JPS6115885B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an improved cation exchange membrane, a cation exchange membrane suitable for electrodialyzing an electrolyte solution containing two or more types of cations with different charges, and selectively permeating cations with a small charge; The present invention relates to a method for electrodialysis of electrolyte substances using the cation exchange membrane. More specifically, it relates to an improved cation exchange membrane in which a non-crosslinkable substance having an anion exchange group having a hydrophilic-lipophilic balance (HLB) and molecular weight in a specific range is present on at least one side of the cation exchange membrane. . In addition, the present invention uses an improved cation exchange membrane in which a non-crosslinkable substance having an anion exchange group with an HLB of 3 to 12 and a molecular weight of 600 to 20,000 is present on at least one side of the cation exchange membrane, and an electrolyte solution The present invention provides an electrodialysis method for electrodialyzing. Conventionally, ^salt has been obtained by concentrating seawater using an electrodialysis method using an ion exchange membrane.
As a result of electrodialysis of Mg ⁺⁺ , K ⁺ , SO ₄ ^-- , etc., gypsum crystals are particularly likely to form in the concentration chamber of the dialysis tank, which in turn causes deterioration of the ion exchange membrane. In addition, in salt production by ion exchange membrane electrodialysis, there are problems such as components other than common salt not only causing unnecessary power consumption, but also increasing the burden of the separation process for Ca ⁺⁺ and the like. These problems are not limited to the process of obtaining salt from seawater, but also apply to all processes that aim to separate ions with different charges. Therefore, various ion exchange membranes or dialysis methods have been proposed that selectively allow ions with low charges to permeate. The present inventors have already made various proposals, in particular adding a substance with a molecular weight of about 100 or more and a functional group that can become a cation in the electrolyte solution to selectively remove cations with a small charge. and a method of electrodialysis for cations with a small electric charge, in which a substance with a molecular weight of about 100 or more and a functional group that can become a cation in the molecule is substantially uniformly present on the surface of a cation exchange membrane. We proposed a cation exchange membrane for electrodialysis with selective permselectivity (patent no.
No. 704599). The above-mentioned cation exchange membrane shows permselectivity with only a slight increase in electrical resistance, and also has the advantage of being easy to perform selective treatment. The effectiveness is reduced and there are problems with durability. As a result of further research in view of the above problems, the present inventors have found that by using a substance with an anion exchange group having a specific range of HLB and molecular weight, the selective permeability of cations is high and two types of We have discovered that an improved cation exchange membrane can be obtained which has particularly excellent permselectivity for monovalent cations among the above cations, and which does not increase electrical resistance even during long-term operation, and has developed the present invention. We have come to offer it. That is, the present invention has an HLB of 3 to 12 and a molecular weight of 600 to 12.
This is an improved cation exchange membrane characterized in that a non-crosslinkable substance (hereinafter simply referred to as a treatment agent) having 20,000 anion exchange groups is present on at least one side of the cation exchange membrane. In addition, the present invention uses an improved cation exchange membrane in which a non-crosslinkable substance having an anion exchange group with an HLB of 3 to 12 and a molecular weight of 600 to 20,000 is present on at least one side of the cation exchange membrane, and an electrolyte solution The present invention also provides an electrodialysis method characterized by electrodialyzing. The cation exchange membrane applied to the present invention is not particularly limited as long as it is a known one, and even if it is an amphoteric ion exchange membrane, the current efficiency is 70% when a 0.5N-salt solution is electrodialyzed at 2A/ ^dm2. Any membrane that substantially functions as a cation exchange membrane can be used. The present invention is characterized by using a treatment agent having an anion exchange group in order to impart selective permeability to cations with a small electric charge to the cation exchange membrane as described above. The processing agent has an HLB of 3 to 12 and a molecular weight of 600.
