JP3396104B2 - Modified bipolar membrane - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bipolar membrane capable of preventing an increase in electric resistance and decomposing water at a low voltage for a long period of time.

[0002]

2. Description of the Related Art A bipolar membrane has a structure in which a cation exchange membrane and an anion exchange membrane are bonded together and is an ion exchange membrane capable of decomposing various salts into acid and alkali. For example, by alternately disposing a bipolar membrane and a cation exchange membrane between the anode and the cathode, a bipolar membrane on the anode side, a salt chamber in which the cation exchange membrane is disposed on the cathode side, and on the anode side. An electrodialysis tank is prepared in which a cation exchange membrane and an alkaline chamber in which a bipolar membrane is arranged on the cathode side are formed. When an aqueous solution of sodium sulfate is supplied to the salt chamber of this electrodialysis tank, sodium ions move to the cathode side, that is, the cation exchange membrane and move to the adjacent alkali chamber, and the sulfate ions do not pass through the bipolar membrane to form salt. Stay in the room. On the other hand, hydroxide ions are generated from the bipolar film on the anode side of the bipolar film, that is, the alkaline chamber, and hydrogen ions are generated from the bipolar film on the cathode side of the bipolar film, that is, the salt chamber. Therefore, in the alkaline chamber, sodium hydroxide is produced by sodium ions that have permeated the cation exchange membrane and hydroxide ions generated from the bipolar membrane, and in the salt chamber, sodium hydroxide is generated from the sulfate ions remaining in the salt chamber and the bipolar membrane. Sulfuric acid is produced with hydrogen ions.

Thus, in the electrodialysis using the bipolar membrane, it is possible to produce the corresponding acid and alkali from the salt solution.

[0004]

However, the above-mentioned bipolar film has a colloidal substance, an ionic organic substance,
Further, when it is brought into contact with the dye-containing solution for a long time, its electric resistance increases, and it becomes difficult for current to flow.

Among colloidal substances and ionic organic substances, there are substances that have extremely poor mobility in the ion-exchange membrane when they are ion-exchanged on the surface. This is called a pollutant. As a pollutant, a molecular weight of 200
To about 2000, particularly organic ionic substances can be mentioned. For example, sodium dodecylbenzene sulfonate, sodium naphthalene trisulfonate, methylene blue, crystal violet, bromophenol blue, congo red, auramine, humic acid,
There are iron colloids. And fouling
That is, the pollutant existing on the side of the desalting chamber migrates to the electrode side opposite to the charge under an electric field and exchanges ions in the ion exchange membrane, thereby increasing the electrical resistance and increasing the current. This is the phenomenon of no flow.

As a method for avoiding fouling of cation exchange membranes and anion exchange membranes by contaminants, substances having opposite charges are present on the surface of these ion exchange membranes,
Methods have been proposed to prevent contaminants from entering the membrane due to repulsion of opposite charges. At this time, the effect was recognized when the film surface having the opposite charge was on the desalting side.

In the bipolar membrane, both sides of the bipolar membrane are always concentration chambers. It was considered that even if the pollutant was present in the concentrating chamber, the pollutant did not cause an electric force in the direction of the bipolar film, so that the bipolar film was not polluted. Further, both sides of the bipolar film are in an acid and alkaline state, and contamination under such a state has not been known so far.

[0008]

Means for Solving the Problems As a result of intensive studies in view of the above problems, the present inventors have found that even if a solution containing a colloidal substance, an ionic organic substance, and a dye is contacted for a long time,
The inventors have found that the electric resistance of the bipolar film does not increase, and therefore a current flows well over a long period of time, and have proposed the present invention.

That is, according to the present invention, the surface of the bipolar membrane on the side of the cation exchange membrane is charged with a cationic substance, and the amount of ion exchange groups possessed by the cationic substance is 0. It is a modified bipolar membrane which is present in an amount of 01 to 5%, and an anionic substance is present on the surface of the bipolar membrane on the side of the anion exchange membrane, and the amount of ion exchange groups possessed by the anionic substance is Of 0.01 to 5% of the ion exchange capacity of the anion exchange membrane ,
Anion exchange of the anion exchange membrane constituting the bipolar membrane
It is a modified bipolar film whose substitution group is an ammonium base .

