JP6928716B2 - Cation exchange membrane, multilayer structure membrane, and electrolytic cell - Google Patents

Description

The present invention relates to a cation exchange membrane, a multilayer structure membrane, and an electrolytic cell.

Examples of various electrochemical devices using an ion exchange membrane as an electrolyte include an alkali metal salt electrolytic cell, a water electrolytic cell, a hydrochloric acid electrolytic cell, and a fuel cell. Among them, one that has matured as an industrial process and is widely used is electrolysis using an alkali metal salt electrolytic cell. Conventionally, an industrial method for producing a halogen gas such as chlorine, a caustic alkali and hydrogen by electrolyzing an aqueous solution of an alkali metal salt, particularly sodium chloride or potassium chloride, is well known. Among them, the ion exchange membrane electrolysis technology using an ion exchange membrane as a diaphragm has been industrialized worldwide as the most advantageous process for reducing power consumption and energy saving.

The following Patent Documents 1 and 2 disclose fluorinated ion exchange polymers containing a pendant side chain as either of the ionic sulfonyl and ionic carboxyl forms.

Special Publication No. 62-3164 Special Publication No. 63-56257

However, even in the above-mentioned ion exchange membrane electrolysis technique, further reduction of power consumption is currently required. In the ion exchange membrane method, the ion exchange membrane, which is a diaphragm, occupies a large part of the power consumption, and it is essential to reduce the power consumption of the ion exchange membrane. The power consumption in the ion exchange membrane method is determined from the electrolytic voltage and the current efficiency. The reduction in power consumption is achieved by low electrolytic voltage and high current efficiency.

The inventions described in Patent Document 1 and Patent Document 2 do not particularly mention reducing the electrolytic voltage and increasing the current efficiency to reduce the power consumption.

Therefore, the present invention is for solving the above-mentioned conventional problems, and in particular, a cation exchange membrane and a multilayer structure membrane capable of reducing power consumption due to low electrolytic voltage and high current efficiency, and , An object of the present invention is to provide an electrolytic cell.

That is, the present invention is as follows.
[1]
A cation exchange membrane containing a fluorine-containing polymer having an ion exchange group.
The cluster diameter before energization measured in a pure water atmosphere is in the range of 3.0 nm or more and 3.5 nm or less, and the crystal index before energization measured in a dry atmosphere is in the range of 0.03 or more and less than 0.09. Is a cation exchange membrane.
[2]
The cation exchange membrane according to [1], wherein the product of the crystal index and the water content measured with pure water at 85 ° C. is 1.0 or more.
[3]
The cation exchange membrane according to [1] or [2], wherein the water content is 25% or less.
[4]
A cation exchange membrane containing a fluorine-containing polymer having an ion exchange group.
The crystal index before energization is in the range of less than 0.09,
A cation exchange membrane in which the product of the crystal index measured in a dry atmosphere and the water content measured in pure water at 85 ° C. is 1.0 or more, and the water content is in the range of 25% or less.
[5]
The fluorine-containing polymer having an ion exchange group is a vinyl fluoride compound (I), a vinyl compound (II) having a carboxylic acid group, and a vinyl compound (III) different from the above (I) and the above (II). The cation exchange membrane according to any one of [1] to [4], which contains and as a monomer component.
[6]
The vinyl compound (III) is selected from the group consisting of 1-trifluorovinyloxy-2-heptafluoropropoxyhexafluoropropane, perfluoroalkyl vinyl ether, perfluorodioxol, and a vinyl compound having a sulfonic acid group. The cation exchange membrane according to [5], which is one or more types.
[7]
The cation exchange membrane according to [5] or [6], wherein the vinyl compound (II) having a carboxylic acid group is a compound represented by the following formula (X).
CF ₂ = CF (OCF ₂ CYF) _n- O (CF ₂ ) _m- COOR (X)
(N represents an integer of 1, m represents an integer of 1 to 4, Y represents F or CF ₃ , R represents CH ₃ , C ₂ H ₅ , or C ₃ H ₇ )
[8]
The cation exchange membrane according to any one of [5] to [7], wherein the vinyl compound (III) is a vinyl compound having a sulfonic acid group.
[9]
The value obtained by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) ^{is in the range of greater than 0 and 3.0 × 10-2} or less [5] to [8]. The cation exchange membrane according to any one of.
[10]
The value obtained by dividing the molar ratio of the vinyl compound (III) by the total molar ratio of the vinyl compound (II) and the vinyl compound (III) is in the range of 0.001 or more and less than 0.25 [5]. ] To [9]. The cation exchange membrane according to any one of [9].
[11]
The cation exchange membrane according to any one of [1] to [10], wherein the total ion exchange capacity is in the range of 0.66 m equivalent / g or more and 1.2 m equivalent / g or less.
[12]
The cation exchange membrane according to any one of [1] to [11], wherein the ion exchange group concentration measured in a 32% sodium hydroxide aqueous solution atmosphere is in the range of 12 mol / L or more and 50 mol / L or less.
[13]
A multilayer structure membrane having at least one A layer composed of the cation exchange membrane according to any one of [1] to [12].
[14]
At least one layer B containing a fluorine-containing polymer B containing a vinyl fluoride compound (I) and a vinyl compound having a sulfonic acid group as monomer components without containing the vinyl compound (II) having a carboxylic acid group. The multilayer structure film according to [13] having a layer.
[15]
The multilayer structure film according to [14], wherein the multilayer structure film has a two-layer structure of the A layer and the B layer.
[16]
The multilayer structure film according to any one of [13] to [15], wherein the layer A is located in the outermost layer of the multilayer structure film.
[17]
The cation exchange membrane according to any one of [1] to [12], which is arranged between an anode and a cathode and is used for salt electrolysis.
[18]
The multilayer structure film according to any one of [13] to [16], which is arranged between an anode and a cathode and is used for salt electrolysis.
[19]
With the anode
With the cathode
The cation exchange membrane according to any one of [1] to [12] or the multilayer structure membrane according to any one of [13] to [16], which is arranged between the anode and the cathode. Electrolytic cell equipped.
[20]
The multilayer structure film according to any one of [13] to [16] is provided.
The electrolytic cell according to claim 19, wherein the layer A is arranged so as to face the cathode.

According to the present invention, it is possible to provide a cation exchange membrane and a multilayer structure membrane capable of reducing power consumption due to low electrolytic voltage and high current efficiency, and an electrolytic cell. Therefore, according to the present invention, it is possible to provide an electrolytic cell that can contribute to energy saving as compared with the conventional case.

FIG. 1 shows a schematic cross-sectional view of the ion exchange membrane of the present embodiment. FIG. 2 is a schematic view showing an example of the electrolytic cell of the present embodiment.

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “the present embodiment”) 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 gist thereof.

First, the present inventors will explain the transition of the technology that led to the development of the cation exchange membrane of the present embodiment. For example, as the salt electrolysis diaphragm using the ion exchange membrane method, an ion exchange membrane in which a layer having a carboxylic acid (carboxylic acid layer) and a layer having a sulfonic acid (sulfonic acid layer) are mainly laminated can be used. .. Of this laminated film, the sulfonic acid layer mainly plays the role of a support layer, and the carboxylic acid layer contributes to the development of high current efficiency. The carboxylic acid layer has a high crystal index and a narrow cluster, which is a path for ions, and allows only desired ions to pass through the interaction between the ions and the ion exchange group existing on the wall surface of the cluster. As a result, selectivity, that is, current efficiency is exhibited. However, a high crystal index makes it difficult for the clusters to connect to each other, resulting in independent clusters, which may cause the clusters to not function as ion path lines. On the contrary, the thin cluster may hinder the passage of ions and increase the electrolytic voltage. Therefore, conventionally, it has been difficult to achieve both high current efficiency and low electrolytic voltage.

Therefore, as a result of diligent research to solve the above problems, the present inventors have conducted diligent research, and as a result, the diameter of an ion cluster formed in the membrane of the cation exchange membrane, for example, a carboxylic acid or a sulfonic acid gathered. It was decided to control the (cluster diameter) and the crystal index of the polymer. As a result, it has been found that both low electrolytic voltage and high current efficiency can be achieved, and the cation exchange membrane of the present embodiment has been developed. That is, the cation exchange membrane of the present embodiment has the following characteristic parts.

The cation exchange membrane according to the first aspect of the present embodiment (hereinafter, also simply referred to as “first cation exchange membrane”) is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group. The cluster diameter before energization measured in a pure water atmosphere is in the range of 3.0 nm or more and 3.5 nm or less, and the crystal index before energization measured in a dry atmosphere is 0.03 or more and less than 0.09. The range. By providing the above configuration, the first cation exchange membrane of the present embodiment makes it possible to achieve both low electrolytic voltage and high current efficiency.
The "pure water" in the present embodiment means water having a conductivity of 100 (μS / cm) or less when measured at 25 ° C.

Further, the cation exchange membrane according to the second aspect of the present embodiment (hereinafter, also simply referred to as “second cation exchange membrane”) is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group. The crystal index before energization is in the range of less than 0.09, and the product of the crystal index measured in a dry atmosphere and the water content measured in pure water at 85 ° C. is 1.0 or more, and the water content is described above. The rate is in the range of 25% or less. By providing the above configuration, the second cation exchange membrane of the present embodiment makes it possible to achieve both low electrolytic voltage and high current efficiency, similarly to the first cation exchange membrane.

Hereinafter, each configuration of the first cation exchange membrane and the second cation exchange membrane of the present embodiment will be described in detail. In the following description, the term "cation exchange membrane" is used to include both the first cation exchange membrane and the second cation exchange membrane.

[Fluorine-containing polymer]
In the present embodiment, the "fluorine-containing polymer having an ion-exchange group" means a fluorine-containing polymer having an ion-exchange group or an ion-exchange group precursor that can become an ion-exchange group by hydrolysis. Further, in the present embodiment, the "ion exchange group" means a carboxylic acid group or a sulfonic acid group.

When the fluorine-containing polymer has an ion exchange group precursor (for example, a carboxylic acid group precursor and a sulfonic acid precursor) that can become an ion exchange group by hydrolysis, the carboxylic acid group precursor is formed after film formation by the method described later. The body is converted to a carboxylic acid group and the sulfonic acid group precursor is converted to a sulfonic acid group. In the fluorine-containing polymer containing a sulfonic acid group or a carboxylic acid group as an ion exchange group, for example, a hydrophobic polymer main chain portion and a hydrophilic carboxylic acid group or sulfonic acid group portion are microscopically separated. Has a structure. As a result, the fluorine-containing polymer has, for example, an ion cluster in which sulfonic acid groups or carboxylic acid groups are gathered.

^{When operated by salt electrolysis, Na +} ions move from the anolyte side to the catholyte side through the ion cluster. Therefore, the ease of passage of such cations depends on the diameter of the ion cluster. The ease of passage of this cation correlates with the electrolysis voltage during salt electrolysis, and the easier it is to pass, the lower the electrolysis voltage. On the other hand, the current efficiency is ^{determined by the amount of OH −} ions of the product caustic soda moving from the cathode side to the anode liquid side through the ion cluster, and the smaller the amount of movement, the higher the current efficiency. As described above, it is considered that the ion exchange membrane performance in salt electrolysis is entirely determined by the ion cluster structure, but the cation exchange membrane of the present embodiment is not limited by the above consideration.

[Cluster diameter]
(In pure water)
In the cation exchange membrane of the present embodiment, the cluster diameter of the ion exchange membrane before energization measured in a pure water atmosphere is in the range of 3.0 nm or more and 3.5 nm or less.

As described above, the fact that the cluster diameter of the ion exchange membrane before energization measured in a pure water atmosphere is 3.0 nm or more means that, for example, in the case of salt electrolysis, ^{the movement of Na +} ions in the cluster is smooth and low electrolysis. It becomes possible to develop a voltage. Further, since the cluster diameter of the ion exchange membrane before energization measured in a pure water atmosphere is 3.5 nm or less, it is possible to prevent OH ⁻ from moving from the cathode side to the anode liquid side, and a high current can be obtained. It is possible to develop efficiency. From the same viewpoint, the cluster diameter is preferably 3.05 nm or more, preferably 3.4 nm or less, and more preferably 3.1 nm or more and 3.35 nm or less.

The cluster diameter can be measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). For example, when two or more multilayer structure membranes are formed and at least one layer is the cation exchange membrane of the present embodiment, the cation exchange membrane of the present embodiment is first physically peeled off. In this way, after separating into a single-layer film, the cluster diameter is measured by SAXS and WAXS in a state of being impregnated with pure water at 25 ° C. The cation exchange membrane is immersed in pure water for at least 1 hour, and then SAXS and WAXS measurements are performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to SAXS and WAXS measurements in the same manner as described above. The details of the measurement of the cluster diameter will be described later in [Method of measuring the cluster diameter].

(NaOH 28%)
This embodiment is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, and is not particularly limited, but the cluster diameter of the ion exchange membrane before energization measured in a 28% NaOH aqueous solution atmosphere is 2. It is preferably in the range of .2 nm or more and 2.7 nm or less.

The cluster diameter is measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with a 28% NaOH aqueous solution at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. After immersing the cation membrane in a 28% NaOH aqueous solution for at least 12 hours, SAXS and WAXS measurements are performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to SAXS and WAXS measurements in the same manner as described above.

