Dyeing - Textile Section

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General information on dry cleaners
Coloring is one of the most distinctive characteristics of a fabric, the manufacturing process that gives color to a raw fabric is called dyeing.
Changing the color of the raw fabric by dyeing significantly increases the economic value of the fabric, so much so that this process has been, since ancient times, the subject of great attention.

Purpose of the processing
The remarkable progress that since the end of the nineteenth century has affected chemistry and technology
they have revolutionized dyeing processes, both in coloring materials and in technologies
and application methodologies. This transformation has also been stimulated by the introduction of
new artificial and synthetic fibers which present very different characteristics and behaviors from the
natural fibers.
Let's now see the most important industrial piece dyeing processes, referring to the type
of dyed fiber and the machine used.
They are systems that allow rapid changes in the color to be given to the fabric in production and
they are mainly used to dye large quantities of fabrics in the same color
cotton and its blends with cellulosic artificial fibers.
Continuous and storage dyes are carried out widely due to the difficulty of penetration of the
dye and to avoid dead creases or permanent canes.


This dyeing system has three main phases:
foularding with auxiliary products and cold coloring matter;
steaming at 102 ° C with wet steam, for a duration that is related to the type of dye; countercurrent washing with auxiliary products.


This dyeing system has four main phases:
1. cold foularding with auxiliary products and coloring materials;
2. wrapping the fabric on a large roll and covering it with a plastic sheet for
prevent access to air and avoid drying and surface oxidation of the roll;
3. storage on the move, with the roll rotating on a special device for 8-24 hours a depending on the type of dye used (direct dyes or reactive dyes);
4. washing with addition of auxiliary products.

Jet multiflow
Process suitable for delicate or knitted fabrics in natural or synthetic fibers (excluding polyester).
The fabric, sewn in rope, is transported by spontaneous fall together with the current of the bath,
with a very reduced bathroom ratio.
This dyeing system, which can take place under light pressure, reaching 108 ° C, replaces
the old reel system in open tank, since it allows a considerable saving of water and, in
some cases, also of coloring materials (for example in dyeing with direct dyes).
Particulars overflow under pressure - for dyeing delicate items or 100% polyester fabrics
or mixed with other cellulosic, synthetic fibers, etc. - reach 130 ° C.
The devices have 1 to 6 channels. The path described is relative to a single channel.
The piece:
it is put into the machine by an auxiliary circular reel controlled at variable speed (A, point 1);
passes from a piece guide comb (fig. A, 2) with a safety stop device through
a funnel (fig. A, 5)
it is dragged together with the bath through a U-tube (fig. A, 3),
reaches the relaxation chamber (fig. A, 4) where it floats in the bathroom without any tension e
through a reel it continues in its path, of which they are adjustable (fabric speed from 10 to
200 meters per minute), the thrust of the circulation pump and the rotation speed of the reel
(fig. A, 1).
The mechanical action exerted on the fabric by the overflow (0.4 Bar) is lower than that caused by the jet
(1.5 Bar) and for this reason it is preferable for dyeing very delicate fabrics.
A controlled aspino outside the machine (fig. A, 11) unloads the pieces in a special tank
perforated, equipped with rollers to move the pieces to the next processes.
The machine is equipped with:
heat exchanger (fig. A, 6), for heating the bathroom;
circulation pump (fig. A, 7) for the overflow tank, connected to a special one
adjustable damper (fig. A, 8), to establish the flow rate of the bath.
A drain valve (fig. A, 9), on the bottom of the tank, allows the residual bath to escape.
An external barrel equipped with a special drain (fig. A, 10) feeds the bath of dyes and
auxiliary substances.
Partially filled dyeing process of the machine, which includes two circulation systems
of the fabric. The first, with bath and fabric circulation, has nozzles below or above the surface of the bath.
The second, for delicate and light fabrics, less powerful nozzles and circulation aided by a reel.
It is a pressurized machine, with 1 or 6 strings, which allows the dyeing of polyester and polyester fibers
synthetics in general, including wool blends.
Processing technology
We describe a modern machine with controlled reel, for its completeness and variety
of use, which allows both the classic dyeing process and other operations.
The collateral air circuit allows in fact to vary the system and the circulation speed of the piece
in the bathroom based on the weight and structure of the fabric and to operate in the bathroom only, in the air and in the bathroom or with only air.
Process in bathroom only (see figure A, path A light blue):
the piece is introduced through the porthole (fig. A, point 1); it then passes directly into the nozzle (fig. A, 2),
transported with the bath to the bottom of the tub which functions as a relaxation chamber (fig. A, 3), passing
in rope over the controlled reel (fig. A, 4), it is sewn with the next piece in a spin,
thus starting the cycle.
The bath is prepared in a tank (fig. A, 5) outside the machine, sucked by a pump of
circulation (fig. A, 6) and introduced into the basket through the nozzle. Once the solution is exhausted, they are closed
the valves and begins the circulation of the bath which continues from the bottom towards a filter, aspirated by the
circulation pump and pushed by it into the nozzle.
Air-water process (fig. A, path A light blue + B red):
same loading system; the air flow increases the penetration of the dye bath
on the fibers and, by moving the fabric, it reduces the probability of formation of folds or abrasions, especially
on delicate fabrics such as linen blends, lycra blends, etc.
Air-only process (fig. A, path B red):
it is used when the dye is completed; through a special damper or valve the circuit is excluded
main of the bathroom on the push nozzle, replaced by the fabric treatment circuit, inserted
on the air circuit and carried out with special auxiliary products. This process is only executable on
some specially prepared machines.
dyeing machine


