Paperboard Packaging Laminate with Vacuum-Coated Film and Curl Compensation
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Solution Overview
Problem
Existing methods for manufacturing paperboard-based packaging laminates face challenges such as curling, pinhole formation, and cracking of thin vacuum coating layers, which affect the water vapor and gas barrier properties, especially at high humidity and temperature, and hinder recycling due to the use of plastic films and aluminum foils.
Innovation Solution
A method involving adjustable press nip positioning during lamination of a paperboard base layer with a vacuum coated film layer, using an adhesive composition to form an adhesive tie layer, which compensates for curling and enhances water vapor barrier properties, with a water vapor transmission rate of less than 30 cc/m²/24 h at 50% relative humidity and 23°C, and allows for recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin vacuum coating layer is deposited directly onto thick low-density paperboard, then water vapor and gas barrier properties are improved, but the substrate requires degassing which dries the board to very low moisture content, causing cracking of the vacuum coating layer upon remoisturizing
Solution Approach 1:
The invention segments the barrier function into two separate layers: a vacuum coating layer for gas barrier properties and an aluminum foil layer for water vapor barrier properties. This segmentation allows each layer to be optimized independently, with the aluminum foil providing the water vapor barrier without requiring vacuum degassing of the paperboard substrate.
Solution Approach 2:
The invention uses a composite structure combining vacuum coated paperboard with an aluminum foil layer. The vacuum coated paperboard provides gas barrier properties while the aluminum foil layer provides water vapor barrier properties, creating a composite material that achieves both barrier functions without the harmful effects of vacuum degassing the paperboard.
2Reliability
If polymer coating layers and aluminum foils are combined to ensure high water vapor barrier properties, then water vapor barrier properties are improved, but costs increase and recycling becomes more difficult
Solution Approach 1:
The invention extracts the water vapor barrier function from the polymer coating layers and assigns it to the aluminum foil layer. This allows the polymer coating layers to be reduced or eliminated, simplifying the structure for recycling while maintaining high water vapor barrier properties through the aluminum foil.
3Strength
If metallized films are laminated to paperboard using water-based adhesive, then adhesion is improved, but wetting of the paperboard substrate causes curling of the web
Solution Approach 1:
The invention introduces a polymeric adhesive layer as an intermediary between the vacuum coated paperboard and the aluminum foil layer. This adhesive layer provides strong adhesion while being applied in a controlled manner that minimizes excessive wetting and curling of the paperboard substrate.
4Strength
If high temperatures are applied during lamination processes, then adhesion and sealing are improved, but the metallized film is stretched and shrunk causing pin holes and cracks
Solution Approach 1:
The invention changes the temperature parameter during lamination by using lower temperatures compared to conventional high-temperature processes. This is made possible by the polymeric adhesive layer which provides adequate adhesion at lower temperatures, thereby preventing stretching and shrinking of the aluminum foil layer that would cause pin holes and cracks.
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 method provides excellent water vapor and liquid barrier properties at high humidity and temperature, facilitates recycling by reducing metal content, and minimizes curling and pinhole formation, while maintaining mechanical integrity.
Implementation Method 1
deposit a thin vacuum coating layer directly onto a substrate using for example chemical or physical vapor deposition techniques
Implementation Method 2
applying an adhesive composition to the paperboard base layer and/or the vacuum coated film layer, d) laminating a surface of the paperboard base layer to a surface of the vacuum coated film layer using the adhesive composition in a press nip
Data Source
AI summary
The present invention relates to method for manufacturing a paperboard based packaging laminate, said method comprising: a) providing a paperboard base layer. b) providing a vacuum coated film layer. c) applying an adhesive composition to the paperboard base layer and/or the vacuum coated film layer. d) laminating a surface of the paperboard base layer to a surface of the vacuum coated film layer using the adhesive composition in a press nip. such that the adhesive composition forms an adhesive tie layer between the paperboard base layer and the vacuum coated film layer, to form a laminate. wherein the position of the press nip is adjusted in a direction perpendicular to the laminated surfaces during the lamination to compensate for changes in curl in the formed laminate.