JP2012129175A - Method for producing polymer electrolyte membrane and polymer electrolyte membrane produced by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polymer electrolyte membrane which is excellent in proton conductivity in the thickness direction thereof.SOLUTION: The method for producing a polymer electrolyte membrane of the present invention includes a step of applying a solution on a support to form a coating film of a block copolymer, the solution being prepared by dissolving the block copolymer having a hydrophobic segment and a hydrophilic segment in a solvent, a step of applying a solution on the coating film of the block copolymer to form a coating film of a random copolymer, the solution being prepared by dissolving the random copolymer in a solvent, and a step of removing the solvent, in the order.

Description

  The present invention relates to a method for producing a polymer electrolyte membrane, and a polymer electrolyte membrane produced by the production method.

  In recent years, new power generation technology with excellent power generation efficiency and environmental performance has been attracting attention. In particular, polymer electrolyte fuel cells have a high output density, and have a lower operating temperature than other types of fuel cells, making them easy to start and stop, so they have been developed as power supplies for electric vehicles and distributed power generation. Progressing.

  A solid polymer fuel cell is called a stack in which a plurality of membrane electrode assemblies each having a polymer electrolyte membrane sandwiched between two electrodes are used in any type using pure hydrogen gas, reformed hydrogen gas, and methanol as fuel. Consists of things.

  The polymer electrolyte membrane is required to be excellent in proton conductivity and fuel permeation deterrence from the viewpoint of improving the output and effectively using the fuel. A fluorine-based polymer electrolyte membrane represented by Nafion (registered trademark), which is known as a polymer electrolyte membrane, has a problem of high fuel permeability. For this reason, recently, polymer electrolyte membranes (hydrocarbon polymer electrolyte membranes) made of hydrocarbon polymers are often used.

  A hydrocarbon-based polymer electrolyte (hereinafter sometimes simply referred to as “polymer electrolyte”) membrane is generally produced by casting a solvent solution of a polymer electrolyte on a support and then drying it. However, at that time, the proton conductivity and the fuel permeation inhibiting property of the obtained polymer electrolyte membrane may be lowered.

  So far, a method for producing a polymer electrolyte membrane, in which proton conductivity and fuel permeation deterrence are hardly lowered, has been developed. For example, in Patent Document 1, after a polymer electrolyte solution is cast on a support to obtain a cast film, the residual solvent amount is reduced to a specific value or less in removing the solvent from the cast film. A method for producing a polymer electrolyte membrane to be adjusted is disclosed.

JP 2008-156622 A

  In a polymer electrolyte fuel cell, protons move from one surface of the polymer electrolyte membrane to the other surface, so it is important that the polymer electrolyte membrane is excellent in proton conductivity in the film thickness direction. However, in the above production method, a polymer electrolyte membrane excellent in proton conductivity in the film thickness direction may not be produced.

  The present invention has been made to solve such problems, and the present inventor has raised the object of providing a method for producing a polymer electrolyte membrane excellent in proton conductivity in the film thickness direction.

  As a result of intensive studies, the present inventor has found that the casting membrane of the polymer electrolyte (particularly, the hydrocarbon block copolymer) is prevented from coming into contact with the atmosphere in the production process of the polymer electrolyte membrane. The present inventors have found that a polymer electrolyte membrane excellent in proton conductivity in the film thickness direction can be produced by removing the solvent from the present invention, and the present invention has been completed.

  That is, the method for producing a hydrocarbon-based polymer electrolyte membrane according to the present invention, which was able to solve the above problems, is a solution in which a block copolymer having a hydrophobic segment and a hydrophilic segment is dissolved in a solvent. On the support and forming a coating film of the block copolymer, and applying a solution obtained by dissolving the random copolymer in a solvent to the coating film of the block copolymer. The step of forming a coating film of the random copolymer and the step of removing the solvent are included in this order.

  In the present specification, the term “on the support” means that a coating film of a block copolymer is provided immediately above the support, or other film (for example, a coating film of a random copolymer described later, It is meant to include the case where it is provided via a copolymer film).

  The “copolymer coating film” means a film formed without coating the copolymer solution on a support or the like and then removing the solvent. The “union film” means a film formed by intentionally removing the solvent from the coating film.

  In the present invention, in the step of forming the block copolymer coating film, a random copolymer coating film is formed on the support by applying a solution obtained by dissolving the random copolymer in a solvent. Thereafter, the coating of the random copolymer is performed by applying a solution of the block copolymer, or the support is applied with a solution in which the random copolymer is dissolved in a solvent, In a preferred embodiment, the solvent is removed to form a random copolymer film, and then the block copolymer solution is applied to the random copolymer film.

Further, the hydrophobic segment of the block copolymer is represented by the chemical formula 1

(Chemical formula 1)

(In the formula, each Z independently represents an O atom or an S atom, Ar ¹ independently represents a divalent aromatic group, and n represents a number of 1 to 100, respectively.)
Represented by
The hydrophilic segment is represented by chemical formula 2

(Chemical formula 2)

Wherein X is independently H or a monovalent cation, Y is a sulfonyl group or carbonyl group, Ar ² is independently a divalent aromatic group, and L is independently O. An atom or an S atom, m represents a number of 1 to 100, respectively)
The hydrophobic segment and the hydrophilic segment are represented by the chemical formula 3

(Chemical formula 3)

(In the formula, p represents 0 or 1, and when p is 1, W represents one or more selected from the group consisting of a direct bond, a sulfonyl group, and a carbonyl group.)
Or Ar ² is represented by the chemical formula 4

(Chemical formula 4)
Is also a preferred embodiment.

  Furthermore, the ratio (m / n) of m in the chemical formula 2 to n in the chemical formula 1 is 0.4 to 1.5, or the fluorine-based heavy polymer having a sulfonic acid group in the random copolymer. It is also preferable that the polymer is a hydrocarbon-based polymer having a coalescence and / or a sulfonic acid group, and the mass ratio of the total amount of the block copolymer and the random copolymer is 99/1 to 1/99. It is an aspect.

  The present invention also includes a hydrocarbon-based polymer electrolyte membrane produced by the above production method, a membrane electrode assembly using the electrolyte membrane, and a fuel cell using the membrane electrode assembly.

  The method for producing a polymer electrolyte membrane of the present invention is excellent in proton conductivity in the film thickness direction because the solvent is removed from the coating film while preventing the coating film of the block copolymer from coming into contact with the atmosphere. An electrolyte membrane could be obtained.

  In the method for producing a hydrocarbon-based polymer electrolyte membrane according to the present invention, a solution obtained by dissolving a block copolymer having a hydrophobic segment and a hydrophilic segment in a solvent is applied on a support, and the block A step of forming a coating film of the copolymer, and a coating solution of the random copolymer is applied to the coating film of the block copolymer to form the coating film of the random copolymer The method includes a step and a step of removing the solvent in this order.

  Although the details about the mechanism by which the polymer electrolyte membrane excellent in proton conductivity in the film thickness direction is obtained by the production method of the present invention are unknown, it is presumed as follows.

  That is, in the conventional method for producing a polymer electrolyte membrane, the polymer electrolyte is obtained by removing the solvent from the coating film while the coating film of the block copolymer having the hydrophobic segment and the hydrophilic segment is in contact with the atmosphere. I got a film. Since the atmosphere is a hydrophobic substance, hydrophobic segments gather on the surface of the electrolyte membrane that comes into contact with the atmosphere, and the distribution of hydrophobic and hydrophilic segments in the electrolyte membrane is uneven in the film thickness direction. It was.

  On the other hand, in this invention, the surface of the coating film of the block copolymer which has a hydrophobic segment and a hydrophilic segment is coat | covered with the coating film of a random copolymer. Even if the solvent is removed from the coating film of the random copolymer in contact with the atmosphere (hydrophobic substance), the distribution of hydrophobic groups and hydrophilic groups hardly changes in the film thickness direction. In addition, since the coating film of the block copolymer is prevented from coming into contact with the atmosphere, the hydrophobic segment and the hydrophilic segment are distributed even if the solvent is removed from the coating film of the block copolymer. Difficult to be uneven in the thickness direction.

  That is, in the polymer electrolyte membrane obtained by the production method of the present invention, hydrophilic groups (hydrophilic segments) involved in proton movement are even in the film thickness direction (in other words, hydrophobic segments are unevenly distributed on the membrane surface). As a result, the proton conductivity in the film thickness direction is estimated to be improved.

  Hereafter, the manufacturing method of the polymer electrolyte membrane of this invention is demonstrated in detail. In this specification, the manufacturing process characterizing the present invention (particularly, the method for preventing the coating film of the block copolymer from coming into contact with the hydrophobic substance) will be described first, followed by the block copolymer and the random copolymer. A specific mode of coalescence will be described.

