Application and uses of Acid Dyes

What are Acid Dyes?

Britannica defines acid dyes as “any bright-colored synthetic organic compound whose molecule contains two groups of atoms—one acidic, such as a carboxylic group, and one colour-producing, such as an azo or nitro group.”

They are known as acid dyes not because they have acidic properties but because they are applied to materials from a dyebath within acidic or neutral conditions.

Acid dyes are generally used for textile dyeing. They are utilised in dyeing natural fibers like wool, silk, jute, etc., synthetic fibres like nylon, and can also be used to dye a blend of these types of fabrics or fibres as well. Acid dyes have many other uses other than textile dyeing as well.

Types of Acid Dyes

Acid Dyes are classified in different ways. They are usually classified according to their leveling performance, dyeing properties, and acidic power. The types and classes of acid dyes are:

Classification By Levelling Performance:

Acid Dyes with Good Levelling Performance: Such acid dyes can provide good light fastness but have a lack of substantive indicated by their poor wash fastness. The dye molecules don’t attract much towards the fibre and hence they migrate slowly onto the fibres.
Acid Dyes with Average Levelling Performance: Such dyes have a moderate substantive. To ensure the substantive, a weak acid like acetic acid is used in the dye bath. They have fair washing fastness and good light fastness.
Acid Dyes with Poor Levelling Performance: Such dyes are also known as fast acid dyes, milling dyes or natural dyeing acid dyes. They have an advanced substantive but in contrast, their levelling performance is low and poor.

Classification By Dyeing Properties

This class of acid dyes are classified according to their dyeing behaviour, dyeing pH, migration ability, and washing fastness. These dyeing properties are further decided by their molecular weight and the degree of sulphonation. The types are;

Acid Levelling Dyes: Such dyes can colour evenly. They are combinable in trichromatic shades. They have low wet fastness.
Fast Acid Dyes: These dyes are usually mono-sulphonated. They possess excellent wet fastness but also possess good migration properties, unlike leveling dyes.
Acid Milling Dyes: These dyes have medium to high wet fastness and come in bright, strong colors. Though some milling dyes in pale shades have poor light fastness.
Metal Complex Dyes: These dyes come in duller shades. Metal and Dye ions are combined to form these complex metal dyes. They have high light fastness and wet fastness.

Classification By Acidic Power:

Neutral acid dyes
Weak acid dyes
Strong acid dyes

Uses & Applications

Acid dyes have a variety of different uses. They are used in many different industries and sectors for various types of applications.

A few textile applications and uses according to the type of dye:

Fast Acid Dyes: Used for dyeing or colouring non-washable knitting yarns, carpet yarns and piece goods. It is possible that a few pale-medium shades of fast acid dyes may be able to be hand washed.
Super Milling Dyes: These can be used to impart bright shades onto products or materials like loose stock, sliver, and yarns that need high wet fastness. They can also be used to impart pale-medium shades that can be machine-washed.
Acid Levelling Dyes: Such dyes can be used to dye or impart colour onto materials like carpet yarn, woollen and worsted fabrics, and such textile products that do not need washing and perspiration fastness.
Acid Milling Dyes: This type of acid dye can be used to impart medium-heavy bright shades on products like piece goods and materials like carpet yarns, knitting yarns, and weaving yarns.
Metal Complex Dyes: Due to their fastness properties, these acid dyes are used to dye womenswear and hosiery and other materials like leather, wood, metals, plastics, etc.

Within the textile and fashion industry, acid dyes have many other uses. Furthermore, they also have uses and applications in other industries other than the fashion and textile industry. They all are:

Medical Industry: Acid dyes are used in the field of Histology for the purposes of research or diagnosis. They are used to stain or colour basic tissue proteins in microscopic examinations.
Food Industry: Acid dyes are used as food colouring in the food industry. They must be approved as being eligible for consumption before use. They are used in bread, condiments, frosting, etc.
Leather Colouration: Due to acid dyes being resistant to migration, they are ideal to colour leather. Usually, all types of acid milling dyes and metal complex dyes are applicable here.
Dyeing of Fur Skins: Due to a few of their properties like fastness, good exhaustion and combinability at 60 to 65 °C, and being able to impart only a light stain as well as trichromatic shades, acid dyes are good for fur skin dyeing.
Dyeing of Double Weave Cloths: One of the dyes used to impart colour only double cloths are metal complex non-bleeding dyes. Double weave cloths or just double cloths are a type of woven textile where different sets of materials like sheep skins, weft yarns, etc are interconnected to form 2 layered cloths.
Wood Staining and Coating: Wood is stained with colour to make it more attractive or to add colour to it. They can be stained in natural wood tones or another colour entirely. For this staining process, generally solvent soluble acid dyes are used. Acid dyes like metal complex dyes are also used to coat stained wood to increase durability and protection.
Ink Formulation: Acid dyes can also be used to make ink for different uses like ink-jet printers, ink pads, ink for ball pens, ink for markers, etc. coloured ink in trichromatic form can also be made.
Jute Dyeing: Jute fabrics and fibres are generally highly demanded to be bright, wash fast and light fast. For this reason, acid dyes with good light fastness properties are used to dye jute.

Saujanya Exports is a leading acid dye manufacturer and exporter in India. We also manufacture and export food colours, dyes, pigments, and chemicals. We use cutting-edge technology to manufacture the best products and believe in high-quality service.

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