JP2014088514A - Anion-exchange membrane and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anion-exchange membrane suppressing organic contamination and excellent in durability and basic characteristics such as membrane resistance and ion transport number property, and to provide its manufacturing method.SOLUTION: An anion-exchange membrane contains a crosslinking-treated polyvinyl alcohol copolymer containing a quaternary ammonium base having the modified amount of over 5 mol%, and has a moisture content of 0.25 and more and less than 0.35.

Description

  The present invention is characterized in that a polyvinyl alcohol copolymer having a quaternary ammonium base having a modification amount of more than 5 mol% is subjected to a crosslinking treatment and has a water content of 0.25 or more and less than 0.35. The present invention relates to an anion exchange membrane. More specifically, the present invention relates to an anion exchange membrane for electrodialysis having low membrane resistance and excellent durability with little organic contamination of the membrane.

  Ion exchange membranes are currently used for a wide variety of applications such as seawater concentration, desalination of ground brine for drinking water, removal of nitrate nitrogen, removal of salt in food manufacturing processes and concentration of active pharmaceutical ingredients. It is used as a membrane in electrodialysis and diffusion dialysis. The useful ion exchange membranes used in these are mainly styrene-divinylbenzene-based homogeneous ion exchange membranes, and various kinds such as monovalent and divalent ion selection, increased specific ion selectivity, low membrane resistance, etc. Technology has been developed and industrially useful separation has been achieved.

  In general, in the synthesis process of organic substances in the above-mentioned fields such as foods, pharmaceuticals, and agricultural chemicals, salts and the like are often by-produced. The salts contained in such organic substances are often separated by electrodialysis. In salt separation by electrodialysis, cation exchange membranes and anion exchange membranes are arranged alternately, and direct current is applied to cause cations to flow on the cathode side of the cation exchange membrane and on the anode side of the anion exchange membrane. Desalting is realized by eliminating the anion and thus removing the salt from the electrolyte solution concentrated in the chamber formed by being sandwiched between the cation exchange membrane on the cathode side and the anion exchange membrane on the anode side. When desalting the treatment liquid by electrodialysis, organic pollutants in the liquid to be treated, especially macromolecules having a charge (hereinafter referred to as giant organic ions) adhere to the ion exchange membrane and reduce the performance of the membrane. The problem of organic contamination of the film arises. In addition, this organic contamination easily contaminates the anion exchange membrane, and the membrane performance gradually deteriorates as the dialysis cycle progresses. When the contamination is significant, the membrane may swell or break down in a relatively short period of time. There is.

  Conventionally, as ion exchange membranes that suppress organic contamination, ion exchange membranes that prevent the entry of giant organic ions into the membrane at the membrane surface layer, and ion exchanges that allow giant organic ions to easily permeate the membrane Membranes have been proposed.

  The above-described ion exchange membrane that prevents the invasion of giant organic ions into the membrane is a membrane in which a thin layer of neutral, amphoteric or oppositely charged ion exchange groups is formed on the membrane surface. The effect of this ion exchange membrane becomes more remarkable as the membrane structure is denser and the molecular weight of the giant organic ions is larger. As a representative example of the above-mentioned ion exchange membrane, an anion exchange membrane in which sulfonic acid groups having opposite charges are introduced into the surface layer portion of a resin membrane having an anion exchange group to suppress the penetration of organic anions into the membrane (patents) Reference 1). Furthermore, an anion exchange membrane (Patent Document 2) is disclosed in which organic contamination is improved by devising the structure of an anion pair of an anion exchange group.

  On the other hand, the method of facilitating the permeation of giant organic ions is easily achieved by loosening the membrane structure.

  However, the ion exchange membrane that prevents the invasion of the giant organic ions into the membrane can exhibit a certain degree of organic contamination resistance, but the formation of an oppositely charged layer provided on the surface layer portion of the resin membrane. As a result, the film resistance is remarkably increased. Furthermore, the method of facilitating the permeation of giant organic ions inevitably has a problem that the ion selectivity is inevitably lowered, and as a result, the efficiency in electrodialysis or the like is lowered.

  In addition, an anion exchange membrane with a modified anion pair structure of an anion exchange group does not satisfy the organic contamination resistance.

  As a polyvinyl alcohol-based anion exchange membrane that is easy to manufacture and excellent in membrane strength, an ion exchange membrane (Non-Patent Document 1) formed by crosslinking a blend film of polyvinyl alcohol and a polyallylamine resin is disclosed. However, since the polyallylamine resin does not participate in the crosslinking reaction, the uncrosslinked resin in the film is eluted over time in the environment of use, and there is a problem that the durability is poor.

