CONTINUOUS HIGH QUALITY FILM
CASTING WITH VENTURI DRYING
Sandvik has announced the successful development of a high quality film casting solution incorporating an innovative Venturi drying system. The system delivers a homogenous layer of liquid product onto a polished steel belt with outstanding consistency of thickness. The cast layer is then transported on the polished steel belt through the Venturi drying unit to achieve a stable, high quality product in an extremely efficient manner.
This delivers efficient continuous production of a high quality film to extremely fine tolerances in terms of thickness and flatness.
The production line begins with a slot die that applies an accurately controlled layer of liquid product onto a polished steel belt. From here it passes through the Venturi dryer where the solvent – aqueous or organic – is evaporated quickly, efficiently and in a manner that leaves the end product almost completely free of tension both laterally and longitudinally.
This dramatically improves the casting process, enabling the production of film products to exceptionally narrow tolerances without any risk of skin formation, and eliminating costly faults and imperfections in the final material. The inherent benefits of this indirect drying solution also result in an exceptionally high degree of energy efficiency.
EXCELLENT THERMAL AND AIR FLOW EFFECTS
The key benefits of the Sandvik Venturi dryer are achieved through the use of a permeable metal foam above the drying film. A flow of tempered air is applied to the upper side of this foam-like metallic material, creating a Venturi effect on the lower side in accordance with the standard laws of pneumatics.
As a result, a constant and even suction flow is formed, delivering a homogeneous drying effect. This minimizes thermally induced shrinkage and eliminates the risk of structural defects in the surface and layer structure of the film.
IMPROVED PRODUCT QUALITY, REDUCED DRYING TIMES
The Sandvik Venturi dryer enables manufacturers to achieve significant improvements in product quality and reproducibility while also enhancing production efficiency. The increase in thermal transfer efficiency compared with conventional dryer systems also enables a reduction in the length of the drying section.
Typical film casting applications include:
Filter membrane (Nitrocellulose)
- Applications: filters for pharmaceutical and food applications
- Film thickness: 40 – 100 μm
Ceramic tape (Polymer resins)
- Applications: semiconductors, fuel cells, solar cells
- Film thickness: 200 – 300 μm
Edible films (Soluble polymers)
- Applications: pharmaceutical capsules, pills
- Film thickness: 40 – 50 μm
Optical films (TAC)
- Applications: LCD top film
- Film thickness: 30-200 μm
Battery film (LI-ION)
- Applications: Battery electrodes
- Film thickness: 10-50 μm
Key benefits of the Venturi dryer include:
- Prevention of skin formation
- Thickness profile to precise tolerances
- Formation of a homogeneous laminar flow
- Elimination of faults and imperfections
- Two-dimensional homogeneous drying profile
- Minimized thermally-induced shrinkage
- Significant increase in product quality
- Significant increase in heat transfer performance
- Significant reduction in drying section length
PILOT PLANT / PRODUCT TESTING
A fully operational film casting system is available for process assessment and product testing at Sandvik’s Industrial Processing Productivity Center near Stuttgart, Germany, and the company will make technicians and engineers available to provide full support in terms of mapping the process in batch mode.