Flash resistant epoxy encapsulating composition and process for preparing same

A process for the preparation of a flash resistant epoxy encapsulating composition comprising:

• (a) blending a flash retarding composition with at least one each of an epoxy resin, a resin hardener, and a catalyst to obtain at least one resulting blend;
• (b) milling each resulting blend between rolls of a differential roll mill which comprises a hot roller and a cold roller spaced between one and six millimeters apart along the lengths thereof, said rollers being rotated in opposite directions toward each other at their upper portions at different surface velocities about their respective longitudinal axes, which are approximately horizontally disposed, the surface temperature of said hot roller being near the melting temperature of said resin for a blend containing resin but at a temperature insufficient to cure said resin within the residence time of the resin on the hot roller of the mill, said mill being further supplied with a series of plows having edges, each of said plows being mounted approximately above the hot roller about a 10.degree. to 50.degree. angle to planes perpendicular to the longitudinal axis of said hot roller, said edges being shaped and said plows being mounted such that each of the edges are within 2 millimeters of the surface of the hot roller for a distance equal to at least 5% of the circumference of the hot roller, said plows being positioned such that each such blend introduced at a feed position of said differential roll mill is forced by said plows along said rotating hot roller to a discharge position of said differential roll mill;
• and
• (c) when more than one blend is made, mixing said milled blends to form the encapsulating composition.