Acid dyes development

The first acid dye, Orange I (1.53 Cl Acid Orange 20), was discovered in 1876. All but a handful of the acid dyes developed since then were evaluated initially with wool dyeing in mind. In terms of adaptability to the coloration of other substrates, however, acid dyes have proved pre-eminent. This is the main reason for their number and variety. As well as the dyeing and printing of nylon and protein fibres, acid dyes are important for the coloration of leather, paper, jute, wood and anodised aluminium. Most of the permitted dyes for food and... 

The requirements of a developer moiety for incorporation into a dye developer are well fulfilled by hydroquinones. Under neutral or acidic conditions hydroquinones are very weak reducing agents and the weakly acidic phenoHc groups confer tittle solubility. In alkali, however, hydroquinones are readily soluble, powerful developing agents. Dye developers containing hydroquinone moieties have solubility and redox characteristics in alkali related to those of the parent compounds. 

Termination of the process is effected by the acid polymer layer of the receiving sheet. Acting as an ion exchanger, the acid polymer forms an immobile polymeric salt with the alkah cation and returns water in place of alkah. Capture of alkaUby the polymer molecules prevents deposition of salts on the print surface. The dye developers thus become immobile and inactive as the pH of the system is reduced. 

In 1894 the first two anthraquinone acid dyes. Cl Acid Violet 43 [4430-18-6] (2) (Cl 60730) and Cl Acid Green 25 [4403-90-1] (3) (Cl 61570) were invented. This encouraged the subsequent development of various kinds of anthraquinone acid dyes, which were used to dye wool in fast, brilliant shades without need for pretreatment. 

In the 1950s acid dyes were successively developed to dye nylon carpet with excellent fastness and uniform leveling. Development of polyacrylonitrile fiber stimulated the invention of anthraquinone basic dyes, modified disperse dyes in which quaternary ammonium groups are introduced. 

The traditional use of dyes is in the coloration of textiles, a topic covered in considerable depth in Chapters 7 and 8. Dyes are almost invariably applied to the textile materials from an aqueous medium, so that they are generally required to dissolve in water. Frequently, as is the case for example with acid dyes, direct dyes, cationic dyes and reactive dyes, they dissolve completely and very readily in water. This is not true, however, of every application class of textile dye. Disperse dyes for polyester fibres, for example, are only sparingly soluble in water and are applied as a fine aqueous dispersion. Vat dyes, an important application class of dyes for cellulosic fibres, are completely insoluble materials but they are converted by a chemical reduction process into a water-soluble form that may then be applied to the fibre. There is also a wide range of non-textile applications of dyes, many of which have emerged in recent years as a result of developments in the electronic and reprographic... 

One of the first applications developed for flow cytometry was cell cycle analysis.2 There are numerous intercalating fluorescent DNA and RNA staining reagents that can be used to determine the amount of DNA in cells, an indicator of cell cycle stage and progression, as demonstrated in Figure 7.3. Nucleic acid dyes may be selective for DNA... 

Difficulties of incompatibility can arise with mixtures of basic dyes on acrylic fibres because of competition for the limited number of dyeing sites available and the differences between dyes in terms of affinity and rate of diffusion. The rate of uptake of each dye when applied in admixture with another is invariably slower than when the dye is applied alone at the same concentration. Competition effects of this kind can lead to serious practical problems unless the dyes are carefully designed and selected to have similar dyeing characteristics [97,98,104,105]. Dyes with exceptionally low affinity and rapid rates of diffusion have been developed, offering improved migration on acrylic fibres [106]. These dyes have migration properties not unlike those of monosulphonated acid dyes on nylon. 

The broad field of nucleic acid structure and dynamics has undergone remarkable development during the past decade. Especially in regard to dynamics, modem fluorescence methods have yielded some of the most important advances. This chapter concerns primarily the application of time-resolved fluorescence techniques to study the dynamics of nucleic acid/dye complexes, and the inferences regarding rotational mobilities, deformation potentials, and alternate structures of nucleic acids that follow from such experiments. Emphasis is mainly on the use of time-resolved fluorescence polarization anisotropy (FPA), although results obtained using other techniques are also noted. This chapter is devoted mainly to free DNAs and tRNAs, but DNAs in nucleosomes, chromatin, viruses, and sperm are also briefly discussed. 

A dye developer is a compound composed of a silver halide developer fragment linked via an insulating group (Z) to a dye moiety. The compounds are intrinsically soluble in alkali because of acid functions contained in the developer fragment, normally a hydroquin-one. On interaction with exposed silver halide the hydroquinone becomes oxidized to the corresponding quinone. This renders the compound insoluble in alkali (Scheme 7). The reaction can be enhanced by the use of a mobile auxiliary developer such as p-methylphenyl-hydroquinone. In the areas of the emulsion layer where there has been no exposure of silver halide, the dye developer cannot be oxidized. It therefore remains soluble and free to transfer to the mordant layer. Thus, the transfer of dye is inversely proportional to the amount of exposed silver halide and the overall result is a positive of an original scene on the receiver. 

Dyes Dispersed and developed dyes are commonly used. Acid dyes are used lor printing. Solution dyed available. 

Yellow, red, and navy blue for leather can be obtained with monoazo dyes. Generally speaking, azo dyes with naphthalene moieties give deeper shades than those with phenyl residues. These classical acid dyes were developed for wool, silk, and polyamide fibers, and suitable ranges are applied to leather. The molecular weight for penetration dyes is below 500. Typical leather penetration dyes are C.I. Acid Yellow 11 18820 [6359-82-6] (7) and C.I. Acid Red 7, 14895 [5 5 -61-7] (8 Orange II), which are still used today. 

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. 

CNC PAL 1000 is a specially developed leveling and scouring agent for acid dyes on nylon. It is particularly effective in the continuous dyeing of nylon carpet. 

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