WO2009119373A1 - Hollow-fiber membrane and process for production thereof - Google Patents
Hollow-fiber membrane and process for production thereof Download PDFInfo
- 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
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- layer
- fiber membrane
- hollow fiber
- less
- dimensional network
- Prior art date
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- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/02—Details relating to pores or porosity of the membranes
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- 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.
Abstract
A hollow-fiber membrane which is usable for water treatment and so on and which has high virus removal performance, high pure water permeability, and high physical endurance and chemical endurance. A thermoplastic resin hollow-fiber membrane constituted of both a layer of three-dimensional network structure and a layer of spherical structure which are laminated with each other, characterized in that when the layer of three-dimensional network structure is thicknesswise divided into thin layers of 0.2μm in thickness, the layer of three-dimensional network structure comprises 10 to 200 thin layers having maximum pore diameters of 0.03 to 0.2μm and zero to two thin layers having maximum pore diameters of less than 0.03μm.
Description
本発明は、液状混合物の成分を選択分離するための中空糸膜およびその製造方法に関する。さらに詳しくは、排水処理、浄水処理、工業用水製造などの水処理に用いられる中空糸精密ろ過膜や中空糸限外ろ過膜等の中空糸膜およびその製造方法に関する。
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.
精密ろ過膜や限外ろ過膜などの分離膜は食品工業、医療、用水製造および排水処理分野などをはじめとして様々な方面で利用されている。特に近年では、飲料水製造分野すなわち浄水処理過程においても分離膜が使われるようになってきている。浄水処理などの水処理用途で用いられる場合、処理しなければならない水量が大きいため、単位体積あたり有効膜面積が大きい中空糸膜が一般的に用いられている。さらに該中空糸膜の純水透過性能が優れていれば、膜面積を減らすことが可能となり、装置がコンパクトになるため設備費が節約でき、膜交換費や設置面積の点からも有利になってくる。また、透過水の殺菌や膜のバイオファウリング防止の目的で次亜塩素酸ナトリウムなどの殺菌剤を膜モジュール部分に添加したり、膜の薬液洗浄として、塩酸、クエン酸、シュウ酸などの酸や水酸化ナトリウム水溶液などのアルカリ、塩素、界面活性剤などで膜を洗浄したりすることがあるため、近年では耐薬品性の高い素材としてポリフッ化ビニリデン系樹脂を用いた分離膜が開発され、利用されている。また、浄水処理分野では、クリプトスポリジウムなどの耐塩素性を有する病原性微生物が飲料水に混入する問題が２０世紀終盤から顕在化してきており、中空糸膜には膜が切れて原水が混入しないような高い強伸度特性が要求されている。
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. When used in water treatment applications such as 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. Furthermore, if 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. Come. In addition, 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, and acid such as hydrochloric acid, citric acid, and oxalic acid is used for cleaning the membrane. In recent years, 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. Moreover, in the field of water purification treatment, the problem that chlorine-resistant pathogenic microorganisms such as Cryptosporidium are mixed in drinking water has become apparent since the end of the 20th century, and the hollow fiber membrane is cut and the raw water is not mixed. Such a high strength and elongation characteristic is required.
さらに、飲料水製造では、医薬品製造、食品工業分野と同様に工程内に微生物よりもサイズの小さいウイルスなどの病原体が混入すると、製造ラインが汚染されるだけでなく、消費者の集団感染を引き起こす危険があり種々の殺菌技術が用いられている、殺菌方法としては、加熱処理や塩素などの化学薬品処理が挙げられるが、熱耐性や薬品耐性を持つウイルスには効果が低い。そこでウイルスを物理的に除去する方法として、分離膜を用いた膜ろ過が注目を集めるようになってきた。膜ろ過では１００％除去が可能であり、分離速度が速く、不純物の混合が必要ないなど利点が多い。
Furthermore, in the production of drinking water, as in the pharmaceutical manufacturing and food industry fields, if a pathogen such as a virus that is smaller in size than microorganisms is mixed in the process, not only the production line is contaminated, but it also causes mass infection of consumers. Examples of sterilization methods that are dangerous and that use various sterilization techniques include heat treatment and chemical treatment such as chlorine, but they are less effective against heat-resistant and chemical-resistant viruses. Therefore, membrane filtration using a separation membrane has attracted attention as a method for physically removing viruses. Membrane filtration has many advantages such as 100% removal, high separation rate, and no need to mix impurities.
ウイルスを除去できる精密ろ過膜、限外ろ過膜としては、種々の方法が開示されている。例えば特許文献１には、平均孔径が３０～１００ｎｍで膜厚が２０μｍ以上の多段ろ過機能を有する再生セルロース膜により、大きさが１２５ｎｍ以上のマイコプラズマを約１０５ＣＦＵ／ｍｌ含有する溶液をろ過した結果、漏洩がなかったことが開示されている。しかし孔径が小さい層が必要以上に厚いために、膜厚が薄いにもかかわらず、純水透過性能は必ずしも十分でない。また再生セルロースからなるため、水処理用途に求められる耐薬品性が低く、除去率の低下、物理的強度の低下が懸念される。さらに一層から形成され、膜厚も薄いため、そもそもの物理的強度が低い。実際、膜間差圧が１気圧を超えると、マイコプラズマの漏洩が始まると記載されており、医療用途には適用できるが、水処理用途には適用できない。
Various methods have been disclosed as microfiltration membranes and ultrafiltration membranes that can remove viruses. For example, in 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 μm or more. As a result, it is disclosed that there was no leakage. However, since 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. Moreover, since it consists of regenerated cellulose, the chemical resistance required for water treatment applications is low, and there is a concern about a reduction in removal rate and a reduction in physical strength. Furthermore, since it is formed from one layer and the film thickness is thin, its physical strength is low in the first place. In fact, it is described that when the transmembrane pressure exceeds 1 atm, leakage of mycoplasma starts, and it can be applied to medical use, but not to water treatment use.
また特許文献２には、等方性、スキンレスのポリフッ化ビニリデン膜であって、膜厚を大きくすることで、高いウイルス除去性能を示す膜について開示されている。しかし膜厚を１００μｍ以上にしないと十分なウイルス除去性能を発現しないこと、親水性を付与するために表面に親水性ポリマーをグラフトさせているが、等方性の構造であり膜全体を親水化しないと効果が低いことから、十分な純水透過性能を得ることはできない。
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 μm, 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.
特許文献３には、医療用途に利用する中空糸膜であって、ポリフッ化ビニリデン樹脂からなり、バブルポイント法で求めた最大孔径が１０～１００ｎｍ、緻密構造層の厚みが膜厚全体の５０％以上とすることで高いウイルス除去性能を示す中空糸膜の記載がある。しかし、連続した構造を有する一層から形成され、さらに膜厚が薄いため、破断強力が非常に低く、水処理用途には適用できない。また緻密層が厚すぎるため、膜厚が薄いにもかかわらず、純水透過性能は低くなっている。
特開平０３－２２８６７１号公報
特開平０７－２６５６７４号公報
国際公開２００３／０２６７７９号パンフレット
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. There exists description of the hollow fiber membrane which shows the high virus removal performance by setting it as the above. However, 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.
Japanese Patent Laid-Open No. 03-228671 Japanese Patent Application Laid-Open No. 07-265684 International Publication No. 2003/026779
本発明では上記のような問題点に鑑み、例えば水処理用途にも使用可能である、高いウイルス除去性能、高い純水透過性能、かつ高い物理的耐久性および化学的耐久性を有する中空糸膜を提供することを目的とする。
In the present invention, in view of the above problems, for example, 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.
上記課題を解決するための本発明は、
（１）三次元網目状構造の層と球状構造の層とが積層されて構成される熱可塑性樹脂からなる中空糸膜であって、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする中空糸膜。
（２）最大孔径が０．０３μｍ未満の薄層が０である（１）に記載の中空糸膜。
（３）球状構造の層における球状の固形分の平均直径が０．９μｍ以上３μｍ以下である（１）に記載の中空糸膜。
（４）三次元網目状構造の層が中空糸膜の最外層に配置されることを特徴とする（１）に記載の中空糸膜。
（５）三次元網目状構造の層１層と、球状構造の層１層とからなることを特徴とする（１）に記載の中空糸膜。
（６）三次元網目状構造の層の厚みが５μｍ以上１００μｍ以下であり、かつ球状構造の層の厚みが１１０μｍ以上４００μｍ以下である（１）に記載の中空糸膜。
（７）球状構造の層がポリフッ化ビニリデン系樹脂からなる（１）に記載の中空糸膜。
（８）三次元網目状構造の層が親水性高分子を含有してなる（１）に記載の中空糸膜。
（９）球状構造の層を形成させる工程、親水性高分子を８重量％以上含有する樹脂溶液を凝固せしめることで三次元網目状構造の層を形成させる工程、酸化剤を含む水溶液に三次元網目状構造の層を接触させる工程、を含む三次元網目状構造の層と球状構造の層から構成される熱可塑性樹脂からなる中空糸膜の製造方法であって、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする中空糸膜の製造方法。
（１０）酸化剤を含む水溶液の濃度が５００ｐｐｍ以上５００００ｐｐｍ以下であり、酸化剤を含む水溶液と三次元網目状構造との接触時間が１時間以上４００時間以下であることを特徴とする（９）に記載の中空糸膜の製造方法、により構成される。 The present invention for solving the above problems is as follows.
(1) A hollow fiber membrane made of a thermoplastic resin 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 has a thickness in the thickness direction. When divided into 0.2 μm thin layers, 10 to 200 thin layers with a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, and 0 to 2 or less thin layers with a maximum pore diameter of less than 0.03 μm A hollow fiber membrane characterized by the above.
(2) The hollow fiber membrane according to (1), wherein the thin layer having a maximum pore diameter of less than 0.03 μm is 0.
(3) The hollow fiber membrane according to (1), wherein an average diameter of a spherical solid content in the layer having a spherical structure is 0.9 μm or more and 3 μm or less.
(4) The hollow fiber membrane according to (1), wherein the layer having a three-dimensional network structure is disposed in the outermost layer of the hollow fiber membrane.
(5) The hollow fiber membrane according to (1), comprising one layer having a three-dimensional network structure and one layer having a spherical structure.
(6) The hollow fiber membrane according to (1), wherein the thickness of the three-dimensional network structure layer is 5 μm or more and 100 μm or less, and the thickness of the spherical structure layer is 110 μm or more and 400 μm or less.
(7) The hollow fiber membrane according to (1), wherein the spherical structure layer is made of a polyvinylidene fluoride resin.
(8) The hollow fiber membrane according to (1), wherein the layer having a three-dimensional network structure contains a hydrophilic polymer.
(9) A step of forming a layer having a spherical structure, a step of forming a layer having a three-dimensional network structure by coagulating a resin solution containing 8% by weight or more of a hydrophilic polymer, and a three-dimensional solution in an aqueous solution containing an oxidizing agent. 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 However, when each thin layer having a thickness of 0.2 μm is divided in the thickness direction, the thin layer having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less is 10 to 200 and the maximum pore diameter is less than 0.03 μm. A method for producing a hollow fiber membrane, characterized in that the thin layer is from 0 to 2.
(10) 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) The method for producing a hollow fiber membrane according to the above.
