Analysis Of Indigo Dyeing Factors

With the popularity of jeans in world,jeans favored by consumers,the demand of indigo used to dye jeans is increasing. Because indigo is a vat dyes and insoluble in water.it must be reduced by the reducing agent before dyeing,makes it becomed thesodium form of soluble and dyed. In factory,hydrosulfite (sodium dithionite) has usually be used as the reducing agent, not only the dosage is large, but dyeing process is complex,much sulphur waste water is produced.In recent years,people began to study the environmental reducing agent used to replace hydrosulfite, thiourea dioxide is one of them,non-toxic tasteless.decomposition products can be biodegradable.reducing is strong.This study is about sodium hydrosulfite and thiourea dioxide as reducing agents, indigo dye concentration 10g/L, the different concentration of reducing agent and sodium hydroxide reducing indigo dye.the relationship between the factors and potential, properties of dyeing cotton fabric.Indigo dye is reduced at 60℃,30min,when the concentration of reducing agent is certain,change the amount of sodium hydroxid;when the concentration of sodium hydroxide is certain,change the amount of reducing agent,measure the potential of solution.Found that the measured potential absolute value value of less than 760, the solution is muddy blue-green,dye is not completely reduced; the potential value more than-760mV, the solution is yellow-green; the potential value far more than-760mV, the solution is yellow, the extra-reducing of dye.The dye solution with different concentrations of penetrant, bath ratio 1:20,the normal temperature dyeing, by air oxidation, soap cooking.washing.drying.testing the K/S value, dry rubbing fastness and wet rubbing fastness test of dyeing fabric.Comprehensive analysis.indigo dye 10g/L, the optimum conditions is sodium hydrosulfite 13g/L,sodium hydroxide 15g/L, anti-alkaline penetrant 0.4g/L,dipping 10min.the dyeing ratio is high.the K/S value, dry rubbing fastness and wet rubbing fastnessof the fabric is excellent.Thiourea dioxide as reducing agent for indigo,the best dyeing conditions is thiourea dioxide 7g/L, sodium hydroxide 13g/L, penetrant 0.5g/L.dipping 10min.high dyeing ratio,low K/S value.the rubbing fastness.better level-dyeing property.adding a small amount of sodium chloride,K/S value increased.Thus, thiourea dioxide replace sodium hydrosulfite is possible.