JP2019065349A - Alkaline water electrolysis diaphragm and production method thereof, and bipolar-type electrolytic bath - Google Patents

Abstract

To provide a large-scale industrial water electrolytic bath for enabling hydrogen production with high efficiency keeping a low cell voltage for a long period of time, in which a diaphragm can be obtained with highly long-term-stable ion conductivity, gas barrier property, and mechanical strength.SOLUTION: An alkaline water electrolysis diaphragm, a production method of the alkaline water electrolysis diaphragm, and a bipolar-type electrolytic bath for alkaline water electrolysis comprise a porous polymer film including at least one kind of polymeric resin fibers and an inorganic compound. The polymeric resin fiber at least comprises a fiber (A) with a fiber diameter ranging from 0.1 μm or more to less than 5.0 μm and a fiber (B) with a fiber diameter between 5.0 μm and 100 μm. The 100 mass% of the polymeric resin fiber includes 20 mass% to 80 mass% of the fiber (A) and 20 mass% to 80 mass% of the fiber (B). The content of the inorganic compound is between 50 mass% and 90 mass% against the total 100 mass% of the fiber (A), the fiber (B), and the inorganic compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a diaphragm for alkaline water electrolysis comprising a polymeric resin fiber and a porous polymer membrane containing an inorganic compound, a method for producing the same, and a bipolar electrolytic cell for alkaline water electrolysis using the same.

  The diaphragm is used in various fields such as concentration, purification, filtration, and dialysis, and development is actively conducted to optimize the material, the pore size, the thickness, and the like. In addition, in recent years, aiming at further performance improvement and specialization of functions for each purpose, in particular, in new energy fields such as fuel cells and renewable energy, and storage batteries such as lithium ion secondary batteries, both safety and performance are compatible. The demand for diaphragms is growing day by day. The development requirements of the diaphragm which can be used especially over a wide temperature, pressure and pH range are very high.

  Hydrogen is widely used industrially, such as petroleum refining, chemically synthesized materials, metal refining, stationary fuel cells and the like. In recent years, the possibility of use in hydrogen stations for fuel cell vehicles (FCVs), smart communities, hydrogen power plants, etc. has also expanded. Furthermore, as the introduction of renewable energy progresses, the need to maintain the balance between supply and demand of the power network has been increased, and the need for hydrogen storage capable of storing a large amount of power for a long time is also increasing. From this point of view, attention has been focused on high purity hydrogen production techniques.

  One of the industrial methods for producing hydrogen is the electrolysis of water. This method has the advantage that hydrogen of high purity can be obtained compared to the method of producing hydrogen for reforming fossil fuels. In the electrolysis of water, it is common to use an aqueous solution to which an electrolyte such as sodium hydroxide or potassium hydroxide is added as an electrolytic solution in order to enhance conductivity. Water is electrolyzed by applying a direct current to the electrolyte with a cathode and an anode.

  An electrolytic cell for performing electrolysis (hereinafter sometimes simply referred to as “electrolysis”) is partitioned into an anode chamber and a cathode chamber via a diaphragm. Oxygen gas is generated in the anode chamber and hydrogen gas is generated in the cathode chamber. The diaphragm is required to have a gas barrier property so that the oxygen gas and the hydrogen gas are not mixed.

  The medium that carries electricity (electrons) in the electrolysis of water is ions. Therefore, in order to perform electrolysis efficiently, high ion permeability is calculated | required by the diaphragm. From this point of view, in Patent Document 1, a diaphragm having a microporous film structure is considered as a diaphragm that exhibits high ion permeability.

  In addition, in order to carry out electrolysis efficiently and stably for a long period of time, physical and chemical stability are required for the anode, the cathode and the diaphragm constituting the electrolytic cell. From this point of view, it is required that the diaphragm be made of a highly durable material and have both gas barrier properties and high ion permeability.

  In addition, polyphenylene sulfide may be used as a substrate or diaphragm material for alkaline water electrolysis as a material having high physical and chemical stability, and in Patent Document 2, plasma is applied to the surface to impart hydrophilicity. Although processing etc. are performed, there is a possibility that the hydrophilic group formed on the surface may be decomposed under high temperature alkaline environment. Moreover, in patent document 3, although plain weave fabric is used in order to give the intensity | strength of a diaphragm, a large area-ization and mass production are difficult.

International Publication No. 2013/183584 JP, 2016-89197, A JP, 2014-152407, A

  Furthermore, as a result of intensive investigations conducted by the present inventor, when using a non-woven fabric forming technology for making a polymer resin fiber of a hardly soluble polymer and applying the polymer resin fiber non-woven fabric as a diaphragm for alkaline water electrolysis, We found a problem that the ion conductivity becomes low due to the fact that it becomes stronger temporally and bubbles are attached. Furthermore, there is a problem that mechanical strength is reduced by extremely thinning fibers, and membrane breakage and pinholes occur during handling and long-term operation.

  A diaphragm for alkaline water electrolysis is required to simultaneously achieve high ion conductivity, high gas barrier property and high mechanical strength, and the form is roughly classified into an ion exchange membrane and a porous membrane. In order to obtain high conductivity, the porous film which can directly use the high conductivity of the electrolyte is excellent, but in order to be compatible with the gas barrier property, the pore diameter of the porous film must be precisely controlled in the submicron size. It does not.

  On the other hand, polymers that can be used in high concentration and high alkali environments where high electrolytic performance can be expected are limited to PTFE and PPS with high hydrolysis resistance, and such poorly soluble polymers control the pores of the porous film It is not easy to do. When using non-woven fabric making technology to make polymer resin fiber of poorly soluble polymer and using polymer resin fiber non-woven fabric as diaphragm for alkaline water electrolysis, hydrophobicity becomes stronger over time and bubbles adhere. The subject which ion conductivity becomes low was discovered. Furthermore, there is a problem that mechanical strength is reduced by extremely thinning fibers, and membrane breakage and pinholes occur during handling and long-term operation.

  The present invention has been made in view of the above problems, and aims to obtain a diaphragm having high ion conductivity and gas barrier properties and mechanical strength stably for a long time, and keeping a low cell voltage for a long time An object of the present invention is to provide a large industrial water electrolytic cell that enables hydrogen production with high efficiency.

  As a result of intensive studies to solve the above problems, the present inventors contain thin polymer resin fibers having a suitable fiber diameter and thick polymer resin fibers in an appropriate ratio, and further contain an inorganic compound. It has been found that the above problems can be solved by incorporating it in an appropriate ratio, and the present invention has been completed.

That is, the present invention is as follows.
[1]
It is composed of a porous polymer membrane containing at least one type of polymer resin fiber and an inorganic compound,
The polymer resin fiber (A) having a fiber diameter of at least 0.1 μm to less than 5 μm, and a polymer resin fiber having a fiber diameter of 5.0 μm to 100 μm (B) 20% by mass to 80% by mass of the polymer resin fiber (A) and 20% by mass to 20% by mass of the polymer resin fiber (B) with respect to 100% by mass of the polymer resin fiber 80% by mass,
The content of the inorganic compound is 50% by mass to 90% by mass with respect to 100% by mass of the total amount of the polymer resin fiber (A) and the polymer resin fiber (B) and the inorganic compound. A diaphragm for alkaline water electrolysis.
[2]
The diaphragm for alkaline water electrolysis of [1], wherein the inorganic compound is a hydrophilic inorganic particle.
[3]
The ratio (Di / Da) of the average fiber diameter (Da) of the polymer resin fiber (A) to the average primary particle diameter (Di) of the hydrophilic inorganic particles is in the range of 0.05 to 3 [ The diaphragm for alkaline water electrolysis as described in 2].
[4]
A diaphragm for alkaline water electrolysis according to any one of [1] to [3], which has a porosity of 30% to 90% and a maximum pore size of 0.2 μm to 2 μm.
The diaphragm for alkaline water electrolysis in any one of [1]-[4] whose said polymeric resin fiber is a polyphenylene sulfide and whose film thickness of the said polymeric porous film is 100 to 500 micrometer.
[6]
[5] The diaphragm for alkaline water electrolysis according to [5], wherein a part of the polymer resin fiber is bound to the polymer resin fiber.
[7]
The diaphragm for alkaline water electrolysis in any one of [1]-[6] in which the said inorganic compound contains a zirconium at least.
[8]
The diaphragm for alkaline water electrolysis in any one of [1]-[7] in which the said polymeric porous membrane further contains a porous support body.
[9]
[8] for alkaline water electrolysis, wherein the porous support is any one selected from the group consisting of a mesh, a non-woven fabric, a woven fabric, and a composite fabric comprising a non-woven fabric and a woven fabric inherent to the non-woven fabric. diaphragm.
[10]
The diaphragm for alkaline water electrolysis as described in [8] or [9] in which the said porous support body contains polyphenylene sulfide.
[11]
Equipped with the alkaline water electrolysis diaphragm according to any one of [1] to [10];
A plurality of bipolar elements including a cathode and an anode are stacked with the alkaline water electrolysis diaphragm interposed therebetween,
A bipolar electrolytic cell for alkaline water electrolysis, wherein the alkaline water electrolysis diaphragm is in contact with the cathode and the anode to form a zero gap structure.
[12]
(A) a step of forming a web by wet papermaking with a fabric weight of 300 to 1000 g / m ² of a slurry containing the polymer resin fiber and the hydrophilic inorganic particles at a volume ratio of 70:30 to 30:70,
(B) a step of drying the web obtained in the step (A) at 60 ° C. to 90 ° C. and then hot pressing it under conditions of 120 ° C. to 260 ° C., 30 MPa to 70 MPa;
The manufacturing method of the diaphragm for alkaline water electrolysis in any one of [1]-[10] including

  By using a thin polymer resin fiber and an inorganic compound for the purpose of controlling the pore diameter of the porous film, it is possible to provide a diaphragm for alkaline water electrolysis in which high ion conductivity and high gas barrier property are compatible, and further, tensile breaking strength By including a thick polymer resin fiber for the purpose of improvement, it is possible to suppress the formation of film breakage and pinholes during long-term operation. According to the present invention, it is possible to provide a large-scale industrial water electrolytic cell that enables hydrogen production with high efficiency while maintaining a low cell voltage for a long time. In addition, it is easy to increase the area, and it can be industrially provided as a diaphragm for a large alkaline water electrolytic cell.

BRIEF DESCRIPTION OF THE DRAWINGS It is a side view shown about the whole of an example of the bipolar | dipolar type electrolytic vessel for alkaline water electrolysis of this embodiment. It is a side view which shows the zero gap structure of an example of the bipolar type electrolytic cell for alkaline water electrolysis of this embodiment about the part of the dashed-lined square frame shown to (A). It is a top view shown about the electrode chamber part of an example of the bipolar electrolytic bath for alkaline water electrolysis of this embodiment. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the outline | summary of an alkaline water electrolysis apparatus provided with an example of the bipolar | dipolar type electrolytic vessel for alkaline water electrolysis of this embodiment. It is a photograph which shows the surface SEM image of the film | membrane produced in Example 7. FIG. The portion surrounded by the solid line in the figure is the portion where the binder fiber is crushed and the fibers are bound, and the portion surrounded by the broken line in the figure is the portion where the fibers are not bound is there.

  Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the invention.

(Separator for alkaline water electrolysis)
(Polymer porous membrane)
The membrane for alkaline water electrolysis of the present embodiment is formed of a porous polymer membrane containing at least one type of polymer resin fiber and an inorganic compound.
The polymer resin fiber comprises a polymer resin fiber (A) having a fiber diameter of at least 0.1 μm to less than 5 μm, and a polymer resin fiber (B) having a fiber diameter of 5.0 μm to 100 μm. It consists of Here, 20% by mass to 80% by mass of the polymer resin fiber (A) and 20% by mass to 80% by mass of the polymer resin fiber (B) with respect to 100% by mass of the polymer resin fiber.
The polymeric porous film contains the inorganic compound in an amount of 50% by mass to 90% by mass based on 100% by mass of the total amount of the polymer resin fiber (A) and the polymer resin fiber (B) and the inorganic compound.

((Polymer resin fiber))
The polymer resin fiber forming the diaphragm for alkaline water electrolysis of the present embodiment is a thick fiber (A) having a thin diameter for controlling pore control and carrying of an inorganic compound, and a thick one for carrying mechanical strength and the fiber (A). The first feature is that the fiber (B) having a diameter is included.
The fiber diameter of the polymer resin fiber (A) is in the range of 0.1 μm to less than 5.0 μm. If it is 0.1 μm or more, high ion permeability can be realized, and the ability to support an inorganic compound described later is high, and hydrophilicity can be easily maintained for a long time. If it is 5.0 μm or less, high gas barrier property can be realized.
On the other hand, the fiber diameter of the fiber (B) is in the range of 5.0 μm to 100 μm. If it is 5.0 μm or more, sufficient mechanical strength can be obtained, and if it is 100 μm or less, high ion permeability can be realized by thinning the porous film, and the fiber (A) The loading capacity is increased, and the porous structure can be maintained for a long time.
Moreover, the content ratio of the polymer resin fiber (A) and the polymer resin fiber (B) is 20% by mass to 80% by mass of the fiber (A) with respect to 100% by mass of the polymer resin fiber, Is preferably 20% by mass to 80% by mass, and 30% by mass to 70% by mass of fiber (A) and 30% by mass to 70% by mass of fiber (B) with respect to 100% by mass of polymer resin fiber More preferably, it is%. If the content ratio is in this range, it is possible to obtain a diaphragm having both ion conductivity, gas barrier properties, and mechanical strength.
The fiber diameter of the polymer resin fiber can be measured using X-ray CT, and is defined as the diameter of a circle giving an area equivalent to the cross-sectional area of the fiber.

The average fiber diameter (Da) of the fiber (A) is preferably in the range of 0.2 μm to 4.0 μm, and if it is 0.2 μm or more, high ion permeability can be realized; If it is 0 μm or less, high gas barrier property can be realized. More preferably, it is in the range of 0.3 μm to 3.0 μm.
On the other hand, the average fiber diameter of the fiber (B) is preferably in the range of 10 μm to 40 μm, and if it is 10 μm or more, sufficient mechanical strength can be obtained, and if it is 40 μm or less, the porous film is thinned. By doing this, high ion permeability can be realized. More preferably, it is in the range of 15 μm to 35 μm.

  As the polymer resin fiber of the present embodiment, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer, which has high hydrolysis resistance Polymer (ECTFE), polyvinylidene fluoride (PVDF) are preferred, and polyphenylene sulfide (PPS) is particularly preferred.

  The average fiber diameter of the polymer resin fiber can be measured using X-ray CT.

(((Binder fiber)))
Some of the polymer resin fibers of the present embodiment may need to be bound to the polymer resin fibers. In order to increase the strength of the polymeric porous film, it is preferable that the polymeric resin fibers be strongly bonded to each other.
However, when the whole is bound, the pores are crushed and the ion conductivity of the porous polymer membrane is lowered. Also, if it is not bound at all, the strength as a diaphragm can not be maintained. When a part is bound, it is possible to form pores while holding the inorganic compound, and it is possible to provide a diaphragm for alkaline water electrolysis in which strength and ion conductivity are well balanced.
As a binder fiber, amorphous PPS fiber is preferable. The binder fiber may be the above-mentioned polymer resin fiber (A) or polymer resin fiber (B), or a mixture thereof.
Usually, the binding properties of porous polymer membranes are achieved by using adhesives such as hot melt type and emulsion type or thermoplastic fibers for bonding, but the method that is resistant to high temperature and high concentration alkaline environment limited. Among them, a method of enhancing binding property by fibrillation of polymer resin fibers, and a method of heat-sealing polymer resin fibers by hot pressing are effective. The most preferable method is a method of containing amorphous PPS fiber and hot pressing. In this case, the temperature of the hot press is preferably 130 ° C. to 260 ° C., and the pressure is preferably 5 MPa to 50 MPa.

(((Sacrifice material)))
By adding fibers serving as a sacrificial material in the paper making process of the present embodiment and forming a film, by selectively removing the sacrificial material, the area where the sacrificial material was present becomes a void, and the porosity is controlled. can do. Preferred materials include soluble polymer resin fibers such as polypropylene, polyethylene, polyvinyl alcohol, polylactic acid, and cellulose, and inorganic fibers such as Si and Al ₂ O ₃ . Cellulose nanofibers (CNF) are particularly desirable from the viewpoint of small fiber diameter, papermaking properties, and removability. The method of removal is not particularly limited as long as it does not adversely affect other constituent materials. Specifically, dissolution, decomposition, melting and the like can be used. For example, when using cellulose as a sacrificial material, it can be removed by hydrolysis with a strong acid or the like.

  The porous polymer membrane forming the diaphragm for alkaline water electrolysis of the present embodiment needs to contain an inorganic compound. In addition, the polymeric porous membrane further comprises a porous support, as necessary.

[Inorganic compounds]
In the present embodiment, the diaphragm must contain an inorganic compound in order to exhibit high electrolyte permeability, high ion permeability and high gas barrier properties. The inorganic compound may be attached to the surface of the membrane, or a part may be buried in the polymer material constituting the porous membrane. In addition, when the inorganic compound is contained in the gap of the diaphragm, it becomes difficult to be detached from the diaphragm, and the performance of the diaphragm can be maintained for a long time.

Examples of inorganic compounds include zirconium, titanium, bismuth, oxides or hydroxides of cerium; oxides of group IV elements in the periodic table; nitrides of group IV elements in the periodic table, and periodic table IV And at least one inorganic substance selected from the group consisting of carbides of group elements. Among these, from the viewpoint of chemical stability, zirconium, titanium, bismuth, oxides of cerium, and oxides of periodic group IV elements are preferable, and zirconium oxide (ZrO ₂ ) and titanium oxide (TiO ₂ ) are preferable. More preferable. These inorganic compounds may be used alone or in combination of two or more. The surface of the inorganic compound is polar. Considering the affinity between the small polar oxygen molecule and hydrogen molecule and the large polar water molecule in the electrolyte solution, which is an aqueous solution, it is considered that the large polar water molecule is more likely to be adsorbed to the inorganic compound. . Therefore, when such an inorganic compound is present on the film surface, water molecules are preferentially adsorbed on the film surface, and bubbles such as oxygen molecules and hydrogen molecules are not adsorbed on the film surface. As a result, adhesion of air bubbles to the surface of the diaphragm can be effectively suppressed.

  The form of the inorganic compound is not particularly limited, but hydrophilic inorganic particles are particularly preferable in that they can uniformly cover the polymer resin fiber.

The average primary particle size (Di) of the hydrophilic inorganic particles is not particularly limited, but is preferably 20.0 nm or more and 300 nm or less, and more preferably 25.0 nm or more and 250 nm or less. When the average primary particle size (Di) of the hydrophilic inorganic particles is in this range, when incorporated into the diaphragm pores, the particle size of secondary particles formed by being aggregated there becomes larger than the pore diameter of the diaphragm, It is possible to prevent the hydrophilic inorganic particles from falling off from the diaphragm. In addition, the surface area of the secondary particles of the hydrophilic inorganic particles can be increased to make the pores of the membrane more hydrophilic. In addition, it is possible to prevent the hydrophilic inorganic particles dropped from the diaphragm from blocking the pores of the porous electrode, and to prevent an increase in overvoltage.
The average primary particle size (Di) of the hydrophilic inorganic particles in the diaphragm can be determined by the following method. The measurement sample was observed from the vertical direction of the film surface with a scanning electron microscope (SEM), and imaged at a magnification at which the hydrophilic inorganic particles can be observed. The image is binarized using image analysis software, the absolute maximum length is measured for each of ten non-aggregated inorganic particles, and the number average is determined.

The average secondary particle size of the hydrophilic inorganic particles is not particularly limited, but is preferably 0.2 μm or more and 10 μm or less from the viewpoints of prevention of detachment from the membrane and of hydrophilization in the porous membrane pores. More preferably, it is 8.0 μm or less. The average secondary particle size is an average particle size in the state of secondary particles formed by the hydrophilic inorganic particles in the diaphragm.
The average secondary particle size can be determined by measuring the average secondary particle size from the volume distribution by laser diffraction / scattering method, using the hydrophilic inorganic particles remaining after dissolving and removing the polymer resin from the diaphragm as a measurement sample. it can. More specifically, it can be determined by the method described in the examples described later.

In the present embodiment, the mass ratio of the inorganic compound to the total amount 100 mass% of the polymer resin fiber (A) and the polymer resin fiber (B) and the inorganic compound contained in the polymer porous film is 50 mass% or more It must be 90% by mass or less.
When the mass ratio of the inorganic compound is 50% by mass or more based on 100% by mass of the total amount of the polymer resin fiber (A) and the polymer resin fiber (B) and the inorganic compound, for example, the hydrophilicity inside the diaphragm also during electrolysis Can be made higher and it is easy to prevent the generated gas from passing through the diaphragm to the opposite electrode chamber. Furthermore, since the electrolyte can penetrate into the diaphragm, the voltage loss of the diaphragm can be kept lower. On the other hand, when the mass ratio of the inorganic compound to the total amount 100 mass% of the polymer resin fiber (A) and the polymer resin fiber (B) and the inorganic compound is 90 mass% or less, the porosity of the diaphragm is higher Easy to control. More preferably, they are 60 mass% or more and less than 80 mass%.
In the present embodiment, the inorganic compound may be attached to the surface of the polymer resin fiber, or a part may be buried in the polymer resin fiber. In addition, when the inorganic compound is contained in the gap of the diaphragm, it becomes difficult to detach from the diaphragm, and the performance of the diaphragm can be maintained for a long time.

[Porous support]
Examples of the porous support which the porous polymer membrane of the present embodiment may contain include a mesh, a non-woven fabric, a woven fabric, a composite fabric including a non-woven fabric and a woven fabric inherent to the non-woven fabric. These may be used alone or in combination of two or more.