The original bipolar film in the present invention is not particularly limited, and a known bipolar film can be used. Therefore, a known bipolar membrane having a structure in which a cation exchange membrane and an anion exchange membrane are laminated can be used. Such a bipolar film can be manufactured by various known methods. For example, a method of laminating and curing a cation exchange membrane and an anion exchange membrane with a mixture of polyethyleneimine-epichlorohydrin (Japanese Patent Publication No. 32-3962), a cation exchange membrane and an anion exchange membrane with an ion exchange adhesive. A method of adhering (Japanese Patent Publication No. 34-3961), a cation exchange membrane and an anion exchange membrane are applied with a fine powder of an ion exchange resin, or a paste-like mixture of an anion or cation exchange resin and a thermoplastic substance and pressure-bonded. Method (Japanese Patent Publication No. 35-14531), a method in which a paste-like substance composed of vinyl pyridine and an epoxy compound is applied to the surface of a cation exchange membrane, and radiation is applied to the substance (Japanese Patent Publication No. 38-16633). ), After attaching the sulfonic acid type polymer electrolyte and allylamines to the surface of the anion exchange membrane, irradiating with ionizing radiation Crosslinking method (Japanese Patent Publication No. 51-4113), and a method of depositing a mixture of a base polymer and a dispersion system of an ion exchange resin having an opposite charge on the surface of an ion exchange membrane (Japanese Patent Application Laid-Open No. 53-37190). A method in which a polyethylene film is impregnated with styrene and divinylbenzene for polymerization and sandwiched into a stainless steel frame, sulfonated on one side, and then the sheet is removed and the remaining portion is chlormethylated and then aminated. (U.S. Pat. No. 3,562,139) or a method of applying a specific metal ion on the surface of an anion-cation exchange membrane and superposing both ion-exchange membranes and pressing (Electrochemica Actor, Vol. 31, pp. 1175-1176 (1986).
Year)).

The base material of the bipolar membrane in the present invention depends on the cation exchange membrane and the anion exchange membrane to be joined, but polyethylene, polypropylene, polyvinyl chloride,
A styrene-divinylbenzene copolymer film, net, knitted fabric, woven fabric, non-woven fabric or the like is used.

The cation exchange group of the cation exchange membrane forming the bipolar membrane is not particularly limited, and known cation exchange groups such as sulfonic acid group and carboxylic acid group can be used. In particular, a sulfonic acid group in which an exchange group is dissociated even under an acidic condition is desirable for the purpose of using the bipolar membrane. The anion exchange group of the anion exchange membrane forming the bipolar membrane is not particularly limited, and known anion exchange groups such as ammonium base, pyridinium base, primary amino group, secondary amino group, and tertiary amino group are used. Ion exchange groups such as groups can be used. Of these, an ammonium base in which the exchange group is dissociated even under basic conditions is preferable.

The ion exchange capacities of these cation exchange membranes and anion exchange membranes are not particularly limited, but in general, it is preferable that each is in the range of 0.5 to 3.0 meq / g, and further 1.0 to It is preferably in the range of 2.5 meq / g.

In the modified bipolar membrane of the present invention, a cationic substance is present on the surface of the cation exchange membrane side. As the cationic substance in the present invention, known compounds can be used without any limitation as long as they are compounds having an anion exchange group.
The anion-exchange group may be a known anion-exchange group, particularly ammonium base, pyridinium base,
Anion exchange groups such as primary amino group, secondary amino group and tertiary amino group are preferred. Specific examples of the cationic substance having an anion exchange group include polymers such as 4-vinylpyridine, 2-vinylpyridine, vinylimidazole and the like, and polymers thereof such as methyl iodide.
Primarily basic, polysulfone is chloromethylated,
Further, quaternary ammonium compounds, polyethyleneimine, poly-vinylbenzyl-trimethylammonium chloride and the like can be mentioned.

In the modified bipolar membrane of the present invention, an anionic substance is present on the surface of the anion exchange membrane side.
As the anionic substance in the present invention, known compounds can be used without any limitation as long as they are compounds having a cation exchange group. The cation exchange group may be a known cation exchange group, and for example, a cation exchange group such as a sulfonic acid group or a carboxylic acid group is preferable. Specific examples of the anionic substance having such a cation exchange group include those obtained by introducing a sulfonic acid group into a polymer such as polysulfone and polyether ether ketone, polystyrene sulfonate sodium, polyacrylate sodium, and polyacrylate. Examples thereof include sodium methacrylate.

