JP2018095663A - Ion-exchange membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion-exchange membrane for suppressing peeling in a membrane even when used for electrolytically producing tetraalkylammonium hydroxide for a long period of time.SOLUTION: There is provided an ion-exchange membrane used in an electrolysis apparatus for producing tetraalkylammonium hydroxide by electrolysis of a tetraalkylammonium salt, which comprises an inorganic particle layer, a layer (S) containing a fluorine-containing polymer having a sulfonic acid type functional group, a layer (C) containing a fluorine-containing polymer having a carboxylic acid type functional group, and an inorganic particle layer in this order, wherein the layer (C) has an ion exchange capacity of 0.95 meq/g dry resin or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ion exchange membrane.

Tetraalkylammonium hydroxide is widely used as a supporting electrolyte for organic electrolysis, a resist developer in the semiconductor manufacturing industry, and the like as a strongly basic organic compound not containing metal ions.
As a method for producing tetraalkylammonium hydroxide, a method based on electrolysis of tetraalkylammonium salt (hereinafter also simply referred to as “electrolysis”) is disclosed (Patent Document 1). More specifically, in the electrolytic apparatus in which the anode chamber and the cathode chamber are separated by the ion exchange membrane described in Patent Document 1, for example, when tetraalkylammonium chloride is used as a raw material, 2Cl ⁻ → Cl _{2 in the} anode chamber. As the oxidation of chloride ions represented by + 2e ⁻ proceeds to chlorine, the reduction of water represented by 2H ₂ O + 2e ⁻ → H ₂ + 2OH ⁻ to hydrogen and hydroxide ions proceeds in the cathode chamber, Production of tetraalkylammonium hydroxide proceeds by reaction of tetraalkylammonium ions that have migrated from the anode chamber through the ion exchange membrane and OH ⁻ .
In Patent Document 1, Nafion (registered trademark) N902 membrane and N966 membrane are specifically disclosed as ion exchange membranes.

JP 2001-271193 A

On the other hand, in recent years, the use of ion exchange membranes for a long time has been demanded from the viewpoint of improving productivity.
When the present inventors performed electrolytic production of the tetraalkylammonium hydroxide using the ion exchange membrane described in Patent Document 1, peeling (peeling) occurs in the ion exchange membrane during long-time use. I found out. When such peeling occurs, there is a concern about an increase in resistance value, which is not preferable.

  In view of the above circumstances, an object of the present invention is to provide an ion exchange membrane in which peeling in a membrane is suppressed even when used for an electrolytic production of tetraalkylammonium hydroxide for a long time.

The present invention has the following configuration.
(1) An ion exchange membrane used in an electrolysis apparatus for producing tetraalkylammonium hydroxide by electrolysis of a tetraalkylammonium salt,
An inorganic particle layer;
A layer (S) containing a fluorine-containing polymer having a sulfonic acid type functional group;
A layer (C) containing a fluorine-containing polymer having a carboxylic acid type functional group;
An inorganic particle layer in this order,
An ion exchange membrane in which the ion exchange capacity of the layer (C) is 0.95 meq / g dry resin or more.
(2) The ion exchange membrane according to (1), wherein a reinforcing material is further disposed in the layer (S).
(3) The ion exchange capacity of the layer (S) is 1.0 to 2.0 meq / g dry resin,
The ion exchange membrane according to (1) or (2), wherein the ion exchange capacity of the layer (C) is 0.95 to 2.05 meq / g dry resin.
(4) The dry thickness of the layer (S) is 50 to 200 μm,
The ion exchange membrane according to any one of (1) to (3), wherein the thickness of the layer (C) when dried is 5 to 30 μm.
(5) The reinforcing material includes at least one reinforcing yarn selected from the group consisting of a reinforcing yarn made of polytetrafluoroethylene, a reinforcing yarn made of polyphenylene sulfide, a reinforcing yarn made of nylon, and a reinforcing yarn made of polypropylene. The ion exchange membrane according to any one of (1) to (4), comprising a reinforcing cloth.
(6) The ion exchange membrane according to any one of (1) to (5), wherein the layer (S) contains a polymer having a structural unit represented by the formula (u1) described later.
(7) The ion exchange membrane according to any one of (1) to (6), wherein the layer (S) contains a polymer having a structural unit represented by the formula (u2) described later.
(8) The ion exchange membrane according to any one of (1) to (7), wherein the layer (S) contains a polymer having a structural unit represented by the formula (u3) described later.
(9) The ion exchange membrane according to (8), wherein the structural unit represented by formula (u3) is a structural unit represented by formula (u4) described later.

  According to the present invention, it is possible to provide an ion exchange membrane in which peeling in the membrane is suppressed even when used for a long time in the electrolytic production of tetraalkylammonium hydroxide.

It is sectional drawing which shows an example of the ion exchange membrane of this invention. It is sectional drawing which shows an example of the ion exchange membrane of this invention. It is a schematic diagram which shows an example of the electrolyzer of this invention.

  The following definitions of terms apply throughout this specification and the claims.

The “ion exchange membrane” is a membrane 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.
The “precursor membrane” is a membrane containing 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.

“Fluorine-containing polymer” means a polymer compound having a fluorine atom in the molecule.
“Monomer” means a compound having a polymerization-reactive carbon-carbon unsaturated double bond.
“Fluorine-containing monomer” means a monomer having a fluorine atom in the molecule.
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, for example, hydrolyzing 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 member used to improve the strength of the 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.

  “Strengthened precursor film” means a film in which a reinforcing material is disposed in a precursor film.

  Hereinafter, although the ion exchange membrane of this invention is demonstrated based on FIG. 1, this invention is not limited to the content of FIG.

[Ion exchange membrane]
The ion exchange membrane of the present invention comprises a layer (hereinafter also referred to as “layer (C)”) containing a fluoropolymer having a carboxylic acid type functional group (hereinafter also referred to as “fluorinated polymer (C)”), And a layer (hereinafter also referred to as “layer (S)”) containing a fluorine-containing polymer having a sulfonic acid type functional group (hereinafter also referred to as “fluorinated polymer (S)”), and a reinforcing yarn. The reinforcing material to be included is arranged in the layer (S). The reinforcing material may include a sacrificial yarn in addition to the reinforcing yarn. In the ion exchange membrane of the present invention, elution holes may be formed by elution of the sacrificial yarn.
The reinforcing material is an arbitrary material and may not be included in the ion exchange membrane.

FIG. 1 is a cross-sectional view showing an example of the ion exchange membrane of the present invention.
The ion exchange membrane 1 is obtained by reinforcing an electrolyte membrane 10 made of a fluorine-containing polymer having an ion exchange group with a reinforcing material 20.

