JPS582970B2 - Youion Koukan Makunoseizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for modifying a fluorine-based cation exchange membrane, and its purpose is to improve its electrochemical properties.

Today, ion exchange membranes are widely used industrially in various fields.

Concentrated salt production from seawater is a typical example of its use.

Further examples include desalination of brine and other techniques for separating ionic and nonionic substances.

In addition, in recent years, salt electrolysis using an ion exchange membrane has been considered as a new technology in the field of salt electrolysis, along with mercury salt electrolysis and diaphragm salt electrolysis.

The ion exchange membranes used for these are cation exchange membranes and anion exchange membranes, and ion exchange membranes with extremely excellent performance are currently being developed.

However, there are various properties required for ion exchange membranes, and these properties are contradictory.

Although an ion exchange membrane that has all of these properties is most desirable, such a membrane has not yet been realized.

Therefore, various ion exchange membranes having membrane properties depending on the purpose of use have been developed.

In general, hydrocarbon-based ion exchange membranes have extremely excellent electrochemical performance, but have limitations in heat resistance and oxidation resistance.

For this purpose, fluorine-based ion exchange membranes in which fluorine atoms are bonded have been proposed, but they have some drawbacks in their electrochemical properties.

That is, since it is not easy to increase the exchange capacity of fluorine-based ion exchange membranes, they generally have high electrical resistance and low transference numbers.

In addition, when synthesizing an ion exchange membrane from a monomer having an ion exchange group or a functional group that can be converted into an ion exchange group, or a monomer into which an ion exchange group can be introduced and a fluorine-based vinyl monomer, However, due to the lack of a suitable crosslinkable fluorine-based vinyl monomer, the mechanical strength of the ion exchange membrane obtained is poor, and the dimensional change of the ion exchange membrane is also significant, making it troublesome to handle. Even the ``natural'' nature is not something to be satisfied with.

In particular, when this type of membrane is used for ion exchange membrane salt electrolysis, the current efficiency of the obtained caustic soda is low, so various methods have been attempted to improve the current efficiency.

For example, one side of a perfluorovinyl ether-based sulfonic acid cation exchange membrane is converted to sulfonic acid amide using ammonia, and anionic or neutral There are some examples, such as a method in which a thin layer is present, and the applicant has separately proposed a fluorine-based cation exchange membrane having a sulfonyl group and a carboxyl group.

All of these methods are effective, but as a result of extensive research, the present inventors have found that after impregnating a fluorine-based polymer film having a specific functional group with a simple polymerizable monomer, The present invention has been proposed based on the discovery that the electrochemical properties of the fluorine-based cation exchange membrane can be significantly improved by polymerizing it and hydrolyzing it if necessary.

That is, the present invention provides a polymer film having a fluorine atom and a sulfonyl group represented by the formula -SO2X [X is a halogen atom (excluding a fluorine atom) or -NHR (R is hydrogen or an alkyl group]], This is a method for producing a cation exchange membrane, which is characterized by impregnating a compound having a polymerizable group, polymerizing it, and hydrolyzing it if necessary.

The fluorine-based cation exchange membrane modified according to the present invention can significantly improve the transfer number, particularly in the electrodialysis of concentrated electrolyte solutions, and further the current efficiency of alkali hydroxide production in the electrolysis of aqueous alkali metal salt solutions.

Although the reason why the current efficiency of the fluorine-based cation exchange membrane obtained by the present invention can be improved is not clear, the inventors of the present invention speculate as follows.

In other words, the effects may vary depending on the type of compound impregnated into the polymer membrane and polymerized, but styrene,
It is thought that when vinyltoluene or the like is impregnated and polymerized, hydrophobic bonds are formed inside the membrane, resulting in a decrease in the water content of the membrane and an increase in solid ion concentration.

Furthermore, when a crosslinkable vinyl monomer such as divinylbenzene is copolymerized with this, the swelling of the cation exchange membrane is suppressed by the three-dimensional structure at the same time as hydrophobic bonding, resulting in a similar decrease in water content and furthermore, fixed ion concentration. It is thought that this increases the number of ions and at the same time creates a dense structure, which inhibits the diffusion and electrophoretic permeation of anions, such as hydroxyl ions, which are extremely easy to permeate through cation exchange membranes.

