Process for polyisocyanates
AssigneeThe Upjohn Company
InventorRichard Hatfield, Jr.
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Abstract
Addition of controlled amounts of water to the reaction mixture produced by phosgenation of a mixture of polymethylene polyphenyl polyamines (and like polyamines produced by condensation of formaldehyde and aromatic amines) prior to complete removal of excess phosgene gives rise to the corresponding polymethylene polyphenyl polyisocyanates having significantly improved properties. Not only is the color of the product, and of polyurethane foams prepared therefrom, significantly lighter but the proportion of higher molecular weight products is significantly less and the viscosity is less. No undesirable by-products are introduced into the polyisocyanate as a result of the process.
Claims11
In a process for the preparation of polymethylene polyphenyl polyisocyanates by phosgenation of the corresponding polyamines in solution in an inert organic solvent followed by removal of excess phosgene and stripping of said solvent the improvement which 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 polyisocyanate present in the reaction mixture.
Dependencies are inferred from the claim text.