JP2010240535A - Hollow fiber membrane and method of manufacturing hollow fiber membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hollow fiber membrane which is composed of nylon 12 and/or a copolymer including nylon 12, and also, has appropriate water permeability and excellent tensile strength. <P>SOLUTION: This hollow fiber membrane is made by dissolving nylon 12 and/or the copolymer containing nylon 12 and a high boiling point solvent such as an aprotic polar solvent e.g. sulfolane, at not less than 100&deg;C in thermal induced phase separation process. In addition, the hollow fiber membrane has a tensile strength of not less than 5 MPa and a water permeability of not less than 100 L/m<SP>2</SP>&times;atm&times;h. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a hollow fiber membrane having excellent strength and appropriate water permeability.

  In recent years, porous filtration membranes such as ultrafiltration membranes and microfiltration membranes have been used in many industrial fields such as water treatment fields such as drinking water production and water and sewage treatment, medical fields such as blood purification, and food industries. Advances have been made in porous filtration membranes with various pore sizes. In particular, a filtration membrane having a pore size of nm to μm, which is frequently used as a porous filtration membrane, is often produced by utilizing phase separation of an organic polymer solution. This method can be applied to many organic polymer compounds and is easy to industrialize, so it is currently the mainstream for industrial production of filtration membranes.

  Phase separation methods can be roughly divided into a non-solvent induced phase separation method (NIPS method) and a thermally induced phase separation method (TIPS method). In the NIPS method, a uniform polymer solution undergoes phase separation due to the concentration change due to the ingress of non-solvent or evaporation of the solvent to the external atmosphere. On the other hand, the TIPS method is a relatively new method, and phase separation is achieved by cooling a uniform polymer solution dissolved at a high temperature to a temperature below the binodal line that is the boundary between the one-phase region and the two-phase region. Induced and fixed structure by polymer crystallization and glass transition.

  Conventionally, polyolefins such as polyethylene and polypropylene, polyvinylidene fluoride, polysulfone, polyether sulfone, polyacrylonitrile, cellulose acetate and the like have been often used as the material for the porous filtration membrane. However, polyolefins, polyvinylidene fluoride, polysulfone, polyethersulfone, etc. are easily hydrophobic because of their strong hydrophobicity, and easily fouling and water permeability due to the property of adsorbing hydrophobic substances such as proteins. There was a problem of lowering. Polyacrylonitrile, cellulose acetate, and the like are resins having relatively high hydrophilicity, but have a problem that the film strength is weak and the temperature and chemical resistance are weak and the use temperature and the use pH range are very narrow.

  Therefore, a method for producing a porous membrane using a polyamide-based resin having relatively high hydrophilicity and strong chemical resistance has been studied. However, polyamide is soluble only in strong acid such as formic acid, concentrated sulfuric acid and expensive fluorine-containing solvents at room temperature, so these solvents have to be used as a production method using the NIPS method. For example, in the methods described in Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4, a film forming method using formic acid as a solvent is disclosed, but there is a problem in safety and health. Patent Document 5 discloses a method of casting nylon 6 mixed with polycaprolactone and dissolving it in hexafluoroisopropanol, and then extracting caprolactone therefrom to make it porous. Also, the polymer to be extracted and removed was expensive and impractical.

  On the other hand, a method using the TIPS method has also been studied, and Non-Patent Document 1 reports that a porous film can be produced using a system of nylon 12 and polyethylene glycol. Patent Document 6 reports that a porous film can be produced using nylon 11 and ethylene carbonate, propylene carbonate, or sulfolane. Non-Patent Document 2 describes that nylon 6 and nylon 12 porous membranes can be prepared using triethylene glycol as a solvent. However, all of these were only capable of forming a porous membrane, and processing into a highly permeable hollow fiber membrane and control of the pore diameter were not possible.

