Industrial Dyeing Process

For the dyeing of cotton, indigo is reduced with sodium dithionite in alkaline solution. The dyer speaks of vatting . When this reaction is carried out in dye- 

Blue jeans acquire their typical appearance only if they are manufactured out of indigo-dyed denim. A particular weave and the poor fastness to rubbing of the indigo dyeing are critical here. Before the weaving, only the warp threads 

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Despite many careful studies of model systems and individual processes, which permit a semiquantitative interpretation of individual steps under standardized conditions, dyeing results still cannot be mathematically predicted unambiguously. Thus, an industrial dyeing process must be supported by dyeing experiments. Recipes are drawn up on the basis of trial dyeings with the help of color measurements. 

This section provides an overview of the synthesis of dyes and pigments used in textiles and related industries. Dyes are soluble at some stage of the application process, whereas pigments, in general, retain essentially their particulate or crystalline form during application. A dye is used to impart color to materials of... 

Eichlerova I, Homolka L, Nerud F (2006) Ability of industrial dyes decolorization and ligninolytic enzymes production by different Pleurotus species with special attention on Pleurotus calyptratus, strain CCBAS 461. Process Biochem 41 941-946... 

Uses. Solvent for high-temperature resins petrochemical processing, in the microelectronics fabrication industry, dyes and pigments, industrial and domestic cleaning compounds agricultural and pharmaceutical formulations... 

Sulfonated azo dyes (reactive dyes) are widely used in the textile industry. Due to the simultaneous hydrolysis in the dyeing process, 15-60 % of the reactive dyes reach the waste water system. In addition, their use strongly increases with the colouring of natural fibres, and so a total of 60 % of all dyes emitted to the waste water are reactive materials. 

The textile industry uses a large number of dyestuffs from each of the dye categories, the choice depending on the shade, fiber, and dyeing process, end-use of the textile product, requirements for fastness, and economic considerations. To provide an understanding of the interrelationships that exist among the various dye classes and fiber types, a brief survey of the major fibers follows. 

The pressure vessels are hollow cylinders, of 100- to 10,000-liter capacity, having a flange onto which the cover is fastened by means of bolts and nuts. The bottom of die vessel is usually hemispherical for greater strength. Autoclaves are almost always made of iron, either cast steel or cast iron, the former being safer to use at high pressures. Sheet iron is also used, in wall thicknesses up to 40 mm., in either riveted or welded construction. The reluctance in many dye plants to use welded autoclaves is entirely unjustified and has arisen simply because in the early days of the industry welding processes had not been perfected. 

Qi and Cussler [26] investigated the removal of ammonia by H2SO4. H2SO4 being a strong acid, the mass resistance offered by the membrane controlled the process. An industrial membrane gas absorption unit for ammonia recovery from an ammonia containing off-gas stream produced in a dyes intermediates production plant has been installed by TNO. The membrane plant is able to remove 99.9% of ammonia and produces aqueous solutions of 27% ammonia that can be reused in the dyes process [38]. 

In a recent industrial application, the multicathode cell of Heraus [59] is used for the indirect reduction of dispersed indigo during a dyeing process [60] (Scheme 2). An iron(II)-triethanolamine complex is the active reducing species. The cathodes consist of folded layers of stainless steel or copper. Graphite felt can also be used for this purpose [61]. The outline of this multicathode cell process is shown in Fig. 6. 

If polydimethylsiloxane oils are emulsified together with fine particulate solids, e.g. fumed silicas, very effective defoaming agents are obtained for aqueous media e.g. for the production of aqueous organic polymer dispersions and for dyeing processes in the textile industry. 

The largest ZOSS and ZOFA systems currently in operation are used in the textile industry for recycling wash water in dyeing processes and for renovating caustic solutions (, T). Systems are also being used for oil-water separation, nuclear Industry applications, and food processing. 

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