(Electrolyte membrane)
The electrolyte membrane 10 is a laminate composed of a layer (C) 12 and a layer (S) 14. In the layer (S) 14, a reinforcing member 20 including a reinforcing yarn is disposed.

The thickness of each layer when the ion exchange membrane is dried is determined using an image software after observing the cross section of the ion exchange membrane with an optical microscope after drying the ion exchange membrane at 90 ° C. for 4 hours.
When a reinforcing material is present between the layers, the thickness of the layer is measured at a position where neither the reinforcing yarn or the sacrificial yarn constituting the reinforcing material is present.

<Layer (C)>
The layer (C) 12 is preferably a layer made of only the fluoropolymer (C) from the viewpoint of electrolytic performance. That is, the layer (C) 12 is preferably a layer made of a fluorine-containing polymer having a carboxylic acid type functional group. In FIG. 1, the layer (C) 12 is shown as a single layer, but may be a layer formed of a plurality of layers. When the layer (C) 12 is formed of a plurality of layers, in each layer, the types of structural units constituting the fluoropolymer (C) and the proportions of the structural units having a carboxylic acid type functional group may be different.

The ion exchange capacity of layer (C) 12 is 0.95 meq / g dry resin or more. When the ion exchange capacity of the layer (C) 12 is 0.95 meq / g dry resin or more, the adhesion with the layer (S) 14 described later is enhanced, and when the ion exchange membrane is used for a long time, the layer ( C) Peeling hardly occurs between the layer 12 and the layer (S) 14.
Among these, 1.0 milliequivalent / gram dry resin or more is preferable, in that peeling (peeling between the layer (C) 12 and the layer (S) 14) is less likely to occur in the ion exchange membrane. Equivalent / gram dry resin or more is more preferable.
In view of maintaining the strength as an ion exchange membrane, the ion exchange capacity of the layer (C) 12 is preferably 2.05 meq / g dry resin or less, more preferably 1.5 meq / g dry resin. 1.1 milliequivalent / gram dry resin is more preferred. Within the above range, it is easy to increase the molecular weight of the fluoropolymer (C) at the time of polymerization, and by using the fluoropolymer (C) having a higher molecular weight, sufficient membrane strength of the ion exchange membrane can be obtained. Can be expressed.
In addition, when the layer (C) 12 is formed of a plurality of layers, it is preferable that the ion exchange capacity of all the layers constituting the layer (C) 12 is in the above range.
The method for measuring the ion exchange capacity of the layer (C) 12 is not particularly limited. For example, a film-like model sample is prepared using the material (fluorinated polymer) constituting the layer (C) 12, and this model sample is prepared. The amount of the carboxylic acid type functional group or the group that can be converted into the carboxylic acid type functional group can be obtained by using a transmission infrared spectroscopic analyzer, and the ion exchange capacity can be calculated. Further, the amount of the carboxylic acid type functional group or the group that can be converted into the carboxylic acid type functional group of the layer (C) in the ion exchange membrane may be directly determined using a transmission infrared spectroscopic analyzer.

  In addition, the difference between the ion exchange capacity of the layer (S) 14 described in detail later and the ion exchange capacity of the layer (C) 12 is not particularly limited. Among these, the ion exchange capacity of the layer (S) 14 and the layer (C) 12 are more difficult to cause in the ion exchange membrane (separation between the layer (C) 12 and the layer (S) 14). The absolute value of the difference from the ion exchange capacity is preferably 0.1 meq / g dry resin or less, more preferably 0.05 meq / g dry resin or less.

The thickness of the layer (C) 12 at the time of drying (when the layer (C) 12 is formed from a plurality of layers) is not particularly limited, but is preferably 5 to 30 μm, more preferably 9 to 28 μm, 9-22 micrometers is further more preferable.
The thickness of the layer (C) 12 affects the water permeability of the ion exchange membrane as well as the ion exchange capacity. In particular, when the thickness of the layer (C) 12 is thin, the water permeability of the ion exchange membrane is increased. On the other hand, the thickness of the layer (C) 12 has a great influence on the quality of the aqueous solution of tetraalkylammonium hydroxide obtained by electrolysis together with the ion exchange capacity. Therefore, if the thickness at the time of drying of the layer (C) 12 is within the above range, an increase in the impurity concentration in the resulting tetraalkylammonium hydroxide aqueous solution and an increase in the electrolysis voltage can be suppressed in a balanced manner.

In the fluoropolymer (C), a 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 described later in step (ib) described later is a carboxylic acid type functional group. It is preferably obtained by conversion to a group.
Examples of the fluorine-containing polymer (C) include a group having a group that can be converted into a carboxylic acid type functional group and a monomer having a fluorine atom (hereinafter also referred to as “fluorine-containing monomer (C ′)”) and a fluorine-containing olefin. Examples thereof include a fluorine-containing polymer obtained by hydrolyzing a polymer (hereinafter also referred to as “fluorinated polymer (C ′)”) to convert a group capable of being converted into a carboxylic acid type functional group into a carboxylic acid type functional group.

As the fluorine-containing monomer (C ′), as long as it is a compound having one or more fluorine atoms in the molecule, an ethylenic double bond, and a group that can be converted into a carboxylic acid type functional group, It does not specifically limit and a conventionally well-known thing can be used.
As the fluorine-containing monomer (C ′), a monomer represented by the following formula (1) is preferable from the viewpoint of excellent production cost of the monomer, reactivity with other monomers, and properties of the resulting fluorine-containing polymer.

_{CF 2 = CF- (O) p} - (CF 2) q - (CF 2 CFX) r - (O) s - (CF 2) t - (CF 2 CFX ') u -A 1 ··· Equation (1 )

Symbols in the formula (1) mean the following.
X and X ′ are a fluorine atom or a trifluoromethyl group. X and X ′ may be the same or different.
A ¹ is a group that can be converted into 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 hydrogen atoms) Or an alkyl group having 1 to 10 carbon atoms, R ² and R ³ may be the same or different.
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. 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.

Specific examples of the monomer represented by the formula (1) include the following compounds. From the viewpoint of easy production, p = 1, q = 0, r = 1, s = 0 to 1, t = Compounds with 0-3 and u = 0-1 are preferred.
_{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.
A fluorine-containing monomer (C ') may be used individually by 1 type, and may be used in combination of 2 or more type.

