JP2021154277A - Anion exchange membrane and method for producing the same - Google Patents

Abstract

To provide an anion exchange membrane which enhances adhesion between a polyolefin-based woven fabric and an anion exchange resin, and can achieve low electric resistance and high strength.SOLUTION: An anion exchange membrane has a base material composed of a polyolefin-based woven fabric and an anion exchange resin, and has an electric resistance measured at 25°C using salt solution of 0.5 M of 1.0 Ωcm2 or more and 2.5 Ωcm2 or less, a burst strength of 0.7 MPa or more and 1.2 MPa or less, and a water permeation amount measured using pressurized water of 0.1 MPa of 300 ml/(m2 hr) or less, in which a thickness of the base material is 90 μm or more and 160 μm or less, and an opening ratio of the base material is 35% or more and 55% or less.SELECTED DRAWING: None

Description

The present invention relates to an anion exchange membrane and a method for producing the same.

The ion exchange membrane has a structure in which an ion exchange resin is held on a specific base material. When the film is formed by the ion exchange resin alone, the strength is low and the morphological change due to swelling that occurs when the film is immersed in a liquid is large, so that it is not suitable for practical use. Therefore, a substrate having an ion exchange resin retained on a substrate having a predetermined strength, not changing its morphology due to swelling, and not impairing the ion exchange ability peculiar to the ion exchange resin is used as an ion exchange membrane. NS.

In the above-mentioned ion exchange membranes, conventionally, a woven fabric made of polyvinyl chloride has been widely used as a base material, but an ion exchange membrane based on polyvinyl chloride has low heat resistance and chemical resistance. There is a drawback. Therefore, recently, an ion exchange membrane based on a polyolefin such as polyethylene or polypropylene has been widely studied.

By the way, the ion exchange membrane based on polyolefin has extremely high heat resistance and chemical resistance as compared with the one based on polyvinyl chloride. However, adhesion between the polyolefin base material and the ion exchange resin Poor sex. Along with this, when swelling and drying (shrinkage) are repeated, the ion exchange resin and the base material are likely to be peeled off, and as a result, the function as a diaphragm is deteriorated, the water permeability is increased, and the current efficiency is increased. There is a problem that is reduced. Furthermore, the low adhesiveness between the polyolefin base material and the ion exchange resin naturally leads to the low durability.

As a means for improving the adhesiveness between the polyolefin base material and the ion exchange resin, a method of irradiating the surface of the polyolefin base material with an electron beam or corona treatment is usually considered, but such a method requires a large-scale device. Not only that, there is a problem that the strength of the polyolefin base material is impaired, so that it is difficult to put it into practical use. Further, when a monomer which is a precursor of an ion exchange resin is applied to a polyolefin base material and polymerized, a part of the polyolefin is melted by raising the polymerization temperature slightly higher than the melting point of the polyolefin to adhere to the ion exchange resin. Although the properties have been improved, the strength of the polyolefin base material decreases due to melting, so it is necessary to increase the base material thickness in order to increase the base material strength. In this case, the electrical resistance of the ion exchange membrane increases as the thickness increases, and the adhesion also decreases with the passage of time. Therefore, various means for improving adhesiveness have been proposed.

For example, Patent Document 1, an ion exchange membrane as a base material a woven fabric made of multifilaments having a weight average molecular weight of 10 ⁵ or more polyethylene (so-called ultra-high molecular weight polyethylene) has been proposed. In such an ion exchange membrane, not only the strength and the like are improved by the multifilament of ultra-high molecular weight polyethylene, but also the contact area between the ion exchange resin and the base material is increased, so that the adhesiveness between the two is enhanced. That is.

Further, in Patent Document 2, a monomer paste for forming an ion exchange precursor resin containing polyethylene fine particles having a particle size of 10 μm or less is applied to a polyethylene cloth-like substrate and polymerized at a temperature higher than the melting point of the polyethylene fine particles. , And a method for producing an ion exchange film in which an ion exchange group is introduced into the ion exchange resin precursor formed thereby has been proposed. According to this method, since the polyethylene fine particles act as a thickener, the monomer paste is imparted with an appropriate viscosity and spinnability, and can be uniformly adhered to the polyethylene cloth-like base material. Further, in the obtained ion exchange membrane, a sea-island structure composed of polyethylene distributed in a sea shape and an ion exchange resin distributed in an island shape is formed, and polyethylene continuously connected in a sea shape is polyethylene. Since it is heat-sealed with the cloth-like base material made of the product, even if the base material is a woven cloth formed of a monofilament, the adhesiveness with the ion exchange resin is improved.

Japanese Unexamined Patent Publication No. 6-322156 Japanese Unexamined Patent Publication No. 3-153740

However, in Patent Document 1, ultra-high molecular weight polyethylene is a special polymer that is usually difficult to mold, so that it is extremely expensive, and its multifilament woven fabric is extremely difficult to obtain. Therefore, there is a demand for a method for improving the adhesiveness even with an easily available and inexpensive monofilament woven fabric.

Further, in Patent Document 2, polymerization at a high temperature (105 degrees in the example) is required to melt the polyethylene cloth-like base material, and there is a problem that the mechanical strength of the obtained ion exchange membrane is lowered. Furthermore, even if high adhesiveness is once obtained, for example, when the ion exchange resin repeatedly expands and contracts, a gap is formed between the base material and the ion exchange resin, and the water permeability increases, resulting in current efficiency. Is low, and further improvement in adhesiveness is required.

