JP2008097905A - Multilayered polymer electrolyte membrane, membrane/electrode assembly, and fuel cell using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane which is superior in methanol permeation suppression characteristics and joining characteristics to an electrode, and suitable for a fuel cell, especially a direct methanol type fuel cell, and also to provide its usage. <P>SOLUTION: A multilayered polymer electrolyte membrane in which two or more layers are laminated is provided, wherein the respective layers are constituted of different polymer electrolytes, and at least one of the polymer electrolyte layers is a sulfonic acid group containing polymer containing a constituting component shown by a chemical formula 1 (X is hydrogen or monovalent cation, Y is sulfonic group or ketone group, and Ar<SP>1</SP>is aromatic compound). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention can be used as a proton exchange membrane of a fuel cell, and can suppress the permeability of fuel such as methanol and hydrogen, and can achieve compatibility with an electrode and a use thereof (membrane) / Electrode assembly, fuel cell).

  In recent years, new power generation technologies with excellent energy efficiency and environmental friendliness have attracted attention. Above all, polymer electrolyte fuel cells using polymer electrolyte membranes have high energy density, and because they have features such as being easy to start and stop because of lower operating temperatures than other types of fuel cells. Developments as power supply devices for electric vehicles and distributed power generation are advancing. Among solid polymer fuel cells, a direct methanol fuel cell that directly supplies methanol as a fuel can be miniaturized, and is being developed for applications such as power supplies for personal computers and portable devices.

  As the polymer solid electrolyte membrane, a membrane containing a proton conductive polymer electrolyte is usually used. In addition to proton conductivity, the polymer solid electrolyte membrane must have characteristics such as fuel permeation deterrence and mechanical strength that prevent permeation of hydrogen and the like of the fuel. As such a polymer solid electrolyte membrane, for example, a membrane containing a perfluorocarbon sulfonic acid polymer into which a sulfonic acid group is introduced is known.

  A direct methanol fuel cell uses an aqueous methanol solution as a fuel, but when methanol passes through the membrane and moves to the air electrode, the output is lowered. Therefore, when a perfluorocarbon sulfonic acid polymer membrane having a high methanol permeability is used in a direct methanol fuel cell, there is a problem that when a high concentration aqueous methanol solution is used, the amount of methanol permeated becomes large and the output is significantly reduced. Thus, non-perfluorocarbon sulfonic acid polymer electrolyte membranes having low methanol permeability have been studied (for example, see Patent Documents 1 to 3).

  However, although these hydrocarbon-based polymer electrolyte membranes are less permeable to methanol than perfluorocarbon sulfonic acid-based polymer electrolyte membranes, their performance as fuel cells has not been sufficient. Also, in perfluorocarbon sulfonic acid polymer electrolyte membranes, the electrodes are usually joined by hot pressing or the like, but joining the electrodes in a similar manner with hydrocarbon polymer electrolyte membranes often results in poor bonding such as peeling. It was easy to occur. Therefore, a further excellent hydrocarbon polymer electrolyte membrane is required.

JP 2003-288916 A JP 2003-331868 A US Patent Application Publication No. 2002/0091225

  The present invention has been made against the background of the problems of the prior art, and both the methanol permeation suppression property and the bonding property with the electrode are good, and a polymer electrolyte membrane suitable for a fuel cell, particularly a direct methanol fuel cell, An object of the present invention is to provide a membrane / electrode assembly and a fuel cell using the polymer electrolyte membrane.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, this invention consists of the following structures.
(1) A multilayer polymer electrolyte membrane in which at least two polymer electrolyte layers having different compositions are laminated, wherein at least one of the multilayer polymer electrolyte layers has a structural unit represented by the following chemical formula 1. A polymer electrolyte membrane comprising a sulfonic acid group-containing polymer.

（ただし、Ｘは水素又は１価のカチオン種、Ｙはスルホン基又はケトン基、Ａｒ^１は下記化学式２で表される分子構造か、又は化学式３及び４で表される分子構造の両方を同時に含む。）

(However, X is hydrogen or a monovalent cation species, Y is a sulfone group or a ketone group, Ar ¹ is a molecular structure represented by the following chemical formula 2 or both of the molecular structures represented by chemical formulas 3 and 4 at the same time. Including)

（ただし、Ａｒ^１が化学式２で表される分子構造である場合、Ｚ^１は酸素原子、ｎは２以上の任意の整数を示す。Ａｒ^１が化学式３及び４で表される分子構造の両方を同時に含む場合、Ｚ^１は独立して酸素原子又は硫黄原子のいずれかを、Ｚ^２は酸素原子、硫黄原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−ＣＨ_２−基、シクロヘキシル基のいずれかを示す。また、Ａｒ^１が化学式３及び４で表される分子構造の両方を同時に含む場合は、上記化学式１と共に下記化学式５及び６の構造単位の両方を同時に含む。）

(However, both the molecular structure Ar ¹ be a molecular structure represented by Formula 2, Z ¹ is an oxygen atom, n represents the .Ar ¹ showing the arbitrary integer of 2 or more is represented by Formula 3 and 4 , Z ¹ independently represents either an oxygen atom or a sulfur atom, Z ² represents an oxygen atom, a sulfur atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, -CH ₂ -group or cyclohexyl group, and when Ar ¹ includes both of the molecular structures represented by Chemical Formulas 3 and 4, the structural units of the following Chemical Formulas 5 and 6 together with the Chemical Formula 1 Including both at the same time.)

（ただし、Ａｒ^２、Ａｒ^３は２価の芳香族基を、Ｚ^３、Ｚ^４は独立して酸素原子又は硫黄原子のいずれかを、Ｚ^５は酸素原子、硫黄原子、−Ｃ（ＣＨ_３）_２−基、−Ｃ（ＣＦ_３）_２−基、−ＣＨ_２−基、シクロヘキシル基のいずれかを示す。）
（２） 前記スルホン酸基含有ポリマーが、下記化学式７で示される構造単位をさらに有する（１）に記載の高分子電解質膜。

(However, Ar ² and Ar ³ are divalent aromatic groups, Z ³ and Z ⁴ are independently oxygen atoms or sulfur atoms, Z ⁵ is an oxygen atom, sulfur atom, —C (CH ₃ ) ₂ -group, -C (CF ₃ ) ₂ -group, -CH ₂ -group, or cyclohexyl group.
(2) The polymer electrolyte membrane according to (1), wherein the sulfonic acid group-containing polymer further has a structural unit represented by the following chemical formula 7.

（ただし、Ａｒ^４は２価の芳香族基を、ｎは２以上の任意の整数を示す）
（３） 前記スルホン酸基含有ポリマーにおける前記化学式５のＡｒ^２及び化学式６のＡｒ^３が、下記化学式８〜１１で表される分子構造から選ばれる１種以上の基である（１）に記載の高分子電解質膜。

(However, Ar ⁴ represents a divalent aromatic group, and n represents an arbitrary integer of 2 or more.)
(3) Ar ^{2 of the} chemical formula 5 and Ar ^{3 of the} chemical formula 6 in the sulfonic acid group-containing polymer are one or more groups selected from a molecular structure represented by the following chemical formulas 8 to 11. Polymer electrolyte membrane.

