JPH08120100A - Fluorine-containing cation-exchange membrane - Google Patents

Abstract

PURPOSE: To prepare a fluorine-contg. cation-exchange membrane which has high resistance to practical conditions, e.g. can maintain a high current efficiency even when electrolysis conditions, such as concn. of caustic soda and electrolysis temp., are varied by laminating films of particular fluorine-contg. polymers. CONSTITUTION: This fluorine-contg. cation-exchange membrane comprises a laminate of a first film of a fluorine-contg. polymer having a sulfonic group and a second film which comprises a fluorine-contg. polymer, comprising repeating units of formulae I, II, and III (wherein R1 is a 1-5C perfluoroalkyl; M is H or an alkali metal; (formula II + formula III) to (formula I + formula II + formula III) molar ratio is 0.12 to 0.25; and formula II to formula III molar ratio is 0.02 to 0.05) and has a thickness smaller than the first film and in the range of from 5 to 50μm and a large specific electrical resistance. The content of the sulfonic group in the first film is pref. 0.7 to 1.5 milli-equivalents/ g-dry resin in terms of ion exchange capacity, and preferred examples of the polymer constituting the first film include a copolymer of CF2 =CF2 with CF2 = CFOCF2 CF(CF3 )OCF2 CF2 SO3 M.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorinated cation exchange membrane, and more particularly to a fluorinated cation exchange membrane suitable for electrolysis of an aqueous solution such as water, an acid or alkali aqueous solution, an alkali halide or an alkali carbonate aqueous solution.

[0002]

2. Description of the Related Art (A), (B) shown in Chemical Formula 2 below,
A cation exchange membrane for electrolysis using a terpolymer having a repeating unit (C) is described in JP-B-62-1652 and JP-A-2-88645. In Japanese Examined Patent Publication No. 62-1652, it is used as an ion exchange membrane for electrolysis for the production of low concentration (20-30% by weight) caustic soda. In Japanese Unexamined Patent Publication (Kokai) No. 2-88645, it is used to laminate with a film of a fluoropolymer having a sulfonic acid group to produce caustic soda in excess of 30% by weight.

[0003]

Embedded image

(R _f is a perfluoroalkyl group having 1 to 5 carbon atoms, M is hydrogen or an alkali metal, B + C / A + B +
C (molar ratio) is 0.12-0.25. )

In these publications, the advantages of the fluorinated cation exchange membrane using the terpolymer are that it can be easily laminated with a film containing a sulfonic acid group and that tetrafluoroethylene / CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) _1-3 COOCH ₃ Compared with a fluorinated cation exchange membrane made of a copolymer, the amount of NaCl contained in the caustic soda formed in the cathode chamber can be reduced. Is listed. However, when the fluorine-containing cation exchange membranes described in the examples of these publications are used, when the operating conditions of the electrolytic cell, for example, the caustic soda concentration in the cathode chamber, the current density, the change in electrolysis temperature, and the like change. However, the current efficiency is reduced, and there is a problem in practical durability.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention Electrolysis conditions such as a change in caustic soda concentration in the cathode chamber and a change in electrolysis temperature without impairing the excellent characteristics of the fluorinated cation exchange membrane comprising the above terpolymer of the present invention It is intended to provide a fluorinated cation exchange membrane having high practical resistance, which can maintain high current efficiency even with variations in temperature.

[0007]

The present invention has been made to solve the above-mentioned problems, and comprises a first film of a fluorine-containing polymer having a sulfone exchange group, and (A) of Chemical formula 3,
A second polymer composed of a fluoropolymer having a carboxylic acid group having a repeating unit of (B) and (C) as an exchange group, having a thickness of 5 to 50 μm smaller than that of the first film and having a large specific electric resistance. A fluorinated cation exchange membrane characterized by being laminated with a film.

[0008]

Embedded image

Here, R _f is a perfluoroalkyl group having 1 to 5 carbon atoms, M is hydrogen or an alkali metal, and B + C / A + B + C (molar ratio) is 0.12 to 0.2.
5, B / B + C (molar ratio) is 0.02-0.25.

