JPS62205135A - Modified cation exchange membrane - Google Patents

Abstract

PURPOSE:To obtain the titled membrane with good selective cation permeability, unaffected by treatment with oxidizing agent as well as highly resistant to contamination by organic matter, by providing the surface(s) with a polymer from a quaternary ammonium base and a vinyl compound carrying vinylbenzyl group. CONSTITUTION:The objective membrane can be obtained by providing either or both surfaces of the original cation exchange membrane with a polymer from a quaternary ammonium base and a vinyl compound carrying at lest three vinylbenzyl groups. Said vinyl compound is such as to be formed by amino conversion of one molecule of a primary amine (e.g. methylamine, ethylamine) with at least three molecules of vinylbenzyl halide (e.g. vinylbenzyl chloride), alternatively, by reaction between one molecule of divalent primary amine and at least three molecules of vinylbenzyl halide followed by, if needed, reaction with an alkylating agent.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a property of selectively permeating cations with a small electric charge, and also has a property of being resistant to contaminating organic substances. Provided is a novel modified cation exchange membrane whose properties do not change even when treated with an oxidizing agent.

More specifically, the present invention provides a modified cation exchange membrane in which a polymer of a compound having a quaternary ammonium base and three or more vinylbenzyl groups is present on at least one surface of the cation exchange membrane. be.

[Prior art and problems to be solved by the invention] Conventionally, as a so-called selectively permeable cation exchange membrane that selectively permeates ions with a small electric charge, an anion exchange material is used in the surface layer of the cation exchange membrane. It is known that what caused the existence of Furthermore, methods of electrodialysis using such permselective cation exchange membranes are also known.
It is described in Japanese Patent Publication No. 23607, Japanese Patent Publication No. 47-3081, etc. That is, in these cases, an anion exchange substance is present on the surface layer of the cation exchange membrane, or a substance that can be crosslinked simultaneously with an anion exchange substance is attached to the surface of the cation exchange membrane, and then crosslinking is performed. It is stated that it can be done. However, although the above-mentioned modified cation exchange membrane has good permselectivity, the durability of the effect is poor, and even if the durability is sufficient, the permselectivity treatment uses an organic solvent, Since harsh treatment conditions are required for ion exchange membranes, such as the need for treatment at high temperatures and high concentrations, this method has not always been industrially satisfactory.

On the other hand, JP-A-56-50933 discloses that two or more quaternary ammonium bases represented by the specified general formula and one
A modified cation exchange membrane has been proposed in which a vinyl compound having one or two vinylbenzyl groups or a polymer of the vinyl compound is present on at least one surface of the cation exchange membrane. This modified cation exchange membrane has excellent cation permselectivity durability and stability against oxidizing agents, and has fairly good cation permselectivity. Further improvement is desired.

[Means for solving problems]

In view of the above-mentioned problems, the present inventors conducted intensive research on permselective cation exchange membranes, and found that a vinyl compound having more than one vinylbenzyl group was identified as quaternary ammonium bases on the surface of the cation exchange membrane. The present inventors have discovered that better cation permselectivity can be achieved by the presence of a polymer, and have thus come to provide the present invention. That is, the present invention provides a modified cation exchange membrane in which a polymer of a vinyl compound having quaternary ammonium bases and three or more vinylbenzyl groups is present on at least one surface of the cation exchange membrane. be.

The modified cation exchange membrane provided by the present invention not only has superior cation permselectivity, but also has various excellent manufacturing methods and properties as described below. That is, when producing a modified cation exchange membrane, the polymer of the above-mentioned specific vinyl compound can be handled at a low concentration, and moreover, it can be treated in an aqueous solution. Furthermore, the modified cation exchange membrane of the present invention has almost no increase in electrical resistance and has good resistance to organic contamination. The various excellent properties described above are long-lasting and do not change even when treated with an oxidizing agent, making it extremely effective.

The present invention will be explained in detail below.