It is carried out on the rope fabric, in multi-channel machines which provide for the circulation of bath and fabric.
It is a dye under pressure, since the necessary temperatures of 140 ° C can be reached for dyeing polyester, synthetic and blended fabrics.
With this machine, savings are made on the bathroom ratio and on the dyeing times.

Processing technology
In filling jet dyeing total, the rope of the fabric remains completely immersed throughout the treatment, the
great speed and strong turbulence favor the uniformity of dyeing and the absence of hiding.
They are generally not present devices to aid transportation of the piece if not for the purpose
to prevent the slippage of the fabric or reduce its speed.
The path indicated here refers to a single channel of the device. The patch, once in the turret
immersion (see figure B, point 1), is pushed downwards into a nozzle or jet, (fig. B, 2),
covering the entire lower part of the appliance in tube and then going up to the upper part of the
machine in a larger tube, with the function of a relaxation chamber (fig. B, 3).
A counter nozzle or counter jet (fig. B, 4) brings the head of the piece back to the turret where, passing over to a controlled cylinder (fig. B, 5), the piece is sewn head to tail and the process can be started.
The advancement of the fabric along the loading tube is regulated by three conveyed suction points
in turn in a single filter (fig. B, 6) with interchangeable cartridges.
The counter nozzle with adjustable throttle valve allows to invert the motion and role of the jet.
The external tray (fig. B, 7) in which the bath with the dye products is formed is connected to one
feed pump (fig. B, 8). The machine pressure is created by the circulation pump
of the bathroom (fig. B, 9) or by means of compressed air.
used dyeing
used dyeing
dyeing jigger
The jigger is the classic machine for wide dyeing, mainly used for traditional fabrics
of cotton. It is still the cheapest and most versatile for pretreatment, bleaching and dyeing
of fabrics with natural fibers, both at atmospheric pressure and under pressure (in an autoclave).
In the more advanced models, the tension-free treatment also allows you to dye silk and fabrics
Knitted. The general principle of the processing involves repeated passages of the fabric in a dye bath,
by transferring the cylinders located above the tank from one to the other. The contact time between the
fabric and bath is short, but the process is completed in the rolling and unrolling on the cylinders.
The machines present in the district today present numerous and interesting diversifications.
The most important elements, which are punctually found in most machines, are:
two winding and unwinding cylinders (see figure A, points 1) which, rotating in one direction
and in the other, they allow the passage of the fabric from one cylinder to another;
a motor unit, mechanical or electric, with a device that moves each cylinder in
independently from the other to obtain the unwinding of the fabric without excessive tension;
a trapezoidal tank (fig. A, 2) containing the dye bath in which the fabric is impregnated, accompanied
by a series of small guide cylinders, for a more regular passage of the fabric;
a steam coil (fig. A, 3) placed on the bottom of the tank for heating the bathroom;
a tilting widening device (fig. A, 4), which eliminates any folds before winding
on the cylinders;
a cover (fig. A, 5) placed on the appliance, which prevents fabric cooling;
a bath circulation pump, for the perfect homogenization of the dye bath;
device for controlling bathroom heating and control panel for regulation
automatic of all process parameters.
The pressure jiggers (see figure B), in the autoclave, also dye synthetic fibers at high temperature.

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