JP2003338298A - Polyamide precursor varnish containing protonic acid group and cross-linked polyamide containing protonic acid group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a varnish which is a row material of a cross-linked polyamide containing protonic acid group with high ionic conductivity; with excellent water-resistance; with excellent methanol-resistance; and with low methanol permeability, to provide an ionic conductivity polymer membrane for fuel cell consisting of the cross-linking polyamide and to provide a fuel cell using the polymer membrane. <P>SOLUTION: A polyamide precursor varnish which contains a proton acid group which contains a proton acid group in a molecular chain and a polyamide precursor of which the end of the molecular chain is dicarboxylic acid or its monoester and a chemical compound with three or four pieces of amino groups in a molecular, and the cross-linking polyamide containing protonic acid group can be obtained by causing imidization of the varnish with thermal treatment. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proton acid group-containing crosslinked polyimide forming an ion conductive polymer membrane applicable to a fuel cell using hydrogen, alcohol, etc. as a fuel, and a proton acid group containing polyimide precursor as a raw material thereof. Regarding body varnish. More specifically, a crosslinked polyimide having a protonic acid group having high ionic conductivity, excellent heat resistance, water resistance, and methanol resistance and a low methanol permeability, and a protonic acid group-containing polyimide precursor that is a raw material of the crosslinked polyimide. Regarding varnish.

[0002]

2. Description of the Related Art In recent years, new energy storage or power generation elements have been strongly demanded in society from the viewpoint of environmental problems.
Fuel cells are also attracting attention as one of them, and are the most promising power generation elements because of their characteristics of low pollution and high efficiency. A fuel cell is a cell in which a fuel such as hydrogen or methanol is electrochemically oxidized using oxygen or air to convert the chemical energy of the fuel into electric energy and to extract it.

Such fuel cells are classified into phosphoric acid type, molten carbonate type, solid oxide type and polymer electrolyte type depending on the type of electrolyte used. The phosphoric acid fuel cell is
It has already been put to practical use for electric power. However, the phosphoric acid fuel cell needs to be operated at a high temperature (around 200 ° C.), so that the startup time is long, it is difficult to downsize the system, and the proton conductivity of phosphoric acid is low. It has a drawback that it cannot take out an electric current.

On the other hand, the operating temperature of the polymer fuel cell is about 80 to 100 ° C. at the highest. Further, since the internal resistance in the fuel cell can be reduced by thinning the electrolyte membrane used, it is possible to operate at a high current, and therefore the size can be reduced. Due to these advantages, research on polymer fuel cells has been actively conducted.

The polymer electrolyte membrane used in this polymer fuel cell is required to have high ionic conductivity of protons involved in the electrode reaction of the fuel cell. As such an ion conductive polymer electrolyte membrane material, a super strong acid group-containing fluoropolymer such as Nafion (produced by DuPont) or Daw membrane (produced by Dow) is known. However, since these polyelectrolyte materials are fluorine-based polymers,
It has the problem of being very expensive. Moreover, since the glass transition temperature of these polymers is low and the water retention at around 100 ° C. which is the operating temperature is not sufficient, the ionic conductivity sharply decreases at a temperature of 100 ° C. or higher, and the polymer can function as a battery. There was a problem of disappearing.
Further, it cannot be applied to a direct methanol fuel cell due to its high methanol permeability.

In order to overcome these problems, many attempts have been made to introduce sulfonic acid groups into an engineering plastic such as polyimide having high heat resistance and chemical resistance to form an ion conductive membrane. In order to increase the proton conductivity of the ion conductive polymer electrolyte membrane, it is necessary to increase the sulfonation degree of the polymer and reduce the ion exchange group equivalent. However, increasing the amount of sulfonic acid groups in the polymer reduces the water resistance and methanol resistance of the polymer,
Problems such as polymer decomposition and dissolution in water and methanol occurred. For this reason, only the polyimide having a low sulfonation degree and a small proton conductivity can be applied to the fuel cell.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems of the prior art and has a high ionic conductivity, that is, a small ion exchange group equivalent and excellent water resistance and methanol resistance. Another object of the present invention is to provide a crosslinked polyimide having a protonic acid group, a polyimide precursor varnish as a raw material thereof, an ion conductive polymer membrane for a fuel cell, and a fuel cell, which are made of the crosslinked polyimide.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that 3 or 4 amino acids are added to a polyimide precursor varnish having a protonic acid group whose molecular chain terminal is dicarboxylic acid or its monoester. It has been found that by adding a compound having a group, it is possible to form a crosslinked structure composed of a strong imide bond between polyimide molecules only by a usual imidization reaction treatment. Further, they have found that the obtained protonic acid group-containing crosslinked polyimide has excellent ionic conductivity, excellent methanol resistance and methanol blocking property, and completed the present invention.

That is, the present invention provides the following [1] to [1]
[0]]. [1] A polyimide precursor containing a protonic acid group in the molecular chain and having a terminal of the molecular chain being a dicarboxylic acid or its monoester, and a compound having 3 or 4 amino groups in the molecule, Proton acid group-containing polyimide precursor varnish.

[2] The polyimide precursor is represented by the general formula (1)

[Chemical 9]

[In the general formula (1), Ar ¹ is

[Chemical 10] Is one of. A is a direct bond, -CH ₂ -, - C
_{(CH 3) 2 -, -} C (CF 3) 2 -, - O -, - SO 2 -
Alternatively, it represents -CO-. a and a ′ are integers of 0 or more and 2 or less, and a + a ′ is a number of 1 or more. M represents hydrogen, lithium, sodium or potassium. n is 0 or a positive integer of 2 or less. ] The repeating structural unit represented by,

General formula (2)

[Chemical 11] In [general formula (2), Ar ¹ is Ar ¹ means the same in formula (1). R ¹ is hydrogen, an alkyl group having 1 to 7 carbon atoms or an aromatic group. ] The protonic acid group-containing polyimide precursor varnish according to [1], which is a sulfonic acid group-containing polyamic acid having a molecular chain terminal represented by

[3] The polyimide precursor contains 20 to 99 mol% of the repeating structural unit represented by the general formula (1) based on all repeating structural units of the precursor, and the general formula (3).

[Chemical 12]

[0014] [Formula (3) was Ar ¹ has the same meaning as Ar ¹ in formula (1). Ar ² is

[Chemical 13] , B, B ′, and B ″ are each independently directly bonded, −
CH₂-, -C (CH₃) ₂-, -C (CF₃)₂-, -O
-, -SO₂-Or-CO-. 〕so
1 to 80 mol% of the repeating structural unit represented,
And having a chain end represented by the general formula (2)
Characterized by a polyamic acid containing a sulfonic acid group
Proton acid group-containing polyimide precursor crocodile according to [1]
Su.

[4] The compound having 3 or 4 amino groups is represented by the general formula (4)

[Chemical 14] [In general formula (4), h is 3 or 4. In general formula (4), h is 3 or 4.

R ² is

[Chemical 15] Is a trivalent or tetravalent group represented by. E is a direct _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (C
F ₃ ) ₂ —, —O— or —CO—. ]
The protonic acid group-containing polyimide precursor varnish according to [1], [2] or [3], which is a branched polyvalent amine compound represented by:

[5] The compound having 3 or 4 amino groups is represented by the general formula (5)

[Chemical 16] [In the general formula (5), G, G 'and G "are each independently a direct _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (C
F ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. i, j and k are each independently 0 or 1
Is. ] The protonic acid group-containing polyimide precursor varnish according to [1], [2] or [3], which is a linear polyvalent amine compound represented by

[6] A protonic acid group-containing crosslinked polyimide obtained by imidizing the protonic acid group-containing polyimide precursor varnish according to any one of [1] to [5].