The present invention has been made in view of this point, and an object of the present invention is to improve the adhesion between the polyolefin-based woven fabric and the anion exchange resin, and to achieve both low electrical resistance and high strength. The purpose is to provide an exchange membrane.

The anion exchange membrane according to the present invention comprises a base material made of a polyolefin-based woven fabric and an anion exchange resin, and has an electrical resistance of 1.0 Ω · cm ^{2 measured using 0.5 M saline solution at 25 ° C.} It is 2.5 Ω · cm ² or less, the burst strength is 0.7 MPa or more and 1.2 MPa or less, and the water permeation amount measured using 0.1 MPa pressurized water is 300 ml / (m ² · hr) or less. The thickness of the base material is 90 μm or more and 160 μm or less, and the opening ratio of the base material is 35% or more and 55% or less.

The base material may be made of a polyethylene-based woven fabric.

The base material may be made of a polyolefin monofilament woven fabric.

A two-chamber cell consisting of an anode (Pt plate) (1.0 mol / L sulfuric acid aqueous solution) / anion exchange film / (0.25 mol / L sulfuric acid aqueous solution) cathode (Pt plate) is used as an electrolytic cell, and the liquid temperature is 25 ° C. After energizing for 1 hour under the condition of a current density of 10 A / dm ² , the current efficiency measured for sulfate ions may be 40% or more.

The anion exchange resin may contain a modified styrene-based thermoplastic resin elastomer modified by a polar group.

The anion exchange resin may be a polystyrene-based anion exchange resin.

The anion exchange resin may have a crosslinked structure.

The method for producing an anion exchange film according to the present invention contains a monomer component containing a functional group into which an anion exchange group can be introduced or a monomer having an anion exchange group and a crosslinkable monomer, and a polymerization initiator. A dipping step of immersing the polymerizable composition for forming an anion exchange resin in a substrate made of a polyolefin-based woven fabric having a thickness of 90 μm or more and 160 μm or less and an opening ratio of 35% or more and 55% or less, and the dipping. After the step, the structure includes a step of copolymerizing the monomer component at 40 ° C. or higher and lower than 80 ° C.

The base material may be made of a polyethylene-based woven fabric.

The polymerizable composition for forming an anion exchange resin may contain the polymerization initiator having a decomposition temperature of 90 ° C. or lower for obtaining a half-life of 10 hours.

The monomer having a functional group into which an anion-exchange group can be introduced or an anion-exchange group may be a styrene-based monomer having a functional group into which an anion-exchange group can be introduced or an anion-exchange group.

The anion exchange membrane according to the present invention has a base material thickness of 90 μm or more and 160 μm or less, a base material opening ratio of 35% or more and 55% or less, and has high electrical resistance as a film and high strength. doing.

Hereinafter, embodiments of the present invention will be described in detail. The following description of preferred embodiments is merely exemplary and is not intended to limit the invention, its applications or its uses.

As described in the column of background techniques and problems to be solved by the invention, when producing an anion exchange membrane based on an inexpensive polyolefin-based woven fabric, the strength of the anion exchange membrane is kept high and the electrical resistance is low. However, since it is difficult to sufficiently increase the adhesion between the polyolefin-based woven fabric and the anion exchange resin, the inventors of the present application have conducted various studies and came up with the invention of the present application.

(Embodiment 1)
The anion exchange membrane according to the first embodiment includes a base material made of a polyolefin-based woven fabric and an anion exchange resin, and has an electric resistance of 1.0 Ω · cm measured using 0.5 M saline solution at 25 ° C. ² or more and 2.5 Ω · cm ² or less, burst strength is 0.7 MPa or more and 1.2 MPa or less, and the amount of water permeation measured using 0.1 MPa pressurized water is 300 ml / (m ² · hr) or less. The thickness of the base material is 90 μm or more and 160 μm or less, and the opening ratio of the base material is 35% or more and 55% or less.

Since the anion exchange membrane of the first embodiment having the above properties has an electric resistance as ^{small as 1.0 Ω · cm 2} or more and 2.5 Ω · cm ² or less, electrodialysis or the like should be efficiently performed. Can be done. The electric resistance is more preferably in the range of ^{1.3 Ω · cm 2} or more and 2.3 Ω · cm ^{2 or less.}

The burst strength of the anion exchange membrane of the present embodiment is more preferably in the range of 0.8 MPa or more and 1.1 MPa or less. Further, the anion exchange membrane of the present embodiment is excellent in anion selectivity and concentration because ^{the water permeability measured using pressurized water of 0.1 MPa is as small as 300 ml / (m 2 · hr) or less.} .. The amount of water permeation ^{is more preferably 50 ml / (m 2} · hr) or less. The lower limit of the water permeation amount is 0 ml / (m ² · hr).

The method for measuring the electrical resistance is as follows. An anion exchange membrane is sandwiched in a two-chamber cell having platinum black electrodes, both sides of the anion exchange membrane are filled with a 0.5 mol / L-NaCl aqueous solution, and resistance between the electrodes at 25 ° C. by an AC bridge (frequency 1000 cycles / sec). ^{The electrical resistance = film resistance (Ω · cm 2} ) was determined by the difference between the electrode-to-electrode resistance and the electrode-to-electrode resistance when the anion exchange membrane was not installed. The anion exchange membrane used for this measurement was previously equilibrated in a 0.5 mol / L-NaCl aqueous solution.

