Dyeing behaviour of relaxed and retractile components in high-bulk yarns

The evolution of dye absorption and fine structure variations due to heat treatment in high-bulk yarns was studied. Two acrylic fibres of different commercial origin were employed. Using these, the following yarns were spun: 100% relaxed (N), 100% retractile (R), 55:45 N/R and 45:55 N/R. The evolution of fibre microstructure induced by the dyeing process was studied through the differential solubility technique in mixtures of dimethylformamide and water.     

New Developments in Acrylic Carpet Fibres for Specific End–uses

There is considerable activity in the introduction of new acrylic fibres, and second–and third–generation fibres are being developed for specific end–uses. Bicomponent fibres have found considerable application in woven carpets because their increased bulk and cover offer advantages over traditionally used fibres. Improved flame–resistant fibres incorporating halogen compounds have been developed to meet flammability requirements for carpets. Modacrylic blends are used for shag and some ‘saxony’ (high–pile low–density) applications. Three acrylic fibres of different dyeability have been developed for continuous piece dyeing: reduced–affinity basic, regular or deep basic, and acidic. Rapid–dyeing fibres are being introduced for use on the Craw ford–Mohasco equipment with which the fixation time is limited to 3 min at 100°C Finally, highshrinkage fibres can be used to impart extra bulk and cover or alternatively to produce sculptured effects in woven or tufted carpets.     

Kinetics of solvent-assisted dyeing of acrylic fibres

The kinetics of dyeing acrylic fibres with cationic dyes in the presence of small amounts of the solvents ethylene carbonate, propylene carbonate, nitromethane and iso-amyl alcohol has been studied. The time of half-dyeing was taken as a measure of the rate of dyeing, which was found to decrease with increasing concentration of the solvent in the dyebath. A linear correlation was observed between the rate of dyeing and the change in glass transition temperature of the fibre.     

The Role of Benzyl Alcohol in the Solvent–assisted Dyeing of Acrylic Fibres

The mechanism of the solvent–assisted dyeing of acrylic fibres using benzyl alcohol has been investigated. The carrier action of benzyl alcohol plays a major role in increasing the rate of dyeing.     

Alternatives to Water in Textile Processing

Attempts have been made to correlate the use of organic solvents as alternatives to water in textile processing with the ‘solubility parameter’ concept. Chlorinated hydrocarbons prove suitable for scouring and some finishing operations since their solubility parameters are ideal for such operations. In dyeing, however, the solubility parameter of polyester fibres, dyes and perchloroethylene are very similar, resulting in poor exhaustion of conventional disperse dyes. New solvent dyeing systems and new dyes, with high partition coefficients in polyester fibres, must be developed for solvent dyeing to become of practical consideration. Other solvents have been examined for solvent assisted dyeing. It has been shown that when benzyl alcohol and 2-phenoxy ethanol are used in dyebaths at concentrations at which these solvents are not completely in solution, both the rate of dyeing and penetration of dye into the fibre can be markedly increased in comparison to normal aqueous dyeing with polyester, nylon and acrylic fibres.     

Influence of Substrate Type on Level Dyeing of Acrylic Yarn Packages

In an earlier paper [1], the influence of flow rate, ramp (constant rate of temperature rise) and package density on the rates of dyeing of two basic dyes on Ex/an, and on the levelness obtained in the resulting dyeings, was investigated, and a relationship was derived to link these factors quantitatively. This work has now been extended to cover the behaviour of various basic dyes on Exlan and other acrylic fibres, under conditions expected to give borderline levelness. It has been shown that the shape of the rate–of–dyeing curve depends on the type of acrylic fibre and, to a lesser extent, on the cationic retarder used, but not on dye type within the group of CV2. 5–3. 5 basic dyes examined. The response of dyeing rate and degree of unlevelness to deliberate variations of ramp, as demonstrated in the previous work on Exlan, is now confirmed on Cashmilon. Evidence of a different type of random unlevelness, not related directly to dyeing rate, was also obtained from dyeings on the various fibres at a slow ramp.     

