Wet Process Film Casting Line
I.Introduction
Wet Process Film Casting Line is composed of pre-treatment emulsifier, reactor, secondary reactor, feeding melt pump, 50 twin-screw extruder, discharge melt pump, dedicated filter, 730mm casting die (the above are referred to as the main machine) and guide assembly, unwinding unit, electromagnetic roller small oven, cooling water tank, haul-off & separation unit, casting cooling unit, slitting unit, compound unwinding & winding unit, edge trim winder (the above are referred to as the auxiliary machine). It is mainly used for polymer material compounding, functional film R&D, process optimization, cost control and small-batch production, etc.
● Materials: PE, PVDF
● Die width: 730mm
● Effective width: 650mm
● Main screw diameter: Φ50.5mm
● L/D ratio: 56
II.Process Analysis
The customer's R&D materials involve PE (Polyethylene) and PVDF (Polyvinylidene Fluoride). PVDF is prone to decomposition during processing and its viscosity is sensitive to temperature, which puts extremely high requirements on the compounding capacity and melt delivery stability of the equipment.
● Raw Material Pre-treatment and Reaction System:
The front end of the production line is equipped with a pre-treatment emulsifier, a reactor and a secondary reactor. According to the requirements of the wet process, customers can complete the pre-dispersion of additives or the preparation of solutions in the reactor to ensure the uniformity of the material system before entering the extrusion section.
● High L/D Ratio Compounding Unit:
The core main machine equipment is a 50 twin-screw extruder (main screw diameter Φ50.5mm, L/D ratio 56:1). Such a high L/D ratio design provides customers with a sufficient adjustable range of residence time. For PVDF materials, low-temperature compounding can be achieved through section temperature control to prevent degradation; for PE materials, high-fill compounding can be achieved through strong shearing.
● Melt Delivery and Filtration:
A feeding melt pump and a discharge melt pump are configured. The introduction of melt pumps effectively eliminates pressure fluctuations caused by feeding fluctuations or screw rotation, ensuring a constant melt flow to the die. A high-precision dedicated filter is located at the front end of the die, which effectively filters out gel points or unmelted particles, which is crucial for the production of high-purity films (such as lithium battery separator direction).
● Wide-width Casting Die:
The melt is finally uniformly extruded through a 730mm casting die, with an effective width of 650mm. The internal flow channel design of the die ensures that the melt flow rate is consistent in the width direction, laying the foundation for obtaining cast sheets with small thickness tolerance in the subsequent process.
