Hollow fiber membrane for humidifiers, method for manufacturing the same, and humidifier containing the hollow fiber membrane.

Abstract

The present invention relates to a hollow fiber membrane comprising a polymer and an antioxidant, wherein the antioxidant is present in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the hollow fiber membrane.

Description

Technical Field

[0001] The present invention relates to a hollow fiber membrane for a humidifier having a novel composition, a method for producing the same, and a humidifier including the hollow fiber membrane.

Background Art

[0002] A fuel cell is a power generation type battery that converts the chemical energy of hydrogen and oxygen into electrical energy through an electrochemical reaction. Different from general chemical batteries such as dry batteries and storage batteries, a fuel cell has the advantage that it continuously produces electricity as long as hydrogen and oxygen are supplied, and its efficiency is more than twice higher than that of an internal combustion engine without heat loss. In addition, since hydrogen and oxygen are used as raw materials and water is generated as a product, it is an energy generation device friendly to an environment free of pollutants. Therefore, a fuel cell has the advantages of being environmentally friendly and reducing the concern about resource depletion due to an increase in energy consumption. Fuel cells can be classified into polymer electrolyte membrane fuel cells (PEMFCs), phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs), and alkaline fuel cells (AFCs), etc. Among these, polymer electrolyte membrane fuel cells are known to be suitable for use in transportation systems because they can operate at low temperatures and have a high output density compared to other fuel cells. On the other hand, in a polymer electrolyte membrane fuel cell, generally, 2 moles of hydrogen and 1 mole of oxygen react in a fuel cell stack during operation to form water, but when an incomplete reaction proceeds, peroxide or hydroxyl radicals may be formed as by-products. When the peroxides or hydroxide radicals generated in this way flow from the fuel cell stack into the membrane humidifier, they induce oxidation of the organic hollow fiber membrane within the membrane humidifier, leading to the decomposition and degradation of the hollow fiber membrane. The decomposition and degradation of the hollow fiber membrane hinders the delivery of sufficiently moist air to the fuel cell stack, reducing the efficiency of the fuel cell stack and the fuel cell as a whole. This has led to an industrial demand for hollow fiber membranes in which decomposition from peroxides or hydroxyl radicals is suppressed. [Overview of the Initiative] [Problems that the invention aims to solve]

[0003] To solve the aforementioned problems, the present invention provides a hollow fiber membrane for humidifiers in which decomposition from peroxides or hydroxyl radicals is suppressed, a method for manufacturing the same, and a humidifier containing the hollow fiber membrane. [Means for solving the problem]

[0004] In one aspect, a hollow fiber membrane for a humidifier is provided, comprising a polymer and an antioxidant, wherein the antioxidant is present in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the hollow fiber membrane. In other words, a method for producing a hollow fiber membrane for a humidifier is provided, comprising the steps of: mixing an antioxidant in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the spinning solution to obtain a spinning solution; spinning the spinning solution through a nozzle into a coagulation tank; and coagulating the spinning solution in the coagulation tank. In another aspect, a humidifier including the hollow fiber membrane is provided. [Effects of the Invention]

[0005] The unilateral hollow fiber membrane for humidifiers contains a polymer and an antioxidant. By including 0.01 to 5 parts by weight of the antioxidant per 100 parts by weight of the hollow fiber membrane, the antioxidant captures and / or decomposes peroxides or hydroxide radicals flowing from the fuel cell stack towards the humidifier containing the hollow fiber membrane, thereby suppressing the decomposition of the hollow fiber membrane from peroxides or hydroxide radicals. This improves the chemical durability of the hollow fiber membrane. [Brief explanation of the drawing]

[0006] [Figure 1] This is a disassembled perspective view of a fuel cell humidifier based on an actual example. [Figure 2] This is a disassembled perspective view of a fuel cell humidifier based on an actual example. [Modes for carrying out the invention]

