JPS6397205A - Treatment of polysulfone resin semipermeable membrane - Google Patents

Abstract

PURPOSE:To obtain a semipermeable membrane having high water permeability without elution of a blended polymer by applying heat treatment and radiation treatment to a specified polysulfone resin semipermeable membrane. CONSTITUTION:A membrane forming soln. is basically prepared from four components: a polysulfone resin (I); a polymer (II) compatible with the resin (I), hydrophilic, and consisting of polyvinyl pyrrolidone, etc.; a solvent (III) capable of dissolving the resin (I) and the polymer (II) and consisting of dimethyl sulfoxide, etc.; an additive (IV) compatible with the solvent (III), used as a good solvent for the polymer (II) and as the nonsolvent or swelling agent for the resin (I), and consisting of water, etc. Heat treatment and radiation treatment are applied to the polysulfone resin semipermeable membrane produced from the soln. the heat treatment must be carried out at 170 deg.C for about 1-10hr when the polyvinyl pyrrolidone is a hydraulic polymer. Besides, the dosage is preferably controlled to 0.5-50Mrad in the radiation treatment, especially in the gamma-ray treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for treating polysulfone resin semipermeable membranes.

[Conventional technology]

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 resistance, 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. Therefore, the molecular weight cut-off is 1
Only those that are as small as 0,000 or less and have low water permeability have 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. 48-176, Japanese Unexamined Patent Publication No. 1444.5/1973
Publication No. 6, Publication No. 57-50506, Publication No. 57-505
(No. 07, No. 57-50508) (2) A method that includes extraction and elution operations after film formation. (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. (Unexamined Japanese Patent Publication No. 56-'15405"
IN Publication, No. 59-58041, No. 59-183
No. 761, No. 59-189903 @ Publication) ■ A method of using ingenuity during spinning (Japanese Unexamined Patent Publication No. 59-2280)
(No. 16 Publication) However, the method (2) only utilizes the difference in solidification rate between polymers, and has not been able to obtain large pores larger than 10,000 molecules. Moreover, since a large amount is blended, the original good performance of the polysulfone resin is likely to be lost.

Furthermore, method (2) is broadly classified into two methods: extraction of the blend polymer and elution of the inorganic granules. In the former, polyethylene glycol and polyvinylpyrrolidone are the main polymers, but it has been difficult to obtain a sufficient pore size and to perform extraction operations.

In the latter example, in the above-mentioned Japanese Patent Application Laid-open No. 58-91822,
After forming a film by mixing silica powder, it was eluted using an alkali to create large pores of 0.05 μm or more, but this manufacturing method produces a film with a pore size distribution of cannot be manufactured.

Method (2) involves mixing a large amount of a polysulfone resin non-solvent or swelling agent with a film-forming stock solution, and forming a film just before the film-forming stock solution undergoes phase separation.

Such a method has the disadvantage that the temperature effect of the coagulation bath cannot be used advantageously.

Method ① involves blowing high-humidity air during film formation.
Although the pore size is enlarged on the surface, this method is effective only on one side, and especially when it comes to hollow fiber membranes, only a small molecular weight fraction can be obtained.

In particular, semipermeable membranes blended with water-soluble polymers such as polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol have problems with elution of the water-soluble polymers and swelling layers of the water-soluble polymers.

It had the disadvantage that only those with low water permeability could be used.

(Problems to be Solved by the Invention) The present inventors analyzed the above-mentioned drawbacks, and as a result of intensive study, they arrived at the present invention. 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 with extremely high water permeability without elution of blend polymers.

[Means for solving problems]

The present invention has the following configuration. That is, (1) a polysulfone resin half produced by adding an additive such as a non-solvent or a swelling agent to the polysulfone resin as a film forming stock solution to a solution in which a polysulfone resin and a hydrophilic polymer are mixed and dissolved; to the permeable membrane.

A method for treating a polysulfone-based resin semipermeable membrane, characterized by subjecting it to heat treatment and/or radiation treatment.

(2) Hydrophilic polymer is polyvinylpyrrolidone = 5
- A method for treating a polysulfone resin semipermeable membrane according to claim 1. - A method for treating a polysulfone resin semipermeable membrane according to claim 1.

The membrane-forming stock solution used in the present invention to produce a polysulfone resin semipermeable membrane basically consists of a polysulfone resin (■), a hydrophilic polymer (■), a solvent (III), and an additive (IV). It is composed of a four-component system. The polysulfone resin (I) mentioned here is not particularly limited, and may generally contain the formula (1) or (2), or may be an alkyl resin.