Developments in the Dyeing of Man-made Fibres

The ways in which methods of dyeing different types of man-made fibres have developed are discussed. Particular attention is paid to the main synthetic-polymer fibres—nylon, acrylic and polyester fibres. Future developments in dyeing are discussed critically, with emphasis on the dyeing of fibre blends, the design of dyeing and other wet-processing machinery, instrumentation and automatic control, solvent processing, and mass pigmentation.     

Dyeing behaviour and fine structure differences in acrylic fibres relaxed under different conditions

Fine structure differences in an acrylic fibre relaxed under different conditions have been studied in terms of dyeing behaviour. From information on the dyeing kinetics obtained at different temperatures, it was deduced that diffusion coefficient increases with degree of relaxation, while activation energy remains almost constant. Glass transition temperature tended not to vary as a function of degree of relaxation, although the temperatures measured under wet conditions or during dyeing tended to decrease slightly for substrates that were highly relaxed.     

Development of Modern Techniques for Dyeing Acrylic Fibres

The development of dyeing processes for acrylic fibres from their introduction 21 years ago to the present day is outlined. The development of empirical dyeing techniques for acrylic fibres already in commercial production was followed by closer theoretical studies leading ultimately to a simple dyeing technique—the Defitherm process—evolved from a study of reaction kinetics and fundamental dyeing mechanisms. This process is described.     

One-bath dyeing of wool/acrylic blends with reactive cationic dyes based on monofluorotriazine

A series of reactive cationic dyes containing the monofluorotriazine structure has been synthesised and their dyeing behaviour on wool, acrylic and a 50:50 wool/acrylic blend studied using a one-bath method. The results indicate that reactive cationic dyes having this structure give a high level of exhaustion and fixation on these fibres. Fastness properties on the wool/acrylic blend were also in general very good.     

Kinetics of Dyeing Acrylic Fibres with Cationic Dyes in the Presence of Polyethoxylated Amines

The role of ethoxylated amines in retarding the rate of absorption of C.I. Basic Green 4 on acrylic fibres has been studied. The influence of degree of ethoxylation, amine concentration and application temperature have been studied. It has been found that these compounds act, in general, as retarders, the retarding effect increasing as the degree of ethoxylation decreases. The dyeing kinetics in the presence of these compounds obey the Williams, Landel and Ferry equation.     

The retarding action of polyacrylamide in acrylic dyeing

Polyacrylamide of different molecular masses was found to act as polycationic retarders in dyeing of acrylic fibres with cationic dyes. The method of retardation is simple and economic, having no adverse effect on final dye exhaustion values. The possible mechanisms involved are discussed.     

A systematic study of dyeing polybutylene succinate fibres

Biodegradable polybutylene succinate (PBS) fibre is a new type of textile fibre, but its application in the textile industry is limited by the lack of related dyeing methods. In this study, the solubility parameters of PBS fibres are calculated, and solvent dyes with similar solubility parameters are proposed to dye PBS fibres to show that the dyeing scheme creatively resolves the difficulty in dyeing PBS fibres. The technical parameters of suitable dyes, and the dyeing conditions with ethanol as the dyeing medium, consisted of a dyeing temperature of 90°C, a dyeing time of 30 minutes and a liquor ratio of 30:1. The dyeing results show that the levelling property is good, the dyebath exhaustion is high, and the washing fastness, the rubbing fastness and the perspiration fastness index of the dyed fibres are satisfactory.     

The Swelling and Plasticization of Poly(ethylene terephthalate) during Carrier Dyeing

A study has been made of the effects of a variety of compounds on undrawn poly(ethylene terephthalate) filaments. The results have been compared with those of a similar investigation using acrylic fibres [6]. From the comparison, further insight into the relative importance of non-polar and other intermolecular forces in carrier-dyeing has been gained. The significance of fibre swelling in relation to the dyeing properties of poly(ethylene terephthalate) fibres is also considered.     

