JP2006070116A - Sulfonated aromatic polyimide and electrolyte membrane made from the polyimide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide which is a new bonded-sulfo-containing polyimide suitable for, e.g., solid electrolyte substances, especially cation exchangers, electrolysis diaphragms, and fuel cell electrolyte membranes which undergo less deterioration in mechanical strength and ion exchange capacity than those made from known polyimides. <P>SOLUTION: The polyimide has no sulfo groups in the main chain and has sulfo groups in side chains and is prepared by using as a constituent diamine compound monomer for the polyimide a compound which is a diamino aromatic carbonyl compound and has a directly or indirectly sulfo-substituted aromatic ring bonded through the carbonyl group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to sulfonated aromatic polyimides. The electrolyte membrane is made of the polyimide.

  Polyimide is used as a general molding resin in general materials such as films, sheets, synthetic fibers, molded products, hollow fibers, and electronic materials, and those having various functional groups are also used in gas separation membrane fields. It is used in the field of medical device materials.

  Among them, a polyimide having an ion exchange group such as a sulfonic acid group or a phosphoric acid group has a large hydrophilicity and becomes a good ion exchange membrane, and is used as another electrolyte membrane for a fuel cell.

  Such a polyimide is generally obtained by polycondensation of a diamine and a tetracarboxylic dianhydride such as pyromellitic anhydride. That is, polyimide is a chain polymer material in which diamine units and tetracarboxylic dianhydride units are alternately connected.

  In that case, an aromatic diamine is generally used as the diamine because an ion exchange group or other functional group can be introduced into the aromatic nucleus.

  For example, an example using an aromatic diamine having a sulfoalkoxy group (Patent Document 1), an example of a diamine represented by the following chemical formulas (18) to (20) (Patent Document 2)

（Ｒ1〜Ｒ8は少なくとも一つがスルホン酸基であり、他にアルキル基、D1は‐O‐、‐SO2‐、‐C(CF3)2‐、アルキレン基）
及び化学式（２２）で示されるジアミン

(At least one of R1 to R8 is a sulfonic acid group, and in addition, an alkyl group, D1 is —O—, —SO2—, —C (CF3) 2-, an alkylene group)
And a diamine represented by the chemical formula (22)

（D2はO、S、CH2、C(CF3)2、Arは一つ以上のスルホン酸基を有する２価の芳香族炭化水素残基、R4〜R7は水素原子、アルキル基）
がそれぞれ記載されている。

(D2 is O, S, CH2, C (CF3) 2, Ar is a divalent aromatic hydrocarbon residue having one or more sulfonic acid groups, R4 to R7 are hydrogen atoms, alkyl groups)
Are described respectively.

  Polyimides containing one of these aromatic diamines as described above have various properties as described above. However, when used in an acidic solution such as an electrolyte membrane or an electrolyte membrane for a fuel cell, the polyimide is subject to hydrolysis. It tends to be easy. In particular, when used for a diaphragm for electrolysis for a long period of time, hydrolysis of the imide ring occurs and the molecular weight decreases, so that the membrane may lose mechanical properties. In addition, there is a phenomenon in which ion exchange groups are eliminated, the ion exchange capacity decreases with time during use, and the performance decreases. These phenomena are particularly noticeable at high temperatures.

  As a result of various studies as to why such a phenomenon occurs, it has been found that one of the causes is that the sulfonic acid group is directly bonded to the aromatic ring constituting the main chain.

  On the other hand, as a compound having a sulfonic acid group in the side chain, a polyimide having a sulfonated aromatic group bonded to an aromatic ring of the main chain via an ether bond (Patent Document 4) or the following general formula (23)

（Ｒは、アルキレン、ハロゲン化アルキレン、アリーレン及びハロゲン化アリーレン、又はエーテル結合を含む有機基）
に示される側鎖にスルホン酸基を有するポリイミドが示されている（特許文献５）。

(R is alkylene, halogenated alkylene, arylene and halogenated arylene, or an organic group containing an ether bond)
The polyimide which has a sulfonic acid group in the side chain shown by this is shown (patent document 5).

  Some of these cation exchange resin membranes made of polyimide resin can be effectively used as polymer electrolyte membranes under operating conditions up to about 80-100 ° C, but at higher temperatures, ie 80-100 ° C. It has been found that degradation over time occurs at temperatures exceeding that.

  Therefore, even when used at a temperature of 80 ° C or higher, it has long-term durability and mechanical strength, can be used in a wide temperature range from low temperature to high temperature, and has a low rate of decrease in proton conductivity at low humidity Development of a polymer electrolyte membrane that can withstand use as an electrolyte membrane for a fuel cell or the like is desired.

  As a result of intensive studies to solve the above problems, the present inventors have found that polyimides using a specific diamine compound as one monomer have extremely high heat resistance, that is, under a temperature condition of 80 to 120 ° C. However, it has been found that a cation exchange resin that maintains high mechanical strength and has little deterioration over time, in particular, a polyimide resin suitable for an electrolyte membrane that can be suitably used for fuel cells, etc. can be obtained, and the present invention is completed. It came.

That is, this invention relates to the polyimide which has a sulfonic acid group in a side chain.
JP 2004-155998 A JP-A-8-33451 JP 2003-64181 A JP 2004-35891 A JP 2004-107484 A

  In view of the above technical background, an object of the present invention is to obtain a polyimide ion exchanger having high mechanical strength and heat resistance and durability, that is, a cation exchange resin having a sulfonic acid group in a side chain. It is in providing the polyimide using a special diamino compound.

The present invention is a sulfonated aromatic polyimide having a repeating structural unit represented by the following general formula (1).

（但し、Ar１は少なくとも１つ以上の芳香環を有する４価の基であり、Ar2は３価のベンゼン環又は３価のナフタレン環であり、Ｘは下記一般式で示される少なくとも一方の基であり、

(However, Ar1 is a tetravalent group having at least one aromatic ring, Ar2 is a trivalent benzene ring or a trivalent naphthalene ring, and X is at least one group represented by the following general formula. Yes,

Ｙは、水素原子、ハロゲン原子、スルホン酸基、又は下記式（３）〜（１６）に示されるいずれか１つの基であり、ｐは０又は１（但し、Yが水素原子又はハロゲン原子のときは１）の整数である。）

Y is a hydrogen atom, a halogen atom, a sulfonic acid group, or any one group represented by the following formulas (3) to (16), and p is 0 or 1 (provided that Y is a hydrogen atom or a halogen atom) Sometimes it is an integer of 1). )

（但し、（３）〜（１６）におけるｎは１〜２の整数）

(However, n in (3) to (16) is an integer of 1 to 2)

  One of the features of the sulfonated aromatic polyimide of the present invention is that the diamine unit represented by (1-a) among the repeating units represented by the above formula (1) in the molecule constituting the polyimide.

