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Abstract:
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Increased economic pressures and inflation have resulted
in the need for improved uniformity and reproducibility in
dyeing. The package dyer is faced with the challenge of
equally and evenly penetrating dye liquor to all parts of a
package, wi th each yarn layer acting as an obstacle and
affecting the levelness and repeatability. Package geometry,
especially density, has long been recognized as an important
variable in obtaining uniform and reproducible dye uptake in
package dyeing. However, the amount of density variation that
can be present to still produce acceptably dyed packages is
not known.
This _. research was conducted to gain a better
understanding of the impact of package densi ty on shade
repeatability and levelness in package dyeing. variables that
were believed to impact density or were believed to be
significantly influenced by density were also evaluated.
Winding systems used in this study were precision and random,
flow rates were 50 psi and 100 psi, and spindle placement was
1 - 4, from top to bottom of.the spindle. Each combination
was used wi thin three dyeing systems; polyester disperse,
cotton direct, and cotton fiber reactive. Each trial was dyed
in a 25 package kier using typical industry dye procedures, wi thout using any enhancing chemicals such as carriers or
levelers to promote a worst case scenario. A 5.0 percent
difference in K/S values was used as the maximum allowable
tolerance for determining levelness and reproducibility.
Based on these processing parameters, the following
results were disclosed:
Within the density ranges studied, the impact of density
on shade repeatability and levelness is dependent on the
dye system. Density has the largest impact within the
polyester disperse dye system and the smallest impact
within the cotton fiber reactive system, with medium
impact occurring wi thin the cotton direct system. Wi thin
the polyester disperse dye system, as package density
increases from 0.402 kg/L to 0.516 kg/L, the resultant
depth of shade decreases 6.9%. within the direct dye
system, as the density increases fromO.314 kg/L to 0.431
kg/L, the depth of shade decreases. For the fiber
reactive dye system, as the density increases from 0.314
kg/L to 0.431 kg/L, there was no change in depth of
shade. To determine the tolerance levels, or maximum amount
of density variation to produce a repeatable shade, the
depth of shade values obtained while increasing density
were used. The predicted tolerance levels are 18.6% for
the disperse system, 38.4% for the direct, and 88.8% for
the fiber reactive dye system. However, these values are
based on density effect only and no other processing
parameters are taken into account.
Precision wound packages exhibit consistently higher
depth of shade values than random wound packages. These
two systems are found to be statistically different from
one another, but not when combined with density.
Varying flow rate from 50 psi to 100 psi significantly
influences depth of shade of dyed packages. Depth
increases at high flow rates. When flow and density
interactions are combined, the effects on depth of shade
are statistically insignificant. Depth of shade is affected by spindle placement
indicating that variations in package placement will
affect repeatability of shade. When spindle placement
and density interactions are combined, the depth of shade
is affected.
The hardness measurement method, using a Durometer III,
is an ~ccurate replacement for calculating density. The
correlation is higher than that of the air permeability
testing and the average testing time, 5.16 sec, was
significantly lower than either the density calculation
and the-air permeability testing.
As densi ty increases wi thin the polyester and cotton
packages, flow decreases. However, an increase in
differential pressure can be used to offset increasing
density and maintain the same flow. Although air
permeability is not an accurate density indication, it is
an accurate indication .. of water flow through a package,
and is therefore a better indication of package behavior
during dyeing.
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