JPH0443099B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a new method for producing an improved ion exchange membrane, and more specifically, a method for easily producing an ion exchange membrane endowed with ion selective permeability and especially conductivity. It's about how to do it.

[Prior art and its problems]

Conventionally, various methods have been attempted to improve or reduce the ion-selective permselectivity of ion exchange membranes, or to change the selectively permselectivity between ions of the same name. In addition, various attempts have been made to impart new functions to ion exchange membranes by impregnating and polymerizing polymerizable vinyl monomers into cation exchange membranes or anion exchange membranes. This has led to a decrease in the amount of acid, an increase in the transfer number, a decrease in the amount of acid leakage, and a decrease in the amount of base leakage. However, these methods generally polymerize vinyl monomers within the membrane, and the ion exchange membrane itself may be swollen by these vinyl monomers, resulting in a decrease in the mechanical strength of the membrane. There are problems that arise. It has also been reported that condensation monomers can be condensed within an ion exchange membrane, but this often requires heat treatment to complete the condensation reaction, which can impair membrane performance. arise.

In view of the above, the present inventors generally form a matrix of another polymer in the matrix of an ion exchanger to change the properties of the ion exchanger and to impart new functions to the ion exchanger. We have repeatedly considered whether this is possible. As a result, by impregnating and polymerizing an ion exchanger with a monomer capable of oxidative polymerization, an improved ion exchanger was obtained in which the properties of the ion exchanger were improved and new useful functions were imparted.

[Means for solving problems]

The present invention provides a simple method for producing an improved membrane ion exchanger, particularly in the production of the above-mentioned improved ion exchanger. That is, the present invention transfers the oxidizing agent from one side and transfers the oxidatively polymerizable monomer from the other side through the ion exchange membrane, and transfers the monomer in the ion exchange membrane. This is a method for producing an improved ion exchange membrane characterized by polymerization.

The ion-exchange membrane of the present invention is not limited to organic ion-exchange membranes.
Heat-molded products are also suitably used. Examples of organic ion exchange membranes include polymeric ion exchangers, so-called styrene-3' vinylbenzene copolymers with ion exchange groups bonded to them, and condensation ion exchangers with cation exchange groups and/or Alternatively, those to which an anion exchange group is bonded are preferably used. As such an ion exchanger, conventionally known homogeneous or heterogeneous ion exchangers can be used, and the substrate of the ion exchanger may be hydrocarbon-based, carbon fluoride-based, or perfluorocarbon-based. Suitable for use regardless of the type of item.

In addition, the ion exchange membrane used in the present invention generally has a
It is not particularly limited as long as it has 15 milliequivalents of ion exchange group bonded thereto. As the ion exchange group, conventionally known cation exchange groups such as sulfonic acid, carboxylic acid, phosphoric acid, phosphorous acid, sulfonic acid ester, phenolic hydroxyl group, thiol group, and tertiary perfluoroalcohol are used. Anion exchange groups include primary, secondary, and tertiary amines,
Onium bases such as quaternary ammonium, tertiary sulfonium, quaternary phosphonium, cobalticinium and the like are preferred.

In addition, the above-mentioned ion-exchange membranes are available in various types as needed, such as those in which the ion-exchange groups are uniformly dispersed in the substrate, those in which the ion-exchange groups are concentrated on one side, and those in which there is a concentration gradient. Suitably used. The ion exchange groups present in such an ion exchange membrane include cases where a cation exchange group is present, and cases where both ion exchange groups are present at the same time. When present at the same time, the two types of ion exchange groups may exist in a layered form over two or more layers, or may exist arbitrarily uniformly. In addition, there is a layer in which cation exchange groups exist, a layer in which cation exchange groups and anion exchange groups are arbitrarily distributed, and then there is another layer in which cation exchange groups exist, or Various types of ion exchangers are formed depending on the state of existence of various ion exchange groups, such as when there is a layer containing a layer containing a ion exchanger, or vice versa. Effectively applied in the method of invention. In addition,
The above-mentioned cation exchange group and anion exchange group do not mean the same type of cation exchange group or anion exchange group, but rather different cation exchange groups such as a carboxylic acid group and a sulfonic acid group. However, it is often particularly effective when different types are used. Further, the above-described inorganic ion exchange membrane and organic ion exchange membrane are not limited to those having a single matrix, but a composite of the two may also be suitably used. Specifically, fine powder of an inorganic ion exchanger is molded into a moldable organic ion exchanger to form an appropriate membrane shape, or a polymer electrolyte or an inert polymer is dissolved in an appropriate solvent. By dispersing an inorganic ion exchanger therein and scattering the solvent, a membrane-shaped ion exchanger can be obtained.

