The effect of reactive dyes upon the uptake and anti bacterial action of poly(hexamethylene biguanide) on cotton. Part 2: Uptake of poly(hexamethylene biguanide) on cotton dyed with β-sulphatoethylsulphonyl reactive dyes

Polyhexamethylene biguanide (PHMB) is a widely used bacteriocide. It is marketed as an aqueous solution of its hydrochloride from which it is readily adsorbed onto cotton, this process depending upon the ability of the cationic PHMB to form electrostatic links with the anionic carboxylate groups present on cotton. The introduction of chemically bound sulphonic acid groups into cotton, which takes place during the process of dyeing with reactive dyes, increases the capacity of cotton to take up PHMB. The saturation levels of PHMB on un-dyed cotton, and cotton dyed individually with a trichromat of warm dyeing dyes, has been measured. Additionally, the effective agent contents of the dyes and their percentage fixation on to the cotton were determined, thus allowing the concentration of sulphonic acid groups present on the cotton to be calculated. From this and knowledge of the saturation value of PHMB on dyed and un-dyed cotton the stoichiometry of the interaction between PHMB and sulphonic acid groups was deduced. For the disulphonated dye, C I Reactive Black 5, each sulphonic acid group appeared to be associated with uptake of an additional 1.12 equiv. of monomeric biguanide unit. For the monosulphonated dyes, C I Reactive Orange 16 and C I Reactive Orange 107, the corresponding values were 1.31.and 1.47, respectively.     

Research on the Chroming of Diacromo Dyes

An attempt has been made to reduce the dyeing time with afterchrome dyes by eliminating the cooling step before afterchroming. This cooling is normally necessary to control the rate of chroming to obtain level dyeings. Other methods of control have been investigated, including the use of chromium fluoride rather than potassium dichromate. Triphenylmethane dyes containing salicylic acid groups can be chromed with chromium(III) at the boil, giving a brighter dyeing and a lower rate of chroming than when dichromate is employed. Salicylic acid azo and some oo′-dihydroxyazo dyes can also be chromed with chromium(III) compounds, but the colours produced differ greatly from those obtained when dichromate is used. With other afterchrome dyes, such as oo′-dihydroxyazo dyes, that have additional substituted or unsubstituted hydroxy] or amino groups capable of interaction with dichromate, the mechanisms of chroming with chromium(III) and chromium(VI) are different.     

Halochromism of acrylic fibres dyed with some disperse dyes

Anomalous dyeing behaviour has been found when regular acrylic fibre treated in hydrochloric acid, in which the sulphonic acid group was present entirely in the acid form, was dyed in neutral condition with azo and anthraquinone disperse dyes. In the very early stages of dyeing there was an abnormally high degree of dye exhaustion, with bathochromic (azo) or hypsochromic (anthraquinone) colour changes on the fibre. These phenomena gradually disappeared after prolonged dyeing, with normal adsorption equilibria and colours eventually being obtained. The results were explained on the basis of protonation by the sulphonic acid groups of treated fibre which occurs at the azo nitrogen or the amino nitrogens of the substituents in the 1 — or 1,4-positions of anthraquinone. The normal adsorption equilibria after prolonged dyeing was attributed to hydrolysis of the cyano side group to form carboxylic acid. This produces ammonia to liberate neutral dye from the protonated dye cation adsorbed electrostatically by the sulphonic acid anion of the treated fibre.     

Decolorising textile effluents

Amendments to the legislation on waste water are making the legal requirements for textile waste water more stringent. In addition to the limits on the metal content and the COD and AOX values, restrictions are also being placed on the colour of the effluent. Anionic dyes (e.g. reactive dyes and metal-complex acid dyes) are removed from spent dye liquors by means of ion pair extraction by long-chain amines. The effect of pH and the structure of the amine has been studied. In reactive dyeing such treatment reduces both the amount of colour and the AOX value. In the case of the metal-complex dyes the removal of the (chelated) metal is of prime importance. The metal-complex dyes can be recovered from the organic phase by extraction with caustic soda and then re-employed in dyeing. The amines that result at the end of dye recovery are practically colourless and may be reused.     

A study of novel bisazo reactive red dyes with good wet fastness

Three series of bisazo reactive red dyes were synthesised using 6‐amino‐1‐naphthol‐3‐sulphonic acid and its derivatives as the coupling components. The dyeing parameters and wash fastness of these dyes on knitted cotton were evaluated and the relationships between the structure and dyeing properties were investigated. It was found that the hydrophilic groups introduced into the dye molecules decrease the substantivity and fixation of the dyes, but increase the build‐up and migration properties. The defined wash‐off factor can directly reflect the wash fastness of the dyes and the build‐up property can be improved by commercialisation using certain auxiliaries. The results indicate that there is the possibility of synthesising a red reactive dye with a satisfying balance between high fixation and good wash fastness and several such dyes have been developed.     

