Organic pigments, inorganic pigments and dyes

The color of a substance depends on a colorant. Any substance that can make a substance show the color required by the design is called a colorant. They are widely used in the textile, pharmaceutical, food, cosmetic, plastic, paint, ink, photography and papermaking industries. Industrial and civil colorants are mainly divided into two categories: dyes and pigments. The traditional use of dyes is to dye textiles, and the traditional use of pigments is to color non-textiles (such as inks, paints, coatings, plastics, rubber, etc.).

Textile dyeing refers to the process of giving textiles a color with a certain fastness, by physically or chemically combining dyes with fibers, or by chemically generating colors on fibers, so that the entire textile becomes a colored object. Textile dyeing chemicals mainly include colorants and auxiliaries. Colorants can be divided into two categories according to the dyeing mechanism: dyes (mostly organic) and pigments (including organic and inorganic pigments).

Dyes are a general term for organic compounds that have a certain affinity for the dyed fibers, are soluble in water or can be converted to be soluble in water under certain conditions, and can be physically or chemically combined with fibers or substrates directly or through certain media to achieve dyeing. Dyes are the main colorants in the textile industry.

Pigments are colored substances that have no affinity for the dyed fibers, are generally insoluble in water, and must be attached to the fibers through adhesives to be colored. Before dyeing, pigments, additives, adhesives, solvents, etc. need to be prepared to obtain a colored dispersion system with a certain viscosity, commonly known as paint. Therefore, pigment dyeing is also called paint dyeing.

Disperse dyes

With the continuous expansion of application fields and the continuous advancement of printing and dyeing technology, the formulations of commercial dyes have also diversified, such as liquid, powder, granular, and disperse dye inks suitable for digital printing. There are two main methods for disperse dye digital printing: ① Digital direct printing: disperse dye ink is directly sprayed onto polyester fabrics, but like reactive dye inkjet printing, it requires necessary pretreatment and high-temperature steaming or baking after printing to develop color; ② Digital thermal transfer printing: first print the disperse dye ink onto transfer printing paper, and then perform sublimation transfer printing.

Acid dyes

Acid dyes are water-soluble dyes that contain acidic groups in their molecular structure, usually sulfonic acid groups. Some acid dyes contain carboxylic acid groups and exist in the form of sodium sulfonate or sodium carboxylate salts. They are easily soluble in water and ionize into dye anions in aqueous solution. Acid dyes can be combined with protein fibers and polyamide fibers by ionic bonds, hydrogen bonds and van der Waals forces, so they are mainly used for coloring and printing wool, silk and nylon.

Reactive dyes

Reactive dyes, also known as reactive dyes, are covalently bonded to cellulose fibers or protein fibers through chemical reactions. They can be used to color cellulose fibers such as cotton, linen, and viscose fibers (made from natural cellulose such as wood, reeds, and cotton linter through chemical processing). They can also be used to color silk, wool, and soybean fibers.

pigment

Pigment coloring and printing have a wide range of adaptability to fabrics, such as protein fiber, cellulose fiber, polyester, nylon, vinylon, acrylic fiber, glass fiber, viscose fiber, polyester-cotton blend, polyester-wool blend, etc. However, pigment-printed fabrics usually have poor hand feel and relatively low wet rubbing fastness and dry cleaning fastness.