JPWO2017164019A1 - Hollow fiber membrane - Google Patents

Abstract

The hollow fiber membrane of the present invention includes a dense layer having only pores having a pore area of 0.28 μm 2 or less in a state observed in a cross section perpendicular to the longitudinal direction of the hollow fiber membrane, and the dense layer is an outer surface of the hollow fiber membrane. The inner diameter is 350 μm or less, the inner diameter is 150 μm or more, the film thickness is 30 μm or more and 90 μm or less, and the surface of the hollow fiber membrane on which the dense layer is arranged has a plurality of surfaces The pores have an average pore diameter of 0.3 μm or more and 0.9 μm or less observed on the surface of the hollow fiber membrane of a plurality of pores, and the thickness of the dense layer (DT) and the thickness of the hollow fiber membrane (WT) The ratio (DT / WT) is 0.24 or more.

Description

  The present invention relates to a hollow fiber membrane.

  Hollow fiber membranes have been widely used in the field from reverse osmosis to microfiltration. As its application, it is widely used for medical applications such as blood purifiers for patients with renal failure and water treatment applications such as for water purifiers.

  As materials for hollow fiber membranes, hydrophobic polymers such as polyethylene and polysulfone are known, and it is known that hollow fiber membranes using these materials are subjected to hydrophilization treatment. For the hydrophilization treatment, a hollow fiber membrane is coated with a hydrophilic polymer after the hollow fiber membrane has been formed, or an injection solution containing a hydrophilic polymer is discharged from a double annular die together with a spinning solution of the hollow fiber membrane to make the hydrophilic There is a method of imparting sex. By performing such a hydrophilic treatment, the water permeability of the hollow fiber membrane is increased.

  Further, the characteristics required for the cartridge for the water purifier are to have resistance to high water pressure, to have high water permeability, to have high substance removal characteristics, and to have a long cartridge life. Therefore, as a hollow fiber membrane for a water purifier, a hollow fiber membrane having high water permeability and sharp substance fractionation performance has been developed while having strength to withstand water pressure.

  For example, Patent Document 1 discloses a method of spinning a hollow fiber membrane at a high spinning draft rate of 100 or 185 in a melt spinning method in order to improve resistance to high water pressure.

  Patent Document 2 discloses a method for increasing the water permeability by controlling the spinning draft rate in a hollow fiber membrane having an asymmetric structure provided with a dense layer, thereby controlling the pore structure of the membrane.

  Further, it is known that increasing the area of the hollow fiber membrane is effective for extending the life of the cartridge for the water purifier.

Japanese Patent Laid-Open No. 04-018112 International Publication No. 2010/029908

  However, the hollow fiber membrane obtained by the production method disclosed in Patent Document 1 is excellent in resistance to high water pressure, but the cross-sectional structure of the hollow fiber membrane is uniform, that is, there are micropores present in the cross section of the hollow fiber membrane. Since all of them are dense, there is a problem that the water permeability is inferior. Here, as a means for improving the water permeability of the hollow fiber membrane, it is conceivable to increase the pore area of the above-mentioned micropores.

  In addition, the hollow fiber membrane disclosed in Patent Document 2 has a dense layer and a non-dense layer, and has excellent water permeability by controlling the pore structure, but is resistant to high water pressure. There is a problem that it is inferior.

  In addition, in order to increase the product life of a water purifier cartridge (hereinafter sometimes referred to as a cartridge) provided with a hollow fiber membrane, when the membrane area of the hollow fiber membrane provided in the water purifier cartridge is increased, the cartridge is increased in size. There are challenges. Therefore, in order to suppress the enlargement of the cartridge while increasing the membrane area of the hollow fiber membrane, it is conceivable to reduce the diameter of the hollow fiber membrane, in this case, this hollow fiber membrane is inferior in resistance to high water pressure, It tends to be inferior in water permeability. In addition, when the hollow fiber membrane having a dense layer is reduced in diameter, the resistance of the hollow fiber membrane to high water pressure is further deteriorated.

  Therefore, in view of the above-mentioned problems, the present invention provides a hollow fiber membrane that is excellent in resistance to high water pressure and excellent in water permeability, and further achieves a long life of a water purifier cartridge equipped with the hollow fiber membrane. The purpose is to do.

In order to solve the above problems, the present invention is characterized by the following (1) to (5).
(1) A hollow fiber membrane including a dense layer having only pores having a pore area of 0.28 μm ² or less in a state observed in a cross section perpendicular to the longitudinal direction of the hollow fiber membrane, wherein the dense layer is the hollow fiber It is arranged on the outer surface side or inner surface side of the membrane, the outer diameter of the hollow fiber membrane is 350 μm or less, the inner diameter of the hollow fiber membrane is 150 μm or more, and the film thickness of the hollow fiber membrane is 30 μm or more 90 μm or less, the surface of the hollow fiber membrane on which the dense layer is arranged has a plurality of holes, and the average pore diameter observed on the surface of the hollow fiber membrane of the plurality of holes is 0.3 μm or more and 0.9 μm A hollow fiber membrane, wherein the ratio (DT / WT) of the dense layer thickness (DT) and the hollow fiber membrane thickness (WT) is 0.24 or more.
(2) The hollow fiber membrane according to (1), wherein the dense layer is disposed on an outer surface side of the hollow fiber membrane.
(3) The hollow fiber membrane according to (1) or (2), wherein a porosity of the surface of the hollow fiber membrane on which the dense layer is disposed is 15% or more and 45% or less.
(4) The hollow fiber membrane according to any one of (1) to (3), comprising a polysulfone-based polymer and polyvinylpyrrolidone.
(5) A water purifier cartridge equipped with the hollow fiber membrane according to any one of (1) to (4).

  ADVANTAGE OF THE INVENTION According to this invention, the hollow fiber membrane which is excellent in the tolerance with respect to a high water pressure, and is excellent also in water permeability is provided, Furthermore, the lifetime improvement of the cartridge for water purifiers which mounts a hollow fiber membrane is realizable.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In the present specification, all percentages and parts expressed by mass are the same as percentages and parts expressed by weight.

