JP4686719B2 - Method for producing crosslinked cation exchange resin membrane having sulfonic acid group and electrolyte membrane for fuel cell comprising said membrane - Google Patents

Description

  The present invention relates to a method for producing a sulfonic acid type crosslinked cation exchange membrane by a novel crosslinking method and a fuel cell electrolyte membrane comprising the membrane.

  A polymer compound having a sulfonic acid group in the molecule is known as a cation exchange resin. Such a cation exchange resin molded into a membrane, that is, a cation exchange resin membrane, has the property of permeating only cations, so that ions can be separated by electropermeation or diffusion dialysis, salt metathesis, etc. Used as an electrolyte membrane for oxidation-reduction reactions and fuel cells.

  A linear polymer compound having a sulfonic acid group as a cation exchange group in a molecule has a high affinity with water because the polarity of the sulfonic acid group is large, and as the ion exchange capacity increases, The film becomes highly swellable, the film shape stability is lowered, and finally the film is dissolved.

  Therefore, it is often performed to crosslink a polymer as a cation exchange resin film that maintains a high cation exchange capacity and has shape stability or excellent mechanical strength.

  For example, in the case of a cation exchange resin membrane of a type in which polystyrene or a styrene monomer is copolymerized and a sulfonic acid group is introduced into a benzene nucleus, generally a crosslinked cation exchange resin membrane can be obtained by copolymerizing divinylbenzene. Has been done.

  In the case of a polycondensation type cation exchange resin membrane such as sulfonated polyimide used for fuel cells or the like, directly or directly on the aromatic ring of a polycondensate of tetracarboxylic dianhydride and diamino aromatic compound. Although a sulfonic acid group is introduced via a substituent, a crosslinked structure is given to the polyimide polymer compound obtained by replacing a part of the diamino aromatic compound with a triamino aromatic compound. Similarly, in a polycondensation type polymer compound such as polyether, polyetherketone or polysulfone, it is conceivable to obtain a resin having a crosslinked structure by co-condensing a trifunctional substance. Polycondensates require a relatively high temperature during polycondensation and tend to gel and become unmoldable before being subjected to the molding process.

  Furthermore, since a polymer having a crosslinked structure generally loses thermoplasticity, it becomes difficult to process a polycondensate. For this reason, it must be molded in the state of a prepolymer and cast (compressed) in the same manner as cast (compressed). Accordingly, it becomes difficult to manufacture a large area film or the like. For this reason, the manufacturing method of the cation exchange resin membrane which has a crosslinked structure which avoids this inconvenience was desired.

  The present invention provides a method for producing a crosslinked cation exchange resin membrane having a sulfonic acid group by forming a polymer compound having a sulfonic acid group into a membrane in advance and then providing a crosslinked structure.

  In particular, as a diaphragm for a fuel cell, polyimide, polyphenylene, polyether, polysulfide, polysulfone, polypolysiloxane having good dimensional stability and high mechanical strength at high temperatures exceeding 80 ° C. and low permeability of organic solvents such as alcohol. An electrolyte membrane of ether sulfone, polyether ketone, polyether ether ketone, or polyoxazole type is provided.

  A feature of the present invention is that a crosslinked structure is formed using a sulfonic acid group of a linear polymer compound having a sulfonic acid group in the main chain or side chain.

  That is, the present invention comprises the following aspects.

(1) a polymer compound having a sulfonic acid group, and a substance having a high carbon atoms electron density bonded hydrogen atoms in the molecule with a dehydrating agent solution, dehydrated from the sulfonic acid group and the hydrogen atom A method for producing a crosslinked cation exchange resin membrane, characterized by reacting .

  (2) The method for producing a crosslinked cation exchange resin membrane according to (1), wherein the substance having a high electron density carbon atom bonded with a hydrogen atom in the molecule is an aromatic ring bonded with an electron donating group. .

  (3) The crosslinked cation exchange according to (1) or (2), wherein at least one compound selected from concentrated phosphoric acid, polyphosphoric acid and phosphorus pentoxide dissolved in a solvent is used as a dehydrating agent. A method for producing a resin film.

  (4) The method for producing a crosslinked cation exchange resin membrane according to (3), wherein the phosphorus pentoxide dissolved in the solvent is phosphorus pentoxide dissolved in methanesulfonic acid.

