Binder systems to make foundry cores and molds polyurethane.

Binder system comprising one phenol resin component and a polyisocyanate component, wherein the phenolic resin component and / or the polyisocyanate component comprises a fatty acid ester and the phenol resin component comprising a phenolic resin modified with alkoxy, wherein less than 25 mol% of the hydroxymethyl groups in the phenolic resin is etherified by a primary or secondary aliphatic monoalcohol with 1 to 10 carbon atoms, and wherein the ratio of solvent phenolic resin component is at most 40% by weight.