Low Liquor Ratio Dyeing Process Of Cotton Knit Fabric With Reactive Dyes

Compared with the conventional dip dyeing process in regular bath ratio, low liquor ratio dyeing of cotton knitted fabric can decrease water&energy consumption, and reduce the dosage of dyestuffs&chemicals, with the benefit of reducing the discharge of effluent. The low liquor meant the higher concentration of dyestuffs under the same dyestuffs o.w.f.%of fabrics, meanwhile the mass ratio of the salt&alkali to the dyestuffs in the dyebath had an effect on the dyeing performance of cotton fabric. Although low liquor ratio dyeing with reactive dyes has been widely used in dyeing, it had rarely been explored including the different dosage of salt and alkali between the conventional and low liquor ratio dyeing under the same color yield. This paper discussed the different dye substantivity,influence of salt and alkali concentration between the conventional and low liquor ratio dyeing under the same color yield as well as dyeing kinetics, which results lay a foundation for further research on low liquor ratio dyeing process of cotton knitted fabrics with reactive dyes.Firstly, this paper aimed the same apparent depth K/S value in the conventional dyeing, he salt and alkali concentration could be obtained in low liquor ratio dyeing by the experiments of Central Composite Design. And the interaction with the dye substantivity, bath ratio and the salt concentration were also discussed. Secondly, methanol is a suitable mode alcohol for substituting cellulosic fiber in dye bath, their hydrolysis and methanolysis kinetics were studied in the different mixture of alkaline solution a at60℃by the high performance liquid chromatography(HPLC).The results showed that, to reach the same color yield obtained from conventional process, low liquor ratio dyeing need less salt and alkali. From the dye hydrolysis and methanolysis kinetics, rate constants of methanolysis and hydrolysis were found to be pseudo-first-order in low liquor ratio dyeing, and the rate constants of methanolysis is larger than the conventional bath ratio dyeing.but the the rate constants of hydrolysis is less than the conventional bath ratio dyeing.It is concluded that low liquor ratio dyeing is beneficial to react with cellulose fiber for the dye and reduce the dye hydrolysis in the competition reaction between the the fixation of reactive dyes on cotton fibre and the hydrolysis reaction in the dyeing process.In brief, the low liquor ratio dyeing is a competitive dyeing technology not only from saving of dyes, reducing the dosage of alkali and salt, but also reducing the discharge the dyeing waste and effluent in dip-dyeing process.