  (5) The crosslinking according to any one of (1) to (4), wherein the polymer compound having a sulfonic acid group has a carbon atom having a high electron density in which hydrogen atoms are bonded in the molecule. A method for producing a cation exchange resin membrane.

  (6) A polymer compound having a sulfonic acid group and a compound having two or more carbons with high electron density in which hydrogen is bonded in the molecule are bonded by a dehydration reaction according to any one of (1) to (4) The manufacturing method of the bridge | crosslinking cation exchange resin membrane of description.

  (7) The polymer compound having a sulfonic acid group is at least one polymer compound selected from polyphenylene, polyether, polysulfide, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyoxazole and polyimide ( A method for producing a crosslinked cation exchange resin membrane according to any one of 1) to (5).

  (8) The method for producing a crosslinked cation exchange resin membrane according to (2), wherein the electron donating group is at least one selected from —O—, —S—, alkyl, alkylene, aryl, and arylene.

  (9) An electrolyte membrane for a fuel cell comprising a crosslinked cation exchange resin membrane obtained by any one of items (1) to (8).

  As described above, the cross-linking reaction in each aspect of the present invention is to combine the two using a dehydration reaction between a sulfonic acid group present in one polymer compound and active hydrogen present in the same or different compound.

  Conventionally, the reaction represented by the following chemical formula (1) is known (SYNTHESIS: April 1984 323-325).

（但し、Ｒ^１，Ｒ^２は芳香族環を表す）
本発明は、化学式（１）と類似な反応を用いるものであるが、スルホン酸基は、必ずしも芳香族環に結合するものでなくてもよく、例えばアルキレン基を介して存在していてもよい。

(However, R ¹ and R ² represent an aromatic ring)
In the present invention, a reaction similar to the chemical formula (1) is used, but the sulfonic acid group does not necessarily have to be bonded to the aromatic ring, and may exist through an alkylene group, for example. .

  Furthermore, the sulfonic acid group may be present in the main chain or may be present in the side chain. As described above, a method using a sulfonic acid group bonded to a polymer compound as a crosslinking means has not been known at all.

  The present inventors have found out as a result of earnest research.

  In the present invention, as a method for producing a cation exchange resin membrane having a crosslinked structure, mainly a membrane-like material is once formed and then crosslinked, so that it is extremely simple and without being restricted by the shape. It can be carried out.

  However, the cation exchange membrane having a cross-linked structure according to the present invention can compensate for the respective drawbacks on the surface and can provide an excellent fuel cell electrolyte membrane.

  In the simple and effective crosslinking method of the present invention, a part of a sulfonic acid group is subjected to a dehydration reaction with an active hydrogen atom bonded to a carbon atom having a relatively high electron density, and a polymer chain is formed via a generated sulfonyl group. It is based on bonding and crosslinking and can be applied to a wide range of sulfonated polymers.

  That is, the polymer compound having a sulfonic acid group is not particularly limited, and a sulfonated product of a copolymer of styrene and another copolymerizable monomer such as ethylene, methyl (meth) acrylate, vinyl chloride, or the like. Cation exchange membranes such as fluorovinyl ether sulfonic acid (for example, Nafion, trade name) for concentration and desalination of sodium chloride, electrolysis of sodium chloride, polyphenylene, polyether, polysulfide, polysulfone, polyethersulfone, polyetherketone, polyether A cation exchange resin membrane comprising a polymer compound having a sulfonic acid group in the main chain or side chain of a polymer having a polycondensation main chain such as ether ketone, polybenzoxazole and polyimide is useful as a fuel cell. Moreover, since it is a polymer compound that is generally difficult to crosslink, As a light of the subject, it is an important polymer compound.

  In FIG. 1, the sulfonic acid group may be directly bonded to the aromatic ring, or may be bonded to a side chain alkyl group or a side chain aromatic ring. If there are active hydrogen atoms bonded to carbon with a relatively high electron density in the polymer main chain or side chain aromatic ring, the polymer film is placed in a liquid dehydrating agent, and the reaction conditions are controlled. As shown in the schematic diagram of FIG. 1, the reaction can be caused to generate a sulfonyl group to introduce a crosslinked structure.

