JPH0323647B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polysulfone resin hollow fiber membrane useful as an ultrafiltration membrane, which has high water permeability, high burst strength, and has a novel structure. Conventionally, there are many documents regarding aromatic polysulfone and aromatic polyethersulfone membranes, but
Literature disclosing membrane structures is limited. Regarding membranes having surface areas and support layers consisting of void layers, Amicon Corporation's JP-A-49
-23183, Gulf South Research Institute, J.Appl.Poly.Sci., 20. pp. 2377-2394 and 2395-2406 (1976), also J.Appl.
Poly.Sci., 21 , pp. 1883-1900 (1977), etc. The former hollow fiber membrane has a surface layer on the inside,
There is no surface layer on the outside, and a cavity with a size of 10 μm or more in the polymer is opened on the outside surface.
Therefore, it has disadvantages such as low mechanical strength, inability to backwash, and easy clogging.
The latter was developed as a support for reverse osmosis membranes, and has pores on its surface with an average pore size of 250 Å to 0.44 μm, but its water permeability is at most 1.3 m ³ /
It is small, ^m2・day・atm, and is of little practical use as an ultrafiltration membrane. The aromatic polysulfone and aromatic polyethersulfone hollow fiber membranes described in JP-A-54-143777 and JP-A-54-145379 are both made of inner and outer surface layers, inner and outer void layers, and an intermediate layer. However, its mechanical properties are weak and its water permeability is poor due to insufficient communication in the intermediate layer. Furthermore, these hollow fiber membranes have a thickness ratio of inner and outer void layers greater than 1.5 times,
The thickness of the inner void layer is greater than the thickness of the outer void layer. Therefore, the amount of polymer is larger on the outside,
Since there is less on the inside, the permeation resistance near the outer surface is high, and the mechanical strength against pressure from the inside is low. The hollow fiber membrane of the present invention is basically
It has a structure similar to that disclosed in Publication No. 145379, but there is no big difference in the thickness of the inner and outer void layers, and the amount of polymer is almost uniformly dispersed, so the resistance is low, and it has a suitable average It differs in that it has a well-developed structure in which pores of the same diameter are connected three-dimensionally, and it also has an intermediate layer of appropriate thickness, and due to this feature, it has high water permeability.
It is an excellent hollow fiber membrane with high bursting strength. That is, the present invention has a five-layer structure of an outer surface layer, an outer void layer, an intermediate layer, an inner void layer, and an inner surface layer, and the ratio of the thickness of the inner and outer void layers is 1.5 or less,
The present invention relates to a polysulfone-based resin hollow fiber membrane characterized in that the thickness of the intermediate layer is 5 μm or more and 7 μm or less, and the total membrane thickness is 100 μm to 600 μm. The present invention will be explained in detail below. The polysulfone resin forming the polysulfone resin hollow fiber membrane of the present invention is an aromatic polysulfone or an aromatic polyether sulfone having a repeating unit represented by the following general formula () or (). (However, X, X', X'', X, X''''', X'''''
' each independently represents methyl, ethyl, n-propyl, n-
Lower alkyl group selected from butyl, F, Cl, I
and non- _dissociative substituents _such as halogen groups selected from Represents an integer. ). These aromatic polysulfone resins suitably have a number average molecular weight of 5,000 to 100,000 as measured by an osmotic pressure method. These aromatic polysulfone resins can provide hollow fiber membranes with excellent heat resistance, acid-alkali resistance, chemical resistance, and mechanical strength. The hollow fiber membrane of the present invention has a five-layer structure made of the polysulfone resin, namely, an outer surface layer (A _p ), an outer void layer (B _p ), an intermediate layer (C), an inner void layer (B _i ), It has a five-layer structure of A _p B _p C B _i A _i of the inner surface layer (A _i ). As the membrane thickness increases, the bursting strength increases, but the water permeability naturally decreases. The hollow fiber of the present invention has a thickness of approximately 100 to 600 μm, preferably 100 to 600 μm.
500 μm, and although the outer diameter and inner diameter of the hollow fiber according to the present invention are not critical, it is generally preferred that the outer diameter is around twice the inner diameter, and therefore the preferred outer diameter of the hollow fiber of the present invention is about It is 300 to 5000 μm.
The outer diameter and inner diameter are determined to appropriate values based on the membrane thickness and the shape of the hollow fiber. The A _p layer and the A _i layer, which are the surface layers of the hollow fiber of the present invention, have almost the same layer structure, and the thicknesses of the A _p layer and the A i layer are approximately the same.
The A _i layer is approximately equal, 0.01 to 10 μm, and usually 1
It is about ~4 μm. For example, it consists of a bead-like connection of small polymer particles of about 0.01 μm, and the distance between the particles is very narrow near the inner and outer surfaces, and they are packed very densely. growing. The inner and outer surface layers appear so smooth that no pores can be observed even when viewed with a scanning electron microscope very close to the surface.
The ultrafiltration membrane has pores with a molecular weight cut-off of 13,000 or less, which was determined by measuring the permeation rejection rate of globular proteins when various different dextran aqueous solutions and protein aqueous solutions were passed through, and the pore size is approximately 10 Å to 100 Å. It is estimated that it exists in the area of This means that dextran with an average molecular weight of 70,000 is cut by more than 70%. The A _p layer and the A _i layer are layers that perform a selective permeation function based on the size of permeable molecules. The thinner this layer is, the better the water permeability is. In the hollow fiber of the present invention,
Since there are two surface layers, the inner and outer layers, even if one of the layers is defective for some reason, the molecules to be cut can be prevented from leaking. It has the advantage of increased safety and the ability to sharply cut off molecular weight. There are countless voids in contact with the A _i layer. A void is a portion where the polymer is missing and has a conical shape. When viewed in cross-section of the hollow fiber, this void has a narrow conical longitudinal cross-sectional shape extending radially from the center of the hollow fiber, and therefore, when viewed in cross-section along the length of the hollow fiber, it appears almost circular. be done.
All the voids in contact with the A _i layer have their apexes facing the A _i layer side, become thicker toward the inside of the hollow fiber, and have a rounded end on the inside of the hollow fiber. When observing the overall state of existence of these voids in a cross section of the hollow fiber, the voids exist in an annular state surrounding the A _i layer and having approximately the same thickness. The ring formed by this void is referred to as a void layer (B _i ) layer in the present invention. In contact with the A _p layer, countless voids similar to those described above exist separately, forming another void layer (B _p ) layer. In this void layer, all the voids exist with their vertices facing the A _p layer side. The thickness of each void layer is defined as the thickness of a straight line drawn in the radial direction from the center of the hollow fiber and the thickness of each void layer in a scanning electron micrograph of a cross section of the hollow fiber cut perpendicular to the fiber axis of the hollow fiber. The distance between two points where the inner and outer peripheries of a ring formed by a large number of voids intersect. The inner and outer circumferences are determined as follows. First, the outer circumference of the Bi layer is determined as follows. Scanning electron micrograph of the entire cross-section of the hollow fiber (at 50 to 300x magnification, six radiation fractions are drawn, one fraction being 60° extending radially from the center of the hollow fiber, and each radiation fraction exists in one radiation fraction. The distance between the inner edge of the void, which extends toward the deepest part of the layer, and the center of the hollow section is measured, and this is done for each of the six radiation fractions to obtain six values.Next: Then draw another 6 radiation fractions with the phase of each fraction shifted by 20° clockwise, obtain 6 values as above, and once again shift the phase of each fraction by 20° clockwise. Then, obtain 6 more values in the same manner as above.The arithmetic mean of the 18 values obtained in this way is set as the radius, and the center of the hollow part of the hollow fiber cross section in the above scanning electron micrograph is used as the radius. The circle drawn as is the outer circumference of the Bi layer.The inner circumference of the B _p layer is obtained by the same method as above.The inner circumference of the B _i layer and the outer circumference of the _{B p} layer are For the latter, the boundary line with the A _p layer is taken as the inner and outer periphery of each.This boundary line is clear and easily identified.The thickness of the void is 10~
