Dyeing and printing processes

Very small concentrations of residual dye can lead to the coloration of the discharged treated water. In addition to aeating a disturbing aesthetic problem, the 

Rearick etal. (1997)ieportedapilot run of re-using spent acid/reactive dye bath. The color shade obtained by the reclaimed dye bath was approximately 20% lighter than with the original formulation. It was assumed that shade adjustment efforts failed due to the interference of high levels of magnesium or siUca and/or peroxide in the bath. 

3 Simplified mechanism of the competing reaction of cellulose and water for a reactive dye with triazine reactive group. 

A technique to produce highly concentrated solutions of recovered basic dyes has been developed and a patent issued (Moser et al 1984). The technology described is based on reverse osmosis and ultrafiltration. More recently, Gupta et al. (2004) developed a process for removal and re-use of the basic dye malachite green, which is a snbstitnted triphenyl methane dye. As adsorbent bottom ash was used, dye adsorption was almost 100%. Bottom ash is itself a waste product from thermal power generation plants. Malachite green was desorbed with acetone almost quantitatively to 96% and the colnmn, loaded with bottom ash, conldbe reused without loss of efficiency. 

Solvent extraction has been described by Mnthnraman and Palanivelu (2005) for anionic dyes. In their study, tetrabutyl ammonium bromide (TBAB) in methylene chloride was used for selective extraction of dye from aqueous solution. The solvent could be regenerated after removal of the dyes, with minor loss in effectiveness. Various compounds were explored to strip the dyes from the organic phase. Salicylic acid in sodium carbonate solution proved to be most snccessfnl. In this case, dye recovery in aqueous solution up to 98% could be achieved. Mineral salts present did not affect the extraction process. 

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Virtually all commercial textile dyeing and printing processes take place by the application of a solution or a dispersion of the dyes to the textile material followed by some type of fixation process. The dye solution or dispersion is almost always in an aqueous medium. A major objective of the fixation step is normally to ensure that the coloured textile exhibits satisfactory fastness to subsequent treatment in aqueous wash liquors. In view of the overriding importance of water as a transfer medium in dyeing and printing it seems reasonable to begin with a discussion of the properties of dyes in solution and in dispersion. 

Schlaeppi, F., "Novel Approaches to Energy Conserving Dyeing and Printing Processes", 176th Amer. Chem. Soc. National Meeting, Cellulose, Paper and Textile Division Miami Beach, Florida, Sept. 11, 1978. 

Uses Antifoam for washing, dyeing and printing processes... 

Antlblaze 19. Antiblaze 19 (Mobil), a flame retardant for polyester fibers (134), is a nontoxic mixture of cycHc phosphonate esters. Antiblaze 19 is 100% active, whereas Antiblaze 19T is a 93% active, low viscosity formulation for textile use. Both are miscible with water and are compatible with wetting agents, thickeners, buffers, and most disperse dye formulations. Antiblaze 19 or 19T can be diffused into 100% polyester fabrics by the Thermosol process for disperse dyeing and printing. This requires heating at 170—220°C for 30—60 s. 

As has been implied already, functional demands for auxiliaries continue to grow, with each dye-fibre system and dyeing or printing process having particular needs. The primary functions of auxiliaries are ... 

Uses. The metal is used in electroplating, in solder for aluminum, as a constituent of easily fusible alloys, as a deoxidizer in nickel plating, in process engraving, in cadmium-nickel batteries, and in reactor control rods. Cadmium compounds are employed as TV phosphors, as pigments in glazes and enamels, in dyeing and printing, and in semiconductors and rectifiers. 

Many commercial processes involving surface dyeing and printing (e.g., on film and containers) employ thermooxidation as a pretreatment step. Dyes adhere poorly to HDPE surfaces but their adhesion can be improved by thermooxidation of the surface layer by treatment with an open flame or 111 a strong electric field. 

In addition to the dyeing and printing of natural and acrylic fibers, triarylmethane dyes are suitable for the coloration of other substrates such as paper, ceramics, leather, fur, anodized aluminium, waxes, polishes, soaps, plastics, drugs, and cosmetics. Several triarylmethane dyes are used as food colorants and aie manufactured under stringent processing controls. 

Chemical synthesis produces dyes of varying particle size. When the dyes are applied in this form, uneven and spotty dyeing results, and the dyeing process may be slow and frequently accompanied by incomplete absorption [46], To assure high yield, good reproducibility, and faultless dyeing and printing in commercial use, especially when densely woven fabric or wound material is involved, the dye must be applied as a fine dispersion that is stable under the process conditions. 

Changhai L. Study on decolorization of dyeing and printing wastewater by electroflocculation process with guide shell. Huagong Huanbao 1999 19 264-268. 

Table 3 gives the main characteristics for treated wastewater of types I—IV. When purified in the treatment, types II anil III have been used — by way of textile experiments on commercial scale — in dyeing and printing polyester knits and in afterprint clearing of the knits. When inspected in quality, the dyed and printed knitted fabrics have been found comparable to those processed with standard technological water. 

Use Lead salts, mordant in dyeing and printing calico, matches, mordant for staining mother-of-pearl, oxidizer in the dye industry, sensitizer in photography, explosives, tanning, process engraving, and lithography. 

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