JP2002216800A - Composite polymer electrolyte membrane and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite polymer electrolyte membrane having sufficient power generation performance regardless of changes in temperature and humidity, and having high hot water resistance, oxidation resistance and creep resistance, and a method for producing the same. . SOLUTION: The composite polymer electrolyte membrane comprises a base material made of a sulfonated polymer compound having a high ion exchange capacity, and a reinforcing material made of a fibrous or porous membrane of a sulfonated polymer compound having a low ion exchange capacity. Having. Each of the sulfonated polymer compounds is a non-fluorinated sulfonated polymer compound, and a sulfonated polymer compound having a high ion exchange capacity and a sulfonated polymer compound having a low ion exchange capacity are the same except for the ion exchange capacity. It has a skeletal structure. H ⁺ of the sulfonic acid group of the sulfonated polymer compound having a low ion exchange capacity is at least partially substituted with Na ⁺ .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite polymer electrolyte membrane used for a fuel cell or the like and a method for producing the same, and more particularly to a high polymer reinforced with a fibrous or porous membrane-like sulfonated polymer compound having a low ion exchange capacity. The present invention relates to a composite polymer electrolyte membrane comprising a sulfonated polymer compound having an ion exchange capacity and a method for producing the same.

[0002]

2. Description of the Related Art Fuel cells have attracted attention as a power source for clean electric motors due to the depletion of petroleum resources and the seriousness of environmental problems such as global warming.
Some have been put to practical use. In particular, when a fuel cell is mounted on an automobile or the like, it is preferable to use a polymer electrolyte membrane fuel cell, but as the polymer electrolyte membrane, a sulfonated fluorine-based polymer compound such as Nafion is widely used. I have. However, Nafion has a problem that it is very expensive. In addition, as the output of the fuel cell increases, a polymer electrolyte membrane having hot water resistance, oxidation resistance, and creep resistance (mechanical strength) that can withstand operation under high temperature and high pressure is required. Nafion is not always enough.

Therefore, various attempts have been made to improve the mechanical strength and the like without deteriorating the ion exchange characteristics of the polymer electrolyte membrane. For example, JP-A-6-29032 proposes a polymer electrolyte membrane having improved mechanical strength by containing an ion exchange resin in the pores of a stretched polymer porous membrane.

Japanese Patent Application Laid-Open No. 8-259710 discloses a structure in which an ion-exchange resin is contained in the pores of a stretched polymer porous membrane to improve the mechanical strength of the polymer electrolyte membrane and increase the membrane resistance. Has proposed a polymer electrolyte membrane that has reduced energy consumption and improved energy efficiency.

Japanese Patent Application Laid-Open No. 2000-231928 discloses a high strength and high ion conductivity (membrane resistance) obtained by adding a reinforcing material made of polyethylene fiber to a polymer electrolyte made of a perfluorocarbon polymer containing a sulfonic acid group. (Low) polymer electrolyte membrane.

However, the porous membranes or fibers used in these polymer electrolyte membranes are made of chemically stable polymers such as polytetrafluoroethylene (PTFE) and polyethylene, and have low ionic conductivity and low temperature and humidity. Expansion and contraction due to changes in On the other hand, ion exchange resins having high ion conductivity have large expansion and contraction due to changes in temperature and humidity. Therefore, there has been a problem that the polymer electrolyte is separated from the porous membrane or the fiber. When the polymer electrolyte peels off, the membrane resistance increases, so that the power generation performance of the fuel cell decreases.

[0007] In order to improve the ion conductivity of the polymer electrolyte membrane, it is necessary to increase the ion exchange capacity of the polymer electrolyte. However, when the ion exchange capacity is increased, the mechanical strength of the polymer electrolyte membrane may decrease. As a result, the polymer electrolyte membrane tends to creep. On the other hand, if the ion exchange capacity is reduced, sufficient ion conductivity cannot be obtained, and the power generation performance of the fuel cell is reduced.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sufficient power generation performance irrespective of changes in temperature and humidity, as well as high hot water resistance and oxidation resistance and mechanical properties such as creep resistance. An object of the present invention is to provide a polymer electrolyte membrane having excellent strength and a method for producing the same.

