JPS5819750B2 - Electrolysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improved ion exchange membrane electrolysis methods and ion exchange membranes.

That is, by using the improved ion exchange membrane of the present invention, stable operation can be performed with high efficiency over a long period of time under high current density.

It goes without saying that there are tangible and intangible benefits that such long-term stable operation brings.

Another major feature of the present invention is that the core material inside the ion exchange membrane has a potential of the same sign as the charge possessed by the ion exchange group of the ion exchange membrane, and the potential applied to the core material is applied to the core material from the outside. By applying a potential lower than the potential exhibited by the core material from the outside of the ion-exchange membrane than would otherwise be applied, the ion-selective permeability can be further improved and the current efficiency can be further increased.

Conventionally, several methods have already been proposed for ion exchange membrane salt electrolysis.

For example, the two-chamber electrolysis method using a fluorine-based ion exchange membrane and the royal electrolysis method using a protective diaphragm in addition to the ion exchange membrane,
Various modifications have been proposed for each of the basic aspects.

However, their common drawback is low current efficiency, otherwise there are problems with membrane durability.

In some cases, the current efficiency may be low to begin with, but in other cases, even if the film exhibits good performance at the beginning of current application, deterioration may gradually be observed in terms of performance such as electrical resistance and current efficiency, and physical properties such as mechanical strength. Become.

There are various possible causes of such deterioration, but since the deterioration progresses markedly when the current density is increased, it is inferred that one major cause is probably heat generation within the membrane during energization.

That is, such heat generation, in conjunction with the current distribution, non-uniformity of the film composition, etc., causes a considerable local temperature rise inside the film, which causes the film to deteriorate.

The inventors of the present invention have taken into consideration the above points, and as a result of various studies,
A thermally conductive base material, that is, a thermally conductive material is used as the core material or backing of the ion exchange membrane, and a potential of the same sign as the charge possessed by the ion exchange groups of the ion exchange membrane is applied to the core material. By loading from the outside of the ion exchange membrane,
We have found that it is possible to solve the problem on paper.

The base material used for the core material in the present invention is not particularly limited as long as it is thermally conductive, but generally the base material has a thermal conductivity of 0.001 m/sec -(z -°C or more, preferably 0.005 (AI, /5ec-α・00 or more is preferably used.

Specifically, a metal or carbonaceous mesh material is particularly preferably used.

Hereinafter, a net-like material will be explained as a representative core material.

There are no particular limitations on the metal network as long as the constituent metals are not severely eroded under electrolytic conditions.

For example, Ti, Zr, Nb, Ta, Mo, W, Fe.
Co, Ni, Cu, Ag, Au, Ru, Rh, Pd
, Co, Ir.

Metals such as Pt, V, Cr, Mn, or alloys thereof can be suitably used.

Further, as the carbonaceous net-like material, in addition to woven fabrics and mats made of various carbon fibers, materials such as graphite film can also be used.

There are no particular restrictions on the shape of these nets, but extremely thick ones are not preferred because they not only make the battery case unnecessarily large but also increase the electrical resistance of the membrane itself.

Generally the thickness is 5mm or less, preferably 2zm or less and 9.0
A length of 51 m or more is preferably used.

Further, there is no restriction on the shape of the mesh, and in addition to various weaving methods, perforated plates, sponge-like materials, and non-woven fabrics may also be used without any inferiority.

That is, the net-like material referred to herein is a general term for perforated plates including perforated plates and sponge-like materials in addition to wires.

Furthermore, the size of the mesh (voids) is generally not limited as long as it does not prevent the passage of ions, but if the mesh has extremely large openings, the effect will be diminished, so it is
The diameter or angle of one basket or less, preferably the diameter or corner of one basket, is suitably used.

Furthermore, since the above-mentioned net-like material is used as a core material of an ion-exchange membrane, the surface of the net-like material may be appropriately processed by etching etc. in order to improve the affinity with the ion-exchange resin component. It works and it works.

