Ermanno Barni

Reactivity and effects of cyclodextrins in textile dyeing

Abstract Four- to 10-fold improvement of colour uniformity and minor changes of colour yield have been found upon dyeing Nylon 66 and microfiber Nylon 6 fabrics in the presence of cyclodextrin compared to dyeing without it. 1 H NMR data supported the role of cyclodextrin as dye complexing agent. Product quality, however, was also dependent on fabric nature, since for conventional Nylon 6, color uniformity was not improved by the presence of cyclodextrin systems.

Disperse and cationic dyes from 2-(o, m, p-Aminophenyl)oxazolo [4,5-b]pyridine

Abstract 2-( o,m,p -Aminophenyl)oxazolo[4,5-b]pyridines were diazotized and coupled with N,N-disubstituted anilines, giving monoazo dyes suitable for polyamide fabrics. Some of the dyes were quaternized to give cationic dyes for acrylic fibres. The colour of dyed materials was assessed in terms of tristimulus colorimetry. Electronic spectra of the amines and NMR spectra of the cationic dyes are briefly discussed.

Preconcentration and removal of iron(III) from aqueous media using micellar-enhanced ultrafiltration

Abstract The use of micelle-based separation methods represents a recent, interesting alternative to the techniques based on classic liquid—liquid extractions. Among them, micellar-enhanced ultrafiltration allows the efficient concentration and removal of organic and inorganic analytes from aqueous solutions. Mixed micelles containing suitable derivatives of salicylic acids having an alkyl substituent of variable length have been investigated as model candidates for preconcentration of iron(III). The metal ion accumulates in the host aggregate after reaction with the cheating ligand and the micelles are successively separated from the bulk solution by passing through hydrophilic membranes of proper pore size. The concentration efficiency depends on the ligand and complex binding to the micelles. The effects of experimental parameters on the ultrafiltration performances have been investigated, and the complete removal of the metal ion has been achieved by properly selecting the surfactants and by modulating the hydrophobicity of the chelating agents.

Quantitative structure-property relationships study of azo dyes using partial least Squares analysis in latent variables (PLS)

Abstract The light, washing, alkali and perspiration fastness of a series of azo dyes are analysed as a function of physicochemical substituent descriptors by the PLS method. The analysis permits relation of the fastness properties to the structural features and the development of a model which can be used to predict the fastness of new dyes of the same series.

NMR investigation of azo disperse dyes

Abstract The 13 C-NMR spectra of a series of monoazo disperse dyes derived from diethylaminoazobenzene were measured and analysed. Depending on the nature and orientation of the substituent in the dyes, different conformers, resultant from inner rotation around the CN bonds, could be identified. The structural data provide a new tool for studies on dye-substrate interactions.

VESICLE PRECURSORS IN THE DYEING OF POLYESTER WITH DISPERSE DYES

Abstract The use of double tailed surfactants suitable for the preparation of synthetic vesicles and the resort to sonication for the setting up of dyebaths in the dyeing of polyester fabrics with a disperse dye is proposed. The dye, having excellent fastnesses, belongs to the diethylamino-azobenzene series and has been designed by chemo-metric procedures. In a selected number of experiments, excellent results are obtained from both the points of view of dyebath exhaustion and uniformity of coloration. Further investigation, involving other dyes, additives and substrates, is under study in order to achieve a rational interpretation of these encouraging technical results.

Effects of additives on the dyeing of nylon-6 with dyes containing hydrophobic and hydrophilic moieties

Abstract A series of azo disperse dyes with variable hydrophobic chain length and hydrophilic (hydroxy or glucosyl group) head were synthesised. 1 H and 13 C NMR spectra indicated that the glucosyl moiety was linked to the azo structure with a β anomeric bond. The dyeing properties on polyamide fibres were assessed with dyeing isotherms and Linitest experiments. The positive effects of additives, as ternary systems (SDS, Brij 35 and octanol) or cyclodextrins, on the dyeing uniformity were shown by tristimulus colorimetry.

Disperse and cationic dyes from aminophenyl-X-azolo-pyridines

Abstract A series of monoazo dyes was obtained by coupling diazotized aminophenyl-X-azolo-pyridines to N,N-diethylaniline. The dyes showed a great versatility towards different substrates such as polyamide, polyester, cellulose acetate and, after quaternization, polyacrylonitrile. In addition to the evaluation of parameters such as physical and spectroscopic constants, fastnesses on dyed fabrics, colour assessment and their correlation with structure, the dyes were also used in investigating the reactivity of the hetaryls. 1 H NMR was used to clarify the structure of the cationic dyes which, in the case of the imidazo-[4,5-c] isomers, proved to be imidazolium salts rather than the pyridinium salts previously observed for dyes containing an X-azolopyridine moiety.

Partial least-squares modelling of dye fastness to light

Abstract Several physicochemical properties ( 13 C-n.m.r., spectrophotometric, chromatographic, calorimetric) were measured for a series of 38 azo dyes in order to test the existence of relationships between one or more of these data sets and the fastness of the dyes on polyester fabric. The partial least-squares method was applied; it had previously proved useful in establishing structure/property relationships for the same dyes. It is shown that 13 C-n.m.r. data can be used successfully to predict dye fastness to light. These data are quickly and cheaply obtained with small amounts of compound.

Disperse and cationic azo dyes from heterocyclic intermediates

Abstract A series of aminophenyl-X-azolopyridines were diazotized and coupled to N,N-diethylaniline. The resulting disperse dyes showed a great versatility towards different fibres such as polyamide polyester and cellulose acetate. The disperse dyes were transformed into cationic dyes by reaction with methyl iodide. The quaternized dyes dyed polyacrylonitrile fibres with excellent uniformity without using a retarding agent. Physical and spectroscopic parameters fastness on dyed fabrics and colour data were correlated with the structure of the dyes. Two-dimensional proton-NMR NOESY experiments were useful for the assessment of particular structures.