Blue dye

Aniline was first isolated in 1826 as a degradation prod uct of indigo a dark blue dye obtained from the West Indian plant Indigofera anil from which the name aniline IS derived... 

Optical Properties. Brightness, or visual whiteness of paper, can be defined as the degree to which light is reflected uniformly over the visible spectmm. Since pulp and typical impurities tend to be yellowish, blue dye is sometimes added in addition to appropriate fillers. The percentage reflectance is usually measured in the blue end of the spectmm at or near 457 nm (14). 

Methanol can be converted to a dye after oxidation to formaldehyde and subsequent reaction with chromatropic acid [148-25-4]. The dye formed can be deterruined photometrically. However, gc methods are more convenient. Ammonium formate [540-69-2] is converted thermally to formic acid and ammonia. The latter is trapped by formaldehyde, which makes it possible to titrate the residual acid by conventional methods. The water content can be determined by standard Kad Eischer titration. In order to determine iron, it has to be reduced to the iron(II) form and converted to its bipyridyl complex. This compound is red and can be determined photometrically. Contamination with iron and impurities with polymeric hydrocyanic acid are mainly responsible for the color number of the merchandized formamide (<20 APHA). Hydrocyanic acid is detected by converting it to a blue dye that is analyzed and deterruined photometrically. 

There is a wide variety of dyes unique to the field of hair coloring. Successive N-alkylation of the nitrophenylenediamines has an additive bathochromic effect on the visible absorption to the extent that violet-blue dyes can be formed. Since the simple A/-alkyl derivatives do not have good dyeing properties, patent activity has concentrated on the superior A/-hydroxyalkyl derivatives of nitrophenylenediamines (29,30), some of which have commercial use (31). Other substituents have been used (32). A series of patents also have been issued on substituted water-soluble azo and anthraquinone dyes bearing quaternary ammonium groups (33). 

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

Tetrasodium hexakiscyanoferrate decahydrate [14434-22-1], Na4[Fe(CN)g] IOH2O, or yellow pmssiate of soda, forms yellow monoclinic crystals that are soluble in water but insoluble in alcohol. It is slightly efflorescent at room temperature, but the anhydrous material, tetrasodium hexakiscyanoferrate [13601 -19-9], Na4[Fe(CN)J, is obtained at 100°C. The decahydrate is produced from calcium cyanide, iron(II) sulfate, and sodium carbonate in a process similar to that for the production of K4[Fe(CN)g] 3H2O. It is used in the manufacture of trisodium hexakiscyanoferrate, black and blue dyes, as a metal surface coating, and in photographic processing. 

On more severe thionation, a third thiamine ring is formed to give a sulfur black. However, if hydroxyl groups instead of amino groups are attached at positions 2 and 2, no ring closure would take place and the blue dye would be stable to heat. These formulas are general expressions for the nuclear stmctures of the blue-to-black sulfur dyes they do not take into consideration the quinonoid formation of each dye and other aspects. 

Cyanide compounds are classified as either simple or complex. It is usually necessary to decompose complex cyanides by an acid reflux. The cyanide is then distilled into sodium hydroxide to remove compounds that would interfere in analysis. Extreme care should be taken during the distillation as toxic hydrogen cyanide is generated. The cyanide in the alkaline distillate can then be measured potentiometricaHy with an ion-selective electrode. Alternatively, the cyanide can be determined colorimetricaHy. It is converted to cyanogen chloride by reaction with chloramine-T at pH <8. The CNCl then reacts with a pyridine barbituric acid reagent to form a red-blue dye. 

The patended method of preparation of the blue dye (120) [19187-01 -0] (81) involves treating the analogous dibromo substituted azo dye with cuprous cyanide in dimethylformamide or A-methylpyrrohdinone at 50°C to effect replacement of the two bromo substituents by cyano groups. 

The greenish-blue dye (117) (82) is prepared in a similar fashion, replacing bromo with cyano by using cuprous cyanide, pyridine, and 2-methoxyethanol as solvent at 85°C. 

Couplers which form scarlet dyes with 4-nitroani1ine and red dyes with 2-amiQO-6-nitrobenzothiazole yield blue dyes with 3-amiQo-5-nitro-2,l-benzisothiazole [14346-19-1]. 

Another bright blue dye from diazotized 2-amiao-6-methoxybenzothiazole [1747-60-0] by azo coupling, eg, with 2(/V-ethy1ani1ino)ethano1 is Basacryl Blue X-3GL [12270-13-2] (133) (Cl Basic Blue 41 Cl 1110S). After couphng, the water-iusoluble dye is methylated at the thiazole nitrogen. 

Blueing agents, which are dyes, provide another approach to maintaining fabric whiteness by a mechanism in which a yellow cast of washed fabrics is covered by the blue dye. Since this approach reduces reflectance, it is less desirable than the use of fluorescent whitening agents that increase reflectance. 

Although the colors of the polycycHc aromatic carbonyl dyes cover the entire shade gamut, only the blue dyes and the tertiary shade dyes, namely, browns, greens, and blacks, are important commercially. Typical dyes are the blue indanthrone [81-77-6] (40), the brown Cl Vat Brown 3 [131-92-0] (Cl 69012), (41), the black Cl Vat Black 27 [2379-81-9] (42), and the green Cl Vat Green 1 [128-58-5] (Cl 59825) (43), probably the most famous of all the polycycHc aromatic carbonyl dyes. 

