JPH0463292A - Production of bipolar membrane - Google Patents

Abstract

PURPOSE:To obtain a bipolar membrane reduced in water electrolysis voltage and excellent in current efficiency and durability by forming a membrane on the surface of an anion exchange membrane, where heavy metal ions are allowed to exist in the membrane, by using a solution of polymer having cation exchange groups or functional groups capable of easily introducing cation exchange groups and then introducing cation exchange groups into the above functional groups. CONSTITUTION:An anion exchange membrane is immersed into a concentrated aqueous solution of hydrochloric acid containing heavy metal ions or this solution is applied or sprayed to or on the anion exchange membrane, by which the heavy metal ions are allowed to exist in the anion exchange membrane. Subsequently, a membrane of cation exchange body is formed on one surface of the above-mentioned anion exchange membrane, where the heavy metal ions are allowed to exist, by using a solution of polymer having cation exchange groups or functional groups capable of easily introducing cation exchange groups, by which the desired superior bipolar membrane can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a method for producing a bipolar membrane that decomposes water at low voltage and has excellent durability.

[Prior art and their intervening points]

A bipolar membrane has a structure in which an anion exchange membrane and an anion exchange membrane are laminated together, and various methods for manufacturing the membrane have been proposed. For example, cation exchange membrane and anion exchange membrane,
A method of laminating and curing adhesive using a mixture of polyethyleneimine and epichlorohydrin (Special Publication No. 32-3962)
, A method of adhering an anion exchange membrane and an anion exchange membrane with an ion exchange adhesive (% Publication No. 34-3961), A method of bonding an anion exchange membrane and an anion exchange membrane with an ion exchange adhesive, is a method of applying a paste mixture of cation-exchanged AT fat and thermoplastic substance and applying pressure (Special Publication No. 35-1).
4531), a method of manufacturing by coating the surface of a cation exchange membrane with a paste-like substance consisting of vinyl pyridine and an epoxy compound and irradiating it with radiation (4I Kosho 38
-16633), a method of attaching a sulfonic acid type polymer electrolyte and allylamines to the surface of an anion exchange membrane, and then irradiating and crosslinking with ionizing radiation (% Publication No. 51-4113).
No. 1), a method of depositing a mixture of a dispersion of an ion exchange resin having an opposite charge and a parent polymer on the surface of an ion exchange membrane (Japanese Patent Application Laid-Open No. 53-37190), Impregnation of polyethylene film with styrene and divinylbenzene 1 The combined sheet-like material is sandwiched between stainless steel plates, the -1000 side is sulfonated, the sort is removed, and the remaining part is chloromethylated and then aQ-nolated (U.S. Patent No. 3).
No. 562139). However, in bipolar membranes obtained by these methods, when attempting to decompose wood, the theoretical electrolytic voltage of water (0
, 83 volts), the housing is stiff, and requires high power consumption.

In addition, Elect-roc Acta (Elect-roc
b, 1ffiaa Acta) Vol, 311
NO9, PPI 175-1176 (1986) has overlapping cation and anion exchange membranes whose surface has been previously coated with one or more inorganic electrolyte solutions such as sodium tungstate, chromium nitrate, sodium metasilicate, and ruthenium trichloride. It has been reported that a bipolar membrane with a low water electrolysis voltage can be obtained by pressing together. However, the bipolar membrane with a low water electrolysis voltage produced by this method has problems such as the water electrolysis voltage rising relatively quickly during use, air bubbles or water bubbles occurring between the anion and anion exchange membranes, and the bipolar membrane having a low water electrolysis voltage. The #I positive and negative ion exchange membrane itself easily peels off, and its durability is questionable.

[Means for resolving gaps]

In view of the above-described shortcomings, the present inventors have made earnest efforts to develop a bipolar membrane that has a low water electrolysis voltage, high current efficiency, and excellent durability. As a result, based on the knowledge that the desired bipolar membrane can be obtained by applying a cation exchanger polymer solution to form a film on the surface of an anion exchange membrane in which heavy metal ions are present within the membrane. This has led to the provision of the present invention. That is, according to the present invention, a film is formed on the surface of an anion exchange membrane in which heavy metal ions are present using a cation exchange membrane or a solution of a polymer having a functional group that can easily introduce a cation exchange group. After letting.

A method for producing a bipolar membrane is provided in which a cation exchange group is introduced into the functional group.

The anion exchange membrane in the present invention is not particularly limited, and any known anion exchange membrane can be used. For example, 4
class ammonium base.

Anion exchange membranes having ion exchange groups such as primary, secondary or tertiary amine groups can be used, but for the purpose of bipolar membranes, quaternary ammonium bases, whose exchange groups are dissociated even under alkaline conditions, can be used. It is desirable to have an anion exchange group. In addition, the anion exchange membrane is a polymerized type.