(Step of forming a coating film of block copolymer)
The solvent used in this step is not particularly limited as long as it can uniformly dissolve or disperse the block copolymer, and may be appropriately selected according to the structure of the block copolymer. And is more preferably an aprotic polar solvent. Examples of the aprotic polar solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, N-morpholine-N-oxide, and hexamethylene. Examples include phosphonamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, and diphenyl sulfone. In particular, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone and dimethyl sulfoxide are preferable. These solvents may be used alone or in combination of two or more. The boiling point of the solvent is preferably in the range of 100 ° C to 300 ° C. If the boiling point is less than 100 ° C., wrinkles or deformation may occur on the surface of the obtained polymer electrolyte membrane. When the boiling point exceeds 300 ° C., a large amount of energy may be required for production of the polymer electrolyte membrane.

  The solid content concentration of the solution of the block copolymer can be appropriately determined according to the molecular weight of the block copolymer, the temperature at the time of coating, and the like, and specifically, it is in the range of 5% by mass to 50% by mass. Is preferred. When the solid content concentration is less than 5% by mass, it may take time to remove the solvent in the subsequent step, and the quality of the film may be lowered. When the solid content concentration exceeds 50% by mass, the viscosity of the solution becomes too high, and handling may be difficult. More preferably, it is 5 mass%-35 mass%.

  The viscosity of the block copolymer solution is not particularly limited, but it is satisfactorily coated on the support (immediately above the support or a random copolymer coating film or random copolymer film described later). It is preferable that it is in the range that can be. More preferably, the viscosity is in the range of 1 to 1000 Pa · s at the coating temperature.

  As a method for applying the block copolymer solution onto the support, known methods can be used, but it is preferable to apply a solution having a constant concentration so as to have a constant thickness. For example, a method of pushing the solution into a gap of a certain gap, such as a doctor blade or an applicator, to make the coating thickness constant, or a method of supplying a block copolymer solution at a constant speed using a slot die, etc. And a method of spraying the block copolymer solution using a spray or the like. Coating on the support may be performed in a batch manner, but it is preferable to perform the coating continuously because the productivity is good.

  The thickness of the coating film of the block copolymer is not particularly limited, but is preferably 10 μm to 1000 μm, and more preferably 50 μm to 500 μm. If the thickness of the coating film is less than 10 μm, the form as a polymer electrolyte film may not be maintained. On the other hand, if the thickness of the coating film is greater than 1000 μm, a non-uniform polymer electrolyte membrane is easily formed.

  The support used in this step is not particularly limited as long as it does not dissolve in the solvent used to dissolve or disperse the block copolymer or the random copolymer described below, but it is flat and flexible. Those are preferred. For example, resin films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, polyamide, polyimide, polyamideimide, polyaramid, and polybenzazole, and inorganic compounds such as silica, titania, and zirconia are coated on the surface. Or a film made of a metal such as stainless steel. From the viewpoints of heat resistance and solvent resistance, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, polyamide, polyimide, and polyaramid are preferable, and polyethylene terephthalate is more preferable from the viewpoint of cost and quality.

(Step of forming a coating film of random copolymer)
By this step, since the surface of the block copolymer coating film is coated with the random copolymer coating film, the block copolymer coating film can be prevented from coming into contact with the atmosphere (hydrophobic atmosphere). .

  Examples of the solvent used in this step include the solvents exemplified as those that can be used to dissolve or disperse the block copolymer. The solvent used in this step may be the same as or different from the solvent used to dissolve or disperse the block copolymer.

  About the solid content concentration and viscosity of the solution of a random copolymer, the suitable range of solid content concentration and the viscosity of the solution of a block copolymer can be used.

  As a method of applying the random copolymer solution, the application method exemplified as the method of applying the block copolymer solution can be used.

  The thickness of the coating film of the random copolymer is not particularly limited, but is preferably 0.2 μm to 100 μm, and more preferably 0.5 μm to 80 μm. If the thickness of the coating film is thinner than 0.2 μm, it may be difficult to form the coating film of the random copolymer. Further, there are cases where contact between the coating film of the block copolymer and the atmosphere cannot be effectively prevented. If the thickness of the coating film is greater than 100 μm, the random copolymer cancels the block copolymerization characteristics, and a polymer electrolyte membrane having excellent proton conductivity may not be obtained.

  In the case where the production method of the present invention is continuously performed, in order to form a random copolymer coating film on the block copolymer coating film, a random copolymer solution coating means is used. What is necessary is just to distribute | arrange to the downstream of the application | coating means of this solution. Further, by using a multi-layer slot die, the block copolymer solution is extruded from the upstream slit in the flow direction of the support, and the random copolymer solution is extruded from the downstream slit. The coating film and the block copolymer coating film can be formed and laminated almost simultaneously.

(Process of applying a random copolymer solution to the support)
In the production method of the present invention, the step of forming a coating film of the block copolymer firstly applies a random copolymer solution to a support to form a random copolymer coating film, The coating film may be applied by applying a solution of a block copolymer.

  Since the support is also a hydrophobic substance, when a coating film of a block copolymer is formed immediately above the support, hydrophobic segments are collected on the contact surface between the coating film of the block copolymer and the support. Thus, in the electrolyte membrane obtained using such a coating membrane, the hydrophobic segment is unevenly distributed on at least one surface thereof, and proton conductivity in the film thickness direction may be lowered. On the other hand, if the coating film of the block copolymer is formed on the support through the coating film of the random copolymer, it is possible to prevent the coating film of the block copolymer from coming into contact with the support. Therefore, the problem can be solved.

  Examples of the random copolymer used in this step include a random copolymer used for forming a coating film of a random copolymer on a coating film of a block copolymer. These random copolymers may be the same as or different from each other.

  As a method of applying the random copolymer solution directly on the support, a method used when applying the random copolymer solution to the block copolymer coating film can be used.

  For the thickness of the coating film of the random copolymer, a suitable range of the thickness of the coating film of the random copolymer formed on the coating film of the block copolymer can be used.

  When the production method of the present invention is carried out continuously, the means for applying the random copolymer solution to the support may be arranged upstream of the means for applying the block copolymer solution. Alternatively, by using a multilayer (three-layer) slot die, each solution of a random copolymer, a block copolymer, and a random copolymer is extruded from each slit in order from the upstream side in the flow direction of the support. The upper and lower layers of the random copolymer coating film and the block copolymer coating film can be formed and laminated almost simultaneously.

(Step of forming a random copolymer film on the support)
In the production method of the present invention, the random copolymer solution is applied to the support as described above to form a random copolymer coating film, and then the solvent is removed from the coating film to remove the random copolymer. Alternatively, a united film may be formed, and a solution of a block copolymer may be applied to the random copolymer film.

  As a method for removing the solvent from the coating film of the random copolymer formed on the support, a conventionally known method can be used. For example, the coating film can be heated, dried under reduced pressure, or mixed with a solvent in the coating film, and the coating film is immersed in a poor solvent such as a block copolymer or a random copolymer. When the solvent is an organic solvent, the solvent is preferably distilled off by heating or drying under reduced pressure.

(Process to remove solvent)
By removing the solvent from the coating film obtained through the above steps, a polymer electrolyte membrane can be obtained.

  The method for removing the solvent from the coating film is not particularly limited, but heating the coating film is preferable because a uniform polymer electrolyte membrane can be obtained. Further, in order to avoid decomposition or alteration of the block copolymer or random copolymer, the block copolymer or the random copolymer may be heated at a temperature as low as possible under reduced pressure.

  In order to make the distribution in the film thickness direction of the hydrophobic segment and the hydrophilic segment uniform, the removal rate of the solvent from the coating film may be adjusted. For example, when removing the solvent by heating, there is a method of lowering the evaporation rate by lowering the temperature in the first stage.

  The heating temperature of the coating film is preferably not more than the boiling point of the solvent, more preferably not more than 300 ° C or not more than 200 ° C. When the heating temperature exceeds 300 ° C., the solvent removal efficiency is improved, but the solvent or block copolymer may be decomposed or altered, and the resulting polymer electrolyte membrane may be deteriorated in form. Moreover, about the minimum of heating temperature, 50 degreeC is preferable. If the heating temperature is less than 50 ° C., it may be difficult to remove the solvent sufficiently. The heating method can be performed by any known method such as hot air, infrared rays, and microwaves. Moreover, you may carry out in inert gas atmosphere, such as nitrogen.

(Acid treatment process)
When the block copolymer or random copolymer used in the present invention has a sulfonic acid group, the sulfonic acid group of the polymer electrolyte membrane may be a salt with a cation. It may be converted to free sulfonic acid.