（４） 前記スルホン酸基含有ポリマーにおける化学式７のＡｒ^４が、化学式８〜１１で表される分子構造から選ばれる１種以上の基である（３）に記載の高分子電解質膜。
（５） 前記スルホン酸基含有ポリマーにおける化学式４のＺ^２及びＺ^５がいずれも硫黄原子である（１）に記載の高分子電解質膜。
（６） 前記高分子電解質において、化学式１、５及び６でそれぞれ表される構造単位、及びその他の構造単位のモル比が数式１〜３を満たすことを特徴とする（１）に記載の高分子電解質膜。
０．９≦（ｎ１＋ｎ２＋ｎ３＋ｎ４）／（ｎ１＋ｎ２＋ｎ３＋ｎ４＋ｎ５）≦１．０
・・・（数式１）
０．０５≦（ｎ１＋ｎ２）／（ｎ１＋ｎ２＋ｎ３＋ｎ４）≦０．７ ・・・（数式２）
０．０１≦（ｎ２＋ｎ４）／（ｎ１＋ｎ２＋ｎ３＋ｎ４）≦０．９５・・・（数式３）
（上記式中、ｎ１はＡｒ^１が化学式３である場合の化学式１で表される構造単位のモル％を、ｎ２はＡｒ^１が化学式４である場合の化学式１で表される構造単位のモル％を、ｎ３は化学式５で表される構造単位のモル％を、ｎ４は化学式６で表される構造単位のモル％を、ｎ５はその他の構造単位のモル％を、それぞれ表す。）
（７） 前記スルホン酸基含有ポリマーにおいて、スルホン酸基含有ポリマーを構成するモノマー成分の少なくとも一部が、下記の化学式１２で表される末端ジヒドロキシ化合物であって、ｎの異なる複数の成分からなり、かつｎの平均値が１＜ｎ≦１０の範囲にあるものである請求項２又は４のいずれかに記載の高分子電解質膜。

(4) The polymer electrolyte membrane according to (3), wherein Ar ⁴ in Chemical Formula 7 in the sulfonic acid group-containing polymer is one or more groups selected from the molecular structure represented by Chemical Formulas 8-11.
(5) The polymer electrolyte membrane according to (1), wherein Z ² and Z ⁵ in Chemical Formula 4 in the sulfonic acid group-containing polymer are both sulfur atoms.
(6) In the polymer electrolyte, the molar ratio of the structural units represented by the chemical formulas 1, 5 and 6 and other structural units satisfies Formulas 1 to 3, respectively. Molecular electrolyte membrane.
0.9 ≦ (n1 + n2 + n3 + n4) / (n1 + n2 + n3 + n4 + n5) ≦ 1.0
... (Formula 1)
0.05 ≦ (n1 + n2) / (n1 + n2 + n3 + n4) ≦ 0.7 (Formula 2)
0.01 ≦ (n2 + n4) / (n1 + n2 + n3 + n4) ≦ 0.95 (Equation 3)
(In the above formula, n1 is the mol% of the structural unit represented by Chemical Formula 1 when Ar ¹ is Chemical Formula 3, and n2 is the mole of the structural unit represented by Chemical Formula 1 when Ar ¹ is Chemical Formula 4. And n3 represents the mol% of the structural unit represented by Chemical Formula 5, n4 represents the mol% of the structural unit represented by Chemical Formula 6, and n5 represents the mol% of the other structural unit.)
(7) In the sulfonic acid group-containing polymer, at least a part of the monomer component constituting the sulfonic acid group-containing polymer is a terminal dihydroxy compound represented by the following chemical formula 12, and consists of a plurality of components having different n. 5. The polymer electrolyte membrane according to claim 2, wherein the average value of n is in the range of 1 <n ≦ 10.

（ただし、ｎは０以上の整数を表す。）
（８） 前記多層高分子電解質膜におけるイオン交換容量が、０．３〜５．０ｍｅｑ／ｇの範囲内である前記（１）に記載の高分子電解質膜。
（９） 多層高分子電解質膜が少なくとも３層からなり、少なくとも一方の最外層のイオン交換容量が、内層のイオン交換容量よりも大きい前記（１）に記載の高分子電解質膜。
（１０） 前記（１）〜（９）のいずれかに記載の高分子電解質膜が電極と接合されてなる高分子電解質膜／電極接合体。
（１１） 前記（１０）に記載の高分子電解質膜／電極接合体を用いた燃料電池。
（１２） メタノールを燃料とする前記（１１）に記載の燃料電池。
である。

(However, n represents an integer of 0 or more.)
(8) The polymer electrolyte membrane according to (1), wherein an ion exchange capacity in the multilayer polymer electrolyte membrane is in a range of 0.3 to 5.0 meq / g.
(9) The polymer electrolyte membrane according to (1), wherein the multilayer polymer electrolyte membrane comprises at least three layers, and the ion exchange capacity of at least one outermost layer is larger than the ion exchange capacity of the inner layer.
(10) A polymer electrolyte membrane / electrode assembly in which the polymer electrolyte membrane according to any one of (1) to (9) is joined to an electrode.
(11) A fuel cell using the polymer electrolyte membrane / electrode assembly according to (10).
(12) The fuel cell according to (11), wherein methanol is used as a fuel.
It is.

  The polymer electrolyte membrane of the present invention has good bondability with the electrode despite its low methanol permeability, and thus an excellent polymer electrolyte membrane / electrode assembly for a fuel cell can be obtained. The fuel cell using can improve the output and durability. The polymer electrolyte membrane of the present invention is particularly suitable for a direct methanol fuel cell.

The present invention will be described in detail below. In addition, the weight in this invention means mass.
The polymer electrolyte membrane of the present invention is a multilayer polymer electrolyte membrane in which two or more polymer electrolyte layers having different compositions are laminated. The different composition means that the composition is different in some respect such as a polymer polymerization composition or a polymer blend composition, and at least one layer of the polymer electrolyte layer contains a sulfonic acid group having a structural unit represented by Formula 1. It is characterized by containing a polymer.

  The polymer electrolyte membrane of the present invention is a layer in which at least one polymer electrolyte layer containing a sulfonic acid group-containing polymer having a structural unit represented by Chemical Formula 1 is included, and two or more layers are laminated. Are layers having different compositions, such as different contents of the structural unit represented by Chemical Formula 1, different types of structural units represented by Chemical Formula 1, and no structural units represented by Chemical Formula 1.

