Water-absorbent resin core-shell structure for liquid diffusibility
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Solution Overview
Problem
Water-absorbent resins used in hygienic materials like disposable diapers and sanitary napkins face challenges in balancing water-retention capacity, water-absorption rate, and water-absorption capacity under load, leading to issues with liquid diffusibility and re-wet amounts.
Innovation Solution
A water-absorbent resin is produced through reversed phase suspension polymerization in a hydrocarbon dispersion medium, using an internal-crosslinking agent, azo-based compounds, and peroxides, with post-crosslinking, achieving a water-absorption capacity of 20 ml/g under 4.14 kPa at 120 minutes and a degree of swelling under load of 70% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If water-absorbent resin shows rapid water-absorption rate, then water-absorption rate is improved, but liquid diffusibility deteriorates and re-wet amount increases
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the resin particles have different properties in different regions. The core maintains high water absorption capacity while the shell or surface is modified to control swelling and maintain porosity, allowing rapid absorption without blocking liquid pathways and reducing re-wet.
Solution Approach 2:
The patent uses composite materials by combining water-absorbent resin with porous particles or modifying the resin structure to create a composite system. This composite structure provides both rapid water absorption capability and maintained liquid diffusibility through the porous network, preventing the gelatinization effect that causes re-wet.
2Quantity of substance
If water-retention capacity is increased, then water-retention is improved, but water-absorption capacity under load deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the crosslinking density and molecular weight distribution of the water-absorbent resin. By carefully controlling these parameters, the resin achieves both high water-retention capacity through extended polymer chains and high water-absorption capacity under load through optimized network structure that prevents excessive swelling.
3Reliability
If crosslinking density is increased to improve structural stability, then reliability is improved, but diffusibility of liquid deteriorates
Solution Approach 1:
The patent applies porous materials by incorporating porous particles or creating a porous structure within the water-absorbent resin matrix. This porous network provides liquid pathways that maintain diffusibility even with increased crosslinking density, while the crosslinked structure provides the necessary structural stability and reliability.
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
This approach enhances the diffusibility of liquids in absorbent materials, reducing re-wet amounts and improving the balance of water-retention and absorption properties.
Implementation Method 1
the water-absorbent resin may locally absorb a to-be-absorbed liquid around a feeding position of the to-be-absorbed liquid
Implementation Method 2
water-absorbent resins have been widely used in the field of hygienic materials
Data Source
AI summary
Provided is a method of producing a water-absorbent resin comprising a step of polymerizing a water-soluble ethylenically unsaturated monomer in the presence of an internal-crosslinking agent, and a step of performing post-crosslinking, wherein:the step of polymerizing comprises one or more polymerization steps;all the polymerization steps are performed in the presence of both one or more azo based compounds and peroxides so that the both are coexistent in the all steps;in each polymerization step, a proportion of the azo compounds is 40-95 mass % relative to an amount of the azo compounds and the peroxides;the water-absorbent resin has a water-absorption capacity of physiological saline under a load of 4.14 kPa at 120 minutes passed from the start of water absorption of 20 ml/g or more; andthe degree of swelling under a load at 30 minutes is 70%.