Scouring Process in Textile: A Complete Technical Guide
Definition
Scouring is the chemical washing process of removing natural impurities such as waxes, oils, pectins, and other non-cellulosic materials from the fabric, especially cotton. It enhances the hydrophilicity of the fabric and prepares it for further wet processes.
Objective
- Remove natural and added impurities from fibers
- Increase water absorbency
- Improve whiteness and cleanliness
- Prepare fabric for dyeing, bleaching, or printing
Flow Chart
Parameters of Scouring
- Temperature: 95°C to 130°C
- Time: 30 to 90 minutes
- Alkali concentration (NaOH): 2–5%
- Wetting agent: 0.5–1 g/L
- Stabilizer (e.g., sodium silicate): 1–3 g/L
Chemicals Used and Their Purpose
Sodium Hydroxide (NaOH): Breaks down waxes, oils, and natural fats.
Wetting Agents: Improve penetration of chemicals into fabric.
Sequestering Agents: Remove hardness of water to prevent staining.
Detergents: Help remove loosened impurities.
Types of Fabric Used
- Cotton (woven and knit)
- Linen
- Blended fabrics (with high cotton content)
Scouring Process (Step-by-Step)
1. Fabric is padded with a hot alkaline solution.
2. Passed through a steamer or J-box for reaction time.
3. Alkali breaks down natural fats and impurities.
4. Fabric is thoroughly washed with hot and then cold water.
5. Neutralized if required and dried.
Machines Used
- Continuous Scouring Range: Includes saturator, steamer, washer, and dryer.
- Winch or Kier Boiler: Common in batch scouring for small to medium fabric lots.
Changes During Scouring
- Removes waxes and oils
- Increases whiteness and absorbency
- Improves dye uptake and uniformity
- Reduces yellowing and patches in dyeing/printing
Examples
- Scoured cotton fabric used for medical textiles due to high absorbency
- Knit fabrics scoured before dyeing for soft hand feel
- Terry towels scoured for better water retention
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