Phenyl isocyanate conversion process

An MDI and/or polymeric MDI manufacturing process, comprising the steps of:

• a) reacting aniline with formaldehyde to produce a mixture of methylene dianiline (MDA), one or more polymethylene polyanilines having at least three aniline groups (PMDA) and unreacted aniline;
• b) removing aniline from the mixture produced in step a) to produce a process stream containing the MDA, PMDA and residual aniline;
• c) phosgenating the process stream from step b) in a non-polar solvent to form an isocyanate process stream containing the non-polar solvent, MDI, one or more polymethylene polyphenylisocyanates that have at least three phenyl isocyanate groups (PMDI) and at least one phenyl isocyanate;
• d) separating the MDI and PMDI from the isocyanate process stream obtained in step c) by distillation to produce a solvent stream containing the non-polar solvent, greater than zero up to 10 weight percent of the at least one phenyl isocyanate based on the weight of the solvent stream and 0 to 5 weight percent, based on the weight of the solvent stream, of the MDI and/or PMDI;
• e) reacting the solvent stream obtained in step d) in the presence of a catalytically effective amount of a carbodiimidization catalyst, to convert at least a portion of the at least one phenyl isocyanate to an N,N′-diphenylcarbodiimide;
• f) optionally removing and/or deactivating the carbodiimidization catalyst;
• and
• g) recycling the N, N′-diphenylcarbodiimide formed in step e), optionally the nonpolar solvent and optionally the carbodiimidization catalyst and/or residues from the deactivation of the carbodiimidization catalyst, directly or indirectly into step d).