Hot Runner Shear for PET Preform Crystallization
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Solution Overview
Problem
Current methods for producing PET containers with enhanced thermal stability and mechanical strength at elevated temperatures are costly and time-consuming, particularly in the neck finish area, due to the need for additional heating steps and complex processing procedures, which increase the overall cost of ownership and reduce production efficiency.
Innovation Solution
The method involves modifying the hot runner system to introduce controlled local friction/shear, synergistically combining macromolecular pre-alignment/orientation and crystallization, creating stratified structures within the preform and container, which enhances thermal resistance and mechanical strength without requiring additional processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If additional heating steps and complex processing procedures are used to enhance thermal stability in the neck finish area, then thermal stability and mechanical strength are improved, but production cost and processing time increase
Solution Approach 1:
The patent applies preliminary action by inducing macromolecular orientation and crystallization in the neck finish area during the injection molding process itself, rather than requiring subsequent heating steps. The hot runner system is designed to create controlled shear stress that orients polymer chains before the material cools and solidifies, pre-establishing the crystalline structure needed for thermal stability.
Solution Approach 2:
The patent changes physical parameters of the injection process, specifically controlling temperature gradients and shear stress parameters in the hot runner system. By adjusting the temperature of the hot runner components and the injection parameters, the process induces localized crystallization in the neck finish area during normal production, eliminating the need for additional post-processing heating steps.
2Strength
If additional heating steps and complex processing procedures are used to enhance thermal stability in the neck finish area, then mechanical strength is improved, but production cost increases
Solution Approach 1:
The patent merges the functions of creating mechanical strength and thermal stability into the single injection molding process. By integrating macromolecular orientation and crystallization induction directly into the hot runner system, the process achieves enhanced mechanical strength in the neck finish area without requiring separate heating or treatment operations, thereby reducing production cost.
Solution Approach 2:
The patent applies self-service by designing the hot runner system to automatically induce the necessary crystallization and orientation during normal injection molding operations. The system uses the inherent energy and material flow of the injection process itself to create the desired structural properties, eliminating the need for external heating equipment or additional processing steps.
3Ease of manufacture
If the preform resin is made amorphous or slightly semi-crystalline to enable stretch blow molding, then processability is improved, but thermal stability at elevated temperatures deteriorates
Solution Approach 1:
The patent applies local quality by creating different structural characteristics in different parts of the preform. The neck finish area is given a highly crystalline structure with oriented macromolecules for thermal stability, while the main body remains amorphous or slightly semi-crystalline to maintain stretch blow molding processability. This localized differentiation allows each region to have the properties needed for its specific function.
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 results in PET containers with superior thermal stability, gas permeation resistance, and mechanical strength, achieved within standard processing times, reducing material usage and production costs while maintaining dimensional stability at elevated temperatures.
Implementation Method 1
modifying the hot runner system to introduce controlled local friction/shear
Implementation Method 2
introduce controlled local friction/shear, synergistically combining macromolecular pre-alignment/orientation and crystallization
Implementation Method 3
synergistically combining macromolecular pre-alignment/orientation and crystallization, creating stratified structures within the preform and container
Implementation Method 4
The higher the crystallinity of the container, the more the container is resistant to said relaxation. Any container part made entirely of amorphous or only slightly semi-crystalline PET may not have enough dimensional stability during a standard hot-fill process to resist the relaxation process
Data Source
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AI summary
An injection blow molding method for making a container comprising the steps of injecting a molten crystallizable polymer in a preform mold via a hot runner system and biaxially stretching the preform by blowing, thereby forming a container, characterized in that said method further comprises means to selectively modify the flow path of the molten crystallizable polymer within the hot runner system.