Non-stratified ion exchange membrane for brine electrolysis and method for manufacturing the same

Abstract

The present invention relates to a non-layered ion exchange membrane for brine electrolysis, in which different functional groups exist simultaneously in a single layer, and a method for manufacturing the same. The membrane is capable of solving the problem of interfacial resistance between different layers and the problem of interfacial layering due to the application of the brine electrolysis process, has a controllable thickness in the process of manufacturing it, and has improved electrochemical performance and durability.

Description

Technical Field

[0001] The present invention relates to a delamination-free ion exchange membrane for brine electrolysis, wherein different functional groups coexist in a single layer, and a method for manufacturing the ion exchange membrane. Background Technology

[0002] Saline water electrolysis is a chemical process that directly produces high-value-added compounds, such as high-purity chlorine, hydrogen, and sodium hydroxide, by applying electricity to an electrolytic cell consisting of ion-exchange membranes and electrodes. The economic feasibility of saline water electrolysis is determined by the energy input required to produce the same amount of compound. This energy is influenced by the inherent resistance of the main components of the electrolytic cell—the ion-exchange membranes and electrodes—and the interfacial resistance between the membranes and electrodes.

[0003] Ion exchange membranes used in brine electrolysis processes require chemical resistance to strong acids and bases, electrochemical stability, high ionic conductivity, low interfacial resistance with electrodes, and ease of mass production. Representative ion exchange membranes used in commercial brine electrolysis exhibit high chemical resistance due to the chemically stable polytetrafluoroethylene (PTFE) backbone and excellent ionic conductivity due to the unique fine phase separation between hydrophilic and hydrophobic properties (e.g., Asahi Glass's Flemion series based on perfluorinated ion polymers, which exhibits excellent ionic conductivity due to the clear fine phase separation between hydrophilic and hydrophobic properties (e.g., F-8080, F-8081, F-9010), Asahi Kasei's Aciplex-F series (e.g., F-6808, F-7001), and Chemours' Nafion series (e.g., N2060, N2030, N982)). To achieve high current efficiency and low energy consumption in terms of productivity and economic feasibility of brine electrolysis, an ion exchange membrane with a bilayer structure was developed. This bilayer includes a carboxylic acid layer (perfluorocarboxylic acid, PFCA) with highly anion-repellent carboxylic acid groups (-COO). - H + As an ion exchanger, and a sulfonic acid layer (perfluorosulfonic acid, PFSA), which has low electrical resistance sulfonic acid groups (-SO3). - H + It is used as an ion exchanger.

[0004] When ion exchange membranes are used in brine electrolysis processes, interlayer delamination can occur under abnormal driving conditions, such as differences in the feed solutions supplied to the negative and positive electrodes or inconsistent applied current. This can act as a resistor, leading to a decrease in electrochemical performance and a reduction in the overall efficiency of the brine electrolysis process.

[0005] Korean Patent Publication No. 2017-0113232 discloses a method for introducing various ion exchangers into a polymer electrolyte base membrane via monomer polymerization after the base membrane has swelled. However, since the ion exchange membranes disclosed in the aforementioned patent are also manufactured using hot pressing or coating methods, a multilayered heterogeneous ion exchanger structure is formed, thus failing to solve the interlayer interface delamination problem that occurs under abnormal driving conditions. Furthermore, when using fluoropolymers with heterogeneous ion exchangers, the membrane is difficult to form due to their poor water solubility, thus hindering its application in practical processes.

[0006] Therefore, it is necessary to address issues such as interlayer delamination caused by the multilayer structure of ion exchange membranes with different types of functional groups and molding problems caused by poor material solubility, and it is also necessary to improve the performance and durability of ion exchange membranes. Summary of the Invention

[0007] Technical problems to be solved

[0008] One object of the present invention is to provide a non-stratified ion exchange membrane for brine electrolysis, which can solve the interfacial resistance problem between different layers in conventional multilayer ion exchange membranes and the interfacial stratification problem caused by the application of brine electrolysis process.

[0009] Another object of the present invention is to provide a method for manufacturing a non-stratified ion exchange membrane for brine electrolysis, which enables control of the thickness of the ion exchange membrane during manufacturing and improves its electrochemical performance and durability.