The method for measuring the burst strength is as follows. The anion exchange membrane was immersed in a 0.5 mol / L- NaCl aqueous solution for 4 hours or more, and thoroughly washed with ion-exchanged water. Next, the burst strength was measured according to JIS-P8112 by a Murren burst tester (manufactured by Toyo Seiki) without drying the membrane.

The method for measuring the amount of water permeation is as follows. When an ion exchange membrane is sandwiched between cylindrical cells, 50 ml of water is put in the upper part, and pressure is applied at 0.1 MPa from above, the amount of water Wpw that permeates the ion exchange membrane in one hour is measured. , The amount of water permeation was calculated according to the following formula. At this time, the effective area of the film is 12.6 cm ² . This measurement was carried out at 25 ° C.

Permeability (ml / (m ² x hr)) = Wpw / (S x t)
In the formula, S is the effective area of the film (m ² ) and t is the test time (hour).

The method for measuring the opening ratio of the equipment is as follows. It was calculated according to the following formula from the wire diameter (μm) and the number of meshes of the threads constituting the base material.

Opening ratio (%) = (opening) ² / (opening + wire diameter) ²
The opening (μm) in the formula is represented by 25400 / number of meshes-wire diameter (μm), and the number of meshes is the number of threads per inch. The numerical value of 25400 is because 1 inch corresponds to 25400 μm.

Further, the anion exchange film according to the present embodiment has a configuration of an anode (Pt plate) (1.0 mol / L sulfuric acid aqueous solution) / anion exchange film / (0.25 mol / L sulfuric acid aqueous solution) cathode (Pt plate). It is preferable that the current efficiency measured for sulfate ions is 40% or more after energizing for 1 hour under the condition of a ^{current density of 10 A / dm 2} at a liquid temperature of 25 ° C. using the two-chamber cell of No. 1 as an electrolytic cell.

<Polyolefin-based woven fabric>
Examples of the polyolefin include homopolymers of α-olefins such as ethylene, propylene, 1-butene and 4-methyl-1-pentene, and random or block copolymers thereof. Specific examples thereof include low-density polyethylene, high-density polyethylene, polypropylene, poly1-butene, and poly4-methyl-1-pentene. Among them, low-density polyethylene, high-density polyethylene, and polypropylene are preferable, and polyethylene-based polymers such as low-density polyethylene and high-density polyethylene are most preferable from the viewpoint of easy availability and chemical resistance.

The polyolefin base material may have any form such as a woven fabric, a non-woven fabric, or a porous film, but a woven fabric is preferable from the viewpoint of strength. The opening ratio of the woven fabric needs to be 35% or more and 55% or less. As the opening ratio of the woven fabric decreases, the electrical resistance increases, and conversely, as the opening ratio increases, the burst strength decreases, and the adhesion between the polyolefin base material and the anion exchange resin decreases. Therefore, the water permeability deteriorates. When the opening ratio is 35% or more and 55% or less, an anion exchange membrane having excellent electrical resistance and adhesion is obtained. The opening ratio is more preferably 40% or more and 50% or less.

The single yarn of the woven fabric can be either multifilament or monofilament, but monofilament is preferable from the viewpoint of adhesion. Further, in order to balance the strength and the film resistance, the thickness of the polyolefin-based woven fabric needs to be 90 μm or more and 160 μm or less, and more preferably 95 μm or more and 140 μm or less. The wire diameter of the single yarn is preferably 1 to 70 denier (10 to 100 μm).

<Anion exchange resin>
The anion exchange resin that forms the anion exchange membrane is a resin that is known per se, for example, a resin that forms a skeleton with an anion exchange group introduced therein. Examples of the resin forming the skeleton include a polymer obtained by polymerizing a monomer having an ethylene-based unsaturated double bond such as vinyl-based, styrene-based, and acrylic-based, a copolymer polymer thereof, and polysulfone and polyphenylene. Examples thereof include hydrocarbon-based resins such as polymers containing an aromatic ring in the main chain such as sulfide, polyether ketone, polyether ether ketone, polyetherimide, polyphenylene oxide, polyethersulfone, and polybenzimidazole. Among them, a styrene-based anion exchange resin mainly composed of a styrene-based monomer is preferable as the resin forming the skeleton.

It is preferable that these anion exchange resins have a crosslinked structure because the resin is densified and the swelling inhibitory property and the film strength are enhanced. The crosslinked structure may be an ionic crosslink, but is preferably a covalent bond crosslink.

Further, the anion exchange group is not particularly limited as long as it is a reactive group that can be positively charged in an aqueous solution. For example, examples of the anion exchange group include a 1-3-amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a quaternary pyridinium group and the like, and generally, a quaternary ammonium group which is a strongly basic group and a quaternary ammonium group and the like. A quaternary pyridinium group is suitable.

<Manufacturing of anion exchange membrane>
The anion exchange membrane according to this embodiment is manufactured as follows.

A polymerizable composition is prepared by mixing a monomer having an anion exchange group, a crosslinkable monomer, a polymerization curable component for forming an anion exchange resin such as a polymerization initiator. The polymerizable composition is dipped in a polyolefin woven fabric as a base material to fill the voids of the woven fabric, and then the polymerizable composition is polymerized and cured to produce an anion exchange resin. As a result, the desired anion exchange membrane can be obtained.

