Studies On Dyeing And Finishing Process Of Milk Fiber

Milk fiber is a novel type fiber which can be produced via graft copolymerization of acrylonitrile on casein. The fiber has good prospect of widely using in textile industry because of its outstanding properties, such as silk-like luster, good wet absorption and wet conduction and soft handling. The research on its chemical stability, bleaching property and dyeing performance provide both a theoretical basis for its development and application and a guideline for its dyeing and finishing process. In this paper, the resistance of milk fiber subjected to wet heat treatment, alkali resistance and hydrogen peroxide bleaching properties of milk fiber were investigated. The influence of neutral electrolytes on alkali resistance and hydrogen peroxide bleaching of the fiber were also discussed. The dyeing properties of non-metallized and 1:2 pre-metallized acid dyes, reactive dyes and cationic dyes on milk fiber were studied. The loss of casein of the milk fiber during dyeing with reactive dyes for the coloration of cotton fabrics was discussed. By these basic researches, the conclusions were concluded as follows:(a) The resistance of milk fiber subjected to wet heat treatment was poor. The weight loss of the fiber was obtained during the fiber was treated in warm or hot water. The weight loss of the fiber might be ascribed to the hydrolysis of casein.(b) The milk fiber had poor alkali resistance, particularly to sodium hydroxide and sodium carbonate. The weight loss of the fiber during the alkaline treatment was primarily caused by the hydrolysis of casein. The hydrolysis of nitrile groups and induced formation of C=N conjugated system were responsible for the yellowing effect of the fiber treated under strongly alkaline medium. X-ray diffraction curves of the treated fiber showed that alkaline treatment did not change the main crystalline structure of the fiber.(c) The hydrogen peroxide bleaching of milk fiber was carried out under alkaline medium. The casein could be lost during bleaching. The whiteness of the treated fiber didn't increase, but decreased instead. The hydrogen peroxide bleaching hardly affected the main crystalline structure of milk fiber.(d) Non-metallized and 1:2 pre-metallized acid dyes were used to dye milk fiber. The effect of pH was prominent on percent exhaustion. The sensibility of the dyeing of milk fiber to pH was greater than that of spun silk and cashmere. The effect of neutral electrolytes on exhaustion indicated that the isoelectric point of the fiber was about 4. The influence of dyeing temperature on percent exhaustion was different because of different kinds of dyes. The effect of dyeing temperature was greater on percent exhaustion of 1:2 pre-metallized acid dyes. The initial uptake rates of acid dyes were high, but the uptake rates for milk fiber were lower than those for spun silk and cashmere under the constant temperature of 80℃. The uptake rates of non-metallized acid dyes were lower than that of 1:2 pre-metallized acid dyes. The building-up power of acid dyes on milk fiber is good, but it was worse than that on spun silk and cashmere. The building-up power of 1:2 pre-metallized acid dyes was little better than that of non-metallized acid dyes.(e) The reactive dyes for the coloration of wool were not suitable for dyeing milk fiber. The vinylsulphone/monochlorotriazaine and diafluorotriazine reactive dyes for the coloration of cotton were more suitable for dyeing this fiber. The dyeing of this fiber with reactive dyes for the coloration of cotton was able to be performed at the temperature close to that of cotton dyeing; in particular only quite smaller amount of sodium carbonate was needed. The building-up properties of vinylsulphone, vinylsulphone/monochlorotriazaine and diafluorotriazine reactive dyes were good. The diafluorotriazine reactive dyes had the best building-up properties of all. The formation of cross-link between macromolecular of milk fiber and dyes was responsible for the fiber dyed with reactive dyes which has difunctional or trifunctional groups. Compared to the fiber which was not dyed, the weight loss of the dyed fiber decreased.(f) The cationic dyes were applied to dye milk fiber. The effect of pH was on percent exhaustion of different dyes was different. The weight loss of the fiber during dyeing was least when the pH was 4. To different dyes, the influence of temperature was discriminating. The dyeing of milk fiber with cationic dyes was able to be performed at lower temperature. Compared to acrylonitrile fiber, the uptake rates for milk fiber and the percent exhaustion on milk fiber under lower temperature were higher. The cationic dyes had good building-up properties.(g) The neutral electrolytes could reduce the extent of the hydrolysis of casein. The milk fiber treated with alkali solutions added neutral electrolytes. Both the weight loss and the whiteness of the treated fiber decreased with the increase in neural electrolytes dosage. The bleaching solutions added neutral electrolytes were used to bleach the fiber. The weight loss decreased sharply and the yellowing index increased with the increase in neural electrolytes dosage. The neutral electrolytes could also reduce the weight loss of milk fiber during dyeing with reactive dyes for the coloration of cotton.