Plastic Waste Purification via Solvent Dissolution and Adsorption
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Solution Overview
Problem
Current plastic recycling methods, such as mechanical recycling and chemical recycling, are inadequate in removing impurities like additives and metals from plastic waste, limiting the purification and reuse of thermoplastics, and often require high energy consumption.
Innovation Solution
A process involving dissolution of plastic feedstock in an organic solvent at specific temperature and pressure conditions, followed by adsorption with an adsorbent, to efficiently separate and recover purified thermoplastics, reducing impurity content to less than 5% by weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical recycling is used to sort plastic waste, then the purity of polymer streams is improved, but impurities such as additives, fillers, dyes, pigments and metals trapped in the polymer matrix cannot be sufficiently removed
Solution Approach 1:
The patent applies parameter changes by dissolving the polymer matrix in a solvent under controlled temperature and pressure conditions, transforming the solid plastic waste into a liquid solution that can be filtered. This allows impurities to be separated from the dissolved polymer, and the polymer can be recovered by evaporating the solvent, achieving purification that mechanical sorting cannot accomplish
Solution Approach 2:
The patent uses a solvent as an intermediary substance to facilitate the separation of impurities from the polymer. The solvent dissolves the polymer matrix, allowing impurities to be removed through filtration, and then the solvent is evaporated to recover the purified polymer, acting as a temporary medium that enables purification
2Productivity
If chemical recycling via pyrolysis is used to reform monomers, then plastic waste can be converted into new polymers, but large consumption of energy is required due to high temperature treatments
Solution Approach 1:
The patent uses milder parameter changes compared to pyrolysis, operating at temperatures between 20-80°C and atmospheric pressure during solvent dissolution and evaporation. This avoids the high-temperature energy-intensive processes of chemical recycling while still achieving polymer recovery and purification
Solution Approach 2:
The patent replaces the high-energy thermal decomposition process of pyrolysis with a lower-energy solvent-based dissolution and evaporation process. Instead of breaking down polymers into monomers through high-heat pyrolysis, the method uses solvent dissolution followed by gentle evaporation to recover and purify the polymer
3Manufacturing precision
If dissolution and purification methods are used to remove impurities, then polymer purity is improved, but efficient processing of soluble impurities remains challenging
Solution Approach 1:
The patent uses activated carbon as an intermediary adsorbent to remove soluble impurities from the polymer solution. The activated carbon selectively adsorbs impurities such as dyes, pigments, and additives from the dissolved polymer solution, simplifying the purification process while achieving high polymer purity
Solution Approach 2:
The patent employs activated carbon, a porous material with high surface area, to adsorb impurities from the polymer solution. The porous structure of the activated carbon provides numerous adsorption sites that efficiently capture soluble impurities, simplifying the purification process compared to complex multi-step procedures
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 effectively purifies thermoplastics by removing impurities, enabling their reuse in new plastic objects with improved aesthetic, mechanical, and rheological properties, while conserving fossil resources and reducing solvent consumption.
Implementation Method 1
a dissolution step, in which the plastic feedstock is placed in contact with a dissolution solvent, at a dissolution temperature of between 100° C. and 300° C. and a dissolution pressure of between 1.0 and 20.0 MPa abs
Implementation Method 2
a step of adsorption, in which the crude polymer solution obtained from step a) is placed in contact with at least one adsorbent, at a temperature of between 100 and 300° C. and a pressure of between 1.0 and 20.0 MPa abs
Data Source
AI summary
The present invention relates to a process for treating a plastic feedstock, comprising:a) a dissolution step involving placing the feedstock in contact with a dissolution solvent, at a dissolution temperature of between 100° C. and 300° C. and a dissolution pressure of between 1 and 20.0 MPa abs, the dissolution solvent having a boiling point of between −50° C. and 250° C., to obtain a crude polymer solution;b) a step of adsorption by placing the crude polymer solution in contact with an adsorbent, at a temperature of between 100 and 300° C. and a pressure of between 1.0 and 20.0 MPa abs, to obtain a refined polymer solution; and thenc) a step of recovering the polymers, to obtain at least one solvent fraction and one purified polymer fraction.