Furthermore, what is interesting is that electrolysis can be carried out by applying a potential of the same sign as the charge possessed by the ion-exchange groups of the ion-exchange membrane to the core material of the ion-exchange membrane as described above from outside the ion-exchange membrane. It is obtained by

That is, in the case of a cation exchange membrane, since the ion exchange group generally has a negative charge, a negative potential of the same sign as the ion exchange group is applied to the core material of the cation exchange membrane from outside the cation exchange membrane. and perform electrolysis.

Generally, all thermally conductive base materials are electrically conductive at the same time, so by applying a potential to the core material, the entire core material is maintained at approximately the same potential.

By appropriately adjusting the magnitude of this potential, if a negative potential is applied to the core material of the cation exchange membrane, it will prevent the passage of anions and reduce the selective passage of the ion exchange membrane. It acts to further improve the

In addition, when carrying out electrolysis by applying a potential to the core material, it goes without saying that the potential must be kept to such an extent that the core material itself does not act as a cathode or an anode.

Furthermore, in the case of the core material of a cation exchange membrane, the potential is less noble, that is, lower than the potential that the core material would exhibit under normal electrolytic conditions, that is, if no potential was applied to the core material from the outside. Like, if you don't keep it, it won't be effective.

In other words, under normal electrolytic conditions, the potential gradually decreases as you move from the anode to the cathode, but the potential is lower than it would be just as you move from the anode to the cathode. In the case of the core material of an ion exchange membrane,
must be maintained.

In this way, the selectivity of the ion exchange membrane is further improved.

In this case, the specific value to maintain the potential within the above limits must be determined on a case-by-case basis in relation to the electrolytic conditions and the properties of the ion exchange membrane (including the core material, of course). No.

For example, in the case of the core material of a cation exchange membrane, depending on the magnitude of the overvoltage of the core material base material, a potential less noble than that of the negative electrode can be maintained depending on the case.

In addition, when attaching a polymer substance having ion exchange properties or which can be converted to ion exchange properties to a thermally conductive and electrically conductive base material used as a core material, the core material and the An insulating material may be interposed between the polymer materials.

For example, after coating the base material that will become the core material in advance with a substance that does not have electrical conductivity or ion conductivity, and then attaching a substance that has ion exchange properties or can easily impart ion exchange properties, the necessary An ion exchange group may be introduced by.

In such a case, the potential to be applied to the thermally conductive and electrically conductive core material is not particularly limited (G).

That is, a potential of several to several hundred square meters may be applied.

At this time, for example, the cation exchange membrane has a negative electrostatic potential, that is, the interface within the pores of the cation exchange membrane has a negative potential, allowing cations to permeate selectively and blocking anions from permeating. The ability to do so is promoted.

Incidentally, the potential applied to the core material of the ion exchange membrane in this manner may be applied continuously at a constant level, or may be applied intermittently.

Alternatively, it may be a pulsating wave obtained by rectifying alternating current.

At this time, the period of the pulsating flow is not particularly limited.

Alternatively, a sawtooth type potential commonly used in the electronics industry may be applied.

In addition, many of the core materials having thermal conductivity and electrical conductivity have excellent mechanical strength, so that they are comparable to others in terms of reinforcing function as a so-called core material.

Furthermore, by maintaining the shape of the core material appropriately, it is also possible to create membranes with complex shapes.

That is, the shape of the core material may be appropriately selected and the ion exchange resin may be coated on it.

For example, a mold that fits the required curved surface may be made, and a mixture of polyesters sandwiched between the core material may be poured into the mold for polymerization, or a thermoplastic resin may be heated and pressure molded together with the core material. An ion exchange membrane of a desired shape can be produced by various methods, such as by forming a flat plate and transforming it into an arbitrary shape after film formation.

The type of ion exchange resin membrane used in the present invention is not particularly limited and can be appropriately selected according to the situation.

Further, the method of manufacturing a membrane using a metal or carbonaceous mesh material as a core material is not limited in any way, and any method that can be thought of by a normal engineer may be adopted.

