JP5772752B2 - Electrolyte membrane manufacturing method and electrolyte membrane manufacturing apparatus - Google Patents

Description

  The present invention relates to a technique for manufacturing an electrolyte membrane.

As a method for producing an electrolyte membrane, a method for producing an electrolyte membrane precursor by hydrolysis is known. Specifically, the electrolyte membrane is obtained by changing the F-type electrolyte resin (terminal group is —SO ₂ F) constituting the electrolyte membrane precursor into an H-type electrolyte resin (terminal group is —SO ₃ H) by hydrolysis. Manufacture. As techniques relating to hydrolysis, for example, Patent Documents 1 and 2 below are known. In the following Patent Document 1, an electrolyte membrane precursor mixed with alkali metal hydroxide (NaOH or KOH) is sandwiched between fuel cell molds, and a hydrolysis treatment is performed by introducing superheated steam into the mold. A technique for performing alkali treatment, which is one step of the above, is described. Patent Document 2 below describes a technique for preventing a concentration change due to evaporation of an alkaline aqueous solution by performing an alkali treatment using an alkaline aqueous solution under a wet inert gas at 100 ° C. or lower.

JP 2010-186721 A Japanese Patent Laid-Open No. 2004-181330

  By the way, conventionally, when performing the alkali treatment which is one step of hydrolysis under a normal atmosphere, alcohol or dimethyl sulfoxide is added to the alkaline aqueous solution as a reaction propellant. However, the problem that the electrolyte resin may be dissolved by these reaction propellants has been pointed out. In addition, when hydrolysis is performed using dimethyl sulfoxide, when an electrode is assembled to the produced electrolyte membrane to form an MEA (membrane electrode assembly), platinum contained in the electrode is converted by dimethyl sulfoxide contained in the electrolyte membrane. Problems have been pointed out that poisoning can lead to performance degradation of fuel cells.

  On the other hand, when alkali treatment is carried out without using a reaction accelerator, the treatment speed decreases. If alkali treatment is performed at a high temperature and high concentration in order to ensure a speed suitable for production, the concentration of the aqueous alkali solution changes greatly due to evaporation of water, and thus concentration adjustment is necessary. However, for example, when an alkaline aqueous solution having a high processing speed of 100 ° C. or higher is used, if water is added to the alkaline aqueous solution for the purpose of adjusting the concentration, bumping may occur and the alkaline aqueous solution may be scattered. It was. Furthermore, in the operation of a fuel cell, it is required to maintain the performance in a high temperature / low humidity environment. However, a fuel cell manufactured using an electrolyte membrane produced by a conventional method is used under high temperature / low humidity conditions. There has been a problem that performance maintenance is not sufficient.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms. One aspect of the present invention is a method for producing an electrolyte membrane, comprising a preparation step of preparing an electrolyte membrane precursor capable of imparting ionic conductivity by hydrolysis; and the electrolyte membrane precursor using an alkaline aqueous solution in contact with superheated steam Performing an alkali treatment that is at least a part of the hydrolysis of the body at a temperature of 100 ° C. or higher, and immersing in an alkaline aqueous solution in the superheated steam provided on a conveyance path for conveying the electrolyte membrane precursor. And an alkali treatment step. If it is such a form, the aqueous alkali solution which contacts thermal steam will be 100 degreeC or more. Since the alkali treatment, which is one step of hydrolysis, is performed with an aqueous alkali solution at 100 ° C. or higher, the reaction rate is faster than the alkali treatment, and the treatment rate can be improved. In addition, regarding the change in the concentration of the alkaline aqueous solution due to the evaporation of water, the alkaline aqueous solution is in contact with the superheated steam, so that the concentration is kept constant by liquefaction of the superheated steam. In addition, the present invention can be realized in the following forms.
(1) According to one form of this invention, the manufacturing method of an electrolyte membrane is provided. The method for producing an electrolyte membrane includes a preparation step of preparing an electrolyte membrane precursor capable of imparting ionic conductivity by hydrolysis; and at least a part of hydrolysis of the electrolyte membrane precursor using an alkaline aqueous solution in contact with superheated steam An alkali treatment step of performing an alkali treatment which is a step of According to the manufacturing method of the electrolyte membrane of this form, the alkaline aqueous solution in contact with the superheated steam is 100 ° C. or higher. Since the alkali treatment, which is one step of hydrolysis, is performed with an aqueous alkali solution at 100 ° C. or higher, the reaction rate is faster than the alkali treatment, and the treatment rate can be improved. In addition, regarding the change in the concentration of the alkaline aqueous solution due to the evaporation of water, the alkaline aqueous solution is in contact with the superheated steam, so that the concentration is kept constant by liquefaction of the superheated steam.

(2) In the method for manufacturing an electrolyte membrane of the above aspect, the alkali treatment step may be performed by adjusting the superheated steam to a predetermined temperature. Under an environment where the pressure is constant, the concentration of the alkaline aqueous solution in contact with the superheated steam is uniquely determined by determining the temperature. Therefore, according to the manufacturing method of the electrolyte membrane of this embodiment, the concentration of the alkaline aqueous solution can be adjusted by adjusting the temperature of the superheated steam.

