Coating solution of polyetherimide oligomers

A process for preparing a coating solution which includes oligomeric polyetherimides comprising:

• (a) reacting at least one aromatic bis(ether anhydride) of the formula:
• ##STR23## with less than a stoichometric amount of at least one diamine of the general formula:
• H.sub.2 N--R.sup.1 --NH.sub.2
• in a suitable solvent to form oligomeric polyetheramic acids containing terminal anhydride groups
• (b) heating the solution of (a) to a temperature between 80.degree. C. and 250.degree. C. to form oligomeric polyetherimide anhydrides
• (c) hydrolizing the oligomeric anhydrides of (b) to form the free acids of the formula:
• ##STR24## (d) adding to the oligomer solution of (c) more of the same or different diamine, and optionally more solvent and water,
• where R is a member selected from the class consisting of (A) divalent organic radicals having the following formulas:
• ##STR25## and (B) divalent organic radicals of the general formula:
• ##STR26## where m is 0 or 1 and X is a member selected from the class consisting of divalent radicals of the formulas, ##STR27## where y is an integer from 1 to 4;
• R.sup.1 is a divalent organic radical selected from the class consisting of (a) aromatic hydrocarbon radicals having from 6 to about 20 carbon atoms and haloginated derivatives thereof, (b) alkylene radicals having from 2 to about 20 carbon atoms, and cycloalkylene radicals having from 3 to about 30 carbon atoms, (c) from C.sub.2 to about C.sub.8 alkylene terminated polydiorganosiloxane, and (d) divalent radicals of the general formula:
• ##STR28## where m is as previously defined and Q is a member selected from the class consisting of ##STR29## where x is an integer from 1 to 5 inclusive, and n is an integer from 0 to 100.