Paper Web Moisture Conditioning to Reduce Corrugated Board Warpage
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Solution Overview
Problem
Conventional corrugated paperboard production faces challenges in maintaining consistent moisture content of paper layers, leading to warpage due to differential expansion and contraction, which is exacerbated by heating for adhesive bonding and unpredictable hygroexpansivity of paper fibers.
Innovation Solution
Adjust the moisture content of paper layers to a range of greater than 10 wt. % to 30 wt. % by applying a thin film of liquid, followed by heating and bonding, while accounting for hygroexpansivity attributes and atmospheric conditions to reduce hygroexpansivity and internal stresses through controlled humidification cycles and drying under restraint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If paper layers are heated to near boiling point for adhesive bonding, then adhesion strength is improved, but moisture content decreases causing warpage
Solution Approach 1:
The patent applies moisture conditioning to paper layers before heating and bonding. By pre-adjusting moisture content to optimal levels (10-30 wt.%), the paper layers are prepared in advance to maintain dimensional stability during subsequent heating, preventing warpage while still achieving strong adhesion bonding.
Solution Approach 2:
The patent controls and adjusts the moisture content parameter of paper layers within a specific range (10-30 wt.%) before bonding. This parameter optimization allows the paper to withstand heating processes without excessive moisture loss, thereby maintaining dimensional stability while achieving adequate adhesion strength.
2Manufacturing precision
If moisture content is increased to prevent warpage, then dimensional stability is improved, but adhesive bonding performance deteriorates
Solution Approach 1:
The patent identifies and controls the optimal moisture content range (10-30 wt.%) for paper layers. Within this range, dimensional stability is maintained while adhesive bonding performance is preserved. This precise parameter control resolves the contradiction between preventing warpage and ensuring bonding quality.
Solution Approach 2:
The patent implements moisture monitoring and control systems that provide feedback during the corrugating process. By continuously measuring and adjusting moisture content, the system maintains optimal levels for both dimensional stability and adhesive bonding, preventing the deterioration of bonding performance while preventing warpage.
3Productivity
If uniform heating is applied to all paper layers, then bonding efficiency is improved, but differential moisture loss causes warpage
Solution Approach 1:
The patent applies different moisture conditioning treatments to different paper layers (liners and medium) based on their specific requirements. By tailoring moisture content adjustments to each layer's characteristics and position in the corrugated structure, the system achieves uniform moisture distribution across all layers, preventing warpage while maintaining bonding efficiency.
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 significantly reduces post-warping by matching expansion and contraction rates, enhancing dimensional stability and tensile strength of the corrugated product.
Implementation Method 1
adjusting a moisture content in a first face-sheet web to a first range of greater than 10 wt. % and up to 30 wt. % by applying a first thin film of liquid to a first surface thereof
Implementation Method 2
heating the first face-sheet web
Implementation Method 3
heating the layers tends to drive out moisture
Implementation Method 4
the bonding surfaces of the liners typically are heated to promote penetration and gelatinization of the starch adhesive that bonds them to the medium
Data Source
AI summary
A network-based system and method for providing desired moisture set point values for individual papers lines based on the physical properties of each liner and the atmospheric conditions associated with a corrugator is disclosed. The desired moisture set point values are based on the hygroexpansivity of each individual paper liner. Once the moisture set point value has been determined, a conditioning apparatus adjusts a moisture value for each liner in order to tune the post-warp characteristics of the final corrugated product.