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Recent Developments In Dyeing

Then Maschinen has introduced the L-shape Airflow® dyeing machine for processing delicate fabrics.

Jürg Rupp, Executive Editor

F or centuries, water has been the most important element in textile finishing. Today, it constitutes an increasingly expensive medium.

Germany-based Then Maschinen GmbH's Airflow® dyeing concept was invented by Wilhelm Christ and subsequently patented in 1978 by Then, which produced the first prototype. Over the years, the system was developed further according to the requirements of the industry.

Dyeing 2
The long tube design, superior fabric displacement and gentle polytetrafluoroethylene rods contribute to the success of smooth treatment meeting high quality demand for Then Maschinen’s newly developed Airflow® Lotus 200 dyeing machine.

Air Instead Of Water

Airflow was the key element of the technology, as air is an ideal transport medium. The replacement of dye liquor with air as a method of transporting piece goods in jet-dyeing machines was a big step toward reducing water and chemicals consumption. Compared to the jet system in which the nozzles are filled with liquor, nozzle pressure is negligible, thus offering optimum protection of sensitive textile surfaces. At the same time, the use of the mass flow principle provides a major improvement in fabric hank laying, thus preventing creasing.

The moisture-saturated airflow ensures the uniform distribution of temperature on the fabric and in the machine, constituting a prerequisite for even and reproducible dyeing. Moreover, the low level of liquor in the dyeing boiler means the fabric is lighter than in conventional machinery and can therefore be accelerated quickly to high speeds. Thus, the risk of draft or strain is minimal, which is particularly advantageous with regard to the finishing of items containing elastane fibers.

The high transportation speeds of the fabric result in very short fabric turn time. High heating-up gradients are possible because a very low liquor ratio is maintained. The unique ability to use a hot drain system and rinsing with fresh water in a running wash system considerably reduces the time required for the dyeing process.

The Airflow technology represents the combined result of the entire range of possibilities provided by the technology. Through the interplay of all technical possibilities and functions, economic and ecological advantages over the traditional dyeing technology are achieved. The main advantages are as follows:
  • unlimited flexibility with regard to all fiber - except pure wool - and fabric weight classes between 30 and 800 grams per square meter, as well as all standard market dyestuffs;
  • the lowest liquor ratio on the market: approximately 1:2 for man-made fibers and 1:3 to 1:4 for natural fibers, depending on the article and structure;
  • energy savings of up to 40 percent, thanks to a frequency converter, and the use of air as a transport medium, while all other systems need water;
  • a reduction in the overall process time of approximately 25 percent; and
  • lowest water/wastewater levels.
The New L-shape Airflow

However, the Airflow dyeing machine had one disadvantage: dyeing of extremely delicate fabrics didn't give a perfect result. Current and future trends pointing toward more and more lightweight fabrics with high contents of elastane in finest yarn counts and gauges prompted the next stage of Airflow machinery design.

To meet the required voluminous hand as well as top-grade quality standards, the world's first long-tube Airflow machine, the Airflow Lotus 200, was developed. The new dyeing machine incorporates the latest advances in Then's Airflow technology and operates according to the original aerodynamic principle. The dye liquor passes the self-cleaning filter and is then evenly applied and finely distributed as a mist with the aid of the blower, assuring outstanding penetration, according to Then.

Schematic drawing of the Airflow® technology: Air is the key element, and is said to be the ideal medium to transport piece goods in dyeing machines.

Handling Delicate Fabrics

The Airflow Lotus 200 is said to be especially suitable for the wet finishing of delicate cellulose- and man-made-fiber knitwear and woven fabrics with a high percentage of elastane. Such fabrics are used in the automotive, lingerie, sports-, leisure- and swimwear segments. Close attention has also been paid to the achievement of significant savings of precious water and energy resources -- similar to the Airflow Synergy dyeing machine.

Extremely safe and gentle product running and outstanding displacement comprise Airflow Lotus 200's characteristics. With its concept in machine design, unmatched results in process technology and unparalleled achievements regarding economy and ecology, the new machine will substantially extend the field for aerodynamic applications, Then reports.

The newly designed dome blower ensures that the fabric is transported just by air. This means the liquor actually is used to do what it is meant to do: dyeing only. The liquor ratio is reduced to between 1:2 and 1:5 and provides savings in terms of water and water treatment, chemical, and energy costs. This will bring up to 80-percent savings of liquor compared with costs associated with outdated hydraulic machines, as well as significant savings of time. Shortest cycle times and loadings of up to 1,200 meters for lightweight fabrics and up to 200 kilograms for average articles allow high daily production rates.

Polyamide Dyeing

Most of the fabrics for lingerie, swimwear and automotive applications are made of polyamide. That's why the new L-shape dyeing machine handles fabrics made of 100-percent polyamide with the same results as previously mentioned fabrics. Then's Roland Adrion, senior sales manager, says that "current and future trends point towards more and more lightweight fabrics with high contents of elastane in finest yarn counts and gauges. Meeting the [voluminous hand specifications] as well as top-grade quality standards were there when we developed the world's first long tube Airflow machine, the Airflow Lotus." Perhaps a more appropriate name for the new machine would have been "Longflow."

March/April 2010