JP4545708B2 - Sulfonated aromatic polyimide - Google Patents

Description

  The present invention relates to novel sulfonated aromatic polyimides useful for cation exchangers, particularly electrolyte membranes.

  The aromatic diamino compound is used as a raw material for resin production such as polyamide and polyimide. Aromatic polyimide is generally obtained by polycondensation of an aromatic diamine such as oxydianiline and a tetracarboxylic dianhydride such as pyromellitic anhydride, and between the diamine residue and the acid anhydride residue. Super-engineering plastics, interlayer insulation materials, etc. because of the strong intermolecular interaction based on the charge transfer interaction of the material, and excellent thin film forming ability, mechanical strength, heat resistance, solvent resistance, and chemical stability. It is used in electronic materials or hollow fiber gas separation membranes. These excellent characteristics are also necessary for ion exchange membranes and electrolyte membranes for fuel cells, and polyimides having ion exchange groups such as sulfonic acid groups (also called sulfo groups) and phosphoric acid groups are particularly good. It is expected as an electrolyte membrane for fuel cells. However, polyimide has a drawback that the imide ring is easily hydrolyzed in an acidic aqueous solution, which is a major weakness compared to other sulfonated aromatic hydrocarbon polymers such as sulfonated polyphenylene and sulfonated polyethersulfone, The solution is a critical issue.

  Therefore, a polyimide having a 6-membered ring imide ring from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) is more resistant to hydrolysis than a 5-membered imide ring from phthalic anhydride. (Non-Patent Document 1), for example, in Patent Document 1, NTDA and sulfonated diamines and non-sulfonated diamines represented by the following chemical formulas (19) to (21) (for example, oxydianiline) It is disclosed that the copolymerized polyimide membrane is excellent as an electrolyte membrane for fuel cells. However, the water resistance of these sulfonated polyimide membranes is not sufficient, and in Patent Document 2, the sulfonated copolymerized polyimide membrane from the sulfonated diamine represented by the chemical formula (22) has further excellent water resistance. Is disclosed. This is because the electron-withdrawing sulfo group is bonded to the phenyl ring away from the phenyl ring to which the amino group is bonded, so that the basicity of the amine is high and the hydrolysis resistance of the imide ring is increased ( For example, it is considered Non-Patent Document 2).

（Ｄ₂はＯ、Ｓ、ＣＨ₂又はＣ（ＣＦ₃）₂等、Ｒ₄〜Ｒ₇は水素原子又はアルキル基、Ａｒはスルホ基を有する芳香環残基である。）

(D ₂ is O, S, CH ₂ or C (CF _{3) 2,} etc., R ₄ to R ₇ is a hydrogen atom or an alkyl group, Ar is an aromatic ring residue having a sulfo group.)

  All of the sulfonated polyimides described above are cases in which the sulfo group is directly bonded to the polymer main chain. In a perfluorosulfonic acid polymer electrolyte membrane, a sulfo group is bonded to the fluoroether end of the side chain, and the hydrophilic sulfo group part is microphase-separated from the hydrophobic main chain part to form a hydrophilic ion channel. It is thought that With the expectation of the same effect, a side chain type sulfonated aromatic hydrocarbon polymer film in which a sulfo group is introduced into a side chain of an aromatic hydrocarbon polymer has been reported so far. For example, poly-1,4-phenylene having a 4- (4-sulfophenoxy) benzoyl group represented by the chemical formula (23) (Non-patent Document 3), polysulfone having a 2-sulfobenzoyl group represented by the chemical formula (24) (Non-patent document 4), polysulfone having an ω-sulfoalkylsulfonyl group represented by chemical formula (25) (non-patent document 5), and polysulfone having an ω-sulfoalkyl group represented by chemical formula (26). Examples thereof include hydrogen-based polymers (Patent Document 3).

  Also in polyimide, a diamine having a ω-sulfoalkoxy group represented by the chemical formula (27) (Non-patent Documents 6 and 4) and a diamine having a sulfophenoxy group represented by the chemical formula (28) (Non-patent Documents 7 and 8). The synthesis and physical properties of the polyimide have been reported. These side-chain sulfonated polyimide membranes have a microphase separation structure and have been shown to have relatively good high temperature water resistance.

