Study On Dyeing Process Of Nylon With Acid Dyes Based On Raman Spectroscopy

Polyamide fiber is the first synthetic fiber to realize industrial production in the world.Because of its good wear resistance,high breaking strength and low density,it is widely used in textile and clothing,military industry,medical treatment and other fields.Polyamide fiber's dyeing process is complex and dyes' levelness on the fiber are poor.Rapid and accurate monitoring of dye concentration change in dyeing bath is the key to control nylon dyeing process and improve the quality of dyed products,which plays an important guiding role in actual production.Presently,the most commonly used detection method of dye concentration is ultraviolet visible absorption spectroscopy,but the problems of single spectral peak and maximum absorption wavelength shift in high concentration hinder its application in quantitative analysis.Raman spectroscopy,as a testing method of material structure analysis,can be used to qualitatively and quantitatively characterize the material through its abundant "fingerprint" information.The combination of Raman spectroscopy and partial least squares method can quickly monitor the concentration of each dye in multicomponent dyeing solution.In this paper,we explored the feasibility of monitoring the dyeing process of nylon fiber with monochromatic and mixed acid dyes by Raman spectroscopy was explored.The specific experimental contents and conclusions are as follows:Firstly,the feasibility of quantitative analysis of acid dye concentration by Raman spectroscopy was studied.We found that there was a good linear relationship between dye concentration and Raman peak intensity when the acid dye concentration was between 0-2.0 g / L.When the dye concentration continued to increase,the measured Raman peak intensity deviated from the linear relationship curve.To explore the cause of this phenomenon,DMF was used to dissolve the dye.It was found that the linear relationship between the concentration of dye DMF solution and the Raman peak intensity was good,which indicated the aggregation behavior of acid dye occurred in aqueous solution,resulting in the deviation between the measured actual dye concentration and the theoretical dye concentration,which affected the quantitative analysis of dye concentration by Raman spectroscopy.In order to further confirm the influence of the aggregation behavior of dyes in aqueous solution on the Raman peak intensity of dyes,the Raman spectra of pure dyes with the same concentration before and after adding salt were compared.The results reflected that the Raman peak intensity of dyes with the same concentration decreased after adding salts.In addition,in the Raman spectra of 4.0 g / L acid e-Blue dye with different salt concentrations,the Raman peak intensity of dye decreased with the increase of salt content.Because inorganic salts will increase the degree of dye aggregation in water,the actual measured dye concentration will decrease,leading to the decrease of Raman peak intensity.Adding urea to the dye solution can increase the solubility of the dye.With the same concentration of dye solution,the Raman peak intensity of the dye solution added urea will be improved,and the range of quantifiable concentration will be increased.It further shows that when the dye concentration is too high,the degree of dye aggregation will increase,so the actual measured dye concentration is lower than the theoretical dye concentration.As a result,the relationship between dye concentration and Raman intensity is not linear.In this study,when the dye concentration is 0-2.0g / L(the bath ratio is 1:30,0-6.0%(o w f),and the dye concentration is 6.0%(OWF)),the linear relationship between the concentration of nine acid dyes and Raman peak intensity is good,and the linear relationship between the concentration of dyes and Raman peak intensity does not change when the p H of dyeing solution is adjusted to about 3.0 by adding acetic acid.So it is feasible to use Raman spectroscopy to monitor the change of dye concentration in the process of dyeing nylon with acid dyes.Raman spectroscopy and partial least squares(PLS)were used to establish two quantitative analysis models of blending dye.The RMSECV and RMSEP of acid e blue and meijiate red were0.0511 and 0.0606 respectively,and 0.0589 and 0.0485 respectively,indicating that the model had a strong predictive ability for blended dye.By comparing the results of dyeing nylon with acid e-Blue and meijiate red at different color matching ratios,it is found that the change of dye matching ratio will affect the initial dye uptake of each dye,and meijiate red with higher affinity to fiber will replace acid e-Blue at the later stage of dyeing.In the quantitative analysis model of meijiate blue and meijiate red,the root mean square error of correction was 0.0808 and 0.1050,and the root mean square error of prediction was 0.0662 and 0.0656,respectively,indicating that the model has a strong prediction ability for the blended dye.Comparing the dyeing process of polyamide fabric with different color matching ratio,we found that the initial dye uptake of two dyes will change with the change of dye matching ratio.Compared with the single component dyeing process,the time for each dye to reach the maximum dye uptake will be delayed.Monitoring the dyeing process of nylon fabric with acid dyes by Raman spectroscopy can provide theoretical guidance for the formulation of dyeing scheme and the study of the compatibility of different dyes in the actual dyeing process.