Anion exchange membrane and method for manufacturing the same

Abstract

An anion exchange membrane having an anion exchange resin layer (3) reinforced by a base sheet (5), characterized in that the anion exchange resin layer (3) contains an anion exchange resin having a pyridinium group obtained by protonating a pyridyl group as an anion exchange group and a vinyl chloride resin as a thickening agent, and the base sheet (5) is a polyethylene woven fabric.

Description

Technical Field

[0001] This invention relates to an anion exchange membrane having a protonated pyridinium group as an anion exchange group and a method for manufacturing the same. Background Technology

[0002] Anion exchange membranes are formed by anion exchange resin layers with a substrate sheet serving as a reinforcing material as the core material. They are widely used in combination with cation exchange membranes and bipolar membranes for salt production, desalination, or electrodialysis to produce acids and alkalis from neutral salts.

[0003] Anion exchange membranes having a pyridinium group as an anion exchange group are known (hereinafter, sometimes referred to as 4VP-based anion exchange membranes). These 4VP-based anion exchange membranes are readily obtained by acid treatment of a precursor having a pyridinium group as a functional group. That is, by placing the pyridinium group in an acidic environment, a pyridinium group that functions as an anion exchange membrane is rapidly generated. When this 4VP-based anion exchange membrane is combined with a bipolar membrane and a cation exchange membrane for desalination via electrodialysis, acid concentration is achieved with high efficiency (see Patent Document 1). This is because the protons (H+) generated in the bipolar membrane... + The leakage into the desalination chamber is blocked by the anion exchange membrane.

[0004] However, 4VP-based anion exchange membranes suffer from the drawback of shrinkage upon contact with water. Specifically, while 4VP-based anion exchange membranes function as ion exchange membranes through the coordination of protons with the nitrogen atom of the pyridine ring, their low pKa value means that protons can only coordinate in acidic environments. Therefore, it is believed that deprotonation occurs upon contact with water, resulting in the expulsion of counterions and the release of hydrated ions, ultimately leading to overall membrane shrinkage.

[0005] In addition, the dimensional stability of 4VP anion exchange membranes can be improved by using polyethylene powder as a thickener, but in this case, there is a problem of reduced membrane current efficiency and consequently poor water permeability.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 5-184877 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Therefore, the purpose of this invention is to provide a 4VP-based anion exchange membrane with excellent dimensional stability that inhibits membrane shrinkage caused by contact with water, and a method for manufacturing the same.

[0011] Another objective of this invention is to provide an anion exchange membrane that, in addition to dimensional stability, has high current efficiency and good water permeability, and a method for manufacturing the same.

[0012] Solution for solving the problem

[0013] According to the present invention, an anion exchange membrane is provided, having an anion exchange resin layer reinforced by a substrate sheet, characterized in that...

[0014] The anion exchange resin layer comprises anion exchange resin and vinyl chloride resin as a thickener, wherein the anion exchange resin contains pyridinium groups formed by protonation of pyridinium groups as anion exchange groups.

[0015] The substrate sheet is made of polyethylene fabric.

[0016] In the anion exchange membrane (i.e., the 4VP-based anion exchange membrane) of the present invention, the following manner is preferred.

[0017] (1) The average degree of polymerization of the vinyl chloride resin is 650 to 1200.

[0018] (2) The anion exchange membrane contains the vinyl chloride resin in an amount of 5 to 25% by mass.

[0019] (3) The polyethylene woven substrate sheet has a thickness of 120-160 μm.

[0020] (4) The polyethylene woven substrate sheet has an opening ratio of 35-55%.

[0021] (5) The shrinkage rate of the membrane after being immersed in 0.5N-HCl aqueous solution and then immersed in pure water for 3 days was less than 2.3%.

[0022] (6) Current efficiency is above 55%, and water permeability is below 1000 ml / m. 2 ·Hr.

[0023] According to the present invention, a method for manufacturing an anion exchange membrane is also provided, comprising:

[0024] A process for preparing a polymerizable composition containing 4-vinylpyridine as a monomer component and vinyl chloride resin as a thickener;

[0025] The process of impregnating the polymeric composition into a polyethylene woven substrate sheet to produce a polymeric sheet;

[0026] The process of overlapping the polymeric sheet and the release sheet and winding them into a roll;

[0027] The polymerization process involves heating the polymeric sheet wound on the roll to polymerize it, thereby obtaining a polymer sheet.

[0028] The peeling process for obtaining an ion exchange precursor membrane by peeling a peeling sheet from the polymer sheet; and the peeling sheet peeling process.

[0029] The protonation process involves immersing the ion exchange precursor membrane in an acid solution to protonate the pyridine matrix, thereby obtaining an anion exchange membrane.

