Polylactic Acid Thin Container Injection Molding
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Solution Overview
Problem
Existing methods for producing thin containers using injection molding of polylactic acid resin struggle to uniformly fill narrow cavities due to variations in cavity size and flow dynamics, leading to inconsistent container formation.
Innovation Solution
Employing an electromagnetic on-off valve to control the opening and closing of gates in the mold, allowing for precise timing of resin injection based on the time required for the molten resin to reach the cavity end, ensuring uniform filling of multiple cavities during a single injection operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If molten resin of polylactic acid is injected into a narrow cavity to produce thin containers with thickness of about 0.7 mm, then container thickness is reduced, but the cavity cannot be filled to the distal end due to insufficient flowability
Solution Approach 1:
The patent applies parameter changes by impregnating the molten polylactic acid resin with supercritical carbon dioxide, changing the physical and chemical parameters of the resin. This impregnation increases the flowability of the resin, enabling it to fill narrow cavities to the distal end while maintaining thin container thickness of about 0.7 mm. The supercritical CO2 acts as a flowability enhancer that resolves the contradiction between reduced thickness and complete cavity filling.
2Productivity
If multi-cavity molds are used to increase production efficiency, then productivity is improved, but uniform filling of each cavity becomes difficult to achieve
Solution Approach 1:
The patent employs feedback mechanisms by detecting the filling state or pressure of the melt in each cavity and controlling the opening quantity or closing time of needle-valves accordingly. This feedback control ensures that each cavity in the multi-cavity mold is filled uniformly, addressing the challenge of maintaining manufacturing precision while improving productivity through multi-cavity molding.
3Manufacturing precision
If the amount of supercritical carbon dioxide impregnated in the molten resin is increased to improve flowability, then cavity filling is improved, but surface smoothness is degraded due to defoaming
Solution Approach 1:
The patent applies partial action by impregnating the molten resin with supercritical carbon dioxide within a specific range (0.5 to 2.5 percent by mass relative to the total amount of resin). This controlled partial impregnation is sufficient to improve flowability and enable complete cavity filling, while avoiding excessive impregnation that would cause defoaming and surface smoothness degradation. The patent precisely controls the amount of supercritical CO2 to achieve the optimal balance between flowability and surface quality.
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 enables the efficient and uniform production of thin containers with consistent thickness and appearance, achieving improved flowability and surface smoothness by optimizing the supercritical carbon dioxide impregnation levels in the polylactic acid resin.
Implementation Method 1
a molten resin of a polylactic acid impregnated with supercritical carbon dioxide in an amount within a particular range has an increased flowability and can fill even the narrow cavity described above to the distal end thereof when injected into the cavity
Data Source
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AI summary
The present invention provides a thin container production method capable of forming a thin container having a thickness of about 0.7 mm by injecting a molten resin of a polylactic acid into a narrow cavity. The production method according to the present invention produces a thin container W having a thickness in a range of 0.3 to 0.7 mm by injection molding of a polylactic acid resin. The molten resin of the polylactic acid impregnated with supercritical carbon dioxide in a range of 0.5 to 2.5 percent by mass relative to the total amount is injected into a cavity 29 corresponding to the thin container W.