JP2008037896A - Sulfonic group-containing thermally crosslinkable polymer, sulfonic group-containing thermally crosslinkable polymer composition, polyelectrolyte film, crosslinked polyelectrolyte film, polyelectrolyte film/electrode assembly, fuel cell and application thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer having a novel structure suitable for the manufacture of a polyelectrolyte film that is highly proton-conductive and resistant to swelling and exhibits excellent processability and the like, and its application. <P>SOLUTION: The sulfonic group-containing thermally crosslinkable polymer contains (A) a structure represented by chemical formula 1, (B) a structure represented by chemical formula 2 and (C) a thermally crosslinkable group in the polymer molecule, and (D) has a softening temperature of 250°C or lower when Y is H. The polyelectrolyte film is obtained from the polymer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sulfonic acid group-containing thermally crosslinkable polymer having a novel structure, a composition of the polymer, a polymer electrolyte membrane using the polymer, a polymer electrolyte membrane / electrode assembly, and a 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.

  As the polymer solid electrolyte membrane, a proton conductive polymer electrolyte membrane 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 as represented by Nafion (registered trademark) manufactured by DuPont, USA is known. However, fluorinated polymer electrolyte membranes such as perfluorocarbon sulfonic acid polymer electrolyte membranes, when used in fuel cells, can cause harmful hydrofluoric acid to enter the exhaust gas depending on the operating conditions, or to the environment when discarded. It also has problems such as giving a large load.

  Although perfluorocarbon sulfonic acid polymer electrolyte membranes have well-balanced characteristics as fuel cell electrolyte membranes, in order to obtain better membranes in terms of cost and performance, hydrocarbon polymer electrolyte membranes Development is actively underway.

  Many hydrocarbon polymer electrolyte membranes use a polymer in which an ionic group such as a sulfonic acid group is introduced into a heat-resistant polymer such as polyimide or polysulfone (see, for example, Patent Document 1).

  In general, it is necessary to introduce more ionic groups in a hydrocarbon polymer electrolyte membrane in order to develop proton conductivity equivalent to that of a perfluorocarbon sulfonic acid polymer electrolyte membrane. However, when the amount of the ionic group is increased, the swellability due to water is increased, which causes problems such as dimensional change and deterioration of physical properties during moisture absorption. For this reason, a hydrocarbon polymer electrolyte membrane with improved polymer structure and further suppressed swelling is also proposed (see, for example, Patent Document 2).

  As one of the measures for suppressing the swelling, mixing with a basic polymer is performed. This intends to suppress swelling by crosslinking the sulfonic acid group in the polymer solid electrolyte by ionic bonding with a basic polymer. For example, a mixture of polyethersulfone having a sulfonic acid group or polyetheretherketone having a sulfonic acid group (acidic polymer) and polybenzimidazole (basic polymer) has been proposed (see, for example, Patent Document 3). ).

  Moreover, swelling is also suppressed by bridge | crosslinking between the sulfonic acid groups which are ionic groups by a covalent bond (for example, refer patent documents 4-6). However, in this method, although swelling can be suppressed, there is a problem in that proton conductivity is lowered because the ionic group does not exhibit ionicity due to a crosslinking reaction.

As a polymer solid electrolyte having a cross-linked structure, a sulfonated product of a styrene / divinylbenzene copolymer is well known because it has been studied for an early polymer electrolyte fuel cell. This polymer solid electrolyte did not exhibit satisfactory properties as a fuel cell because the polymer skeleton itself was poor in durability.
Furthermore, as a polymer solid electrolyte having a crosslinked structure, an ion exchanger obtained by crosslinking a chloromethyl group in a polymer using a Lewis acid as a catalyst has been described (see, for example, Patent Documents 7 and 8). However, the presence of a catalyst is essential for the crosslinking reaction in this method. For this reason, when a polymer and a catalyst are mixed to obtain a molded product, the catalyst remains a problem, and when the polymer molded product is treated with a catalyst, an internal crosslinking reaction hardly occurs.

  On the other hand, a polymer electrolyte membrane into which a crosslinkable group that does not require a catalyst for the crosslinking reaction has been proposed (see, for example, Patent Documents 9 and 10). However, when trying to reduce the swellability, there is a problem that the workability is deteriorated, for example, the bondability with the electrode catalyst layer is often lowered.

JP-T-2004-509224 Japanese Patent Application Laid-Open No. 2004-149779 International Patent Publication WO99 / 54389 JP-A-6-93114 International Publication No. WO99 / 61141 JP 2001-522401 A JP-A-2-248434 Japanese Patent Laid-Open No. 2-245035 JP 2003-217342 A JP 2003-217343 A

  The present invention has been made against the background of the problems of the prior art, and is a polymer electrolyte membrane having high proton conductivity, low swellability, excellent durability, and excellent workability such as bondability with electrodes. It is an object of the present invention to provide a polymer having a novel structure capable of obtaining a polymer electrolyte membrane / electrode assembly and a fuel cell having excellent durability by using the polymer. .

  As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention

(1) The polymer molecule has (A) a structure represented by the following chemical formula 1, (B) a structure represented by the following chemical formula 2, and (C) a thermally crosslinkable group, and (D) A sulfonic acid group-containing thermally crosslinkable polymer characterized in that when Y is H, the softening temperature is 250 ° C. or lower.

［化学式１において、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ^１はＯ又はＳ原子のいずれかを、Ｚ^２は、Ｏ原子、Ｓ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、ｎ１は１以上の整数を表す。化学式２において、Ａｒ^１は二価の芳香族基を、Ｚ^３はＯ又はＳ原子のいずれかを、Ｚ^４は、Ｏ原子、Ｓ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、ｎ２は１以上の整数を表す。］

[In Chemical Formula 1, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, or a cyclohexyl group, and n 1 represents an integer of 1 or more. To express. In Chemical Formula 2, Ar ¹ is a divalent aromatic group, Z ³ is either an O or S atom, Z ⁴ is an O atom, an S atom, a —C (CH ₃ ) ₂ — group, —C ( CF _{3) 2} - group, -CH ₂ - group, any one of a cyclohexyl group, n2 represents an integer of 1 or more. ]

(2) The sulfonic acid group-containing thermally crosslinkable polymer according to (1), wherein the thermally crosslinkable group is one or more groups selected from the group represented by the following chemical formulas (3) to (8).

［式中、Ｒ^１〜Ｒ^９は水素原子、炭素数１〜１０のアルキル基、フェニル基、炭素数６〜２０の芳香族基、ハロゲンのいずれかを、Ａは水素原子、炭素数１〜１０の炭化水素基、ハロゲン、ニトロ基、−ＳＯ_３Ｙ基｛ＹはＨあるいは１価の陽イオンを表す。｝のいずれかを、ｎは１〜４の整数を表す。］

[Wherein R ^{1 to} R ⁹ are any ^one of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a phenyl group, an aromatic group having 6 to 20 carbon atoms, and a halogen; 10 hydrocarbon groups, halogen, nitro group, —SO ₃ Y group {Y represents H or a monovalent cation. }, N represents an integer of 1 to 4. ]

(3) The sulfonate group-containing thermally crosslinkable polymer according to (1), wherein the content of the thermally crosslinkable group in the polymer molecule is 0.000001 to 0.001 mol / g.

(4)
The sulfonic acid group-containing thermally crosslinkable polymer according to (1), wherein Ar ^{1 in} Chemical Formula 2 is one or more groups selected from structures represented by Chemical Formulas 9 to 12 below.

(5) The sulfonic acid group-containing thermally crosslinkable polymer according to (4), wherein Ar ^{1 in} Chemical Formula 2 is a structure represented by Chemical Formula 12.

