JP5834507B2 - Method and apparatus for producing porous hollow fiber membrane - Google Patents

Description

  The present invention relates to a method for manufacturing a porous hollow fiber membrane and a manufacturing apparatus.

  In the fields of food industry, medical care, electronics industry, etc., for the purpose of concentrating and collecting useful components, removing unnecessary components, and making water, etc., microfiltration membranes, ultrafiltration membranes, Osmotic filtration membranes are frequently used. For the formation of the porous hollow fiber membrane, a film-forming resin such as cellulose acetate, polyacrylonitrile, polysulfone, and fluorine resin is used.

  The porous hollow fiber membrane is formed, for example, by spinning a film-forming stock solution containing a film-forming resin, a pore-opening agent, and a solvent and coagulating it in a coagulating liquid. Moreover, since the pore-opening agent and the solvent remain in the porous hollow fiber membrane after the coagulation, the porous hollow fiber membrane is dried after washing and removing those components. As a method for drying the porous hollow fiber membrane, the porous hollow fiber membrane is continuously run in a drying device in which hot air circulates at a wind speed of about several meters per second, and hot air is blown outside the porous hollow fiber membrane. The method of sending and drying is widely used. (For example, patent document 1).

JP-A-2005-220202

  However, in order to sufficiently dry the porous hollow fiber membrane by the above-described hot air circulation type drying device, the porous hollow fiber membrane is reciprocated several times in the drying device, and the porous hollow fiber membrane in the drying device is Need to stay longer. Moreover, when the film-forming speed | rate of a porous hollow fiber membrane is raised, the residence time of the porous hollow fiber membrane in a drying apparatus will become short, and drying will become inadequate. In order to perform drying corresponding to the high-speed film formation, it is conceivable to increase the size of the drying apparatus.

  An object of this invention is to provide the manufacturing method and manufacturing apparatus of a porous hollow fiber membrane which can dry a porous hollow fiber membrane efficiently at low cost and can obtain high productivity.

The method for producing a porous hollow fiber membrane of the present invention comprises a coagulation step of coagulating a membrane-forming stock solution containing a film-forming resin and a pore-opening agent in a coagulation solution to obtain a porous hollow fiber membrane precursor; A porous hollow having a removal step of removing the pore-forming agent from the hollow fiber membrane precursor to form a porous hollow fiber membrane having a porous membrane layer, and a drying step of drying the porous hollow fiber membrane A method for producing a yarn membrane, wherein the drying step includes a first drying step of drying the porous hollow fiber membrane with saturated steam heated to 80 ° C. or more and 120 ° C. or less, and after the first drying step. A second drying step of drying the porous hollow fiber membrane.
In the method for producing a porous hollow fiber membrane of the present invention, the second drying step is preferably a step of drying the porous hollow fiber membrane after the first drying step with hot air.
Moreover, it is preferable that the said porous hollow fiber membrane is a porous hollow fiber membrane which has the said porous membrane layer on the outer side of a hollow reinforcement support body.
Moreover, it is preferable that said 1st drying process is a process of drying the said porous hollow fiber membrane with the said saturated water vapor within the steam drying part which has a labyrinth seal structure.
In the first drying step, it is preferable that the time for which the saturated water vapor is brought into contact with the porous hollow fiber membrane is 10 seconds or more and 300 seconds or less.

The apparatus for producing a porous hollow fiber membrane of the present invention comprises a coagulation means for coagulating a membrane-forming stock solution containing a film-forming resin and a pore-opening agent in a coagulation solution to obtain a porous hollow fiber membrane precursor, Removing means for removing the pore-forming agent from the porous hollow fiber membrane precursor to form a porous hollow fiber membrane having a porous membrane layer; and drying means for drying the porous hollow fiber membrane, The said drying means is an apparatus which has a steam drying part which dries the said porous hollow fiber membrane with the saturated water vapor | steam heated at 80 degreeC or more and 120 degrees C or less .
In the porous hollow fiber membrane production apparatus of the present invention, it is preferable that the drying means has a hot air drying unit that dries the porous hollow fiber membrane dried by the steam drying unit with hot air.

According to the method for producing a porous hollow fiber membrane of the present invention, the porous hollow fiber membrane can be efficiently dried at low cost, and the porous hollow fiber membrane can be produced with high productivity.
Further, the porous hollow fiber membrane production apparatus of the present invention can efficiently dry the porous hollow fiber membrane at low cost, and can produce the porous hollow fiber membrane with high productivity.

It is the schematic which showed an example of the manufacturing apparatus of the porous hollow fiber membrane of this invention. It is the schematic block diagram which showed an example of the support body manufacturing apparatus. It is the figure which showed the structure of the hollow knitted string. It is the enlarged view which showed the mesh of the hollow knitted string.

