JP6378995B2 - Polyamide hollow fiber membrane - Google Patents

Description

  The present invention relates to a polyamide hollow fiber membrane having a high water permeability and a high bubble point, which is an index of a fine pore diameter, used in the fields of semiconductor industry, food industry, pharmaceutical industry, medical product industry and the like, and a method for producing the same. Furthermore, this invention relates to the hollow fiber membrane module using the said polyamide hollow fiber membrane.

  Hollow fiber membranes are generally manufactured by extruding a polymer solution, which is a spinning stock solution, from a double tubular spinneret and then coagulating and drying, and are used for liquid filtration applications in the semiconductor industry, drinking water production, upper and lower It has been used in many industrial fields such as water treatment such as water treatment, medical field such as blood purification, pharmaceutical field such as virus removal, and food industry, and porous filtration membranes having various pore sizes have been developed. ing.

  For the evaluation of microfiltration membranes and ultrafiltration membranes, liquid permeability (water permeability in the case of water) measurement and bubble point measurement are mainly used. The bubble point method is a general method for measuring the maximum pore diameter of a membrane.

  The production method of the porous filtration membrane can be roughly divided into a non-solvent induced phase separation method (NIPS method) and a thermally induced phase separation method (TIPS method). The hollow fiber membrane produced by the NIPS method has a feature that it is easy to form a finger-like macrovoid structure in the cross section, and the membrane strength is difficult to be obtained due to the structure. On the other hand, the hollow fiber membrane produced by the TIPS method has a feature that the cross-section easily forms a sponge-like structure, and the membrane strength is easily obtained in terms of structure.

  Conventionally, polyolefins such as polyethylene and polypropylene, polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile, cellulose acetate and the like are often used as the material for the porous filtration membrane. However, polyolefins, polyvinylidene fluoride, polysulfone, polyethersulfone, and the like have strong hydrophobicity, and thus have a problem of requiring a wet treatment before use and a decrease in water permeability. Polyacrylonitrile, cellulose acetate and the like are relatively hydrophilic resins, but they are often produced by the NIPS method, and there is a problem that the film strength is weak because a finger-like macrovoid structure is formed.

  Therefore, conventionally, a method for producing a porous filtration membrane using a polyamide-based resin having relatively high hydrophilicity has been studied. However, polyamides are soluble only in formic acid, which is a strong acid, concentrated sulfuric acid, and expensive fluorine-containing solvents at room temperature. Therefore, these solvents have been used as production methods using the NIPS method. For example, in the methods described in Patent Documents 1 to 5, a film forming method using formic acid as a solvent is disclosed. However, using formic acid as a solvent has a health and safety problem.

  On the other hand, a method using the TIPS method has also been studied, and Patent Document 6 reports that a porous membrane can be produced using a system of polyamide 11 and ethylene carbonate, propylene carbonate, or sulfolane. However, all of these were only capable of forming a porous membrane, and could not be processed into a hollow fiber membrane having a high water permeability and control of the fine pore diameter.

  Therefore, as a result of intensive investigations on the polyamide hollow fiber membrane and the production method thereof, the present inventors have used a certain type of solvent limited as a membrane-forming solvent, and formed a membrane by the TIPS method, so that hydrophilicity, water permeability It was found that a polyamide hollow fiber membrane having properties such as properties, separability and strength could be produced, and the technical contents thereof were disclosed in Patent Documents 7 and 8.

  As described above, the bubble point test is a general method used to determine the maximum pore size of a membrane. After the membrane is wetted with an organic solvent such as 2-propanol, air pressure is applied to the membrane, and bubbles are generated from the membrane. This is a test to measure the air pressure (bubble point) at the time of occurrence. The higher the bubble point, the smaller the maximum pore size of the membrane.

In the bubble point method stipulated in JIS standard K-3832, the pore diameter can be calculated from the surface tension and bubble point pressure of the liquid used by the following equation.
d = 4Bγ / P
d: pore diameter B: capillary constant γ: surface tension of liquid P: bubble point pressure

  In the bubble point test, the membrane to be measured is first sufficiently wetted with the liquid used, and in the case of a hollow fiber membrane, for example, air is gradually pressurized from the inner surface with air or nitrogen gas, and bubbles are generated from the outer surface of the membrane. Measure the pressure. Bubbles are first generated from the maximum pores of the membrane, and then uniformly generated from the entire membrane as the pressure increases. The pressure at the time when bubbles start to be generated is called an initial bubble point, and the pressure at the time when bubbles are generated from the whole is called a burst bubble point.

  As is clear from the above formula, in the bubble point test, the influence of the surface tension of the liquid used is large. Examples of the liquid generally used for the bubble point test include 2-propanol (surface tension 21 mN / m), ethylene glycol (surface tension 48 mN / m), water (surface tension 72 mN / m), and the like. Among these liquids, a liquid having a low surface tension is suitable for evaluating the pore size at low pressure, and a liquid having good wettability is suitable for sufficiently wetting the membrane. Is widely used. However, when the pore diameter of the hollow fiber membrane is further reduced, the bubble point to be measured is increased even when 2-propanol is used. Therefore, in such a hollow fiber membrane, it is preferable to use a liquid having a lower surface tension. It is easy to measure the maximum pore diameter of the hollow fiber membrane.

Conventionally, bubble points using 2-propanol have been reported for polyamide membranes. For example, Patent Document 5 exemplifies bubble points and water permeation speed (water permeation amount) of polyamide 46 and polyamide 66. However, although the polyamide membrane disclosed in Patent Document 5 has a bubble point as high as 4.1 kg / cm ² (0.40 MPa), the water permeation rate (water permeation amount) of the polyamide membrane is disclosed. ) Is as low as 9.02 ml / cm ² · kg / cm (93.2 L / (m ² · atm · h)).

  In Patent Documents 7 and 8, the bubble point has not been studied, and it has not been possible to specify whether the particle removal rate is due to the pore size of the membrane or the adsorption effect of the polyamide material. Patent Document 9 discloses a polyamide hollow fiber membrane module, and studies on bubble points. However, in Patent Document 9, the amount of water permeation is not studied at all.

JP-A-57-105212 JP 58-65009 A U.S. Pat. No. 4,340,479 U.S. Pat. No. 4,477,598 Japanese Patent Laid-Open No. 3-52927 U.S. Pat. No. 4,247,498 JP 2010-104983 A JP 2012-20231 A JP 2012-183501 A

As described above, in the prior art, it was unclear how to obtain a polyamide hollow fiber membrane having a high bubble point and a high water permeability.
Under such circumstances, a main object of the present invention is to provide a polyamide hollow fiber membrane having a high bubble point and a high water permeability, and a method for producing the same. Another object of the present invention is to provide a hollow fiber membrane module using the polyamide hollow fiber membrane.

