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Developing a standard operating procedure (SOP) for 100% micro-polyester yarn dyeing to improve right-first-time (RFT) %

Suitable standard operating procedures need to be selected or developed for sustainable and efficient production in the industry. Industries nowadays are facing difficulties to ensure right-first-time (RFT) in micro-polyester yarn dyeing in exhaustion dyeing method. Which overall makes this process unsustainable and inefficient. Our project has focused on developing a standard operating procedure (SOP) that will improve the right-first-time (RFT) percentage (%) in micro-polyester yarn dyeing.

 

Developing a standard operating procedure (SOP) for 100% micro-polyester yarn dyeing to improve right-first-time (RFT) %
Developing a standard operating procedure (SOP) for 100% micro-polyester yarn dyeing to improve right-first-time (RFT) %

Figure 1: Comparative thickness of various fibers.

The project has been conducted at the yarn dyeing unit of Southwest composite Ltd. Their existing process of micro-polyester yarn dyeing has been studied. And after making some changes in process parameters and chemicals, a new process has been developed. The developed process has been run for experiment and the material sample developed from the process has been tested.

Color shade variation between the lab sample and the bulk sample has been measured for each process. And color shade variation for the newly developed process and the conventional process have been compared. Besides this various, the color fastness of the samples for these two processes has also been measured and compared for these two processes.

The newly developed process shows better results than the conventional process practiced at the associated factory in terms of the lab to bulk color shade variation and colorfastness. And some problems in machinery have also been noticed whose mitigation could provide much better result in RFT percentage by minimizing the lab to bulk color shade variation to a tolerable level.

Color shade difference between lab sample and bulk sample at an unacceptable level is the main barrier to achieving the RFT in dyeing. RFT can be achieved if the color shade difference between the lab sample and the bulk sample is at an acceptable level for the first attempt of dyeing.

In this project, we have worked with 100% micro-polyester filament yarn. Polyester fiber (polyethylene terephthalate) becomes more popular due to its unique properties such as excellent mechanical characteristics, good resiliency, chemical inertness and heat resistance. Polyester microfiber had been a popular issue in the research field because of its aesthetic and highly soft touch. Polyester microfiber is defined as a fiber or filament with a linear density of less than 1 decitex, which provides excellent hand properties, drape, and comfort. The high moisture absorption capability of the fiber makes it widely used in athletic wear due to its higher surface area per unit volume.

Surface area comparison between ordinary polyester and micro-polyester
Surface area comparison between ordinary polyester and micro-polyester

Figure 2 Surface area comparison between ordinary polyester and micro-polyester.

Experimental Method
Materials
100% polyester microfilament yarn manufactured by Shanghai Lingtech Technology Co., Ltd., China is used. The count of the filament is 0.9 denier. Foron C.I. Disperse Yellow ACE 1.8 %, Foron C.I. Disperse RED ACE 1.4 %, and Foron C.I. Disperse BLUE ACE 0.23 % azo dyes supplied by Orient Chem-Tex Ltd are used. Sodium hydroxide, sodium hydrosulfite, and acetic acid, supplied by local suppliers, are also used. Detergent (Matclean® AFD liquid, non-ionic & SHUNTEX – XPA, Anionic), buffering agent (Matacid® BD liquid, anionic), and dispersing agent (Matlevel® LPF liquid, non-ionic) are used as auxiliaries in the conventional process. On the other hand, detergent (TISSOCYL RC9, non-ionic), buffering agent (SETACID AB Conc, organic buffer system), dispersing agent (ZETESAN DHT, non-ionic), wetting agent (NEWALOL PFN, non-ionic), an anti-foaming agent (CONTRIPON S, non-ionic) are used as auxiliaries in the recommended process.
SandoLab manufactured by COPOWER TECHNOLOGY CO., LTD., China, is used as the lab sample dyeing machine. The sample package dyeing machine from Wuxi Quanrun Machinery CO. LTD, China, is used for bulk sample dyeing.

Sandolab lab sample dyeing machine
Fig3: Sandolab lab sample dyeing machine

Procedure
The lab sample and bulk sample are developed for both processes. Yarn used for lab sample dyeing is 2 gm, and for bulk, sample dyeing 3.2 kg. A bulk sample is developed in a package dyeing machine, and the package density is 0.4 gm/cm3. The liquor ratio is 1:10 For both processes.
In the conventional process, washing is done at 70 ◦c for 20 min with detergent at the beginning. At the next step, dyeing is done with the buffering agent, dispersing agent, and dyes at 135 ◦c for 40 min. For bulk, color dosing is done for 30 min at 70 ◦c. After a cold wash at 35 ◦c for 10 min, reduction cleaning with Sodium hydrosulfite and sodium hydroxide is done at 90 ◦c for 20 min. Acid wash with acetic acid is done at 50 ° C for 10 min after that.
Furthermore, a hot wash at 80 ° C for 20 min is done at the last step. Then, hydro-extracting and drying are also done later.

