STUDIES ON THE DYEING PROPERTIES OF ACID AZO DYES:(VI) CONDUCTIVITY OF FREE DYE ACID SOLUTIONS

Abstract

(Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, Japan) The adsorption of monoazo acid dyes ranging various chemical constitution by 6-nylon has been examined quantitatively. In all cases of dye used the adsorption isotherm shows Langmuir type, the saturation value of dye adsorption is nearly equal to that of the amount of terminal amino endgroup of nylon fiber, and this value increases with the rising temperature. Electrostatic combination between dye acid and the site on fiber is dominant contribution in this case. The standard affinity of these dyes was calculated using Gilbert-Rideal equation. The relation between the standard affinity of dyes carrying two sulfonic acid group and the distance between sulfonic acid groups are explained by means of simple lattice model of dye site. It is suggested that for oxyazo dyes, the dyes carrying hydroxyl group not restricted by intra-molecular hydrogen bond formation, may be adsorbed by the fiber by means of hydrogen bond formation. In the series of substituted azo dyes (substituted aniline G acid), the increase of standard affinity corresponds to the increase in molecular weight, and the nature and position of the substituent is of minor importance, except in the case of solubilizing group and! hydrogen bond forming group. (Received March 27, 1961)