In addition, a polyimide having a sulfo group in the side chain and a sulfonated aromatic group bonded to the aromatic ring of the main chain via an alkylene ether bond (Patent Document 5) or the following general formula (29)
-R-SO ₃ H (29)
A polyimide having a sulfonic acid group in the side chain represented by (R represents alkylene, halogenated alkylene, arylene, halogenated arylene, or ether bond) is shown (Patent Document 6). Some of these ion exchangers have durability and hydrolysis resistance at relatively high temperatures, but further hydrolysis resistance is desired.

Special Table 2000-510511 Japanese Patent Laid-Open No. 2003-64181 JP 2002-110174 A Japanese Patent Laid-Open No. 2004-155998 JP 2004-35891 A JP 2004-107484 A Polymer vol. 42, pages 5097-5105 (2001) Journal Membrane Science Vol. 230, pp. 111-120 (2004) Solid State Ionics, Vol. 147, 189-194 (2002) Macromolecular Rapid Communications, Vol. 23, 896-900 (2002) Journal Membrane Science Vol. 230, pp. 61-70 (2004) Journal Materials Chemistry Vol. 14, pp. 1062-1070 (2004) Transaction Materials Research Society Japan Vol. 29, pages 2541-2546 (2004) Polymer Preprint, Japan 54, 4605-4606 (2005)

  An electrolyte with excellent high-temperature and water-resistance that is a tough and flexible sulfonated polyimide thin film that relies on the strong intermolecular interaction of polyimide and significantly improves the hydrolysis resistance of the imide ring. There is a need to develop membranes. When sulfonated polyimide membranes developed so far are used for a long period of time, hydrolysis of the imide ring occurs and the molecular weight decreases, so the membrane may lose mechanical properties. In addition, during use at a high temperature, there may be a phenomenon that the sulfo group is eliminated over time, the ion exchange capacity is lowered and the performance is lowered. Since these phenomena become particularly noticeable at high temperatures exceeding 100 ° C, they have long-term durability and mechanical strength even when used at temperatures above 100 ° C, and can be used in a wide temperature range. Development of a polymer electrolyte membrane that can withstand use as an electrolyte membrane for a fuel cell with little decrease in proton conductivity under low humidity is desired. Another object of the present invention is to provide a sulfonated polyimide suitable as a polymer electrolyte membrane.

  In order to solve the above-mentioned problems, the present inventors have made extensive studies and found that a polyimide having a sulfophenyl group as a substituent obtained by using a specific diamine compound as a monomer is useful for solving the above problems. The headline and the present invention were completed.

（但し、Ａｒ₁は少なくとも１つの芳香環を有する４価の基であり、Ａｒ₂は下記式（ａ）で示される２価の基である。）

（但し、Ｘは水素原子、アルカリ金属、アンモニウム又はアミンである。） That is, this invention is a sulfonated aromatic polyimide characterized by having the structural unit represented by following formula (1).

(However, Ar ₁ is a tetravalent group having at least one aromatic ring, and Ar ₂ is a divalent group represented by the following formula (a).)

(However, X is a hydrogen atom, an alkali metal, ammonium, or an amine.)

（但し、Ａｒ₃は少なくとも１つの芳香環を有する４価の基であり、Ａｒ₄は少なくとも１つの芳香環を有し、−ＳＯ₃Ｘを有しない２価の基である。） Moreover, this invention is said sulfonated aromatic polyimide which has 5-100 mol% of structural units represented by Formula (1), and 0-95 mol% of structural units represented by following formula (2).

(However, Ar ₃ is a tetravalent group having at least one aromatic ring, and Ar ₄ is a divalent group having at least one aromatic ring and not —SO ₃ X.)

（但し、Ａｒ₅は少なくとも１つの芳香環を有する４価の基であり、Ａｒ₆は少なくとも１つの芳香環を有し、−ＳＯ₃Ｘを有しない３価の基である。） Furthermore, this invention is said sulfonated aromatic polyimide which has 50 mol% or less of structural units represented by following formula (3).

(However, Ar ₅ is a tetravalent group having at least one aromatic ring, and Ar ₆ is a trivalent group having at least one aromatic ring and not —SO ₃ X.)

