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Finding out an effective process to reduce re-dyeing for micro polyester yarn

Abstract:

The tendency of micro polyester fibers not to form a bond with the dye and the tendency of the micro-polyester is to attach to the dye at high temperature which is somewhat more critical than that of other fibers. One of the problems with micro-polyester fiber or yarn dyeing is the shade variation of lab to bulk.

As a result it needs to re-dye which increases the production cost. Important parameters of micro polyester dyeing are temperature, liquor ratio, die size, etc. At present, in the process of dyeing micro polyesters in factories, some of the basic parameters have been changed and the traditional SOP has been compared with the new SOP.

re-dyeing-micro-polyester-yarn
Figure: In the process of dyeing micro polyesters in factories, some of the basic parameters have been changed and the traditional SOP has been compared with the new SOP.

As a result, several changes have been noticed. The amount of die take-up has been found to be higher than before.

Introduction:

Production of micro polyester or ultra-fine polyester has started since about 1950. Usually, Melt blown spinning and Flash spinning techniques are used to make finer fibers than 0.7 denier. The fineness of micro-polyester yarn is 0.25-1.0 denier. So, its surface area is more than ordinary polyester. And since polyester does not form any bond with the dye like other fibers.

Dye and fiber are only attached. So, it is difficult to level dye. Also, the workers who work in dyeing in the factory do not know much about micro polyester and its dyeing material.

So many mistakes are made due to a lack of knowledge in this regard. The most important of these errors are die selection, auxiliary chemical selection, die bath preparation, pH controlling, lab and bulk liqueur ratio variation, heat setting problem, incorrect pipetting, incorrect sample info, and many more.

As a result, large shade variations can be seen in lab and bulk samples. That is why it needs to dye more than once. It results in production cost increases, product quality deteriorates, time is wasted.

In this project, a process has been recommended for keeping these problems in mind so that better results can be obtained than before. Less need of re-dyeing later than before.

This project is proposing a simple solution in which we will dye the yarn with some low or medium energy disperse dye after that we will treat the yarn with a Reduction cleaning process one or two times. As a result, it will show possible-less uneven shade and good fastness properties.

So, re-dyeing will not be needed. And it will save almost 40% cost which generally becomes wasted for re-dyeing purposes. It also will save energy, time, and manpower. Re-dyeing decreases the yarn quality which also will be improved.

Problem Statement:

The usual process of Micro polyester yarn dyeing and some characteristics of micro-polyester yarn such excessive strike absorbing of dye creates shade variation and some others deformity like whiteness in the shade which tends the whole batch to re-dyeing process.

There are some more issues like miss-collaboration between people of lab and bulk. There are some technical issues like lack of proper controlling the measurements of PH level or water level and such other things on the factory which shows huge deformity on the final dyed products and which tends the whole batch to re-dyeing process.

Comparison with normal polyester, micro-polyester needs more amount of dye due to its largest surface than normal polyester. So, when it requires reprocessing the dying it becomes much more costly to the manufacturers. It’s also more time flopping.

So it becomes a countable issue to think about. By solving or reducing this re-dying rate or increasing the RFT% manufacturer can produce dyed micro-polyester yarn with less wastage of dye, less production cost, and less damaged yarn because reprocessing creates other damages to the yarn.

As a result, it increases 50% cost due to the extra required amount of Dye, Acid, Dispersing Agent and it takes 3/4 times extra time to get the desired shade. So it is high time to make a transformation.

Pre- cautions or monitoring aspects:

Better dye house water quality was ensured for the dyeing of goods by testing water hardness, pH etc. in the lab before starting the whole process. The strength and purity of the reagents were checked before using for bulk production.

Lab dip written information was double checked with order sheets. Dyes, yarn were also double checked to ensure expire date, strength, desired color which is updated or required for dyeing, during lab dip development: pre-treatment procedure, dyeing procedure, after-treatment procedure & parameters were checked perfectly such as calculation.

The yarn, dyes and chemicals used for lab dip must be same for the bulk dyeing process. For the bulk dyeing same substrate (yarn) and the same reagents were ensured that was used for lab dip development.

Because materials difference is not acceptable for getting desired result to the bulk production. Each operation involved from lab dip development to bulk dyeing followed with great care for achieving RFT.

