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| Issue date:01/04/2006 |
| ATA Journal for Asia on Textile & Apparel - Apr 2006 Issue |
| Source:Journal for Asia on Textile & Apparel |
| by Mac Isaacs |
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| The world of textile finishing is catching up fast with new demands in market, as products featuring special effects are almost taken for granted |
In today's market place, products abound are made possible by special effects finishing. The wide use of disposable wipes is an example: wash dishes; care for your pet; disinfect ... the list is endless. And these all compose the largest fast-growing segment in the textile business.
Silver-based antimicrobial
Chemical application is a way to give fabrics a variety of special functions, including the antimicrobials that eliminate odors and prevent mildew. A new chemical of this category, DoraFresh, a silver-based nanotechnology antimicrobial, is about to hit the market. Brought by the partnership of Anovotek LLC and M. Dohmen, a global supplier of high-performance textile dyes and chemicals, the new chemical features durability on textile materials and easy application.
Don Alexander, President of Anovotek, says that silver is not only safe, but also highly effective, broad-spectrum antimicrobial. He says that silver has extensive use and exposure to humans, such as fillings for teeth, and there are a number of medical applications, including the fact that many catheters are coated with silver to reduce the risk of infection and its use as wound care.
Numerous publications report studies on the effectiveness of silver antimicrobials, clearly establishing it as a proven technology. For example: "It has long been known that silver and its compound have strong inhibitory and biocidal effects on bacteria. Spadaro found that silver ion had a biocidal effect on as many as 16 kinds of bacteria, including Escherioria coli and staphylococcus aureus. This means it has a broad spectrum of antimicrobial activity."
A number of antimicrobials sometimes experience a development of resistance by bacteria, but it has not happened in the case of silver. One of the primary reasons is that it possesses multiple mechanisms of attacking microbes: it interacts with cell membranes, inhibits protein synthesis, binds to DNA, interferes with electron transport and respiratory chain (cytechromes b and d), and inhibits oxidation of key compounds, including glucose, glycerol fumerate, succinate, lactate.
The effectiveness of silver antimicrobial depends on three factors:
The silver form (solubility, chemistry, size, etc.).
The binder system (polymer permeability, Ag release rate, surface properties, etc.)
Microbial environment (water control, pH, ionic nature/strength, viscosity, flow, etc.)
Anovotek says there are two main components in the new antimicrobial. The active component consists of specifically formulated silver chemistry for controlled ion release in microbial environment (textiles). It is manufactured to specific particle size, shape and morphology for optimal surface coverage and antimicrobial efficacy. The polymeric binder system provides adhesion of silver to the textile material.
The recommend application is 1.0-2.5% owf of blended product. The loading rate depends on end product performance requirements. The low active (silver) concentration - between 0.0024 and 0.0072% (24-72 ppm) is possible through nanotechnology. This results in minimal adverse impacts on shade and hand and cost effective silver antimicrobial treatment.
APPJ technology
Another, perhaps lesser known, example of special effects finishing can be found in Atmospheric Pressure Plasma Jet (APPJ) technology. APPJ is a broad-based platform technology consisting of several different apparatus and methods patents on the use of different applications and designs of plasma sources for generating and using a low-temperature, highly reactive plasma for materials process applications.
Various atmospheric pressure plasma jet models |
APPJ produces a non-thermal, stable, homogeneous discharge, having 50-1,000 times greater production capability of active chemical species than older, competing atmospheric pressure plasmas such as dielectric barriers or corona discharges. Unlike those discharges, APPJ technology requires no insulating plates and is easily scaled up for treatment of large-area substrates.
The technology may be used for cleaning, surface treatment, adhesion promotion, etching and deposition. It operates using either planar or cylindrical electrodes and has three critical, patented elements:
Radio frequency power;
Gap spacing of the electrodes;
Majority concentration of helium in the feedstock gas.
One of the first textile companies to make use of the plasma technology is Avondale Mills.
Avondale's Director of Product Development, Tony Bellamy, noted that Apjet's technology is "all dry" and does not generate wastewater.
Stephen Felker Jr., Manager of Corporate Development for Avondale Mills, adds "We are still in the earliest stages of this program me," he says, "but we have great hopes for the anticipated results."
Felker says the technology should enable the company to impart different characteristics to the fabrics including water repellency, wetting properties, and eventually flame retardancy. Moreover, Felker thinks the technology will enable the company to convert many of its wet processes to dry processes.
Surface finishing
Apart from some innovative finishing methods, many surface finishing methods, as old as time, continue to dominate the special effects finishing segment. Usually, these methods are in batch operations, and multiple passes through the machine are required before getting the desired surface.
