JP3464000B1 - Manufacturing method of high performance hollow fiber microfiltration membrane - Google Patents

Abstract

An object of the present invention is to provide a method for producing a microfiltration membrane having an anisotropic structure having high strength and excellent water permeation performance, and in particular, less clogging in internal pressure filtration. SOLUTION: A method for producing a hollow fiber membrane in which a stock solution and an internal solution are discharged from a double annular nozzle and then passed through an air gap and then coagulated in a coagulation bath, comprising the steps of: A polymer, a solvent for the polymer,
And a hydrophilic polymer, wherein the ratio of the hydrophilic polymer to the film-forming polymer is 20 to 60% by weight; b) the internal liquid is water and at least one or more solvents, and the water content is 35 to 55% by weight; c) The temperature of the stock solution at the nozzle portion is 50 ° C. or more, d) the coagulation bath temperature is 85 to 100 ° C., and e) the ratio of the air gap to the spinning speed is 0.01 to 0.
A method for producing a hollow fiber microfiltration membrane, wherein the filtration rate is 1 m / (m / min).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an anisotropic microfiltration membrane, which has particularly high strength and excellent water permeability,
In addition, the present invention relates to a method for producing a microfiltration membrane with less clogging in internal pressure filtration.

[0002]

Hollow fiber membranes are widely used for industrial applications from microfiltration to ultrafiltration. Polyethylene, cellulose acetate, polysulfone, polyvinylidene fluoride, polycarbonate, polyacrylonitrile, etc. are used as membrane materials. Has been. Conventional hollow fiber membranes made of these materials were developed with a focus on improving filtration performance, so the hollow fiber membranes have a small breaking strength and elongation at break, and do not undergo rapid temperature changes or backwashing. It has been pointed out that the hollow fiber membrane is often ruptured due to the pressure change.

Various attempts have been made to solve this point, but generally, as suggested by the invention described in Patent Document 1, the polymer concentration in the membrane-forming stock solution is increased to A method of increasing the polymer density of the entire hollow fiber membrane can be considered. However, in this method, the strength of the membrane is improved, but the pore diameter of the membrane is reduced and the water permeation rate of the membrane is significantly reduced. Therefore, a hollow fiber membrane having an excellent balance between strength and water permeation performance has not been obtained.

On the other hand, in order to improve the water permeability of the membrane, a method of enlarging the pore size of the membrane is generally carried out, but an increase in the pore size generally leads to a reduction in the membrane fractionation performance and the membrane strength. As described above, according to the prior art, a high performance hollow fiber membrane having a good balance of strength, water permeability and fractionation performance has not been obtained. For example, Patent Document 2 proposes a method for producing a membrane having high strength and excellent water permeability. However, the membrane produced by this method has a large pore size, and water permeability and fractionation performance are well balanced. Not not.

In Patent Document 3, a hollow fiber type microfiltration membrane in which the pore diameter continuously decreases from the outer surface of the membrane toward the inside thereof, and the pore diameter continuously increases again through the minimum pore diameter of the inner portion to open on the inner surface. Is disclosed. However, when liquid or the like is filtered from the hollow side (inner surface side) of the membrane using the membrane of this structure, rapid clogging occurs and stable filtration cannot be performed for a long time.

[0006]

[Patent Document 1] JP-A-59-228016

[Patent Document 2] Japanese Patent Laid-Open No. 4-260424

[Patent Document 3] Japanese Patent Laid-Open No. 2-102722

[0007]

The object of the present invention is to produce an anisotropic microfiltration membrane having high strength and excellent water permeability, and particularly excellent microfiltration membrane with less clogging in internal pressure filtration. To provide a method.

[0008]

[Means for Solving the Problems] As described above, when a liquid or the like is filtered from the hollow side of the membrane (hereinafter also referred to as "internal pressure filtration"), high-precision microfiltration with less clogging and excellent water permeability. There has never been a membrane. This is because, while maintaining high film strength on the inner surface of the film having a graded structure in which the pore diameter continuously decreases from the outer surface to the inner surface of the film,
This is because opening of pores (in the microfiltration region) of 01 μm or more has heretofore been impossible with a hydrophobic polymer such as polysulfone.

In order to prevent clogging, the inventors of the present invention have made extensive studies on an inclined structure in which the pore diameter continuously decreases from the outer surface to the inner surface of the film, and as a result, the present invention has been achieved. is there.