For example, in the case of salt electrolysis, if the cluster diameter of the ion exchange membrane before energization measured in the atmosphere of a 28% NaOH aqueous solution is 2.2 nm or more, ^{the movement of Na +} ions in the cluster is smooth and a low electrolysis voltage is applied. It becomes possible to express. Further, if the cluster diameter of the ion exchange membrane before energization measured in the atmosphere of a 28% NaOH aqueous solution is 2.7 nm or less, ^{it is possible to prevent OH −} from moving from the cathode side to the anode liquid side, and a high current can be obtained. It is possible to develop efficiency.

(NaOH 32%)
This embodiment is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, and is not particularly limited, but the cluster diameter of the ion exchange membrane before energization measured in an atmosphere of a 32% NaOH aqueous solution is 1. The range is preferably 9.9 nm or more and 2.7 nm or less.

The cluster diameter is measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with a 32% NaOH aqueous solution at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. After immersing the cation membrane in a 32% NaOH aqueous solution for at least 12 hours, SAXS and WAXS measurements are performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to SAXS and WAXS measurements in the same manner as described above.

For example, in the case of salt electrolysis, if the cluster diameter of the ion exchange membrane before energization measured in the atmosphere of a 32% NaOH aqueous solution is 1.9 nm or more, ^{the movement of Na +} ions in the cluster is smooth and a low electrolysis voltage is applied. It becomes possible to express. When the cluster diameter of the ion exchange membrane before energization measured in the atmosphere of a 32% NaOH aqueous solution is 2.7 nm or less, ^{it is possible to prevent OH −} from moving from the cathode side to the anode liquid side, resulting in high current efficiency. It becomes possible to express.

[Crystal index (dry)]
In the cation exchange membrane of the present embodiment, the crystal index measured in a dry atmosphere before energization is in the range of 0.03 or more and less than 0.09.

In the present embodiment, the "crystal index" is a numerical value of the crystallinity of the polymer chain in the cation exchange membrane, and the larger this value is, the larger the elastic energy of the polymer is. Usually, it is considered that the size and shape of clusters, which are the paths of ions, are determined by the balance between the hydrophilicity of ion exchange groups and the elastic energy of the polymer. Therefore, the lower the crystal index, the larger the clusters that are the paths of ions and / or the larger the number of clusters. In addition, as the cluster becomes larger, the clusters are locally connected to form a denser network of clusters. Therefore, the smaller the crystal index, the easier it is for ions to pass through the membrane.

For example, in the case of salt electrolysis, if the crystal index before energization measured in a dry atmosphere is 0.03 or more, ^{it is possible to prevent OH −} from moving from the cathode side to the anode solution side, resulting in high current efficiency. It becomes possible to express. Further, if the crystal index before energization measured in a dry atmosphere is less than 0.09, ^{the movement of Na +} ions in the cluster is smooth, and a low electrolytic voltage can be developed. From the same viewpoint, the crystal index is preferably 0.04 or more and 0.087 or less, and more preferably 0.05 or more and 0.085 or less.

The crystal index is measured by wide-angle X-ray scattering (WAXS) in a dry state at 25 ° C. for the cation exchange membrane of the present embodiment. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. When the cation exchange membrane has a coating layer, the WAXS measurement can be performed in the same manner as described above after removing the coating layer with a brush or the like.

(In pure water)
This embodiment is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, and is not particularly limited, but the crystal index before energization measured in a pure water atmosphere is 0.03 or more. The range is preferably less than 0.09.

For example, in the case of salt electrolysis, if the crystal index before energization measured in a pure water atmosphere is 0.03 or more, ^{it is possible to prevent OH −} from moving from the cathode side to the anode solution side, resulting in high current efficiency. Can be expressed. Further, if the crystal index before energization measured in a pure water atmosphere is less than 0.09, ^{the movement of Na +} ions in the cluster is smooth, and a low electrolytic voltage can be developed.

The crystal index is measured by wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with pure water at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. The cation exchange membrane is immersed in pure water for at least 1 hour, and then the WAXS measurement is performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to WAXS measurement in the same manner as described above.

(28% aqueous sodium hydroxide solution)
This embodiment is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, and is not particularly limited, but is measured in a 28% sodium hydroxide aqueous solution (NaOH 28% aqueous solution) atmosphere before energization. The crystal index is preferably in the range of 0.02 or more and less than 0.09.

For example, in the case of salt electrolysis, if the crystal index before energization measured in the atmosphere of a 28% NaOH aqueous solution is 0.02 or more, ^{it is possible to prevent OH −} from moving from the cathode side to the anode solution side, and a high current is obtained. It is possible to develop efficiency. Further, if the crystal index before energization measured in the atmosphere of a 28% NaOH aqueous solution is less than 0.09, ^{the movement of Na +} ions in the cluster is smooth, and a low electrolytic voltage can be developed.

The crystal index is measured by wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with a 28% NaOH aqueous solution at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. The cation exchange membrane is immersed in a 28% NaOH aqueous solution for at least 12 hours, and then the WAXS measurement is performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to WAXS measurement in the same manner as described above.

[Characteristic]
In the present embodiment, as described above, by controlling the cluster diameter and the crystal index of the cation exchange membrane, the electrolytic voltage can be reduced and the current efficiency can be increased.

Specifically, the electrolytic voltage is preferably about 3.1 V / 6 kA or less. The current efficiency is preferably about 95% or more. As a result, power consumption can be reduced. Specifically, the power consumption is preferably about 2100 kWh or less.

In the present embodiment, the cluster diameter and the crystal index are controlled so as to be within the above ranges, but even if a measurement error or deviation occurs due to a measurement error or measurement conditions, for example, by satisfying the above characteristic range, the present invention It is possible to infer that it includes the configuration of the embodiment.

As described above, the lower the crystal index, the larger the cluster diameter, while the higher the crystal index, the smaller the cluster diameter. In this way, there is a correlation between the cluster diameter and the crystal index, but by not specifying only one parameter of the cluster diameter and the crystal index, but specifying the parameter for both, a well-balanced and high current efficiency It is possible to obtain the effect that it can be realized with a low electrolytic voltage to express.

Therefore, by appropriately controlling these two parameters, it is possible to appropriately reduce the electrolytic voltage and increase the current efficiency as described above.

Next, the above-mentioned method for measuring the cluster diameter and the crystal index will be described in detail.

[Measurement method of cluster diameter]
The ion cluster diameter can be measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). An example of the measurement method by SAXS and WAXS is shown below. The SAXS and WAXS measurements are carried out in a state where the monolayer film is impregnated with water or an aqueous NaОH solution at 25 ° C. The cation exchange membrane is subjected to measurement after being immersed in water for at least 1 hour when immersed in water, and for 12 hours or more when immersed in an aqueous NaОH solution. For the SAXS and WAXS measurements, a Rigaku SAXS device NanoViewer is used. An X-ray wavelength of 0.154 nm (CuKα ray) is used. In the small angle region, the distance between the sample and the detector is 841 mm, and PILATUS 100K is used as the detector. In the wide angle region, the distance between the sample and the detector is 75 mm, and measurement is performed using an imaging plate as the detector. Then, by combining both profiles, scattering data in a scattering angle in the range of 0.1 ° <scattering angle (2θ) <30 ° is obtained. The samples are measured in a state of being stacked so that the total film thickness is about 100 μm, and the exposure time is 15 to 60 minutes for both the small angle region and wide angle region measurement. The data obtained by the two-dimensional detector makes the data one-dimensional by the ring averaging. The obtained SAXS profile is subjected to corrections derived from the detector, such as correction of dark current of the detector, and corrections for scattering by substances other than the sample (empty cell scattering correction). If the influence of the X-ray beam shape on the SAXS profile (the influence of smear) is large, the correction (deathmare) on the X-ray beam shape is also performed. For the one-dimensional SAXS profile obtained in this way, Yasuhiro Hashimoto, Naoki Sakamoto, Hideki Iijima, Polymer Papers vol. 63 No. 3 pp. 166 The diameter of the ion cluster (cluster diameter) is determined according to the method described in 2006. That is, assuming that the ion cluster structure is represented by a core-shell type rigid sphere having a particle size distribution, the scattering angle is dominated by the scattering derived from the ion cluster of the SAXS profile actually measured using the theoretical scattering formula based on this model. The average cluster diameter (ion cluster diameter) is determined by fitting the SAXS profile of the region. In this model, it is assumed that the core portion corresponds to the ion cluster and the core diameter is the ion cluster diameter. The shell layer is virtual, and the electron density of the shell layer is the same as that of the matrix part. Further, here, the thickness of the shell layer is 0.25 nm. The theoretical scattering equation of the model used for fitting is shown in the following equation (A). The fitting range is 1.4 <2θ <6.7 °.

In the above, C is a constant, N is the cluster number density, η is the core, that is, the volume fraction when the ion cluster part and the virtual shell around it are assumed to be rigid spheres, λ is the X-ray wavelength used, and t. the shell layer thickness, a ₀ is the average ion cluster radius, gamma (M) is the gamma function, sigma represents a standard deviation of ion cluster radius (core radius). P (a) represents a distribution function of the core radius a, and here it is assumed that the volume distribution of a follows the Schultz-Zimm distribution p (a). M is a parameter representing the distribution. I _b (q) represents background scattering including excessive water-derived scattering and heat-diffuse scattering at the time of measurement, and is assumed to be a constant here. At the time of fitting, among the above parameters, M, η, a ₀ , σ, and Ib (q) are set as variable parameters. In addition, in this specification, an ion cluster diameter means _{the average diameter (2a 0) of an ion cluster.}

The above method for measuring the cluster diameter is applied in Examples described later.

Here, since the cluster total integration rate v can be obtained from the SAXS, WAXS measurement, and fitting described in the above [Measurement method of cluster diameter] and [Cluster diameter], it will be described below.

[Cluster total integral rate]
That is, the total cluster integration rate v can be determined by the following equation (B).

(In pure water)
In the cation exchange membrane of the present embodiment, the cluster total integral ratio v before energization measured in a pure water atmosphere is preferably in the range of 0.23 or more and 0.45 or less.

The total cluster integration rate v is a numerical value of the volume occupied by the cluster in the cation exchange membrane. The larger this value is, the larger the cluster diameter which is the path of ions and / or the larger the number of clusters. Therefore, the larger the total cluster integration rate v, the easier it is for ions to pass through the membrane.

For example, in the case of salt electrolysis, if the cluster total integral ratio v before energization measured in a pure water atmosphere is 0.23 or more, ^{the movement of Na +} ions in the cluster is smooth and a low electrolysis voltage is developed. Is possible. Further, if the cluster total integral ratio v before energization measured in a pure water atmosphere is 0.45 or less, ^{it is possible to prevent OH −} from moving from the cathode side to the anode liquid side, and high current efficiency is exhibited. It becomes possible to do.

The cluster total integration rate v is measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with pure water at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. The cation exchange membrane is immersed in pure water for at least 1 hour, and then SAXS and WAXS measurements are performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to SAXS and WAXS measurements in the same manner as described above.

(NaOH 28%)
The present embodiment is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, and the total cluster integral rate v before energization measured in a 28% NaOH aqueous solution atmosphere is 0.023, although not particularly limited. As mentioned above, it is preferably in the range of 0.05 or less.

For example, in the case of salt electrolysis, if the cluster total integral ratio v before energization measured in the atmosphere of a 28% NaOH aqueous solution is 0.023 or more, ^{the movement of Na +} ions in the cluster is smooth and a low electrolysis voltage is developed. It becomes possible. Further, if the cluster total integral ratio v before energization measured in the atmosphere of a 28% NaOH aqueous solution is 0.05 or less, ^{it is possible to prevent OH −} from moving from the cathode side to the anode liquid side, resulting in high current efficiency. It becomes possible to express.

The cluster total integration rate v is measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with a 28% NaOH aqueous solution at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. The cation exchange membrane is immersed in a 28% NaOH aqueous solution for at least 12 hours, and then SAXS and WAXS measurements are performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to SAXS and WAXS measurements in the same manner as described above.

(NaOH 32%)
This embodiment is a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, and is not particularly limited, but the cluster total integral rate v before energization measured in an atmosphere of a 32% NaOH aqueous solution is 0.01. As mentioned above, it is preferably in the range of 0.022 or less.

For example, in the case of salt electrolysis, if the cluster total integral ratio v before energization measured in an atmosphere of a 32% NaOH aqueous solution is 0.01 or more, ^{the movement of Na +} ions in the cluster is smooth and a low electrolysis voltage is developed. Is possible. Further, if the cluster total integral ratio v before energization measured in the atmosphere of a 32% NaOH aqueous solution is 0.022 or less, ^{it is possible to prevent OH −} from moving from the cathode side to the anode liquid side, and the current efficiency is high. Can be expressed.

The cluster total integration rate v is measured by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) in a state where the cation exchange membrane of the present embodiment is impregnated with a 32% NaOH aqueous solution at 25 ° C. In the case of a multilayer structure membrane, the cation exchange membrane of the present embodiment is separated into a monolayer membrane and then measured. The cation exchange membrane is immersed in a 32% NaOH aqueous solution for at least 12 hours, and then SAXS and WAXS measurements are performed. When the cation exchange membrane has a coating layer, the coating layer can be removed with a brush or the like and then subjected to SAXS and WAXS measurements in the same manner as described above.