Some examples of methods for manufacturing cation exchange membranes using thermally conductive substrates as core materials are shown below.1) In the case of heterogeneous cation exchange membranes, polymerization or condensation A fine powder of a cation exchange resin or an inorganic ion exchanger may be uniformly mixed with a suitable thermoplastic polymer, a mesh material may be embedded therein, and the mixture may be heated and molded into a membrane.

Alternatively, the above-mentioned fine powder ion exchange resin can be uniformly dispersed in a viscous polymer solution in which a linear polymer is dissolved, and this can be coated on a network by coating, dipping, spraying, etc., and the solvent can be scattered to form a film. good.

Alternatively, a membrane may be formed by embedding a mesh in a mixture of an inorganic ion exchanger or the like and cement.

In this way, a network-containing ion exchange membrane can be manufactured by applying conventionally known techniques for manufacturing heterogeneous ion exchange membranes.

2) Similarly, for homogeneous cation exchange membranes, it is possible to fabricate ion exchange membranes containing mesh by applying various techniques conventionally proposed for producing homogeneous ion exchange membranes.

Here are some embodiments: (a) First, a monomer having a polymerizable functional group such as vinyl or allyl is used to directly coat the net by coating, dipping, spraying, etc., and then heat polymerize it. There are ways to do so.

In this case, if it is necessary to prevent the polymerization raw material solution from dripping,
Adjust the viscosity of the polymerization raw material depending on the shape of the net, or
It may be covered with a suitable film such as cellophane.

The liquid viscous coating solution used here uses one or more types of fluorine-containing vinyl and aryl monomers, and in order to increase the viscosity, it is appropriately coated with a soluble oxidation-resistant polymer finely dispersed oxidation-resistant polymer. A polymer may also be present.

This appropriately mixed viscous material is used to directly coat the net-like material by coating, dipping, spraying, etc., and this is heated and polymerized under pressure or normal pressure, and is also subjected to sulfonation, hydrolysis, etc. as necessary. Introduction of a cation exchange group and conversion into a cation exchange group may be carried out by known means.

As long as an insoluble polymer structure is formed, the polymerization may be carried out by radical or ionic polymerization, and radiation, X-rays, light energy, etc. may be used.

(b) Next, there is a method using a linear polymer electrolyte.

That is, a fluorine-containing anionic polymer electrolyte is dissolved in a suitable solvent, and the net is coated with the solution by means such as coating, dipping, or spraying, and then the solvent is scattered to remove the remaining film. Under the conditions in which the substance is used, if it is insoluble, it can be made as is, and if it is soluble, it can be made insolubilized by appropriate means such as radiation irradiation, X-ray irradiation, ultraviolet rays, etc.

In addition, not only the fluorine-containing polymer electrolyte but also other oxidation-resistant soluble polymers and dispersible polymers may be coexisting and coated in a solution state.

In this case, the polymer material becomes insoluble due to van der Waals forces, entanglement of polymer chains, etc., and can adhere well to the network material.

These are just a few examples, and linear polyelectrolytes or compounds that can be converted into linear polyelectrolytes by simple means such as hydrolysis, which can be used in water or with salts, acids, Another effective method is to heat a thermoplastic polymer electrolyte that is insoluble in a basic aqueous solution to coat the network, and to introduce ion exchange groups as necessary.

As this type of linear polymer, those represented by the following formula are particularly effective.

(However, m is a positive integer, l and n are O or a positive integer, and X represents a halogen or -0H group) (C) There is also a method using an inert polymer compound.

That is, thermoplastic polymers such as polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene chloride, polytetrafluoroethylene, etc. are adhered onto the net by thermoforming to form a thin film-like material. An ion exchange group is introduced into this by some method.