That is, the present invention provides (1) a method for producing a hollow fiber membrane in which a stock solution for membrane formation and an internal solution are discharged from a double annular nozzle, and then passed through an air gap and then solidified in a coagulation bath. The stock solution for film formation comprises a film-forming polymer, a solvent for the polymer, and an additive comprising a hydrophilic polymer, and the ratio of the additive to the film-forming polymer is 20 to 60.
% By weight, b) the internal liquid consists of water and at least one or more kinds of solvents, the water content is 35 to 55% by weight, c) the temperature of the stock solution for film formation at the nozzle is 50 ° C. or higher, and d) the coagulation bath. A temperature of 85 to 100 ° C., and e) a ratio of air gap to spinning speed is 0.01 to 0.1 m / (m / min), a method for producing a hollow fiber microfiltration membrane, (2) Further, irradiation is performed with radiation, (3) the manufacturing method according to (1), wherein the ratio of the film thickness to the inner diameter of the film is 0.15 to 0.15.
(1) or (2), wherein the outer diameter of the membrane is 500 μm or less. (1) to (3) Production method,
(5) The production method according to (1) to (4), wherein the film-forming polymer is a polysulfone-based polymer.
(6) The hydrophilic polymer has a weight average molecular weight of 900,000
The production method described in (1) to (5) above, which is polyvinylpyrrolidone, (7) the solvent for the film-forming polymer is N-methyl-2-pyrrolidone (1) To (6), and (8) a spinning method of 60 m / min or more, (1) to (7).

According to the production method of the present invention, the membrane has a sponge structure in which the pore diameter continuously decreases from the outer surface to the inner surface, and the blocking diameter in the internal pressure filtration is 0.015 to 1.
An excellent hollow fiber type microfiltration membrane characterized by having a thickness of μm can be obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing the hollow fiber microfiltration membrane of the present invention (hereinafter also simply referred to as "membrane" or "hollow fiber membrane") will be described below. The hollow fiber microfiltration membrane obtained in the present invention is used for the turbidity of natural water such as river water, lake water, groundwater, and seawater, removal of microorganisms, and the field of waterworks such as preparation of sterile water, and electrodeposition coating solution. It can be applied in a wide range of fields such as paint recovery, ultrapure water production for electronics industry, pharmaceutical / fermentation and food applications.

In the production method of the present invention, a stock solution for film formation essentially consisting of a film-forming polymer, a solvent for the polymer, and an additive consisting of a hydrophilic polymer is treated with an aqueous solution of a good solvent for the polymer at a specific concentration. Is produced from a double annular nozzle together with an internal liquid consisting of ## STR2 ## and passed through an air gap of a specific ratio to the spinning speed, and then solidified in a coagulating bath at a specific temperature.

The film-forming polymer used in the production method of the present invention may be any polymer capable of forming a film by wet film formation, and examples thereof include polysulfone-based polymers, polyvinylidene fluoride-based polymers, polyacrylonitrile-based polymers, and polyacrylonitrile-based polymers. Examples thereof include methacrylic acid-based polymers, polyamide-based polymers, polyimide-based polymers, polyetherimide-based polymers and cellulose acetate-based polymers. Among them, aromatic polysulfone is excellent in its thermal stability, acid resistance, alkali resistance and mechanical strength,
Due to its hydrophobicity, it also clogs river water, lake water, groundwater, seawater, and other natural water, microbial removal, paint recovery from electrodeposition paint solutions, and general industrial fields such as pharmaceuticals and fermentation. The problem was that it was easy. A hydrophilic polymer is added to a film-forming stock solution to form a film, which enables use in the general industrial field and further improves blood compatibility in the medical field, and thus is preferably used. Bisphenol A type polysulfone is particularly preferably used as the aromatic polysulfone.

Examples of the aromatic polysulfone used in the present invention include those having a repeating unit represented by the following formula (1) or formula (2). In addition, A in the formula
r represents a 2-substituted phenyl group at the para position, and the degree of polymerization and the molecular weight are not particularly limited. _{-O-Ar-C (CH 3} ) 2 -Ar-O-Ar-SO 2 -Ar- (1) -O-Ar-SO 2 -Ar- (2)

As the additive, a hydrophilic polymer which is compatible with the solvent and does not dissolve the film-forming polymer is used. If the film-forming polymer is a polysulfone-based polymer, polyvinylpyrrolidone is preferably used as an additive.
Polyvinylpyrrolidone is preferable because it has particularly low toxicity among hydrophilic polymers. When the film-forming polymer is aromatic polysulfone, it is difficult to obtain the film of the present invention by using an additive other than polyvinylpyrrolidone.