The combination of ~20000 is extremely important. Balance of lipophilic and hydrophilic groups in surfactants
The physicochemical properties of HLB, such as its degree of surface activity and solubility, depend on the balance of its two components; generally, the smaller the HLB, the more lipophilic it is, and the larger the HLB, the more hydrophilic it is. Various methods have been used to quantify HLB, but in the present invention, we will use Ryohei Oda and Kazuhiro Teramura, “Synthesis of Surfactants and Their Applications,” 501-
Based on the calculation method described on page 502 (published by Maki Shoten). That is, HLB=inorganic/temporal x k (k=10) Numerical value (strength) of inorganicity=values shown in Table 1 below from the description on page 502 of the above publication. Organic value (strength) = value of one carbon atom is set as 20.

【table】

[Table] Note that the numerical value of the amine and ammonium salt in the above is 400 or more, but in the present invention, it is 400, and the numerical value of the pyridine ring is 15, which is the same as the benzene ring. In the present invention, if the HLB of the treatment agent is high, such as 12 or more, the treatment agent will separate from the membrane when the treated cation exchange membrane is immersed in a dialysis solution such as seawater, and the effects of the present invention will not be fully exhibited. . In the present invention, when using a processing agent with an HLB of 12 or less,
Because the lipophilic part of the cation exchange group and the lipophilic part of the treatment agent form a hydrophobic bond, the treatment agent is difficult to separate from the membrane even if the treated cation exchange membrane is immersed in a dialysis solution. The ion selective permselectivity effect lasts for a long time. However, when a treatment agent having an HLB of 3 or less is used, it is not preferable because the treatment agent forms a hydrophobic film on the surface of the cation exchange membrane and increases electrical resistance. Therefore, in the present invention, the HLB of the treatment agent for the cation exchange membrane is 3 to 3.
12, preferably 4 to 11 are preferably used. Next, the above treatment agent for treating the cation exchange membrane is:
It is also extremely important that the molecular weight is 600 to 20,000 in order to suppress an increase in the electrical resistance of the cation exchange membrane and to maintain the effect of selective ion permeability. If the molecular weight of the treatment agent is 600 or less, the treatment agent will permeate into the cation exchange membrane and inevitably increase the electrical resistance of the membrane. On the other hand, if the molecular weight of the processing agent
If it is more than 20,000, the processing agent tends to separate from the membrane surface and the effect of specific ion permselectivity cannot be sustained. The method for producing the treatment agent having an anion exchange group having an HLB of 3 to 12 and a molecular weight of 600 to 20,000 used in the present invention is not particularly limited, but there are two main methods as follows. (A) Manufacture a compound capable of introducing an anion exchange group whose molecular weight is controlled in advance (adjusted so that the final product has a molecular weight of 600 to 20,000), and then determine the type of anion exchange group to be introduced or the introduction. Adjust the amount so that the HLB is 3 to 12. Examples of anion exchange groups include quaternary ammonium groups, quaternary pyridinium groups,
Known groups such as a phosphonium group, a sulfonium group, an arsonium group, a primary, secondary or tertiary amino group, a pyridine group, an imino group, etc. are appropriately employed. (B) polymerization of the compound itself having an anion exchange group;
Or, by copolymerizing the compound with a compound capable of copolymerization such as styrene or acrylonitrile, the HLB is 3 to 12 and the molecular weight is 600 to 20,000.
