JPH0633475B2 - Method for metathesis of neutral salt - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for metathesis of neutral salts. More specifically, in a three-chamber electrodialysis tank with a combination of specified ion-exchange membranes, it provides a simple method for decomposing neutral salts typified by sodium chloride to produce high-concentration acids and alkalis with high current efficiency. To do.

[Prior art and its problems]

Conventionally, there is a method of using an ion exchange membrane as a means for metathesis of a neutral salt such as sodium chloride to generate an alkali such as hydrochloric acid and sodium hydroxide. Such a method
A cation exchange membrane, a bipolar membrane (composite membrane), and an anion exchange membrane are repeatedly arranged in sequence between the cation and anion electrodes, and a salt chamber and a cation exchange are provided between the cation exchange membrane and the anion exchange membrane. Three-chamber electrodialysis tank comprising a base chamber between the membrane and the anion exchange membrane tank side of the bipolar membrane, and an acid chamber between the cation exchange membrane tank side of the bipolar membrane and the anion exchange membrane Is carried out in. That is, a neutral salt solution in the salt chamber of the three-chamber type ion-exchange membrane electrodialysis tank having the above-described structure, a dilute alkaline solution or water in the base chamber, and a dilute hydrochloric acid or water in the acid chamber are passed through a direct current between both electrodes. By applying a voltage, the neutral salt, for example, sodium ion (Na ⁺ ) and chloride ion (Cl ⁻ ) of sodium chloride permeate the cation exchange membrane and the anion exchange membrane, respectively, and the base chamber and the acid are passed. Sodium hydroxide (NaOH) and hydrochloric acid (HCl) are produced by the hydroxide ion (OH ⁻ ) and hydrogen ion (H ⁺ ) which are discharged into the chamber and at the same time water is dissociated in the bipolar membrane.

However, in such a conventional method of metathesis of neutral salts in a three-chamber type ion exchange membrane electrodialysis tank, neutralization by reverse diffusion of acid and alkali passing through a bipolar membrane or hydrogen ion of anion exchange membrane ( Due to the large H ⁺ ) permeability and the like, there was a problem that the concentration of generated acid and alkali and the current efficiency were low.

[Means for solving problems]

In view of the above problems, as a result of intensive studies, the present inventors have used a three-chamber type ion exchange membrane electrodialysis tank in which a specified cation exchange membrane, a bipolar membrane, and an anion exchange membrane are configured in combination, respectively. It has been found that high-concentration acid and alkali can be produced at a high current and a high rate by supplying an aqueous solution of a neutral salt to a salt chamber and performing electrodialysis treatment, and has led to the present invention. That is, according to the present invention, the exchange capacity of at least one surface is 10 ⁻⁶ to 10 ⁻² eq / cm 2.
^A monovalent cation selective permeable cation exchange membrane having an anion exchange layer in a ratio of ² , anion exchange membrane layer and a cation exchange membrane layer, and a fixed ion concentration of the cation exchange membrane layer is Bipolar film having 10 N or more, and carbon number 9 to
Anion exchange membranes having amino groups bonded with 30 long-chain alkyl groups are repeatedly arranged in sequence between the cation and anion electrodes to form a base between the cation exchange membrane and the anion exchange membrane layer side of the bipolar membrane. Chamber, using a three-chamber electrodialysis tank having an acid chamber between the cation exchange membrane layer side of the bipolar membrane and the anion exchange membrane and a salt chamber between the anion exchange membrane and the cation exchange membrane, Provided is a method for metathesis of neutral salt, which comprises supplying an aqueous solution of neutral salt to a salt chamber for electrodialysis.

The neutral salt used in the present invention is generally an alkali metal chloride such as sodium chloride or potassium chloride, or an aqueous solution of sodium sulfate, potassium nitrate, potassium sulfate, sodium nitrate, or a mixture thereof. The concentration can be selected from 0.1 wt% (Wt)% to saturation, but is generally 20 wt% or more.

In order to obtain a high-concentration acid and alkali with high current efficiency by electrodialyzing a neutral salt as described above in a three-chamber type electrodialysis tank in which the specified three kinds of ion exchange membranes are combined and constructed, A cation exchange membrane having an anion exchange layer on at least one surface as an ion exchange membrane, a cation exchange membrane layer and an anion exchange membrane layer, and a fixed ion concentration of the cation exchange membrane layer is 10 N or more. It is important to use bipolar membranes and anion exchange membranes with amino groups attached to long chain alkyl groups.

