Polyester Primer Composite Film Adhesion Gas Barrier
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Solution Overview
Problem
Polyester/metal composite films face issues with insufficient adhesion between the polyester support and metallic covering, particularly under high temperature and humidity conditions, leading to loss of gas barrier properties and potential health risks in food packaging.
Innovation Solution
A composite film with a cross-linked adhesion primer layer comprising a mixture of acrylic and methacrylic polymers with different gel contents and surface-grafted free weak acid content, applied between the polyester support and metallic covering, enhancing both adhesion and gas barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an adhesion primer layer is applied between polyester support and metallic covering, then adhesion is improved, but gas barrier properties deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesion primer by incorporating specific acrylic and methacrylic polymers with defined gel contents (5-50% range) and functional groups. This parameter optimization allows the primer to achieve both adhesion functionality and reduced gas permeability, resolving the contradiction between improving adhesion and maintaining gas barrier properties
Solution Approach 2:
The patent creates a composite adhesion primer system combining polyester support, metallic covering, and an intermediate primer layer with specific acrylic/methacrylic polymer composition. This composite structure allows each layer to perform its specific function while collectively achieving both adhesion and gas barrier requirements
2Strength
If conventional acrylic latex is used for adhesion primer, then adhesion under dry conditions is achieved, but adhesion under high temperature and humidity conditions deteriorates
Solution Approach 1:
The patent optimizes the gel content parameter of acrylic and methacrylic polymers within specific ranges (5-50%) and adjusts the ratio between different polymer components. This parameter control ensures the primer maintains adhesion strength across varying temperature and humidity conditions, resolving the reliability issue under extreme environments
Solution Approach 2:
The patent creates different local properties within the primer layer by combining polymers with different gel contents and functional characteristics. The primer exhibits different properties at different locations/conditions: optimal adhesion under dry conditions and enhanced stability under high temperature/humidity, resolving the contradiction through spatial and conditional property differentiation
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 solution maintains adhesion and barrier properties in dry and wet conditions, significantly reducing oxygen and water vapor permeability, thus ensuring food safety and extending the composite film's usability in various applications.
Implementation Method 1
a cross-linked adhesion primer layer comprising a mixture of acrylic and methacrylic polymers
Implementation Method 2
significantly reducing oxygen and water vapor permeability
Implementation Method 3
an adhesion primer at the metal/polyester interface
Data Source
AI summary
The aim of the invention is to provide polyester/primer/metallic coating composite films having good adherence of the metallic coating in dry and humid conditions. Said films also form a good gas barrier: oxygen permeability less than or equal to 0.8 cc/m2/d; water vapour permeability less than or equal to 0.3 g/m2/d. To this end, the invention concerns a composite film comprising a polyester substrate, at least one coating adhering on at least one of the faces of the substrate and at least one layer of primer for cross-linked adhesion between the substrate and the coating. Said primer comprises at least one acrylic and/or methacrylic polymer P1, at least one acrylic and/or methacrylic polymer P2 different from P1, at least one cross-linking agent, and, preferably, at least one polyester that is soluble or dispersible in water: —P1 having a gel content TG1>70% by dry weight with respect to P1; —P2 having a gel content TG2≤TG1 and ≤20% by dry weight, with respect to P2; —P1 having a surface-grafted free weak acid content≥0.8 in meq/g of polymer; —[P2]≤60% by weight on dry by weight in respect to P1+P2. The method for producing said film, the adhering primer, and the articles obtained using said film, also form part of the present invention.