Investigations On One-bath Process Of Polyester Fabric For Alkaline Reducation And Dyeing

The traditional dyeing and finishing process of polyester usually begins with alkali reduction under alkaline conditions,follows by dyeing under weak acidic conditions at a p H value of 5-6,and finally reduction clearing under alkaline conditions.The process of repeated acid and alkali change takes a long time and consumes a lot of energy and water.In addition,the fabric treated in the previous step needs to be washed and neutralized repeatedly to ensure the dyeing effect,which brings difficulties to the control of dyeing quality.Alkaline reduction and dyeing with alkali-resistant disperse dyes in one bath can avoid above mentioned problems of traditional process.However,the reduction and dyeing occur simultaneously,which may influence each other.Therefore,it is imperative to study the influencing factors and feasibility of alkali alkaline reduction dyeing system.In this paper,the factors affecting the color stability of fabric obtained by one bath of alkali reduction dyeing were studied,and the feasibility of one bath process was also analyzed by comparing it with the traditional process.The purpose is to apply alkali-resistant disperse dyes into one bath system of alkali reduction dyeing of polyester and provide reference for actual production.In the first part,alkali resistant disperse dyes with three shades were designed and synthesized for the chromatic dyeing of polyester fabrics,and the absorption spectrum properties and the alkali-resistant performance of these three types of disperse dyes were investigated.The results showed that all these alkali-resistant disperse dyes had high molar extinction coefficients in both acetone and DMF solutions,and also had excellent alkali resistance under high temperature conditions.In the second part,the factors affecting alkaline reduction and dyeing in one bath process were studied from three aspects: alkali resistance of disperse dyes,oligomer accumulation and fiber change.The concentration of dye on weight of fiber would change due to the weight reduction of fiber caused by alkali hydrolysis of polyester,and it was corrected based on the final fabric weight.The results showed that the changes of fiber including the etching of surface and finess of fiber were the main influencing factor for color.The etching of fiber surface could increase the saturated adsorption capacity of fiber,which increased the K/S value of dyed fabric.But the decrease of fiber fineness would increase the reflected light,which decreased the K/S value of dyed fabric.It was found that the change in fineness of fiber was the major factor whichinfluence on the color of fabric.In the second part,the difference of fabrics obtained with one bath process and traditional process respectively was analyzed.The results showed that the K/S value of fabrics under the same reduction rate and weight of dye to fiber was same,but the color was diffenent.The curves between reflectivity and absorption wavelength of fabrics coincided with each other except at the part of wavelength of dyes.The reflectivity of fabric obtained with one bath process was higher than the the traditional ones,which increased brightness.In addition,due to the coexistance of alkali reduction and dyeing,the levelness and fastness of the fabric were improved compared with traditional process,and the reduction clearing was not needed.In the third part,the combination of dyes for different color with one bath process was studied.The results showed that when two dyes were used the K/S value of fabric decreased with the increase of the reduction rate and the decrease of the fiber fineness.The color of the fabric also changes smoothly with the change of the ratio of dyes.It was indicated that the red,yellow and blue dyes did not compete with each other.In the paper,several key factors involved in the alkaline reduction and dyeing in one bath system of polyester fabric were analyzed and discussed.The difference between dyeing effect of traditional and one bath process was provided.The feasibility of alkaline reduction and dyeing in one bath process with alkali-resistant disperse dyes was further determined.This study provided an important support offor the development of short process of pretreatment and dyeing of polyester fabric.