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:

>Amylase enzyme
>pH stabiliser
>Chelating agent
>Salt
>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:
Inadequate enzyme
Inappropriate desizing bath pH
Inappropriate desizing-bath temperature
Insufficient fabric pick-up
Insufficient digestion time
Poor enzyme activity
Deactivation of enzyme due to presence of metals or their contaminants
Ineffective wetting agent
Incompatible wetting agent

Remedies:
Sufficient enzyme
Optimum pH
Optimum temperature
Optimum squeeze pressure and Use of wetting agent
Optimum digestion time
Use of good enzymes
Use of soft water and Use of appropriate sequestering agents
Use of good and effective agent
Use of compatible wetting Agent

B. Uneven Desizing (widthways)

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

Remedies:
Uniform squeeze pressure
Uniform bath temperature
Uniform chemical concentration

C. Uneven Desizing (lengthways)

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

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

D. Uneven Desizing (random)

Causes:
Poor wetting agent
Inappropriate bath temperature
Foaming in the bath
Improper use of defoamer
Uneven liquor distribution during padding
Non-uniform washing after desizing

Remedies:
Use of effective and compatible wetting agent
Optimum bath temperature
Use of appropriate defoamers
Use of appropriate defoamers
Uniform liquor distribution during padding
Thorough and uniform washing after desizing

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