Polyurethane Layer for Food Packaging Gas Barrier
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional food packaging laminates with inorganic layers on hydrocarbon substrates, such as polyolefin sheets, exhibit insufficient gas barrier properties and interlayer adhesive strength due to pinholes in the inorganic layer and specific layer configurations.
Innovation Solution
A laminate structure comprising a heat-sealable plastic film substrate, a polyurethane layer formed with a specific composition of xylylene diisocyanate and polyol components, and a metal vapor deposition layer, where the polyurethane layer contains specific groups like xylylene, alkylene, and polyalkylene oxide groups, enhancing gas barrier properties and interlayer adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inorganic layer is formed on a polyolefin substrate, then gas barrier properties are improved, but interlayer adhesive strength deteriorates due to pinholes in the inorganic layer
Solution Approach 1:
The patent introduces a polyurethane resin layer as an intermediary between the polyolefin substrate and the inorganic vapor deposition layer. This intermediate layer improves interlayer adhesive strength by providing better bonding surfaces, while still allowing the inorganic layer to provide gas barrier properties. The polyurethane resin acts as a mediator that resolves the adhesion problem without compromising the gas barrier function.
Solution Approach 2:
The patent creates a composite structure consisting of multiple layers: polyolefin substrate, polyurethane resin layer, and inorganic vapor deposition layer. This composite material approach allows each layer to contribute its specific properties - the polyolefin provides heat sealability, the polyurethane provides adhesion, and the inorganic layer provides gas barrier properties, thereby resolving the contradiction between adhesion and gas barrier performance.
2Strength
If a polyurethane resin layer is introduced between the substrate and inorganic layer, then interlayer adhesive strength is improved, but interface adherence becomes insufficient
Solution Approach 1:
The patent carefully controls the thickness of the polyurethane resin layer and the composition of the coating liquid to optimize both adhesion and interface adherence. By adjusting parameters such as the mass ratio of polyurethane dispersion to water dispersible polyisocyanate (2/1 to 99/1) and the thickness of the polyurethane layer (1 μm to 10 μm), the patent achieves both improved interlayer adhesion and sufficient interface adherence.
3Reliability
If specific polyurethane resin compositions are used, then gas barrier properties are improved, but manufacturing complexity increases
Solution Approach 1:
The patent introduces specific functional groups (xylylene groups, alkylene groups with 2-6 carbon atoms, and polyalkylene oxide groups) at controlled concentrations in the polyurethane resin layer. This local quality approach allows the polyurethane layer to provide enhanced gas barrier properties through specific molecular structures while maintaining a relatively simple overall layer configuration.
Solution Approach 2:
The patent optimizes the concentration ranges of specific functional groups in the polyurethane resin to achieve good gas barrier properties. By controlling parameters such as xylylene group content (10-45 mass%), alkylene group content (0.5-25 mass%), and polyalkylene oxide group content (0.5-10 mass%), the patent achieves effective gas barrier performance without excessive manufacturing complexity.
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 achieves excellent gas barrier properties and interlayer adhesive strength, improving heat sealability and stability, making it suitable for food packaging applications.
Implementation Method 1
a polyurethane layer formed on the substrate, and a metal vapor deposition layer formed on the polyurethane layer, wherein the polyurethane layer is produced on the substrate by applying and drying a coating liquid containing a water dispersible polyisocyanate and a polyurethane dispersion containing polyurethane resin produced by reaction of an isocyanate group-terminated prepolymer with a chain extender
Implementation Method 2
the polyurethane layer is produced on the substrate by applying and drying a coating liquid containing a water dispersible polyisocyanate and a polyurethane dispersion
Implementation Method 3
a metal vapor deposition layer formed on the polyurethane layer
Data Source
AI summary
In a laminate film 1 including a substrate 2, a polyurethane layer 3 formed on the substrate 2, and a metal vapor deposition layer 4 formed on the polyurethane layer 3, a coating liquid is applied on the substrate 2 and dried to produce the polyurethane layer 3. The coating liquid contains a water dispersible polyisocyanate and a polyurethane dispersion containing polyurethane resin produced by reaction of an isocyanate group-terminated prepolymer with a chain extender. The isocyanate group-terminated prepolymer is produced by reaction of a polyisocyanate component including xylylene diisocyanate and/or hydrogenated xylylene diisocyanate and a polyol component including diol having 2 to 6 carbon atoms and an active hydrogen group-containing compound containing a hydrophilic group.