Poly(meth)acrylic Acid Absorbent for Humid Diaper Performance
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Solution Overview
Problem
Disposable diapers face issues with urine leakage and skin rash due to slow urine absorption and poor handleability, especially in humid environments, where existing water-absorbing agents fail to maintain performance and cost-effectiveness.
Innovation Solution
A particulate water-absorbing agent with a poly(meth)acrylic acid (salt)-based resin as the main component, featuring a weight average particle diameter of 300 to 500 μm, a blocking ratio of 0 to 20% after moisture absorption, a surface tension of 60 mN/m or more, and gel capillary absorption of 28.0 g/g or more, achieved through granulation, surface crosslinking, sizing, and mixing with water-insoluble inorganic fine particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional water-absorbing agents are used, then cost is reduced, but liquid absorption speed and handleability deteriorate in humid environments
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size distribution (weight average diameter 300-500 μm, specific diameter ratios) and surface properties (surface tension 60 mN/m or more, blocking ratio 0-20%) of the poly(meth)acrylic acid (salt)-based resin to achieve both rapid liquid absorption and improved handleability in humid conditions
Solution Approach 2:
The patent uses composite materials by combining poly(meth)acrylic acid (salt)-based water-absorbing resin with water-insoluble inorganic fine particles, creating a composite particulate water-absorbing agent that maintains structural integrity and performance in humid environments while improving handleability
2Speed
If particle size is reduced to improve absorption speed, then liquid absorption speed increases, but handleability and production efficiency deteriorate
Solution Approach 1:
The patent optimizes the particle size parameter by setting the weight average particle diameter to 300-500 μm and controlling the ratio of particles in different size ranges, achieving a balance between rapid liquid absorption and production efficiency without excessive fine powder generation
Solution Approach 2:
The patent applies local quality by creating a bimodal particle size distribution where larger particles (300-500 μm) provide structural integrity and handleability, while smaller particles contribute to rapid absorption, with each size range serving its specific function
3Speed
If surface area is increased to improve absorption speed, then liquid absorption speed increases, but blocking ratio increases in humid conditions
Solution Approach 1:
The patent controls the surface tension parameter at 60 mN/m or more and the blocking ratio at 0-20% by optimizing particle morphology and surface properties, preventing excessive blocking in humid conditions while maintaining rapid absorption capability
Solution Approach 2:
The patent introduces water-insoluble inorganic fine particles as an intermediary substance that prevents agglomeration and blocking of the water-absorbing resin particles in humid environments, maintaining both absorption speed 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
The solution enhances the liquid absorption speed of disposable diapers, reduces re-wet amounts, and improves handleability, ensuring reduced urine leakage and skin rash while maintaining production efficiency in humid conditions at a lower cost.
Implementation Method 1
gel capillary absorption (GCA) of 28.0 g/g or more
Implementation Method 2
a water-absorbing resin (SAP/Super Absorbent Polymer), which is a water-swellable and water-insoluble polymeric gelling agent
Data Source
AI summary
A low cost, a disposable diaper is provided that presents no difficulties in disposable diaper manufacture in humid climates, and that has a minimal amount of flowback, and rapid absorption time. A particulate water-absorbing agent is provided having as the principal component a poly (meth)acrylic acid (salt)-based water absorbing resin, wherein the water-absorbing agent has a particle size distribution of a weight average particle diameter of 300 to 500 μm, a blocking ratio after moisture absorption when left for one hour at 25° C. and 90% relative humidity of 20% or less, a surface tension of 60 mN/m or more, and a gel capillary absorption (GCA) of 28.0 g/g or more.