KR20190141865A - A method for manufacturing an ion-exchange membrane using the same - Google Patents

Abstract

One embodiment of the present invention provides a method for manufacturing an ion-exchange membrane, including the following steps: (a) hydrophilizing a porous membrane by plasma treatment of the porous membrane in the presence of mixed gas containing sulfur dioxide (SO_2) and oxygen (O_2); (b) dissolving an electrolyte in a solvent to prepare an electrolyte solution; and (c) impregnating the porous membrane hydrophilized in the step (a) in the electrolyte solution. The present invention has excellent durability and ion-exchange ability while having a low manufacturing cost.

Description

Manufacturing method of ion exchange membrane {A METHOD FOR MANUFACTURING AN ION-EXCHANGE MEMBRANE USING THE SAME}

The present invention relates to a method for producing an ion exchange membrane.

Ion exchange membranes have been used in many fields such as fuel cells, redox flow batteries, water treatment, and desalination of seawater. The ion exchange membrane is attracting worldwide attention as a major clean technology that can reduce environmental pollution by reducing the amount of fossil raw materials, in particular because of its relatively simple manufacturing process, excellent selectivity for specific ions, and wide application range. The ion exchange membrane as described above can selectively separate the cations and anions in the aqueous solution, such as fuel cells, electrodialysis, water decomposition electrodialysis for acid and base recovery, diffusion dialysis to recover acid and metal species from the pickling waste, ultrapure water It is widely used in the process, etc. Recently, the developed range of high-performance ion exchange membrane is developed in advanced countries.

Such ion exchange membranes must have high selectivity and require low permeability of solvent and non-ionic solutes, low resistance to diffusion of selected peroxides, high mechanical strength and chemical resistance. Such ion exchange membranes require excellent mechanical strength and durability. Commonly used methods to meet these demands include a method of preparing a hybrid composite membrane by adding an inorganic substance, a hot press method of hot pressing a catalyst mixture, a method of adding a curing agent, and the like. The hybrid composite membrane manufacturing method has a disadvantage in that if the swelling phenomenon of the membrane is continued, a gap is formed between the additive of the membrane and the polymer membrane, so that the normal ion exchange ability cannot be exhibited. In addition, the method of adding a curing agent also has a disadvantage that the curing agent is eluted with time. Due to the problems described above, there is still a need to develop an ion exchange membrane having high durability and excellent mechanical properties.

Current commercially available ion exchange membranes include sulfonated polystyrene, Nafion ^™ (hereinafter referred to as “Nafion”) manufactured by Du Pont. However, when the sulfonated polystyrene is dried, it becomes brittle due to an increase in brittleness, making it difficult to form a thin film or a composite film, and there is a disadvantage in that mechanical stability is reduced when processing the electrode. In order to improve this disadvantage, there is a method of adjusting the sulfonation ratio of polystyrene or thickening the membrane. In this case, the resistance of the membrane is increased and the ion exchange capacity of the membrane is significantly reduced, so that the performance as an ion exchange membrane cannot be expected. The volume of the system is increased and constrained by space. In addition, Nafion has been widely used as an ion exchange membrane due to high ion conductivity and chemical stability as a fluorine-based material, but has a disadvantage in that the price is very expensive due to fluorine compounds and its use at high temperatures is limited. In fact, expensive ion exchange membranes such as Nafion have been pointed out as a cause for increasing the stack manufacturing price. Since the unit cost of the fluorine-based ion exchange membrane such as Nafion is about 1 million won / m ² , it is one of the problems to be solved. Various researches have been carried out on low-cost non-fluorine ion exchange membranes, in particular, sulfonated poly arylene ether sulfone (SPAES), sulfonated poly ether ether ketone (SPEEK), polybenzimidazole (PBI), sulfonated polysulfone (SPSf) and other synthetic polymers. Research has been extensively carried out on polymers of the same hydrocarbon series.

As such, new materials have been developed and tested for their potential by controlling various factors such as introduction of various functional groups, placement of polymer chains, and control of molecular weight in non-fluorine-based polymers. However, most materials have a limited practical application due to low chemical and physical stability compared to excellent electrical performance.

On the other hand, various methods for improving the performance of the polymer material itself have been proposed, but there is still a problem of low ion selectivity and durability.

