Bleaching acetate

Caution. High concentrations of acetic acid can cause bad burns on contact with skin. However, working strength stop bath is usually only 1% to 2%, less than ordinary household vinegar. DO NOT MIX ACETIC ACID WITH HOUSEHOLD BLEACH. Acetic acid reacts with household bleach to form a highly toxic gas. 

Both acetate and triacetate are susceptible to attack by a number of household chemicals. Acetate and triacetate are attacked by strong acids and bases and by oxidizing bleaches. Acetate has only fair sunlight resistance, whereas the sunl ight resistance of triacetate is superior. Both fibers have good heat resistance below their melting points. 

Dichloranrine-T (p-toluenesulphondichloramide). Prepare about 200 ml. of a saturated solution of calcium hjrpochlorite by grinding a fresh sample of bleaching powder with water and filtering with shght suction. Dissolve 5 g. of p-toluenesulphonamide in as small a volume of the calcium hypochlorite solution as possible (about 150 ml.) and filter the solution if necessary. Cool in ice, and add about 50 ml. of a mixture of equal volumes of glacial acetic acid and water slowly and with stirring until precipitation is complete. The dichloramine T separates out first as a fine emulsion, which rapidly forms colourless crystals. Filter the latter... 

Chemical Properties. Under slightly acidic or basic conditions at room temperature, acetate and triacetate fibers are resistant to chlorine bleach at the concentrations normally used in laundering. 

Phloroglucinol is Hsted in the Colourindex as Cl Developer 19. It is particularly valuable in the dyeing of acetate fiber but also has been used as a coupler for azoic colors in viscose, Odon, cotton (qv), rayon, or nylon fibers, or in union fabrics containing these fibers (157). For example, cellulose acetate fabric is treated with an aromatic amine such as (9-dianisidine or a disperse dye such as A-hydroxyphenylazo-2-naphthylamine and the amine diazotizes on the fiber the fabric is then rinsed, freed of excess nitrite, and the azo color is developed in a phloroglucinol bath at pH 5—7. Depending on the diazo precursor used, intense blue to jet-black shades can be obtained with excellent light-, bleach-, and mbfastness. 

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. 

Carboxylic acids having 6—24 carbon atoms are commonly known as fatty acids. Shorter-chain acids, such as formic, acetic, and propionic acid, are not classified as fatty acids and are produced synthetically from petroleum sources (see Acetic acid Formic acid and derivatives Oxo process). Fatty acids are produced primarily from natural fats and oils through a series of unit operations. Clay bleaching and acid washing are sometimes also included with the above operations in the manufacture of fatty acids for the removal of impurities prior to subsequent processing. 

Further Preparative Reactions. When pulps are to be used in the production of materials that do not retain the original fiber stmcture, such as rayon or ceUulose acetate film, the lignin, hemiceUulose, and other components must be reduced to the lowest possible concentrations. A surfactant (ionic or nonionic) is often added during a hot, weakly alkaline extraction step after chlorination. Another approach, sometimes used in addition to the surfactant step, is to treat the pulp with 6—10% NaOH after most of the oxidative bleaching is finished. This treatment removes most of the hemiceUulose. In most purification plants the final stage includes use of sulfuric acid chelators are optional. 

In a typical process for manufacture on a commercial scale bleached wood pulp or cotton linters are pretreated for 12 hours with 40-50% sulphuric acid and then, after drying, with acetic acid. Esterification of the treated cellulose is then carried out using a mixture of butyric acid and acetic anhydride, with a trace of sulphuric acid as catalyst. Commercial products vary extensively in the acetate/ butyrate ratios employed. 

Procedure (iodometric method). Weigh out accurately about 5.0 g of the bleaching powder into a clean glass mortar. Add a little water, and rub the mixture to a smooth paste. Add a little more water, triturate with the pestle, allow the mixture to settle, and pour off the milky liquid into a 500 mL graduated flask. Grind the residue with a little more water, and repeat the operation until the whole of the sample has been transferred to the flask either in solution or in a state of very fine suspension, and the mortar washed quite clean. The flask is then filled to the mark with distilled water, well shaken, and 50.0 mL of the turbid liquid immediately withdrawn with a pipette. This is transferred to a 250 mL conical flask, 25 mL of water added, followed by 2 g of iodate-free potassium iodide (or 20 mL of a 10 per cent solution) and 10 mL of glacial acetic acid. Titrate the liberated iodine with standard 0.1M sodium thiosulphate. 

Pulp mills. These separate the fibers of wood or other materials, such as rags, Enters, waste-paper, and straw, in order to create pulp. Mills may use chemical, semichemical, or mechanical processes, and may create coproducts such as turpentine and tall oil. Most pulp mills bleach the pulp they produce, and, when wastepaper is converted into secondary fiber, it is deinked. The output of some pulp mills is not used to make paper, but to produce cellulose acetate or to be dissolved and regenerated in the form of viscose fibers or cellophane. 

Highly bleached and purified kraft process wood pulp suitable for conversion into products such as rayon, viscose, acetate, and cellophane... 

Conversely, vesicants have also been thickened with various substances to enhance deployment, increase their persistency, and increase the risk of percutaneous exposure. Thickeners include polyalkyl methacrylates (methyl, ethyl, butyl, isobutyl), poly(vinyl acetate), polystyrene, plexiglas, alloprene, polychlorinated isoprene, nitrocellulose, as well as bleached montan and lignite waxes. Military thickener K125 is a mixture of methyl, ethyl, and butyl polymethacrylates. When thickened, agents become sticky with a consistency similar to honey. Typically, not enough thickener is added to affect either the color or odor of the agent. 

Acedox [Acetic oxidation] A pulp-bleaching process using peracetic acid as the oxidant. Developed by Eka Nobel in 1994 and first commercialized, in combination with Lignox, in Sweden in 1995. 

Acetosolv A wood pulping and bleaching process which uses hydrogen peroxide and acetic acid. See Organosolv. 

INCOMPATIBILITY DS2 is a corrosive material and because of its content, it is incompatible with some metals (e.g., cadmium, tin and zinc) some plastics (e.g., Lexan, cellulose acetate, polyvinyl chloride, Mylar, and acrylic) some paints wool leather oxidizing materials (e.g., Super Tropical Bleach or High Test Hypochlorite) and acids. 

In spin dyed secondary acetate threads, fibers, and films, P.B1.25 exhibits good textile fastness properties the only problem is a certain lack of fastness to bleaching with sodium hypochlorite (Sec. 1.6.2.4). Its fastness to light in 0.1% spin dyed specimens equals step 3-4 on the Blue Scale, while 1% samples equal step 5. 

By Dismutation.—Hydrazobenzene (1-2 g.) is melted in a test tube over a small flame. The orange-red liquid thus produced is carefully heated until the aniline which has been formed begins to boil. On cooling, a semi-solid mixture of red azobenzene and aniline is obtained. The aniline can be shaken out with water and identified by means of the bleaching powder reaction. The azobenzene may be recrystallised from alcohol as described above. If it is desired to isolate the aniline also, when larger amounts of hydrazobenzene are used, the base is separated from the azobenzene by means of dilute acetic acid. From the solution of its acetate the aniline is then liberated with concentrated alkali hydroxide solution, extracted with ether, and purified in the manner already described. 

Furylacrylic acid has usually been prepared from furfural by the Perkin reaction.1 The use of potassium acetate is advantageous, since it allows the reaction to proceed rapidly at relatively lower temperatures. The acid has also been prepared from furfural and malonic acid in the presence of pyridine,2 and by oxidation of furfuralacetone with bleaching powder.3... 

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