The Mechanism of Dyeing with Procion Dyes I—The Mechanism of Alkali Adsorption by Cellulose*

Abstract

A brief historical survey is given of previous work on the mechanism of adsorption of alkali by cellulose, in which three possibilities are considered: adsorption, because the hydroxyl ion has affinity for cellulose, compound formation between alkali and cellulose, and neutralisation of the alkali by the cellulose acting as a weak acid. Using the third mechanism, a theoretical treatment involving the normal concepts of dyeing thermodynamics has been set out; it successfully predicts the amount of sodium hydroxide that will be adsorbed from alkaline baths by both viscose rayon and cotton. A discussion is given of the way in which this treatment enables affinities to be calculated for adsorption of dye from aqueous alkaline dyebaths; and it is also shown how the concept of ionised cellulose hydroxyl groups, produced by neutralisation of alkali by the fibre, provides a mechanism for dyeing with reactive dyes. A brief historical survey is given of previous work on the mechanism of adsorption of alkali by cellulose, in which three possibilities are considered: adsorption, because the hydroxyl ion has affinity for cellulose, compound formation between alkali and cellulose, and neutralisation of the alkali by the cellulose acting as a weak acid. Using the third mechanism, a theoretical treatment involving the normal concepts of dyeing thermodynamics has been set out; it successfully predicts the amount of sodium hydroxide that will be adsorbed from alkaline baths by both viscose rayon and cotton. A discussion is given of the way in which this treatment enables affinities to be calculated for adsorption of dye from aqueous alkaline dyebaths; and it is also shown how the concept of ionised cellulose hydroxyl groups, produced by neutralisation of alkali by the fibre, provides a mechanism for dyeing with reactive dyes.