JP2009217950A - Ion conductive polymer electrolyte membrane, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ion conductive polymer membrane having high dimensional stability against water absorption while holding high ionic conductivity and high water absorbing property. <P>SOLUTION: The ion conductive polymer membrane is a composite membrane composed of a co-continuous phase: formed of a continuous phase consisting of an ion exchange group-containing polymer A having high chemical stability and high proton conductivity and an ion exchange group non-containing polymer B having high mechanical and chemical stability, soluble in the solvent in which the polymer A is not miscible; or formed of the continuous phase and a polymer B dispersed phase. Here, the polymer A is crosslinked to suppress phase separation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ion conductive polymer electrolyte membrane suitable for a polymer electrolyte fuel cell and a method for producing the same.

  A fuel cell is a power generation device with low emissions, high energy efficiency, and low environmental burden, and is therefore in the spotlight again in recent years due to the increase in global environmental protection. Compared to conventional large-scale power generation facilities, this is a power generation device expected in the future as a relatively small-scale distributed power generation facility, and as a power generation device for mobile objects such as automobiles and ships. It is also attracting attention as a power source for small mobile devices and portable devices, and is expected to be installed in mobile phones and personal computers in place of secondary batteries such as nickel metal hydride batteries and lithium ion batteries.

Among them, a polymer electrolyte fuel cell that is attracting attention is generally composed of basic units called membrane electrode assemblies (MEA), and in MEA, an ion conductive polymer membrane (PEM) is sandwiched between a cathode and an anode, The ions formed at the anode are transported to the cathode and a current is passed through an external circuit connected to the electrode. PEMs must not only have adequate ionic conductivity, but must have the mechanical and chemical strengths required under the operating conditions of the power plant.
As such PEM materials, fluoropolymers containing super strong acid groups are known. However, since these PEM materials are fluoropolymers, they are very expensive and have a low glass transition temperature. When the temperature is around 100 ° C., the water retention is not sufficient, so that high ionic conductivity cannot be fully utilized, and the ionic conductivity is drastically lowered, which makes it impossible to function as a battery.

In order to overcome such drawbacks, various PEMs in which sulfonic acid groups are introduced into non-fluorinated aromatic ring-containing polymers have been studied. In view of heat resistance and chemical stability, aromatic polyarylene ether compounds such as aromatic polyarylene ether ketones and aromatic polyarylene ether sulfones are attracting attention as polymer skeletons. (For example, Non-Patent Document 1), sulfonated polyether ether ketone (for example, Patent Document 1), and the like have been reported.
However, those having sulfonic acid groups introduced into these polymers have the disadvantage that the dimensional change during swelling increases with an increase in the amount of sulfonic acid groups introduced, and membrane breakage is likely to occur under operating conditions such as fuel cells. . In order to remedy this drawback, attempts have been reported to introduce structural units capable of forming crosslinks between polymer chains to suppress dimensional changes (for example, Patent Documents 2 to 4). The dimensional change was not sufficiently suppressed.
Attempts to improve performance by blending non-ionic group-containing polymers (for example, Patent Documents 5 and 6) and attempts to form a composite membrane by impregnating an ion-conductive polymer in a porous inert membrane (For example, Patent Document 7) has been reported. However, those that were compatible by blending did not achieve both dimensional stability and proton conductivity, and those that were phase separated showed a decrease in film strength due to delamination. It can be said that the impregnated product is not easy to manufacture. In addition, the film produced from the dispersion is difficult to control the heat treatment, and the film strength is not always sufficient.

JP-A-6-93114 JP 2003-217342 A JP 2003-217343 A JP2003-292609 Japanese Patent Laid-Open No. 2003-502828 JP2003-109624 Journal of membrane science, (Netherlands) 1993, 83, p.211-220

  Therefore, the present invention has been made paying attention to the above circumstances, and the purpose thereof is an ionic group-containing polymer having excellent chemical stability and high proton conductivity, and an ion having excellent mechanical and chemical stability. The purpose of the present invention is to obtain an ion conductive polymer film having excellent heat resistance, processability, and ion conductivity as well as excellent mechanical durability and chemical durability by using a polymer having no functional group.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, the present invention has the following configuration.
1. Co-continuous phase of polymer A having at least an ion exchange group and co-continuous phase of polymer B which is incompatible with polymer A but does not have an ion exchange group soluble in the same solvent, or dispersed phase of polymer B And a polymer A in the membrane is crosslinked, and the ion exchange capacity of the polymer A after crosslinking is 1.0 to 4.0 meq / g. film.

