Layered Absorbent Structure With Central Wicking Layer
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Solution Overview
Problem
Current absorbent laminates in disposable products, such as diapers, do not effectively spread or wick fluid in both longitudinal and transverse directions, leading to reduced absorbency and inefficient drying, and are often 'sided' which complicates handling and manufacturing.
Innovation Solution
A layered absorbent structure with a central hydrogen-bonded airlaid wicking layer and liquid storage layers on either side, composed of superabsorbent polymer and hot melt adhesive fibers, which allows for efficient fluid transfer and maintains integrity, preventing the laminate from being 'sided' and enhancing drying performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wicking layer is added to improve fluid spreading and drying performance, then the wicking performance is improved, but the laminate becomes 'sided' which complicates handling and manufacturing
Solution Approach 1:
The patent applies asymmetry by positioning the wicking layer centrally within the laminate structure rather than at one surface. This creates a symmetric overall configuration (substrate-wicking layer-substrate) that eliminates the 'sided' problem while maintaining the wicking function. The wicking layer is sandwiched between two substrate layers, making both faces of the laminate identical and interchangeable.
Solution Approach 2:
The wicking layer is nested within the laminate structure, positioned between the upper and lower substrate layers. This nesting approach allows the wicking function to be integrated into the core of the laminate rather than added as an external layer, maintaining structural integrity while enabling fluid spreading without creating surface asymmetry.
2Speed
If a wicking layer is used to improve drying performance, then fluid is wicked away from the target location, but the wicking layer retains liquid and presents wetness to the inner liner side
Solution Approach 1:
The wicking layer acts as an intermediary between the liquid storage layers containing SAP particles. It facilitates fluid transfer from the target location to the SAP storage areas by capillary action, then the SAP particles absorb and retain the transferred fluid, preventing it from reaching the inner liner. The wicking layer mediates the fluid movement while the SAP provides the final absorption and containment.
Solution Approach 2:
The laminate structure creates different local functions: the wicking layer provides fluid transport pathways in its unbonded regions, while the SAP-containing storage layers provide fluid absorption and retention. By distributing these different qualities to different locations within the laminate, the system achieves both rapid drying at the target location and prevention of rewet at the liner interface.
3Speed
If liquid is transferred from the wicking layer to adjacent SAP, then drying performance is improved, but the transfer efficiency is insufficient at the periphery of the wetted area
Solution Approach 1:
The wicking layer utilizes porous unbonded regions created by the embossed bonding pattern to facilitate capillary fluid transport. These porous channels extend throughout the wicking layer, enabling efficient fluid movement from the wetted area to the SAP storage layers. The porous structure provides multiple fluid pathways that enhance transfer efficiency across the entire wetted area, including peripheral regions.
Solution Approach 2:
The embossed bonding pattern creates localized unbonded regions with higher porosity specifically where fluid transport is needed, while bonded regions provide structural support. This local variation in quality optimizes fluid transfer efficiency at different locations within the wicking layer, ensuring effective fluid movement from both central and peripheral wetted areas to the SAP storage layers.
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 solution significantly improves fluid transfer and drying efficiency, maintaining laminate integrity and preventing rewet issues, even under repeated insults, while ensuring the laminate is not 'sided' for easier handling and manufacturing.
Implementation Method 1
a wicking layer that improves fluid spreading and rewet performance... the wicking layer is thought to be most effective at drying the target location where liquid has entered the core when the liquid it has wicked away from that location in the x and y directions is transferred to the adjacent storage structures creating capillary suction within the wicking layer
Implementation Method 2
an intermediate layer sandwiched between the upper and lower layers comprising particles of superabsorbent material... each comprising a mixture of superabsorbent polymer (SAP) and hot melt adhesive fibers... adjacent storage structures
Data Source
AI summary
The present invention relates to a layered absorbent structure in the form of a laminate including liquid storage layers comprising particulate superabsorbent material and adhesive fibers. Notably, the absorbent structure includes a wicking layer positioned between the liquid storage layers, with the wicking layer desirably acting to improve fluid spreading and rewet performance of the absorbent structure. The wicking layer preferably comprises airlaid cellulosic fibrous material such as wood pulp, and may optionally include superabsorbent polymer. A bonding pattern of the wicking layer is oriented to enhance wicking and rewet performance.