When monomers with carboxylic acid groups such as acrylic acid and methacrylic acid are impregnated and polymerized, a special interaction between them and hydroxyl ions is expected, and at the same time an increase in ion exchange capacity occurs. .

In addition, when a functional group that can be positively charged, such as vinyl pyridine, is impregnated and polymerized, ionic bonds are formed between this functional group and the positive charge of the cation exchange group, forming a more dense network within the membrane. I think that the.

In any case, as a result of making the structure of the fluorine-based cation exchange membrane dense and increasing the concentration of fixed ions, the permeation of anions such as hydroxide ions, which are extremely easy to permeate through the cation exchange membrane, is extremely inhibited. It is assumed that this is because the

That is, the cation exchange membrane of the present invention produces a specific effect by newly forming a resin structure in the membrane, but it is also possible to have an ion exchange group, particularly a carboxyl group, in the newly formed resin. Therefore, a synergistic effect can be expected.

The present invention will be explained in detail below.

The polymer membrane provided in the present invention has fluorine atoms bonded uniformly within the membrane and has the formula -So2X (X is a halogen atom (excluding a fluorine atom) or -NHR (R is a hydrogen atom or an alkyl group) ] There is no particular restriction as long as it has a sulfonyl group represented by the following.

When X in the above formula -SO2X is a halogen atom, a halogen atom other than a fluorine atom, particularly a chlorine atom, is preferably used.

Further, when the above-mentioned X is one NHR and R is an alkyl group, a lower alkyl group is generally preferably used as shown in the examples described later.

The compound to be impregnated and polymerized in the above polymer membrane is an aliphatic or aromatic compound that has one or more groups having a polymerizable double bond (hereinafter also referred to as vinyl group). A monomer (hereinafter also simply referred to as vinyl monomer) is used.

For example, acrylic acid, methacrylic acid, α-phenylacrylic acid, α-monoethyl acrylic acid, α-halogenated acrylic acid, maleic acid, itaconic acid, α-monotolyl acrylic acid, α-butylacrylic acid, vinylbenzoic acids, Those in which a vinyl group and a carboxyl group are bonded to a naphthalene ring, etc., styrene, vinyltoluenes, methacrylic esters, acrylic esters, acrylonitriles, vinylpyridines, N-vinylpyrrolidones, vinylimidazoles, butadiene class, imprene class, chloroprene class,
Vinyl chloride, hinyl acetate, acrolein, methyl vinyl ketone, chloromethylstyrenes, monochlorostyrenes, polychlorostyrenes, α-fluorostyrene, α
ββ-trifluorostyrene/α-methylstyrene, vinylidene chloride, vinyl fluoride, vinylidene fluoride, chloromethylstyrenes, vinylsulfonic acid and arsenic salts, esters, styrenesulfonic acid and salts, esters, allylsulfonic acid and Salts, esters, vinylphosphonic acid and salts, esters, styrenephosphonic acid and salts, esters, styrenephosphinic acid and salts, esters, vinylphosphinic acid and salts, esters, vinylphenols and salts, esters , vinyl acetate, tetrafluoroethylene, trifluoroethylene; vinyl fluoride, hynylidene fluoride, hexafluoropropylene, trifluoroethylene chloride,
Perfluoro(alkyl vinyl ethers), ethyl vinylbenzenes, maleic esters, itaconic esters, vinyl bromide, and polyvinyl compounds such as 〇1・m-・P-divinylbenzene and mixtures thereof, divinylpyridines, Vinylbenzenes, divinylnaphthalenes, tri-vinylnaphthalenes, isoprene,
Chloroprene, butadiene, divinylchlorobenzenes, divinylethylbenzenes, pimethallyl, biallyl, divinyl ether, divinylacetylene, divinylsulfone, 2,3-diethylbutadiene, halobutadienes, and the like are used.

Furthermore, if necessary, a linear polymer may be dissolved in the above mixture. Examples of the linear polymer to be dissolved for this purpose include styrene-butadiene copolymer, polystyrene, polyacrylic acid esters, and chlorsulfone. polyethylene, polychloroprene, polybutadiene, polyethylene,
Polypropylene, polyvinyl halide, polyvinylidene halide, polytrifluoroethylene, polytetrafluoroethylene, halogenated polyethylenes, halogenated propylene, chlorosulfonated polypropylene, polyvinyl chloride, polyvinylidene chloride, etc. are used. .

