JP5347848B2 - Method for producing polymer electrolyte membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a polymer electrolyte membrane capable of suppressing the occurrence of form failure such as wrinkles and deformation (especially, fine membrane deformation ). <P>SOLUTION: The method of manufacturing an aromatic hydrocarbon polymer electrolyte membrane includes a step of obtaining a casting film of a polymer electrolyte precursor, a step of obtaining the polymer electrolyte precursor, a step of obtaining a polymer electrolyte membrane by converting a salt of the polymer electrolyte precursor into proton, a step of leaving the polymer electrolyte membrane for 1 second to 10 minutes in an atmosphere of a relative humidity 60% RH or more, and a step of cleaning the polymer electrolyte membrane, in this order. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a polymer electrolyte membrane.

  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. Therefore, recently, a polymer electrolyte membrane (aromatic hydrocarbon polymer electrolyte membrane) made of an aromatic hydrocarbon polymer is often used.

  An aromatic hydrocarbon-based polymer electrolyte (hereinafter sometimes simply referred to as “polymer electrolyte”) membrane is generally casted on a support with a solvent solution of the polymer electrolyte, and then dried. Although manufactured, at that time, proton conductivity and fuel permeation suppression 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 Documents 1 and 2, a solvent solution of a polymer electrolyte is cast on a support to obtain a cast film, and then the residual solvent amount is specified when removing the solvent from the cast film. A method for producing a polymer electrolyte membrane that is adjusted to a value below the value is disclosed.

  In Patent Documents 3 to 6, a solvent solution of a polymer electrolyte precursor is cast on a support to obtain a cast film, and then the solvent is removed from the cast film and the residual solvent amount is specified. A method for producing a polymer electrolyte membrane by treating with an acidic solution after preparing a polymer electrolyte precursor membrane adjusted to a value of 1 or less is disclosed.

JP 2008-156622 A JP 2008-159580 A JP 2005-268145 A JP 2006-253002 A JP 2008-181856 A JP 2008-277241 A

  The cause of the decrease in proton conductivity and fuel permeation suppression of the polymer electrolyte membrane is thought to be due to morphological defects such as wrinkles and deformation generated in the polymer electrolyte membrane in the production process. However, the above manufacturing method may not sufficiently prevent the occurrence of wrinkles and undulations, particularly the occurrence of minute deformation. Such problems are more likely to occur as the thickness of the polymer electrolyte membrane is reduced.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a polymer electrolyte membrane capable of suppressing the occurrence of morphological defects (particularly minute membrane deformation) such as wrinkles and deformation. It is to provide a manufacturing method.

  As a result of intensive studies, the present inventors have determined that in order to obtain a polymer electrolyte membrane having a good form (quality) by suppressing the occurrence of morphological defects such as minute deformation of the membrane during the film formation of the polymer electrolyte. It was found that the film atmosphere in this process greatly affects. As a result of further investigation, an appropriate atmospheric condition capable of suppressing minute deformation of the film was established, and the present invention was completed.

  That is, the method for producing an aromatic hydrocarbon-based polymer electrolyte membrane according to the present invention, which has been able to solve the above-mentioned problems, has an aromatic hydrocarbon-based polymer having an acidic group at least partially forming a salt. Casting a solution obtained by dissolving a molecular electrolyte precursor in a solvent on a support to obtain a cast film of the polymer electrolyte precursor; and removing the solvent from the cast film; A step of obtaining a polymer electrolyte precursor membrane, a step of converting the salt of the polymer electrolyte precursor into protons in a solution of an acidic component having a pKa of 3 or less, and obtaining a polymer electrolyte membrane; Placing the molecular electrolyte membrane in an atmosphere of relative humidity of 60% RH or more for 1 second to 10 minutes, and washing the polymer electrolyte membrane with a poor solvent of the polymer electrolyte membrane capable of dissolving the acidic component Are included in this order.

  In the present invention, the period from the step of obtaining the cast membrane to the step of washing is performed in a state where the membrane is supported by the support, or in the step of obtaining the cast membrane, 80 mol% of the acidic groups In the step of forming the salt and obtaining the polymer electrolyte membrane, 90 mol% or more of the salt is converted to protons, the acidic group contains at least a sulfonic acid group, It is preferable that the method includes a step of drying the polymer electrolyte membrane after washing obtained through the step of washing, and the thickness of the polymer electrolyte membrane after drying obtained through the step of drying is 50 μm or less. It is an aspect.

  In the method for producing a polymer electrolyte membrane of the present invention, since the polymer electrolyte membrane obtained in the production process is placed in a predetermined atmosphere, a polymer electrolyte membrane having a small film thickness (specifically, 50 μm or less) is used. Even in the case of manufacturing, the occurrence of minute deformation can be suppressed. As a result, a polymer electrolyte membrane having a good form can be obtained.

  The method for producing an aromatic hydrocarbon polymer electrolyte membrane according to the present invention comprises a solution in which an aromatic hydrocarbon polymer electrolyte precursor having an acidic group, at least part of which forms a salt, is dissolved in a solvent. On a support to obtain a cast film of the polymer electrolyte precursor, to remove the solvent from the cast film to obtain a polymer electrolyte precursor film, and 3 A step of converting the salt of the polymer electrolyte precursor to protons in a solution of an acidic component having the following pKa to obtain a polymer electrolyte membrane, and the polymer electrolyte membrane having a relative humidity of 60% RH or more The method includes a step of placing in an atmosphere for 1 second to 10 minutes and a step of washing the polymer electrolyte membrane with a poor solvent for the polymer electrolyte membrane capable of dissolving the acidic component in this order.

  In general, when a polymer electrolyte membrane is produced (formed) using an aromatic hydrocarbon-based polymer electrolyte, the smaller the film thickness is, the smaller the membrane (polymer electrolyte) becomes in the middle of the film formation. Problems such as deformation are likely to occur. On the other hand, as in the present invention, these problems can be solved by appropriately adjusting the membrane atmosphere until the washing step after the step of obtaining the polymer electrolyte membrane (step of converting the salt of acidic group into proton). Was able to be resolved.

  Hereafter, the manufacturing method of the polymer electrolyte membrane of this invention is demonstrated in detail. In addition, as long as the polymer electrolyte membrane which concerns on this invention is manufactured through the said process, the aspect of the aromatic hydrocarbon type polymer which comprises a polymer electrolyte is not specifically limited. Therefore, in the present specification, the manufacturing process characterizing the present invention (especially, the atmospheric conditions for exposing the polymer electrolyte membrane) will be described first, followed by a description of specific embodiments of the aromatic hydrocarbon polymer. To do.

(Step of obtaining a cast film)
The solvent used in this step is not particularly limited as long as it can uniformly dissolve or disperse the polymer electrolyte precursor, and may be appropriately selected according to the structure of the polymer electrolyte precursor. A polar solvent is preferred, and an aprotic polar solvent is more preferred. 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 to 300 ° C. If it is lower than 100 ° C., the form may be deteriorated during film formation, which is not preferable. If the temperature exceeds 300 ° C., a large amount of energy is required for the production of the polymer electrolyte membrane, and it may be difficult to control the solvent content in the polymer electrolyte precursor membrane to an appropriate range.

  The solid content concentration of the solvent solution of the polymer electrolyte precursor can be appropriately determined depending on the molecular weight of the polymer electrolyte precursor, the temperature at the time of casting, and the like, specifically in the range of 5 to 50% by mass. Preferably there is. If it 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 deteriorate, or the solvent content in the film may not be appropriately controlled. If it exceeds 50% by mass, the viscosity of the solvent solution becomes too high and handling may be difficult. More preferably, it is 5-35 mass%.

  The viscosity of the solvent solution of the polymer electrolyte precursor is not particularly limited, but is preferably in a range where it can be cast on the support satisfactorily. More preferably, the viscosity is in the range of 1 to 1000 Pa · s at the casting temperature.

  As a method of casting the polymer electrolyte precursor solution on the support, a known method can be used, but it is preferable to cast a solution having a constant concentration so as to have a constant thickness. For example, the polymer electrolyte precursor solution is supplied at a constant rate using a method such as a doctor blade or an applicator to push the solution into a gap with a constant gap to make the casting thickness constant, or a slot die. The method of extending is mentioned. The casting on the support may be carried out by a batch method, but it is preferable to carry it continuously because the productivity is good.

