Hot-Filled PET Containers with Reinforced Bottoms
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Solution Overview
Problem
Existing methods for hot filling of beverages in PET containers require thicker, heavier bottles with complex designs to withstand mechanical stresses, leading to increased material consumption and costs, while aseptic filling is complex and costly due to the need for chemical sterilization and high investment in bottling lines.
Innovation Solution
A method for hot filling using thin-walled PET containers with a reinforced domed bottom, capable of withstanding heat without significant deformation, which minimizes shape memory effects and reduces material usage by allowing controlled shrinkage and deformation after cooling, allowing for aseptic guarantee without costly bottling lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thicker container walls and complex geometries are used for hot filling, then mechanical strength and pressure resistance are improved, but weight and material consumption increase significantly
Solution Approach 1:
The patent applies parameter changes by modifying the physical state of the PET material through controlled heating and cooling cycles. The container is heated to temperatures above 80°C during filling, then cooled to below 40°C, and finally reheated to above 80°C before deformation. This thermal parameter cycling allows the material to undergo controlled crystallization and stress relaxation, enabling thin-walled containers to withstand hot filling conditions without requiring increased thickness for structural strength.
Solution Approach 2:
The patent utilizes thermal expansion and contraction effects to manage mechanical stresses. During hot filling, the container material expands thermally, allowing it to accommodate liquid volume and pressure. After filling and sealing, controlled cooling causes contraction that pre-stresses the material. Subsequent reheating and deformation allow the material to relax these stresses in a controlled manner, preventing cracking and maintaining integrity without requiring thicker walls.
2Stress or pressure
If thicker container walls are used for hot filling, then resistance to hydrostatic pressure is improved, but manufacturing complexity and material costs increase
Solution Approach 1:
The patent uses parameter changes in the thermal processing sequence to alter the material's mechanical properties. By cycling temperatures through specific ranges (heating above 80°C, cooling below 40°C, final heating above 80°C), the PET material undergoes controlled crystallization and stress relaxation. This allows thin-walled containers to develop sufficient pressure resistance through material structure changes rather than increased thickness, simplifying the overall container design.
Solution Approach 2:
The patent applies preliminary action by pre-stressing the container material through controlled cooling after filling. The container is cooled to below 40°C to induce contraction and pre-stress the material structure before final heating and deformation. This preliminary stress application prepares the material to better withstand subsequent hydrostatic pressure during hot filling without requiring complex structural reinforcements.
3Reliability
If chemical sterilization and complex bottling lines are used for aseptic filling, then sterile guarantee is improved, but investment costs and process complexity increase
Solution Approach 1:
The patent replaces chemical sterilization methods with a thermal-mechanical approach. Instead of using chemical sterilants that require complex recovery and neutralization systems, the invention uses controlled heating to above 80°C during filling and storage. This thermal process achieves sterilization through heat treatment alone, eliminating the need for chemical additives and their associated handling infrastructure, thereby reducing bottling line complexity while maintaining aseptic guarantee.
Solution Approach 2:
The patent applies self-service by allowing the hot liquid itself to perform the sterilization function. When liquid at temperatures above 80°C is filled into the container and sealed, the thermal energy in the liquid automatically sterilizes both the contents and the container interior through heat treatment. This eliminates the need for separate chemical sterilization steps and complex bottling line equipment, reducing both investment costs and process complexity while ensuring aseptic conditions.
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 enables hot filling of beverages in containers of reduced weight and cost, maintaining aseptic quality with simpler and less expensive packaging lines, reducing material and recycling costs while ensuring mechanical resistance and transparency.
Implementation Method 1
This is the so-called shape memory phenomenon. For thick bottles intended to be used for hot-filled beverages, extrusion blow molding is also used, but with more sophisticated and complex operating parameters.
Implementation Method 2
After reheating this preform, in particular by infrared radiation, up to 100/120° C., the amorphous material is softened and can be blown from the inside
Implementation Method 3
After reheating this preform, in particular by infrared radiation, up to 100/120° C.
Implementation Method 4
The material when stretched after softening, generates an induced but reversible crystallinity, the material remaining transparent.
Implementation Method 5
The cooling causes a double contraction, that of the liquid and that of the air in the head space of said bottle.
Implementation Method 6
inflation by the pressurized air thus introduced. More precisely, the air is first introduced at low pressure to ensure suitable deformation of the material during high amplitudes then at high pressure to ensure plating against the walls of the finishing mold
Implementation Method 7
The molds are also cooled with water in order to dissipate the calories transmitted by contact, which also has the effect of freezing the bottle.
Implementation Method 8
The cooling causes a double contraction, that of the liquid and that of the air in the head space of said bottle.
Data Source
Figure 1~4
AI summary
The method involves providing a container made of a material in accordance with an extrusion/blowing process following a heat resistant treatment. The container is filled with a hot sterilized liquid and the container is closed immediately after it is filled. The container is allowed to cool below a congealing temperature, for deforming the container by a formation of depression in it. The container is heated to bring relaxation of the residual stresses for reduction and generation of internal pressurization of the container to compensate for the deformations caused by the depression effects.