Thermally setting substance mixture and use thereof

A heat-curable composition comprising

• (I) at least one constituent whose molecule comprises on average at least one functional group selected from the group consisting of
• (A) functional groups containing at least one bond activated by means selected from heat, actinic radiation, and mixtures thereof,
• (B) reactive functional groups able to undergo thermal crosslinking reactions with groups selected from the group consisting of reactive functional groups, complementary reactive functional groups, and mixtures thereof,
• and mixtures thereof, with the provisos that there are always groups (A) and (B) in the composition and said constituent may not be a member selected from the group consisting of polyurethane dispersions synthesized from aliphatic polyisocyanates, compounds containing isocyanate-reactive functional groups and containing bonds activated with actinic radiation, aliphatic compounds containing isocyanate-reactive functional groups, compounds containing isocyanate-reactive functional groups and dispersing functional groups, neutralizing agents for the dispersing functional groups, blocking agents for isocyanate groups, compounds containing blocked isocyanate groups wherein the blocked isocyanate groups are introduced into the polyurethane dispersion by the reaction of blocking agents with isocyanate-containing polyurethane prepolymers, and mixtures thereof;
• and
• (II) from 0.5 to 15% by weight, based on the solids of the heat-curable composition, of at least one C-C-cleaving initiator comprising a mixture of monomeric and oligomeric benzpinacol silylethers.