Laminated Preform Injection Molding for Clear Window Sections
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Solution Overview
Problem
Containers made by biaxial stretch blow molding with a longitudinal strip-shaped transparent window section face issues of colored resin mixing into the transparent window section, causing opacity and potential quality changes in the contents due to direct contact with colored resin.
Innovation Solution
A synthetic resin container with a laminated structure comprising a transparent base layer and a light-blocking intermediate layer, formed in a laminated manner, to create a transparent window section without mixing colored resin, using an injection molding method with a specific nozzle configuration to form a non-laminated section as a window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a longitudinal strip-shaped transparent window section is formed in a container made by biaxial stretch blow molding using a conventional injection molding method, then the window section allows observation of contents, but colored resin mixes into the transparent window section causing opacity and potential quality changes in the contents
Solution Approach 1:
The container wall is segmented into multiple layers: a transparent base layer forming the window section, and a light-blocking intermediate layer applied selectively to specific areas. This segmentation allows the transparent portion to remain free of colored resin while the intermediate layer provides light-blocking functionality in non-window areas, preventing content quality degradation.
Solution Approach 2:
The light-blocking intermediate layer is applied locally only to specific areas of the container wall that do not require transparency, such as the upper and lower portions relative to the window section. This local application ensures that the transparent window area maintains its clarity and does not contact colored resin, while still providing light-blocking protection in other areas.
2Object-affected harmful factors
If a light-blocking colored resin is used to protect contents from ultraviolet rays, then the contents are protected, but the colored resin may mix into the transparent window section causing opacity
Solution Approach 1:
The container structure is divided into functional zones: transparent base layer areas where light transmission is needed for the window section, and selectively applied intermediate layer areas where ultraviolet protection is provided. This segmentation allows UV protection without compromising window transparency.
Solution Approach 2:
The transparent resin base layer acts as an intermediary barrier between the colored/light-blocking intermediate layer and the contents. This intermediate transparent layer prevents direct contact between colored resin and contents while allowing light transmission, thus maintaining both UV protection and window transparency.
3Object-affected harmful factors
If the circumferential wall is made completely opaque using colored resin, then the contents are protected from light, but the residual quantity of contents cannot be observed
Solution Approach 1:
The container exhibits different optical properties in different locations: the window section area maintains transparency to allow observation of residual quantity, while other areas are provided with light-blocking intermediate layers for UV protection. This local differentiation resolves the contradiction between light protection and visibility.
Data Source
AI summary
A method of injection molding a test tube-shaped preform for biaxial stretch blow molding includes supplying a major material resin from outer and inner flow paths to a combined flow path for a predetermined time and rate. For a period of time within a range of the predetermined time period during which the major material resin is supplied, the intermediate layer resin is simultaneously supplied from the middle flow path to the combined flow path at a second predetermined supplying rate. A columnar laminated molten resin is injected into a cavity of a metal mold connected to a tip of the nozzle through a gate to fill the cavity, the columnar laminated molten resin being composed of the major material resin and the intermediate layer resin formed in the major material resin in a laminated manner that are combined into a columnar shape at the combined flow path.