CN108699712A - Ion-exchange membrane, method for producing same, and alkali metal chloride electrolysis device - Google Patents

Abstract

Ion-exchange membrane for alkali chloride electrolysis, amberplex precursor film and the alkali chloride electrolysis device of residual quantity of the variation for being easy to control change in size without strictly controlling the sacrifice silk in amberplex are provided.The ion-exchange membrane for alkali chloride electrolysis is characterized in that having:Fluoropolymer layer with ion-exchange group;With the reinforcement material in the inside of the aforementioned fluoropolymer layer with ion-exchange group is set, the reinforcement material includes reinforced wire and sacrifices silk, and the aforementioned average elastic modulus for sacrificing silk is 1.0~7.0GPa.

Description

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

technical field

The present invention relates to ion exchange membranes, their precursor membranes, their production methods, alkali metal chloride electrolysis devices, and their production methods.

Background technique

As an ion exchange membrane used in an alkali metal chloride electrolysis method for producing alkali metal hydroxide and chlorine gas by electrolyzing an aqueous alkali metal chloride solution such as seawater, it is known that a film having an ion exchange group (carboxylic acid group or carboxylate base, and sulfonic acid or sulfonate based) fluorine-containing polymer electrolyte membrane. From the viewpoint of maintaining mechanical strength and dimensional stability, the electrolyte membrane is usually reinforced with a reinforcing material including reinforcing filaments.

As an ion exchange membrane having a reinforcing material, for example, an ion exchange membrane in which each layer of the following (1) to (4) is sequentially laminated is known (Patent Document 1).

(1) Polymer A layer comprising a fluoropolymer having a carboxylic acid type functional group and having an ion exchange capacity of 0.80 mg equivalent/g, (2) comprising a fluoropolymer having a sulfonic acid type functional group, ion exchange capacity A polymer B layer of 0.98 mg equivalent/g, (3) a reinforcing material, (4) a polymer C layer comprising a fluoropolymer having a sulfonic acid type functional group and having an ion exchange capacity of 1.05 mg equivalent/g.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2013-163858

Contents of the invention

The problem to be solved by the invention

The ion exchange membrane for alkali metal chloride electrolysis (hereinafter also referred to as "ion exchange membrane") is caused by the operating conditions of the electrolytic cell, that is, the concentration of the aqueous alkali metal chloride solution, the concentration of the alkali metal hydroxide, and the operating temperature. Dimensional changes due to swelling, shrinkage, etc. The ion-exchange membrane is used fixed in the electrolysis device. Therefore, if the size of the ion-exchange membrane changes, wrinkles may be formed on the membrane, which may cause pinholes due to friction between the membrane and the electrodes, or cracks may occur due to stretching of the membrane. Thus, the membrane is damaged and the like. In order to prevent these problems, 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 the reinforcing material provided inside the ion exchange membrane.

The reinforcing material contained in the ion exchange membrane having ion exchange groups is a material derived from a reinforcing cloth contained in an ion exchange membrane precursor membrane having: a fluoropolymer layer of the group; and a reinforcing cloth disposed inside the fluoropolymer layer. The aforementioned reinforcing cloth generally includes reinforcing yarns and sacrificial yarns, and the sacrificial yarns are formed of a material that elutes when immersed in an alkaline aqueous solution. In the step of immersing the ion-exchange membrane precursor membrane provided with a reinforcing cloth in an alkaline aqueous solution to hydrolyze the groups capable of being converted into ion-exchange groups in the ion-exchange membrane precursor membrane and convert them into ion-exchange groups Among the reinforcing yarns and sacrificial yarns constituting the reinforcing cloth, the reinforcing yarns remain undissolved, and at least a part of the sacrificial yarns dissolve to form a reinforcing material including the reinforcing yarns and the sacrificial yarns in the ion exchange membrane. In addition, in the said process, the reinforcing thread which comprises a reinforcing cloth will not melt|dissolve. That is, the reinforcing material in the ion exchange membrane includes reinforcing filaments and sacrificial filaments remaining without being dissolved in the aforementioned steps.

It is well known to those skilled in the art that the fineness of the reinforcing filaments constituting the reinforcing material contained in the ion exchange membrane and the density of the reinforcing filaments affect the dimensional change of the ion exchange membrane.

As a result of further studies, the present inventors have found that the amount of undissolved remaining sacrificial filaments constituting the reinforcing material contained in the ion-exchange membrane affects the variation in the dimensional change of the ion-exchange membrane. The remaining amount of sacrificial silk is appropriately determined according to the strength required by the ion exchange membrane and the allowable degree of dimensional change. In the grouping process, it is controlled by selecting conditions such as the concentration, temperature, and contact time of the alkaline aqueous solution. These conditions need to be strictly controlled in order to make the remaining amount of the sacrificial wire a predetermined value.

However, especially when the ion-exchange membrane precursor membrane is continuously hydrolyzed in large-scale equipment, the concentration and temperature of the alkaline aqueous solution in the hydrolysis tank are unevenly distributed, and it is difficult to strictly control the concentration of the reinforcing material contained in the ion-exchange membrane. The remaining amount of sacrificial wire.

The object of the present invention is to provide an ion-exchange membrane that can easily control the fluctuation of the dimensional change of the ion-exchange membrane without strictly controlling the amount of sacrificial filaments remaining in the ion-exchange membrane in the electrolysis of alkali metal chlorides using the ion-exchange membrane. Bulk membranes, methods for their manufacture, alkali metal chloride electrolysis devices, and methods for their manufacture.

solutions to problems

The inventors of the present invention conducted research and found that: for an ion exchange membrane using a sacrificial wire having a modulus of elasticity in a specific range as a sacrificial wire constituting a reinforcing cloth or a reinforcing material including a reinforcing wire and a sacrificial wire, the remaining The fluctuation of the dimensional change caused by the fluctuation of the quantity is small.

The present invention has been accomplished based on the above findings. It has the following composition.

[1] An ion exchange membrane, characterized in that it has: a fluoropolymer layer having an ion exchange group; and a reinforcing material provided inside the fluoropolymer layer having an ion exchange group, the The reinforcing material includes reinforcing wires and sacrificial wires, and the average elastic modulus of the aforementioned sacrificial wires is 1.0-7.0 GPa.

[2] The ion exchange membrane according to [1], wherein the fineness of the reinforcing yarn is 20 to 200 denier, and the density of the reinforcing yarn in the reinforcing cloth is 10 to 40 strands/inch.

[3] The ion-exchange membrane for alkali metal chloride electrolysis according to [1] or [2], wherein the sacrificial yarn has a fineness of 5 to 100 denier, and the length of each sacrificial yarn in the reinforcing cloth is Monofilament or multifilament with the number of filaments ranging from 1 to 32.

[4] The ion exchange membrane according to any one of [1] to [3], wherein the sacrificial filaments are partially dissolved and removed.

[5] The ion exchange membrane according to any one of [1] to [4], wherein at least a part of the fluoropolymer layer having an ion exchange group is a fluoropolymer having a sulfonic acid type functional group Floor.

[6] The ion-exchange membrane according to any one of [1] to [4], wherein at least a part of the layer of the fluoropolymer having an ion-exchange group is a fluoropolymer having a carboxylic acid-type functional group Floor.

[7] The ion exchange membrane according to any one of [1] to [6], further comprising a layer containing inorganic particles on at least one outermost surface.

[8] An alkali metal chloride electrolysis device comprising the ion exchange membrane described in any one of [1] to [7] as a means for separating the cathode chamber on the cathode side and the anode chamber on the anode side in the electrolytic cell. electrolytic membrane.

[9] An ion exchange membrane precursor membrane having: a fluorine-containing polymer layer having a group capable of being converted into an ion exchange group; In the reinforcing cloth inside the fluoropolymer layer, the reinforcing cloth includes reinforcing yarns and sacrificial yarns, and the average elastic modulus of the sacrificial yarns is 1.0 to 7.0 GPa.

