TW200950877A - Hollow filament-membrane and preparation methods thereof - Google Patents

Abstract

This invention provides a hollow filament-membrane which has possibility used for a purpose of water treatment, high property of removing virus, high permeability of pure water, and high physical durability and high chemical durability. This invention provides a hollow filament-membrane which is formed with thermoplastic resin which is constituted by laminating a layer with three dimensional mesh structure and a layer with globular structure, wherein the layer with three dimensional mesh structure divides into 0.2 μm per layer at the thickness direction of the said layer, there are 10 to 200 layers with maximum diameter of hole of 0.03 to 0.2 μm and 0 to 2 layers with maximum diameter of hole of less than 0.03 μm.

Description

200950877 VI. Description of the Invention: [Technical Field of the Invention] The present invention relates to a hollow fiber membrane for selecting a component for separating a liquid mixture and a method for producing the same. More specifically, it relates to a hollow fiber membrane such as a hollow fiber precision filtration membrane or a hollow fiber ultrafiltration membrane which is used for water treatment such as drainage treatment, water purification treatment, industrial water production, and the like, and a method for producing the same. [Prior Art] Separation membranes such as precision filtration membranes and ultrafiltration membranes are used in various fields such as food processing, medical treatment, water production, and drainage treatment. In particular, in recent years, separation membranes have been increasingly used in the field of beverage water production, that is, in the water purification process. When it is used for water treatment applications such as water purification treatment, a hollow fiber membrane having a large effective membrane area per unit volume is usually used because the amount of water that must be treated is large. Further, when the pure water permeability of the hollow fiber membrane is excellent, the membrane area can be reduced, and the apparatus can be reduced in size and equipment can be saved, which is advantageous in terms of membrane exchange cost or installation area. Further, for the purpose of sterilizing the permeated water or preventing the biofouling of the membrane, a sterilizing agent such as sodium hypochlorite or a medicinal solution as a membrane is added to the membrane module portion to wash the acid using hydrochloric acid, citric acid, oxalic acid or the like. In the case of washing a film with an alkali such as an aqueous solution of sodium hydroxide, a surfactant, or the like, in recent years, a separation membrane using a polyvinylidene fluoride-based resin has been developed and used as a material having high chemical resistance. Further, in the field of water purification treatment, the problem that chlorine-resistant pathogenic microorganisms such as Cryptosporidium are mixed into beverage water has gradually become apparent in the late 20th century, and the hollow membrane is required to have no raw water due to membrane breakage. High strength elongation characteristics mixed in. In addition, when the beverage water is produced, it is not only the contamination of the manufacturing line but also the pathogen of the virus, which is smaller than the microorganisms, in the same manner as in the field of pharmaceutical manufacturing and food industry-4-200950877. Since the consumer is in danger of collective infection, various sterilization techniques are employed. Although the sterilization method may be a chemical treatment such as heat treatment or chlorine, the effect on the virus having heat resistance or chemical resistance is low. Therefore, membrane filtration using a separation membrane has been attracting attention as a method of physically removing viruses. Membrane filtration has many advantages such as 100% removal, rapid separation, and no need to mix impurities. Φ Various methods are disclosed for precision filtration membranes and ultrafiltration membranes capable of removing viruses. For example, Patent Document 1 discloses a regenerated cellulose membrane having a multi-stage filtration function having an average pore diameter of 30 to 100 nm and a membrane thickness of 20 μm or more, and filtering a mold having a size of about 125 nm/ml and having a size of 125 nm or more. As a result of the solution of Mycoplasma, there was no leakage. However, since the layer having a small pore size is required to be thicker than the above, although the film thickness is thin, the permeation performance of pure water is not necessarily sufficient. Further, since it is composed of regenerated cellulose, there is a concern that the chemical resistance required for water treatment use is low, the removal rate is low, and the physical strength is low. Moreover, since the film is formed of one layer and the film thickness is also thin, the original physical strength is low. In fact, it has been reported that if the differential pressure between the membranes is greater than 1 atmosphere, the mold fungus begins to leak, and although it can be suitably used for medical purposes, it cannot be suitably used for water treatment purposes. Further, Patent Document 2 discloses a film which is an isotropic, skinless polyvinylidene fluoride film which exhibits high virus removal performance by increasing the film thickness. However, when the film thickness is not more than 100 μm, sufficient virus removal performance cannot be exhibited, and the surface is grafted with the hydrophilic polymer in order to impart hydrophilicity, but the structure is directional and the whole film is not hydrophilized. At 200950877, the effect was low and sufficient pure water penetration performance could not be obtained. Patent Document 3 describes a hollow fiber membrane which is used for a medical hollow fiber membrane which is composed of a polyvinylidene fluoride-based resin, and has a maximum pore diameter of 1 〇 to m as determined by a bubble point method. Further, the thickness of the dense structural layer is more than 50% of the entire film thickness to exhibit high virus removal performance. However, since it is formed by having a continuous layer and the film thickness is thin, the breaking strength is very low for use in water treatment. Also, since the dense layer is too thick, even if the film thickness 0, the pure water permeation performance becomes low. [Patent Document 1] Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. In view of the above problems, an object of the present invention is to provide a film which can be used, for example, for water treatment purposes, having high disease φ performance, high purity water permeability, high physical durability and chemical durability [means for solving the problem] In the above aspect, the present invention relates to a hollow fiber membrane characterized in that it is formed of a thermoplastic resin which is formed by laminating a layer of a three-dimensional network structure in which a layer of the three structures is divided into its thickness direction. When the thickness of the layer is 0.2 μm, the maximum pore diameter of 10 or more and 200 or less layers is 0.03 or less and 0.2 μm or less, and the maximum pore diameter is less than 0.03, and the thin layer is 0 or more layers and 2 or less layers. The use of 100 nanometers can not be thinned, and the hollow fiber can be removed. Layer and sphere Dimensional thin layer Micron in the thickness of 200950877 (2) The hollow fiber membrane as in (1) The thin layer having a maximum pore diameter of less than 0.03 μm is 0 layer. (3) The hollow fiber membrane of (1), wherein the spherical solid component of the layer of the spherical structure has an average diameter of 0.9 μm or more and 3 μm or less. (4) The hollow fiber membrane of (1) wherein the three-dimensional network structure is disposed at the outermost layer of the hollow fiber membrane. (5) The hollow fiber membrane of (1), which is formed of a layer of a three-dimensional network structure of one layer and a layer of a spherical structure of one layer. (6) The hollow fiber membrane of (1), wherein the thickness of the layer of the three-dimensional network structure is 5 micrometers or more and 100 micrometers or less, and the thickness of the layer of the spherical structure is 110 micrometers or more and 400 micrometers or less. (7) The hollow fiber membrane of (1), wherein the layer of the