JP2008038043A - Sulfonic group-containing segmented block copolymer and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sulfonic group-containing segmented block copolymer that is more excellent in not only proton-conductivity but also bonding properties to an electrode than existing polymers, and to provide a polyelectrolyte membrane for a fuel cell, and a polyelectrolyte membrane/electrode assembly (MEA) and a fuel cell using the polymer. <P>SOLUTION: The sulfonic group-containing segmented block copolymer has at least one hydrophilic segment and at least one hydrophobic segment in the polymer molecule, where the hydrophilic segment is mainly constituted of a structure represented by chemical formula 1 (wherein X is H or a monovalent cation; Y is a sulfonic group or a carbonyl group; n is an integer of 3-50; and m is an integer of at least 2) and has a softening point of 180°C or lower. The polyelectrolyte membrane, the polyelectrolyte membrane/electrode assembly and the fuel cell are obtained using the polymer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sulfonate group-containing segmented block copolymer having a novel structure and its use. Furthermore, the present invention relates to a composition, a molded product, a polymer electrolyte membrane for fuel cells, and a fuel cell containing the polymer as a constituent component.

  Solid polymer fuel cells (PEFCs) and direct methanol fuel cells (DMFCs) that use polymer membranes as polymer electrolyte membranes are portable and can be miniaturized. Applications to power generation systems and power supplies for portable devices are being promoted. Currently, perfluorocarbon sulfonic acid polymer membranes represented by Nafion (registered trademark) manufactured by DuPont of the United States are widely used as polymer electrolyte membranes.

However, since these films soften at 100 ° C. or higher, the operating temperature is limited to 80 ° C. or lower. When the operating temperature is further increased, there are various advantages such as energy efficiency, downsizing of the apparatus, and improvement of catalytic activity, so that a polymer electrolyte membrane having higher heat resistance is required.
A sulfonated polymer obtained by treating a heat-resistant polymer such as polysulfone or polyetherketone with a sulfonating agent such as fuming sulfuric acid is well known as a heat-resistant polymer electrolyte membrane (see, for example, Non-Patent Document 1). . However, it is generally difficult to control the sulfonation reaction with a sulfonating agent. For this reason, there are problems that the degree of sulfonation is too high or low, polymer decomposition, non-uniform sulfonation and the like are likely to occur.

  Therefore, the use of a polymer polymerized from a monomer having an acidic group such as a sulfonic acid group as a polymer electrolyte membrane has been studied. For example, in Patent Document 1, as a proton conductive polymer, 4,4′-dichlorodiphenylsulfone-3,3′-disulfonic acid soda and 4,4′-dichlorodiphenylsulfone and 4,4′-biphenol are reacted. The resulting copolymer is shown. The polymer electrolyte membrane comprising this polymer as a constituent component has little sulfonic acid group heterogeneity as in the case of using the sulfonating agent described above, and it is easy to control the amount of sulfonic acid group introduced and the polymer molecular weight. . However, improvement of various characteristics such as proton conductivity is desired for practical use as a fuel cell.

  As an attempt to improve the properties, a segmented block copolymer having a sulfonic acid group has been studied. The segmented block copolymer is expected to improve proton conductivity because the hydrophilic segment forms a hydrophilic domain by phase separation. For example, Patent Document 2 describes a sulfonated polyethersulfone segmented block copolymer. One method of obtaining this polymer is sulfonation of a block polymer composed of segments that are easily and easily sulfonated. However, this method has a disadvantage that the sulfonation reaction is selectively performed by the difference in electron density of the benzene ring in each segment, and the polymer structure of each segment is limited. In addition, a benzene ring to which an oxygen atom of an ether group or an electron donating group such as an alkyl group is bonded is easily sulfonated, but a reverse reaction due to heat, hydrolysis, or the like easily occurs. Therefore, the above polymer also has a problem that the stability of the sulfonic acid group in the polymer is low. Moreover, although the separation membrane is mentioned as a use of this polymer, it was not described regarding the use as a polymer electrolyte membrane for fuel cells.

  Patent Document 3 describes that a polymer obtained by sulfonating a segmented block copolymer having a specific repeating unit is used as a polymer electrolyte membrane of a fuel cell. However, since this polymer also utilizes the difference in reactivity to sulfonation as in the polymer of Patent Document 2, the structure of the hydrophobic segment has been limited.

  Examples of other sulfonated segmented block copolymer include the polymers described in Patent Document 4. The polymer of Patent Document 4 is characterized in that the arrangement of the main chain at the block transition part is the same as the inside of the block, but the polymer structure has also been limited.

  Further, Patent Document 5 also describes a polymer electrolyte membrane for a fuel cell using a sulfonated polyethersulfone segmented block copolymer.

  However, when these sulfonated block copolymer are used as a polymer electrolyte membrane of a fuel cell, there are cases where the bonding property with an electrode is not sufficient. Insufficient bonding between the polymer electrolyte membrane and the electrode increases the interfacial resistance between the polymer electrolyte membrane and the electrode catalyst layer in the polymer electrolyte membrane / electrode assembly, or increases the polymer during fuel cell operation. Separation of the electrolyte membrane and the electrode may occur, which causes a decrease in output and durability of the fuel cell. The conventional segmented block copolymer does not sufficiently consider the bonding property between the polymer electrolyte membrane and the electrode, and has a problem when used in a fuel cell.