That is, the cation exchange membrane used in the present invention is a cation exchange membrane having an anion exchange layer on at least one surface thereof, and selectively cations such as sodium ions (Na ⁺ ) and potassium ions (K ⁺ ) are selected. It has a transparent function. Examples of such a selective cation exchange membrane include anion exchange groups such as primary amine groups, secondary amine groups, tertiary amine groups, and quaternary ammonium groups on the surface of a known cation exchange membrane substrate. At least one of the above is allowed to exist as an anion exchange layer at a rate of exchange capacity of 10 ⁻⁶ to 10 ⁻² eq / cm ² , preferably 10 ⁻³ to 10 ⁻² eq / cm ² by an acid amide bond or an ester bond. Although a cation exchange membrane is also used, a cation exchange membrane which is a substrate and has a high degree of crosslinking is preferably used. Specifically, a cation exchange membrane in which a vinyl compound having a quaternary ammonium salt group and a vinylbenzyl group or a polymer thereof is present as an anion exchange layer on the surface of a cation exchange membrane substrate is preferably used. To be
Incidentally, the quaternary ammonium bases in the present specification,
It is a generic term that includes not only quaternary ammonium bases but also so-called onium bases such as quaternary pyridinium bases, sulfonium bases and phosphonium bases. Further, the vinylbenzyl group in the above vinyl compound is
One, two, or three or more may be used. However, when there are too many vinylbenzyl groups in such a vinyl compound, intermolecular or intramolecular polymerization of the vinyl compound is likely to occur and it is difficult to handle the vinyl compound. -100 is preferable. Further, the number of quaternary ammonium bases possessed by the vinyl compound is effectively 1 or more, but if the number is too large, the effect of the present invention will not be exhibited, so generally 1-10.
00 pieces, especially 1 to 50 pieces are preferable. The method for producing such a vinyl compound having a quaternary ammonium salt group and a vinylbenzyl group is not particularly limited, but it is generally synthesized by, for example, the following method.

(1) Alkylate a primary amine such as methylamine or ethylamine with vinylbenzyl chloride.

(2) A divalent primary amine such as ethylenediamine or propylenediamine is reacted with vinylbenzyl chloride, and if necessary, converted to a quaternary ammonium base with an alkylating agent such as methyl iodide or dimethylsulfate.

(3) Trivalent or higher tertiary amino compounds, for example (R _{1 in the} above formula: CH ₃ , CH ₃ CH ₃ , an integer of n ≧ 1) Etc. is reacted with at least one or more vinylbenzyl chloride. Furthermore, if necessary, the unreacted tertiary amino group may be converted to a quaternary amino group with another alkylating agent.

(4) A compound having one or more halogen atoms in the same molecule, for example, Etc. are reacted with vinylphenylalkyl N, N-dialkylamine.

These reaction conditions may be carried out in the absence of solvent, or in water, alcohol, acetone, dimethylformamide, dimethylsulfoxide, benzene, chloroform, or a mixture thereof with stirring at any concentration, and the reaction temperature is generally 0-100. C., and the range of 5 to 80.degree. C. can be suitably adopted. Further, it is generally preferable that the reaction is carried out in the presence of a radical polymerization inhibitor such as hydroquinone.

The method for producing the vinyl compound polymer described above is not particularly limited, and a known method may be adopted, and for example, a known method such as radical polymerization or cationic polymerization may be used. That is, the predetermined vinyl compound is preferably used in a solvent-free manner, in water, in an aqueous solution of an inorganic salt, in an organic solvent such as methanol or ethanol, or in a mixed solvent, preferably 0.1 N to 4.0.
Polymerization may be carried out by adding a radical polymerization initiator or a cationic polymerization initiator in N, particularly preferably 0.2 N to 2.0 N of saline. Examples of the radical polymerization initiator include acetyl peroxide, benzoyl peroxide, lauroyl peroxide,
Peroxides such as potassium peroxodisulfate, ammonium peroxodisulfate, t-butyl hydroperoxide, hydrogen peroxide; azobisisobutyronitrile, azobis-
Azo compounds such as 2-amidinopropane and hydrochloride; further hydrogen peroxide-ammonia, ethylamine, Fe (I
I) salts, etc .; peroxodisulfate-sodium sulfite,
Sodium bisulfite, triethanolamine, Fe
Redox initiators such as (II) salts; sodium perchlorate-sodium sulfite; and the like are also suitably used. Also, ionizing radiation may be applied. Furthermore, as the initiator of the cationic polymerization, aluminum chloride, zinc chloride,
Metal halides such as stannic chloride, titanium chloride, boron trifluoride and antimony pentachloride; protic acids such as phosphoric acid, sulfuric acid, chlorosulfonic acid, perchloric acid; organometallic compounds such as triethylaluminum To be

Any polymerization conditions may be used for the vinyl compound described above, but generally, the polymerization may be carried out at a temperature not higher than the decomposition temperature of the vinyl compound or not higher than the boiling point of the solvent used. The polymerization time varies depending on the type of catalyst used, the polymerization temperature, etc. and cannot be unconditionally limited, but generally 5 minutes to 10 hours when a redox polymerization initiator is used, and when a radical polymerization initiator is used. It is preferable to select from a range of about 3 hours to 3 days.

In the cation exchange membrane of the present invention, the amount of the vinyl compound or polymer thereof as described above to be present on the surface of the cation exchange membrane substrate varies depending on the type of the cation exchange membrane substrate, charge, etc. Is 0.001 mg / cm ² or more and is preferably 1/2 or less, particularly 1/3 or less of the cation exchange membrane layer.