The method of impregnating the above-mentioned fluorine-based polymer film with a polymerizable monomer can be carried out as appropriate, depending on the type of the monomer, at room temperature, under heating, or under normal pressure or pressure in a gas phase or liquid phase. do it.

For example, if the monomer is gaseous at room temperature, it may be pressurized or cooled to a liquid state, and the above-mentioned membrane material may be immersed in this liquid. Alternatively, the monomer may be saturated with vapor. The reaction or polymerization may be carried out by leaving the membrane in a gas at a high pressure and impregnating it as a gas, or the reaction or polymerization may be carried out while being impregnated in a gas at a saturated vapor pressure.

Further, when the monomer is in liquid form, the film-like material may be impregnated by immersion therein, or it may be impregnated in saturated steam.

When the monomer is a solid, it may be dissolved in a suitable solvent and the membrane-like material may be impregnated therewith.

In each of the above cases, the membrane may be swollen with a suitable solvent and then replaced with the monomers mentioned above in the gas or liquid phase.

Next, the monomer impregnated inside the membrane is polymerized and, if necessary, hydrolyzed to obtain the cation exchange membrane of the present invention.

As a polymerization method, a radical polymerization initiator may be impregnated into the monomer when the monomer is impregnated into the polymer membrane, and the polymerization may be carried out by heating.

Alternatively, after the polymer film is impregnated with a monomer, it may be polymerized using a cationic or anionic ionic polymerization catalyst.

Furthermore, polymerization may be performed using radiation, X-rays, ultraviolet rays, or the like.

The catalyst used for radical polymerization, cationic polymerization, and anionic polymerization in this case is not particularly limited, and examples of radical polymerization initiators include penzoyl peroxide, α・α-azoisobutyronitrile, lauryl peroxide, tert
-Butyl peracetate, tert-butyl perbenzoate, 2,5-dimethyl(2,5-dibenzoylperoxy)hexane, 2,5-dimethyl(2,5-dibenzoylperoxy)hexine-3, p -Nontanhydride penoxide, diisopropylbenzene hydroperoxide, αα′-di(tert-butylperoxy)diisopropylbenzene, cyclohexanone peroxide,
tert-butylperoxyisoglobyl carbonate, 2,5-dimethyl-3-hexyne, 2,5-dimethyl-3-hexyne, 2,5-diperoxyisoglopyr, t
ert-butyl peroxylaurate, di-tert-
Petit Roudiperoxyphthalate, l.1'-G (t
ert-butylperoxy)cyclohexane, ■・1'
-G (tert-butylperoxy)-3,3,5-
Trimethylcyclohexane, methyl ethyl peroxide, methyl isobutyl ketone peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, di-tert-amyl peroxide, tert
- Butylcumyl peroxide, dicumyl peroxide,
2,5'-dimethyl 2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl 2,5-di(te
rt-butylperoxy)hexyne-3, and those with a decomposition temperature of 135°C or higher and a half-life of 10 hours or longer include cumene hydroperoxide, 2,5-dimethyl 2,5-
Dihydroperoxyhexane, 2,5-dinotyl 2,5
-dihydroperoxyhexine-3 etc. <<50
As long as it has a half-life of 10 hours or more at a temperature of ℃ or higher, it can be used without any restrictions.

The method of the present invention will be explained in more detail below.

(1) One or more vinyl monomers that do not have a cation exchange group or a functional group that can be converted into a cation exchange group are added to a fluorine-containing polymer film at room temperature or under heating. An effective method is to impregnate the material and polymerize it at room temperature or by heating.

In this case, an acid, an acid group, a radical polymerization initiator, etc. may be impregnated into the membrane at the same time as a catalyst for polymerization. After impregnation, polymerization may be carried out using these catalysts.

Furthermore, it is more effective to coexist a monomer that can form a crosslinkable structure having two or more vinyl groups.

