KR101826451B1 - Porous hollow fiber membrane and method for manufacturing same - Google Patents

Abstract

Can be suitably used in various aqueous fluid treatment apparatuses such as water treatment, drinking water treatment, seawater desalination, and the like, and it is possible to suppress deterioration in performance over time while having excellent fractionation property and permeability, , Separation characteristics, filtration stability, and mechanical strength, and a process for producing the porous hollow fiber membrane. A porous hollow fiber membrane having at least an outer surface and a porous layer containing a thermoplastic resin in the vicinity of the outer surface and having an average pore diameter (Ad) from a surface to a depth of 1 mu m, (Bd) of not more than 0.6 and a process for producing the porous hollow fiber membrane.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a porous hollow fiber membrane,

The present invention relates to a porous hollow fiber membrane excellent in anti-fouling performance, which is mainly used for removing bacteria, viruses, SS components and the like in water. Specifically, the present invention relates to a porous hollow fiber membrane excellent in long-term stable membrane performance and recoverability of membrane performance by washing. The present invention also relates to a porous hollow fiber membrane suitable for water treatment such as a water treatment which can be used as a microfiltration membrane or an ultrafiltration membrane, and a method for producing the porous hollow fiber membrane.

The present application claims priority based on Japanese Patent Application No. 2013-193213, filed on September 18, 2013, and Japanese Patent Application No. 2013-193214, filed on September 18, 2013, The contents are used here.

BACKGROUND ART Conventionally, sand filtration, coagulation sedimentation and sand filtration have been widely used in the field of filtration in the water field for producing tap water from fresh water sources such as river water, lakes, swamps, and ground water. However, in these treatments, there is a concern that contamination of the water source originates from cryptosporidium, which has a high chlorine resistance and can not be totally harmless by chlorination after filtration. In this background, a membrane filtration method capable of removing contaminants easily and with high accuracy has been widely employed in combination with other water treatment techniques such as solely or coagulation sedimentation or sand filtration. On the other hand, even when the seawater is desalinated by the reverse osmosis membrane, the seawater supplied to the reverse osmosis membrane is subjected to pretreatment by pretreatment such as coagulation sedimentation, sand filtration and the like, and then supplied to the reverse osmosis membrane and desalinated. These treatments are also increasingly employed in place of coagulating sedimentation or sand filtration, or in combination with other water treatment techniques, such that the filtration by membrane filtration is employed.

As the required characteristics required for the porous hollow fiber membrane used for membrane separation, for example, the following points can be given.

(1) High removability of the substance to be removed.

(2) High permeability of permeable material.

(3) The permeability of the treatment fluid is high.

(Hereinafter, (1), (2), and (3) are collectively referred to as membrane separation characteristics)

(4) The breaking strength is sufficiently high for tensile, etc., and is difficult to break or leak.

(5) The fractionation characteristic is difficult to deteriorate over time.

(6) The permeability of the treatment fluid is difficult to deteriorate over time.

(Hereinafter, (5) and (6) are collectively referred to as the retainability of the membrane separation characteristic)

(7) Excellent recovery of fraction characteristics by washing.

(8) Excellent recovery of permeability by washing.

(Hereinafter, (7) and (8) are collectively referred to as recoverability of membrane separation characteristics)

Generally, in the membrane filtration process, a phenomenon in which the fouling material adheres to and accumulates on the membrane surface on the side where the raw water is supplied and the membrane filtration resistance increases and the membrane filtration efficiency deteriorates Occurs. At this time, in order to remove the fouling material adhering to the membrane surface, a washing operation such as cleaning, air scrubbing, desalting of the feed water, or chemical cleaning is performed to recover the membrane filtration resistance, and the membrane filtration is resumed. The membrane filtration operation and the cleaning operation are repeated to operate the membrane filtration process. A utility such as electricity and water is required for the cleaning operation, and since the production water can not be obtained during the period during which the cleaning operation is performed, it is preferable that the cleaning operation frequency is low and the cleaning operation time is short. Therefore, it is very useful if it is possible to obtain a separation membrane having a small increase in membrane filtration resistance caused by passage of membrane filtration operation time and a large recovery of membrane filtration resistance by a cleaning operation.

In the prior art, a number of techniques have been developed in the direction of improving the resistance to fouling of the membrane surface, and suppressing the increase in filtration resistance during the membrane filtration operation. For example, when a hydrophilic polymer such as polyvinylpyrrolidone (PVP) or polyvinyl alcohol (PVA) is mixed into a stock solution for use in obtaining a porous film containing a hydrophobic polymer, these hydrophilic polymers remain even after film formation, To improve the hydrophilicity of the surface and improve the fouling resistance. This method is simple and excellent in the production efficiency of the film, but the fouling resistance is still insufficient.

In the prior art, there is a case where a film containing a hydrophobic polymer is formed first, and then various surface treatments are performed to cover the surface of the hydrophobic polymer film with a hydrophilic polymer to improve the resistance to fouling. These methods are more complicated in the manufacturing process than the method of forming the film by mixing the hydrophilic polymer into the raw film-forming solution, and there are many practical problems such as difficulty in controlling the process.

Both of these techniques are based on the technical idea of improving the fouling resistance by the hydrophilization of the film surface in consideration of the chemical properties and the chemical composition of the film surface. On the other hand, Patent Documents 1 and 2 are examples of the relationship between the shape of the film surface and the film separation characteristics. Patent Document 1 discloses an invention relating to a composite reverse osmosis membrane having a polyamide-based skin layer, and the permeability of the composite reverse osmosis membrane is improved by setting the specific surface area of the film surface on the side of the raw water supply to a specific range Lt; / RTI > Patent Document 2 discloses an invention relating to a composite reverse osmosis membrane having a polyamide skin layer in the same manner as described above, and is characterized in that an average value X of horizontal distances between adjacent vertexes of surface irregularities on the film surface on the side to which raw water is supplied Discloses that a composite reverse osmosis membrane exhibiting a high blocking performance can be obtained when the average value Z of the irregularity difference between the apex and the base satisfies a specific relationship. However, in both of Patent Documents 1 and 2, it is a study on a composite reverse osmosis membrane, and further, no improvement is given to the resistance to fouling.

On the other hand, water treatment by a membrane method using a filtration membrane excellent in the completeness of separation and compactness has attracted attention due to heightened interest in environmental pollution and strengthened regulations. In such water treatment applications, a filtration membrane is required to have excellent separation characteristics, water permeability, and high mechanical strength.

BACKGROUND ART Filtration membranes such as polysulfone, polyacrylonitrile, cellulose acetate, or polyvinylidene fluoride, which are conventionally produced by wet or dry wet spinning as a filtration membrane having excellent water permeability, are known. These filtration membranes are produced by micro-separating the polymer solution and solidifying the polymer solution in the non-solvent, have a high porosity, and have an asymmetric structure.

Of the above filtration membrane materials, polyvinylidene fluoride resins are suitably used as materials for separators because of their excellent chemical resistance and heat resistance. However, the filtration membranes containing the polyvinylidene fluoride hollow fiber membranes proposed so far have not been satisfactory in at least one of separation characteristics, filtration stability, and mechanical strength, .

To increase the mechanical strength of the separation membrane, a separation membrane having a hollow braid as a support and a porous layer provided on the surface thereof has been proposed (Patent Document 3). However, this porous layer has a problem that macroporous voids are large inside the film structure due to the production method, and the separation characteristics are liable to be deteriorated due to damage to the outer surface of the film due to external factors.

On the other hand, a separator has been proposed in which the dense layer is made thick to some extent by control of phase separation, and macroboid is suppressed to improve separation characteristics (Patent Document 4). However, when the dense layer is made thick as described above, there is a problem that the extreme ultrafine water or the soluble organic polymer is clogged in the dense layer and the filtration stability is lowered.

On the other hand, a polyvinylidene fluoride resin and a plasticizer are melt-kneaded and extruded, cooled and solidified, and then the plasticizer is extracted to obtain a porous hollow fiber membrane. Thereafter, the outer surface dense layer is stretched in a wet state, (See Patent Document 5). [0005] In order to solve the above problems, However, since the pore size of the dense layer is almost uniform even though the porosity of this technique is high, there still remains a problem that the extreme ultrafine matter or the soluble organic polymer passing through the surface is easily clogged in the dense layer, , It is difficult to combine with a support, and there is a problem that it is difficult to make the mechanical strength compatible.

Japanese Patent Application Laid-Open No. 09-19630 Japanese Patent Application Laid-Open No. 2005-169332 U.S. Patent No. 5472607 International publication 09/142279 pamphlet International publication 2011/007714 brochure

It is an object of the present invention to provide a method for treating aqueous fluids, which can be used in the treatment of various aqueous fluids such as water treatment, beverage treatment or seawater desalination, has excellent fraction characteristics and permeability, And to provide a porous hollow fiber membrane excellent in recoverability of separation characteristics.

Another object of the present invention is to provide a porous hollow fiber membrane which solves this problem and is excellent in separation characteristics, filtration stability, and mechanical strength.

In order to solve the above-described problems, the present invention has the following embodiments.

(1) A porous hollow fiber membrane having at least a porous layer on its outer surface, wherein the average pore size (Ad) from the outer surface to the depth of 1 m in the cross-sectional structure of the porous hollow fiber membrane is an average Wherein the ratio (Ad / Bd) to the pore diameter (Bd) is 0.6 or less.

(2) The porous hollow fiber membrane according to (1), wherein the outer surface has an average pore size P1 of 0.05 to 1.0 占 퐉 and an opening ratio A1 of 15 to 65%.

(3) The porous hollow fiber membrane according to (1) or (2), wherein the average pore size P2 of the layer from the outer surface to the depth of 10 占 퐉 in the cross-sectional structure is 0.1 to 5.0 占 퐉 and the open area ratio A2 is 10 to 50%.

(4) The porous hollow fiber membrane according to any one of (1) to (3), wherein the structure from the outer surface to the depth of 5 占 퐉 is a three-dimensional mesh structure increasing in pore size toward the direction away from the outer surface.

(5) The honeycomb structure according to any one of (1) to (4), wherein the average pore size of the porous layer from the outer surface to the depth of 5 占 퐉 is smaller than the average pore size of the porous layer located at a distance from the outer surface Porous hollow fiber membrane.

(6) The porous hollow fiber membrane according to any one of (1) to (5), wherein an average pore size of the porous layer existing at a portion apart from the outer surface by a depth of 5 占 퐉 is 10 占 퐉 or less.

(7) The porous hollow fiber membrane according to any one of (1) to (6), wherein the thermoplastic resin constituting from the outer surface to the depth of 5 μm comprises the same thermoplastic resin.

(8) The porous hollow fiber membrane according to any one of (1) to (7), wherein the porous layer in a portion not more than 10 μm deep from the outer surface does not contain macrovoids having a pore size exceeding 10 μm and a part thereof.

(9) The porous hollow fiber membrane according to any one of (1) to (8), which is formed by a non-solvent separation method.

(10) The porous hollow fiber membrane according to any one of (1) to (9), wherein the porous layer is formed on the outer surface side of the hollow support body.

(11) The porous hollow fiber membrane according to (10), wherein the hollow fiber-shaped support is heat-treated.

(12) The porous hollow fiber membrane according to (10) or (11), wherein the hollow support is a hollow braid.

(13) The porous hollow fiber membrane according to (11) or (12), wherein the support is a hollow braid having one thread including multifilaments rounded.

(14) A film forming resin solution containing a thermoplastic resin and a hydrophilic compound is discharged from a spinning nozzle, the discharged film-forming resin solution is brought into contact with a non-solvent saturated vapor of the film-forming resin solution component, Wherein the spinning nozzle is a single-ply or double-ply tubular nozzle, and the porous hollow fiber membrane has at least a portion having a depth of 5 mu m from the outer surface of the porous hollow fiber membrane, Is formed from the same film-forming resin solution.