These cationic substances and anionic substances can be obtained by sterilizing the modified bipolar membrane with ultraviolet rays, alcohols, surfactants, bactericides, acids, bases, salts, heat, etc. or washing the bipolar membrane. It is preferably one that does not separate.

The abundances of the above-mentioned cationic substance and anionic substance are not particularly limited, but in order to suppress the increase of the electric resistance of the bipolar film, the cationic substance and the anionic substance are required. The amount of ion exchange groups possessed by each of them must be 0.01 to 5% of the ion exchange capacity of the cation exchange membrane and the anion exchange membrane, respectively.
It is preferable to select 3%.

The method for obtaining the modified bipolar film of the present invention is not particularly limited, but it is generally preferable to manufacture it by the following method. First, there are the following methods for allowing a cationic substance or an anionic substance to exist.

(1) An anionic substance or a cationic substance is preliminarily present on the surface of a polymer film material into which a cation exchange group or an anion exchange group can be introduced, and then the polymer film film is formed. A method of introducing a cation exchange group or an anion exchange group into a substance.

(2) A cation-exchange group or anion-exchange membrane is prepared by first introducing a cation-exchange group or anion-exchange group into a polymer membrane capable of introducing a cation-exchange group or anion-exchange group. A method in which an anionic substance or a cationic substance is allowed to be present on the surface of the prepared substance.

Explaining a concrete method, for example, a method of simply immersing the cation exchange membrane or the anion exchange membrane in an aqueous solution of the cation substance or the anion substance can be mentioned. Others
No. 43857, Japanese Patent Publication No. 62-5179, Japanese Patent Laid-Open No. 62-205135, Japanese Patent Publication No. 45-19980.
JP-B, JP-B-45-30693, JP-B-48-
It is also possible to employ known methods such as those disclosed in JP-A-34676 and JP-A-52-63187. The details of these known methods are as follows.

(1) A base material such as vinyl chloride cloth or polyethylene net and a polymer film made of a styrene / divinylbenzene copolymer are immersed in a mixed solution of chlorosulfonic acid and sulfuric acid to form a sulfonyl chloride group on the benzene ring. Then, a sulfonyl chloride group and a polyamine having a polyvalent amino group such as polyethyleneimine are bonded on the surface of the polymer film, and the sulfonyl chloride group inside the film is dissolved in sodium hydroxide solution. Method of hydrolyzing with.

(2) Pentamethyliminobispropylamine, which is a trivalent tertiary amine, is reacted with three times the amount of chloromethylstyrene to obtain a compound having three quaternary ammonium bases and three vinylbenzyl groups. Then, a cation-exchange membrane is immersed in an aqueous solution of this compound to ion-exchange the surface portion of the cation-exchange membrane, and further vinyl groups on the membrane surface are polymerized.

(3) A polymer film comprising a substrate such as vinyl chloride cloth or polyethylene net and a chloromethylstyrene / divinylbenzene copolymer is immersed in an aqueous trimethylamine solution to introduce a quaternary ammonium group into the chloromethyl group. And then immersed in an aqueous solution of sodium polystyrene sulfonate.

The time when the cation substance and the anion substance are allowed to exist is the individual stage of the cation exchange membrane and the anion exchange membrane before joining the cation exchange membrane and the anion exchange membrane. Alternatively, it may be at the stage of forming a bipolar film after joining them.

[0026]

[Effect] When the modified bipolar membrane of the present invention is used, even if an aqueous solution containing a colloidal substance, an ionic organic substance, and a dye is electrodialyzed, the electric resistance of the bipolar membrane does not increase, and the current is long-term. It flows well. Therefore, according to the present invention, it becomes possible to stably perform bipolar membrane electrodialysis over a long period of time.

[0027]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 20.1 g (0.1 mol) of pentamethyliminobispropylamine, which is a trivalent tertiary amine, and 46 g (0.3 mol) of chloromethylstyrene, were added to 200 ml of methanol.
The reaction was carried out for 48 hours in a medium to obtain a compound having three quaternary ammonium bases and three vinylbenzyl groups. A bipolar membrane "Neoceptor BP-1" (trade name: manufactured by Tokuyama Corp.) was immersed in an aqueous solution containing 1000 ppm of this compound at 30 ° C for 1 hour, and then potassium persulfate and sodium sulfite were used as polymerization initiators in a nitrogen atmosphere. Was added to each so as to be 1000 ppm and stirred vigorously for 10 hours. In this way, a modified bipolar film was obtained.
The ratio of the amount of anion exchange groups of the newly introduced cationic substance to the exchange capacity of the cation exchange membrane of this modified bipolar membrane was 1%.

