JPS6399325A - Hollow yarn membrane of polysulfone resin and production thereof - Google Patents

Abstract

PURPOSE:To obtain the titled membrane having improved water wetting properties and smooth inner surface, slightly causing clogging, by adding an additive to a solution of a polysulfone resin and a hydrophilic high polymer in a solvent to give a stock solution for membrane making and using an injection solution in spinning. CONSTITUTION:First, a polysulfone resin and a hydrophilic high polymer (preferably polyvinyl pyrrolidone) are blended with a solvent (preferably DMF, etc.) and dissolved. Then, the solution is mixed with an additive (preferably water) to give a system, which is used as a stock solution for membrane making. In spinning an injection solution (preferably isopropyl myristate, etc.) to give the aimed membrane which consists of the polysulfone resin containing the hydrophilic high polymer, has >=1,000ml/hr.mmHg.m<2> water permeability, excellent water wetting properties, improved smooth inner surface, >=500Angstrom average pore diameter on the inner surface and contains no >=5mu pores.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a polysulfone resin hollow fiber membrane that has good water wettability, a smooth inner surface, and a pore size that is difficult to clog. .

[Conventional technology]

Membrane separation has made remarkable progress in recent years, and many products are now on the market. However, with regard to the use of high-performance membranes, various restrictions have been imposed on their use, such as not requiring high temperatures and strictly prohibiting drying.

Conventionally, the material for semipermeable membranes has been cellulose acetate.
Many polymeric compounds such as polyacrylonitrile, polymethyl methacrylate, and polyamide have been used. on the other hand,
Polysulfone resins were originally used as engineering plastics, but due to their heat-resistant stability, acid and alkali resistance, biocompatibility, and stain resistance, they are attracting attention as semipermeable membrane materials. There is.

Conventional methods for obtaining semipermeable membranes using polysulfone resins have been described, for example, in Journal of Applied Polymer Science (Vol. 20, pp. 2377-2394, 19
1976) and (Vol. 21, pp. 1883-1900, 1
1977), Japanese Patent Application Laid-open No. 194940/1983, etc. have been proposed. However, the intermolecular cohesive force of this resin is too strong and it closes the surface pores and the internal pores that should be penetrated, making it difficult to control pore formation. For this reason, only low water permeability has been obtained.

On the other hand, in recent years, the following methods have been proposed in an attempt to create large pores on the surface of a membrane using polysulfone resin.

■ A method that utilizes microphase separation between different types of polymers. (
Japanese Patent Publication No. 48-17 [3], Japanese Patent Application Publication No. 54-14445
Publication No. 6, Publication No. 57-50506, Publication No. 57-505
(No. 07 Publication, No. 57-50508 Publication) (2) A method that includes film formation, extraction and elution operations. (Unexamined Japanese Patent Publication No. 5
(No. 4-26283, No. 57-35906, No. 58-91822) (2) A method of forming a film in a metastable liquid dispersion state of a film forming stock solution. (
JP-A-56-154051, JP-A No. 59-58041
No. 59-183761, No. 59-189
(No. 903) ■ A method of using ingenuity during spinning (Japanese Unexamined Patent Publication No. 59-228016) However, these methods do not solve the problem of excessive size of intermolecular cohesive force on the membrane surface during coagulation, which is a characteristic of polysulfone resin. Because of this, it has not been possible to obtain a membrane with good water wettability and high water permeability.

[Problem that the invention seeks to solve]

The present inventors analyzed the above-mentioned drawbacks, and as a result of intensive study, they arrived at the present invention. In particular, polysulfone resin hollow fiber membranes that have a smooth inner surface, are resistant to clogging and dirt, can control water permeability and molecular weight fraction over a wide range, and do not substantially deteriorate in performance even when dried. The purpose is to provide a manufacturing method.

(Means for solving the problems) The present invention has the following configuration. That is, (1) a hollow fiber membrane made of a polysulfone resin containing a hydrophilic polymer, the hollow fiber membrane having a water permeability of 1000 ml/hr;
A polysulfone resin hollow fiber membrane having good water wettability at mmHq, tri or more, a smooth inner surface, an average pore diameter of 500 Å or more, and no pores of 5 μ or more.

(2) The polysulfone resin hollow fiber membrane according to claim 1, which is a crosslinkable polymer capable of fixing a hydrophilic polymer and contains 1 to 30% by weight of the total hollow fiber membrane.

(3) The polysulfone resin hollow fiber membrane according to claim 1, wherein the hydrophilic polymer is polyethylene glycol or polyvinylpyrrolidone.

(4) A polysulfone system characterized by using a system obtained by adding additives to a solution of a polysulfone resin and a hydrophilic polymer mixed and dissolved in a solvent as a film forming stock solution, and using an injection liquid during spinning. A method for producing a resin hollow fiber membrane.

