KR101170971B1 - Cation exchange composite membrane using fabric supports and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a cation exchange composite membrane containing a copolymer of styrene-based monomers using a fabric-like support and a method for preparing the same. More specifically, as a support, fabrics such as polyethylene, polypropylene, nylon, viscose rayon, polyester, etc., and silk, cotton, hemp, etc., which are natural fiber, are fabrics. a polymerization solution containing a styrene monomer, crosslinking agent and initiator in the system, and then polymerization was impregnated fabric sulfonic acid group (-SO ₃ ^-) a styrenic copolymer to the fabric which is made of a series of manufacturing step of forming the introduction of the ion It relates to a cation exchange composite membrane containing. The present invention provides a cation exchange composite membrane having improved ion exchange capacity, ion conductivity, mechanical properties, chemical resistance, and processability of a cation exchange composite membrane prepared using various fabrics as a support, and a method of manufacturing the same.

Fabric, cation exchange membrane, styrene monomer

Description

Cation exchange composite membrane using fabric supports and method for manufacturing the same

The present invention relates to a cation exchange composite membrane comprising a fabric as a support and comprising a styrene-based polymer and a method for producing the same. Specifically, the present invention relates to a method for producing a polystyrene cation exchange membrane, in which styrene and an initiator are absorbed into a porous fabric and polymerized, followed by a sulfonation reaction to form a strong acid sulfonic acid group (-SO _3- ^). The present invention relates to a method for producing a cation exchange membrane capable of increasing the excellent ion permeability and reducing the manufacturing cost by performing a relatively simple production process.

Relatively to introduce the ^- present invention, by absorbing the styrene and the initiator to the porous fabric, and after polymerization of the acid group in sulfonic strong acid cation exchanger to perform sulfonation reaction (-SO ₃₎ relates to a method of manufacturing polystyrene cation exchange membrane The present invention relates to a method of manufacturing a cation exchange membrane capable of increasing ion permeability and reducing manufacturing cost by performing a simple manufacturing process.

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. If the cation is being used in commercial gyohwak film, significantly strong adult acid group as the ion exchange group (-SO ₃ ^-) are roughly divided into and becomes a weakly acidic carboxylic acid group (-COO-), mainly in the case of strong base anion exchange membrane 4 Adults The primary ammonium group (-NR ₃ ⁺ ) has an ion exchange group. The separation process using the ion exchange membrane is capable of relatively high purity separation and purification compared to the separation method using distillation or chemical treatment, has low energy consumption and simple equipment, so that the equipment investment cost is low and the continuous process is possible. It is attracting attention as a separate purification process in various industrial fields because of its excellent processing capacity per hour. Current applications of ion exchange membranes in industry include electrodialysis and water-splitting eletrodialysis for desalination and purification, diffusion dialysis and ultrapure water production to recover acids from pickling liquor. Electrodeionization and the like. In general, commercial membranes should have high ion selective permeability (> 0.95 ~ 0.98), low electrical resistance (<3.0 ~ 4.0Ω㎠), adequate water content, high mechanical strength and chemical resistance.

Conventional ion exchange membranes were prepared using a copolymerization of styrene-divinylbenzene or a copolymer of styrene-butadiene as a base material by a bulk polymerization method, a latex method, or a paste method. Ion-exchange membranes using these methods have relatively good electrochemical properties. However, these manufacturing processes cause an increase in manufacturing cost due to the complexity of the process.

In the case of bulk polymerization, when styrene-divinylbenzene is polymerized alone, a plasticizer should be used because the brittleness is increased and mechanical properties are deteriorated. Furthermore, in order to obtain a thin film, a constant container is required, which increases the overall manufacturing cost of the film. Becomes

In the latex method, a latex of styrene-butadiene copolymer is dipped on a support and dried to form a base film through crosslinking using an oxidative crosslinking method. The ion exchanger is introduced into the base membrane through sulfonation, chloromethylation, and quaternary amination, and this method is based on the mechanical and electrochemical properties of the membrane under the influence of the emulsifier remaining in the latex of the styrene-butadiene polymer. It is very likely to cause poor performance.

