What is Textile Desizing?
Desizing is an essential stage of all textile processing, in which ‘size’ is removed from fabric before completing the pre-treatment process, which is necessary before dyeing, printing and finishing.
Where does the size come from?
Before yarn is woven into fabric, the ‘Warp’ yarns are coated with sizing agents. This strengthens the yarn (decreasing breakages on the loom), reduces friction and improves productivity.
However the sizing agents often resist the dyes and chemicals commonly used in textile processing, so they have to be thoroughly removed before any wet processing can take place.
Most sizing agents (particularly for cotton yarns) are starch-based, for reasons of economy and weaving performance.
Why enzymatic desizing?
Historically, a number of desizing methods have been used in the textile processing industry, involving bulk chemicals, such as acids, caustic soda, detergents or bacterial material. Obviously, these were both costly and harmful to the environment, as they required large amounts of energy, hot water and subsequent effluent treatment and disposal.
Nowadays, enzymatic desizing – removing starch using enzymes – is by far the most widely used method and is accepted as standard by the textile processing industry.
What are the advantages of enzymatic desizing?
- No damage to the fibre
- No use of aggressive chemicals
- Wide variety of application processes
- Some optical brighteners can be incorporated in the desizing process
- High biodegradability
How does Enzymatic Desizing work?
Enzymes are complex organic, soluble proteins, that catalyze chemical reaction in biological processes. A small quantity of enzyme is able to break down a large amount of starch. A typical amylase enzyme hydrolyses the starch (so it can be rinsed away) without damaging cellulose fibre.
Until recently, desizing enzymes could only operate at temperatures below 75°C and within quite a narrow pH range.
But the ‘next generation’ of alpha amylase enzymes, such as PrimaGreen® ALL have been engineered to desize textiles throughout a much broader spectrum of operating conditions (from 20° – 105°C and pH of 6-10).