The method for attaching the polymer is not particularly limited, and for example, one or more of the above-mentioned polymer compounds may be dissolved or dispersed in an appropriate solvent,
A method of immersing the above-mentioned net-like material in this and scattering the solvent, a method of applying and spraying the solution/dispersion onto the above-mentioned net-like material and scattering the solvent, or a method of scattering the solvent in the form of fine powder of the above-mentioned polymer. Electrostatically charged, and on the other hand, the mesh is also charged with the opposite charge,
A method of electrostatically adhering a fine powder and heating it to fuse the fine powder of polymer to form a film, and a method of melting the above polymer at a high temperature that does not cause thermal decomposition. For example, a method in which a net-like material is immersed and attached, a method in which the above-mentioned polymer is molded using a net-like material as a core, etc. are effective.

The most suitable method may be selected depending on the type of polymer compound used, the physical properties of the polymer such as molecular weight, the material and shape of the network, and the intended use of the ion exchange membrane containing the network.

Ion exchange groups must be introduced into the attached polymer compound.

As a method for introducing ion exchange groups, if the attached polymer is a polymer that can be introduced with ion exchange groups, it can be directly treated with an ion exchange group introduction reagent that does not significantly corrode the mesh material. good.

In addition, polymerizable vinyl,
The aryl compound may be impregnated at room temperature or under heating, and at the same time, a radical polymerization initiator may be allowed to coexist, and the impregnated compound may be heated and polymerized under conditions such that the impregnated compound does not scatter, for example, under pressure.

In this case, a crosslinkable polyvinyl compound may be present to form a three-dimensional structure, or a linear structure may be formed.

Moreover, the polymerization means is not limited to radical polymerization, but may be cationic polymerization, anionic polymerization, or redox polymerization.

Furthermore, if the adhered polymer is impregnated with an excessively large amount of vinyl or aryl compound, resulting in significant dimensional changes and weak mechanical strength, add an appropriate solvent to the impregnated amount to dilute and impregnate. May be decreased.

If the amount of impregnation is small, the pre-adhered polymer may be swollen with a solvent and then immersed in the monomer.

Of course, the amount of impregnation can also be increased by heating.

In addition to the above-mentioned impregnation method, a vinyl or aryl monomer may be graft-polymerized onto a polymer attached by radiation or the like.

In this case, the pre-adhered polymer may be irradiated with radiation to form radicals and then immersed in the monomer or monomer mixture, or the polymer may be irradiated with radiation while being immersed. Furthermore, after being impregnated, radiation may be irradiated to polymerize.

Among these various methods, the most suitable one may be adopted depending on the purpose of use of the ion exchange membrane containing the mesh, the type of polymer attached, the shape of the mesh, the material, etc.

For example, a sheet of vinylidene fluoride is heat-fused onto a mesh material, immersed in acrylic acid or a mixture of acrylic acid and styrene, divinylbenzene, etc., and irradiated with radiation to cause graft polymerization. Alternatively, polyethylene is heated to fuse it onto the net-like material, and this is immersed in a heated mixed solution of methacrylic acid, divinylbenzene, and benzoyl peroxide to fully impregnate the attached polyethylene. Then, the structure of the present invention can be obtained by carrying out heating polymerization under high pressure in an autoclave, followed by fluorination treatment.

In addition, styrene sulfonic acid or its salts, styrene sulfonyl chloride esters, acrylic acid, etc. may be graft-polymerized to a fine powder of polyethylene or the like using radiation or the like, and this may be adhered to a net-like material and fused by heating. .

In this case, if necessary, an ion exchange group may be introduced by means such as hydrolysis.

Furthermore, in order to impart oxidation resistance, it may be appropriately fluorinated.

(d) There is also a mold polymerization method.

That is, a crosslinking agent such as divinylbenzene is added to acrylic acid, methacrylic acid, styrene sulfonate esters, vinyl sulfonate esters, etc., a radical polymerization initiator is further added, and other additives such as dilution are added as necessary. A solvent to be used as an agent, a linear polymer, a finely divided crosslinkable polymer, etc. are added and mixed uniformly, and the net is inserted as a core into a mold according to the shape of the net, and then the above monomer is added and mixed uniformly. This is a method of pouring a mixed solution and polymerizing it by heating.

In this case, if there is no oxidation resistance, fluorination treatment may be performed to impart oxidation resistance.