In the conventional technology, when the hollow fiber membrane having a dense layer is made smaller in diameter, the resistance of the hollow fiber membrane to high water pressure is inferior (the strength of the hollow fiber membrane is reduced) and sufficient water permeability is achieved. Cannot be obtained. Accordingly, the present inventors have found that the outer diameter, inner diameter and film thickness of the hollow fiber and the structure of the dense layer greatly affect the strength improvement and water permeability of the hollow fiber membrane, and in the longitudinal direction of the hollow fiber membrane. A hollow fiber membrane provided with a dense layer having only pores having a pore area of 0.28 μm ² or less in a state observed in a vertical cross section, the dense layer being arranged on the outer surface side or inner surface side of the hollow fiber membrane. A hollow fiber membrane in which the outer diameter of the hollow fiber membrane is 350 μm or less, the inner diameter of the hollow fiber membrane is 150 μm or more, the film thickness of the hollow fiber membrane is 30 μm or more and 90 μm or less, and a dense layer is disposed Surface has a plurality of pores, the average pore diameter observed on the hollow fiber membrane surface of the plurality of pores is not less than 0.3 μm and not more than 0.9 μm, and the thickness (DT) of the dense layer and the hollow fiber membrane Ratio (DT / WT) to film thickness (WT) is 0.24 or more It has created a hollow fiber membrane of the invention.

  As described above, since the outer diameter of the hollow fiber membrane of the present invention is as thin as 350 μm or less, a large number of the hollow fiber membranes are mounted on a compact hollow fiber membrane module (hereinafter sometimes referred to as a module) or a water purifier cartridge. The product life of the module or cartridge can be made excellent.

  Further, from the viewpoint of further improving the water permeability and product life of the cartridge, it is preferable that the hollow fiber membrane has a small outer diameter, a large inner diameter, and a thin film thickness. Moreover, from the viewpoint of making the strength of the hollow fiber membrane excellent, it is preferable that the hollow fiber membrane has a large outer diameter, a small inner diameter, and a thick film thickness. In order to satisfy these conflicting conditions, it is important to control the structure of the dense layer. The structure of the dense layer greatly affects the strength retention and water permeability of the membrane. From the above, it is important that the outer diameter of the hollow fiber membrane is 350 μm or less, and the lower limit thereof is preferably 190 μm or more, more preferably 220 μm or more, and further preferably 260 μm or more. . On the other hand, the upper limit is preferably 330 μm or less, and more preferably 310 μm or less. Moreover, it is important that the inner diameter of the hollow fiber membrane is 150 μm or more, and the lower limit thereof is preferably 155 μm or more, and more preferably 160 μm or more. On the other hand, the upper limit is preferably 220 μm or less, more preferably 210 μm or less, and even more preferably 200 μm or less.

  It is important that the thickness of the hollow fiber membrane is 30 μm or more and 90 μm or less, and the lower limit thereof is preferably 40 μm or more, and more preferably 50 μm or more. On the other hand, the upper limit is preferably 80 μm or less, and more preferably 70 μm or less.

The hollow fiber membrane of the present invention has a dense layer, and this dense layer is disposed on the outer surface side or the inner surface side of the hollow fiber membrane. The hollow fiber membrane of the present invention has a plurality of holes on the surface of the hollow fiber membrane on which the dense layer is arranged, and the average pore diameter observed on the hollow fiber membrane surface of the plurality of holes is 0.3 μm or more. For this reason, the water permeability of the hollow fiber membrane is extremely excellent. On the other hand, since the average pore diameter observed on the hollow fiber membrane surface of the above pores is 0.9 μm or less, the strength of the hollow fiber membrane can be improved, and the turbidity removal performance such as bacteria and fine particles can be removed. Can be increased. From the above viewpoint, the lower limit of the average pore diameter of the plurality of holes is preferably 0.35 μm or more, and more preferably 0.40 μm or more. On the other hand, the upper limit of the average pore diameter of the plurality of holes is preferably 0.85 μm or less, and more preferably 0.80 μm or less. Here, the dense layer means that when a cross section perpendicular to the longitudinal direction of the hollow fiber membrane is observed with a scanning electron microscope (SEM), the presence of pores having a pore area exceeding 0.28 μm ² is not observed. , Refers to a layer having only pores with a pore area of 0.28 μm ² or less. Moreover, in the hollow fiber membrane of this invention, it is preferable that the macro void and the finger void are not formed in the membrane cross section.

  Further, the hollow fiber membrane of the present invention has a ratio (DT / WT) of the dense layer thickness (DT) and the hollow fiber membrane thickness (WT) of 0.24 or more. It can be maintained sufficiently, and not only the resistance of the hollow fiber membrane to high water pressure but also excellent workability and handling properties required for modularization can be achieved. The thickness of the dense layer can be measured by the method described in the examples.

  Further, the dense layer of the hollow fiber membrane is preferably disposed on the surface of the hollow fiber membrane in contact with the water to be treated. For example, when water to be treated is permeated from the outer surface side to the inner surface side of the hollow fiber membrane, it is preferable to dispose a dense layer on the outer surface side of the hollow fiber membrane. The reason for this is that turbidity contained in the water to be treated can be prevented from entering the inside of the hollow fiber membrane, thereby suppressing the deterioration of filtration resistance due to the blockage of the pores and suppressing the water permeability of the membrane. It is because it can do.

  In addition, the hollow fiber membrane of the present invention has a plurality of holes on the surface of the hollow fiber membrane on which the dense layer is arranged, and the open area ratio on this surface is preferably 15% or more and 45% or less. A porosity of 15% or more on the surface on the dense layer side of the hollow fiber membrane is preferable because the water permeability is excellent. On the other hand, when the hole area ratio on the surface of the dense layer side of the hollow fiber membrane is 45% or less, the strength and removal performance can be sufficiently maintained. From the above viewpoint, the lower limit of the open area ratio is more preferably 18% or more, and further preferably 21% or more. Further, the upper limit of the open area ratio is more preferably 42% or less, and further preferably 39% or less. In addition, as a means for setting the open area ratio on the dense layer side surface of the hollow fiber membrane in the above range, in the hollow fiber membrane production method, the dry part atmosphere is adjusted and the phase separation rate of the polymer is controlled. Examples include adjusting the content of the hydrophilic polymer.

  The hollow fiber membrane of the present invention preferably contains a hydrophilic polymer. The reason for this is that by imparting hydrophilicity to the membrane surface, it is possible to improve the water permeability and to prevent turbidity from adhering to the membrane. On the other hand, when the content of the hydrophilic polymer is large, the hydrophilic polymer itself retains water, so that it becomes a permeation resistance and water permeability decreases. Therefore, the upper limit of the content of the hydrophilic polymer is preferably 20 parts by mass or less and more preferably 15 parts by mass or less with respect to the mass of the entire hollow fiber membrane. On the other hand, the lower limit is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more. Also, on the membrane surface of the hollow fiber membrane, when a large amount of cross-linked hydrophilic polymer is present, a decrease in water permeability tends to be observed. Therefore, the ratio of the hydrophilic polymer to the hydrophobic polymer (hydrophilic polymer / hydrophobic polymer) on the surface of the hollow fiber membrane where the dense layer is present is preferably 0.80 or less, and more preferably 0.70. The following is preferred. Furthermore, from the above viewpoint, the ratio of the hydrophilic polymer to the hydrophobic polymer (hydrophilic polymer / hydrophobic polymer) on the surface opposite to the surface of the hollow fiber membrane where the dense layer exists is also 0. 80 or less is preferable, and 0.70 or less is more preferable.

