Particle Size and Solubility of Disperse Dyes

A new method for the determination of the solubility of disperse dyes

“…The results are evaluated in a manner similar to that in method 1. This simplified procedure is called solubility titration [5].…”

“…However, the method proves unsatisfactory for determining the solubility of substances in a state of fine dispersion such as commercial disperse dyes. The solubility of very finely dispersed substances is known to depend on their particle size and degree of crystallinity [5]. In a dispersion these two properties will change on heating, primarily as a result of recrystallisation phenomena such as correction of crystal structure defects, Ostwald ripening or sintering together of agglomerated primary particles, or changes in crystal form [5,6].…”

“…The solubility of very finely dispersed substances is known to depend on their particle size and degree of crystallinity [5]. In a dispersion these two properties will change on heating, primarily as a result of recrystallisation phenomena such as correction of crystal structure defects, Ostwald ripening or sintering together of agglomerated primary particles, or changes in crystal form [5,6]. Dispersions are not in a state of equilibrium, and they cannot be brought into such a state without being completely destroyed and the solubility changing.…”

Textile Dyeing, 4. Dyeing of Man-Made Fibers

“…The water solubility and rate of dissolution are influenced by many factors including [46][47][48] The water solubility of pure disperse dyes is a few milligrams per liter and increases strongly with temperature. It is also increased manifold by dispersing agents [46,49].…”

Dyeing with disperse dye

“…As disperse dyes are specifically applied at higher temperature, the dye when added, remains present in bath in two basic forms: (i) a very little part remains in completely soluble form and (ii) the rest in finely dispersed insoluble form; the later remains predominant and the ratio is being determined by solubility of dye in water at that temperature (Braun, 1983). Solubility of disperse dyes is too feeble in water at room temperature (~0.2 mg/l) which is increased with heating of bath beyond 90°C or addition of dispersing agent or both.…”