  Conversion of the sulfonic acid group to sulfonic acid involves immersing the polymer electrolyte membrane in an aqueous solution of at least one acidic component selected from sulfuric acid, hydrochloric acid, methanesulfonic acid, trifluoroacetic acid, etc. at room temperature or under heating. And the method to be performed. The concentration of the acidic component in the aqueous solution is preferably in the range of 1% by mass to 75% by mass. If the concentration is less than 1% by mass, a large amount of aqueous solution is required for conversion to protons, which may cause problems in productivity. If the concentration exceeds 75% by mass, the dissociation degree of the acidic component in the aqueous solution may decrease, and the conversion efficiency may decrease.

(Washing process)
If the acidic component remains in the polymer electrolyte membrane by contact with the aqueous solution of the acidic component, the polymer electrolyte membrane is immersed in a poor solvent for the polymer electrolyte membrane that can dissolve the acidic component, You may perform operation which removes the acidic component in a molecular electrolyte. Examples of the poor solvent used include water, alcohols, ketones, ethers, low molecular hydrocarbons, and halogen-containing solvents. When the acidic component is dissolved in water, it is preferable to use water.

(Drying process)
If the poor solvent of the polymer electrolyte membrane remains in the polymer electrolyte membrane obtained through the above steps, the polymer electrolyte membrane will have poor morphology such as wrinkles and irregularities, adhesion, deformation due to evaporation and leaching of the solvent. There is a high possibility that such problems will occur. For this reason, it is preferable to reduce the amount of solvent remaining in the polymer electrolyte membrane.

  The method for drying the polymer electrolyte membrane is not particularly limited, and examples thereof include air drying at an appropriate temperature, heating with infrared rays or far infrared rays, and distillation under reduced pressure. A drying temperature is not specifically limited, For example, what is necessary is just to perform at 20-50 degreeC.

(Polymer electrolyte membrane)
Whether the polymer electrolyte membrane obtained by the production method of the present invention has two layers or three layers, the mass ratio of the total amount of the block copolymer and the random copolymer is 99/1 to 1/99 ( More preferably 98/2 to 75/25, still more preferably 97/3 to 50/50). When the ratio of the block copolymer is too large (when the mass ratio is more than 99/1), the ratio of the random copolymer is relatively decreased, and it may be difficult to apply a thin layer of the random copolymer solution. is there. When the ratio of the block copolymer is too small (when the mass ratio is less than 1/99), the random copolymer cancels out the characteristics of the block copolymer, and the polymer has excellent proton conductivity in the film thickness direction. An electrolyte membrane may not be obtained.

  The shape of the polymer electrolyte membrane obtained by the production method of the present invention is not particularly limited, and may be any form such as a sheet or a roll. In addition, the support used in producing the polymer electrolyte membrane may not be peeled off, but it is preferable to peel after the production and to laminate the polymer electrolyte membrane with another support because the workability is improved. Another support includes a resin film having an adhesive layer. Examples of such a resin film include, but are not limited to, those made of crystallized polyolefin, amorphous polyolefin, polyester, and the like. Examples of the adhesive layer include, but are not limited to, an acrylic resin adhesive, a polyethylene-vinyl alcohol adhesive, a silicone adhesive, a modified polyolefin resin adhesive, and the like. The new support can be laminated on one or both sides of the polymer electrolyte membrane. When laminating a new support only on one side of the polymer electrolyte membrane, it is preferable to wrap the polymer electrolyte membrane on the inside because it is less affected by changes in humidity during transportation and storage. .

(Characteristics of polymer electrolyte membrane)
<Film thickness>
The polymer electrolyte membrane obtained by the production method of the present invention can have any film 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 10 to 70 μm. If the thickness of the polymer electrolyte membrane is less than 5 μm, handling of the polymer electrolyte membrane becomes difficult, and a short circuit may occur when a fuel cell is produced. On the other hand, if the thickness is greater than 200 μm, the electric resistance value of the polymer electrolyte membrane may increase and the power generation performance of the fuel cell may deteriorate.

  The polymer electrolyte membrane is composed of a random copolymer-derived electrolyte membrane with respect to the thickness of the block copolymer-derived electrolyte membrane (an electrolyte membrane derived from a random copolymer on both sides of an electrolyte membrane derived from a block copolymer). Is a total film thickness) ratio (block copolymer film thickness / random copolymer film thickness) of 99/1 to 1/99 (more preferably 98/2 to 75/25, Preferably 97/3 to 50/50). When the block copolymer film thickness is too thick (when the ratio is more than 99/1), the random copolymer film thickness becomes relatively thin, and it may be difficult to form a random copolymer coating film. is there. When the block copolymer film thickness is too thin (when the above ratio is less than 1/99), the random copolymer cancels out the block copolymer characteristics, and the polymer electrolyte has excellent proton conductivity in the film thickness direction. A film may not be obtained.

<Ion exchange capacity>
The polymer electrolyte membrane ion exchange capacity is preferably 0.5 meq / g to 2.7 meq / g, more preferably 0.7 meq / g to 2.5 meq / g. When the ion exchange capacity is less than 0.5 meq / g, the transportability of magnesium ions may be lowered, and the battery performance may be lowered. When the ion exchange capacity exceeds 2.7 meq / g, the form-retaining property of the polymer electrolyte membrane is poor, and it may be difficult to manufacture the battery.

(Structure of hydrocarbon polymer electrolyte)
The hydrocarbon polymer electrolyte produced in the present invention is preferably an aromatic polymer electrolyte having a main chain skeleton mainly composed of aromatic groups. An example of the aromatic polymer electrolyte is an aromatic hydrocarbon polymer having an ionic group. As such a polymer, at least one selected from an aromatic or aromatic ring and ether bond, sulfone bond, imide bond, ester bond, amide bond, urethane bond, sulfide bond, carbonate bond and ketone bond in the polymer main chain. Non-fluorinated or partially fluorinated ion-conducting polymers having the structure having the above-mentioned bonding groups can be mentioned. Specifically, for example, polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, polyphenylquinoxaline, polyaryl ketone, polyether ketone, polybenzoxazole, polybenz Examples thereof include polymers in which an ionic group is introduced into a polymer containing at least one component such as thiazole, polybenzimidazole, and polyimide. The above polysulfone, polyethersulfone, polyetherketone, etc. are generic names for polymers having a sulfone bond, an ether bond, and a ketone bond in their molecular chains. Polyetherketoneketone, polyetheretherketone, polyetheretherketone It includes ketones, polyether ketones, ether ketone ketones, polyether ketone sulfones, etc., and is not limited to a specific polymer structure.

  Examples of the ionic group include at least one of a sulfonic acid group, a phosphonic acid group, a carboxyl group, a sulfonamide group, a sulfonimide group, and derivatives thereof, and a sulfonic acid group or a phosphonic acid group is preferable.

  Among the above polymers, a polymer having a sulfonic acid group on the aromatic ring can be obtained by reacting a suitable sulfonating agent with a polymer having a skeleton as in the above example. As such a sulfonating agent, for example, one using concentrated sulfuric acid or fuming sulfuric acid which has been reported as an example of introducing a sulfonic acid group into an aromatic hydrocarbon-based polymer (for example, SolidState Ionics, 106, P 219 (1998)), those using chlorosulfuric acid (for example, J. Polym. Sci., Polym. Chem., 22, P. 295 (1984)), those using anhydrous sulfuric acid complex (for example, J. Polym. Sci., Polym. Chem., 22, P. 295 (1984)). Polym. Sci., Polym. Chem., 22, P.721 (1984), J. Polym.Sci., Polym.Chem., 23, P.1231 (1985)) and the like are effective. In order to obtain an ionic group-containing polymer, particularly a polymer having ionic acid conductivity as a sulfonic acid group, these reagents can be used and reaction conditions corresponding to each polymer can be selected. Moreover, it is also possible to use the sulfonating agent described in Japanese Patent No. 2884189.

  The aromatic hydrocarbon polymer having an ionic group can also be synthesized using a monomer containing an acidic group as at least one of monomers used for polymerization. For example, in a polyimide synthesized from an aromatic diamine and an aromatic tetracarboxylic dianhydride, an acidic group-containing polyimide is obtained by using a diamine containing a sulfonic acid group or a phosphonic acid group as at least one of the aromatic diamines. I can do it. Polybenzoxazole synthesized from aromatic diamine diol and aromatic dicarboxylic acid, polybenzthiazole synthesized from aromatic diamine dithiol and aromatic dicarboxylic acid, polybenzimidazole synthesized from aromatic tetramine and aromatic dicarboxylic acid In this case, an acidic group-containing polybenzoxazole, polybenzthiazole, or polybenzimidazole can be obtained by using a sulfonic acid group-containing dicarboxylic acid or a phosphonic acid group-containing dicarboxylic acid as at least one kind of aromatic dicarboxylic acid. Polysulfone, polyethersulfone, polyetherketone, etc. synthesized from aromatic dihalide and aromatic diol are synthesized by using sulfonic acid group-containing aromatic dihalide or sulfonic acid group-containing aromatic diol as at least one monomer. be able to. At this time, it is preferable to use a sulfonic acid group-containing dihalide rather than a sulfonic acid group-containing diol because the degree of polymerization tends to be high and the thermal stability of the obtained acidic group-containing polymer is high.

