Diaphragm for alkaline water electrolysis and method for manufacturing same

Abstract

[Problem] The present invention provides a diaphragm for alkaline water electrolysis in which an inorganic compound for imparting hydrophilicity is not likely to fall off from an organic polymer porous membrane. [Solution] In this diaphragm for alkaline water electrolysis, a thin film that is derived from a titanium alkoxide and / or a zirconium alkoxide is adhered to an organic polymer porous membrane. The organic polymer porous membrane is a polysulfone-based porous membrane or a polyphenylsulfone-based porous membrane, and is supported by a wet nonwoven fabric that has polyphenylene sulfide fibers as constituent fibers. The organic polymer porous membrane supported by the wet nonwoven fabric is immersed in a diluent that is obtained by dissolving a solute, which is composed of a titanium alkoxide and / or a zirconium alkoxide, in a solvent and has a concentration of 0.1-20 vol%. Thereafter, in a situation where the solute is not precipitated, a heat treatment is performed so as to obtain a diaphragm for alkaline water electrolysis, in which a thin film that is derived from a titanium alkoxide and / or a zirconium alkoxide is adhered to the organic polymer porous membrane.

Description

Diaphragm for alkaline water electrolysis and method for producing same

[0001] The present invention relates to a diaphragm for alkaline water electrolysis used in an alkaline water electrolysis apparatus mainly for obtaining hydrogen gas, and a method for producing the same, and more particularly to a diaphragm for alkaline water electrolysis having good hydrophilicity and a method for producing the same.

[0002] Alkaline water electrolysis devices for producing oxygen and hydrogen from water have been known for some time. An alkaline water electrolysis device includes an anode, a cathode, and a diaphragm for alkaline water electrolysis that separates the anode and the cathode. When the anode and the cathode are brought into contact with a high-concentration alkaline aqueous solution, such as a high-concentration (generally 20 to 30% by mass) aqueous potassium hydroxide solution, and a voltage is applied between the anode and the cathode, hydroxide ions migrate from the cathode side to the anode side through the diaphragm for alkaline water electrolysis due to electrolysis of the alkaline aqueous solution, generating oxygen gas on the anode side and hydrogen gas on the cathode side. Therefore, the diaphragm for alkaline water electrolysis is required to be hydrophilic so that generated gas bubbles do not easily adhere to the diaphragm and so as to maintain good ion permeability.

[0003] However, because diaphragms for alkaline water electrolysis are made of organic polymer porous membranes such as polysulfone-based or polyphenylsulfone-based porous membranes, they are hydrophobic and prone to air bubbles, which can impair ion permeability. For this reason, inorganic particles have been added to organic polymer porous membranes to make them hydrophilic (Patent Document 1). Patent Document 1 describes two methods for adding inorganic particles. The first method involves preparing a sheet containing a mixture of an organic polymer and inorganic particles such as titanium oxide or zirconium oxide, and then stretching the sheet to produce an organic polymer porous membrane (Patent Document 1, Examples 1 to 4). The second method involves immersing a previously prepared organic polymer porous membrane in a highly concentrated solution of zirconium butoxide dissolved in butanol, followed by precipitation of zirconium oxide with distilled water, and then adding the inorganic particles to the organic polymer porous membrane (Patent Document 1, Examples 5 to 7). However, adding inorganic particles to an organic polymer porous membrane in the form of particles has the disadvantage that the inorganic particles tend to fall off.

[0004] International Publication No. 2018 / 182006

[0005] An object of the present invention is to provide a diaphragm for alkaline water electrolysis in which an inorganic compound for imparting hydrophilicity is less likely to fall off from the organic polymer porous membrane.

[0006] The present invention solves the above-mentioned problems by attaching an inorganic compound to an organic polymer porous membrane in the form of a thin film rather than in the form of particles. That is, the present invention relates to a diaphragm for alkaline water electrolysis, in which a thin film containing titanium oxide, zirconium oxide, or titanium zirconium oxide is attached to an organic polymer porous membrane, and a method for producing the same.

[0007] The organic polymer porous membrane is a conventionally known membrane that is alkali-resistant and has good ion permeability. Specifically, a polysulfone-based porous membrane or a polyphenylsulfone-based porous membrane is used, although other types of porous membranes may also be used. Organic polymer porous membranes often have low mechanical strength because they contain a large number of pores with maximum pore diameters of 0.1 to 3.0 μm. Therefore, it is preferable for the membrane to be supported by a relatively high-strength support. The support should have a maximum pore size larger than that of the organic polymer porous membrane, i.e., a larger pore size than the organic polymer porous membrane, so as not to inhibit the ion permeability of the organic polymer porous membrane. Examples of such supports include alkali-resistant paper, nonwoven fabric, woven fabric, or knitted fabric. The pulp or fiber constituting the paper and the fiber constituting the nonwoven fabric and knitted fabric are alkali-resistant. Specifically, polyphenylene sulfide-based pulp or fiber is used.

