Dyestuff—fibre interactions

Abstract

Synopsis The strength and nature of dye-fibre interactions vary according to fibre type and dye type. In the case of acid dyes for polyamide fibres, cationic dyes for acrylic fibres, disperse dyes for hydrophobic fibres, and direct dyes for cellulosic fibres, these interactions may be classified as non-covalent, a classification which includes van der Waals (VDW), electrostatic, induction, solvophobic and charge-transfer interactions. Reactive dyes are a notable exception to the above, since the interaction which is responsible for their excellent wet fastness is the dye-fibre covalent bond, however, these dyes are increasingly viewed as environmentally unfriendly due to high salt usage and residual unfixed colour. This situation may be improved by either incorporating amine sites in the cellulose or by reversing the system to incorporate reactive residues in the fibre and nucleophilic sites in the dye. Nonionic disperse dyes are valuable for hydrophobic fibres such as polyester but have made little impact on hydrophilic fibres such as silk, wool and cotton. Experiments to develop simple treatments to render the latter fibres disperse dyeable are described and the combined role of solvophobic and - interactions discussed.

Synthesis and salt‐free dyeing characteristics of cationic reactive dyes containing polyetheramine segments

“…As for cationic reactive dyes, the dyes are absorbed by Coulomb interactions between the cationic dyes and the negatively charged fibre surface, and the dyeing conforms to Langmuir adsorption isotherms, with the formation of a single layer of dye on the surface of the cellulose fibre. On the other hand, as the cationic reactive dyes build up on the fibre, they also exert a restraining effect on further adsorption owing to the concomitant build‐up of positive charge . Moreover, when the concentration of the cationic reactive dyes increases, no further adsorption occurs, and the saturation effect appears, which results in a decrease in primary exhaustion and fixation.…”

The use of reflectance measurements in the determination of diffusion of reactive dyes into cellulosic fiber

“…In exhaust dyeing of cotton with anionic dyes, dye exhaustion gradually decreases with an increase in the concentration of dyes applied. This is due to the gradual build‐up of the dye at the fiber surface, hence retarding the further adsorption of remaining dye from the dyebath . The effect of dye concentration on the extent of dye diffusion as determined by the proposed equation for pad dyeings is shown in Fig.…”

Synthesis of reactive dyes based on the bis‐(N‐carboxymethylamino)monoquaternary‐triazine‐bis‐ethylsulphone reactive group. Part 1: Application to cotton cellulose

“…First, after the β ‐elimination of the CMA‐ES‐ N ‐triazinyl crosslinked dyes (during dyeing process at pH 5/100 °C), two smaller less substantive VS dye molecules are formed which readily desorb from the fibre into the dyebath. Second, under alkaline conditions (pH 11.5), movement of the VS dye into the fibre is restricted by electrostatic repulsion from fixed sulphonated dye as well as the cellulosate anion [15]. The fixation (% F and % T ) values obtained for the CMA‐ES‐ N ‐triazinyl crosslinked dyes applied using novel dyeing method 2 are higher than the values obtained for the SES dye using the alkaline fixation method, as the crosslinked dyes are fixed in the large substantive form.…”