[Measurement method of crystal index]
The crystal index can be measured by, for example, wide-angle X-ray scattering (WAXS). An example of the measurement method by WAXS is shown below. The WAXS measurement is performed on a monolayer film at 25 ° C. in a state of being impregnated with water or an aqueous NaOH solution, and in a vacuum (dry). The cation exchange membrane is immersed in water for at least 1 hour when immersed in water, and for 12 hours or more when immersed in an aqueous NaOH solution, and then subjected to measurement. When measuring in a vacuum, leave it in a vacuum state for at least 15 minutes before starting the measurement. For the WAXS measurement, a Rigaku SAXS device NanoViewer is used. An X-ray wavelength of 0.154 nm (CuKα ray) is used. The distance between the sample and the detector is set to 75 mm, and measurement is performed using an imaging plate as the detector. The exposure time is 15 to 60 minutes. The data obtained by the two-dimensional detector makes the data one-dimensional by the ring averaging. The obtained WAXS profile is subjected to detector-derived corrections such as detector dark current correction and empty cell scattering correction. When the measurement is performed with the sample impregnated with water or an aqueous NaOH solution, the WAXS profile thus obtained contains scattering derived from the immersion liquid. Therefore, the WAXS measurement of the immersion liquid only is also performed under the same conditions as above, and the WAXS profile derived from the one-dimensional immersion liquid is multiplied by a constant and subtracted from the WAXS profile for the cation exchange membrane shown above. Obtain a WAXS profile excluding scattering from the immersion liquid in. The constant multiple at this time is determined so that the WAXS profile shape excluding the scattering derived from the immersion liquid is close to that obtained in the dry state. With respect to the WAXS profile thus obtained, the crystal index is calculated by separating the scattering peaks existing in the range of 6.0 <2θ <25 ° by three Gaussian functions. For peak separation, the Multi-peak Fit function of Wavemetrics software Igor Pro version 6.3.6.4 is used. At the time of peak separation, the baseline is a straight line connecting the scattering intensities at 2θ = 6.0 ° and 2θ = 25.0 °. In addition, the three Gaussian functions set the initial values of the peak positions to 2θ = 15.2 °, 16.5 °, and 17.9 °, respectively, and set the initial peak width and initial peak height so that peak separation is performed well. do. Under these conditions, peak separation is performed with the peak position, peak width, and peak height of each peak as variable parameters, the peak with the narrowest peak width is derived from the crystal, and the sum of the remaining two peaks is derived from the amorphous. The crystal index X is calculated by the formula (C) as the peak of.

In formula _{(C), A} C is the peak area derived from _{crystal, A a1,} A _a2 represents two peak areas are assigned to _{amorphous, A} a1 ₊ A _a2 represents the amorphous peak area.

The above method for measuring the crystal index is applied in Examples described later.

Subsequently, the polymer composition of the cation exchange membrane of the present embodiment, the polymer composition ratio, and the like will be described in detail.

[Polymer composition]
As described above, the fluorine-containing polymer having an ion-exchange group means a fluorine-containing polymer having an ion-exchange group or an ion-exchange group precursor that can become an ion-exchange group by hydrolysis. The fluorine-containing polymer having an ion-exchange group is, for example, composed of a main chain of a fluorinated hydrocarbon, has a functional group that can be converted into an ion-exchange group by hydrolysis or the like as a pendant side chain, and can be melt-processed. Polymers and the like. Such a fluorine-containing polymer will be described below.

The fluorine-containing polymer is a vinyl fluoride compound (I) (also referred to as "vinyl compound (I)") and a vinyl compound (II) having a carboxylic acid group (also referred to as "vinyl compound (II)"). , (I) and (II) are preferably different from vinyl compound (III) (also referred to as "vinyl compound (III)) as a monomer component. In this case, one or more kinds of fluorine-containing polymers are used. It may be in the form of a copolymer obtained by copolymerizing the vinyl compound (I) of the above, one or more kinds of vinyl compounds (II), and one or more kinds of vinyl compounds (III). The fluorine-containing polymer is a copolymer obtained by copolymerizing one or more kinds of vinyl compounds (I) and one or more kinds of vinyl compounds (II), and one or more kinds of vinyl compounds (I). It may be in the form of a blend containing the copolymer obtained by copolymerizing with one or more kinds of vinyl compounds (III).

Examples of the vinyl fluoride compound (I) include vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and perfluoro (alkyl vinyl ether). These compounds may be used alone or in combination of two or more as monomer components. In particular, when the cation exchange membrane according to the present embodiment is used as the cation exchange membrane for alkaline electrolysis, the vinyl fluoride compound (I) is preferably a perfluoromonomer, and is preferably tetrafluoroethylene or hexafluoro. More preferably, it is a perfluoromonomer selected from the group consisting of propylene and perfluoro (alkyl vinyl ether).

In the present embodiment, the "vinyl compound having a carboxylic acid group (vinyl compound (II)" means a vinyl compound having a carboxylic acid group or a carboxylic acid group precursor that can become a carboxylic acid group by hydrolysis. Examples of such a vinyl compound include a compound (monomer) represented by _{the formula (X): CF 2} = CF (OCF _{2 CYF) n-} O (CZF) _{m-COOR (here).} In, n represents an integer of 0 to 2, m represents an integer of 1 to 12, Y and Z each independently _{represent F or CF 3} , and R represents a lower alkyl group).

Among these, the compound represented by the formula (X) is the formula (X2) :.
A compound represented by CF ₂ = CF (OCF ₂ CYF) _n- O (CF ₂ ) _{m-COOR is preferable.} Here, n represents an integer of 0 to 2, m represents an integer of 1 to 4, Y represents F or CF ₃ , and R represents CH ₃ , C ₂ H ₅ , or C ₃ H. Represents _7. Among these, the compound represented by the formula (X2) is preferably a compound represented by the formula (X3): CF ₂ = CF (OCF ₂ CYF) _n- O (CF ₂ ) _m- COOR. Here, n represents an integer of 1, m represents an integer of 1 to 4, Y represents F or CF ₃ , and R represents CH ₃ , C ₂ H ₅ , or C ₃ H ₇ . show.

In particular, when the cation exchange membrane according to the present embodiment is used as the cation exchange membrane for alkaline electrolysis, it is preferable that at least a perfluoro compound is contained as a monomer component (monomer), but the alkyl group of the ester group (R above). The alkyl group (R) does not have to be a perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms, since (see) is lost from the polymer at the time of hydrolysis. Among these, the vinyl compound (II) is more preferably, for example, a monomer component (monomer) represented by the following.
_{CF 2 = CFOCF 2 -CF (CF} 3) OCF 2 COOCH 3,
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH ₃ ,
_{CF 2 = CF [OCF 2 -CF} (CF 3)] 2 O (CF 2) 2 COOCH 3,
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₃ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₂ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃

Examples of the vinyl compound (III) include 1-trifluorovinyloxy-2-heptafluoropropoxyhexafluoropropane, perfluoroalkyl vinyl ether, perfluorodioxol, and a vinyl compound having a sulfonic acid group. .. These compounds may be used alone or in combination of two or more as monomer components.

In particular, when the cation exchange membrane of the present embodiment is used as the cation exchange membrane for alkaline electrolysis, the vinyl compound (III) is preferably a vinyl compound having a sulfonic acid group.

The vinyl compound having a sulbonic acid group means a vinyl compound having a sulfonic acid group or a sulfonic acid group precursor that can become a sulfonic acid group by hydrolysis. Since the vinyl compound having a sulfonic acid group has a higher acidity than the vinyl compound having a carboxylic acid group, it has a high hydrophilicity and has a characteristic of forming a large cluster. Therefore, if a vinyl compound having a sulfonic acid group is selected as the vinyl compound (III), clusters of large sulfonic acid groups are locally formed in the polymer. Then, the clusters formed by the carboxylic acid groups are connected to form a dense network of clusters. This makes it easier for ions to pass through the cluster, making it possible to further reduce the electrolytic voltage. A vinyl compound having a sulfonic acid group or a sulfonic acid group precursor that can become a sulfonic acid group by hydrolysis is represented by, for example, the formula (Y): CF ₂ = CFO-X-CF _2- SO ₂ F. It is preferably a monomer component (monomer) (where X represents a perfluoro group). Specific examples of the monomer component represented by the formula (Y) are shown below.
CF ₂ = CFOCF ₂ CF ₂ SO ₂ F,
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F,
CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₂ SO ₂ F,
CF ₂ = CF (CF ₂ ) ₂ SO ₂ F,
CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] ₂ CF ₂ CF ₂ SO ₂ F,
CF ₂ = CFOCF ₂ CF (CF ₂ OCF ₃ ) OCF ₂ CF ₂ SO ₂ F

Among these, the monomer components represented by the formula (Y) are CF ₂ = CFOCF ₂ CF ₂ SO ₂ F, CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₂ SO ₂ F, and CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F is more preferably one or more selected from the group.

In the present embodiment, in addition to the vinyl compound (I) and the vinyl compound (II), a vinyl compound (III) different from the (I) and (II) is copolymerized to lower the crystal index of the copolymer. be able to. Further, in the form of a blend of a copolymer obtained by copolymerizing a vinyl compound (I) and a vinyl compound (II) and a copolymer obtained by copolymerizing a vinyl compound (I) and a vinyl compound (III). Even if there is, the crystal index can be lowered in the same manner.

In the present embodiment, the "crystal index" is an index showing the degree of crystallinity of the polymer, and the larger this value is, the more rigid the polymer is. On the other hand, when the hydrophilic carboxylic acid group portion is microscopically separated to form a cluster which is a path for ions, the mobility of the carboxylic acid group is lost and it becomes difficult to form a continuous cluster. As a result, for example, problems such as an increase in the electrolysis voltage and an increase in power consumption during electrolysis occur. On the other hand, for example, when the vinyl compound (III) is copolymerized, the regularity of the polymer is lowered and the crystal index is lowered. This increases the mobility of the hydrophilic carboxylic acid groups and facilitates the formation of continuous clusters. As a result, the electrolysis voltage is reduced, and the merit of reducing the power consumption during electrolysis can be obtained. However, if the vinyl compound (III) is excessively added to excessively reduce the crystal index, there is a risk that problems such as a decrease in strength and an excessive expansion of the cluster diameter make it difficult to develop current efficiency.

Therefore, the copolymer of the present embodiment has a fluorine-containing weight having a characteristic that the electrolytic voltage is low and high current efficiency is exhibited by appropriately controlling the composition ratio of the monomers to be copolymerized as described later. Allows the design of coalescing (polymers).

The copolymers obtained from these monomers shall be produced by a polymerization method developed for homopolymerization and copolymerization of ethylene fluoride, particularly a general polymerization method used for tetrafluoroethylene. Can be done. For example, in the non-aqueous method, an inert solvent such as perfluorohydrocarbon or chlorofluorocarbon is used. Then, the polymerization reaction can be carried out under the conditions of a temperature of 0 to 200 ° C. and a pressure of 0.1 to 20 MPa in the presence of a radical polymerization initiator such as a perfluorocarbon peroxide or an azo compound. The copolymer may be a block polymer or a random polymer.

[Polymer composition ratio]
The composition ratio of the fluorine-containing polymer having an ion exchange group in the present embodiment is not particularly limited, but each molar of the vinyl compound (I), the vinyl compound (II), and the vinyl compound (III). The ratio is preferably in the following range. The following composition ratio is the ratio when the total of the molar ratios of the vinyl fluoride compound (I), the vinyl compound (II) and the vinyl compound (III) is 100 mol%.

The vinyl fluoride compound (I) is preferably 80 mol% or more and 94 mol% or less, and more preferably 84 mol% or more and 91 mol% or less.

The vinyl compound (II) is preferably 6 mol% or more and 20 mol% or less, and more preferably 9 mol% or more and 15.2 mol% or less.

The vinyl compound (III) is preferably more than 0 mol% and 3 mol% or less, and more preferably 0.05 mol% or more and 2.0 mol% or less.

For example, in the case of salt electrolysis, if the vinyl compound (I) is 80 mol% or more, the polymer has sufficient strength and excellent handleability. Further, when the vinyl compound (I) is 94 mol% or less, a desired polymer can be polymerized without causing impurities such as PTFE. Further, when the vinyl compound (I) is 84 mol% or more, higher current efficiency can be exhibited. Further, when the vinyl compound (I) is 91 mol% or less, electrolysis can be performed at a more preferably lower voltage.

Further, when the vinyl compound (II) is 6 mol% or more, electrolysis can be performed at a preferably low voltage. Further, when the vinyl compound (II) is 20 mol% or less, problems such as tearing due to an excessively high degree of swelling of the polymer are unlikely to occur. Further, when the vinyl compound (II) is 9 mol% or more, the water content of the cation exchange membrane can be increased and electrolysis can be performed at a lower electrolytic voltage. Further, when the vinyl compound (II) is 15.2 mol% or less, higher current efficiency can be exhibited.

Further, when the vinyl compound (III) exceeds 0 mol%, the electrolytic voltage can be remarkably reduced. Further, when the vinyl compound (III) is 3 mol% or less, high current efficiency can be exhibited. Further, when the vinyl compound (III) is 0.05 mol% or more, the water content of the cation exchange membrane can be increased and electrolysis can be performed at a lower electrolytic voltage. Further, when the vinyl compound (III) is 2.0 mol% or less, the NaCl concentration in the produced NaOH can be reduced.