[7] The method for producing a protonic acid group-containing crosslinked polyimide according to [6], wherein the imidization reaction method is a heat treatment, and the heat treatment temperature is 300 ° C. or lower.

[8] An ion-conducting polymer membrane for a fuel cell, comprising the protonic acid group-containing crosslinked polyimide according to [6].

[9] Ion exchange group equivalent is 1000 g /
The ion-conductive polymer membrane for a fuel cell according to the item [8], which has a solubility of not more than mol and a methanol solubility of less than 15 mass%.

[10] A fuel cell obtained by using the ion conductive polymer membrane for a fuel cell according to [8] or [9].

INDUSTRIAL APPLICABILITY The present invention can be produced under the same conditions as in the general production method of polyimide, and is excellent in heat resistance and chemical resistance, and is useful as a proton conductive membrane for a fuel cell and is useful as a proton conductive group-containing crosslinked polyimide. And a protonic acid group-containing polyimide precursor varnish which is a raw material thereof.

The ion conductive polymer film according to the present invention has high ion conductivity and is excellent in water resistance, solvent resistance and heat resistance. In particular, when a fuel cell is formed using the ion conductive polymer film according to the present invention, a fuel cell having excellent durability, low resistance and high current operation can be obtained.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The protonic acid group-containing crosslinked polyimide according to the present invention and the protonic acid group-containing polyimide precursor varnish as a raw material thereof will be specifically described below. In the present invention, a solution prepared by dissolving a polymer, particularly a polyimide precursor, in an organic solvent is called a varnish.

The protonic acid group-containing polyimide precursor varnish according to the present invention contains a protonic acid group in the molecular chain, and a polyimide precursor having a dicarboxylic acid or its monoester at the molecular chain end and 3 or It is characterized in that it contains a compound having four amino groups.

The protonic acid group-containing crosslinked polyimide according to the present invention contains a protonic acid group in the molecular chain, and a polyimide precursor having a dicarboxylic acid or a monoester thereof at the molecular chain end and 3 or Obtained from a protonic acid group-containing polyimide precursor varnish containing a compound having four amino groups.

The protonic acid group-containing polyimide precursor varnish of the present invention is prepared by adding water or alcohol to a raw material varnish of a protonic acid group-containing polyimide precursor whose molecular chain terminal is an acid anhydride group and terminating the acid anhydride group. To a dicarboxylic acid or a monoester thereof and then adding a compound having 3 or 4 amino groups. The varnish of the present invention is prepared by dissolving a solid protonic acid group-containing polyimide precursor having a dicarboxylic acid or its monoester at the molecular chain end and a compound having 3 or 4 amino groups in an organic solvent. I don't mind.

There is no particular limitation on the concentration of the protonic acid group-containing polyimide precursor whose molecular chain terminal contained in the varnish of the present invention is a dicarboxylic acid or its monoester, and the concentration is arbitrarily adjusted according to the storage stability and coating properties of the varnish. However, in order to obtain a good proton acid group-containing crosslinked polyimide thin film, the concentration of the polyimide precursor is 5 to 50 wt.
%, More preferably in the range of 10 to 40 wt%.

The varnish of the present invention contains a conventionally known imidized compound in addition to a proton acid group-containing polyimide precursor having a dicarboxylic acid or its monoester at the molecular chain end and a compound having 3 or 4 amino groups. It may contain a catalyst for promoting the reaction, a solvent for adjusting the viscosity and storage stability of the varnish, and the like.

The proton acid group-containing polyimide precursor contained in the proton acid group-containing polyimide precursor varnish in the present invention includes a sulfonic acid group, a carboxylic acid group, a phosphoric acid group or a proton acid of any one of these alkali metal salts. A polyamic acid containing a group, a polyamic acid ester,
Polyamic acid silyl ester, polyisoimide, polythioamido acid and the like can be mentioned, but sulfonic acid group or lithium, sodium or potassium salt of sulfonic acid is used as a protonic acid group due to the simplicity of the production method, the price of raw materials and the availability. The polyamic acid contained is most preferred.

A sulfonic acid group-containing polyamic acid and a method for producing the same will be described as a preferred example of the proton acid group-containing polyimide precursor having a dicarboxylic acid or its monoester at the molecular chain end in the present invention.

The sulfonic acid group-containing polyamic acid preferably has a molecular chain terminal comprising a repeating structural unit represented by the following general formula (1) and a dicarboxylic acid represented by the following general formula (2) or a monoester thereof. Have.

[0034]

[Chemical 17]

In the general formula (1), Ar ¹ is

[Chemical 18] Is one of. A is a direct bond, -CH ₂ -, - C
_{(CH 3) 2 -, -} C (CF 3) 2 -, - O -, - SO 2 -
Alternatively, it represents -CO-. a and a ′ are integers of 0 or more and 2 or less, and a + a ′ is a number of 1 or more. M represents hydrogen, lithium, sodium or potassium. n is 0 or a positive integer of 2 or less.

[0036] In the general formula (2), Ar ¹ has the same meaning as Ar ¹ in formula (1). R ¹ is hydrogen, an alkyl group having 1 to 7 carbon atoms or an aromatic group. Specific examples of R ¹ include methyl group, ethyl group, isopropyl group, isopropyl group, butyl group, 1-methylpropyl group, 2-methylpropyl group, 1,1-dimethylethyl group, pentyl group, 1
-Methylbutyl group, 1-ethylpropyl group, 2-methylbutyl group, 1,2-dimethylbutyl group, hexyl group, 1
-Methylpentyl group, 1-ethylbutyl group, cyclohexyl group, phenyl group, toluyl group, benzyl group and the like. The term "dicarboxylic acid or its monoester terminal 1 mol" as described below means 1 mol of the terminal structure represented by the general formula (2).

The sulfonic acid group-containing polyamic acid is
Preferably, the repeating structural unit represented by the general formula (1) is 20 to 99 mol%, and the repeating structural unit represented by the following general formula (3) is 1 to 80 mol% with respect to all the repeating structural units. More preferably, the repeating structural unit represented by the general formula (1) is 30 to 80 mol%, and the repeating structural unit represented by the following general formula (3) is 20 to 70.
It has a molecular chain terminal consisting of a dicarboxylic acid represented by the general formula (2) or a monoester thereof, which is composed of mol%. The arrangement of the repeating structural unit represented by the general formula (1) and the repeating structural unit represented by the general formula (3) may be random or block.

[0038]

[Chemical 19]

[0039] In the general formula (3), Ar ¹ has the same meaning as Ar ¹ in formula (1). Ar ² is

[Chemical 20] , B, B ′, and B ″ are each independently directly bonded, −
CH₂-, -C (CH₃) ₂-, -C (CF₃)₂-, -O
-, -SO₂Either-or-CO-.

The sulfonic acid group-containing polyamic acid having a molecular chain terminal composed of a dicarboxylic acid or a monoester thereof that can be used in the present invention is a carboxylic acid dianhydride containing less than an equivalent amount of a sulfonated aromatic diamine, Alternatively, it can be obtained by reacting a mixture of a sulfonated aromatic diamine and a general aromatic diamine, and further reacting the obtained sulfonic acid group-containing polyamic acid having an acid anhydride group as a terminal group with water or alcohol.