[0030] In the manufacturing method of the present invention, it is preferred that the vinyl chloride resin is incorporated into the polymeric composition in an amount of 5 to 25% by mass in the obtained anion exchange membrane.

[0031] The effects of the invention

[0032] For the anion exchange membrane of the present invention, an anion exchange resin containing a protonated pyridinium group as the anion exchange group is used as the anion exchange resin. Therefore, it is referred to as a 4VP-based anion exchange membrane. However, it is characterized by using a specific substrate sheet (polyethylene fabric) and distributing a specific thickener (vinyl chloride resin) in the anion exchange resin layer. This results in excellent dimensional stability and effectively suppresses membrane shrinkage when in contact with water. For example, as shown in the examples described later, when the membrane treated with a 0.5N HCl aqueous solution was immersed in pure water for 3 days, and the membrane shrinkage rate was measured (detailed conditions are described in the examples), the shrinkage rate of the conventionally known 4VP-based anion exchange membrane (Comparative Example 1; using polyvinyl chloride fabric as the substrate sheet and NBR as the thickener) was 2.8%, but in the 4VP-based anion exchange membrane of the present invention (Examples 1-3), the shrinkage rate was suppressed to about 1.4-2.3%. Furthermore, the current efficiency is greater than 55%, and the water permeability is less than 1000 ml / m³. 2 •Hr, with excellent current efficiency and water permeability.

[0033] Furthermore, in Comparative Examples 2 and 3, where polyethylene powder was used instead of vinyl chloride resin as a thickener, the shrinkage rate was suppressed to a low level of 1.0–1.1%, but the current efficiency was as low as 54% or less, and the water permeability exceeded 40,000 ml / m³. 2 ·Hr, are all inferior to the present invention.

[0034] Thus, the 4VP-based anion exchange membrane of the present invention not only exhibits excellent dimensional stability but also superior current efficiency and water permeability. Therefore, when combined with cation exchange membranes and bipolar membranes for electrodialysis, it can prevent rupture caused by dimensional changes during device cleaning and disassembly and reassembly due to dimensional changes that prevent re-stacking, enabling long-term stable electrodialysis. In particular, the 4VP-based anion exchange membrane is best suited for acid concentration via electrodialysis in combination with bipolar and cation exchange membranes. Attached Figure Description

[0035] Figure 1 This is a schematic cross-sectional view showing the structure of the 4VP-based anion exchange membrane of the present invention. Detailed Implementation

[0036] <4VP anion exchange membrane>

[0037] Reference Figure 1 The 4VP-based anion exchange membrane of the present invention, as indicated by reference numeral 1 in the accompanying drawings, has a basic structure in which the anion exchange resin layer 3 is reinforced by a substrate sheet 5.

[0038] The anion exchange resin used in the formation of anion exchange resin layer 3 contains a pyridinium group as the anion exchange group. That is, the anion exchange resin contains repeating units of 4-vinylpyridine, as shown in the following formula, through proton (H + It functions as an anion exchange group by coordinating with the nitrogen atom in the pyridine ring.

[0039]

[0040] However, pyridine has a low PKa value of 5.25, therefore, the pyridinium group becomes a pyridinium group that functions as an anion exchange group only under acidic conditions through proton coordination. In contrast, conventional anion exchange resins utilize quaternary ammonium groups formed by completely methylating the nitrogen atom of the amino group as anion exchange groups. That is, unlike conventional quaternary ammonium salt-based anion exchange membranes, the generation of the anion exchange group in this invention does not require cumbersome processing or reactions.

[0041] The aforementioned 4VP anion exchange membranes readily allow acid-coordinated protons to pass through, but are prone to deprotonation due to contact with water (or an increase in pH). As mentioned earlier, along with deprotonation, counterions are expelled and hydrated ions are also released, resulting in the disadvantage of significant membrane shrinkage.

[0042] To eliminate such drawbacks, in this invention, a vinyl chloride resin, which functions as a thickener, is dispersed in the anion exchange resin layer 3, and a polyethylene fabric is used as the substrate sheet 5. Figure 1As shown, the fabric is woven using warp yarns 5a and weft yarns 5b. It can be plain weave, twill weave, or satin weave, but from the viewpoint of setting the opening rate within a certain range, plain weave is the preferred option.

[0043] That is, while vinyl chloride resin sheets are known as substrate sheets for ion exchange membranes, the vinyl chloride resin used in this invention is not used as a substrate sheet but as a thickener. Therefore, it is distributed in the anion exchange resin layer 3 in a granular form (i.e., not in a sheet shape but dispersed into islands). Furthermore, the substrate sheet 5 is limited to polyethylene fabric. By employing such a combination, the membrane shrinkage visible in conventionally known 4VP-based anion exchange membranes can be suppressed, resulting in not only high dimensional stability but also excellent current efficiency and water permeability.

