Patent ID: 7628841

Claim:
A process of producing an asymmetric membrane of multi-component polyimide, the process comprising the steps of: (1) preparing a multi-component polyimide blend solution by mixing a polyimide component A having a number-averaged polymerization index N A and a polyimide component B having a number-averaged polymerization index N B , the polyimide component A being raw materials of a polyimide A containing a fluorine atom in the chemical structure thereof and/or a polymerization and imidation reaction product of the raw materials, the polyimide component B being raw materials of a polyimide B and/or a polymerization and imidation reaction product of the raw materials, the polyimide components A and B being combined such that N A and N B satisfy equation 1: 2.35×N A −2.09 <N B <450×N A −1.12 1 wherein N A and N B are calculated using a polymerization index of 0.5 each of an unreacted tetracarboxylic acid component and an unreacted diamine component of a raw material of polyimide A and polyamide B, (2) subjecting the multi-component polyimide blend solution to a polymerization and imidation reaction, and (3) causing a phase inversion in the resulting multi-component polyimide blend solution to form an asymmetric membrane.