(15) The method for producing a porous hollow fiber membrane according to (14), wherein the non-solvent saturated steam is saturated water vapor.

(16) applying the film-forming resin solution to the outer circumferential surface of the hollow support by using a spinning nozzle to form a film-forming resin layer, and then bringing the film-forming resin layer into contact with the non-solvent saturated vapor (14) or (15). ≪ / RTI >

(17) The method for producing a porous hollow fiber membrane according to (16), wherein the support is a heat-treated support.

(18) The method for producing a porous hollow fiber membrane according to (16) or (17), wherein the support is a braid.

(19) The method for producing a porous hollow fiber membrane according to (17) or (18), wherein the support is a hollow-shaped braid having one thread including multifilaments.

Further, the embodiment of the present invention has the following aspects. The first point of the present invention, which solves such problems as described above, is a porous hollow fiber membrane having an opening ratio of 15 to 65% on the outer surface.

The second point of the present embodiment is a method for evaluating a porous hollow fiber membrane having the following steps.

Step (1): The step of observing the cross-section of the porous hollow fiber membrane with a scanning electron microscope and measuring the area of each hole appearing on the cross-section surface

Step (2): The step of integrating the values of the area of each hole measured in the step (1) from the smaller area and calculating the pore corresponding to 50% of the total area as the average pore size index

The present embodiment is a porous hollow fiber membrane having a porous layer containing a thermoplastic resin at least on its outer surface and its vicinity, and has an average pore size Ad from a surface to a depth of 1 m in a cross- Of the average pore size Bd of the porous hollow fiber membrane.

Further, in the present embodiment, a film-forming resin solution containing a thermoplastic resin and a hydrophilic compound is discharged from a spinning nozzle, immediately thereafter in contact with a non-solvent saturated vapor of a film-forming resin, and then immersed in a coagulating solution Thereby forming a porous hollow fiber membrane.

Further, the embodiment of the present invention has the following aspects.

(1A) A porous hollow fiber membrane having a porous layer at least on its outer surface side and an opening ratio of 15 to 65% on an outer surface.

(1A) having an average pore size index P1 of 0.05 to 1.0 (mu m) on the outer surface of the porous membrane (2A).

(1A) or (2A) having a dense layer up to 10 mu m in the vicinity of the outer surface of the dense layer (3A) and an average pore size index (P2) (mu m) of the dense layer in the range of 0.1 to 5.0 mu m.

(4A) The porous hollow fiber membrane according to (3A) wherein the open area ratio A2 (%) of the dense layer is 10 to 50%.

(5A) The porous hollow fiber membrane according to any one of (1A) to (4A), wherein the total thickness of the porous layer is 200 μm or less.

(1A) to (5A) wherein the pore diameters of the continuous porous layer from the outer surface of the porous layer (6A) gradually increase.

(7A) A method for evaluating a porous hollow fiber membrane, the method comprising the steps of:

Step 1: A step of observing the cross-section of the porous hollow fiber membrane with a scanning electron microscope and measuring the area of each hole appearing on the cross-section surface

Step 2: The step of calculating the average pore size index by integrating the value of the area of each hole measured in Step 1 from the smaller area and using the hole corresponding to 50% of the total area

Further, the embodiment of the present invention further has the following aspects.

(1B) A porous hollow fiber membrane having at least an outer surface and a porous layer containing a thermoplastic resin in the vicinity thereof. The average pore Ad from the surface to the depth of 1 m in the cross-sectional structure is an average Porous hollow fiber membrane having a half or less of the pore size Bd.

(2B) A porous hollow fiber membrane according to (1B), wherein the structure from the outer surface to the depth of 5 占 퐉 is a three-dimensional mesh structure having a pore size increasing toward the center.

(1B) or (2B), wherein the average pore size of the porous layer from the outer surface to the depth of 5 mu m is smaller than the average pore size of the porous layer inside the depth of 5 mu m.

(4B) The porous hollow fiber membrane according to any one of (1B) to (3B), wherein the average pore diameter of the porous layer existing at a depth of 5 탆 or less is 10 탆 or less.

(5B) The porous hollow fiber membrane according to any one of (1B) to (4B), wherein the thermoplastic resin constituting from the outer surface to the depth of 5 μm comprises the same thermoplastic resin.

(6B) The porous hollow fiber membrane according to any one of (1B) to (5B), wherein the porous layer from the outer surface to the depth of 10 占 퐉 does not contain macrovoids having an pore size exceeding 10 占 퐉.

(7B) The porous hollow fiber membrane according to any one of (1B) to (6B), wherein the porous layer is formed on the outer surface side of the hollow support body.

(8B) The porous hollow fiber membrane according to (7B), wherein the support in the form of hollow fiber is a hollow braid.

(9B) The porous hollow fiber membrane according to (8B), wherein the hollow fiber-shaped support is a heat-treated hollow fiber.

(10B) The porous hollow fiber membrane according to (8B) or (9B), wherein the support body is a hollow fiber braid having one thread including multifilaments.

(11B) A film-forming resin solution containing a thermoplastic resin and a hydrophilic compound is discharged from a spinning nozzle, brought into contact with a saturated vapor of a non-solvent of the film-forming resin, and then immersed in a coagulating liquid, Method of manufacturing desert.

(12B) The production method of a porous hollow fiber membrane according to (11B), wherein the spinning nozzle is a tubular nozzle having one layer or two or more layers and at least a depth of 4 mu m from the outer surface is formed by the same film-forming resin solution.

(13B) The method for producing a porous hollow fiber membrane according to (12B), wherein the non-solvent saturated steam is saturated water vapor at 100 ° C.

(14B) A method for producing a porous hollow fiber membrane according to (12B) or (13B), wherein the film-forming resin solution discharged from the spinning nozzle is brought into contact with dry air before being brought into contact with the non- .

(15B) The method for producing a porous hollow fiber membrane according to (14B), wherein the dry air is supplied from a nozzle discharge surface in a vertically downward direction, and is then brought into contact with saturated vapor of the non-solvent.

(16B) The method for producing a porous hollow fiber membrane according to (14B) or (15B), wherein the relative humidity of the non-solvent in the atmosphere in the vicinity of the spinneret is made less than 10% by the dry air.

The porous hollow fiber membrane of the present invention is a porous hollow fiber membrane having at least an outer surface and a porous layer containing a thermoplastic resin in the vicinity of the outer surface, wherein the porous hollow fiber membrane has a depth of 1 mu m The ratio of the average pore diameter (Ad) to the average pore diameter (Bd) from the depth of 2 mu m to 3 mu m is 0.6 or less so that the so-called dense layer is thin and as a result, the separation characteristics, the filtration stability, Is an excellent porous hollow fiber membrane.

According to the present invention, it is possible to obtain a porous hollow fiber membrane having at least an outer surface side of the porous hollow fiber membrane and a porous hollow fiber membrane having an opening ratio of 15 to 65% on the outer surface, Structure, it is considered that there is no clogging in the interior and the cleaning recovery property is also high. In addition, a porous hollow fiber membrane excellent in retention and recoverability of membrane separation characteristics can be obtained.

The porous hollow fiber membrane of the present invention can be used in the treatment of various aqueous fluids such as a water purification membrane, a beverage treatment membrane, and a seawater desalination membrane, and can provide a porous hollow fiber membrane suitable for water treatment. In addition, the porous hollow fiber membrane of the present invention has a sufficient membrane strength, which has excellent fraction characteristics and permeability, and does not cause breakage or leakage during module molding or actual use, and suppresses deterioration of these properties over time , And the recovery of the membrane separation characteristics by washing is excellent.

In the porous hollow fiber membrane of the present invention, the average pore Ad from the surface to the depth of 1 占 퐉 from the surface in the cross-sectional structure is 1/2 or less of the average pore Bd from the depth 2 占 퐉 to 3 占 퐉, Resulting in a porous hollow fiber membrane having excellent separation characteristics, filtration stability and mechanical strength.

Fig. 1 is a cross-sectional photograph of a porous layer of the porous hollow fiber membrane obtained in Reference Example 1. Fig.
Fig. 2 is a cross-sectional photograph of the porous layer of the porous hollow fiber membrane obtained in Reference Example 2. Fig.
3 is a cross-sectional photograph of the porous layer of the porous hollow fiber membrane obtained in Reference Example 3. Fig.
4 is a cross-sectional photograph of the porous layer of the porous hollow fiber membrane obtained in Reference Example 4. Fig.
5 is a cross-sectional photograph of the porous layer of the porous hollow fiber membrane obtained in Reference Comparative Example 1. Fig.
6 is a cross-sectional photograph of the porous layer in the vicinity of the outer surface portion of the porous hollow fiber membrane obtained in Reference Example 1. Fig.
7 is a cross-sectional photograph of a porous layer in the vicinity of the outer surface portion of the porous hollow fiber membrane obtained in Reference Example 2. Fig.
8 is a cross-sectional photograph of the porous layer in the vicinity of the outer surface portion of the porous hollow fiber membrane obtained in Reference Example 3. Fig.
9 is a cross-sectional photograph of the porous layer in the vicinity of the outer surface portion of the porous hollow fiber membrane obtained in Reference Example 4. Fig.
10 is a cross-sectional photograph of the porous layer in the vicinity of the outer surface portion of the porous hollow fiber membrane obtained in Reference Comparative Example 1. Fig.
Fig. 11 is a graph showing the change with time in the differential pressure during the filtration operation in the reference example and reference comparative example. Fig.
FIG. 12 is a schematic diagram showing a production apparatus used for manufacturing a porous hollow fiber membrane according to an embodiment of the present invention. FIG.
Fig. 13 is a bottom view showing a ventilation nozzle constituting an apparatus for producing a hollow porous film of Fig. 12; Fig.

Hereinafter, a preferred embodiment of the present invention will be described.

(First Embodiment)

The porous hollow fiber membrane of the present embodiment is a porous hollow fiber membrane having a porous layer on at least the outer surface side of the present embodiment and has an open area ratio of 15 to 60% with respect to the total area of the outer surface. Here, the outer surface refers to the surface on the side facing the outer periphery of the cylinder when the membrane is formed into a hollow hollow (cylindrical) shape on both surfaces of the membrane to form a porous hollow fiber membrane. And the inner surface is the surface facing the inner periphery of the cylinder. Here, the porous layer means a layer having pores of a property described later in a form dispersed substantially over the entire layer. Here, the open area ratio refers to a value obtained by observing the outer surface of the porous hollow fiber membrane with a microscope or the like, measuring the area of the hole by image analysis or the like, / The value obtained as the area of the entire outer surface observed (film area in the field of view). The porous hollow fiber membrane having a porous layer having at least an outer surface side and an open area ratio of 15 to 60% with respect to the total area of the outer surface, the porous hollow fiber membrane having a dense surface and excellent water permeability do. The open area ratio of the outer surface is preferably 20% or more and 60% or less, more preferably 25% or more and 55% or less, relative to the total area of the outer surface.

The average pore size index (or average pore size P1) of each pore of the porous layer of the porous hollow fiber membrane of the present embodiment may be 0.05 to 1.0 (mu m). This results in a porous hollow fiber membrane excellent in recoverability. The average pore diameter of the porous hollow fiber membrane is preferably 0.06 to 0.9 (mu m), and more preferably 0.75 to 0.8 (mu m).

The average pore size index refers to the pore size calculated by performing an arithmetic process on the pore size read from a microscope photograph by using an image analysis software. Thereby, there is an effect of excluding the minute noise due to the density of the pixel. In the present embodiment, the outer surface of the porous hollow fiber membrane is photographed by a microscope, and the average value of the pores of the holes in the photograph is measured and found.

In the porous hollow fiber membrane of the present embodiment, the average pore size P2 of the layer from the surface to the depth of 10 mu m in the cross-sectional structure when observed in the cross section in the thickness direction is 0.1 to 5.0 (mu m) Is preferably 10 to 50%. Within this range, there is an effect that both the clogging and the strength can be achieved.

