PHASE INVERSION WITH GEL SOL/GEL-TREATMENT - A NEW TECHNOLOGY FOR THEFORMATION OF HOLLOW-FIBER MEMBRANES AT A WET SPINNING PROCESS/

The preparation of hollow-fiber membranes with high asymmetric morphol ogy by a wet spinning process by phase inversion of polymer solutions with a nonsolvent medium is normally connected with the formation of a relatively dense unwelcome skin. One possibility to eliminate this di sadvantage is a phase inversion process with gel/sol/gel-treatment, wh ose physicochemical peculiarities are descibed in this paper. In the g el/sol/gel-treatment an initially wet hollow-fiber membrane is contact ed with a solvent and subsequently with a nonsolvent again. Such a tec hnology causes a second phase inversion at the outer surface of the ho llow-fiber membrane. Results about parameters influencing the gel/sol/ gel-process are presented as an illustration for the treatment of poly acrylonitrile hollow-fiber membranes with a special structure. In conc lusion, first ideas of the mechanism of this process are formulated.