  Here, carbon having a high electron density bonded with hydrogen means that it is susceptible to attack by a cationoid reagent, such as hydrogen bonded to an aromatic ring, in particular, an electron donating atom or atom in the aromatic ring. When a group, for example, an oxygen atom such as an ether group or a sulfur atom such as a thio group, an alkyl group such as a methyl group, an alkylene group, an aryl group such as a phenyl group or an arylene group is bonded to an aromatic ring, The carbon in the ortho or para position is carbon having a high electron density.

  That is, those skilled in the art can easily understand what chemical structure is carbon having a high electron density.

  In the present invention, when carbon having a high electron density in which hydrogen is bonded to a polymer compound having a sulfonic acid group is present, a crosslinked network structure can be formed as shown in FIG.

  Of course, the crosslinked cation exchange resin membrane according to the present invention can be formed also between a polymer compound having a sulfonic acid group and a polymer compound having high electron density carbon bonded to hydrogen having no sulfonic acid group. You can also.

  Further, in the case of a high molecular compound having a sulfonic acid group and having hydrogen bonded to high electron density carbon, the low molecular compound having two or more high electron density carbon bonded to hydrogen to the high molecular compound For example, diphenyl ether or the like is impregnated in a polymer compound having a sulfonic acid group using a solvent or the like, and a dehydration reaction is performed as shown in FIG.

  Further, before the polymer compound having a sulfonic acid group is formed into a film shape, the diphenyl ether or the like is mixed, and the diphenyl ether or the like is dissolved in the polymer, and after this is formed, the dehydration treatment is performed. As a result, a crosslinked structure can be formed.

  Next, the dehydration treatment in the present invention generally uses a dehydrating agent such as phosphorus pentoxide or polyphosphoric acid. In general, these are preferably used as liquid dehydrating agents dissolved in a solvent such as methanesulfonic acid, alkylsulfonic acid such as trifluoromethanesulfonic acid, and aromatic sulfonic acid such as chlorobenzenesulfonic acid. In general, as a solution of the dehydrating agent, the solvent / dehydrating agent is used in a range of 10 / 0.1 to 10/2 (weight ratio), particularly 10 / 0.5 to 10 / 1.5. Among these, a dehydrating agent solution composed of methanesulfonic acid / phosphorus pentoxide is preferable.

  The treatment method is achieved by immersing the polymer compound film to be treated in a liquid dehydrating agent. The crosslinking reaction includes the type of dehydrating agent or solvent, the processing temperature, the processing time, the polymer compound to be treated, and the type of compound (polymer compound and / or low molecular compound) containing hydrogen-bonded carbon with high electron density. However, in general, when a system in which phosphorus pentoxide is dissolved in methanesulfonic acid is used as a liquid dehydrating agent, the treatment temperature is 0 ° C. to 150 ° C., preferably 20 ° C. ˜100 ° C., 5 minutes to 1 week, preferably about 30 ° C. for 3 days, 60 ° C. to 80 ° C. for about 5 hours, there is almost no decrease in proton conductivity, and the membrane becomes insoluble in the solvent Moreover, it becomes possible to suppress swelling by water.

  Further, as an embodiment using concentrated phosphoric acid, the film is immersed in 85% concentrated phosphoric acid, and after the phosphoric acid is sufficiently impregnated into the film, the film is dried and further heated to 3 to 10 at 150 ° C. to 180 ° C. By maintaining the time, a suitable crosslinking reaction can be performed in the same manner.

  In particular, a polyimide-type cation exchange resin having a sulfonic acid group, for example, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-bis (4-aminophenoxy) biphenyl-3,3 A copolycondensate of '-disulfonic acid and 1,3-bis (4-aminophenoxy) benzene or the like is a suitable electrolyte membrane for a fuel cell by crosslinking under the above conditions.

  Examples are shown below. Among these, in Examples 1 to 3, since the film already has a sufficiently high mechanical strength, the mechanical strength does not improve even after crosslinking. It can be seen that the breaking strength is almost the same, and the polymer chain is hardly broken by the treatment at 80 ° C. for 5 to 8 hours. It can be seen that the membrane is insoluble in the solvent and is crosslinked. And the long-term durability of the film is improved.