[0009]

Means for Solving the Problems In view of the above-mentioned objects, as a result of intensive studies, it has been found that a sulfonated polymer compound having a high ion exchange capacity is used as a base material and a fibrous or porous membrane-like sulfone having a low ion exchange capacity is used. By adding a polymerized polymer compound as a reinforcing material, it is possible to obtain a polymer electrolyte membrane that improves hot water resistance and oxidation resistance without lowering ion conductivity and has excellent mechanical strength such as creep resistance. And found the present invention.

That is, the composite polymer electrolyte membrane of the present invention comprises a base material composed of a sulfonated polymer compound having a high ion exchange capacity and a fibrous or porous membrane of a sulfonated polymer compound having a low ion exchange capacity. And a reinforcing material.

It is preferable that all the sulfonated polymer compounds are non-fluorinated sulfonated polymer compounds.
The sulfonated polymer compound having a high ion exchange capacity and the sulfonated polymer compound having a low ion exchange capacity preferably have the same skeleton structure except for the ion exchange capacity.
Both sulfonated polymer compounds preferably contain a phenylene group, particularly preferably a sulfonated polyetheretherketone.

Preferably, the ion exchange capacity of the sulfonated polymer compound having a high ion exchange capacity is 1.0 to 2.8 meq / g, and the ion exchange capacity of the sulfonated polymer compound having a low ion exchange capacity is 0.5 to 1.5 meq / g. It is preferably meq / g.

The sulfonic acid group H ⁺ of the sulfonated polymer compound having a low ion exchange capacity is at least partially Na ⁺
Is preferably substituted.

The present invention for producing a composite polymer electrolyte membrane having a matrix composed of a sulfonated polymer compound having a high ion exchange capacity and a reinforcing material composed of a fibrous material of a sulfonated polymer compound having a low ion exchange capacity. The method is characterized in that the fibrous material of the sulfonated polymer compound having a low ion exchange capacity is uniformly dispersed in a solution of the sulfonated polymer compound having a high ion exchange capacity, and a film is formed by a casting method. .

The present invention for producing a composite polymer electrolyte membrane having a matrix composed of a sulfonated polymer compound having a high ion exchange capacity and a reinforcing material composed of a porous membrane of a sulfonated polymer compound having a low ion exchange capacity. Is characterized in that the porous membrane of the sulfonated polymer compound having a low ion exchange capacity is impregnated with a solution of the sulfonated polymer compound having a high ion exchange capacity to form a membrane.

It is preferable to use a non-fluorinated sulfonated polymer compound as the sulfonated polymer compound. The sulfonated polymer compound having a high ion exchange capacity and the sulfonated polymer compound having a low ion exchange capacity can be obtained by sulfonating a polymer compound having the same skeleton structure with a different ion exchange capacity. preferable.

[0017]

DETAILED DESCRIPTION OF THE INVENTION [1] Composite Polymer Electrolyte Membrane The composite polymer electrolyte membrane of the present invention has an ion exchange capacity (1 g).
A base material comprising a sulfonated polymer compound having a high ion-exchange group (for example, a milliequivalent of a sulfonic acid group) per unit;
And a reinforcing material comprising a fibrous material of a sulfonated polymer compound having a low ion exchange capacity or a porous membrane.

The sulfonated polymer compound constituting the base material and the reinforcing material is preferably made of a sulfonated polymer compound having the same skeleton structure except for the ion exchange capacity.
Thereby, the expansion coefficients of the base material and the reinforcing material become substantially equal, and the separation of the base material and the reinforcing material can be prevented.

In order to satisfy the requirements of mechanical strength such as ionic conductivity, hot water resistance, oxidation resistance and creep resistance, and to reduce the cost, a high molecular compound forming a skeleton of any sulfonated high molecular compound is used. Is also preferably a non-fluorinated polymer compound. The sulfonated polymer compound constituting the base material and the reinforcing material is preferably a sulfonated polymer compound having a phenylene group in the main chain, and particularly preferably a sulfonated polyetheretherketone.

The polymer electrolyte of the base material has a high ion exchange capacity, and the polymer electrolyte of a fibrous material or a porous membrane has a low ion exchange capacity. Specifically, the ion exchange capacity of the polymer electrolyte of the base material is 1.0 to 2.8 meq / g, and the ion exchange capacity of the polymer electrolyte of the fibrous material or the porous membrane is 0.5 to 1.5 meq / g. Is preferred.

