JP2011246695A - Composite polymer electrolyte membrane and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a composite polymer electrolyte membrane, which contains an aromatic hydrocarbon-based polymer fiber suitable for compounding with polymer electrolyte and is hardly soluble in solvents, without using such a method as melt blowing or electrolytic spinning by laser beam melting; and to provide a composite polymer electrolyte membrane that is excellent in ionic conductivity, and is controlled from dimensional change and from deterioration of mechanical strength both in a hydrated state.SOLUTION: The method for producing the composite polymer electrolyte membrane is a method for producing a composite polymer electrolyte membrane comprised of an aromatic hydrocarbon-based polymer fiber and a polymer electrolyte membrane, and comprises: a step of making up a nonwoven fabric by electrolytic spinning using spinning stock solution comprised of an aromatic hydrocarbon-based polymer containing a solubility-giving group and a solvent; and a step of impregnating an electrolytic polymer solution to the nonwoven fabric. The spun aromatic hydrocarbon-based polymer fiber is made insoluble in the electrolytic polymer solution by removing the solubility-giving group before the step of impregnating the electrolytic polymer solution. Moreover, the composite polymer electrolyte membrane is a composite polymer electrolyte membrane consisting an aromatic hydrocarbon-based polymer nonwoven fabric and a polymer electrolyte. Since the aromatic hydrocarbon-based polymer nonwoven fabric and the polymer electrolyte have the same polymer structure, the both has compatibility.

Description

  The present invention relates to a composite polymer electrolyte membrane and a method for producing the same.

  BACKGROUND ART A fuel cell is a kind of power generation device that extracts electrical energy by electrochemically oxidizing a fuel such as hydrogen or methanol, and has recently attracted attention as a clean energy supply source. In particular, the polymer electrolyte fuel cell has a low standard operating temperature of around 100 ° C. and a high energy density, so that it is a relatively small-scale distributed power generation facility, a mobile power generator such as an automobile or a ship. As a wide range of applications are expected. It is also attracting attention as a power source for small mobile devices and portable devices, and is expected to be installed in mobile phones and personal computers in place of secondary batteries such as nickel metal hydride batteries and lithium ion batteries.

  In the polymer electrolyte fuel cell, for example, a cell is formed by sandwiching a membrane electrode assembly between two separators, and a plurality of cells are stacked. The membrane electrode assembly includes an anode and a cathode having a catalyst layer, and a polymer electrolyte membrane disposed between the anode and the cathode. Fluorine ion conductive polymers such as perfluorocarbon polymers having sulfonic acid groups have been applied to polymer electrolyte membranes. However, low cost and low environmental impact are anticipated in the future of polymer electrolyte fuel cells. In particular, hydrocarbon-based ion conductive polymers such as aromatic polyether ether ketones having a sulfonic acid group and aromatic polyether ketones and aromatic polyether sulfones have been actively studied. The polymer electrolyte membrane is required to have high proton conductivity. In particular, automobile fuel cells and household fuel cells are required to operate under low humidification conditions with a relative humidity of 60% or less at high temperatures exceeding 80 ° C in order to simplify the water management system. It was necessary to achieve both ion conductivity and durability.

  In order to increase the ionic conductivity of the polymer electrolyte membrane, it is preferable to make the polymer electrolyte membrane thin or increase the ionic group density. However, when the polymer electrolyte membrane is thinned, the mechanical strength of the membrane decreases, and it becomes difficult to process or handle when manufacturing a membrane electrode assembly. In addition, a polymer electrolyte membrane having an increased ionic group density is likely to increase in dimensions in the length direction of the membrane when it contains water, and various adverse effects are likely to occur. For example, since the polymer electrolyte membrane swells due to water generated by the reaction, water vapor supplied with the fuel gas, etc., and the membrane electrode assembly is restrained by a separator or the like, the dimension increase of the polymer electrolyte membrane is It causes local stress concentration. On the contrary, depending on the operating conditions of the fuel cell, the polymer electrolyte membrane is dried and contracted. In this swelling / shrinking cycle, the polymer electrolyte membrane may be damaged, resulting in a decrease in power generation performance or failure.

  Patent Document 1 discloses a polymer electrolyte in which a fluorine-based proton conductive polymer or a hydrocarbon-based ion conductive polymer is reinforced with a fluorine-based nonwoven fabric produced by an electrospinning method using a spinning stock solution containing a fluorine-containing polymer and a solvent. A membrane is disclosed.

  Patent Document 2 proposes a polyether ether ketone non-woven fabric obtained by a melt-blowing method, and Patent Document 3 also proposes a method of melting a thermoplastic resin with a laser beam and electrospinning it into a non-woven fabric.

  On the other hand, Patent Document 4 proposes a method for obtaining a nonwoven fabric by electrospinning using bubbles of a polymer solution, and Patent Document 5 utilizes the incompatibility of an ionic group-containing polymer and an ionic group-free polymer. First, a method has been proposed in which nanofibers are first prepared and formed into a sheet, and then an ionic group-free polymer is melted by heating and melting to form an ion conductive composite polymer film.

JP 2008-243419 A JP 2008-81893 A JP 2009-299212 A JP 2008-25057 A JP 2010-21126 A

  The present inventors have found that there are the following problems.

  First, as a method for producing a polymer electrolyte membrane reinforced with a nonwoven fabric described in Patent Document 1, a method of applying or impregnating a solution containing a proton conductive polymer to a nonwoven fabric (a-1-1), or a nonwoven fabric, A method (a-1-2) of applying or impregnating a dispersion of a proton conductive polymer and a method (a-2) of laminating a membrane of a proton conductive polymer on a nonwoven fabric are described. Here, as in (a-1-1), once the proton conductive polymer is in solution, the proton conductive polymer is in a solid state as in (a-1-2) and (a-2). As it is, there is a problem that the adhesion is insufficient and the permeability of the fuel gas is increased.

  Further, in the method of dissolving the proton conductive polymer as in (a-1-1), the nonwoven fabric is spun from the polymer solution, that is, the solvent at the time of spinning is used for the solution of the proton conductive polymer. There is a problem that the nonwoven fabric dissolves and the solvent to be used is limited.

  Here, in Patent Documents 2 and 3, the polymer that becomes the nonwoven fabric is not spun from the solution, but the nonwoven fabric obtained by the melt-blowing method as in Patent Document 2 has a large average fiber diameter. It could not be used because it was the starting point of film breakage. The method of melting a thermoplastic resin with a laser beam as in Patent Document 3 has problems that the temperature is difficult to control because it is heated with a laser, the polymer is easily decomposed, and the apparatus is expensive and the productivity is poor. It was. Furthermore, in any method, the problem that the above-mentioned adhesion is insufficient is inherent.

  The method of electrospinning using the foam of the polymer solution of Patent Document 4 is also improved in productivity, but can be applied only to a polymer soluble in a solvent. In the process of coating and impregnating, there is a problem that the solvent to be used is limited, and there is a restriction on the design of a high performance composite polymer electrolyte membrane. Also, crystalline polymers such as polyether ketones that are insoluble in the solvent could not be applied.

  Finally, in Patent Document 5 as well, as described above, the realization of a high-performance composite polymer electrolyte membrane is realized by utilizing the “incompatibility” of an ionic group-containing polymer and an ionic group-free polymer. Was difficult.

  The present invention provides a method for producing a composite polymer electrolyte membrane comprising a solvent-insoluble aromatic hydrocarbon polymer fiber suitable for composite with a polymer electrolyte without using a melt blow method or an electrospinning method by laser melting. To do. Moreover, the present invention provides a composite polymer electrolyte membrane that has excellent ionic conductivity and suppresses changes in water-containing dimensions and a decrease in mechanical strength when containing water.

  The present invention employs the following means in order to solve such problems. That is, the method for producing a composite polymer electrolyte membrane of the present invention is a method for producing a composite polymer electrolyte membrane comprising an aromatic hydrocarbon polymer fiber and a polymer electrolyte membrane, and comprising an aromatic carbonization containing a solubility-imparting group. It has a process of making a nonwoven fabric by electrospinning using a spinning stock solution consisting of a hydrogen-based polymer and a solvent, and a process of impregnating the obtained nonwoven fabric with an electrolyte polymer solution. The aromatic hydrocarbon polymer fiber that has been removed and spun is insolubilized in the electrolyte polymer solution.

  The composite polymer electrolyte membrane of the present invention is a composite polymer electrolyte membrane comprising an aromatic hydrocarbon polymer nonwoven fabric and a polymer electrolyte, wherein the aromatic hydrocarbon polymer fiber and the polymer electrolyte are the same polymer. It has a structure and is compatible.

