JP2006253002A - Manufacturing method of ion exchange membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an ion exchange membrane which has extremely little residual solvent and is capable of having both high ion conductivity and impermeability of liquid fuel reconciled and is suitable for a diaphragm for fuel cell. <P>SOLUTION: This is a manufacturing method of an ion exchange membrane for removing solvent after a solvent solution of an ion exchange resin is flowed and extended on a support body. After the good solvent solution of the ion exchange resin having an ion exchange resin concentration of 10-40 wt% and a solvent solution viscosity of 100-3,000 poise at a temperature of 30°C is flowed, the flowed object is made to contact the poor solvent of the ion exchange resin, and at least a part of the good solvent is removed from the flowed object, and further, is dried at a temperature of 250°C or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a method for producing an ion exchange membrane used for a diaphragm for a battery, a diaphragm for dialysis, and the like, and more particularly, a method for producing an ion exchange membrane having excellent ionic conductivity and excellent liquid fuel permeation deterrence as a diaphragm for a fuel cell. It is about.

  In recent years, new power generation technologies with excellent energy efficiency and environmental friendliness have attracted attention. In particular, polymer electrolyte fuel cells using polymer electrolyte membranes have features such as high energy density and low operating temperature compared to other types of fuel cells, making them easy to start and stop. is doing. In particular, fuel cells that use solid polymer electrolyte membranes and use organic solvents as the fuel can supply liquid fuel in the same way as gasoline. Therefore, they are being developed for applications such as power supplies for portable devices. Yes.

  A proton conductive ion exchange resin membrane is usually used as an ion exchange membrane of a fuel cell using liquid fuel. In addition to proton conductivity, the ion exchange membrane of the fuel cell requires characteristics such as fuel permeation deterrence and mechanical strength to prevent fuel permeation. As such a polymer solid electrolyte membrane, for example, a perfluorocarbon sulfonic acid polymer membrane introduced with a sulfonic acid group represented by Nafion (trade name) manufactured by DuPont of the United States or Aciplex (trade name) manufactured by Asahi Kasei of Japan It has been known.

  However, when the perfluorocarbon sulfonic acid polymer introduced with the sulfonic acid group is used by supplying a liquid organic fuel such as methanol to the fuel electrode side, the liquid organic fuel permeates through the electrolyte membrane and is on the air electrode side. The problem of crossover that flows into When this crossover occurs, the liquid fuel and the oxidant directly react to cause a problem of power reduction and a problem that the liquid fuel leaks outside from the air electrode side. Therefore, in order to reduce this crossover, a measure is taken to increase the thickness of the ion exchange membrane. However, if the thickness is increased, the ionic conductivity required for higher output and higher efficiency of the fuel cell is reduced, so it is a problem to achieve both ionic conductivity and liquid fuel permeation deterrence. .

Various sulfonated ion exchange membranes of non-fluorinated aromatic ring-containing polymers such as aromatic polyarylene ether ketones and aromatic polyarylene ether sulfones such as aromatic polyarylene ether ketones from the viewpoint of suppressing liquid fuel permeability (For example, refer nonpatent literature 1 and patent literature 1.). However, even in these polymer materials, it is difficult to produce a thick film in the method of producing a film by casting a solvent solution of the polymer material on a support, and the thickness of the film is also reduced. When the thickness is increased, the ionic conductivity is reduced, and the compatibility between the ionic conductivity and the liquid fuel permeation inhibiting property is not sufficient.
JP-A-6-93114 Journal of Membrane Science (Netherlands) 1993, 83, p. 211-220

  An object of the present invention is to provide an ion exchange membrane having a large membrane thickness and a method for producing the same, which is excellent in achieving both ion conductivity and liquid fuel permeation inhibiting properties with very little residual solvent.

