Hollow fiber membrane, hollow fiber membrane module, and humidity control device

Abstract

The object of the present invention is to provide a hollow fiber membrane and a hollow fiber membrane module that have gas barrier properties, excellent water vapor permeability, and can be effectively used as a humidity control device, fuel cell system, etc. [Solution] A hollow fiber membrane having a layer A on its inner surface, wherein the thickness of layer A is 1 μm or more and 12 μm or less, the outer surface of the hollow fiber membrane has a plurality of pores, and the porosity of the outer surface is 5% or more and 30% or less.

Description

[Technical Field]

[0001] The present invention relates to hollow fiber membranes, hollow fiber membrane modules, and humidity control devices. More specifically, this invention relates to hollow fiber membranes, hollow fiber membrane modules, and humidity control devices suitable for use in humidity control units used in fuel cell systems and air conditioning systems. [Background technology]

[0002] Hollow fiber membranes are widely used in medical applications such as blood purifiers for patients with renal failure, and in water treatment applications such as water purifiers. Furthermore, hollow fiber membranes with pores of a size that allows for gas separation exhibit superior gas separation properties among various inorganic membranes and can be used in environments where chemical resistance and heat resistance are required. For this reason, in recent years, the use of hollow fiber membranes has expanded to methods for humidifying fuel gas to retain moisture in electrolyte membranes built into fuel cell systems, and to dehumidify moisture in compressed air in factories.

[0003] When using hollow fiber membranes for humidification in polymer electrolyte fuel cells, automotive applications require large amounts of air humidification, around 5,000 NL / min, while stationary applications often use hot water as the humidification power source. In either case, durability and heat resistance of the hollow fiber membrane are particularly important. Furthermore, it must also possess gas barrier properties to suppress air leakage from the hollow fiber membrane.

[0004] Several types of hollow fiber membranes that selectively permeate water vapor as described above are currently commercially available, but each has different materials and permeation principles. For example, a membrane that uses polyimide resin as the material and is operated by the dissolution diffusion method has excellent heat resistance and strength, but it has the disadvantage of a low water vapor permeability coefficient. Another example is a membrane that uses fluorine-based ion exchange membranes as the material and operates on the principle of ion hydration, which has a high water vapor permeability coefficient but poor heat resistance and the membrane itself is very expensive.

[0005] On the one hand, a membrane that uses a polyetherimide resin as a material and performs humidification and dehumidification by the capillary condensation method aims to achieve both water vapor permeability and heat resistance, and is adopted in many industrial fields. However, since the absolute strength of the membrane is weak and it lacks flexibility especially, when humidifying and dehumidifying a large amount of gas, there is a high possibility that the hollow fiber membrane will be cut.

[0006] As a humidification application for fuel cells, it is generally widely used as an ultrafiltration membrane, a microfiltration membrane, etc., and a polysulfone-based resin with excellent strength stability under wet humidification conditions is also used.

[0007] A cross-sectional structure of a hollow fiber membrane that can achieve both water vapor permeability and membrane strength has been proposed by dry-wet spinning a spinning dope composed of a water-soluble organic solvent solution of a polysulfone-based resin and a vinylpyrrolidone-based resin (Patent Document 1). However, in the above prior art, pore formation on the outer surface of the hollow fiber membrane may be insufficient, and there is a possibility that water vapor permeability cannot be fully exhibited. Also, as a hollow fiber membrane for a water purifier, a manufacturing method in which the outer surface of the hollow fiber membrane has a high aperture has been disclosed (Patent Document 2). However, because it is a structure of an outside pressure type hollow fiber membrane, the inner surface side becomes a low-density porous structure and does not have a dense layer having a pore diameter necessary for gas barrier properties and water vapor permeability.

[0008] Also, Patent Document 3 discloses a manufacturing method for obtaining a hollow fiber membrane with a multilayer structure by passing through a step of forming a high-density inner layer by a thermal-induced phase separation method and then a step of forming a low-density outer layer by a non-solvent-induced phase separation method by a composite spinning technique. However, from the viewpoint of using two or more types of film-forming dope separately and independently controlling and forming the target layer structure, the idea is different from the manufacturing method of the present invention.

[0009] Patent Document 4 also discloses a porous hollow fiber-shaped water vapor permeation membrane of a polysulfone-based resin. Although the aperture ratio on the outer peripheral surface of the hollow fiber membrane is high, since the layer with fine pores on the inner layer side is thick, it becomes a permeation resistance and there is a possibility that the water vapor permeability is not sufficient.

Prior Art Documents

[0010] [Patent Document 1] International Publication No. 2024 / 043095 [Patent Document 2] Patent No. 06973071 [Patent Document 3] Special Publication No. 2023-552734 [Patent Document 4] Patent No. 07122202 [Overview of the project] [Problems that the invention aims to solve]

[0011] The object of the present invention is to provide a hollow fiber membrane and a hollow fiber membrane module that have gas barrier properties, excellent water vapor permeability, and can be effectively used as a humidity control device, fuel cell system, etc. [Means for solving the problem]

[0012] To achieve the above objectives, the present invention has the following configuration.

[0013] A hollow fiber membrane having a layer A on its inner surface, wherein the thickness of layer A is 1 μm or more and 12 μm or less, the outer surface of the hollow fiber membrane has a plurality of pores, and the porosity of the outer surface is 5% or more and 30% or less. [Effects of the Invention]

[0014] The hollow fiber membrane obtained by the present invention is a hollow fiber membrane having layer A on the inner surface side, wherein the thickness of layer A is 1 μm or more and 12 μm or less, the outer surface of the hollow fiber membrane has a plurality of pores, and the porosity of the outer surface is 5% or more and 30% or less, which has the effect of further improving water vapor permeability. [Brief explanation of the drawing]

[0015] [Figure 1]This figure shows a scanning electron microscope image of the inner surface area in a cross-section of a hollow fiber membrane according to an embodiment of the present invention. [Figure 2] This figure shows a scanning electron microscope image of the outer surface of a hollow fiber membrane according to an embodiment of the present invention. [Figure 3] This figure shows a method for measuring water vapor permeability performance. [Figure 4] This is a block diagram of the power supply system for fuel cell vehicles. [Figure 5] This is a schematic diagram of an air conditioner. [Figure 6] This is a schematic diagram of a total heat exchanger. [Modes for carrying out the invention]

[0016] The hollow fiber membrane of the present invention is a hollow fiber membrane having a layer A on its inner surface side, wherein the thickness of layer A is 1 μm or more and 12 μm or less, the outer surface of the hollow fiber membrane has a plurality of pores, and the porosity of the outer surface is 5% or more and 30% or less.

[0017] The present invention will be described below.

[0018] The hollow fiber membrane of the present invention has a pore area of ​​0.1 μm² on the inner surface side. 2 The material has gas barrier properties due to having layer A, which is a region without pores exceeding a certain limit.

[0019] Furthermore, the pore size in the hollow fiber membrane of the present invention is determined by importing an electron microscope image of the hollow fiber membrane into a computer, analyzing it using image analysis software, and quantifying the result. Specifically, the pore size (diameter of the pore) is determined from the area of ​​the pore portion of the image loaded into the image analysis software using the following formula [1].

[0020] Pore ​​diameter [μm]=2×√(pore area / π) [1] Figure 1 shows a scanning electron microscope image of the area near the inner surface 11 in a cross-section of the hollow fiber membrane 10.

[0021] In the hollow fiber membrane of the present invention, the shape of the pores is not particularly limited, but as can be seen from the above formula [1], the pores are approximated as circular and the pore diameter is calculated from their area. Therefore, if the shape is slit-shaped, spindle-shaped, or irregular, and deviates significantly from a circular shape, the discrepancy between the calculated value and the actual shape will be large, so it is more preferable that the pores be elliptical or circular.

[0022] In the hollow fiber membrane of the present invention, the thickness of layer A is preferably 1 μm or more and 12 μm or less, and more preferably 4 μm or more and 9 μm or less. By having a thickness of layer A of 1 μm or more and 12 μm or less, it is possible to lower the water vapor permeability resistance in the hollow fiber membrane and improve water vapor permeability. If the thickness of layer A is less than 1 μm, defects such as pinholes are more likely to form on the inner surface of the hollow fiber membrane, and the durability and gas barrier properties of the hollow fiber membrane decrease. Also, if the thickness of layer A exceeds 12 μm, the structural parts in which the main components of the hollow fiber membrane are aggregated increase, and the water vapor permeability decreases as the water vapor permeability resistance increases.