（１）三次元網目状構造の層と球状構造の層とが積層されて構成される熱可塑性樹脂からなる中空糸膜であって、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする中空糸膜。
（２）最大孔径が０．０３μｍ未満の薄層が０である（１）に記載の中空糸膜。
（３）球状構造の層における球状の固形分の平均直径が０．９μｍ以上３μｍ以下である（１）に記載の中空糸膜。
（４）三次元網目状構造の層が中空糸膜の最外層に配置されることを特徴とする（１）に記載の中空糸膜。
（５）三次元網目状構造の層１層と、球状構造の層１層とからなることを特徴とする（１）に記載の中空糸膜。
（６）三次元網目状構造の層の厚みが５μｍ以上１００μｍ以下であり、かつ球状構造の層の厚みが１１０μｍ以上４００μｍ以下である（１）に記載の中空糸膜。
（７）球状構造の層がポリフッ化ビニリデン系樹脂からなる（１）に記載の中空糸膜。
（８）三次元網目状構造の層が親水性高分子を含有してなる（１）に記載の中空糸膜。
（９）球状構造の層を形成させる工程、親水性高分子を８重量％以上含有する樹脂溶液を凝固せしめることで三次元網目状構造の層を形成させる工程、酸化剤を含む水溶液に三次元網目状構造の層を接触させる工程、を含む三次元網目状構造の層と球状構造の層から構成される熱可塑性樹脂からなる中空糸膜の製造方法であって、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする中空糸膜の製造方法。
（１０）酸化剤を含む水溶液の濃度が５００ｐｐｍ以上５００００ｐｐｍ以下であり、酸化剤を含む水溶液と三次元網目状構造との接触時間が１時間以上４００時間以下であることを特徴とする（９）に記載の中空糸膜の製造方法、により構成される。 The present invention for solving the above problems is as follows.
(1) A hollow fiber membrane made of a thermoplastic resin 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 has a thickness in the thickness direction. When divided into 0.2 μm thin layers, 10 to 200 thin layers with a maximum pore diameter of 0.03 μm or more and 0.2 μm or less, and 0 to 2 or less thin layers with a maximum pore diameter of less than 0.03 μm A hollow fiber membrane characterized by the above.
(2) The hollow fiber membrane according to (1), wherein the thin layer having a maximum pore diameter of less than 0.03 μm is 0.
(3) The hollow fiber membrane according to (1), wherein an average diameter of a spherical solid content in the layer having a spherical structure is 0.9 μm or more and 3 μm or less.
(4) The hollow fiber membrane according to (1), wherein the layer having a three-dimensional network structure is disposed in the outermost layer of the hollow fiber membrane.
(5) The hollow fiber membrane according to (1), comprising one layer having a three-dimensional network structure and one layer having a spherical structure.
(6) The hollow fiber membrane according to (1), wherein the thickness of the three-dimensional network structure layer is 5 μm or more and 100 μm or less, and the thickness of the spherical structure layer is 110 μm or more and 400 μm or less.
(7) The hollow fiber membrane according to (1), wherein the spherical structure layer is made of a polyvinylidene fluoride resin.
(8) The hollow fiber membrane according to (1), wherein the layer having a three-dimensional network structure contains a hydrophilic polymer.
(9) A step of forming a layer having a spherical structure, a step of forming a layer having a three-dimensional network structure by coagulating a resin solution containing 8% by weight or more of a hydrophilic polymer, and a three-dimensional solution in an aqueous solution containing an oxidizing agent. 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 However, when each thin layer having a thickness of 0.2 μm is divided in the thickness direction, the thin layer having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less is 10 to 200 and the maximum pore diameter is less than 0.03 μm. A method for producing a hollow fiber membrane, characterized in that the thin layer is from 0 to 2.
(10) 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) The method for producing a hollow fiber membrane according to the above.
本発明によれば、化学的および物理的耐久性が高く、かつ高いウイルス除去性能と純水透過性能を有する中空糸膜が提供される。
According to the present invention, a hollow fiber membrane having high chemical and physical durability and high virus removal performance and pure water permeation performance is provided.
１ 厚さ０．２μｍの薄層の１層の範囲
1 Range of one thin layer with a thickness of 0.2 μm
本発明の中空糸膜は、三次元網目状構造の層と球状構造の層とから構成される。ここで三次元網目状構造とは、固形分が三次元的に網目状に広がっている構造のことをいう。一方、球状構造とは、多数の球状（略球状の場合を含む）の固形分が、互いにその一部を共有することで連結している構造のことをいう。三次元網目状構造の層は、被ろ過水中のウイルスを含む汚染物質を安定的に除去する層であり、球状構造の層は物理的強度を担い三次元網目状構造の層を支持する層である。２つの層は各層の性能を高いレベルでバランスさせるため、積層された構造であることが必要である。一般に層を多段に重ねると、各層の界面では層同士が互いに入り込むために緻密になり、透過性能が低下する。層同士が互いに入り込まない場合は、透過性能は低下しないが、接着強度が低下する。従って、積層数は少ない方が好ましく、三次元網目状構造層１層と球状構造層１層の合計２層からなることが特に好ましい。また、中空糸膜における各層の配置は特に制限されないが、三次元網目状構造の層が分離機能を担い、球状構造の層が物理的強度を担うため、三次元網目状構造の層が分離対象側に配置されることが好ましい。比較的孔径の大きい球状構造の層が分離対象側に配置されると、汚染物質が膜構造の内部にまで進入し目詰まりの原因となることがあるからである。また分離対象側は中空糸膜の外表面側であることが好ましく、内表面側の場合、空間の小さい中空部に汚染物質が蓄積し、透過性能が低下することがある。このことから、三次元網目状構造の層が中空糸膜の最外層、球状構造の層が最内層に配置されることが特に好ましい形態である。
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. Here, the three-dimensional network structure refers to a structure in which the solid content spreads in a three-dimensional network. On the other hand, 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. In general, when layers are stacked in multiple stages, the layers enter each other at the interface of each layer and become dense, resulting in a decrease in transmission performance. When the layers do not penetrate each other, 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. In addition, 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. It is preferable to arrange on the side. This is because when a layer having a spherical structure having a relatively large pore diameter is arranged on the separation target side, contaminants may enter the membrane structure and cause clogging. Further, 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.
ウイルスを含む汚染物質を除去する三次元網目状構造の層は高い除去性能と高い透過性能とを満たすことは可能であるが、さらに高い物理的強度を満たすことは非常に困難である。その理由を述べると、まず高い除去性能を得るためには緻密な構造を形成する必要があるが、緻密な構造を有すると透過性能が低下してしまい、透過性能を高くするためには、層の厚みを薄くすること、あるいは低濃度の樹脂原液から緻密な構造を形成することが必要となり、結果的に物理的強度は低下してしまうからである。中空糸膜の物理的強度が低いと、中空糸膜を空気で振動させて洗浄する操作などにより糸切れが起こり、汚染物質の漏洩が起こる。さらには中空糸膜に圧力を加えた際に、中空糸膜の構造が変形して、孔径が拡大すると汚染物質中のウイルスなどの微小成分が漏洩し、逆に孔径が縮小すると透過性能が低下してしまう。水処理用途に用いる場合は、特に大きい外力が中空糸膜に付与されるため、ウイルスなどの微小成分を除去することを目的とする際には、物理的強度を高めることが必要不可欠である。そこで本発明では、鋭意検討の結果、ウイルス除去性能と透過性能が高い三次元網目状構造の層と、物理的強度と透過性能が高い球状構造の層からなる中空糸膜とすることで、ウイルス除去性能、透過性能、物理的強度を高いレベルで併せ有する中空糸膜を得るに至った。さらに製造方法について鋭意検討した結果、三次元網目状構造の層は、特に化学的耐久性の高い樹脂を用いて形成するには困難であった、ウイルス除去性能と透過性能の高い構造を形成させるに至った。
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. Furthermore, when pressure is applied to the hollow fiber membrane, the structure of the hollow fiber membrane is deformed, and if the pore size is enlarged, minute components such as viruses in pollutants leak, and conversely if the pore size is reduced, the permeation performance is reduced. Resulting in. When used for water treatment, a particularly large external force is imparted to the hollow fiber membrane. Therefore, it is indispensable to increase physical strength when it is intended to remove minute components such as viruses. Therefore, in the present invention, as a result of intensive studies, 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.
以下に本発明の具体的な実施形態について述べる。
Specific embodiments of the present invention will be described below.
三次元網目状構造の層は、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする。ここで、厚さ０．２μｍの薄層における最大孔径は次のように測定することができる。走査型電子顕微鏡等を用いて、中空糸膜の径方向の断面を外表面から内表面まで連続的に、構造が明瞭に確認できる倍率、好ましくは６万倍以上で撮影する。得られた連続写真を、三次元網目状構造の層が最外層または最内層にある場合、それぞれ外表面または内表面を起点として球状構造の層との境界まで厚さ０．２μｍの薄層ごとに分け、各薄層にある最大孔径を測定する。三次元網目状構造の層が他の２つの球状構造の層の間にある場合、どちらかの球状構造の層との境界を起点として、もう一つの境界まで厚さ０．２μｍの薄層ごとに分け、各薄層にある最大孔径を測定する。ここで最大孔径とは孔の最大短径である。孔は固形部で囲まれた領域を指し、孔の最大短径とは、薄層内にある孔のなかで、最大の短径の長さを表す。孔の短径は、孔の長径の線分に対して垂直二等分線をひいた場合において、垂直二等分線が孔と重なる線分の長さとする。孔の長径は孔と固形分の境界線上のもっとも離れた２点間の長さとする。また複数の薄層をまたいで孔が存在する場合は、すべての層がその孔を有していることとする。走査型電子顕微鏡写真の奥行き方向に不明瞭に観察される固形分は、写真の手前側に明瞭に観察される固形分が形成する孔には実質的に無関係であるため、その固形分はないものとして取り扱うこととする。
The layer having a three-dimensional network structure has 10 to 200 thin layers having a maximum pore diameter of 0.03 μm to 0.2 μm when divided into thin layers having a thickness of 0.2 μm in the thickness direction, and The thin layer having a maximum pore diameter of less than 0.03 μm is 0 or more and 2 or less. Here, the maximum pore diameter in a thin layer having a thickness of 0.2 μm 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. When the obtained three-dimensional network layer is in the outermost layer or the innermost layer, the thin film having a thickness of 0.2 μm 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. When 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 μm from the boundary with one of the spherical structure layers to the other boundary And measure the maximum pore size in each thin layer. Here, 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. In addition, when a hole exists across a plurality of thin layers, all the layers have the hole. The solid content observed indistinctly in the depth direction of the scanning electron micrograph is substantially irrelevant to the pores formed by the solid content clearly observed on the front side of the photo, so there is no solid content. It will be handled as a thing.
上記のようにして撮影された、本発明の一実施態様に係る中空糸膜の径方向の断面を図１に示す。図１は、三次元網目状構造の層を外表面から連続的に撮影した複数枚の写真をつなげたものの一部であり、図の上下方向は中空糸膜の径方向を示す。図１において、三次元網目状構造の層は、外表面からその厚み方向に厚さ０．２μｍの薄層１ごとに分割されており、本発明では、それぞれの薄層１ごとに最大孔径を測定する。
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. In FIG. 1, the layer of the three-dimensional network structure is divided for each thin layer 1 having a thickness of 0.2 μm in the thickness direction from the outer surface. In the present invention, the maximum pore diameter is set for each thin layer 1. taking measurement.