  As described above, an anion exchange membrane for electrodialysis that has low membrane resistance, little organic contamination of the membrane, and is economical and excellent in durability has not been proposed.

Japanese Patent Publication No.51-40556 Japanese Patent Laid-Open No. 3-146525

Desalination, Vol. 233, p. 157 (2008)

  Therefore, the present invention has been made to solve the above problems, and is excellent in productivity, suppresses organic contamination, and has excellent basic characteristics such as membrane resistance and ion selectivity and durability. The object is to provide an anion exchange membrane.

  The inventors of the present invention have made extensive studies to achieve the above object. As a result, the polyvinyl alcohol copolymer having a quaternary ammonium base having a modification amount of more than 5 mol% is subjected to a crosslinking treatment, and the water content is 0.25 or more and less than 0.35. An anion exchange membrane was found to be an ion exchange membrane for electrodialysis excellent in durability and exhibiting excellent organic contamination resistance without degrading basic properties such as membrane resistance and ion transport number, and the present invention. It came to be completed.

  Since the anion exchange membrane of the present invention has high organic contamination resistance and low membrane resistance, electrodialysis can be performed efficiently and stably over a long period of time.

It is a schematic diagram of the membrane resistance test apparatus of this invention.

  The anion exchange membrane of the present invention is obtained by crosslinking a polyvinyl alcohol (hereinafter referred to as PVA) copolymer having a quaternary ammonium base having a modification amount of more than 5 mol% and having a water content of 0.25. As mentioned above, it is an anion exchange membrane characterized by being less than 0.35.

  Examples of the quaternary ammonium base include those having a structural unit represented by the following general formula (1).

Examples of the counter anion X ⁻ in the general formula (1) include halide ions, hydroxide ions, phosphate ions, carboxylate ions, and the like. Examples of the cationic polymer containing the structural unit represented by the general formula (1) include 3- (meth) acrylamidopropyltrimethylammonium chloride and 3- (meth) acrylamide-3,3-dimethylpropyltrimethylammonium chloride. Examples include homopolymers or copolymers of-(meth) acrylamide-alkyltrialkylammonium salts.

  A feature of the anion exchange membrane of the present invention is that a PVA copolymer having a quaternary ammonium base having a modification amount of more than 5 mol% is subjected to a crosslinking treatment, and the swelling degree is 0.25 or more and less than 0.35. It is a point. Generally, when the amount of ion modification in the polymer increases, the degree of swelling increases and the membrane resistance decreases, but the ion selectivity such as ion transport number deteriorates. In this respect, the membrane resistance is small by controlling the crosslinking state using a PVA copolymer having a hydroxyl group as a crosslinking point in the polymer in the repeating unit, and electrodialysis is efficiently and stably performed over a long period of time. There is an advantage that an anion exchange membrane can be obtained

  In the present invention, the PVA containing a quaternary ammonium base is obtained by copolymerizing a monomer containing a quaternary ammonium base and a vinyl ester monomer and saponifying this by a conventional method. The vinyl ester monomer can be used as long as it can be radically polymerized. For example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valenate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate and the like can be mentioned. Among these, vinyl acetate is preferable.

  Examples of a method for copolymerizing a monomer containing a quaternary ammonium base and a vinyl ester monomer include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. . Among these methods, a bulk polymerization method performed without a solvent or a solution polymerization method performed using a solvent such as alcohol is usually employed. When the copolymerization reaction is carried out using the solution polymerization method, examples of the alcohol used as the solvent include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. As initiators used for the copolymerization reaction, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis (2,4-dimethyl-valeronitrile), 1,1′-azobis (Cyclohexane-1-carbonitrile), azo initiators such as 2,2′-azobis (N-butyl-2-methylpropionamide); peroxide initiators such as benzoyl peroxide and n-propyl peroxycarbonate And known initiators such as an agent. Although there is no restriction | limiting in particular about the polymerization temperature at the time of performing a copolymerization reaction, The range of 5 to 180 degreeC is suitable.

  The vinyl ester polymer obtained by copolymerizing a monomer containing a quaternary ammonium base and a vinyl ester monomer is then saponified in a solvent in accordance with a known method to give an ionic group. It leads to PVA containing.