As a result of intensive studies, the present inventors have found that the above object is achieved. That is, the present invention adopts the following configuration.
1. In a method for producing an ion exchange membrane in which a solvent solution is removed after casting a solvent solution of an ion exchange resin on a support, the good solvent solution of the ion exchange resin having a solvent solution viscosity of 100 to 3000 poise (temperature 30 ° C.) After the casting is brought into contact with a poor solvent of the ion exchange resin to remove at least a part of the good solvent from the casting and further dried at a temperature of 250 ° C. or lower. This is a method for producing an ion exchange membrane.
2. The thickness of the said ion exchange membrane is 20-500 micrometers, It is a manufacturing method of the ion exchange membrane as described in 1st invention characterized by the above-mentioned.
3. The ion exchange membrane manufacturing method according to the first or second invention, wherein the ion exchange resin is an ion exchange resin containing a sulfonic acid group.
4). The ion exchange membrane production method according to the third invention, wherein the ion exchange resin has a sulfonic acid group content of 0.3 to 3.5 meq / g.
5. In the method for producing an ion exchange membrane according to the third or fourth invention, the ion exchange resin is a polyarylene ether compound containing the components represented by the general formula (1) and the general formula (2). is there.

ただし、Ａｒは２価の芳香族基、Ｙはスルホン基またはケトン基、Ｘは水素または１価のカチオン種を示す。

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents hydrogen or a monovalent cation species.

ただし、Ａｒ’は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  According to the present invention, the residual solvent is extremely small, and both high ion conductivity and liquid fuel permeation deterrence can be achieved, and an ion exchange membrane having a large membrane thickness can be provided.

Hereinafter, the present invention will be described in detail.
In the present invention, first, a solution in which an ion exchange resin is dissolved in a good solvent capable of being dissolved is prepared. The ion exchange resin used in the ion exchange membrane of the present invention is preferably a hydrocarbon-based ion exchange resin from the viewpoint of suppressing liquid fuel permeability, and water clusters such as those found in perfluorocarbon sulfonic acid polymers. A hydrocarbon-based ion exchange resin that does not form a structure is the best in terms of performance. In particular, among hydrocarbon ion exchange resins, a polyarylene ether compound in which a sulfonic acid is introduced onto an aromatic ring can provide an ion exchange membrane excellent in liquid fuel permeation inhibition and ion conductivity.

  As the polyarylene ether compound, it is preferable to use a monomer having a sulfonic acid group introduced on an electron-withdrawing aromatic ring. When a 3,3′-disulfo-4,4′-dichlorodiphenylsulfone derivative is used, However, it becomes a polymer in which the sulfonic acid group is not easily released, and when 3,6-dichlorobenzonitrile is used in combination with 3,3′-disulfo-4,4′-dichlorodiphenylsulfone derivative, 3,3′-, which has low polymerizability. An ion exchange membrane that is a disulfo-4,4′-dichlorodiphenylsulfone derivative, can produce a polyarylene ether compound having a high degree of polymerization, and does not form a water cluster structure, and is excellent in liquid fuel permeation deterrence and ion conductivity. Can provide.

ただし、Ａｒは２価の芳香族基、Ｙはスルホン基またはケトン基、Ｘは水素または１価のカチオン種を示す。 The sulfonic acid group-containing polyarylene ether-based compound in the present invention can contain a constituent represented by the general formula (2) together with the following general formula (1).

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents hydrogen or a monovalent cation species.

ただし、Ａｒ’は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  The component represented by the general formula (2) is preferably a component represented by the following general formula (3).

ただし、Ａｒ’は２価の芳香族基を示す。

However, Ar ′ represents a divalent aromatic group.

  In the sulfonic acid group-containing polyarylene ether compound in the present invention, structural units other than those represented by the general formula (1) and the general formula (2) may be included. At this time, it is preferable that structural units other than those represented by the general formula (1) or the general formula (2) are 50% by weight or less. By being 50 mass% or less, it can be set as the composition which utilized the characteristic of the sulfonic acid group containing polyarylene ether type compound.

