Multilayer Plastic Sheet for Food Trays with Reduced Bulk
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Solution Overview
Problem
Existing food packaging trays made of expanded polystyrene provide thermal insulation and low plastic usage but are bulky and difficult to stack, while non-expanded trays are less voluminous but lack rigidity and insulation, necessitating a solution for high structural rigidity, uniform thickness, and reduced environmental impact.
Innovation Solution
A multilayer plastic sheet comprising a first layer of expanded extruded polystyrene with a density between 120 and 160 grams/liter, a second layer of high impact polystyrene, and a barrier plastic film, thermoformed to create trays with side walls less than 1.5 mm thick, featuring disengagement teeth and an annular recess for easy stacking, and a flexible film for modified atmosphere packaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If trays are made of expanded polystyrene with low density (30-50 grams/liter), then thermal insulation and rigidity are improved, but the trays become bulky with increased storage and transport volume
Solution Approach 1:
The patent changes the density parameter of the expanded polystyrene from the conventional low range (30-50 grams/liter) to a higher range (100-200 grams/liter). This parameter change allows the tray to maintain rigidity and structural strength while reducing the overall volume and bulk, enabling more efficient storage and transport without compromising mechanical properties
Solution Approach 2:
The patent creates a composite structure by coupling the expanded polystyrene layer with a plastic film layer having barrier properties. This composite material approach allows the tray to achieve both the rigidity needed for structural support and the reduced volume desired for efficient storage, as the plastic film provides additional structural integrity while being thin and non-bulky
2Volume of moving object
If trays are made of non-expanded plastic material (polypropylene, polyethylenterephthalate), then the trays are less voluminous and easier to stack, but they lack thermal insulation and require more plastic material
Solution Approach 1:
The patent utilizes the porous structure of expanded polystyrene material, which contains numerous air pockets within the expanded cells. This porous structure provides excellent thermal insulation properties while maintaining a compact form factor. The trapped air within the expanded cells acts as a thermal barrier, preventing heat transfer without requiring additional insulating layers that would increase volume
3Volume of stationary object
If trays have side walls with very little slope (nearly vertical) to increase capacity, then inner volume is improved, but the trays become more bulky and difficult to stack and unstack on automatic systems
Solution Approach 1:
The patent divides the tray structure into distinct functional segments: the side walls maintain the necessary slope for easy stacking and unstacking operations, while the base and internal structure are optimized to maximize inner volume. This segmentation allows different parts of the tray to serve different functions - the sloped walls facilitate handling and automation, while the overall geometry and internal configuration maximize capacity
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 solution achieves trays with enhanced structural rigidity, reduced bulk, precise forming capabilities, and improved thermal insulation, enabling efficient stacking and unstacking on automatic systems while minimizing environmental impact and production costs.
Implementation Method 1
packaging comprising trays made of expanded polystyrene ensure a certain thermal insulation, useful during transport
Implementation Method 2
trays made in accordance with the invention via the thermoforming of a sheet
Data Source
Figure 1~3
AI summary
The invention refers to a sheet of multilayer plastic material comprising in succession a first layer of expanded extruded polystyrene with average density, a second layer of shock-resistant polystyrene and a flexible plastic film having barrier properties with respect to gases directly coupled to said second layer, wherein the first layer has a density comprised between 120 and 160 grams/liter, the final sheet having a substantially uniform thickness equal to or less than 1.5 mm, said sheet being particularly recommended for use in making trays for packaging food products and for food packages in protective or modified atmosphere.