Multi-step process for the continuous preparation of cycloaliphatic diisocyanates

摘要

A multistage process for preparation of cycloaliphatic diisocyanate (C1) involves: reacting cycloaliphatic diamine with carbonic acid derivative and alcohol to give cycloaliphatic diurethane (C2), and thermally cleaving (C2). The process involves producing diurethane in two stages, thermally cleaving (C2) freed of low, medium and high boiler to release (C1), discharging portion of cleavage residue, reurethanizing with alcohol and recycling. A multistage process for continuous preparation of cycloaliphatic diisocyanate (C1) involves: reacting cycloaliphatic diamine with carbonic acid derivatives and alcohols to give cycloaliphatic diurethane (C2); and subsequently thermally cleaving (C2) to give (C1). The process involves producing diurethane in two stages, thermally cleaving (C2) freed of low, medium and high boilers to release desired (C1), 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. An independent claim is included for production of polyurethane involving reacting (C1) with a polyol or diol.