Verfahren zur Verminderung des Hydroxylgruppen-Gehaltes von Epoxydharzen

The hydroxyl group content of an OH group containing epoxy resin is reduced by reaction with a cyclic or acyclic vinyl ether of formula in which R and R1 each represent either H halogen or alkyl radicals; R may have the same meaning as R and R11 when R111 represents a monovalent alkyl, aralkyl or aryl radical or alternatively R and R111 taken together may represent a divalent aliphatic group, e.g. a C2-C3 polymethylene chain. A preferred vinyl ether is 3,4-dihydro-2H-pyran. Reaction is effected in the presence of a small quantity of an acid catalyst, e.g. HC1, so that the hydroxyl groups but not any substantial proportion of the epoxy groups react with the vinyl ether. The vinyl ether is preferably more volatile than the epoxy resin and any excess may be distilled off after reaction. The product may be cured with conventional epoxy resin hardeners.