Process for preparation of isocyanate compounds

摘要

A diisocyanate compound substantially free from chlorine is prepared by the following consecutive steps (1), (2) and (3): (1) preparing dimethyl carbonate by a method selected from: (a) a method wherein carbon monoxide and oxygen are reacted with methanol, (b) a method wherein propylene oxide is reacted with carbon dioxide to prepare propylene carbonate, and then, the propylene carbonate is reacted with methanol, and (c) a method wherein a nitrous acid ester is catalytically reacted with carbon monoxide; (2) reacting the dimethyl carbonate with an aliphatic diamine in the presence of an alkali catalyst to prepare a corresponding urethane compound; and (3) thermally decomposing the urethane compound under a reduced pressure of 1 to 700 Torr in a high-boiling point solvent.