Patent ID: 7339074
Filing Date: 2008-03-04
Classification: C07C

Abstract:
1. A multistage process for continuously preparing cycloaliphatic diisocyanates, which comprises: reacting cycloaliphatic diamines with carbonic acid derivatives and alcohols to give cycloaliphatic diurethane and subsequently thermally cleaving the cycloaliphatic diurethane to give cycloaliphatic diisocyanates, wherein said process comprises producing diurethanes in two stages, thermally cleaving the cycloaliphatic diurethane freed of low, medium and high boilers to release the desired cycloaliphatic diisocyanate, and continuously discharging a portion of a cleavage residue from a cleavage apparatus and reurethanizing the cleavage residue with alcohol and recycling the reurethanization product directly into a low-boiler separation.