JPS6329562B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel permselective membrane made of a mixture of aromatic polysulfone and aromatic polycarbonate, and a method for producing the same. A large number of polymer compounds have traditionally been used as materials for selectively permeable membranes, such as cellulose, polyacrylonitrile, polyamide, and polysulfone. There is a need for a membrane that can treat treated water, such as waste water, aqueous protein solutions, etc., without cooling, and that has good chemical resistance, toughness, and excellent permselectivity. As such a membrane, a method of imparting permselectivity by forming a membrane from aromatic polysulfone, which has good heat resistance and chemical resistance, which has been conventionally used as an engineering plastic, has been widely attempted. However, the water permeation rate of conventional polysulfone membranes is extremely low, and even hollow fibrous membranes that can have a large membrane area per unit volume cannot exhibit sufficient processing capacity. In order to overcome this drawback, conventional methods have been to increase the affinity of polysulfone with water or to mix different types of polymers. For example, one way to increase affinity with water is to use aromatic polysulfone in which SO ₃ Na groups are introduced into the aromatic ring (J.Appl.polym.Sci., 20 , 1885 (1976)).
Or a method of adding salt to the membrane forming stock solution (Japanese Patent Application Laid-Open No. 1983-
16378), but in the former case, the contact angle with water only changes and no significant improvement in the water permeation rate can be expected, and in the latter case, the solubility of the polymer in the membrane forming solution deteriorates, resulting in changes over time. The disadvantage is that it is difficult to obtain reproducible films because of the large amount of film. Furthermore, the method of forming a film by mixing different types of polymers is a fairly effective method, but aromatic polysulfone has a large molecular cohesive force and there are few polymers that are compatible with it. Polyvinylpyrrolidone (J.Appl.polym.Sci., 20 ,
2377 (1976)) and a method of blending polysulfones with different structures (Japanese Patent Application Laid-Open No. 144456-1977),
Furthermore, a method of blending aromatic polyethers has been proposed (Japanese Unexamined Patent Publication No. 146279/1983). However, in the polyvinylpyrrolidone mixed system, the main cause of pore formation is the elution of water-soluble polyvinylpyrrolidone from the polysulfone membrane substrate. Therefore, a relatively long coagulation action is required, and a post-process for extracting polyvinylpyrrolidone is required, making the process complicated. Furthermore, due to the formation of pores due to polymer elution, it is not possible to drastically change the membrane structure, particularly the structure of the surface dense layer that almost restricts the water permeation rate, and as a result, no significant improvement in the water permeation rate can be expected. Furthermore, when combining similar polysulfones, although the polymers have good compatibility in the stock solution, there is no significant difference in coagulation behavior between them, and similarly, the structure of the dense layer cannot be drastically changed, resulting in a significant improvement in water permeation rate. I can't hope. Next, blends of aromatic polyethers are considered to be convenient for causing structural changes in polysulfone membranes, but due to the strong intermolecular forces of polysulfones, the polymers have poor compatibility in the stock solution, resulting in short-term It has been difficult to obtain a membrane that is safe and has good performance because phase separation tends to occur and membrane defects (pinholes, etc.) occur as a result. That is, until now, an aromatic polysulfone membrane having high water permeability and high permselectivity has not been obtained, and its development has been awaited. The inventors of the present invention have arrived at the present invention as a result of extensive studies aimed at creating a permselective membrane mainly composed of aromatic polysulfone that satisfies the above requirements. That is, the gist of the present invention is a selectively permeable membrane made of a mixture of aromatic polysulfone and aromatic polycarbonate, and in particular, the ratio of aromatic polysulfone/aromatic polycarbonate is 99/1 by weight.
It is desirable that the ratio is ~50/50, and the membrane form is a hollow fiber membrane that can be assembled into a compact processing device. The present inventors have investigated various polymers from two perspectives: polymers that are compatible with aromatic polysulfone in organic solvents, and polymers that can diversify membrane structures by utilizing differences in solidification behavior during membrane formation. . Polysulfone has a highly polar - SO ₂ - group introduced into the polymer main chain, and its molecular attraction is strong, so polymers that are compatible with polysulfone must also have highly polar functional groups, and further diversification of membrane structures. For this reason, we thought it would be appropriate to introduce a functional group different from the -SO ₂ - bond. i.e.

