Extraction And Dyeing Process Of Natural Dyes

Rhubarb, madder and cetraria islandica were extracted with ethanol/water solution. Rhubarb and madder by reflux method,and cetraria islandica using microwave extraction method. The effects of temperature, time and solvent concentration on the extraction efficiency were determined, so does the optimal extraction process. Natural dye of indigo was modified.The dyeing effect of dyeing time, pH value and dye dosage was studied. By testing K/S value and color fastness determined the optimum conditions. In addition, the influencing factor of stability of dyes were discussed,include the value of pH, temperature and the concentration of oxidant and reducing agent.The result show that:Under the condition that material liquid ratio is 1:20,the optimal extraction process of rhubarb and madder are 80% concentration of ethanol×90℃×50min and 50% concentration of ethanol×80℃×60min respectively. Microwave power 480 W, ethanol concentration 70%, and extraction time 15 min as the optimal conditions for the extraction of cetraria islandica.Pre-mordant dyeing with aluminum salt can not change the color of dye and have a good dyeing effect. The optimized process of three natural dyes are listed in the followings: for Rhubarb, pH = 3.5,dyeing at 80℃for 60mins; Madder: pH=2,70℃×50mins; cetraria islandica: pH=2,80℃×60min.Compared with the direct dyeing method,the dyed fiber of fastness of Madder, Rhubarb and cetraria islandica were improved by pre-mordant with aluminum salt. Rhubarb dyed fibers of color fastness improved by half or one. Dry rubbing fastness of Madder dyed fibers enhanced from 2 ~ 3 to 4 level. The rubbing fastness of cetraria islandica dyed fiber s improved half grade.In addition to ethanol-water extraction of cetraria islandica decompose at 90℃, Rhubarb and Madder extraction perform better stability. The three kinds of natural dyes were resistant to oxidation, reducing agent, and sensitive to pH. The color of extraction gradually deepened as the pH value increases.