The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 27, 2012
Filed:
Feb. 27, 2009
Fritz Pohl, Brunsbüttel, DE;
Andreas Bulan, Langenfeld, DE;
Rainer Weber, Odenthal, DE;
Richard Adamson, Leichlingen, DE;
Matthias Böhm, Leverkusen, DE;
Christian Six, Baytown, TX (US);
Fritz Pohl, Brunsbüttel, DE;
Andreas Bulan, Langenfeld, DE;
Rainer Weber, Odenthal, DE;
Richard Adamson, Leichlingen, DE;
Matthias Böhm, Leverkusen, DE;
Christian Six, Baytown, TX (US);
Bayer MaterialScience AG, Leverkusen, DE;
Abstract
The invention relates to a process for preparing methylenediphenyl diisocyanates which comprises at least the steps: A) reaction of aniline with formaldehyde in the presence of hydrochloric acid as catalyst to give a mixture of diamines and polyamines of the diphenylmethane series (MDA) and subsequent at least partial neutralization of the hydrochloric acid by means of alkali metal hydroxide, B) reaction of the mixture of diamines and polyamines of the diphenylmethane series obtained in step A) with phosgene to give a mixture of diisocyanates and polyisocyanates of the diphenylmethane series (MDI) and hydrogen chloride, wherein C) the hydrochloric acid which has been neutralized in step A) is separated off in the form of a solution containing alkali metal chloride and is subsequently at least partly fed to an electrochemical oxidation to form chlorine, alkali metal hydroxide and optionally hydrogen and D) at least part of the chlorine produced in step C) is used for preparing the phosgene used in step B).