JPH01115407A - Semipermeable membrane and its production - Google Patents

Abstract

PURPOSE:To obtain the title semipermeable membrane having open cells in its thickness direction and having reticular structure without requiring an additive, etc., by forming the membrane from a mixture contg. a specified weight ratio of polyaryl resin and polysulfone resin. CONSTITUTION:(A) The polyaryl resin having a repeating unit shown by formula I or (B) the polysulfone resin having a repeating unit shown by formula II or III are mixed in the weight ratio A/B=0.1-10 (in the formulas I-III, R<1>-R<4> are a 1-5C lower alkyl group). The mixture is dissolved in a solvent such as N-methylpyrrolidone to obtain a membrane forming soln., the soln. is cast on a glass sheet, the sheet is immediately dipped in the liq. coagulant consisting of water, N-methylpyrrolidone, etc., to gel the soln., the gel is washed with water to remove the solvent, and a membrane is formed. The semipermeable membrane thus obtained has the pores having <=0.05mum pore diameter on the surface, and forms fibrillar structure in the cross-sectional direction of the membrane.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a semipermeable membrane and a method for manufacturing the same.

More specifically, the present invention relates to a semipermeable membrane made of a mixture of polyarylate resin and polysulfone resin, and a method for producing the same.

[Prior art and its problems] 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., and in the medical field, semipermeable membranes have been used for 1 artificial dialysis machine, Used in plasma separators, etc.

As the material for the semipermeable membrane, cellulose, cellulose acetate, polyacrylonitrile, polymethyl methacrylate, ethylene-vinyl alcohol copolymer, polyamide, etc. have been used. Furthermore, materials developed as engineering plastics such as polysulfone resin, polyethersulfone resin, and polyarylate resin are also used as semipermeable membrane materials due to their thermal stability, chemical resistance, and good biocompatibility. It's starting to look like this.

In general, in order to form a semipermeable membrane with excellent water permeability using a single polyarylate or polysulfone resin, it is necessary to suppress significant densification of the surface and create a cross-sectional structure that does not impede water permeability. required. In other words, it is desirable that the cross-sectional structure in the thickness direction be a so-called fibrillar structure, which is a network structure with continuous through-holes that does not hinder the permeation of substances, i.e., a void structure or a so-called sponge structure with few through-holes. It is important not to form

However, when a membrane-forming stock solution is prepared by dissolving a single polyarylate resin or a single polysulfone resin in an organic solvent, and a specified membrane in the form of a flat membrane or hollow fiber is manufactured, these resins exhibit intermolecular Due to the strong cohesive force, the membrane surface has a very dense structure, and the structure in the cross-sectional direction of the membrane tends to form a void structure or sponge structure in which a large amount of polymer is missing.These membranes also have low water permeability. Film defects such as voids penetrating the surface also appear, and the mechanical strength is also low.

Therefore, various methods have been employed to solve these problems.

Examples include conventional methods of adding additives to a single resin and its solvent, or adding non-solvents or swelling agents.

The additives used include metal salts such as lithium chloride and calcium chloride, and water-soluble polymers such as polyvinylpyrrolidone, polyvinyl acetate, and polyethylene glycol. Non-solvents or swelling agents include water, methanol, ethanol, inpropatol, ethylene glycol, etc. These additives, non-solvents, 1
1. By adding an appropriate amount of lubricant, etc.! The surface structure of I,
It is known that the cross-sectional structure can be controlled. When the above-mentioned additives are added, it is essential to remove them after 5yfj.

However, since all of the above-mentioned additives are water-soluble, it is thought that they can be easily removed by washing with water, but in reality, as their molecular weight increases, it becomes extremely difficult to remove them from the semipermeable membrane, and they remain. When used in the medical field, it is undesirable to add additives, as this can easily cause problems.

In particular, when using a single polyarylate resin, the solubility of the resin is poor, so adding additives, non-solvents, and swelling agents will further reduce the solubility and make the film-forming stock solution unstable. In some cases, gelation occurs over time and the solution can no longer be used as a membrane forming stock solution.

The present invention was completed under these circumstances.

That is, an object of the present invention is to provide a stable semipermeable membrane and a method for producing a semipermeable membrane by forming a membrane using a mixture of two types of membranes mixed at a predetermined ratio without adding any additives or the like. It is about providing.

By the way, JP-A-59-127602 discloses that a gas-selective permeable membrane is composed of an aromatic polyester having a repeating unit represented by the formula: and at least one polymer having a repeating unit represented by the formula: A gas-selective permeable membrane comprising a mixture is disclosed.