  Here, the hydrophilic polymer means a water-soluble polymer compound or a polymer compound that interacts with water molecules by electrostatic interaction or hydrogen bonding even if it is water-insoluble. Specifically, polyalkylene oxide such as polyethylene oxide and polypropylene oxide, polyvinyl alcohol, polyvinyl pyrrolidone (hereinafter sometimes referred to as PVP), polyvinyl acetate, polydimethylmethoxy acrylate, polydimethylacrylamide, and vinyl pyrrolidone. Nonionic hydrophilic polymers such as copolymers with acrylic acid, copolymers of vinyl acetate and vinylpyrrolidone, anionic hydrophilic polymers such as polyacrylic acid, polyvinyl sulfate, carboxymethyl cellulose, polyallylamine, polylysine, chitosan, poly [ Cationic hydrophilic polymers such as methacrylic acid {2 (dimethylamino) ethyl}], polymethacryloyloxyethyl phosphorylcholine, polymethacryloyloxyethyldimethylan Zwitterionic hydrophilic polymers such as niobium propionate and the like. Two or more hydrophilic polymers may be contained in the hollow fiber membrane. In particular, from the viewpoint of suppressing adhesion of turbidity, nonionic hydrophilic polymers and zwitterionic hydrophilic polymers are preferably used.

  As a material (component) constituting the substrate of the hollow fiber membrane, a hydrophobic polymer is preferable. Examples of the hydrophobic polymer include polysulfone (hereinafter sometimes referred to as PSF), polyethersulfone, and polyarylate. Polysulfone polymers such as polyvinylidene fluoride, fluororesins such as polyvinylidene fluoride, cellulose resins such as cellulose triacetate and cellulose diacetate, polymethyl methacrylate, polyacrylonitrile, polyamide, etc. are preferably used. From the viewpoints of strength and water permeability, polysulfone polymers are preferably used. It is particularly preferable to add PVP to a spinning dope composed of a polysulfone polymer from the viewpoint of easy control of the membrane structure of the present invention.

  The composition ratio of the hollow fiber membrane is preferably 5% to 20% by mass ratio (%) and the polysulfone-based polymer is 5 to 20% with respect to all the components of the hollow fiber membrane.

  The hollow fiber membrane preferably contains polyvinyl pyrrolidone in addition to the polysulfone polymer. Polyvinylpyrrolidone having various molecular weights can be used, but K90 (trade name, manufactured by ISP, weight average molecular weight 1.3 million), K60 (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., weight average molecular weight). 160,000), K30 (trade name, manufactured by BASF, weight average molecular weight 40,000), K17 (trade name, manufactured by ISP, weight average molecular weight 10,000), and other commercially available products can be used conveniently. You may superpose | polymerize and use these mixing and the thing of molecular weight area | regions other than the above.

  In the production process of the hollow fiber membrane, the components of the hollow fiber membrane such as polysulfone polymer and PVP are dissolved in a solvent to obtain a spinning dope. Here, the solvent is preferably a high-boiling polar solvent such as dimethylacetamide (hereinafter abbreviated as DMAc) or N-methylpyrrolidone, but other combinations can be used as long as they can be uniformly dissolved.

The water permeability of the hollow fiber membrane of the present invention is preferably 30 ml / Pa / hr / m ² or more, more preferably 35 ml / Pa / hr / m ² or more, and 40 ml / Pa / hr. / M ² or more is more preferable. Further, the upper limit of the water permeability of the hollow fiber membrane is not particularly limited, but if the water permeability is too high, the fractionation performance may be lowered. Therefore, the upper limit of the water permeability of the hollow fiber membrane is 120 ml / Pa / It is preferably hr / m ² or less, more preferably 110 ml / Pa / hr / m ² or less, and even more preferably 100 ml / Pa / hr / m ² or less.

  As the fractionation performance of the hollow fiber membrane, the removal rate of latex bead particles having a particle diameter of 0.2 μm is preferably 80% or more, and more preferably 90% or more.

  The hollow fiber membrane of the present invention comprises the composition of the spinning dope and the composition of the injection solution, the discharge linear velocity and the injection solution discharge linear velocity when discharging the spinning dope from the die, the dew point / temperature of the cold air in the dry part after discharge, and the cold air velocity. It can be obtained by controlling the draft ratio, the coagulation bath temperature, the washing conditions and the like when discharging the spinning dope.

  Then, the manufacturing method of the hollow fiber membrane of this invention is demonstrated. The hollow fiber membrane of the present invention is not particularly limited, but using an orifice type double ring cap, a spinning stock solution containing a polymer as a material for the hollow fiber membrane is fed from the outer annular slit, and the injected liquid is fed to the inner central pipe. Thus, the hollow fiber membrane having an asymmetric structure can be formed by discharging each, passing through the dry part, and then coagulating in a coagulating solution, followed by washing with warm water.

  The spinning draft rate when producing the hollow fiber membrane of the present invention is preferably 2 or more and 6 or less. Here, the spinning draft rate is a ratio between the discharge linear velocity of the film-forming composition from the outer peripheral slit portion of the double ring die and the winding speed of the hollow fiber membrane, and the winding speed is defined as the film-forming composition. It shows the value divided by the discharge linear velocity. The discharge linear velocity is a linear velocity when the film-forming composition is discharged from the outer peripheral slit of the double ring die, and is a value obtained by dividing the discharge flow rate by the outer slit sectional area.

  By setting the spinning draft rate to 2 or more, the water permeability of the hollow fiber membrane is improved. On the other hand, by setting the spinning draft rate to 6 or less, the spinning stability can be improved and the yarn breakage frequency can be reduced. In particular, when the spinning fiber draft is high when the hollow fiber membrane has a thin yarn diameter (outer diameter), the outer surface of the hollow fiber membrane is affected by the spinning draft when the injected liquid has non-coagulation properties. The smoothness is lost, a pleated structure is formed, and the dense layer tends to be thin. When the thickness of the dense layer is reduced, the fractionation performance of the hollow fiber membrane is reduced, and the resistance of the hollow fiber membrane to high water pressure (hereinafter sometimes referred to as pressure resistance) is reduced. There is concern to cause.