[Ratio represented by Vinyl Fluoride Compound (III) / Vinyl Fluoride Compound (I)]
The cation exchange membrane containing the fluorine-containing polymer of the present embodiment is not particularly limited, but the molar ratio of the vinyl compound (III) in the polymer is set to the molar ratio of the vinyl fluoride compound (I) in the polymer. The value divided by the ratio ^{is preferably greater than 0 and in the range of 3.0 × 10 -2} or less, and preferably in the range of 2.0 × 10 ^-4 or more and 3.0 × 10 ^-2 or less. More preferably, ^{it is in the range of 2.0 × 10 -4} or more and 2.1 × 10 ^-2 or less, and more preferably in the range of 8.2 × 10 ^-4 or more and 2.0 × 10 ^-2 or less. It is even more preferable, and it is particularly preferable that the range is ^{4.7 × 10 -3} or more and 1.8 × 10 ^{-2 or less.}

By the way, by copolymerizing the vinyl compound (III) with the vinyl fluoride compound (I) and the vinyl compound (II) having a carboxylic acid group, the crystal index is compared with the case where the vinyl compound (III) is not copolymerized. Can be reduced. This makes it easier for ions to pass through the membrane, which can contribute to a decrease in the electrolytic voltage. Further, if the ratio of the vinyl compound (III) is appropriately controlled, the crystal index is excessively lowered, and the problem that the current efficiency is not exhibited is less likely to occur. The higher the molar ratio of the vinyl fluoride compound (I), the larger the amount of the vinyl compound (III) required to exert its effect, and the lower the molar ratio of the vinyl fluoride compound (I), the smaller the amount. It can be effective in quantity. Therefore, the appropriate range can be limited by the value obtained by dividing the vinyl compound (III) by the vinyl fluoride compound (I).

For example, in Patent Document 1 and Patent Document 2 mentioned above, the molar ratio of the polymerizable fluorine compound having a sulfonic acid group, which is the vinyl compound (III), is irrespective of the molar ratio of the vinyl fluoride compound (I). It has been decided. However, in such a polymer, the amount of compound (III) becomes excessive, which causes the crystal index to decrease excessively and the cluster diameter to become too large, so that it is difficult to develop current efficiency. On the other hand, in the present embodiment, the cluster diameter is controlled by tuning the amount of the vinyl compound (III) according to the amount of the vinyl fluoride compound (I) and adding an appropriate amount, resulting in high current efficiency and low electrolysis. A cation exchange membrane that is compatible with both voltages can be created.

For example, in the case of sodium chloride electrolysis, as described above, the value obtained by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) is made larger than 0 to lower the crystal index of the polymer. It is possible ^{to smooth the passage of Na +} ions through the film and reduce the electrolytic voltage. Further, by setting the value to 3.0 × 10 ^-4 or more, the electrolytic voltage can be lowered more effectively.

Further, by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) to 3.0 × ^10-2 or less, the crystal index is not excessively lowered. Therefore, the problem of wrinkling due to the swelling of the membrane can be suppressed. Further, ^{by setting the value to 2.0 × 10-2} or less, the crystal index is not excessively lowered, and therefore problems such as strength reduction are less likely to occur.

Further, by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) ^{to be 8.2 × 10 -4} or more, the clusters are connected and a dense network is formed. It is formed. Therefore, the ions easily pass through the cation exchange membrane, and the electrolytic voltage can be lowered.

Further, by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) to 1.3 × ^10-2 or less, the crystal index does not decrease excessively. You can control the size of the cluster. Therefore, it is possible to prevent OH ⁻ from moving from the cathode side to the anode liquid side, and it is possible to exhibit high current efficiency.

Further, by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) ^{to be 4.7 × 10 -3} or more, the clusters are spread and impurities are accumulated. As a result, problems such as deterioration of electrolytic performance are unlikely to occur.

[Ratio indicated by the total molar ratio of vinyl compound (III) / molar ratio of vinyl fluoride compound (II) and vinyl compound (III)]
The cation exchange membrane containing the fluorine-containing polymer of the present embodiment is not particularly limited, but the molar ratio of the vinyl compound (III) is set to the molar ratio of the vinyl fluoride compound (II) and the vinyl compound (III). The value divided by the total of the ratios is in the range of 0.001 or more and less than 0.25, more preferably 0.005 or more and less than 0.20.

When the value obtained by dividing the molar ratio of the vinyl compound (III) by the total of the molar ratios of the vinyl fluoride compound (II) and the vinyl compound (III) is 0.001 or more, the crystal index of the polymer is lowered. It ^{facilitates the passage of Na +} ions through the membrane and lowers the electrolytic voltage. When the value is less than 0.25, the crystal index is not excessively lowered, and problems such as strength reduction are less likely to occur. When the value is 0.005 or more, the clusters can be connected and a dense network can be formed. Therefore, when the value is 0.005 or more, the ions easily pass through the cation exchange membrane, and the electrolytic voltage can be lowered. When the value is less than 0.20, the crystal index does not decrease excessively, and the size of the cluster can be controlled. Therefore, if the value is less than 0.20, it is possible to prevent OH ⁻ from moving from the cathode side to the anode liquid side, and high current efficiency can be exhibited.

The molar ratio of the vinyl fluoride compound (III) / the molar ratio of the vinyl fluoride compound (I), and the molar ratio of the vinyl compound (III) / the vinyl fluoride compound (II) and the vinyl compound (III). The ratio indicated by the total molar ratio may be evaluated by any of IR, F-NMR, ICP, and combustion ion chromatograph. For example, when evaluated by IR, the vinyl fluoride compound (I) is a monomer (X ₁ = F, X ₂ = F) represented by the following general formula (1), and the vinyl fluoride compound (II). Is represented by the following general formula (2), the monomer (a = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the vinyl compound (III) are represented by the following general formula (3). It is assumed that it is a monomer (c = 1, d = 2, Y = CF _3). Thus, the peak height of the peak wavenumber 2,362.37 +/- ^{5 cm -1} derived from CF ₂ in the vinyl compound (I), COO in the vinyl compound (II) ^- peak derived from the peak wavenumber 2,967.91 +/- ^{5 cm -1} From the height, the ratio of the vinyl compound (I) and the vinyl compound (II) can be calculated based on the calibration curve obtained by using a copolymer whose content is known. Also, the peak height of the COOCH ₃ from the peak wavenumber 1,444.8 +/- ^{5 cm -1} in the vinyl compound (II), the peak wavenumber 1467.8 +/- ^{5 cm -1} height of SO ₂ F in the vinyl compound (III) , The molar ratio of the vinyl compound (II) and the vinyl compound (III) can be calculated based on the calibration curve obtained by using a copolymer whose content is known. The molar ratio of the vinyl compound (I), the vinyl compound (II), and the vinyl compound (III) can be calculated from the calculated values. From this molar ratio, the ratio indicated by the molar ratio of the vinyl compound (III) / the molar ratio of the vinyl compound (I), and the molar ratio of the vinyl compound (III) / the vinyl fluoride compound (II) and the vinyl compound (III). The ratio indicated by the total molar ratio of can be calculated respectively.
General formula (1):
CF ₂ = CX ₁ X ₂ (1)
Monomer represented by (X ₁ = F, X ₂ = F)
General formula (2):
CF ₂ = CF- (OCF ₂ CYF) _a- O- (CF ₂ ) _b- COOR (2)
Monomer represented by (a = 1, b = 2, Y = CF ₃ , R = CH ₃ )
General formula (3):
CF ₂ = CF- (OCF ₂ CYF) _c- O- (CF ₂ ) _d- SO ₂ F (3)
Monomer represented by (c = 1, d = 2, Y = CF ₃ )

Further, the molar ratio of the vinyl compound (I), the vinyl compound (II) and the vinyl compound (III) can be calculated from the saponified polymer. After saponification, the structure of the general formula (2) and the general formula (3) is the structure of the monomer (a = 1, b = 2, Y = CF ₃ ) represented by the following general formula (2)'. Since the structure is a monomer (c = 1, d = 2, Y = CF ₃ ) represented by the following general formula (3)', the vinyl compound (I), the vinyl compound (II), and the vinyl compound The molar ratio of (III) can be calculated from the molar ratios of the general formula (1), the general formula (2)'and the general formula (3)'. The molar ratio can be calculated from the height of the peak derived from each monomer by IR. A peak height of a peak wavenumber from CF ₂ in the vinyl compound (I) 2362.37 +/- ^{5cm -1,} the peak height of the COONa derived peak wavenumber 1022.3 +/- ^{5 cm -1} in the vinyl compound (II), The ratio of the vinyl compound (I) and the vinyl compound (II) can be calculated based on the calibration curve obtained by using a copolymer whose content is known. Also, the peak height of the CF ₂ derived peak wavenumber 2,362.37 +/- ^{5 cm -1} in the vinyl compound (I), SO ₃ in the vinyl compound (III) ^- the peak wavenumber 1064.7 +/- ^{5 cm -1} height , The ratio of the vinyl compound (I) and the vinyl compound (III) can be calculated based on the calibration curve obtained by using a copolymer whose content is known. The ratio of the vinyl compound (I), the vinyl compound (II), and the vinyl compound (III) can be calculated from the calculated values. From this molar ratio, the ratio indicated by the molar ratio of the vinyl compound (III) / the molar ratio of the vinyl compound (I), and the molar ratio of the vinyl compound (III) / the vinyl fluoride compound (II) and the vinyl compound (III). The ratio represented by the total molar ratio of can be calculated by the general formula (2)':
CF ₂ = CF- (OCF ₂ CYF) _a- O- (CF ₂ ) _b- COONa (2)'
Monomer represented by (a = 1, b = 2, Y = CF ₃ )
General formula (3)':
CF ₂ = CF- (OCF ₂ CYF) _c- O- (CF ₂ ) _d- SO ₃ Na (3)
Monomer represented by (c = 1, d = 2, Y = CF ₃ )

The molar ratios of the vinyl compound (I), the vinyl compound (II), and the vinyl compound (III) measured by the above two methods are in good agreement.

Next, the total ion exchange capacity, the ion exchange group concentration, MI (melt index), and the content rate will be described in detail.

[Total ion exchange capacity]
The total ion exchange capacity of the cation exchange membrane of the present embodiment is not particularly limited, but is preferably 0.66 m equivalent / g or more and 1.2 m equivalent / g or less, and is preferably 0.7 m equivalent / g. More preferably, it is g or more and 1.1 m equivalent / g or less. When the total ion exchange capacity is 0.66 mg equivalent / g or more, a desired polymer can be polymerized without causing impurities such as PTFE. When the total ion exchange capacity is 1.2 mg equivalent / g or less, the polymer has sufficient strength and excellent handleability. When the total ion exchange capacity is 0.7 mg equivalent / g or more, electrolysis can be performed at a preferably low voltage, and when the total ion exchange capacity is 1.1 mg equivalent / g or less, high current efficiency is exhibited. can do.

In the present embodiment, the "total ion exchange capacity" means the equivalent of the exchange group per unit weight of the dry resin, and the "total ion exchange capacity" can be measured by neutralization titration, IR, or the like. ..

[Ion exchange group concentration]
Since the electrochemical behavior of the ions in the cation exchange membrane is in the water contained in the membrane phase, the water content of the membrane is an important basic element of physical characteristics. In this embodiment, the "ion exchange group concentration" indicates the amount of ion exchange groups present in the polymer containing 1 L of water. The ion exchange group concentration is expressed by the following formula using a 32% NaOH aqueous solution, a water content measured at 90 ° C., and an ion exchange group capacity which is the milliequivalent of the ion exchange group contained in 1 g of the dry resin. .. The "moisture content" will be described in detail later.
Ion exchange group concentration (mol / L) = [(1000 / water content _(NaOH) ) x (100-water content _(NaOH) ) x ion exchange group capacity] / 1000

The above method for measuring the ion exchange group concentration is applied in Examples described later.

The ion exchange group concentration of the cation exchange membrane containing the fluorine-containing polymer having an ion exchange group of the present embodiment is not particularly limited, but is preferably in the range of 12 mol / L or more and 50 mol / L or less. When the ion exchange group concentration is 12 mol / L, the ion selectivity is excellent and high current efficiency can be exhibited. Further, when the ion exchange group concentration is 50 mol / L or less, the ion permeability is excellent, and there is a tendency that salt electrolysis can be performed at a low electrolysis voltage.

[MI (Melt Index)]
MI (melt index) indicates the viscosity of the molten resin, and has a great influence on, for example, the film forming property of extrusion molding. If the MI is too large, the viscosity of the molten resin becomes too low, and in the case of extrusion film formation using a T-die, there is a possibility that the film will not peel off from the roll and that the cation exchange membrane will be disturbed between layers in a multilayer structure. There is.

The MI of the cation exchange membrane containing the fluorine-containing polymer of the present embodiment is not particularly limited, but a load having a temperature of 250 to 290 ° C. and a load using an apparatus having an orifice inner diameter of 2.09 mm and a length of 8 mm is used. When measured under the condition of 21.2N, it is preferably within the range of 0.1 g / 10 minutes or more and 150 g / 10 minutes or less (converted value).

The fact that the MI is 0.1 g / 10 minutes or more means that, for example, when a film is produced by extrusion molding, the film can be formed without rubbing or roughness on the film surface. Further, the fact that the MI is 150 g / 10 minutes or less means that even when a polymer having a crystal index of 0.03 or more and less than 0.09 is formed, there is a problem that the polymer does not peel off from the roll and the multilayer film is disturbed between layers. Problems that occur are unlikely to occur.