[Formula] The introduction of a group is effective, and when this group is introduced into an aromatic ring, the compatibility between polymers improves, and the difference in solidification behavior is large, making it possible to diversify membrane structures during film formation. I got it. The aromatic polysulfone used in the present invention is a polymer in which at least an aromatic ring and -O-, -SO ₂ - are bonded in the polymer main chain, such as etc., but should not be limited to these. On the other hand, aromatic polycarbonate consists of aromatic rings and

[Formula] A polymer that has a group in its main chain, including block bodies, graft bodies, etc. etc., but should not be limited to these. In particular, in the present invention, aromatic polysulfone/
When the ratio of aromatic polycarbonate is in the range of 99/1 to 50/50, especially in the range of 98/2 to 60/40, the water permeability is significantly improved, and is significantly improved compared to conventional polysulfone membranes. , water permeability rate is 5~1000 at 25℃
(/hr・m ²・Kg/cm ² ), and despite this, the membrane has a surprising performance in that the rejection rate of serum albumin exceeds 90%. Although such a membrane has sufficient utility as a flat membrane, a hollow fibrous membrane is more preferable since it can increase the surface area per unit volume. Next, there is a method for producing a permselective membrane having such good performance, the gist of which is to mix at least one aromatic polysulfone and at least one aromatic polycarbonate into a mixture of the polysulfone/polycarbonate. Weight mixing ratio 99/1~5
0/50, and the total amount of polymer is dissolved in an organic solvent to be 10 to 40 wt% based on the film-forming stock solution, and then molded using a wet or wet-dry method. The organic solvent used in the present invention may be any organic solvent as long as it dissolves the aromatic polysulfone and the aromatic polycarbonate.
Particularly preferred are solvents having a temperature of 100°C or higher. Examples include dimethylformamide, dimethylacetamide, dimethylsulfoxide, and acetic acid. In addition, it is essential that the polysulfone/polycarbonate ratio be 99/1 to 50/50, especially 98/2 to 60/50.
A range of 40 is preferred. When this ratio is larger than 99/1, the coexistence effect of polycarbonate is weak and no improvement in water permeation rate can be expected.On the other hand, when this ratio is smaller than 50/50, the composition of polycarbonate increases and there is a tendency for chemical resistance to decrease and the water permeation rate decreases. It will not be improved much and will no longer have any meaning. Furthermore, the total amount of polymer dissolved in the solvent is 10~
It must be 40wt%; if it is less than 10wt%, the viscosity of the stock solution will be too low and molding will be difficult;
Exceeding this is undesirable as a significant decrease in water permeation rate is observed. A further important point is that the present invention requires wet or wet-dry molding. In the dry method and the melting method, the water permeation rate becomes too low and the membrane becomes unusable. Furthermore, in the present invention, 2
It is particularly preferable to produce hollow fibers by using a double tube type nozzle to inject the stock solution from the annular portion of the outer tube and the liquid from the inner tube while simultaneously coagulating the extrusion in a water-based coagulation bath. The aqueous coagulation bath refers to water or a coagulation bath mainly composed of water, and a mixed aqueous solution of water and the solvent used for preparing the membrane-forming stock solution is preferably used. As the liquid injected from the inner tube, a combination of solvent/water, hydrocarbon, fatty acid ester, etc. are used. Another advantage of hollow fibrous membranes is that the water permeation rate can be considerably controlled by stretching the thus obtained hollow fibers in hot water or steam at 20 to 90°C. The membrane thus obtained may be used as it is, or it may be plasticized with glycerin or the like and then dried. The semipermeable membrane made of the aromatic polysulfone/aromatic polycarbonate mixture of the present invention has excellent heat resistance and chemical resistance, high water permeation rate, and high permselectivity, so it can be used in various water treatment fields and medical fields. , it can be effectively used for membrane separation applications in the pharmaceutical industry. Further, the present invention will be illustrated by specific examples. Example 1 15g of aromatic polysulfone shown in formula ()
and aromatic polycarbonate 5 represented by the following formula
g was dissolved in 80 g of dimethylformamide at 130°C, followed by excessive defoaming, uniformly cast on a glass plate using a doctor knife, and coagulated in a 20% dimethylformamide aqueous solution at 40°C. The resulting membrane has a thickness of 80 μm and a water permeation rate of 150 μm.
When an aqueous solution of serum albumin was passed through the ^filter at a rate of 95 ^% , the albumin inhibition rate was 95%. Example 2 A stock solution having the same composition as in Example 1 was used to spin hollow fibers. The nozzle used was a double tubular nozzle, with an outer tube inner diameter of 2 mmφ, an inner tube outer diameter of 1 mmφ, and an inner diameter of 0.5 mm.
mmφ, and the hollow-shaped stock solution is extruded from the annular part at a rate of 23c.c./min and from the inner tube part at a rate of 12c.c./min of a mixture of dimethylformamide/water = 95/5 and extruded from the extrusion nozzle. was dropped 3 cm into the air, coagulated in a 30% dimethylformamide aqueous solution kept at 50°C, then taken up at a speed of 80 m/min, and then
It was stretched 1.5 times, 2.0 times, and 3.0 times in warm water at ℃. The membrane performance measured after making a mini module by bundling 20 of the obtained hollow fibers is as follows.
All showed good performance.