  When a double ring die such as an orifice type double ring die is used for spinning the hollow fiber membrane, the viscosity of the spinning dope is preferably 2 Pa · s or more and 11 Pa · s or less. By setting the viscosity of the spinning dope to 2 Pa · s or more, the spinnability of the hollow fiber membrane is improved. On the other hand, by setting the viscosity of the spinning dope to 11 Pa · s or less, the pressure in the double ring die can be suppressed, and a stable discharging state of the spinning dope can be maintained. Also, from the viewpoint of controlling the thickness of the dense layer, if the viscosity of the spinning stock solution is too low, the phase separation rate of the polymer is increased, and the thickness of the dense layer is too thin. s or more is preferable.

  On the other hand, the liquid to be injected into the center pipe of the double ring cap can be appropriately selected from those that are solidified or non-solidified according to the desired form of the hollow fiber membrane. There is a coagulation value as an index of the coagulation property of the injected liquid. This coagulation value represents the added mass of the injected liquid when the injection solution is added little by little with respect to 50 g of 1% by mass of the main polymer constituting the membrane, and the inside of the system becomes cloudy. It shows that the solidification property of injection | pouring liquid is so high that this solidification value is small. From past empirical rules, if the solidification value is 40 g or more (80% or more of the original liquid amount), the particle structure of the aggregated polymer is not seen on the film surface where the dense layer is formed. It is judged that it has.

  When a solidifying liquid is used for the injection liquid, since solidification starts from the inner surface, a dense layer is formed on the inner surface side of the hollow fiber membrane. On the other hand, when a non-solidifying liquid is used, solidification starts from the outer surface by the coagulation bath provided on the downstream side, so that a dense layer is formed on the outer surface side of the hollow fiber membrane. Therefore, in the case of the water purifier use used by the flow filtered from the outer surface side to the inner surface side of the hollow fiber membrane, a non-solidifying liquid is particularly preferably used.

  In particular, the absolute value of the discharge linear velocity of the spinning dope and the injected liquid and the relative value of both greatly affect the formation of the dense layer structure. This is presumably because the orientation of the polymer is determined by the discharge linear velocity.

  If the absolute value of the discharge linear velocity of the spinning dope is too high, the water permeability of the resulting hollow fiber membrane will be low, and if the absolute value of the discharge linear velocity is too low, the smoothness of the outer surface of the resulting hollow fiber membrane will be lost. In other words, a pleated structure is formed and the dense layer tends to be thin. In any case, the fractionation performance of the hollow fiber membrane is lowered, and the resistance of the hollow fiber membrane to high water pressure is lowered. Therefore, the absolute value of the discharge linear velocity of the spinning dope is preferably 0.05 m / s or more, and more preferably 0.1 m / s or more. On the other hand, it is preferably 0.3 m / s or less, and more preferably 0.25 m / s or less.

  If the absolute value of the discharge linear velocity of the injected liquid is too high, the pressure loss of the center pipe of the double ring cap becomes high, and the outer diameter variation of the hollow fiber membrane obtained increases. Also, if the absolute value of the discharge linear velocity is too low, a pleated structure is formed on the inner surface of the resulting hollow fiber membrane, and the resistance to the high water pressure of the hollow fiber membrane is lowered, and in some cases it is not preferable because yarn breakage is caused. . Therefore, the absolute value of the discharge linear velocity of the injected liquid is preferably 0.05 m / s or more, and more preferably 0.1 m / s or more. On the other hand, it is preferably 0.5 m / s or less, and more preferably 0.3 m / s or less.

  If the relative value of the discharge linear velocity of the spinning dope and the injected liquid is too high, a pleated structure is formed on the outer surface of the resulting hollow fiber membrane, and the dense layer tends to be thin. When the thickness of the dense layer is reduced, the fractionation performance of the hollow fiber membrane is lowered, and the resistance of the hollow fiber membrane to a high water pressure is lowered. In addition, if the relative value of the discharge linear velocity of the spinning dope and the injected liquid is too small, the water permeability of the resulting hollow fiber membrane is lowered, which is not preferable. Here, the relative value of the discharge linear velocity of the spinning stock solution and the injected liquid is a value obtained by dividing the discharge linear velocity of the injected liquid by the discharge linear velocity of the spinning stock solution. Therefore, the relative value of the discharge linear velocity of the spinning solution and the injected liquid is preferably 0.5 or more, and more preferably 0.6 or more. On the other hand, it is preferably 2.0 or less, and more preferably 1.5 or less.

  As the yarn diameter of the hollow fiber membrane is reduced, the outer diameter variation tends to increase, and the hollow fiber membrane structure is disturbed, causing problems in quality such as pressure resistance, water permeability, and fractionation performance. Therefore, the outer diameter variation of the hollow fiber membrane is preferably 15% or less, more preferably 10% or less. The outer diameter variation was evaluated by the method described in the examples. As a means for setting the outer diameter variation of the hollow fiber membrane within the above range, there is control of the size of the annular slit of the double ring cap or the pressure loss of the central pipe of the double ring cap.

  When the phase separation of the hollow fiber membrane is induced by heat in the spinning process of the hollow fiber membrane, the hollow fiber membrane is cooled in a dry part and then rapidly cooled in a coagulation bath to be solidified. When inducing hollow fiber membrane phase separation with a poor solvent in the spinning process of the hollow fiber membrane, the spinning solution is discharged in contact with a coagulation liquid containing the poor solvent and solidified in a coagulation bath comprising the poor solvent. . In the method of inducing the phase separation of the hollow fiber membrane with the poor solvent, the poor solvent is supplied into the hollow fiber membrane by diffusion, so that the supply amount of the poor solvent changes in the thickness direction of the hollow fiber membrane. Therefore, the hole diameter of the cross section in the film thickness direction of the hollow fiber membrane increases from one surface of the hollow fiber membrane toward the other surface. Therefore, it is preferable to contact the coagulating liquid containing the poor solvent and the spinning dope immediately after discharge. If the concentration is adjusted by using the coagulation liquid as a mixture of a poor solvent and a good solvent, the coagulation property is changed, and the minor diameter of the pores on the surface in contact with the coagulation liquid and the thickness of the dense layer can be controlled.

  Further, the side where the coagulating liquid and the spinning dope are in contact with each other induces phase separation so that the solidification progresses quickly and the structure has a small pore size. Further, the pore diameter continuously increases in the direction opposite to the side where the coagulating liquid and the spinning dope come into contact. Here, if the passage time of the dry part is sufficiently long, the hole diameter on the side that does not come into contact with the coagulating liquid grows large. Therefore, by shortening the passage time of the dry part and quickly immersing it in the coagulation bath, solidification on the side not in contact with the coagulation liquid proceeds due to contact with the poor solvent of the coagulation bath, and a dense structure with a small pore diameter is formed. Can be formed.

