JP2009191123A - Block copolymer, electrolyte membrane for fuel cell, membrane-electrode assembly, and solid polymer type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a long-life electrolyte membrane is required in order to put a PEFC or DMFC to practical use. <P>SOLUTION: The long-life electrolyte membrane is obtained by using a block copolymer comprising a hydrophilic segment containing an ion exchange group and a hydrophobic segment not containing an ion exchange group in a main chain and a side chain or having a larger ion exchange group equivalent weight than the hydrophilic segment, wherein the hydrophilic segment is a polyarylene in which a sulfonic acid group bonds to an aromatic ring through an alkylene ether bond. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a block copolymer, a polymer electrolyte membrane, a membrane electrode assembly, and a fuel cell using the same, which are low in cost and excellent in mechanical strength and oxidation resistance.

  As a solid polymer electrolyte membrane of a fuel cell, Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) and the like have high ionic conductivity. Fluorine electrolyte membranes are known, but fluorine electrolyte membranes are very expensive. Also, hydrofluoric acid is generated when incinerated at the time of disposal. Furthermore, since ionic conductivity falls at high temperature, there exists a subject that it cannot be used at high temperature. Further, when used as an electrolyte membrane of a direct methanol fuel cell (hereinafter referred to as DMFC), there are problems such as voltage drop and power generation efficiency drop due to methanol crossover.

  As solid polymer electrolyte membranes for fuel cells, in addition to fluorine-based electrolytes, Patent Documents 1 and 2 describe hydrocarbon-based polymers made of polyethersulfone block copolymers and polyetherketone block copolymers. An electrolyte membrane has been proposed.

By the way, in the fuel cell, a peroxide is generated in the electrode catalyst layer by the electrode reaction, and the peroxide is radicalized while diffusing to become a peroxide radical, which erodes and degrades the electrolyte. Arise. The generation of the peroxide radical is caused by metal ions (Fe ²⁺ , Cu ^2+, etc.) eluted from the supply fuel (gas or liquid) or mist supply piping mixed with the supply fuel to keep the electrolyte in a wet state. Promoted. Therefore, in polymer electrolyte membranes made of polyethersulfone block copolymers and polyetherketone block copolymers, the oxidation resistance is low, so the electrolyte is oxidized and decomposed and deteriorated by hydrogen peroxide radicals. There was a problem that the lifetime was short. In electrolyte membranes using polyethersulfone block copolymers and polyetherketone block copolymers, degradation is caused by oxidation and decomposition of the ether bond sites in the main chain of the electrolyte, and elution due to a decrease in the molecular weight of the electrolyte. Breaking and tearing of the film are considered to be the main causes of deterioration.

  In Patent Document 3 and Patent Document 4, a layer containing a metal oxide that is a hydrogen peroxide decomposition catalyst is formed between the electrode catalyst layer and the electrolyte layer to suppress degradation of the electrolyte membrane. However, these membrane electrode assemblies have a problem that the effect of prolonging the life is small, and the ionic conduction resistance of the electrolyte membrane increases because the additive is added, and the membrane preparation process becomes complicated, resulting in high costs. It was. As hydrocarbon electrolytes excellent in oxidation resistance, Patent Document 5 and Patent Document 6 propose polyarylene polymer electrolytes that do not have an ether bond that is a degradation site in the main chain. However, this polyarylene polymer electrolyte has a rigid polyphenylene skeleton, and has problems in mechanical properties such as elongation at break.

  Patent Document 7, Non-Patent Document 1, and Non-Patent Document 2 show the techniques used in the production of polymers (hydrophilic segments) and copolymers and in the performance inspection of electrolyte membranes in Examples. It is not intended to indicate the technical level of the invention.

Japanese Patent Laid-Open No. 2003-3232 JP 2006-512428 A JP 2005-216701 A JP-A-2005-353408 Japanese National Patent Publication No. 11-515040 JP 2003-187826 A Japanese Patent Laid-Open No. 2004-131661 Macromolecules 1992, vol. 25,5125-5130 Macromolecules 2005, vol. 38,7121-7126

  In view of the above situation, the present inventors have conducted intensive studies to find a hydrocarbon-based polymer electrolyte membrane having excellent oxidation resistance and excellent mechanical properties. In the oxidation resistance test of an electrolyte membrane using a polyethersulfone block copolymer or a polyetherketone block copolymer, the number of sulfonic acid groups in the electrolyte membrane after the test has decreased. It was found that the hydrophilic segment has lower oxidative degradation resistance than the hydrophobic segment, and that the entire polymer deteriorates when the hydrophilic segment deteriorates before the hydrophobic segment.