In the porous membrane layer constituting the porous hollow fiber membrane of the present embodiment, the membrane preferably has a thickness of 200 탆 or less. This is because when the thickness of the porous membrane layer is 200 占 퐉 or less, the permeation resistance at the time of membrane separation is reduced and excellent water permeability is obtained. In addition, when the porous membrane layer is formed by using the membrane- The coagulation time can be shortened, and it is effective in suppressing macroboid (defective site) and tends to obtain excellent productivity. More preferably, the thickness of the porous film layer is 150 mu m or less.

Further, in the porous membrane layer constituting the porous hollow fiber membrane of the present embodiment, it is preferable that the thickness is 100 m or more. This is because the porous film layer having a thickness of 100 占 퐉 or more tends to obtain a mechanical strength that is practically free from problems. However, in the case where the outer diameter of the membrane is small, the mechanical strength can be maintained even if the thickness is less than 100 탆.

The porous film layer has a dense layer at least near the outer surface thereof. Here, the vicinity of the outer surface refers to a portion (inside the porous film layer) adjacent to the outer surface of the porous film layer at a portion inside the porous film layer. Here, the dense layer refers to a region where fine pores having a smaller pore size are gathered in the porous membrane layer. In the present embodiment, since the permeability and separating performance of the porous hollow fiber membrane can be compatible with each other, In the dense layer, the average pore size index is preferably in the range of 0.01 to 1 mu m.

The thickness of the dense layer in the present embodiment is preferably in the range of 10 to 125 탆 from the viewpoints of both improving the stability of separation characteristics and improving the water permeability.

In the dense layer in the vicinity of the outer surface, the thickness is more preferably in the range of 25 to 100 mu m from the standpoint of improving the stability of the separation characteristics. More preferably, the thickness of the dense layer is in the range of 40 to 75 mu m.

It is preferable that the position of the dense layer in the vicinity of the outer surface exists at a position within 20 占 퐉 from the outer surface of the porous film layer from the viewpoint of avoiding an increase in the permeability resistance inside the film. It is particularly preferable that the dense layer constitutes the outer surface of the porous film layer.

The porous film layer preferably has a sponge layer having an average pore diameter of 2 占 퐉 or more on the inner side of the dense layer in the vicinity of the outer surface described above (a portion away from the outer surface and a deep portion as viewed from the outer surface). Since this intermediate porous layer contributes to the water permeability of the porous hollow fiber membrane of the present embodiment, its pore diameter is larger, but if it is too large, macroboid is formed and the mechanical strength thereof is lowered. Therefore, the average pore diameter is preferably 8 탆 or less, and more preferably substantially no pores of 10 탆 or more. More preferably in the range of 3 to 5 mu m.

From the viewpoint of improving the water permeability, in the intermediate porous layer, particularly at a portion distant from the outer surface by 5 mu m or less from the outer surface, it is preferable to face the direction away from the outer surface from the dense layer in the vicinity of the outer surface, It is preferable to have an increasingly inclined structure. Particularly, it is preferable that the intermediate porous layer has a three-dimensional mesh structure in which pores cross each other three-dimensionally.

The average pore size of the porous layer from the outer surface to the depth of 5 占 퐉 is preferably smaller than the average pore size of the porous layer located at a depth deeper than 5 占 퐉 from the outer surface. It is particularly preferable that the average pore size of the porous layer existing at a depth deeper than 5 占 퐉 from the outer surface is 10 占 퐉 or less. With this configuration, it is possible to suppress the clogging of the material that has escaped from the dense layer in the vicinity of the outer surface, and it has an effect that both quality can be compatible.

In addition, the porous layer described so far may be divided into a plurality of layers (for example, a dense layer and a layer other than the dense layer) discontinuously due to a difference in material or average pore diameter. However, For example, the average value of the aperture gradually changes depending on the distance from the surface). In this case, the layer may be referred to as a region (for example, a dense region and other regions).

Next, a method of manufacturing the porous hollow fiber membrane of the present embodiment will be described.

The porous hollow fiber membrane of the present embodiment can be produced by continuously applying a stock solution of the first film forming stock solution and the second film forming stock solution containing the material and the solvent of the porous film layer to the outer peripheral surface of the hollow support by using the annular nozzle, , And coagulating these stock film-forming solutions at the same time.

In this case, the solidification may be solidification only from one side, and by this method, an integral porous film structure can be obtained from the two kinds of film-forming stock solutions.

For example, by using a double annular nozzle as shown in Fig. 1 of Patent Document 7, a hollow support (braid) is passed through the support passage, and the first raw film forming solution (inner layer side After the first film forming stock solution is applied to the outer peripheral surface of the hollow braid, the second film forming stock solution is discharged from the first film forming chamber (the first film forming chamber) It is applied on the application layer of the undiluted solution. Thereafter, the structure of the porous hollow fiber membrane specified in the present embodiment can be obtained by preforming the hollow shaped braids coated with the undiluted film forming solution for a predetermined time, immersing them in the coagulating solution, coagulating the membrane forming solution, washing with water and drying.

In the case of using the double annular nozzle, the first raw film forming solution and the second film forming raw solution may be joined in advance in the nozzle, and they may be simultaneously discharged from the nozzle surface to be applied to the hollow support.

Further, by using the triple annular nozzle having the center portion, the medial portion and the outer portion, the first film forming stock solution from the inner side and the second film forming solution from the outer side are simultaneously discharged while passing the hollow support at the center, Shaped support.

By using the annular nozzle as described above, it is possible to uniformly apply the first film forming stock solution and the second film forming stock solution uniformly, and furthermore, when the first film forming stock solution and the second film forming solution are laminated, . The first film-forming source liquid and the second film-forming source liquid may be sequentially applied. In this case, when the first film-forming stock solution and the second film-forming stock solution are applied, they can be applied continuously or separated from each other. However, when the first film forming stock solution and the second film forming solution are laminated, , It is preferable to perform it continuously.

In this case, two kinds of film-forming stock solutions are used, but all contain a polymer resin, an additive and an organic solvent.

As the polymer resin used for these film-forming solutions, for example, polysulfone resin, polyethersulfone resin, sulfonated polysulfone resin, polyvinylidene fluoride resin, polyacrylonitrile resin, polyimide resin, polyamideimide resin or poly Ester-imide resins, and the like. These can be appropriately selected and used according to need, but polyvinylidene fluoride resin is preferable because of its excellent chemical resistance.

As the additive, it is possible to use for the purpose of control of phase separation or the like, and for example, a hydrophilic polymer resin such as mono-oleic, diol, triol or polyvinylpyrrolidone typified by polyethylene glycol can be used. These can be appropriately selected and used according to need, but polyvinylpyrrolidone is preferable because of its excellent thickening effect.

The organic solvent is not particularly limited as long as it can dissolve the above-mentioned polymer resin and additives, and for example, dimethylsulfoxide, dimethylacetamide or dimethylformamide can be used.

The composition of the two types of film-forming stock solutions is not particularly limited, and the same stock solution may be used or another stock solution may be used. However, from the viewpoint of preventing the interlayer separation and improving the mechanical strength, it is preferable that the solvent and the polymer resin to be used are the same kind in order to form the integral structure from the two kinds of film-forming stock solutions at the time of solidification.

In the case of manufacturing the porous hollow fiber membrane of the present embodiment by the above-described method, it is preferable that the viscosity of the first film-forming stock solution as the inner layer side film forming stock solution is higher than that of the second film forming stock solution as the outer layer side film forming stock solution.

This is because application of the first film-forming stock solution having a higher viscosity to the outer peripheral surface of the hollow support suppresses excessive intrusion of the undiluted solution into the interior of the hollow support to prevent clogging of the hollow portion of the porous hollow fiber membrane Because.

In order to achieve this, it is necessary that the first film-forming solution has a sufficient viscosity, and the viscosity at 40 캜 is preferably 50,000 mPa sec or more. More preferably 100,000 mPa · sec or more, and still more preferably 150,000 mPa · sec or more. Specifically, for example, the viscosity of the stock solution at 40 ° C is in the range of 5 to 250,000 mPa · sec, and the viscosity of the stock solution at 40 ° C is in the range of 10 to 300,000 mPa · sec.

The method of adjusting the viscosity of the stock film-forming liquid is not particularly limited, and may be changed, for example, by changing the molecular weight of the polymer resin or changing the concentration of the polymer resin. As a method of changing the molecular weight of the polymer resin, a method of blending two kinds of polymer resins having different molecular weights may be used.

In the first film-forming stock solution, the concentration of the polymer resin is adjusted to a higher concentration, and the viscosity of the film-forming raw liquid can be appropriately selected as described above. However, even in the inner layer having a slow solidification rate, It tends to be suppressed. Further, by increasing the concentration of the first film-forming raw liquid, the structural stability of the entire porous layer tends to be improved, which is preferable.

On the other hand, in the second film-forming stock solution, it is preferable to adjust the molecular weight of the polymer resin because the opening ratio of the outer surface of the porous film layer tends to be kept high.

As described above, in the case of forming the film by coagulating the stock solution, the porous structure is formed by phase separation. As the porous structure, various structures can be obtained depending on the film forming conditions. Typical porous structures include a sponge structure derived from a sea-island structure in which the polymer resin is located on the sea side, a particle-aggregation structure derived from a sea- And a three-dimensional mesh structure derived from a coercive force structure in which a polymer resin and a solvent are entangled with each other in a network shape by spinodal decomposition.

The porous structure can be appropriately selected from among these structures. However, since the particle aggregation structure tends to have a structure in which the polymer resin layer is aggregated, and the mechanical strength tends to deteriorate, the sponge structure and the three- .

The sponge structure tends to have a homogeneous structure in which the pore size does not significantly change with respect to the film thickness direction, and is a structure suitable for improving the stability of the separation characteristics.

On the other hand, the three-dimensional mesh structure tends to have a high degree of communication between the spots compared with the sponge structure, and is a structure suitable for improving the permeation performance.

The composition of the first film-forming raw stock solution which is the raw layer-side film-forming raw solution can be appropriately selected depending on the film structure to be formed.

The conditions for obtaining the sponge structure from the first film-forming stock solution are the same, and the composition is not particularly limited. However, the mass ratio (additive / polymer resin) of the additive to the polymer resin in the stock solution for coating film is preferably 0.45 or less, more preferably 0.40 or less .

By setting the mass ratio to 0.45 or less, the homogeneous structure tends to be densified and macrovoids also tend to be hard to occur.

On the other hand, if the mass ratio is too low, the pore becomes too small and the permeation performance tends to be lowered. Therefore, the mass ratio is preferably 0.3 or more.

Examples of the composition of the film-forming solution are 20 to 30% by mass of a polyvinylidene fluoride resin, 5 to 12% by mass of polyvinylpyrrolidone and 60 to 85% by mass of dimethylacetamide, based on the total mass of the film-forming stock solution, (Polyvinylpyrrolidone / polyvinylidene fluoride resin) in the range of 0.3 to 0.45 can be cited as examples of the mass ratio of the polyvinylidene fluoride resin and the polyvinylidene fluoride resin.

The conditions for obtaining the three-dimensional mesh structure of the porous layer in the first film-forming solution are not particularly limited, but the mass ratio (additive / polymer resin) of the additive to the polymer resin in the stock solution for film formation is preferably 0.45 or more, more preferably 0.51 or more .

Further, it is preferable that the proportion of the organic solvent is set to 68 mass% or less with respect to the total mass of the stock film-forming solution. This is because the generation of macrovoids tends to be suppressed and the structural stability of the entire porous layer tends to be improved. More preferably, it is 60% by weight or less based on the total mass of the stock solution.