[0010] Technical solution

[0011] According to one aspect of the invention, a method for manufacturing a non-layered ion exchange membrane is provided, comprising the steps of: (i) providing an ion polymer dispersion containing different functional groups simultaneously by supercritical dispersion of an ion polymer precursor comprising different functional groups in a layered structure in a solvent; and (ii) forming an ion exchange membrane using the ion polymer dispersion, wherein the different functional groups are blended in a monolayer.

[0012] According to one implementation scheme, the different functional groups can be carboxylic acid groups and sulfonic acid groups, but are not limited to these.

[0013] According to one embodiment, the ion polymer precursor can be a perfluorinated ion exchange membrane with a bilayer structure including a carboxylic acid layer and a sulfonic acid layer, but is not limited thereto.

[0014] According to one embodiment, the ionomer precursor can be an enhanced composite membrane that also includes a porous support, but is not limited thereto.

[0015] According to one embodiment, the ionomer precursor can be at least one selected from commercially available multilayer ion exchange membranes or ion exchange membranes with a layered structure through chemical modification, but is not limited thereto.

[0016] According to one implementation, the solvent can be a mixture of alcohol and water.

[0017] According to one implementation, the supercritical dispersion may have a temperature of 100°C to 350°C and a pressure of 20 psig to 2800 psig, but is not limited thereto.

[0018] According to one embodiment, the method can also include filtering the dispersion prior to the step of forming the ion exchange membrane to separate the insoluble components and the carrier fibers.

[0019] According to one embodiment, ion exchange membranes can be formed by casting an ion polymer dispersion onto a substrate to form a self-supporting membrane or by impregnating the ion polymer dispersion into a porous support to prepare an enhanced composite membrane.

[0020] According to one embodiment, the method for manufacturing non-layered ion exchange membranes can control the thickness of the ion exchange membrane from 10 μm to 300 μm by changing the conditions of supercritical dispersion.

[0021] According to one implementation scheme, the ion exchange membrane prepared by the preparation method can be applied to brine electrolysis.

[0022] According to another aspect of the invention, a non-layered ion exchange membrane for water electrolysis is provided, wherein different functional groups coexist in a monolayer, wherein the heterogeneous functional groups are carboxylic acid groups and sulfonic acid groups.

[0023] According to one embodiment, the non-stratified ion exchange membrane for brine electrolysis may additionally include a porous support.

[0024] According to one embodiment, the porous carrier may be made of a polymer material selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyether ether ketone, polyethylene, and polypropylene, but is not limited thereto.

[0025] According to one embodiment, the non-stratified ion exchange membrane for brine electrolysis may have a thickness of 10 μm to 300 μm, but is not limited thereto.

[0026] Beneficial effects of the invention

[0027] According to this disclosure, multilayer ion exchange membranes based on perfluorinated ion polymers with different functional groups (PFSA / PFCA) can be prepared by supercritical dispersion to contain carboxylic acid groups (-COO) in a blended form. - H + ) and sulfonic acid groups (-SO3) - H + The dispersed liquid phase allows for easy control of the form (self-supported membrane or reinforced composite membrane) and thickness of the ion exchange membrane according to application characteristics. Furthermore, the non-layered ion exchange membrane manufactured based on this method can fundamentally prevent the interlayer interface resistance problems and delamination phenomena that occur in ion exchange membranes manufactured by existing physical thermal melting methods. This improves the performance and durability of the ion exchange membrane.

[0028] The effects of the present invention are not limited to those described above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description. Attached Figure Description

[0029] Figure 1a Based on the cross-sectional SEM image and EDX analysis results of the ion exchange membrane in Comparative Example 1, Figure 1b The results are based on the cross-sectional SEM image and EDX analysis of the ion exchange membrane in Example 1.

[0030] Figure 2a and Figure 2b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 1.

[0031] Figure 3a and Figure 3b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 2.

[0032] Figure 4a and Figure 4b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 3.

[0033] Figure 5a and Figure 5b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 4.

[0034] Figure 6a and Figure 6b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 5.

[0035] Figure 7a and Figure 7b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 6.

