Reactive dyeing

Reactive dyes are composed of dye precursors, reactive groups, bridging groups and water soluble groups. Reactive dyes are soluble in water and chemically react with hydroxyl groups or amino groups on fiber molecules to form covalent bonds. They can dye cotton fibers, viscose, silk, wool, nylon, etc., and are thus widely used in the textile printing and dyeing industry. Applications.

The characteristics of reactive dyes

The reactive dye has a complete chromatogram, bright color, good level dyeing performance, good color fastness, moderate price, and low cost in dyeing darker shades than vat dyes. The disadvantage is that most of the reactive dyes are not resistant to chlorine bleaching, and some of the reactive dyes have a light-sensitive phenomenon, especially when the dyed light blue fabric has a poor light fastness.

When the reactive dyes are dyed, most manufacturers will use three primary color combinations, and theoretically using three primary colors can match any bud color, but this practice is not practical. Due to the change in compatibility at different dye concentrations, sometimes the color fastness is also 7, ideal, especially when the light-colored fabrics have low light fastness, fail to meet the requirements of customers, so reactive dyeing is generally Use two darker colors.

Reactive dyeing process

The chemical reaction occurs when cellulose fibers are dyed with reactive dyes. The nucleophilic substitution reaction or nucleophilic addition reaction occurs between the reactive groups in the dye molecules and the cellulose molecules and they are covalently bonded together with the fibers. Currently dyes for reactive dyes 2: There are the following.

1. Dyeing

Reactive dye dyeing process is one of the most used dyeing methods. The dyes used are mainly X-type reactive dyes. The process of dyeing with a special dyeing machine is:

Dyeing - Alkali Fixation - Washing - Soaping - Washing - Drying 1. Lamination dyeing

For some specific colors (such as purple), it is more convenient to use the roasting method for dyeing. The dyes used are mostly reactive dyes. The baking process is:

Dip pad dyeing - pre-baking - drying - baking color fixing - washing - soaping - washing - drying Wang rolling steam dyeing

At present, the padding and steaming method is the most commonly used conventional dyeing process, and as long as it is well-controlled, it can fully adapt to the production of small-batch, multi-variety products and has a relatively stable quality. Most printing and dyeing plants in China will be equipped with this continuous pad dyeing unit. The dyes used are XIV type and reactive dyes. The steam-steaming process is:

Dip pad dyeing - pre-baking - drying - padding color fixing liquid - steam fixation - washing - soaping - washing - drying secondary coil cold-rolling reactor dyeing

Roll cold-rolling method dyeing is an energy-saving process, and the dyed product has good core permeability. Due to the elimination of pre-baking and steam fixing, the energy-saving effect of Ming is quite good, but the quality control (mainly color control) is more difficult and is not suitable for the requirements of short delivery and multi-variety production. There are not many manufacturers. The process flow is:

Dip-dyeing bath 〖Dye bath and fixing alkali agent bath-rolling-rotary stacking-washing- soaping-washing-drying