（但し、Ｚ及びＹは、ＣＯ、Ｏ、ＣＯ-Ｐｈ-ＣＯ又は直接結合であり、Ｐｈはフェニレンである。） Here, the Ar _1, Ar ₃ and Ar ₅ is the following formula (4), it is desirable that a tetravalent group represented by (5) or (6).

(However, Z and Y are CO, O, CO-Ph-CO, or a direct bond, and Ph is phenylene.)

（但し、Ｘは式（ａ）と同じである。） Furthermore, this invention is a manufacturing method of the sulfonated aromatic polyimide characterized by carrying out the polymerization reaction of the diamine and aromatic tetracarboxylic dianhydride which contain 5 mol% or more of diamine represented by following formula (7). is there.

(However, X is the same as the formula (a).)

  The sulfonated aromatic polyimide having sulfophenyl as a substituent of the present invention has excellent mechanical strength and is a polyimide in which a sulfonic acid group is directly bonded to an aromatic ring constituting the main chain, and an alkyl via an ether bond. Compared to polyimides with sulfonic acid groups bonded to benzene groups or phenyl groups, etc., when used under harsh conditions such as in aqueous solution at high temperature, etc. Excellent electrolyte membrane that has high barrier properties against liquids such as hydrogen gas of fuel and liquid such as methanol when used as a fuel cell electrolyte membrane. can do. That is, in the polyimide of the present invention, there is no sulfonic acid group which is a hydrophilic group in the portion constituting the main chain, and the hydrophilic sulfonic acid group-containing side chain aromatic ring is separated from the imide ring. Therefore, the hydrophobic main chain portion and the hydrophilic side chain base portion easily have a microphase separation structure. Therefore, the water sorption amount is small in the hydrophobic domain of the polyimide main chain part, and the main chain becomes difficult to undergo hydrolysis when used as an electrolyte membrane. Furthermore, the side chain aromatic ring having a sulfonic acid group is directly bonded to the phenyl ring constituting the main chain, and the side chain aromatic ring is hydrolyzed compared to the polyimide bonded to the main chain via an ether group or the like. Desorption due to decomposition hardly occurs.

  The sulfonated aromatic polyimide of the present invention has a structural unit represented by the formula (1). The sulfonated aromatic polyimide of the present invention can have other structural units other than the structural unit represented by the formula (1). Preferred other structural units are represented by the formulas (2) and (3). There is a structural unit.

  The sulfonated aromatic polyimide of the present invention can be synthesized by reacting a diamine containing a specific aromatic diamine with an aromatic tetracarboxylic acid (preferably an aromatic tetracarboxylic dianhydride). At this time, a triamine, an aromatic tricarboxylic acid anhydride, or the like can be used in combination if necessary.

In the formulas (1), (2) and (3), Ar ₁ , Ar ₃ and Ar ₅ are tetravalent groups having at least one aromatic ring and may be the same or different. In the formulas (1) to (3), aromatic tetracarboxylic acids give Ar ₁ , Ar ₃ and Ar ₅ , and aromatic diamine gives Ar ₂ or Ar ₄ , so preferable Ar _{1 to} Ar ₄ are shown below. It is understood from aromatic tetracarboxylic acids and diamine components. In addition, since Ar ₆ in the formula (3) is a trivalent group derived from triamine, it is understood from the triamine component.

  Aromatic tetracarboxylic acids are not particularly limited. For example, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3 , 3 ′, 4,4′-benzophenone tetracarboxylic 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 acid, or their acid dianhydrides and esterified products. In particular, an acid dianhydride having a naphthalene ring represented by the following formula (8), (9) or (10) and capable of forming a six-membered imide is preferred from the water resistance of the sulfonated polyimide.

In the formulas (9) and (10), Z and Y are CO, O, CO—C ₆ H ₄ —CO or a direct bond. When CO—C ₆ H ₄ —CO, C ₆ H ₄ can be o-, m- or p-phenylene, but is preferably p-phenylene. Z and Y are represented by the following equations.

As the diamine component, an aromatic diamine represented by the formula (7) or a diamine containing the aromatic diamine is used. The aromatic diamine represented by the formula (7) gives Ar ₂ in the formula (1). Ar ₂ is represented by the formula (a).

