JP2017127864A - Polyamide ultrafilter membrane having organic solvent tolerance and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide ultrafilter membrane having tolerance against various types of organic solvents and a manufacturing method for the same.SOLUTION: An ultrafilter membrane formed by using a polyamide resin having tolerance against various types of organic solvents is provided by forming a dense layer over at least one surface. Further, there is provided a method of manufacturing an ultrafilter membrane with a dense layer having dense micropores formed over a membrane surface by bringing a coagulation liquid having compatibility with the organic solvent used for the membrane production stock liquid and low affinity with the polyamide resin in contact with at least one surface of the membrane production stock liquid having extruded in the predetermined shape, in a step of preparing a membrane production stock liquid by dissolving the polyamide resin at a temperature of 100°C or more into an organic solvent which has a boiling point of 150°C or more and is incompatible with the polyamide resin at a temperature of less than 100°C, and then of extruding the membrane production stock liquid into a coagulation bath of 100°C or less in a predetermined shape to coagulate the polyamide resin into a membraneous form.SELECTED DRAWING: Figure 4

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 electronic field, food field, pharmaceutical field, fermentation field, optical field and the like. The present invention also relates to a method for producing the polyamide ultrafiltration membrane. Furthermore, this invention relates to the ultrafiltration membrane module using the said polyamide ultrafiltration membrane.

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

  In filtration using an ultrafiltration membrane, fine pores of a porous membrane in the range of 1 nm to 100 nm can be separated from proteins, polymers, etc. dissolved in water to fine particles such as viruses and colloids. The pore size of the ultrafiltration membrane is difficult to observe and measure even with an electron microscope, and there are variations in the pore size, so the representative 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 delimited before and after the molecular weight cut off, and has a certain width.

  A phase separation method is an example of a method often used industrially when producing an ultrafiltration membrane from a polymer material. Phase separation methods can be broadly divided into non-solvent induced phase separation methods (NIPS methods) and thermally induced phase separation methods (TIPS methods). 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, so that the non-solvent enters and the good solvent elutes into the external atmosphere. This is a method for causing phase separation. The NIPS method has a finger-like structure with macrovoids. Its advantages are that the device is simple, it is easy to create 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. Examples include the fact that it has been used in the production of films. The disadvantages of the NIPS method include that it is difficult to obtain strength and that a good solvent that dissolves at room temperature is required. On the other hand, the TIPS method is a relatively new method. A solvent that does not dissolve in a polymer material at a low temperature but dissolves at a high temperature is selected, and a uniform polymer solution dissolved at a high temperature is converted into a one-phase region and two phases. This is a method in which phase separation is induced by cooling to a temperature below the binodal line that is the boundary of the region, and the structure is fixed by crystallization of the polymer or glass transition. The TIPS method tends to have a sponge-like homogeneous structure, and the advantages are that it can be high strength, and that it can be applied to polymers that do not have a solvent that dissolves at low temperatures, and the disadvantage is that the equipment is complex, asymmetric It is difficult to make a structure and make a fine structure like an ultrafiltration membrane.

  For the reasons described above, there is no commercially available ultrafiltration membrane formed by the TIPS method, and it is possible to produce an ultrafiltration membrane made of cellulose acetate by the TIPS method according to Non-Patent Document 1. Was first shown.

  Conventionally, polymer materials such as cellulose acetate, polyacrylonitrile, polyvinylidene fluoride, polysulfone, and polyethersulfone are known as materials for ultrafiltration membranes. Cellulose acetate has good processability and excellent separation, and is widely used as an ultrafiltration membrane, but has drawbacks in terms of heat resistance and organic solvent resistance. Polyacrylonitrile and polyvinylidene fluoride are superior to cellulose acetate in terms of organic solvent resistance and heat resistance, and have been put to practical use as porous membranes, but organic solvents such as aprotic polar solvents There is a drawback that it dissolves easily, and it cannot be said that it is a film material with sufficiently satisfactory characteristics. Furthermore, polysulfone and polyethersulfone have excellent heat resistance, good workability, and are put to practical use as ultrafiltration membranes including hollow fiber membranes with various fractionation characteristics. There is a problem in terms of solvent.

  In addition, a technique using polyphenylene sulfide (PPS) as an ultrafiltration membrane excellent in organic solvent resistance has been proposed. For example, Patent Document 1 reports that a polyphenylene sulfide (PPS) membrane is very excellent in heat resistance and organic solvent resistance, and Patent Documents 2 and 3 describe a hollow fiber membrane using PPS. The manufacturing method of this is also examined. However, in Patent Documents 1 and 2, the pore formation by the stretching method is adopted, the average pore diameter is large, and it can be used as a microfiltration membrane, but does not have the performance of an ultrafiltration membrane. Furthermore, Patent Document 3 discloses an ultrafiltration membrane produced by a phase separation method, but N-methyl-2-pyrrolidone having a boiling point of 202 ° C. is used as a membrane-forming solvent, and 250 ° C. under pressure. This is a technology that is difficult to put into practical use in industrial production. Patent Document 4 proposes a method for further improving heat resistance and organic solvent resistance by oxidizing a porous body using PPS to convert sulfide bonds to sulfone bonds. However, since the porous body itself using PPS is manufactured by the above-described various methods and then selectively oxidizing sulfide bonds, there remains a problem in terms of fractionation performance and practicality. Yes.

