The Dyeing of Cellulose Acetate with Disperse Dyes VIII– Determination of Fibre Saturation Values

Fibre saturation values have been determined at 60° and 80°c, in presence of a dispersing agent, for 15 disperse dyes on secondary cellulose acetate. In most cases the results agree with those obtained by calculation from aqueous solubilities and partition coefficients in the absence of dispersing agent. With the more hydrophilic disperse dyes, however, e. g. those containing two N–β–hydroxyethyl groups, low values are obtained in presence of dispersing agent. This is attributed to adsorption of dispersing agent rendering the fibre more hydrophobic. When a fibre saturation value is determined by means of a single dyeing carried out in presence of a large amount of commercial dye, the result may be much too high owing to (a) the presence of coloured impurities and shading components and (b) the absence of sufficient dispersing agent to stabilise the concentrated dispersion and so prevent surface adsorption of dye by the fibre.