Epoxy resin compositions comprising latent amine curing agents and novel accelerators

Claim 1

A thermally curable epoxy composition comprising A. an epoxy resin bearing a plurality of 1,2-epoxy groups; B. a latent amine curing agent for said epoxy resin; and C. a small but sufficient amount of at least one sterically hindered urea or thiourea accelerator to increase the rate of reaction between (A) and (B) at elevated temperatures; said accelerator corresponding to the formula ##SPC6## wherein: X is an atom of oxygen or sulfur; n is 1 or 2; R 1 is lower alkyl, chloro or bromo; R 2 is hydrogen, lower alkyl, chloro or bromo; R 3 is hydrogen or an inert organic radical, or R 1 and R 2 or R 1 and R 3 can be joined to form a 5- or 6-membered carbocyclic ring; --NR 4 R 5 is the organic residue derived by the removal of the amino hydrogen atom from a secondary amine; with the proviso that R 1 is located α on the benzene nucleus to at least one of the urea of thiourea substituents; and with the proviso that when n is 2, I is the position isomer having the urea or thiourea substituents located α,α' on the benzene nucleus with respect to R 1 , or, I is a mixture of position isomers consisting essentially of at least about 35 percent of the aforesaid α,α' position isomer and up to about 65 percent of the α,γ isomer.