JP2001149763A - Semipermeable membrane and production method for semipermeable membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semi-permeable membrane having a mesh-like constitutional structure without adding a pore opening agent. SOLUTION: Polysulfone resin (A) and polyether-sulfone resin (B) are dissolved in a ratio to obtain 0.25-4 mixing weight ratio (A/B), and a membrane body is formed in a coagulation liquid by using the obtained membrane-forming raw liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semipermeable membrane and a method for producing the same, and more particularly to blood purification for the treatment of renal diseases or drug intoxication, particularly for use in hemofiltration or hemodiafiltration. The present invention relates to a semipermeable membrane and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, semipermeable membranes have been used, for example, in the industrial field for concentration and purification of beer, juice, milk, etc., desalination of seawater, wastewater treatment, etc. Used in As the material of the semipermeable membrane, cellulose, cellulose acetate, polyacrylonitrile, polymethyl methacrylate, ethylene-vinyl alcohol copolymer, polyamide and the like are used. Furthermore, polysulfone resins developed as engineering plastics have also been used as semipermeable membrane materials because of their thermal stability, chemical resistance, and good biocompatibility.

In general, in order to produce a semipermeable membrane having excellent water permeability, it is required that the membrane surface be prevented from being extremely densified and a structure that does not hinder the water permeability in the thickness direction of the membrane. You. That is, the cross-sectional structure in the thickness direction is desirably a network structure having a small number of continuous through pores that hinder substance permeation, a so-called fibril structure,
It is important not to form a void structure in which the polymer is largely missing or a sponge structure having few through-pores. However, a semipermeable membrane formed from the above-mentioned polysulfone-based resin tends to have a remarkably dense structure on the membrane surface. Further, in the structure in the cross-sectional direction of the semipermeable membrane, the above-described void structure and sponge structure are easily formed. This is considered to be due to the strong intermolecular cohesion of the polysulfone resin. For this reason, a semipermeable membrane made of a single polysulfone-based resin is likely to cause problems such as low liquid permeability, voids penetrating the surface, and low mechanical strength.

[0004] In order to solve such a problem, a pore-forming agent is further added to a solution obtained by dissolving a single resin in a solvent to prepare a stock solution, and a semipermeable membrane is formed from the stock solution. That is being done. As for the above-mentioned polysulfone-based resin, hydrophilic polymers such as polyvinylpyrrolidone and polyethylene glycol are used as pore-forming agents suitable for the polysulfone-based resin. The fibril structure is formed by controlling the surface structure and the cross-sectional structure of the membrane by adding an appropriate amount of such a pore-forming agent (2 to 10% by weight in the film-forming stock solution).

[0005]

When such a pore-forming agent is added, it is essential to remove the pore-forming agent after film formation. Here, it is often thought that hydrophilic polymers such as polyvinylpyrrolidone used as a pore-forming agent can be easily removed by washing with water, but in fact, when the molecular weight of the hydrophilic polymer increases, a semipermeable membrane is used. Very difficult to remove. Therefore, an insolubilizing treatment such as radiation irradiation or heat treatment is performed to crosslink and insolubilize the pore-forming agent that cannot be completely removed by the water washing treatment.

However, when this insolubilization treatment is performed,
Equipment for performing the insolubilization treatment is required, and further, a new problem that the manufacturing process becomes complicated occurs. Further, the amount of the opening agent required to control the pore size is relatively large, generally about 2 to 10% by weight. For this reason, there is a case where a small amount of water cannot be completely removed by the water washing treatment and remains on the semipermeable membrane. When a certain amount or more of the pore-forming agent remains, the efficiency of the insolubilization treatment is reduced to 1 at present.
Since it is not expected to be 00%, all the remaining pore-forming agents cannot be insolubilized, and the pore agents that cannot be completely insolubilized may be eluted from the semipermeable membrane.

The present invention has been proposed in view of such circumstances, and has as its object to obtain a semipermeable membrane having a network structure without adding a pore-forming agent.

[0008]

According to a first aspect of the present invention, there is provided a polysulfone resin comprising a polysulfone resin (A) and a polyethersulfone resin (B). Weight ratio (A /
B) is 0.25 to 4, and has a network-like structure having continuous through holes in the thickness direction of the membrane.