The higher the molecular weight of polyvinylpyrrolidone is, the higher the hydrophilic effect on the membrane is. Therefore, the higher the molecular weight of polyvinylpyrrolidone is, the smaller the amount of polyvinylpyrrolidone is. Therefore, the polyvinylpyrrolidone of the present invention has a weight average molecular weight of 900,000 or more. Is used. It is necessary to leave a large amount of polyvinylpyrrolidone in the membrane in order to impart a hydrophilic effect to the membrane by using polyvinylpyrrolidone having a weight average molecular weight of less than 900,000. Will increase. On the contrary, if the residual amount of polyvinylpyrrolidone having a weight average molecular weight of less than 900,000 in the film is reduced in order to reduce the eluate, the hydrophilic effect becomes insufficient. In addition, since the hydrophilicity in the film thickness portion is insufficient unless polyvinylpyrrolidone having a weight average molecular weight of 900,000 or more is used, the plasma protein that has passed through the inner membrane surface dense layer (inner membrane surface site) has a membrane thickness. It is adsorbed on the part, and as a result, good separation characteristics cannot be exhibited.

As a solvent for the polymer, N-methyl-2
-Pyrrolidone, N, N-dimethylformamide, N, N
Examples of the solvent include dimethylacetamide, and when the film-forming polymer is a polysulfone-based polymer, N-methyl-2-pyrrolidone (hereinafter simply referred to as “NMP”) is preferable. NMP is a solvent having the highest dissolving power for polysulfone-based polymers. For example, it has a dissolving power of about 1.5 times at room temperature as compared with another good solvent, N, N-dimethylacetamide. In order to open a large pore size of 0.01 μm or more on the inner surface of the membrane in a graded structure where the pore size decreases continuously from the outer surface of the membrane to the inner surface, liquid-liquid phase separation is induced by the non-solvent in the inner liquid. It is necessary to lengthen the time from the completion of the separation to the completion of phase separation (solidification), that is, the particle growth time. In polysulfone-based polymers, it is possible to extend the particle growth time by using NMP, which has a very high dissolving power, than by using any solvent. Furthermore, since NMP is the best solvent in the polysulfone-based polymer, the molecular chains of the polysulfone-based polymer in the stock solution for film formation are well entangled with each other, and as a result, a high-strength film can be obtained. For the above reason, when the film-forming polymer is a polysulfone-based polymer, it is difficult to obtain the film of the present invention by using a solvent other than NMP.

The stock solution for film formation is essentially a film-forming polymer, specific additives such as polyvinylpyrrolidone, N-methyl-2.
Consisting of a solvent of a particular polymer such as pyrrolidone. If other additives such as water and metal salts, which are conventionally known as additives, are added to the film-forming stock solution, it is difficult to obtain the film of the present invention.

From the above, the membrane obtained by the production method of the present invention is most preferably composed of aromatic polysulfone and polyvinylpyrrolidone. Furthermore, since the microfiltration membrane obtained by the production method of the present invention is used by internal pressure filtration, it is preferable that the concentration of polyvinylpyrrolidone on the inner surface of the membrane with which the liquid to be filtered comes into contact is 20 to 45% by weight. . When the liquid to be filtered is blood or the like, an important factor for the blood compatibility of the membrane is the hydrophilicity of the inner surface of the membrane that comes into contact with blood, and polysulfone containing polyvinylpyrrolidone (hereinafter also simply referred to as “PVP”). In the membrane, the PVP concentration on the inner surface of the membrane is important. P on the inner surface of the membrane
When the VP concentration is too low, the inner surface of the membrane exhibits hydrophobicity, plasma proteins are easily adsorbed, and blood coagulation easily occurs.
That is, the blood compatibility of the membrane is poor. On the other hand, if the PVP concentration on the inner surface of the membrane is too high, the amount of PVP eluted into the blood system increases, giving unfavorable results. Therefore, the concentration of PVP when blood, plasma, or serum is subjected to internal pressure filtration is 20 to
45% by weight, preferably 25-40% by weight
Is.