  Since the method for producing a composite polymer electrolyte membrane of the present invention can produce a solvent-insoluble aromatic hydrocarbon polymer fiber with high productivity, there is no restriction on the solvent used in the electrolyte polymer solution, and the mechanical polymer composed of the fiber is used. A nonwoven fabric excellent in strength, heat resistance, acid resistance and solvent resistance can be obtained, and the impregnation property of the electrolyte polymer solution into the nonwoven fabric can be improved. In addition, the composite polymer electrolyte membrane of the present invention has excellent proton conductivity, small dimensional change in the wet / dry cycle, and improved mechanical strength when wet, so it has excellent high-temperature / low-humidity power generation performance and power generation durability. A fuel cell with excellent performance can be realized. In particular, it is optimal for fuel cell applications that operate under high humidification conditions such as automobiles and household fuel cells at temperatures exceeding 80 ° C. and a relative humidity of 60% or less.

Schematic configuration diagram of non-woven fabric manufacturing equipment using electrospinning

  Hereinafter, details of preferred embodiments of the present invention will be described.

  The method for producing a composite polymer electrolyte membrane according to the present invention is a method for producing a composite polymer electrolyte membrane comprising an aromatic hydrocarbon polymer fiber and a polymer electrolyte membrane, and comprising an aromatic hydrocarbon type containing a solubility-imparting group An electrospinning process using a spinning solution composed of a polymer and a solvent, a process of making the obtained aromatic hydrocarbon polymer fiber into a nonwoven fabric, and a process of impregnating the obtained aromatic hydrocarbon polymer nonwoven fabric with a polymer electrolyte solution It is essential to remove the solubility-imparting group before the step of impregnating the polymer electrolyte solution and insolubilize the spun aromatic hydrocarbon polymer fiber in the polymer electrolyte solution.

  As a design guideline for the composite polymer electrolyte membrane, the inventors have difficulty in using a solvent having a crystallization ability, a part having a strong interaction in the molecular chain, showing a pseudo-crosslinking structure, and a very large molecular weight. It was conceived that a nonwoven fabric suitable for a composite polymer electrolyte membrane having excellent mechanical strength, heat resistance, acid resistance, and solvent resistance can be obtained by mainly using soluble aromatic hydrocarbon polymer fibers.

  In addition, when combined with a compatible polymer electrolyte membrane with the same polymer structure as the aromatic hydrocarbon polymer fiber, the mechanical strength, heat resistance, acid resistance, and solvent resistance of the composite polymer electrolyte membrane are excellent. In addition, it is possible to achieve both excellent proton conductivity and improved mechanical strength when wet.

  Furthermore, the aromatic hydrocarbon polymer fiber in the composite polymer electrolyte membrane and the polymer electrolyte membrane have the same polymer structure and are compatible with each other. The affinity of the interface of the molecular electrolyte membrane is improved, and the interfacial peeling due to the dimensional change caused by the water content of the two can be suppressed. Especially, the relative humidity is 60% or less at a high temperature exceeding 80 ° C. It has also been found that in a wet and dry cycle power generation test that simulates the operation of repeatedly stopping and operating under low humidification conditions, it exhibits excellent durability.

  However, the production of fibers and non-woven fabrics that can be used as a composite polymer electrolyte membrane using a polymer system that is hardly soluble in the above-described solvent has not been able to be achieved by the techniques known so far. In other words, since the aromatic hydrocarbon polymer fiber and the polymer electrolyte membrane have the same polymer structure and compatibility, in the process of impregnating the solvent and polymer electrolyte solution used in the electrospinning process of the aromatic hydrocarbon polymer fiber. Generally, the same solvent system is used as the solvent to be used. In the impregnation step, the aromatic hydrocarbon polymer fiber is dissolved in the polymer electrolyte solution, the proton conduction path is blocked, and the composite polymer electrolyte membrane is used. As a result, the performance is significantly reduced.

  Therefore, the inventors can manufacture a nonwoven fabric containing a precursor of a solvent-solubilized fiber by an electrospinning method by introducing a solubility-imparting group into the polymer system that is hardly soluble in the solvent and solubilizing it in the solvent. I was inspired by that. And before the step of impregnating the non-woven fabric with the polymer electrolyte solution, it was found that the fiber precursor can be insolubilized by removing the solubility-imparting group. Nonwoven fabrics mainly composed of aromatic hydrocarbon polymer fibers dissolved in the polymer electrolyte solution and succeeded in suppressing the phenomenon that inhibits proton conductivity.

  In the composite polymer electrolyte of the present invention, the same polymer structure is the same polymer structure as long as the groups that bond the aromatic hydrocarbon structure of the main component of the polymer are the same. For example, if the aromatic hydrocarbon polymer fiber is a skeleton containing a polyetherketone structure, the polymer electrolyte membrane is also a skeleton containing a polyetherketone structure, and an aromatic hydrocarbon between a ketone group and an ether group. The portion is not particularly limited, and may be the same or different. As for the aromatic hydrocarbon polymer fiber, the phenyl or biphenyl structure is preferred from the viewpoint of solvent resistance after removal of the solubility-imparting group. Further, regardless of the presence or absence of a substituent such as a sulfonic acid group, the same polymer structure is included as long as the group that binds the aromatic hydrocarbon structure is the same even if the content and the type of the substituent are different.

  Further, in the composite polymer electrolyte membrane of the present invention, the compatibility means, for example, a polymer solution constituting an aromatic hydrocarbon polymer fiber introduced with a soluble group-providing group and a polymer solution constituting a polymer electrolyte membrane. Separately prepared, mixed to make a mixed solution, cast coated, dried into a sheet, then removed the soluble group-providing group to obtain a film, resulting in a co-continuous structure, or the opposite direction through It means that the structure can be mixed with each other to the extent that it can be seen. In the composite polymer electrolyte membrane of the present invention, the aromatic hydrocarbon polymer fiber is insoluble in the polymer electrolyte solution, but the fiber surface is partly swollen in the polymer electrolyte solution, and the aromatic hydrocarbon polymer fiber The interface between the fiber and the polymer electrolyte is mixed with each other, and a state in which the fiber and the polymer electrolyte are not easily peeled off due to the dimensional change of moisture absorption drying can be formed. Even if they have the same polymer structure, depending on the structure of the aromatic hydrocarbon to be selected, there may be a case where the compatibility between the aromatic hydrocarbon polymer fiber and the polymer electrolyte is insufficient. It is important to design the polymer structure considering the compatibility of the electrolyte membrane.

  In order to improve the compatibility, it is also preferable to introduce an ionic group possessed by the polymer electrolyte membrane that is combined with the polymer constituting the aromatic hydrocarbon polymer fiber. In this case, the ionic group density is preferably smaller in the aromatic hydrocarbon polymer fiber from the viewpoint of reducing dimensional change when wet and improving the mechanical strength, and the ionic group density of the composite polymer electrolyte is preferable. Is preferably 50% or less, more preferably 20% or less.

  First, an aromatic hydrocarbon polymer containing a solubility-imparting group will be described.

  The aromatic hydrocarbon polymer in the present invention is a fiber made of a polymer containing an aromatic ring in the main chain or side chain and containing more hydrogen than fluorine bonded to carbon, such as mechanical strength and chemical stability. From the viewpoint, an aromatic hydrocarbon polymer having an aromatic ring in the main chain is more preferable. That is, the main chain structure is not particularly limited as long as it has an aromatic ring, but a structure having sufficient mechanical strength to be used, for example, as an engineering plastic is preferable.

  Specific examples of the aromatic hydrocarbon polymer of the present invention include polysulfone, polyethersulfone, polyphenylene oxide, polyarylene ether polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyparaphenylene, polyarylene polymer, polyarylene ketone, A polymer containing at least one component such as polyether ketone, polyarylene phosphine oxide, polyether phosphine oxide, polybenzoxazole, polybenzthiazole, polybenzimidazole, polyamide, polyimide, polyetherimide, polyimidesulfone, etc. Can be mentioned. Polysulfone, polyethersulfone, polyetherketone, etc., as used herein are generic terms for polymers having a sulfone bond, an ether bond, and a ketone bond in their molecular chains. Polyetherketoneketone, polyetheretherketone, polyetherether It includes ketone ketone, polyether ketone ether ketone ketone, polyether ketone sulfone and the like, and does not limit the specific polymer structure.