It is approximately 370 μm. The thickness of this void layer occupies a major portion of the film thickness, but if the voids are too thick, the bursting strength will decrease. The hollow fiber of the present invention has a high bursting strength due to the intermediate layer, but since the voids in the inner and outer void layers are long in the radial direction, the permeated liquid short-circuits and passes through this membrane thickness area without any resistance. , water can reach the intermediate layer/surface layer from the surface layer, so its permeability is high. Therefore,
It can be said that the B _p layer and the B _i layer greatly contribute to improving the mechanical strength and water permeability of the hollow fiber membrane. Numerous C _p holes (C _p will be described later) are opened on the inner wall surface of the void. The ratio of the thicknesses of the B _i layer and the B _p layer is preferably as close to 1 as possible.
Therefore, the closer the intermediate layer is to the center of the film thickness, the better. If the thicknesses are different, the mechanical strength not only decreases, but also the void layer with the longer void length tends to become thicker and denser, which is not preferable. The ratio of the thickness of the inner and outer bond layers (lB _i /lB _p ) (hereinafter simply referred to as the inner and outer void layer ratio) is
It is preferable that it is 1.5 or less; if it exceeds 1.5, not only the mechanical strength will decrease significantly but also the water permeability will decrease. Furthermore, if the inner/outer void layer ratio is less than 0.6, the water permeability will decrease and it will not be usable. The hollow fiber of the present invention has an intermediate layer (C layer). The C layer means an intermediate layer defined by the voids existing in the B _i layer and the voids existing in the B _p layer, and the thickness of the thinnest part of that layer is defined as the thickness of the C layer. , the thickness of the C layer is 5 to 70 μm.
The thickness of the C layer was measured using a scanning electron micrograph (50 to 3000
(times). The C layer is a network-structured polymer layer with C _p pores that are well connected in three dimensions, and the polymers are strongly bonded in three dimensions, significantly increasing mechanical properties such as bursting strength, compressive strength, and tensile strength. This is the layer that contributes to the The pore size, when viewed independently, is 0.1 to 9 μm in average pore diameter. The thickness of the C layer is 5 to 70 μm. This thickness is extremely large compared to the thicknesses of the A _p layer and the A _i layer. The C _p pores other than the voids in the hollow fiber membrane are communicating pores, and they become larger from the inner and outer surfaces of the membrane toward the inside, reaching the maximum size in the central C layer. Therefore, the water permeability of the hollow fiber membrane can be maintained at a large value even with the presence of the C layer, but the C layer still has a higher permeation resistance than the B layer, and is proportional to the thickness of the C layer. It is inevitable that the water permeability will decrease considerably. When the thickness of the C layer exceeds 70 μm, the water permeability becomes less than 3 m ³ /m ² ·day · atm. On the other hand, the thickness of the C layer has a close relationship with the burst strength of the hollow fiber membrane, and when the thickness is less than 5 μm, the burst strength becomes less than 15 Kg/cm ² . Bursting strength is 15Kg/cm ²
If it is less than that, it will not be able to withstand long-term continuous operation. As is clear from the definition of the thickness of each layer of A _i , B _i , C, B _p , and A _p above, the total thickness of each layer of A _i , B _i , C, B _p , and A _p is not necessarily the film thickness. does not match. Figures 17A and B schematically illustrate one unit of C _p pores in the intermediate layer structure of a conventional hollow fiber membrane and the intermediate layer structure of the present invention.
It was shown to. In the hollow fiber of the present invention, as shown in A, the three-dimensional communication is significantly improved compared to the conventional one shown in B, so that the permeate liquid entering from the upward arrow can be directed to the exit in either direction of the cube. It can also exit through (5 C _p holes). On the other hand, in the conventional type, the communication is poor, so the liquid that enters from above can only exit through the limited C _p hole, seeking an exit through which it can pass. For these reasons, the permeation resistance of the intermediate layer of the hollow fiber membrane of the present invention is significantly reduced. The properties and functions of each layer of the five-layer structure of the hollow fiber of the present invention have been outlined above.Next, a scanning electron micrograph of a cross section of a hollow fiber membrane obtained in an example of the present invention, which will be described later, will be shown. Clarifying the specific form of hollow fibers. FIG. 1 is a diagram schematically showing a cross section of the hollow fiber membrane of the present invention. The figure shows A _p , B _p , C, and
B _i and A _i layers are shown. FIG. 2 is a freeze-fractured cross-sectional scanning electron micrograph (magnification: 83 times ), and the straight line at the bottom of the figure (approximately 4.7cm) is
Represents 500μm. That is, 1 mm represents approximately 10.6 μm. Figure 3 is a scanning electron micrograph (330x magnification) of a frozen fractured surface showing a portion of the total film thickness enlarged, and the straight line (approximately 2 cm) at the bottom of the figure represents 50 μm.
That is, 1 mm indicates 2.5 μm. Figure 4 is a scanning electron micrograph (1400x magnification) of a freeze-fractured cross section showing an enlarged view of part of the A _i and B _i layers.
The straight line (approximately 8 mm) at the bottom of the figure represents 5 μm, that is, 1 mm represents approximately 0.62 μm. Figure 5 is a scanning electron micrograph (magnification: 14,000 times) of a freeze-fractured cross section of an example of the inner surface A _i layer, and the lower straight line (approximately 8 mm) represents 0.5 μm, that is, 1 mm is approximately
Indicates 0.06μm. Figure 6 is a scanning electron micrograph (magnification: 14,000 times) of a freeze-fractured cross section of an example of the outer surface A _p layer, and the lower straight line (approximately 8 mm) represents 0.5 μm, so 1
mm indicates approximately 0.06 μm. Figure 7 is a scanning electron micrograph (magnification: 190
times), and the lower straight line (approximately 1.0 cm) represents 50 μm, so 1 mm represents approximately 5 μm. What is visible in the photo is the inner wall surface of the outer void, and the pore diameter of the C _p pores gradually increases from the outer surface to the inside of the membrane, and the pattern of the density of C _p pores is clearly visible. . FIG. 8 is a scanning electron micrograph (1400x magnification) of a frozen fractured cross section showing an example of the intermediate layer (C layer).
The lower straight line (approximately 0.8 cm) represents 5 μm, so 1 mm represents approximately 0.62 μm. Figure 9 is a scanning electron micrograph (14,000x magnification) of a very large freeze-fractured cross section of the intermediate layer (C layer), where the lower straight line (approximately 1.3 cm) represents 0.5 μm.
Therefore, 1 mm represents approximately 0.04 μm. This photograph shows that the C _p pores of the C layer are communicating pores that are extremely well developed three-dimensionally, and that the C layer has a rather three-dimensional network structure. Table 1 shows data on the thickness, average pore diameter, membrane thickness, and outer diameter of each layer for the hollow fibers of the examples shown in the photographs of FIGS. 2 to 9 above.

