Cleaner Technology Transfer to the Polish Textile ... - Miljøstyrelsen

The dyeing process The reactive dyeing process is outlined in figure 3. During the pre-treatment
the cotton fibres are degreased, and to some extent treated with lye to open the
fibre structure. By mercerization the fibres are furthermore stretched to give
the most open structure, step 1 in figure 3.
Figure 3.
Reactive dyeing of cotton.
(Ciba-Geigy, 1987)
The dye-stuff is poured into the dye-bath and a diffusion of the dye-stuff molecules
between the cellulose fibres takes place.
After some time salt is added to obtain adsorption of the dye-stuff to the cellulose
fibre – step 2 in figure 3. After this, the reaction between the dye-stuff
and the cellulose is completed by adjusting temperature (50-80°C) and pH
(10,5-11,5) – step 3 in figure 3. Some part of the dye-stuff will be hydrolyzed
during this dyeing process, and the absorbed hydrolyzate must be removed in
the succeeding rinse.
The rinsing process The rinse traditionally consists of several rinsing baths, as is seen in table 2,
where a typical example of an existing recipe is outlined.
Table 2.
Existing recipe, typical
example.
Batch
no. Process Waste-water (l) Temp. (°C)
1 Washing & bleaching 700 95
2 Overflow rinse 7300 10
3 Neutralization 700 30
4 Overflow rinse 7300 10
5 Dyeing 700 50
6 Overflow rinse 7300 10
7 Warm rinse 700 50
8 Neutralization 700 60
9 Overflow rinse 7300 10
10 Hot soaping 700 95
11 Warm rinse 700 60
12 Overflow rinse 4300 10
13 Hot soaping 700 95
14 Warm rinse 700 60
15 Overflow rinse 4300 10
16 Neutralization & softening 700 40
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