Calendering, which is the passing of fabric through heavy squeeze rolls, allows different compounds to be added to fabric to produce an effect similar to "kneading" that reduces the harshness of the added compounds. Years ago, these added compounds could have been wax to impart water repellency.
Basic calendering of passing fabric through two roll nips -called roll calendering-progressed to heating the rolls so the surface can receive advantages of heat on the additives. A natural advancement occurs when one roll was driven faster than the other roll, thus producing a "sheen" effect caused by the friction of a metal roll on the fabric - called friction calendering. When one roll is engraved with a pattern, the result is the transfer of the pattern to the fabric - called engraved roll calendering.
When it is not desirable to calender fabrics, a "button-breaker" device can be used. The rolls are studded with spherical metal protrusions (buttons) so each fabric passage caused a breaking down of the harsh surface film on the fabric. Again, a batch operation is used so that the necessary number of passes can be made, satisfying the goals of the garment designer.
Similarly, coating is the application of a semi-liquid material such as rubber, polyvinyl-chloride or polyurethane to one or both sides of a textile material. Once the coating has been dried (and cured, if necessary), it forms a bond with the fabric.
Napping & raising
Napping or raising is the effect of engineered wires that can disturb fibers so they are brought to the fabric surface to yield a soft, fluffy appearance. Napped fabrics have a large acceptance in infant sleepwear.
Italian Lafer SpA manufactures both single and double drum raising machines. Single drum raising machines with 24, 28, 32 or 36 raising rollers and double drum machines with 24, 28 or combined 24/36 raising rollers are available in various widths. Combined raising and shearing units (GLC) are also available.
The company has developed an exclusive system combining both PLC and industrial PC systems with large touchscreen color video to make the raising machine more user-friendly. These systems offer the following advantages:
One million raising programmes storage capacity;
On-screen troubleshooting guide with photos and instructions (over 100 alarms included);
Can connect to a network through Ethernet card (optional) so that production data can be monitored from a remote computer.
Optional modem allows troubleshooting directly from Lafer headquarters.
Electronic fancy brush synchro control prevents damage to raising fillet caused by non-synchronized raising fillet cleaning brushes.
Fabric tension - one of the key parameters in achieving desired effect - is set on the touchscreen and controlled by the computer. Optional load cells placed at the entry and exit of each drum allow automatic maintenance of minimum fabric tension set regardless of the raising energies. This prevents the fabric from becoming too loose at the drum entry and exit points, allowing optimal raising on the entire drum and eliminating bar marks, weft distortions or other defects.
Special pressure rollers fit on the entry and exit draw rollers to prevent fabric slippage and ensure raising uniformity. The drum has adjustable speed and can rotate in both directions compared to the fabric. On the twin drum machine, drum speed and rotation direction can be varied separately. An electronic system maintains the raising energy while varying the fabric or drum speed.
The US-based Gessner Co also launched the LYNX and PUMA raising machines, following their predecessors, Hi-Torc and Uni-Pro raising machines, which have been in operation in the US since the 1950s. The LYNX and PUMA raising machines provide high-product quality and high output for flannel, bedding, tubular fleece, open-width knits, UBL, napery, automotive body cloth, for just about any fabric construction and fiber content.
Features include:
Direct gear drive or constant tension belt drive, depending on application;
Fabric speed and tension control system using PLC-controlled A-C vector drives with independent, shaft-mounted A-C motors, no proprietary software, PC-based control option available;
Touchscreen control panel with all key settings programmable in memory for repeatability in operations, hundreds of recipes can be stored and recalled, maintenance scheduled, production records maintained;
Synchronized cleaning roll system to keep card clothing in excellent condition while effectively removing waste flock;
70- or 90-mm dia seamless steel working rolls to achieve greater raising speeds on wider fabrics.
Foam application
Foamed chemicals are also used to apply additives, mostly to one side of the fabric. Foaming is dependent on the compatibility of the required chemicals to allow the mixture to froth (foam) so it can be applied to the fabric. When the air component of the foamed mixture collapses, the required chemicals are on the fabric and the conventional high-water content is avoided, thus saving energy used for drying.
Foam applications must produce a constant and equal mix to the entire width of the fabric. Current efforts to attain this goal are accomplished with a curved blade applicator, where the parabolic shaped applicator enables uniform addition of foam across the entire width.
US-based Gaston Systems has such a system - the CFS, which is a highly controlled, patented system for accurately applying foamed water soluble or water dispersible chemicals at very low moisture levels onto or into substrates such as textiles, carpet, nonwovens, paper and others. Such low moisture levels virtually eliminate chemical migration in the substrate. This fact, combined with CFS technology, permits precise control of chemical penetration depth.