The ion exchange membrane of the present invention has excellent performance in electrolysis, that is, high current efficiency and low electrolysis voltage, and at the same time, the first film of the copolymer having a sulfonic acid group and the carboxylic acid. It also has the excellent property that the second film having a base can be laminated by a simple method such as roll press lamination. This is because the second film constituting the cation exchange membrane according to the present invention is formed from a fluorine-containing polymer having a carboxylic acid group having repeating units (A), (B) and (C) as described above. Due to that. That is, first of all, first, it has been difficult with a fluorine-containing polymer of this type in the related art, for example, an ion exchange capacity of 1.1 to 50 meg / g or less.
An extremely thin film having a thickness of m can be easily manufactured by extrusion molding or the like, so that a high current efficiency and a low electrolysis voltage can be achieved.

As a second point, CF ₂ = CFO (CF ₂ ) _1-5 COOCH ₃ having a short pendant side chain is used as a monomer having a carboxylic acid group which constitutes the copolymer used for the second film.
Is used, a long side chain monomer such as CF ₂ = CF
OCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ COOCH _{3 Even if the} ion exchange capacity is set as high as 0.85 to 1.30 meq / g as compared with the copolymer having the constituent element, high current efficiency can be obtained.

A third point is that since the constituent elements of the copolymer used for the second film contain a specific amount of (B) units, the binary copolymer composed of only (A) and (C) units has crystallinity. It can be smaller than a polymer. Such a binary copolymer has a high crystallinity at a low ion exchange capacity where a high current efficiency is exhibited, so that the formability of the thin film is remarkably poor, and the adhesiveness with the first film is poor, so that it is difficult to dissolve during hydrolysis. It causes blistering or peeling.

With the second film according to the invention,
Lamination with the first film, for example by roll pressing,
A two-layer film can be easily formed. Further, since the layers can be laminated by roll pressing, it is possible to easily form a multi-layered structure having three or more layers or to reinforce with a cloth, and to manufacture an ion exchange membrane having higher performance.

In the present invention, the film of the fluoropolymer having a sulfonic acid group which constitutes the first film has a large ion exchange capacity and a small specific electric resistance as long as the mechanical strength is sufficient. preferable. The content of the sulfonic acid group is preferably such that the ion exchange capacity is 0.7.
~ 1.5 meq / g dry resin, particularly preferably 0.
8 to 1.2 meq / g dry resin.

The above-mentioned fluorine-containing polymer is preferably a perfluorocarbon polymer, and preferred examples thereof include CF ₂ = CF ₂ and CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F. And a copolymer of CF ₂ = CF ₂ and CF ₂ = CFO (CF ₂ ) _2-5 SO ₂ F. The composition ratio of the monomers forming this polymer is
The fluoropolymer is selected to have the above ion exchange capacity.

In the present invention, the fluoropolymer having a carboxylic acid group as an exchange group which forms the second film is
(A), (B), and (C) of the repeating unit. As an example, CF ₂ = CF ₂ and CF ₂ = CFOR _f (R _f is 1 carbon atom
~ 5 perfluoroalkyl group) and CF ₂ = CFO (CF ₂ ) ₃ COO
An example is a terpolymer with CH ₃ .

The repeating unit (A) in the fluoropolymer,
The composition ratio of (B) and (C) is important because it determines the properties of the film. That is, B + C / A + B + C (molar ratio) is related to the ease of film formation of the film and the adhesion to the first film, but the ratio is set to 0.12 to 0.25. When the ratio is small, the crystallinity is too large and the thin film formability is poor, and the temperature dependence of the viscosity of the molten polymer is too large, so that the improvement of the film forming property is small. On the contrary, when the ratio is large, the mechanical strength of the film is lowered. Further, from the viewpoint of adhesiveness to the first film, a ratio having suitable crystallinity is selected.

On the other hand, C / A + B + C (molar ratio) is related to the exchange capacity of the film. The ratio is selected as an appropriate ion exchange capacity in relation to the concentration of caustic alkali to be produced by electrolysis. However, it is preferably 0.80 to 1.
30 meq / g dry resin, more preferably 0.85
It is chosen to give ˜1.20 meq / g dry resin.

