Textile Bleaching Agents

Bleaching Agent.

A bleaching agent is a substance that can whiten or decolorise other substances.The purpose of bleaching agents is to bleach the natural substances in cotton fibres and cellulose fibres that make the fabric yellowish. 

Bleaching agents essentially destroy chromophores (thereby removing the color), via the oxidation or reduction of these absorbing groups.Bleaching agents also bleach textile colors and hence should be avoided for colored textiles.

Thus, bleaches can be classified as either oxidizing agents or reducing agents .

Type of Bleaching agents

a.Oxidative bleaching agents

Generally oxidative bleachings are carried out using hypochlorites,sodium chlorite or peroxy compounds. Natural fibres like cotton,ramie , jute, wool, bamboo are all generally bleached with oxidative methods.
The double bond breaks in the oxidative bleaching, which makes the substrate colorless,

b.Reductive bleaching agents
Reductive method of bleaching is done with sodium hydrosulphite,sodium sulpfide and sulfur dioxide are powerful reducing agents. Fibres like polyamide, Polyacrylics and Polyacetates can be bleached using reductive bleaching technology.
Double bond is converted into single bond in case of reductive bleaching ,

 c.Enzyme aided Bleaching 

The use of enzyme technology is attractive because enzymes are highly specific and efficient, and work under mild conditions. Furthermore, the use of enzymes results in reduced process times, energy and water savings; improved product quality; and potential process integration. The process of bioscouring(which remove all non-cellulosic components from native cotton  completely or partially.) when combined with bleaching process reduces the process time , cost as well as improves the quality.

for information about enzymes in pretreatment click here

For More information on Hypochlorites Click Here 

Chemistry of bleaches
Bleach action