[Table] (However, the average pore diameters of the B _i and B _p layers are those measured by scanning electron micrographs of C _p pores existing between voids in the void layer.) Figure 10 shows the following: About the hollow fibers of two examples
It was shown how the radius of the C _p pore changes from the inner surface to the outer surface of the hollow fiber. It can be seen that the pore diameter increases from the inner and outer surfaces toward the center. The method for manufacturing the hollow fibers of the present invention will be described later, and the curve -○- shows the case where the polymer concentration is 17.0% by weight, and the curve -x- shows the case where the polymer concentration is 20.0% by weight. It can be seen that the pore diameter is smaller at 20% by weight, which has a higher polymer concentration, and the pores of the hollow fiber membrane are denser.
Therefore, increasing the polymer concentration improves the mechanical properties. FIG. 11 plots the relationship between membrane thickness and water permeability for aromatic polysulfone hollow fibers of the present invention and comparative examples prepared with various membrane thicknesses. In FIG. 11, the curve -◯ shows the case where the polymer concentration is 20.0% by weight, and the curve -△- shows the case where the polymer concentration is 15.0% by weight, and is for the hollow fiber of the present invention.
On the other hand, the curve −●− has a polymer concentration of 15.0% by weight;
This is about a hollow fiber of a comparative example obtained by spinning without adding glycols. FIG. 12 plots the relationship between membrane thickness and water permeability for the aromatic polyether sulfone hollow fiber of the present invention. It can be seen from FIGS. 11 and 12 that in the case of the hollow fiber of the present invention, a directly proportional relationship exists between the membrane thickness and the water permeability. FIG. 13 shows the relationship between the intermediate layer thickness, water permeability, and bursting strength for hollow fibers of the present invention made with various intermediate layer thicknesses. In FIG. 13, the curve -×- shows the water permeability, and the curve -○- shows the bursting strength. It has been shown that the bursting strength increases as the thickness of the intermediate layer increases, and that the water permeability decreases as the thickness increases, and that the decrease becomes particularly noticeable from a certain thickness. Note that the above-mentioned C _p pore refers to the Polymer Proceedings Vol. 1.34,
Considering a very small emulsion of about 100 Å such as the oil in water type described in No. 3 205-216 (1977), the oil or water is occupied by a polymer thick phase or a dilute phase. Refers to a hole that is formed in a hole and has a circular shape when viewed from the surface or cross section. On the other hand, a long and narrow hole is called an U _p hole. In the present invention, the inner and outer void layer ratio refers to the ratio of the inner void layer thickness (l _Bi ) to the outer void layer thickness (l _Bp ) of the aromatic polysulfone resin hollow fiber membrane of the present invention, i.e., l _Bi /l _Bp . l _Bi and l _Bp are determined by the method described above. The ratio of the inner and outer void layers of the aromatic polysulfone resin hollow fiber membrane of the present invention is 1.5 to 0.6, preferably 1.4 to 1.0. Although specific structural photographs and data have been shown above for specific examples of the hollow fiber membrane of the present invention, these specific data are not unrelated to the manufacturing method of the hollow fiber membrane of the present invention. Next, an example of the method for manufacturing the hollow fiber membrane of the present invention will be described.The polysulfone resin hollow fiber membrane of the present invention is made of an aromatic polysulfone resin containing glycols with a polysulfone resin concentration of 15 to 35% by weight. A polar organic solvent solution of the resin is discharged into the air in the form of a hollow fiber from an annular nozzle whose inner width of the polymer discharge annular groove on the discharge surface is 110 to 700 μm, and at the same time it is mixed with the above solvent, but does not dissolve the polysulfone resin. An aromatic polysulfone comprising injecting a liquid as an internal coagulation liquid from inside a nozzle, and then guiding the hollow fiber-shaped discharged body into a coagulation liquid bath consisting of a liquid that is mixed with the above solvent but does not dissolve the aromatic polysulfone resin. Provided is a method for manufacturing a resin hollow fiber membrane.In this manufacturing method, various factors such as addition of glycols to the spinning dope, polymer concentration in the spinning dope, aerial travel distance, and hollow fiber membrane thickness are closely related to each other. The bond is extremely important, and if one of them is missing, the hollow fiber membrane of the present invention cannot be obtained.As the polar organic solvent, any solvent that can dissolve the polysulfone resin can be used, but N- Methylpyrrolidone, dimethylformamide, and especially dimethylacetamide and diethylacetamide are preferably used. In the method for producing hollow fibers of the present invention, the addition of glycols to the spinning stock solution is extremely important. Of course, in the case of a polymer solution consisting of
When adding an aqueous solution of a metal salt of an inorganic acid or a metal salt of an organic acid as in the invention of JP-A-54-145379, or when adding polyvinylpyrrolidone, a hollow fiber with a five-layer structure can be obtained. Even if the hollow fiber membrane of the present invention has an inner and outer void layer ratio of 1.5,
In the following, it is impossible to obtain a hollow fiber membrane having an intermediate layer with extremely good continuity, high burst strength, and extremely excellent water permeability. The addition of glycols is also associated with the formation of an intermediate layer of structure with significantly lower permeation resistance. This makes it possible to spin hollow fiber membranes from a high-concentration polymer stock solution, and significantly improves the mechanical strength of the hollow fiber membranes, compared to conventional techniques. The hollow fiber membrane of the present invention thus obtained has a water permeability of 3 m ³ /m ² ·day · atm or more and a burst strength of