The PVP concentration on the inner surface of the film is determined by X-ray photoelectron spectroscopy (X-ray Photoelectron spectroscopy).
n spectroscopy, hereinafter XPS). That is, the XPS of the inner surface of the film is measured by arranging the samples on the double-sided tape, incising in the fiber axis direction with a cutter, expanding the inside of the film so that it is on the front side, and then measuring by an ordinary method. . That is, C1s, O1s, N1
It means the concentration obtained from the surface intensity of s, S2p spectrum and the surface concentration of nitrogen (nitrogen atom concentration) and the surface concentration of sulfur (sulfur atom concentration) using the relative sensitivity coefficient attached to the device. When is the structure of equation (2), it can be calculated by equation (3). PVP concentration (% by weight) = C ₁ M ₁ × 100 / (C ₁ M ₁ + C ₂ M ₂ ) (3) where C ₁ : nitrogen atom concentration (%) C ₂ : sulfur atom concentration (%) M ₁ : Molecular weight of PVP repeating unit (111) M ₂ : Molecular weight of repeating unit of polysulfone polymer (442)

The polymer concentration of the membrane-forming stock solution used in the present invention is not particularly limited as long as it is within the concentration range in which the membrane can be formed from the stock solution and the obtained membrane has the performance as a membrane. , 10 to 35% by weight, preferably 10 to 30% by weight. In order to achieve high water permeability or large molecular weight cutoff, it is preferable that the polymer concentration is low,
5% by weight is preferred.

What is more important is the amount of the additive (hydrophilic polymer) in the stock solution for film formation, and the mixing ratio of the additive to the polymer is 20 to 60% by weight, preferably 27 to 6%.
It is 0% by weight. If the mixing ratio of the additive to the polymer is less than 20% by weight, the pore size on the inner surface of the membrane tends to be a small pore size of 0.01 μm or less, and if it exceeds 60% by weight, the viscosity of the membrane-forming stock solution becomes high, and It is not preferable because the spinnability tends to deteriorate.

Further, the temperature of the film-forming stock solution is important, and the temperature of the film-forming stock solution at the time of discharge by the nozzle is 50 ° C. or higher, preferably 60 to 100 ° C. If it is less than 50 ° C, the spinnability during film formation is poor.

The internal liquid is used for forming the hollow portion of the hollow fiber membrane, and is composed of water and a good solvent for at least one or more membrane-forming polymers. The water content is preferably 35 to 55% by weight. If the water content is less than 35% by weight, the spinnability during film formation is poor, and if it exceeds 55% by weight, the pore size on the inner surface of the membrane tends to be 0.01 μm or less.

By air gap is meant the gap between the nozzle and the coagulation bath. In order to obtain the membrane of the present invention, the spinning speed (m /
The ratio of air gap (m) to minute) is extremely important. Because the membrane structure of the present invention, the non-solvent in the internal solution is contacted with the film-forming stock solution to induce phase separation over time from the inner surface part of the film-forming stock solution to the outer surface part side,
Further, if the phase separation from the inner surface portion to the outer surface portion of the film is not completed by the time the stock solution for film formation enters the coagulation bath, it cannot be obtained.

The ratio of air gap to spinning speed is 0.
It is preferably from 01 to 0.1 m / (m / min), more preferably from 0.01 to 0.05 m / (m / min). The ratio of air gap to spinning speed is 0.01m /
When it is less than (m / min), it is difficult to obtain a film having the structure and performance of the present invention, and when it exceeds 0.1 m / (m / min), the tension to the film is high, so that the film is formed in the air gap portion. It is not preferable because it often breaks and tends to be difficult to manufacture.

Further, the spinning speed contributes greatly to the production efficiency, so that the faster the spinning speed, the better. However, the spinning speed is fast and the tension is high, so that it is impossible to increase the spinning speed. 60m / min or more, and even 7
0 to 120 m / min is possible. Here, the spinning speed is a series of manufacturing steps of a hollow fiber membrane in which a stock solution for film formation discharged from a nozzle together with an internal solution passes through an air gap and a film coagulated in a coagulation bath is wound, and stretched during the process. It means the winding speed when there is no operation. Also, by enclosing the air gap with a cylindrical tube or the like and flowing a gas having a constant temperature and humidity at a constant flow rate into the air gap, the hollow fiber membrane can be manufactured in a more stable state.

As the coagulation bath, for example, water; methanol,
Liquids such as alcohols such as ethanol; ethers; aliphatic hydrocarbons such as n-hexane and n-heptane that do not dissolve the polymer are used, and water is preferable. Also,
It is also possible to control the coagulation rate and the like by adding a small amount of a solvent that dissolves the polymer to the coagulation bath.
The temperature of the coagulation bath is 85 to 100 ° C., preferably 90 to 1
It is 00 ° C. If the temperature of the coagulation bath is lower than 85 ° C., the pore size on the inner surface of the film tends to be 0.01 μm or less,
If the temperature is 100 ° C. or higher, yarn breakage and the like frequently occur during film formation, which is not preferable.

