Synthesis and reactivity of monodisperse prepolymers with blocked isocyanate end groups

Summary

We describe the synthesis of monodisperse prepolymers containing one or two blocked isocyanate groups on the chain extremities.

The prepolymers containing blocked isocyanate in one end and hydroxyl group in the other end are obtained by chemical transformation of undecylenic acid to acid chloride. This later was converted to the isocyanate by the CURTIUS reaction and blocked with nonyl-phenol. Finally the blocked isocyanate was telomerized with mercapto-ethanol. The resulting product is deblocked at T=105°C.

By action of pure 2.4 T.D.I. (Tolylene diisocyanate) on the later product, we obtain a product containing blocked isocyanate end groups. The removal of the blocking agent could be effected at 100°C or less depending on the compound used to remove the blocking agent (amine).