JPH0686540B2 - Method for manufacturing composite ion exchange membrane - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel method for producing a composite ion exchange membrane, and particularly to decompose a neutral salt to obtain a high concentration of acid and alkali with high current efficiency. It is intended to provide a method for efficiently producing a composite ion-exchange membrane useful in a metathesis method of an organic salt.

(Prior Art) Generally, ion exchange membranes are seawater-concentrated salt production by electrodialysis, desalination of salt water, separation of ionic and nonionic substances, diffusion dialysis, electrolysis of alkali metal salt aqueous solution, organic synthetic electrolytic reaction, reverse osmosis, It is widely used in technical fields such as ultrafiltration and battery separators. It is the ion-exchange group bonded to the polymer membrane that controls the function of such an ion-exchange membrane. That is, depending on the concentration of the ion exchange group in the membrane (fixed ion concentration), the state of distribution of the ion exchange group in the membrane, and the presence of different ion exchange groups when they exist in the membrane, the ion exchange membrane The functions will be completely different.

Therefore, conventionally, as a composite ion exchange membrane for imparting various functions, for example, a bipolar ion exchange membrane in which a cation exchange membrane and an anion exchange membrane are integrated, is disclosed in JP-A-52-6.
No. 8873, JP-A-52-75679 and the like, a cation exchange membrane and an anion exchange membrane in which only a thin layer having a high fixed ion concentration is present only in the surface layer portion of the ion exchange membrane,
For example, a fluorine-containing ion exchange membrane as disclosed in Japanese Patent Application Laid-Open No. 50-108182 has been proposed which is used as a diaphragm for electrolysis of an aqueous solution of an alkali metal salt.

(Problems to be Solved by the Invention) However, in the conventional composite ion-exchange membrane, it is difficult to control the introduction and distribution of the ion-exchange groups to prevent nonuniformity, and the target product can be easily and mass-produced. Is difficult. In addition, these composite ion exchange membranes do not satisfy all the functions required in the above-mentioned technical fields, and are particularly ion exchange membranes that easily cause water dissociation in the metathesis (hydrolysis) of a neutral salt. There is a need for a composite ion exchange membrane suitable for producing high concentrations of acid and alkali with high current efficiency.

(Means for Solving the Problems) In view of the problems described above, the present inventors have diligently studied a method for producing a composite ion-exchange membrane suitable for a metathesis method of a neutral salt, and as a result, polymerized a monomer mixture having a specific composition. A composite ion-exchange membrane in which cross-linking treatment and cation-exchange group introduction were performed on one side of the polymer membrane obtained in this way, and then anion-exchange group was introduced on the other side had good results depending on the purpose. Therefore, the present invention has been proposed. That is,
According to the present invention, a monomer mixture mainly comprising an aromatic compound monomer having a vinyl group capable of being polymerized with a halogen-substituted alkyl group, a nitrile compound monomer having a vinyl group and a polyvalent vinyl compound monomer is polymerized to form a polymer film. After forming a substance, a cross-linking treatment is performed on one surface of the polymer membrane material, a cation exchange group is introduced, and an anion exchange group is introduced on the other surface. A method of manufacturing the same is provided.

Examples of the aromatic compound monomer having a halogen-substituted alkyl group and a polymerizable vinyl group used in the present invention include chloromethylstyrene, chloromethylvinylnaphthalene, bromomethylstyrene and bromomethylvinylnaphthalene. The aromatic compound monomer having a halogen-substituted alkyl group and a polymerizable vinyl group is generally used in an amount of 60% by weight of all monomers in order to make the cation exchange membrane of the resulting composite ion exchange membrane dense and to increase the fixed ion concentration. wt)% or more, especially 60 to 95 wt% is preferable. That is, when the proportion of the aromatic compound monomer is lower than 60 wt%, a dense cation exchange layer cannot be obtained even if a cation exchange group is introduced together with a crosslinking treatment after forming a polymer film. However, the target composite ion exchange membrane with a high fixed ion concentration cannot be obtained. On the other hand, if the ratio of the aromatic compound monomer is higher than 95 wt%, the electric resistance of the obtained composite ion exchange membrane will be high, which is not preferable.

The nitrile compound monomer having a vinyl group used in the present invention is, for example, a low molecular weight monomer such as acrylonitrile or methacrylonitrile, and the monomer accelerates the rate of introduction of a cation exchange group described below and provides a composite ion exchange membrane. In order to lower the electric resistance, generally 5 to 20%, especially 10 to 15% of the total monomer weight is preferable, and 20%
Too much more will reduce the fixed ion concentration in the cation exchange layer.

The polyvalent vinyl monomers used as the crosslinking agent of the present invention include, for example, divinylbenzenes, trivinylcyclohexanes, divinylnaphthalene, divinyltoluenes, dimethacrylates such as propylene glycol, etc. It is preferable to use it in a ratio of 1 to 10 wt%.