[0044] In this invention, the reason why membrane shrinkage is suppressed by using the aforementioned vinyl chloride resin (thickener) and polyethylene fabric, and why current efficiency and water permeability are also improved, is not precisely explained, but the inventors of this invention speculate as follows.

[0045] That is, the thickener is mixed into the polymeric composition (containing 4-vinylpyridine) used to manufacture the anion exchange resin, and is used to increase the viscosity of the polymeric composition to a level that allows it to be coated onto a substrate sheet (woven fabric). It is used in powder or granular form, so that in the resulting anion exchange membrane (anion exchange resin layer 3), it exists in an island-like dispersion within the matrix (sea) of the anion exchange resin. The vinyl chloride resin powder (PVC powder) used as such a thickener has a high affinity for the monomers contained in the polymeric composition, and the monomer components easily penetrate into the PVC powder. Therefore, it is considered that the PVC powder blends well with the resulting ion exchange resin, making it difficult for gaps to form. Furthermore, it has higher strength compared to the polyethylene woven fabric itself, porous membranes, nonwoven fabrics, or vinyl chloride resin-based woven fabrics used as the substrate. Therefore, by combining the use of polyethylene woven fabric and vinyl chloride resin powder (PVC powder), a membrane with not only high dimensional stability (low shrinkage) but also excellent current efficiency and water permeability can be obtained. For example, when polyethylene powder is used instead of vinyl chloride resin powder, dimensional stability is improved because the monomer components are less prone to impregnation. However, because the monomer components of the ion exchange resin are difficult to fuse, gaps are easily formed in the ion exchange resin. Therefore, current efficiency and water permeability become unsatisfactory.

[0046] Furthermore, when using vinyl chloride resin sheets or porous sheets made of polyolefin as substrate sheets, the reinforcing effect of the substrate sheets is low. In particular, when using porous sheets made of polyolefin, the openings of the sheets are small, and thickener particles cannot enter the openings, so the reinforcing effect of the thickener is not apparent. In the 4VP-based anion exchange membrane of the present invention, when manufacturing the anion exchange membrane, from the perspective of ensuring the coatability of the polymerizable composition, the average degree of polymerization of the vinyl chloride resin used as a thickener is preferably in the range of 650 to 1200. This is because the lower the degree of polymerization of vinyl chloride, the greater the thickening effect, and the higher the degree of polymerization of vinyl chloride, the smaller the thickening effect. This range is desired in the present invention. In addition, from the viewpoint of obtaining the shrinkage suppression effect of the membrane without compromising the basic composition of the exchange membrane (anion exchange capacity, resistance, etc.) while ensuring the coatability brought about by thickening, the vinyl chloride resin is preferably present in the anion exchange membrane 1 in an amount of 5 to 25% by mass, particularly 6 to 20% by mass. Furthermore, in this invention, the polyethylene fabric used as the substrate sheet 5 is preferably a polyethylene fabric in a form that does not compromise strength and avoids an increase in resistance caused by the use of vinyl chloride resin.

[0047] For example, the thickness d of the polyethylene woven fabric (substrate sheet 5) is preferably in the range of 120 to 160 μm, and the opening ratio is preferably in the range of 35 to 55%. That is, it is very thin compared to the thickness of various woven fabrics conventionally used as substrate sheets, and the opening ratio is in a relatively large range. In addition, the diameter of the polyethylene monofilaments is relatively fine, in the range of about 60 to 80 μm.

[0048] By selecting the substrate sheet 5 as described above, the resistance of the 4VP-based anion exchange membrane 1, measured in 0.5 mol / L hydrochloric acid at 25°C, is preferably set to 5.0 Ω·cm. 2 The following range is further preferably 4.5 Ω·cm 2 The following range.

[0049] Furthermore, considering strength and operability, the thickness D of the 4VP-based anion exchange resin layer 3 is preferably in the range of approximately 100–200 μm. Additionally, the anion exchange groups (cationized pyridyl groups) in the 4VP-based anion exchange resin are ideally introduced into the resin at a ratio ensuring an ion exchange capacity of approximately 0.9–1.4 meq / g-dry weight. This is because if anion exchange groups are introduced in an amount exceeding the desired level, the shrinkage rate during deprotonation may increase; conversely, if the amount of anion exchange groups is insufficient, the ion exchange capacity cannot be fully utilized.

[0050] As will be seen from the embodiments described later, for the 4VP-based anion exchange membrane 1 of the present invention, the shrinkage rate (size change) is less than 2.5%, the current efficiency is 55% or more, more preferably the shrinkage rate (size change) is less than 2.3%, the current efficiency is 60% or more, and the water permeability is less than 1000 ml / m³. 2 •Hr. Additionally, with a moisture content of approximately 13–21%, its burst strength is approximately 1.0–1.1 MPa. The methods for measuring each parameter are described in the examples.