The term "quaternary ammonium bases" used in the vinyl compound of the present invention is a general term that includes not only quaternary ammonium bases but also so-called onium bases such as quaternary pyridinium bases, sulfonium bases, and phosphonium bases. be. That is, in the present invention, quaternary pyridinium bases, sulfonium bases, and phosphonium salts exhibit similar effects. Furthermore, the more vinylbenzyl groups in the vinyl compound of the present invention, 3 or more, the denser the polymer of the vinyl compound can be obtained. It exhibits the desired effect as a quality cation exchange membrane. However, when such a vinyl compound has too many vinylbenzyl groups, polymerization tends to occur between and within molecules of the vinyl compound, making it difficult to handle. 3 to 100 pieces is preferable.

In addition, it is effective for the number of quaternary ammonium bases possessed by the vinyl compound in the present invention to be 1 or more, but if the number is too large, the effect of the present invention is not exhibited, so -a is 1 to 1.
000 pieces, especially 3 to 50 pieces is preferable. The method for producing such a compound having a quaternary ammonium base and three vinylbenzyl groups is not particularly limited, but it is generally synthesized, for example, by the following method.

(1) Alkylating a primary amine such as methylamine or ethylamine with three vinylbenzyl chlorides.

(2) A divalent primary amine such as ethylene diamine or propylene diamine is reacted with three or more vinylbenzyl chlorides, and if necessary, converted to a quaternary ammonium base using an alkylating agent such as methyl iodide or dimethyl sulfate.

(3) Tertiary amine compounds with a valence of 3 or more, e.g.
1 IIt (RI in the above formula: CH3, CHz CHs, n>
(an integer of 3) (CHz)z N(CHs)t etc. are reacted with at least three or more vinylbenzyl chlorides. Furthermore, if necessary, unreacted tertiary amino groups may be converted to quaternary amino groups using another alkylating agent.

(4) A compound having three or more halogen atoms in the same molecule, such as, for example, is reacted with vinylphenylalkyl N,N-dialkylamine.

These reaction conditions may be carried out without a solvent or in water, alcohol, acetone, dimethylformamide, dimethyl sulfoxide, benzene, chloroform, or a mixed solvent thereof at any concentration, and the reaction temperature is generally 0 to t. o o "c, and a temperature in the range of 5 to 80°C can be suitably employed. In addition, it is generally preferable that the reaction is carried out in the presence of a radical polymerization inhibitor such as hydroquinone.

The method for producing the above-mentioned vinyl compound polymer is not particularly limited, and any known method may be employed, and for example, known methods such as radical polymerization and cationic polymerization may be used. That is, the vinyl compound described above is dissolved in a hot solvent; water; an aqueous solution of an inorganic salt; and a solvent such as methanol, ethanol, etc. alone or in a mixed solvent, preferably from 0.1 N to 4. O
N, particularly preferably 0.2 N to 2. Polymerization may be carried out by adding a radical polymerization initiator or a cationic polymerization initiator to ON saline solution. Examples of radical polymerization initiators include acetyl peroxide, benzoyl peroxide, lauroyl peroxide,
Peroxides such as potassium peroxonisulfate, ammonium peroxonisulfate, t-butyl hydroperoxide, hydrogen peroxide; azobisisobutyronitrile, azobis-
Azo compounds such as 2-amidinopropane and hydrochloride; furthermore, hydrogen peroxide-ammonia, ethylamine, Fe
(n) Salts, etc.; peroxonisulfate - sodium sulfite, sodium hydrogen sulfite, triethanolamine, Fe
Redox initiators such as (■) salts; sodium perchlorate-sodium sulfite; and the like are also preferably used. Also,
Ionizing radiation may also be irradiated.

Further, as initiators for cationic polymerization, halogen compounds such as aluminum chloride, zinc chloride, stannic chloride, titanium chloride, boron trifluoride, and antimony pentachloride; phosphoric acid, sulfuric acid, chlorosulfonic acid, perchloric acid, Protonic acids such as; organometallic compounds such as triethylaluminum, etc. are used.

Any conditions may be used for the polymerization of the vinyl compound, but generally the polymerization may be carried out below the decomposition temperature of the vinyl compound or below the boiling point of the solvent used. In addition, the polymerization time varies depending on the type of catalyst used, polymerization temperature, etc., and cannot be absolutely limited, but generally it is about 5 minutes to 10 hours when a redox polymerization initiator is used, and 3 hours to 3 hours when a radical polymerization initiator is used. It is preferable to choose from a range of about 3 days.