As a fluorine-containing olefin, the C2-C3 fluoroolefin which has a 1 or more fluorine atom in a molecule | numerator is mentioned, for example. Examples of the fluoroolefin include tetrafluoroethylene (CF ₂ = CF ₂ ) (hereinafter referred to as TFE), chlorotrifluoroethylene (CF ₂ = CFCl), vinylidene fluoride (CF ₂ = CH ₂ ), vinyl fluoride ( CH ₂ = CHF), hexafluoropropylene (CF ₂ = CFCF ₃ ) and the like. Among these, TFE is preferable because it is excellent in the production cost of the monomer, the reactivity with other monomers, and the characteristics of the resulting fluoropolymer.
A fluorine-containing olefin may be used individually by 1 type, and may be used in combination of 2 or more type.

In addition to the fluorine-containing monomer (C ′) and the fluorine-containing olefin, another monomer may be used for the production of the fluorine-containing polymer (C ′). 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) and the like. By copolymerizing other monomers, the flexibility and mechanical strength of the ion exchange membrane 1 can be increased. The proportion of other monomers is preferably 30 mol% or less in the total structural units (100 mol%) in the fluoropolymer (C ′) from the viewpoint of maintaining ion exchange performance.

  The ion exchange capacity of the fluoropolymer (C) can be adjusted by changing the content of the structural unit derived from the fluoromonomer (C ′) in the fluoropolymer (C ′). The content of the carboxylic acid type functional group in the fluoropolymer (C) is preferably the same as the content of the group that can be converted into the carboxylic acid type functional group in the fluoropolymer (C ′).

The TQ value of the fluoropolymer (C) is preferably 150 ° C. or higher, more preferably 170 to 340 ° C., and even more preferably 170 to 300 ° C. from the viewpoint of mechanical strength and film-forming property as an ion exchange membrane.
The TQ value is a value related to the molecular weight of the polymer and indicates a temperature at which the volume flow rate is 100 mm ³ / sec. The volume flow rate is the amount of polymer flowing out in units of mm ³ / sec when the polymer is melted and discharged from an orifice (diameter: 1 mm, length: 1 mm) at a constant temperature under a pressure of 3 MPa. is there. A higher TQ value indicates a higher molecular weight.

<Layer (S)>
The layer (S) 14 is preferably a layer made of only the fluoropolymer (S) from the viewpoint of electrolytic performance. That is, the layer (S) 14 is preferably a layer made of a fluoropolymer having a sulfonic acid type functional group. As shown in FIG. 1, a reinforcing material 20 is disposed in the layer (S) 14 in order to increase the mechanical strength of the ion exchange membrane 1. Of the layers (S) 14, the layer (Sa) 14A is located on the layer (C) 12 side (the cathode side in the electrolysis apparatus) from the reinforcing material 20, and is the layer (C) 12 side from the reinforcing material 20. The layer located on the opposite side (the anode side in the electrolysis apparatus) is the layer (Sb) 14B. In FIG. 1, the layer (Sa) 14 </ b> A and the layer (Sb) 14 </ b> B are each shown as a single layer, but may be formed from a plurality of layers. When one or both of the layer (Sa) 14A and the layer (Sb) 14B are formed of a plurality of layers, in each of the layers, the type of structural unit constituting the fluoropolymer (S) and the sulfonic acid type functional group It is good also as a structure from which the ratio of the structural unit to have differs.

Although the thickness of the layer (S) 14 at the time of drying is not specifically limited, 50-200 micrometers is preferable and 60-130 micrometers is more preferable.
If the thickness of the layer (S) 14 at the time of drying is not less than the above lower limit value, the mechanical strength of the ion exchange membrane 1 is sufficiently high. If the thickness of the layer (S) 14 at the time of drying is not more than the above upper limit value, the membrane resistance of the ion exchange membrane 1 can be kept low.

  The ion exchange capacity of the layer (S) is not particularly limited, but is preferably 1.0 to 2.0 meq / g dry resin. In addition, it is preferable that the ion exchange capacity of the whole layer (S) is in the above range, and it is more preferable that both the layer (Sa) 14A and the layer (Sb) 14B have an ion exchange capacity in the above range.

The thickness of the layer (Sa) 14A at the time of drying (when the layer (Sa) 14A is formed of a plurality of layers) is preferably 40 to 110 μm, more preferably 50 to 90 μm, and more preferably 60 to 90 μm. Further preferred.
If the thickness of the layer (Sa) 14A at the time of drying is not less than the above lower limit value, the mechanical strength of the ion exchange membrane 1 is sufficiently high. If the thickness of the layer (Sa) 14A at the time of drying is not more than the above upper limit value, the membrane resistance of the ion exchange membrane 1 can be kept low.
In order to achieve both the mechanical strength and the electrolytic voltage, it is very important that the thickness of the layer (Sa) 14A at the time of drying is within the above range.

The ion exchange capacity of the layer (Sa) 14A is preferably 0.9 to 1.25 meq / g dry resin, more preferably 1.0 to 1.25 meq / g dry resin, More preferably, it is 1.0 to 1.1 meq / g dry resin.
When the layer (Sa) 14A is formed of a plurality of layers, it is preferable that all the layers constituting the layer (Sa) 14A are in the above range. The layer (Sa) 14A is preferably composed of a plurality of layers, and more preferably composed of two layers. In another embodiment, the layer (Sa) 14A is preferably a single layer.
If the ion exchange capacity of the layer (Sa) 14A is not less than the above lower limit, excessive swelling of the fluoropolymer (S) can be suppressed, the electric resistance of the ion exchange membrane is lowered, and an aqueous solution of a tetraalkylammonium salt is electrolyzed. The electrolysis voltage can be reduced. Further, if the ion exchange capacity is not more than the above upper limit, it is easy to increase the molecular weight of the fluoropolymer (S) during polymerization, and the higher molecular weight fluoropolymer (S) is applied to the layer (Sa). By using it, the strength of the layer (Sa) can be further increased.

The thickness of the layer (Sb) 14B at the time of drying (when the layer (Sb) 14B is formed of a plurality of layers) is preferably 6 to 100 μm, more preferably 6 to 50 μm, and more preferably 10 to 40 μm. Further preferred is 15 to 35 μm. If the layer (Sb) is too thin during drying, the reinforcing material immediately below the layer (Sb) will be located very close to the surface of the ion exchange membrane, which may affect the peel resistance and mechanical strength. growing.
Therefore, by setting the thickness of the layer (Sb) 14B at the time of drying to the above lower limit value or more, the reinforcing material 20 is disposed at an appropriate depth position from the surface of the electrolyte membrane 10, and the peeling resistance of the reinforcing material 20 is improved. To do. Moreover, it is difficult for cracks to enter the surface of the electrolyte membrane 10, and as a result, a decrease in mechanical strength is suppressed. When the thickness of the ion exchange membrane 1 is large, the membrane resistance is also increased. Therefore, if the thickness of the layer (Sb) 14B during drying is not more than the above upper limit value, the membrane resistance of the ion exchange membrane 1 can be kept low. , The increase in electrolysis voltage can be suppressed.

