3. Characteristics and performance required in soaping agent for reactive dyestuff

Originally, the goals of reactive-dyestuff soaping are:

• the removal of unfixed dyestuff
  
• the removal of hydrolyzed dyestuff

Setting of a high temperature seems preferable for removal, however, washed-off dyestuff often diffuses and penetrates into the yarn, resulting in re-adsorption and staining.

Moreover, it is not easy to achieve complete, quick soaping on printing paste since the concentration of dyestuff and the amount of paste deposition are high. Thus, the use of a special soaping agent, capable of producing maximum effects in a quick strong soaping at a small bath ratio, while preventing redeposition and staining of white ground regardless of rinsing temperature or any difference in process conditions, is considered most rational.

Though multiple soaping agent structures have been made public so far, it is very difficult for a single chemical structure to satisfy the above description. Fig. 1 shows some interesting chemical structures that are not only restricted to the idea of using surfactants as the base.

Fig.1: Example of soaping agent structure