Copolyimides, their preparation and the use thereof

摘要

Mixtures of salts of organic dicarboxylic acids and organic compounds of non-salt character, dissolved in a C1-C4 alkanol, can be concentrated or separated with a semipermeable membrane made from a copolyimide which contains a first aromatic diamine radical (1) and a second aromatic diamine radical (2) which carries -SO3M groups, wherein M is H(+), a mono-to trivalent metal cation or an ammonium cation. The first amine radical (1) and/or the second diamine radical (2) contains C1-C4 alkyl groups in both o-positions to at least one amino group. These copolyamides are also radiation-sensitive (self-crosslinking) and can be used for the production of protective layers or relief images, development being carried out in an aqueous alkaline medium.