The present invention is directed to the use as a reactive component in the curing of compositions based on epoxy resins of a functionalized α-angelica lactone (XOMAL) having the general formula: ##STR00001##
wherein: R.sup.a is a C.sub.1-C.sub.30 alkyl, C.sub.3-C.sub.30 cycloalkyl, C.sub.6-C.sub.18 aryl or C.sub.2-C.sub.12 alkenyl group.

The invention relates to an impregnation resin mixture and to the use thereof. In one embodiment, an impregnation resin mixture includes a) at least one epoxide resin component selected from the group consisting of polyepoxides based on bisphenol A and/or F, and advancement resin produced therefrom, based on epoxidized halogenated bisphenols and/or epoxidized novolaks and/or polyepoxide esters based on phthalic acid, hexahydrophthalic acid, or based on terephthalic acid, epoxidized polyaddition products from dicyclopentadiene and phenol or cycloaliphatic compounds, b) as reactive diluents, 2 to 30 wt. % lactones with respect to the sum of the epoxy resin components, c) BCI3 and/or BCI3 complexes and/or a compound selected from the group of imidazoles and d) optionally additional additives, wherein the impregnation resin mixture does not contain any carboxylic acid anhydrides.

The present invention is directed to the use as a reactive component in the curing of compositions based on epoxy resins of a functionalized α-angelica lactone (XOMAL) having the general formula:

##STR00001##

wherein: R.sup.a is a C.sub.1-C.sub.30 alkyl, C.sub.3-C.sub.30 cycloalkyl, C.sub.6-C.sub.18 aryl or C.sub.2-C.sub.12 alkenyl group.

The invention relates to an impregnation resin mixture and to the use thereof. In one embodiment, an impregnation resin mixture includes a) at least one epoxide resin component selected from the group consisting of polyepoxides based on bisphenol A and/or F, and advancement resin produced therefrom, based on epoxidised halogenated bisphenols and/or epoxidized novolaks and/or polyepoxide esters based on phthalic acid, hexahydrophthalic acid, or based on terephthalic acid, epoxidized polyaddition products from dicyclopentadiene and phenol or cycloaliphatic compounds, b) as reactive diluents, 2 to 30 wt. % lactones with respect to the sum of the epoxy resin components, c) BCI3 and/or BCI3 complexes and/or a compound selected from the group of imidazoles and d) optionally additional additives, wherein the impregnation resin mixture does not contain any carboxylic acid anhydrides.

Provided is an epoxy resin composition containing an epoxy resin (A), a curing agent (B) and an imidazole adduct-type curing accelerator (C), in which the curing agent (B) contains a compound (B-1) represented by formula (B-1) [R.sup.1 represents a hydrogen atom, a halogen atom, a methoxy group or a hydrocarbon group having 1 to 12 carbon atoms] and a compound (B-2) represented by formula (B-2) [R.sup.2 represents a hydrogen atom, a halogen atom, a methyl group or a methoxy group] and the content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the epoxy resin (A).