WO2017154925A1

WO2017154925A1 - Ion exchange membrane, method for producing same and alkali chloride electrolysis device

Info

Publication number: WO2017154925A1
Application number: PCT/JP2017/009069
Authority: WO
Inventors: 隆之金子; 草野　博光; 泰山木; 拓久央西尾
Original assignee: 旭硝子株式会社
Priority date: 2016-03-08
Filing date: 2017-03-07
Publication date: 2017-09-14
Also published as: CN108699712A; JPWO2017154925A1

Abstract

Provided are: an ion exchange membrane for alkali chloride electrolysis, which is easily controlled with respect to variation in dimensional change without requiring a strict control of the residual amount of sacrificial threads in the ion exchange membrane; an ion exchange membrane precursor membrane; and an alkali chloride electrolysis device. An ion exchange membrane for alkali chloride electrolysis, which comprises a fluorine-containing polymer layer having an ion exchange group and a reinforcing material that is composed of reinforcing threads and sacrificial threads and is provided within the fluorine-containing polymer layer having an ion exchange group, and which is characterized in that the average elastic modulus of the sacrificial threads is 1.0-7.0 GPa.

Description

Ion exchange membrane, method for producing the same, and alkali chloride electrolyzer

The present invention relates to an ion exchange membrane, a precursor membrane thereof, a production method thereof, an alkali chloride electrolysis apparatus, and a production method thereof.

As an ion exchange membrane used in an alkali chloride electrolysis method for producing an alkali hydroxide and chlorine by electrolyzing an aqueous alkali chloride solution such as salt seawater, ion exchange groups (carboxylic acid groups or carboxylate groups, and sulfonic acid groups are used. Alternatively, an electrolyte membrane made of a fluorine-containing polymer having a sulfonate group) is known. The electrolyte membrane is usually reinforced with a reinforcing material made of reinforcing yarn from the viewpoint of maintaining mechanical strength and dimensional stability.

As an ion exchange membrane having a reinforcing material, for example, an ion exchange membrane in which the following layers (1) to (4) are sequentially laminated is known (Patent Document 1).
(1) A polymer A layer containing a fluorinated polymer having a carboxylic acid type functional group and having an ion exchange capacity of 0.80 mg equivalent / g, (2) an ion exchange capacity comprising a fluorinated polymer having a sulfonic acid type functional group A polymer B layer having an ion exchange capacity of 1.05 mg equivalent / g, comprising a polymer B layer having a sulfonic acid type functional group.

Japanese Unexamined Patent Publication No. 2013-163858

The ion exchange membrane for alkali chloride electrolysis (hereinafter also referred to as “ion exchange membrane”) changes in dimensions depending on the operating conditions of the electrolytic cell, that is, swelling / shrinkage due to alkali chloride aqueous solution concentration, alkali hydroxide concentration, operating temperature, etc. To do. Since the ion exchange membrane is used by being fixed in the electrolysis apparatus, if the size of the ion exchange membrane changes, the membrane and the electrode rub against each other due to wrinkles on the membrane, and pinholes are generated or the membrane is pulled. In some cases, the film may be damaged due to cracks. In order to prevent these, it is necessary to suppress unexpected dimensional changes of the ion exchange membrane. The dimensional change of the ion exchange membrane can be suppressed by a reinforcing material provided inside the ion exchange membrane.

The reinforcing material contained in the ion-exchange membrane having an ion-exchange group is an ion-exchange membrane precursor having a fluorine-containing polymer layer having a group that can be converted into an ion-exchange group and a reinforcing cloth provided inside the fluorine-containing polymer layer. It is a material derived from the reinforcing cloth contained in the membrane. The reinforcing fabric is usually composed of a reinforcing yarn and a sacrificial yarn, and the sacrificial yarn is composed of a material that elutes when immersed in an alkaline aqueous solution. In the step of immersing an ion exchange membrane precursor membrane having a reinforcing cloth inside in an alkaline aqueous solution to hydrolyze a group that can be converted into an ion exchange group in the ion exchange membrane precursor membrane and converting it into an ion exchange group Of the reinforcing yarn and sacrificial yarn constituting the reinforcing cloth, the reinforcing yarn remains undissolved, and at least a part of the sacrificial yarn dissolves, and a reinforcing material comprising the reinforcing yarn and the sacrificial yarn is present in the ion exchange membrane. It is formed. In the step, the reinforcing yarn constituting the reinforcing cloth is not dissolved. That is, the reinforcing material in the ion exchange membrane is composed of a reinforcing yarn and a sacrificial yarn that remains without being dissolved in the above process.

It is well known to those skilled in the art that the fineness of the reinforcing yarn constituting the reinforcing material included in the ion exchange membrane and the density of the reinforcing yarn affect the dimensional change of the ion exchange membrane.
Further examination by the present inventors has found that the amount of the sacrificial yarn remaining without dissolving that constitutes the reinforcing material included in the ion exchange membrane affects the variation in the dimensional change of the ion exchange membrane. It was. The remaining amount of the sacrificial yarn is appropriately determined depending on the strength required for the ion exchange membrane and the tolerance of dimensional change, and the above-described step, that is, the group that can be converted into the ion exchange group in the ion exchange membrane precursor membrane is ion-exchanged. In the step of converting to a base, the conditions are controlled by selecting conditions such as the concentration, temperature, and contact time of the alkaline aqueous solution. In order to set the remaining amount of the sacrificial yarn to a predetermined value, it is necessary to strictly control these conditions.
However, especially in large facilities, when the ion-exchange membrane precursor membrane is continuously hydrolyzed, non-uniform distribution occurs in the concentration and temperature of the alkaline aqueous solution in the hydrolysis tank, which is included in the ion-exchange membrane. It was difficult to strictly control the remaining amount of sacrificial yarn in the reinforcing material.

In the alkali chloride electrolysis using an ion exchange membrane, the ion exchange membrane can easily control the variation in the dimensional change of the ion exchange membrane without requiring strict control of the remaining amount of the sacrificial yarn in the ion exchange membrane. It is an object of the present invention to provide an exchange membrane, a precursor film thereof, a production method thereof, an alkali chloride electrolysis apparatus, and a production method thereof.

As a result of the study by the present inventors, an ion exchange membrane using a sacrificial yarn having an elastic modulus in a specific range as a sacrificial yarn constituting a reinforcing cloth or a reinforcing material composed of a reinforcing yarn and a sacrificial yarn is a residual amount of the sacrificial yarn. It was found that the variation of dimensional change due to the variation of was small.
The present invention has been completed based on the above findings. It has the following configuration.
[1] An ion exchange membrane having a fluorine-containing polymer layer having ion exchange groups, and a reinforcing material comprising a reinforcing yarn and a sacrificial yarn provided inside the fluorine-containing polymer layer having ion exchange groups, An ion exchange membrane characterized in that the sacrificial yarn has an average elastic modulus of 1.0 to 7.0 GPa.
[2] The reinforcing yarn has a fineness of 20 to 200 denier, and the density of the reinforcing yarn in the reinforcing cloth is 10 to 40 / inch. [1] An ion exchange membrane.
[3] In the above [1] or [2], the sacrificial yarn has a fineness of 5 to 100 denier, and the number of filaments per sacrificial yarn in the reinforcing fabric is 1 to 32 monofilaments or multifilaments. The ion exchange membrane for alkali chloride electrolysis of description.
[4] The ion exchange membrane according to any one of [1] to [3], wherein the sacrificial yarn is a sacrificial yarn partially dissolved and removed.
[5] The ion exchange membrane according to any one of [1] to [4], wherein at least a part of the fluorine-containing polymer layer having an ion exchange group is a fluorine-containing polymer layer having a sulfonic acid type functional group. .
[6] The ion exchange membrane according to any one of [1] to [4], wherein at least a part of the fluorine-containing polymer layer having an ion exchange group is a fluorine-containing polymer layer having a carboxylic acid type functional group. .
[7] The ion exchange membrane according to any one of [1] to [6], further including a layer containing inorganic particles on at least one outermost surface.
[8] An alkali chloride electrolyzer comprising the ion exchange membrane according to any one of [1] to [7] as an electrolytic membrane separating a cathode chamber on the cathode side and an anode chamber on the anode side in the electrolytic cell.
[9] An ion exchange membrane precursor membrane having a fluoropolymer layer having a group that can be converted into an ion exchange group, and a reinforcing cloth provided inside the fluoropolymer layer having a group that can be converted into an ion exchange group The reinforcing cloth comprises a reinforcing yarn and a sacrificial yarn, and the sacrificial yarn has an average elastic modulus of 1.0 to 7.0 GPa.
[10] The ion exchange membrane precursor according to [9], wherein at least a part of the fluoropolymer layer having a group that can be converted into an ion exchange group is a fluoropolymer layer having a group that can be converted into a sulfonic acid type functional group. Body membrane.
[11] The [9] or [10], wherein at least a part of the fluoropolymer layer having a group that can be converted into an ion exchange group has a fluoropolymer layer that is a group that can be converted into a carboxylic acid type functional group. Ion exchange membrane precursor membrane.
[12] The ion-exchange membrane precursor film according to any one of [9] to [11] is brought into contact with an alkaline aqueous solution to convert a group that can be converted into an ion-exchange group into an ion-exchange group, A method for producing an ion exchange membrane comprising obtaining a ion exchange membrane comprising a fluorine-containing polymer layer having an ion exchange group and a reinforcing material by dissolving and removing at least a part of the sacrificial yarn in the reinforcing fabric.
[13] The method for producing an ion exchange membrane according to [12], wherein a part of the sacrificial yarn in the reinforcing cloth is dissolved and removed.
[14] After obtaining an ion exchange membrane by the production method according to [12] or [13], the ion exchange membrane is divided into an anode chamber on the cathode side and an anode chamber on the anode side in the electrolytic cell. A method for producing an alkali chloride electrolysis apparatus, comprising:

The ion exchange membrane of the present invention is a membrane that can easily control the variation of the dimensional change of the ion exchange membrane without requiring strict control of the remaining amount of the sacrificial yarn in the reinforcing material included in the ion exchange membrane. Since the alkali chloride electrolysis apparatus of the present invention has the ion exchange membrane of the present invention, it does not require strict control of the residual amount of sacrificial yarn in the reinforcing material included in the ion exchange membrane, and the variation in the dimensional change of the ion exchange membrane Is easy to control.
According to the method for producing an ion exchange membrane of the present invention, it is easy to control variation in the dimensional change of the ion exchange membrane without requiring strict control of the remaining amount of the sacrificial yarn in the reinforcing material included in the ion exchange membrane. An ion exchange membrane can be manufactured.
According to the method for producing an alkaline chloride electrolysis apparatus of the present invention, chlorination that does not require strict control of the remaining amount of the sacrificial yarn in the reinforcing material included in the ion exchange membrane and can easily control the variation in the dimensional change of the ion exchange membrane. An alkaline electrolyzer can be manufactured.

The following definitions of terms apply throughout this specification and the claims.
The “ion exchange membrane” is a membrane used for electrolysis of an alkali chloride aqueous solution and containing a polymer having an ion exchange group.
The “ion exchange group” is a group that can exchange at least a part of ions contained in the group with other ions. The following carboxylic acid type functional groups, sulfonic acid type functional groups and the like can be mentioned.
The “carboxylic acid type functional group” means a carboxylic acid group (—COOH) or a carboxylic acid group (—COOM ¹ , where M ¹ is an alkali metal or a quaternary ammonium base).
The “sulfonic acid type functional group” means a sulfonic acid group (—SO ₃ H) or a sulfonic acid group (—SO ₃ M ² , where M ² is an alkali metal or a quaternary ammonium base). To do.
An “ion exchange membrane precursor membrane” is a membrane that is a precursor of an ion exchange membrane and contains a polymer having a group that can be converted into an ion exchange group.
The “group that can be converted into an ion exchange group” means a group that can be converted into an ion exchange group by a known treatment such as hydrolysis treatment or acidification treatment.
The “group that can be converted into a carboxylic acid type functional group” means a group that can be converted into a carboxylic acid type functional group by a known process such as hydrolysis or acidification.
The “group that can be converted into a sulfonic acid type functional group” means a group that can be converted into a sulfonic acid type functional group by a known treatment such as hydrolysis or acidification.

The “perfluorocarbon polymer” means a polymer in which all of hydrogen atoms bonded to carbon atoms in the polymer are substituted with fluorine atoms. Some of the fluorine atoms in the perfluorocarbon polymer may be substituted with one or both of chlorine atoms and bromine atoms.
The “structural unit” means a part derived from a monomer that is present in the polymer and constitutes the polymer. For example, when the structural unit is generated by addition polymerization of a monomer having a carbon-carbon unsaturated double bond, the structural unit derived from the monomer is a divalent structural unit generated by cleavage of the unsaturated double bond. is there. Further, the structural unit may be a structural unit obtained by forming a polymer having a structure of a certain structural unit and then chemically converting the structural unit. In the following, in some cases, a structural unit derived from an individual monomer may be described by a name in which “unit” is added to the monomer name.

“Reinforcing material” means a material used to improve the strength of an ion exchange membrane.
The “reinforcing cloth” means a cloth used as a raw material for a reinforcing material for improving the strength of the ion exchange membrane.
The “reinforcing yarn” is a yarn constituting the reinforcing fabric, and is a yarn made of a material that does not elute even when the reinforcing fabric is immersed in an alkaline aqueous solution (for example, a sodium hydroxide aqueous solution having a concentration of 32% by mass). is there.
The “sacrificial yarn” is a yarn constituting the reinforcing fabric, and is a yarn made of a material that elutes into the alkaline aqueous solution when the reinforcing fabric is immersed in the alkaline aqueous solution.
“Elution hole” means a hole formed as a result of the sacrificial yarn being eluted in an alkaline aqueous solution.

[Ion exchange membrane]
The ion exchange membrane of the present invention has a layer made of a fluorine-containing polymer having ion exchange groups (hereinafter also referred to as “layer (P)”), and a reinforcing material made of reinforcing yarn and sacrificial yarn is layer (P). Is provided inside. The sacrificial yarn may be a sacrificial yarn partially dissolved and removed. In addition, elution holes may be formed in the ion exchange membrane by dissolving and removing part of the sacrificial yarn.

(Reinforcing material)
The reinforcing fabric is usually composed of a reinforcing yarn and a sacrificial yarn, and the sacrificial yarn is composed of a material that elutes when immersed in an alkaline aqueous solution. In the step of immersing an ion exchange membrane precursor membrane having a reinforcing cloth inside in an alkaline aqueous solution to hydrolyze a group that can be converted into an ion exchange group in the ion exchange membrane precursor membrane and converting it into an ion exchange group Of the reinforcing yarn and sacrificial yarn constituting the reinforcing cloth, the reinforcing yarn remains undissolved, and at least a part of the sacrificial yarn dissolves, and a reinforcing material comprising the reinforcing yarn and the sacrificial yarn is present in the ion exchange membrane. It is formed. In the step, the reinforcing yarn constituting the reinforcing cloth is not dissolved. That is, the reinforcing material in the ion exchange membrane is composed of a reinforcing yarn and a sacrificial yarn that remains without being dissolved in the above process.
The reinforcing material is made of reinforcing yarn and sacrificial yarn, and is a material that reinforces the layer (P). The reinforcing material is derived from a reinforcing cloth contained in an ion-exchange membrane precursor film having a fluorine-containing polymer layer having a group that can be converted into an ion-exchange group and a reinforcing cloth provided inside the fluorine-containing polymer layer.

The reinforcing fabric is composed of warp and weft, and the warp and weft are preferably orthogonal. Each of the warp and weft is preferably composed of both a reinforcing yarn and a sacrificial yarn. That is, it is preferable that the warp yarn in the reinforcing fabric is composed of the reinforcing yarn and the sacrificial yarn, and the weft yarn in the reinforcing fabric is composed of the reinforcing yarn and the sacrificial yarn.

The reinforcing yarn is a yarn made of a material that does not elute even when an ion exchange membrane precursor membrane including a reinforcing fabric (hereinafter also referred to as “ion exchange membrane precursor membrane”) is immersed in an alkaline aqueous solution. In the manufacturing process of the ion exchange membrane manufacturing method to be described later, the ion exchange membrane precursor as a yarn constituting the reinforcing material remains undissolved even after the ion exchange membrane precursor membrane including the reinforcing cloth is immersed in an alkaline aqueous solution. This contributes to the maintenance of mechanical strength and dimensional stability.
As the reinforcing yarn, a yarn containing a perfluorocarbon polymer is preferable, a yarn containing polytetrafluoroethylene (hereinafter referred to as “PTFE”) is preferable, and a PTFE yarn made only of PTFE is more preferable.