  In Example 4, since there were no active H atoms in the polymer chain, a small amount of phenyl ether was dissolved in the polymer solution to form a cast film. The phenyl ether dissolved in the membrane was cross-linked with two sulfone groups using the active hydrogen source. This film swelled and dissolved in water at 80 ° C. for several hours before crosslinking, but after the crosslinking, it did not dissolve even when immersed in water at 80 ° C. for a long time, and a remarkable improvement in water resistance was observed. .

  In Example 5, when a high molecular weight polymer film could not be obtained, the uncrosslinked film did not have high breaking stress, but the tensile strength of the film could be improved by crosslinking.

  Examples 6 and 7 show examples of polyethersulfone as examples other than polyimide. An example of using concentrated phosphoric acid as a dehydrating agent is shown in Example 7. In Example 7, since the ion exchange capacity was relatively large (as polyethersulfone), the uncrosslinked membrane swelled greatly in water at 100 ° C., but the crosslinked membrane exhibited excellent high-temperature water resistance.

  Examples are shown below.

  The evaluation method in the present invention is as follows.

[Water absorption rate, Water uptake]
About 100 mg of the membrane sample was dried and the dry weight Wd was measured, and then immersed in water at 30 ° C. and 100 ° 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 Ws during swelling was measured. The water absorption rate (Water uptake; WU) was determined from the following equation.
WU = (Ws−Wd) / Wd × 100%
[water resistant]
A film sample having a film thickness of about 40 μm was immersed in hot water under pressure at 130 ° C. for 192 hours, and then evaluated from the following five stages from the viewpoint of film shape and strength. In addition, the film piece used by II-V is made into the shape of width 5mm and length 2cm after immersion treatment and air drying.
I: The film shape is not maintained. The membrane is broken into many pieces.
II: Grasping both ends of the film piece (grasping allowance is 5 mm) and breaking the film when bent.
III: Break when the film piece is bent and bent so that the angle of the crease is 0 °.
IV: It does not break even when bent with a crease, but breaks when bent back to the base.
V: Even if bent with a crease or bent back, it does not break.
In addition, after the membrane subjected to the pressure water immersion treatment was air-dried, proton conductivity was measured at 60 ° C. and 100 to 80% RH, and evaluated from the viewpoint of proton conductivity in the following three stages.
A: The proton conductivity decreased by 20% or more by the treatment.
B: It decreased by 5 to 19%.
C: No change within experimental error (± 5%).
[Mechanical strength]
A film sample (width 5 mm, length 4 cm) having a film thickness of about 30 μm was subjected to a tensile test using a Tensilon universal testing machine (RTC-1150A, load cell UR-50N-D) manufactured by Orientec Co., Ltd. The measurement was performed on the untreated film and the film which was air-dried after being immersed in hot water under pressure of 130 ° C. for 48 hours and 192 hours.
[Proton conductivity]
A membrane sheet (1.0 cm x 0.5 cm) and four platinum black electrode plates are attached to a proton conductivity measurement cell and set in temperature-controlled water or a temperature / humidity-controlled chamber, manufactured by Hioki Electric Co., Ltd. The electrical resistance R was measured by the complex impedance method in the frequency range of 100 Hz to 100 kHz using an LCR meter (HIOKI 3552-80), and the proton conductivity σ was calculated from the following equation.
_{s = d / (t s w} s R)
Here, d is 2 the distance between the electrodes (0.5 cm), _{t s} and _{w s} is the thickness and width of the film sheet in RH 70% at room temperature. The calculation of proton conductivity in water, with t _s and w _s value in water.

Abbreviations used in the following examples are as follows.
NTDA: 1,4,5,8-naphthalenetetracarboxylic dianhydride BAPBDS: 4,4′-bis (4-aminophenoxy) biphenyl-3,3′-disulfonic acid mBAPBDS: 4,4′-bis ( 3-Aminophenoxy) biphenyl-3,3′-disulfonic acid 2,2′-BSPB: 2,2′-bis (3-sulfopropoxy) benzidine 2,2′-BSPOB: 2,2′-bis (4- Sulfophenoxy) benzidine DASSSPB: 3,5-diamino-3′-sulfo-4 ′-(4-sulfophenoxy) benzophenone BAPB: 4,4′-bis (4-aminophenoxy) benzidine BAPBz: 1,3-bis (4-Aminophenoxy) benzene SDCDPS: 3,3′-disulfo-4,4′-dichlorodiphenylsulfone DCDPS: 4,4′-dichlorodiphe Rusuruhon DPE: 4,4'-dihydroxydiphenyl ether TEA: triethylamine NMP: N-methylpyrrolidone DMAc: N, N-dimethylacetamide DMSO: Dimethyl sulfoxide