Experimental:

Experiments was performed in two methods-

  1. Conventional or Running method.
  2. Recommended method.

Materials:

100D Filament, disperse dyes were collected from the dyes and chemical store of Southwest Composite Ltd, Chandra, Bangladesh and dyeing chemicals and auxiliaries used were collected from the dyes and chemicals store of Harris & Menuk (BD) Ltd.

For lab dyeing, the sample weight was 2grams

For bulk dyeing, the sample weight was 3.18kg

Development of the Lab Dip:

A color standard was selected for the development of lab dip. A recipe was created, and different small amount (2g) were dyed with the relevant recipe. The dyed samples (4 samples i.e. A, B, C, D) were submitted to expert for lab dip approval. The expert-approved the closest sample (A) for the bulk dyeing production.

The shade% of three colors of different sample was-

  1. Low energy Dye:

Name                     Shade%

Forasil ACE Red         1.4

Forasil ACE Yellow    1.8

Forasil ACE Blue        0.23

  1. High energy Dye:

Name                            Shade%

Forasil D/Red SWF          1

Forasil Yellow 4GNLS     0.75

Forasil N/Blue HXF          0.09

The lab recipe of the lab dip along with the sample was preserved for reference.

Recipe:

For Conventional process:

Dyeing:

M:L= 1:10

Pre-treatment:

Rinse with fresh water

Dyeing:

Buffer- 0.5 g/L

Levelling agent-2g/L

Acetic acid- 0.5g/L

Time:40min

Temperature:130°C

Reduction cleaning:

Caustic-2g/L

Hydros-4g/L

Time: 20min

Temperature:70°C

Neutralization:

Acetic acid- 0.5g/L

Time: 10min

For Recommended Process:

Dyeing:

M:L= 1:10

Pre-treatment:

Detergent – 1g/L

Time:20min

Temperature:70°C

Dyeing:

Buffer- 1g/L

Anti-foaming-1g/L

Wetting agent-1g/L

Levelling agent-2g/L

Time:60min

Temperature: 135°C

Reduction Cleaning:

Caustic- 2g/L

Hydros- 2g/L

Time: 20min

Temperature: 70°C

Neutralization:

Acetic acid- 1.5g/L

Time: 20min

Temperature: 60°C

Dyeing procedure:

First, certain amount yarn/filaments are taken then it rinses with water properly. Then it is pre-treated with certain amount (2g/L) non-ionic detergent for 20min at 70°C. Then the yarn or filaments are rinsed with fresh water. After completing the pre-treatment required amount Buffer, Anti-foaming, Wetting Agent, levelling agent are given to the vessel throughout dossing then the machine is run for 10-15 min then Ph of the vessel is checked. pH should be between 3.5 to 4.5.

After confirming the pH range required amount dyes are given to the vessel throughout dossing for 30min. after completing the dyes dossing, the machine temperature is increased 1.5°C per minute till 70°C then 1°C per minute till 135 then the machine is run for 60min at 135°C to complete the dyeing process.

After completing the dyeing process machine temperature is decrease 1.5°C per minute till 50°C or room temperature. Then yarn/filaments are rinsed with water after that it is treated with caustic (2g/L) and Hydrose (2g/L) for 20min at 70°C to complete the reduction cleaning. Then it rinses with water and then it neutralizes with acetic acid for 20min at 60°C then rinses with water then send to drying section.

Graphical Representation of Recommended Process:

Dyeing-curve-recommended-process
Figure 2: Dyeing curve of recommended process.

Result & Discussion:

On this project four experiments have performed on four different aspects which are-

Sample-1: Conventional process with Low energy dye

Sample-2: Conventional process with high-energy dye

Sample-3: Recommended process with low energy dye

Sample-4: Recommended process with high energy dye

Spectrophotometric Evaluation:

All samples were measured by using (Datacolor 650™) under the light source of F11/10 Degree & D65 10 Degree.