[0007] The present inventive concept described below can be modified in various ways and may have many different embodiments. Specific embodiments are illustrated in the drawings and explained in detail in the detailed description. However, this is not intended to limit the present inventive concept to specific embodiments, but rather should be understood to include all modifications, equivalents, or substitutes that fall within the technical scope of the present inventive concept. The terms used hereafter are used solely to describe specific embodiments and are not intended to limit the scope of this invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. Hereafter, terms such as “includes” or “having” describe the presence of features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof as described in the specification, and should not be understood to exclude the presence or possibility of adding one or more other features, numbers, steps, operations, components, parts, ingredients, materials, or combinations thereof. When it is mentioned that one component is “connected” or “joined” with another component, it should be understood that the first component may be directly connected or joined to the other component, but that there may also be a new other component between the first component and the other component. On the other hand, when it is mentioned that one component is “directly connected” or “directly joined” with another component, it should be understood that there is no new other component between the first component and the other component. Throughout the specification, when a part such as a layer, film, region, or plate is described as being "on top of" or "above" another part, this includes not only cases where it is directly above another part, but also cases where there are other parts in between. Throughout the specification, terms such as "first," "second," etc., are used to describe various components, but components should not be limited by these terms. The terms are used solely for the purpose of distinguishing one component from another. As used throughout this specification, the term "polymer" refers to a polymer formed by the polymerization of one or more monomer units, and encompasses polymer resins and polymer macromolecules. The embodiments described below are merely illustrative examples, and various modifications are possible from these embodiments. The hollow fiber membrane for humidifiers, based on one side, contains a polymer and an antioxidant, and may contain 0.01 to 5 parts by weight of the antioxidant per 100 parts by weight of the hollow fiber membrane. According to one example, the antioxidant is contained in 0.1 to 5 parts by weight, for example, 1 to 3 parts by weight, or 2 to 4 parts by weight, and may include any two values ​​from the aforementioned numerical range and a determined range. If the amount of antioxidant in the hollow fiber membrane is less than 0.01 parts by weight, it is insufficient to prevent deterioration of the hollow fiber membrane due to peroxides or hydroxide radicals generated from the fuel cell reaction. If it exceeds 5 parts by weight, the pores of the hollow fiber membrane become blocked, reducing the moisture exchange performance and gas permeability, and the membrane humidifier cannot perform its essential function. In one example, the antioxidant may be dispersed within the polymer. For instance, the antioxidant may have a particulate form and be dispersed within the polymer in an embedded structure. Here, "dispersed" means that the antioxidant is present within the space formed by the polymer skeleton.

[0008] According to one example, the antioxidant may be randomly or uniformly dispersed within the polymer. For example, the antioxidant may be uniformly dispersed within the polymer. In one embodiment, at least a portion of the antioxidant may be exposed on the surface of the polymer. For example, a portion of the antioxidant exposed on the surface of the polymer may be embedded in the polymer, with only a portion of it being exposed to the outside. According to one embodiment, the hollow fiber membrane may include a concentration gradient region in which the concentration of the antioxidant changes within the hollow fiber membrane. For example, the concentration of the antioxidant can increase from the inner surface to the outer surface of the hollow fiber membrane. By configuring the hollow fiber membrane to have an even greater amount of antioxidant on its outer surface, hydrogen peroxide or hydroxide radicals flowing into the humidifier along with high-humidity air from the fuel cell stack can be effectively captured and decomposed. According to one example, the antioxidant may include organic antioxidants, metal antioxidants, organometallic antioxidants, HALS (Hindered amine Light stabilizer) type antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, or combinations thereof. For example, the organic antioxidant may include coumaric acid, dipamine, hydroquinone, phenolphthalein, phthalic acid, acetylsalicylic acid, phenolic antioxidants, niacin, luminol, urea, phytic acid, glyoxal, or any mixture thereof. For example, the metal-based antioxidant may include salts of Ce metal such as Ce(NO3)3, CECl3, and Ce2(SO4)3, salts of Mn metal such as Mn(NO3), metal oxides such as CeO2, CeSiO2, MnO2, and TiO2, or any mixture thereof. For example, the organometallic complex may include a Ce-crown complex, a Ce-phosphoric acid complex, Ce-bypyridine, or any mixture thereof. In one embodiment, the polymer may be selected from among known polymers suitable for forming hollow fiber membranes, and may include, for example, polyvinylidene fluoride (PVDF) polymers, polysulfone polymers, sulfonated polysulfone, cellulose acetate, cellulose triacetate, polymethyl methacrylate, nafion, polystyrene (PS) polymers, polytetrafluoroethylene (PTFE) polymers, perfluorosulfonic acid (PFSA) polymers, polyphenylsulfone polymers, polyethersulfone (PES) polymers, polyacrylonitrile (PAN) polymers, polyetherimide (PEI) polymers, polyimide (PI) polymers, or any combination of the aforementioned polymers. For example, the polymer may include a polystyrene-based polymer. According to one example, the polymer may be present in 10 to 35 parts by weight per 100 parts by weight of the hollow fiber membrane. For example, the polymer may be present in 15 to 30 parts by weight per 100 parts by weight of the hollow fiber membrane.