The present inventor has intensively studied to solve the above problems. As a result, in the method for producing a polyamide hollow fiber membrane by a thermally induced phase separation method in which a polyamide resin and a solvent-containing polymer solution are cooled and the polyamide resin is phase-separated and solidified, a fatty acid amide is allowed to coexist in the polymer solution. It was found that a polyamide hollow fiber membrane having a high bubble point and a high water permeability can be obtained. Specifically, in a bubble point test in which air pressure is applied in a liquid having a surface tension of 12 mN / m at 20 ° C., the initial bubble point is 0.40 MPa or more and the burst bubble point is 0.55 MPa or more. It was found that a polyamide hollow fiber membrane having an internal pressure water permeability using pure water at 50 ° C. of 50 L / (m ² · atm · h) or more can be obtained. Furthermore, it discovered that the polyamide hollow fiber membrane obtained by the said manufacturing method was equipped also with high tensile strength and high tensile elongation. The present invention has been completed by further studies based on these findings.

That is, this invention provides the invention of the aspect hung up below.
Item 1. A polyamide hollow fiber membrane formed of a polyamide resin,
In a bubble point test in which air pressure is applied in a liquid having a surface tension of 12 mN / m at 20 ° C., the initial bubble point is 0.40 MPa or more, and the burst bubble point is 0.55 MPa or more,
A polyamide hollow fiber membrane having an internal pressure water permeability using pure water at 25 ° C. of 50 L / (m ² · atm · h) or more.
Item 2. Item 2. The polyamide hollow fiber membrane according to Item 1, having a tensile strength of 12.0 MPa or more and a tensile elongation of 150% or more at a temperature of 25 ° C and a humidity of 60%.
Item 3. Item 3. The polyamide hollow fiber membrane according to Item 1 or 2, wherein the polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 11, polyamide 12, and polyamide MXD6. .
Item 4. A hollow fiber membrane module in which the polyamide hollow fiber membrane according to any one of Items 1 to 3 is accommodated in a module case.
Item 5. A method of producing a polyamide hollow fiber membrane by a thermally induced phase separation method in which a polymer solution containing a polyamide resin and a solvent is cooled to phase separate and solidify the polyamide resin,
A method for producing a polyamide hollow fiber membrane, wherein a fatty acid amide is allowed to coexist in the polymer solution.
Item 6. The production of the polyamide hollow fiber membrane according to Item 5, wherein the total mass of the polyamide resin and the solvent in the polymer solution is 100 parts by mass, and the addition amount of the fatty acid amide is in the range of 0.01 to 5.00 parts by mass. Method.

  ADVANTAGE OF THE INVENTION According to this invention, the polyamide hollow fiber membrane which has a high bubble point and high water permeability, and its manufacturing method can be provided. Furthermore, according to this invention, the hollow fiber membrane module using the said polyamide hollow fiber membrane can be provided.

It is the schematic of the apparatus which measures the internal pressure water permeability of the polyamide hollow fiber membrane of this invention. It is the schematic of the method of measuring the bubble point of the polyamide hollow fiber membrane of this invention. It is an apparatus figure which shows one embodiment of the method of manufacturing the polyamide hollow fiber membrane of this invention. 2 is a scanning electron micrograph of the polyamide hollow fiber membrane obtained in Example 1. FIG. A is a cross-sectional view, B is an enlarged cross-sectional view, C is a photograph observing the inner surface, and D is a photograph observing the outer surface. A is a photograph observing the appearance of the cross-flow type hollow fiber membrane module obtained in Example 15, and B is a photograph observing the appearance of the dead-end type hollow fiber membrane module obtained in Example 16.

1. Polyamide hollow fiber membrane The polyamide hollow fiber membrane of the present invention is a polyamide hollow fiber membrane formed of a polyamide resin. In a bubble point test in which air pressure is applied in a liquid having a surface tension of 12 mN / m at 20 ° C. The bubble point is 0.40 MPa or more, the burst bubble point is 0.55 MPa or more, and the internal pressure water permeability using pure water at 25 ° C. is 50 L / (m ² · atm · h) or more. Features. Hereinafter, the polyamide hollow fiber membrane of the present invention will be described in detail.

  Specific examples of the polyamide resin that forms the polyamide hollow fiber membrane of the present invention include polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 11, polyamide 12, and polyamide MXD6. Among these, Preferably, polyamide 6, polyamide 66, polyamide 610, polyamide 11, and polyamide MXD6 are mentioned, More preferably, polyamide 6 and polyamide 11 are mentioned. In the present invention, the polyamide hollow fiber membrane may be formed of one type of polyamide resin, or may be formed of a blend polymer of two or more types of polyamide resins.

  The polyamide resin may or may not be crosslinked as long as it can be formed into a fiber shape. From the viewpoint of cost reduction, an uncrosslinked polyamide resin is preferred.

  The polyamide hollow fiber membrane of the present invention may contain additives such as thickeners, surfactants, crystal nucleating agents and lubricants.

  Further, the relative viscosity of the polyamide resin is not particularly limited, but may be, for example, 2.0 to 6.2, preferably 3.0 to 5.8, and more preferably 3.5 to 5.3. By using a polyamide resin having such a relative viscosity, it is possible to easily control the moldability into a hollow fiber membrane and the phase separation. In this specification, the relative viscosity is a value measured with an Ubbelohde viscometer using 96% sulfuric acid, dissolved at a polyamide resin concentration of 1 g / dl, and at 25 ° C.

  When the hollow fiber membrane is used in the most advanced semiconductor field, pharmaceutical field, etc., it is preferable that the filtration accuracy is high, that is, the pore diameter is small, the flow rate is high, the strength is high and the elongation is high. This is because, for example, in the cutting-edge field, it is necessary to capture fine particles such as viruses, gels, and the like, and the flow rate greatly affects productivity and cost. In addition, the hollow fiber membrane should not be cut or cracked during the filtration operation.

  The polyamide hollow fiber membrane of the present invention has an initial bubble point of 0.40 MPa or more and a burst bubble point of 0.55 MPa or more in a bubble point test in which air pressure is applied in a liquid having a surface tension of 12 mN / m at 20 ° C. Preferably, the initial bubble point is 0.45 MPa or more and the burst bubble point is 0.65 MPa or more, more preferably the initial bubble point is 0.55 MPa or more and the burst bubble point is 0.75 MPa or more. This is because when the burst bubble point is less than 0.55 MPa, the pore diameter is large and high accuracy cannot be expected for filtration. The upper limit value of the burst bubble point is about 1.7 MPa. Thus, the polyamide hollow fiber membrane of the present invention having a high value for both the initial bubble point and the burst bubble point in a liquid having a very low surface tension of 12 mN / m at 20 ° C. is described later. It can be manufactured by the manufacturing method of the present invention.

