JP5579365B2 - Anion exchange membrane and method for producing the same - Google Patents

Description

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

  An electrodialysis tank using positive and negative ion exchange membranes is used in the seawater concentration step in the ion exchange membrane salt production method. An ion exchange membrane used for an electrodialysis tank needs to improve the concentration performance without increasing the electrical resistance of the membrane in order to reduce the production cost of salt.

  A number of methods for producing an ion exchange membrane for salt production have been proposed (see, for example, Patent Documents 1 to 3). Among them, a monomer having a functional group into which an ion exchange group can be introduced, and a crosslinking agent. In addition, a method is widely known in which a mixture containing a polymerization initiator as a main component is applied to a woven fabric made of polyvinyl chloride and polymerized, and then ion exchange groups are introduced as necessary.

  However, it has been difficult to improve the concentration performance of the ion exchange membrane obtained by this method without increasing the electrical resistance of the membrane.

  In order to solve such problems, a method of obtaining an ion exchange membrane by impregnating and supporting a polymerizable monomer on a polypropylene fiber substrate or the like and then graft polymerizing with ionizing radiation, or a polymerizable monomer on a polyolefin substrate or the like A method has been proposed in which a polymer is impregnated and supported, followed by partial polymerization with ionizing radiation, followed by heating in the presence of a polymerization initiator to complete the polymerization and obtain an ion exchange membrane (for example, patents). References 4-6).

However, none of the methods yielded satisfactory results in terms of membrane concentration performance.
Japanese Examined Patent Publication No. 39-27861 Japanese Patent Publication No.40-28951 Japanese Patent Publication No. 44-19253 JP-A-51-52489 JP 60-238327 A Japanese Patent Application Laid-Open No. 06-271687

  This invention is made | formed in view of such a subject, Compared with the conventionally used film | membrane about the anion exchange membrane used for salt production, it improves a concentration performance, without increasing an electrical resistance. It is for the purpose.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have filled a porous base material made of polyethylene or the like with a polystyrene copolymer having a quaternary ammonium group or the like. The present inventors have found that the anion exchange membrane improves the concentration performance without increasing the electric resistance as compared with the conventionally used anion exchange membrane for salt production. More specifically, monomers such as chloromethylstyrene and divinylbenzene are filled in the pores of the porous base material made of ultrahigh molecular weight polyethylene and thermally polymerized. It has been found that the anion exchange membrane obtained by introducing a quaternary ammonium group improves the concentration performance without increasing the electric resistance, compared with the conventionally used anion exchange membrane for salt production.

That is, the present invention has achieved the above object by adopting the following configuration.
(1) Chloromethylstyrene and divinylbenzene are formed in the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. And an anion-exchange membrane for electrodialysis for salt production, which is filled with a copolymer having a quaternary ammonium group in a weight ratio of 70 to 85:30 to 15 at least.
(2) Chloromethylstyrene having a functional group capable of introducing a quaternary ammonium group into the pores of a porous film-like substrate made of the aliphatic polyolefin and having an average pore diameter of 0.01 to 2 μm; The anion exchange membrane for electrodialysis for salt production according to the above (1), obtained by filling a polymerizable mixture containing divinylbenzene in a weight ratio of 70 to 85:30 to 15 and performing thermal polymerization.
(3) The anion exchange membrane for electrodialysis for salt production according to (1) or (2), wherein the aliphatic polyolefin is polyethylene.
(4) The anion exchange membrane for electrodialysis for salt production according to (1) or (2), wherein the aliphatic polyolefin is ultrahigh molecular weight polyethylene.
(5) The anion exchange membrane for electrodialysis for salt production according to any one of (2) to (4), wherein the polymerizable mixture contains rubber.
(6) A quaternary ammonium group is formed in the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. Anion exchange for electrodialysis for salt production comprising a step of filling a polymerizable mixture containing chloromethylstyrene and divinylbenzene having a functional group capable of introduction at a weight ratio of 70 to 85:30 to 15 and performing thermal polymerization A method for producing a membrane.
(7) If the functional group capable of introducing the quaternary ammonium group itself is not a quaternary ammonium group, it is treated with a compound capable of imparting a quaternary ammonium group after thermal polymerization. A method for producing an anion exchange membrane for electrodialysis for salt production.
(8) The method for producing an anion exchange membrane for electrodialysis for salt production according to the above (6), wherein the functional group itself capable of introducing the quaternary ammonium group is a quaternary ammonium group.
(9) The method for producing an anion exchange membrane for electrodialysis for salt production according to any one of (6) to (8), wherein the polymerizable mixture contains rubber.

