PET Bottle SiOx Coating with Pre-Cooling Against Thermal Deformation
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Solution Overview
Problem
The deposition of SiOx coatings on plastic containers, such as PET bottles, faces challenges due to thermal loads during the plasma coating process, which can lead to permanent deformation when temperature limits are exceeded, especially in high ambient temperatures and humidity conditions.
Innovation Solution
A method and system that cool the plastic containers before coating, using a container cooling system with a cooling gas device to maintain the temperature below the deformation threshold, ensuring the coating process occurs at a temperature independent of external conditions, and utilizing a plasma generation system with an electrical discharge to deposit the SiOx layer effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high energy input is applied during SiOx deposition to create an effective barrier, then the quality and density of the coating is improved, but the temperature of the plastic container increases leading to permanent deformation
Solution Approach 1:
The plastic container is cooled down to a predetermined temperature (e.g., 20°C or lower) before the SiOx deposition process begins. This preliminary cooling action ensures that even with high energy input during deposition causing temperature rise of 30-35°C, the final temperature remains below the deformation threshold of 60-65°C for PET bottles
Solution Approach 2:
The temperature parameter of the container is actively changed and controlled throughout the process. By adjusting the initial temperature parameter through cooling and monitoring the temperature rise during deposition, the process maintains optimal conditions for high-quality coating while preventing thermal deformation
2Reliability
If the deposition process is intensified to achieve effective barrier properties, then the diffusion barrier performance is improved, but the thermal stress on the plastic container increases
Solution Approach 1:
Cooling the container before deposition reduces the baseline temperature, creating a larger temperature buffer that can accommodate the thermal stress generated during intensified deposition processes while still maintaining the final temperature below deformation limits
Solution Approach 2:
The preliminary cooling action counteracts the subsequent thermal stress generation during deposition. By starting with a lower temperature, the system preemptively compensates for the expected thermal stress, allowing more aggressive deposition parameters to be used for improved barrier performance
3Temperature
If cooling is applied to prevent deformation, then the container temperature is controlled, but additional process steps and equipment are required
Solution Approach 1:
A cooling gas (such as nitrogen or air) is introduced as an intermediary medium to transfer heat away from the container. The cooling gas circulates through the coating chamber, absorbing excess heat from the container during and after deposition without requiring direct thermal contact or complex cooling mechanisms
Solution Approach 2:
The cooling system utilizes pneumatic principles by circulating cooling gas through the chamber. This gas-based cooling approach is simpler than liquid cooling systems and avoids direct thermal contact with the container, reducing complexity while maintaining effective temperature control
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 prevents plastic deformation during the coating process, ensuring a reliable and effective SiOx barrier formation on PET bottles, regardless of ambient conditions, by controlling the temperature and humidity within the coating chamber.
Implementation Method 1
Plasma formation generally occurs using a discharge reaction, which causes SiO2 particles to detach from the surface of a SiOx-containing target and deposit on the inner wall of the container
Implementation Method 2
Plasma formation generally occurs using a discharge reaction
Implementation Method 3
the plastic container is cooled in the coating chamber immediately before coating and/or before introducing a vacuum by means of a container cooling system comprising a cooling gas device
Implementation Method 4
The transport mechanism is ambipolar diffusion. The higher the kinetic energy of the ions on the PET wall, the more effective and dense the SiOx layer grows. The deposition ultimately converts the kinetic energy of the ions into heat on the PET wall
Data Source
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AI summary
The invention relates to a method for coating plastic receptacles (18), in particular PET bottles with a SiOx coating, in which method a SiOx layer is deposited inside the receptacle while a plasma is formed. According to the invention, the plastic receptacle is cooled immediately before being coated.