spherical structure is composed of a polyvinylidene fluoride resin. (8) The hollow fiber membrane according to (1), wherein the layer of the three-dimensional network structure is formed by containing a hydrophilic polymer. (9) A method for producing a hollow fiber membrane characterized by a hollow fiber membrane formed of a thermoplastic resin composed of a layer of a three-dimensional network structure and a layer of a spherical structure, comprising: forming a spherical structure The process of forming a layer of a three-dimensional network structure by solidifying a resin solution containing a hydrophilic polymer containing 8 wt% or more: and a process of contacting a layer of the three-dimensional network structure with an aqueous solution containing an oxidizing agent, wherein When the layer of the three-dimensional network structure is divided into thin layers each having a thickness of 0 to 2 μm in the thickness direction thereof, the thin layer having a maximum pore diameter of 10 or more and 200 or less and having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, and the maximum pore diameter is The thin layer of less than 0.03 μm is more than the tantalum layer and not more than 2 layers. (10) The method for producing a hollow fiber membrane according to (9), wherein the concentration of the aqueous solution containing the oxidizing agent is 500 ppm or more and 500,000 ppm or less, and the contact time of the aqueous solution containing the oxidizing agent and the three-dimensional network structure is 1 hour or more and 400 hours. the following. [Effect of the Invention] According to the present invention, it is possible to provide a hollow fiber membrane having high chemical and physical durability and high virus removal performance and high purity water permeability. [Embodiment] The hollow fiber membrane of the present invention is formed of a layer of a three-dimensional network structure and a layer of a spherical structure. Here, the three-dimensional network structure refers to a structure in which a solid component system is expanded in a three-dimensional mesh shape. On the other hand, the spherical structure refers to a structure in which a plurality of spherical solid elements (including a substantially spherical shape) are partially connected to each other. The layer of the three-dimensional network structure is stable to remove the layer containing the contaminated matter of the filtered virus, and the layer of the spherical structure serves as a layer of physical strength and supporting the layer of the three-dimensional network structure. In order to balance the performance of each layer to a high degree, the two layers must be laminated. In general, when the layers are overlapped in multiple stages, if the interface of each layer becomes dense due to mutual entry between the layers, the permeation performance is lowered. When the layers do not enter each other, although the φ permeability is not lowered, the adhesion strength is lowered. Therefore, it is preferable that the number of the layers is small, and it is particularly preferable that the two layers of the three-dimensional network structure and the one-layer spherical structure are combined, and the arrangement of the hollow fiber membranes is not particularly limited. However, since the layer system of the three-dimensional network structure functions as a separation function, and the layer system of the spherical structure serves as the physical strength, it is preferable that the layer of the three-dimensional network structure is disposed on the side of the separation object. When the layer of the spherical structure having a relatively large pore diameter is disposed on the side of the separation object, the contaminant enters the inside of the membrane structure, which may cause the pores to clog. Further, the side of the separation object is preferably on the outer surface side of the hollow fiber membrane, and on the inner surface side, in the hollow portion where the space is small, the pollutants are accumulated in 200950877, resulting in a decrease in the permeation performance. Therefore, the layer of the three-dimensional network structure is disposed at the outermost layer of the hollow fiber membrane, and the spherical structure is disposed in a particularly preferable form of the innermost layer. Although the layer system excluding the three-dimensional network structure containing the virus can satisfy high removal performance and high permeability, it is extremely difficult to satisfy the high physical strength. When the reason is described, first, in order to obtain high removal performance, it is necessary to form a dense structure, but the permeability is lowered when the structure is dense, and in order to improve the permeation performance, the thickness of the layer must be thinned or from a low concentration of the resin stock solution. A dense structure is formed, and as a result, the physical strength is low. When the physical strength of the hollow fiber membrane is low, the hollow fiber membrane is vibrated by air to perform a washing operation or the like, and a broken wire or a contaminant is leaked. Further, when the hollow fiber membrane is pressurized, when the hollow fiber membrane structure is deformed and the pore diameter is increased, minute components such as viruses in the pollutants may leak, and conversely, the pore permeability is reduced when the pore diameter is reduced. When it is used for water treatment, in particular, in order to impart a large external force to the hollow fiber membrane and to remove minute components such as viruses, it is indispensable to improve physical strength. Therefore, as a result of intensively begging, the present invention can be achieved by a hollow fiber membrane composed of a layer of a three-dimensional network structure having high virus removal performance and permeability, and a layer having a high physical strength and a high permeability spherical structure. A hollow fiber membrane having a high level of virus removal performance, permeability, and physical strength is obtained. In particular, it has been difficult to form a layer of a three-dimensional network structure by using a resin having high chemical durability, and as a result of focusing on the production method, a structure for forming high virus removal performance and high permeability has been achieved. Specific embodiments of the present invention are described below. The layer of the three-dimensional network structure is characterized in that it is divided into a thin layer having a thickness of 0.2 μm per layer in the thickness direction thereof, and has a thin layer of 200950877 having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less in 10 or more layers and 200 layers or less. The thin layer having a maximum pore diameter of less than 0.03 μm is more than the tantalum layer and not more than two layers. Here, the maximum pore diameter of the thin layer having a thickness of 0.2 μm can be measured as follows. By using a scanning electron microscope or the like, the radial cross section of the hollow fiber membrane is continuously photographed from the outer surface to the inner surface, and the magnification of the structure can be clearly confirmed, preferably 60,000 times or more. When the obtained continuous photograph 'the three-dimensional network structure is the outermost layer or the innermost layer, the outer surface or the inner surface is used as a starting point to the boundary of the spherical structure layer, and each layer is a thin layer having a thickness of 0.2 μm. Dividing, measuring the maximum pore diameter of each film. When the layer of the three-dimensional network structure is between the layers of the other two spherical structures, the boundary between the layers of the spherical structure of any one is used as a starting point and to the other boundary, and each layer is thin with a thickness of 0.2 μm. The layers were divided to determine the maximum pore size of each film. Here, the maximum aperture refers to the maximum short diameter of the hole. The hole refers to the area surrounded by the solid portion, and the maximum short diameter of the hole means the length of the largest short diameter among the holes in the thin layer. The short diameter of the hole refers to the line length of the long diameter of the hole, and the length of the line where the vertical bisector is overlapped with the hole when the vertical bisector is drawn. The length of the hole