Disclosed herein is a polyol (A) based on modified amino resins, prepared by reacting: an amino resin (B) comprising three acetalized or etherified N-methylol groups of the general formula (I) >N—CHR—OR1, wherein R is a hydrogen atom, an alkyl group of 1 to 6 carbon atoms or an aryl group of 6 to 10 carbon atoms and R1 is an alkyl group of 1 to 6 carbon atoms; with a polyol (C) of the general formula (II) R2(—OH)n, wherein n is a number from 2 to 6 and R2 is a divalent to hexavalent organic radical; wherein an equivalent ratio of the acetalized or etherified N-methylol groups to the polyol (C) is 0.5:1 to 1.2:1; with elimination of at least 50 mol % of a monoalcohol (D) of the general formula R1—OH, wherein R1 is as defined above, from the amino resin (B).