As is clear from the above, the gist of the present invention resides in the following (1) to (3).
(1) Chloromethylstyrene and divinylbenzene are formed in the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. And an anion exchange membrane for electrodialysis for salt production, which is filled with a copolymer having a quaternary ammonium group in a weight ratio of 70 to 85:30 to 15 at least.
(2) A quaternary ammonium group is formed in the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. As described in (1) above, which is obtained by filling a polymerizable mixture containing chloromethylstyrene having an introduceable functional group and divinylbenzene in a weight ratio of 70 to 85:30 to 15 and performing thermal polymerization. Anion exchange membrane for electrodialysis for salt production.
(3) A quaternary ammonium group is formed in the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. Anion exchange for electrodialysis for salt production comprising a step of filling a polymerizable mixture containing chloromethylstyrene and divinylbenzene having a functional group capable of introduction at a weight ratio of 70 to 85:30 to 15 and performing thermal polymerization A method for producing a membrane.

  According to the present invention, an anion exchange membrane having an improved concentration performance can be provided without increasing the electrical resistance as compared with the anion exchange membrane currently used for salt production, which can contribute to a reduction in salt production cost.

The method for producing an anion exchange membrane for salt production according to the present invention generally comprises a polymerizable monomer having a functional group capable of introducing a quaternary ammonium group into the pores of a porous substrate made of polyolefin, and a crosslinked monomer. It is characterized in that a polymerizable mixture containing a polymerizable monomer is filled, thermal polymerization is performed, and a quaternary ammonium group is introduced using trimethylamine or the like as necessary.
More specifically, the copolymer obtained by performing thermal polymerization by filling monomers such as chloromethylstyrene and divinylbenzene into the pores of a porous base material made of polyethylene or ultrahigh molecular weight polyethylene. In the present invention, a quaternary ammonium group is introduced.

Hereinafter, embodiments of the present invention will be described in detail.
In the present invention, the polyolefin is a polymer of a compound having a double bond in the molecule. Specifically, polymers of aliphatic olefins such as polyethylene, polypropylene, polybutylene and polybutadiene, polymers of aromatic olefins such as polystyrene, poly α-methylstyrene and polydivinylbenzene, polymethyl methacrylate, polyvinyl acetate, Polymers of oxygen-containing olefins such as polyvinyl alcohol, polymers of nitrogen-containing olefins such as polyacrylonitrile and poly-N-methylpyrrolidone, halogen-containing olefins such as polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, and polytetrafluoroethylene A polymer etc. are mentioned. These polyolefins may be used alone or a plurality of polyolefins may be mixed. Further, it may be a copolymer of two or more olefins as described above, or a graft copolymer. It may have a crosslinked structure by copolymerization with a compound having two or more double bonds, electron beam irradiation, plasma irradiation, ultraviolet irradiation, chemical reaction, or the like. Among them, polyethylene is preferable from the viewpoint of chemical stability and cost, and ultrahigh molecular weight polyethylene having a molecular weight of 1,000,000 or more is particularly preferable. In the present invention, the polyolefin may contain various additives such as an antioxidant, an ultraviolet absorber, and an antistatic agent as long as the desired characteristics are not impaired.

The porous substrate in the present invention is a film-like material having an average pore diameter of 0.001 to 50 μm, a thickness of 1 to 300 μm, and a porosity of 1 to 95%. The average pore diameter of the porous substrate is preferably 0.005 to 5 μm, and particularly preferably 0.01 to 2 μm. The thickness of the porous substrate is preferably 5 to 200 μm, particularly preferably 10 to 150 μm. The porosity of the porous substrate is preferably 10 to 90%, particularly preferably 20 to 80%. The porosity here means the apparent density ρa (g / cm ³ ) based on the weight and thickness per unit area of the porous substrate, and the polyolefin constituting the porous substrate (in the case where an additive is included) The value calculated from the true density ρt (g / cm ³ ) of the product including the additive by the following formula.
Porosity (%) = (1−ρa / ρt) × 100

  In the present invention, as a method for producing a porous substrate, a wide variety of conventional methods can be used without any limitation. For example, a melted polymer is made into a sheet, and a laminated lamella structure is formed by heat treatment, and the crystal opening is separated by uniaxial stretching, or the polymer and solvent are heated and melted into a sheet for microphase separation. And a phase separation method in which the solvent is extracted and removed uniaxially or biaxially.