[0023] The thickness of layer A can be determined by the following method, as described in the examples below: Using a scanning electron microscope (SEM), an image is acquired at a magnification that allows observation of the inner surface cross-section from the vertical cross-section of a single hollow fiber membrane. In the field of view obtained by dividing one image vertically into five sections, the pore area is 0.1 μm². 2 The thickness of the region without pores exceeding a certain size was measured, and the thickness of a total of 5 layers A was obtained. This was done similarly for 20 hollow fiber membranes, and the arithmetic mean of the 100 layer A thicknesses was taken as the thickness of layer A. When extracting hollow fiber membranes from a hollow fiber membrane module, 20 arbitrary membranes were selected, and the thickness of a total of 100 layers A was obtained in the same manner as above, and the result of the arithmetic mean was treated as the thickness of layer A. If layer A is not observed on the inner surface side, an image was taken at a magnification that allows the cross-section of the outer surface side to be observed, and the same operation as above was performed to confirm the location and presence or absence of layer A formation.

[0024] The hollow fiber membrane of the present invention has a plurality of pores on its outer surface, and the porosity of the outer surface is 5% or more and 30% or less. When the porosity of the outer surface of the hollow fiber membrane is 5% or more, it becomes easier to take in water vapor from the outer layer side of the hollow fiber membrane, making it possible to improve water vapor permeability. On the other hand, when the porosity of the outer surface is 30% or less, the outer layer side of the hollow fiber membrane becomes less dense due to weakened aggregation of the main component of the hollow fiber membrane, which can suppress a decrease in durability. From the above viewpoint, the lower limit of the porosity is more preferably 7% or more, and even more preferably 10% or more. Furthermore, the upper limit of the porosity is more preferably 28% or less, and even more preferably 25% or less. Furthermore, means of setting the porosity on the outer surface of the hollow fiber membrane within the above range include, in the method of manufacturing the hollow fiber membrane, adjusting the temperature and humidity atmosphere of the dry zone, the cold air velocity and passage time to control the phase separation rate of the polymer, adjusting the content of hydrophilic polymers, and adjusting the compatibility between the main component of the hollow fiber membrane and the hydrophilic polymers.

[0025] The porosity can be determined by the following method: Electron microscope images of the hollow fiber membrane are imported into a computer and analyzed using image analysis software to obtain a numerical value. Specifically, the porosity can be calculated from the image field size loaded into the image analysis software and the total area [S] of the pores in that image using the following formula [2].

[0026] Open area ratio (%)=S(μm 2 ) / Image field of view size (μm) 2 ) × 100 [2] The above procedure was performed on 30 different hollow fiber membranes, and the arithmetic mean was taken as the result.

[0027] Figure 2 shows a scanning electron microscope image of the outer surface 12 of the hollow fiber membrane.

[0028] Furthermore, it is preferable that the hollow fiber membrane of the present invention has an average pore diameter on its outer surface of 0.10 μm or more and 0.30 μm or less. Having an average pore diameter of 0.10 μm or more and 0.30 μm or less on its outer surface facilitates the diffusion of water vapor from the outer surface to the interior of the hollow fiber membrane, thereby further improving water vapor permeability. From this viewpoint, it is more preferable that the average pore diameter on its outer surface be 0.15 μm or more and 0.25 μm or less. Here, the average pore diameter in the hollow fiber membrane of the present invention is determined by importing an electron microscope image of the hollow fiber membrane into a computer, analyzing it using image analysis software, and quantifying the result. Specifically, the average pore area is calculated using the following formula [3] and the average pore diameter using the following formula [4], based on the sum of the areas of the pore portions and the number of pore portions in the image loaded into the image analysis software.

[0029] Average pore area [μm 2 ] = Total area of ​​the holes / Number of holes [3] Average pore diameter [μm]=2×√(average pore area / π)[4] The above procedure was performed on 30 different hollow fiber membranes, and the arithmetic mean was taken as the result.

[0030] Furthermore, when the outer surface of the hollow fiber membrane of the present invention is observed at a magnification of 10,000 times using an electron microscope, the pore density is 0.5 pores / μm. 2 More than 10 pieces / μm 2 The presence of pores is preferable within the following range, and the presence of pores within this range stabilizes the water vapor permeability performance of the hollow fiber membrane, making it possible to suppress performance degradation during long-term operation. The number of pores can be measured by the following method.

[0031] First, 30 images of the outer surface of the hollow fiber membrane were obtained using a scanning electron microscope (SEM). When extracting hollow fiber membranes from a hollow fiber membrane module, 30 arbitrary fibers were selected. The obtained outer surface images were observed, and the number of all open pores was measured and defined as the total number of open pores. The number of pores per unit area was calculated from the total number of open pores and the screen field size. The number of pores per unit area was similarly calculated for all 30 images, and the arithmetic mean of the 30 data points was defined as the number of pores per unit area.

[0032] In addition, the hollow fiber membrane of the present invention preferably has a liquid retention rate of 150% by weight or more and 300% by weight or less, more preferably 170% by weight or more and 280% by weight or less, when measured by immersing in pure water at 80°C for 30 seconds. The liquid retention rate in the present invention is an index indicating the ease of water uptake from the outer surface of the hollow fiber membrane, and is a value calculated by the following formula [5].

[0033] Liquid retention rate [% by weight] = ((W w - W d ) / W d ) × 100 [5] In the above formula [5], W w = weight of the hollow fiber membrane [g], W d = dry weight of the hollow fiber membrane [g]. The weight of the hollow fiber membrane here refers to the weight of the hollow fiber membrane moistened by immersing in pure water at 80°C for 30 seconds. Also, the dry weight is the weight when the hollow fiber membrane is dried under reduced pressure at 1 mmHg or less and 40°C, and the weight measurement is performed every 24 hours, and the weight change is 1% or less compared to the measurement result 24 hours ago.

[0034] The hollow fiber membrane of the present invention preferably has a layer B, which is a region formed including macrovoids, when observing the membrane structure in the direction of the cross-section perpendicular to the longitudinal direction of the hollow fiber membrane (vertical cross-section) at a magnification of 1,000 times using an electron microscope. The macrovoid in the present invention is a pore having a major axis of the pore exceeding 20 μm. The major axis of the pore can be measured by the following method.

[0035] First, five cross-sections are obtained from the hollow fiber membrane. When extracting hollow fiber membranes from a hollow fiber membrane module, any five fibers are extracted. Images of the obtained membrane cross-sections are taken using an SEM at a magnification that is easy to measure. For the pores that appear large, the longest inner diameter is measured and defined as the major axis. If the major axis of a pore exceeds 20 μm, that pore is treated as a macrovoid, and the region where that macrovoid substantially exists is defined as layer B. Here, "substantially present" means that the total area occupied by the macrovoid in the area of ​​layer B is 20% or more. If even one of the five locations substantially contains a macrovoid, the layer is considered to have layer B. Furthermore, the hollow fiber membrane of the present invention preferably has a layer C adjacent to layer B, which is a region where macrovoids are substantially absent, located outside layer B, from the viewpoint of combining water vapor permeability and durability of the hollow fiber membrane. Here, substantially absent macrovoids means that the total area occupied by macrovoids in the area of ​​layer C is less than 20%. By having a total area occupied by macrovoids in the area of ​​layer C of less than 20%, both durability and water vapor permeability of the hollow fiber membrane can be achieved. In addition, the hollow fiber membrane of the present invention preferably has an average major diameter of pores contained in layer C in a vertical cross-section of 0.10 μm or more and 0.50 μm or less. By having an average major diameter of pores contained in layer C of 0.10 μm or more, it is less likely to resist the intake of water vapor from the outside air, and high moisture permeability is provided. In addition, by having an average major diameter of pores contained in layer C of 0.50 μm or less, it is possible to suppress the occurrence of rupture initiation points when pressure is applied to the hollow fiber membrane, and high durability can be provided. It is preferable that layers A, B, and C are formed in this order from the inner surface side of the hollow fiber membrane.

[0036] In the hollow fiber membrane of the present invention, it is preferable that the ratio of the average pore diameter of layer C to the average pore diameter of layer B in the vertical cross-section is 0.005 or more and 0.050 or less. By having a ratio of 0.005 or more and 0.050 or less to the average pore diameter of layer C to the average pore diameter of layer B, it is possible to improve the durability while increasing the water vapor permeability of the hollow fiber membrane. For this reason, 0.005 or more and 0.040 or less is more preferable, and 0.005 or more and 0.030 or less is even more preferable. Here, the average pore diameter of layer B refers to the average pore diameter of macrovoids present in layer B.

[0037] Furthermore, in the vertical cross-section, the pore area is 1260 nm. 2 If we define layer a as a layer having only the following pores, it is preferable that layer a is contained within layer A, and that the thickness of layer a in a perpendicular cross-section is 0.1 μm or more and 0.5 μm or less. Here, layer a is defined as a layer with a pore area of ​​1260 nm when a cross-section perpendicular to the longitudinal direction of the hollow fiber membrane is observed using a scanning electron microscope (SEM). 2 This refers to a layer having only the following pores. The method for measuring the thickness of layer a is described in the examples below. Using a SEM, one image is taken from the vertical cross-section of a single hollow fiber membrane, and in the image obtained by dividing the single image vertically into three parts, the pore area is 1260 nm. 2 The thickness of the region containing only the following pores was measured, and a total of 3 layer a thicknesses were obtained. This was done similarly for 20 hollow fiber membranes, and the arithmetic mean of the 60 layer a thicknesses was taken as the layer a thickness. When extracting hollow fiber membranes from the hollow fiber membrane module, 20 membranes were randomly selected, and the 60 layer a thicknesses were obtained similarly, and the arithmetic mean was treated as the layer a thickness.

