A Study On The Behaviors And Principles Of Dyeing For Polyurethane Fibers

The dyeing behaviors of neutral~ weak acid ~. disperse -. reactive dyes for polyurethane fibers were determined. In general, the exhaustion rates of disperse dyes and 1:2 metal complexes are higher than the others. Some acid dyes take the second place. The dyeing behavior of the reactive dyes is very poor. The relationship between the structures of neutral, weak acid, disperse dyes and their dyeing behaviors is investigated. It抯 found out that there is a tendency that the exhaustion rates of the dyes with the similar chemical structures increase with the decrease in their JOB (inorganic organic balance) value or the increase in their hydrophobicity. The dyeing behaviors of disperse azobenzene dyes are the best. The JOB values of the disperse dyes whose JOB value range from 0.55 to 0.98 exhibit good dyeing behaviors for polyurethane fibers. The JOB values of the neutral dyes whose dyeing behaviors are good are in the scope of 1.5-2.1 .As for weak acid dyes, the LOB values of which suit for dyeing polyurethane fiber vary from 1.85 to 2.78. The exhaustion rates of triphenylmethane dyes are in the highest rank.The main process parameters affecting dyeing behavior such as pH-.temperature time are tested systematically. The optimum conditions are given as follows:neutral dyes (pH =4 -. Temp.=70-800C . dyeing time 40-60mm) disperse dye; (pH=5-6~. Temp.=95- 100 0C -. dyeing time 40-80mm)weak acid dyes (pH=4 Temp.=95-1000C-. dyeing time 60-90mm-. neutralelectrolyte 1 O-20g11).In addition, the mechanisms of the dyeing of polyurethane fibers with neutral dyes and disperse dyes were explored by the study of dyeing thermodynamic. The adsorption isotherm of 1:2 metal complexes on polyurethane fibers belongs to the dual of Langmuir type and Nernst type. indicating that the interaction between 1:2 metal complexes and the polyurethane fiber is by electrostatic and Van Der Waals forces as well as hydrogen bonds. While the JOB value of neutral dyes decreases, the contribution of Nemst type increases and the affinity as well as the exhaustion rates markedly improves. The adsorption isotherms of disperse dyes shows Nemst type.The activation energies of neutral and disperse in polyurethane fiber are lower than those of other dye-fiber systems. Moreover, the diffusion coefficients increase with the increase in their hydrophobicity while the variety of molecular weights has no influence. However, as to disperse dyes, neither the affinity nor the molecular weight has remarkable effect on the diffusion coefficients...