US Patent Application Publication No. 2002/0091225 JP 63-258930 A Japanese Patent Application Laid-Open No. 2001-250567 Japanese Patent Application Laid-Open No. 2001-278978 Japanese Patent Application Laid-Open No. 2003-3232 F. Lufrano et al., “Sulfolated Polysulfone as Promising Membranes for Polymer Electrolite Fuel Cells,” Science), (USA), John Wiley & Sons, Inc., 2000, 77, p. 1250-1257

  The present invention has been made to solve the above-mentioned problems, and the main problem is that the fuel not only exhibits proton conductivity superior to existing polymers but also has excellent bondability with electrodes. Polymer electrolyte membrane for battery, sulfonic acid group-containing segmented block copolymer constituting the polymer electrolyte membrane for fuel cell, composition containing the polymer, membrane / electrode assembly and fuel cell using the polymer Is to provide.

  The present inventors have intensively studied the structure and characteristics of the hydrophilic segment and the hydrophobic segment, and introduced a specific structure into the molecule, whereby a sulfonate group-containing segmented block copolymer has excellent proton conductivity. The present invention has been found and the present invention has been completed.

That is, the present invention
(1) A block copolymer having at least one hydrophilic segment and a hydrophobic segment in the polymer molecule, wherein the hydrophilic segment has the following chemical formula 1;

（式中、ＸはＨ又は１価の陽イオンを、Ｙはスルホン基又はカルボニル基を、ｎは３〜５０の整数を、ｍは２以上の整数を、それぞれ表す。）
で表される構造で主に構成され、かつ、軟化温度が１８０℃以下であることを特徴とするスルホン酸基含有セグメント化ブロック共重合ポリマー。

(In the formula, X represents H or a monovalent cation, Y represents a sulfone group or a carbonyl group, n represents an integer of 3 to 50, and m represents an integer of 2 or more.)
A sulfonic acid group-containing segmented block copolymer characterized by being mainly composed of a structure represented by the formula (II) and having a softening temperature of 180 ° C. or lower.

（式中、Ａｒ^１及びＡｒ^２は電子吸引性基を有する２価の芳香族基を、ｏは３〜５０の整数を、ｐは２以上の整数を、それぞれ表す。）
で表される構造で主に構成される（１）に記載のスルホン酸基含有セグメント化ブロック共重合体ポリマー。 (2) the hydrophobic segment is at least one of the following chemical formulas 2 and 3;

(In the formula, Ar ¹ and Ar ² represent a divalent aromatic group having an electron-withdrawing group, o represents an integer of 3 to 50, and p represents an integer of 2 or more.)
The sulfonic acid group-containing segmented block copolymer polymer according to (1) mainly composed of a structure represented by:

(3) Ar ² of Ar ¹ and Formula 3 in Formula 2 are each independently of the following chemical formulas 4 to 7;

で表される構造からなる群より選ばれる１種以上の構造である（２）に記載のスルホン酸基含有セグメント化ブロック共重合体ポリマー。

The sulfonate group-containing segmented block copolymer polymer according to (2), which is at least one structure selected from the group consisting of structures represented by:

(4) The sulfonate group-containing segmented block copolymer according to (2), wherein n in Chemical Formula 1 and o in Chemical Formulas 2 and 3 are 25 or less.

(5) The sulfonate group-containing segmented block copolymer polymer according to (4), wherein o in Chemical Formulas 2 and 3 is 20 or less.

(6) A polymer composition comprising 1 to 100% by weight of the sulfonic acid group-containing segmented block copolymer according to (1) to (5).

(7) A polymer electrolyte membrane obtained from the polymer composition according to (6).
(8) A polymer electrolyte membrane / electrode assembly comprising the polymer composition according to (6) on at least one of a polymer electrolyte membrane and an electrode catalyst layer.
(9) A fuel cell using the polymer electrolyte membrane / electrode assembly according to (8).
It is.

  The sulfonic acid group-containing block copolymer of the present invention is superior to the sulfonated block copolymer of the present invention both in terms of bondability with an electrode and proton conductivity. The characteristics of the electrolyte membrane / electrode assembly can be improved, and the performance of the fuel cell can be further improved.

  The present invention relates to a sulfonic acid group-containing segmented block copolymer having a specific segment structure and its use. Hereinafter, the present invention will be described in more detail with reference to embodiments. In addition, the weight in this invention means mass.

  The sulfonic acid group-containing segmented block copolymer of the present invention has a hydrophilic segment having a sulfonic acid group and a hydrophobic segment not having a sulfonic acid group. The hydrophilic segment in the present invention has the following chemical formula: The structure represented by 1 is mainly used.

（式中、ＸはＨ又は１価の陽イオンを、Ｙはスルホン基又はカルボニル基を、ｎは３〜５０の整数を、ｍは２以上の整数を、それぞれ表す。）

(In the formula, X represents H or a monovalent cation, Y represents a sulfone group or a carbonyl group, n represents an integer of 3 to 50, and m represents an integer of 2 or more.)

  When used as a polymer electrolyte membrane, it is preferable that X is H because proton conductivity increases. When processing and molding the polymer, it is preferable that X is a monovalent metal ion such as Na, K, Li, because the stability of the polymer is increased. X may be an organic cation such as monoamine. Y is preferably a sulfone group because the solubility of the polymer in a solvent tends to increase. Y is more preferably a carbonyl group because the bondability with the electrode is further enhanced. m represents an integer of 2 or more. M in Chemical Formula 1 may have a distribution consisting of a plurality of numbers. In the case of having a distribution, the average value is rounded off to the nearest decimal point as long as it is 3 or more. More preferably, it is the range of 3-20, More preferably, it is the range of 5-10. Further, when m has a distribution, m only needs to be within the range of the present invention as an average value, and even if the component includes a portion where m is 0 to 2, the average value is within the range of the present invention. The present invention solves the problems of the present invention.

  n represents an integer of 3 to 50. If n is smaller than 3, the improvement effect on the random polymer is lost. When n is large, the retention effect of the film form becomes larger, but when it is larger than 50, the viscosity of the reaction solution increases, so that the reaction with the hydrophobic segment becomes difficult, which is not preferable. It is more preferable that n is 25 or less because the reactivity between segments is excellent.