The anion exchange membrane may be of any type or type, whether homogeneous or nonuniform, depending on the presence or absence of a reinforcing core material and the manufacturing method. Note that even if the anion exchange membrane has some cation exchange groups in it, if the theoretical ion transfer number is 90% or more, it can be used as the anion exchange membrane of the present invention in t minutes. be.

In the ion exchange membrane used in the present invention, it is important to have one metal ion present in the membrane in order to obtain a low water electrolysis voltage (a bipolar membrane. (ions) are elements (ions) with an atomic number of 20 to 9 degrees, excluding halogens and inert gas elements, and are generally iron (n, m), titanium (IV), tin (Il).
Preferred are zirconium (IV), palladium (■), ruthenium (m), and the like. As a method for causing heavy metal ions to be present in the anion exchange membrane, a known method can be adopted as a method for causing heavy metal ions to be present in the rattan ion exchange membrane. Generally, a metal ion exists in a solution as a cation and is not adsorbed into an anion exchanger, but there is a method of incorporating the metal in the form of an anion into an anion exchanger. That is, in a concentrated aqueous hydrochloric acid solution, a specific metal ion is j! It can form complex ions with elementary ions and exist as anions, so this ion can be incorporated into the ion exchanger. Among the metal ions mentioned above, particularly preferable iron (Il, III), titanium (IV'), tin (II, IV), zirconium (■), palladium (■), and ruthenium (m) are all concentrated # A#! It can exist as an anion in aqueous solution. The method of making heavy metal ions exist in the anion exchange membrane in this way is to immerse the anion exchange membrane in a concentrated #A acid ice water solution containing heavy metal ions, or to apply this solution onto the anion exchange membrane. This is achieved by spraying. The abundance of heavy metal ions is usually 0.00
01-10wt attack, preferably α001-5wt ≦
It does not necessarily have to be distributed over the entire thickness direction of the ion exchange membrane, but it is sufficient that it exists on the side where the film of the cation exchanger layer is formed.

Next, a cation exchanger film is formed on one surface of the anion exchange membrane in which the above-mentioned heavy metal ions are present, using a solution of a cation exchange group or a polymer having a functional group that can easily introduce a cation exchange group. It is also extremely complicated to form a desired bipolar film. The polymer having such a cation exchange group or a functional group into which a cation exchange group can be easily introduced is preferably a thermoplastic resin that is soluble in an appropriate solvent in order to prevent the solution used for forming the film. In the resulting bipolar membrane, in order to achieve high water decomposition efficiency and maintain acid resistance, it is most preferable to form the film as a strongly acidic polymer in which the cation exchange groups are mainly sulfonic acid groups. , of course, is not limited to this.

Further, the thickness of such a film is generally 5 to 300 .mu.I, particularly 10 to 200 .mu.I, because the water electrolysis voltage increases as the film becomes thicker, and the current efficiency decreases as it becomes thinner.

Examples of the polymer having a cation exchange group in the present invention include a sulfonic acid group, a carboxylic acid group, a phenolic hydroxyl group, and a 1,000-ol group.

Any of monopolymer, condensate, synthetic polymers, and derivatives of natural polymers having a cation exchange group such as a phosphate group may be used. Specifically, the polymer monomer having a cation exchange group or a functional group into which a cation exchange group can be introduced includes styrene sulfonic acid, styrene sulfonate, vinyl sulfone, vinyl sulfonate,
Methacrylic IJ, methacrylic ester, acrylic acid,
Acrylic acid ester, maleic acid, maleic acid ester, maleic anhydride*, styrene phosphonic acid, styrene phosphonic acid ester, itaconic acid ester, etc. are used. These salts are generally eg styrene, chloromethylstyrene.

It is used as a copolymer with water-insoluble vinyl compounds such as vinyltoluene and acrylonitrile.

Also, f! For example, polymers having functional groups that can be converted into cation exchange groups by chemical reactions such as hydrolysis, such as acid halide groups such as sulfone halide groups, carbonic acid parite groups, and phosphoric acid parite groups, and oxycarbonyl groups, -
For example, partially sulfonated polymers obtained by partially sulfonating polystyrene, polysulfone, polyphenylene oxide, polyetheretherketone, etc. can also be used.

Of course, these polyesters have a cation exchange group or a functional group that can introduce a cation exchange group into the capacitor! - can be used in combination with other polymers such as polystyrene, if necessary.

In addition, when the exchange capacity of polymers having these cation exchange groups is large, the formed film tends to dissolve in water or swell, which reduces the current efficiency of water splitting in bipolar groups, and the exchange capacity is small. Generally speaking, α4 to 1.
8 meq/I 9% and α6-15 meq151 are preferred. In addition, the cation exchange groups of the polymers that form such films are hydrogen ion caps.