The oxidizing agent used in the present invention may be any conventionally known oxidizing agent, such as H ₂ O ₂ , (C ₆ H ₅ CO) ₂
Peroxides such as O ₂ , FeCl ₃ , CuSO ₄ , CuCl ₂ ,
Metal salts such as RuCl ₃ , Na ₂ S ₂ O ₈ , Na ₂ SO ₅ ,
Peroxo acids (salts) such as ( _{NH4 ) 2SO5} , NaClO,
Examples include oxyacid salts such as NaBrO and NaClO ₃ . In other words, metal ions whose charge changes by redox, such as trivalent iron ions, divalent copper ions, and trivalent ruthenium ions, and organic compounds or metal complex ions whose charge changes by redox. Cations such as ions, and oxidizing anions such as persulfate ions, perborate ions, and perchloric acid are preferably used. These cations and anions are suitable because they undergo ion exchange with the exchange groups of the ion exchanger in an oxidized state and are uniformly dispersed within the ion exchanger. Conversely, if you want to carry out the oxidative polymerization reaction only in the surface layer of the ion exchanger,
It is preferable to use a peracid bonded with a long-chain alkyl group, or a peracid group bonded to a compound that cannot easily enter the pores of the ion exchanger, such as a naphthalene ring.

In addition, oxidatively polymerizable monomers used in the present invention include pyrrole and derivatives thereof, such as N-
One or more derivatives of methylpyrrole, 2-ethylpyrrole, etc., thiophene and its derivatives, isothianaphthene and its derivatives, indole, azulene, furan, aniline, phenol, benzene, naphthalene, etc. are preferably used. In particular, heterocyclic compounds such as pyrrole, indole, azulene, thiophene, furan, and their derivatives are preferred because they have good affinity with ion exchange membranes and are uniformly dispersed in the ion exchange membrane upon ion exchange.

Next, the present invention moves a liquid in which an oxidizing agent is dissolved or dispersed in an inorganic solvent from one side through the above-mentioned ion exchange membrane, and transfers it to an organic or inorganic solvent from the other side. Polymerization of the oxidatively polymerizable monomer is achieved in the ion exchange membrane by moving a liquid in which the monomer is dissolved or dispersed. The concentration of the oxidatively polymerizable monomer is not particularly limited, and may range from 0.01% to a saturated solution of the monomer, and may even be polymerized in a suspended state. Polymerization is carried out under cooling at a temperature within a range where the solvent does not freeze, or under heating at a temperature within a range where the solvent does not boil. Further, the polymerization time varies depending on the type of monomer and the type of ion exchange membrane, but generally it can be carried out by selecting an appropriate time from 1 minute or more to 72 hours.

Hereinafter, some specific embodiments will be shown in order to explain the present invention.

(1) A cation exchange membrane cross-linked with styrene-divinylbenzene is incorporated into a cell divided into two chambers.
Place an aqueous solution of iron chloride on one side and an aqueous solution containing pyrrole on the other side, and move each solution.

The membrane thus obtained was thoroughly washed with water,
After thorough conditioning with 1N hydrochloric acid and 0.5N-salt solution to remove Fe ⁺⁺ , hydrogen ions were selectively removed by electrodialysis of the solution containing 0.25N hydrochloric acid and 0.25N salt. permeates through the membrane.

(2) When the electrical conductivity of the membrane-like material synthesized in (1) was measured after drying under reduced pressure, it was found to have an electrical resistance of 1 KΩcm or less. On the other hand, the membrane in which pyrrole was not polymerized had an electrical conductivity of 20 MΩ-cm ² or more.

(3) Incorporate an anion exchange resin membrane with pyridinium base as an anion exchange group into a cell divided into two chambers, put an ammonium persulfate solution in one side and an aqueous solution of pyrrole in the other side, and move the liquid. and polymerized.

Even when this membrane was washed repeatedly with acid-alkali, no elution occurred.

(4) Seal one side of the ion exchanger, which is a tubular membrane made of benzyltrimethylammonium ion as an anion exchange group, inject ammonium persulfate solution, and seal the other side to prevent the liquid from leaking. did. When this tubular ion exchanger was immersed in an aqueous solution of aniline, aniline moved into the anion exchanger and impregnated and polymerized, causing the pale yellow anion exchanger to turn black. When the electrical resistance of this was measured, it was found to be less than 100 Ω-cm, whereas the ion exchanger not impregnated with aniline had an electrical resistance of more than 20 M-cm.

