Shrink-resist Finishing Research Articles

Eco-friendly shrink-resist finishing of wool through synergistic effect of disulfide bond reducing agent and papain

The environmental benefits of utilizing protease as a biocatalyst for wool shrink-resist finishing have been widely recognized. However, the efficacy of individual protease treatment is unsatisfactory due to its incapability towards the outermost cuticle layer of wool fibers that contains hydrophobic fatty acids. In order to weaken the structural integrity of the highly cross-linked scales and promote the enzymatic anti-felting, sodium sulfite and tris (2-carboxyethyl) phosphine hydrochloride (TCEP) were employed in combination with papain, respectively, aiming at obtaining a low shrinkage without unacceptable fiber damages. Based on the synergistic effect of papain and TCEP, the edges of wool scales were slightly destroyed by the reduction of disulfide bonds, accompanied by enzymatic hydrolysis of the keratin component. Through the controlled reduction and hydrolysis of wool scales, satisfactory anti-felting result was achieved without causing severe damage to the fiber interiors. In the presence of 0.25 g/L TCEP and 25 U/mL papain, the area shrinkage of wool fabric decreased to approximately 6 %, with a low strength loss of less than 8 %. Meanwhile, the dyeing behavior of the wool fabric under low-temperature conditions was dramatically improved, leading to decreased energy consumption during production. The present work provides an alternative for eco-friendly finishing of wool fabrics, which can be applied commercially.

An eco-friendly technique for shrink-resist finishing of dyed wool via combined use of hydrolase and cyclamate

Savinase 16L as a type of mature protease for shrink-resist finishing can effectively hydrolyze wool scales, but it is also easy to penetrate into the cell membrane complex (CMC) layer, even easily causing undesired fiber damages. In this study, Savinase 16L was combinedly used with a protective agent of cyclamate, achieving an increase in the size of enzyme protein molecules through the intermolecular forces. This combined operation was intended to make it difficult for protease to enter the CMC layer, conferring protease a more concentrated actions towards wool scales. Meanwhile, a commercial keratinase was applied for wool pretreatment to loosen the structural integrity by hydrolyzing the disulfide bonds in wool scales. The combination use of hydrolase (20 U/mL of keratinase, and 6.5 U/mL protease) and 10 g/L cyclamate endowed the dyed wool fabric with encouraging shrink-resist property, achieving a felting shrinkage of 5.4% ± 0.55% with an acceptable strength loss of 12.3% ± 1.2%. More importantly, color hue of the wool fabric almost did not change compared with to that with chlorination method. As an eco-friendly and energy-saving strategy, it provides an efficient alternative for shrink-resist finishing of white and dyed wool fabrics, and expands the application of biotechnology in wool industry.

Benign Felt-proofing of Wool Fibers Using a Keratinolytic Thermophilic Alkaline Protease

ABSTRACT Felting shrinkage of wool is a major problem which has negative impacts on its performance attributes. Traditional chemical methods used for shrink-resist finishing are suffering from some drawbacks. Therefore, this work aimed at the utilization of microbial protease in wet processing of wool. The bacterial strain Bacillus licheniformis ALW1 produced 52.1 U/mL enzyme activity that was thermophilic with optimum activity at pH 9. Additionally, the enzyme possessed a keratinolytic activity of 4.1 U/mL, suggesting its applicability in wool processing. Therefore, the effects of different treatment conditions; Viz. concentration of the enzyme, temperature, treatment period and pH on some of the physical and chemical characteristics of wool were studied. The felting shrinkage of wool fibers was determined using the Aachener 3-D felting machine. The influence of the enzymatic modification of wool on its dyeability with anionic dye was assessed. Chemical, physical, and mechanical properties of treated samples were evaluated using amino acid analysis, alkali solubility, Fourier Transform Infrared spectroscopy, whiteness index, and tensile properties. Scanning electron microscopy was applied for the examination of wool fibers’ surface. The results proved that the modification of wool fibers with the produced enzyme highly improved their felting resistance and dyeability with acid dye without adverse effects on its inherent properties.

Controlled eco-friendly shrink-resist finishing of wool using bromelain

Shrink-resist finishing is imperative to introduce dimensional stability and characteristic handle for wider acceptance of woolen garments. Conventionally used oxidative anti-felting treatments using sodium hypochlorite, gaseous chlorine, dichloroisocyanuric acid etc. release chlorine leading to high concentration of absorbable organic halides in waste water; application of resin results in stiffer handle because of spot welding effect. In contrast, enzymatic processing using protease is a sustainable alternative to substitute eco-hazardous conventional processes though diffusion of protease deep inside the wool in alkaline pH is the major concern for substantial weight as well as tensile loss thus limiting its application on wool. Treatment with bromelain even at very mild alkaline pH around 7.5 in absence of salt results in considerable damage in wool structure with consequence of higher weight and tensile loss due to partial/complete removal of cuticles on the surface. In this work, bromelain, a type of proteolytic enzyme, was used along with salt in acidic pH for controlled superficial hydrolysis of wool. A two-step acidic bromelain treatment was opted first using Box–Behnken design keeping in view minimum area shrinkage succeeded by optimization of the treatment parameters to achieve least area-shrinkage, weight loss, strength loss along with improved subjective softness. Controlled adsorption of bromelain at the outer surface of wool in presence of salt at pH ∼6 was observed yielding desirable anti-felting behaviour with minimum weight and strength loss. In contrast to conventional chlorine based technologies, acidic bromelain may be used in presence of sodium chloride to yield machine washable wool possessing minimum loss in weight and tensile strength both at industrial level.