The polymerization curing temperature is set to a temperature lower than the melting point of the polyolefin-based woven fabric so as not to reduce the strength of the base material. Although it depends on the type of polyolefin and the polymerization curable component and the polymerization curing time, the upper limit of the polymerization curing temperature is preferably a temperature 40 ° C. or more lower than the melting point of the polyolefin constituting the base material. Specifically, the polymerization curing temperature is preferably 40 ° C. or higher and lower than 80 ° C., more preferably 55 ° C. or higher and lower than 77 ° C. If the polymerization is carried out at an excessively low temperature, voids may be formed at the interface between the polyolefin-based woven fabric and the anion exchange resin, which may lead to a decrease in current efficiency. On the other hand, if the temperature is excessively high, a part of the polyolefin may be dissolved and the strength of the obtained anion exchange membrane may be lowered.

The monomer having an anion exchange group in the polymerization curable component may be one conventionally used for producing an anion exchange resin. For example, aromatic ammonium-based monomers such as vinylbenzyltrimethylammonium and vinylbenzyltriethylammonium, and quaternary ammonium groups such as 2- (meth) acryloyloxyethyltrimethylammonium chloride and 2- (meth) acryloyloxyethyltriethylammonium chloride. Examples thereof include (meth) ammonium acid derivative-based monomers having (meth), nitrogen-containing heterocyclic monomers such as vinylpyridine and vinylimidazole, and salts and esters thereof. These monomers may be used alone or in combination of two or more copolymerizable with each other. Further, the crosslinkable monomer is used for densifying the anion exchange resin to enhance swelling inhibitory property, film strength and the like, and is not particularly limited, but for example, divinylbenzene and divinylsulfone. , Divinyl compounds such as butadiene, chloroprene, divinylbiphenyl, trivinylbenzenes, divinylnaphthalin, diallylamine, and divinylpyridine are mentioned, and divinylbenzene is preferable among them. Generally, such a crosslinkable monomer is preferably 0.1 to 50% by mass, more preferably 1 to 40% of the total monomer components contained in the polymerizable composition for forming an anion exchange resin. Mix% by mass.

Further, in addition to the above-mentioned monomer having an anion exchange group and the crosslinkable monomer, another monomer copolymerizable with these monomers may be added, if necessary. As other monomers, for example, styrene, chloromethylstyrene, acrylonitrile, methylstyrene, ethylvinylbenzene, acrolein, methylvinylketone, vinylbiphenyl and the like are used. The blending amount of the other monomers varies depending on the purpose of addition, but generally, 0.1 to 60% by mass of the total monomer components contained in the polymerizable composition for forming an anion exchange resin is blended. In particular, when flexibility is imparted, it is preferably blended in an amount of 1 to 50% by mass, particularly 5 to 40% by mass.

As the polymerization initiator, conventionally known ones can be used without particular limitation, but the decomposition temperature for obtaining a half-life of 10 hours is preferably 90 ° C. or lower, more preferably 80 ° C. or lower. .. Specifically, 1,1-bis (t-hexylperoxy) cyclohexane, dibenzoylperoxide, t-butylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, 2, 5-2,5-di (2-ethylhexanoylperoxy) hexane, dissuccinic acid peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, dilauroyl peroxide, Di (3,3,5-trimethylhexanoyl) peroxide, t-butylperoxyvivalate, t-hexylperoxybivalate, t-butylperoxyneodecanate, t-hexylperoxyneodecanate, di ( 2-Ethylhexyl) Peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxyneodecanate and other organic peroxides are used. The polymerization initiator is preferably blended in an amount of 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the monomer component contained in the polymerizable composition for forming an anion exchange resin. Mix parts by mass.

The above-mentioned polymerizable composition may further contain an additive made of a thermoplastic resin. Specifically, as thermoplastic resins, polyolefins such as polyethylene and polypropylene and their modified products, styrene-butadiene copolymers and their hydrogenated products and modified products, polyacrylonitriles, butadiene-acrylonitrile copolymers and their hydrogenated products. Preferable examples include substances and modified products, styrene-ethylene-butadiene copolymers and their hydrogenated products and modified products, styrene-isoprene copolymers and their hydrogenated products and modified products, chlorinated polyethylene, polyvinyl chloride and the like. Can be done. Among these, it is preferable to add a thermoplastic resin which is an elastomer, and a styrene-based thermoplastic resin elastomer is particularly preferable. Among the styrene-based thermoplastic resin elastomers, those modified with polar groups are most suitable. Here, the thermoplastic resin preferably has a tensile elastic modulus of 0.01 MPa or more, more preferably 0.1 MPa or more and 1000 MPa or less as measured according to ISO527. The amount of the thermoplastic resin to be blended is not particularly limited, but is 0.5 parts by mass or more and 50 parts by mass with respect to 100 parts by mass of the monomer component contained in the polymerizable composition for forming the anion exchange resin. It is preferably as follows.

The styrene-based thermoplastic resin elastomer is a thermoplastic elastic resin composed of a copolymer of a monomer unit derived from an aliphatic hydrocarbon-based monomer and a monomer unit based on a styrene-based monomer. In the styrene-based thermoplastic resin elastomer, the styrene-based monomer unit portion has a high affinity with the anion exchange resin (particularly polystyrene-based anion exchange resin), and the aliphatic hydrocarbon-based monomer unit portion is a polyolefin-based base material. Since it has a high affinity with, it has a function of improving the adhesion between the anion exchange resin and the polyolefin-based base material. The modified styrene-based thermoplastic resin elastomer has a higher polarity than the unmodified one, and the adhesion to the ion exchange resin is further improved.

Such a styrene-based thermoplastic resin elastomer may be a styrene-ethylene-butylene copolymer, a styrene-ethylene-propylene copolymer, or the like, but usually, styrene and butadiene or isoprene are used because of ease of polymerization and the like. A copolymer with a conjugated diolefin such as the above is preferably used.