[10] The ion-exchange membrane precursor membrane according to [9], wherein at least a part of the fluoropolymer layer having a group capable of being converted into an ion-exchange group has a functional group capable of being converted into a sulfonic acid type. group of fluoropolymer layers.

[11] The ion-exchange membrane precursor membrane according to [9] or [10], wherein at least a part of the fluoropolymer layer having a group capable of being converted into an ion-exchange group is a Acid-type functional group of the fluoropolymer layer.

[12] A method for producing an ion-exchange membrane, characterized in that, by contacting the ion-exchange membrane precursor membrane described in any one of [9] to [11] with an alkaline aqueous solution, the The group of the exchange group is converted into an ion exchange group, and at least a part of the sacrificial filament in the reinforcing cloth is dissolved and removed, thereby obtaining an ion exchange membrane including a fluorine-containing polymer layer having an ion exchange group and a reinforcing material .

[13] The method for producing an ion exchange membrane according to [12], wherein a part of the sacrificial filament in the reinforcing cloth is dissolved and removed.

[14] A method for manufacturing an alkali metal chloride electrolysis device, characterized in that, after the ion exchange membrane is obtained by the manufacturing method described in [12] or [13], the ion exchange membrane is provided as a cathode in the electrolytic cell The cathode compartment on the side and the anode compartment on the anode side are separated by an electrolytic membrane.

The effect of the invention

The ion-exchange membrane of the present invention is a membrane that can easily control fluctuations in dimensional changes of the ion-exchange membrane without strictly controlling the amount of sacrificial filaments remaining in the reinforcing material contained in the ion-exchange membrane. The alkali metal chloride electrolysis device of the present invention has the ion exchange membrane of the present invention, therefore, it is not necessary to strictly control the amount of sacrificial filaments remaining in the reinforcing material contained in the ion exchange membrane, and it is easy to control the fluctuation of the dimensional change of the ion exchange membrane.

According to the method for producing an ion-exchange membrane of the present invention, it is possible to produce an ion-exchange membrane that can easily control fluctuations in dimensional changes of the ion-exchange membrane without strictly controlling the amount of sacrificial filaments remaining in the reinforcing material contained in the ion-exchange membrane.

According to the method for manufacturing an alkali metal chloride electrolysis device of the present invention, it is possible to manufacture an alkali metal chloride that can easily control fluctuations in dimensional changes of the ion exchange membrane without strictly controlling the amount of sacrificial filaments remaining in the reinforcing material included in the ion exchange membrane. electrolysis device.

Detailed ways

The following definitions of terms apply to the entire specification and claims.

The "ion-exchange membrane" refers to a membrane used for electrolysis of an aqueous alkali metal chloride solution, and is a membrane composed of a polymer having an ion-exchange group.

"Ion exchange group" means a group capable of converting at least a portion of the ions contained in the group into other ions. The following carboxylic acid type functional group, sulfonic acid type functional group etc. are mentioned.

"Carboxylic acid functional group" refers to a carboxylic acid group (-COOH), or a carboxylate group (-COOM ¹ . Wherein, M ¹ is an alkali metal or quaternary ammonium salt group.).

The "sulfonic acid functional group" refers to a sulfonic acid group (-SO ₃ H) or a sulfonate group (-SO ₃ M ² . Wherein, M ² is an alkali metal or quaternary ammonium salt group.).

The "ion-exchange membrane precursor membrane" refers to a membrane that is a precursor of an ion-exchange membrane, and is a membrane that includes a polymer having a group that can be converted into an ion-exchange group.

The "group capable of being converted into an ion-exchange group" means a group capable of being converted into an ion-exchange group by known treatments such as hydrolysis treatment and acidification treatment.

The "group capable of being converted into a carboxylic acid type functional group" means a group capable of being converted into a carboxylic acid type functional group by known treatments such as hydrolysis treatment and acidification treatment.

The "group capable of being converted into a sulfonic acid type functional group" means a group capable of being converted into a sulfonic acid type functional group by known treatments such as hydrolysis treatment and acidification treatment.

The "perfluorocarbon polymer" refers to a polymer in which all hydrogen atoms bonded to carbon atoms in the polymer are replaced by fluorine atoms. Part of the fluorine atoms in the perfluorocarbon polymer may be substituted by one or both of chlorine atoms and bromine atoms.

The "structural unit" refers to a portion derived from a monomer that exists in a polymer and constitutes the polymer. For example, when a structural unit is produced 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 produced by cleavage of the unsaturated double bond. In addition, the structural unit may be a structural unit obtained by chemically converting the structural unit after forming a polymer having a structure of the structural unit. In addition, below, the structural unit derived from each monomer may be described with the name which added "unit" to the name of the monomer depending on the case.

The "reinforcing material" refers to a material used to increase the strength of the ion exchange membrane.

The "reinforcing cloth" refers to a cloth used as a raw material of a reinforcing material for increasing the strength of an ion exchange membrane.

The "reinforcing yarn" refers to the yarn constituting the reinforcing cloth, and is made of a material that does not dissolve even when the reinforcing cloth is immersed in an alkaline aqueous solution (for example, a sodium hydroxide aqueous solution having a concentration of 32% by mass).

The "sacrifice yarn" refers to the yarn constituting the reinforcing fabric, and is a yarn formed of a material that dissolves in the alkaline aqueous solution when the reinforcing fabric is dipped in the alkaline aqueous solution.

"Elution pores" refer to pores formed as a result of dissolution of the sacrificial silk in an alkaline aqueous solution.

[Ion exchange membrane]

The ion exchange membrane of the present invention has a layer (hereinafter referred to as "layer (P)") formed by a fluorine-containing polymer having an ion exchange group. Inside the layer (P) is provided a layer comprising a reinforcing wire and a sacrificial wire. reinforcement material. The sacrificial wire may be a sacrificial wire that is partially dissolved and removed. In addition, in the ion exchange membrane, a part of the sacrificial filament is dissolved and removed to form elution pores.

(reinforcement material)

The aforementioned reinforcing cloth generally includes reinforcing yarns and sacrificial yarns, and the sacrificial yarns are formed of a material that elutes when immersed in an alkaline aqueous solution. In the step of immersing the ion-exchange membrane precursor membrane provided with a reinforcing cloth inside in an alkaline aqueous solution and hydrolyzing the groups capable of being converted into ion-exchange groups in the ion-exchange membrane precursor membrane to be converted into ion-exchange groups Among the reinforcing yarns and sacrificial yarns constituting the reinforcing cloth, the reinforcing yarns remain undissolved, and at least a part of the sacrificial yarns dissolve to form a reinforcing material including the reinforcing yarns and the sacrificial yarns in the ion exchange membrane. In addition, in the said process, the reinforcing thread which comprises a reinforcing cloth will not melt|dissolve. That is, the reinforcing material in the ion exchange membrane includes reinforcing filaments and sacrificial filaments remaining without being dissolved in the aforementioned steps.

The reinforcing material includes reinforcing filaments and sacrificial filaments, and is a material of the reinforcing layer (P). The reinforcing material is derived from the reinforcing cloth contained in the ion exchange membrane precursor membrane having a fluoropolymer layer and a reinforcing cloth disposed inside the aforementioned fluoropolymer layer, said fluoropolymer layer comprising group of groups.

The reinforcing cloth is preferably formed of warp yarns and weft yarns, and the warp yarns and weft yarns are perpendicular to each other. The warp and the weft are preferably composed of both reinforcing yarns and sacrificial yarns, respectively. That is, it is preferable that the warp yarns in the reinforcing fabric include reinforcing yarns and sacrificial yarns, and that the weft yarns in the reinforcing fabric include reinforcing yarns and sacrificial yarns.

The reinforcing thread is a thread formed of a material that does not elute even when an ion-exchange membrane precursor membrane (hereinafter, also referred to as "ion-exchange membrane precursor membrane") including a reinforcing cloth is immersed in an alkaline aqueous solution. In the manufacturing process in the manufacturing method of the ion-exchange membrane described later, the ion-exchange membrane precursor membrane including the reinforcing cloth is immersed in an alkaline aqueous solution and does not dissolve and remains, which contributes to Maintain the mechanical strength and dimensional stability of the ion exchange membrane.

