Bifunctional reactive dyes

Bifunctional reactive dyes

Many of the new reactive dyes are bifunctional with identical or different reactive groupings in the dye molecule.Bifunctional dyes carry two reactive groups. They are known for their excellent dyeing efficiency and overall fastness properties. Bifunctional dyes with good dyeing properties are created by the careful selection of the right reactive groups and right chromophores

It can easily be assessed that dyes with two identical reactive groups and dyes with two different  reactive groups exhibit a higher fixation yield than-dyes with one group.

homo and hetero bifunctional dyes
Bifunctional dyes with two similar functional groups are known as homo bifunctional group dyes.
The dyes having two different functional groups are known as hetero bifunctional group dyes.

The dyes were conventional Dichlorotriazine type, with the end condensation of B-sulphato ethyl sulfone to have different type of reactive group in a single molecule. They offer enhanced reproducibility especially for medium to pale shades. Due to triazine ring system, they offer level dyeing performance for even non-critical substrates.

Variables in dyeing with bifunctional dyes
1.Pretreatment of the material
2.Water
3.pH
4.Quality of Electrolyte
5.Alkali system
6.Dyeing temperature and dyeing duration
7.After treatment.

Dyeing method with bifunctional dyes

Method Of Dyeing
Set the dye bath at 20º-30º C and add Glauber's salt, now enter the material.

Run for 20 minutes.

Add half amount of the glauber's salt and continue dyeing.

Now gradually raise the temperature to 60º-65º and dyeing for 15 minutes further

now add soda Ash solution and continue dyeing for 60 minutes.

Wash properly the material.

Washing off procedure for bifunctional dyes

1.Dye bath drain.

2.Intermittent washing in cold

3.Neutralize with acetic acid 

4.Hot wash at 70 Deg C in pressure to remove salt and hydrolysed  dye.

5.Soap at 80-85 deg

6.Hot wash at 90 deg.

7.cold wash.

Dyeing cycle 

Salt & Alkali Requirement for ME Reactive Dyes

Depth of Shade %	Salt g/l (Dye Liquor)	Soda Ash g/l (Dye Liquor)
Up to 0.5	30	10
0.5 to 1.0	35	15
1.0 to 2.0	50	15
2.0 to 4.0	60	20
Above 4.0	80	20

 Advantages of bifunctional dyes
1.They offer enhanced reproducibility especially for medium to pale shades. They have high fixation rate.
2.Due to triazine ring system, they offer level dyeing performance for even non critical substrates. They are less affected by dyeing variables such as temperature , heating rate and alkali dosing.
3.They have high fastness profile especially the washing characteristics.
4.They have a brighter range of colors as compared to VS dyes.
More information on reactive bifunctional dyes
 FAQ about Dyeing and dyes
Multifunctional reactive dyes
Reactive dyeing