The method for producing the sulfonic acid group-containing polyamic acid having an acid anhydride group terminal is not particularly limited, and is represented by the sulfonated aromatic diamine represented by the following general formula (6) and the following general formula (7). Aromatic tetracarboxylic dianhydride,
Alternatively, a sulfonated aromatic diamine represented by the following general formula (6), a general aromatic diamine represented by the following general formula (8), and an aromatic tetracarboxylic dianhydride represented by the following general formula (7). The product can be obtained by reacting the product by a conventionally known method. Raw materials diamine, and the order of charging the aromatic tetracarboxylic dianhydride, the concentration of the reaction, the temperature, the time is not particularly limited, usually polyamic acid, nitrogen, under an inert gas atmosphere such as argon, It can be obtained by reacting a diamine compound and a tetracarboxylic dianhydride in an aprotic polar solvent at about 0 to 60 ° C. for several hours.

[0042]

[Chemical 21] In the general formula (6), A, n, M, a, and a ′ are the general formula (1).
It has the same meaning as A, n, M, a, and a '. Further, in the general formula (7), Ar ¹ has the same meaning as Ar ¹ in formula (1). Further, in the general formula (8), Ar ² is a general formula (3) the same meaning as Ar ² in.

Specific examples of the sulfonated aromatic diamine represented by the general formula (6) that can be used in the present invention include 2,5-diaminobenzenesulfonic acid and 2,4.
-Diaminobenzenesulfonic acid, 3,5-diaminobenzenesulfonic acid, 2,5-diaminobenzene-1,4-
Disulfonic acid, 4,6-diaminobenzene-1,3-disulfonic acid, 4,4'-diamino-2-biphenylsulfonic acid, 4,4'-diamino-3-biphenylsulfonic acid, 4,4'-diamino- 2,2'-biphenyldisulfonic acid, 4,4'-diamino-3,3'-biphenyldisulfonic acid, 2,2'-thiobis (5-aminobenzenesulfonic acid), 2,2'-sulfonbis (5-amino) Benzenesulfonic acid), 2,2'-oxybis (5-aminobenzenesulfonic acid), 2,2'-methylenebis (5
-Aminobenzenesulfonic acid), 2,2'-isopropylidene bis (5-aminobenzenesulfonic acid), 2,5
-Sodium diaminobenzenesulfonate, sodium 2,4-diaminobenzenesulfonate, sodium 3,5-diaminobenzenesulfonate, sodium 2,5-diaminobenzene-1,4-disulfonate, 4,6-diaminobenzene-1 , 3-sodium disulfonate,
Sodium 4,4'-diamino-2-biphenylsulfonate, sodium 4,4'-diamino-3-biphenylsulfonate, sodium 4,4'-diamino-2,2'-biphenyldisulfonate, 4,4'- Diamino
Sodium 3,3'-biphenyldisulfonate, 2,
2'-thiobis (sodium 5-aminobenzenesulfonate), 2,2'-sulfonebis (sodium 5-aminobenzenesulfonate), 2,2'-etherbis (5
-Sodium aminobenzenesulfonate), 2,2'-
Methylenebis (sodium 5-aminobenzenesulfonate), 2,2′-isopropylidenebis (sodium 5-aminobenzenesulfonate), potassium 2,5-diaminobenzenesulfonate, potassium 2,4-diaminobenzenesulfonate, 3 , 5-Diaminobenzenesulfonate, potassium 2,5-diaminobenzene-1,4-disulfonate, 4,6-diaminobenzene-1,3
-Potassium disulfonate, 4,4'-diamino-2-potassium biphenylsulfonate, 4,4'-diamino-3
-Potassium biphenyl sulfonate, 4,4'-diamino-2,2'-potassium biphenyl disulfonate, 4,
4'-diamino-3,3'-biphenyldisulfonic acid
Potassium, 2,2'-thiobis (potassium 5-aminobenzenesulfonate), 2,2'-sulfonebis (potassium 5-aminobenzenesulfonate), 2,2'-oxybis (potassium 5-aminobenzenesulfonate), Two
2'-methylenebis (potassium 5-aminobenzenesulfonate), 2,2'-isopropylidenebis (potassium 5-aminobenzenesulfonate), 2,2'-carbonylbis (5-aminobenzenesulfonate), 3, 3'-
Carbonylbis (6-aminobenzenesulfonic acid),
2,2'-Carbonylbis (sodium 5-aminobenzenesulfonate), 3,3'-Carbonylbis (sodium 6-aminobenzenesulfonate), 2,2'-Carbonylbis (potassium 5-aminobenzenesulfonate) 3,3′-Carbonylbis (6-aminobenzenesulfonate) 3,5-diamino-4-methylbenzenesulfonic acid, 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid, 4,4 '-Diamino-
5,5'-dimethyl-2,2'-biphenyldisulfonic acid, 4,4'-diamino-5,5'-diethyl-2,
2'-biphenyldisulfonic acid, 5,5'-diamino-
6,6'-Dimethyl-3,3'-biphenyldisulfonic acid, bis (4-amino-5-methyl-2-benzenesulfonic acid) methane, 2,2'-bis (4-amino-5-methyl-2) -Benzenesulfonic acid) propane, bis (4-
Amino-5-methyl-2-benzenesulfonic acid) sulfone, 4,4'-diamino-5,5'-dimethyl-2,
Sodium 2'-biphenyldisulfonate, 5,5'-
Sodium diamino-6,6′-dimethyl-3,3′-biphenyldisulfonate, bis (4-amino-5-methyl-2-sodium benzenesulfonate) methane, 2,
2'-bis (4-amino-5-methyl-2-sodium benzenesulfonate) propane, bis (4-amino-5)
-Sodium methyl-2-benzenesulfonate) sulfone, 4,4'-diamino-5,5'-dimethyl-2,
Potassium 2'-biphenyldisulfonate, potassium 5,5'-diamino-6,6'-dimethyl-3,3'-biphenyldisulfonate, bis (4-amino-5-methyl-
2-Benzenesulfonate potassium) methane, 2,2'-
Examples thereof include bis (4-amino-5-methyl-2-benzenesulfonic acid potassium) propane and bis (4-amino-5-methyl-2-benzenesulfonic acid potassium) sulfone. These sulfonated aromatic diamines can be used alone or in admixture of two or more.

Examples of the general aromatic diamine represented by the general formula (7) that can be used in the present invention include m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, 4,4′- Diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, bis (3
-Aminophenyl) sulfide, bis (4-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfide, bis (3-aminophenyl)
Sulfoxide, bis (4-aminophenyl) sulfoxide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) sulfone, bis (4-aminophenyl) sulfone, (3-aminophenyl) ( 4-aminophenyl) sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis ( 4-aminophenoxy) benzene, 1,3-bis (4
-Aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4 ' -Bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] Sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfoxide, bis [4- (4
-Aminophenoxy) phenyl] sulfoxide, bis [4
-(3-aminophenoxy) phenyl] sulfone, bis
[4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether,
Bis [4- (4-aminophenoxy) phenyl] ether, 3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4 ′ -Diamino-4,5'-
Diphenoxybenzophenone, 3,3'-diamino-4
-Phenoxybenzophenone, 4,4'-diamino-5
-Phenoxybenzophenone, 3,4'-diamino-4
-Phenoxybenzophenone, 3,4'-diamino-
5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4 '
-Diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5- Biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl , 2-trifluoromethyl-4,4'-diaminodiphenyl ether, 2'-trifluoromethyl-3,4'-diaminodiphenyl ether, 2,2-bis (3-aminophenyl) -1,1,1,3, 3,3-hexafluoropropane, 2,2-bis (4-aminophenyl) -1,1,
1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) -4-trifluoromethylbenzene, 1,3-bis (3-aminophenoxy) -5
-Trifluoromethylbenzene, 1,3-bis (3-amino-5-trifluoromethylphenoxy) benzene,
1,4-bis (3-amino-5-trifluoromethylphenoxy) benzene, 1,3-bis (3-amino-5-
Trifluoromethylphenoxy) -5-trifluoromethylbenzene, 1,3-bis (3-amino-5-trifluoromethylphenoxy) -4-trifluoromethylbenzene, 1,3-bis (4-amino-2-) Trifluoromethylphenoxy) benzene, 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene,
2,2-bis [4- (3-aminophenoxy) phenyl]
-1,1,1,3,3,3-hexafluoropropane,
2,2-bis [4- (4-aminophenoxy) phenyl]
Examples include -1,1,1,3,3,3-hexafluoropropane and the like. These general aromatic diamines may be used alone or in admixture of two or more.