  The thickness ratio of the various polymer electrolyte layers in the polymer electrolyte membrane of the present invention can take any value depending on the purpose, and is not particularly limited, but the overall ratio of the polymer electrolyte membrane of the present invention is not limited. When the thickness is about 20 to 300 μm, the ratio of the thickness of the polymer electrolyte layer containing the sulfonic acid group-containing polymer having the structural unit represented by Chemical Formula 1 is preferably 10% or more with respect to the total thickness. 10 to 90% is more preferable, and 20 to 80% is more preferable. In addition, the thickness of each layer can also be estimated from the cast thickness of the solution at the time of film formation, or the thickness of each layer can also be measured by dyeing a sulfonic acid group and observing under a microscope.

  The polymer electrolyte membrane of the present invention is preferably composed of at least three layers, and it is preferable that the ion exchange capacity of at least one outer layer is larger than the ion exchange capacity of the inner layer because the bondability between the membrane and the electrode is improved. . As a preferred example, a multilayer ion exchange membrane having an outer layer with a high ion exchange capacity on both sides of an inner layer with a low ion exchange capacity can be mentioned.

  In the polymer electrolyte membrane of the present invention, it is preferable that at least one outermost layer contains a sulfonic acid group-containing polymer of a structural unit represented by Chemical Formula 1 because the bondability between the membrane and the electrode is improved. More preferably, the surface layer contains a sulfonic acid group-containing polymer having a structural unit represented by Chemical Formula 1.

In Chemical Formula 1, X represents hydrogen or a monovalent cation species, and Y represents a —S (═O) ₂ — group or a C (═O) — group. When used in a fuel cell, X is preferably hydrogen. When Y is a —S (═O) ₂ — group, the solubility of the monomer and the polymer can be improved. If it is a —C (═O) — group, the softening temperature of the resulting polymer is lowered. Or photocrosslinkability can be imparted.

One preferred embodiment of Chemical Formula ¹ is a structural unit in the case where Ar ¹ is represented by Chemical Formula 2. It is preferable that Ar ¹ is a structural unit represented by Chemical Formula 2 because the bonding property with the electrode of the obtained polymer electrolyte membrane is particularly good. In this case, Z ² is an oxygen atom, n represents an arbitral integer not less than 2. n may consist of a plurality of different components, and the average value thereof is preferably in the range of 3 to 20, and more preferably in the range of 4 to 10.

In the chemical formula 6, when Ar ³ is a structural unit represented by the chemical formula 2, the polymer electrolyte composed of the sulfonic acid group-containing polymer having the structural unit represented by the chemical formula 1 further includes the structural unit represented by the chemical formula 7. It is preferable. In Chemical Formula 7, n represents an arbitrary integer of 2 or more. Moreover, n may consist of a plurality of different components, and the average value thereof is preferably in the range of 3 to 20, and more preferably in the range of 4 to 10. Ar ⁴ represents any aromatic group, but preferably has an electron-withdrawing group bonded to an aromatic ring bonded to another site, and bonded to the ortho or para position with respect to the bonding site. It is more preferable. Furthermore, examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a carbonyl group, a phosphine oxide group, a nitro group, a cyano group, and a fluorine atom. Moreover, it may couple | bond with the other site | part with the same aromatic ring, or may couple | bond with another aromatic ring. Specific examples include an octafluorobiphenyl group and a molecular structure represented by chemical formulas 8 to 11. The molecular structure of Chemical Formula 8 is preferable because it can increase the solubility of the polymer. The molecular structure of Chemical Formula 9 is preferable because it lowers the softening temperature of the polymer to increase the bondability with the electrode and impart photocrosslinkability. The molecular structure of Chemical Formula 10 or 11 is preferable because the swelling of the polymer can be reduced, and the molecular structure of Chemical Formula 11 is more preferable. Among the chemical formulas 8 to 11, the molecular structure of the chemical formula 11 is most preferable.

In the chemical formula 1, when Ar ¹ is represented by the chemical formula 2, the terminal dihydroxy compound represented by the chemical formula 12 is composed of a plurality of components different from each other, and the average composition is 1 <n ≦ 10. It is preferable to use those in the range as a part of the monomer component.

Another preferred embodiment of Chemical Formula 1 is when Ar ¹ has both a molecular structure represented by Chemical Formula 3 and a molecular structure represented by Chemical Formula 4. At this time, Z ² independently represents either an oxygen atom or a sulfur atom, but if it is a sulfur atom, the oxidation resistance of the polymer is improved. Z ² represents an oxygen atom, a sulfur atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group or a cyclohexyl group, but an oxygen atom, a sulfur atom, A cyclohexyl group is preferred.

If Ar ¹ in Formula 1 contains the molecular structure of both the Formula 3 and 4 at the same time, a sulfonic acid group-containing polymer having a structural unit represented by Formula 1, both of the structural units of the formula 5 and 6 with Formula 1 Including at the same time. In Chemical Formulas 5 and 6, Ar ² and Ar ³ each represent an arbitrary aromatic group, but those in which an electron-withdrawing group is bonded to an aromatic ring bonded to another site are preferable, and On the other hand, those bonded to the ortho-position or para-position are more preferable. Furthermore, examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a carbonyl group, a phosphine oxide group, a nitro group, a cyano group, and a fluorine atom. Moreover, it may couple | bond with the other site | part with the same aromatic ring, or may couple | bond with another aromatic ring. Specific examples include an octafluorobiphenyl group and aromatic groups represented by chemical formulas 8 to 11. The group of Formula 8 is preferable because it can increase the solubility of the polymer. The group of the chemical formula 9 is preferable because it lowers the softening temperature of the polymer to enhance the bondability with the electrode or impart photocrosslinkability. The group of the chemical formula 10 or 11 is preferable because the swelling of the polymer can be reduced, and the group of the chemical formula 11 is more preferable. Of the chemical formulas 8 to 11, the group of the chemical formula 11 is most preferable.

When Ar ¹ in Chemical Formula ¹ is a group of Chemical Formulas 3 and 4, Z ³ and Z ⁴ in Chemical Formulas 5 and 6 independently represent either an oxygen atom or a sulfur atom. Improves conversion. Z ⁵ in Chemical Formula 6 represents an oxygen atom, a sulfur atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, or a cyclohexyl group, A sulfur atom and a cyclohexyl group are preferred.

If Ar ¹ in Formula 1 comprises at the same time both a group of formula 3 and 4, Z ⁵ in Z ² and Formula 6 in Chemical Formula 4 are both excellent polymer electrolyte membrane obtained as a sulfur atom with the electrode This is preferable because it exhibits excellent bonding properties.

In the sulfonic acid group-containing polymer having the structural unit represented by Chemical Formula 1, the molar ratio of the structural unit represented by Chemical Formulas 1, 5, and 6 and the other structural units preferably satisfies Formulas 1 to 3. In Formulas 1 to 3, n1 is the mol% of the structural unit represented by Chemical Formula 1 when Ar ¹ is Chemical Formula 3, and n2 is the structural unit represented by Chemical Formula 1 when Ar ¹ is Chemical Formula 4. N3 represents the mol% of the structural unit represented by Chemical Formula 5, n4 represents the mol% of the structural unit represented by Chemical Formula 6, and n5 represents the mol% of the other structural unit.

