| Vat dye is mainly used to dye cellulose fibers. At home and abroad,Vat dyes are for increasing demand with the development of social economy. It is necessary to use reducing agent to turn such dyes into leuco and then they can go to cotton fabric with good affinity. The traditional methods are mostly based on the sodium thiosulfate as a reducing agent. But it will produce a large number of sulfur-containing pollutants, and can not meet the requirements of green chemistry production. Electrochemical reduction is a potential and friendly environment method,but the studies that have published showed that the electrochemical reduction dyeing made low current efficiency, dyeing slow and the color depth was much less than the traditional process, moreover, the work bath voltage was not stable lead to actual production was difficult.This research used Fe (Ⅲ)-oxalate-calcium gluconate complex for high current efficiency as the media of indirect electrochemical reduction. The experimental results showed it could not only improve the reducing capacity of electrolyte in cathode, but also greatly enchanced the current efficiency. Another, this paper also used new film as isolation mounting, set more efficient electrochemical dyeing device again, and obtained the better dyeing effect. The new process can produce rich and gaudy color, energy saving, environment gaudy friendly, and may provide for industrial production. The main research contents and conclusions are as follows:Firstly, by comparing the cyclic voltammograms of Fe (Ⅲ)-oxalate complexes, Fe (Ⅲ)-calcium gluconate complexes and Fe (Ⅲ)-oxalate-calcium gluconate complex, we can dedicate the possible electrochemical behavior of Fe (Ⅲ)-oxalate-calcium gluconate complex, and what's more, Fe (Ⅱ)-gluconate could be regarded as the critical substance in the electrochemical reduction process. Secondly, using Fe (Ⅲ)-oxalate-calcium gluconate complex as the dyeing media of indirect elecochemical reduction, we successfully dyed cotton fabric with Vat Scarlet R. The effects of various factors on the oxidation peak current, K/S values and current efficiency in the electrochemical reduction and dyeing process were discussed by orthogonal and single factor experiments. The best reduction conditions of Fe (Ⅲ)-oxalate-calcium gluconate complex were showed as follows: Fe2(SO4)3 7.4 g/L, NaOH 50 g/L, C2 H2O4 12.6 g/L, Ca(C6H,,O7)224.4 g/L, dye particle size 0.6-0.7μm, dye concentration 4 g/L, working electrode area 40 cm2, electrochemical reduction time 10 min, voltage 4 V. In this process conditions, the dyeing percentage of vat dye can up to 50% with good dyeing effect. We selected a variety of vat dyes, dyeing with the optimum dyeing process of indirect electrochemical reduction respectively. Comparing their differences in dyeing depth, levelness, color fastness and so on. The obtained resulted showed that:dyed cotton fabric had good dyeing depth, soaping fastness and excellent dry and wet rubbing fastness.Finaly, this paper also compared the dyeing effect between the indirect electrochemical reduction and dyeing in Fe (Ⅲ)-oxalate-calcium gluconate complex and the traditional dyeing process. The results showed that both the two dyeing methods could make dyed cottons have good colored light stability (ΔH*<1); The K/S value of indirect electrochemical reduction and dyeing was almost equal with traditional dyeing process; TheΔK/S value of indirect electrochemical reduction and dyeing was very small with good levelness; the fabrics dyed in the indirect electrochemical reduction and dyeing way had good soaping fastness grade 4-5, the dry rubbing grade 5 and the wet rubbing grade 4-5, was quite similar with the traditional sodium thiosulfate dyeing process, which can meet the requirements of textiles marketing, and have good application prospects. |
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