Patent GB-1012200-A (GB)
Title: Epoxy resin coating compositions and insulated structures
IPC: B29C67/24
Filed: 1964-06-17
Abstract: A curable coating composition comprises by weight (1) 30-60% anhydrous calcium sulphate, (2) 15-50% epoxy resin having an epoxy equivalent 135-220, (3) 2-6% levelling agent, (4) 10-25% carboxylic acid anhydride containing 7-15 carbon atoms per molecule, (5) 2-6% thixotrope.  Optional further ingredients are 0-10% carboxylic acid anhydride containing 4 or 5 carbon atoms, e.g. maleic anhydride, 0-5% aliphatic compound containing 2-5 carbon atoms and 2-3 hydroxy groups, e.g. ethylene glycol, and 0-3% of an activating catalyst, e.g. a boron-trifluorideamine complex or a trialkanolamine borate. Suitable epoxy resins (2), are bisphenol A-epichlorhydrin resins, and 3,4-epoxy-6-methylcyclohexylmethyl - 3,4 - epoxy - 6 - methylcyclohexane carboxylate, and its homologues. The levelling agent, (3), may be a butylated urea-formaldehyde resin or a condensation product of a melamine-formaldehyde, a bisphenol-based diepoxy resin. Suitable anhydrides (4) are nadic, methyl nadic, dodecenyl succinic, dimethyl butenyl tetrahydrophthalic, and chlorendic, hexahydrophthalic and tetrahydrophthalic anhydrides, and any two mixed of this last three, and linear azelaic polyanhydride, and the thixotrope, (5), may be an aliphatic derivative of ammonium bentonite or glyceryl trihydroxystearate.  The solid components are dispersed in the liquid, and the mixture applied to the surface to be coated, where it cures in 1-8 hours at room temperature, final cure requiring 4-20 hours at 120-150 DEG  C.  In Example I anhydrous calcium sulphate is added to a mixture of 3,4-epoxy-6-methylcyclohexylmethyl - 3,4 - epoxy - 6 - methylcyclohexane carboxylate, a urea-formaldehyde liquid resin, methyl nadic anhydride, ethylene glycol, maleic anhydride, a vegetable oil base thixotrope and boron trifluoride-monoethylamine complex.  In Example II the methyl nadic anhydride is replaced by dimethyl butenyl tetrahydrophthalic anhydride.  Test discs are prepared from these compositions and cured at 135 DEG  C. for 8 hours.ALSO:An insulating coating composition comprises by weight 30-60% anhydrous calcium sulphate, 15-50% epoxy resin of epoxy equivalent 135-220, 2-6% levelling agent, 10-25% carboxylic acid anhydride containing 7-15 carbon atoms per molecule, 2-6% thixotrope, and optionally up to 10% carboxylic acid anhydride containing 4 or 5 C atoms, up to 5% aliphatic compound containing 2-5 carbon atoms and 2-3 hydroxy groups, and up to 3% of an activating catalyst (see Division C3).  The composition may be applied, e.g., to a ceramic glazed porcelain bushing by brushing, and cures in 1-8 hours at room temperature, final cure requiring heating to 120-150  DEG C. for 4-20 hours.  The composition is prepared by dispersing the solid components in the liquid, and should be applied immediately.  In examples, anhydrous calcium sulphate is added to a mixture of 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexane carboxylate, a urea-formaldehyde liquid resin (leveller), methyl nadic anhydride or dimethyl butenyl tetrahydrophthalic anhydride, ethylene glycol, maleic-anhydride, a vegetable oil based thixotrope and a boron trifluoride-monoethylamine complex, and the resulting compositions are used to coat porcelain bushings.