Study On Low Temperature Hydrogen Peroxide Bleaching System Of Cotton Fabric

The conventional bleaching processes using hydrogen peroxide of cotton fabrics need high temperature and strong alkali with high energy consumption and aggressive damage of cellulose fiber. The hydrogen peroxide bleaching efficiency is low, which causes a great waste of resources. To solve the problem, Bleach activators or catalysts were used to the pretreatment process of cellulose fabrics lowering temperature and reducing the dosage of sodium hydroxide. This paper selected TBCC, activator A and TAED as activators, and MnTACN as catalyst. The bleaching conditions and performance of selected activators and catalyst were discussed through single factor and orthogonal experiments. The optimal technological parameters of each activator/catalyst were determined. Each activator was combined with catalyst to build compound H2O2/activator/catalyst oxidation systems, which were applied in low temperature hydrogen peroxide bleaching of cotton knits. Kinetics experiments of decolorization of activator/catalyst oxidation systems were designed through the use of morin, one of the nature pigments of cotton. The mechanism of activation and catalytic bleaching was analyzed.The results showed that, each activator/catalyst discussed in this thesis can decrease the bleaching temperature effectively and increase the whiteness when used alone. The bleaching effects were in the order:TBCC> activator A> TAED> MnTACN. There were synergies in compound H2O2/TBCC/MnTACN and H2O2/activator A/MnTACN systems in laboratorial concentration and proportion and the same in some proportion H2O2/TAED/MnTACN system with lower concentrations and every proportion with higher concentration. Further more, the synergistic effect in compound activator/activator systems had been researched by low temperature hydrogen peroxide bleaching process of cotton knits. The results showed that there was little synergistic effect in compound activator/activator systemsl.The kinetics of decolorization for morin has been studied by calculating the maximum reaction rate, discoloration ratio and reaction rate constant in different active/catalytic system.The results indicated that the decolorization were in order:MnTACN> TBCC> TAED>>activator A. It also seems to be have synergies in combined H2O2/TBCC/MnTACN and H2O2/activator A /MnTACN systems. However, the synergistic effect of H2O2/TAED/MnTACN system is not indistinctive. At the same time, the decolorizations for morin in compound activator/activator systems were also researched, but there weren't synergies in those combined systems at all, which result coincides to the conclusions of low temperature bleaching of cotton knits.The paper showed that the combined activative and/or catalytic systems of hydrogen peroxide bleaching oxygenization were beneficial to decrease bleaching temperature, reduce chemicals and improve performance. If used the compound systems in proper proportion, which could dramatically reduce the cost of energy with the same bleaching efficiency compared to conventional bleaching process. In this way, pretreatment of cotton fabrics would achieve energy saving and consumption reduction.