2. 2. The ion conductive polymer electrolyte membrane according to 1, wherein the ion conductivity and area change rate satisfy the following formula (1), and the saturated water absorption rate and area change rate satisfy the following formula (2).
Area change rate (%) / ion conductivity (S / cm) ≦ 100 (1)
Area change rate (%) / saturated water absorption rate (% by weight) ≦ 0.5 (2)
3. Polymer B is polyvinylidene fluoride, polyvinyl fluoride, ethylene-tetraethylene copolymer, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, The above 1 or 2 comprising at least one selected from the group consisting of an ethylene-chlorotrifluoroethylene copolymer, a hexafluoropropylene-vinylidene fluoride copolymer, and a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer The ion conductive polymer electrolyte membrane described in 1.
4). The ion conductive polymer according to any one of 1 to 3 above, wherein the polymer A is a polyarylene having a crosslinkable site, and the ion exchange capacity of the polymer A after crosslinking is 1.0 to 4.0 meq / g. Electrolyte membrane.

5. 5. The ion conductive polymer electrolyte membrane according to 4 above, wherein the polymer A is a polyarylene ether-based compound including a component represented by the general formula (2) together with the general formula (1).
Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, X represents H, a sulfonic acid group, a phosphonic acid group, or a salt thereof.
However, Ar ′ represents a divalent aromatic group.

6). 5. The ion conductive polymer electrolyte membrane according to 4 above, wherein the polymer A is a polyarylene ether-based compound including a structural component represented by the structural formula (4) together with the general formula (3).
X represents H or a monovalent cation species.
7). 7. The ion conductive polymer electrolyte membrane according to any one of 4 to 6, wherein the polymer A has a —SO ₂ X group [X is a halogen or a monovalent cation].
8). 8. The ion conductive polymer electrolyte membrane according to any one of 1 to 7 above, wherein the composition ratio (weight / weight) of polymer A / polymer B is 30/70 to 90/10.
9. Casting a homogeneous mixed solution of polymer A containing an ion exchange group and having a crosslinkable reaction site and polymer B having no ion exchange group, cross-linking the cast membrane in a solvent-containing state, removing the solvent The method for producing an ion conductive polymer electrolyte membrane according to any one of 1 to 8 above, further comprising: a step of acid conversion by treating the ion exchange group in the crosslinked membrane with an acidic aqueous solution.
10. 10. The method for producing an ion conductive polymer membrane according to 9 above, wherein the polymer solution of the mixed solution to be cast has a concentration of 5 to 30% by weight and is crosslinked in a state containing a solvent.

The ion conductive polymer electrolyte membrane of the present invention has a continuous phase composed of an ion exchange group-containing polymer A having excellent chemical stability and high proton conductivity, and is incompatible with the polymer A, but can be dissolved in the same solvent. In the case where it consists of a co-continuous phase with an ion exchange group-free polymer B having excellent mechanical and chemical stability, or a polymer B dispersed phase, and the ion exchange group-containing polymer A is crosslinked and not crosslinked , Because the film is a composite of polymers that are inferior in mechanical properties or cannot stably maintain the state of the film, heat resistance, despite high ion conductivity and high water absorption, Since it possesses a trade-off property of being excellent in processability and dimensional stability, it is a membrane suitable as a polymer electrolyte membrane for fuel cells and the like. The ion conductive polymer electrolyte membrane of the present invention is also characterized by low methanol permeability and is useful as a polymer electrolyte membrane for direct methanol fuel cells.
Further, according to the membrane production method of the present invention, there is no need to produce a porous membrane in advance as in the case of a composite membrane produced by impregnating a porous inert membrane with an ion conductive polymer, and a series of continuous The composite film can be manufactured by the film forming process and is easy to manufacture.

  First, the ion conductive polymer in this invention is demonstrated. The ion conductive polymer electrolyte membrane of the present invention is composed of a polymer A having an ion exchange group and a polymer B having no ion exchange group. The polymer A has a reactive site capable of crosslinking together with an ion exchange group, and is required to be a polymer that can be formed into a film.