  As the porous support in this embodiment, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), chlorotrifluoroethylene-ethylene copolymer, which has high hydrolysis resistance Polymer (ECTFE), polyvinylidene fluoride (PVDF) are preferred, and polyphenylene sulfide (PPS) is particularly preferred.

The polymer resin fibers other than the fibers (A) and the fibers (B) and substances other than the porous polymer membrane are used in the diaphragm in the present embodiment for the purpose of imparting further functions, in a range not inhibiting the function of the diaphragm. It may be included. The diaphragm may contain, for example, additives such as an antioxidant and a heat stabilizer, and the diaphragm may be coated with a fluorine resin or the like.
In particular, the diaphragm for alkaline water electrolysis of the present embodiment is SB from the viewpoint of optimizing the dispersion state of the polymer resin fiber (for example, PPS) and the inorganic compound (for example, ZrO ₂ ) contained in the porous polymer membrane. It is preferred to contain a latex.

In the diaphragm in the present embodiment, the ratio (Di / Da) of the average fiber diameter (Da) of the polymer resin fiber (A) to the primary particle diameter (Di) of the hydrophilic inorganic particles is 0.05 to 3 It is preferably in the range of 0.1 to 2, more preferably in the range of 0.1 to 2, and particularly preferably in the range of 0.2 to 1.
When Di / Da is 0.05 or more, when incorporated into the diaphragm pores, the particle size of the secondary particles formed by being aggregated therein becomes larger than the pore diameter of the diaphragm, and the hydrophilic inorganic particles are Dropping can be suppressed, and by preventing Di / Da to be 3 or less, it is possible to prevent the hydrophilic inorganic particles dropped from the diaphragm from blocking the pores of the porous electrode and to prevent an increase in overvoltage. Can.

(Pore diameter of diaphragm)
In the diaphragm in this embodiment, the pore size must be controlled in order to obtain appropriate membrane properties such as separation ability and strength. Further, in alkaline water electrolysis, it is necessary to control the pore size of the diaphragm from the viewpoint of preventing the mixing of the oxygen gas generated from the anode and the hydrogen gas generated from the cathode and reducing the voltage loss in the electrolysis.

The larger the average pore diameter of the membrane, the better the ion permeability of the membrane and the easier it is to reduce the voltage loss. In addition, the larger the average pore diameter of the membrane, the smaller the contact surface area with the alkaline solution, and thus the deterioration of the polymer tends to be suppressed.
On the other hand, the smaller the average pore diameter of the membrane, the higher the resolution of the membrane, and in electrolysis the gas barrier properties of the membrane tend to be better. Furthermore, in the case where hydrophilic inorganic particles having a small particle size, which will be described later, are supported on a diaphragm, they can be firmly held without being lost. Thereby, high retention ability of hydrophilic inorganic particles can be given, and the effect can be maintained over a long period of time.
Also, the maximum pore size of the diaphragm must be controlled to increase the separation accuracy of the diaphragm. Specifically, the smaller the difference between the average pore size and the maximum pore size, the higher the separation performance tends to be. In particular, in the electrolysis, since the variation in the pore diameter in the diaphragm can be kept small, the possibility of the occurrence of pinholes and the decrease in the purity of the gas generated from both electrode chambers can be reduced.

From such a viewpoint, in the diaphragm of the present invention, the average pore diameter of the diaphragm is preferably 0.1 μm or more and 1.0 μm or less, and the maximum pore diameter is preferably in the range of 0.2 μm or more and 2.0 μm or less.
If the pore size is in this range, it is possible to achieve both excellent gas barrier properties and high ion permeability. In addition, it is preferable that the pore size of the diaphragm be controlled in the temperature range actually used. Therefore, for example, when used as a diaphragm for electrolysis in an environment of 90 ° C., it is necessary to satisfy the above-mentioned range of the pore diameter at 90 ° C.
In addition, the average pore diameter is preferably 0.1 μm or more and 0.5 μm or less, and the maximum pore diameter is 0.5 μm as a range capable of expressing more excellent gas barrier properties and high ion permeability as a diaphragm for alkaline water electrolysis. It is more preferable that the thickness is not less than 1.8 μm.

  The pore diameter of the diaphragm is preferably controlled substantially symmetrically in the thickness direction from the center of the diaphragm to both surfaces. When the pore size distribution of the diaphragm is symmetrical, for example, when the diaphragm is incorporated into the electrolytic cell, the same function can be expressed on either the front or the back, and the handling property is also improved. In addition, foreign substances are less likely to be clogged inside the diaphragm during electrolysis. Furthermore, it is more preferable that the pore diameter of the diaphragm gradually decreases inward in the thickness direction from the surface of the diaphragm. If the pore size gradually decreases toward the inside, high separation ability can be maintained even if, for example, the surface of the diaphragm is damaged by foreign matter during use.

The average pore size and the maximum pore size of the diaphragm can be measured by the following method.
The average pore diameter of the diaphragm means an average water permeation pore diameter measured by the following method using an integrity tester ("Sartocheck Junior BP-Plus" manufactured by Sartorius Japan Ltd.). First, a diaphragm is cut into a predetermined size including a core material, and this is used as a sample. The sample is set in an optional pressure container, and the container is filled with pure water. Next, the pressure resistant container is held in a constant temperature bath set to a predetermined temperature, and the measurement is started after the inside of the pressure resistant container reaches a predetermined temperature. When the measurement starts, the upper surface side of the sample is pressurized with nitrogen, and the numerical value of the pressure and the permeation flow rate when pure water permeates from the lower surface side of the sample is recorded. The average pore size can be determined from the following Hagen-Poiseuille equation, using a pressure between 10 kPa and 30 kPa and a gradient of the hydraulic flow rate.
Average permeability pore size (m) = {32 L L μ ₀ / (εP)} ^0.5
Here, η is the viscosity of water (Pa · s), L is the thickness of the diaphragm (m), μ ₀ is the apparent flow rate, and μ ₀ (m / s) = flow rate (m ³ / s) / flow path area (M ² ). Moreover, (epsilon) is a porosity and P is a pressure (Pa).

The maximum pore size of the diaphragm can be measured by the following method using an integrity tester ("Sartocheck Junior BP-Plus" manufactured by Sartorius Japan). First, a diaphragm is cut into a predetermined size including a core material, and this is used as a sample. The sample is wetted with pure water, the pores of the diaphragm are impregnated with pure water, and this is set in a pressure container for measurement. Next, the pressure resistant container is held in a constant temperature bath set to a predetermined temperature, and the measurement is started after the inside of the pressure resistant container reaches a predetermined temperature. When measurement starts, the upper surface side of the sample is pressurized with nitrogen, and the nitrogen pressure at which bubbles are continuously generated from the lower surface side of the sample is taken as the bubble point pressure. The maximum pore size can be determined from the following bubble point equation obtained by transforming the Young-Laplace equation.
Maximum pore size (m) = 4γ cos θ / P
Here, γ is the surface tension (N / m) of water, cos θ is the contact angle (rad) of the diaphragm surface with water, and P is the bubble point pressure (Pa).

(Porosity of diaphragm)
It is necessary to control the porosity of the diaphragm from the viewpoint of expression of appropriate separation ability and shortening of the life due to clogging. In addition, when the diaphragm is used for electrolysis, from the viewpoint of maintaining the gas barrier property and the hydrophilicity, preventing the decrease in ion permeability due to the adhesion of air bubbles, and further achieving stable electrolytic performance (such as low voltage loss) for a long time. , The porosity of the diaphragm must be controlled. The porosity of the membrane can be said to be related to the proportion of pores having an average pore size and a maximum pore size in the above range in the membrane. The lower limit of the porosity of the diaphragm is preferably 30% or more, preferably 35% or more, in order to express the high function of the diaphragm, in particular the compatibility of the gas barrier property and the low voltage loss in the alkaline water electrolysis diaphragm. Is more preferably 40% or more. In addition, the upper limit of the porosity needs to be 80% or less, and more preferably 70% or less. If the porosity of the membrane is equal to or less than the above upper limit value, the porous structure can be maintained.

Here, the porosity ε of the diaphragm means the open porosity obtained by the Archimedes method, and can be obtained by the following equation.
Porosity ε (%) = (ρ1-ρ2) × 100
ρ 1 represents the saturation density (g / cm ³ ), that is, the density of the sample in a state in which the open pores contain water and become saturated. ρ2 represents the dry density (g / cm ³ ), that is, the density of the sample in a dry state with sufficient removal of water from the open pores. ρ1 and ρ2 measure w: weight (g), d: thickness cm), s: area of surface perpendicular to the thickness direction cm ² ), and 状態 = w / (d × s) Can be determined as
If the water contact surface of the diaphragm sample is low in water absorption, and the thickness and area of the sample do not change significantly between the water-containing state and the dry state, d and s may be regarded as constant values. it can. The porosity ε can be specifically measured in the room set at 25 ° C. according to the following procedure. The diaphragm washed with pure water is cut into three sheets of 3 cm × 3 cm in size, and the thickness d is measured with a thickness gauge. The measurement samples are immersed in pure water for 24 hours, excess water is removed, and the weight w1 (g) is measured. Subsequently, the taken sample is allowed to stand for 12 hours or more in a dryer set at 50 ° C. for drying, and the weight w2 (g) is measured. And porosity is calculated | required from the value of w1, w2, and d. The porosity is determined for three samples, and their arithmetic mean value is taken as the porosity ε of the membrane.

  And, the porosity of the membrane and the degree of opening of the membrane surface are correlated. For example, the higher the porosity, the higher the degree of opening. Also, the higher the degree of opening, the easier it is to receive the effect of the hydrophilic inorganic particles described later, and the higher the tendency to maintain hydrophilicity. For these reasons, it is preferable to control the degree of opening of the diaphragm of this embodiment after controlling the porous structure in the range of the above-mentioned pore diameter. From the viewpoint of maintaining high hydrophilicity, the opening degree needs to be 20% or more, more preferably 25% or more, and still more preferably 30% or more. On the other hand, the opening degree needs to be 80% or less, more preferably 75% or less, and still more preferably 70% or less, in order to maintain the support of the hydrophilic inorganic particles and the strength of the diaphragm surface.

The opening degree of the diaphragm in the present embodiment can be determined by the following method. First, a diaphragm surface image is captured by SEM. Next, this image is binarized with an image analysis software (manufactured by Mitani Corporation, "WinROOF") to separate the hole and the portion other than the hole. Subsequently, the obtained binarized image is analyzed to determine the ratio of holes to the entire image, which is referred to as the opening degree. The opening degree uses the average value of the opening degree acquired from three or more SEM images in which an observation location differs, respectively.

  By forming the diaphragm having the above-described pore diameter and porosity with a polyphenylene copolymer, a diaphragm structure having high mechanical strength and high strength as compared to other polymers can be realized. Furthermore, it has been found that the above-mentioned diaphragm stably exhibits a function over a long time even in a wide temperature, pressure, pH range.