  Although it depends on conditions affecting the progress of phase separation such as the composition of the spinning solution and temperature, the passage time of the dry part is preferably 0.02 seconds or more, more preferably 0.14 seconds or more. On the other hand, 0.40 second or less is preferable, and 0.35 second or less is more preferable.

  The poor solvent concentration in the coagulation bath is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and still more preferably 80 parts by mass or more with respect to the entire coagulation liquid.

  As the temperature of the coagulation bath, since the temperature of the coagulation bath is high, solvent exchange in the coagulation bath is likely to occur, and the amount of residual solvent in the hollow fiber membrane can be reduced. Is more preferable, and 70 ° C. or higher is even more preferable.

  When the temperature of the coagulation bath is high, there is a concern that dew condensation is formed on the surface of the base, which may cause yarn breakage. For this reason, it is possible to prevent dew condensation on the die surface, and the discharge temperature of the spinning dope is preferably 25 ° C. or higher. In addition, if the discharge temperature of the spinning solution is too high, the spinnability tends to become unstable. Therefore, the discharging temperature of the spinning solution is preferably 70 ° C. or less, and more preferably 55 ° C. or less.

  The concentration of the coagulation bath changes with time depending on the supply of the solvent from the spinning dope or the coagulating solution. For this reason, it is preferable to suppress the change in concentration by increasing the amount of the coagulation bath, or to adjust the concentration as needed by monitoring the concentration.

  In the dry section, it is also effective to control the opening of the hollow fiber membrane by providing a traveling section in which the temperature and humidity are more positively controlled, and variation in the performance of the obtained hollow fiber membrane can be reduced. To preferred.

  Further, in the dry section, although not particularly limited, in order to more actively control the humidity of the dry section atmosphere, it is possible to provide a cold wind tube on both sides of the spinning stock solution discharged from the double ring mouthpiece or from the double ring mouthpiece. It is conceivable to surround the discharged spinning stock solution with an annular cold wind tube. When installing cold wind tubes on both sides of the spinning dope discharged from the double ring nozzle, a method of supplying cold air from one side of the cold air tube and exhausting cold air from the other side, or a method of supplying cold air from both sides However, it is preferable because the humidity of the dry part atmosphere can be more positively controlled. In addition, when the periphery of the spinning dope discharged from the double ring die is surrounded by an annular cold wind tube, it is preferable because the dry part is less affected by outside air and the performance variation of the obtained hollow fiber membrane can be reduced.

  In the dry section, the larger the dew point and the wind speed of the cold air, the larger the supply amount of moisture, which is a poor solvent, which is effective when the hole diameter of the outer surface is increased and the hole area ratio is increased. The dew point of the dry part is preferably 18 ° C. or higher, and more preferably 21 ° C. or higher. Further, the wind speed of the cold air in the dry part is preferably 0.1 m / s or more, and more preferably 0.5 m / s or more. On the other hand, by reducing the wind speed of the cold air, it is possible to suppress the disturbance of the surface of the spinning dope under discharge and the fluctuation under the discharge. preferable.

  In addition, the length of the dry part is preferably 10 to 200 mm in order to make the hole diameter on the surface of the hollow fiber membrane suitable, while preventing yarn swinging during film formation.

  The poor solvent is a solvent that does not dissolve the polymer that mainly forms the structure of the hollow fiber membrane at the film forming temperature.

  The poor solvent may be appropriately selected according to the type of polymer, but water is preferably used. The good solvent may be appropriately selected according to the type of polymer, but N, N-dimethylacetamide is preferably used when the polymer that forms the structure of the hollow fiber membrane is a polysulfone polymer.

  According to the above production method, the hollow fiber membrane can be obtained in a wet state, but since the water permeability of the hollow fiber membrane is unstable as it is, drying of moisture and crosslinking reaction of a hydrophilic polymer (PVP, etc.) Is required. As described above, when a hydrophilic polymer (such as PVP) is contained, hydrophilicity can be imparted to the hollow fiber membrane, and water permeability can be improved and turbidity can be prevented from adhering to the membrane. However, the hydrophilic polymer remaining in the film may be slightly eluted. This is undesirable in medical and food industry applications. As a crosslinking reaction for insolubilization, γ-ray irradiation is effective for vinyl-based hydrophilic polymers. In particular, when the hydrophilic polymer is polyvinylpyrrolidone, it can be crosslinked by heating. The drying temperature is preferably 100 ° C. or higher because water is evaporated. The heat treatment temperature for crosslinking is preferably about 5 hours at 170 ° C., about 2.5 hours at 180 ° C., and about 1.5 hours at 190 ° C. If the temperature is further increased, the processing time is shortened accordingly. At 150 ° C. or lower, the treatment time is too long and is not practical.

  When the hollow fiber membrane is dried, if the drying is performed in a state where the hollow fiber membrane contains a large amount of the hydrophilic polymer, the hydrophilic polymer is unevenly distributed on the surface of the hollow fiber membrane. Since the water permeation performance of the membrane and the filtration flow rate when modularized are lowered, it is preferable to wash the obtained hollow fiber membrane with warm water as a pretreatment. As temperature of warm water, 60 ° C or more is preferred, 70 ° C or more is more preferred, and 80 ° C or more is still more preferred. Moreover, it is preferable that it is 99 degrees C or less. The mass of the hydrophilic polymer after washing with warm water is preferably 3 parts by mass or more and 20 parts by mass or less, and more preferably 5 parts by mass or more and 10 parts by mass or less with respect to the mass of the entire film.

  As described above, the hollow fiber membrane of the present invention can be suitably used for a cartridge for a water purifier. Moreover, the conventionally used method can be employ | adopted for the manufacturing method of the cartridge for water purifiers which mounts a hollow fiber membrane.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

(Analysis method and evaluation method)
(1) Viscosity measurement:
It measured using the B-type viscometer shown by JISK7117 (1999), and made the average value of n = 3 into the measured value.