  Furthermore, a technique for producing a film excellent in 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 permeation is small, and it has not reached the 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 low molecular weight. It cannot function as an ultrafiltration membrane having a molecular weight cut off of about 1,000 to 200,000. Furthermore, Patent Documents 6 and 7 report organic solvent-resistant ceramic separation membranes made from inorganic materials, but these ceramic separation membranes require a high-pressure separation operation. The water permeability is low and it has not reached the practical level.

  On the other hand, various methods for producing a porous membrane using a polyamide-based resin have been studied. For example, Patent Documents 8 to 11 disclose a technique of using formic acid as a solvent with respect to a technique for producing a porous membrane using a polyamide-based resin by the NIPS method. There is a problem, and the obtained membrane has a large pore size and cannot function as an ultrafiltration membrane. Patent Document 12 discloses a method in which a polyamide 6 mixed with polycaprolactone and dissolved in hexafluoroisopropanol is cast, and then caprolactone is extracted therefrom to make it porous. In addition, the high molecular compound to be extracted and removed is expensive and causes an increase in manufacturing cost, which is not practical. Furthermore, Patent Document 13 discloses a method of forming a film by dissolving lithium chloride in N-methyl-2-pyrrolidone or dimethyl sulfoxide with respect to a porous film using a semi-aromatic polyamide. Furthermore, it is disclosed that the obtained porous membrane exhibits a high albumin blocking rate. However, the porous membrane described in Patent Document 13 has a problem that the resistance to the organic solvent is remarkably lowered due to the remaining lithium chloride, and the water permeation amount does not reach a practical level unless the film thickness is reduced.

  In addition, a method for producing a porous film using a polyamide-based resin by the TIPS method has been studied. For example, Patent Document 14 discloses a technique for forming various resins into a porous film by the TIPS method. Polyamide 6 is cited as an example, but the porous film described in Patent Document 14 has a pore size. However, it 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-based resin, and the obtained hollow fiber membrane has a very large pore diameter of 1.4 μm and a molecular weight cut off. Cannot function as an ultrafiltration membrane having a molecular weight of about 1,000 to 200,000. Furthermore, Patent Document 15 discloses glycerin and ethylene glycol as polyamide solvents, but even when polyamide films are formed using these solvents, the resulting porous film can only withstand practical use. There is also a drawback that it cannot have strength. Patent Document 16 discloses a method of forming an aliphatic polyamide film using a solvent containing an antioxidant with respect to a method of manufacturing a hydrolysis-stable polyamide film. The maximum pore size is large and cannot be used as an ultrafiltration membrane. Furthermore, Non-Patent Document 3 reports that a porous membrane can be produced using a solvent system containing polyamide 12 and polyethylene glycol. Patent Document 17 reports that a porous membrane can be produced using a solvent system containing polyamide 11 and ethylene carbonate, propylene carbonate, or sulfolane. Non-Patent Document 4 discloses that the porous membranes of polyamide 6 and polyamide 12 can be produced using triethylene glycol as a solvent. However, the porous membranes disclosed in Non-Patent Documents 3-4 and 17 are not usable as an ultrafiltration membrane because of their low strength and large pore diameter. Patent Document 18 discloses an example in which a porous membrane using a semi-aromatic polyamide is produced by the TIPS method. This porous membrane has a large average pore diameter of 0.01 to 10 μm, and is an ultrafiltration membrane. It can not be used as.

  As described above, although various studies have been made on porous membranes using polyamide-based resins, those that have excellent resistance to various organic solvents and can be used as ultrafiltration membranes have not yet been developed. Currently. In addition, regarding porous membranes using high molecular weight materials such as polyethylene, polypropylene, and polytetrafluoroethylene, which are considered to be resistant to organic solvents, although there are reports on microfiltration membranes (MF membranes), they are related to ultrafiltration membranes. There are no reports.

JP 58-67733 A JP 59-59917 A JP-A-60-248202 Japanese Unexamined Patent Publication No. 63-225636 Japanese Patent Laid-Open No. 3-127617 JP 2003-10657 A Japanese Patent Laid-Open No. 2004-911 JP-A-57-105212 JP 58-65009 A U.S. Pat. No. 4,340,479 U.S. Pat. No. 4,477,598 JP 2000-1612 A Republished 2004-6991 JP 58-164622 A JP-A-60-52612 Special table 2003-534908 gazette U.S. Pat. No. 4,247,498 JP 2005-193193 A

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

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

  The inventors of the present invention have made extensive studies in order to solve the above problems. (1) In an organic solvent having a boiling point of 150 ° C. or higher and incompatible with the polyamide resin at a temperature lower than 100 ° C., 100 ° C. or higher. Preparing a film-forming stock solution in which the polyamide resin is dissolved at a temperature of (2), and then coagulating the polyamide resin into a film shape by extruding the film-forming stock solution into a coagulation bath of 100 ° C. or less in a predetermined shape In this case, at least one surface of the film-forming stock solution extruded in a predetermined shape is contacted with a coagulation liquid that is compatible with the organic solvent used in the film-forming stock solution and has a low affinity with the polyamide resin. It was found that an ultrafiltration membrane in which a dense layer having dense micropores was formed on the membrane surface can be produced. Furthermore, it has been found that the ultrafiltration membrane sufficiently satisfies practical levels in terms of molecular weight cut-off and water permeability, and can have excellent resistance to various types of organic solvents. The present invention has been completed by further studies based on such knowledge.

