Patent GB-1011515-A (GB)
Title: Powdered epoxy resin compositions
IPC: C08G59/38
Filed: 1964-06-09
Abstract: A coating composition is a free-flowing powder (of e.g. less than 80 mesh) comprising a triphenol-A based epoxy resin and a phenolformaldehyde (novolac) based epoxy resins in the proportion 1: 1 to 20: 1, together with an carbocyclic polycarboxylic acid anhydride or polyanhydride melting above 50 DEG  C.  The powder should preferably have particle sizes between 5 and 400 microns, and soften above 70 DEG  C., and contain 0.15-0.4 parts by weight of hardener per part of resin.  Preferred bisphenol-A resins are of molecular weight 900-10,000 and softening point 60-140 DEG  C., while the novolac resins are preferably of molecular weight 500-1500 and softening point 30-120 DEG  C.  Suitable hardeners are trimellitic anhydride, glycerol tris-trimellitate anhydride, glycerol bistrimellitate anhydride, ethylene glycol bistrimellitate anhydride, benzophenone dianhydride, pyromellitic dianhydride, phthalic anhydride, and hexachloro - endo - methylenetetrahydrophthalic anhydride.  The powder may contain up to 70% by weight of a mineral filler, e.g. mica, silica, silicates, talc and barytes, and/or a pigment, e.g. phthalocyanine blue, phthalocyanine green, mercury/cadmium oxide and ferric oxide reds and titanium dioxide. The powder may be prepared by mixing the components each previously ground to less than 80 mesh particle size, or, preferably, by grinding a cooled, fused mixture of the resins and any fillers to less than 80 mesh particle size and combining this with the powdered (80 mesh) hardener).  In the examples hardeners used are glycerol tris-trimellitate anhydride, ethylene glycol tris-trimellitate anhydride, trimellitic anhydride, benzophenone dianhydride and tetrachlorophthalic anhydride, and fillers are silica or barytes with phthalocyanine green or blue or iron oxide or TiO2, colloidal silica being added after the anhydride.  Polyvinyl butyral and polyethyleneglycol are added as modifiers and flow control agents. The products are used to coat steel substrates in a fluidized bed technique.ALSO:A powdered coating composition comprises a bisphenol-A based epoxy resin and a novolac (phenolformaldehyde resin) based epoxy resin in the proportion 1:1 to 20:1 and, as hardener, a carbocyclic polycarboxylic acid anhydride or polyanhydride melting above 50  DEG C.  The powder preferably has a particle size between 5 and 400 microns, softens above 70  DEG C., and contains 0,15-0,4 parts by weight of hardener.  It may contain up to 70 weight per cent of a mineral filler and/or a pigment (see Division C3).  The powder may be applied by dry spraying, flame spraying, or fluidized bed techniques.  In examples powders are obtained from bisphenol A and novolac epoxy resins using as hardener glycerol tris trimellitate anhydride, ethylene glycol bis trimellitate anhydride, trimellitic anhydride, benzophenone dianhydride and tetrachlorophthalic anhydride, and as fillers silica or barytes, with phthalocyanine blue or green, or Fe2O3 or TiO2 as pigments, and colloidal silica. Polyvinylbutyral and polyethyleneglycol are added as flow control agents.  The products are used to coat steel or metal substrates including armatures, stators and rotors.