[0009] According to one example, the thickness of the hollow fiber membrane is 60 μm to 300 μm. For example, the thickness of the hollow fiber membrane is 80 μm to 120 μm or 100 μm to 140 μm, but is not limited to these, and can have a variety of arbitrary thickness ranges included in the above range. According to one example, the hollow fiber membrane may further contain additives such as surfactants, hydrophilic organic compounds, or hydrophilic polymers. Such additives may be added in appropriate amounts, selected so as not to impair the inherent properties of the hollow fiber membrane. It would be obvious to any ordinary technician that other materials commonly used in the manufacture of hollow fiber membranes may also be used. According to one example, the hollow fiber membrane may have antioxidants randomly or uniformly dispersed within the polymer. For example, by uniformly dispersing the antioxidant within the polymer, the hollow fiber membrane can achieve improved resistance to peroxides and hydroxyl radicals without significantly inhibiting the porosity of the hollow fiber membrane. According to one example, the hollow fiber membrane may have a cavity inside and may contain a plurality of pores that communicate the inner and outer surfaces with gas. According to one example, a hollow fiber membrane measured under conditions of a shell-side dew point of 75°C, a pressure of 0.8 barg, and a flow rate of 1000 slpm, yielded a water vapor transmission rate of 0.1 g / s / m³. 2 For example, if the water vapor transmission rate is 0.13 g / s / m³ 2 Therefore, if the water vapor permeability satisfies the above range, sufficient moisture exchange performance of the hollow fiber membrane can be expected. According to one example, a hollow fiber membrane exhibits a nitrogen permeability of 100 cc / min / cm² under a pressure of 0.5 bar. 2 For example, if the nitrogen permeability is 80 cc / min / cm 2 That is the case. According to one example, the hollow fiber membrane has an oxygen permeability of 100 cc / min / cm² under a pressure of 0.5 bar. 2 For example, if the oxygen permeability is 80 cc / min / cm 2 That is the case. The hollow fiber membrane has the water vapor permeability, nitrogen permeability, and oxygen permeability described above, and even when an antioxidant for improving durability is introduced, it has sufficient moisture exchangeability and gas permeability, making it suitable for use in a fuel cell humidifier with improved durability. A method for manufacturing a hollow fiber membrane for a humidifier according to one aspect involves mixing a polymer and an antioxidant in an organic solvent, including steps of obtaining a spinning dope by mixing the antioxidant at 0.01 to 5 parts by weight based on 100 parts by weight of the spinning dope, spinning the spinning dope through a nozzle into a coagulation bath, and coagulating the spinning dope in the coagulation bath. Regarding the overlapping configurations in the method for manufacturing the hollow fiber membrane, refer to the above-mentioned content. According to one embodiment, the step of obtaining the spinning dope may include mixing the antioxidant and the polymer in a solvent. The solvent may include at least one of a first solvent, a second solvent, and a third solvent. For example, the solvent is a mixed solvent containing two of the first solvent, the second solvent, and the third solvent.