The cation exchange membrane, which is the substrate of the above-mentioned selective cation exchange membrane, is not particularly limited, but generally, other cation exchange groups or other monomers copolymerizable with a monomer having a functional group suitable for introducing a cation exchange group are used. It is obtained by polymerizing a monomer, a copolymerizable monomer forming a crosslink, a plasticizer, a polymerization catalyst and, if necessary, a fine powder thermoplastic polymer substance as a reinforcing material, a base material and the like by a known method. Examples of the cation exchange group include a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a sulfuric acid ester group, a phosphoric acid ester group, a thiol group,
Examples of the monomer having an active group capable of forming a chelate structure with a heavy metal and having a functional group suitable for introducing an ion exchange group include styrene, a styrenesulfonic acid derivative, a vinylsulfonic acid derivative, an acrylic acid ester, Examples of the copolymerizable monomer such as maleic anhydride include aromatic vinyl monomers such as chloromethylstyrene and vinyl monomers such as acrylonitrile. Examples of copolymerizable monomers (crosslinking agents) that form crosslinks include divinylbenzenes, trivinylcyclohexanes, ethylene glycol dimethacrylates, divinylnaphthalene, divinyltoluene, and propylene glycol diacrylates. further,
Examples of the plasticizer include dioctyl phthalate and diptyl phthalate, and examples of the polymerization catalyst include benzoyl peroxide, azoisobutyronitrile and dicumyl peroxide. It is effective in the present invention that the degree of crosslinking in the cation exchange membrane of the present invention is generally 10 to 50%, preferably 15 to 30%, with the addition ratio of the crosslinking agent as a scale.

The above-mentioned cation exchange membrane may be in a water-containing state or an anhydrous state, but is usually used in a water-containing state. Further, the cation exchange group of the cation exchange membrane may be of a hydrogen type or a salt type, and salts, acids, bases and other substances may be contained in the cation exchange membrane.

In the above-mentioned cation exchange membrane, the method of allowing the vinyl compound or the polymer of the vinyl compound to exist on at least one surface of the cation exchange membrane substrate is not particularly limited, and a known method can be adopted as it is. . The following methods are given as examples of typical methods that are generally adopted industrially. For example, one side or both sides of the cation exchange membrane may be coated or sprayed with the above-mentioned vinyl compound or a polymer of the vinyl compound as it is or in a solution or dispersion thereof in an appropriate solvent. Further, a method of immersing the cation exchange membrane in a solution containing a vinyl compound or a polymer of the vinyl compound, and removing excess vinyl compound or the polymer of the vinyl compound, if necessary, may be adopted. . Furthermore, after optionally incorporating a cation exchange membrane into the electrodialysis tank with a cation exchange membrane and an anion exchange membrane alternately, the vinyl compound or a polymer of the vinyl compound is energized or de-energized. It is also possible to employ a means for circulating a solution containing Furthermore, the means for causing the polymer of the vinyl compound to be present on at least one surface of the cation exchange membrane is such that after the vinyl compound is present on at least one surface of the cation exchange membrane, the vinyl compound is Means for polymerizing can be preferably adopted. As a means for such polymerization, generally, the vinyl compound can be polymerized by contacting a cation exchange membrane having a vinyl compound on at least one surface with a solution containing a polymerization initiator. Depending on the type of polymerization initiator used, a solution containing a vinyl compound and a polymerization initiator is allowed to exist on at least one surface of a cation exchange membrane at a low temperature, and the temperature is raised to increase the vinyl compound. Means for polymerizing the compound can also be adopted. Alternatively, the vinyl compound is present on both sides of the cation exchange membrane,
Then, a means in which only one side is brought into contact with the polymerization initiator is also used. In any case, the above-mentioned polymerization of the vinyl compound is preferably carried out in a nitrogen atmosphere.

Next, the bipolar membrane used in the present invention has the ability to dissociate water under an electric field and is a combined membrane having a cation exchange membrane layer on one side and an anion exchange membrane layer on the other side, and the cation The fixed ion concentration of the exchange membrane layer is preferably 10 N or higher, and particularly preferably 10 to 20 N. That is, in the case of a bipolar membrane in which the fixed ion concentration of the cation exchange membrane layer is less than 10N, the hydrolysis efficiency is low, and the reverse diffusion of hydrogen ion (H ⁺ ) and hydroxyl group (OH ⁻ ) ion is large. . Further, the upper limit of the fixed ion concentration is not particularly limited, but generally, when it is about 20 N and becomes larger than that, the film resistance increases, and in both cases, the current efficiency decreases. The bipolar film is mainly composed of an aromatic compound monomer having a halogen-substituted alkyl group and a polymerizable vinyl group, a nitrile compound monomer having a vinyl group, and a copolymerizing monomer forming a crosslink, particularly a polyvalent vinyl compound monomer. After polymerizing the monomer mixture to form a polymer film, one side of the polymer film is cross-linked and a cation exchange group is introduced, and an anion exchange group is introduced on the other side. The bipolar film obtained by this is preferably used. Examples of the aromatic monomer having a vinyl group capable of polymerizing with a halogen-substituted alkyl group used in the above bipolar film include chloromethylstyrene,
Examples include chloromethylvinylnaphthalene, bromomethylstyrene, bromomethylvinylnaphthalene, and the like. Such an aromatic compound monomer having a halogen-substituted alkyl group and a polymerizable vinyl group is generally used in an amount of 60% by weight of all monomers in order to make the cation exchange membrane layer of the obtained bipolar membrane dense and to increase the fixed ion concentration. wt)% or more, especially 6
0 to 95 wt% is preferable. That is, when the proportion of the aromatic compound monomer is less than 60 wt%, a dense cation exchange membrane layer cannot be obtained even if a cation exchange group is introduced together with the crosslinking treatment after forming the polymer membrane. for,
A bipolar film having a high fixed ion concentration of 10 N or more was not obtained, and the ratio of the aromatic compound monomer was 95 wt%.
If the amount is larger than the above range, the electric resistance of the obtained bipolar film becomes high, which is not preferable. The above-mentioned vinyl group-containing nitrile compound is, for example, a low molecular weight monomer such as acrylonitrile or methacrylonitrile, and the monomer accelerates the introduction rate of a cation exchange group described later and has an electric resistance of the obtained bipolar membrane. To lower the total monomer weight, generally 5-20%, especially 10%.
-15% is preferable, and if it is more than 20%, the fixed ion concentration in the cation exchange membrane layer decreases. Further, the cross-linking agent is not particularly limited to the cross-linking copolymerizable monomer used in the method for producing the cation exchange membrane described above, but in particular divinylbens, trivinylcyclohexanes, divinylnaphthalene, divinyltoluenes, propylene glycol. Polyvalent vinyl compound monomers such as dimethacrylates such as equol are suitable, and it is generally preferable to use them in a proportion of 1 to 10 wt% with respect to the total monomers. It is also possible to use a monomer mixture in which vinyl monomers having a functional group suitable for introducing a cation exchange group as described above are used together with each of the above-mentioned monomers, if necessary.

