Underwater Pelletization of High-Temperature Polymers Without Pellet Defects
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Solution Overview
Problem
Existing processes for producing high-temperature particle foams face issues such as surface defects, internal voids, and reduced quality due to sharp edges and dust formation, along with inefficiencies in processing and transport, particularly in underwater pelletization.
Innovation Solution
A novel underwater pelletization process using a pressurized water circuit with elevated temperatures (105° C. to 180° C.) and pressures (0.2 to 30 bar) minimizes the temperature difference between the polymer melt and water, preventing defects and enhancing pellet quality, followed by optional processing in an unpressurized or low-pressure water circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If strand pelletization is used for high-temperature polymers, then processing is possible at high temperatures, but sharp edges form causing dust and fine particles
Solution Approach 1:
The patent replaces the mechanical strand cutting system with an underwater pelletization system that forms spherical pellets through water impact, eliminating sharp edges and reducing dust generation while maintaining high-temperature processing capability
Solution Approach 2:
The invention transforms the cylindrical strand shape into spherical pellets through underwater pelletization, where the water impact naturally forms rounded shapes without sharp edges, thereby reducing dust and fine particle formation
2Object-generated harmful factors
If conventional underwater pelletization is used, then sharp edges are avoided, but surface defects and internal voids increase
Solution Approach 1:
The patent changes the water temperature parameter to a range of 20°C to 80°C, which is higher than conventional underwater pelletization, to reduce thermal shock and prevent surface defects and internal voids while maintaining the elimination of sharp edges
Solution Approach 2:
The invention uses a dynamic water jet system that adapts the water flow parameters during pelletization to optimize the cooling rate and prevent defects, ensuring high pellet quality while avoiding sharp edges
3Temperature
If low water temperature is used in underwater pelletization, then cooling is effective, but temperature difference causes defects
Solution Approach 1:
The patent raises the water temperature from conventional low temperatures to a range of 20°C to 80°C, reducing the temperature difference between the polymer melt and cooling water to prevent thermal shock, surface defects, and internal voids while maintaining effective cooling
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
The process produces high-quality pellets with minimized defects, enabling uniform pore size distribution and improved handling, suitable for high-temperature applications.
Implementation Method 1
A novel underwater pelletization process using a pressurized water circuit with elevated temperatures (105° C. to 180° C.) and pressures (0.2 to 30 bar) minimizes the temperature difference between the polymer melt and water, preventing defects and enhancing pellet quality
Implementation Method 2
The requisite nozzle temperature is very high in relation to the usual water temperature, which is less than 100° C. This results in a cooling effect on the nozzle and thus in a risk of the polymer melt freezing in the nozzle
Data Source
AI summary
A process can be used for producing (rigid) particle foams from polymer compositions containing at least one polymer having a glass transition temperature according to ISO 11357-2 of at least 180° C. with an underwater pelletization system.