  The ion exchange capacity of the layer (Sb) 14B is not particularly limited, but is preferably 1.0 to 2.5 meq / g dry resin, and 1.0 to 2.2 meq / g dry resin. Is more preferably 1.0 to 2.0 meq / g dry resin.

Although the structure of the polymer contained in the said layer (S) is not specifically limited, It is preferable that a layer (S) contains the polymer which has a structural unit represented by the following Formula (u1) as a fluorine-containing polymer.
_{- [CF 2 -CF (-O-} CF 2 CF (CF 3) -O- (CF 2) m -SO 3 M)] - ··· formula (u1)
m is an integer of 1 to 6, and M is an alkali metal.
Moreover, it is also preferable that the said layer (S) contains the polymer which has a structural unit represented by the following Formula (u2).
_{- [CF 2 -CF (-O- (} CF 2) m -SO 3 M)] - ··· formula (u2)
m is an integer of 1 to 6, and M is an alkali metal.

  At least a part of the fluorine-containing polymer having a sulfonic acid type functional group contained in the layer (S) (preferably the layer (Sb) 14B) is a monomer having two or more, preferably two sulfonic acid type functional groups. A polymer having a structural unit based thereon is preferred. The layer (S) (preferably the layer (Sb) 14B) comprises a polymer having a structural unit based on a monomer having two or more sulfonic acid type functional groups, so that ion exchange groups per unit weight at the same monomer concentration. Since the concentration can be increased, a layer (Sb) having a higher ion exchange capacity can be obtained even with a small amount of monomer as compared with a polymer having a structural unit having only one sulfonic acid type functional group.

  As the structural unit based on a monomer having two or more sulfonic acid type functional groups, a structural unit represented by the following formula (u3) is preferable.

In the formula, Q ¹ is a perfluoroalkylene group which may have an etheric oxygen atom, and Q ² is a single bond or a perfluoroalkylene group which may have an etheric oxygen atom. , R ^f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X ¹ is an oxygen atom, a nitrogen atom or a carbon atom, and when X ¹ is an oxygen atom, a is 0 Yes, when X ¹ is a nitrogen atom, a is 1, when X ¹ is a carbon atom, a is 2, Y ¹ is a fluorine atom or a monovalent perfluoro organic group, and r is 0 Or 1, and M is a hydrogen atom, an alkali metal or a quaternary ammonium base.

X ¹ is preferably an oxygen atom, and Y ¹ is preferably a fluorine atom.

  The structural unit represented by the formula (u3) is preferably a structural unit represented by the formula (u4) from the viewpoint of ease of synthesis, chemical stability, and easy increase in ion exchange capacity.

R ^F11 is a C 1-6 linear perfluoroalkylene group which may have a single bond or an etheric oxygen atom, and R ^F12 is a C 1-6 linear chain Wherein r is 0 or 1, and M is an alkali metal.

The fluorine-containing polymer (S) has a sulfonic acid-type functional group that can be converted into a sulfonic acid-type functional group of the fluorine-containing polymer having a group that can be converted into a sulfonic acid-type functional group described later in the step (ib) described later. It is preferably obtained by conversion to a group.
Examples of the fluorine-containing polymer (S) include a group having a group that can be converted into a sulfonic acid type functional group and a monomer having a fluorine atom (hereinafter also referred to as “fluorine-containing monomer (S ′)”) and a fluorine-containing olefin. Examples thereof include a fluorine-containing polymer obtained by hydrolyzing a polymer (hereinafter also referred to as “fluorinated polymer (S ′)”) to convert a group capable of being converted into a sulfonic acid type functional group into a sulfonic acid type functional group.

As the fluorine-containing monomer (S ′), if it is a compound having one or more fluorine atoms in the molecule, an ethylenic double bond, and a group that can be converted into a sulfonic acid type functional group, It does not specifically limit and a conventionally well-known thing can be used.
The fluorine-containing monomer (S ′) is a compound represented by the following formula (2) or the following formula (3) from the viewpoint of excellent production cost of the monomer, reactivity with other monomers, and properties of the resulting fluorine-containing polymer. ) Is preferred.

^{_{CF 2 = CF-O-R}} f2 -A 2 ··· formula (2)
_{^{CF 2 = CF-R f2 -A}} 2 ··· formula (3)

The symbols in formula (2) and formula (3) mean the following.
R ^f2 is a C 1-20 perfluoroalkyl group, may contain an etheric oxygen atom, and may be linear or branched.
A ² is a group that can be converted into a sulfonic acid type functional group. _{Specifically, -SO 2 F, -SO 2 Cl} , -SO 2 Br , and the like.

Specific examples of the compound represented by the formula (2) include the following compounds. W in a formula 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 the formula (3) include the following compounds. W in a 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 fluorine-containing monomer (S ′), the following compounds are preferable 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.
A fluorine-containing monomer (S ') may be used individually by 1 type, and may be used in combination of 2 or more type.

  By using a monomer having two or more sulfonic acid type functional groups, it is possible to increase the ion exchange group concentration per unit weight at the same monomer concentration, so that the layer (Sb) can be formed without reducing the polymer molecular weight. It becomes easy to increase the ion exchange capacity of the constituting polymer. As a result, while maintaining the quality of tetraammonium hydroxide, a membrane having a higher water permeability and a lower electrolysis voltage can be obtained.

Examples of the fluorinated olefin include those exemplified above, and TFE is preferable from the viewpoint of excellent production cost of the monomer, reactivity with other monomers, and characteristics of the obtained fluorinated polymer.
A fluorine-containing olefin may be used individually by 1 type, and may be used in combination of 2 or more type.

  In addition to the fluorine-containing monomer (S ′) and the fluorine-containing olefin, another monomer may be used for the production of the fluorine-containing polymer (S ′). Examples of the other monomer include those exemplified above. By copolymerizing other monomers, the flexibility and mechanical strength of the ion exchange membrane 1 can be increased. The proportion of other monomers is preferably 30 mol% or less of the total structural units (100 mol%) in the fluoropolymer (S ′) from the viewpoint of maintaining ion exchange performance.

  The ion exchange capacity of the fluoropolymer (S) can be adjusted by changing the content of the structural unit derived from the fluoromonomer (S ′) in the fluoropolymer (S ′). The content of the sulfonic acid type functional group in the fluoropolymer (S) is preferably the same as the content of the group that can be converted into the sulfonic acid type functional group in the fluoropolymer (S ′).

