Semipermeable membrane manufacturing method and semipermeable membrane

Abstract

Provided are a semipermeable membrane manufacturing method and a semipermeable membrane which exhibits both semipermeability and strength. The method comprises: a step for forming a liquid membrane from a membrane-forming solution that includes substances (A)-(C); and a desolvation step for removing a solvent from the liquid membrane. Substance (A): a polymer comprising a repeating unit structure that includes at least one type of structural site selected from the group consisting of an amide group, an imide group, a sulphonyl group, and a heterocycle. Substance (B): a good solvent of substance (A). Substance (C): a salt.

Description

technical field [0001] The present invention relates to a method for producing a semipermeable membrane having both good semipermeability and sufficient strength, and the semipermeable membrane. Background technique [0002] At present, composite membranes and asymmetric membranes are mainly used as reverse osmosis membranes or forward osmosis membranes. These membranes have two layers, a separation functional layer and a support layer. The separation function layer is responsible for a substantial separation function. By having a high physical strength, the support layer provides sufficient strength to the entire membrane to be subjected to a pressurized water permeability test. [0003] In the composite membrane, the support layer has at least one or both of a porous membrane and a substrate. In addition, in the composite membrane, the separation function layer is formed so as to cover the support layer. Most of the composite membranes that have been utilized industria...

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Problems solved by technology

However, it is known that the inclusion of a support layer causes the following two problems: (1) Compared with the original water permeability of the separation functional layer, the water permeability obtained by the entire membrane is low; (2) Salt remains in the support layer internal

[0006] First, with regard to question (1), although there are reports on composite membranes and asymmetric membranes having a thickness of about several tens of μm, there are no reports on composite membranes and asymmetric membranes having a thickness of less than 20 μm at all.

Furthermore, the larger the thickness, the lower the water permeability tends to be.

[0007] Next, regarding the problem (2), when the membrane is used as a forward osmosis membrane, since the salt remains in the support layer, concentration polarization occurs, resulting in a decrease in osmotic pressure

As a result, there occurs a problem that the amount of water permeation decreases significantly (Non-Patent Document 1)

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