Crosslinked membrane of sulfonated polyimide NTDA-BAPBDS / BAPBz (2/1) -r 4,4′-bis (4-aminophenoxy) biphenyl-3,3 by the method described in JP-A-2003-68326 '-Disulfonic acid (BAPBDS) was synthesized. 2.241 g (4.24 mmol) of BAPBDS in a dry 100 ml four-necked flask using BAPBDS as the sulfonated diamine and 1,3-bis (4-aminophenoxy) benzene (BAPBz) as the non-sulfonated diamine. And 1.43 ml of triethylamine (TEA) were added to 21 ml of m-cresol and dissolved, then 0.620 g (2.12 mmol) of BAPBz was added and dissolved, and then 1.702 g (6.36 mmol). Of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and 1.08 g of benzoic acid, and the mixture is stirred at 80 ° C. for 4 hours and at 180 ° C. for 20 hours under a nitrogen gas atmosphere, After cooling the polymerization reaction solution to 80 ° C., 45 ml of m-cresol is added and diluted, and then poured into a large amount of acetone to precipitate. The solid was filtered off, washed with acetone and dried. The solution viscosity η _SP / 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, a 6 wt% solution was cast on a glass plate, and dried at 100 ° C. for 1 hour and at 120 ° C. for 10 hours to obtain a TEA salt type copolymer sulfonated polyimide membrane. It was. This was immersed in methanol for 1 day, then immersed in 1 M sulfuric acid solution at 30 ° C. for 3 days to exchange protons, washed with water, immersed in ultrapure water for 3 days and then air-dried, and finally at 150 ° C. in vacuum for 1 hour. Next, curing was performed at 180 ° C. for 1 hour to obtain a proton type random copolymer sulfonated polyimide NTDA-BAPBDS / BAPBz (2/1) -r film having a film thickness of about 45 μm.

  In a 500 ml round bottom separable flask, 240 g of methanesulfonic acid and 24 g of phosphorus pentoxide were added, dissolved by heating, and then cooled to room temperature. After immersing the sulfonated polyimide membrane (8 cm square, 2-5 sheets) in this solution, heating to 80 ° C. and holding for 5 hours, the membrane was taken out, washed with water, and immersed in ultrapure water for 3 days. Air-dried and cured under vacuum at 150 ° C. for 1 hour to obtain a crosslinked film.

  The film before the crosslinking treatment swelled greatly in m-cresol and was soluble in TEA-containing m-cresol, but the film after the crosslinking treatment was insoluble in the solvent and did not swell.

Crosslinked membrane of sulfonated polyimide NTDA-2,2′-BSPB / BAPB (2/1) -r 2,2′-bis (3-sulfopropoxy) by the method described in JP-A-2004-155998 Benzidine (2,2′-BSPB) was synthesized. Polymerization was conducted in the same manner as in Example 1 except that 2,2′-BSPB was used as the sulfonated diamine and 4,4′-bis (4-aminophenoxy) benzidine (BAPB) was used as the nonsulfonated diamine. Polymerized sulfonated polyimide NTDA-2,2′-BSPB / BAPB (2/1) -r was obtained. The solution viscosity of the obtained product was 6.0 dl / g. This was cast into a film in the same manner as in Example 1 to obtain a sulfonated polyimide NTDA-2,2′-BSPB / BAPB (2/1) -r film.

  This membrane was treated in the same manner as in Example 1 to obtain a crosslinked membrane of sulfonated polyimide NTDA-2,2'-BSPB / BAPB (2/1) -r.

  The film before the crosslinking treatment swelled greatly in m-cresol and was soluble in TEA-containing m-cresol, but the film after the crosslinking treatment was insoluble in the solvent and did not swell.

