Abstract: Thermosetting resin compositions are obtained by mixing a resinous addition product produced by reacting an isocyanate compound having a molecular weight of 100 to 2000 and containing at least two isocyanate groups in its molecule with an epoxyphenol compound represented by the formula, ##EQU1## wherein R is a bi- or more valent group containing phenyl, R.sub.1 is hydrogen, methyl or ethyl, m and n each are an integer of 1-8, and optionally an ordinary thermosetting epoxy resin, and 0.01 to 10 % by weight of a basic heterocycle forming catalyst based on the weight of said resinous addition product, said isocyanate compound and said epoxyphenol compound being blended so that said OH group may be present in an amount of 1/3 to 1 equivalent per equivalent of said isocyanate group and said epoxy group may be present in an amount of one-fifth to two-thirds equivalent per equivalent of said isocyanate group.

Abstract: A thermosetting resin composition is derived from a modified novolak-type resin obtained by the reaction of a phenolic compound with an aralkyl halide or ether. The thermosetting resin is composed of 20 to 80 parts by weight of a thermosetting resin prepared by reacting a modified novolak-type resin represented by, for example, the general formula, ##SPC1##Wherein R is an aromatic nucleus, with formaldehyde in the presence of a basic catalyst, and, in admixture therewith, 80 to 20 parts by weight of a thermosetting resin prepared by reacting the above-mentioned modified novolak-type resin with hexamethylenetetramine. The thermosetting resin is quickly curable and gives a cured article excellent in heat resistance.