(2) Measurement of water permeation performance A hollow fiber membrane is inserted into a case with reflux holes at both ends, and both ends are potted with an epoxy resin adhesive “Quick Mender” (registered trademark) manufactured by Konishi Co., Ltd. A small module having an effective length of 12 cm was produced by cutting the hollow fiber membrane and the potting agent protruding from both ends. From the amount of water passing through the hollow fiber membrane through the hollow fiber membrane and passing through the hollow fiber membrane within a predetermined time, maintained at 37 ° C. in a constant temperature water tank, and the pressure difference between the membranes The water permeability was measured by the calculation method. That is, the water permeability (UFRS) of the hollow fiber membrane was calculated by the following formula.
UFRS (mL / hr / Pa / m ² ) = Qw / T / P / A
Qw: (Pass) Filtration volume (mL)
T: Outflow time (hr)
P: Pressure (Pa)
A: Membrane area of the hollow fiber membrane (m ² )

(3) Measurement of the hole area ratio of the surface of the hollow fiber membrane and the hole diameter of the hole of the hollow fiber membrane A 5000 times image of the outer surface of the hollow fiber membrane was taken with SEM (S-5500, manufactured by Hitachi High-Technologies Corporation). , Imported into the computer. Next, analysis processing was performed with image processing software. The SEM image was binarized to obtain an image obtained by inverting the hole portion to black and the structural polymer portion to white. The total area S of the holes was read, and the aperture ratio (%) per image was calculated by the following formula.
Opening ratio (%) = S (μm ² ) / image size (μm ² ) × 100
The average pore size was similarly analyzed using image processing software. The SEM image was binarized to obtain an image in which the pores were black and the structural polymer portion was white. The total area S (μm ² ) of the holes and the number of black holes (hereinafter referred to as the total number of openings) were read, and the average hole area (μm ² ) was calculated by the following formula. Further, the average pore diameter (μm) was calculated from the average pore area (μm ² ). In addition, this calculation was performed assuming that the hole shape is a perfect circle.
Average pore area (μm ² ) = S (μm ² ) / total number of apertures Average pore diameter (μm) = 2 × √ (average pore area / π)
The above operation was performed on five different hollow fiber membranes, and the arithmetic average was taken as the result.

(4) Measurement of dense layer thickness (DT) The hollow fiber membrane was soaked in water for 5 minutes, then frozen with liquid nitrogen, quickly folded, and perpendicular to the longitudinal direction of the hollow fiber membrane as a cross-sectional observation sample The cross section is observed with SEM (S-5500, manufactured by Hitachi High-Technologies Corporation) at a magnification of 3000 times. The surface side of the dense structure part is the left side of the image, and the structure part is rough. The image was captured in a computer so that the front side of the image was placed on the right side of the image. In the following description, for convenience, a hollow fiber membrane in which the structure portion is dense on the outer surface side and the structure portion is rough on the inner surface side is described as an example. For hollow fibers with a dense structure on the inner surface and a rough structure on the outer surface, read the following explanation for the outer surface as the inner surface and the inner surface as the outer surface. Just do it.
The size of the captured image was 640 pixels × 480 pixels. When observed by SEM and the hollow part of the hollow fiber membrane in the cross section was blocked, the sample preparation was repeated. The clogging of the hollow portion may occur due to deformation of the hollow fiber membrane in the stress direction during the cutting process. In addition, when the dense layer did not fit in the observation field at the measurement magnification, two or more SEM images were synthesized so that the dense layer could fit. By binarization processing, an image in which the hole portion was black and the structure portion was white was obtained. If the structure part cannot be separated from the other parts due to the difference in contrast in the image, the image is cut out at the same contrast part and binarized, and then connected together as before. Returned to the image. Alternatively, the image analysis may be performed by painting other than the structure portion in black. When a hole was observed twice in the depth direction, the measurement was made with the shallower hole. The hole area was obtained by analyzing the portion displayed in black by the above-described binarization processing of the image, that is, the area of a single hole portion by image processing software.
The number of pixels of the scale bar indicating a known length in the image was measured, and the length per pixel number (μm) was calculated. The size of the captured image was 42.38 μm wide × 31.79 μm long.

By image processing, holes with a pore area exceeding 0.28 μm ² are painted in a fluorescent color, and a layer having no pores with a pore area exceeding 0.28 μm ² is used as a dense layer in the direction from the outer surface to the inner surface of the hollow fiber membrane. The thickness of the dense layer was measured. However, due to the influence of the hollow fiber membrane production method, pores having a pore area exceeding 0.28 μm ² may be observed near the dense layer surface. In addition, due to the effect that the image is out of focus, a plurality of holes having a hole area of 0.28 μm ² or less are recognized as one hole in the vicinity of the dense layer surface, and the hole area exceeds 0.28 μm ^2. As a result, the fluorescent color may be filled. If this happens, the accurate dense layer thickness cannot be measured. Therefore, if a hole with a hole area exceeding 0.28 μm ² exists at a position within 10% of the film thickness from the outer surface of the hollow fiber membrane (6 μm when the film thickness is 60 μm), it should be ignored as noise. It was.
Specifically, the thickness of the dense layer was measured as follows. First, a straight line perpendicular to the outer surface was drawn in the thickness direction of the hollow fiber membrane, that is, in the direction from the outer surface to the inner surface of the hollow fiber membrane. From the holes existing on this straight line, a hole having a hole area closest to the outer surface exceeding 0.28 μm ² was searched for. Of the intersection points between the holes and the straight line, an intersection point closer to the outer surface was selected, and the distance between the intersection point and the outer surface was taken as the thickness of the dense layer.

With respect to the captured image (width 42.38 μm × length 31.79 μm), the above image was divided into three in the lengthwise direction, and three images having a field of view 42.38 μm × length 10.6 μm were obtained. Next, the thickness of the dense layer at the vertical midpoint of each field of view was measured as described above.
The thickness of the dense layer was determined from each of the three divided fields of view, and the same measurement was performed from the 20 captured images to obtain a total of 60 measurement data of the thickness of the dense layer. The average value of 60 measurement data was calculated and defined as the thickness (DT) of the dense layer having only pores having a pore area of 0.28 μm ² or less.

(5) Hydrophilic polymer / hydrophobic polymer on the surface of the hollow fiber membrane A hollow fiber membrane measurement sample containing a hydrophilic polymer and a hydrophobic polymer is set in a sample holder, the sample holder is placed on a plate, The knob was turned to bring the prism and the surface (outer surface or inner surface) to be measured of the hollow fiber membrane into close contact. Next, the surface to be measured of the hollow fiber membrane was analyzed using an infrared ATR measurement device (manufactured by JASCO Corporation, infrared spectrophotometer: FT / IR-6000, infrared microscope: IRT-3000). The ratio of hydrophilic polymer to hydrophobic polymer (hydrophilic polymer / hydrophobic polymer) contained on the surface was obtained. Hereinafter, the measurement method will be described in detail by exemplifying a case where PVP is used as the hydrophilic polymer and PSF is used as the hydrophobic polymer.
From the infrared absorption spectrum obtained by analysis by infrared ATR measuring device, the area of the absorption peak of the PSF from the benzene ring C = C in the vicinity of 1580 cm ^-1 (Acc), derived from amide bonds PVP near 1650 cm ^-1 The area (Aco) of the absorption peak was calculated, and the ratio (Aco) / (Acc) of the peak areas was determined. About 30 hollow fiber membranes, the peak area ratio is obtained by the same method, the average value of the measurement data of the total 30 is calculated, and the ratio of PVP to PSF on the surface to be measured of the hollow fiber membranes (PVP / PSF) and did.