  Nylon has been reported as a hollow fiber membrane by the NIPS method using formic acid and the like as described above, and a method for producing a porous membrane by the TIPS method, but it has a low solution viscosity when dissolved at high temperature and a specific gravity. However, it is very difficult to process into a hollow fiber membrane using the TIPS method, and there have been few reports so far. For example, Patent Document 7 discloses porous membrane formation of various resins by the TIPS method, but there is an example of a flat membrane for polyamide, but there is no description about the production of a hollow fiber membrane. Further, Patent Document 8 discloses a method for producing a hollow fiber membrane by the TIPS method, but the obtained hollow fiber membrane has a very large pore diameter of 1.4 μm, and is a normal water treatment intended for the present invention. It could not be used for filtration processes in blood processing, food industry or pharmaceutical industry. Further, as disclosed, a film obtained by forming a film with glycerin or ethylene glycol cannot have a strength sufficient for practical use. Patent Document 9 only describes a general method for producing a nylon hollow fiber membrane by the TIPS method. There is no detailed description of the type of nylon, the solvent used, etc., and no examples. Patent Document 10 discloses a method of adding an antioxidant to suppress the decomposition of the polyamide membrane. However, the solvent used is expensive and is an example of processing into a hollow fiber membrane. No thickener is added, and there is no detailed description on the performance of the obtained hollow fiber membrane except that the maximum pore diameter is as large as 0.87 μm and 0.57 μm.

  On the other hand, the present inventors have already applied for a hollow fiber membrane using a polyamide resin in which the ratio of methylene group to amide group is —CH 2 —: — NHCO— = 4: 1 to 10: 1 (special feature). (Application No. 2008-253798)) Although the hydrophilicity is high, the strength is not sufficient. Furthermore, although a patent has been filed for a hollow fiber membrane using a crosslinked nylon 12 (Japanese Patent Application No. 2008-251952), the viscosity of the solution is still low even when crosslinked, and it is difficult to form a film with this method. It did not become a high hollow fiber membrane.

JP-A-57-105212 JP 58-65009 A U.S. Pat. No. 4,340,479 U.S. Pat. No. 4,477,598 JP 2000-1612 A U.S. Pat. No. 4,247,498 JP 58-164622 A JP-A-60-52612 U.S. Pat. No. 4,915,886 Special table 2003-534908 gazette

Journal of membrane science 108, 219-229 (1995) "Membrane Technology 2nd Edition" by Marcel Mulder, supervised and published by Masakazu Yoshikawa, Tsuyoshi Matsuura, Tsutomu Nakagawa, Inc. 95 pages (1997)

  The present invention solves the above-described problems and provides a hollow fiber membrane made of nylon 12 and / or a copolymer containing nylon 12 having excellent strength and appropriate water permeability. It is what.

  As a result of intensive studies to solve the above problems, the present inventors have dissolved nylon 12 and / or a copolymer containing nylon 12 in a specific organic solvent at a specific high temperature, cooled, and phase-separated. The present inventors have found that a hollow fiber membrane having high strength and appropriate water permeability can be produced by a method for causing the problem.

That is, the first of the present invention is a hollow fiber membrane made of nylon 12 and / or a copolymer containing nylon 12, having a tensile strength of 5 MPa or more and a water permeability of 100 L / m ² · atm · h. The gist of the hollow fiber membrane is as described above.

The second of the present invention is that the nylon 12 and / or the copolymer containing nylon 12 has a boiling point of 150 ° C. or higher and a temperature of 100 ° C. or higher in an organic solvent that is not compatible with the resin at a temperature lower than 100 ° C. A hollow fiber membrane is obtained by dissolving in the above to form a membrane-forming stock solution, forming a hollow fiber by extrusion into a coagulating liquid of less than 100 ° C. using a hollow fiber spinning nozzle, and then immersing in a solvent to remove the organic solvent. The above-described method for producing a hollow fiber membrane is characterized in that, preferably, the organic solvent is an aprotic polar solvent, more preferably, the aprotic polar solvent is sulfolane, γ-butyrolactone, ethylene carbonate, propylene carbonate, 1-methylpyrrolidone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide It is intended to be selected, et al.
Preferably, the hollow fiber membrane obtained by the above-described production method is stretched at a temperature not higher than the glass transition point of the resin to enhance water permeability, or stretched at a temperature not lower than the glass transition point of the resin. This is a method for producing a hollow fiber membrane characterized by increasing the tensile strength.