(5) The method for producing a polysulfone resin hollow fiber membrane according to claim 4, wherein the injection liquid is an inert liquid in the membrane forming stock solution.

(6) The injection solution contains at least 5% by weight of a water-soluble polymer.
The method for producing a polysulfone-based resin hollow fiber membrane according to claim 4 containing the above.

(7) The manufacturing method according to claim 4, wherein the injection liquid is isopropyl myristate. (8) When the injection liquid has a coagulation value of 15 or less, an annular slit type with an inner diameter of the hollow fiber inner diameter ±100 μm is used. A method for producing a polysulfone-based resin hollow fiber membrane according to claim 4, which uses a hollow base.

The present invention will be explained in detail below.

The membrane-forming stock solution used to produce the polysulfone resin semipermeable membrane in the present invention basically consists of a polysulfone resin (■), a hydrophilic polymer (■), a solvent (III), and an additive (1v). It is composed of a four-component system. The polysulfone resin (I> mentioned here usually contains formula (1) or formula (2), or may be an alkyl type resin, and is not particularly limited. ) is a polymer that is compatible with polysulfone resin (I>) and has hydrophilic properties.Polyvinylpyrrolidone is the best, but other examples include modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone, polyvinyl acetate, and polyethylene glycol. Examples include, but are not limited to.

The solvent (III) is a solvent that dissolves both the polysulfone resin (I>) and the hydrophilic polymer (n).

Various solvents can be used, such as dimethyl sulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, and dioxane, but dimethylacetamide, dimethylsulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone are particularly preferred.

The additive (IV) can be anything as long as it is compatible with the solvent (III), serves as a good solvent for the hydrophilic polymer (II), and serves as a non-solvent or swelling agent for the polysulfone resin (I). Good examples include water, methanol, ethanol, isopropanol, hexanol, 1,4-butanediol, and the like. Considering production costs, water is the most desirable.

The additive (1v) may be selected in consideration of the coagulability with respect to the polysulfone resin (I>).

Combinations of each of these are arbitrary, and it is easy for those skilled in the art to consider combinations having the above properties. Further, the solvent (■) and the additive (1■) may be a mixture of two or more types of compounds.

Surprisingly, this membrane-forming stock solution undergoes phase separation on the high temperature side, contrary to the normal phase separation behavior in which phase separation occurs on the low temperature side. This makes it possible to efficiently utilize the effect of the coagulation bath temperature, which is particularly advantageous for producing membranes with large pores. This principle is inferred as follows.

That is, it is assumed that this film-forming stock solution is homogeneous at a certain temperature. However, when the temperature rises, the additive (1v) bound to the hydrophilic polymer is released, causing the polysulfone resin dissolved in the solvent (III) to precipitate and aggregate.
Causes phase separation. The gaps between the aggregated polymers form a so-called porous structure.

As described above, the phase separation behavior of this membrane-forming stock solution is the opposite of normal, and the phase transition is reversible.

As for the composition of the membrane-forming stock solution, the polysulfone resin (1) may be in a concentration range of 5 to 50% by weight as long as it can be formed into a membrane and has properties as a membrane.

In order to obtain high water permeability and a large molecular weight cut-off, it is preferable to use a membrane whose inner surface has an average pore diameter of 500 Å or more. Therefore, the polymer concentration should be lowered, preferably 5
~25% by weight. If it is less than 5% by weight, sufficient film strength cannot be obtained and a practical film cannot be formed.

Moreover, if it exceeds 50% by weight, it becomes difficult to form through holes.

Hydrophilic polymer (I), especially in the case of polyvinylpyrrolidone, is commercially available with molecules ff of 1,360,000, 160,000, 40,000, and 10,000, and it is convenient to use this, but other molecular weights It is also possible to use something. However, one of the reasons for adding the hydrophilic polymer (n) is its thickening effect, so the higher the molecular weight, the smaller the amount needed. Polymers have high efficiency and are advantageous in reducing the risk of elution when membranes are used. Furthermore, since the reversal of the temperature dependence of the phase separation phenomenon becomes remarkable, it is also preferable for obtaining a membrane with high water permeability. The amount of polyvinylpyrrolidone added is 1 to 30% by weight, preferably 1 to 20% by weight,
In particular, 2 to 10% by weight is desirable, but it depends on the molecular weight of the polyvinylpyrrolidone used. In general, if the amount added is too small or if the molecular weight is too low, it will be difficult to reverse the phase separation by 1q, and if the polymer concentration is too high and the polymer molecule opening is too large, cleaning after film formation will be difficult. Therefore, one method is to mix substances with different molecular weights and use them in different roles.

The above two polymers are mixed and dissolved in solvent (I).

Additive (IV) is added here, especially in the case of water.
Since polysulfone resin has high coagulability, it is preferably 7% by weight or less, particularly 1 to 5% by weight.

