JPH0315663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anion exchange membrane and a method for producing the same. More specifically, the present invention relates to an anion exchange membrane that is effectively used as a diffusion dialysis membrane and has excellent peeling resistance and dialysis performance, and a method for producing the same. Since anion exchange membranes have the property of allowing anions to permeate more selectively, this property has been utilized for industrial applications such as electrodialysis, diffusion dialysis, and electrolysis of salts. In order to perform these dialysis or electrolysis efficiently, anion exchange membranes are required to increase the ion dialysis rate per unit membrane area. It is generally known that this dialysis rate can be improved by reducing the membrane thickness, but if the membrane thickness is made extremely thin, the membrane strength will inevitably decrease, making it difficult to handle the membrane, making it impractical. becomes damaged. In order to eliminate these drawbacks, the applicant used a fluoropolymer porous membrane with excellent strength and chemical resistance as a reinforcing support, and added an anion exchange material to this support. Although various coating methods have been investigated, because the adhesion between the support and the coating material is not sufficient, separation of the two is observed during handling of the anion exchange membrane, and this separation also causes anion There were also problems with the exchange membrane itself, such as its dialysis performance being unstable and high performance not expected. In order to solve this problem, the present applicant has added functional groups that can be anodized to a fluoropolymer porous membrane whose surface has been plasma-treated or whose surface has been crosslinked with a polyamine. A porous membrane is coated with an ion-exchangeable group-containing polymer having a quaternary ammonium base as an ion-exchangeable group. (Japanese Patent Application Nos. 57-205816 and 58-205)
No. 53243). Although each of these proposals has achieved its intended purpose, further improvement in dialysis performance has been desired. The present inventors have discovered that such problems can be effectively solved by a method that uses both methods in combination, that is, by using a polyamine crosslinked product of a fluoropolymer porous membrane support whose surface has been plasma treated. Ta. Therefore, the present invention relates to an anion exchange membrane, which comprises a polyamine crosslinked product of a fluoropolymer porous membrane support whose surface has been plasma-treated as an anion exchange group. It is coated with an ion exchange group-containing polymer having an ammonium base. The present invention also relates to a method for producing such an anion exchange membrane, which comprises reacting a fluoropolymer porous membrane support whose surface has been plasma-treated with a polyamine to crosslink it, and then crosslinking it with a polyamine. This is carried out by depositing a solution of a polymer having a functional group in an organic solvent, drying it, and then aminating it with an amine. The porous fluoropolymer membrane, which is the support forming material, is a porous membrane of a fluoropolymer such as polyvinylidene fluoride, polytetrafluoroethylene, and polychlorotrifluoroethylene. The body is not only flat, but also tubular,
Various forms can be used, such as hollow fibers or composites with other membrane-like porous membrane supports. 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 polyamine. Examples of polyamines include ethylene diamine, trimethylene diamine, hexamethylene diamine, N, N, N',
N'-tetramethyl-1,6-hexanediamine,
Diamines such as p-phenylenediamine, 1,
Triamines such as 2,3-triaminopropane are used, and crosslinking is achieved by immersing a plasma-treated fluoropolymer porous membrane in these polyamines or their aqueous solutions, and then heating it if necessary. It is done by doing. After the crosslinking reaction is completed, sufficient water washing is performed to remove unreacted polyamine. An organic solvent solution of a polymer having an aminatable functional group is attached to the plasma-treated fluoropolymer porous membrane crosslinked with polyamine in this manner. Examples of polymers having amino-capable functional groups include styrene-chloromethylstyrene copolymer, chloromethylated polystyrene, chloromethylated polysulfone, chlorinated polyethylene, polyvinyl chloride, polyepichlorohydrin, and further vinyl chloroacetate and chloromethyl. Any polymer containing an active chlorine group can be used, such as a homopolymer or copolymer such as vinyl ether. These polymers are used in the form of organic solvent solutions, and the organic solvent used naturally varies depending on the type of polymer, but since the porous membrane is crosslinked with polyamine and is insoluble in solvents, Organic solvents that cannot be used to dissolve elementary polymers, such as aprotic polar solvents such as dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ,