Dyeing curve of conventional process
Dyeing curve of conventional process

In the recommended process, washing is done at 70 ◦c for 20 min with detergent at the beginning. At the next step, dyeing is done with a buffering agent, dispersing agent, wetting agent, anti-foaming agent, and dyes at 130 ◦c for 60 min. Then, reduction cleaning with Sodium hydrosulfite and sodium hydroxide is done at 70 ◦c for 20 min. Acid wash with acetic acid is done at 60 ° C for 20 min after that. Moreover, at the last step, a hot wash at 50 ◦c for 10 min is done. Hydro-extracting and drying are also done later.
Color differences between lab samples and bulk samples of each process are measured using Spectrophotometer 400 to determine the lab to bulk color difference for each process. Colorfastness to washing (ISO 105 C06 (C1S) method), rubbing (ISO 105 X12 method), perspiration (ISO 105 E04 method), and light (Xenon arc fading lamp test, ISO 105 B02:2014 method) is tested of only the bulk samples of the two processes. Then the results are compared.

Dyeing Curve of Recommended Process
Dyeing Curve of Recommended Process

Results and Discussion
Color shade difference results show that dL* and da* are lower for the recommended process, which means that its bulk sample is lighter and greener than the standard lab sample for this process. The db*, dc*, and dH* are higher for the recommended process, which means that the bulk sample is yellower, more saturated, and deeper than the standard lab sample for this. Finally, the color difference dE* is higher for the conventional (7.72) process than the recommended process (7.37). The recommended process is better than the conventional process for the lower color difference from the standard sample.
Table 1 Color shade variation between lab sample & bulk sample

Color change, staining to Wool, Acrylic, Polyester, Nylon, and Cotton are equal for the samples of both recommended and conventional processes in colorfastness to washing. However, staining to Diacetate is better for the recommended process (4-5) than the conventional process (4) for wash fastness.
Table 2 Colorfastness to wash

Colorfastness to rubbing in dry (4-5) and wet (4-5) tests is equal for both recommended and conventional processes.
Table 3 Colorfastness to rubbing

For colorfastness to perspiration test, color change, staining to Wool, Acrylic, Polyester, Nylon, Cotton and Diacetate (DA) are equal for both recommended and conventional processes colorfastness to perspiration is equal for both.
Table 4 Colorfastness to perspiration

Colorfastness to light for both recommended (6) and conventional (6) processes is also equal as per results.
After all, the recommended process shows better performance with lower color shade variation between the lab sample and bulk sample and better colorfastness to wash than the conventional process, according to the test results.
Table 5 Colorfastness to light

After all, the recommended process shows better performance with lower color shade variation between the lab sample and bulk sample and better colorfastness to wash than the conventional process, according to the test results.

Conclusion
Based on the experimental results, it can be concluded that the recommended process that we have developed shows better color shade variation between the lab sample and bulk sample. It indicates that the use of both non-ionic surfactants in washing and wetting agent and anti-foaming agent with dyes shows a lower color difference between the lab sample to bulk sample than anionic surfactant in washing and not using wetting and anti-foaming agent with dyes. Comparing the results of color fastness of two processes shows that overall color fastness is better for the recommended process than the conventional process.
The experimental results also indicate that dyeing 100 % polyester microfilament yarn at 130 ◦c for 60 min is better than dyeing 135 ◦c for 40 min as it shows better color difference and colorfastness. This research is just an initial study to determine a cost-effective and sustainable dyeing process for 100% polyester microfilament yarn. Further research should be carried out to study the changes in color shade variation between lab sample to bulk sample for changing time and temperature in 100% polyester microfilament yarn dyeing.

My cordial thanks to Md. Salauddin Sk (Technical manager, Harris & Menuk BD Ltd.), Md Mijanur Rahman (AGM, Yarn Dyeing, South West Composite Ltd.), Mustafijur Rahman (Assistant Professor, Dept. of Dyes & Chemicals Engineering, Bangladesh University of Textiles) for their knowledge support and cooperation. And special thanks to Harris & Menuk BD Ltd. for supporting with auxiliaries, South West Composite Ltd. for supporting their yarn dyeing facility and DYSIN-CHEM Ltd. for supporting their testing lab.
At the end thanks a lot to Textile Today for this opportunity to work on this project.;

If anyone has any feedback or input regarding the published news, please contact: info@textiletoday.com.bd

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