The aromatic tetracarboxylic acid dianhydride represented by the general formula (8) that can be used in the production of the sulfonic acid group-containing polyamic acid according to the present invention is specifically pyromellitic acid dianhydride. Anhydrous, 3,3 ', 4,4'-
Biphenyltetracarboxylic dianhydride, 2,2 ', 3,
3'-biphenyltetracarboxylic dianhydride, 2,3
3 ', 4'-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,3,3', 4'-benzophenone tetracarboxylic dianhydride, bis (3 , 4-dicarboxyphenyl)
Sulfide dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1, 1, 1, 3, 3,
3-hexafluoro-2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4
4'-benzophenone tetracarboxylic acid dianhydride, 3-
Methyl-1,2,4,5-benzenetetracarboxylic dianhydride, 3-methyl-1,2,4,5-benzenetetracarboxylic dianhydride, 3,6-dimethyl-1,2,4,4
5-benzenetetracarboxylic dianhydride, 5,5'-dimethyl-3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, bis (5-methyl-3,4-dicarboxyphenyl) ether Dianhydride, bis (5-methyl-
3,4-dicarboxyphenyl) sulfide dianhydride,
Bis (5-methyl-3,4-dicarboxyphenyl) sulfone dianhydride, bis (5-methyl-3,4-dicarboxyphenyl) methane dianhydride, bis (5-methyl-)
3,4-dicarboxyphenyl) propane dianhydride,
1,1,1,3,3,3-hexafluoro-2,2-bis (5-methyl-3,4-dicarboxyphenyl) propane dianhydride, 2,3,6,7-tetramethyl-1 ，
Examples include 4,5,8-tetracarboxylic dianhydride. These aromatic tetracarboxylic dianhydrides can be used alone or in admixture of two or more.

The reaction solvent that can be used for the synthesis of the sulfonic acid group-containing polyamic acid is not particularly limited,
For example, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N,
N-dimethylmethoxyacetamide, N-methyl-2-
Pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphorotriamide, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxy) Ethoxy) ethane, tetrahydrofuran, bis [2-
(2-Methoxyethoxy) ethyl] ether, 1,4-
Any solvent that can be used for synthesizing conventional polyamic acid such as dioxane, dimethyl sulfoxide, dimethyl sulfone, diethyl sulfone, diphenyl ether, sulfolane, diphenyl sulfone, tetramethylurea and anisole can be used. These solvents may be used alone or in combination of two or more.

The sulfonic acid group-containing polyamic acid used in the present invention can be prepared by adjusting the total amount of diamine used.
It is possible to control the amount of the terminal acid anhydride group of the obtained sulfonic acid group-containing polyamic acid, the viscosity of the varnish, and the crosslink density (distance between crosslink points) of the crosslinked polyimide obtained therefrom.

In the synthesis of the sulfonic acid group-containing polyamic acid used in the present invention, it is preferable to use 0.8 to 0.99 mol of diamine per 1 mol of tetracarboxylic dianhydride. If the amount of diamine used is less than 0.8 mol, the strength of the polymer obtained will be low, and the coating film will tend to crack when the varnish is applied or imidized, which is not preferable. When the amount is more than 0.99 mols, the resulting sulfonic acid group-containing polyamic acid has extremely few acid anhydride group terminals,
It may not be able to be sufficiently crosslinked. When 1 mol of tetracarboxylic dianhydride and α mol of diamine are used, the amount of terminal acid anhydride of the obtained sulfonic acid group-containing polyamic acid is (1-α) × 2 mol.

Next, there will be described a method of reacting a sulfonic acid group-containing polyamic acid having an acid anhydride group terminal with water or an alcohol to form a terminal group of dicarboxylic acid or its monoester.

The acid anhydride group-terminated sulfonic acid group-containing polyamic acid used in the present invention may be synthesized in a solvent and remain dissolved in the solvent, or it may be precipitated in a poor solvent to give a solid state. It may be one that has been made.

The sulfonic acid group-containing polyamic acid of which the molecular chain end is a dicarboxylic acid or its monoester of the present invention is hydrolyzed by adding water or alcohol to the polyamic acid whose molecular chain end is an acid anhydride group. The reaction proceeds and can be obtained. Regarding this hydrolysis reaction mechanism, it is expected that the acid anhydride group at the terminal of the molecular chain directly proceeds with water or alcohol or by the reaction formula shown below (where X is a sulfonic acid group-containing group). Diamine-derived main chain part of polyamic acid, Y is main chain part of tetracarboxylic acid dianhydride of sulfonic acid group-containing polyamic acid, R represents hydrogen or hydrocarbon group having 1 to 10 carbon atoms or aromatic group ).

[0052]

[Chemical formula 22]

First, by adding water or alcohol to a sulfonic acid group-containing polyamic acid whose molecular chain end is an acid anhydride, the amide bond in the sulfonic acid group-containing polyamic acid main chain is hydrolyzed and the main chain is cleaved. Thus, two kinds of sulfonic acid group-containing polyamic acid having an amino group and an acid anhydride group at the terminal and dicarboxylic acid or its monoester having a terminal and a sulfonic acid group-containing polyamic acid having an acid anhydride group at the terminal are produced. Next, it is expected that the amino group end generated and the acid anhydride end originally present undergo an amidation reaction, and as a result, a sulfonic acid group-containing polyamic acid whose molecular chain end is a dicarboxylic acid or its monoester is formed.

Examples of the compound that can be used to hydrolyze the sulfonic acid group-containing polyamic acid having an acid anhydride group terminal include, for example, water, methanol, ethanol, 1-propanol, 2-propanol, 1- Butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 2-methyl-2. -Butanol, 1-
Hexanol, 2-hexanol, 3-hexanol,
Examples thereof include cyclohexanol, phenol, cresol, benzyl alcohol and the like. These water and / or alcohol may be used alone or in admixture of two or more.

In the present invention, it is preferable to use 1 to 2 mol of water and / or alcohol for 1 mol of the terminal acid anhydride group. When the amount of water and / or alcohol used is small, the hydrolysis reaction does not proceed sufficiently, so that an acid anhydride group remains at the terminal of the sulfonic acid group-containing polyamic acid and a compound having 3 or 4 amino groups to be added later. Reacts easily and crosslinks, resulting in gelation. Further, when a large amount of water and / or alcohol is used, the amide bond in the sulfonic acid group-containing polyamic acid main chain is hydrolyzed more than necessary, resulting in an excess of amino groups that cannot undergo amidation reaction with the acid anhydride group terminal. Ends are generated,
This may lead to a decrease in molecular weight.