That is, this invention provides the ultrafiltration membrane of the aspect hung up below, its manufacturing method, 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 6. The limit according to Item 1, 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.
Item 3. Item 3. The ultrafiltration membrane according to Item 1 or 2, which has a hollow fiber membrane shape, and a dense layer is formed on at least one of the lumen side surface and the outer surface.
Item 4. Item 4. The ultrafiltration membrane according to any one of Items 1 to 3, wherein the molecular weight cut-off is 1,000 to 200,000.
Item 5. Production method of 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 .;
The step of solidifying the polyamide resin into a film by extruding the film-forming stock solution in a predetermined shape into a coagulation bath of 100 ° C. or less, wherein in the step, the film-forming stock solution extruded in a predetermined shape A film formed in the second step and the second step in which a coagulating liquid that is compatible with the organic solvent used in the film-forming stock solution and has a low affinity with the polyamide resin is brought into contact with at least one surface. 3rd process of removing a solvent from.
Item 6. It is a method for producing a hollow fiber membrane-shaped ultrafiltration membrane,
In the second step, a double tubular nozzle for producing a hollow fiber having a double tube structure is used, and the film-forming stock solution is discharged from the outer annular nozzle and the inner liquid is discharged from the inner nozzle, and immersed in the coagulation bath. 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 a low affinity for the polyamide resin. Manufacturing method.
Item 7. A coagulating liquid that is compatible with the organic solvent used in the film-forming stock solution and has a 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, Item 5 or is 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. 6. The method for producing an ultrafiltration membrane according to 6.
Item 8. The ultrafiltration membrane module in which the ultrafiltration membrane of any one of claim | item 1-4 is accommodated in a module case.

  The ultrafiltration membrane of the present invention has excellent resistance to various organic solvents, and can maintain its membrane characteristics stably even when it comes into contact with various types of industrially used organic solvents. The ultrafiltration membrane of the present invention is also excellent in terms of molecular weight cut-off and water permeability, and can be suitably used in fields such as the food industry, pharmaceutical industry, and semiconductor industry. Further, since the ultrafiltration membrane of the present invention is highly hydrophilic, 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. Therefore, it is possible to prevent fouling in which the hydrophobic material covers the membrane surface and the processing flow rate is lowered, 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. 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 the spinneret for producing the hollow fiber membrane of the present invention. 2 is an electron micrograph of an inner surface and an outer surface of the hollow fiber membrane of Example 1. FIG. 4 is an electron micrograph of the inner surface and outer surface of the hollow fiber membrane of Example 3. FIG. 2 is an electron micrograph of an inner surface and an outer surface of a 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, and is characterized in that 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 polyamide homopolymer, a polyamide copolymer, or a mixture thereof can be used. Specific examples of polyamide homopolymers include polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 612, polyamide 11, polyamide 12, polyamide MXD6, polyamide 4T, polyamide 6T, polyamide 9T, and polyamide 10T. It is done. Specific examples of the polyamide copolymer include a copolymer of polyamide and a polyether such as polytetramethylene glycol or polyethylene glycol. Further, the ratio of the polyamide component in the polyamide copolymer is not particularly limited. For example, the ratio of the polyamide component is preferably 70 mol% or more, and more preferably 80 mol% or more. When the ratio of the polyamide component in the polyamide copolymer satisfies the above range, it is possible to provide further excellent organic solvent resistance.

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

  Moreover, about the relative viscosity of a polyamide resin, although it does not restrict | limit in particular, 2.0-7.0 are mentioned, for example. By providing such a relative viscosity, at the time of manufacturing the ultrafiltration membrane, the moldability and the controllability of phase separation are improved, and it becomes possible to provide excellent shape stability to the ultrafiltration membrane. . Here, the relative viscosity refers to a value measured with an Ubbelohde viscometer at 25 ° C. using a solution obtained by dissolving 1 g of polyamide resin in 100 mL of 96% sulfuric acid.

  In this invention, the said polyamide resin may be used individually by 1 type, and may be used in combination of 2 or more type.

  The ultrafiltration membrane of the present invention may contain a filler, if necessary, as long as the effects of the present invention are not impaired in addition to the polyamide resin. By including a filler, the strength, elongation, and elastic modulus of the ultrafiltration membrane can be improved. In particular, the inclusion of the filler also provides an effect that the ultrafiltration membrane is hardly deformed even when a high pressure is applied during filtration. The type of filler to be added is not particularly limited. For example, glass fiber, carbon fiber, potassium titanate whisker, zinc oxide whisker, calcium carbonate whisker, wollastonite whisker, aluminum borate whisker, aramid fiber, alumina fiber, silicon carbide. Fibrous fillers such as fiber, ceramic fiber, asbestos fiber, stone-brown fiber, metal fiber; talc, hydrotalcite, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, bentonite, asbestos, alumina silicate Silicates such as; 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 powders, ceramic beads, boron nitride, silicon carbide, carbon black, silica, graphite and other non-fiber fillers Is mentioned. These fillers may be used individually by 1 type, and may be used in combination of 2 or more type. Among these fillers, talc, hydrotalcite, silica, clay, and titanium oxide are preferable, and talc and clay are more preferable.