  In the present invention, the bubble point test is a measurement method generally used for obtaining the maximum pore size, and is widely used for estimating the pore size because the measurement is simple and quick. The principle and method of the bubble point test are described in JIS standard K3832. As a liquid having a surface tension of 12 mN / m at 20 ° C., “Fluorinert FC-72” manufactured by Sumitomo 3M, which is a kind of perfluorocarbon, was used. Instead of a liquid having a surface tension of 12 mN / m at 20 ° C., 2-propanol (surface tension 21 mN / m), ethylene glycol (surface tension 48 mN / m), water (surface tension 72 mN / m), etc. are used. Although it is possible to calculate the bubble point by correcting from the above formula, the bubble point becomes large, which makes measurement difficult.

The polyamide hollow fiber membrane of the present invention has an initial bubble point of 0.40 MPa or more in a bubble point test in which air pressure is applied in a liquid having a surface tension of 12 mN / m at 20 ° C., and a burst bubble point of 0.55 MPa or more. is there. In the measurement using 2-propanol whose surface tension at 20 ° C. is 21 mN / m, the initial bubble point can be converted to 0.70 MPa or more and the burst bubble point can be converted to 0.96 MPa or more. Thus far, there has been no report on a polyamide hollow fiber membrane having a very high bubble point and having an internal pressure water permeability of 50 L / (m ² · atm · h) or more using pure water at 25 ° C.

  Specifically, the bubble point test of the present invention can be performed by the method described in Examples described later. In the present invention, the initial bubble point measured by the bubble point test is a pressure at which air begins to permeate from the surface of the membrane when air pressure is applied to the membrane, and specifically described later. It is a value measured by the test described in the examples. Further, in the present invention, the burst bubble point measured by the bubble point test is a pressure at which bubbles come out from almost the entire membrane, specifically, by the test described in the examples described later. It is a measured value.

  The gas used in the bubble point test of the present invention is air. The rate of applying air pressure is usually 0.1 MPa / min to 0.9 MPa / min, preferably 0.3 MPa / min to 0.6 MPa / min. If it is slower than this range, it takes time to measure, and if it is faster than this range, there is a problem that the pressure reading error when a bubble is generated becomes large.

The polyamide hollow fiber membrane of the present invention has a high initial bubble point and a high burst bubble point, and has an internal water permeability of 50 L / (m ² · atm · h using pure water at 25 ° C. ) Or more. In the present invention, the internal pressure water permeation amount is a water permeation amount when water is permeated by applying pressure from the inside to the outside of the hollow fiber membrane, and is an index indicating the permeation performance of the polyamide hollow fiber membrane. The internal pressure water permeability varies depending on the hole diameter. For this reason, as a standard internal pressure permeation amount for each bubble point in the polyamide hollow fiber membrane of the present invention, it is 50 L / (m ² · atm · h) or more in a hollow fiber membrane having a burst bubble point of 0.75 MPa or more. It is preferable that it is 100 L / (m ² · atm · h) or more. In a hollow fiber membrane having a burst bubble point of 0.55 to 0.75 MPa, it is preferably 150 L / (m ² · atm · h) or more, and 200 L / (m ² · atm · h) or more. Further preferred. Since the polyamide hollow fiber membrane of the present invention has such high internal pressure water permeability, the flow rate of the treatment liquid can be set high and the filtration efficiency can be increased. In the polyamide hollow fiber membrane of the present invention, the internal pressure water permeability using pure water at 25 ° C. is usually 1000 L / (m ² · atm · h) or less. In addition to having a high bubble point as described above, the polyamide hollow fiber membrane of the present invention having a high water permeability can be produced by the production method of the present invention described later.

  In the present invention, the internal pressure water permeability of the polyamide hollow fiber membrane is a value measured by internal pressure filtration using pure water at 25 ° C., and specifically, measured by the method described in Examples below. Value. An outline of a method for measuring the internal pressure water permeability of the polyamide hollow fiber membrane will be described with reference to FIG. As shown in FIG. 1, the polyamide hollow fiber membrane 2 is cut into 10 to 20 cm, the injection needles 6 having a diameter matching the inner diameter are inserted into the hollow portions at both ends, set in the apparatus as shown in FIG. Time (minutes) The pure water was passed through the liquid feed pump 1 and permeated through the membrane, and the volume (L) of water stored in the tray 7 was defined as the amount of permeated water, and was obtained by the following equation. The pressure is an average value of the inlet pressure 3 and the outlet pressure 4 in FIG.

Internal pressure water permeation amount = permeate water amount (L) / [inner diameter (m) × 3.14 × length (m) × {(inlet pressure (atm) + outlet pressure (atm)) / 2} × time (h)]

  The tensile strength of the polyamide hollow fiber membrane of the present invention is not particularly limited, but is preferably 12 to 30 MPa, more preferably 13 to 25 MPa, and still more preferably 14 to 20 MPa in an environment of 25 ° C. and a relative humidity of 60%. Can be mentioned. The tensile elongation of the polyamide hollow fiber membrane of the present invention is not particularly limited, but preferably 150 to 400%, more preferably 180 to 350%, and still more preferably 200 to 300%. In the present invention, the tensile strength and tensile elongation of the polyamide hollow fiber membrane are respectively measured at a test length of 50 mm, a tensile speed of 50 mm / min, and a measurement number = 5 in accordance with the provisions of JIS standard L-1013. Value. According to the present invention, a polyamide hollow fiber membrane having a high tensile strength and a high tensile elongation as described above is obtained in addition to a high bubble point and a high water permeability by employing the production method of the present invention described later. It is done.

  The inner diameter and outer diameter of the polyamide hollow fiber membrane of the present invention are not particularly limited and are appropriately set according to the purpose of use and the like. The inner diameter is, for example, 100 to 800 μm, preferably 150 to 600 μm, more preferably. The outer diameter is, for example, 250 to 1800 μm, preferably 3000 to 1500 μm, and more preferably 400 to 1000 μm.