The ionic group of the ion conductive polymer in the present invention is not particularly limited as long as it is an atomic group having a negative charge, but preferably has a proton exchange ability. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group are preferably used. Here, the sulfonic acid group is —SO ₂ (OH), the sulfonimide group is —SO ₂ NHSO ₂ R (where R means an organic group), and the sulfuric acid group is —OSO ₂ (OH), A phosphonic acid group means —PO (OH) ₂ , a phosphoric acid group means —OPO (OH) ₂ , a carboxylic acid group means —CO (OH), and salts thereof. Two or more kinds of these ionic groups can be contained in the polymer solid electrolyte, and may be preferable by combining them. The combination is appropriately determined depending on the structure of the polymer. Among them, it is more preferable to have at least a sulfonic acid group, a sulfonimide group, and a sulfuric acid group from the viewpoint of high proton conductivity, and most preferable to have at least a sulfonic acid group from the viewpoint of hydrolysis resistance. Examples of ion exchange groups include proton acid groups such as sulfonic acid groups, phosphonic acid groups, and sulfonimide groups. Of these, sulfonic acid groups are preferred.

  As the polymer A in the present invention, a polymer having a sufficient mechanical strength and a high ionic group density can be easily synthesized. As a polymer skeleton, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polysulfone, Examples include ether ether sulfone, polyphenylene sulfide, polyimide, polyether imide, polyimidazole, polyoxazole, polyphenylene, polystyrene, and a structure in which these skeleton components are copolymerized.

Among these polymers, it is preferable that the polymer A is a polyarylene ether-based compound including the structural component represented by the general formula (2) together with the general formula (1).
Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, X represents H, a sulfonic acid group, a phosphonic acid group, or a salt thereof.

However, Ar ′ represents a divalent aromatic group.
Furthermore, it is preferable that the polymer A is a polyarylene ether-based compound containing the structural component represented by the structural formula (4) together with the general formula (3).

X represents H or a monovalent cation species.

The molecular weight of these polymers is not particularly limited as long as it is solid at room temperature, but the weight average molecular weight is preferably 1000 or more and 1 × 10 ⁷ or less from the viewpoint of film strength and solubility in a solvent.

  The ion exchange capacity (IEC) after crosslinking in the polymer A having an ionic group used in the present invention is 1.0 to 4.0 meq / g, preferably 1.0 to 3.0 meq / g. . If it is less than 1.0 meq / g, the proton conductivity tends to be low, and if it exceeds 4.0 meq / g, the mechanical strength of the membrane tends to be weak.

In addition, the polymer A in the present invention has crosslinkable reaction sites, and after blending with the polymer B described later, it is necessary that the polymer A be crosslinked through the crosslinkable reaction sites.
In the present invention, the crosslinkable reaction site of the polymer A includes a main chain, a side chain, a terminal group, etc. of the polymer A that are cross-linked by irradiation with energy rays such as ultraviolet rays, infrared rays, radiation, and electron beams. It means a site that crosslinks by reaction, a site that crosslinks by reacting with a crosslinking agent, etc. These sites are introduced after polymerization of polymer A by a method of previously copolymerizing monomers having these sites during polymerization of polymer A Either method may be used.

  Examples of sites that crosslink upon irradiation with energy rays include benzophenone groups, α-diketone groups, acyloin groups, acyloin ether groups, benzyl alkyl ketal groups, acetophenone groups, polynuclear quinones, thioxanthone groups, acylphosphine groups, ethylene. And unsaturated unsaturated groups. Among them, a combination of a group capable of generating a radical by light such as a benzophenone group and a group capable of reacting with a radical such as an aromatic group having a hydrocarbon group such as a methyl group or an ethyl group is preferable. Examples of the groups include the following formulas (A) and (B).

(In the formula, R represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n represents an integer of 1 to 4).

Moreover, as a site | part which reacts with a crosslinking agent, as long as it can react with the reactive group of a crosslinking agent, a main chain, a side chain, a terminal, etc. will not be limited, A thing which can form a new bond between polymer chains by reaction If it is good.
Examples include alcoholic hydroxyl groups, phenolic hydroxyl groups, carboxylic acid groups, acid anhydride groups, halogen groups and sulfonic acid groups and their bases, sulfinic acid groups and their bases, and ionic groups such as modified sulfonic acid groups. However, it is not limited to these.
Among these, a sulfonic acid group is preferable in that it is ion conductive and can be a reactive group of a crosslinking agent.
For example, when thionyl halide such as thionyl chloride is allowed to act on a sulfonic acid group and then treated with an aqueous solution of Na ₂ SO ₃ or the like, a —SO ₂ X group [X is a halogen or a monovalent cation] Furthermore, the —SO ₂ X group can be crosslinked using an organic dihalogenated compound such as 1,8-diiodooctane as a crosslinking agent.

