Aqueous dispersion and a method for applying a coating based on such a dispersion to a substrate

A method for applying a coating to a substrate comprising applying to a substrate an aqueous dispersion comprising a polymer and a crosslinker, wherein the polymer comprises a cyclic anhydride functional group, which polymer is in the form of a copolymer containing 20-50 wt. % cyclic anhydride groups based on the weight of the copolymer, and wherein the crosslinker is a multifunctional hydrazine derivative, wherein the amount of the polymer comprising a cyclic anhydride functional group dispersed in the aqueous phase is 5-70 wt. %, and wherein the size of the dispersed polymer particles is 5-2000 nm, wherein after being applied to the substrate, the aqueous dispersion is dried at a temperature of 10-50° C. to cause water to evaporate, after which curing is effected at a temperature of 70-220° C.