between the long diameter hole and the boundary of the solid component is the distance between the 2 points. Further, when a hole spans and a plurality of thin layers exist, all of the layers have the holes. The solid component that cannot be clearly observed in the depth direction of the scanning electron microscope photograph is considered to have no such solid component because it has no substantial relationship with the pore formed by the solid component which can be clearly observed on the side of the photograph. To handle. A radial cross section of a hollow fiber membrane according to an embodiment of the present invention which is imaged as described above is shown in Fig. 1. Fig. 1 is a part of a plurality of photographs obtained by continuously photographing a layer of a three-dimensional network structure from the outer surface, and the vertical direction of the figure indicates the radial direction of the hollow fiber membrane. In Fig. 1, -10-200950877, the layer of the three-dimensional network structure is divided into thin layers each having a thickness of 0.2 μm from the outer surface in the thickness direction thereof, and the maximum pore diameter is determined for each layer of the respective thin layers in the present invention. . In the layer of the three-dimensional network structure of the present invention, it is necessary to continuously or intermittently have a thin layer having a maximum pore diameter of 10 layers or more and 200 layers or less of 〇.〇3 μm or more and 0.2 μm or less, and the maximum pore diameter is less than 0. The thin layer of 03 μm is 0 or more layers and 2 layers or less. The hollow fiber membrane of the present invention has a very high removal performance for the smallest viruses. The smallest virus has a size of about I2 I micrometer, and the hollow fiber membrane of the present invention has a thin layer of 10 or more layers and 200 or less layers having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, which contains a little less than the minimum virus. The layer of large pore size exists at a certain thickness or more. Although the thin layer having a maximum pore diameter of 0·03 μm or more and 0.2 μm or less has low virus removal performance, such a thin layer is multi-stage filtration mechanism by being present in a plurality of layers, and the removal performance can be improved. That is, using depth filtering. The so-called surface-passing filter that removes the virus by a dense layer that is mostly present in the three layers of the surface and contains no larger pores than the virus having a thickness of about 0.6 μm, that is, a thin layer having a maximum pore diameter of less than 0.03 μm. In comparison, since the hollow fiber membrane of the present invention has a thin layer having a maximum pore diameter of 10 or more and 200 or less and a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, the thin layer having a maximum pore diameter of less than 0.03 μm is reduced to very little. Below 2 layers, it is advantageous in terms of the ability to exhibit high purity water permeability. This is because the pure water permeation performance is proportional to the fourth power of the pore size (Poiseuille rule; Poiseuille rule) and inversely proportional to the thickness of the layer. Even if the layer thickening ratio is reduced, the permeability of pure water can be reduced. In depth filtration, since the removal performance of each thin layer having a thickness of 0.2 μm is -11 - 200950877, the larger the maximum pore diameter is, the higher the pore permeability is, the lower the number of thin layers necessary to exhibit high removal performance is reduced to good. Therefore, in view of the higher effect of the virus removal performance and the pure water permeation performance, it is preferable to have a thin layer having a maximum pore diameter of 10 or more and 75 or less layers of 0.03 μm or more and 0.1 μm or less, and having 10 or more layers, Below 50 layers is preferred. Or a thin layer having a maximum pore diameter of 10 or more and 50 or less layers of 0.03 μm or more and 0.07 μm or less is preferable, and 10 or more layers and 35 or less layers are preferable. When a thin layer having a maximum pore diameter of less than 0.03 μm of three or more layers is used, the permeation performance of pure water is lowered, and even if it has a thin layer having a maximum pore diameter of more than about 200 μm of about 200 or more, sufficient virus removal performance cannot be obtained. Further, when the thickness of the thin layer having a maximum pore diameter of 0.03 μm or more and 0.07 μm or less is less than 10 layers, sufficient virus removal performance cannot be obtained, and when the thickness of the thin layer having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less is 200 or more, sufficient seizure cannot be obtained. Pure water penetration performance. Thus, in order to maximize the removal performance and the pure water permeation performance, the & structure having the relationship of appropriately controlling the relationship between the maximum pore size and the thickness is the feature of the present invention. Therefore, the layer system of the three-dimensional network structure may have a thin layer having a maximum pore diameter of more than 0.2 μm in addition to the above-mentioned depth filter structure having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, but a film having a maximum pore diameter of less than 0.03 μm must be In the case of 2 or less layers, it is preferable to use one layer or less, and it is not preferable at all, and it is effective in order not to lower the permeation performance of pure water. Next, in order to have sufficient physical strength, the spherical solid layer has an average diameter of the spherical solid component of preferably 0.9 μm or more and 3 μm or less. The solid content of the spherical solid component is a solid having a roundness ratio (long diameter/short diameter) of 2 or less and -12 to 200950877. The average diameter of the spherical solid component is the average diameter of the major axis and the minor axis. When the average diameter of the spherical solid component is less than 〇·9 μm, the void formed between the solid components becomes small, and sufficient purity cannot be obtained. Water permeability, when it is larger than 3 μm, the connection of solid components becomes less, and the physical strength is lowered. Further, in order to achieve a high level of pure water permeability and physical strength, the layer of the spherical structure is preferably a uniform structure. In the case where the dense layer or the structural system is changed obliquely, it is difficult to have both pure water permeability and physical strength. Further, in addition to the spherical solid component, the physical strength becomes high, and it is preferable to contain a solid component having a columnar shape with a perfect circular ratio (long diameter/short diameter) of more than 2. The hollow fiber membrane of the present invention is composed of a thermoplastic resin. The thermoplastic resin refers to a resin which can be made of a chain polymer material and which exhibits deformation and flow by external force upon heating. The thermoplastic resin may, for example, be polyethylene, polypropylene, acrylic resin, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resin, polyethylene, acrylonitrile-styrene (AS) resin, vinyl chloride resin. , polyethylene terephthalate, polydecylamine, polyacetal, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyvinylidene fluoride, polyamidoximine, polyether sulfimine , poly maple, polyether mill and mixtures or copolymers of these. In order to stably remove the pollutant containing the virus, the thermoplastic resin which is a layer forming the three-dimensional network structure preferably has high chemical durability, and in order to obtain high-purity water permeability, it is preferred to have high hydrophilicity. Therefore, it is particularly preferable to use a mixture of a polyacrylonitrile-based resin or a polyvinylidene fluoride-based resin and a hydrophilic polymer. Since it is easy to form a homogeneous and dense structure and is excellent in physical strength or thermal characteristics, it is preferable that the polyacrylonitrile-based resin has an ultrahigh polymerization degree, and the intrinsic viscosity is 2 or more, and preferably 2.5 or more and 3.6 or less is 2.9 or more. 3.3 The following is better. Further, the resin is composed