Method for decolorizing textile materials

Patent metadata

Field	Value
Publication number	US-10640914-B2
Application number	US-201815928136-A
Country	US
Kind code	B2
Filing date	Mar 22, 2018
Priority date	Sep 24, 2015
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

The disclosure relates to a method for decolorization of a dye-colored synthetic polymer, which includes the steps of treating a dye-colored synthetic polymer, such as polyester, with a treatment composition at pH 6 or less, the treatment composition comprising sodium formaldehyde sulfoxylate, water, and a ketone. The resulting decolorized synthetic polymer is then separated from the treatment composition.

First claim

The invention claimed is:

1. A method for decolorizing a dye-colored synthetic polymer, comprising:
treating a dye-colored synthetic polymer with a treatment composition, the treatment composition comprising
(a) sodium formaldehyde sulfoxylate,
(b) water, and
(c) a ketone dissolved in the treatment composition;
wherein the treatment composition has a pH of 6 or less, and the treating is carried out at a temperature of at least 50° C. and for a duration of time sufficient to at least partially decolorize the synthetic polymer; and
following the treating, separating at least partially decolorized synthetic polymer from the treatment composition.

2. The method of claim 1 , wherein the treatment composition comprises from 2.5 g/L to 50 g/L of sodium formaldehyde sulfoxylate.

3. The method of claim 1 , wherein the ketone comprises a ketone selected from the group consisting of acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, methyl isobutyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, ethyl ketone, and any combination thereof.

4. The method of claim 1 , wherein the ketone comprises acetone.

5. The method of claim 1 , wherein the ketone consists essentially of acetone.

6. The method of claim 1 , wherein a weight ratio of the water to the ketone in the treatment composition is from 4:1 to 1:4.

7. The method of claim 1 , wherein the treating is carried out at a temperature of at least 70° C.

8. The method of claim 1 , wherein the ratio of the weight of the treatment composition to the weight of the synthetic polymer during the treating step is at least 10:1.

9. The method of claim 1 , wherein the dye-colored synthetic polymer is colored with a dye selected from the group consisting of acridine dyes, anthraquinone dyes, arylmethane dyes, azo dyes, cyanine dyes, nitro dyes, nitroso dyes, phthalocyanine dyes, quinone dyes, thiazine dyes, thiazole dyes, xanthene dyes, fluorene dyes, stilbene dyes, vinyl sulfone dyes, triazine dyes, sulfur dyes, indigoid dyes, and any combination thereof.

10. The method of claim 1 , wherein the dye-colored synthetic polymer material is colored with an azo dye, an anthraquinone dye, or any combination thereof.

11. The method of claim 1 , wherein the synthetic polymer comprises a polymer selected from the group consisting of regenerated celluloses, polyesters, polyamides, polyurethanes, polyolefins, acrylonitriles, and any combination thereof.

12. The method of claim 1 , wherein the synthetic polymer comprises polyethylene terephthalate (PET).

13. The method of claim 1 , wherein the dye-colored synthetic polymer is present in the form of a dye-colored synthetic polymer textile.

14. The method of claim 1 , wherein following the treating, the decolorized synthetic polymer textile has a K/S value of less than 3, as determined using equation (i):

K
⁢

/

⁢
S

=

(

1
-
R

)

2

2
⁢

⁢
R

(
i
)

wherein R=1.0 at 100% reflectance.

15. The method of claim 1 , wherein following the treating, the decolorized synthetic polymer textile has a K/S value as determined using equation (i) which is at least 70% lower than the K/S value of the dye-colored synthetic polymer prior to the treating

K
⁢

/

⁢
S

=

(

1
-
R

)

2

2
⁢

⁢
R

(
i
)

wherein R=1.0 at 100% reflectance.

16. The method of claim 1 , wherein a difference between an intrinsic viscosity of the synthetic polymer before and after the treating is less than plus or minus 5%.

17. The method of claim 1 , further comprising a step of pre-soaking the dye-colored synthetic polymer prior to the treating, wherein the pre-soak composition comprises an aqueous solution of an organic solvent.

18. The method of claim 17 , wherein the organic solvent of the pre-soak composition comprises a ketone.

19. The method of claim 18 , wherein the organic solvent of the pre-soak composition comprises the same ketone as the treatment composition.

20. The method of claim 1 , comprising:
optionally pre-soaking a dye-colored polyethylene terephthalate-containing textile in a presoak composition comprising water and acetone;
treating the dye-colored textile with a treatment composition, the treatment composition comprising
(a) from 2.5 g/L to 50 g/L of sodium formaldehyde sulfoxylate,
(b) water, and
(c) acetone;
wherein the treatment composition has a pH of 6 or less, and the treating is carried out at a temperature of at least 70° C. and for a duration of time sufficient to at least partially decolorize the dye-colored textile; and
following the treating, separating at least partially decolorized textile from the treatment composition.

Assignees

• Univ North Carolina State

Inventors

• Hinks David
• Wang Guan
• Fei Xiuzhu
• Freeman Harold

Classifications

• D06L4/30 Primary

  using reducing agents · CPC title

• D06L4/70

  Multi-step processes · CPC title

• D06P1/65112

  Compounds containing aldehyde or ketone groups · CPC title

• D06P5/134

  with reductants · CPC title

• D06P1/621

  Compounds without nitrogen · CPC title