(6) Measurement of 0.2 μm particle removal rate A small module was produced in the same manner as in (2) above. From the outside of the hollow fiber membrane, a polystyrene latex bead suspension having a concentration of 200 ppm (manufactured by Invitrogen, Sulfate Latex) was supplied, and the concentration of the suspension permeated through the hollow fiber membrane to the inside was measured. Using the values of the supply side concentration of 200 ppm and the transmission side concentration, the rejection rate was determined by the following formula. The latex beads having a particle size of 0.2 μm (actual value 0.203 μm) were used.
Rejection rate = 1-Cp / Cf
Cp: Concentration on the transmission side Cf: Concentration on the supply side The relationship between the absorbance at 260 nm and the latex bead concentration was measured in advance, and the concentration was determined by measuring the absorbance of the suspension on the transmission side. Absorbance was measured using a spectrophotometer (manufactured by Hitachi, Ltd., U-5100).

(7) Measurement of inner diameter and film thickness of hollow fiber membrane The hollow fiber membrane was cut with a single blade in the film thickness direction and set on a microwatcher (VH-Z100, manufactured by KEYENCE). When the cross section of the hollow fiber was crushed by cutting, the cutting was repeated until it became a substantially perfect circle. The cross section of the hollow fiber membrane was observed with a 1000 × lens, the range of the thickness of the hollow fiber membrane was designated on the monitor screen on which the cross section was projected, and the numerical value displayed on the monitor screen was read. Moreover, a numerical value is displayed on a monitor screen by designating the hollow fiber membrane inner diameter as a range of the hollow part width. The same measurement was performed for 30 hollow fiber membranes, and the average value of a total of 30 measurement data was calculated as the inner diameter (ID) and film thickness (WT) of the hollow fiber membranes.

(8) Ratio of dense layer thickness (DT) to film thickness (WT) (DT / WT)
From the thickness (DT) of the dense layer calculated in (4) above and the film thickness (WT) of the hollow fiber membrane calculated in (7) above, the thickness (DT) of the dense layer and the film thickness (WT) of the hollow fiber membrane are calculated. The ratio (DT / WT) was calculated.

(9) Measurement of outer diameter and variation of outer diameter of hollow fiber membrane An outer diameter measuring device (manufactured by KEYENCE, controller part: LS-5500, sensor head part: LS-5040) cut into 30 cm in the longitudinal direction. The outer diameters of the hollow fiber membranes at positions 10 cm from both ends were measured.
The same measurement was performed on 20 hollow fiber membranes, the average value of 40 measurement data was calculated, and the outer diameter (OD) of the hollow fiber membranes was obtained. Furthermore, the largest outer diameter value (MAX) and the smallest outer diameter value (MIN) were selected from a total of 40 measurement data, and the outer diameter variation (ROD) was calculated by the following equation.
ROD (%) = (MAX−MIN) / OD × 100

(10) Pressure resistance A hollow fiber membrane inserted into an acrylic pipe, both ends potted with an epoxy resin adhesive “Quick Mender” (registered trademark) manufactured by Konishi Co., Ltd. A small module was produced by cutting
In the water tank, the small module was connected to a circuit in which an air cylinder, a pressure controller, a pressure meter, a dial gauge, and an open / close cock were connected using a joint.
The dial gauge was gradually opened, and the pressure value when the pressure suddenly decreased due to cracks in the hollow fiber membrane in the small module was defined as pressure resistance. If air leaks along the way, we started over.

(11) Flow rate of hollow fiber membrane module filtration A tube is connected to the non-opening side of the hollow fiber membrane module so that raw water can be supplied, water at 20 ° C. is supplied at 0.1 MPa, and permeates through the hollow fiber membrane. The amount of water per unit time was measured, and the hollow fiber membrane module filtration flow rate (L / min) per unit time was calculated.

(12) Water purifier cartridge turbidity filtration capacity Activated carbon was placed upstream of the produced hollow fiber membrane module and converted into a cartridge, which was then carried out in accordance with the method shown in JIS S 3201: 2004 (house water purifier test method). . The initial flow rate was set at 2.0 L / min.

Example 1
15 parts by mass of a hydrophobic polymer (PSF (Udel Polysulfone (registered trademark) P-3500) manufactured by Solvay), 7 parts by mass of a hydrophilic polymer (PVP (K90 manufactured by ISP)) and N, N-dimethylacetamide ( DMAc) 75 parts by mass and 3.0 parts by mass of water were dissolved and stirred to prepare a spinning dope. This spinning dope had a viscosity at 37 ° C. of 5.0 Pa · s. This spinning dope was discharged from the annular slit of the double ring die. A non-solidifying liquid consisting of 55 parts by mass of DMAc, 30 parts by mass of polyvinyl pyrrolidone (BASF K30, weight average molecular weight 40,000) and 15 parts by mass of glycerin was discharged from the center pipe. The base was kept at 37 ° C. The relative ratio of the injection liquid and the spinning linear solution discharge linear velocity was injection liquid discharge linear velocity / spinning raw solution discharge linear velocity = 0.8.

  A cold wind cylinder was installed in the dry section, and a predetermined dry length was allowed to pass while flowing cold wind gas from both sides of the spinning dope. The dry part dew point during spinning was as shown in Table 1. The spinning stock solution that has passed through the dry section is solidified by immersing it in an 80 ° C. coagulation bath containing 90 parts of water and 10 parts of DMAc mixed solution. A hollow fiber membrane wound up and wet was obtained. The wound hollow fiber membrane had an outer diameter of 300 μm, an inner diameter of 180 μm, and a film thickness of 60 μm. The obtained hollow fiber membrane was cut into 30 cm in the longitudinal direction and washed with hot water at 90 ° C. for 3 hours. The hollow fiber membrane was dried in a dry heat dryer and heat-treated at 160 ° C. or higher to obtain a dry hollow fiber membrane.

  The above-mentioned 1994 hollow fiber membranes in a dry state were folded in a U shape, inserted into a cylindrical case (inner diameter 26 mm, length 45 mm), and the opening was fixed with polyurethane resin to obtain a hollow fiber membrane module.

  Tables 1 and 2 show the configuration and various performances of the obtained hollow fiber membrane, the hollow fiber membrane module filtration flow rate, the water purifier cartridge turbidity filtration capability, and the like.

