Method for producing mdi, especially 2,4'-mdi
OwnerMartin Reif, Bernd Bruchmann +4inventors
InventorsMartin Reif, Bernd Bruchmann, Siegmund Pohl, Carl Bettendorf, Heinz Plaumann, Kai Thiele
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Abstract
MDI is prepared by a process comprising the following steps: A) reaction of aniline and formaldehyde in the presence of an acid to give methylene(diphenyldiamines) and polymethylenepolyphenylenepolyamines, the molar ratio of acid to amine being not more than 0.2, B) reaction of the mixture obtained in step A) with phosgene to give methylene(diphenyl diisocyanates) and polymethylenepolyphenylene polyisocyanates, C) separation of the mixture obtained in step B) into monomeric MDI and polymeric MDI and D) separation of the monomeric MDI obtained in step C) by isolating 2,4′-MDI.
Claims8
A process for the preparation of MDI, comprising the following steps:
- A) reaction of aniline and formaldehyde in the presence of an acid to give methylene(diphenylediamines) and polymethylenepolyphenylenepolyamines, the molar ratio of acid to amine being not more than 0.2,
- B) reaction of the mixture obtained in step A) with phosgene to give methylene(diphenyl diisocyanates) and polymethylenepolyphenylene polyisocyanates,
- C) separation of the mixture obained in step B) into monomeric MDI and polymeric MDI and
- D) separation of the monomeric MDI obtained in step C) with isolation of 2,4′-MDI.
Dependencies are inferred from the claim text.