WO2009119373A1 - Membrane en fibres creuses et son procédé de fabrication - Google Patents

Membrane en fibres creuses et son procédé de fabrication Download PDF

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Publication number
WO2009119373A1
WO2009119373A1 PCT/JP2009/055090 JP2009055090W WO2009119373A1 WO 2009119373 A1 WO2009119373 A1 WO 2009119373A1 JP 2009055090 W JP2009055090 W JP 2009055090W WO 2009119373 A1 WO2009119373 A1 WO 2009119373A1
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layer
fiber membrane
hollow fiber
less
dimensional network
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PCT/JP2009/055090
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English (en)
Japanese (ja)
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尚 皆木
利之 石崎
進一 峯岸
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東レ株式会社
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Priority to JP2009514294A priority Critical patent/JPWO2009119373A1/ja
Publication of WO2009119373A1 publication Critical patent/WO2009119373A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/08—Hollow fibre membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/0283—Pore size

Definitions

  • the present invention relates to a hollow fiber membrane for selectively separating components of a liquid mixture and a method for producing the same. More specifically, the present invention relates to hollow fiber membranes such as hollow fiber microfiltration membranes and hollow fiber ultrafiltration membranes used in water treatment such as wastewater treatment, water purification treatment, and industrial water production, and a method for producing the same.
  • Separation membranes such as microfiltration membranes and ultrafiltration membranes are used in various fields including food industry, medicine, water production and wastewater treatment. Particularly in recent years, separation membranes have been used in the field of drinking water production, that is, in the process of water purification.
  • a hollow fiber membrane having a large effective membrane area per unit volume is generally used because of the large amount of water that must be treated.
  • the hollow fiber membrane has excellent pure water permeation performance, the membrane area can be reduced, and the equipment can be made compact, so that the equipment cost can be saved, and the membrane replacement cost and installation area are advantageous.
  • a disinfectant such as sodium hypochlorite is added to the membrane module for the purpose of sterilizing the permeated water and preventing biofouling of the membrane
  • acid such as hydrochloric acid, citric acid, and oxalic acid is used for cleaning the membrane.
  • separation membranes using polyvinylidene fluoride resin as a highly chemical-resistant material have been developed, as the membrane may be washed with alkali such as sodium hydroxide aqueous solution, chlorine, surfactant, etc. It's being used.
  • Patent Document 1 a solution containing about 10 5 CFU / ml of mycoplasma having a size of 125 nm or more is filtered by a regenerated cellulose membrane having a multistage filtration function having an average pore size of 30 to 100 nm and a film thickness of 20 ⁇ m or more.
  • a regenerated cellulose membrane having a multistage filtration function having an average pore size of 30 to 100 nm and a film thickness of 20 ⁇ m or more.
  • the layer having a small pore diameter is thicker than necessary, the pure water permeation performance is not always sufficient even though the film thickness is small.
  • Patent Document 2 discloses an isotropic, skinless polyvinylidene fluoride film that exhibits high virus removal performance by increasing the film thickness. However, if the film thickness is not more than 100 ⁇ m, sufficient virus removal performance will not be exhibited, and hydrophilic polymer is grafted on the surface to impart hydrophilicity, but the isotropic structure makes the entire film hydrophilic Otherwise, the effect is low, and sufficient pure water permeation performance cannot be obtained.
  • Patent Document 3 discloses a hollow fiber membrane used for medical purposes, which is made of polyvinylidene fluoride resin, has a maximum pore size of 10 to 100 nm determined by the bubble point method, and a dense structure layer has a thickness of 50% of the total thickness.
  • the hollow fiber membrane which shows the high virus removal performance by setting it as the above.
  • it since it is formed from a single layer having a continuous structure and is further thin, its breaking strength is very low and it cannot be applied to water treatment applications. Further, since the dense layer is too thick, the pure water permeation performance is low despite the thin film thickness.
  • a hollow fiber membrane that can be used in water treatment applications and has high virus removal performance, high pure water permeation performance, and high physical durability and chemical durability.
  • the purpose is to provide.
  • 10 to 200 thin layers with a maximum pore diameter of 0.03 ⁇ m or more and 0.2 ⁇ m or less, and 0 to 2 or less thin layers with a maximum pore diameter of less than 0.03 ⁇ m A hollow fiber membrane characterized by the above.
  • a method for producing a hollow fiber membrane comprising a thermoplastic resin comprising a layer having a three-dimensional network structure and a spherical structure layer, the method comprising the step of contacting the layer having a network structure, the layer having a three-dimensional network structure
  • the thin layer having a maximum pore diameter of 0.03 ⁇ m or more and 0.2 ⁇ m or less is 10 to 200 and the maximum pore diameter is less than 0.03 ⁇ m.
  • a method for producing a hollow fiber membrane characterized in that the thin layer is from 0 to 2.
  • the concentration of the aqueous solution containing the oxidizing agent is 500 ppm or more and 50000 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 and 400 hours or less (9)
  • a hollow fiber membrane having high chemical and physical durability and high virus removal performance and pure water permeation performance is provided.
  • the hollow fiber membrane of the present invention is composed of a layer having a three-dimensional network structure and a layer having a spherical structure.
  • the three-dimensional network structure refers to a structure in which the solid content spreads in a three-dimensional network.
