JP2016144774A - Ion exchange membrane with low reverse ion osmosis and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion exchange membrane having low membrane resistance and low ion reverse osmosis.SOLUTION: An ion exchange membrane has a specific degree of crosslinking and comprises an ionic alcoholic polymer, and the ion exchange membrane has excellent ion reverse osmosis, film strength, dimensional stability, and membrane resistance.SELECTED DRAWING: None

Description

  The present invention relates to an ion exchange membrane having low reverse ion permeability and a method for producing the same.

  Ion exchange membranes are used as membranes for electrodialysis in desalination processes such as salt production, food, and underground brine. In general, ion exchange membranes exhibit ion selectivity by introducing ion exchange groups and crosslinks into a styrene / divinylbenzene polymer. In the electrodialysis method, ions are moved by applying DC power to an electrodialysis tank in which an anion exchange membrane and a cation exchange membrane are alternately arranged between both the cathode and the anode. Therefore, a desalination chamber in which the ion concentration decreases and a concentration chamber in which the ion concentration increases are alternately installed.

At this time, due to the concentration difference between the concentration chamber and the desalted material, ions diffuse from the concentration chamber, and the ions move in the opposite direction (from the concentration chamber to the desalted material) when an electric current is applied. Reverse osmosis occurs. This phenomenon tends to occur remarkably as the concentration difference between the desalted solution and the concentrated solution increases, and there are problems such as an increase in desalting time and a decrease in power efficiency.

  In Patent Documents 1 and 2, in order to prevent the reverse diffusion of carbonate ions, a device such as adjusting the pH of the desalting apparatus is provided. However, it is necessary to improve the entire apparatus and cope with various ions. There is a drawback that it cannot be done. (Patent Documents 1 and 2).

  In addition, if the thickness of the membrane is simply increased, the reverse diffusion can be suppressed, but problems such as an increase in the desalination power cost and a decrease in the desalination efficiency occur due to an increase in membrane resistance.

JP 2007-245120 A JP2011-139799A

  Accordingly, an object of the present invention is to provide an ion exchange membrane having a low membrane resistance and low ion reverse osmosis.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have maintained the degree of cross-linking under specific conditions for the vinyl alcohol block copolymer, thereby allowing reverse osmosis of ions, membrane strength, and dimensional stability. Has led to an invention capable of producing an ion exchange membrane having excellent properties and membrane resistance.

That is, the present invention relates to an ion exchange membrane (hereinafter referred to as an anionic vinyl alcohol block copolymer represented by the following general formula (1) or a cationic vinyl alcohol block copolymer represented by the following general formula (2)). The anionic vinyl alcohol block copolymer or the cationic vinyl alcohol block copolymer is referred to as an ionic vinyl alcohol block copolymer), and the degree of crosslinking calculated from IR measurement (C) Is an ion exchange membrane characterized by having a range of 0.25 to 0.33.
[In the formula, 0.5000 ≦ o ¹ / (n ¹ + o ¹ ) ≦ 0.9999, 0.001 ≦ m ¹ / (m ¹ + n ¹ + o ¹ ) ≦ 0.50, and X ⁺ is H ⁺ Or a monovalent cation such as an alkali metal ion or a quaternary ammonium ion. ]
[In the formula, 0.5000 ≦ o ² / (n ² + o ² ) ≦ 0.9999, 0.001 ≦ m ² / (m ² + n ² + o ² ) ≦ 0.50, and Y ⁻ is Halogenated anions of group 5B elements such as PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻ , halogenated anions of group 3B elements such as BF ₄ ⁻ , and halogens such as I ⁻ (I ₃ ⁻ ), Br ⁻ and Cl ^−. Anion, halogenate anion such as ClO ₄ ⁻ , metal halide anion such as AlCl ₄ ⁻ , FeCl ₄ ⁻ , SnCl ₅ ⁻ , nitrate anion represented by NO ₃ ⁻ , p-toluenesulfonate anion, naphthalenesulfonate anion, _{^{CH 3 SO 3 -, CF 3}} SO 3 - and the like organic sulfonic acid _{^{anion, CF 3 COO -, C 6}} H 5 COO - a carboxylic acid anion, OH ^- is a monovalent anion such as ]

The ion exchange membrane is preferably an ion exchange membrane having a membrane resistance of 10 Ωcm ² or less.

  The ionic vinyl alcohol polymer is preferably an ion exchange membrane that has been subjected to a crosslinking treatment with an aldehyde.

