Application of Acid dyes for cotton and silk fabrics
Acid
dyes can be applied to colour protein fibers and polyamide fibers (Nylon). Acid
dyes cannot be applied directly. Although wool has high amorphous region but
common dyeing assistant are essential to apply in acid dyes. Generally these
dyeing assistant are acids. It means when this colouration dye to textile
material in acid bath. According to the concentration of acid bath, dyes are
categorized into basic three classes.
Class
1
In
this class type of dyes applying process it is essential to control lowest pH
level (2-3) for the satisfactory exhaustion of particular acid bath with strong
acids such as H2SO4 acid.
Class
2
In this class, dyes are applied in weakly acid liquor. Commonly it will take 4.4 – 7.0 pH ranges. Commonly used dyeing assistant is 80% of acetic acid in acid bath with above pH range hence, called weakly acid liquor.
Class
3
These
classes of dyes are commonly applied in neutral liquor and it means very weak
acid bath and pH mostly nearest to 7 pH. Therefore pH range cannot be
predicated certainly. This application can be well processed with increasing
temperature. Because these are colodially dispersed in solution at most lower
temperature.
Adding
Glauber’s salt
Above
all dyeing processes, it is an advantage if used glauber’ salt. Because it is
increase dye exhaustion and dye fixing functions with fiber structure and dye
molecules. It is more helpful to keep light fastness and wash fastness of dyed
textiles.