Dyes and pigments

Dyes are organic substances that enable the coloring of materials such as fibers. There are many kinds of dyes, which can be classified into natural dyes (such as vegetable dyes, animal dyes and mineral dyes) and synthetic dyes (or artificial dyes) depending on the source. According to the molecular structure, it can be classified into an azo dye, an anthraquinone dye, a phthalocyanine dye, an arylmethane dye, a nitro dye, and the like. According to the application method, it is divided into acid dye, basic dye, sulfur dye, reactive dye, disperse dye, direct dye and so on. The dye has a color, but the colored material is not necessarily a dye. The dye must have a chromophore and a chromophore. The dye in the ink should also have a water-soluble group such as a sulfonic acid group. Natural dyes are dyes obtained from animals, plants and minerals. According to the source can be divided into: 1 plant dyes, dyes extracted from the roots, stems, leaves and fruits of certain plants, such as indigo (blue) extracted from eucalyptus leaves, curcumin extracted from turmeric (yellow ), alizarin (red) extracted from alfalfa, etc.; 2 animal dyes, dyes extracted from animal bodies, such as carmine, etc. extracted from cochineal; 3 mineral dyes, dyes extracted from mineral colored inorganics Such as chrome yellow, ultramarine blue, manganese brown and so on. Because natural dyes have many disadvantages compared with artificial dyes, such as incomplete chromatogram, inconvenient application, poor fastness, etc., most of them are eliminated except for a few. Synthetic dyes, also known as "artificial dyes". It is mainly processed by chemical processing of coal tar (or petroleum processing) fractionated products (such as benzene, naphthalene, anthracene, carbazole, etc.), sometimes called coal tar dye. Since several of the earliest synthetic dyes are made from aniline, they are also called "aniline dyes". Compared with natural dyes, there are many types of synthetic dyes, complete chromatograms, most of them are bright, washable and light-resistant, and can be produced in large quantities. So the current so-called dyes almost all refer to synthetic dyes. Its dyed products are one of the common judicial identification materials. The pigment is a colored, black, white or fluorescent particulate organic or inorganic solid. It does not dissolve in water, oil or other application media, but it can be uniformly dispersed, and it retains its unique crystal or particle structure throughout the dispersion process without the physical and chemical influence of the media. According to the chemical composition is divided into inorganic pigments and organic pigments; according to the color is divided into white, red, yellow, black and other pigments; according to the source is divided into natural and synthetic pigments, natural pigments are mineral (inorganic) such as Heshi, cinnabar, red clay , realgar, etc., also animal and plant (organic) such as garcinia, cochineal red, etc., synthetic pigments also have two major categories of inorganic and organic; according to the use of color pigments, body pigments and functional pigments. Coloring pigments are inorganic and organic pigments that impart various colors to the application medium. Body pigments are pigments that have no coloring power and no hiding power. They were mainly used to reduce product cost and improve the performance of coatings, plastics, rubber and other products. It is called a filler. Nowadays, there are natural and synthetic products processed into ultrafine particle size. Because the synthetic products have low impurity content, fine particles and can be artificially synthesized and various surface modifications as needed, they can be used to reduce the hiding power. The amount of (such as titanium dioxide) and the improvement of product properties are now more suitable as physical (incremental) pigments. The main varieties of body pigments are processed natural minerals such as natural calcium carbonate, barite powder and talcum powder. , mica powder, diatomaceous earth, quartz powder, china clay, asbestos, etc., a few are synthetic products such as precipitated calcium carbonate, precipitated barium sulfate, synthetic silica, etc.; functional pigments are pigments that impart specific functions to the product, such as The color-changing temperature-changing pigment, the antifouling pigment having the function of poisonous water-killing organism, the luminescent pigment which can emit light in the dark, the rust-preventing pigment which can prevent rust, the pearlescent pigment having pearl luster and the like. Pigments are widely used in the coatings, printing, rubber, plastics, paper, fiber, ceramics and other industries to provide decorative, opaque, durable or special functions. As technology advances, various high performance pigments will be further developed.