How to control. To give a typical example of method (A), polystyrene whose molecular weight is controlled to be between 600 and 20,000 is partially or completely chloromethylated using a chloromethylation solution consisting of chloromethyl ether, carbon tetrachloride, and anhydrous tin tetrachloride. and then quaternary amination with trimethylamine or N·N-diethyldodecylamine. In this case, the HLB is controlled to be 3 to 12 depending on the degree of chloromethylation, the type of amino compound used, and the degree of amination. The compounds used in (A) into which anion exchange groups can be easily introduced include various polymers having halogenated alkyl groups such as phenyl groups, naphthyl groups, and halomethylated phenyl groups, and epoxy groups ( Polyolefins, polyvinyl compounds, polydiene compounds, etc.) are commonly used. In method (B), since the monomer itself has an anion exchange group, HLB is
12 and the molecular weight is 600 to 20,000. Furthermore, the amount of anion exchange groups can be adjusted by copolymerizing a compound having an anion exchange group with a compound such as styrene or acrylonitrile. The compound having an anion exchange group used in (B) generally includes basic nitrogen-containing vinyl compound polymers, such as vinylpyridines, vinylquinolines, vinylpiperidines, and vinylimidazoles. , vinylanilines, vinylbenzylmonoalkylamines, vinylbenzyldialkylamines, vinylbenzyltrialkylammonium salts, and the like are used. Furthermore, some or all of the basic nitrogen of the polymer thus obtained is optionally removed by alkylating halogens such as methyl iodide, methyl bromide, benzyl chloride, and dodecyl bromide; ethylene oxide;
Epoxy compounds such as propylene oxide and styrene oxide; 1,2-dibromoethane,
HLB may be further controlled by treatment with polyalkyl halides such as 1,5-dibromopentane and 1,6-dibromohexane, and other alkylating agents such as epihalohydrin and dimethyl sulfate. In the present invention, there is no particular limitation on the method of making the treatment agent, which is a substance having an anion exchange group with an HLB of 3 to 12 and a molecular weight of 600 to 20,000, exist on the surface of the anion exchange membrane. In general, it is sufficient that the amount is present in an amount of 0.01 mm or more per 1 dm ² of the surface area of the membrane. The methods include immersing the membrane in a treatment agent solution, applying or spraying a treatment agent solution onto the membrane surface, and applying electricity or A method of passing a solution of a processing agent in a non-energized state;
Alternatively, there is a method of adding a treatment agent to an electrolyte solution and performing electrodialysis. The form of the treatment agent present on the surface of the cation exchange membrane is simply adsorption or adhesion, which is sufficient to ensure the sustainability of the effects of the present invention.For example, as a cation exchange membrane, styrene-divinylbenzene-2-methyl-5-
By using partially aminated polychloromethylstyrene as a treatment agent for a film made of vinylpyridyl or the like, unreacted chloromethyl groups in the treatment agent and pyridyl groups in the film can be chemically bonded. In the above embodiment, the method of adding the treatment agent to the electrolyte solution and making it exist on the membrane surface while performing electrodialysis allows processing as much as necessary while measuring the effect of the present invention, and furthermore, it is possible to disassemble it in the battery container. It is preferably adopted because it can be processed as is. For example, a method is adopted in which a treatment agent is added continuously or intermittently to the solution on the anode side or the solution on both electrode sides of the tank for a certain period of time, and then electrodialyzed. The added treatment agent is electrophoresed to the cathode, but it is difficult for the treatment agent to permeate through the cation exchange membrane, and most of it adheres to the anode side of the cation exchange membrane in a short period of time, causing some The various effects of the present invention are achieved by ion exchange. Although the effect of adding a treatment agent varies depending on the type of cation exchange membrane and the composition of the dialysate, good results can generally be obtained if the amount of treatment agent used is 0.1 ppm or more based on the electrolyte solution. In the various embodiments described above, the processing agent is generally used in the form of an aqueous solution, but it may also be used after being dissolved in an organic solvent. The above processing temperature is usually 5-90℃
