Recycled Polystyrene Polymerization via Continuous Filtration
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Solution Overview
Problem
The recycling of post-consumer polystyrene waste is hindered by the low density of expanded polystyrene, which makes collection challenging, and the presence of insoluble materials that cause processing issues during polymerization, leading to poor mechanical properties and reduced recyclate content in the final polymer product.
Innovation Solution
A process and installation that involves continuously filtering a mixture of post-consumer recycled polystyrene dissolved in monovinylaromatic monomer, redirecting the filtered stream back to the dissolver to maintain mixture level and reduce insoluble material content, allowing for higher recyclate content in the final polymer product, and using smaller filtration units to reduce investment costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If PCR-PS is dissolved in monovinylaromatic monomer and filtered continuously, then recyclate content in final polymer is improved, but filtration system size and investment cost worsen
Solution Approach 1:
The patent implements continuous filtration of the polymerization mixture throughout the polymerization process, rather than batch filtration. The mixture is continuously circulated through the filtration system, allowing insoluble material to be progressively removed while maintaining production flow. This continuous action enables effective filtration with smaller equipment compared to batch systems that require large filtration capacity to handle the entire volume at once.
Solution Approach 2:
The filtration process is performed preliminarily during the polymerization process itself, before the final polymer product is obtained. By continuously filtering the polymerization mixture during reaction, insoluble material is removed in advance, preventing it from being incorporated into the final product. This preliminary filtration action allows for higher recyclate content without requiring post-processing filtration of large volumes.
2Ease of operation
If agitation is stopped to empty dissolver, then heavy insoluble material sediments, but light insoluble material floats and cannot be removed
Solution Approach 1:
The patent maintains continuous agitation of the polymerization mixture throughout the process, including during the emptying phase. This continuous agitation prevents both heavy material from sedimenting and light material from floating to the surface. The dissolver is emptied continuously while agitating, ensuring all insoluble material remains suspended and can be effectively removed by the filtration system, achieving complete removal of both heavy and light contaminants.
3Productivity
If filtration is performed in batch mode with dissolver emptying, then productivity is maintained, but insoluble material accumulates and plugging occurs
Solution Approach 1:
The patent implements continuous filtration during the entire polymerization process, eliminating the need to stop agitation and emptying operations. The polymerization mixture is continuously circulated through the filtration system, which progressively removes insoluble material without interrupting production. This continuous operation prevents accumulation of contaminants that would lead to plugging, maintaining both high productivity and reliable filtration system operation.
Solution Approach 2:
The continuous filtration process preliminarily removes insoluble material during polymerization, preventing its accumulation to plugging levels. By continuously eliminating contaminants as they are formed or introduced, the system maintains low contaminant concentrations throughout the process, avoiding the plugging issues that occur in batch operations where material accumulates between emptying cycles.
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
This approach enables efficient recycling of polystyrene with higher recyclate content in the final product, avoiding sedimentation and floating insoluble material issues, and reducing the need for large filtration systems, thus enhancing productivity and maintaining high recyclate content.
Implementation Method 1
The polymerization mixture is filtered in a filtration system in order to obtain a stream of filtered polymerization mixture
Implementation Method 2
mixing the PCR-PS and the monovinylaromatic monomer within the dissolver to dissolve the PCR-PS in the monovinylaromatic monomer
Data Source
AI summary
The invention relates to a process and an installation to produce a monovinylaromatic polymer (3) comprising post-consumer recycled polystyrene (PCR-PS) wherein the process comprises the steps of mixing the PCR-PS (5) and the monovinylaromatic monomer (7) within a dissolver (9) to dissolve the PCR-PS (5) in the monovinylaromatic monomer (7) so as to produce a polymerization mixture (13); and a step of filtering the polymerization mixture (13) that includes continuously redirecting at least a part of the stream of the filtered polymerization mixture (17) back to the dissolver (9) and mixing it with the polymerization mixture (13) so as to continuously reduce the content of insoluble material in the polymerization mixture (13) contained in the dissolver (9).