KR100460454B1 - A swollen cation exchange membrane using water-soluble polymer and preparation method thereof - Google Patents

Abstract

The present invention relates to a water-swellable cation exchange membrane using a hydrophilic polymer and a method for preparing the same, and more particularly, a water-soluble polymer of polyvinyl alcohol (PVA, poly (vinyl alcohol)) and a polystyrene sulfonic acid / maleic acid copolymer (PSSA-). MA and polystyrene sulfonic acid-co-maleic acid (MA) were blended using a certain amount of cation exchange polymer, followed by heat treatment and chemical crosslinking to prepare a water swellable cation exchange membrane. By simultaneously having multiple carboxylic acid groups of the acid, the ion exchange capacity is improved and the crosslinking degree can be improved while reducing the water content compared with the conventional one, and the structure of the membrane is easily controlled, and at the same time, the separation of the organic / metal compound having a relatively high molecular weight Not only suitable for cleaning and refining, but also with no organic solvents St. relates to a cation-exchange membrane and a process for producing the same.

Description

A swollen cation exchange membrane using water-soluble polymer and preparation method

The present invention relates to a water-swellable cation exchange membrane using a hydrophilic polymer and a method for preparing the same, and more particularly, a water-soluble polymer of polyvinyl alcohol (PVA, poly (vinyl alcohol)) and a polystyrene sulfonic acid / maleic acid copolymer (PSSA-). MA and polystyrene sulfonic acid-co-maleic acid (MA) were blended using a certain amount of cation exchange polymer, followed by heat treatment and chemical crosslinking to prepare a water swellable cation exchange membrane. By simultaneously having multiple carboxylic acid groups of the acid, the ion exchange capacity is improved and the crosslinking degree can be improved while reducing the water content compared with the conventional one, and the structure of the membrane is easily controlled, and at the same time, the separation of the organic / metal compound having a relatively high molecular weight Not only suitable for cleaning and purification, but also using organic solvent, eco-friendly and economical St. relates to a cation-exchange membrane and a process for producing the same.

An ion exchange membrane is a kind of polymer separation membrane that can selectively separate anions or cations depending on the species of ion-exchangeable groups introduced into the membrane. For the cation exchange membrane which is being used for commercial, large adult strong acid sulfonic acid group (-SO ^3-) and the weak acid is a carboxylic acid group (-COO ^-) as the ion exchange group becomes is divided into, mainly in the case of an anion exchange membrane Strongly basic quaternary ammonium groups (-NR ₃ ⁺ ) have ion exchange groups. The separation process using the ion exchange membrane is capable of separating and purifying relatively high purity, using less energy, and performing a continuous process than the separation method using distillation and chemical treatment. It is attracting attention as a separate purification process in the field. Examples of applications in the present industry include electrodialysis and water-splitting electrodialysis for desalination and purification, diffusion dialysis to recover acids from pickling liquor and electrodesalting for ultrapure water production. Electrodeionization and the like. In particular, in recent years, interest in ion-exchange membranes has been increasing, suggesting the possibility that the polymer electrolyte fuel cell may exhibit excellent performance.

In general, commercial membranes should have high ion selective permeability (> 0.95 to 0.98), low electrical resistance (<3.0 to 4.0 Ωcm ² ), adequate water content, high mechanical strength and chemical resistance. Existing commercial membranes (eg NEOSEPTA ^TM (Tokuyama Co. Ltd., Japan), SELEMION ^TM (Asahi Glass Company, Japan)) are very hydrophobic polysulfones (PSf, polysulfone) and polystyrene (PS, polystyrene). ) And has a relatively good electrochemical properties. However, their manufacturing process must undergo harsh chemical reactions to introduce ion exchange groups. For example, a cation exchange membrane may include a sulfonation process to introduce an ion exchange group, and a weak sulfonation introduces a small amount of an ion exchange group, which may lead to a decrease in electrochemical properties and a separation ability. Results in a decrease. On the contrary, excessive sulfonation in order to introduce a large amount of ion exchange groups decomposes the main chain of the polymer, thereby limiting the introduction of ion exchange groups such as deterioration of mechanical properties and deterioration of electrochemical performance of the membrane due to side reactions. On the other hand, although the crosslinking agent is introduced to improve the mechanical properties of the membrane, since the change of the structural effect of the membrane through the crosslinking agent is relatively limited, the separation selectivity using the structural effect cannot be expected. In particular, the membrane produced through this method is applied to the removal and concentration of metal ions having a low molecular weight, and is limited to the separation and purification of relatively high molecular weight organic / metal compounds. In addition, these commercial membranes have the disadvantage that the membrane is very expensive and the manufacturing process is complicated. Moreover, the above manufacturing process uses a large amount of organic solvents, which may cause other environmental problems.