[Table] Comparative Example 1 In Example 1, the stock solution composition was changed to only polysulfone.
When a membrane was formed under the same conditions except for the case where the concentration was 20 wt%, the water permeation rate of the membrane was significantly lower to 1.2/hr·m ² ·Kg/cm ² . Example 3 18 parts by weight of polysulfone of formula () and 2 parts by weight of polycarbonate of formula () were dissolved in 80 parts by weight of dimethylacetamide with stirring at 120°C for 3 hours,
After excessive defoaming, a spinning stock solution was prepared. A 30% dimethylacetamide aqueous solution was extruded from the outer ring of a spinneret having a double tube structure and from the inner tube at a rate of 10 ml/min and 5 ml/min, respectively, and the stock solution was immediately coagulated. Spinneret is 50
The hollow fibers were immersed in a 60% dimethylacetamide aqueous solution at ℃, and the spun hollow fibers were wound up at a speed of 6 m/min. The spinneret has an inner diameter of 1 mmφ for the outer tube and an outer diameter of 0.8 for the inner tube.
mmφ, and the inner diameter was 0.5 mmφ. The obtained hollow fibers have an inner diameter of 1 mmφ and a wall thickness of 150 μm. After making a mini module by bundling 10 fibers, the water permeation rate when pure water is poured from inside the hollow fibers is
At 120/hr·m ² ·Kg/cm ² , the inhibition rate in an aqueous solution of 0.1 g/dl serum albumin was 97%. Example 4 12 g of polyether sulfone of formula () and 3 g of polycarbonate of formula () of Example 1 were dissolved in 85 g of dimethyl sulfoxide. The stock solution was cast onto a glass plate using a doctor knife, and the plate was immersed in 60% dimethyl sulfoxide at 60°C. The resulting membrane has a thickness of 100μ and a water permeation rate of
At 700/hr・m ²・Kg/cm ² , the inhibition rate of serum albumin was 91%.

Claims (1)

[Scope of Claims] 1. A permselective membrane comprising a mixture of at least one aromatic polysulfone and at least one aromatic polycarbonate. 2. The permselective membrane according to claim 1, wherein the weight mixing ratio of aromatic polysulfone/aromatic polycarbonate is 99/1 to 50/50. 3. The permselective membrane according to claim 1 or 2, characterized in that the membrane form is a hollow fibrous membrane. 4 The water permeation rate of pure water is 5 to 1000/hr at 25℃.
^m2・Kg/ ^cm2 , and serum albumin inhibition rate is 90%
Claim 1 characterized in that:
The permselective membrane according to item 1, or 2 or 3. 5 At least one aromatic polysulfone and at least one aromatic polycarbonate are mixed at a polysulfone/polycarbonate weight mixing ratio of 99/1 to 5.
0/50 range, the total amount of polymer is dissolved in an organic solvent to be 10 to 40 wt% based on the membrane forming stock solution, and then formed by a wet or wet-dry method. Production method. 6 As an organic solvent, it is soluble in water and has a boiling point.
The method according to claim 5, characterized in that a solvent having a temperature of 100°C or higher is used. 7. During wet or wet-dry molding, a double-tube nozzle is used to coagulate the membrane-forming stock solution from the annular part of the outer tube in an aqueous coagulation bath while simultaneously discharging the liquid from the inner tube to produce a hollow fibrous membrane. The method according to claim 5 or 6, characterized in that: