Bleaching acetate/cellulose

Bleaching of cellulose acetate with peracetic acid... 

Peracetic acid is very suitable for bleaching of cellulose acetate fibres. The liquor should be made-up in the following manner ... 

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. 

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. 

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. 

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. 

Acetylating and dehydrating agent used in the chemical and pharmaceutical industries for the manufacture of cellulose acetate, for textile sizing agents and cold bleaching activators, for polishing metals and for the production of brake fluids, dyes, explosives. 

Our experimental work started from the following original cellulose samples (a) acetate-grade, bleached cotton linters, DP 1800 (b) hot, refined, spruce, sulphite-dissolving pulp, machine dried, ca. 93% a-cellulose, DP — 750 (c) never-dried, normal, rayon-grade, beech sulphite pulp, ca. 90% a-cellulose, DP = 825 (d) commercial cellulose powders obtained by hydrolytic degradation and/or mechanical disintegration of cotton linters or spruce sulphite pulp. 

Cellulose acetate is manufactured by a batch process (see Fig. 12.9). There has been mention in the patent literature of a continuous system, but its utilization as a production process has not been announced. The charge of cellulose, purified, bleached, and shredded, is of the order of 800-1500 lb. It is pretreated with about one third its weight of acetic acid and a very necessary amount of water, about 6 percent of its weight. If it is too dry at the time of use, more H20 must be added to the acetic acid. A small amount of sulfuric acid may be used to assist in swelling the cellulose and to make it accessible to the esterifying mixture. 

Chemistry, Physics, and Biology Laboratories. As a rule, before any artifact is subjected to treatment, the chemistry laboratory determines the causes of any alterations or deterioration. The nature and structure of the artifact, its pigments and inks, are identified to avoid negative reactions to prescribed treatment. Fixatives are recommended if required these may be cellulose acetate dissolved in acetone, soluble nylon, or acrylic resin sprays. Once stains are identified, several possible solvents are selected. For deacidification, either magnesium bicarbonate or barium hydroxide usually is recommended, depending on whether an aqueous or nonaqueous solution is called for. Bleaching is discouraged, but when necessary, hypochlorites are used with suitable antichlors. 

Glaessner, Austria, 1931), ammoniacal bleached shellac (Wruble, 1933), stearic acid, carnauba wax, petrolatum, elm bark, and agar (Miller, 1935, and Worton, 1938), and abietic, oleic, and benzoic acids with methyl abietate (Eldred, 1937). Since 1940, research on enteric coatings has focused on the synthesis of resinous polymers, which are insoluble in acids, such as cellulose acetate phthalate (Hiatt, 1940) and a glycerol-stearic acid-phthalic anhydride ester (Volweiler and Moore, 1940). 

In the preparation of secondary cellulose acetate rayon cotton linters, waste cotton or high-grade wood pulp is purified by boiling with alkali followed by hypochlorite bleaching. After purification the cellulose is dried... 

Aniline-furfural resin n. Furfural yields resinous compounds not only with aniline but with aromatic amines generally. Rosin modified resins have also been produced. Amine-fiirfural resins are dark in color. Bleaching occurs on exposed to light. They possess the unique property of compatibility with cellulose acetate. 

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