Process for preparing an isocyanate

US10703713B2 · kind B2 · utility

Assignee

• Covestro Deutschland AG · DE

Inventors

• Tim Loddenkemper · Dormagen, DE
• Jürgen Arras · Itzehoe, DE
• Markus Dugal · Kempen, DE

Key dates

• Filing date: Dec 18, 2017
• Grant date: Jul 7, 2020
• Expiry date: Dec 18, 2037

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B01D3/141
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

The industrial scale preparation of isocyanates gives rise to distillation bottom streams that are in need of further workup. These distillation bottom streams still also contain, as well as a distillation residue consisting of compounds that can be evaporated without decomposition only with great difficulty if at all (also referred to as residue for short), proportions of the desired target product (i.e. isocyanate to be prepared). The present invention relates to a process that enables recovery, in an efficient manner, of this proportion of isocyanate to be prepared in a distillation bottom stream which is obtained in the workup of the crude liquid process product which contains the isocyanate to be prepared and is formed in an isocyanate preparation process. More particularly, the present invention relates to a drying step in which the isocyanate to be prepared is recovered to form a solid material that has been largely to completely freed of this isocyanate. This drying step is characterized by a minimum content of compounds containing carbodiimide groups of 15% by mass, preferably 20% by mass, more preferably 30% by mass, based on the total mass of the distillation residue fed…