Process for making epoxy novolac resins with low hydrolyzable chlorine and low ionic chloride content

Claim 1

A process for making an epoxy novolac resin with a hydrolyzable chlorine content under 100 ppm and with an ionic chloride content of under 1 ppm, which comprises dissolving the crude epoxy novolac resin, prepared by the reaction of a novolac resin with epichlorohydrin in an alkaline medium, in an inert organic solvent, reducing the water content of the organic solution to less than 0.1% by weight, adding to the essentially anhydrous solution an alkali metal alkoxide, dissolved in an alkanol or in another suitable solvent, in an amount which is 105-200% of the theoretical equivalent amount required to complete the dehydrochlorination reaction, based on the content of hydrolyzable chlorine in the crude resin, at a temperature of 20°-140° C., adding 0.2 to 2% by weight of water, based on the crude resin solution, neutralizing the excess alkali metal alkoxide by the addition of a weak acid at 20°-50° C. until a pH value of 3 to 6 is attained, removing the alkali metal salt formed by treatment with from 0.5 to 5% by weight of the crude resin solution of a filter aid or mixture of filter aids followed by filtration, and isolating the epoxy novolac resin by vacuum distillation of the inert organic solvent at a temperature of 100°-200° C.