It has excellent properties of 15 kg/cm ² or more and tensile strength of 20 kg/cm ² or more [measured with Shimadzu Autograph IM-100 (tensile testing machine manufactured by Shimadzu Corporation, Japan)]. Glycols used in the method of the present invention include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (molecular weight 200
~6000), etc., propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol (molecular weight 200 ~ 6000), etc., glycerin, trimethylolpropane and ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, triethylene Examples include ethylene glycol methyl ether derivatives such as glycol monomethyl ether, and propylene glycol derivatives such as propylene glycol monomethyl ether. The above glycols may be used alone or as a mixture. Among them, those having a molecular weight of approximately the same as tetraethylene glycol are preferred. The addition ratio of glycols may be any ratio as long as it maintains a uniform dissolution state of the polymer solution, and varies depending on the polymer concentration, the type of polar solvent used, etc., but is in the range of approximately 0.5 to 30% by weight. used in Less than 0.5% has little effect; 30
If it exceeds %, the stock solution becomes unstable, devitrification occurs, and film formation becomes difficult, making it impossible to obtain a good film. Preferably 3 to 20% by weight, more preferably 5% by weight.
~15% by weight. The polymer concentration of the film forming stock solution is 15 to 35% by weight or more, preferably 18 to 25% by weight. If it exceeds 35% by weight, the water permeability of the resulting semipermeable membrane becomes so small that it has no practical meaning;
At lower concentrations, the thickness of the intermediate layer is not sufficient, and furthermore, the average pore diameter of the intermediate layer exceeds 9 μm, and only a weak mechanical strength can be obtained. The polymer concentration in the membrane-forming stock solution has a close relationship with the hollow fiber structure obtained from it. That is, in the case of a flat film, if a low concentration stock solution of less than 15% by weight is used, a film having a structure consisting of a surface layer (A) and a void layer (B) in which the void layer is long and developed in the thickness direction of the film can be obtained. On the other hand, when a high concentration stock solution of 15% by weight or more is used, an intermediate layer develops as the polymer concentration increases,
A three-layer structure consisting of a surface layer (A), a void layer (B) and an intermediate layer (C) is formed. This structure is shown in FIG. 14, a scanning electron micrograph. However, in either structure, a flat membrane has extremely low water permeability, and a membrane with high water permeability cannot be obtained. Figure 15 shows the relationship between the membrane thickness and water permeability of the ABC three-layer flat membrane. From Figure 15, when the film thickness is 100 μm or more,
It can be seen that the water permeability is very low. On the other hand, when using a low-concentration stock solution for hollow fibers and coagulating both the inner and outer surfaces of the hollow fibers, A consists of a surface layer (A) in which extremely thin voids in the intermediate layer are arranged irregularly and a void layer (B). Hollow fibers arranged in the order of _i B _i B _p A _p are obtained, but such hollow fibers have weak mechanical strength and cannot withstand continuous operation using backwashing. In addition, by contacting only one side with the coagulating liquid instead of solidifying both sides, a two-layer structure with a surface layer (A) with a surface layer on the inside or outside and a void layer (B) arranged in the order of AB or BA is created. A hollow fiber is obtained.
However, these hollow fibers with a two-layer structure have weak mechanical strength and cannot withstand long-term operation using backwashing. With a five-layer structure including two surface layers, two void layers, and one intermediate layer of appropriate thickness, a hollow fiber having appropriate mechanical strength and high water permeability can be obtained.
In addition, FIG. 16 shows the relationship between the membrane thickness and bursting strength of hollow fibers of the five-layer structure of A _p B _p C B _i A _i , AB structure, and BA structure. It can be seen that the bursting strength of the five-layer hollow fiber is by far superior. The film-forming stock solution is discharged into the air in the form of a hollow fiber from an annular nozzle having an inner width of a polymer discharge annular groove on the discharge surface of 110 to 700 μm. The thickness of the hollow fiber is almost determined by the width of the discharge annular groove of the annular nozzle used, and is not affected much by other spinning conditions. The membrane thickness is usually thinner than the above groove width, and by using an annular nozzle having an inner width of the polymer discharge annular groove of 110 to 700 μm, a hollow fiber having a membrane thickness of 100 to 600 μm can be obtained. can be obtained. Water is most commonly used as the coagulation liquid, but methanol, an organic solvent that does not dissolve the polymer,
Ethanol or the like may be used, or a mixture of two or more of these nonsolvents may be used. It is also possible to use different internal and external coagulating liquids or coagulating baths with different liquid compositions, but preferably the internal coagulating liquid and the coagulating bath liquid are the same. During hollow fiber spinning, a coagulation bath must be used inside and outside the hollow fiber to effect coagulation on both sides. In order to maintain the inner and outer void layer ratio between 0.6 and 1.5, it is necessary to provide an air travel distance to delay contact with the outer coagulation bath, and the air travel distance varies somewhat depending on other spinning conditions, such as , the larger the hollow fiber diameter and membrane thickness, the smaller it needs to be.
