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:
Mar. 16, 2021
Filed:
Jan. 02, 2019
Covestro Intellectual Property Gmbh & Co. KG, Leverkusen, DE;
Thomas Knauf, Dormagen, DE;
Peter Plathen, Krefeld, DE;
Dirk Manzel, Moers, DE;
Stefan Wershofen, Mönchengladbach, DE;
Covestro Intellectual Property GmbH & Co. KG, Leverkusen, DE;
Abstract
The invention relates to a method for producing methylene-diphenylene-diisocyanate and optionally a mixture of methylene-diphenylene-diisocyanate and polymethylene-polyphenylene-polyisocyanate, wherein, in a step α), a fraction () containing a methylene-diphenylene-diisocyanate and secondary components is provided, optionally via a step α.), the separating of methylene-diphenylene-diisocyanate and secondary components from a fraction () containing methylene-diphenylene-diisocyanate and polymethylene-polyphenylene-polyisocyanate, and wherein, in a step β), the fraction () containing methylene-diphenylene-diisocyanate and secondary components is subjected to a purification comprising an isomer separation by distillation and/or crystallization in two or more sub-steps (a, b, . . . ), obtaining two or more methylene-diphenylene-diisocyanate-reinfractions (--, . . . ) and a secondary component fraction (), wherein the secondary component fraction () obtained in step β) is returned to one of the sub-steps of step β), wherein none of the methylene-diphenylene-diisocyanate-reinfractions (--, . . . ) from step β) are obtained as distillation or crystallization, and/or to step α.), insofar as carried out.