Polyolefin Waste Recycling Using Hansen-Parameter Phase Separation
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Solution Overview
Problem
Current recycling methods for polyolefin-containing waste, particularly from mixed and multilayer packaging, suffer from low selectivity and quality, leading to impurities and reduced mechanical properties in the recovered polymers, and existing solvent-based methods are hazardous and inefficient.
Innovation Solution
A method involving a solvent with Hansen parameter δH 0.0 to 3.0 MPa 1/2 and a liquid filtration aid with δH 4.0 to 38.0 MPa 1/2 forming a miscibility gap is used to separate polyolefins, with preferred solvents being hydrocarbon compounds and filtration aids like alcohols, to achieve high-quality polymer recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical recycling with NIR spectroscopy is used, then polyolefin waste can be separated and re-compounded, but the method is limited to mono-material and produces lower-quality products with worse mechanical properties
Solution Approach 1:
The patent changes the fundamental parameter of the recycling approach from mechanical separation to solvent-based dissolution. By selecting a solvent with specific Hansen solubility parameters (δH = 0.0 to 3.0 MPa^1/2) that matches polyolefin solubility characteristics, the process achieves selective dissolution of polyolefin from multilayer mixtures, enabling high-purity recovery (99.9% purity) that mechanical methods cannot achieve
Solution Approach 2:
The patent introduces a solvent as an intermediary substance to facilitate selective separation. The solvent acts as a mediator that dissolves polyolefin selectively while leaving other materials undissolved, enabling purification that direct mechanical separation cannot achieve. The solvent's specific solubility parameters make it an ideal intermediary for this selective extraction
2Manufacturing precision
If aromatic solvents like xylene or toluene are used for selective dissolution, then polyolefin can be separated from mixed plastics, but the solvents are flammable and leave harmful residual traces that degrade polymer quality
Solution Approach 1:
The patent changes the solvent selection criterion from aromatic solvents to solvents with specific Hansen solubility parameters (δH = 0.0 to 3.0 MPa^1/2). This parameter-based selection identifies safe, non-flammable solvents like aliphatic hydrocarbons and esters that provide equivalent or superior selectivity without the harmful properties of aromatic solvents, eliminating flammability and residual contamination issues
Solution Approach 2:
The patent employs solvents that are safer, more environmentally friendly, and easier to handle than aromatic solvents. These solvents can be fully evaporated without leaving harmful residues, effectively making the solvent system disposable and eliminating the need for extensive solvent removal or purification steps that would otherwise be required
3Productivity
If low boiling point solvents are used for dissolution, then polyolefin can be extracted from waste, but the solvents are flammable and require special safety measures
Solution Approach 1:
The patent changes the solvent selection from low boiling point solvents to solvents with specific Hansen solubility parameters that happen to be non-flammable. This parameter-driven selection naturally identifies safe solvent options like esters and aliphatic hydrocarbons with higher boiling points, eliminating flammability risks while maintaining extraction efficiency through optimized solubility matching
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 method achieves high selectivity and purity in polyolefin recovery, reducing impurities by up to 99.9% and improving mechanical properties, while minimizing safety risks and operational costs.
Implementation Method 1
mixing the polyolefin containing waste with a solvent having a Hansen parameter δH from 0.0 to 3.0 MPa 1/2
Implementation Method 2
contacting this mixture with a liquid filtration aid before separating the polyolefin from the mixture, wherein the liquid filtration aid has a Hansen parameter δH of from 4.0 to 38.0 MPa 1/2
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention refers to a method for recycling polyolefin containing waste by using a solvent with a specific Hansen parameter and contacting this mixture with a liquid filtration aid before separating the polyolefin from the mixture. The method comprises the following steps: •Mixing the polyolefin containing waste with a solvent having a Hansen parameter δΗ from 0.0 to 3.0 M Pa1/2; •Contacting this mixture with a liquid filtration aid having a Hansen parameter δΗ > 4.0 M Pa1/2; and •Separating the polyolefin from the mixture.