A range of 0.1 to 30 cm is preferred. If it is less than 0.1 cm, the inner/outer void layer ratio tends to exceed 1.5, and if it exceeds 30 cm, it becomes difficult to form a hollow fiber without deformation. In order to obtain the hollow fiber having the five-layer structure of the present invention, the membrane thickness is designed to be 100 to 600 μm, preferably 100 to 400 μm. Even if hollow fibers are manufactured with each of the above conditions within the specified ranges, if the thickness of the hollow fibers is less than 100 μm, depending on the manufacturing method of the present invention, the hollow fibers with the five-layer structure of the present invention I can't get it. More specifically, FIG. 10 shows that polysulfone (manufactured by Union Carbide) is dissolved in a dimethylacetamide-tetraethylene glycol solvent, and the polysulfone concentration is 17.0% by weight and 20% by weight.
This is an example of a plot of the relationship between the distance (l) from the inner and outer surfaces and the diameter (r) of existing pores for a hollow fiber with a membrane thickness of 300 μm spun from the stock solution. The C _p pore radius gradually increases from the surface to the center, and the polymer concentration
It can be seen that the pore size in the 20% case is relatively much smaller than the 17.0% pore size. The aromatic polysulfone-based resin hollow fiber membrane according to the present invention can pass through globular proteins with a molecular weight of less than 13,000, but it can pass through more than that, such as albumin, globulin, pyrodiene substances contained in body fluids, and bacteria ( 1-2μm), yeast (2-4μm)
m), because it has the property of not passing pathological viruses (molecular weight 2.4 million), it is used for removing pyrogen substances from injection solutions and ring fluids, producing ultrapure water, concentrating protein substances, etc. It is particularly advantageously used in applications that require repeated high-temperature sterilization of membranes and sterilization with acids, alkalis, etc. during purification, ie, purification of pharmaceuticals and foods, and production of ultrapure water. Next, as an example, manufacturing conditions and properties of hollow fibers obtained under those conditions will be shown. Although the present invention will be understood more specifically through these numerous examples, the scope of the present invention is of course not limited to these examples. The water permeability, molecular weight cutoff, and bursting strength of the aromatic polysulfone resin hollow fiber membrane in this example were measured by the following methods. (1) Measurement of water permeability Make a module by sealing one end of a hollow fiber bundle whose outer and inner diameters have been measured in advance, then glue the other end, and use the glued side as the water injection side. Assuming that the effective length is 25 cm and the pressure difference between the inside and outside of the hollow fiber is 1 atm, the amount of permeation of distilled water at 25°C (m ³ /m ²・day・
atm). (2) Measurement of molecular weight fraction To measure the molecular weight fraction, use both ends of a hollow fiber whose outer and inner diameters have been measured in advance as the water injection side and drainage side, respectively. Effective length 25cm, inlet pressure 1.2Kg/ ^cm2 or less,
An aqueous solution of various molecules dissolved in distilled water at 25°C was introduced from the water injection side at an outlet pressure ^of 0.8 Kg/cm ² or more, an average value of inlet and outlet pressures of 1.0 Kg/cm 2 , and a linear velocity of 1.0 m/sec for 10 minutes. Take 0.5ml of the water and calculate the cutting rate from the amount of various molecules contained therein. When using dextran molecules to measure the molecular weight fraction, a concentration of 5% by weight is used, and when globular proteins are used, a concentration of 0.25% by weight is used. However, before injecting the globular protein into the hollow fiber,
The hollow fibers are immersed in an aqueous molecular solution (5°C) for 12 hours to eliminate the effects of adsorption, and then measurements are taken. (3) Measurement of bursting strength Bend both ends of the hollow fiber into a loop and fix. 25℃
Apply the same air pressure from both ends, then 10Kg/
The pressure is increased at a rate of cm ² /min. The pressure at which the hollow fiber bursts is defined as the bursting strength (Kg/cm ² ). Example 1 Dimethylacetamide was selected as the solvent, tetraethylene glycol was selected as the additive, and as the polymer, Borisulfone (hereinafter referred to as polysulfone) having a repeating unit represented by 71:
They were mixed at a ratio of 9:20% by weight to form a uniform solution.
This polymer solution was extruded from an annular nozzle (330 μm) for producing hollow fibers, and purified water was used as the internal and external coagulating liquids to coagulate the polymer solution from the inner and outer surfaces, thereby spinning a hollow porous membrane. At this time, the hollow fiber spinning conditions were as follows. The distance from the nozzle to the external coagulating liquid (hereinafter referred to as air travel distance) is 1.5 cm. The properties of the hollow fibers obtained are as follows:
0.75mm, outer diameter 1.35mm, membrane thickness 0.3mm, water permeability ^12m3 /
^m2・day・ATM・water temperature 25℃, bursting strength 31Kg/ ^cm3 , cut rate for dextran molecular weight ¹⁰⁴ , 4× ¹⁰⁴ , 7× ¹⁰⁴ is 24.0%, 80.0%, respectively.
83.0%, and globular protein cytochrome C
(molecular weight 13000) showed a cutting rate of over 95%. The cross-sectional structure of the obtained hollow fiber showed a five-layer structure (A _p B _p C B _i A _i ) of the present invention, and the inner and outer void layer ratio was 1.3. The results of investigating how the radius of the C _p pores of the obtained hollow fibers changed from the inner surface to the outer surface of the hollow fibers are shown in the curves in FIG. 10. Hollow fibers were obtained in the same manner as above, except that a homogeneous polymer solution obtained by mixing dimethylacetamide, tetraethylene glycol, and polysulfone (Udel) at a weight ratio of 74:9:17 was used. The results of examining how the radius of the C _p pores of the obtained hollow fibers changed from the inner surface to the outer surface of the hollow fibers are shown in the curve -◯- in Fig. 10. Examples 2 to 15 Hollow fiber spinning was carried out in the same manner as in Example 1 with the addition of various additives. Table 2 shows the additives added to the hollow fiber stock solution and the properties of the hollow fibers obtained.
The cross-sectional structure of the obtained hollow fibers was all the five-layer structure of the present invention, and the ratio of inner and outer void layers was 1.0 to 1.3.