The fineness of the reinforcing yarn is preferably 20 to 200 denier, more preferably 50 to 150 denier, and particularly preferably 80 to 100 denier. When the fineness is not less than the lower limit, the mechanical strength of the ion exchange membrane is sufficiently high. If the fineness is less than or equal to the above upper limit value, the membrane resistance of the ion exchange membrane can be kept low, and an increase in electrolytic voltage can be suppressed.

The density (the number of driving) of the reinforcing yarn in the reinforcing cloth for forming the reinforcing material is preferably 10 to 40 / inch, and more preferably 20 to 30 / inch. When the density is equal to or higher than the lower limit, the mechanical strength as a reinforcing material is sufficiently high. When the density is equal to or lower than the upper limit value, the membrane resistance of the ion exchange membrane can be kept low, and an increase in electrolytic voltage can be suppressed.

The sacrificial yarn is a yarn that elutes by immersing the ion exchange membrane precursor membrane including the reinforcing cloth in an alkaline aqueous solution. When the ion exchange membrane precursor membrane including the reinforcing cloth is immersed in an alkaline aqueous solution, it is preferable that a part of the sacrificial yarn is dissolved and removed, and the dissolved residue remains as a sacrificial yarn constituting the reinforcing material. . When at least a part of the sacrificial yarn remains as a dissolution residue, it contributes to maintaining the mechanical strength and dimensional stability of the ion exchange membrane.
In addition, when the ion exchange membrane precursor film | membrane containing a reinforcement cloth is immersed in alkaline aqueous solution, all the sacrifice yarns melt | dissolve and a sacrifice yarn does not need to remain as a thread | yarn which comprises a reinforcement material. Even if the sacrificial yarn does not remain, inclusion of the reinforcing yarn in the reinforcing cloth can contribute to the mechanical strength of the ion exchange membrane precursor membrane.

In the present invention, the average elastic modulus of the sacrificial yarn constituting the reinforcing fabric or the reinforcing material is important, and the sacrificial yarn needs to have an average elastic modulus of 1.0 to 7.0 GPa. If the average elastic modulus is equal to or greater than the lower limit, yarn misalignment is less likely to occur during weaving. If the average elastic modulus is not more than the above upper limit value, the variation in dimensional change due to the remaining amount of sacrificial yarn can be kept low. The average elastic modulus is preferably 2.0 to 6.0 GPa, more preferably 3.0 to 6.0 GPa, and particularly preferably 4.0 to 5.0 GPa.
The average elastic modulus of the yarn including the sacrificial yarn is a specific value determined by the degree of polymerization of the polymer and the polymer material. Therefore, even before the ion exchange membrane precursor membrane including the reinforcing cloth having the sacrificial yarn is immersed in the alkaline aqueous solution, or after the sacrificial yarn in the reinforcing cloth is partially dissolved, the sacrificial yarn is immersed in the alkaline aqueous solution. The modulus of elasticity does not change.

The method for measuring the elastic modulus of the sacrificial yarn in the present invention is determined as follows.
Stress-strain (elongation) when a tensile tester (TENSILON RTC-1210A manufactured by Olintec Corporation) is attached with a sacrificial yarn before dipping in an alkaline aqueous solution at a chuck distance of 50 mm and pulled at a pulling speed of 50 mm / min. The stress at a curve strain (elongation) of 5% was measured, and the value divided by the average cross-sectional area of the sacrificial yarn before dipping in the alkaline aqueous solution was taken as the elastic modulus. For the average elastic modulus, the elastic modulus was measured 5 times, and the average of these values was defined as the average elastic modulus.
The cross-sectional area of the sacrificial yarn before being immersed in the alkaline aqueous solution was observed with an optical microscope and measured using image software. The cross-sectional area is measured at 10 locations of the sacrificial yarn, and the average value of these values is taken as the average cross-sectional area of the sacrificial yarn before being immersed in the alkaline aqueous solution.

In the present invention, the average cross-sectional area of the sacrificial yarns remaining in the ion-exchange membrane is preferably 500 ~ 5000μm ² / mm, and more preferably 1000 ~ 4000μm ² / mm, more preferably 1500 ~ 3000μm ² / mm. If the average cross-sectional area of the sacrificial yarn is greater than or equal to the lower limit, bending or cracking is unlikely to occur when handling the ion exchange membrane. When the average cross-sectional area is less than or equal to the upper limit value, curling is unlikely to occur during and after the ion exchange membrane is formed.
In addition, the measuring method of the average cross-sectional area of the sacrificial yarn remaining on the ion exchange membrane in the present invention is as described later. The cross section of the ion exchange membrane dried at 90 ° C. for 2 hours or more perpendicularly to the length direction of the sacrificial yarn is observed with an optical microscope, and the remaining sacrificial per 1 mm in the width direction of the membrane using image software Defined as the sum of the cross-sectional areas of the yarn. The measurement of the cross-sectional area of the remaining sacrificial yarn is performed at 10 locations, and the average cross-sectional area of the remaining sacrificial yarn is calculated.

The sacrificial yarn in the reinforcing fabric may be a monofilament composed of one filament or a multifilament composed of two or more filaments.
When the sacrificial yarn in the reinforcing fabric is monofilament or multifilament, the number of filaments per sacrificial yarn in the reinforcing fabric is preferably 1 to 32, more preferably 2 to 16, and 2 to 8 Is more preferable. When the number of filaments is equal to or greater than the lower limit, the contact surface between the sacrificial yarn and the alkaline aqueous solution is widened, and the sacrificial yarn is easily eluted into the alkaline aqueous solution. If the number of filaments is less than or equal to the above upper limit, the contact area between the sacrificial yarn and the alkaline aqueous solution is reduced, elution of the sacrificial yarn into the alkaline aqueous solution is suppressed, and a portion of the sacrificial yarn remains. The sacrificial yarn remaining on the ion exchange membrane contributes to the mechanical strength of the ion exchange membrane.

The sacrificial yarn is preferably a yarn containing at least one selected from the group consisting of PET, polybutylene terephthalate (hereinafter referred to as PBT), polytrimethylene terephthalate (hereinafter referred to as PTT), rayon, and cellulose. . Among these, a PET yarn made of PET alone, a PET / PBT yarn made of a mixture of PET and PBT, a PBT yarn made of only PBT, or a PTT yarn made of only PTT is more preferable.

The fineness of the sacrificial yarn in the reinforcing fabric is preferably 5 to 100 denier, more preferably 9 to 60 denier, and further preferably 12 to 40 denier. If the fineness of the sacrificial yarn in the reinforcing fabric is not less than the lower limit, the mechanical strength is sufficiently high and the woven fabric property is sufficiently high. If the fineness of the sacrificial yarn in the reinforcing fabric is less than or equal to the above upper limit value, the elution hole formed after the sacrificial yarn is eluted does not come too close to the surface of the membrane (P), and the surface of the membrane (P) Cracks are difficult to enter, and as a result, a decrease in mechanical strength of the ion exchange membrane can be suppressed.

(Layer made of fluorine-containing polymer having ion exchange groups (P))
The layer (P) is a layer made of a fluorine-containing polymer having an ion exchange group. The layer (P) may be a single layer or a layer formed from a plurality of layers.
In the case where the layer (P) is a single layer, a layer (hereinafter referred to as “layer (C)” consisting of a fluorinated polymer having a carboxylic acid type functional group (hereinafter also referred to as “fluorinated polymer (C)”). Or a layer composed of a fluorinated polymer having a sulfonic acid type functional group (hereinafter also referred to as “fluorinated polymer (S)”) (hereinafter also referred to as “layer (S)”). It is preferable to be configured.

In the case where the layer (P) is formed from a plurality of layers, the layer (P) is preferably composed of a layer (C) and a layer (S). In this case, one or both of the layer (C) and the layer (S) may be a single layer or a plurality of layers.
When one or both of the layer (C) and the layer (S) are formed from a plurality of layers, the type of structural unit constituting the fluoropolymer (C) or the fluoropolymer (S) in each layer, carboxylic acid The proportion of structural units having a functional group or a sulfonic acid type functional group may be different.
At least a part of the layer (P) is preferably composed of the layer (S), and the layer (P) is more preferably composed of the layer (C) and the layer (S).
When the layer (P) is composed of the layer (C) and the layer (S), the reinforcing material is preferably provided in the layer (S).

<Layer (C) made of fluorinated polymer having carboxylic acid type functional group>
The layer (C) may be a single layer or a layer formed from a plurality of layers. A reinforcing material may be provided inside the layer (C). As a layer (C), the layer which does not contain materials other than fluorine-containing polymer (C), such as a reinforcing material, and consists only of fluorine-containing polymer (C) from the point of electrolytic performance.