Preparing an ionic vinyl alcohol block copolymer solution;
Applying a solution of the ionic vinyl alcohol block copolymer on the release sheet to form a coating layer of the ionic vinyl alcohol block copolymer;
A step of superposing a fiber support on the coating layer and impregnating at least a part of the support with an ionic vinyl alcohol block copolymer to form an impregnated body;
Drying the impregnated body in a state where the coating layer and the support are overlapped;
And peeling the release sheet from the dried impregnated body;
It is preferable that it is a manufacturing method of the ion exchange membrane containing this.

  In the above production method, the ion exchange membrane production method is preferred in which the ionic vinyl alcohol block copolymer is subjected to a heat treatment after the peeling step.

An electrodialyzer comprising at least an anode and a cathode, and a desalting chamber and a concentrating chamber formed by alternately arranging an anion exchange membrane and a cation exchange membrane between the anode and the cathode. The anion exchange membrane and the cation exchange membrane are preferably electrodialyzers composed of the ion exchange membrane.

  According to the ion exchange membrane of the present invention, the ion exchange membrane used for the electrodialysis treatment is composed of a vinyl alcohol copolymer having an ionic polymer block and a vinyl alcohol polymer block. As the film, the vinyl alcohol polymer segment has high hydrophilicity, so that the film resistance is small and the film contamination property is low. Further, by performing the crosslinking treatment so that the degree of crosslinking is set within a certain range, it is possible to produce a film having low reverse osmosis of ions.

It is the schematic of the membrane resistance test apparatus of an ion exchange membrane. It is a reverse osmosis evaluation result in an example and a comparative example.

(Ion exchange membrane)
The ion exchange membrane of the present invention contains an ionic vinyl alcohol polymer such as an anionic vinyl alcohol block copolymer or a cationic vinyl alcohol block copolymer.

(Anionic vinyl alcohol block copolymer)
The anionic vinyl alcohol block copolymer used in the present invention is represented by the general formula (1).

In the general formula (1), o ¹ / (n ¹ + o ¹ ) represents a ratio other than vinyl acetate units contained in the vinyl alcohol copolymer component. The lower limit is 0.5000 or more, preferably 0.7000 or more, and more preferably 0.8000 or more.
On the other hand, the upper limit is 0.9999 or less, preferably 0.999 or less, and more preferably 0.995 or less.

In the general formula (1), m ¹ / (m ¹ + n ¹ + o ¹ ) represents a ratio of a polymer component having an anion group contained in a vinyl alcohol copolymer component and a polymer component having an anion group. Regarding the lower limit, it is 0.001 or more, preferably 0.003 or more, more preferably 0.005 or more. The upper limit is 0.50 or less, preferably 0.30 or less, and more preferably 0.25 or less.

X ⁺ in the general formula (1) is preferably a quaternary ammonium ion, more preferably an alkali metal ion or a monovalent cation of H ⁺ ion.

(Cationic vinyl alcohol block copolymer)
The cationic vinyl alcohol block copolymer used in the present invention is represented by the general formula (2).

In the general formula (2), o ² / (n ² + o ² ) represents a ratio other than vinyl acetate units contained in the vinyl alcohol copolymer component. The lower limit is 0.5000 or more, preferably 0.7000 or more, and more preferably 0.8000 or more.
On the other hand, the upper limit is 0.9999 or less, preferably 0.999 or less, and more preferably 0.995 or less.

In the general formula (2), m ² / (m ² + n ² + o ² ) represents the ratio of the polymer component having a cationic group contained in the vinyl alcohol polymer component and the polymer component having a cationic group. Regarding the lower limit, it is 0.001 or more, preferably 0.003 or more, more preferably 0.005 or more. The upper limit is 0.50 or less, preferably 0.30 or less, and more preferably 0.25 or less.

Y ⁻ in the general formula (2) is a halogenated anion of a group 5B element such as PF ₆ ⁻ , SbF ₆ ⁻ or AsF ₆ ^−, a halogenated anion of a group 3B element such as BF ₄ ⁻ , I ⁻ (I ₃ ^{-), Br} -, Cl ^- and a halogen anion, ClO ₄ of ^- such as a halogen _{^{anion, AlCl 4 -, FeCl 4 -}} , SnCl 5 - metal halide anions such as, NO ₃ ^- nitrate anion represented by, p-toluenesulfonate anion, naphthalenesulfonate anion, organic sulfonate anions such as CH ₃ SO ₃ ⁻ and CF ₃ SO ₃ ^— , carboxylic acid anions such as CF ₃ COO ⁻ and C ₆ H ₅ COO ⁻ , Cl ^{− and the} like halogen anion, OH ^- is a monovalent anion such like.