  Alkaline substances are usually used as catalysts for saponification reactions of vinyl ester polymers. Examples thereof include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and alkali metal alkoxides such as sodium methoxide. It is done. The saponification catalyst may be added all at once in the early stage of the saponification reaction, or a part thereof may be added in the early stage of the saponification reaction, and the rest may be added and added during the saponification reaction. Examples of the solvent used for the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, diethyl sulfoxide, dimethylformamide and the like. Of these solvents, methanol is preferred. The saponification reaction can be carried out by either a batch method or a continuous method. After completion of the saponification reaction, the remaining saponification catalyst may be neutralized as necessary, and usable neutralizing agents include organic acids such as acetic acid and lactic acid, and ester compounds such as methyl acetate. .

  Although the saponification degree of PVA containing a quaternary ammonium base is not particularly limited, it is preferably 40 to 99.9 mol%. If the degree of saponification is less than 40 mol%, the crystallinity is lowered and the strength of the anion exchange membrane may be insufficient. The saponification degree is more preferably 60 mol% or more, and further preferably 80 mol% or more. Usually, the saponification degree is 99.9 mol% or less. At this time, the saponification degree when the PVA is a mixture of a plurality of types of PVA refers to the average saponification degree of the whole mixture. The saponification degree of PVA is a value measured according to JIS K6726. The saponification degree of the PVA containing no ionic group used in the present invention is also preferably in the above range.

  The viscosity average polymerization degree of PVA containing a quaternary ammonium base (hereinafter sometimes simply referred to as polymerization degree) is not particularly limited, but is preferably 50 to 10,000. If the degree of polymerization is less than 50, the anion exchange membrane may not be able to maintain sufficient strength in practice. More preferably, the degree of polymerization is 100 or more. If the degree of polymerization exceeds 10,000, the viscosity of the aqueous polymer solution is too high, making it difficult to form a film, and there is a possibility that defects may easily occur in the resulting film. The degree of polymerization is more preferably 8000 or less. In addition, the viscosity average degree of polymerization of PVA is a value measured according to JIS K6726.

  In addition, the PVA containing a quaternary ammonium base used in the present invention is preferably composed only of units enclosed by n in the general formula (1), but it is a monomer unit having no anion exchange group. May be included. Examples of the monomer that gives a monomer unit having no anion exchange group include α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; acrylic acid or a salt thereof, or acrylic. Acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate and isopropyl acrylate; methacrylic acid or salts thereof, or methacryl such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate Acid esters; fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride and other unsaturated carboxylic acids or derivatives thereof; acrylamide derivatives such as acrylamide, N-methylacrylamide, N-ethylacrylamide; methacrylamide N-methylmeta Methacrylamide derivatives such as rilamide, N-ethylmethacrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether; ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, 1, Hydroxyl group-containing vinyl ethers such as 4-butanediol vinyl ether; allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, hexyl allyl ether; monomers having an oxyalkylene group; isopropenyl acetate, 3-butene- 1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-3- Hydroxyl group-containing α-olefins such as buten-1-ol; monomers having sulfonic acid groups such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid; vinyl Examples thereof include monomers having a silyl group such as trimethoxysilane, vinyltriethoxysilane, and vinyltriacetoxysilane. The proportion of the monomer unit having an ion-exchange group in the polymer block (B) is preferably 80 mol% or more, particularly 90 mol% or more.

  In order to develop sufficient ion exchange properties for use as an anion exchange membrane for electrodialysis, the resulting PVA containing a quaternary ammonium base should have an ion exchange capacity of 1.0 meq / g or more. Preferably, it is 1.2 meq / g or more. The upper limit of the ion exchange capacity of the block copolymer is preferably 3.0 meq / g or less, because if the ion exchange capacity becomes too large, hydrophilicity increases and it becomes difficult to suppress the degree of swelling.

  As a solvent used when obtaining a film from a solution of PVA containing a quaternary ammonium base, usually a lower alcohol such as water, methanol, ethanol, 1-propanol, 2-propanol, or a mixed solvent thereof is used. The film is usually obtained by volatilizing these solvents by casting. The film forming temperature for obtaining the film is not particularly limited, but a temperature range of about room temperature to about 100 ° C. is usually appropriate.

  The anion exchange membrane of the present invention preferably has a thickness of about 1 to 1000 μm from the viewpoint of performance required as an electrolyte membrane for electrodialysis, membrane strength, handling properties, and the like. When the film thickness is less than 1 μm, the mechanical strength of the film tends to be insufficient. On the other hand, when the film thickness exceeds 1000 μm, the membrane resistance increases and sufficient ion exchange properties are not exhibited, so that the electrodialysis efficiency tends to decrease. Preferably it is 5-500 micrometers, More preferably, it is 7-300 micrometers.