  Among the polymers, polymers such as polyphenylene sulfide and polyetherketone (PEK) are more preferable in terms of durability such as mechanical strength and water resistance and acid resistance when used as an electrolyte membrane for fuel cells. The PEK-based polymer will be described as an example. The polymer exhibits crystallinity because of its good packing and extremely strong intermolecular cohesion, and does not dissolve in common solvents.

  On the other hand, the method for producing a composite polymer electrolyte membrane of the present invention includes a PEK polymer that has been particularly difficult to be made into a solution by incorporating a solubility-imparting group in an aromatic hydrocarbon polymer. By reducing the crystallinity of the crystalline aromatic hydrocarbon-based polymer, solubility in a solvent is imparted so that it can be used for electrospinning and solution casting.

  Further, in the present invention, after forming into a nonwoven fabric by electrospinning and forming into a non-woven fabric, or after drying the solvent and forming into a film, the molecular chain packing of the polymer is improved, and the intermolecular cohesion and crystallinity are improved. In order to impart, it is necessary to remove a part of the solubility-imparting group and insolubilize the solvent again.

  Examples of the solubility-imparting group used in the aromatic hydrocarbon polymer of the present invention include a hydrolyzable group generally used in organic synthesis, and the hydrolyzable group is a hydrolyzable group at a later stage. It is a substituent that is temporarily introduced on the assumption that it will be removed in step (b). This solubility-imparting group can be appropriately selected in consideration of solvent solubility, reactivity at the time of removal, yield, stability of the solubility-containing group-containing state, production cost, and the like. In addition, the step of introducing the solubility-imparting group in the polymerization reaction may be performed from the monomer stage, the oligomer stage, or the polymer stage, and can be appropriately selected.

  For example, a PEK-based polymer is described as a method of substituting a ketone moiety with an acetal or ketal moiety to form a solubility-imparting group. Examples of the method include an imparting group. In addition, there are a method of using a sulfonic acid as a soluble ester derivative and a method of introducing a t-butyl group as a solubility-imparting group into an aromatic ring, and the like. It can use preferably, without being limited to. In terms of improving solubility in general solvents and reducing crystallinity, an aliphatic group, particularly an aliphatic group containing a cyclic moiety, is preferably used as the solubility-imparting group in terms of large steric hindrance.

The position for introducing the solubility-imparting group is more preferably a functional group present in the main chain of the polymer. Here, the functional group present in the main chain of the polymer is defined as a functional group that breaks the polymer chain when the functional group is deleted. For example, this means that if the ketone group of the aromatic polyether ketone is deleted, the benzene ring and the benzene ring are broken.
If a solubility-imparting group is introduced into the functional group present in the main chain of the polymer, the packing of the molecular chain of the aromatic hydrocarbon polymer will be improved when the solubility-imparting group is removed, and intermolecular cohesion and crystallinity will be improved. Easy to grant.

  Next, an electrospinning process using a spinning stock solution composed of an aromatic hydrocarbon polymer containing a solubility-imparting group and a solvent, and a process for forming the resulting aromatic hydrocarbon polymer fiber into a nonwoven fabric will be described.

  The solvent used when the aromatic hydrocarbon polymer containing the solubility-imparting group is used as a spinning dope is not particularly limited as long as the aromatic hydrocarbon polymer containing the solubility-imparting group can be dissolved. N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, dimethylimidazolidinone, dimethyl sulfoxide, hexamethylphosphonamide, etc. due to solubility, handleability and cost Organic polar solvents are desirable and may be mixtures thereof. There is no particular limitation on the dissolution temperature, and it may be at room temperature or under heating. A low-boiling solvent such as water, alcohols, methyl cellosolves, tetrahydrofuran and toluene may be added as long as the aromatic hydrocarbon polymer containing the solubility-imparting group does not precipitate. Also, for the purpose of imparting stretchability of the spinning dope, addition of a polyhydric alcohol such as ethylene glycol or glycerin is also preferable, and an ionic group such as a sulfonic acid group or a carboxylic acid group is introduced into the aromatic hydrocarbon polymer. Is particularly preferred.

The electrospinning process using the spinning dope is not particularly limited, and generally known methods and equipment can be used. Electrospinning is a method in which fibers are spun electrically by applying a high voltage to a spinning dope. Manufacturing a non-woven fabric mainly composed of fibers having a diameter of 5 μm or less using a normal non-woven fabric facility is severe in terms of conditions and has many restrictions such as the viscosity of the raw material and stretchability. On the other hand, since the electrospinning method is a spinning method using a spinning raw solution, volume shrinkage occurs during the drying process, and since the spinning raw solution has a low viscosity, molding with an ultrafine nozzle is possible. It is easy to obtain continuous fibers of 5 μm or less.

  Also in the process of making the obtained aromatic hydrocarbon polymer fiber into a nonwoven fabric, in the electrospinning process, solidification from the spinning stock solution and spinning by stretching occur simultaneously or sequentially, so that the spun fiber is used as a target. By capturing directly, it can be obtained as a nonwoven fabric in which fibers are bonded. Alternatively, the obtained fiber may be made into a short fiber to form a fleece, which may be made into a non-woven fabric by a normal dry method or a wet method in which it is dispersed in water to make a non-woven fabric such as a paper making process. In that case, as a method for bonding the fleece, a thermal bond method, a chemical bond method, a needle punch method, a hydroentanglement method, or the like can be used.

  In the method for producing a composite polymer electrolyte membrane of the present invention, since a fiber having a smaller fiber diameter is preferable, a nonwoven fabric forming method in which fibers obtained by electrospinning are directly captured and accumulated on a target is preferable from the viewpoint of productivity. .

  An example of the non-woven fabric forming process by electrospinning is shown in FIG. The nonwoven fabric manufacturing apparatus is configured to apply a high voltage between the syringe 10 filled with the spinning dope and the needle 20 of the syringe, and between the conveyor needle 30 and the needle 20 of the syringe and the conveyor drum 30. A voltage power source 40 and a syringe pump 50 that discharges the spinning solution from the syringe at a constant flow rate by moving the plunger portion of the syringe at a constant speed in the discharge direction.

  First, the spinning solution is filled in the syringe 10. A high voltage is applied between the syringe needle 20 and the conveyor drum 30 by a high voltage power source while rotating the conveyor drum 30. The syringe pump 50 is operated to discharge the spinning solution from the tip of the syringe needle 20 at a constant speed. When a voltage is applied to the tip of the needle and the electrostatic attractive force exceeds the surface tension of the spinning stock solution, the spinning stock solution is deformed into a conical shape called Taylor cone at the tip of the needle, and the tip of the cone is further stretched. . The stretched spinning dope is refined by electrostatic repulsion of the positively charged spinning dope. The solvent instantly evaporates from the refined spinning dope, and ultrafine fibers are formed. Positively charged fibers adhere to the negatively charged conveyor drum 30. The nonwoven fabric is formed on the conveyor drum 30 as the fibers gradually accumulate on the rotating conveyor drum 30.

  In the electrospinning step, the viscosity of the spinning solution can be appropriately determined experimentally, but is preferably 0.1 to 100 Pa · sec, more preferably 1 to 10 Pa · sec. The discharge amount of the spinning solution is preferably in the range of 0.001 cc / min to 1 cc / min per syringe, and the inner diameter of the tip of the needle is preferably 0.1 to 2 mm, more preferably 0.1 to 1 mm. . The distance from the tip of the needle to the drum is preferably 5 to 20 cm. The voltage applied between the needle and the drum is preferably 5 to 100 kV. The number of syringes, the peripheral speed of the drum, and the feed speed of the fiber collecting base material can be appropriately determined experimentally depending on the width, length, and thickness of the aromatic hydrocarbon polymer nonwoven fabric to be manufactured. Aromatic carbonization can be performed continuously by supplying a substrate for collecting aromatic hydrocarbon polymer fibers by roll-to-roll, or by stripping the nonwoven fabric from a certain part of a conveyor drum and winding it with a winder. Producing a hydrogen-based polymer nonwoven fabric is also a preferred example.