On the other hand, the paste method is the manufacturing method of the ion exchange membrane is commercially available from Neosepta registered trademark (Tokuyama Co. Ltd., Japan) and Selemion registered trademark (Asahi Glass Company, Japan). Although the paste method has better mechanical and electrochemical properties than the films obtained by the above-mentioned bulk polymerization method or latex method, powder is required in addition to the styrene-divinylbenzene monomer to obtain a paste. In order to obtain physical properties, a plasticizer must be added. This complexity in the manufacturing process acts as a factor to increase the manufacturing cost of the film. (Y. Mizutani, Structure of ion-exchange membranes, J. Membr. Sci. 49 (1990) 121).

Accordingly, the present inventors have made efforts to improve the above problems, and as a result, artificial fiber-based fabrics such as polyethylene, polypropylene, nylon, viscose rayon, polyester, and natural fiber-based silk (Silk) Fabrics such as textiles such as cotton, hemp, etc. have a space in their thin fibrous structure so that the structure has a solid structure, so that the existing problems can be easily solved. sulfonation reaction activity of the styrene-based monomer, cross-linker, initiator and saturated the interior and immersed in a mixed polymerization solution, since then the heat cross-linking polymerizable acid group (-SO ₃ ^-) for introducing the result that the ion exchange capacity is excellent in electrical The present invention finds that a cation exchange membrane having excellent resistance to mechanical properties, chemical properties and processability can be manufactured while having low resistance. It was completed. In addition, the present invention has the advantage of very easy control of ion exchange capacity and ion conductivity by adjusting the composition of the styrene monomer. In addition, by using a support having excellent mechanical strength and various film thicknesses, it was possible to prepare a cation exchange composite membrane having excellent conductivity and mechanical strength compared to an ion exchange membrane prepared by a conventional commercial paste method.

It is an object of the present invention to provide a styrene-based polymer-containing cation exchange composite membrane having a higher ion exchange capacity and improved mechanical and chemical properties than conventional commercial membranes, and a method for preparing the same.

Another object of the present invention is to reduce the basic manufacturing cost by using a fabric having a relatively lower cost than when using the support used in the conventional commercialization membrane, and poly (styrene-based) has better electrochemical properties and mechanical performance than the commercialization membrane ) / Fabric cation exchange composite membrane.

In order to achieve the above object, the present invention impregnates a textile material with a monomer solution containing a mixture of styrene-based monomers, a crosslinking agent and an initiator to saturate the inside of the material, and then crosslinks and thermally polymerizes the sulfonic acid group ( -SO ₃ ^-) to provide a styrene-based polymer a cation-exchange composite membrane and a method comprising the preparation is introduced.

The present invention can provide a cation exchange composite membrane having a low electrical resistance and excellent ion exchange capacity and mechanical and chemical properties, and also very easy to control ion exchange capacity and ion conductivity, and a method for preparing the cation exchange composite membrane. The effect provided can be obtained.

Hereinafter, the present invention will be described in detail.

The present invention is styrene, divinylbenzene, and man-made fibers based impregnation and the polymerization solution containing initiator, textile or natural fiber-based fabric to saturation (Fabric) impregnation and thermal crosslinking polymerization to turn on, a sulfonic acid group (-SO ₃ ^-) introduced a To provide a cation exchange composite membrane of poly (styrene) / fabric.

In the present invention, the polymerization solution is 80 to 90 parts by weight of a styrene monomer and 5 to 20 parts by weight of a crosslinking agent, and 0.1 to 5 initiators based on 100 parts by weight of the monomer mixture (the monomer mixture contains a styrene monomer and a crosslinking agent). It includes parts by weight.

Styrene-based monomers that can be used in the present invention can be used, including those known to the above styrene, alphamethylstyrene, vinylpyridine, trifluorostyrene, 2-vinyl pyridium and the like can be used alone or mixed, It is not limited to this. As the content of the styrene monomer increases, the amount of functional groups capable of introducing sulfonic acid ions during the sulfonation reaction is increased, and the ion exchange ability is improved. When the content of the styrene monomer is less than 80 parts by weight, the amount of sulfonic acid ions is increased. Too small a problem arises that the ion exchange capacity of the membrane falls. Preferably, 80 parts by weight or more of the styrenic monomer active in sulfonation reaction can be used. By using the styrene monomer active in the sulfonation reaction, the cation exchange capacity of the cation exchange composite membrane can be properly adjusted.