[0008] A thin film containing titanium oxide, zirconium oxide, or titanium zirconium oxide is attached to the organic polymer porous membrane. Such a thin film is generally derived from titanium alkoxide and / or zirconium alkoxide. Furthermore, this thin film is preferably attached to the pore inner wall surfaces of the organic polymer porous membrane. Such a thin film is hydrophilic, so that air bubbles are less likely to adhere and ion permeability is less likely to be inhibited. Thin films containing titanium oxide, zirconium oxide, or titanium zirconium oxide are, for example, amorphous and often contain a mixture of two or more bonds selected from the group consisting of Chemical Formulas 1, 2, 3, 4, 5, 6, 7, 8, and 9 below. Such bonds are generally derived from titanium alkoxide and / or zirconium alkoxide and are formed by the partial hydrolysis and polycondensation reaction of the alkoxide. Chemical formulas 1, 4, and 7 result in thin films containing titanium oxide, chemical formulas 2, 5, and 8 result in thin films containing zirconium oxide, and chemical formulas 3, 6, and 9 result in thin films containing titanium zirconium oxide. The hydroxyl groups in chemical formulas 7 to 9 are generated by reaction with moisture in the air. In particular, a thin film containing titanium zirconium oxide having a bond of Chemical Formula 3, Chemical Formula 6, or Chemical Formula 9 exhibits improved alkali resistance and also improved film formability. The thin film has a nano-sized thickness of approximately 2 to 200 nm and is unlikely to clog the pores of the organic polymer porous membrane. Furthermore, the amount of the thin film deposited is preferably approximately 0.1 to 20 mass% of the total mass of the diaphragm for alkaline water electrolysis.

[0009] Specific examples of titanium alkoxides used to obtain thin films include titanium tetra-normal-butoxide, titanium butoxy dimer, and titanium butoxy oligomer. Specific examples of zirconium alkoxides include zirconium tetra-normal-butoxide. In particular, in the present invention, it is preferable to use a titanium alkoxide and a zirconium alkoxide in combination. For example, the use of titanium butoxy dimer or titanium butoxy oligomer in combination with zirconium tetra-normal-butoxide facilitates the formation of thin films and improves the alkali resistance of the thin films.

[0010] A representative example of the method for producing a thin film for alkaline water electrolysis according to the present invention is as follows: That is, the method comprises immersing or applying a diluted solution in which a solute comprising titanium alkoxide and / or zirconium alkoxide is dissolved in a solvent to an organic polymer porous membrane, and then performing a heat treatment under conditions that do not cause precipitation of the solute.

[0011] Porous organic polymer membranes are generally used while supported on a support. A method for producing a porous organic polymer membrane supported on a support is, for example, as follows: A support such as paper, nonwoven fabric, or woven fabric is prepared. Meanwhile, an organic polymer solution containing a dissolved organic polymer such as a polysulfone-based compound or a polyphenylsulfone-based compound is prepared. The support is then immersed in the organic polymer solution, followed by immersion in water such as warm water to solidify the organic polymer, thereby obtaining a porous organic polymer membrane supported on the support. The organic polymer solution may contain a water-soluble pore-forming agent such as polyethylene glycol. After obtaining the porous organic polymer membrane, the pore-forming agent is extracted with water to obtain a porous organic polymer membrane containing numerous pores.

[0012] Next, a dilute solution is prepared by dissolving a solute consisting of titanium alkoxide and / or zirconium alkoxide in a solvent such as a lower alcohol, such as butanol. The concentration of the dilute solution is preferably 0.1 to 20% by volume. If the concentration of the dilute solution is less than 0.1% by volume, it becomes difficult for a thin film to adhere to the organic polymer porous membrane. Furthermore, if the concentration of the dilute solution exceeds 20% by volume, there is a risk that particles derived from titanium alkoxide and / or zirconium alkoxide will adhere in addition to the thin film, which may clog the pores of the organic polymer porous membrane or cause the particles to fall off during use. A small amount of hydrochloric acid may be added to this dilute solution as a catalyst. Adding a volatile acid can promote polycondensation rather than hydrolysis.