  The sulfonic acid group-containing polyarylene ether compound in the present invention preferably has an ion exchange capacity in the range of 0.3 to 3.5 meq / g, more preferably 1.0 to 3.0 meq / g. When it is less than 0.3 meq / g, there is a tendency that it does not show sufficient ion conductivity as an ion conductive membrane, and when it is larger than 3.5 meq / g, the ion conductive membrane is placed under high temperature and high humidity conditions. In some cases, the film swells so much that it is not suitable for use. The sulfonic acid group content can be calculated from the polymer composition.

  In addition, the sulfonic acid group-containing polyarylene ether compound in the present invention preferably includes a component represented by the general formula (5) together with the following general formula (4). By having a biphenylene structure, the film has excellent dimensional stability under high temperature and high humidity conditions, and also has high film toughness.

ただし、Ｘは水素または１価のカチオン種を示す。

X represents hydrogen or a monovalent cation species.

  Furthermore, the sulfonic acid group-containing polyarylene ether compound in the present invention can be polymerized by an aromatic nucleophilic substitution reaction containing compounds represented by the following general formulas (6) and (7) as monomers. Specific examples of the compound represented by the general formula (6) include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3, 3'-disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl sulfone, and those whose sulfonic acid groups are converted to salts with monovalent cation species Can be mentioned. The monovalent cation species may be sodium, potassium, other metal species, various amines, or the like, but is not limited thereto. Examples of the compound represented by the general formula (7) include 2,6-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-dichlorobenzonitrile, 2,4-difluorobenzonitrile, and the like. it can.

ただし、Ｙはスルホン基またはケトン基、Ｘは１価のカチオン種、Ｚは塩素またはフッ素を示す。本発明において、上記２，６−ジクロロベンゾニトリルおよび２，４−ジクロロベンゾニトリルは、異性体の関係にあり、いずれを用いたとしても良好なイオン伝導性、耐熱性、加工性および寸法安定性を達成することができる。その理由としては両モノマーとも反応性に優れるとともに、小さな繰り返し単位を構成することで分子全体の構造をより硬いものとしていると考えられる。

Y represents a sulfone group or a ketone group, X represents a monovalent cation species, and Z represents chlorine or fluorine. In the present invention, the above 2,6-dichlorobenzonitrile and 2,4-dichlorobenzonitrile are in an isomer relationship, and any of them is used, good ion conductivity, heat resistance, workability and dimensional stability. Can be achieved. The reason is that both monomers are excellent in reactivity and that the structure of the whole molecule is made harder by constituting a small repeating unit.

  In the aromatic nucleophilic substitution reaction, various activated difluoroaromatic compounds and dichloroaromatic compounds can be used in combination with the compounds represented by the general formulas (6) and (7) as monomers. Examples of these compounds include 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorodiphenyl sulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, decafluorobiphenyl, and the like. However, other aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like that are active in aromatic nucleophilic substitution can also be used.

  In addition, Ar in the structural component represented by the general formula (1) and Ar ′ in the structural component represented by the general formula (2) are generally the same as those described above in the aromatic nucleophilic substitution polymerization. It is a structure introduced from an aromatic diol component monomer used together with the compounds represented by formulas (6) and (7). Examples of such aromatic diol monomers include 4,4′-biphenol, bis (4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy). Phenyl) propane, bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxy-3) , 5-dimethylphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, bis ( 4-hydroxyphenyl) diphenylmethane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9- (3-methyl-4-hydroxyphenyl) fluorene, hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, etc., but also for the polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction. Various aromatic diols that can be used can also be used. These aromatic diols can be used alone, but a plurality of aromatic diols can be used in combination.

  When the sulfonic acid group-containing polyarylene ether compound in the present invention is polymerized by an aromatic nucleophilic substitution reaction, an activated difluoroaromatic compound including the compounds represented by the general formula (6) and the general formula (7) and / or A polymer can be obtained by reacting a dichloroaromatic compound and an aromatic diol in the presence of a basic compound. The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed.

  The polymerization reaction can be performed in the absence of a solvent, but is preferably performed in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more. Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like, and those that can convert an aromatic diol into an active phenoxide structure may be used. It can use without being limited to.

  In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is performed in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 10 to 40% by weight. When the amount is less than 10% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 40% by weight, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration.

