Abstract
The aim of this study focuses on achieving targeted result from lab to bulk in the first go. This means at every colouring the targeted shade should be achieved the very first time, thus not requiring re-dyeing or re-correcting shade by adding dyes/chemicals.
Usually, light shade gets lighter and dark shade gets darker in bulk production following the lab recipe. From the lighter or darker shade to desired shade it takes multiple number of adjustments. To avoid this adjustment, we need a lab recipe and a SOP which will get us the right shade in first time.
Keywords
RFT; Reactive dyes; Lab to bulk; Liquor to material ratio
Introduction
This Project is basically focused on a standard operating procedure (SOP) for 100% cotton knit dye to modify the lab recipe for light and dark shade. Suitable standard operating procedures need to select or develop for sustainable and efficient production in the industry. In this project, our developed process has been run for experiment and the material sample developed from the process has been tested. And color shade variation for the newly developed process and the conventional process have been compared.
Besides this, color fastness of the samples for these two processes has also been measured and compared. The newly developed process shows better or equal results than the conventional process practiced at the associated factory in terms of the lab to bulk color shade variation and color fastness
The present situation of dying process in Knit sector is well established & successful. But there are new challenges arising everyday which are trying to unsettle this progress. The process can be improved further if some new technologies are introduced under precise condition making sure that the quality of production is improved. The knit dyeing process of cotton is almost entirely using Reactive Dyes & Exhaust methods, which are still undoubtedly successful.
Right-first-time shade means to match the shade of dyed fabric with the required shade at first time without facing minimum dyeing faults. In other word RFT shade is matching the dyed fabric shade with required without topping and re- dyeing.
Experimental:
Material: 100% cotton knitted fabric with GSM 160 g/m2 was used for sample dyeing. We calculated for 5 gm knitted fabric.
Dyes and Chemical:
| Dyes and Chemical | Light Shade | Medium Shade | Dark Shade |
| Reactive yellow 3RS | .02% | 1% | 1.5% |
| Reactive Red 3BS | .03% | .3% | .5% |
| Reactive Black B | .05% | .5% | 4% |
| Glauber’s Salt | 20 g/l | 45 g/l | 80 g/l |
| Soda ash | 6 g/l | 12 g/l | 20 g/l |
| Caustic | 2 g/l | ||
| Soaping agent | 2 g/l | 2 g/l | 2 g/l |
| Acetic Acid | .5 g/l | .5 g/l | .5 g/l |
Material: Liquor = 1:6
Temperature =60°C
Procedure
Laboratory sample dyeing procedure:
- Measuring sample for knit dyeing.
- Making dyeing recipe and calculating
- Pipetting the dyes and chemicals (salt, soda) accurately
- Closing the dyeing pots and shake continuously
- Inserting the sample pot into dyeing machine cabinet
- Running the Machine at 60° C for 60 Minutes
- Cold washing the sample
- Acid washing the sample (for neutralization)
- Taking the wash off chemical into the Dyeing Pot
- Putting the sample on it
- Starting the washing machine to run at 90°C for 20 minutes
- Cold washing the sample
- Starting the Dryer machine to dry the sample at 130’c for 160 seconds
- Ironing the sample.
- Matching the sample with provided swatch
- Increasing the lab to bulk reproducibility
Assuming the above factors are well controlled, actual lab practice is another factor which can seriously impact RFT and lab to bulk reproducibility. Quite often, lab dyeing is carried out on pre-bleached, dry fabric, which can lead to immediate errors, both from a liquor ratio and from a dye concentration point of view.
In bulk practice, we may start with grey fabric, which can contain up to 10% impurities. After pre-treatment, a 100 kg batch can actually weight as little as 90 kg.
However, everything is calculated for 100 kg –dye, salt, alkali, etc. If we start in the lab with dry pre-bleached fabric and base all calculations on this, we have immediate errors – exacerbated if impurity level is high.
When bulk produced according to the lab recipe, the light color becomes lighter and dark color becomes darker shade.
Ideal lab practice is to take customer’s grey fabric and cut into, say, 5 gm portions; then bleach and dry (check weight to confirm amount of impurities – if say 4.8 gm, you know that fabric contains 4% oil, waxes etc.) and then carry out the lab dyeing on this fabric assuming the original weight of 5 gm.
In this project, different weights of sample fabric is taken. Assuming that the fabric sent to the lab has some processing like scouring, bleaching and enzymes so the weight of the fabric is slightly reduced.
So, we will take different sample fabric weights of light, medium and dark shades due to lab to bulk problem. The weight is calculated based on the previous data, factory operating practice and experience. It might be different for different factories. The project was conducted in Fatullah Dyeing & Calendering Mills Ltd.
Conclusion
It’s evident that RFT has huge importance for quality production as everyone got time limitation. A number of points required to be checked and ensured for the correct production with right quality. Consequently, dye house water quality must be ensured for coloring product by testing water hardness, pH etc. Another key purpose has got to be unbroken in mind for obtaining RFT result that right method has to be followed for right production selecting right material in right time. A little deviation from the particular method will build an enormous distinction in quality. Therefore every task must be followed to get desired result.