Further, the repeating unit (B) is a component necessary for improving the moldability, but the operating conditions such as the fluctuation of the caustic soda concentration in the cathode chamber, the salt water concentration in the anode chamber, the variation of the electrolysis temperature and the like. However, in order to maintain high current efficiency, it is preferable that the repeating unit (B) is not excessively increased. In order to satisfy the two required characteristics of easy moldability and high electrolytic performance, B / B + C (molar ratio) is 0.
It is selected in the range of 02 to 0.25, preferably 0.03 to 0.23. When B / B + C is smaller than this range, the effect of improving moldability is not remarkable. If B / B + C is larger than this range, the decrease in current efficiency becomes large due to the change in electrolysis temperature and the change in caustic soda concentration.

The fluoropolymers for the first and second films are produced by various methods. If necessary, these films can be reinforced with a cloth, a nonwoven fabric, a fibril, a porous body or a metal mesh, a porous body, or the like, which is preferably made of a fluoropolymer such as polytetrafluoroethylene.

In the present invention, the first and second fluoropolymer films have a thickness of preferably 130 to 130 in order to maximize the performance of the ion exchange membrane.
300 μm, the thickness of the second film is preferably 5
The thickness ratio of 50 μm, and the thickness of the first film / the second film is preferably 2.0 to 30, particularly 5 to 20. The lamination of the first film and the second film does not necessarily have to be performed within the above-mentioned thickness range, but the first layer made of a sulfonic acid polymer and the carboxylic acid polymer at the stage of completing the film formation as the electrolytic membrane. The second layer consisting of is formed into the above range. For example, for the convenience of the step of introducing a reinforcing material, a reinforcing cloth may be embedded in the sulfonic acid polymer side of the two-layer film, and then the sulfonic acid polymer may be further laminated thereon.

An adhesive layer is basically unnecessary between the first film and the second film, but a blend layer of a carboxylic acid polymer and a sulfonic acid polymer may be interposed. In this case, the thickness of the blend layer is the above-mentioned first or second
It is not included in the film thickness. When using a blend layer, the thickness is usually 1 to 50 μm, preferably 5 to 30 μm.
μm. The ion exchange capacities of the sulfonic acid polymer and the carboxylic acid polymer used in the blend layer are about 0.
7 to 1.3 meq / g dry resin. The weight ratio of sulfonic acid polymer to carboxylic acid polymer is usually 8 /
It is 2 to 1/9, preferably 7/3 to 2/8. If the second film is very thin, it is preferred that the reinforcing material described above be incorporated into the first film.

Appropriate means may be adopted for laminating the first film and the second film, but in any case, it is necessary to integrate the two film-like materials by such laminating.
Thus, such lamination is carried out, for example, preferably by pressing at a temperature of 100-350 ° C. and a pressure of 0.5-100 kg / cm ² . In the present invention, two or more kinds of one or both of the first film and the second film can be used in the present invention for lamination.

Further, the lamination of both films is preferably carried out in the form of an appropriate ion exchange group which does not cause the decomposition of the cation exchange group contained therein, for example, in the case of a carboxylic acid group, in an acid or ester type. Further, in the case of a sulfonic acid group, it is preferable to carry out by —SO ₂ F type. Also, the lamination is
The first film and the second film may not be prepared in advance, and may be coextrusion in which lamination is performed simultaneously with extrusion. The thickness of the cation exchange membrane laminated as the electrolytic membrane is
Preferably 80-500 μm, especially 100-300 μm
It is preferably m.

The cation exchange membrane obtained by laminating the first film and the second film of the present invention exhibits excellent performance as it is, but if necessary, one or both of the membrane surfaces can be used. A porous layer containing gas and liquid permeable particles having electrode activity (see US Pat. No. 4224121, etc.) or a porous layer containing gas and liquid permeable particles having no electrode activity (UK publication) Patent specification No. 2064586
No.) can be provided to further improve the property.

The fluorinated cation exchange membrane of the present invention can be used for electrolysis of various aqueous solutions such as an aqueous solution of alkali chloride as described above. For example, when used for electrolysis of an aqueous solution of alkali chloride, the cation exchange membrane of the present invention can be arranged so that the first film surface faces the anode side and the second film surface faces the cathode side. In this case, the cation exchange membrane of the present invention exerts its maximum performance.

