Synthesis And Annlication Of A Promoter For Indigo Dveing On Cotton Fabric

The denim has good breathable quality, absorbency and comfortableness, which make it popular with different kinds of consumers. As one of the most important dyes for denim, Indigo has its unique position in denim dyeing. Due to low substantivity to cellulose fibre, indigo dyeing requires multiple padding-oxidation and other processes in printing and dyeing enterprises. The burden of sewage treatment was increased by low production efficiency and higher concentration of additives and residual dyes. Therefore, improving the indigo dyeability, reducing the residual amount of the dye bath, shortening the dyeing process, by using a promoter for denim dyeing, have a positive and practical significance for the promotion of energy saving of indigo dyeing on cotton.In this paper, the cationic ring-opening polymerisation of epichlorohydrin in carbon tetrachloride with boron trifluoride etherate as catalyst produces the PECH. The promoter for indigo dyeing on cotton, Polyepichlorohydrin-dimethylamine (PECH-amine) was prepared by the initial polymerisation of epichlorohydrin followed by amination with dimethylamine. The synthesis process of PECH-amine has been optimized and the cationic degree of PECH-amine was measured by tetraphenylborate-back titration method. And the structure is characterized by FTIR and1HNMR, molecular weight was measured by GPC. On this basis, PECH-amine produced under the optimum conditions is used to modify cotton fabric. The pretreatment process could be carried out by exhaust method and pad-dry method. The modification conditions have also been optimized. The modified cotton fabric was characterized by FTIR and SEM analysis. The changes of cotton fiber structure before and after modification were analyzed by the thermal analysis, Zeta potential analysis and XRD. The physical and mechanical properties of cotton before and after modification such as whiteness, strength, moisture content and moisture regain were investigated. The research result shows:The article synthesizes PECH, which has higher yield by the optimum condition which is that reaction temperature32℃, the dosage of CCl4is40mL, the dosage of ECH is0.5mol, the initiator molar ratio of BF3O(C2Hs)2is6%, the initiator molar ratio of EG is5%and the reaction time8h. The article synthesizes PECH-amine by extend agent of dimethylamine. It’s optimum technology as follow:the mass ratio of m(PECH):m(dimethylamine) is0.5, the reaction temperature is90℃and the reaction time is8h. The article got high cationic degree of PECH-amine, and the dyeing K/S value of the modified fabric could reach25.06.Cotton fabric would be pretreated using exhaust method when exposed to10%(o.w.f) PECH-amine,3g/L sodium hydroxide under90℃for40min; while cotton fabric would be pretreated using pad-dry method when exposed to4g/L PECH-amine,6g/L sodium hydroxide,0.8g/L JFC under120℃for4min;The cotton fabrics modified by PECH-amine exhibit positive Zeta potentials and slightly decreased thermal stability and crystalline degree. However, the physical and mechanical properties show little changes. Cotton fabric modified by PECH-amine had a significant increase in K/S value which could reach25.06, while the unmodified was only16.60. The experiments also showed that the same dye depth as that of6-passage dyeing in traditional process could be obtained under the process of modification with2g/L PECH-amine and3-passage stock indigo dyeing. Meanwhile, the dyed samples after modification have high color yield, good color fastness and levelness.