Preparation of methylene diphenylene diisocyanates and polymethylene polyphenylene poly (isocyanates) using an organic sulfonic acid promoter

摘要

An improved process is provided for the preparation of methylene diphenylene diisocyanates (MDI) and polymethylene polyphenylene poly (isocyanates) (PMDI) by the thermal decomposition of a methylene diphenylene bis (dialkylurea) or a polymethylene polyphenylene poly (alkylurea) in a solvent in the presence of an organic sulfonic acid or sulfonated aromatic ion exchange resin as a promoter for conversion of the urea groups to the corresponding isocyanate.