The present invention can easily adjust the ion exchange capacity and ion conductivity by adjusting the composition of the styrene monomer.

Fabrics that can be used in the present invention include man-made fiber-based fabrics such as polyethylene, polypropylene, nylon, viscose rayon, polyester (polyester) and natural fiber-based silk (Silk), cotton, hemp (Iii) and the like can be used. By using such fabrics as a support for the cation exchange composite membrane, the mechanical strength of the cation exchange composite membrane of the present invention can be improved.

Hereinafter, the method for producing a cation exchange composite membrane of the present invention will be described in detail step by step.

Step 1 according to the present invention is a step of saturating the fabric (1) material in a polymerization solution containing a styrene-based monomer (2), a crosslinking agent (3) and an initiator (4).

First, a styrene monomer (2), a crosslinking agent (3), and an initiator (4) are mixed to prepare a polymerization solution. The polymerization solution may contain 80 to 90 parts by weight of the styrene monomer (2) and 5 to 20 parts by weight of the crosslinking agent (3), and may contain 0.1 to 5 parts by weight of the initiator (4) based on 100 parts by weight of the monomer mixture.

As the styrene-based monomer (2) which can be used in the present invention, a known one may be used, and alphamethylstyrene, styrene, 2-vinyl pyridium, trifluorostyrene, and the like may be used alone or in combination. It is not. Preferably, a styrenic monomer which is sulfonation reaction activity can be used.

The crosslinking agent (3) finally serves to influence the swelling degree and the degree of crosslinking of the film. The crosslinking agent that can be used in the present invention is not particularly limited, but general divinylbenzene is used in the present invention. The content of the crosslinking agent (3) is 5 to 20 parts by weight based on 100 parts by weight of the monomer mixture, if the content of the crosslinking agent is less than 10 parts by weight, the degree of crosslinking is insufficient, if the content of the crosslinking agent exceeds 20 parts by weight The problem arises that the crosslinking degree is too high and the brittleness of the film is increased.

The initiator (4) that can be used in the present invention is not particularly limited, but in particular, N, N'-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), cumyl peroxide, lauroyl peroxide and the like. This can be used. The content of this initiator (4) is 0.1-5 weight part with respect to 100 weight part of said monomer mixtures, Preferably it is 1-2 weight part or more. If the content of the initiator is less than 0.1 parts by weight, sufficient crosslinking does not occur, and if the content of the initiator is more than 5 parts by weight, the content of the initiator itself is too high, causing a problem of deterioration of physical properties.

Next, the saturated fabric 5 is formed by impregnating the fabric 1 in a polymerization solution prepared by mixing the above-described components at room temperature for 30 minutes to 24 hours.

The present invention saturates the fabric (1) in a polymerization solution containing a styrene-based monomer (2) to fill the pores of the fabric with the polymerization solution, the network structure of the spaces between each fabric and the fabric is processed It can be plasticized to produce a uniform ion exchange membrane having superior mechanical strength, chemical durability, and uniformity compared to conventional membranes.

Step 2 according to the present invention is a step of preparing a composite membrane 6 of a styrene-based polymer by thermally polymerizing a saturated fabric impregnated in the polymerization solution of step 1.

In step 1, a polymer membrane saturated with the polymerization solution is polymerized to prepare a composite membrane 6 of a styrene-based polymer. The polymerization reaction in the step 2 is left for 30 minutes to 24 hours, preferably 1 to 12 hours in a monomer solution at room temperature so that the monomer and the initiator is sufficiently sorbed to the porous fabric membrane to reach an equilibrium state, the reaction solution is The sorbed membrane is placed on a square glass plate, covered with another glass plate, and then a composite membrane 6 of styrene polymer is prepared by performing polymerization using heat at a temperature of 50 to 100 ° C. for 8 to 24 hours. . After the polymerization reaction is completed, in order to remove the unreacted monomer remaining in the membrane, it is immersed in an organic solvent such as dichloroethane, acetone, toluene and washed several times.

The third step is by a composite film 6 of the styrene-based polymer of the second-step reaction with a mixture of dichloroethane and acetic sulfate sulfonated group (-SO ₃ ^-) as a cation exchanger according to the invention by introducing a cation exchange compound It is a step of manufacturing the film (7).