  As a porous base material concerning this invention, Asahi Kasei Chemicals Co., Ltd. Hypore (product name), Tonen Chemical Nasu Co., Ltd. cetilla (product name), etc. are mentioned, for example.

  In the present invention, a copolymer refers to a polymer having two or more monomers as constituent units. For example, a copolymer produced by addition polymerization of a compound having a double bond such as styrene and chloromethylstyrene, a copolymer produced by polycondensation such as a reaction between a dicarboxylic acid and a dialcohol, Examples thereof include copolymers formed by polyaddition as in the reaction of diisocyanate and dialcohol. Moreover, what has a crosslinked structure like the copolymer of chloromethylstyrene and divinylbenzene is also contained.

  In the present invention, the copolymer comprises at least a copolymer component of chloromethylstyrene and divinylbenzene, but other copolymer components are particularly limited as long as they copolymerize with chloromethylstyrene and divinylbenzene. Absent. For example, styrene monomers such as styrene, α-methyl styrene, vinyl toluene, p-methoxy styrene, p-ethyl styrene, m-ethyl styrene, o-ethyl styrene, methyl acrylate, methyl methacrylate, acrylamide, acrylonitrile Acrylic acid or methacrylic acid monomers such as divinyltoluene, divinylnaphthalene, aromatic dienes such as 1,2-bis (vinylphenyl) ethane, aromatic polyenes such as trivinylbenzene, ethylene glycol dimethacrylate, Examples include acrylic acid dienes such as N, N-methylenebisacrylamide, and acrylic acid polyenes such as pentaerythritol triacrylate.

  In the present invention, the quaternary ammonium group means a cation formed by bonding four carbon atoms to one nitrogen atom, and is widely used as an anion exchange group of an anion exchange membrane. is there. However, the four carbon atoms do not necessarily need to be different carbon atoms, and includes the case where they are the same carbon atom.

  As a method for introducing a quaternary ammonium group into the copolymer, a method of copolymerizing a polymerizable mixture containing chloromethylstyrene and divinylbenzene and then quaternizing the chloromethyl group with an amine, A monomer having, for example, a method of copolymerizing a polymerizable mixture containing bromomethylstyrene and the like, chloromethylstyrene and divinylbenzene, and then quaternizing the halogenated alkyl group with an amine, a monomer having an aromatic ring, For example, a method of copolymerizing a polymerizable mixture containing styrene, chloromethylstyrene and divinylbenzene, then introducing a chloromethyl group by reaction with chloromethyl methyl ether, etc., and quaternizing with an amine, an epoxy group Polymers containing monomers such as glycidyl methacrylate, chloromethylstyrene and divinylbenzene Copolymerization of the mixture followed by quaternization by reaction with trimethylamine or the like, copolymerization of a nitrogen-containing monomer such as vinylbenzyl (dimethyl) amine, a polymerizable mixture containing chloromethylstyrene and divinylbenzene Then, a method of quaternization with methyl iodide or the like, a monomer having a quaternary ammonium group, for example, vinylbenzyl (trimethyl) ammonium hydroxide or the like, a polymerizable mixture containing chloromethylstyrene and divinylbenzene are used together. There are methods for polymerization, and there is no particular limitation. Among them, a method of copolymerizing a polymerizable mixture containing chloromethylstyrene and divinylbenzene and then quaternizing the chloromethyl group with an amine is particularly preferable.

  As amines for quaternizing the chloromethyl group, primary amines such as ammonia, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, methylethylamine, diethylamine, methylpropylamine, etc. Secondary amines, trimethylamine, dimethylethylamine, dimethylpropylamine, dimethylbutylamine, dimethylbenzylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, tertiary amines such as triethanolamine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′-tetramethyl-1,3-propanediamine, N, N, N ′, N′-tetramethyl-1,4-butanediamine, N, N, Diamines such as', N'-tetramethyl-1,6-hexanediamine, triamines such as N, N, N ′, N ′ ′, N ′ ′-pentamethylethylenetriamine, polyethyleneimine, poly-N, Examples thereof include, but are not limited to, polyamines such as N-dimethylallylamine, aromatic amines such as pyridine, pyrrole and aniline, and aliphatic cyclic amines such as piperidine and morpholine.

  When the chloromethyl group is quaternized with an amine, it can be carried out with an amine alone without a solvent, or with a solvent such as water, methanol, ethanol, acetone, N, N-dimethylformamide or the like.

