Study Of The Method Of Bromine Indigo Dyeing

The dress of jeans and clothing appeals to the aesthetic consciousness of modern people and the psychological demand of freedom,coupled with the constant innovation of synchronized fashion,which makes people have a special liking for it.With the improvement of people's material and cultural level,consumers are not satisfied with the single style of traditional indigo denim.All sorts of design and color denim constantly emerging,of which the bromide indigo denim with its gorgeous,delicate bright-coloured color is deep consumer favorite,exhibites certain market potential.However,compared to traditional indio dyeing,there are two main problems in the process of bromide indigo dyeing: the first is high temperature(90 ?)employed in the process of bromide indigo dyeing,that influenced for broken or wraping of yarn and machine running.The second is the low solubility of the bromide indigo and there will be a lot of dye precipitation.Due to the low concentration of the mother liquor,the large amount of the mother liquor must be supplemented to dyebath,the liquid level of the liquid solution will rise slightly in continuous production,and even some of the dye spills,resulting in waste of dye.These two aspects have been puzzling enterprises in industrial production.According to the characteristics of bromide indigo with low solubility and high temperature dyeing,the four main works were exploited in this project:Firstly,the dyeing conditions were set according to orthogonal design where sodium hydrosulfite and thiourea dioxide were employed as reducing agents.Effects of the dosage of reductant,caustic soda,reduction temperature,dyeing temperature on color strength(K/S)of dyeing were discussed.Under their respective optimum conditions,the color strength(K/S)of dyeing,friction fastness,dye bath reduction potential,dye solution conductivity,COD and BOD of dye solution were compared.The results show that the K/S value of dyeing obtained by sodium hydrosulfite was significantly higher than that of thiourea dioxide under the same conditions,the similar K/S values and friction fastness grade achieved at their individual optimized conditions,whereas dye bath reduction potential of thiourea dioxide is more stable than that of sodium hydrosulfite.Secondly,urea was used as solubilizer,effects of the dosage of urea,caustic soda,sodium hydrosulfite,dyeing temperature on bromine indigo dye solubility,dye solutionreduction potential,color strength(K/S),friction fastness,tensile strength of dyeings were explored.The results showed that urea can improve the bromine indigo dye solubility,deepen the fabric dyeing strength,lower dyeing temperature.When 30 g /L of bromine indigo,40g/L of sodium hyposulfite,35g/L of caustic soda,75g/L of urea were put together for reducing at 60? for 60 min,maximum K/S value of dyeings obtained when dyed by diluted solution at 50 ?.The tensile strength and friction fastness of dyeings are kept almost the same.Thirdly,by adding different amounts of dispersants to produce different liquid bromine indigo,comparing their particle size,surface area size and distribution.The dyeing systems were designed using the central composite experimental method for liquid bromide indigo for different dispersants where dosage of sodium hydrosulfite,caustic soda,reduction temperature,dyeing temperature were used as response factors and the K/S values of dyed fabrics were used to evaluate their effects and the dyeing conditions optimized.The results showed that solid bromide 200 g and dispersant MF100 g are ground into liquid bromine indigo,particle size distribution interval is smallest,the distribution is also the most uniform,at the same time,dosage of sodium hydrosulfite is least when dyeing fiber,dyeing temperature is minimum.Finally,the dyeing systems were designed using the central composite experimental method for commercial solid indigo bromide and liquid dispersing indigo bromide respectively based on the same strength of indigo bromide where dosage of sodium hydrosulfite,caustic soda,reduction temperature,dyeing temperature were used as response factors and the K/S values of dyed fabrics were used to evaluate their effects and the dyeing conditions optimized.It is concluded that to achieve the K/S value of 24,the optimal dyeing conditions for liquid dispersion indigo bromide is dosage of sodium hydrosulfite of 30g/L,dosage of caustic soda of 25g/L,the reduction temperature of 40?,the dyeing temperature of 63.4?;the optimal dyeing condition for solid indigo bromide is dosage of sodium hydrosulfite of 41.6g/L,dosage of caustic soda of 25g/L,the reduction temperature of 76.4?,the dyeing temperature 80?.The friction fastness and tensile strength of dyeings are almost the same.