The ion exchange capacity of the polymer electrolyte for the base material is 1.
If it is less than 0 meq / g, the ionic conductivity is insufficient,
If it exceeds 2.8 meq / g, the mechanical strength such as creep resistance is insufficient. On the other hand, if the ion exchange capacity of the fibrous material or the polymer electrolyte for a porous membrane is less than 0.5 meq / g,
Insufficient ionic conductivity and adhesion and 1.5 meq /
If it exceeds g, the creep resistance is insufficient.

The ion exchange capacity of the polymer electrolyte for the base material is preferably at least 0.5 meq / g larger than the ion exchange capacity of the polymer electrolyte for the fibrous material or the porous membrane. The difference between the two
If it is less than 0.5 meq / g, the effect of compounding is insufficient.

When the sulfonated polymer compound having a low ion exchange capacity is fibrous, it may be a long fiber or a short fiber, and in the case of a long fiber, it may be a woven fabric or a nonwoven fabric. In the case of a non-woven fabric, it is preferable that the fibers are appropriately fused by calendering. In any case, the diameter of the sulfonated polymer compound having a low ion exchange capacity is preferably about 1 to 15 μm. If the diameter is less than 1 μm, the reinforcement hardening is insufficient, and
If it exceeds μm, the ionic conductivity of the composite polymer electrolyte membrane decreases.

In the case of a porous membrane, the porosity is preferably about 50 to 80%, and the average pore diameter is preferably about 0.2 to 3 μm. When the porosity and the average pore diameter are less than the above lower limits, the ionic conductivity of the composite polymer electrolyte membrane is insufficient, and when the porosity and the average pore diameter are more than the upper limits, the reinforcing curing is insufficient.
Further, the thickness is preferably 15 to 75 μm because it regulates the performance of the composite polymer electrolyte membrane.

It is preferable that at least a part of H ⁺ of the sulfonic acid group of the low ion exchange capacity sulfonated polymer compound constituting the fibrous material or the porous membrane is substituted with Na ⁺ .
This substitution improves the adhesion between the base material and the fibrous material or the porous membrane, and lowers the membrane resistance of the composite polymer electrolyte membrane.

The weight ratio of the matrix and the fibrous or porous membrane in the composite polymer electrolyte membrane is preferably from 3: 1 to 1: 3. When the weight ratio of the base material / (fibrous material or porous film) is more than 3: 1, the reinforcing effect of the fibrous material or porous film is insufficient, and when it is less than 1: 3, the composite polymer is used. The ionic conductivity of the electrolyte membrane is insufficient. A more preferable weight ratio of the base material / (fibrous material or porous membrane) is 2/1 to 1/1.
1.25.

As described above, by using a sulfonated polymer compound having a high ion exchange capacity as the base material and using a fibrous material or a porous membrane of the sulfonated polymer compound having a low ion exchange capacity as the reinforcing material, Because of high conductivity and high creep resistance, a highly efficient and highly durable composite polymer electrolyte membrane can be obtained. The thickness of the composite polymer electrolyte membrane of the present invention is 15
It is preferably about 75 μm.

[2] Method for Producing Composite Polymer Electrolyte Membrane (A) Preparation of Fibrous Material or Porous Membrane A low ion exchange capacity sulfonated polymer compound is dissolved in an organic solvent such as N-methylpyrroline, Make a homogeneous solution. To make a fibrous or porous membrane from this homogeneous solution,
In the case of fibers, a known spinning method may be used.In the case of a porous film, a predetermined amount of a foaming agent is added to a uniform solution to form a film by a casting method, and a state in which an organic solvent slightly remains. A method may be used in which foaming is performed by heating at a temperature to make the material porous. Of course, the formation of the low ion exchange capacity sulfonated polymer compound into a fibrous or porous membrane is not limited to the above method, and any known method can be adopted.

H ⁺ of the sulfonic acid group of the low ion exchange capacity sulfonated polymer compound constituting the fibrous material or the porous membrane
Is preferably at least partially replaced by Na ⁺ . This replacement can be performed, for example, by immersing the fibrous material or the porous membrane in an aqueous solution containing Na ⁺ such as an aqueous sodium chloride solution. The concentration of the aqueous solution containing Na ⁺ is 0.01 to 2 mol
/ l and the temperature may be about 25 ° C. The immersion time is preferably adjusted so that the degree of substitution of H ⁺ by Na ⁺ is about 5 to 50%.