  The present invention includes a hydrophilic segment containing an ion exchange group and a hydrophobic segment containing no ion exchange group in the main chain and side chain or having an ion exchange group equivalent weight larger than the ion exchange group equivalent weight of the hydrophilic segment. The hydrophilic segment is a block copolymer in which an ion exchange group is a polyarylene bonded to an aromatic ring via an alkylene ether bond, and the hydrophilic segment is represented by the following general formulas (1), (2), (3 And a block copolymer comprising at least one repeating structural unit selected from the group consisting of (4) and (4).

Here, Ar _{1 to} Ar ₆ are at least one of the following bond structures (5) to (7), and may be the same or different. Q is any one of a sulfonic acid group, a phosphoric acid group, and other ion exchange groups, and may be the same or different. R _{1 to} R ₈ are groups independently selected from the group consisting of an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group, and Z is hydrogen or a methyl group.

  According to the present invention, an electrolyte membrane excellent in oxidation resistance can be provided, and thereby the life of the fuel cell can be improved.

  The present inventor has found that in a block copolymer having a hydrophilic segment and a hydrophobic segment, if only the oxidation degradation resistance of the hydrophilic segment is improved, the oxidation resistance can be improved. Conventionally, it was thought that the oxidation resistance of both hydrophilic and hydrophobic segments had to be improved, and since it consisted of a rigid polyphenylene skeleton in order to obtain oxidation resistance, mechanical properties such as elongation at break However, according to the above knowledge, it is possible to maintain the oxidation resistance even if a unit having a bent structure is introduced into the hydrophobic segment, and there are problems in Patent Document 5 and Patent Document 6. The mechanical properties have also been solved.

  In addition, by using polyarylene in which ion exchange groups are bonded to an aromatic ring via an alkylene ether bond in a hydrophilic segment, it is sufficiently resistant to electrolyte polymer degradation due to desorption of ion exchange groups in hot water, etc. Is obtained. The reason why the oxidative degradation resistance of the hydrophilic segment is lower than that of the hydrophobic segment is not clear, but is considered to be influenced by the diffusion of hydrogen peroxide radicals in the electrolyte membrane and the difference in electron density in the electrolyte.

  As described above, the hydrophilic segment has an ion exchange group-containing hydrophilic segment and a hydrophobic segment, and the hydrophilic segment is a polyarylene in which the ion exchange group is bonded to an aromatic ring via an alkylene ether bond, and the hydrophilic segment By using a block copolymer characterized in that it contains at least one repeating structural unit selected from the group consisting of the following general formulas (1), (2), (3) and (4): It was found that a polymer electrolyte membrane having excellent chemical properties can be obtained.

  The block copolymer here is a copolymer containing at least one hydrophilic segment and at least one hydrophobic segment that are covalently bonded to each other directly or indirectly. In a preferred embodiment, the hydrophobic segment and the hydrophilic segment are reacted separately to form a hydrophobic-hydrophilic segment, which is then polymerized, but the synthesis method is not limited. . For example, after synthesizing a hydrophobic-hydrophobic block copolymer, only one of the hydrophobic sites may be hydrophilized with sulfuric acid or chlorosulfuric acid. The hydrophobic segment refers to a copolymer having an ion exchange group equivalent weight of 1200 or more and a larger ion exchange group equivalent weight than the hydrophilic segment.

In addition, the ion exchange group equivalent weight of this invention represents the molecular weight of the polymer per ion exchange group unit equivalent introduce | transduced, and shows that the introduction degree of an ion exchange group is so large that a value is small. The ion exchange group equivalent weight is ¹ H-NMR spectroscopy, elemental analysis, acid-base titration described in JP-B-1-52866, non-hydroxybase titration (the specified solution is a benzene / methanol solution of potassium methoxide), etc. Can be measured. Further, the hydrophilic segment refers to a copolymer having an ion exchange group equivalent weight of 200 to 1500 and a smaller ion exchange group equivalent weight than the hydrophobic segment.

