Method for dyeing modacrylic/cellulosic blend fabrics

1. A method for dyeing a modacrylic/cellulosic blend fabric, comprising the steps of:

providing a modacrylic/cellulosic blend fabric comprising modacrylic fibers and cellulosic fibers;

applying an aqueous vat dye composition comprising water and a vat dye to the modacrylic/cellulosic blend fabric to provide a vat dyed modacrylic/cellulosic blend fabric;

drying the vat dyed modacrylic/cellulosic blend fabric;

contacting the vat dyed modacrylic/cellulosic blend fabric with a reducing agent;

steaming the vat dyed modacrylic/cellulosic blend fabric to promote dye penetration into the fibers

washing the vat dyed modacrylic/cellulosic blend fabric in a first wash step with a wash composition comprising water to remove excess vat dye and reducing agent;

contacting the vat dyed modacrylic/cellulosic blend fabric with an oxidizing agent; and

washing the vat dyed modacrylic/cellulosic blend fabric in a second wash step to remove excess oxidizing agent.

2. The method of claim 1 , wherein the oxidizing agent comprises hydrogen peroxide.

3. The method of claim 1 , wherein the reducing agent comprises at least one selected from the group consisting of sodium hydroxide and sodium hydrosulfite.

4. The method of claim 3 , wherein the step of contacting the vat dyed modacrylic/cellulosic blend fabric with a reducing agent includes providing a wetting agent.

5. The method of claim 1 , wherein the drying step comprises infrared drying.

6. The method of claim 1 , wherein the drying step comprises hot flue drying.

7. The method of claim 1 , wherein the drying step comprises the step of passing the vat dyed modacrylic/cellulosic blend fabric over steam cans.

8. The method of claim 1 , wherein after the second wash step, the vat dyed modacrylic/cellulosic blend fabric is passed over steam cans.

9. The method of claim 1 , wherein the first wash step comprises serial wash steps, each wash step having a graduated temperature that is greater than the preceding wash step.

10. The method of claim 1 , wherein the oxidation agent is 50% hydrogen peroxide titrated to a 5% solution.

11. The method of claim 1 , wherein after the oxidation step the vat dyed modacrylic/cellulosic blend fabric is contacted with an alkaline stable surfactant solution buffered to a pH of from 7.2 to 7.8.

12. The method of claim 1 , wherein the vat dye comprises at least one selected from the group consisting of Vat Red 10, 13, 15 and 31, Vat Orange 1, 2 and 7, Vat Yellow 2 and 33, Vat Green 1 and 3, Vat Blue 6, 66, Vat Violet 1 and 13, Vat Brown 1, 3, and 57, Vat Grey 2, Vat Black 16, 25, and 27, and combinations thereof.

13. The method of claim 1 , wherein the modacrylic fibers comprise at least one selected from the group consisting of Protex-Q, Protex C, and Protex M.

14. The method of claim 1 , wherein the cellulosic fibers comprise at least one selected from the group consisting of cotton, rayon, lyocell (Tencel), flax, ramie, hemp, and jute.

15. The method of claim 1 , wherein the modacrylic fiber has a denier per filament (dpf) of from 1.2 to 2.

16. The method of claim 1 , wherein the modacrylic fibers comprise from 80-20 wt % and the cellulosic fibers comprise 20-80 wt. % of the modacrylic/cellulosic blend fabric.

17. The method of claim 1 , further comprising the step of treating the dyed modacrylic/cellulosic blend fabric with a flame retardant compound comprising at least one selected from the group consisting of THPC: tetrakis hydroxymethyl phosphonium chloride, THPS tetrakis hydroxymethyl phosphonium sulfate, and Pyrovatex.

18. The method of claim 1 , further comprising the step of pre-treating yarn used to make the modacrylic/cellulosic fabric with a moisture control agent.

19. The method of claim 18 , wherein the moisture control agent comprises at least one selected from the group consisting of StaCool and Sorbtek.