ABSTRACT
Acetate rayon dyes: Developed for cellulose acetate and some synthetic fibers Acid dyes: Used for coloring animal fibers via acidified solution (containing sulfuric acid, acetic acid, sodium sulfate, and surfactants) in combination with amphoteric protein Azoic dyes: Contain the azo group (and formic acid, caustic soda, metallic compounds, and sodium nitrate), especially for application to cotton. Basic dyes: Amino derivatives (and acetic acid and softening agents); used mainly for application on paper Direct dyes: Azo dyes, and sodium salts, fixing agents, and metallic (chrome and copper) compounds; used generally on cotton-wool, or cottonsilk combinations Mordant or chrome dyes: Metallic salt or lake formed directly on the fiber by the use of aluminum, chromium, or iron salts that cause precipitation in situ. Lake or pigment dyes: Form insoluble compounds with aluminum, barium, or chromium on molybdenum salts; the precipitates are ground to form pigments used in paint and inks Sulfur or sulf de dyes: Contain sulfur or are precipitated from sodium sulfide bath; furnish dull shades with good fastness to light, washing, and acids but susceptible to chlorine and light Vat dyes: Impregnated into fiber under reducing conditions and reoxidized to an insoluble color. Chemical classification is based on chromogen. For example, nitro dyes have the chromophore-NO The Color Index (C.I.), published by the Society of Dyers and Colourists (United Kingdom) in cooperation with the American Association of Textile Chemists and Colorists (AATC), provides a detailed classification of commercial dyes and pigments by generic name and chemical constitution. This sourcebook also gives useful information on technical performance, physical properties, and application areas. Dyes are synthesized in a reactor, filtered, dried, and blended with other additives to produce the final product. The synthesis step involves reactions such as sulfonation, halogenation, amination, diazotization, and coupling, followed by separation processes that may include distillation, precipitation, and crystallization. In general, organic compounds such as naphthalene are reacted with an acid or an alkali along with an intermediate (such as a nitrating or a sulfonating compound) and a solvent to form a dye mixture. The dye is then separated from the mixture and purified. On completion of the
manufacture of actual color, finishing operations, including drying, grinding, and standardization, are performed; these are important for maintaining consistent product quality.