  The aromatic hydrocarbon polymer having an ionic group may have some higher order structure. Among these, durability and proton conductivity can be achieved by using a polymer that forms a co-continuous structure by phase separation of the hydrophilic part and the hydrophobic part, such as a block copolymer or a polymer in which an ionic group is introduced into the side chain. Is more preferable. Such a block copolymer can include a segmented block copolymer comprising a hydrophilic segment having an ionic group and a hydrophobic segment having no ionic group, and produces such a polymer. As a means to do this, it can be mentioned that the oligomer constituting the segment is obtained directly or by reacting with another compound.

  Aromatic hydrocarbon polymers having ionic groups include polysulfene group-containing polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyphenylene sulfide sulfone, polyarylene ether compounds such as polyether ketone polymers, and polyarylene compounds. It is more preferable that

  Hereinafter, specific embodiments of the hydrocarbon-based polymer electrolyte having the above structure will be described.

(Block copolymer)
As the block copolymer having a hydrophobic segment and a hydrophilic segment used in the production method of the present invention, a hydrophobic segment represented by the following chemical formula 1,

(Chemical formula 1)

(In the formula, each Z independently represents an O atom or an S atom, Ar ¹ independently represents a divalent aromatic group, and n represents a number of 1 to 100, respectively.)
The hydrophilic segment represented by the following chemical formula 2

(Chemical formula 2)

Wherein X is independently H or a monovalent cation, Y is a sulfonyl group or carbonyl group, Ar ² is independently a divalent aromatic group, and L is independently O. An atom or an S atom, m represents a number of 1 to 100, respectively)
Examples thereof include a block copolymer bonded with a group represented by the following chemical formula 3.

(Chemical formula 3)

(In the formula, p represents 0 or 1, and when p is 1, W represents one or more selected from the group consisting of a direct bond, a sulfonyl group, and a carbonyl group.)
Hereinafter, each segment which comprises the said block copolymer, its manufacturing method, and the manufacturing method of the copolymer using the said segment are demonstrated.

(Hydrophobic segment)
The structure of the hydrophobic segment constituting the block copolymer exhibits swelling resistance when the obtained polymer electrolyte membrane is immersed in hot water.

(Chemical formula 1)

(In the formula, each Z independently represents an O atom or S atom, Ar ¹ independently represents a divalent aromatic group, and n represents a number of 1 to 100, respectively). It is preferable that

  In Chemical Formula 1, Z is preferably an O atom from the viewpoint of availability of raw materials and ease of synthesis. However, when Z is an S atom, the oxidation resistance of the polymer electrolyte membrane may be improved.

Ar ¹ may be any known divalent aromatic group mainly composed of an aromatic group, and examples thereof include divalent aromatic groups represented by the following chemical formulas 5A to 5P. .

(In the formula, R represents a methyl group, and q represents an integer of 0 to 2, respectively.)

In Chemical Formulas 5A to 5P, when q is 1 or 2, it may be difficult to obtain a high molecular weight hydrophobic segment, and therefore q is preferably 0. Ar ¹ is more preferably a divalent aromatic group represented by the chemical formulas 5A, 5C, 5E, 5F, 5K, 5M, and 5N, represented by the following chemical formulas 5A ′, 5F ′, and 5M ′. The divalent aromatic group is more preferably a divalent aromatic group represented by the chemical formula 5A ′. Ar ¹ may be composed of different divalent aromatic groups. In that case, in order to show more excellent characteristics, it preferably contains at least one of the divalent aromatic groups represented by the chemical formulas 5A ′, 5F ′, and 5M ′. It is more preferable that any of the bivalent aromatic groups represented by these is included. When a divalent aromatic group represented by the chemical formula 5A ′ is contained, a polymer electrolyte membrane excellent in swelling resistance and durability can be obtained. When a divalent aromatic group represented by the chemical formula 5M ′ is contained, a polymer electrolyte membrane having excellent durability can be obtained.

  In Chemical Formula 1, n represents a number from 1 to 100. It should be noted that n should be an integer in the case of individual hydrophobic segments, but when there is a distribution in the molecular weight of the segments within or between molecules, if n is an average value, n is not necessarily an integer. Disappear. Therefore, when defining the structure of the copolymer, it is substantially effective to express the average value. n can be determined by any known method such as NMR or gel permeation chromatography. n is preferably 10 to 70, and more preferably 20 to 60. When n is 20 to 60, a polymer electrolyte membrane with further improved proton conductivity and durability can be obtained. If n is less than 1, the swellability of the polymer electrolyte membrane may be excessively increased or the durability may be reduced. When n exceeds 100, it may be difficult to control the molecular weight of the hydrophobic segment, and it may be difficult to synthesize a block copolymer having a designed structure.

(Method for producing hydrophobic segment)
The method for producing the hydrophobic segment (hydrophobic oligomer) is not particularly limited. For example, a monomer represented by the following chemical formula 6A or 6B is converted into various bisphenols or various bisthiophenols (for example, the above chemical formula 5A). It can be synthesized by reacting with a compound having both ends of ˜5M ′ at the OH group or SH group.

  In that case, it is preferable that various bisphenols or various bisthiophenols are excessive so that the terminal group of the oligomer is an OH group or an SH group. The degree of polymerization of the oligomer can be adjusted by the molar ratio of the monomer of chemical formula 6A or 6B and various bisphenols or various bisthiophenols.

  The monomer of formula 6A or 6B and various bisphenols or various bisthiophenols can be reacted by any known method, but they can be reacted by an aromatic nucleophilic substitution reaction in the presence of a basic compound. Is preferred.

  Although reaction temperature can be performed in 0-350 degreeC, it is preferable to carry out in 50-250 degreeC. When the reaction temperature is lower than 0 ° C, the reaction may not proceed sufficiently, and when it is higher than 350 ° C, the oligomer may 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 aprotic polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, and sulfolane. It is not limited to this, and any material that can be used as a stable solvent in the aromatic nucleophilic substitution reaction may be used. These solvents may be used alone or in combination of two or more.

  When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge monomers and the like such that the resulting oligomer concentration is 1 to 25% by mass, more preferably 5 to 15% by mass. If it is less than 1% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, when it exceeds 25 mass%, an oligomer may precipitate and reaction may stop.

  The basic compound is not particularly limited as long as it can form various bisphenols and various bisthiophenols into an active phenoxide structure or thiophenoxide structure. For example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate , Sodium hydrogen carbonate, potassium hydrogen carbonate and the like.

  Water generated as a by-product during the reaction is removed by distilling it off with an azeotropic solvent such as toluene, or by using a water-absorbing material such as molecular sieve, or by distilling it off with a polymerization solvent. can do.

  The inorganic salt produced as a by-product during the reaction can be removed by any known method such as dropping the reaction solution into a poor solvent of the hydrophobic oligomer or washing the hydrophobic oligomer with the poor solvent. Examples of the poor solvent for the oligomer include water and an arbitrary organic solvent, and water is preferable for removing the inorganic salt. As the poor solvent to which the reaction solution is first dropped, either water or an organic solvent may be used.

  The organic solvent for the poor solvent can be selected from any organic solvent, but is preferably miscible with the aprotic polar solvent used in the reaction. Examples thereof include ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, dibutyl ketone, dipropyl ketone, diisopropyl ketone, and cyclohexanone, and alcohol solvents such as methanol, ethanol, propanol, isopropanol, and butanol. These organic solvents may be used alone or in combination of two or more.

  It is preferable to remove the organic solvent used in the synthesis and purification as much as possible. The removal of the organic solvent is preferably performed by drying, and more preferably, the hydrophobic oligomer is dried under reduced pressure at a temperature in the range of 10 to 150 ° C.

(Hydrophilic segment)
The structure of the hydrophilic segment constituting the block copolymer has the following chemical formula 2

(Chemical formula 2)

Wherein X is independently H or a monovalent cation, Y is a sulfonyl group or carbonyl group, Ar ² is independently a divalent aromatic group, and L is independently O. An atom or an S atom is preferably represented by m represents a number of 1 to 100.