  The polymer is dissolved in a good solvent for the polymer to form a solution. Good solvents include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphonamide, and alcohols such as methanol and ethanol. An appropriate one can be selected, but is not limited thereto. A plurality of these solvents may be mixed and used within the possible range. At this time, it is important to set the viscosity of the solution at 30 ° C. within the range of 100 to 3000 poise. When the viscosity of the solution is less than 100 poise, when the solution is cast, the solution flows before solidifying by drying, and it is difficult to produce a thick film. In addition, the inventors found that a good film tends to be foamed by drying and cannot be produced, and found that foaming can be greatly reduced when the viscosity is 100 poise or more. On the other hand, when it exceeds 3000 poise, liquid feeding and defoaming become difficult, and it becomes difficult to produce a good film. The presence of bubbles in the solution causes a defect and must be completely eliminated, and can be removed using a known method.

  The polymer concentration is preferably 10 to 40% by weight. When a thick film is produced, the viscosity of the solution is set to 3000 poise as an upper limit, and the production is facilitated by increasing the polymer concentration. When a solution with a low polymer concentration is used, it is necessary to apply a thick coating during casting, and it is necessary to dry and solidify before the solution flows. Therefore, a solution with a polymer concentration of 10% by weight or less produces a thick film. This is very difficult. When the polymer concentration exceeds 40% by weight, it takes a long time to uniformly dissolve the polymer. Further, non-uniform dissolution is not preferable because it causes generation of thickness spots.

  Since the viscosity of the solution depends on the polymer concentration, the logarithmic viscosity of the polymer, the solvent in which the polymer is dissolved, the solvent used, the polymer concentration so that the viscosity of the solution at 30 ° C. is within the range of 100 to 3000 poise. It is necessary to select the logarithmic viscosity of the polymer. The logarithmic viscosity of the polymer measured by the method described later is preferably 0.1 or more. When the logarithmic viscosity is less than 0.1, the membrane is likely to be brittle when formed as an ion conductive membrane. The logarithmic viscosity is more preferably 0.3 or more. On the other hand, when the logarithmic viscosity exceeds 5, dissolution of the polymer may be extremely difficult. As a solvent for measuring the logarithmic viscosity, polar organic solvents such as N-methylpyrrolidone and N, N-dimethylacetamide can be generally used. When the solubility in these is low, concentrated sulfuric acid is used. It can also be measured.

  If necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, a dispersant, a polymerization inhibitor, Various additives such as radical inhibitors, inorganic compounds for controlling the characteristics of the electrolyte membrane, and inorganic-organic hybrid compounds may be included.

  As a method for casting the solution on the support, known methods such as a comma coater, a lip coater, a blade coater, a bar coater, a roll coater, and a knife coater can be used. At this time, if the thickness of the solution at the time of casting is not sufficient, a thick film cannot be produced. As application thickness of the solution at the time of casting, 50-5000 micrometers is preferable, More preferably, it is 100-3000 micrometers, More preferably, it is 300-2000 micrometers. Since the thickness of the film depends on the coating thickness of the solution at the time of casting, it is necessary to apply an amount of solution suitable for the target of the film thickness after removing the solvent on the support. In the method of the present invention, a film having a sufficiently thin film thickness can be manufactured as a matter of course, but it is characterized in that it is possible to manufacture a film having a sufficiently thick film thickness that has been considered difficult in the past.

  As the support for casting the solution, an endless belt or drum made of a metal such as stainless steel, a film made of a resin such as polyethylene terephthalate, glass, or the like can be used, but is not limited thereto. The surface of the support may be modified by applying a mirror treatment to the surface of the support made of metal, or applying a corona treatment to the surface of the resin film.