The present invention is to solve the above-mentioned problems of the prior art, an object of the present invention is to provide a method for producing an ion exchange membrane capable of producing an ion exchange membrane having excellent durability and ion exchange capacity, but low production cost and excellent economy. .

One aspect of the invention, (a) hydrophilizing the porous membrane by plasma treatment the porous membrane in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ); (b) dissolving the electrolyte in a solvent to prepare an electrolyte solution; And (c) impregnating the porous membrane hydrophilized in step (a) into the electrolyte solution.

In one embodiment, the mixed gas may include 50 to 90% by volume of sulfur dioxide and 10 to 50% by volume of oxygen.

In one embodiment, the porous membrane may include 30 to 90% by weight of the two kinds of polyethylene and 10 to 70% by weight of the inorganic filler having different weight average molecular weight.

In one embodiment, the polyethylene may include a first polyethylene having a weight average molecular weight of 1,000,000 to 3,000,000 and a second polyethylene having a weight average molecular weight of 200,000 to 500,000.

In one embodiment, the average particle size of the inorganic filler may be 10 ~ 1,000nm.

In one embodiment, it may include a hydrocarbon layer generated on the surface of the inorganic filler.

In one embodiment, the average pore size of the porous membrane may be 20 ~ 2,000nm.

In one embodiment, the plasma treatment may be performed for 30 to 90 minutes.

In one embodiment, the contact angle of the hydrophilized porous membrane may be 15 ° or less.

In one embodiment, the electrolyte may include a fluorine-based compound.

In one embodiment, the fluorine-based compound is a copolymer of tetrafluoroethylene and fluorovinyl ether containing perfluorosulfonic acid, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), sulfonic acid group, Polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyhexafluoropropylene, and one or more selected from the group consisting of two or more copolymers or combinations thereof.

In one embodiment, the content of the electrolyte in the electrolyte solution may be 10 to 60% by weight.

In one embodiment, the solvent is one selected from the group consisting of esters, ethers, alcohols, ketones, amides, sulfones, carbonates, aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures of two or more thereof Can be.

According to an aspect of the present invention, the porous membrane acting as a support for the ion exchange membrane is subjected to plasma treatment in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ) to hydrophilize the surface of the porous membrane and the surface of the internal pores. By sulfonation, the bonding strength with the electrolyte impregnated in the porous membrane, and thus the durability and ion conductivity of the ion exchange membrane can be improved.

It is to be understood that the effects of the present invention are not limited to the above effects, and include all effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

Figure 1 is a schematic of the hydrophilization step of the porous membrane according to an aspect of the present invention.
2 is a schematic diagram illustrating a method of manufacturing an ion exchange membrane according to another aspect of the present invention.
3 is an SEM image of the cross section of the porous membrane according to the Examples and Comparative Examples of the present invention.

Hereinafter, with reference to the accompanying drawings will be described the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted for simplicity of explanation, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, it includes not only "directly connected" but also "indirectly connected" with another member in between. . In addition, when a part is said to "include" a certain component, this means that it may further include other components, without excluding the other components unless otherwise stated.

One aspect of the invention, (a) hydrophilizing the porous membrane by plasma treatment the porous membrane in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ); (b) dissolving the electrolyte in a solvent to prepare an electrolyte solution; And (c) impregnating the porous membrane hydrophilized in step (a) into the electrolyte solution.

Figure 1 is a schematic of the hydrophilization step of the porous membrane according to step (a). Referring to FIG. 1, the hydrophilization may include plasma treatment of the porous membrane in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ).

The plasma treatment hydrophilizes the surface of the porous membrane and the surface of the inner pores, which serve as a support when preparing an ion exchange membrane to be described later, that is, the surface of the porous membrane and the surface of the inner pores exhibit negative charges. It is possible to improve the bonding strength with the electrolyte, thereby significantly improving the durability of the ion exchange membrane, in particular, long-term durability and ion conductivity.

In order to hydrophilize the surface of the porous membrane and to realize a certain level of ion conductivity, a wet process is mainly used in which the porous membrane is sulphated by immersing the porous membrane for a predetermined time in sulfuric acid or the like. In this case, the wet process precedes the plasma treatment. Alternatively, the process may be complicated by being performed separately from the plasma treatment, such as a subsequent process, and a large amount of process waste may be generated.

