What is the impact of textile dyes on color fastness?
Textile dyes are dyes used for dyeing textiles. Depending on the properties and methods of use, they can be divided into reducing dyes, sulfur dyes, reactive dyes, azo dyes, acid dyes, cationic dyes, direct dyes, and disperse dyes.
1. Acid Dyes
Acid dyes contain acidic groups in their dye molecules and are also known as anionic dyes. They can bond with amino groups in protein fiber molecules through ionic bonds. They are suitable for acidic, weakly acidic, or neutral conditions. These dyes are water-soluble and are mainly used for dyeing wool, silk, and nylon. They have bright colors, but poor wash fastness and light fastness, with significant variation in types.
2. Cationic Dyes (Basic Dyes)
Cationic dyes are a type of textile dye, also known as basic dyes. Cationic dyes dissolve in water in a cationic state. They can ionize in aqueous solution, forming positively charged colored ionic dyes. The cationic part of the dye can bond with the acidic groups of the third monomer in the fabric to dye the fibers. They are suitable for acrylic, polyester fibers, nylon fibers, cellulose, and protein fibers.
3. Direct Dyes
Direct dyes can be heated and boiled in neutral and weakly binding media without the need for mordants. Direct dyes are formed by hydrogen bonding and van der Waals forces between direct dyes and cotton fibers. They can be dyed directly on various cellulose fiber fabrics. Their wash fastness is relatively poor, and light fastness varies, but modified direct dyes can improve wash fastness.
4. Disperse Dyes
Disperse dyes are small molecular textile dyes that do not contain water-soluble groups in their structure. During dyeing, dispersants must be used to evenly disperse the dye in the dye solution to dye fibers such as polyester. The main use of disperse dyes is to dye polyester fibers, acetate fibers, and polyamide fibers in chemical fibers. Disperse dyeing of synthetic textile products results in bright colors and good wash fastness, making it widely applicable.
5. Reactive Dyes
Reactive dyes are a new type of water-soluble textile dye. Reactive dyes contain reactive groups that can react with hydroxyl groups in cellulose and amino groups in protein fibers. During dyeing, they form covalent bonds with the fibers, creating "dye-fiber" compounds.
6. Sulfur Dyes
Dyes dissolved in alkaline sulfides are suitable for cellulose fiber fabrics but not for protein fibers. The colors are gray, mainly navy blue, black, and brown. They have excellent light and wash fastness but poor chlorination fastness. This fabric can damage fibers after long-term storage.
7. Reducing Dyes
Refers to the reduction dyeing of fibers under alkaline conditions, followed by the oxidation of the original insoluble dyes on the fibers, used for dyeing cellulose fibers; insoluble reducing dyes can be made into sodium sulfate, which can become soluble reducing dyes. Suitable for cellulose fiber fabrics. It has good light and wash fastness, as well as resistance to chlorination and other oxidative bleaching.
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