(6)
The sulfonic acid group-containing thermally crosslinkable polymer according to (1), wherein the sulfonic acid group content is 0.3 to 5.0 meq / g.

(7)
The sulfonic acid group-containing thermally crosslinkable polymer according to (1), wherein Z ¹ and Z ^{2 in} Chemical Formula 1 are both O atoms, and n1 is 3 or more.

(8)
The sulfonic acid group-containing thermally crosslinkable polymer according to (7), wherein Z ³ and Z ^{4 in} Chemical Formula 2 are both O atoms, and n2 is 3 or more.

(9)
The sulfonic acid group-containing thermally crosslinkable polymer according to (1), further having a structure represented by the following chemical formula 13.

［化学式１３において、Ｘは−Ｓ（＝Ｏ）_２−基又は−Ｃ（＝Ｏ）−基を、ＹはＨ又は１価の陽イオンを、Ｚ^５はＯ又はＳ原子のいずれかを表す。］

[In Chemical Formula 13, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. . ]

(10) The sulfonic acid group-containing thermally crosslinkable polymer according to (9), further having a structure represented by the following chemical formula 14.

［化学式１４において、Ａｒ^２は２価の芳香族基を、Ｚ^６はＯ又はＳ原子のいずれかを表す。］

[In the chemical formula 14, Ar ² represents a divalent aromatic group, and Z ⁶ represents either O or S atom. ]

(11) The sulfonic acid group-containing thermally crosslinkable polymer according to (10), wherein Ar ^{2 in} Chemical Formula 14 is one or more groups selected from structures represented by Chemical Formulas 9 to 12.

(12)
The sulfonic acid group-containing thermally crosslinkable polymer according to (11), wherein Ar ^{2 in} Chemical Formula 14 has a structure represented by Chemical Formula 12.

(13) The sulfonic acid group-containing thermally crosslinkable polymer according to (9), wherein Z ¹ and Z ^{2 in} Chemical Formula 1 are O or S atoms, and n1 is 1.

(14)
The sulfonic acid group-containing thermally crosslinkable polymer according to (10), wherein Z ³ and Z ^{4 in} Chemical Formula 2 are O or S atoms, and n2 is 1.

(15) It has at least repeating units represented by chemical formulas 1, 2, 13, and 14, respectively, and the mol% of each repeating unit and the mol% of other repeating structures satisfy Formulas 1 to 3 (10) The sulfonic acid group-containing thermally crosslinkable polymer described.

0.9 ≦ (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) ≦ 1.0
(Equation 1)
0.05 ≦ (n3 + n4) / (n3 + n4 + n5 + n6) ≦ 0.7
(Equation 2)
0.01 ≦ (n4 + n6) / (n3 + n4 + n5 + n6) ≦ 0.95
(Formula 3)
(In the above formula, n3 is the mol% of the structure represented by the chemical formula 13, n4 is the mol% of the structure represented by the chemical formula 1, n5 is the mol% of the structure represented by the chemical formula 14, and n6 is the chemical formula. 2 represents the mol% of the structure represented by 2, and n7 represents the mol% of the other repeating structure.)

(16) A sulfonic acid group-containing thermally crosslinkable polymer composition comprising 1 to 100% by weight of the sulfonic acid group-containing thermally crosslinkable polymer according to any one of (1) to (15).

(17) The sulfonic acid group-crosslinked polymer composition according to (16), wherein at least a part of the thermally crosslinkable group of the sulfonic acid group-containing thermally crosslinkable polymer is thermally crosslinked. object.

(18) A polymer electrolyte membrane comprising the sulfonic acid group-containing thermally crosslinkable polymer composition according to (16).

(19) A crosslinked polymer electrolyte membrane comprising the sulfonic acid group-containing crosslinked polymer composition according to (17).

(20) A polymer electrolyte membrane / electrode assembly comprising the sulfonic acid group-containing thermally crosslinkable polymer composition according to (16) in an electrode catalyst layer.

(21) A polymer electrolyte membrane / electrode assembly comprising the sulfonic acid group-containing crosslinked polymer composition according to (17) in an electrode catalyst layer.

(22) A polymer electrolyte membrane / electrode assembly having the polymer electrolyte membrane according to (18).

(23) A polymer electrolyte membrane / electrode assembly having the crosslinked polymer electrolyte membrane according to (19).

(24) A fuel cell using a polymer electrolyte membrane / electrode assembly using the sulfonic acid group-containing polymer composition described in (16) as at least one of a polymer electrolyte membrane and an electrode catalyst layer.

(25) A fuel cell using a polymer electrolyte membrane / electrode assembly using the sulfonic acid group-containing crosslinked polymer composition according to (17) as at least one of a polymer electrolyte membrane and an electrode catalyst layer

  Since the novel sulfonic acid group-containing thermally crosslinkable polymer of the present invention can be thermally crosslinked, the polymer electrolyte membrane obtained by thermally crosslinking can achieve both high proton conductivity and swelling resistance. In addition, a polymer electrolyte membrane / electrode assembly excellent in workability such as bondability with electrodes and excellent in durability can be obtained. For this reason, the polymer electrolyte membrane obtained in the present invention, when used in a fuel cell, enables higher durability and higher output than conventional hydrocarbon polymer electrolyte membranes, and is suitable for a fuel cell. is there.

  Hereinafter, the present invention will be described in detail. In addition, the weight in this invention means mass.

  The sulfonic acid group-containing thermally crosslinkable polymer of the present invention needs to have at least one or more thermally crosslinkable groups and ionic groups in the polymer molecule. The molecular weight of the polymer is preferably between 1,000 and 1,000,000, and preferably between 5,000 and 500,000 because the physical properties and processability can be balanced.

  Examples of the thermally crosslinkable group include multiple bonds such as ethylene group and ethynyl group, benzoxazine group, and oxazole group. These may have a substituent such as a methyl group or a phenyl group. More preferably, the following groups can be mentioned.

（式中、Ｒ^１〜Ｒ^９は水素原子、炭素数１〜１０のアルキル基、フェニル基、炭素数６〜２０の芳香族基、ハロゲンのいずれかを、Ｚは水素原子、炭素数１〜１０の炭化水素基、ハロゲン、ニトロ基、−ＳＯ_３Ｘ基｛ＸはＨあるいは１価の金属イオンを表す。｝のいずれかを、ｎは１〜４の整数を表す。）

(Wherein R ^{1 to} R ⁹ are any ^one of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a phenyl group, an aromatic group having 6 to 20 carbon atoms, and a halogen, Z is a hydrogen atom, Any one of 10 hydrocarbon groups, halogen, nitro group, and —SO ₃ X group {X represents H or a monovalent metal ion}, and n represents an integer of 1 to 4.)

  These groups can be present as side chains or end groups in the polymer. The amount of the thermally crosslinkable group in the polymer is preferably 0.0000001 to 0.01 mol / g, more preferably 0.000001 to 0.001 mol / g, and 0.00001 to 0.0001 mol / g. More preferably, it is g. Moreover, it is preferable that a thermally crosslinkable group exists as a terminal group of a polymer. The thermally crosslinkable group can be introduced into the polymer by reacting a compound having a thermally crosslinkable group as a copolymerization monomer or a terminal terminator.

  The sulfonic acid group-containing thermally crosslinkable polymer of the present invention needs to have a softening temperature of 250 ° C. or lower when the sulfonic acid group is an acid. The softening temperature can be measured, for example, as a temperature at which the elastic modulus in dynamic viscoelasticity rapidly decreases. When the softening temperature exceeds 250 ° C., workability such as bonding with an electrode tends to deteriorate. The range of a preferable softening temperature is 130-230 degreeC, and a more preferable range is 130-210 degreeC.