  In the present invention, the solution cast on the support is poorly soluble in the ion exchange resin but is brought into contact with a poor solvent having high solubility or miscibility in the good solvent of the ion exchange resin. Then, a method of extracting and removing the good solvent of the ion exchange resin is used. In the method of removing by volatilizing the solvent only by heating, it is necessary to spend a long time at a high temperature in the case of a solvent having a high boiling point, and in industrial production, not only the energy consumption during production increases but also the production cost increases. However, the present situation is that it has not been possible to remove the solvent to such an extent that no problem occurs in the practical stage. The present inventors have found that when a method of extracting and removing a solvent by bringing it into contact with a poor solvent is added, the solvent can be extracted efficiently in a shorter time than a method of heating alone.

  The poor solvent in the present invention is a solvent that is at least miscible with the polymer good solvent, and the contacting method may be in a liquid phase state or in a gas phase state. Examples of the poor solvent include water, but also organic solvents such as alcohols, glycols, and glycerin, but are not limited thereto. Although temperature is not specifically limited, The range of 5-80 degreeC is preferable, More preferably, it is the range of 10-60 degreeC, It is preferable to process for 10 seconds or more, and 30 seconds or more are more preferable. The amount of residual solvent is 5% by weight or less, more preferably 1% by weight or less, and still more preferably 0.5% by weight or less based on the ion exchange resin. Spraying the film with a spray for the purpose of improving the solvent extraction efficiency leads to an improvement in productivity.

  The film from which the solvent has been removed is then dried. The temperature in the drying step needs to be 250 ° C. or lower, preferably 80 to 220 ° C., more preferably 90 to 200 ° C. Drying at a temperature of 250 ° C. or higher is not preferable because polymer decomposition and ionic group elimination proceed. Although drying time is not specifically limited, It is preferable to carry out for 10 seconds or more, More preferably, it is 30 seconds or more. In order to improve the dimensional stability, it is preferable to dry the film while fixing both ends of the film with pins or clips.

  The thickness of the film after removing the solvent is 20 to 500 μm, preferably 50 to 300 μm, more preferably 120 to 300 μm. If the thickness is less than 20 μm, the liquid fuel permeation deterrence is lowered, and the power generation performance is lowered. If the film is too thin, pinholes and breakage are likely to occur. On the other hand, if it is thicker than 500 μm, the ion conductivity may be insufficient.

When the ion exchange membrane of the present invention is used as an ion conductive membrane, the sulfonic acid group in the membrane may contain a metal salt, but it can be converted to free sulfonic acid by an appropriate acid treatment. Can do. In this case, it is effective to immerse the membrane in an aqueous solution of sulfuric acid, hydrochloric acid, etc. with or without heating. The ion conductivity of the ion conductive membrane is preferably 1.0 × 10 ⁻³ S / cm or more. When the ion conductivity of 1.0 × 10 ^-3 S / cm or higher, tend to better output is obtained in the fuel cell using the ion conductive membrane, 1.0 × 10 ^-3 S / When it is less than cm, the output of the fuel cell tends to decrease.

Further, the rate at which methanol as a typical liquid fuel permeates, that is, the methanol permeation rate, is preferably in the range of 0.1 to 3.5 mmol / m ² / s, and more preferably 0.2 to 3 It is desirable to be in the range of 0.0 mmol / m ² / s. In the ion exchange membrane of the present invention, the above methanol permeation rate can be achieved with a thinner thickness than conventional ion exchange membranes, high ionic conductivity can also be exhibited, and ionic conductivity and liquid fuel permeation deterrence. Can be made compatible.

  Since the ion exchange membrane of the present invention is excellent in heat resistance, processability, ion conductivity and dimensional stability, it can be used as a membrane for an electrochemical device such as a water electrolyzer or a polymer solid electrolyte membrane / electrode assembly. It can be used for a fuel cell. In addition, it can withstand operation at high temperature, is easy to produce, has good output, and can be used in a fuel cell using methanol as a direct fuel.

Examples of the present invention are shown below, but the present invention is not limited to these Examples. Various measurements were performed as follows.
<Logarithmic viscosity>
The polymer powder was dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dl, the viscosity was measured using a Ubbelohde viscometer in a thermostatic bath at 30 ° C., and evaluated by ln [ta / tb] / c). (Ta is the falling seconds of the sample solution, tb is the falling seconds of the solvent only, and c is the polymer concentration).
<Measurement of solution viscosity>
It measured at 30 degreeC using the E-type viscosity meter (Toki Sangyo Co., Ltd. VISCONIC ED type | mold).

