Ozone Machanism of Denim Washing to Produce Faded Jeans - Bleach without Bleaching

Posted by Sustainable Denim on Monday, August 26, 2019 0

Faded jeans are produced by washing  raw denims with bleach and enzymes. Most widely used bleach are sodium hypochlorite, calcium hypochlorite, hydrogen peroxide, and potassium permanganate. All of these bleaching chemicals are caused corrosion to machines, weaken the fabric strength, and high exposure can be harmful to workers.

As alternative of conventional bleaching process, Ozone (O3) mechanism can be used as Ozone is a powerful bleaching agent that is generated from oxygen (O2). Ozone works quickly and requires less number of rinses compared to other bleaching methods. At the end of the bleaching process the residual Ozone is again converted into oxygen and discharged into atmosphere.

Generation of Ozone:

Ozone can be generated by the following methods-

  • Produced from smog
  • Produced from UV lights
  • Produced from Electrical discharge or Corona discharge
  • Electrolytic ozone production.

Commercially the ozone is produced from Corona discharge and in most denim washing this method is followed.

How Ozone is generated from Corona discharge or dielectric discharge?

Ozone is produced from electrical discharge that is widely known as a spark. Most amount of ozone are produced from lightening during a thunderstorm. Any electrical discharge, or spark creates ozone. The spark splits the oxygen molecule (O2) into single element of oxygen (O). These split Oxygen atoms quickly bind with another oxygen molecule (O2) to form ozone (O3).

The electrical energy used in ozone generation splits the oxygen molecule. The theoretical energy required to split the oxygen molecule is described below:

    0.82 kWh of electrical power for every 1 kg of ozone generated

    0.372 kWh of electrical power for every 1 lb of ozone generated

In a corona discharge ozone generator the electrical discharge will take place in an air gap within the corona cell designed specifically to split the oxygen molecule and produce ozone. In this air gap a dielectric is used to distribute the electron flow evenly across this gap to spread the electron flow to as great a volume of oxygen as possible. Learn more about ozone generation from oxidationtech.com

Treatment of raw denim in Ozonator:

Raw denims are treated in Ozonator to get faded look. Based on the timing of treating garments in Ozonator the intensity of fading is determined. Before treating any raw denim into Ozonator it has to be rinsed in cold water to remove the unfix dyes from the surface. After rinsing the garments are squeezed in a hydro extractor.

Then the garment is put into Ozonator and fix the timing of oxidation and then cleaning successively. After treatment with Ozone the garments are washed with detergent to remove dye particles and the odor of Ozone.

Many reputed companies are offering high technology based Ozonator for denim washing, Jeanologia, Yilmik, Avantec, Brongo are widely known.

How do Indigo molecules break down by ozone to give faded look?

Ozone is treated with Indigo dyes to produce new compound which is called Phenyle Glycine (color less) and Isatin (yellow color). Because of this yellow compound the ozone treated garments are looked a bit yellow and vintage.

Benefits of Ozone finish:
  • Lower costs and higher profitability
  • 60% less and even no water in denim processing
  • Lower the utility costs and cut it up to 50%
  • Used as self anti back staining of denim
  • Maximum full bleach down capability 
  • Bleach without any chemicals
  • Bleach with no water or heated water
  • Creative , safe & productive
  • Water less & green
  • Sustainable, profitable & environment friendly

About the Author

Md. Firoz Kabir(M.Sc in Textile Engineering)

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