Dyestuffs and Pigments

Dyes is a class of organic compounds that can give other substances  bright and firm color.But colored substances are not necessarily dyes.The dye must be able to attach a
certain color to the fiber, and it is not easy to fall off and change color. Dyes are usually soluble in water, and some of the dyes require mordants to make the dyes adhere to
the fiber. Dyes are generally composed of chromophore and auxiliary chromophore.
1.According to the properties and applications,they can be divided into direct dyes, acid dyes, cationic dyes, reactive dyes, insoluble azo dyes, disperse dyes, vat dyes, sulfide dyes,
 Polycondensation dyes, fluorescent brighteners, in addition, there are oxidation dyes for textiles (such as aniline black), solvent dyes, polypropylene dyes and edible pigment.
2.According to the dyeing method, dyes can be divided into direct dyes, acid dyes, basic dyes, acid mordant dyes, vat dyes, insoluble azo dyes, disperse dyes, reactive dyes,
oxide dyes and so on.
3.According to the chemical structure or characteristic groups of dyes, dyes can be divided into azo dyes, anthraquinone dyes, arylmethane dyes, indigo dyes, sulfide dyes,
phthalocyanine dyes, nitro and nitroso dyes, as well as other structural types of dyes, such as methylene and polymethylchuan dyes, stilbene dyes and various heterocyclic dyes.
4.According to the solubility, they can be divided into Acid dyes,Basic dyes,Mordant dyes,Vat dyes,Reactive dyes,Disperse dyes,Sulfur dyes and son on.
5.They also can be divided into natural dyes and synthetic dyes.
Natural dyes are obtained from plants, animals or mineral resources, without artificial synthesis, with little or no chemical processing.
Synthetic dyes, also known as artificial dyes, are mainly fractionated from coal tar (or petroleum processing) through chemical processing, commonly known as "coal tar dyes".
Synthetic dyes are sometimes called "aniline dyes" because they mainly use aniline as raw material in the early stage of development. And they are commonly used in the fields
 of textiles, paints and printing.
The difference between natural dyes and synthetic dyes is that synthetic dyes are chemically manufactured, while natural dyes are pure natural, and the price of natural dyes is
much more expensive than synthetic dyes, so most of the dyes used in industry are synthetic dyes'.

Pigment refers to the insoluble (insoluble in water, organic solvent, color developing agent and colored substance) that can make the substance colored. Pigments can be
divided into inorganic pigments and organic pigments according to their chemical composition, and can be divided into natural pigments and synthetic pigments according to
 their sources.Natural pigments are derived from plants, animals, or minerals and are not synthetic, rarely or without chemical processing. Synthetic pigments were synthesized,
such as titanium dioxide, zinc barium white, lead chrome yellow, iron blue and other inorganic pigments, as well as red powder, even light yellow, phthalocyanine blue,
quinacridone and other organic pigments.
Organic pigments have bright colors, bright tones, wide chromatographic range and many varieties. They have much higher coloring power or coloring strength than
inorganic pigments, and some varieties also have high transparency. suitable for fabric printing, plastics, rubber, ink and high-grade paint coloring.Most of the colors of
inorganic pigments are dark, not bright enough, the variety is too few, the chromatography is not complete, and many inorganic pigments are toxic.
However, the production of inorganic pigments is relatively simple and cheap, so the current output of inorganic pigments is much higher than that of organic pigments.
Pigments are suitable for plastics, glass, ceramics, enamel, coatings and other industries. In addition to bright colors, in terms of physical properties, it also has good covering
power, coloring power, dispersion, oil absorption, light resistance,etc.

Difference:
Dyes and pigments are very fine colored substances, the color of dyes is more bright than pigments, but the coloring ability, covering ability, light and water resistance of dyes
are poor. In the process of pigment coloring, there is no chemical combination between the dye molecules and the pigment molecules, nor is it soluble in water or any solvent,
 while there is a chemical combination between the dye molecules and the pigment, and it is selective to color the object, soluble in water or organic solvent.