Absorbent Core Raised Portions Uncouple Permeability Capillarity
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Solution Overview
Problem
Existing absorbent cores for disposable absorbent articles face a tradeoff between permeability and capillarity, where increasing one parameter leads to a corresponding decrease in the other, making it difficult to achieve simultaneous desirable levels of acquisition rate and fluid movement for secure storage.
Innovation Solution
The development of an absorbent core material with discrete raised portions forming a continuous network of channels, allowing for higher permeability without a decrease in capillary pressure, achieved through processes like ring rolling, SELF, micro-SELF, and rotary knife aperturing, which modify the fibrous web to create heterogeneous regions with localized increases in permeability and capillarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the permeability of absorbent core material is increased to improve acquisition rate, then fluid uptake speed improves, but capillary pressure decreases resulting in poor fluid movement to secure storage
Solution Approach 1:
The absorbent core is divided into multiple discrete layers with different permeability and capillarity characteristics. The first layer has high permeability and low capillarity for rapid fluid uptake, while subsequent layers have decreasing permeability and increasing capillarity to move fluid to secure storage, thus resolving the tradeoff by segmenting the core into functional zones
Solution Approach 2:
Different regions of the absorbent core are assigned different local properties: the layer adjacent to the topsheet has high permeability for fast acquisition, while deeper layers have lower permeability and higher capillarity for secure storage. This spatial variation in material properties allows simultaneous optimization of both acquisition rate and fluid movement
2Reliability
If the capillarity of absorbent core material is increased to improve fluid movement, then fluid transport to secure storage improves, but permeability decreases resulting in slower acquisition rate
Solution Approach 1:
The absorbent core is segmented into multiple layers where the first layer provides high permeability for rapid acquisition and subsequent layers provide high capillarity for reliable fluid movement, allowing each layer to specialize in one function rather than requiring a single material to optimize both conflicting properties
Solution Approach 2:
The absorbent core uses a composite structure of multiple layers with different fiber compositions and properties. Each layer is designed with specific permeability and capillarity characteristics, and the composite arrangement allows the system to achieve both high acquisition rate and reliable fluid transport that cannot be achieved with a single homogeneous material
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 enables faster acquisition rates and greater retained capacity, effectively uncoupling the permeability-capillarity tradeoff, allowing for improved fluid handling properties in absorbent cores.
Implementation Method 1
the capillarity of the fibrous layers is increased with each layer... a layer having high permeability and low capillarity to facilitate quick fluid uptake. From this first layer, the fluid can encounter a layer having less permeability and higher capillarity, such that the fluid continues to move away from the topsheet
Implementation Method 2
with each succeeding layer in a direction away from the topsheet the permeability is decreased... fluid entering through the topsheet first encounters a layer having high permeability and low capillarity to facilitate quick fluid uptake
Data Source
AI summary
An absorbent article that can be a sanitary napkin. The absorbent article comprises a topsheet joined to a backsheet and has an absorbent core material disposed therebetween, the absorbent core material being a fibrous absorbent material exhibiting on one side thereof discrete raised portions. The raised portions define a continuous network of channels, the channels defining a void region adjacent the topsheet of the sanitary napkin.