JP6405177B2 - 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 resins having relatively high hydrophilicity, but they are often produced by the NIPS method, and there is a problem that the film strength is weak because an on-finger 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.

The bubble point test is a general method used to determine the maximum pore size of the membrane. When 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). The higher the bubble point, the smaller the maximum pore size of the membrane. Conventionally, bubble points using 2-propanol have also 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)).

  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. However, 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 due to the adsorption effect of the polyamide material.

  Patent Document 9 discloses a polyamide hollow fiber membrane module and studies 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, it has been found that a polyamide hollow fiber membrane having a high bubble point and a high water permeability can be obtained according to the method for producing a polyamide hollow fiber membrane including the following first to third steps. 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.
First step: A film forming stock solution is prepared by dissolving a polyamide resin 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.
Second step: Using a double tubular nozzle for producing a hollow fiber having a double tube structure, the film-forming stock solution is discharged from an outer annular nozzle, and from diglycerin, polyethylene glycol 200, and dipropylene glycol from the inner nozzle. An internal liquid containing at least one selected from the group is discharged, discharged, and immersed in a coagulation bath to form a hollow fiber membrane.
Third step: The organic solvent is removed from the hollow fiber membrane formed in the second step.

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 the bubble point test in which air pressure was applied in 2-propanol, the initial bubble point was 0.35 MPa or more, and the burst bubble point was 0.40 MPa or more,
A polyamide hollow fiber membrane having an external pressure water permeability of 100 L / (m ² · atm · h) or more at 25 ° C. using pure water.
Item 2. Item 2. The polyamide hollow fiber membrane according to Item 1, having a tensile strength of 10.0 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 process for producing a polyamide hollow fiber membrane comprising the following first to third steps:
A first step of preparing a film-forming stock solution in which a polyamide resin is dissolved 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 .;
Using a double tubular nozzle for producing a hollow fiber having a double tube structure, the film-forming stock solution is discharged from the outer annular nozzle and selected from the group consisting of diglycerin, polyethylene glycol 200, and dipropylene glycol from the inner nozzle. A second step of discharging the internal liquid containing at least one kind and immersing it in a coagulation bath to form a hollow fiber membrane; and a step of removing the organic solvent from the hollow fiber membrane formed in the second step. 3 steps.

  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 external 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 of the inner surface observed, and D is a photograph of the outer surface observed. A is a photograph observing the appearance of the crossflow-type hollow fiber membrane module obtained in Example 14, and B is a photograph observing the appearance of the dead-end hollow fiber membrane module obtained in Example 15.

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 2-propanol, the initial bubble point is 0.35 MPa or more, Moreover, the burst bubble point is 0.40 MPa or more, and the external pressure water permeability using pure water at 25 ° C. is 100 L / (m ² · atm · h) or more. 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.

  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. The reason is that in the cutting-edge field, it is necessary to capture fine particles, gels, and the like, and the flow rate has a great influence on 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 is characterized by having an initial bubble point of 0.35 MPa or more and a burst bubble point of 0.40 MPa or more in a bubble point test in which air pressure is applied in 2-propanol. Furthermore, the polyamide hollow fiber membrane of the present invention preferably has an initial bubble point of 0.40 MPa or more and a burst bubble point of 0.45 MPa or more, an initial bubble point of 0.45 MPa or more, and a burst bubble point. Is preferably 0.50 MPa or more. This is because if the burst bubble point is less than 0.40 MPa, the pore size is large and high accuracy cannot be expected for filtration. The upper limit of the burst bubble point is about 0.85 MPa. Thus, the polyamide hollow fiber membrane of the present invention in which both the initial bubble point and the burst bubble point have high values can be produced by the production method of the present invention described later.

  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.

  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.

  In the present invention, when performing a bubble point test of a polyamide hollow fiber membrane, several polyamide hollow fiber membranes are bundled in a U shape and inserted into a filter case, and the end of the opening is made of urethane resin or the like inside the filter case. After being hardened, it is cut and the hollow part is exposed to produce a mini module.

