JPH0330415B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing an aromatic polysulfone-based separation membrane, and more specifically to a method for producing an aromatic polysulfone-based separation membrane for liquids that has a high degree of water permeability and excellent mechanical strength. This relates to a manufacturing method. [Prior Art] Generally, methods for separating substances from liquid mixtures such as solutions and emulsions include concentration methods by distillation, fractional precipitation methods, centrifugation methods, etc., but filtration methods using separation membranes require mild operating conditions. It has rapidly developed in recent years due to its low operating cost, high separation efficiency, and other factors. Among these, ultrafiltration membranes are capable of separating proteins, colloidal substances, microorganisms, etc., and are therefore being considered for use in fields such as concentration and purification of foods and pharmaceuticals, and treatment of industrial wastewater. Conventionally, such separation membranes have mainly been made of cellulose acetate, but they have not been sufficient in terms of heat resistance, chemical resistance, mechanical strength, etc., and in recent years, membranes that are better in these respects have been developed. Polysulfone resin is attracting attention as a material for this purpose. However, on the other hand, although high water permeability is desired from the viewpoint of filtration efficiency, the wet membrane forming method of ordinary polysulfone resin membranes forms a dense structure on the membrane surface, resulting in high water permeability. It is difficult to obtain a film with For this reason, attempts have been made to add various inorganic swelling agents such as lithium nitrate, lithium chloride, ammonium nitrate, etc. to the resin stock solution, or ethanol, ethylene glycol, etc. as organic swelling agents, but these efforts cannot be said to be sufficiently effective. . It is also possible to increase the amount of water permeation by lowering the resin concentration or thinning the film thickness.
Mechanical strength becomes low, making it impractical. [Object of the Invention] In view of the above circumstances, the present invention was developed based on the results of intensive studies.
By using an aqueous solution of polyethylene glycol instead of water, which is normally used as a coagulating liquid,
The present invention was developed based on the discovery that a membrane with high water permeability can be obtained, and the object thereof is to provide a membrane with high mechanical strength and excellent water permeability. [Structure of the Invention] The present invention provides a method for manufacturing a liquid separation membrane by wet film forming using an aromatic membrane polysulfone polymer, in which an aqueous solution containing 1 to 20% of polyethylene glycol with a molecular weight of 200 to 8000 is added to the coagulation liquid. This is a method for producing an aromatic polysulfone-based liquid separation membrane. The aromatic polysulfone polymer used in the present invention is

〔Example〕

Example 1 18 parts of polysulfone (manufactured by UdelP-1700UCC) having a repeating unit represented by is heated and dissolved in 82 parts of N-methylpyrrolidone to form a homogeneous solution. This solution was cast at a speed of 5 cm/sec onto a horizontally placed smooth glass plate as a casting substrate using a doctor blade with a diameter of 180μ, and after being left at room temperature for 10 seconds, the solution was cast together with the substrate. It was immersed in a 5% aqueous solution of polyethylene glycol having an average molecular weight of 3000 at 20°C to gel the polymer and form a membrane. The produced film was peeled off from the substrate and film performance was measured. As a result, the water permeation rate was 857/hr・m ²・Kg/cm ²
(25℃) and showed excellent water permeability. Also,
0.3% of Dextran T-70 (average molecular weight 70000)
As a result of measuring the rejection rate using an aqueous solution, the rejection rate was 75%. Example 2 The resin stock solution used in Example 1 was extruded from an annular nozzle for manufacturing hollow fibers and used as an internal coagulation liquid in Example 1.
A hollow fiber membrane was obtained by coagulating a 5% aqueous solution of polyethylene glycol having an average molecular weight of 3000, the same as that used in Example 1, from the inner and outer surfaces using purified water as an external coagulating liquid. The obtained hollow fiber had an inner diameter of 1.0 mmφ, an outer diameter of 1.6 mmφ,
The membrane thickness is 0.3mm, and the water permeation rate is 760/hr・
The rejection rate of dextran T-70 at m ² ·Kg/cm ² (25°C) was 80%, and it had a burst strength of 25Kg/cm ² or more. The results are shown in Table 1. Examples 3 to 6 Hollow fiber membranes were obtained in the same manner as in Example 1, except that the type of internal coagulation liquid was changed. Table 1 shows the composition of the internal coagulation liquid and the properties of the hollow fiber membrane obtained. Comparative Example 1 A hollow fiber membrane was obtained using the same resin stock solution as in Example 1 and in the same manner as in Example 2, except that purified water was used as the coagulation liquid. The water permeation rate of this membrane is 270/hr・
m ² ·Kg/cm ² (25°C).

【table】

【table】 Examples 7-9

〔Effect of the invention〕

According to the present invention, it is possible to increase water permeability without reducing the mechanical strength of the membrane;
Since water permeability can be adjusted without the need to add inorganic salts or organic solvents to the resin stock solution, it is possible to use the same resin stock solution to manufacture membranes that suit the purpose, making it an ideal industrial membrane manufacturing method. Very suitable.

Claims (1)

[Claims] 1 Dissolve the aromatic polysulfone polymer in an aprotic polar solvent such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc., or a combination thereof, and manufacture a liquid separation membrane by wet membrane formation. A method for producing an aromatic polysulfone liquid separation membrane, characterized in that the coagulation liquid is an aqueous solution containing 1 to 20% polyethylene glycol having a molecular weight of 200 to 8,000.