【table】

[Table] Comparative Example 1 Using the same polymer solution as in Example 1, it was cast onto a glass plate with a doctor blade film thickness of 400 μm at a stock solution temperature of 25°C, and then left for 1 minute to solidify in water at 25°C. . The properties of the obtained porous flat membrane are as follows: thickness 300 μm, water permeability 0.01 m ³ /
^m2・day・atm・water temperature 25℃, elastic modulus 1311Kg/ ^cm2 ,
Strength 60Kg/ ^cm2 or less. The structure of the obtained flat membrane is ABC
It had a three-layer structure. Flat films of various thicknesses were also cast using the same polymer solution as above and in the same manner as above. FIG. 15 shows the relationship between the thickness and water permeability of the obtained flat membrane. The structure of these flat membranes was an ABC three-layer structure. Comparative Examples 2 and 3 Polysulfone 10g, N-methylpyrrolidone 90g
were mixed at 30°C to form a homogeneous solution. This pouring liquid was cast onto a glass plate using a doctor blade to a film thickness of 250 μm and solidified in water. The properties of the obtained porous flat membrane are as follows.The film thickness is 100μ.
m, water permeability ^5m3 / ^m2・day・atm, water temperature 25℃, elastic modulus 238Kg/ ^cm2 , strength 10Kg/ ^cm2 or less. The structure of the obtained flat membrane was AB structure. Using this solution and using water as the internal coagulation liquid, spin the fibers in the air from a circular nozzle (330 μm) for hollow fiber spinning.
The polymer is coagulated with water inside the hollow fiber,
Hollow fibers were spun with an aerial travel distance of 1.5 cm. The obtained hollow fiber membrane has an inner diameter of 0.75 mm, an outer diameter of 1.35 mm, and a membrane thickness of 0.3 mm.
mm, water permeability 5m ³ /m ²・day・atm, water temperature 25℃, bursting strength 13Kg/cm ² , strength 10Kg/cm ² , elastic modulus 252Kg/
It was warm in ^cm2 . In addition, when the structure of the obtained hollow fiber membrane was examined using a scanning electron microscope, it was found that 5
It was not a hollow fiber with a layered structure. Comparative Examples 4 and 5 20 g of polysulfone as a polymer and 80 g of dimethylacetamide as a solvent were mixed to form a uniform solution. This solution was dissolved and cast onto a glass plate with a film thickness of 350 μm using a doctor blade at a stock solution temperature of 25°C, and then allowed to stand for 1 minute to solidify in water at 25°C. The obtained porous flat membrane has a thickness of 300 μm and a water permeability.
The area was 0.005m ³ /m ²・day・atm, water temperature was 25℃, and the membrane structure was ABC structure. When this solution was used to spin hollow fibers under the same hollow fiber spinning conditions as in Example 1, the properties of the obtained hollow fibers were as follows: inner diameter 0.75 mm, outer diameter 1.35 mm, membrane thickness 0.3
mm, water permeability ^0.01m3 / ^m2・day・atm・water temperature 25℃,
Bursting strength 21Kg/cm ² , Strength 55Kg/cm ² , Elastic modulus 1521
It was Kg/ ^cm2 . The structure of this hollow fiber is A _p B _p C
Although it had a five-layer structure of B _i A _i , it was not the five-layer structure of the present invention. The ratio of inner and outer void layers was 1.7. Comparative Example 6 Udel was used as polysulfone, dimethylacetamide was used as a solvent, and tetraethylene glycol was mixed as an additive in a ratio of 10:81:9% by weight, respectively, to form a uniform solution. After casting this solution on a glass plate using a doctor blade, 1
It was left to stand for a minute and solidified in water at 25°C. The resulting porous flat membrane had a thickness of 300 μm and a water permeability of 5 m ³ /m ²・day・
ATM, water temperature 25℃, elastic modulus 215Kg/cm ² , strength 9Kg/
It was warm in ^cm2 . The structure of the obtained flat membrane was AB structure. Comparative Example 7 80 ml of 50% by weight aqueous sodium nitrate solution was mixed with 2620 ml of dimethylacetamide and dimethyl sulfoxide.
In addition to 1300 ml of the mixed solvent, 750 g of the polysulfone (Udel) of the example was added to form a homogeneous solution.
A hollow fiber semipermeable membrane was obtained from this polymer solution in the same manner as in Example 1. Hollow fiber inner diameter 0.75mm, outer diameter
1.35mm, water permeability ^3.0m3 / ^m2・day・atm・water temperature 25
°C, bursting strength 15Kg/cm ² , elastic modulus 821Kg/cm ² , strength
It was 30Kg/ ^cm2 . Moreover, the cutting rate for dextran having a molecular weight of 7×10 ⁴ was 48%. The vein structure was a five-layered structure of A _p B _p C B _i A _i ,
The inner/outer void layer ratio was 1.7, which was not the one of the present invention. A polymer solution having the same composition as above was dissolved to spin hollow fibers of various thicknesses, and the relationship between the membrane thickness and water permeability is shown by the curve -●- in FIG. Example 16 Polysulfone (PS), dimethylacetamide (DMAc), tetraethylene glycol (TEG)
were mixed at a ratio of 20:71:9wt% to form a uniform solution, and then extruded through nozzles with various hole diameters to spin hollow fibers with an inner diameter of 0.75 mm and an outer diameter of various thicknesses. Other conditions are
This is the same as in Example 1. The obtained hollow fiber membranes all exhibited the five-layer structure of the present invention, had an inner/outer void layer ratio of 1.0 to 1.3, and exhibited excellent bursting strength, elastic modulus, and strength. The relationship between the membrane thickness and water permeability of these hollow fibers is shown in FIG. 11 by -○-. Also, polysulfone (Udel), dimethylacetamide, and tetraethylene glycol, respectively.
The relationship between the membrane thickness and water permeability of the hollow fiber obtained by spinning a homogeneous polymer solution mixed at a weight ratio of 15:70:15 in the same manner as above is shown by the curve -Δ- in FIG. Examples 17-21 Polysulfone (Udel) as a polymer, tetraethylene glycol as an additive, and various solvents
They were mixed at a weight ratio of 20:71:9 to prepare a uniform spinning stock solution, and hollow fibers were spun. The spinning conditions were the same as in Example 1. The cutting rates of the obtained hollow fibers for various dextrans having different molecular weights were almost the same as in Example 1. Other properties are shown in Table 3. The structure of the hollow fiber is the five-layer structure of the present invention (A _p B _p C
B _i A _i ), and the inner and outer void layer ratios were 1.0 to 1.3.

[Table] Examples 22 to 25, Comparative Example 8 Using DMAc as a polysulfone solvent and TEG as an additive, the proportions of polysulfone and DMAc were changed to prepare film-forming stock solutions with different concentrations of polysulfone, and the same as in Example 1 was used. Hollow fibers were spun using this method. Table 4 shows the properties of the hollow fibers obtained. The membrane structure is A _p B _p C B _i A _i 5
However, only in Comparative Example 8, the thickness of the C layer was
The C layer is as thin as 2 μm, is not uniform, and has a void layer (B _i
Disturbances of the void layer were observed in the vicinity where the B layer and the B _p layer) were in contact with the C layer. In Examples 22 to 25, the thickness of the C layer was
It was thicker than that of Comparative Example 8 at 10 to 70 μm, and the polymer portions of both the void layer and the C layer had a uniform structure, and the inner and outer void layer ratios were 1.0 to 1.4.

[Table] Examples 26 to 31, Comparative Examples 9 and 10 Polysulfone (PS), dimethylacetamide (DMAc), tetraethylene glycol (TEG)
After mixing in a ratio of 20:71:9 to make a homogeneous solution, the polymer solution is extruded through an annular nozzle, and purified water is used as an internal and external coagulating liquid to coagulate the polymer from the inside and outside to form a hollow porous membrane. was spun. At this time, the air travel distance from the hollow fiber spinning nozzle to the external coagulation liquid was varied, and the properties of the obtained fibers were examined. The results are shown in Table 5. The membrane structure of the hollow fibers obtained was a five-layer structure (A _p
B _p C B _i A _i ), but in Comparative Example 9, the inner and outer void layer ratio was as large as 2.0, and the thickness of the C layer was also
It was large at 82 μm. In Comparative Example 10, the air travel distance was too long, so the yarn shape did not become hollow. The thickness of the C layer obtained in Examples 26 to 31 was 5 to
It was within the range of 70 μm.