  The fiber diameter of the aromatic hydrocarbon polymer nonwoven fabric obtained by the electrospinning process of the present invention is preferably mainly composed of fibers of 5 μm or less. The term “subject” as used herein means that it accounts for 50% or more of the fibers in the observation field when observed with an electron microscope or the like. The composite polymer electrolyte membrane can be made thin by mainly using fibers of 5 μm or less, which is preferable from the viewpoint of proton conductivity. In addition, in a non-woven fabric consisting only of fibers having a fiber diameter of 5 μm or more, in order to reduce the thickness of the composite polymer electrolyte membrane, the fiber overlap is reduced, that is, the amount of fibers per unit area (hereinafter referred to as the basis weight) is designed to be low. However, the distance between the fibers is inevitably widened, the maximum pore diameter is increased, and a portion that is not locally combined may be generated in the film thickness direction. Depending on the thickness of the composite polymer electrolyte membrane, this part may trigger the deterioration of the composite polymer electrolyte membrane. Therefore, for the purpose of preventing this phenomenon, fibers mainly having an average diameter of 5 μm or less are mainly used. It is preferable to do. In particular, a nonwoven fabric mainly composed of fibers of 1 μm or less can suppress a decrease in proton conductivity due to an increase in the thickness of the composite polymer electrolyte membrane, and can reduce a portion that is not composited in the film thickness direction. More preferably, the fibers contain fibers of 0.5 μm or less. In addition, non-woven fabrics and paper bodies and fabrics made of materials insoluble in solvents such as olefin polymers such as polypropylene and polyethylene, fluorine polymers such as polytetrafluoroethylene, polyphenylene sulfide, and polyethylene terephthalate are used as aromatic hydrocarbon polymer fibers. A collection base material may be used in the present invention as a composite nonwoven fabric obtained by laminating aromatic hydrocarbon polymer fibers by electrospinning. In that case, the collection base material may contain fibers having a diameter of 5 μm or more, but the gap between the fibers is preferably closed by a collection of fibers having a diameter of 5 μm or less as viewed from the surface direction.

  Further, a structure in which fibers are present on the entire surface of the composite polymer electrolyte membrane is preferable, and a state in which a plurality of layers of fibers are laminated is preferable.

  In order to efficiently produce such an aromatic hydrocarbon polymer fiber having a fiber diameter of 0.5 μm or less, a technique of adding the above-described polyhydric alcohol such as ethylene glycol or glycerin to the spinning dope should be adopted. Is preferred. Addition of polyhydric alcohol enables electrospinning without tearing the yarn even when the concentration of the aromatic hydrocarbon polymer containing the solubility-imparting group in the spinning dope is low, and is extremely useful for obtaining fibers of 0.5 μm or less. I found it effective.

  When the fiber diameter is 0.5 μm or less, the concentration of the aromatic hydrocarbon polymer containing the solubility-imparting group in the spinning dope is preferably 15% by weight or less, and the amount of polyhydric alcohol added is in the spinning dope. The addition of 0.1% or more and 10% or less is preferable. The number of hydrogen bonds is increased by the action of polyhydric alcohol and polymer, the apparent molecular weight is increased by pseudo-crosslinking, the spinnability is improved even at a low solid content, and the nonwoven fabric is made of long fibers of 0.5 μm or less. Is possible. In particular, the addition of glycerin is most effective.

  Next, the step of impregnating the polymer electrolyte solution into the obtained aromatic hydrocarbon polymer nonwoven fabric will be described.

  The polymer electrolyte that can be used in the present invention is not particularly limited, but examples include ionic group-containing polyphenylene oxide, ionic group-containing polyether ketone, ionic group-containing polyether ether ketone, ionic group-containing polyether sulfone, Ionic group-containing polyether ether sulfone, ionic group-containing polyether phosphine oxide, ionic group-containing polyether ether phosphine oxide, ionic group-containing polyphenylene sulfide, ionic group-containing polyamide, ionic group-containing polyimide, ionic group Examples thereof include aromatic hydrocarbon polymers having an ionic group, such as a containing polyetherimide, an ionic group-containing polyimidazole, an ionic group-containing polyoxazole, and an ionic group-containing polyphenylene.

  Here, the ionic group is not particularly limited as long as it is a negatively charged atomic group, but is preferably one having proton exchange ability. As such a functional group, a sulfonic acid group, a sulfonimide group, a sulfuric acid group, a phosphonic acid group, a phosphoric acid group, and a carboxylic acid group are preferably used. Such an ionic group includes a case where it is a salt. Examples of the cation forming the salt include an arbitrary metal cation, NR4 + (R is an arbitrary organic group), and the like. In the case of a metal cation, the valence and the like are not particularly limited and can be used.

  Specific examples of preferred metal ions include Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Mn, Al, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, Pt, Rh, Ru, Ir, Pd, etc. are mentioned. Among these, Li, Na, K, Ca, Sr, and Ba are more preferable, and among them, Na and K that are inexpensive and can be easily proton-substituted without adversely affecting the solubility are more preferably used. In addition to the metal salt, the ionic group may be substituted with an ester or the like.

  Two or more kinds of these ionic groups can be contained in the polymer electrolyte, and may be preferable by combining them. The combination is appropriately determined depending on the structure of the polymer. Among them, it is more preferable to have at least a sulfonic acid group, a sulfonimide group, and a sulfuric acid group from the viewpoint of high proton conductivity, and most preferable to have at least a sulfonic acid group from the viewpoint of hydrolysis resistance.

  In recent years, simplification of the water management system is considered important for full-scale spread of fuel cells for automobiles and household fuel cells, and power generation conditions are high temperatures exceeding 80 ° C. and low humidification conditions with a relative humidity of 60% or less. There is a case. Therefore, in order to exhibit sufficient power generation performance at such high temperature and low humidity, the ionic group density of the polymer electrolyte is preferably 2.0 mmol / g or more, and the aromatic hydrocarbon polymer fiber and the polymer electrolyte are preferred. The ionic group density of the composite polymer electrolyte membrane including the membrane is preferably 1.5 mmol / g or more.

  The solvent for dissolving the polymer electrolyte is not particularly limited, and can be selected according to the ionic group-containing polymer. For example, aprotic such as N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphontriamide, etc. Polar solvents, ester solvents such as γ-butyrolactone and butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, alkylene such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether Glycol monoalkyl ether is suitably used, and may be used alone or as a mixture of two or more.

  Also, for adjusting the viscosity of the electrolyte solution, alcohol solvents such as methanol and isopropanol, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate, butyl acetate and ethyl lactate, hydrocarbon solvents such as hexane and cyclohexane, Aromatic hydrocarbon solvents such as benzene, toluene, xylene, halogenated hydrocarbon solvents such as chloroform, dichloromethane, 1,2-dichloroethane, dichloromethane, perchloroethylene, chlorobenzene, dichlorobenzene, diethyl ether, tetrahydrofuran, 1, Ether solvents such as 4-dioxane, nitrile solvents such as acetonitrile, nitrated hydrocarbon solvents such as nitromethane and nitroethane, and various low-boiling solvents such as water can also be mixed and used.

  As a method of impregnating the aromatic hydrocarbon polymer nonwoven fabric with the polymer electrolyte solution, a generally known method can be adopted.

  For example, an aromatic hydrocarbon polymer nonwoven fabric is immersed in a polymer electrolyte solution, and (1) a method of controlling the film thickness by removing excess polymer electrolyte solution while pulling up, or (2) an aromatic hydrocarbon system A method of casting a polymer electrolyte solution on a polymer nonwoven fabric, (3) Laminating an aromatic hydrocarbon polymer nonwoven fabric on another substrate on which the polymer electrolyte solution is cast coated, and impregnating the polymer electrolyte solution The method etc. are mentioned. Also, in the methods (1) and (2), the method of adhering to another base material and drying the solvent in the polymer electrolyte solution can reduce wrinkles and thickness unevenness of the composite polymer electrolyte membrane. It is preferable in terms of quality.

  As another base material used for the composite polymer electrolyte membrane, generally known materials can be used, but endless belts and drums made of metal such as stainless steel, films made of polymers such as polyethylene terephthalate, polyimide, polysulfone, glass, Examples include release paper. For metal, etc., the surface is mirror-finished, for polymer films, etc., the coated surface is corona-treated, peeled off, and when continuously coated in roll form, the back of the coated surface is peeled off and wound. It is also possible to prevent the electrolyte membrane and the back side of the coated base material from adhering after removal. In the case of a film substrate, the thickness is not particularly limited, but 30 μm to 200 μm is preferable from the viewpoint of handling.

  Cast coating methods include knife coating, direct roll coating, gravure coating, spray coating, brush coating, dip coating, die coating, vacuum die coating, curtain coating, flow coating, spin coating, reverse coating, and screen printing. Applicable. Improving the impregnation property by reducing pressure and pressure during the impregnation, heating the polymer electrolyte solution, heating the base material and the impregnation atmosphere, etc. is also effective for improving proton conductivity and productivity. .