  The support for casting the polymer electrolyte precursor solution is not particularly limited as long as it does not dissolve in the solvent used to dissolve or disperse the polymer electrolyte precursor, but it is flat and flexible. Is preferable. For example, resin films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyarylate, polyamide, polyimide, polyamideimide, polyaramid, polybenzazole, etc., 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.

(Process for obtaining a polymer electrolyte precursor film)
In this step, the method of removing the solvent from the cast film of the polymer electrolyte precursor is not particularly limited, and examples thereof include a method of evaporating the solvent by heating the cast film. The solvent content in the precursor film obtained by heating the cast film is preferably 10 to 50% by mass (more preferably 15 to 30% by mass). If it is less than 10% by mass, the polymer electrolyte membrane or the support may be cleaved, and the shape of the polymer electrolyte membrane may deteriorate. When the amount is more than 50% by mass, the swelling property of the polymer electrolyte membrane may be increased.

  The heating temperature of the cast film is preferably 300 ° C. or lower or the boiling point of the solvent or lower, and more preferably 200 ° C. or lower. When the heating temperature exceeds 300 ° C., the solvent removal efficiency is improved, but the solvent and polymer electrolyte precursor are decomposed and altered, and the form of the resulting polymer electrolyte membrane is deteriorated (quality is lowered). There is a case. 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.

  In the present invention, it is preferable to extract the solvent in the precursor film with a poor solvent of the polymer electrolyte precursor that is mixed with the solvent after the cast film is heated to evaporate the solvent. Without such extraction, the amount of the solvent remaining in the polymer electrolyte membrane increases so that problems such as a decrease in ion conductivity and a decrease in characteristics such as an increase in membrane swelling tend to occur.

  As a poor solvent, what is necessary is just to use an appropriate thing according to the kind of solvent used by the precursor film | membrane and the casting process. For example, water, alcohol, ketone, ether, low molecular hydrocarbon, halogen-containing solvent and the like can be mentioned. When the solvent used in the casting process is miscible with water, it is preferable to use water as the poor solvent.

  The method for extracting the solvent in the precursor film with a poor solvent is not particularly limited, but it is preferable to carry out so that the poor solvent uniformly contacts the precursor film. For example, a method of immersing the precursor film in a poor solvent and a method of applying or spraying the poor solvent to the precursor film can be mentioned. These methods may be performed two or more times or in combination.

  The temperature of the poor solvent is preferably not lower than the melting point and not higher than the boiling point of the poor solvent to be used. When the poor solvent is water, it is preferably in the range of 20 to 70 ° C, more preferably 20 to 50 ° C. When the temperature is high, the solvent removal efficiency is improved, but the form and performance of the film may be lowered. Further, when the temperature is low, the solvent removal efficiency is lowered, and the productivity may be lowered.

  In this invention, it is preferable that the content rate of the solvent in the precursor film | membrane obtained through the extraction operation by the said poor solvent is 0.1-3.0 mass%. If it is less than 0.1% by mass, production problems such as peeling of the film from the support may occur in the subsequent steps. If it is greater than 3.0% by mass, the membrane properties may be degraded, such as a decrease in proton conductivity and an increase in swellability. The content of the solvent in the precursor film after the extraction operation is more preferably 0.1 to 2.0% by mass, and further preferably 0.1 to 1.0% by mass.

  The solvent content of the precursor film can be measured by any known method. For example, a method in which the polymer electrolyte precursor is dissolved in another appropriate solvent, and the solvent is quantified by liquid chromatography or gas chromatography, or the solvent is extracted with an appropriate extraction solvent such as water and quantified , NMR measurement of precursor film, method of quantifying from integral value of peak derived from solvent and peak derived from polymer electrolyte precursor, absorption spectrum of precursor film such as infrared, near infrared, ultraviolet, visible Can be used, and a method of quantifying from the absorbance of the solvent component, a method of quantifying by thermogravimetry (TGA) by weight reduction due to evaporation of the solvent during heating, and the like. The measurement may be performed during the manufacturing process, or may be performed off-line by sampling from the process so that the content does not change.

(Process for obtaining a polymer electrolyte membrane)
In this step, an acidic group possessed by the polymer electrolyte precursor having a reduced solvent content using a solution of an acidic component having a pKa of 3 or less (hereinafter sometimes simply referred to as “acidic solution”). Is converted to protons to obtain a polymer electrolyte membrane.

  The acidic solution having a pKa of 3 or less used in this step is at least selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, perchloric acid, methanesulfonic acid, trifluoroacetic acid, sulfonimide, oxo acid and the like. An aqueous solution in which one kind of acidic component is dissolved may be mentioned, and the pKa of the acidic component is preferably equal to or smaller than the salt of the acidic group of the polymer electrolyte precursor. When the acidic group of the polymer electrolyte is a sulfonic acid group, the acidic component is preferably sulfuric acid, hydrochloric acid, methanesulfonic acid, or trifluoroacetic acid, and more preferably sulfuric acid. The concentration of the acidic component in the acidic solution is not particularly limited. For example, when the acid group salt of the polymer electrolyte precursor is a sulfonic acid group salt, the concentration of the acidic component is in the range of 1 to 75% by mass. Is preferred. If the concentration is less than 1% by mass, a large amount of acidic solution is required for conversion to protons, which may cause a problem in productivity. When the concentration exceeds 75% by mass, the dissociation degree of the acidic component in the acidic solution may decrease, and the conversion efficiency may decrease.

  Although there is no particular limitation on the method for converting the salt of the acidic group possessed by the polymer electrolyte precursor into protons using an acidic solution, it is preferable to carry out the acidic solution so that it is in uniform contact with the precursor membrane. For example, the method of immersing a precursor film | membrane in an acidic solution, and the method of apply | coating or spraying an acidic solution to a precursor film | membrane are mentioned. These methods may be performed in two or more times or in combination.

  The contact amount of the acidic solution with respect to the precursor film is not particularly limited, but is preferably an amount that converts 90 mol% or more of the salt of the acidic group of the polymer electrolyte precursor into protons. When the conversion rate to protons is less than 90 mol%, the proton conductivity of the polymer electrolyte membrane is lowered, and there may be a problem that a high output cannot be obtained when a fuel cell is obtained. The higher the conversion rate to protons, the better, more preferably 95 mol% or more, still more preferably 99 mol% or more, and most preferably 100 mol%.

(The process of placing in a predetermined humidity atmosphere)
The present invention includes a step of placing a polymer electrolyte membrane obtained by converting a salt of an acidic group contained in a polymer electrolyte precursor into protons in an atmosphere having a relative humidity of 60% RH or more for 1 second to 10 minutes. By exposing the polymer electrolyte membrane to such an atmosphere, it is possible to effectively prevent minute deformation of the finally obtained polymer electrolyte membrane.

  Here, if the relative humidity of the atmosphere is less than 60% RH, minute deformation is likely to occur in the polymer electrolyte membrane. The relative humidity is preferably 70% RH or more, more preferably 85% RH or more, still more preferably 95% RH or more, and most preferably 100% RH.

  The time (exposure time) for placing the polymer electrolyte membrane in the above atmosphere is 1 second to 10 minutes. When the time is longer than 10 minutes, large deformation such as wrinkles or waves easily occurs in the finally obtained polymer electrolyte membrane. In addition, the shorter the time, the smaller the deformation is suppressed, but if it is less than 1 second, there may be a problem that the cleaning efficiency is lowered by bringing an acidic solution more than the membrane can hold into the cleaning process. is there. The time is preferably 5 seconds to 5 minutes (more preferably 30 seconds to 5 minutes).

  In this invention, it is preferable that the temperature of the said atmosphere is the range of 20-50 degreeC, and it is more preferable that it is the range of 20-40 degreeC. If it is less than 20 ° C., it becomes difficult to control the atmosphere, and the film quality may be deteriorated due to condensation of condensed water. When it exceeds 50 ° C., film quality may be deteriorated due to generation of wrinkles due to thermal expansion. In addition, it is preferable that the said temperature is equivalent to the temperature of an acidic solution or the poor solvent mentioned later, or the temperature difference is less than 10 degreeC. When the temperature difference exceeds 10 ° C., large deformation such as wrinkles easily occurs in the polymer electrolyte membrane.

