HOLLOW FIBER HAVING SELECTIVE GAS PERMEABILITY AND PROCESS FOR PREPARATION THEREOF

摘要

An asymmetric hollow fiber having a selective gas permeability, said fiber having an outer diameter of 0.2 to 3 mm, a ratio of outer diameter/ inner diameter in the range of from 1.1/1.0 to 3.0/1.0 and a nitrogen gas permeability of from 5 % 10-4 to 0.1 cm3 (STF)/cm2?sec?cmHg, and wherein the permeability of the fiber to different gases is proportional to the reciprocals of the square roots of the molecular weights of the respective gases. There is also provided a coated hollow fiber as aforesaid having an external coating film of a film-forming polymer, said film having a thickness of from 0.1 to 300 microns. The hollow fiber is prepared by extruding through the outer tube of a double tube spinneret a solution containing 22 to 33% by weight of a cellulose derivative in a solvent and simultaneously flowing a aqueous liquid or gas through the inner-tube of the spinneret. The spinning solution is extruded into as aqueous coagulating both having a temperature of 0.degree. to 45.degree.C, and after removal therefrom is dipped in water having a temperature of 30.degree. to 100.degree.C. Then free water is removed from the fiber and the fiber is subjected to freeze-drying under vacuum. The coated fiber is prepared by immersing the above-mentioned fiber in a bath containing 0.2 to 5% by weight of the polymer dissolved in a solvent which is a nonsolvent for the cellulose derivative.