Further, in order to obtain the film of the present invention, the ratio of the film thickness to the inner diameter of the film after coagulation is 0.15 to 0.4, preferably 0.2 to 0.3. If the ratio of the film thickness to the inner diameter of the film is less than 0.15, the absolute strength of the film tends to be weak. If the ratio exceeds 0.4, it tends to be difficult to obtain a graded structure in which the pore diameter decreases from the outer surface to the inner surface (or the inner surface portion) of the membrane as in the present invention. Because the ratio of the amount of solvent in the film-forming stock solution to the amount of non-solvent in the internal solution is large, only the amount of non-solvent in the internal solution is enough to remove the amount of non-solvent in the internal solution from the inner surface of the film before entering the coagulation bath. This is because the phase separation up to the outer surface part cannot be completed.

The outer diameter of the membrane is 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less. When the outer diameter of the membrane becomes large, the membrane area (filling amount) in the module is unavoidably reduced, resulting in poor processing capacity per unit time, which is not preferable. On the contrary, in order to increase the outer diameter of the membrane to make the membrane area (filling amount) in the module the same, the module container must be enlarged, resulting in an increase in cost, which is not preferable. In particular, it is necessary to avoid making a module used for medical use into an expensive large module in order to reduce the burden of medical expenses on the patient. The outer diameter of the membrane is preferably 500 μm or less in view of the above-mentioned processing capacity and cost.

Furthermore, the membrane of the present invention can be dried, and it is not necessary to impregnate a humectant such as glycerin at the time of drying. Further, by irradiating the membrane with radiation such as electron rays and γ rays, a part of PVP in the membrane can be insolubilized in water, so that the amount eluted from the membrane can be reduced. Irradiation may be performed before or after modularization. In addition, all PVP in the film
Is insoluble, the swelling property of the membrane deteriorates and the separation performance deteriorates, which is not preferable.

The water-insoluble PVP referred to in the present invention is
It is obtained by subtracting the amount of PVP soluble in water from the total amount of PVP in the membrane. The total amount of PVP in the film can be easily calculated by elemental analysis of nitrogen and sulfur. Also,
The amount of PVP soluble in water can be determined by the following method. For example, when the film-forming polymer is a polysulfone-based polymer, the film is completely dissolved with N-methyl-2-pyrrolidone, and then water is added to the obtained polymer solution to completely precipitate the film-forming polymer. After the polymer solution was allowed to stand still, the amount of PVP in the supernatant was quantified by liquid chromatography to obtain PV that was soluble in water.
P can be quantified.

[0034]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited thereto. Each measuring method is as follows. The hollow fiber membranes used as measurement samples were all in the state of being sufficiently impregnated with water.

(Measurement of water permeation amount) A yarn bundle having an effective length of 180 mm with both ends fixed by an adhesive (110 ± 10 in terms of internal surface area)
A mini-module in which the number of membranes was made uniform so as to be cm ² ) was permeated from the inner surface to the outer surface, and the amount was expressed in mL (milliliter) / (m ² · hr · mmHg). However,
The effective film area was converted to the inner surface.

(Measurement of breaking strength) The film strength was measured by using Autograph AGS-5D manufactured by Shimadzu Corporation at a sample length of 20 mm and a pulling speed of 300 mm / min.

