Layered Water-Absorbent Sheet for Fast Intake and Low Re-Wet
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Solution Overview
Problem
There is a demand for a water-absorbent sheet structure that provides improved liquid permeability, reduced liquid re-wet, and minimized liquid leakage for use in absorbent articles like light incontinence pads, while also being thin and environmentally friendly, avoiding the use of natural materials that require long growth periods.
Innovation Solution
A water-absorbent sheet structure comprising a primary and secondary absorbent layer sandwiched between a water-permeable nonwoven fabric and a water-retaining nonwoven fabric, with a breathable fractionating layer, utilizing a water-absorbent resin and adhesive, and produced using specific nonwoven fabrics and manufacturing methods to enhance liquid permeability and retention properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional water-absorbent sheet structures are used, then sufficient liquid absorbent capacity is achieved, but liquid re-wet and liquid leakage amounts are excessive
Solution Approach 1:
The patent divides the water-absorbent sheet into distinct functional layers: a water-permeable nonwoven fabric layer for rapid liquid intake, a water-absorbent resin layer for bulk absorption, and a water-retaining nonwoven fabric layer for liquid distribution and retention. This segmentation allows each layer to perform its specific function optimally, preventing liquid re-wet and leakage while maintaining high absorbent capacity.
Solution Approach 2:
Different regions of the sheet structure are assigned different properties: the upper nonwoven fabric has high water permeability for fast liquid passage, the absorbent resin provides high absorption capacity, and the lower nonwoven fabric has water-retaining properties. This local differentiation of material properties enables the sheet to simultaneously achieve fast permeation, high absorption, and minimal re-wet/leakage.
2Length of stationary object
If the sheet thickness is reduced for thinning and light-weighing, then body fittability and convenience are improved, but liquid permeation rate and absorbent capacity may be compromised
Solution Approach 1:
The patent employs thin nonwoven fabric layers with optimized basis weights (5-20 g/m² for the upper layer, 10-30 g/m² for the lower layer) that maintain sufficient mechanical integrity and functional performance. These thin films enable rapid liquid permeation while keeping the overall sheet structure thin and flexible for good body fittability.
Solution Approach 2:
The patent optimizes key parameters including the basis weight of nonwoven fabrics, the content and particle size distribution of water-absorbent resin (using both fine particles ≤100 μm for fast absorption and coarse particles >100 μm for high capacity), and the thickness of each layer. These parameter optimizations enable thin sheet design while maintaining fast liquid permeation rate and sufficient absorbent capacity.
3Quantity of substance
If natural materials are used for absorbent articles, then absorbent capacity is achieved, but environmental protection and resource efficiency are compromised due to long growth periods
Solution Approach 1:
The patent replaces natural pulp fibers with synthetic water-absorbent resin particles, changing the material composition parameter. This substitution eliminates the need for long-growth-period natural materials while maintaining or improving absorbent capacity. The synthetic resin can be produced from petrochemical resources without requiring agricultural land, water, or extended growth time, thereby reducing environmental impact and improving resource 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
The structure achieves fast liquid permeability, minimal liquid re-wet, and reduced leakage, ensuring excellent body fitability and environmental sustainability by using synthetic materials with controlled thickness and permeation rates.
Implementation Method 1
an upper nonwoven fabric which is a water-permeable nonwoven fabric having a water permeation rate of 10 s or less
Implementation Method 2
an absorbent layer comprising a water-absorbent resin
Implementation Method 3
a lower nonwoven fabric which is a water-retaining nonwoven fabric having an amount of water absorption of 250 g/m2 or more
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A water-absorbent sheet structure (10) including a structure in which an absorbent layer (13) containing a water-absorbent resin (12) and an adhesive (11) is sandwiched with nonwoven fabrics from an upper side and a lower side of the absorbent layer, the water-absorbent sheet structure (10) comprising (1) an upper nonwoven fabric (14) which is a water-permeable nonwoven fabric having a water permeation rate of 10 s or less; and (2) a lower nonwoven fabric (15) which is a water-retaining nonwoven fabric having an amount of water absorbed of 250 g/m2 or more. The water-absorbent sheet structure (10) of the present invention is thin and is capable of sufficiently exhibiting water-absorbent capacities such as fast liquid permeability, a small amount of liquid re-wet, and a small amount of liquid leakage. Therefore, the water-absorbent sheet structure (10) according to the present invention is used for an absorbent material, whereby hygienic materials which are thin and have excellent body fittability can be provided.