Plastic Recycling With Light Hydrocarbon Solvent Purification
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Solution Overview
Problem
Existing methods for recycling plastics, such as mechanical and chemical recycling, are inefficient in removing impurities like additives, colorants, and metals from plastic waste, limiting the economic upgrading of plastic feedstock.
Innovation Solution
A process involving dissolution of thermoplastic polymers in a light hydrocarbon solvent, followed by purification steps including insoluble matter separation, washing, extraction, and adsorption, and a supercritical separation to recover purified thermoplastic polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical recycling is used to reuse plastic waste, then certain plastic waste can be directly reused in new objects, but impurities such as additives, fillers, colorants, 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 allows impurities to be separated. This chemical parameter change enables purification that mechanical methods cannot achieve
Solution Approach 2:
The patent introduces a solvent as an intermediary substance to facilitate the separation of impurities from the polymer. The solvent dissolves the polymer matrix, allowing additives and other impurities to be removed through filtration or decantation, and then the solvent is evaporated to recover pure polymer
2Manufacturing precision
If chemical recycling via pyrolysis is used to reform monomers, then plastic waste can be converted into olefins and new polymers, but large consumption of energy is required due to high temperature treatments
Solution Approach 1:
The patent uses moderate temperature and pressure parameters for solvent dissolution, avoiding the high-temperature pyrolysis process. The solvent enables polymer dissolution at lower temperatures, and subsequent solvent evaporation recovers the polymer without requiring extreme thermal conditions
Solution Approach 2:
The patent replaces the thermal-mechanical pyrolysis process with a chemical dissolution-precipitation process. Instead of breaking down polymers through high-temperature thermal decomposition, the method uses solvent interaction to dissolve and then recover pure polymer through controlled evaporation
3Manufacturing precision
If dissolution and purification methods are used to remove impurities from plastic waste, then polymer purity can be improved, but the processes described in prior art do not efficiently process soluble impurities
Solution Approach 1:
The patent uses a specifically selected solvent as an intermediary that selectively dissolves the polymer matrix while leaving soluble impurities in the solution or allowing them to be removed through controlled precipitation. The solvent acts as a mediator that facilitates selective separation based on solubility differences
Solution Approach 2:
The patent applies local quality by creating different zones in the dissolution system - one where the polymer dissolves selectively, another where impurities remain separated or precipitate. This spatial differentiation of dissolution properties enables efficient separation of polymer from both insoluble and soluble impurities
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
Efficiently removes impurities from plastic waste, allowing the recovery of purified thermoplastics with low residual solvent content, suitable for reuse in new plastic products, while minimizing energy consumption and cost.
Implementation Method 1
the dissolution of the thermoplastic polymers in a light hydrocarbon solvent, in particular based on alkane(s)
Implementation Method 2
an optimized step of separating the polymer and the solvent in order to recover purified thermoplastic polymers
Data Source
AI summary
The present invention relates to a process for purifying a plastic feedstock, involving:a) a dissolution step involving placing the plastic feedstock in contact with a dissolution solvent comprising a hydrocarbon-based compound with a boiling point of between −15 and 100° C., at a dissolution temperature of between 120° C. and 250° C. and a dissolution pressure of between 1.0 and 25.0 MPa, to obtain a crude polymer solution;b) a step of purifying the crude polymer solution to obtain a purified polymer solution, involving:b1) separating out the insoluble matter;b2) washing, by contact with a dense solution;b3) extraction, by contact with an extraction solvent; and/orb4) adsorption of the impurities; and thenc) a solvent-polymer separation step, using a supercritical separation section, operated between 160 and 300° C. and at a pressure between 2.7 and 10.0 MPa, followed by at least one solvent recovery section, to obtain purified thermoplastics.