Some remarks on the Donnan approach to the equilibrium sorption of cationic dyes by acrylic fibres

Recent developments in the theoretical study of the dyeing of acrylic fibres with cationic dyes are reported. By using a simple Donnan approach and by assuming that the acrylic fibres contain strongly (K₁) and weakly (K₂) acidic groups, it has proved to be possible to determine the values of the distribution coefficients for the inorganic ions and the values of the dissociation constants of the acidic groups, which are not otherwise directly measurable. The distribution coefficients of the cationic dyes were then determined, based on experimental sorption measurements at different sodium concentrations and at different pH values.     

Differential Solubility of Acrylic Fibres as a Function of Stabilisation Process Variables

Acrylic tow, partially relaxed during the first stage of a conventional manufacturing process, was fully relaxed, or stabilised, in steaming equipment under different conditions of time and temperature based on a central rotatable design of experiments. The shrinkage of the samples thus obtained was measured and differential solubility curves in a mixture of dimethy/formamide and water were obtained. From these results simple functional relationships between shrinkage and solubility on the one hand, and the process variables, temperature and time, have been obtained. Response surfaces showing an excellent fit have also been obtained. A very good negative linear correlation between the logarithm of shrinkage undergone during steaming and the logarithm of differential solubility, and also between the logarithms of overall shrinkage and differential solubility have been found. The differential solubility test has a very high sensitivity to relaxation process variables and, as shown by the correlations obtained, it is highly recommendable as a relaxation control measure in production plant.     

The Significance of Theoretical Results in the Dyeing of Acrilan 16 with Basic Dyes from an Anhydrous Perchloroethylene Dyebath

Theoretical principles used in an investigation of the mechanism of carrier dyeing and the plasticization of acrylic fibres have been applied successfully to the dyeing of Acrilan 16 with basic dyes from an anhydrous solvent dyebath. Part I deals with the selection of plasticizing agents and Part II describes the dyeing procedure and properties of the resulting basic dyeings.     

Modelling cationic dyeing-consideration of ionic and hydrophobic interactions in a modified Donnan approach

A modified Donnan model has been derived, based on hydrophobic and ionic interactions between dyes and fibres. This model gives a good prediction of a cationic dye equilibrium sorption on an acrylic fibre under different dyeing conditions. The decrease in dye sorption with increasing salt concentration, followed by an increase in the dye sorption following further increase in the concentration of some salts (such as sulphates and phosphates), can be interpreted by this model. The study provides a quantitative approach to the dual functions of simple electrolytes during cationic dyeing, i.e. the competition of sorption sites with dyes through ionic interactions and the promotion of the dye sorption through hydrophobic interactions.     

Relationship between the solubility of disperse dyes and the equilibrium dye adsorption in supercritical fluid dyeing

In order to understand the dyeing behaviour of synthetic fibres in supercritical carbon dioxide, the solubility of some disperse dyes in supercritical fluid, as well as the rate of dyeing and the equilibrium adsorption of these dyes, have been studied. Dye solubility was measured by a dynamic analytic method at a range of pressure (7.5–25 MPa) and temperature (50–145 °C). The apparent rate of dyeing was measured and the dyeing isotherm was obtained by plotting the equilibrium dye adsorption against the equilibrium dyebath concentration. Linear isotherms were obtained when poly(ethylene terephthalate) samples were dyed with the disperse dyes. The mechanism of dyeing using supercritical carbon dioxide was discussed by considering the solubility, the dyeing rate and the dyeing isotherm.     

Acid-dyeable acrylic fibres copolymerised with amino alkyl methacrylates for differential cross-dyeing

The equilibrium adsorption of acid dyes on acrylic fibres copolymerised with dimethyl amino ethyl methacrylate has been investigated. A typical characteristic of this type of fibre is its excellent stable dyeability over a wide pH range. This is due to the strong basicity of alkylamino groups in the copolymerised component, which makes it possible to dye the fibre thoroughly even in a weakly acidic dyebath using a normal dyeing processes of acrylic fibre with cationic dye. Consequently it is useful for differential cross-dyeing in a single dyebath.