The fluoropolymer (C) is a hydrolyzable group that can be converted to a carboxylic acid type functional group of a fluoropolymer having a group that can be converted to a carboxylic acid type functional group (hereinafter also referred to as “fluorinated polymer (C ′)”). It was obtained by decomposing and converting to a carboxylic acid type functional group.
As the fluoropolymer (C), a fluoropolymer having a structural unit based on the following monomer (1) and a structural unit based on the following monomer (2) (hereinafter referred to as “fluorinated polymer (C′1)”). And a fluorine-containing polymer in which Y is converted to —COOM (wherein M is an alkali metal) (hereinafter also referred to as “fluorinated polymer (C1)”).
CF ₂ = CX ¹ X ² (1)
_{_{_{_{CF 2 = CF- (O) p}}}} - (CF 2) q - (CF 2 CFX 3) r - (O) s - (CF 2) t - (CF 2 CFX 4) u -Y ··· (2)

X ¹ and X ² are each independently a fluorine atom, a chlorine atom, or a trifluoromethyl group, and a fluorine atom is preferred from the viewpoint of chemical durability of the ion exchange membrane.

Examples of the monomer (1) include CF ₂ = CF ₂ , CF ₂ = CFCl, CF ₂ = CFCF _{3 and the} like, and CF ₂ = CF ₂ is preferable from the viewpoint of chemical durability of the ion exchange membrane.

X ³ and X ⁴ are each independently a fluorine atom or a trifluoromethyl group.
Y is a group that can be converted to a carboxylic acid type functional group. Specifically, —CN, —COF, —COOR ¹ (where R ¹ is an alkyl group having 1 to 10 carbon atoms), —COONR ² R ³ (where R ² and R ³ are each independently And a hydrogen atom or an alkyl group having 1 to 10 carbon atoms).
p is 0 or 1. q is an integer of 0 to 12. r is an integer of 0 to 3. s is 0 or 1. t is an integer of 0 to 12. u is an integer of 0 to 3. However, p and s are not 0 simultaneously, and r and u are not 0 simultaneously. That is, 1 ≦ p + s and 1 ≦ r + u. Particularly preferred are compounds in which p = 1, q = 0, r = 1, s = 0 to 1, t = 0 to 3, and u = 0 to 1.

Specific examples of the compound represented by the formula (2) include the following. In addition, a monomer (2) may be used individually by 1 type, and may be used in combination of 2 or more type.
CF ₂ = CF—O—CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF ₂ CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF ₂ —O—CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF ₂ —O—CF ₂ CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF ₂ —O—CF ₂ CF ₂ CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF ₂ CF ₂ —O—CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ —COOCH ₃ ,
CF ₂ = CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ CF ₂ —COOCH ₃ .

In addition to the monomer (1) and the monomer (2), another monomer may be used for the production of the fluorine-containing polymer (C ′). Other monomers include CF ₂ = CFR ^f1 (where R ^f1 is a perfluoroalkyl group having 2 to 10 carbon atoms), CF ₂ = CF—OR ^f2 (where R ^f2 is 1 to 10 carbon atoms) And CF ₂ ═CFO (CF ₂ ) _v CF═CF ₂ (where v is an integer of 1 to 3). By copolymerizing other monomers, the flexibility and mechanical strength of the ion exchange membrane can be increased. The proportion of other monomers is preferably 30% by mass or less of the total monomers (100% by mass) from the viewpoint of maintaining ion exchange performance.

The thickness of the layer (C) is preferably 5 to 50 μm, more preferably 10 to 35 μm. If the thickness is equal to or greater than the lower limit of the above range, the amount of chloride ions that permeate the ion exchange membrane can be suppressed, and the quality of the alkali hydroxide produced can be maintained well. If the thickness is not more than the upper limit of the above range, the membrane resistance of the ion exchange membrane can be kept low and the electrolysis voltage can be made sufficiently low.
In addition, in this invention, the thickness of the layer of an ion exchange membrane means the thickness of each layer in the ion exchange membrane dried at 90 degreeC for 2 hours or more.

<Layer made of fluorine-containing polymer having sulfonic acid type functional group (S)>
The layer (S) may be a single layer or a layer formed from a plurality of layers. A reinforcing material may be provided inside the layer (S). As the layer (S), a reinforcing material is preferably provided inside from the viewpoint of increasing the mechanical strength of the ion exchange membrane. It is more preferable that the reinforcing material is provided in the layer (S) than in the layer (C) because the reinforcing effect can be obtained without affecting the electrolytic performance.

The fluoropolymer (S) is a hydrolyzate of a group that can be converted to a sulfonic acid type functional group of a fluoropolymer having a group that can be converted to a sulfonic acid type functional group (hereinafter also referred to as “fluorinated polymer (S ′)”). It is preferably obtained by decomposition treatment and conversion to a sulfonic acid type functional group.
The fluorine-containing polymer (S) includes a fluorine-containing polymer (hereinafter referred to as “containing a polymer”) having a structural unit based on the monomer (1) and a structural unit based on at least one of the following monomer (3) or monomer (4). Fluoropolymer (S′1) ”) is hydrolyzed to convert Z into —SO ₃ M (where M is an alkali metal) (hereinafter referred to as“ fluorine polymer ( S1) ”) is preferred.

CF ₂ = CF—O—R ^f3 —Z (3)
CF ₂ = CF—R ^f3 —Z (4)

R ^f3 is a perfluoroalkyl group having 1 to 20 carbon atoms, may contain an etheric oxygen atom, and may be linear or branched.
Z is a group that can be converted into a sulfonic acid type functional group. Specific examples include —SO ₂ F, —SO ₂ Cl, —SO ₂ Br, and the like.

Specific examples of the compound represented by the formula (3) include the following compounds. In the formula, w is an integer of 1 to 8, and x is an integer of 1 to 5.
CF ₂ ═CF—O— (CF ₂ ) _w —SO ₂ F,
CF ₂ = CF—O—CF ₂ CF (CF ₃ ) —O— (CF ₂ ) _w —SO ₂ F,
CF ₂ = CF— [O—CF ₂ CF (CF ₃ )] _x —SO ₂ F.

Specific examples of the compound represented by the formula (4) include the following compounds. W in the formula is an integer of 1 to 8.
CF ₂ ═CF— (CF ₂ ) _w —SO ₂ F,
CF ₂ ═CF—CF ₂ —O— (CF ₂ ) _w —SO ₂ F.

As the monomer (3) or monomer (4), the following compounds are preferred from the viewpoint of easy industrial synthesis.
CF ₂ = CF—O—CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—O—CF ₂ CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—O—CF ₂ CF ₂ CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—O—CF ₂ CF (CF ₃ ) —SO ₂ F,
CF ₂ = CF—CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—CF ₂ CF ₂ CF ₂ —SO ₂ F,
CF ₂ = CF—CF ₂ —O—CF ₂ CF ₂ —SO ₂ F.
Monomer (3) or monomer (4) may be used alone or in combination of two or more.

In the production of the fluoropolymer (S ′), in addition to at least one of the monomer (1) and the monomer (3) or the monomer (4), another monomer may be used. Other monomers include CF ₂ = CFR ^f (where R ^f is a perfluoroalkyl group having 2 to 10 carbon atoms), CF ₂ = CF—OR ^f1 (where R ^f1 is 1 to 10 carbon atoms) And CF ₂ ═CFO (CF ₂ ) _v CF═CF ₂ (where v is an integer of 1 to 3). By copolymerizing other monomers, the flexibility and mechanical strength of the ion exchange membrane can be increased. The proportion of other monomers is preferably 30% by mass or less of the total monomers (100% by mass) from the viewpoint of maintaining ion exchange performance.

The total thickness of the layer (S) is preferably 40 to 200 μm, more preferably 40 to 140 μm. When the reinforcing material is provided inside the layer (S), the thickness of the layer (S1) on the layer (C) side of the reinforcing material in the layer (S) is preferably 30 to 140 μm, more preferably 30 to 100 μm. . Further, the thickness of the layer (S2) on the opposite side of the layer (C) from the reinforcing material in the layer (S) is preferably 10 to 60 μm, more preferably 10 to 40 μm. If the thickness of the layer (S1) and the layer (S2) is equal to or greater than the lower limit of the above range, a certain film thickness can be secured, and the film strength is increased. If the thickness of the layer (S1) and the layer (S2) is not more than the upper limit of the above range, the electrolysis voltage can be sufficiently lowered.
Each of the layer (S1) and the layer (S2) may be a single layer or a layer formed of a plurality of layers.

