Abstract: The suitable nitration approach for biomass alizarin was selected based on different reaction conditions. And the structure of modified alizarin was characterized by FT-IR, HPLC-MS and 1H NMR. The nitrated alizarin was then used to dye superfine polyester fabrics. The levelness, color fastness of the dyed samples with traditional alizarin and 3-nitroalizarin were investigated respectively. The results show that the modified alizarin, i.e. 3-nitroalizarin, can be got by reacting with concentrated nitric acid in glacial acetic acid at 40 ℃ for 8 h. The average purity of products is 97%. Compared with the color fastnesses of dyed samples with traditional alizarin, the better grade of those of dyed samples can be obtained by dyeing with modified alizarin under auxiliary-free condition. The soaping fastnesses, wet rubbing fastnesses and levelness are also raised by half grade with modified alizarin. It indicated that the significant reduction in both dyeing cost and wastewater pollution can be achieved if using modified alizarin.

Key words: alizarin, 3-nitroalizarin, levelness, color fastness, auxiliary-free dyeing