For example, a method in which a fluorine-containing polymer membrane is impregnated with a mixture of vinylpyridine, divinylbenzene, and penzoyl peroxide, and then heated and polymerized in an autoclave.

A method in which a fluorine-containing polymer membrane is impregnated with styrene, vinyltoluene, etc., and then immersed in an ionic polymerizable catalyst such as concentrated sulfuric acid for polymerization.

A method in which styrene, acenaphthylene, vinyl toluene, etc. are mixed with penzoyl peroxide, etc., impregnated into a film-like material having sulfonyl chloride groups, and this is heated and polymerized in an autoclave, at the same time reacting with the sulfonyl chloride groups.

Furthermore, if necessary, cationic groups are introduced into the obtained fluorine-containing polymer membrane.

(2) Although it does not have the various cation exchange functional groups mentioned in (1) or a functional group that can be easily converted into a cation exchange functional group, it is possible to introduce a cation exchange group. A method of impregnating and polymerizing one or more vinyl monomers having groups into a fluorine-containing polymer film.

For example, a fluorine-containing polymer film obtained by impregnating and polymerizing styrene-divinylbenzene may be sulfonated using an appropriate sulfonating reagent.

In this case, in addition to sulfonation, it is generally effective to introduce a functional group that can exchange cations, that is, a functional group that can have a negative charge in an aqueous solution.

Chemists can easily think of phosphoric acid groups, carboxylic acid groups, phosphorous acid groups, sulfuric ester groups, phosphite ester groups, phenolic hydroxyl groups, thiol groups, and metal chelate compounds that can have negative charges. One or more of these cation exchange functional groups can be introduced by any method available.

The cation exchange functional groups may be introduced so as to be distributed uniformly with respect to the cross section of the membrane-like material, or may be distributed non-uniformly.

That is. A large amount of cation-exchangeable functional groups may be introduced only in the surface layer, and less or no amount may be introduced in the interior, or conversely, it may be introduced more in the interior and less in the surface layer.

Alternatively, a large number of cation-exchangeable functional groups may be introduced on one side, and fewer cation-exchangeable functional groups may be introduced on the back side.

In this case, if the parent fluorine-containing polymer film does not have a cation exchange group introduced therein, it is necessary to introduce a cation exchange group therein as well.

(3) An effective method is to impregnate a fluorine-containing polymer membrane with one or more vinyl monomers having a cation-exchangeable functional group and polymerize at room temperature or under heating.

In this case, a monomer that does not have a cation-exchangeable functional group may coexist, and a monomer having one or more other polymerizable groups may also coexist to form a three-dimensional structure. Even better results can be obtained in some cases.

For example, the above-mentioned fluorine-containing polymer film is immersed in a mixture of methacrylic acid, styrene, divinylbenzene, and a radical polymerization initiator at room temperature or under heating, and then impregnated.
Then, a method of heating and polymerizing this in an autoclave,
Another example is to impregnate the membrane-like material with the above monomer mixture to which no radical polymerization initiator is added, and then to immerse it in an ionic polymerization catalyst for polymerization.

Of course, in this case as well, a cation exchange group may be introduced into the membrane material if necessary.

(4) After impregnating a fluorine-containing polymer membrane with one or more vinyl monomers having a functional group that can be easily exchanged with a cation exchange group at room temperature or under heating, and then polymerizing the same, There is a method of converting a group that can be converted into a cation exchange group into a cation exchange group.

Examples of groups that can be converted into cation exchange groups in this case include esters such as carboxylic acid esters, sulfonic acid esters, and phosphate esters, and groups that can be converted into cation exchange groups by normal gentle reactions such as nitrile groups. It is.

For example, acrylic acid mono-n-butyl ester is impregnated with a radical polymerization initiator such as penzoyl peroxide into the above-mentioned fluorine-containing polymer film, then heated to polymerize, and then refluxed with concentrated hydrochloric acid to form an ester bond. These include those that are hydrolyzed into carboxylic acid groups.

As exemplified in each of the above methods, it is generally desirable to impregnate a polymerizable monomer into a membrane and polymerize it, but depending on the type of monomer, there are some that do not easily polymerize or copolymerize. Under polymerization conditions, it often not only undergoes simple polymerization but also forms a stable chemical bond with the substrate of the polymer membrane.

