Patent GB-1004556-A (GB)
Title: Insulated electrical conductors and polyesters for use in making the same
IPC: C09D5/25
Filed: 1964-05-05
Abstract: An electrical conductor has an undercoat of a branched thermosetting resin and an overcoat of a branched polyester of iso- and/or terephthalic acid or an ester-forming derivative thereof and a polyhydric alcohol component comprising 10-25% tris-(2-hydroxyethyl) isocyanurate and 90-75% of a dihydric alcohol. The undercoat may be a thermosetting polyester of 15-46% iso- and/or terephthalic acid or an ester-forming derivative thereof and the remainder a polyhydric alcohol component containing at least 50% of tris-(2-hydroxyethyl) isocyanurate. Ester-forming derivatives specified are methyl, ethyl, propyl, butyl, amyl, hexyl and octyl esters and diesters, anhydrides and chlorides.  The acid may be supplemented with up to an equal quantity of hemimellitic, edipic, trimesic, sebacic, trimellitic, phthalic or hexachloro - endomethylene - tetrahydrophthalic acid. The polyhydric alcohol component of the undercoat may also contain a diol of an aliphatic hydrocarbon, e.g. ethylene, butylene, pentylene, or neopentylene glycols, but-2-ene-1,4 - diol, but - 2 - yne - 1,4 - diol, 2,2,4,4-tetramethylcyclobutan - 1,3 - diol, and 1,4 - di-(hydroxy methyl) cyclohexane or an alcohol of 3 or more hydroxy groups per molecule, e.g. glycerol, pentaerythritol, hexane-1,2,3-triol, sorbitol, mannitol, 1,1,1 - tri - (hydroxymethyl) ethane and 1,1,1-tri-(hydroxymethyl)ethane. The polyhydric alcohol component of the overcoat may also contain an alkane diol of 2-5 carbon atoms.  Any of those specified for the undercoat may be used. Polyesterification may be accomplished at a temperature between 80 DEG  C. and the boiling point of the mixture. 0.2-1% of a drier and 0.001-4% of a tetraalkyltitinate may be added.  Driers specified are Zn, Pb, Ca and Cd linoleate, octoate and resinate and Co and Mn naphthenate.  Titinates specified are those in which alkyl is methyl, propyl, isopropyl, butyl and hexyl.  Either polyester may be modified by treatment with a polyisocyanate. 10-40% may be used for the undercoat and 5-40% for the overcoat. The polyisocyanate may have 3 or more reactive groups which may optionally be blocked by a radical, e.g. carbamate which will split off during the reaction.  Isocyanates specified are the reaction products of 2,4- and 2,6-tolylene diisocyanate and trimethylol propane blocked with phenol and cyclic trimers of 2,4- and 2,6-tolylene diisocyanate blocked with m-cresol. Polyurethane formation may be at 340-430 DEG  C. with or without use of a solvent.  The conductors may be coated by dipping in a solution of the insulator or by use of a die.  The polyester undercoat is soluble in cresylic acid or o-, m- or p-cresol optionally containing 0-60% of a hydrocarbon, e.g. xylene or a heavy coal tar naphtha.  It may be cured after application. Other undercoats specified are oil modified phenol / formaldehyde resin and bisphenol/ epichlorohydrin resin.  The overcoat polyester may be mixed with 5-40% polyethylene terephthalate and dissolved in a chlorophenol solvent, e.g. 30-50%, o-, m- or p-chlorophenol, 3 - methyl - 4 - chlorophenol or 2-sec-butyl-4-chlorophenol, 10-35% cresol and 25-50% phenol to give a solution containing 25% solids. In examples (1), (5) and (6) litharge is used as catalyst in both undercoat and overcoat preparation. In Example (2) melamine/formaldehyde resin was added to the undercoat. Specifications 715,231, 718,921, 775,081, 775,082, 840,401, 962,980 and 978,717 are referred to.ALSO:An electrical conductor is provided with an undercoat of a non-linear thermosetting resin and an overcoat of a non-linear polyester formed from terephthalic acid and/or isophthalic acid or an ester forming derivative thereof and a polyhydric alcohol component consisting of a mixture of 90-75 equivalent per cent of a dihydric alcohol and 10-25 equivalent per cent of tris(2-hydroxyethyl)isocyanurate.  The undercoat may be an oil modified phenol/formaldehyde resin, a bisphenol/epichlorohydrin epoxy-resin or a polyester formed from iso- and/or tere-phthalic acid or an ester-forming derivative thereof and a polyhydric alcohol component at least 50 equivalent per cent of which is tris(2-hydroxyethyl)isocyanurate.  The remaining polyhydric alcohol may be an alkylene glycol or an alcohol having more than 2 hydroxyl groups.  Other di-, tri and tetra-carboxylic acids may be present during the preparation of the undercoat polyester.  Both undercoat and overcoat polyesters may be mixed with tetralkyl titanates and may be treated with polyisocyanurates to give a polyurethane.  Metal salt driers may be added to the undercoat. Several examples are given of each of the materials used.  The electrical conductor may be a magnet wire comprising 18 gauge (A.W.G.) copper wire.  Coating may be by dipping or die application.  Solvents for the undercoat are o-, m- or p-cresol, or cresylic acid (b.p. 185-230  DEG C.) optionally mixed with xylene, coal tar or petroleum naphtha.  Solvents for the overcoat are o-, m- or p-chlorophenol optionally mixed with cresols and phenols. 25% solutions are used.  Several coats may be applied to a total thickness of 3 mils.  After each coat the wire may be passed at 25 feet per minute through a wire enamel tower at 400  DEG C. Specifications 715,231, 718,921, 775,081, 775,082, 840,401, 962,980 and 978,717 are referred to.