が存在することにある。かかるジアミンユニットは、そこに存在するスルホン酸基の全ポリイミド重量に対する割合が大きいほど、得られるポリイミド樹脂の単位重量当りの陽イオン交換容量は増大する。しかし、スルホン酸基は、きわめて親水性であり、一般にスルホン酸基の存在量が多くなると樹脂の吸水率が高くなり、膨潤し、変形し、極端な場合には水溶性となる。

Is that there exists. In such a diamine unit, the cation exchange capacity per unit weight of the resulting polyimide resin increases as the ratio of the sulfonic acid groups present therein to the total polyimide weight increases. However, sulfonic acid groups are extremely hydrophilic. In general, when the amount of sulfonic acid groups present increases, the water absorption of the resin increases, swells and deforms, and in extreme cases, becomes water-soluble.

  For this reason, in this invention, the abundance of the diamine unit containing a sulfonic acid group is controllable.

  That is, in the present invention, up to 90 mol% of the diamine unit (1-a) has other aromatic rings and does not have a sulfonic acid group (hereinafter also referred to simply as a co-condensation unit, The monomer constituting the unit can also be substituted with a group consisting of a diamine (hereinafter simply referred to as divalent), particularly a co-condensation monomer. The substitution should preferably be 10-90 mol%, more preferably 30-70 mol%. Further, a triamine having no sulfonic acid group (hereinafter referred to as a trivalent cocondensation unit) can be used together with a divalent cocondensation unit or independently as a cocondensation monomer. Since the polyimide having a trivalent co-condensation unit forms a branched network-like crosslinked structure, the substitution amount is preferably up to 25%.

  The present invention has a sulfonic acid group only in the side chain in the polyimide molecule, and is an excellent ion exchanger. Of the polyimides of the present invention, linear polycondensates and polycondensates with a low degree of crosslinking are excellent in processability and are soluble in organic solvents such as dimethyl sulfoxide, N-methylpyrrolidone, etc. It can be formed into other shapes.

  Further, as the degree of crosslinking is increased, the solubility in a solvent decreases and the gel tends to gel. In this case, it is preferable to perform molding by means such as cast polycondensation.

  In any case, the polyimide of the present invention has durability at a high temperature, for example, 80 to 120 ° C. as a cation exchanger having moldability, excellent mechanical strength, high proton conductivity, It has high proton conductivity especially under low humidity, and also has high barrier properties against gases such as hydrogen, oxygen and methane, and liquids such as methanol and ethanol, so that it is a solid electrolyte membrane, especially an electrolyte for fuel cells. An excellent effect as a film can be expected.

  The greatest feature of the present invention is that the polyimide has a repeating unit represented by the general formula (1). The unit further includes each unit of the following diamine unit formula (1-a) and tetracarboxylic acid unit formula (1-b).

よりなり、それぞれ下記一般式（２４）で示されるジアミン化合物及び例えば下記一般式（２５）で示される少なくとも一つの芳香環を有し、４個のカルボン酸基よりなる二無水物（以下、カルボン酸無水物ともいう）を各モノマーとした重縮合体である。

A diamine compound represented by the following general formula (24) and a dianhydride (hereinafter referred to as a carboxylic acid group) having at least one aromatic ring represented by the following general formula (25) and having four carboxylic acid groups. (Also referred to as acid anhydride).

  In the present invention, a polyimide having the above-mentioned excellent effect can be obtained by having the structure of formula (1-a), that is, by using the monomer represented by formula (24).

  Here, the monomer represented by the formula (24) is preferably a diamino aromatic carbonyl compound represented by the following general formula (26).

  However, X is an aromatic hydrocarbon residue which has a sulfonic acid group and may further have a substituent.

  As a particularly preferred aromatic hydrocarbon residue, one having a structure represented by the following formula (2) is recommended.

  Here, p is 0 or 1 (where Y is 1 when hydrogen is a hydrogen atom or a halogen atom), Y is a group such as a hydrogen atom, halogen, sulfonic acid group, and the following formulas (3) to (16 Etc.) are preferred.

  One or more sulfonic acid groups may be bonded to these aromatic rings, and further, an alkylene group such as an oxygen atom, a sulfur atom, a methylene group, a propylene group, or a perfluoroalkylene group, or An aromatic ring is bonded via a sulfonyl group or the like, and a sulfonic acid group may be bonded to them. Preferred examples of such groups include the following chemical formulas (3) to (16) or (17).

  Thus, when the aromatic ring is further bonded to the aromatic ring bonded to the aromatic carbonyl group such as a benzoyl group bonded to the amino group, the aromatic ring bonded to the aromatic carbonyl group bonded to the amino group. It is preferable that the sulfonic acid group is not substituted or only one is substituted.

  Further, as X in the general formula (1), those represented by the following formula (17) are also effective.

(Where m is an integer from 2 to 30, n is an integer from 1 to 2, z is a direct bond, -O-, -S-, -SO2-, -CO-, -CH2-, -CF2-, or- C (CF3) 2-
In addition, when a polymer chain such as polyphenylene oxide in which z represented by the formula (17) is oxygen is present, if the polymer chain is too long, it causes trouble in the formation of polyimide, and a sufficient degree of polymerization cannot be obtained. Therefore, m in the formula (17) is up to about 30, preferably 2-8.

  Although the manufacturing method of the said monomer in this invention is not specifically limited, It can manufacture by methods, such as the example of the following scheme.

  That is, instead of biphenyl ether in the above scheme examples, benzene, naphthalene or derivatives thereof, biphenyl thioether, polyphenylene oxide, biphenyl sulfone, diphenylmethylene, etc. can be used to obtain the corresponding diamino aromatic carbonyl compounds.