  • the spherical structure refers to a structure in which a large number of spherical (including substantially spherical) solids are connected by sharing a part thereof.
  • the three-dimensional network layer is a layer that stably removes contaminants including viruses in the filtered water, and the spherical layer is a layer that supports physical strength and supports the three-dimensional network layer. is there.
  • the two layers need to have a laminated structure in order to balance the performance of each layer at a high level.
  • the layers enter each other at the interface of each layer and become dense, resulting in a decrease in transmission performance.
  • the transmission performance does not decrease, but the adhesive strength decreases. Therefore, it is preferable that the number of stacked layers is small, and it is particularly preferable that the number of stacked layers is two layers, that is, one three-dimensional network structure layer and one spherical structure layer.
  • the arrangement of each layer in the hollow fiber membrane is not particularly limited, but the layer of the three-dimensional network structure is responsible for the separation function, and the layer of the spherical structure is responsible for the physical strength.
  • the separation target side is preferably the outer surface side of the hollow fiber membrane, and in the case of the inner surface side, contaminants may accumulate in the hollow portion having a small space, and the permeation performance may be lowered. From this, it is a particularly preferable embodiment that the layer of the three-dimensional network structure is disposed in the outermost layer of the hollow fiber membrane and the layer of the spherical structure is disposed in the innermost layer.
  • a layer having a three-dimensional network structure for removing contaminants including viruses can satisfy high removal performance and high permeation performance, but it is very difficult to satisfy higher physical strength.
  • the reason is as follows. First, in order to obtain a high removal performance, it is necessary to form a dense structure, but if it has a dense structure, the transmission performance decreases, and in order to increase the transmission performance, This is because it is necessary to reduce the thickness or form a dense structure from a low-concentration resin stock solution, resulting in a decrease in physical strength. If the physical strength of the hollow fiber membrane is low, thread breakage may occur due to an operation of washing the hollow fiber membrane by vibrating with air, etc., resulting in leakage of contaminants.
  • a hollow fiber membrane comprising a three-dimensional network structure layer having high virus removal performance and permeation performance and a spherical structure layer having high physical strength and permeation performance is obtained.
  • a hollow fiber membrane having a high level of removal performance, permeation performance and physical strength has been obtained. Furthermore, as a result of intensive studies on the manufacturing method, the layer of the three-dimensional network structure has a structure with high virus removal performance and permeation performance, which was difficult to form using a resin with particularly high chemical durability. It came to.
  • the layer having a three-dimensional network structure has 10 to 200 thin layers having a maximum pore diameter of 0.03 ⁇ m to 0.2 ⁇ m when divided into thin layers having a thickness of 0.2 ⁇ m in the thickness direction, and
  • the thin layer having a maximum pore diameter of less than 0.03 ⁇ m is 0 or more and 2 or less.
  • the maximum pore diameter in a thin layer having a thickness of 0.2 ⁇ m can be measured as follows. 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 at a magnification at which the structure can be clearly confirmed, preferably 60,000 times or more.
  • the thin film having a thickness of 0.2 ⁇ m is formed from the outer surface or the inner surface to the boundary with the spherical structure layer. And measure the maximum pore size in each thin layer.
  • the layer of the three-dimensional network structure is between the other two spherical structure layers, every thin layer with a thickness of 0.2 ⁇ m from the boundary with one of the spherical structure layers to the other boundary And measure the maximum pore size in each thin layer.
  • the maximum hole diameter is the maximum short diameter of the hole.
  • the hole refers to a region surrounded by the solid portion, and the maximum short diameter of the hole represents the length of the maximum short diameter among the holes in the thin layer.
  • the minor axis of the hole is the length of the line segment where the vertical bisector overlaps the hole when a perpendicular bisector is drawn with respect to the major axis of the hole.
  • the major axis of the hole is the length between the two most distant points on the boundary between the hole and the solid content.
  • FIG. 1 shows a radial cross section of a hollow fiber membrane according to an embodiment of the present invention, which was photographed as described above.
  • FIG. 1 is a part of a combination of a plurality of photographs obtained by continuously photographing layers of a three-dimensional network structure from the outer surface, and the vertical direction in the figure indicates the radial direction of the hollow fiber membrane.
  • the layer of the three-dimensional network structure is divided for each thin layer 1 having a thickness of 0.2 ⁇ m in the thickness direction from the outer surface.
  • the maximum pore diameter is set for each thin layer 1. taking measurement.
  • the layer of the three-dimensional network structure in the present invention has a thin layer having a maximum pore diameter measured in this way of 0.03 ⁇ m or more and 0.2 ⁇ m or less continuously or intermittently 10 or more and 200 or less, and
  • the thin layer having a maximum pore diameter of less than 0.03 ⁇ m needs to be 0 or more and 2 or less.
  • the hollow fiber membrane of the present invention has a very high removal performance against the smallest virus.
  • the size of the smallest virus is about 0.02 ⁇ m, and that the hollow fiber membrane of the present invention has a thin layer with a maximum pore size of 0.03 ⁇ m or more and 0.2 ⁇ m or less of 10 or more and 200 or less than the smallest virus. In other words, a layer having a slightly larger pore diameter exists with a certain thickness.
  • each thin layer with a maximum pore size of 0.03 ⁇ m or more and 0.2 ⁇ m or less is not high, the presence of such thin layers over multiple layers results in a multi-stage filtration mechanism and removal performance.
