1956 Volume 12 Issue 12 Pages 903-906
By using selected substantive dyes we have studied the dyeing behaviour of the crystalline regions of natural and regenerated cellulose fibers gained by Maeda's method, and obtained the following results:
(1) The dye accessibility of a crystalline region varies with the change of dyeing conditions. The change is particularly remarkable when the salt content in the dyebath differs. As a rule, the dyeing behaviour of a crystalline region greatly changes according to the concentration of salt in the dyebath.
Such being the case, the dye-accessibility of crystalline region is not always greater than that of a fiber itself. It was observed that, when a dyeing is carried out under a mild condition, which means a low degree of exhaustion, the dye-accessibility of a cristalline region is lower than that of a fiber itself. On the contrary, when a dyeing is carried out under the reverse condition, the dye-accessibility of a crystalline region becomes greater than that of fiber itself.
(2) Addition of salt in the dyebath increases the absorption of direct dye on the crystalline regions from the fiber much more than it does on the fiber itself, and the covering effect on the surface is mainly observed, particularly in the crystalline regions. This effect is all the more evident as a dyeing is carried out at a higher temperature with the addition of more salt into dyebath. These results seem mainly due to the change of the cohesive forces or that of the colloidal dispersed state of each dye molecules.
(3) There is a wide difference in dyeing behaviour between the crystalline regions separated from a fiber and the crystalline regions contained in a fiber. This is presumably due to the nature of the crystalline region in the fibers, which is not fully in contact with dye molecules during dyeing, and the polar groups on the crystalline regions which probably remain inactive, are not accessible to dyemolecules.
It seems hardly possible to ascertain the dyeing machanisms in the micromolecular structure of fibers by these indirect dyeing experiments.