  The film thickness of the composite polymer electrolyte membrane obtained in the present invention is not particularly limited and can be determined by the aromatic hydrocarbon polymer nonwoven fabric to be used, but usually 3 to 500 μm is suitably used. . A thickness of more than 3 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 500 μm is preferable for reducing membrane resistance, that is, improving power generation performance. A more preferable range of the film thickness is 5 to 200 μm, and a more preferable range is 10 to 100 μm. This film thickness can be controlled by various methods depending on the coating method of the polymer electrolyte solution. For example, when coating with a comma coater or direct coater, it can be controlled by the solution concentration or the coating thickness on the substrate, and by slit die coating, it is controlled by the discharge pressure, the clearance of the die, the gap between the die and the base material, etc. be able to.

  In the method for producing a composite polymer electrolyte membrane of the present invention, after impregnating the polymer electrolyte solution into the aromatic hydrocarbon polymer nonwoven fabric, the solvent of the coating solution is dried. Can be decided. It is preferable to dry at least to such an extent that it becomes a self-supporting film even if it is peeled off from the substrate. In that case, it is preferable to dry at a decomposition temperature or less in consideration of the heat resistance of the aromatic hydrocarbon-based polymer nonwoven fabric. It is preferable to experimentally determine the heating temperature based on the balance between the aromatic hydrocarbon polymer nonwoven fabric used and the performance of the resulting composite polymer electrolyte membrane. In some cases, the glass transition point of the aromatic hydrocarbon polymer nonwoven fabric And drying at a temperature below the melting point is also preferable for the purpose of maintaining the strength of the aromatic hydrocarbon polymer nonwoven fabric. The drying method can be selected from known methods such as heating of the substrate, hot air, and an infrared heater.

  In the method for producing a composite polymer electrolyte membrane of the present invention, it is necessary to remove the solubility-imparting group before the step of impregnating the polymer electrolyte solution, and to insolubilize the spun aromatic hydrocarbon polymer fiber in the polymer electrolyte solution. There is. The method for removing the solubility-imparting group can be appropriately selected depending on the introduced solubility-imparting group, and includes chemical treatment such as acid or alkaline solution, heat treatment, ultraviolet treatment, radiation treatment, and the like, which can be used in combination. Of these, chemical treatment with an aqueous acid solution or heat treatment with hot air is preferred for the purpose of reducing the residue of components derived from the solubility-imparting group. Furthermore, it is most preferable from the viewpoint of productivity to control conditions such as voltage, collection substrate temperature, spinning atmosphere temperature, etc., and to remove the solubility-imparting group of the aromatic hydrocarbon polymer simultaneously with the electrospinning step.

  In the method for producing a composite polymer electrolyte membrane of the present invention, when an ionic group such as a sulfonic acid group in the composite electrolyte membrane is used in a metal salt state, the metal salt is contacted with an acidic aqueous solution. It is preferable to have a step of proton exchange. Further, by bringing the composite polymer electrolyte membrane into contact with water or an acidic aqueous solution, water-soluble impurities, residual monomers, solvents, residual salts, etc. remaining in the membrane can be removed. When the solubility-imparting group is also contained in the polymer electrolyte solution, it can be removed in this step. Water and acidic aqueous solution may be heated to promote the reaction. The acidic aqueous solution is not particularly limited, such as sulfuric acid, hydrochloric acid, nitric acid, and acetic acid, and the temperature, concentration, and the like can be appropriately selected experimentally. From the viewpoint of productivity, it is preferable to use a 30% by weight or less sulfuric acid aqueous solution of 80 ° C. or less.

  In particular, when the composite polymer electrolyte membrane is continuously produced, it is preferable to perform contact with water and / or an acidic solution while being attached to a support such as a substrate. By contacting with water and / or an acidic solution without peeling off from the substrate, it is possible to prevent rupture of the film due to swelling, wrinkles during drying, and surface defects. This is particularly effective when the composite polymer electrolyte membrane is thin. When the composite polymer electrolyte membrane is thin, the mechanical strength during liquid swelling decreases, the membrane tends to break during manufacturing, and wrinkles occur during drying after contact with water and / or acidic solution. And surface defects are likely to occur. For example, when producing a composite polymer electrolyte membrane having a thickness of 50 μm or less at the time of drying, it is preferable to perform contact with water and / or an acidic solution without peeling off the membrane from the substrate. A thickness of 30 μm or less is more preferable.

  In addition, the composite polymer electrolyte membrane of the present invention has improved mechanical strength and improved thermal stability of ionic groups, improved water resistance, improved solvent resistance, improved radical resistance, and coating properties of the coating liquid. Crystallization nucleating agents, plasticizers, stabilizers, mold release agents, antioxidants, radical scavengers, inorganic fine particles used in crosslinking agents and ordinary polymer compounds for purposes such as improving storage stability Additives such as fillers or fine particles of polyetherketone and polyphenylene sulfide can be added within the range not contrary to the object of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. In addition, the measurement conditions of each physical property are as follows.

A. Ionic acid group density The following procedure is repeated 5 times, and the average value of the three points excluding the maximum and minimum values is defined as the ionic acid group density (mmol / g). The unit of concentration is% by weight, and the unit of weight is g.
(1) The produced electrolyte membrane was cut into 5 cm × 5 cm, dried under reduced pressure at 80 ° C. for 12 hours or more with a vacuum dryer, and the weight (Wm) was measured accurately (four digits after the decimal point).
(2) About 30 ml of about 0.2 wt% KCl aqueous solution was prepared in a sample bottle with a lid, and the weight (Wk) and K ion concentration (C ₁ ) of the KCl aqueous solution were measured. The K ion concentration was measured with a capillary electrophoresis apparatus “CAPI-3300” manufactured by Otsuka Electronics. The measurement conditions are as follows.

Measurement method: Drop method (25mm)
Electrophoresis: Otsuka Electronics Cation Analysis Electrophoresis 5 (α-CFI105)
Measurement voltage: 20kV
(3) The electrolyte membrane was immersed in an aqueous KCl solution having a known weight and K ion concentration for 2 hours.
(4) The K ion concentration (C ₂ ) of the aqueous KCl solution was measured again with a capillary electrophoresis apparatus. From the measured value, the sulfonic acid group density was calculated according to the following formula.
Sulfonic acid group density (mmol / g) = [{Wk × (C ₁ -C ₂ ) × 1000} / 39] / Wm
B. Measurement Method of Fiber Diameter The aromatic hydrocarbon polymer nonwoven fabric was observed with an optical microscope or a scanning electron microscope (SEM), and the average value of the diameter of 20 arbitrary fibers on the screen was shown. Further, when the fiber diameter was difficult to measure and the composite polymer electrolyte membrane were observed by the following method.

  A composite polymer electrolyte membrane dried under reduced pressure at 60 ° C. for 24 hours is cut out with a cutter, embedded with an electron microscope epoxy resin (Quetol 812 manufactured by Nissin EM), and the epoxy resin is placed in an oven at 60 ° C. for 48 hours. After curing, an ultrathin section having a thickness of about 100 nm was prepared with an ultramicrotome (Ultracut S manufactured by Leica).

  The prepared ultrathin section was mounted on a 100-mesh Cu grid manufactured by Oken Shoji Co., Ltd., and TEM observation was performed at 100 kV acceleration voltage using a Hitachi transmission electron microscope H-7100FA, and the fiber diameter was measured.

C. Film thickness It measured using Mitutoyo ID-C112 type | mold set to Mitutoyo granite comparator stand BSG-20.

D. Viscosity measurement Viscosity at a temperature of 25 ° C. was measured using a rotary viscometer (Rheometer RC20 manufactured by Rheotech Co., Ltd.) at a shear rate of 100 (s ⁻¹ ). The geometry was taken from the RHEO2000 software using a cone and plate (attachment to fill the sample). C25-1 (2.5 cmφ) was used as the cone, and when measurement was difficult (less than 10 poise), it was changed to C50-1 (5.0 cmφ).

E. Composite Polymer Electrolyte Dimensional Change Rate The electrolyte membrane was cut into a 6 cm × 1 cm strip, and a marked line was written about 5 mm from both ends on the long side (distance between marked lines: 5 cm). The sample was allowed to stand for 2 hours in a constant temperature bath at a temperature of 23 ° C. and a humidity of 45%, and was quickly sandwiched between two slide glasses, and the distance between marked lines (L ₁ ) was measured with a caliper. Further, after immersing the sample in hot water at 80 ° C. for 2 hours, the sample was quickly sandwiched between _two glass slides, the distance between the marked lines (L ₂ ) was measured with calipers, and the dimensional change rate was calculated according to the following formula.