2. Production method of polyamide hollow fiber membrane The polyamide hollow fiber membrane of the present invention is a thermally induced phase separation method (TIPS method) in which a polymer solution containing a polyamide resin and a solvent is cooled to phase separate and solidify the polyamide resin. It can be suitably produced by allowing the fatty acid amide to coexist in the polymer solution. More specifically, the method for producing a polyamide hollow fiber membrane of the present invention is produced through the following first to third steps.
First step: A polyamide resin and a fatty acid amide are dissolved in a solvent to prepare a polymer solution.
Second step: Using a double tubular nozzle for producing a hollow fiber having a double tube structure, the polymer solution is discharged from an outer annular nozzle, an inner liquid is discharged from an inner nozzle, and introduced into a coagulation bath. A hollow fiber membrane is formed by pulling at a constant pulling rate.
Third step: The solvent is removed from the hollow fiber membrane formed in the second step.

  Hereinafter, the manufacturing method of the polyamide hollow fiber membrane of the present invention will be described in detail for each step.

First Step In the first step, a polymer solution is prepared by dissolving a polyamide resin and a fatty acid amide in a solvent in order for the fatty acid amide to coexist in the polymer solution. In order to dissolve the polyamide resin in the solvent, the polyamide resin is dissolved in the high boiling point solvent at a high temperature.

  Examples of such high-boiling solvents include aprotic polar solvents, glycerin esters, glycols, organic acids and organic acid esters, higher alcohols, glycols 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 the glycerin esters 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 glycols include glycerin, diglycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, butylene glycol, hexylene glycol, polyethylene glycol (molecular weight 200 to 600), 1,3-butane. Diol etc. are mentioned. 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 a polyamide hollow fiber membrane having high strength, a homogeneous and fine pore size, preferably an aprotic polar solvent, more preferably sulfolane, dimethyl sulfone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, ethylene carbonate, propylene carbonate, particularly preferably sulfolane and dimethyl sulfone. These solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

  Among these solvents, a mixed solvent of sulfolane and dimethyl sulfone is particularly effective in forming a fine pore size, and is preferably used in the present invention. When a mixed solvent of sulfolane and dimethyl sulfone is used, the mixing ratio is, for example, a mass ratio of sulfolane: dimethylsulfone of 100: 50 to 1000, preferably 100: 100 to 500, and more preferably 100: 200 to 400.

  Examples of fatty acid amides to coexist in the polymer solution include monoamides (saturated fatty acid amides, unsaturated fatty acid amides), substituted amides, bisamides (saturated fatty acid bisamides, unsaturated fatty acid bisamides, aromatic bisamides), methylolamides, and ester amides. . Examples of the saturated fatty acid amide include lauric acid amide, palmitic acid amide, stearic acid amide, purified stearic acid amide, high-purity behenic acid amide, and hydroxystearic acid amide. Examples of unsaturated fatty acid amides include purified oleic acid amide and purified erucic acid amide. Examples of the substituted amide include N-oleyl palmitate, N-stearyl stearate, N-stearyl oleate, N-oleyl stearate, N-stearyl erucamide. Examples of methylolamide include methylol stearamide. Examples of saturated fatty acid bisamides include methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis lauric acid amide, ethylene bis stearic acid amide, ethylene bishydroxy stearic acid amide, ethylene bisbehenic acid amide, and hexamethylene bis stearic acid. Examples include amide, hexamethylene bisbehenic acid amide, hexamethylene bishydroxystearic acid amide, N, N′-distearyl adipic acid amide, N, N′-distearyl sebacic acid amide, and the like. Examples of unsaturated fatty acid bisamides include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide, and the like. Is mentioned. Examples of the aromatic bisamide include m-xylylene bis stearic acid amide, m-xylylene bishydroxy stearic acid amide, N, N′-distearyl isophthalic acid amide, and the like. Examples of fatty acid ester amides include stearamide ethyl stearate. Among these fatty acid amides, monoamides and bisamides are preferable, and bisamides are more preferable. Among bisamides, ethylene bislauric acid amide, ethylene bisstearic acid amide, and ethylene bishydroxystearic acid amide are preferable. In addition, fatty acid amide may be used individually by 1 type, and may be used in combination of 2 or more types.

  As the addition amount of the fatty acid amide to the polymer solution, the total mass of the polyamide resin and the solvent in the polymer solution is 100 parts by mass (100% by mass), preferably 0.01 to 5.00 parts by mass (0.01 to 5.00% by mass), more preferably 0.05 to 4.00 parts by mass (0.05 to 4.00% by mass), and still more preferably 0.10 to 3.00 parts by mass (0.15 to 3. 00% by mass).

  Further, in order to control the pore size of the polyamide hollow fiber membrane and improve the performance, additives such as the above-mentioned thickeners, surfactants, crystal nucleating agents and lubricants may be added to the polymer solution as necessary. .

  Although the density | concentration at the time of melt | dissolving a polyamide resin in the said solvent is not limited unless the effect of this invention is impaired, Preferably it is 18-35 mass%, More preferably, it is 20-30 mass%. By satisfy | filling such a density | concentration range, it becomes possible to satisfy internal pressure water permeability within the range mentioned above.

  In addition, when the polyamide resin is dissolved in the solvent, the temperature of the solvent needs to be 100 ° C. or higher. Specifically, it is preferable to dissolve at a temperature 10 to 50 ° C. higher than the phase separation temperature of the system, preferably 20 to 40 ° C. and lower than the boiling point 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 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.

Second Step In the second step, a double tubular nozzle for producing a hollow fiber membrane having a double tube structure is used, and the above polymer solution (film forming stock solution) is discharged from the outer annular nozzle and the inner solution is discharged from the inner nozzle. A hollow fiber membrane is formed by discharging, introducing into a coagulation bath, and drawing at a constant take-up speed.

  Here, as the double tubular nozzle for producing a hollow fiber, any nozzle can be used as long as the effects of the present invention are not impaired. The diameter of the outer annular nozzle and the diameter of the inner nozzle may be appropriately set according to the inner diameter and outer diameter of the polyamide hollow fiber membrane.

  In the second step, as the internal liquid discharged from the nozzle inside the double tubular nozzle, any fluid can be used as long as the effect of the present invention is not impaired, but a liquid is preferable to a gas. The liquid used as the internal liquid is not particularly limited, but when it is desired to enlarge the pores on the inner surface of the polyamide hollow fiber, a good solvent having a high affinity with the polyamide resin is used, and the pores on the inner surface of the polyamide hollow fiber are reduced. If desired, a poor solvent can be used. Specific examples of such good solvents include glycerin, diglycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, glycerol diacetate, γ-butyrolactone, ε-caprolactone, propylene glycol, benzyl alcohol, 1,3 -Butanediol, sulfolane and the like. Specific examples of such a poor solvent include polyethylene glycol (300 to 600), glycerol triacetate, higher fatty acids, liquid paraffin, and the like. These solvents may be used alone or in combination of two or more for adjusting the pore diameter, that is, the bubble point. In addition, when the polymer solution has high viscosity and excellent spinnability, a method of flowing a gas such as an inert gas may be used. Further, inorganic salts such as ammonium chloride, calcium chloride, sodium chloride, potassium chloride, sodium sulfate and the like may be dissolved in the above solvent.

