Water Absorbing Agent Void Structure for Pressure Retention
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Solution Overview
Problem
Conventional water absorbent resins in high-concentration absorbent cores of sanitary materials like diapers do not adequately meet performance requirements, particularly in terms of absorbing and retaining aqueous liquids under pressure, dispersing liquids, and maintaining liquid retention.
Innovation Solution
A water absorbing agent comprising water absorbent resin particles with a cross-linked structure, polymerized from water-soluble ethylenic unsaturated monomers, which have a pressurized void average radius index of 140 or more, and are characterized by a specific particle size distribution and surface cross-linking, enhancing their absorption and retention capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the ratio of water absorbent resin in the absorbent core is increased to reduce thickness, then the thickness of the sanitary material is reduced, but the performance under pressure (absorption, retention, and dispersion) deteriorates
Solution Approach 1:
The invention changes the physical and chemical parameters of the water absorbent resin by controlling the cross-linking structure and particle size distribution. Specifically, it uses a cross-linking structure with a pressurized void average radius index of 1.4 or more and a particle size distribution where the ratio of particles with 0.15mm to 0.45mm diameter is 70 mass % or more, thereby maintaining high performance under pressure while reducing material thickness.
Solution Approach 2:
The invention creates a composite structure within the water absorbent resin by combining a cross-linked polymer network with specific pore structures and particle size distributions. This composite approach allows the resin to maintain both thickness reduction and pressure performance by optimizing the internal architecture rather than simply increasing resin concentration.
2Length of stationary object
If the ratio of water absorbent resin in the absorbent core is increased to reduce thickness, then the thickness of the sanitary material is reduced, but the liquid dispersion capability deteriorates
Solution Approach 1:
The invention optimizes the particle size distribution parameter, specifically ensuring that particles with diameters between 0.15mm and 0.45mm constitute 70 mass % or more of the total. This parameter optimization enhances liquid dispersion capability while maintaining reduced thickness, as the specific particle size range provides optimal balance between absorption capacity and liquid distribution.
3Length of stationary object
If the ratio of water absorbent resin in the absorbent core is increased to reduce thickness, then the thickness of the sanitary material is reduced, but the liquid retention capability deteriorates
Solution Approach 1:
The invention changes the cross-linking structure parameter by controlling the pressurized void average radius index to be 1.4 or more. This structural modification enables the resin to maintain excellent liquid retention capability even at reduced thickness, as the enhanced cross-linking structure prevents excessive swelling and improves retention under pressure conditions.
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 water absorbing agent effectively disperses and retains aqueous liquids in high-concentration absorbent cores, reducing urine leakage and enabling the production of thinner sanitary materials with improved performance.
Implementation Method 1
a water absorbent resin which has absorbed liquid and a gel particle diameter distribution in a swollen gel state
Implementation Method 2
water absorbent resin particles which are obtained by polymerizing a water-soluble ethylenic unsaturated monomer and which internally include a cross-linked structure
Implementation Method 3
a pressurized void average radius index is 140 or more, where the pressurized void average radius index is a swollen gel void radius (d50) corresponding to 50% of a cumulative void water content in a physiological saline water under a load of 2.07 kPa
Data Source
AI summary
A water absorbing agent includes water absorbent resin particles which are obtained by polymerizing a water-soluble ethylenic unsaturated monomer and which internally include a cross-linked structure, wherein a pressurized void average radius index is 140 or more. As a result, it is possible to provide a water absorbing agent which essentially includes water absorbent resin particles and is suitable for use in a sanitary material. Specifically, it is possible to improve not only a performance for absorbing and retaining aqueous liquid without pressure or under pressure but also (i) a performance for quickly absorbing aqueous liquid with a great help of a performance of a fibrous material, (ii) a performance for dispersing the aqueous liquid after absorbing the aqueous liquid, and (iii) a performance for retaining the aqueous liquid after absorbing the aqueous liquid.