JP7174597B2 - Ion-exchange membrane, method for producing ion-exchange membrane, and electrolytic cell - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ion-exchange membrane, a method for producing an ion-exchange membrane, and an electrolytic cell.

Fluorine-containing ion-exchange membranes have excellent heat resistance and chemical resistance. It is widely used and is expanding into new applications.

Among these, in recent years, the ion-exchange membrane method has become mainstream in the electrolysis of alkali chloride for producing chlorine and alkali hydroxide. In addition, in order to reduce the power unit consumption, a natural circulation zero-gap electrolytic cell in which an ion-exchange membrane, an anode, and a cathode are in close contact with each other has become the mainstream for alkali chloride electrolysis by the ion-exchange membrane method. Various performances are required for ion-exchange membranes used for electrolysis of alkaline chlorides. Among them, a cation exchange membrane with a particularly low electrolysis voltage is demanded. Since the electrolysis voltage of chloride-alkali electrolysis greatly affects the power unit consumption, even a reduction of 10 mV is very beneficial. In the alkali chloride electrolysis, it is generally known that the electrolysis voltage increases due to the adhesion of the gas generated by the electrolysis reaction to the surface of the ion exchange membrane. As a countermeasure, Patent Document 1 proposes that by providing a layer (surface layer) containing a binder and inorganic particles on the surface of the membrane, gas adhesion to the ion-exchange membrane surface is suppressed and the electrolysis voltage is lowered. ing.

JP 2016-79453 A

Patent Document 1 describes that when the mass ratio of the binder to the total of the inorganic particles and the binder contained in the surface layer is 0.3 or less, a high gas adhesion suppressing effect is obtained. However, when the binder ratio is greater than 0.3, a sufficient effect of suppressing gas adhesion cannot be obtained, and there is a problem that the electrolysis voltage rises significantly. Thus, the conventional technology still has room for improvement from the viewpoint of further lowering the electrolysis voltage.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an ion-exchange membrane, a method for producing an ion-exchange membrane, and an electrolytic cell that can reduce the electrolysis voltage when subjected to electrolysis.

The inventors of the present invention have made intensive studies to solve the above problems, and as a result, found that the surface of the coating layer containing inorganic particles has a certain level of roughness or more, thereby exhibiting an effect of suppressing gas adhesion. . Based on this result, as a result of further intensive research, the surface roughness of the coating layer can be kept constant even if the binder ratio is increased by optimizing the diameter of the coating droplets when forming the coating layer. The inventors have found that it is possible to achieve the above, and have completed the present invention.

That is, the present invention is as follows.
[1]
a membrane body containing a fluorine-containing polymer having ion exchange groups;
a coating layer disposed on at least one surface of the membrane body;
An ion exchange membrane having
The coating layer contains inorganic particles and a binder,
The mass ratio of the binder to the total mass of the inorganic particles and the binder in the coating layer is more than 0.3 and 0.9 or less,
The ion exchange membrane, wherein the coating layer has a surface roughness of 1.20 μm or more.
[2]
The inorganic particles are particles containing at least one inorganic substance selected from the group consisting of oxides of group IV elements of the periodic table, nitrides of group IV elements of the periodic table, and carbides of group IV elements of the periodic table. The ion exchange membrane according to [1].
[3]
The ion exchange membrane according to [1] or [2], wherein the inorganic particles are zirconium oxide particles.
[4]
The membrane body comprises a layer S containing a fluoropolymer having a sulfonic acid group, a layer C containing a fluoropolymer having a carboxylic acid group, and a layer S disposed inside the layer S, and reinforcing threads and sacrificial layers. a plurality of reinforcements functioning as at least one of the threads;
When the ion exchange membrane is viewed from the top, the average thickness of the membrane cross section in pure water in the region where the reinforcing material is not present is A, and the region where the reinforcing yarns intersect and the reinforcing yarn and the sacrificial yarn are The ion-exchange membrane according to any one of [1] to [3], wherein A and B satisfy formula (1), where B is the membrane cross-sectional average thickness in pure water of the intersecting region. .
2.0≦B/A≦5.0 (1)
[5]
A step of spraying a coating liquid containing inorganic particles, a binder and a solvent by a spray method and drying it to form a coating layer on the surface of the membrane body,
The method for producing an ion-exchange membrane, wherein the average droplet size during spraying is 100 μm or less.
[6]
A step of spraying a coating liquid containing inorganic particles, a binder and a solvent by a spray method and drying it to form a coating layer on the surface of the membrane body,
The method for producing an ion-exchange membrane, wherein the surface temperature of the membrane body during drying is 40° C. or higher and the boiling point of the solvent or lower.
[7]
An electrolytic cell comprising the ion exchange membrane according to any one of [1] to [4].

According to the present invention, it is possible to provide an ion-exchange membrane, a method for producing an ion-exchange membrane, and an electrolytic cell that can reduce the electrolysis voltage when subjected to electrolysis.

It is a cross-sectional schematic diagram which shows one Embodiment of an ion-exchange membrane. FIG. 4 is a schematic diagram for explaining the aperture ratio of a reinforcing material that can constitute an ion exchange membrane. It is a top view schematic diagram which shows an example of the measurement position of the film thickness which concerns on this embodiment. It is a cross-sectional schematic diagram which shows an example of the thickness a measurement position of the ion-exchange membrane which concerns on this embodiment. It is a cross-sectional schematic diagram which shows an example of the thickness a measurement position of the ion-exchange membrane which concerns on this embodiment. It is a cross-sectional schematic diagram which shows an example of the thickness b measurement position of the ion-exchange membrane which concerns on this embodiment. It is a cross-sectional schematic diagram which shows an example of the thickness b measurement position of the ion-exchange membrane which concerns on this embodiment. FIG. 4 is a schematic diagram for explaining a method of forming communicating pores in an ion exchange membrane; It is a cross-sectional schematic diagram which shows one Embodiment of an electrolytic cell. 5 is a graph showing the relationship between the average droplet size and voltage in Examples 1-5 and Comparative Examples 1-5.

EMBODIMENT OF THE INVENTION Hereinafter, the form (only henceforth "this embodiment") for implementing this invention is demonstrated in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of the gist thereof.
In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and overlapping descriptions are omitted. In addition, unless otherwise specified, the positional relationships in the drawings, such as top, bottom, left, and right, are based on the positional relationships shown in the drawings, and the dimensional ratios in the drawings are not limited to those shown in the drawings. However, the drawings merely show an example of the present embodiment, and the present embodiment should not be construed as being limited thereto.

The ion-exchange membrane of the present embodiment is an ion-exchange membrane having a membrane body containing a fluorine-containing polymer having ion-exchange groups, and a coating layer disposed on at least one surface of the membrane body, , the coating layer contains inorganic particles and a binder, the mass ratio of the binder to the total mass of the inorganic particles and the binder in the coating layer is more than 0.3 and 0.9 or less, and the coating layer The surface roughness is 1.20 μm or more. Because of this configuration, the ion exchange membrane of the present embodiment can reduce the electrolysis voltage when subjected to electrolysis. Therefore, the ion-exchange membrane of the present embodiment and the electrolytic cell containing the same can be preferably used for alkali chloride electrolysis (particularly salt electrolysis).

FIG. 1 is a schematic cross-sectional view showing one embodiment of an ion exchange membrane. The ion exchange membrane 1 of this embodiment has a membrane body 10 containing a fluorine-containing polymer having ion exchange groups, and coating layers 11 a and 11 b formed on both sides of the membrane body 10 .

As illustrated in FIG. 1, in the ion exchange membrane 1, the membrane body 10 has ion exchange groups derived from sulfo groups (groups represented by —SO ₃ ^— , hereinafter also referred to as “sulfonic acid groups”). It can be provided with a sulfonic acid layer 3 and a carboxylic acid layer 2 having an ion exchange group derived from a carboxyl group (a group represented by —CO ₂ ^— , hereinafter also referred to as “carboxylic acid group”). Further, strength and dimensional stability may be enhanced by a reinforcing material 4, which will be described later. When the ion exchange membrane 1 comprises the sulfonic acid layer 3 and the carboxylic acid layer 2, it tends to exhibit superior performance as an ion exchange membrane.

The ion exchange membrane of this embodiment is not limited to the configuration illustrated in FIG. 1, and may have only one of the sulfonic acid layer and the carboxylic acid layer. In addition, the ion exchange membrane of the present embodiment does not necessarily have to be reinforced with a reinforcing material, and the arrangement state of the reinforcing material is not limited to the example shown in FIG. Furthermore, the coating layer does not necessarily have to be arranged on both surfaces of the membrane body, and may be arranged only on one surface of the membrane body.

