In textile industry, various pre-treatment process are applied on textile material (viz. fibers, yarn, woven and knit fabrics) to prepare the material for dyeing, printing or finishing. Pre-treatment process plays a crucial role in preparing fabrics for subsequent processes such as dyeing, printing, and finishing. Once the grey fabric is produced by weaving or knitting, the developed fabric passes through several pre-treatment processes before coloration activity. As the grey fabric will have lot of impurities, these impurities hampering the subsequent processes has to be removed and made absorbent to ease the further processes like bleaching, dyeing, finishing, etc. Similarly, the fabric is also subjected to the several finishing processes based on the customer requirements or end use need. But when an apparel manufacturing industry receives a fabric, that fabric must be subjected to all the pre-processing, processing and finishing activities mentioned in the following article. The pre-processing steps involved are generally used to remove the natural and added impurities to the grey fabric during several stages of manufacturing like winding, warping, sizing weaving or knitting, etc. The processing operations are the activities to impart color to the fabric. The main object of pre-treatment is to impart a uniform and high degree of absorptivity for aqueous liquors with the minimum possible damage to the material.
Flow Chart of Pre-treatment Process in Textile:
The general process flow chart of the pre-treatment sequence in textile is provided below.
Receipt of grey fabric from the fabric manufacturer after inspection
↓
Singeing (Singeing process to remove the unwanted protruding fibers)
↓
Desizing (Process of removing the size applied on the warp yarn in sizing)
↓
Scouring (To remove the remaining size particles and other impurities)
↓
Bleaching (To remove the natural coloring matters from fiber and prepare the fabric suitable for dyeing)
↓
Mercerisation (To increase the fabric softness through alkali treatment. This is an optional step.)
↓
Dyeing (Coloration of fabric as requested by the customer)
↓
Finishing (Chemical or mechanical finishing based on the fabric end use requirements)
↓
Heat setting (After all the treatment process, the fabric will pass through compacting or stenter to improve the dimensional stability)
↓
Packing and dispatch (Packing and dispatch to the apparel manufacturing unit for garment production)
Once the fabric from the weaving or knitting industry is received based on the requirements, the fabric will be passing through the various stages as mentioned above. In those reported activities, except for the singeing and mercerization activities, all other activities are common for all the fabrics to achieve good quality for the export. All the pre-processing activities improves the fabric quality and increases the coloration efficiency of the dyeing (known as processing) process. This article details the individual activities and their main objectives for the better understanding of the processes. This will help you to get an overall view of each process and improve the costing process.
1. Singeing: The main aim of the singeing process is to burn the protruding fibers in the fabric through flame or heat. In spinning process, due to the use of staple fibers, the generation of hairiness is unavoidable. But the presence of hairiness will spoil the overall look of the fabric and diminish the quality of dyeing and printing process.
Hence, the process is used to remove the protruding fiber from the fabric surface. The singeing process is performed both the side of the fabric and sometimes, it performed along with the desizing process (next in sequence) in the same machine to improve the productivity and reduce the manufacturing cost.
2. Desizing: Desizing is a process of removal of the applied size paste from the warp yarn. The size paste applied on the yarn improves the yarn strength and helps the warp thread to withstand the stress imparted during fabric production. However, due to the hydrophobic nature of the chemicals used in the process, the fabric cannot be used in the dyeing process as such. The surface coated size pastes must be removed from the yarn to make the yarn more hydrophilic. In this process, the desizing is generally performed by treating the fabric with acid or enzymes along with other ingredients like wetting agent, bleach and sodium chloride as needed.
3. Scouring: It is the process used to remove the impurities from the textile substrate. In this process, the textile material is treated with alkali, surfactants or organic solvents to remove the wax, pectin, proteins, oil stains by lubricant oil and other size residues completely.
4. Bleaching: As the scouring operation removes only the impurities, the coloring matters present in the cotton fiber are removed by the bleaching process. The usual yellow and brown color in the grey fabric need to be removed completely by this process. In this process, different types of bleaching agents are used to remove the color and impart whiteness to the fabric.
5. Mercerization: In this process, the cotton fabric is treated with alkali to improve its luster, appearance and feel of the cotton. It is a non-essential operation. This is performed on cotton fabric whenever, the product needs a special look than the other normal fabric.
6. Dyeing: Dyeing is a process of coloring textile fabric. There are several dyeing methods based on dyes used and machines available based on the type of fiber used in the fabric. The dyeing process penetrates the color particles into the fiber and colors the material. The dyed fabric immediately passes through washing and drying process before moving to the next finishing process.
7. Finishing: The finishing process is again a non-essential process, or value adding process to the fabric. In this process, based on the requirement we can improve the performance of the fabric by treating the fabric with special chemical. Example, flame retardant fabrics, hydrophobic fabric, etc.
8. Heat setting: It is a general process used in the synthetic textile. However, in recent times, all the fabrics are treated with heat setting process in different names like stentering or compacting. The dimensional changes of fabric in the chemical processing stages will be stabilized during this process (both length and width wise), and then passed to the garment manufacturing process.
Conclusion:
Satisfactory pre-treatment process of fabric before any value addition process such as bleaching, dyeing, printing and finishing makes major contributions to consistent attainment of the desired end-product quality. In order to get the best results, we should conduct right pretreatment right at first instance. Each pre-treatment process in textile, from singeing to heat setting, plays an important role in achieving the desired characteristics and performance in the final textile product.
References:
- Handbook of Textile and Apparel Costing by Dr. R. Rathinamoorthy, Dr. R. Surjit and Dr. K. J.Vishnu Vardhini
- Pretreatment of Textile Substrates by Mathews Kolanjikombil
- Handbook of Value Addition Processes for Fabrics By B. Purushothama
- Chemical Technology in the Pre-Treatment Processes of Textiles by S. R. Karmakar
From this reel i had came to many ideas about how textile was made