Technology

Improved Process for the preparation of Polymethylene Polyphenyl Polyisocyanates (PMDI) by Phosgenation of the corresponding Mixture of Polyamines (PMDA) in Solution in an inert Organic Solvent followed by removal of excess Phosgene and stripping of said Solvent wherein the improvement comprises introducing into the Reaction Mixture, after completion of the Phosgenation but prior to completion of removal of Phosgene therefrom, from about 0.1 percent by weight to about 5 percent by weight of Water, based on the amount of Polyisocyanate present in the Reaction Mixture.