Enzymatic Desizing Of Cotton In Supercritical Carbon Dioxide

This thesis developed a new and green desizing method on the basis of the supercritical CO2 fluid technology, which can effectively reduce the use of poisonous and harmful traditional chemicals. It has great significance to cut down the consumption of energy and water, and realized the energy conservation and emissions reduction in textile printing and dyeing.This thesis discussed the effects of the fluid temperature, pressure, time on alpha amylase activity. Then a mixture of alpha amylase, cellulase, pectinase and lipase was prepared for enzymatic desizing of cotton in supercritical CO2 fluid. By application the microemulsion of 2-ethylhexyl succinate sodium sulfonate(AOT)/water/ ethanol/ enzyme in supercritical CO2 fluid, the low activity of enzymes in nonpolar medium was solved. The effects of supercritical CO2 fluid temperature,pressure, time on the desizing effect were investigated, as well as the optimization of the amount of AOT and water, enzyme concentration, pH value. Through orthogonal experiment design and analysis, the role of various components in enzymatic desizing was discussed. Besides, the bleaching with laccase in supercritical carbon dioxide fluid improved the whiteness of fabric after enzymatic desizing was also explored, as well as the bleaching parameters, such as the amount of laccase, fluid temperature, pressure, time. Finally, the chemical structure, surface morphology, the aggregation structure, infiltration properties and fabric handle of the treated substrate,were investigated by infrared spectroscopy(FT-IR), scanning electron microscope(SEM), X-ray diffraction(WAXS) and contact angle test.Studies have shown that alpha amylase has higher activity after supercritical CO2 fluid treatment. The optimized parameters of temperature, pressure, time, are50 ℃, 15 MPa pressure, time 150 min, respectively. Temperature had the greatestinfluence on the enzyme activity, the rise of temperature under low temperature increased the enzyme activity, high temperature caused decline in enzyme activity deactivation.Pressure have less effect on the enzyme activity, but also led to a slightly activity reduced under high pressure.Processing time made the enzyme activity increased,then felt slightly after peakedness.Good results from the enzyme desizing experiments, proved the feasibility of enzymatic desizing in supercritical CO2 fluid. But fabric whiteness was low after desizing, still need bleaching processing. Enzymatic desizing in supercritical CO2 fluid optimization process condition was: temperature of 50 ℃, pressure for 13 MPa,the time was 90 min, the amount of AOT in the desizing working liquid was 0.6 g,water was 40 ml, enzyme concentration was 2.5%, the pH was 7. Enzyme orthogonal combination experiment showed that cellulase had a greater influence on weight loss rate, lipase hydrolysis waxed on the surface of the fiber to improved the hydrophilic,and alpha amylase was still the most important enzyme in desizing process.Laccase bleaching of fabric after desizing and fluid cleaning experiment showed that laccase bleaching in supercritical CO2 fluid improved the whiteness of the fabric in a certain extent after desizing, but compared with other conventional bleaching treatment, the white degree was lower,needed to be further studied.Cleaning process with supercritical CO2 fluid can remove residue on the fabric after desizing and bleaching, but whiteness degree dropped more that cleaning at high temperature.After a series of supercritical fluid handling, the cotton fabric infrared spectra showed that fabric macromolecules functional group structure didn’t change significantly, SEM showed that cotton fiber surface became smooth, fiber texture cleared, X- ray diffraction(WAXS) showed that fiber crystallinity increased, contact Angle test showed that the fabric wettability increased, bending stiffness test showed that felt good.