The cation exchange membrane used in the present invention is not particularly limited, and any known cation exchange membrane can be used.

For example, ion exchange membranes with ion exchange groups such as sulfonic acid groups, carboxylic acid groups, phosphonic acid groups, sulfate ester groups, phosphate ester groups, thiol groups, and active groups that can form chelate structures with heavy metals are used. Can be used. The cation exchange membrane may be of any polymer type, condensation type, homogeneous type, non-uniform type, with or without a reinforcing core material, or of any type or type depending on the manufacturing method. Another 0.5
An N-salt solution is electrodialyzed at a current density of 2 A/da", and if the current efficiency is 70% or more and it is substantially a cation exchange membrane, it is generally called an amphoteric ion exchange membrane. Even if it exists, it can be used as the cation exchange membrane of the present invention.

The ordinary cation exchange membrane used in the present invention may be in a water-containing state or in an anhydrous state, but it is usually used in a water-containing state. Further, the cation exchange group of the cation exchange membrane may be of a hydrogen type or a salt type, and salts, acids, bases, and other substances may be contained in the cation exchange membrane.

In the present invention, the method for making the vinyl compound polymer present on at least one surface of the cation exchange membrane is not particularly limited, and any known method can be employed as is. Examples of typical methods generally employed industrially include the following methods. That is, a method can also be suitably employed in which the vinyl compound is made to exist on at least one surface of the cation exchange membrane and then the vinyl compound is polymerized. As a means for such polymerization, generally, the vinyl compound can be polymerized by bringing a cation exchange membrane, on which the vinyl compound is present on at least one surface, into contact with a solution containing a polymerization initiator. Depending on the type of polymerization initiator used, a solution containing a vinyl compound and a polymerization initiator may be present on at least one surface of the cation exchange membrane at a low temperature, and the vinyl compound may be removed by increasing the temperature. It is also possible to employ means for polymerizing. Alternatively, a method may be used in which the vinyl compound is present on both sides of the cation exchange membrane, and then only one side is brought into contact with the polymerization initiator. In any case, the above-mentioned polymerization of the vinyl compound is preferably carried out under a nitrogen atmosphere.

In the modified cation exchange membrane of the present invention, the amount of the vinyl compound polymer present on the surface of the cation exchange membrane varies depending on the type of cation exchange membrane, electric charge, etc. The pH of the solution to be dialysed must not change significantly, the critical current density of the electrodialysis tank must not be significantly reduced, and the critical current density of the modified cation exchange membrane must be 10% or more of the critical current density of the cation exchange membrane. − may be determined by taking into account the following. -0.001mg for a
It is preferable that the amount of waste is greater than or equal to /d, and it may be selected from a range in which the limiting current density of the modified cation exchange membrane does not become less than ]05 of the limiting current density of the above-mentioned cation exchange membrane.

[Effect]

Although the detailed mechanism of action by which the modified cation exchange membrane of the present invention exhibits a number of excellent properties is currently not clear, the present inventors estimate as follows. That is, since the vinyl group of the vinyl compound used in the present invention is styrene-based, it is mechanically and chemically strong, and the cation exchange group of the cation exchange membrane and the polymer of the vinyl compound with the opposite charge are more This is probably because it is strongly present on the surface of the cation exchange membrane. Specifically, in the present invention, a modified cation exchange membrane in which a polymer of a vinyl compound having a quaternary ammonium base and three or more vinylbenzyl groups is present on the surface, the polymer of the vinyl compound is a polymer. As cations, a crowded borisalt is formed at a depth of several microns within the surface layer of the cation exchange membrane, so it is extremely tightly intertwined and has a thickness of approximately 100 angstroms from the surface of the cation exchange membrane outward. A polycation layer is formed. Moreover, since the polycation layer in the modified cation exchange membrane of the present invention is a polymer of vinyl compounds having three or more vinylbenzyl groups, it is a polymer having one or two vinylbenzyl groups. Since the degree of crosslinking is denser and stronger than that of coalescence, it is thought that the properties of -valent cation selective permeability and organic contamination resistance are strongly exhibited.