  The specific mode of this step is not particularly limited. For example, for a polymer electrolyte membrane pulled up from an acidic solution, a constant temperature and humidity oven set in the above temperature / humidity range is taken over a predetermined time. And then immersed in a poor solvent described later.

(Washing process)
In this invention, in order to remove the acidic component which remain | survives in the polymer electrolyte membrane obtained through the said process, the process of wash | cleaning a polymer electrolyte membrane is included. Specifically, for example, a method in which a poor solvent for a polymer electrolyte membrane that can dissolve an acidic component is brought into contact with the polymer electrolyte membrane can be used. 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.

  The content of the acidic component in the polymer electrolyte membrane is preferably 1% by mass or less, and more preferably 0.1% by mass or less. If the content of the acidic component is large, the acidic component may be eluted, causing corrosion and chemical damage.

  The content rate of the acidic component in the polymer electrolyte membrane can be measured by any known method. For example, the content rate can be measured by extracting an elution component from a polymer electrolyte membrane with a solvent such as water and quantifying an acidic component in the solvent. Water is preferably used for extraction, and water with few impurities such as ion exchange water and ultrapure water is preferable. For extraction, methods such as immersion, boiling, ultrasonic treatment, and Soxhlet extraction can be used. The acidic component can be quantified by methods such as neutralization titration with alkali, pH measurement of the extract, ion chromatography, liquid chromatography, gas chromatography and the like.

In the present invention, the following method was adopted. That is, 0.100 g of the polymer electrolyte was immersed in 50 mL of pure water at 25 ° C. in a sealed container and stirred for 24 hours. Then, the acidic component in water was quantified using ion chromatography. The content of the acidic component was determined by the following formula.
Content of acidic component (mass%) = Amount of acidic component in water (mg / L) × 50 ÷ 1000 ÷ 00.1 × 100

  The method for contacting the poor solvent with the polymer electrolyte membrane is not particularly limited, and the method may be the same as the method for extracting the solvent in the precursor membrane with the poor solvent.

(Drying process)
If the solvent of the acidic solution or 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 morphological defects such as wrinkles or irregularities due to evaporation or leaching of the solvent. There is a high possibility that problems such as adhesions will occur. For this reason, it is preferable to reduce the amount of solvent remaining in the polymer electrolyte membrane. For example, when water is used as the solvent or poor solvent of the acidic solution, the solvent content (water content) in the polymer electrolyte membrane is preferably 5 to 30% by mass (more preferably 7 to 20% by mass). 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. Although a drying temperature is not specifically limited, For example, it can carry out at 20-50 degreeC.

  The solvent content (for example, water content) of the polymer electrolyte membrane can be measured by any known method, and is not limited. For example, a method using an infrared moisture meter, a Karl Fischer moisture content, and the like. A method using a meter, a method of obtaining the solvent content (moisture content) by measuring the weight at the time of solvent containing (water containing) and absolutely dry, the solvent content (moisture content by the weight reduction during heating by thermogravimetric analysis ).

(Support by support)
In the production method of the present invention, after the step of obtaining the precursor film, the step of obtaining the polymer electrolyte membrane, the step of placing in a predetermined atmosphere, or the step of washing, the precursor film or the polymer The electrolyte membrane may be peeled from the support, and the subsequent steps (a step of obtaining a prepolymer electrolyte membrane, a step of placing in a predetermined atmosphere, a washing step, or a drying step) may be performed. It is preferable to perform all the steps included in a state where a membrane (a precursor membrane, a polymer electrolyte membrane, etc.) is supported by a support (in other words, the membrane is not peeled off from the support). When the membrane is peeled from the support, the shape of the polymer electrolyte membrane may be deteriorated, for example, wrinkles or irregularities are generated in the polymer electrolyte membrane.

(Polymer electrolyte membrane properties)
According to the production method of the present invention, even a polymer electrolyte membrane made of an aromatic hydrocarbon polymer that has a small film thickness and is difficult to form can be produced with good form and high productivity. . Specifically, even an aromatic hydrocarbon polymer electrolyte membrane having a film thickness of 50 μm or less (thinner is 40 μm or less, even thinner is 35 μm or less, and even thinner is 30 μm or less) The molecular electrolyte membrane can be produced with high productivity. If the thickness of the polymer electrolyte membrane is greater than 50 μm, it tends to be difficult to obtain a balance between characteristics, quality, and productivity. The lower limit of the thickness of the polymer electrolyte membrane that is the subject of the production method of the present invention is not particularly limited, and is preferably as thin as possible from the viewpoint of proton conductivity, but is preferably 3 μm. It is more preferable that When the thickness of the polymer electrolyte membrane is thinner than 3 μm, it becomes difficult to handle the polymer electrolyte membrane, and a short circuit may occur when a fuel cell is manufactured.

  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 for manufacturing the polymer electrolyte membrane may not be peeled off. However, after manufacturing, if the polymer electrolyte membrane is laminated with another support, the workability is improved. It is preferable. 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. .

  As mentioned above, although the manufacturing method of the polymer electrolyte membrane of this invention was explained in full detail, the structure of the polymer electrolyte which can be used suitably for this manufacturing method is demonstrated below.

(Polymer electrolyte precursor)
The polymer electrolyte precursor used in the present invention is composed of an aromatic hydrocarbon polymer having an acidic group, and at least a part of the acidic group forms a salt.

  An aromatic hydrocarbon polymer has an aromatic ring in the polymer main chain, and this aromatic ring is a single bond, an ether bond, a sulfone bond, an imide bond, a heterocyclic bond, an ester bond, an amide bond, a urethane bond, A non-fluorinated or partially fluorinated ion-conducting polymer having a structure bonded with at least one linking group selected from a sulfide bond, a carbonate bond, and a ketone bond.

  Examples of the aromatic hydrocarbon polymer having such a structure include polyparaphenylene, polyphenylene oxide, polysulfone, polyethersulfone, polyimide, polyphenylquinoxaline, polybenzoxazole, polybenzthiazole, polybenzimidazole, aromatic polyester, Aromatic polyamide, aromatic polyurethane, polyphenylene sulfide, polyphenylene sulfide sulfone, aromatic polycarbonate, polyaryl ketone, polyether ketone (polyether ketone, polyether ketone ketone, polyether ether ketone, polyether ether ketone ketone, polyether Ketone ether ketone ketone, polyether ketone sulfone) and the like. The polymer electrolyte (precursor) may be composed of these aromatic hydrocarbon polymers alone or in combination of two or more. In particular, aromatic hydrocarbon polymers include polyarylene polymers such as poly (p-phenylene) and poly (m-phenylene); polysulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene oxide, polyether sulfone, polyether ketone. A polyarylene (thio) ether-based polymer such as a polyarylene; preferably the polyarylene / polyarylene (thio) ether copolymer-based polymer, and may have a side chain composed of an aromatic group or an aliphatic group. Good.

  Examples of the acidic group possessed by the aromatic hydrocarbon polymer include a sulfonic acid group, a phosphonic acid group, a carboxyl group, a sulfonamide group, a sulfonimide group, and derivatives thereof. The aromatic hydrocarbon polymer may be configured to have only one of these acidic groups, or may be configured to have two or more types. In the present invention, it preferably has a sulfonic acid group or a phosphonic acid group. The acidic group may be held at any position of the aromatic hydrocarbon polymer, for example, on the aromatic ring constituting the polymer main chain, on the aromatic group constituting the polymer side chain, or on the aliphatic group. The aspect which has an acidic group is mentioned.

  At least a part of the acidic group of the aromatic hydrocarbon polymer of the present invention forms a salt, and such a salt is preferably a monovalent cation salt other than a proton. When the valence is 2 or more, the polymer electrolyte precursor may gel, or the shape (quality) of the resulting polymer electrolyte membrane may deteriorate. Examples of the monovalent cation include alkali metal ions such as lithium, sodium, and potassium, and monoammonium salts. Alkali metal ions are preferable, and sodium and potassium are more preferable. The salt of the acidic group may be composed of a single type of salt selected from the group of these monovalent cation salts, or may be composed of a plurality of types of salts obtained by combining two or more types.