For example, when a membrane material having an acid halogen group such as a sulfonyl halide is impregnated with styrene or the like and radically polymerized, a chemical bond is formed between the membrane substrate and the impregnated styrene.

Furthermore, when arylamine is impregnated into a sulfonyl halide type polymeric material and heated, a partial polymerization reaction occurs, but at the same time, the arylamine is bonded to the sulfonyl halide group of the polymeric material through an acid amide bond, and most of the polymerization occurs. The heavy bonds remain unreacted.

Although it is effective as it is, the state of the membrane can be further improved by polymerizing it in an ionic polymerization catalyst.

In addition, fluorine-containing vinyl monomers such as ethylene tetrafluoride, ethylene monochloride trifluoride, hexafluoropropylene, vinyl fluoride, vinylitene fluoride, α- One or more types of fluorostyrene, α/β/β-trifluorostyrene, perfluorovinyl ether, perfluorophtadiene, perfluorinated vinyl ether sulfonic acid and salts, esters, perfluorovinyl ether sulfonyl halide, etc., as they are, or after radical polymerization is initiated. When the polymer is impregnated in the coexistence of a polymeric agent and then heated in an autoclave, all or part of the monomer polymerizes depending on the type of monomer or heating conditions, and the remainder participates in the reaction on the membrane-like polymer substrate. It turns out.

Further, during polymerization, the terminal ends bond with the membrane-like polymer substrate to form a crosslinked structure in the membrane-like polymer.

In the cation exchange membrane obtained in this way or by hydrolysis as necessary, stronger hydrophobic bonds are formed inside the membrane due to the water-repellent action unique to fluorine-based polymers, and at the same time, the water content of the cation exchange membrane is reduced. As a result, the concentration of fixed ions in the membrane increases, and at the same time, if such binding occurs inside the membrane or at the surface layer, (1) If a layer with a high concentration of fixed ions exists with respect to the cross section of the membrane. , ■ If a cross-linked dense layer is formed due to the presence of a layer with rough or no ion exchange groups in the cross section of one membrane, ■ If one ■ and ■ are formed at the same time, one ■ one ■, one ■ If any one of the above four conditions is formed at the same time, the performance of the ion exchange membrane of the present invention is significantly improved.

Note that the step of polymerizing or reacting may be performed after impregnating the monomer, or may be performed while impregnating the monomer.

In addition, when the cation exchange membrane obtained by the present invention is used as a diaphragm for salt electrolysis, etc., a fluorine-containing polymer membrane is impregnated with a hydrocarbon polymer chain in advance, and then a gas phase or By chlorinating or fluorinating the membrane in the liquid phase, the resistance of the membrane to oxidizing agents can be significantly improved.

Note that the polymer impregnated and polymerized into the cation exchange membrane may exist completely uniformly within the membrane, intertwined with the parent polymer chains of the membrane, or may exist unevenly with respect to the cross section of the membrane. may exist in

That is, the impregnated polymerized layer may be present in large numbers near the surface and may become coarser as it goes inside the film-like object, or may become denser to coarser from one surface of the film-like object to the back surface of the film-like object. good.

It is also effective when there is a dense layer of impregnation polymerization on one side of the membrane-like material, and a coarse layer of impregnation polymerization or a layer that is not impregnated and polymerized on the other side. ,
Similarly, a dense layer of impregnation polymerization may exist inside or on both sides of the membrane-like object, and a coarse layer of impregnation polymerization or a layer without impregnation polymerization may exist on both sides or inside of the membrane-like object. .

Therefore, a multilayer film may be obtained by adhering one or more of each of a densely and uniformly impregnated film-like material, a coarsely impregnated-polymerized film-like material, or a non-impregnated and non-polymerized film-like material.

Cation exchange membranes obtained by impregnating and polymerizing vinyl monomers into such fluorine-based polymer membranes and hydrolyzing them as necessary can be used to improve transportability, especially in electrodialysis of concentrated electrolyte solutions, and even alkali metal salts. When chlorine, hydrogen, oxygen, and alkali hydroxide are obtained by electrolysis of an aqueous solution, the current efficiency for producing alkali hydroxide is significantly improved.