[0036] Figure 8a and Figure 8b This is a graph showing the surface XPS analysis results of the ion exchange membrane prepared in Example 7.

[0037] Figure 9 This is a graph showing the current-voltage characteristics of ion exchange membranes according to the embodiments and comparative examples.

[0038] Figure 10 This is a graph illustrating the electrochemical durability of ion exchange membranes according to the embodiments and comparative examples by applying a constant current.

[0039] The best embodiment for carrying out the present invention

[0040] The method for manufacturing a non-stripping ion exchange membrane according to the embodiment includes the following steps: supercritically dispersing an ion polymer precursor containing different functional groups in a layered structure in a solvent to provide an ion polymer dispersion containing different functional groups simultaneously; and forming an ion exchange membrane in which different functional groups are blended within a monolayer using the ion polymer dispersion. The different functional groups may be carboxylic acid groups (-COO). - H + ) and sulfonic acid group (-SO3) - H + (but not limited to this).

[0041] According to the implementation plan, the non-layered ion exchange membrane can be an ion exchange membrane in which different functional groups are blended in a single layer. Specifically, it can be a perfluorinated ion exchange membrane in which carboxylic acid groups and sulfonic acid groups are blended.

[0042] Thus, perfluorinated ion exchange membranes containing different functional groups within a single layer are suitable for use as ion exchange membranes for brine electrolysis and exhibit non-stratified properties, resulting in excellent performance and durability. Detailed Implementation

[0043] The present disclosure will be described in more detail below with reference to embodiments. However, the following embodiments are presented by way of example to aid in understanding the invention, and the scope of the invention is not limited thereto. Various changes can be applied to the present disclosure, and it can be implemented in various different forms, and should be understood to include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present disclosure.

[0044] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0045] A method for manufacturing a non-layered ion exchange membrane includes the steps of: (i) providing an ion polymer dispersion containing different functional groups simultaneously by supercritical dispersion of an ion polymer precursor comprising different functional groups in a layered structure in a solvent; and (ii) forming an ion exchange membrane using the ion polymer dispersion, wherein the different functional groups are blended in a monolayer. The different functional groups may be carboxylic acid groups (-COO). - H + ) and sulfonic acid groups (-SO3) - H + (but not limited to this).

[0046] The ion exchange membrane prepared by this method can be a perfluorinated ion exchange membrane, wherein carboxylic acid groups and sulfonic acid groups, which are different functional groups, are blended in a monolayer. As described above, perfluorinated ion exchange membranes in which different functional groups coexist in a monolayer are suitable for use as ion exchange membranes for brine electrolysis and exhibit non-stratification, thus possessing excellent performance and durability.

[0047] The non-stratified ion exchange membrane for brine electrolysis according to the present invention can be a self-supporting membrane made solely of ionomers or a reinforced composite membrane comprising a porous support. Furthermore, the non-stratified ion exchange membrane for brine electrolysis can have a thickness from 10 μm to 300 μm, but is not limited thereto.

[0048] The ion-polymer precursor used in preparing the dispersion can be a perfluorinated ion-exchange membrane with a bilayer structure comprising a carboxylic acid layer and a sulfonic acid layer. The perfluorinated ion-exchange membrane used as the ion-polymer precursor can be a reinforced composite membrane comprising a pure membrane or a porous support.

[0049] In addition, commercially available perfluorinated ion exchange membranes or multilayer ion exchange membranes prepared directly from chemically modified ion polymers can be used as ion polymer precursors without particular limitations to prepare ion polymer dispersions containing different functional groups.

[0050] Furthermore, regardless of the standard and condition of the ion exchange membrane, such as defects that occur during the production process or unused portions due to differences in manufacturing and usage standards, the ion exchange membrane can be used in this technology.

[0051] Examples of ion exchange membranes with different functional layers include, but are not particularly limited to, Asahi Glass’s Flemion series (e.g., F-8080, F-8081, F-9010), Asahi Kasei’s Aciplex-F series (e.g., F-6808, F-7001), and Chemours’ Nafion series (e.g., N2060, N2030, N982).

