Investigation Of One-bath Process For Low-temperature Bleaching And Reactive Dyeing Of Cotton Fabric

N-[4-(triethylammoniomethyl)benzoyl]lactam chloride(TBLC)is a so-called bleach activator which can react with H2O2 under near-neutral conditions to generate peracid.The generated peracid is a more effective oxidant agent and leads to bleaching at low temperatures.Hence,the activated peroxide bleaching system of TBLC/H2O2/NaHCO3 has advantages in reducing the damage to cotton and energy consumption.In this project,we discussed the bleaching and dyeing performance of cotton knitted fabric which was bleached by an activated peroxide system at a pilot plant scale,and tried to build a new one-bath process which combined bleaching and dyeing.This project was carried out in two parts.In the first part,the TBCC-activated peroxide system was scaled up for bleaching of cotton fabric at a pilot plant scale.The bleaching performance,usages of resources,and dyeability of bleached cotton fabric were evaluated by comparing the TBCC-activated peroxide system to a conventional hydrogen peroxide system.The results showed that there was no apparent difference in degree of whiteness between cotton fabrics bleached with the two bleaching systems.The TBCC-activated peroxide system provided a little inferior water absorbency of cotton fabric compared to the conventional peroxide system,but the water absorbency in 4 seconds could technically be adequate for reactive dyeing.Moreover,the TBCC-activated peroxide system had two extreme attractive aspects.First,it was superior to the conventional hydrogen peroxide system in reducing chemical damage on cotton fiber.Second,it saved 18 % time,83 % water,29 % steam and 15 % power.Therefore,the TBCC-activated peroxide system provided a much more environmental benign approach for bleaching of cotton.In the second part,the effects of trisodium citrate on activated peroxide bleaching and reactive dyeing were discussed,based on which a new bleaching and dyeing one-bath process was constructed.By using trisodium citrate which has a good property of pH adjustment,we set up a new neutral bleaching system of TBCC/H2O2/Na3C6H5O7.In this system,the molar ratio of TBCC to hydrogen peroxide was fixed at 1:1.The results illustrated that the new activated bleaching system had a good bleaching performance.Cotton knitted fabric could be bleached with a CIE whiteness value of above 71,and increasing the dosage of trisodium citrate would not cause an apparent decrease in whiteness.Meanwhile,in the reactive dyeing process of cotton fabric,we used trisodium citrate or sodium chloride as an accelerant.We found that the K/S values of both dyed fabrics was comparable.Based on the dual role of trisodium citrate in bleaching and dyeing,we used the trisodium citrate from activated bleaching system to act as an accelerating agent in the reactive dyeing,and tried to construct a new bleaching and dyeing one-bath process.The results showed that the dyed cotton fabric by the new process had a good colorfastness but its color depth was not comparable to the dyed cotton fabric by the conventional two-bath process.When the dyeing and fixing were carried out at the same time,it can achieve better dyeing performance.