Hereinafter, it demonstrates in detail, showing an example of the manufacturing method and manufacturing apparatus of the porous hollow fiber membrane of this invention.
(manufacturing device)
A porous hollow fiber membrane manufacturing apparatus 100 illustrated in FIG. 1 (hereinafter simply referred to as “manufacturing apparatus 100”) uses a membrane-forming stock solution containing a film-forming resin, a pore-opening agent, and a solvent. This is an apparatus for producing a yarn membrane.
As shown in FIG. 1, the production apparatus 100 of the present embodiment coagulates a membrane-forming stock solution to form a porous hollow fiber membrane precursor 1 </ b> A (hereinafter referred to as “hollow fiber membrane precursor 1 </ b> A”). 10, a cleaning means 20 for removing the solvent remaining in the hollow fiber membrane precursor 1A, and a porous hollow fiber membrane 1 having a porous membrane layer by removing the pore-opening agent remaining in the hollow fiber membrane precursor 1A Removing means 30, drying means 40 for drying the porous hollow fiber membrane 1, and winding means 50 for winding the porous hollow fiber membrane 1. The travel of the porous hollow fiber membrane 1 in the manufacturing apparatus 100 is regulated by the guide member 61.

  The coagulation means 10 of this example has a spinning nozzle 12 that spins the film-forming stock solution and a coagulation tank 16 that stores a coagulating liquid 14 that coagulates the film-forming stock solution, and an empty space between the spinning nozzle 12 and the coagulating liquid 14. A means for performing dry and wet spinning provided with a running section 18. In this coagulation means 10, the film-forming stock solution spun from the spinning nozzle 12 is immersed in the coagulation liquid 14 in the coagulation tank 16, and the film-forming stock solution is solidified by the coagulation liquid 14 to form the hollow fiber membrane precursor 1A. Thereafter, the hollow fiber membrane precursor 1 </ b> A is drawn out from the coagulation liquid 14.

The form of the spinning nozzle 12 can be appropriately selected according to the structure of the porous hollow fiber membrane to be produced. For example, it may be a nozzle for forming a porous hollow fiber membrane 1 consisting only of a hollow porous membrane layer, which discharges only the membrane-forming stock solution into a cylindrical shape, It may be a nozzle for forming a porous hollow fiber membrane 1 in which a porous membrane layer is laminated on the outside of the reinforcing support, which is discharged so as to apply a membrane-forming stock solution on the outside.
The spinning nozzle 12 may be a nozzle for discharging a single film-forming stock solution to form the porous hollow fiber membrane 1 having a single porous membrane layer. It may be a composite nozzle for forming a porous hollow fiber membrane 1 which is discharged in a concentric cylindrical shape and in which a plurality of porous membrane layers are laminated.

As the coagulation tank 16, a coagulation liquid 14 can be accommodated, and a film-forming stock solution spun from the spinning nozzle 12 can be immersed in the coagulation liquid 14, and the hollow fiber membrane precursor 1 A formed by coagulation can be extracted from the coagulation liquid 14. If it is, it will not specifically limit.
The coagulation tank 16 is preferably provided with temperature adjusting means capable of adjusting the temperature of the coagulating liquid 14.

  The coagulation means 10 is not limited to the dry and wet means described above. For example, the idle running section 18 is not provided between the spinning nozzle 12 and the coagulation liquid 14 in the coagulation tank 16, and the film-forming stock solution is directly used as the coagulation liquid 14. You may employ | adopt the wet spinning which spins in.

The cleaning means 20 is means for removing the solvent remaining in the hollow fiber membrane precursor 1A by cleaning with a cleaning liquid. The cleaning means 20 in this example is a means for cleaning the hollow fiber membrane precursor 1A by running the hollow fiber membrane precursor 1A in the cleaning liquid 22 accommodated in the cleaning tank 24.
The cleaning tank 24 is not particularly limited as long as it can store the cleaning liquid 22 and can be drawn out after running the hollow fiber membrane precursor 1 </ b> A in the cleaning liquid 22.

  The cleaning means 20 is not limited to this form, and means usually used as means for removing the solvent remaining in the hollow fiber membrane precursor 1A can be adopted. For example, a means for causing the cleaning liquid to flow in an inclined bowl-shaped cleaning bath and causing the hollow fiber membrane precursor 1A to travel in the cleaning liquid may be employed.

  As the removing means 30, those usually used as means for removing the pore-forming agent remaining in the hollow fiber membrane precursor 1A can be used. For example, a chemical solution holding unit that holds a chemical solution containing an oxidizing agent in the hollow fiber membrane precursor 1A and a thermal decomposition unit that oxidatively decomposes the pore-opening agent by heating the hollow fiber membrane precursor 1A holding the chemical solution in a gas phase. And a means having a washing / removing part that removes the pore-opening agent having a reduced molecular weight from the hollow fiber membrane precursor 1A by washing with a washing liquid.