Examples of the polar group include a hydroxy group, an alkoxy group, a carbonyl group, an epoxy group, a carboxy group, an acidic group, an ester group, an amide group, an acid anhydride group, an amino group and a halogen group. An acidic group or an acid anhydride group is preferable because of its affinity with the exchange group. The acidic group is not particularly limited, such as a sulfo group, a phospho group, and a carboxy group, but a carboxy group is preferable. On the other hand, the acid anhydride group is preferably an anhydrideized group of the above carboxy group. Specifically, if it is a cyclic acid anhydride group, it is a maleic anhydride group, a phthalic anhydride group, a succinic anhydride group, or a glutal anhydride. Acid groups and the like can be mentioned, and examples of the acyclic acid anhydride group include an acetate group anhydride, a propionic anhydride group, a benzoic anhydride group and the like. The most preferred modifying group is a maleic anhydride group. The amount of modification of the polar group with respect to the styrene-based thermoplastic resin elastomer is not particularly limited, but is 0.1 to 20% by mass, preferably 0.2 to 10% by mass, more preferably 0.2 to 10% by mass, based on the polymer. Is preferably 0.2 to 5% by mass.

Further, the above-mentioned polymerizable composition may further contain a thickener, a known additive and the like, if necessary.

Examples of the thickener include polyolefin powders having an average grain size of 10 μm or less, ethylene-propylene copolymers, saturated aliphatic hydrocarbon-based polymers such as polybutylene, and styrene-based polymers such as styrene-butadiene copolymers. By using such a thickener, the viscosity can be adjusted within a range that can effectively prevent sagging during the film forming operation.

Further, as the additive, a plasticizer such as dioctyl phthalate, dibutyl phthalate, tributyl phosphate, tributyl acetylcitrate, an alcohol ester of a fatty acid or an aromatic acid, a hydrochloric acid scavenger such as styrene oxide or ethylene glycol diglycidyl ether, etc. Can be mentioned. The amount of the additive to be blended varies depending on the purpose of addition, but is 0.1 to 50 parts by mass, particularly 0.5 to 50 parts by mass, based on 100 parts by mass of the monomer component contained in the polymerizable composition for forming an anion exchange resin. It is preferably blended in an amount of 30 parts by mass.

The method of impregnating the voids of the base material of the polyolefin-based woven fabric of the polymerizable composition is not particularly limited. For example, it is carried out by immersing a polyolefin base material in a tank filled with the above-mentioned polymerizable composition. Of course, instead of dipping, impregnation of the polymerizable composition can be performed by a method such as spray coating or coating using a doctor blade.

As described above, the polymerizable composition impregnated in the polyolefin-based woven fabric is heated in a polymerization apparatus such as a heating oven, copolymerized, and cured.

In this polymerization step, a method of sandwiching a polyolefin-based woven fabric filled with a polymerizable composition between films such as polyester and raising the temperature from room temperature under pressure is generally adopted. The pressurization is generally performed at a pressure of about 0.1 to 1.0 MPa by pressurizing with an inert gas such as nitrogen or a roll. By this pressurization, the excess polymerizable composition existing at the outer interface of the polyolefin-based woven fabric is pressed into the voids of the polyolefin-based woven fabric, and the polymerization is carried out, which is effective in generating resin pools and the like. Can be prevented.

Other polymerization conditions depend on the type of polymerization-curable component and the like, and may be appropriately selected and determined from known conditions. As described above, the polymerization temperature is set to a temperature significantly lower than the melting point of the polyolefin-based woven fabric (specifically, 40 ° C. or higher and lower than 80 ° C.), and the polymerization time varies depending on the polymerization temperature and the like. Generally, it takes about 3 to 20 hours. Upon completion of the polymerization curing, an anion exchange membrane supported by the polyolefin-based woven fabric is obtained.

Further, in the present embodiment, instead of the polymerization curable component for forming an anion exchange resin, an anion exchange membrane is used by using a polymerization curable component for forming an anion exchange resin precursor resin having a reactive group into which an anion exchange group can be introduced. Can also be formed. Specifically, instead of the monomer having an anion exchange group, a monomer having a reactive group capable of introducing an anion exchange group is blended into the polymerizable composition to produce an anion exchange membrane precursor. In this case as well, the anion exchange membrane precursor may be prepared in the same manner as in the case of blending the monomer having an anion exchange group, except that the anion exchange group introduction step described later is added.

The monomer having a reactive group into which an anion exchange group can be introduced may be one conventionally used for producing an anion exchange resin. For example, vinylpyridine, methylvinylpyridine, ethylvinylpyridine, vinylpyrrolidone, vinylcarbazole, vinylimidazole, aminostyrene, alkylaminostyrene, dialkylaminostyrene, trialkylaminostyrene, chloromethylstyrene, acrylic acid amide, acrylamide, oxime, Styrene, vinyltoluene and the like are suitable. These monomers may be used alone or in combination of two or more copolymerizable with each other.

In addition to the monomer having a reactive group into which an anion exchange group can be introduced and the crosslinkable monomer, other monomers can be used if necessary. Examples of other monomers include acrylonitrile, acrolein, methyl vinyl ketone and the like.