<Measurement of ion exchange capacity>
100 mg of the membrane was immersed in 50 ml of 0.01N NaOH aqueous solution and stirred at 25 ° C. overnight. Then, neutralization titration with 0.05N HCl aqueous solution was performed. The ion exchange capacity was determined by the following formula.
Ion exchange capacity [meq / g] = (10-titration [ml]) / 2
<Measurement of film thickness>
The thickness of the membrane was measured using a micrometer (Mitutoyo standard micrometer 0-25 mm 0.01 mm). Measurement was performed at 10 locations, and the average value was taken as the thickness.

<Ion conductivity measurement>
A platinum wire (diameter: 0.2 mm) was pressed against the surface of the strip-shaped film sample on a self-made measuring probe (manufactured by Teflon (registered trademark)), and a constant temperature and humidity oven at 80 ° C. and 95% RH (Nagano Co., Ltd.) The specimen was held in Science Machine Mfg. Co., Ltd., LH-20-01), and the impedance between the platinum wires was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. The measurement was performed while changing the distance between the electrodes, and the conductivity obtained by canceling the contact resistance between the film and the platinum wire was calculated from the gradient obtained by plotting the distance measured between the electrodes and the resistance measurement value estimated from the CC plot.
Conductivity [S / cm] = 1 / film width [cm] × film thickness [cm] × resistance interelectrode gradient [Ω / cm]

<Methanol permeation rate>
The liquid fuel permeation rate of the ion exchange membrane was measured as the permeation rate of methanol by the following method. An ion exchange membrane immersed in a 5 mol / liter methanol aqueous solution adjusted to 25 ° C. for 24 hours is sandwiched between H-type cells, 100 ml of 5 mol / liter methanol aqueous solution is placed on one side of the cell, and 100 ml of ultrapure is placed on the other cell. It was calculated by injecting water (18 MΩ · cm) and measuring the amount of methanol diffusing into the ultrapure water through the ion exchange membrane while stirring the cells on both sides at 25 ° C. (The area of the ion exchange membrane is 2.0 cm ² ). Specifically, it was calculated using the following formula from the methanol concentration change rate [Ct] (mmol / L / s) of the cell containing ultrapure water.
Methanol permeation rate [mmol / m ² / s] = (Ct [mmol / L / s] × 0.1 [L]) / 2 × 10 ⁻⁴ [m ² ]

<Example 1>
625 g of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt, 508 g of 2,6-dichlorobenzonitrile, 779 g of 4,4′-biphenol, 665 g of potassium carbonate, 4780 g of N-methyl-2-pyrrolidone The mixture was stirred at 150 ° C. for 60 minutes in a nitrogen atmosphere, and then the reaction temperature was raised to 200 ° C., and the reaction was continued with the aim of sufficiently increasing the viscosity of the system (about 15 hours). After cooling, it was precipitated in strands in water. The obtained polymer was washed in water for 40 hours and then dried. The logarithmic viscosity of the polymer was 2.13. The resulting polymer was subjected to sulfonation treatment by immersing it in 95% sulfuric acid at 55 ° C. with light stirring, and then the sulfuric acid concentration was gradually lowered until the pH of the aqueous solution finally reached 6.5. The washing was repeated. Thereafter, when the obtained polymer was dried, a polymer having an ion exchange capacity of 1.47 meq / g was obtained. Using this polymer as a solvent, N-methyl-2-pyrrolidone was used to prepare a solution so that the polymer concentration was 15% by weight. The viscosity of the solution at 30 ° C. was 210 poise. After defoaming the adjusted solution, the solvent was removed by casting at a temperature of 26 ° C. using a glass plate as a support so that the thickness when applied was 1050 μm and contacting with water at a temperature of 50 ° C. for 30 minutes. . Thereafter, the membrane was fixed to a metal frame and dried at a temperature of 100 ° C. for 5 minutes to produce a membrane. The residual solvent amount of the obtained film was 0.2% by weight.