Above, some examples of making an ion exchange membrane using the thermally conductive and electrically conductive base material of the present invention as a core material, generally as a core material of a mesh material, have been described. is not limited in any way.

Basically, any material in which a thermally conductive or electrically conductive network material and a cation exchange membrane are integrated by some method may be used.

For example, Nafion (trade name of DuPont)
It is also possible to melt and integrate a thick film containing O2F or -80201 into a network and then hydrolyze it to form a cation exchanger such as -'5O3H.

In addition, when monomers are polymerized or copolymerized on a net-like material in the manufacturing process, cellophane, vinylon, fluorine-containing material is In some cases, it may be desirable to cover one or both of the net-like materials and polymerize them with a polymer or the like.

It is also possible to polymerize while rotating the electrodes in the autoclave so that the resin components do not shift.

Furthermore, the ion exchange membrane used in the present invention has a membrane-like structure made of a polymer having cation exchange groups, and contains a network inside the membrane.

In order to perform good electrolysis, the presence of minute cracks and pinholes is not allowed.

That is, it is preferable that the permeation of water under pressure be as low as that of a normal ion exchange resin membrane.

That is, the water permeability is 10-5CG/ffl・atm-3eC
The following is desirable.

When the above-mentioned ion exchange membrane is used for alkali metal salt electrolysis, it is necessary to add an anion exchange thin layer on one membrane surface as we proposed earlier in order to improve the current efficiency of the generated alkali hydroxide. It may be present or a thin neutral layer may be present.

In this case, it is particularly preferred if the thin layer is crosslinked and becomes dense.

In addition, the presence of this anion exchange or neutral thin layer is such that when the cation exchange resin part and the thin layer are physically or chemically attached or adsorbed, the polymer chain is formed at the interface between the cation exchange resin part and the thin layer. They may be attached through entanglement, or may exist through ionic bonds, covalent bonds, coordinate bonds, etc.

The thin layer may then be present in a layered manner on top of the cationic resin part, or may be present by a suitable chemical reaction towards the interior of the formed cationic exchange resin part.

In addition, the method of impregnating and polymerizing cation-exchanging, neutral, and anion-exchanging monomers that we proposed earlier is also effective.

In this case, fluorination may be performed afterwards.

The above treatment provides advantages such as improving the current efficiency of the cation exchange membrane itself and improving the purity of the alkali metal hydroxide produced. However, if the post-treatment material does not have oxidation resistance, it may be necessary to fluorinate it or Alternatively, it may be present on the cathode side where no oxidizing agent is present or inside the membrane.

Further, as the ion exchange group to be present bound to the cation exchange resin portion of the cation exchange membrane used in the present invention, any conventionally known functional group that can be negatively charged in an aqueous solution can be used without any restriction.

That is, a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphorous acid group, a sulfuric acid ester group, a phosphoric acid ester group, a phosphorous acid ester group, a phenolic hydroxyl group, a thiol group, a halonic acid group, a silicate group, Such as stannic acid.

It is sufficient that these ion exchange groups are present to the extent that it functions as an ion exchange membrane.

In addition, the anion exchange thin layer present in the surface layer has functional groups that can be negatively charged in an aqueous solution, such as primary, secondary, tertiary amines, quaternary ammonium, Onium bases such as secondary sulfonium, quaternary phosphonium, arsonium, stibonium, and cobaltidinium.

As a neutral thin layer, it is effective both when there is no functional group that can dissociate in an aqueous solution and when the above-mentioned anion exchange group and cation exchange group are present in approximately equal amounts. .

In addition, when a thin layer exists on the surface layer, a cation exchange resin component exists on top of this anion exchange thin layer and neutral thin layer, forming a sandwich of anion exchange and cation exchange resin components. Exchangeable thin layers may also be present.

The electrolysis of alkali metal salts in the present invention can be used to electrolyze halides, sulfates, nitrates, phosphates, etc. of lithium, sodium, potassium, rubidium, and cesium.