It is easily assumed that when an additive with low coagulability is used, the amount added will be large.

In the present invention, since this first V component is added, the amount of hydrophilic polymer can be reduced. Additives (IV
) becomes higher, the phase separation temperature of the membrane forming stock solution decreases. The phase separation temperature can be set arbitrarily depending on the desired water permeability and molecular weight cutoff of the membrane. For example, in order to obtain high water permeability and molecular weight cutoff, a low phase separation temperature is required to strongly promote phase separation during membrane formation. All you have to do is set . Further, the same effect can be obtained even if the temperature of the coagulation bath is increased. The film-forming stock solution used in the present invention becomes homogeneous at low temperatures and therefore has good stock solution stability.

A polysulfone resin semipermeable membrane is obtained under the above conditions.

A known technique may be used for the film forming operation.

In the production of hollow fiber membranes, usually after discharging it into the air,
Wet-dry spinning is performed by dipping in a coagulation bath, but is not limited thereto. In such cases, an injection solution is used to maintain the hollow shape.

The composition of the injection liquid has a large influence on the formation of the inner surface. Usually, the injection solution is a mixture of the solvent and coagulant used in the membrane-forming stock solution, but in this case, in order to make it smooth and prevent clogging, particles smaller than the particles to be filtered are required. In terms of pore size, for example, if the size is at the level of blood cells, it is necessary that the inner surface does not have pores larger than 5 μm. In order to obtain such a membrane with a small surface pore size, a liquid that is inert to the membrane forming stock solution is preferable, and as such an injection liquid, isopropyl myristate is preferable.

That is, a material that does not coagulate or dissolve the polysulfone resin (I>) and that does not easily cause diffusion of solvents and the like is suitable.

For this purpose, a poor solvent for the polysulfone resin (I) is used, or a polymer that can be extracted later is dissolved in the injection solution by usually 5% or more, preferably 10% or more, although it varies depending on its molecular weight. Alternatively, a non-aqueous liquid can be used. It is also possible to add or mix coagulants, solvents, other extractable additives, and water-soluble polymers to these. It is preferable that the water-soluble polymer contains 5 m% or more.

Furthermore, when using a highly coagulable injection liquid, depending on the degree of coagulation of the injection liquid, cracks may occur due to drafts in the dry part during spinning, making it impossible to form a smooth inner surface. If the coagulability becomes too high, the inner circumferential length of the hollow fiber during discharge cannot be contracted, and the hollow portion deforms into a polygon or star shape. In order to prevent this phenomenon, use an injection liquid with a coagulation value of 15 or less, and keep the inner diameter of the target hollow fiber ±
It is preferred to use a hollow cap with an inner diameter of 100 μm, preferably ±50 μm of the hollow fiber inner diameter.

For example, if the hollow fiber is 250 μm, the inner diameter of the cap is 200 μm.
It is preferable to set the thickness to 300 μm.

Here, the coagulation value refers to the value (d) at which precipitation occurs when the injection solution is added to 5 Qml of a polysulfone-based resin 1% dimethylacetamide solution at 25°C.

In the dry part, the discharged yarn is exposed to the atmosphere of a coagulation bath, and the temperature rise and moisture absorption promote phase separation of the stock solution, thereby improving water permeability. Further, the temperature of the coagulation bath is desirably high in order to increase the progress of phase separation and the coagulation rate, and also to increase the extraction rate of the hydrophilic polymer (n).

Even if the remaining hydrophilic polymer is water-soluble, the polysulfone resin hollow fiber membrane with a smooth inner surface obtained by this method becomes insoluble in water by crosslinking with gamma rays or heat, and at the same time becomes water permeable. 1000 ml/hr, mmHO
, Td or higher. By allowing the hydrophilic polymer to remain in the membrane in this manner, it is also possible to produce a completely dry membrane that maintains water wettability and has a smooth inner surface.

It goes without saying that the above method can be fully applied to the production of flat membranes.

〔Example〕

The following examples briefly illustrate the invention in detail, but are not intended to limit the invention.

The measurement method used is as follows.

(1) - Water permeability - A hollow fiber membrane was inserted into a glass case with holes for reflux liquid at both ends, a small module was made using a commercially available potting agent, and the hollow fiber membrane was kept at 37°C. Water permeability was calculated from the amount of water permeated to the outside through the membrane in a certain period of time by applying water pressure to the inside of the yarn, the effective membrane area, and the pressure difference between the membranes.

(2) -Surface pore diameter- This was determined by photographic observation using a scanning electron microscope (Akashi Seisakusho α-9).

(3) - Inner surface smoothness - The inner surface of the film was photographically observed at 200x magnification using a scanning electron microscope.
The condition was compared with the evaluation criteria shown in FIGS. 7 to 9 (3 levels of ○, Δ, and X, with all other than X passing) and ranking.

