JP6675335B2 - Polyamide ultrafiltration membrane having organic solvent resistance and method for producing the same - Google Patents

Description

  The present invention relates to a polyamide ultrafiltration membrane having excellent resistance to organic solvents. More specifically, the present invention relates to a polyamide ultrafiltration membrane having excellent resistance to various organic solvents used in the fields of electronics, foods, pharmaceuticals, fermentation, optics, and the like. The present invention also relates to a method for producing the polyamide ultrafiltration membrane. Further, the present invention relates to an ultrafiltration membrane module using the polyamide ultrafiltration membrane.

  Conventionally, ultrafiltration membranes remove bacteria and viruses in the water purification field, separate or concentrate heat-sensitive substances such as proteins and enzymes in the industrial field, artificial dialysis in the medical field, viruses and proteins in the production of pharmaceuticals and medical water. Removal, production of ultrapure water, collection of electrodeposition paint, treatment of sewage of thread and pulp mills, treatment of oil-containing wastewater, treatment of building wastewater, clarification of fruit juice, production of sake, concentration and desalination of cheese whey, It has been put into practical use in various fields such as production of concentrated milk, concentration of egg white, utilization in bioreactors, removal of fine particles in gas, and water treatment of nuclear power plants. And, since the ultrafiltration membrane is used in various fields, it is sometimes used for processing a solution containing an organic solvent, and in order to enhance its practicality, it has excellent organic solvent resistance. Is required.

  In the filtration using an ultrafiltration membrane, fine pores of a porous membrane in the range of 1 nm to 100 nm can separate proteins, polymers and the like dissolved in water from fine particles such as viruses and colloids. The pore size of an ultrafiltration membrane is difficult to observe and measure even with an electron microscope, and the pore size varies, so the typical pore size of the membrane is not sufficient to express the separation performance of the membrane. The molecular weight cutoff is mainly used as an index of separation performance. The size of the target substance that can be separated by the ultrafiltration membrane is not clearly divided before and after the molecular weight cutoff, but has a certain width.

  A phase separation method is an industrially frequently used method for producing an ultrafiltration membrane using a polymer material as a raw material. The phase separation method can be roughly classified into a non-solvent induced phase separation method (NIPS method) and a thermally induced phase separation method (TIPS method). In the NIPS method, a uniform polymer solution is prepared by dissolving a polymer material in a good solvent, and the polymer solution is immersed in a non-solvent. This is a method of causing phase separation. In the NIPS method, a finger-like structure is formed by macrovoids, and the advantages are that the device is simple, it is easy to make an asymmetric structure with a dense layer formed on the surface, it is easy to increase the flow rate, and it has a long history of many porous materials. It is used in the production of a film and has a track record. Disadvantages of the NIPS method include low strength and the necessity of a good solvent that dissolves at room temperature. On the other hand, the TIPS method is a relatively new method, in which a solvent that does not dissolve at a low temperature but dissolves at a high temperature in a polymer material is selected, and a uniform polymer solution dissolved at a high temperature is mixed with a one-phase region and a two-phase solution. This is a method of inducing phase separation by cooling to a temperature below a binodal line, which is a boundary of a region, and fixing the structure by crystallization or glass transition of a polymer. The TIPS method tends to have a sponge-like homogenous structure, and has advantages in that it can have high strength and can be applied to a polymer having no solvent that dissolves at a low temperature. It is difficult to make a structure and to make a microstructure such as an ultrafiltration membrane.

  For the reasons described above, there is no commercially available ultrafiltration membrane formed by the TIPS method, and according to Non-Patent Document 1, an ultrafiltration membrane made of cellulose acetate can be produced by the TIPS method. Was just shown for the first time.

  Conventionally, as a material for an ultrafiltration membrane, a polymer material such as cellulose acetate, polyacrylonitrile, polyvinylidene fluoride, polysulfone, and polyethersulfone has been known. Cellulose acetate has good processability and excellent separability, and is often used as an ultrafiltration membrane, but has drawbacks in terms of heat resistance and organic solvent resistance. Further, polyacrylonitrile and polyvinylidene fluoride are superior to cellulose acetate in terms of organic solvent resistance and heat resistance, and although they are practically used as porous membranes, they are not suitable for organic solvents such as aprotic polar solvents. It has the drawback of easy dissolution, and cannot be said to be a film material with sufficiently satisfactory properties. Furthermore, polysulfone and polyethersulfone have excellent heat resistance, good workability, and are practically used as ultrafiltration membranes including hollow fiber membranes having various fractionation characteristics. There is a problem in terms of solvent properties.

  In addition, a technique using polyphenylene sulfide (PPS) as an ultrafiltration membrane having excellent organic solvent resistance has been proposed. For example, Patent Document 1 reports that a polyphenylene sulfide (PPS) film is extremely excellent in heat resistance and organic solvent resistance, and Patent Documents 2 and 3 disclose a hollow fiber membrane using PPS. Is also being studied. However, in Patent Documents 1 and 2, the use of a porous method by a stretching method is employed, and the average pore diameter is large, so that it can be used as a microfiltration membrane but does not have the performance of an ultrafiltration membrane. Further, Patent Document 3 discloses an ultrafiltration membrane produced by a phase separation method, and uses N-methyl-2-pyrrolidone having a boiling point of 202 ° C as a membrane-forming solvent and pressurizes at 250 ° C. Therefore, it can be said that the technology is difficult to be put into practical use in industrial production. Patent Document 4 proposes a method for further improving heat resistance and organic solvent resistance by converting a sulfide bond into a sulfone bond by oxidizing a porous body using PPS. However, the porous body itself using PPS is processed by the above-described various methods and then manufactured by a method of selectively oxidizing a sulfide bond, leaving a problem in terms of fractionation performance and practicality. I have.

  Furthermore, a technique for producing a film having excellent organic solvent resistance using a material other than PPS has been reported. For example, Patent Document 5 reports that an organic solvent-resistant membrane can be produced by using a polyfunctional amino group compound, but requires a separation operation at a very high pressure and can be processed. There is a problem that the amount of water permeability is small, and it has not reached a practical level. Non-Patent Document 2 discloses a nanofiltration membrane using polyimide, but polyimide is an expensive material, and the nanofiltration membrane is intended for separation of geraniol having a very small molecular weight, It cannot function as an ultrafiltration membrane having a molecular weight cut-off of about 1,000 to 200,000. Further, Patent Documents 6 and 7 report organic solvent-resistant ceramic separation membranes using inorganic materials as raw materials. These ceramic separation membranes require high-pressure separation operations, The water permeability is low, and it has not reached the practical level.