When the layer (Sa) 14A includes a plurality of layers, for example, when the layer (Sa) 14A includes two layers, the layer in contact with the layer (C) 12 is a layer (Sa-1) 14Aa (hereinafter referred to as “layer” as shown in FIG. (Also referred to as (Sa-1) ”), and the layer in contact with the layer (Sb) 14B is a layer (Sa-2) 14Ab (hereinafter also referred to as“ layer (Sa-2) ”). ) 14A is composed of two layers. In this case, the layer (Sa-1) 14Aa has an ion exchange capacity of the layer (Sa-1) lower than that of the layer (Sa-2) from the viewpoint of adhesiveness with the layer (C) 12. It is preferable. The ion exchange capacity of the layer (Sa-1) is preferably 0.9 to 1.25 meq / g dry resin, more preferably 0.9 to 1.15 meq / g dry resin.
The thickness of the layer (Sa-1) at the time of drying may be an appropriate thickness that contributes to adhesiveness, preferably 1 to 55 μm, and more preferably 1 to 40 μm.

(Reinforcing material)
The reinforcing material 20 is a material that reinforces the electrolyte membrane 10, and preferably includes a reinforcing cloth (preferably a woven cloth). In addition to the reinforcing cloth, fibrils and porous materials can be used as the reinforcing material.

  The reinforcing fabric is composed of warp and weft, and the warp and weft are preferably orthogonal. The reinforcing cloth is preferably composed of a reinforcing yarn and a sacrificial yarn.

The reinforcing yarn is a yarn made of a material that does not elute even when the reinforced precursor film is immersed in an alkaline aqueous solution. Even after the sacrificial yarn is immersed in an alkaline aqueous solution and the sacrificial yarn is eluted from the reinforcing fabric, it remains without dissolving as a yarn constituting the reinforcing material, maintaining the mechanical strength and dimensional stability of the ion exchange membrane. Contribute to.
The reinforcing cloth is preferably a reinforcing cloth containing at least one kind of reinforcing thread selected from the group consisting of a reinforcing thread made of polytetrafluoroethylene, a reinforcing thread made of polyphenylene sulfide, a reinforcing thread made of nylon, and a reinforcing thread made of polypropylene. .
That is, the reinforcing yarn 22 is preferably at least one reinforcing yarn selected from the group consisting of a reinforcing yarn made of polytetrafluoroethylene, a reinforcing yarn made of polyphenylene sulfide, a reinforcing yarn made of nylon, and a reinforcing yarn made of polypropylene.

The sacrificial yarn is a yarn from which at least a part thereof is eluted by immersing the reinforced precursor film in an alkaline aqueous solution. One sacrificial yarn may be a monofilament composed of one filament or a multifilament composed of two or more filaments.
As the sacrificial yarn 24, a PET yarn made of only PET, a PET / PBT yarn made of a mixture of PET and polybutylene terephthalate (hereinafter referred to as PBT), a PBT yarn made of only PBT, or a polytrimethylene terephthalate (hereinafter referred to as the “polytrimethylene terephthalate”). PTT yarn consisting only of PTT) is preferred, and PET yarn is more preferred.

The ion exchange membrane of the present invention is preferably produced through the following step (i). Thereafter, the ion exchange membrane of the present invention is placed in an electrolytic cell in the following step (ii).
Step (i): A step of immersing the reinforcing precursor film on which the reinforcing cloth is disposed in an alkaline aqueous solution to convert the fluorine-containing polymer having a group that can be converted into an ion-exchange group into a fluorine-containing polymer having an ion-exchange group.
Step (ii): A step of placing the ion exchange membrane obtained through the above step (i) in an electrolytic cell and performing a conditioning operation before the main operation of electrolysis of a tetraalkylammonium salt.

  In the case where the reinforcing fabric is composed of the reinforcing yarn and the sacrificial yarn, the reinforcing material 20 can be optionally combined with the reinforcing yarn 22 because at least a part of the sacrificial yarn of the reinforcing fabric in the reinforcing precursor film is eluted through the step (i). And the sacrificial yarn 24 included in. The reinforcing material 20 is composed of the reinforcing yarn 22 and the remaining undissolved sacrificial yarn 24 when part of the sacrificial yarn 24 is dissolved, and is composed of only the reinforcing yarn 22 when the entire sacrificial yarn 24 is dissolved.

  In the step (i), at least a part of the sacrificial yarn 24 is eluted, and as a result, an elution hole 28 is formed.

  In the ion exchange membrane 1, as shown in FIG. 1, a part of the sacrificial yarn 24 remains even after the step (i), and an elution hole 28 is formed around the remaining melted filament 26 of the sacrificial yarn 24. It is preferable. Thereby, when handling the ion exchange membrane 1 or installing the ion exchange membrane 1 in the electrolytic cell during the conditioning operation, the ion exchange membrane 1 is less likely to be damaged such as cracks.

(Inorganic particle layer)
The ion exchange membrane 1 further includes an inorganic particle layer (not shown) on both of its outermost surfaces. That is, the inorganic particle layer is provided so as to be exposed on both outermost surfaces of the ion exchange membrane 1. In other words, the ion exchange membrane 1 has an inorganic particle layer, a layer (S) 14, a layer (C) 12, and an inorganic particle layer in this order.
When the gas generated by electrolysis of the tetraalkylammonium salt adheres to the surface of the ion exchange membrane 1, the electrolysis voltage increases during electrolysis of the tetraalkylammonium salt. The inorganic particle layer is provided in order to suppress adhesion of a gas generated by electrolysis of the tetraalkylammonium salt to the surface of the ion exchange membrane 1 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 to an aqueous solution of a tetraalkylammonium salt 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 and ZrC are more preferable, and ZrO ₂ Is more preferable.

  The average particle diameter of the inorganic particles is preferably 0.5 to 1.5 μm, more preferably 0.7 to 1.3 μm. If the average particle diameter of the inorganic particles is not less than the above lower limit value, a high gas adhesion suppressing effect can be obtained. If the average particle diameter of the inorganic particles is less than or equal to the above upper limit value, the inorganic particles are excellent in the drop-off resistance.

  As the binder, those having excellent corrosion resistance to an aqueous solution of a tetraalkylammonium salt and having hydrophilicity are preferable, a fluorine-containing polymer having a carboxylic acid group or a sulfonic acid group is preferable, and a fluorine-containing polymer having a sulfonic acid group is more 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 mass ratio of the binder to the total mass of the inorganic particles and the binder in the inorganic particle layer (hereinafter referred to as the binder ratio) is preferably 0.15 to 0.3, more preferably 0.15 to 0.25, and 0.0. 16 to 0.20 is more preferable. If the binder ratio in the inorganic particle layer is not less than the above lower limit value, the drop-off resistance of the inorganic particles is excellent. When the binder ratio in the inorganic particle layer is not more than the above upper limit value, a high gas adhesion suppressing effect can be obtained.