Crosslinked membrane of sulfonated polyimide NTDA-2,2′-BSPOB / BAPB (2/1) -r 2,2 ′ by the method described in Literature, Polymer Preprint Japan, Vol. 54, page 1434 (2005) -Bis (4-sulfophenoxy) benzidine (2,2'-BSPOB) was synthesized. Polymerization was conducted in the same manner as in Example 1 except that 2,2′-BSPOB was used as the sulfonated diamine and BAPB was used as the non-sulfonated diamine, and the random copolymerized sulfonated polyimide NTDA-2,2′-BSPOB / BAPB (2 / L) -r was obtained. The solution viscosity of the obtained product was 4.0 dl / g. This was cast into a film in the same manner as in Example 1 to obtain a random copolymerized sulfonated polyimide NTDA-2,2′-BSPOB / BAPB (2/1) -r film.

  This membrane was treated in the same manner as in Example 1 to obtain a crosslinked membrane of sulfonated polyimide NTDA-2,2'-BSPOB / BAPB (2/1) -r.

  The film before the crosslinking treatment swelled greatly in m-cresol and was soluble in TEA-containing m-cresol, but the film after the crosslinking treatment was insoluble in the solvent and did not swell.

Crosslinked Membrane of Sulfonated Polyimide NTDA-mBAPBDS According to the method described in Literature, Polymer Vol. 42, pages 359-373 (2001) and Journal Polymer Science, Polymer Chemistry Vol. 42, pages 1432-1440 (2004) '-Bis (3-aminophenoxy) biphenyl-3,3'-disulfonic acid (mBAPBDS) was synthesized. Polymerization was performed in the same manner as in Example 1 except that mBAPBDS was used and non-sulfonic acid diamine was not used, to obtain sulfonated polyimide NTDA-mBAPBDS. The solution viscosity was 2.0 dl / g. The product polymer and 2 wt% of the phenyl ether of the polymer weight are dissolved in m-cresol, cast on a glass plate, formed into a film and post-treated as in Example 1, and a small amount of phenyl ether-containing sulfonated polyimide. An NTDA-mBAPBDS film was obtained.

This membrane was treated in the same manner as in Example 1 except that the membrane was held at 30 ° C. for 72 hours to obtain a crosslinked membrane of sulfonated polyimide NTDA-mBAPBDS.
The film before the crosslinking treatment swelled greatly in m-cresol and was soluble in TEA-containing m-cresol, but the film after the crosslinking treatment was insoluble in the solvent and did not swell.

Crosslinked membrane of sulfonated polyimide NTDA-DASSPB / BAPBz (3/2) -s 3,5-diamino-3 by the method described in Literature, Polymer Preprint Japan, Vol. 53, 4766-4767 (2004) '-Sulfo-4'-(4-sulfophenoxy) benzophenone (DASSSPB) was synthesized. In a dry 100 ml four-necked flask, 1.670 g (3.6 mmol) of DASSPB and 2.1 ml of TEA were dissolved in 24 ml of m-cresol and then 1.287 g (4.8 mmol) of NTDA. And 1.53 g of benzoic acid were added and the mixture was stirred at 80 ° C. for 4 hours and at 180 ° C. for 5 hours under a nitrogen gas atmosphere. After cooling the polymerization reaction solution to room temperature, 15 ml of m-cresol, 0.701 g (2.4 mmol) of BAPBz, 0.536 g (2.0 mmol) of NTDA and 0.51 g of benzoic acid were added, and the reaction solution was added. Was stirred at 80 ° C. for 4 hours and then at 180 ° C. for 15 hours. The reaction solution was cooled to room temperature, poured into a large amount of acetone, the precipitated solid was filtered off, washed with acetone and dried. The solution viscosity of the obtained product was 0.8 dl / g. This was cast into a film in the same manner as in Example 1 to obtain a sequenced block copolymer sulfonated polyimide NTDA-DASSPB / BAPBz (3/2) -s film.

  This membrane was immersed in the same methanesulfonic acid / phosphorus pentoxide solution as in Example 1 and held at 30 ° C. for 3 days. The membrane was taken out, washed with water, immersed in ultrapure water for 3 days, air-dried, and vacuum-treated. Under curing at 150 ° C. for 1 hour, a crosslinked film of sulfonated polyimide NTDA-DASSPB / BAPBz (3/2) -s was obtained.

  The film before the crosslinking treatment swelled greatly in m-cresol and was soluble in TEA-containing m-cresol, but the film after the crosslinking treatment was insoluble in the solvent and did not swell. The elastic modulus, breaking stress, and breaking elongation of the film are 1.3 GPa, 56 MPa, and 8%, respectively, for the uncrosslinked film, and 1.2 GPa, 70 MPa, and 20%, respectively, for the crosslinked film. The film strength was improved.