[0010] The first solvent is a solvent that does not dissolve the polymer at room temperature (e.g., 23 - 25°C) but dissolves it at high temperature (e.g., 80°C or higher), and may include butanol, isobutanol, octanol, pentanol, isopentanol, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, polyoxyethylene octyl phenyl ether, or a combination thereof. The second solvent is a solvent that does not dissolve the polymer and may include water, methanol, ethanol, isopropanol, acetone, hexane, pentane, benzene, toluene, carbon tetrachloride, o-dichlorobenzene, polyethylene glycol, or a combination thereof. The third solvent is a solvent that dissolves the polymer even at room temperature and may include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, tetrahydrofuran, tetramethyl urea, or trimethyl phosphate. A typical technician may use a mixture of one or more of the first, second, and third solvents, taking into consideration the desired properties of the hollow fiber membrane and the characteristics of the polymer. According to one example, when the solvent is a mixed solvent of two or more solvents, the mixing ratio of the solvents is 1:9 to 9:1 by weight, but is not limited to this, and can be selected within an appropriate range by an ordinary technician considering the polymer and antioxidant content, the viscosity of the spinning solution, and the physical properties of the final hollow fiber membrane. According to one example, the polymer content in the spinning solution is 10 to 35% by weight. For example, the polymer content is 15 to 30% by weight, but is not limited to this range, and an ordinary engineer can select an appropriate content range considering the physical properties and gas permeability of the final hollow fiber membrane. According to one example, the content of the antioxidant in the spinning solution is 0.01 to 5 parts by weight. For example, the content of the antioxidant is 1 to 5 parts by weight, or 2 to 4 parts by weight, but is not limited to these, and an ordinary engineer can select an appropriate content range considering the physical properties of the final hollow fiber membrane, gas permeability, etc. According to one example, in the step of obtaining the spinning solution, the temperature at which the polymer, antioxidant, and solvent are mixed is 10 to 130°C, for example, 50 to 90°C or 60 to 80°C. According to one example, the time for mixing the spinning solution is 2 to 24 hours, for example, 5 to 22 hours or 6 to 20 hours, but is not limited to these, and the mixing is performed within the aforementioned time range until the spinning solution is uniformly mixed. According to one example, the viscosity of the spinning solution is 5,000 cps to 30,000 cps at 50°C. When the viscosity of the spinning solution satisfies the above range, smooth dispensing of the spinning solution into the hollow fiber membrane is facilitated.

[0011] The spinning dope can be discharged from the outer tube of the multi-shaped spinning nozzle, and at the same time, the core liquid can be discharged from the inner tube. The core liquid plays a role in forming the hollow fiber membrane and is a mixed solution obtained by mixing water, one solvent selected from the group consisting of polyvinylpyrrolidone, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), methyl ethyl ketone (MEK), gamma-butyrolactone, sulfolane, 1,3-dimethyl(dimethyl)-2-imidazolidinone, and mixtures thereof, with an additive selected from the group consisting of ethanol, sorbitol, polyethylene glycol, ethylene glycol, polypropylene glycol, propylene glycol, diethylene glycol, glycerin, lithium chloride, lithium bromide, and mixtures thereof. The core solution has a mixed weight ratio of the solvent to the additive of 70:30 to 40:60. When the weight ratio of the additive is less than 30, finger-shaped macropores are formed throughout the hollow fiber membrane, and when the weight ratio of the additive exceeds 60, a hollow fiber membrane with a slow phase transition rate and a closed internal structure is obtained. According to one embodiment, the step of spinning the spinning stock into a coagulation tank includes the step of spinning the discharged liquid using a multi-tubular spinning apparatus, for example, a double-tubular spinning apparatus or a triple-tubular spinning apparatus. However, it is not limited to such a multi-tubular shape, and any discharge method that forms a hollow shape can be used without limitation. In one example, in the step of spinning the spinning solution into a coagulation tank, the spinning temperature is 25 to 100°C, for example, 30 to 50°C. According to one example, in the step of spinning the spinning stock into a coagulation tank, the discharge rate is 6 to 25 g / min, for example, 6 to 23 g / min or 8 to 20 g / min. If the discharge rate exceeds 25 g / min, it becomes difficult to obtain a uniform thickness and porosity of the hollow fiber membrane, and if it is less than 6 g / min, there is a risk of nozzle clogging. After the spinning solution is spun into a coagulation tank, the spinning solution is coagulated by the coagulation solution. According to one example, the solidification tank consists of one unit, but is not limited to this, and can be configured with two or more solidification tanks arranged in sequence. When there are two or more solidification tanks, the solidifying liquid used in each solidification tank is either the same or different from one another. According to one example, the coagulation liquid provided to the coagulation tank plays the role of solidifying the discharged liquid, which is ejected through the nozzle, into a hollow fiber membrane. The coagulation liquid used in this process can be appropriately selected and used by an ordinary technician from among known coagulation liquids. For example, the coagulation solution can be selected from an acidic solution, water, ethanol, sorbitol, polyethylene glycol, ethylene glycol, polypropylene glycol, propylene glycol, diethylene glycol, glycerin, lithium chloride, lithium bromide, and mixtures thereof.