Ethers such as dioxa, halogenated hydrocarbons such as carbon tetrachloride, etc. can be used as desired, and organic solvents with high affinity for these fluorine-based polymers can be used as the solvent for the adhesion solution. When the porous membrane support is coated with the ion-exchangeable group-containing polymer membrane, there is hardly any peeling. Adhesion of an organic solvent solution to a film-like body is generally approximately
This is done by applying a solution prepared to a polymer concentration of 0.1 to 20% by weight by means such as dipping or spraying. 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. The anion exchange membrane produced in this way, which is a porous membrane coated with an ion exchange group-containing polymer having a quaternary ammonium base as an anion exchange group, is crosslinked with a polyamine,
Since the support is a solvent-insoluble fluoropolymer porous membrane, it has excellent strength even if the membrane is thin, and is not only easy to handle, but also compatible with plasma treatment before polyamine crosslinking. The ion exchange material does not peel off from the support during the water washing process after the amination treatment and when the anion exchange membrane is attached to or detached from the dialysis cell, so the dialysis rate ratio between acid and its salt or alkali is high. ,
It is also effective in terms of diffusion dialysis performance. Next, the present invention will be explained with reference to examples. Example Polyvinylidene fluoride (Pennwalt product)
A dimethylacetamide solution containing 20% by weight of Kynar) and 2% by weight of polyethylene glycol (Hani Chemical Products #6000) was cast onto a glass plate with a spacer thickness of 0.2mm, and a porous solution was cast using a wet-dry method using water as a coagulant. A quality film was formed. This porous membrane has a dense layer on the surface of the membrane and has an asymmetric structure with a large number of pores inside and on the surface (see Japanese Patent Application No. 15183/1983). After air-drying, this porous membrane was placed in a plasma reaction vessel and heated at a frequency of 13.56M under a nitrogen pressure of 0.1Torr.
Plasma treatment was performed by irradiating high-frequency waves at Hz and output of 50 W for 1 minute. Thereafter, this plasma-treated porous membrane was immersed for 2 hours in a 50% by weight aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine at 30°C to cause a crosslinking reaction. The obtained polyamine crosslinked product was washed with water and air-dried, then immersed in a 3% by weight carbon tetrachloride solution of styrene-chloromethylstyrene copolymer for 1 minute, air-dried, and then immersed in the N,
It was immersed in an aqueous N,N',N'-tetramethyl-1,6-hexanediamine solution for 2 hours and washed with water. At this stage, no peeling of the ion-exchangeable group-containing polymer coating layer was observed at all. Nakatsuta. The obtained ion exchange membrane was installed in a two-chamber dialysis cell, and dialysis tests using a mixture of 2N sulfuric acid and 1N ferrous sulfate aqueous solution were performed twice to determine the dialysis rate of sulfuric acid and the dialysis of both. The speed ratio was measured and the average value was determined. The measurement results obtained are shown in the table below. Incidentally, even after this dialysis test, no peeling of the coating layer was observed. Comparative Example 1 In the example, the porous membrane support was not subjected to plasma treatment. Comparative Example 2 In the example, polyamine crosslinking of the plasma-treated porous membrane support was not performed. The measurement results for these comparative examples are also listed in the following table. 【table】

Claims (1)

[Scope of Claims] 1. A polyamine crosslinked product of a fluoropolymer porous membrane support whose surface has been plasma treated is treated with an ion exchange group-containing polymer having a quaternary ammonium base as an anion exchange group. Anion exchange membrane coated with 2. The anion exchange membrane according to claim 1, wherein the fluoropolymer porous membrane support is a polyvinylidene fluoride porous membrane support. 3 After crosslinking the fluorine-based polymer porous membrane support whose surface has been plasma-treated with a polyamine, an organic solvent solution of a polymer having a functional group that can be aminated is applied, and this is dried. 1. 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, which is then aminated with an amine. 4. The method for producing an anion exchange membrane according to claim 3, wherein the fluoropolymer porous membrane support is a polyvinylidene fluoride porous membrane support.