  • So-called depth filtration can be used.
  • So-called surface filtration that removes viruses with a dense layer that does not contain larger pores than viruses with a thickness of about 0.6 ⁇ m, that is, a layer with about 3 thin layers with a maximum pore size of less than 0.03 ⁇ m.
  • the hollow fiber membrane of the present invention has 10 or more and 200 or less thin layers with a maximum pore diameter of 0.03 to 0.2 ⁇ m, and 2 or less thin layers with a maximum pore diameter of less than 0.03 ⁇ m.
  • the pure water permeation performance is proportional to the fourth power of the pore diameter (Poiseuille's law) and inversely proportional to the first power of the layer thickness. That is, the decrease in pure water permeation performance is smaller when the layer is thicker than when the pore diameter is small.
  • the removal performance of each thin layer having a thickness of 0.2 ⁇ m increases as the maximum pore size decreases. Therefore, in order to improve pure water permeation performance, the thin layer necessary to exhibit high removal performance It is preferable to reduce the number of. From this, as a more effective form considering virus removal performance and pure water permeation performance, it is preferable to have a thin layer having a maximum pore diameter of 0.03 ⁇ m to 0.1 ⁇ m of 10 to 75, more preferably 10 It is having 50 or less. Or it is preferable to have 10 or more and 50 or less thin layers with a maximum pore diameter of 0.03 ⁇ m or more and 0.07 ⁇ m or less, and more preferably 10 or more and 35 or less.
  • the layer of the three-dimensional network structure may have a thin layer having a maximum pore diameter exceeding 0.2 ⁇ m other than the above-described depth filtration structure having a maximum pore diameter of 0.03 ⁇ m to 0.2 ⁇ m.
  • a thin layer having a maximum pore diameter of less than 0.03 ⁇ m is required to be 2 or less, preferably 1 or less, and more preferably not at all is effective in order not to lower the pure water permeation performance.
  • the average diameter of the spherical solid content is 0.9 ⁇ m or more and 3 ⁇ m or less.
  • the spherical solid content is defined as a solid content having a roundness ratio (major axis / minor axis) of 2 or less.
  • the average diameter of each spherical solid is the average value of the major axis and the minor axis. If the average diameter of the spherical solid content is less than 0.9 ⁇ m, the voids formed between the solid content will be small and sufficient pure water permeation performance will not be obtained, and if it exceeds 3 ⁇ m, the solid content will be less connected.
  • the spherical structure layer preferably has a homogeneous structure in order to achieve both a high level of pure water permeation performance and physical strength. If a dense layer is provided or the structure is changed in an inclined manner, it is difficult to achieve both pure water permeation performance and physical strength.
  • the spherical solid content it is preferable to include a columnar solid content having a roundness ratio (major axis / minor axis) of more than 2 because the physical strength is further increased.
  • the hollow fiber membrane of the present invention is made of a thermoplastic resin.
  • the thermoplastic resin is a resin made of a chain polymer material, and exhibits a property of being deformed / flowed by an external force when heated.
  • this thermoplastic resin include polyethylene, polypropylene, acrylic resin, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resin, polystyrene, acrylonitrile-styrene (AS) resin, vinyl chloride resin, polyethylene terephthalate, polyamide, polyacetal, Examples thereof include polycarbonate, modified polyphenylene ether, polyphenylene sulfide, polyvinylidene fluoride, polyamideimide, polyetherimide, polysulfone, polyethersulfone, and mixtures and copolymers thereof.
  • the thermoplastic resin forming the layer of the three-dimensional network structure preferably has high chemical durability in order to stably remove contaminants including viruses, and to obtain high pure water permeation performance. It is preferable that is highly hydrophilic. Therefore, a polyacrylonitrile resin or a mixture of a polyvinylidene fluoride resin and a hydrophilic polymer is particularly preferably used.
  • a polyacrylonitrile resin or a mixture of a polyvinylidene fluoride resin and a hydrophilic polymer is particularly preferably used.
  • the polyacrylonitrile-based resin a homogenous and dense structure is easily formed, and since it has excellent physical strength and thermal characteristics, those having a very high degree of polymerization are preferable, and the intrinsic viscosity is 2 or more, preferably 2 It is 0.5 or more and 3.6 or less, More preferably, it is 2.9 or more and 3.3 or less.
  • the resin is an acrylonitrile homopolymer or an acrylonitrile copolymer comprising acrylonitrile in an amount of 90 mol% or more, preferably 95 mol% or more and 5 mol% or less of a vinyl compound having a copolymerizability with respect to acrylonitrile.
  • the vinyl compound is not particularly limited as long as it is a compound having copolymerizability with respect to various known acrylonitriles.
  • Preferred copolymer components include acrylic acid, itaconic acid, methyl acrylate, methyl methacrylate, Examples include vinyl acetate, sodium allyl sulfonate, sodium methallyl sulfonate, sodium p-styrene sulfonate, and the like.
  • the polyvinylidene fluoride 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 copolymers.
  • the vinylidene fluoride copolymer is a polymer having a vinylidene fluoride residue structure, and is typically a copolymer of a vinylidene fluoride monomer and other fluorine-based monomers.
  • copolymer examples include a copolymer of vinylidene fluoride and at least one selected from vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, and trifluoroethylene chloride. Further, a monomer such as ethylene other than the fluorine-based monomer may be copolymerized to such an extent that the effects of the present invention are not impaired.