(Production method)
The ion exchange membrane of the present invention is preferably produced through the above step (i), but the step (i) preferably comprises the following step (ia) and step (ib).

Step (ia): A step of obtaining a reinforced precursor film by disposing a reinforcing cloth composed of a reinforcing yarn and a sacrificial yarn on a fluorine-containing polymer having a group that can be converted into an ion exchange group.
Step (ib): Fluorine-containing polymer having a group that can be converted into an ion-exchange group by bringing the reinforced precursor film obtained in step (ia) into contact with an alkaline aqueous solution to form a fluorine-containing polymer having an ion-exchange group A step of converting to a polymer and eluting at least a part of the sacrificial yarn of the arranged reinforcing cloth to obtain an ion exchange membrane in which a reinforcing material containing a reinforcing yarn is arranged in a fluorine-containing polymer having an ion exchange group.

  In step (ib), 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 (ia)>
The reinforced precursor film is preferably manufactured by stacking and arranging reinforcing cloths when the precursor film is stacked and manufactured. The precursor film may be a film made of a single layer of a fluoropolymer having a group that can be converted into an ion exchange group, or may be a film made of a plurality of layers.
In the step (ia), first, a layer made of a fluorine-containing polymer having a group that can be converted into a carboxylic acid type functional group by a coextrusion method (hereinafter also referred to as “layer (C ′)”), and a sulfonic acid A laminated film having a layer made of a fluorine-containing polymer having a group that can be converted into a functional group (hereinafter also referred to as “layer (S′a)”) is obtained. Separately, a film (hereinafter referred to as “film (hereinafter referred to as“ layer (S′b) ”)) comprising a layer made of a fluorine-containing polymer having a group that can be converted into a sulfonic acid type functional group by a single-layer extrusion method”. S'b) ".
Next, the film (S′b), the reinforcing cloth, and the laminated film are arranged in this order, and these are laminated using a laminating roll or a vacuum laminating apparatus. At this time, the laminated film is disposed so that the layer (S′a) side is in contact with the reinforcing cloth. The reinforced precursor film thus obtained is laminated in the order of the layer (S′b), the reinforcing cloth, the layer (S′a), and the layer (C ′).

Note that the layer (C ′), the layer (S′a), and the layer (S′b) are converted into the layer (C), the layer (Sa), and the layer (Sb), respectively, in the step (ib) described later. Is done. Further, the thickness of the layer (C), the layer (Sa) and the layer (Sb) in the ion exchange membrane upon drying, and the layer (C ′), the layer (S′a) and the layer (S′b) in the reinforced precursor film are also shown. ) Is approximately in the relationship of the following formula (I).
Thickness of each layer in the reinforced precursor film ≒ Thickness of each layer at the time of drying in the ion exchange membrane x 0.9 (I)
Therefore, in order to obtain the desired thicknesses of the layers (C), (Sa) and (Sb) in the ion exchange membrane, the corresponding layers (C ′) and (S ′ What is necessary is just to let the thickness of a) and a layer (S'b) be the thickness calculated | required by the said Formula (I).

  When the layer (Sa) has two or more layers, a film made of a layer made of a fluorine-containing polymer having a group that can be converted into a sulfonic acid type functional group is obtained separately, and between the reinforcing cloth and the laminated film. You may laminate | stack so that a layer (Sa) may consist of a several layer.

<Process (ib)>
In the step (ib), a group that can be converted into an ion exchange group of the strengthened precursor film by bringing the strengthened precursor film obtained in the step (ia) into contact with an alkaline aqueous solution is converted into an ion exchange group. A predetermined ion exchange membrane is obtained by converting and eluting at least part of the sacrificial yarn of the reinforcing precursor membrane.
The conversion of the ion exchange group is preferably performed by a method using a mixture of a water-soluble organic compound and an alkali metal hydroxide as described in, for example, Japanese Patent Application Laid-Open No. 1-140987. Examples of the water-soluble organic compound include dimethyl sulfoxide and ethanol. Examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.
As shown in FIG. 1, the layer (C ′) is converted into the layer (C) 12, the layer (S′a) is converted into the layer (Sa) 14 A, and the layer (S′b) is converted into the layer (C) by conversion of the ion exchange groups. Sb) respectively converted to 14B.
When the layer (Sa) 14A is composed of a plurality of layers, for example, when the layer (Sa) 14A is composed of two layers, the layer (Sa-1) 14Aa and the layer (Sa-2) 14Ab are composed of layers (Sa) as shown in FIG. ) 14A and the layer (S) 14 together with the layer (Sb) 14B.

  The elution of the sacrificial yarn is preferably performed by hydrolyzing the material constituting the sacrificial yarn.

[Electrolysis equipment]
An electrolysis apparatus for producing tetraalkylammonium hydroxide by electrolysis of the tetraalkylammonium salt of the present invention (hereinafter also simply referred to as “electrolysis apparatus for tetraalkylammonium hydroxide”) has the ion exchange membrane of the present invention. A publicly known aspect can be adopted. FIG. 3 is a schematic view showing an example of an electrolysis apparatus for tetraalkylammonium hydroxide of the present invention.
The electrolytic apparatus 100 for tetraalkylammonium hydroxide of this embodiment includes an electrolytic cell 110 including a cathode 112 and an anode 114, a cathode chamber 116 on the cathode 112 side, and an anode chamber 118 on the anode 114 side in the electrolytic cell 110. And an ion exchange membrane 1 mounted in the electrolytic cell 110 so as to be separated.
The ion exchange membrane 1 is mounted in the electrolytic cell 110 such that the layer (C) 12 is on the cathode 112 side and the layer (S) 14 is on the anode 114 side.

  The cathode 112 may be disposed in contact with the ion exchange membrane 1 or may be disposed at a distance from the ion exchange membrane 1.

As a material constituting the cathode chamber 116, a material resistant to alkali hydroxide and hydrogen is preferable. Examples of the material include stainless steel and nickel.
The material constituting the anode chamber 118 is preferably a material resistant to alkali chloride and chlorine. Examples of the material include titanium.

As the base material for the cathode, stainless steel, nickel and the like are preferable from the viewpoints of resistance to tetraalkylammonium hydroxide and hydrogen, workability, and the like.
As the anode base material, titanium or the like is preferable from the viewpoint of resistance to tetraalkylammonium salt 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.