  According to the hollow fiber membrane of the present invention, it has moderate water permeability and high strength, and therefore can be suitably used in the fields of water and sewage treatment, food industry, and pharmaceutical industry. In particular, the use of the membrane separation activated sludge method in the sewage treatment using the hollow fiber membrane while directly washing it by aeration has the advantage that the problem of cutting or stretching can be solved.

It is an apparatus figure which shows one embodiment of the method of manufacturing the hollow fiber membrane of this invention. It is a schematic diagram of the spinneret for producing the hollow fiber membrane of the present invention. It is the schematic of the apparatus which measures the water permeability of the hollow fiber membrane of this invention. 2 is a scanning electron micrograph of the hollow fiber membrane obtained in Example 1. FIG. A: Cross section B: Enlarged cross section C: Inner surface D: Outer surface

  Hereinafter, the present invention will be described in detail.

  The resin used in the present invention is nylon 12 and / or a copolymer containing nylon 12, and is not particularly limited as long as the effects of the present invention are not impaired. Although the relative viscosity is not particularly limited, it is better to improve the tensile strength and elastic modulus, preferably 1.8 or more, and more preferably 2.0 or more.

  In addition, the resin used in the present invention may be copolymerized with other polymers or may be crosslinked. Examples of the copolymer containing nylon 12 include Pebax series from Arkema, UBESTA XPA series from Ube Industries, Ltd., and the like. As the cross-linking agent, acrylic cross-linking agents, epoxy cross-linking agents, and acid anhydride cross-linking agents are suitable. For example, Arkema's LOTRYL series, LOTADAR series, BONDINE series, etc. Can be mentioned. When the crosslinking agent is added, a method of adding 0.01 to 5% by mass, preferably 0.05 to 2% by mass, and kneading at a temperature equal to or higher than the melting point of the resin is used.

  The hollow fiber membrane of the present invention has a tensile strength of 5 MPa or more, preferably 6 MPa or more, more preferably 7 MPa or more. When the tensile strength is lower than the above, there is a problem that the material is cut during use, or the pore diameter becomes large due to elongation and the particles to be filtered are transmitted.

  The hollow fiber membrane of the present invention preferably has an elastic modulus of 25 MPa or more, and more preferably 40 MPa or more. When the elastic modulus is lower than the above, there is a problem that the stretched hole diameter is easily increased with a little force.

  The hollow fiber membrane of the present invention preferably has an unstretched tensile elongation of 150% or more, and more preferably 200% or more. When the tensile elongation is lower than the above, there is a problem that it is easily cut.

  The above-mentioned tensile strength, elastic modulus, and tensile elongation are values measured by the method described in JIS L-1013 using Shimadzu Autograph GS-J.

  The hollow fiber membrane of the present invention has a pore size corresponding to a microfiltration membrane or an ultrafiltration membrane, and the rejection rate of 0.1 μm particles is desirably 90% or more, preferably 95% or more. Yes, more preferably 99% or more. If the blocking rate of 0.1 μm particles is lower than this range, it will not be possible to pass through what is to be filtered.

  Here, the blocking rate of 0.1 μm particles in the present invention is the addition of 1 ml of 100 nm polystyrene fine particles 3100A made by Duke Scientific to 299 ml of 0.1% Triton X-100 aqueous solution, and this is stirred and dispersed for 3 hours. Was passed through a water permeability measuring device to be described later, the liquid that permeated the membrane was collected, the absorbance at 380 nm of the liquid before and after permeation of the membrane was measured, and the following formula was obtained.

      0.1 μm particle blocking rate = (initial absorbance−permeate absorbance) / initial absorbance × 100

The hollow fiber membrane of the present invention has a water permeability of 100 L / m ² · atm · h or more, preferably 150 L / m ² · atm · h or more. If the water permeability is lower than this range, there is a problem that it takes filtration time, which is not practical.

