| abstract |
The use of certain catalysts provide for an improved process for the preparation of soluble polyimides, polyamides, and polyamideimides. The catalysts are alkali metal salts of formula MOR, wherein R represents alkyl or aryl and M represents an alkali metal. The improved process comprises reacting organic diisocyanates with polycarboxylic compounds consisting of tetracarboxylic acids or the intramolecular dianhydrides thereof, tricarboxylic acids or the monoanhydrides thereof, dicarboxylic acids, and mixtures thereof, in the presence of said catalysts. The polymers are obtained in solution at low reaction temperatures and short reaction times thereby avoiding side-reactions which otherwise would be detrimental to polymer molecular weight and ultimate polymer properties. |