本発明における三次元網目状構造の層は、このようにして測定される最大孔径が０．０３μｍ以上０．２μｍ以下の薄層を、連続的にあるいは断続的に１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることが必要である。本発明の中空糸膜はもっとも小さいウイルスに対して非常に高い除去性能を有する。もっとも小さいウイルスの大きさは約０．０２μｍであり、本発明の中空糸膜が、最大孔径が０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有するということは、もっとも小さいウイルスよりも少し大きい孔径を含む層がある程度以上の厚みをもって存在することになる。
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 μm or more and 0.2 μm 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 μm 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 μm, and that the hollow fiber membrane of the present invention has a thin layer with a maximum pore size of 0.03 μm or more and 0.2 μm 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.
最大孔径が０．０３μｍ以上０．２μｍ以下の各薄層のウイルス除去性能は高くないが、そのような薄層が幾層にもわたって存在することで、多段的なろ過機構になり除去性能を高めることができる、いわゆるデプスろ過を利用する。多くが表面に存在する、厚みが０．６μｍ程度のウイルスよりも大きな孔を含まない緻密層、すなわち最大孔径が０．０３μｍ未満の薄層が３程度ある層によりウイルスを除去する、いわゆる表面ろ過と比べると、本発明の中空糸膜は、最大孔径が０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有することに加え、最大孔径が０．０３μｍ未満の薄層を２以下と非常に少なくしていることから、高い純水透過性能を発現させることが出来る点で有利である。なぜなら純水透過性能は孔径の４乗に比例し（ポワズイユの法則）、層の厚みの１乗に反比例するからである。すなわち孔径を小さくするよりも、層を厚くする方が、純水透過性能の低下が小さくなるからである。
Although the virus removal performance of each thin layer with a maximum pore size of 0.03 μm or more and 0.2 μm 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 μm, that is, a layer with about 3 thin layers with a maximum pore size of less than 0.03 μm. 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 μm, and 2 or less thin layers with a maximum pore diameter of less than 0.03 μm. Since it is very small, it is advantageous in that high pure water permeation performance can be expressed. This is because 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.
デプスろ過において、厚さ０．２μｍの各薄層の除去性能は、最大孔径が小さいほど高くなることから、純水透過性能を向上させるためには、高い除去性能を示すために必要な薄層の数をより少なくすることが好ましい。このことから、ウイルス除去性能と純水透過性能を考慮したより効果の高い形態としては、最大孔径０．０３μｍ以上０．１μｍ以下の薄層を１０以上７５以下有することが好ましく、より好ましくは１０以上５０以下有することである。あるいは最大孔径０．０３μｍ以上０．０７μｍ以下の薄層を１０以上５０以下有することが好ましく、より好ましくは１０以上３５以下有することである。
In depth filtration, the removal performance of each thin layer having a thickness of 0.2 μm 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 μm to 0.1 μm 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 μm or more and 0.07 μm or less, and more preferably 10 or more and 35 or less.
最大孔径が０．０３μｍ未満の薄層を３以上有した場合、純水透過性能が低下し、最大孔径が０．２μｍを超える薄層を２００程度以上有しても十分なウイルス除去性能が得られない。また最大孔径０．０３μｍ以上０．０７μｍ以下の薄層が１０未満でも十分なウイルス除去性能を得ることができず、最大孔径が０．０３μｍ以上０．２μｍ以下の薄層が２００以上では十分な純水透過性能を得ることができない。
When there are 3 or more thin layers having a maximum pore size of less than 0.03 μm, the pure water permeation performance is lowered, and even when there are about 200 or more thin layers having a maximum pore size exceeding 0.2 μm, sufficient virus removal performance is obtained. I can't. In addition, sufficient virus removal performance cannot be obtained even if a thin layer having a maximum pore size of 0.03 μm or more and 0.07 μm or less is less than 10, and a thin layer having a maximum pore size of 0.03 μm or more and 0.2 μm or less is sufficient if it is 200 or more. Pure water permeation performance cannot be obtained.
このように除去性能と純水透過性能とを最大限高くするために、最大孔径と厚さとの関係を適切に制御したデプスろ過の構造を有することが、本発明の特長である。そのため、三次元網目状構造の層は、上述した最大孔径０．０３μｍ以上０．２μｍ以下のデプスろ過の構造以外には、最大孔径が０．２μｍを超える薄層を有してもよいが、最大孔径が０．０３μｍ未満の薄層が２以下であることが必要で、好ましくは１以下、さらに好ましくは全く有さないことが純水透過性能を低下させないために有効である。
Thus, in order to maximize the removal performance and pure water permeation performance, it is a feature of the present invention to have a depth filtration structure in which the relationship between the maximum pore diameter and the thickness is appropriately controlled. Therefore, the layer of the three-dimensional network structure may have a thin layer having a maximum pore diameter exceeding 0.2 μm other than the above-described depth filtration structure having a maximum pore diameter of 0.03 μm to 0.2 μm. A thin layer having a maximum pore diameter of less than 0.03 μm 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.
次に、球状構造の層は十分な物理的強度を有するために、球状の固形分の平均直径が０．９μｍ以上３μｍ以下であることが好ましい。球状の固形分とは真円率（長径／短径）が２以下である固形分とする。各球状の固形分の平均直径は、長径と短径との平均値とする。球状の固形分の平均直径が０．９μｍ未満の場合、固形分の間に形成される空隙が小さくなり、十分な純水透過性能が得られなくなり、３μｍを超えると、固形分のつながりが少なくなり、物理的強度が低くなる。また球状構造の層は純水透過性能と物理的強度とを高いレベルで両立させるために、均質な構造であることが好ましい。緻密な層を有したり、傾斜的に構造が変化していたりすると純水透過性能と物理的強度との両立が困難になる。また球状の固形分以外に、真円率（長径／短径）が２を超える、柱状の固形分を含むことは、物理的強度がさらに高くなるため好ましい。
Next, since the layer having a spherical structure has sufficient physical strength, it is preferable that the average diameter of the spherical solid content is 0.9 μm or more and 3 μm 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 μm, 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 μm, the solid content will be less connected. Thus, the physical strength is lowered. In addition, 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. In addition to 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.
本発明の中空糸膜は熱可塑性樹脂からなる。熱可塑性樹脂とは、鎖状高分子物質からできており、加熱すると、外力によって変形・流動する性質が現れる樹脂のことをいう。この熱可塑性樹脂の例としては、ポリエチレン、ポリプロピレン、アクリル樹脂、ポリアクリロニトリル、アクリロニトリル－ブタジエン－スチレン（ＡＢＳ）樹脂、ポリスチレン、アクリロニトリル－スチレン（ＡＳ）樹脂、塩化ビニル樹脂、ポリエチレンテレフタレート、ポリアミド、ポリアセタール、ポリカーボネート、変成ポリフェニレンエーテル、ポリフェニレンスルフィド、ポリフッ化ビニリデン、ポリアミドイミド、ポリエーテルイミド、ポリスルホン、ポリエーテルスルホンおよびこれらの混合物や共重合体が挙げられる。
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. Examples of 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.
三次元網目状構造の層を形成する熱可塑性樹脂としては、ウイルスを含む汚染物質を安定的に除去するために、高い化学的耐久性を有することが好ましく、また高い純水透過性能を得るためには親水性が高いことが好ましい。このことからポリアクリロニトリル系樹脂、あるいはポリフッ化ビニリデン系樹脂と親水性高分子の混合物などが特に好ましく用いられる。ポリアクリロニトリル系樹脂としては、均質で緻密な構造が形成されやすく、物理的強度や熱的特性に優れていることから、超高重合度であるものが好ましく、極限粘度が２以上、好ましくは２．５以上３．６以下、さらに好ましくは２．９以上３．３以下である。さらに該樹脂はアクリロニトリルを９０モル％以上、好ましくは９５モル％以上と、アクリロニトリルに対して、共重合性を有するビニル化合物５モル％以下とからなる、アクリロニトリルホモポリマーもしくはアクリロニトリル共重合体である。
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. As 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. Further, 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.
上記ビニル化合物としては、公知の各種アクリロニトリルに対して共重合性を有する化合物であればよく、特に限定されないが、好ましい共重合成分としては、アクリル酸、イタコン酸、アクリル酸メチル、メタクリル酸メチル、酢酸ビニル、アリルスルホン酸ソーダ、メタリルスルホン酸ソーダ、ｐ－スチレンスルホン酸ソーダなどを例示することができる。
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.
ポリフッ化ビニリデン系樹脂とはフッ化ビニリデンホモポリマーおよび／またはフッ化ビニリデン共重合体を含有する樹脂を意味し、複数の種類のフッ化ビニリデン共重合体を含有しても構わない。フッ化ビニリデン共重合体は、フッ化ビニリデン残基構造を有するポリマーであり、典型的にはフッ化ビニリデンモノマーとそれ以外のフッ素系モノマーなどとの共重合体である。かかる共重合体としては、例えば、フッ化ビニル、四フッ化エチレン、六フッ化プロピレン、三フッ化塩化エチレンから選ばれた１種類以上とフッ化ビニリデンとの共重合体が挙げられる。また、本発明の効果を損なわない程度に、前記フッ素系モノマー以外の例えばエチレンなどのモノマーが共重合されていても良い。
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. Examples of the copolymer 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.
親水性高分子としては、主鎖および／または側鎖に分子ユニットとして、セルロースエステル、脂肪酸ビニルエステル、ビニルピロリドン、エチレンオキサイド、プロピレンオキサイド、アクリロニトリル、アクリル酸エステル、メタクリル酸エステルから選ばれる少なくとも１種を有するものであれば特に限定されず、これら以外の分子ユニットが存在しても良い。上記分子ユニット以外の分子ユニットとしては、例えば、エチレン、プロピレンなどのアルケン、アセチレンなどのアルキン、ハロゲン化ビニル、ハロゲン化ビニリデンなどが挙げられる。特にエチレン、ハロゲン化ビニリデンは、比較的安価に入手可能であり、化学的耐久性が高いため好ましく用いられる。該親水性高分子は、ポリフッ化ビニリデン系樹脂とともに三次元網目状構造を形成するために用いるので、ポリフッ化ビニリデン系樹脂と適当な条件で混和することが好ましい。
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. As long as it has, there is no particular limitation, and 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. In particular, 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.
球状構造の層は、三次元網目状構造の層を支持する層であることから、物理的強度と共に特に高い化学的耐久性を必要とするため、ポリエチレン、ポリプロピレン、ポリフッ化ビニリデン系樹脂からなることが好ましく、さらに好ましくはポリフッ化ビニリデン系樹脂からなることである。
Since 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.
このような本発明の中空糸膜は、その効果として、純水透過性能、破断強力、破断伸度、ウイルス除去性能を高いレベルで有する。すなわち５０ｋＰａ、２５℃における純水透過性能が０．２ｍ３／ｍ２／ｈｒ以上、破断強力４Ｎ／本以上、破断伸度２０％以上、かつウイルス除去性能４ｌｏｇ以上の性能を有する。また本発明の実施条件を最適化することにより純水透過性能が０．３ｍ３／ｍ２／ｈｒ以上、破断強力４Ｎ／本以上、破断伸度２０％以上、かつウイルス除去性能４ｌｏｇ以上の性能を得ることができる。さらに膜の使用条件などにより必要であれば球状構造の層を厚くして、純水透過性能が０．３ｍ３／ｍ２／ｈｒ以上、破断強力９Ｎ／本以上、破断伸度２０％以上、かつウイルス除去性能４ｌｏｇ以上の性能を有する膜を得ることができる。
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. Further, if necessary depending on the conditions of use of the membrane, 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, In addition, a membrane having a virus removal performance of 4 logs or more can be obtained.