of 90 mol% of acrylonitrile, preferably 95 mol% or more, and 5 mol% or less of a vinyl compound having a copolymerization property of -13 to 200950877 with respect to acrylonitrile. Acrylonitrile is a homopolymer or an acrylonitrile copolymer. The vinyl compound is not particularly limited as long as it is a compound having a copolymerization property with respect to acrylonitrile. However, preferred examples of the copolymerization component include acrylic acid, itaconic acid, methyl acrylate, and methacrylic acid. Ester, ethyl acetate, sodium allylsulfonate, sodium methallylsulfonate, sodium p-styrenesulfonate, and the like. Ο 所谓 The term "polyvinylidene fluoride-based resin" means a resin containing a vinylidene fluoride homopolymer and/or a vinylidene fluoride copolymer, and may contain a plurality of types of vinylidene fluoride copolymer. The vinylidene fluoride copolymer is a polymer having a structure of a vinylidene fluoride residue, and is typically a copolymer of a vinylidene fluoride monomer and another fluorine-based monomer. The copolymer may, for example, be a copolymer of at least one type selected from the group consisting of fluoroethylene, tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene and vinylidene fluoride. Further, it is also possible to copolymerize with a monomer such as ethylene other than the above-mentioned fluorine-based monomer to the extent that the effects of the present invention are not impaired. The hydrophilic polymer has a cellulose ester, a fatty acid vinyl ester, a vinyl pyrrolidone, an ethylene oxide, a propylene oxide, an acrylonitrile, an acrylate, or a methacrylate in the main chain and/or a side chain. At least one type of molecular unit is not particularly limited, and molecular units other than these may be present. Examples of the molecular unit other than the above molecular unit include an olefin such as ethylene or propylene, an acetylene such as acetylene, a vinyl halide, or a vinylidene halide. Since it can be obtained relatively inexpensively and has high chemical durability, it is preferred to use ethylene or vinylidene halide. The hydrophilic polymer is for use with a polyvinylidene fluoride tree

It is preferred to mix a vinyl fluoride resin. The proper condition and the polyposition II because the layer of the spherical structure supports the layer of the three-dimensional network structure has the physical strength of the material - also has a particularly high chemical durability, from polyethylene, polypropylene It is more preferable that the polyvinylidene fluoride-based resin is composed of a polyvinylidene fluoride-based resin. The effect of such a hollow fiber membrane of the present invention is a high level of pure water permeability, breaking strength, elongation at break, and virus removal performance. That is, the pure water permeation performance at 50 kPa and 25 ° C is 0.2 m 3 /m 2 /hr or more, the breaking strength is 4 N / or more, the elongation at break is 20% or more, and the virus removal performance is 4 Iog or more. Further, by optimizing the conditions of the present invention, it is possible to have a pure water permeability of not less than 3 m 3 /m 2 /hr, a breaking strength of 4 N / branch or more, a fracture elongation of 20% or more, and a virus removal performance of 41 og. The above performance. Further, the layer of the spherical structure may be thickened as necessary depending on the conditions of use of the film, etc., and the pure water permeation performance may be 〇.3 m 3 /m 2 /hr or more, the breaking strength may be 9 N/support or more, and the elongation at break may be 20% or more. And the virus removal performance is 41 ng or more. The hollow fiber membrane composed of a thermoplastic resin comprising a layer of a three-dimensional network structure of the present invention and a layer of a spherical structure can be produced by various methods. For example, on a hollow fiber membrane composed of a spherical structure, a layer of a three-dimensional network structure is laminated and oxidized. In this method, a hollow fiber membrane composed of a spherical structure is first produced. An example of a method of using a polyvinylidene fluoride-based resin for a resin will be described below. The polyvinylidene fluoride-based resin is dissolved in a weak solvent or a good solvent of the resin at a relatively high concentration of 20% by weight or more and 60% by weight or less and at a temperature equal to or higher than the crystallization temperature. When the resin concentration is high, a hollow fiber membrane having a high strength elongation property can be obtained. However, the void ratio of the hollow fiber membrane produced when it is too high becomes small, and the permeability of pure water is low. Further, if the viscosity of the prepared resin solution is not within an appropriate range, the hollow fiber membrane cannot be formed. Therefore, the resin concentration is more preferably in the range of 30% by weight -15 to 200950877% or more and 50% by weight or less. Further, 'weak solvent' means that the polyvinylidene fluoride-based resin cannot be dissolved in an amount of 5% by weight or more at a low temperature of less than 60 ° C, but is not more than 601: and not less than the melting point of the polyvinylidene fluoride-based resin (for example, When the polyvinylidene fluoride-based resin is composed of a polyvinylidene fluoride homopolymer, it is 178. The high-temperature region (about:) can dissolve the solvent in an amount of 5% by weight or more. When the temperature is less than 60 ° C, the solvent in which the polyvinylidene fluoride-based resin is dissolved in an amount of 5% by weight or more can be defined as a strong solvent, and the melting point of the polyvinylidene fluoride-based resin or the boiling point of the solvent can not be reached. The solvent in which the fluoroethylene resin is dissolved or swelled is defined as a non-solvent. Here, examples of the weak solvent of the polyvinylidene fluoride-based resin include cyclohexanone, isophorone, butyrolactone, and methyl isoamyl ketone. A medium chain length alkyl ketone such as propylene carbonate, an ester, an organic carbonate, or the like, and a mixed solvent thereof. Further, examples of the good solvent include N-methyl-2-pyrrolidone, dimethyl hydrazide, and dimethyl Ethylamine, dimethylformamide, methyl ethyl ketone, acetone Lower alkyl ketones such as tetrahydrofuran, tetramethyl urea, and trimethyl phosphate, esters, decylamines, and the like, and mixed solvents thereof. Further, examples of the non-solvent include water, hexane, pentane, benzene, toluene, methanol, ethanol, and tetra. Aliphatic groups such as carbon chloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, low molecular weight polyethylene glycol a hydrocarbon, an aromatic hydrocarbon, an aliphatic polyol, an aromatic polyol, a chlorinated hydrocarbon, or another chlorinated organic liquid, a mixed solvent thereof, etc. Further, a hollow fiber membrane composed of a spherical structure is used The resin solution is cooled by a heat-induced phase separation method for phase separation of the resin solution, and the resin solution is discharged from a tube outside the double-tube nozzle for spinning a hollow fiber membrane and the hollow portion is formed into a liquid layer from the double layer. The inside of the tube nozzle is spit -16-200950877 and is cooled and solidified in a cooling bath. It is weaker than the cooling bath system 〇 °C or more, 30 ° C or less, and the concentration is 50% by weight or more and 95% by weight or less. Solvent or good solvent, and concentration of 5% by weight or more, 50 weight A mixed liquid composed of a non-solvent of less than % is preferable. Further, since it is easy to maintain the composition of the cooling liquid, it is preferable to use the same weak solvent as the resin solution as the weak solvent. However, when a high-concentration good solvent is used, the temperature is not maintained. When it is lowered to a very low level, it does not solidify, or the solidification is slow, so that the surface of the hollow fiber membrane cannot be smoothed. Further, a weak solvent or a good solvent may be mixed as long as it does not deviate from the above concentration range. However, when a high concentration non-solvent is used, In the case where a dense layer is formed on the outer surface of the hollow fiber membrane, the permeation performance of the pure water is remarkably lowered. Further, the liquid is formed in the hollow