Process for the preparation of enamel coating based on polyamide-imide and enamel coating obtained therefrom

摘要

Process for the manufacture of an enamelling varnish based on polyamide-imides, in which an aromatic diisocyanate or a corresponding diamine is condensed with an aromatic polycarboxylic acid containing at least three carboxyl functional groups, or an anhydride, ester or halide of corresponding acid, in solution in N-methylpyrrolidone, characterised in that the polyamide-imides are isolated in powder form from the reaction solution by removal of the N-methylpyrrolidone, and in that the polyamide-imide powder is then dissolved in a solvent made up at least partially of an aprotic polar solvent other than N-methylpyrrolidone. Varnish manufactured by this process, stable in storage and exhibiting a reduced viscosity which makes enamelling easier. IMAGE