(3) In the manufacturing method of the electrolyte membrane of the said form, the predetermined temperature of the said superheated steam is good also as 100 degreeC or more and 250 degrees C or less. According to the method for producing an electrolyte membrane of this aspect, the alkaline membrane is used under superheated steam at a temperature of 100 ° C. or higher, at which water is stably present as water vapor, and at 250 ° C. or lower, at which the electrolyte membrane starts thermal decomposition. Since the treatment is performed, the treatment can be performed while avoiding thermal decomposition of the electrolyte membrane.

(4) In the method for manufacturing an electrolyte membrane of the above aspect, the predetermined temperature of the superheated steam may be 130 ° C. or higher and 180 ° C. or lower. According to the method for producing an electrolyte membrane of this embodiment, the electrolyte membrane produced by the production method is at a temperature at which a clear performance improvement is found at 130 ° C. or more, and the temperature at which the strength of the electrolyte membrane is reduced. Alkaline treatment can be performed under superheated steam at 180 ° C. or lower.

(5) In the method for manufacturing an electrolyte membrane of the above aspect, the alkali treatment step may include a step of immersing in an alkaline aqueous solution in the superheated steam provided on a transport path for transporting the electrolyte membrane precursor. . According to the method for manufacturing an electrolyte membrane in this aspect, the alkali treatment can be continuously performed while the electrolyte membrane precursor is conveyed, so that the manufacturing efficiency of the electrolyte membrane can be increased.

(6) In the method for producing an electrolyte membrane of the above aspect, the electrolyte membrane produced by the production method further forms an electrode on the electrolyte membrane precursor prepared in the preparation step prior to the alkali treatment step. The alkali treatment step may be performed on the electrolyte membrane precursor on which the electrode is formed. According to the method for manufacturing an electrolyte membrane in this form, an electrolyte membrane in which a catalyst electrode is formed can be generated by hydrolysis.

(7) Moreover, according to the other form of this invention, the electrolyte membrane manufacturing apparatus which manufactures an electrolyte membrane is provided. The electrolyte membrane manufacturing apparatus includes: a storage unit that stores an alkaline aqueous solution that contacts superheated steam; and an alkaline aqueous solution stored in the storage unit for the electrolyte membrane precursor that can impart ion conductivity by hydrolysis. An alkali treatment unit that performs alkali treatment that is part of the decomposition. The alkaline aqueous solution in contact with the superheated steam is 100 ° C. or higher. According to this electrolyte membrane manufacturing apparatus, since the alkali treatment is performed with an alkaline aqueous solution at 100 ° C. or higher, the reaction rate can be increased and the treatment rate can be improved as compared with the alkali treatment at room temperature.

  A plurality of constituent elements of each aspect of the present invention described above are not indispensable, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with another new component, and partially delete the limited contents of some of the plurality of components. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

  For example, one embodiment of the present invention can be realized as a manufacturing method including one or more elements of two elements of a preparation process and an alkali treatment process. That is, this manufacturing method may have a preparatory process and does not need to have it. Moreover, this manufacturing method may have an alkali treatment process and does not need to have it. Such a manufacturing method can be realized as a manufacturing method of an electrolyte membrane, for example, but can also be realized as a manufacturing method of other things than the electrolyte membrane. According to such a form, it is possible to solve at least one of various problems such as high-speed processing, low cost, resource saving, easy manufacturing, improved usability, and improved manufacturing efficiency. Some or all of the technical features of the respective forms of the electrolyte membrane manufacturing method described above can be applied to this manufacturing method.

  Note that the present invention can be realized in various modes. For example, ion exchange membrane, ion exchange membrane production apparatus and production method, fuel cell, fuel cell production system and production method, electrolyte membrane, electrolyte membrane production system, hydrolysis treatment method, hydrolysis treatment apparatus, alkali treatment method It can be realized in the form of an alkali treatment apparatus.

It is explanatory drawing explaining the structure of a single cell. It is process drawing which shows the manufacturing process of a single cell. It is process drawing which shows the manufacturing process of an electrolyte membrane. It is explanatory drawing explaining a hydrolysis process. It is explanatory drawing which shows the process in which sodium hydroxide aqueous solution is produced | generated. It is a graph which shows the correlation of the density | concentration of sodium hydroxide aqueous solution, and a boiling point. It is explanatory drawing which shows the structure of a hydrolysis processing apparatus. It is explanatory drawing which shows the process conditions of the alkali process of Examples 1-3 and Comparative Examples 1 and 2. FIG. It is a graph which shows the measurement result of a cell voltage. It is explanatory drawing explaining the alkali treatment part of the modification 3.

A. First embodiment:
(A1) Configuration of fuel cell:
FIG. 1 is an explanatory view illustrating the configuration of a single cell 10 in a fuel cell manufactured by employing the method for manufacturing an electrolyte membrane as the first embodiment of the present invention. The figure schematically shows a cross section of the single cell 10. The fuel cell of the present embodiment is a polymer electrolyte fuel cell, and has a stack structure in which a plurality of single cells 10 are stacked. As shown in the figure, the unit cell 10 includes a membrane electrode assembly (hereinafter also referred to as MEA) 12 containing an electrolyte, a pair of gas diffusion layers 16 and 17 that sandwich the MEA 12 from both sides to form a sandwich structure, The sandwich structure is further composed of a pair of separators 20 and 21 sandwiching the sandwich structure from both sides.