(membrane body)
First, the membrane body 10 constituting the ion exchange membrane 1 of this embodiment will be described.
The membrane main body 10 has a function of selectively permeating cations and contains a fluorine-containing polymer having an ion exchange group. A fluorine-based polymer can be appropriately selected and used.

The fluorine-containing polymer having ion-exchange groups in the membrane body 10 can be obtained, for example, from a fluorine-containing polymer having an ion-exchange group precursor capable of becoming an ion-exchange group by hydrolysis or the like. Specifically, for example, the main chain consists of a fluorinated hydrocarbon, has a group (ion-exchange group precursor) that can be converted to an ion-exchange group by hydrolysis or the like as a pendant side chain, and is melt-processable. (hereinafter sometimes referred to as "fluorine-containing polymer (a)") to prepare a precursor of the membrane body 10, and then convert the ion-exchange group precursor into ion-exchange groups, A membrane body 10 can be obtained.

The fluorine-containing polymer (a) comprises, for example, at least one monomer selected from Group 1 below and at least one monomer selected from Group 2 and/or Group 3 below. It can be produced by copolymerization. It can also be produced by homopolymerization of one monomer selected from any one of Group 1, Group 2, and Group 3 below.

Examples of the first group of monomers include, but are not limited to, vinyl fluoride compounds. Examples of vinyl fluoride compounds include, but are not limited to, vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and perfluoro(alkyl vinyl ether). . In particular, when the ion exchange membrane of the present embodiment is used for alkaline electrolysis, the vinyl fluoride compound is preferably a perfluoromonomer, and the group consisting of tetrafluoroethylene, hexafluoropropylene and perfluoro(alkyl vinyl ether). A more selected perfluoromonomer is preferred.

Examples of the second group of monomers include, but are not limited to, vinyl compounds having a functional group that can be converted into a carboxylic acid type ion exchange group (carboxylic acid group). Examples of the vinyl compound having a functional group convertible to a carboxylic acid group include, but are not limited to, a monomer represented by CF ₂ ═CF(OCF ₂ CYF) _s —O(CZF) _t —COOR. (where s represents an integer of 0 to 2, t represents an integer of 1 to 12, Y and Z each independently represents F or CF ₃ , and R represents a lower alkyl group A lower alkyl group is, for example, an alkyl group having 1 to 3 carbon atoms.).

Among these, compounds represented by CF ₂ =CF(OCF ₂ CYF) _n --O(CF ₂ ) _m --COOR are preferred. 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 ₇ .

When the ion-exchange membrane of the present embodiment is used as an ion-exchange membrane for alkaline electrolysis, it is preferable to use at least a perfluoro compound as a monomer, but the alkyl group of the ester group (see R above) is hydrolyzed. The alkyl group (R) does not have to be a perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms, because the alkyl group (R) is lost from the polymer at the point in time.

As the second group of monomers, the following monomers are more preferable among the above.
CF2 ₌ CFOCF2 _- CF( _CF3 ) _{OCF2COOCH3 ,}
CF2 _{= CFOCF2CF ( CF3} )O(CF2) _{2COOCH3 ,}
CF2 ₌ CF[ _{OCF2 -} CF( _CF3 )] _2O (CF2) _{2COOCH3 ,}
CF2 _{= CFOCF2CF ( CF3} )O(CF2) _{3COOCH3 ,}
CF2 ₌ CFO ₍ CF2) _{2COOCH3 ,}
CF2 ₌ CFO _{( CF2} ) _3COOCH3 .

Examples of the third group of monomers include vinyl compounds having a functional group convertible to a sulfone-type ion exchange group (sulfonic acid group). As a vinyl compound having a functional group convertible to a sulfonic acid group, for example, a monomer represented by CF ₂ =CFO-X-CF ₂ -SO ₂ F is preferable (here, X is a perfluoroalkylene group represents ). Specific examples thereof include the monomers shown below.
_{CF2 = CFOCF2CF2SO2F ,
CF2 = CFOCF2CF ( CF3} ) _OCF2CF2SO2F ,
_{CF2 = CFOCF2CF ( CF3 ) OCF2CF2CF2SO2F} ,
CF2 ₌ CF _{( CF2} ) _2SO2F ,
_{CF2 = CFO} [ _{CF2CF ( CF3} )O] _2CF2CF2SO2F ,
_{CF2 = CFOCF2CF ( CF2OCF3 ) OCF2CF2SO2F} .

Among these, CF2 _{= CFOCF2CF ( CF3} ) _{OCF2CF2CF2SO2F} and _{CF2 = CFOCF2CF ( CF3} ) _{OCF2CF2SO2F are more} preferred.

Copolymers obtained from these monomers can be produced by polymerization methods developed for homopolymerization and copolymerization of ethylene fluoride, particularly by general polymerization methods used for tetrafluoroethylene. . For example, in the non-aqueous method, inert solvents such as perfluorohydrocarbons and chlorofluorocarbons are used in the presence of radical polymerization initiators such as perfluorocarbon peroxides and azo compounds at a temperature of 0 to 200° C. and a pressure of 0.5°C. A polymerization reaction can be carried out under conditions of 1 to 20 MPa.

In the above-mentioned copolymerization, the type and proportion of the combination of the above-mentioned monomers are not particularly limited, and can be selected and determined according to the type and amount of functional groups desired to be imparted to the obtained fluorine-containing polymer. For example, in the case of producing a fluorine-containing polymer containing only carboxylic acid groups, at least one monomer may be selected from each of the first group and the second group and copolymerized. In the case of producing a fluorine-containing polymer containing only sulfonic acid groups, at least one monomer may be selected from each of the first group and the third group and copolymerized. Furthermore, in the case of a fluorine-containing polymer having a carboxylic acid group and a sulfonic acid group, at least one monomer is selected from each of the first group, second group and third group monomers and co-polymerized. polymerize it. In this case, the desired fluorine-containing system can also be produced by separately polymerizing the copolymer comprising the first group and the second group and the copolymer comprising the first group and the third group, and then mixing them. A polymer can be obtained. In addition, the mixing ratio of each monomer is not particularly limited, but when increasing the amount of functional groups per unit polymer, if the ratio of the monomers selected from the second group and the third group is increased good.

The total ion exchange capacity of the fluorine-containing polymer is not particularly limited, but is preferably 0.5 equivalents/g or more and 2.0 mg equivalents/g or less, and 0.6 equivalents/g or more and 1.5 mg equivalents/g or less. is more preferable. Here, the total ion exchange capacity means the equivalent of exchange groups per unit weight of the dry resin, and can be measured by neutralization titration or the like.

In the membrane body 10 of the ion exchange membrane 1 illustrated in FIG. are stacked. When the membrane body 10 has such a layered structure, the selective permeability of cations such as sodium ions tends to be further improved.

When the ion-exchange membrane 1 illustrated in FIG. 1 is arranged in an electrolytic cell, the sulfonic acid layer 3 is usually arranged on the anode side of the electrolytic cell, and the carboxylic acid layer 2 is arranged on the cathode side of the electrolytic cell. be.

The sulfonic acid layer 3 is preferably made of a material with low electrical resistance, and preferably thicker than the carboxylic acid layer 2 from the viewpoint of film strength. The film thickness of the sulfonic acid layer 3 is preferably 2 to 25 times that of the carboxylic acid layer 2, more preferably 3 to 15 times.

It is preferable that the carboxylic acid layer 2 has a high anion exclusion property even if the film thickness is thin. The term "anion exclusion" as used herein refers to the property of preventing anions from entering or permeating the ion-exchange membrane 1 . In order to increase the anion exclusion property, it is effective to provide a carboxylic acid layer having a small ion exchange capacity with respect to the sulfonic acid layer.

As the fluorine-containing polymer used for the sulfonic acid layer 3, for example, a polymer obtained by using CF2 _{= CFOCF2CF ( CF3} ) _OCF2CF2SO2F as a monomer of the _third group is used. It is preferable to use

As the fluorine-containing polymer used for the carboxylic acid layer ₂ , for example, a polymer obtained by using CF2 _{= CFOCF2CF (} CF2)O(CF2) _2COOCH3 as the monomer of the _second group. is preferably used.

(coating layer)
The ion exchange membrane of this embodiment has a coating layer disposed on at least one surface of the membrane body. In the ion exchange membrane 1 illustrated in FIG. 1, coating layers 11a and 11b are formed on both surfaces of the membrane body 10, respectively.