As the reinforcing thread, a thread containing a perfluorocarbon polymer is preferable, a thread containing polytetrafluoroethylene (hereinafter also referred to as "PTFE") is preferable, and a PTFE thread containing only 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. The mechanical strength of an ion exchange membrane becomes high enough that this fineness is more than the said lower limit. When this fineness is below the said upper limit, the membrane resistance of an ion-exchange membrane can be suppressed low, and the raise of an electrolysis voltage can be suppressed.

The density (weft density) of the reinforcing threads in the reinforcing cloth used to form the reinforcing material is preferably 10 to 40 threads/inch, more preferably 20 to 30 threads/inch. When this density is more than the said lower limit, the mechanical strength as a reinforcement becomes high enough. When this density is below the said upper limit, the membrane resistance of an ion-exchange membrane can be suppressed low, and the raise of an electrolysis voltage can be suppressed.

The sacrificial silk is a silk eluted by immersing an ion exchange membrane precursor membrane including a reinforcing cloth in an alkaline aqueous solution. When the ion-exchange membrane precursor membrane including the reinforcing fabric is immersed in an alkaline aqueous solution, it is preferable that a part of the sacrificial filaments be dissolved and removed, and the dissolved residue remains as sacrificial filaments constituting the reinforcing material. By leaving at least a part of the sacrificial filament as a dissolved residue, it contributes to maintaining the mechanical strength and dimensional stability of the ion exchange membrane.

In addition, when the ion-exchange membrane precursor membrane containing a reinforcement fabric is immersed in an alkaline aqueous solution, all sacrificial yarns may be melt|dissolved and the sacrificial yarn may not remain as a yarn which comprises a reinforcing material. Even if the sacrificial filaments do not remain, the mechanical strength of the ion-exchange membrane precursor membrane can be contributed by including the reinforcing filaments in the reinforcing cloth.

In the present invention, the average elastic modulus of the sacrificial yarn constituting the reinforcement cloth or the reinforcing material is important, and the average elastic modulus of the sacrificial yarn needs to be 1.0 to 7.0 GPa. When this average elastic modulus is more than the said lower limit value, it will become difficult to generate|occur|produce displacement of a thread at the time of fabric weaving. When the average modulus of elasticity is not more than the aforementioned upper limit, fluctuations in dimensional changes due to the remaining amount of sacrificial yarns can be kept low. The average modulus of elasticity is preferably 2.0 to 6.0 GPa, more preferably 3.0 to 6.0 GPa, particularly preferably 4.0 to 5.0 GPa.

The average modulus of elasticity of the yarn including the sacrificial yarn is a unique value determined by the degree of polymerization of the polymer and the raw material of the polymer. Therefore, before the ion exchange membrane precursor membrane including the reinforcing cloth having sacrificial filaments is immersed in an alkaline aqueous solution, or after a part of the sacrificial filaments in the reinforcing cloth is immersed in an alkaline aqueous solution and dissolved, the elastic modulus of the sacrificial filaments Neither will change.

The method of measuring the modulus of elasticity of the sacrificial yarn in the present invention is determined as follows.

The sacrificial yarn before dipping in the alkaline aqueous solution was mounted on a tensile tester (TENSILON RTC-1210A manufactured by ORIENTEC CORPORATION) at a chuck distance of 50 mm, and the stress-strain (elongation) when stretched at a tensile speed of 50 mm/min was measured. ) curve is the stress when the strain (elongation) is 5%, and divided by the average cross-sectional area of the sacrificial silk before being immersed in the alkaline aqueous solution, and the obtained value is regarded as the modulus of elasticity. About the average elastic modulus, five elastic moduli were measured, and the average value of these values was made into the average elastic modulus.

In addition, the cross-sectional area of the sacrificial wire before being immersed in an alkaline aqueous solution was observed using an optical microscope and measured using image software. The cross-sectional area was measured at 10 places of the sacrificial silk, and the average value of these values was taken as the average cross-sectional area of the sacrificial silk before being immersed in the alkaline aqueous solution.

In the present invention, the average cross-sectional area of the sacrificial filament remaining in the ion exchange membrane is preferably 500 to 5000 μm ² /mm, more preferably 1000 to 4000 μm ² /mm, and still more preferably 1500 to 3000 m ² /mm. When the average cross-sectional area of the sacrificial filament is more than the above-mentioned lower limit value, bending, cracks, etc. are less likely to occur when the ion-exchange membrane is handled. When this average cross-sectional area is below the said upper limit, curling will not generate|occur|produce easily during membrane formation of an ion-exchange membrane, and after membrane formation.

In addition, the measuring method of the average cross-sectional area of the sacrificial filament remaining in the ion exchange membrane in this invention is mentioned later. Observe the cross-section of the ion exchange membrane dried at 90°C for 2 hours or more with an optical microscope and cut it perpendicular to the longitudinal direction of the sacrificial filament, and use image software to define it as the cross-sectional area of the sacrificial filament remaining per 1 mm in the width direction of the membrane. total value. The measurement of the cross-sectional area of the remaining sacrificial wire was carried out at 10 places, and the average cross-sectional area of the remaining sacrificial wire was calculated.

The sacrificial yarn in the reinforcing cloth may be a monofilament composed of one filament, or may be a multifilament composed of two or more filaments.

When the sacrificial yarns in the reinforcing cloth are monofilaments or multifilaments, the number of filaments per sacrificial yarn in the reinforcing cloth is preferably 1 to 32, more preferably 2 to 16, and even more preferably 2 to 8. When the number of filaments is more than the aforementioned lower limit, the contact area between the sacrificial yarn and the alkaline aqueous solution becomes large, and the sacrificial yarn is easily eluted into the alkaline aqueous solution. When the number of filaments is below the above-mentioned upper limit, the contact area of the sacrificial filaments and the alkaline aqueous solution decreases, the elution of the sacrificial filaments into the alkaline aqueous solution is suppressed, and a part of the sacrificial filaments remains. The sacrificial filaments remaining in the ion exchange membrane contribute to the mechanical strength of the ion exchange membrane.

As the sacrificial yarn, it is preferable to include PET, polybutylene terephthalate (hereinafter, also referred to as PBT.), polytrimethylene terephthalate (hereinafter, also referred to as PTT.), rayon, and A filament of at least one of the group consisting of cellulose. Among them, PET yarn consisting of only PET, PET/PBT yarn comprising a mixture of PET and PBT, PBT yarn comprising only PBT, or PTT yarn comprising only PTT are more preferable.

The fineness of the sacrificial yarn in the reinforcing cloth is preferably 5 to 100 denier, more preferably 9 to 60 denier, and still more preferably 12 to 40 denier. When the fineness of the sacrificial yarn in the reinforcing cloth is equal to or greater than the aforementioned lower limit value, the mechanical strength becomes sufficiently high, and the weaving property becomes sufficiently high. When the fineness of the sacrificial yarn in the reinforcing cloth is below the aforementioned upper limit, the elution pores formed after the sacrificial yarn is eluted are not too close to the surface of the membrane (P), and cracks are less likely to occur on the surface of the membrane (P). As a result, A reduction in the mechanical strength of the ion exchange membrane can be suppressed.

(Layer (P) formed of fluoropolymer having ion-exchange groups)

Layer (P) is a layer formed of a fluoropolymer having ion-exchange groups. The layer (P) may be a single layer or a layer composed of multiple layers.

When the layer (P) is a single layer, it is preferably formed by a layer (hereinafter, also referred to as "layer") formed by a fluorine-containing polymer (hereinafter, also referred to as "fluorine-containing polymer (C)") having a carboxylic acid type functional group. (C)".) or a layer (hereinafter also referred to as "layer (S)") formed by a fluoropolymer (hereinafter also referred to as "fluoropolymer (S)") having a sulfonic acid-type functional group .) in any one constitutes.