  The sulfonic acid group-containing polymer of the present invention needs to have a softening temperature of 180 ° C. or lower when the sulfonic acid group is an acid. The softening temperature can be measured, for example, as a temperature at which the elastic modulus in dynamic viscoelasticity rapidly decreases. When the softening temperature exceeds 180 ° C., workability such as bonding with an electrode tends to deteriorate. A more preferable softening temperature range is 130 to 170 ° C, and a further preferable range is 130 to 160 ° C.

  In Chemical Formula 1, an electron-withdrawing group such as a sulfone group or a carbonyl group reduces the electron density of the bonded phenyl group, thereby suppressing the elimination reaction of the sulfonic acid group and improving the stability of the polymer. Usually, when a polymer is sulfonated, a portion having a high electron density is preferentially sulfonated, so that it is difficult to obtain a hydrophilic segment of Formula 1 by sulfonating a block having no sulfonic acid group. is there.

  The hydrophilic segment of the present invention can be synthesized by reacting a sulfonated monomer represented by the following chemical formula 8 with a bisphenol compound represented by the following chemical formula 9.

  In Chemical Formula 8, X represents H or a monovalent cation, Y represents a sulfone group or a carbonyl group, and Z represents a halogen element. X is preferably Na or K, and Z is preferably F or Cl, respectively. In chemical formula 9, m represents an integer of 3 or more. A plurality of compounds having different m can also be used in combination, but in that case, the value obtained by rounding off the decimal point of the average value of m may be 3 or more. The preferable range of m is 3 to 20, and more preferably 5 to 10.

  The hydrophobic segment in the sulfonate group-containing segmented block copolymer of the present invention is at least one of the following chemical formulas 2 and 3;

（式中、Ａｒ^１及びＡｒ^２は電子吸引性基を有する２価の芳香族基を、ｏは３〜５０の整数を、ｐは２以上の整数を、それぞれ表す。）
で表される構造で主に構成されることを特徴とする。

(In the formula, Ar ¹ and Ar ² represent a divalent aromatic group having an electron-withdrawing group, o represents an integer of 3 to 50, and p represents an integer of 2 or more.)
It is mainly comprised by the structure represented by these.

  o represents an integer of 3 to 50, but if o is smaller than 3, the improvement effect on the random polymer is lost. When o is large, the retention effect of the film form becomes larger, but when it is larger than 50, the viscosity of the reaction solution increases, so that the reaction with the hydrophilic segment becomes difficult. o is more preferably 25 or less, and o is more preferably 20 or less because the reactivity between segments is excellent. When the polymer molecule contains both structures of chemical formulas 2 and 3, o may be the same or different.

Ar ¹ and Ar ² each independently represent a divalent aromatic group mainly composed of an aromatic group and having an electron-withdrawing group on the aromatic group to which O is bonded. Examples of the electron-withdrawing group include a sulfone group, a cyano group, a sulfoxide group, a carbonyl group, a halogen, and a nitro group, and a sulfonyl group, a carbonyl group, and a cyano group are preferable. Specific examples of the structure include structures represented by the following chemical formulas 10A to G.

  Among these, structures represented by the chemical formulas 10A, 10B, and 10C are preferable, and structures represented by any of the following chemical formulas 10A ′, 10A ″, 10B ′, and 10C ′ are more preferable, and 10A ′ or 10B. One of 'is most preferred.

Preferable examples of Ar ¹ and Ar ² include groups represented by chemical formulas 4 to 7.

  In the case where the hydrophobic segment is represented by Chemical Formula 2, the retention of the form of the polymer electrolyte membrane can be improved by the liquid crystalline biphenylene group. The hydrophobic segment of Chemical Formula 2 can be obtained by reacting 4,4′-biphenol with a monomer represented by the following Chemical Formulas 11A to 11D.

  In Chemical Formulas 11A to D, Z represents a halogen atom, and F or Cl is particularly preferable.

  When the hydrophobic segment is represented by Chemical Formula 3, the bonding property with the electrode can be further improved. In Chemical Formula 3, p represents an integer of 2 or more. P in Chemical Formula 1 may have a distribution consisting of a plurality of numbers. In the case of having a distribution, the average value is rounded off to the nearest decimal point as long as it is 3 or more. More preferably, it is the range of 3-20, More preferably, it is the range of 5-10. In addition, when p has a distribution, p may be within the range of the present invention as an average value, and even if the component includes a portion where p is 0 to 2, the average value is within the range of the present invention. The present invention solves the problems of the present invention. The hydrophobic segment of Chemical Formula 3 can be synthesized by reacting the compound of Chemical Formula 12 with the compounds represented by Chemical Formulas 11A to 11D.

  In chemical formula 12, p represents an integer of 3 or more. A plurality of compounds having different p can also be used in combination, but in that case, the value obtained by rounding off the decimal point of the average value of p may be 3 or more. The preferable range of p is 3 to 20, and 5 to 10 is more preferable.

  The hydrophobic segment of the present invention may consist of either chemical formula 2 or 3, or may consist of chemical formulas 2 and 3.