  In the present invention, by using these diamino compounds as monomers, a polyimide having no sulfonic acid group in the main chain is obtained. Furthermore, one of the important points of the present invention is a polyimide in which a sulfonic acid group is present only in the side chain bonded to the main chain via a carbonyl group, so that the sulfonic acid group is directly attached to the aromatic ring constituting the main chain. Even when used under harsh conditions such as in an acidic solution at a much higher temperature, compared to polyimides with sulfonic acid groups bonded to aromatic rings via ether bonds or alkylene bonds, etc. There is little degradation over time such as cleavage of the polymer chain by hydrolysis or elimination of the sulfonic acid group. The reason for this is that, since the hydrophilic sulfonic acid group is not present in the main chain and the sulfonic acid group is present only in the side chain, the polyimide microstructure has a hydrophobic main chain and a hydrophilic main chain. Micro-phase separation in the side chain part, the water sorption amount of the hydrophobic domain is small, it is difficult to undergo hydrolysis of the main chain, and the sulfonic acid group is attached to the aromatic ring of the side chain via the carbonyl group Therefore, it is judged that the elimination of the sulfonic acid group under severe conditions is reduced.

  In the present invention, the diamino unit constituting the chemical formula (1) is also a preferred embodiment in which the formula (1-a) is constituted only by the monomer of the formula (24). In the above formula (24), for the purpose of suppressing the increase in mechanical strength and water absorption when the membrane is used as a membrane such as an electrolyte membrane and preventing the decrease of the fixed ion concentration during use of the membrane, Diamine having at least one aromatic ring not having a sulfonic acid group, 90 mol% or less, preferably 70 mol% or less, for example 2 to 90 mol%, preferably 5 to 70 mol%, of the monomer (26) A compound and / or a triamine compound can be substituted for use. In particular, when substituted with a triamine compound or a mixture of diamine and triamine, the resulting polyimide has a cross-linked structure, and when used as an electrolyte membrane, the heat resistance is improved, and a membrane by sorption of water or the like. Swelling and deformation are less likely to occur, which may be preferable.

  That is, in these copolycondensation polyimides, 90 mol% or less of the groups constituting = Ar2-C (O) -X in the formula (1-a) have an aromatic ring, and sulfonic acid In polyimides substituted with divalent and / or trivalent groups that are not bonded to groups, the group that constitutes = Ar2-C (O) -X with sulfonic acid groups is statistically included in the polyimide chain. The form dispersed and present is a preferred embodiment for adjusting the ion exchange capacity.

  In addition, among the groups constituting = Ar2-C (O) -X in formula 1-a, 90 mol% or less is a divalent group having an aromatic ring and not bound to a sulfonic acid group. In the substituted polyimide, the form in which the group constituting the = Ar2-C (O) -X is unevenly distributed in a polyimide chain is high in a cation exchange membrane such as an electrolyte membrane. There is an advantage that the proton conductivity is maintained and the mechanical strength and the like are enhanced.

  Further, among the groups constituting = Ar2-C (O) -X in formula 1-a, 90 mol% or less of the divalent and trivalent groups having an aromatic ring and not having a sulfonic acid group bonded thereto. In the polyimide substituted with a group, the group constituting the = Ar2-C (O) -X exists in a block-like manner in the polyimide chain and is not bound to a sulfonic acid group. The polyimide having a cross-linked structure substituted with a group has the advantage of suppressing water absorption, suppressing swelling and deformation of the membrane during use, maintaining high proton conductivity and improving mechanical strength and the like. .

  Among these diamino or triamino compounds having at least one aromatic ring not having a sulfonic acid group, examples of the diamino compound include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 4,4 ′ -Diaminodiphenyl sulfide, benzidine, metaphenylenediamine, paraphenylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, bis [4- (4-aminophenoxy) phenyl] sulfone, bis- (4-aminophenoxy) Phenyl) sulfide, bis- (4-aminophenoxyphenyl) biphenyl, 1,4-bis- (4-aminophenoxy) benzene, 1,3-bis- (4-aminophenoxy) benzene, 3,4'-diaminodiphenyl ether 4,4′-bis (4-amino Nophenoxy) biphenyl, bis {4- {3-aminophenoxy) phenyl} sulfone, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoro Examples include, but are not limited to, propane, 2,2-bis [4- (4-amonophenoxy) phenyl) propane, 2,2′-bis (trifluoromethyl) -benzidine and the like.

  Further, as a triamine compound, in order to facilitate a crosslinking reaction, two amino groups are not bonded to the same aromatic ring adjacent to each other, particularly two or more first amino groups are bonded to the same aromatic ring. Those which are not bonded are preferable, and for example, 1,3,5-tri (4-aminophenoxy) benzene, tri (4-aminophenyl) amine, 1,3,5-triaminobenzene and the like are preferably used.

  These triamine compounds can be mixed with a diamino compound represented by the formula (24) and a diamine having no sulfonic acid group and subjected to copolycondensation, or a carboxylic dianhydride and a compound of the formula (24) and In (co) condensation polymerization with a diamine having no sulfonic acid group, a carboxylic acid anhydride-terminated sulfonated polyimide oligomer is synthesized by adding an excess of carboxylic acid anhydride to the diamine, and then triamine is synthesized. By adding an equal equivalent amount and reacting, it is possible to provide a branched crosslinked polyimide film in which sulfonated polyimide oligomers are connected in a network.

  In the present invention, 1,4,5,8-naphthalenetetracarboxylic dianhydride has been described as a tetracarboxylic acid compound to be reacted with a diamine compound in order to constitute a polyimide. Of course, in the present invention, a tetracarboxylic acid is used. If it reacts with a diamine compound as a component and forms imide, it will not specifically limit.

  That is, in the polyimide of this invention, what is used as a monomer for general polyimide manufacture can be used as a tetracarboxylic acid component without being restrict | limited at all. For example, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 3 , 3 ′, 4,4′-diphenyl ether tetracarboxylic acid, bis (3,4-dicarboxyphenyl) methane, 2,2-bis (3,4-dicarboxyphenyl) propane, pyromellitic acid, 1,4 5,8-naphthalenetetracarboxylic acid, 3,4,9,10-perylenetetracarboxylic acid, 4,4 '-(hexafluoroisopropylidene) diphthalic acid, m- (terphenyl) 3,4,3 ", 4 "-Tetracarboxylic acids, or their acid dianhydrides and esterified products. Among these, 1,4,5,8-naphthalenetetracarboxylic acid, or its acid dianhydride or esterified product is particularly preferable because a crosslinked sulfonated polyimide having good water resistance can be easily obtained.