  In the bubble point test of the present invention, 2-propanol is used. Since the value of the bubble point test varies depending on the surface tension of the solution to be immersed, use 2-propanol with the highest purity as much as possible. Propene is penetrated firmly into the membrane by operations such as sending propanol to the mini-module.

  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 high burst bubble point, and has an external pressure water permeability of 100 L / (m ² · atm · h using pure water at 25 ° C. ) Or more. In the present invention, the external pressure water permeability is the water permeability when water is permeated by applying pressure from the outside to the inside of the hollow fiber membrane, and is an index indicating the permeation performance of the polyamide hollow fiber membrane. The external pressure water permeability varies depending on the hole diameter. For this reason, as a standard external pressure water permeation amount for each bubble point in the polyamide hollow fiber membrane of the present invention, in a hollow fiber membrane having a burst bubble point of 0.66 to 0.85 MPa, 100 L / (m ² · atm · h) or higher, more preferably 150 L / (m ² · atm · h) or higher. Moreover, in the hollow fiber membrane having a burst bubble point of 0.51 to 0.65 MPa, it is preferably 200 L / (m ² · atm · h) or more, and 300 L / (m ² · atm · h) or more. More preferably. Furthermore, in the hollow fiber membrane having a burst bubble point of 0.51 to 0.40 MPa, it is preferably 400 L / (m ² · atm · h) or more, and 1000 L / (m ² · atm · h) or more. More preferably. Since the polyamide hollow fiber membrane of the present invention has such high external 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 amount of external pressure water permeation using pure water at 25 ° C. is usually 2500 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 external pressure water permeability of the polyamide hollow fiber membrane is a value measured by external pressure filtration using pure water at 25 ° C., and specifically measured by the method described in the examples below. Value. The outline of the method for measuring the external pressure water permeability of the polyamide hollow fiber membrane will be described with reference to FIG. As shown in FIG. 1, the hollow fiber membrane is cut into 9 to 12 cm, the injection needles having a diameter matching the inner diameter are inserted into the hollow portions at both ends, one injection needle is sealed with a cap 7, and the other injection needle 1 is connected to the discharge port 8 and set in the apparatus as shown in FIG. 1, and then the pure water is passed through the liquid feed pump 1 for a predetermined time (time) and the valve of the two-way valve 6 is adjusted to be constant. The volume (L) of water stored in the tray 9 through the membrane is measured as the amount of permeated water, and calculated by the following equation. The pressure is measured from the average value of the inlet pressure 4 and the outlet pressure 5 in FIG.

External pressure water permeability = permeate water volume (L) / [outer diameter (m) × 3.14 × length (m) × {(inlet pressure (atm) + outlet pressure (atm)) / 2} × time (h)]

  Although it does not restrict | limit especially as a tensile strength of the polyamide hollow fiber membrane of this invention, Preferably it is 10-30 MPa, More preferably, it is 11-25 MPa, More preferably, 12-20 MPa is 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 were measured at a test length of 50 mm, a tensile speed of 50 mm / min, and a number of measurements = 5, respectively, in accordance with JIS 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 can be produced by employing specific production conditions by the TIPS method. Specifically, the polyamide hollow fiber membrane of the present invention is produced through the following first to third steps.
First step: A film forming stock solution is prepared by dissolving a polyamide resin 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.
Second step: Using a double tubular nozzle for producing a hollow fiber having a double tube structure, the film-forming stock solution is discharged from an outer annular nozzle, and from diglycerin, polyethylene glycol 200, and dipropylene glycol from the inner nozzle. An internal liquid containing at least one selected from the group is discharged and immersed in a coagulation bath to form a hollow fiber membrane.
Third step: The organic 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 film forming stock solution is prepared by dissolving a polyamide resin 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.

  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 esters, glycols, organic acids and organic acid esters, Examples include alcohols and glycols. 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 organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

  Among the organic solvents, in particular, 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.

  Further, in order to control the pore diameter of polyamide hollow fiber membranes and improve performance, additives such as thickeners, surfactants, crystal nucleating agents and lubricants may be added to these organic solvents as necessary. Good.