(Thickness of diaphragm)
The thickness of the diaphragm of this embodiment has to be controlled in order to obtain appropriate film physical properties and electrolytic performance. In alkaline water electrolysis, it must be properly controlled to increase the mechanical strength and the electrolysis efficiency of the diaphragm.
From this point of view, the thickness of the diaphragm may have to be 100 μm or more and 500 μm or less. If the thickness of the membrane is 100 μm or more, the membrane is unlikely to be broken, and the strength against impact is further improved. From this viewpoint, the lower limit of the thickness of the diaphragm is more preferably 200 μm or more, and still more preferably 300 μm or more.
On the other hand, when the thickness of the diaphragm is 500 μm or less, thickness unevenness can be reduced at the time of film formation, and the control of the pore diameter can be facilitated. Further, when the diaphragm is used for electrolysis, the ion permeability is hardly inhibited by the resistance of the electrolytic solution contained in the pores, and the more excellent ion permeability can be maintained. From this viewpoint, the upper limit of the thickness of the diaphragm is more preferably 400 μm or less, and still more preferably 350 μm or less.

(Mechanical strength)
The tensile breaking strength of the diaphragm of the present embodiment is preferably 10 MPa or more and 45 MPa or less. If it is a diaphragm which has this tensile breaking strength, the handling property at the time of incorporating in an electrolytic cell will be high, and it will become a diaphragm which a tear and a pinhole do not generate easily. Moreover, it is preferable that the tensile strength at break of the diaphragm is controlled in the temperature range actually used. Therefore, for example, when used as a diaphragm for electrolysis in an environment of 90 ° C., it is necessary to satisfy the above-mentioned range of tensile breaking strength at 90 ° C. The tensile strength at break can be measured by a method according to JIS K 7161.

(Hydrolytic resistance)
In the present embodiment, from the viewpoint of obtaining stable performance for a long time, the diaphragm preferably has high hydrolysis resistance. Since the membrane is always immersed in a high temperature and high concentration alkaline solution during diaphragm electrolysis, the polymer resin fiber may be gradually degraded and become brittle if the hydrolyzability is insufficient. The fragile polymer resin fiber is corroded by the circulating electrolyte and generated gas, and the pores of the porous polymer membrane become large and the porosity also becomes large. As a result, the gas barrier property is reduced, and the gases generated from both electrodes are mixed to easily reduce the gas purity.

(Contact angle)
The water contact angle of the porous membrane is not particularly limited, but can be 10 ° or more and 110 ° or less, preferably 20 ° or more and 100 ° or less, from the viewpoint of gas barrier properties and electrolyte permeability. It is more preferable that the angle is not less than 90 °. When the water contact angle is in this range, the gas generated at the electrode can be prevented from adhering to the electrode surface to inhibit the electrode reaction, and the electrolytic efficiency can be further enhanced.
The water contact angle of the porous membrane can be controlled by controlling the hydrophilicity of a material such as a polymer constituting the surface of the porous membrane. Here, the water contact angle of the porous electrode refers to the tangent and the surface of the porous electrode when water is dropped on the surface of the porous electrode and a tangent line is drawn from the site where the water droplet contacts the porous electrode to the surface of the water droplet. It is the angle that
The water contact angle of the porous electrode can be measured by the θ / 2 method using a commercially available contact angle meter.

(Zero gap structure)
The bipolar electrolytic cell for alkaline water electrolysis according to the present embodiment is not particularly limited, but as shown in FIG. 2, a so-called "zero gap structure" Z is formed in which the diaphragm 4 is in contact with the anode 2a and the cathode 2c. Is preferred. In the “zero gap structure”, the anode and the diaphragm are in contact with each other over the entire surface of the electrode and the cathode and the diaphragm are in contact with each other, or the distance between the electrodes is substantially the same as the thickness of the diaphragm over the entire surface of the electrode The distance between the anode and the diaphragm, and the cathode and the diaphragm can be maintained with almost no gap.
In the alkaline water electrolysis, when there is a gap between the diaphragm and the anode or the cathode, a large amount of gas bubbles generated by the electrolysis stay in this part besides the electrolytic solution, and the electric resistance becomes very high.
On the other hand, when the zero gap structure is formed, the space between the anode and the cathode (hereinafter, also referred to as “inter-electrode distance”) is obtained by quickly releasing the generated gas to the opposite side of the electrode through the pores of the electrode. While reducing, it is possible to suppress the voltage loss due to the electrolytic solution and the generation of gas accumulation near the electrodes as much as possible, and to suppress the electrolytic voltage low.

Several means for forming a zero gap structure have already been proposed, for example, a method of processing the anode and the cathode completely smooth and pressing the membrane so as to sandwich the membrane, a spring or the like between the electrode and the membrane An elastic body is arrange | positioned and the method of supporting an electrode by this elastic body is mentioned.
In the bipolar electrolyzer for alkaline water electrolysis of the present embodiment, a preferred embodiment of the means for forming the zero gap structure will be described later.

(Bipolar electrolysis cell for alkaline water electrolysis)
Hereinafter, an example of the bipolar | dipolar type electrolytic vessel for alkaline water electrolysis of this embodiment provided with the cathode mentioned above, an anode, and a diaphragm is demonstrated, referring a figure.
In addition, the bipolar electrolytic cell for alkaline water electrolysis of this embodiment is not limited to what is demonstrated below. Moreover, members other than an anode, a cathode, and a diaphragm contained in the bipolar | dipolar type electrolytic cell for alkaline water electrolysis are not limited to what is mentioned below either, A well-known thing can be selected suitably, it can be used etc. .

The side view about the whole of an example of the bipolar | dipolar type electrolytic cell for alkaline water electrolysis of this embodiment is shown in FIG.
In FIG. 2, the side view about the part of the dotted square frame which shows the zero gap structure of an example of the bipolar type electrolytic cell for alkaline water electrolysis of this embodiment to (A) is shown.
In FIG. 3, the top view about the electrode chamber part of an example of the bipolar | dipolar type electrolytic vessel for alkaline water electrolysis of this embodiment is shown.
The bipolar electrolytic cell for alkaline water electrolysis according to the present embodiment, as shown in FIG. 1, includes a plurality of electrolytic cells including an anode, a cathode, a partition separating the anode and the cathode, and an outer frame bordering the partition. It is a bipolar electrolytic cell 50 in which 65 is superimposed with a diaphragm interposed therebetween.

In the bipolar electrolytic cell for alkaline water electrolysis of the present embodiment, although not particularly limited, it is preferable that a zero gap structure Z in which the diaphragm 4 is in contact with the anode 2a and the cathode 2c is formed (see FIG. 2).
Further, in the bipolar electrolytic cell according to the present embodiment, an electrode chamber 5 through which the electrolytic solution passes is defined by the partition 1, the outer frame 3 and the diaphragm 4, and the electrode chamber 5 is formed along the partition. A plurality of rectifying plates 6 disposed in parallel to the direction D1 are provided (see FIGS. 2 and 3).

((Bipolar element))
As shown in FIGS. 2 to 3, the bipolar element 60 used in an example of the bipolar electrolytic cell for alkaline water electrolysis has a partition 1 for separating the anode 2a and the cathode 2c, The frame 3 is provided. More specifically, the partition 1 has conductivity, and the outer frame 3 is provided along the outer edge of the partition 1 so as to surround the partition 1.

  In the present embodiment, the bipolar element 60 may be generally used such that a given direction D1 along the partition wall is in the vertical direction. Specifically, as shown in FIG. 2 and FIG. 3, when the plan view shape of the partition wall 1 is rectangular, a given direction D1 along the partition wall is a direction of one of two opposing sides. It may be used in the same direction as (see FIGS. 1 to 3). And in this specification, the above-mentioned perpendicular direction is also called an electrolysis solution passage direction.

In the present embodiment, as shown in FIG. 1, the bipolar electrolyzer 50 is configured by laminating the required number of bipolar elements 60.
In the example shown in FIG. 1, in the bipolar electrolytic cell 50, the fast head 51g, the insulating plate 51i and the anode terminal element 51a are arranged in order from one end, and further, the anode side gasket portion 7, the diaphragm 4 and the cathode side gasket portion 7 and the bipolar elements 60 are arranged in this order. At this time, the bipolar element 60 is disposed so as to direct the cathode 2 c to the anode terminal element 51 a side. The anode side gasket portion 7 to the bipolar element 60 are repeatedly arranged by the number required for the design production amount. After arranging from the anode side gasket part 7 to the bipolar element 60 repeatedly as many times as necessary, again, the anode side gasket part 7, the diaphragm 4 and the cathode side gasket part 7 are arranged side by side, and finally the cathode terminal element 51c, insulation The plate 51i and the loose head 51g are arranged in this order. The bipolar electrolyzer 50 is integrated by tightening the whole with a tie rod 51r (see FIG. 1) or a tightening mechanism such as a hydraulic cylinder system, and becomes the bipolar electrolyzer 50.
The arrangement of the bipolar electrolytic cell 50 can be arbitrarily selected from the anode 2 a side or the cathode 2 c side, and is not limited to the above-described order.

  As shown in FIG. 1, in the bipolar electrolyzer 50, the bipolar element 60 is disposed between the anode terminal element 51a and the cathode terminal element 51c, and the diaphragm 4 is bipolar to the anode terminal element 51a. It is disposed between the elements 60, between adjacently arranged bipolar elements 60, and between the bipolar elements 60 and the cathode terminal element 51c.

  Further, in the bipolar electrolytic cell 50 in the present embodiment, as shown in FIGS. 2 and 3, the partition 1, the outer frame 3, and the diaphragm 4 define an electrode chamber 5 through which the electrolytic solution passes.

  Specifically, the electrode chamber 5 has an electrolyte inlet for introducing the electrolyte into the electrode chamber 5 and an electrolyte outlet for discharging the electrolyte from the electrode chamber 5 at the boundary with the outer frame 3. More specifically, the anode chamber 5a is provided with an anode electrolyte inlet for introducing the electrolyte into the anode chamber 5a and an anode electrolyte outlet for discharging the electrolyte drawn from the anode chamber 5a, and the cathode chamber 5c is provided. A cathode electrolyte inlet for introducing the electrolyte into the cathode chamber 5c and a cathode electrolyte outlet for discharging the electrolyte discharged from the cathode chamber 5c are provided.

  In the example shown in FIGS. 1 to 3, the rectangular partition wall 1 and the rectangular partition wall 4 are arranged in parallel, and the partition wall of the rectangular outer frame 3 provided at the edge of the partition wall 1 Since the inner surface on the 1 side is perpendicular to the partition wall 1, the shape of the electrode chamber 5 is a rectangular parallelepiped.