According to the above publication, the structure of the gas-selective permeable membrane has an average pore diameter of o, ooi to 0. It is said to have an asymmetric pore size structure with a dense layer that is OIILm, and its specific structure is a void structure in which the inner pores extend perpendicularly to the membrane surface to the bottom surface, and are regularly arranged. The sponge structure of the wall that partitions the inner hole is also more dense. That is, the structure of the gas-selective permeable membrane is not a uniform fibrillar structure in that it has an asymmetric pore size structure and that it has a void structure in which the inner pores have grown into elongated shapes.

This is presumed to be due to the method of coagulating the film-forming stock solution by immersing it in a solvent or water, or by heating the film-forming stock solution after casting to partially evaporate the solvent.

The above publication relates to a gas-selective permeable membrane, and according to the description in the publication, as the mixing ratio of the aromatic polyester and the polymer approaches 1, the average pore diameter increases and the surface dense layer is also disturbed. Although the gas permeability increases, the gas selective permeability decreases. This is said to be due to the maximum decrease in miscibility between different types of polymers, and the mixing ratio is 1:
It is clearly stated that it is not desirable near construction sites.

[Means for achieving the above-mentioned object] In order to achieve the above-mentioned object, the present inventor conducted extensive research and arrived at the present invention.

That is, the first aspect of the present invention for achieving the object of the present invention
The composition includes a poly7-arylate resin (A) and a polysulfone resin (B), and the mixing weight ratio (A)/(B) of the polyarylate resin (A) and polysulfone resin (B) is 0.1. ~1O, and is a semipermeable membrane characterized by having a network structure with continuous through holes in the thickness direction of the membrane. The mixing weight ratio (A) of the resin (B) and the polyarylate resin (A) and polysulfone resin (B)
/(B) is dissolved in an organic solvent at a ratio of 0.1 to 1O, and the obtained film-forming stock solution is used to form a film body with a coagulating liquid containing water and an organic solvent. This is a method for manufacturing a permeable membrane.

The semipermeable membrane according to the present invention is produced by using a membrane-forming stock solution obtained by dissolving a mixture of a polyarylate resin and a polysulfone resin at a specific mixing ratio without using any additives, nonsolvents, swelling agents, etc., using a specific coagulation liquid. It can only be produced by solidifying it, and its structure is symmetrical and fibrillar, making it extremely stable. Flow is less obstructed by the membrane support layer,
It is ideal for semi-permeable membranes.

Next, the semipermeable membrane according to the present invention will be described in detail along with the method for manufacturing the semipermeable membrane according to the present invention.

The semipermeable membrane of the present invention contains a polyarylate resin having a predetermined structure and a polysulfone resin in a predetermined ratio. This semipermeable membrane can be obtained by coagulating a mixture of the polyarylate resin, polysulfone resin, and organic solvent with a coagulating liquid consisting of water and an organic solvent.

The polyarylate resin suitable for this invention has the formula (1
) has an eel return unit.

(However, in the formula, R1 and R2 are lower alkyl groups having 1 to 5 carbon atoms, and the R1 and R2 may be the same or different, respectively.) As the R1 and R2, for example, Examples include methyl group, ethyl group, propyl group, butyl group, and pentyl group. Preferred R1 and R2 are methyl groups.

The preferred polyarylate resin in this invention is not particularly limited as long as it has the repeating unit represented by formula (1) as the main repeating unit, and may contain other repeating units as long as it does not impede the purpose of the invention. Also good.

Next, the preferred polysulfone resin is the formula (
2): (However, in formula 1, R3 and R4 are lower alkyl groups having 1 to 5 carbon atoms, and R3 and R4 may be the same or different, respectively.) and a polysulfone resin (B) having at least one of repeating units represented by formula (3);

The lower alkyl group represented by R3 and R4 is the same as the lower alkyl group for R1 and R2.

In the method of the present invention, the polyarylate resin (A), polysulfone resin (B), and organic solvent are mixed at a mixing weight ratio of (A)/(B) = o, r to lO1, preferably 0.
3 to 4 to prepare a membrane forming stock solution.

When the mixing weight ratio (A)/(B) is outside the range,
The cross section of the semipermeable membrane does not have a fibrillar structure.

The organic solvent is not particularly limited as long as it is a good solvent for the polyarylate resin and polysulfone resin, such as tetrahydrofuran, dioxane, dimethylformamide, dimethylacetamide, N-methyl-
Examples include 2-pyrrolidone. Among these, tomethyl-2-pyrrolidone is preferred.

When mixing, use the above-mentioned IP! ! The concentration of the mixture of polyarylate resin (A) and polysulfone resin (B) in the stock solution is usually 10 to 25% by weight, preferably 12 to 20% by weight.

When the concentration is lower than 10% by weight, the membrane strength may decrease and may not be practical, and when it is higher than 25% by weight, the porosity of the membrane may decrease and its properties may deteriorate. In addition, it is not practical because the Igi stock solution tends to gel.

