JPH0315934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing an anion exchange membrane.
More specifically, the present invention relates to a method for producing an anion exchange membrane coated with an ion exchange group-containing polymer having a quaternary ammonium base as an anion exchange group. The present inventors first reacted a fluorine-based polymer porous membrane support whose surface was plasma-treated with a polyamine to crosslink it, and then attached an organic solvent solution having a functional group that can be aminated. We have proposed a method for producing an anion exchange membrane in which the membrane is dried, aminated with amino, and coated with an ion exchange group-containing polymer having a quaternary ammonium base as an anion exchange group (particularly (Gan Sho 58-75575). The anion exchange membrane produced by this method uses a solvent-insoluble fluoropolymer porous membrane cross-linked with polyamine as a support, so it has excellent strength even if the membrane is thin. Not only is it easy to handle, but in combination with plasma treatment before polyamine crosslinking, ion exchange material is removed from the support during the water washing step after amination treatment and when attaching or detaching the anion exchange membrane to the dialysis cell. There is no peeling, and therefore the dialysis rate ratio between acid and its salt or alkali is high, and the effect is that it is excellent in terms of diffusion dialysis performance. Although the anion-exchange membrane proposed above can be effectively used as a diffusion dialysis membrane, etc., the ion-exchange base coating layer may have an uneven thickness or its film formation may be difficult. In some cases, there are drawbacks such as easy formation of pinholes and smearing, and further improvements in these points have been desired. It was also desired to further improve the selective permeability of anions. Therefore, as a result of various studies in search of a solution to this problem, the present inventors discovered that, in the method for producing the anion exchange membrane, an amine was reacted with a fluoropolymer porous support whose surface was plasma-treated. The inventors have discovered that the above object can be achieved by repeating the steps of applying a solution of a polymer having an aminatable functional group in an organic solvent, drying it, and aminating it with an amine several times after crosslinking. . Therefore, the present invention relates to a method for manufacturing an anion exchange membrane carried out in this manner. The porous fluoropolymer membrane used as a support forming material is a porous membrane of a fluoropolymer such as polyvinylidene fluoride, polytetrafluoroethylene, or polychlorotrifluoroethylene. The body can be of various shapes, such as not only a flat membrane, but also a tube, a hollow fiber, or a composite with another membrane-like porous support. The porous structure can be formed, for example, by dissolving a fluorine-based polymer in a water-soluble organic solvent and immersing it in water after casting, wet-dry spinning, etc. Alternatively, a commercially available product itself can be used. can. These porous membrane-like bodies have a wall thickness of about 5 to
1000μ, preferably about 10 to 500μ, and surface pore diameters of about 0.005 to 2μ, preferably about 0.01 to 1μ are generally used. Plasma treatment of porous membranes includes glow discharge,
This is carried out using plasma generated by corona discharge or the like according to the method shown in Japanese Patent Application No. 57-205816 and the drawings. In the plasma treatment performed in this way, the permeability of the plasma into the porous membrane is extremely low, so the treatment is limited to only the very surface area of the porous membrane, and therefore the physical properties originally possessed by the porous membrane are almost completely lost. maintained without any damage. The plasma-treated fluoropolymer porous membrane is crosslinked with amine. Examples of amines include monoamines such as butylamine and hexylamine, ethylenediamine, trimethylenediamine, hexamethylenediamine, N, N, N',
N'-tetramethyl-1,6-hexanediamine, p
-Diamines such as phenylenediamine, 1,2,
Triamines such as 3-triaminopropane are used, and crosslinking is achieved by immersing a plasma-treated fluoropolymer porous membrane in these amines or their aqueous solutions, and heating it if necessary. This is done by After the crosslinking reaction is completed, sufficient water washing is performed to remove unreacted amine. An organic solvent solution of a polymer having an aminatable functional group is attached to the plasma-treated fluoropolymer porous membrane crosslinked by amine in this manner. Examples of polymers having a functional group that can be aminated include styrene-chloromethylstyrene copolymer, chloromethylated polystyrene,
Chloromethylated polysulfone, chlorinated polyethylene, polyvinyl chloride, polyepichlorohydrin,
Furthermore, any polymer containing an active chloro group can be used, such as a homopolymer or copolymer of vinyl chloroacetate, chloromethyl vinyl ether, etc. These polymers are used in the form of an organic solvent solution, and the organic solvent used naturally varies depending on the type of polymer, but when the porous membrane is crosslinked with an amine,
Organic solvents that cannot be used to dissolve fluoropolymers because they are solvent insoluble, such as aprotic polar solvents such as dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone, acetone, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone, ethers such as dioxane, halogenated hydrocarbons such as carbon tetrachloride, etc. can be used as desired, and organic compounds with high affinity for these fluorinated polymers can be used. When a solvent is used as a solvent for the adhesion solution, there is an effect that almost no peeling is observed between the porous membrane support and the ion exchange group-containing polymer membrane coated thereon. be given Adhesion of an organic solvent solution to a film-like body is generally approximately
It is carried out by applying a solution prepared to a polymer concentration of 0.1 to 20% by weight by means such as dipping or pouring. Thereafter, it is generally air-dried at about 20 to 60°C and subjected to the next amination process. As the aminating agent, aliphatic or aromatic one
A variety of secondary, secondary or tertiary amines are used, in particular N,N,N',N'-tetramethyl-1,6-hexanediamine, N,N,N',N'-tetramethylethylenediamine, N , N,N',N'-tetramethyl-p-phenylenediamine and the like are preferred. When such a polyamine is used as an aminating agent, since the polyamine also serves as a crosslinking agent, three-dimensionalization is performed at the same time as quaternary ammonium salt formation by amination.