According to a second aspect of the present invention, the polysulfone resin has the formula (1)

Embedded image Wherein the polyethersulfone resin has a repeating unit represented by the formula:

Embedded image The semipermeable membrane according to claim 1, which is a resin having a repeating unit represented by the following formula:

According to a third aspect of the present invention, the polysulfone resin (A) and the polyethersulfone resin (B) are mixed at a mixing weight ratio (A / B) of the polysulfone resin and the polyethersulfone resin of 0.25. Dissolved at a rate of ~ 4,
A method for producing a semipermeable membrane, characterized in that a membrane is formed in a coagulation solution using the obtained membrane-forming stock solution.

[0011]

Embodiments of the present invention will be described below. The semipermeable membrane of the present invention uses a polysulfone resin and a polyether sulfone resin as main membrane materials. As the polysulfone resin, a resin having a repeating unit represented by the following formula (1) can be suitably used. This polysulfone resin has been used for many years as a blood purification membrane used in blood purification therapy, and its safety has been established. Equation (1)

Embedded image

Here, R1 and R2 have 1 to 1 carbon atoms.
5 lower alkyl groups, for example, a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group. Preferred R1
And R2 are methyl groups. These R1 and R2
May be the same or different. The polysulfone resin is not particularly limited as long as the repeating unit represented by the formula (1) is the main repeating unit, and may contain another repeating unit as long as the object of the present invention is not impaired.

As the above polyether sulfone resin, a resin having a repeating unit represented by the following formula (2) can be preferably used. In addition, this polyether sulfone resin has also been used for many years as a blood purification membrane used in blood purification therapy, and its safety has been established. Equation (2)

Embedded image

The polyether sulfone resin is not particularly limited as long as the repeating unit represented by the formula (2) is the main repeating unit, and may contain other repeating units as long as the object of the present invention is not impaired. Is also good.

The production of the semipermeable membrane is performed by using a stock solution prepared by dissolving the polysulfone resin and the polyethersulfone resin in an organic solvent, and coagulating the stock solution in a coagulating solution. Next, a method for manufacturing a semipermeable membrane will be described.

First, a stock solution is prepared. Here, a polysulfone resin (A) and a polyether sulfone resin (B) are dissolved in an organic solvent at a mixing weight ratio of (A / B) = 0.25 to 4 to prepare a stock solution for film formation. I do.
Here, if the mixing weight ratio (A / B) is out of the range of 0.25 to 4, the cross section of the manufactured semipermeable membrane has, for example, a sponge structure.

The organic solvent is not particularly limited as long as it is a good solvent for the polysulfone resin and the polyethersulfone resin. For example, tetrahydrofuran, dioxane, dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone (hereinafter, referred to as NMP) can be given. Among these organic solvents, NMP is preferred.

Then, the ratio of the mixture of the polysulfone resin and the polyether sulfone resin is set to, for example, 15% by weight, and the ratio of the organic solvent is set to, for example, 85% by weight. Each resin is dissolved in the organic solvent to prepare a stock solution for film formation. The temperature of the organic solvent during this dissolution is usually 30 to 100 ° C, preferably 50 to 80 ° C.

For the purpose of imparting hydrophilicity to the semipermeable membrane,
A trace amount in the stock solution (less than 1.0% by weight in the stock solution)
May be added.

After the stock solution is prepared, the stock solution is discharged from a nozzle and solidified in a coagulating solution to produce a semipermeable membrane having a predetermined shape. This semipermeable membrane can be manufactured in any shape, for example, a flat membrane, a tube, or
It can be made into a hollow fiber shape.

Here, in order to produce a semipermeable membrane having a uniform fibril structure, it is preferable to use a mixed liquid of an organic solvent and water as a coagulating liquid. As the organic solvent used for the coagulation liquid, the organic solvent used for dissolving the resin can be suitably used. For example, tetrahydrofuran, a good solvent for resins,
Dioxane, dimethylformamide, dimethylacetamide, NMP and the like can be used. Among these organic solvents, NMP is preferred. In addition, even if the organic solvent used for the coagulation liquid is different from the organic solvent used for dissolving the resin, a semipermeable membrane having the above structure can be produced. When the proportion of water in the coagulating liquid is too large, a void structure is easily generated in the thickness direction of the film. On the other hand, if the proportion of water is too small, the through-pores become too thick and too coarse, and a long time is required for solidifying the resin, making film formation difficult. Considering this point, the proportion of water in the coagulation liquid is preferably 30 to 80% by weight.

Further, for the purpose of adjusting the coagulation rate, methanol, ethanol, isopropanol,
Alcohols such as glycerin and glycols such as ethylene glycol and propylene glycol may be added.