However, at the same time, it is unavoidable to some extent that the electrical resistance of the film increases.

Even if the electric power consumption rate is reduced by improving the current efficiency, if the electrical resistance of the membrane increases significantly, its industrial usefulness will be reduced.

Therefore, it is desirable that the increase in electrical resistance by the impregnation polymerization method of the present invention does not exceed 10 times that of the untreated film when measured in 0.5N-NaOH at 25°C. - The amount of monomer to be polymerized may be appropriately determined in consideration of the electrical resistance.

Now, the cation exchange membrane of the present invention can be used without any restrictions in systems using conventionally known ion exchange membranes, and can be used in conventionally known devices without any restrictions.

That is, dialysis or electrodialysis systems in which solutes are moved by a concentration gradient, and solutes are moved by a potential gradient, such as diffusion dialysis, electrodialysis, and membranes for electrode reactions.

In particular, it is suitable for electrodialyzing a solution containing an oxidizing agent or as a diaphragm for an electrode reaction in which an oxidizing agent is generated.

For example, it is particularly suitable for electrolysis of alkali metal salts.

In addition, the device using the ion exchange membrane of the present invention is a multi-chamber device with two or more chambers in diffusion dialysis and electrodialysis.
It can be used for both water tank type and tightening type.

The same applies to membranes used in electrode reactions, and when used in the electrolysis of alkali metal salts, a two-chamber electrolytic cell requires a neutral porous membrane between the cation exchange membrane and the anode, and a porous cation exchange membrane. It may also be used in three-chamber electrolysis using a membrane or an oxidation-resistant cation exchange membrane.

Furthermore, when a cation exchange membrane with relatively low oxidation resistance is disposed between the cation exchange membrane of the present invention and the anode,
An alkali metal salt or a solution of an alkali metal salt hydroxide may be passed through the intermediate chamber.

Although the cation exchange membrane of the present invention will be specifically explained in the following examples, the present invention is not restricted in any way by the following examples.

In addition, the electrolytic experiments in the examples were carried out using a two-chamber alkaline electrolytic cell or a three-chamber alkaline electrolytic cell.

That is, in the case of two-chamber electrolysis, the anode is coated with ruthenium oxide and titanium oxide, the cathode is a nickel mesh, the ion exchange membrane of the present invention is placed in the middle, and the anode chamber is coated with a saturated alkali metal. Salt water was supplied, and pure water was quantitatively added to the cathode chamber to obtain a constant concentration of alkali metal hydroxide.

The effective current carrying area is 0.5dm2, and the current density is 2OA.
/dm2, and the electrolysis temperature was 60°C to 70°C.

In the case of three-chamber electrolysis, water pressure was applied to the intermediate chamber using a water-permeable neutral diaphragm made of asbestos, salt water was supplied to the anode chamber, and pure water was supplied to the cathode chamber to obtain a constant concentration of NaOH.

The electrode effective membrane area, current density, and electrolysis temperature are the same as in the case of two-chamber electrolysis.

Further, electrodialysis was performed using a clamp type electrodialysis tank with an effective membrane area of 1 dm2.

The logarithm was used in lO pairs. The electrical resistance of the membrane was determined by A.D. for 1000 cycles in 0.5N NaOH at 25°C. Measured at C.

Example 1 A 0.2 mm film of vinylidene fluoride was swollen with tetralin and then immersed in chlorosulfonic acid at 70° C. for 4 hours to obtain a film-like polymer having chlorsulfone groups.

This was immersed in the reactants shown in Table 1 at room temperature for 16 hours to bond tetraethylenepentamine and the like to the surface layer of the membrane through acid amide bonds.

Next, apply this membrane to 2. 6 in caustic soda of ON-NaOH
The sulfonyl chloride inside the membrane was immersed at 0°C for 10 hours to change to sodium sulfonate, and the membrane was then soaked in 2N-HCI.
It was immersed in water to convert it into an acid form and dried in Kazama.

