Subject:-

Dyeing of Natural and Synthetic Fiber

Topic:-

Pad Thermosol Dyeing Machine

Prepared by:-

HajiKarim Aman BST-VII

Dated:-04-02-2014Haji Karim Aman Page 1

Pad Thermosol Dyeing Machine:-

This dyeing machine is used to dyed fabric from dark to medium shades. It is based on method to dry to dry the fabric without any contact with steaming. This machine is able to carry the following processes.

Reactive dyeing Disperse dyeing Vat dyeing Pigment dyeing.

PROCESS SEQUENCE IN PAD THERMOSOL Batcher ↓ Screy ↓ Cooling drums

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↓ Padding ↓ IR ( pre-drying) ↓ Drying and curing chamber ↓ Cooling drums ↓ Screy ↓ Batcher

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1-Scary or J-box:- It stores the fabric. It is J-shaped metal holder for fabric. It prevents the down stop of the machine by storing excess length of the fabric during the batcher change. It also avoids the slackness and crease formation in fabric, which is formed due to speed variation in machine and batcher, scary synchronize themovement between them.

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2-Fluff removal chamber:- The fabric is passed between two brushes in order to remove the fluff.3-Guide roller:- These rollers steel rollers used to guide the fabric and to provide tension which prevents the crease formation.4-Compensator:-These are used to provide tension to the fabric. If thefabric loosens from any roller during the process, thismoves up and down to maintain the tension. 5-Dye Padder:-

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The padder or the padding mangle is meant to apply dye liquor in an even manner to the entire width and the length to a batch of fabric. The padding operation consist of two parts: first immersion of the fabric in dye-liquor in a trough, and second passing the fabric between the two roller to force the dye-liquor into thefabric and also to squeeze excess amount liquor back tothe trough. Padder is the most sensitive components dyeing system as any fault developed at the padding stage will not be corrected later. Padders usually havetwo rollers although the 3 roller types with 2 dip troughs were also marketed but these are used mainly for applying finishes to the heavy weight fabric.

Nip rolls must be clean and within hardness specification of 70-80 shore for woven and 50-60 shore for knitted fabric.Nip rolls are damaged by

Build up of sodium silicate on rollers Incorrect cleaning Age deterioration

Resulting in poor appearance of the dyed fabric andpick up variation.

The padder roll has a steel mandrel that is covered with hard rubber, topped by 15mm of the soft rubber.

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Both the rollers should have exactly the same hardness otherwise there will be a color difference in the face and back side of the fabric.

The material of the rubber should be chemically resistant to dye liquor and auxiliary products. The bottom roller is coupled with a variable speed motor sothat the fabric may is run at the linear speed ranging from 30 to 90 m/mins.The usual liquor pick up in a modern padder for the different fibers are

Cotton =60-70% P/C (50:50)=45-50% Viscose = 80% Nylon = 30%

6-Padding Trough:- The volume in the pad trough should be relatively small 20-50 liters and automatically controlled at constant level throughout the run.Pad bath level variation are caused by

Malfunctioning level controller Blocked feed pipes Malfunctioning pumpResulting in shade difference caused by variations inimmersion time and pick up.

The pad liquor turnover time should be as fast aspossible less than 5 minutes.

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The pad liquor should be distributed uniformly across the full width of the padder through a perforated tube.

The trough is placed below and in front of the padder and consists of a U-shaped box with one or more free-running guide rollers of about 10cm diameter each.An expander roller is fitted before the nip of the rolls to eliminate any crease that may developed duringpassage of fabric through the trough. The dye is fed inthrough a perforated pipe running across the entire length of the tank with perforations pointing towards the wall of the trough and away the fabric so as to avoid spraying of the liquor to fabric. Ideally a trough should contain the minimum quantity of the dye-liquor consistent with adequate pick up so as to reducewastage of the unused dye at the end of the process and

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more importantly to have a high liquor replacement value.

The pick up,immersion time,speed should be constant through out of the process.Pick up:-Must be uniform aross the width acoss the consistent from batch to batch.Pick up depend upon,

Pad pressure and speed (fabric pentration, wetting out)

Dye level in the trough ( dip to nip time) Dyebath chemicals (penetation accelerant) Fabric (fibre and construction).

Immersion time:- Should be 1-2s for cotton and 2-4s for viscose.

