A new ultrasound-based finishing technology developed by Sonovia with Brückner and Weber Ultrasonics offers some crucial advantages in the production of antimicrobial textiles.

With the new sono-finishing technique, impregnation meets industrial requirements for wash resistance ensuring the antimicrobial finish remains effective for a long period of time – even against coronaviruses. It also minimises the environmental impacts associated with conventional textile finishing.

Most impregnations that protect against bacteria, viruses and fungi use chemical binding agents that only deliver limited wash resistance, so the protective effect is limited. In addition, the chemicals and substances used can be harmful to the environment and can also result in pollutant residues on finished products.

“To ensure antimicrobial textiles like those used in clothing for medical workers, hospital linen/laundry and respiratory face masks significantly reduce the risk of infection, the impregnation must be able to withstand frequent laundering at the high temperatures required in the medical sector,” says Liat Goldhammer, chief technical officer at Sonovia. “They cannot lose efficacy over the course of their useful life.”

Background

In 2017, the Israeli start-up Sonovia began industrializing its patented sono-finishing process developed at Bar-Ilan University. The one-step, sonochemical finishing process is suitable for all types of textiles – whether from natural or synthetic fibres or their blends.

The process uses zinc-oxide nanoparticles as an active medium and is based on the physical phenomenon of acoustic cavitation – when exposed to ultrasound, small bubbles continuously form in the solution mixed with the nanoparticles, which then expand and collapse within split seconds.

This creates high-energy microstreaming patterns, which move at around 500 metres per second. These patterns carry the particles with them and embed them firmly in the textiles. “

This is a distinctive feature of our technology compared to conventional textile finishing processes that use chemical binding agents,” explains Goldhammer. “With sono-finishing technology, the particles are mechanically embedded, so the antimicrobial properties remain in place for a long time. What’s more, no polluting binding agents are required in the process, and the use of chemicals can be reduced by up to 50 per cent.”

The formation of cavitation bubbles via ultrasound is crucial to ensure the reliable application of the antimicrobial zinc-oxide particles. Standard ultrasonic systems cannot be used for this.

Industrial partners

To transfer the technology from the large to large-scale industrial production, Sonovia partnered with Brückner, the well-known manufacturer of textile finishing systems headquartered in Leonberg, Germany, and ultrasound technology components maker Weber Ultrasonics, of Karlsbad, Germany.

The R&D department at Weber Ultrasonics came up with a made-to-measure ultrasonic concept and Brückner developed and built a corresponding application unit that can also be integrated into a wider, continuous finishing process.

Advantages

The first system prototype for the sonochemical process has been in use at Brückner’s technology centre since early 2019.

In addition to ensuring maximum process reliability, key aspects in its development included meeting the modern textile industry’s high standards in terms of productivity, reliability, sustainability, ease of maintenance and cost effectiveness.

 “Although development is not yet complete, initial, conservative calculations suggest potential savings of around 10 per cent from the reduction of chemicals used,” says Goldhammer.

The new application unit, which is similar to a padding mangle, can easily be integrated into existing plants and lines. It can be used for finishing both woven and knitted fabrics, as well as nonwovens and carpeting.

Proven

To prove the lasting and reliable antimicrobial efficacy of sonochemical textile finishing, Sonovia conducted testing with textile research and certification institutes which confirmed that the finished fabrics retain their full antimicrobial properties after multiple wash cycles at high temperatures.

Sonovia now manufactures and sells antimicrobial respiratory masks that use the technology. Tests carried out in summer 2020 revealed more than 99 per cent efficacy against SARS-CoV-2. Additionally, the mask filters 95 per cent of 3 microns particles – the particle size which has been identified by the WHO as relevant to the spread of Covid-19.

The new technology’s proven, lasting protective effects, in addition to the user-friendly and sustainable process, make it an optimal solution for finishing clothing for medical and care workers and laundry/linen in hospitals, senior homes, and hotels, as well as many other areas where hygiene and infection control are critical. The fashion and sportswear industries, as well as the automotive sector are also interested in sonochemically finished textiles. Relevant tests are set to be carried out at Brückner’s technology centre starting in the second quarter of 2021.

www.brueckner-textile.com

www.weber-ultrasonics.com

www.sonoviatech.com