  The MEA 12 includes an electrolyte membrane 13, and an anode (fuel electrode) 14 and a cathode (oxygen electrode) 15 formed on both surfaces of the electrolyte membrane 13. The electrolyte membrane 13 is a proton-conducting ion exchange membrane formed of a fluororesin and exhibits good electrical conductivity in a wet state. The electrolyte membrane 13 will be described in detail later. The anode 14 and the cathode 15 are gas diffusible catalyst electrodes on which a catalyst that promotes an electrochemical reaction (for example, platinum (Pt)) is supported.

  The gas diffusion layers 16 and 17 are configured by members having gas permeability and conductivity. In the present embodiment, the gas diffusion layers 16 and 17 are formed of a carbon porous member such as carbon cloth or carbon paper. By providing the gas diffusion layers 16 and 17, the gas supply efficiency to the electrodes can be improved, the current collecting property between the separators 20 and 21 and the electrodes can be improved, and the electrolyte membrane 13 can be further protected. . The gas diffusion layers 16 and 17 may be formed of other conductive porous members such as a metal porous material such as titanium or stainless steel instead of the carbon porous member.

  The separators 20 and 21 are gas-impermeable conductive members, and are formed of, for example, dense carbon that has been made gas impermeable by compressing carbon, a metal member, or the like. The separators 20 and 21 are formed with rib portions of a predetermined shape on the surfaces thereof, and the fuel gas and oxidizing gas flow paths 20P and 21P are formed between the gas diffusion layers 16 and 17 adjacent to each other. To do. When the single cell 10 is stacked to form a fuel cell and perform power generation, the fuel gas (hydrogen gas) is supplied to the flow path 20P in the single cell, and the oxidizing gas (air containing oxygen) is supplied to the flow path 21P of the single cell. Are supplied respectively. Then, the fuel gas and the oxidizing gas cause an electrochemical reaction in the electrolyte membrane 13 through the gas diffusion layers 16 and 17, the anode 14, and the cathode 15, thereby generating electric power. The configuration of the single cell 10 has been described above.

(A2) Fuel cell manufacturing method:
FIG. 2 is a process diagram for explaining the manufacturing process of the single cell 10. As shown in the drawing, as a manufacturing process of the unit cell 10, first, the electrolyte membrane 13 is manufactured (process S110). The method for manufacturing the electrolyte membrane 13 will be described in detail later. After manufacturing the electrolyte membrane 13, the MEA 12 is generated by forming the anode 14 on one surface of the electrolyte membrane 13 and the cathode 15 on the other surface (step S130). Specifically, a catalyst ink containing platinum, carbon powder, and ionomer is applied to both surfaces of the electrolyte membrane 13 and dried by warm air. Thereafter, carbon porous members as the gas diffusion layers 16 and 17 are laminated on both surfaces of the generated MEA 12 (step S140), and the outside is sandwiched between the separators 20 and 21 to manufacture the single cell 10 (step S150). ).

(A3) Manufacturing method of electrolyte membrane:
Next, the manufacturing method of the electrolyte membrane 13 shown in step S110 of FIG. 2 will be described. FIG. 3 is a process diagram showing a manufacturing process of the electrolyte membrane 13. In the present embodiment, an electrolyte membrane using a porous membrane as a reinforcing member is manufactured. As a manufacturing process of the electrolyte membrane 13, first, a porous membrane as a reinforcing member is generated (step S112). Specifically, a paste made of PTFE (polytetrafluoroethylene) fine powder is formed into a cylindrical shape by extrusion molding. Then, the cylindrical paste is formed into a tape-like PTFE tape by roll rolling. Further, the PTFE tape is stretched to an area ratio of 900 times while being heated to a predetermined temperature using a multiaxial stretching machine to produce a porous film having a thickness of about 20 μm.

After the porous film is generated, a thin film made of an electrolyte precursor (hereinafter also referred to as F-type electrolyte thin film) is generated (step S114). Specifically, an F-type electrolyte resin (terminal group is —SO ₂ F: polymer Nafion (registered trademark) manufactured by DuPont), which is a precursor polymer of the electrolyte resin, is thickened by a T-type coat hanger die of an extrusion molding machine. Form a thin film of about 12 μm.

  After the formation of the F-type electrolyte thin film, the F-type electrolyte thin film is bonded to both sides of the porous film (step S116), and the impregnation treatment is performed by impregnating the F-type electrolyte resin into the porous film by a roll press at a temperature of 230 ° C. An electrolyte membrane precursor having a thickness of 30 μm is generated (step S118). And an electrolyte membrane is produced | generated by performing a hydrolysis process with respect to the produced | generated electrolyte membrane precursor (process S120).

