Planetary Roller Extrusion With Melt Pump for Homogeneous Polymer Melt
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Solution Overview
Problem
Existing extrusion technologies for producing porous films, such as membrane films, face challenges in achieving homogeneous mixing of polymers and plasticizers due to limitations in mixing quality, speed, and explosion protection, particularly with high molecular weight polymers like UHMWPE, leading to reduced discharge and poorer homogenization performance.
Innovation Solution
The use of a planetary roller extruder in conjunction with a melt pump, where the polymer melt is transferred under pressure through a shielded pressure line to ensure optimal mixing and prevent degassing, allowing for the direct injection of the plasticizer into the extruder and maintaining high pressure to ensure air is pressed out, thereby achieving a homogeneous polymer melt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the speed of the twin-screw extruder is increased to improve mixing quality, then the homogeneity of the polymer melt improves, but the melt temperature quickly reaches the maximum permissible temperature due to frictional heat, limiting further speed increases
Solution Approach 1:
A melt pump is introduced as an intermediary device between the extruder and the die. The melt pump receives the polymer melt from the extruder and delivers it to the die under controlled conditions. This intermediary allows the system to operate at lower extruder speeds (reducing frictional heating) while still achieving the required melt pressure and flow rate through the pump's positive displacement action.
2Productivity
If twin-screw extruders with large screw diameters and long process lengths are used to improve homogenization performance, then the discharge capacity increases, but the machine costs increase
Solution Approach 1:
The melt pump serves as a compact intermediary that achieves high discharge capacities without requiring oversized extruders. By decoupling the mixing function (performed by a smaller, more efficient extruder) from the pressure-building and delivery function (performed by the melt pump), the system achieves high productivity with reduced machine size and lower capital costs.
Solution Approach 2:
The melt pump operates on positive displacement principles similar to hydraulic systems, using controlled displacement of melt volumes to achieve high pressure and flow rates. This allows compact design while maintaining high discharge capacity, avoiding the need for large-diameter, long-barrel extruders that would be required to achieve the same performance through traditional extrusion alone.
3Ease of operation
If individual components are fed to the extruder to simplify handling, then the ease of operation improves, but the demands on mixing quality increase to achieve homogeneous distribution
Solution Approach 1:
The melt pump acts as a mixing-enhancing intermediary between component feeding and final product formation. As the polymer melt passes through the pump chambers, the mechanical action of the pump elements provides additional mixing and homogenization, ensuring that even when components are fed individually (simplifying operation), the final melt achieves the required homogeneity for quality porous film production.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This setup achieves a highly homogeneous polymer melt with improved mixing performance, increased discharge capacity, and controlled temperature management, enabling the production of high-quality porous films while maintaining safety by preventing oxidation and explosion risks.
Implementation Method 1
the melt temperature quickly reaches the maximum permissible melt temperature applicable for explosion protection (depending on the self-ignition temperature of the liquid component) due to the frictional heat introduced during speed increases
Implementation Method 2
a melt pump is connected directly after the planetary roller extruder to build up pressure
Implementation Method 3
The connection is in the form of a shielded pressure channel or as a shielded pressure line with respect to the ambient atmosphere
Data Source
AI summary
An installation for producing a polymer melt for a porous film, in particular for a membrane film, comprises a planetary roller extruder. Said extruder is used to produce a flowable polymer melt from thermoplastics. The planetary roller extruder has a filling opening and a discharge side for delivering the polymer melt. A melt pump is further provided. The discharge side of the planetary roller extruder is connected to a downstream inlet side of the melt pump for further conveying the polymer melt. The connection is in the form of a pressure channel shielded from the ambient atmosphere or a pressure line shielded from the ambient atmosphere. The planetary roller extruder and the melt pump are designed and/or can be driven in such a manner that the polymer melt is applied or can be transferred under pressure at the melt pump on the inlet side.