本発明の三次元網目状構造の層と球状構造の層とが積層されて構成される熱可塑性樹脂からなる中空糸膜は、種々の方法で製造することができる。例えば、球状構造からなる中空糸膜の上に、三次元網目状構造の層を積層し、酸化処理する方法がある。この方法においては、まず球状構造からなる中空糸膜を製造する。例として、樹脂にポリフッ化ビニリデン系樹脂を使用した方法について述べる。ポリフッ化ビニリデン系樹脂を２０重量％以上６０重量％以下の比較的高濃度で、該樹脂の貧溶媒もしくは良溶媒に結晶化温度以上の温度で溶解する。樹脂濃度は高くなれば高い強伸度特性を有する中空糸膜が得られるが、高すぎると製造した中空糸膜の空孔率が小さくなり、純水透過性能が低下する。また調整した樹脂溶液の粘度が適正範囲になければ、中空糸膜に成形することができない。従って樹脂濃度は３０重量％以上５０重量％以下の範囲とすることがより好ましい。
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.
またここで貧溶媒とは、ポリフッ化ビニリデン系樹脂を６０℃未満の低温では５重量％以上溶解させることができないが、６０℃以上かつポリフッ化ビニリデン系樹脂の融点以下（例えばポリフッ化ビニリデン系樹脂がポリフッ化ビニリデンホモポリマー単独で構成される場合は１７８℃程度）の高温領域で５重量％以上溶解させることができる溶媒のことである。貧溶媒に対し６０℃未満の低温でもポリフッ化ビニリデン系樹脂を５重量％以上溶解させることが可能な溶媒を良溶媒、ポリフッ化ビニリデン系樹脂の融点または溶媒の沸点まで、ポリフッ化ビニリデン系樹脂を溶解も膨潤もさせない溶媒を非溶媒と定義する。
Here, 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). Is a solvent that can be dissolved by 5 wt% or more in a high temperature region of about 178 ° C. when the polyvinylidene fluoride homopolymer is used alone. A solvent capable of dissolving 5% by weight or more of the polyvinylidene fluoride resin at a low temperature of less than 60 ° C. with respect to the poor solvent is a good solvent, and the polyvinylidene fluoride resin is melted to the melting point of the polyvinylidene fluoride resin or the boiling point of the solvent. A solvent that does not dissolve or swell is defined as a non-solvent.
ここでポリフッ化ビニリデン系樹脂の貧溶媒としてはシクロヘキサノン、イソホロン、γ－ブチロラクトン、メチルイソアミルケトン、プロピレンカーボネート等の中鎖長のアルキルケトン、エステル、および有機カーボネート等、およびその混合溶媒が挙げられる。また良溶媒としてはＮ－メチル－２－ピロリドン、ジメチルスルホキシド、ジメチルアセトアミド、ジメチルホルムアミド、メチルエチルケトン、アセトン、テトラヒドロフラン、テトラメチル尿素、リン酸トリメチル等の低級アルキルケトン、エステル、アミド等、およびその混合溶媒が挙げられる。
Here, examples of the poor solvent for the polyvinylidene fluoride resin include medium chain length alkyl ketones such as cyclohexanone, isophorone, γ-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.
さらに非溶媒としては、水、ヘキサン、ペンタン、ベンゼン、トルエン、メタノール、エタノール、四塩化炭素、ｏ－ジクロルベンゼン、トリクロルエチレン、エチレングリコール、ジエチレングリコール、トリエチレングリコール、プロピレングリコール、ブチレングリコール、ペンタンジオール、ヘキサンジオール、低分子量のポリエチレングリコール等の脂肪族炭化水素、芳香族炭化水素、脂肪族多価アルコール、芳香族多価アルコール、塩素化炭化水素、またはその他の塩素化有機液体およびその混合溶媒などが挙げられる。
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.
また球状構造からなる中空糸膜は、該樹脂溶液を冷却により相分離させる熱誘起相分離法により製造される。該ポリフッ化ビニリデン系樹脂溶液を中空糸膜紡糸用の二重管式口金の外側の管から吐出し、中空部形成液体を二重管式口金の内側の管から吐出しながら冷却浴中で冷却固化する。冷却浴には０℃以上３０℃以下で、濃度が５０重量％以上９５重量％以下の貧溶媒あるいは良溶媒と、濃度が５重量％以上５０重量％以下の非溶媒からなる混合液体が好ましい。さらに貧溶媒としては樹脂溶液と同じ貧溶媒を用いることが、冷却浴組成を維持しやすいことから好ましく採用される。ただし高濃度の良溶媒を用いるときは温度を十分に低くしないと凝固しなかったり、凝固が遅く中空糸膜表面が平滑にならなかったりする場合がある。また、前記の濃度範囲を外れない限りにおいて、貧溶媒、良溶媒を混合しても良い。ただし、高濃度の非溶媒を用いると中空糸膜の外表面に緻密層が形成され純水透過性能が著しく低下する場合がある。また、中空部形成液体には、冷却浴同様、濃度が５０重量％以上９５重量％以下の貧溶媒あるいは良溶媒と、濃度が５重量％以上５０重量％以下の非溶媒からなる混合液体が好ましい。さらに貧溶媒としては樹脂溶液と同じ貧溶媒を用いることが好ましく採用される。
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. Solidify. 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. Furthermore, it is preferable to use the same poor solvent as the resin solution as the poor solvent because the cooling bath composition is easily maintained. However, when 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. In addition, a poor solvent and a good solvent may be mixed as long as the concentration range is not deviated. However, if a high concentration non-solvent is used, 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.
ここで熱誘起相分離法により製造する場合、主に２種類の相分離機構が利用される。一つは高温時に均一に溶解したポリマー溶液が、降温時に溶液の溶解能力低下が原因でポリマー濃厚相と希薄相とに分離し、その後構造が結晶化により固定される液－液相分離法、もう一つが高温時に均一に溶解したポリマー溶液が、降温時にポリマーの結晶化が起こりポリマー固体相と溶媒相とに相分離する固－液相分離法である。前者の方法では主に三次元網目状構造が、後者の方法では主に球状組織で構成された球状構造が形成される。本発明では後者の相分離機構が利用され、固－液相分離が誘起される樹脂濃度、温度、樹脂溶液の溶媒、冷却浴の組成、温度の組み合わせが重要である。前者の相分離機構で形成される三次元網目状構造は、強伸度性能と純水透過性能とを高いレベルで両立させることが困難である。三次元網目状構造は筋状の固形分が三次元的に均一に連結した構造をしており、球状の固形分が不均一に互いにその一部を共有することで強固に連結した球状構造に比べて、孔径が小さくなる。そのため同じ強伸度性能でも純水透過性能が低くなると考えられる。
Here, 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. In the former method, a three-dimensional network structure is mainly formed, and in the latter method, a spherical structure mainly composed of a spherical structure is formed. In the present invention, 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. In 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.
以上の製造工程に加えて、空隙を拡大し純水透過性能を向上させることおよび破断強力を強化するために延伸を行うことも有用であり好ましい。延伸の方法は好ましくは５０℃以上１４０℃以下、より好ましくは５５℃以上１２０℃以下、さらに好ましくは６０℃以上１００℃以下の温度範囲で、好ましくは１．１倍以上４倍以下、より好ましくは１．１倍以上２倍以下の延伸倍率である。５０℃未満の低温雰囲気で延伸した場合、安定して均質に延伸することが困難である。１４０℃を超える温度で延伸した場合、ポリフッ化ビニリデン系樹脂の融点に近くなるため、構造組織が融解し空隙が拡大せず透水性は向上しない。また、延伸は液体中で行う方が、温度制御が容易であり好ましいが、スチームなどの気体中で行っても構わない。液体としては水が簡便で好ましいが、９０℃程度以上で延伸する場合には、低分子量のポリエチレングリコールなどを用いることも好ましく採用できる。一方、このような延伸を行わない場合は、延伸を行う場合と比べて、純水透過性能および破断強力は低下するが、破断伸度および除去性能は向上する。したがって、延伸工程の有無および延伸工程の延伸倍率は中空糸膜の用途に応じて適宜設定することができる。
In addition to the above manufacturing steps, it is also useful and preferable to perform stretching in order to expand the voids and improve the pure water permeation performance and to strengthen the breaking strength. 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. When stretching in a low temperature atmosphere of less than 50 ° C., it is difficult to stably and uniformly stretch. When it is stretched at a temperature exceeding 140 ° C., it becomes close to the melting point of the polyvinylidene fluoride resin, so that the structural structure is melted and the voids are not enlarged and the water permeability is not improved. In addition, stretching is preferably performed in a liquid because temperature control is easy, but may be performed in a gas such as steam. As the liquid, 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. On the other hand, when such stretching is not performed, 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.
次に、このようにして形成された球状構造からなる中空糸膜の上に、三次元網目状構造の層を形成する。この工程では最大孔径０．２μｍ以下の薄層を適度な数（厚み）だけ有する三次元網目状構造を形成させる必要がある。またマクロボイドと呼ばれる数μｍ以上の不均一な巨大孔を実質的に有さないことが、除去性能を高めるために好ましい。その方法は特に限定されないが、三次元網目状構造を形成する樹脂溶液が親水性高分子を高濃度で含有する方法が好適である。例として、樹脂にポリアクリロニトリル系樹脂、およびポリフッ化ビニリデン系樹脂と親水性高分子の混合物を使用した方法について述べる。
Next, a layer having a three-dimensional network structure is formed on the hollow fiber membrane having the spherical structure formed as described above. In this step, it is necessary to form a three-dimensional network structure having an appropriate number (thickness) of thin layers having a maximum pore diameter of 0.2 μm or less. Moreover, it is preferable not to have substantially non-uniform macropores of several μm or more called macrovoids in order to improve removal performance. 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. As an example, a method using a polyacrylonitrile resin as a resin and a mixture of a polyvinylidene fluoride resin and a hydrophilic polymer will be described.
まずポリアクリロニトリル系樹脂を使用した方法について述べる。
First, the method using polyacrylonitrile resin will be described.
ポリアクリロニトリル系樹脂を溶解する有機溶媒は、ジメチルスルホキシド、ジメチルホルムアミド、ジメチルアセトアミド、エチレンカーボネート、ブチルラクトンなどを例示することができるが、特にジメチルスルホキシドが好ましく用いられる。ポリアクリロニトリル系樹脂溶液の樹脂濃度は８重量％以上２０重量％以下の範囲であり、好ましくは９重量％以上１６重量％以下である。８重量％よりも低くなると最大孔径０．２μｍ以下の薄層がほとんど形成されず、十分なウイルス除去性能を発現しない。また２０重量％を超えると、最大孔径０．０３μｍ未満の薄層が数多く形成されるため、その後に酸化剤に接触させる工程を経ても、ウイルス除去性能を維持しつつ十分に純水透過性能を向上させることが困難となり、また粘度が高くなることによって成形性が悪くなり好ましくない。溶解は８０℃以上１７０℃以下の比較的高温で行うことにより均一な溶液が得られる。
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 μm 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 μm are formed. Therefore, even after the step of contacting with an oxidant, pure water permeation performance is sufficiently maintained while maintaining virus removal performance. It is difficult to improve, and the moldability is deteriorated due to an increase in viscosity. A uniform solution can be obtained by dissolving at a relatively high temperature of 80 ° C. or higher and 170 ° C. or lower.
