Disperse Dyeing Process
Prepare the recipe of Disperse Dyeing or Polyester Dyeing for the shades given by customer. Number of trials per shade depends on the loading capacity of the machine to be used and the numbers of shades received. aaa
- Accurately weigh the dyes (+/-2% of the required weight) and dissolve in an accurately measured volume of water. Volumetric flask is preferable for water measurement. Dye solutions should be stored in erlenmeyer flask for easily shaking up before use because disperse dyes settled at the bottom after some time standing. It is to be stored at room temperature and discarded after two days. The solution concentration should be appropriate for the depth of shade to avoid dispensing small volume. See table for cotton on dye solution preparation.
- Check and weigh whether the substrate sample is within +/- 2%.
- Pipette the required volume of dyestuff accurately also using the electronic dispensing pipette. If graduated glass pipettes is to be used avoid using chipped pipettes or pipettes with broken tips and select pipette with correct capacity. For example :
| Pipette Capacity | Optimum Working Range |
| 0.2 ml | 0.10 – 0.20 ml |
| 0.5 ml | 0.201 – 0.50 ml |
| 1.0 ml | 0.51 – 1.0 ml |
| 2.0 ml | 1.01 – 2.0 ml |
| 5.0 ml | 2.01 – 5.0 ml |
| 10.0 ml | 5.01 – 10.0 ml |
| 20.0 ml | 10.01—20.0 ml |
- Add auxiliaries and chemicals to be used like in bulk.
- Calculate the quantity of water required, allowing for dye and chemical additions and add to the Polyester Dyeing beakers.
- Add the rolled up substrate (avoid folding/creasing), seal the dyeing beakers and vigorously shake the vessel to ensure even liquor uptake.
- Place the Polyester Dyeing vessel into the dyeing machine at the set Disperse Dyeing temperature.
- At the end of the dyeing program remove the beakers individually and wash the samples in cold running water for 2 minutes.
- Separate the medium and dark shade samples and load again in the Polyester Dyeing machine for reduction clearing process. See recipe for reduction clearing.
- After reduction clearing program is finished then the samples are washed with cold running water then acidify with 0.5 g/l acetic at 40 degrees for 10 minutes, and unload, wash with cold water.
- The samples are then burn out or dissolved in 70% prepared sulphuric acid to dissolved the cotton part and assessed the polyester part remained after drying. If polyester part samples is okay with the customer standard then cotton part can be start to match. This is in case of double dyeing or two-part Disperse Dyeing.
One Bath Dyeing of PES/Cotton
- Follow procedure i – vii of disperse dyeing. At procedure iv, selected reactive dyes will be pipetted also and added with disperse dyes already pipetted.
- On procedure v, salt will be also added together with dispersing chemicals and auxiliaries .
- Water for dyeing has sequesterant and lubricant agent already so this will be the one to be added to the dyeing vessel as the calculated water needed in procedure vi
- The dyeing beakers will be loaded at the new select program when all the needed dye, chemicals, fabrics and water are input. The dyeing temperature and time will be for polyester part dyeing first then after it will be cool down to the required cotton dyeing temperature.
- The machine will run for 10 minutes at the cotton dyeing temperature then all dyeing beakers will be unload placing on the beaker rack individually for alkali addition. Alkali and acid must not be added together on this one bath dyeing at the start because disperse dyeing is done on acidic medium. The pH must be check after alkali addition to see if it is on the range of 10.5-11 (cotton part dyeing pH required).
- Load the dyeing beakers after alkali addition then continue the new select program , that is cotton part dyeing.
- When dyeing program is complete, proceed for after treatment of reactive dyeing. This new select program is not applicable for dark shades which required reduction clearing because this need only after treatment like cotton part dyeing.
- Reduction clearing chemicals will strip or reduce to a big % the cotton dyes from the fabric.
Conclusion
Dry the samples of Disperse Dyeing or Polyester Dyeing, condition and assess the shade. If shade matches with the standard then samples will be filed for approval but if not then it needs to be re-matched.