Classification Of Reactive Dyeing
According to different reactive groups, reactive dyes can be divided into two types: symmetrical triazene type and vinylsulfone type.
Symmetric triazene type: In this type of reactive dyes, the chemical properties of active chlorine atoms are more active. During the dyeing process, chlorine atoms are replaced by cellulose fibers in alkaline medium and become leaving groups. The reaction between the dye and the cellulose fiber is a bimolecular nucleophilic substitution reaction.
Vinyl sulfone type: vinyl sulfone (D-SO2CH = CH2) or β-hydroxyethyl sulfone sulfate. During the dyeing process, β-hydroxyethyl sulfone sulfate precipitates in an alkaline medium to form a vinyl sulfone group. The vinyl sulfone group combines with the cellulose fiber to undergo a nucleophilic addition reaction to form a covalent bond.
The two reactive dyes mentioned above are the main varieties of reactive dyes with the largest output in the world. In order to improve the fixation rate of reactive dyes, two reactive groups have been introduced into the dye molecule in recent years, namely dual reactive dyes.
Reactive dyes can be divided into several series according to their different reactive groups:
1. The X-type reactive dye contains dichloro-s-triazine reactive group, which is a low-temperature reactive dye, suitable for dyeing cellulose fiber at 40-50℃.
2. K-type reactive dye contains monochlorotriazine reactive group, which is a high temperature reactive dye, suitable for printing and pad dyeing of cotton fabrics.
3. KN type reactive dyes contain reactive groups of hydroxyethyl sulfone sulfate, which are middle temperature reactive dyes. The dyeing temperature is 40-60℃, suitable for cotton roll dyeing, cold bulk dyeing, and reverse dye printing as the background color; also suitable for the dyeing of hemp textiles.
4. The M-type reactive dye contains double reactive groups and belongs to the middle temperature reactive dye. The dyeing temperature is 60°C. It is suitable for medium temperature printing and dyeing of cotton and linen.
5. KE type reactive dyes contain double reactive groups and belong to high temperature reactive dyes, which are suitable for dyeing cotton and linen fabrics.
1. The dye can react with the fiber to form a covalent bond. Under normal circumstances, this combination will not dissociate, so once the reactive dye is dyed on the fiber, it will have a good color fastness, especially wet treatment. In addition, the fiber will not be brittle like some vat dyes after dyeing.
2. It has good leveling performance, bright colors, good brightness, easy to use, complete chromatogram, and low cost.
3. It can already be mass-produced in China, which can fully meet the needs of the printing and dyeing industry; it has a wide range of uses, not only for the dyeing of cellulose fibers, but also for the dyeing of protein fibers and some blended fabrics.
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Post time: Mar-09-2021