Layered Packaging Film With Epoxy Adhesive for Retort Oxygen Barrier
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Solution Overview
Problem
Existing packaging materials with inorganic coatings suffer a significant decrease in oxygen barrier properties during retort sterilization due to thermal shrinkage and defects in the vapor-deposited layer.
Innovation Solution
A layered body for packaging is developed with a barrier film having an inorganic coating on a thermoplastic resin film, an adhesive layer formed of an epoxy-based adhesive, and a heat-sealing resin layer, where the adhesive layer exhibits a high storage elastic modulus, particularly above 39 MPa at 120°C, to maintain oxygen barrier properties during retort sterilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vapor-deposited film of aluminum or silicon oxide is provided on a resin film to improve gas barrier properties, then oxygen barrier properties are improved, but thermal shrinkage and defects occur in the vapor-deposited layer during retort sterilization causing significant decrease in oxygen barrier properties
Solution Approach 1:
The invention uses a composite structure consisting of a resin film substrate, a vapor-deposited inorganic coating layer (aluminum or silicon oxide), and an overcoating layer. This composite structure protects the vapor-deposited layer from thermal shrinkage and defects during retort sterilization while maintaining excellent oxygen barrier properties. The overcoating layer acts as a protective barrier that prevents the inorganic coating from deforming under heat stress.
Solution Approach 2:
The invention changes the physical and chemical parameters of the coating system by introducing an overcoating layer with specific properties (thickness, material composition, and thermal characteristics). This overcoating layer has different thermal expansion characteristics compared to the vapor-deposited inorganic coating, thereby compensating for thermal shrinkage during retort sterilization and preventing defect formation.
2Ease of manufacture
If a heat-sealing resin layer is bonded to the barrier film using an adhesive layer to enable pouch production, then ease of manufacture is improved, but the adhesive layer and substrate film shrinkage cause defects in the vapor-deposited layer during retort sterilization
Solution Approach 1:
The invention creates a multi-layer composite structure where the adhesive layer is integrated with the barrier film and heat-sealing resin layer. This composite structure is designed to accommodate thermal shrinkage during retort sterilization without causing defects in the vapor-deposited inorganic coating, thereby maintaining both manufacturability and oxygen barrier reliability.
Solution Approach 2:
The invention optimizes the thermal and mechanical parameters of the adhesive layer and heat-sealing resin layer to match or complement the thermal shrinkage characteristics of the substrate film. By carefully controlling the glass transition temperature, melting point, and elastic modulus of these layers, the invention ensures that they shrink in a coordinated manner during retort sterilization, preventing stress concentration and defect formation in the vapor-deposited layer.
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 layered body maintains excellent oxygen barrier properties before and after retort sterilization, suitable for retort food packaging, by suppressing thermal shrinkage and crack formation in the inorganic coating.
Implementation Method 1
the shrinkage of the substrate film and the generation of defects in a vapor-deposited layer due to heating during the retort sterilization
Implementation Method 2
the adhesive layer is formed of an epoxy-based adhesive... storage elastic modulus of the adhesive layer is higher than 39 MPa at 120° C.
Implementation Method 3
a barrier film having an inorganic coating formed on a surface of a thermoplastic resin film... exhibits excellent oxygen barrier properties
Implementation Method 4
the adhesive layer is formed of an epoxy-based adhesive... an adhesive layer provided on the inorganic coating
Data Source
AI summary
The layered body for packaging of the present invention includes a barrier film (1) having an inorganic coating (1b) formed on the surface of a thermoplastic resin film (1a), and an adhesive layer 3 provided on the inorganic coating (1b). The adhesive layer (3) is formed of an epoxy-based adhesive.