The anion exchange group introduction step is performed after the polymerizable composition is polymerized and cured to obtain a film of an anion exchange resin precursor resin. In this step, in order to introduce a 1st to 3rd grade amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a quaternary pyridinium group and the like, the 1st to 3rd grade as an anion exchange group introduction agent is introduced into the obtained precursor resin. An anion exchange group is introduced by allowing an amine or the like to act on it, or by performing a treatment such as alkylation or amination. As a result, the desired anion exchange membrane can be obtained.

Further, in the present embodiment, instead of the method using the above-mentioned polymerizable composition for forming an anion exchange resin or forming an anion exchange resin precursor resin, an anion exchange group-containing polymer is dissolved in a solvent to exchange anions. A solution of the group-containing polymer can also be filled in the voids of the polyolefin-based woven fabric.

The thickness of the anion exchange membrane produced as described above is preferably in the range of 100 to 300 μm. If this thickness is too thin, the strength of the anion exchange membrane may be significantly reduced. If the thickness is excessively thick, there is a risk of causing inconvenience such as an increase in electrical resistance.

The burst strength of the anion exchange film depends on the thickness, but the filament diameter and thickness of the polyolefin-based woven fabric and the crosslinkable monomer in the polymerization curable component so as to be 0.7 MPa or more and 1.2 MPa or less. The blending amount is adjusted.

The anion exchange membrane according to the present embodiment uses a polyolefin-based woven fabric as a base material, has an electrical resistance of 1.0 Ω · cm ² or more and 2.5 Ω · cm ² or less, and a burst strength of 0.7 MPa or more. It is 2 MPa or less, and the amount of water permeation measured using 0.1 MPa pressurized water is 300 ml / (m ² · hr) or less. That is, the anion exchange membrane according to the present embodiment uses a thin polyolefin-based woven fabric having a large opening ratio as a base material, has sufficiently high burst strength, low electrical resistance, and adherence between the anion exchange resin and the base material. It also has the property that the amount of water permeation, which is an index of, is small. The small amount of water permeation means that the amount of gaps generated when a constant pressure is applied during the manufacturing process of the anion exchange membrane and the measurement of the amount of water permeation is small. Therefore, it is shown that the anion exchange resin is firmly adhered to the polyolefin-based woven fabric. Therefore, in the anion exchange membrane of the present embodiment, the base material and the anion exchange body filled in the voids of the base material are firmly adhered to each other, and as a result, the durability is excellent and the electrical resistance is small. The current efficiency when used for electrodialysis is also high. When the anion exchange resin is copolymerized from the monomer, the copolymerization is carried out at a temperature lower than the melting point of the polyolefin as the base material, so that the strength of the polyolefin-based woven fabric is not lowered by the copolymerization.

The anion exchange membrane of the present invention having such properties is used as a membrane for electrodialysis used in salt production and desalting processes in the food field, as an electrolyte membrane for fuel cells, and metal ions generated in the steel industry and the like. It can be usefully used in many fields such as membranes for diffusion dialysis used for acid recovery from acids containing.

(Example)
Examples and comparative examples are shown below. Various characteristics of the polyolefin-based woven fabric and the anion exchange membrane were measured by the following methods.

1. 1. Opening ratio of polyolefin-based woven fabric The wire diameter (μm) and the number of meshes of the threads constituting the polyolefin-based woven fabric were calculated according to the following formula.

Opening ratio (%) = (opening) ² / (opening + wire diameter) ² (1)
In equation (1),
Opening (μm) = 25400 / number of meshes-wire diameter (μm)
Number of meshes = number of threads per inch (average value)
become.

2. Water Permeation of Anion Exchange Membrane When an anion exchange membrane is sandwiched between cylindrical cells, 50 ml of water is put in the upper part, and pressure is applied at 0.1 MPa from above, the ion exchange membrane is permeated in 1 hour. The amount of water coming Wpw was measured, and the amount of water permeation was calculated according to the following formula. At this time, the effective area of the film is 12.6 cm ² .

Permeability (ml / (m ² x hour)) = Wpw / (S x t) (2)
In equation (2),
S: Effective area of membrane (m ² )
t: Test time

3. 3. Anion exchange capacity and water content The anion exchange membrane is immersed in a 1 mol / L-HCl aqueous solution for 10 hours or more. After that, the counterion was replaced with nitrate ion from chloride ion with 1 mol / L-NaNO ₃ aqueous solution, and the liberated chloride ion was used with a potentiometric titrator (AT-710, manufactured by Kyoto Denshi Kogyo Co., Ltd.) using silver nitrate aqueous solution. Quantified (Amol).

Next, the same anion exchange membrane was immersed in a 1 mol / L- NaCl aqueous solution for 4 hours or more, and thoroughly washed with ion-exchanged water. Then, the water on the surface was wiped off with a tissue paper, and the mass (Wg) of the film when wet was measured. Further, it was dried under reduced pressure at 60 ° C. for 5 hours, and the weight (Dg) at the time of drying was measured. Based on the above measured values, the anion exchange capacity and water content of the anion exchange membrane were determined by the following equations.

Anion exchange capacity [meq / g-dry mass] = A × 1000 / D
Moisture content [%] = 100 × (WD) / D

4. Thickness of anion exchange membrane After immersing the anion exchange membrane in a 0.5 mol / L-NaCl solution for 4 hours or more, wipe off the moisture on the surface of the membrane with tissue paper, and micrometer (MED-25PJ, manufactured by Mitutoyo Co., Ltd.). ) Was used for measurement.