(Measurement of blocking diameter) The pore diameter on the inner surface of the membrane is 0.0
If it is smaller than 5 μm or if it is a slit-shaped hole, it does not make sense because the error becomes large even if the size of the hole diameter is measured. It was used as an index of pore size. The blocking diameter in the internal pressure filtration in the present invention was determined by the following method. 1)
Bond both ends of a stock solution prepared by suspending polystyrene latex particles with a particle size accuracy of ± 4% within a concentration of 0.02% by volume in a 0.2% by weight sodium dodecyl sulfate aqueous solution. The average pressure of the inlet pressure and the outlet pressure is 0.5 kgf / cm ^{2 for} a yarn bundle fixed with an agent and having an effective length of 180 mm (the number of films is arranged so that the inner surface area is 110 ± 10 cm ² ). Internal pressure filtration was carried out under the condition of a cross flow of fluid linear velocity = 1 cm / sec, and the blocking rate of the concentration of the filtrate and the original solution after 40 minutes was obtained. At this time, it is necessary that the blocking rate does not change with time, and after 20 minutes, 40 minutes, and 6 minutes.
The deviation of the absolute value of each blocking rate after 0 minutes must be within ± 10%. The concentrations of the obtained filtrate and the original solution are measured with an ultraviolet spectrophotometer at a wavelength of 280 nm, and are substituted into the following formula (4) to calculate the blocking rate. 2) Next, the minimum particle size of the latex particles used in 1) where the blocking rate is 90% or more was taken as the blocking diameter of the film. Blocking rate (%) = {1- (absorbance of filtrate) / (absorbance of original solution)} × 100 (4) 0.01 was used for measuring the blocking diameter.
47 μm (Magsphere, polystyrene polymer, 0.0147 μm), 0.028 μm (Magsphere
Sphere, polystyrene-based polymer, 0.02
8 μm), 0.037 μm (manufactured by Magsphere,
Polystyrene polymer, 0.037 μm), 0.06
2 μm (Polymer-based polymer manufactured by Seradyn, 0.062 μm), 0.088 μm (Serady
n latex company polystyrene polymer, 0.088 μm) and 0.102 μm (Seradyn polystyrene polymer, 0.102 μm) latex particles (each particle size accuracy ± 4%) were used.

(Measurement of Porosity of Membrane Surface) The aperture ratio was determined by numerically analyzing the electron micrograph of the outer surface of the membrane by image analysis. The aperture ratio referred to in the present invention is defined as a percentage of the total area of the open hole portions with respect to the area of the image that is worked on, and is given by the following formula (5). Note that 10 pixels or less were regarded as noise and were excluded from the counting. Open area ratio (%) = (sum of open area of open area / area of captured image) × 100 (5)

(Measurement of Mean Pore Diameter on Membrane Surface) The shape and size of pores opened on the surface of the membrane were observed and measured using an electron microscope. Further, the average pore diameter D of the holes opened on the inner surface and the outer surface is a value represented by the following formula (6). D = [{(D _i ² ) ² + ... + (D _n ² ) ² } / {D _i ² + ... + D _n ² }] ^1/2 (6) where D is the average pore size and D _i is The measured diameter of the i-th hole and D _n are the measured diameter of the _n- th hole. However, the measured diameters of D _i and D _n are represented by the diameter of the hole when the hole is close to a circle, and by the diameter of a circle having the same area as the hole when the hole is not circular.

[0040]

[Example 1] (Film formation and removal of residual solvent) Polysulfone (Amoco Engineering Polymer)
rs P-1700) 20.0 wt%, polyvinylpyrrolidone (BASF K90, weight average molecular weight 1,
200,000) 4.4% by weight was dissolved in N-methyl-2-pyrrolidone 75.6% by weight to obtain a uniform solution.
Here, the mixing ratio of polyvinylpyrrolidone to polysulfone in the film-forming stock solution was 22.0% by weight. This film-forming stock solution was kept at 60 ° C., and the spinneret (double ring) was formed together with an internal solution (water content was 46% by weight) consisting of a mixed solution of 54% by weight of N-methyl-2-pyrrolidone and 46% by weight of water. Nozzle 0.1 mm-0.2 mm-0.3 mm, nozzle temperature 60 ° C., temperature of film-forming stock solution at nozzle part 60 ° C.), and air gap of 0.96 m is passed to reach 95
It was immersed in a coagulation bath consisting of water at ± 1 ° C. At this time, the spinneret and the coagulation bath were surrounded by a cylindrical tube and sealed so that outside air did not enter. The spinning speed was fixed at 80 m / min. here,
The ratio of air gap to spinning speed is 0.012m /
(M / min). After cutting the wound yarn bundle, the residual solvent in the film was removed by washing from above the cut surface of the yarn bundle with a hot water shower at 80 ° C. for 2 hours. further,
PV in the film by irradiation with γ-ray of 2.5 Mrad
Part of P was insolubilized.

Observation of the obtained film with an electron microscope revealed that the film had a sponge structure in which the pore diameter continuously decreased from the outer surface to the inner surface of the film. Table 1 shows other film structures and film performances. It was revealed that the rupture strength of the membrane was as high as 50 kgf / cm ² or more, and was a microfiltration membrane having an excellent water permeability of 1,000 mL / m ² · hr · mmHg or more. Further, even in the internal pressure filtration of latex particles having an average particle diameter of 0.062 μm, the amount of the filtrate was maintained stable for a long time without sudden clogging.