(Synthesis of block copolymer)
There are mainly two methods for synthesizing a polymer in which the polymer component obtained by polymerizing the cationic monomer or the anionic monomer of the present invention and the vinyl alcohol polymer component form a block copolymer. It is divided roughly into. (1) A method in which a desired block copolymer is produced and then a cationic group or an anionic group is bonded to a specific block, and (2) at least one cationic monomer or anionic monomer In this method, a desired block copolymer is obtained by polymerization. Among these, for (1), one or more monomers are block copolymerized in the presence of a vinyl alcohol polymer having a mercapto group at the terminal, and then one or more monomers in the block copolymer are used. In the method of introducing a cationic group or an anionic group into a polymer component of the kind, (2), at least one cationic monomer or anionic monomer in the presence of a vinyl alcohol polymer having a mercapto group at the terminal. A method of synthesizing a block copolymer by radical polymerization of a monomer is preferable from the viewpoint of industrial ease.
In particular, since the kind and amount of each component in the block copolymer can be easily controlled, at least one kind of cationic monomer or anionic monomer in the presence of a vinyl alcohol polymer having a mercapto group at the terminal. A method of synthesizing a block copolymer by radical polymerization of a monomer is preferred.

  The vinyl alcohol polymer having a mercapto group at the terminal used for the synthesis of these block copolymers can be obtained by, for example, the method described in JP-A-59-187003. That is, a method of saponifying a vinyl ester polymer obtained by radical polymerization of a vinyl ester monomer such as vinyl acetate in the presence of thiolic acid can be mentioned. Examples of a method for obtaining a block copolymer using a vinyl alcohol polymer having a mercapto group at the terminal and an ionic monomer include the method described in JP-A-59-189113. It is done. Here, the ionic monomer means a cationic monomer or an anionic monomer. That is, a block copolymer can be obtained by radical polymerization of an ionic monomer in the presence of a vinyl alcohol polymer having a mercapto group at the terminal. This radical polymerization can be carried out by a known method such as bulk polymerization, solution polymerization, pearl polymerization, emulsion polymerization, etc., but a solvent capable of dissolving a vinyl alcohol polymer containing a mercapto group at the terminal, such as water or dimethyl It is preferably carried out in a medium mainly composed of sulfoxide. As the polymerization process, any of a batch method, a semi-batch method, and a continuous method can be employed.

  The ion exchange membrane of the present invention may contain a nonionic surfactant in the copolymer constituting the ionic vinyl alcohol block copolymer, if necessary. Here, the ionic vinyl alcohol block copolymer refers to a cationic vinyl alcohol block copolymer or an anionic vinyl alcohol block copolymer.

(Production of ion exchange membrane)
The ion exchange membrane of the present invention is a step of preparing an ionic vinyl alcohol block copolymer solution;
Applying the ionic vinyl alcohol block copolymer solution on a release sheet to form a coating layer of the ionic vinyl alcohol block copolymer;
A step of superposing a fiber support on the coating layer and impregnating at least a part of the support with an ionic vinyl alcohol block copolymer to form an impregnated body;
Drying the impregnated body;
And a step of peeling the release sheet from the dried layer.

(Ionic vinyl alcohol block copolymer solution preparation process)
More specifically, the above ionic vinyl alcohol block copolymer is dissolved in a solvent such as water or DMSO to prepare an ionic vinyl alcohol block copolymer solution (preferably an aqueous solution).
The obtained ionic vinyl alcohol block copolymer solution may have a viscosity of, for example, 300 to 5000 mPa · s, preferably 400 from the viewpoint of satisfactorily forming an impregnation layer on the support. It may be ˜4000 mPa · s, more preferably 500 to 3000 mPa · s. The concentration can be appropriately set according to the type of the ionic vinyl alcohol block copolymer, but may be, for example, 1 to 50 wt%, preferably 2 to 45 wt%, more preferably 3 It may be ˜40 wt%.

(Coating layer forming process)
Then, the obtained ionic vinyl alcohol block copolymer solution (preferably an aqueous solution) is applied to the release sheet using various application means such as a bar coater, a gravure coater, a knife coater, a blade coater, and the like. A layer (cast layer) is formed. The release sheet is not particularly limited as long as it can form a uniform coating layer and can be finally peeled off. A known or commonly used release film or sheet (for example, PET film, polyethylene film, silicone sheet, etc.) is used. can do.
The thickness of the coating layer may be, for example, about 300 μm to 1500 μm, preferably about 500 μm to 1400 μm, more preferably about 600 μm to 1300 μm.

(Support impregnation step composed of fibers)
Prior to the drying step, this coating layer is overlaid with a support composed of fibers, impregnated with the support, impregnated with an ionic vinyl alcohol block copolymer solution, and embedded in the support. Integrated.