  As described above, the polycondensation reaction between a diamino compound monomer (some of which includes a triamino compound) and a carboxylic acid anhydride can be used without any limitation on the means conventionally used for synthesizing polyimide. Although it is possible, a general scheme is now shown for the cases of homopolycondensation, random copolycondensation, block copolycondensation and branched bridge copolycondensation.

(In these reaction formulas, TEA represents triethylamine, PhCOOH represents benzoic acid, NTDA represents naphthalenetetracarboxylic dianhydride, and Ar represents a divalent group having an aromatic ring.)
Examples are shown below.

(Example)

The 1HNMR data shown in the following examples were measured by JEOL EX-270 using deuterated dimethyl sulfoxide (DMSO-d6) as a solvent. Moreover, the evaluation method in this invention is as follows.
[Thermogravimetric analysis]

Thermogravimetric analysis is performed with a TG-MS analyzer (TG-MS system 220) manufactured by Seiko Electronics Co., Ltd. at a heating rate of 5 ° C./min in a He stream, and sulfonic acid groups or sulfo groups at 200 to 300 ° C. The initiation temperature Td for the decomposition of the propoxy group was determined.
[Water uptake]
About 80 mg of the membrane sample was dried, the dry weight Wd was measured, and then immersed in water at 30 ° C. for 2 to 4 hours. The membrane sample was taken out of the water, the water adhering to the surface quickly was wiped off with tissue paper, and the membrane weight W3 at the time of swelling was measured. The absorption rate (Water uptake; WU) was calculated from the following equation.
WU = (Ws-Wd) / Wd × 100%
[water resistant]

A film sample having a thickness of 30 to 40 μm was immersed in hot water under pressure at 130 ° C. for 48 hours, and then evaluated from the viewpoint of film shape and strength in the following three stages. I: The film shape is not maintained. II: When the film was taken out with tweezers and bent as it was at 120 degrees, the film was broken. III: The film did not break even when bent at 120 degrees. In addition, after drying the membrane soaked in pressurized water, proton conductivity was measured in water at 50 ° C. and evaluated from the viewpoint of proton conductivity in the following three stages. (1): The proton conductivity decreased by 20% or more by the treatment. (2): Decreased by 5 to 20%. (3): No change within experimental error (± 5%) range.
[Proton conductivity]

Attach a membrane sheet (1.0cm x 0.5cm) and four platinum black electrode plates to the proton conductivity measurement cell and place it in temperature-controlled water or temperature / humidity-controlled chamber. Using a meter (HIOKI3552-80), the electrical resistance R was measured by the complex impedance method in the frequency range of 100 Hz to 100 kHz, and the proton conductivity σ was calculated from the following equation.
s = d / (ts
ws R)
Here, d is the distance between two electrodes (0.5 cm), and ts and ws are the thickness and width of the film sheet at 70% RH at room temperature. To calculate proton conductivity in water, ts and ws values in water were used.
[Methanol permeability coefficient]

  A membrane sheet is sandwiched between a supply side cell (capacity 350 ml) and a permeation side cell (capacity 100 ml) of the liquid permeation measurement cell via a fluoro rubber seal plate. Put a 30wt% aqueous methanol solution on the membrane supply side, add distilled water on the permeate side, measure the liquid composition on the supply side and the permeate side at arbitrary time intervals using a gas chromatograph, and obtain the methanol permeability coefficient PM. It was. In addition, the swelling film thickness was used for calculation of PM.

Sulfonated polyimide NTDA-DBSPBDS
(1) Synthesis of 4- [4- (3,5-diaminobenzoyl) -2-sulfophenoxy] -benzene-1,3-disulfonic acid (DBSPBDS) (a) 4- (3,5-dinitrobenzoyl) phenyl Synthesis of ether (a) To a well-dried 100 ml four-necked flask was added AlCl3 (7 g, 0.0525 mol) and 25 ml dichloromethane, and the mixture was cooled to -10 ° C and kept at that temperature for 3,3 5-Dinitrobenzoyl chloride (11.528 g, 0.05 mol) was added. Diphenyl ether (8.50 g, 0.05 mol) was dissolved in dichloromethane (5 ml) and slowly dropped into the mixture over 1 hour using a dropping funnel. Meanwhile, the temperature was kept at 0 ° C. or lower with stirring. After the addition, the mixture was left overnight with stirring at room temperature. The reaction solution was poured into a large amount of ice (about 100 g with a few drops of hydrochloric acid added). The mixture was filtered, and the solid separation was washed with a large amount of water until neutral, and dried in vacuo at 60 ° C. for 10 hours to obtain 12.5 g of a crude product. Add to 400 ml of ethanol and heat at reflux temperature for 2 hours to dissolve impurities, then filter off the solid under heating and vacuum dry at 60 ° C. for 6 hours to obtain 11.9 g (yield 65.4%) Of pure light white solid product. This was confirmed by 1H NMR (270 MHz, DMSO-d6), and δ: 7.10-7.13 (2H), 7.14-7.21 (2H), 7.24-7.30 (1H), 7.31-7.53 (2H), 7.88-7.92 (2H), 8.77 (2H), 9.02-9.04 (1H) has a peak,
Furthermore, as a result of confirmation by FT-IR and DSC (m = 159.8 ° C.), it was confirmed to be 4- (3,5-dinitrobenzoyl) phenyl ether. This compound is referred to as (a).

(B) Synthesis of [4- (4- (3,5-dinitrobenzoyl) -2-sulfophenoxy) benzene-1,3-disulfonic acid 4- (3,4) in a 100 ml three-necked flask equipped with a magnetic stirrer 5-Dinitrobenzoyl) phenyl ether (a) (3.64 g, 10 mmol) was added, and after cooling with an ice bath, 4 ml of concentrated sulfuric acid was slowly added with stirring. After complete addition of sulfuric acid, the mixture was stirred and slowly warmed to room temperature at 30 ° C. for 30 minutes to completely dissolve (a). The mixture was cooled again in an ice bath and 4 ml of fuming sulfuric acid (60%, 55.2 mmol) was added slowly. After complete addition of fuming sulfuric acid, the mixture was kept at 0 ° C. with stirring for 1 hour. Then it was slowly warmed to 60 ° C. and kept at 60 ° C. for 8 hours. After cooling to room temperature, the mixture was poured into 100 g of crushed ice. The mixture was then neutralized with 10% NaOH until the pH was neutral and filtered. The filtrate was concentrated to give a solid. 50 ml of dimethyl sulfoxide (DMSO) was added and the insoluble solid was filtered off. Subsequently, the solid obtained by concentrating the filtrate was separated by filtration and vacuum-dried at 80 ° C. for 10 hours to obtain 6.3 g (yield 94%) of a pale yellow solid product. According to 1H NMR (270 MHz, DMSO-d6), δ: 6.77-6.80 (1H), 6.87-6.90 (1H), 7.64-7.81 (1H), 8.14-8.15 (1H), 8.29-8.30 (1H) , 8.78-8.80 (2H), 9.03-9.05 (1H), and FT-IR showed 4- [4- (3,5-dinitrobenzoyl) -2-sulfophenoxy] benzene-1,3- It was confirmed to be disulfonic acid. This compound is referred to as (b).