[0051] <Fabrication of 4VP-based Anion Exchange Membrane 1>

[0052] The 4VP-based anion exchange membrane 1 of the present invention, as described above, is manufactured through a polymerizable composition preparation process, a polymerizable sheet fabrication process, a winding process, a polymerization process, a release sheet peeling process, and a protonation process.

[0053] The following is a description of each process step in turn.

[0054] Preparation process of polymeric composition;

[0055] This process is for preparing a polymeric composition for obtaining a polymer (anion exchange resin precursor) that becomes an anion exchange resin by protonation.

[0056] Therefore, 4-vinylpyridine must be included as a monomer component, but shrinkage becomes significant with only 4-vinylpyridine. Therefore, other monomers, crosslinking monomers, and polymerization initiators are used to adjust the physical properties.

[0057] It should be noted that 4-vinylpyridine is a compound that serves as a source of anion exchange groups. Therefore, in this polymerizable composition, it is used in an amount that enables the aforementioned ion exchange capacity, for example, in an amount of 15 to 35 parts by mass, particularly 18 to 30 parts by mass, relative to the total amount of the polymerizable composition (equivalent to 100 parts by mass of anion exchange resin).

[0058] Other monomers that can copolymerize with 4-vinylpyridine include styrene, vinyltoluene, vinylxylene, α-methylstyrene, vinylnaphthalene, and acrylonitrile.

[0059] In addition, in principle, monomers with anion exchange groups that have been used in the past, such as vinylimidazole, vinylbenzyltrimethylamine, vinylbenzyltriethylamine and other nitrogen-containing vinyl compounds, can also be used.

[0060] In addition, crosslinking monomers are used to densify anion exchange resins, improve swelling inhibition, membrane strength, etc., and there are no particular limitations. For example, divinyl compounds as shown below can be cited.

[0061] Divinylbenzene

[0062] Divinyl sulfone

[0063] butadiene

[0064] Chloroprene

[0065] Divinylbiphenyl

[0066] Trivinylbenzene

[0067] Divinylnaphthalene

[0068] Diallylamine

[0069] Divinylpyridine

[0070] 1,2-Bis(vinylphenyl)ethane

[0071] Ethylene glycol dimethacrylate

[0072] N,N-Methylenebisacrylamide

[0073] Such crosslinking monomers are typically used in amounts of 0.1 to 50 parts by mass, particularly 1 to 40 parts by mass, relative to 100 parts by mass of the total amount of 4-vinylpyridine and other monomers that can copolymerize with it (hereinafter referred to as the basic monomer component).

[0074] As polymerization initiators, conventionally known polymerization initiators can be used without particular restrictions. Specifically, organic peroxide-based polymerization initiators such as octanoyl peroxide, lauroyl peroxide, tert-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, tert-butyl peroxyisobutyrate, tert-butyl peroxylaurate, tert-hexyl peroxybenzoate, and di-tert-butyl peroxide, and azo-based polymerization initiators such as azobisisobutyronitrile can be used.

[0075] The polymerization initiator is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of the basic monomer component, and more preferably 0.5 to 10 parts by mass.

[0076] Furthermore, in this invention, in the polymerizable composition containing the various components described above, vinyl chloride resin is used as a thickener to ensure a coatable viscosity without causing sagging or the like. This vinyl chloride resin preferably has the aforementioned average degree of polymerization and is used in powder or granular form. This average particle size varies due to heating during polymerization, and therefore differs from the dispersed particle size of the vinyl chloride resin in the anion exchange resin; for example, it may be the 50% particle size (D) calculated from the volume determined by laser diffraction scattering. 50The preferred particle size is in the range of 0.1 to 50 μm. If the particle size is large, it becomes difficult for the material to enter the openings in the polyethylene woven fabric (substrate sheet 5), thus potentially reducing the shrinkage inhibition effect of the membrane. Conversely, if the particle size is too small, not only does operation become difficult, but it is also difficult to obtain.

[0077] As previously mentioned, the amount of vinyl chloride resin used as such a thickener is in the range of 5% to 25% by mass, particularly 6% to 20% by mass, in the final anion exchange membrane 1, and is used in an amount that exhibits moderate coatability of the polymerizable composition (typically about 5 to 30 parts by mass relative to 100 parts by mass of the polymerizable composition).

[0078] It should be noted that in this invention, any thickener other than vinyl chloride resin can be used as long as it does not impede the film shrinkage inhibition effect of the vinyl chloride resin by a small amount. Examples of such thickeners include the following.