  In the present invention, the salt conversion rate (cation substitution rate) of the acidic group is preferably 80 mol% or more, preferably 90 mol% or more, more preferably 99 mol% or more, and most preferably 100 mol%. %. If the salt conversion rate is less than 80 mol%, decomposition or alteration of the solvent or polymer electrolyte may occur in the dissolution process or drying process when the polymer electrolyte membrane is produced. In the present invention, the amount of acidic groups forming the salt is preferably in the range of 0.1 to 5.0 meq / g.

  In the production method of the present invention, the reason why at least a part (more preferably 80 mol% or more) of the acidic groups of the aromatic hydrocarbon polymer is used as a salt is as follows. That is, in the polymer electrolyte membrane of the present invention, the salt of the acidic group of the aromatic hydrocarbon polymer is finally converted to protons in order to develop excellent proton conductivity. On the other hand, when the acidic group does not form a salt, the aromatic hydrocarbon polymer may be decomposed by heat or the like in the process of forming the polymer electrolyte membrane. Therefore, in the process of forming the polymer electrolyte membrane, the acidic group is made into a salt form, and converted into protons by acid treatment after the film formation.

  The polyelectrolyte precursor used in the present invention includes a segmented block copolymer, a polymer having a long-chain or short-chain branch (for example, a homopolymer or a random copolymer of the above aromatic hydrocarbon polymer) The polymer may have a higher order structure such as a comb polymer) or a star polymer. In particular, the use of a copolymer that can form a co-continuous structure by phase separation of a hydrophilic part and a hydrophobic part, such as a segmented block copolymer, improves the durability and proton conductivity of the polymer electrolyte membrane. Is preferable. Examples of such a segmented block copolymer include a copolymer of a hydrophilic segment having a salt of an acidic group and a hydrophobic segment having no acidic group and its salt. Such a segmented block copolymer can be obtained, for example, by polymerizing an oligomer constituting the segment directly or via another compound.

  The molecular weight of the polymer electrolyte precursor is not particularly limited, but the number average molecular weight measured using gel permeation chromatography with polyethylene glycol as a standard is preferably in the range of 10,000 to 500,000. If it is less than 10,000, the physical properties of the film may deteriorate. The larger the molecular weight, the better from the viewpoint of mechanical properties. However, if the molecular weight is too large, the concentration of the solvent solution of the polymer electrolyte precursor must be lowered when the polymer electrolyte membrane is produced using the polymer electrolyte precursor. May cause problems in removing the solvent.

  The logarithmic viscosity of the polymer electrolyte precursor is preferably in the range of 0.1 to 10.0 dL / g, and more preferably in the range of 0.3 to 5.0 dL / g. If the logarithmic viscosity is less than 0.1 dL / g, it may be difficult to form a film. On the other hand, if the logarithmic viscosity exceeds 10.0 dL / g, the viscosity of the film-forming solution may become too high or the concentration may become too low, making film formation difficult.

  The softening temperature of the polymer electrolyte precursor is preferably 120 ° C. or higher, and more preferably 140 to 300 ° C.

(Method for producing polymer electrolyte precursor)
The polymer electrolyte precursor used in the present invention (the aromatic hydrocarbon polymer having an acidic group, a part of which forms a salt) may be produced by any method. For example, after introducing an acidic group into an aromatic hydrocarbon polymer, after converting the acidic group into a salt, or after polymerizing a monomer component having an acidic group to obtain an aromatic hydrocarbon polymer having an acidic group And a method of converting this acidic group into a salt. The method for converting an acidic group into a salt is not particularly limited, and examples thereof include a method of immersing in an aqueous solution containing a cation.

  Among the methods for introducing acidic groups into an aromatic hydrocarbon polymer, in particular, as a method for introducing a sulfonic acid group onto the aromatic ring of an aromatic hydrocarbon polymer, for example, aromatic carbon having a skeleton as described above is used. A method of introducing a suitable sulfonating agent by reacting with a hydrogen-based polymer while appropriately selecting reaction conditions according to the polymer can be mentioned. As such a sulfonating agent, for example, concentrated sulfuric acid or fuming sulfuric acid (for example, Solid State Ionics, 106, P219 (1998)) reported as an example of introducing a sulfonic acid group into an aromatic hydrocarbon polymer. , Chlorosulfuric acid (for example, J. Polym. Sci., Polym. Chem., 22, P295 (1984)), sulfuric anhydride complex (for example, J. Polym. Sci., Polym. Chem., 22, P721 (1984)). , J. Polym. Sci., Polym. Chem., 23, P1231 (1985)), and a sulfonating agent described in Japanese Patent No. 2884189. These sulfonating agents may be used alone or in combination of two or more.

  Moreover, as a method of polymerizing a monomer component having an acidic group to obtain an aromatic hydrocarbon polymer having an acidic group, for example, an aromatic diamine having an acidic group (such as a sulfonic acid group or a phosphonic acid group) is included. A method of polymerizing a diamine and an aromatic tetracarboxylic dianhydride to obtain an acidic group-containing polyimide; a dicarboxylic acid containing an aromatic dicarboxylic acid having an acidic group, an aromatic diamine diol, an aromatic diamine dithiol, an aromatic A method of polymerizing an aromatic tetramine to obtain an acidic group-containing polybenzoxazole, an acidic group-containing polybenzthiazole, or an acidic group-containing polybenzimidazole; and polymerizing an aromatic dihalide and an aromatic diol to form a polysulfone, a polyethersulfone, In obtaining a polyetherketone, it has an aromatic dihalide having an acidic group or an acidic group. The method or the like using that aromatic diols. The degree of polymerization tends to be higher when an aromatic dihalide having an acidic group is used than when an aromatic diol having an acidic group is used, and the thermal stability of the aromatic hydrocarbon polymer having an acidic group is higher. Since it becomes high, it is preferable.

  The outline of the polymer electrolyte precursor used in the present invention and the production method thereof have been described above. Below, the said precursor and the especially preferable aspect of the manufacturing method are demonstrated more concretely.

(Preferred example of polymer electrolyte precursor)
The polymer electrolyte precursor used in the present invention is particularly preferably an aromatic hydrocarbon polymer having a repeating unit represented by the general formula 1.

[In General Formula 1, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ¹ represents either an O or S atom. , Z ² represents an O atom, an S atom, a —CH ₂ — group, a —C (CH ₃ ) ₂ — group, a —C (CF ₃ ) ₂ — group, a cyclohexylene group, or a direct bond, and n1 represents Represents an integer of 1 or more. ]

In General Formula 1, when X is a —S (═O) ₂ — group, the solubility in a solvent is improved. When X is a —C (═O) — group, the softening temperature of the polymer can be lowered to further enhance the bonding property with the electrode, or the polymer electrolyte membrane can be imparted with photocrosslinkability. Y is preferably an alkali metal such as Na or K. This is because when Y is an H atom, it is easily decomposed by heat or the like during the production process of the polymer electrolyte membrane. In order to obtain a polymer electrolyte membrane excellent in proton conductivity, it is preferable to finally convert Y to H atoms to obtain a polymer electrolyte membrane. When Z ¹ is an O atom, there are advantages such as little coloring of the polymer and easy availability of raw materials. When Z ¹ is an S atom, the oxidation resistance is improved. When Z ² is an O atom or an S atom, the bondability with the electrode is further improved. When Z ² is a direct bond, the dimensional stability of the obtained polymer electrolyte membrane is improved. n1 is preferably in the range of 1-30. In n1 is 3 or more, and Z ² is the case of the O atoms, bonding between the polymer electrolyte membrane and the electrode is particularly enhanced. In addition, when n1 is 2 or more, Z ² may be composed of different bonding groups.

  The polymer electrolyte precursor used in the present invention is preferably an aromatic hydrocarbon polymer containing a repeating unit represented by the general formula 1 and a repeating unit represented by the general formula 2. Such an aromatic hydrocarbon polymer has an appropriate softening temperature, and when it is used as a polymer electrolyte membrane, it bonds well with the electrode.

