Benzodifuranone Dyes

Benzodifuranone Dyes. These (BDF) dyes are challenging anthraquiaone dyes. The BDF chromogen is one of the very few novel chromogens to have been discovered ia this ceatury. As with many other discoveries (10) the BDF chromogen was detected by accideat. The... 

Keywords anthraquinone dyes, azine dyes, azo dyes, benzodifuranone dyes, color index, methine dyes, quinopthalone dyes, perinone dyes, photochromic dyes, sulfur dyes, vat dyes. 

The benzodifuranones constitute one of the more recently introduced groups of carbonyl dyes. They were launched commercially in the late 1980s by ICI as disperse dyes for application to polyester. This group of dyes, of which compound 62 is a representative example, are capable of... 

The discovery in 1979 of the benzodifuranone chromogen (1.14) and its exploitation in red disperse dyes for polyester fibres [23,24] emerged from ICI research towards new chromogens of high colour value, brightness and substantivity to overcome the relative weakness of anthraquinones and dullness of monoazo alternatives in the red disperse dye area. A striking improvement in build-up properties was found by introducing asymmetry... 

A new cross-conjugated methine-type chromogen was introduced in 1984. The dye Cl Disperse Red 356 (6.232) exemplifies this system, which contains two a,co-donor-acceptor dienone segments. The development of such benzodifuranone disperse dyes has been described [87]. 

Indigoid Dyes Like the anthraquinone. benzodifuranone. and polycyclic aromatic carbonyl dyes, the indigoid dyes also contain carbonyl groups. They are also vat dyes. 

The two overriding trends in traditional colorants research for many years have been improved cost-effectiveness and increased technical excellence. Improved cost-effectiveness usually means replacing tinctorially weak dyes such as anthraquinones, until recently the second largest class after the azo dyes, with tinctorially stronger dyes such as heterocyclic azo dyes, triphendioxazines, and benzodifuranones. This theme will be pursued throughout this chapter, in which dyes are discussed by chemical structure. 

The carbocyclic azo dyes are highly cost-effective and have good all-around fastness properties. However, they generally lack brightness and consequendy cannot compete with anthraquinone dyes in this respect. This shortcoming of carbocyclic azo dyes is overcome by heterocyclic azo dyes, as well as other dye classes such as triphenodioxazines and benzodifuranones. 

The most famous dyestuff is probably indigo, an ancient dye that used to be isolated from plants but is now made chemically. It is the colour of blue jeans. More modern dyestuffs can be represented by ICI s benzodifuranones, which give fashionable red colours to synthetic fabrics like polyesters. 

Disperse dyes vary in the type of chromophore present and include azo, anthraquinone, nitro, methine, benzodifuranone, and quinoline based structures. Examples of the first three types are given in Table 13.4, and representative of the latter three types are C.I. Disperse Blue 354, C.I. Disperse Yellow 64, and C.I. Disperse Red 356. Most disperse dyes have azo ( 59%) or anthraquinone ( 32%) structures. Azo disperse dyes cover the entire color spectrum, whereas the important anthraquinone disperse dyes are mainly red, violet, and blue. The azo types offer the advantages of higher extinction coefficients (emax = 30,000-60,000) and ease of synthesis, and the anthraquinones are generally brighter and have better photostability (lightfastness). The key weaknesses associated with the anthraquinone dyes are their low extinction... 

Disperse Polyester, pol)f-amide, acetate, acrylic, and plastics Fine aqueous dispersions often applied by high temperature or pressure or lower temperature carrier methods dye may be padded on cloth and baked or thermofixed Azo, anthraquinone, styryl, nitro, and benzodifuranone... 

As has been the case with most new chromogenic systems, the benzodifuranones were discovered in the laboratory by chance. A considerable amount of industrial development was needed subsequently to establish commercially-viable synthetic routes to the dyes, and the difficulties experienced explain, at least in part, the significant time gap between the initial discovery and the appearance of the first commercial dyes. In particular, processes were required to provide the unsymmetrical molecules, which proved to have superior dyeing properties as disperse dyes for polyester. A successful approach, as illustrated in Scheme 4.9, involves the reaction of the /(-hydroquinone, 4.36, with mandelic acid, 4.37a, to give intermediate 4.38, which may subsequently be reacted with the substituted mandelic acid, 4.37b, to give the benzodifuranone, 4.13. ... 

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