When the layer (P) is formed of multiple layers, it is preferably composed of the layer (C) and the layer (S). At this time, one or both of the layer (C) and the layer (S) may be a single layer or may be formed of multiple layers.

When one or both of the layer (C) and the layer (S) are formed of multiple layers, it can be configured as follows: in each layer, the fluorine-containing polymer (C) or the fluorine-containing polymer (S) The types of structural units and the ratio of structural units having carboxylic acid-type functional groups or sulfonic acid-type functional groups are different.

It is preferable that at least a part of layer (P) contains layer (S), and it is more preferable that layer (P) contains layer (C) and layer (S).

When the layer (P) includes the layer (C) and the layer (S), the reinforcing material is preferably provided inside the layer (S).

<Layer (C) formed of fluoropolymer having carboxylic acid type functional group>

The layer (C) may be a single layer or a layer composed of multiple layers. Reinforcing material may be provided inside layer (C). The layer (C) is preferably a layer composed of only the fluoropolymer (C) that does not contain materials other than the fluoropolymer (C), such as a reinforcing material, from the viewpoint of electrolytic performance.

The fluorine-containing polymer (C) is obtained by converting a fluorine-containing polymer (hereinafter also referred to as "fluorine-containing polymer (C')") having a group capable of being converted into a carboxylic acid type functional group to It is obtained by subjecting a group that is a carboxylic acid type functional group to a hydrolysis treatment to convert it into a carboxylic acid type functional group.

As the fluoropolymer (C), it is preferable to use a fluoropolymer having a structural unit based on the following monomer (1) and a structural unit based on the following monomer (2) (hereinafter also referred to as "Fluoropolymer (C'1)".) A fluoropolymer (hereinafter also referred to as "fluoropolymer (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)

X1 and ^X2 are each independently ^a fluorine atom, a chlorine atom, or a trifluoromethyl group, and a fluorine atom is preferable from the viewpoint of the 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 the chemical durability of the ion exchange membrane.

^X3 and ^X4 are each independently a fluorine atom or a trifluoromethyl group.

Y is a group capable of being converted into a carboxylic acid type functional group. Specifically, -CN, -COF, -COOR ¹ (wherein, R ¹ is an alkyl group having 1 to 10 carbon atoms.), -COONR ² R ³ (wherein, R ² and R ³ are each independently a hydrogen atom or an alkyl group with 1 to 10 carbons.).

p is 0 or 1. q is an integer of 0-12. r is an integer of 0-3. s is 0 or 1. t is an integer of 0-12. u is an integer of 0-3. Among them, p and s are not 0 at the same time, and r and u are not 0 at the same time. That is, 1≤p+s, 1≤r+u. Compounds in which p=1, q=0, r=1, s=0-1, t=0-3, u=0-1 are particularly preferred.

Specific examples of the compound represented by formula (2) include the following. In addition, the monomer (2) may be used individually by 1 type, and may use it in combination of 2 or more types.

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 the production of the fluoropolymer (C'), other monomers other than the monomer (1) and the monomer (2) can be used. Examples of other monomers include CF ₂ =CFR ^f1 (wherein R ^f1 is a perfluoroalkyl group having 2 to 10 carbons), CF ₂ =CF-OR ^f2 (wherein R ^f2 is a perfluoroalkyl group having 1 to 10 carbons perfluoroalkyl group.), CF ₂ ═CFO(CF ₂ ) _v CF=CF ₂ (wherein, v is an integer of 1 to 3.), etc. By copolymerizing other monomers, the flexibility and mechanical strength of the ion exchange membrane can be improved. The ratio of other monomers is preferably 30% by mass or less in all 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. When this thickness is more than the lower limit value of the said range, the quantity of the chloride ion which permeate|transmits an ion-exchange membrane can be suppressed, and the quality of the alkali metal hydroxide produced|generated can be maintained favorably. When the said thickness is below the upper limit of the said range, the membrane resistance of an ion-exchange membrane can be suppressed low, and electrolysis voltage can be fully reduced.

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 (S) formed of fluoropolymer having sulfonic acid type functional group>

The layer (S) may be a single layer or a layer composed of a plurality of layers. Reinforcing material may be provided inside the layer (S). As the layer (S), it is preferable to provide a reinforcing material inside from the viewpoint of improving the mechanical strength of the ion exchange membrane. It is more preferable to arrange the reinforcing material inside the layer (S) than to arrange it inside the layer (C) because the reinforcing effect can be obtained without affecting the electrolytic performance.

The fluorine-containing polymer (S) is preferably obtained by converting the fluorine-containing polymer (hereinafter also referred to as "fluorine-containing polymer (S')") having a group capable of being converted into a sulfonic acid type functional group into The group of the sulfonic acid type functional group is subjected to a hydrolysis treatment to be converted into a sulfonic acid type functional group, thereby obtaining.

As the fluorine-containing polymer (S), it is preferable to have a structural unit based on the aforementioned monomer (1) and a structural unit based on at least one of the following monomer (3) or monomer (4). A fluoropolymer (hereinafter also referred to as "fluoropolymer (S'1)") is hydrolyzed to convert Z to -SO ₃ M (where M is an alkali metal.) Fluoropolymer (hereinafter , also referred to as "fluoropolymer (S1)".).

CF ₂ ＝CF-OR ^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 either linear or branched.

Z is a group capable of being converted into a sulfonic acid type functional group. Specifically, -SO ₂ F, -SO ₂ Cl, -SO ₂ Br, etc. are mentioned.

Specific examples of the compound represented by formula (3) include the following compounds. In the formula, w is an integer of 1-8, and x is an integer of 1-5.

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 formula (4) include the following compounds. w in the formula is an integer of 1-8.

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 the monomer (4), the following compounds are preferable from the viewpoint of ease of 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'), other monomers may be used in addition to the monomer (1) and at least one of the monomer (3) or the monomer (4). Examples of other monomers include CF ₂ =CFR ^f (wherein R ^f is a perfluoroalkyl group having 2 to 10 carbons), CF ₂ =CF-OR ^f1 (wherein R ^f1 is a perfluoroalkyl group having 1 to 10 carbons perfluoroalkyl group.), CF ₂ ═CFO(CF ₂ ) _v CF=CF ₂ (wherein, v is an integer of 1 to 3.), etc. By copolymerizing other monomers, the flexibility and mechanical strength of the ion exchange membrane can be improved. The ratio of other monomers is preferably 30% by mass or less in all monomers (100% by mass) from the viewpoint of maintaining ion exchange performance.

The total thickness of the layers (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) closer to the layer (C) than the reinforcing material in the layer (S) is preferably 30 to 140 μm, more preferably 30 to 100 μm. In addition, the thickness of the layer (S2) on the side opposite to the layer (C) than the reinforcing material in the layer (S) is preferably 10 to 60 μm, more preferably 10 to 40 μm. When the thickness of layer (S1) and layer (S2) is more than the lower limit of the said range, since constant film thickness can be ensured, film strength will become high. When the thickness of layer (S1) and layer (S2) is below the upper limit of the said range, electrolytic voltage can fully be reduced.

Layer (S1) and layer (S2) may each be a single layer, or may be a layer composed of multiple layers.

(inorganic particle layer)

The ion exchange membrane may have an inorganic particle layer on one or both of the outermost surfaces. The inorganic particle layer is preferably provided on at least one outermost surface of the ion exchange membrane, more preferably on both outermost surfaces of the ion exchange membrane.

When the gas generated by the electrolysis of the alkali metal chloride adheres to the surface of the ion exchange membrane, the electrolysis voltage becomes high during the electrolysis of the alkali metal chloride. The inorganic particle layer is provided to suppress the adhesion of gas (chlorine gas or hydrogen gas) generated by the electrolysis of the alkali metal chloride to the surface of the ion exchange membrane, and to suppress the increase of the electrolysis voltage. The inorganic particle layer includes inorganic particles and a binder.