Dyeing and antimicrobial studies on polyamine/epichlorohydrin condensate incorporated viscose rayon fibres

Modified viscose rayon fibres were produced by incorporating different doses of polyamine/epichlorohydrin condensate in the dope. The modified fibres show excellent dyeability with heterobifunctional reactive dyes without electrolyte. The wash fastness and the light fastness of the modified fibres dyed with reactive dyes were good. The modified fibres also showed excellent dyeability on dyeing with different acid and metal-complex dyes. The amount of additive present in the fibre was assessed from its nitrogen content and percentage exhaustion was found to increase with increasing quantity of additive. Tonal changes and increase in light fastness with acid and metal-complex dyes have been attributed to the aggregation of dye in the fibre. Fibres containing more than 3% additive in the dope showed greater than 99% bacteria reduction on testing the antimicrobial activity against Escherichia coli and Staphylococcus aureus . It was observed that the antimicrobial activity deactivated on repeated washing using surfactants. The acid-dyed fibres also showed a decrease in antimicrobial activity.     

Functionalisation of lyocell. Part 1: Amination of lyocell with m-phenylenediaminesulphonic acid derivatives

A series of four colourless, water-soluble agents, based on m -phenylenediaminesulphonic acid, and designed to aminate lyocell, have been synthesised. Each agent carried one or two aromatic amino groups ortho to a water solubilising sulphonic acid group, together with one or two electrophilic groups. The electrophilic groups studied were dichlorotriazinyl, monochlorotriazinyl, vinylsulphonyl and triazinyl betaine. The agents were applied to lyocell by padding techniques, and neutral-exhaustion dyeing of the aminated fibres, with low, medium and high reactivity reactive dyes, in the presence of salt, were performed. Only the high reactivity dichlorotriazinyl dye gave encouraging results. The aminated fabrics, containing aromatic amino groups with an o -sulphonic acid, were insufficiently nucleophilic to allow significant covalent bonding with the low/medium reactivity dyes at both 60 and 80 °C.     

Low-temperature ultrasonic dyeing of silk

Silk was dyed with cationic, acid and metal-complex dyes at low temperatures in the presence of ultrasonic energy for relatively short durations. The results in terms of dye uptake were compared with those obtained by conventional processes run at higher temperatures and for longer dyeing times. It was found that the ultrasonic energy helps in obtaining good fast dyeings, simultaneously conserving energy and reducing the time required for the dyeing process. In some cases the dye uptake was even higher than that obtained by the conventional dyeing procedures.     

Studies on the Donnan Potential in Systems Containing Cellulose and Aqueous Electrolyte Solution

Donnan potentials in undyed and dyed regenerated cellulose-aqueous potassium chloride solution systems have been investigated. Eight direct dyes of different structures were used to dye regenerated-cellulose sheets over a wide range of concentrations of adsorbed dye. The measured Donnan potential depends solely on the value of the total surface charge and is independent of the structure of the dyes used. The contribution to the surface charge by the intrinsic ionised carboxyl and the sulphonic acid groups (of the adsorbed dye) depends only on the total number of such groups present and not on whether the adsorbed dye is a mono- or poly-sulphonated dye. Only approximately 25 % of the total ionisable surface groups [carboxyl groups or the sulphonic acid groups (or both)] from adsorbed dye are dissociated. Direct experimental evidence has been obtained from these measurements of potential to support the use of a variable-volume term, instead of a constant-volume term, to describe the volume of the internal charged cellulose phase. The nature of this variation indicates that the total volume of the internal Donnan phase is a function of the thickness of the electrical double layer, as suggested in a theory of dyeing recently proposed.     

Chrome dyeing using anionic bivalent chromium complexes as mordants

Chrome dyeings are normally produced by first applying an acid dye containing ligand groups and then afterchroming with hexavalent chromium derivatives such as dichromate salts. The latter can damage wool fibres and also are toxic components in dyehouse effluents, so afterchroming with mixtures of Cr(III) salts and organic acids has been studied. It has been shown that the anionic complexes that form from trivalent chromium and the organic acids are fibre substantive at pH 2–4 and have the correct stability profile for exchanging ligands to bind the chromium with ligand groups in the dye. Dyeings produced generally show colour yields and fastness properties similar to the normal Cr(VI) dyeing process; the exception are these chromophores which undergo oxidative change in the dichromate process.     