As the process conditions for electrolyzing the aqueous alkali chloride solution using the ion exchange membrane of the present invention, known conditions as described in JP-A-54-112398 can be adopted. For example, in the anode chamber preferably 2.5-
A 5.0N (N) aqueous solution of alkali chloride is supplied, and water or diluted alkali hydroxide is supplied to the cathode chamber, and electrolysis is preferably performed at 80 ° C to 120 ° C and a current density of 10 to 100 A / dm ² . In such a case, heavy metal ions such as calcium and magnesium in the aqueous alkali chloride solution cause deterioration of the ion exchange membrane, and therefore it is preferable to make them as small as possible. Further, an acid such as hydrochloric acid can be added to the aqueous alkali chloride solution in order to minimize generation of oxygen at the anode.

In the present invention, the electrolytic cell may be a monopolar type or a bipolar type as long as it has the above constitution. Further, the material constituting the electrolytic cell is, for example, in the case of electrolysis of an aqueous solution of alkali chloride, in the case of the anode chamber, a material resistant to the aqueous solution of alkali chloride and chlorine, such as valve metal or titanium, and in the case of the cathode chamber. For example, iron, stainless steel, nickel, or the like that is resistant to alkali hydroxide and hydrogen is used.

When the electrodes are arranged in the present invention, the electrodes may be arranged in contact with the ion exchange membrane, or may be arranged at an appropriate interval. The above has mainly described the use of the membrane of the present invention for an example of the electrolysis of an alkali chloride aqueous solution,
Needless to say, the same can be applied to electrolysis of water, halogen acid (hydrochloric acid, hydrobromic acid), and alkali carbonate.

Next, the present invention will be described with reference to examples, but it goes without saying that the present invention is not limited to these examples.

[0031]

【Example】

Stainless steel pressure vessel of Example 1 Contents 20000 cm ^3, the ion-exchanged water 13700 g, the _{C 8 F 17 COONH 4 48g,} Na 2 HPO 4 · 12H 2
68 g of O, 40 g of NaH ₂ PO ₄ .2H ₂ O, 8.2 g of (NH ₄ ) ₂ S ₂ O ₈ ;
Charge 1.23 g of n-hexane, then 1760 g of CF ₂ = CF
O (CF ₂ ) ₃ COOCH ₃ and 292 g of CF ₂ = CFO (CF ₂ ) ₃ F were charged.
After sufficiently degassing, the polymerization temperature was raised to 57 ° C., and the pressure was raised to a predetermined pressure of 13.7 kg / cm ² with ethylene tetrafluoride to carry out the reaction. Polymerization was carried out while introducing tetrafluoroethylene, and the pressure was kept at a predetermined pressure. After 7 hours, the reaction was stopped, and the obtained latex was coagulated with concentrated sulfuric acid.
Then, wash the polymer thoroughly with water and
Ion exchange capacity after treatment at ℃ for 16 hours and further drying
3.0 kg of a terpolymer of 0.95 meq / g was obtained. ¹⁹ F-
When analyzed by NMR, CF ₂ = CFO (CF ₂ ) ₃ F and CF ₂ = CFO (CF
_The molar ratio of ₂ ) ₃ COOCH _{3 in} the polymer was 16:84. The terpolymer was extruded at 250 ° C to form a film,
A 35 μm thin film was obtained.

Next, in the same reaction vessel, 5.92 kg of 1,1,2-trichloro-1,2,2-trifluoroethane,
Charged with α, α'-azobisisobutyronitrile 12g,
Next, 11.27 kg of CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F was charged. After sufficiently degassing, the polymerization temperature was raised to 70 ° C., and the pressure was raised to a predetermined pressure of 12.3 kg / cm ^{2 with} tetrafluoroethylene to cause the reaction. Polymerization was carried out while introducing tetrafluoroethylene, and the pressure was kept at a predetermined pressure. The reaction was stopped after 9 hours, and the obtained polymer was thoroughly washed and dried to obtain a copolymer having an ion exchange capacity of 1.00 meq / g and 2.6
I got kg. The copolymer was extruded at 220 ° C to form a film having a thickness of 11
A 0 μm film was obtained.

