Maria L. Longo

Carrier dyeing of polyester fibre with some disperse azo dyes

Abstract This paper reports the effects of phenol, as a carrier, on the kinetics and thermodynamics of the dyeing of polyester fibre with some substituted benzothiazolyl azo dyes. The dyeing rate constants, the thermodynamic affinity and the apparent diffusion coefficients depend on the carrier concentration and on the dye structure, i.e. the presence of hydroxy groups in the N,N-diethylamino moiety of the coupler and of the phenyl ring between the thiazole and azo group. The results indicate the phenol does not behave by plasticizing the fibre, but it mainly acts as dispersant of the dye in the dyebath.

Dyeing properties of basic azo-dyes from 2-amino thiadiazole

Abstract Some new basic azo-dyes derived from thiadiazole were synthesized to evaluate the dyeing parameters on polyester fibre (PET) for optimizing the dyeing process. The kinetics of dyeing were performed at various temperatures (80°, 90° and 100°C) in the absence and in the presence of phenol, benzoic acid and salicylic acid as carriers. Thermodynamic affinities were also measured. The dyeing rate constants increase on increasing the concentration of carrier, while low affinity values were observed for the dyes bearing hydroxyl groups, owing to increased solubility of the dye in the dyebath. This behaviour is less evident in the dyes bearing a methyl group in the thiadiazole ring. The dyes show good fastness to light, perspiration and dry cleaning.

The Role of Electrolytes in the Cationic Dye-Acrylic Fiber System

Dyeing rates and sorption isotherms were measured for Basic Red 29 on acrylic fiber in the presence of various electrolytes. The amount of the dye uptake is markedly influenced by the type of the cation, decreasing with increasing size of the ion. The tetrabutylammonium chloride appears to be a strong competitor for dye cation, being much more effective than the alkali metal cations. Moreover, various parameters are operative when different ions are present in the dyebath. The equilibrium adsorption isotherms can adequately be described by the Langmuir-type equation.

Adsorption thermodynamics and diffusion of disperse anthraquinone dyes in acetate fibre

Abstract Diffusion coefficients, thermodynamic parameters and adsorption equilibrium isotherms of some anthraquinone dyes for acetate fibre are reported. The chemical constitution seems to be more important than the size factor in determining dye diffusion into the interior of the fibres. The activation energies of diffusion decreased strongly when o-dichlorobenzene was present, due to the plasticising effect of carrier. Nernst partition isotherms were obtained, up to saturation. Substantivity decreased when water-solubilising groups are present in the molecule. The aqueous solubilities and heats of solution have been measured; the higher ΔH w values were found for the derivatives which can form intermolecular hydrogen bonding in the crystalline state.

Effects of the phenol on the dyeing of polyester fibre with some disperse azo-dyes

Abstract The effects of the phenol, as carrier, on the dyeing rates, apparent diffusion coefficients, solubilities, thermodynamic affinities and T D values of some disperse azo-dyes on polyester fibre are reported. The dyeing rates of less soluble dyes are higher than those of more soluble hydrophilic dyes, while the affinity and T D values show a reversed behaviour. The carrier efficiency on the dyeing parameters studied appears to be correlated with the structure of dyes.

Kinetic and Thermodynamic Characteristics of Azo Dyes for Polyester Fibre in the Presence of Phenol as a Carrier

Abstract This paper reports the synthesis of some new basic azo dyes obtained by coupling diazotized 7-amino-3,4-dihydro-iso-carbostyril with N,N-disubstituted anilines. The effects of phenol, as carrier, on the dye solubilities and on the kinetics, diffusion coefficients, and thermodynamics of the dyeing of polyester (PET) fibre are also investigated. At lower concentrations ( mol kg ), phenol acts as a dispersant of the dye in the dye bath, whereas, at higher concentrations (30.2 mol kg ), it has a greater influence on the desorption process.

Protonation equilibria of 1-arylazo-4-naphthols and 1-arylazo-4-methoxynaphthalenes

The spectroscopic behaviour of substituted 1-arylazo-4-naphthols and 1-arylazo-4-methoxynaphthalenes has been investigated in a solvent system consisting of 20% v/v ethanol and 80% v/v sulphuric acid–water in order to measure the protonation equilibrium constants. Some naphthols (I; X = H, o-OCH3, p-OCH3, o-CH3, p-Cl) and all the methoxynaphthalenes (II) show two absorption bands due to the free base and the conjugate acid, with a characteristic isosbestic point. For these compounds, pkBH+ values have been calculated using Jaffes acidity function. Other naphthols (I; X =m-OCH3, m-CH3, p-CH3, o-Cl, m-Cl) show a single absorption band which shifts on changing the acidity of the medium. The lack of an isosbestic point has been ascribed to the overlap of the azo–hydrazone equilibrium with the protonation equilibrium of the azo-group. For methoxynaphthalenes, separate correlations of pKBH+ values with σm and σp of the substituents are found, owing to the presence in the molecules of two distinct basic centres.