  Although the density | concentration at the time of melt | dissolving a polyamide resin in the said organic 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 satisfying such a concentration range, it is possible to satisfy the external pressure permeation amount and the particle rejection rate within the above-described range.

  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, 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 having a double-pipe structure is used, and the film-forming stock solution is discharged from an outer annular nozzle and diglycerin, polyethylene glycol 200, and di- An internal liquid containing at least one selected from the group consisting of propylene glycol is discharged and immersed in a coagulation bath to form a hollow fiber membrane.

  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, the internal liquid discharged from the inner nozzle of the double tubular nozzle is an internal liquid containing at least one selected from the group consisting of diglycerin, polyethylene glycol 200, and dipropylene glycol. Use. In the present invention, a polyamide hollow fiber membrane having a high bubble point and a high water permeability as described above is obtained by forming a hollow fiber membrane using such a specific internal liquid in step 2. Furthermore, by using such a specific internal liquid in Step 2, a polyamide hollow fiber membrane having a high tensile strength and a high tensile elongation as described above can be obtained.

  In step 2, the internal liquid may contain a liquid other than diglycerin, polyethylene glycol 200, and dipropylene glycol. Such a liquid is not particularly limited. However, 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 when it is desired to reduce the pores on the inner surface of the polyamide hollow fiber. An anti-solvent can be used. Specific examples of such good solvents include glycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, glycerol diacetate, γ-butyrolactone, ε-caprolactone, propylene glycol, benzyl alcohol, 1,3-butanediol, sulfolane and the like. Can be mentioned. 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 the internal liquid used in Step 2 of the present invention, when using the other liquid described above, the total ratio of diglycerin, polyethylene glycol 200, and dipropylene glycol in the internal liquid is preferably 10% by mass or more, More preferably, it is 50 mass% or more, More preferably, 70 mass% or more is mentioned.

  Furthermore, inorganic salts such as ammonium chloride, calcium chloride, sodium chloride, potassium chloride, sodium sulfate may be dissolved in the internal solution and used.

  In the second step, any solidification 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. By employing such a coagulation bath, it is possible to form a polyamide hollow fiber having the above characteristics. 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 satisfy the external pressure water permeability and particle rejection of the polyamide hollow fiber within the above-described ranges. It is particularly preferably used above. 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 40-70: 60-30 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 rate can be changed by changing the temperature of the coagulation bath, performances such as bubble point, external pressure water permeability, tensile strength, etc. 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 solution contained in the film-forming stock solution and the crystallization speed of the resin itself. In order to satisfy the external pressure water permeability and the 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. If 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 external pressure water permeability and bubble point of the polyamide hollow fiber within the aforementioned range. .

  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 for example 2 to 40 g / min, preferably 5 to 30 g / min, Preferably 8-20 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, and the like. 0.1 to 2 times, preferably 0.2 to 1 times, and more preferably 0.4 to 0.7 times the flow rate.

  The take-up speed of the hollow fiber membrane is not particularly limited, but it is good if 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 carrying out the second step, the membrane forming stock solution discharged from the double tubular nozzle for producing hollow fibers 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. Especially when the polyamide hollow fiber membrane of the present invention is used for semiconductor industry, food industry, and water purification, the remaining of impurities, organic solvents, etc. becomes a problem. It is desirable to do.