As a chemical | medical solution holding | maintenance part, what has a chemical | medical solution tank which accommodates a chemical | medical solution, and hold | maintains a chemical | medical solution by making hollow fiber membrane precursor 1A run in the chemical | medical solution is mentioned.
As the thermal decomposition part for heating the hollow fiber membrane precursor 1A holding the chemical solution, one that heats the hollow fiber membrane precursor 1A using a heating fluid under atmospheric pressure is preferable. An oxidizing agent such as hypochlorite It is more preferable to use a fluid having a high relative humidity as the heating fluid and heat it under wet heat conditions from the standpoint of preventing drying of the substrate and performing an efficient decomposition treatment.
As the cleaning / removal unit, for example, the form described in the cleaning unit 20 can be adopted.
The porous membrane layer is formed by removing the pore-forming agent remaining in the coagulated membrane layer where the membrane-forming stock solution in the hollow fiber membrane precursor 1A is solidified, and forming pores in the portion where the pore-forming agent remains. Is formed, the porous hollow fiber membrane 1 is obtained.

The drying means 40 includes a steam drying unit 42 that dries the porous hollow fiber membrane 1 with heated saturated water vapor, and a hot air drying unit 44 that dries the porous hollow fiber membrane 1 dried in the steam drying unit 42 with hot air. doing.
The steam drying unit 42 can supply heated saturated water vapor therein, and can run the porous hollow fiber membrane 1 in the saturated water vapor. Inside the steam drying section 42, the porous hollow fiber membrane 1 is heated by the heated saturated water vapor, and the moisture contained in the porous hollow fiber membrane 1 is partially evaporated to perform drying.

The structure of the steam drying part 42 should just be a structure which can make the porous hollow fiber membrane 1 drive | work stably in the heated saturated water vapor | steam. For example, the steam drying unit 42 may have a labyrinth seal structure that suppresses a large amount of saturated water vapor from leaking to the outside.
Moreover, the steam drying part 42 may be adapted to spray heated saturated water vapor onto the porous hollow fiber membrane 1 traveling inside.

The hot air drying unit 44 can circulate hot air at a speed of about several meters per second, and the guide member 61 changes the traveling direction of the porous hollow fiber membrane 1 so that a plurality of porous hollow fiber membranes 1 are formed inside. It can be reciprocated twice. Inside the hot air drying unit 44, drying is performed by blowing hot air to the traveling porous hollow fiber membrane 1.
As the hot air drying unit 44, for example, a known hot air dryer used for drying a porous hollow fiber membrane can be used.

  The winding means 50 only needs to be able to wind the porous hollow fiber membrane 1 around a bobbin or the like. For example, the tension of the porous hollow fiber membrane 1 is controlled by a tension roll, a torque motor or the like, and the guide or bobbin is traversed. What has the structure which winds up the porous hollow fiber membrane 1 is made to be made.

The guide member 61 regulates the travel of the porous hollow fiber membrane 1 from the coagulation means 10 to the cleaning means 20, the removal means 30, the drying means 40, and the winding means 50 in the manufacturing apparatus 100. By providing the guide member 61, it is possible to suppress the drooping of the yarn, thereby preventing the porous hollow fiber membrane 1 from coming into contact with the inside / outside of each means or the vicinity of the entrance / exit.
As the guide member 61, those usually used for the production of a porous hollow fiber membrane can be used, and examples thereof include a metal or ceramic guide member.

(Production method)
Hereinafter, the manufacturing method using the said manufacturing apparatus 100 is demonstrated as an example of the manufacturing method of the porous hollow fiber membrane of this invention.
The manufacturing method of the porous hollow fiber membrane of this embodiment has the following coagulation | solidification process, a washing | cleaning process, a removal process, a drying process, and a winding-up process.
Coagulation step: a step of forming the hollow fiber membrane precursor 1A by coagulating the membrane-forming stock solution in the coagulation solution 14 by the coagulation means 10.
Washing step: a step of washing the hollow fiber membrane precursor 1A by the washing means 20 to remove the solvent remaining in the hollow fiber membrane precursor 1A.
Removal step: A step of forming the porous hollow fiber membrane 1 by removing the pore-opening agent remaining in the hollow fiber membrane precursor 1A by the removing means 30.
Drying step: a step of drying the porous hollow fiber membrane 1 by the drying means 40.
Winding step: A step of winding the porous hollow fiber membrane 1 after drying by the winding means 50.