In the present invention, as a method of filling the copolymer having a quaternary ammonium group into the pores of the porous substrate, a wide range of conventionally performed methods can be used without any limitation. For example, a method of removing the solvent after immersing the porous substrate in a copolymer solution having a quaternary ammonium group, and filling the pores of the porous substrate with a monomer having a quaternary ammonium group Then, a method of polymerizing by light irradiation, filling a polymerizable mixture containing chloromethylstyrene, divinylbenzene, a polymerizable monomer, a crosslinkable monomer, etc. in the pores of the porous substrate, There is a method of performing polymerization and quaternization with an amine, but in particular, the polymerizability containing chloromethylstyrene, divinylbenzene, a polymerizable monomer, a crosslinkable monomer, etc. in the pores of the porous substrate. A method of filling the mixture, performing thermal polymerization, and quaternizing with an amine is preferable. In addition, as a method of filling a polymerizable mixture containing chloromethylstyrene, divinylbenzene, a polymerizable monomer, a crosslinkable monomer, etc. in the pores of the porous substrate, the polymerizable mixture or a solution thereof can be used. A method of immersing the porous substrate is preferred.

  In the present invention, the polymerizable mixture is a mixture of a polymerizable monomer, a crosslinkable monomer, rubber, a linear polymer substance, a plasticizer, a polymerization initiator, and the like.

In the present invention, the polymerizable monomer having a functional group capable of introducing a quaternary ammonium group has a functional group that easily introduces a quaternary ammonium group, or a polymerizable monomer having a quaternary ammonium group. Specifically, the monomers listed below are listed.
(1) A monomer having a halogenated alkyl group. For example, chloromethyl styrene, bromomethyl styrene, α-methyl (chloromethyl) styrene, vinyl (chloromethyl) naphthalene, (2-chloroethyl) styrene, (6-chlorohexyl) styrene and the like.
(2) A monomer having an aromatic ring. For example, styrene, α-methyl styrene, vinyl toluene, p-methoxy styrene, p-ethyl styrene, m-ethyl styrene, vinyl naphthalene and the like.
(3) A monomer having an epoxy group. For example, glycidyl methacrylate, epoxy styrene, butadiene monoxide and the like.
(4) A monomer containing nitrogen. For example, vinyl benzyl (dimethyl) amine, vinyl pyridine, 2-methyl-5-vinyl pyridine, ethyl vinyl pyridine, vinyl pyrrolidone, vinyl carbazole, vinyl imidazole, aminostyrene, (methylamino) styrene, (dimethylamino) styrene and the like.
(5) A monomer having a quaternary ammonium group. For example, vinyl benzyl (trimethyl) ammonium hydroxide, trimethyl vinyl ammonium chloride, trimethyl allyl ammonium chloride and the like.

  In the present invention, the crosslinkable monomer can be used without particular limitation as long as it has at least two double bonds in the molecule. For example, aromatic dienes such as divinylbenzene, divinyltoluene, divinylnaphthalene, 1,2-bis (vinylphenyl) ethane, aromatic polyenes such as trivinylbenzene, ethylene glycol dimethacrylate, N, N-methylenebisacrylamide Acrylic acid-based polyenes such as acrylic acid-based dienes such as pentaerythritol triacrylate and tetramethylolmethane tetraacrylate, and divinylbenzene is particularly preferable.

  In order to impart flexibility to the synthesized anion exchange membrane, it is also effective to add an elastic body such as rubber to the polymerizable mixture. As the rubber, those conventionally used for ion-exchange membranes for salt production can be used without any limitation. For example, nitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), natural rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, acrylic rubber, hydrogenated nitrile butadiene rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene Norbornene rubber or the like can be used, and these can be used alone or in admixture of two or more. Among them, NBR and SBR are particularly preferable.

  In addition, in order to impart flexibility to the synthesized anion exchange membrane, for example, polyvinyl chloride fine powder, polyethylene fine powder, polypropylene fine powder or the like may be added to the polymerizable mixture as a linear polymer substance. It is effective and can be used alone or in admixture of two or more. For the same purpose, it is also effective to add dioctyl phthalate, di-2-ethylhexyl phthalate, dibutyl phthalate, tributyl phosphate or aliphatic acid, alcohol ester of aromatic acid, etc. as a plasticizer to the polymerizable mixture. is there.