[0052] Furthermore, the solvent used for supercritical dispersion of ionic polymer precursors containing heterogeneous functional groups in a layered structure to provide ionic polymer dispersions containing different functional groups simultaneously without a layered structure can be a mixture of alcohol and water. Supercritical fluids at or above their critical point exhibit liquid-like solubility, very low surface tension, and gas-like permeability, and the density of supercritical fluids can enhance their solubility. In supercritical fluids, the low viscosity of the solute promotes mass transfer, thus exhibiting the high solute diffusivity of ion exchange membranes.

[0053] The solubility of this specific solute can be further improved by introducing a mixed solvent. In one embodiment of the invention, an alcohol and water are used together as a co-solvent to enhance the polarity and solvation strength of the supercritical fluid by forming hydrogen bonds. Meanwhile, for the preparation of an ion exchange membrane from the dispersion, it is preferable that the alcohol content is higher than the water content to induce rapid solvent evaporation during subsequent ion exchange membrane fabrication, and for example, an alcohol:water volume ratio of 55:45 to 99:1 is suitable.

[0054] The alcohols that can be used in this invention may be, for example, methanol, ethanol, 1-propanol, isopropanol, butanol, isobutanol, 2-butanol, tert-butanol, n-pentanol, isopentanol, 2-methyl-1-butanol, neopentanol, diethylmethanol, methylpropyl carbinol, methyl isopropyl carbinol, and dimethyl ethylmethanol. (carbinol), 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol and mixtures thereof, but not particularly limited thereto.

[0055] According to one embodiment, it is used to prepare a carboxylic acid group (-COO) therein. - H + ) and sulfonic acid groups (-SO3) - H +The supercritical temperature for the high-concentration dispersion of the blend is 100°C to 350°C, and the pressure is preferably 20 psig to 2800 psig. When the temperature is below 100°C or the reaction pressure is below 20 psig, the prepared dispersion exists in a partially dispersed state, making it difficult to have uniform dispersion characteristics. Conversely, when the temperature exceeds 350°C or the pressure exceeds 2800 psig, high-temperature and high-pressure reaction conditions must be maintained, which is therefore economically infeasible.

[0056] In this invention, the carboxylic acid group (-COO) is used to prepare the product. - H + ) and sulfonic acid groups (-SO3) - H + The specific temperature and pressure ranges of the blended dispersion can be varied depending on the ion exchange membrane material and the type and proportion of alcohol used, and the concentration of the dispersion can be adjusted according to the intended use, thus achieving very high utilization.

[0057] As described above, the supercritically dispersed carboxylic acid groups (-COO) - H + ) and sulfonic acid groups (-SO3) - H + The dispersion in blend form exhibits unique dispersion characteristics, and when the monolayer ion exchange membrane prepared based on it is introduced into the electrochemical cell, it can improve the electrochemical performance and durability.

[0058] For the use of supercritical dispersion in mixed solvents with carboxylic acid groups (-COO) - H + ) and sulfonic acid groups (-SO3) - H + The blended ionomer dispersion is cooled and filtered to separate insoluble components (e.g., substrate, inorganic additives, etc.). When the ionomer precursor is a reinforced composite membrane, the carrier fibers can also be separated through the filtration process.

[0059] Ionic polymer dispersions blended with heterogeneous functional groups can be easily separated using ordinary filter paper, specifically filter paper with an average pore size of 0.45 μm to 10 μm. However, other filters or separation devices besides filter paper can also be used, and there are no particular limitations. Meanwhile, the liquid dispersion passing through the filter paper or filtration device is characterized by the presence of carboxylic acid groups (-COO). - H + ) and sulfonic acid groups (-SO3) - H +An ion-exchange membrane dispersion is a polymer dispersion dispersed in a mixed solvent of water and alcohol, and can contain small amounts of water-soluble materials, such as antioxidants. Since additives such as antioxidants are components used in the manufacture of ion-exchange membranes, dispersions containing small amounts of water-soluble materials such as antioxidants can be used as is in the preparation of ion-exchange membranes.