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

  The production of the polyamide hollow fiber membrane of the present invention may be carried out through the first to third steps described above, and the apparatus used for the production is not particularly limited, but is preferably dry and wet as shown in FIG. The general apparatus used for spinning is mentioned. 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 film-forming stock solution prepared in the first step is accommodated in the container 22. Or you may implement the 1st process of melt | dissolving resin and a film-forming solvent in the container 22 under high temperature, and may prepare a film-forming stock solution. The film-forming stock solution accommodated in the container 22 and the internal liquid introduced from the internal liquid introduction port 24 are respectively measured by the metering pump 23 and fed to the double tubular nozzle (spinning nozzle) 25 for producing hollow fibers. . The raw film forming solution discharged from the double tubular nozzle (spinneret) 25 for producing hollow fibers is introduced into the coagulation bath 26 through a slight air gap, and is cooled and solidified. In the process of cooling and solidifying the membrane-forming stock solution, heat-induced phase separation occurs, and a polyamide hollow fiber membrane 27 having a sea-island structure is obtained. The polyamide hollow fiber membrane 27 thus obtained is taken up by a bobbin winder 29 provided with a bobbin while being taken up by a constant speed take-up machine 28. By removing the coagulation bath solvent and the organic solvent which is an island component of the sea-island structure remaining in the hollow fiber membrane, and the internal liquid poured into the hollow portion in the pure water shower 30 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.

<External pressure water permeability>
Using an apparatus as schematically 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 external pressure water permeability was calculated by the above 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 in a U shape, and heat sealed at about 1 cm at the end of the opening of the hollow fiber membrane to close 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 up 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 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,
2-Propanol used in the test is introduced into the glass container 16 and the above (1) to ((
The hollow fiber membrane mini-module 15 produced in 4) was immersed, and the liquid was filled into the holes by reducing the pressure for several seconds.
(6) The hollow fiber membrane mini-module 15 immersed in 2-propanol was set as shown in FIG. 2, and air was sent 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>
The polyamide hollow fiber membrane is cut to about 10 cm, and this is set on an autograph AGS-100G manufactured by Shimadzu Corporation. The tensile strength and tensile elongation are measured at a test length of 50 mm, a tensile speed of 50 mm / min, and a measurement number = 5. did.

<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
260 g of polyamide 6 chip (Unitika A1030BRT, relative viscosity 3.53) 260 g, sulfolane (Tokyo Kasei Co., Ltd.) 197 g, dimethyl sulfone (Tokyo Kasei Co., Ltd.) 543 g at 180 ° C. for 1.5 hours. A film-forming stock solution was prepared by stirring and dissolving. The stock solution was sent to a spinneret (double tubular nozzle for producing a hollow fiber 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 200 = 1: 1 weight ratio mixing liquid was allowed to flow at a feed rate of 4.0 g / min. The extruded stock solution for spinning was put into a coagulation bath made of 60 mass% propylene glycol aqueous solution at 5 ° C. through a 10 mm air gap, cooled and solidified, and wound at a winding speed of 40 m / min. The obtained hollow fiber was immersed in water for 24 hours to extract the solvent, and then dried with a hot air dryer at 50 ° C. for 1 hour to obtain a polyamide hollow fiber membrane.

The obtained polyamide hollow fiber membrane has an outer diameter of 550 μm, an inner diameter of 300 μm, an external pressure water permeability of 450 L / (m ² · atm · h), an initial bubble point of 0.53 MPa, and a burst bubble point of 0.60 MPa. there were. The resulting hollow fiber membrane had a tensile strength of 15.0 MPa and a tensile elongation of 250%. 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 macro voids, and many dense pores were observed on both the inner and outer surfaces.

Example 2
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that the coagulation bath was changed to a 45% by mass propylene glycol aqueous solution. The obtained polyamide hollow fiber membrane had a water permeability of 230 L / (m ² · atm · h), an initial bubble point of 0.55 MPa, and a burst bubble point of 0.64 MPa. The resulting hollow fiber membrane had a tensile strength of 16.0 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 the coagulation bath was changed to a glycerin: 2-propanol = 7: 3 mass mixed solution. The obtained polyamide hollow fiber membrane had a water permeability of 200 L / (m ² · atm · h), an initial bubble point of 0.45 MPa, and a burst bubble point of 0.50 MPa. The resulting hollow fiber membrane had a tensile strength of 10.0 MPa and a tensile elongation of 200%.