Examples of the composition of the film-forming solution are 20 to 30% by mass of polyvinylidene fluoride resin, 10 to 20% by mass of polyvinylpyrrolidone and 55 to 68% by mass of dimethylacetamide based on the total mass of the film-forming stock solution, And the mass ratio of polyvinylidene fluoride resin (polyvinylpyrrolidone / polyvinylidene fluoride resin) is 0.45 or more.

The composition of the second film-forming stock solution, which is the outer layer-side film-forming stock solution, is not particularly limited as long as it has a dense layer in the vicinity of the outer surface of the porous film layer and an inclined structure in which the pore size gradually increases toward the inner surface of the porous film layer can be formed by phase separation It is not limited.

The composition of the second film-forming raw liquid can be appropriately selected according to the objective film structure, but it is preferable that the ratio of the organic solvent is 70% by mass or more in order to increase the surface opening ratio of the porous film layer.

Further, since there is a tendency to form a tilted structure without large macrovoids, the mass ratio of the additive / polymer resin is preferably 0.45 or more. Examples of the composition of the film-forming solution are 15 to 25% by mass of a polyvinylidene fluoride resin, 5 to 15% by mass of polyvinylpyrrolidone, 70 to 80% by mass of dimethylacetamide, and (polyvinylpyrrolidone / Lidene resin) is 0.45 or more.

The thickness of the outer layer and the inner layer can be appropriately set, but when the outer layer having a higher tendency of the organic solvent is thickened, macrovoids tend to be generated at the time of film formation. Therefore, Or less. More preferably not more than 100 mu m, further preferably not more than 80 mu m. On the other hand, the lower limit of the film thickness of the outer layer is 5 mu m.

In the case of using a hollow-shaped braid as a support, it is possible to impregnate the supporter in advance with a non-solvent for the undiluted undiluted solution in advance, since excessive undesirable intrusion of the undiluted solution into the support is prevented. As a non-solvent in the case of using the film-forming stock solution of the above composition, glycerin can be exemplified. However, when the coagulating ability of the coating film stock solution to be used is excessively high or the non-solvent is excessively high, the penetration of the porous film layer into the support is inhibited and the peeling resistance is largely lowered.

When polyvinylpyrrolidone is used as an additive, it is preferable to clean the porous hollow fiber membrane with sodium hypochlorite or the like in the cleaning after formation of the membrane structure from solidification.

(Porous film)

Examples of the material of the porous film layer include polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyvinylpyrrolidone, and polyethylene glycol. From the viewpoints of chemical resistance and heat resistance, polyvinylidene fluoride, The combination of vinylidene and polyvinylpyrrolidone is preferred.

The porous film layer may be a monolayer of a layer containing any one of these constituent materials or a composite porous film layer formed by laminating two or more monolayers thereof.

(Second Embodiment)

Hereinafter, another preferred embodiment of the present embodiment will be described.

In the hollow porous hollow fiber membrane of the present embodiment, the average pore size Ad of the layer from the surface to the depth of 1 占 퐉 (hereinafter referred to as the porous layer A) Is less than or equal to 0.6, preferably less than or equal to 0.5 (less than or equal to 0.5), based on the size of the layer having a depth of 2 탆 to 3 탆 (hereinafter, referred to as porous layer B) Bd.

This is because the porous hollow fiber membrane of the present embodiment has a film having the layer having the smallest pore size in the porous layer A forming the outer surface is substantially less than 1 mu m and the extreme ultrafine material or soluble organic polymer, It is difficult to clog the inside.

Further, it is more preferable that the porous hollow fiber membrane porous layer A of the present embodiment and the layer having a depth ranging from 4 탆 to 5 탆 (hereinafter referred to as the porous layer C) exhibit a structure in which the pore diameter gradually increases. When the pore size is uniform, extremely fine water or soluble organic polymer that has escaped from the outer surface tends to be clogged in the layer near the outer surface, resulting in lowering of filtration stability. The film by the thermal organic phase separation method, the plasticizer extraction method or the stretching method is likely to form such a structure. On the other hand, when the pore size is discontinuously increased, the thickness of the layer including the outer surface is reduced, and the mechanical strength is lowered, causing problems such as peeling of the outer surface.

The larger the proportion of the increase in the pore size, the more difficult the filtration stability is improved because the extremely minute water or the soluble organic polymer that has passed through the porous layer A is less likely to be clogged in the layer on the inner surface side than the porous layer A. However, Only the layer including the outer surface is formed, and the separation characteristics are likely to be deteriorated due to external factors or the like. Therefore, in the cross-sectional structure, the pore Bd of the porous layer B may be 5/3 or more (that is, Ad / Bd is 0.6 or less) with respect to the pore Ad of the porous layer A forming the outer surface. Bd is preferably not less than 2 times (Ad / Bd is not more than 0.5), more preferably not less than 3 times (Ad / Bd is not more than 0.33), more preferably not less than 4 times (Ad / Bd is not more than 0.25 ) Is more preferable. When the separation property can be maintained, it is more preferable to be 5 times or more (Ad / Bd is 0.2 or less).

The porous layer B preferably means a porous layer A constituting the outer surface and a layer adjacent to the porous layer A with one layer interposed therebetween. Even in the non-porous organic phase separation method in which the pore size of the porous layer tends to increase toward the interior (direction away from the outer surface), this region immediately below the outer surface has a high diffusion rate of coagulation liquid and a sufficient phase separation It is difficult to form the porous layer B having a sufficiently large structure with respect to the porous layer A.

In the present embodiment, since the permeability and separation characteristics of the porous hollow fiber membrane can be compatible, the pore diameter Ad is set to be in the range of 0.01 to 1 μm More preferably in a range of 0.02 to 0.5 mu m, and still more preferably in a range of 0.04 to 0.2 mu m.

It is preferable that the pore diameter from the porous layer C to the layer forming the inner surface is larger than the pore size from the porous layer A to the porous layer C in the porous hollow fiber membrane in the present embodiment. When the pore size from the porous layer C to the inner surface forming layer becomes smaller, the extreme ultrafine water or soluble organic polymer that has escaped from the porous layer C tends to be clogged in the inside of the membrane.

The pore size from the porous layer C to the layer forming the inner surface is appropriately selected according to the purpose. It is preferable that the water permeability is higher than that of the system in which the water permeation performance is prioritized. In this case, the pore diameter from the porous layer C to the layer forming the inner surface is preferably 8 mu m or less, more preferably substantially no pore of 10 mu m or more . More preferably 5 mu m or less. In the formation of the structure from the porous layer C to the layer forming the inner surface, another dope may be laminated to form a multilayer structure of two or more layers or a method of controlling the composition and temperature of the coagulating solution .

On the other hand, the layers from the porous layer A to the porous layer C are preferably formed from one dope. That is, the same constituent material, more specifically, a thermoplastic resin of the same compound substantially constituting the layer and other film constituent additives, and the like are included. In the case of a multi-layer structure, there is a possibility that the interfacial structure is generated between the layers, and the extreme ultrafine water or the soluble organic polymer which has exited from the outer surface is likely to be clogged and the strength of each layer is lowered, It is because.

It is preferable that the porous hollow fiber membrane in this embodiment does not have a defective portion called pseudo-void having a pore size of 10 mu m or more. As a method of increasing the structure in the vicinity of the outer surface toward the inside, it is conceivable to considerably lower the viscosity of the doping, but in such a method, macrovoids are likely to occur simultaneously in the vicinity of the outer surface, . Therefore, in the present embodiment, it is preferable that no macroboid or part of macrovoid is present between the porous layer A and the porous layer C. Particularly, it is more preferable that the porous layer from the outer surface to the layer having a depth of 10 mu m does not contain macrovoids having a pore size exceeding 10 mu m, or a part thereof. When the cross-sectional structure is observed, It is more preferable that it does not contain any of them.

Incidentally, the term " macroboid and its part from the outer surface to the layer having a depth of 10 mu m " in the present embodiment means that a part of the macrovoid extends from the outer surface to the outer side It is also included in the case of hanging.

The hollow porous hollow fiber membrane of the present embodiment may include only the above-described porous layer, but it is particularly preferable to have the porous layer on the hollow support because excellent mechanical strength can be obtained. Here, in order to clarify the positional relationship between the porous layer and the support, it is referred to as a support. However, the porous layer may be impregnated into the support through the pores of the support. In this embodiment, the porous layer is formed on the outer surface side of the hollow support body.

The support may be appropriately selected and used as long as it has high mechanical strength and can be integrated with the porous layer. Although it is not particularly limited, the support is low, and the flexibility and the shape stability (circularity) And is also excellent in adhesion to the porous layer, so that a braid is preferable. Among them, it is preferable that one yarn including the multifilament is a hollow hollow blade. As the constituent material of the support, polyester fiber, acrylic fiber, polyvinyl alcohol fiber, polyamide fiber or polyolefin fiber and polyvinyl chloride fiber are preferable from the viewpoint of excellent chemical resistance, Acrylic fiber, or polyvinyl chloride fiber is particularly preferable. Further, it is preferable that the support is heat-treated at a temperature higher than the heat distortion temperature of the fibers and lower than the melting temperature of the fibers while regulating the outer diameter. This configuration has the effect of stabilizing the outer diameter of the support, suppressing the stretchability, and densifying the void portion of the support.

In this case, the porous layer and the support (hollow-shaped braid) do not have to be in close contact with each other. However, if the adhesiveness is low, there is a possibility that when the hollow fiber membrane is stretched, the porous layer is separated and the porous layer is lost. Therefore, in the hollow porous hollow fiber membrane of the present embodiment, it is preferable that a part of the porous layer is infiltrated into the braid through the stitch of the hollow braid to integrate the porous layer and the hollow braid.

In order to impart sufficient adhesion to the porous layer and the support, it is more preferable that the porous layer penetrate at least 50% of the hollow blade thickness. In addition, it is more preferable that the porous layers which have penetrated by 50% or more through other stitches are connected to each other and a part of the support is wrapped around from the viewpoint of resistance to peeling. Further, when the portion of the support body that surrounds a part of the support body is connected in the fiber axis direction, the peel resistance is further increased. Further, if the method of connecting in the direction of the fiber axis is a spiral shape, the peeling resistance is remarkably improved, which is more preferable. Also in this case, the above-mentioned film thickness in the present embodiment means the thickness of the portion exposed on the support.

The porous layer is formed of a film-forming resin. As the film-forming resin, a thermoplastic resin can be used as described above, and examples thereof include a polysulfone resin, a polyethersulfone resin, a sulfonated polysulfone resin, a polyvinylidene fluoride resin, a polyacrylonitrile resin, a polyimide resin , A polyamide-imide resin, or a polyester-imide resin. Of these, polyvinylidene fluoride resins are preferred because of their excellent chemical resistance.

Next, a method of producing the hollow porous hollow fiber membrane of the present embodiment will be described.

The porous hollow fiber membrane of the present embodiment is preferably formed by a non-solvent-phase separation method. The non-expropriation method is a multi-republic method of inducing phase separation by the introduction of non-expense items (water, etc.).

In the thermal organic phase separation method of inducing phase separation by heat, since the propagation speed of heat is fast, it is difficult to form a structure in which the pore size of the porous layer gradually increases toward the inside. A homogeneous structure is formed according to the method of electron beam irradiation, the method of multiplying by microparticle charging or drawing. With respect to these methods, the non-solvent separation method has an effect of easily forming an increasing structure towards the inside because the diffusion rate of the non-solvent is slow.

Specifically, in the porous hollow fiber membrane of the present embodiment, a film-forming resin containing a material of a porous layer and a solvent is applied to the outer surface of a hollow support by using an annular nozzle to form a film-forming resin layer, Contacting the surface of the film-forming resin layer with saturated water vapor (conditions such as temperature will be described later), and solidifying the solution with a coagulating liquid.

