Plastic Container Closure Low-Temperature Joining
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Solution Overview
Problem
Existing methods for producing closures in plastic containers using the blow-fill-seal process face challenges in achieving a secure, inseparable connection while minimizing microbial contamination and avoiding thermal degradation of plastics, which can lead to toxic byproducts and insufficient adhesion.
Innovation Solution
A low-temperature, long-term joining process is employed, where the sealant and flexible membrane are heated between 105 °C and 140 °C for at least 10 minutes under autoclaving conditions, utilizing internal pressure to generate contact pressure and achieve a secure, cohesive connection, thereby reducing microbial contamination and preventing thermal degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature welding (220-285°C) is used to join sealant and container wall, then adhesion strength is improved, but thermal degradation of plastics occurs producing toxic byproducts
Solution Approach 1:
The invention changes the temperature parameter from conventional high-temperature welding (220-285°C) to low-temperature joining (105-140°C). This parameter change allows the sealant and container wall to join through controlled softening and adhesion without reaching temperatures that cause thermal degradation or produce toxic byproducts, thus resolving the contradiction between achieving strong adhesion and avoiding harmful thermal effects
Solution Approach 2:
The invention uses a composite material system consisting of the BFS container wall material and a thermoplastic sealant that can adhere at low temperatures. The sealant is specifically selected to be compatible with the container wall material, enabling strong bonding through controlled softening and molecular interdiffusion at temperatures below 140°C, avoiding the need for high-temperature welding that causes degradation
2Productivity
If high-temperature welding process is applied, then joining speed is improved, but insufficient adhesion and thermal degradation risks increase
Solution Approach 1:
The invention changes the temperature parameter from high (220-285°C) to low (105-140°C) and extends the joining time from a few seconds to several minutes. This parameter transformation allows the sealant to gradually soften, flow, and form strong molecular bonds with the container wall, achieving reliable adhesion without the risks associated with rapid high-temperature welding
Solution Approach 2:
The invention applies preliminary heating to the sealant and container wall area before the actual joining process. This preliminary action softens the materials in advance, preparing them for optimal adhesion during the subsequent low-temperature, extended-duration joining process, ensuring reliable bonding without requiring excessive heat or speed
3Loss of time
If conventional welding process is used, then joining time is reduced, but germ count reduction in the enclosed space is insufficient
Solution Approach 1:
The invention merges the joining process with the autoclaving sterilization process into a single integrated operation. The low-temperature, extended-duration joining process is performed simultaneously with autoclaving at 121°C for 20 minutes, which not only joins the sealant to the container wall but also thoroughly sterilizes the entire enclosed space, achieving both joining and germ count reduction in one step
Solution Approach 2:
The invention performs the joining process under autoclaving conditions, where the extended exposure to elevated temperature (105-140°C for several minutes) preliminarily reduces microbial load before final sterilization. This preliminary action, combined with the subsequent autoclaving cycle, ensures comprehensive germ count reduction in the enclosed space while maintaining secure adhesion
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 ensures a secure, cohesive connection between the closure cap and the container while significantly reducing microbial contamination, achieving a 1000-fold depletion of germs and providing effective re-sealing without the need for high-temperature sterilization.
Implementation Method 1
the joining partners are heated to a temperature between 105 °C and 140 °C
Implementation Method 2
a joining pressure pressing the joining partners together is at least partially generated by the internal pressure of the filled container acting on the membrane
Implementation Method 3
a germ count reduction is carried out in a space between a closure cap and the container wall in which the joining partners are heated
Data Source
Figure 1
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Figure 4~5
AI summary
The invention relates to a method for producing a closure in a container made of plastic in a blow moulding method, wherein a joining process is carried out in order to form an inseparable connection between a region (8) of the container wall (6) - provided for a removal process and preferably forming an insertion site - and a sealing material (28) made of a joinable plastic, such as a thermoplastic elastomer, wherein the joining partners (28, 6) are heated to a joining temperature that is significantly below the welding temperature thereof and are pressed against one another with slowly increasing pressure in order to integrally join same, characterised in that the joining process is carried out between the sealing material (28) and a flexible membrane (8) of the container wall (6) forming the removal region in such a way that the joining partners (28, 8) are slowly heated in an autoclaving process, and that a joining contact pressure pressing together the joining partners (28, 8) is generated by the internal pressure of the container acting on the membrane (8) during the autoclaving process, and this simultaneously brings about a bacterial count reduction in the space (34) between the closure cap (12) and the end wall (6).