The modified cation exchange membrane of the present invention is preferably used in an electrodialysis method that selectively permeates cations with a small number of charges from an electrolyte solution containing two or more types of cations with different charges.

In addition, organic cations and inorganic salts can be separated from a solution containing them by electrodialysis, but the method and purpose of use are not particularly limited, and conventionally known membrane materials having cation exchange groups can be used. There are no restrictions on the system (applicable; that is, it applies to any system in which the phenomenon of osmosis or dialysis occurs, such as diffusion dialysis, Donnan dialysis, pressure dialysis,
Other methods include electrodialysis and reverse osmosis. It may also be used extremely effectively as a diaphragm for electrode reactions.

Furthermore, the solution system used may be, without limitation, inorganic neutral hydrochloric acid, alkaline solution, organic salt, organic acid, organic base, or the like. Note that the apparatus using the modified cation exchange membrane of the present invention is not particularly limited, and any conventionally known apparatus using each membrane-like polymer can be used without any restriction.

Examples are shown below, and the properties of the modified cation exchange membranes obtained here were measured as follows.

That is, the electrical resistance is 0.5N-Na (AC 1 in J solution)
The value at 25°C using 000 cycles (Ω・el+). The current efficiency is 0.5 N - Na C1, placed on both sides of the modified cation exchange membrane, and 2.OA/dm". Electrodialysis was performed under stirring for 1 hour at current density, and the amount of ion movement through the modified cation exchange membrane was determined from the concentration change in the compartment.
On the other hand, the current efficiency was calculated by determining the amount of current supplied using a steel coulometer. In addition, ion selective i3 permeability showed the property of selectively permeating cations with small charges using the pure salt ratio. The pure salt rate is a seawater flow rate of 6 in a continuous seawater concentrator with an effective membrane area of 1 dm, in which the modified cation exchange membrane of the present invention and an anion exchange membrane that selectively permeates anions with a small charge are arranged alternately. .0 am/sec, temperature 30°C, current density 3.
It was determined by the following equation by analyzing the concentrated solution that reached equilibrium when electrodialyzed at OA/dm''.

(Na”] ; tl Concentration of Na + in condensate (N) (
K”): Concentration of Ni゛ in c test solution (N) [α゛]
: Concentration of α- in the concentrate (N) Regarding organic stain resistance, 0. IN-NaCJ! , by adding 1000 ppn+ dodecylpyridinium chloride to the aqueous solution,
? 8 liquid was electrodialyzed for 4 hours at a current density of 0.3 A/dra”0), and the change in electrical resistance of the modified cation exchange membrane was recorded with a recording needle, and the DC electrical resistance (Ω・cd) was recorded after 4 hours.
). The device used was the same as that used to measure the selective permeation coefficient.

The following two oxidation treatments (A) and (B) were performed.

(8) Immerse in a 1% aqueous hydrogen peroxide solution for 24 hours at 25°C with stirring.

(B) Immerse in a sodium hypochlorite aqueous solution with an available chlorine concentration of 300 ppm at 25° C. for 6 hours with stirring.

The above-mentioned properties were also measured using the same method for the cation exchange membrane and the modified cation exchange membrane after the oxidation treatment.

Example 1 20.1 g (0.1 mol) of N,N,N',N',N''-pentamethyliminobispropylamine and 46 g (0.3 mol) of chloromethylstyrene were heated to room temperature in 200 mJ of methanol. The reaction was carried out for 48 hours to obtain a compound having three quaternary ammonium bases and three vinylbenzyl groups.An aqueous solution containing 11,000 pp of this compound and a 1.0N-NaCj! solution were each injected with a cation exchange membrane. Neo Sebuta CM (manufactured by Tokuyama Soda) at 40℃
Then, under a nitrogen atmosphere, potassium persulfate and sodium sulfite were added as polymerization initiators at 11% each.
000 pp, and the solution was vigorously stirred. After 10 hours, the modified cation exchange membranes were taken out and washed with water.

After that, oxidation treatment was performed in oxidation treatment (B). Table 1 shows the electrical resistance, current efficiency, pure salt rate, and organic contamination resistance of the obtained modified cation exchange membrane and the cation exchange membrane before modification.

