Laminating of nonwoven materials using ultrasonics
The general principle of ultrasonic welding can also be applied to nonwoven materials. The thermoplastic fibers are activated by mechanical vibrations thus melting and bonding in pre-defined patterns. A weld tool, referred to as Sonotrode, transmits the vibration into the nonwoven material. In industrial applications, ultrasonic frequencies between 20 and 35 kHz are common, with amplitudes (tool travel distances) of 10 µm to 50 µm. Processing of nonwoven materials is often performed in continuous processes at high web speed. By application of rotary tools, it is possible to achieve processing speeds of up to 800 meters/minute. A specifically engraved drum is used as welding, embossing, or cutting anvil. The contour of the anvil drum focuses the energy and precisely defines the weld spots required for the respective product.