The method for forming a polymer film-like material using the above-mentioned monomer mixture may be carried out according to a known method for producing an ion exchange membrane. For example, there is a method of polymerizing and molding the above-mentioned monomer mixture into a film or a method of impregnating and polymerizing the monomer mixture into a linear polymer compound such as cloth and film. At this time, the same polymerization catalyst as that used in the production of the cation exchange membrane, a plasticizer, or a fine powdered thermoplastic polymer substance as a reinforcing material, if necessary, and, for example, glass fiber, vinylon, canecarone, teviron, A known cloth-like or net-like base material such as Saran, Bonnell (above, trade name), polyethylene, polypropylene, etc. is appropriately used. Next, one surface of the polymer film obtained above is subjected to a crosslinking treatment to introduce a cation exchange group, thereby forming a predetermined cation exchange membrane layer. A method of forming such a cation exchange layer on one side of a polymer film material is generally a method in which a film of polypropylene, polyvinyl fluoride, polytetrafluoroethylene or the like is attached to one surface of the polymer film material, or It is achieved by exposing one side only by a method such as sandwiching a polymer film-like substance between two frames, and then performing a crosslinking treatment via a haloalkyl group and introducing a cation exchange group on the one side. . Such a crosslinking treatment with a haloalkyl group can be carried out using a generally known Friedel-Crafts catalyst such as sulfuric acid, aluminum chloride, tin tetrachloride or titanium tetrachloride. When a sulfone group is introduced as a cation exchange group, cross-linking can be achieved at the same time by using concentrated sulfuric acid, chlorosulfonic acid or a mixture thereof. In addition to the sulfone group, a carboxyl group, a phosphon group, or the like is introduced as the cation exchange group by a known method. The degree of crosslinking in the cation exchange membrane layer thus obtained is
Generally, it is appropriately adjusted by controlling the diffusion rate of concentrated sulfuric acid, chlorosulfonic acid, etc. in the membrane. If the degree of this cross-linking becomes small, the fixed ion concentration of the obtained cation-exchange membrane layer will be high, and a dense cation-exchange membrane layer will not be obtained. Conversely, if the degree of cross-linking will become large, the membrane resistance will increase. Is also not preferable. The thickness of such a cation exchange membrane layer is 1 to 50% of the thickness of the bipolar membrane,
It is preferably 5 to 30%, and if it exceeds this range, the film resistance increases.

Further, an anion exchange group is introduced to the other surface of the above-mentioned polymer film-like material (the surface of the polymer film-like material to which the film is adhered, the film is removed) to form an anion-exchange membrane layer. To obtain a bipolar film. As for the type and introduction method of such anion exchange group, known methods can be used without particular limitation. For example, a compound containing at least one kind of primary amine, secondary amine and tertiary amine, especially a strongly basic compound, can be used. Immersion of the polymer membrane having a cation exchange membrane layer on one side in a bath prepared by dissolving a compound containing a tertiary amine suitable as an anion exchange group in water, alcohol, acetone or the like. It is a method to do. At this time, the amine compound used is, for example, trimethylamine,
Examples include triethylamine and triethanolamine. After that, a target bipolar film is obtained by generally performing a conditioning treatment in dilute hydrochloric acid, water, or dilute sodium chloride solution. The fixed ion concentration in the anion exchange membrane layer of the obtained bipolar membrane is
Generally, it is 5 to 20N.