In the following description and examples, all parts are parts by weight. The amount of rubber, linear polymer material and plasticizer added to the polymerizable mixture containing chloromethylstyrene and divinylbenzene is not particularly limited, but is a polymerizable monomer containing chloromethylstyrene and divinylbenzene. And 100 parts by weight of the crosslinkable monomer, the rubber is preferably 50 parts or less, the linear polymer substance is preferably 30 parts or less, the plasticizer is preferably 50 parts or less, particularly the rubber is 30 parts or less, the linear high The molecular substance is preferably 20 parts or less, and the plasticizer is preferably 30 parts or less.
In the polymerizable mixture, the use ratio (weight ratio) of chloromethylstyrene and divinylbenzene is preferably in the range of 0.05 to 1 when the former is 1, and 0.07 to 0.55. A range is particularly preferred. If the proportion of divinylbenzene used is too small relative to chloromethylstyrene, the copolymer having a quaternary ammonium group may be peeled off when formed into an anion exchange membrane, and if too large, the membrane resistance will be too high.

  In the present invention, a wide variety of conventional methods can be used for thermal polymerization without any limitation. It is possible to polymerize only by heating without using a polymerization initiator, but after immersing the porous substrate in a polymerizable mixture containing chloromethylstyrene and divinylbenzene to which a polymerization initiator has been added, A method in which the substrate is sandwiched between glass plates and heated in a dryer is suitable.

  Although the polymerization initiator used for thermal polymerization is not particularly limited, azobisisobutyronitrile (AIBN), 1,1′-azobiscyclohexane-1-carbonitrile, dimethyl-2,2′-azobis (2- Azo polymerization initiators such as methylpropionate) and 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide (BPO), t-butyl peroxybenzoate, dilauryl peroxide, ditoxide peroxide -Peroxide-based polymerization initiators such as butyl and disuccinic peroxide can be used, and AIBN and BPO are particularly preferable.

  Specific examples of thermal polymerization are shown below. The porous substrate is immersed in a polymerizable mixture in which 80 parts of chloromethylstyrene, 20 parts of divinylbenzene, 5 parts of NBR, and 1 part of AIBN are mixed at room temperature for 3 seconds to 12 hours. After a predetermined time, the porous substrate is taken out, sandwiched between glass plates, and placed in a dryer. The temperature of thermal polymerization is 30 to 120 ° C., preferably 50 to 100 ° C., and is maintained for 3 to 24 hours.

  As a next step, a quaternary ammonium group is introduced into a porous substrate filled with a copolymer of chloromethylstyrene and divinylbenzene in the pores. The introduction of the quaternary ammonium group can be performed without any limitation by a wide range of methods conventionally used. Specific examples are shown below.

  A porous base material in which a copolymer of chloromethylstyrene and divinylbenzene and the like is mixed in a 1: 1 (by weight) mixed solution of trimethylamine 30% aqueous solution and methanol in a pore at 0 to 50 ° C. for 30 minutes to 7 days. Immerse and react. After reacting for a predetermined time, the membrane is thoroughly washed with water.

  Hereinafter, the anion exchange membrane of the present invention and the production method thereof will be described in more detail based on examples. In addition, this invention is not limited to this Example.

Example 1
In a glass container, 80 parts of chloromethylstyrene (chloromethylstyrene CMS-P (product name) manufactured by AGC Seimi Chemical Co., Ltd.), divinylbenzene (55% divinylbenzene (isomer mixture) manufactured by Wako Pure Chemical Industries, Ltd.) (product name) ) 20 parts, 5 parts of NBR and 1 part of AIBN were added, and Tonen Chemical Nasu Co., Ltd. Setira E30MMS (thickness 31 μm, pore diameter 0.051 μm, porosity 38%), which is a porous substrate made of ultrahigh molecular weight polyethylene ) For 3 hours at room temperature. After the immersion, Setilla E30MMS was taken out, sandwiched between glass plates, put into a dryer, and subjected to thermal polymerization at 60 ° C. for 16 hours and at 90 ° C. for 3 hours.

  Cetilla E30MMS after thermal polymerization was immersed in a 1: 1 (by weight) mixed solution of trimethylamine 30% aqueous solution and methanol for 72 hours at room temperature, and the membrane was then thoroughly washed with water. The obtained anion exchange membrane was stored in 0.5N-NaCl aqueous solution.

Further, the anion exchange membrane and a commercially available cation exchange membrane (Asahi Glass Co., Ltd. CSO) were mounted on a small electrodialysis apparatus (membrane area 8 cm ² ), and a concentration test was performed at 25 ° C. A 0.5N-NaCl aqueous solution was used as the feed solution under the concentration conditions of a desalting chamber flow rate of 6 cm / s and a current density of 3 A / dm ² .