[0013] After immersing or applying the organic polymer porous membrane in the dilution, the membrane is heated under conditions that prevent the precipitation of the solute consisting of titanium alkoxide and / or zirconium alkoxide. To prevent the precipitation of the solute, the immersed or applied dilution should not be brought into contact with water. Contact with water tends to hydrolyze the resulting oxide upon heating, resulting in a particulate state. Heating the dilution without contacting water with the organic polymer porous membrane allows the polycondensation reaction of titanium alkoxide and / or zirconium alkoxide to proceed, resulting in the formation of a thin film of hydroxide and / or oxide. The heat treatment in the present invention is carried out to evaporate the solvent and form a thin film. The heat treatment temperature is preferably 100°C or higher, and more preferably approximately 140°C. The heat treatment time is preferably 5 minutes or longer, and most preferably approximately 1 hour.

[0014] As the titanium alkoxide or zirconium alkoxide, a titanium alkoxide dimer, a titanium alkoxide oligomer, a zirconium alkoxide dimer, or a zirconium alkoxide oligomer can be used. However, since zirconium alkoxide oligomers and titanium zirconium alkoxide oligomers are not readily available as commercial products, an oligomer (including a dimer) can be produced using a titanium alkoxide monomer or a zirconium alkoxide monomer as a raw material, and the diaphragm for alkaline water electrolysis according to the present invention can also be produced. That is, the diaphragm for alkaline water electrolysis according to the present invention can be obtained by a method in which a titanium alkoxide and / or a zirconium alkoxide is dissolved in 2-methoxyethanol or 2-ethoxyethanol to obtain a glycol ether solution, a liquid containing water is added to the glycol ether solution, and the titanium alkoxide and / or the zirconium alkoxide is polycondensed to produce an oligomer selected from the group consisting of a titanium alkoxide oligomer, a zirconium alkoxide oligomer, and a titanium zirconium alkoxide oligomer, and then an organic polymer porous membrane is immersed in or coated with a diluted solution containing the oligomer, followed by heat treatment.

[0015] First, titanium alkoxide and / or zirconium alkoxide are prepared. These are generally prepared as monomers. Then, these are dissolved in 2-methoxyethanol or 2-ethoxyethanol to obtain a glycol ether solution. The reason 2-methoxyethanol or 2-ethoxyethanol is used as the solvent is that their boiling points are below 140°C, allowing them to be evaporated and removed in the final heat treatment. 2-Methoxyethanol, which has a low boiling point, is particularly preferred. A liquid containing water is added to the obtained glycol ether solution. Adding water to the glycol ether solution partially hydrolyzes the titanium alkoxide and / or zirconium alkoxide, causing the polycondensation reaction to proceed. Adding water alone may cause the polycondensation reaction to proceed too quickly, resulting in the formation of macromolecules and precipitation. Therefore, it is preferable to add a mixture of water and a cellosolve. In particular, it is most preferable to add a mixture of water and 2-methoxyethanol or water and 2-ethoxyethanol. By adding such a mixed solution, after the polycondensation reaction has progressed moderately, an oligomer selected from the group consisting of titanium alkoxide oligomers, zirconium alkoxide oligomers, and titanium zirconium alkoxide oligomers can be produced that is stable and exhibits little change over time. When the mixed solution is added to the glycol ether solution, the amount of water in the mixed solution is preferably 0.5 to 1.0 moles relative to the total number of moles of titanium and zirconium in the oligomer in the glycol ether solution. If the amount of water is less than 0.5 moles, it becomes difficult to obtain the oligomer. On the other hand, if the amount of water exceeds 1.0 moles, the polycondensation reaction may proceed too far, resulting in the formation of macromolecules. A diluted solution is obtained using the resulting solution containing the oligomer. Specifically, as described above, the diluted solution is prepared by diluting the solution containing the oligomer with a lower alcohol such as butanol.

[0016] An organic polymer porous membrane is immersed in or coated with this diluted solution, and then heat-treated. This heat treatment promotes a polycondensation reaction of an oligomer selected from the group consisting of titanium alkoxide oligomers, zirconium alkoxide oligomers, and titanium zirconium alkoxide oligomers, resulting in the production of a thin film of hydroxide and / or oxide. This heat treatment is carried out to evaporate small amounts of water and lower alcohols, such as 2-methoxyethanol, to form a thin film. The heat treatment temperature is preferably 100°C or higher, and more specifically, approximately 140°C is most preferred. The heat treatment time is preferably 5 minutes or longer, and more specifically, approximately 1 hour is most preferred.

