In the process of semi-continuous dyeing that
consists of pad-batch, pad-jig, pad-roll the fabric is first impregnated
with the dye-liquor in, what is called a padding machine. Then it is
subjected to batch wise treatment in a jigger. It could also be stored
with a slow rotation for many hours. In the pad-batch this treatment is
done at room temperature while in pad-roll it is done at increased
temperature by employing a heating chamber. This helps in fixation of
the dyes on to the fiber. After this fixation process, the material in
full width is thoroughly cleansed and rinsed in continuous washing
machines. There is only one point of difference between Continuous and
semi-continuous dyeing process is that in semi-continuous dyeing, the
dye is applied continuously by a padding. The fixation and washing
remaining discontinuous. Liquor Ratio in semi-continuous dyeing is not
of much importance and is not taken as a parameter. One of the widely
used techniques for semi-continuous dyeing process is the Pad Batch
Dyeing a schematic diagram is given here for the semi-continuous dyeing
process.
The following table shows some of the important machineries for
semi-continuous and continuous dyeing processes.
Make up |
Process |
Equipment |
Woven and Knitted Fabric, tufted
carpet |
Rope |
Continous |
Padding Machine for Piece in rope form |
Open width |
Semi Continous |
Pad batch (or carp-o-roll for carpet) |
Padding Machine+ Washing Machine |
Pad batch (or carp-o-roll for carpet) |
Padding Machine+ Washing Machine |
|
Pad -jig |
Padding Machine+ Jigger+ Washing
Machine |
Continous |
Pad stream |
Padding Machine+ Steamer+ Washing Machine |
Pad Dry |
Padding Machine+ Stenter frame+ Washing Machine |
Pad Batch Dyeing is one of the widely used technique
for semi-continuous dyeing process. It is mainly used in the dyeing of
cellulosic fiber like cotton or viscose (knit and woven fabric) with
reactive dyes. Pad batch dyeing is a textile dyeing process that offers
some unique advantages in the form of versatility, simplicity, and
flexibility and a substantial reduction in capital investment for
equipment. It is primarily a cold method that is the reason why it is
sometimes referred to as the cold pad batch dyeing.
The technique or process used in pad-batch dyeing
starts with saturating first the prepared fabric with pre-mixed dye
liquor. Then it is passed through rollers. The rollers, or padders,
effectively forces the dyestuff into the fabric. In the process, excess
dye solution is also removed. After removal of excess dye stuff the
fabric is subsequently "batched". This batching is done by
either storing it in rolls or in boxes. It takes a minimum of 4-12
hours. The batches are generally enclosed by plastic films. This
prevents absorption of carbon dioxide and water evaporation. Finally as
the reaction is complete the fabrics are washed. This is done by becks,
beams, or any other washing devices.