GB1333939A - Electrical conductors coated with polyamideimide resins prepared from the reaction of aromatic diisocyanates with mixtures of polycarboxylic acids and anhydrides - Google Patents

Abstract

1333939 Polyamide-imides SCHENECTADY CHEMICALS Inc 10 Nov 1970 53446/70 Heading C3R [Also in Divisions B2 and H1] An electrical conductor has a continuous coating of a polyamide-imide resin made by reacting (A) 0À95 to 1À01 moles of an aromatic diisocyanate with each mole of (B) a mixture of carboxylic reactants consisting of (i) 5 to 40 mol. per cent of an aromatic dicarboxylic acid in which the COOH groups are not ortho, (ii) 1 to 30 mol. per cent of an aromatic dianhydride and (iii) trimellitic anhydride. Various such reactants are specified as are solvents in which they may be reacted and diluents which may be included in the resulting wire enamel. Such solutions may be applied to copper, silver, aluminium or stainless steel wire by the "free dip" or "die application" procedures described in U.S.A. Specification 3,201,276 with one or more passes to provide the desired build, e.g. at 15 to 45 feet/minute at 250‹ to 800‹ F. to a build of 0À005 to 0À001 inches. The coating may be applied directly to the conductor or over a cured polyester base coat. Various suitable polyesters are mentioned, those from terephthalic acid, ethylene glycol and tris-(2-hydroxyethyl) isocyanurate according to U.S.A. Specification 3,249,578 being preferred. In examples, polyamide-imides are prepared from (A) 4,4<SP>1</SP> - diisocyanato - diphenyl methane, (B) (i) terephthalic acid, (B) (ii) trimellitic and/or benzophenone dianhydride and (B) (iii) trimellitic anhydride in N-methyl pyrrolidone and the products diluted with various diluents and used either to provide 6 coats directly on copper wire or 2 or 3 coats on such a wire having 3 or 4 base coats of the preferred polyester blended with a cresol-formaldehyde resin. Reference is made to Specifications 1,009,956 and 1,217,041.