[0060] According to the present invention, the carboxylic acid group (-COO) is used. - H + ) and sulfonic acid groups (-SO3) - H + Ion exchange membranes prepared from ion-polymer dispersions in a blended form exhibit excellent ionic conductivity. Furthermore, due to the preparation of a monolayer structure in which different types of functional groups are blended, non-stratification is ensured, thus improving electrochemical performance and durability when used as ion exchange membranes in batteries or water electrolysis devices.

[0061] Furthermore, in this invention, when an ion exchange membrane is manufactured using a dispersion in which different types of functional groups are blended, the thickness can be freely adjusted from 10 μm to 300 μm. As the ion exchange membrane thickens, the ohmic resistance increases, and the electrochemical performance of the battery or water electrolysis device incorporating the ion exchange membrane may deteriorate. To prevent this, it is preferable to adjust the thickness as much as possible while maintaining the mechanical and chemical durability of the ion exchange membrane. The levels of mechanical and chemical durability vary depending on the type of battery or water electrolysis device using the ion exchange membrane, and the thickness is adjusted according to each driving environment to manufacture the ion exchange membrane for use in various fields. Therefore, by controlling the thickness of the ion exchange membrane prepared according to this invention, it is possible to improve electrochemical performance.

[0062] Simultaneously, according to the present invention, the carboxylic acid group (-COO) is... - H + ) and sulfonic acid groups (-SO3) - H + The dispersed dispersion is applied to a porous support to create a composite membrane, thereby improving the efficiency of electrochemical reactions and chemical durability.

[0063] According to the present invention, the step of forming an ion exchange membrane using an ion polymer dispersion containing heterogeneous functional groups can be performed, for example, by casting the ion polymer dispersion onto a substrate to form a monolayer membrane or by impregnating the ion polymer dispersion into a porous support to produce a reinforced composite membrane.

[0064] According to one embodiment, when preparing an enhanced composite membrane using an ionomer dispersion containing different functional groups, the porous support can be, for example, at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, polyetheretherketone, polyethylene, and polypropylene, but is not limited thereto. In this invention, unlike existing bilayer ion exchange membranes, the dispersion is not manufactured by thermal melting, but rather coated onto a porous support, and the dispersion fills the pores. Therefore, interfacial delamination that occurs in bilayer ion exchange membranes is prevented, and the lifespan of the ion exchange membrane is improved by ensuring mechanical and gas barrier properties, thereby contributing to improved electrochemical performance and durability.

[0065] The invention will be described in more detail below by way of embodiments. However, the following embodiments are presented by way of example to aid in understanding of the disclosure, and the scope of the disclosure should not be construed as limited thereto.

[0066] Example 1

[0067] 1-Propanol was selected as the alcohol solvent for supercritical dispersion using Flemion, a multilayer ion exchange membrane based on perfluorinated ion-exchange polymers with different functional groups (PFSA / PFCA) from Asahi Glass, to prepare the membrane containing the carboxylic acid group (-COO). - H + ) and sulfonic acid groups (-SO3) - H + The dispersion is a blend in which 1-propanol was purchased and prepared from Aldrich Chemical Co. without further purification.

[0068] Flemion (22.3 g, 9 wt.%) was added to a glass liner containing 123.8 g of 1-propanol and 101.2 g of ultrapure water (weight ratio 55:45). The glass liner was installed in a high-pressure / high-temperature reactor (4560 Mini-Bench Reactor System, PARR, USA), and the reactor reaction mixture was subjected to a high-temperature reaction at 4.25 °C for [min]. −1 The mixture was heated to 350°C at a heating rate, and the reaction was maintained for 3 hours at a pressure of 2600 psig. The mixture was then slowly cooled at atmospheric pressure (14.7 psig) to obtain a dispersion. The dispersion was separated from the carrier fibers and filtered using filter paper with an average pore size of 5 μm to 10 μm. In addition to the carrier fibers, inorganic substances were removed by centrifugation at 4000 RPM for 15 minutes using a centrifuge (T04B, Hanil Science, Korea).

[0069] To evaluate its use as a single-layer ion exchange membrane for brine electrolysis, an ion exchange membrane was prepared using the dispersion described above via a solution coating method. For this purpose, the prepared dispersion was cast onto a hydrophilized glass plate, cured in a vacuum oven at 50°C for 3 hours, and then heat-treated at 210°C for 1 hour to prepare the membrane, with the membrane thickness controlled to 50 μm during the process.