  The ion exchange capacity of the segmented block copolymer of the present invention is preferably from 0.5 to 2.5 meq / g. If it is 0.5 meq / g or less, the proton conductivity is too low, which is not preferable. If it is 2.5 meq / g or more, the water absorption becomes too large and the swelling becomes too large, which is not preferable. When it is in the range of 0.7 to 2.0 meq / g, it has more preferable characteristics such as proton conductivity and swelling resistance. Furthermore, when it is in the range of 0.7 to 1.6 meq / g, the methanol permeability is small, so that it is particularly suitable for a polymer electrolyte membrane for a direct methanol fuel cell.

  The segmented block copolymer of the present invention can be obtained by previously synthesizing a hydrophilic segment and a hydrophobic segment in advance, and then reacting both, or one segment that has been polymerized in advance, The other segment can be added to the polymerized solution and further reacted. At that time, the end groups of each segment may be directly reacted with each other, or the end groups of each segment may be the same, and both may be reacted using a chain extender.

  When the sulfonic acid group-containing segmented block copolymer polymer of the present invention and each segment are polymerized by an aromatic nucleophilic substitution reaction, the aromatic bishalide compound and the aromatic bisphenol are reacted in the presence of a basic compound. A polymer can be obtained. The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed.

  The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more. Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like, and any compound that can form an aromatic diol into an active phenoxide structure. It can be used without being limited to these. Water produced as a by-product should be removed by distillation with an azeotropic solvent such as toluene, or by using a water absorbing material such as molecular sieve, or by distillation with a polymerization solvent. Can do. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by weight. When the amount is less than 5% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration.

  The chain length of each segment can be adjusted by the molar ratio of monomers used for polymerization. Further, the terminal group of each segment can be determined by polymerization, which monomer is excessive. The chain length of the segment can be calculated from the charged amount, but it is more preferably quantified by NMR or the like. In order to connect segments, each segment can be treated as a macromonomer and reacted in the same manner as the monomer.

  The hydrophilic segment is not particularly limited as long as it has a structure in the range shown above. Examples of preferable structures are shown in Chemical Formulas 13A and 13B.

  Examples of structures preferable as the hydrophobic segment are shown in Chemical Formulas 14A to 14H, but the present invention is not limited to these.

  The molecular weight of the sulfonic acid group-containing block copolymer of the present invention is 0.3 or more when expressed in terms of logarithmic viscosity when a 0.5 g / dl N-methyl-2-pyrrolidone solution is measured at 30 ° C. Is preferable from the viewpoint of physical properties, more preferably 0.5 or more, and still more preferably 0.9 or more. If it is less than 0.3, the physical properties are remarkably deteriorated. When the logarithmic viscosity is more than 3.0, the viscosity of the solution in which the polymer is dissolved becomes extremely high, which may make it difficult to handle.

  The sulfonic acid group-containing block copolymer polymer of the present invention can also be used as a composition by mixing other compounds. Examples of compounds to be mixed include heteropolyacids such as phosphotungstic acid and phosphomolybdic acid, acidic compounds such as low molecular weight sulfonic acid, phosphonic acid and phosphoric acid derivatives, inorganic substances such as silicic acid compounds and zirconium phosphoric acid. Can be mentioned. The content of the inorganic substance in the composition is preferably less than 50% by mass. If it is 50% by mass or more, the physical properties of moldability are impaired, which is not preferable.

  Furthermore, it can also be used as a composition mixed with other polymers. Examples of these polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyamides such as nylon 6, nylon 66, nylon 610, and nylon 12, polymethyl methacrylate, polymethacrylates, and polymethyl. Acrylate resins such as acrylates and polyacrylates, polyacrylic acid resins, polymethacrylic acid resins, polyethylene, polypropylene, various polyolefins including polystyrene and diene polymers, polyurethane resins, cellulose acetate, cellulose such as ethyl cellulose Resin, polyarylate, aramid, polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethers Thermal curing of aromatic polymers such as phon, polyetheretherketone, polyetherimide, polyimide, polyamideimide, polybenzimidazole, polybenzoxazole, polybenzthiazole, epoxy resin, phenol resin, novolac resin, benzoxazine resin There are no particular restrictions on the conductive resin. A composition with a basic polymer such as polybenzimidazole or polyvinylpyridine can be said to be a preferable combination for improving polymer dimensionality. If a sulfonic acid group is further introduced into these basic polymers, the composition The workability of the product becomes more preferable.

  When used as these compositions, the sulfonic acid group-containing block copolymer polymer of the present invention is preferably contained in an amount of 50% by mass or more and less than 100% by mass of the entire composition. More preferably, it is 70 mass% or more and less than 100 mass%. When the content of the sulfonic acid group-containing block copolymer of the present invention is less than 50% by mass of the entire composition, the sulfonic acid group concentration of the polymer electrolyte membrane containing this composition is lowered, and good proton conduction is achieved. Tend to be not obtained, and the unit containing a sulfonic acid group becomes a discontinuous phase and tends to lower the mobility of ions to be conducted. In addition, the composition of the present invention, if necessary, for example, an antioxidant, a heat stabilizer, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, an antibacterial agent, an antifoaming agent, Various additives such as a dispersant and a polymerization inhibitor may be included.

  The sulfonic acid group-containing block copolymer of the present invention can be used as a composition in a solution dissolved in an appropriate solvent. Solvents include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, sulfolane, diphenylsulfone, N-methyl-2-pyrrolidone, hexamethylphosphonamide, methanol, ethanol, etc. However, the present invention is not limited to these alcohols. Among these, it is preferable to dissolve in N-methyl-2-pyrrolidone, N, N-dimethylacetamide and the like. A plurality of these solvents may be used as a mixture within a possible range. The compound concentration in the solution is preferably in the range of 0.1 to 50% by mass. If the compound concentration in the solution is less than 0.1% by mass, it tends to be difficult to obtain a good molded product, and if it exceeds 50% by mass, the workability tends to deteriorate. You may mix and use the above-mentioned compound etc. in a solution.

