Patent GB-1121325-A (GB)
Title: Aqueous solutions of polyamide acids
Inventor: REYNOLDS REGINALD JOHN WILLIAM
IPC: C08G73/10
Filed: 1964-11-11
Abstract: Polyamide acids derived from amines having 2 primary or secondary amine groups and organic acids having three or more carboxyl groups at least two of which are attached to adjacent carbon atoms are neutralized with at least a stoichiometric amount of a salt-forming organic base and dissolved in water.  Specified organic bases are amines preferably having a dissociation constant, at 25 DEG  C. (Kb) of 10-5 or higher (corresponding to a pKa of 9 or higher). Numerous salt-forming bases and polyamide-acid forming reactants are specified.  The aqueous solution may be used for forming films, filaments and coatings and may be diluted with organic liquids, e.g. ethers, alcohols, nitriles or N,N-dialkyl-carboxamides, to reduce the viscosity. The solutions may be applied by dipping, spraying or air- or doctor-knife coating to substrates such as plastics, metal (Cu, Al, brass, steel), wood, rubber, glazed or unglazed ceramics, glass or mineral materials which may be pretreated to improve adhesion (etching metals, corona discharge-roughened plastics) and may be in the form of sheets, fibres, wires, foam or fabrics. Absorbent substrates (glass or asbestos fibre mats) may be impregnated and built up into laminates.  Films deposited on smooth substrates may be removed before conversion to polyimide to give self-supporting films or parts only of a coating may be converted to polyimide and the remainder removed, e.g. in a process of selective etching to form printed circuits.  Thin coatings of metal may be applied to polyimide films obtained from the solutions.  Fibres may be obtained by spinning the solution into a non-solvent, e.g. dioxan.ALSO:Polyamide acids derived from amines having 2 primary or secondary amine groups and organic acids having three or more carboxyl groups at least two of which are attached to adjacent carbon atoms are neutralised with at least a stoichiometric amount of a saltforming organic base and dissolved in water.  Specified organic bases are amines preferably having a dissociation constant, at 25 DEG C, (Kg) of 10-5 or higher (corresponding to a pKa of 9 or higher).  Numerous salt-forming bases and polyamide-acid forming reactants are specified.  The aqueous solution may be used for forming films, filaments and coatings and may be diluted with organic liquids, e.g. ethers, alcohols, nitriles or N, N-dialkyl-carboxamides, to reduce the viscosity. The solutions may be applied by dipping, spraying or air- or doctor-knife coating to substrates such as plastics, metal (Cu, Al, brass, steel), wood, rubber, glazed or unglazed ceramics, glass or mineral materials which may be pretreated to improve adhesion (etching metals, corona discharge roughened plastics) and may be in the form of sheets, fibres, wires, foam or fabrics. Absorbent substrates (glass or asbestos fibre mats) may be impregnated and built up into laminates. Films deposited on smooth substrates may be removed before conversion to polyimide to give self supporting films or parts only of a coating may be converted to polyimide and the remainder removed e.g. in a process of selective etching to form printed circuits.  Thin coatings of metal may be applied to polyimide films obtained from the solutions.  Fibres may be obtained by spinning the solution into a non-solvent e.g. dioxan.