[Method for producing tetraalkylammonium hydroxide]
The method for producing tetraalkylammonium hydroxide of the present invention is carried out by electrolyzing a tetraalkylammonium salt with the electrolytic apparatus for tetraalkylammonium hydroxide having the ion exchange membrane of the present invention.
For example, when an aqueous solution of tetraalkylammonium hydrogen carbonate is electrolyzed to produce an aqueous solution of tetraalkylammonium hydroxide, an aqueous solution of tetraalkylammonium hydrogencarbonate (in addition, an aqueous solution of tetraalkylammonium hydrogencarbonate (note that In FIG. 3, an aqueous solution of tetramethylammonium hydrogen carbonate (TMA-HCO ₃ ) is supplied, and a solvent for dissolving tetraalkylammonium hydroxide (for example, highly purified water) is supplied to the cathode chamber 116. .
When a DC voltage is applied between the electrodes while circulating the solution supplied to the anode chamber and the cathode chamber, electrolysis of the tetraalkylammonium hydrogen carbonate proceeds in the anode chamber, and the tetraalkylammonium ions are exchanged through the ion exchange membrane. It moves to the chamber, becomes tetraalkylammonium hydroxide, and its concentration increases with circulation.

  In the above description, tetraalkylammonium hydrogen carbonate is described as a raw material. However, other tetraalkylammonium salts may be used, and examples thereof include tetraalkylammonium chloride and tetraalkylammonium hydrogensulfate.

  Moreover, although carbon number of the alkyl group in tetraalkylammonium salt is not specifically limited, A 1-10 alkyl group is mentioned, A 1-3 alkyl group is preferable. Specific examples include tetramethylammonium salt and tetraethylammonium salt.

Although the current density at the time of applying a DC voltage is not specifically limited, 1-50 kA / m < ² > is preferable. Moreover, although the temperature of an anode chamber and a cathode chamber is not specifically limited, 10-80 degreeC is preferable.
A method for supplying the solution to the anode chamber and the cathode chamber is not particularly limited, and examples thereof include a circulation method and a continuous method. Although the residence time of the solution in an anode chamber and a cathode chamber is not specifically limited, About 1 to 60 second is preferable.
The concentration of the tetraalkylammonium salt in the aqueous solution of the tetraalkylammonium salt supplied to the anode chamber is not particularly limited, but is preferably 2 to 70% by mass. In addition, alcohol may be contained in the aqueous solution as necessary.

  In addition, in FIG. 3, although the aspect in which an ion exchange membrane is arrange | positioned in the position which divides an anode chamber and a cathode chamber was described, it is not limited to this aspect, For example, as shown to Unexamined-Japanese-Patent No. 3-20489, 2 is shown. An embodiment using a single ion exchange membrane may be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.

(TQ value)
The TQ value is a value related to the molecular weight of the polymer, and was determined as a temperature indicating a volume flow rate: 100 mm ³ / sec. The capacity flow rate is a Shimadzu flow tester CFD-100D (manufactured by Shimadzu Corporation), and a fluorine-containing polymer having a precursor group of an ion exchange group is orificed at a constant temperature under a pressure of 3 MPa (diameter: 1 mm, length: 1 mm). ) From the melted and flowed out (unit: mm ³ / sec).

(Measurement of ion exchange capacity)
About 0.5 g of a fluorine-containing polymer having a group that can be converted into an ion exchange group was pressed into a film by a heated flat plate press to prepare a model sample. The obtained film model sample was analyzed by a transmission infrared spectroscopic analyzer. Using the height of each of the CF ₂ peak, CH ₃ peak, OH peak, CF peak, and SO ₂ F peak of the obtained spectrum, convert to a carboxylic acid type functional group or a sulfonic acid type functional group. A sample having a known ion exchange capacity as a ratio of a structural unit having a carboxylic acid type functional group or a sulfonic acid type functional group in a fluorine-containing polymer obtained after the hydrolysis treatment by calculating the proportion of the structural unit having a group that can be formed Was used as a calibration curve to determine the ion exchange capacity.

Example 1
Fluorine-containing polymer having a group that can be converted into a carboxylic acid type functional group by copolymerizing TFE and a fluorine-containing monomer having a group that can be converted into a carboxylic acid type functional group represented by the following formula (1-1) TQ: 225 ° C. (hereinafter referred to as polymer C1). A model sample was prepared using this polymer, and the ion exchange capacity was measured and found to be 1.08 meq / g dry resin.
_{CF 2 = CF-O-CF} 2 CF 2 -CF 2 -COOCH 3 ··· (1-1)

  Fluorine-containing polymer (TQ) having a group that can be converted into a sulfonic acid type functional group by copolymerizing TFE and a fluorine-containing monomer having a group that can be converted into a sulfonic acid type functional group represented by formula (2-1) : 225 ° C.) (hereinafter referred to as polymer S1). A model sample was prepared using this polymer, and the ion exchange capacity was measured and found to be 1.10 meq / g dry resin.

The polymer C1 and the polymer S1 are molded by a co-extrusion method, and a precursor layer (C′1) (thickness: 12 μm) made of the polymer C1 and a precursor layer (S′1) made of the polymer S1 (thickness: 68 μm) The film A having a two-layer structure was obtained.
Moreover, polymer S1 was shape | molded by the melt-extrusion method, and the film B (thickness: 30 micrometers) which consists of a precursor layer (S'2) was obtained.

  After rapidly stretching the PTFE film, a monofilament PTFE yarn obtained by slitting to a thickness of 100 denier and a PET yarn composed of 30 denier multifilaments obtained by aligning six 5 denier PET filaments, PTFE Plain weaving was performed in an alternating arrangement of two PET yarns on one yarn to obtain a reinforcing material (woven fabric, density of PTFE yarn: 27 yarns / inch, density of PET yarn: 53 yarns / inch).

Film B, reinforcing material, film A, PET film for release (thickness: 100 μm) in this order, and rolls so that the precursor layer (C′1) of film A is on the release PET film side Were laminated. The release PET film was peeled off to obtain a reinforced precursor film.
A paste composed 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 is used as a reinforcing precursor. It transferred by the roll press to the upper layer side of the precursor layer (S'2) of a body film, and formed the inorganic substance particle layer. The adhesion amount of zirconium oxide was 20 g / m ² .

The reinforced 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. Thus, -COOCH ₃ of polymers C1, and the -SO ₂ F of the polymer S1 is hydrolyzed, converted to ion exchange groups, the precursor layer (C'1) to the layer (C), the precursor layer A film having (S′1) and the precursor layer (S′2) as the layer (S) layer was obtained.

Next, a dispersion liquid in which zirconium oxide (average particle size: 1 μm) was dispersed at a concentration of 13% by mass in an ethanol solution containing 2.5% by mass of the acid type polymer of the polymer S1 was prepared. This dispersion was sprayed on the layer (C) side of the membrane to form an inorganic particle layer, and an ion exchange membrane having an inorganic particle layer formed on both sides was obtained. The amount of zirconium oxide deposited was 3 g / m ² .

