Polyurethane and its use for producing solvent-free coating substances

A reactive polyurethane having a number average molecular weight Mn of from 800 to 14000 daltons, a degree of branching of from 0.0 to 3.0 mol/kg, and an isocyanate functionality from 2.0 to 6.0 per mole, comprising the reaction product of:

• at least one polyester that has at least two isocyanate-reactive functional groups, a molecular mass of from 400 to 2500 daltons, and a degree of branching of from 0 to 3.5 mol/kg;
• at least one of at least one polyol having a molecular mass of from 62 to 400 daltons and a functionality of from 2 to 4, at east one polyamine, and at least one alkanolamine, wherein at least one of the polyamine and the alkanolamine is present in the reaction product;
• at least one compound comprising at least one functional group capable of forming anions and at least one isocyanate-reactive functional group;
• at least one of at least one polyisocyanate and at least one polyisocyanate adduct;
• at least one blocking agent for the isocyanate groups, wherein the blocking agent is eliminated at a sufficient reaction temperature from the isocyanate groups that are blocked by the blocking agent, or the blocking agent is released by a substitution reaction in the presence of a crosslinking agent;
• and
• at least one neutralizing agent for anionic stabilization in an aqueous medium comprising at least one of an organic base and an inorganic base;
• wherein the reaction product does not contain a polyether.