Research On A Novel Low Add-on Technology Of Dyeing Cotton Fabric With Reactive Dyestuff

Low add-on dyeing is a sort of low wet pick-up and low chemical consumption dyeingprocess.Traditional dyeing technique is generally associated with pollution and high consumption in water and energy,which could be changed with the development and maturation of low add-on technology.In the 1970 s and 1980 s,a great deal of attention was paid to diverse low add-on applications,but the finite of technical equipment level at that time limited their development.Foam dyeing is one of the most promising technology among these technologies,and the industrial production haven’t been realized for sake of its leveling problem.In this paper,a novel low add-on technology of dyeing cotton fabric with reactive dyestuff was achieved successfully.The optimal dyeing process was investigated,and the dyeing properties were compared with traditional pad dyeing via the evaluation of K/S value and dye fixation rate.Fixation mechanism of the low add-on dyeing technology with overheated steam was also explored.Besides,the application of biodegradable organic alkali salts in low add-on technology was also studied.In this study,heating curve of the wet fabric in steamer was tested,and the effect of steaming temperature,relative humidity and water ratio of the fabric on the heating process of the fabric were investigated firstly.Thermogravimetric analysis of wet fabric with different water ratios and changes of water ratio of the wet fabric during overheated steaming were also studied.Secondly,the optimal dyeing process of low add-on technology of dyeing cotton fabric with C.I.Reactive Black 5 was also conducted,including build-up properties,wet pick-up,the concentration of alkaline agent,electrolyte,and urea via the evaluation of K/S value and dye fixation rate.Steaming process was investigated through evaluating the effect of steaming temperature,steaming time,relative humidity and water ratio on dye properties.In combination of the changes of surface temperature and water ratio of the wet fabric,fixation mechanism of lowadd-on dyeing technology was investigated.The cotton fabric was dyed with Reactive Red,Reactive Yellow and Reactive Blue to certify the optimized dyeing process.Finally,biodegradable alkaline organic salts tetrasodium N,N-biscarboxylatomethylLglutamate(T-GLDA)and trisodium nitrilotriacetate(T-NTA)were applied to low add-on technology of dyeing cotton fabric with saturated steam.The effect of T-GLDA and T-NTA with different concentrations on p H and C.I.Reactive Black 5 dye properties were also studied.Comparison between dye properties of low add-on dyeing with biodegradable alkaline organic salts and traditional inorganic salt and alkaline using saturated steam were also investigated.The results indicated:There were four heating stages of the wet fabric during overheated steaming: rapid temperature rise stage,temperature platform stage,the second temperature rise stage and temperature equilibrium stage.The higher overheated temperature,the faster heating rate and the shorter different stages.When relative humidity was increased,temperature of the platform stage was increased.If the relative humidity was too high,the temperature platform was prolonged and heating rate of the surface temperature of the wet fabric was decreased.Fixation between the dyes and fabric surface mainly happened during temperature platform stage.Increasing the initial water ratio of the wet fabric had no effect on the platform temperature and the platform stage was prolonged,which had a negligible influence on fixation.Dye fixation rate improved significantly during the second temperature rise stage.In the temperature equilibrium stage,the highest fixation rate mostly emerged within 3 min.The extended steaming time had little favorable influence on the improvement of fixation rate and too much steaming should be avoided.The optimal dyeing process of the novel low add-on technology of dyeing cotton fabric with C.I.Reactive Black 5 was: dyestuff 7.07% o.w.f,wet pick-up 40%,Na2CO315 g/L,steaming for 3min at 150 ℃ overheated steam with relative humidity 60% and steaming for 3 min at 102 ℃saturated steam with 60 g/L Na2SO4,respectively.Under the circumstances of the same amount of dyes on per unit area of fabric between the novel low add-on technology and pad steam dyeing,Reato Me? Reactive Black,Red,Yellow and Blue were used in those two processes.Dye fixation rate and K/S value of the fabric dyed with low add-on technology were comparable to that of pad dyeing.The results indicated that the fabric dyed with low add-on process had excellent washing fastness,rubbing fastness,similar color shade and superior levelness in comparison with conventional one-bath pad-steam dyeing.Biodegradable alkaline organic salts T-NTA and T-GLDA were used to substitute inorganic Na2CO3 and Na2SO4in low add-on technology using saturated steam.As to C.I.Reactive Black 5,the optimal recipe was 100 g/L T-NTA and 75 g/L T-GLDA and dye properties of cotton dyed withT-GLDA was better.Four reactive dyes were used to dye the cotton fabric in the optimized recipe and the K/S value,color fastness,levelness and color shade of the fabrics dyed with three fixation systems were similar.