In the formula (7) and the formula (a), X is H, an alkali metal (Li, Na, K, Rb, Cs, etc.), NH ₄ or an amine. The position where the phenyl group (referred to as sulfophenyl group) substituted with SO ₃ X group (referred to as sulfo group) is substituted with the benzene ring constituting 4,4′-diaminobiphenyl is the 3,3′-position, 2,2 ′ -Position, 2,3'-position, etc., with 2,2'-position being preferred. The sulfophenyl group includes an o, m or p-sulfophenyl group, and a p-sulfophenyl group is preferred.

In the formula (2), Ar ₄ is a divalent organic group having no sulfo group, and is a group generated from another diamine other than the aromatic diamine represented by the formula (7). As such other diamines, known aromatic diamines can be used. For example, in addition to paraphenylenediamine, metaphenylenediamine, 4,4′-oxydianiline, 3,4′-oxydianiline, 9,9-bis (4-aminophenyl) fluorene, Ar _{4 includes the following} divalent compounds: Preferred examples include diamines that give the organic group.

  Among these diamines, 4,4′-bis (4-aminophenoxy) biphenyl (BAPB) and 1,4-bis (4-aminophenoxy) benzene (BAPBz) are preferable.

In the present invention, a trifunctional amine (triamine) can be used in addition to the diamine. By using triamine, it can be set as the sulfonated aromatic polyimide which has a branched crosslinked structure in a molecule | numerator. The triamine is preferably an aromatic amine such as 1,3,5-tris (4-aminophenoxy) benzene (TAPB) from the viewpoint of heat resistance of the polyimide. The residue (Ar ₆ ) arising from TAPB is represented by the following formula.

Two or more aromatic tetracarboxylic acids, diamine components, or triamine components that give Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ , Ar ₆ may be used.

  In addition to the structural unit represented by the formula (1), the sulfonated aromatic polyimide of the present invention can have 1 or 2 of the structural unit represented by the formula (2) and the formula (3), It can have a small amount of other structural units as long as the effects of the present invention are not impaired. The structural unit represented by the formula (1) may be contained in a range of 5 to 100 mol%, preferably 50 to 100 mol%. The structural unit represented by the formula (2) may be contained in the range of 0 to 95 mol%, preferably 10 to 70 mol%. The structural unit represented by the formula (3) may be contained in the range of 0 to 50 mol%, preferably 5 to 25 mol%. In addition, the polyimide terminal is excluded from the calculation.

  Preferred examples of the sulfonated aromatic polyimide of the present invention include polyimides composed of the following structural units. 1) Polyimide consisting only of the structural unit represented by Formula (1), 2) Polyimide consisting of the structural unit represented by Formula (1) and the structural unit represented by Formula (2), 3) Formula (1) A polyimide composed of a structural unit represented by formula (3) and a structural unit represented by formula (3), 4) a structural unit represented by formula (1), a structural unit represented by formula (2), a structural unit and a formula ( 3) Polyimide comprising the structural unit represented by 3).

  When a plurality of structural units are included, the molar ratio of the formula (1) / [formula (2) + formula (3)] is in the range of 5/95 to 95/5, preferably 10/90 to 95 / 5, More preferably, it is 50 / 50-95 / 5, Most preferably, it is 70 / 30-95 / 5. In the sulfonated aromatic polyimide, when the unit represented by the formula (1) is less than 5 mol% with respect to the total structural unit, it is difficult to develop characteristics such as ion exchange capacity and proton conductivity, which is not preferable. Moreover, the structure of the sulfonated aromatic polyimide in the case of having a plurality of structural units may be any of a random copolymer, a block copolymer, and a branched crosslinked structure.

  The sulfonated aromatic polyimide of the present invention has a solution viscosity (35 ° C., 0.5 wt% solution) of 0.7 to 20 dl / g, preferably 2.0 to 10 dl / g. It is preferable in terms of film forming properties and film properties. Although there are no restrictions on the use of this sulfonated aromatic polyimide, it is suitable for uses such as electrodialysis, diffusion dialysis, and battery diaphragm because of its electrolyte property, ion exchange property, and conductivity. . When forming a film, it is obtained by applying a sulfonated aromatic polyimide or its precursor (polyamic acid) solution on a substrate to a predetermined thickness, and drying and curing.