[0070] Example 2

[0071] The dispersion was prepared in the same manner as in Example 1, except that when using a high-pressure / high-temperature reactor to prepare the dispersion, the reaction mixture in the reactor was heated to 4.25°C for 1 minute. −1 The temperature was increased to 250°C at a heating rate, and the reaction was maintained for 3 hours when the pressure reached 2600 psig. The membrane was then prepared in the same manner as in Example 1.

[0072] Example 3

[0073] The dispersion was prepared in the same manner as in Example 1, except that when using a high-pressure / high-temperature reactor to prepare the dispersion, the reaction mixture in the reactor was heated to 4.25°C for 1 minute. −1 The temperature was increased to 100°C at a heating rate, and the reaction was maintained for 3 hours when the pressure reached 2600 psig, and the membrane was prepared in the same manner as in Example 1.

[0074] Example 4

[0075] The dispersion was prepared in the same manner as in Example 1, except that when using a high-pressure / high-temperature reactor, the reaction mixture in the reactor was subjected to a high-temperature reaction at 4.25°C for [time missing]. −1 The temperature was increased to 350°C, and the reaction was maintained for 3 hours when the pressure reached 1300 psig.

[0076] Example 5

[0077] The dispersion was prepared in the same manner as in Example 1, except that when using a high-pressure / high-temperature reactor, the reaction mixture in the reactor was subjected to a high-temperature reaction at 4.25°C for [time missing]. −1 The temperature was increased to 350°C at a heating rate, and the reaction was maintained for 3 hours when the pressure reached 30 psig.

[0078] Example 6

[0079] The dispersion was prepared in the same manner as in Example 1, except that when using a high-pressure / high-temperature reactor, the reaction mixture in the reactor was subjected to a high-temperature reaction at 4.25°C for [time missing]. −1 The temperature was increased to 250°C, and the reaction was maintained for 3 hours when the pressure reached 1000 psig.

[0080] Example 7

[0081] The membrane was prepared in the same manner as in Example 1, except that, in the process of preparing the ion exchange membrane, the dispersion and the porous support were prepared together during the casting onto the hydrophilic glass plate, and the ion exchange resin dispersion was immersed in the porous reinforced composite membrane support at a temperature of 40°C or below for 1 hour or less.

[0082] Comparative Example 1

[0083] Using Flemion from Asahi Glass.

[0084] Comparative Example 2

[0085] The dispersion was prepared in the same manner as in Example 1, except that a high-pressure / high-temperature reactor was used, the temperature was 80°C, the pressure was atmospheric pressure, and the reaction was maintained for 3 hours. The membrane was then prepared in the same manner as in Example 1. The prepared dispersion had a very low concentration, and because the dispersion was not uniformly dispersed in the solvent, there were dispersion characteristic problems. Furthermore, the dispersion was not prepared into an ion exchange membrane.

[0086] Experimental Example 1: SEM-EDX Analysis

[0087] To observe the cross-section of the membranes prepared by the methods of Comparative Example 1 and Example 1, and by using Na... + EDX line scanning was used to confirm whether the film was fabricated as a monolayer. Cross-sectional analysis was performed using SEM-EDX, and the SEM images are shown below. Figure 1a and Figure 1b Prior to analysis, the membranes prepared by the methods of Comparative Example 1 and Example 1 were soaked in 0.5M NaCl aqueous solution for two days, then soaked in ultrapure water for another two days and washed. This process was to allow the NaCl to be dissolved in water. + Combined with carboxylic acid groups and sulfonic acid groups, compare the relationship between carboxylic acid groups (weak acids) and sulfonic acid groups (strong acids) and Na. + The bonding strength is used to confirm whether a single layer has been manufactured. In the case of Comparative Example 1, as... Figure 1a As shown, Na was confirmed. + The bonding strength gradually increases from top to bottom, and it was confirmed to be a two-layer structure, consisting of a strong acid (sulfonic acid) base layer with strong bonding strength and a weak acid (carboxylic acid) base layer with weak bonding strength. On the other hand, in the case of Example 1, as... Figure 1b As shown, it can be confirmed that Na + The bonding strength remains constant from the top to the bottom of the cross-section and is manufactured as a single layer.