Next, these two kinds of films are subjected to 225 ° C.
After laminating with a roll to form a two-layer film, hydrolysis is carried out in an aqueous solution of 30% by weight of dimethyl sulfoxide and 15% by weight of caustic potash, and then in a 2% aqueous solution of NaOH,
The membrane was immersed. Next, using this membrane, electrolysis was performed as follows.

Using a small tank having an effective film area of 0.25 dm ² , an anode RuO ₂ / Ti expanded metal, a cathode active nickel / Fe expanded metal, and a gap of 3 mm, 200 g / lNa
An electrolytic test was conducted at 85 ° C. and a current density of 40 A / dm ² while supplying Cl and water to the anode chamber and the cathode chamber. As a result, the current efficiency at the generated caustic concentration of 32% NaOH was 97.4%. Current efficiency when shifting to a caustic concentration of 35% is 97.3%
Met.

Comparative Example 1 13700 g of ion-exchanged water, 48 g of C ₈ F ₁₇ COONH ₄ and Na ₂ HPO ₄ · 12H ₂ were placed in a stainless steel pressure vessel having an internal capacity of 20000 cm ^3.
68 g of O ₂ , 40 g of NaH ₂ PO ₄ .2H ₂ O, 6.9 g of (NH ₄ ) ₂ S ₂ O ₈
1.1 g of n-hexane was charged, and then 2074 g of CF ₂ = CF
O (CF ₂ ) ₃ COOCH ₃ and 666 g of CF ₂ = CFO (CF ₂ ) ₃ F were charged.
After sufficiently degassing, the polymerization temperature was raised to 57 ° C. and the pressure was raised to a predetermined pressure of 12.7 kg / cm ² with ethylene tetrafluoride to cause the reaction. Polymerization was carried out while introducing tetrafluoroethylene, and the pressure was kept at a predetermined pressure. The reaction was stopped after 6 hours, and the obtained latex was coagulated with concentrated sulfuric acid,
Then, wash the polymer thoroughly with water and
Ion exchange capacity after treatment at ℃ for 16 hours and further drying
2.8 kg of a terpolymer of 0.95 meq / g was obtained. ¹⁹ F-
When analyzed by NMR, CF ₂ = CFO (CF ₂ ) ₃ F and CF ₂ = CFO (CF
_The molar ratio of ₂ ) ₃ COOCH _{3 in} the polymer was 27:73. The terpolymer was extruded at 220 ° C to form a film,
A 35 μm thin film was obtained.

Thereafter, a sulfonic acid polymer was laminated in the same manner as in Example 1, and after membrane treatment, an electrolytic test was conducted. The current efficiency at the generated caustic concentration of 32% NaOH was 97.3%, but the current efficiency decreased to 96.0% when the caustic concentration was shifted to 35%.

Example 2 The two kinds of films obtained in Example 1 were treated at 225 ° C.
Laminating lamination was performed using a roll press. Next, 29.0% by weight of zirconium oxide having an average particle size of 1 μm, 1.3% by weight of methylcellulose, 4.6% by weight of cyclohexanol,
A paste composed of 1.5% by weight of cyclohexanone and 63.6% by weight of water was transferred to the first layer side (copolymer layer having a sulfonic acid group) of the laminated film by roll pressing.

The amount of zirconium oxide deposited at this time is
It was 20 g / m ² . Next, this film was hydrolyzed in the same manner as in Example 1, and then 10 g / m ^{2 of} zirconium oxide particles was applied to the second layer side of the laminated film by a spray method.
I attached it.

To this film, an electrode in which a punched metal of Ti was coated with a solid solution of ruthenium oxide, iridium oxide and titanium oxide, and a cathode in which Raney nickel containing ruthenium was electrodeposited on a stainless steel punched metal were brought into contact with each other to form an anode chamber. Then, an electrolytic test was conducted at a current density of 40 A / dm ² and a temperature of 85 ° C. while supplying a 200 g / l sodium chloride aqueous solution to the cathode chamber while supplying water to the cathode chamber. As a result, the concentration of caustic soda produced is 32% and
The current efficiency at 35% was 97.3%.