The anion exchange membrane used in the present invention needs to have an amino group to which a long-chain alkyl group is bonded. In order to obtain such an anion exchange membrane, it is preferable that the long-chain alkyl group generally has 9 to 30 carbon atoms, particularly 11 to 18 carbon atoms as the vinyl monomer having an amino group to which a long-chain alkyl group is bonded. That is, when the carbon number of the long-chain alkyl group is smaller than 9, the fixed ion concentration of the obtained anion exchange membrane tends to decrease, and the carbon number of 3 is 3.
When it is larger than 0, the electric resistance of the obtained anion exchange membrane tends to increase. The long-chain alkyl group is preferably a straight-chain alkyl group because it improves the fixed ion concentration, but it may be branched. The long-chain alkyl group of the vinyl monomer has at least one of the above amino groups.
Need to be connected. That is, as a conventional method of increasing the fixed ion concentration of the anion exchange membrane, there is a method of reacting an amino group of the anion exchange membrane with a long chain alkyl halide to bond the long chain alkyl group, but in this method, only the surface layer portion is formed. There is a problem in that the long-chain alkyl group is bonded to and the fixed ion concentration cannot be increased to the inside of the anion exchange membrane. On the other hand, in the above method, by using a monomer having an amino group to which a long-chain alkyl group has already been bonded as a monomer constituting the anion exchange membrane, high immobilization can be achieved without causing the above problems. Thus, an anion exchange membrane having an ion concentration and an ion exchange capacity can be obtained. The number of long-chain alkyl groups bonded to the amino group of the vinyl monomer used above is 1 or 3
Two cases are preferable to two cases because they are particularly excellent in the effect of improving the fixed ion concentration of the obtained anion exchange membrane.

The vinyl monomer having an amino group having a long-chain alkyl group bonded thereto is not particularly limited as long as it has an amino group having at least one long-chain alkyl group bonded.
Illustrative of this suitable vinyl monomer is the general formula However, in the formulas (1) to (4), R ₁ is an alkyl group having 9 to 20 carbon atoms, R ₂ is an alkyl group having 1 to 20 carbon atoms, and n is 1
In particular, vinyl benzenes and vinyl naphthalenes having an integer of 4 to 4 are mentioned. Of the vinyl monomers represented by these general formulas, typical ones will be specifically shown. Etc.

In order to obtain the anion exchange membrane of the present invention, it is preferable to form a crosslinked structure in the anion exchange membrane by using a crosslinking agent to reduce the degree of swelling and maintain a high fixed ion concentration. The polyfunctional vinyl monomer copolymerizable with the vinyl monomer having an amino group is used without particular limitation. Examples of typical cross-linking agents include divinylbenzenes, trivinylcyclohexanes, ethylene glycol dimethacrylates, divinylnaphthalene,
Examples include divinyltoluenes, polyvinylpyridines, propylene glycol dimethacrylates, propylene glycol diacrylates and the like.

The anion exchange membrane used in the present invention contains the above-mentioned vinyl monomer having an amino group to which a long-chain alkyl group is bonded and a cross-linking agent, and if necessary, is used in combination with another vinyl monomer copolymerizable with these monomers. It consists of a polymer of the monomer mixture. When the other vinyl monomer is used in combination in the above-mentioned monomer mixture, the vinyl monomer is used in an amount of 40% by weight or less, preferably 30% by weight or less based on the vinyl monomer having an amino group having a long-chain alkyl group bonded. It is preferable to keep the fixed ion concentration of the obtained anion exchange membrane high. In addition, the ratio of the cross-linking agent used is 2 with respect to the total amount of the above vinyl monomers.
-100% by weight, preferably 5-40% by weight is suitable. Typical examples of the other vinyl monomers described above include aromatic vinyl monomers such as styrene, vinyltoluene, chloromethylstyrene, chloromethylvinylnaphthalene, and bromomethylstyrene, methyl acrylate, ethyl acrylate, and the like. Known copolymerizable monomers such as acrylic acid esters, methacrylic acid esters such as methyl methacrylate, ethyl methacrylate and the like can be mentioned.

In the production of the anion exchange membrane of the present invention, a polymerization initiator such as benzoyl peroxide, azobisisobutyronitrile, dicumyl peroxyside, kayabutyl D, kayabutyl C, perbutyl L is added to the above-mentioned mixed monomer. A general method is to polymerize after molding into a film. In this case, a powdery thermoplastic resin soluble as a reinforcing material in the mixed monomer, such as polyethylene, polypropylene, polyvinyl chloride, acrylonitrile-vinyl chloride copolymer, vinyl chloride-vinylidene chloride copolymer, N.
BR, SBR, polybutadiene, etc. are added, or mixed monomers are used to reinforce non-woven fabrics, porous membranes, woven fabrics, etc. made of polymers such as Teviron, Tetoron, Saran, Nylon, Bonnel (above, trade name), polyethylene, polypropylene, etc. A method of applying it to a material and polymerizing it is suitably adopted.

In addition, the anion exchange membrane obtained by the above method may have an alkyl group introduced into an amino group to which a long-chain alkyl group is bonded, if necessary. As such an alkyl group, an alkyl group having 1 to 6, preferably 1 to 3 carbon atoms is suitable for preventing an increase in electric resistance of the film-shaped material.
As a method for introducing an alkyl group, a known method is adopted without particular limitation, and it is generally carried out, for example, by reacting the above alkyl halide having an alkyl group with an amino group.