  On the other hand, various methods for producing a porous film using a polyamide resin have been studied. For example, Patent Documents 8 to 11 disclose a technique using a formic acid as a solvent for a technique for producing a porous membrane using a polyamide resin by a NIPS method. There was a problem, and the resulting membrane had a large pore size and could not function as an ultrafiltration membrane. Patent Document 12 discloses a method of casting polyamide 6 mixed with polycaprolactone and dissolving in hexafluoroisopropanol, and extracting caprolactone therefrom to make it porous. In addition, the polymer compound to be extracted and removed is expensive, and causes an increase in production cost, which is not practical. Further, Patent Document 13 discloses a method for forming a film by dissolving N-methyl-2-pyrrolidone or dimethylsulfoxide by adding lithium chloride to a porous film using a semi-aromatic polyamide. It is also disclosed that the resulting porous membrane exhibits a high albumin rejection. However, the porous membrane described in Patent Document 13 has a problem that the resistance of the organic solvent is significantly reduced due to the remaining lithium chloride, and a problem that the water permeability does not reach a practical level unless the film thickness is reduced.

  Further, a method of manufacturing a porous film using a polyamide-based resin by a TIPS method has been studied. For example, Patent Document 14 discloses a technique of forming various resins into a porous film by the TIPS method, and polyamide 6 is mentioned as an example. However, the porous film described in Patent Document 14 has a pore diameter of Cannot be used as an ultrafiltration membrane. Patent Document 15 discloses a method for producing a hollow fiber membrane by a TIPS method using a polyamide resin. The obtained hollow fiber membrane has a very large pore diameter of 1.4 μm and a molecular weight cutoff. However, it cannot function as an ultrafiltration membrane of about 1000 to 200,000. Further, Patent Document 15 discloses glycerin and ethylene glycol as a solvent for polyamide, but even if a polyamide film is formed using these solvents, the resulting porous film is only practically usable. There is also a drawback that strength cannot be provided. Patent Document 16 relates to a method for producing a hydrolysis-stable polyamide film, and discloses a method for producing an aliphatic polyamide using a solvent containing an antioxidant. It has a large maximum pore size and cannot be used as an ultrafiltration membrane. Further, Non-Patent Document 3 reports that a porous film can be produced using a solvent system containing polyamide 12 and polyethylene glycol. Patent Literature 17 reports that a porous film can be produced using a solvent system containing polyamide 11 and ethylene carbonate, propylene carbonate, or sulfolane. Non-Patent Document 4 discloses that a porous membrane of polyamide 6 and polyamide 12 can be produced using triethylene glycol as a solvent. However, the porous membranes disclosed in Non-Patent Literatures 3-4 and Patent Literature 17 cannot be used as ultrafiltration membranes because of their low strength and large pore size. Patent Literature 18 discloses an example in which a porous membrane using a semi-aromatic polyamide is manufactured by a TIPS method. This porous membrane has a large average pore size of 0.01 to 10 μm, and has an ultrafiltration membrane. It cannot be used as.

  As described above, although various studies have been made on a porous membrane using a polyamide-based resin, those that have excellent resistance to various organic solvents and can be used as an ultrafiltration membrane have not yet been developed. It is the current situation. Regarding a porous membrane using a polymer material such as polyethylene, polypropylene, and polytetrafluoroethylene which is considered to be resistant to organic solvents, although there is a report on a microfiltration membrane (MF membrane), it relates to an ultrafiltration membrane. There are no reports.

JP-A-58-67733 JP-A-59-59917 JP-A-60-248202 JP-A-63-225636 JP-A-3-127617 JP-A-2003-10657 JP-A-2004-911 JP-A-57-105212 JP-A-58-65009 U.S. Pat. U.S. Pat. No. 4,477,598 JP-A-2000-1612 No. 2004-6991 JP-A-58-164622 JP-A-60-52612 JP-T-2003-534908 U.S. Pat. No. 4,247,498 JP 2005-193193 A

K. Hirami, Y .; Ohmukai, T .; Maruyama, H .; Matsuyama, Desalin. Water. Treat. , 17, 262-267 (2010). R. Valadez-Blanco, A .; G. FIG. Livingston, Journal of Membrane Science 326, 332-342 (2009). B. J. Cha, K .; Char, J.A. J. Kim, S.M. S. Kim, C.A. K. Kim, Journal of membrane science 108, 219-229 (1995). "Membrane Technology 2nd Edition", written by Marcel Mulder, supervised by Masakazu Yoshikawa, Tsuyoshi Matsuura, Tsutomu Nakagawa, published by IPC Inc., p. 95 (1997)

  An object of the present invention is to solve the above problems and to provide a polyamide ultrafiltration membrane having resistance to various types of organic solvents.

  The present inventors have conducted intensive studies in order to solve the above problems, (1) an organic solvent having a boiling point of 150 ° C. or more and not compatible with the polyamide resin at a temperature of less than 100 ° C., 100 ° C. or more (2) a step of coagulating the polyamide resin into a film by extruding the film forming stock solution into a coagulation bath at a temperature of 100 ° C. or lower in a predetermined shape. In step (1), a coagulating liquid having compatibility with the organic solvent used in the film forming stock solution and having low affinity with the polyamide resin is brought into contact with at least one surface of the film forming stock solution extruded in a predetermined shape. By doing so, it has been found that an ultrafiltration membrane having a dense layer having dense micropores formed on the membrane surface can be produced. Further, they have found that the ultrafiltration membrane sufficiently satisfies practical levels in terms of the molecular weight cutoff and the amount of water permeation, and can have excellent resistance to various types of organic solvents. The present invention has been completed by further study based on such findings.

That is, the present invention provides the following ultrafiltration membrane, a method for producing the same, and an ultrafiltration module.
Item 1. An ultrafiltration membrane formed using a polyamide resin, wherein a dense layer is formed on at least one surface.
Item 2. Item 4. The limit according to item 1, which has resistance to at least one organic solvent selected from the group consisting of alcohols, aprotic polar solvents, hydrocarbons, higher fatty acids, ketones, esters, and ethers. Filtration membrane.
Item 3. Item 3. The ultrafiltration membrane according to Item 1 or 2, wherein the ultrafiltration membrane has a hollow fiber shape and a dense layer is formed on at least one of the inner surface and the outer surface.
Item 4. Item 4. The ultrafiltration membrane according to any one of Items 1 to 3, wherein the fractional molecular weight is 1,000 to 200,000.
Item 5. A method for producing an ultrafiltration membrane having the following first to third steps:
A first step of preparing a film-forming stock solution in which a polyamide resin is dissolved at a temperature of 100 ° C. or higher in an organic solvent having a boiling point of 150 ° C. or higher and not compatible with the polyamide resin at a temperature lower than 100 ° C.
A step of extruding the film-forming stock solution into a coagulation bath at a temperature of 100 ° C. or lower in a predetermined shape to coagulate the polyamide resin in a film shape. A second step of contacting at least one surface with a coagulating liquid that is compatible with the organic solvent used in the film forming stock solution and has a low affinity for the polyamide resin, and a film formed in the second step Third step of removing the solvent from the.
Item 6. A method for producing a hollow fiber membrane-shaped ultrafiltration membrane,
The second step uses a double tubular nozzle for hollow fiber production having a double pipe structure, discharges the film forming stock solution from an outer annular nozzle and discharges an internal solution from an inner nozzle, and is immersed in a coagulation bath. In the process of
Item 5. The ultrafiltration membrane according to Item 4, wherein at least one of the internal solution and the coagulation bath uses a coagulation solution that is compatible with the organic solvent used in the membrane-forming stock solution and has low affinity with the polyamide resin. Manufacturing method.
Item 7. The coagulating liquid which is compatible with the organic solvent used in the film-forming stock solution and has low affinity with the polyamide resin is water, an aqueous solution having a water content of 80% by mass or more, 1-propanol, 2-propanol, isopropanol. Item 5 or at least one selected from the group consisting of butanol, polyethylene glycol having a molecular weight of 300 or more, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, propylene glycol monoethyl ether, triacetin, and propylene glycol monoethyl ether acetate. 7. The method for producing an ultrafiltration membrane according to 6.
Item 8. An ultrafiltration membrane module, wherein the module case contains the ultrafiltration membrane according to any one of Items 1 to 4.