  Examples of the support include woven fabric, non-woven fabric, and mesh. If there is no air permeability to some extent, bubbles may be generated in the film. However, if the strength of the support itself is low, the strength of the film may be lowered when they are overlapped.

(Drying process)
In the drying step, the impregnated body is dried. The drying conditions may be room temperature drying or hot air drying, but it is preferable to use a hot air dryer in order to increase the working efficiency. When using a hot air dryer, there is no restriction | limiting in particular as drying temperature, For example, about 50-110 degreeC may be sufficient, Preferably it may be about 60-90 degreeC.

(Peeling process)
In the peeling step, the release sheet can be peeled from the dried impregnated body to obtain an ion exchange membrane on which an ion exchange layer is formed.

(Post-processing after ion exchange membrane formation)
In the present invention, it is preferable to perform heat treatment after forming the ion exchange layer. By performing the heat treatment, the crystallinity of the ionic vinyl alcohol block copolymer is increased, so that the number of physical crosslinking points is increased and the mechanical strength of the resulting ion exchange membrane is increased. In addition, since the cation group or anion group is concentrated in the amorphous part and the formation of the ion exchange path is promoted, the charge density is increased and the counter ion selectivity is improved. The method of heat treatment is not particularly limited, and a hot air dryer or the like is generally used. Although the temperature of heat processing is not specifically limited, It is preferable that it is 50-250 degreeC. If the temperature of the heat treatment is less than 50 ° C., the effect of increasing the mechanical strength of the resulting ion exchange membrane may not be sufficient. The temperature is more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher. If the temperature of the heat treatment exceeds 250 ° C, the ionic vinyl alcohol block copolymer may be melted. The temperature is more preferably 230 ° C. or less, and further preferably 200 ° C. or less. The heat treatment time is usually about 1 minute to 10 hours. The heat treatment is desirably performed in an inert gas (eg, nitrogen gas, argon gas, etc.) atmosphere.

(Crosslinking treatment)
In the present invention, the ionic vinyl alcohol block copolymer is cross-linked with a cross-linking agent that causes acetal cross-linking so that the ion exchanger has a degree of cross-linking of 0.25 to 0.33. It is preferable. It is more preferable to introduce a cross-linking bond by performing a cross-linking treatment after drying the ion exchange membrane. Adjustment of the cross-linking degree to 0.25 or more and 0.33 or less can be performed by selecting reaction conditions such as cross-linking reaction time and pH of the reaction solution. By introducing a crosslink, swelling of the resulting ionic vinyl alcohol block copolymer is suppressed, and the mechanical strength and durability of the ion exchange membrane are improved. Further, since the charge density is increased, the counter ion selectivity is improved.

  The method for the crosslinking treatment is not particularly limited as long as it is a method capable of bonding the molecular chains of the polymer by an acetal bond. Usually, a method of immersing the ion exchange membrane in a solution containing a crosslinking agent that causes acetal crosslinking is used. Examples of the crosslinking agent include glutaraldehyde, formaldehyde, gliogizar, benzaldehyde, succinaldehyde, malondialdehyde, adipine aldehyde, terephthalaldehyde, and nonane dial. Of these, glutaraldehyde, formaldehyde, glyoxal and the like are preferable, and dialdehydes such as glutaraldehyde and glyoxal are more preferable. Glutaraldehyde is particularly preferred because of the stability of the crosslinked structure. The concentration of the crosslinking agent is usually 0.001 to 10% by volume of the crosslinking agent relative to the solution.

  In the manufacturing method, the crosslinking treatment may be performed without performing a heat treatment, but it is preferable to perform the crosslinking treatment after the heat treatment or the heat press treatment. This is because a part that is difficult to be cross-linked is generated by performing heat treatment or a hot press treatment, and then the cross-linking part and a part that is not cross-linked are mixed to increase the film strength. It is particularly preferable to carry out in the order of hot press treatment, heat treatment, and crosslinking treatment from the viewpoint of mechanical strength of the resulting ion exchange membrane. Further, when the ionic vinyl alcohol copolymer is a water-soluble polymer, elution can be prevented by performing a crosslinking treatment after the heat treatment and the heat press treatment.

  In the post-treatment, all of the heat treatment and the crosslinking treatment may be performed, one of them may be performed, or only one of them may be performed. The order of processing to be performed is not particularly limited. A plurality of treatments may be performed simultaneously, but it is preferable to perform a crosslinking treatment after the heat treatment. This is because a part that is difficult to be cross-linked is generated by performing heat treatment, and then a cross-linking part, in particular a chemical cross-linking part, is performed so that the cross-linked part and the non-cross-linked part coexist, thereby increasing the film strength. It is particularly preferable in the order of the heat treatment and the crosslinking treatment from the viewpoint of the mechanical strength of the resulting ion exchange membrane.