The concentration of the processing agent is 0.1 mg to 10 g, preferably 1 mg to 1 g. The treatment time is 10 minutes to several days, and the treatment conditions may be determined as appropriate, such as temperature, concentration, pH, time, etc., depending on the properties of the cation exchange membrane to be treated and the properties of the treatment agent used. . The treated cation exchange membrane of the present invention has the following effects: a small increase in the electrical resistance of the cation exchange membrane, a high specific permselectivity for monovalent cations, and an extremely long-lasting effect. have The reason why the specific permselectivity between cations is favorably improved in the present invention is surmised as follows. In other words, it was thought that the higher the density of anion exchange groups, the more effective the treatment agent for cation exchange membranes, but what is actually important is the treatment agent on the surface of the cation exchange membrane, the anion exchange It is the state of existence of a substance having a group. The treatment agent used in the present invention has a small HLB of 3 to 12, so the treatment agent and the cation exchange membrane form a hydrophobic bond on the surface of the membrane. Due to the adhesion of many processing agents,
It is thought that polyvalent cations are strongly repelled by the cations of this treatment agent, and monovalent cations that are weakly repelled are selectively transmitted. Furthermore, the reason why the effect of the present invention lasts is that when the HLB of the treatment agent is high, the treatment agent becomes hydrophilic. The processing agent has a strong tendency to be separated from the membrane. However, as in the present invention, when the HLB is 3 to 12, the lipophilicity of the treatment agent increases, and when this is applied to a cation exchange membrane, the lipophilic portion of the membrane surface and the lipophilic portion of the treatment agent are hydrophobic. Detachment is avoided in order to form a bond. Therefore, the improved cation exchange membrane of the present invention is preferably used in an electrodialysis method that selectively permeates cations with a small number of charges from an electrolyte solution containing two or more types of cations with different charges. The method and purpose of its use are not particularly limited, and it can be applied to any system using a membrane-like material having a conventionally known cation-exchangeable ion-exchange group. i.e. penetration,
Applicable to any system in which the phenomenon of dialysis occurs,
Examples include diffusion dialysis, Donnan dialysis, pressure dialysis, other electrodialysis reverse osmosis, and the like. It may also be used extremely effectively as a diaphragm for electrode reactions. Furthermore, the solution system used is not limited to inorganic neutral salt solutions, acid solutions, alkaline solutions, organic salt solutions, organic acid solutions, organic base solutions, etc., and especially electrolyte solutions. Note that the apparatus using the membrane of the present invention is not particularly limited, and any conventionally known apparatus using each of the membrane-like polymers can be used without any restriction. In order to explain the present invention more specifically, examples will be given and explained below. In the examples, molecular weight,
HLB, electrical resistance, and pure salt rate were determined as follows. Molecular weight: Determined by gel permeation chromatography (GPC) method. The GPC equipment is Liquid Chromatography 635 manufactured by Hitachi, Ltd., and the column is A803. Shown as number average molecular weight ( _N ) and weight average molecular weight ( _W ). HLB: Calculated according to the method of Ryohei Oda mentioned above. Electrical resistance (R): Measured in a saline solution at 25°C using 1000 cycles of alternating current, and expressed as electrical resistance (Ω·cm ² ) per unit membrane area. The measured values obtained by this method generally agree with the electrical resistance values under the conditions of use. Pure salt rate (β): A large number of anion and cation exchange membranes are arranged in pairs and seawater is flowed through each compartment at a flow rate of 6 cm/sec.
The concentrated liquid was analyzed when current was applied at a current density of 3.0 A/dm ² through electrodes provided at both ends, and the liquid composition reached equilibrium, and the concentration was determined from the following formula. Pure salt ratio (β) = [Na] + [K] / [Cl] × 100% The closer this value is to 100%, the higher the selective permselectivity of monovalent cations can be said to be a cation exchange membrane. Example 1 20 parts of polyvinyl chloride fine powder, 80 parts of styrene, 50 parts
% divinylbenzene, 20 parts of acetyl dobutyl citrate, and 1 part of benzoyl peroxide were uniformly mixed and applied to a polyvinyl chloride cloth, then both ends were covered with cellophane and polymerized by heating to obtain a film-like polymer. Ta. After treating this film-like polymer in a 1:1 mixture of chlorosulfonic acid and concentrated sulfuric acid at 40°C for 1 hour, 98
%, 80% and 40% sulfuric acid solutions sequentially.
Furthermore, it was immersed in a 10% caustic soda aqueous solution for 2 hours.