Solidification process:
A film-forming stock solution containing a film-forming resin, a pore-opening agent and a solvent is prepared. In the coagulation means 10, the film-forming stock solution is discharged from the spinning nozzle 12, coagulated with the coagulation liquid 14 contained in the coagulation tank 16, A thread membrane precursor 1A is formed. The film-forming stock solution discharged from the spinning nozzle 12 is immersed in the coagulation liquid 14, so that the coagulation liquid 14 diffuses into the film-forming stock solution and the film-forming resin and the pore-opening agent coagulate while causing phase separation. Thus, a hollow fiber membrane precursor 1A having a solidified membrane layer having a three-dimensional network structure in which the membrane-forming resin and the pore opening agent are interlaced with each other is formed. At this stage, it is presumed that the pore opening agent is three-dimensionally entangled with the film-forming resin in a gel state. By removing the pore opening agent of the coagulated membrane layer in a removing step described later, pores are formed in the portion where the pore opening agent remains to form a porous membrane layer.

The film-forming resin is not particularly limited as long as it can form a porous film layer with a coagulation liquid. Polysulfone resins such as polysulfone and polyethersulfone; Fluorine resins such as polyvinylidene fluoride; polyacrylonitrile; cellulose derivatives; polyamides Polyester, polymethacrylate, polyacrylate and the like. In addition, copolymers of these resins may be used, or those obtained by introducing a substituent into a part of these resins and copolymers may be used.
A film-forming resin may be used alone or in combination of two or more. Further, the same kind of polymers having different molecular weights may be blended and used.

  The film-forming resin is preferably a fluorine-based resin because it has excellent durability against oxidizing agents such as hypochlorous acid, and is a polyvinylidene fluoride or a copolymer made of vinylidene fluoride alone and other monomers. Is more preferable. Therefore, for example, when the porous hollow fiber membrane 1 is treated with an oxidizing agent in the removing step, it is preferable to select a fluororesin as the film-forming resin.

  The pore-opening agent is added to adjust the viscosity of the membrane-forming stock solution to a range suitable for the formation of the porous hollow fiber membrane and stabilize the membrane-forming state. Examples of the pore opening agent include polyethylene glycol and polyvinyl pyrrolidone. As the pore-opening agent, polyvinylpyrrolidone and a copolymer obtained by copolymerizing other monomers with polyvinylpyrrolidone are preferable from the viewpoint of controlling the pore diameter of the porous hollow fiber membrane 1 and strength.

One type of pore-opening agent may be used alone, or two or more types may be used in combination.
The higher the molecular weight of the pore-opening agent, the easier it is to form a porous hollow fiber membrane 1 with a good membrane structure. On the other hand, the lower the molecular weight of the pore opening agent, the easier it is to remove the pore opening agent in the removal step described later. Therefore, depending on the purpose, the same kind of pore opening agents having different molecular weights may be appropriately blended and used.

A film-forming stock solution can be prepared by mixing the film-forming resin and the pore-opening agent in a solvent (good solvent) in which they are soluble.
The solvent is not particularly limited, and when dry and wet spinning is employed, the pore diameter of the porous hollow fiber membrane 1 is adjusted by absorbing the membrane-forming stock solution in the idle running section 18, so that the solvent is easily mixed uniformly with water. Is preferably selected. Examples of such a solvent include N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N-methylmorpholine-N-oxide and the like.
A solvent may be used individually by 1 type and may use 2 or more types together. Moreover, as long as the solubility of the film-forming resin and the pore-opening agent in the solvent is not impaired, a poor solvent such as the film-forming resin and the pore-opening agent may be mixed and used.
Other additive components may be added to the film-forming stock solution as necessary.

The content of the film-forming resin in the film-forming stock solution (100% by mass) is preferably 10% by mass or more from the viewpoint that stability during film formation is improved and an excellent porous film structure is easily formed. More than mass% is more preferable. Further, for the same reason, the content of the film-forming resin is preferably 30% by mass or less, and more preferably 25% by mass or less.
The content of the pore-opening agent in the membrane-forming stock solution (100% by mass) is preferably 1% by mass or more and more preferably 5% by mass or more from the viewpoint that the formation of the porous hollow fiber membrane 1 is facilitated. In addition, the content of the pore-opening agent is preferably 20% by mass or less, and more preferably 12% by mass or less from the viewpoint of the handleability of the film-forming stock solution.
The temperature of the film-forming stock solution is preferably 20 to 40 ° C.

The coagulating liquid 14 is a solvent that does not dissolve the film-forming resin and needs to be a good solvent for the pore opening agent. Examples of the coagulating liquid 14 include water, ethanol, methanol, and a mixture thereof. Among these, from the viewpoint of work environment and operation management, a mixed solution of a solvent and water used for the film-forming stock solution is preferable.
The temperature of the coagulating liquid 14 is preferably 60 to 90 ° C.

