Direct Yellow

Stilbene dyes of importance aie mosdy direct yellow dyes for ceUulosic fibers, especially paper. There have been several red and blue stilbene-containing dyes reported, but they have not (ca 1996) been developed to commercial importance. There are brown leather dyes which are stilbene-based. The most important stilbene dyes are those known siace the 1880s. The commercial importance of Direct Yellow 11 (1883), Direct Orange 15 (1888), Direct Yellow 4 (1886), and Direct Yellow 106 (1936) attest to the value, properties, and durabiUty of stilbene yellow dyes. 

Self-condensation products of 4-nitrotoluene-2-sulfonic acid or its derivative 4,4 -dinitto-2,2 -stilbenedisulfonic acid or 4,4 -dinitto-2,2 -dibenzyldisulfonic acid [728-42-7] and products of their treatment with teduciag or oxidizing agents. An example is Direct Yellow 11 (Cl... 

Condensation products of 4-nitiotoluene-2-sulfonic acid oi its detivatives together with phenols, naphthols, or aminophenols. An example here is Direct Yellow 19 (Cl 40030) (3) ... 

Coupling tetra2o (7) with o-cresol has been reported to give a dye (19) which is less alkah-sensitive than Direct Yellow 4 (Cl 24890) and to have better cold-water solubiUty than Direct Yellow 12 (Cl 24895) (18). One reference is made to a stilbene laser dye (10) and two each to dyes for 1ight-po1ari2ing films (34,35) and reprographic inks (36,37). 

Direct Yellow 4, Direct Yellow 11, Direct Yellow 106, and Direct Orange 15 are the most important stilbene dyes, accounting for most sales of this type. Estimated volumes and values for Hquid and powder forms appear in Table 3 (38). 

Oxidation of Aromatic Amines. The technically important dye Direct Yellow 28 (23) [10114-47-3] (Cl 19555) for cotton usage is manufactured by oxidation of dehydrothio- i ra-toluidinesulfonic acid sodium salt with sodium hypochlorite ia aqueous alkaline solutioa. 

DAS (11.7) is synthesised from 4-nitrotoluene-2-sulphonic acid (11.6) by the route outlined in Scheme 11.1. An important factor in the preparation of DAST brighteners in the purity necessary for good performance is the purity of the DAS used as starting material. At one time DAS made in this way contained significant amounts of yellow azoxy compounds similar to 11.8, which formed the main components of the obsolescent dye Sun Yellow (Cl Direct Yellow 11) made by the partial reduction and self-condensation of intermediate 11.6. Today the major manufacturers supply DAS essentially free from these undesirable impurities [37]. 

The yellow ink jet dyes (and pigments) are metal-free azo dyes, such as Cl Direct Yellow 132 and Cl Acid Yellow 23 (Tartrazine).48,49 Most of the magentas are azo dyes derived from H-acid (l-amino-8-naphthol-3,6-disulfonic acid), such as (62), and xanthenes, such as Cl Acid Red 52 and Cl Acid Red 289.48,49 Where high lightfastness is a requirement, a copper complex azo dye, Cl Reactive Red 23 (63), is used. However, such dyes are dull (see Section 9.12.3.2). Nickel complex PAQ dyes, such as (22), are claimed to be brighter and to have similar high lightfastness... 

Direct Yellow 12 Direct Green 6 Direct Brown 2 Direct Black 38 Direct Blue 15 Direct Red 23 Congo Red Direct Orange 26 Tartrazine P. chrysosporium ZrOCl2-activated pumice [54]... 

Affinity values of the symmetrical disazo dyes Cl Direct Yellow 12 (3.6), Red 2 (3.8 X = CH3, Y = H) and Blue 1 (3.2) on cellophane have been measured recently under hydrostatic pressures up to 600 Mpa [120]. The affinity of Yellow 12 increased slightly but values for the other two dyes decreased considerably with increasing hydrostatic pressure (Table 3.23). The sulpho groups on the central stilbene nuclei of the Yellow 12 molecule tend to inhibit aggregation, whereas Red 2 and Blue 1 aggregate much more readily. The small increase in the affinity observed with Yellow 12 may indicate that isomerisation from the cis to the more stable Linns form may occur as the hydrostatic pressure is increased. 

The simplest monoazo dyes fail to meet these requirements, but by choosing intermediates known to confer substantivity and by building up the molecule to provide the necessary length and coplanarity (section 3.2.1), direct dyes can be produced from this class. Thus the highly substantive character of the benzothiazole nucleus is exploited in Cl Direct Yellow 8 (4-58), as is the alignment of the azo, ureido and acylamino groups in the substituted J acid coupling component of Cl Direct Red 65 (4-59). 

---