Usage & Application in Textile Industry

Sodium Hydroxide (NaOH), also known as Caustic Soda, is one of the most essential chemicals in textile processing. In liquid form (32–45%), it is widely used in scouring, bleaching, mercerization, dyeing preparation, and wastewater treatment.

1. Main Applications in Textile Processing

✔ 1. Scouring of Cotton & Cellulosic Fibers

Caustic soda is the primary alkali used in scouring to remove:

Natural waxes

Oils and fats

Pectins

Impurities and dirt

Benefits:

Improves fabric absorbency

Enhances dye uptake and levelness

Prepares fabric for bleaching or dyeing

✔ 2. Mercerization Process

One of the most important uses of liquid NaOH.

Functions:

Swells cellulose fibers

Increases dye affinity

Improves color brilliance and depth

Enhances tensile strength and luster

Concentration used:
Usually 24–28° Bé (around 28–32% NaOH), but liquid 32–45% can be diluted accordingly.

✔ 3. Bleaching Preparation

Used together with hydrogen peroxide in bleaching.

Benefits:

Provides alkaline medium required for H₂O₂ activation

Ensures complete removal of natural pigments

Improves fabric whiteness and brightness

✔ 4. pH Adjustment in Dyeing Processes

Helps maintain alkaline pH for:

Reactive dyeing of cotton

Vat dyeing

Sulphur dyeing (reduction stage)

Effects:

Improves dye fixation

Enhances color yield

Ensures stable dye bath conditions

✔ 5. Neutralization & Chemical Cleaning

Used for cleaning dyeing machines, pipelines, and vessels:

Removes grease and organic deposits

Helps dissolve residues before batch changes

Stabilizes equipment performance

✔ 6. Textile Wastewater Treatment

Sodium hydroxide is used for:

pH adjustment before flocculation

Acid neutralization

Precipitation of metals

Supporting coagulation of dye and chemical residues

2. Dosage Guidelines (Industry Range)

Dosage depends on fabric type, equipment, and process parameters.

Scouring: 5–60 g/L (depending on process)

Mercerization: 24–28° Bé (adjusted from 32–45% NaOH)

Bleaching (with H₂O₂): 2–10 g/L

Reactive dyeing pH control: 1–5 g/L

Machine cleaning: 1–4% solution

3. Advantages in Textile Processing

Strong and effective alkaline agent

Enhances fabric absorbency and dyeability

Improves brightness and color depth

Ensures stable bleaching and dyeing performance

Compatible with automated dosing systems

Easier to handle compared to flakes

4. Safety & Handling

Corrosive → avoid skin and eye contact

Store in PVC/HDPE tanks only

Wear gloves, goggles, and protective clothing

Keep away from acids and incompatible organic materials