The coating layer in this embodiment contains inorganic particles and a binder, and the surface roughness of the coating layer is 1.20 μm or more. Here, the surface roughness of the coating layer means a value calculated by a measuring method described in Examples described later. In this embodiment, since the surface roughness is sufficiently large, gas adhesion to the ion-exchange membrane during electrolysis can be suppressed, and as a result, the electrolysis voltage can be sufficiently reduced. From the same point of view, the surface roughness is preferably 1.25 μm or more, more preferably 1.30 μm or more. Although the upper limit of the surface roughness is not particularly limited, it is preferably 2.50 μm or less from the viewpoint of peel durability.
Although the surface roughness of the coating layer in the present embodiment is not limited to the following, for example, as described later, by sufficiently reducing the average droplet diameter of the coating liquid when the coating liquid is sprayed, it is adjusted to the above range. can do.

Although the average particle diameter of the inorganic particles in the present embodiment is not particularly limited, it is preferably 0.90 μm or more. When the average particle size of the inorganic particles is 0.90 μm or more, the resistance to impurities tends to be further improved. In this embodiment, it is preferable to use inorganic particles having an irregular shape, and it is more preferable to use inorganic particles obtained by pulverizing raw stones.

Also, the average particle size of the inorganic particles can be 2 μm or less. If the average particle size of the inorganic particles is 2 μm or less, it tends to be possible to further prevent film damage caused by the inorganic particles. The average particle diameter of the inorganic particles is more preferably 0.90 μm or more and 1.2 μm or less. More preferably, it is 1 μm or more and 1.2 μm or less.

In the present specification, the average particle diameter means the median diameter (D50), which can be measured by a particle size distribution meter ("SALD2200" Shimadzu Corporation).

The inorganic particles in this embodiment are preferably hydrophilic. Hydrophilicity indicates the property that a solid surface is easily wetted with water. In general, those with a small contact angle can be evaluated as hydrophilic. For example, inorganic particles with a contact angle of about 90° can also be evaluated as hydrophilic, and the contact angle is preferably 90° or less, and 40° or less. is more preferable. Here, the contact angle means the angle formed by the tangent line of the liquid surface and the solid surface at the contact point between the solid and the liquid. It can be calculated by bringing a droplet into contact with and analyzing the image at the time of droplet landing. When the inorganic particles are hydrophilic, they tend to be oriented on the surface of the coating layer to further suppress gas adhesion to the ion-exchange membrane during electrolysis. More preferably, it contains at least one inorganic material selected from the group consisting of oxides of Group IV elements of the periodic table, nitrides of Group IV elements of the Periodic Table, and carbides of Group IV elements of the Periodic Table. Specific examples of these include, but are not limited to, zirconium oxide, silica oxide, tin oxide, titanium oxide, nickel oxide, SiC, ZrC, and the like. Zirconium oxide particles are more preferable from the viewpoint of durability.

The inorganic particles in the present embodiment are preferably inorganic particles produced by pulverizing raw inorganic particles. It is also possible to manufacture inorganic particles by melting and purifying raw inorganic particles, and to use spherical particles having a uniform particle size as inorganic particles in the coating layer.

Pulverization methods include, but are not limited to, ball mills, bead mills, colloid mills, conical mills, disc mills, edge mills, milling mills, hammer mills, pellet mills, VSI mills, Willy mills, roller mills, and jet mills. Moreover, it is preferable to wash after pulverization, and as a washing method at that time, acid treatment is preferable. As a result, impurities such as iron adhering to the surfaces of the inorganic particles can be reduced.

In this embodiment, the coating layer contains a binder. The binder is a component that holds the inorganic particles on the surface of the ion exchange membrane to form a coating layer. The binder preferably contains a fluorine-containing polymer from the viewpoint of resistance to electrolytic solutions and products produced by electrolysis. The fluorine-containing polymer contained in the coating layer as a binder may be of the same type as the fluorine-containing polymer constituting the film body, or may be of a different type. In addition to such fluorine-containing polymers, various known compounds can be used as the binder component in the coating layer, but the content of the fluorine-containing polymer in the binder is preferably 90% by mass or more.

The binder in the present embodiment is a fluorine-containing polymer having a carboxylic acid group or a sulfonic acid group, from the viewpoint of resistance to the electrolytic solution and products of electrolysis, and adhesion to the surface of the ion exchange membrane. is more preferred. When a coating layer is provided on a layer containing a fluorine-containing polymer having a sulfonic acid group (sulfonic acid layer), it is more preferable to use a fluorine-containing polymer having a sulfonic acid group as the binder for the coating layer. . Further, when a coating layer is provided on a layer (carboxylic acid layer) containing a fluorine-containing polymer having a carboxylic acid group, a fluorine-containing polymer having a carboxylic acid group can be used as a binder for the coating layer. More preferred.

In this embodiment, the mass ratio of the binder to the total mass of the inorganic particles and the binder in the coating layer is more than 0.3 and 0.9 or less. The present inventors have found that the ion permeation resistance of the ion exchange membrane itself is reduced by increasing the mass ratio of the binder in the coating layer. That is, when the mass ratio of the binder exceeds 0.3, the ion permeation resistance of the ion exchange membrane itself is further reduced. Voltage can be greatly reduced. From the same point of view, the mass ratio of the binder is preferably more than 0.3 and 0.7 or less, more preferably 0.4 or more and 0.6 or less.

The distribution density of the coating layer in the ion exchange membrane is not particularly limited, but is preferably 0.05 mg or more and 2 mg or less per 1 cm ² , more preferably 0.5 mg or more and 2 mg or less per 1 cm ² . The above distribution density can be measured by the method described in Examples below. Moreover, the distribution density can be adjusted within the above range by, for example, changing the discharge amount during spraying for coating or changing the number of times of recoating.

(reinforcing material)
The ion-exchange membrane of this embodiment preferably has a reinforcing material disposed inside the membrane body.

In the present embodiment, the reinforcing material functions as at least one of reinforcing yarns and sacrificial yarns, and examples thereof include, but are not limited to, woven fabrics woven with reinforcing yarns and sacrificial yarns. . By arranging the reinforcing material inside the membrane main body, the expansion and contraction of the ion exchange membrane can be controlled within a desired range. Such an ion-exchange membrane does not expand or contract more than necessary during electrolysis or the like, and can maintain excellent dimensional stability for a long period of time.

The configuration of the reinforcing material is not particularly limited, and for example, it may be formed by spinning a thread called a reinforcing thread. The reinforcing thread as used herein is a member that constitutes the reinforcing material, and is a thread that can impart desired dimensional stability and mechanical strength to the ion-exchange membrane and can stably exist in the ion-exchange membrane. That's what I mean. By using a reinforcing material obtained by spinning such a reinforcing yarn, it is possible to impart even more excellent dimensional stability and mechanical strength to the ion-exchange membrane.

The material of the reinforcing material and the reinforcing yarn used therefor is not particularly limited, but it is preferably a material that is resistant to acids, alkalis, etc., and from the viewpoint of imparting long-term heat resistance and chemical resistance, fluorine-containing heavy weights are used. Fibers composed of coalescence are preferred.

As the fluorine-containing polymer used for the reinforcing material, those used for the membrane body described above can also be used. ), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer, trifluorochloroethylene-ethylene copolymer and vinylidene fluoride polymer (PVDF). Among these, from the viewpoint of heat resistance and chemical resistance, it is preferable to use fibers composed of polytetrafluoroethylene.

The diameter of the reinforcing thread used for the reinforcing material is not particularly limited, but is preferably 20 to 300 denier, more preferably 50 to 250 denier. The weave density (number of strands per unit length) is preferably 5 to 50 strands/inch. The form of the reinforcing material is not particularly limited, and for example, woven fabric, non-woven fabric, knitted fabric, etc. are used, but the form of woven fabric is preferable. The thickness of the woven fabric is preferably 30-250 μm, more preferably 30-150 μm.

Woven or knitted fabrics may be monofilaments, multifilaments, or yarns thereof, slit yarns, etc., and various weaving methods such as plain weave, leno weave, knit weave, cord weave, and shearsack can be used.

The weaving method and arrangement of the reinforcing material in the membrane main body are not particularly limited, and the arrangement can be suitably selected in consideration of the size and shape of the ion-exchange membrane, the physical properties desired for the ion-exchange membrane, the usage environment, and the like.