  In Formula 1, when (n1 + n2 + n3 + n4) / (n1 + n2 + n3 + n4 + n5) is smaller than 0.9, good characteristics tend not to be obtained with the polymer electrolyte membrane. More preferred is a range of 0.95 to 1.0.

  In Formula 2, when (n1 + n2) / (n1 + n2 + n3 + n4) is smaller than 0.05, the ion conductivity of the polymer electrolyte membrane tends to be insufficient. On the other hand, if it is larger than 0.9, the swelling property of the polymer electrolyte membrane tends to be remarkably increased. A more preferred range is from 0.1 to 0.7.

  When used as a polymer electrolyte membrane of a fuel cell using hydrogen as a fuel, (n1 + n2) / (n1 + n2 + n3 + n4) in Formula 2 is preferably in the range of 0.3 to 0.8, preferably 0.4 to 0.00. A range of 7 is more preferable. If it is less than 0.3, there is a tendency that a sufficient output cannot be obtained, and if it is more than 0.8, swelling may be remarkably increased.

  When used as a polymer electrolyte membrane of a fuel cell using a liquid such as methanol as fuel, (n1 + n2) / (n1 + n2 + n3 + n4) in Formula 2 is preferably in the range of 0.07 to 0.5, 0.1 More preferably, it is in the range of -0.4. If it is greater than 0.5, the fuel permeability may increase. If it is smaller than 0.07, the ion conductivity tends to decrease and the resistance tends to increase.

  In Formula 3, when (n2 + n4) / (n1 + n2 + n3 + n4) is less than 0.01, the joining property with the electrode catalyst layer tends to decrease when a polymer electrolyte membrane is formed. If it is larger than 0.95, the swelling property when the polymer electrolyte membrane is obtained may become too large. 0.05 to 0.8 is a more preferable range. When used for a polymer electrolyte membrane of a fuel cell using hydrogen as a fuel, it is preferably in the range of 0.05 to 0.4, and used for a polymer electrolyte membrane of a fuel cell using a liquid such as methanol as a fuel. In some cases, the range of 0.5 to 0.8 is more preferable.

  In the sulfonic acid group-containing polymer in the present invention, the bonding mode of each structural unit represented by each chemical formula is not particularly limited, and any of random bonds, alternating bonds, bonds in a continuous block structure, etc. But you can.

  The ion exchange capacity of the polymer electrolyte membrane of the present invention is preferably in the range of 0.3 to 5.0 meq / g. If it is less than 0.3, sufficient ion conductivity cannot be obtained, and there are cases where sufficient output cannot be obtained when the fuel cell is formed. On the other hand, if it is greater than 5.0, the polymer electrolyte will swell so much that the deformation of the membrane tends to increase. More preferably, it is the range of 0.5-3.0 meq / g. When used in a fuel cell using methanol as a fuel, the range is from 0.5 to 1.5 meq / g. When used in a fuel cell using hydrogen as a fuel, the range is from 1.5 to 2.5 meq / g. Each of these ranges is preferable.

  Among the polymer electrolyte layers, at least one layer is in the range of 0.5 to 1.2 meq / g, and at least another layer has an ion exchange capacity of 1.0 to 3.0 meq / g. It is preferable. At least one of the outermost layers preferably has a larger ion exchange capacity than the inner layer.

  Preferred examples of the structural unit of the sulfonic acid group-containing polymer having the structural unit represented by Chemical Formula 1 in the polymer electrolyte membrane of the present invention are shown below, but are not limited thereto, and satisfy the requirements of the present invention. If it is a thing, it can be used conveniently as a polymer which comprises the polymer electrolyte membrane for fuel cells. In the following specific examples of the polymer skeleton, n, n ′, n ″, m, m ′, m ″, o, o ′, o ″, p, p ′, p ″ are each independently an integer of 1 to 1000 Represents. f represents an integer of 3 to 21.

  Examples of the polymer constituting the polymer electrolyte layer other than the sulfonic acid group-containing polymer having the structural unit represented by Chemical Formula 1 in the polymer electrolyte layer of the polymer electrolyte membrane of the present invention include polystyrene sulfonic acid, poly (tri Fluorostyrene) sulfonic acid, polyvinyl phosphonic acid, polyvinyl carboxylic acid, an ionomer containing at least one polyvinyl sulfonic acid component, and aromatic polymers such as polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, There are few components such as polyparaphenylene, polyarylene polymer, polyphenylquinoxaline, polyaryl ketone, polyether ketone, polybenzoxazole, polybenzthiazole, polyimide, etc. Both the polymer containing one, sulfonic acid group, may be mentioned polymer phosphonic acid group, a carboxyl group, and at least one of these derivatives have been introduced. Polysulfone, polyethersulfone, polyetherketone, and the like referred to here are generic names for polymers having a sulfone bond, an ether bond, and a ketone bond in the molecular chain thereof. Polyetherketoneketone, polyetheretherketone, It includes polyether ether ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone and the like, and is not limited to a specific polymer structure.

  The other polymer electrolyte is preferably a polymer having excellent mechanical properties and heat resistance. Examples include sulfonic acid group-containing polysulfone, sulfonic acid group-containing polyether sulfone, sulfonic acid group-containing polyphenylene oxide, sulfonic acid group-containing polyphenylene sulfide, sulfonic acid group-containing polyphenylene sulfide sulfone, and sulfonic acid group-containing polyether ketone polymer. And sulfonic acid group-containing polyarylene ether-based polymers. Further, if the polymer electrolyte layer having a softening temperature of 250 ° C. or higher is in the outermost layer, the bondability with the electrode may be lowered, so that the inner layer is preferable.

  Preferred examples of other polymer electrolytes are shown below, but are not limited thereto.

  In order to synthesize a sulfonic acid group-containing polymer containing the structural unit represented by Chemical Formula 1 in the present invention, for example, a method of obtaining a polymer by reacting monomers having a molecular structure represented by the following Chemical Formulas 18 to 21. However, it is not limited thereto, and can be synthesized from any raw material by any method.

In Chemical Formulas 18 to 21, X is a —S (═O) ₂ — group or —C (═O) — group, Y is H or a monovalent cation, and Z ⁶ and Z ⁹ are each independently Any one of Cl atom, F atom, I atom, Br atom and nitro group, Z ⁷ and Z ¹⁰ are each independently OH group, SH group, —O—NH—C (═O) —R group, -S-NH-C (= O) -R group is represented by [R represents an aromatic or aliphatic hydrocarbon group. Z ⁸ is any of O atom, S atom, —C (CH ₃ ) ₂ — group, —C (CF ₃ ) ₂ — group, —CH ₂ — group, cyclohexyl group, Ar ⁴ is in the molecule And an aromatic group having an electron-withdrawing group such as a perfluoroalkyl group such as a sulfone group, a carbonyl group, a sulfonyl group, a phosphine group, a cyano group or a trifluoromethyl group, a nitro group or a halogen group.

