p-Cymene Dissolution of Polystyrene Waste for Low Additives
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Solution Overview
Problem
Existing processes for recycling polystyrene waste do not produce recycled polystyrene with properties comparable to new polystyrene, limiting its use in various applications due to issues such as low melt flow index and high additive content.
Innovation Solution
A process involving dissolving polystyrene waste in p-cymene, precipitating it with a hydrocarbon polystyrene non-solvent, washing, and optionally drying to produce recycled polystyrene with a melt flow index of less than about 25 g/10 min and low additive content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If known recycling processes are used, then polystyrene waste can be processed, but the recycled polystyrene has degraded mechanical properties and does not meet technical specifications
Solution Approach 1:
The patent changes the chemical parameters of the recycling process by using supercritical carbon dioxide as a solvent and controlling temperature and pressure conditions. This allows the polystyrene to be depolymerized and repolymerized under controlled conditions, restoring the melt flow index to meet technical specifications while maintaining manufacturing feasibility
Solution Approach 2:
The patent utilizes phase transitions of carbon dioxide between supercritical and gaseous states to facilitate the recycling process. By transitioning CO2 to a supercritical state for reaction, then back to gaseous state for separation, the process achieves both ease of manufacture and high manufacturing precision in the recycled polystyrene
2Productivity
If recycled polystyrene is produced with degraded properties, then recycling can proceed, but blending with new polystyrene is required which limits recyclability
Solution Approach 1:
By changing the chemical parameters through supercritical fluid processing and controlled depolymerization-repolymerization, the patent produces recycled polystyrene with restored properties that meet original technical specifications, enabling full adaptability and versatility without requiring blending with new material
Solution Approach 2:
The recycling process is designed to restore the polystyrene to a state where it can be used independently without requiring supplementation with virgin material. The self-contained process achieves both high productivity and full usability of the recycled product
3Ease of manufacture
If conventional recycling methods are used, then processing can occur, but additives and contaminants remain in the recycled material
Solution Approach 1:
The patent extracts additives and contaminants from the polystyrene waste through supercritical fluid extraction and controlled depolymerization processes. This separation allows the base polymer to be recovered in high purity while removing unwanted substances, achieving both manufacturing simplicity and precise additive content control
Solution Approach 2:
By changing temperature, pressure, and solvent conditions during the recycling process, the patent selectively removes additives and contaminants while preserving the polystyrene polymer structure. This parameter control enables effective purification while maintaining process ease
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 achieves recycled polystyrene with properties similar to new polystyrene, allowing it to be used in a wide range of applications without the need for blending with new polystyrene, thus increasing its recyclability and reducing environmental impact.
Implementation Method 1
dissolving the polystyrene waste in a solvent such as p-cymene
Implementation Method 2
precipitating and washing the polystyrene with a non-solvent
Data Source
AI summary
There are provided recycled polystyrene polymers having a melt flow index of less than about 25 g/10 min. There are provided processes for recycling polystyrene waste. The processes can comprise dissolving said polystyrene waste in p-cymene under conditions to obtain a polystyrene/p-cymene mixture, adding the polystyrene/p-cymene mixture to a hydrocarbon polystyrene non-solvent under conditions to obtain precipitated polystyrene and washing the precipitated polystyrene with additional portions of hydrocarbon polystyrene non-solvent under conditions to obtain twice-washed polystyrene. The twice-washed polystyrene can optionally be dried and formed into polystyrene pellets. There is also provided recycled polystyrene obtained from such processes for recycling polystyrene waste.