Method for spray bleaching cellulosic fabrics
View Patent ↗A method is provided for spray bleaching cellulosic fabrics. A bleaching composition comprises a wetter, hydrogen peroxide, a caustic, a stabilizer, an optical brightener, and water. The bleaching composition is sprayed on at least one surface of the cellulosic fabric, subjected to steam to fix the bleaching composition to the fabric, and rinsed to remove any residual bleaching composition.
1. A method for spray bleaching cellulosic fabrics, comprising:
(a) mixing together a wetter, hydrogen peroxide, a caustic, a stabilizer, an optical brightener, and water to form a bleaching composition wherein the weight percent of water is selected to produce in a single spray operation a whiteness on the cellulosic fabric of at least 125 when measured with an X-Rite spectrophotometer
(b) spraying the bleaching composition on at least one surface of the cellulosic fabric;
(c) subjecting the fabric to heat to fix the bleaching composition to the fabric; and
(d) rinsing the bleached fabric to remove any residual bleaching composition.
2. The method of claim 1 , wherein the wetter comprises a surfactant.
3. The method of claim 2 , wherein the surfactant comprises between about 32 g/l and 64 g/l of the bleaching composition.
4. The method of claim 1 -wherein the hydrogen peroxide comprises between about 80 g/l and 150 g/l of the bleaching composition.
5. The method of claim 1 , wherein the caustic is sodium hydroxide.
6. The method of claim 5 , wherein the sodium hydroxide comprises between about 5 g/l and 90 g/l of the composition.
7. The method of claim 1 , wherein the stabilizer is an organophosphorus compound.
8. The method of claim 7 , wherein the organophosphorus compound comprises between about 5 g/l and 50 g/l of the composition.
9. The method of claim 1 , wherein the optical brightener is a distyryl biphenyl compound.
10. The method of claim 9 , wherein the distyryl biphenyl compound comprises between about 0.1 g/l and 1 g/l of the composition.
11. The method of claim 1 wherein the water comprises between about 64 and 81 percent by weight of the bleaching composition.
12. The method of claim 1 , wherein the bleaching composition further comprises a chelator.
13. The method of claim 12 , wherein the chelator is a softener.
14. The method of claim 1 , wherein the bleaching composition further comprises a silicate.
15. The method of claim 14 , wherein the silicate is sodium silicate.
16. The method of claim 15 , wherein the sodium silicate comprises between about 10 g/l and 90 g/l of the composition.
17. The method of claim 1 , wherein the wetter, hydrogen peroxide, caustic, stabilizer, optical brightener, and water are mixed together simultaneously before entering the spray head.
18. The method of claim 17 , wherein the components are mixed together in a manifold having a corkscrew mixer therein.
19. The method of claim 1 , wherein the cellulosic fabric is a knitted tubular fabric.
20. The method of claim 1 , wherein the composition is sprayed with nozzles above and beneath the tubular fabric.
21. The method of claim 1 , further comprising moving the cellulosic fabric at a rate between about 20 and 80 yards per minute with respect to the spray nozzles.
22. The method of claim 21 , wherein the cellulosic fabric is moved at a rate of about 40 yards per minute.
23. The method of claim 22 , wherein the fabric weighs between about 0.5 pounds per yard.
24. The method of claim 1 wherein the bleaching composition is sprayed on the cellulosic fabric at a rate of at least 0.1 gallons per minute.
25. The method of claim 24 wherein the bleaching composition is sprayed on the cellulosic fabric at a rate of between 0.1 and 0.3 gallons per minute.
26. The method of claim 25 , wherein the cellulosic fabric has a wet pickup of at least 60 percent.
27. The method of claim 26 , wherein the wet pickup is between 60 percent and 80 percent.
28. The method of claim 1 , wherein a liquor ratio of water to fabric of the bleaching composition is between about 0.03:1 and 0.09:1.
29. The method of claim 1 , wherein the sprayed fabric is subjected to heat at atmospheric pressure of between about 180 and 190 degrees Fahrenheit.
30. The method of claim 1 , wherein a liquor ratio of water used in rinsing the fabric is about 2.5:1.
31. The method of claim 1 , wherein a total liquor ratio of water used in the method for spray application and rinsing is between about 2.53:1 and 2.59:1.
32. The method of claim 1 , wherein the bleaching composition produces a whiteness on the cellulosic fabric of between about 125 and 135 when measured with an X-Rite spectrophotometer.