The sulfonic acid group-containing thermally crosslinkable polymer of the present invention has an appropriate softening temperature due to the structure represented by Chemical Formula 1 and Chemical Formula 2, and has improved processability. In Chemical Formula 1, X is preferably a —S (═O) ₂ — group because solubility in a solvent is improved. It is preferable that X is a —C (═O) — group because the softening temperature of the polymer can be lowered to further enhance the bonding property with the electrode, or the photocrosslinking property can be imparted to the electrolyte membrane. When used as a polymer electrolyte membrane, Y is preferably an H atom. However, if Y is an H atom, it is easily decomposed by heat or the like. Therefore, during processing such as manufacturing of an electrolyte membrane, Y is set as an alkali metal salt such as Na or K, and Y is converted to H atom by acid treatment after processing. A polymer electrolyte membrane can also be obtained by conversion. Z ¹ is preferably O since it has advantages such as less coloring of the polymer and easy availability of raw materials. Z ¹ is preferably S because oxidation resistance is improved. n1 is preferably in the range of 0 to 30, and when n1 is 3 or more, a plurality of units different in n1 may be included. When n1 is 1 or more, Z ² represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, a cyclohexyl group, and an O atom S atoms are preferred because the bondability is further improved. n1 When in the case of 3 or more is Z ² is O atom, preferably in particular for improving bondability between the electrode catalyst layer in the case of the polymer electrolyte membrane.

In the chemical formula 2 in the sulfonic acid group-containing thermally crosslinkable polymer of the present invention, it is preferable that Z ³ is O because there are advantages such as little polymer coloring and easy availability of raw materials. Z ³ is preferably S because oxidation resistance is improved. n2 is preferably in the range of 0 to 30, and when n2 is 3 or more, a plurality of units different in n2 may be included. When n2 is 1 or more, Z ⁴ represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, a cyclohexyl group, and an O atom S atoms are preferred because the bondability is further improved. n2 When the case 3 or more is Z ⁴ is O atom, preferably in particular for improving bondability between the electrode catalyst layer in the case of the polymer electrolyte membrane.

  The molar ratio of the structure represented by Chemical Formula 1 and the structure represented by Chemical Formula 2 is preferably in the range of 5:95 to 90:10. The molar ratio of 5:95 means that the number of moles of the structure represented by Chemical Formula 2 is 95 when the number of moles of the structure represented by Chemical Formula 1 is 5. When the structure represented by Chemical Formula 1 is less than the molar ratio of 5:95, the ionic conductivity tends to be reduced when a polymer electrolyte membrane is obtained. When the structure represented by the chemical formula 1 is larger than the molar ratio of 90:10, the swelling property of the polymer electrolyte membrane tends to be too large or water-soluble. More preferably, it is the range of 10: 90-70: 30.

  When used as a polymer electrolyte membrane of a fuel cell using hydrogen as a fuel, the molar ratio between the structure represented by Chemical Formula 1 and the structure represented by Chemical Formula 2 is in the range of 30:70 to 80:20. It is preferable that it is in the range of 40:60 to 70:30.

  When used as a polymer electrolyte membrane of a fuel cell using a liquid such as methanol as a fuel, the molar ratio of the structure represented by Chemical Formula 1 to the structure represented by Chemical Formula 2 is 7:93 to 50:50. The range is preferable, and the range of 10:90 to 40:60 is more preferable. When the structure represented by the chemical formula 1 is larger than the molar ratio of 50:50, the fuel permeability may be increased when the polymer electrolyte membrane is formed. If the structure represented by the chemical formula 1 is less than the molar ratio of 7:93, the ion conductivity when the polymer electrolyte membrane is formed tends to be reduced and the resistance tends to increase.

Ar ¹ in Chemical Formula 2 is preferably a divalent aromatic group having an electron-withdrawing group. Examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a sulfonic acid group, a sulfonic acid ester group, a sulfonic acid amide group, a sulfonic acid imide group, a carboxyl group, a carbonyl group, a carboxylic acid ester group, a cyano group, a halogen group, Although a trifluoromethyl group, a nitro group, etc. can be mentioned, it is not limited to these, What is necessary is just a well-known arbitrary electron withdrawing group.

A preferred structure of Ar ¹ is a structure represented by chemical formulas 9-12. The structure of Chemical Formula 9 is preferable because it can increase the solubility of the polymer. The structure of Chemical Formula 10 is preferable because it lowers the softening temperature of the polymer to enhance the bonding property with the electrode and impart photocrosslinkability. The structure of Chemical Formula 11 or 12 is preferable because the swelling of the polymer can be reduced, and the structure of Chemical Formula 12 is more preferable. Among the chemical formulas 9 to 12, the structure of the chemical formula 12 is most preferable.

  The sulfonic acid group content in the sulfonic acid group-containing thermally crosslinkable polymer of the present invention is preferably in the range of 0.1 to 10 meq / g, more preferably 0.3 to 5.0 meq / g. More preferably, it is 5-4 meq / g. If it is less than 0.1 meq / g, the ionic conductivity tends to be too low when the polymer electrolyte membrane is formed. As the sulfonic acid group content increases, the ionic conductivity increases, but if it exceeds 10 meq / g, the swellability tends to increase remarkably.

The sulfonic acid group-containing thermally crosslinkable polymer in the present invention has a structure represented by the chemical formula 13 in addition to the structures represented by the chemical formulas 1 and 2 to form a polymer electrolyte membrane. It is preferable because the morphological stability can be improved. In Chemical Formula 13, X is preferably an —S (═O) ₂ — group because solubility in a solvent is improved. It is preferable that X is a —C (═O) — group because the softening temperature of the polymer can be lowered to further enhance the bonding property with the electrode, or the photocrosslinking property can be imparted to the electrolyte membrane. When used as a polymer electrolyte membrane, Y is preferably an H atom. However, if Y is an H atom, it is easily decomposed by heat or the like. Therefore, during processing such as manufacturing of an electrolyte membrane, Y is set as an alkali metal salt such as Na or K, and Y is converted to H atom by acid treatment after processing. A polymer electrolyte membrane can also be obtained by conversion. Z ⁵ is preferably O, because there are advantages such as little polymer coloring and easy availability of raw materials. Z ¹ is preferably S because oxidation resistance is improved.

When the sulfonic acid group-containing thermally crosslinkable polymer in the present invention further has a structure represented by chemical formulas 1, 2, and 13, Z ¹ and Z ² are O or S atoms, and , N1 is preferably 1, since the bonding property with the electrode catalyst layer and the morphological stability of the membrane in the case of a polymer electrolyte membrane are improved. In addition, when Z ³ and Z ⁴ are O or S atoms and n2 is 1, the bonding property with the electrode catalyst layer and the morphological stability of the membrane in the case of a polymer electrolyte membrane are further improved. This is preferable.

When the sulfonic acid group-containing thermally crosslinkable polymer in the present invention further has a structure represented by the chemical formula 14 in addition to the structures represented by the chemical formulas 1, 2, and 13, the polymer electrolyte membrane is obtained. Further, it is more preferable because the bondability with the electrode catalyst layer and the morphological stability of the membrane can be greatly improved. Z ⁶ in the chemical formula 14 is preferably O, since there are advantages such as little polymer coloring and easy availability of raw materials. Z ⁶ is preferably S because oxidation resistance is improved. Ar ² in Chemical Formula 14 is preferably a divalent aromatic group having an electron-withdrawing group. Examples of the electron-withdrawing group include a sulfone group, a sulfonyl group, a sulfonic acid group, a sulfonic acid ester group, a sulfonic acid amide group, a sulfonic acid imide group, a carboxyl group, a carbonyl group, a carboxylic acid ester group, a cyano group, a halogen group, Although a trifluoromethyl group, a nitro group, etc. can be mentioned, it is not limited to these, What is necessary is just a well-known arbitrary electron withdrawing group.