The molecular weight of the sulfonic acid group-containing polyamic acid of which the molecular chain terminal of the present invention is a dicarboxylic acid or its monoester is not particularly limited, and may be arbitrarily selected depending on the viscosity of the varnish and the physical properties of the crosslinked polyimide obtained therefrom. However, when the logarithmic viscosity is shown, it is 0.
It is preferably in the range of 3 to 2.0 dl / g (measured in N, N-dimethylacetamide at a concentration of 0.5 g / dl at 35 ° C.). If the logarithmic viscosity is lower than 0.3 and is too low, the strength of the polymer is low, and the coating film may be cracked when a varnish is applied and imidized. Also, 2.0
When it is too high, the number of terminal carboxylic acid groups and / or its monoester groups of the polyamic acid obtained is extremely small, so that it becomes difficult to obtain the effect of improving the physical properties by crosslinking.

Next, 3 contained in the varnish of the present invention
Alternatively, a compound having four amino groups will be described.

The compound having 3 or 4 amino groups in the present invention is a branched polyvalent amine compound represented by the following general formula (3) or a linear polyvalent amine represented by the following general formula (4). Compounds.

[0059]

[Chemical formula 23]

In the general formula (4), h is 3 or 4. R ² is

[Chemical formula 24] Is a trivalent or tetravalent group represented by. E is a direct _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (C
F ₃ ) ₂ —, —O— or —CO—. Further, in the general formula (5), G, G ′, and G ″ are each independently a direct bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C.
_{(CF 3) 2 -, -} O -, - it is or -CO- either - SO _2. i, j and k are each independently 0 or 1.

Specific examples of the branched polyvalent amine compound represented by the general formula (4) include, for example, tris (4-aminophenyl) methane and tris (3-aminophenyl).
Methane, tris (4-aminophenyl) methyl alcohol, tris (4-aminophenyl)) amine, N, N,
N ', N'-tetrakis (4-aminophenylbenzidine), N, N, N', N'-tetrakis (3-aminophenylbenzidine), 1,3,5-tris (4'-aminophenoxy) benzene, 1,3,5-Tris (3'-
Aminophenoxy) benzene, 1,3,5-tris (3′-aminobenzyl) benzene, 1,3,5-tris (4′-aminobenzyl) benzene, 1,3,5-tris (4′-aminobenzoyl) ) Benzene, 1,3,5
-Tris (1- (4'-aminophenyl) -1-methylethyl) benzene and the like can be mentioned. Specific examples of the linear polyvalent amine compound represented by the general formula (4) include, for example, 3,3 ′, 4-triaminobiphenyl,
3,4,4'-triaminobiphenyl, 3,3 ', 5-
Triaminobiphenyl, 3,3 ', 4,4'-tetraaminobiphenyl, 3,3', 5,5'-tetraaminobiphenyl, 3,3 ', 4-triaminodiphenyl ether, 3,3', 4 4'-tetraaminodiphenyl ether, 3,3 ', 5,5'-tetraaminodiphenyl ether, 3,3', 4-triaminodiphenylmethane,
3,3 ', 4,4'-tetraaminodiphenylmethane,
3,3 ', 5,5'-tetraaminodiphenylmethane,
3,3 ', 4-triaminobenzophenone, 3,3',
4,4'-tetraaminobenzophenone, 3,3 ',
5,5'-tetraaminobenzophenone, 3,3 ', 4
-Triaminodiphenyl sulfone, 3,3 ', 4,4'
-Tetraaminodiphenyl sulfone, (3,4-aminophenyl) (3-aminophenyl) sulfone, 2,2-
Bis (3 ', 4'-diaminophenyl) propane, 2,
2-bis (3 ', 5'-diaminophenyl) propane,
2,2-bis (3 ′, 4′-diaminophenyl) hexafluoropropane, 3,5-bis (3′-aminophenoxy) aniline, 3,5-bis (3′-aminobenzyl) aniline, 3,3 '-Bis (3 "-aminophenoxy) -5,5'-diaminobiphenyl, 3,3'-bis (3" -aminophenoxy) -5,5'-diaminodiphenyl ether, 3,3'-bis (3 " -Aminophenoxy) -5,5'-diaminobenzophenone, 3,3 '
-Bis (3 "-aminobenzyl) -5,5'-diaminodiphenyl ether, etc. These compounds having 3 or 4 amino groups may be used alone or in combination of two or more kinds. I can.

In the present invention, the amount of the compound having 3 or 4 amino groups is 0.2 to 1.0 with respect to 1 mol of the dicarboxylic acid of the sulfonic acid group-containing polyamic acid or its monoester terminal group. Mol, preferably 0.
It is 3 to 0.7 mol. When the amount of the compound used is large or small, the ratio of uncrosslinked molecular chains in the obtained polyimide is large, and the effect of improving heat resistance and chemical resistance tends to be small.

Further, since the sulfonic acid group-containing polyamic acid having a dicarboxylic acid or its monoester at the molecular chain end does not react with a compound having 3 or 4 amino groups at the molecular chain end, the varnish is gelled. It can be stably stored and stored without becoming solid. However, under the reaction conditions for desolvating and imidizing the varnish, the dicarboxylic acid at the terminal of the molecular chain or its monoester is dehydrated or dealcoholized and converted into an acid anhydride group having high reactivity with an amino group. The acid anhydride group at the terminal of this molecular chain reacts with the amino group of the compound having 3 or 4 amino groups to form an imide bond through an amic acid bond, whereby the polymer ends are cross-linked.

When the terminal of the molecular chain is an acid anhydride group, the terminal of the molecular chain of the sulfonic acid group-containing polyamic acid reacts with the amino group of the compound having 3 or 4 amino groups at room temperature to form an amic acid bond. Is formed. A sulfonic acid group-containing polyamic acid having an acid anhydride group at the molecular chain end is not preferable because the varnish gels due to this bond formation.

Since the sulfonic acid group-containing polyamic acid contained in the varnish of the present invention is a straight chain having no cross-linking site, it can be handled in the same manner as ordinary polyamic acid varnish, that is, cast, cast or the like. Further, since a crosslinked structure is formed at the same time as the imidization by heat treatment for ordinary imidization, a protonic acid group-containing crosslinked polyimide can be obtained under the conventionally known production conditions for a linear polyimide.

The polyimide obtained by imidizing the varnish of the present invention and the imidization reaction method thereof will be described below.

The proton acid group-containing crosslinked polyimide of the present invention is a molecular chain represented by the general formula (2) of a polyimide precursor having a repeating structural unit having a sulfonic acid group represented by the following general formula (9). It is a polyimide having a crosslinked structure due to the reaction between the terminal and the amino group of the compound having 3 or 4 amino groups represented by the general formula (4) or (5) to form an imide bond.

[0068]

[Chemical 25] In the general formula ^{(9), Ar 1, n} , A, M, a and a 'is Ar ^1, n in the general formula (1), A, M, a and a'
Is the same meaning as.

Further, the protonic acid group-containing crosslinked polyimide of the present invention contains 20 to 99 mol% of the repeating structural unit having a sulfonic acid group represented by the general formula (9) with respect to all repeating structural units of the polymer, The repeating structural unit represented by the following general formula (10) is contained in an amount of 1 to 80 mol%, and the molecular chain terminal represented by the general formula (2) and the general formula (4) are contained.
Alternatively, it is a polyimide having a crosslinked structure formed by reacting with an amino group of a compound having 3 or 4 amino groups represented by (5) to form an imide bond.