A header, which is a pipe for distributing or collecting an electrolytic solution, is usually attached to the bipolar electrolytic cell 50, and the electrolytic solution is added to the anode chamber 5 a below the outer frame 3 at the end edge of the partition 1. And an anode inlet header for introducing an electrolyte into the cathode chamber 5c. Similarly, an anode outlet header for discharging the electrode solution from the anode chamber 5a and a cathode outlet header for discharging the electrolyte solution from the cathode chamber 5c are provided above the outer frame 3 at the edge of the partition wall 1 .
As a disposition mode of the header attached to the bipolar electrolytic cell 50 shown in FIGS. 1 to 3, there are representatively an inner header type and an outer header type, but in the present invention, any type is used. It may be adopted and is not particularly limited.

  In the bipolar electrolyzer 50 according to the present embodiment, the electrolyte distributed by the anode inlet header is introduced into the anode chamber 5a through the anode electrolyte inlet, passes through the anode chamber 5a, and the anode electrolyte outlet It is led out from the anode chamber 5a and collected at the anode outlet header.

  And the electrode chamber in this embodiment is provided with the several flow straightening plate 6 arrange | positioned in parallel with respect to the given direction D1 in alignment with the partition 1, as shown to FIG. 2, FIG.

  The rectifying plate 6 reduces the convection generated in the electrode chamber 5 due to the disturbance of the flow of gas and liquid in the electrode chamber 5 and suppresses the local rise in temperature of the electrolytic solution.

  In particular, in the example shown in FIGS. 1 to 3, the plurality of rectifying plates 6 have a constant interval (vertical direction) to a given direction along the partition 1 (in the example shown, the electrolyte passing direction) D1. Provided at a pitch).

In one example of the bipolar battery unit 50, the rectifying plate 6 has a length substantially the same as the height of the electrode chamber 5, is provided perpendicularly to the partition 1, and a given direction D1 along the partition 1 The through holes are formed at a predetermined pitch (in the illustrated example, the electrolytic solution passing direction).
In the present invention, the shape of the electrode chamber 5 is not limited to the rectangular parallelepiped in the example shown in FIGS. 1 to 3, and the plan view shape of the partition 1 or the diaphragm 4 and the inner surface of the outer frame 3 on the partition 2 side Depending on the angle with the partition 2 or the like, the shape may be modified as appropriate, as long as the effects of the present invention can be obtained.

  In the present invention, the arrangement of the rectifying plate 6 in the electrode chamber 5 is not limited to the example shown in FIGS. 1 to 3.

In the present invention, the number of the straightening vanes 6 and the fixed interval (pitch) in the direction perpendicular to the given direction D1 along the dividing wall 1 of the straightening vanes 6 are appropriately determined as long as the effect of the present invention is obtained. Good. Here, the distance between the straightening vanes 6 may not be constant.
Further, in the present invention, the length of the straightening vane 6, the angle between the straightening vane 6 and the dividing wall 1, the number of through holes, and the constant spacing (pitch) in a given direction D1 along the dividing wall 1 of the through holes are As long as the effect of the present invention can be obtained, it may be determined appropriately. Here, the distance between the through holes may not be constant.

  In the example shown in FIGS. 1 to 3, although the partition walls 1, the anodes 2a, and the cathodes 2c are all in the form of a plate having a predetermined thickness, the present invention is not limited thereto and all of the cross sections Alternatively, it may have a zigzag or wavy shape, or it may have a rounded end.

(Zero gap structure)
In the bipolar element 60 in the zero gap type cell, a spring, which is an elastic body, is disposed between the electrode 2 and the partition 1 as a means for reducing the distance between the poles, and the electrode 2 is supported by this spring. Is preferred. For example, in the first example, a spring made of a conductive material may be attached to the partition wall 1 and the electrode 2 may be attached to the spring. In the second example, a spring may be attached to the electrode rib 6 attached to the partition wall 1 and the electrode 2 may be attached to the spring. In the case of employing such an elastic body, the strength of the spring, the number of springs, the shape, etc. may be appropriately adjusted so that the pressure at which the electrode 2 contacts the diaphragm 4 does not become uneven. There is a need to.

  In addition, the rigidity of the other electrode 2 of the pair of electrodes 2 supported via an elastic body is increased (for example, the rigidity of the anode is made stronger than the rigidity of the cathode), so that there is little deformation even when pressed It has a structure. In the case of the electrode 2 supported by the elastic body, the flexible structure that deforms when the diaphragm 4 is pressed absorbs irregularities due to tolerances in manufacturing accuracy of the electrolytic cell 50, deformation of the electrode 2, etc. Then, the zero gap structure Z can be maintained.

  More specifically, the current collector 2r is attached to the tip of the current plate 6 (rib 6), and the conductive elastic body 2e is formed on the upper surface side of the current collector 2r, that is, on the side opposite to the partition 1 side. It is possible to form an at least three-layer structure in which the electrode 2 is attached to the upper surface side, that is, the portion on the diaphragm 4 side adjacent to the conductive elastic body 2e. The current collector 2r and the conductive elastic body 2e constitute an elastic body.

  In the bipolar electrolytic cell 50 for alkaline water electrolysis according to this embodiment, as shown in FIG. 2, the conductive elastic body 2 e and the current collector 2 r are electrically conductive between the cathode 2 c or the anode 2 a and the partition wall 1. The elastic body 2e is provided so as to be sandwiched between the cathode 2c or the anode 2a and the current collector 2r.

(Alkaline water electrolysis system)
An example of the alkaline water electrolysis apparatus which can use the bipolar electrolytic cell for alkaline water electrolysis of this embodiment is shown in FIG.
The alkaline water electrolyzer 70 is added to the bipolar electrolyzer 50 for alkaline water electrolysis of the present embodiment, and in addition to the liquid feed pump 71, the gas-liquid separation tank 72, and the water replenisher 73, a rectifier 74, an oximeter A hydrogen concentration meter 76, a flow meter 77, a pressure gauge 78, a heat exchanger 79, a pressure control valve 80, and the like may be provided.

(Alkaline water electrolysis)
By circulating the electrolytic solution in the alkaline water electrolysis apparatus provided with the bipolar electrolytic cell for alkaline water electrolysis of the present embodiment and performing electrolysis, excellent electrolytic efficiency even in the case of high density current operation and after variable power operation And while maintaining high generated gas purity, highly efficient alkaline water electrolysis can be performed.

As an electrolyte solution which can be used for alkaline water electrolysis of this embodiment, it may be an alkaline aqueous solution in which an alkaline salt is dissolved, and, for example, a NaOH aqueous solution, a KOH aqueous solution and the like can be mentioned.
Although it does not specifically limit as a density | concentration of an alkali salt, 20 mass%-50 mass% are preferable, and 25 mass%-40 mass% are more preferable.
Among them, a 25% by mass to 40% by mass KOH aqueous solution is particularly preferable from the viewpoint of ionic conductivity, dynamic viscosity, and freezing at cold temperature.

The temperature of the electrolytic solution in the electrolytic cell is not particularly limited, but is preferably 80 ° C. to 130 ° C.
Within the above temperature range, deterioration of the members of the electrolytic device such as the gasket and the diaphragm due to heat can be effectively suppressed while maintaining high electrolytic efficiency.
The temperature of the electrolytic solution is more preferably 85 ° C to 125 ° C, and particularly preferably 90 ° C to 115 ° C.

In alkaline water electrolysis of this embodiment that, as the current density applied to the electrolytic cell is not particularly limited, is preferably ^{4kA / m 2 ~20kA / m 2} , a 6kA / m ² ~15kA / m ² Is more preferred.
In particular, in the case of using a variable power supply, it is preferable to set the upper limit of the current density to the above range.

  In the alkaline water electrolysis of this embodiment, the pressure in the electrolysis cell is not particularly limited, but is preferably 3 kPa to 1000 kPa, and more preferably 3 kPa to 300 kPa.

  The flow rate of the electrolyte solution per electrode chamber and other conditions may be appropriately controlled in accordance with each configuration of the bipolar electrolytic layer for alkaline water electrolysis.

  As described above, the bipolar electrolytic cell for alkaline water electrolysis according to the embodiment of the present invention has been described by way of example with reference to the drawings, but the bipolar electrolytic cell for alkaline water electrolysis of the present invention is limited to the above example. The above embodiment can be modified as appropriate.

(Gas barrier evaluation)
Evaluation of the bubble point of a diaphragm is mentioned as one of the evaluation indexes of gas barrier property of the diaphragm of this embodiment. The bubble point in this evaluation method is to fully wet the diaphragm with pure water, fill the pores with pure water, then pressurize one side of the diaphragm with nitrogen, and from the opposite side of the diaphragm at a rate of 150 mL / min. The pressure at which bubbles are continuously generated. The lower the gas barrier property of the diaphragm, the smaller the bubble point value, and the higher the gas barrier property of the diaphragm, the harder the gas can pass through, and the larger the bubble point value.

  The bubble point of the diaphragm is not particularly limited, but is preferably 10 kPa or more. If the bubble point of the diaphragm is 10 kPa or more, since there is no pinhole of 0.2 μm or more, the separation ability of the diaphragm can be secured. In addition, when the diaphragm is used for electrolysis, the generated gas can not easily permeate the diaphragm even when the differential pressure is applied to the cathode chamber and the anode chamber, so the mixing of oxygen and hydrogen can be effectively suppressed. . From this point of view, the bubble point of the diaphragm is more preferably 100 kPa or more.

(Evaluation of ion permeability)
The ion permeability of a diaphragm is mentioned as one of the evaluation indexes of the cell voltage at the time of electrolyzing using the diaphragm for alkaline water electrolysis of this embodiment. If the ion permeability is high, the electrical resistance at the time of electrolysis can be reduced, and accordingly, the voltage loss due to the alkaline water electrolysis diaphragm can also be reduced. In this respect, since the diaphragm for alkaline water electrolysis of the present embodiment can maintain high ion permeability, the cell voltage at the time of electrolysis can be reduced by using this.

The cell voltage at the time of performing electrolysis using the diaphragm for alkaline water electrolysis of this embodiment can be evaluated by the following method, for example. A diaphragm is placed between the nickel electrodes, and the two electrode chambers separated by the diaphragm are filled with a 30% by weight aqueous KOH solution at 90 ° C. A direct current with a current density of 0.60 A / cm ² is applied between both electrodes, and electrolysis is performed for a long time. The potential difference between both electrodes 24 hours after the start of electrolysis is measured, and the potential difference between both electrodes is taken as the cell voltage. Since water in a KOH aqueous solution is consumed by electrolysis during electrolysis, pure water is periodically added so that the KOH concentration becomes constant. Further, the electrolyte in the both electrode chambers is circulated by a pump so that oxygen and hydrogen generated from the electrodes do not stay in the electrolysis cell. When operated under such conditions, the cell voltage in the case of using the diaphragm of this embodiment is not particularly limited, but if a preferable example is mentioned, 1.80 V at a current density of 0.60 A / cm ² The cell voltage can be reduced to 1.75 V or less depending on the operating conditions. If the voltage loss in the diaphragm can be reduced, the water can be efficiently electrolyzed with a small amount of power. Furthermore, even when operating at a high current density for a long time, the risk of overheating the electrolyte in the electrolytic cell due to heat generation due to voltage loss, and the risk of accelerating the deterioration of materials such as the electrolytic cell and electrodes are reduced. be able to.