  In Chemical Formula 2, it is preferable that X is H because proton conductivity increases. When processing and molding the block copolymer, it is preferable that X is a monovalent metal ion such as Na, K, or Li because the stability of the copolymer is increased. X may be an organic cation such as monoamine.

  In Formula 2, it is preferable that Y is a sulfonyl group because the solubility of the block copolymer in a solvent tends to increase.

Ar ² may be any known divalent aromatic group mainly composed of aromatic groups, and examples thereof include divalent aromatic groups represented by the following chemical formulas 4A to 4C. A divalent aromatic group represented by 4B is preferable because of excellent swelling resistance and polymerization reactivity.

(In the formula, L ′ represents a sulfide group or a sulfonyl group.)

  In Chemical Formula 2, m represents a number from 1 to 100. For the same reason as n in Chemical Formula 1, when defining the structure of the copolymer, it is substantially effective to express m as an average value. m can be determined by any known method such as NMR or gel permeation chromatography. m is preferably 3 to 70, and more preferably 10 to 55. When m is less than 1, it is not preferable because only the same characteristics as a film made of a random copolymer can be obtained. If m exceeds 100, it may be difficult to synthesize a copolymer having a designed structure.

(Method for producing hydrophilic segment)
The method for producing the hydrophilic segment (hydrophilic oligomer) is not particularly limited. For example, the sulfonated monomer represented by the following chemical formula 7 is reacted with various bisphenols or various bisthiophenols for synthesis. Can do. In addition, a dihalide such as 4,4′-dichlorodiphenylsulfone or 2,6-dichlorobenzonitrile is reacted with a sulfonated monomer represented by the following chemical formula 7 and reacted with various bisphenols or various bisthiophenols. May be synthesized.

(Chemical formula 7)

  In Chemical Formula 7, X represents H or a monovalent cation, Y represents a sulfonyl group or a carbonyl group, and A represents a halogen element. X is preferably Na or K, and A is preferably F or Cl, respectively. Moreover, it is preferable that various bisphenols or various bisthiophenols are excessive so that the terminal group of the oligomer is an OH group or an SH group. The degree of polymerization of the oligomer can be adjusted by the molar ratio of the monomer of formula 7 and various bisphenols or various bisthiophenols.

  Although the monomer of Chemical formula 7 and various bisphenols or various bisthiophenols can be reacted by any known method, it is preferably reacted by an aromatic nucleophilic substitution reaction in the presence of a basic compound. .

  Regarding the reaction temperature, the basic compound that can be used, and the method for removing water produced as a by-product, the reaction temperature, basic compound, and removal method that can be used in the production of the hydrophobic segment can be used.

  When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to prepare monomers and the like so that the resulting oligomer concentration is 5 to 50% by mass, and more preferably 20 to 40% by mass. If it is less than 5% by mass, the degree of polymerization tends to be difficult to increase. On the other hand, if it exceeds 50% by mass, the reaction system tends to be too viscous to make post-treatment of the reaction product difficult.

  The inorganic salt produced as a by-product during the reaction can be removed by any known method such as filtration of the reaction solution, decantation after centrifugal sedimentation, dialysis or salting out after adding water to the reaction solution. Filtration is preferable in terms of production efficiency and yield. When the inorganic salt is removed by filtration or centrifugal sedimentation, the hydrophilic oligomer can be recovered by dropping the reaction solution into a poor solvent for the hydrophilic oligomer. When the inorganic salt is removed by dialysis, the hydrophilic oligomer can be recovered by evaporation to dryness, and when the inorganic salt is removed by salting out, the hydrophilic oligomer can be recovered by filtration.

  The isolated hydrophilic oligomer is preferably purified by washing with a poor solvent, reprecipitation, dialysis or the like, and washing is preferred from the viewpoint of work efficiency and purification efficiency. As a poor solvent, the poor solvent enumerated as what can be used in the case of manufacture of a hydrophobic oligomer can be used.

  It is preferable to remove the organic solvent used in the synthesis and purification as much as possible. The removal of the organic solvent is preferably performed by drying, and more preferably dried under reduced pressure at 10 to 150 ° C.

(Linking group)
In the block copolymer, the hydrophobic segment and the hydrophilic segment have the following chemical formula 3

(Chemical formula 3)

(Wherein p represents 0 or 1, and when p is 1, W represents one or more selected from the group consisting of a direct bond (single bond), a sulfonyl group, and a carbonyl group). It is preferable that it is couple | bonded with group. With this configuration, it is possible to obtain a polymer electrolyte membrane having high swelling resistance against hot water.

  In Chemical Formula 3, when p is 0, synthesis of the block copolymer is somewhat difficult, and therefore, p is preferably 1. When W is a direct bond between benzene rings, the characteristics and durability of the polymer electrolyte membrane can be improved. When W is a sulfonyl group, side reactions during the synthesis of the block copolymer can be reduced.

(Block copolymer structure)
The block copolymer used in the present invention includes, in the molecule, at least one hydrophobic segment represented by the above chemical formula 1, at least one hydrophilic segment represented by the above chemical formula 2, and the above chemical formula 3. It is preferable that it is a di- or multiblock copolymer having a connecting group. A multi-block copolymer is particularly preferable because the strength of the polymer electrolyte membrane is improved.

  As the block copolymer in which the hydrophobic segment and the hydrophilic segment are bonded to each other via the linking group, for example, the hydrophilic segment and the hydrophobic segment are alternately connected via the linking group. And a block copolymer in which each segment is randomly connected and the hydrophilic segment and the hydrophobic segment are connected via a connecting group.

  Since the hydrophilic segment is highly water-soluble, a block (co) polymer consisting only of the hydrophilic segment may cause problems such as elution when used as a polymer electrolyte membrane. For this reason, the block copolymer of this invention needs to contain the hydrophilic segment and the hydrophobic segment in a molecule | numerator. The content of the hydrophilic segment in the block copolymer is preferably 10% by mass to 70% by mass, and more preferably 30% by mass to 60% by mass. When the content of the hydrophilic segment is less than 10% by mass, proton conductivity may be significantly reduced. When the content of the hydrophilic segment exceeds 70% by mass, the swellability with respect to water increases, and the film strength may be significantly reduced.

  In the block copolymer, the value of m / n, which is the molar ratio of the hydrophilic segment to the hydrophobic segment, is preferably 0.4 to 1.5 (more preferably 0.6 to 1.3). When in this range, the polymer is suitable for a proton conducting membrane. When the value of m / n is less than 0.4, the output of the fuel cell may be significantly reduced, and when the value of m / n is more than 1.5, the swelling of the electrolyte membrane may be significantly increased.

In addition, although the molecular weight of each segment (oligomer) can be calculated | required by well-known arbitrary methods, such as a gel permeation chromatography method, it is preferable to quantitate a terminal group and to obtain | require a number average molecular weight. The end group can be quantified by any known method such as titration, colorimetric method, labeling method, NMR method, elemental analysis, but is preferable because the NMR method is simple and excellent in accuracy. ¹ H-NMR The method is more preferred.

  The hydrophobic oligomer constituting the block copolymer is characterized by having a benzonitrile structure, but due to its structure, the solubility in a solvent is poor. Therefore, in the case of NMR measurement, if it is not dissolved in a suitable deuterated solvent, deuterated dimethyl sulfoxide is added to a solution dissolved in a normal solvent in which a hydrophobic oligomer is dissolved, such as N-methyl-2-pyrrolidone. It is preferable to measure by adding a deuterated solvent such as

  The sulfonic acid group of the block copolymer may be an acid or a salt with a cation, but is preferably a salt with a cation from the viewpoint of the stability of the sulfonic acid group. Conversion to an acid when the sulfonic acid group is a salt can be performed, for example, by acid treatment after molding.

(Characteristics of block copolymer)
The block copolymer has a logarithmic viscosity measured at 30 ° C. of a 0.5 g / dL solution using N-methyl-2-pyrrolidone as a solvent in a range of 0.5 to 5.0 dL / g. preferable. When the logarithmic viscosity is less than 0.5 dL / g, it may be difficult to mold into a film due to poor moldability. On the other hand, when the logarithmic viscosity exceeds 5.0 dL / g, the viscosity of the solution in which the block copolymer is dissolved becomes too high, which adversely affects workability. The logarithmic viscosity is more preferably in the range of 1.0 to 4.0 dL / g, and still more preferably in the range of 1.5 to 3.5 dL / g.

(Method for producing block copolymer)
The block copolymer can be synthesized by any known method. For example, it can be produced by combining a previously synthesized hydrophilic oligomer and hydrophobic oligomer with a linking agent. The molar ratio of the linking agent to the sum of both oligomers is preferably close to 1.