  The content of these groups in the polymer is preferably from 0.01 to 5 mmol / g, more preferably from 0.1 to 2.5 mmol / g. If it is less than 0.01 mmol / g, crosslinking tends to be insufficient and phase separation cannot be sufficiently suppressed, and if it exceeds 5 mmol / g, the resulting film tends to be hard and brittle, and processability and durability are improved. May have adverse effects.

  The polymer B used in the present invention is not particularly limited as long as it is incompatible with the polymer A but can be dissolved in the same solvent. Specific examples include polyethylene, polypropylene, polybutadiene, polystyrene, polycarbonate, polyarylate. , Polymethyl methacrylate, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, polyvinylidene fluoride, polyhexafluoropropylene, polytetrafluoroethylene, polyvinylidene chloride, polyvinyl chloride, polyvinyl alcohol, polyvinyl pyrrolidone, polyamide and polyether Examples thereof include ketones, and the polymer A may be a single type, a mixture of two or more types, or a copolymer.

The molecular weight of these polymers is not particularly limited as long as it is solid at room temperature, but the weight average molecular weight is preferably 1000 or more and 1 × 10 ⁷ or less from the viewpoint of film strength and solubility in a solvent.

  The ion conductive polymer membrane of the present invention comprises a continuous phase composed of a polymer A having an ion exchange group and a polymer B which is incompatible with the polymer A but does not have an ion exchange group which can be dissolved in the same solvent. It is a composite membrane composed of a co-continuous phase or a polymer B dispersed phase, and the polymer A needs to be cross-linked to suppress phase separation. Since the polymer A is crosslinked, phase separation between the polymer A and the polymer B is suppressed and the membrane structure can be maintained. However, when the polymer A is not crosslinked, the membrane collapses during use. It will lead to.

A continuous phase composed of a polymer A having an ion exchange group and a co-continuous phase of a polymer B that is incompatible with the polymer A but does not have an ion exchange group that can be dissolved in the same solvent, or a polymer B dispersed phase As a method for forming the polymer, a solution blend method in which both the polymer A and the polymer B are dissolved in a solvent is preferable.
The solvent used for blending is not particularly limited as long as both the polymer A and the polymer B are soluble, but N-methyl-2-pyrrolidone, N, N-dimethyl are considered in terms of solubility, handling properties, and cost. Desirable organic polar solvents such as acetamide, N, N-dimethylformamide, tetramethylurea, dimethylimidazolidinone, dimethyl sulfoxide, hexamethylphosphonamide, or a mixture thereof. There is no particular limitation on the dissolution temperature, and it may be at room temperature or under heating.
The polymer concentration after dissolution of both polymer A and polymer B is preferably 5 to 30% by weight. If the polymer concentration exceeds 30% by weight, film formation becomes difficult because the solution viscosity is too high, and even if it is less than 5% by weight, film formation becomes difficult because the solution viscosity is too low.

  The composition ratio (weight / weight) of polymer A / polymer B is preferably 30/70 to 90/10. If the ratio of the polymer A is too small, proton conductivity tends to deteriorate, and if it is too large, the effect of blending cannot be expected.

In order to suppress the phase separation between the polymer A and the polymer B, it is necessary to crosslink the polymer A. The method for crosslinking the polymer A is not particularly limited as long as the phase separation can be suppressed. However, by using the crosslinkable reaction site of the polymer A, the use of a crosslinking agent, energy by ultraviolet rays, electron beams, and the like. It is preferable to crosslink by irradiation with a beam or the like.
The amount of the crosslinking site is not particularly limited as long as the polymer A is introduced after the crosslinking reaction so that the polymer A is not redissolved in an organic solvent such as N-methylpyrrolidone or N, N-dimethylformamide.
The ion conductive polymer membrane crosslinked with the polymer A of the present invention comprises a continuous phase composed of the polymer A and a co-continuous phase with the polymer B, or a polymer B dispersed phase. In the case where the dispersion layer is formed, it is preferable that the aspect ratio of the polymer B, which is an island component, is in the range of 2 to 100 and the size is 5 μm or less in the observation of the morphology of the film cross section with an electron microscope.

