Sustainable Dyeing And Finishing
Textile World looks at some recent dyeing and finishing developments that are economically and ecologically efficient and achieve high-quality results.
Jürg Rupp, Executive Editor
Economical and ecological efficiency involves minimization of costs and maximum profit as well as reproducible quality with minimal environmental damage. Therefore, process optimization is a must to fulfill all parameters and requirements for right-first-time production. Western wet-finishing costs are more and more apparent in various Asian countries as well, and can be divided into the following approximate cost proportions:
- 42-percent labor;
- 29-percent dyestuffs and chemicals;
- 6-percent water;
- 12-percent energy;
- 6-percent environment and safety measures; and
- 5-percent maintenance.
Monfort's Montex 6500 tenters feature heat recovery systems that can reduce energy usage by up to 30 percent.
The catalog of modern, up-to-date dyestuffs and dyeing and finishing equipment offers a blend of modern technology and chemistry. Major requirements are as follows:
- reduced water consumption;
- varying load capacity;
- time savings;
- comparable economy and ecology;
- highly optimized rinsing processes;
- controller units;
- downstream processing advantages;
- wet finishing process;
- economical finishing; and
- monitoring and controlling.
Cornerstone Research And Development
"Sustainability is one of the companies' three topics in R&D, besides ecology and best quality output," states Germany-based Fong's Europe GmbH, formerly Then Maschinen GmbH and Goller Textilmaschinen GmbH. "As the inventor of the short liquor ratio technology, the company ever since put a lot of emphasis on sustainability."
At Thies GmbH & Co. KG, Germany, the main emphasis is on the efficiency and sustainability of its products and proceedings, according to the motto, "Go green with Thies." All of the company's yarn- and piece-dyeing machines reduce process times and energy as well as other resource usage. Thies reports its iMaster H20 presents pioneering innovations including versatility and adaptability, and offers the dyer product flexibility, which Thies says has never been obtained before now.
For Fong's Europe, the most successful model is still the Then-Airflow® Synergy, whose latest version is model SYN 600 G2. The main reason for this success, the company reports, is the Airflow technology itself. "The technology is unrivaled in batch dyeing with its unbeatable dyeing economy and dyeing ecology, resulting in huge savings and typically offering one batch more per day, not to mention the wide range of fabrics," Fong's Europe explains, noting that the comparison with a model from some five to 10 years ago shows some significant improvements: Because of the 30-percent-greater batch size and technical machine design improvements — including new nozzle section, wheel and flexible chamber device, and the power rinse system — overall water, energy and chemicals consumption could be further reduced by around 15 to 20 percent.
On the other hand, Thies remarks that the liquor ratio doesn't play as important a role as in the past. The importance today relates more to consumption in liters of water per kilogram of goods (l/kg). Today, the influence of the product on water consumption is greater than the influence of the system. The fleet relationship detail only tells how much water per treatment bath is used; it does not give the number of required baths. The detail of water consumption in l/kg, however, gives information about system efficiency.
Huntsman Textile Effects, Singapore, mentions that the textile industry is notorious for consuming vast amounts of water, especially during dyeing and finishing. Up to 100 liters of water are used to dye 1 kg of cotton fabric. The company has been able to improve dyeing technology considerably with the development of a new chemistry for dyeing of cellulosic fibers. AVITERA™ SE is a new tri-reactive dye range for exhaust application on cellulosic fibers.
Only 15 to 20 liters of water are required to dye 1 kg of material. Avitera SE dyes and ERIOPON® LT clearing additive comply with new environmental sustainability standards and give top-quality results, achieved in time, Huntsman reports, adding that the process also saves time and energy and reduces carbon dioxide (CO2) emissions; and that with the new dyeing technology, 1.3 liters of fresh water per person per day potentially could be saved in textile-processing countries such as China, India or Bangladesh.
Most reactive dye molecules have one or two reactive groups that bond with the fiber and remain permanently fixed. Dye that fails to bond is hydrolyzed and cannot be fixed on the fiber. In conventional dyeing, 20 to 40 percent of the dye molecules typically are hydrolyzed. To achieve highly colorfast fabrics, unfixed dye needs to be fully removed — a long, hot, expensive, water- and energy-intensive process.
Best Available Technology (BAT) improves conventional warm dyeing systems, and already consumes less water during the washing-off process. When using Avitera SE and Eriopon LT, the dyeing and washing-off processes require temperatures no higher than 60°C, and the number of rinsing baths needed to obtain the required colorfastness is greatly reduced, Huntsman reports.
Tentering is virtually the most important process after dyeing to give a fabric the required properties. A. Monforts Textilmaschinen GmbH & Co. KG, Germany, a leader in the global tenter market, says that rising cost pressure remains a major issue in the textile industry, especially for textile finishing. Reasons include steadily rising energy, water and effluent treatment costs; consumer demand for green and responsibly made garments; and the need for textile finishing to be very innovative. Therefore, modern textile finishing equipment must fulfill requirements such as responsible use of natural resources, cost-effectiveness and high flexibility.
Monfort's Montex 6500 tenters feature heat recovery systems, which are available for all Montex tenters. The systems can reduce energy usage by up to 30 percent, saving both natural resources and production costs. Even on existing machines, heat recovery systems can be added. The Energy Tower 7000 is a universal stand-alone system providing the same performance as a built-in system. Depending on the exhaust airflow and temperature, up to 30 percent of the heat generated can be recovered. According to Monforts, very good access to the heat exchange modules and a large condensed water tank make the Energy Tower very maintenance-friendly, with consistent performance between maintenance cycles.
In the area of continuous dyeing processes on cotton, Monforts offers the Econtrol® process. In contrast with pad-dry-thermofix or pad-dry-pad-steam processes, Econtrol dyeing using a Thermex 6500 Hotflue does not need a separate fixing process. According to Monforts, the Econtrol climate inside the Thermex chamber ensures a perfect dyeing result during the drying process.
For dyeing of polyester/cotton blends, Monforts has now developed a single-bath process that uses the Econtrol technique without intermediate reduction clearing. The process does not use separate baths, and reduction clearing is not necessary, saving significant amounts of chemicals, water and energy, as well as production costs.
For the near future, Fong's Europe mentions more easy-to-handle machines that have the lowest water and energy consumption, give best-quality results, and are reasonably priced. Thies foresees a similar direction: Future developments will be directed by economics, but the environment also will be taken into account. Suitable aftertreatments will be developed with the target of recycling dyeworks effluent, and other developments will be aimed at emissions reductions. There will be much movement in this area in the future.
Click here to view Table 1: Dyeing Technology Developments