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A Review Of The Theory Of Dyeing
Jan 30, 2018

The fiber immersed in a certain temperature in the dye aqueous solution, the dye moved from the water to the fiber, at this time the amount of dye in the water gradually reduced, after a period of time, to achieve a balanced state. The dye that is reduced in water is the dye that moves toward the fiber. At any time to remove the fiber, even if twisted, the dye is still in the fiber, and can not simply make the dye completely out of the fiber, the dye combined in the fiber phenomenon, is called dyeing. If the sponge immersed in the dye solution, the dye can also enter the sponge inside, but even if the time is long, the concentration of the dye solution does not change, the sponge out of the twist, dye and water also from the sponge extrusion, so that the sponge has not been stained.

(i) The basic process of dyeing according to modern staining theory, dyes are able to dye fibers, and in the fiber fabric has a certain fastness, because of the dye molecule and the fiber between the various gravitational reasons, the dyeing principle of various dyes and dyeing process, due to the characteristics of dyes and fibers vary greatly, Can not be generalized, but in terms of its dyeing process, roughly can be divided into three basic stages.

1. Adsorption when the fiber into the dye bath, the dye gradually from the solution diffusion transfer to the fiber surface, this process is called adsorption. Over time, the dye concentration in the fiber gradually increased, and the dye concentration in the solution gradually decreased, after a period of time, to achieve a balanced state. The inverse process of adsorption is desorption, while adsorption and desorption are simultaneous in the process of dyeing.

2. The dye diffusion adsorbed on the surface of the fiber spreads to the fibers, until the dye concentration of the fibers is consistent. Because the concentration of dye adsorbed on the fiber surface is greater than the dye concentration inside the fiber, the dye is diffused from the fiber surface to the fiber. At this point, the dye diffusion destroyed the initial adsorption equilibrium, the dye in the solution will continue to be adsorbed to the fiber surface, adsorption and desorption again to achieve balance.

3. Fixation is the process of the combination of dyes and fibers, with different dyes and fibers, the combination of the same way.

The above three stages often exist simultaneously in the dyeing process and cannot be separated completely. It is only during a certain period of staining that a process prevails.

(ii) dyes in the fiber in the way the dye is fixed in the fiber, can be considered to be the dye to maintain the process of the fiber. Different dyes and different fibers, they are fixed between the principle is also different, in general, dyes are fixed on the fiber there are two kinds of types.

1. Pure chemical fixation refers to the chemical reaction between the dye and the fiber, and the dye is fixed on the fiber.

For example: dyeing cellulose fibers with reactive dyes, forming ether bond with each other. The formula is as follows:

Drx+cell-oh→dr-0-cell+hx

DRX: Reactive dyes molecule

X: Active Groups

Cell-oh: Means cellulose

2. Physical and chemical bonding is due to the mutual attraction between dyes and fibers and the formation of hydrogen bonds, and the dye is fixed on the fiber. Many dyes dyed cotton, such as direct dyes, sulfur dyes, VAT dyes and so on are dependent on this gravity and solid in the fiber.