  Further, it may be dispersed in a mixture of alcohols such as methanol, ethanol, propanol and butanol and water, or in a non-solvent such as water.

  The sulfonic acid group of the polymer in the sulfonic acid group-containing block copolymer polymer composition in the present invention may be an acid or a salt with a cation, but from the viewpoint of the stability of the sulfonic acid group, It is preferable that it is a salt. When it is a salt, it can be converted to an acid by acid treatment as necessary, such as after molding.

  The sulfonic acid group-containing block copolymer of the present invention and the composition thereof can be formed into a molded body such as a fiber or a film by any method such as extrusion, spinning, rolling or casting. Among these, it is preferable to mold from a solution dissolved in an appropriate solvent.

  A method of obtaining a molded body from a solution can be performed using a conventionally known method. For example, the molded product can be obtained by removing the solvent by heating, drying under reduced pressure, immersion in a compound non-solvent that can be mixed with a solvent that dissolves the compound, or the like. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure. At this time, it can be formed into various shapes such as a fiber shape, a film shape, a pellet shape, a plate shape, a rod shape, a pipe shape, a ball shape, and a block shape in a composite form with other compounds as required. . When combined with a compound having a similar dissolution behavior, it is preferable in that good molding can be achieved. The sulfonic acid group in the molded article thus obtained may contain a salt form with a cation, but if necessary, it can be converted to a free sulfonic acid group by acid treatment. You can also.

  An ion conductive membrane can also be produced from the sulfonic acid group-containing block copolymer of the present invention and the composition thereof. The ion conductive membrane is not limited to the sulfonic acid group-containing copolymer of the present invention, and may be a composite membrane with a support such as a porous membrane, a nonwoven fabric, fibril, or paper. The obtained ion conductive membrane can be used as a polymer electrolyte membrane for fuel cells.

  The most preferable method for forming the ion conductive membrane is casting from a solution, and the ion conductive membrane can be obtained by removing the solvent from the cast solution as described above. The removal of the solvent is preferably by drying from 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 at the lowest temperature possible under reduced pressure. Further, when the viscosity of the solution is high, when the substrate or the solution is heated and cast at a high temperature, the viscosity of the solution is lowered and the casting can be easily performed. The thickness of the solution at the time of casting is not particularly limited, but is preferably 10 to 1000 μm. More preferably, it is 50-500 micrometers. If the thickness of the solution is thinner than 10 μm, the form as an ion conductive film tends to be not maintained, and if it is thicker than 1000 μm, a non-uniform ion conductive film tends to be easily formed. As a method for controlling the cast thickness of the solution, a known method can be used. For example, the thickness can be controlled by the amount and concentration of the solution by making the thickness constant using an applicator, a doctor blade or the like, or making the cast area constant using a glass petri dish or the like. The cast solution can obtain a more uniform film by adjusting the solvent removal rate. For example, in the case of heating, the evaporation rate can be reduced by lowering the temperature in the first stage. In addition, when immersed in a non-solvent such as water, the coagulation rate of the compound can be adjusted by leaving the solution in air or an inert gas for an appropriate time.

The polymer electrolyte membrane of the present invention can have any thickness depending on the purpose, but is preferably as thin as possible from the viewpoint of proton conductivity. Specifically, the thickness is preferably 5 to 200 μm, more preferably 5 to 100 μm, and most preferably 20 to 80 μm. When the thickness of the polymer electrolyte membrane is less than 5 μm, the handling of the polymer electrolyte membrane becomes difficult and a short circuit or the like tends to occur when a fuel cell is produced. When the thickness is greater than 200 μm, the electrical resistance value of the polymer electrolyte membrane is high. Therefore, the power generation performance of the fuel cell tends to decrease. When used as a polymer electrolyte membrane, the sulfonic acid group in the membrane may contain a metal salt, but it can be converted to free sulfonic acid by an appropriate acid treatment. In this case, it is also effective to immerse the membrane obtained in an aqueous solution of sulfuric acid, hydrochloric acid, etc. with or without heating. The proton conductivity of the polymer electrolyte membrane is preferably 1.0 × 10 ⁻³ S / cm or more. When the proton conductivity is 1.0 × 10 ⁻³ S / cm or more, a good output tends to be obtained in a fuel cell using the polymer electrolyte membrane, and 1.0 × 10 ⁻³ S When it is less than / cm, the output of the fuel cell tends to decrease.

  In order to promote the phase separation of the hydrophilic segment and the hydrophobic segment in the polymer electrolyte membrane, a film can be formed by adding a non-solvent such as water to the polymer solution.

  Moreover, the assembly of the polymer electrolyte membrane or film of the present invention and the electrode can be obtained by installing the above-described polymer electrolyte membrane or film of the present invention on the electrode. As a method for producing this joined body, a conventionally known method can be used. For example, a method of applying an adhesive to the electrode surface and bonding the polymer electrolyte membrane and the electrode, or a polymer electrolyte membrane and the electrode There is a method of heating and pressurizing. Among these, the method of applying and bonding an adhesive mainly composed of the sulfonic acid group-containing polyarylene ether compound of the present invention and the composition thereof to the electrode surface is preferable. This is because the adhesion between the polymer electrolyte membrane and the electrode is improved, and it is considered that the proton conductivity of the polymer electrolyte membrane is less impaired.