As the inorganic particles, those having excellent corrosion resistance against an aqueous alkali metal chloride solution or an aqueous alkali metal 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 preferred, SiO ₂ , SiC, ZrO ₂ , or ZrC are more preferred, and ZrO is particularly preferred. ₂ .

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 this average particle diameter is more than the said lower limit, the high effect of suppressing gas adhesion can be acquired. When this average particle diameter is below the said upper limit, the fall-off resistance of an inorganic material particle is excellent. In addition, the average particle diameter here means the average particle diameter of the average secondary particle which the primary particle aggregated, and was calculated|required as follows. The particles were dispersed in ethanol so that the concentration became 0.01% by mass or less, and measured using MICROTRAC (UPA-150 manufactured by Nikkiso Co., Ltd.), and the cumulative volume distribution curve with the total volume of the obtained particle size distribution as 100% The particle diameter (D50) at the point where the cumulative volume becomes 50% was defined as the average secondary particle diameter.

As the binder, it is preferably a hydrophilic binder having excellent corrosion resistance to an aqueous alkali metal chloride solution or an aqueous alkali metal hydroxide solution, preferably a fluorine-containing polymer having a carboxylic acid group or a sulfonic acid group, and more preferably Fluoropolymers having sulfonic acid groups are preferred. The fluorine-containing polymer may be a homopolymer of a monomer having a carboxylic acid group or a sulfonic acid group, or may be a copolymer of a monomer having a carboxylic acid group or a sulfonic acid group and a monomer copolymerizable with the monomer.

The mass ratio of the binder in the inorganic particle layer to the total mass of the inorganic particles and the binder (hereinafter also referred to as the binder ratio) is preferably 0.15 to 0.3, more preferably 0.15 to 0.25, even more preferably 0.16 to 0.20. When the binder ratio is more than the above lower limit, the inorganic particle particles are excellent in drop-off resistance. When this binder ratio is below the said upper limit, the high effect of suppressing gas adhesion can be acquired.

[Ion exchange membrane precursor membrane]

The ion-exchange membrane precursor membrane of the present invention has a layer (hereinafter also referred to as "layer (P')") formed of a fluoropolymer having a group capable of converting into an ion-exchange group. In the layer (P ') is provided with the aforementioned reinforcing cloth including reinforcing wires and sacrificial wires.

The layer (P') may be a single layer or a layer composed of multiple layers.

When the layer (P') is a single layer, it is preferably a layer formed of a fluoropolymer (C') (hereinafter, also referred to as a layer (C').) or a layer formed of a fluoropolymer (S'). The layer (hereinafter, also referred to as layer (S').) Any one of the configuration.

When layer (P') is formed of multiple layers, it is preferably composed of layer (C') and layer (S'). In this case, one or both of the layer (C') and the layer (S') may be a single layer or may be formed of multiple layers.

When one or both of the layer (C') and the layer (S') is formed of multiple layers, it can be configured as follows: In each layer, the fluoropolymer (C') or the fluoropolymer The kind of structural unit of (S') and the ratio of the structural unit which has a carboxylic acid type functional group or a sulfonic acid type functional group differ.

At least a part of layer (P') preferably includes layer (S'), and layer (P') more preferably includes layer (C') and layer (S').

When the layer (P') includes the layer (C') and the layer (S'), the reinforcing cloth is preferably provided inside the layer (S').

Layer (C') and layer (S') may each be a single layer or a layer composed of multiple layers.

[Manufacturing method of ion exchange membrane]

The ion exchange membrane of the present invention can be produced, for example, through the following steps (a) and (b).

Step (a): The step (a) is a step of disposing a reinforcing cloth comprising reinforcing filaments and sacrificial filaments inside a fluorine-containing polymer having a group capable of being converted into an ion-exchange group to obtain an ion-exchange membrane precursor membrane, The ion-exchange membrane precursor membrane has a fluorine-containing polymer layer having groups capable of being converted into ion-exchange groups, and a reinforcing cloth provided inside the layer.

Step (b): step (b) is to convert the group that can be converted into an ion-exchange group into an ion-exchange group by making the ion-exchange membrane precursor membrane obtained in the step (a) contact with an alkaline aqueous solution to obtain A process of an ion exchange membrane having a fluorine-containing polymer layer having an ion exchange group, and a reinforcing material provided therein. In this step, at least a part of the sacrificial filaments in the reinforcing cloth is dissolved and removed under the condition that the ion-exchange membrane precursor membrane is brought into contact with the alkaline aqueous solution.

It should be noted that, in the step (b), it is preferable to dissolve and remove a part of the sacrificial filaments of the reinforcing cloth to obtain a reinforcing material including a fluorine-containing polymer layer having an ion-exchange group, a reinforcing filament and remaining sacrificial filaments. ion exchange membrane.

For the dissolution of the sacrificial filaments, the ratio of the cross-sectional area of the sacrificial filaments remaining after dissolution to the cross-sectional area of the sacrificial filaments before dissolution is preferably 1 to 70%, more preferably 5 to 55%, and most preferably 10 to 40%.

In addition, in step (b), after converting a group convertible into an ion-exchange group into an ion-exchange group, salt exchange for exchanging a counter cation of the ion-exchange group may be performed if necessary. In salt exchange, for example, the counter cation of the ion exchange group is exchanged from potassium to sodium. A known method can be used for salt exchange.

(Process (a))

In the step (a), an ion exchange membrane precursor membrane having a layer (P') and a reinforcing cloth provided inside the layer (P') is manufactured.

For the ion exchange membrane precursor membrane, depending on the composition of the layer (P'), when the layer (C') and the layer (S') are laminated, it can be laminated by inserting a reinforcing cloth between any of the layers to produce a layer with a layer (P') The inner reinforced cloth ion exchange membrane precursor membrane. The layer (C') is preferably a layer formed of a fluorine-containing polymer (C'1) (hereinafter also referred to as "layer (C'1)"), and the layer (S') is preferably a layer formed of a fluorine-containing polymer (C'1). A layer (hereinafter also referred to as "layer (S'1)") formed of the substance (S'1).

For example, when the layer (P') includes the layer (C') and the layer (S') and a reinforcement cloth is provided inside the layer (S'), it can be Fabric and layer (S') are laminated in this order to manufacture. It should be noted that, when the layer (S') is composed of two layers (S') in this way, it may be a layer (S') formed of the same fluorine-containing polymer, or each may be different from each other. A layer (S') formed of a fluoropolymer.

(Process (b))

In the step (b), the group convertible into an ion-exchange group of the ion-exchange membrane precursor membrane obtained in the step (a) is hydrolyzed to be converted into an ion-exchange group. Thereby, the ion-exchange membrane precursor membrane having groups capable of being converted into ion-exchange groups is converted into an ion-exchange membrane having ion-exchange groups.

As a method of hydrolysis, for example, a method using a mixture of a water-soluble organic compound and an alkali metal hydroxide as described in JP-A-03-6240 is preferable.

Layer (C') is transformed into layer (C) and layer (S') into layer (S) by conversion of ion exchange groups.

It is preferable to remove a part of the sacrificial yarns in the reinforcing cloth by dissolving a part of the sacrificial yarns with the alkaline aqueous solution used in the aforementioned hydrolysis.

[Alkali metal chloride electrolysis device]

The alkali metal chloride electrolysis device of the present invention can adopt known schemes except having the ion exchange membrane of the present invention.

As one aspect of the alkali metal chloride electrolysis device of the present invention, the alkali metal chloride electrolysis device has: an electrolytic cell equipped with a cathode and an anode; The ion exchange membrane of the present invention installed in an electrolytic cell.

When the ion exchange membrane of the present invention includes a layer (C) and a layer (S), it is arranged in an 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 arranged in contact with the ion exchange membrane, or may be arranged at a distance from it.

As a material constituting the cathode chamber, a material resistant to alkali metal hydroxide and hydrogen is preferable. Examples of the material include stainless steel, nickel, and the like. As a material constituting the anode chamber, a material resistant to alkali metal chlorides and chlorine is preferable. Titanium etc. are mentioned as this material.