A preferred structure of Ar ² is a structure represented by chemical formulas 9-12. The structure of Chemical Formula 9 is preferable because it can increase the solubility of the polymer. The structure of Chemical Formula 10 is preferable because it lowers the softening temperature of the polymer to further enhance the bondability with the electrode or impart photocrosslinkability. The structure of Chemical Formula 11 or 12 is preferable because the swelling of the polymer can be reduced, and the structure of Chemical Formula 12 is more preferable. Among the chemical formulas 9 to 12, the structure of the chemical formula 12 is most preferable.

  When the sulfonic acid group-containing thermally crosslinkable polymer in the present invention has all the repeating units represented by the chemical formulas 1, 2, 13, and 14, respectively, mol% of each repeating unit and other repeating structures It is preferable that the mol% of satisfy | fills Formula 1-3.

  When (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) is smaller than 0.9, good characteristics cannot be obtained when a polymer electrolyte membrane is obtained, which is not preferable. More preferred is a range of 0.95 to 1.0.

  When (n3 + n4) / (n3 + n4 + n5 + n6) is smaller than 0.05, it is not preferable because sufficient ion conductivity tends to be not obtained when a polymer electrolyte membrane is obtained. On the other hand, when the ratio 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, (n3 + n4) / (n3 + n4 + n5 + n6) is preferably in the range of 0.3 to 0.8, and in the range of 0.4 to 0.7. It is more preferable that 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 a fuel, (n3 + n4) / (n3 + n4 + n5 + n6) is preferably in the range of 0.07 to 0.5, preferably 0.1 to 0.00. A range of 4 is more preferable. 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.

  When (n4 + n6) / (n3 + n4 + n5 + n6) 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, a range of 0.4 to 0.8 is more preferable.

  Preferred examples of the sulfonic acid group-containing heat-crosslinkable polymer in the present invention include a polymer having a heat-crosslinkable group as at least one of the terminal groups of the polymer skeleton represented by the following structure. The present invention is not limited to these, and any polymer that falls within the scope of the present invention can be suitably used. In the following specific examples of the polymer skeleton, n, n ′, n ″, m, m ′, m ″, o, o ′, o ″, p, p ′, p ″, f are each independently 1 or more. Represents an integer.

  Examples of the thermally crosslinkable group include structures represented by Chemical Formulas 3 to 8, but are not limited thereto. Specific examples are shown below, but are not limited thereto.

  The above-mentioned thermally crosslinkable group can be introduced by using it as a component of a monomer when polymerizing a sulfonic acid group-containing thermally crosslinkable polymer. For example, the following compounds can be mixed and reacted with other monomers, or reacted with terminal groups of a polymer skeleton synthesized in advance.

  Among the above compounds, those having a phenolic hydroxyl group can be reacted with the activated aromatic halide end of the backbone polymer by reacting with a base to form a phenolate ion. In addition, halides such as allyl chloride can be reacted with phenolate ion ends of the backbone polymer. In addition, it can introduce | transduce using a well-known reaction.

  Moreover, the following groups can also be introduced as the thermal crosslinking group.

  The heat-crosslinkable group can be obtained by reacting formaldehyde and amine with a polymer having a phenolic hydroxyl group terminal of the skeleton polymer as described below.

（式中、Ｒは水素原子、炭素数１〜１０のアルキル基、フェニル基、炭素数６〜２０の芳香族基を表す）

(In the formula, R represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a phenyl group, or an aromatic group having 6 to 20 carbon atoms)

  When a bisthiophenol compound is used for the synthesis of the backbone polymer in the introduction of the heat crosslinkable group, the heat crosslinkable group is introduced into the aromatic mercapto end in the same manner as the above phenolic hydroxyl group. be able to.

  The sulfonic acid group-containing thermally crosslinkable polymer of the present invention can also be used as a composition by dissolving and dispersing in a suitable solvent. Solvents that can be used include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphonamide, N-morpholine oxide, and the like. Polar solvents such as aprotic organic polar solvents, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone, ether solvents such as diethyl ether, mixtures of these organic solvents, and mixtures with water However, it is not limited to these.

  The concentration of the polymer solution is preferably in the range of 0.1 to 50% by weight. When a film, fiber, or the like is molded from a solution, the concentration is more preferably in the range of 5 to 50% by weight, and further preferably in the range of 10 to 40% by weight. When the solution is used as an adhesive between the electrode and the polymer electrolyte, the concentration is more preferably in the range of 0.1 to 20% by weight. When the solution is used as an adhesive, it may contain other components such as carbon particles carrying a catalyst such as Pt and Pt—Ru, and a fluororesin.

  The thermally crosslinkable solid polymer electrolyte of the present invention can be crosslinked by heat treatment. The heat treatment is preferably performed in an inert gas such as nitrogen or argon. The temperature of heat processing can be performed in the range of 100-400 degreeC. The heat treatment time can be performed between 1 second and 100 hours. Depending on the case, you may add arbitrary well-known polymerization initiators, such as an azo polymerization initiator and a peroxide polymerization initiator. At the time of thermal crosslinking, the polymer electrolyte itself of the present invention can be heat-treated to form a crosslinked structure, but it can also be thermally crosslinked after forming a composition with another non-crosslinkable polymer. In that case, the non-crosslinkable polymer may contain an ionic group in the molecular chain as in the crosslinkable polymer of the present invention, or may contain no ionic group. Examples of the basic structure of the non-crosslinkable polymer 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 polymethacrylate. , Acrylate resins such as polymethyl acrylate and polyacrylic acid esters, polyacrylic acid resins, polymethacrylic acid resins, various polyolefins including diene polymers, polyurethane resins, cellulose acetate, ethyl cellulose Resin, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyester Polyetherimide, polyimide, polybenzoxazole, polybenzthiazole, polybenzimidazole, and aromatic polymers such as polyamide-imide, not particularly limited.

  In the sulfonic acid group-containing thermally crosslinkable polymer of the present invention, the repeating structure represented by Chemical Formulas 1 and 2 increases the flexibility of the polymer, makes it difficult to break against deformation, and decreases the glass transition temperature. As a result, the effect of increasing the bondability with the electrode is brought about. In addition, the repeating structures represented by the chemical formulas 13 and 14 have the effect of reducing the swelling property of the whole polymer and reducing the methanol permeability.

  The polymer electrolyte membrane in the present invention can have any thickness, but if it is 10 μm or less, it becomes difficult to satisfy the predetermined characteristics, and therefore it is preferably 10 μm or more, and more preferably 20 μm or more. Moreover, since manufacture will become difficult when it becomes 300 micrometers or more, it is preferable that it is 300 micrometers or less.

  The polymer electrolyte membrane in the present invention may contain other polymers. Examples of such polymers 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, polymethacrylates, poly Acrylate resins such as methyl acrylate and polyacrylates, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, ethyl cellulose, etc. Cellulosic resin, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyether Thermosetting of aromatic polymers such as ruphone, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin There are no particular restrictions on the conductive resin. A resin composition with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferable combination for improving the polymer dimensionality, and when a sulfonic acid group is further introduced into these basic polymers, The processability of the composition becomes more preferable. 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 obtained from the polymer composition of the present invention by any method such as extrusion, rolling or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent. 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. At this time, if necessary, it can be molded in a form combined with other compounds. 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 is converted to a free sulfonic acid group by acid treatment if necessary. You can also. The timing of reacting the thermally crosslinkable group may be before or after molding, but is preferably performed after molding from the viewpoint of processability.