[0038] The hollow fiber membrane of the present invention preferably has a porosity of 65% to 80% throughout the entire membrane, and more preferably 68% to 77%. By having a porosity of 65% to 80% throughout the entire membrane, the density of the polymer skeleton of the main component in the hollow fiber membrane increases, making it possible to improve durability. If the porosity of the entire membrane is less than 65%, the amount of structural parts where the main component of the hollow fiber membrane has aggregated increases, which may reduce water vapor permeability. If it exceeds 80%, the polymer aggregation of the main component of the hollow fiber membrane weakens, making it easier for coarse pores to form throughout the thickness of the hollow fiber membrane, which may reduce durability. The porosity can be determined by the following method. First, hollow fiber membranes of a certain length are dried in a dryer set to 50°C for 24 hours. Next, the number of hollow fiber membranes is adjusted so that the weight after drying is in the range of 1g to 5g. The volume of the hollow fiber membrane is calculated from the number and length of the hollow fiber membranes used, as well as the outer and inner diameters of the membranes. The porosity is then calculated using the dry weight and the density of the polymer, which is the main component of the hollow fiber membrane.

[0039] The hollow fiber membrane of the present invention has an oxygen permeability of 0 cc / min / cm at a pressure of 0.7 bar. 2 More than 100cc / min / cm 2 The following is preferable: 80 cc / min / cm 2 The following is more preferable: 50 cc / min / cm 2 The following is even more preferable: 25 cc / min / cm 2 The following is most preferable: The oxygen permeability is 100 cc / min / cm². 2 This is because exceeding this limit could effectively reduce the water vapor permeability performance of the hollow fiber membrane.

[0040] The hollow fiber membrane of the present invention preferably has a tensile strength of 100 gf / fiber or more, more preferably 200 gf / fiber or more, and even more preferably 250 gf / fiber or more. By having layer A on the inner surface side of the hollow fiber membrane of the present invention, the mechanical and physical properties are improved and a tensile strength satisfying the above range can be ensured.

[0041] The materials constituting the hollow fiber membrane of the present invention are not particularly limited, but examples include polysulfone polymers, polystyrene, polyurethane, polyethylene, polypropylene, polycarbonate, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, and polyester. Among these, it is preferable that the hollow fiber membrane contains a polysulfone polymer from the viewpoint of excellent heat resistance and ease of forming a hollow fiber membrane. Furthermore, although the content of the polysulfone polymer is not particularly limited, it is preferable that the polysulfone polymer is the main component of the hollow fiber membrane.

[0042] Here, polysulfone polymers are polymers having sulfone groups in their main chain, and examples include polysulfone, polyphenylsulfone, polyethersulfone, and polyarylethersulfone. Furthermore, the main component refers to the raw material that is present in an amount of 90% to 100% by mass relative to 100% by mass of the entire hollow fiber membrane.

[0043] In the present invention, a polysulfone polymer represented by the following chemical formulas (1) and / or (2) is preferably used as the main component of the hollow fiber membrane, but is not limited to these. In the formula, n is an integer of 1 or more, preferably 50 to 80. If n has a distribution, the average value of n is taken as n.

[0044] [ka]

[0045] The polysulfone polymer that can be used in the hollow fiber membrane of the present invention is preferably a polymer consisting only of repeating units represented by formula (1) and / or (2) above, but it may also be copolymerized with other monomers or be a modified form, as long as it does not hinder the effects of the present invention. When copolymerized with other monomers, the copolymerization ratio of the other monomers is preferably 10% by mass or less of the total polysulfone polymer.

[0046] Specific examples of polysulfone polymers that can be used in the hollow fiber membrane of the present invention include "Udel" polysulfone P-1700, P-3500 (manufactured by Solvay), "Ultrasson" S3010, P3010, S6010 (manufactured by BASF), "Victrex" (manufactured by Sumitomo Chemical Co., Ltd.), "Radel" polyphenylsulfone R-5000NT (manufactured by Solvay), "Belladel" polyethersulfone 3000MP, 3600MP (manufactured by Solvay), and "Ultrasson" E (manufactured by BASF).

[0047] While there are various methods for manufacturing the hollow fiber membrane module of the present invention, depending on its application, the process can be broadly divided into two steps: the manufacturing step of the hollow fiber membrane and the step of assembling the hollow fiber membrane into a module.

[0048] When a polysulfone polymer is the main component of the hollow fiber membrane material of the present invention, it is preferable that a hydrophilic polymer is included. Here, a hydrophilic polymer refers to a water-soluble polymer compound or a polymer compound that, even if not water-soluble, interacts with water molecules through electrostatic interactions or hydrogen bonding.

[0049] Examples of hydrophilic polymers include polyalkylene oxides such as polyethylene oxide and polypropylene oxide, polyvinyl alcohol, polyethylene glycol, polydimethylmethoxyacrylate, polydimethylacrylamide, polyvinylpyrrolidone, copolymers of acrylic acid and vinylpyrrolidone, and vinylpyrrolidone copolymers. Among these, hydrophilic polymers with a glass transition temperature higher than 150°C are preferred because they can provide hollow fiber films with excellent heat resistance.

[0050] Specific examples of the aforementioned vinylpyrrolidone polymers include vinylpyrrolidone polymers such as "Coridon" K12PF, K17PF, K25, K30, K90F, "Socalan" K17P, K30P, K80P, K90P, "Coridon" VA64, VA64 fine, "Socalan" VA64P (manufactured by BASF), and povidone K30, K78 / 81, K85, K90, K120 (manufactured by Ashland).

[0051] The polyvinylpyrrolidone mentioned as an example is preferable for humidification applications in fuel cell systems because of its excellent compatibility with polysulfone polymers and its high glass transition temperature of 180°C. In other words, it is particularly preferable that the hollow fiber membrane of the present invention contains both a polysulfone polymer and a vinylpyrrolidone polymer.

[0052] Furthermore, in the manufacturing process of hollow fiber membranes, the components of the hollow fiber membrane, such as polysulfone polymers and vinylpyrrolidone polymers, are dissolved in a solvent to prepare the spinning solution. Here, high-boiling point polar solvents such as dimethylacetamide (hereinafter abbreviated as DMAc) and N-methylpyrrolidone are preferred as solvents, but other combinations can be used as long as they can be dissolved uniformly.

[0053] Methods for achieving a thickness of 1.0 μm to 12.0 μm and a thickness of 0.1 μm to 0.5 μm in a hollow fiber membrane include using a poor solvent that has the effect of agglomerating and solidifying the film-forming stock solution, and controlling the viscosity and polymer agglomeration during phase separation by adjusting the concentration of the polysulfone polymer in the film-forming stock solution and the mixing ratio of the polysulfone polymer to the vinylpyrrolidone polymer. A poor solvent is a solution that is insoluble in the film-forming stock solution. During film formation, layers a and A can be formed by contacting the film-forming stock solution with a core solution containing a poor solvent immediately after dispensing the film-forming stock solution from the nozzle. However, since polymer agglomeration is too fast with only a poor solvent, making film formation difficult, it is preferable to use a core solution which is a mixture of a poor solvent and a solvent that dissolves resin (a good solvent).

[0054] One method for achieving a porosity of 65% to 80% across the entire hollow fiber membrane is to adjust the skeletal density of the polymer that forms the main component of the hollow fiber membrane. In other words, in this method, it is important to control the concentration of the polysulfone polymer in the film-forming stock solution.

[0055] The concentration of the polysulfone polymer in the film-forming solution is preferably 18% by mass or more and 35% by mass or less of the total film-forming solution. More preferably, it is 23% by mass or more and 30% by mass or less. If the concentration of the polysulfone polymer in the film-forming solution is less than 18% by mass, the porosity of the hollow fiber membrane will be high, and its durability will tend to be low.

[0056] In order to form layer B, which has macrovoids, in a vertical cross-section, it is important to control the phase separation rate and the void growth rate by designing the film-forming stock solution and the core solution. Specifically, the viscosity of the film-forming solution is preferably 1 Pa·s to 10 Pa·s, and more preferably 2 Pa·s to 8 Pa·s. If the viscosity of the film-forming solution is higher than 10 Pa·s, layer A and layer a tend to become thicker, resulting in lower water vapor permeability. In addition, it may not be possible to form layer B which has macrovoids. If the viscosity of the film-forming solution is lower than 1 Pa·s, layer a tends to become thinner, resulting in a hollow fiber membrane with low strength and a weak membrane.