[Moisture content]
Moisture content is a parameter that correlates with clusters, which are the paths of ions, and affects electrolytic voltage and current efficiency. Moisture content can be measured in two ways.

(In pure water)
An example of a method for measuring the water content in pure water is shown below. The water content is measured by immersing a membrane having a thickness of 500 μm or less and a weight of 0.5 g or more in pure water at 85 ° C. for 4 hours, and then measuring the weight of the membrane. Let this weight be W _(pure) . Next, the film is dried at −0.1 MPa and 90 ° C. for 3 hours with an air dryer, and the weight of the film is measured. Let this weight be W _(dry) . The water content is expressed by the following formula.
Moisture content _(pure) = (W _(pure) -W _(dry) ) / W _(dry)

(In 32% NaOH)
An example of a method for measuring the water content in 32% NaOH (32% aqueous sodium hydroxide solution) is shown below. The water content is measured by immersing a film having a thickness of 500 μm or less and a weight of 0.5 g or more in a 32% NaOH aqueous solution at 90 ° C. for 4 hours, and then measuring the weight of the film. Let this weight be W _(NaOH) . Next, after washing the membrane with pure water, it is immersed in pure water at 25 ° C. for 15 hours, and further immersed in pure water at 90 ° C. for 2 hours. Then, the film is dried at −0.1 MPa and 90 ° C. for 3 hours with a vacuum dryer, and the weight of the film is measured. Let this weight be W _(dry) . The water content is expressed by the following formula.
Moisture content = (W _(NaOH) -W _(dry) ) / W _(dry)

In both measurement methods, the same treatment is performed on 10 films to obtain the water content, and the average value thereof is calculated.

The above method for measuring the water content is applied in Examples described later.

The 32% sodium hydroxide aqueous solution of the cation exchange membrane of the present embodiment and the water content (average value) measured at 90 ° C. are not particularly limited, but are preferably in the range of 1% or more and 8% or less. .. For example, in the case of salt electrolysis, a 32% aqueous sodium hydroxide solution and a water content measured at 90 ° C. of 1% or more means that the cation exchange membrane has excellent ion permeability and electrolysis is performed at a low voltage. Can be done. Further, when the water content of 32% sodium hydroxide aqueous solution and the water content measured at 90 ° C. is 8% or less, the ion selectivity of the cation exchange membrane is excellent and high current efficiency can be exhibited.

The water content (average value) of the cation exchange membrane of the present embodiment measured at 85 ° C. is not particularly limited, but is preferably in the range of 0.1% or more and 25% or less. For example, in the case of salt electrolysis, when the water content of pure water measured at 85 ° C. is 0.1% or more, the ion permeability of the cation exchange membrane is excellent, and electrolysis can be performed at a low voltage. Further, when the water content of pure water measured at 85 ° C. is 25% or less, the ion selectivity of the cation exchange membrane is excellent, and high current efficiency can be exhibited.

The water content is measured after separating the cation exchange membrane of the present embodiment into a monolayer membrane in the case of a multilayer structure membrane containing the cation exchange membrane of the present embodiment as described later. If the separated membranes weigh less than 0.5 g, collect multiple membranes to fill 0.5 g and _{find W (dry)} , W _(pure) , and W _(NaOH) in total. , Calculate the water content.

The product of the crystal index measured in a dry state of the cation exchange membrane containing the fluorine-containing polymer having an ion exchange group of the present embodiment and the water content measured in pure water at 85 ° C. is not particularly limited. , 1.0 or more (preferably 1.0 or more and 1.6 or less), and the water content is preferably 25% or less. For example, if the product of the crystal index measured in a dry state and the water content measured in pure water at 85 ° C. is 1.0 or more and 1.6 or less, the crystal index and the cluster diameter can be controlled within a preferable range. It is possible to satisfy both high current efficiency and low voltage. When the water content is 25% or less, the problem of strength decrease can be avoided without excessive swelling of the film.

[Membrane composition]
The cation exchange membrane of the present embodiment described above may be used as a monolayer structure membrane or may be used in combination with another layer.

[Multilayer structure film]
The multilayer structure membrane of the present embodiment has at least one A layer composed of the cation exchange membrane of the present embodiment. The multilayer structure film is a laminated film composed of two or more layers, and in the case of a two-layer structure film, it is composed of an A layer and a B layer. At least the A layer is a cation exchange membrane containing the fluorine-containing polymer A having the ion exchange group of the present embodiment.

In the multilayer structure film, the layer A is preferably located at the outermost layer from the viewpoint of cluster shrinkage.

For example, in salt electrolysis, when a multilayer structure film (for example, a two-layer structure film) is installed as a component in an electrolytic cell for electrolysis, it is arranged between an anode and a cathode, and layer A is placed on the cathode side. From the viewpoint of cluster contraction, it is preferable to face the surface (arranged so as to face the cathode).
When the position of the A layer approaches the cathode solution having a high pH, the clusters are more contracted and high current efficiency is likely to be developed.

The thickness of the A layer is not particularly limited, but is preferably 5 μm or more and 50 μm or less. The thickness of the B layer is not particularly limited, but is preferably 30 μm or more and 150 μm or less, and more preferably 50 μm or more and 140 μm or less. When the thicknesses of the A layer and the B layer are within the above ranges, the strength of the film body can be sufficiently maintained. The total thickness of the layer A and the layer B is preferably 35 μm or more and 200 μm or less, and more preferably 55 μm or more and 190 μm or less.

(B layer (sulfonic acid layer))
In the case of a multilayer structure membrane having two or more layers, at least one layer (layer A) is a cation exchange membrane containing the fluorine-containing polymer A of the present embodiment, and the remaining layers are the following sulfonic acid layers. It is preferable that at least one layer or more is contained as the B layer. The B layer (sulfonic acid layer) does not contain a vinyl compound (II) having a carboxylic acid group, and is a fluorine-containing polymer containing a vinyl fluoride compound (I) and a vinyl compound having a sulfonic acid group as constituents. It is a layer containing B. In the multilayer structure membrane, if at least one layer is the above-mentioned B layer (sulfonic acid layer), the multilayer structure membrane can exhibit suitable strength and low electrolytic voltage. Examples of the vinyl compound having a sulfonic acid group include those exemplified in the above-mentioned "Vinyl compound having a sulfonic acid group".

Further, when the multilayer structure film contains two or more layers of B (sulfonic acid layer), each of the two or more layers of B is a cation containing a fluorine-containing polymer B having a different monomer as a constituent component. It may be an exchange membrane, or it may be a cation exchange membrane containing a fluorine-containing polymer B having the same monomer as a constituent. Further, in the case of a cation exchange membrane containing a fluorine-containing polymer B containing the same monomer as a constituent component, different total ion exchange capacities may be used.

The multilayer structure film preferably has a two-layer structure of an A layer and a B layer. The layer A is a cation exchange membrane containing the fluorine-containing polymer A of the present embodiment. The B layer is preferably a cation exchange membrane (sulfonic acid layer) containing the above-mentioned fluorine-containing polymer B. If the B layer is a cation exchange membrane containing the fluorine-containing polymer B, the two-layer structure membrane can exhibit suitable strength and low electrolytic voltage.

(Reinforced core material)
The cation exchange membrane of the present embodiment preferably contains a reinforced core material in the membrane. The reinforced core material can enhance the strength and dimensional stability of the ion exchange membrane, and is preferably present inside the membrane body. The reinforced core material is preferably a woven fabric woven with reinforced yarn. The material of the reinforced core material is preferably a fiber made of a fluorine-based polymer because it needs to have long-term heat resistance and chemical resistance. The material of the reinforcing core material is not particularly limited, and for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), and the like. Examples thereof include a tetrafluoroethylene-hexafluoropropylene copolymer, a trifluorochloroethylene-ethylene copolymer and a vinylidene fluoride polymer (PVDF). In particular, it is preferable to use a fiber made of polytetrafluoroethylene.

The yarn diameter of the reinforced core material is preferably 20 to 300 denier, more preferably 50 to 250 denier, and the weaving density (number of threads per unit length) is preferably 5 to 50 threads / inch. Examples of the shape of the reinforced core material include woven fabric, non-woven fabric, and knitted fabric, but the shape of the woven fabric is preferable. The thickness of the woven fabric is preferably 30 to 250 μm, more preferably 30 to 150 μm.

The woven fabric or knitted fabric is not particularly limited, and for example, monofilament, multifilament, or these yarns, slit yarns, etc. are used, and the weaving method is various weaves such as plain weave, entwined weave, knitted weave, cord weave, and shasacka. Is used.

The aperture ratio of the reinforced core material is not particularly limited, but is preferably 30% or more, more preferably 50% or more, and 90% or less. The aperture ratio is preferably 30% or more from the viewpoint of the electrochemical properties of the ion exchange membrane, and 90% or less from the viewpoint of the mechanical strength of the membrane. The aperture ratio is the ratio of the total area (S2) through which substances such as ions can pass to the total surface area (S1) of the ion exchange membrane, and is represented by (S2) / (S1). (S2) is the total area of the region of the ion exchange membrane in which ions, the electrolytic solution, and the like are not blocked by the reinforcing core material, the reinforcing yarn, and the like contained in the ion exchange membrane. The method for measuring the aperture ratio is as follows. That is, the transmission image of the ion exchange membrane (removes the coating or the like that interferes with the acquisition of the transmission image) is taken from the film surface direction, and the core material (sacrificial core material and communication holes are not included) does not exist. The above (S2) can be obtained from the area of the portion. Then, the above (S1) is obtained from the area of the surface image of the ion exchange membrane, and the aperture ratio is obtained by dividing the above (S2) by the above (S1).

Among these various reinforced core materials, a particularly preferable form is, for example, a tape yarn obtained by slitting a high-strength porous sheet made of PTFE into a tape shape. Alternatively, as the reinforcing core material, 50 to 300 denier of highly oriented monofilament made of PTFE is used, the weave density is 10 to 50 lines / inch, and the thickness is in the range of 50 to 100 μm. And the opening ratio is preferably 60% or more.

Further, the woven fabric may contain auxiliary fibers usually called a sacrificial core material for the purpose of preventing the reinforcing core material from being misaligned in the film manufacturing process. By including this sacrificial core material, a communication hole can be formed in the cation exchange membrane.

The sacrificial core material has solubility in the manufacturing process of the membrane or in an electrolytic environment, and is not particularly limited, and for example, rayon, polyethylene terephthalate (PET), cellulose, polyamide and the like are used. The mixed weaving amount in this case is preferably 10 to 80% by mass, more preferably 30 to 70% by mass of the woven fabric or the entire knitted fabric.

(Communication hole)
The cation exchange membrane of the present embodiment may have a communication hole in the membrane. In the present embodiment, the communication hole means a hole that can serve as a flow path for cations and an electrolytic solution generated during electrolysis. By forming the communication holes, the mobility of alkaline ions and the electrolytic solution generated during electrolysis tends to be further improved. The shape of the communication hole is not particularly limited, but according to the manufacturing method described later, the shape of the sacrificial core material used for forming the communication hole can be used.

In the present embodiment, the communication holes are preferably formed so as to alternately pass through the anode side and the cathode side of the reinforced core material. With such a structure, in the portion where the communication hole is formed on the cathode side of the reinforced core material, the cations (for example, sodium ion) transported through the electrolytic solution filled in the communication hole are reinforced. It can also flow to the cathode side of the core material. As a result, the flow of cations is not blocked, so that the electrical resistance of the ion exchange membrane tends to be further reduced. FIG. 1 shows a schematic cross-sectional view of the ion exchange membrane 1. Reference numerals 2a and 2b indicate communication holes, reference numeral 3 indicates a reinforcing core material, reference numeral 4 indicates a layer A, reference numeral 5 indicates a layer B, and reference numerals 6 and 7 indicate a coating layer. Reference numeral 8 indicates a portion of the A layer facing the anode side surface. The reinforcing core material 3 is, for example, a woven fabric of PTFE monofilament, and for example, PET fibers are woven between the monofilaments in the same manner as the monofilament. The same applies to the warp and weft threads. As shown in FIG. 1, the communication holes 2a and 2b are formed so as to alternately pass through the anode (α) side and the cathode (β) side of the reinforcing core material 3.

(coating)
By having the coating layer, the cation exchange membrane of the present embodiment can prevent gas from adhering to the cathode side surface and the anode side surface during electrolysis.

The material constituting the coating layer is not particularly limited, but preferably contains an inorganic substance from the viewpoint of preventing gas adhesion. Examples of the inorganic substance include zirconium oxide and titanium oxide. The method for forming the coating layer on the film body is not particularly limited, and a known method can be used. For example, a method of applying a liquid in which fine particles of an inorganic oxide are dispersed in a binder polymer solution by spraying or the like can be mentioned.

Examples of the binder polymer include vinyl compounds having a functional group that can be converted into a sulfone-type ion exchange group. The coating conditions are not particularly limited, and for example, a spray can be used at 30 to 90 ° C. Examples of methods other than the spray method include roll coating and the like.

The average thickness of the coating layer is preferably 1 to 10 μm from the viewpoint of preventing gas adhesion and increasing electrical resistance due to the thickness.

Subsequently, a method for producing the cation exchange membrane of the present embodiment will be described.