The ion conductive polymer membrane crosslinked with the polymer A of the present invention preferably has an ion conductivity and area change rate of the following formula (1), and a water absorption rate and area change rate of the following formula (2). .
Area change rate (%) / ion conductivity (S / cm) ≦ 100 (1)
Area change rate (%) / water absorption rate (% by weight) ≦ 0.5 (2)
Furthermore, it is preferable that the area change rate (%) / ion conductivity (S / cm) ≦ 50 and the area change rate (%) / water absorption rate (% by weight) ≦ 0.2 are satisfied.
That is, the ion-conducting polymer membrane of the present invention has a characteristic that the dimensional stability of the membrane is superior to that of the prior art, despite the high ion conductivity and water absorption of the polymer A having an ion exchange group. It is a feature.

The ion conductive polymer film in which the polymer A of the present invention is crosslinked can be produced through the following main steps.
That is, a step of casting a homogeneous mixed solution of a polymer A containing an ion exchange group and having a crosslinkable reaction site and a polymer B having no ion exchange group, a step of crosslinking the cast membrane in a solvent-containing state, a solvent It can be manufactured through a step of removing acid and a step of acid conversion by treating the ion exchange group in the crosslinked membrane with an acidic aqueous solution.

  In the step of crosslinking in a solvent-containing state, it is preferable that at least 5 to 30% by weight of the solvent is included during the crosslinking. Further, in consideration of the boiling point of the solvent to be used, heating can be performed during the crosslinking. Furthermore, it is preferable to perform the crosslinking time in the range of 1 to 300 minutes.

The method for removing the solvent is preferably from the viewpoint of the uniformity of the ion conductive membrane. Moreover, in order to avoid decomposition | disassembly and alteration of a compound or a solvent, it can also dry under reduced pressure.
The ion conductive film of the present invention can have any film thickness depending on the purpose, but is desirably as thin as possible from the viewpoint of ion conductivity. Specifically, the thickness is preferably 5 to 250 μm, and more preferably 5 to 100 μm. If the thickness of the ion conductive membrane is less than 5 μm, it is difficult to handle the ion conductive membrane and a short circuit or the like tends to occur when a fuel cell is formed. If the thickness is greater than 250 μm, the electric resistance value of the ion conductive membrane is high. Therefore, the power generation performance of the fuel cell tends to decrease.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited by the following examples, but should be implemented with appropriate modifications within a range that can meet the gist of the preceding and following descriptions. Of course, any of them is also included in the technical scope of the present invention.

Various measurements were performed as follows.
1. Reduced viscosity The polymer powder dried under reduced pressure at 80 ° C. overnight was dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.5 g / dl, and the viscosity was measured using a Ubbelohde viscometer in a high temperature bath at 25 ° C. The reduced viscosity ηsp / c = [(t−t0) / t0] / c was evaluated. [T0: dropping time of solvent only (s), t: dropping time of sample solution (s), c: concentration of sample solution (g / dl)]

2. Ion exchange capacity 50 mg of the polymer dried under reduced pressure at 80 ° C. overnight was weighed and stirred in 60 ml of 0.01 M NaOH aqueous solution for 1 hour. Thereafter, 50 ml of the solution was taken out and titrated with an aqueous 0.02M HCl solution using an automatic titrator (HIRANUMA TITSTATION TS-980). The ion exchange capacity (IEC) was calculated from the following equation.
IEC = [average blank dripping amount (ml) −sample dripping amount (ml)] × 1.2 × (2/100) / sample weight (g)

3. Ion conductivity A platinum wire (diameter: 0.2 mm) is pressed against the surface of a strip-shaped membrane sample having a width of 1 cm on a probe for measurement (made of PTFE), and the sample is placed in a constant temperature and humidity chamber at 80 ° C. and a relative humidity of 95%. The AC impedance at 10 kHz between the platinum wires was measured by SOLARTRON 1250 FREQUENCY RESPONSE ANALYSER. Measured by changing the distance between the electrodes from 1 cm to 4 cm at 1 cm intervals, and canceling the contact resistance between the film and the platinum wire using the following formula from the slope Dr (Ω / cm) of the straight line plotting the distance between the electrodes and the measured resistance value And calculated.
σ (S / cm) = 1 / [film width (cm) × film thickness (cm) × Dr (Ω / cm)]

