Patent GB-1026510-A (GB)
Title: Polyamic acid compositions
IPC: C08L79/08
Filed: 1963-10-01
Abstract: A liquid coating composition comprises as the essential film-forming components, a polyamic acid having the recurring unit <FORM:1026510/C3/1> where <FORM:1026510/C3/2> is an organic tetravalent radical containing at least 2 carbon atoms, no more than 2 carbonyl groups of each recurring unit being joined to any one carbon atom of said radical and originating from at least one tetracarboxylic acid dianhydride of the formula <FORM:1026510/C3/3> -R1- is a divalent radical of at least one organic diamine of the formula H2N-R1-NH2 and contains at least 2 carbon atoms, the two amino groups being attached to separate carbon atoms, and from 5 to 45 parts by weight per 100 parts of acid of a 2:4-diamino-6-substituted s-triazone, both in solution in a mutual organic solvent which is non-reactive therewith.  Many suitable diamines and tetracarboxylic acid anhydrides are specified. Specified solvents are N:N-dimethyl formamide, N:N-dimethyl acetamide, N - methyl caprolactam, N - methyl - 2-pyrrolidone, N - acetyl - 2- pyrrolidone, dimethyl sulphoxide, tetramethylene urea, pyridine, dimethyl sulphone, tetramethylene sulphone, formamide, N-methyl formamide and hexamethyl phosphoramide alone or in combination with dioxane, butyrolactone, benzonitrile, benzene, toluene, xylene or cyclohexane. Specified s-triazines are 2:4-diamino-6-phenyl-, 2:4 - diamino - 6 - cyanopropyl-, 2:4 - diamino - 6 - cyanoethyl-, 2:4 - diamino-6 - nitrophenyl-, 2:4 - diamino - 6 - tolyl, 2:4-diamino - 6 - anisoyl, 2:4 - diamino - 6 - (N -anilino)-, 2:4 - diamino - 6 - naphthyl - and 2:4 - diamino - 6 - biphenyl - 1:3:5 - s - triazine. Pigments, e.g. titanium dioxide, carbon black, calcium carbonate, blanc fixe, asbestine, mica and silica may be present in the compositions. The polyamic acids are cured to polyimides by heat or chemical reaction.  The Specification describes the preparation of polyamic acid solutions from: (I) 4:41-diamino diphenyl ether, pyromellitic dianhydride, N:N-dimethyl acetamide and N-methyl-2-pyrrolidone, (II) 4:41-oxydianiline, benzophenone tetracarboxylic acid dianhydride, N:N-dimethyl acetamide and N-methyl-2-pyrrolidone and (III) m-phenylene diamine, pyromellitic dianhydride, N-methyl-2-pyrrolidone and N:N-dimethylacetamide, the compositions being mixed with s-triazines, coated on to substrates and cured to polyimides.ALSO:Coated articles are made by coating substrates with a composition comprising a polyamic acid having a recurring unit <FORM:1026510/B1-B2/1> (see Division C3), from 5 to 45 parts by weight per 100 parts of acid of a 2:4-diamino-6-substituted-s-triazine and, as solvent, a mutual organic solvent which is non-reactive therewith and airing the polyamic acid to polyimide at a temperature of 100 to 200 DEG C. A plurality of coats may be applied.  Specified substrates are copper, brass, aluminium or steel sheet, fibres, wire or screening; glass sheets, fibres, fabrics or foams; cellulosic materials, polyethylene, polypropylene, polystyrene, polyamides, polyvinyl acetals, polyethylene terephthalate, polyurethanes, polytetrafluoroethylene or tetrafluoroethylene-hexafluoropropylene copolymers in the form of sheets, fibres, foams, woven and non-woven fabrics, screenings or coatings or leather sheets.  The examples describe the preparation of polyimide coatings on aluminium, brass and copper panels, copper wire, polytetrafluoroethylene coated copper wire, copper wire coated with a copolymer of tetrafluoroethylene and hexafluoropropylene and plywood panels and for the coating of glass fabrics.