  The hydrophobic segment preferably includes a structural unit represented by the following general formula (8) or (9).

  Here, X and Y are any one of the following (10) to (19) and may be the same or different.

  g is 0 or an integer of 1 or more, and h is an integer of 1 or more. Further, 0 ≦ i, j, k, and l ≦ 1. Furthermore, V and W are either a direct bond, -O- or -S-, and may be the same or different.

Ar ₇ is any one of the following formulas (20) to (24), or a substituent may be introduced to them.

Here, Ar ₈ and Ar ₉ are tetravalent groups having at least one aromatic ring. Z ₂ and Z ₃ each represent —O—, —S— or —NR— (R represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or 6 carbon atoms). Represents an aryl group of 10 to 10, and the alkyl group, alkoxy group and aryl group may be substituted), and two Z ₂ may be the same or different.

  According to the present invention, the hydrophobic segment includes a structural unit represented by the general formula (2), (3), or (4), and the hydrophilic segment includes a structural unit represented by the general formula (1). A block copolymer is provided.

  The block copolymer preferably has an ion exchange group equivalent weight of 300 to 1500 g / mol.

  In the block copolymer, it is desirable that a structural unit represented by the general formula (6) or (7) is included between the hydrophobic segment and the hydrophilic segment.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the present invention, it has a hydrophilic segment and a hydrophobic segment containing an ion exchange group, and the hydrophilic segment is a polyarylene in which an ion exchange group is bonded to an aromatic ring via an alkylene ether bond, and the hydrophilic segment is It is within the scope of the invention to include at least one repeating structural unit represented by the following general formulas (1), (2), (3), and (4).

Examples of the hydrophilic segment include the following (25) to (44) when R _{1 to} R ₁₀ are 1, but in the present invention, R _{1 to} R ₈ have 1 to 6 carbon atoms. Any group selected from the group consisting of an alkyl group and a fluoroalkyl group may be used, and the group is not limited to the following.

  Here, n is an integer of 1 or more, but each is independent and may be the same or different from each other. In addition, if the chemical structure of the hydrophilic segment includes at least one of the repeating structural units represented by the general formula (1), (2), (3) or (4), it is within the scope of the invention. is there. Although there is no limitation on the ion exchange group of the hydrophilic segment, a sulfonic acid group or a phosphoric acid group is preferable.

  The hydrophobic segments used in the present invention include polyimide copolymers, polybenzimidazole copolymers, polyquinoline copolymers, polysulfone copolymers, polyethersulfone copolymers, and polyketone copolymers. Polymer, polyetheretherketone copolymer, polyetherketone copolymer, polyphenylenesulfide copolymer, polyetherimide copolymer, polyacrylonitrile copolymer, polystyrene copolymer, There are aromatic hydrocarbon polymers such as polysulfide copolymers, polyphenylene copolymers, and polyether ether sulfone copolymers, but the present invention is not limited to the examples shown here.

  The number average molecular weight of the block copolymer constituting the polymer electrolyte of the present invention is 10,000 to 250,000 in terms of the molecular weight in terms of polystyrene by GPC method. Preferably it is 20000-220,000, More preferably, it is 25000-200000. If it is smaller than 10,000, the strength of the electrolyte membrane is lowered, and if it exceeds 220,000, the output performance may be lowered, which is not preferable.

  Moreover, the ion exchange group equivalent weight of the block copolymer of this invention is 200-2000. Preferably it is 300-1500. If it is less than 200, the water absorption rate of the electrolyte membrane is increased, the membrane strength in water or in humidification is lowered, and if it exceeds 2000, ionic conduction is reduced, and the output performance of the fuel cell may be lowered.

  The electrolyte membrane used in the present invention is a film formed after dissolving the block copolymer, which is the polymer electrolyte of the present invention, in a solvent. In the electrolyte membrane, a porous substrate, an antioxidant, and an additive , Inorganic materials, other polymer electrolytes, carbon-supported Pt catalysts, and carbon-supported Pt-Ru catalysts.

