Cotton bleaching

Table 10.12 AOX values for cotton bleached with various oxidising agents [223]...

Handle (flexibility) grey cotton bleached cotton > <... 

Crease recovery angle grey cotton bleached cotton < >... 

Uses. The most important commercial use for benzonitrile is the synthesis of benzoguanamine, which is a derivative of melamine and is used in protective coatings and molding resins (see Amino RESINS Cyanamides). Other uses for benzonitrile are as an additive in nickel-plating baths, for separating naphthalene and alkylnaphthalenes from nonaromatics by azeotropic distillation (qv), as a jet-fuel additive, in cotton bleaching baths, as a drying additive for acrylic fibers, and in the removal of titanium tetrachloride and vanadium oxychloride from silicon tetrachloride. 

It s important to gas out new clothing and to wash new items a number of times before wearing them. Most clothing is treated with many chemicals, such as pesticides on the cotton, bleach, synthetic paint, treatments in the production process and in the transportation containers, and so on. You should definitely not wear clothing that has just come from the dry cleaner, unless the dry cleaner does not use harmful chemicals, in which case the clothes are probably safe for MCS patients sooner. Be careful and well informed if you want to use this green alternative. Green does not necessarily mean it is also tolerable or safe for MCS patients. See Part VI for web addresses on this subject. 

Sodium hypochlorite, used commercially in cotton bleaching, is made by the electrolysis of brine, the electrolyte being agitated to mix the anode and cathode products. At the cathode, 2H+ + 2e -> Hg increases the concentration of OH , while at the anode, 2C1 CI2 + 2e releases chlorine. These combine ... 

Hydrogen peroxide was discovered in 1818 and its use in bleaching textiles was first suggested in 1866. However, its high cost limited its use in cotton bleaching until 1935. The problem was partially solved by the process using barium peroxide and phosphoric acid. In 1926 hydrogen peroxide was manufactured by an electrolytic process based on the decomposition of persulphuric acid (H SOj) [15]. 

In practice cotton bleaching with hydrogen peroxide is carried out at 90-100°C, but the temperature may be increased to 120°C in the case of pressurised equipment with a corresponding reduction in process time. The rate of bleaching increases with the increase in temperature, but at the same time solution becomes unstable and degradation of cotton increases. Below 80 C, the evolution of perhydroxyl ion is very slow so also the rate of bleaching. 

If the cellulosic portion is cotton, bleaching is invariably required for this fibre. If the acrylic portion does not require bleaehing, then a peroxide treatment can be done at pH 9.5. The alkaline eondition should not be high as otherwise it would cause degradation of the fibre. The fabric is treated with a solution containing 7.5-10.0 g/1 H,Oj (35%), 3 g/1 sodium silicate (79°Tw) and 1 g/1 sodium carbonate at 90 C for 45-60 min. After bleaching the bath is cooled slowly to 50°C, rinsed and neutralised. 

The Structure of the Fibertect fabric allows different types of fibers such as polyester, raw cotton, bleached cotton, among others, to be used for different applications such as industrial cleaning and oil absorption. Raw cotton-based Fibertect wipes can be used to absorb oil and adsorb volatile vapors that emanate from polycyclic aromatic hydrocarbotts. ... 

The original Mn-Mejtacn complex contains PF6 - as a counter ion, which simplifies purification and handling and improves storage stability, but reduces the solubility of the catalyst. Recent developments in using Mn-Mejtacn derivatives for raw cotton bleaching, the pulp and paper industry, and industrial cleaning are based on more soluble counter ions such as chloride, sulfate, or acetate. Such catalysts are more cost-effective to produce, and allow stable weak acidic solutions to be prepared [39]. 

At elevated temperatures all air-dry samples have very different AH values, which are significantly larger than values (Table 8.8). The AHJAH ratios indicate that the strength of water Ill-fiber interactions in air-dry materials decreases in a row cotton> bleached flax > flax. The differences in AH and AH /AH for swollen samples were much smaller. The inset in Figure 8.28 shows the temperatures at which thermal destruction of fiber samples started. These temperatures are a little higher than values obtained in TG measurements, perhaps due to a higher heating rate in DSC experiments. 

A range of novel structures and finishing components have been developed and fully characterised by using commercial and relatively inexpensive medical-grade fibres such as bleached cotton, bleached viscose, bleached lyocell, and other natural, biodegradable and non-toxic fibres and finishing components by using conventional materials, equipment, and chemicals. 

NPB11 Tertiary blends Polyester/ viscose/ Cotton (bleached) 3.3 40/3.3 40/ 1.8 22 33%/33%/ 33% Needlepunched (both sides)... 

Peracetic acid (Steiner N, 1995, Evaluation of peracetic acid as an environmentally friendly alternative for hypochorite . Textile Chemist Colorist 27 (8), pp. 29-32) as well as a waterless bleaching system that uses oxygen gas (Mowbray J 2008, Light fantastic , Ecotextile News No. 17 Aug/ Sep, pp. 22-24) have been reported as alternate and enviromnent-friendly methods for bleaching cotton. Ozone also can be used as another waterless process to bleach cotton. Bleaching removes residual impiuities and changes the natural color of cotton fabric to clear white rather than the off-white (i.e. various shades of yellow). 

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