  The fuel cell of the present invention can be produced using the polymer electrolyte membrane or the polymer electrolyte membrane / electrode assembly of the present invention. The fuel cell of the present invention includes, for example, an oxygen electrode, a fuel electrode, a polymer electrolyte membrane sandwiched between the electrodes, an oxidant flow path provided on the oxygen electrode side, and a fuel electrode side. The fuel flow path is provided. A fuel cell stack can be obtained by connecting such unit cells with a conductive separator.

  Since the polymer electrolyte membrane of the present invention has a low methanol permeability in addition to a polymer electrolyte fuel cell (PEFC) using hydrogen as a fuel, it also applies to a methanol direct fuel cell (DMFC) using methanol as a fuel. Is suitable. Moreover, since it is excellent in heat resistance and barrier properties, it is also suitable for a fuel cell of a type in which hydrogen is taken out from a hydrocarbon such as methanol, gasoline, ether, etc. by a reformer.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.

<Solution viscosity>
The polymer powder was dissolved in N-methyl-2-pyrrolidone at a concentration of 0.5 g / dl, the viscosity was measured using a Ubbelohde viscometer in a thermostatic bath at 30 ° C., and the logarithmic viscosity ln [ta / tb] / Evaluation was carried out by c (ta represents the falling seconds of the sample solution, tb represents the falling seconds of the solvent alone, and c represents the polymer concentration).

<Ion exchange capacity>
100 mg of the dried sample was immersed in 50 ml of 0.01N NaOH aqueous solution and stirred at 25 ° C. overnight. Then, neutralization titration with 0.05N HCl aqueous solution was performed. For neutralization titration, a potentiometric titrator COMMITE-980 manufactured by Hiranuma Sangyo Co., Ltd. was used. The ion exchange equivalent was calculated by the following formula.
Ion exchange capacity [meq / g] = (10-titration [ml]) / 2

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

<Softening temperature>
While heating a 5 mm wide acid-type film at a chuck width of 10 mm from 50 ° C. to 250 ° C. at a rate of 2 ° C./min, a dynamic strain of 10 Hz is applied to give dynamic viscoelasticity, Rheogel E-4000 (Toki Sangyo) The measurement was performed using The temperature at the inflection point at which E ′ greatly decreased was defined as the softening temperature.

<Methanol permeability>
In a room at 25 ° C, two glass water tanks are connected with a sample as a diaphragm, 5M aqueous methanol solution is added to one water tank, distilled water is added to the other water tank, and the methanol concentration on the side containing distilled water is determined for an appropriate time. Quantified every time. Methanol was quantified by gas chromatography, and the methanol concentration was calculated using a calibration curve prepared from the peak area when a methanol solution having a predetermined concentration was injected in advance. From the slope when the obtained methanol concentration was plotted against the elapsed time, the methanol permeability coefficient was determined by the following equation.
Methanol permeation rate (mmol · m ⁻² · sec ⁻¹ ) = slope of plot (mmol · sec ⁻¹ ) ÷ membrane area (m ² ) × film thickness (m)

Power generation evaluation of direct methanol fuel cell (DMFC): After adding a small amount of ultrapure water and isopropyl alcohol to carbon supported on Pt / Ru catalyst (TEC61E54, Tanaka Kikinzoku Kogyo Co., Ltd.), DuPont 20% Nafion (registered) (Trademark) solution (product number: SE-20192) was added so that the weight ratio of Pt / Ru catalyst-carrying carbon to Nafion was 2.5: 1. Next, stirring was performed to prepare an anode catalyst paste. The catalyst paste is applied and dried by screen printing on carbon paper TGPH-060 manufactured by Toray Industries, Inc. as a gas diffusion layer so that the amount of platinum deposited is 2 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for the anode. did. Moreover, after adding a small amount of ultrapure water and isopropyl alcohol to a Pt catalyst-supporting carbon (Tanaka Kikinzoku Kogyo TEC10V40E) and moistening, a 20% Nafion (registered trademark) solution (product number: SE-20192) manufactured by DuPont, A cathode catalyst paste was prepared by adding the Pt catalyst-carrying carbon and Nafion in a weight ratio of 2.5: 1 and stirring. The catalyst paste was applied and dried on carbon paper TGPH-060 manufactured by Toray Industries, Ltd., which had been subjected to water repellent treatment, so that the amount of platinum deposited was 1 mg / cm ² , thereby producing a carbon paper with an electrode catalyst layer for cathode. . A membrane sample is sandwiched between the above two types of carbon paper with an electrode catalyst layer so that the electrode catalyst layer is in contact with the membrane sample, and heated and pressurized at 150 ° C. and 6 MPa for 3 minutes by a hot press method. When the electrolyte membrane and the electrode catalyst layer were satisfactorily joined, “◯” was given, and when peeling occurred, “x” was given.

<Production method of polymer electrolyte membrane>
A polymer (with a sulfonic acid group in a salt form) (5.0 g) is dissolved in 15 ml of N-methyl-2-pyrrolidone (abbreviation: NMP), cast on a glass plate with a thickness of 250 μm using an applicator, and 100 ° C. It was dried by heating at 150 ° C. for 1 hour for 1 hour. Thereafter, the glass plate was allowed to cool to near room temperature, and the membrane was peeled off with water attached to the membrane. The peeled membrane is immersed in pure water, then immersed in 2 mol / liter sulfuric acid for 1 hour, and further immersed in new 2 mol / liter sulfuric acid for 1 hour to convert the sulfonic acid group into an acid form. The polymer was washed 10 times to remove free sulfuric acid, and was sandwiched between filter papers, pressed with a glass plate, allowed to stand for 2 days and dried to obtain a polymer electrolyte membrane.