4). A sample having a water absorption of 5 cm square was vacuum-dried at 80 ° C. overnight, and the dry weight was measured. The dry sample was kept in water at 80 ° C. for 1 day or longer, and the weight after saturated water absorption (weight when the weight change disappeared after the start of measurement) was determined to calculate the water absorption rate (%) of the sample from the following formula.
Saturated water absorption (%) = [(weight after saturated water absorption / dry weight) -1] × 100

5. Area change rate A sample of 5 cm square was vacuum-dried at 80 ° C. overnight, and then the area after drying was measured. The dried sample was kept in water at 80 ° C. for 1 day or longer, and the area after saturated water absorption (the area when the area change disappeared after the start of measurement) was determined, and the area change rate (%) of the sample was calculated from the following formula.
Area change rate (%) = [(Area after saturated water absorption / Area after drying) -1] × 100

(Synthesis of polymer A1)
3,3′-disulfo-4,4′-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) 15.0 g [0.03026 mol], 2,6-dichlorobenzonitrile (abbreviation: DCBN) 2.81 g [0.01629 mol], 4,4′-biphenol 8.6747 g [0.04655 mol] and potassium carbonate 7.0775 g were weighed into a 200 ml four-necked flask and flushed with nitrogen. After adding 89.1 ml of NMP and stirring at 150 ° C. for 1 hour, the reaction temperature was raised to 195-200 ° C., and the reaction was continued with the aim of sufficiently increasing the viscosity of the system (about 6 hours). Thereafter, the mixture was allowed to cool and precipitated into strands in water. The obtained polymer was washed in water and then dried. The reduced viscosity of the polymer was 1.93 (dl / g), and the IEC was 2.3 (meq / g). Subsequently, 15 g of the polymer obtained, 200 ml of thionyl chloride, and 10 ml of DMF were weighed into a 300 ml four-necked flask and flushed with nitrogen. After reacting at 70 ° C. for about 3 hours, thionyl chloride was distilled off at 90 ° C. Thereafter, thionyl chloride was removed by repeating the work of dissolving in 150 ml of THF and reprecipitating in 2-propanol. 18 g of the obtained product was weighed into a 2 L Erlenmeyer flask, 1 L of 2M-Na ₂ SO ₃ was added, and reacted at 70 ° C. for 24 hours. The product was filtered, and the obtained filtrate was placed in a 10% LiCl aqueous solution, stirred at room temperature for 24 hours, and salt exchanged to synthesize polymer A1. As a result of ¹ H NMR analysis, this polymer A1 had 73% of all sulfonic acid groups converted to SO ₂ Li.

(Synthesis of polymer A2)
Four 200 ml of 6.017 g [0.018 mol] decafluorobiphenyl, 5.378 g [0.016 mol] of 4,4′-hexafluoroisopropylidenediphenol (abbreviation: 6F-BPA) and 6.62 g [0.048 mol] potassium carbonate. Weighed into a neck flask and flushed with nitrogen. 80 ml of DMAc was added and the temperature was raised to 120 ° C. in 2 hours, and then maintained for 4 hours. Thereafter, the mixture was allowed to cool and precipitated into strands in water. The obtained oligomer was washed in water and then dried under reduced pressure at 80 ° C. to obtain oligomer A2. Subsequently, 4.412 g [0.0089 mol] of S-DCDPS, 1.862 g [0.01 mol] of 4,4′-biphenol, and 2.75 g of potassium carbonate were weighed in a 500 ml four-necked flask, and nitrogen was allowed to flow. 35 ml of NMP was added and reacted at 150 ° C. for 4 hours, and then reacted at 180 ° C. for 18 hours and 195 ° C. for 4 hours. After cooling this reaction solution to 90 ° C., a solution prepared by dissolving 6.021 g of oligomer A2 in NMP at 10% by weight was added in several portions, and then reacted at 110 ° C. for 24 hours. When the viscosity increased during the reaction, NMP was added appropriately. The obtained polymer solution was allowed to cool and precipitated in water into strands. The obtained polymer was washed in water and then dried under reduced pressure at 80 ° C. The reduced viscosity of the polymer was 1.51 (dl / g), and the IEC was 1.5 (meq / g).
Subsequently, 10 g of the obtained polymer, 150 ml of thionyl chloride, and 5 ml of DMF were weighed into a 300 ml four-necked flask, and nitrogen was allowed to flow. After reacting at 70 ° C. for about 3 hours, thionyl chloride was distilled off at 90 ° C. Thereafter, thionyl chloride was removed by repeating the work of dissolving in 150 ml of THF and reprecipitating in 2-propanol. 10 g of the obtained product was weighed into a 1 L Erlenmeyer flask, 600 ml of 2M-Na ₂ SO ₃ was added, and reacted at 70 ° C. for 24 hours. The product was filtered, and the obtained filtrate was placed in a 10% LiCl aqueous solution, stirred at room temperature for 24 hours, and subjected to salt exchange to synthesize polymer A2. As a result of ¹ H NMR analysis, this polymer A1 had 53% of all sulfonic acid groups converted to SO ₂ Li.

