Table of Contents
Important factors to be considered for reactive dyes:
The following factors are very important factors to be considered for reactive dyes: https://bdfabric.com/cotton-dyeing-process-by-reactive-dye-batch-method/
1. Dyeing temperature
2. Concentration of electrolytes
3. Time of dyeing
4. Liquor ratio
5. PH of the dye bath
1. Dyeing temperature:
Dyeing temperature 200C-350C is recommended for most reactive dyes. But reactive dyes in sodium bicarbonate alkali provide maximum color value at a temperature of 50°C-60°C.
2. Concentration of electrolytes:
The concentration of an adequate amount of exhaustion has to be changed in proportion to the liquor. That is, if the liquor ratio decreases, the amount of salt also has to decrease. It has been found that 10 g/liter of salt is required for pale shade. But for medium or deep shade this amount should be increased up to 20 g/liter to 30 g/liter.
3. Time of dyeing:
Generally in a dye bath dye is divided into two parts. Salt is also added in two parts. Then 20-30 minutes of exhaustion occurs. Then alkali is added and continuous dyeing is done for 30-90 minutes. The time of dyeing is decided based on the depth of the shade and the reactivity of the dye. Requires more dyeing time for relatively deep shade.
4. Liquor ratio:
When the liquid ratio is low, both exhaustion and fixation occur at a slightly increased rate. In this case, the lower amount of salt is the optimum color. In addition to dye, salt, and alkali, wetting, defoaming and mild oxidant (m-nitrobenzene sulphonate) are added to the dye bath.
5. PH of the dye bath:
It helps to ionize the dye molecule but at a higher pH, the ionization decreases. As the temperature of the dye bath increases, the pH value decreases. For most dye, the pH value is kept at 10.8-11.
The function of different chemicals used in reactive dyeing:
The functions of all the auxiliaries used during dyeing by reactive dye are as follows:
Due to the high absorption capacity of salt towards the water, the salt falls on the dyestuff as soon as it is added to the water. It spreads the dye evenly everywhere.
# Soda Ash:
It acts as a fixing agent. After the product is dyed, it helps the product to hold the dye.
It plays an important role in making the dye heavier or lighter. You have to pay more urea for heavy coloring and less urea for light coloring.
# Sodium Alginate:
It is used to inhibit the migration of dye molecules. This means that after dyeing the cloth, a small amount of adhesive sodium alginate is used to prevent the dye from moving from one place to another.
Soaping increases the brightness of the color. Soaping also eliminates floating color.
After treatment of reactive dyes:
When dyeing with reactive dyes, some of the dye fibers stick to the hydroxyl, which is usually boiled for 30 minutes in a bath with 20% soap solution and 1% soda solution. However, this kind of after-treatment gives good results in the case of precision dye but it is inconvenient in the case of remazol dye.
In that case, the product must be neutralized with acetic acid before soaping. The sticky dyes are boiled only in a detergent solution. When boiled at high temperatures, the color spreads out from the inside of the fiber. If sodium silicate is used as an alkali for fixing, there is no need to use extra acetic acid. Because the fiber becomes very uneven.