  Among these internal liquids, it is preferable to mix two or more kinds of glycerin, triethylene glycol, tetraethylene glycol, polyethylene glycol 200 to 600, and calcium chloride. Thereby, the bubble point and internal pressure water permeability of a polyamide hollow fiber membrane can be set suitably in said range.

  In the second step, any coagulation bath can be used as long as the effects of the present invention are not impaired. Preferable examples of such a coagulation bath include a coagulation bath containing water, a polyhydric alcohol, or a mixed liquid of polyhydric alcohol and water. Specific examples of the polyhydric alcohol used in the coagulation bath include glycerin, ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, polyethylene glycol (200 to 400), 1,3-butanediol and the like. Among these polyhydric alcohols, glycerin, ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, and polyethylene glycol 200 are particularly suitable for satisfying the internal pressure water permeability of the polyamide hollow fiber within the above-described range. used. These polyhydric alcohols may be used individually by 1 type, and may be used in combination of 2 or more type.

  In addition, when a mixed liquid of polyhydric alcohol and water is used as the coagulation bath, the mixing ratio thereof is not particularly limited. For example, the mass ratio of polyhydric alcohol: water is 25-80: 75-20. , Preferably 30-65: 70-35 is mentioned.

  Although the temperature of a coagulation bath is not specifically limited, Usually, -20-100 degreeC, Preferably it is -10-80 degreeC, More preferably, 0-40 degreeC is mentioned. Since the crystallization speed can be changed by changing the temperature of the coagulation bath, the performance such as bubble point, water permeability, tensile strength and the like can be changed. Generally, when the temperature of the coagulation bath is low, the bubble point increases, and the water permeability decreases and the strength tends to increase.When the temperature of the coagulation bath increases, the bubble point decreases and the water permeability increases and the strength increases. However, it may vary depending on the solubility of the solvent and the internal liquid contained in the polymer solution and the crystallization speed of the resin itself. In order to satisfy the internal pressure water permeability and bubble point of the polyamide hollow fiber membrane within the above-mentioned range, the coagulation bath is preferably at a low temperature, but it is not always necessary to have a low temperature depending on the conditions. When the temperature of the coagulation bath is within the above range, the strength of the membrane can be increased and the energy required for temperature control can be reduced while satisfying the water permeability and bubble point of the polyamide hollow fiber within the above-described ranges.

  Further, the flow rate when the polymer solution is discharged from the outer annular nozzle of the double tubular nozzle for producing hollow fibers is not particularly limited, but is, for example, 2 to 40 g / min, preferably 5 to 30 g / min, and more preferably. 8-20 g / min is mentioned. Further, 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 hollow fiber production, the type of internal liquid used, the flow rate of the polymer solution, etc. Is 0.1 to 2 times, preferably 0.2 to 1 times, and more preferably 0.4 to 0.7 times.

  The take-up speed of the hollow fiber membrane is not particularly limited, but it is sufficient that the membrane does not become flat due to incomplete solidification. Usually, 1-200 m / min, Preferably it is 10-150 m / min, More preferably, 20-100 m / min is mentioned. In order to increase the take-up speed, it is possible to produce a hollow fiber membrane having no flatness by lowering the coagulation bath temperature or using a solvent having a high solidification rate as the solvent of the coagulation bath.

  Thus, by performing the second step, the polymer solution (film forming stock solution) discharged from the hollow fiber manufacturing double tubular nozzle is solidified in a coagulation bath to form a polyamide hollow fiber membrane.

Third Step In the third step, the solvent is removed from the hollow fiber membrane formed in the second step. The method for removing the solvent from the hollow fiber membrane is not particularly limited, and may be a method of evaporating the solvent by drying with a drier, but it is immersed in an extraction solvent to cause phase separation inside the hollow fiber membrane. A method of extracting and removing the existing solvent is preferred. The extraction solvent used for solvent extraction and removal is preferably an inexpensive solvent having a low boiling point that can be easily separated by a difference in boiling point after extraction, such as water, methanol, ethanol, 2-propanol, acetone, diethyl ether, Examples include hexane, petroleum ether, and toluene. Among these, Preferably water, methanol, ethanol, 2-propanol, acetone, More preferably, water is mentioned. Moreover, when extracting the organic solvent insoluble in water, such as a phthalate ester and a fatty acid, 2-propanol, petroleum ether, etc. can be used suitably. In addition, the time for immersing the hollow fiber 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. Can be mentioned. In order to effectively extract and remove the organic solvent remaining in the polyamide hollow fiber, the extraction solvent may be replaced or stirred. In particular, when the polyamide hollow fiber membrane of the present invention is used for semiconductor industry, food industry, water purification, the remaining of impurities, organic solvents, etc. becomes a problem, so the third step is thoroughly performed over time. It is desirable.

  Thus, the polyamide hollow fiber membrane of the present invention is manufactured by performing the third step.

  The apparatus used in the method for producing a polyamide hollow fiber membrane of the present invention is not particularly limited, but a general apparatus used for dry and wet spinning as shown in FIG. 3 is preferable. Taking the apparatus shown in FIG. 3 as an example, the production flow of the polyamide hollow fiber membrane of the present invention will be outlined below. The polymer solution (film forming stock solution) prepared in the first step is accommodated in the container 20. Alternatively, a polymer solution may be prepared by performing the first step of dissolving the resin and the film-forming solvent in the container 20 at a high temperature. The polymer solution accommodated in the container 20 and the internal liquid introduced from the internal liquid inlet 22 are respectively measured by a metering pump 21 and fed to a double tubular nozzle (spinner) 23 for producing a hollow fiber membrane. . The polymer solution discharged from the double tubular nozzle (spinneret) 23 for producing the hollow fiber membrane is introduced into the coagulation bath 24 through the air gap and cooled and solidified. In the process of cooling and solidifying the polymer solution, heat-induced phase separation occurs, and a polyamide hollow fiber membrane 25 having a sea-island structure is obtained. The polyamide hollow fiber membrane 25 thus obtained is taken up by a bobbin winder 27 provided with a bobbin while being taken up by a constant speed take-up machine 26. By removing the solvent of the coagulation bath, the organic solvent that is an island component of the sea-island structure remaining in the hollow fiber membrane, and the internal liquid that has flowed into the hollow portion in the pure water shower 28 simultaneously with winding on the bobbin, A polyamide hollow fiber membrane is obtained.

