Abstract: Resins based on a copolymerizate reacted with by a polyisocyanate, partially and transitorily blocked in the form of urea by an amino derivative, in which i) the polymerizate is based on styrene, at least two acrylic monomers of formula (I), H.sub.2 C.dbd.C(R)--COOR.sub.1, where R.dbd.hydrogen or methyl, R.sub.1 .dbd.hydrogen, linear or branched C.sub.1 -C.sub.14 alkyl radical, C.sub.1 -C.sub.4 hydroxyalkyl radical, and amongst which at least one of these acrylic monomers possesses a hydroxyl group, and at least one vinyl ester of a C.sub.9 -C.sub.19 trialkylacetic acid, ii) the polyisocyanate is chosen from the group of aliphatic polyisocyanates of formula (II) O.dbd.C.dbd.N--A--N.dbd.C.dbd.O where A represents a linear or branched C.sub.4 -C.sub.10 alkylene group and cyclic aromatic or cyclic aliphatic polyisocyanates and iii) this polyisocyanate is partially and transitorily blocked in the form of urea by a pyrazole group of formula (III) ##STR1## where R.sub.2, R.sub.3 and R.sub.4 .dbd.H or C.sub.1 -C.