In addition, the method for producing a porous hollow fiber membrane of the present invention is a porous hollow fiber in which a porous membrane layer is formed outside a hollow reinforcing support for the purpose of obtaining a porous hollow fiber membrane having higher strength. The film 1 may be formed. That is, the coagulation step may be a step of spinning so as to apply the film-forming stock solution to the outside of the reinforcing support, and coagulating the film-forming stock solution with the coagulation solution.
Examples of the reinforcing support include hollow knitted cords and braids made of various fibers, and various materials can be used alone or in combination. Examples of the fiber used for the hollow knitted string and braid include synthetic fiber, semi-synthetic fiber, regenerated fiber, and natural fiber. The form of the fiber may be any of monofilament, multifilament, and spun yarn.

Cleaning process:
In the hollow fiber membrane precursor 1A formed in the coagulation step, a pore-forming agent and a solvent remain, and sufficient water permeability cannot be exhibited at this stage. Further, when the pore-opening agent is dried in the film, it may cause a decrease in the mechanical strength of the film. On the other hand, when the pore-opening agent is oxidatively decomposed (lower molecular weight) using an oxidizing agent in the removing step described later, if the solvent remains in the hollow fiber membrane precursor 1A, the solvent and the oxidizing agent are Since it reacts, the oxidative decomposition of the pore-opening agent is inhibited. Therefore, in the present embodiment, after the solidification step, the solvent remaining in the hollow fiber membrane precursor 1A is removed in the washing step, and then the pore-opening agent remaining in the hollow fiber membrane precursor 1A is removed in the removal step.

  In the cleaning step, the solvent remaining in the hollow fiber membrane precursor 1A is removed by cleaning the hollow fiber membrane precursor 1A with the cleaning liquid 22 by the cleaning means 20. The solvent in the hollow fiber membrane precursor 1A diffuses and moves from the inside of the membrane to the membrane surface, and also diffuses and moves from the membrane surface to the cleaning liquid 22 to be removed from the hollow fiber membrane precursor 1A.

  The cleaning liquid 22 is preferably water because of its high cleaning effect. Examples of the water used include tap water, industrial water, river water, and well water. Moreover, you may mix and use alcohol, inorganic salts, an oxidizing agent, surfactant, etc. for these. Further, as the cleaning liquid 22, a mixed liquid of a solvent and water contained in the film-forming stock solution can also be used. However, when using this mixed solution, the concentration of the solvent is preferably 10% by mass or less.

The temperature of the cleaning liquid 22 is preferably 50 ° C. or higher and more preferably 80 ° C. or higher from the viewpoint of improving the diffusion transfer rate of the solvent remaining in the hollow fiber membrane precursor 1A.
In the cleaning step, the solvent in the hollow fiber membrane precursor 1A is mainly removed, but the pore opening agent is partially removed by cleaning the hollow fiber membrane precursor 1A.

Removal process:
In the removing step, the pore-opening agent remaining in the hollow fiber membrane precursor 1A is removed by the removing means 30 to form the porous hollow fiber membrane 1 having a porous membrane layer.
As the removal step, for example, the hollow fiber membrane precursor 1A is immersed in a chemical solution containing an oxidant, the hollow fiber membrane precursor 1A is held in the chemical solution, and then the hollow fiber membrane precursor 1A is heated in the gas phase. Then, oxidative decomposition of the pore-opening agent is performed, and then the hollow fiber membrane precursor 1A is washed to remove the pore-opening agent having a reduced molecular weight.

  Examples of the oxidizing agent include hypochlorite, ozone, hydrogen peroxide, permanganate, dichromate, persulfate, and the like. Of these, hypochlorite is preferable from the viewpoints of strong oxidizing power, excellent decomposition performance, excellent handleability, and low cost. Examples of the hypochlorite include sodium hypochlorite and calcium hypochlorite, and sodium hypochlorite is particularly preferable.

  It is easy to suppress the oxidative decomposition of the pore-opening agent remaining in the hollow fiber membrane precursor 1A from proceeding in the chemical solution, and the pore-opening agent dropped into the chemical solution is further oxidatively decomposed to prevent the oxidizing agent from being wasted. From the point of being easy to do, the temperature of a chemical | medical solution has preferable 50 degrees C or less, and 30 degrees C or less is more preferable. Moreover, the temperature of a chemical | medical solution is 0 degreeC or more, and 10 degreeC or more is more preferable from the point by which the cost etc. for controlling a chemical | medical solution to low temperature are suppressed.

