PVC-Free Polymer Sealing Element for Press-on Twist-off Closures
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Solution Overview
Problem
Existing Press-on twist-off closures for vessels with larger openings face challenges in using PVC-free polymer-based sealing elements that maintain sealing properties under sterilization conditions and comply with legal regulations regarding component migration, while avoiding the use of plasticizers and ensuring sufficient flowability during production.
Innovation Solution
The development of a polymer-based sealing element for Press-on twist-off closures, utilizing a copolymer composed of polyethylene and an alkene monomer like octene, processed without liquid extenders or plasticizers, and tailored for Shore A hardness and rheological properties to ensure sealing integrity and compliance with legal standards, using a method involving thermal extrusion and shaping to create a sealing insert that can withstand high temperatures and prevent component migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PVC-containing compounds are used for sealing elements in PT caps, then sufficient flowability during manufacturing is achieved, but harmful acidic gases are produced during incineration and plasticizers are required which pose health risks
Solution Approach 1:
The invention extracts and removes the harmful PVC component from the sealing element composition while retaining the necessary sealing functionality. The patent specifically excludes PVC and plasticizers from the compound formulation, replacing them with alternative polymers that provide comparable flowability during manufacturing without the harmful byproducts.
Solution Approach 2:
The invention changes the chemical composition parameters of the sealing element by substituting PVC-based compounds with alternative polymer systems. This parameter change eliminates the production of acidic gases during incineration and removes the need for plasticizers, while maintaining adequate flowability through careful selection of alternative polymer materials and their formulation.
2Reliability
If polymer material is used for sealing elements in larger diameter closures, then PVC-free and plasticizer-free formulation is achieved, but sufficient flowability during manufacturing and sealing properties under sterilization conditions must be maintained
Solution Approach 1:
The invention employs composite material formulation by combining multiple polymer components in specific ratios. The compound includes polymers such as polyethylene, polypropylene, and elastomers in controlled proportions, creating a composite material that exhibits both adequate flowability during manufacturing and maintains sealing integrity under sterilization conditions. The composite structure allows optimization of conflicting properties through synergistic combination of materials.
Solution Approach 2:
The invention optimizes manufacturing flowability and sealing reliability by carefully controlling physical and chemical parameters of the polymer compound. This includes adjusting molecular weight distribution, crosslinking density, and additive packages to achieve the desired balance between processability at manufacturing temperatures and performance retention at sterilization temperatures (121°C or 132°C).
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 PVC-free, polymer-based sealing element that maintains sealing properties under sterilization conditions, prevents component migration into food or drinks, and meets legal regulations, ensuring effective vacuum retention and pressure management for vessels with larger openings.
Implementation Method 1
a polymer compound is made sufficiently fluid by heating and applied to the container closure in the area of the sealing element to be produced
Implementation Method 2
which it retains after cooling
Data Source
Figure 1~3
AI summary
The present invention relates to a method for manufacturing a Press-on twist-off® vessel closure for vessels with an opening to be closed by the vessel closure having an inner diameter of more than 2 cm, comprising a polymer-based sealing element which is arranged in the vessel closure such that it seals against the opening of the vessel in the closed state, wherein a polymer compound is made sufficiently flowable by heating and applied to the vessel closure in the area of the sealing element to be produced and mechanically formed into the desired shape, which it retains after cooling, characterized by a Shore A hardness of the polymer compound between 40 and 90, wherein the polymer compound exhibits a compression set between 30% and 70% in the compression deformation test determined according to ASTM after 22 hours of storage at 70 °C and a compression of 25%, and the polymer compound does not contain PVC.The polymer compound contains a copolymer comprising polyethylene units on the one hand and an alkene monomer selected from propene, butene, hexene and, in particular, octene on the other, and the polymer compound is designed such that the sealing element can be used under pasteurization conditions (at up to 98 °C).