Patent ID: 9211508
Filing Date: 2015-12-15
Classification: B01D

Abstract:
1. A method of making a polybenzoxazole membrane comprising (a) fabricating a self-cross-linkable aromatic polyimide polymer membrane from the self-cross-linkable aromatic polyimide polymer comprising both hydroxyl functional groups and carboxylic acid functional groups; (b) cross-linking the self-cross-linkable aromatic polyimide polymer membrane to form a self-cross-linked aromatic polyimide polymer membrane by heating the membrane at 250° C. to 300° C. under an inert atmosphere; and (c) thermal heating the self-cross-linked aromatic polyimide polymer membrane at a temperature from about 350° to 500° C. under an inert atmosphere, to convert the self-cross-linked aromatic polyimide polymer membrane into a polybenzoxazole membrane; wherein said self-cross-linkable aromatic polyimide polymer used for the preparation of PBO membrane comprises a formula (I): wherein X 1 and X 2 are selected from the group consisting of and mixtures thereof, respectively; X 1 and X 2 are the same or different from each other; Y 1 —COOH is and mixtures thereof; Y 2 —OR is selected from the group consisting of and mixtures thereof, and —R— is selected from the group consisting of —H and a mixture of —H and —COCH 3 , and —R′— is selected from the group consisting of and mixtures thereof; n and m are independent integers from 2 to 500; the molar ratio of n/m is in a range of 1:1 to 1:20.