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AssigneeBASF SE
InventorsDietrich Scherzer, Roland Minges, Bernd Bruchmann, Wolfgang Heider, Willy van Pee, Peter Keller
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Mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (crude MDI) of reduced iodine color number are prepared by reacting the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylenepolyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, at least one monohydric or polyhydric polyoxyalkylene alcohol, preferably having a functionality of from 2 to 3, and advantageously having a hydroxyl number of from 20 to 1800, or mixtures thereof in an effective amount, expediently in an amount of from 0.1 to 10% by weight, based on the weight of the crude MDI, being introduced into the reaction mixture when the phosgenation is complete, the phosgene and the inert organic solvent then being removed, up to 5% by weight, based on the weight of crude MDI, of at least one phenol-based antioxidant and/or aryl phosphite being added, if desired to the reaction product, and the reaction mixture being heated.
A process for the preparation of mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates of reduced iodine color number, by reacting the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylene polyamines with phosgene in the presence of at least one inert organic solvent at elevated temperature, removing the excess phosgene and solvent when the phosgenation is complete, and heating the reaction product, the improvement which comprises incorporating monohydric or polyhydric polyoxyalkylene alcohols or mixtures thereof in an effective amount into the reaction mixture when the phosgenation is complete.
Dependencies are inferred from the claim text.