On the other hand, the process gas used in the plasma treatment includes not only conventional air, oxygen and / or inert gas, but also a certain amount of sulfur dioxide gas, so that a single process called plasma treatment is performed without a wet process such as dipping the porous membrane into sulfuric acid. Through a dry process of the functional layer such as -SO _-3 on the surface of the porous membrane and the surface of the internal voids, that is, sulfonation can maximize the hydrophilicity and ion conductivity of the porous membrane, Conventional complicated processes can be simplified and are also environmentally advantageous.

The mixed gas which is a process gas used in the plasma treatment is 50 to 90% by volume of sulfur dioxide and 10 to 50% by volume of oxygen, preferably 60 to 80% by volume of sulfur dioxide and 20 to 40% by volume of oxygen, more preferably, It may include 70 to 80% by volume of sulfur dioxide and 20 to 30% by volume of oxygen. If the content of sulfur dioxide in the mixed gas is less than 50% by volume can not implement the level of hydrophilicity required for the porous membrane, if more than 90% by volume the process may be unstable.

The plasma treatment may be performed for 0.5 to 20 minutes. If the plasma treatment is performed in less than 0.5 minutes, the porous membrane may not be hydrophilized and sulfonated to the required level. If the plasma treatment is performed in more than 20 minutes, hydrophilicity and sulfonation may converge to a predetermined level, thereby lowering process efficiency. .

The average pore size of the porous film hydrophilized by the method may be 20 ~ 2,000nm, the contact angle may be 15 degrees or less, the absolute value of the zeta potential measured as a negative value (-) on the surface of the porous film May be at least 10 mV, preferably at least 15 mV, more preferably at least 20 mV. In addition, the porosity of the porous membrane may be 50 to 80% by volume.

The porous membrane may include 30 to 90% by weight of two kinds of polyethylene and 10 to 70% by weight of inorganic filler having different weight average molecular weights. The polyethylene may include a first polyethylene having a weight average molecular weight of 1,000,000 to 3,000,000 and a molecular weight distribution of 3 to 4, and a second polyethylene having a weight average molecular weight of 200,000 to 500,000 and a molecular weight distribution of 4 to 7. For example, the polyethylene may include 30 to 70% by weight of the first polyethylene and 30 to 70% by weight of the second polyethylene.

In general, the wider the molecular weight distribution (Mw / Mn), the shear stress is reduced and the viscosity is lower, so the workability is improved, but the physical properties are lowered, the narrower the molecular weight distribution is lowered, but the physical properties are improved. As such, even when two or more polymer materials are kneaded and used in the form of a composition, physical properties and processability may not be harmoniously implemented if the respective molecular weight distributions are similar. Therefore, by mixing the first and second polyethylene having a different weight average molecular weight and molecular weight distribution as described above, it is possible to more harmoniously implement the physical properties and processability of the porous membrane.

The inorganic filler is a group consisting of silica (SiO ₂ ), TiO ₂ , Al ₂ O ₃ , zeolite, AlOOH, BaTiO ₂ , talc, Al (OH) ₃ , CaCO ₃ and mixtures of two or more thereof. It may be one selected from, it is preferably a spherical nanoparticles having an average particle size of 10nm ~ 1,000nm, preferably the surface may be hydrophobized or hydrophilized nanoparticles. The content of the inorganic filler in the porous membrane may be 10 to 70% by weight, preferably 10 to 60% by weight. When the content of the inorganic filler is less than 10% by weight, the mechanical strength, acid resistance, chemical resistance, and flame retardancy of the porous membrane may be lowered. If it is more than 70% by weight, the flexibility and processability of the porous membrane may be reduced.

For example, silica (SiO ₂ ) may be formed on the surface of the hydrocarbon layer consisting of hydrophobic linear hydrocarbon (linear hydrocarbon) molecules. Since the silica itself has hydrophilic properties, spherical silica nanoparticles coated with straight chain hydrocarbon molecules such as (poly) ethylene are suitable for improving compatibility with hydrophobic polyethylene.