[0070]

[Chemical formula 26] In the general formula (10), Ar ¹ has the same meaning as Ar ¹ in formula (1). Ar ² has the same meaning as Ar ^{2 in} formula (3).

The crosslinked polyimide of the present invention exhibits higher chemical resistance than conventional linear polyimides having no crosslinked structure. Furthermore, the crosslinked polyimide of the present invention can have higher mechanical strength and methanol blocking property than a polyimide having no crosslinked structure.

The protonic acid group-containing crosslinked polyimide of the present invention is the varnish of the present invention, which is an imidization reaction of a protonic acid group-containing polyamic acid whose molecular chain end is a dicarboxylic acid or its monoester, and 3 or 4 amino acids. It can be obtained by reacting a compound having a group with a polyamide terminal. In the present invention, the imidization reaction method is not particularly limited, and a conventionally known chemical or thermal imidization reaction method can be used. As a known imidization reaction method, for example, a method in which a varnish applied on a base material is dried with hot air, a cast film is peeled from the base material, and further heat treatment is performed at a high temperature, a high temperature while the cast film is attached to the base material is used. And a method of chemically immersing in a dehydrating agent such as acetic anhydride to chemically dehydrate and imidize.

When a proton acid group-containing crosslinked polyimide is produced by thermal imidization of a film obtained by casting the varnish of the present invention, the imidization reaction conditions are those of ordinary polyamic acid thermal imidization reaction conditions. Is sufficient, and further high temperature treatment for cross-linking and long-time annealing treatment are not necessary. Although the temperature during the thermal imidization reaction is not limited, it is particularly preferably 300 ° C. or lower in order to suppress deterioration of the resulting protonic acid group-containing crosslinked polyimide due to oxidation or the like.

The sulfonic acid group at the time of the thermal imidization reaction may be of a protic acid type, but when heated to 200 ° C. or higher, it may be of a lithium, sodium or potassium metal salt type in order to suppress elimination of the sulfonic acid group. preferable.

The ion-conducting polymer film of the present invention is a protonic acid group-containing crosslinked polyimide film obtained by imidizing the cast film obtained from the above varnish. The thickness of the ion conductive polymer film is not particularly limited, but is 10 to 100 μm,
Particularly, 30 to 80 μm is preferable. Within the above range, the mechanical strength of the film that can withstand practical use can be obtained, and the film resistance can be reduced to a level that is practically sufficient, that is, sufficient power generation performance can be obtained. The film thickness can be controlled by the concentration of the protonic acid group-containing polyamic acid contained in the varnish or the coating thickness on the substrate.

The ion exchange group equivalent of the preferred ion conductive polymer membrane varies depending on the type and use of the fuel cell, but is usually 1000 g / mol or less, preferably 250 to 950.
It is g / mol. When used as an ion-conductive polymer membrane, the sulfonic acid group state of the protonic acid group-containing crosslinked polyimide is preferably a free protonic acid state having the highest proton conductivity.

Next, a fuel cell obtained by using the ion conductive polymer membrane of the present invention will be described. The fuel cell according to the present invention can be roughly classified into a general polymer electrolyte fuel cell (PEMFC) using hydrogen as a fuel and a direct methanol polymer electrolyte fuel cell (DMFC) using methanol as a fuel. It can be manufactured by a known method of bonding a conductive substance as a catalyst for an electrode and a current collector to both surfaces of a conductive polymer film.

The PEMFC electrode catalyst is not particularly limited as long as it can activate the redox reaction of hydrogen and oxygen, and known ones can be used. It is preferable to use fine particles. Platinum fine particles are often used by being supported on particulate or fibrous carbon such as activated carbon or graphite. Known materials can be used for the conductive substance as the current collector, but a porous carbon nonwoven fabric or carbon paper is preferable for efficiently transporting the raw material gas to the catalyst.

In the case of DMFC, a known catalyst can be used as the electrode catalyst. For example, as the catalyst for the methanol electrode, a platinum catalyst, an alloy catalyst such as a platinum-ruthenium alloy or a platinum-tin alloy, or a supported catalyst in which fine particles of these catalysts are dispersed and supported on a carrier such as carbon is used. As the catalyst for the air electrode, platinum fine particles similar to PEMFC are used. As the conductive material as the current collector, a known material such as porous carbon nonwoven fabric or carbon paper can be used as in the PEMFC.

As a method for producing a bonded body of a gas diffusion electrode and an ion conductive polymer membrane, a method of directly forming a gas diffusion electrode on the ion conductive polymer membrane, a PTFE (polytetrafluoroethylene) film or the like is used. A method in which a gas diffusion electrode is once formed into a layer on a substrate and then transferred to an ion exchange membrane, a method in which a gas diffusion electrode and an ion conductive polymer membrane are hot-pressed, and a method in which they are adhered to each other with an adhesive liquid Various known methods can be applied.

The fuel cell of the present invention is less expensive to manufacture than a conventional fuel cell using expensive perfluorocarbon sulfonic acid. Further, since the protonic acid group-containing crosslinked polyimide film of the present invention has higher heat resistance than conventional perfluorocarbon sulfonic acid, it can be used at high temperature. Furthermore, since the protonic acid group-containing crosslinked polyimide membrane of the present invention has a small ion exchange group equivalent, it has a high ionic conductivity, so that a fuel cell capable of operating at high current can be manufactured.

[0082]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. The test methods for various tests in the examples are as follows. (B) Logarithmic viscosity of polymer The polymer varnish was diluted with dimethylacetamide (DMAc) so that the polymer concentration was 0.005 g / ml, and measured with an Ubbelohde viscometer at 35 ° C.

(B) Proton exchange The metal salt of protonic acid was returned to free protonic acid by the following method. 1) The proton acid group-containing polyimide film was immersed in 2N sulfuric acid overnight.
2) The acid-treated membrane was immersed in distilled water overnight. 3) Dry the acid treated and distilled water washed membrane at 150 ° C. for 4 hours,
A film containing free protic acid was obtained.

(C) Ion conductivity The width of the ion conductive membrane is 5 m.
m, length 40 mm, cut out, placed on a polytetrafluoroethylene (PTFE) holder, pressure-contacted four electrodes, and measured the resistivity from the arc of the Cole-Cole plot obtained by the AC impedance method in the 4-terminal method. It was measured. The distance between the voltage terminals was 20 mm. The impedance was measured using an LCR meter (3532 manufactured by Hioki Electric Co., Ltd.). The temperature change is carried out by placing the sample with the electrode connected in a thermostat made of aluminum block.
The conductivity was measured in the range of ℃ to 110 ℃. All measurements were carried out under humidification, but this humidification was carried out by introducing steam into a thermostatic chamber at atmospheric pressure, and the temperature measured by the steam generator was 100
Distilled water was heated to a constant temperature of a constant temperature bath temperature of + 5 ° C. when the measured temperature was lower than 100 ° C., and 120 ° C. when the measured temperature was 100 ° C. or higher. Further, the film thickness required for calculation of ionic conductivity was measured in a dry state using a micrometer.

(D) Methanol solubility The ion conductive membrane dried at 150 ° C. for 4 hours was immersed in methanol and allowed to stand at 25 ° C. for 24 hours. Take out the ion exchange membrane again 15
After drying at 0 ° C. for 4 hours, the weight loss rate was measured.
(E) Methanol permeability Distilled water at room temperature and 1 mol /
L 3 aqueous methanol solution was contacted via a proton conductive membrane having a diameter of 23 mmφ, and the change in methanol concentration on the distilled water side for up to 3 hours was measured by gas chromatography. The methanol permeability was calculated from the slope of the obtained methanol concentration increase straight line.