The manufacturing apparatus of the present embodiment will be described. Fig. 12 shows a manufacturing apparatus according to the present embodiment. The manufacturing apparatus 1g according to the present embodiment includes a spinning nozzle 10, a processing container 20A disposed on the downstream side of the spinning nozzle 10, a coagulation bath 30 for storing the coagulation solution B , And scavenging means (40A) for scavenging the scavenging gas on the discharge surface (10a) of the spinning nozzle.

(Processing vessel)

The processing container 20A contains a film containing a non-solvent of the film-forming resin (hereinafter referred to as a " processing gas "), and a yarn A 'discharged from the spinning nozzle 10, Is brought into contact with the processing gas.

Here, the non-solvent refers to a solvent which is not capable of dissolving the film-forming resin (for example, having a solubility of less than 1 mass% at room temperature) under the reaction conditions of this process. As the non-solvent, alcohols such as water and ethanol, acetone, toluene, ethylene glycol, or a mixture of water and a good solvent used in a film-forming resin solution can be used. Among them, water is particularly preferable.

The processing container 20A used in the present embodiment is a cylindrical body having a flat plate-like ceiling portion 21, a flat plate bottom portion 22 and a cylindrical side portion 23, And a second opening 22a through which the filament body A 'is introduced is formed in the bottom portion 22. The first opening 21a is formed in the bottom portion 22a. The openings of the first opening 21a and the second opening 22a are equal to each other or the processing gas in the processing container 20A is heated from the first opening 21a by a thermal buoyancy more than the second opening 22a The diameter of the opening of the second opening 22a may be larger than the diameter of the opening of the first opening 21a in order to suppress leakage. Further, the second opening 22a is disposed above the liquid level of the coagulation liquid B in the coagulation bath 30. That is, in this embodiment, the processing container 20A is separated from the coagulating liquid B in the coagulation bath, and the second opening 22a is not clogged with the coagulating liquid B.

In this processing container 20A, the yarn body A 'is introduced from the first opening portion 21a, and the yarn body A' in contact with the processing gas in the processing container 20A flows from the second opening portion 22a to the outside .

The processing gas supplied from the gas supply pipe 24 is discharged from the first opening 21a and the second opening 22a after passing through the interior of the processing container 20A.

(Scavenging means)

The scavenging means 40A is a scavenging means configured to remove the processing gas discharged from the spinning nozzle 10 by replacing the processing gas with a scavenging gas and is a scavenging nozzle provided on the discharge surface 10a of the spinning nozzle 10, (41), and a gas supply means (42) for supplying a gas to the scavenging nozzle (41).

The scavenging nozzle 41 includes an annular member and includes a central circular opening 41a and a gas introducing chamber 41b connected to the gas supplying means 42 and including an annular space into which the gas for gas is introduced And an annular gas discharge port 41c for discharging the gas to be supplied from the gas introduction chamber 41b toward the discharge surface 10a of the spinning nozzle 10 exposed in the circular opening 41a.

The center of the circular opening 41a is arranged so as to coincide with the center of the support discharge port of the spinning nozzle 10 and the center of the resin solution discharge port. Therefore, the filament body A 'passes through the circular opening 41a. The gas introducing chamber 41b is formed concentrically with the scavenging nozzle 41 on the outer peripheral side of the circular opening 41a. The gas discharge port 41c communicates with the gas introducing chamber 41b and opens toward the center of the circular opening 41a as shown in Fig. 13, so that the gas for discharging the gas is discharged to the outer peripheral side of the circular opening 41a To the center thereof.

In the present embodiment, a protective box 50 for covering and protecting the yarn body A 'is provided on the lower surface of the scavenging nozzle 41 in the scavenging means 40A.

The protective box 50 is a cylindrical member, and a through hole 50a is formed. The upper end portion 51 of the protective box 50 is closely fixed to the lower surface of the scavenging nozzle 41 such that the through hole 50a communicates with the circular opening 41a of the scavenging nozzle 41. [ A lower end portion 52 of the protective box 50 is provided apart from the processing container 20A and a gap Q is formed between the protective box 50 and the treatment container 20A.

It is preferable that the opening area of the through hole 50a and the opening area of the opening 52a on the side of the lower end 52 are small in a range in which the yarn body A ' The smaller the cross-sectional area of the through hole (50a), the faster the supply rate of the gas for the furnace can be, and the scavenging ability can be improved. The smaller the opening area of the opening 52a on the side of the lower end 52 is, the more the processing gas flowing out of the first opening 21a can be prevented from flowing into the through hole 50a.

However, it is preferable that the flow rate of the gas for purifying gas toward the first opening 21a from the side of the lower end portion 52 should not be increased more than necessary, and the opening area of the opening portion 52a on the side of the lower end portion 52 should be made smaller . If the flow rate of the gas for the gas toward the first opening 21a is excessively fast or if the opening area of the opening 52a of the lower end 52 is excessively small, the gas for gas flows through the first opening 21a There is a possibility of invasion of the processing vessel 20A and variation of the temperature and humidity of the gas in the processing vessel 20A.

The material of the protective box 50 is preferably a material which is not corroded or immersed by the gas flowing out of the processing container 20A. Polyethylenes, polypropylenes, fluorine resins, stainless steel, aluminum, ceramics, glass, and the like can be given to satisfy these requirements. It is preferable that the material of the protective barrel 50 is low in heat conductivity so as to suppress the temperature change of the gas for blowing due to the heat radiation of the blowing gas flowing through the through hole 50a and the heat radiation from the external atmosphere. Examples of the material having a low thermal conductivity include polyethylene, polypropylene, fluororesin, ceramics, glass, and the like. As the material of the protective box 50, it is preferable that the state of the filament body A 'running through the through hole 50a can be observed from the outside, so that it is preferable that the transparency is high, and the polyethylene having high transparency, polypropylene having high transparency, The tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) of high fluorine resin or glass is particularly preferable.

It is preferable that the protective box 50 is detachable from the scavenging nozzle. If the protective box 50 is detachable, it can be removed from the scavenging nozzle 41, so that the hand can easily touch the vicinity of the discharge surface 10a, and operability at the start of film formation can be improved. As the attaching / detaching means, a mechanical attaching / detaching means such as a screw or a clamp, or a magnet attaching / detaching means using a metal sucking the magnet and the magnet is convenient and suitable.

In this embodiment, the yarn body A 'discharged from the spinning nozzle 10 passes through the through hole 50a of the protective barrel 50 after passing through the gas discharge port 41c.

The exhaust gas discharged from the gas discharge port 41c of the scavenging nozzle 41 is discharged from the upper end portion 51 to the lower end portion 52 in parallel with the gathers A 'around the gathers A' passing through the through holes 50a. As shown in Fig. Then, the gas is discharged from the through hole (50a) toward the processing gas flowing out from the first opening (21a). Thereafter, the gas for purge gas flows outward with the gap Q, away from the first opening 21a together with the processing gas flowing out from the first opening 21a.

The scavenging means 40A can replace the processing gas discharged from the first opening 21a with the scavenging gas and can be removed from the vicinity of the discharging face 10a, Condensation can be prevented. This makes it possible to precisely control the membrane surface structure of the obtained porous hollow fiber membrane (A), to make the membrane surface structure uniform, and to improve the quality of the porous hollow fiber membrane (A).

Drying air is preferred as the gas for the furnace. In the present embodiment, dry air refers to a gas having a relative humidity (vapor pressure against saturated vapor pressure) of 0 to 9%. In the case where dry air having a relative humidity of about 1% at room temperature is supplied from a factory or the like, it is preferable to adjust the dry air to a predetermined temperature by the gas temperature adjusting means to make heated dry air and supply it to the scavenging nozzle 41 Do.

(Production method of porous hollow fiber membrane)

The production method of the porous hollow fiber membrane (A) using the production apparatus (1a) will be described. The present manufacturing method has a spinning process, a scavenging process and a solidifying process.

[Spinning process]

In the spinning process in the present embodiment, the film-forming resin solution is discharged downward from the resin solution discharge port while discharging the hollow-cord-like support A1 downward from the support discharge port of the spinning nozzle 10, (A2) of the film-forming resin solution is formed on the outer circumferential surface of the substrate (A1) to prepare a hollow filament body (A ').

The film-forming resin solution usually includes a film-forming resin, a hydrophilic resin and a solvent for dissolving the resin. The film-forming resin solution may contain other additive components as required. The hydrophilic resin is added in order to adjust the viscosity of the film-forming resin solution to a range suitable for forming the hollow porous hollow fiber membrane (A) and to stabilize the film formation state, and polyethylene glycol or polyvinyl pyrrolidone And is preferably used. Of these, copolymers in which other monomers are copolymerized with polyvinyl pyrrolidone or polyvinyl pyrrolidone are preferable from the viewpoints of controlling the pore diameter of the obtained hollow porous hollow fiber membrane and the strength of the hollow porous hollow fiber membrane.

The hydrophilic resin may be used by mixing two or more kinds of resins. For example, when a hydrophilic resin having a higher molecular weight is used, there is a tendency that a hollow porous hollow fiber membrane having a good film structure tends to be formed. On the other hand, the hydrophilic resin having a low molecular weight is suitable because it is more likely to be removed from the hollow porous hollow fiber membrane (A). Accordingly, a homogeneous hydrophilic resin having a different molecular weight may be suitably blended and used depending on the purpose.

Examples of the solvent include N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, N-methyl-2-pyrrolidone, N-methylmorpholine- One or more of these may be used. In addition, a film-forming resin or a poor solvent of a hydrophilic resin or a non-solvent may be mixed and used within a range that does not impair the film-forming ability of the solvent or the solubility of the hydrophilic resin.

The temperature of the film-forming resin solution is not particularly limited, but is usually 20 to 40 占 폚. The viscosity of the film-forming resin solution at 40 캜 is preferably 20,000 to 500,000 mPa · s, more preferably 50,000 to 300,000 mPa · s, and even more preferably 70,000 to 250,000 mPa · s . If the viscosity is excessively low, the phase separation speed increases and Ad and Bd become too large to deteriorate the separation characteristics. On the other hand, if the viscosity is excessively high, the speed of phase separation lowers, and it becomes difficult to make Bd sufficiently larger than Ad.

If the concentration of the film-forming resin in the film-forming resin solution is too light or too thick, the stability at the time of film formation lowers, and it tends to make it difficult to obtain a desired hollow porous hollow fiber membrane. With respect to the total mass of the solution, the lower limit is preferably 10 mass%, more preferably 15 mass%. The upper limit is preferably 30% by mass, more preferably 25% by mass, based on the total mass of the film-forming resin solution. Specifically, the film-forming resin may be in a range of 10 to 30 mass%, preferably 15 to 25 mass%, based on the total mass of the film-forming resin solution.

On the other hand, the lower limit of the concentration of the hydrophilic resin is preferably 1% by mass, more preferably 5% by mass with respect to the total mass of the film-forming resin solution in order to make the hollow porous hollow fiber membrane easier to form. The upper limit of the concentration of the hydrophilic resin is preferably 20% by mass, more preferably 12% by mass with respect to the total mass of the film-forming resin solution in terms of handling property of the film-forming resin solution. Specifically, it may be in the range of 1 to 20 mass%, preferably 5 to 20 mass%, based on the total mass of the film-forming resin solution.

The composition of the film-forming resin solution is not particularly limited as long as it can form a structure gradually increasing from the porous layer A to the porous layer C by phase separation. From the viewpoint of increasing the surface opening ratio of the porous layer, Is preferably 68% by mass or more, more preferably 70% by mass or more based on the total mass of the film-forming resin solution.

In addition, since there is a tendency to form an incremental structure without a large macrovoid, the mass ratio of the hydrophilic resin / film-forming resin is preferably 0.45 or more. Below this value, the macrovoid tends to be easily formed, and the sea-island structure tends to be formed rather than the air-moving structure. As a result, the surface open area ratio is lowered or a homogeneous structure is formed .