In order to overcome this problem, environmentally friendly manufacturing processes based on the separation of large molecular weight organic / metal ions and cation exchange membranes for fuel cells have been actively studied. Processes for the preparation of water-swellable PVA / PSSA membranes that are environmentally friendly and exhibit the relaxed structural properties of the membranes have also been reported as studies of this type [T. Uragami, R. Nakamura, and M. Sugihara, Makromol. Chem., Rapid Commun. Vol. 3, pp 467, 1982 and Nakano et al., US Patent No. 5,409,785, 1995]. Membranes made of water-soluble polymers, such as PVA / PSSA membranes, have a greater water content than cation exchange membranes for general desalting applications, and thus are applicable as dialysis membranes of metal ions and high molecular weight organic ions. However, since they have a large moisture content, they have disadvantages of poor permselectivity and chemical stability compared to general commercial ion exchange membranes (eg, Nafion ^™ (DuPont)). In order to overcome the performance degradation of the membrane due to such a large moisture content, a method of preparing a PVA-branded water-swellable polymer membrane containing an aliphatic sulfonic acid group and containing multiple carboxylic acids has been reported, but in this case, an aliphatic sulfonic acid Because of the use as a separation function, the separation efficiency is reduced compared to the membrane based on the aromatic sulfonic acid (generally, aromatic sulfonic acid shows a superior separation performance than aliphatic sulfonic acid). Therefore, in order to solve the above problems of the membrane, the development of membranes with increased ion exchange ability, ion permeability, and chemical stability are urgently needed.

Therefore, the present inventors have solved the above problems, polyvinyl alcohol (PVA, poly (vinyl alcohol)) water-soluble polymer and polystyrene sulfonic acid / maleic acid copolymer (PSSA-MA, polystyrene sulfonic acid-co-maleic acid) By blending with a certain amount of cation exchange polymer of, a water-swellable cation exchange membrane was prepared through heat treatment and chemical crosslinking, and the membrane had a benzene sulfonic acid group, which is an aromatic sulfonic acid, and multiple carboxylic acid groups simultaneously as a cation exchange group. The invention has been completed.

Therefore, the present invention is to have a benzene sulfonic acid group and a plurality of carboxylic acid groups in the cation exchange membrane at the same time, while reducing the water content as compared to the conventional ion exchange capacity is improved, and the degree of crosslinking can be adjusted, the structure of the membrane is easy to control, At the same time, the present invention is not only suitable for the separation and purification of relatively large molecular weight organic / metal compounds, but also to provide an environmentally friendly and economical water-swellable cation exchange membrane and a method for producing the same, without using an organic solvent.

Figure 1 shows the manufacturing process of the PVA / PSSA-MA membrane of the present invention.

Figure 2 shows the surface (a) and the cross-section (b) of the cation exchange membrane according to Example 1 of the present invention using an electron scanning microscope (SEM).

3 is a graph comparing voltage-current curves of Example 4 and a commercial film (CMX, Tokuyama Co. Ltd.) according to the present invention.

4 is a cross-sectional view of a composite film coated with a PVA / PSSA-MA film on polyethylene (nonwoven fabric) of Example 4 according to the present invention using an electron scanning microscope (SEM).

The present invention is a cation exchanger containing 50 to 90% by weight of polyvinyl alcohol solids and 10 to 50% by weight of polystyrene sulfonic acid / maleic acid copolymer solids, wherein benzenesulfonic acid groups and multiple carboxylic acid groups are introduced together as a cation exchanger. The membrane is characterized by that.