[0042]

[Example 2] The polyvinylpyrrolidone in the stock solution for film formation was adjusted to 10%.
%, N-methyl-2-pyrrolidone 70% by weight
The same operation as in Example 1 was performed except for the above. Made at this time
Polyvinylpyrrolidone for polysulfone in membrane stock solution
The admixture ratio was 50.0% by weight. The resulting film is charged
When observed with a submicroscope,
It has a sponge structure in which the pore size becomes smaller continuously.
It became clear. Other membrane structures and membrane performance
It shows in Table 1. The breaking strength of the membrane is 50 kgf / cm ²And above
Shows high strength and further 1,000 mL / m²・ Hr ・
A microfiltration membrane with excellent water permeability of mmHg or more.
Became clear. Furthermore, it is used to measure the blocking diameter.
Internal pressure filtration of latex particles with an average particle size of 0.037 μm
The filtrate volume is stable for a long time without sudden clogging
Maintained.

[0043]

Example 3 The same operation as in Example 1 except that an internal liquid (water content of 37% by weight) consisting of a mixed solution of 63% by weight of N-methyl-2-pyrrolidone and 37% by weight of water was used. I went. When the obtained film was observed with an electron microscope,
It was revealed that the sponge structure has a pore size that continuously decreases from the outer surface to the inner surface of the membrane. Table 1 shows other film structures and film performances. The breaking strength of the film is 5
High strength of 0 kgf / cm ² or more, and 1,0
It was revealed that the microfiltration membrane has an excellent water permeability of 00 mL / m ² · hr · mmHg or more. Further, even in the internal pressure filtration of the latex particles having an average particle diameter of 0.102 μm used for the measurement of the inhibition diameter, the amount of the filtrate was stable for a long time without sudden clogging.

[0044]

Example 4 The same operation as in Example 1 except that an internal solution (water content of 54% by weight) consisting of a mixed solution of 46% by weight of N-methyl-2-pyrrolidone and 54% by weight of water was used. I went. When the obtained film was observed with an electron microscope,
It was revealed that the sponge structure has a pore size that continuously decreases from the outer surface to the inner surface of the membrane. Table 1 shows other film structures and film performances. The breaking strength of the film is 5
High strength of 0 kgf / cm ² or more, and 1,0
It was revealed that the microfiltration membrane has an excellent water permeability of 00 mL / m ² · hr · mmHg or more. Further, even in the internal pressure filtration of the latex particles having an average particle diameter of 0.028 μm used for the measurement of the blocking diameter, the amount of the filtrate was maintained stable for a long time without sudden clogging.

[0045]

[Example 5] The polyvinylpyrrolidone in the stock solution for film formation was changed to 6.
The same operation as in Example 1 was performed except that 6% by weight and 73.4% by weight of N-methyl-2-pyrrolidone were used. At this time, the mixing ratio of polyvinylpyrrolidone to polysulfone in the film-forming stock solution was 33.0% by weight. When the obtained film was observed by an electron microscope, it was revealed that the film had a sponge structure in which the pore size continuously decreased from the outer surface to the inner surface. Table 1 shows other film structures and film performances. The breaking strength of the membrane is 50 kgf / cm ²
Shows high strength as above, further 1,000 mL / m ² ·
It has been clarified that it is a microfiltration membrane having an excellent water permeability of at least hr · mmHg. Further, even in the internal pressure filtration of the latex particles having an average particle diameter of 0.088 μm used for measuring the inhibition diameter, the amount of the filtrate was maintained stable for a long time without sudden clogging.

[0046]

[Comparative Example 1] The polyvinylpyrrolidone in the stock solution for film formation was compared with 3.
The same operation as in Example 1 was performed except that 4% by weight and N-methyl-2-pyrrolidone were set to 76.6% by weight. At this time, the mixing ratio of polyvinylpyrrolidone to polysulfone in the film-forming stock solution was 17.0% by weight. When the obtained film was observed by an electron microscope, it was revealed that the film had a sponge structure in which the pore size continuously decreased from the outer surface to the inner surface. Table 2 shows other film structures and film performances. The average pore size on the inner surface of the membrane is 0.01 μm
It was below. Further, since the blocking rate of 0.0147 μm latex particles was 100% from the initial stage, it was revealed that the blocking diameter of this film was less than 0.0147 μm.

