Study On Low Temperature Pretreatment Processes Of Cotton Fabric

Conventional scouring and bleaching pretreatment in cotton fabrics not only consumes large quantities of water and energy, but also might result in decreased tensile strength of fabrics for the strong alkali and high temperature. In order to reduce the consumption of energy in pretreatment steps and improve the quality of cotton fabrics, the pretreatment processes must be improved upon. In recent years, enzymes and the hydrogen peroxide/activator system have been widely used in cotton pretreatment, and create a wider space for the improvement of pretreatment processes. In this research, enzymes were used in desizing and scouring processes of cotton, and the temperature of the follow-up bleaching process was decreased to 80℃. To ensure the effect of bleaching at 80℃, the hydrogen peroxide pre-bleaching process was added to the processes of enzymatic desizing and scouring. The cotton fabric could obtain better treatment effect after being bleached at 80℃which was followed up after the enzymatic scouring/ hydrogen peroxide pre-bleaching process. One bath processes of enzymatic scouring/ hydrogen peroxide pre-bleaching as well as the 80℃steaming bleaching processes was optimized in detail.Aamylase 2H-15 and alkaline pectinases150 which exhibited good efforts in practice were used. The tolerance to alkali and hydrogen peroxide of these two enzymes were researched respectively. The results showed that these two enzymes had certain tolerance to hydrogen peroxide under the condition of room temperature and low alkaline. Aamylase 2H-15 could be used in room temperature desizing processes with the pH less than 9 and hydrogen peroxide (30%) 30g/L. Alkaline pectinases150 had a good tolerance to hydrogen peroxide in room temperature and pH=9, and the addition of some hydrogen peroxide might increase the enzyme activity to a certain extent.Through the comparison of five kinds of bleaching stabilizers, stabilizer D was proved to have effective control effects on the decomposition of H2O2. Five kinds of bleaching activators were compared to different processes as well. The results showed that the activator A could improve the bleaching efficiency in cold-pad processes and bleaching processes (80℃, p.H=9). Under the condition of 80℃and pH=11 with the addition of bleaching stabilizers, the activator S had an obvious improvement on the bleaching efficiency.According to the enzymatic properties and the comparison results of bleaching stabilizers and activators, the one bath processes of enzymatic scouring/ hydrogen peroxide pre-bleaching as well as the 80℃steaming bleaching processes were discussed and optimized by single factor experiments. The optimum conditions are:Cold pad-batch process (aamylase2H-15 2g/L, alkaline pectinases150 4g/L, H2O2(30%) 30g/L, activator A 10μmol/L, stabilizer D 2g/L, penetrant 4g/L, buffer system pH=9,40℃forl4-18h)→Steaming bleaching process (sourcing agent 4g/L, activator S 4-6g/L, stabilizer D 4g/L, H2O2 (30%) 30g/L, pH=11,80℃for 45-60min)Compared to conventional high temperature scouring and bleaching pretreatment, this process not only reduces the amount of alkali and steam energy, but also to obtain better treatment effect, as well as to reduce the damage caused to the fabric by pre-treatment processes.