Dyeing of nylon 6 fabric with a bifunctional sulphatoethylsulphone reactive disperse dye

A bifunctional reactive disperse dye containing two temporarily anionic sulphatoethylsulphone groups was synthesised and applied to nylon 6 fabric by exhaust dyeing at a variety of pH levels and temperatures. A monofunctional reactive disperse dye containing one temporarily anionic sulphatoethylsulphone group was also synthesised, and its dyeing behaviour was compared with the bifunctional dye. The bifunctional reactive disperse dye exhibited high exhaustion and total fixation yield under alkaline conditions. The results also indicate that the introduction of two temporarily anionic sulphatoethylsulphone groups of the bifunctional dye gave an enhancement in dyeing performance compared with that of the monofunctional dye. The dyes also showed very good levelling and fastness properties on nylon 6 fabric.     

Reactive dyeing of silk using commercial acid dyes based on a three‐component Mannich‐type reaction

Acid dyes are employed for commercially dyeing silk, which results in ionic bonds between the silk fibroin and the dye. This generally leads to low wet fastness properties for dyed silk fabrics. In this work, three commercial acid dyes with aromatic primary amine structures were selected to dye silk using a Mannich‐type reaction, resulting in improved wet fastness of dyed silk by forming covalent bonds between silk fibroin and dye. The Mannich‐type reactive dyeing was applied to silk fabrics at both 30 and 90°C in trials. Dyeing at 90°C can shorten the dyeing time compared with dyeing at 30°C, even although dye exhaustion and relative fixation at 90°C were a little lower. The dyeing process was optimised when the dyeing temperature was 90°C, dyebath pH 4, dye‐to‐formaldehyde ratio 1:30 and holding dyeing time 60 minutes. The results showed that the dye exhaustion on silk fabrics for the three aromatic primary amine‐containing acid dyes exceeded 94% and their relative fixation was over 80%. Their washing and rubbing fastness reached grade 4 or higher. Hence, the colour fastness properties of dyed silk fabrics using the Mannich‐type reactive dyeing method is superior to the conventional acid dyeing method using the same aromatic primary amine‐containing acid dyes. The Mannich‐type reactive dyeing for silk fabrics at 90°C can be developed into a novel and rapid reactive dyeing method, promising an effective dyeing process with excellent colour fastness.     

Aggregation Behaviour of Acid Dyes in N,N-Dimethylformamide-Trichloroethylene Solvent Mixtures - A Quasielastic Light-scattering Study

A new technique, quasielastic light scattering, was employed to study the aggregation behaviour of three acid dyes in dimethylformamide—trichloroethylene solvent mixtures. Observations on the aggregation of these dyes showed that they behaved differently in these mixtures than in aqueous solution. The extent of aggregation was found to vary with the number of sulphonic acid groups present in the dye molecule. Both monosulphonated and disulphonated acid dyes showed a tendency to aggregate with increase either in dye concentration or in trichloroethylene content in dimethylformamide. The low dielectric constant of trichloroethylene was responsible for the tendency of dye to aggregate with increase in trichloroethylene content. The trisulphonated acid dye showed least tendency to aggregate; this may be accounted for by the fact that sulphonic acid groups in the dye molecule are located at sites unfavourable to aggregation.     

Dispersant‐free dyeing of poly(lactic acid) fabric with temporarily solubilised disperse dyes from azopyridone derivatives

Poly(lactic acid) fibre is derived from annually renewable crops and known to be 100% compostable. In order to extend its environmental friendliness into the dyeing process, dispersant‐free dyeing of poly(lactic acid) fabric with three temporarily solubilised azo disperse dyes based on hydroxypyridone moiety containing a β‐sulphatoethylsulphonyl group was investigated. The dyes were successfully applied to poly(lactic acid) fabric without the use of dispersants. The colour yields of the dyes on poly(lactic acid) fabric were observed to be dependent on dyebath pH and dyeing temperature. The optimum results were obtained at pH 4–5 and 110 °C. One of the dyes showed a colour yield as good as that of a commercial disperse dye and good build‐up on poly(lactic acid) fabric. All of the dyes could be alkali cleared owing to ionisation of the dye under mild alkaline conditions. Wash fastness was good to very good, and light fastness was good. The chemical oxygen demand levels of the poly(lactic acid) dyeing effluent from the dyes were considerably lower than those from a commercial disperse dye.     

N-Alkylbetaines in Wool Dyeing

The influence of N-alkylbetaines, with alkyl chain lengths from eight to 18 carbon atoms, on the dyeing of wool with acid dyes has been studied. In the first part of the study the presence of N-alkylbetaines was found to cause spectral changes of the dye in solution, and two clearly differentiated dissociation stages have been observed. These represent the formation of dye-betaine complexes and the solubilisation of these complexes in the betaine micelles. The second part of the study examined how the presence of betaines influenced dyeing kinetics. Generally N-alkylbetaines were found to increase the rate of dyeing, the type and amount of betaine present being important factors.     

