JPH06339620A - Method for treating polysulfone resin semipermeable membrane - Google Patents

Abstract

PURPOSE:To obtain a semi-permeable membrane with no eluation of blended polymers and high water permeability by applying radiation treatment on a polysulfone resin semi-permeable membrane and thereby corsslinking a hydrophilic polymer. CONSTITUTION:Radiation treatment is applied on a polysulfone resin semi-permeable membrane prepd. by using a system wherein an additive being a non-solvent or a swelling agent to the polysulfone resin is added into a soln, prepd. by mixing and dissolving a polysulfone resin and a hydrophilic polymer, as a film- forming stock soln. to crosslink the hydrophilic polymer. The polysulfone resin ordinally consists of a repeating unit of formula I or II but it may contain a functional group or it may be an alkyl type. As the hydrophilic polymer, polyvinyl pyrrolidone is the best and modified polyvinyl pyrrolidone, polyethylene glycol etc., can be cited. As the solvent, dimethylacetamide, dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone are especially pref. As the additive, water is most pref. from the view point of production cost.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for treating a polysulfone-based resin semipermeable membrane.

[0002]

2. Description of the Related Art Conventionally, many polymer compounds such as cellulose acetate, polyacrylonitrile, polymethylmethacrylate, and polyamide have been used as materials for semipermeable membranes. On the other hand, polysulfone resins have been originally used as engineering plastics, but because of their excellent heat resistance stability, acid / alkali resistance, biocompatibility, and stain resistance, they have attracted attention as semipermeable membrane materials. Has been done.

As a method for obtaining a semipermeable membrane using a polysulfone resin, for example, Journal of Applied Polymer Science (20, 2377-2394, 19)
1976) and (21, pp. 1883 to 1900, 1977), JP-A-58-104940, and the like. However, since the intermolecular cohesive force of the resin is too strong, the pores on the surface and the internal pores to be penetrated are closed, so that the control of pore formation becomes difficult. Therefore, only those having a small molecular weight cutoff of 100,000 or less and a low water permeability are obtained. On the other hand, in recent years, the following means have been proposed as an attempt to open a large hole in the surface of a film using a polysulfone resin.

A method that utilizes microphase separation between heterogeneous polymers. (Japanese Patent Publication No. 48-176, Japanese Patent Application Laid-Open No. 54-
No. 144456, No. 57-50506, No. 5
7-50507 and 57-50508) A method having an extraction / elution operation after film formation. (JP-A-5
No. 4-26283, No. 57-35906, No. 58-91822) A method for forming a film in a metastable liquid dispersion state of a film forming stock solution.
(JP-A-56-154051, JP-A-59-5804)
1 gazette, the same 59-183761, the gazette 59-18.
No. 9903) A method of devising a device during spinning (Japanese Patent Laid-Open No. 59-2280).
However, the above method merely utilizes the difference in the coagulation rate between polymers, and has not yet obtained large pores having a molecular weight cutoff of 100,000 or more. Moreover, since a large amount of blending is performed, the original good performance of the polysulfone resin is likely to be lost.

The method (1) is broadly classified into two methods: extraction of blended polymer and elution of inorganic granules. In the former, polyethylene glycol and polyvinylpyrrolidone are the main polymers, but it was difficult to obtain a sufficient pore size and to perform the extraction operation. In the latter example,
In JP-A-58-91822 described above, silica powder is mixed to form a film, which is then eluted with an alkali to give 0.0
Although it has succeeded in making a large hole of 5 μm or more, this manufacturing method cannot manufacture a film having another pore size distribution from the same film forming solution.

In the method of (1), a large amount of a non-solvent of a polysulfone resin or a swelling agent is mixed with a stock solution for film formation, and a film is formed immediately before phase separation of the stock solution for film formation. This method has the drawback that the temperature effect of the coagulation bath cannot be used to advantage.

The method of (1) realizes the expansion of the pore diameter on the surface by blowing a high-humidity air at the time of film formation. However, this method has the effect only on one side, and particularly in the case of the hollow fiber membrane. Yields only those having a small molecular weight cutoff.

Particularly, a semipermeable membrane prepared by blending a water-soluble polymer such as polyvinylpyrrolidone, polyethylene glycol or polyvinyl alcohol has a low water permeability due to a problem of elution of the water-soluble polymer and a swelling layer of the water-soluble polymer. It had the drawback that it could only do so.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have reached the present invention as a result of analyzing the above-mentioned drawbacks and making intensive studies. In particular, it is an object of the present invention to provide a method for treating a polysulfone-based resin semipermeable membrane in order to obtain a semipermeable membrane having extremely high water permeability without elution of the blended polymer.