Effects of cutinase on the enzymatic shrink-resist finishing of wool fabrics

A novel microbial cutinase from Thermobifida fusca WSH04 was applied in the pretreatment of wool fabrics followed by protease treatment, aiming at improving the wettability of the samples by hydrolyzing the outmost bound lipids in the wool surface. Cutinase pretreatment could increase the efficacy of the subsequent protease treatment by improving the wettability, dyeability, and shrink-resistance of the wool fabrics. The data obtained by the XPS method showed the changes of elemental concentration in the wool surface after cutinase pretreatment. Compared with the fabrics treated with hydrogen peroxide and protease, the combination of cutinase and protease treatments produced better results in terms of wettability and shrink-resistance with less strength loss. The anti-felting property of the fabrics treated with the enzymatic resist-shrink technique is very promising to meet the commercial standard.

Immobilization of proteases with a water soluble–insoluble reversible polymer for treatment of wool

A commercial protease, Esperase, was covalently linked to Eudragit S-100, a reversible soluble–insoluble polymer by carbodiimide coupling. When compared to the native enzyme, the immobilized form presented a lower specific activity towards high molecular weight substrates but a higher thermal stability at all temperatures tested. The optimum pH of the immobilized protease was shifted towards the alkaline side by about one pH unit while there was no change in optimum temperature between the free and immobilized protease. The immobilized protease exhibited a good storage stability and re-usability. Enzymatic treatment of wool using proteases has been investigated for wool shrink-resist finishing. It was found that using the immobilized protease in the enzymatic treatment of wool there was a reduction of weight and fibre tensile strength loss because the proteolytic attack is only limited to the cuticle surfaces of wool fibres. This novel approach is a promising alternative for wool shrink-resist finishing to replace the conventional chlorine treatments. This environmentally friendly bioprocess needs to be further characterized to a complete understanding and optimization.

Sodium Hydroxide Pretreatments of Wool for Shrink-resist Polymer Finishes

(1982). Sodium Hydroxide Pretreatments of Wool for Shrink-resist Polymer Finishes. The Journal of The Textile Institute: Vol. 73, No. 6, pp. 293-296.

Applying Shrink Resist Polymers to Wool Fabrics at Room Temperature Using Pad-Store Methods

Shrink-resist finishing of wool fabrics using aqueous based polymer systems is usually carried out using an energy intensive pad → dry → heat cure technique. This paper describes fabric shrink-resist finishing using the Bunte salt terminated polyether, Lankrolan SHR3 (Diamond Shamrock), by a simple pad → store (room temperature) → wash-off procedure. Advantages of the method include low energy consumption, no fiber yellowing due to the absence of high temperature treatments under alkaline conditions, and ease of post dyeing. Evidence is presented for covalent reaction of the polymer with the fiber to form mixed disulphides, improving the stability of the shrink-resist finish to such agencies as post dyeing.

Treatment of Wool Fabrics with Mixtures of Fluorochemicals and Shrink-Resist Polymers

The influence of polymeric shrink-resist finishes on the durability on wool of fluorochemical stain and soil repellents was examined. In some cases the durability to washing, drycleaning, and abrasion of the fluorochemical (as judged by oil and water-repellency tests) was improved. The best results were obtained by addition of FC-234 (3M Company) to Sirolan BAP pad treatments. This combination also showed improved durability on cotton and polyacrylonitrile when cured with organo metallic catalysts.

Shrink-Resisting Wool with Poly(Dimethylsilozane)-α,ω-Diols and Aminofunctional Silane Crosslinking Agents

This and the following paper study shrink-resist finishes for wool using poly(dimethyliloxane)-α ω-diols (I) and poly functional silane crosslinking agents. In this paper treatment of wool fabric from organic solvents with the diols (I) of various molecular weights and a single silane, 3(2-aminoethylamino)propyltrimethoxysilane, (II) was examined in detail. Important factors for effective shrink resistance were the molecular weight of the diol (I), the concentration of amino functional silane (II), the extent of reaction before and after application to wool, the reaction with water, and the presence of an organotin catalyst or polyalkoxysilanes such as methyltrimethoxysilane. These findings were used to modify a commercial silicone shrink-resist finish for use in a durable press treatment.

19—SHRINK-RESISTING WOOL WITH SILICONS COPOLYMERS

An investigation is reported in which some silicone copolymers were prepared and evaluated as shrink-resist finishes for wool. The most effective were: alkoxy-terminated polydimethylsiloxanes, graft-copolymerized with acrylic acid esters; epoxy-functional polydimethylsiloxanes containing poly(alkylene oxide) side chains. The shrink-resist effectiveness of these copolymers differed only slightly from that of the corresponding silicones, and in some cases the non-silicone part of the polymer appeared to contribute to the shrink-resistance. The incorporation of poly(ethylene oxide) chains into epoxysilicones facilitates aqueous application.

Polybutadiene Shrink-Resist and Durable-Press Finishes for Wool

Liquid low-molecular-weight polybutadienes have been investigated as potential shrink-resist finishes for wool. These polymers could be crosslinked thermally, but a better method used reactions of functional end-groups such as amino, carboxyl, or hydroxyl. For example, polybutadienes with hydroxyl or carboxyl groups could be crosslinked on wool with polyisocyanates, and aminopoly-butadienes with polyepoxides. Many of these polybutadiene finishes imparted a high level of shrink resistance to an untreated worsted wool fabric, and the properties of fabrics treated by some of these have been compared. Durable-press finishes were produced with polybutadienes, including a delayed-cure treatment.