The CFS hardware is composed of three components:
The Foam Generator provides foam at the correct mixture and density (up to over 100:1 blow ratio).
The Applicator applies the foam under pressure onto or into the substrate. Its unique parabolic design assures uniform application across the width without streaks.
A PLC Control System controls both units, which gears foam delivery to range speed and controls foam pressure to achieve the application depth desired.
Proper chemical formulation is also a vital factor in a successful application. Gaston Systems uses its more than 20 years' foam application experience to assist customers in finding the right formulation to meet specific application needs.
Key to the CFS System's success is its microbubble technology, which enables predictably managed and controlled foam application. A varying bubble size represents an unbalanced bath density and will never produce an even chemical treatment. CFS confines and controls the foam for accurate and repeatable results.
Rubbing
Sometimes, surface modifications are also accomplished by simply rubbing the fabric against itself. This is usually done in rope form and in a machine similar to a beck/dye jet. One supplier of such a machine is Biancalani SpA of Italy, which offers either dry or wet rubbing of fabric. Since the system is a batch operation, the number of passes can be controlled to gain desired surface effect.
Biancalani's Airo 4 finishing machine |
The company's Airo Softening & Tumbling machine is a batch-type unit where fabric is treated in rope form at speeds up to 1,000 ypm. The machine is available with wet treatment for maximum hand improvement.
The global acceptance of blue jeans has fostered techniques to change the denim surface appearance. Abrasion with pumice (stone washed), acidic agents (acid washed), sanding (brushed look), shot pellets (hole look), enzymes (soft look) and bleaching agents (streaked look) are example of some of the treatments designed for this specific fabric type. These individual characteristics are usually done on the garment in a rotary laundry machine so additives and cycle time are managed to accomplish the desired look.
Sanding & sueding
Sanding or sueding is an abrasive finishing operation used to alter the surface of fabrics, primarily those made of manmade fibers.
Lafer's MicroSand |
Lafer pioneered the drum type sueding machine in the mid 80s and has developed a wide range of sueding machines. In 1999, Lafer introduced the Aquasand wet sueding machine equipped with the Carbosynt long-lasting emery for woven products. It was subsequently replaced by the Microsand, which uses the same Carbosynt emery. In 2000, Lafer introduced yet another new technology for knit fabric finishing, the UltraSoft. This led to another development specifically for tubular knits, the UltraSoft SMT.
Sueding on a drum gives a much softer and uniform finish since the fabric touches around 300 sueding rollers as it passes over the drum, compared to only 4-6 rollers on traditional machines. The high number of contacts gives an extremely soft and uniform sueding finish.
The Delta system, patented by Lafer and used on the UltraSoft has special adjustable plates, which create a continuous spreading effect during the process to ensure a uniform effect. It eliminates selvage-to-center differences and prevents streaking.
Gessner's multi-roll Sensi-Touch II sanding/sueding machine imparts a luxurious suede finish on woven, knitted and nonwoven fabrics. Irrespective of the fabric's construction, weight or fiber content, the Sensi-Touch II can be equipped to produce superior fabric surfaces.
Heavy woven twills, denims and lightweight or knit fabrics with micro denier fiber can all be processed in the same machine. This is because each Sensi-Touch II has five individually controlled (speed and direction) abrasive roll positions with the choice of three unique working cylinders depending on application:
Contact cylinder - a super rigid, lightweight, temperature-resistant fiberglass composite material wrapped with emery paper of various abrasive sizes...recommended for the majority of woven fabrics.
Interrupted contact cylinder - each of lightweight aluminum and populated with six abrasive-coated Duralene tubes producing a softening and aging effect due to the beating action caused by interrupted contact...recommended for certain heavy woven fabrics, where softening (or de-sizing) as well as the sueding effect is desired.
Brush-soft cylinder - a brush with special abrasive filament bristles produces a dense, very low pile for a soft suede, peach skin type effect and is suitable for less stable fabrics like knits, fabrics containing Lycra or fragile constructions...a similar effect can also be achieved on woven fabrics.
These unique working cylinders are quickly and easily maintained or replaced using Gessner's Quick Change chuck system.
Curtin-Hebert Co has been manufacturing sanding machinery for over 100 years. Its precision sanding machines can utilize a complete range of abrasive papers from 36 to 1,000 grit, depending on the application. These precision machines are built to be durable and easy to operate. The sanding drum is the heart of the machine. It is a centrifugally cast cylinder, bored, turned and dynamically balanced. There are several applications where a tolerance of +/- .0005 in. over 100 in. wide is achieved. The equipment is so precise it can sand the print from a sheet of ordinary newspaper without harming the paper itself.
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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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