Patent GB-1119791-A (GB)
Title: Improvements in or relating to the manufacture of polyamide-imide resins and products thereof
IPC: H01B3/30
Filed: 1965-07-01
Abstract: Polyamide-imides of the formula <FORM:1119791/C3/1> wherein the R1's are aliphatic or aromatic radicals, R2 and R3 are aliphatic, alicyclic or aromatic radicals, and n represents the degree of polymerization, are prepared by heating a solution in a polar solvent of a polyamic acid polymer of the formula <FORM:1119791/C3/2> which has been prepared by reacting a tetracarboxylic acid dianhydride of the formula <FORM:1119791/C3/3> with a diamine or mixture of diamines of the formula H2N-R3-NH2 in a polar solvent. The tetracarboxylic acid dianhydride may itself be prepared from a mono-acid halide monoanhydride of a tricarboxylic acid and a diamine H2N-R2-NH2. Specified polar solvents are N,N-dimethylformamide, N,N-dimethyl acetamide, dimethyl sulphoxide, dimethyl sulphone, pyridine and N-methyl-2-pyrrolidone. The intermediate polyamic acid polymer solution may be further admixed with epoxy resins, polyisocyanates or masked polyisocyanates to give modified polyamide-imides after subsequent curing.  Alternatively, the viscosity of the intermediate polyamic acid polymer solution may be adjusted by suitable addition of solvent naphtha, xylene, benzene or toluene. The intermediate polyamic acid polymer solution or modified forms thereof may be spread on glass plates and cured to give flexible films, applied to copper wire as an insulation varnish and cured to give a hard insulation coating, and used to impregnate sheets of glass cloth, glass matt or asbestos which are subsequently stacked in layers and compressed and cured to form laminates.ALSO:A tetracarboxylic acid dianhydride having two amide bonds in the molecule and represented by the formula <PICT:1119791/C2/1> wherein R1 is an aliphatic or aromatic radical and R2 is R1 or an alicyclic radical, is prepared by reacting a diamine of the formula H2N-R2-NH2\t with an acid halide of the formula <PICT:1119791/C2/2> wherein X represents a halogen atom. In Examples 1 to 3 compounds of the first formula are prepared by reacting 4-chloroformyl phthalic anhydride, with para-phenylene diamine, 4,41-diamino-diphenylmethane or 4,41-diamino-diphenyl ether respectively.ALSO:Copper wire, asbestos, sheets of glass cloth, plate or matt are coated and impregnated respectively with solutions in polar solvents of polyamic acid polymers of the formula:- <FORM:1119791/B1-B2/1> wherein the R1's are aliphatic or aromatic radicals, R2 and R3 are aliphatic, alicyclic or aromatic radicals, and n represents the degree of polymerisation, said solutions being chemically modified if desired by addition of epoxy resins, polyisocyanates or masked isocyanates (e.g. phenol masked 4. 4\sv - diphenyletherdiisocyanate), or being viscosity modified if desired by addition of solvent naphtha, xylene, benzene or toluene.  The sheets of glass cloth or glass matt are subsequently dried at 140 DEG C., or air dried at room temperature prior to stacking together and curing at temperatures above 160 DEG C., and pressures of 200 kg/cm2., to form laminates. The coated copper wire is cured by heating to a temperature of 450 DEG C., when the polyamic acid or modified polyamic acid insulation varnish applied thereto is converted to polyamide-imide coatings of the formula:-  <FORM:1119791/B1-B2/2> or epoxide or polyisocyanate modified derivatives thereof. Specified polar solvents serving as the varnish base are N.N - dimethylformamide, pyridine, N.N - dimethylacetamide, dimethylsulfoxide, dimethyl sulfone and N - methyl - 2 - pyrrolidone.