[Manufacturing method of ion exchange membrane]
The method for producing the ion exchange membrane of the present embodiment is not particularly limited, but it is preferable to have the following steps 1) to 5).
1) A step of producing a fluorine-containing polymer having an ion-exchange group or an ion-exchange group precursor that can become an ion-exchange group by hydrolysis (polymer production step).
2) The process of obtaining a reinforced core material woven with sacrificial yarn (manufacturing process of reinforced core material) and
3) A step of filming a fluorine-containing polymer having an ion exchange group or an ion exchange group precursor that can become an ion exchange group by hydrolysis (film formation step).
4) A step of embedding the reinforced core material and the film to form a composite film (embedding step).
5) A production method including a step of hydrolyzing the composite film with an acid or an alkali (hydrolysis step) is preferable.

Among the above steps, the cation exchange membrane of the present embodiment controls the composition of the fluorine-containing polymer in, for example, the polymer production step of 1). Hereinafter, each step will be described in detail.

1) Process (polymer manufacturing process)
The cation exchange membrane containing the fluorine-containing polymer having an ion exchange group of the present embodiment is not particularly limited, but as described above, it is composed of at least one monomer selected from the vinyl compound (I). , Vinyl compound (II) and at least one monomer selected from vinyl compound (III) can be produced by copolymerizing. As for the vinyl compound (III), two or more kinds can be selected and copolymerized.

For example, it is composed of a two-layer structure membrane consisting of an A layer and a B layer, and when at least the A layer is the cation exchange membrane of the present embodiment, the A layer can be copolymerized as described above. The polymerization method is not particularly limited, but for example, a polymerization method generally used for the polymerization of ethylene fluoride, particularly tetrafluoroethylene can be used. For example, when polymerizing by the non-aqueous method, an inert solvent such as perfluorohydrocarbon or chlorofluorocarbon is used. Then, the reaction can be carried out under the conditions of a temperature of 0 to 200 ° C. and a pressure of 0.1 to 20 MPa in the presence of a radical polymerization initiator such as a perfluorocarbon peroxide or an azo compound.

In the production of a cation exchange membrane containing a fluorine-containing polymer having an ion exchange group, the type and ratio of the combination of the above-mentioned monomers are not particularly limited, and the type of functional group to be imparted to the obtained fluorine-containing polymer is not particularly limited. It can be appropriately determined depending on the amount and the like.

In the present embodiment, in order to control the total ion exchange capacity of the fluorine-containing polymer, the mixing ratio of the raw material monomers may be adjusted when producing the fluorine-containing polymer forming each layer.

The above-mentioned B layer is a cation containing a fluorine-containing polymer B having a vinyl compound (I) and a vinyl compound having a functional group that can be converted into a sulfonic acid type ion exchange group (sulfonic acid group) as constituents. It is preferably an exchange film (sulfonic acid layer). The sulfonic acid layer does not have to contain the vinyl compound (III).

2) Process (manufacturing process of reinforced core material)
The ion exchange membrane of the present embodiment preferably has a reinforcing core material embedded in the membrane from the viewpoint of further improving the strength of the membrane. When the ion exchange membrane has communication holes, the sacrificial yarn is also woven into the reinforced core material. In this case, the mixed weaving amount of the sacrificial yarn is preferably 10 to 80% by mass, more preferably 30 to 70% by mass of the entire reinforced core material. The sacrificial yarn is preferably polyvinyl alcohol having a thickness of 20 to 50 denier and made of monofilament or multifilament.

3) Process (filming process)
The method for forming the fluorine-containing polymer obtained in the step 1) into a film is not particularly limited, but it is preferable to use an extruder. Examples of the method of making a film include the following methods.

When the present embodiment has, for example, a two-layer structure of an A layer and a B layer, the cation exchange membrane containing the fluorine-containing polymer A of the present embodiment constituting the A layer and the B layer are formed. Examples thereof include a method of separately forming a cation exchange membrane (sulfonic acid layer) containing a fluorine-containing polymer B into a film.

When the B layer has a two-layer structure composed of the fluorine-containing polymer B-1 and the fluorine-containing polymer B-2, for example, the fluorine-containing polymer B-2 and the fluorine-containing polymer A are composited by coextrusion. It is a film. Then, separately, the fluorine-containing polymer B-1 can be independently formed into a film. Alternatively, the fluorine-containing polymer B-1 and the fluorine-containing polymer B-2 are coextruded to form a composite film. Then, separately, the fluorine-containing polymer A can be independently formed into a film. Of these, coextrusion of the fluorine-containing polymer B-2 and the fluorine-containing polymer A is preferable because the adhesive strength at the interface can be increased.

4) Process (embedding process)
In the embedding step, it is preferable to embed the reinforcing core material obtained in the step 2) and the film obtained in the step 3) on a heated drum. On the drum, the pressure is reduced at a temperature at which the fluorine-containing polymer constituting each layer is melted through a heat-resistant paper pattern having air permeability, and the air is embedded and integrated while removing the air between the layers. Thereby, a composite film can be obtained. The drum is not particularly limited, and examples thereof include a drum having a heating source and a vacuum source and having a large number of pores on the surface thereof.

Examples of the order in which the reinforcing core material and the film are laminated include the following methods according to the above 3) step.

When the A layer and the B layer each form a single layer, a method of laminating a paper pattern, an A layer film, a reinforcing core material, and a B layer film on the drum in this order can be mentioned.

When the B layer has a two-layer structure composed of the fluorine-containing polymer B-1 and the fluorine-containing polymer B-2, a release paper, a film of the fluorine-containing polymer B-1 and reinforcement are placed on the drum. The core material, the composite film of the fluorine-containing polymer B-2 and the A layer are laminated in this order. Alternatively, the release paper, the composite film of the fluorine-containing polymer B-1 and the fluorine-containing polymer B-2, the reinforcing core material, and the A layer are laminated on the drum in this order.

Further, in order to provide a convex portion on the film surface of the ion exchange membrane of the present embodiment, a convex portion made of a molten polymer can be formed at the time of embedding by using a pre-embossed paper pattern.

5) Step (hydrolysis step)
The composite membrane obtained in the above step 4) is hydrolyzed with an acid or an alkali. Hydrolysis is carried out, for example, in an aqueous solution of potassium hydroxide (KOH) having a concentration of 2.5 to 4.0 (N) and DMSO (Dimethyl sulfoxide) in an amount of 20 to 40% by mass at 40 to 90 ° C. for 10 minutes to 24. It is preferable to do it for a long time. Then, under the condition of 80 to 95 ° C., it is preferable to carry out the salt exchange treatment using a 0.5 to 0.7 equivalent (N) caustic soda (NaOH) solution. The treatment time of the salt exchange treatment is preferably less than 2 hours from the viewpoint of preventing an increase in the electrolytic voltage.

Subsequently, the electrolytic cell provided with the cation exchange membrane of the present embodiment will be described.

[Electrolytic cell]
The electrolytic cell of the present embodiment includes the cation exchange membrane of the present embodiment. FIG. 2 shows a schematic view of an example of the electrolytic cell of the present embodiment. The electrolytic cell 13 shown in FIG. 2 includes an anode 11, a cathode 12, and a two-layer structure ion exchange membrane 1 (hereinafter referred to as a two-layer structure film 1) arranged between the anode and the cathode. However, the electrolytic cell of the present embodiment is not limited to the electrolytic cell 13 of FIG. 2, and is the cation exchange membrane of the present embodiment or the present embodiment arranged between the anode, the cathode, and the anode and the cathode. It suffices to have a multilayer structure film of.

The two-layer structure film 1 is composed of a layer A, which is a cation exchange membrane containing the fluorine-containing polymer A of the present embodiment, and a layer B (sulfonic acid layer) containing the fluorine-containing polymer B. The A layer is arranged toward the cathode side. The fluorine-containing polymer A of the present embodiment may be a single-layer film, or may have a multi-layer structure of three or more layers. note that. In the case of a multilayer structure of three or more layers, at least one layer is a cation exchange membrane containing the fluorine-containing polymer A of the present embodiment.

In the salt electrolysis using the electrolytic cell shown in FIG. 2, Na ⁺ ions can be passed from the anode chamber side to the cathode chamber side, while OH ⁻ ions move from the anode chamber side to the cathode chamber side. Can be inhibited. Further, in the two-layer structure film 1, by arranging a layer (sulfonic acid layer) containing the fluorine-containing polymer B on the anode side as the B layer, it is possible to further increase the strength and the low electrolytic voltage.

Here, conventionally, a carboxylic acid layer is often used as the A layer facing the cathode side (arranged so as to correspond to the cathode) in the two-layer structure film. However, the carboxylic acid layer has a high crystal index, and the clusters that are the paths of ions have a thin feature. The fact that it does not function as an ion or that the cluster is thin also causes an increase in the electrolytic voltage by obstructing the passage of ions.

On the other hand, in the present embodiment, the above-mentioned cation exchange membrane or the second cation exchange membrane is provided as the cation exchange membrane used as the A layer. As a result, it is possible to achieve both high current efficiency and low electrolytic voltage as compared with the conventional case. Therefore, the required power consumption can be reduced and energy saving can be contributed. This is clearly proved by the experiments described later.

The electrolysis conditions are not particularly limited and can be carried out under known conditions. For example, the anode chamber is supplied with an aqueous alkali chloride solution of 2.5 to 5.5 (N), the cathode chamber is supplied with water or a diluted alkaline aqueous hydroxide solution, the electrolysis temperature is 50 to 120 ° C., and the current density is high. It can be electrolyzed under the condition of 0.5 to 10 kA / m ^2.

The configuration of the electrolytic cell of the present embodiment is not particularly limited, and may be, for example, a single pole type or a double pole type. The material constituting the electrolytic cell is not particularly limited, but for example, the material of the anode chamber is preferably titanium which is resistant to alkali chloride and chlorine, and the material of the cathode chamber is resistant to alkali hydroxide and hydrogen. Chloride or the like is preferable. The electrodes may be arranged with an appropriate distance between the ion exchange membrane and the anode, but the anode and the ion exchange membrane may be arranged in contact with each other. Further, the cathode is generally arranged at an appropriate interval from the ion exchange membrane, but may be a contact type electrolytic cell (zero gap type electrolytic cell) having no such interval.

The salt electrolysis process conditions are not particularly limited, but the salt water concentration in the anode chamber is 180 to 215 g / L, preferably 185 to 205 g / L. The concentration of the cathode liquid is 28 to 35%, preferably 30 to 33%. Further, the current density is 1 to 6 kA / m ² , and the temperature is 70 to 90 ° C. The type of the electrolytic cell, the feeding method, or the type of the electrode can be applied to all known types and methods, but in particular, the cation exchange membrane of the present embodiment has a wide range from the finite gap to the zero gap electrode arrangement. Can be applied.

Hereinafter, the present embodiment will be described in detail with reference to Examples. The present embodiment is not limited to the following examples.

In Examples and Comparative Examples, the ion cluster diameter, crystal index, water content, and ion exchange group concentration were measured, respectively.

These measurement methods are described in detail in [Measurement method of cluster diameter], [Measurement method of crystal index], [Water content], and [Ion exchange group concentration], so refer to them.

[Electrolytic performance evaluation]
It is necessary to perform electrolysis under the following conditions using the electrolytic cell shown in FIG. 2 (the A layer of the ion exchange membrane faces the cathode side) to produce 1 ton of NaOH based on the electrolysis voltage and current efficiency. The electrolytic performance was evaluated based on the amount of electricity consumed.
The power consumption is preferably less than 2100 (kWh) as the electrolytic performance, and more preferably less than 2090 (kWh).

[Measurement of electrolytic voltage]
The electrolytic cell used for electrolysis has a structure in which an ion exchange membrane is arranged between the anode and the cathode, and four naturally circulating zero-gap electrolytic cells are arranged in series. As the cathode, a woven mesh was used in which fine nickel wires having a diameter of 0.15 mm coated with cerium oxide and ruthenium oxide were woven with 50 mesh openings as a catalyst. In order to bring the cathode and the ion exchange membrane into close contact with each other, a mat woven with fine nickel wires was placed between the current collector made of nickel expanded metal and the cathode. As the anode, an expanded metal made of titanium coated with ruthenium oxide, iridium oxide and titanium oxide was used as a catalyst. Using the above electrolytic cell, salt water was supplied to the anode side while adjusting the concentration to 205 g / L, and water was supplied while maintaining the caustic soda concentration on the cathode side at 32% by mass. The temperature of the electrolytic cell was set to 85 ° C., ^{and electrolysis was performed at a current density of 6 kA / m 2 under} the condition that the hydraulic pressure on the cathode side of the electrolytic cell was 5.3 kPa higher than the hydraulic pressure on the anode side. The pair-to-cathode voltage between the positive and negative electrodes of the electrolytic cell was measured daily with a KEYENCE voltmeter TR-V1000, and the average value for 7 days was determined as the electrolytic voltage.

The current efficiency was determined by measuring the mass and concentration of the caustic soda produced and dividing the number of moles of caustic soda produced in a certain period of time by the number of electrons of the current flowing during that period.

[Measurement of total ion exchange capacity]
The obtained film was measured with a transmission infrared spectroscopic analyzer (FTIR-4200 manufactured by JASCO Corporation). From the heights of the obtained infrared peaks CF ₂ , COO ⁻ , COOCH ₃ , and SO ₂ F, the ratio of structural units having groups that can be converted into carboxylic acid functional groups and sulfonic acid functional groups was calculated. These are used as the ratio of the structural units having the carboxylic acid functional group and the sulfonic acid functional group of the polymer obtained by hydrolyzing the fluoropolymer, and the sample having the known ion exchange capacity calculated by the titration method is used as the calibration line. The ion exchange capacity was determined.

