dyes offered by us are insoluble Azo dyestuffs that are produced on fiber
through application of Naphthol to fiber and then combining it with
diazotized base at low temperatures. This helps in producing insoluble dye
molecule within fiber.
Classified as fast dyes, Naphthol dyes are slightly cheaper than Vat dyeing
with the method of application complex and range of colors limited.
- Soluble in alkaline solution
- Substantive to cotton (particularly in presence of salt)
Anilides of BON acid are soluble in dilute NaOH solution, forming
corresponding naphtholate ion. These small molecules are of low to moderate
substantivity for cotton and diffuse rapidly into fibres.
Naphtholate ions are always coplanar and have elongated molecular
structures. With a behavior as colorless, low molecular weight direct dyes,
its substantivity increases with an increase in molecular size of
naphtholate ion. The addition of salt also promotes better exhaustion of
bath with more being needed for Naphtols of lower substantivity.
These are available as free amine base or amine salts like hydrochloride
with many of amines used being simple substituted aniline derivatives with
no ionic substituent.
General Dyeing Procedure:
Application of naphthols consists of following steps:
- Dissolution of naphthol component
- Exhaustion of naphthol solution onto substrate/absorption of
naphtholate ion by cotton
- Removal of excess naphthol from material by squeezing/ or brine
- Diazotization of base component
- Development/treatment with diazonium ion solution to bring about
- Neutralization, Soaping at boil to remove superficial pigment
(followed by rinsing & drying)
Napthols can be applied through several methods such as:
- Open beck
- Circulating liquor
- Naphthols are available in micro pulverized form
- These dyes are water insoluble and contain simple water soluble
- Nature of solutions of Naphthols during application is highly alkaline
having approx. pH of 12-14