[Waste Process]

The scavenging step in the present embodiment is a step of sending a scavenging gas to the discharge surface 10a of the spinning nozzle 10. [

Specifically, in the scavenging step, first, the gas for gas supplied from the gas supplying means 432 is filtered by the gas filtering means 43, the temperature and humidity are adjusted by the gas adjusting means 44, And supplies it to the introduction chamber 41b. At this time, the dew condensation on the discharge surface 10a can be further radiated, so that the gas adjusting means 44 preferably adjusts the gas so that the dew point is lower than the surface temperature of the discharge surface of the spinneret 10 . When it is desired to keep the temperature of the spinning nozzle 10 or the gumming body A 'unchanged from the set state, it is preferable that the temperature is set to the same temperature as the set temperature of the temperature spinning nozzle 10 of the substrate.

Subsequently, in the gas introduction chamber 41b, the pressure distribution of the gas for combustion is uniformized by the resistance imparting member 41d provided in the gas discharge port 41c. Subsequently, the gas for gas in the gas introducing chamber 41b is discharged toward the center of the circular opening 41a through the resistance applying body 41d of the gas discharging opening 41c, It sends the gas. The exhaust gas discharged from the gas discharge port 41c flows from the upper end portion 51 toward the lower end portion 52 in parallel with the gathers A 'around the gathers A' passing through the through holes 50a. Then, the gas is discharged from the through hole (50a) toward the processing gas flowing out from the first opening (21a). Thereafter, the substrate for purge gas is discharged to the outside with the gap Q, away from the first opening 21a together with the processing gas flowing out from the first opening 21a.

The dew point of the non-solvent in the atmosphere in the vicinity of the spinning nozzle 10 is set to be less than the surface temperature of the spinning nozzle 10 in the scouring step. When the dew point of the non-solvent in the atmosphere near the spinning nozzle 10 becomes more than the spinning nozzle 10, it becomes difficult to emit condensation. Here, the " dew point of the non-solvent in the atmosphere " means that the amount of non-solvent contained in the atmosphere is equal to the amount of non-solvent contained in the atmosphere, and when the ambient temperature is lowered, Is the temperature at which the spent fuel begins to condense.

In addition, it is preferable that the relative humidity of the non-solvent in the atmosphere in the vicinity of the spinneret is made less than 10%, because the dew condensation can be more prevented by the above-described scavenging step. Here, Is a value (unit:%) obtained by the amount of non-solvent contained in an atmosphere at a certain temperature / the saturation cost amount of the temperature × 100.

[Solidification process]

The solidifying step is a step of immersing the film-forming resin solution discharged from the spinning nozzle 10 into the coagulating solution (B) in the coagulation bath (30) after making contact with the treatment gas in the treatment vessel (20A).

In the coagulation step in the present embodiment, the gumming body A 'is brought into contact with the processing gas in the processing container 20A and the coagulation liquid B in the coagulation bath 30, whereby the coating film of the film- (A2) is solidified to obtain a porous hollow fiber membrane (A).

Specifically, the yarn body A ', in which the coating film A2 of the film-forming resin solution is formed in the spinning process, is introduced into the interior of the processing container 20A from the first opening 21a of the processing container 20A, And brought into contact with the treatment gas. The non-solvent component contained in the treatment gas diffuses and enters the coating film A2 in contact with the treatment gas, and phase separation begins.

Examples of the treatment gas include air in which the non-solvent is saturated, air in which the non-solvent is not saturated, and saturated vapor of non-solvent. In order to obtain the porous hollow fiber membrane of the present embodiment, .

When the film-forming resin is a hydrophobic polymer, water, ethanol and other alcohols, acetone, toluene, ethylene glycol and the like can be used as the non-solvent, and water is particularly preferable.

When the gas for treatment is a non-solvent saturated steam, the periphery of the gathers A 'passing through the treatment container 20A is filled with non-solvent. Hereinafter, characteristics in the case where the treatment gas is saturated steam under atmospheric pressure will be described.

The saturated water vapor temperature under atmospheric pressure is about 100 DEG C, and the space in the processing vessel 20A filled with saturated water vapor is filled with 100% water molecules. Therefore, when saturated steam is used as the processing gas, the atmosphere temperature and humidity around the filament body A 'can be made uniform.

In addition, the saturated water vapor can increase the amount of water and the amount of heat supplied per unit time to the filament body A 'passing through the processing container 20A, as compared with the gas containing other moisture. In addition, since the amount of heat of condensation when condensing water vapor is very large and the heat efficiency of condensation is high, it is possible to instantaneously raise the temperature near the surface layer of the filament body A 'to about 100 ° C.

Therefore, by the water supply and the heat supply in the saturated water vapor condensation due to the temperature difference with the gumming body A ', the phase separation behavior completely different from the case where the gum body A' is passed through the gas including water in the non-saturated state can be generated .

That is, since the outer surface of the membrane is immediately advanced to solidification through phase separation by a large amount of water supply, if the viscosity of the film-forming resin solution is adjusted to be relatively high, a dense structure suitable for filtration can be formed on the outer surface of the membrane . Then, a large amount of water can readily diffuse into the inside of the film to cause phase separation of the surface layer of the filament body A 'while the filament body A' is in the processing container 20A.

Here, since the temperature in the vicinity of the surface layer of the filament body A 'rises to about 100 ° C, the phase separation speed is very fast, thereby forming a sufficiently large structure for the structure of the porous layer A in the surface layer inside the porous layer A Lt; / RTI >

As described above, the gum body A ', whose outer surface structure is fixed and the phase separation progresses to the surface layer in the processing vessel 20A, is then introduced into the coagulation bath 30, . As a result, the non-solvent component of the coagulating liquid (B) diffuses into the interior of the coating film (A2) of the film-forming resin solution. Since the coagulating liquid (B) is a liquid, a large amount of non-coagulant rapidly penetrates into the porous hollow fiber membrane (A) as compared with saturated water vapor, and solidifies through the phase separation to the inside.

The coagulating solution (B) is a non-solvent for the film-forming resin, and is a good solvent for the hydrophilic resin. Examples of the solvent include water, ethanol, methanol and mixtures thereof. Among them, The mixed liquid is preferable in terms of safety and operation control.

When a mixed solution of a solvent and water used in the film-forming resin solution is used, the solvent preferably has a concentration of 5 to 50% by mass of the solvent, 10 to 40% by mass of the solvent Is more preferable. Below this range, the rate of increase of the non-solvent becomes faster, and the internal structure may become excessively dense. In addition, if the amount exceeds the above range, a sufficient amount of non-solvent can not penetrate and solidification may not be completed in the coagulation bath.

The temperature of the coagulating liquid (B) is preferably in the range of 30 to 95 占 폚, and preferably 40 to 85 占 폚. By setting the temperature of the coagulating solution (B) to the lower limit value or more, the water permeability of the obtained hollow porous hollow fiber membrane is enhanced, and if it is made lower than the upper limit value, the film quality of the hollow porous hollow fiber membrane is improved.

When a polymer such as polyvinyl pyrrolidone is used as the hydrophilic resin, it is preferable that the porous hollow fiber membrane (A) is washed with hot water and then treated with an oxidizing agent-containing liquid to decompose and remove the hydrophilic resin.

The method of manufacturing the porous hollow fiber membrane of the present embodiment and the hollow fiber membrane produced thereby can be applied to the field of water treatment. For example, the method can be used for a method for producing a porous hollow fiber membrane of the present embodiment, a method for water treatment using a hollow fiber membrane produced thereby, and other methods for water treatment. Further, the method for producing a porous hollow fiber membrane of the present embodiment and the hollow fiber membrane produced thereby can be used for a water purification apparatus equipped with the hollow fiber membrane, and can be used for a manufacturing method of the water purification apparatus.

Further, in these applications, each of the structures of the above-described embodiments can be appropriately used in combination.

Example

The present embodiment will be described concretely by the following embodiments and the like.

(Image analysis)

The physical properties of the porous film were measured by image analysis as follows.

(1) Average pore size index of the porous film

The cross-section and the surface of the porous film were photographed using a scanning electron microscope (SEM), and the average pore size of the internal structure and the surface was obtained from the image analysis by the computer of the photograph. The average pore size obtained by the image analysis varies slightly with image quality adjustment for image analysis and image analysis software, but the difference is within the range of normal experimental error.

The outer surface of the obtained porous film is observed with a scanning electron microscope (SEM). When the porous membrane is a porous hollow fiber membrane, a reference point on the outer surface of the porous hollow fiber membrane is determined, and the reference point is set at 0 °, and SEM photographs are taken from four directions of 90 °, 180 ° and 270 °. Observation magnification is 10,000 to 100,000 times in the case of a microfiltration membrane, although it can not be said uniformly because it depends on a desired fraction pore size. If it is out of this range, the pore size of the outer surface can not be sufficiently observed at a size of 5000 times or less, and when the size is 1000000 times or more, the number of pores in the field of view becomes smaller and it is difficult to say that the average size is too large. The pore size of the whole hole in the SEM photograph is calculated with the diameter of the hole recognized by the image analysis software as the pore size and the pore size index is calculated from the average value thereof to thereby quantitatively evaluate the structure of the surface or the cross section of the porous film. Here, the data are arranged in descending order of the calculated total holes in the area, and the areas from the upper holes are integrated to calculate the pore size index using holes extending to an arbitrary ratio of 50% with respect to the total area do. For example, the arbitrary ratio A is not limited.

(2) Open area ratio of porous film

The SEM photograph of the porous film was subjected to the image analysis to measure the area of the hole, and the opening ratio of the porous film was determined.

Open area ratio (%) = sum of areas of all holes recognized by image analysis / SEM image area in the field of view

(Outer diameter of the support)

The outer diameter of the support was measured by the following method.

The sample to be measured was cut to about 10 cm, several pieces were bundled, and the whole was covered with a polyurethane resin. The polyurethane resin was allowed to enter the hollow portion of the support.

After curing the polyurethane resin, a flake with a thickness of about 0.5 mm (in the longitudinal direction of the film) was sampled using a razor blade.

Next, the cross section of the support sampled was observed with an objective lens 100 times using a projector (PROFILE PROJECTOR V-12 made by Nikon Corporation).

A mark (line) was fitted to the position of the outer surface of the support body in the X direction and the Y direction to observe the outer diameter. This was measured three times to obtain an average value of the outer diameter.

(Inner diameter of the support)

The inner diameter of the support was measured by the following method.

The sample to be measured was sampled in the same manner as the sample whose outer diameter was measured.

Next, the cross section of the support sampled was observed with an objective lens 100 times using a projector (PROFILE PROJECTOR V-12 made by Nikon Corporation).

Marks (lines) were fitted to the positions of the inner surface in the X direction and the Y direction on the surface of the support member to be observed, and the inner diameter was read. This was measured three times to obtain an average value of the inner diameter.

(Outer diameter of porous hollow fiber membrane)

The outer diameter of the porous hollow fiber membrane was measured by the following method.

The sample to be measured was cut to about 10 cm, several pieces were bundled, and the whole was covered with a polyurethane resin. The polyurethane resin was allowed to enter the hollow portion of the support.

After curing the polyurethane resin, a flake with a thickness of about 0.5 mm (in the longitudinal direction of the film) was sampled using a razor blade.

Next, the cross-section of the sampled porous hollow fiber membrane was observed with an objective lens 100 times using a projector (PROFILE PROJECTOR V-12 made by Nikon Corporation).

Marks (lines) were fitted to the outer surface positions of the observed porous hollow fiber membrane cross sections in the X and Y directions, and the outer diameters were read. This was measured three times to obtain an average value of the outer diameter.

(Inner diameter of porous hollow fiber membrane)

The inner diameter of the porous hollow fiber membrane was measured by the following method.

The sample to be measured was sampled in the same manner as the sample whose outer diameter was measured.