[Example 1]
As the fluorine-containing polymer A forming the A layer, the following general formula:
CF ₂ = CX ₁ X ₂ (1)
Monomer represented by (X ₁ = F, X ₂ = F) and the following general formula:
CF ₂ = CF- (OCF ₂ CYF) _a- O- (CF ₂ ) _b- COOR (2)
The monomers represented by (a = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the following general formula:
CF ₂ = CF- (OCF ₂ CYF) _c- O- (CF ₂ ) _d- SO ₂ F (3)
The monomer represented by (c = 1, d = 2, Y = CF ₃ ) was copolymerized at a molar ratio of 87.6: 11.2: 1.2, and the total ion exchange capacity was 0.88 m equivalent. A / g polymer was obtained. The total ion exchange capacity is represented by the ion exchange group derived from the monomer (a = 1, b = 2, Y = CF ₃ , R = CH ₃ ) represented by the general formula (2) and the general formula (3). It is the sum of the ion exchange groups derived from the monomers (c = 1, d = 2, Y = CF _{3) to be produced.} The total ion exchange capacity was also confirmed in the following examples and comparative examples. In addition, the molar ratio in the polymer was confirmed by IR using (Method 1) and (Method 2) from the height of the peak derived from each monomer.
(Method 1)
_{From the peak height of CF 2} derived peak wave number 2362.37 +/- 5 cm ^-1 in the general formula (1) and the peak height of COO ⁻ derived peak wave number 2967.91 +/- 5 cm ^{-1 in} the general formula (2). , The ratio of the general formula (1) and the general formula (2) was calculated based on the calibration curve obtained by using a copolymer whose content is known. Also, the peak height of the COOCH ₃ from the peak wavenumber 1,444.8 +/- ^{5 cm -1} in the general formula (2), from the general formula (3) in the SO ₂ peak wavenumber 1467.8 +/- ^{5 cm -1} height F , The ratio of the general formula (2) and the general formula (3) was calculated based on the calibration curve obtained by using a copolymer whose content is known. The ratio of the general formula (1), the general formula (2), and the general formula (3) was calculated from the calculated values.
(Method 2)
From the polymer after saponification, the molar ratios of the general formula (1), the general formula (2), and the general formula (3) were calculated. After saponification, the structures of the general formula (2) and the general formula (3) become the structures of the following general formula (2)'and the following general formula (3)', so that the general formula (1) and the general formula (1) The molar ratios of 2) and the general formula (3) were calculated from the same molar ratios of the general formula (1), the general formula (2)'and the general formula (3)'. The molar ratio was calculated from the height of the peak derived from each monomer by IR. A peak height of CF ₂ derived peak wavenumber 2362.37 +/- ^{5 cm -1} in the general formula (1), from the peak heights of the general formula (2) from COONa in 'peak wavenumber 1,022.3 +/- ^{5 cm -1} , The ratio of the general formula (1) and the general formula (2)'was calculated based on the calibration curve obtained by using a copolymer whose content is known. Further, the peak wave number _{of CF 2} derived from CF 2 in the general formula (1) is ^{2362.37 +/- 5 cm -1} , and the peak wave number _{of SO 3} ⁻ in the general formula (3)'is ^{1064.7 +/- 5 cm -1} height. Therefore, the ratio of the general formula (1) and the general formula (3)'was calculated based on the calibration curve obtained by using a copolymer whose content is known. The ratio of the general formula (1), the general formula (2)'and the general formula (3)' was calculated from the respective calculated values.
General formula (2)':
CF ₂ = CF- (OCF ₂ CYF) _a- O- (CF ₂ ) _b- COONa
Monomer represented by (a = 1, b = 2, Y = CF ₃ , R = CH ₃ )
General formula (3)':
CF ₂ = CF- (OCF ₂ CYF) _c- O- (CF ₂ ) _d- SO ₃ Na
Monomer represented by (c = 1, d = 2, Y = CF ₃ )

As a result of comparing the molar ratios of the general formula (1), the general formula (2), and the general formula (3) calculated by (method 1) and (method 2), it was confirmed that the values were the same.

In addition, except for the fluorine polymer A of Example 8, the molar ratio in the polymer was also confirmed in the following Examples and Comparative Examples.

As the fluorine-containing polymer B forming the B layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (3) (c). = 1, d = 2, Y = CF ₃ ) were copolymerized at a molar ratio of 5: 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The fluorine-containing polymer A was prepared in more detail by the solution polymerization shown below.

_{First, CF 2} = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH ₃ and CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ SO ₂ F and CF ₃ CHFCHFCF in a stainless steel 20L autoclave. _{2 A} CF ₃ (HFC43-10mee) solution was charged, and the inside of the container was sufficiently replaced with nitrogen. Then, it was further _{replaced with CF 2} = CF ₂ (TFE), heated until the temperature inside the container became stable at 35 ° C., and pressurized with TFE.

Then, a 5% HFC43-10mee solution _{of (CF 3} CF ₂ CF ₂ COO) ₂ was added as a polymerization initiator to initiate the reaction. While intermittently feeding TFE with stirring at 35 ° C., _{a 5% HFC43-10methanol solution of (CF 3} CF ₂ CF ₂ COO) ₂ was added in the middle, the TFE pressure was lowered, and a predetermined amount of TFE was supplied. Then, methanol was added to stop the polymerization. After releasing the unreacted TFE out of the system, the obtained polymerization solution was dried under reduced pressure to distill off the unreacted monomer and HFC43-10mee to obtain a fluorine-containing polymer A. The obtained fluorine-containing polymer A was pelletized by a twin-screw devolatilization extruder.

Further, the fluorine-containing polymer B was obtained by the same method as that of the polymer A except _{that CF 2} = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH _{3 was not charged.}

The obtained fluorine-containing polymer A and fluorine-containing polymer B were jointly pressed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and the thickness was 170 μm. A layered film was obtained. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 85 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 mg equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine-containing polymer layer A of this ion exchange membrane was 3.11 nm in a pure water atmosphere, and the crystal index was 0.07 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2086 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 2]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2). (A = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ). The same procedure as in Example 1 was carried out except that the polymer was copolymerized at a molar ratio of 87.37: 12.38: 0.25 to obtain a polymer having a total ion exchange capacity of 0.90 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 60 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.15 nm in a pure water atmosphere, and the crystal index was 0.075 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2084 (kWh).} As described above, the power consumption was less than 2100 (kWh), and low power consumption was exhibited.

[Example 3]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2). (A = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ). The same procedure as in Example 1 was carried out except that the polymer was copolymerized at a molar ratio of 86.9: 11.9: 1.2 to obtain a polymer having a total ion exchange capacity of 0.92 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 50 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.13 nm in a pure water atmosphere, and the crystal index was 0.064 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2075 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 4]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2). (A = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) are polymerized. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at a ratio of 86.2: 13.3: 0.5 to obtain a polymer having a total ion exchange capacity of 0.95 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 60 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.21 nm in a pure water atmosphere, and the crystal index was 0.057 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2084 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 5]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2). (A = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) are polymerized. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at a ratio of 86.3: 12.5: 1.2 to obtain a polymer having a total ion exchange capacity of 0.95 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 65 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.24 nm in a pure water atmosphere, and the crystal index was 0.059 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2065 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 6]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2). (A = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) are polymerized. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at a ratio of 85.2: 14.6: 0.2 to obtain a polymer having a total ion exchange capacity of 1.00 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 85 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.34 nm in a pure water atmosphere, and the crystal index was 0.046 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2071 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 7]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2). (A = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) are polymerized. Copolymerization was carried out at a ratio of 88.1: 10.1: 1.8 to obtain a polymer having a total ion exchange capacity of 0.86 m equivalent / g in the same manner as in Example 1.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 85 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.12 nm in a pure water atmosphere, and the crystal index was 0.08 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2084 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 8]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the following general formula (4) (e = 1, f = 2, Y = CF _{3) in molar ratio.} The same procedure as in Example 1 was carried out except that the polymer was copolymerized at 87.0: 12.6: 0.4 to obtain a polymer having a total ion exchange capacity of 0.89 m equivalent / g.
CF ₂ = CF- (OCF ₂ CYF) _e- O- (CF ₂ ) _{f- CF 3} (4)

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 50 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.13 nm in a pure water atmosphere, and the crystal index was 0.075 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2089 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 9]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) in a molar ratio of 86. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at 9: 11.9: 1.2 to obtain a polymer having a total ion exchange capacity of 0.92 m equivalent / g.

The fluorine-containing polymer B-1 forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

Further, as the fluorine-containing polymer B-2 forming the B layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the simple compound represented by the general formula (3). Examples except that a polymer (c = 1, d = 2, Y = CF ₃ ) was copolymerized at a molar ratio of 5.7: 1 to obtain a polymer having a total ion exchange capacity of 0.98 m equivalent / g. Same as 1.

Fluorine polymer A and fluorine polymer B-2 are prepared and co-pushed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and two layers having a thickness of 93 μm are used. I got a film. As a result of observing the cross section of the film with an optical microscope, the thickness of the fluorine-containing polymer layer B-2 was 80 μm, and the thickness of the layer A was 13 μm. Further, a single-layer film of layer B-1 having a thickness of 20 μm was obtained with a single-layer T-die.

Subsequently, a breathable heat-resistant paper pattern, a single-layer film, a reinforced core material, and a two-layer film were laminated in this order on a drum having a heating source and a vacuum source inside and having a large number of micropores on the surface. .. Then, under a temperature of 230 ° C. and a reduced pressure of −650 mmHg, the materials were integrated while removing air between the materials to obtain a composite film. The B layer in the obtained composite film contains the reinforcing core material as described above, but in the table below, the thickness of the B layer is described as 100 μm as the thickness excluding the thickness of the reinforcing core material. bottom.

The reinforced core material used in the above was as follows. Polytetrafluoroethylene (PTFE) 100 denier tape yarn is twisted 900 times / m to form a yarn, and 30 denier, 6 filament polyethylene terephthalate (PET) is used as the warp of the auxiliary fiber (sacrificial yarn). Prepare one with a twist of times / m, 35 denier as a weft, and one with a twist of 10 times / m on an 8-filament PET yarn, and sacrifice these yarns with 24 PTFE yarns / inch. A woven fabric having a thickness of 100 μm was obtained by plain weaving in an alternating arrangement so that the yarns were 64 threads / inch, which was four times that of PTFE. The obtained woven fabric was crimped with a heated metal roll to adjust the thickness of the woven fabric to 70 μm. At this time, the aperture ratio of only the PTFE yarn was 75%.

This composite membrane was saponified by immersing it in an aqueous solution at 60 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.13 nm in a pure water atmosphere, and the crystal index was 0.064 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2001 (kWh).} in this way. It was less than 2100 (kWh) and exhibited low power consumption.

[Example 10]
As the fluorine-containing polymer A, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a = 1, b = 2). , Y = CF ₃ , R = CH ₃ ) were copolymerized at a molar ratio of 87.3: 12.7 to obtain a polymer having a total ion exchange capacity of 0.90 m equivalent / g.

The fluorine-containing polymer A was prepared in more detail by the solution polymerization shown below.

_{First, CF 2} = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH ₃ and HFC-43-10mee solution are charged in a stainless steel 20L autoclave, and the inside of the container is sufficiently replaced with nitrogen, and then CF ₂ = It _{was replaced with CF 2} (TFE), warmed until the temperature inside the container became stable at 35 ° C., and pressurized with TFE.

Then, a 5% HFC43-10mee solution _{of (CF 3} CF ₂ CF ₂ COO) ₂ was added as a polymerization initiator to initiate the reaction. At this time, methanol was added as a chain transfer agent. While intermittently feeding TFE with stirring at 35 ° C., methanol was added in the middle to lower the TFE pressure, and polymerization was stopped when a predetermined amount of TFE was supplied. After releasing the unreacted TFE out of the system, methanol was added to the obtained polymerization solution to aggregate and separate the fluorine-containing polymer. Further, after drying, a fluorine-containing polymer A was obtained. The obtained fluorine-containing polymer was pelletized by a twin-screw extruder.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 50 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.13 nm in a pure water atmosphere, and the crystal index was 0.087 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2097 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 11]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the following general formula (5) (g = 2) in a molar ratio of 88.2: 10.4: 1 The same procedure as in Example 1 was carried out except that the polymer was copolymerized in No. 4 to obtain a polymer having a total ion exchange capacity of 0.87 m equivalent / g.
CF ₂ = CF-O- (CF ₂ ) _g- SO ₂ F (5)

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having an exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 75 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.05 nm in a pure water atmosphere, and the crystal index was 0.087 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2084 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Example 12]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the following general formula (5) (g = 2) in a molar ratio of 87.0: 11.9: 1. The same procedure as in Example 1 was carried out except that the polymer was copolymerized in Section 1 to obtain a polymer having a total ion exchange capacity of 0.93 m equivalent / g.
CF ₂ = CF-O- (CF ₂ ) _g- SO ₂ F (5)

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having an exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 50 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.24 nm in a pure water atmosphere, and the crystal index was 0.071 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 1. As shown in Table 1, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2087 (kWh).} As described above, it was less than 2100 (kWh), and low power consumption was exhibited.