When a hollow fiber-shaped semipermeable membrane is produced, it is preferable to use the same liquid as the coagulating liquid as the core liquid.

In the semipermeable membrane manufactured as described above,
It was confirmed by observation that it had a two-layer structure composed of a skin layer formed near the film surface and a support layer supporting the skin layer. As for the skin layer, it was confirmed that the cross-sectional structure in the thickness direction formed a network-like structure (so-called fibril structure) having continuous through-pores that hardly hinder the permeation of the substance. The reason that the fibril structure could be formed is considered to be that the coagulation state of the entire system could be appropriately controlled by changing the mixing ratio of these two resins having different coagulation rates. That is, polysulfone resin and polyethersulfone resin, which have different aggregation speeds, are used.
When the two types of resins are mixed and formed into a film, the two resins agglomerate at different rates. Here, when the mixing ratio of the resins is set to a specific ratio, unlike the case of using a single resin that can only have a certain coagulation speed, the difference in the cohesion speed of both resins results in a continuous in the thickness direction of the film. It is believed that through pores are formed.

In this semipermeable membrane, a fibril structure can be formed without adding a pore-forming agent to the stock solution. Therefore, it is not necessary to wash and remove the pore-forming agent after the film is formed. Thereby, simplification of manufacturing equipment and simplification of a manufacturing process can be achieved. Since no pore-forming agent is used, the pore-forming agent does not elute from the semipermeable membrane. Therefore, a highly safe semipermeable membrane can be manufactured as a medical separation membrane such as a blood purification membrane. Furthermore, since the semipermeable membrane uses a polysulfone resin and a polyethersulfone resin, which have been used as medical separation membranes, as membrane materials, a highly safe separation membrane for medical use can be provided.

[0026]

Next, the present invention will be described more specifically by showing embodiments of the present invention. Here, each of the following samples manufactured by changing the mixing ratio of the polysulfone resin and the polyether sulfone resin will be described.

(Sample 1) The polysulfone resin of the above formula (1) and the polyether sulfone resin of the above formula (2) were added to NMP (N-methyl-2-pyrrolidone),
The solution was dissolved while heating to prepare a film-forming stock solution. here,
The mixing weight ratio of the polysulfone resin (A) and the polyethersulfone resin (B) was set to 1.5: 13.5 (A / B =
0.11). In addition, the ratio of the mixed resin is 15% by weight.
The ratio of NMP as an organic solvent was set to 85% by weight. Next, this film forming stock solution was cast on a smooth glass substrate, and immediately, this was mixed with 50% by weight of water and 50% by weight of NMP.
In the coagulation liquid whose liquid temperature has been adjusted to about 25 ° C.
The gel was formed by immersion for minutes. Thereafter, the gel was left in running water for about 1 hour to completely remove the solvent, thereby forming a film. Then, the surface and cross section (thickness direction) of the obtained film body were observed with a scanning electron microscope. Table 1 shows the test results.

(Sample 2) The mixing weight ratio of the polysulfone resin (A) and the polyether sulfone resin (B) was set to 3.
A stock solution was prepared at a ratio of 5: 11.5 (A / B = 0.30), and a membrane was prepared from the stock solution. The other conditions were the same as those of Sample 1. Then, the surface and cross section (thickness direction) of the obtained film body were observed with a scanning electron microscope. Table 1 shows the test results.

(Sample 3) The mixing weight ratio of the polysulfone resin (A) and the polyethersulfone resin (B) was 7.
5: 7.5 (A / B = 1.00) to prepare a membrane-forming stock solution, and a membrane was prepared from this membrane-forming stock solution. The other conditions were the same as those of Sample 1. Then, the surface and cross section (thickness direction) of the obtained film body were observed with a scanning electron microscope. Table 1 shows the test results.

(Sample 4) The mixing weight ratio of the polysulfone resin (A) and the polyether sulfone resin (B) was 11.
5: 3.5 (A / B = 3.29) to prepare a membrane-forming stock solution, and a membrane was prepared from this membrane-forming stock solution. The other conditions are the same as those of the sample 1. Then, the surface and cross section (thickness direction) of the obtained film body were observed with a scanning electron microscope. Table 1 shows the test results.

(Sample 5) The mixing weight ratio of the polysulfone resin (A) and the polyether sulfone resin (B) was 13.
A stock solution was prepared at 5: 1.5 (A / B = 9.00), and a membrane was prepared from the stock solution. The other conditions are the same as those of the sample 1. Then, the surface and cross section (thickness direction) of the obtained film body were observed with a scanning electron microscope. Table 1 shows the test results.