The temperature at which the polyarylate resin and borisulfone resin are dissolved in the organic solvent is usually 30 to 100°C, preferably 50 to 80°C.

In the preparation of the above-mentioned MHI solution, the present invention does not particularly require non-solvents, 11 lubricants, water-soluble polymers, etc. as additives. The above-mentioned non-solvent may be added as long as it does not impair the stability of the solvent.

In the present invention, the FIRM liquid prepared above is formed into a membrane body of a predetermined shape.

The shape of the membrane body may be flat membrane, tube, or hollow fiber, but in order to form a uniform fibril structure in the present invention, the coagulation liquid should be used to dissolve the resin rather than water alone. A mixed solvent of the used organic solvent and water is preferred; if the water content is too large, a void structure tends to develop in the cross-sectional direction of the film. In addition, if the water content is too small, the fibrils will become too thick and coarse, and at the same time coagulation will be slow and film formation will be difficult. is 30
As the organic solvent to be mixed, which is preferably contained in an amount of ~80% by weight, good solvents for resins such as tetrahydrofuran, dioxane, dimethylformamide, dimethylacetamide, n-methyl-2-pyrrolidone, etc. can be used; For speed adjustment, methanol,
Alcohols such as ethanol, isopropanol, and glycerin, and glycols such as ethylene glycol and propylene glycol may also be added.

In order to make the membrane body into a hollow fiber shape, it is preferable to use the same liquid as the coagulating liquid for the core liquid.

Surprisingly, although it is a mixture of hydrophobic resins, the film-forming stock solution in which the two types of mixtures are dissolved exhibits remarkable stability when kept at a relatively low temperature of 5 to 15 degrees Celsius. It has been found that phase separation and the like are less likely to occur.

By this, by spinning at the above temperature,
It is possible to obtain hollow fibers with an extremely excellent fibril structure.

The semipermeable membrane according to the present invention obtained as described above contains a polyarylate resin (A) and a polysulfone resin (B), and the mixing weight ratio of the polyarylate resin (A) and polysulfone resin (B) is (A)/(B) is 0.1~1O
1 is preferably 0.3 to 4, more preferably around 1, the membrane surface does not have an average pore diameter of more than 0.05 pm, and will be specifically described in the cross-sectional direction of the membrane.

(Example 1) Poly7-arylate tree # in which R1 and R2 are methyl groups in the formula (1) [hereinafter abbreviated as PA]. ] (■Made by Unitika, product name: U Polymer■"U-2030J")
and the polysulfone resin represented by the above formula (3) [hereinafter, P
It is abbreviated as ES. ] (Manufactured by ICI, product name: V 1c
tr@i@r4800P J ) and tomethylpyrrolidone [hereinafter abbreviated as NMP. ] and was dissolved while heating at 60° C. to prepare a membrane forming stock solution. At this time, the resin concentration was 15% by weight, and PA,! :The mixing weight ratio with PES was 1:1.

This film-forming stock solution was cast onto a smooth glass substrate, and immediately immersed in a coagulation solution consisting of 50% by volume of water and 50% by volume of NMP to gel it for 5 minutes.

Thereafter, the gelled product was left in running water for about 1 hour to completely remove the solvent and form a film.

The obtained film body was examined using a scanning electron microscope [hereinafter, SEM
It is abbreviated as. ] The surface and cross section (thickness direction) of the membrane were observed, and the water permeability was measured.

To measure water permeability, the membrane was cut to a diameter of 90 mm, set in a holder, and the amount of distilled water permeated was measured under nitrogen pressure.

In the SEM observation, as shown in FIG. 1, which is a cross-sectional photograph of the membrane, the membrane structure in the cross-sectional direction was a network structure having continuous through holes, that is, a fibril structure.

The experimental results are shown in Table 1.

(Examples 2 and 3) The same raw resin as in Example 1 was used, and in Example 2, the mixing weight ratio of FA and PES was set to 6-5:8.5. The same procedure as in Example 1 was carried out, except that the mixing weight ratio of r't p A and PES was 9=6 (the resin concentration was 15% by weight in both Examples 2 and 3).

The obtained membrane was observed by SEM in the same manner as in Example 1, and its water permeability was measured.

The results are shown in Table 1.

(Example 4) In Example 1, a polysulfone resin [hereinafter abbreviated as PS] in which R3 and R4 in formula (2) are methyl groups was used instead of PES. ] (manufactured by Union Carbide, trade name; P-3,500) was used, but the same procedure as in Example 1 was used.

The obtained membrane was subjected to SEM observation in the same manner as in Example 1, and its water permeability was measured.

The results are shown in Table 1.

