion according to claim 1, wherein the volume average particle size determined by a dynamic light scattering method is 100 nm to 200 µm.   The polymer electrolyte emulsion according to claim 1 or 2, wherein the polymer electrolyte is an aromatic hydrocarbon polymer. The polymer electrolyte emulsion according to any one of claims 1 to 3, wherein the polymer electrolyte is a polymer electrolyte having a segment represented by the following formula (1) as a segment having an acidic group.

(In the formula, m represents an integer of 5 or more, Ar ¹ represents a divalent aromatic group, and the divalent aromatic group may have a substituent. (A part or all of Ar ¹ has an acidic group. X represents a direct bond or a divalent group.) The polymer according to any one of claims 1 to 4, wherein the polymer electrolyte is a polymer electrolyte having a segment represented by the following formula (3) as a segment having substantially no ion exchange group. Electrolyte emulsion.

(In the formula, a, b and c each independently represent 0 or 1, and n represents an integer of 5 or more. Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ independently represent a divalent aromatic group. Wherein these divalent aromatic groups are optionally substituted alkyl groups having 1 to 20 carbon atoms, optionally substituted alkoxy groups having 1 to 20 carbon atoms, An aryl group having 6 to 20 carbon atoms which may have a substituent, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, and 2 to 2 carbon atoms which may have a substituent. It may be substituted with an acyl group of 20 or an optionally substituted arylcarbonyl group, X and X ′ each independently represent a direct bond or a divalent group, and Y and Y ′ Independently represents an oxygen atom or a sulfur atom.)   The polymer electrolyte emulsion according to any one of claims 1 to 5, which is used for an electrode of a solid polymer fuel cell.   The polymer electrolyte emulsion according to claim 6, wherein the content of the good solvent with respect to the polymer electrolyte is 200 ppm or less.   The catalyst composition containing the polymer electrolyte emulsion in any one of Claims 1-7, and a catalyst component.   An electrode for a polymer electrolyte fuel cell comprising the catalyst composition according to claim 8.   A membrane electrode assembly having the polymer electrolyte fuel cell electrode according to claim 9.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 10.

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