| abstract |
1463128 Polyimide-coated inorganic materials INTERNATIONAL BUSINESS MACHINES CORP 4 July 1974 [24 Aug 1973] 29706/74 Heading B2E A surface of inorganic material such as glass, quartz, aluminium (which may be in the form of a cable) or Al alloy has an electrically insulating coating of polyimide resin applied thereto by wetting the surface with a solution of an organic silicon, compound, evaporating off the solvent in a dry atmosphere by hanging the wetted surface over a further quantity of the solvent being boiled in a vessel and condensing the solvent vapour on cooling coils in the vessel after passage over the surface so that fresh, dry vapour continuously passes thereover and absorbs traces of moisture, coating the surface with a solution of uncured polyimide resin and curing the resin. The wetting step may be effected by spraying with, or immersing in, a solution of aminopropyltriethoxysilane in CCl 3 F 3 . The resin solution may comprise a polyamide acid derived from an aromatic amine (particularly 4, 4'-diaminodiphenyl ether) and pyromellitic 'acid anhydride in a solvent mixture containing N-methyl-2-pyrrolidone or dimethylacetamide. It is applied by spraying or, in the case of flat substrates, by centrifugal distribution or screen printing, curing then being effected by one or two heating steps. |