[0010]

The present invention has the following configuration. That is, “a polysulfone-based resin semipermeable membrane produced by using a solution prepared by mixing and dissolving a polysulfone-based resin and a hydrophilic polymer with an additive which is a non-solvent or a swelling agent to the polysulfone-based resin is used as a membrane-forming stock solution. , A method for treating a polysulfone-based resin semipermeable membrane, characterized in that the hydrophilic polymer is crosslinked by subjecting it to radiation treatment. "The membrane-forming stock solution used for producing the polysulfone-based resin semipermeable membrane in the present invention is , Basically polysulfone resin (I),
Hydrophilic polymer (II), solvent (III) and additive (IV)
It is composed of a four-component system. The polysulfone-based resin (I) referred to here is usually represented by the formula (1) or the formula (2)

[Chemical 1] However, it may be a functional unit-containing or alkyl-based repeating unit and is not particularly limited.

The hydrophilic polymer (II) is a polymer which is compatible with the polysulfone resin (I) and has hydrophilicity. Polyvinylpyrrolidone is the best, and other examples include modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone, polyvinyl acetate, polyethylene glycol, etc.
It is not limited to these.

The solvent (III) is a solvent that dissolves both the polysulfone resin (I) and the hydrophilic polymer (II). Various solvents such as dimethylsulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone and dioxane are used, and dimethylacetamide, dimethylsulfoxide, dimethylformamide and N-methyl-2-pyrrolidone are particularly preferable.

The additive (IV) 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). Any material may be used, such as water, methanol, ethanol, isopropanol, hexanol, and 1,4-butanediol. Water is the most desirable considering the production cost. The additive (IV) may be selected after considering the coagulability with respect to the polysulfone resin (I).

The combination of each of these is arbitrary,
It is easy for those skilled in the art to consider a combination having the above properties. In addition, solvent (III) / additive (IV)
May be a mixed system of two or more compounds.

As the composition of the membrane-forming stock solution, the polysulfone resin (I) may be in a concentration range capable of forming a membrane and having characteristics as a membrane, and is 5 to 50% by weight. In order to obtain high water permeability and a large molecular weight cutoff, the polymer concentration should be lowered, and in this case, it is preferably 5 to 20% by weight. If it is less than 5% by weight, a sufficient viscosity of the stock solution for film formation cannot be obtained and a film cannot be formed. Also, 50% by weight
If it exceeds, it becomes difficult to form through holes. The hydrophilic polymer (II) has a molecular weight of 3 especially in the case of polyvinylpyrrolidone.
Those having a molecular weight of 60,000, 160,000, 40,000 and 10,000 are commercially available, and it is convenient to use this, but of course other molecular weights may be used. However, since one of the reasons for adding the hydrophilic polymer (II) is a thickening effect,
The higher the amount added, the smaller the amount added, and the better the film-forming property. Addition amount of polyvinylpyrrolidone is 1
-20% by weight, especially 3-10% by weight is desirable, but depends on the molecular weight of the polyvinylpyrrolidone used. In general, when the amount added is too small, the film forming property is poor when the molecular weight is too low, and the polymer concentration is high, and when the polymer molecular weight is too large, washing after film formation becomes difficult. Therefore, it is also one method to mix and use those having different molecular weights by sharing the roles.

The above two polymers are mixed and dissolved in the solvent (III). Additive (IV) is added here, but especially in the case of water, the polysulfone resin has high coagulability,
15% by weight or less, preferably 1 to 12% by weight, particularly 1 to
5% by weight is desirable. It is easily presumed that the amount of addition increases when an additive having a small solidification property is used. In the present invention, since the fourth component is added, the amount of hydrophilic polymer can be reduced.

A polysulfone resin semipermeable membrane is obtained under the above conditions. A known technique may be used for the film forming operation. For a flat film, the stock solution for film formation is spread on a flat substrate and then immersed in a coagulation bath. For hollow fiber membranes,
An injection solution is used to maintain the hollow form. As for the injection liquid, spinning stability is better if it is lower than that having high coagulability with respect to the membrane-forming stock solution, but the correlation between the coagulation bath temperature, phase separation temperature and spinneret temperature causes Since the smoothness changes, the best composition may be determined appropriately. Inactive hydrocarbons such as decane, octane, and undecane may be used for the polysulfone-based resin. Alternatively, a hollow form may be maintained by injecting gas. The dry length is 0.1 to 20 cm, and especially 0.
The spinning stability of 5 to 5 cm is good and more desirable. When membranes are formed with the same composition and under the same conditions, the diameter of the pores formed on the surface tends to be larger in the flat membrane than in the hollow fiber membrane.