Example 3 Ethylene tetrafluoride and CF ₂ = CFO (CF ₂ ) ₃ F, CF ₂ = CFO (CF ₂ ) ₃ COO
Ion exchange capacity 1.25 meq / g dry resin obtained by copolymerizing CH ₃ , CF ₂ = CFO (CF ₂ ) ₃ F and CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃
Was mixed with a carboxylic acid polymer having a ratio of 27:73 and a sulfonic acid polymer having an ion exchange capacity of 1.0 meq / g dry resin obtained in the same manner as in Example 1 at a weight ratio of 7: 3 and extruded at 220 ° C. 20 μm thick by filming
Was obtained. This film and the 35 μm-thick carboxylic acid polymer film used in Example 1 were laminated at 225 ° C. by a roll press. Further, the sulfonic acid polymer film of Example 1 was laminated on the blend polymer layer side of the laminated film at 220 ° C. by roll pressing. Hereinafter, the film treatment was performed in the same manner as in Example 2 and electrolytic evaluation was performed. Generated caustic concentration 32
The current efficiency in% NaOH was 97.4%. Caustic concentration 35
The current efficiency when shifting to% was 97.2%.

Example 4 13700 g of ion-exchanged water, 48 g of C ₈ F ₁₇ COONH ₄ and Na ₂ HPO ₄ · 12H ₂ were placed in a stainless steel pressure vessel having an internal capacity of 20000 cm ^3.
68 g of O, 40 g of NaH ₂ PO ₄ .2H ₂ O, 8.2 g of (NH ₄ ) ₂ S ₂ O ₈ ;
Charge 1.23 g of n-hexane, then 1760 g of CF ₂ = CF
O (CF ₂ ) ₃ COOCH ₃ and 81 g of CF ₂ = CFO (CF ₂ ) ₃ F were charged. After sufficiently degassing, the polymerization temperature was raised to 57 ° C., and the pressure was raised to a predetermined pressure of 13.7 kg / cm ² with ethylene tetrafluoride to carry out the reaction. Polymerization was carried out while introducing tetrafluoroethylene, and the pressure was kept at a predetermined pressure. After 7 hours, the reaction was stopped, and the obtained latex was coagulated with concentrated sulfuric acid.
Then, wash the polymer thoroughly with water and
Ion exchange capacity after treatment at ℃ for 16 hours and further drying
3.1 kg of a terpolymer of 0.99 meq / g was obtained. ¹⁹ F-
When analyzed by NMR, CF ₂ = CFO (CF ₂ ) ₃ F and CF ₂ = CFO (CF
_The molar ratio of ₂ ) ₃ COOCH _{3 in} the polymer was 4:96. The terpolymer was extruded at 250 ° C to form a film with a thickness of 35
A thin film of μm was obtained.

Thereafter, a sulfonic acid polymer was laminated in the same manner as in Example 2, and a membrane treatment and a coating treatment were conducted to carry out an electrolytic test. The current efficiency in the produced caustic concentration of 32% NaOH was 97.5%, and the current efficiency when shifting to the caustic concentration of 35% was 97.4%.

Example 5 CF ₂ = CF ₂ / CF ₂ = CFO (CF ₂ ) ₃ F / CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ Terpolymer (Ion exchange capacity 1.14 meq / g dry resin ,
CF ₂ = CFO (CF ₂ ) ₃ F / CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ = 20/80 (molar ratio)) 20 μm thick film and CF ₂ = CF ₂ / CF ₂ =
CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ SO ₂ F Binary copolymer (Ion exchange capacity 1.1 meq / g dry resin) 140 μm thick film was used at 220 ° C. using a roll press. Laminated.

Next, 29.0% by weight of zirconium oxide having an average particle size of 1 μm, 1.3% by weight of methylcellulose, 4.6% by weight of cyclohexanol, 1.5% by weight of cyclohexanone,
A paste composed of 63.6% by weight of water was transferred to the first layer side (the copolymer layer having a sulfonic acid group) of the laminated film by a roll press. The amount of zirconium oxide attached at this time was 20 g / m ² . Then, hydrolysis was carried out in an aqueous solution of 30% by weight of dimethyl sulfoxide and 11% by weight of caustic potash, and 10 g / m ^{2 of} zirconium oxide particles was deposited on the second layer side of the laminated film by a spray method.

