Low-temperature Dyeing of Wool Processed for Shrinkage Control

Abstract

Wool dyeing is a degradative process involving high temperature for long periods in acidic to neutral pH medium to achieve good penetration, optimum fastness, and dyebath exhaustion. The results can be harsh handle, discomfort, and a deterioration of properties that impact consumer wear, care, and aesthetic appreciation. Low temperature dyeing at temperatures below 100°C has been the subject of many investigations, some leading to the design of proprietary dyebath additives, enzymatic assistance, and plasma treatments [7,17,20,22]. The shape of the conventional dye uptake curve is consistent with an initial dwell time (20 to 40°C) when dye is transported 1 through the medium, a primary exhaustion stage (40 to 60°C) when dye levels at the fiber surface and diffuses within, and a secondary stage (60 to 90°C and above) during which time the dye disperses Abstract Wool fabrics treated for shrinkage control by applying a novel two-step ARS process 3 involving an activated peroxide bleach followed by enzyme treatment were dyed at lower temperatures within shorter dyeing times than conventional dyeing with acid dyes which require 90°C or higher for 60 minutes or longer. The shrinkage control process involved bleaching pretreatment with dicyandiamide in alkaline hydrogen peroxide and with gluconic acid additive at 30°C (86°F) for 30 minutes followed by sulfite-assisted serine protease treatment for biopolishing and shrinkage prevention at 45°C (113°F) for 40 minutes. Dye uptake with time over the temperature range of dyeing showed that untreated fabrics and pretreated fabrics exhibited sigmoidal dyeing behavior with exhaustion within 55-70 minutes at 55-60°C. Fabrics pretreated and subsequently treated with enzyme exhibited exponential dyeing behavior with exhaustion within 20-30 minutes at 30-55°C. We attributed low temperature dyeing with reduced dyeing times to changes in wool morphology and chemical structure as documented by both scanning electron and confocal fluorescent microscopy. The ARS process provides shrinkage control with greater ease of bleaching and dyeing.

Influence of acetated‐based and bromo‐based ionic liquids treatment on wool dyeing with acid blue 7

“…The exhaustion curves of IL‐treated and untreated samples dyeing at 80°C are shown in Figure 2, while Table I lists the results of time of half dyeing ( t 1/2 ), percentage of exhaustion at equilibrium ( E at E m ) and substantivity ( K ) obtained from Figure 2. From Figure 2, it is clear that there are two stages during dyeing wool fibers with acid dyes, which are the adsorption and diffusion of dyes to the fiber (the initial dyeing stage) and the dispersion and immobilization of dyes within the fiber (the equilibrium exhaustion stage),7, 39 respectively.…”

“…Recently, low‐temperature dyeing has received increasing attentions due to its energy saving, and other advantages such as shrinkage prevention, comfortable wearability and bright shades 7. The results of low temperature dyeing of the [Emim]Ac‐treated sample are shown in Figure 6.…”

Effects of Oxygen Plasma Treatment on the Physical and Chemical Properties of Wool Fiber Surface

“…Moreover, they lead to cleavage of cystine amino acid to cysteic acid groups and conferred anionic charge into the wool fibers. These methods used to impart polarity to the fiber surface and to increase water permeability, dye penetration and the rate of dyeing [6]. They could be replaced with physical methods such as low temperature plasma (LTP), which is an environmental friendly process that can modify only the surface of wool fibers [7,8].…”

Thermodynamics of Wool Dyeing

“…The shape of the conventional dye uptake curve is consistent with an initial dwell time (20 to 40°C) when dye is transported 1 through the medium, a primary exhaustion stage (40 to 60°C) when dye levels at the fiber surface and diffuses within, and a secondary stage (60 to 90°C and above) during which time the dye disperses and immobilizes within the fiber. There is much resistance to dye penetration from the epicuticle layer of the cuticle cell of the wool [9].…”

“…the transcellular route shown in Figure 2) [11]. A continuous phase of membrane cells, the cell membrane complex underneath the cuticle, forms a network of penetrating canals to help mediate the impedance of the lipid barrier to dye diffusion, thereby facilitating dye penetration into the fiber interior [9].…”