[0017] The diaphragm for alkaline water electrolysis according to the present invention is installed between the anode and the cathode of an alkaline water electrolysis device to separate them. Hydrogen gas produced using this alkaline water electrolysis device is used as an energy carrier for storing unstable electricity from sources such as solar and wind power generation, and as a fuel or chemical raw material.

[0018] The diaphragm for alkaline water electrolysis according to the present invention has a thin film containing titanium oxide, zirconium oxide, or titanium zirconium oxide attached to an organic polymer porous membrane, and therefore exhibits the advantages of being less likely to clog the pores of the organic polymer porous membrane and less likely to fall off during use, compared to a membrane having oxide particles produced by hydrolysis of titanium alkoxide and / or zirconium alkoxide attached. Furthermore, the thin film attached has higher hydrophilicity and does not inhibit ion permeability.

[0019] [Preparation of Organic Polymer Solution (1)] 17 parts by mass of polysulfone (P-3703NT manufactured by Solvay Specialty Polymers Japan) was added to 83 parts by mass of N-methylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.) with stirring, and the mixture was heated to 80° C. to dissolve the polysulfone. After the polysulfone was dissolved, 1.7 parts by mass of polyethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 20,000) was added and dissolved to prepare an organic polymer solution (1).

[0020] [Preparation of Organic Polymer Solution (2)] Organic polymer solution (2) was prepared in the same manner as for organic polymer solution (1), except that polyphenylsulfone (R-5600NT manufactured by Solvay Specialty Polymers Japan) was used instead of polysulfone.

[0021] [Preparation of Organic Polymer Porous Membrane (1)] A wet-laid nonwoven fabric (PS0060 (basis weight 60 g / m) manufactured by Hirose Paper Co., Ltd.) containing polyphenylene sulfide fibers as constituent fibers was used as a support. 2 )] was used, which was cut into a size of 11 cm x 30 cm, set on a coater plate, and then set in an automatic film applicator (Yasuda Seiki Seisakusho Co., Ltd., No. 542-AB). A No. 2 bar was used. 7 ml of organic polymer solution (1) was dropped onto the film, which was quickly bar-coated, and the film was coagulated by immersion in pure water (70°C). After rinsing with water, the film was dried in an oven at 105°C for 5 minutes to prepare an organic polymer porous membrane (1).

[0022] [Preparation of Organic Polymer Porous Membrane (2)] An organic polymer porous membrane (2) was prepared in the same manner as in the case of the organic polymer porous membrane (1), except that the organic polymer solution (2) was used instead of the organic polymer solution (1).

[0023] Example 1 0.72 ml of titanium tetra-n-butoxide (TA-21, manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 14.1% by mass) was added to 19.28 ml of 1-butanol (special grade reagent, manufactured by Kanto Chemical Co., Ltd.) and stirred to prepare a diluted solution. The diluted solution was transferred to a Petri dish, and an organic polymer porous membrane (2) was immersed in it for 1 minute. The diluted solution on the surface of the organic polymer porous membrane (2) was scraped off with a spatula, and the organic polymer porous membrane (2) impregnated with the diluted solution was placed on a stainless steel wire mesh and subjected to heat treatment in an oven at 140°C for 1 hour to obtain a diaphragm for alkaline water electrolysis.

[0024] A diluted solution was prepared by adding 0.54 ml of titanium butoxide dimer (TA-23 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 17.4% by mass) to 19.46 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 1.

[0025] Example 3 A diluted solution was prepared by adding 3.35 mL of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) to 16.65 mL of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same manner as in Example 1.

[0026] Example 4 A diluted solution was prepared by adding 1.68 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) to 18.32 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 1.

[0027] Example 5 A diluted solution was prepared by adding 0.34 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) to 19.66 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 1.

[0028] Example 6 A diluted solution was prepared by adding 1.73 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 18.27 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was prepared using this diluted solution in the same way as in Example 1.

[0029] Example 7 A diluted solution was prepared by adding 0.87 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 19.13 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 1.

[0030] Example 8 A diluted solution was prepared by adding 0.17 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 19.83 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 1.

[0031] Example 9 A diluted solution was prepared by adding 1.68 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) and 0.87 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 17.45 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was prepared using this diluted solution in the same way as in Example 1.

[0032] Example 10 A diluted solution was prepared by adding 0.84 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) and 0.43 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 18.73 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was prepared using this diluted solution in the same way as in Example 1.

[0033] Example 11 A diluted solution was prepared by adding 0.17 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) and 0.09 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 19.74 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. This diluted solution was used to obtain a diaphragm for alkaline water electrolysis in the same way as in Example 1.

