The Influence Of Cotton Wettability On Reactive Dyeing Property In Siloxane Non-Aqueous Medium

Conventional reactive dyeing is generally performed in water base system,resulting a high dyeing effluent,low fixation rate and high electrolyte,which seriously restrict the development of dyeing industry.In recent years,with the increasingly severe environmental pollution,people have begun to study the new dyeing methods to reduce the dyeing pollution.Among them,siloxane non-aqueous medium(decamethyl cyclopentasiloxane,or D5 for short)for dyeing is a green environmental technology,which can replace water in the dyeing application.However,it easily leads to uneven dyeing because of the relatively rapid dyeing rate in D5 medium even in the case of no electrolyte,which affects the dyeing qualities.In order to solve this problem,this paper maily focuses on the influence of wettability of cotton products(woven fabrics and yarns)on the dyeing rate and dyeing quality of reactive dyes in D5 medium system.At the same time,the mechanism of dyeing in D5 medium was studied to provide more systematic guidance for staining in non-aqueous medium.In the siloxane non-aqueous dyeing system,reactive dyes and alkali were dissolved in a small amounts of water,and then were emulsified o form a stable reverse microemulsion system under the action of surfactant and co-surfactant in D5 medium.When reactive dyes(Reactive Red 3BS and Reactive Blue KN-R)concentration was 2%(o.w.f)and the bath ratio was 1:20,the optimal dyeing process for reactive dye in siloxane reverse microemulsion is as follow:moisture content 150%(o.w.f),Na2CO3 60 g/L(relative to the water),AEO-3 30 g/L(relative to the D5),octyl alcohol 30 g/L(relative to the D5),fixing in 80 oC for 30 min.In this study,five kinds of cotton products(cotton woven fabric and cotton yarn)with different wetting properties were prepared by different pretreatment processes.And then they were dyed in D5 medium and traditional water bath separately to explore the relationship between wetting property of cotton products and deying rate,fixation rate,dyeing quality.The experimental results showed that the dyeing rates of Reactive Red 3BS and Reactive Blue KN-R were increased with the improvement of wettability of cotton products.And,the levelness of cotton increased firstly and then decreased.However,the fixation rate was almost the same in D5 mediun.Although both of the two reactive dyes had higher fixation rate in D5 medium than that in traditional water bath,the levelness of cotton products in D5 medium was worse.Forthermore,based on the pseudo-first-order kinetic model and the pseudo-second-order kinetic model,the dyeing kinetics of these two reactive dyes in D5 medium and traditional water base system were investigated in detail.The results showed that the adsorption behaviors of these two dyes were in accord with the pseudo-second-order kinetic model both in both systems.In D5 medium,the dyeing rate constant increased with the increasing of cotton wettability,but almost unchanged in traditional water bath system.Most remarkably,the final uptake of dyeing in D5 medium was almost the same,more than double what it was in traditional water bath.And,the half-dyeing time decreased significantly in D5 medium.In addition,the adsorption rates and equilibrium adsorption values increased with increasement of dyeing temperature.When total concentration of these two reactive dyes was 2%(o.w.f),the values of L*,a*,b* of cotton products all increased with the increase of amout of Reactive Red 3BS.In the same compound proportion,cotton products dyed in D5 medium had a higher a* value and a lower b*value than those in water.The values of L*,b* increased firstly,and then decreased with increase of the fixing temperature in D5 medium while a* value is opposite.Cotton fiber was treated with fluorescent dyes firstly,and then laser scanning confocal microscope was used to observe the cross section and the longitudinal surface of treated fiber.The results showed that D5 could hardly swell cotton fiber.The D5 film coated on the surface of the cotton fiber could slow down the diffusion of water to fiber surface.And,the mechanical strength of D5 medium could not strip the water film absorbed on the surface of the cotton fiber originally.