(F) Ion-exchange group equivalents The sulfonated photocurable film was precisely weighed in a glass container capable of being sealed, an excess amount of calcium chloride aqueous solution was added thereto, and the mixture was stirred overnight. The hydrogen chloride generated in the system was titrated with a 0.1N sodium hydroxide standard aqueous solution using a phenolphthalein indicator and calculated.

(Synthesis Example 1) 30 ml of aniline and 10.36 g (80 mmol) of aniline hydrochloride were added to a 100 ml three-neck reaction vessel under a nitrogen atmosphere and the temperature was raised to 150 ° C. Purity 75% by mass 1,3,5 while stirring in the reaction solution
-Tris (1-chloro-1-methylethyl) benzene
After adding 5.0 g (12.2 mmol) at 150 ℃, 180 ℃
It was stirred for 5 hours. The reaction solution was cooled to 150 ° C. and added to a mixed solvent of 200 ml of hexane and 400 ml of ethyl acetate to precipitate crystals. After cooling to 15 ° C,
The crystals were filtered off. The aniline hydrochloride was removed by reslurrying the obtained crystals in 200 ml of water. The crystals were separated by filtration, dispersed in a mixed solution of 50 ml of ethyl acetate and 50 ml of water, and neutralized with a 10% aqueous sodium hydroxide solution. After separating the organic phase, the solvent was concentrated. Recrystallization was performed using hexane to obtain 1,3,5-
3.88 g of tris (1- (4-aminophenyl) -1-methylethyl) benzene (purity 98% by mass, 8.1 mmol,
Isolation yield 66%) was obtained. The physical properties of the target product are as follows.

Melting point 143.3-143.8 ° C. ¹ H-NMR (CDCl ₃ ).
δ: 1.52 (s, 18H), 3.53 (br, 6H), 6.55 (dd, 6H, J =
8.6, 1.9 Hz), 6.89 (s, 3H), 6.91 (dd, 6H, J = 8.
6, 1.9 Hz) FD-mass 477 (M ⁺ )

[0089]

[Chemical 27]

Example 1 A 300 ml five-necked reactor equipped with a nitrogen inlet tube, a thermometer and a stirrer was charged with 4,4 ′.
-Diamino-2,2'-diphenyldisulfonic acid sodium salt 11.65 g (30.0 mmol) and 4,
3.50 g of 4'-diaminodiphenyl (19.0 mmo
1) and DMAc (50.70 g) were charged and the mixture was stirred at room temperature to dissolve the diamine. Subsequently, 13.41 g (50 mmo) of 1,4,5,8-naphthalenetetracarboxylic dianhydride.
34.99 g of dimethylacetamide (DMAc)
It was charged with the mixture and stirred at room temperature for 24 hours. The resulting 25 wt% acid anhydride group-terminated sulfonic acid group-containing polyamic acid varnish had a logarithmic viscosity η of 0.86 dl / g (DMA
c, 35 ° C).

In a flask equipped with a stirrer and a nitrogen introducing tube,
57.12 g of the obtained acid anhydride group-terminated sulfonic acid group-containing polyamic acid varnish (equivalent to 14.28 g of polyamic acid and 1 mmol of acid anhydride group at the molecular chain end) and methanol 1
14.28 g of N, N-dimethylacetamide
The solution diluted with was charged and hydrolyzed by stirring for 6 hours under a nitrogen atmosphere to obtain a sulfonic acid group-containing polyamic acid having a dicarboxylic acid or its methyl ester at the molecular chain end. The sulfonic acid group-containing polyamic acid in the obtained varnish had an inherent viscosity η of 0.84 dl / g.

Next, 0.15 g (0.33 mmol) of 1,3,5-tris (1- (4-aminophenyl) -1-methylethyl) benzene obtained in Synthesis Example 1 was charged, and nitrogen was added. The mixture was stirred in the atmosphere for 6 hours and dissolved to obtain the varnish of the present invention. The sulfonic acid group-containing polyamic acid in the obtained varnish had an inherent viscosity η of 0.88 dl / g.

The obtained polyamic acid varnish containing 20 wt% sulfonic acid group was coated on a glass plate, and the temperature was raised from room temperature to 250 ° C. in an inert oven under a nitrogen atmosphere at normal pressure.
The temperature was raised over time, and the temperature was maintained at 250 ° C. for 4 hours to remove DMAc, imidize and crosslink. The glass plate was immersed in water to remove the sulfonic acid group-containing crosslinked polyimide film, and the sulfonic acid was returned to the free protonic acid type from the sodium salt type by the method described in (b). The obtained film was flexible and tough. About this membrane
Ionic conductivity was measured by the method described in (c), methanol solubility was measured by the method described in (d), methanol permeability was measured by the method described in (e), and ion exchange group equivalent was measured by the method described in (f).
The measurement results are shown in Table 1.

Example 2 3.32 g (18.0 mmol) of 4,4'-diaminodiphenyl and 2 of methanol were added.
mmol, 0.31 g of 1,3,5-tris (1- (4-aminophenyl) -1-methylethyl) benzene
A varnish of the present invention was obtained in the same manner as in Example 1 except that (0.67 mmol) was used. The logarithmic viscosity η of the sulfonic acid group-containing polyamic acid in the varnish was 0.76 dl / g. A sulfonic acid group-containing crosslinked polyimide membrane was prepared in the same manner as in Example 1, and various measurements were carried out after ion exchange with a protonic acid type by the method described in (b). The results are shown in Table 1.

(Example 3) 4,63 '(18 mmol) of 4,4'-bis (3-aminophenoxy) biphenyl was used in place of 4,4'-diaminodiphenylsulfone, and 60.60 as DMAc for dissolving a diamine compound. 0
A sulfonic acid group-containing polyamic acid varnish having an acid anhydride group terminal was synthesized in the same manner as in Example 1 except that 7 g was used.

Then, in the same manner as in Example 2, the obtained sulfonic acid group-containing polyamic acid varnish 6 having an acid anhydride group terminal was obtained.
3.38 g (corresponding to 15.85 g of polyamic acid and 2 mmol of acid anhydride group at the molecular chain end) was reacted with 2 mmol of methanol to obtain a polyamic acid whose molecular chain end was dicarboxylic acid or its methyl ester. The sulfonic acid group-containing polyamic acid in the obtained varnish had a logarithmic viscosity η of 0.98.
It was dl / g. A sulfonic acid group-containing crosslinked polyimide membrane was prepared in the same manner as in Example 1, and various measurements were carried out after ion exchange with a protonic acid type by the method described in (b). The results are shown in Table 1.

(Example 4) 4,4'-diamino-2,
2'-diphenyldisulfonic acid sodium salt was added to 18.6
4 g (48.0 mmol), D for dissolving the diamine without using 4,4′-diaminodiphenyl sulfone
A sulfonic acid group-containing polyamic acid varnish having an acid anhydride group terminal was synthesized in the same manner as in Example 1 except that the amount of MAc was 61.13 g.

Then, in the same manner as in Example 2, the sulfonic acid group-containing polyamic acid varnish 6 having an acid anhydride group terminal was obtained.
4.08 g (equivalent to 16.02 g of polyamic acid and 2 mmol of acid anhydride group at the terminal of the molecular chain) was reacted with 2 mmol of methanol to obtain a polyamic acid having a molecular end of dicarboxylic acid or its methyl ester. The logarithmic viscosity η of the sulfonic acid group-containing polyamic acid in the obtained varnish was 0.69.
It was dl / g. A sulfonic acid group-containing crosslinked polyimide membrane was prepared in the same manner as in Example 1, and various measurements were carried out after ion exchange with a protonic acid type by the method described in (b). The results are shown in Table 1.