(A4) Hydrolysis treatment:
FIG. 4 is an explanatory diagram for explaining the hydrolysis treatment (FIG. 3: step S120) in the present embodiment. The hydrolysis treatment in the present embodiment is performed by a hydrolysis treatment device 30 as an electrolyte membrane manufacturing device. The hydrolysis treatment apparatus 30 includes a feeding part 32, an alkali treatment part 40, a water washing part 50, an acid treatment part 52, a water washing part 54, a winding part 34, and transport rollers R1 to R10.

  A thin film roll RL made of an electrolyte membrane precursor is set in the feeding portion 32. The thin film roll RL is obtained by attaching a back sheet for conveyance assistance (not shown) to the belt-shaped thin film FL made of the electrolyte film precursor generated in steps S112 to S118 in FIG. . The feeding unit 32 feeds the thin film FL on which the conveyance assisting backsheet is bonded to each processing unit (the alkali processing unit 40, the water washing unit 50, the acid processing unit 52, and the water washing unit 54). The transport rollers R <b> 1 to R <b> 10 constitute a transport path for transporting the thin film FL fed from the feed unit 32 to each processing unit, and finally transport the thin film FL to the winding unit 34.

The alkali treatment unit 40 performs the alkali treatment by immersing the thin film FL fed from the feeding unit 32 in an alkaline aqueous solution (in this embodiment, a sodium hydroxide aqueous solution) adjusted in temperature and concentration. The alkali treatment performed by the alkali treatment unit 40 will be described in detail later. By the alkali treatment in the alkali treatment unit 40, the following reaction occurs in the F-type electrolyte resin of the thin film FL, and the terminal group is changed from —SO ₂ F to —SO ₃ Na.

_{-SO 2 F + 2NaOH → -SO 3} Na + NaF + H 2 0

The water washing part 50 wash | cleans alkaline aqueous solution from the thin film FL after an alkali treatment. The acid treatment unit 52 performs acid treatment on the thin film FL after the alkali treatment. Specifically, the thin film FL is immersed in nitric acid accommodated in the acid treatment unit 52 for a predetermined time. By acid treatment in the acid treatment unit 52, it occurs following reaction in the thin film FL, terminal device changes from -SO ₃ Na in -SO ₃ H.

-SO ₃ Na + HNO ₃ → -SO ₃ H + NaNO ₃

The water washing part 54 flushes nitric acid from the thin film FL after acid treatment. The winding unit 34 winds the thin film FL that has passed through the water washing unit 54 and has been dried. The thin film FL is changed from the F-type electrolyte resin not having proton conductivity to the H-type electrolyte resin having proton conductivity (the polymer chain end is —SO ₃ H) by the processing performed by each processing unit of the hydrolysis treatment apparatus 30. It changes to the electrolyte membrane which consists of. In this way, the hydrolysis apparatus 30 performs the hydrolysis process on the thin film FL. The thin film FL wound around the winding unit 34 is then cut into a predetermined shape and incorporated into a single cell through the steps S130 to S150 shown in FIG.

(A5) Alkali treatment:
Next, details of the alkali treatment performed by the alkali treatment unit 40 will be described. As shown in FIG. 4, the alkali treatment unit 40 includes a superheated steam generator 41, a chamber 42, and a storage unit 44. The superheated steam generator 41 and the chamber 42 communicate with each other through a flow path 46. The chamber 42 has an open port 45 with the outside.

  The superheated steam generator 41 is a device that generates steam at a predetermined temperature of 100 ° C. or higher. The superheated steam generator 41 adjusts the temperature of the superheated steam to be generated by a heater and a thermistor provided therein. The superheated steam generator 41 supplies the generated superheated steam to the chamber 42 via the flow path 46. The superheated steam introduced from the superheated steam generator 41 through the flow path 46 fills the chamber 42 and is discharged from the opening 45.

  The chamber 42 includes an accommodating portion 44 therein. The accommodating part 44 accommodates the sodium hydroxide aqueous solution as alkaline aqueous solution. The aqueous sodium hydroxide solution stored in the storage unit 44 is generated inside the chamber 42 by the superheated steam supplied from the superheated steam generator 41.

  FIG. 5 is an explanatory diagram illustrating a process in which an aqueous sodium hydroxide solution is generated in the chamber 42. FIG. 5 shows the accommodating portion 44 placed inside the chamber 42. As the production of the aqueous sodium hydroxide solution, solid sodium hydroxide 47 is introduced into the accommodating portion 44 whose interior is empty (step C1). At this time, superheated steam is not supplied into the chamber 42.

  After putting solid sodium hydroxide 47 into the housing 44, the superheated steam generator 41 is operated to supply steam adjusted to about 100 ° C. to the chamber 42 (step C2). The solid sodium hydroxide 47 filled with water vapor is dissolved by deliquescence, and an alkaline aqueous solution is generated in the housing portion 44.

