The term “acid dye” derives from the dyeing procedure, which is carried out in an acidic aqueous solution. Acid dyestuff is so-called primarily because of two reasons. To begin with, these classes of dyestuff were used in a bath consisting of mineral or organic acids like sulphuric, acetic, or formic acid, and secondly, a lot of them are sodium salts of natural acids. Acid dye was made in 1862 by working with an insoluble dye. They are generally used for dyeing fibres (e. g. woollen and silk) and nylon fibres. Acid dyes are anionic, and their adversely charged anions are drawn in by positively charged amino groups in wool under acidic conditions.
Properties of Acid Dyes:
Considering that these are marketed as a sodium salt, as a result, this kind of large anions in the aqueous medium.
The primary properties of acid dyes are:
•Acid dyestuff is soluble in water.
•These dyes are anionic.
•They are normally combined with basic dyes.
•These acid dyes for wool, silk, polyamide, and changed acrylics.
•Acid dye has molecular weights in the range of 300– 1000 g mol-1.
•These dyes are normally applied in the presence of acids like sulphuric, acetic, or formic acid to a neutral pH bath
•These dyes have no fondness for cotton cellulose and are therefore not suitable for cellulosic.
•These dyes integrate with the fibre by hydrogen bonds, forces, or ionic links.
•When acid dyestuffs are treated with a reducing agent they are generally decolorized.
•The colored acid colours have good light fastness and modest washing fastness, however, their wet fastness properties are a limitation. These dyes are good to generate combination tones.
Application of Acid Dyes
Due to their excellent level-dyeing properties, these dyes are ideal for dyeing fabric and thread in hank form, particularly carpet yarns. Acid dyes can be used for dyeing natural fibres such as woollen and silk. They are also used for dyeing polyamide. acid dyes are anionic, and in solution, they will ionise into sodium ions plus huge negatively charged colored ions. In comparison to woollen, polyamide has fewer sites available for dyeing, and hence the tones created on polyamide are weaker than on woollen yet of higher fastness.
Regular Applications For Acid Dyes:
Levelling or equalising:
Carpet yarn, specifically high spin types for which penetration is an issue.
Woollen and worsted fabrics, especially for brilliant tones on carbonised products and for snugly built materials, such as gabardines. Fashion and interior fabric products for which washing and sweating fastness is not needed.
Quick acid, half-milling, or optimised half-milling:
Rug yarn, and knitting thread that will not carry a cleanable treatment claim.
Milling:
Medium-heavy intense tones on piece goods, carpet, and knitting threads
Super milling and optimised milling:
Brilliant shades on loose stock, sliver, and threads that require high wet fastness to milling and similar processes. It may also use in pale-medium tones for machine-washable efficiency
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