Example 4
A polyamide hollow fiber membrane was obtained in the same manner as in Example 1, except that the membrane-forming stock solution was extruded at 25 g / min, the internal solution was fed at 10 g / min, and wound up at a winding speed of 100 m / min. The obtained polyamide hollow fiber membrane had a water permeability of 160 L / (m ² · atm · h), an initial bubble point of 0.50 MPa, and a burst bubble point of 0.56 MPa. The resulting hollow fiber membrane had a tensile strength of 14.0 MPa and a tensile elongation of 280%.

Example 5
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that N-methyl-2-pyrrolidone was used as sulfolane, which is one of the solvents for the membrane-forming stock solution. The obtained polyamide hollow fiber membrane had an external pressure water permeability of 130 L / (m ² · atm · h), an initial bubble point of 0.40 MPa, and a burst bubble point of 0.52 MPa. The resulting hollow fiber membrane had a tensile strength of 10.0 MPa and a tensile elongation of 160%.

Example 6
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that diglycerin was used as the solvent for the inner solution in the preparation of the membrane forming stock solution. The obtained polyamide hollow fiber membrane had an external pressure water permeability of 240 L / (m ² · atm · h), an initial bubble point of 0.60 MPa, and a burst bubble point of 0.65 MPa. The resulting hollow fiber membrane had a tensile strength of 14.0 MPa and a tensile elongation of 210%.

Example 7
A polyamide hollow fiber membrane was prepared in the same manner as in Example 1 except that the polyamide 6 tip was changed to 180 g, the solvent was sulfolane 219 g, and dimethyl sulfone 601 g, and the coagulation bath was changed to pure water. . The obtained polyamide hollow fiber membrane had an external pressure water permeability of 500 L / (m ² · atm · h), an initial bubble point of 0.50 MPa, and a burst bubble point of 0.60 MPa. The resulting hollow fiber membrane had a tensile strength of 15.0 MPa and a tensile elongation of 260%.

Example 8
In the preparation of the membrane forming stock solution, the polyamide 6 chip was 350 g, the solvent was sulfolane 173 g, and dimethyl sulfone 477 g, the membrane forming stock solution was flowed at 6.0 g / min, and the internal solution was flowed at 4.0 g / min. Except for the above, a polyamide hollow fiber membrane was produced in the same manner as in Example 1. The obtained polyamide hollow fiber membrane has an outer diameter of 480 μm, an inner diameter of 300 μm, an external pressure water permeability of 100 L / (m ² · atm · h), an initial bubble point of 0.65 MPa, and a burst bubble point of 0.75 MPa. there were. The resulting hollow fiber membrane had a tensile strength of 20.0 MPa and a tensile elongation of 240%.

Example 9
In Example 1, a hollow fiber membrane was similarly produced except that the internal liquid was polyethylene glycol 200 and the coagulation bath temperature was changed to 40 ° C. The obtained polyamide hollow fiber membrane had an external pressure water permeability of 350 L / (m ² · atm · h), an initial bubble point of 0.45 MPa, and a burst bubble point of 0.48 MPa. The resulting hollow fiber membrane had a tensile strength of 12.0 MPa and a tensile elongation of 210%.

Example 10
A polyamide hollow fiber membrane was produced in the same manner as in Example 1 except that the internal liquid was changed to polyethylene glycol 200: polyethylene glycol 400 = 1: 1. The obtained polyamide hollow fiber membrane had an external pressure water permeability of 300 L / (m ² · atm · h), an initial bubble point of 0.60 MPa, and a burst bubble point of 0.68 MPa. The resulting hollow fiber membrane had a tensile strength of 13.0 MPa and a tensile elongation of 240%.

Example 11
A polyamide hollow fiber membrane was prepared in the same manner as in Example 1 except that polyamide 6 (A1050 manufactured by Unitika Ltd., relative viscosity 5.79) was used as the polyamide resin in the preparation of the membrane forming stock solution. The obtained polyamide hollow fiber membrane had an external pressure water permeability of 210 L / (m ² · atm · h), an initial bubble point of 0.50 MPa, and a burst bubble point of 0.53 MPa. The resulting hollow fiber membrane had a tensile strength of 13.0 MPa and a tensile elongation of 250%.

