Scouring is the pretreatment process of wet processing technology. It is the first stage of pre-treatment consequently. Before dying or printing textile materials natural fibers must pass the scouring process. The scouring process bears great importance in wet processing undoubtedly.
Scouring is the process by which natural (oil, wax, gum, fat, etc) as well as added (during the fabrication process) impurities wash out completely as possible. The especially hydrophobic character which is present in the fiber of fabric removes by this process.
Objectives of Scouring:
The scouring process is a pre-treatment for textile fiber and fabrics. Scoured textile materials are suitable for the dyeing and printing process. The scouring process has some important objectives. The objectives of the scouring process are as follows. They are-
- Firstly, the main purpose of the scouring is to remove impurities from the textile materials.
- Secondly, the textile materials are leave in a highly absorptive condition without undergoing any chemical or physical damage significantly.
- Above all, after scouring process materials become suitable for next bleaching process.
Effects of Scouring:
The following changes occurred during the scouring process:
- Firstly, saponifiable oils and free fatty acids convertes into soaps.
- Secondly, pectose and pectin changes into soluble salts of pectic acid.
- Thirdly, proteins hydrolyse into soluble degradation products.
- Then, mineral matters dissolves in the water.
- After all, unsaponifiable oils and waxes are emulsified by the soaps form from saponification.
- Lastly, dust particles remove and held in suspension.
In the above, I have written about the saponification process. So, saponification is the reaction by which the insoluble and water-immiscible materials convert into water-soluble products. The reaction is as follows:
Oil + Caustic soda + Water = Soap + glycerin
Methods of Scouring:
The scouring process performs in the following two ways. They are:
- Continuous process: In this process, scouring of the fabric is doing continuously in a J-Box. In this machine, pretreatment and dyeing process continuously perform for next process. Although, this type of application applies very limited way.
- Discontinuous process: This type of process also called batch process. Here, scouring is done discontinuously in Kier Boiler, Jigger or Winch dyeing machine. By the same token, different batch or lot is creates before dyeing process.
In the dyeing machine, different controlling parameters control strictly. I like to give a sample recipe for the scoring process of cotton in the kier boiler.
Scouring process recipe:
Caustic Soda = 0.5 to 3% on the weight of fabric (owf)
Sodium-bi-Carbonate = 0.5 to 1% owf
Wetting Agent = 0.5 to 1% owf
Materials: Liquor = 1: 6/8/10/12 (as required)
Temperature = 100 to 140 degree Celsius
Pressure = 10 to 30 PSI
Time = 60 to 90 minutes
Material forms = Rope or Open width
Scouring is generally done for natural fiber. In fact, better dyeing or printing performance depends on better scouring of the materials. Otherwise, different types of dyeing or printing faults are appearing on the face of the fabric. So, it needs to take care of the scouring process. It also depends on the shade of the fabric. Generally, it is important for light shade dyeing.
Lastly, the Scouring agent is supplied by different textile chemical manufacturing companies. Before using, the scouring agent one should ensure the properties of the scouring agent.
Additionally, scouring is a part of pre-treatment for the production unit. The management should ensure compliance and workplace safety issues. Moreover, the producer can practice 5S, Kaizen, TQM, and TPM for improving the working environment and increasing the profit margin.