What is the rule of nylon reactive dyes for spandex dyeing?

1. The general law of fastness after dyeing of spandex: washing>perspiration (acid)>water immersion, and the wet rubbing fastness is much better than the dry rubbing fastness. The reason is analyzed. After the spandex is colored, the dye or the spandex colorant and the dye combination will migrate under the external pressure for a long time under wet conditions, and it is a slow process (spandex is a hydrophobic fiber, water molecules It will not quickly enter the fiber, and the dye will not migrate quickly), so its washing fastness is good. Secondly, under the acidic conditions of perspiration, it is conducive to the ionization of the amide bond on the spandex spandex or the amino group on the spandex colorant, which can capture the migration of The dye or spandex colorant is combined with the dye, so the acid fastness to perspiration is better than the neutral water fastness. Under the action of friction, dry grinding will generate heat, resulting in thermal migration of the dye on the surface of the spandex, which does not happen under wet conditions.

2. Cooking soda ash after the spandex dyeing will reduce the fastness by about 0.5 grade. This is because under alkaline conditions, the combination of the spandex colorant with the fibers and dyes will be destroyed, thereby reducing the fastness. Secondly, after the spandex is dyed, use a cationic fixing agent to fix the color, and its fastness is improved more than an anionic fixing agent. The cationic fixing agent can react with the water-soluble group (-SO3-) generated by the dye to block the water-soluble group. The water solubility of the dye is reduced, and the fixing agent forms a film on the surface of the fiber, which can isolate the dye and improve the dry rubbing fastness accordingly.

3. The light fastness of acid, disperse and nylon dyed spandex with reactive dyes is worse than that of polyester or nylon filaments. The main reason is that the crystallinity of spandex is low, and it is in a high elastic state at room temperature. It is easier for air to enter the inside of the fiber, and the color changes under the action of sunlight. Furthermore, the spandex itself will turn yellow under the action of sunlight. Causes of low light fastness.