Dimensional change rate (%) = (L ₂ −L ₁ ) / L ₁ × 100
F. Tensile strength of composite polymer electrolyte membrane when wet
Based on JIS K7127, the sample piece is 1/2 size of dumbbell No. 2 (sample width: 3.0mm, sample length: 16.5mm, 40mm between grips), and the equipment is auto made by Shimadzu with constant temperature and humidity chamber The test was performed at a speed of 200 mm / min using Graph AG-IS 100N. The measurement atmosphere was 80 ° C. and a relative humidity of 94%.

G. Electricity generation evaluation of membrane electrode assembly (MEA) using composite polymer electrolyte membrane (1) Measurement of hydrogen permeation current Commercial electrode, gas diffusion electrode for fuel cell “ELAT (registered trademark) LT120ENSI” 5 g / Prepare a pair of m ² Pt cut to 5 cm square, overlap each other so as to sandwich the composite polymer electrolyte membrane as a fuel electrode and an oxidation electrode, and perform a heat press at 150 ° C. and 5 MPa for 3 minutes, An evaluation MEA was obtained.

Set this MEA in JARI standard cell “Ex-1” (electrode area 25 cm ² ) manufactured by Eiwa Co., Ltd., cell temperature: 80 ° C., supply hydrogen as fuel gas to one electrode and supply nitrogen gas to the other electrode The test was conducted under humidifying conditions: hydrogen gas 90% RH and nitrogen gas 90% RH. The voltage was kept at OCV until it became 0.2 V or less, and the voltage was swept from 0.2 to 0.7 V at 1 mV / sec to examine the change in the current value. In this example, measurement was performed before and after the following start / stop test, and the value at 0.6 V was examined. When the membrane breaks, the amount of hydrogen permeation increases and the permeation current increases. In addition, this evaluation was carried out using a Solartron electrochemical measurement system (Solartron 1480 Electrochemical Interface and Solartron 1255B Frequency Response Analyzer).

(2) Durability test Using the above cell, cell temperature: 80 ° C., fuel gas: hydrogen, oxidizing gas: air, gas utilization rate: hydrogen 70% / oxygen 40%, humidification condition: hydrogen gas 60% RH, air : The test was performed under the condition of 50% RH. The conditions are: hold for 1 minute at OCV, generate electricity for 2 minutes at a current density of 1 A / cm ² , finally stop supplying hydrogen gas and air for 2 minutes, and repeat this as one cycle A sex test was performed. The hydrogen permeation current was measured before and after 3000 cycles and the difference was examined. In addition, the load fluctuation in this test was performed using an electronic load device “PLZ664WA” manufactured by Kikusui Electronics Corporation.

(3) Evaluation of power generation under low humidification The above fuel cell has a cell temperature of 80 ° C., fuel gas: hydrogen, oxidizing gas: air, gas utilization rate: hydrogen 70% / oxygen 40%, humidification condition; anode side 30% RH / Current-voltage (IV) measurement was performed at a cathode of 30% RH and a back pressure of 0.1 MPa (both electrodes). A value obtained by dividing the point at which the product of the current and voltage in the current-voltage curve becomes the highest by the electrode area was taken as the output density.

[Synthesis Example 1; monomer having a solubility-imparting group]
Synthesis of 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane (G1) Montmorillonite clay K10 (150 g), 99 g of dihydroxybenzophenone were distilled in 242 mL of ethylene glycol / 99 mL of trimethyl orthoformate to produce by-products. The reaction was carried out at 110 ° C. After 18 hours, 66 g of trimethyl orthoformate was added and reacted for 48 hours of synthesis. To the reaction solution was added 300 mL of ethyl acetate, and after filtration, extraction was performed 4 times with a 2% aqueous sodium hydrogen carbonate solution. Further, after concentration, the desired 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane was obtained by recrystallization from dichloroethane.

[Synthesis Example 2: Monomer having ionic group]
Synthesis of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone (G2) 109.1 g of 4,4′-difluorobenzophenone (Aldrich reagent) and 150 mL of fuming sulfuric acid (50% SO3) (Wako Pure Chemicals) The mixture was reacted at 100 ° C. for 10 hours. Thereafter, the mixture was poured little by little into a large amount of water, neutralized with NaOH, and 200 g of sodium chloride was added to precipitate the composite. The resulting precipitate was filtered off and recrystallized with an aqueous ethanol solution to obtain disodium 3,3′-disulfonate-4,4′-difluorobenzophenone.

Reference Example 1 Production Example of Spinning Stock Solution A of Aromatic Hydrocarbon Polymer Having Soluble Group-Providing Group
In a 5 L reaction vessel equipped with a stirrer, a nitrogen introduction tube, and a Dean-Stark trap, 37 g of 4,4′-biphenol (Aldrich reagent) and monomer 2,2-bis (having a solubility-imparting group synthesized in Synthesis Example 1) 4-hydroxyphenyl) -1,3-dioxolane 207 g, 4,4′-difluorobenzophenone 223 g (Aldrich reagent), and after nitrogen substitution, N-methyl-2-pyrrolidone (NMP) 1500 g and toluene 500 g were added, After confirming that all the monomers were dissolved, 152 g of potassium carbonate (Aldrich reagent) was added, dehydrated at 160 ° C. while refluxing, heated to remove toluene, and subjected to desalting polycondensation at 190 ° C. for 1 hour. Next, NMP was added and diluted so that the viscosity of the polymerization stock solution was 0.5 Pa · s.
Next, the polymerization stock solution was directly centrifuged using an inverter / compact high-speed cooling centrifuge manufactured by Kubota Seisakusho (model No. 6930 with an angle rotor RA-800, 25 ° C., 30 minutes, centrifugal force 20000 G). Since the precipitated solid (cake) and the supernatant (coating solution) could be separated cleanly, the supernatant was recovered. Next, the solution was distilled under reduced pressure at 80 ° C. with stirring to remove NMP until the viscosity reached 5 Pa · s, and further filtered under pressure with a 5 μm polytetrafluoroethylene (PTFE) filter to obtain a spinning dope A. .

[Reference Example 2: Production Example of Spinning Stock Solution B of Aromatic Hydrocarbon Polymer Having Soluble Group-Providing Group]
Monomer 2,2-bis having a solubility-imparting group synthesized in Synthesis Example 1 and 43 g of 4,4′-dihydroxybenzophenone (Aldrich reagent) in a 5 L reaction vessel equipped with a stirrer, a nitrogen introduction tube, and a Dean-Stark trap 207 g of (4-hydroxyphenyl) -1,3-dioxolane, 200 g of 4,4′-difluorobenzophenone (Aldrich reagent), (Aldrich reagent), and disodium 3 which is a monomer containing the ionic group synthesized in Synthesis Example 2 , 3′-disulfonate-4,4′-difluorobenzophenone 44 g, and after nitrogen substitution, 1700 g of N-methyl-2-pyrrolidone (NMP), 500 g of toluene, 24 g of 18-crown-6 as a polymerization stabilizer (Wako Pure) Drug reagent) and after confirming that all of the monomer has dissolved, 276 g (Aldrich reagent, 2.0 mol) and the mixture was dehydrated at 160 ° C. under reflux, heated and then toluene is removed and subjected to 1 hour desalting polycondensation 190 ° C.. The resulting polymer had an ionic group density of 0.45 mmol / g and a weight average molecular weight of 360,000. Next, NMP was added so that the viscosity of the polymerization stock solution was 0.5 Pa · s, and then NMP was added and diluted so that the viscosity of the polymerization stock solution was 0.5 Pa · s.

  Next, the polymerization stock solution was directly centrifuged using an inverter / compact high-speed cooling centrifuge manufactured by Kubota Seisakusho (model No. 6930 with an angle rotor RA-800, 25 ° C., 30 minutes, centrifugal force 20000 G). Since the precipitated solid (cake) and the supernatant (coating solution) could be separated cleanly, the supernatant was recovered. Next, the solution was distilled under reduced pressure at 80 ° C. with stirring to remove NMP until the viscosity reached 10 Pa · s, and further filtered under pressure through a 5 μm polytetrafluoroethylene (PTFE) filter to obtain a spinning dope B .

