Dye manufacture

For fluorine-free products, the labiUty of fluorine in fluoronitrobenzenes and other activated molecules permits it to serve as a handle in hair-dye manufacturing operations, high performance polymers such as polyetheretherketone (PEEK), production of dmgs such as diuretics, and fiber-reactive dyes. Labile fluorine has also been used in analytical appHcations and biological diagnostic reagents. 

Ethylbenzene. This alkylben2ene is almost exclusively used as an intermediate for the manufacture of styrene monomer [100-42-5]. A small amount (<1%) is used as a solvent and as an intermediate in dye manufacture (1,39,40). The current ethylben2ene growth rate projections for 1990—1995 range from 3.0 to 3.5%/yr (39). 

In 1991, over 1 x 10 t sulfonic acids were produced in the United States (24). The materials, for the most part, were used as intermediates for the manufacture of sulfonates in the detergent market, dye manufacture, dispersing agents, catalysts, polymers, etc. Production of dodecjlbenzenesulfonic acids derivatives dominated the sulfonic acid market (Table 2). These had a 38% overall share. The differences between the production tons and the tons sold is accounted for by in-plant use by various manufacturers verses merchant market production. 

Dyes and the Environment, ADMI Reports on Selected Dyes and their Effects, Vol. 1 (Sept. 1973) and Vol. 2 (Sept. 1974), American Dye Manufacturers Institute. 

Nearly all dye manufacturers use letters and numerals in the names of their products to define the hue. Thus B is blue G, yellow (gelb in German) or green R, red and Y, yellow. Numerals, ie, 2G (or GG), 3G, 4G, etc indicate, in this case, a successively yellower or greener shade. Occasionally, suffixed letters are used to feature other properties such as solubiHty, lightfastness, brightness, and use on synthetic fibers. 

Azo Coupling. The coupling reaction between an aromatic diazo compound and a coupling component is the single most important synthetic route to azo dyes. Of the total dyes manufactured, about 60% are produced by this reaction. Other methods iaclude oxidative coupling, reaction of aryUiydraziae with quiaones, and oxidation of aromatic amines. These methods, however, have limited iadustrial appHcations. 

Large amounts of inorganic materials are consumed in both intermediates and dyes manufacture. 

Fig. 11. Layout of a2o dye manufacturing plant. 1, storage tanks for liquid starting materials 2, storage dmms for solid starting materials 3, dia2oti2ation vessel 4, coupling component vessel 5, ice machine 6, coupling vessel 7, isolation vessel 8, filter presses 9, filtrate to waste liquor treatment plant 10,...

Dyes for cellulose fiber include the direct, sulfur, vat, a2oic, and reactive dyes. R D activities of world dye manufacturers have been focused on the area of reactive dyes, because reactive dyes offer brighter shades and excellent wet-fastness and have been increasingly used for dyeing cotton. 

World dye manufacturers have already begun to develop new types of dyes that can replace the anthraquinones technically and economically (1). Some successful examples can be found in a2o disperse red and blue dyes. Examples are brilliant red [68353-96-6] and Cl Disperse Blue 165 [41642-51 -7] (Cl 11077). They have come close to the level of anthraquinone reds and blues, respectively, in terms of brightness. In the reactive dye area intensive studies have continued to develop triphenodioxa2ine compounds, eg, (13), which are called new blues, to replace anthraquinone blues. In this representation R designates the substituents having reactive groups (see Dyes, reactive). 

Reflectance Spectrophotometry. Because of discrepancies that can occur between strength and shade evaluations in solution and on textile substrates, the latter is often the preferred evaluation technique. In the case of dye manufacture, many dyes are standardized in solution but there is always a final control step where dyeings are prepared. Historically, such dyeings have been evaluated visually for the relative strength and the shade of the dye under test on the substrate, compared to the standard. More and more attempts are being made to do such evaluations objectively. Guidelines for the use of this technique have been pubflshed (43). 

Color Difference Evaluation. Shade evaluation is comparable in importance to relative strength evaluation for dyes. This is of interest to both dye manufacturer and dye user for purposes of quaUty control. Objective evaluation of color differences is desirable because of the well-known variabihty of observers. A considerable number of color difference formulas that intend to transform the visually nonuniform International Commission on Illumination (CIE) tristimulus color space into a visually uniform space have been proposed over the years. Although many of them have proven to be of considerable practical value (Hunter Lab formula, Friele-MacAdam-Chickering (FMC) formula, Adams-Nickerson formula, etc), none has been found to be satisfactorily accurate for small color difference evaluation. Correlation coefficients for the correlation between average visually determined color difference values and those based on measurement and calculation with a formula are typically of a magnitude of approximately 0.7 or below. In the interest of uniformity of international usage, the CIE has proposed two color difference formulas (CIELAB and CIELUV) one of which (CIELAB) is particularly suitable for appHcation on textiles (see Color). 

Pollution Prepention Guidance Manualfor the Dye Manufacturing Industry, U.S. Environmental Protection Agency and U.S. Operating Committee of ETAD, Washington, D.C., Dec. 1991. 

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