  In the method for producing an ion exchange membrane of the present invention, it is preferable to perform a heat treatment. By performing the heat treatment, physical crosslinking occurs, and the mechanical strength of the resulting ion exchange membrane is increased. 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, In the case of PVA, it is preferable that it is 50-250 degreeC. If the temperature of the heat treatment is less than 50 ° C., the mechanical strength of the obtained ion exchange membrane may be insufficient. The temperature is more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher. When the temperature of the heat treatment exceeds 250 ° C., the crystalline polymer may be melted. The temperature is more preferably 230 ° C. or less, and further preferably 200 ° C. or less.

  In the method for producing an ion exchange membrane of the present invention, it is essential to perform a crosslinking treatment. By performing the crosslinking treatment, the mechanical strength of the obtained ion exchange layer is increased. 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 chemical bonding. Usually, a method of immersing in a solution containing a crosslinking agent is used. Examples of the crosslinking agent include glutaraldehyde, formaldehyde, glyoxal and the like. The concentration of the crosslinking agent is usually 0.001 to 1% by volume of the crosslinking agent relative to the solution.

  In the manufacturing method, both heat treatment and crosslinking treatment may be performed, or only one of them may be performed. When both the heat treatment and the crosslinking treatment are performed, the crosslinking treatment may be performed after the heat treatment, the heat treatment may be performed after the crosslinking treatment, or both may be performed simultaneously. It is preferable from the viewpoint of the mechanical strength of the resulting ion exchange membrane to perform a crosslinking treatment after the heat treatment.

  Hereinafter, examples will be given to describe the present invention in more detail, but the present invention is not limited to these examples. In the examples, “%” and “parts” are based on weight unless otherwise specified. The characteristics of the ion exchange membranes shown in Examples and Comparative Examples were measured by the following methods.

1) Membrane moisture content (H)
The dry weight of the ion exchange membrane was measured in advance, and then the wet weight was measured when it was immersed in deionized water and reached a swelling equilibrium. The membrane water content, H, was calculated by the following equation.
_{H = <(W w -D w} ) /1.0> / <(W w -D w) /1.0+ (D w /1.3)>
Here, 1.0 and 1.3 indicate the specific gravity of water and polymer, respectively.
H: Membrane moisture content [-]
D _w : Dry weight of the film [g]
W _w : wet weight of the film [g]

2) Measurement of ion exchange capacity The ion exchange membrane is immersed in a 1 mol / l HCl aqueous solution for 10 hours or more. Thereafter, in the case of an anion exchange membrane, the chloride ion type is replaced with the nitrate ion type with 1 mol / l NaNO ₃ aqueous solution, and the liberated chloride ion is detected with a potentiometric titrator (COMMITE-900; manufactured by Hiranuma Sangyo Co., Ltd.). Quantified (Amol).

Next, the same ion exchange membrane is immersed in a 1 mol / l HCl aqueous solution for 4 hours or more, washed thoroughly with ion exchange water, taken out of the membrane, wiped off the moisture on the surface with tissue paper or the like, and weighed when wet ( W) was measured. The ion exchange capacity was calculated by the following formula.
Ion exchange capacity = A × 1000 / W [mmeq / g]

3) Measurement of membrane resistance The membrane resistance was measured by sandwiching an ion exchange membrane in a two-chamber cell having a platinum black electrode plate shown in FIG. 2, filling a 0.5 mol / L-NaCl solution on both sides of the ion exchange membrane, and alternating current. The resistance between the electrodes at 25 ° C. was measured by a bridge (frequency: 1000 cycles / second), and the resistance was determined 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.

4) Durability test An ion exchange membrane was incorporated into a tabletop electrodialysis apparatus Microacylator S-3 (manufactured by Astom Co., Ltd.), and 0.05 mol / L-NaCl in raw water at a predetermined current density (J = 10 mA ⁻² ). A batch treatment was performed with the solution, and the treatment water concentration was set to be a 0.005 mol / L-NaCl solution after 6 hours, which was defined as one cycle. By repeating this, electrodialysis was performed for a total of 72 hours. An effective membrane area of 49.5 cm ² (4.5 cm × 11 cm) was performed with 10 cell pairs. Thereafter, the membrane was taken out and the membrane resistance was measured (R ₁ ). The ratio of the membrane resistance (R ₀ ) before electrodialysis to r = R ₁ / R ₀ was used as an index of membrane durability.