(C) Synthesis of DBSPBDS 4- [4- (3,5-dinitrobenzoyl) -2-sulfophenoxy] benzene-1,3-disulfonic acid (b) in a 100 ml four-necked flask equipped with a magnetic stirrer (b) ( 3.35 g, 5 mmol), stannous chloride dihydrate (11.63 g, 50 mmol), 50 ml ethanol and 10 ml water were added, and concentrated hydrochloric acid (8.75 ml, 50 mmol) was added under a nitrogen atmosphere. The reaction mixture was stirred for 4 hours at room temperature and then filtered. The filtrate was recrystallized from ethanol / water (v / v = 3/2) and dried in vacuo at 60 ° C. for 10 hours to obtain 2.1 g (yield). 77.3%) of a gray solid product was obtained. This is the peak of δ: 6.06-6.08 (1H), 6.12-6.79 (2H), 6.79-6.85 (2H), 7.58-7.67 (2H), 8.14-8.16 (2H) by 1HNMR (270MHz, DMSO-d6). showed that. It was also confirmed by DBFTBDS by FT-IR.

(2) Synthesis of sulfonated polyimide NTDA-DBSPBDS 2.176 g (4.0 mmol) DBSPBDS and 2.1 ml triethylamine (TEA) were dissolved in 16 ml m-cresol in a dry 100 ml four-necked flask and then 1.072 g (4.0 mmol) of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and 0.68 g of benzoic acid are added and the mixture is stirred at 80 ° C. for 4 hours and at 180 ° C. for 10 hours. The mixture was stirred for 10 hours, 10 ml of N-methylpyrrolidone (NMP) was added, and the mixture was further stirred at 180 ° C. for 10 hours. The polymerization reaction solution was cooled to 80 ° C., diluted with 10 ml of NMP, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The resulting product had a solution viscosity ηSP / c (solvent: 1 wt% LiCl-containing DMSO; 0.5 wt%; 35 ° C.) of 2.5 dl / g. The product was dissolved in DMSO, cast on a glass plate, and dried at 80 ° C. for 10 hours to obtain a TEA salt type sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in a 0.5 M sulfuric acid solution for 2 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to obtain a proton-type sulfonated polyimide NTDA-DBSPBDS membrane. This membrane had a high ion exchange capacity (IEC) but was dissolved in water at 50 ° C.

Random copolymerized sulfonated polyimide NTDA-DBSPBDS / BAPPS (1/1) -r
DBSPBDS synthesized in Example 1 was used as the sulfonated diamine, and 4,4′-bis (3-aminophenoxy) phenylsulfone (BAPPS) was used as the non-sulfonate diamine. After dissolving 1.088 g (2.0 mmol) DBSPBDS and 1.1 ml TEA in 16 ml m-cresol in a dry 100 ml four-necked flask, then adding 0.865 g (2.0 mmol) BAPPS to dissolve. 1.072 g (4.0 mmol) of NTDA and 0.68 g of benzoic acid are added and the mixture is stirred for 4 hours at 80 ° C. and 10 hours at 180 ° C. under a nitrogen gas atmosphere, and 10 ml of NMP is added at 180 ° C. Stir for 10 hours. The polymerization reaction solution was cooled to 80 ° C., diluted with 10 ml of NMP, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The resulting product had a solution viscosity ηSP / c (solvent: 1 wt% LiCl-containing DMSO; 0.5 wt%; 35 ° C.) of 2.0 dl / g. The product was dissolved in DMSO, cast on a glass plate, and dried at 80 ° C. for 10 hours to obtain a TEA salt type copolymer sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in a 0.5 M sulfuric acid solution for 2 days to exchange protons, washed with water and vacuum dried at 150 ° C. for 10 hours to obtain proton type random copolymer sulfonated polyimide NTDA-DBSPBDS / BAPPS ( A 1/1) -r film was obtained. Table 1 shows the characteristic evaluation results of this film. Fig. 1 shows the relative humidity dependence of proton conductivity and Fig. 2 shows the temperature dependence.

Sequenced copolymerized sulfonated polyimide NTDA-DBSPBDS / BAHF (1/1) -s
DBSPBDS synthesized in Example 1 was used as the sulfonated diamine, and 2,2′-bis (4-aminophenoxy) hexafluoropropane (BAHF) was used as the non-sulfonate diamine. Dissolve 1.088 g (2.0 mmol) DBSPBDS and 1.1 ml TEA in 10 ml m-cresol in a dry 100 ml four-necked flask, then add 0.643 g (2.4 mmol) NTDA and 0.42 g benzoic acid. The mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 5 hours under a nitrogen gas atmosphere. Cool the solution to room temperature, add 0.668 g (2.0 mmol) BAHF, 0.429 g (1.6 mmol) NTDA, 0.42 g benzoic acid and 10 ml NMP sequentially and stir at 80 ° C. for 4 hours and at 180 ° C. for 20 hours. did. The polymerization reaction solution was cooled to 80 ° C., diluted with 10 ml of NMP, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The solution viscosity ηSP / c of the obtained product (solvent: DMSO containing 1 wt% LiCl; 0.5 wt%; 35 ° C.) was 2.5 dl / g. The product was dissolved in DMSO, cast on a glass plate, and dried at 80 ° C. for 10 hours to obtain a TEA salt type copolymer sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in a 0.5M sulfuric acid solution for 2 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to obtain proton type sequence copolymerized sulfonated polyimide NTDA-DBSPBDS / BAHF. A (1/1) -s film was obtained. Table 1 shows the characteristic evaluation results of this film. FIG. 1 shows the relative humidity dependence of proton conductivity, and FIG. 2 shows the temperature dependence.