Next, this sulfonic acid type cation exchange membrane having acid amide bonds and some primary or secondary amines on the surface layer was prepared using monomers consisting of 20 parts of acrylic acid, 10 parts of divinylbenzene, and 0.5 parts of penzoyl peroxide. 4 in body mixed solution
After soaking for a time to impregnate the cation exchange membrane, both sides were covered with cellophane and heated at 80° C. in a nitrogen atmosphere for 16 hours to polymerize the impregnated monomers.

2. ON-NaOH and 2. After conditioning by alternately equilibrating with ON-HCI, saturated saline was electrolyzed by three-chamber electrolysis.

The results are shown in Table 1. Example 2 A chamber was formed by pairing the cation exchange membrane and neutral membrane (made of cellulose) manufactured in Example 1, and 10 pairs of these were arranged to form a concentration chamber and a dilution chamber.

A mixed solution of 0.5% caustic soda and sodium chlorate is poured into the dilution chamber, and electrodialysis is performed at a current density of IA/dm2 to concentrate the caustic soda and sodium chlorate, resulting in 6.5% caustic soda. and sodium chlorate mixture was obtained.

The current efficiency of concentration at this time was 40%.

However, when the membrane of Example 1, which had not been impregnated and polymerized, was used as a cation exchange membrane, it was 23%.

The perfluorinated vinyl ether sulfonic acid type cation exchange membrane shown in Example 3 was refluxed in thiol chloride in a conventional manner to convert the sulfonic acid groups into sulfonyl chloride.

Next, after drying this film-like material in nitrogen, a 0.01% benzene solution of peroxide cinnamic acid is sprayed onto the surface of the film to scatter the acetone, which partially penetrates into the inside of the film and removes the surface layer. Peroxide was present in the sample.

Next, this is left in an autoclave under the saturated vapor pressure of tetrafluoroethylene and heated to polymerize part of the tetrafluoroethylene in the surface layer of the membrane and simultaneously react with the sulfonyl chloride group to form a polymer in the surface layer. A polymerized layer of tetrafluoroethylene was formed.

Then, apply this film to 4. 60°C for 48 hours in ON-NaOH
Soaked in.

Using this membrane, saturated saline was electrolyzed at 2OA/dm2 by a two-chamber method to constantly obtain 20% NaOH, and the current efficiency was 89%.6. The amount of NaCl in ON-NaOH was 0.002N.

On the other hand, when saturated saline was electrolyzed under similar conditions using the same perfluorinated cation exchange membrane that had not been subjected to such treatment, the current efficiency was 63%. ON-Na
The amount of NaCl in OH was 0.008N.

The electrical resistance of the membrane without the treatment of the present invention was 3.2 Ω-cm 2 , while that of the membrane treated with the present invention was 5.3 Ω-cm 2 .

Example 4 The perfluorinated vinyl ether sulfonic acid type cation exchange membrane used in Example 3 was changed to have the sulfonic acid group in the sulfonyl chloride type in the same manner as in Example 3, and trichloroacetyl peroxide was added to trifluoroethylene chloride. The sample was immersed in the dissolved material at room temperature to be impregnated, and then polymerized in an autoclave at -15°C for 10 days.

The electrical resistance of this film was 10.3 Ω-cm 2 .

When saturated saline was electrolyzed at 30 A/dm2 using this membrane, 6. Obtained ON-NaOH and current efficiency 93
%Met.

This membrane was subjected to two-chamber electrolysis under the same conditions for three months, but there was no significant deterioration in performance.

Example 5 A perfluorinated polymer film having the following structure was immersed in a monomer mixture having the composition shown in Table 2 to impregnate it with the monomers, and then heated and polymerized at 90°C.

Next, this film-like material was heated at 50°C 6. The unreacted sulfonyl fluoride groups inside the membrane were immersed in ON-NaOH for 24 hours to convert them into sodium sulfonate, and the unreacted monomers were eluted and the saturated saline solution was electrolyzed in a two-chamber electrolytic cell. carried out.

The results are shown in Table 2.

Claims (1)

[Scope of Claims] 1. A polymer film having a fluorine atom and a sulfonyl group represented by the formula -SO2X [X is a halogen atom (excluding a fluorine atom) or -NHR (R is hydrogen or an alkyl group)] ,
Impregnated with a compound having a polymerizable group and then polymerized,
A method for producing a cation exchange membrane, which comprises hydrolyzing as necessary.