[In General Formula 2, Ar ¹ represents a divalent aromatic group, Z ³ represents either an O atom or an S atom, Z ⁴ represents an O atom, an S atom, a —CH ₂ — group, —C (CH _{3) 2} - group, -C (CF _{3) 2} - group, cyclohexylene group, either a direct bond, n2 is an integer of 1 or more. ]

In the general formula 2, when Z ³ is an O atom, there are advantages such that the coloring of the polymer is small and the raw materials are easily available. When Z ³ is an S atom, the oxidation resistance is improved. When Z ⁴ is an O atom or an S atom, the bondability is further improved. When Z ⁴ is a direct bond, the dimensional stability of the resulting polymer electrolyte membrane is improved. n2 is preferably in the range of 1 to 30, and when n2 is 2 or more, Z ⁴ may be composed of different linking groups. When n2 is 3 or more and Z ⁴ is an O atom, the bondability between the polymer electrolyte membrane and the electrode is particularly improved.

Ar ¹ in the general formula 2 is preferably a divalent aromatic group having an electron-withdrawing group. The electron-withdrawing group may be a known electron-withdrawing group, and is not particularly limited. For example, sulfo group such as sulfone group, sulfonyl group, sulfonic acid group, sulfonic acid ester group, sulfonic acid amide group, sulfonic acid imide group and derivatives thereof; carboxyl group such as carboxyl group and carboxylic acid ester group and derivatives thereof; carbonyl A cyano group; a halogen group; a perfluoroalkyl group such as a trifluoromethyl group; a nitro group; a phosphine group. These electron withdrawing groups may be used alone or in combination of two or more.

Ar ¹ is preferably represented by General Formulas 3 to 6. In the case of general formula 3, the solubility of the polymer can be increased. In the case of general formula 4, the softening temperature of the polymer can be lowered to enhance the bondability with the electrode, or the photocrosslinking property can be imparted. In the case of the general formulas 5 and 6, the swelling of the polymer can be reduced. Such an effect is larger in the general formula 6. Of the general formulas 3 to 6, the general formula 6 is most preferable.

The polymer electrolyte precursor used in the present invention contains a repeating unit represented by the general formula 1 in addition to a repeating unit represented by the general formula 2, and both Z ¹ and Z ² in the general formula 1 are O. It is more preferable that the aromatic hydrocarbon polymer is an atom and n1 is 3 or more. The polymer electrolyte membrane obtained using such an aromatic hydrocarbon-based polymer has particularly improved bondability with the electrode.

In such an aromatic hydrocarbon polymer, it is more preferable that Z ³ and Z ⁴ in the general formula 2 are both O atoms, and n2 is 3 or more. The polymer electrolyte membrane obtained by using such an aromatic hydrocarbon polymer further improves the bondability with the electrode.

  When the polymer electrolyte precursor used in the present invention is an aromatic hydrocarbon polymer mainly composed of a repeating unit represented by the general formula 1 and a repeating unit represented by the general formula 2, The molar ratio is preferably in the range of 7:93 to 70:30. The molar ratio of 7:93 means that when the number of moles of the repeating unit represented by the general formula 1 is 7, the number of moles of the repeating unit represented by the general formula 2 is 93. When the number of repeating units represented by the general formula 1 is larger than the molar ratio of 70:30, the fuel permeability when used as a polymer electrolyte membrane may increase, which is not preferable. When the number of repeating units represented by the general formula 1 is less than the molar ratio of 7:93, it is not preferable because the proton conductivity when the polymer electrolyte membrane is made decreases and the resistance increases. The molar ratio is more preferably in the range of 10:90 to 50:50, and still more preferably in the range of 10:90 to 40:60.

  The polymer electrolyte precursor used in the present invention is more preferably an aromatic hydrocarbon polymer containing a repeating unit represented by general formula 7 in addition to general formula 1 and general formula 2. By using such an aromatic hydrocarbon polymer, it is possible to improve the form stability of the membrane when it is used as a polymer electrolyte membrane.

[In General Formula 7, X represents a —S (═O) ₂ — group or —C (═O) — group, Y represents H or a monovalent cation, and Z ⁵ represents either an O or S atom. Represent. ]

The reason why it is preferable that X, Y, and Z ^{5 in the} general formula 7 are the above-described embodiments is the same as the reason described for X, Y, and Z ¹ in the general formula ¹ , respectively.

Such an aromatic hydrocarbon-based polymer has a bonding property between a polymer electrolyte membrane and an electrode, and a membrane when Z ¹ and Z ² in formula 1 are O atoms or S atoms and n1 is 1. This is preferable because the morphological stability becomes better. Further, when Z ³ and Z ⁴ in the general formula 2 are O atoms or S atoms and n2 is 1, the bondability between the polymer electrolyte membrane and the electrode and the morphological stability of the membrane are further improved. This is preferable.

  The polymer electrolyte precursor used in the present invention is an aromatic hydrocarbon polymer containing a repeating unit represented by the general formula 8 in addition to the repeating units represented by the general formulas 1, 2, and 7. More preferably. By using such an aromatic hydrocarbon polymer, the bondability between the polymer electrolyte membrane and the electrode and the morphological stability of the membrane can be greatly improved.

[In General Formula 8, Ar ² represents a divalent aromatic group, and Z ⁶ represents either an O atom or an S atom. ]

In General Formula 8, it is preferable that Z ⁶ is the above-described aspect, and a preferable specific aspect of Ar ² is the same as the reason described for Z ³ and Ar ¹ in General Formula 2, respectively.

When the polyelectrolyte precursor used in the present invention is an aromatic hydrocarbon polymer having all the repeating units represented by the general formulas 1, 2, 7, and 8, mol% of each repeating unit, And it is preferable that mol% of other repeating units satisfy | fill the following Numerical formulas 1-3.
0.9 ≦ (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7)
≦ 1.0 (Formula 1)
0.05 ≦ (n3 + n4) / (n3 + n4 + n5 + n6)
≦ 0.7 (Formula 2)
0.01 ≦ (n4 + n6) / (n3 + n4 + n5 + n6)
≦ 0.95 (Formula 3)

(In the above formula, n3 is the mol% of the repeating unit represented by the general formula 7, n4 is the mol% of the repeating unit represented by the general formula 1, and n5 is the mol of the repeating unit represented by the general formula 8. %, N6 represents the mol% of the repeating unit represented by the general formula 2, and n7 represents the mol% of the other repeating unit.)

  If (n3 + n4 + n5 + n6) / (n3 + n4 + n5 + n6 + n7) is smaller than 0.9, good characteristics may not be obtained when a polymer electrolyte membrane is obtained. More preferred is a range of 0.95 to 1.0.

  If (n3 + n4) / (n3 + n4 + n5 + n6) is smaller than 0.05, sufficient proton conductivity may not be obtained when a polymer electrolyte membrane is obtained. On the other hand, if it is greater than 0.7, the swellability of the polymer electrolyte membrane may be remarkably increased.

  (N3 + n4) / (n3 + n4 + n5 + n6) is preferably in the range of 0.07 to 0.5, and more preferably in the range of 0.1 to 0.4.

  When (n4 + n6) / (n3 + n4 + n5 + n6) is less than 0.01, the bondability between the polymer electrolyte membrane and the electrode may be lowered. When it is larger than 0.95, the swelling property of the polymer electrolyte membrane may become too large. The range of 0.05-0.8 is more preferable, and the range of 0.4-0.8 is more preferable.

  In the aromatic hydrocarbon polymer, the bonding mode of each repeating unit represented by each general formula is not particularly limited, and examples thereof include random bonding, alternating bonding, and bonding in a continuous block structure. It is done. The aromatic hydrocarbon-based polymer may be composed of a single bonding mode or a combination of two or more bonding modes.

(Preferred example of method for producing polymer electrolyte precursor)
The aromatic hydrocarbon polymer having a repeating unit represented by the above general formula 1 or the like is a monomer represented by the following general formulas 9 to 11 (for example, (activated) dihalogen aromatic compound, aromatic diol, aromatic Group dithiols, dinitroaromatic compounds, etc.) can be produced by a known method (for example, a polymerization reaction by a known aromatic nucleophilic substitution reaction in the presence of a basic compound). Further, it is preferable to further use a monomer represented by the general formula 12 because physical properties such as film form stability are improved.

In the general formulas 9 to 12, Z ⁷ and Z ¹⁰ are each independently any one of Cl atom, F atom, I atom, Br atom and nitro group, and Z ⁸ and Z ¹¹ are each independently OH group. , SH group, -O-NH-C (= O) -R group, -S-NH-C (= O) -R group. R represents an aromatic or aliphatic hydrocarbon group. X, Y, Z ² , n1, and Ar ¹ are the same as X, Y, Z ² , n1, and Ar ¹ , respectively.

