Лако-красочные материалы — производство

These dyes are now of only minor commercial importance, but are of interest for their small molecular structures. The early nitro dyes were acid dyes used for dye­ing natural animal fibers such as wool and silk. They are nitro derivatives of phe­nols, e. g., picric acid (4) or naphthols, e. g., C. I. Acid Yellow 1, 10316 [846-70-8] (5).

These small molecules are ideal for penetrating dense fibers such as polyester and are therefore used as disperse dyes for polyester. All the important dyes are yellow: (6) (X = H) is C. I. DisperseYellow 14, 10340 [961-68-2] and (6) (X = OH) is C. I. DisperseYellow 9, 10375 [6373-73-5]. Although the dyes are not terribly strong (єmax ca. 20 000), they are cost-effective because of their easy synthesis from inexpensive intermediates. C. I. Disperse Yellow 42 and C. I. Disperse Yellow 86 are important lightfast dyes for automotive-grade polyester.

Nitroso dyes are metal-complex derivatives of o-nitrosophenols or — naphthols. Tautomerism is possible in the metal-free precursor between the nitrosohydroxy tautomer (7) and the quinoneoxime tautomer (8).

The only nitroso dyes important commercially are the iron complexes of sulfo — nated 1-nitroso-2-naphthol, e. g., C. I. Acid Green 1, 10020 [19381-50-1] (9); these inexpensive colorants are used mainly for coloring paper.