Foamed Plastic Container Wall Gradient for Gas Barrier Protection
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Solution Overview
Problem
Conventional stretched and foamed polyester containers face issues with decreased content protection performance due to large foamed cells on the inner surfaces, which compromise oxygen barrier properties, and existing methods either increase wall thickness or result in molding defects like cracks and blisters.
Innovation Solution
A stretched and foamed plastic container with a body wall featuring a foamed region where foamed cells have a length gradient, decreasing from the outer surface to the inner surface, produced by injection-molding a molten resin containing a foaming agent and subsequent blow-molding, effectively suppressing foaming and maintaining a smooth nozzle surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If foamed cells are distributed in the container wall to provide light-shielding performance, then opaque property is improved, but content protection performance deteriorates due to large foamed cells on the inner surface allowing gas migration
Solution Approach 1:
The patent applies local quality by creating a gradient structure where foamed cell sizes vary through the wall thickness. Small foamed cells are concentrated near the inner surface to protect contents from gas migration, while larger foamed cells are positioned toward the outer surface to provide light-shielding performance. This spatial differentiation of cell sizes allows each region to optimize its function.
Solution Approach 2:
The patent changes the parameter of foamed cell size as a function of position through the wall thickness. By controlling the cell size parameter to decrease from outer surface to inner surface, the patent simultaneously achieves light shielding (requiring sufficient foam density) and content protection (requiring small cells at the content interface).
2Reliability
If wall thickness is increased to improve content protection performance, then gas barrier property is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent utilizes porous foamed structure with controlled cell sizes to achieve gas barrier functionality. The gradient distribution of small foamed cells toward the inner surface creates effective gas blocking without requiring increased wall thickness, thereby maintaining structural simplicity while improving protection performance.
3Illumination intensity
If foaming is applied to the entire container including nozzle, then light-shielding performance is improved, but strength and sealing performance deteriorate due to foamed structure at the nozzle
Solution Approach 1:
The patent applies local quality by creating a gradient structure where foamed cell sizes vary through the wall thickness. Small foamed cells are concentrated near the inner surface to protect contents from gas migration, while larger foamed cells are positioned toward the outer surface to provide light-shielding performance. This spatial differentiation of cell sizes allows each region to optimize its function.
Solution Approach 2:
The patent applies partial foaming action by allowing foamed cells to be distributed throughout the body wall for light shielding, while controlling the nozzle region to have minimal or no foaming. This partial application of foaming achieves the desired light-shielding performance in the body while preserving the strength and sealing requirements at the nozzle.
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 length gradient of foamed cells enhances content protection by reducing gas migration, prevents molding defects, and maintains light-shielding performance without increasing wall thickness, while ensuring a strong and transparent nozzle with improved appearance and sealing.
Implementation Method 1
forming a gas-imbibing molded body by injecting and filling a molten resin with an inert gas in a mold cavity
Implementation Method 2
the obtained gas-imbibing molded body is selectively heated so as to be selectively foamed by the formation of bubbles due to the imbibed gas
Data Source
AI summary
[Problems] To provide a foamed plastic container in which the cell diameters are varying along a gradient so will not to decrease the content protection performance, quite differently from the foamed cells distributed in the conventional foamed containers.[Means for Solution] The foamed plastic container has a container wall 10 formed by using a plastic material and in which foamed cells 1 are distributed, the lengths of the foamed cells in the surface direction of the container wall 10 decreasing from the outer surface of the container toward the inner surface thereof.