Yoshio Suda

A STUDY ON THE DYEING BEHAVIOUR OF A MODEL FIBRE FOR A FALSE TWISTED NYLON YARN WITH A DISPERSE DYE

In order to obtain some fundamental data on the dyeing of a false twisted nylon yarn (dry heated) with disperse dyes, the diffusion coefficient of C. I. Disperse Red 7 into a model fibre and the surface dye concentration have been studied by microspectrophotometric (MSP) method.The model fibre, prepared by twisting and dry heating of nylon fibre drawn-3 times, has its cross section of a chestnut-like shape, which comprises a part of a near triangle and an arc.The diffusion coefficients on the arc part of the model fibre are much smaller than that for the fibre prepared by dry heating under no tension, and the former values correspond to that for the fibre obtained under the tension of 0.75g/d. The diffusion coefficients on the triangle part are much larger than those at the arc part.Similar tendencies are found in the case of the surface dye concentration.These results are explained by the tension in the preparation process of the model fibre for the arc part and the compression for the triangle part. Micro irregular dyeing of a false twisted nylon yarn may be partly due to the above mentioned mechanism.The usefulness of the present method in the studies of dyeing of conjugated and textured yarns is suggested.

Adsorption of Direct Dyes from Aqueous Alcoholic Solutions

Equilibrium uptake of ten direct dyes on cellulose from aqueous alcoholic solutions has been determined at 50°C. The dyes used have two to five sulfonic groups.Dye uptake decreases remarkably at first, passes through a minimum, and increases as the concentration of alcohol increases. Adsorption of dyes seems to be influenced by the propor-tion of alcohol in aqueous solution in two ways, as was pointed out by Hayashi and Yabe, one of which is a depressing action and the other an accelerating action. The larger the carbon number of an alcohol is and the less the solubility of a dye is, the more remarkable the both influencesare.It is suggested from these results that, due to the reduction of the degree of dissociation of a dye by the increasing proportion of alcohol, the adsorption from a dissociated state decreases and that from an un-dissociated state increases.

STUDIES ON DYEING IN POLYMER SOLUTION

The effects of polymer-electrolyte solution in direct dyeing were studied from the view points of the equilibrium adsorption and the diffusion coefficient of dye within the fiber. The followings were used; Polymer-electrolytes-Sodium Alginate and Sodium Carboxymethyl Cellulose, Dyestuffs-Direct Scarlet B and Chrysophenine G, and Fiber-Viscose Rayon Staple.The results are1) In direct dyeing, cations dissociated from polymer-electrolyte act as well as those from inorganic electrolyte.-effect (1).2) Adversely, polymer-electrolyte adsorbs direct dye itself, therefore, apparent concentration of dye in solution decreases and dye adsorbed on fiber decreases, too.-effect (2).3) Increased salt concentration decreases effect-(1) and increases effect-(2).4) The reciprocal correlation between effect-(1) and effect-(2) makes characteristic change of the equilibrium adsorption and the diffusion coefficient.