The present invention is a process of blending 50 to 90% by weight of polyvinyl alcohol solids and 10 to 50% by weight of polystyrene sulfonic acid / maleic acid copolymer solids, a process of naturally drying the mixture at room temperature to obtain a film, 70 to 70 Heat treatment at 150 ° C. for 0.5 to 5 hours to introduce benzenesulfonic acid group and multiple carboxylic acid groups into a cation exchanger, and to the cation exchange membrane with 0.05 to 10 wt% glutaaldehyde and 1 to 5 wt% Another method is to prepare a cation exchange membrane including a step of impregnating HCl with a mixed solution mixed with acetone and crosslinking at 15 to 50 ° C. for 1 to 10 hours.

Referring to the present invention in more detail as follows.

The present invention is a water swellable hydrate having a large change in the structure of the membrane due to the change in the degree of crosslinking. At the same time, by introducing a cation exchange membrane, the ion exchange capacity is improved and the structure of the membrane is changed by controlling the degree of crosslinking to increase the separation selectivity of the substance to be separated, while at the same time suppressing the use of organic solvents in manufacturing. A hydrophilic cation exchange membrane and a method for producing the same.

The cation exchange membrane according to the present invention serves as a support to improve the mechanical properties and at the same time 50 polyvinyl alcohol (PVA) to the water swelling role to be suitable for the separation of the organic / metal compound having a relatively high molecular weight in the whole cation exchange membrane It is preferable to contain from 90 to 90% by weight, preferably from 60 to 80% by weight, and if the content is less than 50% by weight, it is relatively dissolved in water due to the introduction of a large amount of the ion exchanger, so that the ion exchange membrane cannot be prepared. If it exceeds 90% by weight, a relatively small amount of ion exchanger is introduced, leading to a decrease in separation efficiency. The PVA uses a PVA hydrate having a weight average molecular weight of 30,000 to 150,000, a degree of saponification of 70 to 100%, preferably a weight average molecular weight of 50,000 to 120,000, and a degree of saponification of 80 to 100%.

In addition, the PSSA-MA copolymer in which maleic acid (MA) was added to polystyrene sulfonic acid (PSSA) was added to the total cation exchange membrane in order to improve ion exchange capacity and reduce water content in the cation exchange membrane of the present invention. It is preferable to contain%, if the content is less than 10% by weight, even if the mechanical properties are improved due to the increase of the PVA relatively, a small amount of ion exchanger is introduced, leading to a decrease in separation efficiency and electrochemical properties, If the content exceeds 50% by weight, it is impossible to prepare the ion exchange membrane by dissolving in water as well as the decrease in mechanical properties due to the relatively decrease in PVA. The PSSA may use 30% stock solution. In addition, the MA has a high ion exchange capacity per equivalent by having two carboxylic acid ion exchange groups per mole of monomer, and also has a low degree of hydration compared to sulfonyl groups, thereby reducing excessive moisture content of the membrane. . The PSSA-MA copolymer may have a weight average molecular weight of 5,000 to 40,000, preferably a weight average molecular weight of 10,000 to 30,000. The copolymerization ratio of said PSSA and MA is 1/3 to 10/1 molar ratio, Preferably 1/1 to 5/1 molar ratio is good.

The cation exchange membrane of the present invention containing the polyvinyl alcohol and the polystyrene sulfonic acid / maleic acid copolymer as described above has an advantage of excellent ion exchange capacity while reducing water content by simultaneously containing a benzene sulfonic acid group and multiple carboxylic acid groups. .

Hereinafter, a method of manufacturing a cation exchange membrane according to the present invention will be described in more detail with reference to FIG. 1.

First, the PSSA-MA copolymer copolymerizes PSSA and MA in a molar ratio of 1/3 to 10/1, preferably 1/1 to 5/1, and is substituted with a sodium ion (NA ⁺ ) type PSSA-MA air. Use coalescing The PSSA-MA copolymer substituted with the sodium ion (NA ⁺ ) type is used by re-substituting the H ⁺ − type using diffusion dialysis (Donnan dialysis). The reason why the PSSA-MA copolymer is substituted with H ⁺ -type is that in thermal crosslinking, sulfonyl group or carboxylic acid group promotes hydrogen bonding force with hydroxyl group of PVA to maintain membrane stability to improve mechanical properties. (In general, in the case of NA ⁺ -type, it is known that secondary bonding by hydrogen bonding is difficult to form). Donnan dialysis was performed using a cell consisting of two electrolyte baths. A cation exchange membrane (CMX, Tokuyama Co. Ltd., Japan) was fixed between the stolen dialysis tanks (effective area of about 20 cm ² ), one solution of PSSA-MA solution (Na ⁺ -type), and the other side of 2N HCl aqueous solution was added and stirred until reaching a constant pH (about 0.5) to replace PSSA-MA (Na ⁺ -type) with PSSA-MA (H ⁺ -type).