[Table] Examples 32, 33 Using the same spinning stock solution as in Examples 26 to 31, the polymer was coagulated using an environmental nozzle at an air travel distance of 1.5 cm, using methanol as the internal and external coagulation liquid. The obtained hollow fiber has an inner and outer diameter of 0.75 mm and a diameter of 1.35 mm.
Good results were obtained in mm, bursting strength, water permeability, elastic modulus, and strength. The membrane structure in each case was the five-layer structure of the present invention. Similarly, even when methanol was used as the internal coagulating liquid and water was used as the external coagulating liquid, good bursting strength, water permeability, elastic modulus, and strength were obtained. The membrane structure in each case was the five-layer structure of the present invention. Comparative Example 11 A homogeneous solution of polysulfone, dimethylacetamide, and tetraethylene glycol mixed in a ratio of 20:65:15% by weight, respectively, was used as a stock solution for film forming, and a circular nozzle for manufacturing hollow fibers of various sizes of this polymer was used. A _p B _p
By coagulating hollow fibers with various film thicknesses with a five-layer structure of C B _i A _i on one side using air on the inside and water on the outside, B _i , A _p , using water on the inside and air on the outside Hollow fibers with a two-layer structure of A _i B _p of various thicknesses were formed, and their burst strength was measured.
It is shown in FIG. Example 34 Dimethylacetamide (DMAc) as solvent,
Tetraethylene glycol (TEG) as an additive
was selected as a polymer.

Polyether sulfone (hereinafter referred to as polyether sulfone VICTREX manufactured by ICI) having a repeating unit represented by the following formula was mixed in a ratio of 65:15:20 (%) to form a uniform solution. Extrude this polymer solution from an annular nozzle (330 μm) for hollow fiber production,
Purified water was used as the internal and external coagulating liquids to coagulate the polymer solution from the inside and outside, and a hollow porous membrane was spun. At this time, the hollow fiber spinning conditions were as follows. The distance from the nozzle to the external coagulating liquid (hereinafter referred to as aerial travel distance) is 1.5 cm. The properties of the hollow fibers obtained were as follows. Inner diameter 0.75mm, outer diameter 1.35mm, film thickness 0.3mm, water permeability
1.5m ³ /m ²・day・atm・water temperature 25℃, bursting strength 33
Kg/cm ² , tensile modulus 1700Kg/cm ² , strength 70Kg/cm ² ,
The cutting rates for dextran molecular weights of 10 ⁴ , 4×10 ⁴ and 7×10 ⁴ were 20%, 65% and 82%, respectively. The membrane structure is the five-layer structure of the present invention, and the internal and external void ratio is
It was 1.3. Examples 35 to 48 Hollow fiber spinning was carried out under the same conditions as in Example 34 with the addition of various additives. Table 6 shows the additives added to the hollow fiber stock solution and the properties of the hollow fibers obtained. The membrane structure was the five-layer structure of the present invention, and the ratio of inner and outer void layers was 1.0 to 1.5.

【table】

[Table] Comparative Example 12 Using the polymer solution of Example 34, stock solution temperature 25℃
After casting on a glass plate with a doctor blade film thickness of 400 μm, the mixture was left to stand for 1 minute and solidified in water at 25°C. The properties of the obtained porous flat membrane were as follows. Film thickness 300μm, water permeability ^0.001m3 /
^m2・day・atm・water temperature 25℃. The structure of the flat membrane was ABC structure. Comparative Examples 13 and 14 10 g of polyether sulfone and 90 g of N-methylpyrrolidone were mixed at 30°C to form a uniform solution. This solution was cast onto a glass plate using a doctor blade to a film thickness of 250 μm. The properties of the obtained porous flat membrane were as follows. Film thickness
100μm, water permeability ^5m3 / ^m2・day・atm・water temperature 25
℃, elastic modulus 221Kg/cm ² , strength 10Kg/cm ² or less. The structure of the flat membrane was AB structure. Using this solution and using water as an internal coagulation liquid, fibers were spun in the air from an annular nozzle for hollow fiber spinning to coagulate the polymer from the inside of the hollow system and spin hollow fibers. The obtained hollow fiber membrane has an inner diameter of 0.75 mm and an outer diameter of 1.35 mm.
mm, membrane thickness 0.3 mm, water permeability 5 m ³ /m ² ·day · atm, water temperature 25°C, elastic modulus 323 Kg/cm ² , and bursting strength of 10 Kg/cm ² or less. As a result of examination with a scanning electric microscope, this hollow fiber was not a hollow system having the five-layer structure unique to the present invention. Comparative Examples 15 and 16 20 g of polyether sulfone as a polymer and 80 g of dimethylacetamide as a solvent were mixed to form a uniform solution. This solution was cast onto a glass plate with a doctor blade film thickness of 400 μm at a stock solution temperature of 25°C, and then left for 1 minute to solidify in water at 25°C. The obtained porous flat membrane has a thickness of 300 μm and a water permeability.
0.005m ³ /m ²・day・atm・Water temperature was 25℃. The flat membrane structure was an ABC structure. When this solution was used to spin hollow fibers under the same hollow fiber spinning conditions as in Example 34, the properties of the obtained hollow fibers were as follows: inner diameter 0.75 mm, outer diameter 1.35 mm, membrane thickness 0.3
mm, water permeability ^0.01m3 / ^m2・day・atm・water temperature 25℃,
The bursting strength was 30 kg/cm ² . The inner and outer void layer ratio is
1.7, and was not a five-layer structure unique to the present invention. Example 49 Using the same polymer solution as in Example 34, hollow fiber membranes with an inner diameter of 0.75 μm and different outer diameters and membrane thicknesses were spun using various annular nozzles. The relationship between water permeability and membrane thickness of this hollow fiber membrane is shown in FIG. Both hollow fiber membrane structures had the five-layer structure of the present invention, and the ratio of inner and outer void layers was 1.3. Comparative Example 17 Add 10 ml of 30% aqueous sodium sulfate solution to 490 ml of dimethyl sulfoxide to make a homogeneous solution. In this solution, the formula

Polyether sulfone having a repeating unit represented by [Formula]
125g was dissolved to obtain a polymer solution. The viscosity of this polymer solution is 1900 centipoise (20°C).
This polymer solution was extruded from a hollow fiber manufacturing annular nozzle (330 μm) and coagulated from the inside and outside using water as a coagulating liquid. The inner and outer diameters of the hollow fiber are 0.75mm and 1.35mm, and the water permeability is 2.
m ³ / m ² / day / ATM / water temperature 25℃, bursting strength 14Kg /
It was warm in ^cm2 . Furthermore, the cutting rate for dextran having a molecular weight of 70,000 was 70%. Examples 50 to 55 The intermediate yarn membrane structure had a five-layer structure, but the inner and outer void layer ratio was 1.7. Examples 50 to 55 In the same manner as in Example 34, various types of polyether sulfone as a polymer solution and tetraethylene glycol as an additive were added. Hollow fiber spinning was performed using a solvent. Table 7 shows the properties of the hollow fibers obtained. The hollow fiber membrane structure was the five-layer structure of the present invention, and the inner and outer void layer ratio was 1.0 to 1.3.