  Thereafter, the superheated steam generator 41 constantly supplies the superheated steam adjusted to a desired temperature to the chamber 42, and the inside of the chamber 42 is filled with the superheated steam (step C3). Of the supplied superheated steam, superheated steam that does not fit inside the chamber 42 circulates in the chamber 42 and is released from the opening 45 (see FIG. 4). That is, the pressure inside the chamber 42 is substantially equal to the outside pressure, and is about 1 atm in this embodiment. When the superheated steam is continuously supplied to the chamber 42 for a predetermined time, the sodium hydroxide aqueous solution in the housing portion 44 becomes a temperature substantially equal to the superheated steam due to the superheated steam. A sodium hydroxide aqueous solution in superheated steam having a constant temperature has a constant temperature and a constant concentration. The reason why the concentration of the sodium hydroxide aqueous solution is constant will be described in detail later. After the sodium hydroxide aqueous solution having a predetermined constant concentration is generated, the thin film FL is immersed in the sodium hydroxide aqueous solution by the transport roller R2, and alkali treatment is performed (step C4).

  Next, the principle that the concentration of the aqueous sodium hydroxide solution in the superheated steam at a constant temperature is constant in step C3 will be described. FIG. 6 is a graph showing the correlation between the concentration of sodium hydroxide aqueous solution at 1 atm and the boiling point. The correlation between the concentration of the aqueous solution and the boiling point at a predetermined pressure (1 atm in the present embodiment) is uniquely determined depending on the medium dissolved in water. As shown in the graph of FIG. 6, the boiling point of the aqueous sodium hydroxide solution increases as the concentration increases. This graph will be used to explain that the concentration of the aqueous sodium hydroxide solution in the superheated steam at a constant temperature is constant.

  As an example, the case where the superheated steam generator 41 is controlled to supply the chamber 42 with superheated steam at 130 ° C. for alkali treatment (hereinafter also referred to as Example 1) will be described. In this case, the sodium hydroxide aqueous solution in the accommodating portion 44 approaches about 130 ° C. At this time, if the concentration of the sodium hydroxide aqueous solution in the container 44 is 40 (%) or less (for example, 30%), the boiling point of the sodium hydroxide aqueous solution is 130 ° C. or less as shown in the graph of FIG. (For example, when the concentration is 30%, the boiling point is 116 ° C.). Therefore, when heated by superheated steam at about 130 ° C. and the sodium hydroxide aqueous solution reaches 116 ° C., water evaporates from the sodium hydroxide aqueous solution. Actually, the evaporation of water in the aqueous sodium hydroxide solution and the liquefaction of superheated steam on the surface of the aqueous sodium hydroxide solution occur simultaneously, and the amount of evaporation of water is larger than the liquefied amount of superheated steam.

  As the water evaporates, the concentration of the aqueous sodium hydroxide increases. As shown in FIG. 6, the boiling point increases as the concentration of the aqueous sodium hydroxide solution increases. When the concentration of the aqueous sodium hydroxide solution reaches about 40% due to evaporation of water, the boiling point becomes 130 ° C., which is the same as the temperature of the superheated steam (130 ° C.). At this time, evaporation of water of the sodium hydroxide aqueous solution and liquefaction of superheated steam are in an equilibrium state. Therefore, the increase in the concentration of the sodium hydroxide aqueous solution stops. Moreover, since the temperature of superheated steam is 130 degreeC, the temperature of sodium hydroxide aqueous solution does not rise to 130 degreeC or more. Accordingly, the concentration of the sodium hydroxide aqueous solution is constant at 40%.

  Next, if the sodium hydroxide aqueous solution adjusted to a concentration of 40% is charged with solid sodium hydroxide and the concentration is increased (for example, the concentration is increased to 50%), the graph shown in FIG. Thus, the boiling point of the aqueous sodium hydroxide solution is 143 ° C. At this time, since the temperature of the superheated steam (130 ° C.) is lower than the boiling point of the sodium hydroxide aqueous solution, the amount of superheated steam liquefied on the surface of the sodium hydroxide aqueous solution exceeds the amount of water evaporated in the sodium hydroxide aqueous solution. In effect, water is added to the aqueous sodium hydroxide solution. Accordingly, the concentration of the sodium hydroxide aqueous solution decreases. As shown in the graph of FIG. 6, the boiling point decreases as the concentration of the aqueous sodium hydroxide solution decreases. And when the boiling point of sodium hydroxide aqueous solution falls to 130 degreeC with the fall of a density | concentration, it becomes the same as the temperature (130 degreeC) of superheated steam. Since the temperature of the superheated steam is 130 ° C., the temperature of the aqueous sodium hydroxide solution does not fall below 130 ° C. At this time, the evaporation of water in the aqueous sodium hydroxide solution and the liquefaction of superheated steam are in an equilibrium state. Therefore, the decrease in the concentration of the aqueous sodium hydroxide solution stops and becomes constant at a concentration of 40%.

  That is, the alkali treatment unit 40 can perform the alkali treatment by controlling the temperature of the superheated steam supplied from the superheated steam generator 41 to the chamber 42 to control the concentration of the sodium hydroxide aqueous solution in the storage unit 44. . Further, since the alkali treatment unit 40 performs the alkali treatment with an alkali aqueous solution at 100 ° C. or higher, the reaction rate is faster than when the alkali treatment is performed with an aqueous sodium hydroxide solution at 100 ° C. or less, and the alkali treatment is performed in a short time. It can be carried out. In this way, the alkali processing unit 40 performs alkali processing on the thin film FL.