Although it may be made of Na ion, the metal ion type used in the present invention is preferable.

Furthermore, in the present invention, a polymer having a cation exchange group or a functional group that can be converted into a cation exchange group is combined with a polymer having two or more reactive groups to form a film, and the above functional group and a polymer having two or more reactive groups are combined. By reacting with a reactive group and introducing a cation exchange group as necessary, a bipolar membrane with excellent durability can be obtained by forming a film of a cation exchanger having a crosslinked structure. Poly! has such a cation exchange group or a functional group into which a cation exchange group can be introduced and two or more reactive groups! - Examples include styrene sulfonyl chloride and styrene;
Copolymer of chloromethylstyrene; styrene sulfone
! ! 4 and styrene, chloromethylstyrene copolymer;
Polymers such as polystyrene, polyphenylene oxide, and polyether ether ketone partially converted into varnish A/lk and further chloromethylated are used. After forming a film on one side of a mature ion exchange membrane containing heavy metal ions with a solution prepared by dissolving such a polymer in an appropriate organic solvent, it is generally exposed to ultraviolet rays, gamma rays, and IC.
A film of a cation exchanger having a crosslinked structure can be formed by a method of irradiating with radiation such as a sub-beam.

The film of these cross-linked cation exchangers becomes brittle when the exchange capacity is large, making it difficult to use as a bipolar membrane, and when the exchange capacity is small, the electrical resistance becomes high and the electrolysis voltage of water increases. Therefore, generally α3~z o
meq/Ji+, especially α5~L5+! Ieq/,
p is preferred.

In the preparation of the polymer solution in the present invention, the above-mentioned polymers are mixed, for example, with ethylene chloride, chloroform,
Tetrahydrofuran.

The solution is dissolved in an organic solvent such as dimethylformamide, N-methylpyrrolidone, or methyl alcohol, and then sprayed onto the surface of an anion exchange membrane to adjust the concentration and viscosity to a level suitable for forming a desired film. In addition, the specific formation of the film is as follows:
Generally, the surface of anion exchange membrane containing heavy metal ions (
A method in which a polymer solution is applied or sprayed onto one side) and then dried to remove the solvent, or an impermeable film.

It can be obtained by a method in which an anion exchange membrane containing l metal ions coated on one side with a glass plate or the like is immersed in a polymer solution, pulled up, and then dried in the same manner.

In addition, in the present invention, the surface Ifi of the anion exchange membrane containing heavy metal ions must be washed with water to remove free heavy metals before applying the polymer solution, and then thoroughly dried. It is preferable to roughen the surface so that an anion exchange film can be formed with good adhesion and a bipolar membrane with excellent durability can be obtained. As a method for roughening the surface, the surface of the ion exchange membrane is generally treated with sandpaper or the like to form fine irregularities.

Furthermore, when manufacturing and inspecting a long anion exchange membrane, it is also possible to provide unevenness on the guide roll and to make the surface of the iron membrane uneven by contact.

〔Effect of the invention〕

According to the method of the present invention, although the mechanism of action is not yet fully clear, a bipolar membrane with low water electrolysis voltage and excellent durability can be easily obtained. Therefore, in the electrolysis of water using such a bipolar membrane of the present invention, it contributes to the effect of greatly reducing the electric power consumption rate. In particular, recently, it has become difficult to dump salts, which are the products of neutralization between acids and alkalis, into the open sea due to stricter wastewater regulations. Extremely useful.

[Actually! example〕

Examples and comparative examples of the present invention will be shown below.
The present invention is not limited to these examples.

Note that the characteristics of the bipolar membranes in Examples and Comparative Examples were determined by the following measurements. That is, using a platinum plate as an electrode, there is an effective area of 10 cm between them! A predetermined bipolar membrane is provided, and l,ooN-
jJi! I! Aqueous solution 1001 and 10 on the exchange membrane side
A 0N aqueous solution of 90% sodium hydroxide was added to 100%
After applying current for 4 to 16 hours at a current density of A/d Otori, the amounts of acid, base, and salt in the solutions on both sides were measured, and the current efficiency of hydroxyl ions η( OH), hydrogen ion current efficiency η(
H), the current efficiency 7 (CA') of chloride ions, and the current efficiency η (Na) of sodium ions were determined. The voltage drop across the bipolar membrane was also measured using a platinum T&. Furthermore, the content of metal ions in the anion exchange membrane was determined from the amount of decrease in metal ions before and after immersion of the membrane. Note that metal ions were analyzed by atomic absorption spectrometry.