[0034] Example 12 A diluted solution was prepared by adding 0.36 ml of titanium tetra-n-butoxide (TA-21 manufactured by Matsumoto Fine Chemical Co., Ltd., TiTi content 14.1% by mass) and 0.43 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 19.21 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. This diluted solution was used to prepare a diaphragm for alkaline water electrolysis in the same way as in Example 1.

[0035] Example 13 A diluted solution was prepared by adding 0.27 ml of titanium butoxy dimer (TA-23 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 17.4% by mass) and 0.43 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 19.3 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was prepared using this diluted solution in the same way as in Example 1.

[0036] Example 14 0.72 ml of titanium tetra-n-butoxide (TA-21 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 14.1% by mass) was added to 19.28 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirred to prepare a diluted solution. The diluted solution was transferred to a Petri dish, and an organic polymer porous membrane (1) was immersed in it for 1 minute. The diluted solution on the surface of the organic polymer porous membrane (1) was scraped off with a spatula, and the organic polymer porous membrane (1) impregnated with the diluted solution was placed on a stainless steel wire mesh and subjected to heat treatment in an oven at 140°C for 1 hour to obtain a diaphragm for alkaline water electrolysis.

[0037] Example 15 A diluted solution was prepared by adding 0.54 ml of titanium butoxy dimer (TA-23 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 17.4% by mass) to 19.46 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 14.

[0038] Example 16 A diluted solution was prepared by adding 1.68 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) to 18.32 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was obtained using this diluted solution in the same way as in Example 14.

[0039] Example 17 A diluted solution was prepared by adding 0.87 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 19.13 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. This diluted solution was used to produce a diaphragm for alkaline water electrolysis in the same way as in Example 14.

[0040] Example 18 A diluted solution was prepared by adding 0.84 ml of titanium butoxide oligomer (PC-200 manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 6.7% by mass) and 0.43 ml of zirconium tetra-n-butoxide (ZA-65 manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) to 18.73 ml of 1-butanol (special grade reagent manufactured by Kanto Chemical Co., Ltd.) and stirring the mixture. A diaphragm for alkaline water electrolysis was prepared using this diluted solution in the same way as in Example 14.

[0041] Comparative Example 1 The organic polymer porous membrane (1) was used as a diaphragm for alkaline water electrolysis without any modification.

[0042] Comparative Example 2 The organic polymer porous membrane (2) was used as a diaphragm for alkaline water electrolysis as it was.

[0043] Comparative Example 3: A wet-laid nonwoven fabric containing polyphenylene sulfide fiber as a support [PS0060 (basis weight 60 g / m) manufactured by Hirose Paper Co., Ltd.] 2 ) )] was used as a diaphragm for alkaline water electrolysis.

[0044] [Measurement of maximum pore diameter (μm)] The maximum pore diameter of the diaphragms for alkaline water electrolysis obtained in Examples 1 to 18 and Comparative Examples 1 to 3 was measured by the following method. Specifically, a 3 cm square test piece was cut out from each diaphragm for alkaline water electrolysis, immersed in perfluoropolyether (trade name "Galwick" manufactured by Porous Materials, Inc.), and then placed in a measuring device, Perm Porometer CFP-1200-AEXC-P manufactured by Porous Materials, Inc., for measurement. The pore diameter calculated from the pressure at the bubble point was taken as the maximum pore diameter. The results are shown in Table 1.

[0045] [Measurement of Contact Angle (°)] The contact angles of the diaphragms for alkaline water electrolysis obtained in Examples 1 to 18 and Comparative Examples 1 to 3 were measured by the following method. Specifically, test pieces cut into 3 cm squares from each diaphragm for alkaline water electrolysis were immersed in a 25% by mass aqueous potassium hydroxide solution (liquid temperature: 90°C) for 1 hour and then washed with pure water. After washing, the test pieces were dried in an oven at 105°C for 5 minutes and fixed to a glass substrate with double-sided tape. The contact angle was measured by the sessile drop method using a high-performance automatic contact angle meter DSA30 manufactured by KRUSS. Pure water was used as the solvent, and the shape of a 2 μl droplet was fitted by the Young-Laplace method 3 seconds after contact with the liquid to determine the contact angle. In addition, cases where the entire droplet was absorbed within 3 seconds were recorded as "total absorption." The measurement was performed 5 times, and the average value was shown. The results are shown in Table 1.