The hydrophilic polymer (II) is a polymer that is compatible with the polysulfone resin (I) and has hydrophilic properties. Polyvinylpyrrolidone is best, and other examples include, but are not limited to, 6-modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone, polyvinyl acetate, and polyethylene glycol.

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 can be used, and dimethylacetamide, dimethylsulfoxide, dimethylformamide, and N-methyl-2-pyrrolidone are particularly preferred.

The additive (l'V) is compatible with the solvent (III),
Anything can be used as long as it serves as a good solvent for the hydrophilic polymer (n) and as a non-solvent or swelling agent for the polysulfone resin (I), such as water, methanol, ethanol, isopropanol, hexanol, , 4-butanediol, etc. Considering production costs, water is the most desirable.

The additive (IV) may be selected in consideration of the coagulability of 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 (I) and the additive (IV) 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.

Now, it is assumed that this film-forming stock solution is in a homogeneous system at a temperature T.

In this case, the additive (IV) is shielded from the polysulfone resin (I) by the hydrophilic polymer (I[) and cannot directly interact with the polysulfone resin (I>. Therefore, the polysulfone In a system where the hydrophilic polymer (II) is not mixed, the system resin (I) naturally coagulates, and the additive (IV) is added to such a concentration that phase separation occurs.
This means that even after adding , the system remains homogeneous without phase separation. Here, when the temperature is raised, the mobility of molecules increases, especially the hydrophilic polymer (II) and the additive (
The bond with IV) becomes weaker, the hydrogen bond is broken, and the apparent concentration of the additive (IV) that is not bonded to the hydrophilic polymer (II) increases from that at temperature T.For this reason, polysulfone-based The interaction between the resin (I> and the additive (IV) ultimately causes coagulation and phase separation of the polysulfone resin (I). In other words, the membrane forming stock solution is Phase separation will occur.Furthermore, if the amount of additive (IV) in this system is increased, even at the temperature T, in this stock solution system, the hydrophilic polymer (
Since the additive (IV) is added in an amount equal to or greater than the amount of the additive (IV) held at the temperature T in II), the membrane forming stock solution undergoes phase separation. However, when the temperature is further lowered, the molecular mobility of the hydrophilic polymer (II) decreases, the amount of binding with the additive (IV) increases, and the apparent additive (IV) decreases by 1 degree, resulting in The system becomes a homogeneous system again. When the temperature is raised again, the system becomes non-uniform, but this time the hydrophilic polymer (
When adding n), the hydrophilic polymer (I[) changes to the additive (I
The amount of bonding with V> increases, and the system becomes uniform. As mentioned above, the phase separation behavior of this membrane-forming stock solution is the opposite of normal;
It also has reversibility in phase transition.

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, the polymer concentration should be lowered, preferably 5 to 20% by weight. If it is less than 5% by weight, it will not be possible to obtain a sufficient viscosity of the film-forming stock solution, making it impossible to form a film. Also, 50
If it exceeds % by weight, it becomes difficult to form through holes. Hydrophilic polymer (II), especially in the case of polyvinylpyrrolidone, is commercially available with molecular weights of 360,000, 160,000, 40,000, and 10,000, and it is convenient to use this, but of course, other molecular weights are also available. You may use the one. However, one of the reasons for adding the hydrophilic polymer (II) is its thickening effect, so the higher the molecular weight, the smaller the amount added, and the reversal of the temperature dependence of the phase separation phenomenon. This is advantageous for obtaining a membrane with high water permeability. The amount of polyvinylpyrrolidone added is 1 to 20% by weight, especially 3% by weight.
~10% by weight is desirable, but depends on the molecular weight of the polyvinylpyrrolidone used. In general, if the amount added is too small or the molecular weight is too low, it is difficult to achieve a phase separation reversal phenomenon, and if the polymer concentration is too high and the polymer molecular weight is too large, cleaning after film formation becomes 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 the solvent (III>).

Additive (IV) is added here, especially in the case of water.
Since the polysulfone resin has high coagulability, it is preferably 15% by weight or less, preferably 1 to 12% by weight, 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 fourth component is added, the amount of hydrophilic polymer can be reduced. As the concentration of additive (IV) increases, 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, to obtain high water permeability and molecular weight cutoff, it is necessary to set a low phase separation temperature to strongly promote phase separation during membrane formation. Just change the temperature setting. 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.

