|
|
| Issue date:16/04/2009 |
| ATA Journal for Asia on Textile & Apparel - Apr 2009 Issue |
| Source:Journal for Asia on Textile & Apparel |
|
| Ian Holme outlines a variety of application areas where Bio wash denim jeans treatments, a major member of biotreatments, can contribute in the field of dyeing and finishing |
Pretreatments are based upon the use of enzymes, and over the last two decades, an increasing number of biotreatments have been introduced into textile dyeing and finishing, mainly for natural fibres. Enzyme treatments are a major part of the biotechnology push, which is slowly transforming the textile industry. In particular, the use of enzymes as biocatalysts to operate chemical transformations more rapidly at lower temperatures-thereby saving both process time and energy consumption-can lead to cost savings in textile wet processing, as well as to novel effects in appearance, handle and performance.
The major research and application areas for biotechnology in textiles so far have centred upon the following:
Synthetic fibre production, e.g. production of lactic acid for PLA (polylactide acid or polylactic fibres)
Colorant production, e.g. potential synthesis of anthraquinone for dye manufacture
Bio pretreatments, e.g. silk degumming, cotton bioscouring, enzyme retting of flax, biobleaching, biocarbonising using a cocktail of different enzymes, and residual peroxide removal.
Biofinishing treatments, e.g. biopolishing, shrink-resist finishing of wool, controlled hydrolysis of polyester and enzyme finishing of silk
Waste water treatment, e.g. a wide range of enzymes have been studied for decolorisation of dyes, especially for anionic and fibre-reactive dyes which do not absorb onto the biomass in conventional activated sludge waste water treatment plants
Use of low energy enzyme-based detergents that enable garments to be washed in domestic washing machines at temperatures as low as 30°C.
In textile dyeing and finishing, varied enzymes can be combined to enable integrated processing to be attained, e.g. combined enzyme desizing / bioscouring and bioscouring / biopolishing. In addition, single bath combined bioscouring / dyeing, single bath bleach clean up and dyeing, and single bath biopolishing and dyeing can also be achieved. Single bath processing has the additional benefits of decreasing water consumption and effluent treatment costs. Bioscouring not only saves on the cost of alkaline chemicals, but can also yield handle improvements and more uniform dyeings.
An area now attracting a greater interest from biotechnology research and development teams is that enzymes can open up through the functionalisation and activation of fibre surfaces. Such surface-modified fibres may thus be subjected to chemical finishes using innovative chemicals that can lead to novel effects, e.g. improved durability and performance of water repellents, flame retardants or self-cleaning finishes. Alternatively, the fibre surface activation process could lead to treatments that could repair fibre surface damage with improvements in performance in areas such as pilling and abrasion.
Bio-washed denim captures consumer hearts
Enzyme treatment of indigo-dyed denim, as well as sandblasting, and bleaching treatments have all lead to fashionable garments with an irregular coloured appearance. Many other effects have been obtained on cotton yarns dyed with vat, sulphur or pigment colours. Sand blasting followed by cellulase enzyme treatment can be followed by overdyeing of the abraded areas, further varying the dyed surface appearance of cotton garments.
Much research and development has been directed towards finding a cost-effective ecofriendly dye decolorisation / degradation process. However, this is by no means a simple matter, and aerobic treatments (i.e. in presence of oxygen) and anaerobic treatments (absence of oxygen) have both been studied.
Specific problems surrounding effective decolorisation of coloured waste streams relate to the specificity of the microorganism (e.g. bacteria, fungi, algae and yeast) for particular dye molecular structures. Thus, Bacillus subtilis bacteria may utilise an azo reductive enzyme that is capable of degrading the azo chromophore in azo dyestuffs leading to decolorisation. However, isolation of the strain of bacteria capable of dye decolorisation is time-consuming. Another problem is that the presence of different functional groups (e.g. auxochromes) on the dye molecule can exert a marked effect upon the rate of decolorisation.
Bio wash denim jeans are unique and ecofriendly (photo: PRPS) |
It is known that the presence of salts and anionic auxiliaries can inhibit the action of the enzymes that decolorise dyes. The varying composition of dyehouse effluent, the slow rate of reaction of many enzymes and the difficulties associated with the isolation and commercial production of suitable enzymes for dye decolorisation have so far limited this approach.
It is to be hoped that further research and development over the next decade will lead to a biotechnological breakthrough, namely, new enzyme decolorisation treatments that are rapid acting and more cost-effective than current physicochemical treatment methods, especially for highly water-soluble reactive dyes.
In the search for a greater range of end-uses for bast (i.e. lignocellulosic) fibres like flax, jute and so forth, there has been a considerable effort expended in attempting to produce more efficient retting / pretreatment processes using enzymes in order to produce finer, softer fibres. From a technical viewpoint, the results on flax have been promising but so far the enzyme-based treatments are still not cost-effective compared with traditional dew-retting.
Bacteria help kill cigarette smoke odour
In the area of novel fabric finishes, there is a considerable scope for the application of enzymes both for producing textile finishes as well as for fibre surface functionalisation for the attachment of chemical finishes. For example, the production of fabrics containing genetically-engineered bacteria and cell strains could enable the production of agents, destroying odours like tobacco smoke on fabrics or providing an approach to self-cleaning fabrics.
Cyclodextrin-based finishes depend upon a unique molecular structure, similar to a molecular bucket. The internal surfaces of the molecule are hydrophobic and can be utilised to trap hydrophobic odours, thereby enabling garments to smell fresher for longer and extending the wear time before laundering is required. It is possible to produce cyclodextrins from starch using cyclising enzymes, e.g. cyclodextrin glycosyl transferase, and such an approach may prove feasible in the future for enzymatic engineering of novel finishes.
The surface functionalisation of fibres is potentially a fruitful approach for surface activation and reaction with appropriate chemical finishes. The application of hydrolase enzyme to polyester fibres based upon polyethylene terephthalate can cause fission of the ester bonds leading the production of hydroxyl- and carboxyl end- capped shorter chain molecules in the fibre surface. Diffusion of the enzyme within the fibre structure is prevented because of the compact physicochemical structure of polyester fibres. Introduction of hydroxyl and carboxyl groups offers greater opportunities for durably attaching surface finishes, as well as increasing the adhesion of textile coatings and laminating films.
On natural protein fibres such as wool, mohair, alpaca, cashmere and silk, the controlled application of protease enzymes that cause scission of the polypeptide bonds will lead to a greater concentration of amino and carboxyl groups in the fibre surface. In wool, for example, this could create greater opportunities for chemical reaction and greater durability of a novel shrink-resist agent to wet treatments, e.g. washing treatments.
It is clear that the potential for biotreatments in textile dyeing and finishing is considerable, but such treatments require careful process control, e.g. enzyme concentration, pH, temperature, and time to achieve optimum results.
|
| We are collecting readers' comment for improving our website. If you are willing to help, please CLICK HERE to complete a survey. Your comments matter. |
|
|
|
|
| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
|
| Copyright © Adsale Publishing Limited. Any party needs to reprint any part of the content should get the written approval from Adsale Publishing Ltd and quote the source "ATA Journal for Asia on Textile & Apparel", Adsale Textile English Website - www.AdsaleATA.com. We reserve the right to take legal action against any party who reprints any part of this article without acknowledgement. For enquiry, please contact Editorial Department. |
|
|
|
Close
|
|
|
Write a mail to the editor : 
