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Denim is a classic woven fabric, made up of warp dye:I yarn and weft white yarn, the common used dyeing methods of warp have pulp dyeing joint, beam dyeing, spiral dyeing, etc., indigo dye is the most commonly used dyes. But the powdered indigo dyeing often appear poor gorgeous color, poor color depth, not pure color, poor reproducibility, reduction temperature high, huge dyestuff usage, and so on.This paper uses powdered indigo as the main raw material, added special dispersion system, and prepares liquid dispersed indigo by grinding, analyzed dispersion and stable performance, choosing different reducing agent and sodium hydroxide concentration reduction of the liquid indigo, then dyeing the fabric, tested the fabric color, K/S and friction fastness and optimized redox system, obtained the optimal value reduction system.Liquid dispersion indigo uses sodium lignin sulfonate as dispersant, dispersant quality was5%of dye dosage, grinding4h, mass concentration was20%, the decentralized system can place60days at room temperature without metamorphism, and the centrifugal stability is well.Compared with powdered indigo, liquid dispersed indigo grain diameter smaller, specific surface area increased, particles is more uniform, more conducive to dyeing, and the use of dyestuff is lower. After optimization design, through the regression analysis and significant analysis, sodium hydrosulfite and sodium hydroxide concentration have a significant influence for the dyeing properties of the dyed fabric (L*,a*,b*,C*,H°, soap boiling before and after K/S value), and conforms to the linear regression equation. Measured its optimal solution follows as:1) liquid indigo, reduction temperature of40℃, the reduction time46min, sodium hydrosulfite concentration of126g/L, sodium hydroxide concentration of98g/L;2) the powder indigo, reduction temperature of56℃, the reduction time26min, sodium hydrosulfite concentration of165g/L, sodium hydroxide concentration of108g/L; the result shows that the liquid dyestuff usage is lower and the fabric dyeing rate is high, color deep, liquid dispersion system of indigo COD value is relatively lower; By Raman spectroscopy and fabrics of K/S test, it proves that liquid indigo fabric dyeing rate higher, deeper dyeing.
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