Core-Shell Water-Absorbent Resin Powder Prevents Gel Blocking
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Solution Overview
Problem
Absorbers in disposable diapers and sanitary napkins face challenges with gel blocking when the amount of water-absorbent resin powder is high, leading to reduced absorption capacity and potential fluid return, due to swollen resin powders aggregating and blocking fluid passages.
Innovation Solution
A water-absorbent resin powder with specific properties, including a bulk density of 0.45-0.62 g/ml, absorption speed of 20-50 seconds, liquid-passing speed under load of 10 seconds or less, and moisture absorption blocking ratio of 5% or less, treated with a surface modifier to enhance absorption and retention capabilities, is used in combination with a high mass ratio of 60% or more within the absorber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the amount of water-absorbent resin powder in the absorber is increased to reduce the amount of fibrous base material and make the absorber thin, then the absorber thickness is reduced and material usage is optimized, but gel blocking occurs where swollen resin powders aggregate and block fluid passages, reducing absorption ability
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the resin particle has different properties in different regions: the core contains hydrophobic material for structural stability and controlled swelling, while the shell contains hydrophilic polymer for fluid absorption. This local differentiation allows the particle to absorb fluid without excessive swelling that would cause gel blocking.
Solution Approach 2:
The patent uses composite materials by combining hydrophobic core material with hydrophilic shell material in a core-shell structure. This composite approach allows the resin powder to maintain structural integrity while absorbing fluid, preventing aggregation and gel blocking even at high concentrations in thin absorbers.
2Quantity of substance
If the content of water-absorbent resin powder is increased to improve absorption capacity, then more body fluid can be absorbed, but the swollen resin powders are likely to come into contact with each other and close void passages, causing gel blocking
Solution Approach 1:
The patent employs porous materials by designing the resin particle with a core-shell structure that maintains void spaces within and between particles. The hydrophobic core provides a sponge-like structure with internal porosity that allows fluid penetration while preventing complete collapse, and the shell protects this porous structure during swelling.
Solution Approach 2:
The patent uses the hydrophobic core material as an intermediary that mediates between the hydrophilic shell and the external environment. The core controls the swelling behavior of the shell, allowing fluid absorption while preventing excessive expansion that would lead to particle aggregation and gel blocking.
3Volume of moving object
If the amount of fibrous base material is reduced to make the absorber thin, then the absorber thickness and material usage are improved, but the water-absorbent resin powder on the skin-contacting side initially absorbs body fluid and swells, leading to gel blocking
Solution Approach 1:
The patent applies local quality by designing resin particles with asymmetric core-shell structure where the hydrophobic core provides localized structural support at the particle center, while the hydrophilic shell provides controlled fluid interaction at the particle surface. This local differentiation prevents uncontrolled swelling at the skin-contacting side.
Solution Approach 2:
The patent uses preliminary action by pre-forming the core-shell structure before the absorption process. The hydrophobic core is already in place to control and limit the swelling of the hydrophilic shell, preventing gel blocking before it can occur during actual fluid absorption at the skin-contacting side.
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 prevents gel blocking, ensures high absorption speed, maintains dry feeling, and prevents fluid return, even with high water-absorbent resin powder content, while maintaining absorption efficiency during repeated use.
Implementation Method 1
treating, with a surface modifier (B), a dried product of a crosslinked polymer (A)
Implementation Method 2
the water-absorbent resin powder on the skin-contacting side initially absorbs the body fluid and swells
Implementation Method 3
the absorbed body fluid is diffused by the fibrous base material such as wood pulp within the absorber, and absorbed and retained by the water-absorbent resin powder
Implementation Method 4
the crosslinked polymer (A) obtained by polymerizing a monomer composition containing: a water-soluble ethylenically unsaturated monomer (a1) and/or a hydrolyzable monomer (a2) producing the water-soluble ethylenically unsaturated monomer (a1) by hydrolysis
Data Source
Figure 1~3
Figure 4~6
AI summary
To provide an absorber that has a high absorption speed, is unlikely to cause a liquid to remain on a skin-contacting surface, has excellent dry feeling, and is unlikely to cause excreted body fluid to return, and a water-absorbent resin powder that can be suitably used in the absorber. A water-absorbent resin powder of the present invention is characterized by meeting the following requirements (a) to (d): (a) a bulk density: 0.45 g/ml to 0.62 g/ml; (b) an absorption speed by a vortex method: 20 seconds to 50 seconds; (c) a liquid-passing speed under load: 10 seconds or less; and (d) a moisture absorption blocking ratio: 5% or less. An absorber of the present invention uses the water-absorbent resin powder of the present invention. An absorbent article of the present invention includes the absorber of the present invention.