As a bipolar membrane electrodialysis tank, as shown in FIG. 1, a cation exchange membrane "Neoceptor CM" is provided between a pair of anion and anode.
S "(trade name: manufactured by Tokuyama Corp.) and modified bipolar membranes are alternately 6 sheets and 5 sheets (cation exchange membrane and bipolar membrane have an effective membrane area of 1 dm ² and a total membrane area of 6 dm, respectively). ² and 5 dm ² ), and a filter press type bipolar membrane electrodialysis tank in which a base chamber and an acid / salt mixing chamber were formed was used. 100p for acid / salt mixing chamber
100 liters of 2N-sodium acetate solution containing pm of methylene blue, and 2 liters of 0.5N-NaOH aqueous solution in the base chamber were provided with corresponding tanks, respectively.
It was supplied and circulated at a linear velocity of cm / sec. In each of the anode chamber and the cathode chamber, 5 liters of a 10% sodium hydroxide aqueous solution was circulated, and electrodialysis was performed at 40 ° C. and a current density of 10 A / dm ² .

The initial voltage and the voltage after 30 hours at this time were both 1.8 V / unit cell, and no increase in voltage was observed. After disassembling the electrodialysis tank, the cation exchange membrane side of the bipolar membrane was not colored with methylene blue.

Comparative Example 1 The same operation as in Example 1 was carried out except that unmodified "Neoceptor BP-1" (trade name: manufactured by Tokuyama Corp.) was used in place of the modified bipolar film. The initial voltage and the voltage after 30 hours at this time were 1.8 V / unit cell and 2.1 V / unit cell, respectively, and an increase in voltage was observed. After disassembling the electrodialysis tank, the cation exchange membrane side of the bipolar membrane was colored with methylene blue.

Example 2 A polyvinyl chloride cloth substrate and a polymer film containing a styrene / divinylbenzene polymer as a main component were mixed with chlorosulfonic acid /
It was immersed in a mixed solution of sulfuric acid (1: 1) at 40 ° C. for 30 minutes to introduce a sulfonyl chloride group into the benzene ring. Then, it was sequentially diluted with sulfuric acid and washed with water to obtain a polymer film having a sulfonyl chloride group. Then, this film-like material was immersed in a 10% aqueous polyethyleneimine solution at 25 ° C. for 24 hours to bond the sulfonyl chloride group and the polyethyleneimine. Then, the sulfonyl chloride group inside the membrane is replaced by 1
It was hydrolyzed with a 0% sodium hydroxide aqueous solution to obtain a modified cation exchange membrane. Then, one side of the modified cation exchange membrane was roughened with sandpaper and dried. A 15% chloroform solution of aminated polysulfone (polysulfone chloromethylated and then quaternary aminated with trimethylamine, exchange capacity 1.1 meq / g) prepared in advance is cast to evaporate the solvent to evaporate the present invention. A modified bipolar film of was obtained. The ratio of the amount of anion exchange groups of the newly introduced cationic substance to the exchange capacity of the cation exchange membrane of this modified bipolar membrane was 1.4%. The same electrodialysis tank as in Example 1 was assembled and the same operation was performed except that the above modified bipolar membrane was used.

The initial voltage and the voltage after 30 hours at this time were both 2.5 V / unit cell, and no increase in voltage was observed. After disassembling the electrodialysis tank, the cation exchange membrane side of the bipolar membrane was not colored with methylene blue.

Example 3 10 parts of sodium polystyrene sulfonate having a molecular weight of 4000 was used.
"Neoceptor BP-1" in an aqueous solution containing 00 ppm
(Trade name: manufactured by Tokuyama Corporation) was immersed at 40 ° C. for 2 hours to obtain a modified bipolar film. The ratio of the amount of cation exchange groups of the newly introduced anionic substance to the exchange capacity of the anion exchange membrane of this modified bipolar membrane was 0.2%.