  Although it does not specifically limit about content of a filler, For example, a filler is 5-100 mass parts per 100 mass parts of polyamide resins, Preferably it is 10-75 mass parts, More preferably, 25-50 mass parts is mentioned. By including the filler with such a content, the strength, elongation, and elastic modulus of the ultrafiltration membrane can be improved.

  In addition, for 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 to control the pore size and improve 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 micropores are gathered, and a region where no pores are substantially observed in a scanning electron microscope (SEM) photograph at a magnification of 10,000 times. Indicates. In the polyamide ultrafiltration membrane of the present invention, the thickness of the dense layer is not particularly limited, but is, for example, 0.01 to 2.0 μm, preferably 0.1 to 1.5 μm.

  The ultrafiltration membrane of the present invention only needs to 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. 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 lumen side 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 almost determined by the dense layer portion, 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 hinder strength and fluid permeation.

  About the thickness of the ultrafiltration membrane of this invention, although suitably set according to the use, the thickness of a dense layer, the water permeability to provide, etc., 50-600 micrometers, Preferably it is 100-300 micrometers.

The flow rate of the ultrafiltration membrane of the present invention is not particularly limited, but the water permeability when tested with 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 permeation amount, it is possible to perform a filtration process in an amount excellent in filtration efficiency and satisfying 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, inserted into a nylon hard tube having an outer diameter of 8 mm and an inner diameter of 6 mm, a rubber stopper on the opposite side, and a two-component mixed type. 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 permeation amount evaluation apparatus as shown in FIG. 1, and pure water at 25 ° C. is caused to flow inside the hollow fiber membrane by the liquid feed pump 13, and a pressure of about 0.6 MPa is applied for a predetermined time ( Min), water permeated to the outside of the membrane is collected in the pan 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 permeation amount 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 had 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, and 25 ° C. pure water is flowed to collect the permeated water at a predetermined pressure, and the capacity (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 fractional molecular weight is not particularly limited and can be appropriately set by appropriately adjusting the thickness of the dense layer, the pore diameter of the region other than the dense layer, etc. 200000, Preferably it is 1000-40000, More preferably, it is 1000-6000. The molecular weight cut off represents the pore size of the membrane capable of blocking a substance having a specific molecular weight by 90% or more, and is represented by the molecular weight of the substance capable of blocking.

  Specific examples of substances having a specific molecular weight used for the measurement of the molecular weight cut off include polyethylene glycol (molecular weight: 200 to 40,000), dextran (molecular weight: 10,000 to 200,000), and 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 substances 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. The liquid that has permeated the membrane can be collected and evaluated by obtaining the blocking 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 fractional molecular weight of the ultrafiltration membrane.

The ultrafiltration membrane of the present invention has characteristics (organic solvent resistance) that stably maintain the membrane structure by suppressing changes in strength and elongation even when contacting with various types 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 such organic solvents include the following.
Alcohols: primary alcohols such as methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, secondary alcohols such as isopropyl alcohol and isobutanol, tertiary alcohols such as tertiary butyl alcohol, ethylene glycol, diethylene glycol, tri 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, dimethyl sulfoxide, 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 suitable example of the organic solvent resistance of the ultrafiltration membrane of the present invention is that it has resistance to at least one, 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, dimethyl sulfoxide, 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 be resistant to phenols, halogen-containing solvents and lower organic acids as shown below.
Phenols: phenol, cresol, etc.
Halogen-containing solvent: dichloromethane, chloroform, trichloroethylene, trifluoroethanol, hexafluoroisopropanol and the like.
Lower organic acid: 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 changes in strength and elongation of the ultrafiltration membrane after immersion are changed before immersion. Is less than ± 30%, preferably less than ± 20%. Specifically, the change in strength and elongation is calculated according to the following formula.

  Here, the strength and elongation of the ultrafiltration membrane are the breaking strength and breaking strength measured when a tensile test is performed with a tensile tester under conditions of a distance between chucks of 50 mm, a tensile speed of 50 mm / min, and a temperature of 25 ° C. It is elongation. When the ultrafiltration membrane is a flat membrane shape, it is measured using a strip-shaped sample having a width of 10 mm and a length of 100 mm. When the ultrafiltration membrane is a hollow fiber shape, a sample with 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. The hollow fiber membrane shape is a unit of the ultrafiltration module. Since the filtration area per volume is large and the ultrafiltration treatment can be performed efficiently, it is suitable in the present invention. In addition, the ultrafiltration membrane of the present invention may be produced alone as a self-supporting membrane, or may have a shape laminated on a microfiltration membrane support. Such a support is preferably a material resistant to an organic solvent, specifically, a polymer material such as polyamide, polyethylene, polypropylene, polytetrafluoroethylene, polyphenylene sulfide, or polyether ether ketone; Examples include inorganic materials such as metals and ceramics.