  The most preferable method for forming the polymer electrolyte membrane of the present invention is casting 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 less than 10 μm, the form as a polymer electrolyte membrane tends to be not maintained, and if it is more than 2000 μm, a non-uniform film tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, the thickness can be controlled by the amount and concentration of the solution by making the thickness constant using an applicator, a doctor blade or the like, or making the cast area constant using a glass petri dish or the like. 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. In the processing, when heating is involved, it is preferable that the sulfonic acid group in the sulfonic acid group-containing polymer forms a salt with a cation because stability is improved. However, for use as a polymer electrolyte membrane, it can be converted to free sulfonic acid by an appropriate acid treatment. In this case, it is effective to immerse the membrane in an aqueous solution of sulfuric acid, hydrochloric acid, etc. with or without heating.

  One of the preferred methods for obtaining the polymer electrolyte membrane of the present invention is that a membrane is prepared from the polymer composition of the present invention in which the thermally crosslinkable group is in an unreacted state, and the prepared membrane is thermally crosslinkable. This is a method of reacting groups. A more preferable method is to prepare a film in a state where the sulfonic acid group of the sulfonic acid group-containing heat-crosslinkable polymer in the polymer composition forms a salt, react the heat-crosslinked group on the prepared film, and then perform acid treatment. In this method, the sulfonic acid group of the heat-crosslinkable polymer containing a sulfonic acid group is returned to an acid.

  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 the electrode There is a method of heating and pressurizing. A method in which an adhesive mainly composed of the polymer composition of the present invention is applied and adhered to the electrode surface is preferable, and it is more preferable to use a polymer composition in a state in which the thermally crosslinkable group in the polymer composition has not reacted. preferable. This is because the adhesion between the polymer electrolyte membrane and the electrode is improved, and it is considered that the proton conductivity of the polymer electrolyte membrane is less impaired. Since the polymer electrolyte membrane and the polymer composition of the present invention have an appropriate softening temperature, they are particularly suitable for a method of joining a polymer electrolyte membrane and an electrode by pressure heating. Further, the sulfonic acid group-containing thermally crosslinkable polymer of the present invention can be used as an adhesive with an electrode or a catalyst for films other than the polymer electrolyte membrane of the present invention. When the sulfonic acid group-containing thermally crosslinkable polymer of the present invention is used as an adhesive, it is preferable that Y in the chemical formulas 1 and 13 is H and the sulfonic acid group is in acid form. When the sulfonic acid group is used in the form of a salt with a cation, the sulfonic acid group can be converted into an acid form by acid treatment after bonding.

  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. Since the polymer electrolyte membrane of the present invention has low swellability, it 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.

  To synthesize the sulfonic acid group-containing polymer of the present invention, for example, a monomer having a structure represented by the following chemical formulas 19 to 21 is reacted to form a polymer skeleton, and then a thermally crosslinkable group is introduced into the terminal group. Although it can mention as an example, it is not limited to it, It can synthesize | combine by arbitrary methods from arbitrary raw materials. In the previous method, it is preferable to further add a monomer having a structure represented by Chemical Formula 22 because physical properties such as film form stability are improved.

In Chemical Formulas 19 to 22, X is a —S (═O) ₂ — group or —C (═O) — group, Y is H or a monovalent cation, and Z ⁷ and Z ¹⁰ are each independently Any one of Cl atom, F atom, I atom, Br atom and nitro group, Z ⁸ and Z ¹¹ 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 ⁹ represents any one of an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, and a cyclohexyl group, and Ar ⁴ represents a molecule 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 19 include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 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'-dichlorodiphenylsulfone, potassium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone 3,3′-Disulfonic acid potassium-4,4′-dichlorodiphenyl ketone, 3,3′-di Sulfonic acid 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 20 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, and 1,1-bis (4-hydroxyphenyl) cyclohexane are preferable.

  The monomer represented by the chemical formula 20 has the effect of increasing the flexibility of the polymer, making it difficult to break against deformation, and increasing the bondability with the electrode by lowering the glass transition temperature. ing.

  Examples of the compound represented by Chemical Formula 21 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 the chemical formula 22 include 4,4'-biphenol, 4,4'-dimercaptobiphenol, and 4,4'-biphenol is preferable.

  In the above aromatic nucleophilic substitution reaction, other various activated dihalogen aromatic compounds, dinitroaromatic compounds, bisphenol compounds, and bisthiophenol compounds can be used in combination with the compounds represented by chemical formulas 19-22. .

  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.

  When the sulfonic acid group-containing polymer in the present invention is polymerized by an aromatic nucleophilic substitution reaction, a compound having a structure represented by chemical formulas 19 to 22 and, if necessary, other activated dihalogen aromatic compounds or dinitroaromatic compounds. And aromatic diols or aromatic dithiols can be added and reacted in the presence of a basic compound to obtain a polymer. 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 weight. When the amount is less than 5% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high, and the 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.

  Thermally crosslinkable groups are introduced by reacting the above-mentioned thermally crosslinkable compounds with the phenolic hydroxyl end, aromatic mercapto end, and aromatic halide end of the polymer skeleton synthesized as described above. Thus, the sulfonic acid group-containing polymer of the present invention can be obtained. In the synthesis of the polymer skeleton, a crosslinkable compound may be added as a component of the monomer and reacted. Further, a thermally crosslinkable group may be formed by reacting the phenolic hydroxyl group end or aromatic mercapto group end of the polymer skeleton synthesized as described above with formaldehyde and an amine compound.

  The sulfonic acid group-containing polymer in the present invention 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.

  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.

  Logarithmic viscosity: The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, and the viscosity was measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / Evaluation was made by c (ta is the number of seconds for dropping the sample solution, tb is the number of seconds for dropping only the solvent, and c is the polymer concentration).

Proton conductivity: A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped membrane sample on a probe for self-made measurement (made of tetrafluoroethylene resin), in water at 25 ° C. or 80 ° C., constant humidity of 95% The sample was held in a thermostatic bath, 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: 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 in an H-type cell, 100 mL of 5 M aqueous methanol solution is placed on one side of the cell, and 100 ml of ultrapure water is placed on the other cell. (18 MΩ · cm) was injected, and the amount of methanol that diffused into the ultrapure water through the polymer electrolyte membrane was measured using a gas chromatograph while stirring the cells on both sides at 25 ° C. (The area of the polymer electrolyte membrane was 2.0 cm ² ). A methanol permeability coefficient was determined from the obtained methanol permeation rate and the film thickness of the sample.

Power generation evaluation of hydrogen-fueled fuel cell (PEFC): Commercially available 40% Pt catalyst-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd. Fuel Cell Catalyst TEC10V40E) and DuPont's 20% Nafion (registered trademark) solution After adding ultrapure water and isopropanol, the mixture was stirred until uniform to prepare a catalyst paste. This catalyst paste was uniformly applied to Toray carbon paper TGPH-060 so that the amount of platinum deposited was 0.5 mg / cm ² and dried to prepare a gas diffusion layer with an electrode catalyst layer. By sandwiching the polymer electrolyte membrane between the gas diffusion layers with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane, pressurizing and heating at 130 ° C. and 2 MPa for 3 minutes by a hot press method, A membrane-electrode assembly was obtained. The joined body was assembled in an evaluation fuel cell FC25-02SP manufactured by Electrochem, and hydrogen and air humidified at 75 ° C. were supplied to the anode and the cathode at a cell temperature of 80 ° C., and the power generation characteristics were evaluated. The output voltage at a current density of 0.5 A / cm ² immediately after the start was taken as the initial characteristics. Moreover, as durability evaluation, continuous operation was performed on said conditions, measuring an open circuit voltage at the rate of once per hour. The time when the open circuit voltage decreased by 10% or more from the value immediately after the start was defined as the endurance time. Durability evaluation was performed with 1000 hours as the upper limit.