Under the above conditions, a polysulfone resin semipermeable membrane is obtained. A known technique may be used for the film forming operation. For flat membranes, the membrane-forming stock solution is spread on a flat substrate and then immersed in a coagulation bath. For hollow fiber membranes, an injection solution is used to maintain their hollow form. As for the injection liquid, it is better to use one with low coagulability compared to one with high coagulability compared to the membrane forming stock solution for better spinning stability, but due to the correlation with coagulation bath temperature, phase separation temperature, and die temperature, Since the smoothness changes, the best composition may be determined appropriately. Hydrocarbons such as decane, octane, and undecane, which are inert to the polysulfone resin, may also be used.

Alternatively, the hollow shape may be maintained by injecting gas. The dry length is 0.1 to 20 cm, and 0.5 to 5 cm is particularly desirable as it provides good spinning stability. When membranes are formed with the same composition and under the same conditions, the diameter of the pores formed on the surface of a flat membrane tends to be larger than that of a hollow fiber membrane.

The polysulfone-based resin semipermeable membrane obtained by this method can have improved water wettability by allowing the hydrophilic polymer to remain in the membrane. However, when the remaining hydrophilic polymer is water-soluble, it is unavoidable to elute the hydrophilic polymer, and it also has the drawback that it is difficult to obtain high water permeability relative to the pore size. The present invention fully compensates for this drawback by first irradiating the obtained polysulfone-based semipermeable membrane with heat and/or radiation to an extent that does not cause the polysulfone-based resin to be deformed, altered, or rendered unpractical. In this way, the hydrophilic polymer is treated to become water insolubilized by heat and/or radiation. The polysulfone resin semipermeable membrane may have any form, whether flat membrane or hollow fiber membrane, as long as it can undergo such treatment. Furthermore, the radiation treatment referred to here includes α rays, β rays, γ rays, X rays, and electron beams, but γ rays are most desirable from the viewpoint of material penetration.

When polyvinylpyrrolidone is a hydrophilic polymer, the heat treatment needs to be carried out at 170'C for 1 hour or more and about 10 hours. If it is less than 1 hour, insolubilization is insufficient, and 1
If the time exceeds 0 hours, the process will be disadvantageous. Preferably it is 3 to 8 hours.

Setting the temperature to 180℃ will shorten the processing time, starting from 20 minutes.
About 8 hours is fine. More preferably, it is 3 to 5 hours. If the temperature is further increased, the processing time will be further shortened, but care must be taken since the polysulfone resin itself may be deformed. On the other hand, if the temperature is lowered, the insolubilization of the hydrophilic polymer may not progress and it takes too long for 2 hours, which is not practical.

Regarding radiation treatment, particularly gamma ray treatment, it is most preferable to irradiate gamma rays while the semipermeable membrane is wet with water, but even in a dry state there is moisture in the air, so this is not possible. The dose is preferably from 0.5 Mrad to 5Q Mrad, and especially from the viewpoint of maintaining the mechanical properties of the semipermeable membrane, Q, 5 Mrad
to 10 Mrad is preferred.

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

A solution obtained by heating a 0.5C membrane with 50CC of 70'C hot water for 1 hour has 0 UV absorption at a wavelength of 350 to 220 μm.
．． 1 or less, 0.01 N K) Indicates a consumption of ln04 aqueous solution of 1.0 ml or less, and can pass the test.

Furthermore, what is surprising here is that the treated semipermeable membrane not only solves the problem of eluates, but also has dramatically improved water permeability, and, considering its average pore size, when blood is passed through it, for example. It also has the excellent feature of less clogging of red blood cells and various proteins. In the heat treatment, it is also possible to intentionally apply heat higher than the heat deformation temperature of the polysulfone resin to slightly reduce the pore diameter to adjust the fractionated molecular teeth.

〔Example〕

The invention will be explained in greater detail by the following examples.

The measurement method used is as follows.

(1) In the case of a water-permeable hollow fiber membrane, the hollow fiber membrane is inserted into a glass case with holes for reflux liquid at both ends, and a small module is made using a commercially available botting agent. Water permeability was measured using a method in which water pressure was applied to the inside of the hollow fiber while maintaining the temperature at °C, and the water permeability was calculated from the amount of water that permeated to the outside through the membrane over a certain period of time, the effective membrane area, and the pressure difference between the membranes.