[0057] Furthermore, even when using the same polymer, using a polymer with a larger molecular weight will increase the viscosity of the film-forming solution, while using one with a smaller molecular weight will decrease the viscosity. Additionally, viscosity changes depending on the amount added. It is necessary to select the type of polymer, molecular weight, and amount added so that the viscosity of the film-forming solution is within the range of 1 Pa·s to 10 Pa·s.

[0058] Regarding the solvent ratio of the core solution, increasing the ratio of organic solvents that dissolve the polymer in the film-forming stock solution (good solvents: aprotic polar solvents such as dimethylformamide, NN-dimethylacetamide, and N-methyl-2-pyrrolidone) slows down polymer aggregation during film formation, making it less likely for macrovoids to form. If the ratio of solvents insoluble in the polymer of the film-forming stock solution (poor solvents) is high, rapid aggregation occurs between the core solution and the film-forming stock solution, making it easier for macrovoids to form. In other words, the formation of macrovoids can also be controlled by adjusting the type and ratio of solvents in the core solution. The concentration of good solvents in the core solution is preferably 10% to 60% by mass, and more preferably 20% to 50% by mass.

[0059] Furthermore, the size of the voids can be controlled by combining the film-forming stock solution with a low-viscosity core liquid such as water, a low-viscosity solvent, or a water / low-viscosity solvent solution, or a highly viscous core liquid such as a solvent containing a polymer such as glycerin or polyvinylpyrrolidone.

[0060] The vinylpyrrolidone polymer added to the film-forming stock solution as the hydrophilic polymer has a weight-average molecular weight of approximately 1,000 (equivalent to K-15) to 1,200,000 (equivalent to K-90), preferably approximately 40,000 (K-30) to 1,200,000 (equivalent to K-90), and is preferably used in a ratio of 5 to 50% by mass, more preferably 8 to 30% by mass, per 100% by mass of the polysulfone polymer. If the amount is less than 5% by mass relative to the polysulfone polymer, hydrophilicity cannot be imparted to the hollow fiber membrane surface, and there is a concern that the affinity for water vapor will be low. If the amount exceeds 50% by mass, the strength of the hollow fiber membrane may decrease, making film formation difficult.

[0061] The hollow fiber membrane of the present invention preferably has an inner diameter of 500 μm or more and 1200 μm or less. If the inner diameter is less than 500 μm, when a high flow rate of air is passed through the hollow portion of the hollow fiber membrane, the pressure from the inlet to the outlet of the hollow portion increases, and in the worst case, the hollow fiber membrane may break. On the other hand, if it exceeds 1200 μm, the airflow outside the hollow fiber membrane may become uneven in a module equipped with the hollow fiber membrane, and the hollow fiber membrane may not be able to be used effectively. Also, if the hollow fiber membrane is too thick, the size of the module tends to become large, which is not suitable for space saving. For this reason, the inner diameter is preferably 500 μm or more and 1200 μm or less.

[0062] Furthermore, the thickness of the hollow fiber membrane is preferably between 60 μm and 200 μm. If the thickness is less than 60 μm, the rupture strength of the hollow fiber membrane decreases, and the membrane may break when a high flow rate of air is applied. If the thickness exceeds 200 μm, the structural control stability during film formation of the hollow fiber membrane is lacking, and the reproducibility of film formation in the void portions of the hollow fiber membrane may be poor. Moreover, if the thickness is too high, the permeability resistance in the film-thickened areas increases, and the water vapor permeability decreases, so it is preferable to keep the thickness within the above range.

[0063] Furthermore, in order to enhance water vapor permeability, the water permeability of the hollow fiber membrane of the present invention is preferably in a range of a certain small amount rather than being zero.

[0064] The hollow fiber membrane of the present invention is preferably used as a dehumidifying hollow fiber membrane because of its excellent water vapor permeability. This dehumidifying hollow fiber membrane is preferably used, for example, as a fuel cell humidifying membrane or a dehumidifying membrane for air conditioners.

[0065] The hollow fiber membrane module of the present invention comprises a hollow fiber membrane for dehumidification and humidification of the present invention, housed in a bundle case having an opening on its side for fluid conduction. The shape of the bundle case is not particularly limited, but examples include cylindrical or substantially rectangular. From the viewpoint of easily filling the inside of the bundle case with hollow fiber membrane, a cylindrical shape is preferred.

[0066] More specifically, a hollow fiber membrane module of the present invention is created by filling a cylindrical or rectangular bundle case with the hollow fiber membrane for dehumidification and humidification of the present invention, and fixing both ends of the hollow fiber membrane with a potting material. As the potting material, polyurethane, epoxy, silicone, nylon, etc., can be appropriately selected and used.

[0067] One method for producing the hollow fiber membrane of the present invention is as follows: A film-forming stock solution (the concentration of the polysulfone polymer is preferably 18% to 35% by mass, and more preferably 23% to 30% by mass) is prepared by dissolving a polysulfone polymer and a vinylpyrrolidone polymer in a mixed solution of a good solvent for polysulfone (N,N-dimethylacetamide, dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, dioxane, etc.) and a poor solvent, and a core liquid is flowed inside when the stock solution is discharged from a double annular nozzle. After running through a dry zone humidified by cold air, the stock solution is allowed to solidify in a solidification solution. At this time, because the humidity of the dry zone has an effect, it is possible to accelerate the phase separation behavior near the outer surface by supplying moisture from the outer surface of the membrane while running through the dry zone, thereby expanding the pore size and consequently reducing the permeation resistance during humidification. However, if the wind speed or relative humidity of the cold air is too high, solidification of the raw material at the outer surface becomes dominant, which conversely reduces the pore size and tends to increase the permeation resistance during humidification. Therefore, a wind speed of 0.1 to 1.0 m / s is preferable for the cold air. Furthermore, a relative humidity of 50 to 90% is preferable for the cold air. In addition, for process suitability, it is preferable to use a core solution composition based on the solvent used in the film-forming raw material. As for the core solution concentration, for example, when N,N-dimethylacetamide is used, an aqueous solution of 10 to 60% by mass, and more preferably 20 to 50% by mass, is used.

[0068] The solidified hollow fiber membrane is washed with warm water between 40°C and 90°C and then wound up. If the washing temperature is below 40°C, the cleaning of organic solvents and other substances may be insufficient, and substances leached from the hollow fiber membrane may affect its use. If the washing temperature exceeds 90°C, the hydrophilic polymer may be washed excessively, which may reduce the hydrophilicity of the hollow fiber membrane.

[0069] Next, a dry hollow fiber membrane is obtained by heat treatment to fix the desired void size. Heat treatment involves drying the wet hollow fiber membrane, thereby reducing the size of the voids. After this treatment, moisturizing the hollow fiber membrane (by adding glycerin or filling with water) becomes unnecessary.

[0070] As a heat treatment method for hollow fiber membranes, it is preferable to divide the hollow fiber membrane into several hundred to several thousand strands and dry them in a dry heat dryer at 40°C to 170°C for 30 minutes or more. More preferably, the temperature is 50°C to 170°C, and even more preferably 50°C to 150°C.

[0071] If the drying temperature is lower than 40°C, drying will take longer, and depending on the external atmosphere, temperature control may be difficult, making it impossible to control the size of the voids. If the drying temperature is higher than 170°C, when using polysulfone polymers, the temperature will approach the glass transition point, which may damage the hollow fiber membrane. A drying time of 30 minutes or more is preferable. More preferably, it is 5 hours or more. There is no particular upper limit for the drying time, but considering work efficiency, it is preferable to keep it within 72 hours. If the drying time is shorter than 30 minutes, it may not be possible to completely remove the moisture from the hollow fiber membrane, and there may be areas that have not been heat-treated. In this case, areas where the voids in the hollow fiber membrane have shrunk and areas where they have not shrunk may coexist, resulting in insufficient separation of moisture in the water vapor and air, which may lead to air leakage. In addition, when heat is applied during use, the size of the voids in areas where the voids have not shrunk may change, which may cause fluctuations in the initial performance.

