Foamed Polypropylene Multilayer Sheet for Food Barrier Packaging
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Solution Overview
Problem
Existing food packaging materials, such as LDPE coated paper board, lack optimal barrier properties against oxygen and moisture penetration, leading to shorter shelf life and complicate recycling processes, while foamed high melt strength polypropylene sheets do not adequately address the needs of perishable food applications like dairy products.
Innovation Solution
A multilayer sheet comprising a foamed layer of high melt strength polypropylene and a coated non-foamed polypropylene layer, where the layers are in adherent contact, providing improved barrier and insulation properties with enhanced mechanical strength, suitable for perishable food packaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LDPE coated paper board is used for dairy packaging, then the packaging can be produced with good mechanical properties, but the barrier properties against oxygen and moisture penetration are not optimal leading to shorter shelf life
Solution Approach 1:
The patent uses a composite structure consisting of a polypropylene foam core layer combined with a polypropylene coating layer. This composite material approach creates a multi-functional packaging solution where the foam provides mechanical strength and insulation while the coating layer provides superior barrier properties against oxygen and moisture, thereby extending shelf life of dairy products.
2Ease of manufacture
If LDPE coated paper board is used, then packaging can be produced, but the multicomponent system makes the recycling process more awkward and expensive
Solution Approach 1:
The patent employs homogeneity by using polypropylene as the base material for both the foam core layer and the coating layer. This single-polymer system eliminates the need for complex separation processes during recycling, as the entire structure can be processed together through conventional polypropylene recycling streams, significantly simplifying the recycling operation compared to multi-material composites.
3Strength
If foamed sheet of high melt strength polypropylene is used, then mechanical strength is improved, but barrier properties needed for perishable food applications are not adequate
Solution Approach 1:
The patent divides the packaging material into two distinct functional segments: a polypropylene foam core layer that provides mechanical strength, insulation properties, and structural integrity, and a separate polypropylene coating layer that specifically provides barrier properties against oxygen and moisture penetration. This segmentation allows each layer to optimize its specific function while working together as an integrated packaging solution.
Data Source
AI summary
The present invention relates to a multilayer sheet comprising at least two layers (A) and (B) in adherent contact with each other, wherein layer (A) is a foamed sheet comprising a high melt strength polypropylene composition and layer (B) is a coated non-foamed layer, which comprises a polypropylene composition, a process for producing said multilayer sheet, an article comprising said multilayer sheet and the use of said multilayer sheet for the production of an article with improved water vapor transmission and oxygen transmission properties.