  The sulfonated aromatic polyimide of the present invention can be obtained by polymerizing a diamine containing 5 mol% or more of the diamine represented by the above formula (7) with an aromatic tetracarboxylic acid. For this polymerization reaction, a known polyimide synthesis method can be employed. For example, in a polar solvent, a reaction raw material mainly comprising an aromatic diamine and an aromatic tetracarboxylic dianhydride, a tertiary amino compound, toluene or xylene as an azeotropic solvent is added, and the mixture is heated to 140 to 220 ° C. This can be easily achieved by performing a condensation polymerization reaction for 0.5 to 100 hours while removing the produced water together with the azeotropic solvent. Here, examples of the tertiary amino compound include trimethylamine and triethylamine. If necessary, benzoic acid, isoquinoline and the like may be added as a catalyst. The molar ratio of the amino group of aromatic diamine (including triamine when triamine is used) and aromatic tetracarboxylic dianhydride is preferably in the range of 0.95 to 1.05. It is not preferable because the strength of the film obtained by lowering the molecular weight of polyimide is lowered.

Abbreviations used in the examples are as follows.
2,2'-BSPhB: 2,2'-bis (4-sulfophenyl) benzidine
BAPB: 4,4'-bis (4-aminophenoxy) biphenyl
TAPB: 1,3,5-tris (4-aminophenoxy) benzene
NTDA: 1,4,5,8-Naphthalenetetracarboxylic dianhydride
TEA: Triethylamine

Synthesis example 1
step 1
To a three-necked flask containing a stirrer, 75 g of 3-nitrodiphenyl, 430 mL of ethyl alcohol, 215 mL of 30 wt% sodium hydroxide aqueous solution, and 84 g of zinc powder were sequentially added, and the reaction was performed at the boiling temperature for 5 hours. After cooling to room temperature, the reaction solution was filtered to remove zinc powder, and the residue was washed well with ethyl acetate. The organic layer was separated, washed with water, dried and concentrated to recover 65 g of the azo compound.

Step 2
In a three-necked flask containing a stir bar, 60 g of the azo compound obtained in Step 1 and 196 mL of solvent ethyl alcohol were dissolved. Thereafter, a saturated aqueous ammonium chloride solution and zinc powder were sequentially added to the reaction vessel and refluxed for 1 hour. The reaction solution was cooled to room temperature, filtered, and zinc powder and white solid product were collected by filtration and washed well with water. Next, the filter residue was washed with ethyl acetate to dissolve the product, and the zinc powder was separated. The filtrate was dried and concentrated to obtain 40 g of the desired white hydrazo compound.

Step 3
In a three-necked flask containing a stir bar, 30 g of the hydrazo compound obtained in Step 3 was dissolved in 500 mL of THF as a solvent. 5N hydrochloric acid was added dropwise, and the reaction was carried out by stirring at 0 ° C. to room temperature. An ice-cold aqueous sodium hydroxide solution was added to the reaction solution for neutralization and liquid separation, and the THF layer was recovered. The aqueous layer was extracted three times with toluene, dried, concentrated and purified to obtain 15 g of 2,2′-bisphenylbenzidine (2,2′-BPhB) as a white powder. Melting point 152 ° C.

Step 4
6.72 g (20.0 mmol) of 2,2′-BPhB was placed in a 100 ml three-necked flask, cooled in an ice bath, and 10 ml of concentrated sulfuric acid was slowly added with stirring. After 2,2′-BPhB was completely dissolved, 5 ml of fuming sulfuric acid (SO ₃ : 60%) was slowly added. After complete addition of fuming sulfuric acid, the mixture was held at 0 ° C. with stirring for 0.5 hours. Then slowly warmed to 60 ° C. and kept at 60 ° C. for 2 hours. After cooling to room temperature, the mixture was poured into 200 ml of methanol to precipitate a white solid. The solid was filtered off and recrystallized from water to obtain 8.63 g of a solid product (yield 87%).