Example 1 A mixed solution consisting of 85 parts by weight of chloromethylstyrene, 151 parts by weight of divinylbenzene with a purity of 55%, and 3 parts by weight of benzoyl peroxide was mixed with a copolymer of ethylene-vinyl acetate having a width of 14 parts by weight of vinyl acetate. After soaking the film at a temperature of 40°C for 30 minutes, the film was sandwiched between polyester films and soaked at a temperature of 70°C for 15 minutes.
It took 1 hour. Next, this film was mixed with a 3011% trimethylamine aqueous solution and methanol at a volume ratio of 1=1.
An anion exchange membrane was obtained by amination treatment in a mixed solution.

This anion exchange membrane was treated with sandpaper to create unevenness on one surface, and then ferric chloride (F@C
/3) at 25°C in a 2N-hydrochloric acid aqueous solution containing 21% of
After being immersed in water for one day, it was thoroughly washed with ion-exchanged water and air-dried at room temperature. The treated anion exchange membrane had an exchange capacity of 15 m@q/ga and an iron content of 1.2 wt ≦ of the weight of the anion exchange membrane.

Next, a solution prepared by dissolving partially sulfonated polystyrene in dimethylformamide with an exchange volume of 1.03 m@q/jl to a concentration of 1 O1 was added to the roughened surface of the anion exchange membrane described above. Apply to the surface and dry to a thickness of 1
A film of an ion exchanger made of partially sulfonated polystyrene with a thickness of 0.00 μm was formed.

As a result of measuring the performance of the obtained bipolar membrane, the electrolytic voltage was 14 V, and the current effect *izy+(H) = 99.2.
Rumor, η(OH)=99.2%.

η (C1) = o, 3q & and 1 (N a) =
It was 0.5. In addition, the performance of these bipolar membranes is
No change was observed even after two months had passed, and no bubbles or blisters were observed in the film.

Comparative Example 1 A bipolar membrane was manufactured using the same procedure as in Example 1, except that the anion exchange membrane was not treated with an aqueous solution of ferric chloride.

The performance of the obtained bipolar membrane is that the electrolytic voltage is 3.2 V.
So, the current efficiency is 7 (H) = 99.3%.

W (OH): 99.31 V (C!ri = 0.3
! : and (Na)=α4%. Further, this performance did not change even after two months had passed, and no bubbles or water bubbles were observed in the film.

Example 2 A partially sulfonated polysulfone having an exchange capacity of 1.10 yrθq/N was dissolved in a mixed solution of methanol and chloroform in a volume ratio of 1:1 to prepare a 14-weight solution. Next, the above partially sulfonated polysulfone solution was applied to the roughened surface of the iron ion-containing anion exchange membrane obtained in Example 1, and dried at room temperature for 10 hours to form a cation exchanger. A film with a thickness of 80 μm was formed.

As a result of measuring the performance of the obtained bipolar membrane, the electrolytic voltage was L3V, the current efficiency was η(H) = 99.1%,
? (OH) = 911 regret.

'IccI) = α5 幡 and +7 (Na) = α4 attack. Further, the performance of this bipolar membrane did not change even after three months had passed, and no bubbles or water bubbles were observed in the membrane.

Example 3 One side of the anion exchange membrane obtained in Example 1 was roughened with sandpaper in advance, and then tin chloride (C2C12)
The sample was immersed in a 2N aqueous hydrochloric acid solution containing 11111% of 11% of chlorine at 25°C for 1 day, then thoroughly washed with ion-exchanged water, and air-dried at room temperature. The treated anion exchange membrane had a tin ion content of Q, 5 wt%.

Next, sodium styrene sulfonate, styrene, and chloromethylstyrene in a molar ratio of 1:6:3 were dissolved in dimethylformamide to form a solution of 151M sodium chloride, and then dissolved in penzoyl chloride. was used as an initiator for 10 hours at 70°C under a nitrogen atmosphere, and the resulting precipitate was filtered and dried. Obtained union.

Dissolve this copolymer in dimethylform and ml! I did 1
A 5-weight polymer solution was applied to the roughened surface of the anion exchange membrane described above, dried, and then heat irradiated for 30 minutes using a high-pressure ultraviolet lamp to form a 60μ thick film that did not dissolve in dimethylformamide. A cation exchanger film was formed.

As a result of measuring the performance of the obtained bipolar membrane, the electrolytic voltage was 1.3 V, and the current efficiency was η (H) = 99.
0%, η(OH)=99.0 whisper.

η(C1)=0.6% and η(Na)=α4 arc. This performance did not change even after two months had passed, and no bubbles or water bubbles were observed in the film.

patent issuer Tokuyama Soda Co., Ltd.

Claims (1)

[Claims] 1) After forming a film on the surface of an anion exchange membrane in which heavy metal ions are present in the membrane with a solution of a cation exchange group or a polymer having a functional group that can easily introduce a cation exchange group, A method for producing a bipolar membrane characterized by introducing a cation exchange group into the base.