Recycled Polyolefin Composition With Low-Residue Solvent Purification
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Solution Overview
Problem
Existing recycling methods for polyolefin-containing waste from landfills are hindered by high levels of contaminants, leading to low-quality recyclates unsuitable for many applications, particularly due to the presence of foreign polymers, solvent traces, and mechanical properties degradation.
Innovation Solution
A method involving mixing polyolefin waste with a solvent having a Hansen parameter δH from 0 to 3, followed by contacting with a filtration aid having δH > 10, and separating the polyolefin to produce a recyclate with low impurity levels, achieving purity similar to virgin material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical recycling (recompounding) is used for polyolefin waste, then processing is simplified, but the quality and purity of the recycled material deteriorates due to contaminants and foreign polymers
Solution Approach 1:
The patent applies extraction by dissolving the polyolefin material in a selective solvent to separate it from contaminants and foreign polymers. The solvent selectively dissolves the target polyolefin while leaving other materials undissolved, allowing for purification through filtration and subsequent recovery of high-purity polyolefin recyclate.
Solution Approach 2:
The patent uses a selective solvent as an intermediary substance to facilitate the separation of polyolefin from contaminants. The solvent acts as a mediator that temporarily holds the polyolefin in solution, enabling selective removal and purification before the polyolefin is recovered and precipitated.
2Manufacturing precision
If solvent-based recycling with aromatic solvents (xylene, toluene) is used, then polyolefin purity is improved, but residual solvent traces negatively impact the applicability of the recovered polymer
Solution Approach 1:
The patent changes the parameter of solvent selection from traditional aromatic solvents (xylene, toluene) to more selective solvents that achieve effective polyolefin dissolution and separation while leaving minimal harmful residues. This parameter change maintains high purity recovery while reducing the harmful effects of solvent traces in the final product.
3Productivity
If multi-layer plastic packaging is recycled by mechanical methods, then recycling is attempted, but separation techniques fail due to material complexity, resulting in downcycling to low-value applications
Solution Approach 1:
The patent applies extraction by dissolving the polyolefin components of multi-layer packaging in a selective solvent, separating them from incompatible polymers and other contaminants. This allows the recovered polyolefin to achieve sufficient purity for higher-value applications rather than downcycling, thereby improving both recycling rate and material quality.
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 results in a recycled polyolefin with reduced impurities, enabling its use as a 'drop-in' substitute for virgin plastics, with improved mechanical properties and reduced solvent residues.
Implementation Method 1
mixing the polyolefin containing waste with a solvent having a Hansen parameter δH from 0 to 3
Implementation Method 2
contacting this mixture with a filtration aid having a Hansen parameter δH > 10
Implementation Method 3
separating the polyolefin from the mixture
Data Source
AI summary
A homogeneous recycled polyolefin comprising polyethylene and polypropylene, characterised in that it comprises: a) from 1 to 10,000 ppm of soluble impurities; b) from 0.001 to 5 wt % of insoluble impurities, which are particulates having a maximum dimension of from 20 microns to 1 mm, by total weight of the recycled polyolefin; c) from 0.0005 to 1 % (5 to 10,000 ppm) of solvent having a Hansen parameter δH from 0 to 3; and d) from 0.1 ppm to 10,000 ppm of a filtration aid having a Hansen parameter δH > 10; which may be obtained from a method comprising the steps of:- a) mixing polyolefin-containing waste with a solvent having a Hansen parameter δH from 0 to 3; b) contacting this mixture with a filtration aid having a Hansen parameter δH of greater than 10; and c) separating the polyolefin from the mixture.