[0072] The method for producing the hollow fiber membrane module of the present invention is not particularly limited, but one example is as follows. First, the hollow fiber membrane is cut to the required length and placed in a bundle case. Then, temporary caps are placed on both ends, and potting material is placed in both ends of the hollow fiber membrane. At this time, a preferred method is to place the potting material while rotating the module with a centrifuge, as this ensures that the potting material is filled uniformly. After the potting material has solidified, both ends of the hollow fiber membrane are cut so that both ends are open, thereby obtaining the hollow fiber membrane module. <Potential applications of hollow fiber membrane modules> The hollow fiber membrane module of the present invention is applicable to hydrogen production equipment, carbon dioxide separation and recovery equipment, exhaust gas separation and recovery equipment, natural gas separation equipment, deodorizing equipment, humidity control equipment, dehumidifiers, humidifiers, dehumidifying and humidifying equipment and other air conditioners, fuel cell systems, desiccant air conditioning systems, total heat exchangers, and the like. <Humidity control device> Next, a humidity control device equipped with a hollow fiber membrane module according to an embodiment of the present invention will be described. This humidity control device is a device that exchanges water vapor between two fluids via a hollow fiber membrane. For example, by supplying water or air containing water vapor to the inside of the hollow fiber membrane and supplying air to the outside of the hollow fiber membrane, water vapor permeates to the outside of the hollow fiber membrane, humidifying the air supplied to the outside of the hollow fiber membrane. Alternatively, for example, by supplying dry air or a hygroscopic liquid such as an aqueous lithium chloride solution to the inside of the hollow fiber membrane and supplying air containing water vapor to the outside of the hollow fiber membrane, water vapor permeates through the hollow fiber membrane, dehumidifying the air outside the hollow fiber membrane. The humidity control device of the present invention can be suitably used in air conditioners, fuel cell systems, and total heat exchangers, but it can also be applied to other devices such as inkjet printers and composting equipment. <Fuel cell system> Next, a fuel cell system equipped with a hollow fiber membrane module according to an embodiment of the present invention will be described. This fuel cell system can be applied, for example, to fuel cell vehicles and household fuel cells.

[0073] A fuel cell system comprises at least the hollow fiber membrane module (30) and a fuel cell (31) described above. While there are no particular limitations on the examples of this fuel cell system, one example is a system in which humidified air and / or hydrogen are supplied to the fuel cell using the hollow fiber membrane module while simultaneously providing power. In the case of a fuel cell vehicle, for example, as shown in Figure 4, the power obtained is supplied to the motor (33) and battery (34) via a power control unit (32). Furthermore, the hollow fiber membrane module (30) functions as a humidifier and is housed in a metal or resin casing. The required specifications can be adjusted by freely changing the number of hollow fiber membrane modules installed depending on the application. The fuel cell system can also be used as a mobile vehicle. Examples of mobile vehicles include two-wheeled or four-wheeled automobiles, ships, and aircraft. <Air conditioner> Next, an air conditioner equipped with a hollow fiber membrane module according to an embodiment of the present invention will be described. This air conditioner is a device that controls humidity in general households, buildings, offices, factories, etc., such as a humidifier, dehumidifier, dehumidifying and humidifying unit, or air conditioner.

[0074] The air conditioner of the present invention is a device that adjusts the humidity of the incoming outside air (46) by the hollow fiber membrane module described above. An example of a schematic diagram of the air conditioner is shown in Figure 5. When outside air (46) is taken into the air conditioner (40), it passes through the air filter (41), cooling coil (42), heating coil (43), hollow fiber membrane module (44), and blower (45) in that order and is supplied to the room. The cooling coil (42) and heating coil (43) operate depending on whether the room needs to be humidified or dehumidified. Alternatively, humidification or dehumidification may be performed by adding a desiccant to the hollow fiber membrane of the hollow fiber membrane module (44). <Total heat exchanger> Next, a total heat exchanger equipped with a hollow fiber membrane module according to an embodiment of the present invention will be described. A total heat exchanger is a device that ventilates by exchanging heat and water vapor between indoor air and outdoor air, and is widely used in houses, buildings, and factories as an energy-saving measure.

[0075] The total heat exchanger of the present invention is a device that exchanges heat and water vapor in the air while suppressing pressure loss between the indoor and outdoor units using the hollow fiber membrane module described above. A schematic diagram of an example of a total heat exchanger is shown in Figure 6. The total heat exchanger (50) has an outdoor intake port (52) for drawing in outside air (59) and an outdoor outlet port (54) for exhausting indoor air (58) on the outdoor side of the hollow fiber membrane module (51), while the indoor side of the hollow fiber membrane module (51) has an outdoor air supply passage (53) for supplying outside air (59) into the room and an indoor air discharge passage (55) for releasing indoor air (58) to the outside.

[0076] Furthermore, a fan (56) for exhausting indoor air (58) is provided between the outdoor air outlet (54) and the hollow fiber membrane module (51), and a fan (57) for taking in outside air (59) is provided between the outside air supply passage (53) and the hollow fiber membrane module (51). By using the total heat exchanger (50), the outside air (59) exchanges water vapor and heat with the exhausted indoor air (58) via the hollow fiber membrane module (51) and is supplied to the room through the outside air supply passage (53), thus eliminating the need to add excess latent heat and sensible heat to the outside air (59). [Examples]

[0077] The present invention will be described in more detail below based on examples. However, the present invention is not limited to the following examples. Each evaluation method in the examples is described in (1) to (12) below.

[0078] (1) Dimensional measurement of hollow fiber membrane Hollow fiber membranes were cut with a single blade in the direction of film thickness and set in a microwatcher (KEYENCE VH-Z100). If the cross-section of the hollow fiber membrane was crushed during cutting, the cutting was repeated until it was nearly perfectly circular. The cross-section of the hollow fiber membrane was observed with a 1000x lens, and the film thickness width of the hollow fiber membrane was specified on the monitor screen projecting the cross-section, and the value displayed on the monitor screen was read. The inner diameter of the hollow fiber membrane was also displayed on the monitor screen by specifying the width of the hollow section. The same measurement was performed on 30 hollow fiber membranes, and the average value of the 30 measurement data points was calculated to determine the inner diameter and film thickness of the hollow fiber membrane.

[0079] (2) Preparation of samples for SEM observation of hollow fiber membrane cross-sections The hollow fiber membranes obtained by film formation were moistened by immersing them in water for more than one hour, then frozen with liquid nitrogen and quickly folded to prepare samples for cross-sectional observation of the hollow fiber membranes. If the voids in the hollow portion or the film thickness portion of the hollow fiber membrane were blocked, the sample preparation was repeated. Blockage of the hollow portion may occur when the hollow fiber membrane deforms in the direction of stress during the cutting process.

[0080] In each of the following methods, when using SEM images, the sample for observation was prepared and the image obtained using the method described herein.

[0081] (3) Thickness measurement of layer A A 5,000x magnification image of the inner surface cross-section of the hollow fiber membrane was captured using a scanning electron microscope (SEM) and imported into a computer. Next, the number of pixels of a scale bar indicating a known length in the image was measured using image processing software, and the length per pixel (μm) was calculated. The size of the acquired image was 25.4 μm wide x 19.05 μm high. The image contrast and brightness were adjusted to make the pores of the mesh structure easier to recognize, with the pore areas made black and the membrane areas white. A threshold was then set, and the image was binarized and analyzed.

[0082] The lower limit area of ​​pores to be detected during image analysis is 0.1 μm. 2 Set to a pore area of ​​0.1 μm² 2 Pores exceeding 0.1 μm² are colored with a fluorescent color, and the pore area is 0.1 μm². 2A layer without pores exceeding a certain value was defined as layer A, and the thickness of layer A was measured in the direction from the inner surface to the outer surface.

[0083] The captured image (25.4 μm wide × 19.05 μm high) was divided vertically into five sections, obtaining five images with a field of view of 25.4 μm wide × 3.81 μm high. A straight line perpendicular to the surface was drawn in the thickness direction of the hollow fiber membrane, that is, from the inner surface side where layer A is located to the outer surface side. The inner surface where layer A is located and the closest point on the straight line to the inner surface with a pore area of ​​0.1 μm were identified. 2 The distance between the end of the pore exceeding a certain size on the straight line mentioned above and the end of the pore on the side where layer A is located (the end closer to layer A) was defined as the thickness of layer A. In the field of view of the 5,000x image, the pore area was 0.1 μm². 2 If no holes exceeding a certain size were found and analysis was not possible, images were taken with appropriately adjusted magnification, and the thickness of layer A was measured in the same manner as above. Five thicknesses of layer A were obtained for each captured image. The above procedure was repeated for 20 captured images, and the average value of a total of 100 data points was calculated and used as the thickness of layer A.

[0084] (4) Measurement of the porosity, average pore diameter, and number of pores per unit area of ​​the outer surface of the hollow fiber membrane A 10,000x magnification image of the outer surface of the hollow fiber membrane was captured using a SEM (S-5500, Hitachi High-Technologies Corporation) and imported into a computer. Next, the image was processed using image processing software. The SEM image was binarized to obtain an image inverted, with the pore areas in black and the structural polymer areas in white. The total pore area S was read, and the porosity (%) per image was calculated using the following formula.

[0085] Open area ratio (%)=S(μm 2 ) / Image field of view size (μm) 2 ) × 100 Similarly, the average pore size was also analyzed using image processing software. The SEM image was binarized to obtain an image in which the pores were black and the structural polymer parts were white. Total pore area S (μm²) 2 Read the number of black holes (hereinafter referred to as the total number of open holes) and the average pore area (μm²) using the following formula. 2 The average pore area (μm²) was calculated. 2The average pore size (μm) was calculated from the given data. Furthermore, this calculation assumed that the pore shape was perfectly circular.

