Special Dyeing Processes

Air as Transport Medium. A clear economic advantage is observed when air is used as the transport medium for the textile material (e.g. Then Air Jet). Here, efforts are made to prevent foam formation. The small amount of aqueous dye liquor present carries dyes and auxiliaries. 

Dyeing from Organic Solvents. Chlorinated hydrocarbons, in particular, have been recommended as a medium for continuous or batch dyeing of acetate and PES fibers. For continuous dyeing, dye application from either chlorinated hydrocarbons or an aqueous liquor with fixation in solvent vapor is possible. This method is disfavored for ecological and toxicological reasons [82, p. 676], 

Dyeing via the Gas Phase. Dyeing with dye vapor in the vacuum or in a gas stream as the medium has also been investigated. Although advantageous from an energy standpoint, the problems encountered on a practical scale have not been solved [129], 

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A third approach utilised copper salts, especially copper(II) sulphate, in conjunction with dyes containing chelatable groupings such as salicylic acid or o,o -dihydroxyazo moieties. Indeed, special ranges of copperable direct dyes, for which the treatment with copper(II) sulphate was really part of the dyeing process rather than an optional aftertreatment, were introduced. In the past the main use of this chelation treatment was to enhance light fastness, but it is little used for this purpose nowadays. 

The manufacturing processes for textile filament, staple and industrial filament yams have become so specialized that it is not possible to make one such class of fibers on the others equipment. Within these classes, there are production machines specialized for certain types of fibers for specific types of consumer products. Large machines designed to produce high volumes of commodity products (e.g. staple for cotton blending) at high efficiency and low cost are not well suited to the efficient production of specialty staple variants (e.g. fibers with special dyeing properties) and vice-versa. 

An important innovative technique to replace water as the solvent in dyeing processes is the use of supercritical fluids, for example, supercritical CO2 for dyeing processes. Successful trials have been conducted in various scales with different fibers and full-scale production has been performed in the case of PES dyeing [62,63]. Besides the handling of high pressure equipment, the development of special dyestuff formulations is required. 

In a specially designed process, warp yam dyeings with indigo can be imitated [79],... 

Artificial silk was first produced from cotton waste in the early 1900s. Three Englishmen are credited with discovering how to produce viscose (rayon) from a cellulose solution using wood and woody materials. During World War I, this process was used to make guncotton (by nitrating the cellulose) and other explosives. The rayon was also used as artificial silk. Special dyes, now known as acid dyes, had to be developed to color this product. 

On the other hand, the processing-fastness-requirements depend on the very special sequence of operations that are made around the actual dyeing process. The best representation of the expert s knowledge in this area is given by a set of rules that catches the expert s considerations when he derives these requirements. 

Aromatic compounds have not only been of academic interest ever since organic chemistry became a scientific discipline in the first half of the nineteenth century but they are also important products in numerous hydrocarbon technologies, e.g. the catalytic hydrocracking of petroleum to produce gasoline, pyrolytic processes used in the formation of lower olefins and soot or the carbonization of coal in coke production [1]. The structures of benzene and polycyclic aromatic hydrocarbons (PAHs) can be found in many industrial products such as polymers [2], specialized dyes and luminescence materials [3], liquid crystals and other mesogenic materials [4]. Furthermore, the intrinsic (electronic) properties of aromatic compounds promoted their use in the design of organic conductors [5], solar cells [6],photo- and electroluminescent devices [3,7], optically active polymers [8], non-linear optical (NLO) materials [9], and in many other fields of research. 

Wetting is often one of the first steps for the effect of a surfactant. A special case is the penetration of fluids into porous material such as a bundle of fibres in the dyeing process or the stone matrix in enhanced oil recovery. One of the steps of lubrication is wetting of the surfaces by lubricant liquids. Because often further conditions have to be considered, the use of phosphorus-containing surfactants can be favourable. 

Mordant. This class is now restricted to that group of special wool dyes, the dyeings from which are treated with aqueous bichromate in order to improve wet fastness. This treatment may be apphed to the fabric before dyeing, during the dyeing process or afterwards. Application after dyeing or after chrome process is the method most widely used. 

Of special interest are the chelate complexes that form when mordanting takes place in the dyeing process. One more metaphor associated with chelates the Latin word mordere means to bite, and a mordant is a substance that allows the dye molecule to bite into it. In so doing, the dye and the mordant form a new chemical substance as we see above in the reaction of the copper(II) ion with two molecules of 2,4-pentanedione. Using a mordant with a dye has some important effects ... 

Alumina trihydrate (ATH) is made from waste generated by the almninum metal purification process. It has high brightness but low refi active index. At low levels of substitution for Ti02, 25% or less, optical properties can be maintained. Like the synthetic silicas, ATH can be used as a paper brightning pigment when opacity is not as important. ATH is used in NCR (no carbon required) papers where it favorably affects the special dyes used in the paper. ATH is also known for its flame retardant properties. ATH retards bmming by the release of water at rather low temperatures. It is added to impart flame retardance to certain specialty papers. 

An important assumption, however, is assumption 6, since it separates convection and dispersion. Assumptions 7 and 8 aim to further incorporate the adsorption factor into the model. According to the theory and practice, these assrrmptions are reasonable. These basic assiunptions, and special definitions for some individttal cases, provide a basis for mathematical modelling of the dyeing process. 

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