(Method of manufacturing diaphragm)
The diaphragm for alkaline water electrolysis of this embodiment is not particularly limited, and can be formed by a known method. For example, dry methods such as card type and air laid type, wet methods such as papermaking, spun bond method and melt blow method, etc. may be mentioned. In order to stably exhibit the features of the present invention over a wide area, a papermaking method having two steps described below is preferable.

(Step A) A step of forming a web by wet papermaking with a fabric weight of 300 to 1000 g / m ² of a slurry containing a polymer resin fiber and a hydrophilic inorganic particle at a volume ratio of 70:30 to 30:70.
(Step B) A step of drying the web obtained in Step (A) at 60 ° C. to 90 ° C. and then hot pressing it under the conditions of 120 ° C. to 260 ° C. and 30 to 70 MPa.

  Each step will be described in detail below.

(Step A)
The raw material may be as described in the description of the diaphragm for alkaline water electrolysis of the present embodiment, but for example, PPS fibers having an average fiber diameter of 2 μm, PPS fibers having an average fiber diameter of 20 μm, an average primary particle diameter (Di) 50 nm It is desirable to use the following ZrO ₂ particles, optionally a latex. Binder fibers may be additionally used, and amorphous PPS fibers contained in PPS fibers may be used.

Examples of the latex include natural rubber latex, BR latex, MBR latex, SB latex and the like, and in particular, SB latex is preferable from the viewpoint of adhesiveness and formulation stability.
The latex can adhere the ZrO ₂ particles to the PPS surface, disperse the mixture in water, and form a web on the mesh by a wet papermaking process.
The SB latex added to the mixture is not particularly limited, but is preferably 5 parts by mass or more and 20 parts by mass or less when the total of the mixture is 100 parts by mass. Within this range, the ZrO ₂ particles sufficiently penetrate the PPS surface, and the dispersed state of the mixture becomes good, so that a diaphragm with high homogeneity can be obtained.

  As a binder fiber, the amorphous PPS fiber contained in PPS fiber is preferable.

The volume ratio of the polymer resin fiber to the hydrophilic inorganic particle is preferably 70:30 to 30:70. The polymer resin fiber here may be the above-mentioned polymer resin fiber (A) and the polymer resin fiber (B).
The basis weight is preferably 100 to 700 g / m ² .

(Step B)
The drying temperature is not particularly limited, but is preferably less than the glass transition point of the polymer resin fiber.
The hot press temperature is not particularly limited, but is preferably not less than the glass transition point of the polymer resin and less than the melting point. The hot press pressure is preferably 200 to 280 ° C. When it contains the above-mentioned amorphous PPS, 130-240 ° C is most preferred.

  Hereinafter, the present invention will be described in more detail by way of examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
After heat treating 35 g of cotton-like PPS fiber (manufactured by Asahi Kasei Co., Ltd.) having an average fiber diameter of 2 μm prepared by the meltblown method in an oven at 200 ° C. for 2 hours, it is mixed with 6965 g of distilled water, and is used with a hollanda beater It was beaten for 2 hours to prepare a 0.5 wt% PPS-water suspension.
To 104 g of the above suspension, 425 mg of PPS short fibers (fiber diameter: 20 μm, fiber length: 5 mm, manufactured by KB Salen Co., Ltd.) were added, and 125 mg of SB latex (Asahi Kasei, trade name: L5930) was further added.
Aside from the above mixture, 1420 mg of zirconium oxide ("EP zirconium oxide", average primary particle size (Di): 30 nm, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter referred to as ZrO ₂ ) is added to 200 g of distilled water, and a homogenizer A water-ZrO ₂ dispersion dispersed under the conditions of 25000 rpm and 1 min was prepared by (manufactured by IKA, T25 digital) and added to the above mixed solution to prepare a suspension for papermaking.
Then, the above-mentioned suspension for paper making is charged at a basis weight of 420 g / m ² on the upstream side of a square column type batch type paper machine having an inner cross section of 7 cm × 7 cm, and a polyester fiber sheet with an opening of 50 μm is sandwiched on the downstream side. A non-woven web was produced on a polyester fiber sheet by applying a pressure of 10 kPa in absolute pressure. The produced web is dried in an oven at 90 ° C. for 2 hours, the polyester fiber sheet is removed, and hot pressing is carried out using a batch-type hot press (manufactured by Imoto Machinery Co., Ltd.) at 160 ° C., 40 MPa for 10 minutes. A diaphragm for electrolysis was obtained.
The thickness of the obtained diaphragm was 360 μm, the maximum pore diameter was 1.0 μm, and the porosity was 40%. And the cell voltage at the time of using the obtained diaphragm was 1.85 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 20 MPa. There was no binding of fibers.

Example 2
A membrane for alkaline water electrolysis was prepared in the same manner as in Example 1 except that the amount of 2 μm diameter PPS-water suspension used for the papermaking suspension was changed to 85 g and the amount of 20 μm diameter PPS short fiber to 520 mg. Obtained.
The thickness of the obtained diaphragm was 360 μm, the maximum pore diameter was 1.0 μm, and the porosity was 35%. And the cell voltage at the time of using the obtained diaphragm was 1.90 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 30 MPa. There was no binding of fibers.

[Example 3]
A membrane for alkaline water electrolysis was prepared in the same manner as in Example 1 except that the amount of 2 μm diameter PPS-water suspension used for the papermaking suspension was changed to 126 g and the amount of 20 μm diameter PPS short fiber was changed to 315 mg. Obtained.
The thickness of the obtained diaphragm was 360 μm, the maximum pore diameter was 0.6 μm, and the porosity was 60%. And the cell voltage at the time of using the obtained diaphragm was 1.75 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 15 MPa. There was no binding of fibers.

Example 4
35 g of cotton-like PP fibers with an average fiber diameter of 200 nm prepared by the electrospinning method are mixed with 6965 g of distilled water, beaten for 2 hours with a hollanda beater (made by Toyo Seiki Co., Ltd.) and 0.5 wt% PP-water suspension Made. 312 mg of PPS short fibers (fiber diameter: 20 μm, fiber length: 5 mm, manufactured by KB Salen) were added to 126.6 g of the above suspension, and 125 mg of SB latex (manufactured by Asahi Kasei, trade name: L5930) was further added.
Aside from the above mixture, 1420 mg of zirconium oxide ("EP zirconium oxide", average primary particle size (Di): 30 nm, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter referred to as ZrO ₂ ) is added to 200 g of distilled water, and a homogenizer A water-ZrO ₂ dispersion dispersed under the conditions of 25000 rpm and 1 min was prepared by (manufactured by IKA, T25 digital) and added to the above mixed solution to prepare a suspension for papermaking.
A diaphragm for alkaline water electrolysis was obtained in the same manner as in Example 1 except that the above papermaking solution was used.
The thickness of the obtained diaphragm was 360 μm, the maximum pore diameter was 0.4 μm, and the porosity was 70%. And the cell voltage at the time of using the obtained diaphragm was 1.71 V at current density 0.60 A / cm < ² >, and the tensile strength at break was 8 MPa. There was no binding of fibers.

[Example 5]
After heat-treating 35 g of cotton-like PPS fiber (manufactured by Asahi Kasei Co., Ltd.) having an average fiber diameter of 2 μm prepared by the meltblown method in an oven at 200 ° C. for 2 hours, it is mixed with 6965 g of distilled water, and 2 hours is used with a hollanda beater A refining treatment was carried out to prepare a 0.5 wt% PPS-water suspension. To 102 g of the above suspension, 384 mg of PPS short fiber (fiber diameter: 20 μm, fiber length: 5 mm, manufactured by KB Salen) is added, and 124 mg of SB latex (trade name: L5930, manufactured by Asahi Kasei Co., Ltd.) is further added. 248 mg of cellulose nanofibers with a fiber diameter of 400 nm (manufactured by Asahi Kasei Corp., hereinafter referred to as CNF) were added.
Aside from the above mixture, 1340 mg of zirconium oxide ("EP zirconium oxide", average primary particle size (Di): 30 nm, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter referred to as ZrO ₂ ) is added to 200 g of distilled water, and a homogenizer A water-ZrO ₂ dispersion dispersed under the conditions of 25000 rpm and 1 min was prepared by (manufactured by IKA, T25 digital) and added to the above mixed solution to prepare a suspension for papermaking.
Then, the above-mentioned suspension for paper making is charged at a basis weight of 420 g / m ² on the upstream side of a square column type batch type paper machine having an inner cross section of 7 cm × 7 cm, and a polyester fiber sheet with an opening of 50 μm is sandwiched on the downstream side. A non-woven web was produced on a polyester fiber sheet by applying a pressure of 10 kPa in absolute pressure. The produced web is dried in an oven at 90 ° C. for 2 hours, the polyester fiber sheet is removed, and hot pressing is performed with a batch-type hot press (manufactured by Toyo Seiki Co., Ltd.) at 160 ° C., 40 MPa for 10 minutes. A ZrO ₂ -CNF composite sheet was obtained.
The obtained sheet was immersed in a 90 wt% aqueous H ₂ SO ₄ solution for 24 hours to obtain a diaphragm for alkaline water electrolysis.
The thickness of the obtained diaphragm was 360 μm, the maximum pore diameter was 0.9 μm, and the porosity was 45%. The cell voltage when using the obtained diaphragm was 1.78 V at a current density of 0.60 A / cm ² , and the tensile strength at break was 14 MPa. There was no binding of fibers.

[Example 6]
The same procedure as in Example 5 was followed except that the amount of 2 μm diameter PPS-water suspension used in the papermaking suspension was changed to 89.4 g, the amount of 20 μm diameter PPS short fibers to 447 mg, and the amount of CNF to 396 mg. A diaphragm for alkaline water electrolysis was obtained by the method.
The thickness of the obtained diaphragm was 350 μm, the maximum pore diameter was 1.1 μm, and the porosity was 40%. The cell voltage when using the obtained diaphragm was 1.79 V at a current density of 0.60 A / cm ² , and the tensile strength at break was 13 MPa. There was no binding of fibers.