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

For example, when using the alkali metal chloride electrolysis device of the present invention to electrolyze an aqueous sodium chloride solution to produce an aqueous sodium hydroxide solution, the aqueous sodium chloride solution is supplied to the anode chamber of the alkali metal chloride electrolysis device, and the hydroxide solution is supplied to the cathode chamber. In the aqueous sodium solution, 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 or suppressing dimensional changes. The remaining sacrificial filaments in the ion-exchange membrane play a role in maintaining the mechanical strength of the ion-exchange membrane together with the reinforcing filaments. Therefore, in order to maintain a certain mechanical strength that can withstand practical use, it is necessary to lower the average elastic modulus of the sacrificial filaments in the present invention. The average modulus of elasticity above the limit.

On the other hand, the inventors of the present invention have found that the residual amount of sacrificial yarn also contributes to the suppression of dimensional change, and if the residual amount of sacrificial yarn changes, the rate of dimensional change will fluctuate, and the higher the average elastic modulus of the sacrificial yarn, the higher the The fluctuation in the dimensional change rate due to the change in the remaining amount of the sacrificial wire becomes larger. That is, when the average elastic modulus of the sacrificial yarn is not more than the upper limit value of the average elastic modulus of the sacrificial yarn in the present invention described above, it is possible to suppress fluctuations in the rate of dimensional change due to changes in the remaining amount of the sacrificial yarn, and as a result , It is possible to suppress dimensional changes caused by unexpected changes in operating conditions of the electrolytic cell.

In this way, by adjusting the average elastic modulus of the sacrificial yarn, the maintenance of the mechanical strength required by the ion exchange membrane and the suppression of fluctuations in the dimensional change rate can be satisfied in a balanced manner. In particular, by setting the average elastic modulus of the sacrificial yarn to be Below the upper limit of the average modulus of elasticity of the aforementioned sacrificial filaments in the present invention, fluctuations in the dimensional change rate can be suppressed, and therefore, ion exchange membranes can be produced without strictly controlling the sacrificial filaments in the reinforcing material contained in the ion exchange membranes. residual amount.

Example

Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited and interpreted by these examples.

[Measurement of average elastic modulus of sacrificial wire]

The sacrificial yarn before dipping in the alkaline aqueous solution was mounted on a tensile tester (TENSILON RTC-1210A manufactured by ORIENTEC CORPORATION) at a chuck distance of 50 mm, and the stress-strain (elongation) when stretched at a tensile speed of 50 mm/min was measured. The stress at which the strain (elongation) of the curve is 5% is divided by the average cross-sectional area of the sacrificial yarn before being immersed in the alkaline aqueous solution, and the obtained value is regarded as the modulus of elasticity. About the average elastic modulus, five elastic moduli were measured, and the average value of these values was made into the average elastic modulus.

In addition, the cross-sectional area of the sacrificial silk before being immersed in an alkaline aqueous solution was observed using an optical microscope and measured using image software. The measurement of the cross-sectional area was performed for 10 sacrificial yarns, and the average value of these values was defined as the average cross-sectional area of the sacrificial yarn before being immersed in an alkaline aqueous solution.

[Measurement of average dimensional change rate of ion exchange membrane in sodium hydroxide aqueous solution]

Two marking lines (distance: 160 mm) were drawn on the ion exchange membrane, and the marking line distance L0 after storage in a 25° C. constant temperature room for 16 hours was measured using a digital caliper. Thereafter, it was immersed in a 32 mass % sodium hydroxide aqueous solution at 25° C. for 2 hours, and the marking line distance L1 was measured using a digital caliper. The dimensional change rate ΔL1 (%) was obtained from the following formula (A). The measurement was performed twice, and the average value of these values was defined as the average dimensional change rate ΔL1.

ΔL1=(L1-L0)/L0×100···(A)

When installing the ion exchange membrane in 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 installed in an electrolytic cell and in contact with an alkaline aqueous solution.

[Measurement of average dimensional change rate of ion exchange membrane in sodium chloride aqueous solution]

Two marking lines (distance: 160 mm) were drawn on the ion exchange membrane, and the marking line distance L0 after storage in a 25° C. constant temperature room for 16 hours was measured using a digital caliper. Thereafter, it was immersed in a 32 mass % sodium hydroxide aqueous solution at 25° C. for 7 days to dissolve all the sacrificial yarns. In addition, the film cross section was observed with an optical microscope, and when sacrificial filaments remained, it was immersed again in a 32 mass % sodium hydroxide aqueous solution at 25° C., and the immersion was continued until the sacrificial filaments were completely dissolved. The ion-exchange membrane immersed in the sodium hydroxide aqueous solution was washed with water, and then, in the state immersed in the sodium chloride aqueous solution, a reading microscope with a telescope (manufactured by Nippon Koki Manufacturing Co., Ltd., Digitalcassette meter)) Measure the marking line distance L2 when immersed in 125g/L sodium chloride aqueous solution at 90°C for 30 minutes. The dimensional change rate ΔL2 (%) was obtained from the following formula (B). The measurement was performed twice, and the average value of these values was defined as the average dimensional change rate ΔL2.

ΔL2=(L2-L0)/L0×100···(B)

Although sacrificial filaments remain when the ion exchange membrane is installed in the electrolytic cell, the sacrificial filaments are dissolved during electrolysis operation. This evaluation simply simulates the elongation of the ion-exchange membrane when the concentration of the aqueous sodium chloride solution decreases when the ion-exchange membrane is installed in the electrolytic cell and the sacrificial filaments are completely dissolved in the subsequent operation.

[Measurement of Average Cross-sectional Area of Sacrificial Filament Remaining in Ion Exchange Membrane]

For the cross-sectional area of the sacrificial wire remaining in the ion-exchange membrane, observe the cross-section of the ion-exchange membrane dried at 90° C. for more than 2 hours with an optical microscope and cut it perpendicular to the longitudinal direction of the sacrificial wire, and set it as measured using image software, The total value of the cross-sectional area of the sacrificial wire remaining per 1 mm in the width direction of the film. The measurement of the cross-sectional area was performed for 10 sacrificial wires, and the average value of these values was taken as the average cross-sectional area of the remaining sacrificial wires.

[Evaluation of weaving property]

The reinforcing fabric is woven from reinforcing filaments and sacrificial filaments, and it is important to strictly control the dimensions between the filaments. However, the dimensions between the filaments designed before weaving may deviate during weaving and after weaving, causing dimensional changes. Usually, even if weaving, there is no dimensional change before and after weaving, and the reinforcement fabric with the designed silk density is evaluated as "A". On the other hand, the case where a reinforcing cloth having the designed thread density was obtained was evaluated as "B", and the case where the size change before and after weaving was large, and the case where the reinforcing cloth having the designed thread density could not be obtained even if it was adjusted during weaving was evaluated as "B". C".

[Alkali metal chloride electrolysis device]

As an electrolytic cell (effective current-conducting area: 25 cm ² ), an electrolytic cell with the following structure was used: the inlet of the supply water of the cathode chamber was arranged at the lower part of the cathode chamber, the outlet of the generated sodium hydroxide aqueous solution was arranged at the upper part of the cathode chamber, and the outlet of the anode chamber was arranged at the upper part of the cathode chamber. The inlet of the aqueous sodium chloride solution is arranged at the lower part of the anode chamber, and the outlet of the aqueous sodium chloride solution diluted by the electrolytic reaction is arranged at the upper part of the anode chamber.

As the anode, titanium punched metal (opening shape: rhombus) (short diameter: 4 mm, long diameter: 8 mm) covered with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide was used. As the cathode, a cathode in which ruthenium-doped Raney nickel was electrodeposited on SUS304 punched metal (opening shape: rhombus) (short diameter: 5 mm, long diameter: 10 mm) was used.