[0079] Saturated aliphatic hydrocarbon polymers such as ethylene-propylene copolymers and polybutene;

[0080] Styrene-butadiene copolymers and other styrene-based polymers;

[0081] Various types of rubber, including nitrile rubber, hydrogenated nitrile rubber, epichlorohydrin rubber, and chlorinated polyethylene rubber;

[0082] Substances obtained by copolymerizing various comonomers (such as vinyltoluene, vinylxylene, chlorostyrene, chloromethylstyrene, α-methylstyrene, α-halostyrene, α,β,β'-trihalostyrene and other styrene monomers, monoolefins such as ethylene and butene, conjugated dienes such as butadiene and isoprene, etc.) with the above-mentioned polymers.

[0083] Furthermore, in the above-mentioned polymerizable composition, in order to impart flexibility to the polymerized film, a plasticizer can be mixed in an appropriate amount as needed. As plasticizers, phthalates such as dioctyl phthalate and dibutyl phthalate, adipates such as dioctyl adipate and diisononyl adipate, epoxy compounds such as styrene oxide, and ethers such as diphenyl ether and dibenzyl ether can be used.

[0084] The above components are uniformly mixed in a typical liquid stirring blade tank, thereby preparing a polymerizable composition.

[0085] Polymer sheet manufacturing process;

[0086] The polymeric composition prepared as described above is coated onto a polyethylene fabric, which serves as the substrate sheet 5, to create a polymer sheet in which the openings of the fabric are filled with the polymeric composition. This polymer sheet becomes... Figure 1The anion exchange resin layer 3 forms the basis of which the aforementioned polyethylene fabric, which serves as a core material and has a reinforcing effect, is contained within it.

[0087] There are no particular limitations on the method of coating the polymeric composition onto polyethylene fabric. Common methods include brushing, roller coating, and impregnating the polyethylene fabric with the polymeric composition. Spraying is also an option. Furthermore, depending on the viscosity of the polymeric composition, methods such as contacting the polymeric composition with the polyethylene fabric under reduced pressure can also be used.

[0088] The thickness of the polymer sheet produced in this way (the coating thickness of the polymeric composition) is set so that the thickness after polymerization and curing is the same as the thickness of the aforementioned anion exchange resin layer 3 (approximately 100 to 200 μm).

[0089] The winding process;

[0090] In this invention, the polymer sheet prepared as described above is overlapped with a release sheet and wound into a roll. The resulting roll is used for efficient heating in the subsequent polymerization process. That is, heating in the state of the polymer sheet requires a large oven, which increases production costs, but heating in the form of a roll can be carried out in a compact oven.

[0091] It should be noted that, without overlapping with the release liner, the coating layers of the polymeric composition adhere tightly to each other, thus making it impossible to roll them up.

[0092] That is, the release sheet used above is unnecessary as an anion exchange membrane and is therefore removed after polymerization. Therefore, as long as the release sheet does not adversely affect the polymerization of the polymerizable composition and can be easily removed from the polymer, various materials can be used. Typically, readily available polyethylene terephthalate (PET) film is used.

[0093] Polymerization process;

[0094] As can be understood from the above description, the roll of polymer sheet overlapping the peeling sheet obtained above is heated, thereby obtaining a polymer of polymeric composition.

[0095] The heating temperature used for polymerization is set to an appropriate range based on the monomer composition used in combination with 4-vinylpyridine, the type of polymerization initiator, etc. Of course, it should be set to a temperature lower than the melting point of polyethylene used as the substrate sheet 5 and vinyl chloride resin used as the thickener, usually in the range of 70 to 90°C.

[0096] Alternatively, polymerization can be carried out using an oven or in an air atmosphere, but polymerization is sometimes hindered by oxygen in the air, so it is desirable to carry it out in a nitrogen atmosphere. Furthermore, the polymerization time varies depending on the polymerization temperature, and is typically around 2 to 5 hours.

[0097] Peeling process for release sheets;

[0098] After polymerization, the aforementioned roll is unwound, and the release sheet is peeled off, thereby removing the polymer sheet obtained by polymerization of the polymeric composition. This polymer sheet is referred to as an ion-exchange precursor membrane.

[0099] Protonation process;

[0100] This process involves coordinating protons with the nitrogen atoms of the pyridinium group contained in the aforementioned ion exchange precursor membrane to generate pyridinium, which can function as an anion exchange group.

[0101] Such protonation is carried out by contacting the ion exchange precursor membrane with an acid, which can usually be easily done by impregnating the ion exchange precursor membrane in an aqueous acid solution.

[0102] Various acids can be used as the acid, but hydrochloric acid, sulfuric acid, and phosphoric acid are usually preferred, and the acid concentration is preferably around 1 to 3 N.

