Patent GB-918467-A (GB)
Title: Epoxy resins as adhesives for bonding polyurethane to metal
IPC: B05D7/14
Filed: 1960-07-18
Abstract: A process for bonding urethane polymers to metal surfaces with a degree of adhesion of at least 80 pounds per inch at a static 90 degree pull comprises coating a metal surface with a layer of a fluid, incompletely cured 1,2-polyepoxide adhesive resin containing from 6 to 10 parts by weight of an amine curative per 100 parts of resin, the layer having a film thickness of at least 0,023 gram per square inch of metal surface, applying a layer of fluid, incompletely cured polyurethane prepolymer possessing unreacted isocyanate groups and containing an amine curative upon the layer of 1,2-polyepoxide resin, and subsequently fully curing the 1,2-polyepoxide resin and the polyurethane prepolymer. Foaming agents may be included.  The prepolymer may be one formed by reacting an aromatic diisocyanate with castor oil, diacid glycol polyesters or polyalkylene glycol polyethers.  The use of a film of at least the specified minimum thickness ensures that neither the polyurethane intermediate nor the 1,2-polyepoxide cures before a minimum mutual diffusion occurs at their interface. Cross-linking bonds between the two resins are thought to be formed.  As amine curing catalysts for the prepolymer there are specified 3,31-dichloro-4,41-diamino diphenyl methane, 3,31-dichloro-4,41-diamino diphenyl and ethanolamine. The polyepoxides may be those obtained by reaction of epichlorohydrin with bisphenol A, tetrachlorobisphenol A, diphenolic acid, novolaks, cashew phenols and aliphatic diols and triols.  As amine curatives for the epoxide there can be used ethylene diamine, polyethylene polyamines, dicyandiamide, piperidine, symmetrical or asymmetric N-(hydroxyethyl) diethylene triamine, primary and secondary aromatic amines and hydroxyamines.  Sand, silica, aluminium powder, graphite, carbon black and asbestos are suitable fillers for the polyepoxide. Metals which can be laminated with the polyurethanes include iron, steel, aluminium, copper, brass, magnesium and titanium.  In Example (1) there are applied successively to a cleaned metal plate coatings of a 1,2-polyepoxide resin and trimethylene tetramine dissolved in benzene and acetone and a pourable mixture of a polytetramethylene glycol-2,4-toluylene diisocyanate prepolymer and 3,31-dichloro-4,41-diamino diphenylmethane, and curing is effected in an oven.  Other examples use prepolymers prepared from polyethylenepropylene adipate and various proportions of 2,4-toluene diisocyanate.ALSO:A process for bonding urethane polymers to metal surfaces with a degree of adhesion of at least 80 pounds per inch at a static 90 degrees pull comprises coating a metal surface with a layer of a fluid, incompletely cured 1,2-polyepoxide adhesive resin containing from 6 to 10 parts by weight of an amine curative per 100 parts of resin, the layer having a film thickness of at least 0,023 gram per square inch of metal surface, applying a layer of fluid, incompletely cured polyurethane prepolymer possessing unreacted isocyanate groups and containing an amine curative upon said layer of 1,2-polyepoxide resin, and subsequently fully curing the 1,2-polyepoxide resin and the polyurethane prepolymer. The prepolymer may be one formed by reacting an aromatic diisocyanate with castor oil, diacid glycol polyesters or polyalkylene glycol polyethers.  The use of a film of at least the specified minimum thickness ensures that neither the polyurethane intermediate nor the 1,2-polyepoxide cures before a minimum mutual diffusion occurs at their interface. Cross-linking bonds between the two resins are thought to be formed. As amine curing agents for the prepolymer there are specified 3,31-dichloro-4,41-diamino diphenylmethane, 3,31-dichloro-4,41-diamino diphenyl and ethanolamine. The polyepoxides may be those obtained by reaction of epichlorhydrin with bisphenol A, tetrachlorobisphenol A, diphenolic acid, novolaks, cashew phenols and aliphatic diols and triols.  As amine curatives for the epoxides there may be used ethylene diamine, polyethylene polyamine, dicyandiamide, piperidine, symmetrical or asymmetric N-(hydroxyethyl) diethylene triamine, primary and secondary aromatic amines and hydroxyamines. Sand, silica, aluminium powder, graphite, carbon black and asbestos are suitable fillers for the polyepoxide. Metals which may be laminated with the polyurethanes include iron, steel, aluminium, copper, brass, magnesium and titanium.  In Example (1) there are applied successively to a cleaned metal plate coatings of a 1,2-polyepoxide resin and trimethylene tetramine dissolved in benzene and acetone and a pourable mixture of a polytetramethylene glycol/2,4-toluene diisocyanate prepolymer and 3,31-dichloro-4,41-diamino diphenylmethane, and curing is effected in an oven.  Other examples use prepolymers prepared from polyethylene-propylene adipate and various proportions of 2,4-toluene diisocyanate.