Patent ID: 7041740

Claim:
A curable solid resin made by the process comprising the steps of: A) providing a heat-settable mixture comprising a resin component comprising a thermosetting resin selected from the group consisting of epoxy resin, cyanate ester resin and bismaleimide resin, a curing agent component comprising a curing agent for said thermosetting resin and a particulate component, said heat-settable mixture having a curing temperature of between 120° C. and 220° C., such that said heat-settable mixture forms a cured resin when heated to a temperature equal to or greater than said curing temperature and wherein said particulate component comprises particles of a rigid-rod polymer having diameters of from 0.1 to 1000 microns and wherein said rigid-rod polymer particles dissolve in said resin component at a dissolution temperature, which is between 20° C. and 100° C. below said curing temperature, said particulate component being present in an amount ranging from 5 to 35 weight percent of said heat-settable mixture such that said heat-settable resin mixture forms a heat-set mixture when said heat-settable resin mixture is heated to a temperature that is equal to or above said dissolution temperature and below said curing temperature; B) heating the heat-settable resin mixture to a temperature that is equal to or above said dissolution temperature and below said curing temperature for a sufficient time to form said heat-set mixture; and C) cooling said heat-set mixture to a temperature below said dissolution temperature to form said curable solid resin.