Dyeing machine is Device in which the textile material which
is to be dyed (as distinct from Dyeing machine, circulating) is agitated in
more-or-less stationary liquor – for example: padder, rope-winch vat, jigger, continuous
dyeing machine, paddle dyeing machine, star frame and, among others, modern
processors such as the pad-jigger, pad-roll, pad-steam, pad-wet and pad-winch
processes. The dyeing machines which are in use today for batch dyeing consist
of the following basic elements:
– The vat as the stationary zone,
– The pump for circulating the liquor,
– The mechanical elements for controlling the liquor(pipes
and valves),
– The heat exchanger (heating unit),
– The mechanical elements for transporting the material and
circulating the liquor, such as guide bars, reversing winches, transporter
winches, material carriers and immersion wetting-out apparatus.
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| Fig. 1: Types of flow between
fabric and liquor |
Dye movement in the solution is brought about by convection whilst
liquor movement is brought about by agitation or circulation pumps. High
temperatures and liquor exchange accelerate this process so that the overall dyeing
speed is not adversely affected by diffusion.
Diffusion is the dynamic dispersion of dye particles caused
by the system’s tendency towards a state of equal concentration of particles
throughout the liquor irrespective of the liquor movement. Optimum flow at the
interface and through the textile material to produce the highest possible
degree of levelness depends on the liquor-exchange system of the dyeing machine
in question.
High flow rates accelerate the dye absorption, the various
machine designs produce different types of Different machines or apparatus are
used according to the material being dyed. There are dyeing machines in which
the liquor is stationary and the material is moving and dyeing machines in
which the liquor is moving and the material is stationary (Fig. 2).
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| Dyeing is carried out according to the makeup of the material
to be dyed: |
Dyeing is carried out according to the makeup of the material
to be dyed:
I. Dope-dyed synthetic fibres: In synthetic fibre production
the dye pigment (insoluble but finely divided dyestuff) is added to the
spinning solution so that a coloured fibre is produced when extruded through
the spinneret.
II. Loose stock dyeing: Loose stocks can be dyed by batch
(non-continuous or continuous methods). In the case of batch dyeing, the fibre
material is packed in a perforated vessel through which the dye liquor is forced.
Coloration is not always evenly distributed but this is immaterial as the loose
fibres are subsequently dispersed in the spinning mill and evenly mixed so that
the colour ultimately appears to be uniform. In the case of continuous dyeing,
dye solution is continuously applied to the stock on a padder and the dye fixed
in a steam ager. The material is then washed and dried. Stock of different colours can be used for colour blending.
III. Sliver dyeing (slubbing dyeing): top or combed sliver
consists of a continuous sliver from which the short fibres have been combed
out on a combing machine. This sliver can be, for example, dyed in ball form.
There are several areas where slubbing dyed material can be used in coloured
wool yarn production.
a) Sold shade yarn: the essential advantage of dyeing combed
sliver is the high fastness achieved. However, it is only economically viable
where large batches are involved.
b) Melange yarn: in a melange yarn specified percentages of
combed slivers are dyed in different colours. These different-coloured slivers
are then mixed together at the drawing stage and spun.
c) Vigoureux yarns: In this case, printing paste is applied at
different intervals by means of a printing roller and fixed. When the combed
sliver is drafted during the spinning cycle, the coloured and non-coloured
areas intermix so as to create the characteristic melange yarn. In the
vigoureux printing process, the individual fibres are striped zebra fashion.
The patterning in the finished product resulting from this process is so small
that the eye can only perceive a mixed colour. For example, from a mixture of
black and white stripes the resulting colour is grey. In melange products, on
the other hand, the eye is still able to identify the individual black and white
fibres.