(5) A pyridinium base-type membrane-like anion exchanger was installed in a cell divided into two chambers, an aqueous ammonium persulfate solution was placed on one side, and aniline was placed on the other side, and polymerization was caused by mutual diffusion. . When this membrane-like material was taken out and the selective permeability of sulfate ions and chloride ions was measured, it was found that when polyaniline was not present, when 1 equivalent of chlorine ions permeated, 0.3 equivalents of sulfate ions permeated. The value was 0.01 for those impregnated with polyaniline.

(6) A pyridinium base type membrane anion exchanger is placed in a cell divided into two compartments, one side is filled with an aqueous solution of pyrrole, and the other side is filled with an aqueous solution of ferric chloride to allow mutual diffusion. Pyrrole was polymerized within the membrane. After taking out this film-like material and washing it with water and drying it, I placed a platinum plate on both sides and measured the voltage with a digital voltmeter.
It was 0.4V. A battery was formed in an ion exchange membrane.

〔Effect of the invention〕

As described above, the present invention uses a simple method, and the obtained ion exchanger membrane has a change in ion permeability, especially selective permeability between ions of the same sign, and is generally used for highly charged ionic species and small hydrated ion radius. The penetration of ionic species becomes blocked. Furthermore, depending on the method of oxidative polymerization of monomers, an electron conductive function can be imparted to the ion exchange membrane, turning it into a new functional substance such as a sensor. Further, by the polymerization method, an electromotive force is generated and a battery is formed.

〔Example〕

EXAMPLES Hereinafter, the content of the present invention will be explained in more detail in Examples, but the present invention is not limited to the following Examples.

Example 1 Ion exchange capacity with sulfonic acid group bonded is 2.3
Milliequivalent/g dry film polymer film (7.0×7.0
cm ² ) was placed in a cell divided into two chambers, a 5% aqueous solution of ferric chloride was placed in one side, a 2% aqueous solution of pyrrole was placed in the other side, and the inside of each cell was stirred. After leaving it for 16 hours, I took it out, washed it with water, washed it with ethanol, immersed it in 1N hydrochloric acid, changed the hydrochloric acid repeatedly, and then looked at the absorption of iron using fluorescent X-rays. Iron had been removed.

This is an acrylic cell divided into two chambers using this membrane, each with an internal volume of 120 c.c.
Filled with NaCl and 0.25 normal _CaCl2 . In addition, before incorporating the membrane into a two-chamber cell, this 0.25 standard must be met.
Thorough equilibration was achieved with a solution of NaCl and 0.25N CaCl ₂ .

This cell was equipped with silver and silver chloride electrodes in both chambers, and electrodialysis was carried out through these electrodes at a current density of 1 A/dm ² . The effective current carrying area was 0.1 ^dm2 . 2
After electricity was applied for a certain period of time, the amount of cations that permeated through the membrane was determined, and the current efficiency was 97%, and when 1 equivalent of Na ⁺ permeated through the membrane, the amount of Ca ²⁺ that permeated through the membrane was 0.2 equivalent. On the other hand, for comparison, measurements were made under the same conditions using a normal sulfonic acid type membrane that was not impregnated with pyrrole and polymerized, and the current efficiency was 98%, and when 1 equivalent of Na ⁺ permeated the membrane, the current efficiency was 98%. , Ca ²⁺ is 2.1
An equivalent amount permeated the membrane.

Next, the electrodialyzed membrane was taken out, equilibrated with 1N hydrochloric acid, dried under reduced pressure, and its electrical resistance was measured to be 28 Ω-cm. Also,
When an ordinary cation exchange membrane without pyrrole impregnation polymerization was measured under the same conditions, the electrical resistance was 20 MΩ-cm or more.

In addition, when the voltage was measured using a digital voltmeter with the side in contact with iron chloride of the film prepared by oxidative polymerization of pyrrole as the positive electrode and the side in contact with pyrrole as the negative electrode, an electromotive force of 0.38V was observed.

The cation exchange membrane used here was produced by copolymerizing styrene and divinylbenzene, and the divinylbenzene content was 5%. In addition, to measure the electrical resistance, apply silver paste with a 1 cm gap between a 1 cm wide film, dry it, and measure it with a conductivity meter.
The electrical resistance was calculated by converting the thickness of the film. The same thing was done in the following examples.