  The ultrafiltration membrane of the present invention has excellent resistance to various kinds of organic solvents, and can maintain stable membrane characteristics even when it comes into contact with various types of organic solvents used industrially. Further, the ultrafiltration membrane of the present invention is also excellent in the molecular weight cutoff and water permeability, and can be suitably used in the fields of food industry, pharmaceutical industry, semiconductor industry and the like. In addition, the ultrafiltration membrane of the present invention has high hydrophilicity, so that when the substance to be removed is hydrophilic, the removal performance can be improved by the adsorption effect, while the adsorption of the hydrophobic substance is suppressed. Accordingly, fouling in which the hydrophobic substance covers the membrane surface and the processing flow rate is reduced can be prevented, and efficient filtration processing can be realized.

It is the schematic of the apparatus which measures the water permeability of the hollow fiber membrane of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is an apparatus figure which shows one Embodiment of the method of manufacturing the hollow fiber membrane of this invention. It is a schematic diagram of a spinneret for manufacturing the hollow fiber membrane of the present invention. 3 is an electron micrograph of the inner surface and the outer surface of the hollow fiber membrane of Example 1. 4 is an electron micrograph of the inner surface and outer surface of the hollow fiber membrane of Example 3. 5 is an electron micrograph of the inner surface and outer surface of the hollow fiber membrane of Comparative Example 1.

1. Ultrafiltration Membrane The ultrafiltration membrane of the present invention is an ultrafiltration membrane formed using a polyamide resin, wherein a dense layer is formed on at least one surface. Hereinafter, the ultrafiltration membrane of the present invention will be described in detail.

  The polyamide resin used in the present invention is not particularly limited, and a homopolymer of polyamide, a copolymer of polyamide, or a mixture thereof can be used. Specific examples of the homopolymer of polyamide include polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide MXD6, polyamide 4T, polyamide 6T, polyamide 9T, polyamide 10T and the like. Can be Specific examples of the copolymer of polyamide include a copolymer of polyamide with a polyether such as polytetramethylene glycol or polyethylene glycol. In addition, the ratio of the polyamide component in the polyamide copolymer is not particularly limited. For example, the ratio occupied by the polyamide component is preferably 70 mol% or more, more preferably 80 mol% or more. When the ratio of the polyamide component in the polyamide copolymer satisfies the above range, more excellent organic solvent resistance can be provided.

  The polyamide resin used in the present invention may or may not be crosslinked, but preferably is not crosslinked from the viewpoint of reducing the production cost.

  Further, the relative viscosity of the polyamide resin is not particularly limited, and for example, may be 2.0 to 7.0. By having such a relative viscosity, at the time of manufacturing an ultrafiltration membrane, the formability and controllability of phase separation are improved, and the ultrafiltration membrane can be provided with excellent shape stability. . Here, the relative viscosity refers to a value measured by a Ubbelohde viscometer at 25 ° C. using a solution in which 1 g of a polyamide resin is dissolved in 100 mL of 96% sulfuric acid.

  In the present invention, the polyamide resin may be used alone or in combination of two or more.

  The ultrafiltration membrane of the present invention may contain a filler, if necessary, in addition to the polyamide resin described above, as long as the effects of the present invention are not impaired. By including a filler, the strength, elongation, and elastic modulus of the ultrafiltration membrane can be improved. In particular, by including a filler, an effect that the ultrafiltration membrane is hardly deformed even when a high pressure is applied during filtration can be obtained. There are no particular restrictions on the type of filler to be added. Fibrous filler such as fiber, ceramic fiber, asbestos fiber, masonry fiber, metal fiber; talc, hydrotalcite, wollastenite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, bentonite, asbestos, alumina silicate Metal compounds such as silicon oxide, magnesium oxide, alumina, zirconium oxide, titanium oxide and iron oxide; carbonates such as calcium carbonate, magnesium carbonate and dolomite; sulfates such as calcium sulfate and barium sulfate; Metal hydroxides such as calcium oxide, magnesium hydroxide, and aluminum hydroxide; inorganic materials such as glass beads, glass flakes, glass powder, ceramic beads, non-fiber fillers such as boron nitride, silicon carbide, carbon black, silica, and graphite Is mentioned. These fillers may be used alone or in a combination of two or more. Among these fillers, preferably, talc, hydrotalcite, silica, clay, titanium oxide, and more preferably, talc and clay are used.

  Although the content of the filler is not particularly limited, for example, the filler is 5 to 100 parts by mass, preferably 10 to 75 parts by mass, more preferably 25 to 50 parts by mass per 100 parts by mass of the polyamide resin. By including the filler at such a content, the strength, elongation, and elastic modulus of the ultrafiltration membrane can be improved.

  Further, in the ultrafiltration membrane of the present invention, a thickener, an antioxidant, a surface modifier, a lubricant, a surfactant and the like are added as necessary for controlling the pore size and improving the membrane performance. An agent may be included.

  In the ultrafiltration membrane of the present invention, a dense layer is formed on at least one surface. In the present invention, the “dense layer” is a region where dense fine pores are gathered, and a region where substantially no pore is recognized in a scanning electron microscope (SEM) photograph at a magnification of 10,000 times. Is shown. In the polyamide ultrafiltration membrane of the present invention, the thickness of the dense layer is not particularly limited, but may be, for example, 0.01 to 2.0 μm, and preferably 0.1 to 1.5 μm.

  The ultrafiltration membrane of the present invention may have a dense layer formed on at least one of its surfaces. For example, when the ultrafiltration membrane of the present invention has a flat membrane shape, a dense layer may be formed on at least one of the front surface and the back surface. Further, for example, when the ultrafiltration membrane of the present invention has a hollow fiber shape, a dense layer may be formed on at least one of the inner surface and the outer surface.

  In the ultrafiltration membrane of the present invention, the region other than the dense layer has a porous structure. Hereinafter, a region other than the dense layer may be referred to as a “porous region”. Specifically, the porous region refers to a region where the presence of pores is substantially recognized in a scanning electron microscope (SEM) photograph at a magnification of 2000 times. Since the performance of the ultrafiltration membrane of the present invention is determined by the portion of the dense layer, the porous region can be considered as a so-called support layer, and the pore size in the porous region is such that the dense layer is retained. There is no particular limitation as long as it does not significantly impair strength and fluid permeation.

