Pratik nilay minjAjay Sangwan

DISPERSE DYES

DISPERSE DYES•Disperse dyes are organic colouring compounds having low molecular weight (approx, 300-700), virtually water insoluble dyes.• Suitable for colouring hydrophobic fibres, like cellulose triacetate, nylon, polyester and some extent polypropylene, acrylic and modacrylic fibres from an aqueous dispersion.• British Dyestuff Corporation in 1924 introduced first member of disperses family – Dispersol dyes, dispersed with soap or Turkey red oil. •The first disperse dyes were developed more than 60 years ago for the dyeing of secondary cellulose acetate with dispersing agent employed like sulphated ricinoleic acid and widely known as SRA Dyes

The original disperse dyes dating from the 1920s were applied solely to acetate rayon

Many developments in dye structure were found necessary when other synthetic fibers such as nylon and polyester came into the market.

The dyeing on those fibers and their blends posed many problems.

[A] Monoazo dyes [B] Bisazo dyes [C] Styryl dyes [D] Coumarin dyes [E] Nitrodiphenyl amine dyes [F] Anthraquinone dyes [G] Naphthaquinone dyes [H] Naphthalamides dyes [I] Naphtholactum dyes [J] Miscellaneous dyes

CLASSIFICATION OF DISPERSE DYES

Disperse dyes have low solubility in water, but they can interact with the polyester chains by forming dispersed particles. 

Their main use is the dyeing of polyesters, and they find minor use dyeing cellulose acetates and polyamides. 

The general structure of disperse dyes is small, planar and non-ionic, with attached polar functional groups like -NO2 and -CN. 

The shape makes it easier for the dye to slide between the tightly-packed polymer chains, and the polar groups improve the water solubility, improve the dipolar bonding between dye and polymer and affect the colour of the dye. 

MECHANISM

The dye is generally applied under pressure, at temperatures of about 130oC. 

At this temperature, thermal agitation causes the polymer's structure to become looser and less crystalline, opening gaps for the dye molecules to enter. 

The interactions between dye and polymer are thought to be Van-der-Waals and dipole forces.

The volatility of the dye can cause loss of colour density, and staining of other materials at high temperatures. 

This can be counteracted by using larger molecules, or making the dye more polar (or both). 

This has a drawback, however, in that this new larger, more polar molecule will need more extreme forcing conditions to dye the polymer.

Example of a disperse dye

The dye must be brought into a state of fine suspension in the dye bath.

Before application of dye stuff approximately 1-1.5 kg of synthetic dispersing agent per 1000 litres should be put in liquor.

This assists in maintaing a stable suspension and increase solubility of pigment.

The goods are entered cold and temperature raised slowly to between 70-85 C .

Dyeing is continued till 1 hour . Disperse dyes differ greatly in exhaustion rate

and levelling properties.

APPLICATION OF DISPERSE DYES

Heat water in a suitable container (do not use iron, copper or aluminium). If using water from a hard water area, add 3gm Calgon to help counter its alkalinity. Water can be tested using indicator paper.

Weigh out disperse dye powder (0.4gm for pale colours to 4gm for stronger colours) and sprinkle into a small amount of tepid water to make a solution.

Add the dye solution to the dye bath along with 3gm of dispersing agent and stir well with a wooden, stainless steel or plastic spoon.

Add the fabric to the dye bath and stir gently whilst raising the temperature slowly to 95-100°C over 15-30 minutes (if dyeing acetate, keep the temperature at 85°C). The longer the fabric remains in the dye bath the stronger the shade.

Allow the bath to cool to 50°C and check the colour. Add more dye solution to strengthen it and raise the temperature to 80-85°C for a further 10 minutes.

Continue step 5 until the desired colour has been achieved. To complete the process, remove the fabric from the dye bath,

rinse in tepid water, spin dry and iron.

Disperse Dye Bath Technique:To dye 100gm fabric in 3 litres of water

Carrier Dyeing

High Temperature High Pressure (HTHP) Dyeing

Thermosol Dyeing

METHODS OF DYEING

Carrier dyeing is carried out under atmosphere pressure by an addition of carrier to the dyeing liquor. Methylnaphthalene or chlorobenzene type carrier is used generally, which is added in concentration of 2-7 g/L to the dyeing liquor.

