Cellulosic fibers, colorants

Anthraquiaone vat dyes have been used to dye cotton and other cellulose fibers for many decades. Despite their high cost, relatively muted colors, and difficulty ia appHcation, anthraquiaone vat dyes stUl form one of the most important dye classes of synthetic dyes because of their all-around superior fastness. 

Anthraquinone leuco dyes are widely known as vat dyes.10 Vat dyes possess extensively conjugated aromatic systems containing two or more carbonyl groups, e.g., anthraquinone, indigoid chromophores. The colored form of vat dyes are insoluble in water. The dyes are applied by a process whereby the dye is converted to the reduced form (leuco dye) which is soluble in water and can penetrate into a cellulosic fiber. On exposure to the atmosphere the leuco form is oxidized to the original quinoid form which then precipitates as an aggregate. Vat dyes generally have excellent chemical and photochemical stability. 

Fiber cement siding, which is produced from a blend of cement, sand, and cellulose fibers. This blend is extruded into board, which is then cured by pressurized steam. Unlike composites, fiber cement siding does not require surface treatment. Normally, a primer is applied first, followed by another coating to achieve the desired color. 

This compound is a very effective dye that renders cotton and regenerated cellulose fibers a clear blue shade on prolonged treatment in the presence of an acid-binding agent. The resulting color prove to be veiy light- and waterfast. 

Vat dyes have been used for many decades to color cotton and other cellulose fibers. Despite their high cost and their muted colors, these dyes are extremely important for certain textiles because of their superior fastness. Very few new vat dyes have been developed over the past few years. 

Water-insoluble vat dyes are converted to soluble anthrahydroquinones by reducing agents, such as sodium dithionite (hydrosulfite) in the presence of sodium hydroxide. The sodium salts of these mostly deep colored leuco compounds penetrate cellulose fibers. The insoluble dye is attached firmly to the fiber after reoxidation (see Section 4.5). Representative of a special form are the water-soluble sulfuric acid esters of the anthrahydroquinone compounds, namely, the leuco esters of vat dyes). 

The leuco esters of vat dyes are anthraquinoid or indigoid vat dyes (Section 3.4) that have been made water soluble by reduction and esterification of the hydroxyl groups with sulfuric acid. These dyes are used mainly for dyeing high-quality articles of cellulose fibers in light colors and polyester-cellulose blends to moderate depths of shade [58], [59, p. 568],... 

Sodium chlorite is a powerful and stable oxidizing agent and is capable of bleaching much of the coloration in cellulosic materials without weakening the cellulose fibers. It finds uses in the pulp and textile industries, particularly in the final whitening of kraft paper. 

Calafell M, Diaz C, Hadzhiyska H et al (2007) Bio-catalyzed coloration of cellulose fibers. Biocatal Biotransform 25 336-340... 

Celluloid, which was patented in the USA in 1870, is a combination of pyroxylin, camphor, and cellulose fiber. It could be molded under pressure, and could be made in any color. Later experiments revealed that certain additives increased its flexibility and luster. Most early celluloid was used to make small household and decorative objects, often in a white or cream color to imitate ivory. With the invention of motion pictures, celluloid became commonly used as film. 

Direct dyes are anionic colorants that have affinity for cellulosic fibers.17 They were the first dyes that could be used to dye cotton in the absence of a mordanting agent, giving rise to the term direct-cotton dyes. Like acid dyes, direct dyes contain one or more -SOjNa groups, making them water-soluble. Unlike acid dyes, they interact with cellulose (Cell-OH) chains via secondary valency forces (e.g., H-bonding and dipole-dipole interactions), as illustrated in... 

CASSOFIX TW is a cationic aftertreating agent that markedly improves the wet and perspiration fastness of direct colors (substantive dyes) on cotton, rayon, or other cellulosic fibers. 

WARCOFIX 808 fixative reduces bleeding and staining of colors and improves washfastness of direct colors on cellulosic fibers. WARCOFIX 808 fixative can be applied in the finish mix or by exhaustion after the dyeing cycle. 

Capracyl [Du Pont], TM for a group of neutral-dyeing, premetalized acid colors that produce the highest possible degree of lightfastness on nylon. Also suitable for dyeing wool, particularly in blends with cellulosic fibers. 

Microsol [Novartis], TM for aqueous pigment dispersions for spin-coloring of regenerated cellulose fibers. 

The digestion of plant cellulose fibers to make paper is facilitated by a variety of inorganic compounds including NaOH, Na2S04 and S02. Bleaching agents (which act by oxidizing colored... 

Fading of composite materials depend on many factors, some of them are related to the WPC composition (wood fiber content, type of cellulosic fiber, amount of UV stabilizers and antioxidants and amount and type of colorants) and some to the outdoor conditions (covered or open deck and amount of moisture on the deck and other climatic conditions). It does not appear that processing of WPC and the profile manufacturing noticeably affect the material fading. 

Cassurit . [Hoechst Celanese/Colorants Surf. Hoechst AG] Reactant resins for resin finishing of cellulosic fibers. 

The finished xanthate, colored a strong red-orange by the trithiocarbonate by-product, is dissolved in dilute caustic to.form viscose (ts ically, 6-9 per cent cellulose and 5-8 per cent sodium hydroxide plus by-products of carbon disulfide hydrolysis, of viscosity 30-50 poises at 20°C). Viscose, in turn, yields regenerated cellulose fibers or film when extruded into an acid coagulating and regenerating bath. The instability of the xanthate halfester under acid conditions makes rapid regeneration possible. 

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