[0012] In this case, when a mixed solution of two solutions is used as the coagulation solution, the first solution and the second solution are mixed in a volume ratio of 1:9 to 9:1, for example, 2:8 to 8:2, 3:7 to 7:3, 4:6 to 6:4, or 5:5. The type and concentration of the coagulation solution can be appropriately selected by an ordinary engineer, taking into consideration the type of doping stock and core solution of the hollow fiber membrane and the physical properties of the hollow fiber membrane. According to one example, the hollow fiber membrane obtained through the coagulation tank can undergo a post-processing step. According to one example, the post-treatment step may include chemical treatment and / or physical treatment. For example, the chemical treatment among the post-treatment steps is performed to remove and dry the solidified liquid contained in the pores after the formation of the hollow fiber membrane, and may include washing with water, washing, hot water treatment, etc. For example, the physical treatment among the post-processing steps may include stretching and shrinking to control the size and appearance of the internal pores of the hollow fiber membrane and to improve the strength and durability of the hollow fiber membrane. A humidifier with a single side may include the hollow fiber membrane for humidifiers mentioned above. The information regarding hollow fiber membranes is as described above, and the humidifier will be explained below with reference to Figures 1 and 2. Figures 1 and 2 are perspective views relating to a fuel cell humidifier 100 according to one embodiment of the present invention. As shown in Figures 1 and 2, the fuel cell humidifier 100 of the present invention includes an intermediate case 110, a cap case 120, a fixing part 130, and a hollow fiber membrane bundle 200. The intermediate case 110 is combined with the cap case 120 to form the outer shape of the membrane humidifier 100. The intermediate case 110 and the cap case 120 are made of hard plastic such as polycarbonate or metal. The intermediate case 110 and the cap case 120 have a circular cross-sectional shape in the width direction, as shown in Figure 1, or a polygonal cross-sectional shape in the width direction, as shown in Figure 2. The polygon can be a rectangle, square, trapezoid, parallelogram, pentagon, hexagon, etc., and the corners of the polygon may be rounded. The circular shape may also be an ellipse. The intermediate case 110 has a second fluid inlet 112 through which the second fluid is supplied and a second fluid outlet 113 through which the second fluid is discharged. Figures 1 and 2 illustrate that multiple hollow fiber membranes 210 are arranged in the intermediate case 110 in the shape of a single hollow fiber membrane bundle 200. However, the hollow fiber membranes 210 may also be arranged in the intermediate case 110 in a state where they are divided and housed in two or more cartridges. A fluid inlet / outlet 121 is formed in the cap case 120. One of the cap cases 120, which are connected to both ends of the intermediate case 110, has a fluid inlet / outlet 121 that serves as the first fluid inlet, and the other cap case 121 has a fluid inlet / outlet 121 that serves as the first fluid outlet. The first fluid that flows in through the fluid inlet / outlet 121 that functions as the first fluid inlet passes through the internal conduit [i.e., the lumens] of the hollow fiber membrane 210 housed inside the intermediate case 110, and then flows out to the fluid inlet / outlet 121 that functions as the first fluid outlet.