  The block copolymer of the present invention is used in a polymer membrane state in a fuel cell. Examples of the method for producing a film include a solution casting method, a melt press method, a melt extrusion method, and the like that form a film from a solution state. Among these, the solution casting method is preferable. For example, after casting a polymer solution on a substrate, the solvent is removed to form a film. The solvent used in the film formation is not particularly limited as long as it can be removed after dissolving the block copolymer of the present invention. For example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2- Aprotic polar solvents such as pyrrolidone and dimethyl sulfoxide, or alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether, iso-propyl alcohol, t- Examples include alcohols such as butyl alcohol and tetrahydrofuran. Moreover, a porous film, a nonwoven fabric, a fibril, a filler, etc. can be used as a reinforcing material of the said film in the range which does not impair the effect of this invention.

  The thickness of the polymer electrolyte membrane of the present invention is preferably 5 to 200 μm, more preferably 10 to 100 μm. If it is less than 5 μm, it is difficult to obtain a membrane strength that can withstand practical use, and if it exceeds 200 μm, the ion conduction resistance increases and it is difficult to obtain the desired power generation performance improvement. When the film is formed by the solution casting method, the thickness of the film can be controlled by adjusting the concentration of the solution used or the amount of solution applied onto the substrate. Moreover, when manufacturing the electrolyte of this invention, additives, such as a crosslinking agent, a plasticizer, a stabilizer, a mold release agent, etc. which are used for a normal polymer can be used in the range which does not impair the effect of this invention.

  As a method for joining the electrolyte membrane for the fuel cell and the electrode, a known method can be used. For example, carbon carrying platinum catalyst powder is mixed with a polytetrafluoroethylene suspension, applied to carbon paper, and heat-treated to form a catalyst layer. Next, there is a method in which the same electrolyte solution as the electrolyte membrane is applied to the catalyst layer and integrated with the electrolyte membrane by hot pressing. In addition, a method of coating the electrolyte solution on the platinum catalyst powder in advance, a method of applying the catalyst paste to the electrolyte membrane, a method of electrolessly plating the electrode on the electrolyte membrane, a platinum group metal complex ion adsorbed on the electrolyte membrane and then reducing There are ways to do this.

  In the present invention, for example, a polymer electrolyte solution containing a copolymer (electrode catalyst coating solution) is added to the electrode catalyst-supporting carbon and uniformly dispersed to prepare a catalyst paste, and then the catalyst paste is used as a fuel cell. It is preferable to apply to both sides of the polymer electrolyte and dry it. And it is preferable that the said electrode catalyst is a platinum group metal or its alloy.

  In the present invention, various types of fuel cells can be provided by using the block co-aggregate as an electrolyte membrane. For example, the gas diffusion sheet is in close contact with the oxygen electrode side and the hydrogen electrode side of the polymer electrolyte membrane / electrode assembly in which one side of the main surface of the electrolyte membrane is sandwiched between an oxygen electrode and the other side is sandwiched between hydrogen electrodes. A solid polymer fuel cell single cell comprising a conductive separator provided on the outer surface of the gas diffusion sheet and having a gas supply passage to the oxygen electrode and the hydrogen electrode can be formed.

  Moreover, the portable power supply which has a hydrogen cylinder which stores said fuel cell main body and the hydrogen supplied to this fuel cell main body in a case can be provided. Furthermore, a reformer for reforming into an anode gas containing hydrogen, a fuel cell for generating electricity from the anode gas and a cathode gas containing oxygen, and a high-temperature anode gas exiting the reformer and the reformer are supplied. A fuel cell power generation device including a heat exchanger that exchanges heat with a low-temperature fuel gas can be provided.

  In addition, the gas diffusion sheet is in close contact with the oxygen electrode side and the methanol electrode side of the polymer electrolyte membrane / electrode assembly in which one side of the main surface of the electrolyte membrane is sandwiched between the oxygen electrode and the other side is sandwiched between the methanol electrodes. A direct methanol fuel cell single cell comprising a conductive separator provided on the outer surface of the gas diffusion sheet and having gas and liquid supply passages to the oxygen electrode and the methanol electrode can be formed.

(Example)
The present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the examples disclosed herein.

