From the Sector

ACG Kinna Automatic and ACG Nyström – members of TMAS, the Swedish textile machinery association – have delivered the first microfactory for the production of fully finished filter bags to an international filtration industry customer, in cooperation with JUKI Central Europe.

The microfactory’s configuration is based on two separate interconnecting modules – the Smart Filter Line (SFL) and the Filtermaster 2.0. The SFL handles the fabric feeding from rolls and its folding prior to seam construction, which can either be by automatic sewing, welding or with sewing and taping, depending on specifications. Very rapid changeover of the modular seaming methods can be achieved during product changes. The specific size of the now fully-tubular fabric is then precisely cut to size for each individual unit and further folded ready to be fed into the Filtermaster 2.0. The Filtermaster 2.0 then automatically attaches the reinforcement, bottom and snap rings onto the filter tube with a second Juki sewing head on a robotic arm, to form the fully finished filter bag ready for packaging.

Filter bags are employed in a wide range of industrial processes and while they may be largely under the radar as products, they represent a pretty significant percentage of overall technical textiles production.
They are used in foundries, smelters, incinerators, asphalt plants and energy production plants. Other key manufacturing fields – often where dust is generated – include the production of timber, textiles, composites, waste handling and minerals, in addition to chemicals, food production, pharmaceuticals, electronics and agriculture.

As a further example of the scale of the industry and the high volumes of fabrics involved, one supplier has delivered a single order of 30,000 filter bags to be used for flue gas cleaning at a European power plant. The bags can also be anywhere up to twelve metres in length and frequently have to be replaced.

Textiles are a given in civil engineering: they stabilize water protection dams, prevent runoff containing pollutants from landfills, facilitate the revegetation of slopes at risk of erosion, and even make asphalt layers of roads thinner. Until now, textiles made of highly resistant synthetic fibers have been used for this purpose, which have a very long lifetime. For some applications, however, it would not only be sufficient but even desirable for the auxiliary textile to degrade in the soil when it has done its job. Environmentally friendly natural fibers, on the other hand, often decompose too quickly. The German Institutes of Textile and Fiber Research Denkendorf (DITF) are developing a bio-based protective coating that extends their service life.

Depending on humidity and temperature, natural fiber materials can degrade in the soil in a matter of months or even a few days. In order to significantly extend the degradation time and make them suitable for geotextiles, the Denkendorf team researches a protective coating. This coating, based on lignin, is itself biodegradable and does not generate microplastics in the soil. Lignin is indeed biodegradable, but this degradation takes a very long time in nature.

Together with cellulose, Lignin forms the building materials for wood and is the "glue" in wood that holds this composite material together. In paper production, usually only the cellulose is used, so lignin is produced in large quantities as a waste material. So-called kraft lignin remains as a fusible material. Textile production can deal well with thermoplastic materials. All in all, this is a good prerequisite for taking a closer look at lignin as a protective coating for geotextiles.

Lignin is brittle by nature. Therefore, it is necessary to blend the kraft lignin with softer biomaterials. These new biopolymer compounds of brittle kraft lignin and softer biopolymers were applied to yarns and textile surfaces in the research project via adapted coating systems. For this purpose, for example, cotton yarns were coated with lignin at different application rates and evaluated. Biodegradation testing was carried out using soil burial tests both in a climatic chamber with temperature and humidity defined precisely according to the standard and outdoors under real environmental conditions. With positive results: the service life of textiles made of natural fibers can be extended by many factors with a lignin coating: The thicker the protective coating, the longer the protection lasts. In the outdoor tests, the lignin coating was still completely intact even after about 160 days of burial.

Textile materials coated with lignin enable sustainable applications. For example, they have an adjustable and sufficiently long service life for certain geotextile applications. In addition, they are still biodegradable and can replace previously used synthetic materials in some applications, such as revegetation of trench and stream banks.

Thus, lignin-coated textiles have the potential to significantly reduce the carbon footprint: They reduce dependence on petroleum-based products and avoid the formation of microplastics in the soil.

Further research is needed to establish lignin, which was previously a waste material, as a new valuable material in industrial manufacturing processes in the textile industry.

The research work was supported by the Baden-Württemberg Ministry of Food, Rural Areas and Consumer Protection as part of the Baden-Württemberg State Strategy for a Sustainable Bioeconomy.

In the latest technology innovation from members of TMAS (the Swedish textile machinery association), ACG Kinna and ACG Nyström have teamed up with Juki Corporation – the world’s leading sewing machine manufacturer – in the development of a new automated line concept that can considerably speed up the production of finished filter bags.

Woven or nonwoven filter bags employed in a wide range of industrial processes may be under the radar as products, but they represent a pretty significant percentage of technical textiles production.

According to a recent report from BCC research, a leading US analyst covering this sector, industrial filtration represented a $555 million market in 2019 and some of the key areas where such filter bags are employed include:

• Metal fabrication, with effective filtration required for manual and automated welding, thermal cutting, blasting and machining, especially for coolant filtration.
• The process and energy industries, including foundries, smelters, incinerators, asphalt works and energy production plants.
• Other key manufacturing fields – often where dust is generated – including the production of timber, textiles, composites, waste handling and minerals, in addition to chemicals, food production, pharmaceuticals, electronics and agriculture.

Line integration
The new SFL-2000 line is the result of a four-year development project between Juki Central Europe, headquartered in Poland, and the two ACG companies.

It is capable of handling a wide range of different filter media, and as an all-in-one solution, can produce high quality and accurate seams to pre-defined parameters, with optional modules allowing for customised constructions.