Patent ID: 7579392

Claim:
A curable, low volatile organic solvent, epoxy resin-containing formulation comprising: (1) a low-viscosity epoxy resin, being either a liquid at 20° C. or having an average formula weight per epoxy equivalent of no more than 350 for all non-halogen atoms in the molecule; (2) a phenolic chain extender which contains an average 1.8-2.1 phenolic hydroxyl groups per molecule and whose concentration is from 0.1 to less than 0.6 equivalents of phenolic hydroxyl group per epoxide equivalent of the low-viscosity epoxy resin; (3) a catalyst containing amine, phosphine, heterocyclic nitrogen ammonium, phosphonium, arsonium sulfonium moieties that promotes self-curing reactions between epoxy groups containing on average no more than about 1 active hydrogen moiety per molecule; (4) an inhibitor which is a Lewis acid in an inhibiting amount of from at least 0.3 mole to 3 moles of inhibitor per mole of catalyst which inhibits the activity of the catalyst during B-staging so as to retard the curing reaction of epoxy resin with epoxy resin at B-stage and which is selected from the group consisting of boric acid, metaboric acid, boroxine, and boron oxide; (5) from at least 5 weight percent to no more than 20 weight percent of a volatile organic solvent; and (6) a multifunctional cross-linking agent containing on average more than two active hydrogen moieties per molecule; wherein the formulation contains at least 0.01 equivalents of multifunctional cross-linking agent per epoxide equivalent; wherein the viscosity of the resultant curable, low volatile organic solvent, epoxy resin-containing formulation for making composites or laminates at 20° C. is no more than 800 mP·s; and wherein the formulation contains no more than 0.5 equivalents of phenolic chain extender and multifunctional cross-linking agent per epoxide equivalent.