Example 2 Polyvinyl chloride fine powder was added to a mixture of styrene, divinylbenzene and 4-vinylpyridine, and then benzoyl peroxide as a polymerization initiator was added to form a viscous paste-like mixture,
This was applied to a polyvinyl chloride cloth, both sides covered with cellophane, and heated and polymerized at 70°C in a nitrogen atmosphere to form a polymer film. This was added to an alkylation bath consisting of a mixed solution of hexane and methyl iodide.
It was immersed at 25° C. for 24 hours to obtain an anion exchange membrane having a quaternary ammonium base as an anion exchange group.

This was assembled into a cell divided into two chambers, a 10% aqueous solution of ammonium persulfate was placed on one side, and a 5% aqueous solution of aniline dispersed on the other side, and the inside of each cell was stirred at room temperature for 8 hours.

Next, take this out and add 1N hydrochloric acid and 0.5
After conditioning with normal ammonia water, a 1:1 mixed solution of 0.25N-mirabilite and 0.25N-salt was electrodialyzed in the same manner as in Example 1.
Comparing the membrane permeability of SO ^- ₄ ^- and Cl ^- , it was found that 0.3 equivalent of SO ^- ₄ ^- permeated per 1 equivalent of Cl ^- in the membrane that was not impregnated with aniline and polymerized; Only 0.01 equivalent permeated through the membrane in which the membrane was polymerized.

After electrodialysis, the aniline-impregnated and polymerized anion exchange membrane was dried under reduced pressure, and the electrical resistance was measured to be 12 Ω-cm.

Example 3 Benzoyl peroxide was added to a paste mixture obtained by adding fine powder of polyvinyl chloride to a mixture of styrene, 4-vinylpyridine, and divinylbenzene, and this was applied to a polypropylene nonwoven fabric and heated. It was polymerized to form a film-like product. This is 97
% sulfuric acid and was gently sulfonated for 3 days. Next, this was once immersed in 0.1N caustic soda and then immersed in a bath consisting of hexane and methyl iodide to alkylate the pyridine ring. The cation exchange capacity of the amphoteric ion exchange membrane thus obtained was 0.81 meq/g dry membrane, and the anion exchange capacity was 1.12 meq/g dry membrane.

Using this, we performed the following two processes. The treatment was carried out by incorporating the above amphoteric ion exchange membrane into a cell divided into two chambers.

(a) placed in an aqueous solution of ruthenium trichloride on one side and a 2% aqueous solution of pyrrole on the other side;
Both chambers were stirred for 16 hours each at room temperature. After impregnating and polymerizing pyrrole in the amphoteric ion exchange membrane,
After washing with water and methanol, it was dried under reduced pressure and its electrical resistance was measured to be 25 Ω-cm.

(b) a 5% aqueous solution of sodium persulfate on one side and a 1% aqueous solution of aniline on the other side;
The mixture was stirred in each chamber for 24 hours at room temperature to polymerize, washed with water and methanol, and then dried under reduced pressure, showing an electrical resistance of 19 Ω-cm.

Furthermore, when both membranes were electrodialyzed with a 1:1 mixed solution of 0.25N hydrochloric acid and 0.25N table salt, the membrane impregnated with pyrrole had a current efficiency of 95%.
Therefore, 21 equivalents of hydrogen ions per 1 equivalent of Na ⁺ permeated the membrane. Furthermore, the membrane impregnated with polyaniline had a current efficiency of 97%, and 30 equivalents of hydrogen ions per 1 equivalent of Na ⁺ permeated therethrough.

Example 4 A block copolymer was synthesized by living anionic polymerization of styrene, butadiene and N,N'-ditylvinylbenzylamine. When this was casted on a flat plate and observed as a film under an electron microscope, it was found that a phase-separated structure was formed. That is, it was divided into a styrene region, a butadiene region, and an N,N'-dimethylvinylbenzylamine region. This was sulfonated with sulfuric acid to introduce a sulfonic acid group into the styrene, then substituted with methanol, and then treated with methyl iodide to introduce a quaternary ammonium base.