The electrodialysis tank used in the present invention comprises a cation exchange membrane, an anion exchange membrane and a cation exchange membrane, a bipolar membrane and an anion exchange membrane, which are repeatedly arranged in this order between the anode and the cathode. A salt chamber, a base chamber between the cation exchange membrane and the anion exchange membrane layer side of the bipolar membrane, and an acid chamber between the cation exchange membrane layer side of the bipolar membrane and the anion exchange membrane. It is a three-chamber basic structure configured, and is not particularly distinguished from a known three-chamber electrodialysis tank such as a filter press type or unit cell type. The number of membranes used in such a three-chamber electrodialysis tank or the flow passage interval (membrane interval) between the salt chamber, the base chamber and the acid chamber (and the electrolysis chamber as necessary), etc., is the type and concentration of the neutral salt to be treated and the treatment. It is appropriately selected according to the amount.

The method of metathesis of a neutral salt using the above-mentioned three-chamber electrodialysis tank of the present invention is an aqueous solution of the above-mentioned neutral salt in the salt chamber of the three-chamber electrodialysis tank, and a dilute alkali metal hydroxide in the base chamber. Dilute hydrochloric acid is supplied to the solution (NaOH, etc.) in the acid chamber, and if necessary, the electrode solution consisting of electrolyte solution such as saline solution is also supplied to the cathode and cathode chambers. It is carried out by passing a direct current between them. That is,
In the present invention, the neutral salt supplied to the salt chamber, for example, Na ⁺ and Cl ⁻ of common salt, is supplied by energizing in the above state.
Respectively pass through the cation exchange membrane and the anion exchange membrane to move to the base chamber and the acid chamber, and at the same time, are bound to OH ⁻ and H ⁺ generated by hydrolysis, and NaOH and H
Generate Cl. In this case, since the above-mentioned specific ion exchange membrane is used in the present invention, generally 1 to 20 wt% hydrochloric acid and 1 to 20 wt% alkali metal hydroxide aqueous solution can be obtained with a current efficiency of 90% or more.

In such electrodialysis, the voltage applied to the three-chamber electrodialysis tank, the current density, the treatment time, and the supply (replenishment) of neutral salt
The amount and the like are appropriately selected.

[Action and effect]

As described above, according to the neutral salt metathesis method of the present invention, a simple method of supplying an aqueous solution of a neutral salt to a three-chamber electrodialysis tank in which specific ion-exchange membranes are combined and configured, High concentrations of acid and alkali can be produced with high current efficiency. The reason why such effects of the present invention are exerted is not clear, but the combination of the characteristics of each of the predetermined cation exchange membrane, bipolar membrane and anion exchange membrane used in the three-chamber electrodialysis tank of the present invention is , It is recognized that it acts extremely effectively in the metathesis of neutral salts. That is, in the bipolar membrane used in the present invention, since the cation exchange group is uniformly present in the cation exchange layer and an extremely dense crosslinked structure is formed, a proton (H ⁺ ) during the metathesis of the neutral salt, Hydroxyl group (O
H ^-) is extremely small despreading and electro-osmotic water such. Further, the anion exchange membrane used in the present invention has a high fixed ion concentration over the entire layer, a high ion exchange capacity, and a low electric resistance. Therefore, the anion selectivity is high,
Moreover, the permeation of proton (H ⁺ ) ions and the amount of electroosmotic water (including the amount of permeated water) are extremely small. Further, the cation exchange membrane used in the present invention has high selectivity performance for monovalent cations and further shows low electric resistance.

〔Example〕

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not particularly limited to these examples.

In addition, "part" of an Example shows a "weight part." In the examples, the fixed ion concentration of the membrane was determined by equilibrating the ion exchange membrane with 1N hydrochloric acid, washing the membrane several times with methanol, washing and removing the hydrochloric acid adsorbed on the membrane, and then using 0.2N-sodium nitrate. After washing ion exchange, the washing liquid was collected and concentrated, and the contained chlorine ions were quantified. With this, the exchange capacity (EC) of the membrane was measured. On the other hand, the membrane was weighed after being equilibrated with 0.5 N salt water, the wet weight (Wet W) was measured, and then the membrane was dried at 30 ° C. under reduced pressure for 16 hours, and then the membrane weight was measured. The fixed ion concentration of the membrane whose dry weight (Dry W) was measured was calculated by the formula I asked for it.

The metathesis performance of the neutral salt was measured by arranging a cation exchange membrane, a bipolar membrane and an anion exchange membrane between both electrodes of the cathode and the anode, and tightening them to form a three-chamber electrodialysis tank (effective area ² dm ² ). Using a dialysis tank, 25 wt% NaCl solution in the salt chamber, 1-10% HCl in the acid chamber, 1-10% Na in the base chamber.
OH was supplied, and dialysis was performed at a temperature of 20 to 50 ° C. and a current density of 0.1 to 10 A / dm ² . At this time, H
The initial concentration of Cl and NaOH, the concentration after dialysis, and the current efficiency were measured.

Example 1. (Production of bipolar membrane A) 100 parts of chloromethylstyrene, 12 acrylonitrile
Parts, chlorosulfonated polyethylene rubber 7 parts, purity about 5
A monomer mixed solution consisting of 20 parts of 5% divinylbenzene and 4 parts of benzoyl peroxide was applied to a polypropylene plain woven cloth, and both sides were covered with a polyester film.
Polymerization was carried out by heating at 80 ° C. for 10 hours to obtain a polymer film. A polypropylene film was attached to one side of this polymer film-like material and immersed in a mixed solution of chlorosulfonic acid and sulfuric acid by a conventional method to introduce a sulfonic acid group on one side. Then, it was hydrolyzed, washed with water, and immersed in dilute hydrochloric acid. After that, the film was peeled off and immersed in a 10% trimethylamine aqueous solution at room temperature for 24 hours. Further, the bipolar film of the present invention was obtained by immersing in a solution of dilute hydrochloric acid, water, and a 0.5 N sodium chloride aqueous solution.