3. Hollow fiber membrane module using polyamide hollow fiber membrane The polyamide hollow fiber membrane of the present invention is housed in a module case equipped with a liquid inlet to be treated, a permeate outlet, and the like for suitable use as a filtration filter. Used as a hollow fiber membrane module.

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

  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 module in which a hollow fiber membrane bundle is folded and filled into a U shape, and the end of the hollow fiber membrane bundle is cut and opened after opening; hollow A dead-end type module in which a hollow opening at one end of a yarn membrane bundle is closed straight by heat sealing or the like, and the end of the hollow fiber membrane bundle that is open is sealed and cut and opened. A dead-end module in which the hollow fiber membrane bundle is filled straight, both ends of the hollow fiber membrane bundle are sealed and only one end is cut to expose the opening; the hollow fiber membrane bundle is filled straight and hollow For example, a cross flow type module in which both ends of the yarn membrane bundle are sealed, the sealing portions at both ends of the hollow fiber membrane bundle are cut, and two flow paths are formed on the side surface of the filter case.

  The filling rate of the polyamide hollow fiber membrane inserted into the module case is not particularly limited. For example, the volume of the polyamide hollow fiber 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%. -75 volume%, More preferably, 40-65 volume% is mentioned. By satisfying such a filling rate, it is possible to facilitate the filling operation of the polyamide hollow fiber membrane into the module case while ensuring a sufficient filtration area, and to facilitate fluid flow between the hollow fiber membranes.

  The potting agent used for the production of the hollow fiber membrane module is not particularly limited, and examples thereof include polyurethane resin, epoxy resin, polyamide, silicon resin, melamine resin, polyethylene, polypropylene, phenol resin, polyimide, polyurea resin and the like. It is done. 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 polyurethane resin, epoxy resin, polyamide, silicon resin, and polyethylene, and more preferably polyurethane resin, epoxy resin, and polyamide. 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.

  The hollow fiber membrane module using the polyamide hollow fiber membrane of the present invention is used for purification of water, removal of foreign substances, etc. in the fields of semiconductor industry, food industry, pharmaceutical industry, medical product industry and the like. For example, in the field of semiconductor industry, the polyamide hollow fiber membrane module of the present invention showing fineness and high hydrophilicity is extremely effective in recent years when wiring has been miniaturized. In the field of the pharmaceutical industry, removal of viruses has become an important issue in the manufacturing process of blood products and biopharmaceuticals. For example, this is a high bubble point for removing small viruses such as parvoviruses. The polyamide hollow fiber membrane module of the invention is preferably used.

  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, each physical property value of the hollow fiber membrane was measured by the following method.

<Internal pressure water permeability>
Using the apparatus shown in FIG. 1, a hollow fiber membrane having a length of 11 cm was installed, the permeate was collected at a pressure of 0.05 MPa for 5 minutes, and the internal pressure water permeability was calculated by the above-described formula.

<Bubble point>
Using a device as schematically shown in FIG. 2, the bubble point was measured by the following method.
(1) Ten hollow fiber membranes having a length of 20 cm were prepared, bent into a U shape, and heat-sealed at about 1 cm at the end of the opening of the hollow fiber membrane, thereby closing the hollow portion.
(2) A 5 cm long soft nylon tube for air piping (outer diameter 8 mm, inner diameter 6 mm) was prepared, one end was closed with a silicon stopper, and a potting agent (polyurethane resin) was introduced to about 4 cm.
(3) The hollow fiber membrane bundle was inserted into the potting agent from the heat-sealed end and allowed to stand until the potting agent was cured.
(4) After curing, the hollow fiber membrane was cut above the heat-sealed portion to open the hollow portion of the hollow fiber membrane. At this time, it was visually confirmed whether the potting agent did not enter the hollow part or whether the potting agent was filled between the hollow fiber membranes. If the hollow was maintained without any problems, the test was started.
(5) In the bubble point test, it is necessary to fill a liquid in the hole of the hollow fiber membrane. Therefore, the liquid (for example, Fluorinert FC-72 manufactured by Sumitomo 3M, surface tension 12 mN / m at 20 ° C., 2-propanol) used in the test is introduced into the glass container 14, and the above (1) to (4) The produced hollow fiber membrane mini-module 13 was immersed and the pressure was reduced for several seconds to fill the holes with liquid.
(6) The hollow fiber membrane mini-module 13 immersed in the test solution was set as shown in FIG. 2, and air was supplied to the inside of the hollow fiber membrane at 0.4 MPa / min to increase the pressure. First, the pressure when bubbles were generated from the hollow fiber membrane was confirmed, and this was used as the initial bubble point. The pressure was increased as it was, and the pressure when bubbles were generated from almost the entire membrane was confirmed, and this was taken as the burst bubble point.

<Tensile test of hollow fiber membrane>
Nylon hollow fiber membrane is cut to about 10 cm in an environment of room temperature 25 ° C. and humidity 60%, and the hollow fiber membrane is set on Autograph AGS-100G manufactured by Shimadzu Corporation, and the tensile strength and tensile elongation are set to a test length of 50 mm, Measurement was performed at a tensile speed of 50 mm / min and a measurement number n = 5.

<Inner and outer diameter of polyamide hollow fiber membrane>
The inner diameter and outer diameter of the polyamide hollow fiber membrane were measured by observing the cross section of the polyamide hollow fiber membrane 200 times with an optical microscope and calculated as an average value of n = 3.

<Production of polyamide hollow fiber membrane>
Example 1
280 g of polyamide 6 chip (Unitika A1030BRT, relative viscosity 3.53) 280 g, sulfolane (Sumitomo Seika Co., Ltd.) 192 g, dimethyl sulfone (Tokyo Kasei Co., Ltd.) 528 g, ethylenebis stearamide ( 0.10% by mass (1.0 g) (Alfro H-50L, manufactured by NOF Corporation) was stirred and dissolved at 180 ° C. for 1.5 hours to prepare a polymer solution (film forming stock solution). Next, the polymer solution was fed to a spinneret (double tubular nozzle for producing a hollow fiber membrane having a double tube structure) via a metering pump, and extruded at 10 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. In the internal liquid, a glycerin: polyethylene glycol 400 = 4: 6 weight ratio mixed solution was flowed at a feeding rate of 4.0 g / min. The extruded stock solution for spinning was put into a coagulation bath composed of a 40% by mass propylene glycol aqueous solution at 5 ° C. through a 30 mm air gap, cooled and solidified, and wound at a winding speed of 40 m / min. The obtained hollow fiber membrane was immersed in water for 24 hours to extract the solvent, and then dried for 1 hour in a hot air dryer at 50 ° C. to obtain a polyamide hollow fiber membrane.

