Method for coloring cellulose

Abstract

A method for coloring of cellulose in a supercritical CO.sub.2 medium by an uncharged hydrophobic dye, including at least the steps including of: (i) provision of cellulose fibers, (ii) placing the cellulose fibers in the presence of: a) an effective quantity of at least one uncharged mono organo-urea primer of formula RNHCONH.sub.2, where R represents a linear or branched, saturated or unsaturated, hydrocarbon chain possessing at least 3 carbon atoms, or a saturated or unsaturated cyclic hydrocarbon radical, which is bonded directly or via a methylene or ethylene group to a nitrogen atom, and if appropriate substituted under conditions conducive to the forming of a covalent carbamatic bond between the cellulose and the molecules of the organo-urea; and b) at least one hydrophobic dye in a supercritical CO.sub.2 medium, under conditions conducive to the immobilization of the dye on the fibers.

Claims

1. A process for coloring cellulose in supercritical CO.sub.2 medium with a hydrophobic dye, comprising at least the steps: (i) providing cellulose fibers, (ii) placing said cellulose fibers in contact with: a) an effective amount of at least one uncharged primary monoorganourea selected from the group consisting of 4-methoxyphenylurea and octadecylurea, under conditions suitable for establishing a covalent bond of carbamate type between the cellulose and each molecule of said organourea; and b) at least one hydrophobic dye, in supercritical CO.sub.2 medium, under conditions suitable for immobilizing said dye on said fibers.

2. The process as claimed in claim 1, in which the operations for placing in contact in steps a) and b) are performed successively.

3. The process as claimed in claim 2, in which step a) is performed in solvent medium, and step b) is performed in supercritical CO.sub.2 medium.

4. The process as claimed in claim 2, in which step a) is performed in solvent medium in the presence of dimethyl sulfoxide, and step b) is performed in supercritical CO.sub.2 medium.

5. The process as claimed in claim 1, in which the operations for placing in contact in steps a) and b) are performed concomitantly.

6. The process as claimed in claim 1, in which the supercritical CO.sub.2 medium is generated in situ by heating liquid CO.sub.2 under pressure.

7. The process as claimed in claim 1, in which the operations for placing in contact under consideration in steps a) and b) are performed in a same reactor.

8. The process as claimed in claim 1, in which a concentration of primary organourea is between 1% and 20% by weight relative to a weight of cellulose to be treated.

9. The process as claimed in claim 1, in which a concentration of dye is between 1% and 20% by weight relative to a weight of cellulose to be treated.

10. The process as claimed in claim 1, in which a temperature applied in steps a) and b) is between 100 C. and 140 C.

11. The process as claimed in claim 1, in which a pressure applied in steps a) and b) is between 250 bar and 350 bar.

12. The process as claimed in claim 1, in which a temperature and pressure conditions applied in steps a) and b), performed successively or concomitantly, are maintained for a time ranging from 1 minute to 60 minutes.

13. The process as claimed in claim 1, in which the cellulose is a paper cellulose.

14. The process as claimed in claim 1, in which a temperature applied in steps a) and b) is between 120 C. and 130 C.

15. The process as claimed in claim 1, in which a pressure applied in steps a) and b) is between 280 bar and 320 bar.

16. The process as claimed in claim 1, in which a temperature and pressure conditions applied in steps a) and b), performed successively or concomitantly, are maintained for a time ranging from 10 minutes to 40 minutes.

17. The process as claimed in claim 1, wherein the at least one uncharged primary monoorganourea is 4-methoxyphenylurea.

18. The process as claimed in claim 1, wherein the at least one uncharged primary monoorganourea is octadecylurea.

Description

EXAMPLE 1

Coloring of a Blotting Paper in Two Steps, With the Dye Disperse Red 13

(1) An autoclave, of microreactor type, is charged with 1.62 g of blotting paper and 162 mg of octadecylurea. The reactor is sealed and then charged with liquid CO.sub.2.

(2) The temperature and pressure conditions are adjusted, inside the reactor, so as to reach a temperature of 130 C. and a pressure of 280 bar. After stabilizing the system, the reactor is kept for 10 minutes under these conditions. On conclusion of this pretreatment, the cellulose carbamate is obtained.

(3) 100 mg of Disperse Red 13 dye are then introduced into the reactor. The same temperature and pressure conditions as those used previously are applied a second time for 10 minutes. The pressure is then reduced slowly and heating is stopped. The paper obtained, which is dyed to the core, is then removed from the autoclave.

(4) The liquid CO.sub.2 and the excess dye are readily separated and can be reused.

EXAMPLE 2

Coloring of a Blotting Paper in a Single Step, With the Dye Disperse Red 13

(5) An autoclave is charged with 1.62 g of blotting paper, 162 mg of octadecylurea and 100 mg of Disperse Red 13 dye. The autoclave is sealed and then charged with liquid CO.sub.2.

(6) The temperature is adjusted to 130 C. and the pressure to 280 bar so as to convert the liquid CO.sub.2 into supercritical CO.sub.2.

(7) After stabilizing the system, the reactor is kept under these conditions for 10 minutes. The pressure is then reduced slowly and heating is stopped. The paper obtained, which is dyed to the core, is then removed from the autoclave.

(8) The liquid CO.sub.2 and the excess dye are readily separated and may be reused.

EXAMPLE 3

Coloring of a Blotting Paper With the Dye Foron Bleu RD-E

(9) An autoclave is charged with 1.20 g of blotting paper, 100 mg of octadecylurea and 100 mg of Foron Bleu RD-E dye. The autoclave is sealed and then charged with liquid CO.sub.2.

(10) The temperature is adjusted to 120 C. and the pressure to 310 bar so as to convert the liquid CO.sub.2 into supercritical CO.sub.2.

(11) After stabilizing the system, the reactor is kept under these conditions for 10 minutes. The pressure is then reduced slowly and heating is stopped. The paper obtained, which is dyed to the core, is then removed from the autoclave.

EXAMPLE 4

Coloring of a Blotting Paper With the Dye Disperse Red 13

(12) An autoclave is charged with 1.25 g of blotting paper, 100 mg of 4-methoxyphenylurea and 100 mg of Disperse Red 13 dye. The autoclave is sealed and then charged with liquid CO.sub.2.

(13) The temperature is adjusted to 120 C. and the pressure to 260 bar so as to convert the liquid CO.sub.2 into supercritical CO.sub.2.

(14) After stabilizing the system, the reactor is kept under these conditions for 10 minutes. The pressure is then reduced slowly and heating is stopped. The paper obtained, which is dyed to the core, is then removed from the autoclave.

EXAMPLE 5

Coloring of a Blotting Paper With the Dye Disperse Red 19

(15) An autoclave is charged with 1.15 g of blotting paper, 100 mg of 4-methoxyphenylurea and 100 mg of Disperse Red 19 dye. The autoclave is sealed and then charged with liquid CO.sub.2.

(16) The temperature is adjusted to 140 C. and the pressure to 280 bar so as to convert the liquid CO.sub.2 into supercritical CO.sub.2.

(17) After stabilizing the system, the reactor is kept under these conditions for 10 minutes. The pressure is then reduced slowly and heating is stopped. The paper obtained, which is dyed to the core, is then removed from the autoclave.