For example, the reinforcing material may be arranged along a predetermined direction of the membrane body, but from the viewpoint of dimensional stability, the reinforcing material is arranged along a predetermined first direction and Another stiffener is preferably arranged along a second direction which is substantially perpendicular thereto. By arranging a plurality of reinforcing members substantially orthogonally inside the longitudinal direction membrane body of the membrane body, it is possible to impart more excellent dimensional stability and mechanical strength in multiple directions. For example, it is preferable that the surface of the membrane body is woven with a reinforcing member (warp) arranged along the longitudinal direction and a reinforcing member (warp) arranged along the transverse direction. Plain weave, in which the warp and weft threads are alternately undulated and woven, tangle weave, in which two warp threads are twisted and woven together with the weft thread, and two or more warp threads are aligned and the same number of weft threads are woven into the warp threads. From the viewpoint of dimensional stability, mechanical strength and ease of manufacture, it is more preferable to employ a diagonal weave or the like.

In particular, it is preferable that the reinforcing members are arranged along both the MD direction (Machine Direction) and the TD direction (Transverse Direction) of the ion exchange membrane. That is, it is preferable that the fabric is plain woven in the MD direction and the TD direction. Here, the MD direction refers to the direction (flow direction) in which the membrane body and the reinforcing material are transported in the ion-exchange membrane production process described later, and the TD direction refers to the direction substantially perpendicular to the MD direction. A yarn woven along the MD direction is called an MD yarn, and a yarn woven along the TD direction is called a TD yarn. An ion-exchange membrane used for electrolysis is usually rectangular, and often the longitudinal direction is the MD direction and the width direction is the TD direction. By weaving the reinforcing material that is the MD yarn and the reinforcing material that is the TD yarn, it is possible to impart more excellent dimensional stability and mechanical strength in multiple directions.

The arrangement interval of the reinforcing members is not particularly limited, and it can be appropriately arranged in consideration of the physical properties desired for the ion-exchange membrane, the usage environment, and the like.

The open area ratio of the reinforcing member is not particularly limited, and 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 preferably 90% or less from the viewpoint of the mechanical strength of the ion-exchange membrane.

The open area ratio of the reinforcing material is the total surface area through which substances such as ions (electrolyte and cations contained therein (e.g., sodium ions)) can pass in the area (A) of the surface of either one of the membrane bodies. Refers to the ratio (B/A) of (B). The total area (B) of the surface through which substances such as ions can pass can be said to be the total area of the region in the ion exchange membrane where cations, electrolytic solution, etc. are not blocked by the reinforcing material etc. contained in the ion exchange membrane. .

FIG. 2 is a schematic diagram for explaining the aperture ratio of the reinforcing material that constitutes the ion exchange membrane. FIG. 2 is an enlarged view of a portion of the ion-exchange membrane, showing only the arrangement of the reinforcing members 21 and 22 within that region, and omitting the illustration of other members.

The area surrounded by the reinforcing members 21 arranged in the longitudinal direction and the reinforcing members 22 arranged in the horizontal direction, and the area (A) of the region including the area of the reinforcing members is calculated from the total area ( By subtracting C), the total area (B) of the regions through which substances such as ions can pass in the area (A) of the regions described above can be obtained. That is, the aperture ratio can be obtained by the following formula (I).
Aperture ratio = (B) / (A) = ((A) - (C)) / (A) ... (I)

Among the reinforcing materials, a particularly preferred form is a tape yarn containing PTFE or a highly oriented monofilament from the viewpoint of chemical resistance and heat resistance. Specifically, a tape yarn obtained by slitting a high-strength porous sheet made of PTFE into a tape shape, or a highly oriented monofilament made of PTFE with a denier of 50 to 300, and a weaving density of 10 to 50 filaments/ More preferably, the reinforcing material is plain weave in inches and has a thickness in the range of 50-100 μm. It is more preferable that the ion exchange membrane containing such a reinforcing material has an aperture ratio of 60% or more.

Examples of the shape of the reinforcing thread include round thread and tape-like thread. Round threads are preferred.

(Communication hole)
The ion-exchange membrane of the present embodiment preferably has communicating pores inside the membrane body.

A communicating hole is a hole that can serve as a flow path for cations generated during electrolysis or an electrolytic solution. Further, the communication hole is a tubular hole formed inside the main body of the membrane, and is formed by elution of the later-described reinforcing material (sacrificial thread). The shape and diameter of the communication hole can be controlled by selecting the shape and diameter of the reinforcing material (sacrificial thread).

By forming communicating pores in the ion exchange membrane, it is possible to secure the mobility of alkali ions generated during electrolysis and the electrolyte. The shape of the communication hole is not particularly limited, but according to the manufacturing method described later, the shape of the reinforcing material (sacrificial thread) used for forming the communication hole can be used.

In this embodiment, the communicating holes are preferably formed so as to alternately pass through the anode side (sulfonic acid layer side) and the cathode side (carboxylic acid layer side) of the reinforcing material. With such a structure, in the portion where the communicating hole is formed on the cathode side of the reinforcing material, cations (for example, sodium ions) transported through the electrolyte filling the communicating hole are transferred to the cathode of the reinforcing material. It can also flow to the side. As a result, since the flow of cations is not blocked, the electrical resistance of the ion exchange membrane can be further reduced.

The communicating holes may be formed along only one predetermined direction of the membrane body constituting the ion exchange membrane of the present embodiment. and laterally.

(Membrane cross-sectional average thickness)
In this embodiment, the membrane body comprises a sulfonic acid layer (layer S) containing a fluoropolymer having a sulfonic acid group, a carboxylic acid layer (layer C) containing a fluoropolymer having a carboxylic acid group, and the and a plurality of reinforcing members disposed inside the layer S and functioning as at least one of reinforcing yarns and sacrificial yarns, and the reinforcing members are present when the ion exchange membrane of the present embodiment is viewed from above. Let A be the membrane cross-sectional average thickness in pure water in the region where no is B, it is preferable that A and B satisfy formula (1).
2.0≦B/A≦5.0 (1)

[Membrane cross-sectional average thickness A]
The membrane cross-sectional average thickness A is calculated as follows.
The position indicated by "○" in FIG. 3 is the central part of the region (window part) where the reinforcing yarn and the sacrificial yarn constituting the reinforcing material do not exist when the ion exchange membrane is viewed from above, and the thickness a is measured. position. As shown in FIG. 4 or FIG. 5, the thickness a is the film thickness in pure water at this position in the cross-sectional direction of the membrane. When there is a convex portion formed only of the exchange resin, the distance from the surface of the layer C to the base of the convex portion is defined as the thickness a.
The method for measuring the thickness a is to use a razor or the like to cut a cross section of the relevant portion of the ion exchange membrane that has been immersed in pure water in advance to a width of about 100 μm, and immerse in pure water with the cross section facing upward. The thickness may be measured using a microscope or the like, or the thickness may be measured using a tomographic image of the relevant portion of the ion exchange membrane immersed in pure water observed using X-ray CT. You may
The thickness a is measured at 15 points, and the thickness of the thinnest portion is defined as a (min).
Three points of a (min) are calculated at different positions, and the average value is the thickness A.
The value of A can be measured by the above-described method before or after forming the coating layer in the present embodiment.
From the viewpoint of ensuring sufficient film strength, the thickness A is preferably 40 μm or more, more preferably 50 μm or more.
For the thickness A, for example, in addition to controlling the respective thicknesses of the layers S and C, the manufacturing conditions (temperature conditions and stretch ratio) at the time of manufacturing the ion exchange membrane (especially at the time of lamination of the film and the reinforcing material) are appropriately set as described below. It is possible to achieve the above-mentioned preferable range by setting it to a range such as More specifically, for example, when the film temperature during lamination is increased, the thickness A tends to decrease, and when the draw ratio during stretching is decreased, the thickness A tends to increase. In addition, it is not limited to the above. For example, it is preferable to appropriately adjust the temperature conditions during lamination and the draw ratio during stretching, taking into consideration the flow characteristics of the fluorine-containing polymer to be used.