  The thickness of the ultrafiltration membrane of the present invention is appropriately set depending on the use thereof, the thickness of the dense layer, the amount of water permeability to be provided, and the like, and is, for example, 50 to 600 μm, and preferably 100 to 300 μm.

Although the flow rate of the ultrafiltration membrane of the present invention is not particularly limited, the amount of water permeation when tested using pure water is, for example, 1 L / (m ² · atm · h) or more, preferably 10 L / ( m ² · atm · h) or more, more preferably 20 to 200 L / (m ² · atm · h). By providing such a water permeability, it is possible to perform filtration treatment in an amount that is excellent in filtration efficiency and satisfies a practical level.

Here, when the ultrafiltration membrane has a hollow fiber shape, the water permeability is a value measured by internal pressure filtration, and is measured by the following procedure. First, 10 hollow fiber membranes were cut into a length of 30 cm, bent into a U-shape, the ends were inserted into a nylon hard tube having an outer diameter of 8 mm and an inner diameter of 6 mm, and a rubber stopper was provided on the other side. A room-temperature-curable urethane or epoxy resin is introduced and sealed, and after solidification, the lower part is cut to produce a module having an open inner portion of the hollow fiber membrane. Next, this module is set in a water permeability evaluation device as shown in FIG. 1, pure water at 25 ° C. is flowed inside the hollow fiber membrane by the liquid sending pump 13 and a pressure of about 0.6 MPa is applied thereto for a predetermined time ( Min), the water permeated to the outside of the membrane is collected in a tray 18 and the volume (L) is measured. The water permeability (L / (m ² · atm · h)) is calculated by the following equation.

When the ultrafiltration membrane has a flat membrane shape, the water permeability is a value measured by dead-end filtration, and is measured by the following procedure. Using a Sepa-CF flat membrane test cell manufactured by GE Water Technologies, to which a high-pressure pump was connected, a flat membrane-shaped ultrafiltration membrane having a predetermined size (19.1 cm × 14.0 cm, effective membrane area in the cell: It is cut to 155 cm ² ) and fixed to the cell. Pure water at 25 ° C. is flowed to collect permeated water at a predetermined pressure, and the volume (L) is measured. The water permeability (L / (m ² · atm · h)) is calculated by the following equation.

  In the ultrafiltration membrane of the present invention, the molecular weight cut-off is not particularly limited, and can be appropriately set by appropriately adjusting the thickness of the dense layer, the pore size of a region other than the dense layer, and for example, 1000 to 1000. 200,000, preferably 1,000 to 40,000, more preferably 1,000 to 6,000. The molecular weight cutoff indicates the pore size of a membrane capable of blocking 90% or more of a substance having a specific molecular weight, and is represented by the molecular weight of the substance capable of blocking the substance.

  Specific examples of the substance having a specific molecular weight used for measuring the molecular weight cutoff include polyethylene glycol (molecular weight: 200 to 40,000), dextran (molecular weight: 10,000 to 200,000), raffinose (molecular weight). : 590), vitamin B12 (molecular weight: 1,360), insulin (molecular weight: 5,700), cytochrome C (molecular weight: 13,400), myoglobin (molecular weight: 17,000), hepsin (molecular weight: 35,000) , Ovalbumin (molecular weight: 43,000), bovine serum albumin (molecular weight: 67,000), aldolase (molecular weight: 142,000), γ-globulin (molecular weight: 150,000) and the like. The molecular weight cut-off is obtained by dissolving the above-exemplified substance in pure water at 0.1 to 1.0% by mass, and performing filtration at a pressure of 0.10 to 1.00 MPa with a filtration device as shown in FIG. It can be evaluated by collecting the liquid that has passed through the membrane and determining the rejection rate from the substance concentration in the permeated liquid. Among the substances having a rejection rate of more than 90% determined as described above, the minimum molecular weight is the molecular weight cut off of the ultrafiltration membrane.

The ultrafiltration membrane of the present invention has a characteristic (organic solvent resistance) that suppresses changes in strength and elongation and stably maintains the membrane structure even when it comes into contact with various kinds of organic solvents. More specifically, it has resistance to organic solvents such as alcohols, aprotic polar solvents, hydrocarbons, higher fatty acids, ketones, esters, and ethers. Specific examples of the type of the organic solvent include the following.
Alcohols: primary alcohols such as methanol, ethanol, n-propanol, n-butanol and benzyl alcohol, secondary alcohols such as isopropyl alcohol and isobutanol, tertiary alcohols such as tertiary butyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol Polyhydric alcohols such as ethylene glycol, tetraethylene glycol, propylene glycol, 1,3-butanediol, and glycerin.
Ketones: acetone, methyl ethyl ketone, cyclohexanone, diisopropyl ketone and the like.
Ethers: tetrahydrofuran, diethyl ether, diisopropyl ether, 1,4-dioxane and the like. And glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and propylene glycol monomethyl ether.
Aprotic polar solvents: N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, sulfolane and the like.
Esters: ethyl acetate, isobutyl acetate, ethyl lactate, dimethyl phthalate, diethyl phthalate, etc., ethylene carbonate, propylene carbonate, propylene glycol monomethyl ether acetate, etc.
Hydrocarbons: petroleum ether, pentane, hexane, heptane, benzene, toluene, xylene, liquid paraffin, gasoline, and mineral oil.
Higher fatty acids: fatty acids having 4 or more (preferably 4 to 30) carbon atoms other than carboxyl groups such as oleic acid, linoleic acid, and linolenic acid.

In particular, a preferred example of the organic solvent resistance of the ultrafiltration membrane of the present invention is that the ultrafiltration membrane has resistance to at least one, and preferably all, of the following organic solvents.
Ketones: acetone, methyl ethyl ketone, cyclohexanone, diisopropyl ketone and the like.
Ethers: tetrahydrofuran, diethyl ether, diisopropyl ether, 1,4-dioxane and the like. And glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and propylene glycol monomethyl ether.
Aprotic polar solvents: N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, sulfolane and the like.
Esters: ethyl acetate, isobutyl acetate, ethyl lactate, dimethyl phthalate, diethyl phthalate, etc., ethylene carbonate, propylene carbonate, propylene glycol monomethyl ether acetate, etc.

The ultrafiltration membrane of the present invention may not have resistance to the following phenols, halogen-containing solvents, and lower organic acids.
Phenols: phenol, cresol and the like.
Halogen-containing solvents: dichloromethane, chloroform, trichloroethylene, trifluoroethanol, hexafluoroisopropanol and the like.
Lower organic acids: formic acid, acetic acid, butyric acid.

  As the organic solvent resistance of the ultrafiltration membrane of the present invention, specifically, when immersed in the organic solvent at 25 ° C. for 14 hours, the change in the strength and elongation of the ultrafiltration membrane after immersion is increased before immersion. ± 30% or less, and preferably less than ± 20%. Specifically, the changes in the strength and the elongation are calculated according to the following equations.

