Basf Aktiengesellschaft

Willy Van Pee

Bernd Bruchmann

Dietrich Scherzer

Roland Minges

Peter Keller

Wolfgang Heider

Werner Langer

Arnold Schmitt

Mixtures of diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (crude MDI) having a reduced iodine color number are prepared by reacting the corresponding mixtures of diphenylmethanediamines and polyphenylpolymethylene-polyamines with phosgene in the presence of one or more inert organic solvents at elevated temperatures by a process in which low molecular weight alkanols, polyhydric alcohols, preferably dihydric to octahydric alcohols having a molecular weight of from 60 to 350, or mixtures thereof are incorporated in an effective amount, advantageously in an amount of from 0.01 to 5% by weight, based on the weight of crude MDI, into the reaction mixture after the end of the phosgenation, the phosgene and the inert organic solvent are then separated off, from 0 to 5% by weight, based on the weight of crude MDI, of one or more phenol-based antioxidants and/or aryl phosphite are added to the reaction product, and the reaction mixture is subjected to a thermal treatment.

Preparation of mixtures of diphenylmethane diisocyanates and

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.

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Kapellen, Germany

Willy Van Pee