Epoxy Resin Layer Adhesion for Retort Packaging
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Solution Overview
Problem
The interlayer adhesiveness between the substrate and the cured product layer of epoxy resin compositions in gas barrier films is unstable, particularly with amine-based epoxy resin curing agents, which affects the integrity of packaging materials during retort processes.
Innovation Solution
A gas barrier packaging material is developed with a cured resin layer composed of an epoxy resin composition containing an epoxy resin, an amine-based curing agent, and an acidic compound, where the molar equivalent ratio of basic nitrogen to acid groups is set between 0.60 and 20, enhancing adhesiveness and resistance to retort processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PVDC layer is formed as a gas barrier layer, then good barrier properties and transparency are achieved, but organic substances and acid gases are generated during incineration causing environmental problems
Solution Approach 1:
The patent changes the material composition parameter by replacing PVDC with PVA and adding a specific inorganic layer structure. This substitution maintains the gas barrier function while eliminating the harmful incineration byproducts, as PVA decomposes into less harmful substances and the inorganic layer provides additional barrier protection without generating organic pollutants.
Solution Approach 2:
The patent creates a composite structure consisting of a PVA layer combined with a specific inorganic layer (alumina or silica). This composite material approach combines the benefits of PVA's gas barrier properties with the thermal stability and environmental compatibility of inorganic materials, achieving both functionality and environmental sustainability.
2Reliability
If a PVA layer is formed to achieve excellent gas barrier properties under low humidity, then the gas barrier properties rapidly decrease at a relative humidity of approximately 70% or higher due to high hygroscopicity
Solution Approach 1:
The patent combines PVA with a hydrophobic inorganic layer (alumina or silica) to create a composite structure. The inorganic layer acts as a protective barrier that prevents water molecules from penetrating to the PVA layer, thereby maintaining the gas barrier properties even at high relative humidity conditions where pure PVA would fail.
Solution Approach 2:
The inorganic layer serves as an intermediary between the external humid environment and the PVA layer. It mediates the interaction by blocking water vapor from reaching the hygroscopic PVA, thus preserving the PVA's gas barrier functionality under varying humidity conditions.
3Reliability
If an inorganic vapor-deposited film is used to achieve good gas barrier properties and transparency, then cracks are generated in the vapor-deposited inorganic layer during bending causing significant reduction of gas barrier properties
Solution Approach 1:
The patent creates a composite structure where a flexible PVA layer is combined with a thin inorganic vapor-deposited layer. The PVA layer acts as a flexible substrate that can accommodate bending deformations, preventing crack formation in the inorganic layer while maintaining the overall gas barrier function.
Solution Approach 2:
The patent uses a thin PVA film as a flexible base layer that can deform without cracking. This flexible film structure allows the rigid inorganic vapor-deposited layer to be applied without generating cracks during bending, as the PVA layer absorbs the mechanical stress through its flexibility.
4Strength
If a cured product of epoxy resin composition containing amine-based curing agent is formed to improve bending resistance, then the interlayer adhesiveness between the substrate and the cured product layer becomes unstable
Solution Approach 1:
The patent modifies the chemical composition parameters of the epoxy resin system by carefully selecting the ratio of amine-based curing agent to epoxy resin and adding specific additives. This parameter optimization ensures that the cured product achieves both the required bending resistance and stable interlayer adhesiveness to the inorganic vapor-deposited layer.
Solution Approach 2:
The patent creates a composite adhesive system combining epoxy resin with amine-based curing agent and specific additives. This composite material approach allows the cured adhesive layer to simultaneously provide bending resistance and maintain stable interlayer adhesiveness, resolving the contradiction between mechanical strength and bonding reliability.
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 material exhibits excellent resistance to retort processing and prevents delamination between the base and the cured resin layer, making it suitable for retort food packaging applications.
Implementation Method 1
a method for vapor-depositing an inorganic substance, such as alumina (Al2O3) or silica (SiO2)
Implementation Method 2
a cured resin layer which is a cured product of an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent containing an amine-based curing agent, and an acidic compound
Data Source
AI summary
Provided is a gas barrier packaging material including a base and a cured resin layer, the base having a surface constituted of an inorganic substance. The cured resin layer is a cured product of an epoxy resin composition including an epoxy resin, an epoxy resin curing agent containing an amine-based curing agent, and an acidic compound, and a ratio (basic nitrogen/acid groups) of a molar equivalent of basic nitrogen in the epoxy resin composition to a molar equivalent of acid groups derived from the acidic compound is from 0.60 to 20.