[0013] The ends of the hollow fiber membranes 210 are potted to the fixing portions 130. The fixing portions 130 bind the hollow fiber membranes 210 together while filling the gaps between the hollow fiber membranes 210 and the gap between the hollow fiber membranes 210 and the intermediate case 110. As a result, each end of the intermediate case 110 is sealed by the fixing portions 130, and a flow path for the second fluid is formed inside. The material of the fixing portions 130 is known and will not be described in detail herein. In the following, an embodiment of the present invention will be described through examples and comparative examples, and there is no intention to limit the scope of the present invention to these examples. (Examples) Example 1 A dope stock solution was prepared by mixing 20% ​​by weight of polystyrene (PS), 6% by weight of polyvinylpyrrolidone (PVP), and 32% by weight of the antioxidant Ce(NO3) with 72% by weight of the solvent N-methylpyrrolidone (NMP). A core solution was then prepared by mixing N-methylpyrrolidone (NMP) and ethanol in a volume ratio of 6:4. The dope stock solution was discharged through the outer tube of a double-tube nozzle, and the core solution was discharged through the inner tube, thereby immersing the spun material in a coagulation tank containing a coagulation solution. The spun material came into contact with the coagulation solution in the coagulation tank and formed a hollow fiber membrane. The coagulation solution used was water and PEG in a 1:1 (v / v) ratio, and the temperature was adjusted to 40°C. The hollow fiber membrane that passed through the coagulation tank was washed with 40°C water in a washing tank and then dried to obtain a hollow membrane. The thickness of the hollow fiber membrane was set to 100 μm. The antioxidant used in Example 1 was Ce(NO3)3, but the same effect as in Example 1 was confirmed when other antioxidants such as ethylenebis(oxyethylene)bis[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] or benzeneamine were used. Example 2 A hollow fiber membrane was produced in the same manner as in Example 1, except that the antioxidant content was changed to 3% by weight and the solvent was changed to 71% by weight. Example 3 A hollow fiber membrane was produced in the same manner as in Example 1, except that the antioxidant content was changed to 5% by weight and the solvent was changed to 69% by weight. Example 4 A hollow fiber membrane was produced in the same manner as in Example 1, except that the antioxidant content was changed to 0.1% by weight and the solvent was changed to 73.9% by weight. Comparative Example 1 Hollow fiber membranes were manufactured using the same method as in Example 1, except that no antioxidant was added and the solvent was changed to 74% by weight. Comparative Example 2 A hollow fiber membrane was produced in the same manner as in Example 1, except that the antioxidant content was changed to 6% by weight and the solvent was changed to 68% by weight. Evaluation Example 1: Evaluation of Humidifying Film Degradation / Decomposition The humidified films prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were immersed in Fenton reagent (3% H2O2, 1 ppm FeSO4) at 80°C for 24 hours, and their molecular weight was analyzed. The change in molecular weight of the humidified film after immersion compared to the humidified film before immersion was measured and is shown in Table 1 below. [Table 1] Percentage of molecular weight reduction = [(Molecular weight of initial humidified film - Molecular weight of humidified film after immersion) / Molecular weight of initial humidified film] × 100 As shown in Table 1 above, when Ce(NO3)3 is added as an antioxidant to the composition of the humidifying film, and when its content increases, it was confirmed that the degradation and decomposition of peroxides and hydroxide radicals are prevented.

[0014] Evaluation Example 2: Performance Evaluation of Humidifying Film (Evaluation method) Water vapor transmission: Water vapor transmission is measured by passing dry air through the hollow and moist air through the shell, and measuring the amount of water vapor transferred to the dry air side after passing through the hollow. After preparing a sample for water vapor transmission measurement, it is connected to an evaluation device, and 70°C, 20 slpm, and 0.1 barg are applied to the dry air side, and a dew point of 75°C, a pressure of 0.8 barg, and a flow rate of 20 slpm are applied to the shell side. The dew point of the portion escaping into the hollow is measured, and the water vapor transmission is calculated. Tensile strength: Tensile strength is measured using a general UTM (universal testing machine). The humidified film is grasped at both ends of the grip and pulled at a speed of 50 mm / min, and the strength at the moment of breakage is measured. Nitrogen permeability: Nitrogen permeability is measured using CFP equipment, with nitrogen at a pressure of 0.5 bar blown into the hollow while the other side of the hollow is sealed with polyurethane. The flow rate of nitrogen escaping to the shell side is measured during this process. Oxygen permeability: Evaluated using the same method as for nitrogen permeability, and only the gas used is converted to air. The hollow fiber membranes prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to measurements of water vapor permeability, tensile strength, nitrogen permeability, and oxygen permeability using the method described above, to confirm whether they possessed the physical properties suitable for use in fuel cell humidifiers. The results are shown in Table 2 below. [Table 2] The hollow fiber membranes treated with antioxidants in Examples 1 to 4 exhibited similar water vapor permeability to Comparative Example 1, which did not have antioxidants applied. This confirms that the antioxidants dispersed within the polymer do not significantly affect the formation and porosity of the hollow fiber membrane, making it suitable for use in fuel cell membrane humidifiers.

[0015] However, as in Comparative Example 2, when the antioxidant is added in excess of 5% by weight, specifically at 6% by weight, the porous structure of the polymer is not sufficiently formed during the hollow fiber membrane formation process, resulting in a decrease in water vapor permeability to less than 0.1, confirming that it is unsuitable for use as a hollow fiber membrane in membrane humidifiers. In other words, the hollow fiber membrane of Comparative Example 2 exhibited a water vapor permeability unsuitable for use in fuel cell membrane humidifiers. Furthermore, both nitrogen and oxygen permeability decreased in Comparative Example 2, which is thought to be due to the excessive presence of the antioxidant within the polymer, preventing sufficient formation of the polymer's porous structure. Based on these results, it appears that when used in amounts of 0.01 to 5 parts by weight, the antioxidant can be used to prevent deterioration of the hollow fiber membrane from oxidizing substances, making it suitable for use as a hollow fiber membrane in fuel cell humidifiers.