  Here, the strength and elongation of the ultrafiltration membrane refer to the breaking strength and the breaking measured when a tensile test is performed with a tensile tester at a distance between chucks of 50 mm, a tensile speed of 50 mm / min, and a temperature of 25 ° C. The elongation. When the ultrafiltration membrane has a flat membrane shape, it is measured using a strip-shaped sample having a width of 10 mm and a length of 100 mm, and when the ultrafiltration membrane has a hollow fiber shape, a sample having a length of 100 mm is used. Measured.

  The shape of the ultrafiltration membrane of the present invention is not particularly limited, and can be selected from any shape such as a flat membrane shape and a hollow fiber membrane shape. Since the filtration area per volume is large and the ultrafiltration can be performed efficiently, it is suitable in the present invention. Further, the ultrafiltration membrane of the present invention may be produced as a self-supporting membrane by itself, or may be in a shape laminated on a support of a microfiltration membrane. Such a support is preferably a material resistant to an organic solvent, specifically, a polymer material such as polyamide, polyethylene, polypropylene, polytetrafluoroethylene, polyphenylene sulfide, polyether ether ketone; Examples include inorganic materials such as metals and ceramics.

2. Manufacturing method of ultrafiltration membrane The ultrafiltration membrane of the present invention has a dense layer formed on at least one surface, and a region other than the dense layer has a porous structure. Although it cannot be manufactured under the manufacturing conditions employed alone, it is manufactured by using the principles of both the TIPS method and the NIPS method. Specifically, the ultrafiltration membrane of the present invention is manufactured through the following first to third steps.
First step: A film-forming stock solution is prepared by dissolving a polyamide resin at a temperature of 100 ° C or higher in an organic solvent having a boiling point of 150 ° C or higher and not compatible with the polyamide resin at a temperature of lower than 100 ° C.
Second step: a step of coagulating the polyamide resin into a film by extruding the film-forming stock solution in a predetermined shape into a coagulation bath at a temperature of 100 ° C. or lower. A coagulation solution that is compatible with the organic solvent used in the film-forming stock solution and has low affinity with the polyamide resin is brought into contact with at least one surface of the film-forming stock solution.
Third step: The solvent is removed from the ultrafiltration membrane formed in the second step.

  Hereinafter, the method for producing an ultrafiltration membrane of the present invention will be described in detail for each step.

First Step In the first step, a stock solution is prepared by dissolving a polyamide resin at a temperature of 100 ° C. or higher in an organic solvent having a boiling point of 150 ° C. or higher and being incompatible with the polyamide resin at a temperature lower than 100 ° C. I do.

  Examples of the organic solvent having a boiling point of 150 ° C. or higher and not compatible with the polyamide resin at a temperature lower than 100 ° C. include, for example, aprotic polar solvents, glycerin ethers, polyhydric alcohols, organic acids, and organic acid esters. And higher alcohols. Specific examples of the aprotic polar solvent include sulfolane, dimethyl sulfone, dimethyl sulfoxide, γ-butyrolactone, δ-valerolactone, ε-caprolactone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl- 2-pyrrolidone, ethylene carbonate, propylene carbonate and the like. Specific examples of glycerin ethers include diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, and tetraethylene glycol dimethyl ether. Specific examples of polyhydric alcohols include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, hexylene glycol, 1,3-butanediol, and polyethylene glycol (molecular weight: 100 to 10,000). Specific examples of organic acids and organic acid esters include dimethyl phthalate, diethyl phthalate, diisopropyl phthalate, dibutyl phthalate, butyl benzyl phthalate, methyl salicylate, oleic acid, palmitic acid, stearic acid, lauric acid, and the like. No. Among them, from the viewpoint of obtaining an ultrafiltration membrane having higher strength, preferably, an aprotic polar solvent, polyhydric alcohols; more preferably, sulfolane, dimethyl sulfone, γ-butyrolactone, δ-valerolactone , Ε-caprolactone, propylene glycol, hexylene glycol, 1,3-butanediol, polyethylene glycol (molecular weight 100 to 600); particularly preferably, sulfolane, dimethyl sulfone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone No. One of these organic solvents may be used alone, or two or more thereof may be used in combination. Sufficient effects can be obtained by using one of these organic solvents alone. However, by using two or more of them in a mixed state, the order and structure of phase separation are different, so that more effective effects can be obtained. In some cases, ultrafiltration membranes can be made.

  The concentration of the polyamide resin in the stock solution is not particularly limited, but is, for example, 5 to 50% by mass, preferably 10 to 40% by mass, and more preferably 12 to 35% by mass. When the concentration of the polyamide resin in the stock solution for film formation satisfies the above range, the ultrafiltration membrane can have excellent strength and can have an appropriate liquid permeability.

  In dissolving the polyamide resin in the organic solvent, it is necessary to keep the temperature of the solvent at 100 ° C. or higher. Specifically, the dissolution is preferably performed at a temperature higher by 10 to 50C than the phase separation temperature of the system, preferably by 20 to 40C. The phase separation temperature of the system is a temperature at which a mixture of a polyamide resin and a solvent at a sufficiently high temperature is gradually cooled to cause liquid-liquid phase separation or solid-liquid phase separation by crystal precipitation. The measurement of the phase separation temperature can be suitably performed by using a microscope equipped with a hot stage.

  In addition, fillers, thickeners, antioxidants, surface modifiers, lubricants, surfactants, etc. may be added to the membrane forming solution as needed to control the pore size and improve the performance of the ultrafiltration membrane. You may.

Second step The second step is a step of extruding the film-forming stock solution in a predetermined shape into a coagulation bath at 100 ° C. or lower to coagulate the polyamide resin into a film. A coagulation liquid that is compatible with the organic solvent used in the film-forming stock solution and has low affinity with the polyamide resin is brought into contact with at least one surface of the extruded film-forming stock solution.

Here, a coagulating liquid that is compatible with the organic solvent used in the film-forming stock solution and has a low affinity for the polyamide resin (hereinafter, also referred to as a coagulating liquid for forming a dense layer) is 25 ° C. It refers to a solvent that is compatible with the organic solvent used in the film-forming stock solution at the following temperature but does not dissolve the polyamide resin at a temperature equal to or lower than the boiling point or 200 ° C. or lower. Such dense layer forming the coagulating liquid, specifically, the molecular weight of 300 or more polyethylene glycol, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, glycol ethers such as propylene glycol monoethyl ether; triacetin, propylene glycol Glycol acetates such as monoethyl ether acetate are exemplified. Among these, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, triacetin, and triethylene glycol monomethyl ether are preferred.

  In the second step, a dense layer is formed on the surface of the stock solution extruded in a predetermined shape into the coagulation bath in contact with the coagulating solution for forming a dense layer. In the vicinity of the surface where the film forming stock solution was in contact with the coagulating liquid for forming a dense layer, non-solvent phase separation by solvent exchange proceeded more predominantly than heat-induced phase separation by cooling, and a denser structure than the conventional TIPS method on the surface. It is formed.