Examples 2 to 15 are anion exchange membranes synthesized by a method different from Example 1, and Examples 1 and 2 are membranes currently used as anion exchange membranes for salt production (Asahi Glass Co., Ltd. ASA). Table 1 shows the physical properties of the porous substrate used for the synthesis of the anion exchange membrane, and Table 2 shows the thermal polymerization conditions and the membrane properties of the obtained anion exchange membrane. In Examples 9 to 13, cetera F23DHA after thermal polymerization was immersed in a 30% aqueous solution of trimethylamine instead of a 1: 1 (by weight) mixed solution of 30% aqueous solution of trimethylamine and methanol for 72 hours at room temperature. After sufficiently washing with water, the obtained anion exchange membrane was stored in a 0.5N-NaCl aqueous solution. In Examples 14 and 15, cetera F23DHA after thermal polymerization was immersed in a 30% aqueous solution of N, N, N ′, N′-tetramethyl-1,6-hexanediamine for 4 hours at room temperature, and then trimethylamine was further added. The membrane was immersed in a 30% aqueous solution for 48 hours, the membrane was thoroughly washed with water, and the obtained anion exchange membrane was stored in a 0.5N-NaCl aqueous solution. The membrane resistance is measured by mounting the anion exchange membrane on a membrane resistance measurement cell (membrane area 1.8 cm ² ), filling both sides of the membrane with a 0.5N-NaCl aqueous solution, and using a milliohm meter at 25 ° C. and a frequency of 1 kHz. Then, the anion exchange membrane was removed, and the electrical resistance of the blank was measured under the same conditions, and the difference between the two was taken as the membrane resistance. The brine concentration was determined by measuring the Cl concentration of the concentrated NaCl aqueous solution obtained in the concentration test.

FIG. 1 shows the relationship between membrane resistance and brine concentration as a result of the concentration test.
As shown in Table 2 and FIG. 1, all the membranes synthesized according to the present invention exhibited high concentration performance as compared with commercially available anion exchange membranes for salt production. In addition, the straight line shown in FIG. 1 is a straight line which shows the concentration performance equivalent to a commercially available ion exchange membrane, and it can be said that all the membrane performance shown above a straight line is higher concentration performance than a commercial membrane.

It is a graph showing the relationship between the membrane resistance of an anion exchange membrane and the brine concentration in the Example and comparative example of this invention.

Claims (9)

70 ml of chloromethylstyrene and divinylbenzene are contained in the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. An anion exchange membrane for electrodialysis for salt production, which is filled with a copolymer having a quaternary ammonium group as a copolymerization component at a weight ratio of ˜85: 30 to 15. Chloromethylstyrene and divinylbenzene having a functional group capable of introducing a quaternary ammonium group in the pores of a porous film-like substrate made of the aliphatic polyolefin and having an average pore diameter of 0.01 to 2 μm The anion exchange membrane for electrodialysis for salt production according to claim 1, which is obtained by filling a polymerizable mixture contained in a weight ratio of 70 to 85:30 to 15 and performing thermal polymerization. The anion exchange membrane for electrodialysis for salt production according to claim 1 or 2, wherein the aliphatic polyolefin is polyethylene. The anion exchange membrane for electrodialysis for salt production according to claim 1 or 2, wherein the aliphatic polyolefin is ultrahigh molecular weight polyethylene.   The anion exchange membrane for electrodialysis for salt production according to any one of claims 2 to 4, wherein the polymerizable mixture contains rubber. A quaternary ammonium group can be introduced into the pores of a porous film-like substrate made of at least one aliphatic polyolefin selected from polyethylene, polypropylene and polybutylene and having an average pore diameter of 0.01 to 2 μm. 2. The salt for electrodialysis for salt production according to claim 1, comprising a step of filling a polymerizable mixture containing chloromethylstyrene having a functional group and divinylbenzene in a weight ratio of 70 to 85:30 to 15 and performing thermal polymerization. A method for producing an ion exchange membrane.   The electrodialysis for salt production according to claim 6, wherein when the functional group capable of introducing the quaternary ammonium group is not a quaternary ammonium group, it is treated with a compound capable of imparting a quaternary ammonium group after thermal polymerization. For producing an anion exchange membrane.   The method for producing an anion exchange membrane for electrodialysis for salt production according to claim 6, wherein the functional group itself capable of introducing the quaternary ammonium group is a quaternary ammonium group.   The method for producing an anion exchange membrane for electrodialysis for salt production according to any one of claims 6 to 8, wherein the polymerizable mixture contains a rubber.

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