Crosslinked membrane of sulfonated polyallyl ether sulfone DPE-SDCDPS / DCDPS (1/2) -r 3, 3 by the method described in Journal of Polymer Science, Polymer Chemistry 41, 2264-2276 (2003) '-Disulfo-4,4'-dichlorodiphenylsulfone (SDCDPS) was synthesized, and then 2 mmol of SDCDPS and 4 mmol of 4,4'-dichlorodiphenylsulfone (DCDPS) were converted to 6 mmol of 4,4'-dihydroxydiphenyl ether (DPE). To obtain a polymer product. The solution viscosity (solvent: DMAc; 0.5 wt%; 35 ° C.) of the produced polymer was 1.5 dl / g. The product was dissolved in DMAc, and a 7 wt% solution was cast on a glass plate and dried at 100 ° C. for 1 hour and at 120 ° C. for 10 hours to obtain a Na salt type copolymer sulfonated polymer membrane. This was immersed in a 1M sulfuric acid solution at 30 ° C. for 3 days to exchange protons, washed with water, immersed in ultrapure water for 3 days and then air-dried, and finally cured in vacuum at 150 ° C. for 10 hours to obtain proton type random A copolymerized sulfonated polyallyl ether sulfone DPE-SDCDPS / DCDPS (1/2) -r membrane was obtained.

  This membrane was immersed in the same methanesulfonic acid / phosphorus pentoxide solution as in Example 1 and held at 80 ° C. for 8 hours. The membrane was taken out, washed with water, immersed in ultrapure water for 3 days, air-dried, Curing was performed at 150 ° C. for 1 hour under vacuum to obtain a crosslinked film of random copolymer sulfonated polyallyl ether sulfone DPE-SDCDPS / DCDPS (1/2) -r.

  The membrane before the crosslinking treatment was soluble in NMP, but the membrane after the crosslinking treatment was insoluble in the solvent and did not swell. The uncrosslinked film was dissolved in methanol, but the crosslinked film was insoluble in methanol and hardly swelled.

Crosslinked membrane of sulfonated polyallyl ether sulfone DPE-SDCDPS / DCDPS (2/3) -r Polymerization was carried out in the same manner as in Example 6 except that the molar ratio of SDCDPS / DCDPS was changed to 2/3. Got. The solution viscosity of the resulting polymer was 2.2 dl / g. The product was dissolved in DMAc and formed into a membrane in the same manner as in Example 5 to obtain a proton type random copolymer sulfonated polyallyl ether sulfone DPE-SDCDPS / DCDPS (2/3) -r membrane.

  The membrane was immersed in 85% concentrated phosphoric acid solution for 10 hours at room temperature, then removed, wiped with tissue paper, and heated in vacuo at 60 ° C. for 5 hours, 100 ° C. for 5 hours, and 170 ° C. for 24 hours. . Thereafter, the membrane was immersed in ultrapure water for 3 days, air-dried, and cured at 150 ° C. for 1 hour under vacuum to randomly copolymerize sulfonated polyallyl ether sulfone DPE-SDCDPS / DCDPS (2/3) -r. A crosslinked film was obtained.

The membrane before the crosslinking treatment was soluble in NMP, but the membrane after the crosslinking treatment was insoluble in the solvent and did not swell. The uncrosslinked film was dissolved in methanol and swelled greatly in a 50 wt% methanol aqueous solution, but the crosslinked film was insoluble in methanol and hardly swollen in a 50 wt% methanol aqueous solution.
(Evaluation result of membrane)
The water resistance, water absorption, and proton conductivity of the uncrosslinked membrane before crosslinking treatment and the crosslinked membrane after crosslinking treatment prepared in the above examples were evaluated. The results are shown in Table 1. Table 2 shows the results of the film tensile test and the bending test before and after the water resistance test of the uncrosslinked films and the crosslinked films of Examples 2 and 3.

  From the above results, the following can be understood.

  1) In any of the examples, the high temperature water resistance of the film was greatly improved by the crosslinking treatment. In Examples 2 and 3, the uncrosslinked film has a considerably high water resistance, but it can be seen from the tensile test results in Table 2 that the water resistance is further improved by crosslinking.

