Abstract: The present invention relates to a modified epoxy resin, a method for the preparation thereof and an epoxy resin composition using the modified epoxy resin. In particular, it relates to a modified epoxy resin of the general formula (I) which is prepared by incorporating a monomaleimide having a carboxy group useful as a heat resistance-improving agent of a resin composition containing an epoxy resin and maleimides into an epoxy resin, and an epoxy resin composition for sealing a semiconductor element having the improved heat resistance and moldability by the modified epoxy resin. ##STR1## wherein, R represents a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms (C.sub.1 to C.sub.10), andn is 0 to 100, and m is 1 to 100.

Abstract: Epoxy resin compositions for sealing semiconductor elements are disclosed and include an epoxy resin, a maleimide-modified siloxane compound represented by the formula (1) and an allylphenol-novolac resin represented by the formula (2) as a curing agent, and demonstrate low stress, high heat resistance and moldability. ##STR1## wherein, R.sub.1 denotes a methylene group a phenylene group or a substituted phenylene group,R.sub.2 denotes a methyl group, a phenyl group or a substituted phenyl group,n denotes 1 when R.sub.1 denotes phenylene or substituted phenylene groups, or 3 or 4 when R.sub.1 denotes a methylene group,m denotes an integer of from 1 to 100,l denotes an integer of from 1 to 100, and.kappa. denotes an integer of from 1 to 100.

Abstract: A modified epoxy resin of the general formula (I) is prepared by dissolving an epoxy resin in a solvent, adding the mixture to allyl magnesium halide at -70.degree. C. under a nitrogen atmosphere, and removing the solvent and salts from the resultant product. The modified epoxy resin is useful for epoxy maleimide resin compositions as a heat resistance enhancer. An epoxy resin composition for sealing semiconductor elements comprising the modified epoxy resin as a heat resistance enhancer is an amount of from 0.1 to 30% by weight, based on the total weight of the composition, is also provided. ##STR1## wherein, R represents H or C.sub.1 to C.sub.10 -alkyl group and m represents an integer of 0 to 100 and n represents an integer of 1 to 100.

Abstract: The present invention relates to novel epoxy resin compositions for sealing semiconductor elements, which comprise 0.1 to 20.0% by weight of imide-epoxy resins represented by the general formula (I) together with epoxy resins, curing agents, curing promoters and plasticizers, and which has improved heat resistant and moisture resistant properties: ##STR1## wherein, R.sub.1 and R.sub.2 represent H or --CH.sub.2).sub.n CH.sub.3 group, andn represents an integer of 0 or 1.