portion in the same manner as the cooling bath, and the concentration is 50% by weight or more and 95% by weight or less. A weak solvent or a good solvent and a mixed liquid composed of a non-solvent having a concentration of 5 wt% or more and 50 wt% or less are preferred, and a weak solvent similar to the resin solution is preferably used as the weak solvent. Here, when manufacturing by the heat-induced phase separation method, two types of phase separation mechanisms are mainly used. One is a polymer solution which is uniformly dissolved at a high temperature, and the solution of the polymer is separated from the dilute phase due to a decrease in the solubility of the solution at the time of cooling, followed by liquid-liquid phase separation by structural crystallization, and One is a polymer solution which is uniformly dissolved at a high temperature, and the polymer is crystallized upon cooling, resulting in a solid-liquid phase separation method in which the solid phase of the polymer and the solution phase are phase separated. The former method mainly forms a three-dimensional network structure, and the latter method mainly forms a spherical structure composed of spherical tissue. In the present invention, it is important to use a phase separation mechanism of the latter to induce a combination of a resin concentration of a solid-liquid phase separation, a temperature, a solvent of a resin solution, a composition of a cooling bath, and a temperature. With the three-dimensional network structure formed by the phase separation mechanism described above, it is difficult to have high elongation performance and pure water penetration at a high level -17-200950877. The three-dimensional network structure is a structure in which the solid components of the ribs are three-dimensionally and uniformly connected, and the pore diameter becomes smaller as compared with the spherical structure in which the spherical solid components are not uniform and share a part of each other and are firmly connected. . Therefore, it is considered that even with the same strong elongation property, the permeability of pure water is deteriorated. In addition to the above processes, it is useful to perform stretching in order to expand the voids to enhance the permeability of pure water and to enhance the breaking strength. The stretching method is preferably 50° C. or higher and 140° C. or lower, preferably 55 t: or more and 120° C. or less, and is preferably in a temperature range of 60° C. or higher and 10° C. or lower. It is preferably 1.1 times or more and 4 times or less, and more preferably 1.1 times or more and 2 times or less. When stretching in a low temperature environment of less than 50 ° C, it is difficult to stably and uniformly stretch the system. When stretching at a temperature of more than 140 °C, the structure is melted due to the melting point of the polyvinylidene fluoride-based resin, so that the voids cannot be enlarged and the permeability cannot be improved. Further, since the temperature control is easy, it is preferable to stretch in a liquid, but it may be carried out in a gas such as steam. Because of the simplicity, the liquid is preferably water, but when stretched at or above 90 °C, low molecular weight polyethylene glycol is also suitable. On the other hand, when such stretching is not carried out, the pure water permeability and the breaking strength are lowered as compared with the stretching, but the elongation at break and the removal performance are improved. Therefore, the presence or absence of the stretching process and the stretching ratio of the stretching process can be appropriately set in accordance with the use of the hollow fiber membrane. Next, a layer of a three-dimensional network structure is formed on the hollow fiber membrane composed of the spherical structure formed as described above. In this process, it is necessary to form a three-dimensional network structure having a film having a maximum number of pores of 0.2 μm or less in an appropriate number (thickness). Further, in order to improve the removal performance, it is preferable that there is substantially no uneven macropores of a few micrometers or more which are called large voids. The method is not particularly limited, and a resin solution having a three-dimensional network structure is high in concentration -18 - 200950877. A method comprising a hydrophilic polymer is preferred. An example of a method of using a polyacrylonitrile-based resin and a mixture of a polyvinylidene fluoride-based resin and a hydrophilic polymer in a resin will be described below. First, a method of using a polyacrylonitrile-based resin will be described. The organic solvent in which the polyacrylonitrile-based resin is dissolved may, for example, be dimethyl hydrazine, dimethylformamide, dimethylacetamide, ethylene carbonate, butyrolactone or the like. It is especially good to use dimethyl sub-grinding. The resin concentration of the polyacrylonitrile-based resin solution is preferably 8% by weight or more and 20% by weight or less, and more preferably 9% by weight or more and 16% by weight or less. When the amount is less than 8% by weight, a film having a large pore diameter of 0.2 μm or less is hardly formed, and sufficient virus removal performance cannot be exhibited. Moreover, when it is more than 20% by weight, since a large number of thin layers having a maximum pore diameter of less than 0.03 μm are formed, even if it is subsequently subjected to a process of contacting with an oxidizing agent, it is difficult to improve the permeability of pure water while maintaining the virus removal performance, and The viscosity is increased to deteriorate the formability, which is not preferable. By carrying out the dissolution at a relatively high temperature of 80 ° C or higher and 170 ° C or lower, a more uniform solution can be obtained. The polyacrylonitrile-based resin solution is applied onto the surface of the hollow fiber membrane composed of a spherical structure, and then solidified in a coagulation bath mainly composed of a non-solvent of a polyacrylonitrile-based resin solution. To cover the three-dimensional network structure. The coating method is not particularly limited, and a method in which a hollow fiber membrane is immersed in a polyacrylonitrile-based resin solution or a spray coating of a hollow fiber membrane is suitably used. Moreover, the method of controlling the amount applied to the hollow fiber membrane is to scrape a portion of the resin solution by passing it through the nozzle or to blow it by pneumatic scraping, in addition to controlling the coating amount of the resin solution. The method of walking is also suitable for use. The coagulation bath is mainly composed of a non-solvent of a polyacrylonitrile-based resin solution, and contains the above-mentioned polyacrylonitrile in the range of -19-200950877 in an amount of 0% by weight or more and 30% by weight or less. The organic solvent of the resin is preferred. The non-solvent of the polyacrylonitrile-based resin solution may, for example, be water, an alcohol, an aliphatic ketone, glycerin or polyethylene glycol, and water is particularly preferred. Moreover, since the temperature of the coagulation bath is too high, film shrinkage occurs, and the permeation performance of pure water is lowered. The temperature of the coagulation bath is 5 ° C or more and 70 ° C or less, and 5 ° C or more and 40 ° C or less. It is better. Next, a method of using a mixture of a polyvinylidene fluoride-based resin and a hydrophilic polymer will be described. A solvent in which a mixture of a polyvinylidene fluoride-based resin and a hydrophilic polymer is dissolved can be suitably used as a good solvent for a polyvinylidene fluoride-based resin. Further, the solution of the mixture of the polyvinylidene fluoride-based resin and the hydrophilic polymer is preferably 18% by weight or more and 30% by weight or less based on the total concentration of the polyvinylidene fluoride-based resin and the hydrophilic polymer. It is more preferable to adjust the range of 20% by weight or more and 30% by weight or less. In addition, in order to obtain the above-described configuration, the concentration of the hydrophilic polymer must be adjusted to be in the range of 8% by weight or more and 20% by weight or less, and more preferably 9% by weight or more and 16% by weight or less. By dissolving the solution at a relatively high temperature of 80 ° C or higher and 170 ° C or lower, a uniform solution can be obtained.