[Membrane cross-sectional average thickness B]
The membrane cross-sectional average thickness B is calculated as follows.
The positions indicated by "Δ" in FIG. 3 are regions where the reinforcing yarns forming the reinforcing material intersect each other, and the positions indicated by "□" in FIG. These are areas where the thickness b is measured. As shown in FIG. 6 or FIG. 7, the thickness b is the film thickness in pure water at the thickest position in this region in the cross-sectional direction of the film. When there is a convex portion formed only of the ion-exchange resin forming the exchange membrane, the distance from the surface of the layer C to the base of the convex portion is defined as the thickness b. The example shown in FIG. 7 corresponds to the case where the surface of the layer S has convex portions formed of an ion-exchange resin forming an ion-exchange membrane and a reinforcing material. Let the distance be the thickness b.
The method for measuring the thickness b is to use a razor or the like to cut a cross-section of the relevant portion of the ion-exchange membrane that has been immersed in pure water in advance to a width of about 100 μm, and immerse in pure water with the cross-section facing upward. The thickness may be measured using a microscope or the like, or the thickness may be measured using a tomographic image of the relevant portion of the ion exchange membrane immersed in pure water observed using X-ray CT. You may
The thickness b is measured at 15 points, and the thickness of the thickest portion is defined as b(max).
Three points of b(max) are calculated at different positions, and the average value is the thickness B.
The value of B can be measured by the above-described method before or after forming the coating layer in the present embodiment.
In alkaline chloride electrolysis using a zero-gap electrolytic cell, the distance between the electrodes is determined by the thickness of the ion-exchange membrane. tend to rise. Therefore, the thickness B is preferably 260 μm or less, more preferably 240 μm or less, even more preferably 220 μm or less.
The thickness B, for example, controls the thickness of each of the layers S and C, as well as the thread diameter of the reinforcing material, the manufacturing conditions (especially when the film and the reinforcing material are laminated) (temperature conditions and stretching ratio) can be set to the above-mentioned preferred range by setting it to the appropriate range described later. More specifically, for example, when the ambient temperature during lamination is lowered, the thickness B tends to decrease, and when the draw ratio during stretching is decreased, the thickness B tends to increase. In addition, it is not limited to the above. For example, it is preferable to appropriately adjust the temperature conditions during lamination and the draw ratio during stretching, taking into consideration the flow characteristics of the fluorine-containing polymer to be used.

[Thickness ratio B/A]
The thickness ratio B/A is a value obtained by dividing the average cross-sectional thickness B by the average cross-sectional thickness A.
By increasing B/A, the thickness of the window portion through which cations pass tends to be thin, and the electrolysis voltage can be reduced. Therefore, B/A is preferably 2.0 or more, more preferably 2.3 or more, and even more preferably 2.5 or more.
On the other hand, if the unevenness of the membrane surface becomes excessively large, the gas bubbles generated by the electrolysis with alkaline chloride tend to accumulate in the recessed windows, and the gas adheres to the surface of the ion-exchange membrane, producing cations. B/A is preferably 5.0 or less, more preferably 4.5 or less, from the viewpoint of sufficiently reducing the electrolysis voltage by preventing this because it tends to hinder permeation. It is more preferably 0 or less.

〔Production method〕
The method for producing the ion-exchange membrane according to the present embodiment is not particularly limited as long as the ion-exchange membrane having the structure described above can be obtained, but it is preferable to produce by a method having the following steps (1) to (6). .
(1) Step: A step of producing a fluorine-containing polymer having an ion-exchange group or an ion-exchange group precursor capable of becoming an ion-exchange group by hydrolysis.
(2) Step: If necessary, at least a plurality of reinforcing threads and a sacrificial thread having a property of dissolving in acid or alkali and forming communicating holes are woven between adjacent reinforcing threads. Obtaining a stiffener in which the sacrificial threads are arranged.
(3) Step: A step of forming a film from the fluorine-containing polymer having ion-exchange groups or ion-exchange group precursors capable of becoming ion-exchange groups by hydrolysis.
(4) Step: A step of embedding the reinforcing material in the film as required to obtain a membrane main body having the reinforcing material disposed therein.
(5) Step: a step of hydrolyzing the membrane body obtained in step (4) (hydrolysis step).
(6) Step: A step of providing a coating layer on the membrane body obtained in the (5) step (coating step).

The method for producing an ion-exchange membrane according to the present embodiment is mainly characterized in that, in the coating step (6), the average droplet size is reduced when the coating liquid is sprayed. Each step will be described in detail below.

(1) Step: Step of producing a fluorine-containing polymer In the step (1), a fluorine-containing polymer is produced using the raw material monomers described in the first to third groups. In order to control the ion exchange capacity of the fluoropolymer, the mixing ratio of the raw material monomers may be adjusted in the production of the fluoropolymer forming each layer.

(2) Process: manufacturing process of reinforcing material The reinforcing material is a woven cloth or the like woven with reinforcing threads. By embedding the reinforcing material in the membrane, it is possible to obtain a membrane body in which the reinforcing material is present. When forming an ion-exchange membrane having communicating pores, a reinforcing material in which sacrificial threads are also woven together is used. In this case, the mixed weave amount of the sacrificial yarn is preferably 10 to 80% by mass, more preferably 30 to 70% by mass, of the entire reinforcing material. By weaving the sacrificial thread, it is also possible to prevent misalignment of the reinforcing material.

The sacrificial thread is soluble in the membrane manufacturing process or in an electrolytic environment, and rayon, polyethylene terephthalate (PET), cellulose, polyamide, and the like are used. Polyvinyl alcohol or the like having a thickness of 20 to 50 denier and consisting of monofilament or multifilament is also preferable.

In the step (2), the opening ratio, the arrangement of the communicating holes, etc. can be controlled by adjusting the arrangement of the reinforcing material.

(3) Step: Film forming step In step (3), the fluorine-containing polymer obtained in step (1) is formed into a film using an extruder. The film may have a single-layer structure, a two-layer structure of a sulfonic acid layer and a carboxylic acid layer as described above, or a multi-layer structure of three or more layers.

Examples of film forming methods include the following.
A method in which a fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group are separately formed into films.
A method of forming a composite film by co-extrusion of a fluorine-containing polymer having a carboxylic acid group and a fluorine-containing polymer having a sulfonic acid group.

A plurality of films may be used. Moreover, coextrusion of films of different types is preferable because it contributes to increasing the adhesive strength of the interface.

(4) Step: Step of obtaining a membrane body In step (4), the reinforcing material obtained in step (2) is embedded in the film obtained in step (3), thereby forming a membrane body containing the reinforcing material. obtain.

As a preferred method for forming the main body of the film, (i) a fluorine-containing polymer having a carboxylic acid group precursor (for example, a carboxylic acid ester functional group) located on the cathode side (hereinafter, a layer composed of this is referred to as the first layer). and a fluorine-containing polymer having a sulfonic acid group precursor (for example, a sulfonyl fluoride functional group) (hereinafter, a layer consisting of this is referred to as a second layer) is formed into a film by a coextrusion method, and if necessary, a heat source and Using a vacuum source, the reinforcing material and the second layer/first layer composite film are laminated in this order on a flat plate or drum having a large number of pores on the surface, with air permeable heat-resistant release paper interposed therebetween. (ii) A method of integrating while removing air between each layer by reducing pressure at a temperature at which each polymer melts; Film the fluorine-based polymer (third layer) alone in advance, and use a heat source and a vacuum source as necessary to form a permeable heat-resistant film on a flat plate or drum having many pores on the surface. A composite film consisting of a third layer film, a reinforcing material, and a second layer/first layer is laminated in this order via release paper, and air between each layer is removed by reducing pressure at a temperature at which each polymer melts. There is a method of integration.

Here, co-extrusion of the first layer and the second layer is preferable because it contributes to increasing the adhesive strength at the interface.

In addition, the method of integrating under reduced pressure tends to increase the thickness of the third layer on the reinforcing material compared to the pressure pressing method, and furthermore, the reinforcing material is fixed to the inner surface of the membrane body. , is preferred because it tends to maintain sufficient mechanical strength of the ion-exchange membrane.

Note that the variation of lamination described here is just an example, and a suitable lamination pattern (for example, a combination of layers, etc.) is appropriately selected in consideration of the layer structure and physical properties of the desired film body, and then co-extruded. can do.

For the purpose of further enhancing the electrical performance of the ion exchange membrane, a second layer made of a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor is placed between the first layer and the second layer. It is also possible to interpose four additional layers, or to use a fourth layer made of a fluorine-containing polymer having both a carboxylic acid group precursor and a sulfonic acid group precursor instead of the second layer.

The method of forming the fourth layer may be a method of separately producing a fluorine-containing polymer having a carboxylic acid group precursor and a fluorine-containing polymer having a sulfonic acid group precursor, and then mixing them. A method of using a copolymer obtained by copolymerizing a monomer having a group precursor and a monomer having a sulfonic acid group precursor may also be used.