  For example, in the case of forming a hollow fiber-shaped ultrafiltration membrane, a double-tube structure hollow fiber-producing double tubular nozzle is used to discharge the membrane-forming stock solution from the outer annular nozzle and the inner nozzle. The internal liquid may be discharged from the container and immersed in a coagulation bath. At this time, a coagulating liquid for forming a dense layer may be used for at least one of the internal liquid and the coagulating bath. In addition, at least one of the internal liquid and the coagulation bath contains a coagulation liquid that is compatible with the organic solvent used in the film forming stock solution and has a high affinity with the polyamide resin (hereinafter referred to as a porous structure forming liquid). (Sometimes referred to as a coagulating liquid). A porous structure is formed on the surface of the membrane-forming stock solution that has come into contact with the coagulating liquid for forming a porous structure. That is, when the coagulating liquid for forming a dense layer is used for both the inner liquid and the coagulating bath, a dense layer is formed on both the inner surface and the outer surface, and the inside is a hollow fiber-shaped ultra-fine region having a porous region. A filtration membrane is manufactured. When a coagulating liquid for forming a dense layer is used as an internal liquid and a coagulating liquid for forming a porous structure is used as a coagulating bath, a dense layer is formed on the inner surface of the lumen, and the inner and outer surfaces are porous. A hollow fiber-shaped ultrafiltration membrane, which is a quality region, is produced. When a coagulating liquid for forming a porous structure is used as the internal liquid and a coagulating liquid for forming a dense layer is used as a coagulating bath, a dense layer is formed on the outer surface, and the inner surface and the inner surface are porous. A hollow fiber-shaped ultrafiltration membrane, which is a quality region, is produced.

  Here, the coagulating liquid for forming a porous structure refers to a solvent that is compatible with the organic solvent used for the film forming stock solution at a temperature of 25 ° C. or lower and that dissolves the polyamide resin at a temperature of a boiling point or lower. Specific examples of such a coagulating liquid for forming a porous structure include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, propylene glycol, 1,3-butanediol, sulfolane, N- Examples thereof include methyl-2-pyrrolidone, γ-butyrolactone, δ-valerolactone, and an aqueous solution containing 20% by mass or more of these. Among these, preferably, at least one selected from the group consisting of glycerin, propylene glycol, diethylene glycol, and polyethylene glycol 200, and an aqueous solution containing these at a ratio of 25 to 75% by mass; more preferably, glycerin, diethylene glycol , Tetraethylene glycol, and propylene glycol, and an aqueous solution containing these at a ratio of 40 to 80% by mass.

  In the formation of the hollow fiber ultrafiltration membrane, since the temperature of the double tubular nozzle at the time of membrane formation reaches 100 ° C. or higher, a coagulating liquid for forming a dense layer used as an internal liquid or a liquid for forming a porous structure is used. As the coagulation liquid, it is preferable to select a coagulation liquid having a boiling point higher than the nozzle temperature at the time of film formation from those exemplified in the above coagulation bath.

  Further, as the double tubular nozzle for producing a hollow fiber, a die having a double tubular structure such as that used for producing a core-sheath type composite fiber in melt spinning can be used. FIG. 2 shows an example of a cross-sectional structure of a double tubular nozzle for producing a hollow fiber. The diameter of the outer annular nozzle and the diameter of the inner nozzle of the double tubular nozzle for producing a hollow fiber may be appropriately set according to the inner diameter and the outer diameter of the hollow fiber membrane.

  Further, the flow rate at the time of discharging the membrane-forming stock solution from the annular nozzle outside the hollow fiber manufacturing double tubular nozzle is not particularly limited, but is, for example, 2 to 30 g / min, preferably 3 to 20 g / min, and furthermore Preferably, 5 to 15 g / min is used. In addition, the flow rate of the internal solution is appropriately set in consideration of the diameter of the inner nozzle of the double tubular nozzle for hollow fiber production, the type of the internal solution to be used, the flow rate of the stock solution, and the like. The flow rate is 0.1 to 2 times, preferably 0.2 to 1 times, and more preferably 0.4 to 0.7 times.

  When forming a flat membrane-shaped ultrafiltration membrane, the coagulating solution for forming a dense layer is used as a coagulating bath, and the membrane-forming stock solution is extruded and immersed in the coagulating bath in a predetermined shape. Just do it.

  In the third step, the temperature of the coagulation bath may be 100 ° C or lower, preferably 0 to 100 ° C, more preferably 5 to 60 ° C. The preferred temperature of the coagulation bath varies depending on the organic solvent used for the film-forming solution and the composition of the coagulation solution. Generally, the lower the temperature, the higher the priority of the heat-induced phase separation, and the higher the temperature. Solvent phase separation tends to proceed preferentially. That is, when manufacturing a hollow fiber membrane having a dense layer formed on the lumen side surface, it is preferable to set the coagulation bath to a low temperature in order to bring the dense layer on the lumen side surface closer to the internal structure. In order to make the dense layer on the lumen side surface more dense and make the internal structure coarser, it is preferable to set the coagulation bath to a high temperature.

  By performing the second step in this way, the membrane forming solution is coagulated in the coagulation bath, and an ultrafiltration membrane having a dense layer formed on at least one surface is formed.

Third step In the third step, the solvent is removed from the ultrafiltration membrane formed in the second step.
The method for removing the coagulation liquid from the hollow fiber membrane is not particularly limited, and may be a method in which the coagulation liquid is volatilized by drying with a dryer, but may be immersed in an extraction solvent and subjected to phase separation in the ultrafiltration membrane. The method of extracting and removing the coagulating solution causing the bleeding is preferred. As the extraction solvent used for the extraction and removal of the organic solvent, those which are inexpensive and have a low boiling point and can be easily separated by a difference in boiling point after the extraction are preferable, for example, water, glycerin, methanol, ethanol, isopropanol, acetone and diethyl ether. , Hexane, petroleum ether, toluene and the like. Among these, water, methanol, ethanol, isopropanol and acetone are preferred, and water, methanol and isopropanol are more preferred. In particular, in the case of extracting a coagulation solution that dissolves in water, if winding is performed while showering with water, solvent extraction can be performed at the same time, which is efficient. When extracting a water-insoluble organic solvent such as a phthalic acid ester or a fatty acid, isopropyl alcohol, petroleum ether or the like can be suitably used. The time for immersing the ultrafiltration membrane in the extraction solvent is not particularly limited, but is, for example, 0.2 hours to 2 months, preferably 0.5 hours to 1 month, more preferably 2 hours to 10 days. Is mentioned. In order to effectively extract and remove the coagulation solution remaining in the ultrafiltration membrane, the extraction solvent may be replaced or stirred.

  By carrying out the third step in this way, the ultrafiltration membrane of the present invention is manufactured.

