PVDC Tie Layer Materials for Retort Sterilization
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Solution Overview
Problem
Existing tie layer materials for poly(vinylidene chloride) (PVDC) in co-extruded film structures, such as EVA, EMA, and EAA, are not suitable for retort applications due to their low melting points and inability to withstand heat sterilization temperatures above 121° C.
Innovation Solution
The use of polyether polyester copolymers, polyurethanes with melting temperatures above 121° C, and blends of polyamides with ethylene copolymers containing amine reactive functional groups as tie layers, which provide improved heat resistance and bonding capabilities with PVDC layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional tie layer materials (EVA, EMA, EAA) are used with PVDC, then bonding capability is achieved, but heat resistance is insufficient for retort applications
Solution Approach 1:
The patent changes the key parameter of tie layer melting temperature from below 121°C to above 121°C by selecting specific polymer materials (polyethylene copolymers with amine reactive groups, polyamides, polyester polymers) that maintain PVDC bonding capability while withstanding retort sterilization temperatures
Solution Approach 2:
The patent uses composite tie layer structures combining multiple polymer components (e.g., polyethylene copolymer with amine reactive groups and polyamide, or polyester polymer blends) to achieve both PVDC bonding affinity and high temperature stability required for retort applications
2Ease of manufacture
If tie layer materials with low melting points are used, then ease of manufacture is improved, but reliability during steam sterilization deteriorates
Solution Approach 1:
The patent raises the melting temperature parameter of the tie layer material above 121°C while maintaining processability through selection of specific polymers (polyethylene copolymers, polyamides, polyester polymers) that offer an optimal balance between manufacturing ease and sterilization reliability
3Strength
If miscibility-based bonding is used between tie layer and PVDC, then bonding strength is achieved, but heat sterilization resistance is lost
Solution Approach 1:
The patent employs composite tie layer materials combining polyester polymers with polyethylene copolymers or polyamides, where the polyester component provides heat sterilization resistance while the other components ensure bonding strength through miscibility and chemical reactivity with PVDC
Solution Approach 2:
The patent assigns different functional properties to different components within the tie layer: one component (e.g., polyester polymer) provides high temperature stability while another component (e.g., polyethylene copolymer with amine reactive groups) provides bonding capability, creating local specialization within the tie layer structure
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 proposed solution enables the creation of multiple layer structures that can withstand moist heat sterilization, ensuring the integrity and functionality of PVDC-based films and containers, particularly in retortable packaging applications.
Implementation Method 1
the tie layer material should be resistant to heat sterilization, for example, at temperatures greater than about 121° C. Tie layer materials such as EVA, EMA and EAA all have melt points below 121° C. and are not able to resist mechanical deformation during steam sterilization
Implementation Method 2
A good tie layer usually needs to have some miscibility with the substrate to create entanglement at the interface, or have chemical reactivity with the substrate to create chemical bonds
Data Source
AI summary
Multiple layer structures comprising one or more poly(vinylidene chloride) layers and containers made from the multiple layer structures are provided. In a general embodiment, the present disclosure provides a multiple layer structure comprising one or more PVDC layers comprising a component selected from the group consisting of a poly(vinylidene chloride), a poly(vinylidene chloride) copolymer, and combinations thereof. The multiple layer structure further comprises one or more tie layers attached to the PVDC layer. The tie layer comprises a component selected from the group consisting of (a) polyether polyester copolymers, (b) polyurethanes having a melting temperature above about 121° C., (c) a blend comprising a polyamide and an ethylene copolymer containing an amine reactive functional group, and combinations thereof.