  It can also be produced by modifying one end group of a previously synthesized hydrophilic oligomer or hydrophobic oligomer with a linking agent and then reacting the other oligomer. In this case, the modified oligomer and the other oligomer are preferably reacted in an equimolar amount. However, in order to prevent gelation due to a side reaction during the reaction, it is preferable that the modified oligomer is slightly excessive. The degree of excess varies depending on the molecular weight of the oligomer and the molecular weight of the target copolymer, but is preferably in the range of 0.1 mol% to 50 mol%, and in the range of 0.5 mol% to 10 mol%. More preferably. In addition, the hydrophobic oligomer is preferably modified with the linking agent. Depending on the structure of the hydrophilic oligomer, the modification reaction may not proceed well.

  Examples of the linking agent that bonds oligomers or modifies the end of one oligomer include compounds having structures represented by the following chemical formulas 9A to 9D. Among them, compounds of chemical formulas 9A and 9B are preferred, More preferred are compounds.

  As the hydrophobic oligomer and the hydrophilic oligomer, one or more kinds of oligomers selected from the group consisting of oligomers having different structures, molecular weights, and molecular weight distributions can be used.

  The block copolymer may be produced using an oligomer purified and isolated after oligomer synthesis or using a solution of this oligomer. Moreover, you may manufacture a block copolymer using an unpurified thing (reaction solution after oligomer synthesis | combination). Any oligomer may be purified and isolated, but a hydrophobic oligomer is preferred because it is easier.

  In the production of the block copolymer, the sulfonic acid group in the hydrophilic oligomer is preferably an alkali metal salt, more preferably Na or K. When ions forming a salt with a sulfonic acid group are of a plurality of types, an accurate molecular weight can be obtained by analyzing the composition in advance by elemental analysis. Alternatively, the hydrophilic oligomer may be once treated with an excess of acid and then treated with a metal salt or an alkali metal hydroxide to form one kind of ion that forms a salt with a sulfonic acid group. The hydrophilic oligomer is preferably dried immediately before the synthesis of the block copolymer to remove the adsorbed moisture. Drying may be performed by heating the hydrophilic oligomer to 100 ° C. or higher, and it is more preferable to dry under reduced pressure.

  The linking agent used for the production of the block copolymer is preferably an aromatic linking agent substituted with fluorine. This is because fluorine is highly reactive and can suppress side reactions such as a decrease in segment length. The aromatic linking agent preferably has 3 or more fluorine atoms in one molecule, more preferably 2 or more fluorine atoms are adjacent to each other, and is a perfluoro compound. More preferred. This is because the reactivity is higher.

  The aromatic coupling agent may have an electron-withdrawing property as a substituent, and the electron-withdrawing group is preferably in the ortho position or the para position with respect to the fluorine atom. Examples of the electron withdrawing group include a cyano group, a sulfonyl group, a sulfinyl group, and a carbonyl group.

  Examples of the aromatic linking agent include a single aromatic ring (which may have an electron-withdrawing group as a substituent), or an aromatic ring in which a plurality of aromatic groups are linked with an electron-withdrawing group. Mention may be made of perfluorinated compounds. Specific examples include hexafluorobenzene, decafluorobiphenyl, decafluorobenzophenone, decafluorodiphenyl sulfone, and pentafluorobenzonitrile. Decafluorobiphenyl and decafluorodiphenyl sulfone are preferable, and decafluorobiphenyl is more preferable. These linking agents may be used alone or in combination of two or more.

  In addition, compounds in which some of the fluorine atoms in these compounds are substituted can be used as a linking agent. Examples of the substituent for the fluorine atom include a hydrogen atom, other halogen atoms such as chlorine, bromine and iodine, hydrocarbon groups such as a phenoxy group, a phenyl group and a methyl group.

  When a block copolymer is produced by combining a hydrophilic oligomer and a hydrophobic oligomer with a linking agent, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide In the presence of a basic compound such as potassium carbonate or sodium carbonate in an aprotic polar solvent such as diphenylsulfone or sulfolane in an amount of 1 to 5 moles of the oligomeric phenol or thiophenol end, potassium carbonate or sodium carbonate The reaction is preferably carried out at a temperature of 70 ° C to 130 ° C.

  The reaction is preferably carried out under an inert gas stream such as nitrogen. The solid concentration in the reaction solution may be 1% by mass to 25% by mass, but it is preferably 5% by mass to 20% by mass considering the poor solubility of the reactive and hydrophobic oligomers. . Most preferably, it is 8 mass%-15 mass%. The solid content concentration here is the concentration of the block copolymer in the solution. Whether or not the hydrophobic oligomer is dissolved can be determined by whether it is transparent by visual inspection or not.

  The degree of polymerization of the block copolymer and the content of the hydrophilic segment and the hydrophobic segment in the block copolymer can be adjusted by the molar ratio of the oligomer used in the reaction. Alternatively, the end point may be determined from the viscosity of the reaction solution, and the polymerization degree may be adjusted by stopping the polymerization reaction by cooling or stopping the end.

  Isolation and purification of the block copolymer from the reaction solution can be performed by any known method. For example, there is a method of solidifying the block copolymer by dropping the reaction solution into a poor solvent of the block copolymer such as water, acetone or methanol. As the poor solvent, water is preferable because it is easy to handle and inorganic salts can be removed. Further, in order to remove residual oligomer components and highly hydrophilic components, hot water at 60 ° C. to 100 ° C., water and organic solvents (ketone solvents such as acetone, alcohol solvents such as methanol, ethanol, and isopropanol). It is preferable to wash with a mixed solvent or the like.

  The block copolymer of the present invention can also be used as a composition by mixing a third component. Examples of the third component include fibrous substances; heteropolyacids such as phosphotungstic acid and phosphomolybdic acid; acidic compounds such as low-molecular sulfonic acid, phosphonic acid and phosphoric acid derivatives; silicic acid compounds and zirconium phosphoric acid. Can be mentioned. The content of the third component is preferably less than 50% by mass in the composition. If it is 50% by mass or more, the physical properties of the molded product may be impaired. As the third component, a fibrous substance is preferable in order to suppress the swellability of a molded product obtained using the composition, and an inorganic fibrous substance such as potassium titanate fiber is more preferable.

  Moreover, it can replace with the said 3rd component or it can replace with a 3rd component, and can also be used as a composition which mixed the other polymer. Examples of these polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 6,6, nylon 6,10, and nylon 12; poly (meth) acrylic acid ester Acrylate resins such as polyphenols; poly (meth) acrylic acid resins; various polyolefins including diene polymers such as polyethylene, polypropylene and polystyrene; polyurethane resins; cellulose resins such as cellulose acetate and ethyl cellulose; polyarylate, aramid, Polycarbonate, polyphenylene sulfide, polyphenylene oxide, polysulfone, polyethersulfone, polyetheretherketone, polyetherimide, polyimide, polyamide , Polybenzimidazole, polybenzoxazole, aromatic polymers such as poly benzthiazole; epoxy resins, phenolic resins, novolak resins, thermosetting resins such as benzoxazine resins.

  When using a block copolymer as a composition, it is preferable that the block copolymer of this invention is contained 50 to 100 mass% of the whole composition. More preferably, it is 70 mass% or more and less than 100 mass%. When the content of the block copolymer is less than 50% by mass of the entire composition, the sulfonic acid group concentration of the polymer electrolyte membrane obtained using this composition is low, and good proton conductivity cannot be obtained. In some cases, the unit containing a sulfonic acid group becomes a discontinuous phase and the mobility of ions to be conducted is lowered.

  The composition of the present invention can be used as necessary, for example, antioxidants, heat stabilizers, lubricants, tackifiers, plasticizers, crosslinking agents, viscosity modifiers, antistatic agents, antibacterial agents, antifoaming agents, and dispersing agents. Various additives such as a polymerization inhibitor may be included.

(Random copolymer)
The random copolymer used in the production method of the present invention is not particularly limited as long as it can prevent the coating film of the block copolymer from coming into contact with a hydrophobic substance such as the air or a support. In order that the electrolyte membrane derived from the copolymer has proton conductivity, a hydrocarbon polymer having a sulfonic acid group or a fluorine polymer having a sulfonic acid group is preferable.

  Examples of the hydrocarbon-based polymer having a sulfonic acid group include polyarylene ether compounds described in Japanese Patent No. 3928611.

  The polyarylene ether compound can be prepared by charging the monomer components used when preparing the block copolymer.

  More specifically, for example, the monomer represented by Chemical Formula 6A or 6B and the sulfonated monomer represented by Chemical Formula 7 can be synthesized by reacting with various bisphenols or various bisthiophenols. At that time, a dihalide such as 4,4'-dichlorodiphenylsulfone or 2,6-dichlorobenzonitrile may be used in combination.