(Crosslinking degree)
The degree of crosslinking can be adjusted by the concentration of the crosslinking agent and the crosslinking time. The film after cross-linking is thoroughly washed with water, and the cross-linking agent present on the film surface and inner surface is washed away. Thereafter, the film is sufficiently dried at a low temperature using a vacuum dryer or the like. The film after drying is measured by reflection type IR spectrum measurement, but the definition of the degree of crosslinking in the present invention is to measure with the reflection type (ATR) once with the release sheet surface side described above as the measurement surface. Is preferred.

Degree of crosslinking in the present invention, the area of the intensity peak area of 3743~3000cm ^-1 (peak derived from OH group) (A) and the peak of 3000~2700cm ^-1 (peak derived from stretching modes of CH bonds) (B) is calculated, and the area ratio ((B) / (A)) is defined as the degree of crosslinking (C). When the value of the degree of crosslinking is large, it means that the crosslinking has progressed. Conversely, when the value of the degree of crosslinking is small, it means that the crosslinking has not progressed. The degree of crosslinking is 0.25 ≦ degree of crosslinking (C) ≦ 0.33, and preferably 0.27 ≦ degree of crosslinking (C) ≦ 0.30. When the degree of crosslinking is outside the above range, the reverse osmosis of ions may be increased.

(Use of ion exchange membrane)
The ion exchange membrane of the present invention can be used for various applications. For example, the ion exchange membrane of the present invention having an ion exchange layer made of either a cationic vinyl alcohol block copolymer or an anionic vinyl alcohol block copolymer is excellent in organic contamination resistance and has a membrane resistance. Electrodialysis can be performed stably and efficiently over a long period of time. Therefore, such ion exchange membranes are used for desalting organic substances (food, pharmaceutical raw materials, etc.), desalting whey, concentrating salts, desalting sugar solutions, desalting seawater and brine, desalting tap water, Suitable for softening water. In general, it is particularly preferably used as an ion exchange membrane in which organic contamination is remarkable.

  Hereinafter, the present invention will be described in detail using examples. In the following examples and comparative examples, “%” and “parts” are based on mass unless otherwise specified. Analysis and evaluation in Examples and Comparative Examples were performed according to the following methods.

(1) Burst strength measurement The burst strength measurement was performed using a Murren low pressure burst test (No. 305-YPL, manufactured by Yasuda Seisakusho). The sample size was 60 × 60 mm or more, and was performed by the method specified in JIS-P8110.

(2) Membrane resistance measurement Membrane resistance was measured by sandwiching an ion exchange membrane in a two-chamber cell having a platinum black electrode plate shown in FIG. 1 and filling a 0.5 mol / L-NaCl solution on both sides of the membrane. The resistance between the electrodes at 25 ° C. was measured at a frequency of 1000 cycles / second), and was obtained from the difference between the resistance between the electrodes and the resistance between the electrodes when no ion exchange membrane was installed. The membrane used for the above measurement was previously equilibrated in a 0.5 mol / L-NaCl solution.

(3) Evaluation of reverse osmosis of ions A desktop desalting apparatus (manufactured by S3 ASTOM Co., Ltd.) was used as the desalting test apparatus. A NaCl (20 S / m) aqueous solution adjusted with ion-exchanged water as a concentrate and K ₂ SO ₄ (500 mS / m) adjusted with ion-exchanged water as a desalting solution were prepared. As an electrode solution, K ₂ SO ₄ (5 S / m) adjusted with ion-exchanged water was adjusted. Using the apparatus, a desalting test was performed, and Cl ^- ions that reversely osmosis toward the desalting solution side were analyzed by ion chromatography. The reverse osmosis rate of Cl ^- ion was calculated from the slope of the straight line plotting the electrodialysis time and Cl ^- ion concentration change.

(4) Evaluation of degree of crosslinking of ion exchanger on electrode surface The degree of crosslinking of the produced ion exchanger was calculated by a total reflection method (ATR method) of infrared spectroscopy (FT-IR). The sample size was 2 × 3 cm, and the degree of crosslinking on the electrode surface was calculated using an infrared spectrophotometer JIR-5500 manufactured by JEOL. 2920cm around ^-1 area of the peak area of the reference peak for (CH bond peak derived from stretching mode) (B) of ^{(2700cm -1 ~3000cm} -1), ^3380cm around ^{-1 (3000cm -1 ~3743cm -1)} (B) / (A) showing the ratio was used as the degree of crosslinking (C) of the ion exchanger.

