Liquid Packaging Board Couching for Reduced Folding Delamination
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Solution Overview
Problem
Liquid packaging board (LPB) experiences cracking during creasing and folding due to the risk of delamination at the interfaces during the creasing operation, which is necessary for converting LPB into packages.
Innovation Solution
A method of producing a multi-layered LPB comprising a print layer, a back layer, and a middle layer, where each layer is formed with a furnish containing hydrophobic size, and the layers are merged by couching at a dryness above 10%, enhancing the z-directional strength and reducing delamination, particularly using chemithermomechanical pulp (CTMP) with specific refining and starch application to optimize interface strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bulky middle ply is used to obtain high bending stiffness with low fiber amount, then bending stiffness is improved, but cracking tendency during folding increases
Solution Approach 1:
The patent changes the physical and chemical parameters of the middle ply by applying hydrophobic size and controlling couching dryness above 10%, which modifies the interface properties to reduce cracking while maintaining bending stiffness
Solution Approach 2:
The patent applies different treatments to different parts of the structure - specifically treating the interface regions with hydrophobic size and controlled couching conditions to improve local bonding strength where cracking occurs, while maintaining the overall bulky structure for stiffness
2Strength
If layers are merged by couching at low dryness, then interface strength is improved, but production efficiency decreases
Solution Approach 1:
The patent identifies a specific parameter threshold (couching dryness above 10%) that optimizes the balance between interface strength and production efficiency, allowing faster drying while maintaining bonding quality
3Strength
If hydrophobic size is added to furnish, then interface cohesion is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the hydrophobic size application with the existing couching process, integrating the interface strengthening function into the already-present layer merging operation rather than adding a separate processing step
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 significantly reduces the cracking tendency during folding and forming by improving the z-directional strength and interface cohesion, thereby enhancing the structural integrity of the LPB.
Implementation Method 1
forming a middle layer furnish comprising the CTMP and hydrophobic size; forming a print layer web from a print layer furnish in the forming section, which print layer furnish comprises hydrophobic size; forming a back layer web from a back layer furnish in the forming section, which print layer furnish comprises hydrophobic size
Implementation Method 2
merging the print layer web to the middle layer web by couching, preferably at a couching dryness above 10%, such as above 13%
Implementation Method 3
providing a chemithermomechanical pulp (CTMP) and forming a middle layer furnish comprising the CTMP
Data Source
AI summary
There is provided a method of producing a multi-layered liquid packaging board (LPB) comprising a print layer, a back layer and a middle layer, said method comprising the steps of: —providing a chemithermomechanical pulp (CTMP) and forming a middle layer furnish comprising the CTMP and hydrophobic size; —forming a middle layer web from the middle layer furnish in a forming section of a full-scale paperboard machine; —forming a print layer web from a print layer furnish in the forming section, which print layer furnish comprises hydrophobic size; —forming a back layer web from a back layer furnish in the forming section, which print layer furnish comprises hydrophobic size; —merging the print layer web to the middle layer web by couching at a couching dryness above 10%, such as above 13%, wherein the z strength of the CTMP is at least 150 kPa, such as at least 180 kPa, when measured according to ISO 15754:2009 after sheet forming according to ISO 5269-2:2004.