PURPOSE: To provide titled composition of high moisture resistance and rust- proofness, suitable as sealing resin for semiconductor devices and electronic circuit parts, comprising epoxy resin, curing agent, dithiophosphoric acid derivative metal salt and an additive consisting of organosiloxana polymer of specific formula.

CONSTITUTION: The objective composition comprising (A) most pref. phenol- novolak-based or cresal-novolak-based epoxy resin, (B) curing agent (pref. phenolic resin, cresol resin), (C) dithiophosphoric acid derivative metal salt (e.g. ginc diisopropyldithiophosphate) and (D) an additive consisting of organosiloxane polymer of formula (R1WR10 are each alkyl, aryl, alkenyl, aralkyl, H, or OH; n and m are 0 or ≥1). The amounts of the components (C) and (D) to be incorporated are pref. 0.1W10pts.wt. and 0.1W5pts.wt. per 100pts.wt. of the component (A), respectively.

EFFECT: Excellent in adhesivity and electrical insulation.

USE: Coatings, adhesives, etc.