[0046] [Table 1] ------------------------------------------------- Maximum pore size (μm) Contact angle (°) ------------------------------------------------- Example 1 1.29 44.1 Example 2 1.29 43.4 Example 3 1.33 Total absorption Example 4 1.32 Total absorption Example 5 1.29 53.2 Example 6 1.32 26.5 Example 7 1.32 36.8 Example 8 1.48 50.6 Example 9 1.33 16.6 Example 10 1.53 20.1 Example 11 1.48 27.7 Example 12 0.82 43.8 Example 13 1.61 27.1 Example 14 1.39 36.1 Example 15 1.00 36.1 Example 16 1.55 36.1 Example 17 1.43 37.3 Example 18 1.34 20.0 Comparative Example 1 0.70 82.0 Comparative Example 2 1.40 71.8 Comparative Example 3 1.90 91.0

[0047] As can be seen from the results in Table 1, the diaphragms for alkaline water electrolysis in Examples 1 to 18 have smaller contact angles and improved hydrophilicity compared to the diaphragms for alkaline water electrolysis in Comparative Examples 1 to 3.

[0048] [Preparation of Organic Polymer Solution (3)] 17 parts by mass of polyphenylsulfone (R-5000 manufactured by Solvay Specialty Polymers Japan) was added to 83 parts by mass of N-methylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.) with stirring, and the mixture was heated to 80° C. to dissolve the polyphenylsulfone. After the polyphenylsulfone was dissolved, 3.4 parts by mass of polyvinylpyrrolidone (K-30 manufactured by Nippon Shokubai Co., Ltd.) was added and dissolved to prepare an organic polymer solution (3).

[0049] [Preparation of Organic Polymer Porous Membrane (3)] A wet-laid nonwoven fabric (PS0060 (basis weight 60 g / m) manufactured by Hirose Paper Co., Ltd.) containing polyphenylene sulfide fibers as constituent fibers was used as a support. 2 )] was used, which was cut into a size of 11 cm x 30 cm, set on a coater plate, and then set in an automatic film applicator (Yasuda Seiki Seisakusho Co., Ltd., No. 542-AB). A No. 2 bar was used. 7 ml of organic polymer solution (3) was dropped onto the film, which was quickly bar-coated, and the film was coagulated by immersion in pure water (15°C). After rinsing with water, the film was dried in an oven at 120°C for 5 minutes to prepare an organic polymer porous membrane (3).

[0050] Example 19 In a nitrogen-purged glove bag, 3.54 ml of titanium tetra-normal-butoxide (TA-21, manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 14.1% by mass) and 6.45 ml of 2-methoxyethanol (special grade reagent, manufactured by Kanto Chemical Co., Ltd.) were charged into a glass bottle and stirred to obtain a glycol ether solution. Separately, a mixed solution was obtained by mixing 10 ml of pure water and 90 ml of 2-methoxyethanol. The mixed solution was added to the glycol ether solution with stirring and continued stirring for 1 hour to produce a titanium butoxide oligomer. When producing the titanium butoxide oligomer, the amount of pure water added to the mixed solution was equimolar with the number of moles of titanium in the titanium tetra-normal-butoxide. The obtained solution containing the titanium butoxide oligomer remained clear even after standing for 24 hours. After standing for 24 hours, 10 ml of the solution was diluted with 90 ml of 1-butanol to obtain a diluted solution. The diluted solution was transferred to a petri dish, and the organic polymer porous membrane (3) was immersed in it for 1 minute. The diluted solution on the surface was written off with a spatula, and the membrane was placed on a stainless steel wire mesh and subjected to heat treatment in an oven at 140°C for 1 hour to obtain a diaphragm for alkaline water electrolysis.

[0051] Example 20 In a nitrogen-purged glove bag, 4.60 ml of zirconium butoxide (ZA-65, manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) and 5.40 ml of 2-methoxyethanol (special grade reagent, manufactured by Kanto Chemical Co., Ltd.) were charged into a glass bottle and stirred to obtain a glycol ether solution. Separately, a mixed solution was obtained by mixing 10 ml of pure water and 90 ml of 2-methoxyethanol. The mixed solution was added to the glycol ether solution with stirring and continued stirring for 1 hour to produce a zirconium butoxide oligomer. When producing the zirconium butoxide oligomer, the amount of pure water added to the mixed solution was equimolar with the number of moles of zirconium in the zirconium butoxide. The obtained solution containing the zirconium butoxide oligomer remained clear even after standing for 24 hours. After standing for 24 hours, 10 ml of the solution was diluted with 90 ml of 1-butanol to obtain a diluted solution. The diluted solution was transferred to a petri dish, and the organic polymer porous membrane (3) was immersed in it for 1 minute. The diluted solution on the surface was written off with a spatula, and the membrane was placed on a stainless steel wire mesh and subjected to heat treatment in an oven at 140°C for 1 hour to obtain a diaphragm for alkaline water electrolysis.