(B) Preparation of Composite Polymer Electrolyte Membrane To prepare a composite polymer electrolyte membrane containing a fibrous material, a fibrous material (low) is added to an organic solvent solution of a sulfonated polymer compound having a high ion exchange capacity. (Ion exchange capacity sulfonated polymer compound) is added, cast into a flat mold, and dried.

In order to produce a composite polymer electrolyte membrane containing a porous membrane of a sulfonated polymer compound having a low ion exchange capacity, a porous membrane is impregnated with a solution of a sulfonated polymer compound having a high ion exchange capacity. You can do it.

[0032]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 A high-sulfonated polyetheretherketone having an ion exchange capacity of 1.5 meq / g and N-methylpyrroline were mixed at a weight ratio of 95: 5 to prepare a polymer electrolyte solution. Also, low-sulfonated polyetheretherketone having an ion exchange capacity of 1.0 meq / g is dissolved in N-methylpyrroline, and the resulting solution (copolymer concentration: 10% by weight) is spun to obtain an average diameter of 5 μm. Into fibers. The ion exchange capacity was adjusted by changing the acid treatment conditions (concentration of fuming sulfuric acid, immersion time). Then, it was immersed in a 2N aqueous solution of sodium chloride at 25 ° C. for 30 minutes to replace H ⁺ of the sulfonic acid group with Na ⁺ to obtain a fibrous reinforcing material. A fibrous reinforcing material was uniformly mixed with this polymer electrolyte solution at a solid content weight ratio of 90:10, and a composite polymer electrolyte membrane having a dry film thickness of 50 μm was prepared by a casting method.

Example 2 A high-sulfonated polyetheretherketone having an ion exchange capacity of 1.5 meq / g and N-methylpyrroline were mixed at a weight ratio of 95: 5 to prepare a polymer electrolyte solution. Further, particles such as layered silicates having poor acid resistance were mixed with low sulfonated polyetheretherketone having an ion exchange capacity of 1.0 meq / g and cast. By subjecting the obtained film to an acid treatment with 5N hydrochloric acid, particles were missing, and a porous film was obtained. Thus, a porous film having a thickness of 30 μm was formed. The average pore diameter of the obtained porous membrane was 2 μm, and the porosity was 65%. This porous membrane was immersed in a 2N aqueous solution of sodium chloride at 25 ° C. for 30 minutes to replace H ⁺ of the sulfonic acid group with Na ⁺ to obtain a reinforcing material.
This polymer electrolyte solution was impregnated into a porous membrane-like reinforcing material at a solid content weight ratio of 70:30 to prepare a composite polymer electrolyte membrane having a dry film thickness of 50 μm.

Comparative Example 1 A solution of a partial copolymer of styrene and divinylbenzene (styrene: divinylbenzene = 20: 1) was prepared in the same manner as in Example 1 of JP-A-8-259710. The solution has a diameter of 5
A reinforcement made of μm PTFE fiber was uniformly mixed. A PTFE fiber reinforcing material was added to the polymer electrolyte solution at a solid content weight ratio of 90:10, and a composite polymer electrolyte membrane having a dry film thickness of 50 μm was prepared by a casting method.

Comparative Example 2 In the same manner as in Example 6 of JP-A-8-259710, two PTFE-stretched porous membranes (8 cm × 8 cm, film thickness 15 μm, porosity 70%) were prepared. A 6 cm × 6 cm window was provided at the center. A PTFE-stretched porous membrane with a window is placed on a glass plate (8 cm × 8
cm), and the same solution of the raw material for ion exchange resin as in Comparative Example 1 was injected into the window of the stretched porous membrane (gap width: 55 cm).
μm), the copolymerization was completed in this state. After removing the glass plate, the ion exchange resin raw material was sulfonated with fuming sulfuric acid. The pores of the porous PTFE stretched membrane of the obtained ion exchange membrane retained the ion exchange resin (ion exchange thickness: 50 μm).

