Method for drying solvent based film

In a method for producing a thin polymeric film, the method being of the type including steps of providing a source of a solution of polymer and solvent;

• providing an endless casting belt having a width, an outer surface for receiving a cast layer of polymer and solvent and an opposite, inner surface;
• advancing the endless belt while casting the layer of polymer and solvent onto the outer surface at a location along the casting belt, the layer having a transverse width somewhat narrower than the width of the casting belt;
• directing a flow of dryer gas to the layer to evaporate solvent;
• and removing gas and solvent from the vicinity of the casting belt, the improvement wherein the directing and removing steps comprise:
• at first locations extended substantially across the width of the casting belt downstream of the first locations along the casting belt, directing flows of gas toward the outer surface of the casting belt to remove solvent evaporating from the cast layer of polymer and solvent, the first locations being spaced from each other along at least a first portion of the length of the outer surface;
• and
• at least at one, second location extended substantially across the width of the belt between the first locations, receiving flows of gas and solvent and directing the gas and solvent away from the layer along flow paths substantially normal to the outer surface.