[0052] Example 21 In a nitrogen-purged glove bag, 1.77 ml of titanium tetra-n-butoxide (TA-21, manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 14.1% by mass), 2.26 ml of zirconium isopropoxide (ZA-45, manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 21.0% by mass), and 5.97 ml of 2-methoxyethanol (special grade reagent, manufactured by Kanto Chemical Co., Ltd.) were charged into a glass bottle and stirred to obtain a glycol ether solution. Meanwhile, a mixed solution was obtained by mixing 10 ml of pure water and 90 ml of 2-methoxyethanol. The mixed solution was added to the glycol ether solution with stirring, and stirring was continued for 1 hour to produce a titanium zirconium butoxide propoxide oligomer. When producing the titanium zirconium butoxide propoxide oligomer, the amount of pure water added to the mixed solution was equimolar to the total molar amount of titanium in titanium tetra-normal-butoxide and zirconium in zirconium isopropoxide. The obtained solution containing titanium zirconium butoxide propoxide oligomer remained clear even after standing for 24 hours. 10 ml of the solution after standing for 24 hours was diluted with 90 ml of 1-butanol to obtain a diluted solution. The diluted solution was transferred to a petri dish, and an organic polymer porous membrane (3) was immersed in it for 1 minute. The diluted solution on the surface was written out with a spatula, placed on a stainless steel wire mesh, and heat-treated in an oven at 140°C for 1 hour to obtain a diaphragm for alkaline water electrolysis.

[0053] Comparative Example 4 In a nitrogen-purged glove bag, 3.54 ml of titanium tetra-n-butoxide (TA-21, manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 14.0% by mass) and 6.45 ml of isopropyl alcohol (reagent grade 1, manufactured by Kanto Chemical Co., Ltd.) were charged into a glass bottle and stirred to prepare an isopropyl alcohol solution. Separately, a mixed solution was prepared by mixing 10 ml of pure water and 90 ml of isopropyl alcohol. The mixed solution was added to the isopropyl alcohol solution with stirring, and stirring was continued for 1 hour to prepare a titanium butoxide oligomer. During this preparation, the amount of pure water added to the mixed solution was equimolar with the number of moles of titanium in the titanium tetra-n-butoxide. However, the polymerization reaction proceeded, and titanium butoxide oligomer could not be prepared. Titanium oxide particles precipitated, making the solution cloudy, and a solution suitable for obtaining a diaphragm for alkaline water electrolysis having a titanium oxide-containing thin film attached thereto could not be obtained.

[0054] Comparative Example 5 In a nitrogen-purged glove bag, 4.60 mL of zirconium butoxide (ZA-65, manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 20.7% by mass) and 5.40 mL of isopropyl alcohol (Grade 1 Reagent, manufactured by Kanto Chemical Co., Ltd.) were charged into a glass bottle and stirred to prepare an isopropyl alcohol solution. Separately, a mixed solution was prepared by mixing 10 mL of pure water and 90 mL of isopropyl alcohol. The mixed solution was added to the isopropyl alcohol solution with stirring, and stirring was continued for 1 hour to prepare a zirconium butoxide oligomer. During this preparation, the amount of pure water added to the mixed solution was equimolar with the number of moles of zirconium in the zirconium butoxide. However, the polymerization reaction proceeded, and zirconium butoxide oligomer could not be prepared. Instead, zirconium oxide particles precipitated, making the solution cloudy, and a solution for obtaining a diaphragm for alkaline water electrolysis having a thin film containing zirconium oxide attached thereto could not be obtained.

[0055] Comparative Example 6 In a nitrogen-purged glove bag, 3.19 ml of titanium tetra-normal-butoxide (TA-21, manufactured by Matsumoto Fine Chemical Co., Ltd., Ti content 14.1% by mass), 0.45 ml of zirconium isopropoxide (ZA-45, manufactured by Matsumoto Fine Chemical Co., Ltd., Zr content 21.0% by mass), and 6.36 mL of isopropyl alcohol (Reagent Grade 1, manufactured by Kanto Chemical Co., Ltd.) were charged into a glass bottle and stirred to prepare an isopropyl alcohol solution. Meanwhile, a mixed solution was obtained by mixing 10 ml of pure water and 90 ml of isopropyl alcohol. The mixed solution was added to the isopropyl alcohol solution with stirring, and stirring was continued for 1 hour to prepare a titanium zirconium butoxide propoxide oligomer. During this preparation, the amount of pure water added to the mixed solution was equimolar with the total number of moles of titanium in the titanium tetra-normal-butoxide and the number of moles of zirconium in the zirconium isopropoxide. However, the polymerization reaction proceeded, and titanium zirconium butoxide propoxide oligomer could not be produced. Titanium zirconium oxide particles precipitated, making the solution cloudy, and it was not possible to obtain a solution suitable for producing a diaphragm for alkaline water electrolysis having a thin film containing titanium zirconium oxide attached thereto.

