Читать книгу Sustainable Practices in the Textile Industry - Группа авторов - Страница 20

1 Indigoid dyes: This group includes Indigo and Tyrian purple dye. Indigo is extracted from Indigofera tinctoria and considered the most primitive dye. Woad plant (Isatis tinctoria) also has indigo as the chief blue dyeing component.

2 Anthraquinone dyes: Most of the red natural dyes from both plant and mineral origin are based on the anthraquinoid structure. Madder, Lacs, Cochineal are some examples of this group. Alizarin and purpurin are the main chromophores in Rubia tinctorum.

3 Alpha naphthoquinones: Lawsone (henna) is a most important member of this class. Another dye is juglone, isolated from the shells of unripe walnuts.

4 Flavonoids: Yellow dyes obtained from this group and can be classified under flavones, isoflavones, aurones and chalcones. These yellows are found in a variety of plants, including Persian berries (Rhamnus spp.), young fustic (Cotinus coggygria), old fustic (Chlorophora tinctoria) and yellow wood (Solidago virgaurea).

5 Di-hydropyrans: In chemical structure, di-hydropyrans are similar to the flavones. These natural dyes give dark shades on cotton, wool and silk. Logwood and Sappan-wood are the most common examples.

6 Anthocyanidins: Orange dye carajurin obtained from leaves of Bignonia chica. Carajurin is a chemical member of this class.

7 Carotenoids: The class name carotene is derived from the orange pigment found in carrots. In these, the color is due to the presence of long conjugated double bonds. Usually, red, orange and yellow colors come in this category and can be obtained from different plants, e.g. yellow, orange color in sunflower [37, 38].