The obtained polyamide hollow fiber membrane has an outer diameter of 560 μm, an inner diameter of 300 μm, an internal pressure water permeability of 200 L / (m ² · atm · h), an initial bubble point using Fluorinert FC-72 of 0.60 MPa, burst The bubble point was 0.91 MPa. The resulting hollow fiber membrane had a tensile strength of 15.0 MPa and a tensile elongation of 300%. Moreover, the electron micrograph of the obtained hollow fiber membrane is shown in FIG. It was observed that there were dense and uniform pores in the cross section and no macrovoids, and ultrafine and dense pores were observed on both the inner and outer surfaces. For reference, Table 1 shows initial bubble points and burst bubble points using 2-propanol.

Example 2
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in preparing the polymer solution, the solvent of the internal solution was changed to a glycerin: polyethylene glycol 300 = 3: 7 weight ratio mixed solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 240 L / (m ² · atm · h), an initial bubble point of 0.55 MPa, and a burst bubble point of 0.83 MPa. The resulting hollow fiber membrane had a tensile strength of 14.5 MPa and a tensile elongation of 290%.

Example 3
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in the preparation of the polymer solution, the solvent of the internal liquid was changed to a polyethylene glycol 200: polyethylene glycol 400 = 4: 6 weight ratio mixed solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 300 L / (m ² · atm · h), an initial bubble point of 0.45 MPa, and a burst bubble point of 0.80 MPa. The resulting hollow fiber membrane had a tensile strength of 13.0 MPa and a tensile elongation of 280%.

Example 4
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in preparing the polymer solution, a mixed solution of glycerin: calcium chloride = 99: 1 by weight, in which the solvent of the internal solution was uniformly mixed, was used. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 200 L / (m ² · atm · h), an initial bubble point of 0.56 MPa, and a burst bubble point of 0.90 MPa. The resulting hollow fiber membrane had a tensile strength of 14.0 MPa and a tensile elongation of 270%.

Example 5
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in the preparation of the polymer solution, the solvent of the internal solution was glycerin in which calcium chloride was dissolved at a concentration of 4% by weight. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 70 L / (m ² · atm · h), an initial bubble point of 0.85 MPa, and a burst bubble point of 1.12 MPa. The resulting hollow fiber membrane had a tensile strength of 13.5 MPa and a tensile elongation of 250%.

Example 6
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in the preparation of the polymer solution, the addition amount of ethylenebisstearic acid amide as an additive was changed to 0.5% by mass (5.0 g). The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 170 L / (m ² · atm · h), an initial bubble point of 0.75 MPa, and a burst bubble point of 1.05 MPa. The resulting hollow fiber membrane had a tensile strength of 15.5 MPa and a tensile elongation of 290%.

Example 7
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in the preparation of the polymer solution, the addition amount of ethylenebisstearic acid amide as an additive was 1.5% by mass (15 g). The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 110 L / (m ² · atm · h), an initial bubble point of 0.89 MPa, and a burst bubble point of 1.20 MPa. The resulting hollow fiber membrane had a tensile strength of 16.5 MPa and a tensile elongation of 280%.

Example 8
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in the preparation of the polymer solution, the additive amount of ethylenebisstearic acid amide as an additive was changed to 4.5% by mass (45 g). The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 50 L / (m ² · atm · h), an initial bubble point of 0.94 MPa, and a burst bubble point of 1.21 MPa. The resulting hollow fiber membrane had a tensile strength of 18.5 MPa and a tensile elongation of 220%.

Example 9
A polyamide hollow fiber membrane was prepared in the same manner as in Example 1 except that ethylene bislauric acid amide was used as the additive in the preparation of the polymer solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 300 L / (m ² · atm · h), an initial bubble point of 0.48 MPa, and a burst bubble point of 0.63 MPa. The resulting hollow fiber membrane had a tensile strength of 13.0 MPa and a tensile elongation of 270%.

Example 10
A polyamide hollow fiber membrane was prepared in the same manner as in Example 1 except that ethylenebishydroxystearic acid amide was used as the additive in the preparation of the polymer solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 150 L / (m ² · atm · h), an initial bubble point of 0.65 MPa, and a burst bubble point of 0.89 MPa. The resulting hollow fiber membrane had a tensile strength of 13.5 MPa and a tensile elongation of 280%.

Example 11
A polyamide hollow fiber membrane was prepared in the same manner as in Example 1 except that stearamide was used as the additive in the preparation of the polymer solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 350 L / (m ² · atm · h), an initial bubble point of 0.42 MPa, and a burst bubble point of 0.60 MPa. The resulting hollow fiber membrane had a tensile strength of 12.0 MPa and a tensile elongation of 260%.

Example 12
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that in the preparation of the polymer solution, the additive was methylene bis stearamide. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 290 L / (m ² · atm · h), an initial bubble point of 0.55 MPa, and a burst bubble point of 0.75 MPa. The resulting hollow fiber membrane had a tensile strength of 14.0 MPa and a tensile elongation of 270%.

Example 13
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that a polyamide 610 chip (CM2001 manufactured by Toray Industries, Inc.) was used as the polyamide resin in the preparation of the polymer solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 70 L / (m ² · atm · h), an initial bubble point of 0.59 MPa, and a burst bubble point of 0.84 MPa. The resulting hollow fiber membrane had a tensile strength of 13.0 MPa and a tensile elongation of 300%.

Example 14
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that a polyamide MXD6 chip (S6121 manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used as the polyamide resin in the preparation of the polymer solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 150 L / (m ² · atm · h), an initial bubble point of 0.55 MPa, and a burst bubble point of 0.80 MPa. The resulting hollow fiber membrane had a tensile strength of 12.0 MPa and a tensile elongation of 200%.

Comparative Example 1
The internal pressure water permeability, bubble point, tensile strength, and tensile elongation of a commercially available polyamide 6 flat membrane filter (nominal pore diameter 10 nm) were measured. As a result, the internal pressure water permeability was 490 L / (m ² · atm · h), the initial bubble point was 0.15 MPa, and the burst bubble point was 0.21 MPa. The flat film had a tensile strength of 2.8 MPa and a tensile elongation as low as 90%.

Comparative Example 2
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that no additive was added in the preparation of the polymer solution. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 250 L / (m ² · atm · h), an initial bubble point of 0.35 MPa, and a burst bubble point of 0.40 MPa. The resulting hollow fiber membrane had a tensile strength of 14.1 MPa and a tensile elongation of 310%.

Comparative Example 3
A polyamide hollow fiber membrane was produced in the same manner as in Comparative Example 2 except that the internal liquid was single. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 600 L / (m ² · atm · h), an initial bubble point of 0.26 MPa, and a burst bubble point of 0.31 MPa. The resulting hollow fiber membrane had a tensile strength of 13.0 MPa and a tensile elongation of 250%.

