Super Absorbent Polymer Surface Cross-Linking for Pulpless Rewet
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Solution Overview
Problem
Super absorbent polymers used in pulpless diapers face challenges in maintaining high absorption performance and fast absorption rates while also exhibiting excellent rewet properties without the presence of pulp.
Innovation Solution
A super absorbent polymer is developed, comprising a base resin with a cross-linked polymer of an acrylic acid-based monomer and an internal cross-linking agent, further cross-linked on the surface using a surface cross-linking agent. This polymer satisfies specific conditions for water retention capacity, extractable content, absorption rate, and bulk density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If pulp content is reduced or eliminated to provide thinner hygiene articles, then thickness is reduced, but rewet performance deteriorates
Solution Approach 1:
The patent applies local quality by creating a surface cross-linked layer on the base resin particles. This surface layer has different properties (higher cross-linking density) than the interior, providing fast absorption rate and good rewet properties at the surface while maintaining high absorption capacity in the bulk. This resolves the contradiction by locally enhancing performance where it matters most for rewet behavior without adding pulp.
Solution Approach 2:
The patent changes physical and chemical parameters of the super absorbent polymer, specifically controlling bulk density within 0.40-0.70 g/ml and water retention capacity within 25-35 g/g. These parameter optimizations allow the pulpless structure to achieve both thin profile and good rewet performance by tuning the polymer's fundamental properties rather than relying on pulp content.
2Quantity of substance
If super absorbent polymer is used without pulp to act as both absorbent and pulp substitute, then pulp content is reduced, but absorption rate must be increased to compensate
Solution Approach 1:
By creating a surface cross-linked layer with different properties from the bulk, the patent enhances the surface area reactivity and liquid wicking capability. This local enhancement at the particle surface dramatically improves absorption rate without requiring additional pulp material, allowing the SAP to compensate for the reduced pulp content.
Solution Approach 2:
The surface cross-linking is performed in advance during manufacturing, creating a pre-prepared surface structure that immediately enhances absorption kinetics. This preliminary modification ensures that when the product is used, the fast absorption rate is already built-in, eliminating the need for pulp to provide this function.
3Quantity of substance
If bulk density is increased to improve absorption capacity, then absorption capacity is improved, but absorption rate may be reduced
Solution Approach 1:
The patent resolves this contradiction by creating a dual-structure particle where the surface layer has high cross-linking density (providing fast absorption rate through surface wicking) while the bulk maintains optimized density for high absorption capacity. This local differentiation allows both speed and capacity to be optimized simultaneously without compromise.
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 super absorbent polymer achieves excellent rewet properties while maintaining equal or better absorption capacity and absorption rate compared to conventional polymers, even without pulp content.
Implementation Method 1
a base resin including a cross-linked polymer of an acrylic acid-based monomer having at least partially neutralized acidic groups
Implementation Method 2
a cross-linked polymer of an acrylic acid-based monomer having at least partially neutralized acidic groups and an internal cross-linking agent
Implementation Method 3
a surface cross-linked layer formed by further cross-linking the cross-linked polymer using a surface cross-linking agent on the base resin
Implementation Method 4
a super absorbent polymer capable of absorbing 500 to 1000 times its own weight of moisture
Implementation Method 5
capable of absorbing 500 to 1000 times its own weight of moisture
Data Source
AI summary
A super absorbent polymer has excellent absorption rate and absorption performance while exhibiting excellent rewet properties even without containing pulp. A preparation method of the super absorbent polymer is also provided.