JPH0141366B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polysulfone-based semipermeable membrane. More specifically, the present invention relates to a method for producing an anisotropic polysulfone semipermeable membrane with excellent permeability and high water permeation rate. More specifically, a polysulfone-based polymer is dissolved in an aprotic solvent containing polyacrylamide to prepare a film-forming stock solution, and then the stock solution is formed into a film-like material of a desired shape, and then brought into contact with a coagulation medium. An object of the present invention is to provide a method for producing a polysulfone separation membrane, which is characterized in that the membrane is formed by coagulating a polysulfone polymer. In recent years, separation technologies for various substances using semipermeable membranes have been attracting attention in a wide range of application fields such as wastewater treatment, seawater desalination, food industry, and medical fields, and even greater development is expected in the future. As such membrane separation techniques, various methods such as ultrafiltration and reverse osmosis have been proposed depending on the size of substances suspended, dispersed, or dissolved in the aqueous medium. In other words, it goes without saying that the performance required of the membrane differs depending on the purpose of separation mentioned above, but the commonly required performance is a high permeation rate for aqueous media and excellent semipermeability for various substances. It has high mechanical strength, excellent heat resistance, and chemical resistance. Conventionally, various materials have been proposed for use in semipermeable membranes, and among them, acetyl cellulose semipermeable membranes are well-known as having excellent permeability. However, acetylcellulose membranes have drawbacks, particularly in chemical resistance, heat resistance, microbial resistance, etc., and are therefore not necessarily suitable membranes. On the other hand, polysulfone-based semipermeable membranes, especially semipermeable membranes made of aromatic polysulfone, have excellent mechanical strength, chemical resistance, heat resistance, and microbial resistance, and cannot be used with acetyl cellulose semipermeable membranes. It is attracting attention because it has the potential to be used in fields that have not yet been developed. Various membrane forming methods have been proposed for polysulfone-based semipermeable membranes. For example, US Patent No.
No. 3615024, JP-A-49-23183, JP-A-51-129880
etc. All of these film-forming methods employ a wet film-forming method, which basically involves dissolving the polysulfone polymer in a solvent to prepare a film-forming stock solution, then casting the stock solution, and then applying it to a coagulation bath. In this method, the membrane is manufactured by immersing it in water to remove the solvent. The above-mentioned patent states that in the above-mentioned film-forming method, a non-solvent is added to the good solvent to the extent that polysulfone does not precipitate. However, when using the non-solvent specifically disclosed in these prior documents, had many disadvantages, such as difficult membrane forming operations and poor membrane performance. Here, as a result of intensive research into a method for manufacturing a polysulfone-based semipermeable membrane that overcomes the above-mentioned drawbacks and has excellent membrane performance, the present inventors have discovered that N,N - By using dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, sulfolane or N-methylpyrrolidone and specifying the amount of polyacrylamide added, semi-transparent polysulfone with excellent mechanical strength and anisotropy After manufacturing the membrane, we discovered a certain fact and arrived at the present invention. That is, the purpose of the present invention is to have a high water permeation rate,
An object of the present invention is to provide a method for producing an asymmetric polysulfone-based semipermeable membrane with excellent permeability. Another object of the present invention is to provide a method for producing polysulfone-based semipermeable membranes that can be designed to have separation performance suitable for various application fields, such as microfiltration membranes, ultrafiltration membranes, and reverse osmosis membrane substrates. be. The purpose of the present invention described above is to dissolve a polysulfone-based polymer in an aprotic polar solvent containing polyacrylamide to prepare a film-forming stock solution, and then form the stock solution into a film-like substance of a desired shape. This is achieved by a manufacturing method characterized by coagulating a polysulfone polymer by contacting it with a coagulating medium. The polysulfone polymer according to the present invention is preferably aromatic, for example polysulfone having a repeating unit of

A polyarylether sulfone having a repeating unit of the formula can be cited as a representative example. Suitable semipermeable membranes have a degree of polymerization in the range of 40 to 200. It is essential to use an aprotic polar solvent containing polyacrylamide as the solvent for the polysulfone. Examples of aprotic polar solvents include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), dimethylsulfoxide,
N-methylpyrrolidone (NMP), sulfolane,
Examples include hexamethylphosphonamide, among which N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, and sulfolane are preferred. The molecular weight of polyacrylamide is 500 or more.
Something in the range of 100000 is good, especially 1000 or more
A range of 60,000 is preferred. If a material with a small molecular weight is used, the amount of permeated water will be reduced, but the overeffect will be improved. Furthermore, if a material with a large molecular weight is used, the amount of permeated water will increase, but the overeffect will be worse than a material with a small molecular weight. By adjusting the molecular weight of polyacrylamide, the superperformance and water permeation rate can be adjusted within a suitable range. On the other hand, the amount of polyacrylamide added should be in the range of 5 to 30% based on the total weight of polyacrylamide and the aprotic polar solvent. If the amount of polyacrylamide added is small, it will be difficult to obtain a sufficient water permeation rate, and if the amount added is too large, the mechanical strength of the polysulfone semipermeable membrane will be reduced. Preferably, the amount of polyacrylamide added is maintained in the range of 7 to 15%. The film-forming stock solution prepared by dissolving the polysulfone polymer in the above-mentioned mixed solvent is cast onto a flat plate, endless belt, rotating drum, etc., or extruded through a slit-shaped, annular-shaped, etc. By this method, it is formed into a desired membrane-like material such as a flat membrane, a tube, or a hollow fiber. The film-forming material is solidified by contacting it with an inert atmosphere such as air or nitrogen, or by directly contacting it with a solidification medium. As the coagulating medium, any coagulating medium such as water, an aqueous solution containing the above-mentioned mixed solvent, or a water-soluble substance having compatibility with the above-mentioned miscible solvent can be employed. In order to better understand the present invention, typical examples of the present invention will be shown next, but the scope of the present invention is not limited in any way by the description of these examples. Note that all percentages and parts shown in the examples are based on weight unless otherwise specified. Example 1 Polyarylether sulfone (trade name: UDEL)
P3500 (manufactured by Union Carbide) was dissolved in a mixture of 100 g of dimethylformamide and the additives shown in Table 1. This solution is casted onto a glass plate to form a film. Then 25℃
Gently immerse in water kept at a constant temperature to solidify. After soaking for 1 minute, wash and store in water. Distilled water permeability and polyethylene glycol (average molecular weight 20000) 2000ppm of the obtained membrane
The polyethylene glycol removal rate was measured using an aqueous solution of The results are shown in Table 1. Incidentally, the amount of distilled water permeation was measured at 25° C. and a pressure of 4 Kg/cm ² . Moreover, the concentration of polyethylene glycol was measured by gravimetric method after drying the aqueous solution.

【table】

Claims (1)

[Claims] 1. After dissolving a polysulfone-based polymer in an aprotic polar solvent containing polyacrylamide to prepare a film-forming stock solution, and then forming the stock solution into a film-like material of a desired shape, A method for producing a polysulfone semipermeable membrane, which comprises forming a membrane by coagulating a polysulfone polymer by bringing it into contact with a coagulation medium. 2. The method according to claim 1, wherein the aprotic polar solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, sulfolane or N-methylpyrrolidone. 3. The method according to claim 1, wherein polyacrylamide is used in a proportion of 5 to 30 g per 100 g of aprotic polar solvent.