2 is a schematic diagram illustrating a method of manufacturing an ion exchange membrane according to an aspect of the present invention. Referring to FIG. 2, in the method of manufacturing an ion exchange membrane according to an aspect of the present invention, (a) plasma treatment of the porous membrane in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ) may be used to close the porous membrane. Hydration; (b) dissolving the electrolyte in a solvent to prepare an electrolyte solution; And (c) impregnating the porous membrane hydrophilized in step (a) into the electrolyte solution.

In the step (a), the porous membrane may be hydrophilized by plasma treatment of the porous membrane in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ), and the mixed gas, plasma treatment, and hydrophilization may be used. Etc. are as described above.

In step (b), the electrolyte may be dissolved in a solvent to prepare an electrolyte solution. The electrolyte may include a fluorine compound. For example, the fluorine-based compound is a copolymer of tetrafluoroethylene and fluorovinyl ether including perfluorosulfonic acid, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), sulfonic acid group, polytetra Fluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, polyhexafluoropropylene, and one or more selected from the group consisting of two or more copolymers or combinations thereof, and preferably, may be perfluorosulfonic acid It is not limited to this.

The electrolyte may further include a sulfonated polymer. For example, the sulfonated polymer may be polysulfone series, poly (ethersulfone) series, poly (thiosulfone) series, poly (etheretherketone) series, polyimide series, polystyrene series, polyphosphazene series, and the like. It may be one sulfonated hydrocarbon-based polymer selected from the group consisting of two or more mixtures, preferably sulfonated polysulfone, but is not limited thereto.

The sulfonation degree of the sulfonated polymer may be 60 to 90%. As used herein, the term "degree of sulfonation" refers to the total number of moles of the plurality of monomers constituting the sulfonated polymer, m, the number of moles of monomers substituted with at least one sulfonic acid group of the sulfonated polymer. In this case, the formula n / m may be calculated. For example, when n / m is 1, the sulfonation degree may be 100%.

In general, the higher the sulfonation degree of the polymer electrolyte, the higher the ionic conductivity of the polymer, while excessively high hydrophilicity is dissolved in water or severely swelling occurs. On the contrary, when sulfonation degree is low, while hydrophobicity is strong and water resistance and durability improve, there exists a problem that ion conductivity falls. Therefore, by adjusting the sulfonation degree of the polymer electrolyte in the range of 60 to 90%, it is possible to balance the ion conductivity, water resistance and durability.

The content of the electrolyte in the electrolyte solution may be 10 to 60% by weight. If the content of the polymer electrolyte is less than 10% by weight, the ion conductivity of the ion exchange membrane may be lowered. If the content of the polymer electrolyte is more than 60% by weight, the ion conductivity is no longer improved, and thus unnecessary raw materials are consumed, which is disadvantageous in terms of economic efficiency.

The solvent may be one selected from the group consisting of esters, ethers, alcohols, ketones, amides, sulfones, carbonates, aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures of two or more thereof, preferably May be an amide solvent, more preferably N-methyl-2-pyrrolidone.

Examples of the ester solvent include methyl acetate, ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl acetate, 3-methoxybutyl acetate, methyl butyrate, ethyl butyrate, and propyl propionate. However, the present invention is not limited thereto.

Examples of the ether solvent include diethyl ether, dipropyl ether, dibutyl ether, butyl ethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, octyl ether, hexyl ether, and the like. It may include, but is not limited thereto.

Examples of the alcohol solvent include methanol, ethanol, propanol, isopropanol, n-butanol, amyl alcohol, cyclohexanol, octyl alcohol, decanol, and the like, but are not limited thereto.

The ketone solvent may include acetone, cyclohexanone, methyl amyl ketone, diisobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone, and the like, but is not limited thereto.

Examples of the amide solvent include N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methylformamide, dimethylformamide, dimethylacetamide, and the like, but are not limited thereto.

Examples of the sulfone solvent include dimethyl sulfoxide, diethyl sulfoxide, diethyl sulfone, tetramethylene sulfone, and the like, but are not limited thereto.

Examples of the carbonate solvent include ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate and dibutyl carbonate, but are not limited thereto.

The aliphatic hydrocarbon solvents include pentane, hexane, heptane, octane, nonane, decane, dodecane, tetradecane, hexadecane, and the like, and the aromatic hydrocarbon solvents include benzene, ethylbenzene, chlorobenzene, toluene, Xylene and the like, but is not limited thereto.

In the step (c), the porous membrane hydrophilized in the step (a) may be impregnated and / or coated in the electrolyte solution to fill the pores of the porous membrane with the electrolyte, and if necessary, the surface of the porous membrane. Even the electrolyte may be coated to a certain thickness. The thickness of the porous membrane may be 10 ~ 100μm, the thickness of the ion exchange membrane filled and / or coated with the electrolyte according to step (c) may be 30 ~ 200μm.

The impregnation and / or coating may include (i) impregnating the hydrophilized porous membrane in an impregnation tank filled with the electrolyte solution for a predetermined time, (ii) a coating apparatus for delivering the hydrophilized porous membrane to the electrolyte solution, For example, the coating may be performed by a roll coater, a bar coater, or the like, or a combination of the above (i) and (ii).

In particular, when the step (c) is made in the manner using the roll coater of the (ii), the roll coater is a first roll to transfer the electrolyte solution to one side of the hydrophilized porous membrane, and the hydrophilized A suction means of a predetermined structure and shape is mounted therein while supporting and transporting the porous membrane in contact with the other surface of the porous membrane so that the electrolyte solution delivered from the first roll smoothly passes through the pores of the porous membrane. A second roll may be included to allow for filling without space. In addition, the electrolyte solution delivered in excess of the amount required for coating is sucked by the suction means mounted in the second roll and then transferred to the means for supplying the electrolyte solution to the first roll so that the electrolyte solution Can be reused.

As described above, the hydrophilized porous membrane has a hydrophilicity with -SO ₃ groups formed on the surface and the surface of the inner pores, and thus, due to the high affinity with the electrolyte which is inherently hydrophilic, It can be easily bonded, and the bonding strength can be enhanced, so that the durability of the ion exchange membrane can be remarkably improved, and the ion conductivity can also be improved since the loss of hydrophilic groups contained in the porous membrane and the electrolyte is minimized.

Hereinafter, embodiments of the present invention will be described in detail.

Preparation Example 1 Preparation of Porous Support and Hydrophilization Treatment

20 parts by weight of nano-silica particles having an average particle size of 600 nm coated with ethylene, 65 parts by weight of liquid paraffin oil having a kinematic viscosity of 40 cSt (@ 40 ° C.), 20 parts by weight of the first polyethylene having a weight average molecular weight of 1,500,000, and a weight average molecular weight 20 parts by weight of this 350,000 second polyethylene was mixed and the nanosilica particles were dispersed using a high speed mixer.

Thereafter, the microbubbles generated in the mixing process were removed through a vacuum defoaming process. The melt kneading was carried out at a temperature of 190 to 230 ° C. using a twin screw extruder equipped with a 350 mm wide tee-die. At this time, the input content was controlled so that the content of nanosilica in the porous support is 51.4% by weight. The melt kneaded material extruded through the tee-die was solidified by cooling at room temperature through a casting roll at 60 ° C., and the thickness of the sheet was adjusted to 1 to 2 mm.

Then, the extruded porous support was stretched in a transverse direction of 800% and in a longitudinal direction of 800% using a biaxial stretching machine heated to 120 ° C. to prepare a film. The stretched film was immersed in methylene chloride at 40 ° C. for 1 hour to remove liquid paraffin oil, and then dried at room temperature to remove residual solvent. Thereafter, 10% transverse direction, 5% contraction after stretching, 5% contraction after 10% stretching in longitudinal direction, heat set for 30 seconds, heat set, and then a porous support having an average pore size of 150 nm was obtained. Prepared.

The surface of the porous support was treated with a vacuum plasma to modify it. Prior to the plasma treatment, the porous support was placed in a mold capable of being flattened and purged with nitrogen to remove impurities on the support.

The chamber size of the apparatus for vacuum plasma treatment was 150 mm wide, 200 mm deep, and 120 mm high, and a flat electrode for generating plasma was mounted in parallel with the chamber upper surface at a position 25 mm from the upper surface. The porous support was positioned parallel to the planar electrode at a position 20 mm away from the planar electrode, and vacuum conditions were established until the pressure in the chamber became 0.1torr.

The gas having a composition according to Table 1 was purged while maintaining the pressure inside the chamber at 0.5torr for 2 minutes while flowing into the chamber at a flow rate of 100 sccm. In addition, a high frequency power source having a frequency of 50KHz was applied as an output of 100W to treat the porous support for the time according to Table 1 below. After the treatment, the chamber was opened by purging with air for 2 minutes while blocking the gas inflow into the chamber and maintaining the pressure at 0.5 torr, and releasing the vacuum condition.

The upper and lower surfaces of the porous support were inverted and positioned in the same manner as above in the chamber, and the same process was repeated to uniformly treat both surfaces, that is, the upper and lower surfaces of the porous support.

The contact angle of the secondary distilled water droplets was measured on the surface of the surface-treated porous support to evaluate the hydrophilic property change of the porous support, and the zeta potential of the surface of the porous support was measured by using a flow potential method. The charging properties of the porous support were evaluated. Measurement and evaluation results are shown in Table 1 below.

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Gas composition
(O ₂ : SO ₂ , vol%) 50: 50 20: 80 20: 80 20: 80 20: 80 - air Plasma Treatment Time (sec) 120 120 90 60 30 - 120 Contact angle (degrees, degrees) 2 0 0 3 11 105 92 Zeta potential (mV) -10 -25 -23 -18 -12 0 -2

Referring to Table 1, the porous support without plasma surface treatment (Comparative Example 1), while the hydrophobicity is very strong and the surface is not charged at all, the plasma is mixed with oxygen and sulfur dioxide in a certain ratio as a process gas Surface-treated porous supports (Examples 1 to 5) had a negative charge on the surface thereof and markedly improved hydrophilicity.

In addition, when the polyethylene surface porous film of Comparative Example 1 and the plasma surface treated substrate porous film of Example 1 were immersed in distilled water, the substrate porous film of Comparative Example 1 did not penetrate water into the pores and the surface was uneven. On the other hand, the substrate porous film of Example 1 can be immersed in water well due to water penetration into the pores while floating in water due to the nature of contact with air and opaque due to the difference in refractive index between the pores and the polyethylene material. And appear transparent due to the relaxed refractive index difference between the water filling the voids and the polyethylene material.

In addition, it can be seen from Examples 1 and 2 that the surface of the porous support is more effectively hydrophilic when the ratio of sulfur dioxide in the process gas is larger than oxygen.

Preparation Example 2 Preparation of Ion Exchange Membrane

It was dissolved in a mixed solvent containing 20 g of perfluorosulfonic acid, 20 mL of perfluorosulfonic acid, 30 mL of water, and 70 mL of alcohol, equipped with a mechanical stirrer, a gas inlet, and a cooler, and stirred at room temperature for at least 2 hours for sufficient dissolution. . After stirring, 10 mL of NMP was further added thereto, followed by stirring for 30 minutes or more to prepare an electrolyte solution. The porous supports of Examples 1, 2 and Comparative Example 1 were impregnated into the electrolyte solution to prepare ion exchange membranes.

The performance and durability of the prepared membrane was evaluated by the following method, and the results are shown in Table 2 below.

Ion conversion rate (IEC, meq / g): The ion conversion rate indicates the degree of inclusion of ion exchange groups in the ion exchange membrane, and was measured using an acid-base titration method. The ion exchange membrane was immersed in 0.01 N sodium chloride solution for 24 hours and then titrated using 0.01 N sodium hydroxide solution, and the ion conversion rate was calculated using Equation 1 below.

<Equation 1>

Ion Conversion Rate (meq / g) = (V _NaOH XN _NaOH ) / W _dry

In Formula 1, V _NaOH is the volume of the aqueous sodium hydroxide solution used for titration, N _NaOH is the normal concentration of the aqueous sodium hydroxide solution, W _dry is the weight of the dried ion exchange membrane.

Water uptake (%): In order to measure the water absorption rate of the ion exchange membrane, the ion exchange membrane was washed several times with deionized water, and the washed ion exchange membrane was immersed in deionized water for 24 hours and then taken out to the surface. The weight (W _wet ) was measured after removing the water present. Subsequently, the same ion exchange membrane was dried again in a reduced pressure dryer at 120 ° C. for 24 hours, and then measured again by weight (W _dry ), and water absorption was calculated using Equation 2 below.

<Equation 2>

% Water absorption = {(W _wet -W _dry ) / W _dry } X 100

-Dimensional stability (Δl, Δt, ΔV,%): Dimensional stability is the same as the method of measuring the water absorption rate, but instead of weight, the length, thickness, volume change of the ion exchange membrane was measured, and the dimensional change rate was Calculated.

<Equation 3>

Length change rate (Δl,%) = {(l _wet -l _dry ) / l _dry } X 100

Thickness Change (Δt,%) = {(t _wet -t _dry ) / t _dry } X 100

Volume change rate (ΔV,%) = {(V _wet -V _dry ) / V _dry } X 100

division IEC Δl Δt ΔV Water absorption Comparative example 1.05 5.63 6.99 19.41 13.02 Example 1 1.20 0.70 0.77 2.81 9.46 Example 2 1.15 0.45 10.37 21.17 5.87

Referring to Table 2, an ion exchange membrane (Examples 1 and 2) prepared by impregnating an electrolyte in a substrate porous membrane treated with plasma in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ ), Compared to the ion exchange membrane (Comparative Example 1) prepared by impregnating the electrolyte in the substrate porous membrane which has not been subjected to plasma surface treatment, the ion conversion rate is about 1.1 meq / g or more, so that the ion conductivity is excellent and the length change rate is about 80 ~. The dimensional stability was improved by 90%, and the water absorption rate was also lowered to 10% or less, indicating that the durability as an ion exchange membrane was excellent.

The above description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the invention is indicated by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims (13)

(a) hydrophilizing the porous membrane by plasma treating the porous membrane in the presence of a mixed gas containing sulfur dioxide (SO ₂ ) and oxygen (O ₂ );
(b) dissolving the electrolyte in a solvent to prepare an electrolyte solution; And
(c) impregnating the porous membrane hydrophilized in step (a) into the electrolyte solution. The method of claim 1,
The mixed gas is 50 to 90% by volume sulfur dioxide and 10 to 50% by volume of the ion exchange membrane production method. The method of claim 1,
A method for producing an ion exchange membrane, wherein the porous membrane comprises 30 to 90 wt% of two kinds of polyethylene having different weight average molecular weights and 10 to 70 wt% of an inorganic filler. The method of claim 3,
Wherein said polyethylene comprises a first polyethylene having a weight average molecular weight of 1,000,000 to 3,000,000 and a second polyethylene having a weight average molecular weight of 200,000 to 500,000. The method of claim 3,
Method for producing an ion exchange membrane having an average particle size of the inorganic filler 10 ~ 1,000nm. The method of claim 3,
Method of producing an ion exchange membrane comprising a hydrocarbon layer formed on the surface of the inorganic filler. The method of claim 1,
Method for producing an ion exchange membrane of the average pore size of the porous membrane is 20 ~ 2,000nm. The method of claim 1,
Method for producing an ion exchange membrane wherein the plasma treatment is performed for 30 to 90 minutes. The method of claim 1,
A method for producing an ion exchange membrane, wherein the contact angle of the hydrophilized porous membrane is 15 ° or less. The method of claim 1,
A method of producing an ion exchange membrane wherein the electrolyte contains a fluorine compound. The method of claim 10,
The fluorine-based compound is a copolymer of tetrafluoroethylene and fluorovinyl ether containing perfluorosulfonic acid, poly (perfluorosulfonic acid), poly (perfluorocarboxylic acid), sulfonic acid group, polytetrafluoroethylene, Polyvinyl fluoride, polyvinylidene fluoride, polyhexafluoropropylene and a method for producing an ion exchange membrane is one selected from the group consisting of two or more of these copolymers or combinations thereof. The method of claim 1,
Method of producing an ion exchange membrane of the content of the electrolyte in the electrolyte solution 10 to 60% by weight. The method of claim 1,
Method for producing an ion exchange membrane wherein the solvent is one selected from the group consisting of esters, ethers, alcohols, ketones, amides, sulfones, carbonates, aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures of two or more thereof .

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