When the fourth layer is composed of an ion-exchange membrane, the first layer and the fourth layer are co-extruded to form a film, and the third layer and the second layer are independently formed into a film as described above. Alternatively, the three layers of the first layer/fourth layer/second layer may be co-extruded at once to form a film.

In this case, the direction in which the extruded film flows is the MD direction. In this manner, a membrane body containing a fluorine-containing polymer having ion exchange groups can be formed on the reinforcing material.

In addition, the ion exchange membrane of the present embodiment preferably has protruding portions, that is, protrusions, made of a fluorine-containing polymer having a sulfonic acid group on the surface side of the sulfonic acid layer. A method for forming such convex portions is not particularly limited, and a known method for forming convex portions on a resin surface can be employed. Specifically, for example, there is a method of embossing the surface of the film body. For example, when the composite film and the reinforcing material are integrated, the convex portions can be formed by using pre-embossed release paper. When the convex portions are formed by embossing, the height and arrangement density of the convex portions can be controlled by controlling the embossed shape to be transferred (the shape of the release paper).

(5) Hydrolysis step In step (5), the membrane body obtained in step (4) is hydrolyzed to convert ion-exchange group precursors into ion-exchange groups (hydrolysis step).

In the step (5), elution holes can be formed in the membrane body by dissolving and removing the sacrificial threads contained in the membrane body with acid or alkali. Note that the sacrificial thread may remain in the communication hole without being completely dissolved and removed. Moreover, the sacrificial threads remaining in the communicating holes may be dissolved and removed by the electrolytic solution when the ion exchange membrane is subjected to electrolysis.

The sacrificial thread is soluble in acid or alkali in the manufacturing process of the ion-exchange membrane or in an electrolysis environment, and the elution of the sacrificial thread forms a communicating hole at the site.

The step (5) can be performed by immersing the membrane body obtained in the step (4) in a hydrolysis solution containing acid or alkali. As the hydrolysis solution, for example, a mixed solution containing KOH and DMSO (dimethyl sulfoxide) can be used.

The mixed solution preferably contains 2.5 to 4.0 N of KOH and 25 to 35 mass % of DMSO.

The hydrolysis temperature is preferably 70 to 100°C. The higher the temperature, the thicker the apparent thickness can be. More preferably, it is 85 to 100°C.

The hydrolysis time is preferably 10 to 120 minutes. The longer the time, the thicker the apparent thickness can be. More preferably, it is 20 to 120 minutes.

Here, the step of forming the communication holes by eluting the sacrificial thread will be described in more detail. FIGS. 8A and 8B are schematic diagrams for explaining a method of forming communicating pores in an ion exchange membrane according to this embodiment.

8(a) and 8(b) show only the reinforcing thread 52, the sacrificial thread 504a, and the communicating hole 504 formed by the sacrificial thread 504a, and other members such as the membrane body are not shown. ing.

First, the reinforcing thread 52 and the sacrificial thread 504a for forming the communication holes 504 in the ion exchange membrane are woven together to form a reinforcing material. Then, in the step (5), the communication holes 504 are formed by eluting the sacrificial threads 504a.

According to the above method, the weaving method of the reinforcing yarns 52 and the sacrificial yarns 504a can be adjusted according to the arrangement of the reinforcing yarns and the communication holes in the main body of the ion exchange membrane, which is convenient.

FIG. 8(a) illustrates a plain-woven reinforcing material in which reinforcing yarns 52 and sacrificial yarns 504a are woven along both the vertical and horizontal directions of the paper. and the arrangement of the sacrificial thread 504a.

(6) Coating Step In step (6), a coating liquid containing inorganic particles, a binder and a solvent is sprayed and dried to form a coating layer on the surface of the film body.
In the present embodiment, the average droplet size of the coating liquid during spraying is preferably 100 μm or less. In the present embodiment, from the viewpoint of further reducing the ion permeation resistance of the ion exchange membrane itself, the mass ratio of the binder to the total mass of the inorganic particles and the binder in the coating liquid is more than 0.3 and 0.9 or less. is preferred. From the same point of view, the mass ratio of the binder is more preferably 0.3 or more and 0.7 or less. Since the binder mass ratio in the coating liquid as the charge ratio described above matches the binder ratio after forming the coating layer, the binder ratio in the coating layer in the ion-exchange membrane can be specified from the charge ratio. can.
In the present embodiment, by making the droplets sufficiently small at the time of spraying, the thickness of the binder layer existing around the inorganic particles contained in the droplets is reduced, and in that state the droplets come into contact with the main body of the film. Then, the inorganic particles are likely to be exposed on the surface. Therefore, the inorganic particles are easily oriented on the surface side of the coating layer to be formed. By making the droplets sufficiently small during spraying in this manner, the surface roughness of the coating layer can be sufficiently increased even though a coating liquid having a high binder ratio is used.
Specifically, by setting the average droplet diameter to 100 μm or less, it tends to be possible to prevent the thickness of the binder layer existing around the inorganic particles contained in the droplet from becoming excessively large. Since the droplets contact the film main body, the inorganic particles are less likely to be buried in the binder and become difficult to be exposed on the surface. Therefore, the inorganic particles are easily oriented on the surface side of the coating layer to be formed. By reducing the size of droplets during spraying in this way, there is a tendency to sufficiently increase the surface roughness of the coating layer even when a coating liquid having a high binder ratio is used.
From the viewpoint described above, the average droplet diameter is preferably 80 μm or less, more preferably 50 μm or less.
The average droplet diameter can be measured by the method described in Examples. Further, the average droplet diameter can be adjusted within the above range by, for example, the nozzle diameter of the spray.
In this embodiment, when the coating layer is dried, if the surface temperature of the main body of the ion-exchange membrane that is the substrate (hereinafter also referred to as "substrate surface temperature") is low, the average during spraying Even if the diameter of the droplets is small, the drying of the coating layer is not accelerated, and the droplets that have landed on the droplets tend to adhere to each other, which may reduce the surface roughness.
Therefore, when using a coating liquid with a high binder ratio, from the viewpoint of sufficiently increasing the surface roughness, not only the droplet diameter during spraying is reduced, but also the substrate surface temperature is raised and the drying is performed. is preferred.
Furthermore, if the substrate surface temperature is too high, the coating layer becomes brittle and tends to fall off easily. It tends to be difficult to sufficiently increase the surface roughness of
From the viewpoint described above, it is preferable that the substrate surface temperature during drying of the coating layer is 40° C. or higher and the boiling point of the solvent or lower.
The substrate surface temperature can be measured with a contact thermometer. Moreover, the method of heating the surface of the base material can be adjusted within the above range, for example, by using a heater, warm air, or the like.
From the viewpoint of adjusting the surface roughness of the coating layer in the ion exchange membrane of the present embodiment to a more preferable range, in the coating step (6), the average droplet diameter of the coating liquid during spraying is 100 μm or less, and the coating layer It is particularly preferable that the surface temperature of the base material during drying is 40° C. or higher and the boiling point of the solvent or lower.

As the inorganic particles, those obtained by pulverizing raw stones can be preferably used, and as the binder, a fluorine-containing polymer having an ion-exchange group precursor, dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) are used. A binder (for example, a fluorine-containing polymer having a carboxyl group or a sulfo group) obtained by hydrolyzing in an aqueous solution containing the polymer and then immersing it in hydrochloric acid to replace the counter ion of the ion exchange group with H + can be preferably used. Such binders are preferable because they are easily dissolved in water or ethanol, which will be described later.

It is preferable to dissolve the binder in, for example, a mixed solution of water and ethanol. The volume ratio of water to ethanol is preferably 10:1 to 1:10, more preferably 5:1 to 1:5, still more preferably 2:1 to 1:2. A coating liquid is obtained by dispersing inorganic particles in the solution obtained in this manner by means of a ball mill. At this time, the average particle size of the inorganic particles can also be adjusted by adjusting the time and rotation speed during dispersion. The preferred blending amounts of the inorganic particles and the binder at that time are as described above.

The concentrations of the inorganic particles and the binder in the coating liquid are not particularly limited, but it is preferable to use a thin coating liquid. As a result, it becomes possible to uniformly coat the surface of the ion exchange membrane.

Further, a surfactant may be added to the dispersion when the inorganic particles are dispersed. As the surfactant, nonionic surfactants are preferred, and examples include, but are not limited to, HS-210, NS-210, P-210 and E-212 manufactured by NOF Corporation.

A coating layer is formed by applying the obtained coating liquid to at least one surface of the membrane body by spray coating, and the ion-exchange membrane of the present embodiment is obtained.