A Na ⁺ type cation exchange membrane was obtained. The electrical resistance of this film was 2.0Ω·cm ² . On the other hand, styrene was subjected to living anionic polymerization in tetrahydrofuran, naphthalene, and sodium. The molecular weight _N of the obtained polymer is 1500
( _W was 1650). This polymer was chloromethylated to a degree of chloromethylation of 80% in a chloromethylation solution consisting of chloromethyl ether, carbon tetrachloride, and anhydrous tin tetrachloride. 75% of the chloromethyl groups of this product were quaternary aminated with triethylamine. The above cation exchange membrane was immersed in a 100 ppm aqueous solution of the above aminated polymer at 40°C for 6 hours. Table 2 shows the results of concentrating seawater for 60 consecutive days using these treated and untreated cation exchange membranes.

[Table] From the above results, it can be seen that compared to the untreated cation exchange membrane, the treated one had an extremely high salt purity ratio, and therefore monovalent cations Na ⁺ and K ⁺ selectively permeated. Comparative Example Instead of the treatment agent used in Example 1, HLB was 17.5.
So, polyethyleneimine with a molecular weight of 10,000
The same procedure as in Example 1 was carried out except that a 100 ppm methanol solution was used for immersion treatment at room temperature for 16 hours. As a result, the resistance (R) was 2.2Ω・cm ² , the pure salt rate (β) was 92%, and the rate of change in the pure salt rate (Δβ) was 9.
It was ×10 ^-2 . This result shows that the larger the HLB, the greater the effect on the pure salt ratio and its rate of change. Example 2 100 parts of chloromethylstyrene, 5 parts of dodecylmercaptan and 4 parts of azobisisobutyronitrile
A portion was polymerized in ethylene dichloride. The molecular weight _N of this product was 2000, and the molecular weight _W was 3600. This is 4
Divide 25% of the chloromethyl group of these substances, 50
%, 75% and all were reacted with triethylamine in a pressure bottle. The cation exchange membrane used in Example 1 was immersed in a 50 ppm aqueous solution of each of the obtained treatment agents at 50° C. for 2 hours for treatment. Table 3 shows the results of concentrating seawater for 60 days using the cation exchange membrane treated in this way.

[Table] From the above results, even if the treatment agents have almost the same molecular weight, the pure salt ratio is higher when using a treatment agent with a smaller HLB value than when using one with a HLB value of 12 or more, and the effect lasts longer. It turns out that sex is also a big deal. Example 3 Stirring 4-vinylpyridine, thiophethle and azobisisobutyronitrile in methanol,
A polymer of 4-vinylpyridine was obtained by heating.
The molecular weight of the product was 500 for _N and 750 for _{W.Furthermore} , the pyridyl group of this product was quaternized by 50% with dodecyl bromide.The resulting treatment agent was added to a 100ppm methanol solution.
The cation exchange membrane of Example 1 was soaked for 24 hours at room temperature. The results of concentrating seawater for 60 days using the cation exchange membrane treated in this way are shown in Table 4.

[Table] Example 4 Each polyethyleneimine having a predetermined molecular weight shown in Table 5 was treated with benzyl chloride to cause half of the nitrogen in the polyethyleneimine to react with the benzyl group. Each of these was made into a 100 ppm methanol solution, and the cation exchange membrane used in Example 1 was immersed at room temperature for 16 hours. The results of concentrating seawater for 60 days using the cation exchange membrane treated in this way are shown in Table 5.

[Table] From Table 5, even if the treatment agent is almost the same HLB, if the molecular weight is less than 600, the pure salt ratio will be good, but the sustainability of the effect will be short and the electrical resistance will be high. Furthermore, it can be seen that when the molecular weight becomes 20,000 or more, the sustainability of the pure salt ratio decreases.

Claims (1)

[Claims] 1. HLB on at least one side of the cation exchange membrane.
An improved cation exchange membrane characterized in that a non-crosslinkable substance having an anion exchange group having a molecular weight of 3 to 12 and a molecular weight of 600 to 20,000 is present. 2 HLB on at least one side of the cation exchange membrane
An electrodialysis method characterized by electrodialyzing an electrolyte solution using an improved cation exchange membrane containing a non-crosslinkable substance having an anion exchange group with a molecular weight of 3 to 12 and a molecular weight of 600 to 20,000.