Water-absorbent Sheet Composition for Diaper Shape Retention

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Solution Overview

Problem

Conventional absorbent materials in disposable diapers face challenges such as 'gel-blocking' phenomena and deformation due to high amounts of water-absorbent resins, leading to reduced liquid diffusibility and leakage, despite efforts to thin and lighten these materials.

Innovation Solution

A water-absorbent sheet composition is developed, where a water-absorbent resin and hot melt adhesive are sandwiched between two or more hydrophilic nonwoven fabrics, with the hydrophilic fibers like rayon, to immobilize the resin uniformly, preventing deformation and gel-blocking while maintaining high absorbency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a large amount of water-absorbent resin is used to reduce hydrophilic fibers for thinning, then the thickness and weight are reduced, but gel-blocking phenomenon occurs and liquid diffusibility is markedly lowered

Engineering Contradiction:

Improvethickness of absorbent materialVSAvoidliquid permeation rate

Core Design Contradiction:

Volume of moving objectVSSpeed

Solution Approach 1:

The absorbent material is segmented into multiple layers with different functions: a first nonwoven fabric layer for liquid distribution, a water-absorbent resin layer for absorption, and a second nonwoven fabric layer for shape retention. This segmentation allows each layer to optimize its function without compromising overall liquid permeation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining hydrophilic nonwoven fabrics with water-absorbent resin particles. The nonwoven fabric matrix provides structural integrity and liquid distribution pathways, while the resin particles provide absorption capacity, creating a composite material that avoids gel-blocking.

Inventive Principle:

Principle #40Composite materials

2Volume of moving object

If a large amount of water-absorbent resin is used to thin the material, then the thickness is reduced, but the absorbent material undergoes deformation of shape due to twisting or tearing

Engineering Contradiction:

Improvethickness of absorbent materialVSAvoidshape retention of absorbent material

Core Design Contradiction:

Volume of moving objectVSShape

Solution Approach 1:

The composite structure of nonwoven fabric and water-absorbent resin creates a material that combines the flexibility and shape retention of fabric with the absorption capacity of resin. The fabric matrix prevents twisting and tearing even when resin content is high.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the absorbent material have different properties: the nonwoven fabric layers provide structural strength and shape retention, while the resin layer provides absorption. This local differentiation of functions allows the material to maintain shape while achieving thinness.

Inventive Principle:

Principle #3Local quality

3Weight of moving object

If hydrophilic fibers are reduced to lighten the material, then the weight is reduced, but liquid diffusibility is slowed down due to gel-blocking

Engineering Contradiction:

Improveweight of absorbent materialVSAvoidliquid diffusion rate

Core Design Contradiction:

Weight of moving objectVSSpeed

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The nonwoven fabric layers provide a porous structure with interconnected voids that facilitate rapid liquid distribution throughout the absorbent material. This porous network prevents gel-blocking by maintaining open pathways for liquid flow even when resin content is high.

Inventive Principle:

Principle #31Porous materials

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 composition achieves sufficient absorbency without shape deformation, preventing liquid leakage and maintaining thinness, suitable for disposable diapers and other applications, with enhanced liquid permeation rates and retention capacities.

Implementation Method 1

a water-absorbent resin existing near a surface layer absorbs the liquid to even more densify soft gel that forms near the surface layer

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Implementation Method 2

water-absorbent resin having a high surface cross-linking density

Methodology Applied

Scientific EffectOsmosis: Osmosis

Implementation Method 3

a water-absorbent resin and a hot melt adhesive are sandwiched with two or more sheets of hydrophilic nonwoven fabrics

Methodology Applied

Scientific EffectThermal bonding: Heating

Data Source

PatentEP2314264B1Water-absorbent sheet composition

Publication Date: 2014.10.08 SUMITOMO SEIKA CHEM CO LTD

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Figure 4

AI summary

A water-absorbent sheet composition comprising a structure in which a water-absorbent resin and a hot melt adhesive are sandwiched with two or more sheets of hydrophilic nonwoven fabrics, wherein the hydrophilic nonwoven fabrics have a basis weight of 25 g/m2 or more, and wherein the water-absorbent resin is contained in an amount of from 200 to 400 g/m2, and wherein the hot melt adhesive is contained in an amount of from 0.10 to 0.50 times that of the amount of the water-absorbent resin contained (based on weight). According to the present invention, a water-absorbent sheet composition which has sufficient absorbency without undergoing deformation of shape after liquid absorption, while being thin in style can be provided.