The membrane thus obtained, in which the cation exchange region, neutral region, and anion exchange region are distributed in a mosaic pattern, is assembled into a cell divided into two chambers, and an aqueous solution of iron trichloride is placed in one side. A 2% acetonitrile solution of pyrrole was placed on the other side, and the inside of each cell was stirred for 12 hours at room temperature to allow polymerization. Pyrrole was impregnated mainly into the region where sulfonic acid groups were present and oxidatively polymerized. When we measured the permeability of this membrane to common salt and sucrose, the membrane impregnated with pyrrole and not subjected to oxidative polymerization had a permeability coefficient of 1/81 for sucrose compared to common salt, but it was 1/210. It was decreasing.

Furthermore, when we measured the electrical resistance of another membrane made in the same way by washing it with water and methanol and drying it under reduced pressure, we found that the membrane had conductivity in the thickness direction, but no conductivity in the two-dimensional direction of the membrane. It was a bad idea. In other words, it was an anisotropically conductive film.

Example 5 A mixture of styrene and divinylbenzene is mixed with fine powder of polyethylene to make a viscous paste mixture, and this is applied to a polypropylene cloth, and then only one side of the membrane is reacted in a reaction device that can react on only one side of the membrane. was sulfonated with concentrated sulfuric acid to introduce sulfonic acid groups on only one side.

Next, this membrane was assembled into a cell divided into two chambers, and one side was filled with a 5% aqueous solution of ruthenium trichloride and the other side was filled with a 10% ethyl alcohol solution of pyrrole, and each chamber was incubated at room temperature for 16 hours. When stirred, pyrrole was impregnated only in the sulfonic acid group and oxidatively polymerized. When this was washed with water, washed with methanol, and dried under reduced pressure and its conductivity was measured, only one side of the membrane was found to be conductive in the two-dimensional direction, and the back side was an insulator.

Example 6 The membrane that had been sulfonated on only one side in Example 5 was again incorporated into a reaction device capable of reacting on only one side, and the unreacted side was brought into contact with a carbon tetrachloride solution of chloromethyl ether and tin tetrachloride to remove chloromethyl groups. introduced on one side of the membrane. Next, this membrane was immersed in a water-acetone solution of trimethylamine to carry out an amination reaction, thereby producing a membrane having a sulfonic acid group on one side and a quaternary ammonium base on the other side.

The membrane obtained above is incorporated into a cell divided into two chambers,
Place a 5% aqueous solution of sodium persulfate on one side;
When a 5% ethanol solution of aniline was placed on the other side and each cell was stirred at room temperature for 10 hours, aniline was polymerized in the anion exchange group. This part was found to be electrically conductive.

Next, this membrane was again assembled into a cell divided into two chambers, and one side was filled with a 5% aqueous solution of ferric chloride, and the other side was filled with a 2% ethanolic solution of pyrrole. When stirred,
Pyrrole polymerized in the area where the cation exchange group was present, and when the conductivity was measured after washing with water and drying under reduced pressure, conductivity was also observed on this surface.

Example 7 Polychloromethylstyrene was extruded from a nozzle and molded to obtain a tubular polymer. This was contacted with a solution of aluminum chloride in carbon disulfide to form a crosslinking reaction via a Friedel-Crafts reaction. Next, this was immersed in a mixed solution of trimethylamine, water, and acetone, and subjected to amination treatment to obtain a tubular anion exchanger having a quaternary ammonium base.

Next, one side of this tubular ion exchanger was sealed, and after injecting an aqueous ammonium persulfate solution,
The other side was also sealed to prevent it from leaking. Next, this tubular ion exchanger was immersed in an aqueous solution of pyrrole to obtain a tubular substance of the present invention. As a result, no electrical conductivity was observed in those without polymerized pyrrole, but electrical conductivity was observed in those with polymerized pyrrole.

Example 8 A fine powder of a cation exchange resin obtained by sulfonating a copolymer of styrene and divinylbenzene was mixed with polyethylene and extruded from a nozzle in the same manner as in Example 8 to form a tubular cation exchanger. Synthesized. After boiling this with pure water, one side was sealed, an aqueous solution of iron trichloride was injected, and the other side was also sealed to prevent leakage.

Next, this was immersed in a 2% aqueous solution of thiophene, heated to 50°C, and left for 24 hours.

This tubular ion exchanger was taken out, washed with water, dried under reduced pressure, and its electrical conductivity was measured, and it was found to have electrical conductivity.

Claims (1)

[Claims] 1. A method characterized in that an oxidizing agent is transferred from one side of the ion exchange membrane and a monomer capable of oxidative polymerization is transferred from the other side to polymerize the monomer in the ion exchange membrane. A method for producing an improved ion exchange membrane.