[0088] Experiment Example 2 XPS Analysis

[0089] The presence of sulfonic acid groups and carboxylic acid groups on the surface of the membranes prepared by the methods of Examples 1 to 7 (E1 to E7) was detected, and chemical structure analysis was performed by XPS to determine the presence or absence of sulfonic acid groups and carboxylic acid groups.

[0090] Figure 2a and Figure 2b The XPS analysis results are based on the membrane manufactured according to Example 1. Figure 3a and Figure 3b This is the XPS analysis result of Example 2. Figure 4a and Figure 4b These are the XPS analysis results from Example 3. Figure 5a and Figure 5b This is the XPS analysis result of Example 4. Figure 6a and Figure 6b These are the XPS analysis results from Example 5. Figure 7a and Figure 7b These are the XPS analysis results from Example 6. Figure 8a and Figure 8b These are the XPS analysis results from Example 7. As shown in Figures 2 to 8, the presence of sulfonic acid groups was confirmed by two peaks between 164 eV and 166 eV. At the same time, the peaks of carboxylic acid groups were identified by the C=O peak at 288 eV and the CO peak at 286 eV, confirming that both are present in the membrane.

[0091] Experimental Example 3: Measurement of Ionic Conductivity

[0092] The Na content was measured using membranes prepared using the methods described in Examples 1 to 7 (E1 to E7) and Comparative Example 1 (C1), as well as commercially available membranes. + Ionic conductivity. After measuring the ohmic resistance or bulk resistance using the four-point probe AC ​​impedance spectroscopic method, Na is calculated using Equation 1. + Ionic conductivity.

[0093] [Equation 1],

[0094] σ = L / RS

[0095] [In equation 1, σ: Na + Ionic conductivity (S / cm), R: ohmic resistance of polymer electrolyte (Ω), L: distance between electrodes (cm), S: electrolyte area through which constant current flows (cm)], and the ionic conductivity measured at the actual driving temperature of 90°C for the brine electrolysis process in each embodiment are shown in Table 1.

[0096] from Figure 9 It can be seen that, compared to Comparative Example 1 (C1), which is a representative commercially available bilayer membrane with carboxylic acid and sulfonic acid groups, the monolayer membranes of Examples 1 to 7 (E1 to E7) that simultaneously contain sulfonic acid and carboxylic acid groups using a supercritical dispersion method have improved conductivity. Furthermore, Examples 2 and 3, which have low temperatures, and Examples 3 and 4, which have low pressures, show lower conductivity than Example 1, and in the case of Example 7, which is a reinforced composite membrane preparation, it can be confirmed that the conductivity is higher than that of Examples 1 to 6.

[0097] Table 1

[0098]

[0099] Experiment Example 4: Current-Voltage Characteristics

[0100] When the films prepared by the methods described in Examples 1, 3, 6, 7 (E1, E3, E6 and E7) and Comparative Example 1 (C1) are applied to a cell, the voltage is measured by applying a current density from 0 A / cm to 0.6 A / cm.

[0101] A solution with pH 2 was obtained by adding 0.02M HCl to a 25wt% NaCl aqueous solution and circulating it to the anode at a flow rate of 1000 ml / min. A 30.7wt% NaOH aqueous solution was circulated to the cathode at a flow rate of 500 ml / min. The battery and the entire process temperature were set to 90°C, and then current was applied.

[0102] pass Figure 9 It was confirmed that, compared to Comparative Example 1, which is a commercially available carboxylic acid-sulfonic acid bilayer membrane, Examples 1, 3, 6, and 7, which are monolayer membranes in which both sulfonic acid and carboxylic acid groups coexist, exhibited lower voltages, thus demonstrating further improved cell performance. Furthermore, it was confirmed that Example 7, prepared as an enhanced composite membrane, exhibited a lower voltage compared to Examples 1, 3, and 6, and that Examples 3 and 6, where the temperature and pressure were adjusted to lower levels, had higher voltages than Example 1, indicating lower cell performance.

