Thomas Bechtold

Natural dyes in modern textile dyehouses — how to combine experiences of two centuries to meet the demands of the future?

Abstract Plant materials which are available from farming regions in the moderate Austrian climate were investigated to serve as sources for natural dyes in textile dyeing operations. The extraction of the dye components from the plant materials was performed with boiling water without addition of chemicals or solvents. Based upon a rigorous selection of possible plant sources, a selection of natural dyestuffs applicable in a one-bath dyeing step was established. A broad variation in shade and color depth can be achieved by applying mixtures of natural dyestuffs in various combinations of iron- and alum-mordants. More than 60% of tested dyeings achieved acceptable fastness properties. On the basis of the developed natural dyestuff-based dyeing procedures, a comparison was made between the effluents from processes based upon them and those based upon the current ‘state-of-the-art’ techniques utilizing synthetic dyes. The comparison revealed that a lowering of the chemical load released with waste water can be expected by shifting to the plant-based dyes.

Anthraquinones as mediators for the indirect cathodic reduction of dispersed organic dyestuffs

Abstract 9,10-Anthraquinone-2-sulfonic acid Na-salt (AQS2), 9,10-anthraquinone-1,5-disulfonic Na-salt (AQDS1,5) and 1,4-dihydroxy-9,10-anthraquinone (DHAQ1,4) were investigated as to their ability to act as mediators for indirect electrochemical reduction of dispersed organic dyestuffs. A characterisation of the reducing efficiency was obtained from CV-experiments when comparing the cathodic current maxima of the AQ solution containing the dyestuff with the cathodic peak current without reducible vat dye. Voltammograms in a flow cell show that the limiting current density is dependent mainly on the diffusion transport of the AQ, while the addition of reducible dispersed dyestuff is of minor influence. Spectroelectrochemical experiments performed with 9,10-anthraquinone-1,5-disulfonic Na-salt in presence of Vat Yellow 1 permit a photometric observation of the coupled redox reactions.

Characterization of cellulosic fibers and fabrics by sorption/desorption

Three cellulosic substrates: lyocell (CLY), viscose (CV), and modal (CMD) in the form of fibers and fabrics were subjected to wet/dry or wash/dry treatments. The accessibility of untreated and treated substrates to water and iodine was investigated using dynamic water-vapor sorption, moisture retention, and iodine sorption methods, to study the influence of treatments on sorption-desorption hysteresis, fraction of moisture sorbed as a monomolecular layer, water retention, and iodine sorption. It was found that the sorption properties of untreated and treated substrates differed with sorbate type as well as substrate type and form.

Indirect Electrochemical Reduction of Dispersed Indigo Dyestuff

Iron-triethanolamine complexes are well suited for the indirect reduction of dispersed dyestuffs, e.g., finely dispersed indigo in a dyebath. Experiments to develop basic data for the scale-up of an electrochemical cell usable for the indirect reduction of indigo, vat dyes, and sulfur dyes are described. Planar electrodes show that the current density at the cathode is limited by diffusion controlled transport phenomena in the mediator system. The characterization of the iron triethanolamine mediator system is performed by reduction experiments in a divided flow cell with parallel geometry. An optimization of this cell type was achieved with three-dimensional flow through electrodes, leading to high specific electrode areas and a good space/time yield with the investigated electrochemical system. The characterization of the different cell types was performed with electrolysis experiments using the mediator alone and in the presence of dispersed indigo dyestuff

Process balance and product quality in the production of natural indigo from Polygonum tinctorium Ait. applying low-technology methods

Indigo is the most important blue component in the class of natural dyes for cellulose and protein fibres. In the moderate European climate Polygonum tinctorium Ait. could be an interesting source for natural indigo (Vat blue 1). Following a cultivation of the plant material a simple procedure for the extraction of the indigo precursor indican was investigated with regard to crop and quality of dye obtained. The dependence of the crop on the storage conditions of the harvested plant material was investigated. The results quantify the distinct sensitivity of the fresh material to the time of storage before extraction with regard to the amount of natural indigo obtained, the photometrically determined indigo content in the product and the shade and colour depth observed in standardised dyeing experiments. A basic set of data is presented, which describes the process in terms of consumption of energy, water and chemicals and organic waste released from the extraction step.