このようなポリアクリロニトリル系樹脂溶液を球状構造からなる中空糸膜の表面に塗布した後、主にポリアクリロニトリル系樹脂溶液の非溶媒からなる凝固浴中で凝固せしめることで、三次元網目状構造の層を被覆する。塗布する方法としては、特に限定されないが、中空糸膜をポリアクリロニトリル系樹脂溶液中に浸漬したり、中空糸膜にスプレーコーティングしたりする方法が好ましく用いられる。さらに中空糸膜に塗布される量を制御する方法としては該樹脂溶液の塗布量を制御する以外に、該樹脂溶液を塗布した後にノズル内を通過させることにより一部を掻き取ったり、エアナイフにより吹き飛ばしたりする方法も好ましく用いられる。前記凝固浴は主にポリアクリロニトリル系樹脂の非溶媒からなり、０重量％以上３０重量％以下の範囲で前記ポリアクリロニトリル系樹脂を溶解する有機溶媒を含むことが好ましい。ポリアクリロニトリル系樹脂の非溶媒としては水、アルコール類、脂肪族ケトン、グリセリン、ポリエチレングリコールなどが挙げられるが、特に水が好ましく採用される。また該凝固浴の温度は高すぎると膜の収縮が起こり、純水透過性能が低下するので、５℃以上７０℃以下、好ましくは５℃以上４０℃以下である。
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. Further, as a method for controlling the amount applied to the hollow fiber membrane, in addition to controlling the amount of the resin solution applied, a part of the resin solution is scraped by passing through the nozzle after being applied, or by using an air knife. A method of blowing off is also preferably used. 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%. Examples of 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. Further, if 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.
次にポリフッ化ビニリデン系樹脂と親水性高分子との混合物を使用した方法について述べる。
Next, a method using a mixture of a polyvinylidene fluoride resin and a hydrophilic polymer will be described.
ポリフッ化ビニリデン系樹脂と親水性高分子との混合物を溶解する溶媒としては、ポリフッ化ビニリデン系樹脂の良溶媒を用いることが好ましく採用される。またポリフッ化ビニリデン系樹脂と親水性高分子との混合物の溶液は、ポリフッ化ビニリデン系樹脂濃度と親水性高分子濃度との和が１８重量％以上３０重量％以下が好ましく、さらに好ましくは２０重量％以上３０重量％以下の範囲になるように調整することが好ましい。またここで前述した構造を得るためには親水性高分子濃度が、８重量％以上２０重量％以下、好ましくは９重量％以上１６重量％以下の範囲になるように調整する必要がある。溶解は８０℃以上１７０℃以下の比較的高温で行うことにより均一な溶液が得られる。
As 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. In the solution of the mixture of the polyvinylidene fluoride resin and the hydrophilic polymer, 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%. In order to obtain the structure described above, it is necessary to adjust the hydrophilic polymer concentration so that it is 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.
このようなポリフッ化ビニリデン系樹脂と親水性高分子との混合物の溶液を球状構造からなる中空糸膜の表面に塗布した後、主にポリフッ化ビニリデン系樹脂の非溶媒からなる凝固浴中で凝固せしめることで、三次元網目状構造の層を被覆する。塗布する方法としては、前記の方法が用いられる。凝固浴は主にポリフッ化ビニリデン系樹脂の非溶媒からなり、０重量％以上３０重量％以下の範囲で前記ポリフッ化ビニリデン系樹脂の良溶媒または貧溶媒を含んでいてもよい。また該凝固浴の温度は１０℃以上７０℃以下、好ましくは２０℃以上５０℃以下である。
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. As a method for applying, the above-described method is used. 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.
三次元網目状構造の層と球状構造の層とが積層されて構成される熱可塑性樹脂からなる中空糸膜の別の製造方法として、三次元網目状構造を形成する樹脂溶液と球状構造の層を形成する樹脂溶液とを三重管式口金から同時に吐出して固化せしめる方法も好ましく採用される。すなわち、三次元網目状構造の層が中空糸膜の外層、球状構造の層が内層に配置される中空糸膜を製造する場合、三次元網目状構造を形成する樹脂溶液を外側の管から、球状構造の層を形成する樹脂溶液を中間の管から、中空部形成液体を内側の管から同時に吐出し、凝固浴中で固化せしめることにより得ることができる。
As another method for producing a hollow fiber membrane made of a thermoplastic resin formed by laminating a layer of a three-dimensional network structure and a layer of a spherical structure, 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.
以上のようにして形成された中空糸膜において、三次元網目状構造の層は、最表層に最大孔径が０．０３μｍ未満の緻密な薄層を有し、表層から層の内部方向にかけて孔径が連続的に大きくなる傾斜構造からなる。このような傾斜構造は、最大孔径が０．０３μｍ未満の薄層を３以上含む構造であり、ウイルス除去性能は高いが十分な純水透過性能を示さない。しかし、この傾斜構造からなる層の孔径を適度に拡大させることができれば、表層側に本発明で必要な最大孔径が０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が２以下であることを特徴とし、層の内部には比較的大きな孔を有する層を形成させることが可能となり、ウイルスの除去性能を維持しつつ純水透過性能を飛躍的に向上させることができる。
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 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 μm, and has high virus removal performance but does not exhibit sufficient pure water permeation performance. However, if the pore diameter of the layer composed of this inclined structure can be appropriately increased, 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 μm, and A thin layer having a maximum pore diameter of less than 0.03 μm 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.
本発明者らは、そこで得られた中空糸膜を、比較的高い濃度で酸化剤を含む水溶液に、適当な時間接触させることにより、本発明の中空糸膜を製造できることを見いだした。三次元網目状構造の層を形成する樹脂は、酸化剤を含む水溶液に対して、該水溶液が低濃度である場合、または該水溶液との接触が短時間である場合は特に影響を受けないが、高濃度または長時間の接触の場合にその一部が化学的に分解される樹脂を含むことが必要である。このような樹脂としては前述した親水性高分子が好ましく挙げられる。
The present inventors have found that 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.
三次元網目状構造の層を形成する樹脂の一部が酸化剤により化学的に分解されることにより、三次元網目状構造の層の構造が変化する。すなわち三次元網目状構造の層の最表層に存在した最大孔径が０．０３μｍ未満の薄層の孔径が拡大することで、最大孔径が０．０３μｍ未満の薄層が３未満になり、最大孔径０．０３μｍ以上０．２μｍ以下の薄層が１０以上２００以下である三次元網目状構造の層が形成される。ここで、酸化剤を含む水溶液に接触させる前の三次元網目状構造を、ポリフッ化ビニリデン系樹脂と親水性高分子との混合物の溶液から形成させた場合、酸化剤を含む水溶液に接触させた後の三次元網目状構造の層には、実質的に親水性高分子が残っていなくてもよいが、その場合疎水性のポリフッ化ビニリデン系樹脂のみからなることになる。純水透過性能を高めるなどの観点からは、最終的に親水性高分子を含むことが好ましい。このために酸化剤を含む水溶液に接触させる前の三次元網目状構造の層の構造および組成に併せて、該酸化剤の種類、濃度、接触時間を制御することが重要である。また球状構造の層を形成する樹脂が、該酸化剤により化学的に分解されることにより物理的強度が低下しないために、球状構造の層を形成する樹脂には耐薬品性の高い樹脂を選択すること、あるいは該酸化剤の種類、濃度、接触時間を制御することが必要である。
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 μm 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 μm 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 μm or more and 0.2 μm or less is 10 or more and 200 or less is formed. Here, when 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. In the subsequent layer of the three-dimensional network structure, 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. For this purpose, it is important to control 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. In addition, since 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.
ここで酸化剤としては、水溶性であれば特に限定されないが、次亜塩素酸ナトリウム、過酸化水素、過マンガン酸カリウム、ニクロム酸カリウム、ハロゲン、濃硫酸、硝酸、クロラミンなどが好ましく、特に次亜塩素酸ナトリウムが好ましく用いられる。該酸化剤の濃度は５００ｐｐｍ以上５００００ｐｐｍ以下であり、かつ該酸化剤との接触時間は１時間以上４００時間以下である。好ましくは該酸化剤の濃度が１０００ｐｐｍ以上１００００ｐｐｍ以下であり、該酸化剤との接触時間が１０時間以上２００時間以下であり、さらに好ましくは該酸化剤の濃度が２０００ｐｐｍ以上８０００ｐｐｍ以下であり、該酸化剤との接触時間が２０時間以上１００時間以下である。該酸化剤の濃度が５００ｐｐｍ未満の場合、三次元網目状構造の層に十分な構造の変化が起こらない、あるいは十分に構造を変化させるのに４００時間を超える長い時間が必要であり実用的でなくなるため好ましくない。該酸化剤の濃度が５００００ｐｐｍを超える場合、球状構造の層の樹脂が化学的に分解され、物理的強度が低下してしまう可能性がある。また該酸化剤との接触時間が１時間未満では三次元網目状構造の層に十分な構造の変化が起こらない、あるいは十分に構造を変化させるのに５００００ｐｐｍを超える高い濃度が必要であり、球状構造の層の樹脂が化学的に分解され物理的強度が低下してしまう可能性がある。４００時間を超える場合、球状構造の層の樹脂が少なからず化学的に分解され、物理的強度が低下してしまう可能性があること、また実用的でないことなどから好ましくない。
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. Preferably, 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. 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 a long time exceeding 400 hours is required to sufficiently change the structure. Since it disappears, it is not preferable. When the concentration of the oxidizing agent exceeds 50000 ppm, 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.
本発明の効果を最大限発現させるためには、三次元網目状構造の層と球状構造の層との、それぞれの厚さも重要である。三次元網目状構造の層は、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が２以下であればよいため、該層の厚さは５μｍ以上１００μｍ以下が良く、好ましくは１０μｍ以上６０μｍ以下、さらに好ましくは１５μｍ以上３５μｍ以下である。三次元網目状構造の層を５μｍ未満の厚さで形成しようとすると欠陥が生じやすく、除去性能が低下してしまう。また該層の厚さが１００μｍを超えると、球状構造の層によって三次元網目状構造の層に耐圧性を付与している効果が低くなり、三次元網目状構造の層が変形し、孔径が拡大すると除去性能が低下し、逆に孔径が縮小すると純水透過性能が低下してしまう。球状構造の層の厚さは１１０μｍ以上４００μｍ以下が良く、好ましくは１５０μｍ以上３００μｍ以下である。球状構造の層の厚さが１１０μｍ未満では十分な物理的強度が得られず、４００μｍを超えると純水透過性能が低下してしまう。
In order to maximize the effects of the present invention, 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 μm or more and 0.2 μm or less and a thin layer with a maximum pore diameter of less than 0.03 μm of 2 or less as long as it has only 2 or less. The thickness of the layer is preferably 5 μm to 100 μm, preferably 10 μm to 60 μm, and more preferably 15 μm to 35 μm. If an attempt is made to form a layer having a three-dimensional network structure with a thickness of less than 5 μm, defects are likely to occur, and the removal performance is degraded. On the other hand, if the thickness of the layer exceeds 100 μm, the effect of imparting pressure resistance to the layer of the three-dimensional network structure due to the spherical structure layer is reduced, the layer of the three-dimensional network structure is deformed, and the pore diameter is reduced. If it enlarges, removal performance will fall, and conversely, if a hole diameter reduces, pure water permeation performance will fall. The thickness of the layer having a spherical structure is preferably 110 μm or more and 400 μm or less, and preferably 150 μm or more and 300 μm or less. If the thickness of the spherical structure layer is less than 110 μm, sufficient physical strength cannot be obtained, and if it exceeds 400 μm, the pure water permeation performance deteriorates.