(Synthesis of polymer A3)
S-DCDPS 17.1414 g [0.03489 mol], DCBN 4.0013 g [0.02326 mol], 4,4′-biphenol 10.8392 g [0.05816 mol], 4,4′-difluorobenzophenone 1.4101 g [0.00546 mol], bis (4-Hydroxy-2,5-dimethylphenyl) methane and 10.2711 g of potassium carbonate were weighed into a 200 ml four-necked flask and flushed with nitrogen. After adding 103 ml of NMP and stirring at 150 ° C. for 1 hour, the reaction was continued by raising the reaction temperature to 195-200 ° C. and sufficiently increasing the viscosity of the system (about 6 hours). Thereafter, the mixture was allowed to cool and precipitated into strands in water. The obtained polymer was washed in water and then dried. The reduced viscosity of the polymer was 0.79 (dl / g), and the IEC was 2.21 (meq / g).

Example 1
12 g (10% by weight) of NMP solution of polymer A1 and 8 g (10% by weight) of NDF solution of PVDF (Mw = 180,000) were mixed to obtain a uniform NMP solution. Thereto, 42.1 μl (0.180 mmol) of 1,8-diiodooctane (purity = 85%) was added as a cross-linking agent, stirred for 5 minutes, cast to a thickness of about 400 μm on a glass plate, and kept at 25 ° C. for 3 hours. The polymer A1 was cross-linked and then dried under reduced pressure at 120 ° C. for 3 hours. The obtained film was treated in a 2M-NaOH aqueous solution at 80 ° C. for 12 hours, treated in a 2M-H ₂ SO ₄ aqueous solution at 80 ° C. for 12 hours, and then washed with pure water to obtain a composite film. Table 1 summarizes the characteristics of the obtained composite membrane 1 such as IEC, ion conductivity, water absorption, and area change rate. A TEM (transmission electron microscope) observation photograph of the film cross section is shown in FIG.

(Example 2)
Example 1 except that the ratio of polymer A1 / PVDF was changed to 5/5 (% by weight) and the amount of 1,8-diiodooctane (purity = 85%) was changed to 35.1 μl (0.150 mmol). It implemented by the same method. The obtained film properties are summarized in Table 1.
(Example 3)
Example 1 except that the ratio of polymer A1 / PVDF was changed to 4/6 (% by weight) and the amount of 1,8-diiodooctane (purity = 85%) was changed to 28.1 μl (0.120 mmol). It implemented by the same method. The film properties obtained are summarized in Table 1.
Example 4
The same procedure as in Example 1 was performed except that the polymer A1 was changed to the polymer A2. The film properties obtained are summarized in Table 1.