In the present invention, it is also possible to use a monomer mixture in which vinyl monomers having a functional group suitable for introducing a cation exchange group are used together with each of the above-mentioned monomers, if necessary. Examples of vinyl monomers having a functional group suitable for introducing such a cation exchange group include styrene, vinyltoluene, chlorostyrene, vinylnaphthalene, styrenesulfonyl chloride, hydroxystyrene, methyl acrylate, and acrylic acid such as ethyl acrylate. Examples thereof include esters and methacrylic acid esters.

The polymer membrane material of the present invention can be obtained by using a mixture of the above-mentioned monomers according to a known method for producing an ion exchange membrane. For example, there is a method of polymerizing and molding the above-mentioned monomer mixture into a film, or a method of impregnating and polymerizing the monomer mixture into a linear polymer compound such as a cloth or film. At this time, a polymerization catalyst, a plasticizer, or, if necessary, a fine powder plastic polymer substance as a reinforcing material, a base material, etc. are appropriately used. Examples of the polymerization catalyst include benzoyl peroxide, azobisisobutyronitrile, and dicumyl peroxide, and examples of the plasticizer include dioctyl phthalate and dibutyl phthalate. Further, as the finely divided thermoplastic polymer substance, for example, polyethylene, polyvinyl chloride, acrylonitrile-vinyl chloride copolymer, vinyl chloride-vinylidene chloride copolymer, NBR, S
As the base material of BR, polybutadiene, or the like, a known cloth-like or net-like material such as glass fiber, vinylon, canecarone, teviron, saran, bonnel (above, trade name), polyethylene, polypropylene is used.

Next, in the present invention, one side of the polymer film obtained by the above method is subjected to a crosslinking treatment to introduce a cation exchange group to form a target cation exchange layer. The method for forming this cation exchange layer on one side of a polymer film is as follows.
Generally, only one side is exposed by attaching a film of polypropylene, polyvinyl fluoride, polytetrafluoroethylene, etc. to one side of the polymer film, or by sandwiching the polymer film between two frames. After that, it is achieved by carrying out a crosslinking treatment via a haloalkyl group and introducing a cation exchange group on the one surface. Such a crosslinking treatment with a haloalkyl group can be carried out using a generally known Friedel-Crafts catalyst such as sulfuric acid, aluminum chloride, tin tetrachloride or titanium tetrachloride. In the case of introducing a sulfone group as a cation exchange group, crosslinking can be simultaneously achieved by using concentrated sulfuric acid, chlorosulfonic acid or a mixture thereof. Incidentally, as the cation exchange group, a carboxyl group, a phosphon group and the like other than the sulfone group are introduced by a known method. The degree of crosslinking in the cation exchange layer thus obtained is generally adjusted appropriately by controlling the diffusion rate of concentrated sulfuric acid, chlorosulfonic acid or the like in the membrane. If the degree of cross-linking is small, the fixed ion concentration is high and a dense cation exchange layer cannot be obtained, and conversely, if the degree of cross-linking is large, the membrane resistance becomes large, which is not preferable. The thickness of such a cation exchange layer is 1 to 50%, preferably 5 to 30% of the membrane thickness, and if it exceeds this range, the membrane resistance increases. The fixed ion concentration of the cation exchange layer thus obtained is generally 10 to 20N.

Furthermore, the present invention introduces an anion-exchange group into the other surface of the above-mentioned polymer membrane (in the case of the polymer membrane with the film adhered, the surface from which the film has been peeled) to introduce a complex ion-exchange group. Get the membrane. As the type of anion exchange group and the method of introducing the anion exchange group, known methods are used without particular limitation, and examples thereof include primary amine, secondary amine,
One side as described above in a bath prepared by dissolving a compound containing at least one tertiary amine, particularly a compound containing a tertiary amine suitable for forming a strongly basic anion-exchange group, in water, alcohol, acetone or the like. The method is, for example, a method of immersing a polymer film having a cation exchange layer therein. At this time, the amine compound used is, for example, trimethylamine, triethylamine, triethanolamine or the like. After this,
In general, the target composite ion-exchange membrane can be obtained by performing the conditioning treatment in dilute hydrochloric acid, water, or dilute sodium chloride solution. The fixed ion concentration in the anion exchange layer of the obtained composite ion exchange membrane is generally 5 to 20N.

(Action and Effect) As described above, according to the present invention, it is easy to introduce cation and anion exchange groups into the polymer membrane and control the distribution of the exchange groups, and the obtained composite ion exchange membrane is Since the ion exchange layer has a dense cation exchange layer with a high fixed ion concentration, the hydrolysis efficiency is high, especially when applied to the metathesis method of neutral salts, and the amount of electroosmotic water (permeated water) and proton ions (H ⁺ The reverse diffusion of) is extremely small, and a high-concentration acid or alkali can be generated with high current efficiency.

(Examples) Examples of the present invention will be shown below, but the present invention is not limited to these examples.

Example 1 100 parts of chloromethylstyrene, 12 parts of acrylonitrile,
A monomer mixture solution consisting of 7 parts of chlorosulfonated polyethylene rubber, 20 parts of divinylbenzene with a purity of about 55% and 4 parts of benzoyl peroxide was applied to a polypropylene plain woven cloth, and both sides were covered with a polyester film.
Polymerization was carried out by heating for a period of time to obtain a polymer film. A polypropylene film was attached to one side of this polymer film-like material and immersed in a mixed solution of chlorosulfonic acid and sulfuric acid by a conventional method to introduce a sulfonic acid group on one side. Then peel off the film,
It was immersed in a 10% trimethylamine solution at room temperature for 16 hours. Then, the composite ion exchange membrane of the present invention was obtained by immersing in dilute hydrochloric acid, water, and a 0.5N aqueous sodium chloride solution.