<Example 2>
A polymer prepared by the method described in Example 1 was prepared using N-methyl-2-pyrrolidone as a solvent, and the solution was adjusted so that the polymer concentration was 22% by weight. The viscosity of the solution at 30 ° C. was 1430 poise. Thereafter, a membrane was produced by the method described in Example 1. The residual solvent amount of the obtained film was 0.3% by weight.

<Example 3>
723 g of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt, 411 g of 2,6-dichlorobenzonitrile, 712 g of 4,4′-biphenol, 607 g of potassium carbonate, 4658 g of N-methyl-2-pyrrolidone The mixture was stirred at 150 ° C. for 60 minutes in a nitrogen atmosphere, and then the reaction temperature was increased to 200 ° C., and the reaction was continued with a sufficient increase in system viscosity (approximately 8 hours). After cooling, it was precipitated in strands in water. The polymer obtained was washed in water for 42 hours and then dried. The logarithmic viscosity of the polymer was 0.94. The polymer obtained was immersed in 95% sulfuric acid at 50 ° C. with light agitation, and after sulfonation, the sulfuric acid concentration was gradually lowered until the pH of the aqueous solution finally reached 6.5. Washing was repeated. Thereafter, when the obtained polymer was dried, a polymer having an ion exchange capacity of 1.79 meq / g was obtained. A solution of this polymer was prepared using N-methyl-2-pyrrolidone as a solvent so that the polymer concentration was 31% by weight. The viscosity of the solution at 30 ° C. was 2340 poise. After defoaming the prepared solution, casting was performed at a temperature of 24 ° C. so that the thickness when applied was 1250 μm using a glass plate as a support, and then the solvent was removed by contacting with water at a temperature of 60 ° C. for 180 minutes. did. Thereafter, the membrane was fixed to a metal frame and dried at a temperature of 100 ° C. for 5 minutes to produce a membrane. The amount of residual solvent in the obtained film was 0.4% by weight.

<Example 4>
763 g of 3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt, 540 g of 2,6-dichlorobenzonitrile, 865 g of 4,4′-biphenol, 738 g of potassium carbonate, 5439 g of N-methyl-2-pyrrolidone The mixture was stirred at 150 ° C. for 60 minutes under a nitrogen atmosphere, and then the reaction temperature was increased to 200 ° C., and the reaction was continued with a sufficient increase in system viscosity (about 7 hours). After cooling, it was precipitated in strands in water. The polymer obtained was washed in water for 48 hours and then dried. The logarithmic viscosity of the polymer was 1.24. The polymer obtained was immersed in 95% sulfuric acid at 60 ° C. with light stirring, and then subjected to sulfonation treatment, and then the sulfuric acid concentration was gradually lowered until the pH of the aqueous solution finally reached 6.5. Washing was repeated. Then, when the obtained polymer was dried, the polymer whose ion exchange capacity is 1.58 meq / g was obtained. A solution of this polymer was prepared using N-methyl-2-pyrrolidone as a solvent so that the polymer concentration was 24% by weight. The viscosity of the solution at 30 ° C. was 1430 poise. After defoaming the prepared solution, casting was performed at a temperature of 24 ° C. so that the thickness when applied was 1300 μm using a glass plate as a support, and then the solvent was removed by contacting with water at a temperature of 55 ° C. for 90 minutes. did. Thereafter, the membrane was fixed to a metal frame and dried at a temperature of 100 ° C. for 5 minutes to produce a membrane. The residual solvent amount of the obtained film was 0.3% by weight.

<Comparative Example 1>
A polymer prepared by the method described in Example 4 was prepared using N-methyl-2-pyrrolidone as a solvent, and the solution was adjusted so that the polymer concentration was 27% by weight. The viscosity of the solution at 30 ° C. was 3780 poise. An attempt was made to degas the adjusted solution, but it was very difficult. This solution was cast at a temperature of 24 ° C. so that the thickness upon application was 1300 μm using a glass plate as a support, but a large amount of bubbles were mixed during liquid feeding, and a good film could not be produced. It was.

