Polypropylene Barrier Laminate for Retort-Stable Packaging Bags
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Solution Overview
Problem
Packaging bags using a laminate with a polypropylene-based stretched substrate and an inorganic oxide layer suffer from deteriorated gas barrier properties after retort treatment.
Innovation Solution
A laminate structure comprising a first substrate and a second substrate, both containing polypropylene as a main component, with at least one substrate including an inorganic oxide layer, and a sealant layer with specific adhesive layers having defined elasticity and softening points, enhances gas barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a stretched substrate containing polypropylene as a main component is used as a barrier substrate with an inorganic oxide layer, then recyclability is improved, but gas barrier properties deteriorate after retort treatment
Solution Approach 1:
The patent uses a composite laminate structure combining polypropylene stretched substrate, inorganic oxide layer, and polyadipic acid-modified polyethylene terephthalate adhesive layer. This composite approach maintains recyclability while the specific adhesive layer prevents inorganic oxide layer detachment during retort treatment, preserving gas barrier properties.
Solution Approach 2:
The patent modifies the adhesive layer by incorporating polyadipic acid to change its chemical composition and thermal properties. This parameter change enables the adhesive to maintain bonding strength at high temperatures during retort treatment, preventing layer separation and maintaining gas barrier performance.
2Productivity
If the adhesive layer is made thinner to reduce laminate thickness, then productivity is improved, but reliability of gas barrier properties deteriorates
Solution Approach 1:
The patent changes the chemical composition of the adhesive layer by adding polyadipic acid modification to the polyethylene terephthalate. This enables the adhesive to function effectively at thinner dimensions (1-5 μm) while maintaining bonding strength and preventing inorganic oxide layer detachment, thus preserving gas barrier properties at reduced thickness.
3Ease of manufacture
If the adhesive layer is made softer to improve bonding, then ease of manufacture is improved, but gas barrier properties deteriorate due to layer separation at high temperature
Solution Approach 1:
The patent modifies the adhesive layer's thermal parameters by incorporating polyadipic acid, which raises the softening point and maintains structural integrity at high temperatures. This enables the adhesive to provide good bonding at manufacturing temperatures while resisting thermal softening and layer separation during retort treatment.
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 laminate structure effectively maintains gas barrier properties after retort treatment, ensuring high recyclability and stability of the packaging bag.
Implementation Method 1
an inorganic oxide layer containing alumina, silica, or the like is formed on a surface of a polyester film
Implementation Method 2
a first adhesive layer, a second substrate, a second adhesive layer, and a sealant layer in this order in a thickness direction
Data Source
Figure 1~2
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Figure 5~6
AI summary
A laminate that includes a first substrate, a first adhesive layer, a second substrate, a second adhesive layer, and a sealant layer in this order in a thickness direction, wherein the first substrate includes a polypropylene stretched substrate, the second substrate includes a polypropylene stretched substrate, at least one selected from the first substrate and the second substrate is a barrier substrate further including an inorganic oxide layer, the sealant layer contains polypropylene as a main component, the first adhesive layer has a modulus of elasticity of 35.0 MPa or less, the first adhesive layer has a softening point of 200°C or more and 330°C or less, and the first adhesive layer has a thickness of 1.0 µm or more.