Reference Example 3 Production Example of Spinning Stock Solution C of Aromatic Hydrocarbon Polymer Having Soluble Group-Providing Group
In a 5 L reaction vessel equipped with a stirrer, a nitrogen introduction tube, and a Dean-Stark trap, 37 g of 4,4′-biphenol (Aldrich reagent) and monomer 2,2-bis (having a solubility-imparting group synthesized in Synthesis Example 1) 4-hydroxyphenyl) -1,3-dioxolane 207 g, 4,4′-difluorobenzophenone 223 g (Aldrich reagent), and after nitrogen substitution, N-methyl-2-pyrrolidone (NMP) 1500 g and toluene 500 g were added, After confirming that all the monomers were dissolved, 152 g of potassium carbonate (Aldrich reagent) was added, dehydrated at 160 ° C. while refluxing, heated to remove toluene, and subjected to desalting polycondensation at 190 ° C. for 1 hour. Next, NMP was added and diluted so that the viscosity of the polymerization stock solution was 0.5 Pa · s.

  Next, the polymerization stock solution was directly centrifuged using an inverter / compact high-speed cooling centrifuge manufactured by Kubota Seisakusho (model No. 6930 with an angle rotor RA-800, 25 ° C., 30 minutes, centrifugal force 20000 G). Since the precipitated solid (cake) and the supernatant (coating solution) could be separated cleanly, the supernatant was recovered. Next, NMP was removed under reduced pressure at 80 ° C. with stirring until the viscosity reached 1 Pa · s. 3 parts by weight of glycerin was added to this solution, followed by pressure filtration with a 5 μm polytetrafluoroethylene (PTFE) filter to obtain a spinning dope C.

[Reference Example 4: Production Example of Polymer Electrolyte Solution A]
129 g of monomer 2,2-bis (4-hydroxyphenyl) -1,3-dioxolane having a solubility-imparting group synthesized in Synthesis Example 1 in a 5 L reaction vessel equipped with a stirrer, nitrogen introduction tube, and Dean-Stark trap , 4,4′-biphenol 93 g (Aldrich reagent) and 422 g (1.0 mol) of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone which is a monomer containing the ionic group synthesized in Synthesis Example 2 ), And after nitrogen substitution, 3000 g of N-methyl-2-pyrrolidone (NMP), 450 g of toluene, and 232 g of 18-crown-6 (Wako Pure Chemical Reagent) as a polymerization stabilizer were added, and it was confirmed that all the monomers were dissolved. Then, 304 g of potassium carbonate (Aldrich reagent) was added, dehydrated at 160 ° C. while refluxing, and heated to increase the temperature. And ene removed and subjected to 1 hour desalting polycondensation 200 ° C.. The obtained polymer had an ionic group density of 3.52 mmol / g and a weight average molecular weight of 320,000. Next, NMP is added and diluted so that the viscosity of the polymerization stock solution becomes 0.5 Pa · s, and an inverter / compact high-speed cooling centrifuge manufactured by Kubota Manufacturing Co., Ltd. (Model No. 6930 is set with an angle rotor RA-800, 25 ° C., 30 ° C.) The polymerization stock solution was directly centrifuged at a centrifugal force of 20000 G) for a minute. Since the precipitated solid (cake) and the supernatant (coating solution) could be separated cleanly, the supernatant was recovered. Next, it is distilled under reduced pressure at 80 ° C. while stirring, NMP is removed until the viscosity becomes 2 Pa · s, and further filtered under pressure with a 5 μm polytetrafluoroethylene (PTFE) filter to obtain the polymer electrolyte solution A. Obtained.

Example 1
Using spinning stock solution A, using an electrospinning unit manufactured by Kato Tech Co., Ltd., voltage 40 kV, syringe pump discharge speed 0.05 cc / min, traverse speed 50 mm / min, peripheral speed of drum type target (diameter 100 mm) 0.8 m Electrospinning was performed under the conditions of 100 mm / min and a distance between the syringe and the target of 100 mm.

  The average diameter of the obtained aromatic hydrocarbon polymer fibers was 400 nm, and the fibers were collected on a target to obtain an aromatic hydrocarbon polymer nonwoven fabric A having a thickness of 15 μm.

  When this aromatic hydrocarbon polymer nonwoven fabric A was partially cut out and immersed in NMP, it was found that insoluble matter was seen and the solubility-imparting group was removed in the electrospinning process.

  Next, the polymer electrolyte solution A of Reference Example 4 was cast and applied onto a 125 μm PET film (“Lumirror (registered trademark)” manufactured by Toray), and an aromatic hydrocarbon polymer nonwoven fabric A was formed thereon. The polymer electrolyte solution A was impregnated in the voids of the aromatic hydrocarbon polymer nonwoven fabric A. The aromatic hydrocarbon-based polymer nonwoven fabric A remained in its original form without dissolving in the polymer electrolyte solution A containing the same solvent. Next, it was put into a hot air dryer, and the solvent was removed by drying at 100 ° C. for 10 minutes and at 150 ° C. for 20 minutes. Next, it is immersed in a 10% by weight sulfuric acid aqueous solution at 40 ° C. for 30 minutes while remaining attached to the PET substrate to remove proton exchange and solubility-imparting groups of the polymer electrolyte, and is washed until the washing water becomes neutral. And after re-drying at 60 ° C., it was peeled off from the PET substrate to obtain a composite polymer electrolyte membrane A. The produced aromatic hydrocarbon polymer fibers and the polymer electrolyte were compatible with the same polymer structure.

The ionic group density of this composite polymer electrolyte membrane A was 2.6 mmol / g. Using this composite polymer electrolyte membrane A, the dimensional change was measured and found to be 1.0%, and the tensile strength at break when wet was 50 MPa. The output of the fuel cell using the composite polymer electrolyte membrane A under low humidification is 550 mW / cm ² , and the hydrogen permeation current before and after the power generation durability evaluation test was measured. after evaluated at / cm ² was good is durability 0.51MA / cm ^2.

Example 2
Except that the spinning solution B was used and the voltage was set to 20 kV, the electrospinning was carried out in the same manner as in Example 1, and the aromatic hydrocarbon type having an average fiber diameter of 450 nm and consisting of an aromatic hydrocarbon type polymer fiber having a thickness of 20 μm. A polymer nonwoven fabric B was obtained. As the solubility-imparting group removal step of this aromatic hydrocarbon-based polymer nonwoven fabric B, it is immersed in a 10% by weight sulfuric acid aqueous solution at 60 ° C. for 60 minutes until the solubility-imparting group is removed by hydrolysis, and the washing water becomes neutral. Washing with water was repeated, followed by drying with hot air at 60 ° C. When a part of the aromatic hydrocarbon polymer nonwoven fabric B after removal of the solubility-imparting group was cut out and immersed in NMP, insoluble matters were observed.

  Next, the polymer electrolyte solution A of Reference Example 4 was cast and applied onto a 125 μm PET film (“Lumirror (registered trademark)” manufactured by Toray Industries, Inc.), and an aromatic hydrocarbon polymer nonwoven fabric B was formed thereon. The polymer electrolyte solution A was impregnated into the voids of the aromatic hydrocarbon polymer nonwoven fabric B. The aromatic hydrocarbon polymer non-woven fabric B remained in its original form without dissolving in the polymer electrolyte solution A containing the same solvent. Next, it was put into a hot air dryer, and the solvent was removed by drying at 100 ° C. for 10 minutes and at 150 ° C. for 20 minutes. Next, it is immersed in a 10% by weight sulfuric acid aqueous solution at 40 ° C. for 30 minutes while remaining attached to the PET substrate to remove proton exchange and solubility-imparting groups of the polymer electrolyte, and is washed until the washing water becomes neutral. Was repeated after drying with hot air at 60 ° C., and then peeled off from the PET substrate to obtain a composite polymer electrolyte membrane B. The produced aromatic hydrocarbon polymer fibers and the polymer electrolyte were compatible with the same polymer structure.

The ionic group density of this composite polymer electrolyte membrane B was 2.8 mmol / g. Using this composite polymer electrolyte membrane B, the dimensional change was measured and found to be 1.0%, and the tensile strength at break when wet was 60 MPa. The output of the fuel cell using the composite polymer electrolyte membrane B under low humidification is 590 mW / cm ² , and the hydrogen permeation current before and after the power generation durability evaluation test was measured. After the evaluation at / cm ^2, it was 0.60 mA / cm ² and the durability was good.