Speed:- Must be constant throughout the run-no stoppages.

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7-Airing zone:-Airing zone is used because some times the light GSM fabric has face and back variation so we used airing zone. The airing zone is placed between the padding anddrying for better swelling and peneration of the dye.

8-Infra-Red Predryer:-To get even and uniform results especially for medium and deep shades, the dye-padded fabric is required to be dried before the dye is made to diffuse into the fibers by steam thermo fixation. It is important that after applying the dye liquor evenly, there is no irregular migration of the dye during drying. So during the intermediate drying phase, dye molecule tend to diffuse with water molecule as they migrate from the wetter towards the drier part if the fabric.Dye molecules continue to migrate as long as free watermolecules diffuse from the surface of the fabric.Migration stops when only bonded water molecules and moisture content of the fabric dropped below 30%.How to control dye migration:-

Lower pick up (less surface or free water molecule) Skying between padding and drying (better swelling

and penetration) Addition of electrolyte to increase dye affinity

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Infra-red pre-drying (most important) Well balanced air flow in the dryer.

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This is a pre-drying chamber fixed vertically above thepadder after the skying or airing zone. These are heated by electrically or by gas. The infra-red radiations selected are 3µm wavelength as textile fibers perfectly absorb this water is evaporated from the fabric. The operating temperature reached in 5-8 seconds and the temperature is uniform over height and width of radiatiors.The fabric in the IR dryer is threading under the tension with the compensator and the IR rays should be contact with both side of the fabric by uniform distribution of the rays.And removal of as much as 40 to 50% of the water from the padded fabric in the absence of strong air currentand fabric to metal contacts which accelerate dye migration.

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Requirement of an Infrared pre-driers:-

Gas or electrically heated. The emitted IR wavelength should correspond

maximum absorption value of water (3µm) Equilibrium setting up time. Air passage before pre-drying (dye penetration). Moisture content of the fabric after pre-drying. Cleaning of guide rollers.

9-Thermofixation:-In the thermofixation (also incorrectly called thermosol) process of dyeing the synthetic fibers, thedisperse dyes diffuse into the polyster fibers on bringing the dye-padded fabrics to temperature of 200-220ċ for a contact time of 60-30 seconds because the polyester has the compact structure and having 85% of crystalline area so at high temperature the pores of the fiber are open which allows to enter the dye in thehighly crystalline area.

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The conditions are set according to fabric weight, fabric construction, fiber composition (Co, Co/PES, PES, etc.), pickup, etc. to Air circulation system of the THERMFIX prevent migration.

Each THERMFIX chamber is suitable for The air circulation system is shown in the drying (PAD-DRY) or for thermosetting illustration. High uniformity of air flow, air (PADTHERMOSOL) temperature and air humidity over length processes.

The controlled and width in the THERMFIX chamber is removal of exhaust air is important for economically ensured by two diagonally located, frequency optimized drying conditions. Frequency controlled circulation fans (1). The controlled radial fans (9) are used to air flows from the fabric chamber through adjust from Haji Karim Aman Page 13

the panel the amount of exhaust the lint sieve (2) and is heated (3) either by air. An automatic closed loop control with an oil-to-air or steam-to-air heat exchangers electronic moisture probe in the exhaust airor direct gas heating. From the mixing tube stream is available as an option. The feeding (4) the air enters the large distribution air enters the fabric chamber through adjustable chamber (5). The air is distributed over vents (8). length and width and uniformly pressurised through the nozzle elements (6) into the fabric chamber. In each chamber the air quantity and temperature is controlled.

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It is heating and curing chamber. Dyes which placed on the surface are fixed into the fabric in this chamber.This consist of the 5 chambers each portion has different temperature and varying according to the quality of the fabic.

Fabric 1 2 3 4 5Pc 120 140 160 200 200cotton 100 120 150 165 165

In the curing chamber the fabric is threading vertically to dry evenly the both side of the fabric and the fabric should be under tension which is controlled by the compensator when it lose.

10-Cooling drum:- These are provided at the inlet and outlet side of the thermosol machine. These are hollow steel drums

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and used to maintain the temperature of the whole lot water filled inside the drum to cool it.

Reference:- Wet processing of the cellulosic textiles by Dr.

Ahmed Niaz. www.bennigergroup.com.

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