  The monomer component can be reacted by any known method, but is preferably reacted by an aromatic nucleophilic substitution reaction in the presence of a basic compound.

  Regarding the reaction temperature, the basic compound that can be used, and the method for removing water produced as a by-product, the reaction temperature, basic compound, and removal method that can be used in the production of the hydrophobic segment can be used.

  In addition, with regard to the charged amount of monomer components, the method for removing inorganic salts produced as by-products, and the method for isolating and purifying the resulting polyarylene ether compound, conditions and methods that can be used in the production of hydrophilic segments Can be used.

  Examples of the fluorinated polymer having a sulfonic acid group include compounds described in “Chemical One Point Fuel Cell, Second Edition (Kyoritsu Shuppan, 1992)”.

(Sulphonic acid group content of random copolymer)
The random copolymer used in the present invention preferably has a sulfonic acid group content in the range of 0.3 to 3.5 meq / g. When it is less than 0.3 meq / g, there is a tendency that it does not show sufficient ion conductivity when used as an electrolyte membrane. When scented, the film swells so much that it tends to be unsuitable for use. More preferably, it is 0.5-3.0 meq / g.

(Random copolymer polymer log viscosity)
The random copolymer used in the present invention has a logarithmic viscosity measured at 30 ° C. of a 0.5 g / dL solution using N-methyl-2-pyrrolidone as a solvent in a range of 0.5 to 5.0 dL / g. It is preferable that When the logarithmic viscosity is less than 0.5 dL / g, it may be difficult to mold into a film due to poor moldability. On the other hand, when the logarithmic viscosity exceeds 5.0 dL / g, the viscosity of the solution in which the random copolymer is dissolved becomes excessively high, which adversely affects the workability. The logarithmic viscosity is more preferably in the range of 1.0 to 4.0 dL / g, and still more preferably in the range of 1.5 to 3.5 dL / g.

(Fuel cell electrode assembly)
By using the polymer electrolyte membrane produced by the production method of the present invention, a fuel cell assembly can be obtained. 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 There is a method of heating and pressing the electrode. Among these, the method of applying and bonding the sulfonic acid group-containing block copolymer or sulfonic acid group-containing random copolymer of the present invention and an adhesive mainly comprising the composition 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.

  A fuel cell can also be produced using the above-mentioned joined body. Since the polymer electrolyte membrane of the present invention is excellent in heat resistance, processability, and proton conductivity, it can withstand operation at high temperatures and can provide a fuel cell having good output. 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.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to these examples, and can be implemented with appropriate modifications within a range that can be adapted to the above and the gist described below. These are all included in the technical scope of the present invention. In the following examples and comparative examples, “parts” and “%” mean parts by mass and mass%, respectively.

  First, methods for measuring the logarithmic viscosity, ion exchange capacity, stacking ratio, and proton conductivity of block copolymers and random copolymers produced in Examples and Comparative Examples are described below.

(Logarithmic viscosity)
A block copolymer or random copolymer powder is dissolved in N-methylpyrrolidone at a concentration of 0.5 g / dL, and the viscosity is measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C. Viscosity ln [ta / tb] / c was evaluated (ta is the number of seconds that the sample solution was dropped, tb was the number of seconds that the solvent was dropped, and c was the polymer concentration of the sample solution [unit: dL / g]).

(Ion exchange capacity)
100 mg of the polymer electrolyte membrane dried at 120 ° C. for 1 hour 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 capacity (IEC) was calculated by the following formula.
Ion exchange capacity [meq / g] = (10-titration [ml]) / 2

(Lamination ratio)
The polymer electrolyte membrane is electron-stained in a solution containing a heavy metal salt, embedded in an epoxy resin, and then an ultrathin section is cut out with a microtome and observed at a magnification of 10,000 using a JEM2100 transmission electron microscope manufactured by JEOL. The thickness of each layer of the polymer electrolyte membrane (laminated film) was determined.

(Proton conductivity in film thickness direction)
A platinum wire (diameter: 0.2 mm) was pressed against the surface of a strip-shaped membrane sample cut out from the polymer electrolyte membrane on a polytetrafluoroethylene probe. At that time, one platinum wire to be pressed was disposed on the surface of the sample, and the other platinum wire was disposed on the back surface of the sample. Then, the sample was hold | maintained in 80 degreeC90% RH constant temperature and humidity oven (Nagano Science, Inc., LH33-12P), and the impedance between platinum wires was measured using 1250 FREQUENCY RESPONSE ANALYSER of SOLARTRON. Measured by changing the distance between the poles (distance between the platinum wires when the sample is viewed from the front), and from the slope plotting the resistance measurement value estimated from the distance between the poles and the C-C (core-coll) plot, The proton conductivity in the film thickness direction was evaluated by calculating the conductivity with which the contact resistance between the film and the platinum wire was canceled by the following formula.
Conductivity [S / cm] = (1 / film width [cm]) × (film thickness [cm]) × (resistance-to-resistance gradient [Ω / cm])

(Synthesis Example 1 Production of Block Copolymer)
<Production of hydrophobic oligomer>
2,6-dichlorobenzonitrile (abbreviation: DCBN) 49.97 g (290.5 mmol), 4,4′-biphenol (abbreviation: BP) 54.99 g (295.3 mmol), potassium carbonate 46.94 g (339.6 mmol) ), 750 mL of N-methyl-2-pyrrolidone (abbreviation: NMP) and 150 mL of toluene are placed in a 1000 mL branch flask equipped with a nitrogen introduction tube, a stirring blade, a Dean-Stark trap and a thermometer, and stirred in an oil bath. 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 15 hours. In another 1000 mL branch flask equipped with a nitrogen introduction tube, a stirring blade, a cooling reflux tube, and a thermometer, NMP 200 mL and 4.85 g of perfluorobiphenyl were placed and stirred at 110 ° C. in an oil bath while stirring under a nitrogen stream. Heated. The reaction solution of DCBN and BP was added thereto with stirring over 2 hours using a dropping funnel, and the mixture was further stirred for 2 hours after completion of the addition. The reaction solution was cooled to room temperature, poured into 3000 mL of pure water to solidify the oligomer, and further washed with pure water three times to remove NMP and inorganic salts. The oligomer washed with water was separated by filtration, dried at 100 ° C. for 2 hours, cooled to room temperature, and washed twice with 3000 mL of acetone to remove excess perfluorobiphenyl. The oligomer was again filtered off and dried under reduced pressure at 120 ° C. for 16 hours to obtain a hydrophobic oligomer. ^The number average molecular weight determined by ¹ H-NMR measurement was 13880. The chemical structure of the hydrophobic oligomer is shown below.

<Production of hydrophilic oligomer>
4,4′-dichlorodiphenylsulfone-3,3′-sodium disulfonate (abbreviation: S-DCDPS) 250.0 g (508.9 mmol), BP 97.04 g (520.7 mmol), sodium carbonate 66.23 g (624. 9 mmol), 650 mL of NMP, and 150 mL of toluene were placed in a 2000 mL branch flask equipped with a nitrogen introduction tube, a stirring blade, a Dean-Stark trap, and a thermometer, and heated under a nitrogen stream while 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 16 hours. Subsequently, 500 mL of NMP was added and cooled to room temperature while stirring. The obtained solution was subjected to suction filtration with a 25G2 glass filter, whereby a yellow transparent solution was obtained. The obtained solution was dropped into 3 L of acetone to solidify the oligomer. The oligomer was further washed three times with acetone, then filtered and dried under reduced pressure to obtain a hydrophilic oligomer. ^The number average molecular weight determined by ¹ H-NMR measurement was 25560. The chemical structure of the hydrophilic oligomer is shown below.

<Copolymerization reaction>
45.00 g of the above hydrophilic oligomer and 24.61 g of hydrophobic oligomer, 0.28 g of sodium carbonate, and 400 mL of NMP were put into a 1000 mL branch flask equipped with a nitrogen introduction tube, a stirring blade, a Dean-Stark trap, and a thermometer. The mixture was stirred and dissolved in an oil bath at 50 ° C. under an air flow, then heated to 110 ° C. and reacted for 10 hours. Then, it cooled to room temperature and it was dripped in 3L pure water, and the product (block copolymer) in a reaction solution was solidified. The obtained block copolymer was washed 3 times with pure water, then treated at 80 ° C. for 16 hours while immersed in pure water, and then the block copolymer was taken out from the pure water and washed with hot water. After repeating the hot water washing once more, the block copolymer from which water was removed was immersed in a mixed solvent of 1000 mL of isopropanol and 500 mL of water at room temperature for 16 hours, and then the block copolymer was taken out and washed with pure water. . The same operation (immersion in a mixed solvent and washing with pure water) was performed once more. Thereafter, the block copolymer was separated by filtration and dried under reduced pressure at 120 ° C. for 12 hours. The logarithmic viscosity of the obtained block copolymer was 2.1 dL / g. The chemical structural formula of the block copolymer is shown below.