2. Method for Producing 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, and a general TIPS method or NIPS method is used. 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 lower than 100 ° C.
Second step: a step of solidifying the polyamide resin into a film shape by extruding the film-forming stock solution in a predetermined shape into a coagulation bath of 100 ° C. or lower, and in the step, the extruded extruded in a predetermined shape At least one surface of the film-forming stock solution is brought into contact with a coagulation liquid that is compatible with the organic solvent used in the film-forming stock solution and has a low affinity with the polyamide resin.
Third step: The solvent is removed from the ultrafiltration membrane formed in the second step.

  Hereafter, the manufacturing method of the ultrafiltration membrane of this invention is explained in full detail for every process.

First Step In the 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 less than 100 ° C. To 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 aprotic polar solvents, glycerin ethers, polyhydric alcohols, organic acids, and organic acid esters. Higher alcohols and the like. 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- Examples include 2-pyrrolidone, ethylene carbonate, and propylene carbonate. 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 the polyhydric alcohols include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, hexylene glycol, 1,3-butanediol, 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. Can be mentioned. Among these, from the viewpoint of obtaining an ultrafiltration membrane having higher strength, preferably an aprotic polar solvent, a polyhydric alcohol; 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, ε-caprolactone Can be mentioned. These organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type. Even if these organic solvents are used singly, sufficient effects can be obtained, but by using two or more kinds in combination, the order and structure of phase separation are different, which is more effective. In some cases, ultrafiltration membranes can be made.

  Although it does not restrict | limit especially as a density | concentration of the polyamide resin in a film forming undiluted | stock solution, For example, 5-50 mass%, Preferably it is 10-40 mass%, More preferably, 12-35 mass% is mentioned. When the concentration of the polyamide resin in the membrane-forming stock solution satisfies the above range, the ultrafiltration membrane can be provided with excellent strength and can be provided with appropriate liquid permeability.

  Further, when 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 solution is dissolved at a temperature 10 to 50 ° C. higher, preferably 20 to 40 ° C. higher than the phase separation temperature of the system. The phase separation temperature of the system is a temperature at which solid-liquid phase separation by liquid-liquid phase separation or crystal precipitation occurs by gradually cooling a mixture of polyamide resin and solvent at a sufficiently high temperature. The phase separation temperature can be suitably measured 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 stock solution as necessary to control the pore size of ultrafiltration membranes and improve performance. May be.

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

  Here, a coagulation liquid that is compatible with the organic solvent used in the film-forming stock solution and has a low affinity with the polyamide resin (hereinafter sometimes referred to as a coagulation 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 below the boiling point or 200 ° C. or below. As such a coagulating liquid for forming a dense layer, specifically, water, an aqueous solvent such as an aqueous solution having a water content of 80% by mass or more; monohydric alcohols such as 1-propanol, 2-propanol, and isobutanol; Examples include glycol ethers such as polyethylene glycol having a molecular weight of 300 or more, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, and propylene glycol monoethyl ether; glycol acetates such as triacetin and propylene glycol monoethyl ether acetate. Among these, Preferably, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 600, triacetin, and triethylene glycol monomethyl ether are mentioned.

  In the second step, a dense layer is formed on the surface of the film-forming stock solution extruded in a predetermined shape in the coagulation bath in contact with the coagulating liquid for forming the dense layer. In the vicinity of the surface where the film-forming stock solution is in contact with the coagulating liquid for forming the dense layer, non-solvent phase separation by solvent exchange proceeds 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 tubular nozzle for producing a hollow fiber having a double tube structure is used, and the membrane forming stock solution is discharged from an outer annular nozzle and an inner nozzle The internal liquid may be discharged from and then immersed in the coagulation bath. At this time, a dense layer forming coagulation liquid may be used in at least one of the internal liquid and the coagulation bath. In addition, at least one of the internal solution and the coagulation bath has a coagulation solution that is compatible with the organic solvent used in the film-forming stock solution and has a high affinity for the polyamide resin (hereinafter, for forming a porous structure). (It may be expressed as a coagulating liquid). A porous structure is formed on the surface of the film-forming stock solution in contact with the coagulating liquid for forming a porous structure. That is, when the coagulating liquid for forming the 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 hollow fiber-like limit is formed in which the inside is a porous region. A filtration membrane is produced. In addition, when the coagulating liquid for forming the dense layer is used as the inner liquid and the coagulating liquid for forming the porous structure is used as the 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 that is a quality region is produced. In addition, when a coagulating liquid for forming a porous structure is used as the inner liquid and a coagulating liquid for forming a dense layer is used as the 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 that 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 in the film-forming stock solution at a temperature of 25 ° C. or lower and dissolves the polyamide resin at a temperature of the 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 thereof. Among these, Preferably, at least 1 sort (s) selected from the group which consists of glycerol, propylene glycol, diethylene glycol, and polyethyleneglycol 200, and the aqueous solution which contains these in the ratio of 25-75 mass%; More preferably, glycerol, diethylene glycol , Tetraethylene glycol, and propylene glycol, and an aqueous solution containing these in a proportion of 40 to 80% by mass.

