Foamed Plastic Container Cell Gradient for Light Shielding and Barrier
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Solution Overview
Problem
Conventional stretched and foamed polyester containers face issues with content protection performance due to large foamed cells on the inner surfaces, leading to decreased oxygen barrier properties, and challenges in achieving sufficient light-shielding and smooth nozzle surfaces without compromising strength and appearance.
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, is produced by injection-molding a molten resin containing a foaming agent and subsequent blow-molding, ensuring fine cell diameters and preventing foaming in the nozzle area.
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 different foamed cell size characteristics at different locations within the container wall. Specifically, the inner surface layer has smaller foamed cells (average diameter ≤ 100 μm) to prevent gas migration and protect content, while the outer surface layer has larger foamed cells to provide effective light-shielding. This spatial variation in cell size quality resolves the contradiction between light-shielding and content protection.
Solution Approach 2:
The container wall is segmented into distinct layers with different foaming characteristics. The patent divides the wall structure into an inner surface layer with controlled small cells and an outer surface layer with larger cells. This segmentation allows each layer to independently fulfill its specific function: the inner layer protects against gas permeation while the outer layer provides optical shielding.
2Illumination intensity
If wall thickness is increased to improve light-shielding performance without coloring agents, then opaque property is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the physical parameters of the foamed cells (specifically size distribution and density) rather than increasing wall thickness to achieve light-shielding. By controlling the average cell diameter in the inner surface layer to be ≤ 100 μm and creating a specific cell density distribution, the patent attains effective light shielding while maintaining a thin wall structure, thus avoiding increased structural complexity.
3Weight of moving object
If foaming is applied throughout the container wall to reduce weight, then weight is reduced, but molding defects like cracks and blisters occur
Solution Approach 1:
The patent applies local quality by creating different foaming densities in different regions of the container wall. The inner surface layer has controlled foaming with small cells to prevent defects, while the outer surface layer has more extensive foaming for weight reduction. This localized approach to foaming allows weight reduction while maintaining molding quality and preventing cracks and blisters.
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
This approach effectively maintains content protection performance while achieving high light-shielding and smooth surfaces, preventing foaming-related defects like blisters and strength reduction, and enhancing the container's appearance and sealing capabilities.
Implementation Method 1
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
Implementation Method 2
it can be contrived to provide a foamed container by making the bubbles present in the container wall
Data Source
AI summary
A foamed plastic container in which the cell diameters vary along a gradient so as not to decrease the content protection performance, in a manner quite different from the foamed cells distributed in the conventional foamed containers. The foamed plastic container has a container wall formed by using a plastic material and in which foamed cells are distributed, the lengths of the foamed cells in the surface direction of the container wall decreasing from the outer surface of the container toward the inner surface thereof.