Thermosetting epoxy resin composition comprising a) at least one epoxy resin A having an average of more than one epoxy group per molecule; b) at least one curing agent B for epoxy resins, where the curing agent B is a dihydrazide selected from the group consisting of glutaric dihydrazide, adipic dihydrazide and pimelic dihydrazide, preferably adipic dihydrazide; and c) at least one accelerator C of the formula (Ia) or (Ib) where R 1 is H or an n-valent aliphatic, cycloaliphatic or araliphatic radical; R 2 and R 3 are either each independently an alkyl group or aralkyl group; or together are a divalent aliphatic radical which has 3 to 20 carbon atoms and is part of an optionally substituted heterocyclic ring having 5 to 8, preferably 6, ring atoms; R 1' is an n'-valent aliphatic, cycloaliphatic or araliphatic radical; R 2' is an alkyl group or aralkyl group or alkylene group; R 3' is independently H or an alkyl group or aralkyl group; and n and n' each have a value of 1 to 4, especially 1 or 2, and where the dihydrazide has a median particle size D 50 of ≤ 100 μm, ≤ 50 μm, 0.5-50 μm, 1-50 μm, 1-40 μm, especially 1-20 μm, preferably 2-20 μm, especially preferably 2-15 μm, where the median particle size D 50 is determined by laser diffractometry. a) at least one epoxy resin A having an average of more than one epoxy group per molecule; b) at least one curing agent B for epoxy resins, where the curing agent B is a dihydrazide selected from the group consisting of glutaric dihydrazide, adipic dihydrazide and pimelic dihydrazide, preferably adipic dihydrazide; and c) at least one accelerator C of the formula (Ia) or (Ib) where R 1 is H or an n-valent aliphatic, cycloaliphatic or araliphatic radical; R 2 and R 3 are either each independently an alkyl group or aralkyl group; or together are a divalent aliphatic radical which has 3 to 20 carbon atoms and is part of an optionally substituted heterocyclic ring having 5 to 8, preferably 6, ring atoms; R 1' is an n'-valent aliphatic, cycloaliphatic or araliphatic radical; R 2' is an alkyl group or aralkyl group or alkylene group; R 3' is independently H or an alkyl group or aralkyl group; and n and n' each have a value of 1 to 4, especially 1 or 2, and where the dihydrazide has a median particle size D 50 of ≤ 100 μm, ≤ 50 μm, 0.5-50 μm, 1-50 μm, 1-40 μm, especially 1-20 μm, preferably 2-20 μm, especially preferably 2-15 μm, where the median particle size D 50 is determined by laser diffractometry. where R 1 is H or an n-valent aliphatic, cycloaliphatic or araliphatic radical; R 2 and R 3 are either each independently an alkyl group or aralkyl group; or together are a divalent aliphatic radical which has 3 to 20 carbon atoms and is part of an optionally substituted heterocyclic ring having 5 to 8, preferably 6, ring atoms; each independently an alkyl group or aralkyl group; or together are a divalent aliphatic radical which has 3 to 20 carbon atoms and is part of an optionally substituted heterocyclic ring having 5 to 8, preferably 6, ring atoms; R 1' is an n'-valent aliphatic, cycloaliphatic or araliphatic radical; R 2' is an alkyl group or aralkyl group or alkylene group; R 3' is independently H or an alkyl group or aralkyl group; and n and n' each have a value of 1 to 4, especially 1 or 2, and where the dihydrazide has a median particle size D 50 of ≤ 100 μm, ≤ 50 μm, 0.5-50 μm, 1-50 μm, 1-40 μm, especially 1-20 μm, preferably 2-20 μm, especially preferably 2-15 μm, where the median particle size D 50 is determined by laser diffractometry.