  Specific examples of the compound represented by Chemical Formula 18 include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, and 3,3′-. Disulfo-4,4′-dichlorodiphenyl ketone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3,3′-disulfobutyl-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfobutyl- 4,4′-difluorodiphenyl sulfone, 3,3′-disulfobutyl-4,4′-dichlorodiphenyl ketone, 3,3′-disulfobutyl-4,4′-difluorodiphenyl sulfone, and their sulfonic acid groups are monovalent Examples include salts with cation species. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. Examples of the compound represented by Chemical Formula 10 in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-disulfonic acid. Sodium-4,4′-difluorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylketone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylsulfone, 3,3 'Sodium disulfonate-4,4'-difluorodiphenyl ketone, potassium 3,3'-disulfonate 4,4'-dichlorodiphenyl sulfone, potassium 3,3'-disulfonate 4,4'-difluorodiphenyl sulfone, 3, , 3′-Disulfonic acid potassium 4,4′-dichlorodiphenyl ketone, 3,3′-disulfone Potassium 4,4'-difluoro diphenyl sulfone, etc. 3,3'-disulfonic acid potassium 4,4'-difluoro diphenyl ketone and the like.

  Specific examples of the compound represented by Chemical Formula 19 include 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 4 , 4′-thiobisbenzenethiol, 4,4′-oxybisbenzenethiol, bis (4-hydroxyphenyl) sulfide, 4,4′-dihydroxydiphenyl ether, 1,1-bis (4-hydroxyphenyl) cyclohexane, etc. 4,4′-thiobisbenzenethiol, bis (4-hydroxyphenyl) sulfide, 1,1-bis (4-hydroxyphenyl) cyclohexane, terminal hydroxyl group-containing phenylene ether oligomer (represented by the following chemical formula 22) Of the molecular structure).

  The monomer having the molecular structure represented by Chemical Formula 19 increases the flexibility of the polymer, makes it difficult to break against deformation, and increases the bondability with the electrode by lowering the glass transition temperature. Can bring.

Examples of the compound represented by the chemical formula 20 include compounds having a leaving group in a nucleophilic substitution reaction such as halogen and nitro group on the same aromatic ring and an electron-withdrawing group that activates the same. Specific examples include 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4,4′-dichlorodiphenylsulfone, 4,4 ′. -Difluorodiphenyl sulfone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, decafluorobiphenyl, and the like, but not limited thereto, other aromatics active in aromatic nucleophilic substitution reaction A group dihalogen compound, an aromatic dinitro compound, an aromatic dicyano compound, and the like can also be used.
Examples of the compound represented by Chemical Formula 21 include 4,4′-biphenol, 4,4′-dimercaptobiphenol, and 4,4′-biphenol is preferred.
In the above aromatic nucleophilic substitution reaction, other various activated dihalogen aromatic compounds, dinitro aromatic compounds, bisphenol compounds, and bisthiophenol compounds can be used in combination with the compounds represented by chemical formulas 18 to 21. .

  Examples of other bisphenol compounds or bisthiophenol compounds include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and bis (4-hydroxyphenyl). ) Sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4- Hydroxy-3,5-dimethylphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane , Hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, 1,4-benze And dithiol, 1,3-benzenedithiol, phenolphthalein, 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and the like. However, in addition to this, various aromatic diols or various aromatic dithiols that can be used for the polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction can also be used, and are not limited to the above compounds. Absent.

  In the present invention, when a sulfonic acid group-containing polymer having a structural unit represented by Chemical Formula 1 is polymerized by an aromatic nucleophilic substitution reaction, a compound having a molecular structure represented by Chemical Formulas 18 to 21, and other compounds as necessary. A polymer can be obtained by adding an activated dihalogen aromatic compound, a dinitro aromatic compound, an aromatic diol, or an aromatic dithiol and reacting in the presence of a basic compound. The polymerization degree of the resulting polymer can be adjusted by adjusting the molar ratio of the reactive halogen group or nitro group to the reactive hydroxy group and thiol group in the monomer to an arbitrary molar ratio. Is preferably in the range of 0.9 to 1.1, more preferably in the range of 0.95 to 1.05, and a high degree of polymerization is 1. It is most preferable because the polymer can be obtained.

  The polymerization can be carried out in the temperature range of 0 to 350 ° C, but preferably in the range of 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more.

  Examples of basic compounds include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, etc., but aromatic diols and aromatic dimercapto compounds can be made into an active phenoxide structure. If it is a thing, it is not limited to these but can be used. The basic compound can be polymerized satisfactorily when used in an amount of 100 mol% or more with respect to the total of the bisphenol compound and the bisthiophenol compound, preferably 105 to The range is 125 mol%. An excessive amount of bisphenol compound or bisthiophenol compound is not preferable because it causes side reactions such as decomposition.

  Further, in the above polymerization reaction, a bisphenol compound or bisthiophenol compound reacted with an isocyanate compound to form a carbamoylate without using a basic compound, and an activated dihalogen aromatic compound or dinitro aromatic compound are directly combined. It can also be reacted.

  In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is in the range of 5 to 50% by mass. When the amount is less than 5% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by mass, the viscosity of the reaction system becomes too high, and post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration. In addition, a polymer solution can be obtained by removing by-product salts by filtration.

  In the present invention, the sulfonic acid group-containing polymer having the structural unit represented by Chemical Formula 1 preferably has a polymer log viscosity measured by a method described later of 0.1 dl / g or more. When the logarithmic viscosity is less than 0.1 dl / g, the membrane tends to become brittle when molded as a polymer electrolyte membrane. The logarithmic viscosity is more preferably 0.3 dl / g or more. On the other hand, if the logarithmic viscosity exceeds 5 dl / g, problems in processability such as difficulty in dissolving the polymer occur, which is not preferable. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

  In the polymer electrolyte membrane of the present invention, each polymer electrolyte layer may contain a polymer that is not a polymer electrolyte. Examples of polymers that are not polyelectrolytes include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides such as nylon 6, nylon 66, nylon 610, and nylon 12, polymethyl methacrylate, and polymethacrylates. Acrylate resins such as polymethyl acrylate and polyacrylates, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, ethyl cellulose Cellulose resins such as polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, poly Heat of aromatic polymers such as ether sulfone, polyether ether ketone, polyether imide, polyimide, polyamide imide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin There is no restriction | limiting in particular, such as curable resin. A combination with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferable combination for improving the polymer dimensionality. When a sulfonic acid group is further introduced into these basic polymers, the composition The processability is more preferable. The content of the polymer that is not a polymer electrolyte in each polymer electrolyte layer of the polymer electrolyte membrane of the present invention is preferably 50% by mass or less, and more preferably 30% by mass or less. When the content is 50% by mass or more, the sulfonic acid group concentration of the polymer electrolyte membrane tends to be low, and good ionic conductivity tends not to be obtained, and the unit containing the sulfonic acid group becomes a discontinuous phase. The mobility of conducting ions tends to decrease. The polymer electrolyte membrane of the present invention can be used as necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, and an antifoaming agent. Various additives such as an agent, a dispersant, and a polymerization inhibitor may be included.

