Textile bleaching

Textile applications Textile bags Textile bleaching Textile cord Textile dyeing Textile fibers Textile finishes Textile finishing... 

Early demand for chlorine centered on textile bleaching, and chlorine generated through the electrolytic decomposition of salt (NaCl) sufficed. Sodium hydroxide was produced by the lime—soda reaction, using sodium carbonate readily available from the Solvay process. Increased demand for chlorine for PVC manufacture led to the production of chlorine and sodium hydroxide as coproducts. Solution mining of salt and the avadabiHty of asbestos resulted in the dominance of the diaphragm process in North America, whereas soHd salt and mercury avadabiHty led to the dominance of the mercury process in Europe. Japan imported its salt in soHd form and, until the development of the membrane process, also favored the mercury ceU for production. 

Textiles. Sorbitol sequesters iron and copper ions in strongly alkaline textile bleaching or scouring solutions (see Textiles). In compositions for conferring permanent wash-and-wear properties on cotton fabrics, sorbitol is a scavenger for unreacted formaldehyde (252) and a plasticizer in sod-resistant and sod-release finishes (253). 

Two sohd organic peracids have been utilized ia textile bleaching products. Diperoxydodecanedioic acid, (16), [66280-55-5] a hydrotropic peracid, and the magnesium salt [78948-87-5] of monoperoxyphthaUc acid, (17), [2311-91-3] a hydrophilic peracid, were contained in bleaching products for a short period of time (142). 

The reducing agents generally used in bleaching include sulfur dioxide, sulfurous acid, bisulfites, sulfites, hydrosulfites (dithionites), sodium sulfoxylate formaldehyde, and sodium borohydride. These materials are used mainly in pulp and textile bleaching (see Sulfur compounds Boron compounds). 

Because they are unstable, hypobromites are usually prepared just before use for such jobs as textile bleaching and desizing. In alkaline solutions at 50—80°C bromine reacts to form bromide and bromate. This reaction is reversed in acidic solutions. 

Dibasic magnesium hypochlorite can be used as a toilet bowl cleaner (227—229), in laundry and textile bleaches (230,231), and in scouring cleansers (232,233). 

Sodium chlorite has also been used for treatment and removal of toxic and odorous gases such as hydrogen sulfide and mercaptans. Chlorine dioxide from chlorite is also useful for microbial and slime control in paper mills and alkaline paper machine systems (164,165). The use of sodium chlorite in textile bleaching and stripping is well known. Cotton is not degraded by sodium chlorite because the oxidation reactions are specific for the hemiceUulose and lignin components of the fibers. 

Titanium impellers have been used in pumps employed for the conveyance of corrosive and erosive ore slurries, for organic chlorides containing hydrochloric acid and free chlorine , for handling moist chlorine gas, and in the wood-pulp and the textile-bleaching industry, particularly with sodium hypochlorite . 

Most of the hydrogen peroxide solution supplied for textile bleaching is acidic (pH 4.5-5.0) because it shows maximum stability under these conditions. Additives are present to increase its stability further at this pH. 

Sodium hypochlorite is commercially available as an alkaline solution, normally containing the equivalent of 12-14% available chlorine. However, this is so unstable that analytical testing of its strength is always necessary before use. Calcium hypochlorite (bleaching powder), stabilised by adding lime, has been used in the past but this product is no longer used in textile bleaching. 

During preparation of peracetic acid solutions for textile bleaching operations, the reaction mixture must be kept acid. Under alkaline conditions, highly explosive diacetyl peroxide separates from solution [1], An excess of the anhydride has the same effect [2],... 

Immobilized catalases, for textile bleaching effluent treatment, 4 68—69 Immobilized cells, 3 670 Immobilized enzyme biosensors,... 

Textile bleaching, 4 44-45, 71-73 enzyme applications, 4 66-67 enzymes for effluent treatment, 4 67-69 Textile carding, 17 498-499 Textile (hying, microwave technology in, 16 530... 

Sodium sulfite (Na SO ) is an antioxidant, used as a preservative except with meats. It is also used for water treatment and in photography and textile bleaching. 

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