The PSSA-MA copolymer substituted with the H ⁺ -type obtained by the above method is prepared in an aqueous solution, and separately polyvinyl alcohol is prepared in an aqueous solution.

Then, the PVA aqueous solution and the PSSA-MA aqueous solution are filtered through a filter paper to remove impurities, and then blended and poured into a plastic petri dish and naturally dried in a clean room for 5 to 7 days. The mixture contains 50 to 90% by weight of polyvinyl alcohol solids and 10 to 50% by weight of polystyrene sulfonic acid / maleic acid copolymer solids.

Then, the PVA / PSSA-MA film obtained above was heat-treated at 70 to 150 ° C. for 0.5 to 5 hours, preferably at 80 to 130 ° C. for 1 to 3 hours, and a carboxyl group and multiple carboxyl groups were used as a cation exchanger. A cation exchange membrane was prepared in which acid groups were introduced simultaneously.

Finally, the heat-treated cation exchange membrane was mixed with 0.05 to 10% by weight of glutaraldehyde and 1 to 5% by weight of HCl in acetone, preferably 0.1 to 6% by weight of glutaaldehyde 1 to 3% by weight of HCl is impregnated into a mixed solution mixed with acetone and subjected to chemical crosslinking at 15 to 50 ° C. for 1 to 10 hours. Such chemical crosslinking is crosslinking by ether bonding using acetylation reaction of PVA and glutaraldehyde, and the degree of crosslinking can be increased with increasing concentration of glutaldehyde, thereby changing the structural characteristics of the cation exchange membrane. Increase the separation selectivity of the material to be separated.

The cation exchange membrane according to the present invention prepared through the above process is washed and dried to obtain a final cation exchange membrane. Storage is impregnated with distilled water for at least one day, and then immersed in 0.5 M NaCl electrolyte solution.

The cation exchange membrane according to the present invention as described above has a water content of 40 to 250%, an ion exchange capacity of 0.5 to 3.5 meq./g, and an electrical resistance of 0.98 to 2.35 Ωcm. ^In the range of ² , the water content is decreased while the ion exchange capacity is improved. In addition, the ion selectivity of the cation exchange membrane, that is, the transport number for the cation (Na ⁺ ) is 0.93 to 0.98, which is excellent in ion selectivity.

In addition, in order to improve the mechanical properties of the membrane prepared in the present invention, a polyethylene (PE, poly (ethylene)) support (non-woven fabric) is a film which dip coating the cation exchange membrane according to the present invention (dip coating). The thickness of the cation exchange membrane, which is the coating layer, is preferably about 50 to 70 μm. If the thickness is less than 50 μm, the ion permeability of the membrane may be lowered. If the thickness is more than 70 μm, the electrical resistance of the membrane is increased. It may cause unnecessary waste of power.

As such, PVA / PSSA-MA membrane according to the present invention can be applied as a membrane for diffusion dialysis (Donnan dialysis) and electrodialysis with excellent ion selectivity, electrical properties and mechanical properties. In addition, the method for producing a cation exchange membrane of the present invention is more environmentally friendly because it suppresses the use of an organic solvent and uses a solvate.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by Examples.

Examples 1-3

First, a PSSA-MA copolymer having PSSA and MA in a molar ratio of 1: 1 was purchased from Aldrich (USA) and used. Since the PSSA-MA copolymer is Na ⁺ -type, it was converted to H ⁺ -type using diffusion dialysis (Donnan dialysis) (In the case of Donnan dialysis using a cation exchange membrane, the composition of the polymer solution is maintained and the Na ⁺ ions and H ^{+ are} maintained. Has the advantage of selectively interchange only ions). Then, 10% by weight of PVA was dissolved in 90% by weight of distilled water, and 20% by weight of PSSA-MA (H ⁺ -type) was dissolved in 80% by weight of distilled water. Blending the PVA aqueous solution and the PSSA-MA aqueous solution (in the case of Examples 1 to 3, the blending weight ratio of the PVA / PSSA-MA solution = 3/1), followed by natural drying at room temperature, followed by heat treatment at 100 ° C. for 2 hours and 30 minutes, thickness 90 A micron cation exchange membrane was prepared. The heat-treated cation exchange membrane was impregnated in glutaaldehyde / acetone / HCl [1 wt.%] Crosslinking mixture and chemically crosslinked at 25 ° C. for 4 hours. At this time, the content of glutaraldehyde was 0.1% by weight (Example 1), 1% by weight (Example 2), 3% by weight (Example 3).

