The dyeing and mordanting behavior of cellulosic fibers such as cotton, rayon, diacetate, and triacetate, whose structural backbone is cellulose, were investigated using logwood extract dye solutions, and the effects of the internal environment of the dyeing site of each fiber on their dyeing and mordanting behaviors were discussed. All the fibers used could be dyed with the unadjusted logwood extract dye. However, the optimum dyeing temperatures for each fiber were different, with hydrophilic cotton and rayon dyeing at lower temperatures, while hydrophobic diacetate and triacetate dyeing at higher temperatures. The difference in dyeing behavior with increasing temperature between cotton and rayon suggests that the amorphous aggregation structure of rayon is less focused than that of cotton. On the other hand, diacetate and triacetate hardly form dyeable sites at low temperatures, but as the temperature rises, some regions where segmental motion is activated serve as dense dyeable sites with high dye affinity due to hydrogelation of the molecular chains constituting them. Furthermore, in all fibers, the dyed logwood dyes form metal complexes by mordanting at 90°C with iron, copper, and aluminum, but none of the central metals are presumed to be coordinated with the molecular chains that constituent the dyeing sites.

This research aims to develop synthetic leather that can be dyed with disperse dyes. In this study, films were first prepared using polyurethane (PU) resins at different glass transition temperatures (Tg), and the dyeing behavior and color fastness of the films were investigated. Thereafter, a grain-dyeable artificial leather dyed with a disperse dye was prepared as the base material. PU resin was overcoated on these surfaces, and the relationship between the dye migration prevention performance and Tg was investigated. In addition, synthetic leather was obtained using these PU resins as the grain layer resin. Reduction cleaning was performed after dyeing, and the dyeability and color fastness of the PU resin were evaluated. The results suggest that the dyeing speed at each dyeing temperature changes according to the Tg. During low-temperature dyeing, PU resin with low Tg possessed faster dyeing speed and higher dyeing amount. At a dyeing temperature of 100 °C, dyeing proceeded rapidly for all the PU resin films, and the equilibrium dyeing amount was confirmed to increase with an increase in Tg. In contrast, when the dye migration prevention performance of PU resin was examined, the migration of dye molecules was confirmed to suppress with an increase in Tg. Furthermore, when PU resin was used as the grain layer of synthetic leather, it was confirmed that the PU resin with high Tg can be used for reduction cleaning, and it shows good results in terms of dyeability and color fastness.