Supercritical Fluid PGSS Purification of LDPE
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Solution Overview
Problem
Low density polyethylene (LDPE) produced through high-pressure radical polymerization contains contaminants such as low molecular weight ethylene derived polymers, peroxide solvents, and initiator residues, which pose challenges for applications like healthcare and food packaging, requiring additional purification steps and equipment cleaning.
Innovation Solution
A process involving the use of supercritical fluids to mix with melted LDPE, creating a saturated solution that is then expanded to form high-purity LDPE particles, effectively separating impurities from the polymer, utilizing the Particle from Gas Saturated Solutions (PGSS) method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional high-pressure radical polymerization is used to produce LDPE, then production efficiency is maintained, but the polymer contains contaminants requiring additional purification steps
Solution Approach 1:
The invention extracts and removes contaminants (low molecular weight ethylene derived polymers, peroxide solvents, initiator residues) from the LDPE composition through a filtration step, separating the harmful components from the desired polymer product to achieve high purity without compromising production efficiency
Solution Approach 2:
The invention changes the physical parameters of the LDPE composition by controlling temperature and pressure conditions during the filtration process, transforming the contaminated melt into a purified product while maintaining production continuity
2Manufacturing precision
If additional purification steps are added to remove contaminants, then purity of LDPE is improved, but process complexity and time consumption increase
Solution Approach 1:
The invention introduces a filtration step as an intermediary process between polymerization and final product formation, using a filter as a mediating device to remove contaminants in a single operation rather than requiring multiple complex purification stages
Solution Approach 2:
The filtration system is designed to operate continuously within the existing production flow, allowing the purification process to serve itself through the natural flow of the polymer melt without requiring separate batch processing or additional manual intervention
3Manufacturing precision
If traditional separation processes are used to remove contaminants, then some purification is achieved, but time and energy consumption increase significantly
Solution Approach 1:
The invention implements a rapid filtration step that quickly removes contaminants from the LDPE composition in a single pass through the filter, rushing through the purification process in one continuous operation rather than requiring multiple slow separation stages
Solution Approach 2:
The invention replaces traditional mechanical separation methods (such as centrifugation or filtration requiring multiple stages) with a streamlined filtration approach that uses controlled pressure and temperature to achieve purification in a single step, reducing both time and energy consumption
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 process significantly increases the purity of LDPE by removing contaminants, reducing the need for further purification steps and allowing direct use of the particles in applications like masterbatch and carpet backing without mechanical grinding.
Implementation Method 1
providing particles comprising the LDPE from the melted composition by: b1) mixing a supercritical fluid in the melted composition to obtain a solution saturated with the supercritical fluid
Implementation Method 2
b2) expanding the solution through an opening to obtain the particles
Data Source
AI summary
A process for increasing purity of a low density polyethylene (LDPE) composition, comprising the steps of: a) providing a melted composition comprising LDPE having Mn of at least 5.0 kg/mol according to size exclusion chromatography, Mw of at least 50 kg/mol according to size exclusion chromatography, a density of 915 to 935 kg/m3 according to ISO1183 and a melt flow rate of 0.10 g/10 min to 80 g/10 min according to ISO1133:2011 measured at 190° C. and 2.16 kg, and b) providing particles from the melted composition by: b1) mixing a supercritical fluid in the melted composition to obtain a solution saturated with the supercritical fluid and b2) expanding the solution through an opening to obtain the particles.