[0032]

[Table 1]

As a result of microscopic observation, regarding Samples 2, 3, and 4, no pores exceeding 0.05 μm were observed on the surface of the membrane, and the membrane was smooth. In each of these samples, the cross section in the thickness direction of the film had a uniform fibril structure. On the other hand, Samples 1 and 5 had a so-called sponge structure having almost no through pores or very few through pores.

From these results, the polysulfone resin (A) and the polyether sulfone resin (B)
It can be understood that a semipermeable membrane having a fibril structure can be produced by appropriately adjusting the mixing weight ratio (A / B) of the above.

When comparing Sample 1 and Sample 2, the film of Sample 1 (A / B = 0.11) has a sponge structure, and Sample 2 (A / B = 0.31).
In (0), a semi-permeable membrane having a fibril structure is obtained. That is,
It can be seen that the lower limit of the mixed weight ratio (A / B) of both resins is in the range of 0.11 to 0.30. In addition, comparing Sample 4 with Sample 5, Sample 4 (A / B
= 3.29), a fibril-structured semipermeable membrane is obtained, and in sample 5 (A / B = 9.00), the membrane has a sponge structure. That is, the mixing weight ratio of both resins (A / B)
It can be seen that the upper limit of is within the range of 3.29 to 9.00.

As described above, by setting the mixture weight ratio (A / B) of the polysulfone resin (A) and the polyethersulfone resin (B) in the stock solution for film formation within the range of 0.25 to 4.00, fibril is obtained. It is considered that a semipermeable membrane having a structure can be produced. Further, the mixing weight ratio (A / B) is set to 0.30.
When it is set in the range of (Sample 2) to 3.29 (Sample 4), it is possible to reliably produce a semipermeable membrane having a fibril structure. Further, when the mixing weight ratio (A / B) is set to 1.00 (sample 3), the production of a semipermeable membrane having a fibril structure can be performed more reliably.

[0037]

As described above, according to the present invention, the following excellent effects are exhibited. According to the invention described in claim 1 and claim 3, the polysulfone resin and the polyether sulfone resin are dissolved in a mixing weight ratio of the polysulfone resin and the polyether sulfone resin of 0.25 to 4, Since the membrane was formed in the coagulation solution using the obtained membrane-forming solution, a network-like structure having continuous through holes in the thickness direction of the film was formed without adding a pore-forming agent to the membrane-forming solution. Can be.

Therefore, it is not necessary to wash and remove the pore-forming agent after the film formation. Thereby, simplification of manufacturing equipment and simplification of a manufacturing process can be achieved. Further, the pore-forming agent does not elute from the semipermeable membrane. Therefore, a highly safe semipermeable membrane can be provided as a medical separation membrane such as a blood purification membrane.

According to the second aspect of the present invention, a polysulfone resin and a polyethersulfone resin, which have been established as safe separation membranes for medical use, are used as membrane materials.
A highly safe semipermeable membrane can be provided as a medical separation membrane.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidehiko Sumi 3-1 Hokuyodai, Kanazawa-shi, Ishikawa Nikkoso Co., Ltd. Kanazawa Seisakusho Co., Ltd. (72) Inventor Masashi Yoshida 3-1 Hokuyodai, Kanazawa-shi, Ishikawa Nikkiso Kanazawa Seisakusho F-term (reference) 4D006 GA07 GA13 MA01 MA02 MA03 MA25 MA28 MC62X MC63X NA04 NA05 NA16 NA17 PC47

Claims (3)

[Claims] 1. A membrane comprising a polysulfone resin (A) and a polyethersulfone resin (B), wherein the mixing weight ratio (A / B) of the polysulfone resin and the polyethersulfone resin is 0.25 to 4, A semipermeable membrane having a network structure having through holes continuous in the thickness direction of the semipermeable membrane. 2. The polysulfone resin has the formula (1) Wherein the polyether sulfone resin is a resin having a repeating unit represented by the following formula (2): The semipermeable membrane according to claim 1, which is a resin having a repeating unit represented by the following formula: 3. A polysulfone resin (A) and a polyethersulfone resin (B) having a mixing weight ratio (A / B) of the polysulfone resin and the polyethersulfone resin of 0.
A method for producing a semipermeable membrane, comprising dissolving at a ratio of 25 to 4 and forming a membrane in a coagulation solution using the obtained membrane-forming stock solution.