IV. Yarn dyeing: The following different machines are used
for dyeing yarns:
a) Hank dyeing machines: the yarn is wound into hanks, the
individual hanks laid on a roller conveyor and the hanks passed through the
dyebath on the rollers.
b) Spray-dyeing: in this case, hanks are laid over a
perforated tube out of which the dye liquor flows. The hanks are placed at
regular intervals so that dyeing is uniform. The amount of dye liquor required
for this machine is significantly less than for a).
c) Pack cage: the hanks are placed in a cage and dyed in a
similar way to the loose stock dyeing process.
d) Assembling columns of cross-wound packages and subjecting
these to a stream of dye liquor in an autoclave.
V. Piece dyeing: there is a whole series of machines which
can be used for dyeing fabrics. Modern dyeing machines operate via mechanical
systems using program controllers or microprocessors, the whole dyeing process
being controlled by a program.
a) Winch vat: these machines are suitable for qualities which
are not subject to running cracks. The cloth is passed through the dye liquor
at boiling point as a continuous rope with a rotating winch providing the traction.
Temperatures can be as high as 100°C (Fig. 3).
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Fig. 4: “Krantz” overflow machine for fabrics in rope form.
|
1 = dwell chamber; 2 = liquor-exchange pipe; 4 = circulation
pump; 5 = liquor extraction; 6 = heat exchanger; 7 = liquor injection; 8 =
wetting-out device; 9 = wetted-out fabric; 10 = return winch.
b) Jet dyeing machine or Overflow machine: the overflow machine
has been especially designed for dyeing fabric which is sensitive to tensile
stress. These fabrics can be dyed using this apparatus with the minimum
possible tensile loading. In this type of machine (Fig. 4), both the fabric and
the liquor are in motion. The construction can be either vertical or horizontal.
In jet dyeing machines, the liquor is caused to move by jets from nozzles, thus
causing the fabric to move at the same time. In most cases, the fabric is also
driven by means of a winch.
Dyeing machines, circulating liquor type:
These are differentiated into package systems, Hussong type systems
and spindle-and-separator systems. The principles differ according to working
methods: stationary liquor - moving material (dye machines: padder, winch vat,
jigger, roller box and hank-dyeing machine); stationary material - moving
liquor (less significance, particularly common for loose stock and bulk dyeing
in, for example, garment dyeing and hat dyeing; garment dyeing machines and
paddle-dyeing machines). Examples of these are:
a) Cheese dyeing machine: the packages are on perforated
plastic tubes which are stacked on perforated spindles and then put into a
sealed vessel (Fig. 5). In this vessel the dye liquor can be forced through the
packages under pressure. Dyeing temperatures > 100°C are possible.
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| Fig. 5: Cross-wound package yarn dyeing machine. |
b) HT Beam dyeing machine: In this case, dyeing is carried
out at temperatures above 100°C. The fabric is wound on to a perforated
cylinder and inserted into a sealed vessel (Fig. 6). The dye liquor can be pumped
in an inward or outward direction through the rolled fabric.
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Fig. 6: Operational cross-section of a dyeing machine for open-width
piece dyeing.
|
1 = coupled dye beams with outward circulation; 2 = stock reservoirs
with separate pump; 3 = main pump; 4 = heat exchanger.
Dyeing methods for dyeing machine
These have been the subject of continual development over
the years especially because of the need to rationalize or for reasons related
to color levelness and dye compatibility or because of new problems appearing
with new substrates. Thus, there is a whole series of possibilities for
variation such as short-liquor dyeing, foam applications, thermosol processes,
jet dyeing (jet-dye machines), overflow dyeing, (overflow dyeing machines), HT
dyeing processes, pad-steam dyeing processes and continuous wet-steam processes
among others. In order to optimize the dyeing process, the dyeing procedure is
controlled according to a program and process control systems are used o
control the operations. This means that a set of measurement instruments of
maximum reliability continually records certain parameters and issues
appropriate commands to the valves etc. Actuators, for example, are used for
speed/time control and other operational control aspects for individual forms
of apparatus, machine or automatic process management and control systems.
Development in the area of textile dyeing and dyestuffs and in relation to
technical applications is very dynamic.
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