(Inorganic particle layer)
The ion exchange membrane may further include an inorganic particle layer on one or both of its outermost surfaces. The inorganic particle layer is preferably provided on at least one outermost surface of the ion exchange membrane, and more preferably provided on both outermost surfaces of the ion exchange membrane.
When the gas generated by the alkali chloride electrolysis adheres to the surface of the ion exchange membrane, the electrolysis voltage increases during the alkali chloride electrolysis. The inorganic particle layer is provided to suppress adhesion of a gas (chlorine gas or hydrogen gas) generated by alkali chloride electrolysis to the surface of the ion exchange membrane, and to suppress an increase in electrolysis voltage. The inorganic particle layer includes inorganic particles and a binder.

As the inorganic particles, those having excellent corrosion resistance with respect to an aqueous alkali chloride solution or an aqueous alkali hydroxide solution and having hydrophilicity are preferable. Specifically, at least one selected from the group consisting of oxides, nitrides and carbides of Group 4 elements or Group 14 elements is preferable, SiO ₂ , SiC, ZrO ₂ , or ZrC is more preferable, and ZrO ₂ Is particularly preferred.

The average particle diameter of the inorganic particles is preferably 0.5 to 1.5 μm, more preferably 0.7 to 1.3 μm. When the average particle diameter is not less than the lower limit, a high gas adhesion suppressing effect can be obtained. When the average particle size is not more than the above upper limit value, the inorganic particles are excellent in drop-off resistance. In addition, the average particle diameter here means the average particle diameter of the average secondary particle which the primary particle has aggregated, and is calculated | required as follows. Particles are dispersed in ethanol so that the concentration is 0.01% by mass or less and measured using Microtrac (UPA-150 manufactured by Nikkiso Co., Ltd.). The particle diameter (D50) at the point where the cumulative volume in the volume distribution curve becomes 50% was taken as the average secondary particle diameter.

As the binder, those having excellent corrosion resistance with respect to an aqueous alkali chloride solution or an aqueous alkali hydroxide solution and having hydrophilicity are preferred, a fluorinated polymer having a carboxylic acid group or a sulfonic acid group is preferred, and a fluorinated polymer having a sulfonic acid group is more preferred. preferable. The fluorine-containing polymer may be a homopolymer of a monomer having a carboxylic acid group or a sulfonic acid group, and is a copolymer of a monomer having a carboxylic acid group or a sulfonic acid group and a monomer copolymerizable with the monomer. Also good.

The binder mass ratio (hereinafter referred to as binder ratio) to the total mass of inorganic particles and binder in the inorganic particle layer is preferably 0.15 to 0.3, more preferably 0.15 to 0.25, and More preferably, it is 16 to 0.20. When the binder ratio is equal to or higher than the lower limit, the inorganic particles are excellent in the drop-off resistance. When the binder ratio is not more than the upper limit, a high gas adhesion suppressing effect can be obtained.

[Ion exchange membrane precursor membrane]
The ion exchange membrane precursor membrane of the present invention has a layer made of a fluorine-containing polymer having a group that can be converted into an ion exchange group (hereinafter also referred to as “layer (P ′)”). The aforementioned reinforcing cloth is provided inside the layer (P ′).
The layer (P ′) may be a single layer or a layer formed from a plurality of layers.
When the layer (P ′) is a single layer, a layer made of a fluoropolymer (C ′) (hereinafter also referred to as layer (C ′)) or a layer made of a fluoropolymer (S ′) (hereinafter, The layer (also referred to as a layer (S ′)) is preferable.
When the layer (P ′) is formed of a plurality of layers, the layer (P ′) is preferably composed of a layer (C ′) and a layer (S ′). In this case, one or both of the layer (C ′) and the layer (S ′) may be a single layer or a plurality of layers.

When one or both of the layer (C ′) and the layer (S ′) are formed from a plurality of layers, the type of structural unit constituting the fluoropolymer (C ′) or the fluoropolymer (S ′) in each layer Alternatively, the proportion of structural units having a carboxylic acid type functional group or a sulfonic acid type functional group may be different.
At least a part of the layer (P ′) is preferably composed of the layer (S ′), and the layer (P ′) is more preferably composed of the layer (C ′) and the layer (S ′).
When the layer (P ′) is composed of the layer (C ′) and the layer (S ′), it is preferable that the reinforcing cloth is provided in the layer (S ′).
Each of the layer (C ′) and the layer (S ′) may be a single layer or a layer formed of a plurality of layers.

[Production method of ion exchange membrane]
The ion exchange membrane of this invention can be manufactured through the following processes (a) and (b), for example.

Step (a): In the step (a), a reinforcing cloth comprising a reinforcing yarn and a sacrificial yarn is arranged inside a fluoropolymer having a group that can be converted into an ion exchange group, and a group that can be converted into an ion exchange group is formed. This is a step of obtaining an ion exchange membrane precursor membrane having a fluorine-containing polymer layer having a reinforcing cloth provided therein.
Step (b): In the step (b), the ion exchange membrane precursor film obtained in the step (a) is brought into contact with an alkaline aqueous solution to convert a group that can be converted into an ion exchange group into an ion exchange group. This is a step of obtaining an ion exchange membrane comprising a fluorine-containing polymer layer having a group and a reinforcing material provided therein. In this step, depending on the conditions for bringing the ion exchange membrane precursor membrane into contact with the alkaline aqueous solution, at least a part of the sacrificial yarn in the reinforcing cloth is dissolved and removed.

In the step (b), a part of the sacrificial yarn of the reinforcing cloth is dissolved and removed, and the ion exchange includes a fluoropolymer layer having an ion exchange group and a reinforcing material composed of the reinforcing yarn and the remaining sacrificial yarn. It is preferable to obtain a membrane.
For the dissolution in the sacrificial yarn, the ratio of the cross-sectional area of the sacrificial yarn remaining after dissolution to the cross-sectional area of the sacrificial yarn before melting is preferably 1 to 70%, more preferably 5 to 55%, and more preferably 10 to 40%. Most preferred.
In step (b), after converting a group that can be converted into an ion exchange group into an ion exchange group, if necessary, salt exchange for exchanging a counter cation of the ion exchange group may be performed. In salt exchange, for example, the counter cation of the ion exchange group is exchanged from potassium to sodium. A known method can be employed for salt exchange.

(Process (a))
In the step (a), an ion exchange membrane precursor membrane having a layer (P ′) and a reinforcing cloth provided in the layer (P ′) is produced.
When the layer (C ′) and the layer (S ′) are stacked according to the configuration of the layer (P ′), the ion exchange membrane precursor film is stacked by inserting a reinforcing cloth between any of the layers (C ′) and the layer (S ′). Thus, an ion exchange membrane precursor membrane having a reinforcing cloth provided inside the layer (P ′) can be produced. The layer (C ′) is preferably a layer comprising a fluoropolymer (C′1) (hereinafter also referred to as “layer (C′1)”), and the layer (S ′) is preferably a fluoropolymer (S ′). 1) (hereinafter also referred to as “layer (S′1)”) is preferable.
For example, when the layer (P ′) includes the layer (C ′) and the layer (S ′), and the reinforcing cloth is provided inside the layer (S ′), the layer (C ′) and the layer (S It can manufacture by laminating | stacking in order of '), a reinforcement cloth, and a layer (S'). In addition, when the layer (S ′) is composed of two layers (S ′) as described above, the layers (S ′) may be composed of the same fluoropolymer, or may be composed of different fluoropolymers. It may be a layer (S ′).

(Process (b))
In the step (b), a group that can be converted into an ion exchange group of the ion exchange membrane precursor membrane obtained in the step (a) is hydrolyzed and converted into an ion exchange group. Thereby, the ion exchange membrane precursor film | membrane which has the group which can be converted into an ion exchange group is converted into the ion exchange membrane which has an ion exchange group.
As the hydrolysis method, for example, a method using a mixture of a water-soluble organic compound and an alkali metal hydroxide as described in Japanese Patent Application Laid-Open No. 03-6240 is preferable.
By the conversion of the ion exchange group, the layer (C ′) is converted into the layer (C), and the layer (S ′) is converted into the layer (S).

The removal of a part of the sacrificial yarn in the reinforcing cloth is preferably performed by elution of a part of the sacrificial yarn by the alkaline aqueous solution used during the hydrolysis described above.