COMPARATIVE EXAMPLE 3 Instead of low sulfonated polyetheretherketone, PT
Example 1 except that FE was used for a fibrous reinforcing material having a diameter of 5 μm
In the same manner as described above, a composite polymer electrolyte membrane having a dry film thickness of 50 μm was produced.

Evaluation (1) Q value The cycle of immersing the polymer electrolyte membranes of Examples 1 and 2 and Comparative Examples 1 to 3 in hot water at 80 ° C. and water at 20 ° C. for 10 minutes was repeated 30 times. Thereafter, electrodes were applied to both surfaces of each polymer electrolyte membrane, and the potential when a current of 0.2 A / cm ² was passed was measured. Further, a Q value as an index of the adhesion between the base material and the reinforcing material was measured according to the following method. Table 1 shows the measurement results.

The measurement of the Q value is performed using the electrolyte membrane-electrode complex shown in FIG. This electrolyte membrane-electrode complex has an electrode 10 only on one side of the polymer electrolyte membrane 1. Electrode 10
Consists of a catalyst layer 2 and a diffusion layer 3 (underlayer 4 and carbon paper 5). The surface of the polymer electrolyte membrane 1 where the electrode 10 is not provided is brought into contact with a sulfuric acid aqueous solution 9 having a pH of 1, and the electrode 10 side is brought into contact with nitrogen gas. The reference electrode 8 is placed in an aqueous sulfuric acid solution 9,
The control electrode 7 is connected to the sulfuric acid aqueous solution 9 and the diffusion layer 3 of the electrode structure.

When a voltage is applied between the diffusion layer 3 and the aqueous sulfuric acid solution 9 by the potentiostat 6, protons in the aqueous sulfuric acid solution 9 pass through the polymer electrolyte membrane 1 and reach the electrode 10, where electrons are exchanged. That is, electrons are transferred from platinum when the protons reach the platinum surface in the catalyst particles. In the opposite case, electrons are transferred from the adsorbed hydrogen atoms to platinum and diffuse as protons into the aqueous sulfuric acid solution.

The voltage is scanned from -0.1 V to +0.7 V, and the Q value (C / cm ² ) can be obtained from the peak area on the proton adsorption side. FIG. 2 shows a typical measurement example. In the discharge curve shown in FIG. 2, the Q value indicates the amount of charge per area of the electrode structure. The Q value can be used as an index of the adhesiveness between the electrode 10 and the polymer electrolyte membrane 1, and the value is 0.09 to 0.09.
It was found that an excellent electrolyte membrane-electrode composite can be obtained by adjusting to 0.18 C / cm ² .

(2) Mechanical strength The tensile strength of each composite polymer electrolyte membrane was measured according to JIS K7127. Table 1 shows the measurement results.

[0043]

[Table 1]

From the above measurement results, the composite polymer electrolyte membrane of the present invention has improved power generation potential, higher adhesion to the reinforcing material, and improved mechanical strength as compared with the conventional polymer electrolyte membrane. You can see that it is doing.

[0045]

The composite polymer electrolyte membrane of the present invention is obtained by compounding a matrix consisting of a sulfonated polymer compound having a high ion exchange capacity and a reinforcing material consisting of a sulfonated polymer compound having a low ion exchange capacity. As a result, they have good ionic conductivity, are excellent in adhesion between them, and have good mechanical strength. Therefore, the composite polymer electrolyte membrane of the present invention has excellent hot water resistance, oxidation resistance and creep resistance (durability).

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an apparatus for measuring a Q value of an electrode structure according to the present invention.

FIG. 2 In order to determine the Q value of the electrode structure of the present invention,
5 is a graph showing a discharge curve obtained as a result of measuring the current density within a certain voltage range.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solid polymer electrolyte membrane 2 ... Catalyst layer 3 ... Diffusion layer 4 ... Underlayer 5 ... Carbon paper 6 ... Potentiostat 7 ... Control electrode 8 ... Reference electrode 9: Dilute sulfuric acid aqueous solution 10: Electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08L 71:00 C08L 71:00 101: 02 101: 02 (72) Inventor Nobuhiro Saito Wako-shi, Saitama 1-4-1, Chuo, Honda R & D Co., Ltd. (72) Inventor Hiroshi Soma 1-4-1, Chuo, Wako, Saitama, Japan In Honda R & D Co., Ltd. (72) Inventor Masaaki Nanami, Wako, Saitama 1-4-1 Chuo F-term in Honda R & D Co., Ltd. (Reference) 4F071 AA51 AD01 AD03 AF42 BB02 BC01 FA03 FA11 FB07 FC01 FC04 FC05 FC06 FC11 FD03 4F072 AB05 AB15 AC15 AD46 AD53 AG16 AH04 AH23 AK05 AL12 5G301 CD01 CD10 5H026 AA06 BB03 BB04 BB08 CX02 CX05 EE18 HH00