<Comparative example 2>
A polymer prepared by the method described in Example 4 was prepared using N-methyl-2-pyrrolidone as a solvent, and the solution was adjusted so that the polymer concentration was 12.5% by weight. The viscosity of the solution at 30 ° C. was 54 poise. After defoaming the prepared solution, casting was performed at a temperature of 25 ° C. so that the thickness when applied was 2000 μm using a glass plate as a support, and then the solvent was removed by contacting with water at a temperature of 55 ° C. for 90 minutes. did. Thereafter, the membrane was fixed to a metal frame and dried at a temperature of 100 ° C. for 5 minutes to produce a membrane. The obtained film was uneven and had very large thickness unevenness.

<Comparative Example 3>
The polymer film produced by the method described in Example 1 was fixed to a metal frame and dried at 270 ° C. for 20 minutes to produce a film. The result of measuring the ion exchange capacity of the membrane was 0.28 meq / g. It is considered that the ionic group was eliminated by drying at high temperature for a long time.

<Comparative example 4>
The solution prepared by the method described in Example 3 was cast at a temperature of 26 ° C. so that the thickness when applied was 1250 μm using a glass plate as a support, and then the solvent was removed by drying at a temperature of 200 ° C. for 10 hours. To produce a membrane. A good film could not be produced due to foaming during drying. Further, the amount of residual solvent in the obtained film was 2.3% by weight, and the solvent could not be removed sufficiently.

<Comparative Example 5>
A Nafion (trade name) 117 membrane manufactured by DuPont was used. This membrane consists of a perfluorocarbon sulfonic acid polymer.

  The physical property values of Examples 1, 2, 3, 4 and Comparative Examples 1, 2, 3, 4, 5 are shown in Table 1.

  From Examples 1, 2, 3, 4 and Comparative Examples 1, 2, it can be seen that the viscosity of the solution is preferably in the range of 100 to 3000 poise. In addition, Examples 1, 2, 3, 4 and Comparative Example 3 show that drying is preferably performed at 250 ° C. or less. Further, Examples 1, 2, 3, 4 and Comparative Example 4 show that the method of the present invention is more efficient than the method of removing the solvent by volatilizing it only by heating, and the amount of residual solvent can be further reduced. It can also be seen that the membrane made of the hydrocarbon ion exchange resin of the present invention is superior to the perfluorocarbon sulfonic acid polymer membrane in terms of both high ionic conductivity and methanol permeation deterrence.

  According to the present invention, it is possible to easily provide a thick ion exchange membrane capable of achieving both high ion conductivity and liquid fuel permeation inhibiting properties as compared with conventional ones. For example, when used in a fuel cell that uses a liquid organic fuel such as methanol, a high-performance fuel cell with high power generation efficiency can be supplied.

Claims (5)

  In a method for producing an ion exchange membrane in which a solvent solution is removed after casting a solvent solution of an ion exchange resin on a support, the good solvent solution of the ion exchange resin having a solvent solution viscosity of 100 to 3000 poise (temperature 30 ° C.) After the casting is brought into contact with a poor solvent of the ion exchange resin to remove at least a part of the good solvent from the casting and further dried at a temperature of 250 ° C. or lower. A method for producing an ion exchange membrane.   The method for producing an ion exchange membrane according to claim 1, wherein the thickness of the ion exchange membrane is 20 to 500 µm.   The method for producing an ion exchange membrane according to claim 1 or 2, wherein the ion exchange resin is an ion exchange resin containing a sulfonic acid group.   The method for producing an ion exchange membrane according to claim 3, wherein the sulfonic acid group content of the ion exchange resin is 0.3 to 3.5 meq / g. 5. The method for producing an ion exchange membrane according to claim 3, wherein the ion exchange resin is a polyarylene ether compound containing the components represented by the general formula (1) and the general formula (2).

Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, and X represents hydrogen or a monovalent cation species.

However, Ar ′ represents a divalent aromatic group.