The heating of the hollow fiber membrane precursor 1A holding the chemical solution is preferably performed using a heated fluid under atmospheric pressure.
As the heating fluid, it is preferable to use a fluid having a high relative humidity, that is, heating under humid heat conditions, from the viewpoint that drying of the oxidant is suppressed and a more efficient decomposition treatment is possible. In this case, the relative humidity of the heating fluid is preferably 80% or more, more preferably 90% or more, and particularly preferably around 100%.
The heating temperature is preferably 50 ° C. or higher, and more preferably 80 ° C. or higher, because the processing time can be shortened when continuous processing is performed. Further, the heating temperature is preferably 100 ° C. or lower in the atmospheric pressure state.

  As a method for removing the pore-opening agent having a reduced molecular weight, a method for washing the hollow fiber membrane precursor 1A is preferable. The cleaning method is not particularly limited, and the cleaning methods mentioned in the cleaning step can be adopted.

Drying process:
The porous hollow fiber membrane 1 is dried by the drying means 40.
The drying step of the present embodiment includes a first drying step of drying the porous hollow fiber membrane 1 with heated saturated steam by the steam drying unit 42, and the porous hollow fiber membrane 1 after the first drying step. A hot air drying unit 44 has a second drying process of drying with hot air.

In the first drying step, the porous hollow fiber membrane 1 is caused to travel in the heated saturated water vapor in the steam drying unit 42, whereby the porous hollow fiber membrane 1 is heated by the saturated water vapor, and the porous hollow fiber is obtained. A part of the water contained in the film 1 is evaporated.
The temperature of the saturated water vapor is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, from the viewpoint that the treatment time can be shortened. Further, the temperature of the saturated water vapor is industrially preferably 150 ° C. or lower, more preferably 120 ° C. or lower, from the viewpoint of reducing an excessive amount of steam.

  In the first drying step, low-pressure saturated steam or pressurized saturated steam can be used as saturated steam, and in particular, low-pressure saturated steam having a degree of vacuum of 50 kPa or more is more preferable from the viewpoint of shortening the treatment time. .

The traveling time of the porous hollow fiber membrane 1 in saturated water vapor, that is, the time for which the saturated water vapor is brought into contact with the porous hollow fiber membrane 1 is preferably 10 seconds or more, more preferably 60 seconds or more from the viewpoint of drying efficiency. The time is preferably 300 seconds or less, more preferably 180 seconds or less from the viewpoint of productivity.
The running time of the porous hollow fiber membrane 1 in saturated water vapor can be adjusted by the running speed of the porous hollow fiber membrane 1. The traveling speed of the porous hollow fiber membrane 1 in the steam drying section 42 is preferably 5 to 30 m / min.

By such a first drying step, about 10% by mass of water contained in the porous hollow fiber membrane 1 is removed.
The first drying step may be a method of spraying heated saturated water vapor onto the porous hollow fiber membrane 1 that travels.

  In the second drying step, the hot air drying unit 44 dries the porous hollow fiber membrane 1 dried by the steam drying unit 42 with hot air. In the hot air drying unit 44, the porous hollow fiber membrane 1 is continuously reciprocated a plurality of times inside the hot air circulated at a wind speed of about several meters per second, and the porous hollow fiber membrane 1 is dried from the outer peripheral side. To do.

The speed of hot air is preferably 0.5 to 5.0 m / sec.
The temperature of the hot air is preferably 70 to 140 ° C. If the temperature of the hot air is equal to or higher than the lower limit value, the porous hollow fiber membrane 1 can be easily dried. If the temperature of the hot air is not more than the upper limit value, the amount of heat to be used is not excessive, which is industrially preferable.

  The residence time of the porous hollow fiber membrane 1 inside the hot air drying section 44 in the second drying step is preferably 1 to 30 minutes. If the residence time of the porous hollow fiber membrane 1 in the hot air drying part 44 is not less than the lower limit value, the porous hollow fiber membrane 1 is easily dried sufficiently. If the residence time of the porous hollow fiber membrane 1 in the hot air drying unit 44 is equal to or less than the upper limit value, the productivity is improved.

Winding process:
By the winding means 50, the porous hollow fiber membrane 1 after drying is wound up.

  In the method and apparatus for producing the porous hollow fiber membrane of the present invention described above, the porous hollow fiber membrane is dried at low cost and efficiently by drying the porous hollow fiber membrane using heated saturated water vapor. The membrane can be dried. Therefore, a porous hollow fiber membrane can be manufactured at low cost and high productivity.

Note that the porous hollow fiber membrane production apparatus of the present invention can be used in the production apparatus 100 as long as the drying means has a steam drying section that dries the porous hollow fiber membrane with heated saturated water vapor. Is not limited. For example, the manufacturing apparatus 100 employs dry and wet spinning in which an idle running section 18 is provided between the spinning nozzle 12 and the coagulating liquid 14 in the coagulation tank 16, but employs wet spinning in which the idle running section 18 is not provided. May be. Further, the drying means 40 has the hot air drying unit 44 that dries the porous hollow fiber membrane 1 with hot air. However, the drying of the porous hollow fiber membrane dried by the steam drying unit is performed by the hot air drying unit 44. Is not limited.
Further, the porous hollow fiber membrane production apparatus of the present invention may not have the winding means 50.