[0047]

Comparative Example 2 The polysulfone used in Example 1 (20% by weight), polyvinylpyrrolidone (13% by weight), and N-methyl-2-pyrrolidone (67% by weight) could not be dissolved into a uniform solution. .

[0048]

[Comparative Example 3] The same operation as in Example 1 except that an internal solution (water content of 57% by weight) consisting of a mixed solution of 43% by weight of N-methyl-2-pyrrolidone and 57% by weight of water was used. I went. When the obtained film was observed with an electron microscope,
It was revealed that the sponge structure has a pore size that continuously decreases from the outer surface to the inner surface of the membrane. Table 2 shows other film structures and film performances. The average pore diameter on the inner surface of the membrane was 0.01 μm or less. Also, 0.0147μ
Since the blocking rate of the latex particles of m was 100% from the beginning, it was revealed that the blocking diameter of this film was less than 0.0147 μm.

[0049]

[Comparative Example 4] The same operation as in Example 1 except that an internal liquid consisting of a mixed solution of 62% by weight of N-methyl-2-pyrrolidone and 38% by weight of water (the content of water was 62% by weight) was used. However, the yarn was frequently broken and the spinning could not be performed.

[0050]

[Comparative Example 5] The temperature of the film forming solution was 45 ° C and the nozzle temperature was 4
The same operation as in Example 2 was carried out except that the temperature was 5 ° C. (the temperature of the stock solution for film formation at the nozzle portion was 45 ° C.), but yarn breakage occurred frequently and spinning was not possible.

[0051]

Comparative Example 6 The same operation as in Example 1 was carried out except that the solvent was changed from N-methyl-2-pyrrolidone to N, N-dimethylacetamide. When the obtained film was observed by an electron microscope, it was revealed that the film had a sponge structure in which the pore size continuously decreased from the outer surface to the inner surface. Table 2 shows other film structures and film performances. The average pore diameter on the inner surface of the membrane was 0.01 μm or less. Also,
Since the blocking rate of 0.0147 μm latex particles was 100% from the beginning, the blocking diameter of this film was 0.01
It was revealed to be less than 47 μm.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

The membrane obtained by the production method of the present invention is a microfiltration membrane having an anisotropic structure having high strength and excellent water permeability, and excellent microfiltration with less clogging especially in internal pressure filtration. Since it is a film, it can be used for pharmaceutical applications, medical applications, and general industrial applications.

Claims (8)

(57) [Claims] 1. The pore size increases from the outer surface to the inner surface of the membrane.
Consisting of a continuously smaller sponge structure for internal pressure filtration
The blocking diameter is 0.015 to 1 μm.
In the method for producing a hollow fiber microfiltration membrane, the method for producing a hollow fiber membrane in which a membrane-forming stock solution and an internal solution are discharged from a double annular nozzle and then passed through an air gap and then coagulated in a coagulation bath, a) The film-forming stock solution is a film-forming polymer, a solvent for the polymer,
And a hydrophilic polymer, the ratio of the hydrophilic polymer to the film-forming polymer is 27 to 60% by weight, b) the internal liquid is water and at least one solvent, and the water content is 35 to 55% by weight, c) The temperature of the film forming stock solution in the nozzle part is 60 to 100 ° C. or higher, d) the coagulation bath temperature is 90 to 100 ° C., and e) the ratio of the air gap to the spinning speed is 0.01 to 0.
It is 1 m / (m / min), The manufacturing method of the hollow fiber microfiltration membrane characterized by the above-mentioned. 2. The manufacturing method according to claim 1, further comprising irradiation with radiation. 3. The ratio of the film thickness to the inner diameter of the film is 0.15.
It is-0.4, The manufacturing method of Claim 1 or 2 characterized by the above-mentioned. 4. The manufacturing method according to claim 1, wherein the outer diameter of the film is 500 μm or less. 5. The method according to claim 1, wherein the film-forming polymer is a polysulfone-based polymer. 6. The hydrophilic polymer has a weight average molecular weight of 90.
It is polyvinylpyrrolidone of 10,000 or more, The manufacturing method in any one of Claims 1-5 characterized by the above-mentioned. 7. The solvent for the film-forming polymer is N-methyl-2.
-Pyrrolidone, Process according to any one of claims 1 to 6, characterized in that it is pyrrolidone. 8. The manufacturing method according to claim 1, wherein the spinning speed is 60 m / min or more.