Reactive dye

The reactive dyeing based on the 1954 made ​​discovery that bind certain dyes with a dichlorotriazine rest under alkaline dyeing conditions by covalent bonds to the fiber and thus can provide very true- coloring.

Due to the small molecular size with correspondingly narrower absorption band can be with these suitable both for cotton, wool, polyamide and viscose brilliant coloration and very wash-resistant colors with high saturation achieve.

Examples of reactive dyes are Basilene ®, Nova ® Crone, Lanasole ®, Procione ®, Remazole ®.

Reactive dyes

Reactive dyes made ​​from a coloring chromophore, one or more solubilizing groups, and one or more reactive anchors, which are separated by bridge members of the chromophore. These bridge members separate chromophore and anchor so that the anchor effect of the color of the dye is minimized. As chromophores commonly used are acidic monoazo and anthraquinone dyes, but also phthalocyanine, formazan or triphendioxazine residues as solubilizing groups, however, usually sulfonate groups.

Reactive dyes have reactive anchor as often chlorinated unsaturated heterocyclic radicals, which react by elimination of hydrogen chloride ( HCl) with the nucleophilic hydroxyl groups of the Färbeguts and can form a stable covalent ether linkage. Also used as an anchor group 2 sulfonylethyl hydrogen sulfates, which in an alkaline medium cleave sulfate ions, whereby highly reactive vinyl sulfones arise, which add in a Michael addition nucleophilic groups, as in the first example, this time stable ether linkages arise.

The bridge members eventually prevent a reaction between the chromophore and reactive anchor, each dye molecule can have several such anchor groups. Here, in recent years, namely reactive dyes having two reactive anchors, so-called bifunctional dyes, has become increasingly important because their fixation is 90 %, which allows a reduction of both the dye consumption and environmental impact.

Reactive dyes on cellulose applied to achieve high wet fastness, what makes them so popular. Compared with direct dyes and vat dyes are, however, limits their light fastness properties.

Implementation

To obtain a sufficient reaction rate, the liquor is heated to temperatures between 20 and 102 ° C, where it is, however, with increasing temperature and unwanted side reactions such as hydrolysis of the dye. The hydrolyzed, thus unfixed dye portions have to be followed to achieve the desired wet fastness washed out again.