5. Electrical resistance of anion exchange membrane An anion exchange membrane is sandwiched in a two-chamber cell having a platinum black electrode, both sides of the anion exchange membrane are filled with a 0.5 mol / L-NaCl aqueous solution, and 25 by an AC bridge (frequency 1000 cycles / sec). ^{The resistance between the electrodes at ° C was measured, and the electrical resistance (Ω · cm 2} ) was determined by the difference between the resistance between the electrodes and the resistance between the electrodes when the ion exchange membrane was not installed. The anion exchange membrane used for the above measurement was previously equilibrated in a 0.5 mol / L-NaCl aqueous solution.

6. Current efficiency of anion exchange membrane A two-chamber cell having the following configuration was used.
Anode (Pt plate) (1.0 mol / L-sulfuric acid aqueous solution) / Anion exchange film / (0.25 mol / L-sulfuric acid aqueous solution) Cathode (Pt plate)
After energizing at a liquid temperature of 25 ° C. and a current density of 10 A / dm ² for 1 hour, the solution on the cathode side was recovered. The sulfuric acid concentrations of the recovered liquid and the initial liquid were quantified by a potentiometric titrator (AT-710, manufactured by Kyoto Denshi Kogyo Co., Ltd.) using an aqueous sodium hydroxide solution, and the current efficiency was calculated using the following formula.

Current efficiency (%) = (CB-CS) / (I × t / F) × 100
In the above formula,
CB: Concentration of initial liquid CS: Concentration of liquid recovered after energization I: Current value (A)
t: Energizing time (sec)
F: is the Faraday constant (96500C / mol)
Is.

7. Rupture strength of anion exchange membrane The anion exchange membrane was immersed in a 0.5 mol / L-NaCl aqueous solution for 4 hours or more, and thoroughly washed with ion-exchanged water. Next, the burst strength was measured according to JIS-P8112 by a Murren burst tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) without drying the membrane.

<Example 1>
A mixture of the following formulations was prepared.

16.6 parts by mass of styrene (St) Divinylbenzene (DVB) (57% purity, the rest is ethylvinylbenzene) 16.8 parts by mass p-chloromethylstyrene (CMS) 66.6 parts by mass Tributyl acetylcitrate (ATBC) 25.0 parts by mass Styrene oxide (StO) 3.4 parts by mass t-butylperoxy-2-ethylhexanoate (BPE) (trade name: Perbutyl O, manufactured by Nikko Co., Ltd.) 3.3 parts by mass This mixture Add 20.7 parts by mass of a styrene-butadiene triblock copolymer (trade name: Tuftec M1913, manufactured by Asahi Kasei Co., Ltd.) to which a polystyrene content of 30% by weight is added and modified with maleic anhydride. Stirring at ° C. for 20 hours gave a uniform polymerizable composition.

Next, the following high-density polyethylene monofilament woven fabric (PE30D-100) was prepared.

High density polyethylene monofilament woven fabric (PE30D-100);
Warp: 100 mesh-wire diameter 68 μm (30 denier)
Weft: 100 mesh-wire diameter 68 μm (30 denier)
Thickness: 128 μm
Opening rate: 54%
The polymerizable composition obtained above was applied onto the above-mentioned high-density polyethylene monofilament woven fabric (PE30D-100), and the polyester film was coated on both sides as a release material, and then polymerized at 70 ° C. for 5 hours. ..

Next, the obtained film-like polymer was immersed in methanol for 20 hours to remove the plasticizer and the polymerization residue, and then an amination reaction was carried out at 30 ° C. for 16 hours using an aqueous solution of 5% by weight of trimethylamine and 25% by weight of acetone. To obtain an anion exchange membrane. The characteristics of the obtained anion exchange membrane are as follows and are shown in Table 2. The configuration of the anion exchange membrane is shown in Table 1.

Thickness: 159 μm
Ion exchange capacity: 2.0 meq / g-dry mass Moisture content: 34%
Electrical resistance: 1.7Ω ・ cm ²
Permeability: 0 ml / (m ² · hour)
Current efficiency: 44%
Burst strength: 0.89MPa
<Example 2>
The following polyethylene woven fabric (PE33D-100) was prepared as a polyolefin-based monofilament base material.

High density polyethylene monofilament woven fabric (PE33D-100);
Warp: 100 mesh-wire diameter 76 μm (33 denier)
Weft: 100 mesh-wire diameter 76 μm (33 denier)
Thickness: 132 μm
Opening rate: 49%
An anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polyethylene woven fabric (PE33D-100) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

<Example 3>
The following polyethylene woven fabric (PE33D-120) was prepared as a polyolefin-based monofilament base material.

High density polyethylene monofilament woven fabric (PE33D-120);
Warp: 120 mesh-wire diameter 76 μm (33 denier)
Weft: 120 mesh-wire diameter 76 μm (33 denier)
Thickness: 132 μm
Opening rate: 41%
An anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polyethylene woven fabric (PE33D-120) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

<Example 4>
The following polyethylene woven fabric (PE33D-130) was prepared as a polyolefin-based monofilament base material.

High density polyethylene monofilament woven fabric (PE33D-130);
Warp: 130 mesh-wire diameter 76 μm (33 denier)
Weft: 130 mesh-wire diameter 76 μm (33 denier)
Thickness: 132 μm
Opening rate: 37%
An anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polyethylene woven fabric (PE33D-130) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

<Example 5>
The following polypropylene woven fabric (PP30D-100) was prepared as a polyolefin-based monofilament base material.