Sulfonated polyimide NTDA-DBSPBS
(1) Synthesis of 4- [4- (3,5-diaminobenzoyl) -2-sulfophenoxy] -benzenesulfonic acid (DBSPBS) (a) 4- [4- (3,5-dinitrobenzoyl) -2- Synthesis of sulfophenoxy] benzenesulfonic acid First, the compound (a) is used for sulfonation. That is, 4- (3,5-dinitrobenzoyl) phenyl ether (a) (3.64 g, 10 mmol) was placed in a 100 ml three-necked flask equipped with a magnetic stirrer, cooled in an ice bath, and 4 ml of concentrated sulfuric acid was added. Slowly added with stirring. The mixture was held with stirring at 0 ° C. for 30 minutes. Thereafter, the mixture was slightly heated to room temperature so that (a) was completely dissolved. The mixture was cooled again in an ice bath, 2 ml of fuming sulfuric acid (60%, 27.6 mmol) was added slowly and after complete addition of the fuming sulfuric acid, stirring was continued at 0 ° C. for another 0.5 hour, then to 40 ° C. The temperature was raised slowly and maintained at that temperature for 4.5 hours, then cooled to room temperature, the mixture was poured into 50 g of crushed ice, neutralized with 10% NaOH until pH neutral, and then filtered. After concentrating the resulting solution, 50 ml of DMSO was added. Insoluble solids were filtered off, the filtrate was concentrated, and the resulting solid was filtered off and dried in vacuo at 80 ° C. for 10 hours to give 5.0 g (88%) of a pale yellow solid product. This was confirmed by 1H NMR (270 MHz, DMSO-d6). Δ: 6.87-6.90 (1H), 6.97-7.07 (2H), 7.68-7.70 (2H), 7.76-7.84 (1H), 8.31-8.32 (1H ), 8.76-8.80 (2H), 9.02-9.04 (1H), and it was confirmed to be 4- [4- (3,5-dinitrobenzoyl) -2-sulfophenoxy] benzenesulfonic acid.

(B) Synthesis of 4- [4- (3,5-diaminobenzoyl) -2-sulfophenoxy] benzenesulfonic acid 4- [4- (3,5-dinitrobenzoyl) -2 obtained in (a) above -Sulfophenoxy] benzenesulfonic acid is used to reduce the nitro group in the same manner as in item (1) (c) of Example 1. Yield 80%, δ: 6.07-6.07 (1H), 6.13 (2H) 6.83-6.86 (1H), 6.95-6.98 (2H) 7.62-7.69 (3H), 8.15 by 1H NMR (270 MHz, DMSO-d6) The peak of -8.18 (1H) was confirmed to be DBSPBS.

(2) Synthesis of sulfonated polyimide NTDA-DBSPBS In a dry 100 ml four-necked flask, 1.856 g (4.0 mmol) of DBSPBS and 1.4 ml of TEA were added to 16 ml of m-cresol and dissolved, and then 1.072 g (4.0 Millimoles) of NTDA and 0.68 g of benzoic acid were added and the mixture was stirred at 80 ° C. for 4 hours and 180 ° C. for 10 hours under nitrogen gas atmosphere, 10 ml of NMP was added and further stirred at 180 ° C. for 10 hours. The polymerization reaction solution was cooled to 80 ° C., diluted with 10 ml of NMP, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The resulting product had a solution viscosity ηSP / c (solvent: 1 wt% LiCl-containing DMSO; 0.5 wt%; 35 ° C.) of 3.0 dl / g. The product was dissolved in DMSO, cast on a glass plate, and dried at 80 ° C. for 10 hours to obtain a TEA salt type sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in a 0.5 M sulfuric acid solution for 2 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to obtain a proton-type sulfonated polyimide NTDA-DBSPBS membrane. Table 1 shows the characteristic evaluation results of this film.

Sequenced copolymerized sulfonated polyimide NTDA-DBSPBS / BAHF (2/1) -s
DBSPBS synthesized in Example 4 was used as the sulfonated diamine, and BAHF was used as the non-sulfonate diamine. Dissolve 0.928 g (2.0 mmol) DBSPBDS and 0.7 ml TEA in 10 ml m-cresol in a dry 100 ml four-necked flask, then add 0.643 g (2.4 mmol) NTDA and 0.41 g benzoic acid. The mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 5 hours under a nitrogen gas atmosphere. The solution was cooled to room temperature and 0.334 g (1.0 mmol) BAHF, 0.161 g (0.6 mmol) NTDA, 0.11 g benzoic acid and 10 ml NMP were added sequentially and stirred at 80 ° C. for 4 hours and at 180 ° C. for 20 hours. did. The polymerization reaction solution was cooled to 80 ° C., diluted with 10 ml of NMP, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The resulting product had a solution viscosity ηSP / c (solvent: 1 wt% LiCl-containing DMSO; 0.5 wt%; 35 ° C.) of 2.6 dl / g. The product was dissolved in DMSO, cast on a glass plate, and dried at 80 ° C. for 10 hours to obtain a TEA salt type copolymer sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in a 0.5M sulfuric acid solution for 2 days to exchange protons, washed with water and vacuum dried at 150 ° C. for 10 hours to obtain proton type sequence copolymerized sulfonated polyimide NTDA-DBSPBS / BAHF. A (2/1) -s film was obtained. Table 1 shows the characteristic evaluation results of this film.

Branched and crosslinked sulfonated polyimide NTDA-DBSPBS / TAPB (5/4)
(1) Synthesis of 1,3,5-tris (4-aminophenoxy) benzene (TAPB)
49.6 g (0.35 mol) of 4-fluoronitrobenzene, 12.6 g (0.1 mol) of 1,3,5-trihydroxybenzene and 20.7 g (0.15 mol) of potassium carbonate are added to a mixed solution of DMSO 200 ml and toluene 50 ml, Heated under a nitrogen stream. The produced water was removed while refluxing toluene at 140 ° C. for 4 hours. While removing toluene, the temperature was raised to 175 ° C. and heated for 16 hours. The reaction solution was cooled, poured into a large amount of methanol, and the precipitated solid product was washed with water and dried.