(Comparative Examples 1 to 4) FA in Comparative Example 1, PES in Comparative Example 2,
In Comparative Example 3, a single resin was used for each PS (resin concentration: 15% by weight), and a membrane was produced in the same manner as in Example 1.

The obtained membrane was subjected to SEM observation in the same manner as in Example 1, and its water permeability was measured.

The results are shown in Table 1.

As shown in FIG. 3, which is an electron micrograph of the cross section of the membrane obtained in Comparative Example 1, and FIGS. 4 to 6, which are electron micrographs of the cross section of the membrane obtained in Comparative Example 2, the membrane was , had a structure having a diaphragm with almost no through holes or few through holes, and the amount of water permeation was also smaller than the amount of water permeation of the membrane in the example.

(Example 5) An mx solution having the same composition as in Example 1 was prepared, and the core solution (NMP 40% by volume, water 60% by volume) was added from the inside of a double-tube spinning rod, and the S stock solution was poured from the outside. 50 in the air
After passing through mm, it was introduced into a coagulation solution and gelled, to obtain a hollow fiber membrane. The temperature of the double-tube spinning rod was 50° C., and the coagulation liquid composition was a mixture of 50% by volume of NMP and 50% by volume of water.

The obtained hollow fiber membrane was washed with water, dried, and the structure of the inner surface, outer surface, and cross section of the membrane was observed using SEM.

No pores exceeding 0.051 Lm were observed on the inner and outer surfaces of the membrane, which were smooth and had a homogeneous fibrillar structure in cross section.

[Effects of the Invention] The semipermeable membrane of the present invention contains polyarylate resin and polysulfone resin in a predetermined ratio, and has 0.051 Lm on the membrane surface.
The membrane has excellent water permeability because it has a network structure, that is, a fibril structure, with continuous through-holes in the cross-sectional direction of the membrane, and does not have bores exceeding .

Furthermore, according to the manufacturing method of the present invention, a wag solution in which a polyarylate resin and a polysulfone resin are dissolved in an organic solvent in a specific ratio is used, and no additives, non-solvents, swelling agents, etc. are used. , the semipermeable membrane can be manufactured.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional photograph of the membrane obtained in Example 1, Figures 2 and 3 are cross-sectional photographs of the membrane obtained in Example 4, and Figure 4 is a cross-sectional photograph of the membrane obtained in Example 5. Photograph No. 551J is a cross-sectional photograph of the membrane obtained in Comparative Example 1, and FIGS. 6 to 8 are cross-sectional photographs of the membrane obtained in Comparative Example 2. Figure 2, 3711 - Figure 4, Figure 5, Figure 6, Figure 7, Figure 8 Procedural Amendment (Blade side February 17, 1988)

Claims (6)

[Claims] (1) Polyarylate resin (A) and polysulfone resin (
B), and the mixing weight ratio (A)/(B) of the polyarylate resin (A) and polysulfone resin (B) is 0.
1 to 10, and has a network structure having continuous through holes in the thickness direction of the membrane. (2) The above polyarylate resin has the formula (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) (However, in the formula, R^1 and R^2 have 1 to 5 carbon atoms.
is a lower alkyl group, and R^1 and R^2 may be the same or different. ) The polysulfone resin is a resin having a repeating unit represented by the formula (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) (However, in the formula, R^3 and R^4 are carbon numbers is 1-5
is a lower alkyl group, and the above R^3 and R^4 may be the same or different. ) and/or a resin having a repeating unit represented by formula (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) as set forth in claim 1 above. Semipermeable membrane. (3) The semipermeable membrane according to claim 1, wherein the semipermeable membrane has a hollow fiber shape. (4) Polyarylate resin (A) and polysulfone resin (
B), the mixing weight ratio (A)/(B) of the polyarylate resin (A) and polysulfone resin (B) is 0.1 to
1. A method for manufacturing a semipermeable membrane, which comprises dissolving it in an organic solvent at a ratio of 10 to 10, and using the obtained membrane forming stock solution to form a membrane body with a coagulating liquid containing water and an organic solvent. (5) The above polyarylate resin has the formula (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) (However, in the formula, R^1 and R^2 have 1 to 5 carbon atoms.
is a lower alkyl group, and R^1 and R^2 may be the same or different. ) The polysulfone resin is a resin having a repeating unit represented by the formula (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) (However, in the formula, R^3 and R^4 are carbon numbers is 1-5
is a lower alkyl group, and the above R^3 and R^4 may be the same or different. ) and/or a resin having a repeating unit represented by the formula (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) Method for manufacturing semipermeable membrane. (6) The method for manufacturing a semipermeable membrane according to claim 4, wherein the semipermeable membrane has a hollow fiber shape.