Production of anthraquinone reactive dyes based on derivatives of bromamine acid (8) was first commercialized in 1956. Some improvements have been made and now they ate predominandy used among the reactive blue dyes. Cl Reactive Blue 19 [2580-78-1] (9) (Cl 61200) (developed by Hoechst in 1957) has the greatest share among them including dye chromophores other than anthraquinones. 

World dye manufacturers have already begun to develop new types of dyes that can replace the anthraquinones technically and economically (1). Some successful examples can be found in a2o disperse red and blue dyes. Examples are brilliant red [68353-96-6] and Cl Disperse Blue 165 [41642-51 -7] (Cl 11077). They have come close to the level of anthraquinone reds and blues, respectively, in terms of brightness. In the reactive dye area intensive studies have continued to develop triphenodioxa2ine compounds, eg, (13), which are called new blues, to replace anthraquinone blues. In this representation R designates the substituents having reactive groups (see Dyes, reactive). 

Anthraquinone-a,a -disulfonic acids and Related Compounds. Anthraquinone-a,a -disulfonic acids and their derivatives are important intermediates for manufacturing disperse blue dyes (via 1,5-, or 1,8-dihydroxyanthraquinone, or 1,5-dichloroanthraquinone) and vat dyes (via... 

Dichloroanthraquinone [82-46-2] (46) is an important iatermediate for vat dyes and disperse blue dyes. Examples are Cl Vat Violet 13 [4424-87-7] (170), Cl Vat Orange 15 [2379-78-4] (154), and Cl Disperse Blue 56 [31810-89-6] (11). 1,5-DichloroantliraquiQone is prepared by the reaction of anthraquiQone-l,5-disulfonic acid with NaClO iu hot hydrochloric acid solution. Alternative methods from 1,5-dinitroanthraquiaone (49) by reaction of chlorine at high temperature ia the presence of phthaUc anhydride have been proposed (66). 

DihydroxyanthraquiQone (anthranifin) [117-12-4] (47) is an important iatermediate for manufacturiag disperse blue dyes, eg. Cl Disperse Blue 73 (113), and is prepared from anthraquiQone-l,5-disulfonic acid by heating with an aqueous suspension of calcium oxide and magnesium chloride under pressure at 200—250°C (67). Alternative methods have been proposed, ie, direct replacement of the NO2 groups of 1,5-dinitroanthraquiaone (49) (68) or the route via 1,5-dimethoxyanthraquiaone [6448-90-4] (48) and subsequent hydrolysis (69). 

OCjOC -Dinitroanthraquinones and Related Compounds. 1,5- and 1,8-Dinitroanthraquiaone are the key iatermediates for manufacturiag disperse blue dyes via dinitrodihydroxyanthraquiaoae and vat dyes via diaminoanthraquiaones. 1,5-Diaitroanthraquinone [82-35-9] (49) and 1,8-dinitroanthraquinone [129-39-5] (50) are prepared by nitration of anthraquiaone with nitric acid ia sulfuric acid. a,P -Dioitroanthraquiaoaes are also formed ia the reactioa. 

High purity of 1,5-dimethoxyanthraquiaone is required for manufacturiag disperse blue dyes (Cl Disperse Blue 56 (11)). A small amount of unreacted 1,5-dinitroanthraquiaone ia 1,5-dimethoxyanthraquiaoae affects the brightness of the dye and makes it much duller. Improved processes have been reported (84,85). 

Cl Disperse Blue 56 is the most important blue dye for polyester fibers because it has a brilliant shade, excellent lightfastness, and good leveling properties. 

The principle of each process is briefly described ia the Hterature (170). Some anthraquiaoae dyes and pigments appear to be used ia combination with other dye or pigment classes such as phthalocyaniaes and carbazole violets, etc. Two examples described ia pateats are the red pigment and blue dye that foUow ... 

The red pigment has been proposed to be usable ia both the pigment dispersioa method and the electro deposition method (171,172). The blue dye may be used ia the dyeiag method fabricatioa process (173). 

Although there is still demand for indigotin for dyeing blue jeans, it has lost a good part of the market to other blue dyes with better dyeing properties. At present, practically all the indigotin consumed in the United States comes from abroad. 

Theoretically, the dye or chromogen can be any colored species. Of course, requirements for fastness, solubiUty, tinctorial value, ecology, and economy must be met. Most commonly used chromophores parallel those of other dye classes. Azo dyes (qv) represent the largest number with anthraquiaone and phthalocyanine making up most of the difference. Metallized azo and formazan dyes are important and have gained ia importance as a chromophore for blue dyes duriag receat years (6) (see Dyes and dye intermediates). 

Blue dyes are derived from anthraquiaone, phthalocyanine, or metallised formasan (7) (see Dyes, anthraquinone) (Figs. 1 and 2). There are also oxasiae and thiasine dyes reported (13) (see AziNEDYEs) (Fig. 2). 

Color/Transparency. Almost all amorphous engineering thermoplastics, except PC and some polyester carbonates, are inherently colored. Even polycarbonates have yellowness indexes (YI) (36) of 0.1 to 5.0. Colorless material is produced from these resins by compounding with complementary blue dyes which reduce transmission. Ha2e in amorphous resins is an indication of particulates. Ha2e reduces optical clarity and transmission. 

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