  Here, the water permeability in the present invention is measured by the following method. The hollow fiber membrane is cut into 10 to 20 cm, an injection needle having a diameter matching the inner diameter is inserted into the hollow portions at both ends, set in an apparatus as shown in FIG. The volume (L) of water stored in the tray 18 through water and passing through the membrane was defined as the amount of permeated water, and was obtained by the following equation.

Permeability = permeate amount (L) / [inner diameter (m) × 3.14 × length (m) × {(inlet pressure (atmospheric pressure) + outlet pressure (atmospheric pressure)) / 2} × time]

  Next, the manufacturing method of the hollow fiber membrane of this invention is demonstrated.

  The hollow fiber membrane of the present invention is soluble in a solvent at a high temperature because nylon 12 and / or a copolymer containing nylon 12 has no solvent in which room temperature is soluble except formic acid, concentrated sulfuric acid and some fluorinated solvents. It is preferable to manufacture by applying the TIPS method. The hollow fiber membrane of the present invention first has nylon 12 and / or a copolymer containing nylon 12 at 100 ° C. in an organic solvent having a boiling point of 150 ° C. or higher and incompatible with the resin at a temperature of less than 100 ° C. Dissolve at the above temperature to make a stock solution.

  Examples of the organic solvent having a boiling point of 150 ° C. or higher and incompatible with nylon 12 and / or a copolymer containing nylon 12 at a temperature lower than 100 ° C. include aprotic polar solvents, glycerin esters, glycols, organic Examples include 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, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate Specific examples of 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, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3 Examples include butylene glycol, hexylene glycol, polyethylene glycol (molecular weight: 100 to 600), 1,3-butanediol, and 1,4-butanediol. 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. Of these, aprotic polar solvents are preferable, sulfolane, ethylene carbonate, propylene carbonate, 1-methylpyrrolidone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide are more preferable, sulfolane, γ-butyrolactone. 1-methylpyrrolidone is most preferred. By using an aprotic polar solvent, the advantage of improving the strength and elongation of the hollow fiber membrane of the present invention can be obtained.

  As a density | concentration at the time of melt | dissolving the copolymer containing nylon 12 and / or nylon 12 in the above-mentioned organic solvent, 5 mass%-50 mass% are preferable, and 10 mass%-30 mass% are more preferable. 10% by mass to 20% by mass is most preferable. If the concentration of the resin is lower than this range, there is a problem that the strength of the film becomes weak and the particle blocking rate is lowered, and if it is higher than this range, there is a problem that the water permeability is lowered.

  Further, when dissolving the nylon 12 and / or the copolymer containing nylon 12 in the organic solvent described above, 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, preferably 20 to 40 ° C. higher than the phase separation temperature of the system.

  The phase separation temperature of the system is a temperature at which a solid-liquid phase separation by liquid-liquid phase separation or crystal precipitation occurs when a resin and a solvent are mixed at a sufficiently high temperature and uniformly dissolved and gradually cooled. The phase separation temperature can be suitably measured by using a microscope equipped with a hot stage.

  In the present invention, the membrane-forming stock solution prepared as described above is then extruded into a coagulating liquid of less than 100 ° C. using a hollow fiber spinning nozzle to form a hollow fiber. By rapidly cooling to the set temperature of the coagulating liquid, phase separation is induced to form a porous structure. When it is desired to set the cooling temperature to 0 ° C. or lower, salts can be added, or ethylene glycol, glycerin, or the like can be mixed.

  Here, as a nozzle for hollow fiber spinning, a die having a double circular shape used when producing a core-sheath type composite fiber in melt spinning can be used.

