Alkalische Hydrolyse von Polyimiden

1,154,480. Aromatic tetracarboxylic acids and diamines. E. I. DU PONT DE NEMOURS & CO. 5 Jan., 1967 [6 Jan., 1966], No. 754/67. Heading C2C. [Also in Division C3] Aromatic tetracarboxylic acids and aromatic diamines are obtained by hydrolysing scrap polyimide in 1 to 30 wt. per cent aqueous ammonia or alkali metal hydroxide in sufficient amount to provide at least 2 moles OH per mole imide N at 100‹ to 200‹ C.; precipitating the diamine by cooling and separating it from the mother liquor; precipitating tetracarboxylic acid with a mineral acid, and separating the precipitated acid. The solution may be decolorized with carbon black. The application of the process to the polypyromellitimide of bis- (4-aminophenyl)-ether is exemplified and numerous other tetra-acids and diamines which can be similarly obtained are listed.