  Specific examples of the monomer represented by the general formula 9 include 3,3′-disulfo-4,4′-dichlorodiphenyl sulfone, 3,3′-disulfo-4,4′-difluorodiphenyl sulfone, 3,3 ′. -Disulfo-4,4'-dichlorodiphenyl ketone, 3,3'-disulfo-4,4'-difluorodiphenyl ketone, 3,3'-disulfobutyl-4,4'-dichlorodiphenyl sulfone, 3,3'-disulfobutyl Dihalogen aromatic compounds such as -4,4'-difluorodiphenyl sulfone, 3,3'-disulfobutyl-4,4'-dichlorodiphenyl ketone, 3,3'-disulfobutyl-4,4'-difluorodiphenyl ketone, and these In which the sulfonic acid group forms a salt with a monovalent cation. Specific examples of the cation are as described above.

  Examples of the compound represented by the general formula 9 in which the sulfonic acid group is a salt include sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-disulfone Sodium salt-4,4′-difluorodiphenylsulfone, sodium 3,3′-disulfonate-4,4′-dichlorodiphenylketone, sodium 3,3′-disulfonate-4,4′-difluorodiphenylketone, 3, 3′-potassium disulfonate-4,4′-dichlorodiphenylsulfone, 3,3′-potassium disulfonate-4,4′-difluorodiphenylsulfone, 3,3′-potassium disulfonate-4,4′-dichlorodiphenyl Examples thereof include ketones and potassium 3,3′-disulfonate-4,4′-difluorodiphenyl ketone.

  Specific examples of the monomer represented by the general formula 10 include 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) methane, and 2,2-bis (4-hydroxyphenyl) hexafluoropropane. Bis (4-hydroxyphenyl) sulfide (4,4′-thiobisphenol), 4,4′-dihydroxydiphenyl ether, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′-dihydroxydiphenyl sulfone (bisphenol) S), aromatic diols such as terminal hydroxyl group-containing phenylene ether oligomers (structures represented by the following general formula 13); 4,4′-thiobisbenzenethiol, 4,4′-oxybisbenzenethiol, etc. Aromatic dithiols and the like, and in particular, bis (4- Hydroxyphenyl) sulfide, 1,1-bis (4-hydroxyphenyl) cyclohexane, terminal hydroxyl group-containing phenylene ether oligomer, 4,4'-thiobisbenzenethiol is preferred.

[In General Formula 13, n is an integer of 1 or more, and a mixture of a plurality of components with different n may be used. ]

  The monomer represented by the general formula 10 increases the flexibility of the polymer electrolyte membrane, and brings about effects such as prevention of breakage against deformation and improvement in bondability with an electrode due to a decrease in glass transition temperature.

  Examples of the monomer represented by the general formula 11 include monomers having a leaving group in a nucleophilic substitution reaction such as halogen or nitro group and an electron-withdrawing group that activates the same aromatic ring. Specifically, 2,6-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,6-difluorobenzonitrile, 2,4-difluorobenzonitrile, 4,4′-dichlorodiphenyl sulfone, 4,4′- Examples include, but are not limited to, activated dihalogen aromatic compounds such as difluorodiphenyl sulfone, 4,4′-difluorobenzophenone, 4,4′-dichlorobenzophenone, and decafluorobiphenyl. In addition, other aromatic dihalogen compounds, aromatic dinitro compounds, aromatic dicyano compounds and the like that are active in aromatic nucleophilic substitution can also be used.

  Examples of the monomer represented by the general formula 12 include aromatic diols such as 4,4'-biphenol and 4,4'-dimercaptobiphenol, and 4,4'-biphenol is particularly preferable.

  In the present invention, other various activated dihalogen aromatic compounds, dinitro aromatic compounds, bisphenol compounds, and bisthiophenol compounds can be used in combination with the monomers represented by the general formulas 9 to 12 as monomers. Examples of the bisphenol compound or bisthiophenol compound include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, and bis (4-hydroxyphenyl). Sulfone, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 3,3-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxy) -3,5-dimethylphenyl) propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-2,5-dimethylphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, Hydroquinone, resorcin, bis (4-hydroxyphenyl) ketone, 1,4-ben Njichioru, 1,3 benzenedithiol, phenolphthalein, 10- (2,5-dihydroxyphenyl) -9,10-dihydro-9-oxa-10-phosphatonin phenanthrene-10-oxide, and the like. In addition, various aromatic diols or various aromatic dithiols that can be used for polymerization of polyarylene ether compounds by aromatic nucleophilic substitution reaction may be used.

  Moreover, as a raw material of the polymer of another embodiment constituting the polymer electrolyte used in the present invention, aromatic tetraamino compounds such as 3,3 ′, 4,4′-tetraaminodiphenylsulfone and 3,3′-diaminobenzidine And aromatic dicarboxylic acids having an ionic group such as monosodium 2,5-dicarboxybenzenesulfonate and 3,5-dicarboxyphenylphosphonic acid. Polycondensation can be performed using these monomers to obtain a polyazole polymer electrolyte such as polybenzimidazole.

  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, the method of measuring the logarithmic viscosity, residual solvent amount, cation substitution rate, ambient temperature and humidity of the polymer electrolyte precursor (membrane) and polymer electrolyte (membrane) produced according to the examples and comparative examples, and the form (quality) The evaluation method will be described below.

<Logarithmic viscosity of polymer electrolyte precursor>
The polyelectrolyte precursor 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. to obtain a logarithmic viscosity ln [ta / tb]. Evaluation was made using / c (ta is the drop time of the sample solution, tb is the drop time of the solvent alone, and c is the polymer concentration of the sample solution [unit: g / dL]).

<Measurement of residual solvent>
Moisture of the polymer electrolyte precursor film to be measured is wiped off with a filter paper, left in a room at 23 ° C. and 50% RH for 1 hour, dissolved in deuterated dimethyl sulfoxide, and a Varian 400-MR manufactured by Varian is used. Then, ¹ H-NMR spectrum was measured at 25 ° C. with 128 times of integration. The residual solvent amount with respect to the polymer electrolyte precursor was calculated from the integral value of the peak with respect to the polymer electrolyte precursor and the solvent previously assigned. If the polymer electrolyte precursor does not dissolve in deuterated dimethyl sulfoxide, the solvent is extracted from the polymer electrolyte precursor with water using a Soxhlet extractor, and the solvent concentration in water is determined by gas chromatography. The amount of residual solvent was calculated by quantification.

<Polymer electrolyte and cation substitution rate of acidic group of its precursor>
Quantification of Na and K in the polymer electrolyte (precursor) was performed by inductively coupled plasma atomic emission spectrometry. The cation substitution rate was determined from the amount of acidic groups of the polymer electrolyte (precursor), the amount of Na and the amount of K determined by the ¹ H-NMR analysis.
Cation substitution rate (mol%)
= {(C _Na /23.0+C _K /39.1)÷1000}÷C _I × 100
C _Na represents the Na content (mg / kg), C _K represents the K content (mg / kg), and C _I represents the acidic group content (mmol / g).

<Measurement of ambient temperature and humidity>
In the constant temperature and humidity furnace where the polymer electrolyte membrane obtained through the step of immersing in the sulfuric acid aqueous solution passes before moving to the next cleaning step, the measurement probe of the temperature and humidity measuring device is placed at a height within 50 cm from the membrane. Place and measure temperature and relative humidity.

<Water content of polymer electrolyte>
The mass of the polymer electrolyte membrane (10 cm × 10 cm) obtained through the drying process was measured (Wwet). Thereafter, the polymer electrolyte membrane was dried in a hot air dryer at 120 ° C. for 2 hours, and the mass was immediately measured (Wdry). The water content was determined by the following formula.
Moisture content (mass%) = (Wwet−Wdry) ÷ (Wdry) × 100

<Polymer electrolyte membrane quality>
About the polymer electrolyte membrane after manufacture, 100 samples having a size of 2 cm × 2 cm were randomly collected. Place this sample on a flat plate and measure the height from the reference surface to the highest position of the sample sled portion or the top of the sample convex portion when the flat plate surface is used as the reference surface, whichever is higher Was adopted as an index representing the magnitude of deformation. The deformation of the film having a height of 0.1 mm or more was counted as a minute deformation.
A: 30 or less samples having microdeformation, and the number of microdeformations having a size of 1 mm or less was 90% or more.
A: 30 or less samples having microdeformation, and the number of microdeformations having a size of 1 mm or less was 90% or less.
Δ: 31 to 60 samples having minute deformation.
X: What was 61-100 samples which have a micro deformation | transformation.

