Italian tannery drying equipment maker Cartigliano introduced the latest versions of its radiofrequency, or RF dryers, at the Simac Tanning Tech fair in Milan last February. The latest models follow 30 years of research and development in the technology.
The company has invested €5 million in the development of two new versions for the leather industry, known as RF Crust and RF Finishing. Suitable for all types of hides and skins for all applications, the RF dryers are a more efficient method of drying the leather as they focus their energy output solely on the moisture inside the leather, rather than wasting energy heating up the inside of the drying tunnel or the conveyor. Water contained inside the leather is dielectric, therefore, the RF technology acts on the water molecules by changing their polarity 27 million times a second according to Cartigliano. This transforms the water into steam, which is then driven out of the leather, opening up the interfibrillar spaces, making the leather more open. The final humidity is uniform throughout the leather structure.
Located after vacuum drying for crust leather, the final moisture content in the leather is controlled for the subsequent mechanical steps such as staking and finishing. For finished leather, the RF Finishing drying line operates at low temperatures between 30-35oc to avoid shrinkage (up to 2-5% area yield is lost in drying ovens) or damage to the leather caused by rapid heating of the base or top coats. In other words, no water from the rollercoater or spray finish line is dried inside the tunnel and only a few grams of water inside the leather finish is heated. The leathers themselves remain cool during RF drying.
Cartigliano says there is no loss in area yield and the dried leathers retain good fullness, handle and roundness. For instance, a 15-metre-long drying line will typically have nine metres dedicated for the drying chamber (some lines can be as long as 18m). The RF Drying line can be connected to a manual or automated loading/unloading system.