After the amination treatment, washing with water is performed. In the present invention, the above-described deposition of an organic solvent solution of a polymer having an aminatable functional group, its drying, and amination with an amine are repeated multiple times, generally about 2 to 4 times. Plasma treatment increases the thickness of the ion-exchangeable base coating layer formed on the amine-crosslinked fluoropolymer porous support, thereby increasing the thickness non-uniformity and the formation of pinholes. At the same time, it is possible to further improve the selective permeation performance of anions as indicated by the dialysis rate ratio under an appropriate ion permeation rate per unit membrane area. . Next, the present invention will be explained with reference to examples. Example 1 Polyvinylidene fluoride (Pennwalt product)
A dimethylacetamide solution containing 20% by weight of Kynar) and 2% by weight of polyethylene glycol (Hani Chemicals #6000) was added to the spacer with a thickness of 0.2%.
A porous film was formed by casting the film onto a glass plate using a dry-wet method using water as a coagulant. After air-drying the obtained porous membrane, it was placed in a plasma reaction vessel and heated at a frequency of 0.1 Torr under nitrogen pressure.
Irradiate high frequency of 13.56MHz, output 50W for 5 minutes,
Plasma treatment was performed. This plasma-treated film was treated with 50% N by weight at 30°C.
It was immersed in an aqueous solution of N,N',N'-tetramethyl-1,6-hexanediamine for 2 hours to cause a crosslinking reaction. The obtained amine crosslinked membrane was washed with water, dried, and then immersed for 1 minute in a 3% by weight carbon tetrachloride solution of styrene-chloromethylstyrene copolymer (introduced chlorine amount: 0.027% by weight), dried, and then the same process was performed. The following steps were performed under the same conditions: immersion in an amine aqueous solution, immersion in a chloromethylstyrene copolymer carbon tetrachloride solution, and immersion in an amine aqueous solution. The anion exchange membrane thus obtained was
Installed in a chamber-type dialysis cell, 2N−H ₂ SO ₄ and 1N−
A dialysis test was conducted at 30°C using a mixture of FeSO ₄ aqueous solution, and the dialysis rate of sulfuric acid and the ratio of dialysis rates between the two were measured. Comparative Example 1 In Example 1, immersion in the amine aqueous solution and immersion in the chloromethylstyrene copolymer carbon tetrachloride solution were performed only once. Example 2 In Example 1, chloromethylated polystyrene (introduced chlorine amount: 0.025% by weight) was used instead of the styrene-chloromethylstyrene copolymer. Comparative Example 2 In Example 2, the amine aqueous solution immersion and the chloromethylated polystyrene carbon tetrachloride solution immersion were performed only once. The measurement results for each of the above examples and comparative examples are as follows:
The average values of three measurements are shown in the following table. 【table】

Claims (1)

[Claims] 1. After crosslinking a fluorine-based polymer porous membrane support whose surface has been plasma-treated with an amine,
1. A method for producing an anion exchange membrane, which comprises repeating the steps of depositing a solution of a polymer having an aminatable functional group in an organic solvent, drying it, and aminating it with an amine several times. 2. The method for producing an anion exchange membrane according to claim 1, wherein the fluorine-based polymer porous membrane is a polyvinylidene fluoride porous membrane.