Polyolefin Purification With Membrane Solvent Recovery
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Solution Overview
Problem
Existing recycling methods for polyolefins fail to adequately remove contaminants with molecular weights between 400 and 800 Dalton, which can impair the quality of recycled materials, particularly for food and medical packaging, and are energy-intensive and solvent-intensive.
Innovation Solution
A method utilizing membrane filters to separate polyolefin solutions into permeate and retentate, allowing contaminants with molecular weights <2000 Dalton to be removed efficiently, followed by solvent regeneration using multiple membrane filters and evaporators, minimizing solvent use and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If membrane separation is used to remove solvent from polymer matrix, then solvent recovery is improved, but contaminants with molecular weight 400-800 Dalton remain in the retentate and cannot be removed
Solution Approach 1:
The invention extracts and removes contaminants with molecular weight 400-800 Dalton from the polymer matrix before membrane separation. By pre-extracting these specific contaminants using selective solvents or extraction techniques, the subsequent membrane separation step can focus on solvent recovery without being burdened by these intermediate-molecular-weight contaminants that would otherwise pass through or be retained incorrectly by the membrane.
Solution Approach 2:
The purification process is segmented into multiple distinct steps: (1) pre-treatment to remove large contaminants, (2) selective extraction for contaminants with MW 400-800 Dalton, and (3) membrane separation for solvent recovery. This segmentation allows each step to be optimized for its specific function, with the extraction step targeting specific contaminant molecular weights while the membrane step handles solvent-polymer separation.
2Manufacturing precision
If solvent-based extraction methods are used to remove contaminants, then contaminant removal is improved, but large amounts of solvent are required and energy-intensive evaporation is needed
Solution Approach 1:
The invention changes the parameters of the extraction process by using supercritical fluids or ionic liquids instead of conventional volatile organic solvents. These alternative extraction media can be tuned by adjusting pressure and temperature parameters, allowing effective contaminant removal while eliminating or minimizing the need for energy-intensive evaporation steps, as supercritical fluids can be depressurized to return to liquid state without phase change energy requirements.
Solution Approach 2:
The invention replaces the thermal evaporation mechanism with a pressure-based separation mechanism. Instead of using heat to evaporate solvent and separate it from extracted contaminants, the process uses pressure changes to transition supercritical extraction fluid back to liquid state, enabling solvent recovery without the energy-intensive evaporation step required by conventional extraction methods.
3Manufacturing precision
If tightly controlled input materials from selected applications are used, then contaminant levels are reduced, but the number of required recycling streams increases and adaptability decreases
Solution Approach 1:
The invention creates a universal purification system that can handle multiple types of polyolefin waste streams through a single integrated process. The combination of selective extraction (targeting contaminants with MW 400-800 Dalton) and membrane separation provides a multi-functional approach that works across different polyolefin sources, eliminating the need for separate specialized recycling streams for different application origins.
Solution Approach 2:
The invention uses adjustable extraction parameters (solvent type, temperature, pressure, extraction time) to adapt the process to different polyolefin waste streams. By changing these parameters rather than creating separate physical recycling streams, the system maintains high polymer purity across diverse input materials while preserving process flexibility and reducing system complexity.
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
Achieves high-purity polyolefin regenerates with minimal solvent loss and reduced energy use, enabling recycling of polyolefins for high-quality applications without the need for energy-intensive distillation.
Implementation Method 1
the solvent and the raw polymer dissolved therein are fed to a membrane filter and are separated in the membrane filter into a solvent-containing retentate and a solvent-containing permeate
Implementation Method 2
The dissolved polymer is separated by the membrane filter into a permeate which consists of solvent and low molecular weight components of the polymer, and a retentate which consists of solvent and higher molecular components of the polymer
Implementation Method 3
solvent regeneration using multiple membrane filters and evaporators
Data Source
AI summary
A purification method for producing a polyolefin (PO) regenerate (r), including (a) mixing superficially cleaned PO waste (p), referred to as raw polymer (p), with solvent and dissolving the raw polymer (p) in the solvent, (b) recovering the purified polymer from the solvent, (c) preparing the solvent, (d) returning the solvent to step (a), (e) separating residues (e1, e2), and (f) extruding the purified PO regenerate (r) to form pellets (r). Step (c) is carried out using at least one membrane filter (c1).