Single-step dyeing and finishing treatment of cotton with 1,2,3,4-butanetetracarboxylic acid

A single-step dyeing and finishing (SDF) process was developed to eliminate dyeing problems associated with cotton crosslinked by polycarboxylic acid such as 1,2,3,4-butanetetracarboxylic acid (BTCA). This process consisted of several steps: (a) impregnation of the fabric by the bath containing BTCA, dye, and catalyst; (b) drying; and (c) curing at high temperature. Color strength (K/S) and dye fixation of cotton treated by the SDF process were excellent, especially with reactive dyes containing mono- or dichlorotriazinyl compounds and, in some cases, were higher than those of the sample dyed by a conventional batch process without finishing treatment. The presence of dye in the SDF process did not interfere with crosslinking of cotton. We believed that the reaction occurred between carboxyl groups of BTCA and s-triazinyl groups in reactive dyes in the presence of imidazole and other catalyst. FTIR, Raman, and X-ray fluorescence spectroscopies were used to confirm the mechanism of dye fixation. Elemental analysis also supported this mechanism. The SDF process can be an excellent way to dye fabric that also requires crosslinking treatment for smooth drying appearance. © 1994 John Wiley & Sons, Inc.     

Dyeing properties of soya fibre with reactive and acid dyes

In order to determine the most suitable type of dye for soya bean fibre, the dyeing properties of three acid dyes and three bifunctional reactive dyes were compared. Additionally, the effect of a range of reactive groups on dyeing performance were studied, including difluorochloropyrimidine, monofluorotriazine, monochlorotriazine and β-sulphatoethyl sulphone, and of these the first was found to perform best. Irrespective of reactive group, however, the main factor affecting build-up was found to be the substantivity of the dye for soya fibre. The monofunctional reactive dyes in general were found to exhibit good wash fastness.     

Synthesis of temporarily solubilised azo disperse dyes containing a β‐sulphatoethylsulphonyl group and dispersant‐free dyeing of polyethylene terephthalate fabric

Disperse dyes containing a β‐sulphatoethylsulphonyl group have temporary solubility and can be applied for dispersant‐free dyeing of hydrophobic fibre. Six novel temporarily solubilised azo disperse dyes having a β‐sulphatoethylsulphonyl group in their structures were synthesised, and their dyeing properties on polyester were investigated. As a dye intermediate, a diazo component having dibromo groups was prepared, and 4‐diethylamino‐4′‐(2‐sulphatoethylsulphonyl‐4,6‐dibromo)azobenzene dyes were prepared by a diazo‐coupling reaction. Then, the dyes containing dicyano groups were prepared by cyanation of corresponding dyes with dibromo groups. The absorption maxima of the dyes were affected by the substituents in the diazo and coupling component rings and varied from 434 to 616 nm in dimethylformamide. Polyethylene terephthalate woven fabric could be dyed with the synthesised temporarily solubilised dyes without using any dispersants. Dyebath pH affected the K/S value at maximum absorption as well as percentage exhaustion on polyethylene terephthalate fabric, and the optimum pH was 5. The dyes gave brownish orange, red, purple, and greenish blue hues on polyethylene terephthalate fabrics, and colour build‐up was good. Wash fastness was good to excellent, rubbing fastness was moderate to excellent, and light fastness was poor to moderate.     

Effect of reactive dyes upon the uptake and antibacterial action of poly(hexamethylene biguanide) on cotton. Part 1: Effect of bis(monochlorotriazinyl) dyes

Poly(hexamethylene biguanide) (PHMB) is of interest as a bactericide for fabrics. It has affinity for cotton by reaction with the cellulosic carboxylate groups. In this study, the capacity of undyed cotton to absorb PHMB has been determined and compared with cotton dyed with anionic bis(monochlorotriazinyl) reactive dyes. When cotton is dyed with these dyes the absorption of PHMB increases, the dye providing sulphonic acid sites with which the PHMB can react. The reacted PHMB and the percentage fixation of reactive dye were determined and from this the concentration of sulphonic acid on the dyed fibre. In the case of cotton dyed with Procion Yellow H-E4R, the dye increased the absorption of PHMB to approximately 1.45 mequiv. of biguanide per sulphonic acid group. For Procion Red H-E3B and Navy H-ER the figures were 1.18 and 1.00, respectively.     

Latest developments in the low-temperature dyeing of wool with 1:2 metal-complex and milling acid dyes*

The advantages of dyeing wool at low temperatures with metal-complex and milling acid dyes are examined. Details of variations in conventional dyeing practice are discussed in detail and recommendations for applying selected dyes are given. The cost implications of dyeing at temperatures below the boil are reviewed, and some techniques for the low-temperature dyeing of woo/nylon blends briefly mentioned.