Example 1
(1) Production of polymer a (hydrophobic segment) After the inside of a 300 ml four-necked round bottom flask equipped with a stirrer, thermometer, reflux condenser connected with a calcium chloride tube was purged with nitrogen, 0.156 mol of Synthesis of a polymer having an end group F using 4,4-difluorodiphenylsulfone, 0.150 mol of 4,4-biphenol, 0.174 mol of potassium carbonate, 40 ml of toluene as a solvent, and 100 ml of N-methyl-2-pyrrolidone (NMP). Do. Furthermore, 0.1 mol of 1-naphthol is added to make all the ends naphthalene. Polymer a is obtained by reprecipitating the solution after synthesis with methanol after filtration. The number average molecular weight Mn of the polymer a is 2 × 10 ⁴ .

(2) Preparation of polymer b (hydrophilic segment) Monoquine i is obtained by adding 2-fold equivalent of dibromobutane to hydroquinone and allowing potassium carbonate to react for 24 hours while refluxing in an acetone solution. Next, monomer i and FeCl ₃ are put into nitrobenzene and reacted for 24 hr by the method described in Non-Patent Document 1. Polymer b is obtained by reprecipitating the solution after synthesis with methanol after filtration. When the polymer b thus obtained is all substituted with sulfonic acid for Br of the polymer B by the method described in Patent Document 7, the polymer obtained is water-soluble at room temperature.

(3) Production of block copolymer 1 Polymer a, polymer b and FeCl ₃ synthesized in the above (1) and (2) were placed in a DMF solution and refluxed for 24 hours by the method described in Non-Patent Document 1. React. Furthermore, all Br of the polymer B is substituted with sulfonic acid by the method described in Patent Document 7. The block copolymer 1 is obtained by reprecipitating the solution after synthesis with methanol after filtration. The blend ratio of polymer a and polymer b is adjusted so that the ion exchange group equivalent weight is 600. The number average molecular weight Mn of the obtained block copolymer is 4 × 10 ⁴ or more, and the ion exchange group equivalent weight measured by NMR is 620.

(4) Production of Polymer Electrolyte Membrane 1 and Its Characteristics The block copolymer 1 obtained in (3) above is dissolved in DMF so as to have a concentration of 20% by weight. This solution is cast-coated on glass, vacuum dried at 80 ° C., then immersed in sulfuric acid and water and dried to obtain a polymer electrolyte membrane 1 having a film thickness of 45 μm. The ionic conductivity of the polymer electrolyte membrane 1 in water at 70 ° C. is 0.15 S / cm. When the oxidation resistance was examined by the method described in Non-Patent Document 2, the weight loss rate after 90 min test at 80 ° C. was 3%.

(5) Production of membrane electrode assembly (MEA) 1 Mixed solvent of 1 wt-propanol, 2-propanol and water of catalyst powder in which platinum fine particles are dispersed and supported by 50 wt% on a carbon support and 5 wt% polyperfluorosulfonic acid Then, an anode electrode having a thickness of about 20 μm, a width of 30 mm, and a length of 30 mm is produced in a polytetrafluoroethylene (PTFE) sheet shape by screen printing.

  Next, a slurry of a water / alcohol mixed solvent is prepared using a catalyst powder supporting 50 wt% platinum fine particles on a carbon support and a mixed solvent of 1-propanol of polyperfluorosulfonic acid, 2-propanol and water as a binder. A cathode electrode having a thickness of about 20 μm, a width of 30 mm, and a length of 30 mm is produced on the PTFE sheet by screen printing.

  A membrane in which anode and cathode electrodes are formed on both surfaces of the polymer electrolyte membrane 1 by sandwiching both sides of the polymer electrolyte membrane 1 produced in (4) above with an anode electrode and a cathode electrode and hot pressing at 100 ° C. and 10 MPa. An electrode assembly (MEA) was produced. A cross-sectional view thereof is shown in FIG. The anode electrode 2 and the cathode electrode 3 are joined with their positions aligned so as to overlap each other.

(6) Power generation performance of fuel cell (PEFC) The battery performance is measured by incorporating the diffusion layer composed of the MEA 1 and carbon cloth using the small unit cell using hydrogen as shown in FIG.

  In FIG. 2, 1 is a polymer electrolyte membrane, 2 is an anode electrode, 3 is a cathode electrode, 4 is an anode diffusion layer, 5 is a cathode diffusion layer, 6 is electrode chamber separation and a gas supply passage to the electrode. The fuel flow path of the conductive separator (bipolar plate) that also serves as a role, 7 is the air conduit of the separator, 8 is hydrogen + water, 9 is hydrogen, 10 is air + water, and 11 is air. A small single battery cell is installed in a thermostat, and the temperature of the thermostat is controlled so that the temperature by a thermocouple (not shown) inserted in the separator becomes 70 ° C.

