Abstract: A process for producing polyacrylonitrile membranes for use in reverse osmosis, which comprises dissolving an acrylonitrile polymer in formamide (FA)-containing dimethylformamide (DMF) to prepare an acrylonitrile polymer solution for membrane formation; shaping the solution into a membranous product of a desired form while maintaining the temperature of the solution within a specific range; removing the solvent from the membranous product under a specified solvent removal condition (solidifying condition); subjecting the thus-obtained membrane to a heat treatment, and further to a plasma treatment. The polyacrylonitrile membrane thus obtained is asymmetric and porous in structure, and excellent both in separation ability and in mechanical strength. This membrane is very suitable for use in reverse osmosis.

Abstract: A method of producing synthetic resin spinnerettes. Vertically extending synthetic filaments are mounted on a frame structure and placed in a mold. A thermoplastic or themosetting resin is poured into the mold and allowed to set. The molded body is removed from the mold and the filaments are removed therefrom to leave orifices.