If dye adds are needed, the temperature
is dropped slowIy back to below 180F
(80C) before continuing. It is important
that the temperature drop is slow because
the thermoplasticity of acrylic fibers
makes crack marks on fabric easy to
obtain if cooling is too rapid.
When dyeing is complete, the goods are
cooled slowly to ca. 120F (50C), rinsed
well, scoured with a little nonionic surfactant
(0.5% owg) and a little acetic acid (0.5
to 1% owg glacial acetic acid). The last
step is to rinse and apply softener as
needed.
Alternative small dyeing variants are
used for dyeing the goods in different
physical forms (3). But some processes
such as constant temperature dyeing are
successful mainly with raw stock where
uniformity and levelness are not particularly
critical.