Next, the cross-section of the sampled porous hollow fiber membrane was observed with an objective lens 100 times using a projector (PROFILE PROJECTOR V-12 made by Nikon Corporation).

A mark (line) was fitted to the position of the inner surface of the support in the X and Y directions of the observed cross-section of the porous hollow fiber membrane, and the inner diameter was read. This was measured three times to obtain an average value of the inner diameter.

(Film Thickness of Porous Film Layer)

The thickness of the porous membrane layer in the examples and the like is the thickness from the surface of the support to the surface of the porous hollow fiber membrane and is measured by the following method.

The sample to be measured was sampled in the same manner as the sample whose outer diameter was measured.

Next, the cross section of the sampled porous hollow fiber membrane was observed with an objective lens 100 times using a projector (PROFILE PROJECTOR V-12, manufactured by Nikon Corporation).

Marks (lines) were fitted to the positions of the outer surface and the inner surface of the film thickness at the position of 3 o'clock position of the observed porous hollow fiber membrane section, and the film thickness was read. Similarly, the film thickness was read in the order of 9 o'clock, 12 o'clock and 6 o'clock. This was measured three times to obtain an average value of the inner diameter.

(Pore size of the porous film layer)

The pore size of the porous layer was measured by the following method.

The cross-sectional structure to be measured was photographed at a magnification of 10,000 times using a scanning electron microscope, and the average pore size of the structure was determined by image analysis processing of the obtained photograph. As image analysis processing software, IMAGE-PRO PLUS version 5.0 of Media Cybernetics Inc. was used.

(Permeability of porous hollow fiber membrane)

The permeability of the porous hollow fiber membrane was measured by the following method.

The sample to be measured was cut to 4 cm, and the hollow section was sealed with a polyurethane resin on one end face.

Next, the sample was depressurized in ethanol for 5 minutes or more, and then immersed in pure water for substitution.

Pure water (25 ° C) was placed in the vessel, connected to the other end of the sample through a tube, and air pressure of 200 kPa was applied to the vessel to measure the amount of pure water from the sample for 1 minute. This was measured three times to obtain an average value. This value was divided by the surface area of the sample to obtain permeability.

(Separation Characteristics of Porous Hollow Fiber Membrane)

The separation characteristics of the porous hollow fiber membrane were evaluated from the maximum pore size determined in accordance with JIS K 3832 by the bubble point method. Ethanol as a measurement medium.

(Average pore size index, aperture ratio)

The average pore size was evaluated by image analysis using an SEM photograph (30,000 times) and Image-Pro Plus manufactured by Planetron Co., and the average pore size of the outer surface photographs observed from each direction was determined. The average pore diameter and the opening ratio were calculated by the following series of steps.

Step (1)

The cross-sectional surface of the porous hollow fiber membrane was observed with an SEM, and the pore area of the whole hole that can be grasped by an electron microscope photograph was measured.

Step (2)

In the step (1), data are arranged in descending order of the calculated pore size, the area is accumulated from the upper pore, and holes corresponding to a specific ratio B (50%) to the total area are used , And the area is regarded as a hole and the diameter (pore diameter) thereof is calculated as an average pore diameter index.

(Example 1)

Polyester fiber (polyethylene terephthalate (PET), fineness: 84 dtex, filament count: 36, warp yarn) was used as the yarn for the hollow reinforcing support. As the bobbins used in the production of the hollow reinforcing support, five pieces of polyester fibers wound about 5 kg were prepared, and as a circular knitting machine, a tablet-type cord knitting machine (manufactured by Sonoi Sengen Kaisha, number of knitted needles: 12, Gauge, circumference diameter of spindle: 8 mm) was used. A Nelson roll was used as the strap feeding device and the pulling device. As the heating die, a stainless steel die (outer diameter D: 5 mm, inner diameter d: 2.5 mm, length L: 300 mm) having heating means was used.

Five polyester fibers drawn from a bobbin were folded in one piece (total fineness: 420 dtex), and a hollow braid was knitted by circular knitting with a circular knitting machine. The hollow braid was passed through a heating die at 210 DEG C and the heat-treated hollow braid was used as a hollow reinforcing support and wound at a winding speed of 200 m / hour by a winding device.

The obtained hollow reinforcing support had an outer diameter of about 2.5 mm and an inner diameter of about 1.7 mm. The number of loops of the hollow braids constituting the hollow reinforcing supporter was 12 per week, and the maximum opening width of the stitches was about 0.1 mm. The length of the hollow reinforcing support was 12,000 m.

, 11.5% by mass of polyvinylidene fluoride (manufactured by Arkema Corporation, product name: Kana 301F), 11.5% by mass of polyvinylidene fluoride (product name: Kaga 9000LD, trade name; manufactured by Nippon Shokubai Co., Ltd., trade name: K-80) were dissolved in 65% by mass of N, N-dimethylacetamide while stirring to prepare a first film-forming resin solution. The viscosity of this first film-forming resin solution at 40 占 폚 was 210,000 mP 占 퐏.

19% by mass of polyvinylidene fluoride (product name: Kana 301F) and 10% by mass of polyvinylpyrrolidone (trade name; K-80 made by Nippon Shokubai Co., Ltd.) were dissolved in N, N-dimethylacetamide 71 By mass with stirring to prepare a second film-forming resin solution. The viscosity of this second film-forming resin solution at 40 캜 was 130,000 mPsec.

Subsequently, a porous hollow fiber membrane was produced using the production apparatus shown in Fig. In this example, as the spinning nozzle, a through-hole for the support through which the hollow reinforcing support is passed and a flow path for the resin solution of the two film-forming resin solutions (the first resin solution flow path and the second resin solution flow path) The formed multiple ring nozzles were used. In this spinning nozzle, a support discharge port, a first resin solution discharge port, and a second resin solution discharge port are formed on the lower surface.

(Preparation of porous hollow fiber membrane)

A treatment container was disposed above the coagulation bath so that a gap of 10 mm from the coagulation liquid level was formed. The treatment container and the protective barrel were arranged such that a gap of 5 mm was formed between the lower end opening of the protective barrel and the first opening of the treatment container. The scavenging nozzle was arranged so that the upper surface thereof and the lower surface of the spinning nozzle were adhered to each other.

Dry air having a relative humidity of less than 1% at a temperature of 32 ° C was supplied to the scavenging nozzle at 6 L / min. Saturated water vapor at 100 占 폚 was supplied to the processing container as a processing gas. While the temperature of the thermocouple having a diameter of 0.5 mm inserted 5 mm inside from the first opening was monitored while the dry air was supplied to the desired nozzle at 6 L / min, the flow rate adjusting valve was opened little by little, Was set at a lower limit flow rate which was stabilized at 100 DEG C for 10 minutes or more. In the adjusted state, the steam discharged from the flow rate regulating valve was cooled and liquefied, and the mass of the drain water obtained per unit time was measured, and it was equivalent to about 5 NL / min in terms of the steam vapor volume at 100 캜.

In the coagulation bath, 10% by mass of N, N-dimethylacetamide as a solvent component and a coagulation liquid having a composition of 90% by mass of pure water as a non-solvent component were filled. The coagulation bath was kept at 75 캜.

The film-forming resin solution 1 at 32 占 폚 was fed at 23.2 cm3 / min and the film-forming resin solution 2 at 32 占 폚 was fed at a feed rate of 25.0 cm3 / min to the spinning nozzle. Subsequently, the film-forming resin solution 1 and the film-forming resin solution 2 were discharged concentrically from the resin solution discharge port, and the film-forming resin solutions 1 and 2 . Thus, a filament body A 'having the film-forming resin solution applied to the hollow braid substrate was obtained. The gumming material A 'was passed through a nozzle, a treatment container, and a coagulating solution in this order to obtain a porous hollow fiber membrane.

The obtained porous hollow fiber membrane was degassed by passing it through hot water at 98 占 폚 for 1 minute. Subsequently, the substrate was immersed in an aqueous solution of 30,000 mg / L sodium hypochlorite, followed by heat treatment in a steam bath at 98 占 폚 for 2 minutes. Subsequently, the resultant was washed in hot water at 98 占 폚 for 15 minutes, dried at 110 占 폚 for 10 minutes, and wound up to obtain a porous hollow fiber membrane.

The cross section of the obtained porous hollow fiber membrane frozen with liquid nitrogen was observed by SEM and photographed. The obtained photographs were subjected to image analysis using Image-Pro Plus (manufactured by Planetron, Inc.), and the average pore size of each layer was calculated. The results are shown in Table 1.

(Example 2)

19% by mass of polyvinylidene fluoride (ARKEMASA, trade name Kana 761A) and 12% by mass of polyvinylpyrrolidone (trade name K-80 made by Nippon Shokubai Co., Ltd.) as the first and second film- Dimethylacetamide in 69% by mass of N, N-dimethylacetamide was used as a coagulating solution, and 20% by mass of N, N-dimethylacetamide and 80% by mass of pure water as a non-solvent component % By weight of a coagulating liquid having a composition of 100% by weight.

The viscosity of this film-forming resin solution at 40 占 폚 was 250,000 mP 占 퐏.

With respect to the obtained porous hollow fiber membrane, the average pore size of each layer was calculated in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)

15% by mass of polyvinylidene fluoride (ARKEMASA, trade name Kana 761A) and 11% by mass of polyvinylpyrrolidone (trade name K-80 manufactured by Nippon Shokubai Co., Ltd.) as the first and second film- In 74% by mass of N, N-dimethylacetamide was used in place of the film-forming resin solution prepared in Example 6, to obtain a porous hollow fiber membrane.

The viscosity of this film-forming resin solution at 40 캜 was 80,000 mPsec.

With respect to the obtained porous hollow fiber membrane, the average pore size of each layer was calculated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)

The same first and second film-forming resin solutions as in Example 1 were used.

The coagulation bath was filled with a coagulation solution having a composition of 8 mass% N, N-dimethylacetamide as a solvent component and 92 mass% pure water as a non-solvent component. The coagulation bath was kept at 70 ° C.

The film-forming resin solution 1 at 32 ° C was supplied at 17.4 cm 3 / min and the film-forming resin solution 2 at 32 ° C was supplied at a supply rate of 18.7 cm 3 / min to the spinning nozzle. Subsequently, the film-forming resin solution 1 and the film-forming resin solution 2 were discharged concentrically from the resin solution discharge port, and the film-forming resin solutions 1 and 2 . Thus, a filament body A 'having the film-forming resin solution applied to the hollow braid substrate was obtained.

The obtained gum body A 'was introduced into a cover for forming a high-temperature and high-humidity atmosphere filled with steam of a coagulating liquid (temperature: 70 ° C) and subjected to high temperature and high humidity treatment. At that time, the distance that the filament body A 'traveled in the high temperature and high humidity atmosphere in the cover for forming the high temperature and high humidity atmosphere was 67 mm.

Subsequently, the filament A 'subjected to high temperature and high humidity treatment was passed through a coagulating solution (temperature: 70 ° C) in the coagulation bath. Thus, a coagulating solution was attached to the outer circumferential surface of the gum body A ', and the coating film of the film-forming resin solution was solidified to obtain a porous hollow fiber membrane.

The obtained porous hollow fiber membrane was washed and dried in the same manner as in Example 1.

With respect to the obtained porous hollow fiber membrane, the average pore size of each layer was calculated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)

The average pore size of each layer of the porous hollow fiber membrane (ZeeWeed 500) manufactured by GE was calculated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)

The average pore size of each layer was calculated in the same manner as in Example 1 with respect to the porous hollow fiber membrane of type (510) manufactured by Kubota Corporation. The results are shown in Table 1.

<Filtration evaluation>

Modules were made using the porous hollow fiber membranes obtained in Examples 1 to 3 and Comparative Example 1, respectively, and the number of activated sludge was measured using MLSS (suspended solids concentration) = 9000 mg / L, Filtration was carried out.