[Measurement of current efficiency]

Use the ion-exchange membrane with layer (C) and layer (S), with the mode that layer (C) faces cathode, arrange in the alkali metal chloride electrolysis device, the sodium hydroxide aqueous solution concentration in cathode chamber: 32 mass %, Concentration of aqueous sodium chloride solution in the anode chamber: 200g/L, temperature 90°C, current density: 6kA/m ² Under the conditions of electrolysis of aqueous sodium chloride solution, the current efficiency will be measured for 3 to 10 days from the start of operation The average value of the values was taken as the average current efficiency (%).

[Example 1-1]

A stainless steel reactor (autoclave) with an internal volume of 94L was vacuum degassed, and then a compound having a carboxylic acid type functional group represented by the following formula (2-1) (hereinafter also referred to as "monomer M") was added. ) was dissolved in CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ H (hereinafter also referred to as "solvent S") at a concentration of 37.4% by mass, and 66.2 kg of a solution obtained was heated up until the inside of the reactor The temperature becomes 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 became 1.116 MPaG, and 4.0 L of a solution obtained by dissolving azobisisobutyronitrile as a polymerization initiator in a solvent S at a concentration of 0.031% by mass was added to start polymerization reaction. During the polymerization reaction, the internal pressure of the reactor was maintained at 1.116 MPaG (gauge pressure?), while CF ₂ =CF ₂ was continuously added, and the molar ratio of CF ₂ =CF ₂ /monomer M was equivalent to 6.2 Monomer M. When the introduction amount of CF ₂ =CF ₂ from the start of the reaction reached 4.9 kg, the reactor was cooled to 40°C, unreacted CF ₂ =CF ₂ was released outside the system, and the polymerization was terminated. Then, under reduced pressure and heating, the solvent S and liquid unreacted monomer M were distilled off, and dried under reduced pressure at 0.5 kPaA (absolute pressure) and 92° C. for 12 hours to obtain 7.4 kg of powdery fluoropolymer. (C'1-1). The functional group concentration of the obtained fluoropolymer (C'1-1) was 13.89 mol%, and the ion exchange capacity after hydrolysis treatment was 1.08 meq/g dry resin.

Using the same method as the aforementioned polymerization reaction, CF ₂ ═CF ₂ and CF ₂ ═CF-O-CF ₂ CF(CF ₃ )-O-CF ₂ CF ₂ -SO ₂ F were copolymerized to obtain fluorine-containing polymer (S '1-1). The ion exchange capacity after the hydrolysis treatment of the obtained fluoropolymer (S'1-1) was 1.1 meq/g dry resin.

The fluorine-containing polymer (C'1-1) and the fluorine-containing polymer (S'1-1) are formed into a film by a co-extrusion method to obtain a layer (C'1-1) formed of the fluorine-containing polymer (C'1-1). Film A consisting of two layers of 'a) (thickness: 12 μm) and layer (S'a) (thickness: 68 μm) formed of a fluoropolymer (S'1-1).

The 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) formed of the fluoropolymer (S'1-1).

The stretched PTFE film was slit into a thickness of 100 denier, and the obtained monofilament was twisted 2,000 times/m into a PTFE yarn as a reinforcing yarn.

A PET yarn formed of a 30-denier multifilament yarn obtained by sintering six 5-denier PET filament yarns (elastic modulus: 4.9 GPa) was used as a sacrificial yarn.

Plain weaving was carried out in such a manner that one reinforcing yarn and two sacrificial yarns were alternately arranged to obtain a reinforcing cloth (density of reinforcing yarn: 27 yarns/inch, density of sacrificial yarn: 54 yarns/inch).

Film B, reinforcement fabric, film A, and PET film for mold release (thickness: 100 μm) are stacked in order so that layer (C'a) of film A is on the side of PET film for mold release, and laminated using a roller. The PET film for mold release was peeled off to obtain an ion exchange membrane precursor membrane.

A paste containing 29.0% by mass of zirconia (average particle diameter: 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 was transferred using a roller press. Printed onto the upper side of the layer (S'b) of the precursor film to form a layer of inorganic particles. The deposited amount of zirconia was set at 20 g/m ² .

The precursor film in which the inorganic particle layer was formed on one surface was immersed in an aqueous solution of 5 mass % dimethyl sulfoxide and 30 mass % potassium hydroxide at 95° C. for 8 minutes. Thus, -COOCH ₃ of the fluoropolymer (C'1-1) and -SO ₂ F of the fluoropolymer (S'1-1) are hydrolyzed to be converted into ion exchange groups, and the precursor Layer (C'a) is a film of layer (Ca), layer (S'a) is layer (Sa), and layer (S'b) is layer (Sb).

At this time, the average cross-sectional area of the sacrificial filaments remaining in the ion exchange membrane was 1800 μm ² /mm.

Zirconia (average particle diameter: 1 μm) was dispersed at a concentration of 13% by mass in an ethanol solution of an acid-type polymer containing 2.5% by mass of the fluoropolymer (S'1-1) to prepare a dispersion. The dispersion liquid was sprayed on the layer (Ca) side of the membrane to form a gas-releasing coating layer, thereby obtaining an ion exchange membrane having gas-releasing coating layers formed on both surfaces. The deposited amount of zirconia was 3 g/m ² .

[Example 1-2]

The precursor film with the inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95° C. for 15 minutes. -1 Operated in the same manner to obtain an ion exchange membrane. The average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane after hydrolysis was 690 μm ² /mm.

[Example 2-1]

As a sacrificial yarn, a PET yarn made of a 20-denier multifilament yarn made of six 3.3-denier PET filament yarns (elastic modulus: 4.4GPa) was used as a reinforcing fabric. 1 yarn and 4 sacrificial yarns are alternately arranged in plain weave, and the density of the reinforcing yarn is 27 yarns/inch, and the density of the sacrificial yarn is 108 yarns/inch. In addition, the same as Example 1-1 In the same manner, an ion exchange membrane was obtained. The average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane after hydrolysis was 983 μm ² /mm.

[Example 2-2]

The precursor film with the inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95° C. for 15 minutes. -1 Operated in the same manner to obtain an ion exchange membrane. In the ion exchange membrane after hydrolysis, no sacrificial filament remained.

[Example 3-1]

As the sacrificial yarn, a PET yarn of 18 denier multifilament formed by combining two PET filaments of 9 denier (elastic modulus: 7.2 GPa) was used. -1 Operated in the same manner to obtain an ion exchange membrane. The average cross-sectional area of the sacrificial filaments remaining in the ion-exchange membrane after hydrolysis was 3660 μm ² /mm.

[Example 3-2]

The precursor film with the inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95° C. for 15 minutes. -1 Operated in the same manner to obtain an ion exchange membrane. The average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane after hydrolysis was 1711 μm ² /mm.

[Example 3-3]

The precursor film with the inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95° C. for 19 minutes. -1 Operated in the same manner to obtain an ion exchange membrane. The average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane after hydrolysis was 61 μm ² /mm.

[Example 4-1]

As the sacrificial yarn, a PBT yarn formed of a 30-denier multifilament yarn obtained by combining six 5-denier PBT filaments (elastic modulus: 1.2 GPa) was used. The precursor membrane of the layer was immersed in an aqueous solution of 5% by mass dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95°C for 90 minutes, except that it was performed in the same manner as in Example 1-1 to obtain ion exchange membrane.

It should be noted that, in the weaving of the reinforcing fabric of this example, dimensional changes occur before and after the weaving, and therefore, adjustments are required to obtain the designed thread density during weaving. The average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane after hydrolysis was 3010 μm ² /mm.

[Example 4-2]

The precursor film with the inorganic particle layer formed on one side was immersed in an aqueous solution of 5% by mass dimethyl sulfoxide and 30% by mass of potassium hydroxide at 95° C. for 180 minutes. -1 Operated in the same manner to obtain an ion exchange membrane. The average cross-sectional area of the sacrificial filaments remaining in the ion-exchange membrane after hydrolysis was 1410 μm ² /mm.