Other conditions of the dyeing liquor are the same as those for high temperature dyeing.

The temperature is raised gradually from 40-60°C and continued for 90-120 min at 100°C.

In carrier dyeing, in some case the troubles such as tarring of dye or carrier spot are taken from the no stability of emulsifier in the carrier under high temperature or some other conditions.

Therefore, it is necessary to select the carrier so as to prevent the troubles.

CARRIER DYEING

Set up the dyebath with the following auxilaries and chemicals:

Lyogen DFT = 0.5 gpl Sandozen PES = 1.0 gpl Acetic Acid = 1 gpl Check pH to 5.5 to 6.0

High temperature high pressure dyeing 

Set the dyebath with the above materials. Raise the temperature to 50°C and run for 10 minutes.

Dissolve the dyestuff with soft water at 50°C and filter it.

Add the dyestuff slowly in to the bath. Check the pH to 5.5. to 6.

Raise the temperature to 115°C at 2°C per minute and run 10 minutes.

Raise the temperature further from 115°C t0 135°C at 0.5°C per minute.

Hold for 45 to 60 minutes according to the depth of the shade.

Lower the temperature to 80°C and drain the bath.

Do Hot Wash (70°C) for 10 minutes followed by cold wash.

Dyeing process for nylon, triacetate, polyester and acrylic fibers.

At A set bath at 50°A - Add Auxiliaries & Acetic AcidAt B add Disperse Dyes (pre-dispersed)

Thermosol dyeing is a continuous dyeing method which is applied mainly for the polyester/cotton blended materials. General dyeing condition is as follows.

Dye and 0.5-2g/L of migration inhibiter (for example, sodium alginate) and also wetting agent if necessary are added to the padding liquor.

Squeezing is carried out at room temperature, pick up 65-70%. Drying at 70-90_C.

After padding and intermediate drying, thermosol fixation is carried out by dry heating for 60-120 sec. at 180- 210°C depending on the form of the material and type of disperse dyes.

Thermosol dyeing 

This is the process to improve the fastness of the dyed material by removing all the dyestuff that is superficially adhearing to the fabric and staining the cotton portion of the blend. The following method is found to be most suitable for any depth of dyeing.

Recipe: Cyclonon ECO = 2 gpl Acetic Acid = 2 gpl Treat the fabric at 70°C for 20 minutes. Do hot

wash and cold wash. Drain and unload the batch.

Reduction Clearing

Jet Dyeing MachineMACHINES USED

This is the most modern machine used for the dyeing of polyester using disperse dyes.

In this machine the cloth is dyed in rope form which is the main disadvantage of the machine.

In this machine, the dye tank contains disperse dye, dispersing agent, leveling agent and acetic acid.

The solution is filled up in the dye tank and it reaches the heat exchanger where the solution will be heated which then passed on to the centrifugal pump and then to the filter chamber.

The solution will be filtered and reaches the tubular chamber.

Here the material tobe dyed will be loaded and the winch is rotated, so that the material is also rotated.

Here the material to be dyed will be loaded and the winch is rotated, so that the material is also rotated.

Again the dye liquor reaches the heat exchanger and the operation is repeated for 20 to 30 minutes at 135o C.

Then the dye bath is cooled down, after the material is taken out.

Advantages Jet Dyeing Machine Dyeing time is short compared to beam dyeing. Material to liquor ratio is 1:5(or) 1:6 Production is high compared to beam

dyeing machine. Disadvantages Jet Dyeing Machine Cloth is dyed in rope form Risk of entanglement Chance for crease formation.

Disperse dye inks are used in the inkjet textile printing of polyester fabrics.

ADVANCEMENTS

Disperse dyes are used for printing on synthetic fibers such as acrylic fibers, nylon and polyester.

These dyes are called such because they require a dispersing agent to spread the dye over the fabric.

The inks formed from dispersed dyes, are able to generate shinny and reproducible colors in polyester fibers.

These inks have excellent and complete end-use properties. 

Disperse Dye Ink for Digital Textile Printing

THANKYOU