[Alkali chloride electrolyzer]
The alkali chloride electrolysis apparatus of the present invention can employ a known embodiment except that it has the ion exchange membrane of the present invention.
As one aspect of the alkali chloride electrolysis apparatus of the present invention, the alkali chloride electrolysis apparatus includes an electrolysis tank provided with a cathode and an anode, an electrolysis tank so as to divide the electrolysis tank into a cathode chamber on the cathode side and an anode chamber on the anode side. And the ion exchange membrane of the present invention to be mounted on.
When the ion exchange membrane of the present invention comprises a layer (C) and a layer (S), the ion exchange membrane is disposed in the electrolytic cell so that the layer (C) is on the cathode side and the layer (S) is on the anode side.
The cathode may be disposed in contact with the ion exchange membrane, or may be disposed at an interval.

The material constituting the cathode chamber is preferably a material resistant to alkali hydroxide and hydrogen. Examples of the material include stainless steel and nickel. As a material constituting the anode chamber, a material resistant to alkali chloride and chlorine is preferable. Examples of the material include titanium.

As the cathode base material, stainless steel, nickel and the like are preferable from the viewpoints of resistance to alkali hydroxide and hydrogen, workability, and the like. As the anode base material, titanium or the like is preferable from the viewpoints of resistance to alkali chloride and chlorine, workability, and the like. The surface of the electrode substrate is preferably coated with, for example, ruthenium oxide or iridium oxide.

For example, when producing an aqueous sodium hydroxide solution by electrolyzing a sodium chloride aqueous solution using the alkali chloride electrolyzer of the present invention, the sodium chloride aqueous solution is supplied to the anode chamber of the alkali chloride electrolyzer and the cathode chamber is filled with water. An aqueous sodium oxide solution is supplied, and the aqueous sodium chloride solution is electrolyzed while maintaining the concentration of the aqueous sodium hydroxide solution discharged from the cathode chamber at 18 to 36% by mass (for example, 32% by mass).

The reinforcing material in the ion exchange membrane has the effect of maintaining the mechanical strength of the ion exchange membrane and suppressing dimensional changes. The sacrificial yarn remaining in the ion exchange membrane plays a role of maintaining the mechanical strength of the ion exchange membrane together with the reinforcing yarn. Therefore, in order to maintain a certain mechanical strength that can withstand practical use, the sacrificial yarn of the present invention An average elastic modulus equal to or higher than the lower limit of the average elastic modulus is required.
On the other hand, the present inventors also contributed to the suppression of the dimensional change due to the remaining amount of the sacrificial yarn, the dimensional change rate fluctuates when the remaining amount of the sacrificial yarn changes, and the change in the remaining amount of the sacrificial yarn. It has been found that the variation in the dimensional change rate increases as the average elastic modulus of the sacrificial yarn increases. That is, if the average elastic modulus of the sacrificial yarn is less than or equal to the upper limit value of the average elastic modulus of the sacrificial yarn in the present invention described above, the variation in the dimensional change rate due to the change in the remaining amount of the sacrificial yarn can be suppressed. It is possible to suppress dimensional changes accompanying unexpected changes in the operating conditions of the tank.
Thus, maintenance of the mechanical strength required for the ion exchange membrane and suppression of fluctuations in the dimensional change rate can be satisfied in a balanced manner by adjusting the average elastic modulus of the sacrificial yarn. By setting the average elastic modulus to be equal to or less than the upper limit value of the average elastic modulus of the sacrificial yarn in the present invention described above, fluctuations in the dimensional change rate can be suppressed, so that the remaining amount of the sacrificial yarn in the reinforcing material included in the ion exchange membrane is reduced. An ion exchange membrane can be produced without requiring strict control.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not construed as being limited by these examples.

[Measurement of average elastic modulus of sacrificial yarn]
Stress-strain (elongation) when a tensile tester (TENSILON RTC-1210A manufactured by Olintec Corporation) is attached with a sacrificial yarn before dipping in an alkaline aqueous solution at a chuck distance of 50 mm and pulled at a pulling speed of 50 mm / min. The stress at a curve strain (elongation) of 5% was measured, and the value divided by the average cross-sectional area of the sacrificial yarn before dipping in the alkaline aqueous solution was taken as the elastic modulus. For the average elastic modulus, the elastic modulus was measured 5 times, and the average value of these values was defined as the average elastic modulus.
The cross-sectional area of the sacrificial yarn before being immersed in the alkaline aqueous solution was observed with an optical microscope and measured using image software. The cross-sectional area was measured at 10 locations of the sacrificial yarn, and the average value of these values was taken as the average cross-sectional area of the sacrificial yarn before being immersed in the alkaline aqueous solution.

[Measurement of average dimensional change rate of ion exchange membrane in aqueous sodium hydroxide solution]
Two marked lines (distance: 160 mm) were drawn on the ion exchange membrane, and the distance L0 between marked lines after being stored in a constant temperature room at 25 ° C. for 16 hours was measured using a digital caliper. Then, it immersed in 25 mass% sodium hydroxide aqueous solution at 25 degreeC for 2 hours, and measured distance L1 between marked lines using digital calipers. The dimensional change rate ΔL1 (%) was obtained from the following equation (A). The measurement was performed twice, and the average of these values was defined as the average dimensional change rate ΔL1.
ΔL1 = (L1−L0) / L0 × 100 (A)
When the ion exchange membrane is attached to the electrolytic cell, the cathode chamber is filled with about 30% by mass of sodium hydroxide. This evaluation simply simulates the elongation of the ion exchange membrane in a state where the ion exchange membrane is attached to the electrolytic cell and is in contact with the alkaline aqueous solution.

[Measurement of average dimensional change rate of ion exchange membrane in sodium chloride solution]
Two marked lines (distance: 160 mm) were drawn on the ion exchange membrane, and the distance L0 between marked lines after being stored in a constant temperature room at 25 ° C. for 16 hours was measured using a digital caliper. Thereafter, all the sacrificial yarns were dissolved by immersing them in a 32% by mass aqueous sodium hydroxide solution at 25 ° C. for 7 days. When the sacrificial yarn remained when the film cross section was observed with an optical microscope, the sacrificial yarn was again immersed in a 32% by mass sodium hydroxide aqueous solution at 25 ° C. and continued to be immersed until the sacrificial yarn was completely dissolved. After washing the ion exchange membrane after immersion in aqueous sodium hydroxide, the distance L2 between the marked lines when immersed in a 125 g / L aqueous sodium chloride solution at 90 ° C. for 30 minutes is read with a telescope while immersed in the aqueous sodium chloride solution The measurement was performed using a microscope (manufactured by Nihon Kogyo Seisakusho, digital cassette meter). The dimensional change rate ΔL2 (%) was determined from the following equation (B). The measurement was performed twice, and the average of these values was defined as the average dimensional change rate ΔL2.
ΔL2 = (L2−L0) / L0 × 100 (B)
The sacrificial yarn remains when the ion exchange membrane is attached to the electrolytic cell, but the sacrificial yarn dissolves during the electrolysis operation. This evaluation simply simulates the elongation of the ion exchange membrane when the concentration of sodium chloride aqueous solution is low when the ion exchange membrane is attached to the electrolytic cell and the sacrificial yarn is completely dissolved during the subsequent operation. Is.

[Measurement of average cross-sectional area of sacrificial yarn remaining in ion exchange membrane]
The cross-sectional area of the sacrificial yarn remaining in the ion-exchange membrane was determined by observing a cross-section of the ion-exchange membrane dried at 90 ° C. for 2 hours or more perpendicularly to the length direction of the sacrificial yarn with an optical microscope. The total cross-sectional area of the sacrificial yarn remaining per 1 mm in the width direction of the film was measured using The cross-sectional area was measured at 10 locations on the sacrificial yarn, and the average of these values was taken as the average cross-sectional area of the remaining sacrificial yarn.

[Evaluation of fabric properties]
Reinforcing fabrics are woven from reinforcing yarns and sacrificial yarns, but it is important to closely control the dimensions between these yarns. However, the dimension between yarns designed before weaving may change between the weaving and after weaving, resulting in dimensional changes. Even if the fabric is woven normally, there is no change in dimensions before and after the woven fabric, and “A” indicates that the reinforced fabric having the designed yarn density was obtained. "B" for which the reinforced fabric having the designed yarn density was obtained, and the dimensional change before and after the woven fabric was large, and the reinforced fabric having the designed yarn density could not be obtained even when adjusted during woven fabric Was evaluated as “C”.