  30 g of the obtained solid, 60 mg of iron (III) chloride and 2 g of carbon on platinum were added to 110 ml of 2-methoxyethanol, the mixture was heated to 90 ° C., and 18.9 g of hydrazine monohydrate was added dropwise over 2 hours. . The reaction solution was heated at 110 ° C. for 2 hours, cooled to room temperature, and filtered. 20 ml of concentrated hydrochloric acid was added to the filtrate to precipitate a solid. The solid was filtered off and dried to give a TABP yellow solid.

(2) Synthesis of Branched Crosslinked Sulfonated Polyimide NTDA-DBSPBS / TAPB (5/4) DBSPBS synthesized in Example 4 was used as the sulfonated diamine. In a dry 100 ml four-necked flask, 1.856 g (4.0 mmol) DBSPBS and 1.4 ml TEA are dissolved in 20 ml m-cresol and then 1.34 g (5.0 mmol) NTDA and 0.85 g benzoic acid are added. The mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 20 hours under a nitrogen gas atmosphere. The solution was cooled to room temperature, 0.340 g (0.67 mmol) TABP and 20 ml NMP were added and stirred at 60 ° C. for 4 hours. The obtained solution was cast on a glass plate and dried by heating at 80 ° C, 95 ° C and 110 ° C for 1 hour, 130 ° C for 8 hours, and 200 ° C for 10 hours, respectively. A polyimide film was obtained. This was immersed in methanol for 2 days, then immersed in a 0.5 M sulfuric acid solution for 2 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to form proton-type branched cross-linked sulfonated polyimide NTDA-DBSPBS / TAPB (5 / 4) A film was obtained. Table 1 shows the characteristic evaluation results of this film.

Sulfonated polyimide NTDA-DBPBS
(1) Synthesis of 4- [4- (3,5-diaminobenzoyl) -phenoxy] -benzenesulfonic acid (DBPBS) First, sulfonation is performed using the compound (a). The procedure is the same as that for obtaining the compound (b), except that 28 mmol of 60% fuming sulfuric acid is used with respect to 10 mmol of (a), and the sulfonation reaction condition is 0 ° C. for 1 hour.

  Using the 4- [4- (3,5-dinitrobenzoyl) phenoxy] benzenesulfonic acid thus obtained, the nitro group was reduced in the same manner as in (1) (c) of Example 1 to obtain a yellow solid. 2.0 g (95%) of product was obtained. This shows a peak of δ: 6.07-6.14 (1H), 6.15 (2H), 7.05-7.10 (4H), 7.67-7.76 (4H) by 1H NMR (270 MHz, DMSO-d6), and is DBPBS. confirmed.

(2) Synthesis of sulfonated polyimide NTDA-DBPBS In a dry 100 ml four-necked flask, 1.682 g (4.0 mmol) of DBPBS and 1.4 ml of TEA were dissolved in 15 ml of m-cresol, and then 1.072 g (4.0 Millimoles) of NTDA and 0.68 g of benzoic acid were added and the mixture was stirred at 80 ° C. for 4 hours and 180 ° C. for 10 hours under nitrogen gas atmosphere, 10 ml of NMP was added and further stirred at 180 ° C. for 10 hours. The polymerization reaction solution was cooled to 80 ° C., diluted with 10 ml of NMP, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The solution viscosity ηSP / c of the obtained product (solvent: DMSO containing 1 wt% LiCl; 0.5 wt%; 35 ° C.) was 1.8 dl / g. The product was dissolved in DMSO, cast on a glass plate, and dried at 80 ° C. for 10 hours to obtain a TEA salt type sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in a 0.5 M sulfuric acid solution for 2 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to obtain a proton-type sulfonated polyimide NTDA-DBPBS membrane. Table 1 shows the evaluation results of the characteristics of this film.
(Comparative Example 1)

Random copolymerized sulfonated polyimide NTDA-BAPBDS / BAPB (2/1) -r
4,4′-bis (4-aminophenoxy) biphenyl-3,3′-disulfonic acid (BAPBDS) was synthesized by the method described in JP2003-68326A. BAPBDS was used as the sulfonated diamine, and 4,4′-bis (3-aminophenoxy) phenylsulfone (BAPPS) was used as the non-sulfonate diamine. In a dry 100 ml four-necked flask, 1.056 g (2.0 mmol) BAPBDS and 0.68 ml TEA are dissolved in 12 ml m-cresol and then 0.368 g (1.0 mmol) BAPB is added and dissolved. Then 0.804 g (3.0 mmol) NTDA and 0.51 g benzoic acid were added and the mixture was stirred at 80 ° C. for 4 hours and 180 ° C. for 20 hours under nitrogen gas atmosphere. The polymerization reaction solution was cooled to 80 ° C., diluted with 20 ml of m-cresol, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The solution viscosity ηSP / c (solvent: m-cresol; 0.5 wt%; 35 ° C.) of the obtained product was 2.8 dl / g. The product was dissolved in m-cresol, cast on a glass plate, and dried at 120 ° C. for 10 hours to obtain a TEA salt type copolymer sulfonated polyimide membrane. This was immersed in methanol for 2 days, then immersed in 0.5 M sulfuric acid solution for 2 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to obtain proton type random copolymer sulfonated polyimide NTDA-BAPBDS / BAPB ( 2/1) -r film was obtained. Table 1 shows the characteristic evaluation results of this film. Fig. 1 shows the relative humidity dependence of proton conductivity.
(Comparative Example 2)

Random copolymerized sulfonated polyimide NTDA-3,3'-BSPB / BAPPS (2/1) -r
3,3′-bis (3-sulfopropoxy) benzidine (3,3′-BSPB) was synthesized by the method described in JP-A-2004-155998. Random copolymerized sulfonated polyimide NTDA as in Comparative Example 1 except that 0.96 g (2.0 mmol) of 3,3′-BSPB was used as the sulfonated diamine and 0.433 g (1.0 mmol) of BAPPS was used as the non-sulfonate diamine. -3,3'-BSPB / BAPPS (2/1) -r membrane was obtained. Table 1 shows the characteristic evaluation results of this film. Fig. 1 shows the relative humidity dependence of proton conductivity and Fig. 2 shows the temperature dependence.
(Comparative Example 3)

Perfluorosulfonic acid-based electrolyte membrane A perfluorosulfonic acid-based electrolyte membrane (manufactured by Company D, thickness 50 μm) was used. Table 1 shows the characteristic evaluation results of this film.