Example 1
<Production of polymer electrolyte precursor>
The reactor was charged with 778 parts of sodium 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (S-DCDPS), 553 parts of 2,6-dichlorobenzonitrile (DCBN), 4,4′-biphenol (BP 893 parts, 763 parts of potassium carbonate and 5631 parts of N-methyl-2-pyrrolidone (NMP) were added and reacted at 200 ° C. for 10 hours in a nitrogen atmosphere. After allowing to cool, the polymer was precipitated in water as a strand, and the resulting polymer was washed 5 times with 10 L of water and then dried to obtain a polymer electrolyte precursor. The logarithmic viscosity of this polymer electrolyte precursor was 1.21 dL / g.

<Manufacture of polymer electrolyte precursor film>
A precursor solution having a solid content concentration of 24% by mass was prepared using NMP as a solvent. Next, on the non-adhesive polyethylene terephthalate film as a support, while continuously casting the precursor solution at a temperature of 25 ° C. with a blade coater so as to have a thickness of 200 μm, it is dried at 90 ° C. for 60 minutes, A polymer electrolyte precursor film 1 having a residual amount of NMP of 21% by mass was produced.

  The obtained polymer electrolyte precursor film 1 is immersed in water at 30 ° C. for 25 minutes without peeling from the support to produce a polymer electrolyte precursor film 2 having a residual amount of NMP of 0.3% by mass. did.

(Manufacture of polymer electrolyte membrane)
The obtained polymer electrolyte precursor film 2 was immersed in a 20% by mass sulfuric acid aqueous solution (pKa = −3.0) at 30 ° C. for 25 minutes without peeling from the support to obtain a polymer electrolyte film. The obtained polymer electrolyte membrane was passed through an atmosphere of 25 ° C. and 60% RH, then immersed in pure water at 30 ° C. for 20 minutes without peeling off the membrane, and subsequently immersed in fresh 30 ° C. pure water for 20 minutes. Immerse for a minute. The time for the polymer electrolyte membrane to pass through the atmosphere was 3 minutes.

(Drying process)
Further, the polymer electrolyte membrane was air-dried at 25 ° C. for 15 minutes without removing the polymer electrolyte membrane from the support to obtain a 30 μm thick polymer electrolyte membrane laminated on the support (water content: 9%).

(Example 2)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the atmospheric conditions for passing the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 25 ° C. and 75% RH (water content: 9% ).

(Example 3)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the atmospheric conditions for passing through the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 25 ° C. and 85% RH (water content: 10% ).

Example 4
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the atmospheric conditions for passing through the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 25 ° C. and 95% RH (water content: 10% ).

(Example 5)
A polymer electrolyte membrane was obtained (water content: 10%) in the same manner as in Example 1 except that the atmospheric conditions for passing the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 30 ° C. and 85% RH. ).

(Example 6)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the time required for the polymer electrolyte membrane to pass through the atmosphere was 5 minutes (water content: 9%).

(Example 7)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the time for the polymer electrolyte membrane to pass through the atmosphere was 1 minute (water content: 11%).

(Example 8)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the time for the polymer electrolyte membrane to pass through the atmosphere was 10 minutes (water content: 8%).

Example 9
In the production of the polymer electrolyte precursor, 800.0 parts of S-DCDPS, 356.5 parts of DCBN, 600.5 parts of BP, 96.9 parts of 4,4′-thiobisphenol (BPS), 562.7 parts of potassium carbonate, NMP4624. A polymer electrolyte membrane (water content: 11%) was obtained in the same manner as in Example 1 except that the polymer electrolyte precursor having a logarithmic viscosity of 1.28 dL / g obtained using 3 parts as a raw material was used.

(Example 10)
In the production of the polyelectrolyte precursor, 310.1 parts of dried S-DCDPS, 253.3 parts of DCBN, and a terminal hydroxyl group-containing phenylene ether oligomer (a component of SPECIANOL DPE-PL manufactured by DIC, wherein n is 1 to 8) Logarithmic viscosity obtained using (DPE) 1156.5 parts, potassium carbonate 319.0 parts, NMP 5165.3 parts and a reaction time of 8 hours. A polymer electrolyte membrane (0.85 dL / g) was used in the same manner as in Example 1 except that the polymer electrolyte precursor was used and the concentration of the solution was 31% by mass in the production of the polymer electrolyte precursor membrane 1. Water content; 12%) was obtained.

(Example 11)
In Example 1, a polymer having a logarithmic viscosity of 1.43 dL / g obtained by using 721 parts of 3,3′-disulfo-4,4′-dichlorodiphenyl ketone disodium salt instead of 778 parts of S-DCDPS A polymer electrolyte membrane (water content: 9%) was obtained in the same manner as in Example 1 except that the electrolyte precursor was used.

(Example 12)
Weigh out 1.20 parts of 9,9-bis (4-hydroxyphenyl) fluorene, 2.00 parts of bisphenol S, 2.90 parts of difluorodiphenyl sulfone, and 1.82 parts of potassium carbonate in a 100 ml four-necked flask, and under nitrogen flow 40 ml of NMP was added and the reaction temperature was set at around 175 ° C. for 7 hours. After allowing to cool, it was reprecipitated in about 300 ml of methanol and washed with water 5 times using a mixer to obtain a polymer. The logarithmic viscosity of the obtained polymer was 0.61 dL / g. The polymer sample was stirred with concentrated sulfuric acid (98%) with a magnetic stirrer at room temperature to perform a sulfonation reaction. After completion of the reaction, the sulfuric acid solution was poured into excess ice water to stop the reaction, and the resulting precipitate was collected by filtration and washed with water to obtain a polymer electrolyte precursor. A polymer electrolyte membrane (water content: 12%) was obtained in the same manner as in Example 1 except that this polymer electrolyte precursor was used.

(Example 13)
45 parts of 3,3 ′, 4,4′-tetraaminodiphenylsulfone, 42 parts of monosodium 2,5-dicarboxybenzenesulfonate, 615 parts of polyphosphoric acid (phosphorus pentoxide content 75%), 500 parts of phosphorus pentoxide Weighed into a polymerization vessel, flushed with nitrogen, heated to 120 ° C. while slowly stirring in an oil bath, held for 1 hour, then heated to 200 ° C. and allowed to react for 6 hours. Then, it is left to cool, and water is added to take out the polymer. After repeating washing with water five times using a home mixer, this water-immersed polymer is neutralized by adding sodium carbonate, and further washing with water is repeated. After confirming that the pH was neutral and did not change, a polymer electrolyte precursor having a logarithmic viscosity of 1.55 dL / g was obtained. In the production of the polymer electrolyte precursor membrane 1 using this precursor, the polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the solution was obtained by heating the solvent to 170 ° C. to dissolve the precursor. (Water content; 13%) was obtained.

(Example 14)
3,3 ′, 4,4′-tetraaminodiphenylsulfone 18.3 parts, 2,5-dicarboxybenzenesulfonic acid monosodium 5.30 parts, 3,5-dicarboxyphenylphosphonic acid 11.3 parts, polyphosphorus 250 parts of acid (phosphorus pentoxide content 5%) and 200 parts of phosphorus pentoxide were weighed in a polymerization vessel, and a polymer electrolyte precursor having a logarithmic viscosity of 1.51 dL / g was obtained in the same manner as in Example 13. A polymer electrolyte membrane (water content: 13%) was obtained in the same manner as in Example 1 except that this polymer electrolyte precursor was used.

(Example 15)
<Production Example 1: Hydrophobic oligomer>
DCBN 49.97 g (290.5 mmol), BP 54.99 g (295.3 mmol), potassium carbonate 46.94 g (339.6 mmol), NMP 750 mL, toluene 150 mL, nitrogen inlet tube, stirring blade, Dean-Stark trap, thermometer attached The flask was placed in a 1000 mL branch flask and heated under a nitrogen stream with 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 15 hours. In another 1000 mL branch flask equipped with a nitrogen inlet tube, stirring blade, reflux condenser, and thermometer, 200 mL of NMP 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 filtered off, dried at 100 ° C. for 2 hours, further cooled to room temperature, and then 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 13910. The chemical structure of the hydrophobic oligomer is shown below.