After coating a solution of a mixture of a polyvinylidene fluoride-based resin and a hydrophilic polymer on the surface of a hollow fiber membrane composed of a spherical structure, by using a non-polyvinylidene fluoride resin The solidified bath composed of a solvent is solidified to coat a layer of a three-dimensional network structure. The coating method can be carried out by the aforementioned method. The coagulation bath is mainly composed of a non-solvent of a polyvinylidene fluoride-based resin, and may contain a good solvent or a weak solvent of the polyvinylidene fluoride-based resin in a range of 0% by weight or more and 30% by weight or less. Further, the temperature of the coagulation bath is preferably 10 ° C or more and 70 ° C or less, and more preferably 20 ° C or more and 50 ° C -20 to 200950877 or less. A method for separately producing a hollow fiber membrane composed of a thermoplastic resin composed of a layer of a three-dimensional network structure and a layer of a spherical structure, which will form a resin solution of a three-dimensional network structure and a resin solution of a layer forming a spherical structure A method of simultaneously discharging and solidifying a three-layered nozzle is also suitable. That is, when the layer system for fabricating the three-dimensional network structure is disposed on the outer layer of the hollow fiber membrane and the layer of the spherical structure is disposed in the hollow fiber membrane of the inner layer, the resin solution forming the three-dimensional network structure can be removed from the outer side. The tube and the resin solution of the layer forming the spherical structure are simultaneously discharged from the middle tube and the liquid which forms the hollow portion from the inner tube, and are solidified in the coagulation bath. In the hollow fiber membrane formed as described above, the layer of the three-dimensional network structure has a dense thin layer having a maximum pore diameter of less than 0.03 μm in the outermost layer, and the inner diameter direction from the surface layer to the layer is inclined by continuously increasing the pore diameter. Structured. This inclined structure contains three or more films having a maximum pore diameter of less than 0.03 μm, and although the virus removal performance is not shown, sufficient pure water permeability is not exhibited. However, if the pore diameter of the layer composed of such a slanted structure can be appropriately enlarged, the present invention must have a maximum pore diameter of 10 or more layers and 200 or less layers on the surface layer side, which is 〇3 μm or more and 0.2 μm or less. The thin layer and the thin layer having a maximum pore diameter of less than 0.03 μm are characterized by two or less layers, and a layer having relatively large pores can be formed inside the layer, and the pure water can be dramatically improved while maintaining the virus removal performance. Penetration performance. The inventors of the present invention have found that the hollow fiber membrane of the present invention can be produced by bringing the hollow fiber membrane obtained here into contact with an aqueous solution containing a relatively high concentration of an oxidizing agent for a suitable period of time. The resin forming the layer of the three-dimensional network structure is not particularly affected when the aqueous solution is at a low concentration or when the aqueous solution is in a short contact with the aqueous solution for a short period of time, but the period from 21 to 200950877 is high. A resin which is partially chemically decomposed at a concentration or a long time of contact is necessary. The above-mentioned hydrophilic polymer can be suitably used for such a resin. A part of the resin which forms a layer of a three-dimensional network structure is chemically decomposed by an oxidizing agent, and the structure of the layer of the three-dimensional network structure changes. That is, by the maximum pore size existing in the outermost layer of the layer of the three-dimensional network structure, the layer of the thin layer having a maximum pore diameter of less than 0.03 μm becomes less than 3 layers' and can form a maximum of 10 layers or more and 200 layers or less. A layer of a polyvinylidene fluoride-based resin having a pore diameter of 0.03 μm or more and 0.2 μm or less. Here, the three-dimensional network structure before the contact with the aqueous solution containing the oxidizing agent is formed by a solution of a mixture of a polyvinylidene fluoride-based resin and a hydrophilic polymer, although the three-dimensional network structure after contacting the aqueous solution containing the oxidizing agent The layer may not substantially remain as a hydrophilic polymer, but in this case, it is composed only of a hydrophobic polyvinylidene fluoride-based resin. From the viewpoint of improving the permeation performance of pure water, it is preferred to finally contain a hydrophilic polymer. Therefore, it is important to control the type, concentration, and contact time of the oxidant to match the structure and composition of the layer of the three-dimensional network structure before contacting the aqueous solution containing the oxidizing agent. Further, since the resin forming the layer of the spherical structure is chemically decomposed by the oxidizing agent to lower the physical strength, the resin forming the layer of the spherical structure selects a resin having high chemical resistance, or controls the type of the oxidizing agent, Concentration and contact time are necessary. Here, the oxidizing agent is not particularly limited as long as it is water-soluble, and sodium hypochlorite, hydrogen peroxide, potassium permanganate, potassium dichromate, halogen, concentrated sulfuric acid, nitric acid, chloramine or the like is preferably used, and hypochlorous acid is preferred. good. The concentration of the oxidizing agent is 500 ppm or more and 50,000 ppm or less, and the contact time with the oxidizing agent is 1 hour or more and 400 hours or less. The concentration of the oxidizing agent is 1000 ppm or more and 1000 ppm or less, and the contact time with the oxidizing agent is -22 to 200950877 for 10 hours or more and 200 hours or less, and the concentration of the oxidizing agent is 2000 ppm or more and 8000 ppm or less, and the oxidizing agent is used. It is more preferable that the contact time is 20 hours or more and 100 hours or less. When the concentration of the oxidizing agent is less than 500 ppm, a sufficient structural change does not occur in the layer of the three-dimensional network structure, or it is necessary to have a sufficient structure for more than 400 hours without practicality, but is not good. When the concentration of the oxidizing agent is more than 50,000 ppm, the resin of the layer having a spherical structure is chemically decomposed, resulting in a possibility that the physical strength is lowered. Further, if the contact time with the oxidizing agent is less than 1 hour, a sufficient structural change cannot be produced in the layer of the three-dimensional network structure, and a spherical structure is required in order to cause a sufficient structural change to have a high concentration of more than 50,000 ppm. The layer is chemically decomposed, resulting in the possibility of low physical strength. If it is more than 400 hours, there are many resins having a spherical structure which are chemically decomposed, resulting in a possibility of low physical strength, and also have no practicality, which is not preferable. In order to maximize the effect of the present invention. The respective thicknesses of the three-dimensional network structure and the layers of the spherical structure are also important. The layer having a three-dimensional network structure has a maximum pore diameter of 10 layers or more and 200 layers or less and a thin layer of 0.03 μm or more and 0.2 μm or less, and the thin layer having a maximum pore diameter of less than 0.03 μm is less than 2 layers, so The thickness of the layer may be 5 μm or more and 100 μm or less, preferably 10 μm or more and 60 μm or less, and more preferably 15 μm or more and 35 μm or less. When the layer of the three-dimensional network structure is formed to a thickness of less than 5 μm, defects are easily generated and the removal performance is lowered. Further, when the thickness of the layer is more than 100 μm, the effect of imparting pressure resistance to the layer of the three-dimensional network structure by the layer of the spherical structure is lowered, the layer of the three-dimensional network structure is deformed, and the removal performance is lowered when the aperture is enlarged. Conversely, when the pore size is reduced, the permeability of pure water is low. The