Power generation evaluation of direct methanol fuel cell (DMFC): Pt / Ru catalyst-supported carbon (Tanaka Kikinzoku Kogyo Co., Ltd. TEC61E54) was moistened with a small amount of ultrapure water and isopropyl alcohol, and then DuPont 20% Nafion (registered) (Trademark) solution (product number: SE-20192) was added so that the weight ratio of Pt / Ru catalyst-carrying carbon to Nafion was 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. The catalyst paste was applied to Toray carbon paper TGPH-060 to be a gas diffusion layer by screen printing so that the adhesion amount of platinum was 2 mg / cm ^2, and a carbon paper with an electrode catalyst layer for anode was produced. . Moreover, after adding a small amount of ultrapure water and isopropyl alcohol to a Pt catalyst-supporting carbon (Tanaka Kikinzoku Kogyo TEC10V40E) and moistening, a 20% Nafion (registered trademark) solution (product number: SE-20192) manufactured by DuPont, A cathode catalyst paste was prepared by adding the Pt catalyst-carrying carbon and Nafion in a weight ratio of 2.5: 1 and stirring. The catalyst paste was applied and dried on carbon paper TGPH-060 manufactured by Toray Industries, Ltd., which had been subjected to water repellent treatment, so that the amount of platinum deposited was 1 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for cathode. . By sandwiching the membrane sample between the two types of carbon paper with the electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, by pressurizing and heating at 170 ° C. and 8 MPa for 3 minutes by a hot press method, A membrane-electrode assembly was obtained. This joined body 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 was performed at a cell temperature of 40 ° C. while supplying high purity air gas (80 ml / min) adjusted to 40 ° C. and a 5 mol / liter aqueous methanol solution (1.5 ml / min) to the anode and the cathode, respectively. . The output voltage at a current density of 0.02 A / cm ² and the resistance value measured by the current interruption method were measured.

  Electrode bondability: After the evaluation of power generation of the DMFC, “◯” was given when no peeling was observed between the polymer electrolyte membrane and the electrode catalyst layer, and “X” was given when peeling occurred.

  Swellability: After a 5 cm square square polymer electrolyte membrane was immersed in pure water at 80 ° C. for 1 hour, water on the surface was quickly removed and placed in a sealed container, and the weight of the hygroscopic membrane was measured. Thereafter, the membrane was dried under reduced pressure at 100 ° C. for 1 hour, then placed in a sealed container, and the weight of the dried membrane was measured. The water content was determined by subtracting the weight of the hygroscopic film from the weight of the dry film, and the weight% of the water content relative to the weight of the dry film was defined as swellability.

  Ion exchange capacity: A sample dried for 1 hour at 100 ° C. and allowed to stand overnight at room temperature in a nitrogen atmosphere was weighed, stirred with an aqueous sodium hydroxide solution, and then ion exchange capacity was determined by back titration with an aqueous hydrochloric acid solution.

  Softening temperature: While heating an acid-type film having a width of 5 mm at a chuck width of 10 mm from 50 ° C. to 250 ° C. at a rate of 2 ° C./min, a dynamic strain of 10 Hz was applied to give a dynamic viscoelasticity, Rhegel E-4000 ( Measured by Toki Sangyo Co., Ltd.). The temperature at the inflection point at which E ′ greatly decreased was defined as the softening temperature.

<Synthesis Example 1>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation: S-DCDPS) 31.212 g (0.06354 mol), 2,6-dichlorobenzonitrile (abbreviation: DCBN) 18.609 g (0 1082 mol), terminal hydroxyl group-containing phenylene ether oligomer (SPECIANOL DPE-PL manufactured by Dainippon Ink & Chemicals, Inc .; in the following chemical formula 23, n is a mixture containing 1 to 8 components, and the average value of n is 5 Things) (abbreviation: DPE) 94.411 g (0.1717 mol), potassium carbonate 26.107 g (0.1889 mol), N-methyl-2-pyrrolidone (abbreviation: NMP) 420.00 g were weighed into a 1000 ml four-necked flask. Was taken and flushed with nitrogen. Heating was performed while stirring, and the reaction solution was allowed to react for 12 hours so that the temperature of the reaction solution was 190 to 200 ° C. Then, after cooling the reaction solution to 140 ° C., 0.410 g (0.0034 mol) of 4-ethynylphenol was added and reacted at 140 ° C. for 3 hours with stirring. Then, it cooled to room temperature and poured the reaction solution into water, and precipitated in strand form. The precipitated polymer was washed three times with room temperature water and once in boiling water, and then dried at 110 ° C. to obtain a polymer. It was confirmed by ¹ H-NMR analysis of the polymer that there was a signal derived from an ethynyl group (3.1 ppm), and introduction of a thermally crosslinkable group was confirmed.

<Synthesis Example 2>
S-DCDPS 26.323 g (0.05358 mol), DCBN 19.586 g (0.1139 mol), DPE 64.452 g (0.1184 mol), 4,4′-dihydroxydiphenyl ether 10.158 g (0.05023 mol) potassium carbonate 25 .458 g (0.1842 mol), NMP 361.03 g, 0.174 g (0.0024 mol) of 1-chloro-2-propyne instead of 4-ethynylphenol, and a polymer was obtained in the same manner as in Synthesis Example 1. . It was confirmed by ¹ H-NMR analysis of the polymer that there was a signal derived from an ethynyl group (3.2 ppm), and introduction of a thermally crosslinkable group was confirmed.

<Synthesis Example 3>
S-DCDPS 31.136 g (0.06338 mol), DCBN 61.7979 g (0.3592 mol), 4,4′-biphenol (abbreviation: BP) 19.670 g (0.1056 mol), 4,4′-dihydroxydiphenyl sulfide (Abbreviation: BPS) 68.478 g (0.3137 mol), potassium carbonate 64.239 g (0.4648 mol), NMP 432.511 g, 4-ethynylphenol 0.756 g (0.0064 mol) were used and the same as in Synthesis Example 1. A polymer was obtained by the following procedure.

<Synthesis Example 4>
S-DCDPS 30.54 g (0.06118 mol), DCBN 47.940 g (0.2787 mol), BP 15.822 g (0.08497 mol), BPS 55.083 g (0.2524 mol), potassium carbonate 51.673 g (0. 3739 mol), NMP 374.014 g, 4-hydroxystyrene 0.600 g (0.0050 mol) was used instead of 4-ethynylphenol, and a polymer was obtained in the same manner as in Synthesis Example 1. It was confirmed by ¹ H-NMR analysis of the polymer that there was a signal derived from a vinyl group (5.3 ppm), and introduction of a thermally crosslinkable group was confirmed.

<Synthesis Example 5>
S-DCDPS 28.512 g (0.05804 mol), DCBN 39.934 g (0.2322 mol), BP 13.510 g (0.07255 mol), BPS 47.031 g (0.2155 mol), potassium carbonate 44.119 g (0. 3192 mol), 324.900 g of NMP, and 0.520 g (0.0044 mol) of 4-ethynylphenol, a polymer was obtained in the same manner as in Synthesis Example 1.

