4-hydroxynaphthalene-1-sulphonic acid 84-87-7

Industry knowledge

Specific role of 4-Hydroxy-naphthalene-1-sulphonic Acid (CAS: 84-87-7) in the production of acid dyes

4-hydroxy-naphthalene-1-sulphonic acid is an important aromatic chemical intermediate, which is widely used in the synthesis of acid dyes, especially in the dye industry as an important precursor for dye synthesis. Its structure contains a hydroxyl group (OH) and a sulfonic acid group (SO₃H), which gives it unique chemical and physical properties in dye production.

1. Chemical structure and properties of 4-HNSA
The molecular structure of 4-hydroxy-naphthalene-1-sulphonic acid contains a benzene ring with a hydroxyl group (-OH) at one position and a sulfonic acid group (-SO₃H) at the other position. This structure makes it highly hydrophilic while retaining the stability and chemical reactivity of the aromatic ring. The hydroxyl group provides the ability to react with other chemicals, while the sulfonic acid group gives the acid dye the required water solubility and hydrophilicity. Its molecular formula is C₁₀H₈O₃S, and it has high solubility and can show good ionization characteristics in aqueous solution.

2. Role in the synthesis of acid dyes
In the synthesis of acid dyes, 4-HNSA, as a key intermediate, plays a vital role in multiple steps, mainly reflected in the following aspects:

a) Introduction and connection of dye groups
The synthesis of acid dyes often requires the introduction of hydrophilic groups during the synthesis process to improve the water solubility and dyeing effect of the dye. 4-HNSA can react with other chemical reagents through its sulfonic acid group and hydroxyl group to form the basic structure of the dye molecule. For example, 4-HNSA often reacts with aromatic amine compounds, aromatic aldehydes or other chemicals containing active groups to generate new color bases through nitration, coupling and other reactions, thereby obtaining the final acid dye.

In this way, 4-HNSA not only participates in the formation of dye pigments, but also determines the water solubility, dyeing depth and durability of the dye. Acid dyes generally require the addition of sulfonic acid groups to the dye molecule, which can increase the solubility of the dye in water and improve its affinity with the fiber, thereby enhancing the dyeing effect.

b) Regulating the hydrophilicity and charge properties of the dye
The notable feature of acid dyes is their negative charge in aqueous solution, which enables them to interact with the fiber surface during the dyeing process, especially in combination with the positive charge on natural fibers (such as wool and silk) or synthetic fibers (such as nylon and polyester). The sulfonic acid group of 4-HNSA can effectively regulate the hydrophilicity and charge characteristics of the dye by carrying a negative charge.

This regulation allows the dye molecule to dissolve better in water, thereby improving the uniformity of dyeing. More importantly, this solubility allows the dye to quickly penetrate into the fabric and give full play to its dyeing effect. At the same time, the sulfonic acid group in the acid dye can improve the water resistance, light resistance and color fastness of the dye.

c) Improving the dyeing performance and color of the dye
As one of the intermediates in the synthesis of acid dyes, 4-HNSA can significantly affect the color of the dye through its unique structural characteristics during the synthesis of the dye. The introduction of sulfonic acid groups not only helps the dissolution of dyes, but also enhances the binding force between dyes and fibers during the dyeing process. Through coupling reactions with other dye groups, 4-HNSA can affect the hue and color fastness of the final dye. For example, through reactions with other groups, 4-HNSA can sometimes synthesize dyes of red, blue, purple and other shades, which are bright and stable in color.

d) Environmental protection and sustainability
With the increasing global attention to environmental issues, the dye industry is also gradually moving towards green and environmental protection. The synthesis process of 4-HNSA is relatively environmentally friendly, its preparation process does not involve complex toxic and hazardous chemicals, and the product itself has a low environmental burden. As a dye intermediate, 4-HNSA produces fewer by-products during the production process, so it meets the requirements of modern environmental protection and sustainable production. In addition, the acid dyes synthesized by 4-HNSA have good dyeing quality and low pollution emissions, which helps to improve the green manufacturing level of the dye industry.

3. Application of 4-HNSA in the production of different dyes
4-HNSA is widely used in the synthesis of different types of acid dyes, especially in the synthesis of acid anthraquinone dyes, acid anthracene dyes, acid indigo dyes, etc., and plays a pivotal role. These dyes are widely used in textiles, leather, paper, food and other fields. Its unique chemical properties and application performance make 4-HNSA one of the indispensable raw materials in the modern dye industry.