  The polymer electrolyte membrane of the present invention can be produced by any method such as extrusion, rolling and casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. For example, it can be obtained by applying and drying a solution of the second polymer electrolyte layer on the first polymer electrolyte layer prepared in advance. Application | coating of an applicator, a coater, etc. may be used for application | coating of a solution, and you may spray using a spray etc. As the solvent to be used, aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and hexamethylphosphonamide, alcohols such as methanol and ethanol, An appropriate solvent can be selected from the mixed solvents of these organic solvents and water, but is not limited thereto. A plurality of these solvents may be used as a mixture within a possible range. The polymer concentration in the solution is preferably in the range of 0.1 to 50% by mass. If the polymer concentration in the solution is less than 0.1% by mass, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by mass, the processability tends to deteriorate. A method of obtaining a molded body from a solution can be performed using a conventionally known method. For example, the molded product can be obtained by removing the solvent by heating, drying under reduced pressure, immersion in a compound non-solvent that can be mixed with a solvent that dissolves the compound, or the like. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure. When combined with a compound having a similar dissolution behavior, it is preferable in that good molding can be achieved. The sulfonic acid group in the molded article thus obtained may contain a salt form with a cationic species, but it can be converted to a free sulfonic acid group by acid treatment as necessary. You can also.

  The most preferable method for forming the polymer electrolyte membrane in the present invention is a casting method from a solution, and the polymer electrolyte membrane can be obtained by removing the solvent from the cast solution as described above. Examples of the solution include a solution using an organic solvent such as N-methylpyrrolidone, N, N-dimethylformamide, and dimethyl sulfoxide, and in some cases, an alcohol solvent. The removal of the solvent is preferably by drying in view of the uniformity of the polymer electrolyte membrane. Moreover, in order to avoid decomposition | disassembly and alteration of a compound or a solvent, it can also dry at the lowest temperature possible under reduced pressure. Further, when the viscosity of the solution is high, when the substrate or the solution is heated and cast at a high temperature, the viscosity of the solution is lowered and the casting can be easily performed. The thickness of the solution at the time of casting is not particularly limited, but is preferably 10 to 2000 μm. More preferably, it is 50-1500 micrometers. If the thickness of the solution is thinner than 10 μm, the shape as a polymer electrolyte membrane tends to be not maintained, and if it is thicker than 2000 μm, a non-uniform polymer electrolyte membrane tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, using an applicator, doctor blade, etc. to make the cast thickness of the solution constant, using a glass petri dish, etc. to make the cast area constant and controlling the thickness with the amount and concentration of the solution, etc. The method can be used. The cast solution can obtain a more uniform film by adjusting the solvent removal rate. For example, in the case of heating, the evaporation rate can be reduced by lowering the temperature in the first stage. In addition, when immersed in a non-solvent such as water, the coagulation rate of the compound can be adjusted by leaving the solution in air or an inert gas for an appropriate time. When used as a polymer electrolyte membrane, the sulfonic acid group in the membrane may contain a metal salt, but can be converted to free sulfonic acid by an appropriate acid treatment. In this case, it is also effective to immerse the membrane in an aqueous solution of sulfuric acid, hydrochloric acid, etc. with or without heating.

  The thickness of the polymer electrolyte membrane in the present invention can be arbitrarily set, but if it is less than 20 μm, it may be difficult to satisfy the predetermined characteristics, so that it is preferably 20 μm or more, more preferably 50 μm or more. preferable. Moreover, since manufacture may become difficult when it exceeds 300 micrometers, it is preferable that it is 300 micrometers or less.

  The membrane / electrode assembly of the present invention can be obtained by bonding the polymer electrolyte membrane of the present invention to an electrode. As a method for producing this joined body, a conventionally known method can be used. For example, a method of applying an adhesive to the electrode surface and bonding the polymer electrolyte membrane and the electrode, or a polymer electrolyte membrane and There is a method of heating and pressing the electrode. As the adhesive, in addition to a commercially available polymer electrolyte composition such as a Nafion (trade name) solution, a hydrocarbon system such as a polymer electrolyte comprising a sulfonic acid group-containing polymer containing the structural unit represented by the above chemical formula 1 A polymer electrolyte can be used.

  In the polymer electrolyte membrane of the present invention, when the polymer electrolyte layer containing the sulfonic acid group-containing polymer of the structural unit represented by Chemical Formula 1 is used as the outermost layer, the polymer electrolyte surface has an appropriate softening temperature. It is particularly suitable for a method of joining a polymer electrolyte membrane and an electrode by pressure heating.

  The fuel cell of the present invention can be produced using the polymer electrolyte membrane or the polymer electrolyte membrane / electrode assembly of the present invention. The fuel cell of the present invention includes, for example, an oxygen electrode, a fuel electrode, a polymer electrolyte membrane sandwiched between the electrodes, an oxidant flow path provided on the oxygen electrode side, and a fuel electrode side. The fuel flow path is provided. A fuel cell stack can be obtained by connecting such unit cells with a conductive separator.

  The polymer electrolyte membrane of the present invention is suitable for a polymer electrolyte fuel cell. The polymer electrolyte membrane of the present invention is suitable for a fuel cell using a liquid as a fuel, such as a direct methanol fuel cell using methanol as a fuel. In addition, the polymer electrolyte membrane of the present invention has high durability because it has excellent bonding properties between the polymer electrolyte membrane and the electrode, and not only fuel cells that use liquids such as direct methanol fuel cells but also hydrogen as fuel. Suitable for fuel cells. Moreover, it can be used suitably also for the fuel cell which uses other substances, such as a dimethyl ether and a formic acid, as a fuel, It can use for arbitrary uses well-known as polymer electrolyte membranes, such as an electrolytic membrane and a separation membrane.

EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.
<Solution viscosity>
The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, the viscosity was measured using a Ubbelohde viscometer in a thermostatic bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / c was evaluated. (Ta is the drop time of the sample solution, tb is the drop time of the solvent only, and c is the polymer concentration).