In order to analyze the properties of the cation exchange membranes of Examples 1 to 3, ion exchange capacity, water content, transport water for cations, area resistance, and degree of crosslinking were measured by the following methods, and the results are shown in Table 1 below. Membrane characterization is described in J.-H., Choi, H.-J., Lee, and S.-H., Moon, J. Colloid & Interf. Sci., Vol. 238, p188, 2001; J.-H., Choi, S.-H., Kim, and S.-H., Moon, J. Colloid & Interf. Sci., Vol. 241, p120, 2001], and the results are shown in Table 1 below.

[Measurement Method of Membrane]

(1) Water content: The difference between the wet weight of the membrane and the weight difference after drying in an oven at 60 ° C. for 24 hours was divided by the weight after drying.

(2) Ion-exchange capacity: 1M HCl aqueous solution was impregnated for 24 hours or more, the membrane surface was washed, re-impregnated in 1M NaCl aqueous solution, and determined by the amount of hydrogen ions ion-exchanged inside the membrane by acidic titration (meq./ g dry membrane).

(3) Electrical resistance: Calculated by using impedance value and phase angle measured by LCZ meter in 0.5M NaCl aqueous solution.

(4) Transport water and V-I curve: It measured using the cell (film effective area: 0.785 cm <2>) of the structure which has both electrolyte tanks. The transport water was calculated by adding different concentrations of aqueous NaCl solution (0.001M / 0.005M NaCl) to both electrolyte baths and measuring the voltage difference between the Ag / AgCl electrodes fixed at both ends of the membrane.The VI curve was calculated using the same cell. The voltage difference across the membrane was measured while increasing, and 0.025M NaCl aqueous solution was used as the electrolyte.

(5) Crosslinking degree: The crosslinking degree in this invention means the evaluation regarding the chemical crosslinking degree except a thermal crosslinking. The degree of crosslinking was calculated by the following equation using the difference between the weight of the PVA / PSSA-MA membrane after thermal crosslinking and the weight of the membrane after glutaraldehyde treatment.

The degree of crosslinking in the present invention was increased with the increase of the concentration of glutaraldehyde and the range of the degree of crosslinking was adjusted to the range of 3 to 50%.

As shown in Table 1, the membranes of Examples 1 to 3 according to the present invention were found to have an excellent water exchange rate of 50 to 100%, while having an ion exchange capacity of about 2.20 meq./g. In addition, it was confirmed that the transport water for the cation (Na ⁺ ) is about 0.93 to 0.98, which is higher than that of Comparative Example 1. In addition, in the case of the Example, the area resistance was about 1.3 to 2.25 Ωcm ² , and it was confirmed that the area resistance was lower than that of Comparative Example 1.

On the other hand, it is shown in Table 1 that the degree of crosslinking is increased with the increase of the glutaaldehyde concentration, and despite the almost same ion exchange capacity (Examples 1 to 3) with the increase of the degree of crosslinking (in general, the increase in the ion exchange capacity is high. This leads to an increase in the water content), which indicates that the structure of the membrane is indirectly controlled by a change in the degree of crosslinking. In other words, the high degree of crosslinking reduces the free volume inside the membrane, which may contain water. In addition, also in the crosslinking degree and the transport water relationship to the cation (Na ⁺ ), as the degree of crosslinking decreases, the structure of the membrane indicates that the transport water is reduced because the selectivity of the cation ion (Na ⁺ ) is reduced to allow a large free volume. In addition, the increase in the degree of crosslinking increases the compactness of the membrane structure, thereby increasing the area resistance of the membrane.