Example 12
A polyamide hollow fiber membrane was prepared 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 membrane forming stock solution. The obtained polyamide hollow fiber membrane had an external water permeability of 120 L / (m ² · atm · h), an initial bubble point of 0.55 MPa, and a burst bubble point of 0.65 MPa. The resulting hollow fiber membrane had a tensile strength of 16.0 MPa and a tensile elongation of 160%.

Example 13
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 membrane forming stock solution. The obtained polyamide hollow fiber membrane had an external pressure water permeability of 100 L / (m ² · atm · h), an initial bubble point of 0.53 MPa, and a burst bubble point of 0.58 MPa. The resulting hollow fiber membrane had a tensile strength of 10.0 MPa and a tensile elongation of 150%.

Comparative Example 1
The 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 water permeability was 480 L / (m ² · atm · h), the initial bubble point was 0.26 MPa, and the burst bubble point was 0.37 MPa. The tensile strength of this flat membrane was 2.3 MPa, and the tensile elongation was low with 50%.

Comparative Example 2
The water permeability, bubble point, tensile strength, and tensile elongation of a commercially available polysulfone hollow fiber ultrafiltration membrane were measured. As a result, the water permeability was 51 L / (m ² · atm · h), the initial bubble point was 0.48 MPa, and the burst bubble point was 0.82 MPa. The tensile strength of this hollow fiber membrane was 6.8 MPa, and the tensile elongation was as low as 31%.

<Summary of physical properties of polyamide hollow fiber membrane>
Table 1 shows the production conditions and physical property values of the polyamide hollow fiber membranes of Examples 1 to 13 and Comparative Examples 1 and 2. From these results, the initial bubble point is 0.35 MPa or more and the burst bubble point is 0.40 MPa or more by adopting a specific composition as the film forming stock solution, the internal solution, and the coagulation bath, A high-performance polyamide hollow fiber membrane having an external pressure water permeability of 100 L / (m ² · atm · h) or more, a tensile strength of 10.0 MPa or more, and a tensile elongation of 150% or more is obtained. Became clear (see Example 1-13).

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
IBP: Initial bubble point BBP: Burst bubble point In addition, “〃” in the table indicates the same condition as the upper cell.

Example 14: 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 fusion 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 15: Production of dead-end type 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: external pressure water permeability measuring jig 4: inlet side pressure gauge 5: outlet side pressure gauge 6: two-way valve 7: injection needle 8: cap 9: saucer 10: air flow Inlet 11: Regulator 12: Booster tank 13: Speed controller 14: Pressure sensor 15: Hollow fiber membrane module 16: Glass container 17: 2-propanol solution 18: Digital pressure indicator 19: Two-way valve 20: Stirring motor 21: Pressurized gas inlet 22: Container 23: Metering pump 24: Internal liquid inlet 25: Double tubular nozzle for producing hollow fiber (spinner)
26: Coagulation bath 27: Polyamide hollow fiber membrane 28: Constant speed take-up machine 29: Bobbin winder 30: Pure water shower

Claims (5)

A polyamide hollow fiber membrane formed of a polyamide resin,
In the bubble point test in which air pressure was applied in 2-propanol, the initial bubble point was 0.60 MPa or more and the burst bubble point was 0.65 MPa or more and 0.85 MPa or less ,
The external pressure water permeability using pure water at 25 ° C. is 240 L / (m ² · atm · h) or more.
Polyamide hollow fiber membrane.   The polyamide hollow fiber membrane according to claim 1, having a tensile strength of 10.0 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 process for producing a polyamide hollow fiber membrane comprising the following first to third steps:
A first step of preparing a film-forming stock solution in which a polyamide resin is dissolved 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. at a concentration of 20 to 30% by mass ;
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 selected from the group consisting of diglycerin and polyethylene glycol 200 / polyethylene glycol 400 from the inner nozzle. A second step of discharging the internal liquid containing at least one kind and immersing it in a coagulation bath to form a hollow fiber membrane; and a step of removing the organic solvent from the hollow fiber membrane formed in the second step. 3 steps.