Anthocyanin dyes extracted from grape pomace for the purpose of textile dyeing

BACKGROUND Pomace from different grape varieties was studied with regard to the content of extractable anthocyanins. RESULTS Total anthocyanin concentrations of 24.5-126 mg dm(-3) were found in the extracts. The amount of extractable pigment was dependent on the variety of grape. The extracts were applied in textile dyeing operations using cotton fabric pre-mordanted with tannin as textile substrate. Red/violet shades were obtained that showed good water-fastness; however, limited light-fastness indicated need for improvement to fulfil requirements for textile application. CONCLUSION Colour measurement by means of CIE-Lab coordinates and Kubelka-Munk value showed a direct correlation between extractable anthocyanin concentration and colour depth of the dyed material. Thus the analytically determined concentration of anthocyanins in the aqueous extract can serve as a measure of quality of grape pomace as raw material for textile dyeing application. Copyright

Fiber Friction in Yarn—A Fundamental Property of Fibers

Friction between fibers inside yarns is generally important for determining the physical behavior of textiles. The tendency of cellulosic fibers to slide in a yarn directly influences the extent of fuzz formation during abrasive treatment. This paper presents a test method to determine the slipping behavior of fibers in a yarn as a function of yarn twist. Different kinds of cellulosic fibers tested with the method include lyocell, modal, viscose, and cotton. To obtain a quantitative measure, a mathematical model is established to estimate the force for fibers slipping in a yam as a function of two basic fiber parameters. μ and α: μ is the coefficient of friction of fibers in a yam and α describes fiber adherence. As a result of the calculations, these fibers can be characterized by their frictional properties in a yarn.

In-situ deposition of Cu2O micro-needles for biologically active textiles and their release properties

Metal/metal oxide containing fibres are gradually increasing in textile industrialization recently, owing to their high potential for application as antimicrobial textiles. In this study, the reducing properties of cellulose were applied to synthesize cuprous oxide in-situ. The direct formation of Cu2O on viscose fabrics was achieved via quite simple technique in two subsequent steps: alkalization and sorption. Cu contents in fabrics before and after rinsing ranged between 45.2-86.4mmol/kg and 18.1-67.7mmol/kg, respectively. Uniform micro-needles of Cu2O were obtained with regular size and dimensions of 1.60±0.20μm in length and 0.13±0.03μm in width. Release of Cu1+/2+ ions from selected samples was studied in water, physiological fluid and artificial sweat. Copper containing fabrics exhibited a percent of 96.8-97.8% and 85.5-89.0% for reduction in microbial viability, which was tested for S. aureus (as gram positive bacteria), E. coli (as gram-negative bacteria) and C. albicans and A. niger (as fungal species), respectively after 24h contact time.

Alkali-stable iron complexes as mediators for the electrochemical reduction of dispersed organic dyestuffs

Several complexones and amino compounds have been investigated as to their ability to form alkali-stable coordination compounds with iron, which can be used as mediators for the indirect electrochemical reduction of dispersed organic dyestuffs with different structures. A characterisation of the reducing efficiency can be obtained when the cathodic current maxima of the mediator solution containing the dyestuff is compared with the cathodic peak current without the reducible vat dye.

Electrochemical Vat Dyeing Combination of an Electrolyzer with a Dyeing Apparatus

A standard dyeing apparatus for yarn on X-cones has been coupled to a multicathode eletrolyzer for indirect reduction of dispersed oxidized vat dyes. An alkaline solution containing 0.01 M iron-triethanolamine complex was used as mediator solution. In test runs current efficiencies better than 80% were obtained at cell currents up to 10 A. The cathode was built up from 10 insulated sheets of steel fabric with a total area of 0.96 m 2 . In batch experiments cones of cotton yarn with an average mass of 900 g yarn were dyed. Different dyes were applied in light to dark shades at a dyeing temperature of 60(C. During the electrochemical dyeing process the cell must carry out different functions: reduction of dissolved oxygen, indirect reduction of dispersed oxidized vat dye buildup of a certain reduction capacity against air oxygen, and control of redox potential in the dyeing apparatus by adjustment of cell current. A description of the concentrations of dissolved oxygen and reduced form of the mediator during electrolysis can be achieved by a simple mathematical model, which permits efficient optimization of important technical parameters for process design and scale-up.