Comparative Example 1

10 wt% of PVA was dissolved in 90 wt% of distilled water, and 20 wt% of PSSA was dissolved in 80 wt% of distilled water. The PVA aqueous solution and the PSSA aqueous solution were blended (the blending weight ratio of PVA / PSSA solution = 3/1), followed by natural drying at room temperature, followed by heat treatment at 100 ° C. for 2 hours 30 minutes to prepare a cation exchange membrane having a thickness of 90 μm. The heat treated cation exchange membrane was impregnated in glutaaldehyde [3 wt%] / acetone / HCl [1 wt%] crosslinking mixture and chemically crosslinked at 25 ° C. for 4 hours.

In order to analyze the characteristics of the cation exchange membrane of Comparative Example 1, ion exchange capacity, water content, transport water for cations, and area resistance were measured by the method of Example 1, and the results are shown in Table 1 above.

Test Example 1

The surface (a) and cross section (b) of the PVA / PSSA-MA cation exchange membrane prepared in Example 1 were measured by an electron scanning microscope (SEM), and the results are shown in FIG. 2.

As shown in FIG. 2, in the cation exchange membrane of Example 1 according to the present invention, a phase separation phenomenon and no pinholes were found in the entire membrane, and thus a uniform and defect-free membrane was prepared by forming a uniform phase between the PVA resin and the PSSA-MA resin. Could confirm.

Example 4

First, a PSSA-MA copolymer having PSSA and MA in a molar ratio of 1: 1 was purchased from Aldrich (USA) and used. Since the PSSA-MA copolymer is Na ⁺ -type, it was converted to H ⁺ -type using diffusion dialysis (Donnan dialysis). Then, 10% by weight of PVA was dissolved in 90% by weight of distilled water, and 20% by weight of PSSA-MA (H ⁺ -type) was dissolved in 80% by weight of distilled water. After blending the PVA aqueous solution and the PSSA-MA aqueous solution, the mixture was impregnated with a polyethylene support (nonwoven fabric) to prepare a membrane, and then naturally dried at room temperature. Then, heat treated at 100 ° C. for 2 hours and 30 minutes, impregnated with glutaaldehyde [3 wt%] / acetone / HCl [1 wt%] crosslinking mixture, and chemical crosslinking at 25 ° C. for 4 hours to form a cation exchange membrane on the polyethylene support. The coated composite membrane was prepared.

The thickness of the ion exchange coating layer of the prepared composite membrane was about 50 μm and the thickness of the whole membrane was about 170 μm.

The transport water for the cation (Na ⁺ ) and the area resistance of the prepared composite membrane were measured by the method of Example 1, and the transport water for the cation (Na ⁺ ) was about 0.95 to 0.96 and the area as in Example 1 The resistance was measured at 1.2-1.5 Ωcm ² .

In addition, the voltage-current density curves of the PVA / PSSA-MA membrane and the commercial cation exchange membrane (CMX, Tokuyama Co. Ltd., Japan) coated on the PE support of Example 4 are shown in FIG. 3. The voltage-current curve is a general electrochemical analysis method that shows the mass transfer phenomenon on the surface of the membrane, especially the concentration polarization phenomenon on the surface of the membrane. As shown in FIG. 3, the membrane according to the present invention exhibits a voltage-current density curve almost similar to that of a commercial membrane, and it can be seen that the prepared PVA / PSSA-MA membrane can be applied not only as a dialysis but also as a general desalination ion exchange membrane. there was.

In addition, the tensile strength of the membrane of Example 4 was measured using a universal test machine (Instron, USA), and it was confirmed that the mechanical properties of the membrane were greatly improved by introducing a PE support having a maximum tensile strength of about 38.4 MPa.

Test Example 2

The cross section of the composite membrane coated with VA / PSSA-MA cation exchange membrane on the polyethylene (nonwoven fabric) prepared in Example 4 was measured by an electron scanning microscope (SEM), the results are shown in FIG.

As shown in Figure 4, the composite membrane of Example 4 according to the present invention is a phase separation phenomenon and no pinholes are found in the entire membrane, so that the PVA resin and PSSA-MA resin is a uniform phase, uniform and defect-free membrane is uniform on the nonwoven fabric It could be confirmed that it is being applied.

Test Example 3

The composite membrane prepared in Example 4 was impregnated with 2M HCl and 2M NaOH aqueous solution at 50 ° C. for at least one day, and the membrane area resistance in 0.5M NaCl solution was measured, and the results are shown in Table 2 below.