〔Example 5〕

As the reinforcing yarn, a PTFE yarn obtained by applying 2000 twists/m to a monofilament obtained by rapidly stretching a PTFE film and cutting it into a thickness of 100 denier was used. As a sacrificial yarn, 6 wires were used. PBT yarn made of 5 denier PBT filament (elastic modulus: 0.6GPa) and 30 denier multifilament yarn are plain woven in such a way that one reinforcing yarn and two sacrificial yarns are alternately arranged , Weaving the reinforcing cloth with a density of 27 filaments/inch and a density of 54 filaments/inch of the sacrificial filaments, the dimensional change before and after weaving is large, and the reinforcing fabric with the designed filament density cannot be obtained.

In each example except Example 5, in which a reinforcing cloth having the designed silk density could not be obtained and could not be measured, in a 32% by mass sodium hydroxide aqueous solution at 25°C and a 125g/L sodium chloride aqueous solution at 90°C The dimensional change ratios of the ion-exchange membranes are shown in Table 1. In addition, the current efficiency was 96% or more in all the examples except Example 5, in which the reinforcing cloth having the designed thread density could not be obtained and could not be measured.

[Table 1]

As shown in Table 1, in Example 1-1 and Example 1-2, Example 2-1 and Example 2-2, and Example 4-1 and Example 4-2 using the ion exchange membrane satisfying the conditions of the present invention, The dimensional change caused by the amount of sacrificial filaments remaining in the ion exchange membrane in a 32 mass% sodium hydroxide aqueous solution at 25°C is small, and the dimensional change is not affected by the average cross-sectional area of the sacrificial filaments remaining in the ion exchange membrane , roughly constant.

In Example 3-1, Example 3-2, and Example 3-3, which exhibit a higher average modulus of elasticity of the sacrificial silk than the conditions of the present invention, ion exchange in 32% by mass sodium hydroxide aqueous solution at 25°C The dimensional change of the membrane due to the amount of remaining sacrificial filaments in the ion-exchange membrane fluctuates greatly, and it can be seen that the dimensional change greatly varies depending on the average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane.

As shown in Table 1, in 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 , The ion exchange membrane in the 125g/L sodium chloride aqueous solution at 90°C has little change in dimensional change caused by the residual amount of sacrificial wire in the ion exchange membrane, and the dimensional change is not affected by the residual sacrificial wire in the ion exchange membrane The effect of the average cross-sectional area is approximately constant.

Ion exchange in 125 g/L sodium chloride aqueous solution at 90° C. in Example 3-1, Example 3-2 and Example 3-3 showing higher average elastic modulus of sacrificial silk than the conditions of the present invention The dimensional change of the membrane due to the amount of remaining sacrificial filaments in the ion-exchange membrane fluctuates greatly, and it can be seen that the dimensional change greatly varies depending on the average cross-sectional area of the remaining sacrificial filaments in the ion-exchange membrane.

From the above results, it can be seen that the ion exchange membrane of the present invention whose average elastic modulus of the sacrificial filament is within a specific range is not affected by the average cross-sectional area of the sacrificial filament remaining in the ion exchange membrane, and the fluctuation of the dimensional change is approximately constant, and it is easy to Control size changes.

On the other hand, it was found that the ion-exchange membrane whose average elastic modulus of the sacrificial filament is higher than the conditions of the present invention, the dimensional change largely fluctuates depending on the average cross-sectional area of the sacrificial filament remaining in the ion-exchange membrane. That is, by making the average modulus of elasticity of the sacrificial filaments in the reinforcing material inside the ion-exchange membrane within the specific range of the present invention, even if the average cross-sectional area of the remaining sacrificial filaments changes, the size of the ion-exchange membrane There are few variations of changes. Therefore, even if the average cross-sectional area of the remaining sacrificial filaments is not strictly controlled based on the hydrolysis conditions of the alkaline aqueous solution, the dimensional change rate of the ion-exchange membrane can be kept within a certain range, and the unexpected ion-exchange membrane can be reduced. Problems such as wrinkles, pinholes, and cracks in ion exchange membranes caused by dimensional changes. This effect is particularly remarkable in a large-scale hydrolysis tank, when it is difficult to uniformize the hydrolysis conditions such as the temperature in the tank and the concentration of the alkaline aqueous solution.

Industrial availability

In addition, all the content of the specification, a claim, and the abstract of the Japanese patent application 2016-44534 for which it applied on March 8, 2016 is referred here, and it takes in as an indication of the specification of this invention.

Claims (14)

1. An ion-exchange membrane for alkali metal chloride electrolysis, characterized in that it has: a fluoropolymer layer with ion-exchange groups; and is arranged inside the fluoropolymer layer with ion-exchange groups A reinforcing material comprising reinforcing wires and sacrificial wires, The average elastic modulus of the sacrificial wire is 1.0-7.0 GPa. 2. The ion-exchange membrane for alkali metal chloride electrolysis according to claim 1, wherein the fineness of the reinforcing filaments is 20 to 200 deniers, and the density of the reinforcing filaments in the cloth is 10 to 40 strands/inch . 3. The ion exchange membrane for alkali metal chloride electrolysis according to claim 1 or 2, wherein the sacrificial yarn has a fineness of 5 to 100 denier, and the number of filaments per sacrificial yarn in the cloth is 1 to 32 monofilaments or multifilaments. 4. The ion-exchange membrane for alkali metal chloride electrolysis according to any one of claims 1 to 3, wherein the sacrificial wire is a sacrificial wire that is partially dissolved and removed. 5. The ion-exchange membrane for alkali metal 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 sulfonic acid-type functional group. Fluoropolymer layer. 6. The ion-exchange membrane for alkali metal 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 carboxylic acid-type functional group. Fluoropolymer layer. 7. The ion-exchange membrane for alkali metal chloride electrolysis according to any one of claims 1 to 6, further comprising a layer containing inorganic particles on at least one outermost surface. 8. An alkali metal chloride electrolysis device, which is equipped with the ion exchange membrane for the alkali metal chloride electrolysis described in any one of claims 1 to 7 as the cathode chamber on the cathode side and the anode side in the electrolytic cell The electrolytic membrane separating the anode compartment. 9. An ion-exchange membrane precursor membrane for alkali metal chloride electrolysis, characterized in that it has: a fluoropolymer layer with a group that can be converted into an ion-exchange group; Ion-exchange groups of groups of fluoropolymer layers inside the reinforcement cloth, The reinforcing cloth includes reinforcing filaments and sacrificial filaments, and the average elastic modulus of the sacrificial filaments is 1.0-7.0 GPa. 10. The ion-exchange membrane precursor membrane for alkali metal chloride electrolysis according to claim 9, wherein at least a part of the fluoropolymer layer having a group capable of being converted into an ion-exchange group is The fluoropolymer layer is a group of sulfonic acid type functional groups. 11. The ion-exchange membrane precursor membrane for alkali metal chloride electrolysis according to claim 9 or 10, wherein at least a part of the fluoropolymer layer having a group capable of being converted into an ion-exchange group has Fluoropolymer layer of groups capable of converting into carboxylic acid type functional groups. 12. a kind of manufacture method of ion-exchange membrane for alkali metal chloride electrolysis, it is characterized in that, by making the ion-exchange membrane precursor membrane described in any one in claim 9～11 contact with alkaline aqueous solution, thereby will be able to The group converted into an ion-exchange group is converted into an ion-exchange group, and at least a part of the sacrificial filament in the reinforcing cloth is dissolved and removed, thereby obtaining a fluorine-containing polymer layer having an ion-exchange group and a reinforcing material. ion exchange membrane. 13. The method for producing an ion-exchange membrane for alkali metal chloride electrolysis according to claim 10, wherein a part of the sacrificial filament in the reinforcing cloth is dissolved and removed. 14. A manufacturing method of an alkali metal chloride electrolysis device, characterized in that, after obtaining the ion exchange membrane for alkali metal chloride electrolysis by the manufacturing method described in claim 12 or 13, the ion exchange membrane is set as the electrolytic cell The cathode compartment on the cathode side and the anode compartment on the anode side are separated by an electrolytic membrane.