A process for the preparation of multifunctional polycarbodiimides, which are used as crosslinking agents, in which the polycarbodiimide is prepared by reacting mono- and polyisocyanates in the presence of a mono- or polyisocyanate that contains one or multiple additional reactive functional groups and in the presence of a carbodiimide catalyst, and thereafter terminating or chain extending the polycarbodiimide chain. Between 0 and 10% of an organic solvent and/or between 0 and 30% of a plasticizer and/or between 0 and 30% of a surface active component is added to the product during, before or after the polycarbodiimide forming reaction and/or the capping reaction and/or the chain extending reaction. Further, the invention relates to a coating mixture in which the polycarbodiimide is used as crosslinking agent and to the cured material obtained with the coating mixture.