[0086] Average pore area (μm 2 ) = S(μm 2 ) / Total number of openings Average pore diameter (μm)=2×√(average pore area / π) Furthermore, regarding the number of pores per unit area, the total number of open pores obtained from the above analysis and the screen viewing size (μm) are also considered. 2 ) was calculated using the following formula.

[0087] Number of pores per unit area (pores / μm) 2 ) = Total number of open holes / Screen viewing area (μm) 2 ) The above procedure was performed on 30 different hollow fiber membranes, and the arithmetic mean was taken as the result.

[0088] (5) Measurement of the fluid retention rate of hollow fiber membranes Ten hollow fiber membranes were prepared, each 20 cm long with the ends aligned. Approximately 1 cm of each end was heat-sealed using a heat sealer to create a sample with the hollow portion of the membrane completely closed. The prepared sample was dried under reduced pressure at 40°C at a pressure of 1 mmHg or less. Weight measurements were taken every 24 hours, and the dry weight (W) was defined as the weight when the weight change compared to the measurement 24 hours prior was less than 1%. d )

[0089] A constant temperature bath filled with pure water was heated to 80°C, and once it stabilized at 80°C for more than 30 minutes, the sample was immersed in it. After 30 seconds of immersion, the sample was removed from the constant temperature bath, and only the water droplets adhering to the sample surface were wiped off with gauze. The weight of the sample, which had been moistened by the 80°C pure water absorbed from the outer surface of the hollow fiber membrane, was measured, and this was used as the weight of the hollow fiber membrane (W). w The fluid retention rate was calculated using the following formula.

[0090] Retention rate [wt%]=((W w -W d ) / W d ) × 100 (6) Measurement of layer B Multiple 1,000x magnification images of the hollow fiber membrane cross-section were taken using a SEM. These images were then combined into a single image to allow observation of the entire cross-section and imported into a computer. Next, the number of pixels of the scale bar indicating a known length within the SEM image was measured using image processing software, and the length per pixel (μm) was calculated. The size of the imported image was 126.98 μm wide × 95.24 μm high. The contrast and brightness were adjusted to make the pores in the mesh structure easier to recognize, with the pore areas made black and the membrane areas white. After setting a threshold, the image was binarized and analyzed.

[0091] For macro-sized coarse pores that were clearly observed to be large in the image, the major axis in the thickness direction of the hollow fiber membrane was measured, and coarse pores with a major axis exceeding 20 μm were treated as macrovoids. By binarization, the area of ​​the pore portion of each macrovoid was obtained by analyzing it with image processing software. The area (μm) of all macrovoids observed on the cross-section of the hollow fiber membrane was obtained using a similar procedure. 2 ) is calculated, and the total area VA (μm²) of the macrovoids is calculated. 2 The following was calculated. Here, if macrovoids exist in multiple layers in the film thickness direction in the cross-section of the hollow fiber membrane, only the macrovoids formed on the innermost surface were analyzed.

[0092] Next, in the macrovoids analyzed above, the area C1 (μm²) of the approximate circle formed by joining the ends closest to the inner surface of the macrovoids observed in the cross-section of the hollow fiber membrane is calculated. 2 ) and the edges of the macrovoids closest to the outer surface are joined together to form the area C2 (μm²) of the approximate circle. 2 The area of ​​the layer where macrovoids exist is calculated using the following formula BA(μm²) 2 ) was calculated.

[0093] BA(μm 2 ) = C2(μm 2 )-C1(μm 2 ) Furthermore, the area BA (μm²) of the layer where macrovoids exist is also a region. 2 ) and the total area of ​​the macrovoid (μm 2The percentage (%) occupied by macrovoids was calculated using the following formula. If the percentage of macrovoids was 20% or more, it was considered that macrovoids were substantially present, and that region was treated as layer B.

[0094] Macrovoid occupancy rate (%) = VA / BA × 100 Furthermore, the total area VA (μm²) of the above macrovoids is also included. 2 The average macrovoid area was calculated from the total number of macrovoids. Furthermore, the average macrovoid area (μm) was calculated. 2 The average pore size (μm) was calculated from the above. Furthermore, this calculation assumed that the pore shape of the macrovoids was perfectly circular. The above average pore size was treated as the average pore size of layer B.

[0095] Average macrovoid area (μm 2 ) = VA(μm 2 ) / Total number of macrovoids Average pore diameter (μm) = 2 × √ (average macrovoid area / π) (7) Measurement of layer C Similar to (6) above, multiple 1,000x magnification images of the hollow fiber membrane cross-section were taken using SEM, and the images were merged into a single image so that the entire cross-section of the hollow fiber membrane could be observed, and then imported into a computer. Next, the number of pixels of the scale bar indicating a known length in the SEM image was measured using image processing software, and the length per pixel (μm) was calculated. The size of the imported image was 126.98 μm wide × 95.24 μm high. The contrast and brightness were adjusted to make the pores of the mesh structure easier to recognize, the pore areas were made black and the membrane areas white, and then a threshold was set to obtain a binarized image, which was then analyzed.

[0096] The area C2 (μm²) of the approximate circle formed by joining the ends of the macrovoids closest to the outer surface, as calculated in (6) above. 2 ) and the outer surface of the hollow fiber membrane are joined together to form an approximate circle area C3 (μm²) 2 From this, the area CA (μm²) of the layer adjacent to layer B is calculated using the following formula. 2 ) was calculated.

[0097] CA(μm 2) = C3(μm 2 )-C2(μm 2 ) Next, the total area of ​​the pore portion of the macrovoids present within area CA is VA2 (μm²). 2 The area CA (μm²) of the layer adjacent to layer B was obtained by analyzing it using image processing software. 2 ) and the total area of ​​macrovoids within area CA VA2 (μm 2 The percentage (%) occupied by macrovoids was calculated using the following formula. If the percentage of macrovoids was less than 20%, it was assumed that macrovoids were not substantially present, and that region was treated as layer C.

[0098] Macrovoid occupancy rate (%) = VA2 / CA × 100 Furthermore, the average pore diameter of layer C was determined by analyzing and quantifying all pores in the thickness region identified as layer C using image analysis software. Specifically, the pore diameter (average pore diameter) was calculated using the following formula from the sum of the areas of the pores and the number of pores in the image loaded into the image analysis software.

[0099] Average pore area [μm 2 ] = Total area of ​​the holes / Number of holes Pore ​​diameter (average pore diameter) [μm] = 2 × √ (average pore area / π) (8) Thickness measurement of layer a A 30,000x magnification image of the inner surface of the hollow fiber membrane was captured using a SEM and imported into a computer. Next, the image was processed using image processing software. The SEM image was adjusted for contrast and brightness to make the pores in the mesh structure easier to recognize. The pore areas were made black and the membrane areas white, and then a threshold was set to obtain a binarized image. The threshold was set to prevent the pores from connecting and appearing larger than they actually are. If the structural parts and other parts could not be separated by the difference in contrast within the image, the image was cut at areas with the same contrast, each part was binarized, and then the original images were joined back together. Alternatively, the non-structural parts could be blacked out and the image analyzed. If two pores were observed in the depth direction, the measurement was taken at the shallower pore.

[0100] The pore area was obtained by analyzing the area of ​​the individual pores (the parts displayed in black after binarization of the above image) using image processing software. The number of pixels of the scale bar, which indicates a known length in the image, was measured, and the length per pixel (μm) was calculated. The size of the captured image was 4.21 μm wide × 3.16 μm high.

[0101] The lower limit area of ​​pores to be detected during image analysis is 1260 nm. 2 Set to , with a pore area of ​​1260nm 2 Pores exceeding 1260 nm are filled with fluorescent color, and the pore area is 1260 nm. 2 A layer without pores exceeding a certain value was defined as layer a, and the thickness of layer a was measured in the direction from one surface to the other surface.

[0102] A straight line perpendicular to the above surface is drawn in the thickness direction of the hollow fiber membrane, that is, from one surface to the other surface. The surface of the hollow fiber membrane where layer a exists (hereinafter referred to as the dense surface) and the point on the above line closest to the dense surface have a pore area of ​​1260 nm. 2 The distance between the end of the hole exceeding a certain value on the straight line and the dense surface side is defined as the thickness of layer a.

[0103] The captured image (4.21 μm horizontal × 3.16 μm vertical) was divided vertically into three sections, obtaining three images with a field of view of 4.21 μm horizontal × 1.05 μm vertical. Next, the thickness from the pore closest to the dense surface to the dense surface was measured in each field of view, obtaining the thickness of three dense layers for each captured image. The same measurement was performed on 20 captured images, and the average value of the measurement data for a total of 60 layers a was calculated and defined as the thickness of layer a.