[0103] After the protonation process, the membrane is washed with water and cut into appropriate sizes for use as anion exchange membranes.

[0104] The 4VP-based anion exchange membrane 1 obtained in this way is suitable for various electrodialysis methods, especially for electrodialysis devices used in combination with bipolar membranes and cation exchange membranes, and is most suitable for acid concentration.

[0105] Example

[0106] The following embodiments are provided to illustrate the present invention in more detail, but the present invention is not limited to these embodiments.

[0107] The following shows the substrate and thickener used in this embodiment and comparative example.

[0108] 1) Substrate;

[0109] Polyolefin fabric

[0110] High-density polyethylene monofilament fabric (PE-33D-120: NBC Meshtec Co., Ltd.)

[0111] Warp yarn: 76μm diameter - 120 yarns per inch (33 denier)

[0112] Weft yarn: 76μm diameter - 120 yarns per inch (33 denier)

[0113] Thickness: 132μm

[0114] Opening ratio: 41%

[0115] Polyvinyl chloride fabric

[0116] Manufactured by Teijin Co., Ltd. Product name: V-7275

[0117] Warp yarn: 274μm - 86 yarns per inch (84dtex)

[0118] Weft yarn: 213μm - 73 threads per inch (84dtex)

[0119] Thickness: 86μm

[0120] Opening ratio: 3%

[0121] 2) Thickener;

[0122] PVC powder

[0123] PQB-83: Made by Shin-Daiichi Polyvinyl Chloride Co., Ltd.

[0124] (Particle size 10–50 μm, average degree of polymerization: 700)

[0125] P-22: Made by Shin-Daiichi PVC Co., Ltd.

[0126] (Particle size 0.1–10 μm, average degree of polymerization: 1050)

[0127] PE powder

[0128] LE-1080: Made by Sumitomo Seika Co., Ltd.

[0129] (Particle size 0.1–10 μm)

[0130] EA-209: Made by Sumitomo Seika Co., Ltd.

[0131] (Particle size 0.1–15 μm)

[0132] Other thickeners;

[0133] H-NBR:

[0134] Hydrogenated nitrile rubber

[0135] (Product name: zetpol2000L manufactured by Zeon Co., Ltd., Japan)

[0136] NBR:

[0137] The properties of the ion exchange membranes shown in the examples and comparative examples of nitrile rubber (trade name: N230SH, manufactured by JSR Corporation) were determined by the following methods.

[0138] <Aperture Ratio of Filament Substrate>

[0139] The calculation is performed according to the following formula (1) based on the yarn diameter (μm) and mesh count of the yarn constituting the substrate.

[0140] Opening ratio (%) = (opening) 2 / (opening + wire diameter) 2 …(1)

[0141] The coefficients in equation (1) above are as follows.

[0142] Aperture (μm) = 25400 / mesh count - wire diameter (μm)

[0143] Mesh count = the number of yarn threads per inch (average).

[0144] <Shrinkage rate>

[0145] The ion exchange membrane was immersed in 0.5 mol / L HCl aqueous solution for more than 12 hours, and then the size (L0) of the ion exchange membrane was measured.

[0146] The ion exchange membrane was then thoroughly washed with ion-exchange water and immersed in ion-exchange water for 72 hours. The membrane size (L1) was then measured, and the shrinkage rate was calculated using the following formula (2).

[0147] Shrinkage rate (%) = (1 - L1 / L0) × 100…(2)

[0148] Current efficiency

[0149] Use a 2-compartment unit with the following structure.

[0150] Cathode (silver chloride plate);

[0151] (0.5 mol / L hydrochloric acid) / anion exchange membrane / (3 mol / L hydrochloric acid)

[0152] Anode (silver plate);

[0153] At a liquid temperature of 25°C and a current density of 10 A / dm 2 One hour after energizing, the solution on the cathode side was recovered. The hydrochloric acid concentration of the recovered liquid and the initial liquid was quantified using a sodium hydroxide aqueous solution via a potentiometric titration apparatus (KEM AutoTitrator), and the current efficiency was calculated using the following formula (3).

[0154] Current efficiency (%) = {1 - (C)} S -C B ) / (I×t / F)}×100…(3)

[0155] The coefficients in equation (3) above are as follows.

[0156] C B Initial solution concentration

[0157] C S Concentration of the recovered liquid after energization

[0158] I: Current value (A)

[0159] t: Power-on time (sec)

[0160] F: Faraday constant (96500 C / mol)

[0161] <Rupture strength of ion exchange membranes>

[0162] The ion exchange membrane was immersed in a 0.01 mol / L HCl aqueous solution for at least 4 hours, and then thoroughly washed with ion-exchanged water. Next, without drying the membrane, the burst strength was determined using a Mullen burst tester (manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS-P812.