Comparative Example 1
Except not adopting the solubility-imparting group removal step of the aromatic hydrocarbon polymer nonwoven fabric B of Example 2, the impregnation step of the polymer electrolyte solution was carried out in the same manner as in Example 2, and the composite polymer electrolyte membrane C Got. However, the aromatic hydrocarbon polymer fiber was dissolved in the polymer electrolyte solution A and did not remain in its original form, and the fiber could not be observed even with TEM. The composite polymer electrolyte membrane C had an ionic group density of 2.8 mmol / g, a dimensional change rate of 1.0%, and a tensile strength at break of 60 MPa when wet. However, the output of the fuel cell using the composite polymer electrolyte membrane C under low humidification is 81 mW / cm ² , and the aromatic hydrocarbon polymer nonwoven fabric B is dissolved in the composite polymer electrolyte membrane C. A layer with low proton conductivity was formed.

Comparative Example 2
In place of the aromatic hydrocarbon polymer nonwoven fabric A, a polyvinyl alcohol (PVA) nonwoven fabric having an average fiber diameter of 300 nm was used, and a composite polymer electrolyte membrane D was obtained in the same manner as in Example 1. The ionic group density of this composite polymer electrolyte membrane D was 2.5 mmol / g. Using this composite polymer electrolyte membrane D, the dimensional change rate was measured and found to be 1.8%, and the tensile strength at break when wet was 45 MPa. The output of the fuel cell using the composite polymer electrolyte membrane D under low humidification is 350 mW / cm ² , and the hydrogen permeation current before and after the power generation durability evaluation test was measured. After evaluation at 4 cm / cm ^2, it was 40.5 mA / cm ² and the durability was poor. This non-woven fabric made of PVA was not manufactured by the electrospinning method, and had no compatibility with a polymer structure different from that of the polymer electrolyte, so that the durability was insufficient.

Example 3
Spinning was performed except that a polyphenylene sulfide (PPS) paper product (Toray Industries Paper (registered trademark)) manufactured by Toray was set on the target of the electrospinning process of Example 1 and having an average fiber diameter of 10 μm and a basis weight of 10 g / m ^2. Electrospinning was performed in the same manner using the stock solution A, and a composite aromatic hydrocarbon polymer nonwoven fabric A in which the voids of the PPS paper body were filled with an aromatic hydrocarbon polymer fiber having an average fiber diameter of 400 nm was obtained. .

  The polymer electrolyte solution A of Reference Example 4 was cast coated on a 125 μm PET film (“Lumirror (registered trademark)” manufactured by Toray Industries, Inc.), and the resultant composite aromatic hydrocarbon system was obtained thereon. The polymer nonwoven fabric A was bonded together, and the polymer electrolyte solution A was impregnated in the voids of the composite aromatic hydrocarbon-based polymer nonwoven fabric A. The composite aromatic hydrocarbon polymer nonwoven fabric A remained in its original form without being dissolved in the polymer electrolyte solution A containing the same solvent. Next, it was put into a hot air dryer, and the solvent was removed by drying at 100 ° C. for 10 minutes and at 150 ° C. for 20 minutes. Next, it is immersed in a 10% by weight sulfuric acid aqueous solution at 40 ° C. for 30 minutes while remaining attached to the PET substrate to remove proton exchange and solubility-imparting groups of the polymer electrolyte, and is washed until the washing water becomes neutral. And after re-drying at 60 ° C., it was peeled from the PET base material to obtain a composite polymer electrolyte membrane E. The aromatic hydrocarbon polymer fiber, which is a main component of the composite aromatic hydrocarbon polymer nonwoven fabric A, and the polymer electrolyte had compatibility with the same polymer structure.

The ionic group density of this composite polymer electrolyte membrane E was 2.5 mmol / g. Using this composite polymer electrolyte membrane E, the dimensional change was measured and found to be 0.6%, and the tensile strength at break when wet was 80 MPa. The output of the fuel cell using the composite polymer electrolyte membrane E under low humidification is 530 mW / cm ² , and the hydrogen permeation current before and after the power generation durability evaluation test was measured. After the evaluation at / cm ^2, it was 0.35 mA / cm ² and the durability was good.
Example 4
Using the spinning dope C, electrospinning was carried out in the same manner as in Example 1 to obtain an aromatic hydrocarbon polymer nonwoven fabric C having a thickness of 20 μm and comprising aromatic hydrocarbon polymer fibers having an average fiber diameter of 150 nm. As a process for removing the solubility-imparting group of the aromatic hydrocarbon-based nonwoven fabric C, it is immersed in a 10% by weight sulfuric acid aqueous solution at 60 ° C. for 60 minutes until the solubility-imparting group is removed by hydrolysis, and the washing water shows neutrality. Washing with water was repeated, followed by drying with hot air at 60 ° C. When a part of the aromatic hydrocarbon polymer nonwoven fabric C after the removal of the solubilizing group was cut out and immersed in NMP, insoluble matters were observed.

  Next, the polymer electrolyte solution A of Reference Example 4 was cast and applied onto a 125 μm PET film (“Lumirror (registered trademark)” manufactured by Toray), on which an aromatic hydrocarbon polymer nonwoven fabric C was applied. And the polymer electrolyte solution A was impregnated in the voids of the aromatic hydrocarbon polymer nonwoven fabric C. The aromatic hydrocarbon-based polymer nonwoven fabric C remained intact without being dissolved in the polymer electrolyte solution A containing the same solvent. Next, the PET substrate was brought into contact with the hot plate, and the impregnation promotion and the solvent were removed by drying at 100 ° C. for 15 minutes. Next, it is immersed in a 10% by weight sulfuric acid aqueous solution at 60 ° C. for 30 minutes while remaining attached to the PET substrate to remove proton exchange and solubility-imparting groups of the polymer electrolyte, and is washed until the washing water becomes neutral. Was repeated after drying with hot air at 60 ° C., and then peeled off from the PET substrate to obtain a composite polymer electrolyte membrane F. The produced aromatic hydrocarbon polymer fibers and the polymer electrolyte were compatible with the same polymer structure.

The ionic group density of this composite polymer electrolyte membrane F was 3.2 mmol / g. Using this composite polymer electrolyte membrane F, the dimensional change rate was measured and found to be 1.1%, and the tensile strength at break when wet was 58 MPa. The output of the fuel cell using the composite polymer electrolyte membrane F under low humidification is 605 mW / cm ² , and the hydrogen permeation current before and after the power generation durability evaluation test was measured. After the evaluation at / cm ^2, it was 0.53 mA / cm ² and the durability was good.

  The method for producing a composite polymer electrolyte membrane of the present invention is capable of producing a composite polymer electrolyte membrane having excellent ionic conductivity and small dimensional change in a wet / dry cycle, and the composite polymer electrolyte obtained in the present invention. The membrane can be applied to various electrochemical devices (for example, a fuel cell, a water electrolysis device, a chloroalkali electrolysis device, etc.). Among these devices, it is suitable for a fuel cell, particularly suitable for a fuel cell using hydrogen or a methanol aqueous solution as a fuel, a mobile phone, a personal computer, a PDA, a video camera (camcorder), a digital camera, a handy terminal, an RFID reader. , Digital audio players, portable devices such as various displays, electric appliances such as electric shavers and vacuum cleaners, electric tools, household power supply machines, cars such as passenger cars, buses and trucks, motorcycles, forklifts, electric assist bicycles, electric It is preferably used as a power supply source for a cart, an electric wheelchair, a moving body such as a ship and a railway, various robots, and a cyborg. Especially in portable devices, it is used not only for power supply sources, but also for charging secondary batteries installed in portable devices, and also suitable as a hybrid power supply source used in combination with secondary batteries, capacitors, and solar cells. Available to:

10: Syringe 20: Needle 30 of syringe: Conveyor drum 40: High voltage power supply 50: Syringe pump

Claims (3)

A method for producing a composite polymer electrolyte membrane comprising an aromatic hydrocarbon polymer fiber and a polymer electrolyte membrane, the electrospinning process using a spinning stock solution comprising an aromatic hydrocarbon polymer containing a solubility-imparting group and a solvent A step of making the obtained aromatic hydrocarbon polymer fiber into a non-woven fabric, and a step of impregnating the obtained aromatic hydrocarbon polymer non-woven fabric with a polymer electrolyte solution, and a step of impregnating the polymer electrolyte solution A method for producing a composite polymer electrolyte membrane, comprising removing a solubility-imparting group previously and insolubilizing a spun aromatic hydrocarbon polymer fiber in a polymer electrolyte solution. The method for producing a composite polymer electrolyte membrane according to claim 1, wherein a polyhydric alcohol is added to the spinning dope. A composite polymer electrolyte membrane comprising an aromatic hydrocarbon polymer nonwoven fabric and a polymer electrolyte, wherein the aromatic hydrocarbon polymer fiber and the polymer electrolyte have the same polymer structure and are compatible Composite polymer electrolyte membrane.

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