thickness of the layer of the spherical structure may be 133-200950877, which is 110 micrometers or more and 400 micrometers or less, preferably 150 micrometers or less. The thickness of the layer of the spherical structure is less than 110 μm to a sufficient physical strength, and pure water permeates 大于 greater than 400 μm. [Examples] Hereinafter, the present invention will be described by way of specific examples, but it is not limited to the examples. Here, the parameters of the comparative examples and comparative empty fiber membranes were measured by the following methods. (1) The thickness of the layer of the three-dimensional network structure is 0.2 μm and the number of layers is the layer of the three-dimensional network of the hollow fiber membrane from the outer surface to the spherical shape using a scanning electron microscope Knot: Boundary, or layer without a spherical structure, attached to the inner surface, with a microscope photograph of 60,000, a thin layer with a thickness of 0.2 μm from the outer surface to the inner surface, and measured in each thin layer Each of the layers having a maximum pore diameter of less than 0.03 μm, a layer of 0.03 μm or more and less than 0.07 μm, a layer having a maximum pore diameter of not less than 0.1 μm, and a layer having a maximum pore diameter of 0.1 μm or less were obtained. The job is performed at any three locations and is obtained. (2) The thickness of the layer of the three-dimensional network structure and the layer of the spherical structure. The radial section of the hollow fiber membrane is photographed using a scanning type of electricity of 00 to 1000 times, and the thickness and spherical shape of the three-dimensional network at any 20 positions are measured. The thickness of the layer of the structure, and the average number of each of the layers (3) The average diameter of the spherical solid component of the layer of the spherical structure is the radial section of the hollow fiber membrane, and the photograph of any 20 positions is taken by scanning the electric motor 3000 times. And the respective fi, the upper and the 300 micron can not be reduced. It is the edge of the layer of the groove of the cross section of the largest hole of the film in the yarn of the present invention. The continuous shooting surface is divided into the maximum aperture. The maximum pore diameter is 0.07 μm or more, 0.2 and is obtained by a layer of a structure of a number of flat microscopes. The sub-microscope is obtained by taking the diameter of 20 spherical -24-200950877 spherical solid components and counting the average. (4) Virus removal performance An aqueous solution containing distilled water of Bacteriophage MS-2 (Bacteriophage MS-2 ATCC 15597-B1) having a size of about 25 nm was prepared as a virus stock solution at a concentration of about 1.0 x 107 PFU/ml. Here, the distilled water was autoclaved at 121 ° C for 20 minutes using distilled water from a pure water production apparatus AUTOSTATE (manufactured by YAMATO Scientific Co., Ltd.). A small module made of glass having a length of about 20 cm, which is composed of four hollow fiber membranes, is produced, and the virus stock solution is fed at a temperature of about 20 ° C and a filtration differential pressure of pure 〇〇 kPa (external pressure). . After filtering about 10 ml, take about 5 ml of the filtrate and dilute it to 0 to 1000 times with distilled water. Based on the Overlay agar assay Standard Method 9211-D (APHA, 1989, S t an dar d me odsf or the ex amina tion of water and wastewater) Method), 18th ed.), and 1 ml of the diluted liquid was inoculated to the assay glass culture dish, and the concentration of Bacteriophage MS-2 was determined by calculating the plaque. Performance removal is expressed in logarithms. For example, the 21og system means 21ogl. , and the residual concentration is one percent. Also, when the plaque could not be measured at all in the filtrate, it was 2 71 og. (5) Pure water permeation performance A small component consisting of 4 hollow fiber membranes having a length of about 20 cm was produced, and the reverse osmosis membrane treated water was treated at a temperature of 25 ° C and a filtration differential pressure of 16 kPa (external pressure). The enthalpy obtained by measuring the amount of permeated water (m3) for a predetermined period of time is converted into unit time (hr), unit effective membrane area (m2), average 50 kPa - (6) breaking strength, and elongation at break - 25 - 200950877 Tensile testing machine (TENSILON (registered trademark) / RTM-100 manufactured by Toyo BALDWIN Co., Ltd.), and the hollow fiber membrane moistened with reverse osmosis treated water, with a test length of 50 mm and a full scale of 5 kg It was measured at a crosshead speed of 50 mm/min. This operation was performed by changing the sample and performing the number of times 10 times. (Example 1) 38% by weight of a polyvinylidene fluoride homopolymer having a weight average molecular weight of 417,000 and 62% by weight of r-butyrolactone were dissolved at 160 °C. The resin solution was discharged from the tube on the outer side of the double tube nozzle, and an 85 wt% aqueous solution of r-butyrolactone was discharged from the inner tube of the double tube type, and was dissolved in an aqueous solution of 8 wt% of T-butyrolactone. The composition was allowed to cure in a bath at a temperature of 10 ° C. Thereafter, it was stretched 1.5 times in water at 90 °C. The obtained hollow fiber membrane is a hollow fiber membrane composed of a spherical structure. Next, a polymer having 100 mol% of acrylonitrile and an intrinsic viscosity of 3.2 was polymerized in dimethyl hydrazine, and further diluted with dimethyl hydrazine to obtain a 13.5 wt% film-forming stock solution. The film forming stock solution was uniformly coated on the surface of the hollow fiber membrane composed of a spherical structure, and immediately solidified in a 20% by weight aqueous solution of dimethyl argon at 23 ° C to produce a layer in a spherical structure. A hollow fiber membrane formed by forming a layer of a three-dimensional network structure. Subsequently, the hollow fiber membrane was immersed in a 3000 ppm aqueous sodium hypochlorite solution for 180 hours. The obtained hollow fiber membranes had an outer diameter of 1,430 μm and an inner diameter of 880 μm, and the membrane structure and membrane properties were as shown in Table 1. -26- 200950877 [Table i] Layer of biliary film street refusing three-dimensional network structure - spheroidal layer virus except pure water osmotic strength extension thickness 〇_2 μm f » maximum 5 number of layers diameter layer of layer Performance performance shouting) Degree ~0.03 0·03 ～ 0.07 〜 0.1~ 0.2 Thickness (μm) Thickness (log) (m3/m2/h) (%) Micron 0.07 0.1 0.2 μm ~ (μm) (μm) Micron Micron Example 1 1 25 15 51 168 52 1.4 236 0.30 10.7 82 0 33 21 125 71 50 1.4 234 0.35 10.1 71 2 10 12 32 169 45 1.4 233 0.21 11.3 58 Comparative Example 1 4 10 12 131 88 49 1.4 234 0.10 11.0 90 Comparative Example 2 1 1 1 6 191 40 1.4 238 3.2 0.43 10.5 32 Comparison 3 3 12 15 113 57 40 • 0 0.11 0.3 107 Ratio 4 0 0 1 3 211 43 2.8 248 1.5 0.41 6.8 43 A (Example 2 The hollow fiber membrane was produced in the same manner as in Example 1 except that the hollow fiber membrane was immersed in a 3000 ppm sodium hypochlorite aqueous solution for 3 to 60 hours. The obtained hollow fiber membranes had an outer diameter of 1420 μm and an inner diameter of 890 μm, and the membrane structure and membrane properties were as shown in Table 1. (Example 3) First, a hollow fiber membrane composed of a spherical structure was produced in the same manner as in Example 1. Next, 12% by weight of a polyvinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 9% by weight of cellulose acetate (EASTMAN CHEMICAL, CA435-75S: cellulose triacetate), 79% by weight of N-A The benzyl-2-pyrrolidone was dissolved and mixed at 150 ° C to obtain a film forming stock solution. The film forming stock solution was cooled to 70 ° C and uniformly coated on the surface of the hollow fiber membrane composed of a spherical structure, and immediately solidified in water at 27 ° C to produce a three-dimensional shape on the layer of the spherical structure. Hollow fiber membrane made of a layer of a network structure. Subsequently, the hollow fiber membrane was immersed in a 6000 ΡΡΠ1 sodium hypochlorite aqueous solution for 22 hours. The obtained hollow fiber membranes had an outer diameter of 1410 μm and an inner diameter of 880 μ -27 to 200950877 m, and the membrane structure and membrane properties were as shown in Table 1. (Comparative Example 1) A hollow fiber membrane was produced in the same manner as in Example 1 except that it was not immersed in an aqueous sodium hypochlorite solution. The obtained hollow fiber membranes had an outer diameter