Storage-stable impregnating resins and electrical insulating tapes

An anhydride-free impregnating resin for an electrical insulation body, wherein the impregnating resin comprises:

• an epoxy resin, a hardener and nanosize and/or microsize inorganic particles,
• wherein the hardener is selected from the group consisting of a substituted guanidine, an aromatic diamine, an N-acylimidazole, a metal salt complex of an imidazole, a carboxylic hydrazide, a triazine derivative, melamine, a melamine derivative, a cyanoacetyl compound, an N-cyanoacylamide compound, an acylthiopropylphenol, a urea derivative, an aliphatic diamine, a cycloaliphatic diamine, an aliphatic polyamine, a cycloaliphatic polyamine and mixtures thereof,
• wherein the hardener is suspended in a solid state in the epoxy resin.