Solvent Separation of Reclaimed PE/PP for Virgin-Like Purity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods struggle to effectively separate and purify mixed streams of contaminated reclaimed polyethylene (crPE) and polypropylene (crPP) into separate streams with 'virgin-like' optical properties, while being economical and operating in a single plant.
Innovation Solution
A method involving solvent extraction, dissolution, settling, and purification steps using a swing mode operation in a single plant, utilizing specific temperature and pressure conditions to produce purified recycled polyethylene (vlPE) and polypropylene (vlPP) with virgin-like optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If mechanical recycling is used to process mixed streams of plastics, then energy consumption and greenhouse gas emissions are reduced compared to other recycling methods, but the ability to separate and purify mixed streams of polyethylene and polypropylene is lost
Solution Approach 1:
The patent uses solvent extraction with controlled temperature and pressure parameters to separate PE and PP. By adjusting extraction temperature (affecting solubility) and pressure (affecting phase behavior), the process achieves selective separation of polyethylene and polypropylene from mixed contaminated streams, producing purified recyclates with distinct polymer compositions
Solution Approach 2:
The patent extracts polyethylene and polypropylene from contaminated mixed streams using selective solvents. The extraction process removes target polymers from the mixed waste stream, separating them from contaminants and from each other based on their differential solubility and phase behavior in the extraction solvent under controlled conditions
2Manufacturing precision
If dissolution and purification steps are implemented to achieve virgin-like optical properties, then product quality is improved, but process complexity and equipment requirements increase
Solution Approach 1:
The patent combines multiple purification functions (extraction, dissolution, settling, and purification) into an integrated process flow using a limited number of unit operations. The same equipment performs multiple functions in sequence, achieving virgin-like optical properties through combined actions rather than separate dedicated units for each purification step
Solution Approach 2:
The patent exploits phase transitions of polymers in solvent systems to achieve purification. By controlling temperature and pressure, the process induces phase changes that separate dissolved polymers from suspended contaminants, with the dissolved phase containing purified polymer and the suspended phase containing impurities that settle out
3Adaptability or versatility
If a single production plant operates in swing mode to produce both vlPE and vlPP, then operational flexibility and resource utilization are improved, but process control and timing coordination become more difficult
Solution Approach 1:
The patent implements swing mode operation where a single production plant alternates between producing vlPE and vlPP in periodic cycles. The plant operates in sequences, dedicating specific time periods to each polymer type, allowing flexible production scheduling while using the same equipment for both products without requiring permanent dual-line configuration
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 the separation and purification of crPE and crPP into vlPE and vlPP with desired optical properties, reducing contamination and color, suitable for high-quality applications like food and drug contact packaging.
Implementation Method 1
The method comprises: (a) Extracting said mixed stream of crPE and crPP with a polyethylene (PE) extraction solvent in a PE extractor at a PE extraction temperature, a PE extraction pressure
Implementation Method 2
Dissolving said PE heavy stream in a PE dissolution solvent and in a PE dissolution equipment at a PE dissolution temperature, a PE dissolution pressure
Implementation Method 3
Settling said first PE suspension in a PE settling equipment at a PE settling temperature and a PE settling pressure
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method of separating and purifying a mixed stream of contaminated reclaimed polyethylene and contaminated reclaimed polypropylene is provided. The method comprises the steps of extraction, dissolution, settling, purification, and solvent separation to produce separate streams of purified recycled polyethylene and purified recycled polypropylene. Both separate streams are produced in the same production plant operating in swing mode, and have virgin-like optical properties.