Coating solution of polyetherimide-forming monomers

Claim 1

A highly concentrated homogeneous coating solution of monomeric bis(ether dicarboxylic acid) and diamine reactants, comprising (1) at least one aromatic bis(ether dicarboxylic acid) selected from the group consisting of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl] propane; 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl] propane; 4-(2,3-dicarboxyphenoxy)-4'-(3,4-dicarboxyphenoxy)diphenyl-2,2-propane; and mixtures thereof; (2) at least one organic diamine selected from the group consisting of 4,4'-methylenedianiline, 4,4'-oxydianiline, m-phenylenediamine, and mixtures thereof; and (3) an organic solvent selected from the group consisting of monoalkyl ethers of ethylene glycol having from 1 to 4 carbon atoms in the alkyl group, monoalkyl ethers of diethylene glycol having from 1 to 4 carbon atoms in the alkyl group, dipolar aprotic organic solvents selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylsulfoxide, tetramethylurea, and mixtures thereof; said bis(ether dicarboxylic acid) and said diamine being dissolved in said organic solvent in a combined amount of at least 0.67 part by weight per one part by weight of said organic solvent, said diamine being dissolved in an amount from about 0.5 to about 2.0 moles per mole of said bis(ether dicarboxylic acid), said solution remaining homogeneous for at least one week when stored at about 20° C. to 30° C. in a tightly stoppered glass container.