How are cellulose fiber yarn dyed?

1. Dyeing with reactive dyes

It can be dissolved in water, and its molecular structure contains one or several reactive groups (customarily called active groups). Under appropriate conditions, it can interact with hydroxyl groups in cellulose fibers, amino groups in protein fibers and polyamide fibers, etc. React to form a covalent bond, so reactive dyes are also called reactive dyes.

Features:

① Cheap price, bright color, complete color spectrum, good level dyeing property and excellent wet fastness.

② However, some dyes have poor light fastness and chlorine bleaching fastness, and some dyes have low weather fastness. In addition, dyes have hydrolysis reactions, resulting in low utilization rates.

Dyeing principle of reactive dyes

Dyeing: the dyeing percentage is low, but the spreadability is high and the leveling property is good. Neutral electrolytes such as sodium sulfate are often added to promote dyeing.

Color fixation: treatment after soaping with alkaline agent

Dyeing process of reactive dyes

Generally, one-bath two-step method is adopted

2. Dyeing of vat dyes

Does not contain water-soluble groups and cannot be directly dissolved in water;

There are two or several carbonyl groups in the molecular structure;

When dyeing, the dye is first reduced to soluble leucosome sodium salt under the action of strong reducing agent and alkali, which has affinity for cellulose fiber and can dye the fiber. After oxidation, the leuco becomes an insoluble dye and fixes on the fiber.

It is mainly used for dyeing cotton fabrics and polyester-cotton blended fabrics. It is a very important dye for cellulose fiber dyeing.

The color is bright, the chromatogram is relatively complete (there are fewer red varieties, and there is no bright red), and the fastnesses are generally relatively high, especially the light fastness and washing fastness are inferior to other dyes.

Business name:

(1) Shihlin dyes: high light fastness;

(2) Ashlin dye: poor light fastness.

3. Dyeing with direct dyes

Direct dyes are soluble in water and have high affinity to cellulose fibers. They can directly dye cellulose fibers without using other chemicals, and can also dye protein fibers and nylon in weakly acidic or neutral media.

Applications are subject to certain restrictions.