Abstract: In order to improve the low rate of indigo uptake for cotton fabric, the cationic ring-opening polymerisation of epichlorohydrin in carbon tetrachloride with boron trifluorideetherate as catalyst produces the polyepichlorohydrin(PECH) polymer. ZL was prepared by the initial polymerisation of epichlorohydrin followed by amination with dimethylamine. And the modification conditions have been optimized, the K/S value and the color fastness had been measured. The condition was as follow：ZL 2g/l, NaOH 4 g/l, 80℃ and 40min. Cotton fabric modified by ZL had a significant increase in K/S value which could reach 25.06,while the unmodified was only 16.60. The experiments also showed that the same dye depth as that of 6-passage dyeing in traditional process could be obtained under the process of modification with 2 g/L ZL and 3-passage stock indigo dyeing. Meanwhile, the color fastness is also good.

Key words: modification, promoter ZL, indigo dyeing, K/S value