(Synthesis of polyvinyl alcohol having a mercapto group at the end)
Polyvinyl alcohol (PVA-1) having a mercapto group at the end was synthesized by the method described in JP-A-59-187003. The degree of polymerization of the obtained polyvinyl alcohol was 1550, and the degree of saponification was 99.9%.

(Synthesis of block copolymer P-1: PVA-b-PSS)
In a 500 mL four-necked separable flask equipped with a reflux condenser and a stirring blade, 117 g of water, 25.0 g of a terminal mercapto group-containing polyvinyl alcohol (PVA-1) and sodium parastyrene sulfonate (PSS: manufactured by Aldrich) 12.6 g was charged, heated to 90 ° C. with stirring, and dissolved while bubbling nitrogen. After nitrogen substitution, 6.2 mL of a 2.0% aqueous solution of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -2-propionamide] was sequentially added to the above aqueous solution over 1.5 hours. The polymerization is started by adding to the polymer, and then allowed to proceed. Then, the system temperature is maintained at 90 ° C. for 24 hours to further promote the polymerization, and then cooled to block copolymer of polyvinyl alcohol and sodium parastyrenesulfonate. An aqueous solution P-1 of (PVA-b-PSS) was prepared. The pH of the aqueous solution was 6.5. A part of the aqueous solution P-1 was dried, dissolved in heavy water, and subjected to ¹ H-NMR measurement at 500 MHz. As a result, the amount of modification of the sodium parastyrenesulfonate unit was 10 mol%.

(Synthesis of block copolymer P-2: PVA-b-VBTAC)
In a 500 mL four-necked separable flask equipped with a reflux condenser and a stirring blade, 137 g of water, 25.0 g of terminal mercapto group-containing polyvinyl alcohol (PVA) and 13 vinylbenzyltrimethylammonium chloride (VBTAC: Aldrich) were added. .4 g was charged and heated to 90 ° C. with stirring to dissolve nitrogen while bubbling. After nitrogen substitution, 12.2 mL of a 2.0% aqueous solution of 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -2-propionamide] was sequentially added to the above aqueous solution over 1.5 hours. The polymerization is started and allowed to proceed, and then the system temperature is maintained at 90 ° C. for 4 hours to allow the polymerization to proceed further, followed by cooling to block copolymer of polyvinyl alcohol and vinylbenzyltrimethylammonium chloride. An aqueous solution P-2 of (PVA-b-VBTAC) was prepared. The pH of the aqueous solution was 8.0. A part of the aqueous solution P-2 was dried, dissolved in heavy water, and subjected to ¹ H-NMR measurement at 500 MHz. As a result, the amount of modification of the vinylbenzyltrimethylammonium chloride unit was 10 mol%.

(Production of cation exchange membrane CEM-1)
A P-1 aqueous solution having a concentration of 12 wt% was prepared using deionized water. This polymer aqueous solution was applied to a PET film to a thickness of 800 μm using a bar coater to form a coating layer (cast layer). A vinylon nonwoven fabric was placed thereon as a support and impregnated with resin. Then, after drying with a hot air dryer DKM400 (manufactured by YAMATO) at a temperature of 80 ° C. for 40 minutes, the PET film was peeled off to prepare an impregnated coating film. The film thus obtained was heat treated at 160 ° C. for 30 minutes to cause physical crosslinking. Next, a 2 mol / L sodium sulfate aqueous electrolyte solution was prepared, concentrated sulfuric acid was added to the aqueous solution so that the pH was 1, and the film was immersed in a 3% by volume glutaraldehyde aqueous solution. The mixture was stirred using a time stirrer to carry out a crosslinking treatment. Here, as the glutaraldehyde aqueous solution, a product obtained by diluting “glutaraldehyde” (25% by volume) manufactured by Ishizu Pharmaceutical Co., Ltd. with water was used. After the cross-linking treatment, the film was immersed in deionized water, and while deionized water was exchanged several times in the middle, the film was immersed until the film reached a swelling equilibrium to obtain a cation exchange membrane CEM-1.
(Manufacture of CEM-2)
In the production of CEM-1, CEM-2 was produced in the same manner except that the reaction time was 3 hours.
(Manufacture of CEM-3)
In the production of CEM-1, CEM-3 was produced in the same manner except that the aqueous glutaraldehyde solution was changed to 5% by volume and the reaction time was changed to 5 hours.
(Manufacture of CEM-4)
CEM-4 was produced in the same manner as in the production of CEM-1, except that the aqueous glutaraldehyde solution was changed to 10% by volume and the reaction time was 5 hours.
(Manufacture of CEM-5)
CEM-5 was produced in the same manner as in the production of CEM-1, except that no crosslinking treatment with glutaraldehyde was performed.
(Manufacture of CEM-6)
In the production of CEM-1, CEM-6 was produced in the same manner except that the film was immersed in a 1% by volume glutaraldehyde aqueous solution, stirred at 25 ° C. for 24 hours using a stirrer, and subjected to crosslinking treatment.
(CEM-7)
The same applies except that a commercially available hydrocarbon-based cation exchange membrane (ASTOM CMX) was used.
(CEM-8)
The same applies except that a commercially available hydrocarbon cation exchange membrane (CMV manufactured by Asahi Glass Co., Ltd.) was used.