[Alkali chloride electrolyzer]
As an electrolytic cell (effective energization area: 25 cm ² ), the supply water inlet of the cathode chamber is arranged at the lower part of the cathode chamber, the generated sodium hydroxide aqueous solution outlet is arranged at the upper part of the cathode chamber, and the sodium chloride aqueous solution inlet of the anode chamber is arranged. A sodium chloride aqueous solution outlet disposed at the lower part of the anode chamber and diluted by an electrolytic reaction was disposed at the upper part of the anode chamber.
As the anode, a titanium punched metal (opening shape: rhombus) (minor axis: 4 mm, major axis: 8 mm) coated with a solid solution of ruthenium oxide, iridium oxide and titanium oxide was used. As the cathode, a SUS304 punched metal (opening shape: rhombus) (short diameter: 5 mm, long diameter: 10 mm) electrodeposited with ruthenium-containing Raney nickel was used.

[Measurement of current efficiency]
An ion exchange membrane having a layer (C) and a layer (S) is used, placed in an alkali chloride electrolyzer so that the layer (C) faces the cathode, and a sodium hydroxide aqueous solution concentration in the cathode chamber: 32% by mass Sodium chloride aqueous solution was electrolyzed under the conditions of sodium chloride aqueous solution concentration in the anode chamber: 200 g / L, temperature 90 ° C., current density: 6 kA / m ² , and measured current efficiency between 3 and 10 days from the start of operation. Was the average current efficiency (%).

[Example 1-1]
A stainless steel reactor (autoclave) having an internal volume of 94 L is degassed to vacuum, and then CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ H (hereinafter also referred to as “solvent S”) is expressed by the following formula ( 26.2) 66.2 kg of a solution in which 37.4% by mass of a compound having a carboxylic acid type functional group (hereinafter also referred to as “monomer M”) represented by formula (2-1) is added, and the internal temperature of the reactor is increased. The temperature was raised to 75 ° C.
CF ₂ = CF—O—CF ₂ CF ₂ —CF ₂ —COOCH ₃ (2-1)
CF ₂ = CF ₂ was added until the internal pressure of the reactor reached 1.116 MPaG, and 4.0 L of a solution obtained by dissolving 0.031% by mass of azobisisobutyronitrile as a polymerization initiator in solvent S was added. The polymerization reaction was started. During the polymerization reaction, CF ₂ = CF ₂ / monomer M has a molar ratio of CF ₂ = CF ₂ / monomer M at the same time that CF ₂ = CF ₂ is continuously added so that the internal pressure of the reactor is maintained at 1.116 MPaG (gauge pressure?). Monomer M corresponding to 6.2 was added continuously. When the amount of CF ₂ = CF ₂ introduced from the start of the reaction reached 4.9 kg, the reactor was cooled to 40 ° C., and unreacted CF ₂ = CF ₂ was discharged out of the system to complete the polymerization. . Thereafter, the solvent S and the liquid unreacted monomer M are distilled off under heating under reduced pressure, dried under reduced pressure at 0.5 kPaA (absolute pressure) and 92 ° C. for 12 hours, and 7.4 kg of a powdery fluoropolymer ( C′1-1) was obtained. The functional group concentration of the obtained fluoropolymer (C′1-1) was 13.89 mol%, and the ion exchange capacity after the hydrolysis treatment was 1.08 meq / g dry resin.

In the same manner as in the polymerization reaction described above, CF ₂ ═CF ₂ and CF ₂ ═CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ —SO ₂ F were copolymerized and contained. A fluoropolymer (S′1-1) was obtained. The resulting fluorine-containing polymer (S′1-1) had an ion exchange capacity of 1.1 meq / g dry resin after hydrolysis.

The fluorine-containing polymer (C′1-1) and the fluorine-containing polymer (S′1-1) were formed into a film by a coextrusion method, and the layer (C′a) (C′a) comprising the fluorine-containing polymer (C′1-1) ( A film A having a two-layer structure comprising a thickness (12 μm) and a layer (S′a) (thickness: 68 μm) made of a fluoropolymer (S′1-1) was obtained.

Fluoropolymer (S′1-1) was formed into a film by a melt extrusion method to obtain a film B having a layer (S′b) (thickness: 30 μm) made of the fluoropolymer (S′1-1).

A PTFE yarn obtained by slitting a stretched PTFE film to a thickness of 100 denier with a twist of 2000 times / m on a monofilament was used as a reinforcing yarn.
A sacrificial yarn was a PET yarn composed of 30 denier multifilaments in which six 5-denier PET filaments (elastic modulus: 4.9 GPa) were aligned.
Plain weaving was performed so that one reinforcing yarn and two sacrificial yarns were alternately arranged to obtain a reinforcing fabric (reinforcing yarn density: 27 yarns / inch, sacrificial yarn density: 54 yarns / inch).

Using a roll, the film B, the reinforcing cloth, the film A, and the release PET film (thickness: 100 μm) are stacked in this order so that the layer (C′a) of the film A is on the release PET film side. And laminated. The release PET film was peeled off to obtain an ion exchange membrane precursor membrane.

Consists of 29.0% by mass of zirconium oxide (average particle size: 1 μm), 1.3% by mass of methylcellulose, 4.6% by mass of cyclohexanol, 1.5% by mass of cyclohexane and 63.6% by mass of water. The paste was transferred to the upper layer side of the precursor film layer (S′b) by a roll press to form an inorganic particle layer. The adhesion amount of zirconium oxide was 20 g / m ² .

The precursor film having an inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 8 minutes. As a result, —COOCH _{3 of} the fluorine-containing polymer (C′1-1) and —SO ₂ F of the fluorine-containing polymer (S′1-1) are hydrolyzed and converted into ion exchange groups, and the precursor layer ( A film having C′a) as the layer (Ca), the layer (S′a) as the layer (Sa), and the layer (S′b) as the layer (Sb) was obtained.
At this time, the average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane was 1800 μm ² / mm.

A dispersion was prepared by dispersing zirconium oxide (average particle size: 1 μm) at a concentration of 13% by mass in an ethanol solution containing 2.5% by mass of an acid type polymer of the fluoropolymer (S′1-1). The dispersion was sprayed on the layer (Ca) side of the membrane to form a gas releasable coating layer, and an ion exchange membrane having a gas releasable coating layer formed on both sides was obtained. The adhesion amount of zirconium oxide was 3 g / m ² .

[Example 1-2]
Ion ions were formed in the same manner as in Example 1-1 except that a precursor film having an inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 15 minutes. An exchange membrane was obtained. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 690 μm ² / mm.

[Example 2-1]
As the sacrificial yarn, a PET yarn composed of 20 denier multifilaments in which six 3.3 denier PET filaments (modulus of elasticity: 4.4 GPa) are aligned is used. As the reinforcing fabric, one reinforcing yarn and the sacrificial yarn 4 are used. Ion ion was applied in the same manner as in Example 1-1 except that a plain weave was used so that the books were alternately arranged, and a reinforcing fabric with a reinforcing yarn density of 27 / inch and a sacrificial yarn density of 108 / inch was used. An exchange membrane was obtained. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 983 μm ² / mm.

[Example 2-2]
Ion ions were formed in the same manner as in Example 2-1, except that a precursor film having an inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 15 minutes. An exchange membrane was obtained. No sacrificial yarn remained in the ion exchange membrane after hydrolysis.

[Example 3-1]
An ion exchange membrane was prepared in the same manner as in Example 2-1, except that a PET yarn consisting of 18 denier multifilaments in which two 9 denier PET filaments (elastic modulus: 7.2 GPa) were aligned was used as the sacrificial yarn. Obtained. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 3660 μm ² / mm.

[Example 3-2]
Ion ions were formed in the same manner as in Example 3-1, except that a precursor film having an inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 15 minutes. An exchange membrane was obtained. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 1711 μm ² / mm.

[Example 3-3]
Ion ions were formed in the same manner as in Example 3-1, except that a precursor film having an inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 19 minutes. An exchange membrane was obtained. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 61 μm ² / mm.

[Example 4-1]
As a sacrificial yarn, a precursor film in which an inorganic particle layer is formed on one side using a sacrificial yarn as a PBT yarn composed of 30 denier multifilaments in which six 5-denier PBT filaments (elastic modulus: 1.2 GPa) are aligned, An ion exchange membrane was obtained in the same manner as in Example 1-1 except that it was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 90 minutes.
In the woven fabric of the reinforcing fabric of this example, since a dimensional change occurred before and after the woven fabric, it was necessary to adjust the yarn density to the design when woven. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 3010 μm ² / mm.