Example 2 Dimethylarylamine was polymerized (average molecular weight: 1390
A tertiary polyamine of 0) was obtained.

Dissolve 8.5 g (0.1 mole) of this material in 200 mj! of methanol, and add 15.3 g of chloromethylstyrene.
g (0.1 mol) and reacted at 40°C for 3 days.
The tertiary polyamine was quaternized and 10 vinylhensyl groups were introduced.

A cation exchange membrane (Neosepta CM-1) was added to a 0.5 N sodium sulfate aqueous solution containing 500 ppm of this material.
It was immersed at 0° C. for 3 hours, and then 11,000 pp of azobis-2-amidinopropane hydrochloride was added as a polymerization initiator and polymerized for 10 hours.

The electrical resistance of the obtained modified cation exchange membrane was 1.4Ω.
- ci, and there was almost no increase in electrical resistance due to treatment.

Furthermore, oxidizing agent treatment (A) was performed, the seawater was concentrated, and the pure salt rate was measured.

The values after 6 months were as shown in Table 2.

Table 2 Example 3 Anionic polymerization of 3-vinylpyridine to form the molecule flt
3000 poly-4-vinylpyridine was obtained.

10.4 g (0.1 mol) of this stuff in 200 m
1 of methanol, then 15.3 g (0.1 mol) of chloromethylstyrene was added, and 40
The reaction was carried out at .degree. C. for 7 days to convert polyvinylpyridine into a quaternary pyridinium salt and introduce two vinylbenzyl groups.

A cation exchange membrane (Neosebuta CH-45T) was immersed in an aqueous solution containing 3000 ppm of this substance at 40°C for 3 days.

The ion exchange membrane was taken out of the aqueous solution and immersed in a mixture of 11,000 ppm aqueous solutions of ammonium persulfate and potassium sulfite for 10 hours under a nitrogen atmosphere. The electrical resistance of the cation exchange membrane taken out was 1.4Ω·C.

The pure salt percentage when seawater was concentrated was 98.7.98.3% at the initial stage and after 6 months, respectively.

Claims (12)

[Claims] (1) A modified cation exchange membrane in which a polymer of a quaternary ammonium base and a vinyl compound having three or more vinylbenzyl groups is present on at least one surface of the cation exchange membrane. (2) A vinyl compound having a quaternary ammonium base and three or more vinylbenzyl groups is obtained by aminating a primary amine with three or more vinylbenzyl halides, as described in claim (1). Modified cation exchange membrane. (3) The modified cation exchange membrane according to claim (2), wherein the primary amine is methylamine or ethylamine. (4) The modified cation exchange membrane according to claim (2) or (3), wherein the vinylbenzyl halide is vinylbenzyl chloride. (5) A vinyl compound having a quaternary ammonium base and three or more vinylbenzyl groups is produced by reacting a divalent primary amine with three or more vinylbenzyl halides, and optionally with an alkylating agent. The resulting modified cation exchange membrane according to claim (1). (6) The modified cation exchange membrane according to claim (5), wherein the divalent primary amine is ethylene diamine or propylene diamine. (7) The modified cation exchange membrane according to claim (5), wherein the alkylating agent is methyl iodide or dimethyl sulfate. (8) A vinyl compound having a quaternary ammonium base and three or more vinylbenzyl groups is obtained by reacting a trivalent or higher tertiary amine compound with three or more vinylbenzyl chlorides, and optionally using an alkylating agent. A modified cation exchange membrane according to claim (1) obtained by the reaction. (9) A vinyl compound having a quaternary ammonium base and three or more vinylbenzyl groups reacts with a vinylphenylalkyl N,N-dialkylamine to a compound having three or more halogen atoms in the same molecule. A modified cation exchange membrane according to claim (1) obtained by (10) After a vinyl compound having a quaternary ammonium base and three or more vinylbenzyl groups is present on the surface of the cation exchange membrane, the vinyl compound is polymerized to form a polymer of the vinyl compound. Claim No. 1 (1)
) Modified cation exchange membrane described in section 2. (11) The modified cation exchange membrane according to claim (1), which has cation permselectivity. (12) Claim No. (1) having organic stain resistance
Modified cation exchange membrane as described in Section.