(A6) Performance evaluation:
Next, in order to evaluate the effect of the alkali treatment using the alkali treatment unit 40, as Example 1 of the present embodiment, a hydrolysis treatment including an alkali treatment in which the temperature of the superheated steam is controlled to 130 ° C. is performed, and the electrolyte membrane is changed. Generated. That is, in the alkali treatment, the concentration of the sodium hydroxide aqueous solution is controlled to about 40%. As Example 2, a hydrolysis treatment including an alkali treatment in which the temperature of superheated steam was controlled at 160 ° C. was performed to produce an electrolyte membrane. That is, in the alkali treatment, the concentration of the sodium hydroxide aqueous solution is controlled to about 60%. Moreover, as Example 3, the electrolyte membrane was produced | generated by performing the hydrolysis process containing the alkali process which controlled the temperature of the superheated steam to 180 degreeC. That is, in the alkali treatment, the concentration of the sodium hydroxide aqueous solution is controlled to about 65%. About these thin film FL after the alkali treatment by Examples 1-3, when the structural analysis by FT-IR (Fourier transform infrared spectrophotometer) was conducted, it was confirmed that the alkali treatment was completed.

  Furthermore, as Comparative Example 1, a hydrolysis treatment was performed using a hydrolysis treatment device 70 different from the hydrolysis treatment device 30 (see FIG. 4), and an electrolyte membrane was generated. FIG. 7 is an explanatory diagram for explaining the configuration of the hydrolysis treatment apparatus 70. The difference from the hydrolysis treatment apparatus 30 used in Examples 1 to 3 is that the alkali treatment unit 40 is changed to the alkali treatment unit 71. The other water washing part 50, the acid treatment part 52, and the water washing part 54 are the same as the hydrolysis processing apparatus 30. The alkali processing unit 71 contains a 40% sodium hydroxide aqueous solution. The alkali treatment unit 71 heats and keeps the aqueous sodium hydroxide solution at 130 ° C. with a heater (not shown). When an alkali treatment was attempted in the normal atmosphere by such an alkali treatment portion 71, the water of the sodium hydroxide aqueous solution evaporated during the alkali treatment, and the concentration increased. Thereafter, precipitation of sodium hydroxide occurred from the aqueous sodium hydroxide solution. An attempt was made to add pure water to reduce the concentration of the aqueous sodium hydroxide solution, but bumping occurred with the addition of pure water. Since the aqueous sodium hydroxide solution was scattered by bumping, alkali treatment was stopped. As a result, no electrolyte membrane was produced.

  Further, as Comparative Example 2, a hydrolysis treatment apparatus 70 is used, a 40% concentration sodium hydroxide aqueous solution is accommodated in the alkali treatment unit 71, heated and kept at a temperature of 80 ° C. by a heater, and subjected to alkali treatment in a normal atmosphere. went. The immersion time of the thin film FL in the sodium hydroxide aqueous solution was 10 minutes. The reason for setting the immersion time to 10 minutes is that the structure analysis by FT-IR (Fourier transform infrared spectrophotometer) was performed on the thin film FL which had been subjected to the alkali treatment with the immersion time of 1 minute to 9 minutes. This is because was not completed. When the immersion time was 10 minutes (600 seconds), it was confirmed by FT-IR that the alkali treatment was completed. After performing such alkali treatment, hydrolysis treatment was performed through the steps of water washing by the water washing section 50, acid treatment by the acid treatment section 52, and water washing by the water washing section 54, thereby producing an electrolyte membrane. In Comparative Example 2, an electrolyte membrane could be obtained by performing a hydrolysis treatment including an alkali treatment.

  FIG. 8 is an explanatory diagram summarizing the processing conditions of the alkali treatment according to Examples 1 to 3 and Comparative Examples 1 and 2. As shown in the figure, for each example and each comparative example, the type of the alkali treatment part used for the alkali treatment, the temperature, concentration and treatment time of the aqueous sodium hydroxide solution, and finally the electrolyte by the hydrolysis treatment including the alkali treatment It shows whether or not the film was formed. In Comparative Example 1, bumping occurred due to the addition of pure water to the aqueous sodium hydroxide solution, and the alkali treatment was stopped, so that no electrolyte membrane was formed.

  Next, in order to evaluate the performance of the electrolyte membranes obtained in Examples 1 to 3 and Comparative Example 2, a single cell was manufactured using each electrolyte membrane. Then, the fuel gas (hydrogen) and the oxidizing gas (air) were supplied to the in-unit cell flow path 20P and the in-cell flow path 21P of each single cell, and the cell voltage at a predetermined temperature and current value was measured. FIG. 9 is a graph showing the measurement result of the cell voltage. In this graph, the cell voltage of each single cell is plotted with the alkali treatment temperature on the horizontal axis and the cell voltage on the vertical axis. As a result, as shown in the figure, it was confirmed that the single cell using the electrolyte membranes produced in Examples 1, 2 and 3 had a higher cell voltage and improved performance than Comparative Example 2. This is because it is possible to cause the electrolyte membrane to contain water at a temperature above the glass transition point by stably performing an alkali treatment at a temperature of 100 ° C. or higher, and the moisture content of the electrolyte membrane is improved by hydrolysis at room temperature. It is thought to be caused by this. Moreover, it was confirmed that the electrolyte membrane produced | generated by Example 1 has the highest cell voltage, and its performance as an electrolyte membrane is high.