  • the hydrophilic polymer is at least one selected from cellulose ester, fatty acid vinyl ester, vinyl pyrrolidone, ethylene oxide, propylene oxide, acrylonitrile, acrylic acid ester, and methacrylic acid ester as molecular units in the main chain and / or side chain.
  • molecular units other than these may exist.
  • Examples of molecular units other than the above molecular units include alkenes such as ethylene and propylene, alkynes such as acetylene, vinyl halides, and vinylidene halides.
  • ethylene and vinylidene halide are preferably used because they are available at a relatively low cost and have high chemical durability. Since the hydrophilic polymer is used to form a three-dimensional network structure together with the polyvinylidene fluoride resin, it is preferably mixed with the polyvinylidene fluoride resin under appropriate conditions.
  • the spherical layer is a layer that supports the three-dimensional network layer, it requires a particularly high chemical durability as well as physical strength, so it is made of polyethylene, polypropylene, or polyvinylidene fluoride resin. Is more preferable, and it is more preferably made of a polyvinylidene fluoride resin.
  • Such a hollow fiber membrane of the present invention has, as its effect, pure water permeation performance, breaking strength, breaking elongation, and virus removal performance at a high level. That is, pure water permeation performance at 50 kPa and 25 ° C. is 0.2 m 3 / m 2 / hr or more, breaking strength 4 N / piece or more, breaking elongation 20% or more, and virus removal performance 4 log or more. Further, by optimizing the implementation conditions of the present invention, pure water permeation performance is 0.3 m 3 / m 2 / hr or more, breaking strength is 4 N / piece or more, breaking elongation is 20% or more, and virus removal performance is 4 log or more. Can be obtained.
  • the layer having a spherical structure is thickened, the pure water permeation performance is 0.3 m 3 / m 2 / hr or more, the breaking strength is 9 N / piece or more, the breaking elongation is 20% or more,
  • a membrane having a virus removal performance of 4 logs or more can be obtained.
  • a hollow fiber membrane made of a thermoplastic resin formed by laminating a layer having a three-dimensional network structure and a spherical structure according to the present invention can be manufactured by various methods. For example, there is a method of laminating a layer of a three-dimensional network structure on a hollow fiber membrane having a spherical structure and performing an oxidation treatment. In this method, a hollow fiber membrane having a spherical structure is first manufactured. As an example, a method using a polyvinylidene fluoride resin as a resin will be described.
  • the polyvinylidene fluoride resin is dissolved in a poor solvent or a good solvent of the resin at a temperature higher than the crystallization temperature at a relatively high concentration of 20 wt% or more and 60 wt% or less. If the resin concentration is high, a hollow fiber membrane having high strength and elongation characteristics can be obtained. However, if the resin concentration is too high, the porosity of the produced hollow fiber membrane is reduced and the pure water permeation performance is lowered. If the viscosity of the adjusted resin solution is not within an appropriate range, it cannot be formed into a hollow fiber membrane. Therefore, the resin concentration is more preferably in the range of 30% by weight to 50% by weight.
  • the poor solvent means that the polyvinylidene fluoride resin cannot be dissolved by 5% by weight or more at a low temperature of less than 60 ° C., but it is 60 ° C. or more and below the melting point of the polyvinylidene fluoride resin (for example, polyvinylidene fluoride resin).
  • a solvent that does not dissolve or swell is defined as a non-solvent.
  • examples of the poor solvent for the polyvinylidene fluoride resin include medium chain length alkyl ketones such as cyclohexanone, isophorone, ⁇ -butyrolactone, methyl isoamyl ketone, and propylene carbonate, esters, organic carbonates, and the like, and mixed solvents thereof.
  • examples of good solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethyl urea, trimethyl phosphate, and other lower alkyl ketones, esters, amides, and the like, and mixed solvents thereof. Is mentioned.
  • Non-solvents include water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol. , Hexanediol, aliphatic hydrocarbons such as low molecular weight polyethylene glycol, aromatic hydrocarbons, aliphatic polyhydric alcohols, aromatic polyhydric alcohols, chlorinated hydrocarbons, or other chlorinated organic liquids and mixed solvents thereof Is mentioned.
  • a hollow fiber membrane having a spherical structure is produced by a thermally induced phase separation method in which the resin solution is phase-separated by cooling.
  • the polyvinylidene fluoride resin solution is discharged from the outer tube of the double tube die for spinning the hollow fiber membrane, and the hollow portion forming liquid is cooled in the cooling bath while being discharged from the inner tube of the double tube die.
  • the cooling bath is preferably a mixed liquid composed of a poor solvent or a good solvent having a concentration of 50% to 95% by weight and a non-solvent having a concentration of 5% to 50% by weight at 0 ° C. to 30 ° C.
  • the same poor solvent as the resin solution is used as the poor solvent because the cooling bath composition is easily maintained.
  • a high concentration good solvent is used, solidification may not occur unless the temperature is sufficiently lowered, or the hollow fiber membrane surface may not be smooth due to slow solidification.
  • a poor solvent and a good solvent may be mixed as long as the concentration range is not deviated.
  • a dense layer may be formed on the outer surface of the hollow fiber membrane, and the pure water permeation performance may be significantly reduced.