[Comparative Example 1]
As the fluorine-containing polymer A, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a = 1, b = 2). , Y = CF ₃ , R = CH ₃ ) were copolymerized at a molar ratio of 88.3: 11.7 to obtain a polymer having a total ion exchange capacity of 0.85 m equivalent / g.

The fluorine-containing polymer A was prepared in more detail by the solution polymerization shown below.

_{First, CF 2} = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH ₃ and HFC-43-10mee solution are charged in a stainless steel 20L autoclave, and the inside of the container is sufficiently replaced with nitrogen, and then CF ₂ = It _{was replaced with CF 2} (TFE), warmed until the temperature inside the container became stable at 35 ° C., and pressurized with TFE.

Then, a 5% HFC43-10mee solution _{of (CF 3} CF ₂ CF ₂ COO) ₂ was added as a polymerization initiator to initiate the reaction. At this time, methanol was added as a chain transfer agent. While intermittently feeding TFE with stirring at 35 ° C., methanol was added in the middle to lower the TFE pressure, and polymerization was stopped when a predetermined amount of TFE was supplied. After releasing the unreacted TFE out of the system, methanol was added to the obtained polymerization solution to aggregate and separate the fluorine-containing polymer. Further, after drying, a fluorine-containing polymer A was obtained. The obtained fluorine-containing polymer was pelletized by a twin-screw extruder.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine-containing polymer A and fluorine-containing polymer B were jointly pressed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and the thickness was 170 μm. A layered film was obtained. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 85 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and F ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 2.96 nm in a pure water atmosphere, and the crystal index was 0.094 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2142 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

[Comparative Example 2]
As the fluorine-containing polymer A, the monomer (X ₁ = F, X ₂ = F) represented by the general formula (1) and the monomer (a = 1, b =) represented by the general formula (2). 2, Y = CF ₃ , R = CH ₃ ) were copolymerized at a molar ratio of 89.2: 10.8 to obtain a polymer having a total ion exchange capacity of 0.80 m equivalent / g, which was the same as in Comparative Example 1. I made it.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and a two-layer film having a thickness of 170 μm is formed. Got As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane is hydrolyzed in an aqueous solution containing 30 wt% DMSO and 15 wt% KOH at a temperature of 75 ° C. for 45 minutes, washed with water, converted to Na type with 0.5 N NaOH at 85 ° C., and finally 2 at 25 ° C. Equilibration treatment was performed with% NaOHCO _3.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 2.75 nm in a pure water atmosphere, and the crystal index was 0.102 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2149 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

[Comparative Example 3]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) in a molar ratio of 81. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at .7: 13.4: 4.9 to obtain a polymer having a total ion exchange capacity of 1.14 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine-containing polymer A and fluorine-containing polymer B were jointly pressed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and the thickness was 170 μm. A layered film was obtained. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 60 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine-containing polymer A of this ion exchange membrane was 3.72 nm in a pure water atmosphere, and the crystal index was 0.021 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated by the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2210 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

[Comparative Example 4]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) in a molar ratio of 80. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at 2: 10.9: 8.9 to obtain a polymer having a total ion exchange capacity of 1.19 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine-containing polymer A and fluorine polymer B are co-pressed by a device equipped with two extruders, a T-die for co-extrusion for two layers, and a take-up machine, and two layers having a thickness of 170 μm. I got a film. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 60 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.76 nm in a pure water atmosphere, and the crystal index was 0.010 or less in a dry atmosphere, which could not be measured.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2322 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

[Comparative Example 5]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (3) (c = 1, d = 2, Y = CF ₃ ) in a molar ratio of 78. The same procedure as in Example 1 was carried out except that the polymer was copolymerized at .5: 18.0: 3.6 to obtain a polymer having a total ion exchange capacity of 1.26 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine-containing polymer A and fluorine-containing polymer B were jointly pressed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and the thickness was 170 μm. A layered film was obtained. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 50 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₃ SO ₂ having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. A fluorine-based polymer having a sulfonic acid group obtained by hydrolyzing the F copolymer was dissolved in an amount of 20% by mass. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.74 nm in a pure water atmosphere, and the crystal index was 0.018 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2526 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

[Comparative Example 6]
As the fluorine-containing polymer A, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a = 1, b = 2). , Y = CF ₃ , R = CH ₃ ) was copolymerized at a molar ratio of 87.5: 12.5 to obtain a polymer having a total ion exchange capacity of 0.89 m equivalent / g, which was the same as in Comparative Example 1. I made it.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine-containing polymer A and fluorine-containing polymer B were jointly pressed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and the thickness was 170 μm. A layered film was obtained. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane is hydrolyzed at a temperature of 50 ° C. for 24 hours in an aqueous solution containing 30% by mass of DMSO and 4.0 eq (N) KOH, and then a 0.6 eq (N) NaOH solution under 90 ° C. conditions. Was used for salt exchange treatment.

_{CF 2} = CF ₂ and CF ₂ = CFO _{CF 2} CF (CF ₃ ) O (CF ₂ ) ₃ SO having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. a copolymer of _{2 F} the fluorinated polymer having a hydrolyzable to become sulfonic acid groups was dissolved 20% by weight. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.10 nm in a pure water atmosphere, and the crystal index was 0.09 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2150 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

[Comparative Example 7]
As the fluoropolymer A forming the A layer, the monomer represented by the general formula (1) (X ₁ = F, X ₂ = F) and the monomer represented by the general formula (2) (a). = 1, b = 2, Y = CF ₃ , R = CH ₃ ) and the monomer represented by the general formula (5) (g = 2) in a molar ratio of 83.0: 9.4: 7. The same procedure as in Example 1 was carried out except that the polymer was copolymerized in No. 6 to obtain a polymer having a total ion exchange capacity of 1.25 m equivalent / g.

The fluorine-containing polymer B forming the B layer was the same as in Example 1 to obtain a polymer having a total ion exchange capacity of 1.05 m equivalent / g.

The obtained fluorine-containing polymer A and fluorine-containing polymer B were jointly pressed by a device equipped with two extrusion machines, a T-die for co-extrusion for two layers, and a take-up machine, and the thickness was 170 μm. A layered film was obtained. As a result of observing the cross section of the film with an optical microscope, the thickness of the A layer was 35 μm and the thickness of the B layer was 135 μm.

This composite membrane was saponified by immersing it in an aqueous solution at 50 ° C. containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) for 1 hour. Then, it was immersed in an aqueous solution containing 0.5 N of sodium hydroxide (NaOH) at 50 ° C. for 1 hour to replace the counter ion of the ion exchange group with Na, and then washed with water. It was further dried at 60 ° C.

_{CF 2} = CF ₂ and CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₃ SO ₂ having a total ion exchange capacity of 1.0 m equivalent / g in a mixed solution of 50/50 parts by mass of water and ethanol. A fluorine-based polymer having a sulfonic acid group obtained by hydrolyzing the F copolymer was dissolved in an amount of 20% by mass. 40% by mass of zirconium oxide having an average primary particle size of 1 μm was added to the solution, and a suspension uniformly dispersed by a ball mill was obtained. A coating layer was formed by applying this suspension to both surfaces of the ion exchange membrane after the hydrolysis and salt exchange treatment by a spray method and drying it.

The ion cluster diameter of the fluorine polymer layer A of this ion exchange membrane was 3.69 nm in a pure water atmosphere, and the crystal index was 0.028 in a dry atmosphere.

The ion exchange membrane obtained as described above was electrolyzed and evaluated. These results are shown in Table 2. As shown in Table 2, when the electrolytic performance was evaluated with the power consumption required to produce 1 ton of NaOH at a current density of 6 ^{kA / m 2, it was 2318 (kWh).} In this way, it became 2100 (kWh) or more, resulting in high power consumption.

Tables 1 and 2 show the composition, characteristics, etc. of the ion exchange membranes produced in each Example and Comparative Example.

As shown in Tables 1 and 2, it was found that the power consumption of the examples was lower than that of the comparative examples. In the embodiment, both low electrolytic voltage and high current efficiency can be achieved at the same time. As described above, it was found that it is preferable to control the cluster diameter and the crystal index in order to achieve both low electrolytic voltage and high current efficiency.

As shown in Table 1, in this example, the cluster diameter measured in a pure water atmosphere is in the range of 3.0 nm or more and 3.5 nm or less, and the crystal index measured in a dry atmosphere is 0.03 or more and 0.03 or more. It was found to be in the range less than 09. On the other hand, in the comparative example, it was found that either or both of the cluster diameter and the crystal index of this example were outside these numerical ranges.

Further, in Examples 1 to 9, 11 and 12, the value obtained by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) was larger than 0, 3.0 × ^10-2. It was found to be in the following range. On the other hand, in Examples 10 and Comparative Examples 1 to 7, the values of (III) / (I) were larger than 0 ^{and out of the range of 3.0 × 10-2} or less, and the physical properties were balanced in Examples. It was found that 1 to 9, 11 and 12 were superior. In Example 10, although the above value is 0, the ion cluster diameter and the crystal index satisfy the predetermined ranges, so that the physical property balance is superior to those of Comparative Examples 1 to 7 which do not satisfy the predetermined ranges.

Further, in this example, it was found that the total ion exchange capacity in the layer A was in the range of 0.5 mg equivalent / g or more and 1.2 mg equivalent / g or less.

Further, in this example, it was found that the ion exchange group concentration in the A layer measured in a NaOH 32% atmosphere was in the range of 12 mol / L or more and 50 mol / L or less.

The cation exchange membrane and the multilayer structure membrane in the present invention are used, for example, for fuel cells, water electrolysis, steam electrolysis, or salt electrolysis, and are particularly preferably used for salt electrolysis.

1 Two-layer structure membrane (ion exchange membrane)
2a, 2b Communication hole 3 Reinforced core material 4 A layer 5 B layer 6, 7 Coating layer 8 A-layer facing the anode side surface 11 Anode 12 Cathode 13 Electrolytic cell

Claims (15)

A cation exchange membrane containing a fluorine-containing polymer having an ion exchange group.
The crystal index before energization is in the range of less than 0.09,
Crystalline index was measured in a dry atmosphere, the product of the water content measured at 85 ° C. pure water, is 1.0 or more, the water content Ri range der of 25% or less,
The fluorine-containing polymer having an ion exchange group is a vinyl fluoride compound (I), a vinyl compound (II) having a carboxylic acid group, and a vinyl compound (III) different from the above (I) and the above (II). And, as a monomer component,
The vinyl compound (III) is selected from the group consisting of 1-trifluorovinyloxy-2-heptafluoropropoxyhexafluoropropane, perfluoroalkyl vinyl ether, perfluorodioxol, and a vinyl compound having a sulfonic acid group. One or more cation exchange membranes. The cation exchange membrane according to claim 1 , wherein the vinyl compound (II) having a carboxylic acid group is a compound represented by the following formula (X).
CF ₂ = CF (OCF ₂ CYF) _n- O (CF ₂ ) _m- COOR (X)
(N represents an integer of 1, m represents an integer of 1 to 4, Y represents F or CF ₃ , R represents CH ₃ , C ₂ H ₅ , or C ₃ H ₇ ) The cation exchange membrane according to claim 1 or 2 , wherein the vinyl compound (III) is a vinyl compound having a sulfonic acid group. Any of claims 1 to 3 in which the value obtained by dividing the molar ratio of the vinyl compound (III) by the molar ratio of the vinyl fluoride compound (I) is greater than 0 and in ^{the range of 3.0 × 10-2 or less.} The cation exchange membrane according to item 1. Claim that the value obtained by dividing the molar ratio of the vinyl compound (III) by the total of the molar ratios of the vinyl compound (II) and the vinyl compound (III) is in the range of 0.001 or more and less than 0.25. The cation exchange membrane according to any one of 1 to 4. The cation exchange membrane according to any one of claims 1 to 5 , wherein the total ion exchange capacity is in the range of 0.66 m equivalent / g or more and 1.2 m equivalent / g or less. The cation exchange membrane according to any one of claims 1 to 6 , wherein the ion exchange group concentration measured in a 32% sodium hydroxide aqueous solution atmosphere is in the range of 12 mol / L or more and 50 mol / L or less. A multilayer structure membrane having at least one A layer composed of the cation exchange membrane according to any one of claims 1 to 7. At least one layer B containing a fluorine-containing polymer B containing a vinyl fluoride compound (I) and a vinyl compound having a sulfonic acid group as monomer components without containing the vinyl compound (II) having a carboxylic acid group. The multilayer structure film according to claim 8, which has layers. The multilayer structure film according to claim 9 , wherein the multilayer structure film has a two-layer structure of the A layer and the B layer. The multilayer structure film according to any one of claims 8 to 10 , wherein the layer A is located in the outermost layer of the multilayer structure film. The cation exchange membrane according to any one of claims 1 to 7 , which is arranged between an anode and a cathode and is used for salt electrolysis. The multilayer structure film according to any one of claims 8 to 11 , which is arranged between an anode and a cathode and is used for salt electrolysis. With the anode
With the cathode
The cation exchange membrane according to any one of claims 1 to 7 or the multilayer structure membrane according to any one of claims 8 to 11 arranged between the anode and the cathode. Electrolytic cell equipped. The multilayer structure film according to any one of claims 8 to 11 is provided.
The electrolytic cell according to claim 14 , wherein the layer A is arranged so as to face the cathode.

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