(Synthesis Example 2 Production of Random Copolymer)
Reaction of 250.00 g (508.9 mmol) of S-DCDPS, 49.97 g (290.5 mmol) of DCBN, 152.00 g (816.00 mmol) of BP, 133.00 g (964.00 mmol) of potassium carbonate, and 3000 g of N-methyl-2-pyrrolidone It put into the container and made it react at 200 degreeC by nitrogen atmosphere for 10 hours. After standing to cool, the product in the reaction solution was precipitated in water in the form of a strand, and the resulting precipitate was washed 5 times with 10 L of water and then dried to obtain a random copolymer. The logarithmic viscosity of the random copolymer was 1.25 dL / g.

Example 1
The block copolymer obtained in Synthesis Example 1 and the random copolymer obtained in Synthesis Example 2 were each dissolved using NMP as a solvent to prepare a copolymer solution having a copolymer concentration of 12% by mass. . Among the prepared polymer solutions, first, a random copolymer solution was continuously formed on a polyethylene terephthalate film having a width of 30 cm as a support with a blade coater at a temperature of 25 ° C. so as to have a width of 22 cm and a thickness of 10 μm. After coating to form a random copolymer coating film, the block copolymer solution was applied to the coating film so as to have a thickness of 90 μm (100 μm in total) using the same blade coater. A polymer coating film is formed, and further, a random copolymer solution is applied to the block copolymer coating film so as to have a thickness of 10 μm (total 110 μm) using a blade coater. A combined coating film was formed. Then, the laminated body of the coating film was dried at a temperature of 120 ° C. for 3 minutes to obtain a self-supporting copolymer film (laminated polymer electrolyte film) in a state of being in close contact with the support. Subsequently, the film is continuously immersed in a 20% by mass sulfuric acid aqueous solution at 30 ° C. for 12 minutes without peeling off the copolymer film from the support, and then in pure water at 30 ° C. without peeling off the copolymer film from the support. After dipping for 18 minutes, dipped in pure water at 30 ° C. for 18 minutes, and further air-dried for 30 minutes in an environment of 30 ° C. and relative humidity 60 ± 5% without peeling off the copolymer film from the support. A laminated polymer electrolyte membrane having a thickness of 10 μm adhered to the polyethylene terephthalate film was obtained. The IEC of the obtained film was 2.2.

  Moreover, the thickness of the random copolymer layer-block copolymer layer-random copolymer layer in the obtained laminated polymer electrolyte membrane was 1.1 μm / 7.8 μm in order from the polyethylene terephthalate film side of the support. /1.1 μm, and a random copolymer layer was disposed on both sides of the block copolymer layer.

  When the obtained laminated polymer electrolyte membrane was peeled from the polyethylene terephthalate film as a support and the proton conductivity was measured, it showed a very high proton conductivity in the film thickness direction of 0.28 S / cm.

(Comparative Example 1)
The block copolymer obtained in Synthesis Example 1 was dissolved using NMP as a solvent to prepare a copolymer solution having a copolymer concentration of 12% by mass. The prepared copolymer solution was continuously applied on a 30 cm wide polyethylene terephthalate film as a support with a blade coater to a width of 22 cm and a thickness of 110 μm at a temperature of 25 ° C., and then at a temperature of 120 ° C. for 3 minutes. It dried and obtained the copolymer film (polymer electrolyte membrane) which has self-supporting property in the state closely_contact | adhered on the support body. Subsequently, the film is continuously immersed in a 20% by mass sulfuric acid aqueous solution at 30 ° C. for 12 minutes without peeling off the copolymer film from the support, and then in pure water at 30 ° C. without peeling off the copolymer film from the support. Immersion for 18 minutes, then immersion in pure water at 30 ° C. for 18 minutes, and further air drying for 30 minutes in an environment of 30 ° C. and relative humidity 60 ± 5% without peeling off the copolymer film from the support. A polymer electrolyte membrane having a thickness of 10 μm, which was in close contact with the polyethylene terephthalate film was obtained. The IEC of the obtained film was 2.2, which was the same as the film of Example 1.

  When the obtained 10 μm polymer electrolyte membrane was peeled from the polyethylene terephthalate film and measured for proton conductivity, it showed 0.22 S / cm, which was inferior to Example 1 in proton conductivity in the film thickness direction. Met.

(Comparative Example 2)
The random copolymer obtained in Synthesis Example 2 was dissolved using N-methyl-2-pyrrolidone as a solvent to prepare a copolymer solution having a copolymer concentration of 12% by mass. A polymer solid electrolyte membrane having a thickness of 10 μm was obtained in the same manner as in Comparative Example 1 except that the copolymer solution was used. The IEC of the obtained film was 2.2, which was the same as the film of Example 1.

  When the obtained 10 μm polymer electrolyte membrane was peeled from the polyethylene terephthalate film and measured for proton conductivity, it showed 0.18 S / cm, which was inferior to Example 1 in proton conductivity in the film thickness direction. Met.

  According to the production method of the present invention, a polymer electrolyte membrane having excellent proton conductivity in the film thickness direction can be produced. Therefore, it is used for a direct methanol fuel cell (DMFC), a solid polymer fuel cell (PEFC), and the like. As a means for providing a polymer electrolyte membrane, it greatly contributes to the industry.

Claims (11)

Applying a solution obtained by dissolving a block copolymer having a hydrophobic segment and a hydrophilic segment in a solvent on a support to form a coating film of the block copolymer;
Applying a solution obtained by dissolving a random copolymer in a solvent to the coating film of the block copolymer to form the coating film of the random copolymer;
Removing the solvent;
In this order, a method for producing a hydrocarbon-based polymer electrolyte membrane. The step of forming a coating film of the block copolymer,
After applying a solution in which a random copolymer is dissolved in a solvent to the support to form a coating film of the random copolymer, the block copolymer is coated on the coating film of the random copolymer. The method for producing a hydrocarbon-based polymer electrolyte membrane according to claim 1, which is carried out by applying a solution. The step of forming a coating film of the block copolymer,
A solution in which a random copolymer is dissolved in a solvent is applied to the support, and then the solvent is removed to form a random copolymer film. Then, the block copolymer is applied to the random copolymer film. The method for producing a hydrocarbon-based polymer electrolyte membrane according to claim 1, which is carried out by applying a polymer solution. The hydrophobic segment of the block copolymer is represented by Formula 1
(Chemical formula 1)
(In the formula, each Z independently represents an O atom or an S atom, Ar ¹ independently represents a divalent aromatic group, and n represents a number of 1 to 100, respectively.)
Represented by
The hydrophilic segment is represented by chemical formula 2
(Chemical formula 2)
Wherein X is independently H or a monovalent cation, Y is a sulfonyl group or carbonyl group, Ar ² is independently a divalent aromatic group, and L is independently O. An atom or an S atom, m represents a number of 1 to 100, respectively)
The hydrophobic segment and the hydrophilic segment are represented by the chemical formula 3
(Chemical formula 3)
(In the formula, p represents 0 or 1, and when p is 1, W represents one or more selected from the group consisting of a direct bond, a sulfonyl group, and a carbonyl group.)
The manufacturing method of the hydrocarbon type polymer electrolyte membrane as described in any one of Claim 1 to 3 couple | bonded by group represented by these. Ar ² is represented by the chemical formula 4
(Chemical formula 4)
The manufacturing method of the hydrocarbon type polymer electrolyte membrane of Claim 4 represented by these.   In the block copolymer, the ratio (m / n) of m in the chemical formula 2 to n in the chemical formula 1 is 0.4 to 1.5. A method for producing a molecular electrolyte membrane.   The hydrocarbon polymer electrolyte membrane according to any one of claims 1 to 6, wherein the random copolymer is a fluoropolymer having a sulfonic acid group and / or a hydrocarbon polymer having a sulfonic acid group. Manufacturing method.   The method for producing a hydrocarbon-based polymer electrolyte membrane according to any one of claims 1 to 7, wherein a mass ratio of a total amount of the block copolymer and the random copolymer is 99/1 to 1/99.   A hydrocarbon-based polymer electrolyte membrane produced by the production method according to any one of claims 1 to 8.   A membrane / electrode assembly comprising the hydrocarbon-based polymer electrolyte membrane according to claim 9. A fuel cell using the membrane electrode assembly according to claim 10.