Abstract: An insulating varnish comprising water-soluble polyesters and which can be used as an enamel or protective coating for electric wires is disclosed. The insulating varnish is prepared by reacting an aromatic dicarboxylic acid component and a polyhydric alcohol component to produce a high molecular weight polyester resin, addition reacting a polybasic acid with the resulting polyester resin to obtain a carboxyl group-containing polyester resin and dissolving the resulting polyester resin in water using a basic compound.

Abstract: An aqueous insulating varnish which comprises an aqueous medium containing dissolved therein a polyester resin having an acid value of about 20 to 200 with a volatile basic compound, the resin being obtained by reactingA. an organic polycarboxylic acid component comprisingA. at least 30 mol% of at least one of an aromatic tricarboxylic acid and the anhydride thereof, in which up to about 30 mol% of the tricarboxylic acid and anhydride thereof can be replaced by at least one of an aromatic tetracarboxylic acid and the anhydride thereof, andB. about 0 to 70 mol% of at least one of a dicarboxylic acid and the anhydride thereof, andB. an organic polyhydric alcohol component containing at least 20 mol% of a polyethylene terephthalate oligomer represented by the formula ##STR1## wherein n is an integer of 1 to 5, in a OH/COOH equivalent ratio of about 1.0 to 2.0.

Abstract: A concentrated solution suitable for forming thermal resisting polymers having a high degree of polymerization comprising a mixture of a prepolymer solution prepared by the reaction of an organic diisocyanate or diamine and a molar excess of 1,2,3,4-butanetetracarboxylic acid or an anhydride of the acid, and a blocked polyisocyanate.