Patent ID: 7420080
Filing Date: 2008-09-02
Classification: C07C

Abstract:
1. A multistage process for continuously preparing a cycloaliphatic diisocyanate, comprising: reacting a cycloaliphatic diamine with urea and/or an urea derivative and an alcohol to give a cycloaliphatic diurethane; freeing the cycloaliphatic diurethane of low and medium boilers, to obtain a purified cycloaliphatic diurethane; subsequently thermally cleaving the purified cycloaliphatic diurethane in a cleavage apparatus to give a cycloaliphatic diisocyanate and a cleavage residue, continuously discharging a portion of the cleavage residue from the cleavage apparatus and reurethanizing said portion of the cleavage residue with alcohol, to obtain a reurethanized stream; and thereafter removing high boiler components from said reurethanized stream, and recycling the reurethanized stream into the process into at least one step selected form the group consisting of the diurethane preparation, the low and medium boiler removal, and the diurethane cleavage.