  • the hollow portion forming liquid is preferably a mixed liquid comprising a poor solvent or a good solvent having a concentration of 50% by weight to 95% by weight and a non-solvent having a concentration of 5% by weight to 50% by weight, as in the cooling bath. . Further, it is preferable to use the same poor solvent as the resin solution as the poor solvent.
  • phase separation mechanisms when manufacturing by the thermally induced phase separation method, two kinds of phase separation mechanisms are mainly used.
  • One is a liquid-liquid phase separation method in which a polymer solution that is uniformly dissolved at a high temperature is separated into a polymer rich phase and a dilute phase due to a decrease in solution dissolving ability when the temperature is lowered, and then the structure is fixed by crystallization.
  • the other is a solid-liquid phase separation method in which a polymer solution that is uniformly dissolved at a high temperature causes crystallization of the polymer when the temperature is lowered and phase-separates into a polymer solid phase and a solvent phase.
  • a three-dimensional network structure is mainly formed
  • a spherical structure mainly composed of a spherical structure is formed.
  • the latter phase separation mechanism is utilized, and the combination of the resin concentration, temperature, resin solution solvent, cooling bath composition, and temperature at which solid-liquid phase separation is induced is important.
  • the three-dimensional network structure formed by the former phase separation mechanism it is difficult to achieve both high elongation performance and pure water permeation performance at a high level.
  • the three-dimensional network structure has a structure in which streaky solids are uniformly connected three-dimensionally, and the spherical solids are non-uniformly shared with each other to form a strongly connected spherical structure. In comparison, the hole diameter is reduced. Therefore, it is considered that the pure water permeation performance is lowered even with the same high elongation performance.
  • the stretching method is preferably 50 ° C. or higher and 140 ° C. or lower, more preferably 55 ° C. or higher and 120 ° C. or lower, more preferably 60 ° C. or higher and 100 ° C. or lower, preferably 1.1 times or higher and 4 times or lower, more preferably Is a draw ratio of 1.1 to 2 times.
  • stretching is preferably performed in a liquid because temperature control is easy, but may be performed in a gas such as steam.
  • a gas such as steam.
  • water is convenient and preferable, but when stretching at about 90 ° C. or higher, it is also possible to preferably employ a low molecular weight polyethylene glycol or the like.
  • pure water permeation performance and breaking strength are reduced, but breaking elongation and removal performance are improved as compared with the case of stretching. Therefore, the presence / absence of the stretching step and the stretching ratio of the stretching step can be appropriately set according to the use of the hollow fiber membrane.
  • a layer having a three-dimensional network structure is formed on the hollow fiber membrane having the spherical structure formed as described above.
  • the method is not particularly limited, but a method in which the resin solution forming the three-dimensional network structure contains a hydrophilic polymer at a high concentration is preferable.
  • a method using a polyacrylonitrile resin as a resin and a mixture of a polyvinylidene fluoride resin and a hydrophilic polymer will be described.
  • Examples of the organic solvent for dissolving the polyacrylonitrile-based resin include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, ethylene carbonate, and butyl lactone, and dimethyl sulfoxide is particularly preferably used.
  • the resin concentration of the polyacrylonitrile resin solution is in the range of 8 wt% to 20 wt%, preferably 9 wt% to 16 wt%. If it is lower than 8% by weight, a thin layer having a maximum pore diameter of 0.2 ⁇ m or less is hardly formed, and sufficient virus removal performance is not exhibited. On the other hand, when the amount exceeds 20% by weight, many thin layers having a maximum pore size of less than 0.03 ⁇ m are formed.
  • a uniform solution can be obtained by dissolving at a relatively high temperature of 80 ° C. or higher and 170 ° C. or lower.
  • the polyacrylonitrile resin solution After applying such a polyacrylonitrile resin solution to the surface of a hollow fiber membrane having a spherical structure, the polyacrylonitrile resin solution is solidified in a coagulation bath consisting mainly of a non-solvent of the polyacrylonitrile resin solution, thereby forming a three-dimensional network structure. Cover the layer.
  • the method of applying is not particularly limited, but a method of immersing the hollow fiber membrane in a polyacrylonitrile resin solution or spray coating the hollow fiber membrane is preferably used.
  • a part of the resin solution is scraped by passing through the nozzle after being applied, or by using an air knife.
  • the coagulation bath is preferably composed mainly of a non-solvent of polyacrylonitrile-based resin and contains an organic solvent that dissolves the polyacrylonitrile-based resin in the range of 0 wt% to 30 wt%.
  • the non-solvent for the polyacrylonitrile-based resin include water, alcohols, aliphatic ketones, glycerin, polyethylene glycol, and the like, and water is particularly preferably used.
  • the temperature of the coagulation bath is too high, the film contracts and the pure water permeation performance is lowered, so that it is 5 ° C. or higher and 70 ° C. or lower, preferably 5 ° C. or higher and 40 ° C. or lower.
  • the solvent for dissolving the mixture of the polyvinylidene fluoride resin and the hydrophilic polymer it is preferable to use a good solvent for the polyvinylidene fluoride resin.
  • the sum of the polyvinylidene fluoride resin concentration and the hydrophilic polymer concentration is preferably 18% by weight to 30% by weight, and more preferably 20% by weight. It is preferable to adjust so that it may become the range of 30 to 30 weight%.
  • hydrophilic polymer concentration in the range of 8 wt% to 20 wt%, preferably 9 wt% to 16 wt%.
