Reactive Formazan Dyes

There are bi-, tri-, and tetradentate formazan dyes7 but only the tetradentate copper complex formazan dyes have found use as commercial products. The dye Cl Reactive Blue 160, of generic structure (41), is a representative example. Because of the intensity of their colors, the metal complex formazan dyes have also found application in analysis. Thus, the dye (42) detects zinc at a concentration of 1 part in 50 million.31... 

An appropriate ion-specific electrode was found to provide a convenient, precise and relatively inexpensive method for potentiometry of copper(II) ion in copper-complex azo or formazan dyes. Copper(II) ion in copper phthalocyanine dyes can be quantified after anion exchange. Twelve commercial premetallised dyes evaluated using this technique contained copper(II) ion concentrations in the range 0.007 to 0.2%. Thus many copper-complex direct or reactive dyes are likely to contribute low but possibly significant amounts of ionic copper to textile dyeing effluents [52]. 

Rate constants and the products formed in the hydrolysis of Cl Reactive Red 194 (7.76) at 50 °C and pH values in the 10-12 region were determined by high-pressure liquid chromatography. In addition to the normal hydrolysis of the two reactive systems, the imino link between the triazine and benzene nuclei was also hydrolysed [67]. The heterobifunctional copper formazan dye Cl Reactive Blue 221 and two blue anthraquinone monofunctional reactive dyes of the bromamine acid type, namely the aminochlorotriazine Blue 5 and the sulphatoethylsulphone Blue 19, were compared in terms of their sensitivity to... 

Formazan dyes bear a formal resemblance to azo dyes, since they contain an azo group. The most important formazan dyes are the metal complexes, particularly copper complexes, of letradentate formazans. They are used as reactive dyes far cotton. 

Formazan dyes have become important reactive dyes for cotton. Formazan dyes are also used in analytical chemistry because of the high color intensity of many of their metal complexes. The chemistry of formazans was first exploited in 1962 by MacDonald to produce color photographs [81],... 

Virtually every conceivable chromophore has been used in the synthesis of reactive dyes, including monoazo and disazo species, metal complexes of azo dyes, formazan dyes, anthraquinones, triphenodioxazines, and phthalocyanines. The product lines offered by the major dye producers in most cases feature comparable chromophores, differing primarily in the nature of the reactive systems and the particular substitution patterns adopted. 

Copper complexes of the formazan dye series (see Sections 2.10 and 3.11) are another alternative to reactive anthraquinone dyes they produce red to greenish-blue shades. Like triphenodioxazine dyes, copper formazans exhibit high molar extinctions ( e = 25 000 -30 000). These materials are derived from l-(2-hydroxyphe-nyl)-3-phenyl-5-(2-carboxyphenyl)formazan (22), in which all three rings are capable of supporting groups that increase the compound s reactivity and solubility. 

Dyes 8-12 belong to the family of azo conqiounds, while 13 is a formazan dye. Formazan dyes are more commonly used as dyes for cellulose-based fibers, in which case they would contain a reactive moiety, and are 1 1 Cu-complexed dyes (1 metal per dye molecule) (6). Metal complexes of the 1 2 type (1 metal per 2 dye molecules) are used for polyamide and protein fibers. In the latter case, Cr and Co complexes... 

These factors have been demonstrated elegantly in a detailed evaluation by pad-batch dyeing of cotton with three commercially important copper formazan reactive dyes ... 

Fig. 2. Phlhalocyanine (S) and metallized formazan (6,7) and azine (8) blue reactive dyes. Reactive Blue 15 (Cl 74459) (5) Reactive Blues (6) and (7) Reactive Blue 204 (8). Other blue oxazine dyes ate other fluorotriazines and a dichlorotriazine.

Reactive Dyes. These dyes form a covalent bond with the fiber, usually cotton, although they are used to a small extent on wool and nylon. This class of dyes, first introduced commercially in 1956 by ICI, made it possible to achieve extremely high washfastness properties by relatively simple dyeing methods. A marked advantage of reactive dyes over direct dyes is that their chemical structures are much simpler, their absorption spectra show narrower absorption bands, and the dyeings are brighter. The principal chemical classes of reactive dyes are azo (including metallized azo), triphendioxazine, phthalocyanine, formazan, and anthraquinone (see Section 3.1). 

Reactive cotton, wool, silk, and nylon reactive site on dye reacts with functional group on fiber to bind dye covalently under influence of heat and pH (alkaline) azo, anthraquinone, phthalocyanine, formazan, oxazine, and basic... 

Stability of the Dye-Fiber Bond. Because of the large variety of reactive dyes, generalizations about colorfastness are difficult. While wetfastness is determined mainly by the anchor system used, most other fastness properties depend on the dye as a whole or the chromophore present. Most reactive dyes are azo or anthra-quinone derivatives whose standard of fastness varies greatly. Phthalocyanine, formazan, and triphenodioxazine derivatives are also very important. In addition, application conditions and finishing processes of the dyed goods can affect fastness properties. Thus, with some resin-finished textiles (dimethylolpropyleneurea finish) a decrease in lightfastness is observed. 

Special Processes and Development Trends [36, 37], Many attempts have been made to remedy the weak points of the reactive dyeing system. Lightfastness could be significantly improved over a wide range of shades by development of effective chromophores (e g., triphenodioxazine and copper formazan for blues). However, in the red range, reactive dyes are still inferior in lightfastness to vat and naphthol dyes. 

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