<Synthesis Example 6>
S-DCDPS 63.215 g (0.1287 mol), DCBN 28.171 g (0.1638 mol), BP 48.523 g (0.2606 mol), BPS 6.384 g (0.02925 mol), potassium carbonate 44.463 g (0. 3217 mol), NMP 376.370 g, and 4-ethynylphenol 0.614 g (0.0052 mol) were used to obtain a polymer in the same manner as in Synthesis Example 1.

<Synthesis Example 7>
S-DCDPS 73.792 g (0.1502 mol), DCBN 32.885 g (0.1912 mol), BP 54.866 g (0.2974 mol), BPS 7.452 g (0.03414 mol), potassium carbonate 51.902 g (0. 3755 mol), NMP 376.329 g, 4-ethynylphenol 0.709 g (0.0060 mol), and a polymer was obtained in the same manner as in Synthesis Example 1.

<Synthesis Example 8>
S-DCDPS 80.156 g (0.1632 mol), DCBN 30.405 g (0.1768 mol), BP 50.759 g (0.2726 mol), BPS 11.130 g (0.05099 mol), potassium carbonate 51.680 g (0. 3739 mol), 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (Sanko's HCA-HQ) (abbreviation: HCQ) Using 409 g (0.01360 mol), NMP 387.234 g, and 4-ethynylphenol 0.662 g (0.0056 mol), a polymer was obtained in the same manner as in Synthesis Example 1.

<Synthesis Example 9>
S-DCDPS 82.451 g (0.1678 mol), DCBN 19.247 g (0.1119 mol), BP 44.348 g (0.2382 mol), BPS 6.106 g (0.02797 mol), potassium carbonate 42.528 g (0. 3077 mol), HCQ 3.628 g (0.01190 mol), NMP 344.897 g, 4-ethynylphenol 0.567 g (0.0048 mol), and a polymer was obtained in the same manner as in Synthesis Example 1.

<Synthesis Example 10>
S-DCDPS 30.135 g (0.06134 mol), DCBN 42.207 g (0.2454 mol), BP 13.707 g (0.07361 mol), 4,4′-thiobis (benzenethiol) 57.786 g (0.2308 mol) , 46.631 g (0.3374 mol) of potassium carbonate, 366.159 g of NMP and 0.543 g (0.0046 mol) of 4-ethynylphenol were used to obtain a polymer by the same operation as in Synthesis Example 1.

<Synthesis Example 11>
S-DCDPS 31.234 g (0.06358 mol), DCBN 46.624 g (0.2711 mol), BP 12.463 g (0.06693 mol), 2,2-bis (4-hydroxyphenyl) propane 60.504 g (0. 26507 mol), 50.875 g (0.3681 mol) of potassium carbonate, 381.102 g of NMP, and 0.638 g (0.0054 mol) of 4-ethynylphenol, and a polymer was obtained in the same manner as in Synthesis Example 1.

<Synthesis Example 12>
S-DCDPS 30.941 g (0.06298 mol), DCBN 34.307 g (0.1995 mol), BP 11.728 g (0.06298 mol), 2,2-bis (4-hydroxyphenyl) hexafluoropropane 66.390 g ( 0.1975 mol), potassium carbonate 39.898 g (0.2887 mol), NMP 374.703 g, 4-ethynylphenol 0.473 g (0.0040 mol) was used, and a polymer was obtained in the same manner as in Synthesis Example 1.

<Synthesis Example 13>
S-DCDPS 31.743 g (0.06462 mol), DCBN 44.459 g (0.2585 mol), BP 14.439 g (0.07754 mol), 1,1-bis (4-hydroxyphenyl) cyclohexane 65.233 g (0. 2430 mol), potassium carbonate 49.119 g (0.3554 mol), NMP 398.919 g, 4-ethynylphenol 0.567 g (0.0050 mol), and a polymer was obtained in the same manner as in Synthesis Example 1.

<Comparative Synthesis Example 1>
A polymer was obtained in the same manner as in Synthesis Example 1 except that the amount of DPE was 94.421 g (0.1717 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 2>
A polymer was obtained in the same manner as in Synthesis Example 2 except that the amount of DPE was 64.452 g (0.1172 mol) and the 1-chloro-2-propyne reaction was not performed.

<Comparative Synthesis Example 3>
A polymer was obtained in the same manner as in Synthesis Example 3 except that the amount of BPS was 69.170 g (0.3169 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 4>
A polymer was obtained in the same manner as in Synthesis Example 4 except that the amount of BPS was 55.639 g (0.2549 mol) and 4-hydroxystyrene was not reacted.

<Comparative Synthesis Example 5>
A polymer was obtained in the same manner as in Synthesis Example 5 except that the amount of BPS was 47.506 g (0.2177 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 6>
A polymer was obtained in the same manner as in Synthesis Example 6 except that the amount of BP was 49.013 g (0.2632 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 7>
A polymer was obtained in the same manner as in Synthesis Example 7 except that the amount of BP was 55.942 g (0.3004 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 8>
A polymer was obtained in the same manner as in Synthesis Example 8 except that the amount of BP was 51.272 g (0.2754 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 9>
A polymer was obtained in the same manner as in Synthesis Example 9 except that the amount of BP was 44.796 g (0.2406 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 10>
A polymer was obtained in the same manner as in Synthesis Example 10 except that the amount of 4,4′-thiobis (benzenethiol) was 58.370 g (0.2331 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 11>
A polymer was obtained in the same manner as in Synthesis Example 11 except that the amount of 2,2-bis (4-hydroxyphenyl) propane was 61.115 g (0.2677 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 12>
A polymer was obtained in the same manner as in Synthesis Example 12 except that the amount of 2,2-bis (4-hydroxyphenyl) hexafluoropropane was 67.061 g (0.1995 mol) and 4-ethynylphenol was not reacted. .

<Comparative Synthesis Example 13>
A polymer was obtained in the same manner as in Synthesis Example 13 except that the amount of 1,1-bis (4-hydroxyphenyl) cyclohexane was 65.892 g (0.2455 mol) and 4-ethynylphenol was not reacted.

<Comparative Synthesis Example 14>
S-DCDPS 30.54 g (0.06118 mol), DCBN 47.940 g (0.2787 mol), BP 62.655 g (0.3365 mol), potassium carbonate 51.673 g (0.3739 mol), NMP 374.014 g, 4- A polymer was obtained by the same procedure as in Synthesis Example 1 except that 0.803 g (0.0068 mol) of ethynylphenol was used.

<Examples 1 to 13>
A solution prepared by dissolving 8 g of each of the polymers obtained in Synthesis Examples 1 to 13 in 32 g of dimethylacetamide was cast on a glass plate with a thickness of 200 μm and dried under reduced pressure at 70 ° C. for 3 days. After peeling off the film from the glass plate, it was fixed to a metal frame, treated at 250 ° C. for 1 hour in a nitrogen atmosphere, and allowed to cool to room temperature. Thereafter, the membrane was dipped in 1 mol / liter sulfuric acid at 80 ° C. for 1 hour twice to convert the sulfonic acid group into an acid form, and further washed with water until no acid could be detected. The washed membrane was sandwiched between filter papers, further sandwiched between glass plates, loaded, and allowed to stand for 2 days to dry. The obtained polymer electrolyte membrane was evaluated.

<Comparative Examples 1-14>
For the polymers obtained in Comparative Synthesis Examples 1 to 14, polymer electrolyte membranes were obtained in the same manner as in the examples. The obtained polymer electrolyte membrane was evaluated.

  Table 1 shows the evaluation results of the polymer electrolyte membranes of Examples and Comparative Examples.