The humidification of the anode and the cathode is performed using an external humidifier, and the temperature of the humidifier is controlled between 70 to 73 ° C. so that the dew point near the humidifier outlet becomes 70 ° C. In addition to measuring the dew point with a dew point meter, the consumption of humidified water is constantly measured to confirm that the dew point obtained from the flow rate, temperature, and pressure of the reaction gas is a predetermined value. Electricity was generated at a load current density of 250 mA / cm ² , a hydrogen utilization rate of 70%, and an air utilization rate of 40%. PEFC using MEA1 shows an output of 0.7 V or more and is stable. A PEFC using MEA 1 is referred to as Example 1.
(Comparative example)
(1) Polymerization of polymer c (hydrophobic segment) After the inside of a 300 ml four-necked round bottom flask equipped with a stirrer, thermometer, reflux condenser connected with a calcium chloride tube was purged with nitrogen, 0.150 mol of 4,4-difluorodiphenylsulfone, 0.156 mol of 4,4-biphenol, 0.174 mol of potassium carbonate, 40 ml of toluene as an azeotrope, and 100 ml of NMP as a solvent are used for synthesis at 170 ° C. for 10 hours. Polymer c is obtained by reprecipitation of the solution after synthesis with methanol.

(2) Polymerization of polymer d (hydrophilic segment) After the inside of a 300 ml four-necked round bottom flask equipped with a stirrer, thermometer, reflux condenser connected with a calcium chloride tube was purged with nitrogen, 0.150 mol Sulfonated-4,4-difluorodiphenyl sulfone, 0.156 mol of 4,4-biphenol, 0.174 mol of potassium carbonate, 40 ml of toluene as an azeotrope, and 100 ml of NMP as a solvent, at 170 ° C. for 10 hours Synthesize. Polymer d is obtained by reprecipitation of the solution after synthesis with methanol.

(3) Preparation of block copolymer 2 After replacing the inside of a 300 ml four-necked round bottom flask equipped with a stirrer, a thermometer, and a reflux condenser connected with a calcium chloride tube with nitrogen, in Comparative Example (1) A solution containing the synthesized polymer c and a solution containing the polymer d synthesized in Comparative Example (2), sulfonated 4-4dichlorodiphenylsulfone, potassium carbonate, 40 ml of toluene as an azeotrope, and 100 ml of NMP as a solvent are used. The block copolymer 2 is obtained by synthesizing at 170 ° C. for 10 hours, filtering the synthesized solution, and reprecipitating with methanol.

The blend ratio of polymer c, polymer d, and sulfonated 4-4 dichlorodiphenyl sulfone is adjusted so that the ion exchange group equivalent weight is 600. The number average molecular weight Mn of the resulting block copolymer is 4 × 10 ⁴ or more, the ion-exchange equivalent weight as measured by NMR is 630.

(4) Production of Polymer Electrolyte Membrane and Its Characteristics The block copolymer 2 obtained in (3) of Comparative Example 1 is dissolved in DMF to a concentration of 20% by weight. The solution is cast on glass after being filtered, air-dried, vacuum-dried at 80 ° C., then immersed in sulfuric acid and water, and dried to form a polymer membrane having a thickness of 40 μm as the polymer electrolyte membrane 2. . The polymer electrolyte membrane has an ionic conductivity at room temperature of 0.15 S / cm. When the oxidation resistance was examined in the same manner as in Example (4), the weight loss rate after the 80 ° C. 90 min test was 60%.

(Example 2)
(1) Production of polymer f (hydrophilic segment) In Example 1 (2), the mixing ratio of hydroquinone and dibromobutane was changed, and Example 1 (excluding adding 1 equivalent of dibromobutane to hydroquinone) Monomer j is obtained by the same method as in 2). Further, a polymer f is obtained by the same method as in Example 1. When all Br of the obtained polymer f is substituted with sulfonic acid, the obtained polymer is water-insoluble at room temperature.

