Reactive Dyes (Printing & Dyeing)

 

Reactive dyes, which are highly-coloured organic substances, are used to colour textile dyes. Reactive dyes are chemical reactions that occur when reactive dyes are applied to fiber. Covalent bonds are formed between the dye molecule and the fiber. This is one of strongest chemical reactions. It ensures that the colouring remains permanent.

We are committed to producing the highest quality, safest, and most environmentally-friendly reactive dyes possible. We are constantly improving our processes and sourcing the best raw materials to make our products more durable in order to meet the needs of our customers. We are our own critics and competitors. Therefore, we strive to be more successful in achieving our business goals.

While most reactive dyes are used to dye cellulose fibers like cotton and viscose (and other materials), they are increasingly being used to dye wool and polyamide. There are many dyeing methods that can be used because of the wide range of reactive dyes available. These chemicals and their auxiliaries can be used to dye cellulose fibers using reactive dyes.

1-Alkali (sodium carbonate or bicarbonate and caustic soda)

2-Salt (primarily sodium chloride or sulphate).

In continuous processes, 3-Urea can be added to the padding liquor

In cold pad-batch, you can add 4-Sodium silicate.

Poor dye fixation is a problem with reactive dyes for a long time, especially in batch dyeing of cellulose fibers. In these cases, a lot of salt is added to increase dye exhaustion and dye fixation. Reactive dyes are known to have major environmental problems due to the presence of color and salt in their effluent. Both the unfixed and hydrolyzed forms of reactive dye are water-soluble. Many reactive dyes contain some halogens. It is not attached to chromosphere.

Both as part of the chromospheres and as impurities in production processes, heavy metals may be present. This is the case with phthalocyanine dyes, which are still used extensively for blues and shades of turquoise.

When they come in contact with a fiber molecule, reactive dyes create a new chemical compound. Reactive dyes can be applied from either a solution that has a high pH or from neutral solutions which are then alkalized using a separate process. Heat can sometimes be used to bring out different shades in textile dyes.

Under alkaline conditions, reactive dyes react with cellulose to form covalent bonds between dye and fiber. There are many types of reactive dyes: monochlorotriazine, vinyl sulphone, etc. and each requires a different strength of alkali to ensure optimal fixation.

There are four components to reactive dyes:

1-The chromogen, or the chromophoric portion, which adds color to the dye.

2-The reactive system is what allows the dye to react with its substrate. This component can react with water molecules in the dye bath. This is a phenomenon known as hydrolysis of reactive dyes, which is undesirable during dyeing.

3-A bridging unit which joins the reactive and chromophoric parts.

4-The solubilizing groups attached to the chromophoric gruping confer water solubility to dye.

Properties of reactive dyes

Textiles coloured with reactive dyes generally have excellent light-fastness. The light-fastness rating is about 6. These dyes are very resistant to sunlight's degrading effects because of their electronic structure. Some reactive dyes have only fair light-fastness. Reactive dyes that contain azo chromophore have lower light-fastness. Higher light-fastness is found in metal complex azo reactive dyes. Reactive dyes are good for textiles. They have a wash-fastness rating of around four to five. This is due to the covalent bond between the dye molecule of the cellulosic fiber and the dye molecule. Textile materials printed or dyed with reactive dyes may be affected by sweat and other acidic substances, such as atmospheric pollution. This can lead to some fading. Textiles with bactericidal monochlorotriazine-reactive dyes containing Hexachlorophene have a broad spectrum of bactericidal activity (Kalontarov & Kalandarov 1993). The dye functionality, which is based on phenol-OH-groups, is believed to be responsible for this effect. The effect with monofunctional dyes is eight times greater than that observed for dyes containing disubstituted Hexachlorophene residual.

Principles of reactive dye applications:

These are the methods reactive dyes can use:

1-Exhaust method (on the jigger/winch).

2-Padding method