Reactive compositions with an extended pot life

A reactive composition comprising

• (A) an NCO prepolymer based on an aliphatic and/or cycloaliphatic polyisocyanate and having an NCO content of 1 to 8 wt. % based on the aliphatic and/or cycloaliphatic polyisocyanate and a monomeric polyisocyanate content of less than 2 wt. %,
• (B) an amine-free chain extender comprising at least 50 equivalent percent, relative to the NCO-reactive groups of the chain extender, of a compound melting between 50° and 160° C. and having the formula (I)
• HO—X—Y—X—OH (I)
• wherein
• Y denotes methylene, ethylene, —C≡C—, 1,4-, 1,3-, or 1,2-cyclohexylene, or 1,4-, 1,3-, or 1,2-phenylene, and
• X denotes methylene, —OCH2CH2— (wherein oxygen is bonded to group Y), or 1,4-, 1,3-, or 1,2-cyclohexylene, and
• (C) 0 to 20 wt. %, relative to component (A), of inert organic solvents, wherein the equivalent ratio of the free NCO groups of component (A) to the NCO-reactive groups of component (B) is 0.90 to 1.35.