As shown in FIG. 2, the bipolar membrane electrodialysis cell has an anion exchange membrane "Neoceptor AM" between a pair of anion anodes.
H "(trade name: manufactured by Tokuyama Corporation) and modified bipolar membranes are alternately 6 and 5 sheets (anion exchange membrane and bipolar membrane have an effective membrane area of 1 dm ² and a total membrane area of 6 dm, respectively). ² and 5 dm ² ) arranged, base
A filter press type bipolar membrane electrodialysis tank in which a salt mixing chamber and an acid chamber were formed was used. The base / salt mixing chamber contains 100 ppm of sodium polyacrylate having a molecular weight of 1
00 liters of 2N-ammonium acetate solution and 2 liters of 0.5N-HCl aqueous solution were provided in the acid chambers with corresponding tanks and supplied and circulated at a linear velocity of 6 cm / sec. Each of the anode chamber and the cathode chamber circulates 5 liters of a 10% sodium hydroxide aqueous solution at 30 ° C and a current density of 5A.
Electrodialysis was performed at / dm ² .

The initial voltage and the voltage after 30 hours at this time were both 1.6 V / unit cell, and no increase in voltage was observed.

Comparative Example 2 The same operation as in Example 3 was carried out except that unmodified "Neoceptor BP-1" (trade name: manufactured by Tokuyama Corporation) was used instead of the modified bipolar film. The voltages at the initial stage and after 30 hours at this time were 1.6 V / unit cell and 2.0 V / unit cell, respectively, and an increase in voltage was observed.

Example 4 The cation-exchange membrane-side modified bipolar membrane obtained in Example 1 was immersed in an aqueous solution containing 1000 ppm of sodium polystyrene sulfonate having a molecular weight of 3000 at 40 ° C. for 3 hours to prepare an anion-exchange membrane-side film. A modified bipolar film whose surface was also modified was obtained. The ratio of the amount of cation exchange groups of the newly introduced anionic substance to the exchange capacity of the anion exchange membrane of this modified bipolar membrane was 0.5%. The ratio of the amount of anion exchange groups of the newly introduced cation substance to the exchange capacity of the cation exchange membrane of this modified bipolar membrane was 1%. Using the modified bipolar membrane described above, and using sodium dodecylbenzene sulfonate 100 in the base chamber.
The same electrodialysis tank as in Example 1 was assembled and the same operation was performed except that 2 liters of a 0.5 N-NaOH aqueous solution containing ppm was circulated.

The initial voltage and the voltage after 30 hours at this time were 1.8 V / unit cell, and no increase in voltage was observed. After disassembling the electrodialysis tank, the cation exchange membrane side of the bipolar membrane was not colored with methylene blue.

Comparative Example 3 "Neoceptor BP-1" (trade name: as a bipolar film)
The same electrodialysis tank as in Example 4 was assembled and the same operation was performed, except that Tokuyama Corporation was used. The initial voltage and the voltage after 30 hours at this time were 1.8 V / unit cell and 2.3 V / unit cell, respectively, and an increase in the voltage was recognized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the structure of an electrodialysis tank used in Example 1.

FIG. 2 is a schematic diagram showing the structure of the electrodialysis tank used in Example 3.

[Explanation of symbols]

1 anode 2 cathode 3 base room 4 Acid / salt mixing chamber 5 base / salt mixing chamber 6 Acid chamber C1-C6 cation exchange membrane A1 to A6 anion exchange membrane B1-B5 bipolar film

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Claims (3)

(57) [Claims] 1. A cation exchange membrane-side surface of a bipolar membrane is provided with a cation substance, and the amount of ion exchange groups possessed by the cation substance is 0.0 of the ion exchange capacity of the cation exchange membrane.
A modified bipolar film made to exist so as to be 1 to 5%. 2. An anionic substance is formed on the surface of the bipolar membrane on the side of the anion exchange membrane, and the amount of ion exchange groups possessed by the anionic substance is 0.0 of the ion exchange capacity of the anion exchange membrane.
1 to 5% of the bipolar film is present.
The anion-exchange group of the anion-exchange membrane that constitutes
A modified bipolar film that is an um base . 3. A cation-exchange membrane-side surface of a bipolar membrane is provided with a cation substance, and the amount of ion-exchange groups possessed by the cation substance is 0.0 of the ion-exchange capacity of the cation-exchange membrane.
1 to 5%, and an anionic substance is present on the surface of the bipolar membrane on the side of the anion exchange membrane, and the amount of ion exchange groups possessed by the anionic substance is the ion exchange of the anion exchange membrane. A modified bipolar film which is present so as to have a capacity of 0.01 to 5%.