Scouring | Types of Scouring Process | Application of Scouring in the textiles dyeing industry

Introduction: Scouring is a procedure through which natural impurities (oil, wax, gum, fat, etc) and added impurities are eliminated fully during the manufacturing process. 

All raw textiles are referred to as 'gray fabric material' when in natural form. This gray fabric is natural with color, odor, and impurity not appropriate for clothing. Not only are the natural impurities remaining on the gray matter but also the additional products produced during cultivation, e.g. raw cotton has impurities such as water, nitrogen, mineral matter, waxes, pigment residues, etc. 

The elimination of these natural colorants and add-ons to create the material in a phase ready for dyeing is called scouring.

Scouring objectives: The principal aim of scouring is to remove textile material impurities. Some other objectives are;

• In order to make the material extremely hydrophilic.
• To considerably absorb textile products without suffering chemical or physical harm.
• A neat material is generated by adding alkaline.
• For cotton removal of non-cellulosic material.
• In order to make the textile material prepared for subsequent bleaching.

Scouring Process in Dyeing Industry

Method of Scouring: Scouring may be done separately or in conjunction with other treatments (usually bleaching or de-sizing) in all types of substrates;

• Woven fabric (sized or de-sized).
• Knitted fabric.
• Yarn.

For yarn and knitted textiles, scouring is typically a batch process carried out on the same material that is later used for dyeing. Woven fabric is continuously scoured using the pad-steam method.

So, actually, there are two types of method are using for scouring;

1. Batch process/Discontinuous process. (by Kier Boiling/Jigger/Winch dyeing machine)
2. Continuous process. (by J-Box machine)

1. Batch process/Discontinuous process: In the batch or discontinuous process, Kier Boiling machine is mostly used. There also we used Jigger and Winch dyeing machine. But here we only discussed the scouring process of Kier Boiling machine. 

Kier Boiler is a cylindrical long, mild steel or a cast-iron container fitted with two tubular perforations (disc with several holes). One of them is on the ground, and one is on the top. These disks are linked to the upper compartment with a number of tunes which bring the liquor. Steam is carried through the center of the bay. Thus, the liquor pipes are surrounded by steam that heats them.

Kier Boiler Machine

Recipe for batch scouring process:

SL. No.	Parameter	Amount
1	M:L ratio	1:100
2	Caustic Soda	0.5 – 2.4 g/L, 50 – 240 gm
3	Soda ash	0.5 – 1g/L, 50 – 100 gm
4	Wetting agent	0.5 – 1g/L, 50 – 100 gm
5	Sequestering agent	0.5 – 1g/L, 50 – 100 gm
6	Temperature	100-120ºC

Precaution needs before batch scouring:

• Clean the kier boiler.
• The material must be uniformly packaged.
• Full immersion of the need for the fabric.
• The liquor should be removed without water after boiling.
• Check all joining components before beginning.
• Scouring solution should always remain for Fabric. 

Process Description of batch scouring: 

1. The fabric is packed into M/C and stored in a tube shape. 
2. A circular tube to the fabric pumps the warm liquor and spray it. 
3. The liquor goes through the packed cloth slowly and collects on the opposite side of the kier. The liquor pumped to the heater again using a centrifugal pump and this cycle is repeated. 
4. After scoring, 80⁰ C water is used to remove material impurities from the textile.
5. Afterward, 0.1% acetic acid is neutralized and cold cleaning is done.

2. Continuous scouring process: In the Continuous process, J-Box machine is used. It is called J-Box machine because the scouring vessel looks like the English letter ‘J’. The J-box is mainly a steel chute with big capacity fabrics. In comparison to a keir where it is first in the last out, the fabric is supplied from one end and pulled from the other (first out). The internal side of the J-box is polished and is insulated to minimize thermal losses. De-sizing, scoring, and bleaching can be performed at once in this system. 

J-Box Machine

Recipe for Continuous Scouring process:

SL. No.	Parameter	Amount
1	M:L ratio	1:100
2	Caustic Soda	5 g/L, 500 gm
3	Wetting agent	1- 4.5 g/L, 100-450 gm
4	Sequestering agent	1-5 g/L, 100-500 gm
5	Impregnation temperature	70-80ºC
6	Storing time in J-Box	2- 4 hours
7	J-Box temperature	100-105ºC

The Continuous Souring process can be separated into four parts of J-Box:

1. Saturation.
2. Pre-heater.
3. J-Box.
4. Washing unit.

1. Saturation: Saturation is made without caustic soda by the above-mentioned recipe. The fabric is then taken into the solution via the guide roller. In this case, the temperature is approximately 0-80 ° C.

2. Pre-heater: The material is transferred to the J-box during pre-heating at the temperature of 110-120 ° C.

3. J-Box: Caustic soda solution from J-Box is maintained and this solution is placed in the fabric. The temperature here is approximately 100 ° C. NaOH responds with and removes the impurities in the fabric in J-Box.

4. Washing unit: Here, the water-soluble impurities or products are removed. The material is first cleaned in warm water and then dried in cold water.

Advantages and disadvantages of Discontinuous and Continuous Scouring process:

SL. No.	Discontinuous Process	Continuous Process
1	In this process fabric is scoured in rope from.	In this process fabric is scoured in open width form.
2	This process is suitable for small order.	This process is not suitable for small order.
3	Uneconomical process for large order.	Economical process for large order
4	More time required then continuous process	Less time consumption process

Scouring is a very important process before dyeing. Scouring will depend on the kinds of fabric, the color of the fabric, the cleanness of fabric, the twisting of fabric, the count of fabric, and the fabric construction. 

By the scouring process, Pectose and pectin are transformed into pactic acid-soluble salts. It dissolves mineral matter. Particles of dust will be removed. Residual materials are divided into soluble products.

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