As the ion exchange resin portion of the ion exchange membrane used in the present invention, it is generally preferable to use a fluorine-based resin having oxidation resistance.

In the present invention, if the cation exchange resin part is made of a material that is resistant to oxidizing agents such as fluorine-based or inorganic substances, it may be used as it is by placing it between the anode and the cathode. If the cation exchange resin part is made of a material that does not have oxidation resistance,
Moreover, when oxidizing substances are generated from the anode during electrolysis, in order to prevent oxidative deterioration of the resin part due to this, the cation exchange membrane part is treated with acid resistance such as fluorination and chlorination, as described above. do it.

Hereinafter, some examples will be given, but the present invention is not limited to these examples in any way.

Example 1 200 parts of styrene, 200 parts of methacrylic acid, purity 55
20 parts of styrene-butadiene copolymer rubber was uniformly dissolved in the monomer mixture consisting of 100 parts of divinylbenzene and 200 parts of stearyl methacrylate, and carbon fibers having a length of about 01 cm and equivalent to 3 denier were added to the monomer mixture. After adding 15 parts of the chopped powder produced by the company, and stirring and dispersing the mixture uniformly using a homogenizer, 7 parts of lauryl methyl peroxide (trade name: Perbutyl L, manufactured by NOF Corporation) was dissolved therein.

Next, this was applied with 120 denier thread to a carbon fiber cloth with 35 threads both vertically and horizontally while degassing it evenly, and both sides of this were covered with cellophane.
The mixture was heated to 0°C and polymerized for 24 hours.

The obtained film-like material had carbon fiber chops uniformly dispersed between the meshes of the carbon fiber woven fabric, and had electrical conductivity.

Next, this was immersed in 6.0N NaOH at 50°C for 24 hours to change the carboxylic acid to sodium carboxylate, and the electrical resistance was measured in 6.0N NaOH at 70°C.3
．． It was 2Ω-saw.

Using this membrane, electrolysis of saturated saline water was carried out according to the royal method.

That is, a water-permeable porous diaphragm made of polytetrafluoroethylene is placed between the anode and the cation exchange membrane of the present invention to prevent oxidative deterioration of the diaphragm of the present invention due to the oxidizing agent generated from the anode, and to prevent the diaphragm from being removed from the catholyte. 6.0N NaOH was obtained.

That is, using an electrolytic cell (royal electrolytic cell) made of polyvinyl chloride with an effective current-carrying area of 0.5 parts m and consisting of an anode chamber, an intermediate chamber, and a cathode chamber, a saturated saline solution was poured into the anode chamber. Electrolysis was carried out by supplying

A water-permeable porous diaphragm made of polytetrafluoroethylene was placed between the anode chamber and the intermediate chamber to prevent oxidative deterioration of the diaphragm of the present invention due to the oxidizing agent generated from the anode.

A saturated saline solution was flowed into the intermediate chamber, and a cation exchange membrane (diaphragm) of the present invention was placed between the intermediate chamber and the cathode chamber.

6.0N NaOH was obtained from the cathode chamber.

When hydrochloric acid was added to the anode chamber to adjust the pH to 2, the pH of the intermediate chamber became 9.

In this case, the current density is 30A/di' and the electrolysis temperature is 70℃.
And so.

The anode used here was an insoluble anode made of a titanium lath material coated with titanium dioxide and ruthenium dioxide, and the cathode was a soft iron lath material.

Now, the temperature of the solution during electrolysis is 70℃ 30A/
When carried out at a current density of dm, the current efficiency is 6.0NNaO
H was obtained and the result was 92, but this conductive cation exchange membrane was supplied with -2,OV from another power source to the anode.
The cation exchange membrane was negatively charged by applying a potential of 30 A/ctm? When carried out, 6.0NNa
After obtaining OH, the current efficiency was 95.

Note that the amount of NaCJ' in NaOH is 50% NaOH
In terms of conversion, when electrolyzed under the same conditions as Example 1, 45p
pm, but when a potential of -2.OV was applied to the cation exchange membrane with respect to the anode, NaCIJ in NaOH
The amount was 30 ppm in terms of 50% NaOH.