  2) The water absorption at 100 ° C. is reduced by crosslinking except in Example 2, and the decrease is large in Examples 4 and 7 where the water absorption at high temperature of the uncrosslinked film is high.

  3) Although the proton conductivity was slightly reduced by crosslinking, the proton conductivity was sufficiently high even after crosslinking.

  4) In Example 2, since the water absorption increased due to crosslinking, the proton conductivity slightly increased.

  5) Even in membranes that are soluble or greatly swell in methanol as in Examples 6 and 7, the membrane becomes insoluble in methanol due to crosslinking, and membrane swelling is greatly suppressed. Application as an electrolyte membrane for a methanol direct fuel cell becomes possible.

  The present invention is a novel method for producing a sulfonic acid type cation exchange resin membrane, and the resulting sulfonic acid type cation exchange membrane is prepared by concentrating an aqueous salt solution such as salt, desalting, deoxidizing fruit juice, salt such as sodium chloride, etc. It can be used for applications such as decomposition of fuel cells and diaphragms of fuel cells.

In this invention, it is a schematic diagram in the case of bridge | crosslinking the polymeric material which does not have a sulfonic acid group and the polymeric material which does not have a sulfonic acid group but has a high electron density which couple | bonded hydrogen. In this invention, it is a schematic diagram in the case of having both a sulfonic acid group and carbon with high electron density in which hydrogen is bonded in one molecule to crosslink a polymer compound. In the present invention, a polymer compound having a sulfonic acid group but having no hydrogen-bonded high electron density is cross-linked via a low-molecular compound having two or more hydrogen-bonded high electron density carbons. FIG. 1 is a schematic diagram showing the structure of a crosslinked cation exchange resin obtained in Example 1. FIG. 3 is a schematic diagram showing the structure of a crosslinked cation exchange resin obtained in Example 2. FIG. 4 is a schematic diagram showing the structure of a crosslinked cation exchange resin obtained in Example 3. FIG. 6 is a schematic diagram showing the structure of a crosslinked cation exchange resin obtained in Example 4. FIG. 6 is a schematic diagram showing the structure of a crosslinked cation exchange resin obtained in Example 6. FIG.

Claims (9)

A polymer compound having a sulfonic acid group and a substance having an electron-dense carbon atoms bonded hydrogen atoms in the molecule with a dehydrating agent solution, thereby dehydration reaction from the sulfonic acid group and the hydrogen atom A method for producing a crosslinked cation exchange resin membrane characterized by the following.
  The method for producing a crosslinked cation exchange resin membrane according to claim 1, wherein the substance having a carbon atom having a high electron density in which hydrogen atoms are bonded in a molecule is an aromatic ring to which an electron donating group is bonded.   3. The method for producing a crosslinked cation exchange resin membrane according to claim 1, wherein at least one compound selected from concentrated phosphoric acid, polyphosphoric acid and phosphorus pentoxide dissolved in a solvent is used as the dehydrating agent.   The method for producing a crosslinked cation exchange resin membrane according to claim 3, wherein the phosphorus pentoxide dissolved in the solvent is phosphorus pentoxide dissolved in methanesulfonic acid.   The crosslinked cation exchange resin membrane according to any one of claims 1 to 3, wherein the polymer compound having a sulfonic acid group has a carbon atom having a high electron density in which hydrogen atoms are bonded in the molecule. Manufacturing method.   The crosslinked cation according to any one of claims 1 to 3, wherein a polymer compound having a sulfonic acid group and a compound having two or more carbons having high electron density in which hydrogen is bonded in the molecule are bonded by a dehydration reaction. A method for producing an exchange resin membrane.   The polymer compound having a sulfonic acid group is at least one polymer compound selected from the group consisting of polyphenylene, polyether, polysulfide, polyetherketone, polysulfone, polyethersulfone, polyetheretherketone, polybenzoxazole, and polyimide. 5. A method for producing a crosslinked cation exchange resin membrane according to any one of items 1 to 4.   The method for producing a crosslinked cation exchange resin membrane according to claim 2, wherein the electron donating group is at least one selected from -O-, -S-, alkyl, alkylene, aryl and arylene.   An electrolyte membrane for a fuel cell comprising the crosslinked cation exchange resin membrane according to any one of claims 1 to 7.

Images