Color reduction of polymethylene polyphenyl polyisocyanates
AssigneeMiles Inc.
InventorsRick L. Adkins, Clarence D. Blue
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Abstract
The present invention is directed to a process for the production of polymethylene polyphenyl polyisocyanates by phosgenating the corresponding polyamines in solution in an inert organic solvent, removing excess phosgene, and stripping the solvent. The improvement resides in adding at least 0.02 parts by weight of reducing agent per 150 parts by weight of polyamine to the polyamines at any time prior to the stripping step.
Claims4
In a process for the production of polymethylene polyphenyl polyisocyanates comprising phosgenating the corresponding polyamines in solution in an inert organic solvent, removing excess phosgene, and stripping said solvent, the improvement wherein at least 0.02 parts by weight of reducing agent per 150 parts by weight of polyamine are added to said polyamines at any time prior to said stripping step.
Dependencies are inferred from the claim text.