[0104] (9) Ratio of the average pore diameter of layer C to the average pore diameter of layer B The ratio of the average pore diameter of layer C to the average pore diameter of layer B (average pore diameter of layer C / average pore diameter of layer B) was calculated from the average pore diameter of layer B calculated in (6) above and the average pore diameter of layer C calculated in (7) above.

[0105] (10) Measurement of water vapor transmission rate Water vapor permeability was measured as follows. First, hollow fiber membrane modules were connected as shown in Figure 3. Using the hollow fiber membrane modules, dry air at a temperature of 80°C and a pressure of 100 kPaG was introduced into the inside of the hollow fiber membrane, and conditioned air at a temperature of 70°C, a dew point of 71°C, and a pressure of 75 kPaG was introduced from the outside of the hollow fiber membrane in a counterflow manner. The amount of water vapor permeability per unit time was measured, and the water vapor permeability rate per unit area and per unit time (g / s / m²) was measured. 2 The value was calculated by converting it to ( ).

[0106] (11) Measurement of oxygen permeability A pressure regulator is installed on an oxygen gas cylinder and connected to stainless steel piping so that the oxygen gas flows through it. Gas flow meters are installed at the front and rear ends of the piping, and tubes containing hollow fiber membranes obtained in the examples and comparative examples are attached. The hollow fiber membrane is positioned inside a 10 mm diameter tube using adhesive so that the oxygen gas flows inside the hollow fiber membrane. One end of the hollow fiber membrane is sealed to allow the oxygen gas to flow from the inside to the outside, and then the flow rates at the front and rear ends of the piping are measured while maintaining a pressure of 0.7 bar. The oxygen permeability was calculated by dividing the average of the measured flow rates by the membrane area of ​​the hollow fiber membrane.

[0107] (12) Measurement of tensile strength A single dry hollow fiber membrane with an effective sample length of 50 mm was subjected to a tensile test at a speed of 50 mm / min. A tensile testing machine (Shimadzu Corporation, EZ-LX) was used for the measurement, and the ambient temperature was 25°C. The tensile strength was calculated as (gf / fiber) from the load (gf) applied when the sample fractured. This procedure was repeated for 30 hollow fiber membranes, and the arithmetic mean was used as the tensile strength result.

[0108] (Example 1) A film-forming stock solution was prepared by heating and dissolving 28% by mass of polysulfone (Solvay's "Udel" P-3500) and 15% by mass of vinyl acetate-vinylpyrrolidone copolymer (BASF's "Socalan" VA64P) in a total of 100% by mass of 55% by mass of N,N-dimethylacetamide and 2% by mass of ethylene glycol. A 100% by mass solution of 20% by mass of N,N-dimethylacetamide and 80% by mass of water was used as the core solution.

[0109] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 700 μm, and the film thickness was 95 μm. The bundle of wound hollow fiber membranes was dried in a dry heat dryer at 100°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane revealed that layer A was observed on the inner surface side in the vertical cross-section of the hollow fiber membrane, but layers B and C were not formed. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0110] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with very low oxygen permeability and high water vapor permeability was obtained.

[0111] (Example 2) A hollow fiber membrane module was obtained using the same experimental method as in Example 1, except that the film-forming stock solution was heated and dissolved with 26% by mass of polysulfone and 57% by mass of N,N-dimethylacetamide. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with very low oxygen permeability and high water vapor permeability was obtained.

[0112] (Example 3) A film-forming stock solution was prepared by heating and dissolving 26% by mass of polysulfone (Solvay's "Udel" P-3500) and 7% by mass of polyvinylpyrrolidone (BASF's "Socalan" K30P) in a total of 100% by mass of 66% by mass of N,N-dimethylacetamide and 1% by mass of ethylene glycol. A 100% by mass solution of 20% by mass of N,N-dimethylacetamide and 80% by mass of water was used as the core solution.

[0113] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 700 μm, and the film thickness was 95 μm. The bundle of wound hollow fiber membranes was dried in a dry heat dryer at 100°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane confirmed that layers A, B, and C were formed in that order from the inner surface side in the vertical cross-section of the hollow fiber membrane. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0114] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and high water vapor permeability was obtained.

[0115] (Example 4) A dry hollow fiber membrane with an inner diameter of 700 μm and a film thickness of 95 μm was obtained using the same experimental method as in Example 3, except that the humidified dry zone atmosphere was set to a relative humidity of 60%. SEM observation of the cross-section of the hollow fiber membrane confirmed that layers A, B, and C were formed in that order from the inner surface side in the vertical cross-section of the hollow fiber membrane. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0116] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and high water vapor permeability was obtained.

[0117] (Example 5) A hollow fiber membrane module was obtained using the same experimental method as in Example 4, except that the discharge volumes of the film-forming stock solution and core solution were changed to produce a hollow fiber membrane with an inner diameter of 800 μm and a film thickness of 95 μm. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and high water vapor permeability was obtained.

[0118] (Example 6) A hollow fiber membrane module was obtained using the same experimental method as in Example 4, except that the discharge volumes of the film-forming stock solution and core solution were changed to produce a hollow fiber membrane with an inner diameter of 800 μm and a film thickness of 105 μm. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and high water vapor permeability was obtained.

[0119] (Example 7) A film-forming stock solution was prepared by heating and dissolving 26% by mass of polysulfone (Solvay's "Udel" P-3500) and 7% by mass of vinyl acetate-vinylpyrrolidone copolymer (BASF's "Socalan" VA64P) in a total of 100% by mass of 66% by mass of N,N-dimethylacetamide and 1% by mass of water. A 100% by mass solution of 20% by mass of N,N-dimethylacetamide and 80% by mass of water was used as the core solution.

[0120] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 750 μm, and the film thickness was 95 μm. The bundle of wound hollow fiber membranes was dried in a dry heat dryer at 100°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane confirmed that layers A, B, and C were formed in that order from the inner surface side in the vertical cross-section of the hollow fiber membrane. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0121] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and very good water vapor permeability was obtained.

[0122] (Example 8) A film-forming stock solution was prepared by heating and dissolving 28% by mass of polysulfone (Solvay's "Udel" P-3500) and 5% by mass of vinyl acetate-vinylpyrrolidone copolymer (BASF's "Socalan" VA64P) in a total of 100% by mass of 66% by mass of N,N-dimethylacetamide and 1% by mass of water. A 100% by mass solution of 20% by mass of N,N-dimethylacetamide and 80% by mass of water was used as the core solution.

[0123] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 750 μm, and the film thickness was 95 μm. The bundle of wound hollow fiber membranes was dried in a dry heat dryer at 100°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane confirmed that layers A, B, and C were formed in that order from the inner surface side in the vertical cross-section of the hollow fiber membrane. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0124] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and very good water vapor permeability was obtained.

[0125] (Example 9) A hollow fiber membrane module was obtained using the same experimental method as in Example 3, except that a hollow fiber membrane with an inner diameter of 450 μm and a film thickness of 90 μm was fabricated using a mixture of 22% by mass of polysulfone (Solvay's "Udel" P-3500), 8% by mass of polyvinylpyrrolidone (BASF's "Socalan" K30P), 69% by mass of N,N-dimethylacetamide, and 1% by mass of water. Due to the low tensile strength of the hollow fiber membrane, some fibers broke when filling the stainless steel case, requiring the creation of the hollow fiber membrane module to be repeated. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and high water vapor permeability was obtained, but because the inner diameter was less than 500 μm, there was a tendency for high pressure loss during water vapor permeation rate measurement.

[0126] (Example 10) A hollow fiber membrane module was obtained using the same experimental method as in Example 9, except that the discharge volumes of the film-forming stock solution and core solution were changed to produce a hollow fiber membrane with an inner diameter of 550 μm and a film thickness of 90 μm. Furthermore, due to the low tensile strength of the hollow fiber membrane, some fibers broke when filling the hollow fiber membrane into the stainless steel case, requiring the creation of the hollow fiber membrane module to be repeated. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and high water vapor permeability was obtained.

[0127] (Example 11) A hollow fiber membrane module was obtained using the same experimental method as in Example 3, except that a hollow fiber membrane with an inner diameter of 950 μm and a film thickness of 125 μm was fabricated using 26.5% by mass of polysulfone (Solvay "Udel" P-3500), 12% by mass of polyvinylpyrrolidone (BASF "Socalan" K30P), 60.3% by mass of N,N-dimethylacetamide, and 1.2% by mass of water. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability, higher water vapor permeability, and very good tensile strength was obtained.

[0128] (Example 12) A hollow fiber membrane module was obtained using the same experimental method as in Example 3, except that a hollow fiber membrane with an inner diameter of 950 μm and a film thickness of 125 μm was fabricated using 26.5% by mass of polyethersulfone (Solvay "Belladel" 3000 MP). The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability, higher water vapor permeability, and very good tensile strength was obtained.