5) Measurement of organic contamination resistance In the anion exchange membrane, after conditioning the obtained anion exchange membrane, the ion exchange membrane is sandwiched between two chamber cells having silver and silver chloride electrodes, A 0.05 mol / L-NaCl solution was placed, and a mixed solution of 1000 ppm sodium dodecylbenzenesulfonate and 0.05 mol / L-NaCl was placed in the cathode chamber. The liquid in both chambers was stirred at 1500rpm rotational speed, was electrodialysis at a current density of 0.2 A / dm ^2. At this time, a platinum wire was fixed in the vicinity of both membrane surfaces, and the transmembrane voltage was measured. When organic contamination occurs during energization, the transmembrane voltage increases. The voltage across the membrane 30 minutes after the start of energization was measured, and the voltage difference (ΔE) between when the organic contaminant was added and when it was not added was taken as a measure of the contamination of the membrane.

(Synthesis of P-1)
A 6 L separable flask equipped with a stirrer, temperature sensor, dropping funnel and reflux condenser was charged with 1875 g of vinyl acetate, 605 g of methanol, and 101 g of a methanol solution containing 20% by mass of amidopropyltrimethylammonium methacrylate under stirring. After the system was purged with nitrogen, the internal temperature was raised to 60 ° C. To this system, 20 g of methanol containing 0.8 g of 2,2′-azobisisobutyronitrile (total amount of methanol: 625 g) was added to initiate the polymerization reaction. While adding 346 g of a methanol solution containing 20% by mass of methacrylic acid amidopropyltrimethylammonium chloride to the system from the start of polymerization, the polymerization reaction was carried out for 4 hours, and then the polymerization reaction was stopped. The solid content concentration in the system when the polymerization reaction was stopped, that is, the solid content with respect to the entire polymerization reaction slurry was 23% by mass. Subsequently, by introducing methanol vapor into the system, unreacted vinyl acetate monomer was driven off to obtain a methanol solution containing 55% by mass of a vinyl ester copolymer.

  In a methanol solution containing 55% by mass of this vinyl ester copolymer, the molar ratio of sodium hydroxide to vinyl acetate units in the copolymer is 0.02, and the solid content concentration of the vinyl ester copolymer is 30% by mass. Then, methanol and a methanol solution containing 10% by mass of sodium hydroxide were added in this order with stirring, and the saponification reaction was started at 40 ° C.

  Immediately after the saponification reaction has occurred, the gelled product is taken out from the reaction system and pulverized. Then, when 1 hour has passed since the gelated product was formed, methyl acetate is added to the pulverized product. Thus, neutralization was performed to obtain a cationic polymer of poly (vinyl alcohol-amidopropyltrimethylammonium chloride) in a swollen state. To this swollen cationic polymer, methanol was added in an amount 6 times (bath ratio 6 times) by mass, washed for 1 hour under reflux, and the polymer was collected by filtration. The polymer was dried at 65 ° C. for 16 hours. The obtained polymer was dissolved in heavy water and subjected to 1H-NMR measurement at 400 MHz. As a result, the amount of modification of amidopropyltrimethylammonium methacrylate units was 5 mol%. Further, the viscosity of a 4% aqueous solution measured with a B-type viscometer was 18 milliPa · s (20 ° C.), and the degree of saponification was 98.5 mol%.

(Synthesis of P-2 to P-3)
P-2 to P- were prepared in the same manner as P-1, except that the polymerization conditions such as the type and amount of the cationic group-containing monomer and the amount of polymerization initiator used were changed as shown in Table 2. 3 was obtained. Table 1 shows the physical properties of the obtained polymer.

[Example 1]
(Production of ion exchange membrane)
In a 200 mL Erlenmeyer flask, 150 mL of deionized water is added, 22.2 g of the quaternary ammonium base-containing polymer P-1 is added, and the mixture is heated and stirred in a 95 ° C. water bath. Dissolved. The PVA aqueous solution was poured onto an acrylic cast plate having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film. The film thus obtained was heat treated at 140 ° C. for 30 minutes to cause physical crosslinking. Subsequently, the film was immersed in an aqueous electrolyte solution of 2 mol / L sodium sulfate for 24 hours. Concentrated sulfuric acid was added to the aqueous solution so that the pH was 1, and then the film was immersed in a 1.0% by volume glutaraldehyde aqueous solution and stirred with a stirrer at 25 ° C. for 24 hours 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 crosslinking 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, thereby obtaining an ion exchange membrane.