(2) Production of Block Copolymer 3 Using the polymer a of Example 1 (1) and the polymer f of Example 2 (1), the block copolymer was produced in the same manner as in Example 1 (3). Get 3. The blend ratio of polymer a and polymer f is blended so that the ion exchange group equivalent weight is 600. The number average molecular weight Mn of the obtained block copolymer 3 is 4 × 10 ⁴ or more, and the ion exchange group equivalent weight measured by NMR is 610.

(3) Production of polymer electrolyte membrane 3 and its characteristics The polymer electrolyte membrane 3 is obtained in the same manner as in Example 1 (4) using the block copolymer 3 obtained in (2) above. The polymer electrolyte membrane 3 has an ionic conductivity in water at 70 ° C. of 0.10 S / cm, which is lower than that of the polymer electrolyte membrane 1. When the oxidation resistance was examined by the method described in Non-Patent Document 2, the weight loss rate after a 90-minute test at 80 ° C. was 5%.

(Example 3)
(1) Production of polymer g (hydrophilic segment) Monoquine k is obtained by the same method as in Example 1 (2) except that hydroquinone is replaced with 4,4-dihydroxybiphenyl. Further, a polymer g is obtained by the same method as in Example 1. When all Br of the obtained polymer g is substituted with sulfonic acid, the obtained polymer is water-soluble at room temperature.

(2) Production of block copolymer 4 Using the polymer a of Example 1 (1) and the polymer g of Example 3 (1), the block copolymer was produced in the same manner as in Example 1 (3). Get 4. The blending ratio of polymer a and polymer g is so adjusted that the ion exchange group equivalent weight is 600. The obtained block copolymer 4 has a number average molecular weight Mn of 4 × 10 ⁴ or more and an ion exchange group equivalent weight measured by NMR of 630.

(3) Production of polymer electrolyte membrane 4 and its characteristics The polymer electrolyte membrane 4 is obtained in the same manner as in Example 1 (4) using the block copolymer 4 obtained in (2) above. The polymer electrolyte membrane 4 has an ionic conductivity of 0.13 S / cm in water at 70 ° C., and its oxidation resistance was examined by the method described in Non-Patent Document 2. The weight after a 90-minute test at 80 ° C. The reduction rate is 18%.

Example 4
(1) Production of polymer h (hydrophilic segment) Monoquine 1 is obtained in the same manner as in Example 1 (2) except that hydroquinone is replaced with 2,6-dihydroxynaphthalene. Further, a polymer h is obtained by the same method as in Example 1. When all Br of the obtained polymer h is substituted with sulfonic acid, it is water-soluble at room temperature.

(2) Preparation of block copolymer 5 Using the polymer a of Example 1 (1) and the polymer h of Example 4 (1), the block copolymer was produced in the same manner as in Example 1 (3). Get 5. The blending ratio of polymer a and polymer h is adjusted so that the ion exchange group equivalent weight is 600. The number average molecular weight Mn of the obtained block copolymer 5 is 4 × 10 ⁴ or more, and the ion exchange group equivalent weight measured by NMR is 610.

(3) Production of Polymer Electrolyte Membrane 5 and Its Characteristics The polymer electrolyte membrane 5 is obtained in the same manner as in Example 1 (4) using the block copolymer 5 obtained in (2) above. The polymer electrolyte membrane 4 has an ionic conductivity of 0.12 S / cm in water at 70 ° C., and its oxidation resistance was examined by the method described in Non-Patent Document 2. The weight after a 90-minute test at 80 ° C. The reduction rate is 15%.

(Example 5)
(1) Production of polymer n (hydrophilic segment) In Example 1 (2), hydroquinone was changed to methoxyphenol, and 1-fold equivalent of dibromobutane was used with respect to methoxyphenol. Monomer m is obtained by the same method. Further, a polymer n is obtained by the same method as in Example 1.

(2) Production of block copolymer 6 Using the polymer a of Example 1 (1) and the polymer n of Example 5 (1), the block copolymer was produced in the same manner as in Example 1 (3). 6 is obtained. The blending ratio of polymer a and polymer n is adjusted so that the ion exchange group equivalent weight is 600. The number average molecular weight Mn of the obtained block copolymer 6 is 4 × 10 ⁴ or more, and the ion exchange group equivalent weight measured by NMR is 600.