[Example 7]
35 g of cotton-like PPS fiber (manufactured by Asahi Kasei Co., Ltd.) having an average fiber diameter of 2 μm prepared by the meltblown method is mixed with 6965 g of distilled water, and beaten for 2 hours with a hollanda beater (manufactured by Toyo Seiki Co., Ltd.) A water suspension was made.
174 mg of PPS cut fiber (average fiber diameter: 4 μm, fiber length: 3 mm, manufactured by KB Salen) is added to 18.4 g of the above suspension, and PPS short fiber (average fiber diameter: 20 μm, fiber length: 5 mm) , 174 mg of KB Salen, 43 mg of amorphous PPS fibers (average fiber diameter: 25 μm, fiber length: 5 μm, KB Salen), and 75 mg of CNF with an average fiber diameter of 400 nm. did.
Aside from the above mixture, 1310 mg of zirconium oxide ("EP zirconium oxide", average primary particle diameter (Di): 30 nm, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter referred to as ZrO ₂ ) is added to 200 g of distilled water, and a homogenizer A water-ZrO ₂ dispersion dispersed under the conditions of 25000 rpm and 1 min was prepared by (manufactured by IKA, T25 digital) and added to the above mixed solution to prepare a suspension for papermaking.
Then, the above-mentioned suspension for paper making is charged at a basis weight of 420 g / m ² on the upstream side of a square column type batch type paper machine having an inner cross section of 7 cm × 7 cm, and a polyester fiber sheet with an opening of 50 μm is sandwiched on the downstream side. A non-woven web was produced on a polyester fiber sheet by applying a pressure of 10 kPa in absolute pressure. The produced web is dried in an oven at 90 ° C. for 2 hours, the polyester fiber sheet is removed, and hot pressing is performed with a batch-type hot press (manufactured by Toyo Seiki Co., Ltd.) under conditions of 240 ° C., 15 MPa for 10 minutes. A ZrO ₂ -CNF composite sheet was obtained.
The obtained sheet is immersed in a 90 wt% aqueous solution of H ₂ SO ₄ for 24 hr, dried in an oven at 90 ° C. for 2 hr, and then hot pressed under conditions of 240 ° C., 5 MPa for 10 minutes using a batch hot press. , A diaphragm for alkaline water electrolysis was obtained.
The thickness of the obtained diaphragm was 350 μm, the maximum pore diameter was 1.0 μm, and the porosity was 40%. And the cell voltage at the time of using the obtained diaphragm was 1.80 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 27 Mpa. According to SEM observation, a part of fibers were bound, and in the binding evaluation of the whole film by ultrasonic cleaning, it was binding.

[Example 8]
Thirty-five grams of cotton-like PTFE fibers with an average fiber diameter of 2 μm prepared by the electrospinning method are mixed with 6950 g of IPA, beaten for 2 hours with a hollanda beater (made by Toyo Seiki), and 0.5 wt% PTFE-IPA suspension is obtained Made. In addition, 35 g of cotton-like PPS fibers with an average fiber diameter of 2 μm prepared by the meltblown method is mixed with 6965 g of distilled water, beaten with a hollanda beater (made by Toyo Seiki Co., Ltd.) for 2 hours and 0.5 wt% PPS-water suspension Was produced.
34.8 g of the above PTFE-IPA suspension and 18.4 g of the above PPS-water suspension were mixed, and 174 mg of PPS cut fiber (average fiber diameter: 4 μm, fiber length: 3 mm, manufactured by KB Salen) was added. Further, 174 mg of PPS short fiber (average fiber diameter: 20 μm, fiber length: 5 mm, manufactured by KB Salen) is added, and amorphous PPS fiber (average fiber diameter: 25 μm, fiber length: 5 μm, KB Salen) 43 mg was added, and further 75 mg of CNF having an average fiber diameter of 400 nm was added. Aside from the above mixed solution, 1310 mg of zirconium oxide ("EP zirconium oxide", manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter described as ZrO2) is added to 200 g of distilled water, and 25000 rpm with a homogenizer (manufactured by IKA, T25 digital) A water-ZrO ₂ dispersion dispersed under the conditions of 1 min was prepared and added to the above mixed solution to prepare a suspension for papermaking.
Then, the above-mentioned suspension for paper making is charged at a basis weight of 420 g / m ² on the upstream side of a square column type batch type paper machine having an inner cross section of 7 cm × 7 cm, and a polyester fiber sheet with an opening of 50 μm is sandwiched on the downstream side. A non-woven web was produced on a polyester fiber sheet by applying a pressure of 10 kPa in absolute pressure. The produced web is dried in an oven at 90 ° C. for 2 hours, the polyester fiber sheet is removed, and hot pressing is performed with a batch-type hot press (manufactured by Toyo Seiki Co., Ltd.) under conditions of 240 ° C., 15 MPa for 10 minutes. A ZrO ₂ -CNF composite sheet was obtained.
The obtained sheet is immersed in a 90 wt% aqueous solution of H ₂ SO ₄ for 24 hr, dried in an oven at 90 ° C. for 2 hr, and then hot pressed under conditions of 240 ° C., 5 MPa for 10 minutes using a batch hot press. , A diaphragm for alkaline water electrolysis was obtained.
The obtained diaphragm had a thickness of 350 μm, a maximum pore diameter of 1.2 μm, and a porosity of 43%. And the cell voltage at the time of using the obtained diaphragm was 1.82 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 13 MPa. According to SEM observation, a part of fibers were bound, and in the binding evaluation of the whole film by ultrasonic cleaning, it was binding.

Comparative Example 1
A membrane for alkaline water electrolysis was prepared in the same manner as in Example 1 except that the amount of 2 μm diameter PPS-water suspension used in the papermaking suspension was changed to 21 g and the amount of 20 μm diameter PPS short fiber was changed to 841 mg. Obtained.
The thickness of the obtained diaphragm was 360 μm, the maximum pore diameter was 10.0 μm, and the porosity was 40%. And the cell voltage at the time of using the obtained diaphragm was 2.20 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 41 MPa. There was no binding between fibers

Comparative Example 2
A membrane for alkaline water electrolysis was prepared in the same manner as in Example 1 except that the amount of 2 μm diameter PPS-water suspension used for the papermaking suspension was changed to 174 g and the amount of 20 μm diameter PPS short fiber was changed to 76 mg. Obtained.
The thickness of the obtained diaphragm was 370 μm, the maximum pore diameter was 0.3 μm, and the porosity was 80%. And the cell voltage at the time of using the obtained diaphragm was 1.70 V at current density 0.60 A / cm < ² >, and the tensile strength at break was 3 MPa. There was no binding between fibers

Comparative Example 3
The amount of 2 μm diameter PPS-water suspension used for the papermaking suspension is 168 g, the amount of 20 μm diameter PPS short fiber is 632 mg, the amount of ZrO ₂ is 368 mg, and the amount of SB latex is 204 mg In the same manner as in Example 1, a diaphragm for alkaline water electrolysis was obtained.
The thickness of the obtained diaphragm was 370 μm, the maximum pore diameter was 15.0 μm, and the porosity was 10%. The cell voltage when using the obtained diaphragm was 2.50 V at a current density of 0.60 A / cm ² , and the tensile strength at break was 17 MPa. There was no binding between fibers

Comparative Example 4
Example 1 was repeated except that the amount of 2 μm diameter PPS-water suspension used in the papermaking suspension was 185 g, the amount of 20 μm diameter PPS short fiber was 19 mg, and the amount of ZrO ₂ was 18.0 g. A diaphragm for alkaline water electrolysis was obtained by the method.
The thickness of the obtained diaphragm was 340 μm, the maximum pore diameter was 1.0 μm, and the porosity was 40%. And the cell voltage at the time of using the obtained diaphragm was 1.80 V at current density 0.60 A / cm < ² >, and tensile breaking strength was 2 MPa. There was no binding between fibers

[Method of measuring and evaluating physical properties]
Hereinafter, a method of measuring and evaluating physical properties of the diaphragm will be described.

<Maximum pore size>
The maximum pore size of the diaphragm was measured by the following method using an integrity tester ("Sartocheck Junior BP-Plus" manufactured by Sartorius Japan Ltd.). First, the diaphragm, including the core material, was cut into a predetermined size and used as a sample. The sample was wetted with pure water, the pores of the membrane were impregnated with pure water, and this was set in a pressure container for measurement. Next, the pressure resistant container was held in a constant temperature bath set to a predetermined temperature, and the measurement was started after the inside of the pressure resistant container reached a predetermined temperature. When measurement starts, the upper surface side of the sample is pressurized with nitrogen, and the nitrogen pressure at which bubbles are continuously generated at a rate of 150 mL / min from the lower surface side of the sample is taken as the bubble point pressure. The maximum pore size was determined from the following bubble point equation obtained by transforming the Young-Laplace equation.
Maximum pore size (m) = 4γ cos θ / P
Here, γ is the surface tension (N / m) of water, cos θ is the contact angle (rad) between the diaphragm surface and water, and P is the bubble point pressure (Pa).

<Average Primary Particle Size of Hydrophilic Inorganic Particles>
The measurement of the average primary particle size of the hydrophilic inorganic particles of the diaphragm was performed using a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, “MiniscopeTM 3000”). First, the diaphragm, including the core material, was cut into a predetermined size and used as a sample. This sample was metal-coated for 1 minute using a magnetron sputtering apparatus (manufactured by Vacuum Device, “MSP-1S type”). Next, this sample was set on the observation sample stand of the SEM to start measurement. At this time, a diaphragm as a measurement sample was set so that observation by SEM could be performed from the vertical direction of the film surface to be measured. The measurement was started, the magnification was adjusted (preferably 20,000 times or more is preferable) so that the inorganic particles to be observed could be seen, and the imaged screen was stored as an image. The obtained image is binarized using image analysis software (manufactured by Mitani, "WinROOF"), the absolute maximum length is measured for each of 10 non-aggregated inorganic particles, and the number average is calculated. Calculated. This average was taken as the primary particle size of the hydrophilic inorganic particles.

<Porosity>
The porosity of the diaphragm was measured in a room kept at 25 ° C. using an electronic balance.
The diaphragm was cut into 3 pieces of 3 cm × 3 cm (9 cm ² ) to obtain a measurement sample, and the thickness d (cm) was measured with a thickness gauge. Next, the measurement sample was immersed in pure water for 24 hours to remove excess water, and the weight w1 (g) was measured. Subsequently, they were allowed to stand for 12 hours or more in a drier set at 50 ° C. for drying, and the weight w2 (g) was measured.
The diaphragm to be measured had a very low water absorption property on the water contact surface, and the thickness and the area of the measurement sample did not change significantly between the water-containing state and the dry state. Therefore, the thickness d and the area were regarded as constant values, and the porosity was determined from the values of w1 and w2 by the following equation.
Porosity (%) = {(w1-w2) / (d × 9)} × 100
The porosity was determined for each of the three measurement samples, and the arithmetic mean value of them was used as the porosity ε of the membrane.

<Attachability of fiber>
The binding property of the polymer resin fiber was evaluated by examining the presence or absence of fiber detachment by SEM observation and ultrasonic cleaning.
In addition, the integrity of the film as a whole was evaluated by ultrasonic cleaning.
The diaphragm is cut into 3 pieces of 3 cm × 3 cm (9 cm ² ) and used as a measurement sample, and placed in an ultrasonic cleaner (Branson, Model: 1800) containing 1.5 L of distilled water, and a frequency of 40 kHz The sample is taken out after a cavitation test which performs ultrasonic cleaning treatment of sound pressure 190 Pa, 190 db for 10 minutes, and the content of the polymer resin fiber contained in the liquid is 1 mass of the polymer resin fiber contained in the sample before the cavitation test When it was less than%, it was determined that binding was present, and when it was 1% by mass or more, it was judged that binding was not present.
As an example, FIG. 5 shows a surface SEM image of the film produced in Example 7. The part surrounded by the solid line in FIG. 5 is the part where the binder fiber is crushed and the fibers are bound, and the part surrounded by the dotted line in FIG. It is a place.
Based on this index, when all is in a state enclosed by a solid line is "general binding" and when it is in a state partially enclosed by a solid line "partial binding" The case where it was all surrounded by a dotted line was judged as "no binding".

