Overview
Naphthol AS (色酚色基) is a naphthol derivative primarily used as a coupling component in azoic dye synthesis. It reacts with diazonium salts to form insoluble azo dyes, which are critical for coloring cellulose-based textiles like cotton. First commercialized in the early 20th century, it remains a staple in the dye industry due to its colorfastness and versatility. The compound is synthesized by condensing 2-hydroxy-3-naphthoic acid with aniline. Its molecular structure includes a naphthalene ring and an amide group, enabling strong hydrogen bonding with fibers. Industrial grades typically exceed 98% purity, with impurities affecting dye brightness.
Physical and Chemical Properties
Naphthol AS appears as a fine crystalline powder with a light beige to brown hue. It has a melting point of 243–245°C and decomposes at higher temperatures without boiling. The compound is hydrophobic, dissolving readily in polar organic solvents like ethanol but showing negligible solubility in water. Key chemical properties include its reactivity with diazonium salts under alkaline conditions, forming intense red to violet azo dyes. The stability of these dyes arises from the planar structure of Naphthol AS, which facilitates strong π-π stacking with cellulose fibers. Its shelf life exceeds two years when stored properly, with moisture being the primary degradation factor.
Main Applications
The primary use of Naphthol AS is in textile dyeing, where it enables the production of wash-fast and light-fast shades on cotton, rayon, and other plant-based fabrics. It is applied via a two-step process: fabric impregnation with Naphthol AS (alkaline solution), followed by coupling with a diazo component. Beyond textiles, it serves as an intermediate for organic pigments and specialty inks. Niche applications include histology stains and colorants for paper. Its derivatives, such as Naphthol AS-BO and AS-D, extend the color palette to oranges and blues, catering to diverse industrial needs.
Safety and Storage
Naphthol AS poses moderate health risks, with potential skin and eye irritation upon contact. Dust inhalation should be avoided by using NIOSH-approved respirators in poorly ventilated areas. Spills require containment with inert absorbents like sand, followed by disposal as hazardous waste. Storage recommendations include airtight containers in cool (below 30°C), dry conditions, separated from oxidizers. Compatibility testing is advised when mixing with other dye intermediates. Regulatory compliance includes SDS documentation under REACH and GHS hazard classification (H315, H319).
B2B Procurement Guide
Bulk buyers should prioritize suppliers offering technical data sheets (TDS) and batch-specific certificates of analysis (CoA). Key parameters to verify are purity (≥98%), melting point range, and absence of heavy metals (e.g., <10 ppm lead). Spot purchases typically range from 25kg drums to metric-ton shipments, with discounts for long-term contracts. Logistics considerations include moisture-proof packaging and climate-controlled transport. For dye houses, small-scale trial batches (1–5kg) are recommended to test color yield before large orders.
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