DIRECT DYEING OF CELLULOSE

(PART XIII). THE DYEING PROPERTIES OF DISAZO DYES CONTAINING H-ACID AS COUPLING COMPONET

Abstract

This report deals with the effects of an amino group at the end of the dye molecule on the dyeing properties. The dyes used were p-nitroaniline→p-cresidine→H-acid whose nitro group was reduced to amino group (I) and aniline→p-cresidine→H-acid (II). The dyes (I) and (II) are different from each other only in the presence or non-presense of an amino group in the benzene ring which is most remote from sulphonic groups.
1) The rate of dyeing and the amount of the dyes on fibre at equilibrium were measured on cupro-ammonium rayon at 90°, 80°, 70° and 60°C. The apparent diffusion coefficient of the dye (I) was smaller than that of the dye (II), but the standard affinity of the former is larger than the latter. The dye (I) is about of the same size as that the dye (II). Therefore, the apparent diffusion coefficients of these dyes seem to depend only on the affinity of the dye on the rayon. Since the affinity has a retarding effect on the apparent diffusion coefficient, the apparent diffusion coefficient of the dye (II) seems to be larger than that of the dye (I). The apparent diffsion coefficients of these dyes increase in presence of sodium chloride (0.05 mol/l).
2) The degree of swelling of cupro-ammonium rayon in a solution containing 0.05, 0.1, 0.15 and 0.2 mol sodium chloride per liter is determined by measuring the imbibition of the salt solution by the rayon. The degree of the swelling of the rayon decreases with increase of the concentration of the salt and such a decrease of the swelling is a recognized even at a very low salt concentration of 0.05 mol per liter.
3) The standard affinity for cotton, ramie and cupro-ammonium rayon at 90°C was determind.
The standard affinity of dye (I) is larger that of the dye (II).
From these results it may be concluded that the dye with amino group at the end of molecule has larger substantivity than the dye without the amino group.