<Tension breaking stress>
It measured by the method according to JISK7161 in the atmosphere of temperature 23 degreeC and humidity 65% RH. Test pieces were cut into a width of 10 mm and a length of 100 mm along the longitudinal direction and the lateral direction of the alkaline water electrolysis diaphragm, respectively. Using “Autograph AGS-1kNX” (manufactured by Shimadzu Corporation), a tensile test is performed on the test piece under conditions of 50 mm chuck length and 100 mm / min tensile speed, and measurement is performed 5 times each in the longitudinal and transverse directions The arithmetic mean of the values was taken as the measured value of tensile strength at break (MPa). It evaluated by the following evaluation criteria.
[Evaluation criteria]
:: The average of the tensile breaking strength in the longitudinal direction and the transverse direction is more than 25 MPa ○: The average of the tensile breaking strength in the longitudinal direction and the transverse direction is more than 10 MPa and 25 MPa or less Δ: The average of the tensile breaking strength in the longitudinal direction and the transverse direction is more than 5 MPa 10 MPa or less ×: Average of tensile rupture strength in the longitudinal direction and transverse direction is 5 MPa or less

[Electrolysis test]
Using the diaphragms of the example and the comparative example, alkaline water electrolysis was performed by continuously applying electricity for 2500 hours under a high current density of 10 kA / m ² .
After 2500 hours, the average value of the pair voltage of four electrolytic cells was calculated for each example and comparative example, and evaluated as the cell voltage (V).

  Hereinafter, the used bipolar electrolytic cell and the electrolytic system will be described.

[Bipolar electrolysis cell]
An electrolyzer having a bipolar zero gap structure as shown in FIG. 1 composed of an anode terminal element, a cathode terminal element, and four bipolar elements was produced. The diaphragms of the respective examples and comparative examples are incorporated in each electrolytic cell.
As the electrodes, Ni expanded metal was used for both the anode and the cathode.
The header pipe of the electrolytic cell was an external header type.

<Gasket>
The gasket is a square with a 4.0 mm thickness and an inner dimension of 60 mm × 50 mm,
The one having a slit structure for holding by inserting the diaphragm inside was used. In the slit structure, a 0.4 mm gap is provided in the width direction 6 mm inside the gasket in order to accommodate the edge of the diaphragm. The gasket was made of fluorine-based rubber and had an elastic modulus of 4.0 MPa at 100% deformation.

<Conductive elastic body>
The conductive elastic body has a wave height of 5 m, which is a woven nickel wire with a wire diameter of 0.15 mm.
It used what was wave-processed so that it might become m. The thickness was 5 mm, the repulsive force at 50% compression deformation was 150 g / cm ² , and the number of meshes was about 5 mesh.

<Bipolar element>
The bipolar element was a 90 mm × 70 mm rectangle, and the area of the anode and the cathode was 58 mm × 48 mm. The depth of the anode chamber (anode chamber depth) was 10 mm, the depth of the cathode chamber (cathode chamber depth) 10 mm, and the material was nickel. The thickness of the nickel partition wall to which 11 mm high and 1.5 mm thick anode rib and 11 mm high and 1.5 mm thick cathode rib attached by welding was 2 mm.

  A nickel expanded metal having a thickness of 1 mm, an opening length of 4.5 mm, and a longitudinal length of 3.2 mm was used as a current collection pair. The conductive elastic body described above was fixed by spot welding on the current collector. The zero gap bipolar element was stacked through a 60 mm × 50 mm diaphragm to form a zero gap structure in which the cathode and the anode were pressed against the diaphragm.

[Electrolysis system]
The above-mentioned bipolar electrolytic cell was incorporated into the electrolytic device 70 shown in FIG. 4 and used for alkaline water electrolysis.
Hereinafter, the outline of the electrolysis system will be described with reference to FIG.
In the gas-liquid separation tank 72 and the external header type bipolar electrolytic cell 50, a 30% KOH aqueous solution is enclosed as an electrolytic solution. The electrolytic solution is supplied between the anode chamber and the anode gas-liquid separation tank (oxygen separation tank 72o) by the liquid feed pump 71, and between the cathode chamber and the cathode gas-liquid separation tank (hydrogen separation tank 72h). It is circulating. The flow rate of the electrolytic solution was adjusted to 10 L / min as measured by the flow meter 77, and the temperature was adjusted to 120 ° C. by the heat exchanger 79. As the electrolyte solution contact portion of the circulation flow passage, a 20A piping was used, in which the SGP carbon steel piping was subjected to Teflon (registered trademark) lining inner surface processing.
The gas-liquid separation tank 72 (72 h and 72 o) used had a height of 500 mm and a volume of 0.02 m ³ . The amount of liquid in each of the gas-liquid separation tanks 72h and 72o was about 50% of the design volume. Electricity was supplied from the rectifier 74 to the cathode and the anode of each electrolysis cell at a predetermined electrode density.
The pressure in the cell after the start of energization was measured by the pressure gauge 78, and adjusted so that the pressure on the cathode side was 301 kPa and the pressure on the oxygen side was 300 kPa. Pressure adjustment was performed by installing a pressure control valve 80 downstream of the pressure gauge 78.

As the rectifier 74, KCA2F7-15-2500CL manufactured by Sansha Electric Mfg. Co., Ltd. was used.
As the oximeter 75, GPR-2500 manufactured by Advanced Instruments was used.
As the hydrogen concentration meter 76, SD-D58 · AC manufactured by Riken Keiki Co., Ltd. was used.
As the pressure gauge 78, EJA-118W manufactured by Yokogawa Electric Corporation was used.
As the flow meter 77, the heat exchanger 79, the liquid feed pump 71, the gas-liquid separation tanks 72 (72 h and 72 o), the water supplier 73 and the like, those commonly used in the relevant technical field were used.

  According to the present invention, it is possible to provide a diaphragm for alkaline water electrolysis in which high ion conductivity and high gas barrier property are compatible by the thin polymer resin fiber and the inorganic compound for the purpose of controlling the pore diameter of the porous film. Furthermore, thick polymer resin fibers for the purpose of improving the tensile strength at break can be contained to suppress film breakage and formation of pinholes during long-term operation. According to the present invention, it is possible to provide a large-scale industrial water electrolytic cell that enables hydrogen production with high efficiency while maintaining a low cell voltage for a long time. According to the present invention, it is easy to increase the area of a diaphragm for an alkaline water electrolytic cell, and a large diaphragm can be industrially provided.

Reference Signs List 1 partition 2 electrode 2a anode 2c cathode 2e conductive elastic body 2r current collector 3 outer frame 4 diaphragm 5 electrode chamber 5a anode chamber 5c cathode chamber 6 rectifying plate (rib)
DESCRIPTION OF SYMBOLS 7 gasket 50 bipolar type electrolytic cell 51g fast head, loose head 51i insulating plate 51a anode terminal element 51c cathode terminal element 51r tie rod 60 bipolar type element 65 electrolysis cell 70 electrolysis apparatus 71 liquid feed pump 72 gas liquid separation tank 72h hydrogen separation Tank 72o Oxygen separation tank 73 Water supply device 74 Flow regulator 75 Oximeter 76 Hydrogen concentration meter 77 Flow meter 78 Pressure gauge 79 Heat exchanger 80 Pressure control valve D1 Given direction along the partition (direction of electrolyte passage)
Z zero gap structure

Claims (12)

It is composed of a porous polymer membrane containing at least one type of polymer resin fiber and an inorganic compound,
The polymer resin fiber has a polymer resin fiber (A) having a fiber diameter of at least 0.1 μm to less than 5.0 μm, and a polymer resin fiber having a fiber diameter of 5.0 μm to 100 μm. 20% by mass to 80% by mass of the polymer resin fiber (A) and 20% by mass of the polymer resin fiber (B) with respect to 100% by mass of the polymer resin fiber % To 80% by mass,
The content of the inorganic compound is 50% by mass to 90% by mass with respect to 100% by mass of the total amount of the polymer resin fiber (A) and the polymer resin fiber (B) and the inorganic compound. A diaphragm for alkaline water electrolysis.   The diaphragm for alkaline water electrolysis according to claim 1, wherein the inorganic compound is a hydrophilic inorganic particle.   The ratio (Di / Da) of the average fiber diameter (Da) of the polymer resin fiber (A) to the average primary particle diameter (Di) of the hydrophilic inorganic particles is in the range of 0.05 to 3 The diaphragm for alkaline water electrolysis as described in claim 2.   The diaphragm for alkaline water electrolysis according to any one of claims 1 to 3, wherein the porosity is 30% or more and 90% or less and the maximum pore diameter is 0.2 μm or more and 2.0 μm or less.   The diaphragm for alkaline water electrolysis as described in any one of Claims 1-4 whose said polymeric resin fiber is a polyphenylene sulfide and the film thickness of the said polymeric porous film is 100 micrometers or more and 500 micrometers or less.   The diaphragm for alkaline water electrolysis according to claim 5, wherein a part of the polymer resin fiber is bound to the polymer resin fiber.   The diaphragm for alkaline water electrolysis according to any one of claims 1 to 6, wherein the inorganic compound contains at least zirconium.   The diaphragm for alkaline water electrolysis as described in any one of Claims 1-7 in which the said polymeric porous membrane further contains a porous support body.   The alkaline water according to claim 8, wherein the porous support is any one selected from the group consisting of a mesh, a non-woven fabric, a woven fabric, and a composite fabric comprising a non-woven fabric and a woven fabric inherent to the non-woven fabric. Membrane for electrolysis.   The diaphragm for alkaline water electrolysis according to claim 8 or 9, wherein the porous support contains polyphenylene sulfide. The diaphragm for alkaline water electrolysis according to any one of claims 1 to 10, comprising:
A plurality of bipolar elements including a cathode and an anode are stacked with the alkaline water electrolysis diaphragm interposed therebetween,
A bipolar electrolytic cell for alkaline water electrolysis, wherein the alkaline water electrolysis diaphragm is in contact with the cathode and the anode to form a zero gap structure. (A) a step of forming a web by wet papermaking with a fabric weight of 300 to 1000 g / m ² of a slurry containing the polymer resin fiber and the hydrophilic inorganic particles at a volume ratio of 70:30 to 30:70,
(B) a step of drying the web obtained in the step (A) at 60 ° C. to 90 ° C. and then hot pressing it under conditions of 120 ° C. to 260 ° C., 30 MPa to 70 MPa;
The manufacturing method of the diaphragm for alkaline water electrolysis as described in any one of Claims 1-10 which contains these.