As a result, in the module manufactured using the porous hollow fiber membrane of Comparative Example 1, the filtration pressure difference remarkably increased from two days after the operation, whereas in the module manufactured using the porous hollow fiber membranes of Examples 1 to 3, So that it can be operated stably.

&Lt; Reference Example 1 >

(Preparation of porous hollow fiber membrane)

A porous hollow fiber membrane 1 was prepared using a porous hollow fiber membrane production apparatus.

Polyvinylidene fluoride B (trade name: Gaina 301F), polyvinylidene fluoride C (trade name: Gaina 9000LD), polyvinylidene fluoride A (trade name: Kana 761A) , And N, N-dimethylacetamide were mixed so as to have a mass ratio shown in Table 2 to prepare film-forming stock solutions (1) and (5) Respectively.

The film forming stock solution 1 was applied to the outer layer and the film forming stock solution 5 was applied to the inner layer in a complex manner under the conditions of a film forming speed of 20 m / min, a 100% steam midpoint region length of 5 mm and a coagulating bath temperature of 75 캜, Respectively.

The obtained porous hollow fiber membrane 1 had an outer diameter of about 2.80 mm, an inner diameter of about 1.2 mm, an average film thickness of about 150 m, a bubble point Pi of 210 mm and a water permeability of 49 m 3 / m 2 / h / MPa. The surface opening ratio A1 was 40% and the pore size index P1 was 0.21 占 퐉. The opening ratio A2 in the inner most dense layer was 27% and the pore size P2 was 0.46 mu m.

The filtration test was performed under the conditions shown in Table 4 for the MBR filtration operating conditions.

&Lt; Reference Example 2 >

(Preparation of porous hollow fiber membrane)

A porous hollow fiber membrane 2 was prepared in the same manner as in Reference Example 1 by using a porous hollow fiber membrane production apparatus.

Polyvinylidene fluoride B (trade name: Gaina 301F), polyvinylidene fluoride C (trade name: Gaina 9000LD), polyvinylidene fluoride A (trade name: Kana 761A) (5) were prepared by mixing the polyvinyl pyrrolidone (trade name: K-80, manufactured by Nippon Shokubai Co., Ltd.) and N, N-dimethylacetamide so that the mass ratios shown in Table 2 were obtained. Respectively.

The film forming stock solution 2 was applied to the outer layer and the film forming stock solution 5 was applied to the inner layer in a complex manner under the conditions of a film forming speed of 20 m / Min, a 100% steam middle point area of 5 mm and a coagulating bath temperature of 75 캜, Respectively.

The obtained porous hollow fiber membrane 2 had an outer diameter of about 2.80 mm, an inner diameter of about 1.2 mm, an average film thickness of about 150 mu m, a bubble point Pi of 197 mu m and a water permeability of 49 m & h / MPa. The surface opening ratio A1 was 41% and the pore size index P1 was 0.23 占 퐉. The opening ratio A2 in the inner most dense layer was 23% and the pore size index P2 was 0.45 mu m.

<Reference Example 3>

(Preparation of porous hollow fiber membrane)

A porous hollow fiber membrane 3 was prepared in the same manner as in Reference Example 1 by using a porous hollow fiber membrane production apparatus.

Polyvinylidene fluoride B (trade name: Gaina 301F), polyvinylidene fluoride C (trade name: Gaina 9000LD), polyvinylidene fluoride A (trade name: Kana 761A) (K-80) and N, N-dimethylacetamide were mixed so as to have the mass ratios shown in Table 2 to prepare film-forming stock solutions (3) and (5) Respectively. The film forming stock solution 3 was applied to the outer layer and the film forming stock solution 5 was applied to the inner layer in a complex manner under the conditions of a film forming speed of 20 m / Min, a 100% water vapor central region length of 5 mm and a coagulating bath temperature of 75 캜, Respectively.

The obtained porous hollow fiber membrane 3 had an outer diameter of about 2.80 mm, an inner diameter of about 1.2 mm, an average film thickness of about 150 탆, a bubble point Pi of 164 ㎪ and a water permeability of 98 m 3 / m 2 / h / MPa. The surface opening ratio A1 was 45% and the pore size index P1 was 0.31 占 퐉. The opening ratio A2 in the inner most dense layer was 25% and the pore size index P2 was 0.67 mu m.

<Reference Example 4>

(Preparation of porous hollow fiber membrane)

A porous hollow fiber membrane 4 was prepared in the same manner as in Reference Example 1, using a porous hollow fiber membrane production apparatus.

(Manufactured by Nippon Shokubai Co., Ltd., trade name: K-2), polyvinylidene fluoride B (trade name: Kana 301F), polyvinylidene fluoride C 80) and N, N-dimethylacetamide were mixed so as to have the mass ratios shown in Table 2 to prepare film forming stock solutions (4) and (5).

The film forming stock solution 4 was applied to the outer layer and the film forming stock solution 5 was applied to the inner layer in a complex manner under the conditions of a film forming speed of 20 m / min, a 100% steam midpoint region length of 5 mm and a coagulating bath temperature of 75 캜, Respectively.

The obtained porous hollow fiber membrane 4 had an outer diameter of about 2.80 mm, an inner diameter of about 1.2 mm, a thickness of the porous membrane layer 11 of about 150 탆 on average, a bubble point Pi of 91 ㎪ and a water permeability of 168 m 3 / / MPa. The surface opening ratio A1 was 50% and the pore size index P1 was 0.36 占 퐉. The opening ratio A2 in the inner most dense layer was 26%, and the pore size index P2 was 1.1 탆.

<Reference Comparative Example 1>

(Preparation of porous hollow fiber membrane)

A porous hollow fiber membrane 5 was prepared using a porous hollow fiber membrane production apparatus.

(Manufactured by Nippon Shokubai Co., Ltd., trade name: K-2), polyvinylidene fluoride B (trade name: Kana 301F), polyvinylidene fluoride C 80) and N, N-dimethylacetamide were mixed so as to have the mass ratios shown in Table 2 to prepare film forming stock solutions (4) and (5). The film forming source liquid 4 was applied to the outer layer and the film forming stock solution 5 was applied to the inner layer in a complex manner under the conditions of a film forming speed of 12.5 m / min, a high-humidity and high-temperature region length of 63.5 mm and a coagulating bath temperature of 75 캜 .

The obtained porous hollow fiber membrane 4 had an outer diameter of about 2.80 mm, an inner diameter of about 1.2 mm, a thickness of the porous membrane layer 11 of about 150 탆 on average, a bubble point Pi of 170 ㎪ and a water permeability of 46 m 3 / / MPa. The surface opening ratio A1 was 26% and the pore size index P1 was 0.17 占 퐉. The opening ratio A2 in the inner most dense layer was 5% and the pore size index P2 was 0.13 mu m.

According to the present embodiment, it is possible to use it in the treatment of various aqueous fluids such as water treatment, beverage treatment, seawater tanning, etc., and it is possible to suppress deterioration of performance over time while having excellent fraction characteristics and permeability, A porous hollow fiber membrane excellent in recoverability of characteristics and an evaluation method thereof can be provided.

The porous hollow fiber membrane of the present embodiment has a structure in which the pore diameter of the inner layer is sufficiently large with respect to the pore size of the layer forming the outer surface, Therefore, the hollow porous hollow fiber membrane of the present embodiment has high filtration stability and is suitable as a filtration membrane used for water treatment such as microfiltration, water treatment by ultrafiltration and the like.

1: Manufacturing apparatus
10: Spinning nozzle
11: through hole for support
12: flow path for resin solution
20A: Processing vessel
21: ceiling
21a: a first opening
22a: a second opening
22c: through hole
23: side
24: gas supply pipe
25: tube
30: Coagulation bath
31: first guide roll
32: second guide roll
33: Ceiling board
33a, 33b:
40A, 40B, 40C: ventilation means
41: ventilation nozzle
41a: circular opening
41b: gas introduction chamber
41c: a gas outlet
41d:
42: gas supply means
43: Gas filtration means
44: gas adjusting means
50: Protector
50a: Through hole
51:
52:
52a: opening
A: Porous hollow membrane
A1: Hollow string-shaped support
A2: Coating film of the film-forming resin solution
B: High amount

Claims (19)

A porous hollow fiber membrane having at least a porous layer on its outer surface,
(Ad / Bd) to the average pore diameter (Bd) of from 2 mu m to 3 mu m in depth from the outer surface to the depth of 1 mu m in the cross-sectional structure in the thickness direction of the porous hollow fiber membrane A porous hollow fiber membrane having a Young's modulus of 0.6 or less. The porous hollow fiber membrane according to claim 1, wherein the outer surface has an average pore size P1 of 0.05 to 1.0 mu m and an open area ratio A1 of 15 to 65%. The porous hollow fiber membrane according to claim 1 or 2, wherein the average pore size P2 of the layer from the outer surface to the depth of 10 占 퐉 in the cross-sectional structure is 0.1 to 5.0 占 퐉 and the open area ratio A2 is 10 to 50%. The porous hollow fiber membrane according to claim 1 or 2, wherein the structure from the outer surface to the depth of 5 占 퐉 is a three-dimensional mesh structure increasing in pore size toward the direction away from the outer surface. The porous hollow fiber membrane according to claim 1 or 2, wherein the average pore size of the porous layer from the outer surface to the depth of 5 占 퐉 is smaller than the average pore size of the porous layer located at a distance of 5 占 퐉 from the outer surface. The porous hollow fiber membrane according to claim 1 or 2, wherein an average pore diameter of the porous layer existing at a portion distant from the outer surface by 5 mu m is 10 m or less. The porous hollow fiber membrane according to claim 1 or 2, wherein the thermoplastic resin constituting from the outer surface to a depth of 5 占 퐉 comprises a thermoplastic resin of the same compound. The porous hollow fiber membrane according to claim 1 or 2, wherein the porous layer in a portion not more than 10 mu m deep from the outer surface does not contain macrovoids having a pore size exceeding 10 mu m and a part thereof. The porous hollow fiber membrane according to claim 1 or 2, formed by a non-solvent separation method. The porous hollow fiber membrane according to claim 1 or 2, wherein the porous layer is formed on the outer surface side of the hollow support body. 11. The porous hollow fiber membrane according to claim 10, wherein the hollow support is a heat-treated support. The porous hollow fiber membrane according to claim 10, wherein the hollow fiber-shaped support is a hollow braid. 12. The porous hollow fiber membrane according to claim 11, wherein the support is a hollow hollow fiber having one thread including multifilament. A film-forming resin solution containing a thermoplastic resin and a hydrophilic compound is discharged from a spinning nozzle, and the discharged film-forming resin solution is brought into contact with a non-solvent saturated vapor of the film-forming resin solution component, To thereby obtain a porous hollow fiber membrane, wherein the porous hollow fiber membrane is solidified by immersing the hollow fiber membrane into a porous hollow fiber membrane,
Wherein the spinning nozzle is a single-ply or double-ply tubular nozzle,
And a scavenging gas having a relative humidity of 0 to 9% is scavenged in the vicinity of the discharge surface of the spinning nozzle,
Wherein the porous hollow fiber membrane is formed by the same film-forming resin solution at least at a depth of 5 mu m from the outer surface of the porous hollow fiber membrane. 15. The method of manufacturing a porous hollow fiber membrane according to claim 14, wherein the non-solvent saturated steam is saturated water vapor. 16. The method according to claim 14 or 15, wherein a film-forming resin solution is applied to the outer peripheral surface of the hollow support by using a spinning nozzle to form a film-forming resin layer, and then the film- Of the porous hollow fiber membrane. The method of manufacturing a porous hollow fiber membrane according to claim 16, wherein the support is a heat-treated support. 17. The method of manufacturing a porous hollow fiber membrane according to claim 16, wherein the support is a braid. 18. The method of manufacturing a porous hollow fiber membrane according to claim 17, wherein the support is a hollow hollow braid having one thread including multifilaments.

Images