  The production of the ultrafiltration membrane of the present invention may be performed through the first to third steps described above, and the apparatus used for the production is not particularly limited, but produces a hollow fiber ultrafiltration membrane. In such a case, a general apparatus used for dry-wet spinning as shown in FIG. 3 is preferably used. The production flow of a hollow fiber ultrafiltration membrane will be outlined below, taking the apparatus shown in FIG. 3 as an example. The stock solution prepared in the first step is contained in the container 3. Alternatively, the first step may be performed in the container 3 to prepare a stock solution for film formation. The film forming stock solution contained in the container 3 and the internal solution introduced from the internal solution inlet 5 are respectively measured by the metering pump 4 and sent to the hollow fiber manufacturing double tubular nozzle (spinneret) 6. . The film forming stock solution discharged from the hollow fiber manufacturing double tubular nozzle (spinneret) 6 is introduced into the coagulation bath 7 through a slight air gap, and cooled and solidified. During the process of cooling and solidifying the membrane-forming stock solution, heat-induced phase separation occurs, and a hollow fiber membrane-shaped ultrafiltration membrane 8 having a sea-island structure is obtained. The thus obtained hollow fiber ultrafiltration membrane 8 is wound up by a winder 9 while being wound up by a bobbin winder 10 equipped with a bobbin. The wound hollow fiber ultrafiltration membrane 8 is used to remove the coagulation liquid using an extraction solvent to obtain a hollow fiber membrane ultrafiltration membrane.

3. Ultrafiltration Membrane Module The ultrafiltration membrane of the present invention is housed in a module case having an inlet for a liquid to be treated and an outlet for a permeate, and used as an ultrafiltration module.
When the ultrafiltration membrane of the present invention has a hollow fiber shape, it is used as a hollow fiber membrane module.

  Specifically, in the hollow fiber membrane module, the hollow fiber ultrafiltration membrane of the present invention is bundled, housed in a module case, and one or both ends of the hollow fiber ultrafiltration membrane bundle is sealed with a potting agent. Any structure may be used as long as it is stopped and fixed. The hollow fiber membrane module includes, as an inlet for the liquid to be treated or an outlet for the filtrate, an opening connected to a flow path passing through the outer wall surface of the hollow fiber ultrafiltration membrane, and a hollow portion of the hollow fiber ultrafiltration membrane. It suffices if an opening is provided that is connected to.

  The shape of the hollow fiber membrane module is not particularly limited, and may be a dead end type module or a cross flow type module. As the shape of the hollow fiber membrane module, specifically, a dead end type in which the hollow fiber membrane bundle is bent into a U-shape and filled, and the end of the hollow fiber ultrafiltration membrane bundle is cut and opened after sealing. Module: A hollow fiber-shaped ultrafiltration membrane bundle with a hollow opening at one end closed by heat sealing or the like is filled straight, and the open end of the hollow fiber-shaped ultrafiltration membrane bundle is cut after sealing. Dead-end type module opened by opening; the hollow fiber ultrafiltration membrane bundle was filled straight, the both ends of the hollow fiber ultrafiltration membrane bundle were sealed, and only one end was cut to expose the opening. Dead-end module: filling the hollow fiber ultrafiltration membrane bundle straight, sealing both ends of the hollow fiber ultrafiltration membrane bundle, cutting the sealing parts at both ends of the hollow fiber ultrafiltration membrane bundle, Cross flow type with two flow paths on the side of the case Jules, and the like.

  The filling factor of the hollow fiber ultrafiltration membrane to be inserted into the module case is not particularly limited. For example, the volume of the hollow fiber ultrafiltration membrane containing the volume of the hollow portion with respect to the volume inside the module case is 30 to 90% by volume. , Preferably 35 to 75% by volume, more preferably 45 to 65% by volume. By satisfying such a filling rate, the filling operation of the hollow fiber ultrafiltration membrane into the module case is facilitated while securing a sufficient filtration area, and the potting agent easily flows between the hollow fiber ultrafiltration membranes. can do.

  The potting agent used for manufacturing the hollow fiber membrane module is not particularly limited, but when the hollow fiber membrane module is used for treating an organic solvent, it is desirable that the hollow fiber membrane module has organic solvent resistance. Examples of the potting agent include polyamide, silicone resin, melamine resin, polyethylene, polypropylene, phenol resin, polyimide, and polyurea resin. Among these potting agents, those that have a small degree of shrinkage and swelling when cured, and that are not too hard are preferred. Preferable examples of the potting agent include polyamide, silicone resin, and polyethylene. These potting agents may be used alone or in a combination of two or more.

  The material of the module case used for the hollow fiber membrane module is not particularly limited, for example, polyamide, polyester, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl chloride, polysulfone, polyether sulfone, polycarbonate, Polyarylate, polyphenylene sulfide and the like can be mentioned. Among them, preferably, polyamide, polyethylene, polypropylene, polytetrafluoroethylene, polycarbonate, polysulfone, polyethersulfone, and more preferably, polyamide, polyethylene, polypropylene, and polytetrafluoroethylene are exemplified.

  When the ultrafiltration membrane of the present invention is in the form of a flat membrane, it is used as a sheet-type module such as a plate-and-frame type or a stack type, a spiral-type module, a rotary flat-film type module, or the like.

  The ultrafiltration membrane module using the ultrafiltration membrane of the present invention is used in fields such as the semiconductor industry, the food industry, the pharmaceutical industry, and the medical products industry for water purification and foreign matter removal.

  Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

  In the examples, the water permeability of the hollow fiber ultrafiltration membrane was determined by the method described above. The rejection of the polymer was measured using polyethylene glycol for a molecular weight of 20,000 or less and dextran for a molecular weight of more than 20,000, each of which was dissolved in water at 0.1% by mass as a stock solution. The permeated liquid was recovered, the solute concentration in the permeated liquid was measured by high performance liquid chromatography, and the solute rejection was calculated according to the following formula.

Example 1
170 g of polyamide 6 chips (A1030BRT manufactured by Unitika Ltd., relative viscosity 3.53) and 830 g of sulfolane (manufactured by Tokyo Chemical Industry Co., Ltd.) are stirred and dissolved at 180 ° C. for 1.5 hours, and the stirring speed is reduced for 1 hour. Defoaming was performed to prepare a film forming stock solution. The stock solution was fed to a spinneret via a metering pump and extruded at 13.0 g / min. The spinneret used had an outer diameter of 1.5 mm and an inner diameter of 0.6 mm. Polyethylene glycol 300 (PEG 300) was flowed into the internal liquid at a liquid sending rate of 5.0 g / min. The extruded film-forming stock solution was put into a coagulation bath composed of a 50% by mass aqueous propylene glycol solution at 5 ° C. through an air gap of 10 mm, solidified by cooling, and taken up at a take-up speed of 20 m / min. The obtained hollow fiber was immersed in water for 24 hours to extract the solvent, thereby obtaining a hollow fiber membrane.

The obtained hollow fiber membrane has a water permeability of 10 L / (m ² · atm · h), a solute rejection ratio of 98% using dextran 40000 (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 32000 to 45000), and polyethylene The solute rejection using Glycol 20000 (Wako Pure Chemical Industries, molecular weight 15,000 to 25000) was 88%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope (10000 times), the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and a sponge-like porous layer was formed. Through the structure, the outer surface became porous (see FIG. 4).