<Proton conductivity>
A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped film sample on a self-made measuring probe (manufactured by Teflon (registered trademark)), and a constant temperature / humidity oven at 80 ° C. and 95% relative humidity (Nagano Science) A sample was held in Machine Seisakusho, LH-20-01), and the impedance between the platinum wires was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. The measurement was performed while changing the distance between the electrodes, and the conductivity obtained by canceling the contact resistance between the film and the platinum wire was calculated from the gradient obtained by plotting the distance measured between the electrodes and the resistance measurement value estimated from the CC plot.
Conductivity [S / cm] = 1 / film width [cm] × film thickness [cm] × resistance interelectrode gradient [Ω / cm]

<Methanol permeability coefficient>
The liquid fuel permeation rate of the polymer electrolyte membrane was measured as the methanol permeation rate by the following method. A polymer electrolyte membrane immersed in a 5 M (mol / liter) aqueous methanol solution adjusted to 25 ° C. for 24 hours is sandwiched between H-type cells, 100 ml of 5 M aqueous methanol solution is added to one side of the cell, and 100 ml of the other cell is over 100 ml. Inject pure water (18 MΩ · cm) and measure the amount of methanol diffusing into ultrapure water through the polymer electrolyte membrane while stirring the cells on both sides at 25 ° C using a gas chromatograph. (The area of the polymer electrolyte membrane was 2.0 cm ² ). A methanol permeation coefficient was determined from the obtained methanol permeation rate and film thickness by the following formula.
Methanol permeability coefficient [μmol · m ⁻¹ · sec ⁻¹ ] = Methanol permeation rate [mmol · m ⁻² · sec ⁻¹ ] × film thickness [μm] × 1000

<Evaluation of bondability with electrode>
After adding a small amount of ultrapure water and isopropyl alcohol to a Pt / Ru catalyst-supporting carbon (Tanaka Kikinzoku Kogyo Co., Ltd., TEC61E54) and moistening it, a 20% Nafion solution (product number: SE-20192) manufactured by DuPont was added to the Pt / Ru. The catalyst-supporting carbon and Nafion were added in a mass ratio of 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. This catalyst paste is coated and dried by screen printing on carbon paper (Toray Industries, TGPH-060) serving as a gas diffusion layer so that the amount of platinum deposited is 2 mg / cm ^2, and carbon paper with an electrode catalyst layer for an anode Was made. Further, after adding a small amount of ultrapure water and isopropyl alcohol to a Pt catalyst-supporting carbon (Tanaka Kikinzoku Kogyo Co., Ltd., TEC10V40E) and moistening it, a DuPont 20% Nafion solution (product number: SE-20192) is added to the Pt catalyst-supporting carbon. A cathode catalyst paste was prepared by adding carbon and Nafion at a mass ratio of 2.5: 1 and stirring. This catalyst paste was applied and dried on carbon paper (Toray Industries, TGPH-060) subjected to water repellent treatment so that the amount of platinum deposited was 1 mg / cm ^2, and the carbon paper with the electrode catalyst layer for cathode was applied. Produced. A membrane sample is sandwiched between the above two types of carbon paper with an electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, and is heated and pressurized at 140 ° C. and 6 MPa for 3 minutes by a hot press method. An electrode assembly was obtained. The completed membrane / electrode assembly was observed, and the bondability was evaluated from the peeling of the electrode. The case where peeling did not occur at all was rated as “◯”, the case where peeling occurred as “X”, and the case where cracking occurred as “Δ”.

<Evaluation of power generation>
The obtained membrane / electrode assembly was incorporated into an evaluation fuel cell FC25-02SP manufactured by Electrochem, and a power generation test was performed using a fuel cell power generation tester (manufactured by Toyo Technica). Power generation is performed at a cell temperature of 40 ° C. while supplying high purity air (80 ml / min) adjusted to 40 ° C. and an aqueous methanol solution (1.5 ml / min) having a concentration of 5 mol / l to the anode and cathode, respectively. It was. The voltage at a current density of 0.05 A / cm ² was taken as the output voltage.

<Handling>
When the obtained polymer electrolyte membrane was cut by 1 mm and pulled lightly by hand, the one that was easily torn was indicated as x, the one that was torn when applied with force was Δ, and the one that was difficult to tear was indicated as ○.

<Ion exchange capacity>
The mass of the sample dried at 100 ° C. for 1 hour and allowed to stand overnight at room temperature in a nitrogen atmosphere was measured, and after stirring with an aqueous sodium hydroxide solution, the ion exchange capacity was determined by back titration with an aqueous hydrochloric acid solution.

<Synthesis Example 1>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation: S-DCDPS) 50.00 g, 2,6-dichlorobenzonitrile (abbreviation: DCBN) 102.70 g, bis (4-hydroxyphenyl) ) Sulfide (abbreviation: BPS) 112.56 g, 4,4′-biphenol (abbreviation: BP) 30.32 g, potassium carbonate 103.16 g, molecular sieve 80.0 g were weighed into a 2000 ml four-necked flask and nitrogen was passed. did. After adding 800 ml of N-methyl-2-pyrrolidone (abbreviation: NMP) and stirring at 160 ° C. for 60 minutes, the reaction temperature is increased to 195 to 200 ° C. Continued (about 9 hours). After allowing to cool, the molecular sieve was removed by filtration and precipitated in water into a strand. The obtained polymer was washed twice in boiling water, then washed three times with pure water at room temperature, and dried.

<Synthesis Examples 2-16>
The polymers of Synthesis Examples 2 to 16 were synthesized in the same manner as Synthesis Example 1 except that the monomer composition and composition ratio were changed. The results are shown in Table 1.

<Example 1>
15 g of the polymer of Synthesis Example 13 was dissolved in 45 ml of NMP, cast onto a glass plate on a hot plate to a thickness of 60 μm, and dried at 80 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 2 hours to obtain a film. In a state where the obtained film is on a glass plate, a solution of 15 g of the polymer of Synthesis Example 1 dissolved in 45 g of NMP is cast to a thickness of 170 μm on the surface of the film, and 80 ° C. for 1 hour, 120 ° C. for 1 hour, Dry at 150 ° C. for 2 hours. Thereafter, the obtained film was peeled off, fixed to a glass plate with a heat-resistant tape so that the opposite surface was an upper surface, the polymer solution of Synthesis Example 1 was cast at a thickness of 170 μm, and at 80 ° C. It was dried for 1 hour at 120 ° C. for 1 hour and at 150 ° C. for 2 hours. Then, it cooled to room temperature and peeled the film from the glass plate. The obtained film was immersed in pure water at room temperature for 1 hour and then immersed twice in an aqueous sulfuric acid solution having a concentration of 2 mol / liter for 1 hour. Thereafter, the film was washed with pure water until the washing water became neutral, and allowed to stand in the air and dried to obtain a polymer electrolyte membrane. The obtained polymer electrolyte membrane was evaluated.
<Examples 2 to 12>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the type of polymer and the thickness ratio were changed. The obtained polymer electrolyte membrane was evaluated.

