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| Issue date:12/04/2010 |
| ATA Journal for Asia on Textile & Apparel - Apr 2010 Issue |
| Source:Journal for Asia on Textile & Apparel |
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| Blue denim is a global phenomenon and well accepted by consumers worldwide. "Green" denim can be produced using innovative industrial biotechnology, writes Ian Holme |
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| More jeans treated with biotechnology are positioned as an eco-friendly product |
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The global denim jeans market is set to exceed US$65 billion by 2015, according to a new report by Global Industry Analysts Inc. The jeans market is in fashion almost every year, and manufacturers and retailers constantly keep alive with the latest fashion trends in denim in order to maximise the market potential. In the USA, for example, Global Industry Analysts Inc reports that some 450 million pairs of denim jeans are purchased every year, and hence manufacturers must differentiate their brand in order to maintain sales growth.
Major factors such as better-fit, superior style, durable quality offered at an affordable price tag have driven the denim jeans market. Additional factors also contribute to the market growth, according to Global Industry Analysts Inc, such as lifestyle factors, fashion trends, celebrity endorsements and employment conditions.
Denim is now modified through many different treatments in order to ring the fashion changes. With more advanced industrial biotechnology, biotreatments using enzymes have replaced some of the older stonewash treatments and other chemical treatments to provide a softer, more supple fabric.
Some 50,000 tons of synthetic indigo dyestuff were manufactured in 2005, according to DyStar. Of which 97% was used in continuous warp dyeing for the production of blue denim. In the last decade, denim was mainly dyed with indigo (67%), sulphur black (26%) and other sulphur colours (6%). The changing fashion trends have also led to Indanthren (vat), reactive and direct dyestuffs, as well as pigments being used to colour denim. However, each of these classes of colorants account for less than 1% of the total amount of dyes applied to denim.
DyStar introduced the Econfidence denim technology for sustainable denim production. Natural starch and starch derivatives are considered by DyStar to have a market share of 73% of the warp sizing market for denim. Enzymatic desizing based upon the use of £\-amylases and amyloglucosidase is widely used to remove such products from denim fabric.
Biopolishing and biostoning produce desired denim effects
Many other biotreatments based upon enzymes are used on denim to modify the surface appearance and handle, particularly on indigo-dyed denim for jeans. Cellulase enzymes are used for biopolishing and biostoning treatments and laccase and glucose oxidase enzymes can be used for bleaching. Washing treatments can utilise lipases, proteases and hemicellulases.
Denim processors are increasingly seeking biotreatments that can integrate two separate enzyme treatments into a combined treatment, thereby saving process cycle time and considerable water and energy consumption.
Advanced Enzyme Technologies Ltd (India) provides Fadex HB 2M, a one-step process for enzymatically desizing and stone washing dyed denim. Denim jeans have, over many years, been washed in a finishing laundry with pumice stones or synthetic stones to abrade the surface of ring-dyed indigo blue cotton fibres, removing the colour to produce the fashionable localised stone-washed effect. The company also offers a variety of cellulases for the abrasion of denim. The neutral cellulases (Neutrastone series) are designed to act in the pH range 6-8, whilst the Denicell Series (acid cellulases) act in the pH 4-6 range and their hybrid cellulases (Addcool Series) operate in the pH 5-6.5 range.
Biostoning enzymes are applied to produce a controlled erosion of the fabric surface, creating special effects. This can result in a softer handle or in a specific type of surface finish generated by the partial or complete removal of cellulose macrofibrils from the surfaces of the fibres. Biostoning enzymes often contain a pH buffering system, an anti-back staining system and surfactants.
It is important in all biostoning treatments to produce fashionable abrasion effects and a soft, smooth handle whilst at the same time avoiding garment damage. It is now generally accepted that controlled treatments can replace the use of pumice stones and chemicals with significant processing and fabric performance advantages. In particular, enzyme biostoning treatments can provide more consistent washing, better abrasion and colour contrast that lead to a superior bio stone wash effect coupled with an enhanced fabric handle.