Fabrication of fuel cell Random copolymer sulfonated polyimide NTDA-DBSPBDS / BAPPS (1/1) -r membrane (thickness 35μm) produced in the same manner as in Example 2 was previously applied to the catalyst active layer with 5% Nafion solution (USA) Dupont coated and dried Pt catalyst supported gas diffusion electrode (made by E-TEK, USA, Pt supported amount (0.75mg / cm2) with scissors at 135 ° C for 10 minutes at 60kg / cm2 pressure and membrane electrode An assembly (MEA) was fabricated with an effective electrode area of 5 cm2.The MEA was incorporated into a single cell made by E-TEK and set in a fuel cell evaluation device (nF, model As-510) made by nF. PEFC power generation performance was measured under the conditions of cell temperature 90 ° C, anode (H2) / cathode (O2) humidification temperature 88 ° C / 85 ° C, supply gas flow rate 150 / 100ml / min, back pressure 0.3MPa. It is shown in FIG.

Summary of Evaluation Results 1) As in Examples 1 and 4, homosulfonated polyimide membranes from diamines (DBSPBDS, DBSPBS) having 3 or 2 sulfonic acid groups and high IEC are soluble in water? Or it has a large WU, and the high-temperature water resistance in terms of film strength is not good.
2) The copolymerized sulfonated polyimide membrane having an IEC adjusted to an appropriate size (around 2) by copolymerization with a non-sulfonic acid diamine as in Examples 2, 3, and 5 has an appropriate WU. In addition, the membrane has a microphase separation structure, and has excellent high-temperature water resistance in terms of membrane strength despite the relatively high IEC. In this respect, it is superior to the main chain copolymer sulfonated polyimide membrane of Comparative Example 1.
3) As in Examples 2, 3, 5, 6 and 7, the decomposition temperature of the sulfonic acid group is 290 to 290 ° C., which is 30 to It is 40 ° C higher and has excellent high-temperature water resistance from the viewpoint of proton conductivity. This indicates that the sulfonated polyimide membrane in this patent is less susceptible to sulfonic acid group elimination in high-temperature water, and is superior in this respect to the side chain sulfonated polyimide membrane of Comparative Example 2. .
4) Compared to Comparative Examples 1 and 2, the sulfonated polyimide membrane in this patent has a high proton conductivity, and in particular, the decrease in proton conductivity at low humidity is small compared to the polymer of the comparative example. . (Table 1 and Figure 1)
5) The sulfonated polyimide membrane in this patent has high proton conductivity without decreasing proton conductivity even at a high temperature of 100 ° C. or higher. (Figure 2)
6) The sulfonated polyimide membrane in this patent has a very low methanol permeability coefficient compared to the perfluorosulfonic acid membrane of Comparative Example 3, and the ratio of proton conductivity to methanol permeability coefficient φ (φ = σ / PM) ) Is 3 times or more larger and is suitable as a polymer electrolyte membrane for direct methanol fuel cells.
7) As in Example 8, the solid polymer electrolyte fuel cell (PEFC) using the sulfonated polyimide membrane in this patent has excellent power generation characteristics and is therefore suitable as a polymer electrolyte membrane for PEFC. It is.

  The present invention is a solid electrolyte with high proton conductivity, high heat resistance, and high mechanical strength. Polyimide, as a cation exchanger, and as a diaphragm for various electrolysis, barrier properties against gases and liquids. In particular, it has excellent properties as an electrolyte membrane for fuel cells.

These are figures showing the relationship between humidity and conductivity at 50 ° C. for polyimide films. These are figures which show the relationship between the temperature and conductivity in 50% of humidity, 80%, and 100% about a polyimide film. These are figures which show the electric power generation characteristic of the fuel cell using the polyimide membrane manufactured in Example 8. FIG.

Claims (9)

A sulfonated aromatic polyimide having repeating structural units represented by the following general formula (1).

However, Ar1 is a tetravalent group having at least one aromatic ring, Ar2 is a trivalent benzene ring and a trivalent naphthalene ring, and X is at least one group represented by the following general formula. ,

Y is a hydrogen atom, a halogen atom, a sulfonic acid group, or any one group represented by the following formulas (3) to (16), and p is 0 or 1 (provided that Y is a hydrogen atom or a halogen atom) Sometimes it is an integer of 1).

However, n in (3)-(16) is an integer of 1-2. The sulfonated aromatic polyimide according to claim 1, wherein X is a group represented by the following formula (17).

(However, Z represents an aromatic ring directly bonded, —O—, —S—, —SO 2 —, —CF 2 —, —C (CF 3) 2 —, m is 1 to 30, and n is 1 to 2. Represents an integer.)   90% by mole or less of the groups constituting = Ar2-C (O) -X is substituted with a divalent or trivalent group having an aromatic ring and not bound to a sulfonic acid group The sulfonated aromatic polyimide according to claim 1 or 2.   2 to 90 mol% of the groups constituting = Ar2-C (O) -X are substituted with a divalent group having an aromatic ring and not bound to a sulfonic acid group. 3. The sulfonated aromatic polyimide according to 3.   2 to 30 mol% of the groups constituting = Ar2-C (O) -X are substituted with a trivalent group having an aromatic ring and not bound to a sulfonic acid group 3. The sulfonated aromatic polyimide according to 3.   90% by mole or less of the groups constituting = Ar2-C (O) -X is substituted with a divalent and / or trivalent group having an aromatic ring and not bound to a sulfonic acid group. 4. The sulfonated aromatic polyimide according to claim 3, wherein the groups constituting the = Ar2-C (O) -X are statistically dispersed in the polyimide chain.   90% by mole or less of the groups constituting = Ar2-C (O) -X is substituted with a divalent and / or trivalent group having an aromatic ring and not bound to a sulfonic acid group. The sulfonated aromatic polyimide according to claim 3, wherein the group constituting the = Ar2-C (O) -X is present in a block-like manner in a polyimide chain.   = Ar2-C (O) -X is a cross-linked structure in which 90 mol% or less is substituted with a trivalent group having an aromatic ring and not bound to a sulfonic acid group. The polyimide according to any one of claims 3, 5, and 6.   The electrolyte membrane which consists of a sulfonated aromatic polyimide of any one among the sulfonated aromatic polyimides of Claim 1 thru | or 8.

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