A Study Oxidation Pretreatment Process For Cotton Fabric

At present,in the traditional pretreatment,we always introduce caustic soda?NaOH?at high concentration in desizing and scouring firstly,and then hydrogen peroxide?H₂O₂?in bleaching for cotton fabric.However,this pretreatment process not only wastes water and energy,but also causes serious environmental pollution for wastewater with high alkality,deep colority and high chemical oxygen demand(COD_cr).In addition,in the process of bleaching,the decomposition rate of H₂O₂ is controlled so difficultly that the strength loss of bleached fabric is large.During the previous research of undertaking the National Key Technology R&D Program for the 11th five-year plan,our research group had developed the new technology called "the biological catalysis and controlled oxidation coordination treatment new technology".In this technology,we didn't use caustic soda with high concentration.And we introduced compound enzyme and H₂O₂ to process cambrayon so that those impurities of cambrayon were catalyzed and degraded effectively to some small molecules,such as starch,PVA,pectin,wax,pigment and cotton seed,and then these small molecules were easy removal.And process of the technology has a strong adaptability and obvious effect on energy conservation and emission reduction.In order to further optimize the new technology and achieve the purpose of saving energy and reducting emission,the controlled decomposition technology on H₂O₂ was researched systematacially in this study.In this article,cotton fabric was desized and scoured by the process of the composite enzyme firstly,which had been optimized by our research group members.And then some parameters of controlled oxidation process are optimized by the method of orthogonal experiment for cotton fabric.Through we tested starch desizing rate,pectin removal rate,wax removal rate,whiteness,instant water absorbability and breaking strength of the cotton fabric,we focused on studying influence of decomposition rate of H₂O₂ on the inpurities removal and the performance of cotton fabric.And the result showed that about 85%is decomposition rate of H₂O₂ on the fabric after steam.Secondly,we studied the decomposition law of H₂O₂ in the bleaching liquid.And based on this study,we analysed some differences of three types of PVA liquid,which were blank controller and reacted separately with NaOH and H₂O₂.We found that the PVA would be degraded to some small size molecules H₂O₂,and then these small molecules would be washed and removed easily.And however,if the PVA liquid was treated by the NaOH,the PVA liquid would be yellow and not be degraded effectively,so that the duty of washing become heavy.Finally,we discussed the possibility of two times washing with cold water,which replaces multiple times washing with high tempreture water after desizing and scouring of cambrayon.And the result showed that the properties of bleached fabric would not be difference,such as whiteness,instant water absorbability and breaking strength.But also the water and energy consumption would be reduced,and the COD_cr content of pretreatment wastewater would be reduced 23%at least.