  • a uniform solution can be obtained by performing dissolution at a relatively high temperature of 80 ° C. or higher and 170 ° C. or lower.
  • a solution of such a mixture of polyvinylidene fluoride resin and hydrophilic polymer is applied to the surface of a hollow fiber membrane having a spherical structure, and then coagulated in a coagulation bath mainly composed of a non-solvent of polyvinylidene fluoride resin. By covering, the layer of the three-dimensional network structure is covered.
  • the coagulation bath is mainly composed of a non-solvent of the polyvinylidene fluoride resin, and may contain a good solvent or a poor solvent of the polyvinylidene fluoride resin in the range of 0% by weight to 30% by weight.
  • the temperature of the coagulation bath is 10 ° C. or higher and 70 ° C. or lower, preferably 20 ° C. or higher and 50 ° C. or lower.
  • a resin solution forming a three-dimensional network structure and a layer of a spherical structure A method of simultaneously discharging and solidifying a resin solution that forms a solid from a triple tube die is also preferably employed. That is, when producing a hollow fiber membrane in which the layer of the three-dimensional network structure is disposed in the outer layer of the hollow fiber membrane and the layer of the spherical structure is disposed in the inner layer, the resin solution forming the three-dimensional network structure is removed from the outer tube. It can be obtained by simultaneously discharging the resin solution forming the spherical structure layer from the intermediate tube and the hollow portion forming liquid from the inner tube and solidifying it in the coagulation bath.
  • the layer of the three-dimensional network structure has a dense thin layer having a maximum pore diameter of less than 0.03 ⁇ m on the outermost layer, and the pore diameter from the surface layer to the inner direction of the layer. It consists of an inclined structure that grows continuously.
  • Such an inclined structure is a structure including three or more thin layers having a maximum pore diameter of less than 0.03 ⁇ m, and has high virus removal performance but does not exhibit sufficient pure water permeation performance.
  • the maximum pore diameter required in the present invention on the surface layer side is from 10 to 200 thin layers having a maximum pore diameter of 0.03 to 0.2 ⁇ m, and A thin layer having a maximum pore diameter of less than 0.03 ⁇ m is 2 or less, and it is possible to form a layer having relatively large pores inside the layer.
  • the transmission performance can be dramatically improved.
  • the hollow fiber membrane of the present invention can be produced by bringing the hollow fiber membrane obtained there into contact with an aqueous solution containing an oxidizing agent at a relatively high concentration for an appropriate time.
  • the resin forming the layer of the three-dimensional network structure is not particularly affected when the aqueous solution has a low concentration with respect to the aqueous solution containing an oxidizing agent or when the contact with the aqueous solution is short. It is necessary to include a resin that is partly chemically decomposed in the case of high concentration or prolonged contact. As such a resin, the hydrophilic polymer mentioned above is preferably mentioned.
  • a part of the resin forming the layer of the three-dimensional network structure is chemically decomposed by the oxidizing agent, so that the structure of the layer of the three-dimensional network structure is changed. That is, by expanding the pore diameter of a thin layer having a maximum pore diameter of less than 0.03 ⁇ m existing in the outermost layer of the layer of the three-dimensional network structure, the thin layer having a maximum pore diameter of less than 0.03 ⁇ m is less than 3, and the maximum pore diameter is A layer having a three-dimensional network structure in which a thin layer of 0.03 ⁇ m or more and 0.2 ⁇ m or less is 10 or more and 200 or less is formed.
  • the three-dimensional network structure before being brought into contact with the aqueous solution containing an oxidizing agent is formed from a solution of a mixture of a polyvinylidene fluoride resin and a hydrophilic polymer, it is brought into contact with the aqueous solution containing the oxidizing agent.
  • the hydrophilic polymer may not substantially remain, but in this case, it is composed of only the hydrophobic polyvinylidene fluoride resin. From the standpoint of improving pure water permeation performance, it is preferable that a hydrophilic polymer is finally included.
  • the type, concentration, and contact time of the oxidizing agent in accordance with the structure and composition of the layer of the three-dimensional network structure before contacting with the aqueous solution containing the oxidizing agent.
  • the resin forming the spherical structure layer is not chemically degraded by the oxidizing agent, the physical strength does not decrease. Therefore, a resin with high chemical resistance is selected as the resin forming the spherical structure layer. It is necessary to control the kind, concentration and contact time of the oxidizing agent.
  • the oxidizing agent is not particularly limited as long as it is water-soluble, but sodium hypochlorite, hydrogen peroxide, potassium permanganate, potassium dichromate, halogen, concentrated sulfuric acid, nitric acid, chloramine and the like are preferable. Sodium chlorite is preferably used.
  • the concentration of the oxidizing agent is 500 ppm or more and 50000 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 10,000 ppm or less
  • the contact time with the oxidizing agent is 10 hours or more and 200 hours or less, more preferably the concentration of the oxidizing agent is 2000 ppm or more and 8000 ppm or less
  • the contact time with the agent is 20 hours or more and 100 hours or less.
  • 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 a long time exceeding 400 hours is required to sufficiently change the structure. Since it disappears, it is not preferable.