Comparative Example 4
In the preparation of the polymer solution, polyamide 6 chips (Unitika A1030BRT, relative viscosity 3.53) 170 g, sulfolane (Sumitomo Seika Co., Ltd.) 221 g, dimethyl sulfone (Tokyo Kasei Co., Ltd.) 609 g A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that. The obtained polyamide hollow fiber membrane had an internal pressure water permeability of 4500 L / (m ² · atm · h), an initial bubble point of 0.11 MPa, and a burst bubble point of 0.13 MPa. The resulting hollow fiber membrane had a tensile strength of 7.1 MPa and a tensile elongation of 130%.

<Summary of physical properties of polyamide hollow fiber membrane>
Table 1 summarizes the production conditions and physical property values of the polyamide hollow fiber membranes of Examples 1 to 14 and Comparative Examples 1 to 4. From these results, when a fatty acid amide is allowed to coexist in the polymer solution, a liquid having a surface tension of 12 mN / m at 20 ° C. and an air pressure is applied, the initial bubble point is 0.40 MPa or more, and the burst bubble point is 0.00. High-performance polyamide hollow fiber having a pressure of 55 MPa or more, an internal pressure water permeability of 50 L / (m ² · atm · h) or more, a tensile strength of 12.0 MPa or more, and a tensile elongation of 150% or more It was revealed that a film was obtained (see Example 1-14).

The annotations in Table 1 are as follows.
PA6: Polyamide 6
PA610: Polyamide 610
MXD6: Polyamide MXD6
PA6 flat membrane: Polyamide 6 flat membrane PSf UF membrane: Polysulfone ultrafiltration membrane PEG200: Polyethylene glycol 200
PEG300: Polyethylene glycol 300
PEG400: Polyethylene glycol 400
Gly: Glycerin CaCl ₂ : Calcium chloride IBP: Initial bubble point BBP: Burst bubble point In addition, “〃” in the table indicates the same condition as the above cell.

Example 15: Production of cross-flow type module The hollow fiber membrane obtained in Example 1 was cut into a length of 250 mm, 50 bundles were bundled, and both ends were fused and sealed using a heat sealer. As the module case, a cylindrical pipe made of vinyl chloride having an outer diameter of 20 mm, an inner diameter of 17 mm, and a length of 140 mm, each having a water inlet / outlet at a portion of 35 mm from both ends, was produced. Next, a PTFE pot having the same outer diameter as the module case and 25 mm long is filled with a two-component polyurethane potting agent manufactured by Sanyu Rec Co., Ltd. It was pushed in until it hits the bottom of a polytetrafluoroethylene (PTFE) pot. It left still in this state for 10 hours, and potted one end. After solidification, the PTFE pot was pulled out while being pulled, and the polyurethane resin coming out of the module case was cut together with the membrane bundle to expose the hollow portion. The end portion of the other membrane bundle was similarly potted and cut, so that the hollow portions were exposed at both ends. A cap having a water inlet / outlet on both ends was attached and adhered, and a cross flow type module was produced (see A in FIG. 5). The effective membrane length of this cross flow type module was 115 mm × 50.

Example 16: Production of dead-end module The hollow fiber membrane obtained in Example 1 was cut into a length of 200 mm, 50 bundles were bundled and bent into a U shape, and the ends were fused and sealed using a heat sealer. did. The module case was a cylindrical pipe made of vinyl chloride having an outer diameter of 20 mm, an inner diameter of 17 mm, and a length of 60 mm. Next, a PTFE pot having the same outer diameter as the module case and 25 mm long is filled with a two-component polyurethane potting agent manufactured by Sanyu Rec Co., Ltd., and one end of the filter case is attached to the top, and a U-shaped membrane bundle is attached. Was pushed in from the top until it hits the bottom of the PTFE pot. In this state, it was allowed to stand for 10 hours and potted. After solidification, the PTFE pot was pulled out while being pulled, and the polyurethane resin coming out of the module case was cut together with the membrane bundle to expose the hollow portion. A cap having a water inlet / outlet was put on both ends of the module case and adhered, and a dead-end type module was produced (see B in FIG. 5). The effective membrane length of this dead-end type module was 80 mm × 50.

1: liquid feed pump 2: hollow fiber membrane 3: inlet side pressure gauge 4: outlet side pressure gauge 5: two-way valve 6: injection needle 7: receiving pan 8: air inlet 9: regulator 10: pressure increasing tank 11: speed Controller 12: Pressure sensor 13: Hollow fiber membrane module 14: Glass container 15: Fluorinert FC-72 liquid 16: Digital pressure indicator 17: Two-way valve 18: Stirring motor 19: Pressurized gas inlet 20: Container 21: Determination Pump 22: Internal liquid inlet 23: Double tubular nozzle for producing hollow fibers (spinner)
24: Coagulation bath 25: Polyamide hollow fiber membrane 26: Constant speed take-up machine 27: Bobbin winder 28: Pure water shower

Claims (6)

A polyamide hollow fiber membrane formed of a polyamide resin,
In a bubble point test in which air pressure is applied in a liquid having a surface tension of 12 mN / m at 20 ° C., the initial bubble point is 0.40 MPa or more, and the burst bubble point is 0.55 MPa or more,
A polyamide hollow fiber membrane having an internal pressure water permeability using pure water at 25 ° C. of 50 L / (m ² · atm · h) or more.   The polyamide hollow fiber membrane according to claim 1, which has a tensile strength of 12.0 MPa or more and a tensile elongation of 150% or more at a temperature of 25 ° C and a humidity of 60%.   The polyamide hollow fiber according to claim 1 or 2, wherein the polyamide resin is at least one selected from the group consisting of polyamide 6, polyamide 66, polyamide 46, polyamide 610, polyamide 11, polyamide 12, and polyamide MXD6. film.   A hollow fiber membrane module in which the polyamide hollow fiber membrane according to any one of claims 1 to 3 is accommodated in a module case. A method for producing a polyamide hollow fiber membrane by a thermally induced phase separation method, in which a polymer solution containing a polyamide resin and a solvent is cooled, and the polyamide resin is phase-separated and solidified.
A method for producing a polyamide hollow fiber membrane, wherein a fatty acid amide is allowed to coexist in the polymer solution.   6. The polyamide hollow fiber membrane according to claim 5, wherein the total mass of the polyamide resin and the solvent in the polymer solution is 100 parts by mass, and the addition amount of the fatty acid amide is in the range of 0.01 to 5.00 parts by mass. Production method.