Bifunctional Reactive Dyes Research Articles

Capillary electrophoretic analysis of the reactions of bifunctional reactive dyes under various conditions including a study of the analysis of the traditionally difficult to analyse phthalocyanine dyes

Good analytical techniques for the separation and detection of reactive dyes are necessary not only to monitor residual liquors and effluents but also to aid in optimisation of dye synthesis, purification, formulation and application. HPLC, although generally widely employed, often has difficulty in analysing certain reactive dyes, especially the phthalocyanine-based dyes. CE analysis of several gifunctional reactive dyes has been carried out with subsequent activation and hydrolysis reactions for a bis-sulfatoethyl sulfone dye, under different pH and temperature conditions, being monitored. A variety of buffers were investigated; the use of acetonitrile in a micellar buffer system proving to be particularly successful.

Structure reactivity correlations of azo reactive dyes based on H-acid. III. Dye degradation by peroxide

In this paper we report on the influence of substituents on the degradation of azo reactive dyes based on H-acid caused by the action of hydrogen peroxide in aqueous solution and on cellulose. The results support the view that the perhydroxyl radical anion is the active agent in the dye degradation by hydrogen peroxide. We suggest that, predominantly, the dissociated form of the ortho-hydroxyazo dyes undergoes the degradation, and thus the pK a value of the dye is an important criterion for the fastness to peroxide. With this background, an expanded version of the Hammett correlation including the pK a values of the dyes yields a linear free energy relationship. On cellulose, bifunctional reactive dyes seem to be more stable to peroxide bleaching liquor than monofunctional reactive dyes with comparable pK a values.

Kinetics of hydrolysis of some model bifunctional reactive dyes

The hydrolysis in alkaline solution of some model bifunctional reactive dyes has been studied using 1H-NMR. The kinetics of the hydrolysis of the monochlorotriazine group and the vinylsulfone group were studied by the chloride ion-selective electrode method and by 1H-NMR respectively. HMO theory was used to calculate the reactive indices on the two reactive sites and a very good relationship was found between In k and super delocalizability, S N r: For the monochlorotriazine group, T ln k 1( × 10 −3) = 1.397S r1 7 −3.957 and For the vinylsulfone group. T ln k 2( × 10 −3) = 0.777S r2 N −3.287

Dye‐fibre bond stabilities of dyeings of bifunctional reactive dyes containing a monochlorotriazine and a ß‐hydroxyethylsulphone sulphuric acid ester group

The dye‐fibre bond stabilities of various bifunctional dyes (commercially known as Sumifix Supra dyes) have been investigated by measuring the kinetics of dye‐cotton bond hydrolysis in aqueous buffer solution at 98d̀C. The stabilities are generally found to be somewhat higher than those of comparable monofunctional reactive dyes. Significantly better, however, is the fixation yield of the bifunctional dyes. Reasons for a very low uptake of a non‐commercial bromamine acid‐based bifunctional dye are discussed.

Determination of the Viscosity in Cadoxen Solvent of Cellulosic Materials Dyed with Reactive Dyes

A modified cadoxen solvent was used to determine the viscosity of reactive‐dyed cellulosic materials. The conditions for completely dissolving cellulosic materials dyed with different types of reactive dyes were standardised. Reactive‐dyed cotton materials showedno anomalous viscosity behaviour in the cadoxen solvent. With viscose rayon samples dyed with bifunctional reactive dyes, higher viscosity values were observed when measurements were carried out immediately after dissolution. However, on storing the solutions for a further 24 h, the viscosity values became independent of the type or the amount of dye andwere identical with those of undyed rayon. Thus, measurements of the viscosity of reactive‐dyed materials can be conveniently carried out in cadoxen solvent.