  In forming a hollow fiber-shaped ultrafiltration membrane, the temperature of the double tubular nozzle at the time of membrane formation reaches 100 ° C. or higher. 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, among those exemplified in the above coagulation bath.

  In addition, as the double tubular nozzle for producing a hollow fiber, a die having a double tubular structure that is used when producing a core-sheath type composite fiber in melt spinning can be used. An example of a cross-sectional structure of a double tubular nozzle for producing hollow fibers is shown in FIG. What is necessary is just to set suitably about the diameter of the annular nozzle of the outer side of the double tubular nozzle for hollow fiber manufacture, and the diameter of an inner nozzle according to the internal diameter and outer diameter of a hollow fiber membrane.

  Further, the flow rate when the film-forming stock solution is discharged from the annular nozzle outside the double tubular nozzle for producing hollow fibers is not particularly limited, but is, for example, 2 to 30 g / min, preferably 3 to 20 g / min. Preferably 5-15 g / min is mentioned. The flow rate of the internal liquid is appropriately set in consideration of the diameter of the inner nozzle of the double tubular nozzle for manufacturing hollow fibers, the type of internal liquid to be used, the flow rate of the film-forming stock solution, etc. The flow rate is 0.1 to 2 times, preferably 0.2 to 1 time, and more preferably 0.4 to 0.7 times.

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

  In the third step, the temperature of the coagulation bath may be 100 ° C. or less, 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 in the film-forming stock solution and the composition of the coagulation solution, but in general, the heat-induced phase separation takes precedence by setting the temperature to a lower temperature. Solvent phase separation tends to preferentially proceed. That is, when producing a hollow fiber membrane having a dense layer formed on the lumen side surface, it is preferable to set the coagulation bath at 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 coarse the internal structure, it is preferable to set the coagulation bath at a high temperature.

  Thus, by carrying out the second step, the membrane-forming stock solution is solidified 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 of evaporating the coagulation liquid by drying with a drier, but it is immersed in an extraction solvent and phase-separated in the ultrafiltration membrane. A method of extracting and removing the coagulating liquid causing the slag is preferred. The extraction solvent used for the extraction and removal of the organic solvent is preferably an inexpensive solvent having a low boiling point that can be easily separated by a difference in boiling point after extraction, for example, water, glycerin, methanol, ethanol, isopropanol, acetone, diethyl ether. , Hexane, petroleum ether, toluene and the like. Among these, water, methanol, ethanol, isopropanol, and acetone are preferable, and water, methanol, and isopropanol are more preferable. In particular, when extracting a coagulation solution that dissolves in water, it is efficient to perform solvent extraction at the same time if winding is performed while showering with water. Moreover, when extracting the organic solvent insoluble in water, such as a phthalate ester and a fatty acid, isopropyl alcohol, petroleum ether, etc. can be used suitably. Further, the time for immersing the ultrafiltration membrane in the extraction solvent is not particularly limited, but 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 liquid remaining on the ultrafiltration membrane, the extraction solvent may be replaced or stirred.

  Thus, the ultrafiltration membrane of the present invention is manufactured by performing the third step.

  The ultrafiltration membrane of the present invention may be manufactured through the first to third steps described above, and the apparatus used for the manufacture is not particularly limited, but a hollow fiber-shaped ultrafiltration membrane is manufactured. In such a case, a general apparatus used for dry and wet spinning as shown in FIG. 3 is preferably used. Taking the apparatus shown in FIG. 3 as an example, the manufacturing flow of a hollow fiber-shaped ultrafiltration membrane is outlined below. The film-forming stock solution prepared in the first step is accommodated in the container 3. Alternatively, the first step may be performed in the container 3 to prepare a film forming stock solution. The film-forming stock solution accommodated in the container 3 and the internal liquid introduced from the internal liquid introduction port 5 are respectively measured by the metering pump 4 and fed to the double tubular nozzle (spinning nozzle) 6 for producing hollow fibers. . The film-forming stock solution discharged from the double tubular nozzle (spinneret) 6 for producing hollow fibers is introduced into the coagulation bath 7 through a slight air gap and cooled and solidified. In 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 hollow fiber membrane ultrafiltration membrane 8 thus obtained is wound up by the bobbin winder 10 provided with the bobbin while being wound up by the winder 9. The wound hollow fiber membrane ultrafiltration membrane 8 removes the coagulating 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 accommodated in a module case provided with a liquid inlet to be treated, a permeate outlet and the like, 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 and accommodated in a module case, and one or both ends of the hollow fiber ultrafiltration membrane bundle are sealed with a potting agent. Any structure may be used as long as it is stopped and fixed. The hollow fiber membrane module includes an opening connected to a flow path passing through the outer wall surface of the hollow fiber-shaped ultrafiltration membrane, and a hollow portion of the hollow fiber-shaped ultrafiltration membrane as an inlet of the liquid to be treated or an outlet of the filtrate. It is only necessary to provide an opening 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 folded and filled into a U shape, and the end of the hollow fiber membrane is filtered and then opened. Module: The hollow opening at one end of the hollow fiber-shaped ultrafiltration membrane bundle is straightly filled with the one closed by heat sealing or the like, and the end of the open hollow fiber-shaped ultrafiltration membrane bundle is cut after sealing Opened dead-end module; filled with a hollow fiber-like ultrafiltration membrane bundle straightly, sealed both ends of the hollow fiber-like ultrafiltration membrane bundle, and cut only one end to expose the opening Dead-end module: Fills the hollow fiber-shaped ultrafiltration membrane bundle straightly, seals both ends of the hollow-fiber ultrafiltration membrane bundle, cuts the sealing portions at both ends of the hollow-fiber ultrafiltration membrane bundle, and filters Cross flow type with two flow paths on the side of the case Jules, and the like.