Example 2 Tetrafluoroethylene and perfluoro(3,6=dioxa-4-methyl-7-octensulfonyl fluoride) CF2-CFOCF2-CF(CF3)OCF2-CF
It was made by melt-molding a polymer membrane using a 2SO2F copolymer.

Two of these membranes were used: one with a thickness of 1 mm and an exchange capacity of 0.91 milJ equivalent/g dry membrane, and the other with a thickness of 0.05 mm and an exchange capacity of 0.67 milJ equivalent/g dry membrane. Then, an iron wire mesh was sandwiched between them and heat fused to form a polymer membrane with the wire mesh as a core.

This was immersed in 6.0NKOH and hydrolyzed to obtain a cation exchange membrane having potassium sulfonate as an ion exchange group.

The electrical resistance of a cation exchange membrane with a wire mesh core is 0.5NN.
a 5.2 Ω-d, measured in Cl at 25°C.

This film-like material having the wire mesh as its core could be formed into any shape without being damaged or producing pinholes.

Next, using the obtained melted film, electrolysis of saturated saline solution was carried out under different conditions as follows.

(2) The same anode and cathode as in Example 1 are installed, and the fusing membrane of the present invention is placed between the anode chamber and the cathode chamber, and the pressure is applied to the cathode chamber at 6.0N.
NaOH was obtained constantly.

The effective current-carrying area of the electrolytic cell was 0.5 dm, the electrolysis temperature was 70° C., and saturated saline was supplied to the anode chamber.

Current efficiency was 74%.

The current density was 30 A/dm'.

Also, the amount of NaCl in NaOH is 48% NaOH
It was converted to 80 ppm.

2. The fused film of the present invention was placed in the same electrolytic cell as in 1 above, and electrolysis was performed by applying a potential of -2.2 V to the anode from another rectifier to the fused film.6. ONN a
Obtaining OH, the current efficiency was 85%, and Na in NaOH
The amount of Cl was 50 ppm in terms of 48% NaOH.

The electrolytic conditions were 70° C. and a current density of 30 A/dm, the anode was a titanium oxide and ruthenium oxide coated on a titanium mesh, and the cathode was an iron mesh.

Example 3 A film-like material was molded using a polymer obtained from a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether sulfonyl fluoride and resulting in a dry resin with an exchange capacity of 0.91 meq/g.

That is, a 100-mesh nickel wire mesh was immersed in a dimethylformamide dimethylformamide solution of polyvinylidene fluoride, pulled out, air-dried, and further heated in an air dryer at 180°C to dissolve the nickel. A thin film of polyvinylidene fluoride was formed on the wire mesh to insulate it.

Next, the above-mentioned copolymer of sulfonyl fluoride type was fused to this core material from both sides to form a fused film.

This was immersed in 6.0NKOH to be hydrolyzed and converted into potassium sulfonate.

Using this membrane, electrolysis of saturated saline was carried out using the two-chamber method.

That is, using saturated saline as the anolyte, 6.0
NNaOH was obtained.

The current efficiency at this time was 72%.

Next, the negative pole of a 200-inch DC power supply was connected to this fused film, and the positive pole of the DC power supply was connected to the cathode and electrolysis was carried out in the same manner, and the current efficiency was 86.

In addition, the current density during electrolysis was 30 A/dm, and the liquid temperature was 75
It was ℃.

Claims (1)

[Claims] 1 When electrolyzing an alkali metal salt using a cation exchange membrane as a diaphragm, a cation exchange membrane with a thermally conductive base material as a core material is used as the diaphragm, and the core material contains the ions. The ion exchange membrane is charged with a potential that is the same as the charge held by the ion exchange group of the exchange membrane, but lower than the potential that the core material would exhibit if no potential was applied to the core material from the outside. A method for electrolyzing an alkali metal salt, which is characterized in that the electrolysis is carried out by loading the salt from the outside.