High density polypropylene monofilament woven fabric (PP30D-100);
Warp: 100 mesh-wire diameter 68 μm (30 denier)
Weft: 100 mesh-wire diameter 68 μm (30 denier)
Thickness: 128 μm
Opening rate: 54%
An anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polypropylene woven fabric (PP30D-100) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

<Comparative example 1>
The following polyethylene woven fabric (PE33D-80) was prepared as a polyolefin-based monofilament base material.

High density polyethylene monofilament woven fabric (PE33D-80);
Warp: 80 mesh-wire diameter 76 μm (33 denier)
Weft: 80 mesh-wire diameter 76 μm (33 denier)
Thickness: 130 μm
Opening rate: 58%
The anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polyethylene woven fabric (PE33D-80) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

In Comparative Example 1, the amount of water permeation is significantly worse than that in Example. From this, it was confirmed that if the opening ratio of the base material is too large, the adhesion between the resin and the base material deteriorates.

<Comparative example 2>
The following polyethylene woven fabric (PE200) was prepared as a polyolefin-based monofilament base material.

High density polyethylene monofilament woven fabric (PE200);
Warp: 156 mesh-wire diameter 86 μm (50 denier)
Weft: 100 mesh-wire diameter 86 μm (50 denier)
Thickness: 185 μm
Opening rate: 32%
The anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polyethylene woven fabric (PE200) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

In Comparative Example 2, the resistance is worse than that in Example. From this, it was confirmed that a film having a preferable low resistance cannot be obtained if the opening ratio of the base material is too small.

<Comparative example 3>
The following polyethylene woven fabric (PE120) was prepared as a polyolefin-based monofilament base material.

High density polyethylene monofilament woven fabric (PE120);
Warp: 96 mesh-wire diameter 106 μm (62 denier)
Weft: 76 mesh-wire diameter 122 μm (71 denier)
Thickness: 260 μm
Opening rate: 38%
The anion exchange membrane of the present invention was obtained in the same manner as in Example 1 except that the above polyethylene woven fabric (PE120) was used. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

In Comparative Example 3, the resistance is worse than that in Example. From this, it was confirmed that if the base material is too thick, a film having a preferable low resistance cannot be obtained.

<Comparative example 4>
The anion exchange membrane of the present invention was obtained in the same manner as in Example 3 except that the polymerization temperature was 105 ° C. The membrane characteristics of the obtained anion exchange membrane are shown in Table 2.

In Comparative Example 4, the burst strength is worse than that in Example. From this, it was confirmed that if the polymerization temperature is too high, a film having a preferable high strength cannot be obtained.

(Other embodiments)
The above-described embodiment is an example of the present invention, and the present invention is not limited to these examples, and well-known techniques, conventional techniques, and known techniques may be combined or partially replaced with these examples. The invention of the present application also includes modified inventions that can be easily conceived by those skilled in the art.

Claims (11)

An anion exchange membrane comprising a base material made of a polyolefin woven fabric and an anion exchange resin.
The electrical resistance measured using 0.5 M saline solution at 25 ° C. is 1.0 Ω · cm ² or more and 2.5 Ω · cm ² or less.
The burst strength is 0.7 MPa or more and 1.2 MPa or less.
The water permeability measured using 0.1 MPa pressurized water is 300 ml / (m ² · hr) or less.
The thickness of the base material is 90 μm or more and 160 μm or less.
An anion exchange membrane having an opening ratio of 35% or more and 55% or less of the base material. The anion exchange membrane according to claim 1, wherein the base material is a polyethylene-based woven fabric. The anion exchange membrane according to claim 1 or 2, wherein the base material is a polyolefin monofilament woven fabric. A two-chamber cell consisting of an anode (Pt plate) (1.0 mol / L sulfuric acid aqueous solution) / anion exchange film / (0.25 mol / L sulfuric acid aqueous solution) cathode (Pt plate) is used as an electrolytic cell, and the liquid temperature is 25 ° C. The anion exchange film according to any one of claims 1 to 3, wherein the current efficiency measured for sulfate ions is 40% or more after being energized for 1 hour under the condition of a current density of 10 A / dm ^2. The anion exchange membrane according to any one of claims 1 to 4, wherein the anion exchange resin contains a modified styrene-based thermoplastic resin elastomer modified by a polar group. The anion exchange membrane according to any one of claims 1 to 5, wherein the anion exchange resin is a polystyrene-based anion exchange resin. The anion exchange membrane according to any one of claims 1 to 6, wherein the anion exchange resin has a crosslinked structure. A polymerizable composition for forming an anion-exchange resin containing a monomer component containing a functional group into which an anion-exchange group can be introduced or a monomer having an anion-exchange group and a crosslinkable monomer, and a polymerization initiator. A dipping step of immersing in a substrate made of a polyolefin-based woven fabric having a thickness of 90 μm or more and 160 μm or less and an opening ratio of 35% or more and 55% or less.
A method for producing an anion exchange membrane, which comprises a step of copolymerizing the monomer component at 40 ° C. or higher and lower than 80 ° C. after the dipping step. The method for producing an anion exchange membrane according to claim 8, wherein the base material is a polyethylene-based woven fabric. The production of the anion exchange membrane according to claim 8 or 9, wherein the polymerizable composition for forming an anion exchange resin contains the polymerization initiator having a decomposition temperature of 90 ° C. or lower for obtaining a half-life of 10 hours. Method. The styrene-based monomer having a functional group into which an anion-exchange group can be introduced or an anion-exchange group is a styrene-based monomer having a functional group into which an anion-exchange group can be introduced or an anion-exchange group. The method for producing an anion exchange film according to any one of them.