Patent GB-1068362-A (GB)
Title: Improvements in or relating to the coating,sealing or impregnation of articles with a synthetic resin
IPC: H01B3/18
Filed: 1964-04-10
Abstract: 1,068,362. Moulding electrical insulation. SIEMENS-SCHUCKERTWERKE A.G. April 10, 1964 [April 11, 1963], No. 15013/64. Heading B5A. [Also in Division H2] A process for electrically insulating an article or a part of an article by coating and/or sealing and/or impregnating the article or the part of the article with a synthetic thermosetting resin comprises the steps of (a) immersing the article or part of the article in a bath, which contains a composition comprising a system of substances capable of entering into a polymerization or poly-addition reaction to form said synthetic thermo-setting resin, said article or part of an article having applied thereto and/or incorporated therein before it is immersed in said bath an accelerator for said polymerization or poly-addition reaction and being enclosed in a mould or envelope which contains no accelerator and through which said composition can pass, (b) maintaining the enclosed article or part of an article in said bath for a time sufficient to enable a quantity of said composition to penetrate said mould or envelope and contact said accelerator, and to enable the system of substances present in said quantity to react together to an extent which ensures that said quantity is retained by said mould or envelope after it is removed from said bath, and (c) removing the treated article or part of an article from said bath. The resin composition may be formed from an unsaturated polyester plus a copolymerizable monomer such as styrene; a solution of butadiene-styrene in styrene or a similar monomer; a mixture of styrene with a cross-linking agent such as divinyl benzene, divinyl acetylene and the like; a liquid polysiloxane containing vinyl groups; or a bi- or poly-functional acrylate or methacrylate or mixtures thereof. These mixtures may contain organic peroxides as initiators. The accelerators which are added to the article to be coated may be mixed aliphatic-aromatic tertiary amines or oxygen-carrying metallic salts. Other resins which may be used include mixtures of epoxide resins and acid anhydride hardeners the accelerator for which may be a tertiary amine or a complex boron compound, for example triethanolamene borate or a complex formed from boron trifluoride and an amine, or a soluble zinc salt, for example zinc oleate or zinc naphthenate. In an example, a conductor bar consisting of a multiplicity of component conductors insulated from one another is wrapped with several layers of a mica ribbon comprising mica flakes attached to a flexible backing of rice paper, woven fabric or synthetic plastic foil and covered by a further layer of the same material, this ribbon containing the accelerator for the subsequent resin impregnation, and further wrapped with a layer of the same or a similar mica ribbon containing no accelerator; this conductor bar is then introduced into the slots of the stator of a dynamoelectric machine. The stator including the conductor bar is dipped into a bath of the impregnating medium, if necessary in vacuo. In Fig. 6 a pole coil made up of a plurality of conductors 17 to 20 separated by insulating spacers 21 is surrounded by a mould comprising the 4 plates 22 to 25, the spaces between the conductors are filled with quartz meal plus an accelerator, and the whole is then immersed in a bath of a resin-hardener mixture, optionally under vacuum. The mixture penetrates the mould at the edges, which are not sealed, and through perforations 26, and partially gels. The mould is then removed from the bath and the resin completely cured by heating.