-Water Wettability- The membrane was once dried and then immersed in water again for 30 minutes, and then the water permeability was measured and evaluated based on the water permeability.

Examples 1 to 6 Polysulfone (Needel P-3500: hereinafter abbreviated as PSF), polyvinylpyrrolidone (Ni-90; hereinafter abbreviated as PVP), 8 parts of water, and 2.4 parts of water were mixed with dimethylacetamide (hereinafter abbreviated as D).
(abbreviated as MAC) and heated to dissolve. This membrane-forming stock solution was prepared by adding a small amount of water so as to cause phase separation at 60°C. The diameter of the cap was 10-0.7φ, the temperature was 45°C, and water at 80°C was used for the coagulation bath. Under these conditions, sampling was performed by changing the injection solution. The resulting untreated system was washed with boiling water for 1 hour, then dry heat treated at 170°C for 3 hours, and then treated with boiling water for 1 hour.
It was dried at ℃ for 3 hours to obtain a dry hollow fiber membrane. As shown in Table 1, the obtained sample had satisfactory data in terms of water permeability, surface pore size, smoothness, and water wettability.

Example 7 DMA079 17 parts PSF, 2 parts PVP, 2.6 parts water
and heated to dissolve. This stock solution is 0.5-0.3φ
With an annular orifice type hollow mouthpiece, DHAC is used as injection liquid
/water = 65/35 (coagulation value = 4.6), and spinning and post-treatment were performed in the same manner as in Example 1. As shown in Table 1, both performance and quality were excellent.

Comparative Examples 1 to 3 Similar to Examples 1 to 6, sampling was performed by changing the injection solution, but as shown in Table 1, the surface pore size was too large, the inner surface was rough, and even the star-shaped hollow. (DHAC/water = 50150 coagulation value 4.2)
etc.

DS Dimethyl sulfoxide G Glycerin DC Dimethylacetamide v3 Polyvinylpyrrolidone (K2O) E Polyethylene glycol ($1400) IPH Isopropyl myristate □ [Effects of the invention] The polysulfone resin semipermeable membrane of the present invention has excellent heat resistance and chemical resistance, Furthermore, it has excellent water wettability, and at the same time has a smooth inner surface that is resistant to clogging.

Therefore, it can be used as a high-performance ultrafiltration membrane (or microfiltration membrane) for solid-liquid separation in general industrial applications and as a blood component separation membrane in the medical field.

[Brief explanation of the drawing]

FIGS. 1, 2 and 3 are Embodiment 2 of the present invention, an actual M
This is the inner surface morphology of the hollow fibers obtained in Example 4 and Example 7. 4 and 5 show the inner surface morphology of the hollow fiber obtained in Comparative Example 1 and Comparative Example 2, and FIG. 6 shows the cut surface morphology of the hollow fiber obtained in Comparative Example 3. Figures 7, 8, and 9 show the 1iffi standard (0, Δ, and
This is a typical example. Patent applicant Toshi Co., Ltd. Company procedure manual (
method)

Claims (8)

[Claims] (1) A hollow fiber membrane made of polysulfone resin containing a hydrophilic polymer, the hollow fiber membrane having a water permeability of 1000 ml.
/hr. mmHg. A polysulfone resin hollow fiber membrane having good water wettability with m^2 or more, a smooth inner surface, an average pore diameter of 500 Å or more, and no pores of 5 μ or more. (2) The polysulfone resin hollow fiber membrane according to claim 1, which is a crosslinkable polymer capable of fixing a hydrophilic polymer and contains 1 to 30% by weight of the total amount of the hollow fiber membrane. (3) The polysulfone resin hollow fiber membrane according to claim 1, wherein the hydrophilic polymer is polyethylene glycol or polyvinylpyrrolidone. (4) A polysulfone system characterized by using a system in which additives are added to a solution of a polysulfone resin and a hydrophilic polymer mixed and dissolved in a solvent as a film forming stock solution, and an injection liquid is used during spinning. A method for producing a resin hollow fiber membrane. (5) The method for producing a polysulfone-based resin hollow fiber membrane according to claim 4, wherein the injection liquid is a liquid that is inert to the membrane-forming stock solution. (6) The method for producing a polysulfone resin hollow fiber membrane according to claim 4, wherein the injection liquid contains at least 5% by weight of a water-soluble polymer. (7) The method for producing a polysulfone resin hollow fiber membrane according to claim 4, wherein the injection liquid is isopropyl myristate. (8) If the injected liquid has a coagulation value of 15 or less, the hollow fiber inner diameter ±
The method for producing a polysulfone-based resin hollow fiber membrane according to claim 4, which uses an annular slit-type hollow base having an inner diameter of 100 μm.