As shown in Table 2, the composite film according to the present invention had almost no change in electric area resistance. Therefore, the composite membrane of the present invention was found to have excellent mechanical strength and chemical stability.

Test Example 4

The composite membrane and the commercial cation exchange membrane (CMX) prepared in Example 4 were impregnated with 0.5M NaCl and 0.5M Lysine-HCl aqueous solution at 25 ° C. for at least one day, and the membrane area resistance in each solution was measured. The results are shown in Table 3 below.

As shown in Table 3, the composite membrane according to the present invention can be seen that the area resistance to high molecular weight organic ions is significantly lower than the commercial cation exchange membrane, and thus, when applied to the separation of lactic acid and various amino acids, it has an excellent power consumption reduction effect. It can be seen that. This result is due to the structural properties of the membrane, and because it is made from water-soluble polymers, it shows a large swelling effect, and thus has a wider free volume than a commercial membrane. Therefore, it can be seen that the composite membrane of the present invention is suitable for electrodialysis and diffusion dialysis of high molecular weight organic ions or metal ions. It is also a feature of the cation exchange membrane of the present invention to easily control the crosslinking degree of the membrane to control the free volume of the membrane and thus to prepare a membrane suitable for the separation of certain ionic materials.

As described above, the cation exchange membrane according to the present invention has a benzene sulfonic acid group of polystyrene sulfonic acid and multiple carboxylic acid groups of maleic acid as a cation exchange group in the membrane, so that a large amount of ion exchange groups can be introduced. In addition to improving the capacity, the ion exchange capacity is not changed, and the change in the membrane structure due to the control of the degree of crosslinking is large, and by controlling it appropriately, the membrane properties can be changed to suit the ionic material to be separated. It can be applied to the separation and purification of relatively high molecular weight organic / metal compounds. In addition, the present invention is environmentally friendly by suppressing the use of organic solvents, the manufacturing method is simple and inexpensive, and the electrical properties similar to the conventional commercial ion exchange membrane, so that instead of the existing processes using the ion exchange resin, the clean technology of the ion exchange membrane It is possible to introduce the various processes used, and through this has the advantage of reducing the environmental pollution and the cost required for the regeneration of the ion exchange resin.

Claims (6)

A cation containing 50 to 90% by weight of polyvinyl alcohol solids and 10 to 50% by weight of polystyrene sulfonic acid / maleic acid copolymer solids, wherein a benzenesulfonic acid group and a plurality of carboxylic acid groups are introduced together as a cation exchanger. Exchange membrane. The polyvinyl alcohol has a weight average molecular weight of 30,000 to 150,000, a saponification degree of 70 to 100%, and the polystyrene / maleic acid copolymer has a weight average molecular weight of 5,000 to 40,000, and A cation exchange membrane, wherein the copolymerization ratio of maleic acid is from 1/3 to 10/1 molar ratio. Blending 50 to 90% by weight of polyvinyl alcohol solids with 10 to 50% by weight of polystyrene sulfonic acid / maleic acid copolymer solids, Obtaining a film by naturally drying the mixture at room temperature, Heat-treating the film at 70-150 ° C. for 0.5-5 hours to introduce benzenesulfonic acid groups and multiple carboxylic acid groups into a cation exchanger, and The cation exchange membrane is impregnated with a mixed solution of 0.05 to 10% by weight of glutaaldehyde and 1 to 5% by weight of HCl in acetone and crosslinked at 15 to 50 ° C. for 1 to 10 hours. A method of producing a cation exchange membrane. 4. The polyvinyl alcohol has a weight average molecular weight of 30,000 to 150,000 and a saponification degree of 70 to 100%. The polystyrene / maleic acid copolymer has a weight average molecular weight of 5,000 to 40,000, and A method for producing a cation exchange membrane, characterized in that the copolymerization ratio of maleic acid is from 1/3 to 10/1 molar ratio. The method of claim 3, wherein the cationic crosslinked polystyrene sulfonic acid / maleic acid copolymer is prepared by converting Na ⁺ -type into H ⁺ -type by diffusion dialysis. Polyethylene composite membrane formed by coating the cation exchange membrane according to claim 1.