Patent ID: 7692318

Claim:
A liquid epoxy resin potting composition comprising (A) a liquid epoxy resin, said liquid epoxy resin being liquid at 25° C., (B) an aromatic amine curing agent, wherein the total amount of the aromatic amine curing agent is such that the ratio of the epoxy equivalent of the liquid epoxy resin to the amine equivalent of the aromatic amine curing agent is in the range from 0.7:1 to 1.2:1, (C) from 0.5 to 20 parts by weight per 100 parts by weight of components (A) and (B) combined of microcapsules containing a phenolic hydroxy-bearing benzoic acid derivative having the general formula (2): wherein R 4 , R 5 and R 6 are each independently selected from the group consisting of hydrogen, hydroxyl, C 1 -C 10 alkoxy, and substituted or unsubstituted monovalent C 1 -C 12 hydrocarbon groups which may be separated by at least one atom selected from oxygen, nitrogen, sulfur and silicon, said microcapsules employing as their shell material a member selected from the group consisting of: polymers composed of (meth)acrylic monomers, polymers composed of monofunctional monomers, and polymers composed of polyfunctional monomers; said (meth)acrylic monomers selected from the group consisting of C 1 -C 8 alkyl esters of acrylic acid, C 1 -C 8 alkyl esters of methacrylic acid, C 1 -C 8 alkyl esters of itaconic acid, C 1 -C 8 alkyl esters of crotonic acid, and substituted derivatives thereof wherein the alkyl group is substituted with an allyl group; said monofunctional monomers selected from the group consisting of styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, and vinyl acetate; and said polyfunctional monomers selected from the group consisting of ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, bisphenol A di(meth)acrylate, and methylenebis(meth)acrylamide, said phenolic hydroxyl-bearing benzoic acid derivative being enclosed within the polymer shell, wherein said microcapsules (C) have an average particle size of 0.5 to 10 μm, and wherein an amount of the phenolic hydroxy-bearing benzoic acid derivative leached out from said microcapsules with cresol at 30° C. for 15 minutes is at least 70% by weight of the total content of the phenolic hydroxy-bearing benzoic acid derivative in said microcapsules, and (D) 50 to 1,200 parts by weight per 100 parts by weight of epoxy resin (A) and aromatic amine curing agent (B) combined of an inorganic filler having an average particle size of 2 to 20 μm and a maximum particle size of up to 75 μm.