From Table 1, the polymer electrolyte membranes (Examples 1 to 5 and 10 to 13) for direct methanol fuel cells (DMFC) in the present invention are polymer electrolyte membranes of Comparative Examples (Comparative Examples 1 to 5 and 10). Compared with ˜13), the methanol permeability is lowered, the output of the fuel cell is improved, and the crosslinking effect by the thermally crosslinkable group is obtained. Moreover, there was no problem in the bonding property with the electrode. In Comparative Example 14, which has a thermally crosslinkable group but the polymer structure is outside the scope of the present invention, there is a problem in the bonding property between the polymer electrolyte membrane and the electrode, and the resistance when used as a fuel is remarkably high and low. Only output was obtained. Thus, compared with the polymer electrolyte membrane having the same polymer skeleton, the polymer electrolyte membrane of the present invention has an advantage that it is excellent in workability and output when used in a fuel cell.
Moreover, the polymer electrolyte membranes (Examples 6 to 9) for the fuel cell (PEFC) using hydrogen as a fuel are compared with the polymer electrolyte membranes of the comparative polymer electrolyte membranes (Comparative Examples 6 to 9). Although the initial voltages are the same, the durability time is greatly improved, and it is clear that the polymer electrolyte membrane has excellent durability.

  The polymer electrolyte membrane obtained by using the novel sulfonic acid group-containing thermally crosslinkable polymer of the present invention and further thermally cross-linking can provide a polymer electrolyte membrane / electrode assembly having excellent durability. In the field of batteries, compared to conventional hydrocarbon polymer electrolyte membranes, it is possible to achieve higher durability and higher output, contributing to the industry.

Claims (25)

The polymer molecule has (A) a structure represented by the following chemical formula 1, (B) a structure represented by the following chemical formula 2, and (C) a thermally crosslinkable group, and (D) Y is H In this case, the heat-crosslinking polymer containing a sulfonic acid group is characterized in that the softening temperature is 250 ° C. or lower.

[In Chemical Formula 1, X represents an —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, Z ¹ represents either an O or S atom, Z ² represents an O atom, an S atom, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a —CH ₂ — group, or a cyclohexyl group, and n 1 represents an integer of 1 or more. To express. In Chemical Formula 2, Ar ¹ is a divalent aromatic group, Z ³ is either an O or S atom, Z ⁴ is an O atom, an S atom, a —C (CH ₃ ) ₂ — group, —C ( CF _{3) 2} - group, -CH ₂ - group, any one of a cyclohexyl group, n2 represents an integer of 1 or more. ] The sulfonic acid group-containing thermally crosslinkable polymer according to claim 1, wherein the thermally crosslinkable group is one or more groups selected from the group represented by the following chemical formulas (3) to (8).

[Wherein R ^{1 to} R ⁹ are any ^one of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a phenyl group, an aromatic group having 6 to 20 carbon atoms, and a halogen; 10 hydrocarbon groups, halogen, nitro group, —SO ₃ Y group {Y represents H or a monovalent cation. }, N represents an integer of 1 to 4. ]   The heat-crosslinkable polymer containing a sulfonic acid group according to claim 1, wherein the content of the heat-crosslinkable group in the polymer molecule is 0.000001 to 0.001 mol / g. The sulfonic acid group-containing thermally crosslinkable polymer according to claim 1, wherein Ar ^{1 in} Chemical Formula 2 is one or more groups selected from structures represented by Chemical Formulas 9 to 12 below.

The sulfonic acid group-containing thermally crosslinkable polymer according to claim 4, wherein Ar ^{1 in} Chemical Formula 2 has a structure represented by Chemical Formula 12.   The sulfonic acid group-containing thermally crosslinkable polymer according to claim 1, wherein the sulfonic acid group content is 0.3 to 5.0 meq / g. The sulfonic acid group-containing thermally crosslinkable polymer according to claim 1, wherein Z ¹ and Z ^{2 in} Chemical Formula 1 are both O atoms, and n1 is 3 or more. The sulfonic acid group-containing thermally crosslinkable polymer according to claim 7, wherein Z ³ and Z ^{4 in} Chemical Formula 2 are both O atoms, and n2 is 3 or more. The sulfonic acid group-containing heat-crosslinkable polymer according to claim 1, further having a structure represented by the following chemical formula 13.

[In Chemical Formula 13, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. . ] The sulfonic acid group-containing thermally crosslinkable polymer according to claim 9, further having a structure represented by the following chemical formula 14.

[In the chemical formula 14, Ar ² represents a divalent aromatic group, and Z ⁶ represents either O or S atom. ] The sulfonic acid group-containing thermally crosslinkable polymer according to claim 10, wherein Ar ^{2 in} Chemical Formula 14 is one or more groups selected from structures represented by Chemical Formulas 9 to 12. The sulfonic acid group-containing thermally crosslinkable polymer according to claim 11, wherein Ar ^{2 in} Chemical Formula 14 has a structure represented by Chemical Formula 12. The sulfonic acid group-containing thermally crosslinkable polymer according to claim 9, wherein Z ¹ and Z ^{2 in} Chemical Formula 1 are O or S atoms and n1 is 1. The sulfonic acid group-containing thermally crosslinkable polymer according to claim 10, wherein Z ³ and Z ^{4 in} Chemical Formula 2 are O or S atoms and n2 is 1. The sulfone according to claim 10, having at least repeating units represented by chemical formulas 1, 2, 13, and 14, wherein mol% of each repeating unit and mol% of other repeating structures satisfy Formulas 1 to 3. Acid group-containing thermally crosslinkable polymer.
0.9 ≦ (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) ≦ 1.0
(Equation 1)
0.05 ≦ (n3 + n4) / (n3 + n4 + n5 + n6) ≦ 0.7
(Equation 2)
0.01 ≦ (n4 + n6) / (n3 + n4 + n5 + n6) ≦ 0.95
(Formula 3)
(In the above formula, n3 is the mol% of the structure represented by Chemical Formula 13, n4 is the mol% of the structure represented by Chemical Formula 1, n5 is the mol% of the structure represented by Chemical Formula 14, and n6 is the chemical formula. 2 represents the mol% of the structure represented by 2, and n7 represents the mol% of the other repeating structure.)   A sulfonic acid group-containing thermally crosslinkable polymer composition comprising 1 to 100% by weight of the sulfonic acid group-containing polymer according to any one of claims 1 to 15.   The sulfonic acid group-containing thermally crosslinkable polymer composition according to claim 16, wherein at least a part of the thermally crosslinkable group of the sulfonic acid group-containing thermally crosslinkable polymer is thermally crosslinked.   A polymer electrolyte membrane comprising the sulfonic acid group-containing thermally crosslinkable polymer composition according to claim 16.   A crosslinked polymer electrolyte membrane comprising the sulfonic acid group-containing crosslinked polymer composition according to claim 17.   A polymer electrolyte membrane / electrode assembly comprising the sulfonic acid group-containing thermally crosslinkable polymer composition according to claim 16 in an electrode catalyst layer.   A polymer electrolyte membrane / electrode assembly comprising the sulfonic acid group-containing crosslinked polymer composition according to claim 17 in an electrode catalyst layer.   A polymer electrolyte membrane / electrode assembly comprising the polymer electrolyte membrane according to claim 18.   A polymer electrolyte membrane / electrode assembly comprising the crosslinked polymer electrolyte membrane according to claim 19.   A fuel cell using a polymer electrolyte membrane / electrode assembly in which the sulfonic acid group-containing thermally crosslinkable polymer composition according to claim 16 is used for at least one of a polymer electrolyte membrane and an electrode catalyst layer.   A fuel cell using a polymer electrolyte membrane / electrode assembly in which the sulfonic acid group-containing crosslinked polymer composition according to claim 17 is used in at least one of a polymer electrolyte membrane and an electrode catalyst layer.