  • the resin of the spherical structure layer may be chemically decomposed and the physical strength may be reduced. Further, if the contact time with the oxidant is less than 1 hour, a sufficient structural change does not occur in the layer having a three-dimensional network structure, or a high concentration exceeding 50000 ppm is necessary to sufficiently change the structure. There is a possibility that the resin of the structural layer is chemically decomposed and the physical strength is lowered. When the time exceeds 400 hours, the resin of the layer having a spherical structure is not preferable because it is chemically decomposed and the physical strength may be lowered, and it is not practical.
  • the thicknesses of the three-dimensional network layer and the spherical layer are also important.
  • the layer of the three-dimensional network structure has a thin layer with a maximum pore diameter of 0.03 ⁇ m or more and 0.2 ⁇ m or less and a thin layer with a maximum pore diameter of less than 0.03 ⁇ m of 2 or less as long as it has only 2 or less.
  • the thickness of the layer is preferably 5 ⁇ m to 100 ⁇ m, preferably 10 ⁇ m to 60 ⁇ m, and more preferably 15 ⁇ m to 35 ⁇ m.
  • the thickness of the layer having a spherical structure is preferably 110 ⁇ m or more and 400 ⁇ m or less, and preferably 150 ⁇ m or more and 300 ⁇ m or less. If the thickness of the spherical structure layer is less than 110 ⁇ m, sufficient physical strength cannot be obtained, and if it exceeds 400 ⁇ m, the pure water permeation performance deteriorates.
  • a layer having a maximum pore diameter of less than 0.03 ⁇ m, a layer having a maximum pore diameter of 0.03 ⁇ m or more and less than 0.07 ⁇ m, a layer having a maximum pore diameter of 0.07 ⁇ m or more and less than 0.1 ⁇ m, and a layer having a maximum pore diameter of 0.1 ⁇ m or more and 0.2 ⁇ m or less Each number was determined. This operation was carried out at arbitrary three locations and obtained by number averaging.
  • Virus removal performance An aqueous solution of distilled water containing bacteriophage MS-2 (Bacteriophage MS-2 ATCC 15597-B1) having a size of about 25 nm at a concentration of about 1.0 ⁇ 10 7 PFU / ml As prepared.
  • the distilled water used here was distilled water from a pure water production apparatus Auto Still (manufactured by Yamato Kagaku) and subjected to high pressure steam sterilization at 121 ° C. for 20 minutes.
  • a small glass module having a length of about 20 cm consisting of four hollow fiber membranes was prepared, and the virus stock solution was fed under conditions of a temperature of about 20 ° C. and a filtration differential pressure of about 10 kPa (external pressure).
  • Example 1 38% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 41,000 and 62% by weight of ⁇ -butyrolactone were dissolved at 160 ° C.
  • This resin solution is discharged from the outer tube of the double-tube base, and at the same time, an 85% by weight aqueous solution of ⁇ -butyrolactone is discharged from the inner tube of the double-tube base, and the temperature of the aqueous solution of 85% by weight of ⁇ -butyrolactone is 10%.
  • the obtained hollow fiber membrane was a hollow fiber membrane having a spherical structure.
  • a polymer having an acrylonitrile of 100 mol% and an intrinsic viscosity of 3.2 was polymerized in dimethyl sulfoxide, and further diluted with dimethyl sulfoxide to obtain a 13.5 wt% film-forming stock solution.
  • the membrane-forming stock solution is uniformly applied to the surface of a hollow fiber membrane having a spherical structure, and immediately solidified in a 20% by weight dimethyl sulfoxide aqueous solution at 23 ° C., and a layer having a three-dimensional network structure is formed on the layer having a spherical structure.
  • a hollow fiber membrane formed with was prepared. Thereafter, the hollow fiber membrane was immersed in an aqueous solution of 3000 ppm sodium hypochlorite for 180 hours.
  • the obtained hollow fiber membrane had an outer diameter of 1430 ⁇ m and an inner diameter of 880 ⁇ m, and the membrane structure and membrane performance were as shown in Table 1.
  • Example 2 A hollow fiber membrane was produced in the same manner as in Example 1 except that the hollow fiber membrane was immersed in an aqueous solution of 3000 ppm sodium hypochlorite for 360 hours.
  • the obtained hollow fiber membrane had an outer diameter of 1420 ⁇ m and an inner diameter of 890 ⁇ m, and the membrane structure and membrane performance were as shown in Table 1.
  • Example 3 a hollow fiber membrane having a spherical structure was produced in the same manner as in Example 1.
  • a film-forming stock solution was obtained by mixing and dissolving at 150% by weight.
  • This membrane-forming stock solution is cooled to 70 ° C. and uniformly applied to the surface of the hollow fiber membrane having a spherical structure, and immediately solidified in water at 27 ° C. to form a three-dimensional network structure layer on the spherical structure layer.
  • the formed hollow fiber membrane was produced. Thereafter, the hollow fiber membrane was immersed in an aqueous solution of 6000 ppm sodium hypochlorite for 22 hours.
  • the obtained hollow fiber membrane had an outer diameter of 1410 ⁇ m and an inner diameter of 880 ⁇ m, and the membrane structure and membrane performance were as shown in Table 1.
  • Example 1 A hollow fiber membrane was obtained in the same manner as in Example 1 except that it was not immersed in an aqueous sodium hypochlorite solution.
  • the obtained hollow fiber membrane had an outer diameter of 1440 ⁇ m and an inner diameter of 870 ⁇ m, and the membrane structure and membrane performance were as shown in Table 1.
