High Gloss Recycled Polypropylene Composition
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Solution Overview
Problem
Recycled polypropylene materials face challenges in achieving desired gloss levels, particularly when transitioning from grey to white, as conventional methods like using titanium dioxide can compromise mechanical properties, and there is a need to minimize black spot contamination in injection molding processes.
Innovation Solution
A polypropylene composition is developed with specific crystalline and soluble fraction content ranges, low ethylene content, and controlled inorganic residues, allowing for high gloss without excessive titanium dioxide and minimizing black spot contamination, achieved by blending recycled propylene monomer units with virgin polypropylene homopolymer and optional nucleating agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If titanium dioxide is added in considerable amounts to lighten recycled polypropylene, then the white color is achieved, but the mechanical properties particularly impact performance are compromised
Solution Approach 1:
The invention changes the concentration parameter of titanium dioxide from conventional high levels (6 wt.-% or higher) to a reduced level (0.1-5 wt.-%), combined with optimizing the recyclate composition parameters (crystalline fraction 91-96 wt.-%, soluble fraction 4-9 wt.-%, specific ethylene content 2.5-5.0 wt.-%) to achieve white color while preserving mechanical properties
Solution Approach 2:
The invention creates a composite material system combining recycled polypropylene with specific compositional characteristics (defined crystalline and soluble fractions) and titanium dioxide, where the optimized composition of the recyclate component enables reduced filler content while maintaining performance
2Illumination intensity
If conventional recycling methods are used for polypropylene, then recycled material is obtained, but gloss is insufficient particularly when white color is desired
Solution Approach 1:
The invention optimizes multiple parameters of the recyclate: crystalline fraction content (91-96 wt.-%), soluble fraction content (4-9 wt.-%), ethylene content (2.5-5.0 wt.-%), and intrinsic viscosity of soluble fraction (1.25 to below 1.75 dl/g), enabling high gloss without requiring excessive titanium dioxide addition
3Productivity
If recycled polypropylene is used for injection molding, then material utilization is improved, but black spot contamination occurs
Solution Approach 1:
The invention specifies a controlled inorganic residues content (0.1-3.0 wt.-%) in the recyclate composition, which limits the amount of contamination sources while maintaining the economic benefit of using recycled material in injection molding applications
Data Source
AI summary
A polypropylene composition (C) obtainable by blending: a mixed-plastics polypropylene blend with a virgin polypropylene homopolymer.