Claims

1. A hollow fiber membrane for humidifiers, comprising a polymer and an antioxidant, wherein the antioxidant is present in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the hollow fiber membrane.

2. The hollow fiber membrane for a humidifier according to claim 1, wherein the antioxidant is dispersed within the polymer.

3. The hollow fiber membrane for a humidifier according to claim 1, wherein at least a portion of the antioxidant is exposed on the surface of the polymer.

4. The hollow fiber membrane for a humidifier according to claim 1, wherein the concentration of the antioxidant increases from the inner surface to the outer surface of the hollow fiber membrane.

5. The hollow fiber membrane for a humidifier according to claim 1, wherein the antioxidant comprises an organic antioxidant, a metal antioxidant, an organometallic antioxidant, a HALS (hindered amine light) antioxidant, a sulfur antioxidant, a phosphorus antioxidant, or a combination thereof.

6. The hollow fiber membrane for a humidifier according to claim 5, wherein the antioxidant comprises a metal-based antioxidant.

7. The hollow fiber membrane for a humidifier according to claim 1, comprising 0.1 to 5 parts by weight of the antioxidant.

8. The hollow fiber membrane for a humidifier according to claim 1, wherein the polymer includes polyvinylidene fluoride (PVDF) polymers, polysulfone polymers, sulfonated polysulfone, cellulose acetate, cellulose triacetate, polymethyl methacrylate, nafion, polystyrene (PS) polymers, polytetrafluoroethylene (PTFE) polymers, perfluorosulfonic acid (PFSA) polymers, polyphenylsulfone polymers, polyethersulfone (PES) polymers, polyacrylonitrile (PAN) polymers, polyetherimide (PEI) polymers, polyimide (PI) polymers, or combinations thereof.

9. The hollow fiber membrane for a humidifier according to claim 8, wherein the polymer includes a polystyrene-based polymer.

10. The hollow fiber membrane for a humidifier according to claim 1, wherein the polymer is contained in 10 to 35 parts by weight per 100 parts by weight of the dope stock.

11. The hollow fiber membrane for a humidifier according to claim 1, wherein the thickness of the hollow fiber membrane is 60 to 300 μm.

12. The hollow fiber membrane has a water vapor transmission rate of 0.1 g / s / m² measured under a pressure of 1 bar and a temperature of 80°C. ２ The hollow fiber membrane for a humidifier according to claim 1 is as described above.

13. The hollow fiber membrane has a nitrogen permeability of 100 cc / min / cm² under a pressure of 0.5 bar. ２ The hollow fiber membrane for a humidifier according to claim 1 is as follows:

14. The hollow fiber membrane has an oxygen permeability of 100 cc / min / cm² under a pressure of 0.5 barg. ２ The hollow fiber membrane for a humidifier according to claim 1 is as follows:

15. A method for producing a hollow fiber membrane for a humidifier, comprising the steps of: mixing an antioxidant in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the spinning solution to obtain a spinning solution; spinning the spinning solution through a nozzle into a coagulation tank; and coagulating the spinning solution in the coagulation tank.

16. The step of obtaining the spinning solution includes the step of mixing the antioxidant and the polymer in a solvent, The method for producing a hollow fiber membrane for a humidifier according to claim 15, wherein the solvent comprises at least two solvents selected from a first solvent, a second solvent, and a third solvent.

17. The first solvent comprises butanol, isobutanol, isooctanol, pentanol, isopentanol, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, polyoxyethylene octylphenyl ether, or a combination thereof. The second solvent comprises water, methanol, ethanol, isopropanol, acetone, hexane, pentane, benzene, toluene, carbon tetrachloride, o-dichlorobenzene, polyethylene glycol, or a combination thereof. The method for producing a hollow fiber membrane for a humidifier according to claim 16, wherein the third solvent comprises N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, tetrahydrofuran, tetramethylurea, or trimethyl phosphate.

18. A method for producing a hollow fiber membrane for a humidifier according to claim 15, further comprising a post-processing step after the step of coagulating the spinning solution.

19. The method for producing a hollow fiber membrane for a humidifier according to claim 18, wherein the post-processing step includes a chemical treatment and / or a physical treatment.

20. A humidifier comprising a hollow fiber membrane for humidifiers according to any one of claims 1 to 14.

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