Polyurethane-polyisocyanurate compounds and processes for preparing polyurethane-polyisocyanurate compounds are disclosed herein. A process includes mixing component (a) polyisocyanate with component (b) a mixture obtainable by introducing an alkali metal or alkaline earth metal salt into a compound R—NH—CO—R containing urethane groups, where R is not hydrogen and is not COR, component (c) compounds containing one or more epoxide groups, component (d) one or more compounds having at least two isocyanate-reactive groups, comprising compounds having NH2 and/or primary OH groups, and component (e) optionally fillers and other additives, to form a reaction mixture, and reacting the reaction mixture to form the polyurethane-polyisocyanurate compound, wherein the molar amount of alkali metal and/or alkaline earth metal ions in the reaction mixture per mole of urethane group in component (b) is 0.0001 to 3.5 and the isocyanate index is greater than 150. Use of polyurethane-polyisocyanate compounds for producing vehicle parts is also disclosed.