以下に具体的な実施例を挙げて本発明を説明するが、本発明はこれら実施例により何ら限定されるものではない。ここで実施例・比較例に関連する中空糸膜のパラメーターは以下の方法で測定した。
Hereinafter, the present invention will be described with specific examples, but the present invention is not limited to these examples. Here, the parameters of the hollow fiber membranes related to Examples and Comparative Examples were measured by the following methods.
（１）三次元網目状構造の層における厚さ０．２μｍの薄層の最大孔径と薄層の数
走査型電子顕微鏡を用いて、中空糸膜の径方向の断面の三次元網目状構造の層を、外表面から球状構造の層との境界、あるいは球状構造の層がない場合は内表面まで連続的に６万倍で撮影した。撮影した顕微鏡写真において、外表面を起点とし内表面までを厚さ０．２μｍの薄層ごとに分け、各薄層にある最大孔径を測定した。また最大孔径０．０３μｍ未満の層、最大孔径０．０３μｍ以上０．０７μｍ未満の層、最大孔径０．０７μｍ以上０．１μｍ未満の層、および最大孔径０．１μｍ以上０．２μｍ以下の層の数をそれぞれ求めた。この作業を任意の３箇所について実施し、数平均により求めた。 (1) The maximum pore diameter and the number of thin layers of a thin layer having a thickness of 0.2 μm in the layer of the three-dimensional network structure, using a scanning electron microscope, the three-dimensional network structure of the radial cross section of the hollow fiber membrane The layer was photographed continuously at a magnification of 60,000 times from the outer surface to the boundary with the spherical structure layer, or to the inner surface when there was no spherical structure layer. In the photographed micrograph, the outer surface was used as a starting point and the inner surface was divided into thin layers having a thickness of 0.2 μm, and the maximum pore diameter in each thin layer was measured. In addition, a layer having a maximum pore diameter of less than 0.03 μm, a layer having a maximum pore diameter of 0.03 μm or more and less than 0.07 μm, a layer having a maximum pore diameter of 0.07 μm or more and less than 0.1 μm, and a layer having a maximum pore diameter of 0.1 μm or more and 0.2 μm or less Each number was determined. This operation was carried out at arbitrary three locations and obtained by number averaging.
走査型電子顕微鏡を用いて、中空糸膜の径方向の断面の三次元網目状構造の層を、外表面から球状構造の層との境界、あるいは球状構造の層がない場合は内表面まで連続的に６万倍で撮影した。撮影した顕微鏡写真において、外表面を起点とし内表面までを厚さ０．２μｍの薄層ごとに分け、各薄層にある最大孔径を測定した。また最大孔径０．０３μｍ未満の層、最大孔径０．０３μｍ以上０．０７μｍ未満の層、最大孔径０．０７μｍ以上０．１μｍ未満の層、および最大孔径０．１μｍ以上０．２μｍ以下の層の数をそれぞれ求めた。この作業を任意の３箇所について実施し、数平均により求めた。 (1) The maximum pore diameter and the number of thin layers of a thin layer having a thickness of 0.2 μm in the layer of the three-dimensional network structure, using a scanning electron microscope, the three-dimensional network structure of the radial cross section of the hollow fiber membrane The layer was photographed continuously at a magnification of 60,000 times from the outer surface to the boundary with the spherical structure layer, or to the inner surface when there was no spherical structure layer. In the photographed micrograph, the outer surface was used as a starting point and the inner surface was divided into thin layers having a thickness of 0.2 μm, and the maximum pore diameter in each thin layer was measured. In addition, a layer having a maximum pore diameter of less than 0.03 μm, a layer having a maximum pore diameter of 0.03 μm or more and less than 0.07 μm, a layer having a maximum pore diameter of 0.07 μm or more and less than 0.1 μm, and a layer having a maximum pore diameter of 0.1 μm or more and 0.2 μm or less Each number was determined. This operation was carried out at arbitrary three locations and obtained by number averaging.
（２）三次元網目状構造の層と球状構造の層との厚み
中空糸膜の径方向の断面を、走査型電子顕微鏡を用いて３００～１０００倍で撮影し、任意の２０箇所の三次元網目状構造の層の厚みおよび球状構造の層の厚みを測定し、それぞれ数平均して求めた。 (2) Thickness of three-dimensional network structure layer and spherical structure layer The cross-section in the radial direction of the hollow fiber membrane was photographed at 300 to 1000 times using a scanning electron microscope. The thickness of the layer having a network structure and the thickness of the layer having a spherical structure were measured and obtained by averaging each.
中空糸膜の径方向の断面を、走査型電子顕微鏡を用いて３００～１０００倍で撮影し、任意の２０箇所の三次元網目状構造の層の厚みおよび球状構造の層の厚みを測定し、それぞれ数平均して求めた。 (2) Thickness of three-dimensional network structure layer and spherical structure layer The cross-section in the radial direction of the hollow fiber membrane was photographed at 300 to 1000 times using a scanning electron microscope. The thickness of the layer having a network structure and the thickness of the layer having a spherical structure were measured and obtained by averaging each.
（３）球状構造の層の球状の固形分の平均直径
中空糸膜の径方向の断面の球状構造の層を、走査型電子顕微鏡を用いて３０００倍で任意の２０カ所の写真を撮影し、それぞれ任意の２０個の球状の固形分の直径を測定し、数平均して求めた。 (3) The average diameter of the spherical solid content of the layer having a spherical structure The spherical structure layer having a radial cross section of the hollow fiber membrane was photographed at 20 times at 3000 magnifications using a scanning electron microscope, The diameters of any 20 spherical solids were measured and determined by number averaging.
中空糸膜の径方向の断面の球状構造の層を、走査型電子顕微鏡を用いて３０００倍で任意の２０カ所の写真を撮影し、それぞれ任意の２０個の球状の固形分の直径を測定し、数平均して求めた。 (3) The average diameter of the spherical solid content of the layer having a spherical structure The spherical structure layer having a radial cross section of the hollow fiber membrane was photographed at 20 times at 3000 magnifications using a scanning electron microscope, The diameters of any 20 spherical solids were measured and determined by number averaging.
（４）ウイルス除去性能
大きさが約２５ｎｍのバクテリオファージＭＳ－２（Ｂａｃｔｅｒｉｏｐｈａｇｅ ＭＳ－２ ＡＴＣＣ １５５９７－Ｂ１）を約１．０×１０７ＰＦＵ／ｍｌの濃度で含有する蒸留水の水溶液をウイルス原液として調製した。ここで蒸留水は純水製造装置オートスチル（ヤマト科学製）の蒸留水を１２１℃で２０分間高圧蒸気滅菌したものを用いた。中空糸膜４本からなる長さ約２０ｃｍのガラス製の小型モジュールを作製し、温度約２０℃、ろ過差圧約１０ｋＰａ（外圧）の条件でウイルス原液を送液した。約１０ｍｌろ過後、ろ液を約５ｍｌ採取し、０～１０００倍に蒸留水で希釈した。Ｏｖｅｒｌａｙ ａｇａｒ ａｓｓａｙ、Ｓｔａｎｄａｒｄ Ｍｅｔｈｏｄ ９２１１－Ｄ（ＡＰＨＡ、１９９８、Ｓｔａｎｄａｒｄ ｍｅｔｈｏｄｓ ｆｏｒ ｔｈｅ ｅｘａｍｉｎａｔｉｏｎ ｏｆ ｗａｔｅｒ ａｎｄ ｗａｓｔｅｗａｔｅｒ, １８ｔｈ ｅｄ．）の方法に基づいて、希釈したろ液１ｍｌを検定用シャーレに接種し、プラックを計数することによってバクテリオファージＭＳ－２の濃度を求めた。除去性能は対数で表した。例えば２ｌｏｇとは２ｌｏｇ１０のことであり、残存濃度が１００分の１であることを意味する。またろ液中にプラックがまったく計測されない場合、≧７ｌｏｇとした。 (4) 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). After about 10 ml of filtration, about 5 ml of the filtrate was collected and diluted 0 to 1000 times with distilled water. Based on the method of Overlay agar assay, Standard Method 9211-D (APHA, 1998, Standard methods for the examination of water and wastewater, 18th ed.) To determine the concentration of bacteriophage MS-2. Removal performance was expressed logarithmically. For example, 2 log means 2 log 10 and means that the residual concentration is 1/100. When no plaque was measured in the filtrate, ≧ 7 log was set.
大きさが約２５ｎｍのバクテリオファージＭＳ－２（Ｂａｃｔｅｒｉｏｐｈａｇｅ ＭＳ－２ ＡＴＣＣ １５５９７－Ｂ１）を約１．０×１０７ＰＦＵ／ｍｌの濃度で含有する蒸留水の水溶液をウイルス原液として調製した。ここで蒸留水は純水製造装置オートスチル（ヤマト科学製）の蒸留水を１２１℃で２０分間高圧蒸気滅菌したものを用いた。中空糸膜４本からなる長さ約２０ｃｍのガラス製の小型モジュールを作製し、温度約２０℃、ろ過差圧約１０ｋＰａ（外圧）の条件でウイルス原液を送液した。約１０ｍｌろ過後、ろ液を約５ｍｌ採取し、０～１０００倍に蒸留水で希釈した。Ｏｖｅｒｌａｙ ａｇａｒ ａｓｓａｙ、Ｓｔａｎｄａｒｄ Ｍｅｔｈｏｄ ９２１１－Ｄ（ＡＰＨＡ、１９９８、Ｓｔａｎｄａｒｄ ｍｅｔｈｏｄｓ ｆｏｒ ｔｈｅ ｅｘａｍｉｎａｔｉｏｎ ｏｆ ｗａｔｅｒ ａｎｄ ｗａｓｔｅｗａｔｅｒ, １８ｔｈ ｅｄ．）の方法に基づいて、希釈したろ液１ｍｌを検定用シャーレに接種し、プラックを計数することによってバクテリオファージＭＳ－２の濃度を求めた。除去性能は対数で表した。例えば２ｌｏｇとは２ｌｏｇ１０のことであり、残存濃度が１００分の１であることを意味する。またろ液中にプラックがまったく計測されない場合、≧７ｌｏｇとした。 (4) 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). After about 10 ml of filtration, about 5 ml of the filtrate was collected and diluted 0 to 1000 times with distilled water. Based on the method of Overlay agar assay, Standard Method 9211-D (APHA, 1998, Standard methods for the examination of water and wastewater, 18th ed.) To determine the concentration of bacteriophage MS-2. Removal performance was expressed logarithmically. For example, 2 log means 2 log 10 and means that the residual concentration is 1/100. When no plaque was measured in the filtrate, ≧ 7 log was set.