<Synthesis Example 1: Hydrophobic segment A>
35.07 g of 4,4-dichlorodiphenylsulfone (abbreviation: DCDPS), terminal hydroxyl group-containing phenylene ether oligomer (SPECIANOL DPE-PL manufactured by Dainippon Ink & Chemicals, Inc .; a mixture containing 1 to 8 components in chemical formula 9 (The structure is such that the average value of n is 5) (abbreviation: DPE) 63.80 g, potassium carbonate 17.64 g, NMP 350 ml, toluene 150 ml, a nitrogen introduction tube, a stirring blade, a Dean-Stark trap, and a thermometer were attached. It put into a 1000 ml branch flask, and heated under nitrogen stream, stirring in an oil bath. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 13 hours. Subsequently, the solution cooled to room temperature was poured into 1000 ml of pure water, re-precipitated, washed with boiling water three times, and then the polymer was separated by filtration and dried under reduced pressure to obtain a hydrophobic segment A.

<Synthesis Examples 2-6: Hydrophobic Segments B-F>
The hydrophobic segment was polymerized in the same manner as in Synthesis Example 1 except that the monomer and the molar ratio were changed. The results are shown in Table 1.

<Example 1>
Sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (abbreviation: S-DCDPS) 30.00 g, BPE 34.12 g, potassium carbonate 9.43 g, NMP 150 ml, toluene 100 ml, a nitrogen introduction tube, It put into the 500 ml branch flask equipped with the stirring blade, the Dean-Stark trap, and the thermometer, and heated under nitrogen stream, stirring in an oil bath. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 18 hours. After the solution is cooled to room temperature, 14.99 g of hydrophobic segment A dissolved in 70 ml of NMP is added, heated to 210 ° C. for 12 hours, poured into 1000 ml of pure water, re-precipitated, and washed three times with boiling water. The polymer was filtered off and dried under reduced pressure to obtain a polymer. The structure of the polymer was confirmed by ¹ H-NMR measurement that the proton adjacent to the sulfonic acid group of S-DCDPS had a signal at 8.3 ppm and the proton of the phenyl group of DPE had a signal at 7.1 ppm, respectively. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

<Example 2>
S-DCDPS 30.00 g, BPE 34.39 g, potassium carbonate 9.51 g, NMP 150 ml, toluene 100 ml were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer, and in an oil bath. The mixture was heated under a nitrogen stream with stirring. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 13 hours. After cooling the solution to room temperature, 144.53 of hydrophobic segment B dissolved in 70 ml of NMP was added, heated to 210 degrees, reacted for 9 hours, poured into 1000 ml of pure water, re-precipitated, and washed 3 times with boiling water The polymer was filtered off and dried under reduced pressure to obtain a polymer. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

<Example 3>
S-DCBP (30.00 g), BPE (36.82 g), potassium carbonate (10.18 g), NMP (150 ml) and toluene (100 ml) were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap and thermometer, and stirred in an oil bath. While heating, it was heated under a nitrogen stream. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 10 hours. After the solution is cooled to room temperature, 15.88 g of hydrophobic segment C dissolved in 70 ml of NMP is added, heated to 200 ° C. for 13 hours, poured into 1000 ml of pure water, re-precipitated, and washed with boiling water three times. The polymer was filtered off and dried under reduced pressure to obtain a polymer. The structure of the polymer was confirmed by ¹ H-NMR measurement that the proton adjacent to the sulfonic acid group of S-DCBP had a signal at 8.2 ppm and the proton of the phenyl group of DPE had a signal at 7.1 ppm, respectively. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

<Example 4>
S-DCDPS 30.00 g, BPE 40.38, potassium carbonate 11.17 g, NMP 120 ml, toluene 100 ml were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer, and in an oil bath. The mixture was heated under a nitrogen stream with stirring. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 8 hours. After cooling the solution to room temperature, 64.73 g of hydrophobic segment D dissolved in 120 ml of NMP is added, heated to 200 ° C. for 11 hours, poured into 1000 ml of pure water, re-precipitated, and washed three times with boiling water. The polymer was filtered off and dried under reduced pressure to obtain a polymer. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

<Example 5>
S-DCDPS 30.00 g, BPE 42.05 g, potassium carbonate 11.63 g, NMP 120 ml, toluene 100 ml were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer, and in an oil bath. The mixture was heated under a nitrogen stream with stirring. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 10 hours. After cooling the solution to room temperature, 70.27 g of hydrophobic segment E dissolved in 150 ml of NMP is added, heated to 200 ° C., reacted for 15 hours, poured into 1000 ml of pure water, re-precipitated, and washed three times with boiling water. The polymer was filtered off and dried under reduced pressure to obtain a polymer. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

<Example 6>
S-DCDPS 30.00 g, BPE 38.48 g, potassium carbonate 10.64 g, NMP 120 ml, toluene 100 ml were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer, and in an oil bath. The mixture was heated under a nitrogen stream with stirring. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 10 hours. After cooling the solution to room temperature, 89.01 g of hydrophobic segment F dissolved in 120 ml of NMP was added, heated to 200 ° C., reacted for 13 hours, poured into 1000 ml of pure water, re-precipitated, and washed three times with boiling water. The polymer was filtered off and dried under reduced pressure to obtain a polymer. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

  Table 2 shows the composition of the hydrophilic segments in Examples 1 to 6.