The fixed ion concentration of this membrane is the cation exchange membrane layer 17.1
N, an anion exchange membrane layer 12.5N.

(Production of Anion Exchange Membrane A) 100 parts of vinylbenzyldilaurylamine (NN dilaurylacinomethylstyrene), 10 parts of divinylbenzene with a purity of about 55%, 30 parts of styrene, acrylonitrile rubber (Nippon Zeon Co., Ltd. Hiker 1042) 10 parts and 4 parts of azoisobutyronitrile were mixed to obtain a pasty mixture, which was applied to a polyvinyl chloride cloth,
Degas, then cover both sides with polyester film,
A polymer film was obtained by heating and polymerizing at 75 ° C. for 5 hours. Then, it was immersed in n-hexane at 30 ° C. for 6 hours to obtain an anion exchange membrane of the present invention.

(Production of Cation Exchange Membrane A) NNN'N'N "Tetramethyl 1.6 hexanediamine 17.3 g and chloromethylstyrene 30.6 g were reacted in 100 ml of methanol at room temperature for 24 hours to give a quaternary ammonium base. A compound having a vinylbenzyl group and a vinylbenzyl group each was obtained, and 30 cation-exchange membrane Neosepta CM (manufactured by Tokuyama Soda Co., Ltd., a strongly acidic cation-exchange group) was added to a 1.0N saline solution containing 1000 ppm of this compound. After dipping for 2 hours at 0 ° C., potassium persulfate and sodium sulfite as polymerization initiators were added at 1000 ppm each under a nitrogen atmosphere, and the solution was vigorously stirred.After 10 hours, the membrane was taken out and the cation of the present invention was added. An exchange membrane was obtained.

Using the obtained anion exchange membrane A, bipolar membrane A and cation exchange membrane A, metathesis was carried out under the above conditions. The results are shown in Table 1.

Comparative Example 1 (Production of Bipolar Membrane B) Monomer composed of 100 parts of chloromethylstyrene, 20 parts of divinylbenzene having a purity of about 55%, 1.5 parts of dioctyl phthalate, 7 parts of chlorosulfonated polyethylene rubber and 4 parts of benzoyl peroxide. The mixed solution was applied to a polypropylene plain woven cloth, covered on both sides with a polyester film, and polymerized by heating at 80 ° C. for 8 hours to give a polymer film.
Thereafter, the same procedure as in Example 1 was carried out to obtain a bipolar film for comparison. The fixed ion concentration of this membrane is the cation exchange membrane layer 9
N, an anion exchange membrane layer was 8.5N.

Using the obtained bipolar membrane B and the cation exchange membrane A and the anion exchange membrane A synthesized in Example 1, metathesis of the neutral salt was carried out under the above conditions. The results are shown in Table 1.

Example 2. (Production of bipolar film C) 100 parts of chloromethylstyrene, 1 of methacrylonitrile
A monomer mixed solution consisting of 5 parts, 7 parts of acrylonitrile-butadiene rubber, 15 parts of divinylbenzene having a purity of about 80% and 4 parts of benzoyl peroxide was applied to a plain woven cloth of polyvinyl chloride and polypropylene, and both surfaces were coated with polyester film. And polymerized by weighting at 80 ° C. for 10 hours to obtain a polymer film. Thereafter, a bipolar film was obtained in the same manner as in Example 1. The fixed ion concentration of this membrane was 12.5N for the cation exchange membrane layer and 10N for the anion exchange membrane layer.

(Production of Anion Exchange Membrane B) Vinylbenzyldioctylamine 70 parts, purity about 80%
15 parts of divinylbenzene, 6 parts of acrylonitrile-butadiene rubber, and 3 parts of azoisobutyronitrile were mixed and applied to a plain weave cloth of polyvinyl chloride and polypropylene, followed by degassing. Then, both surfaces were covered with a polyester film and polymerized by heating at 75 ° C. for 7 hours to obtain a polymer film. The obtained film-like product was added to methyl iodide and n-hexane at 30 ° C. for 2 hours.
It was immersed for 4 hours and then washed with n-hexane to obtain the anion exchange membrane of the present invention.

(Production of cation exchange membrane B) 100 parts of styrene, divinylbenzene 1 having a purity of about 80%
2 parts, dioctyl phthalate 8 parts and polyvinyl chloride fine powder 15 parts were heated and stirred, and after standing to cool, benzoyl peroxide 3
The mixed solution containing the parts was applied to a plain weave cloth made of polyvinyl chloride, both sides were covered with a polyester film, and heat-polymerized at 110 ° C. for 5 hours to obtain a polymer film. Then, the membrane was immersed in a mixed solution of chlorosulfonic acid and sulfuric acid at 40 ° C. for 1 hour.
It was soaked for a period of time to produce about 60% of sulfonyl chloride. Apply a viscous mixture of about 50% polyethyleneimine and dioctylamine to one side of this membrane and apply at room temperature for 16
After being left for a time, washed with water and hydrolyzed, the cation exchange membrane of the present invention (the amount of cation exchange groups present is 2 × 10 ⁻³ eq /
cm ² ) was obtained.

