Method for producing a liquid formulation of salts of sulphonic-acid azo dyes
View Patent ↗A process for producing a liquid formulation of salts of sulfonated azo dyes by coupling an at least equimolar amount of diazotized aminoarylsulfonic acids I H 2 N—Ar—SO 3 H (I), where Ar is phenylene (which may be monosubstituted by sulfo) or naphthylene (which may be mono- or disubstituted by sulfo and/or monosubstituted by hydroxyl) onto the coupling product of an unsubstituted or methyl-substituted phenylenediamine with itself comprises dissolving the azo dye in a basic medium and then subjecting the solution to a nanofiltration.
1. A process for producing a liquid formulation of salts of sulfonated azo dyes, which process comprises:
(a) forming an azo dye by coupling at least an equimolar amount of diazotized aminoarylsulfonic acids of the formula I
H 2 N—Ar—SO 3 H (I),
wherein Ar is phenylene, which may be monosubstituted by sulfo, or naphthylene, which may be mono- or disubstituted by sulfo and/or monosubstituted by hydroxyl, onto the coupling product of an unsubstituted or methyl-substituted phenylenediamine coupled with itself;
(b) dissolving the azo dye in a basic medium; and then
(c) subjecting the solution to a nanofiltration;
wherein the process for producing the liquid formulation avoids isolation of the dye as a solid and the liquid formulation produced has an inorganic salt content of less than 2% by weight based on 100% pure dye.
2. The process for producing a liquid formulation according to claim 1 wherein the dye is dissolved with aqueous sodium hydroxide solution and a nitrogenous base.
3. The process for producing a liquid formulation according to claim 1 wherein the dye is dissolved with aqueous sodium hydroxide solution and ammoniacal water.
4. The process for producing a liquid formulation according to claim 2 wherein the molar ratio of aqueous sodium hydroxide solution/nitrogenous base is in the range from 1/19 to 19/1.
5. The process for producing a liquid formulation according to claim 1 wherein the dye is dissolved by adjusting the pH of the reaction mixture to a value in the range from 8.5 to 11.
6. The process for producing a liquid formulation according to claim 1 wherein the solution is subjected to nanofiltration employing a nanofiltration membrane having ceramic separating layers.
7. The process for producing a liquid formulation according to claim 1 wherein the dye is dissolved with aqueous sodium hydroxide solution and a nitrogenous base and the pH is kept constant with the nitrogenous base during nanofiltration.
8. The process for producing a liquid formulation according to claim 1 wherein the azo dyes are prepared starting from o-, m- and/or p-aminobenzenesulfonic acid diazo component.
9. The process for producing a liquid formulation according to claim 1 wherein the unsubstituted or methyl-substituted coupling product of a phenylenediamine with itself and diazo component I are used in a stoichiometric ratio in the range from 1:1 to 1:4.
10. A process for producing a liquid formulation of salts of sulfonated azo dyes comprising:
a) preparing a coupling product of an unsubstituted or methyl-substituted phenylenediamine coupled with itself;
b) without intervening isolation of this coupling product, coupling at least an equimolar amount of diazotized aminoarylsulfonic acids of the formula I
H 2 N—Ar—SO 3 H (I),
wherein Ar is phenylene, which may be monosubstituted by sulfo, or naphthylene, which may be mono- or disubstituted by sulfo and/or monosubstituted by hydroxyl, onto the coupling product obtained according to a), to form a dye;
c) dissolving the dye in a basic medium; and
d) subjecting the solution obtained according to c) to nanofiltration;
wherein the process for producing the liquid formulation avoids isolation of the dye as a solid and the liquid formulation produced has an inorganic salt content of less than 2% by weight based on 100% pure dye.
11. The process for producing a liquid formulation according to claim 1 , wherein the dye is dissolved in the basic medium to produce a solution with a dye content in the range from 3% to 10% by weight.
12. The process for producing a liquid formulation according to claim 10 , wherein the dye is dissolved in the basic medium to produce a solution with a dye content in the range from 3% to 10% by weight.
13. The process for producing a liquid formulation according to claim 1 , wherein the dye is dissolved in the basic medium to produce a solution with a dye content in the range from 3% to 6% by weight.
14. The process for producing a liquid formulation according to claim 10 , wherein the dye is dissolved in the basic medium to produce a solution with a dye content in the range from 3% to 6% by weight.
15. The process for producing a liquid formulation according to claim 1 , wherein the liquid formulation produced has a NaCl content of less than 2% by weight based on 100% pure dye.
16. The process for producing a liquid formulation according to claim 10 , wherein the liquid formulation produced has a NaCl content of less than 2% by weight based on 100% pure dye.
17. The process for producing a liquid formulation according to claim 1 , wherein the solution is subjected to nanofiltration employing a nanofiltration membrane having molecular weight cutoffs of 200 to 2000 daltons, a transmembrane pressure ranging from 1 to 50 bar, and a temperature up to 100° C.
18. The process for producing a liquid formulation according to claim 10 , wherein the solution is subjected to nanofiltration employing a nanofiltration membrane having molecular weight cutoffs of 200 to 2000 daltons, a transmembrane pressure ranging from 1 to 50 bar, and a temperature up to 100° C.