The dyeing of polyester fabric using disperse dyes can be carried out by four methods
Carrier dyeing method
* High temperature dyeing method
* Thermosol dyeing method
* Solvent dyeing
Certain hydrocarbons, amino acids, amides, alcohols, phenols, and esters accelerate the rate of dyeing of polyester fibres with the disperse dyes from aqueous medium at temperature of up to 100C. the dyeing assistants alter the dispersing properties of the dyes and the physical properties of the fibre so that more of the dye transfers from the dye bath liquor to the fibre substrate. These additives are called as carriers, which swells the fibre and ultimately cause relaxation. They reducing intermolecular forces operating in the fibre and act as molecular lubricants thereby allows the dye molecule to force itself inside the fibre. The carrier that are used are also called swelling agents for the polyester fibre.
Typical dyeing procedure with carriers is as follows
The dye bath is set at 60C temperature and with pH 4-5. Fabric material is run for 10 min and aqueous dispersion of dye along with carrier (3-5 gpl) is added in two stages with a gap of 15 min. Carrier is dispersed in water at least for 30 min before use to avoid insoluble particle of carrier, which may cause a carrier mark in the fabric. dyeing is continued for about 60-90 mins. Other auxiliaries such as dispersing agent 0.5to 1 mg per lit. is also added to ensure good dispersion throughout the dyeing.
Disadvantages of carrier dyeing
1. Centre selvage variation may occur
2. Carrier mark problem
3. Tailing effect
4. This method is suitable only for light and medium depths
5. Complete removal of residual carrier is difficult
6. Most of carriers are toxic, gives unpleasant smell to fabric
7. Dyeing process takes more time as compare to other methods
8. It may turn out to be costly process due to high prices of carrier themselves.