Reverse-Printed Retort Packaging with Crosslinked Ink Layers
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Solution Overview
Problem
Flexible retort packaging materials face challenges in maintaining print quality under extreme humidity, pressure, and temperature conditions, with digital prints often deteriorating and experiencing delamination issues during retorting.
Innovation Solution
A flexible multilayer substrate is developed with a reverse-printed layer comprising a primer sandwiched between crosslinked ink layers, which is produced using digital printing followed by electron beam irradiation, ensuring the ink layers remain damage-free and maintaining image sharpness and colorfastness during retorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If digital printing is used on flexible retort packaging, then print throughput and productivity are improved, but print quality deteriorates under retort conditions due to delamination and image degradation
Solution Approach 1:
The patent applies a multi-layer composite ink structure consisting of a primer layer, intermediate layer, and top coat layer. Each layer serves a specific function: the primer ensures adhesion to the substrate, the intermediate layer provides color and design, and the top coat offers protection against delamination and degradation during retort processing. This composite material approach resolves the contradiction by maintaining both high productivity through digital printing and reliable print quality under extreme retort conditions.
Solution Approach 2:
The patent utilizes electron beam irradiation to change the physical and chemical parameters of the ink layers, inducing crosslinking that enhances the ink's resistance to heat, pressure, and humidity during retort processing. This parameter change transforms the ink from a state susceptible to delamination to a crosslinked network structure that maintains integrity under retort conditions, thereby preserving print quality while retaining the productivity benefits of digital printing.
2Ease of manufacture
If conventional liquid ink processes are used, then ease of manufacture is improved, but energy consumption increases and environmental harm worsens due to solvent evaporation and high drying temperatures
Solution Approach 1:
The patent replaces the conventional thermal drying mechanism with electron beam irradiation for ink curing. Instead of using high-temperature ovens to evaporate solvents and dry the ink, the electron beam provides direct energy to the ink molecules, inducing rapid crosslinking and curing at ambient or reduced temperatures. This substitution eliminates the need for energy-intensive drying ovens, significantly reducing energy consumption while maintaining the simplicity of the digital printing process and eliminating harmful solvent emissions.
3Object-generated harmful factors
If UV or electron beam curable inks are used to reduce solvent emissions, then environmental harm is reduced, but print quality deteriorates during retort due to ink film brittleness and delamination
Solution Approach 1:
The patent employs a composite ink system with multiple functional layers designed to work synergistically. The primer layer provides flexible adhesion to the substrate, the intermediate layer contains the colorants and design elements with appropriate plasticizers to maintain flexibility, and the top coat layer provides protective properties including resistance to delamination and degradation. This composite structure eliminates solvent emissions while preventing the brittleness and delamination issues that plague single-layer UV or EB curable inks during retort processing.
Solution Approach 2:
The patent introduces an intermediate layer between the primer and top coat that acts as a mediator. This intermediate layer contains specific polymers and plasticizers that maintain flexibility and prevent stress concentration at the interfaces during thermal cycling. It mediates between the adhesive primer layer and the protective top coat, ensuring that the entire ink film system remains flexible and adherent under retort conditions while still providing the environmental benefits of solvent-free curing.
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 substrate withstands retorting temperatures without significant print deterioration, maintaining image sharpness and colorfastness, with bond strengths enhanced by electron beam crosslinking, ensuring the print quality and integrity of the packaging.
Implementation Method 1
the print being obtained from digital printing of conventional inks, which are subsequently crosslinked through electron beam irradiation
Implementation Method 2
the ink layers remain damage-free and maintaining image sharpness and colorfastness during retorting
Data Source
AI summary
The present invention is related to a retortable package comprising a flexible multilayer substrate comprising a reverse-printed layer, said reverse-printed layer comprising one or more crosslinked ink layer(s), and to a method for producing said multilayer laminate.