In Step 3, the fire sulfone (-SO ₃ ^-) as a cation exchanger in the composite membrane (6) of the styrene-based polymer of the second step uses. Although the concentration at the time of reaction does not have a big restriction | limiting in reaction, More preferably, 1 weight part or more is used. The crosslinked membrane is immersed in the sulfonated solution thus prepared, and maintained at 35 ° C. for 1 to 16 hours, preferably 8 to 14 hours, to allow sufficient reaction. After the reaction is completed, in order to remove the unreacted substances remaining in the composite membrane, washed several times in ultrapure water or an organic solvent (at room temperature 25 ℃), soaked again in ultrapure water or an organic solvent overnight, washed several times to a sulfonizer ( -SO ₃ ^-) are prepared by the introduction of the cation exchange membrane (7).

By using the styrene-based monomers in the tissue-based fabrics and natural fiber-based fabrics as described above, it is possible to produce a cation exchange composite membrane having excellent mechanical properties, high ion conductivity, low electrical resistance, and excellent processability.

The present invention will be described in more detail based on the following examples, but the present invention is not limited to these examples.

Cation Exchange Using Polyester Fabrics Of composite membrane  Produce

Example  One

A polymerization solution was prepared in which styrene: divinylbenzene was mixed at a weight ratio of 90:10 and adjusted to 1 part by weight of an initiator N, N'-azobisisobutyronitrile (AIBN) based on 100 parts by weight of the monomer mixture. . This polymerization solution was saturated impregnated into a polyester fabric of about 140 μm thickness for 5 hours.

The polyester fabric impregnated with the polymerization solution was placed on a square glass plate and covered with another glass plate and then sealed with a tape to prevent loss of the polymerization solution. This was carried out in an oven at 60 ° C. for 16 hours. When the polymerization was completed, the membrane was separated from the glass plate, immersed in dichloroethane at room temperature, left for 12 hours, then taken out and immersed in fresh dichloroethane again to remove unreacted monomers several times.

The composite membrane prepared by the polymerization reaction was immersed in a mixed solution of 1 part by weight of acetic sulfate and 99 parts by weight of dichloroethane and sulfonated at 35 ° C. for 10 hours. When the sulfonation reaction is completed, the pH is reduced by washing with ethanol to remove the unreacted ions remaining in the completed composite membrane, washed several times with ultrapure water (at room temperature 25 ° C), immersed in ultrapure water overnight, and then again several times. washed sulfonic acid group (-SO ₃ ^-) it was prepared such that the introduction of the cation exchange membrane. In this process, the total film thickness of about 200 ㎛ of polyester fabric / a sulfonic acid group (-SO ₃ ^-) were prepared ionized styrene-based polymer containing a cation exchange membrane, the physical properties were measured according to the method of measuring the physical properties of the following, The results are shown in Table 1.

Comparative example  One

Using a commercially available commercially available membrane (Astom, Japan, CMX, thickness of about 140 ㎛) manufactured by a conventional paste method, the physical properties were measured according to the following physical property measurement method, and the results are shown in Table 1. It was.

Comparative example  2

Except for using 20 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 1, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 1.

Comparative example  3

Except for using 15 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 1, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 1.

Comparative example  4

Except for using 5 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 1, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 1.

How to measure property

1) Water content: The cation exchange membrane is immersed in ultrapure water for more than 24 hours, and then the membrane is sufficiently swollen. Then, the surface water is carefully wiped off and the increased weight W ₁ (g) is measured. It is dried in a vacuum oven at 120 ° C. for 24 hours and then the dry weight W ₂ (g) is measured. The moisture content (%) is obtained by the following formula:

Moisture Content (%) = [(W ₁ -W ₂ ) / W ₂ ] × 100

2) Determination of the ion exchange capacity: After measuring the dry weight of the cation exchange membrane, immerse in 1.0M HCl solution for 5 hours to completely replace the sulfonic acid group in the form of -SO ₃ H ⁺ , the pH of the filtered water using ultrapure water is The solution was sufficiently washed until 7, and the sulfonic acid group was treated for 5 hours to be replaced with -SO ₃ Na ⁺ using 2.0M NaCl solution, followed by titration using 0.1M NaOH solution. The amount of NaOH consumed (ml) was measured by the following equation, where ion exchange capacity (IEC, unit meq / g) was measured, where Wy is the weight of the dried membrane, V is the amount of NaOH consumed, and C is used for titration. The concentrations of NaOH solutions are shown respectively:

Ion exchange capacity (IEC, unit meq / g) = (V × C) / Wy

3) Membrane area resistance: The membrane area resistance of the cation exchange membrane was calculated by the following equation using the impedance value and phase angle measured by LCZ meter in 0.5 M NaCl aqueous solution, where Z is impedance value and θ is phase Represents the angle:

Membrane Area Resistance (Ω㎠) = Membrane Area × cosθ × [Z]

As shown in Table 1, the cation exchange composite membrane of Example 1, in which styrene was used to prepare a polymerization solution, had a difference in ion exchange capacity and membrane area resistance related to the function of the cation exchange membrane compared to Comparative Examples 2, 3, and 4. You can see that occurs. In the cation exchange composite membrane of Example 1, the water content of the cation exchange composite membrane increased from 4 to Comparative Example 2, and the resistance value decreased. From these results, it can be seen that the cation exchange composite membrane of Example 1 is significantly lower in brittleness of the membrane than the cation exchange composite membranes of Comparative Examples 2 to 4, thereby improving mechanical strength, and thus suitable for mass production.

Since the ion-exchange composite membrane (200 micrometers in thickness) of Example 1 is thicker than the commercial membrane CMX (about 140 micrometers in thickness) of the comparative example 1, it turns out that film area resistance is higher than the commercial membrane CMX of the comparative example 1.

1 is a scanning electron microscope (SEM) photograph of the polyester used in Example 1 of the present invention, Figure 1 (a) is a photograph of the surface of the polyester fabric (x 100), (b) is a polyester ionization (C) is a SEM photograph of the surface (x 500) of the composite membrane containing the vinyl benzyl polymer, and (C) is a SEM photograph of the cross section (x 200) of the composite membrane containing the polyester ionized vinyl benzyl polymer. It can be seen from the SEM photograph that the entire polyester fabric is completely filled with resin and no phase separation phenomenon and pinholes are found.

Cation exchange using silk Of composite membrane  Produce

Example  2

A polymerization solution was prepared by mixing the components of the composition ratios shown in Table 2 below, and after distilling about 120 μm-thick silk into the polymerization solution and leaving it for 5 hours, the polymerization reaction was the same as in Example 1 except that The physical properties were measured according to the property measurement method described above, and the results are shown in Table 2.

Comparative example  5

Using a commercially available commercially available membrane (Astom, Japan, CMX, thickness of about 140 ㎛) manufactured by the conventional paste method, the physical properties were measured according to the following physical property measurement method, and the results are shown in Table 2. It was.

Comparative example  6

Except for using 20 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 2, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 2.

Comparative example  7

Except for using 15 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 2, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 2.

Comparative example  8

Except for using 5 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 2, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 2.

As shown in Table 2, the cation exchange composite membrane of Example 2, in which styrene was used to prepare a polymerization solution, had a difference in ion exchange capacity and membrane area resistance related to the function of the cation exchange membrane compared to Comparative Examples 6, 7, and 8. You can see that occurs. In the cation exchange composite membrane of Example 2, the water content of the cation exchange composite membrane increased from 8 to Comparative Example 6, and the resistance value decreased. From these results, it can be seen that the cation exchange composite membrane of Example 2 is significantly lower in brittleness of the membrane than the cation exchange composite membranes of Comparative Examples 6 to 8, thereby improving mechanical strength, and thus suitable for mass production.

Cation Exchange Using Viscose Rayon Fabrics Of composite membrane  Produce

Example  3

To prepare a polymerization solution by mixing the components of the composition ratio shown in Table 3, Example 1 except that the viscose rayon fabric of about 120 ㎛ thickness was immersed in the polymerization solution and left for 5 hours, and then proceeded with the polymerization reaction. The physical properties were measured in the same manner as described above, and the physical properties were measured according to the method for measuring physical properties, and the results are shown in Table 3.

Comparative example  9

Using a commercially available commercially available membrane (Atom Japan, CMX, thickness of about 140 ㎛) manufactured by a conventional paste method, the physical properties were measured according to the following physical property measurement method, and the results are shown in Table 3. It was.

