Post-Consumer Recycled Polypropylene Composition Fractionation
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Solution Overview
Problem
Post-consumer recycled polypropylene materials face challenges such as low purity, high contamination levels, moderate homogeneity, and limited end-use applications due to residual benzene contamination and odor issues.
Innovation Solution
A polypropylene mixed color blend with a crystalline fraction content of 85.0 to 95.0 wt.-%, a soluble fraction content of 5.0 to 15.0 wt.-%, and a total ethylene content of 2.0 to 10.0 wt.-%, along with specific color and ethylene content ranges, is developed. This blend is produced through a method involving sieving, sorting, washing, and drying of post-consumer plastic recycling streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If post-consumer plastic waste is recycled through mechanical recycling processes, then plastic material can be reused and environmental issues can be addressed, but the recycled material contains mixtures of different plastics and contaminant materials resulting in low purity and moderate homogeneity
Solution Approach 1:
The patent applies segmentation by separating the recycled plastic stream into different fractions based on solubility. The process divides the mixed recyclate into a soluble fraction (containing contaminants and lower-quality polymers) and an insoluble fraction (containing high-purity polypropylene), thereby achieving both recycling versatility and manufacturing precision through fractional separation
Solution Approach 2:
The patent implements extraction by removing the soluble fraction (contaminants and impurities) from the recycled plastic stream through selective dissolution. This extraction process isolates and removes unwanted components while retaining the desired high-purity polypropylene in the insoluble fraction
2Ease of manufacture
If conventional washing and separation methods are used to purify PCR plastic material, then some contaminant removal is achieved, but residual amounts of benzene and other contaminants remain blocking end-uses in medical and food packaging
Solution Approach 1:
The patent applies parameter changes by utilizing selective solubility parameters to separate contaminants from polypropylene. By choosing a solvent system where contaminants are soluble but polypropylene is insoluble, the process achieves deep purification and removes residual benzene and other harmful substances that conventional washing cannot eliminate
Solution Approach 2:
The patent employs oxidative treatment to decompose and remove residual organic contaminants including benzene. The oxidation process breaks down harmful substances into harmless byproducts, enabling the recycled material to meet stringent purity requirements for medical and food packaging applications
3Productivity
If mixed color polypropylene recyclates are produced without strict fractionation, then production cost is reduced, but the material exhibits moderate homogeneity and surface contamination in injection molded products
Solution Approach 1:
The patent applies segmentation by dividing the recyclate into soluble and insoluble fractions, where the insoluble fraction provides the homogeneous, high-quality base material needed for premium applications. This segmentation enables production efficiency while ensuring manufacturing precision through controlled fractionation
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 resulting polypropylene mixed color blend achieves high purity, low contamination, improved homogeneity, and enhanced mechanical properties, such as tensile strength and processability, while minimizing odor and volatile organic compound emissions.
Implementation Method 1
a soluble fraction (SF) content determined according to CRYSTEX QC analysis, as determined herein, in the range from 5.0 to 15.0 wt.-%
Data Source
AI summary
The present invention concerns a polypropylene mixed color blend having (i) a crystalline fraction (CF) content determined according to CRYSTEX QC analysis, in the range from 85.0 to 95.0 wt.-%, (ii) a soluble fraction (SF) content in the range from 5.0 to 15.0 wt.-%, (iii) a total ethylene content (C2), in the range from 2.0 to 10.0 wt.-%, (iv) said crystalline fraction (CF) has a propylene content (C3 (CF)) as determined by FT-IR spectroscopy calibrated by quantitative 13C-NMR spectroscopy, in the range from 93.0 to 99.0 wt.-%; (v) said crystalline fraction (CF) has an ethylene content (C2 (CF)), as determined by FT-IR spectroscopy calibrated by quantitative 13C-NMR spectroscopy, in the range from [C2]-3.4 wt.-% to [C2]-0.2 wt.-%, wherein [C2] is the total ethylene content (C2) defined in (iii), (vi) a CIELAB color space (L*a*b*) measured according to DIN EN ISO 11664-4, of L* from 30.0 to 73.0; a* from −10 to 25; and b* from −5 to 20. The invention also concerns a method for obtaining the above polypropylene mixed color blend and its use for household applications, automotive applications, appliances, packaging, or wire and cable applications. The invention further concerns articles made from the above polypropylene mixed color blend, e.g. for caps, closures, bottles, containers, automotive articles, and wire and cable articles.