Desizing

The aim of desizing is the elimination of the size material from the fabric. Fabric which has not been desized is very stiff, causing difficulty in its treatment with different solutions in subsequent processes.

After singeing operation the size material is removed by making the starch water soluble and washing it out with warp water.

Object:

1. To remove the starch from the fabric.
2. To increase absorbency of the fabric.
3. For perfect action of scouring and bleaching.

Singeing ingredients:

1. Starch: Corn, Potato, Sago.
2. Natural gum: Locust bean.
3. Proteins: Glue, Gelatin.
4. Synthetic Sizes: PVA.
5. Additives: Thickeners, waxes.

Methods of desizing:

1. Hydrolytic method:
1. Rot steeping.
2. Alkali steeping.
3. Acid steeping.
4. Steeping in enzymes.
2. Oxidative method:
1. Bromide desizing.
2. Chloride desizing.

Rot Steeping:

Controlling point:

i. Store time = 12-24 hours.

ii. Temperature = 40ºC (24 hours).

                                 = 60ºC (12 hours).

Advantage:

i. Not expensive method.

ii. No chemical use.

Disadvantage:

i. Large floor space required.

ii. Very slow process.

Alkali steeping:

Controlling points:

i. 0.4-0.6% caustic soda.

ii. Time: 8 to 10 hours.

iii. Temperature: 40ºC (10 hours).

                                 : 60ºC (8 hours).

Acid Steeping:

i. 0.5-1.0% H2SO4 or HCl.

ii. Time = 4-6 hours.

iii. Temperature = 40ºC (6 hours).

                                  = 60ºC (4 hours).

Enzymatic process:

Desizing conditions:

Types of enzyme	Temperature	pH	Concentration(g/L)
Pancreatic	50-55	7-7.5	1.5
Malt extract	50-60	5-7	3-2
Bacterial	65-75	5.5	0.5-1