Injection Molding Preform Color Gradation via Resin Flow Control
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Solution Overview
Problem
Existing methods for decorating PET bottles with color gradations are limited by the difficulty in creating uniform and constant gradation patterns due to issues with resin flow and layer thickness control during injection molding, leading to unsatisfactory decorativeness, especially in light colors, and require precise alignment of resin injection behaviors.
Innovation Solution
A process for biaxially drawing and blow molding bottles with a laminar structure featuring a main resin layer and a colored resin layer, where the colored resin layer's thickness is gradually reduced in the upward or downward direction to create a thin boundary area, resulting in a continuous and light color gradation pattern, achieved through precise control of resin flow and injection timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a colored intermediate layer is formed intermittently in the preform, then color gradation is achieved, but the gradation is limitative and decorativeness is unsatisfactory
Solution Approach 1:
The patent applies local quality by creating a colored resin layer with non-uniform thickness distribution, where the thickness gradually changes from the bottom upward of the preform. This gradual thickness variation in the colored layer produces sophisticated color gradations in specific local areas of the bottle, enhancing decorativeness while maintaining manufacturing feasibility through controlled injection molding parameters
2Manufacturing precision
If the thickness of the colored resin layer is increased or decreased in a continued manner, then color gradation is created, but it is difficult to put an emphasis on the gradation and light colors show problems
Solution Approach 1:
The patent employs dynamics by utilizing the flow characteristics of molten resin during injection molding to create a dynamically varying layer thickness. The colored resin layer thickness naturally transitions from thicker at the bottom to thinner upward, creating emphasized gradation patterns that are particularly effective for light colors. This dynamic thickness variation is achieved through controlled injection parameters rather than static layer formation
3Adaptability or versatility
If the flow of molding resin material is changed, then the thickness of the colored resin layer changes, but the decoration based on color gradation is difficult to obtain and the form is not constant
Solution Approach 1:
The patent applies parameter changes by systematically controlling injection molding parameters including injection rate, resin temperature, and mold temperature to achieve consistent colored resin layer thickness variation. By optimizing these parameters, the process produces constant and reproducible color gradation decorations despite the inherent complexity of resin flow behavior during the molding process
4Manufacturing precision
If the injecting behavior of main resin and colored resin is aligned, then layer structure is controlled, but the control is troublesome and difficult
Solution Approach 1:
The patent applies segmentation by dividing the injection process into distinct stages: first injecting the colored resin to form the intermediate layer, then injecting the main resin to complete the preform. This segmented injection approach simplifies the control of layer structure by treating each resin injection as a separate, controllable operation rather than attempting to simultaneously coordinate complex multi-resin flow behaviors
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 creation of highly decorative and stable color gradation patterns on PET bottles, enhancing their visual appeal by ensuring consistent and sophisticated color changes across the bottle surface.
Implementation Method 1
utilize a tendency of gradual decrease in the thickness of the layer of the colored resin caused by the flow of the main resin inside the preform mold when the main resin and the colored resin are injected into the mold
Implementation Method 2
the thin boundary area of the preform is further thinned by the biaxial drawing and blow molding into the bottle
Data Source
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AI summary
The technical problem to be solved by the invention is to change the thickness of the colored resin layer of the preform gradually in the upward or downward direction, by utilizing a tendency of gradual decrease in the thickness of the colored resin layer caused by the flow of the main resin inside the preform mold when the main resin and the colored resin are injected into the mold. The objects of this invention is to provide a biaxially drawn, blow molded bottle having new decorativeness created in which sophisticated color gradations associated with color density are created in the body of this bottle. The means of accomplishing this object involves adjusting the injection pattern including the time of starting and ending the supply of the main resin and the colored resin, and pressure or velocity profiles, reducing the thickness of the colored resin layer in the multi-layered molten resin fluid gradually at an upstream or downstream point of the flow, injection-molding the preform in which a color-gradated portion associated with the thickness of the colored resin layer has been formed, and biaxially drawing and blow molding this preform into a bottle having a color-gradated portion associated with the color density or color shade created on the body of the bottle.