In the case of a flat membrane, measurements were made in the same manner using a stirred cylindrical cell. The unit was unified to ml/m2@hr 6 mmHo.

Example 1 Polysulfone (Needel P-3500>15 parts, polyvinylpyrrolidone (K2O) 8 parts, 1,4-butanediol 8 parts were added to 69 parts of dimethylacetamide, and 80'C
It was heated and dissolved. This membrane-forming stock solution became a low-temperature solution that undergoes phase separation at 60'C.

The mixture was spread on a glass plate at 60'C using a Beichiro one-set applicator, and then coagulated in a water coagulation bath at 50°C. This was heat-treated at 170°C for 5 hours to make polyvinylpyrrolidone insoluble in water. Water permeability 48000ml/Tr12
e hr I mmH (], the eluate also has an absorbance of 0.08
It was 5.

Examples 2-6 15 parts of polysulfone, polyvinylpyrrolidone (K2O)
8 parts, 2 parts of water and 4 parts of dimethylacetamide to 75 parts of dimethylacetamide.
The mixture was heated and dissolved at °C. This membrane-forming stock solution became a low-temperature solution that undergoes phase separation at 65°C. Dimethyl sulfoxide/glycerin/polyvinylpyrrolidone (K2O
) = 63/7/30, outer diameter 1.0 mm, inner diameter 0
．． It is discharged from the mouth hole consisting of a 7 mm annular orifice, and 1. The mixture was passed through a coagulation bath with water maintained at 80° C. placed below the Qcm, washed with water in the usual manner, and then wound into a skein to obtain a hollow fiber membrane. The cap was kept warm at 49°C. Table 1 below shows the post-treatment method, water permeability, and absorbance of the eluate.

17 Example 7 Polyether sulfone (Pictrex 300P) 15
8 parts of polyvinylpyrrolidone (K2O) and 9 parts of water were dissolved in 75 parts of dimethylacetamide by heating at 1°O'C. This membrane-forming stock solution became a low-temperature solution that undergoes phase separation at 55°C. This was spun in the same manner as in Example 2 to obtain a hollow fiber membrane. This was heat treated at 190'C for 3 hours, and the water permeability was measured to be 9500, and the absorbance of the eluate was also 0.054.

Comparative Example 1 When the water permeability of the flat membrane of Example 1 was measured without heat treatment, it was 8.
It was 30. Moreover, the absorbance of the eluate was 1.03.

Comparative Example 2 The water permeability of the hollow fiber membranes of Examples 2 to 6 without heat treatment was measured and found to be 730. In addition, the absorbance of the eluate is 1.
It was 58.

Comparative Example 3 12 parts of polysulfone and 6 parts of polyvinylpyrrolidone were mixed with N-
The mixture was added to 82 parts of methylpyrrolidone and dissolved by heating. This stock solution was kept warm at 50'C, and a film was formed in the same manner as in Example 1. This was heat-treated at 170'C for 15 hours to make polyvinylpyrrolidone insoluble in water.

The water permeability was substantially O.

Comparative Example 4 The water permeability of the hollow fiber membrane of Example 7 without heat treatment was measured and found to be 640. In addition, the absorbance of the eluate was 2.08
Met.

〔Effect of the invention〕

By carrying out the treatment of the present invention, a semipermeable membrane with extremely high water permeability can be obtained without elution of the blended hydrophilic polymer. Furthermore, due to its good water wettability, which allows it to recover water permeability simply by immersing it in water at normal pressure, it can easily be used as a completely dry membrane. Moreover, this effect lasts almost permanently.

The polysulfone resin semipermeable membrane obtained by this treatment is
Because it is resistant to clogging and dirt, it can be used as blood component separation membranes in general industrial applications and in the medical field, from reverse osmosis membranes to high-performance ultrafiltration membranes (or microfiltration membranes).

Claims (2)

[Claims] (1) A polysulfone resin semipermeable membrane prepared by adding a non-solvent or a swelling agent additive to the polysulfone resin to a mixed solution of a polysulfone resin and a hydrophilic polymer as a membrane forming stock solution. , heat treatment and/or
A method for treating a polysulfone-based resin semipermeable membrane, characterized by subjecting it to radiation treatment. (2) The method for treating a polysulfone resin semipermeable membrane according to claim 1, wherein the hydrophilic polymer is polyvinylpyrrolidone.