  In addition, liquid or gas can be used as the fluid to be injected into the core portion that becomes the hollow portion. However, since the film-forming stock solution is low in viscosity and can be spun even under difficult conditions, the liquid is generally used. There are many. Any liquid can be used as the liquid. When it is desired to enlarge the hole on the inner surface of the hollow fiber, a good solvent having a high affinity with nylon 12 and / or a copolymer containing nylon 12 is used. When it is desired to reduce the thickness, a poor solvent can be used. Specific examples of such solvents include good solvents such as glycerin, diethylene glycol, triethylene glycol, and sulfolane. Poor solvents include higher fatty acids, liquid paraffin, and any fluid that has a high boiling point and is not compatible with nylon. Can be used. In addition, when the film-forming stock solution has high viscosity and excellent spinnability, a method of flowing a gas such as an inert gas may be used.

  Any coagulation liquid can be used as long as the effects of the present invention are not impaired. Alcohols such as water, ethanol and isopropanol, polyhydric alcohols such as glycerin, ethylene glycol, diethylene glycol and triethylene glycol, acetone and ethyl Ketones such as methyl ketone can be suitably used, and these can be used alone or as a mixed solvent in which two or more kinds are mixed. Among these, water, glycerin, and ethylene glycol are preferable, and water is more preferable. The temperature of the coagulation liquid is not particularly limited, but is preferably −20 ° C. to 100 ° C., more preferably −10 ° C. to 80 ° C., and most preferably 0 ° C. to 50 ° C. Since the crystallization speed can be changed by changing the temperature of the coagulation liquid, the pore size, water permeability, and strength can be changed. In general, if the temperature of the coagulating liquid is low, the pore size is reduced and the water permeability is lowered and the strength is improved. If the temperature of the coagulating liquid is high, the pore size is increased and the water permeability is improved and the strength is reduced. There are many exceptions because it varies depending on the solubility of the solvent in the coagulation liquid and the crystallization speed of the resin itself. When the temperature of the coagulation liquid is lower than this range, there is a problem that a large amount of energy is required for temperature control. When the temperature is higher than this range, there is a problem that the strength of the film becomes weak.

  In the present invention, the hollow fiber membrane of the present invention can then be obtained by immersing the obtained hollow fiber in a solvent and extracting and removing the organic solvent causing phase separation in the hollow fiber. Such an extraction solvent 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, glycerin, methanol, ethanol, isopropanol, acetone, diethyl ether, hexane, petroleum ether, And toluene. Among these, water, methanol, ethanol, isopropanol, and acetone are preferable, and water, methanol, and isopropanol are particularly preferable. In particular, when extracting a solvent that dissolves in water, if a water bath is used in the above-described cooling step, solvent extraction can be performed simultaneously, which is efficient. When extracting a solvent insoluble in water such as phthalic acid ester and fatty acid, alcohols, acetone, petroleum ether and the like can be suitably used. Moreover, the time to immerse in a solvent tank is not specifically limited unless the effect of this invention is impaired, It is 1 hour-2 months, Preferably it is 5 hours-1 month, More preferably, it is 10 hours-14 days. In order to effectively extract and remove the organic solvent, the extraction solvent can be replaced or stirred. In particular, when the hollow fiber membrane of the present invention is used for the food industry or water purification, the remaining of the organic solvent becomes a problem.

  In order to suitably carry out the above-described method for producing a hollow fiber membrane of the present invention, a general apparatus used for dry and wet spinning as shown in FIG. 1 is used. Further, for the production of the hollow fiber, a die having a double circular shape as shown in FIG. 2 can be used.

  Nylon 12 and / or a copolymer containing nylon 12 are mixed and dissolved at a high temperature with the above-described organic solvent to form a film-forming stock solution and stored in the container 3. The film-forming stock solution and the inflowing liquid (or gas) are each measured by the metering pump 4 and sent to the spinneret 6. The raw film forming solution discharged from the die 6 is introduced into a liquid bath (coagulation bath 7) that does not substantially dissolve nylon 12 resin such as water through a slight air gap, and is cooled and solidified. In the process of cooling and solidifying the film-forming stock solution, heat-induced phase separation occurs, and a hollow fiber 8 having a sea-island structure is obtained. After winding up the hollow fiber 8 obtained in this way, an organic solvent which is an island component of a sea-island structure using an extraction solvent such as water and a liquid poured into the hollow portion in a solvent extraction bath 10. Removal of the hollow fiber membrane is obtained.

