GB1348575A - Electrical wire insulation - Google Patents

Abstract

1348575 Nitrogenous polymers HUGHES AIRCRAFT CO 19 April 1971 [9 Feb 1971] 25942/71 Heading C3R [Also in Division H1] Cured nitrogenous polymer coatings are formed on an electrical conductor by applying thereto a defined prepolymer and heating it to the cured state. The prepolymer is defined as having an inherent viscosity of 0À045 to 0À05 (2À5 g./100 c.c. dimethyl formamide at 25‹ C.) and comprising the reaction product of a tetraester of benzophenone tetracarboxylic acid with 3,3<SP>1</SP>,4,4<SP>1</SP> - tetraaminobenzophenone and being soluble in dioxan and chloroform. It may be formed by heating the reactants at up to 215‹ C. for up to 50 minutes then terminating the reaction. The conductor may be a mono- or multifilament metal wire. A solution of the prepolymer may be applied to an insulating film, e.g. polyimide tape, and the coating dried and heat set for 2¢ minutes at 250‹ C. The coated tape is then wrapped around the conductor and cured, e.g. for 4 to 5 hours at 550‹ to 650‹ C. In examples the prepolymer is prepared from the tetraethyl ester. A 28 wt. per cent solution of the prepolymer (inherent viscosity 0À56) is coated on a 1 mil. x # inch polyimide tape which is passed therethrough, dried and heat-set. It is then double or treble-wrapped with 50% overlap and reversal of direction on a silver plated multifilament copper wire while heated at 600Œ100‹ F. in the vicinity of the wrapping point. The wrapped wire is then passed through a curing oven at 600Œ50‹ F. and post-cured in an argon atmosphere for 4 to 8 hours at 600‹ F. Other methods of applying the coating are generally described, e.g. a melt or solution may be applied directly to a bare or wrapped wire in one or more applications with preliminary drying and curing of each coating as applied or of all the coatings in a subsequent step. Reference has been directed by the Comptroller to Specification 1,101,641.