  The filling rate of the hollow fiber ultrafiltration membrane inserted into the module case is not particularly limited. For example, the volume of the hollow fiber ultrafiltration membrane including 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, it is easy to fill the module case with the hollow fiber ultrafiltration membrane while ensuring a sufficient filtration area, and the potting agent easily flows between the hollow fiber ultrafiltration membranes. can do.

  The potting agent used for the production of the hollow fiber membrane module is not particularly limited. However, when the hollow fiber membrane module is used for the treatment of an organic solvent, it is desirable that the potting agent has an organic solvent resistance. Examples of the potting agent include polyamide, silicon resin, melamine resin, polyethylene, polypropylene, phenol resin, polyimide, polyurea resin and the like. Among these potting agents, those which are small in shrinkage and swelling when cured and are not too hard are preferable. Preferable examples of the potting agent include polyamide, silicone resin, and polyethylene. These potting agents may be used individually by 1 type, and may be used in combination of 2 or more type.

  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, polyethersulfone, polycarbonate, Examples include polyarylate and polyphenylene sulfide. Among these, polyamide, polyethylene, polypropylene, polytetrafluoroethylene, polycarbonate, polysulfone, and polyethersulfone are preferable, and polyamide, polyethylene, polypropylene, and polytetrafluoroethylene are more preferable.

  Further, when the ultrafiltration membrane of the present invention has a flat membrane shape, it is used as a sheet-type module such as a plate-and-frame type or a stack type, a spiral type module, a rotating flat membrane type module or the like.

  The ultrafiltration membrane module using the ultrafiltration membrane of the present invention is used for purification of water, removal of foreign matters, etc. in the fields of semiconductor industry, food industry, pharmaceutical industry, medical product industry and the like.

  EXAMPLES The present invention will be specifically described below 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 measured by the method described above. In addition, the blocking rate of the polymer was measured using polyethylene glycol for a molecular weight of 20000 or less, and dextran for a molecular weight above 20000, and each 0.1% by mass dissolved in water was passed 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 chip (Unitika A1030BRT, relative viscosity 3.53) 170 g and sulfolane (Tokyo Kasei Co., Ltd.) 830 g were stirred and dissolved at 180 ° C. for 1.5 hours, and the stirring speed was lowered for 1 hour. Defoamed and a film-forming stock solution was prepared. The stock solution was sent to the spinneret via a metering pump and extruded at 13.0 g / min. As the hole diameter of the spinneret, an outer diameter of 1.5 mm and an inner diameter of 0.6 mm were used. Polyethylene glycol 300 (PEG300) was passed through the internal liquid at a liquid feed rate of 5.0 g / min. The extruded film-forming stock solution was put into a coagulation bath composed of a 50 mass% propylene glycol aqueous solution at 5 ° C. through a 10 mm air gap, cooled and solidified, 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 to obtain a hollow fiber membrane.

The obtained hollow fiber membrane has a water permeability of 10 L / (m ² · atm · h), a solute rejection using dextran 40000 (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 32000-45000) is 98%, polyethylene The solute rejection using glycol 20000 (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight: 15000 to 25000) was 88%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope (10,000 times), the surface on the lumen side was a skin layer (dense layer) in which pores were not visible, and the sponge-like porous Through the structure, the outer surface had a porous structure (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 using dextran 40000 is 99%, a solute rejection using polyethylene glycol 20000 is 97%, polyethylene glycol The solute rejection using 6000 (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 7300-9300) was 90%. When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the inner surface was a skin layer (dense layer) in which pores were not visible, and the outer surface had a porous structure. It was.

Example 3
A hollow fiber membrane was produced in the same manner as in Example 1 except that the internal liquid was changed to triacetin. The obtained hollow fiber membrane has a water permeability of 3 L / (m ² · atm · h), a solute blocking rate using polyethylene glycol 6000 of 98%, polyethylene glycol 2000 (manufactured by Wako Pure Chemical Industries, molecular weight 1850 to 2150). ) Was 91%. 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 skin layer thickness was obtained in Example 1. Thicker than the film formed. Further, the inside was a sponge-like porous structure, and the outer surface was a porous structure (see FIG. 5).

Example 4
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 liquid. The water permeability of the obtained hollow fiber membrane is 150 L / (m ² · atm · h), the solute rejection using dextran 200000 (manufactured by Wako Pure Chemical Industries, average molecular weight 180000-210000) is 98%, The solute rejection using Dextran 60000 (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 60000-90000) 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 the solvent used for the membrane forming stock solution. The obtained hollow fiber membrane had a water permeability of 18 L / (m ² · atm · h), the solute rejection using dextran 40000 was 95%, and the solute rejection using polyethylene glycol 20000 was 90%. . When the surface structure of the obtained hollow fiber membrane was observed with a scanning electron microscope, the inner surface was a skin layer (dense layer) in which pores were not visible, and the outer surface had a porous structure. It was.