(Example 5)
12 g (10% by weight) of NMP solution of polymer A3 and 8 g (10% by weight) of NDF solution of PVDF (Mw = 180,000) were mixed to obtain a uniform NMP solution. The solution was cast on a glass plate to a thickness of about 400 μm, irradiated with an ultraviolet irradiation device (ORC3000) for 1 hour, and then dried under reduced pressure at 120 ° C. for 3 hours. The obtained film was treated in a 2M-H ₂ SO ₄ aqueous solution at room temperature for 12 hours, and then washed with pure water to obtain a composite film. Table 1 shows the characteristics of the obtained composite membrane, such as IEC, ionic conductivity, water absorption, and area change rate.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that no crosslinking agent was added. The obtained film characteristics are summarized in Table 1. However, the water absorption rate and area change rate could not be measured because the film collapsed during the immersion. A TEM observation photograph of the film cross section is shown in FIG.
(Comparative Example 2)
A single membrane of polymer A was prepared by the same method as in Example 1 without adding PVDF and a crosslinking agent, and the properties such as IEC, ion conductivity, water absorption rate, area change rate, etc. of the obtained membrane were summarized in Table 1. It was.
(Comparative Example 3)
The same evaluation as in Example 1 was performed on a single membrane using Nafion (registered trademark; DuPont) 112, and the characteristics are summarized in Table 1.

From the above results, it can be seen that the composite membrane of the present invention is excellent in dimensional stability against water absorption despite high ion conductivity and high water absorption.

  The ion conductive polymer electrolyte membrane of the present invention is a material that exhibits outstanding performance as a polymer electrolyte membrane such as a fuel cell excellent in heat resistance, workability, and dimensional stability as well as ion conductivity, It is also characterized by low methanol permeability and is useful as a polymer electrolyte membrane for direct methanol fuel cells.

2 is a TEM observation photograph of a cross section of the ion conductive polymer film obtained in Example 1. FIG. 4 is a TEM observation photograph of a cross section of the ion conductive polymer film obtained in Comparative Example 1.

Claims (10)

  Co-continuous phase of polymer A having at least an ion exchange group and co-continuous phase of polymer B which is incompatible with polymer A but does not have an ion exchange group soluble in the same solvent, or dispersed phase of polymer B And a polymer A in the membrane is crosslinked, and the ion exchange capacity of the polymer A after crosslinking is 1.0 to 4.0 meq / g. film. The ion conductive polymer electrolyte membrane according to claim 1, wherein the ion conductivity and area change rate of the membrane satisfy the following formula (1), and the saturated water absorption rate and area change rate of the membrane satisfy the following formula (2).
Area change rate (%) / ion conductivity (S / cm) ≦ 100 (1)
Area change rate (%) / saturated water absorption rate (% by weight) ≦ 0.5 (2)   Polymer B is polyvinylidene fluoride, polyvinyl fluoride, ethylene-tetraethylene copolymer, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, 2. The composition according to claim 1, comprising at least one selected from the group consisting of an ethylene-chlorotrifluoroethylene copolymer, a hexafluoropropylene-vinylidene fluoride copolymer, and a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer. 2. The ion conductive polymer electrolyte membrane according to 2.   The ion conductivity according to any one of claims 1 to 3, wherein the polymer A is a polyarylene having a crosslinkable reaction site, and the ion exchange capacity of the polymer A after crosslinking is 1.0 to 4.0 meq / g. Polymer electrolyte membrane. The ion conductive polymer electrolyte membrane according to claim 4, wherein the polymer A is a polyarylene ether-based compound including a component represented by the general formula (2) together with the general formula (1).
Here, Ar represents a divalent aromatic group, Y represents a sulfone group or a ketone group, X represents H, a sulfonic acid group, a phosphonic acid group, or a salt thereof.
Ar ′ represents a divalent aromatic group. 5. The ion conductive polymer electrolyte membrane according to claim 4, wherein the polymer A is a polyarylene ether compound containing a structural component represented by the structural formula (4) together with the general formula (3).
X represents H or a monovalent cation species.
Ion conductive polymer electrolyte membrane according to any one of claims 4-6 polymer A [the X cations halogen or a monovalent] -SO 2 _X group having.   The composition ratio (weight / weight) of polymer A / polymer B is 30/70 to 90/10. The ion conductive polymer electrolyte membrane according to any one of claims 1 to 7.   Casting a homogeneous mixed solution of polymer A containing an ion exchange group and having a crosslinkable reaction site and polymer B having no ion exchange group, cross-linking the cast membrane in a solvent-containing state, removing the solvent The method for producing an ion conductive polymer membrane according to any one of claims 1 to 8, further comprising a step of acid conversion by treating the ion exchange group in the crosslinked membrane with an acidic aqueous solution.   The method for producing an ion conductive polymer electrolyte membrane according to claim 9, wherein the polymer solution in the mixed solution to be cast has a concentration of 5 to 30% by weight and is crosslinked in a state containing a solvent.