  1. Colour difference of Sample-01 was 3.25 for D65 10 deg. and 3.15 for F11 10 and metamerism index is 0.48.
  2. Colour difference of Sample-02 was 4.89 for D65 10 deg. and 5.12 for F11 10 and metamerism index is 0.39.
  3. Colour difference of Sample-03 was 5.17 for D65 10 deg. and 4.90 for F11 10 and metamerism index is 0.67.
  4. Colour difference of Sample-04 was 3.12 for D65 10 deg. and 3.08 for F11 10 and metamerism index is 1.25.

Among all the data of four different sample, Sample-04 which means “Recommended process with high energy dye” is showing the lower color difference than others.

Colour fastness to Wash (ISO 105 C06 (C1S)): Grading has been done according to greyscale for colour change & staining.

Table: 01 Colour fastness to wash
Sl No Sample Name CH Staining
Wool Acrylic Poly Nylon Cotton DA
1 Low + Conventional 4 – 5 4 – 5 4 – 5 4 – 5 3 – 4 4 – 5 4
2. Low + Recommended 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5

Colour fastness to rubbing (ISO 105 X12): Grading has been done according to grey scale for staining

Table: 02 Colour fastness to rubbing
Sl. No Sample Name Grade
Dry Wet
Low + Conventional 4 – 5 4 – 5
Low + Recommended 4 – 5 4 – 5

Colour fastness to Perspiration (Alkali, ISO 105 E04): Grading has been done according to grey scale for colour change & staining.

Table: 03 Colour fastness to perspiration (Alkali)
Sl No Sample Name CH Staining
Wool Acrylic Poly Nylon Cotton DA
1 Low + Conventional 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5
2. Low + Recommended 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5

Colour fastness to Perspiration (Acid, ISO 105 E04): Grading has been done according to grey scale for colour change & staining.

Table: 04 Colour fastness to perspiration (Acid)
Sl No Sample Name CH Staining
Wool Acrylic Poly Nylon Cotton DA
1 Low + Conventional 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5
2. Low + Recommended 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5 4 – 5

Colour Fastness to Artificial light: Xenon arc fading lamp test (ISO 105 B02:2014): Grading has been done according to reference blue wool

Table 05 Colour fastness to artificial light
 

Sl. No

Sample Name Grading
1. Low + Conventional 6
2. Low + Recommended 6

 Result Discussion methodically:

By analysis the experiments data, it can be said that the color fastness on Wash, Acid, Alkali, and Perspiration all the samples are quite good. However, in all the samples in CMC Data color test, the color difference of Sample-4.  I.e. the sample dyed in the recommended process with High Energy Dye is the lowest.

Therefore, it can be said that if micro-polyester is dyed in the recommended process of this project with high-energy dye, then better results will come. However, several more improvements are needed to obtain RFT.

The result implies that factory will get better result than other process if micro polyester yarn is dyed by recommended process of this project with high-energy dye.

From the above discussions we can easily find out that the limitation to get the RFT dyeing is the manual measurement of dyes and chemicals. If we can minimize this problem, then we can get the Right First Time dyeing. For increasing RFT efficiency this problem should be minimized.

Conclusion:

In conclusion it can be said that It is possible to bring RFT through regular practice and good knowledge about all aspects of dyeing product and its application. RFT comprises great importance for quality production within delivery time. It is not RFT but a challenge for smooth production with quality products without waste of money & time.

So many points needed to be checked and ensured for the right production with right quality. Accordingly, dye house water quality needs to be ensured for dyeing goods by testing water hardness, pH etc.

Acknowledgement:

First and foremost, praises and thanks to the God, the Almighty, for His showers of blessings throughout my project work to complete the project successfully.

I would like to express my deep and sincere gratitude to my academic supervisor Maitry Bhattacharjee, Departmental head, Shyamoli Textile Engineering  College,  helped me by providing the information of academical topic about my project. As Industry expert Md. Salauddin Sk Technical, Manager-ARL, Harris & Menuk Chemicals(BD) Ltd helped me in finding it’s root cause and it’s solution in this project.

To sum up my whole project and to do various experiments in industry I got initial help from Mizanur Rahman, AGM(yarn dying), Southwest composite Ltd as my industry supervisor.

I would like to cordially thanks Textile Today and Peoples Team for giving me this platform and taking the initiative to fulfil my vision and helping the new generation to restrict the upcoming damage of our environment as well as on our economy.

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

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