# US 2021/0276944 A1 · Method for recovering diisocyanates from distillation residues > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0276944 A1 - Document ID: US20210276944A1 - Status: Published application - Kind: A1 - Application number: 17/260,624 - Filed: 2019-07-15 - Published: 2021-09-09 - Earliest claimed: 2018-07-18 - Assignees: Covestro Deutschland AG - Applicants: Covestro Deutschland AG - Inventors: Anna-Marie Zorn; Thomas Guttmann; Claudine Stoye; Sascha Tadjbach; Thomas Voigt; Irene Cristina Latorre Martinez; Joerg Morawski - Web page: https://patentgrep.com/patent/US20210276944A1 ## CPC - C07C 263/20: Separation; Purification - B01D 1/065: {by film evaporating} - B01D 1/22: by bringing a thin layer of the liquid into contact with a heated surface {(B01D1/065 takes precedence)} - B01D 3/34: with one or more auxiliary substances - C07C 263/10: by reaction of amines with carbonyl halides, e.g. with phosgene - C08G 18/42: Polycondensates having carboxylic or carbonic ester groups in the main chain - C08G 18/4238: {derived from dicarboxylic acids and dialcohols} - C08G 18/7678: {containing condensed aromatic rings} - C07C 2601/16: the ring being unsaturated - C07C 2602/10: the other ring being six-membered, e.g. tetraline - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS ## Abstract The invention relates to a method for recovering a diisocyanate which is solid at room temperature from a distillation residue from a process for producing the diisocyanate, comprising the following steps: (i) mixing the distillation residue with a bitumen such that a mixture is obtained which contains 70 to 90 wt % of the distillation residue and 10 to 30 wt % of the bitumen, each in relation to the mixture, (ii) distilling the mixture in a thin-film evaporator or a falling film evaporator to obtain a sump discharge and a gaseous product stream, (iii) condensing the gaseous product stream and obtaining a solid containing the diisocyanate which is solid at room temperature. The invention further relates to the use of a thin-film evaporator or falling film evaporator, to a composition containing the diisocyanate which is solid at room temperature, and to a method for producing an elastomer from this composition and to the elastomer itself. ## Claims ### Claim 1 A method of separating a room temperature solid diisocyanate from a distillation residue from a method for preparing the diisocyanate, comprising the following steps: mixing the distillation residue with a bitumen in such a way as to obtain a mixture containing 70% to 90% by weight of the distillation residue and 10% to 30% by weight of the bitumen, based in each case on the mixture, (ii) distilling the mixture in a thin-film evaporator or a falling-film evaporator to obtain a bottoms output and a gaseous product stream, (iii) condensing the gaseous product stream to obtain a solid material comprising the room temperature solid diisocyanate. ### Claim 2 (depends on 1) The method as claimed in claim 1, characterized in that the bitumen in the mixture from step (i) has a sulfur content of 2.5% to 3.1% by weight, based in each case on the bitumen. ### Claim 3 (depends on 1) The method as claimed in claim 1, characterized in that the distillation residue in step (i) contains from 30% to 70% by weight of the room temperature solid diisocyanate, based in each case on the distillation residue. ### Claim 4 (depends on 1) The method as claimed in claim 1, characterized in that, in step (i), 85% to 70% by weight of the distillation residue is mixed with from 15% to 30% by weight of the bitumen, based in each case on the sum total of the masses of the distillation residue and the bitumen. ### Claim 5 (depends on 1) The method as claimed in claim 1, characterized in that step (ii) is performed at a temperature of 130° C. to 160° C. and a pressure of 0.4 to 4 mbar. ### Claim 6 (depends on 1) The method as claimed in claim 1, characterized in that the bottoms output from step (ii) is not in solid form at the prevailing temperature at the outlet from the thin-film evaporator or falling-film evaporator. ### Claim 7 (depends on 1) The method as claimed in claim 1, characterized in that the solid material from step (iii) contains at least 95% by weight of the room temperature solid diisocyanate, based on the solid material. ### Claim 8 (depends on 1) The method as claimed in claim 1, characterized in that the method for preparing the diisocyanate is a phosgenation of a diamine. ### Claim 9 (depends on 1) The method as claimed in claim 1, characterized in that the room temperature solid diisocyanate is naphthalene 1,5-diisocyanate, naphthalene 1,8-diisocyanate, phenylene 1,4-diisocyanate, tetralin diisocyanate, o-toluidine diisocyanate, durene diisocyanate, benzidine diisocyanate and/or anthrylene 1,4-diisocyanate. ### Claim 10 The use of a mixture containing 70% to 90% by weight of a distillation residue from a method for preparing a room temperature solid diisocyanate and 10% to 30% by weight of a bitumen, based in each case on the mixture, in a method of separating the diisocyanate by distillation by means of a thin-film evaporator or falling-film evaporator. ### Claim 11 (depends on 1) A composition comprising a solid material comprising a room temperature solid diisocyanate from step (iii) of a method as claimed in claim 1 and at least one NCO-reactive compound, preferably at least one polyester polyol. ### Claim 12 (depends on 11) A method of producing an elastomer, in which at least one composition as claimed in claim 11 is chemically reacted, optionally while heating. ### Claim 13 (depends on 12) An elastomer produced or producible by a method as claimed in claim 12.