  Moreover, the fuel cell using the electrolyte membrane produced | generated by Example 1, 2, 3 was drive | operated under high temperature and low humidity, and performance evaluation was performed by the predetermined method. As a result, the fuel cells using the electrolyte membranes produced in Examples 1, 2 and 3 were less hot and low in humidity than the fuel cells using the electrolyte membranes produced by alkali treatment in a normal atmosphere. It has been found that the rate of performance degradation is low and high performance is maintained. As described above, this is considered to be due to the improvement of the moisture content of the electrolyte membrane by the alkali treatment at a temperature of 100 ° C. or higher.

  Based on the results of these performance evaluations, the temperature of the superheated steam supplied to the chamber 42 in the alkali treatment is not less than the temperature at which water is stably present as the steam and not more than the temperature at which the electrolyte membrane starts thermal decomposition. preferable. Specifically, the temperature of the superheated steam is preferably 100 ° C. or higher and 250 ° C. or lower. Further, the temperature of the superheated steam supplied to the chamber 42 is equal to or higher than the temperature at which a clear effect on the performance is found in the electrolyte membrane in the above embodiment, and the strength at which the strength of the thin film FL and the back sheet for conveyance assistance decreases. The following is more preferable. Specifically, the temperature of the superheated steam is more preferably 130 ° C. or higher and 180 ° C. or lower.

  As described above, the alkali treatment using the alkali treatment unit 40 in the present embodiment can be performed stably at a high temperature (100 ° C. or higher) and a high concentration aqueous alkali solution. Therefore, the reaction rate is faster than when the alkali treatment is performed at 100 ° C. or lower, and the treatment speed of the alkali treatment can be improved and the treatment time can be shortened. Specifically, in the alkali treatment under a normal atmosphere of 100 ° C. or less (for example, Comparative Example 2), the treatment time was several minutes, but in the alkali treatment under superheated steam as in this embodiment, Processing time can be reduced to a few seconds.

  As can be seen from Comparative Examples 1 and 2, when alkali treatment is performed in a normal atmosphere, it is necessary to measure the temperature and concentration of the aqueous alkali solution and to add a necessary amount of water to keep the concentration constant. Met. On the other hand, the concentration of the alkaline aqueous solution under the superheated steam is uniquely determined by the temperature of the superheated steam. Therefore, in the alkali treatment using the alkali treatment unit 40, the temperature and the concentration of the alkaline aqueous solution are controlled by controlling the temperature of the superheated steam. Can be controlled. Therefore, the measurement work of the temperature and concentration of the alkaline aqueous solution can be omitted. Furthermore, the alkali treatment unit 40 can perform the alkali treatment by keeping the concentration of the aqueous alkali solution constant by keeping the temperature of the superheated steam constant. Therefore, the operation of adding water for adjusting the concentration of the alkaline aqueous solution can be omitted. Moreover, the alkali treatment part 40 can maintain the temperature and density | concentration of aqueous alkali solution constant by controlling the temperature of superheated steam. Therefore, it becomes easy to perform alkali treatment under the same treatment conditions every time, and an electrolyte membrane with stable quality can be generated. Further, as described above, a fuel cell using an electrolyte membrane produced by performing an alkali treatment under superheated steam can maintain high performance even in operation at high temperatures and low humidity.

  Furthermore, since the hydrolysis process in this embodiment can be performed using the conveyance path using a conveyance roller, continuous production of an electrolyte membrane can be enabled. In addition, since the alkali treatment speed can be increased as described above, it is possible to reduce the size of the equipment even when the electrolyte membrane is mass-produced, and the production cost of the electrolyte membrane can be reduced and the production cost can be reduced. Can be realized.

B. Variation:
The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
(B1) Modification 1:
In the above embodiment, the electrolyte membrane precursor is hydrolyzed, but an MEA precursor in which electrodes (FIG. 1: anode 14 and cathode 15) are formed on the electrolyte membrane precursor is generated, and the MEA precursor is produced. Hydrolysis treatment may be performed on. In addition, a catalyst electrode having an F-type electrolyte resin as a constituent element may be formed on the electrolyte membrane precursor and subjected to hydrolysis treatment. The F-type electrolyte resin is hardly denatured even at a certain high temperature. Therefore, when a catalyst electrode made of an F-type electrolyte resin is formed on the electrolyte membrane precursor and dried by a hot plate or hot air, it can be dried at a high temperature. Moreover, it can suppress that MEA12 denatures by drying. In this case, a catalyst ink containing an F-type electrolyte resin is applied on the electrolyte membrane precursor, dried with a hot plate or hot air to generate an MEA precursor, and the MEA precursor wound on a roll is fed to the feeding unit 32. It can be realized by setting and performing the same hydrolysis treatment as in the above embodiment. Also, as will be described later in Modification Example 5, when an electrolyte membrane is applied in an electrolytic capacitor, hydrolysis can be performed after the electrode of the electrolytic capacitor is formed on the electrolyte membrane precursor.

