Particulate Water-Absorbing Agent with Spacer for Diaper Absorption
Solution Overview
Problem
Conventional water-absorbing agents for disposable diapers face challenges in achieving a balance between high absorption capacity, re-wet amount, and liquid absorption time, with contradictory properties such as liquid permeability and centrifuge retention capacity often requiring trade-offs that result in insufficient absolute absorption amounts.
Innovation Solution
A particulate water-absorbing agent containing a surface-crosslinked polyacrylic acid (salt)-type resin, with specific ranges of free swell capacity, centrifuge retention capacity, absorption against pressure, and vertical diffusion absorption under pressure, achieved by incorporating a polyamine polymer, water-soluble polyvalent metal cation, and water-insoluble fine particles to enhance diffusion and absorption performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid permeability is improved by surface crosslinking, then liquid absorption speed increases, but centrifuge retention capacity decreases
Solution Approach 1:
The patent applies surface crosslinking only to the outer layer of the water-absorbing resin particles, creating a hydrophilic crosslinked layer with thickness of 1-10 μm. This localized modification improves liquid permeability at the surface while preserving the high absorption capacity in the particle interior, thus resolving the contradiction between absorption speed and retention capacity.
Solution Approach 2:
The water-absorbing resin particles are segmented into distinct functional zones: a surface crosslinked layer for rapid liquid uptake and an inner core for bulk absorption. This segmentation allows the surface to provide fast liquid permeability while the interior maintains high centrifuge retention capacity, eliminating the need to trade off between these properties.
2Quantity of substance
If absorption capacity is increased, then more liquid can be absorbed, but re-wet amount increases
Solution Approach 1:
The patent changes the crosslinking density parameter in the surface layer, creating a hydrophilic crosslinked structure with specific crosslinking agent concentrations (0.1-5 mmol/g). This parameter optimization allows the surface to rapidly absorb and redistribute liquid, reducing re-wet while maintaining overall high absorption capacity of the particle.
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 results in a well-balanced absorption performance, increasing the absolute absorption amount and reducing re-wet in disposable diapers while maintaining cost-effectiveness and environmental benefits by optimizing the properties of the water-absorbing agent.
Implementation Method 1
water-absorbing agent containing a polyacrylic acid (salt)-type water-absorbing resin as a main component
Implementation Method 2
a water-absorbing resin is caused to swell in physiological saline and then dehydration is carried out by centrifugation
Implementation Method 3
dehydration is carried out by centrifugation (CRC method: Centrifuge Retention Capacity method; centrifugation method)
Implementation Method 4
vertical diffusion absorption under pressure (VDAUP-4.83 kPa) of 30 to 80 g
Implementation Method 5
surface-crosslinked polyacrylic acid (salt)-type water-absorbing resin
Data Source
Figure 1
AI summary
Provided is a water-absorbing agent having enhanced performance in both the centrifuge retention capacity and the absorption against pressure (particularly, the vertical diffusion absorption amount) of a water-absorbing resin, and also, a water-absorbing agent which can provide an absorbent core having a large absorption amount in a diaper, having improved diffusibility and liquid permeability, and having a smaller re-wet amount, is provided at low cost. Disclosed is a particulate water-absorbing agent containing a surface-crosslinked polyacrylic acid (salt)-type water-absorbing resin as a main component, and containing at least one spacer selected from a polycation and water-insoluble fine particles, the particulate water-absorbing agent satisfying an free swell capacity (FSC) of 55 to 65 [g/g], an absorption against pressure (AAP-4.83 kPa) of 20 to 30 [g/g], and a vertical diffusion absorption amount under pressure (VDAUP-4.83 kPa) of 30 to 80 g.