(Example 5) 1,3,5-tris (1-
Varnish of the present invention in the same manner as in Example 1 except that 0.07 g (0.33 mmol) of 3,4 ′, 4-triaminodiphenyl ether was used instead of (4-aminophenyl) -1-methylethyl) benzene. Got Logarithmic viscosity η of sulfonic acid group-containing polyamic acid in varnish is 0.82
It was dl / g. A sulfonic acid group-containing crosslinked polyimide membrane was prepared in the same manner as in Example 1, and various measurements were carried out after ion exchange with a protonic acid type by the method described in (b). The results are shown in Table 1.

Example 6 A varnish of the present invention was obtained in the same manner as in Example 1 except that 1 mmol of water was used instead of 1 mmol of methanol. The sulfonic acid group-containing polyamic acid in the obtained varnish had an inherent viscosity η of 0.87 dl /
It was g. A sulfonic acid group-containing crosslinked polyimide film was obtained in the same manner as in Example 1. Table 1 shows various measurement results.
(Example 7)

Water 2 mm instead of methanol 2 mmol
A varnish of the present invention was obtained in the same manner as in Example 2 except that ol was used. The sulfonic acid group-containing polyamic acid in the obtained varnish had an inherent viscosity η of 0.74 dl / g. A sulfonic acid group-containing crosslinked polyimide film was obtained in the same manner as in Example 1. Table 1 shows various measurement results.

(Comparative Example 1) 1,3,5-tris (1-
A varnish was prepared in the same manner as in Example 1 except that (4-aminophenyl) -1-methylethyl) benzene was not used. In the same manner as in Example 1, the varnish was cast on a glass plate and heated to a curing temperature of 250 ° C. for 4 hours under a nitrogen stream to remove the solvent and imidize the varnish. Table 1 shows various measurement results of the obtained sulfonic acid group-containing crosslinked polyimide film.

Comparative Example 2 A varnish was prepared in the same manner as in Example 1 except that methanol was not used. As a result, 1,3,5-tris (1- (4-aminophenyl) obtained in Synthesis Example 1 was obtained. ) -1-Methylethyl) benzene was charged,
When stirring was carried out under a nitrogen atmosphere, the viscosity was remarkably increased in a short time and the stirring became impossible. It was considered that the polyamic acid was crosslinked, and the reaction product was gelled in a jelly form.

Comparative Example 3 A polyamic acid varnish was synthesized in the same manner as in Example 1 except that the charged amount of 4,4′-diaminobiphenyl was changed to 3.68 g (20 mmol). The polyamic acid in the obtained varnish had an inherent viscosity η of 0.92 dl / g. A polyimide film was obtained in the same manner as in Example 1. Table 1 shows various measurement results.

Comparative Example 4 Nafion (registered trademark) membrane (A
The ionic conductivity, methanol solubility, and methanol permeability were measured in the same manner as in Example 1 using a reagent from ldrich). Table 1 shows various measurement results.

[0106]

[Table 1]

It is apparent that Examples 1 to 7 have a lower methanol solubility, that is, a significantly improved methanol resistance, as compared with the non-heat-crosslinked polymers of Comparative Examples 1 and 3.
Also, it can be seen that the ionic conductivity is on the same order as that of the Nafion (registered trademark) membrane of Comparative Example 4, but the methanol permeability is low.

[0108]

EFFECTS OF THE INVENTION By using the varnish of the present invention, it is possible to provide a fuel cell having excellent durability, low resistance and high current operation, high ionic conductivity, and excellent methanol resistance and methanol barrier property. Provided is an ion-conducting polymer film composed of a crosslinked polyimide containing a protonic acid group. Furthermore, an excellent fuel cell using the same is provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takehiko Omi             580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals, Inc.             Inside the company (72) Inventor Masashi Tamai             580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals, Inc.             Inside the company F term (reference) 5H026 AA08 BB10 CX05 EE17 HH05                       HH08

Claims (10)

[Claims] 1. A polyimide precursor containing a protonic acid group in the molecular chain and having a dicarboxylic acid or a monoester thereof at the molecular chain end, and a compound having 3 or 4 amino groups in the molecule. A polyimide precursor varnish containing a protonic acid group, characterized in that 2. The polyimide precursor is represented by the general formula (1): [In the general formula (1), Ar ¹ is Is one of. A is a direct bond, -CH ₂ -, - C
_{(CH 3) 2 -, -} C (CF 3) 2 -, - O -, - SO 2 -
Alternatively, it represents -CO-. a and a ′ are integers of 0 or more and 2 or less, and a + a ′ is a number of 1 or more. M represents hydrogen, lithium, sodium or potassium. n is 0 or a positive integer of 2 or less. ] And a repeating structural unit represented by the general formula (2): In [general formula (2), Ar ¹ is Ar ¹ means the same in formula (1). R ¹ is hydrogen, an alkyl group having 1 to 7 carbon atoms or an aromatic group. ] The protonic acid group-containing polyimide precursor varnish according to claim 1, which is a sulfonic acid group-containing polyamic acid having a molecular chain terminal represented by 3. The polyimide precursor is a full repeat of the precursor.
It is represented by the general formula (1) with respect to the repeating structural unit.
20-99 mol% of repeating structural units, and general formula
(3) [Chemical 4] [Ar in the general formula (3)¹Is Ar of the general formula (1)¹Same meaning as
The taste. Ar²Is [Chemical 5] , B, B ′, and B ″ are each independently directly bonded, −
CH₂-, -C (CH₃) ₂-, -C (CF₃)₂-, -O
-, -SO₂Either-or-CO-. 〕so
Consisting of 1 to 80 mol% of the repeating structural unit represented,
Which has a molecular chain end represented by the general formula (2)
A contract characterized by being a polyamic acid containing a rufonic acid group
Proton acid group-containing polyimide precursor crocodile according to claim 1
Su. 4. The compound having 3 or 4 amino groups is represented by the general formula (4): [In general formula (4), h is 3 or 4. R ² is Is a trivalent or tetravalent group represented by. E is a direct _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (C
F ₃ ) ₂ —, —O— or —CO—. ]
A protonic acid group-containing polyimide precursor varnish according to claim 1, 2 or 3, which is a branched polyvalent amine compound represented by: 5. The compound having 3 or 4 amino groups is represented by the general formula (5): [In the general formula (5), G, G 'and G "are each independently a direct _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (C
F ₃ ) ₂ —, —O—, —SO ₂ — or —CO—. i, j and k are each independently 0 or 1
Is. ] The protonic acid group-containing polyimide precursor varnish according to claim 1, 2 or 3, which is a linear polyvalent amine compound represented by the following formula. 6. A protonic acid group-containing crosslinked polyimide obtained by imidizing the protonic acid group-containing polyimide precursor varnish according to claim 1. 7. The method for producing a protonic acid group-containing crosslinked polyimide according to claim 6, wherein the imidization reaction method is a heat treatment, and the heat treatment temperature is 300 ° C. or lower. 8. An ion conductive polymer membrane for a fuel cell, which comprises the crosslinked polyimide containing a protonic acid group according to claim 6. 9. The ion conductive polymer membrane for a fuel cell according to claim 8, which has an ion exchange group equivalent of 1000 g / mol or less and a methanol solubility of less than 15% by mass. 10. A fuel cell obtained by using the ion conductive polymer membrane for a fuel cell according to claim 8.