Claims (15)

[Claims] The present invention is characterized in that it has a matrix composed of a sulfonated polymer compound having a high ion exchange capacity and a reinforcing material composed of a fibrous material or a porous membrane of a sulfonated polymer compound having a low ion exchange capacity. Composite polymer electrolyte membrane. 2. The composite polymer electrolyte membrane according to claim 1, wherein each of the sulfonated polymer compounds is a non-fluorinated sulfonated polymer compound. 3. The composite polymer electrolyte membrane according to claim 2, wherein the sulfonated polymer compound having a high ion exchange capacity and the sulfonated polymer compound having a low ion exchange capacity are the same except for the ion exchange capacity. A composite polymer electrolyte membrane having a skeleton. 4. The composite polymer electrolyte membrane according to claim 1, wherein the ion exchange capacity of the sulfonated polymer compound having a high ion exchange capacity is 1.0 to 2.8 meq / g.
Wherein the ion exchange capacity of the sulfonated polymer compound having a low ion exchange capacity is 0.5 to 1.5 meq / g. 5. The composite polymer electrolyte membrane according to claim 1, wherein H ⁺ of the sulfonic acid group of the sulfonated polymer compound having a low ion exchange capacity is at least partially replaced with Na ⁺ . A composite polymer electrolyte membrane characterized in that: 6. The composite polymer electrolyte membrane according to claim 3, wherein each of the sulfonated polymer compounds contains a phenylene group. 7. The composite polymer electrolyte membrane according to claim 6, wherein each of the sulfonated polymer compounds is a sulfonated polyetheretherketone. 8. A method for producing a composite polymer electrolyte membrane comprising a base material comprising a sulfonated polymer compound having a high ion exchange capacity and a reinforcing material comprising a fibrous material of a sulfonated polymer compound having a low ion exchange capacity. 3. The method according to claim 1, wherein the fibrous material of the sulfonated polymer compound having a low ion exchange capacity is uniformly dispersed in a solution of the sulfonated polymer compound having a high ion exchange capacity, and the film is formed by a casting method. 9. A method for producing a composite polymer electrolyte membrane comprising a matrix composed of a sulfonated polymer compound having a high ion exchange capacity and a reinforcing material composed of a porous membrane of a sulfonated polymer compound having a low ion exchange capacity. 3. The method according to claim 1, wherein the porous membrane of the sulfonated polymer compound having a low ion exchange capacity is impregnated with a solution of the sulfonated polymer compound having a high ion exchange capacity. 10. The method according to claim 8 or claim 9, wherein
A method comprising using a non-fluorinated sulfonated polymer compound as the sulfonated polymer compound. 11. The method according to claim 10, wherein the sulfonated polymer compound having a high ion exchange capacity and the sulfonated polymer compound having a low ion exchange capacity are reacted with a polymer compound having the same skeleton structure. A process characterized by being obtained by sulfonation with different ion exchange capacities. 12. The method according to claim 11, wherein the ion exchange capacity of the sulfonated polymer compound having a high ion exchange capacity is 1.0 to 2.8 meq / g, and the ion exchange capacity of the sulfonated polymer compound having a low ion exchange capacity is not greater than 1.0. 0.5-1.5 ion exchange capacity
A method characterized by meq / g. 13. The method according to claim 8, wherein H ⁺ of a sulfonic acid group of the sulfonated polymer compound having a low ion exchange capacity is at least partially substituted with Na ^+. And how. 14. The method according to claim 8, wherein each of the sulfonated polymer compounds contains a phenylene group. 15. The composite polymer electrolyte membrane according to claim 14, wherein each of the sulfonated polymer compounds is a sulfonated polyetheretherketone.