[Electrolyzer]
The ion exchange membrane of this embodiment can be used as a constituent member of an electrolytic cell. That is, the electrolytic cell of this embodiment includes the ion exchange membrane of this embodiment. FIG. 9 is a schematic diagram of one embodiment of the electrolytic cell according to this embodiment.

The electrolytic cell 100 of this embodiment includes at least an anode 200 , a cathode 300 , and the ion exchange membrane 1 of this embodiment arranged between the anode 200 and the cathode 300 . Here, the electrolytic cell 100 provided with the above-described ion exchange membrane 1 is described as an example, but the present invention is not limited to this, and various configurations may be modified within the scope of the effects of the present embodiment. be able to.

Although the electrolytic cell 100 can be used for various electrolysis, the case where it is used for electrolysis of an alkaline chloride aqueous solution will be described below as a typical example.

Electrolysis conditions are not particularly limited, and known conditions can be used. For example, a 2.5 to 5.5 N (N) alkali chloride aqueous solution is supplied to the anode chamber, and water or a diluted alkali hydroxide aqueous solution is supplied to the cathode chamber, and electrolysis is performed with direct current.

The configuration of the electrolytic cell according to this embodiment is not particularly limited, and may be, for example, a monopolar type or a bipolar type. Although the material constituting the electrolytic cell 100 is not particularly limited, for example, the material for the anode chamber is preferably titanium, which is resistant to alkali chloride and chlorine, and the material for the cathode chamber is alkali hydroxide and hydrogen. Nickel or the like, which is resistant, is preferred. The electrodes may be arranged with an appropriate gap between the ion-exchange membrane 1 and the anode 200, but even if the anode 200 and the ion-exchange membrane 1 are arranged in contact with each other, they can be used without any problem. can. In addition, the cathode is generally arranged with an appropriate gap from the ion exchange membrane, but even a contact-type electrolytic cell (zero-gap type electrolytic cell) without such a gap can be used without any problems. .

The present embodiment will be described in more detail below based on examples. This embodiment is not limited only to these examples.

[Example 1]
As the reinforcing yarn, a 100-denier tape yarn made of polytetrafluoroethylene (PTFE) was twisted at 900 turns/m to form a yarn (hereinafter referred to as PTFE yarn). As warp sacrificial yarns, 35-denier, 8-filament polyethylene terephthalate (PET) yarns twisted at 200 turns/m were used (hereinafter referred to as PET yarns). As a sacrificial weft yarn, 35 denier, 8 filament polyethylene terephthalate (PET) yarn twisted at 200 turns/m was used (hereinafter referred to as PET yarn). First, the fabric was plain woven with 24 PTFE threads per inch and two sacrificial threads between adjacent PTFE threads to obtain a woven fabric with a thickness of 100 μm.

Next _, a dry resin polymer ₍ A1) which is a copolymer of CF2 ₌ CF2 and CF2 _{= CFOCF2CF ( CF3} ) _{OCF2CF2COOCH3} and has an ion exchange capacity of 0.85 mg equivalent/g. , a copolymer of _{CF2 =} CF2 and CF2 _{= CFOCF2CF ( CF3} ) _OCF2CF2SO2F and having an ion _- exchange capacity of 1.03 mg equivalent/g. Got ready. Using these polymers (A1) and (B1), a two-layer film X having a polymer (A1) layer thickness of 20 μm and a polymer (B1) layer thickness of 94 μm was obtained by a co-extrusion T-die method. rice field. The ion-exchange capacity of each polymer indicates the ion-exchange capacity when the ion-exchange group precursor of each polymer is hydrolyzed and converted into ion-exchange groups.

A copolymer of CF ₂ =CF ₂ and CF ₂ =CFO--CF ₂ CF(CF ₃ )O--(CF ₂ ) ₂ --SO ₂ F gave a polymer having an ion exchange capacity of 1.05 meq/g. . This was extruded with a monolayer T die to obtain a monolayer film Y with a thickness of 20 μm.

Subsequently, pre-embossed release paper, film Y, reinforcing material (the woven fabric obtained above) and film X were placed on a drum having a heating source and a vacuum source inside and having micropores on its surface. After stacking in order and heating and depressurizing for 2 minutes at a drum temperature of 240° C. and a degree of pressure reduction of 0.067 MPa, the release paper was removed to obtain a composite film having an uneven shape. The resulting composite membrane was saponified by immersing it in an aqueous solution containing 30% by mass of dimethyl sulfoxide (DMSO) and 15% by mass of potassium hydroxide (KOH) at 90°C for 1 hour. It was immersed in NaOH for 1 hour to replace the ions attached to the ion exchange groups with Na, and then washed with water. It was further dried at 60° C. to obtain a membrane body.

and a dry resin polymer ₍ B3) which is a copolymer of _{CF2 =} CF2 and CF2 _{= CFOCF2CF ( CF3} ) _OCF2CF2SO2F and has an ion exchange capacity of 1.05 mg equivalent/g. was hydrolyzed and acidified with hydrochloric acid. Zirconium oxide particles having a primary particle size of 1.15 μm were added to a solution obtained by dissolving this acid-type polymer (B3) in a 50/50 (mass ratio) mixture of water and ethanol at a rate of 5% by mass. Polymer (B3) was added so that the mass ratio of polymer (B3) to the total mass of (B3) and zirconium oxide particles was 0.33. Thereafter, the zirconium oxide particles were dispersed in the suspension by a ball mill until the average particle diameter reached 0.94 μm to obtain a suspension. As the zirconium oxide, raw stone pulverized was used. The average particle diameter is the median diameter (D50) and was measured by a particle size distribution analyzer ("SALD2200" Shimadzu Corporation).

The suspension was applied to both surfaces of the ion exchange membrane by a spray method. At that time, the average droplet size of the spray was adjusted to 46 μm. Further, the surface temperature of the membrane body was adjusted to 57° C. and dried to obtain an ion-exchange membrane having a coating layer containing the polymer (B3) and zirconium oxide particles. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass. Note that the average droplet diameter means the volume average diameter D (4, 3), and the measurement was performed using a Malvern "Spraytec" in an atmosphere of 25° C. from the tip of the nozzle in the direction of droplet ejection. The diameter of the droplet was obtained from the scattered light intensity of the laser, targeting the droplet at a position of 200 mm. In the following, the average droplet diameter was obtained in the same manner.

As a result of qualitative and quantitative determination of elements present in the dried coating layer by fluorescent X-ray measurement, the coating density was calculated to be 0.5 mg per 1 cm ² .
Further, the surface roughness of the coating layer was measured with a laser microscope ("VK-9700" manufactured by Keyence Corporation). That is, the surface roughness was obtained by obtaining the line roughness with a laser microscope, correcting the inclination of the undulation of the main body of the film, and extracting only the coating roughness. When obtaining the line roughness, when the surface of the coating layer is viewed from above, four areas adjacent to the areas where there are no communicating holes derived from the reinforcing yarns and the sacrificial yarns (that is, the shaded areas in FIG. 3) are measured. The measurement line width was set to 20 μm, and 10 points were measured to obtain an average value. Further, in tilt correction, a function of a laser microscope (“VK-9700” manufactured by Keyence Corporation) that corrects the tilt of the object when the object is tilted was used. As a result, the surface roughness of the coating layer was 1.34 μm.

[Evaluation of electrolysis]
The electrolytic cell used for electrolysis had a structure in which an ion exchange membrane was arranged between an anode and a cathode, and four natural circulation zero-gap electrolytic cells arranged in series were used. As a cathode, a woven mesh was used, which was woven with a 50-mesh opening of nickel fine wires with a diameter of 0.15 mm coated with cerium oxide and ruthenium oxide as catalysts. In order to bring the cathode and the ion-exchange membrane into close contact with each other, a mat made of nickel fine wires was placed between the cathode and a current collector made of nickel expanded metal. As the anode, a titanium expanded metal 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 to the cathode side while maintaining the concentration of caustic soda at 32% by mass. The temperature of the electrolytic cell was set to 85° C., and electrolysis was carried out at a current density of 6 kA/m ² under the condition that the liquid pressure on the cathode side of the electrolytic cell was 5.3 kPa higher than the liquid pressure on the anode side. The voltage between the anode and the cathode in the electrolytic cell was measured every day with a voltmeter TR-V1000 manufactured by KEYENCE, and the average value for 7 days was obtained as the electrolytic voltage.