[0056] As is clear from a comparison of Examples 19 to 21 and Comparative Examples 4 to 6, when 2-methoxyethanol, a cellosolve, is used, various oligomers can be obtained, but when isopropyl alcohol is used, it is difficult to obtain oligomers.

Claims

1. A diaphragm for alkaline water electrolysis in which a thin film containing titanium oxide, zirconium oxide or titanium zirconium oxide is attached to an organic polymer porous membrane.

2. The diaphragm for alkaline water electrolysis according to claim 1, wherein the thin film is derived from titanium alkoxide and / or zirconium alkoxide.

3. The diaphragm for alkaline water electrolysis according to claim 1, wherein the thin film is attached to at least the inner wall surfaces of the pores of the organic polymer porous membrane.

4. The diaphragm for alkaline water electrolysis according to claim 2, wherein the titanium alkoxide is titanium tetrabutoxide, titanium butoxide dimer or titanium butoxide oligomer, and the zirconium alkoxide is zirconium tetrabutoxide.

5. The diaphragm for alkaline water electrolysis according to claim 4, which has attached thereto thin films derived from both titanium tetra-normal-butoxide, titanium butoxide dimer or titanium butoxide oligomer and zirconium tetrabutoxide.

6. The diaphragm for alkaline water electrolysis according to claim 1, wherein the organic polymer porous membrane is supported on a support having coarser pores than the porous membrane.

7. The diaphragm for alkaline water electrolysis according to claim 6, wherein the support is paper, nonwoven fabric, woven fabric or knitted fabric.

8. The diaphragm for alkaline water electrolysis according to claim 7, wherein the support is made of polyphenylene sulfide fiber.

9. The diaphragm for alkaline water electrolysis according to claim 1, wherein the organic polymer porous membrane is a polysulfone-based porous membrane or a polyphenylsulfone-based porous membrane.

10. An alkaline water electrolysis apparatus comprising an anode, a cathode, and the diaphragm for alkaline water electrolysis according to any one of claims 1 to 9 separating the anode and the cathode.

11. A method for producing a diaphragm for alkaline water electrolysis according to claim 1 or 2, characterized in that the organic polymer porous membrane is immersed in or coated with a diluted solution in which a solute comprising titanium alkoxide and / or zirconium alkoxide is dissolved in a solvent, and then heat treatment is carried out under conditions that do not cause precipitation of the solute.

12. The method for producing a diaphragm for alkaline water electrolysis according to claim 11, wherein the concentration of the diluent is 0.1 to 20% by volume.

13. A method for producing a diaphragm for alkaline water electrolysis according to claim 1 or 2, characterized in that titanium alkoxide and / or zirconium alkoxide are dissolved in 2-methoxyethanol or 2-ethoxyethanol to obtain a glycol ether solution, a liquid containing water is added to the glycol ether solution, and the titanium alkoxide and / or the zirconium alkoxide are polycondensed to produce an oligomer selected from the group consisting of titanium alkoxide oligomers, zirconium alkoxide oligomers, and titanium zirconium alkoxide oligomers, and then an organic polymer porous membrane is immersed in or coated with a diluted solution containing the oligomer, followed by heat treatment.

14. The method for producing a diaphragm for alkaline water electrolysis according to claim 13, wherein the water-containing liquid is a mixture of water and 2-methoxyethanol or a mixture of water and 2-ethoxyethanol.

15. The method for producing a diaphragm for alkaline water electrolysis according to claim 13, wherein the amount of water added to the water-containing liquid is 0.5 to 1.0 mol relative to the total number of moles of titanium or zirconium derived from the titanium alkoxide and / or zirconium alkoxide.

16. The method for producing a diaphragm for alkaline water electrolysis according to claim 13, wherein the titanium alkoxide does not contain a titanium alkoxide dimer or a titanium alkoxide oligomer, and the zirconium alkoxide does not contain a zirconium alkoxide dimer or a zirconium alkoxide oligomer.

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