(Evaluation of ion exchange membrane)
The anion exchange membrane thus produced was cut into a desired size to produce a measurement sample. Using the obtained measurement sample, according to the above method, the membrane water content, ion exchange capacity, membrane resistance, durability test, and organic contamination resistance were measured. The obtained results are shown in Table 2.

[Examples 2-3]
In Example 1, the membrane characteristics of the anion exchange membrane were measured in the same manner as in Example 1 except that the anion exchange resin, the heat treatment temperature, and the crosslinking conditions were changed to those shown in Table 2. The obtained measurement results are shown in Table 2.

[Comparative Examples 1-3]
In Example 1, the membrane characteristics of the anion exchange membrane were measured in the same manner as in Example 1 except that the anion exchange resin, the heat treatment temperature, and the crosslinking conditions were changed to those shown in Table 2. The obtained measurement results are shown in Table 2.

[Comparative Example 4]
(Production of ion exchange membrane)
150 mL of deionized water is placed in a 200 mL Erlenmeyer flask, 20 g of PVA117 (manufactured by Kuraray Co., Ltd .: degree of saponification 98.5 mol%, viscosity average degree of polymerization 1700), and 2.2 g of polyallylamine (manufactured by Nittobo Co., Ltd.) After the addition, the mixture was heated and stirred in a 95 ° C. water bath to dissolve the polyallylamine. The PVA aqueous solution was poured onto an acrylic cast plate having a length of 270 mm and a width of 210 mm to remove excess liquid and bubbles, and then dried on a hot plate at 50 ° C. for 24 hours to prepare a film. The film thus obtained was heat treated at 140 ° C. for 30 minutes to cause physical crosslinking. Subsequently, the film was immersed in an aqueous electrolyte solution of 2 mol / L sodium sulfate for 24 hours. Concentrated sulfuric acid was added to the aqueous solution so that the pH was 1, and then the film was immersed in a 0.5% by volume glutaraldehyde aqueous solution and stirred with a stirrer at 25 ° C. for 24 hours for 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 crosslinking 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, thereby obtaining an ion exchange membrane.

(Evaluation of ion exchange membrane)
The anion exchange membrane thus produced was cut into a desired size to produce a measurement sample. Using the obtained measurement sample, according to the above method, the membrane water content, ion exchange capacity, membrane resistance, durability test, and organic contamination resistance were measured. The obtained results are shown in Table 2.

[Comparative Example 5]
In Example 1, the membrane characteristics of the ion exchange membrane were measured in the same manner as in Example 1 except that Neoceptor AM-1 (manufactured by Tokuyama Corporation) was used for the anion exchange membrane. The obtained measurement results are shown in Table 2.

  From the results shown in Table 2, the PVA copolymer having a quaternary ammonium base having a modification amount exceeding 5 mol% is subjected to a crosslinking treatment, and the water content is 0.25 or more and less than 0.35. It can be seen that by using the anion exchange membrane as described above, the membrane resistance is low and the durability and organic contamination resistance are excellent (Examples 1 to 3). In particular, when the ion exchange capacity is 1.0 meq / g or more, it can be seen that the membrane resistance is lower and the organic contamination resistance is excellent (Example 3). On the other hand, when the moisture content of the membrane was less than 0.25, the membrane resistance increased (Comparative Example 1). Furthermore, if the crosslinking treatment was not performed, the ion exchange membrane was swollen and the membrane characteristics could not be measured (Comparative Example 2). In addition, the blend film of PVA and polyallylamine had low durability due to elution of polyallylamine during the electrodialysis test (Comparative Example 4). When a commercially available membrane was used, the organic contamination resistance was poor (Comparative Example 5).

Claims (4)

  Anion exchange, characterized in that a polyvinyl alcohol copolymer having a quaternary ammonium base having a modification amount exceeding 5 mol% is subjected to a crosslinking treatment and has a water content of 0.25 or more and less than 0.35 film. The anion exchange membrane according to claim 1, wherein the repeating unit of the quaternary ammonium base is a polyvinyl alcohol copolymer represented by the following general formula (1).

  The anion exchange membrane according to claim 1 or 2, wherein the ion exchange capacity is 1.0 meq / g or more.   A film containing a PVA copolymer is heat-treated at a temperature of 100 ° C. or higher, then subjected to a crosslinking treatment with a dialdehyde compound in water, alcohol or a mixed solvent thereof under an acidic condition, and then washed with water. The manufacturing method of the anion exchange membrane of any one of Claims 1-3 characterized by the above-mentioned.

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