（５）純水透過性能
中空糸膜４本からなる長さ約２０ｃｍの小型モジュールを作製し、温度２５℃、ろ過差圧１６ｋＰａ（外圧）の条件で逆浸透膜処理水を送液し、一定時間の透過水量（ｍ３）を測定して得た値を、単位時間（ｈｒ）、単位有効膜面積（ｍ２）、５０ｋＰａ当たりに換算して算出した。 (5) Pure water permeation performance A small module of about 20 cm in length consisting of four hollow fiber membranes was prepared, and reverse osmosis membrane treated water was fed under conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa (external pressure). The value obtained by measuring the amount of permeated water (m 3 ) over time was calculated by converting per unit time (hr), unit effective membrane area (m 2 ), and 50 kPa.
中空糸膜４本からなる長さ約２０ｃｍの小型モジュールを作製し、温度２５℃、ろ過差圧１６ｋＰａ（外圧）の条件で逆浸透膜処理水を送液し、一定時間の透過水量（ｍ３）を測定して得た値を、単位時間（ｈｒ）、単位有効膜面積（ｍ２）、５０ｋＰａ当たりに換算して算出した。 (5) Pure water permeation performance A small module of about 20 cm in length consisting of four hollow fiber membranes was prepared, and reverse osmosis membrane treated water was fed under conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa (external pressure). The value obtained by measuring the amount of permeated water (m 3 ) over time was calculated by converting per unit time (hr), unit effective membrane area (m 2 ), and 50 kPa.
（６）破断強力、破断伸度
引張試験機（（株）東洋ボールドウィン製ＴＥＮＳＩＬＯＮ（登録商標）／ＲＴＭ－１００）を用いて、逆浸透膜処理水で湿潤させた中空糸膜を試験長５０ｍｍ、フルスケール５ｋｇの加重でクロスヘッドスピード５０ｍｍ／分にて測定した。この操作を、試料を変えて１０回実施し、数平均することで求めた。 (6) Tensile strength at break, elongation at break Using a tensile tester (TENSILON (registered trademark) / RTM-100 manufactured by Toyo Baldwin Co., Ltd.), a hollow fiber membrane wetted with reverse osmosis membrane-treated water was tested at a test length of 50 mm. Measurement was performed at a crosshead speed of 50 mm / min with a full scale load of 5 kg. This operation was carried out 10 times while changing the sample, and the number average was obtained.
引張試験機（（株）東洋ボールドウィン製ＴＥＮＳＩＬＯＮ（登録商標）／ＲＴＭ－１００）を用いて、逆浸透膜処理水で湿潤させた中空糸膜を試験長５０ｍｍ、フルスケール５ｋｇの加重でクロスヘッドスピード５０ｍｍ／分にて測定した。この操作を、試料を変えて１０回実施し、数平均することで求めた。 (6) Tensile strength at break, elongation at break Using a tensile tester (TENSILON (registered trademark) / RTM-100 manufactured by Toyo Baldwin Co., Ltd.), a hollow fiber membrane wetted with reverse osmosis membrane-treated water was tested at a test length of 50 mm. Measurement was performed at a crosshead speed of 50 mm / min with a full scale load of 5 kg. This operation was carried out 10 times while changing the sample, and the number average was obtained.
（実施例１）
重量平均分子量４１．７万のフッ化ビニリデンホモポリマー３８重量％とγ－ブチロラクトン６２重量％を１６０℃で溶解した。この樹脂溶液を二重管式口金の外側の管から吐出し、同時にγ－ブチロラクトン８５重量％水溶液を二重管式口金の内側の管から吐出し、γ－ブチロラクトン８５重量％水溶液からなる温度１０℃の浴中で固化させた。その後９０℃の水中で１．５倍に延伸した。得られた中空糸膜は球状構造からなる中空糸膜であった。 Example 1
38% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 41,000 and 62% by weight of γ-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 γ-butyrolactone is discharged from the inner tube of the double-tube base, and the temperature of the aqueous solution of 85% by weight of γ-butyrolactone is 10%. Solidified in a bath at 0 ° C. Thereafter, the film was stretched 1.5 times in 90 ° C. water. The obtained hollow fiber membrane was a hollow fiber membrane having a spherical structure.
重量平均分子量４１．７万のフッ化ビニリデンホモポリマー３８重量％とγ－ブチロラクトン６２重量％を１６０℃で溶解した。この樹脂溶液を二重管式口金の外側の管から吐出し、同時にγ－ブチロラクトン８５重量％水溶液を二重管式口金の内側の管から吐出し、γ－ブチロラクトン８５重量％水溶液からなる温度１０℃の浴中で固化させた。その後９０℃の水中で１．５倍に延伸した。得られた中空糸膜は球状構造からなる中空糸膜であった。 Example 1
38% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 41,000 and 62% by weight of γ-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 γ-butyrolactone is discharged from the inner tube of the double-tube base, and the temperature of the aqueous solution of 85% by weight of γ-butyrolactone is 10%. Solidified in a bath at 0 ° C. Thereafter, the film was stretched 1.5 times in 90 ° C. water. The obtained hollow fiber membrane was a hollow fiber membrane having a spherical structure.
次いで、アクリロニトリル１００モル％、極限粘度３．２の重合体をジメチルスルホキシド中で重合し、さらにジメチルスルホキシドで希釈して１３．５重量％の製膜原液を得た。この製膜原液を球状構造からなる中空糸膜表面に均一に塗布し、すぐに２３℃の２０重量％ジメチルスルホキシド水溶液中で凝固させて、球状構造の層の上に三次元網目状構造の層を形成させた中空糸膜を作製した。その後、中空糸膜を３０００ｐｐｍの次亜塩素酸ナトリウム水溶液に１８０時間浸漬した。
Next, 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.
得られた中空糸膜は外径１４３０μｍ、内径８８０μｍであり、膜構造および膜性能は表１に示す通りであった。
The obtained hollow fiber membrane had an outer diameter of 1430 μm and an inner diameter of 880 μm, and the membrane structure and membrane performance were as shown in Table 1.
（実施例２）
中空糸膜を３０００ｐｐｍの次亜塩素酸ナトリウム水溶液に３６０時間浸漬した以外は実施例１と同様にして中空糸膜を作製した。 (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.
中空糸膜を３０００ｐｐｍの次亜塩素酸ナトリウム水溶液に３６０時間浸漬した以外は実施例１と同様にして中空糸膜を作製した。 (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.
得られた中空糸膜は外径１４２０μｍ、内径８９０μｍであり、膜構造および膜性能は表１に示す通りであった。
The obtained hollow fiber membrane had an outer diameter of 1420 μm and an inner diameter of 890 μm, and the membrane structure and membrane performance were as shown in Table 1.
（実施例３）
まず、実施例１と同様の方法で球状構造からなる中空糸膜を作製した。 (Example 3)
First, a hollow fiber membrane having a spherical structure was produced in the same manner as in Example 1.
まず、実施例１と同様の方法で球状構造からなる中空糸膜を作製した。 (Example 3)
First, a hollow fiber membrane having a spherical structure was produced in the same manner as in Example 1.
次いで、重量平均分子量２８．４万のフッ化ビニリデンホモポリマーを１２重量％とセルロースアセテート（イーストマンケミカル社、ＣＡ４３５－７５Ｓ：三酢酸セルロース）を９重量％、Ｎ－メチル－２－ピロリドンを７９重量％の１５０℃で混合溶解し製膜原液を得た。この製膜原液を７０℃に降温し球状構造からなる中空糸膜表面に均一に塗布し、すぐに２７℃の水中で凝固させて、球状構造の層の上に三次元網目状構造の層を形成させた中空糸膜を作製した。その後、中空糸膜を６０００ｐｐｍの次亜塩素酸ナトリウム水溶液に２２時間浸漬した。
Then, 12% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 9% by weight of cellulose acetate (Eastman Chemical Co., CA435-75S: cellulose triacetate), and 79% of N-methyl-2-pyrrolidone. 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.
得られた中空糸膜は外径１４１０μｍ、内径８８０μｍであり、膜構造および膜性能は表１に示す通りであった。
The obtained hollow fiber membrane had an outer diameter of 1410 μm and an inner diameter of 880 μm, and the membrane structure and membrane performance were as shown in Table 1.
（比較例１）
次亜塩素酸ナトリウム水溶液に浸漬しなかった以外は、実施例１と同様にして中空糸膜を得た。 得られた中空糸膜は外径１４４０μｍ、内径８７０μｍであり、膜構造および膜性能は表１に示す通りであった。 (Comparative 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 μm and an inner diameter of 870 μm, and the membrane structure and membrane performance were as shown in Table 1.
次亜塩素酸ナトリウム水溶液に浸漬しなかった以外は、実施例１と同様にして中空糸膜を得た。 得られた中空糸膜は外径１４４０μｍ、内径８７０μｍであり、膜構造および膜性能は表１に示す通りであった。 (Comparative 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 μm and an inner diameter of 870 μm, and the membrane structure and membrane performance were as shown in Table 1.
（比較例２）
まず、実施例１と同様の方法で球状構造からなる中空糸膜を作製した。 (Comparative Example 2)
First, a hollow fiber membrane having a spherical structure was produced in the same manner as in Example 1.
まず、実施例１と同様の方法で球状構造からなる中空糸膜を作製した。 (Comparative Example 2)
First, a hollow fiber membrane having a spherical structure was produced in the same manner as in Example 1.
次いで、重量平均分子量３８．７万のフッ化ビニリデンホモポリマー１２重量％とセルロースアセテート（イーストマンケミカル社、ＣＡ４３５－７５Ｓ：三酢酸セルロース）７．２重量％、Ｎ－メチル－２－ピロリドン８０．８重量％を９５℃で混合溶解し製膜原液を得た。この製膜原液を７０℃に降温し球状構造からなる中空糸膜表面に均一に塗布し、すぐに２７℃の水中で凝固させて、球状構造の層の上に三次元網目状構造の層を形成させた中空糸膜を作製した。
Subsequently, 12% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 38.7 million, 7.2% by weight of cellulose acetate (Eastman Chemical Co., CA435-75S: cellulose triacetate), 80% of N-methyl-2-pyrrolidone. 8% by weight was mixed and dissolved at 95 ° C. to obtain a film-forming stock solution. 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.
得られた中空糸膜は外径１４５０μｍ、内径９００μｍであり、膜構造および膜性能は表１に示す通りであった。
The obtained hollow fiber membrane had an outer diameter of 1450 μm and an inner diameter of 900 μm, and the membrane structure and membrane performance were as shown in Table 1.
（比較例３）
アクリロニトリル１００モル％、極限粘度３．２の重合体をジメチルスルホキシド中で重合し、さらに希釈して１３．０重量％の樹脂溶液を得た。この樹脂溶液を二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド８０重量％水溶液を二重管式口金の内側の管から吐出し、温度３０℃の水浴中で固化させた。得られた中空糸膜は三次元網目状構造からなる中空糸膜であった。 (Comparative Example 3)
A polymer having an acrylonitrile of 100 mol% and an intrinsic viscosity of 3.2 was polymerized in dimethyl sulfoxide and further diluted to obtain a 13.0 wt% resin solution. This resin solution was discharged from the outer tube of the double-tube die, and at the same time, an 80% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube die, and solidified in a water bath at a temperature of 30 ° C. The obtained hollow fiber membrane was a hollow fiber membrane having a three-dimensional network structure.