Example 6
150 g of polyamide 11 chip (Rilsan BESV0 A FDA, manufactured by Arkema Inc., relative viscosity 2.50) is used as the resin, and 850 g of γ-butyrolactone (manufactured by Wako Pure Chemical Industries, Ltd.) is used as the film-forming stock solution. The mixture was dissolved by stirring, and the stirring rate was lowered to degas for 1 hour to prepare a membrane forming stock solution. A hollow fiber membrane was produced in the same manner as in Example 1 except that this membrane-forming stock solution was used. The obtained hollow fiber membrane has a water permeability of 5 L / (m ² · atm · h), a solute rejection using dextran 40000 is 99%, a solute rejection using polyethylene glycol 20000 is 98%, 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 inner surface was a skin layer (dense layer) in which pores were not visible, and the outer surface had a porous structure. It was.

Example 7
Example 1 except that 170 g of polyamide MXD6 chip (Reny 6121 manufactured by Mitsubishi Engineering Plastics Co., Ltd., relative viscosity 3.49) was used as the resin, and the dissolution temperature at the time of producing the film forming stock solution was 170 ° C. Thus, a hollow fiber membrane was produced. The obtained hollow fiber membrane has a water permeability of ² L / (m ² · atm · h), a solute rejection using dextran 40000 is 99%, a solute rejection using polyethylene glycol 20000 is 97%, 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 inner surface was a skin layer (dense layer) in which pores were not visible, and the outer surface had a porous structure. It was.

Example 8
A hollow fiber membrane was produced in the same manner as in Example 1 except that 200 g of polyamide 6 resin and 800 g of sulfolane were changed. The obtained hollow fiber membrane has a water permeability of 5 L / (m ² · atm · h), a solute rejection using dextran 40000 is 99%, and a solute rejection of polyethylene glycol 20000 is 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 inner surface was a skin layer (dense layer) in which pores were not visible, and the outer surface had a porous structure. It 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 liquid. The water permeability of the obtained hollow fiber membrane was 2400 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 lumen side surface and the outer surface had a porous structure, and a dense layer was not formed on the surface (FIG. 6).

Test Example 1: Organic solvent resistance test 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. For comparison, the same evaluation was performed using a hollow fiber membrane (Comparative Example 2) of an ultrafiltration membrane laboratory module SLP-1053 (manufactured by Asahi Kasei Chemicals, nominal molecular weight 10,000) made of polysulfone.

  The obtained results are shown in Table 1. From this result, in the hollow fiber membranes (Examples 1, 6 and 7) having a dense layer formed on the surface, even when immersed in various organic solvents, the strength and elongation do not change and are maintained stably. It was. On the other hand, in the polysulfone ultrafiltration membrane (Comparative Example 2) in which a dense layer was not formed on the surface, the strength and elongation were greatly changed by most organic solvents, and the resistance to organic solvents was inferior.

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-up machine 10: Bobbin winder (with water shower)
11: Internal liquid (or gas) inflow hole 12: Film forming raw material inflow hole 13: Liquid feed pump 14: Pressure gauge 15: Hollow fiber membrane 16: Pressure release valve 17: Sauce pan

Claims (8)

  An ultrafiltration membrane formed using a polyamide resin, wherein a dense layer is formed on at least one surface.   The limit according to claim 1, 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. Outer filtration membrane.   The ultrafiltration membrane according to claim 1 or 2, wherein the ultrafiltration membrane has a hollow fiber membrane shape, and a dense layer is formed on at least one of the lumen side surface and the outer surface.   The ultrafiltration membrane according to any one of claims 1 to 3, wherein the molecular weight cut-off is 1,000 to 200,000. Production method of 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 .;
The step of solidifying the polyamide resin into a film by extruding the film-forming stock solution in a predetermined shape into a coagulation bath of 100 ° C. or less, wherein in the step, the film-forming stock solution extruded in a predetermined shape A solvent formed in the second step, in which a coagulating solution having compatibility with the organic solvent used in the film-forming stock solution and having a low affinity with the polyamide resin is brought into contact with at least one surface, and the second step. A third step of removing It is a method for producing a hollow fiber membrane-shaped ultrafiltration membrane,
In the second step, a double tubular nozzle for producing a hollow fiber having a double tube structure is used, and the film-forming stock solution is discharged from the outer annular nozzle and the inner liquid is discharged from the inner nozzle, and immersed in the coagulation bath. The process of
6. The ultrafiltration according to claim 5, wherein at least one of the internal liquid and the coagulation bath uses a coagulation liquid that is compatible with the organic solvent used in the film-forming stock solution and has a low affinity for the polyamide resin. A method for producing a membrane.   A coagulating liquid that is compatible with the organic solvent used in the film-forming stock solution and has a 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, 6. 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. Or the manufacturing method of the ultrafiltration membrane of 6.   The ultrafiltration membrane module in which the ultrafiltration membrane of any one of Claims 1-4 is accommodated in a module case.