The polysulfone-based resin semipermeable membrane obtained by such a method is prepared by leaving a hydrophilic polymer in the membrane.
Water wettability can be improved. However, when the residual hydrophilic polymer is water-soluble, it has the drawback that elution of the hydrophilic polymer is unavoidable and that it is difficult to obtain high water permeability for the pore size. The present invention sufficiently compensates for this drawback. First, the obtained polysulfone-based semipermeable membrane is crosslinked by irradiating the polysulfone-based resin with a radiation that does not cause deformation, deterioration, or impracticality. The water-insolubilization treatment of the hydrophilic polymer is carried out. The polysulfone-based resin semipermeable membrane may have any form as long as the treatment can be performed regardless of whether it is a flat membrane or a hollow fiber membrane. In addition, radiation processing here means α rays,
β-rays, γ-rays, X-rays and electron rays can be mentioned, but γ-rays are most preferable from the viewpoint of substance permeability.

For the radiation treatment, particularly for the γ-ray treatment, it is most preferable to perform the γ-ray irradiation with the semipermeable membrane wet with water. The dose is preferably 0.5 Mrad to 50 Mrad, and particularly from the viewpoint of maintaining the mechanical properties of the semipermeable membrane,
Preference is given to 0.5 Mrad to 10 Mrad.

The polysulfone resin semipermeable membrane of the present invention was evaluated as follows based on the artificial organ standard eluate test method.

The solution prepared by heating 0.5 g of the film with 50 cc of hot water at 70 ° C. for 1 hour had a UV absorption of 0.1 or less at a wavelength of 350 to 220 μm and a consumption of 0.01N KMnO ₄ aqueous solution of 1.
It shows 0 ml or less and can pass the test.

[0022]

The present invention will be described in more detail by the following examples.

The measuring methods used are as follows.

In the case of a water-permeable hollow fiber membrane, the hollow fiber membrane is inserted into a glass case having holes for reflux liquid at both ends, and a small module is prepared using a commercially available potting agent, and the temperature is set to 37 ° C. The water permeation performance was measured by a method in which water pressure was applied to the inside of the hollow fiber and the water was permeated to the outside through the membrane for a certain period of time, and was calculated from the effective membrane area and the transmembrane pressure difference.

Example 1 15 parts of polysulfone, polyvinylpyrrolidone (K90)
80 parts of water and 2.4 parts of water to 75 parts of dimethylacetamide
It melted by heating at ℃. This stock solution for film formation became a low temperature dissolution type stock solution that phase-separated at 65 ° C. Dimethyl sulfoxide / glycerin / polyvinylpyrrolidone (K30) =
63/7/30, outer diameter 1.0 mm, inner diameter 0.7 mm
It is discharged from the mouth hole consisting of the annular orifice of, and passed through a coagulating bath with water kept at 80 ° C, which is installed 1.0 cm below the surface of the mouth. Got The base was kept warm at 49 ° C. When the membrane was subjected to γ-ray irradiation treatment of 2.5 Mrad, the water permeability was 4800 ml / hr / m ² / mmHg, and the absorbance of the eluate was 0.0
It was 98.

Comparative Example 1 The water permeability of the hollow fiber membrane of Example 1 measured without γ-ray irradiation was 730. The absorbance of the eluate is
It was 1.58.

[0027]

The treatment of the present invention makes it possible to obtain a semipermeable membrane having extremely high water permeability without elution of the blended hydrophilic polymer. Further, it can be easily developed for use as a completely dry membrane due to its good water wettability, which recovers the water permeability by simply immersing it in water under normal pressure. Also, this effect lasts almost permanently.

Since the polysulfone-based resin semipermeable membrane obtained by this treatment is strong against clogging and dirt, it can be used for general industrial applications and reverse osmosis membranes to high-performance ultrafiltration membranes (or microfiltration membranes). It can be used as a blood treatment membrane in the medical field.

Claims (2)

[Claims] 1. A semipermeable membrane of polysulfone resin produced by using a solution prepared by mixing and dissolving a polysulfone resin and a hydrophilic polymer with an additive which is a nonsolvent or a swelling agent to the polysulfone resin as a stock solution for film formation. A method for treating a polysulfone-based resin semipermeable membrane, which comprises cross-linking the hydrophilic polymer by subjecting the membrane to radiation treatment. 2. The method for treating a polysulfone-based resin semipermeable membrane according to claim 1, wherein the hydrophilic polymer is polyvinylpyrrolidone or polyethylene glycol.