<Comparative Examples 1-6>
A polymer was obtained in the same manner as in Example except that all monomers were reacted simultaneously with the same monomer composition as in Examples 1-6. A polymer electrolyte membrane was obtained from the obtained polymer by the above method. The polymer composition is shown in Table 3.

<Comparative Example 7>
DCDPS 52.60 g, BP 33.54 g, potassium carbonate 27.40 g, NMP 300 ml, toluene 250 ml were placed in a 1000 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap and thermometer, and stirred in an oil bath. While heating, it was heated under a nitrogen stream. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 13 hours. Subsequently, the solution cooled to room temperature was poured into 2000 ml of pure water, re-precipitated, washed 3 times with boiling water, and then the polymer was filtered and dried under reduced pressure to obtain a hydrophobic segment G. S-DCDPS 30.00 g, BP 11.66 g, potassium carbonate 9.52 g, NMP 150 ml, toluene 100 ml were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer, and in an oil bath. The mixture was heated under a nitrogen stream with stirring. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 11 hours. After cooling the solution to room temperature, 24.74 g of hydrophobic segment G dissolved in 70 ml of NMP was added, heated to 210 ° C., reacted for 14 hours, poured into 1000 ml of pure water, re-precipitated and washed with boiling water three times. The polymer was filtered off and dried under reduced pressure to obtain a polymer. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

<Comparative Example 7>
Add 159.78 g of DCDPS, 102.35 g of BP, 83.56 g of potassium carbonate, 800 ml of NMP, and 300 ml of toluene into a 2000 ml branch flask equipped with a nitrogen introduction tube, a stirring blade, a Dean-Stark trap, and a thermometer, and stir in an oil bath. While heating, it was heated under a nitrogen stream. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 200 degreeC and heated for 14 hours. Subsequently, the solution cooled to room temperature was poured into 3000 ml of pure water and reprecipitated, washed with boiling water three times, and then the polymer was separated by filtration and dried under reduced pressure to obtain a hydrophobic segment H. S-DCDPS 30.00 g, BP 12.00 g, potassium carbonate 9.80 g, NMP 300 ml, toluene 150 ml were placed in a 500 ml branch flask equipped with a nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer, and in an oil bath. The mixture was heated under a nitrogen stream with stirring. After dehydration by azeotropy with toluene at 140 ° C., all toluene was distilled off. Then, it heated up at 210 degreeC and heated for 12 hours. After cooling the solution to room temperature, 110.78 g of hydrophobic segment G dissolved in 200 ml of NMP was added, heated to 210 ° C., reacted for 14 hours, poured into 2000 ml of pure water, re-precipitated, and washed with boiling water three times. The polymer was filtered off and dried under reduced pressure to obtain a polymer. A polymer electrolyte membrane was obtained from the obtained polymer by the above method.

  Table 4 shows the evaluation results of the polymer electrolyte membranes of Examples and Comparative Examples.

  From Table 4, the polymer electrolyte membrane made of the segmented block copolymer of the present invention has a higher methanol permeability than the polymer electrolyte membrane made of a random copolymer having the same composition, although the methanol permeability is equivalent. It can be seen that the proton conductivity is excellent. Further, the polymer electrolyte membranes made of the block copolymers outside the scope of the present invention in Comparative Examples 7 to 8 have poor bonding properties with the electrodes, whereas they consist of the segmented block copolymers of the present invention. It can be seen that the polymer electrolyte membrane has good bondability with the electrode and excellent workability.

  The polymer electrolyte membrane comprising the sulfonic acid group-containing segmented block copolymer of the present invention can provide a polymer electrolyte membrane / electrode assembly excellent in proton conductivity and processability and excellent in durability, In the field of batteries, compared to conventional hydrocarbon polymer electrolyte membranes, it is possible to achieve higher durability and higher output, contributing to the industry.

Claims (9)

A block copolymer having at least one hydrophilic segment and hydrophobic segment in each polymer molecule, wherein the hydrophilic segment has the following chemical formula 1;

(In the formula, X represents H or a monovalent cation, Y represents a sulfone group or a carbonyl group, n represents an integer of 3 to 50, and m represents an integer of 2 or more.)
A sulfonic acid group-containing segmented block copolymer characterized by being mainly composed of a structure represented by the formula (II) and having a softening temperature of 180 ° C. or lower. The hydrophobic segment is at least one of the following chemical formulas 2 and 3;

(In the formula, Ar ¹ and Ar ² represent a divalent aromatic group having an electron-withdrawing group, o represents an integer of 3 to 50, and p represents an integer of 2 or more.)
The sulfonate group-containing segmented block copolymer polymer according to claim 1 mainly composed of a structure represented by: Ar ² in formula 2 of the Ar ¹ and Formula 3 are each independently, the following chemical formula 4-7;

The sulfonic acid group-containing segmented block copolymer polymer according to claim 2, which has at least one structure selected from the group consisting of structures represented by:   The sulfonate group-containing segmented block copolymer according to claim 2, wherein n in Chemical Formula 1 and o in Chemical Formulas 2 and 3 are 25 or less.   The sulfonate group-containing segmented block copolymer polymer according to claim 4, wherein o in Chemical Formulas 2 and 3 is 20 or less.   A polymer composition comprising 1 to 100% by weight of the sulfonic acid group-containing segmented block copolymer according to claim 1.   A polymer electrolyte membrane obtained from the polymer composition according to claim 6.   A polymer electrolyte membrane / electrode assembly comprising the polymer composition according to claim 6 on at least one of a polymer electrolyte membrane and an electrode catalyst layer.   A fuel cell using the polymer electrolyte membrane / electrode assembly according to claim 8.