PET Bottle Sterilization Using Internal Pressure to Prevent Thermal Shrinkage
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Solution Overview
Problem
Aseptic filling systems for plastic bottles, particularly PET bottles, face challenges in sterilization as high temperatures cause thermal shrinkage and deformation, while low-temperature methods prolong sterilization time and increase costs due to the need for expensive heat-resistant materials or complex processes.
Innovation Solution
Injecting heated sterilizing fluid at 65° C.-90° C. into an inflated bottle under a slightly positive pressure of 1 kPa-20 kPa, followed by immediate cooling with cold water to prevent thermal shrinkage, allowing for efficient sterilization without deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hot water or heated sterilizer is injected at normal sterilizing temperature (70°C-95°C) onto the inner surface of a plastic bottle, then sterilizing effect is improved, but thermal shrinkage occurs causing bottle deformation
Solution Approach 1:
The patent applies preliminary anti-action by maintaining a slightly positive internal pressure (1 kPa-20 kPa) in the bottle before and during the sterilization process. This pre-established pressure counteracts the thermal shrinkage forces that occur when hot sterilizing fluid contacts the bottle inner surface, preventing deformation while allowing effective sterilization at normal temperatures (70°C-95°C).
Solution Approach 2:
The patent changes the pressure parameter from atmospheric or negative pressure to slightly positive pressure (1 kPa-20 kPa) during sterilization. This parameter change enables the bottle to resist thermal shrinkage effects, allowing the use of optimal sterilizing temperatures without causing deformation.
2Shape
If sterilizing temperature is reduced below 70°C to avoid thermal shrinkage, then bottle deformation is prevented, but sterilizing time is prolonged decreasing production efficiency
Solution Approach 1:
By pre-establishing slightly positive internal pressure (1 kPa-20 kPa), the system prevents thermal shrinkage at all temperatures, enabling the use of high sterilizing temperatures (70°C-95°C) that achieve rapid sterilization and maintain high production efficiency without causing deformation.
Solution Approach 2:
The system performs preliminary action by pressurizing the bottle interior before sterilization begins. This preparatory step creates the conditions necessary for high-temperature sterilization to proceed rapidly without deformation, thus maintaining high productivity.
3Shape
If expensive heat resistant plastic resin is used to prevent thermal shrinkage, then bottle deformation is avoided, but manufacturing cost increases significantly
Solution Approach 1:
The patent changes the pressure parameter to slightly positive (1 kPa-20 kPa) during sterilization, which enables standard plastic bottles to resist thermal shrinkage at normal sterilizing temperatures. This eliminates the need for expensive heat-resistant materials, significantly reducing manufacturing costs while preventing deformation.
Solution Approach 2:
Instead of using expensive heat-resistant plastic resin, the patent employs a simple pressure control method that allows standard, cheaper plastic bottles to be sterilized effectively. This substitutes a low-cost process control approach for high-cost material substitution.
4Shape
If cooling water is supplied to the outer surface simultaneously with hot water injection to prevent thermal shrinkage, then bottle deformation is prevented, but heat transmission is hindered prolonging sterilizing time
Solution Approach 1:
The patent extracts the cooling function from the sterilization process by eliminating the need for simultaneous outer surface cooling. The slightly positive internal pressure (1 kPa-20 kPa) alone is sufficient to prevent thermal shrinkage, allowing uninterrupted heat transmission to the inner surface and enabling rapid sterilization without deformation.
Solution Approach 2:
By pre-establishing slightly positive internal pressure, the system prevents thermal shrinkage without requiring concurrent cooling. This eliminates the heat transmission barrier created by simultaneous cooling, allowing rapid heat penetration and short sterilizing time.
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 method enables rapid sterilization within the normal sterilizing temperature range without thermal shrinkage, reducing production time and costs by avoiding the need for heat-resistant materials and complex cooling processes, thus improving production efficiency and maintaining bottle integrity.
Implementation Method 1
injecting heated sterilizing fluid at 65° C.-90° C. at least onto an inner surface of a bottle
Implementation Method 2
supplying cooling water on the inner surface or the outer surface of the bottle immediately after completion of sterilizing of the bottle
Data Source
AI summary
A method for sterilizing a plastic bottle in an aseptic filling system according to which at least an inner surface or an outer surface of a bottle is sterilized by injecting a heated sterilizing fluid at 65° C.-90° C. while maintaining internal pressure of the bottle at 1 kPa-20 kPa.