  Moreover, the manufacturing method of the porous hollow fiber membrane of this invention will be limited to the method of using the manufacturing apparatus 100 mentioned above, if a drying process is a method which has said 1st drying process and 2nd drying process. Not. For example, the drying of the porous hollow fiber membrane in the second drying step in the drying step is not limited to the above-described drying with hot air.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Example 1]
Manufacturing process of reinforced support:
A reinforcing support body made of a hollow knitted string was manufactured using the support body manufacturing apparatus 70 shown in FIG. The support manufacturing apparatus 70 supplies a bobbin 71, a circular knitting machine 73 that circularly knits a yarn 72 drawn from the bobbin 71, and a string supply that pulls a hollow knitted string 74 knitted by the circular knitting machine 73 with a constant tension. A device 75; a heating die 76 for heat-treating the hollow knitted string 74; a take-up device 77 for picking up the reinforcing support X obtained by heat-treating the hollow knitted string 74; and a winding for winding the reinforcing support X around the bobbin. And a take-off machine 78.
As the raw yarn, polyester fiber (fineness: 84 dtex, number of filaments: 36) was used. As the bobbin 71, five pieces of the polyester fiber wound with 5 kg were prepared. As the circular knitting machine 73, a table type knitting machine (manufactured by Sakurai Textile Machinery Co., Ltd., number of knitted needles: 12, needle size 116 gauge, spindle circumferential diameter: 8 mm) was used. A Nelson roll was used as the string supply device 75 and the take-up device 77. As the heating die 76, a stainless steel die having a heating means (inner diameter D (inlet side): 5 mm, inner diameter d (outlet side): 2.2 mm, length: 300 mm) was used.
The polyester fibers drawn from the bobbin 71 are combined into one yarn 72 (total fineness is 420 dtex), and then circular knitted by a circular knitting machine 73 to form a hollow knitted string 74. The hollow knitted string 74 Was passed through a heating die 76 at 195 ° C., and the heat-treated hollow knitted string 74 was wound around the winding device 78 at a winding speed of 100 m / hr as the reinforcing support X. Production of the reinforced support X was continued until the polyester fiber of the bobbin 71 was exhausted.
The obtained reinforcing support X had an outer diameter of about 2.1 mm and an inner diameter of 1.3 mm. As shown in FIGS. 3 and 4, the hollow knitted string 74 constituting the reinforcing support X is formed by continuously forming a loop 72 a (black portion in FIG. 4) in which the yarn 72 is curved in a spiral shape, These loops 72a are connected in the vertical direction, and as shown in FIG. 4, a mesh 74a is provided in the loop 72a and at the connecting portion between the loops 72a. The number of the loops 72a was 12 per round, and the maximum opening width L of the mesh 74a was about 0.05 mm. The length of the reinforcing support X was 12000 m.

Preparation process of film forming stock solution:
Polyvinylidene fluoride (PVDF) (trade name, Kyner 301F, manufactured by Arkema) as a film-forming resin, and polyvinyl pyrrolidone (PVP) (product name, PVP-K79, manufactured by Nippon Shokubai) as a pore-opening agent, N, N-dimethylacetamide The first film-forming stock solution having a mass ratio of 20% by mass of PVDF, 10% by mass of PVP, and 70% by mass of DMAc was prepared by introducing into the mixture and dissolving by kneading.
Further, PVDF obtained by mixing the first PVDF (made by Arkema, trade name: Kyner 301F) and the second PVDF (made by Arkema, trade name: PVDF9000HD) at a mass ratio of 1.1: 1, and PVP (made by Nippon Shokubai, product) No. PVP-K79) is introduced into dimethylacetamide and kneaded and dissolved to obtain a second film-forming stock solution having a mass ratio of 39 mass% PVDF, 19 mass% PVP, and 42 mass% DMAc. Was prepared.

Solidification process:
Next, a hollow porous membrane was manufactured using the manufacturing apparatus 100 illustrated in FIG. The spinning nozzle 12 is kept at 30 ° C., and the spinning nozzle 12 is used to apply the first film-forming stock solution to the outer peripheral surface of the reinforcing support X, and further discharge the second film-forming stock solution to the outside to form a film. The film-forming stock solution 2 was applied on the stock solution.
Next, the reinforcing support X coated with the first film-forming stock solution and the second film-forming stock solution is placed in a coagulation tank 16 containing an 8% by mass N, N-dimethylacetamide aqueous solution kept at 80 ° C. Then, the membrane-forming stock solution was solidified to form a hollow fiber membrane precursor 1A, which was pulled up from the coagulation tank 16.

