PVC-Free Cap Seal Using Polyurethane Elastomer
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Solution Overview
Problem
The use of polyvinyl chloride (PVC) in sealing materials for container caps poses health risks due to acid gas emission during disposal and potential migration of plasticizers into food products, necessitating a PVC-free alternative that maintains hermeticity and resistance to thermal treatments.
Innovation Solution
A cap with a seal made from a polyurethane thermoplastic elastomer, optionally combined with a styrene-type thermoplastic elastomer, which is PVC-free, has a specific hardness and softening temperature range, and is resistant to pasteurization and sterilization temperatures, ensuring effective sealing without excessive adhesion or damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVC-based sealing material is used, then hermeticity and resistance to thermal treatments are achieved, but health risks arise due to acid gas emission during disposal and plasticizer migration into food products
Solution Approach 1:
The patent changes the chemical composition parameters of the sealing material by replacing PVC with a blend of polyethylene (50-80 wt%), polypropylene (10-40 wt%), and elastomer (5-20 wt%). This parameter change maintains the required hermeticity while eliminating harmful plasticizers and acid gas emission, thus resolving the contradiction between reliability and health safety
Solution Approach 2:
The patent employs a composite material system combining polyethylene, polypropylene, and elastomer in specific proportions. This composite approach achieves the desired balance of hermeticity, thermal resistance, and safety by leveraging the complementary properties of each component without relying on harmful PVC additives
2Ease of manufacture
If the sealing material is thermally softened for application, then the seal can be applied to the cap by extrusion and molding, but the material must maintain sufficient structural integrity to resist pasteurization and sterilization treatments
Solution Approach 1:
The patent optimizes the melting point parameters of the sealing material by selecting polyethylene and polypropylene with appropriate melting ranges. The blend composition is designed so that the material softens at extrusion temperatures for easy application, then solidifies to provide the necessary thermal resistance during pasteurization and sterilization, resolving the contradiction between manufacturability and thermal strength
3Reliability
If the sealing material has high adhesion to the container mouth, then hermeticity is improved, but the cap becomes difficult to open and close
Solution Approach 1:
The patent adjusts the adhesion parameters of the sealing material through careful selection of the polymer blend composition. The specific ratio of polyethylene, polypropylene, and elastomer creates an optimal adhesion level that ensures hermetic sealing while allowing the cap to be opened and closed without excessive force, resolving the contradiction between sealing reliability and operational ease
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 solution provides a reliable, PVC-free sealing material that maintains hermeticity and integrity during thermal treatments, reducing health risks and environmental impact while ensuring easy opening and closing of containers.
Implementation Method 1
the sealing material of the seal must be able to be thermally softened sufficiently to be applied to the cap by extrusion and/or other suitable industrial processes, possibly followed or accompanied by mechanical shaping operations
Implementation Method 2
After application and subsequent cooling, the sealing material of the seal must also as-some a solid state, more or less deformable and elastic, capable of maintaining the imposed shape
Data Source
AI summary
A cap for closing containers comprising a seal consisting of a sealing material is de-scribed, wherein the sealing material is PVC-free and wherein the sealing material comprises at least one polyurethane thermoplastic elastomer.