The Development And Application Of Dyestuff Based On Modified Natural Dyes

Nowadays, synthetic dyes are the main coloring substances used in the textile due to their relatively complete chromatographic color range, bright color, good washing and light fastnesses, and low price, etc. Synthetic dyes, however, have some disadvantages, such as coming from the non-renewable raw materials and causing severe pollution of dyeing wastewater. Owing to their good environmental compatibility, biodegradability and renewability, natural dyes have got a renewed interest of researchers. But, there are still many disadvantages of natural dyes, such as the poor color fastnesses, the sensitivity to dyeing environment, and the using of heavy metal mordant, etc. Therefore, it is necessary to do some modification for natural dyes. As for the affinity and the color fastnesses of natural dyes, they can be improved by simple structure modification without damaging original matrix chromospheres. The dyes'chromatographic color range can also extended by modification due to the change of the original matrix chromospheres'absorption wavelength.In this paper, the modified approaches for nature dyes, such as esterification and etherification for curcumin, nitration and esterification for alizarin, were selected and studied in details. And the modified dyes' structures were characterized by melting points, FT-IR, HPLC-MS and 1H NMR. The build-up property of modified natural dyes, and the color parameter (brightness L*, red-green shaft a*, yellow-blue shaft b*, saturation C*, hue angle h), K/S value, levelness and color fastness (soaping fastness, rubbing fastness) of the dyed samples were investigated respectively.The main results are summarized as following:(1) The yield of the esterified curcumin is very low, and the product is a mixture, which is hard to separate and purify. Further more, etherification is not a reasonable modified approach for curcumin. (2) There are two suitable approaches for 1,2-diethanoylhydroxyanthraquinone. One is that alizarin reacts with acetic anhydride (60 mL/g alizarin) and concentrated sulfuric acid sodium (0.1 mL/0.03 mol alizarin) at 60℃for 2 h. The other is that alizarin reacts with acetic anhydride (60 mL/g alizarin) and sodium acetate (3.5 mol/mol alizarin) as tied acid agent at 60℃for 1.5 h. The average purity of products is up to 98%, and the melting point is 181℃-183℃. The amount of acetic anhydride is the main factor which affects the yield. The more the amount is, the lower the yield will be.(3) The best modified approach of 3-nitroalizarin is that alizarin reacts with concentrated nitric acid (1.5 mol/mol alizarin) in glacial acetic acid (10 mL/g alizarin) at 40℃for 6h. The average purity of products is up to 97%, and the melting point is 244℃-245℃. The amount of glacial acetic acid is the main factor which affects the yield. The more the amount is, the lower the yield will be.(4) It's easy for alizarin,1,2-diethanoylhydroxyanthraquinone and 3-nitroalizarin to dye fibers such as wool, nylon and cellulose acetate. And they can also dye polyester. The red tone of the fabrics dyed with 1,2-diethanoylhydroxyanthraquinone, alizarin and 3-nitroalizarin respectively increases in turn.(5) The polyester staining, wet rubbing fastness and levelness of the polyester samples dyed with 1,2-diethanoylhydroxyanthraquinone exhibit half level higher than that of the unmodified one. Meanwhile, the wet rubbing fastness and levelness of the nylon samples dyed with 3-nitroalizarin also show half level higher than that of the unmodified one.