On-line Monitoring Methods And Influncing Factors Of Reactive Dyes

On-line monitoring of the dye concentration can master the real-time dye uptake.This would result in controlled and optimized dyeing processes,detection the errors and faults during dyeing processes,this would also be used for evaluating the compatibility of the dyes,for guiding the dye screening and match colors.It can be used to compare the function and performance of the chemical additives.The detailed fibers or fabrics exhaustion curves can be used to study the physical or chemical properties of them,and improve fiber spinning process or fabrics structure.At the same time,this technique can also improve product quality,reduce environmental impact.The economic advantages that result from this technique can promote the rapid development of the dyeing and printing industry and also can be extremely important in today's competitive textile markets.Due to the conditions of industrial level dyeing are more complicated than that of laboratorial dyeing,the reproducibility is bad when the process parameters is set accordingly to the laboratorial dyeing process.The real-time monitoring of industrial dyebath is indispensable in order to achieve "right first-time dyeing" and a higher level of closed-loop control over the dyeing process.The spectrophotometry is the most important means for online monitoring of dye concentration at present.In this paper,different performances of instruments were compared and the Agilent Cary 60 UV-VIS was selected in the experiment.Because of the indescribable scanning speed(full wavelength scanning requires less than 3s),it could satisfy the requirements of absorbance measurement.This UV-VIS cooperated with the cuvettes of different optical path length(including 0.1mm,1mm,10mm)was suitable for the practical concentration range of dyes.Results showed that the dyebath temperature could affect the measured absorbance,so in order to ensure the temperature constant,it was necessary to add a thermostat into the experimental apparatus and let the dyebath pass through it before measuring the absorbance.In order to determine the exhaustion curves,it was necessary to calculate the residual dye concentration in the dyebath,continuously throughout the dyeing process by spectrophotometric techniques and using the Beer-Lambert law.But in this paper,some factors which could affect the measured absorbance were found,such as salt,alkali and the dyebath heating time.So simply obtaining the absorbance data to detennine accurate concentration of the dyes is unreliable.In consideration of these problems,this paper mainly focuses on the following two ways to study:(1)this problem could be solved by incorporating into calibration model of the spectral dye behavior under different concentrations of salt and soda.(2)Processing fabric blank dyebath according to the recommend dyeing process of the selected dyes,and measure the absorbance continuously throughout the progress which is saved as absorbance contrast initial value.Then dyed the fabric by the same dyeing process and obtain the absorbance of the dyebath.The exhaustion curves can be calculated by these two groups of absorbance data.The accuracy of these two methods for detecting the dye concentration and the exhaustion rate of individual dye were very high,both errors were less than 3%.The method of Calibration model required a lot of basic experiments,the application of it was relatively different.But the fabric blank dyebath contrastive method was intuitive,simple,ease of operation,and its reliability could meet the requirements.So it was suitable for laboratorial and industrial application.Results showed that combine the create calibration model method and the maximum absorption wavelength-simultaneous equations could determine concentrations of combination dyeing with two or three dyes.But the detection error was bigger,this paper could only get the dye concentration and dye up-take at limited error of about 5%.So,improving performance of instruments and selecting better calculation method about on-line monitoring of the combination dyeing could still have much room for research.The achievements of this paper(including the equipment and two different solutions)could be applied on the real-time monitoring of the dyeing process.