Asymmetric barrier film containing polyamide offers numerous advantages such as improved deep-drawing quality, transparency, printability and sealability. A disadvantage, however, is that such film has a strong tendency to roll up. This so-called curling often creates serious problems in the downstream processing. Cutting, winding, printing and bagging is frequently difficult if not totally impossible. Curling is caused by the different crystallisation behaviour of the individual film layers as the melt cools.
A water bath is therefore indispensable when producing asymmetric deep-drawn film. The film web is routed through the tempered bath. The combination of temperature and residence time as well as the absorption of water in the outer PA layer succeeds in significantly reducing the curling effect. Alpine's water bath was developed especially for this application and is simple to operate. There are different sizes available with working widths of between 1600 and 2600 mm, and the water baths can also be retrofitted to existing film blowing lines.