Anti-back staining agents can be used to prevent the colour contrast between the blueness of the indigo-dyed warp yarns and the whiteness of the undyed weft yarns being decreased, because of the pickup of indigo dye removed from the warp yarns being absorbed by the whiter areas of the fabric. Anti-back staining agents can consist of dispersing agents, chelating agents, and emulsifying agents, but their effectiveness is influenced by water hardness, i.e. presence of electrolytes such as calcium and magnesium salts that can increase the exhaustion of indigo, increasing back staining. Polyglycol ether derivatives and polymer phosphates provide a built-in sequestering effect in hard water, decreasing back staining. It is also possible to use enzymes as anti-back staining agents such as cutinase enzymase or other lipolytic enzymes.
However, this approach is more costly than the use of oxidising agents such as low concentrations of hydrogen peroxide (e.g. 0.5-1%), which inhibit the reducing action of the glucose liberated during stone or enzyme washing, thereby decreasing the reducing power of the glucose and enabling zero back staining to be obtained.
Laccase enzymes are copper-containing oxidases, which can generate one electron oxidation reactions on organic molecules. Laccases need to be applied with a mediator molecule, which functions as the substrate of the laccase. It then mediates the electron transfer from indigo to molecular oxygen. Laccase-mediated enzymes can be used in denim washing treatments where they can be employed to bleach indigo, enhance abrasion and to decrease back staining.
Some enzymes are active under both acidic and neutral pH conditions. This versatility allows denim processors to generate different creative effects during biowashing simply by pH regulation using only one enzyme. Clariant's newly launched cellulase enzyme Bactosol CNX liq c is one of such enzymes. When it is applied in an acidic medium, backstaining can occur producing a trendy faded appearance, aided by the white yarns turning slightly bluish. However, when Bactosol CNX liq c is applied under neutral pH conditions the backstaining is prevented and hence a sharp colour contrast is maintained between the yarns.
Another new offering by Clariant, namely acid cellulase Bactosol P liq c, provides controlled biopolishing and fading of denim fabric. It is designed to provide denim processors with consistent and reproducible wash down effects from batch-to-batch. Both Bactosol BP liq c and Bactosol CNX liq c are totally biodegradable and their use leads to savings in water usage and effluent loadings, the company says.
Reducing carbon emissions with innovative enzyme solutions
Genencor, a division of Denmark-based Danisco A/S, has recently extended its PrimaGreen range of enzymes for textile processing, especially on denim. Now denim can be stonewashed and bleached in a single bath with significant processing savings in terms of water and energy consumption.
PrimaGreen Super is a low-temperature acting cellulase enzyme designed for denim abrasion to produce the stone washed appearance. Treatment combining PrimaGreen Ecolight 1 with PrimaGreen Super can generate the vintage style look of denim using with 50% less of water and 40% less of energy, making it an attractive cost-saving option for textile processors, the company says. PrimaGreen Ecolight 1 has other considerable advantages due to biodegradability and its production with renewable resources.
PrimaGreen EcoFade LT100 is a novel laccase enzyme incorporating a new type of mediator from Genencor used along with PrimaGreen Super to produce an aged look in denim garment. This combined enzyme treatment is claimed by Genencor to reduce over 60% of water consumption while decreasing more than 70% of energy used.
On the other hand, PrimaGreen EcoFade LT100 (Genencor) enables denim bleaching to be carried out at neutral pH and low temperature, providing savings in rinsing water and neutralisation chemicals, and up to 90% of the heating energy used in denim bleaching.
From the carbon emission viewpoint, PrimaGreen EcoFade LT100 should enable abrasion, shade adjustment and bleaching of denim to be carried out with 90% lower emissions of carbon dioxide. The use of PrimaGreen EcoFade LT100 can be further enhanced by combining it with the low-temperature cellulase processing technology of the Genencor IndiAge Super product portfolio.
Genencor stresses the eco-friendly properties of the PrimaGreen products. As an example, Huntsman's Gentle Power Bleach with PrimaGreen EcoWhite bleaching enzyme is registered under Bluesign and can be applied as part of the Better Cotton Initiative, Genencor explains. Textile products complied with the Bluesign standard are those made with environmentally friendly manufacturing approaches.
Further, the PrimaGreen enzyme solutions are said to offer an opportunity for textile processors to maintain a win-win situation with their partners in the textiles production chain: The company says biodegradable enzymes used in the PrimaGreen solutions allow the textile processing to complete with much less water and energy, and ensuring better garments featuring softer, bulkier, brighter fabrics. This can become an attracting point to merchandisers and consumers.
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| 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. |
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| 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. |
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