(Example 2)
A wet hollow fiber membrane was obtained in the same manner as in Example 1. The obtained hollow fiber membrane was cut into 30 cm in the longitudinal direction, the hollow fiber membrane was dried in a dry heat drier, and heat-treated at 160 ° C. or higher to obtain a dry hollow fiber membrane.

  The above-mentioned 1994 hollow fiber membranes in a dry state were folded in a U shape, inserted into a cylindrical case (inner diameter 26 mm, length 45 mm), and the opening was fixed with polyurethane resin to obtain a hollow fiber membrane module.

  Tables 1 and 2 show the configuration and various performances of the obtained hollow fiber membrane, the hollow fiber membrane module filtration flow rate, the water purifier cartridge turbidity filtration capability, and the like.

(Example 3)
A wet hollow fiber membrane was obtained in the same manner as in Example 1. The obtained hollow fiber membrane was cut into 30 cm in the longitudinal direction and washed with hot water at 90 ° C. for 3 hours. The hydrophilic polymer in the hollow fiber membrane was crosslinked by gamma ray irradiation (25 kGy).

  The above-mentioned 1994 hollow fiber membranes after gamma ray irradiation were folded in a U shape, inserted into a cylindrical case (inner diameter 26 mm, length 45 mm), and the opening was fixed with polyurethane resin to obtain a hollow fiber membrane module.

  Tables 1 and 2 show the configuration and various performances of the obtained hollow fiber membrane, the hollow fiber membrane module filtration flow rate, the water purifier cartridge turbidity filtration capability, and the like.

(Comparative Example 1)
The same method as in Example 1 except that the spinning dope is discharged from the annular slit of the double ring die at a discharge linear velocity of 0.003 m / s and the injection liquid is discharged from the injection liquid pipe at a discharge linear velocity of 0.04 m / s. As a result, a dry hollow fiber membrane was obtained. The yarn diameter of the hollow fiber membrane was an outer diameter of 300 μm, an inner diameter of 180 μm, and a film thickness of 60 μm. The relative ratio of the spinning linear solution and the injection liquid discharge linear velocity was injection liquid discharge linear velocity / spinning raw solution discharge linear velocity = 13.3.

  The above-mentioned 1994 hollow fiber membranes in a dry state were folded in a U shape, inserted into a cylindrical case (inner diameter 26 mm, length 45 mm), and the opening was fixed with polyurethane resin to obtain a hollow fiber membrane module.

  Tables 1 and 2 show the configuration and various performances of the obtained hollow fiber membrane, the hollow fiber membrane module filtration flow rate, the water purifier cartridge turbidity filtration capability, and the like. When the outer surface of the hollow fiber membrane was observed with SEM (S-5500, manufactured by Hitachi High-Technologies Corporation), the membrane structure of the outer surface was stretched in the longitudinal direction, and a pleated structure was formed. Therefore, the thickness of the dense layer in the hollow fiber membrane was reduced, and a hollow fiber membrane having low pressure resistance was obtained.

(Comparative Example 2)
The hollow fiber membrane was wound around the skein frame by the same operation as in Example 1 except that the viscosity of the spinning dope was set to 1.5 Pa · s and discharged from the annular slit of the double ring die. The yarn breakage between the base and the coagulation bath repeatedly occurred, making it difficult. The evaluation results of the hollow fiber membrane are shown in Tables 1 and 2. The hollow fiber membrane that was partially collected had a thin dense layer and a very large ROD of 27%. Since the ROD was large, the performance of the hollow fiber membrane became unstable, and the quality of the hollow fiber membrane deteriorated. In addition, the quality of the hollow fiber membrane of the comparative example 2 was inferior, and this hollow fiber membrane could not be bundled into a U shape. Therefore, a hollow fiber membrane module cannot be produced to evaluate the module filtration flow rate, and in the hollow fiber membrane of Comparative Example 2, the hollow fiber membrane module filtration flow rate and the water purifier cartridge turbidity filtration ability can be evaluated. I could not do it.

(Comparative Example 3)
The same method as in Example 1 except that the spinning dope is discharged from the annular slit of the double ring die at a discharge linear velocity of 0.28 m / s and the injection liquid is discharged from the injection liquid pipe at a discharge linear velocity of 0.22 m / s. As a result, a dry hollow fiber membrane was obtained. The hollow fiber membrane had an outer diameter of 360 μm, an inner diameter of 220 μm, and a film thickness of 70 μm. The relative ratio between the spinning solution and the injection liquid discharge linear velocity was injection solution discharge linear velocity / spinning solution discharge linear velocity = 0.79.

  1384 hollow fiber membranes in the dry state were folded in a U shape, inserted into a cylindrical case (inner diameter 26 mm, length 45 mm), and the opening was fixed with polyurethane resin to obtain a hollow fiber membrane module.

  Tables 1 and 2 show the configuration and various performances of the obtained hollow fiber membrane, the hollow fiber membrane module filtration flow rate, the water purifier cartridge turbidity filtration capability, and the like.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on March 22, 2016 (Japanese Patent Application No. 2006-056695), the contents of which are incorporated herein by reference.

  The present invention can be used as a hollow fiber membrane applicable to a hollow fiber membrane module or a water purifier cartridge in the field of water treatment. In addition to the water purifier, it can also be used for medical applications such as a plasma separation membrane.

Claims (5)

A hollow fiber membrane comprising a dense layer having only pores having a pore area of 0.28 μm ² or less in a state observed in a cross section perpendicular to the longitudinal direction of the hollow fiber membrane,
The dense layer is disposed on the outer surface side or the inner surface side of the hollow fiber membrane,
The hollow fiber membrane has an outer diameter of 350 μm or less,
The hollow fiber membrane has an inner diameter of 150 μm or more,
The hollow fiber membrane has a thickness of 30 μm or more and 90 μm or less,
The surface of the hollow fiber membrane on which the dense layer is disposed has a plurality of holes, and the average pore diameter observed on the surface of the hollow fiber membrane of the plurality of holes is 0.3 μm or more and 0.9 μm or less,
The hollow fiber membrane whose ratio (DT / WT) of the thickness (DT) of the said dense layer and the film thickness (WT) of the said hollow fiber membrane is 0.24 or more.   The hollow fiber membrane according to claim 1, wherein the dense layer is disposed on an outer surface side of the hollow fiber membrane.   The hollow fiber membrane according to claim 1 or 2, wherein a porosity of a surface of the hollow fiber membrane on which the dense layer is arranged is 15% or more and 45% or less.   The hollow fiber membrane according to any one of claims 1 to 3, comprising a polysulfone polymer and polyvinylpyrrolidone.   The cartridge for water purifiers which mounts the hollow fiber membrane of any one of Claims 1-4.