Surface-Crosslinked Water-Absorbing Agent for Gel Blocking
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Solution Overview
Problem
Current particulate water-absorbing agents used in absorbent articles like disposable diapers face challenges in maintaining liquid absorption speed and fluid retention capacity under pressure, especially after repeated use, leading to reduced performance and increased re-wet amounts.
Innovation Solution
A particulate water-absorbing agent with a polyacrylic acid (salt)-based resin, surface-crosslinked and having a specific particle size distribution, elastic modulus index, and recovery rate, which maintains absorption speed and reduces re-wet even under heavy loads after swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the content of water-absorbing agent is increased to reduce product thickness, then water absorption capacity is improved, but gel blocking occurs and liquid diffusibility is reduced
Solution Approach 1:
The water-absorbing agent particles are designed with surface crosslinking that creates a gradient structure: the surface layer has higher crosslinking density for structural stability and gel blocking resistance, while the internal core maintains lower crosslinking density for high water absorption capacity. This local differentiation allows simultaneous achievement of high absorption and good diffusibility.
Solution Approach 2:
The patent optimizes specific parameters including particle size distribution (D10=150-300μm, D50=300-500μm, D90=500-850μm), bulk specific gravity (0.3-0.7 g/cm³), and crosslinking density gradient to prevent gel blocking while maintaining high water absorption capacity, enabling increased water-absorbing agent content without sacrificing liquid diffusibility.
2Quantity of substance
If water-absorbing resin is used to absorb water, then water absorption capacity is improved, but the resin turns into soft gel and reduces liquid diffusibility
Solution Approach 1:
Surface crosslinking creates a differentiated structure where the outer shell provides mechanical strength and gel stability while the inner core maintains high water absorption capacity, preventing the entire particle from becoming a soft gel that blocks liquid flow.
Solution Approach 2:
The water-absorbing agent combines polyacrylic acid-based resin with surface crosslinking agents to create a composite particle structure that integrates the high absorption capability of the resin with the structural stability of the crosslinked surface layer.
3Length of stationary object
If hydrophilic fiber content is decreased to increase water-absorbing agent proportion, then product thickness is reduced, but absorbing capability is compromised
Solution Approach 1:
The patent optimizes particle size distribution (D10=150-300μm, D50=300-500μm, D90=500-850μm) and bulk specific gravity (0.3-0.7 g/cm³) of water-absorbing agent particles to achieve high absorption capacity per unit volume, allowing reduced hydrophilic fiber content and product thickness while maintaining absorbing capability.
Solution Approach 2:
The surface crosslinked structure provides localized structural support that prevents gel blocking, enabling higher water-absorbing agent concentration in a thinner product configuration without sacrificing overall absorbing performance.
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 ensures high fluid retention capacity and liquid permeability, maintaining excellent physical properties and absorption performance even after multiple uses and under heavy loads, enhancing the effectiveness of absorbent articles.
Implementation Method 1
Water-absorbing resin (super absorbent polymer [SAP]) is a water-swellable, water-insoluble polymer gelling agent
Implementation Method 2
A water-absorbing agent that absorbs water turns into a soft gel-like water-absorbing agent
Implementation Method 3
a gel blocking phenomenon occurs. This phenomenon causes a considerable reduction in diffusibility of a liquid in a sanitary product
Data Source
Figure 1
Figure 2~3
Figure 4(a)~4(b)
AI summary
A particulate water absorbing agent having a polyacrylic acid (salt)-based water-absorbing resin as a main component, being surface-crosslinked and satisfying physical properties (1) to (3) below: (1) a proportion of particles with a particle diameter of not less than 150 µm and less than 850 µm is not less than 90% by weight; (2) an elastic modulus index (EMI) of particles with a particle diameter of not less than 500 µm and less than 600 µm is not less than 5500; and (3) a recovery rate defined as Rec.CRC/CRC is 1.05 to 1.20, the particulate water absorbing agent being particularly useful for absorbent articles.