Bleaching with sodium chlorite

Synthetic Fibers. Most synthetic fibers are sufficientiy white and do not requite bleaching. For white fabrics, unbleached synthetic fibers with duorescent whitening agents are usually used. When needed, synthetic fibers and many of theit blends are bleached with sodium chlorite solutions at pH 2.5—4.5 for 30—90 min at concentrations and temperatures that depend on the type of fiber. Solutions of 0.1% peracetic acid are also used at pH 6—7 for 1 h at 80—85°C to bleach nylon. 

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. 

As an alternative to oxidative bleaching with sodium chlorite, acrylic fibres may be given a reductive bleach using sodium bisulphite in the presence of oxalic acid. This method is... 

Synthetic Fibers. Most synthetic fibers are sufficiently white and do not require bleaching, When needed, synthetic fibers and many of their blends ane bleached with sodium chlorite solutions. Solutions of 0.1% peracetic acid are also used,... 

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... 

Recipe for One-Stage Bleaching with Sodium Chlorite... 

Other Cellulosics. Rayon is bleached similarly to cotton but under milder conditions since the fibers are more easily damaged and since there is less colored material to bleach. Cellulose acetate and triacetate are not usually bleached. They can be bleached like rayon, except a slightly lower pH is used to prevent hydrolysis. The above fibers are most commonly bleached with hydrogen peroxide. Linen, dax, and jute requite more bleaching and mil der conditions than cotton, so multiple steps are usually used. Commonly an acidic or neutral hypochlorite solution is followed by alkaline hypochlorite, peroxide, chlorite, or permanganate, or a chlorite step is done between two peroxide steps. A one-step process with sodium chlorite and hydrogen peroxide is also used. 

OXIDATION OF PRIMARY ALCOHOLS TO CARBOXYLIC ACIDS WITH SODIUM CHLORITE CATALYZED BY TEMPO AND BLEACH 4-METHOXYPHENYLACETIC ACID... 

One feature of this oxidation system is that it can selectively oxidize primary alcohols in preference to secondary alcohols, as illustrated by Entry 2 in Scheme 12.5. The reagent can also be used to oxidize primary alcohols to carboxylic acids by a subsequent oxidation with sodium chlorite.34 Entry 3 shows the selective oxidation of a primary alcohol in a carbohydrate to a carboxylic acid without affecting the secondary alcohol group. Entry 5 is a large-scale preparation that uses NaC102 in conjunction with bleach as the stoichiometric oxidant. 

The light fastness of the vic-triazole 11.17 on nylon is 4-5 as on cotton this is significantly superior to that of the DAST derivatives. Unlike the DAST types, the vic-triazole is also stable towards a sodium chlorite bleach. Applied to nylon in combination with sodium chlorite, compound 11.17 can give exceptionally high whiteness and excellent fastness properties. 

Type B brighteners can be applied in the absence of bleach, of course, but show their best results when applied simultaneously with sodium chlorite, where they are capable of giving exceptionally high whiteness. 

This process is a lower-cost method of providing bromine chemistry to large cooling systems, where conventional BCDMH or similar chemistry is cost-prohibitive (see Section 6.2.7 on bromine chemistry). In addition, bleach is often used as a raw material, with sodium chlorite, for the on-site production of chlorine dioxide (see Section 6.2.6). 

A non-dusting auxiliary used in conjunction with sodium chlorite to supress the chlorine dioxide fumes generated in bleaching. 

Zhao, M. Li,J. Mano, E. Song, Z. T chaen, D. M. Grabowski, E.J.J. Reider, P.J., Oxidation of Primary Alcohols to Carboxylic Acids with Sodium Chlorite Catalyzed by TEMPO and Bleach. ... 

Bleaching of acetate fibres with sodium chlorite... 

It is more safe to carry out bleaching of acetate fibres with sodium chlorite than with hydrogen peroxide. Bleaching can be carried out with sodium chlorite (0.5-2 g/1) in presence of mono substituted ammonium phosphate (0.5-2 g/1) and non-ionic detergent at 70-80 C for 60-100 min. 

Scouring and bleaching of jute with sodium chlorite with an acceptable whiteness can be achieved, but the process is a time consuming two step process. Moreover, sodium chlorite is metal corrosive and health hazardous. 

Oxidations. The oxidation of primary alcohols to acids with sodium chlorite is catalyzed by TEMPO and bleach. On the other hand, when the oxidation is carried out at 0° with a silica-supported TEMPO in the presence of KBr and in a biphasic solvent system (aqueous phase pH 9.1) primary alcohols afford aldehydes. ... 

Exner-Freisfeld, H., Kronenberger, H., Meier-Sydow, J. Nerger, K.H. (1988) [A case of bleach poisoning with sodium chlorite. The toxicology and clinical course.] Dtsch. Med. Wochenschr. Ill, 1927-1930 (in German). 

In bleaching fiber is usually treated with sodium chlorite and links are developed between lignin and carbohydrates. Removal of noncellulosic compounds by chemical treatments resulted in improvement of mechanical and physical characteristics as well as of fiber strength [33]. 

Chemical treatments, such as alkalization, bleaching with sodium hypochlorite (NaClO) or chlorite (NaCl02), are applied on the fiber bxmdles to extract the technical fiber that can stand the loads of tension and torsion. Chemical treatments are effective in removing the extra celulosic materials and exposing the cellulose. However, if the alkalization conditions are too strong, this may cause damage in the fiber [15]. 

Gaseous chlorine dioxide, CIO2, is used to bleach flour and in water treatment. It is produced by the reaction of chlorine with sodium chlorite Clj + 2 NaC102 2 CIO2 + 2 NaCl. How many liters of ClOj, measured at 0.961 atm and 31°C, will be produced by 283 L CI2 at 2.92 atm and 21 °C ... 

Subsequently the wood material was subjected to a bleach pretreatment with sodium chlorite (NaQ02) to remove lignins, resins, waxes. In case of very small samples or poorly preserved fragments the temperature and the time of each step was individually match. In the next stages of samples preparation to dating the combustion in vacuum to obtain carbon dioxide from organic material and reduction were used. Finally, graphite with iron was pressed to form a cathode ready for AMS measurement. 

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. 

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

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