1. Shree guru gobind singhji institute of
engineering and technology
DEPARTMENT OF TEXTILE TECHNOLOGY
2. Desizing
INTRODUCTION:- Removal of size paste/ starch after weaving from the fabric. Fabric becomes free from the size paste by this .
CLASSIFICATION OF METHODS FOR DESIZING:-
1.HYDROLYTIC :- 2. OXYIDATIVE:-
Rot steeping
Alkaline Chlorite
Acid desizing Bromite
Enzymatic desizing
3. Objectives of desizing
To remove starch paste from fabric
To increase the absorbency power of fabric
To increase affinity of fabric to dry chemicals.
To make fabric suitable for next process.’
To increase the lustre of fabric and dyeing and printing.
4. Rot steeping desizing.
advantages :-
1. Cheapest method compare to other.
2. No chemicals are required.
Disadvantages:-
1. Requires more space.
2. It is slow process, so desizing time is long
3. Mildew may attack the cloth during steeping.
4. And cause scales on fabric.
6. Process –
1. Hydrochloric acid or dilute supjhuric acid used to hydrolyse the starch from fabric.
2. 0.25% -0.5% solution of acid at room temperature is suitable for this process.
3. The cloth is impregnated with diluteacid soln. in a bowl for 8 – 12 hours in a closed concrete pit.
7. Advantages-
1. It is economical process.
2. This process is effective and give fairly uniform desizing.
3. This process is qquicker than rot steeping.
Disadvantages-
1. The mineral acid which harmful to cellulose fibres if proper care is not taken.
2. Especially during storage stage, acid- wet fabric must not allowed to dry.
3. This would cause formation of hydrocellulose ,which will weaken the fibre,
9. Enzymatic desizing
What is enzyamatic desizing ?
--- its main intension is to remove starch from fabric. Contain amylase.
How does amylase works on starch?
1. effect of inadequate desizing .
2. checking effectiveness of desizing
3. some typical size may not be affected by enzyme action i.e. tapiaco starch.
10. enzymes
What Is enzyme ?
Types of enzyme:-
a substance produced by a living organism which acts as a catalyst to bring
about a specific biochemical reaction.
Vegetable Distase
Bacteria Rapidase
animal Amylase
Desizing enzymes are:
Animal origin: Viveral, Degomma, waste pancrease,
cotted blood, liver etc.
Vegetable origin:
i, biolase, Taka etc.
11. Condition for enzymatic desizing:-
Enzyme Concentr
ate g/L
Temperat
ure (ºC)
pH
Pancreati
c (animal)
1-3 50-60 6-7.5
Malt
extract
3-18 50-60 6-7.5
Bacterial 0.5-1 60-70 5.5-7.5
12. Advantages :-
Time require for enzymatic desizing is less.
No fibre damage occur.
It is continuous process so greater production is possible by this.
There is no chance for cellulose to hydrolysed like acid desizing.
Disadvantages:-
If condition like temperature ,pH, time not maintained properly the desizing activity of enzyme
is destroyed.