Ultrasonic technology has been used in the nonwovens industry for decades, and today the bonding method is being used for a number of end-use products, from diapers and feminine care pads to filter media and hospital gowns. Ultrasonic bonding is defined as “the use of high frequency sound to generate localized heat through vibration and cause thermoplastic fibers to bond to one another” by INDA, the association of the nonwoven fabrics industry. In other words, this technology can replace other bonding methods utilized in the industry such as adhesive and thermal.

Herrmann Ultrasonics, with global headquarters in Karlsbad, Germany, and U.S. headquarters outside of Chicago, is one of the major players supplying ultrasonic bonding technology to machinery builders and end users such as diaper manufacturers. Herrmann is trying to simulate any kind of process, especially in the hygiene industry, which is now currently done either with glue or heat pressure, or solely pressure systems. “Simply put, if you have glue, we replace the glue and with ultrasonics, which means there is no consumable—no added materials,” says Uwe Peregi, executive vice president and general manager, Herrmann Ultrasonics. “With ultrasonics, companies reduce their operational costs and set up time and maintenance time is significantly lower.”

The company opened its nonwovens division in 1994 with its eyes on the hygiene industry. “Hygiene is a stable market, but ultrasonic has been seen as an enabling, growing technology that can transform the current diaper design, which is mostly glued, into a glue free diaper for the 21st century,” Peregi says.

As part of its efforts to help create a glue free diaper, Herrmann recently collaborated with The Dow Chemical Company on new technology for backsheet lamination. Through its understanding of polyethylene (PE) material science expertise, film structure design and film processing, Dow developed a PE film that bonds well to polypropylene (PP) nonwovens and offers better softness and reduced noise compared to PP-based films, according to Fabricio Arteaga Larios, global platform technology leader, Dow. Dow’s new PE film formulation in combination with Herrmann Ultrasonics’ VE Microbond CSI technology offers “Adhesive Free In-line Lamination,” delivering a more comfortable product that is softer and makes less noise in comparison to PP backsheets.

In diapers, Herrmann’s ultrasonic technology is also used for layer bonding/ADL attachment, leg cuffs, ear attachments, fastening systems, elastic entrapment (2017) and the landing zone. “With ultrasonics, it is possible to make a glue-free diaper. All of the processes have been established either with Herrmann’s rigid or rotary sonotrode technology,” Peregi says.

While there aren’t any manufacturers currently bonding diaper components ultrasonically on a single machine, Herrmann’s customers are interested in doing so in the future, and Peregi expects to see such a product on the market in the coming years.

Herrmann’s technology is also being used for the side seams of training pants. Engineers at the company have developed a new ultrasonic module designed for intermittent cross seal applications. According to Herrmann, the system has become more rigid overall; with optimized control of the amplitude peaks, frequency shifts and with finite measuring and control technology. Due to new software and modifications within the generator and the controller, the process can now be optimized even more and the force can be controlled more accurately.

The machine provides consistent seal strength, can weld multi-layer materials with varying layers (four to eight), and offers an attractive visual appearance and softness on the final product. A significantly higher inline speed is also achieved—cross seaming up to 300 meters or faster per minute. “This is really new—no one else can do this in the market,” Peregi says.

Herrmann also recently expanded the capabilities of its high-speed ultrasonic laboratory calender (ULC 500) at its North American headquarters, increasing its process rate capabilities. Now called the ULC 600+, the calender can run up to 600 meters per minute or 2000 feet per minute for laminating various materials. Customers use Herrmann’s nonwoven lab for material evaluation, feasibility tests and consultations on how ultrasonics technology can be incorporated into their production environment.

“It’s probably one of the fastest and most modern lab calenders in the U.S.,” Peregi says.

Aurizon Introduces Elastic Entrapment System
Aurizon Ultrasonics, founded in 2009 as a spin-off from Kimberly-Clark, has specialized in ultrasonic technology for over 30 years. The company designs, develops, manufactures and services a high power rotary ultrasonic solution that can be customized to a variety of industrial processes.