Comparative example  10

Except for using 20 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 3, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 3.

Comparative example  11

Except for using 15 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 3, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 3.

Comparative example  12

Except for using 5 parts by weight of divinylbenzene in the polymerization solution was carried out in the same manner as in Example 3, the physical properties were measured according to the following physical properties measurement method, the results are shown in Table 3.

As shown in Table 3, the cation exchange composite membrane of Example 3, in which styrene was used to prepare a polymerization solution, had a difference in ion exchange capacity and membrane area resistance related to the function of the cation exchange membrane compared to Comparative Examples 10, 11, and 12. You can see that occurs. In the cation exchange composite membrane of Example 3, the water content of the cation exchange composite membrane increased from 12 to 12 in Comparative Example 10, and the resistance value decreased. From these results, it can be seen that the cation exchange composite membrane of Example 3 is significantly lower in brittleness of the membrane than the cation exchange composite membranes of Comparative Examples 10 to 12, thereby improving mechanical strength, and thus suitable for mass production.

Sulfonation  Cation exchange over time Of composite membrane  Produce

Example  4 to 15

When preparing the sulfonated solution was carried out in the same manner as in Example 1 except for the sulfonation time to determine the change in IEC value, water content, and resistance value according to the sulfonation time, the physical properties were measured according to the following physical property measurement method, The results are shown in Table 4.

As shown in Table 4, the cation exchange composite membranes of Examples 4 to 15 generally had higher ion exchange capacity and higher water content as the sulfonation time was changed, and lower membrane area resistance.

However, the reason that the resistance of the cation exchange composite membranes of Examples (thickness about 200 µm) 4 to 15 is higher is thicker than that of the commercial membrane CMX of Comparative Example 16 (thickness of about 140 µm), so that the membrane area resistance is higher than that of the commercial membrane CMX of Comparative Example 16. You can see that this is high.

FIG. 1 shows the surface of a polyethylene support used in the present invention (FIG. 1 (a), (100), the surface of a composite membrane containing ionized styrenic polymers (FIG. 1 (b), 500) and ionized An electron scanning microscope (SEM) photograph of the cross section (FIG. 1 (c), x 200) of the composite film containing a styrene polymer is shown.

FIG. 2 is a SEM photograph (FIG. 2 (a), × 500) of the surface of a commercially available cation exchange membrane (CMX) used in Comparative Example 1 according to the present invention.

Claims (12)

A styrene-based polymer comprising 90 parts by weight of styrene monomer and 10 parts by weight of divinylbenzene is formed on a fabric selected from the group consisting of viscose rayon, silk, cotton and hemp. Cation exchange composite membrane. delete The cation exchange composite membrane according to claim 1, comprising 0.1 to 5 parts by weight of initiator with respect to 100 parts by weight of the monomer mixture. The cation exchange composite membrane according to claim 1, wherein the styrene monomer is one or a mixture of two or more selected from the group consisting of alphamethylstyrene, styrene, and trifluorostyrene. delete Viscose rayon, silk and cotton in a polymerization solution comprising 90 parts by weight of a styrene monomer and 10 parts by weight of divinylbenzene, and 0.1 to 5 parts by weight of an initiator based on 100 parts by weight of the monomer mixture. impregnating a fabric selected from the group consisting of cotton and hemp (step 1); Polymerizing the impregnated fabric to prepare a composite film of a styrene-based polymer (step 2); And Preparing by introducing a cation exchange membrane (Step ³⁾ of the styrene-based composite membrane dichloroethane and acetic sulfate of the polymer mixture to yield a sulfonic acid group (-SO ₃₎ on the composite film of the styrene-based polymer Method for producing a cation exchange composite membrane of claim 1 comprising a. delete delete The method of claim 6, wherein the initiator is one or more selected from the group consisting of N, N'-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), cumyl peroxide and lauroyl peroxide. Method for producing a cation exchange composite membrane characterized in that. 7. The method of claim 6, wherein the styrene monomer is one or a mixture of two or more selected from the group consisting of alphamethylstyrene, styrene, vinylpyridine and trifluorostyrene. delete The method of claim 6, wherein the polymerization reaction of Step 2 is carried out for 1 to 24 hours at a temperature of 50 ~ 100 ℃.

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