Gas Barrier Coating Process for Flexible Films
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Solution Overview
Problem
Existing gas barrier coatings, particularly those using polyvinyl alcohol (PVA) and ethylene-vinyl alcohol (EVOH) copolymers, face challenges in achieving a balance between gas barrier properties and bond strength between flexible plastic films, often requiring high coating weights that compromise press speeds and film adhesion.
Innovation Solution
A process is developed where a gas barrier coating comprising clay and PVA/EVOH is applied between two flexible plastic films, with specific ratios of oxygen transmission rate, bond strength, and coating weight optimized to achieve a balance of properties, ensuring both effective gas barrier and adequate bond strength through controlled application and curing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high coating weight is used to ensure adequate gas barrier properties, then oxygen barrier performance is improved, but bond strength between films deteriorates and press speed decreases
Solution Approach 1:
The patent changes the physical-chemical parameters of the coating composition by incorporating a surfactant that modifies the interfacial properties between the coating and the film. This allows achieving adequate gas barrier properties with reduced coating weight while maintaining bond strength, as the surfactant improves wetting and adhesion at the coating-film interface.
Solution Approach 2:
The patent creates a composite coating system combining the polymer coating material with a surfactant additive. This composite formulation enables the coating to simultaneously provide gas barrier functionality and maintain strong adhesion to the film substrate, resolving the contradiction between barrier performance and bond strength.
2Reliability
If high coating weight is used to achieve adequate gas barrier properties, then oxygen barrier performance is improved, but productivity deteriorates due to slower press speeds
Solution Approach 1:
The patent modifies the coating composition parameters by adding a surfactant that reduces the required coating weight to achieve the same gas barrier performance. This parameter change allows the coating to be applied at lower weights that do not compromise press speed, thereby maintaining productivity while ensuring adequate barrier properties.
3Productivity
If thin coating is used to improve bond strength and productivity, then press speed increases and bond strength improves, but gas barrier properties deteriorate
Solution Approach 1:
The surfactant acts as an intermediary substance that mediates between the coating material and the film substrate. It enhances the interfacial interaction, allowing the coating to achieve adequate adhesion and gas barrier properties even when applied as a thin layer, thus resolving the contradiction between thin coating benefits and barrier performance requirements.
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
This approach allows for a thin, efficient gas barrier coating that enhances oxygen barrier properties while maintaining strong film adhesion, enabling faster production with improved laminate material integrity.
Implementation Method 1
gas barrier coatings, particularly having the ability to block the passage of oxygen
Implementation Method 2
an adhesive coating is applied to either or both of the coated side of the first film or to a second flexible polymer film; and the first and second films are adhered together
Data Source
AI summary
A process for enhancing the gas barrier properties of a composite laminate material whilst maintaining adequate bond strength, in which a gas barrier coating comprising a clay dispersion and a polymer solution or dispersion is positioned between two flexible plastics films using an adhesive, wherein a coating is applied to a first flexible polymer film at a coating weight (D), an adhesive is applied to either or both of the coated side of the first film or to a second polymer film and adhering the first and second films together to provide a material in which: (A/B). (C/D)>200, and in which: A/B>75; C>1.0; and D<1.5; wherein: A=Oxygen Transmission Rate for the laminate at 23 0C and 50% RH without the coating; B=Oxygen Transmission Rate for the laminate at 23 0C and 50% RH with the coating; C=Bond Strength in N/15 mm after the adhesive has fully cured; D=Coating Weight in g/m2 (dry).