[Table] Examples 56 to 59, Comparative Example 18 Using DMAc as a polyethersulfone solvent and TEG as an additive, the proportions of polyethersulfone and DMAc were changed to create film-forming stock solutions with different concentrations of polyethersulfone. Making, Example 34
The hollow fibers were thread-proofed in the same manner. Table 8 shows the properties of the hollow fibers obtained. The hollow fiber membrane structures of Examples 56 to 59 all show the five-layer structure of the present invention,
The ratio of inner and outer void layers was 1.0 to 1.5. In the hollow fiber of Comparative Example 18, the thickness of the C layer was as thin as 2 μm, and the C layer was not uniform, and the void layer was disordered near where the void layer (B _i layer, B _p layer) was in contact with the C layer. . In Examples 56 to 59, the thickness of the C layer was within the range of 10 to 70 μm, which was thicker than that of Comparative Example 18, and the polymer portion of both the void layer and the C layer had a uniform structure.

[Table] Examples 60 to 65, Comparative Examples 19 and 20 Polyether sulfone DMAc and TEG were mixed in a ratio of 20:71:9 (%), respectively, to form a homogeneous solution, and then the polymer solution was extruded through an annular nozzle. Using purified water as the internal and external coagulating liquids, the polymer was coagulated from the inside and outside, and a hollow porous membrane was spun. At this time, the air travel distance from the hollow fiber spinning nozzle to the external coagulation liquid was varied, and the properties of the resulting fibers were examined. The results are shown in Table 9. The hollow membrane structures of Examples 60 to 65 were the five-layer structure of the present invention. On the other hand, the thickness of the C layer of the hollow fibers of Examples 60 to 65 was within the range of 5 to 70 μm.

[Table] Examples 66 and 67 Using the same spinning stock solution as in Examples 60 to 65, the polymer was coagulated using an annular nozzle with an air travel distance of 1.5 cm, and methanol was used as the internal and external coagulation liquid. The obtained hollow fiber has an inner and outer diameter of 0.75 mm and a diameter of 1.35 mm.
Good results were obtained in mm, bursting strength, water permeability, elastic modulus, and strength. The membrane structure was a five-layer structure according to the present invention, and the ratio of inner and outer void layers was 1.0 to 1.5. Similarly, even when methanol was used as the internal coagulating liquid and water was used as the external coagulating liquid, good bursting strength, water permeability, elastic modulus, and strength were obtained. The membrane structure was a five-layer structure according to the present invention, and the ratio of inner and outer void layers was 1.0 to 1.5.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a cross section of the hollow fiber membrane of the present invention. The figure shows A _p , B _p , C, and
Each layer of B _i and A _i is shown. FIG. 2 is a scanning electron micrograph (magnification: 82 times) of a freeze-fractured cross section showing the entire cross section of the hollow fiber membrane of the present invention taken along a plane perpendicular to the fiber axis. FIG. 3 is a scanning electron micrograph (330x magnification) showing an enlarged part of the cross section of the hollow fiber membrane shown in FIG. FIG. 4 is a scanning electron micrograph magnified (1400 times) showing part of the A _i layer and B _i layer of the cross section of the hollow fiber membrane shown in FIG. 2. FIG. 5 is a scanning electron micrograph (magnification: 14,000 times) of the inner surface A _i layer of the cross section of the hollow fiber membrane shown in FIG. FIG. 6 is a scanning electron micrograph (magnification: 14,000 times) of a freeze-fractured cross section of the outer surface A _p layer of the cross section of the hollow fiber membrane shown in FIG.
FIG. 7 is a scanning electron micrograph (190x magnification) of the circular inner part of the hollow fiber of the present invention obtained by freezing and cutting the hollow fiber diagonally as shown. FIG. 8 is a scanning electron micrograph (magnification: 1400 times) showing the intermediate layer (C layer) in the cross section of the hollow fiber membrane shown in FIG. FIG. 9 is a scanning electron micrograph (14,000 times magnification) of the intermediate layer (C layer) shown in FIG. 8 at a very high magnification. FIG. 10 is a graph showing the relationship between the distance from the inner and outer surfaces of the hollow fiber and the radius of existing C _p pores. FIG. 11 is a graph showing the relationship between membrane thickness and water permeability of aromatic polysulfone hollow fibers of the present invention and comparative examples. FIG. 12 is a graph showing the relationship between the membrane thickness and water permeability of the aromatic polyethersulfone hollow fiber of the present invention. FIG. 13 is a graph showing the relationship between the thickness, water permeability, and bursting strength of the hollow fiber intermediate layer of the present invention. Figure 14 is
This is a scanning electron micrograph of a cross section of a flat membrane with an ABC three-layer structure. FIG. 15 is a diagram showing the relationship between the film thickness and water permeability of the ABC flat membrane. Figure 16 shows A _p B _p
C B _i A _i 5-layer hollow fiber membrane and AB or BA 2
FIG. 3 is a diagram showing the relationship between membrane thickness and bursting strength for a layered hollow fiber membrane. FIG. 17 is a perspective view schematically showing one unit of C _p holes in the intermediate layer structure of the hollow fiber of the present invention in comparison with a conventional one, where A shows the invention and B shows the conventional one. .

Claims (1)

[Claims] 1. It has a five-layer structure of an outer surface layer, an outer void layer, an intermediate layer, an inner void layer, and an inner surface layer, and the ratio of the thickness of the inner and outer void layers is 1.5 or less, The thickness of the intermediate layer is 5 μm or more and 70 μm or less, and the total film thickness is 100 μm or more.
A polysulfone resin hollow fiber membrane characterized by a thickness of 600 μm. 2. The polysulfone resin hollow fiber membrane according to claim 1, wherein the membrane has a water permeability of 3 m ³ /m ² ·day · atm or more. 3. The polysulfone resin hollow fiber membrane according to claim 1, which has a molecular weight cut-off of 13,000 or less. 4. The polysulfone resin hollow fiber membrane according to claim 1, wherein the polysulfone resin is aromatic polysulfone or aromatic polyethersulfone. 5. The polysulfone resin hollow fiber membrane according to claim 1, wherein the ratio of inner and outer void maximum thickness is 0.6 or more and 1.5 or less.