Product Introduction

FDDI-22/44 wet process cast extrusion machine is a lab and pilot-scale core equipment specially developed for UHMWPE lithium-ion battery composite separators. It fully adapts to the whole process of wet phase separation technology, and can complete melt blending, cast extrusion, cooling shaping, traction and winding of UHMWPE and white oil compound system.

Ideal for separator formula development, process parameter optimization and small-batch trial production, it helps lithium battery separator manufacturers accelerate the pilot test and mass production of high-performance composite separators such as PP/PE/PVDF composite types. Targeted at the high viscosity and poor processability of UHMWPE material, the machine adopts twin-screw precise compounding with large length-diameter ratio, wide T-die and high-precision cast cooling structure, ensuring uniform film thickness, controllable micropore structure and stable mechanical properties of separators.

Product Features

●Perfect Adaptation to Wet Process: Designed exclusively for UHMWPE wet-process separators. Compatible with the blending system of UHMWPE powder and liquid white oil. It precisely controls the phase separation process, and produces separators with micropore size of 0.04–0.12 μm and porosity of 40%–60%, meeting the requirements of ion conduction and electrical insulation for lithium battery separators.

●High-efficiency Twin-screw Compounding System: Equipped with Φ22 mm co-rotating parallel twin screws with a length-diameter ratio of 44. Featuring independent temperature control, vacuum degassing and accurate liquid dosing, it realizes thorough plasticization and uniform dispersion of UHMWPE and white oil, avoiding material degradation and incomplete plasticization.

●High-precision Casting & Shaping: Adopts 200 mm wide downward extrusion T-die with adjustable die lip gap and high-accuracy temperature control system.

●Full-process Intelligent Control: Integrated control via PLC and touch screen. Temperature control accuracy reaches ±1℃, with pressure monitoring range from 0 to 50 MPa. It is equipped with servo synchronous traction and winding unit. All parameters can be saved and traced. One-click start and emergency stop ensure safe and easy operation.

●Powerful Expandability: Optional upgrade modules including multi-layer co-extrusion, online extraction, biaxial stretching and composite coating. Compatible with PP, PE, PVDF and other materials, supporting R&D of single-layer/composite separators as well as hydrophilic and modified separators.

Application Range

●Lithium Battery Separator R&D: Development of formulas and processes for UHMWPE wet separators, PP/PE composite separators and PVDF modified separators used in power batteries, consumer batteries and energy storage batteries.

●New Material Pilot Production: Small-batch trial production for universities, research institutes and enterprise R&D centers. Quickly verify the influence of material ratio and process parameters on separator performance including pore size, porosity, tensile strength and thermal stability. 

●Process Optimization: Parameter optimization for key procedures of wet-process separators, such as compounding, cast extrusion and phase separation.

Working Principle (Wet Process Technology)

This process uses ultra-high molecular weight polyethylene (PE-UHMW) with a viscosity-average molecular weight of 1.2 million as the core raw material and food-grade liquid paraffin as a diluent (good solvent). It utilizes the thermally induced phase separation (TIPS) method to prepare high-performance microporous membranes for lithium batteries. The overall process includes raw material mixing—melt plasticizing—extrusion casting—cooling phase separation—composite molding—extraction pore formation—post-treatment and shaping. Throughout the process, parameters are optimized through uniform design experiments to ensure uniform membrane pore size, consistent thickness, and stable porosity.

Specific process flow:

PE-UHMW resin is premixed with precisely proportioned liquid paraffin and fed into a hopper. The material is then fed into a twin-screw extruder. Under the synergistic effect of strong shear from the screws and constant-temperature heating, the polymer resin is completely melted and uniformly dissolved, forming a homogeneous polymer-solvent melt. The melt is metered and pumped to a T-shaped casting die, where it is uniformly cast onto the surface of a high-precision temperature-controlled casting roller. Simultaneously, the substrate in the unwinding system is conveyed at a constant speed by a constant tension motor, precisely adhering to the molten strip on the casting roller. Under the uniform traction pressure of the roller, a double-layer composite molding is completed. The composite membrane is then cooled by gradient cooling, resulting in solid-liquid thermal phase separation. The PE-UHMW polymer chains crystallize to form a skeletal network, with liquid paraffin uniformly filling the intercrystalline gaps and network pores. Finally, all liquid paraffin solvent is removed from the membrane using a specialized extraction device. The original solvent-filled spaces form a continuous and uniform microporous structure, ultimately yielding a high-performance PE-UHMW lithium battery separator.