Common Problems/Causes and Remedies in Enzymatic Desizing

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Desizing:
The purpose of a desizing process is to remove sizes that have been attached to warp yarns during a weaving process. Prior to the desizing process, therefore, the size analysis should be performed in order to set desizing conditions suitable for the sizes.

Desizing Methods:
Different methods of desizing are: A desizing method is selected on the basis of analysis of size , type of fabric , eco friendliness , ease of removal , cost of desizing and effluent treatment.

Different methods of desizing are:
1. Enzymatic desizing
2. Oxidative desizing
3. Acid steeping
4. Rot steeping
5. Desizing with hot caustic soda treatment, and
6. Hot washing with detergents.

The most commonly used methods for cotton are enzymatic desizing. This desizing process consists of three main steps: application of the enzyme, digestion of the starch and removal of the digestion products. The common components of an enzymatic desizing bath are as follows:

1. Amylase enzyme
2. pH stabiliser
3. Chelating agent
4. Salt
5. Surfactant, and
Optical brightener

Though enzymatic desizing process is most popular and effective but it has some problems. The main problems/defects of enzymatic desizing process are point out below.

A. Incomplete desizing
B. Uneven desizing (widthways)
C. Uneven desizing (lengthways)
D. Uneven desizing (random)

Causes and Remedies of these Problems are Discussed following:

A. Incomplete Desizing

Causes:
1. Inadequate enzyme
2. Inappropriate desizing bath pH
3. Inappropriate desizing-bath temperature
4. Insufficient fabric pick-up
5. Insufficient digestion time
6. Poor enzyme activity
7. Deactivation of enzyme due to presence of metals or their contaminants
8. Ineffective wetting agent
9. Incompatible wetting agent

Remedies:
1. Sufficient enzyme
2. Optimum pH
3. Optimum temperature
4. Optimum squeeze pressure and Use of wetting agent
5. Optimum digestion time
6. Use of good enzymes
7. Use of soft water and Use of appropriate sequestering agents
8. Use of good and effective agent
9. Use of compatible wetting Agent

B. Uneven Desizing (widthways)

Causes:
1. Uneven pad pressure [across the width]
2. Non-uniform pad temperature
3. Non-uniform chemical concentration in the bath

Remedies:
1. Uniform squeeze pressure
2. Uniform bath temperature
3. Uniform chemical concentration

C. Uneven Desizing (lengthways)

Causes:
1. Uneven pick-up (along the length)]
2. Preferential drying of outer layers of the batch
3. Temperature variation during digestion

Remedies:
1. Uniform pick-up along the fabric length
2. Covering the batch with polythene or other suitable sheet and  Keeping the batch rolling
3. Covering the batch with polythene or other suitable sheet and Keeping the batch rolling

D. Uneven Desizing (random)

Causes:
1. Poor wetting agent
2. Inappropriate bath temperature
3. Foaming in the bath
4. Improper use of defoamer
5. Uneven liquor distribution during padding
6. Non-uniform washing after desizing

Remedies:
1. Use of effective and compatible wetting agent
2. Optimum bath temperature
3. Use of appropriate defoamers
4. Use of appropriate defoamers
5. Uniform liquor distribution during padding
6. Thorough and uniform washing after desizing.

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