(Manufacture of anion exchange membrane AEM-1)
A P-2 aqueous solution having a concentration of 12 wt% was prepared using deionized water. This polymer aqueous solution was applied to a PET film to a thickness of 800 μm using a bar coater to form a coating layer (cast layer). A vinylon nonwoven fabric was placed thereon as a support and impregnated with resin. Then, after drying with a hot air dryer DKM400 (manufactured by YAMATO) at a temperature of 80 ° C. for 40 minutes, the PET film was peeled off to prepare an impregnated coating film. The film thus obtained was heat treated at 160 ° C. for 30 minutes to cause physical crosslinking. Next, a 2 mol / L sodium sulfate aqueous electrolyte solution was prepared, concentrated sulfuric acid was added to the aqueous solution so that the pH was 1, and the film was immersed in a 3% by volume glutaraldehyde aqueous solution. The mixture was stirred using a time stirrer to carry out a crosslinking treatment. Here, as the glutaraldehyde aqueous solution, a product obtained by diluting “glutaraldehyde” (25% by volume) manufactured by Ishizu Pharmaceutical Co., Ltd. with water was used. After the cross-linking treatment, the film was immersed in deionized water, and while deionized water was exchanged several times in the middle, the film was immersed until the film reached a swelling equilibrium to obtain an anion exchange membrane AEM-1.
(Production of AEM-2)
In the production of AEM-1, AEM-2 was produced in the same manner except that the reaction time was 3 hours.
(Manufacture of AEM-3)
In the production of AEM-1, AEM-3 was produced in the same manner except that the aqueous glutaraldehyde solution was changed to 5% by volume and the reaction time was changed to 5 hours.
(Production of AEM-4)
In the production of AEM-1, AEM-4 was produced in the same manner except that the aqueous glutaraldehyde solution was changed to 10% by volume and the reaction time was 5 hours.
(Production of AEM-5)
In the synthesis of AEM-1, AEM-5 was produced in the same manner except that no crosslinking treatment with glutaraldehyde was performed.
(Production of AEM-6)
In the production of AEM-1, AEM-6 was produced in the same manner except that the film was immersed in a 1% by volume glutaraldehyde aqueous solution, stirred at 25 ° C. for 24 hours using a stirrer, and subjected to crosslinking treatment.
(AEM-7)
The same applies except that a commercially available hydrocarbon-based anion exchange membrane (ASTM AMX) was used.
(AEM-8)
The same applies except that a commercially available hydrocarbon-based anion exchange membrane (AMV manufactured by Asahi Glass Co., Ltd.) was used.

(Evaluation of ion exchange membrane)
The ion exchange membrane thus produced was cut into a desired size, and IR measurement was performed as described above to measure the degree of crosslinking of the membrane. Moreover, the film thickness, rupture strength, and membrane resistance of each ion exchange membrane were measured by the method described above. The results are shown in Table 1. As for CEM-5 and AEM-5, since no membrane cross-linking was formed, the PVA resin was eluted in water in the water-containing state, so the membrane resistance could not be measured (the film thickness was measured when the membrane was dried). Thickness). CEM-7, 8 and AEM-7, 8 do not describe the degree of crosslinking because the hydroxyl group is poor and it is difficult to estimate the degree of crosslinking correctly.

Example 1
CEM-1 and AEM-1 were cut into a desired size to prepare a measurement sample. Using the obtained measurement sample, it was set in the cell of the desalting apparatus, and reverse osmosis evaluation of ions was performed. The evaluation results are shown in FIG.
(Example 2)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-2 and AEM-2 were used. The evaluation results are shown in FIG.
(Example 3)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-3 and AEM-3 were used. The evaluation results are shown in FIG.
(Comparative Example 1)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-4 and AEM-4 were used. The evaluation results are shown in FIG.
(Comparative Example 2)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-5 and AEM-5 were used. The evaluation results are shown in FIG.
(Comparative Example 3)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-6 and AEM-6 were used. The evaluation results are shown in FIG.
(Comparative Example 4)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-7 and AEM-7 were used. The evaluation results are shown in FIG.
(Comparative Example 5)
Ion reverse osmosis was evaluated in the same manner as in Example 1 except that CEM-8 and AEM-8 were used. The evaluation results are shown in FIG.