Cleaning process, removal process:
In the cleaning means 20, the hollow fiber membrane precursor 1 </ b> A was run in the cleaning tank 24 containing hot water (90 ° C.) as the cleaning liquid 22 to remove the solvent.
Next, in the removing means 30, the hollow fiber membrane precursor 1 </ b> A is run for 2 minutes in the chemical tank in which an aqueous solution of hypochlorite having a temperature of 20 ° C. and a concentration of 5 mass% is placed to hold the chemical liquid. Then, the hollow fiber membrane precursor 1A was heated in saturated steam at a temperature of 100 ° C. under the condition of a residence time of 3 minutes. Thereafter, the pore-opening agent reduced in molecular weight by washing in a washing tank containing warm water (60 ° C.) was removed to form a porous hollow fiber membrane 1.

Drying and winding processes:
In the steam drying part 42 of the drying means 40, the porous hollow fiber membrane 1 was run in saturated steam at 100 ° C. under the condition that the residence time was 30 seconds, and the porous hollow fiber membrane 1 was dried. The moisture content of the porous hollow fiber membrane 1 before drying was 60.2% by mass. Thereafter, in the hot air drying unit 44, hot air having a temperature of 120 ° C. and a wind speed of 3 m / second is circulated inside, and the porous hollow fiber membrane 1 is allowed to travel under the condition of a residence time of 300 seconds to dry the porous hollow fiber membrane 1. Then, it was wound around the winding means 50.
The moisture content of the porous hollow fiber membrane 1 after drying by the steam drying unit 42 was 50% by mass, and the moisture content of the porous hollow fiber membrane 1 after drying by the hot air drying unit 44 was 0.5% by mass. .

[Comparative Example 1]
A porous hollow fiber membrane 1 was produced in the same manner as in Example 1 except that drying by the steam drying unit 42 was not performed.
The moisture content of the porous hollow fiber membrane 1 before drying was 60.2% by mass, and the moisture content of the porous hollow fiber membrane 1 after drying was 1.0% by mass.

DESCRIPTION OF SYMBOLS 1 Porous hollow fiber membrane 1A Porous hollow fiber membrane precursor 10 Coagulation means 12 Spinning nozzle 14 Coagulating liquid 20 Washing means 30 Removal means 40 Drying means 42 Steam drying part 44 Hot air drying part 50 Winding means 100 Porous hollow fiber membrane Manufacturing equipment

Claims (7)

A coagulation step of coagulating a film-forming stock solution containing a film-forming resin and a pore-opening agent in a coagulation solution to obtain a porous hollow fiber membrane precursor, and removing the pore-opening agent from the porous hollow fiber membrane precursor A method for producing a porous hollow fiber membrane comprising a removing step of forming a porous hollow fiber membrane having a porous membrane layer, and a drying step of drying the porous hollow fiber membrane,
In the drying step, a first drying step of drying the porous hollow fiber membrane with saturated steam heated to 80 ° C. or higher and 120 ° C. or lower, and the porous hollow fiber membrane after the first drying step are dried. A method for producing a porous hollow fiber membrane comprising: a second drying step.   The method for producing a porous hollow fiber membrane according to claim 1, wherein the second drying step is a step of drying the porous hollow fiber membrane after the first drying step with hot air. The method for producing a porous hollow fiber membrane according to claim 1 or 2, wherein the porous hollow fiber membrane is a porous hollow fiber membrane having the porous membrane layer outside a hollow reinforcing support. The porous hollow according to any one of claims 1 to 3, wherein the first drying step is a step of drying the porous hollow fiber membrane with the saturated water vapor in a steam drying unit having a labyrinth seal structure. Yarn membrane manufacturing method. The porous hollow fiber membrane according to any one of claims 1 to 4, wherein, in the first drying step, the time for which the saturated water vapor is brought into contact with the porous hollow fiber membrane is 10 seconds or more and 300 seconds or less. Manufacturing method. A coagulating means for obtaining a hollow fiber membrane precursor by coagulating a membrane-forming stock solution containing a film-forming resin and a pore-opening agent in a coagulation solution; removing the pore-opening agent from the porous hollow fiber membrane precursor; An apparatus for producing a porous hollow fiber membrane comprising a removing means for forming a porous hollow fiber membrane having a porous membrane layer and a drying means for drying the porous hollow fiber membrane,
An apparatus for producing a porous hollow fiber membrane, wherein the drying means has a steam drying section that dries the porous hollow fiber membrane with saturated steam heated to 80 ° C or higher and 120 ° C or lower . The manufacturing apparatus of the porous hollow fiber membrane of Claim 6 with which the said drying means has a hot air drying part which dries the porous hollow fiber membrane dried in the said steam drying part with a hot air.

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