The Studay On Print Processing Of Colored Cotton By Using Metal Salts

With the growing popularity of the concept of green environmental protection, market preference of "green" textiles and consumers' demand for natural colored cotton products are increasing. There are therefore great prospects for the development of new colored cotton products in China.Presently, the chromatic spectrum of natural colored cotton is tedious, mainly for two series of colors: brown and green. In addition, there are some problems about color change, fading and staining in the products. Improvement of existing coloring scope and quality, and the development of new colored cotton products are key to the industrial development of natural color cotton products in China. But by now, such substantial progresses have been slow.In the study of improving the color stability of natural colored cotton, metal salts fixation is a viable way of maintaining the environmental characteristics of natural colored cotton. Various experiments have indicated that the adoption of fixation by metal salts is equivalent to "post-mordant dyeing" in natural mordant dyes, which results in an improvement of color fastness to washing and perspiration. During which the treatments of using Ferric Chloride, Ferrous Sulfate, Ferric Sulfate Amine, Aluminum Sulfate, Potassium, Nitrate and Silver salts lead to a marked improvement of color fastness to washing and perspiration, but the shortcoming is that the original color shades of the products would be changed.The purpose of this study is to solve the problems associated with metal salt fixation, that is, change in color shade resulting into the "print" effect, and therefore the widely believed phenomena that dyeing and printing of natural colored cotton cannot be achieved without influencing the original color while at the same time maintaining its environmental characteristics will be disputed. This is done with a view to developing new products for the processing of natural colored cotton.The Brown Cotton was selected as the raw material for this study. Firstly, fiber structure and pigment distribution of natural colored cotton were discussed in order to understand their basic physical and chemical properties. On this basis, metal salts that are compatible with the pigments were chosen by optimization mechanism under a rule of that the printed products would gain a significant discoloration while remain the properties of harmless to humans and the environment. Secondly, comparative analyses on color change were done before and after metal salt treatments of natural colored cotton, which include the acid-base and oxidation-reduction properties under the action of chemicals, to predict the color stability of the printed colored cotton fabrics.In order to maintain the ecological nature of colored cotton products, this study describes the necessity of application of biological enzymes, and explores their effectiveness. Experiments show that the enzymatic pretreatment of natural colored cotton could strengthen the complex effects between metal salts and the pigments.During printing preparation, a number of basic experiments on different kinds of print pastes ware conducted. Guar gum was found to be the most suitable gum that can bind with natural colored cotton and be fully compatible with metal salts as well. In the printing experiments, the processing parameters followed by their impacts on shade and colorfastness were studied, accordingly an "orthogonal " test program was set and comprehensive comments on the effects of the test program was given. At last, the optimum processing parameters in the printing process of the Brown Cotton fabric were found to be:The Brown Cotton weft plain knitted fabric - enzymatic pretreatment - deckle finishing - hand flat screen printing - steaming: 15min - drying - washing and removing waste paste - drying. Enzymatic treatment temperature: 55℃; pH value : 6-8; Guar paste concentration: 7%; Ferric Chloride salt ions concentration: 2g /l Steaming temperature: 100℃; Steaming time: 15minThis research on the print processing of the Brown Cotton by using metal salts obtained pioneer results. It has applied for a national patent as an invention and is expected to provide useful reference for the developing new products of natural colored cotton.