A heat-setting mixture which has a long shelf life at room temperature, can be used as a coating composition, an adhesive or a sealant material or as an undersealant for motor vehicles, and comprises a polyisocyanate and one or more compounds which are reactive toward isocyanate groups and may or may not contain additives, such as protective colloids, solvents, plasticizers, pigments, fillers, dyes or other assistants conventionally used in surface coating technology, wherein the polyisocyanate, in the form of discrete particles having a diameter of from 0.1 to 150 .mu.m, is dispersed in a saturated or unsaturated amino-, hydrazide-, mercaptan- and/or carboxyl-containing polymer, polycondensate or polyadduct which has a functionality of more than 1 and may or may not contain the stated additives and not more than 95% of which may be replaced by polyols, and the polyisocyanate particles are deactivated at their surface, with the proviso that from 0.01 to 20 equivalent percent of the total amount of isocyanate groups present is deactivated.