アクリロニトリル１００モル％、極限粘度３．２の重合体をジメチルスルホキシド中で重合し、さらに希釈して１３．０重量％の樹脂溶液を得た。この樹脂溶液を二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド８０重量％水溶液を二重管式口金の内側の管から吐出し、温度３０℃の水浴中で固化させた。得られた中空糸膜は三次元網目状構造からなる中空糸膜であった。 (Comparative Example 3)
A polymer having an acrylonitrile of 100 mol% and an intrinsic viscosity of 3.2 was polymerized in dimethyl sulfoxide and further diluted to obtain a 13.0 wt% resin solution. This resin solution was discharged from the outer tube of the double-tube die, and at the same time, an 80% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube die, and solidified in a water bath at a temperature of 30 ° C. The obtained hollow fiber membrane was a hollow fiber membrane having a three-dimensional network structure.
得られた中空糸膜は外径２９０μｍ、内径２１０μｍであり、膜構造および膜性能は表１に示す通りであった。
The obtained hollow fiber membrane had an outer diameter of 290 μm and an inner diameter of 210 μm, and the membrane structure and membrane performance were as shown in Table 1.
（比較例４）
重量平均分子量４１．７万のフッ化ビニリデンホモポリマー３８重量％とγ－ブチロラクトン６２重量％を１７０℃で溶解した。この樹脂溶液を二重管式口金の外側の管から吐出し、同時にγ－ブチロラクトンを二重管式口金の内側の管から吐出し、γ－ブチロラクトン８０重量％水溶液からなる温度２０℃の浴中で固化させた。得られた中空糸膜は球状構造からなる中空糸膜であった。 (Comparative Example 4)
38% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 41,000 and 62% by weight of γ-butyrolactone were dissolved at 170 ° C. This resin solution is discharged from the outer tube of the double-tube die, and at the same time, γ-butyrolactone is discharged from the inner tube of the double-tube die, in a bath of 20 ° C. composed of an 80% by weight aqueous solution of γ-butyrolactone. Solidified. The obtained hollow fiber membrane was a hollow fiber membrane having a spherical structure.
重量平均分子量４１．７万のフッ化ビニリデンホモポリマー３８重量％とγ－ブチロラクトン６２重量％を１７０℃で溶解した。この樹脂溶液を二重管式口金の外側の管から吐出し、同時にγ－ブチロラクトンを二重管式口金の内側の管から吐出し、γ－ブチロラクトン８０重量％水溶液からなる温度２０℃の浴中で固化させた。得られた中空糸膜は球状構造からなる中空糸膜であった。 (Comparative Example 4)
38% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 41,000 and 62% by weight of γ-butyrolactone were dissolved at 170 ° C. This resin solution is discharged from the outer tube of the double-tube die, and at the same time, γ-butyrolactone is discharged from the inner tube of the double-tube die, in a bath of 20 ° C. composed of an 80% by weight aqueous solution of γ-butyrolactone. Solidified. The obtained hollow fiber membrane was a hollow fiber membrane having a spherical structure.
次いで、重量平均分子量２８．４万のフッ化ビニリデンホモポリマー１２重量％とセルロースアセテート（イーストマンケミカル社、ＣＡ４３５－７５Ｓ：三酢酸セルロース）７．２重量％、Ｎ－メチル－２－ピロリドン８０．８重量％を９５℃で混合溶解し製膜原液を得た。この製膜原液を７０℃に降温し球状構造からなる中空糸膜表面に均一に塗布し、すぐに４３℃の水中で凝固させて、球状構造の層の上に三次元網目状構造の層を形成させた中空糸膜を作製した。その後、中空糸膜を３０００ｐｐｍの次亜塩素酸ナトリウム水溶液に３００時間浸漬した。
Then, 12% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 7.2% by weight of cellulose acetate (Eastman Chemical Co., CA435-75S: cellulose triacetate), 80% of N-methyl-2-pyrrolidone. 8% by weight was mixed and dissolved at 95 ° C. to obtain a film-forming stock solution. This membrane-forming stock solution is cooled to 70 ° C., uniformly applied to the surface of the hollow fiber membrane having a spherical structure, and immediately solidified in 43 ° C. water 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 3000 ppm sodium hypochlorite for 300 hours.
得られた中空糸膜は外径１３６０μｍ、内径８００μｍであり、膜構造および膜性能を表１に示す。
The obtained hollow fiber membrane has an outer diameter of 1360 μm and an inner diameter of 800 μm, and the membrane structure and membrane performance are shown in Table 1.
実施例に示されたように、三次元網目状構造の層と球状構造の層とが積層されて構成されてなり、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下である熱可塑性樹脂からなる中空糸膜を作製することにより、純水透過性能、破断強力、破断伸度、ウイルス除去性能を高いレベルで有する中空糸膜を得ることができる。一方、比較例１は酸化剤で処理しなかったため、最大孔径が０．０３μｍ未満の薄層が４と多く、純水透過性能が低い。比較例２、４は親水性高分子濃度が７．２重量％と低く、最大孔径０．０３μｍ以上０．２μｍ以下の薄層が少ないために、ウイルス除去性能が低い。また、比較例３は球状構造の層がないため破断強力が低い。
As shown in the examples, 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 μm in the thickness direction. Thermoplastic having 10 to 200 thin layers with a maximum pore size of 0.03 μm to 0.2 μm and a thin layer with a maximum pore size of less than 0.03 μm of 0 to 2 when divided into thin layers By producing a hollow fiber membrane made of a resin, a hollow fiber membrane having a high level of pure water permeation performance, breaking strength, breaking elongation, and virus removal performance can be obtained. On the other hand, 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 μm 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 μm or more and 0.2 μm 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.
Claims (10)
- 三次元網目状構造の層と球状構造の層とが積層されて構成される熱可塑性樹脂からなる中空糸膜であって、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする中空糸膜。 A hollow fiber membrane made of a thermoplastic resin 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 has a thickness of 0.2 μm in the thickness direction. In the case where each thin layer is divided, the thin layer having a maximum pore diameter of 0.03 μm or more and 0.2 μm or less is 10 or more and 200 or less, and the thin layer having a maximum pore diameter of less than 0.03 μm is 0 or more and 2 or less. A hollow fiber membrane characterized by
- 最大孔径が０．０３μｍ未満の薄層が０である請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, wherein the thin layer having a maximum pore diameter of less than 0.03 µm is zero.
- 球状構造の層における球状の固形分の平均直径が０．９μｍ以上３μｍ以下である請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, wherein an average diameter of a spherical solid content in the layer having a spherical structure is 0.9 µm or more and 3 µm or less.
- 三次元網目状構造の層が中空糸膜の最外層に配置されることを特徴とする請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, wherein the layer having a three-dimensional network structure is disposed in the outermost layer of the hollow fiber membrane.
- 三次元網目状構造の層１層と、球状構造の層１層とからなることを特徴とする請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, comprising one layer having a three-dimensional network structure and one layer having a spherical structure.
- 三次元網目状構造の層の厚みが５μｍ以上１００μｍ以下であり、かつ球状構造の層の厚みが１１０μｍ以上４００μｍ以下である請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, wherein the thickness of the layer having a three-dimensional network structure is 5 µm or more and 100 µm or less, and the thickness of the layer having a spherical structure is 110 µm or more and 400 µm or less.
- 球状構造の層がポリフッ化ビニリデン系樹脂からなる請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, wherein the spherical layer is made of a polyvinylidene fluoride resin.
- 三次元網目状構造の層が親水性高分子を含有してなる請求項１に記載の中空糸膜。 The hollow fiber membrane according to claim 1, wherein the layer having a three-dimensional network structure contains a hydrophilic polymer.
- 球状構造の層を形成させる工程、親水性高分子を８重量％以上含有する樹脂溶液を凝固せしめることで三次元網目状構造の層を形成させる工程、酸化剤を含む水溶液に三次元網目状構造の層を接触させる工程、を含む三次元網目状構造の層と球状構造の層から構成される熱可塑性樹脂からなる中空糸膜の製造方法であって、三次元網目状構造の層が、その厚み方向に厚さ０．２μｍの薄層ごとに分割した場合において、最大孔径０．０３μｍ以上０．２μｍ以下の薄層を１０以上２００以下有し、かつ最大孔径が０．０３μｍ未満の薄層が０以上２以下であることを特徴とする中空糸膜の製造方法。 A step of forming a layer of a spherical structure, a step of forming a layer of a three-dimensional network structure by coagulating a resin solution containing 8% by weight or more of a hydrophilic polymer, a three-dimensional network structure in an aqueous solution containing an oxidizing agent A method for producing a hollow fiber membrane comprising a thermoplastic resin comprising a layer having a three-dimensional network structure and a layer having a spherical structure, wherein the layer having a three-dimensional network structure is When divided into thin layers each having a thickness of 0.2 μm in the thickness direction, the thin layer has a maximum pore diameter of 0.03 μm or more and 0.2 μm or less of 10 to 200 and a maximum pore diameter of less than 0.03 μm. Is 0 or more and 2 or less, The manufacturing method of the hollow fiber membrane characterized by the above-mentioned.
- 酸化剤を含む水溶液の濃度が５００ｐｐｍ以上５００００ｐｐｍ以下であり、酸化剤を含む水溶液と三次元網目状構造との接触時間が１時間以上４００時間以下であることを特徴とする請求項９に記載の中空糸膜の製造方法。 The concentration of the aqueous solution containing an oxidizing agent is 500 ppm or more and 50000 ppm or less, and the contact time between the aqueous solution containing an oxidizing agent and the three-dimensional network structure is 1 hour or more and 400 hours or less, A method for producing a hollow fiber membrane.
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| JP2013510717A (en) * | 2010-12-16 | 2013-03-28 | 天津膜天膜科技股▲分▼有限公司 | Method for producing polyvinylidene fluoride composite reinforced liquid separation membrane |
| WO2014208592A1 (en) | 2013-06-26 | 2014-12-31 | ダイキン工業株式会社 | Composition, porous polymer membrane and hydrophilic agent |
| 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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| JP2006281202A (en) * | 2005-03-11 | 2006-10-19 | Toray Ind Inc | Hollow fiber membrane, dipped type membrane module using it, separating apparatus, and production method of hollow fiber membrane |
| WO2008001426A1 (en) * | 2006-06-27 | 2008-01-03 | Toray Industries, Inc. | Polymer separation membrane and process for producing the same |
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| JP2006281202A (en) * | 2005-03-11 | 2006-10-19 | Toray Ind Inc | Hollow fiber membrane, dipped type membrane module using it, separating apparatus, and production method of hollow fiber membrane |
| WO2008001426A1 (en) * | 2006-06-27 | 2008-01-03 | Toray Industries, Inc. | Polymer separation membrane and process for producing the same |
| WO2008012872A1 (en) * | 2006-07-25 | 2008-01-31 | Toray Industries, Inc. | Fluororesin polymer separation membrane and process for producing the same |
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| JP2013510717A (en) * | 2010-12-16 | 2013-03-28 | 天津膜天膜科技股▲分▼有限公司 | Method for producing polyvinylidene fluoride composite reinforced liquid separation membrane |
| WO2014208592A1 (en) | 2013-06-26 | 2014-12-31 | ダイキン工業株式会社 | Composition, porous polymer membrane and hydrophilic agent |
| 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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