  • the obtained hollow fiber membrane had an outer diameter of 1450 ⁇ m and an inner diameter of 900 ⁇ m, and the membrane structure and membrane performance were as shown in Table 1.
  • the obtained hollow fiber membrane had an outer diameter of 290 ⁇ m and an inner diameter of 210 ⁇ m, and the membrane structure and membrane performance were as shown in Table 1.
  • the obtained hollow fiber membrane has an outer diameter of 1360 ⁇ m and an inner diameter of 800 ⁇ m, and the membrane structure and membrane performance are shown in Table 1.
  • a layer having a three-dimensional network structure and a layer having a spherical structure are laminated, and the layer having a three-dimensional network structure has a thickness of 0.2 ⁇ m in the thickness direction.
  • Thermoplastic having 10 to 200 thin layers with a maximum pore size of 0.03 ⁇ m to 0.2 ⁇ m and a thin layer with a maximum pore size of less than 0.03 ⁇ m of 0 to 2 when divided into thin layers
  • Comparative Example 1 since Comparative Example 1 was not treated with an oxidizing agent, the number of thin layers having a maximum pore diameter of less than 0.03 ⁇ m is as large as 4, and the pure water permeation performance is low. In Comparative Examples 2 and 4, the hydrophilic polymer concentration is as low as 7.2% by weight, and there are few thin layers having a maximum pore diameter of 0.03 ⁇ m or more and 0.2 ⁇ m or less, and thus the virus removal performance is low. Moreover, since the comparative example 3 does not have a layer of a spherical structure, its breaking strength is low.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Abstract

L'invention porte sur une membrane en fibres creuses qui est utilisable pour le traitement d'eau et ainsi de suite et qui a une performance d'élimination de virus élevée, une perméabilité de l'eau pure élevée et une endurance physique et une endurance chimique élevées. L'invention porte sur une membrane en fibres creuses en résine thermoplastique constituée à la fois d'une couche de structure de réseau tridimensionnel et d'une couche de structure sphérique qui sont stratifiées l'une avec l'autre, caractérisée par le fait que, lorsque la couche de structure de réseau tridimensionnel est divisée dans la direction de l'épaisseur en couches minces de 0,2 µm d'épaisseur, la couche de structure de réseau tridimensionnel comprend 10 à 200 couches minces ayant des diamètres de pores maximaux de 0,03 à 0,2 µm et zéro à deux couches minces ayant des diamètres de pores maximaux inférieurs à 0,03 µm.
PCT/JP2009/055090 2008-03-25 2009-03-17 Membrane en fibres creuses et son procédé de fabrication WO2009119373A1 (fr)

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JP2013510717A (ja) * 2010-12-16 2013-03-28 天津膜天膜科技股▲分▼有限公司 ポリフッ化ビニリデン複合補強型液体分離膜の製造方法
WO2014208592A1 (fr) 2013-06-26 2014-12-31 ダイキン工業株式会社 Composition, membrane polymère poreuse et agent hydrophile
US11364327B2 (en) * 2016-08-31 2022-06-21 Terumo Kabushiki Kaisha Heat exchanger, oxygenator, and method of manufacturing a heat exchanger

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JP6782788B2 (ja) * 2016-11-04 2020-11-11 旭化成メディカル株式会社 多孔膜及び多孔膜の製造方法

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JP2006281202A (ja) * 2005-03-11 2006-10-19 Toray Ind Inc 中空糸膜、それを用いた浸漬型膜モジュール、分離装置、ならびに中空糸膜の製造方法
WO2008001426A1 (fr) * 2006-06-27 2008-01-03 Toray Industries, Inc. Membrane de séparation de polymère et son procédé de fabrication
WO2008012872A1 (fr) * 2006-07-25 2008-01-31 Toray Industries, Inc. Membrane de séparation à base de polymère de fluororésine et procédé de production de celle-ci
JP2008036559A (ja) * 2006-08-08 2008-02-21 Toray Ind Inc フッ素樹脂系高分子分離膜の酸化加工処理方法

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JP2006281202A (ja) * 2005-03-11 2006-10-19 Toray Ind Inc 中空糸膜、それを用いた浸漬型膜モジュール、分離装置、ならびに中空糸膜の製造方法
WO2008001426A1 (fr) * 2006-06-27 2008-01-03 Toray Industries, Inc. Membrane de séparation de polymère et son procédé de fabrication
WO2008012872A1 (fr) * 2006-07-25 2008-01-31 Toray Industries, Inc. Membrane de séparation à base de polymère de fluororésine et procédé de production de celle-ci
JP2008036559A (ja) * 2006-08-08 2008-02-21 Toray Ind Inc フッ素樹脂系高分子分離膜の酸化加工処理方法

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Publication number Priority date Publication date Assignee Title
JP2013510717A (ja) * 2010-12-16 2013-03-28 天津膜天膜科技股▲分▼有限公司 ポリフッ化ビニリデン複合補強型液体分離膜の製造方法
WO2014208592A1 (fr) 2013-06-26 2014-12-31 ダイキン工業株式会社 Composition, membrane polymère poreuse et agent hydrophile
US11364327B2 (en) * 2016-08-31 2022-06-21 Terumo Kabushiki Kaisha Heat exchanger, oxygenator, and method of manufacturing a heat exchanger

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