(B2) Modification 2:
In the above embodiment, sodium hydroxide is used as the substance used for the alkali treatment. However, the present invention is not limited to this, and other substances may be used. For example, an alkali metal hydroxide having a relatively high ionization tendency such as potassium hydroxide, lithium hydroxide, or calcium hydroxide can be used.

(B3) Modification 3:
In the above embodiment, the alkali treatment unit 40 fills the chamber 42 with superheated steam to bring the sodium hydroxide aqueous solution into contact with the superheated steam, but it may be brought into contact with other methods. FIG. 10 is an explanatory diagram illustrating an alkali treatment unit 80 as an example. As shown in the figure, the water vapor supplied from the superheated water vapor generator 41 is directly introduced into the sodium hydroxide aqueous solution in the housing portion 44 through the flow path 81. Even in this case, the temperature of the sodium hydroxide aqueous solution can be made substantially equal to the temperature of the superheated steam by adjusting the amount of superheated steam supplied to the sodium hydroxide aqueous solution. Therefore, as in the above embodiment, the temperature and concentration of the aqueous sodium hydroxide solution can be controlled by controlling the temperature of the superheated steam to be supplied, and the same effect as in the above embodiment can be obtained. Moreover, in the case of the modification 3, the accommodating part 44 can be made semi-sealed and the chamber 42 can be omitted. Therefore, further downsizing and cost reduction of the equipment can be realized.

(B4) Modification 4:
In the above embodiment, a series of hydrolysis treatments including alkali treatment, water washing, acid treatment, and water washing were performed to generate the electrolyte membrane. However, the treatment may be stopped only in a part of these hydrolysis treatment steps. For example, when an electrolyte membrane precursor subjected to only alkali treatment can be used for a predetermined application, only alkali treatment may be performed. Even when only the alkali treatment is performed, the alkali treatment can be stably performed at high speed by employing the alkali treatment according to the above-described embodiment. Moreover, the electrolyte membrane precursor after the alkali treatment with stable quality can be generated.

(B5) Modification 5:
In the above embodiment, the electrolyte membrane produced by the hydrolysis treatment is used for the fuel cell, but it may be used for an electrolytic capacitor (such as an electric double layer capacitor). Further, the produced electrolyte membrane may be used for other purposes as an ion exchange membrane. For example, it can be used for artificial skin and dialysis machines.

10 ... Single cell 12 ... MEA
DESCRIPTION OF SYMBOLS 13 ... Electrolyte membrane 14 ... Anode 15 ... Cathode 16 ... Gas diffusion layer 20 ... Separator 20P ... Single-cell flow path 21P ... Single-cell flow path 30 ... Hydrolysis processing device 32 ... Feeding part 34 ... Winding part 40 ... Alkali Processing unit 41 ... Superheated steam generator 42 ... Chamber 44 ... Storage unit 45 ... Opening port 46 ... Flow path 47 ... Solid sodium hydroxide 50, 54 ... Water washing unit 52 ... Acid treatment unit 70 ... Hydrolysis treatment device 71 ... Alkaline treatment Part 80 ... Alkali treatment part 81 ... Flow path R1-R29 ... Conveyance roller RL ... Thin film roll FL ... Thin film

Claims (6)

An electrolyte membrane manufacturing method comprising:
A preparation step of preparing an electrolyte membrane precursor capable of imparting ionic conductivity by hydrolysis;
There at least a part of the line at a temperature of more than 100 ° C. The alkali treatment is a step of hydrolysis of the electrolyte membrane precursor with an alkaline aqueous solution in contact with the superheated steam, provided on the transport path for transporting the electrolyte membrane precursor And an alkaline treatment step comprising a step of immersing in an alkaline aqueous solution in the superheated steam obtained . A method for producing an electrolyte membrane according to claim 1,
The method for producing an electrolyte membrane, wherein the alkali treatment step is performed in a space in which the superheated water vapor is constantly supplied and the open superheated water vapor is opened . A method for producing an electrolyte membrane according to claim 1 or claim 2,
The alkali treatment step, the manufacturing method of the electrolyte membrane, by adjusting the temperature of the superheated steam to 100 ° C. or higher 250 ° C. or less. A method for producing an electrolyte membrane according to claim 3,
The alkali treatment step, the manufacturing method of the electrolyte membrane, by adjusting the temperature of the superheated steam to 130 ° C. or higher 180 ° C. or less. The method for producing an electrolyte membrane according to any one of claims 1 to 4 , further comprising:
Prior to the alkali treatment step, comprising the step of forming an electrode on the electrolyte membrane precursor prepared in the preparation step,
The alkali treatment step is performed on the electrolyte membrane precursor on which the electrode is formed. An electrolyte membrane manufacturing apparatus for manufacturing an electrolyte membrane,
A container for containing an alkaline aqueous solution in contact with superheated steam;
By immersing the electrolyte membrane precursor capable of imparting ionic conductivity by hydrolysis in an alkaline aqueous solution in the superheated steam accommodated in the accommodating portion provided on the conveyance path for conveying the electrolyte membrane precursor . An electrolyte membrane manufacturing apparatus comprising: an alkali treatment unit that performs an alkali treatment that is a part of the hydrolysis at a temperature of 100 ° C. or higher .

Images