  In the present invention, by further stretching the hollow fiber membrane obtained as described above, improvement in water permeability and improvement in tensile strength can be expected.

  The stretching method employed in the present invention is not particularly limited. The stretching temperature is preferably −10 ° C. to 140 ° C., more preferably 0 ° C. to 100 ° C. Specifically, in order to mainly improve the water permeability, cold drawing is preferred, in which the drawing is performed below the glass transition point of the resin that is the material. On the other hand, the material is mainly used to improve the tensile strength and elastic modulus by crystallization. Thermal stretching above the glass transition point of a certain resin is preferred.

  For example, when nylon 12 is taken as an example, since the glass transition point of nylon 12 is about 37 ° C., it is preferably 37 ° C. or lower, and more preferably 30 ° C. or lower, mainly for improving water permeability. In order to improve the tensile strength and elastic modulus mainly by crystallization, stretching at 37 ° C. or higher is preferable, and stretching at 50 ° C. or higher is more preferable.

  The stretching may be performed continuously by changing the rotation speed of the roll, or may be performed individually by grasping both ends of a piece cut to a certain length.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the examples, the tensile strength, water permeability, and particle rejection rate of the hollow fiber membrane were measured by the methods described above.

Example 1
80 g of nylon 12 chips (Rilsan AECN0TL manufactured by Arkema Co., Ltd., relative viscosity 2.25) and 320 g of sulfolane (manufactured by Tokyo Chemical Industry Co., Ltd.) were stirred and dissolved at 230 ° C. for 1.5 hours to prepare a film forming stock solution. The temperature was lowered to 220 ° C., the solution was fed to the spinneret via a metering pump, and extruded at 0.05 MPa. The extrusion rate at this time was 18 g / min. The hole diameter of the spinneret was 1.58 mm in outer diameter and 0.83 mm in inner diameter. Triethylene glycol was allowed to flow through the internal solution at a feed rate of 7.0 g / min. The extruded spinning solution was put into a 0 ° C. water bath through a 5 mm air gap, cooled and solidified, and wound at a winding speed of 38 m / min. The obtained hollow fiber was immersed in water for 24 hours to extract the solvent to obtain a hollow fiber membrane. As shown in Table 1, the obtained hollow fiber membrane was sufficiently strong, had a high elastic modulus, had a high particle rejection rate, and had water permeability. An electron micrograph of the obtained hollow fiber membrane is shown in FIG. 4. It is observed that the cross-section has dense and uniform pores and no macrovoids, and a dense skin layer is present on the outside. It was observed that

Example 2
A hollow fiber membrane was produced in the same manner as in Example 1 except that the temperature of the water bath was changed to 40 ° C. As shown in Table 1, the obtained hollow fiber membrane was sufficiently strong and had a high elastic modulus although its tensile strength and elongation were reduced as compared with Example 1. Moreover, water permeability improved.

Example 3
A hollow fiber membrane was prepared in the same manner as in Example 1, except that the nylon 12 tip was changed to 60 g and the sulfolane was changed to 340 g. As shown in Table 1, the obtained hollow fiber membrane was reduced in strength because the resin concentration was lowered, but was still sufficiently strong and high in elastic modulus. The water permeability was improved by lowering the concentration, but 0.1 μm particles were almost completely blocked.

Example 4
In Example 3, the extrusion rate was reduced to 10.3 g / min. As a result, a hollow fiber membrane having a thin outer diameter and a thin membrane pressure was obtained. The tensile strength was sufficiently high as shown in Table 1, and the water permeability was also improved.

Example 5
The hollow fiber membrane obtained in Example 4 was stretched twice at 20 ° C. The strength was improved as shown in Table 1, and the water permeability was greatly improved to 1137 L / m ² · atm · h.