The obtained solid product was subjected to ¹ HNMR measurement by JEOL JEOL EX-270 using deuterated dimethyl sulfoxide (DMSO-d ₆ ) as a solvent. ^{According to 1} HNMR (270 MHz, DMSO-d ₆ ), δ: 6.34-6.40 (2H, S), 6.40-6.49 (2H, D), 6.62-6.78 (6H, M), 7.24-7.34 (4H, D) It showed a peak and was confirmed to be 2,2′-BSPhB represented by the following formula. Melting point is 300 ° C or higher.

Example 1
In a dry 100 ml four-necked flask, 2.480 g (5.0 mmol) 2,2′-BSPhB and 1.7 ml TEA were dissolved in 22 ml m-cresol, then 1.340 g (5.0 mmol) NTDA and 0.85 g of benzoic acid was added and the mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 20 hours under a nitrogen gas atmosphere. The polymerization reaction solution was cooled to 80 ° C., diluted with 30 ml of m-cresol, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The resulting product had a reduced viscosity η _SP / c (solvent: m-cresol; 0.5 wt%; 35 ° C., the same shall apply hereinafter) of 3.8 dl / g.

  The product was dissolved in m-cresol, cast onto a glass plate, and dried at 100 ° C. for 1 hour and 120 ° C. for 10 hours to obtain a TEA salt type sulfonated polyimide membrane. This was immersed in methanol for 1 day, then immersed in a 0.5 M sulfuric acid solution for 3 days to exchange protons, washed with water, and vacuum dried at 150 ° C. for 10 hours to obtain a proton type sulfonated polyimide NTDA-2 represented by the following formula: Therefore, 2'-BSPhB membrane was obtained.

Example 2
2,2′-BSPhB was used as the sulfonated diamine, and BAPB was used as the non-sulfonate diamine. In a dry 100 ml four-necked flask, 2.976 g (6.0 mmol) 2,2'-BSPhB and 2.10 ml TEA were dissolved in 35 ml m-cresol and then 1.104 g (3.0 mmol) BAPB was dissolved. After addition and dissolution, 2.412 g (9.0 mmol) NTDA and 1.53 g benzoic acid were added and the mixture was stirred at 80 ° C. for 4 hours and 180 ° C. for 20 hours under a nitrogen gas atmosphere. The polymerization reaction solution was cooled to 80 ° C., diluted with 35 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 η _{SP /} c of the obtained product was 3.0 dl / g. The product was dissolved in m-cresol, cast on a glass plate, and dried at 100 ° C. for 1 hour and 120 ° C. for 10 hours to obtain a TEA salt type copolymer sulfonated polyimide membrane. This was immersed in methanol for 1 day, then immersed in 0.5 M sulfuric acid solution for 3 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-2,2 ′ A BSPhB / BAPB (2/1) -r membrane was obtained. The FTIR spectrum of this film is shown in FIG. FIG. 2 shows a ¹ HNMR spectrum obtained by dissolving this film in DMSO-d ₆ . From the assignment and integral intensity, it was confirmed that the product was NTDA-2,2′-BSPhB / BAPB (2/1) represented by the following formula.

Example 3
A polyimide was synthesized in the same manner as in Example 2 except that the molar ratio of 2,2′-BSPhB and BAPB was changed to 3/2. The product obtained had a reduced viscosity η _SP / c of 2.8 dl / g. The product was dissolved in m-cresol, cast into a film and treated in the same manner as in Example 2, and the proton type random copolymer sulfonated polyimide NTDA-2,2'-BSPhB / BAPB ( A 3/2) -r film was obtained.

Example 4
1.488 g (3.0 mmol) 2,2'-BSPhB and 1.05 ml TEA are dissolved in 15 ml m-cresol in a dry 100 ml four-necked flask, then 1.340 g (5.0 mmol) NTDA and 0.85 g of benzoic acid was added and the mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 10 hours under a nitrogen gas atmosphere. After cooling the reaction solution to room temperature, 5 ml of m-cresol and 0.736 g (2.0 mmol) of BAPB were added, and the mixture was stirred at 80 ° C. for 4 hours and 180 ° C. for 10 hours under a nitrogen gas atmosphere. The solution was cooled to 80 ° C., diluted with 30 ml of m-cresol, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The product obtained had a reduced viscosity η _SP / c of 3.3 dl / g. The product was dissolved in m-cresol, cast into a film and treated in the same manner as in Example 2, and the proton type sequenced copolymer sulfonated polyimide NTDA-2,2'-BSPhB / BAPB represented by the following formula A (3/2) -s film was obtained.

