Foamed Stretched Plastic Container Mouth Sealing
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Solution Overview
Problem
The hot-parison method is challenging for producing foamed and stretched plastic containers using microcellular technology due to difficulties in controlling foaming, especially in the mouth portion, which affects sealing and strength, leading to poor practicability.
Innovation Solution
A method involving injection-molding with a molten polymer dissolving inert gas, where pressure is applied to suppress foaming initially, and then foaming occurs naturally due to the resin's temperature, allowing for a specific distribution of foamed cells in the container wall, with the mouth portion remaining unfoamed to maintain sealing and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the hot-parison method is used to produce foamed and stretched plastic containers, then the heat energy is effectively utilized and facility cost is reduced, but the foaming control becomes difficult especially in the mouth portion
Solution Approach 1:
The mold is divided into two distinct zones: a first mold portion for forming the mouth portion and a second mold portion for forming the body portion. This segmentation allows independent temperature control and foaming management for each zone, enabling precise control over where foaming occurs while maintaining efficient heat utilization in the body portion.
Solution Approach 2:
Different thermal conditions are applied to different regions of the mold. The first mold portion (mouth area) is maintained at a lower temperature to suppress foaming, while the second mold portion (body area) is maintained at a higher temperature to promote controlled foaming. This local differentiation of thermal properties resolves the contradiction between heat utilization and foaming control.
2Illumination intensity
If foaming is allowed in the mouth portion, then light-blocking capability is improved, but sealing and strength are compromised
Solution Approach 1:
The container is segmented into a foamed body portion and a non-foamed mouth portion. The foaming process is spatially controlled to occur only in the body portion, which provides light-blocking capability, while the mouth portion remains dense and non-foamed to ensure proper sealing and structural strength for cap engagement.
Solution Approach 2:
Different structural properties are created in different regions of the container. The body portion is engineered with a foamed structure for light-blocking, while the mouth portion is engineered with a solid non-foamed structure for sealing. This local differentiation of material properties simultaneously achieves both light-blocking capability and reliable sealing.
3Reliability
If the mouth portion is cooled to prevent foaming, then sealing and strength are maintained, but the overall foaming efficiency is reduced
Solution Approach 1:
The cooling strategy is segmented: only the first mold portion (mouth area) is actively cooled to prevent foaming, while the second mold portion (body area) is allowed to maintain higher temperature for efficient foaming. This selective cooling approach maintains sealing integrity without significantly reducing overall foaming efficiency.
Solution Approach 2:
Different thermal management strategies are applied locally: the mouth portion receives active cooling to suppress foaming and ensure sealing, while the body portion receives minimal cooling to maintain temperature for efficient foaming. This localized thermal management resolves the contradiction between maintaining sealing and preserving foaming efficiency.
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 method achieves foamed and stretched plastic containers with improved light-blocking capability and surface smoothness, preventing foaming in the mouth portion, thus enhancing the containers' practicability and maintaining sealing effectiveness.
Implementation Method 1
a molten polymer in which an inert gas is dissolved
Implementation Method 2
after the pressure is released, if the foaming is permitted to take place by utilizing the temperature of the resin itself
Implementation Method 3
foaming is permitted to take place by utilizing the temperature of the resin itself that is forming the preform
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(b2)
AI summary
A foamed and stretched plastic container having a basic structure which includes a mouth portion and a body wall continuous to the mouth portion and is stretch-formed, the body wall forming a foamed region where foamed cells are distributed, and the mouth portion being an unfoamed region where no foamed cell is present, wherein the foamed cells present in the foamed region have a flat shape being stretched in the direction of stretch, and the foamed cells positioned in the central portion in the direction of thickness of the container wall have the largest lengths in the direction of maximum stretch.