Prashant Dave
Textile Technologist, India
Email: prashant.c.dave@gmail.com
Overview: Cold pad batch peroxide bleach is done to remove color and impurities from textiles, particularly cotton fabrics. It is called “cold” because it is carried out at a lower temperature compared to traditional hot bleaching methods, which helps to conserve energy and reduce the risk of damage to the fabric. Cold oxidative process is started long ago and it’s basically carried out through peroxide with low temperature up to 48°C when conventional hot bleach is carried out at high temp between 80°C to 115°C.
Due to Low temperature it is safest process in terms of minimum damage to fibre. It’s slow reaction that’s why needed batch time high 10-24 hour depends on fibre quality type. Peroxide activator can increase the reaction rate.
Pros:
Minimum fibre damage & High strength compare to hot bleach method
Less Machinery also can operate the process, benefited to small scale industries also.
Where process water is used its best practice to follow to reduce possibility of catalytic reaction.
Linen, Tencel and regenerated fabric also can be applied on it.
High Lycra blends some times more curl in long process could be overcome curling in Oxidative-wash or Oxidative-tight bleach route.
Cons:
Batch time is high 10-24 hr can increase the process time effect on productivity
Chemical dosage required high compare to hot bleach due to slow reaction rate to achieve desired quality results.
Due to temp, time and residual peroxide difference in the fabric layers’ top to bottom quality have slightly more variation compare to hot bleach, it can be optimized by minimum batch size and optimum rotation time with use of peroxide activator, and high pick up wetting agent.
Starch removing difficult in this process up to some extent it can be overcome with use of sodium Per-sulphate.
Factor:
Liquor pick up – It needs high pick up above 80%-100%
Bath pH – It needs alkaline pH >11
optimum Liquor bath quantity – High liquor give risk of size build up.
Penetration – After padding require some air passage time to penetrate in to fibre.
Rotation – Rotation speed need slow and consistent till end dwell time to distribute excess chemical uniformly.
Wrapping – Wrapping prevent the treated fabric form outer environment air to reach to fabric it can dry up the fabric lead the high concentration of chemical and can degrade or create difference in whiteness or quality aspect.
Washing – High temp washing can extract the impurities and proper water flow can adhere the re-deposition of it.
Booster – Use of Caustic with Extracting and surfactant in first two wash box can boost the results.
1) For Cotton, PC & Cotton Lycra (Route – Cold Pad Oxidative – Rotation – Wash):
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