  Table 1 summarizes the ion exchange capacities of the layers (C) and (S) and the dry thickness (thickness at the time of drying) in the obtained ion exchange membrane.

(Examples 2-4, Comparative Examples 1-2)
Except for adjusting the ion exchange capacity of the layers (C) and (S) in the ion exchange membrane, and the type of polymer used and the thickness of the precursor layer so that the dry thickness is within the range shown in Table 1. Obtained an ion exchange membrane in the same manner as in Example 1.

(Peeling evaluation)
Using the ion exchange membranes of Examples 1 to 4 and Comparative Examples 1 and 2, peeling evaluation was performed according to the following procedure.
First, an anode made of RuO ₂ —TiO ₂ deposited on expanded titanium, a cathode made of stainless steel (perforated plate), and immersed in a 10% tetramethylammonium hydroxide (TMAH) solution for 24 hours In this way, the electrolytic cell was equipped with an ion exchange membrane whose state was adjusted in advance, thereby obtaining an electrolysis apparatus (see FIG. 3).
Next, the anode chamber was filled with 200 g / l TMA-HCO ₃ aqueous solution, and the cathode chamber was filled with 100 g / l TMAH aqueous solution. The electrolyzer was heated with a heater and the cathode chamber was made inert by injecting argon.
When the temperature of the fluid in the electrolyzer reached 50 ° C., the power switch was turned on and the current was increased by 1 A every 3 minutes until it reached 15 A, ie 3 kA / m ² . In addition, the input of water to the electrolyzer was 100 g / h, and the input of TMA-HCO ₃ was 125 g / h (588 g / l solution).
Under these conditions, after carrying out the electrolysis operation for 14 days, the voltage value is confirmed. If it is less than 3.5V, ◎, if it is 3.5V or more and less than 4.0V, ○, 4.0V or more. If it was less than 4.5V, it was judged as Δ and 4.5V or more as x.
Further, the operation was stopped, the electrolysis apparatus was disassembled, and the state of peeling of the ion exchange membrane was visually observed. At the time of observation, one in which at least one peeling having a diameter of 5 mm or more was confirmed within the electrolytic surface was judged as “with peeling”, and one with no peeling of 5 mm or more being judged as “no peeling”.
The evaluation results are summarized in Table 1.

In Table 1, “layer (S) side” in the “inorganic particle layer” column is “present” when there is an inorganic particle layer on the layer (S), and “none” when there is no inorganic particle layer.
In the “inorganic particle layer” column, “layer (C) side” is “present” when there is an inorganic particle layer on the layer (C), and “none” when there is no inorganic particle layer.

As shown in Table 1, in Examples 1 to 4 in which the ion exchange capacity of the layer (C) is within a predetermined range, a desired effect was obtained.
In particular, comparison between Examples 1 to 3 and Example 4 confirmed that the voltage value was lower when the ion exchange capacity of the layer (C) was 1.05 meq / g dry resin or more.

1 ion exchange membrane 10 electrolyte membrane 12 layers (C)
14 layers (S)
14A layer (Sa)
14Aa layer (Sa-1)
14Ab layer (Sa-2)
14B layer (Sb)
20 Reinforcing Material 22 Reinforcing Yarn 24 Sacrificial Yarn 26 Filament 28 Elution Hole 100 Electrolyzer for Tetraalkylammonium Hydroxide 110 Electrolyzer 112 Cathode 114 Anode 116 Cathode Chamber 118 Anode Chamber

Claims (9)

An ion exchange membrane used in an electrolysis apparatus for producing tetraalkylammonium hydroxide by electrolysis of a tetraalkylammonium salt,
An inorganic particle layer;
A layer (S) containing a fluorine-containing polymer having a sulfonic acid type functional group;
A layer (C) containing a fluorine-containing polymer having a carboxylic acid type functional group;
An inorganic particle layer in this order,
An ion exchange membrane, wherein the ion exchange capacity of the layer (C) is 0.95 meq / g dry resin or more.   The ion exchange membrane according to claim 1, wherein a reinforcing material is further arranged in the layer (S). The layer (S) has an ion exchange capacity of 1.0 to 2.0 meq / g dry resin,
The ion exchange membrane according to claim 1 or 2, wherein the ion exchange capacity of the layer (C) is 0.95 to 2.05 meq / g dry resin. The thickness of the layer (S) when dried is 50 to 200 μm,
The ion exchange membrane of any one of Claims 1-3 whose thickness at the time of drying of the said layer (C) is 5-30 micrometers.   Reinforcing cloth in which the reinforcing material includes at least one type of reinforcing yarn selected from the group consisting of reinforcing yarn made of polytetrafluoroethylene, reinforcing yarn made of polyphenylene sulfide, reinforcing yarn made of nylon, and reinforcing yarn made of polypropylene. The ion exchange membrane according to any one of claims 1 to 4, comprising: The ion exchange membrane according to any one of claims 1 to 5, wherein the layer (S) includes a polymer having a structural unit represented by the following formula (u1).
_{- [CF 2 -CF (-O-} CF 2 CF (CF 3) -O- (CF 2) m -SO 3 M)] - ··· formula (u1)
m is an integer of 1 to 6, and M is an alkali metal. The ion exchange membrane according to any one of claims 1 to 6, wherein the layer (S) includes a polymer having a structural unit represented by the following formula (u2).
_{- [CF 2 -CF (-O- (} CF 2) m -SO 3 M)] - ··· formula (u2)
m is an integer of 1 to 6, and M is an alkali metal. The ion exchange membrane according to any one of claims 1 to 7, wherein the layer (S) includes a polymer having a structural unit represented by the following formula (u3).

Q ¹ is a perfluoroalkylene group which may have an etheric oxygen atom, Q ² is a perfluoroalkylene group which may have a single bond or an etheric oxygen atom, R ^f1 is a perfluoroalkyl group which may have an etheric oxygen atom, X ¹ is an oxygen atom, a nitrogen atom or a carbon atom, and when X ¹ is an oxygen atom, a is 0 When X ¹ is a nitrogen atom, a is 1, when X ¹ is a carbon atom, a is 2, Y ¹ is a fluorine atom or a monovalent perfluoro organic group, and r Is 0 or 1, and M is an alkali metal. The ion exchange membrane according to claim 8, wherein the structural unit represented by the formula (u3) is a structural unit represented by the formula (u4).

R ^F11 is a C 1-6 linear perfluoroalkylene group which may have a single bond or an etheric oxygen atom, and R ^F12 is a C 1-6 linear chain Wherein r is 0 or 1, and M is an alkali metal.