[0163] <Resistivity>

[0164] An ion-exchange membrane is placed between two compartments containing platinum black electrodes. The membrane is filled with 0.5 mol / L HCl aqueous solution on both sides. The resistance between the electrodes at 25°C is measured using an AC bridge (frequency 1000 cycles / second). The membrane resistance (Ω·cm) is calculated by comparing this resistance with the resistance without the ion-exchange membrane. 2 ).

[0165] It should be noted that the ion exchange membrane used in the above determination was a membrane that had been pre-equilibrated in a 0.5 mol / L HCl aqueous solution.

[0166] <Film thickness>

[0167] After immersing the ion exchange membrane in 0.5 mol / L HCl solution for more than 4 hours, the surface of the membrane was wiped with cotton paper, and the measurement was performed using a micrometer MED-25PJ (manufactured by Mitutoyo Co., Ltd.).

[0168] <Permeability>

[0169] An ion exchange membrane was sandwiched in a cylindrical unit, and 50 ml of water was added to the top. A pressure of 0.1 MPa was then applied from above, and the amount of water permeating the ion exchange membrane (W) was measured over one hour. pw The permeability is calculated according to the following formula (4). At this point, the effective area of ​​the membrane is 12.6 m². 2 .

[0170] Permeability (mL / (m)2 ·hr))=W pw / (S×T)…(4)

[0171] The coefficients in equation (4) above are as follows.

[0172] S: Effective area of ​​the membrane (m²) 2 )

[0173] T: Test time (hr)

[0174] <Ion exchange capacity and water content>

[0175] The ion exchange membrane was immersed in a 1 mol / L HCl aqueous solution for at least 10 hours. Then, the counter ions were replaced from chloride ions to nitrate ions with a 1 mol / L NaNO3 aqueous solution, and the free chloride ions were quantified using a silver nitrate aqueous solution potentiometric titration apparatus (COMTITE-900, manufactured by Hiranuma Sangyo Co., Ltd.) (the quantification value was set as Amol).

[0176] Next, the same ion exchange membrane was immersed in a 1 mol / L NaCl aqueous solution for more than 4 hours and then thoroughly washed with ion-exchanged water.

[0177] Afterwards, the surface moisture was wiped off with cotton paper, and the mass W of the membrane when wet was measured.

[0178] Then, the membrane was dried under reduced pressure at 60°C for 5 hours, and its weight D during drying was measured. Based on the above measurements, the ion exchange capacity and water content of the ion exchange membrane were calculated using the following formulas (5) and (6).

[0179] Ion exchange capacity [meq / g - dry mass] = A × 1000 / D…(5)

[0180] Moisture content [%] = 100 × (WD) / D…(6)

[0181] <Calculation Method for Polyvinyl Chloride Content>

[0182] Cut the ion exchange precursor membrane and substrate sheet into 10cm squares and weigh them. Calculate the polyvinyl chloride content using the following formula (7).

[0183] The percentage of polyvinyl chloride in ion exchange membranes [%] = T × (MB) × 100…(7)

[0184] The coefficients in equation (7) above are as follows.

[0185] M: Weight (g) of a 10cm square ion exchange precursor.

[0186] B: Weight (g) of a 10cm square substrate sheet

[0187] T: The proportion of polyvinyl chloride in the polymeric composition.

[0188] <Example 1>

[0189] Prepare a mixture according to the following formula.

[0190] 50 parts by weight of styrene (St)

[0191] 57% Divinylbenzene (DVB)

[0192] (Other components are ethyl vinylbenzene) 21 parts by weight

[0193] 29 parts by weight of 4-vinylpyridine

[0194] 5.3 parts by weight of benzoyl peroxide (BW) (NYPER BW manufactured by Nippon Yushi Co., Ltd.) were added to the mixture along with 30 parts by weight of polyvinyl chloride powder (PQB-83) to obtain a homogeneous polymerizable composition.

[0195] Next, a high-density polyethylene monofilament fabric (PE-33D-120) was prepared as a polyolefin-based fabric. The polymerizable composition obtained above was coated on the high-density polyethylene monofilament fabric (PE-33D-120), and after covering both sides with a polyester film as a release material, polymerization was carried out at 75°C for 3 hours.

[0196] Next, the obtained membrane polymer was impregnated in 2 mol / L hydrochloric acid at 35°C for 23 hours to obtain a pyridinium-modified anion exchange membrane. The composition of the anion exchange membrane is shown in Table 1. Furthermore, the properties of the obtained anion exchange membrane are shown in Table 2.

[0197] <Examples 2-3, Comparative Examples 1-3>

[0198] Using the mixing amounts shown in Table 1, and employing the substrate and thickener shown in Table 1, the anion exchange membrane was prepared in the same manner as in Example 1. The membrane properties of the resulting anion exchange membrane are shown in Table 2.

