Desizing

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DESIZING Desizing :

Desizing is the first wet processing step in textile technology employed to remove the sizing material from the fabric specially the woven fabrics).

Objects of desizing: To remove starch from the fabric. To increase absorbency of the fabric. To increase lusture of dyeing and printing. To perfect action of scouring and bleaching. To make the fabric ready for the next subsequent process.

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DESIZING Methods of Desizing Hydrolytic method Oxidative method. Rot Steeping. Bromite de

sizing. Alkali steeping Chlorite de

sizing. Acid steeping. Ammonium per Enzymatic steeping. sulphate

desizing.

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METHODS OF DESIZING Rot Steeping: In this method, fabric is passed through a padding mangle

containing warm water of 400C-600C and the fabric is kept for prolonged stocking.

Starch is removed by rotting. It is very oldest method when man cannot know the use of enzymes or other special chemicals.

No special chemicals are required. If warm water temp 40˚ C then the fabric is stored for 24 hours stocking &

if warm water temp 60˚ C then the fabric is stored for 12 hours.

Advantage:

a. No chemical used.

b. Cheap process. Dis-advantage:

a. Large floor space required.

b. Very slow process.

c. Dis continuous process.4

METHODS OF DESIZINGAlkali steeping: In this method the starch is removed

by the alkaline hydrolysis. The fabric is treated with 0.4-0.6% Caustic soda solution at 60˚C to 70˚C and stored for 8 to 10 hours.

Precaution: Care must be taken that, goods do not dry up, otherwise, it causes partial concentration of alkali.

Advantage: Economically use and cheap. Mercerizing can be done in same alkali (reusable). Dis-advantage: Considerable shrinkage may occur.

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METHODS OF DESIZINGAcid steeping: In this method , 0.5-1.0 % dilute

Sulphuric acid solution or HCl acid at 40-60˚C is used for 4-6 hrs to hydrolyses the starch from the sized fabric.

Advantage: The amount of size removed is comparatively greater. Good de sizing is obtained and not possible to shrinkage. Dis-advantage: Very risky process, due to hydrolytic degradation will occur

which fall the strength of cotton. Large floor space required. Dis-continuous process

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METHODS OF DESIZINGEnzymatic steeping / Enzymatic de sizing: This method is traditional process and most

commonly used now a days. Enzyme: Enzyme is one kind of Bio-catalyst. Its

molecular wt is high but different from chemical catalyst. The action of enzymes controlled by temp, concentration, time and pH of the solution. Most enzyme have no action at temp. above 75˚C

Enzymes are living organism. It is based on protein. Its main function is fermentation of starch.

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ENZYMATIC STEEPING / ENZYMATIC DE SIZING

Types of enzymes: Mainly two types: Cellulose enzymes: (degrade cellulose and if more time then

cellulose damage and convert glucose) Amalysis enzymes: Outstanding features are – only

hydrolyses the starch but do not attack cellulose. So it is used for de sizing.

Types of amalysis enzymes and its examples: Malt extract /malt preparation enzymes. Bacterial extract enzymes. Pancreatic analysis enzymes.

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ENZYMATIC STEEPING / ENZYMATIC DE SIZING

Enzymatic desizing process/Continuous desizing process:

Continuous process of cotton de sizing by enzymatic desizing process as below;

Recipe:

Malt extract: 0.5 – 2%

Time→ 3-4 hrs. (for stronger solution 5 min.)

Temp →50-60˚C

pH→6-7.5 Here malt extract used as desizing agent. The whole process of desizing

is completed by following stage. Preparation of desizing mixture: Padded in padding mangle Storing: Washing:

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SOME DESIZING MACHINES

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SOME DESIZING MACHINES

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