[0129] (Example 13) A hollow fiber membrane module was obtained using the same experimental method as in Example 12, except that the diameter of the nozzle and the discharge volume of the film-forming solution were changed to produce a hollow fiber membrane with an inner diameter of 950 μm and a film thickness of 210 μm. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. A hollow fiber membrane with low oxygen permeability and very good tensile strength was obtained. Because the film thickness was very thick at 210 μm, many macrovoids were present near the outer surface of the membrane, and layer C was not formed.

[0130] (Comparative Example 1) A film-forming stock solution was prepared by heating and dissolving 28% by mass of polysulfone (Solvay's "Udel" P-3500) and 5% by mass of polyvinylpyrrolidone (BASF's "Socalan" K30P) in a total of 100% by mass of 66% by mass of N,N-dimethylacetamide and 1% by mass of water. A 100% by mass solution of 30% by mass of N,N-dimethylacetamide and 70% by mass of water was used as the core solution.

[0131] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 700 μm, and the film thickness was 95 μm. The bundle of wound hollow fiber membranes was dried in a dry heat dryer at 100°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane confirmed that layers A, B, and C were formed in that order from the inner surface side in the vertical cross-section of the hollow fiber membrane. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0132] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, both ends of the hollow fiber membrane were opened, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. Due to the presence of layer A, the oxygen permeability was low, but the water vapor permeability was also low because the low porosity of the outer surface prevented sufficient water vapor from being absorbed.

[0133] (Comparative Example 2) A film-forming stock solution was prepared by heating and dissolving 28% by mass of polysulfone (Solvay's "Udel" P-3500) and 5% by mass of polyvinylpyrrolidone (BASF's "Socalan" K90P) in a total of 100% by mass of 66% by mass of N,N-dimethylacetamide and 1% by mass of water. A 100% by mass solution of 30% by mass of N,N-dimethylacetamide and 70% by mass of water was used as the core solution.

[0134] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 700 μm, and the film thickness was 95 μm. The bundle of wound hollow fiber membranes was dried in a dry heat dryer at 100°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane revealed that layer A was confirmed on the inner surface side in the vertical cross-section of the hollow fiber membrane, but layers B and C were not formed. The results of the analysis of the images obtained from the SEM observation are shown in Table 1. The thickness of layer A was very thick.

[0135] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. Due to the presence of layer A, the oxygen permeability was low, but the water vapor permeability was low because the thickness of layer A was very thick, which increased the resistance of water vapor that entered through the openings on the outer surface.

[0136] (Comparative Example 3) A film-forming stock solution was prepared by heating and dissolving 15% by mass of polysulfone (Solvay's "Udel" P-3500) and 7% by mass of polyvinylpyrrolidone (BASF's "Socalan" K90P) in a total of 100% by mass of 75% by mass of N,N-dimethylacetamide and 3% by mass of water. A core solution was prepared by dissolving a total of 100% by mass of 55% by mass of N,N-dimethylacetamide, 30% by mass of polyvinylpyrrolidone (BASF's "Socalan" K30P), and 15% by mass of glycerin.

[0137] The film-forming solution was sent to the spinneret section and discharged from the outer tube of the orifice-type double-tube spinneret, while the core solution was discharged from the inner tube. The discharged film-forming solution passed through a dry zone atmosphere (relative humidity 80%) humidified by cold air, then was led to a coagulation bath, where it underwent a water washing process at 80°C, and the resulting wet hollow fiber membrane was wound into a bundle. The inner diameter of the hollow fiber membrane was 300 μm, and the film thickness was 80 μm. The bundle of wound hollow fiber membranes was washed with hot water at 90°C for 3 hours, and then dried in a dry heat dryer at 160°C for 24 hours to obtain a dry hollow fiber membrane. Furthermore, SEM observation of the cross-section of the hollow fiber membrane revealed that no formation of layers A, B, or C was observed in the vertical cross-section of the hollow fiber membrane. The results of the analysis of the images obtained from the SEM observation are shown in Table 1.

[0138] The obtained hollow fiber membrane was filled into a stainless steel case, and both ends of the hollow fiber membrane were fixed to the ends of the stainless steel case with potting material. By cutting a portion of the ends of the potting material, the hollow fiber membrane at both ends was opened on both sides, creating a hollow fiber membrane module. The oxygen permeability and water vapor permeability of the filled hollow fiber membrane were measured using the obtained hollow fiber membrane module. The results are shown in Table 1. The oxygen permeability was very high because layer A was not present, making it impossible to evaluate the water vapor permeability.

[0139] [Table 1] [Industrial applicability]

[0140] The present invention relates to hollow fiber membranes, hollow fiber membrane modules, and humidity control devices. More specifically, it relates to hollow fiber membranes and hollow fiber membrane modules suitably used in humidity control devices for fuel cell systems and air conditioning dehumidification systems. [Explanation of symbols]

[0141] 10: Hollow fiber membrane 11 :Inner surface 12:Outer surface 20: Air flow meter 21: DRY gas inlet 22: Wet gas outlet 23: Hollow fiber membrane module 24: DRY gas outlet 25: Temperature and humidity measurement locations 26: Wet gas inlet 27: Humidifying container 28: Hollow fiber membrane 30: Hollow fiber membrane module 31:Fuel cell 32: Power control unit 33: Motor 34: Battery 40:Air conditioner 41: Air filter 42: Cooling coil 43: Heating coil 44: Hollow fiber membrane module 45: Blower 46: Outside air 47: Intake air 50: Total heat exchanger 51: Hollow fiber membrane module 52: Outdoor intake port 53: Outside air supply passage 54:Outdoor air outlet 55: Indoor air exhaust passage 56: Blower 57: Blower 58: Indoor air 59: Outside air

Claims

1. On the inner surface side, the pore area is 0.1 μm². ２ A hollow fiber membrane having a layer A which is a region without pores exceeding a certain limit, wherein the thickness of layer A is 1 μm or more and 12 μm or less, the outer surface of the hollow fiber membrane has a plurality of pores, and the porosity of the outer surface is 5% or more and 30% or less.

2. The hollow fiber membrane according to claim 1, wherein the average pore diameter on the outer surface of the hollow fiber membrane is 0.10 μm or more and 0.30 μm or less.

3. When the outer surface of a hollow fiber membrane was observed at a magnification of 10,000x using an electron microscope, the pore density was 0.5 pores / μm. ２ More than 10 pieces / μm ２ The hollow fiber membrane according to claim 1 or 2, as described below.

4. The hollow fiber membrane according to claim 1 or 2, wherein the liquid retention rate measured by immersing the hollow fiber membrane in pure water at 80°C for 30 seconds is 150% by weight or more and 300% by weight or less.

5. The hollow fiber membrane according to claim 1 or 2, wherein when the membrane structure in the direction of a cross section perpendicular to the longitudinal direction of the hollow fiber membrane (vertical cross section) is observed at a magnification of 1,000 times using an electron microscope, the membrane has a layer B which is a region formed by including macrovoids.

6. The hollow fiber membrane according to claim 5, further comprising a layer C which is a region adjacent to the layer B where macrovoids are substantially absent.

7. The hollow fiber membrane according to claim 6, wherein in the vertical cross-section, the ratio of the average pore diameter of layer C to the average pore diameter of layer B is 0.005 or more and 0.050 or less.

8. The hollow fiber membrane has an oxygen permeability of 0 cc / min / cm² at a pressure of 0.7 bar. ２ More than 100cc / min / cm ２ The hollow fiber membrane according to claim 1 or 2, wherein the hollow fiber membrane is as follows:

9. The hollow fiber membrane according to claim 1 or 2, wherein the hollow fiber membrane has a tensile strength of 100 gf / fiber or more.

10. The hollow fiber membrane according to claim 1 or 2, wherein the hollow fiber membrane comprises a polysulfone polymer and a vinylpyrrolidone polymer.

11. The inner diameter of the hollow fiber membrane is 500 μm or more and 1200 μm or less. The hollow fiber membrane according to claim 1 or 2, wherein the thickness of the hollow fiber membrane is 60 μm or more and 200 μm or less.

12. A hollow fiber membrane for dehumidification using the hollow fiber membrane according to claim 1 or 2.

13. A hollow fiber membrane module comprising a hollow fiber membrane for dehumidification and humidification as described in claim 12, housed in a bundle case having an opening for fluid conduction on its side.

14. A humidity control device comprising the hollow fiber membrane module described in claim 13.

15. An air conditioner comprising the hollow fiber membrane module described in claim 13.

16. A total heat exchanger comprising the hollow fiber membrane module described in claim 13.

17. A fuel cell system comprising the hollow fiber membrane module according to claim 13.

18. A two-wheeled or four-wheeled vehicle using the fuel cell system described in claim 17.

19. A ship using the fuel cell system described in claim 17.

20. An aircraft using the fuel cell system described in claim 17.

21. A mobile body using the fuel cell system described in claim 17.

Images