[0103] Experimental Example 5: Electrochemical Durability

[0104] For membranes prepared by the methods described in Examples 1, 3, 6, 7 (E1, E3, E6, and E7) and Comparative Example 1 (C1) and commercially available membranes, an electrochemical acceleration condition was maintained at a current density of 0.6 A / cm for 6 hours under the driving conditions as described in Experimental Example 4, followed by a 6-hour period without current density application. This process was repeated 10 times to confirm electrochemical durability. To prevent OH- precipitates due to concentration differences during the 6-hour period after current density application was stopped... − The flow proceeds from the cathode to the anode, with deionized water being introduced into each anode and cathode.

[0105] It can be seen that, compared to Comparative Example 1, which is a commercially available carboxylic acid-sulfonic acid bilayer membrane, Examples 1, 3, 6, and 7, which are monolayer membranes in which both sulfonic acid and carboxylic acid groups coexist, exhibited no voltage rise under low voltage driving conditions and within the same time frame. Therefore, it was found that the electrochemical performance was improved due to similar or better durability than Comparative Example 1 and the maintenance of low voltage. (Refer to...) Figure 10 As can be seen, as in Experimental Example 4, Examples 3 and 6, which have low temperature and low pressure, are driven at higher voltages, while Example 7, which has an enhanced membrane form, is driven at a lower voltage than the other Examples 1, 3, 6 and 7, thereby having improved electrochemical performance.

[0106] From the foregoing description, those skilled in the art will understand that this disclosure can be implemented in other specific forms without altering its technical spirit or essential characteristics. In this regard, it should be understood that the above embodiments are illustrative in all respects and not restrictive. The scope of the invention should be construed as including all variations or modifications derived from the meaning and scope of the claims described later and their equivalents, rather than from the specific embodiments.

Claims

1. A method for manufacturing a non-stratified ion exchange membrane, comprising the following steps: (i) providing an ionic polymer dispersion containing different functional groups simultaneously by supercritical dispersion of an ionic polymer precursor containing different functional groups in a layered structure in a solvent; and (ii) using the ionic polymer dispersion to form an ion exchange membrane, wherein the different functional groups are blended in a monolayer.

2. The method according to claim 1, wherein the different functional groups are carboxylic acid groups and sulfonic acid groups.

3. The method according to claim 1, wherein the ion polymer precursor is a perfluorinated ion exchange membrane with a bilayer structure comprising a carboxylic acid layer and a sulfonic acid layer.

4. The method according to claim 3, wherein the ionomer precursor can be an enhanced composite membrane further comprising a porous support.

5. The method according to claim 1, wherein the solvent is a mixture of alcohol and water.

6. The method of claim 1, wherein the supercritical dispersion temperature is from 100°C to 350°C and the pressure is from 20 psig to 2800 psig.

7. The method according to claim 1, further comprising the following step: Before forming the ion exchange membrane, the insoluble components and carrier fibers are separated by filtering the dispersion.

8. The method of claim 1, wherein the formation of the ion exchange membrane can be performed by casting the ion polymer dispersion onto a substrate to form a self-supporting membrane or by impregnating the ion polymer dispersion into a porous carrier to form a reinforced composite membrane.

9. The method according to claim 1, wherein the thickness of the ion exchange membrane is controlled to be from 10 μm to 300 μm by changing the conditions of supercritical dispersion.

10. The method according to claim 1, wherein the ion exchange membrane is applied to brine electrolysis.

11. A perfluorinated non-layered ion exchange membrane for brine electrolysis, wherein different functional groups coexist in a monolayer, wherein the different functional groups are carboxylic acid groups and sulfonic acid groups.

12. The non-layered ion exchange membrane according to claim 11, wherein the non-layered ion exchange membrane for brine electrolysis further comprises a porous support.

13. The non-layered ion exchange membrane according to claim 12, wherein the porous support is made of at least one polymer material selected from polytetrafluoroethylene, polyvinylidene fluoride, polyetheretherketone, polyethylene, and polypropylene.

14. The non-layered ion exchange membrane according to claim 11, wherein the non-layered ion exchange membrane for brine electrolysis has a thickness of 10 µm to 300 µm.

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