[Example 4-2]
Ion ions were formed in the same manner as in Example 4-1, except that a precursor film having an inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass of dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95 ° C. for 180 minutes. An exchange membrane was obtained. The average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane after hydrolysis was 1410 μm ² / mm.

[Example 5]
As a reinforcing yarn, a PTFE yarn obtained by rapidly stretching a PTFE film and slitting to a thickness of 100 denier and then twisting 2000 times / m of the monofilament was used. As a sacrificial yarn, a 5-denier PBT filament ( Using PBT yarns consisting of 30 denier multifilaments with 6 elastic moduli (0.6 GPa), weave plain so that one reinforcing yarn and two sacrificial yarns are arranged alternately. The reinforced fabric was woven so that the density was 27 / inch and the density of the sacrificial yarn was 54 / inch, but the dimensional change before and after the woven fabric was large, and a reinforced fabric having the designed yarn density could not be obtained. .

Ion exchange in 32% by weight sodium hydroxide aqueous solution at 25 ° C. and 125 g / L sodium chloride aqueous solution at 90 ° C. in each example except Example 5 in which a reinforcing fabric having the designed yarn density was not obtained and could not be measured The dimensional change rate of the film is shown in Table 1. The current efficiency was 96% or more in all examples except Example 5 in which a reinforcing fabric having the designed yarn density was not obtained and could not be measured.

As shown in Table 1, Examples 1-1 and 1-2, Examples 2-1 and 2-2, and Examples 4-1 and 4-2 using ion exchange membranes satisfying the conditions of the present invention were used. Therefore, the variation in the dimensional change due to the residual amount of the sacrificial yarn in the ion exchange membrane in the 32 mass% sodium hydroxide aqueous solution at 25 ° C. is small, and the dimensional change does not depend on the average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane. Was almost constant.
In Examples 3-1, 3-2, and 3-3, which show an average elastic modulus of the sacrificial yarn that is higher than the conditions of the present invention, the ion exchange membrane in 32% by mass aqueous sodium hydroxide solution at 25 ° C. It became clear that the variation in dimensional change due to the remaining amount of sacrificial yarn in the exchange membrane was large, and that the dimensional change varied greatly depending on the average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane.

As shown in Table 1, Examples 1-1 and 1-2, Examples 2-1 and 2-2, and Examples 4-1 and 4-2 using ion exchange membranes satisfying the conditions of the present invention were used. Then, the fluctuation of the dimensional change of the ion exchange membrane in the 125 g / L sodium chloride aqueous solution at 90 ° C. due to the remaining amount of the sacrificial yarn in the ion exchange membrane is small, and the dimensional change is caused by the sacrificial yarn remaining in the ion exchange membrane. It was almost constant regardless of the average cross-sectional area.
In Examples 3-1, 3-2 and 3-3, which show higher average elastic modulus of the sacrificial yarn than the conditions of the present invention, the ion exchange of the ion exchange membrane in an aqueous 125 g / L sodium chloride solution at 90 ° C. It has been clarified that the variation in dimensional change due to the remaining amount of sacrificial yarn in the membrane is large, and the dimensional change varies greatly depending on the average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane.

From the above results, in the ion exchange membrane of the present invention in which the average elastic modulus of the sacrificial yarn is in a specific range, the variation in dimensional change is almost constant regardless of the average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane. It was clear that the dimensional change was easy to control.
On the other hand, it became clear that the dimensional change of the ion exchange membrane in which the average elastic modulus of the sacrificial yarn is higher than the conditions of the present invention varies greatly depending on the average cross-sectional area of the sacrificial yarn remaining in the ion exchange membrane. That is, the average elastic modulus of the sacrificial yarn in the reinforcing material provided inside the ion exchange membrane is in the specific range of the present invention, so that even if the average cross-sectional area of the remaining sacrificial yarn changes, the ion exchange membrane There is little variation in the dimensional change. Therefore, the dimensional change rate of the ion exchange membrane can be kept within a certain range without strictly controlling the hydrolysis conditions with the alkaline aqueous solution and strictly controlling the average cross-sectional area of the remaining sacrificial yarn. Troubles such as wrinkles, pinholes and cracks in the ion exchange membrane due to dimensional changes of the outer ion exchange membrane can be reduced. This effect is particularly remarkable in a large hydrolysis tank when it is difficult to make uniform the hydrolysis conditions such as the temperature in the tank and the concentration of the alkaline aqueous solution.

The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2016-44534 filed on March 8, 2016 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims

An ion exchange membrane for alkaline chloride electrolysis comprising a fluorine-containing polymer layer having an ion exchange group, and a reinforcing material comprising a reinforcing yarn and a sacrificial yarn provided inside the fluorine-containing polymer layer having the ion exchange group,
An ion exchange membrane for alkaline chloride electrolysis, wherein the sacrificial yarn has an average elastic modulus of 1.0 to 7.0 GPa.
2. The ion exchange membrane for alkaline chloride electrolysis according to claim 1, wherein the reinforcing yarn has a fineness of 20 to 200 denier and a density of the reinforcing yarn in the cloth is 10 to 40 yarns / inch.
3. The alkali chloride electrolysis according to claim 1, wherein the sacrificial yarn is a monofilament or a multifilament having a fineness of 5 to 100 denier and a filament number of 1 to 32 per sacrificial yarn in the cloth. Ion exchange membrane.
The ion exchange membrane for alkali chloride electrolysis according to any one of claims 1 to 3, wherein the sacrificial yarn is a sacrificial yarn partially dissolved and removed.
The ion exchange membrane for alkali chloride electrolysis according to any one of claims 1 to 4, wherein at least a part of the fluorine-containing polymer layer having an ion exchange group is a fluorine-containing polymer layer having a sulfonic acid type functional group.
The ion exchange membrane for alkali chloride electrolysis according to any one of claims 1 to 5, wherein at least a part of the fluorine-containing polymer layer having an ion exchange group is a fluorine-containing polymer layer having a carboxylic acid type functional group.
The ion exchange membrane for alkaline chloride electrolysis according to any one of claims 1 to 6, further comprising a layer containing inorganic particles on at least one outermost surface.
An alkali chloride electrolysis apparatus comprising the ion exchange membrane for alkaline chloride electrolysis according to any one of claims 1 to 7 as an electrolyte membrane separating a cathode chamber on the cathode side and an anode chamber on the anode side in the electrolytic cell.
An ion exchange membrane precursor for alkaline chloride electrolysis, comprising: a fluorine-containing polymer layer having a group that can be converted into an ion-exchange group; and a reinforcing cloth provided inside the fluorine-containing polymer layer having a group that can be converted into an ion-exchange group A membrane,
The ion-exchange membrane precursor membrane for alkaline chloride electrolysis, wherein the reinforcing fabric comprises reinforcing yarns and sacrificial yarns, and the sacrificial yarns have an average elastic modulus of 1.0 to 7.0 GPa.
The ion exchange membrane for alkali chloride electrolysis according to claim 9, wherein at least a part of the fluorine-containing polymer layer having a group that can be converted into an ion-exchange group is a fluorine-containing polymer layer having a group that can be converted into a sulfonic acid type functional group. Precursor film.
The ion for alkali chloride electrolysis according to claim 9 or 10, wherein at least a part of the fluorine-containing polymer layer having a group that can be converted into an ion exchange group is a fluorine-containing polymer layer having a group that can be converted into a carboxylic acid type functional group. Exchange membrane precursor membrane.
The ion-exchange membrane precursor film according to any one of claims 9 to 11 is brought into contact with an alkaline aqueous solution to convert a group that can be converted into an ion-exchange group into an ion-exchange group, and at the same time, a sacrifice in a reinforcing cloth A method for producing an ion exchange membrane for alkaline chloride electrolysis, comprising obtaining a ion exchange membrane comprising a fluorine-containing polymer layer having an ion exchange group and a reinforcing material by dissolving and removing at least a part of the yarn.
The method for producing an ion exchange membrane for alkaline chloride electrolysis according to claim 10, wherein a part of the sacrificial yarn in the reinforcing cloth is dissolved and removed.
After obtaining the ion exchange membrane for alkali chloride electrolysis by the production method according to claim 12 or 13, the ion exchange membrane is used as an electrolyte membrane that separates the cathode chamber on the cathode side and the anode chamber on the anode side in the electrolytic cell. A method for producing an alkali chloride electrolytic device, comprising: