Preparation And Dyeing Properties Of Metal Complex Natural Dyes

In order to improve the dye uptake and color fastness,natural dyes often need mordant treatment,resulting in long dyeing process and a large number of metal ions in wastewater.Metal ions are pre introduced into natural dye molecules through complexation reaction,and then dyed,which can shorten the processing process and realize energy conservation and emission reduction.In this paper,four metal complex natural dyes were prepared by complexing plant pigments catechin and hydroxyalizarin with Fe2+ and Al3+,and their structures were characterized.The dyeing properties of four metal complex natural dyes on wool yarn,silk fabric and nylon 56 fabric were further discussed.The preparation experiment of complex dyes showed that the optimum conditions for the preparation of catechin metal complex dyes were as follows:the molar ratio of catechin to metal ions was 1:2,the complexation temperature was 50℃,pH was 5,and stirring for 60 minutes.Under these conditions,the complexation yield of C-Fe is 65%,and the complexation yield of C-Al is 62%.The optimum conditions for the preparation of hydroxyalizarin metal complex dye are as follows:the molar ratio of hydroxyalizarin to metal ions is 1:1,the complexation temperature is 60℃,pH is 5,and stirring for 60 minutes.Under these conditions,the complexation yield of P-Fe is 71%,and the complexation yield of P-Al is 71%.The energy spectrum test shows that the complex dyes C-Fe,C-Al,P-Fe and P-Al contain Fe or Al elements in addition to C and O elements.The content analysis of constituent elements and the structure analysis of complex dyes by energy spectrum scanning showed that C-Fe and C-Al were 1:2 complex,and P-Fe and P-Al were 1:1 complex.UV-Vis spectrum analysis showed that the maximum absorption wavelength of catechin and hydroxyalizarin was red shifted after complexation with metal ions.Infrared spectrum analysis showed that new absorption peaks were produced at 556 cm-1 for C-Fe,750 cm-1 for C-Al,560 cm-1 for P-Fe and 747 cm-1 for P-Al,respectively.The X-ray photoelectron spectroscopy of the dyes before and after complexation showed that the coordination of metal ions had different effects on the whole molecular chemical environment.The complexation dyes occurred on the adjacent hydroxyl group on the benzene ring or on the adjacent hydroxyl group and carbonyl group.The dyeing properties of four metal complex natural dyes on wool yarn,silk fabric and nylon 56 fabric were studied by alkali dissolution method and grinding dispersion method.Metal complex natural dyes C-Fe and C-Al are suitable for alkali dissolution dyeing,and P-Fe and P-Al are suitable for grinding dispersion dyeing.The optimum dyeing process of wool is as follows:dyeing pH value is 4,temperature is 100℃,time is 60 min;The optimum dyeing process of silk is as follows:dyeing pH value is 4,temperature is 90℃,time is 60 min;The optimum dyeing process of nylon 56 is as follows:dyeing pH value is 5,temperature is 80℃,time is 60 min;Under these conditions,the dyed wool yarn,silk fabric and nylon 56 fabric have better fastness to soaping and perspiration,the light fastness of wool yarn is better,the light fastness of silk fabric and nylon 56 fabric is slightly worse,and the light fastness of hydroxyalizarin complex dye is better than that of catechin complex dye.The UPF values of silk and nylon 56 fabrics dyed with four metal complex natural dyes are greater than 40,which shows a good anti ultraviolet effect;The antibacterial rates of dyed wool yarn against Staphylococcus aureus and Escherichia coli were higher than 70%.