(no SO3-, dye is usually NOT water soluble)

history of azoic dyes:

• 1880- commercial dyeings with “para red”

  • combination of 2 water soluble components to form an insoluble colorant inside the fiber

    

                                       para red
    

• “azoic” = the azo variety (contain azo chromaphore)

• dyes for cellulosic fibers

• water insoluble (final form)

• fixation mechanism= physical entrapment (or mechanical entrapment)

• high WF and good LF

• useful for printing on cotton (youll do in pcc lab)

• mainly monoazo dyes represented

• mostly orange and red

  • most economical way to achieve deep orange, scarlet and red shades on cellulose

• do not exist “on the shelf”

• complex chemistry to apply; formed/synthesized inside fiber using 2 components

  • azoic diazo component
  • azoic coupling component

• also called naphthol dyes

blank = beta naphthol (aka 2 naphthol)

orange= diathol (diazo)

pink = coupling agent (naphthol)