Example 5
In a dry 100 ml four-necked flask 1, 1.488 g (3.0 mmol) 2,2'-BSPhB and 1.05 ml TEA are dissolved in 10 ml m-cresol and then 0.7236 g (2.7 mmol) NTDA. And 0.46 g of benzoic acid were added and the mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 10 hours under a nitrogen gas atmosphere. In a dry 100 ml four-necked flask 2, 0.736 g (2.0 mmol) BAPB and 7 ml m-cresol are added, then 0.6164 g (2.3 mmol) NTDA and 0.39 g benzoic acid are added, and nitrogen gas is added. Under atmosphere, the mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 10 hours. After cooling the reaction solution to room temperature, put the reaction solution in Flask 2 into Flask 1 under a nitrogen gas atmosphere, wash Flask 2 3 times with 1 ml of m-cresol, and put the solution into Flask 1 as well. The mixed solution was stirred at 80 ° C. for 10 hours and at 180 ° C. for 48 hours. The polymerization reaction solution was cooled to 80 ° C., diluted with 30 ml of m-cresol, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The product obtained had a reduced viscosity η _{SP /} c of 3.0 dl / g. The product was dissolved in m-cresol, cast into a film and treated in the same manner as in Example 2, and the proton type block / block copolymer sulfonated polyimide NTDA-2,2′-BSPhB / A BAPB (3/2) -b film was obtained.

Example 6
The TABP used was synthesized by reacting 1,3,5-trihydroxybenzene and 4-fluoronitrobenzene and then reducing.
In a dry 100 ml four-necked flask, 1.984 g (4.0 mmol) 2,2'-BSPhB 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 Of benzoic acid was added and 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 m-cresol were added, and the mixture was 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 further at 200 ° C for 10 hours, respectively. A polyimide film was obtained. This is immersed in methanol for 2 days, then immersed in a 0.5M sulfuric acid solution for 3 days to exchange protons, washed with water and vacuum dried at 150 ° C. for 10 hours, and then a proton-type branched cross-linked sulfonated polyimide NTDA represented by the following formula: A -2,2'-BSPhB / TAPB (5/4) film was obtained.

IR spectrum of the polyimide obtained in Example 2 ¹ HNMR spectrum of the polyimide obtained in Example 2

Claims (5)

A sulfonated aromatic polyimide having a structural unit represented by the following formula (1):

(However, Ar ₁ is a tetravalent group having at least one aromatic ring, and Ar ₂ is a divalent group represented by the following formula (a).)

(However, X is a hydrogen atom, an alkali metal, ammonium, or an amine.) 2. The sulfonated aromatic polyimide according to claim 1, comprising 5 to 100 mol% of a structural unit represented by the formula (1) and 0 to 95 mol% of a structural unit represented by the following formula (2).

(However, Ar ₃ is a tetravalent group having at least one aromatic ring, and Ar ₄ is a divalent group having at least one aromatic ring and not —SO ₃ X.) The sulfonated aromatic polyimide according to claim 1 or 2 having 50 mol% or less of a structural unit represented by the following formula (3).

(However, Ar ₅ is a tetravalent group having at least one aromatic ring, and Ar ₆ is a trivalent group having at least one aromatic ring and not —SO ₃ X.) Ar ₁ , Ar _3, and Ar ₅ are tetravalent groups represented by the following formula (4), (5), or (6): The sulfonated aromatic polyimide according to claim 1.

(However, Z and Y are, CO, O, a CO-C ₆ H ₄ -CO or a direct bond.) The manufacturing method of the sulfonated aromatic polyimide characterized by carrying out the polymerization reaction of the diamine and aromatic tetracarboxylic dianhydride which contain 5 mol% or more of diamine represented by following formula (7).

(However, X is a hydrogen atom, an alkali metal, ammonium, or an amine.)

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