Source: The Stitch Times
Over the last eight years, Ozone has made a prominent place for itself in the garment processing industry all over the world. Widely used as a bleaching agent, Ozone remains a powerful, secret tool within the denim industries that gave denim garments an unique and distinctive look and feel from other traditional processing.
Even today, many manufacturers in India still feel that by using Ozone Gas their denim garments they would simply bleach them to lighter blue only. This is true since the Indian denim manufacturers and users are used to the brighter colour of Indigo achieved with the help of optical brighteners that sometimes it is difficult for them to accept the duller colours achieved through Ozone processing.
Though it changes the colour of the Indigo dye, Ozone eliminates tinting from the reverse of the denims as also from the sewing thread, pocket fabric, labels, zippers, buttons etc. giving the garment a cleaner look. Ozone also destroys all air borne micro-organisms including bacteria, virus, mold, fungi, spores, etc. It also oxidizes the volatile organic chemicals, including aromatic chemicals reducing them into lower molecular organics which are no more aromatic in nature; hence the hand-feel in garments is enhanced after the treatment. Furthermore, the discharge of the Ozone purifies the atmosphere by adding freshness and giving clear, pollution free-oxygen rich air.
Since ozone has the bleaching property, low ozone dosage helps in avoiding bleaching action, while enabling the washed clothes come out brighter it also sanitized them at the same time. Ozone's sanitizing property makes it very relevant to the hospitals as also the hotels. The use of ozone reduces the requirement of detergents and also the wash can be achieved at lower temperatures. Thus, a specially designed Ozone system helps in reducing the use of water as well as energy cost for heating, resulting in large savings. Besides this, the added advantage is that the waste water from the laundry has much lower detergent contents which requires very little or no waste water treatment prior to letting it out in to the sewage system.
In the Ozone processing system, first the Ozone is generated by isolating pure Oxygen from atmospheric air through sophisticated electrodes and pump that air to next equipment fitted with another set of electrodes that convert oxygen into ozone and pumps it for garment processing. To maintain the purity of the ozone generated, the temperature is kept below 14C during the conversion for which chilled water is used. Special chillers are used for this purpose along with ozone generators.
Tumbler is the third part of this process, where ozone gas is introduced and removed after processing. The process time is 15 to 20 min. per batch, as the volume of the tumbler requires 10 to 12 min. to refill and 8 to 10 min. holding time for the Ozone gas. During this time; tumbling action slowly turns over the garments for even exposure to the gas circulating in the entire tumbler. Later, with the help of the exhaust pipe the gas in the tumbler is flushed into the atmosphere or to effluent treatment system.
About the Author
S.P. Keshan is Managing Director of Spectrum Washing Private Ltd., Sonepat, who has been successfully using ozone system from Dr Aykan Textiles and Celikhan Makine, Istanbul, Turkey.
Ozone is tri-atomic oxygen, it exists in nature within the stratosphere (from a height of 10 kms to 50 kms), small amounts of ozone is constantly being produced by the action of sun's UV radiation that splits oxygen (O2) to from single oxygen atoms. These atoms combine with the remaining oxygen molecules to form Ozone (O3) molecules, which are very effective at absorbing suns UV rays.
Ozone is also formed from the pollution from burning fossil fuel which creates smoke and carbon monoxide, and lighting creates nitrogen oxides. All of these chemicals, combined together with unstable compounds and in the presence of sunlight, form ozone as a by-product. At ground level, ozone at atmospheric conditions is very unstable, due to this unstable nature; it reduces to oxygen within a very short span of 60 min. in air and 20 mins. in water. This reduction reaction releases one atom of oxygen with act as a very powerful oxidizing agent as a very powerful disinfectant, on the principle of oxidation the garments are treated and the color, look appears on the treated garments.
Originally published in The Stitch Times; May 2009