To this film, an electrode in which Ti punched metal was coated with a solid solution of ruthenium oxide, iridium oxide, and titanium oxide, and a cathode in which stainless steel punched metal was electrodeposited with Raney nickel containing ruthenium were brought into contact with each other, and an anode chamber was prepared. A 200 g / l sodium chloride aqueous solution was subjected to an electrolytic test at a current density of 30 A / dm ² and a temperature of 85 ° C. while supplying water to the cathode chamber. As a result, the current efficiency at 35% NaOH was 97.0%. Then reduce the temperature to 75 ° C and use 35% NaOH.
Then, electrolysis was performed, and the current efficiency was 97.2%.

Comparative Example 2 CF ₂ = CF ₂ / CF ₂ = CFO (CF ₂ ) ₃ F / CF ₂ = on a carboxylic acid polymer
CFO (CF ₂ ) ₃ COOCH ₃ terpolymer (ion exchange capacity 1.01 meq / g dry resin, CF ₂ = CFO (CF ₂ ) ₃ F / CF ₂ = CFO (CF ₂ ) ₃ C
OOCH ₃ = 27/73 (molar ratio)) was used, and film formation, film treatment and electrolysis were carried out in the same manner as in Example 5. 35% NaOH, 85 ° C
Current efficiency was 96.8%, but 35% NaOH, 75 ℃
The current efficiency at was reduced to 94%.

Comparative Example 3 CF ₂ = CF ₂ / CF ₂ = CFO (CF ₂ ) ₃ F / CF ₂ = on a carboxylic acid polymer
CFO (CF ₂ ) ₃ COOCH ₃ terpolymer (ion exchange capacity 0.99 meq / g dry resin, CF ₂ = CFO (CF ₂ ) ₃ F / CF ₂ = CFO (CF ₂ ) ₃ C
OOCH ₃ = 38/62 (molar ratio)) was used, and film formation, film treatment and electrolysis were carried out in the same manner as in Example 5. 35% NaOH, 90 ° C
Current efficiency was 96.7%, but 35% NaOH, 80 ℃
The current efficiency in the device decreased to 93%.

[0048]

EFFECTS OF THE INVENTION A fluorinated cation exchange membrane which is easy to manufacture and has high practical resistance that can maintain a high current efficiency even when the electrolytic conditions change such as the concentration change of caustic soda and the change of electrolysis temperature is provided. .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C25B 13/08 302 302 // C08L 27:12 (72) Inventor Yoshihiko Saito Hazawa, Kanagawa-ku, Yokohama-shi, Kanagawa 1150, Machi Asahi Glass Co., Ltd. Central Research Institute (72) Inventor Yoshiaki Higuchi 1150, Hazawa-machi, Kanagawa-ku, Yokohama, Kanagawa Pref. Central Research Institute Co., Ltd.

Claims (2)

[Claims] 1. A first film of a fluorine-containing polymer having a sulfonic acid group and a fluorine-containing polymer having a carboxylic acid group having the following repeating units (A), (B) and (C) as an exchange group. Composed of a united body and having a thickness smaller than that of the first film
A fluorine-containing cation exchange membrane characterized by being laminated with a second film having a large specific electric resistance of 50 μm. Embedded image Here, R _f is a perfluoroalkyl group having 1 to 5 carbon atoms, M is hydrogen or an alkali metal, and B + C / A
+ B + C (molar ratio) is 0.12-0.25, B / B +
C (molar ratio) is 0.02-0.25. 2. The copolymer used in the first film is
CF ₂ = CF ₂ and CF ₂ = CFOCF ₂ CF (CF ₃ )
The membrane according to claim 1, which is made of a copolymer with OCF ₂ CF ₂ SO ₃ M (M is the same as above) and has an ion exchange capacity of 0.8 to 1.25 meq / g dry resin.