SELECTIVE SEPARATION MEMBRANE FOR CARBON DIOXIDE AND SELECTIVE SEPARATING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To improve separating property and permeability for carbon dioxide of a separation membrane to be used to selectively transmit and separate carbon dioxide from a mixture containing carbon dioxide and methane, by using a fluorine-contg. polyimide resin having specified or higher rotation barrier energy of the main chain. SOLUTION: This separation membrane used to selectively transmit and separate carbon dioxide from a mixture containing carbon dioxide and methane is prepared by using a fluorine-contg. polyimide resin having the following property. In this resin, the rotation barrier energy of the main chain is >=150cal/ cm<3> per unit Van der Waals volume in the min. repeating unit molecular structure. The one surface of the separation membrane thus produced is brought into contact with a mixture containing carbon dioxide and methane to treat the mixture to selectively transmit and separate carbon dioxide through the membrane. In this method, the fluorine-contg. polyimide resin is preferably controlled to have 0.53 to 0.7nm d-spacing measured by large-angle X-ray diffraction method.