[0199] [Table 1]

[0200]

[0201] St: Styrene

[0202] DVB: 57% divinylbenzene (other components are ethylvinylbenzene)

[0203] 4VP: 4-Vinylpyridine

[0204] BW: Benzoyl peroxide (trade name: NYPER BW / Japan Oils & Fats Co., Ltd.)

[0205] [Table 2]

[0206]

[0207] As can be seen from the above examples and comparative examples, when the membrane treated with 0.5N HCl aqueous solution was immersed in pure water for 3 days, and the shrinkage rate of the membrane was measured (detailed conditions are described in the examples), the shrinkage rate of the conventionally known 4VP-based anion exchange membrane (Comparative Example 1; using polyvinyl chloride fabric as the substrate sheet and NBR as the thickener) was 2.8%. However, in the 4VP-based anion exchange membrane of the present invention (Examples 1-3), the shrinkage rate was suppressed to about 2.1-2.3%. Furthermore, the current efficiency was greater than 55%, and the water permeability was less than 1000 ml / m³. 2 •Hr, with excellent current efficiency and water permeability.

[0208] Furthermore, in Comparative Examples 2 and 3, where polyethylene powder was used instead of vinyl chloride resin as a thickener, the shrinkage rate was suppressed to a low level of 1.6–1.9%, but the current efficiency was as low as 54% or less, and the water permeability exceeded 40,000 ml / m³. 2 ·Hr, are all inferior to the present invention.

[0209] Explanation of reference numerals in the attached figures

[0210] 1:4VP anion exchange membrane

[0211] 3: Anion exchange resin layer

[0212] 5: Substrate sheet (polyethylene woven fabric)

Claims

1. An anion exchange membrane having a layer of an anion exchange resin reinforced by a substrate sheet, characterized in that, the layer of an anion exchange resin contains an anion exchange resin containing a pyridinium group resulting from protonation of a pyridyl group as an anion exchange group, and a vinyl chloride resin as a thickening agent in an amount of 5 to 25 mass% in the anion exchange membrane, the substrate sheet is a polyethylene woven fabric.

2. The anion exchange membrane according to claim 1, wherein, the vinyl chloride resin has an average degree of polymerization of 650 to 1200.

3. The anion exchange membrane according to claim 1 or 2, wherein, the anion exchange membrane does not contain a polyethylene powder.

4. The anion exchange membrane according to claim 1, wherein, the substrate sheet of the polyethylene woven fabric has a thickness of 120 to 160 μm.

5. The anion exchange membrane according to claim 4, wherein, the substrate sheet of the polyethylene woven fabric has an opening rate of 35 to 55%.

6. The anion exchange membrane according to claim 1, wherein, the size L0 of the ion exchange membrane is measured after immersion in a 0.5N-HCl aqueous solution for 12 hours or more, and thereafter the ion exchange membrane is sufficiently washed with ion exchange water, and the size L1 of the membrane is measured after immersion in pure water for 3 days, and the shrinkage of the membrane calculated using the following formula (2) is 2.3% or less, Shrinkage (%) = (1 - L1 / L0) x 100... (2).

7. The anion exchange membrane according to claim 6, wherein, Current efficiency of 55% or more, water permeability of less than 1000 ml / m 2 • Hr.

8. A method for producing the anion exchange membrane according to any one of claims 1 to 7, comprising: a step of preparing a polymerizable composition containing 4-vinylpyridine as a monomer component and containing a vinyl chloride resin as a thickening agent; a step of impregnating the polymerizable composition in a polyethylene woven substrate sheet to produce a polymerizable sheet; a step of overlapping the polymerizable sheet with a release sheet and winding into a roll; a polymerization step of heating the polymerizable sheet wound in the roll to polymerize, to obtain a polymer sheet; a release sheet peeling step of peeling the release sheet from the polymer sheet to obtain an ion exchange precursor membrane; and a protonation step of immersing the ion exchange precursor membrane in an acid solution to protonate the pyridyl group, to obtain an anion exchange membrane.

9. The anion exchange membrane according to any one of claims 1 to 8, wherein, the polyethylene woven fabric substrate sheet has a thickness of 120 to 160 μm.

10. The anion exchange membrane according to any one of claims 1 to 8, wherein, the polyethylene woven fabric substrate sheet has an opening rate of 35 to 55%.

11. The anion exchange membrane according to any one of claims 1 to 8, wherein, the shrinkage of the ion exchange membrane is 2.3% or less.

12. The anion exchange membrane according to any one of claims 1 to 8, wherein, the ion exchange membrane does not contain a polyethylene powder.

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