Polyurethane system with long pot life and rapid hardening

A process for preparing a polyurethane, comprising:

• mixing
• a) a first polyisocyanate,
• b) a compound obtained by introducing at least one of an alkali metal salt and an alkaline earth metal salt into a urethane group-comprising compound, which is present in solid or liquid form at 20° C. and which has a formula of R—NH—CO—O—R′, where R is other than hydrogen and COR″,
• wherein the compound contains exclusively monodentate urethane groups in relation to the salt anion and/or salt cation of the alkali metal salt and/or the alkaline earth metal salt, and wherein R, R′ and R″ independently represent organic radicals;
• c) a compound comprising at least one epoxide group,
• optionally d) a polyol,
• optionally e) a chain extender,
• optionally f) a filler, and
• optionally a further additive,
• to form a reaction mixture;
• and
• reacting the reaction mixture, to obtain the polyurethane, wherein an amount of alkali metal ions or alkaline earth metal ions per urethane group in the compound (b) is 0.0001 to 3.5, based on the number of alkali metal ions or alkaline earth metal ions and urethane groups.

A process for preparing a polyurethane, comprising:

• mixing
• a) a first polyisocyanate,
• b) a compound (b) obtained by mixing at least one of an alkali metal salt and an alkaline earth metal salt with a urethane group-comprising compound, wherein the urethane group-comprising compound is in solid or liquid form at 20° C. and is obtained by reacting:
• (i) at least one selected from the group consisting of 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, naphthylene diisocyanate, oligomers thereof, polycyclic homologs thereof and mixtures thereof, with
• (ii) at least one selected from the group consisting of a monol, a diol and a polyol, to form a monodentate compound;
• c) a compound comprising at least one epoxide group,
• optionally d) a polyol,
• optionally e) a chain extender,
• optionally f) a filler, and
• optionally a further additive,
• to form a reaction mixture;
• and
• reacting the reaction mixture, to obtain the polyurethane, wherein an amount of alkali metal ions or alkaline earth metal ions per urethane group in the compound (b) is 0.0001 to 3.5, based on the number of alkali metal ions or alkaline earth metal ions and urethane groups.