Study On Improving The Dyeing Performance Of Natural Dyes

There are many problems when we dye the cotton with natural dyes.In order to solve the dyeing problem of natural dyes,this paper aimed to improve the wash fastness and rub fastness of natural dyes by pre-treating the cotton fabric with mordant.And we prepared a kind of macromolecule additive with a lot of carboxyl groups to improve its light fastness and rub fastness.Firstly,we tested basic parameters of five natural dyes(gardenia yellow,annatto,cochineal red,sorghum red and green tea),such as liquid content,UV-visible spectrum and gram extinction coefficient.Then these natural dyes were used for dyeing cotton fibers and their optimal dyeing conditions were explored.In the thesis,the cotton fiber was pretreated by zinc chloride solution with the mass fraction of 65%.The optimal temperature,time and liquor ratio of pretreatment were explored by quantitative analysis of zinc element.The mechanism for pretreatment was investigated by SEM,XRD and ATR-IR.The un-mordant and pre-mordant cotton were dyed with five natural dyes,and then dyeing results were compared.The results showed that,under the optimal conditions,there were 8.00 mg of zinc on 2.00 g of cotton fiber.The interaction of zinc ions and cotton fabric is not coordination complex,the ions were deposited on the fiber surface through etching the fibers.With the pretreatment of cotton fabric and the same dyeing conditions,the exhaustion of gardenia yellow increased by nearly 15%,and its K/S value increased by nearly 125%;The exhaustion of annatto increased by nearly 30%,its K/S value increased by about 125%.The exhaustion of cochineal red increased by nearly 34%,and its K/S value increased by nearly 600%.The K/S value of sorghum red ncreased by nearly 15%,and The K/S value of green tea increased by nearly 150%.The color fastness of dyed cotton fabrics were tested and the results show that after the pretreatment of Zn Cl2,the rub fastness of the five dyes decreased by 0.5-1 grade.The wash fastness of both cochineal red and green tea decreased by 2 grade.The light fastness of gardenia yellow,cochineal red and sorghum red all decreased by 1 grade.In order to improve the light fastness and rub fastness of natural dyes,we prepared a macromolecule auxiliary with poly(allylamine-co-acrylic acid)as skeleton,acrylic acid content of 43.5%,and the grafting rate of cyanuric chloride condensed product with glycine is about 15%.The average molecular weight of the macromolecule auxiliary is 12848.The results showed that,after the treatment with the auxiliary,the light fastness of gardenia yellow and annatto reached 3-4 grade,increased by 1-1.5 grade,and wet rub fastness increased by half grade.Rubbing fastness of cochineal red and sorghum red also enhanced by half grade.