A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous, and requires a mordant to improve the fastness of the dye on the fiber. Dyes can be precipitated with an inert salt to produce a lake pigment, and based on the salt used they could be aluminum lake, calcium lake or barium lake pigments. Dyes can be precipitated with an inert salt to produce a lake pigment, and based on the salt used they could be aluminum lake, calcium lake or barium lake pigments. Dye, any substance, natural or synthetic, used to color various materials, especially textiles, leather, and food. Natural dyes are so called because they are obtained from plant. Some materials, e.g., silk and wool, can be colored simply by being dipped in the dye (the dyes so used are consequently called direct dyes), others, including cotton, commonly require the use of a mordant (see also lake). Dyeing is an ancient industry. The Chinese, Persians, and Indians used natural dyes many centuries ago, including indigo, probably the oldest dye in use, and Tyrian purple, derived from a species of snail. The major users of dyes in India are textiles, paper, plastics, printing ink and foodstuffs. Dye intermediates are discussed in depth. These falls conveniently into aromatic carbocyclic intermediates and aromatic heterocyclic intermediates.

There are several ways for classification of dyes. It should be noted that each class of dye has a very unique chemistry, structure and particular way of bonding.

Classification of dyes-

1)     Organic/inorganic

2)     Natural/synthetic

3)     Chemical classification

4)     By nature of the electronic excitation

5)     According to the dyeing methods: anion in, direct, disperse

6)     Advocate by us international trade commission

7)     By area and method of application

The Indian dyestuff industry is only about 40 years old though a few MNCs set up dyestuff units in the pre independence era. India contributes about 6% of the share in the global market with a CAGR of more than 15% in the last decade. The demand for dyes and dye intermediates is expected to grow at around 6%, backed by strong demand from the textiles, leather, and inks industries. Globally the dyestuffs industry has seen an impressive growth. Dyes and Dye Intermediates are synthesized in a reactor, filtered, dried, and blended with other additives to produce the final product.  Equipment and manufacture of dyes and dye intermediates are dealt with, as are economic aspects. Health and safety aspects, including toxicology and registration of dyes, and environmental factors, such as treatment of dye effluent, are also covered.

FURTHER INFORMATION:

The complete technology book on dyes and dye intermediates describes the detailed information on subject. The major contents of this book are- Dyes & Dye Intermediates, Azo Dyes, Reactive Dyes, Carbonyl Chloride as Reactive Group, Anthraquinone Dyes, Acid Dyes, Sulfur Dyes, Cyanine Dyes, natural dyes, applications of dye, dyeing processes, dye and non-textile application, dye intermediates, manufacturing processes.

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