Example 2
A hollow fiber membrane was produced in the same manner as in Example 1 except that the coagulation bath was changed to PEG300. The obtained hollow fiber membrane has a water permeability of 4 L / (m ² · atm · h), a solute rejection rate of 99% using dextran 40000, a 97% solute rejection rate using polyethylene glycol 20000, and polyethylene glycol. The solute rejection using 6000 (manufactured by Wako Pure Chemical Industries, molecular weight 7300 to 9300) was 90%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the outer surface was a porous structure. Was.

Example 3
A hollow fiber membrane was produced in the same manner as in Example 1, except that the internal solution was changed to triacetin. The water permeability of the obtained hollow fiber membrane was 3 L / (m ² · atm · h), the solute rejection using polyethylene glycol 6000 was 98%, and the polyethylene glycol 2000 (manufactured by Wako Pure Chemical Industries, molecular weight 1850-2150) ) Was 91%. Observation of the surface structure of the obtained hollow fiber membrane with a scanning electron microscope revealed that the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the skin layer thickness was obtained in Example 1. It was thicker than the film. Further, the inside had a sponge-like porous structure, and the outside surface had a porous structure (see FIG. 5).

Reference Example 1
A hollow fiber membrane was produced in the same manner as in Example 1 except that the coagulation bath was water at 40 ° C. and sulfolane was used as the internal solution. The water permeability of the obtained hollow fiber membrane was 150 L / (m ² · atm · h), and the solute rejection using dextran 200000 (manufactured by Wako Pure Chemical Industries, average molecular weight 180,000 to 210,000) was 98%. The solute rejection using Dextran 60000 (manufactured by Wako Pure Chemical Industries, molecular weight 60000 to 90000) was 28%.

Example 5
A hollow fiber membrane was produced in the same manner as in Example 1 except that 609 g of dimethyl sulfone and 221 g of sulfolane were used as solvents used for the stock solution for film formation. The obtained hollow fiber membrane had a water permeability of 18 L / (m ² · atm · h), a solute rejection rate using dextran 40000 of 95%, and a solute rejection rate using polyethylene glycol 20,000 of 90%. . When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the outer surface was a porous structure. Was.

Example 6
Using 150 g of polyamide 11 chips (Rilsan BESV0 A FDA, relative viscosity 2.50, manufactured by Arkema) and 850 g of γ-butyrolactone (manufactured by Wako Pure Chemical Industries, Ltd.) as a resin for film formation, 1.5 hours at 180 ° C. The mixture was stirred and dissolved, and the mixture was defoamed for 1 hour at a reduced stirring speed to prepare a membrane-forming stock solution. A hollow fiber membrane was produced in the same manner as in Example 1 except that this stock solution for membrane production was used. The resulting hollow fiber membrane has a water permeability of 5 L / (m ² · atm · h), a solute rejection of 99% using dextran 40000, a 98% solute rejection using polyethylene glycol 20000, and polyethylene. The solute rejection using Glycol 6000 was 90%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the outer surface was a porous structure. Was.

Example 7
Same as Example 1 except that 170 g of polyamide MXD6 chips (Lenny 6121, manufactured by Mitsubishi Engineering-Plastics Corporation, relative viscosity: 3.49) were used as the resin, and the dissolution temperature was 170 ° C. when the stock solution was produced. To produce a hollow fiber membrane. The obtained hollow fiber membrane has a water permeability of ² L / (m ² · atm · h), a solute rejection of 99% using dextran 40000, a 97% solute rejection using polyethylene glycol 20000, and polyethylene. The solute rejection using Glycol 6000 was 92%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the outer surface was a porous structure. Was.

Example 8
A hollow fiber membrane was produced in the same manner as in Example 1, except that the polyamide 6 resin was changed to 200 g and the sulfolane was changed to 800 g. The water permeability of the obtained hollow fiber membrane was 5 L / (m ² · atm · h), the solute rejection using dextran 40000 was 99%, the solute rejection of polyethylene glycol 20000 was 94%, The solute rejection of polyethylene glycol 6000 was 45%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the outer surface was a porous structure. Was.

Comparative Example 1
A hollow fiber membrane was produced in the same manner as in Example 1, except that glycerin was used as the internal solution. The water permeability of the obtained hollow fiber membrane was 2,400 L / (m ² · atm · h), and the solute rejection using dextran 200000 was 5%. When the surface structure of the obtained hollow fiber membrane was observed with an electron microscope, both the inner surface and the outer surface had a porous structure, and a dense layer was not formed on the surface (FIG. 6).

Test Example 1: Test for resistance to organic solvents The hollow fiber membranes obtained in Examples 1, 6 and 7 were dried at 50 ° C for 1 hour, immersed in each organic solvent shown in Table 1 at 25 ° C for 14 hours, and immersed. The subsequent change in strength and elongation (%) was evaluated by the method described above. In addition, as a comparison, the same evaluation was performed using a hollow fiber membrane (Comparative Example 2) of a polysulfone ultrafiltration membrane lab module SLP-1053 (manufactured by Asahi Kasei Chemicals, nominal molecular weight cut off 10,000).

  Table 1 shows the obtained results. From these results, in the hollow fiber membranes (Examples 1, 6, and 7) having a dense layer formed on the surface, even when immersed in various kinds of organic solvents, the strength and elongation are not changed and are stably maintained. Was. On the other hand, in the polysulfone ultrafiltration membrane having no dense layer formed on the surface (Comparative Example 2), the strength and elongation were largely changed by most organic solvents, and the organic solvent resistance was poor.

1: stirring motor 2: pressurized gas inlet 3: container 4: metering pump 5: internal liquid (or gas) inlet 6: spinneret 7: coagulation bath 8: hollow fiber ultrafiltration membrane 9: take-off machine 10: Bobbin take-up machine (with washing shower)
11: Internal liquid (or gas) inlet 12: Membrane stock solution inlet 13: Liquid feed pump 14: Pressure gauge 15: Hollow fiber membrane 16: Depressurizing valve 17: Receiving tray

Claims (3)

A ultrafiltration membrane formed by using a polyamide resin, on at least one surface, is not observed the presence of magnification 10,000 times a scanning electron micrograph odor Te pores and dense layer is formed,
The polyamide resin is polyamide 6, polyamide 66, is selected polyamide 46, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide MXD6, polyamide 4T, polyamide 6T, polyamide 9T, and polyamide 10 T or Ranaru group At least one,
Characterized by having resistance to at least one organic solvent selected from the group consisting of alcohols, aprotic polar solvents, hydrocarbons, higher fatty acids, ketones, esters, and ethers, Filtration membrane.   The ultrafiltration membrane according to claim 1, wherein the ultrafiltration membrane has a hollow fiber shape and a dense layer is formed on at least one of the inner surface and the outer surface.   An ultrafiltration membrane module in which the ultrafiltration membrane according to claim 1 is housed in a module case.