Dyeing is a process which are combined with fibers to send physical or chemical bonds, or chemical methods are used to generate pigments on fibers, so that the entire textile has a certain color. Dyeing is carried out under certain conditions of temperature, time, PH value and required dyeing auxiliaries. Dyeing products should be uniform in color and luster, and also need to have good color fastness. So, what are the commonly used dyes for textiles, and what is the process of the dyeing process?
Dyestuff are substances that can color fibers and other materials, and are divided into two categories: natural and synthetic. Dyestuff are colored substances, but colored substances are not necessarily dyestuff. As a dye, it must be able to adhere to the fiber with a certain color and not easily fall off and change color. According to the nature and application of dyestuff, they can be divided into the following types.
1. Direct dye. It refers to some water-soluble dyes. They have high directness to fibers and can directly dye cellulose fibers without prior treatment, so usually call them direct dyes. Widely used in cotton, silk, rayon fabrics. It can also be mixed with acid dyes or neutral dyes to dye chinlon silk fabrics.
2. Acid dyes. Usually contain sulfonic acid groups, and their sodium salts are easily soluble in water. Since such dyes must be dyed in an acidic medium in the early stage of development, they are called acid dyes. Later, some dyes that can be dyed in acid baths or neutral baths were gradually developed
Acid dyes are one of the most common types of dyes. They are used in the dyeing of protein fibers such as silk and wool, as well as polyamide fibers. They are also used in the coloring of leather, paper, food, and the preparation of inks, etc.
3. Reactive dyes the molecular structure of reactive dyes contains active groups, which can chemically react with the functional groups of some fiber molecules under certain conditions to form a covalent and cheap bond. At present, reactive dyes are used for dyeing cotton, mainly dyeing some light variegated colors, very little wool dyeing, and silk is mainly used for rayon dyeing.
4. Sulfur dyeing. Because organic raw materials or intermediates are co-thermally vulcanized with sodium polysulfide or sulfur during manufacture, and sodium sulfide is used for reduction and dissolution during dyeing, it is called sulfur dyes. Mainly used for blue-black cotton dyeing, in addition to cotton dyeing, it is also used for overdyeing of polyester-cotton and other blended interwoven fabrics.
The dyeing process can be divided into three stages
1. Adsorption: the dye is adsorbed on the fiber surface. Generally, during the dyeing process, the dye is first dyed on the fiber surface and then gradually enters the fiber interior.
2. Diffusion: the dye adsorbed on the fiber surface diffuses into the fiber until the concentration of each part of the fiber is uniform.
3. Fixation: the dye is fixed inside the fiber.
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