Patent ID: 7812099

Claim:
A process for preparation of particles of a pulverulent polyimide-polyimide block copolymer of the formula (I): said process comprising the steps of: (i) continuously passing into a boiling aprotic dipolar solvent a solution of a polyimide-polyamidecarboxylic acid block copolymer having the following structure: or a solution of a polyamidecarboxylic acid-polyamidecarboxylic acid block copolymer, having the following structure: (ii) converting the polyamidecarboxylic acid portion of the block copolymers represented by formulas (A) or (B) into an insoluble polyimide-polyimide block copolymer via thermal imidation and water elimination; (iii) precipitating the insoluble polyimide-polyimide block copolymer; and (iv) removing the resulting water from the reaction mixture, wherein: n and m=from 2 to 20; x=from 1 to 300; R 1 and R 3 are defined as follows: R 2 and R 4 are defined as follows: —C n′ H 2n′ —; n′ is from 1 to 12; with the proviso that R 1 and R 3 , and R 2 and R 4 , may not simultaneously take the same values, and further wherein said particles have particle size d50 of from 0.4 to 70 μm.