After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolysis performance was evaluated using this ion-exchange membrane. As a result, the voltage showed a low value of 3.07V. .

[Measurement of membrane cross-sectional average thickness A]
After removing the coating layer from the ion-exchange membrane after the coating layer is formed, cut from the layer C side or the layer S side in a direction perpendicular to the surface of the layer, and have a long side of 6 mm or more and a short side of about A sample with a thickness of 100 μm was obtained. At that time, as shown in FIG. 4, each side of the sample was made parallel to each of the four reinforcing threads. The thickness was actually measured using an optical microscope with the cross section facing upward in the hydrated state. At that time, the parts to be cut are two or more adjacent reinforcing threads, two or more adjacent communicating holes (derived from sacrificial threads), and the central part of the area surrounded by the reinforcing threads and communicating holes. 3 and the part indicated by "○". Also, the pieces to be cut were made to include at least six reinforcing threads perpendicular to the cutting direction, and the pieces were collected at three locations. From the cross-sectional view of each fragment obtained, a was measured as shown in FIGS. , 120 μm.

[Measurement of Membrane Cross-sectional Average Thickness B]
After removing the coating layer from the ion-exchange membrane after the coating layer is formed, cut from the layer C side or the layer S side in a direction perpendicular to the surface of the layer, and have a long side of 6 mm or more and a short side of about A sample with a thickness of 100 μm was obtained. At that time, as shown in FIG. 4, each side of the sample was made parallel to each of the four reinforcing threads. The thickness was actually measured using an optical microscope with the cross section facing upward in the hydrated state. At that time, the part to be cut off was the central part of the reinforcing yarn, and included the parts indicated by □ and Δ in FIG. 3 . Also, the pieces to be cut were made to include 15 or more reinforcing threads perpendicular to the cutting direction, and the pieces were collected at three locations. From the cross-sectional view of each fragment obtained, b was measured as shown in FIGS. , 260 μm. That is, the value of B/A was 2.17.

[Example 2]
An ion-exchange membrane was produced in the same manner as in Example 1, except that the adjustment of the average droplet diameter of the spray was changed to 80 μm. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.32 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a low value of 3.07V.

[Example 3]
In Example 1, an ion exchange membrane was prepared in the same manner as in Example 1, except that a suspension was used in which the mass ratio of polymer (B3) to the total mass of polymer (B3) and zirconium oxide particles was 0.4. made. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.49 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a low value of 3.06V.

[Example 4]
In Example 3, an ion-exchange membrane was produced in the same manner as in Example 1, except that the adjustment of the average droplet diameter of the spray was changed to 80 μm. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.24 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a low value of 3.07V.

[Example 5]
In Example 1, an ion exchange membrane was prepared in the same manner as in Example 1, except that a suspension was used in which the mass ratio of polymer (B3) to the total mass of polymer (B3) and zirconium oxide particles was 0.6. made. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.51 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a low value of 3.05V.

[Example 6]
An ion-exchange membrane was produced in the same manner as in Example 3, except that the surface temperature of the membrane body during spraying was changed to 46°C. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.23 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a low value of 3.07V.

[Example 7]
In Example 1, an ion exchange membrane was prepared in the same manner as in Example 1, except that a suspension was used in which the mass ratio of polymer (B3) to the total mass of polymer (B3) and zirconium oxide particles was 0.7. made. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.36 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a low value of 3.07V.

[Comparative Example 1]
An ion-exchange membrane was produced in the same manner as in Example 1, except that the adjustment of the average droplet diameter of the spray was changed to 154 μm. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.19 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a high value of 3.09V.

[Comparative Example 2]
In Example 1, an ion exchange membrane was prepared in the same manner as in Example 1, except that a suspension was used in which the mass ratio of polymer (B3) to the total mass of polymer (B3) and zirconium oxide particles was 0.2. made. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.48 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a high value of 3.10V.

[Comparative Example 3]
In Example 1, a suspension was used in which the mass ratio of polymer (B3) to the combined mass of polymer (B3) and zirconium oxide particles was 0.2, and the average droplet size of the spray was adjusted to 154 μm. An ion-exchange membrane was produced in the same manner as in Example 1, except for the changes. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.18 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a high value of 3.10V.

[Comparative Example 4]
An ion-exchange membrane was produced in the same manner as in Example 3, except that the adjustment of the average droplet diameter of the spray was changed to 154 μm. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.12 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a high value of 3.16V.

[Comparative Example 5]
An ion-exchange membrane was produced in the same manner as in Example 5, except that the adjustment of the average droplet diameter of the spray was changed to 154 μm. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.13 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a high value of 3.15V.

[Comparative Example 6]
An ion-exchange membrane was produced in the same manner as in Example 3, except that the surface temperature of the membrane body during spraying was changed to 25°C. In this ion exchange membrane, the content of the fluorine-containing polymer in the binder was 100% by mass.

The coating density of the dried coating layer was measured in the same manner as in Example 1 and found to be 0.5 mg per 1 cm ² . Further, the surface roughness of the coating layer was measured in the same manner as in Example 1 and found to be 1.07 μm. Furthermore, the average cross-sectional thickness A, the average cross-sectional thickness B, and A/B were measured in the same manner as in Example 1 and found to be 120 μm, 260 μm, and 2.17, respectively.

[Evaluation of electrolysis]
After moistening the ion-exchange membrane having a dry coating layer so as to increase the amount by 2% by mass, the electrolytic performance was evaluated under the same conditions as in Example 1, except that this ion-exchange membrane was used. As a result, The voltage showed a high value of 3.11V.

Based on the above results, FIG. 10 shows the relationship between the average droplet size and the voltage in Examples 1 to 5 and Comparative Examples 1 to 5 (substrate surface temperature was 57° C. in all Examples and Comparative Examples). In the examples in which the average droplet size was controlled to a desired value or less, the voltage tended to decrease as the binder ratio increased.

DESCRIPTION OF SYMBOLS 1... Ion-exchange membrane, 2... Carboxylic acid layer, 3... Sulfonic acid layer, 4... Reinforcing material, 10... Membrane main body, 11a, 11b... Coating layer, 21, 22... Reinforcing material, 100... Electrolytic bath, 200... Anode , 300... cathode, 52... reinforcing thread, 504a... sacrificial thread, 504... communicating hole 504.

Claims (7)

a membrane body containing a fluorine-containing polymer having ion exchange groups;
a coating layer disposed on at least one surface of the membrane body;
An ion exchange membrane having
The coating layer contains inorganic particles and a binder,
The mass ratio of the binder to the total mass of the inorganic particles and the binder in the coating layer is more than 0.3 and 0.9 or less,
The ion exchange membrane, wherein the coating layer has a surface roughness of 1.20 μm or more. The inorganic particles are particles containing at least one inorganic substance selected from the group consisting of oxides of group IV elements of the periodic table, nitrides of group IV elements of the periodic table, and carbides of group IV elements of the periodic table. The ion exchange membrane according to claim 1, wherein the ion exchange membrane is 3. The ion exchange membrane according to claim 1, wherein the inorganic particles are zirconium oxide particles. The membrane body comprises a layer S containing a fluoropolymer having a sulfonic acid group, a layer C containing a fluoropolymer having a carboxylic acid group, and a layer S disposed inside the layer S, and reinforcing threads and sacrificial layers. a plurality of reinforcements functioning as at least one of the threads;
When the ion exchange membrane is viewed from the top, the average thickness of the membrane cross section in pure water in the region where the reinforcing material is not present is A, and the region where the reinforcing yarns intersect and the reinforcing yarn and the sacrificial yarn are The ion exchange membrane according to any one of claims 1 to 3, wherein A and B satisfy the formula (1), where B is the membrane cross-sectional average thickness in pure water of the intersecting region. .
2.0≦B/A≦5.0 (1) A method for producing an ion exchange membrane according to any one of claims 1 to 4,
A step of spraying a coating liquid containing inorganic particles, a binder and a solvent by a spray method and drying it to form a coating layer on the surface of the membrane body,
The method for producing an ion-exchange membrane, wherein the average droplet size during spraying is 100 μm or less. A method for producing an ion exchange membrane according to any one of claims 1 to 4,
A step of spraying a coating liquid containing inorganic particles, a binder and a solvent by a spray method and drying it to form a coating layer on the surface of the membrane body,
The method for producing an ion-exchange membrane, wherein the surface temperature of the membrane body during drying is 40° C. or higher and the boiling point of the solvent or lower. An electrolytic cell comprising the ion exchange membrane according to any one of claims 1 to 4.

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