(3) Production of polymer electrolyte membrane 6 and its characteristics The polymer electrolyte membrane 6 is obtained in the same manner as in Example 1 (4) using the block copolymer 6 obtained in (2) above. The ionic conductivity of this polymer electrolyte membrane 6 in water at 70 ° C. is 0.11 S / cm. When the oxidation resistance was examined by the method described in Non-Patent Document 2, the weight loss rate after a 90-minute test at 80 ° C. was 10%.

Sectional drawing of the membrane electrode assembly by this invention. 1 is a developed perspective view of a fuel cell according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Polymer electrolyte membrane, 2 ... Anode electrode, 3 ... Cathode electrode, 4 ... Anode diffused layer, 5 ... Cathode diffused layer, 6 ... It played the role of electrode chamber separation and the gas supply path to an electrode Fuel flow path of conductive separator (bipolar plate), 7 ... Air passage of separator, 8 ... Hydrogen + water, 9 ... Hydrogen, 10 ... Air + water, 11 ... Air

Claims (12)

It consists of a hydrophilic segment containing an ion exchange group and a hydrophobic segment that does not contain an ion exchange group in the main chain and side chain or whose ion exchange group equivalent weight is larger than the ion exchange group equivalent weight of the hydrophilic segment. The segment is a block copolymer of polyarylene in which an ion exchange group is bonded to an aromatic ring via an alkylene ether bond, and the hydrophilic segment is represented by the following general formulas (1), (2), (3) and (4 A block copolymer comprising at least one repeating structural unit selected from the group consisting of:

Here, Ar _{1 to} Ar ₆ are at least one of the following bond structures (5) to (7), and may be the same or different. Q is any one of a sulfonic acid group, a phosphoric acid group, and other ion exchange groups, and may be the same or different. R _{1 to} R ₈ are groups independently selected from the group consisting of an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group, and Z is hydrogen or a methyl group.

  The block copolymer according to claim 1, wherein the hydrophilic segment is water-soluble.   The block copolymer according to claim 1, wherein ion exchange groups of the hydrophilic segment and the hydrophobic segment are sulfonic acid groups. 2. The block copolymer according to claim 1, wherein the hydrophobic segment includes a structural unit represented by the following general formula (8) or (9).

Here, X and Y are any one of the following (10) to (19) and may be the same or different.

g is 0 or an integer of 1 or more, and h is an integer of 1 or more. Further, 0 ≦ i, j, k, and l ≦ 1. Furthermore, V and W are either a direct bond, -O- or -S-, and may be the same or different.
Ar ₇ is any one of the following formulas (20) to (24), or a substituent group which may be introduced.

Here, Ar ₈ and Ar ₉ are tetravalent groups having at least one aromatic ring.
Z ₂ and Z ₃ each represent —O—, —S— or —NR— (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or 6 carbon atoms). Represents an aryl group of 10 to 10, and the alkyl group, alkoxy group and aryl group may be substituted), and two Z ₂ may be the same or different.   The hydrophobic segment includes a structural unit represented by the general formula (2), (3), or (4), and the hydrophilic segment includes a structural unit represented by the general formula (1). 2. The block copolymer according to 1.   The block copolymer according to claim 1, wherein the block copolymer has an ion exchange group equivalent weight of 300 to 1500 g / mol.   6. The block copolymer according to claim 5, comprising a structural unit represented by the formula (6) or (7) between the hydrophobic segment and the hydrophilic segment.   A polymer electrolyte membrane comprising the block copolymer according to claim 1 formed into a film.   A polymer electrolyte membrane comprising a porous substrate filled with the block copolymer of claim 1.   A membrane electrode comprising a polymer electrolyte membrane, and a cathode electrode and an anode electrode sandwiching the polymer electrolyte membrane, wherein the cathode electrode and the anode electrode include at least carbon, an electrode catalyst supported on the carbon, and a polymer electrolyte. The membrane electrode assembly, wherein at least one of the polymer electrolyte membrane and the polymer electrolyte is the block copolymer according to claim 1.   A membrane electrode assembly comprising an electrolyte membrane, a cathode electrode and an anode electrode sandwiching the polymer electrolyte membrane, wherein the cathode electrode and the anode electrode include at least carbon, an electrode catalyst supported on the carbon, and a polymer electrolyte The membrane electrode assembly is characterized in that the polymer electrolyte membrane is the polymer electrolyte membrane according to claim 8 or 9.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 10 or 11.

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