Dan Sorensen, director, Aurizon Ultrasonics, says the company’s ultrasonic system differentiates itself in two ways—with the ultrasonic technology and with the rotary feature. “The ultrasonic portion of the solution offers a low maintenance system design, a high service life, increased operational efficiency, material cost savings, improved product comfort and better elastic performance,” he explains, while the rotary system “delivers a high-speed solution that is robust to process and web upsets such as nonwoven splices, elastic splices and machine stop/start events.”

For hygiene applications, Aurizon’s equipment bonds, attaches, embosses and laminates thermoplastics materials, and has engineered solutions for feature attachment, core bonding, acquisition layers and backsheets. “We can develop comprehensive and customized ultrasonic processing solutions that consider key parameters such as horn metallurgy, acoustic designs and geometries, component fabrication and system engineering,” he says.

A recent development from the Kimberly, WI-based company is its Elastic Entrapment System, which directly entraps tensioned elastic within a thermoplastic substrate, providing advantages to producers and converters of elasticized fabrics.

The ultrasonic process creates bond points within the nonwoven material that surround the elongated, smaller diameter elastic strand. When relaxed, the elastic expands between the narrow bond points and cannot slip or creep—issues common with applications using adhesives. “The process is robust to temperature, time and end-user solvents because the elastic is entrapped in the thermoplastic substrate, not attached to it with a susceptible binder material,” Sorensen explains.

The Elastic Entrapment System, which was introduced by Aurizon in 2015, will be commercial with several customers in 2017.

Outside of hygiene, Aurizon is confident that ultrasonics will find applications for other new developments in nonwovens including “smart” fabrics, home wraps and protective apparel. “[The technology] has proved to be suitable for applications that require bonding lofty layers with a powder fill such as for filtration or when bonding fabrics with different compositions together,” Sorensen says.

Sonobond Technology Combats Bedwetting
Meanwhile, Sonobond Ultrasonics of West Chester, PA, began bonding nonwoven disposables such as medical gowns and booties for Kimberly-Clark in 1996. “Around that time OSHA (Occupational Safety and Health Administration) was considering the problem of pathogen transfer through stitched gowns used by doctors in operating theaters, so they were looking at alternate assembly methods. OSHA later issued a directive concerning pathogen transfer in medical gowns and that caused an increase in interest in the ultrasonic seaming,” says Sonobond’s president Janet Devine.

Other markets have opened up since that time, not just limited to hygiene or nonwovens, she says, but there are many new hygiene products, especially in diapers and incontinence, which has been a growing area for ultrasonic technology.

Sonobond’s innovations include the SeamMaster Ultrasonic Sewing Machine systems, which include a floor model (SM86) and table model (SM10), as well as Off-the-Arm and Around-the-Arm cylinder machines and plunge welders operating at 20kHz and at 35kHz. The SeamMaster and the plunge welders are available as modular units for integration into web handling and production/assembly lines. Its units are also customizable for special or unique applications.

According to Devine, the SeamMaster SM86 was the first ultrasonic textile machine to utilize a patented rotary system where both the horn and the pattern wheel rotate during the bonding process so the seams are soft and smooth against the skin. “Ultrasonic welding can produce watertight seams and seam layers of material of different types. The same equipment can be used to cut and seal edges, preventing edge fraying, or for seaming with a variety of ‘stitch’ or other patterns,” she says, adding that it’s up to four times faster than conventional sewing machines and up to ten times faster than adhesive methods.

SeamMaster machines can be used for assembling medical protective apparel that meets AAMI standards for fluid protection, which include hygiene products, surgical gowns, caps and booties, facemasks and disposable products such as lint-free wound dressings and institutional mattress covers.

More recently, Sonobond has been promoting the use of its SeamMaster High Profile Ultrasonic Sewing Machines for assembling children’s underwear used for bedwetting protection. The machine bonds the insert pocket’s water repellent pad to form a leak resistant barrier that is strong and comfortable and that prevents leaks from occurring between the absorbent insert and the underwear. “Sonobond Ultrasonic systems can work around contours, are easily controlled to accommodate various material thicknesses, can weld over existing seams or multiple layers of nonwoven and absorbent materials and can adjust to the thinner, more comfortable contours without damage to the fabric,” Devine says.