<Production Example 2: Hydrophilic oligomer>
S-DCDPS 250.0 g (508.9 mmol), BP 97.04 g (520.7 mmol), sodium carbonate 66.23 g (624.9 mmol), NMP 650 mL, toluene 150 mL, nitrogen introduction tube, stirring blade, Dean-Stark trap, thermometer Were placed in a 2000 mL branch flask and heated in 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 25610. The chemical structure of the hydrophilic oligomer is shown below.

<Production Example 3: Segmented block polymer polymer electrolyte precursor>
Add 45.00 parts of hydrophilic oligomer, 24.61 parts of hydrophobic oligomer, 0.28 part of sodium carbonate, and 400 mL of NMP to 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 stream. Then, it heated to 110 degreeC and made it react for 10 hours. Thereafter, the polymer was cooled to room temperature and dropped into 3 L of pure water to solidify the polymer. After washing with pure water three times, it was treated at 80 ° C. for 16 hours while immersed in pure water, and then the hot water was washed by removing the pure water. Thereafter, hot water washing was repeated once more. Further, the polymer 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 the polymer was taken out and washed. The same operation was performed again. Thereafter, the polymer was filtered off and dried under reduced pressure at 120 ° C. for 12 hours to obtain a polymer electrolyte precursor composed of a sulfonate group-containing segmented block polymer and having a logarithmic viscosity of 2.6 dL / g.

  A polymer electrolyte membrane (water content: 14%) was prepared in the same manner as in Example 1 except that the obtained polymer electrolyte precursor was used to produce a polymer electrolyte precursor membrane 1 with a solution concentration of 10% by mass. ) Further, when the obtained polymer electrolyte membrane was observed with a transmission electron microscope, a phase-separated structure in which a hydrophilic domain and a hydrophobic domain were co-continuous in a lamellar shape was observed. The chemical structure of the obtained polymer electrolyte precursor is shown below.

(Example 16)
After the production of the polymer electrolyte precursor film 2, the film was peeled off from the support, and the subsequent steps (after the step of immersing in the sulfuric acid aqueous solution) were carried out without the support in the same manner as in Example 1, except that the polymer An electrolyte membrane (water content: 10%) was obtained.

(Example 17)
After the polymer electrolyte precursor membrane 2 is immersed in a sulfuric acid aqueous solution to obtain a polymer electrolyte membrane, the membrane is peeled from the support, and the subsequent steps (after the step of passing through a predetermined atmosphere) are performed without the support. A polymer electrolyte membrane (water content: 11%) was obtained in the same manner as in Example 1 except for the above.

(Example 18)
In the production of the polymer electrolyte precursor membrane 1, a polymer electrolyte membrane having a thickness of 20 μm was obtained in the same manner as in Example 3 except that the casting thickness of the polymer electrolyte precursor solution was 130 μm (water content; 8%).

(Example 19)
In the production of the polymer electrolyte precursor film 1, a polymer electrolyte film having a thickness of 25 μm was obtained in the same manner as in Example 3 except that the casting thickness of the polymer electrolyte precursor solution was 150 μm (water content: 9 %).

(Comparative Example 1)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the atmospheric conditions for passing the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 30 ° C. and 50% RH (water content: 13% ).

(Comparative Example 2)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the atmospheric conditions for passing through the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 30 ° C. and 30% RH (water content: 14% ).

(Comparative Example 3)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the atmospheric conditions for passing through the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 60 ° C. and 20% RH (water content: 15% ).

(Comparative Example 4)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the time required for the polymer electrolyte membrane to pass through the atmosphere was 15 minutes (water content: 14%).

(Comparative Example 5)
A polymer electrolyte membrane was obtained in the same manner as in Example 1 except that the time required for the polymer electrolyte membrane to pass through the atmosphere was 30 minutes (water content: 15%).

(Comparative Example 6)
Example 1 except that the atmospheric conditions for passing the polymer electrolyte membrane obtained by immersion in an aqueous sulfuric acid solution were 30 ° C. and 20% RH, and the time for the polymer electrolyte membrane to pass through the atmosphere was 20 minutes. In the same manner as above, a polymer electrolyte membrane was obtained (water content: 15%).

(Comparative Example 7)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 9 was used as the polymer electrolyte precursor (water content). 14%).

(Comparative Example 8)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 10 was used as the polymer electrolyte precursor (water content). ; 13%).

(Comparative Example 9)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 11 was used as the polymer electrolyte precursor (water content). 10%).

(Comparative Example 10)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 12 was used as the polymer electrolyte precursor (water content). 14%).

(Comparative Example 11)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 13 was used as the polymer electrolyte precursor (water content). 14%).

(Comparative Example 12)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 14 was used as the polymer electrolyte precursor (water content). 15%).

(Comparative Example 13)
A polymer electrolyte membrane having a thickness of 30 μm was obtained in the same manner as in Comparative Example 1 except that a polymer membrane electrolyte precursor produced in the same manner as in Example 15 was used as the polymer electrolyte precursor (water content). 16%).

  Table 1 shows the evaluation results of the polymer electrolyte precursors (membranes) and polymer electrolytes (membranes) obtained in Examples and Comparative Examples.

  From Examples 1 to 19, a polymer electrolyte membrane having a film thickness of 20 to 30 μm excellent in form (quality) was obtained by placing the polymer electrolyte membrane in an atmosphere having a relative humidity of 60% RH or more for 1 second to 10 minutes. It can be seen that it can be manufactured.

  From Comparative Examples 1 to 3 and 6 to 13, it was found that when the relative humidity was less than 60% RH, a polymer electrolyte membrane excellent in form (quality) could not be produced.

  From Comparative Examples 4 and 5, it was found that a polymer electrolyte membrane excellent in form (quality) could not be produced when the time in an atmosphere with a relative humidity of 60% RH or more exceeded 10 minutes.

  The method for producing a polymer electrolyte membrane of the present invention has a small film thickness (preferably 50 μm or less, more preferably 40 μm), which is particularly difficult to manufacture from the viewpoint of the form and characteristics of the membrane and is made of an aromatic hydrocarbon electrolyte. Hereinafter, more preferably 35 μm or less) In producing the polymer electrolyte membrane, the occurrence of minute deformation of the membrane can be suppressed. Therefore, since a high-performance, high-grade fuel cell membrane can be produced economically, means for providing a polymer electrolyte membrane used for a direct methanol fuel cell (DMFC), a polymer electrolyte fuel cell (PEFC), etc. As a major contribution to industry.

Claims (6)

A solution obtained by dissolving an aromatic hydrocarbon-based polymer electrolyte precursor having an acidic group, at least a part of which forms a salt, in a solvent is cast on a support, and the polymer electrolyte precursor Obtaining a cast film;
Removing the solvent from the cast film to obtain a polymer electrolyte precursor film;
Converting the salt of the polymer electrolyte precursor into protons in a solution of an acidic component having a pKa of 3 or less to obtain a polymer electrolyte membrane;
Placing the polymer electrolyte membrane in an atmosphere having a relative humidity of 60% RH or more for 1 second to 10 minutes;
And a step of washing the polymer electrolyte membrane in this order with a poor solvent for the polymer electrolyte membrane capable of dissolving the acidic component. A method for producing an aromatic hydrocarbon polymer electrolyte membrane, comprising:   The manufacturing method according to claim 1, wherein the process from the step of obtaining the cast film to the step of cleaning is performed in a state where the film is supported by the support.   In the step of obtaining the cast membrane, 80 mol% or more of the acidic groups form a salt, and in the step of obtaining the polymer electrolyte membrane, 90 mol% or more of the salt is converted into protons. The manufacturing method of Claim 1 or 2.   The manufacturing method according to claim 1, wherein the acidic group includes at least a sulfonic acid group.   The manufacturing method as described in any one of Claim 1 to 4 including the process of drying the polymer electrolyte membrane after washing | cleaning obtained through the said process to wash | clean.   The manufacturing method according to claim 5, wherein a film thickness of the polymer electrolyte membrane after drying obtained through the drying step is 50 μm or less.