Removal of monomeric aliphatic diisocyanate in an aliphatic polyisocyanate using scavengers

Abstract

The present invention relates to a process for the effective removal of residual monomeric aliphatic isocyanate from a reaction mixture comprising aliphatic polyisocyanate comprising (i) providing a reactor containing a scavenger comprising a zeolitic material, wherein the zeolitic material comprises SiO2 and optionally X2O3 in its framework structure, wherein X is a trivalent element; (ii) providing a reaction mixture comprising aliphatic polyisocyanate and monomeric aliphatic isocyanate; (iii) contacting the scavenger in the reactor with the reaction mixture provided in (ii) at a temperature lower than the boiling point of the residual monomeric aliphatic isocyanate for obtaining a product comprising aliphatic polyisocyanate with a reduced monomeric aliphatic isocyanate content, wherein if the zeolitic material comprises X2O3, the zeolitic material has an SiO2 to X2O3 molar ratio higher than 2.8:1, preferably higher than 5:1, more preferably higher than 30:1.

Dependencies are inferred from the claim text.