An integrated process for the preparation of methylene diphenylene diisocyanates and polymethylene polyphenylene poly (isocyanates) from diamines and polyamines

摘要

A multi-step process for the preparation of methylene diphenylene diisocyanates (MDI) or polymethylene polyphenylene poly (isocyanates) (PMDI) from methylene diphenylene diamines or polymethylene polyphenylene polyamines comprises reacting the diamine or polyamine with isocyanic acid to form a urea which is then reacted with a dialkyl amine to give a corresponding dialkyl urea or poly (alkyl urea) product which is then thermally reacted in the presence of various reaction promoters to give the corresponding isocyanate MDI or PMDI product.