of 1,440 micrometers and an inner diameter of 870 micrometers, and the membrane structure and membrane properties were as shown in Table 1. (Comparative Example 2) First, a hollow fiber membrane composed of a spherical structure was produced in the same manner as in Example 1. _ Next, 12% by weight of a polyvinylidene fluoride homopolymer having a weight average molecular weight of 387,000, 7.2% by weight of cellulose acetate (EASTMAN CHEMICAL, CA4 35 -7 5S: cellulose triacetate), 80 · 8 The weight % Ν-methyl-2-pyrrolidone was dissolved and mixed at 95 t to obtain a film forming stock solution. The film forming stock solution was cooled to 70 ° C and uniformly coated on the surface of the hollow fiber membrane composed of a spherical structure, and immediately solidified in water at 27 ° C to be formed on the layer of the spherical structure. A hollow fiber membrane formed by forming a layer of a three-dimensional network structure. The obtained hollow fiber membranes had an outer diameter of 1,450 micrometers and an inner diameter of 900 micrometers, and the membrane structure and membrane properties were as shown in Table 1. (Comparative Example 3) A polymer having 100 mol% of acrylonitrile and an intrinsic viscosity of 3.2 was polymerized in dimethyl hydrazine and further diluted to obtain a resin solution of 13.0% by weight. The resin solution was discharged from the tube outside the double tube nozzle, and an 80% by weight aqueous solution of dimethyl hydrazine was discharged from the inner tube of the double tube type, and solidified in a water bath at a temperature of 30 °C. The obtained hollow fiber membrane is a hollow fiber membrane composed of a three-dimensional network structure. The obtained hollow fiber membranes had an outer diameter of 290 μm and an inner diameter of 210 μ-28 to 200950877 m, and the membrane structure and membrane properties were as shown in Table 1 (Comparative Example 4) A weight average molecular weight of 38% by weight. 417,000 of polyvinylidene fluoride homopolymer and 62% by weight of 7-butyrolactone were dissolved at 170 °C. The resin solution was discharged from the tube outside the double tube nozzle, and 7-butyrolactone was discharged from the inner tube of the double tube type, and the temperature was 20 in the 80% by weight aqueous solution of 7-butyrolactone. It is allowed to cure in a bath of °C. The obtained hollow fiber membrane is a hollow fiber membrane composed of a spherical structure. A Next, 12% by weight of a polyvinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 7.2% by weight of cellulose acetate (EASTMAN CHEMICAL, CA435-75S: cellulose triacetate), 80.8 wt% N- The methyl-2-pyrrolidone was dissolved and mixed at 95 ° C to obtain a film forming stock solution. The film forming stock solution was cooled to 70 ° C and uniformly coated on the surface of the hollow fiber membrane composed of a spherical structure, and immediately solidified in water at 43 ° C to produce a three-dimensional shape on the layer of the spherical structure. A hollow fiber membrane made of a layer of a network structure. Subsequently, the hollow fiber membrane was immersed in a 3000 ppm aqueous sodium hypochlorite solution for 300 hours.中空 The obtained hollow fiber membrane has an outer diameter of 1 360 μm and an inner diameter of 800 μm, and the membrane structure and membrane properties are shown in Table 1. As shown in the embodiment, the layer is formed by laminating a layer of a three-dimensional network structure and a layer of a spherical structure, and the layer of the three-dimensional network structure is divided into thin layers each having a thickness of 0.2 μm in the thickness direction thereof. In the case of a thin layer having a maximum pore diameter of 10 or more and 200 or less and a thickness of 0.03 μm or more and 0.2 μm or less, and a thin layer having a maximum pore diameter of less than 0.03 μm is a thermoplastic resin composed of 0 or more layers and 2 or less layers or less. The silk film can obtain a high level of hollow fiber membrane with pure water permeability, breaking strength, elongation at break, and virus removal -29-200950877. On the other hand, in Comparative Example 1, the film having a maximum pore diameter of less than 0.03 μm was inferior in permeability to pure water because of the treatment. Comparative Examples 2 and 4 have a low hydrophilicity of 7.2% by weight and a small pore layer having a maximum pore diameter of 0.03 μm or less, and the virus removal performance is low. Further, in the case of a layer having no spherical structure, the breaking strength is low. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a photograph obtained by taking a section of φ in an embodiment of the present invention at a magnification of 60,000 times. [Description of main component symbols] 1 Range of 1 layer of a thin layer having a thickness of 0.2 μm 2 External surface 3 Radial unused oxidant multilayer of hollow fiber membrane is 4 layers, polymer concentration U, 0.2 μm Comparative Example 3 Due to the radial direction of the air film

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Claims (1)

200950877 VII. Patent application scope: 1. A hollow fiber membrane characterized by a thermoplastic resin formed by laminating a layer of a three-dimensional network structure and a layer of a spherical structure in which a layer of the three-dimensional network structure is When the thickness direction is divided into a thin layer having a thickness of 〇·2 μm per layer, a thin layer having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less having 10 or more layers and 200 or less layers and a maximum pore diameter of less than 0.03 μm is used. The thin layer is more than the enamel layer and not more than two layers. 2. A thin layer of a hollow fiber membrane as claimed in claim 1 wherein the thin layer having a maximum pore diameter of less than 0.03 μm is a tantalum layer. 3. The hollow fiber membrane of the first aspect of the patent application, wherein the spherical solid component in the layer of the spherical structure has an average diameter of from 0. 9 μm to 3 μm. 4. The hollow fiber membrane of claim 1 wherein the three-dimensional network structure is disposed at the outermost layer of the hollow fiber membrane. 5. The hollow fiber membrane as claimed in claim 1 is formed of a layer of a three-dimensional network structure of one layer and a layer of a spherical structure of one layer. 0 6. The hollow fiber membrane of claim 1 wherein the thickness of the layer of the three-dimensional network structure is 5 micrometers or more and 1 micrometer or less and the thickness of the layer of the spherical structure is 110 micrometers or more and 400 micrometers. the following. 7. The hollow fiber membrane of claim 1, wherein the layer of the spherical structure is composed of a polyvinylidene fluoride resin. 8. The hollow fiber membrane of claim 1, wherein the layer of the three-dimensional network structure is formed by a hydrophilic polymer. 9. A method for producing a hollow fiber membrane, the method comprising the steps of: forming a hollow fiber membrane formed of a thermoplastic resin composed of a layer of a three-dimensional network structure and a layer of a spherical structure of -31-200950877, comprising: forming a process for forming a layer of a spherical structure; a process of forming a layer of a three-dimensional network structure by solidifying a resin solution containing 8% by weight or more of a hydrophilic polymer; and bringing a layer of the three-dimensional network structure into contact with an aqueous solution containing an oxidizing agent a process in which a layer of a three-dimensional network structure is divided into a thin layer each having a thickness of 0.2 μm in a thickness direction thereof, and has a thin layer having a maximum pore diameter of 10 or more and 200 or less and a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, and The thin layer having a maximum pore diameter of less than 〇.〇3 μm is 0 layer ❹ or more and 2 layers or less. 10. The method for producing a hollow fiber membrane according to claim 9, wherein the concentration of the aqueous solution containing the oxidizing agent is 500 ppm or more and 50,000 ppm or less and the contact time between the aqueous solution containing the oxidizing agent and the three-dimensional network structure is 1 hour or more, 4 0 0 hours or less. -32- 200950877 IV. Designated representative map: (1) The representative representative of the case is: (1). (2) The symbol of the symbol of this representative figure is briefly described as follows: 1 The range of 1 layer of the thin layer with a thickness of 0.2 μm The outer surface 3 The radial direction of the hollow fiber membrane ❹ 5. If there is a chemical formula in this case, please reveal the best invention. Characteristic chemical formula: