Cotton peroxide bleaching

The most common chemical bleaching procedures are hypochlorite bleach for cotton hydrogen peroxide bleach for wool and cotton sodium chlorite bleach for cotton, polyamide, polyester, and polyacrylonitrile and reductive bleaching with dithionite for wool and polyamide. 

When bleaching is requited, a reductive bleach with sodium hydrosulfite and sodium metabisulfite is used. Cotton blends may requite a hydrogen peroxide bleach at pH 9.0—9.5 prior to or iastead of the normal reductive bleach. Chlorine-type bleaches which damage elastomeric fibers are avoided. 

Thus the detailed mechanism of peroxide bleaching is not yet finally resolved. It should be borne in mind, however, that the work of Dannacher and Schlenker was carried out at 60 °C on tea-stained cotton, whereas Spiro and Griffith studied the decolorisation of individual colorants at 21-25 °C in the absence of a textile substrate. 

Most cotton is bleached with peroxide, by far the greater proportion by continuous methods. Synthetic fibres seldom require bleaching, but where it is necessary either peroxide or chlorite bleaches are recommended. Most regenerated cellulosic fabrics are only bleached... 

FBA may be applied by exhaustion from the same bath. If the polyester portion of the blend is to be bleached with sodium chlorite, the cotton is usually brightened in a second step since most FBAs for cotton are destroyed by sodium chlorite. Both types of FBA are normally compatible with a hydrogen peroxide bleaching process. 

Cotton and Cotton-Polyester. Cotton is the principal fiber bleached today, and almost all cotton is bleached. About 80-90% of all cotton and cotton-polyester fabric is bleached with hydrogen peroxide. 

Anionic softener for fabric finishing can be combined with all types of filling agents softener with stabilizing effects in peroxide bleaching of cotton yarns. 

PLEX HT is a blend of chelating agents which has the ability to dissolve iron rust from cotton and cotton blend fabrics in strong caustic solutions such as are used in saturation of cotton fabric prior to continuous peroxide bleaching. It also has the ability to keep the chelated iron from redeposition as the pH drops during subsequent rinsing. 

SEQ 100 is used in preparation of cotton and cotton blend fabrics and also can be used in scouring synthetic fabrics when there is a substantial amount of interfering heavy metals on the fabrics. A concentration of 0.1% on the weight of the bath in the caustic scour prior to peroxide bleaching will remove calcium, magnesium and copper but very little iron as the metal or as the rust. If it is necessary to remove ron or rust, other products such as SEQ CF in strong caustic are recommended. 

Alkaline hydrogen peroxide bleaching is the most preferred system for polyester/ cotton blends and bleaching can be carried out on various equipment using batchwise, semi-continuous and continuous method. Table 6.9 shows conditions for bleaching... 

The most effective method of bleaching polyester/cotton is sodium chlorite, which may be followed by peroxide bleaching. Chlorite bleaches the husk, but does not destroy them completely. Polyester/cotton blends may be bleached with sodium chlorite in long liquors and also by pad-steam process [Table 6.10]. The... 

A single stage combined scouring and bleaching of polyester/cotton blended fabric can also be done for economy. There are various approaches which include alkali treatment with detergent and peroxide hot bleach alkali treatment with detergent and sodium chlorite bleach sodium chlorite and peroxide bleach and peroxide cold and peroxide hot bleach. 

Sanperox . [Sandoz] Stabilizer with sequestering and dispersing properties for peroxide bleaching of cotton and blends. 

Sdvatex. [Leatex] Penetrant sud>ilizo, and sequestrantfor peroxide bleaching trfcotton and cotton blends. 

Sdvatex. [Leatex] Pnietran stabilizer, and sequestrant for peroxide bleaching d cotton and cotton bkaids. 

Buschie-Diller, G., Mogahzy, E. Y., Inglesby, M. K., and Zeronian, S. H. (1998). Effect of scouring with enzymes, organic solvents and caustic soda on the properties of hydrogen peroxide bleached cotton yam. Text Res. 

Maekawa, M., Hashimoto, A., and Tahara, M. (2007). Effects of pH in hydrogen peroxide bleaching of cotton fabrics pretreated with ferrous sulphate.. Text Res. L 77(4), 222-226. 

Table 8.2 Example of a hydrogen peroxide bleach formulation for cotton (Reicher, 1992)...

Evans B. A., Boleslawski L. and BoUek J. E. (1997), Cotton Hosiery Bleaching with Hydrogen Peroxide , Textile Chemists arul Colorist, Vol. 29, No. 3, 28. 

Detergent, emulsifier, dispersant, wetting agent. Similar to CHEMPHOS TR-421 but better compatibility in strong electrolyte systems. Emulsifier in waterless hand cleaners, detergent in dry-cleaning formulations. Pesticide emulsifier with liquid fertilizer blends. Used in caustic boil and peroxide bleach for cotton processing. 

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