The anion exchange membrane B, the bipolar membrane C and the cation exchange membrane B thus obtained were incorporated in the same manner as in Example 1 (however,
The treated side of the cation exchange membrane B is installed so as to face the neutral salt chamber. ) Double decomposition was performed under the same conditions. The performance effects at that time are shown in Table 1.

Comparative Example 2. Using the bipolar membrane C, the cation exchange membrane B and the anion exchange membrane ACS (manufactured by Tokuyama Soda Co., Ltd., strong basic anion exchange membrane) synthesized in Example 2, Example 1 In the same manner as above, built-in was carried out and double decomposition was performed under the same conditions. The results are shown in Table 1.

Example 3 (Production of Bipolar Membrane D) 120 parts of chloromethylstyrene, 15 acrylonitrile
Part, 5 parts of styrene, 15 parts of bisvinylphenylethane having a purity of about 89%, 8 parts of chlorosulfonated polyethylene rubber and 5 parts of benzoyl peroxide are applied to a polypropylene plain woven cloth, and both surfaces are coated. The film was covered with a polyester film and heat-polymerized at 70 ° C. for 3 hours and 80 ° C. for 6 hours to obtain a polymer film. A polypropylene film was attached to one surface of this polymer film-like material and immersed in a mixed solution of chlorosulfonic acid and sulfuric acid by a conventional method to introduce a sulfonic acid group on one surface. Next, the product was hydrolyzed, washed with water, immersed in dilute hydrochloric acid, peeled off the film, and immersed in a 10% aqueous trimethylamine solution at room temperature for 24 hours. Further, the bipolar film of the present invention was obtained by immersing in a solution of dilute hydrochloric acid, water, and a 0.5 N sodium chloride aqueous solution.

(Production of anion exchange membrane C) 100 parts of vinylbenzyldecylamine, 12 parts of divinylbenzene having a purity of about 80%, 5 parts of finely powdered polyvinyl chloride,
A paste-like mixture obtained by mixing 4 parts of acrylonitrile-butadiene rubber and 5 parts of azoisobutyronitrile was applied to a plain woven fabric of polypropylene and vinyl chloride intertwisted, deaerated, and then covered on both sides with a polyester film. Polymerization was carried out at 75 ° C. for 5 hours to obtain a polymer film. Then, it was immersed in n-hexane at 30 ° C. for 12 hours to obtain an anion exchange membrane of the present invention.

(Production of Cation Exchange Membrane C) 3-vinylpyridine is anionically polymerized to give a molecular weight of 300.
0 poly-4 vinyl pyridine was obtained. This thing 10.4
g (0.1 mol) is dissolved in 200 ml of methanol,
Then chloromethylstyrene 15.3 g (0.1 mol)
Was added and reacted at 40 ° C. for 7 days to make polyvinyl pyridine a quaternary pyridinium salt and to introduce two vinylbenzyl groups.

A cation exchange membrane (Neoceptor CM, manufactured by Tokuyama Soda Co., Ltd.) was immersed in an aqueous solution containing 3000 ppm of the product at 40 ° C. for 3 days. The cation-exchange membrane was taken out of the aqueous solution, and was put into a mixed solution of 1000 ppm aqueous solutions of ammonium persulfate and potassium sulfite under a nitrogen atmosphere for 10 times.
After immersion for a period of time, a cation exchange membrane of the present invention was obtained. (Abundance of anion exchange groups was 1 × 10 ⁻³ eq / cm ² on each side) The obtained anion exchange membrane C, bipolar membrane D and cation exchange membrane C were treated in the same manner as in Example 1. Built-in and carried out double decomposition under the same conditions. The performance results at that time are shown in Table 1.

Comparative Example 3. Similar to Example 1 using the bipolar membrane D, the anion exchange membrane C and the cation exchange membrane CM (strong acid cation exchange membrane manufactured by Tokuyama Soda Co., Ltd.) synthesized in Example 3. It was built in and was subjected to multiple decomposition under the same conditions. The results are shown in Table 1.

Claims (2)

[Claims] 1. An exchange capacity of 10 ^-6 to at least one surface.
Monovalent cation selective permeation cation exchange membrane having anion exchange layer at a rate of 10 ^-2 eq / cm ² , cation exchange membrane layer and cation exchange membrane layer, and the cation exchange membrane A bipolar membrane having a fixed ion concentration of 10 N or more in the layer and an anion exchange membrane having an amino group to which a long-chain alkyl group having 9 to 30 carbon atoms is bonded are sequentially arranged between the positive and negative electrodes, A base chamber is provided between the ion exchange membrane and the anion exchange membrane layer side of the bipolar membrane, an acid chamber is provided between the cation exchange membrane layer side of the bipolar membrane and the anion exchange membrane, and the anion exchange membrane and the cation exchange membrane are provided. Method for the double decomposition of neutral salt, characterized in that an aqueous solution of neutral salt is supplied to the salt chamber for electrodialysis using a three-chamber electrodialysis tank having a salt chamber formed between 2. The method according to claim 1, wherein the neutral salt is sodium chloride.