Example 6
The hollow fiber membrane obtained in Example 4 was stretched twice in boiling water at 100 ° C. The strength was improved as shown in Table 1, and the water permeability was 550 L / m ² · atm · h.

Example 7
A hollow fiber membrane was produced in the same manner as in Example 1 except that the solvent was changed to γ-butyrolactone, the nylon 12 resin and the solvent were stirred and dissolved at 200 ° C., and the extrusion temperature was changed to 200 ° C. The obtained hollow fiber membrane showed high strength as shown in Table 1, and 0.1 μm particles were completely blocked and water permeable.

Example 8
A hollow fiber membrane was prepared in the same manner as in Example 1, except that the resin was changed to Pebax 7233SA01 (manufactured by Arkema), which is a copolymer of nylon 12, and the stirring and dissolving temperature and the extrusion temperature were changed to 180 ° C. The obtained hollow fiber membrane showed high tensile strength as shown in Table 1, and 0.1 μm particles were completely blocked and water permeable.

Example 9
A hollow fiber membrane was prepared in the same manner as in Example 8, except that the solvent was changed to γ-butyrolactone and the stirring and dissolving temperature and the extrusion temperature were changed to 180 ° C. The obtained hollow fiber membrane showed high tensile strength as shown in Table 1, and 0.1 μm particles were completely blocked and water permeable.

Comparative Example 1
A hollow fiber membrane was prepared in the same manner as in Example 1 except that the solvent was changed to propylene glycol and the stirring and dissolution temperature and the extrusion temperature were changed to 170 ° C. As shown in Table 1, the obtained hollow fiber membrane showed low values for both strength and elongation.

Comparative Example 2
A hollow fiber membrane was prepared in the same manner as in Example 1, except that the resin was changed to nylon 6 chips (Unitika Ltd., relative viscosity 3.53) and the extrusion temperature was 210 ° C. The obtained hollow fiber membrane had water permeability as shown in Table 1, but was inferior in tensile strength and elastic modulus.

1: Stirring motor 2: Pressurized gas inlet 3: Container 4: Metering pump 5: Internal liquid (or gas) inlet 6: Spinneret 7: Coagulation bath 8: Hollow fiber 9: Winder 10: Solvent extraction bath 11: Internal liquid (or gas) inflow hole 12: Film-forming stock solution inflow hole 13: Liquid feeding pump 14: Inlet pressure gauge 15: Hollow fiber membrane 16: Outlet pressure gauge 17: Outlet valve 18: Dish

Claims (6)

A hollow fiber membrane made of nylon 12 and / or a copolymer containing nylon 12, having a tensile strength of 5 MPa or more and a water permeability of 100 L / m ² · atm · h or more Yarn membrane.   Nylon 12 and / or a copolymer containing nylon 12 is dissolved in an organic solvent having a boiling point of 150 ° C. or higher and incompatible with the resin at a temperature lower than 100 ° C. A hollow fiber membrane is obtained by forming a hollow fiber by extrusion into a coagulating liquid of less than 100 ° C. using a hollow fiber spinning nozzle and then immersing in a solvent to remove the organic solvent. Item 2. A method for producing a hollow fiber membrane according to Item 1.   The method for producing a hollow fiber membrane according to claim 2, wherein the organic solvent is an aprotic polar solvent.   The hollow fiber according to claim 3, wherein the aprotic polar solvent is selected from sulfolane, γ-butyrolactone, ethylene carbonate, propylene carbonate, 1-methylpyrrolidone, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide. A method for producing a membrane. A method for producing a hollow fiber membrane, wherein the water permeability is increased by stretching the hollow fiber membrane obtained by the production method according to any one of claims 2 to 4 at a temperature not higher than the glass transition point of the resin. A method for producing a hollow fiber membrane, wherein the tensile strength is increased by stretching the hollow fiber membrane obtained by the production method according to any one of claims 2 to 4 at a temperature equal to or higher than the glass transition point of the resin.