In the case of using a membrane having a degree of cross-linking of 0.25 ≦ degree of cross-linking (C) ≦ 0.33, the reverse osmosis of ions is higher than that of commercially available ion exchange membranes (Comparative Examples 4 and 5). It turns out that it is low. On the other hand, when a membrane with a cross-linking degree outside the above range is used (Comparative Examples 1 and 3), the result is that the reverse osmosis of ions is as high as that of a commercially available ion exchange membrane. There is a possibility that the desalting time increases or the power efficiency decreases. Further, according to the present invention, it is possible to produce an ion exchange membrane having a low membrane resistance without extremely increasing the film thickness and suppressing the reverse osmosis of ions.

  The ion exchange membrane according to the present invention has a low resistance and can suppress reverse osmosis of ions. From this result, without increasing the power cost, it becomes a membrane with high desalting efficiency, and there is industrial applicability.

Although the preferred embodiments of the present invention have been described above by way of example, those skilled in the art can make various modifications, additions and substitutions without departing from the scope and spirit of the present invention disclosed in the claims. It will be understandable.

Claims (6)

An anion exchange membrane containing an anionic vinyl alcohol block copolymer represented by the following general formula (1) or a cationic vinyl alcohol block copolymer represented by the following general formula (2) (hereinafter referred to as the anionic vinyl) An alcohol block copolymer or a cationic vinyl alcohol block copolymer is referred to as an ionic vinyl alcohol block copolymer.) The degree of crosslinking (C) measured by IR measurement is 0.25 or more. An ion exchange membrane having a range of 0.33 or less.
[In the formula, 0.5000 ≦ o ¹ / (n ¹ + o ¹ ) ≦ 0.9999, 0.001 ≦ m ¹ / (m ¹ + n ¹ + o ¹ ) ≦ 0.50, and X ⁺ is H ⁺ Or a monovalent cation such as an alkali metal ion or a quaternary ammonium ion. ]
[In the formula, 0.5000 ≦ o ² / (n ² + o ² ) ≦ 0.9999, 0.001 ≦ m ² / (m ² + n ² + o ² ) ≦ 0.50, and Y ⁻ is Halogenated anions of group 5B elements such as PF ₆ ⁻ , SbF ₆ ⁻ , AsF ₆ ⁻ , halogenated anions of group 3B elements such as BF ₄ ⁻ , and halogens such as I ⁻ (I ₃ ⁻ ), Br ⁻ and Cl ^−. Anion, halogenate anion such as ClO ₄ ⁻ , metal halide anion such as AlCl ₄ ⁻ , FeCl ₄ ⁻ , SnCl ₅ −, nitrate anion represented by NO ₃ ⁻ , p-toluenesulfonate anion, naphthalenesulfonate anion, _{^{CH 3 SO 3 -, CF 3}} SO 3 - and the like organic sulfonic acid _{^{anion, CF 3 COO -, C 6}} H 5 COO - a carboxylic acid anion, OH ^- is a monovalent anion such as ] The ion exchange membrane according to claim 1, wherein the membrane resistance of the ion exchange membrane is 10 Ωcm ² or less. The ion exchange membrane according to claim 1, wherein the ionic vinyl alcohol polymer is subjected to a crosslinking treatment with an aldehyde. Preparing an ionic vinyl alcohol block copolymer solution;
Applying a solution of the ionic vinyl alcohol block copolymer on the release sheet to form a coating layer of the ionic vinyl alcohol block copolymer;
A step of superposing a fiber support on the coating layer and impregnating at least a part of the support with an ionic vinyl alcohol block copolymer to form an impregnated body;
Drying the impregnated body in a state where the coating layer and the support are overlapped;
And peeling the release sheet from the dried impregnated body;
The manufacturing method of the ion exchange membrane containing this.   5. The method for producing an ion exchange membrane according to claim 4, wherein the ionic vinyl alcohol block copolymer is subjected to a heat treatment after the peeling step. An electrodialyzer comprising at least an anode and a cathode, and a desalting chamber and a concentrating chamber formed by alternately arranging an anion exchange membrane and a cation exchange membrane between the anode and the cathode. The anion exchange membrane and the cation exchange membrane are electrodialyzers each comprising the ion exchange membrane according to any one of claims 1 to 5.