Various properties of this composite ion exchange membrane were measured by the following methods.

The thickness of the layer having a sulfonic acid group was measured by observing the cross section with a microscope after dyeing with crystal violet. The concentration of acid-alkali produced and the efficiency of hydrolysis are 100 cc of 0.5 normal hydrochloric acid on the side of the cation exchange base layer and 0.5 cc of sodium hydroxide on the side of the anion exchange base layer of the composite ion exchange membrane with an effective membrane area of 0.1 dm ^2. Put 100cc, 15
While stirring at 00 rpm, after energizing for 40 minutes at a current density of 5 A / dm ² , by measuring the change in concentration of the solution, the hydrolysis efficiency of the composite ion exchange membrane, that is, the current of hydrogen ion and hydroxide ion The efficiencies (η _H , η _OH ) and the chloride ion current efficiency (η _cl ) were determined. The electric resistance of the film is 0.5.
It was measured by alternating current for 1000 cycles at 25 ° C. in normal saline.

Also, the ion exchange capacity of the membrane is 0 for a membrane acidified with hydrochloric acid.
Equilibration was performed with 5N saline, and the ion-exchanged hydrogen ions were titrated with 1 / 10N caustic soda. Regarding the anion exchange capacity of the membrane, after soaking the membrane in 1N hydrochloric acid to make it a chlorine ion type, thoroughly washing it with methanol to remove the chlorine ions adsorbed on the membrane, and then 0.2N sodium nitrate solution Treatment several times to elute chlorine ions in the membrane,
This amount was analyzed and determined. The water content of the membrane was measured by measuring the wet weight of sodium type or chloride ion type, then dried in an air dryer at 70 ° C. for 2 hours, stored in a desiccator containing calcium chloride as a desiccant, and then weighed. This was defined as the dry weight, and the difference between the wet weight and the dry weight was divided by the dry weight to obtain the value. The exchange capacity was expressed as the exchange capacity per gram of the dry membrane (Na type or cl type). The results are also shown in Table 1.

Comparative Example 1 A monomer mixture solution consisting of 120 parts of chloromethylstyrene, 10 parts of styrene, 5 parts of dioctylphthalate, 7 parts of chlorosulfonated polyethylene rubber, 15 parts of divinylbenzene having a purity of about 55% and 4 parts of benzoyl peroxide was prepared in Example 1. The same operation as above was performed to obtain a composite ion exchange membrane for comparison.

The same items as in Example 1 were measured for the obtained composite ion-exchange membrane. The results are shown in Table 1.

Example 2 100 parts of chloromethylstyrene, 15 methacrylonitrile
Parts, acrylonitrile butadiene rubber 7 parts, styrene 5
Part, 15 parts of divinylbenzene having a purity of about 80% and 4 parts of benzoyl peroxide are applied to a plain weave cloth made of polyvinyl alcohol, and both sides are covered with a polyester film. At 70 ° C for 3 hours, at 80 ° C. Polymerization was carried out by heating for 5 hours to obtain a polymer film. A polypropylene film was attached to one side of this polymer film-like material, and immersed in a mixed solution of chlorosulfonic acid and sulfuric acid by a conventional method to introduce a sulfonic acid group on one side.

Then, the film was peeled off and immersed in a trimethylamine solution at room temperature for 16 hours. Further, by further dipping in dilute hydrochloric acid, water, 0.5 N sodium chloride aqueous solution,
A composite ion exchange membrane of the present invention was obtained.

The same items as in Example 1 were measured for the obtained composite ion-exchange membrane. The results are shown in Table 1.

Claims (6)

[Claims] 1. A polymer film-like product obtained by polymerizing a monomer mixture mainly comprising an aromatic compound monomer having a vinyl group capable of polymerizing with a halogen-substituted alkyl group, a nitrile compound monomer having a vinyl group and a polyvalent vinyl compound monomer. After forming a polymer ion-exchange membrane, one side of the polymer membrane is cross-linked and a cation exchange group is introduced, and an anion exchange group is introduced on the other side. Method. 2. The production method according to claim 1, wherein a monomer mixture containing 60% by weight or more of an aromatic compound monomer having a halogen-substituted alkyl group and a polymerizable vinyl group is used. 3. The production method according to claim 1, wherein a monomer mixture containing 1 to 10% of a polyvalent vinyl compound monomer is used. 4. The production method according to claim 1, wherein a monomer mixture having a vinyl group-containing nitrile compound monomer in an amount of 5 to 20% by weight is used. 5. The fixed ion concentration of the cation exchange layer is 10 to 20.
The manufacturing method according to claim (1), wherein N is N. 6. The method according to claim 1, wherein the composite ion exchange membrane is a bipolar membrane.