<Comparative Example 1>
A solution obtained by dissolving 15 g of the polymer of Synthesis Example 1 in 45 g of NMP was cast on a glass plate on a hot plate with a thickness of 400 μm, and dried at 80 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 2 hours. The obtained film was immersed in pure water at room temperature for 1 hour, and then immersed twice in an aqueous sulfuric acid solution having a concentration of 2 mol / l for 1 hour. Thereafter, the film was washed with pure water until the washing water became neutral, and allowed to stand in the air and dried to obtain a polymer electrolyte membrane. The obtained polymer electrolyte membrane was evaluated.
<Comparative Examples 2-4>
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the type of polymer was changed. The obtained polymer electrolyte membrane was evaluated.

  Table 2 shows the evaluation results of the polymer electrolyte membranes obtained in the examples and comparative examples. In Table 2, the ratio of the thickness of each electrolyte layer is a value calculated from the mass ratio of each polymer during film formation. About Comparative Examples 1-4, it means that it is an electrolyte membrane which consists only of each polymer.

  From Table 2, it can be seen that the polymer electrolyte membranes of the examples have good output voltage when formed into a fuel cell, and are excellent in bonding properties with electrodes and handling properties. On the other hand, although the polymer electrolyte membrane of Comparative Example 1 has good bondability and handling properties, it can be seen that the power generation output is low and inferior to the examples. The polymer electrolyte membrane of Comparative Example 2 has membrane characteristics such as methanol permeability coefficient and proton conductivity that are equivalent to those of the Examples, but has poor adhesion with the electrode and can generate power when it is used as a fuel cell. It cannot be seen that it is inferior to the examples. In addition, the polymer electrolyte membrane of Comparative Example 3 consisting only of a polymer containing the structural unit represented by Chemical Formula 1 with the same characteristics as the Examples has good output voltage and bonding properties, but is somewhat difficult to handle. I understand that there is. In addition, it can be seen that the polymer electrolyte membrane of Comparative Example 4 is fragile and cracks when bonded to the electrode, and the output voltage is low. Moreover, handling property is also bad and it turns out that it is inferior to an Example.

The polymer electrolyte membrane of the present invention can obtain a high output when used in a fuel cell, has good bondability with an electrode, and can improve the durability of the fuel cell. Since it is a polymer electrolyte membrane excellent in both methanol permeation suppression and electrode bonding properties, it is particularly suitable for direct methanol fuel cells.
Further, it can be suitably used for fuel cells using hydrogen or other substances such as dimethyl ether and formic acid as fuel, and further used for any known application as a polymer electrolyte membrane such as an electrolytic membrane and a separation membrane. It is possible to contribute to the industry.

Claims (12)

A multilayer polymer electrolyte membrane in which at least two polymer electrolyte layers having different compositions are laminated, and at least one of the multilayer polymer electrolyte layers has a structural unit represented by the following chemical formula 1 A polymer electrolyte membrane comprising a group-containing polymer.

(However, X is hydrogen or a monovalent cation species, Y is a sulfone group or a ketone group, Ar ¹ is a structural unit represented by the following chemical formula 2 or both molecular structures represented by chemical formulas 3 and 4 at the same time. Including)

(However, both the molecular structure Ar ¹ be a molecular structure represented by Formula 2, Z ¹ is an oxygen atom, n represents the .Ar ¹ showing the arbitrary integer of 2 or more is represented by Formula 3 and 4 , Z ¹ independently represents either an oxygen atom or a sulfur atom, Z ² represents an oxygen atom, a sulfur atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, -CH ₂ -group or cyclohexyl group, and when Ar ¹ includes both of the molecular structures represented by Chemical Formulas 3 and 4, the structural units of the following Chemical Formulas 5 and 6 together with the Chemical Formula 1 Including both at the same time.)

(However, Ar ² and Ar ³ are divalent aromatic groups, Z ³ and Z ⁴ are independently oxygen atoms or sulfur atoms, Z ⁵ is an oxygen atom, sulfur atom, —C (CH ₃ ) ₂ -group, -C (CF ₃ ) ₂ -group, -CH ₂ -group, or cyclohexyl group. The polymer electrolyte membrane according to claim 1, wherein the sulfonic acid group-containing polymer further has a structural unit represented by the following chemical formula 7.

(However, Ar ⁴ represents a divalent aromatic bond unit, and n represents an arbitrary integer of 2 or more.) The Ar ^{2 of the} chemical formula 5 and the Ar ^{3 of the} chemical formula 6 in the sulfonic acid group-containing polymer are one or more groups selected from divalent aromatic groups represented by the following chemical formulas 8 to 11. The polymer electrolyte membrane as described.

4. The polymer electrolyte membrane according to claim 3, wherein Ar ⁴ of Chemical Formula 7 in the sulfonic acid group-containing polymer is one or more groups selected from divalent aromatic groups represented by Chemical Formulas 8 to 11. 5. ^2. The polymer electrolyte membrane according to claim 1, wherein Z ² and Z ⁵ in Chemical Formula 4 in the sulfonic acid group-containing polymer are both sulfur atoms. 2. The polymer electrolyte membrane according to claim 1, wherein in the polymer electrolyte, the molar ratio of the structural units represented by chemical formulas 1, 5 and 6 and the other structural units satisfies Formulas 1 to 3. 3.
0.9 ≦ (n1 + n2 + n3 + n4) / (n1 + n2 + n3 + n4 + n5) ≦ 1.0
... (Formula 1)
0.05 ≦ (n1 + n2) / (n1 + n2 + n3 + n4) ≦ 0.7 (Formula 2)
0.01 ≦ (n2 + n4) / (n1 + n2 + n3 + n4) ≦ 0.95 (Equation 3)
(In the above formula, n1 is the mol% of the structural unit represented by Chemical Formula 1 when Ar ¹ is Chemical Formula 3, and n2 is the mole of the structural unit represented by Chemical Formula 1 when Ar ¹ is Chemical Formula 4. And n3 represents the mol% of the structural unit represented by Chemical Formula 5, n4 represents the mol% of the structural unit represented by Chemical Formula 6, and n5 represents the mol% of the other structural unit.) In the sulfonic acid group-containing polymer, at least a part of the monomer component constituting the sulfonic acid group-containing polymer is a terminal dihydroxy compound represented by the following chemical formula 12 and consists of a plurality of components different from each other, and n 5. The polymer electrolyte membrane according to claim 2, wherein an average value of is in a range of 1 <n ≦ 10.

(However, n represents an integer of 0 or more.)   2. The polymer electrolyte membrane according to claim 1, wherein an ion exchange capacity in the multilayer polymer electrolyte membrane is within a range of 0.3 to 5.0 meq / g.   The polymer electrolyte membrane according to claim 1, wherein the multilayer polymer electrolyte membrane is composed of at least three layers, and the ion exchange capacity of at least one outermost layer is larger than the ion exchange capacity of the inner layer.   A polymer electrolyte membrane / electrode assembly obtained by bonding the polymer electrolyte membrane according to any one of claims 1 to 9 to an electrode.   A fuel cell using the polymer electrolyte membrane / electrode assembly according to claim 11.   The fuel cell according to claim 11, wherein methanol is used as a fuel.