# US 11,299,633 B2 · Leucoindigo salt solution with very low content of aniline and method of making same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,299,633 B2 - Document ID: US11299633B2 - Status: Granted - Kind: B2 - Application number: 16/637,874 - Filed: 2018-08-10 - Published: 2021-01-14 - Granted: 2022-04-12 - Earliest claimed: 2017-08-11 - Assignees: Archroma IP GmbH - Applicants: Archroma IP GmbH - Inventors: Erwin Lucic; Jorg Hubner; David Hyett; Michele Catherine Christianne Janssen; Karin Hendrika Maria Bessembinder; Pierre L. Woestenborghs; Marinus Petrus Wilhelmus Maria Rijkers - Web page: https://patentgrep.com/patent/US11299633B2 ## CPC - C09B 7/02: Bis-indole indigos - C09B 67/0083: {Solutions of dyes} - C09B 67/0096: {Purification; Precipitation; Filtration} - D06P 1/228: {Indigo} - B01D 3/14: Fractional distillation {or use of a fractionation or rectification column} - C09B: ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES {, e.g. PIGMENTS}; MORDANTS; LAKES (fermentation or enzyme using processes to synthesise a desired chemical compound C12P) - D06P: DYEING OR PRINTING TEXTILES; DYEING LEATHER, FURS OR SOLID MACROMOLECULAR SUBSTANCES IN ANY FORM - 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) ## Abstract Stable aqueous leucoindigo solution comprising an aromatic amine in the form of aniline or aniline and N-methylaniline, wherein said leucoindigo is in the form of an alkali metal salt; wherein the concentration of the aromatic amine is below 40 ppm determined according to ISO 14362-1:2017(E); and wherein the concentration of the leucoindigo salt is in a concentration range of from 10 to 45% by weight based on the total weight of the solution, and wherein the stability of the solution is measured at a temperature of 23° C.; or wherein the concentration of the leucoindigo salt is in a concentration range of from 45 to 65% by weight based on the total weight of the solution, and wherein the stability of the solution is measured at a temperature of 60° C. ## Claims ### Claim 1 Method of removing an aromatic amine in the form of aniline or aniline and N-methylaniline from an aqueous leucoindigo solution comprising said aromatic amine in order to obtain a purified leucoindigo solution, wherein said leucoindigo is in the form of an alkali metal salt, the method comprising steps (A) and (B): (A) adding water to the aqueous leucoindigo solution in order to obtain a diluted leucoindigo solution; and (B) subjecting the diluted aqueous leucoindigo solution obtained in step (A) to distillation such that water is distilled off in a weight which at least equals the weight of said aqueous leucoindigo solution used in step (A). ### Claim 2 (depends on 1) Method of claim 1, wherein the concentration of the leucoindigo salt in the solution used in step (A) is in the range of from 5 to 65% by weight, based on the total weight of the solution. ### Claim 3 (depends on 1) Method of claim 1, wherein the concentration of said aromatic amine in the solution used in step (A) is in the range of from 2,000 ppm to 10,000 ppm. ### Claim 4 (depends on 1) Method of claim 1, wherein the concentration of aniline in the solution used in step (A) is in the range of from 1,000 ppm to 3,000 ppm and the concentration of N-methylaniline is in the range of from 500 to 2,000 ppm. ### Claim 5 (depends on 1) Method of claim 1, wherein in step (A) adding water in a weight sufficient to allow in step (B) distilling off water in a weight which at least is one and half times the weight of said aqueous leucoindigo solution used in step (A). ### Claim 6 (depends on 1) Method of claim 1, wherein in step (A) adding water in a weight sufficient to allow in step (B) distilling off water in a weight which at least is twice the weight of said aqueous leucoindigo solution used in step (A). ### Claim 7 (depends on 1) Method of claim 1, wherein in step (B) distillation is performed under a flow of inert gas. ### Claim 8 (depends on 1) Method of claim 1, wherein the weight of water added in step (A) and the water distilled off in step (B) are selected such that after step (B) the concentration of the leucoindigo salt in the purified solution is in the range of from 40 to 65% by weight, based on the total weight of the solution. ### Claim 9 (depends on 8) Method of claim 8, wherein the concentration is adjusted to a range of from 10 to 45% by weight, if necessary by addition of water. ### Claim 10 (depends on 1) Method of claim 1, wherein step (A) comprises: (α) providing a liquid stream comprising said aqueous leucoindigo solution comprising said amine(s); (β) providing a water stream; (δ) bringing into contact said liquid stream with said water stream. ### Claim 11 (depends on 10) Method of claim 10, wherein step (γ) comprises steps (γ1) and (γ2), and step (B) comprises steps (δ) and (ε): (γ1) feeding said liquid stream and (γ2) feeding said water stream into a distillation column configured to bring into contact said liquid stream with said aqueous stream; (δ) discharging from the distillation column water comprising aniline or aniline and N-methylaniline; and (ε) discharging from the distillation column an aqueous aniline-free or aniline-free and N-methylaniline-free leucoindigo solution. ### Claim 12 (depends on 11) Method of claim 11, wherein said (γ1) liquid stream and said (γ2) water stream are fed into the column via inlets in the sidewalls of the column, and said (δ) water comprising aniline or aniline and N-methylaniline is discharged at the top of the column, and the (ε) aqueous aniline-free or aniline-free and N-methylaniline-free leucoindigo solution is discharged at the bottom of the column. ### Claim 13 (depends on 11) Method of claim 11, wherein the distillation column is a column provided with trays or packing materials. ### Claim 14 Stable aqueous leucoindigo solution comprising an aromatic amine in the form of aniline or aniline and N-methylaniline, wherein said leucoindigo is in the form of an alkali metal salt; wherein the concentration of the aromatic amine is below 40 ppm; and wherein the concentration of the leucoindigo salt is in a concentration range of from 10 to 45% by weight based on the total weight of the solution, and wherein the stability of the solution is measured at a temperature of 23° C.; or wherein the concentration of the leucoindigo salt is in a concentration range of from 45 to 65% by weight based on the total weight of the solution, and wherein the stability of the solution is measured at a temperature of 60° C., wherein the solution is stable if no crystallization or precipitation is present at the measured temperature. ### Claim 15 (depends on 14) Stable aqueous leucoindigo solution of claim 14, wherein the concentration of the aromatic amine is below 30 ppm. ### Claim 16 (depends on 14) Stable aqueous leucoindigo solution of claim 14, wherein the concentration of the aromatic amine is below 10 ppm. ### Claim 17 (depends on 1) Method of claim 1, further comprising oxidizing the purified aqueous leucoindigo solution. ### Claim 18 (depends on 17) Method of claim 17, comprising, prior to oxidizing the purified aqueous leucoindigo solution, treating a textile with the purified leucoindigo solution. ### Claim 19 Method of making an aqueous aniline-free or aniline-free and N-methylaniline-free leucoindigo solution from an aqueous leucoindigo solution comprising aniline or aniline and N-methylaniline, wherein said leucoindigo is in the form of an alkali metal salt, the method comprising steps (A) and (B): (A) adding water to the aqueous leucoindigo solution in order to obtain a diluted leucoindigo salt solution; and (B) subjecting the diluted aqueous leucoindigo solution obtained in step (A) to distillation such that water is distilled off in a weight which at least equals the weight of said aqueous leucoindigo solution used in step (A).