Coated Water-Absorbing Polymer Prevents Gel Blocking
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Solution Overview
Problem
There is a need for water-absorbing materials in absorbent articles that exhibit high active fluid transportation, initial uptake rate, and core shell saline flow conductivity to enhance the performance of ultrathin hygiene products, such as diapers, while maintaining high absorption capacity and resistance to deformation to prevent gel blocking.
Innovation Solution
The development of absorbent structures comprising water-absorbing polymer particles coated with a film-forming polyurethane and hydrophilic pyrogenic silica, where the coating is applied in a specific weight ratio and heat-treated to enhance the material's properties, allowing for efficient fluid absorption and transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If water-absorbing polymer particles are used to absorb body fluids, then absorption capacity is improved, but gel blocking occurs that inhibits fluid distribution
Solution Approach 1:
The patent applies surface crosslinking to create a crosslinked shell layer on the outer surface of the polymer particles, while the interior remains lightly crosslinked. This local differentiation allows the surface to resist deformation and prevent gel blocking, while the interior maintains high absorption capacity. The crosslinked shell acts as a protective layer that prevents the particle from deforming and blocking capillary void spaces during fluid absorption.
Solution Approach 2:
The patent creates a composite structure with a lightly crosslinked polymer interior and a crosslinked surface shell. This composite architecture combines the high absorption capacity of the lightly crosslinked interior with the deformation resistance of the crosslinked exterior shell, resolving the contradiction between absorption capacity and gel blocking prevention.
2Strength
If surface crosslinking is increased to prevent gel blocking, then resistance to deformation is improved, but total absorption capacity decreases
Solution Approach 1:
The patent implements local quality by concentrating the crosslinking at the particle surface while keeping the interior lightly crosslinked. This allows the surface shell to provide the necessary deformation resistance without significantly impacting the overall absorption capacity, as the bulk of the particle retains its ability to absorb fluids.
Solution Approach 2:
The patent applies partial crosslinking rather than complete crosslinking of the entire particle. By crosslinking only the surface shell to a limited extent, the patent achieves sufficient deformation resistance while preserving the absorption capacity of the particle interior, thus avoiding the excessive crosslinking that would reduce total absorption capacity.
3Ease of operation
If absorbent articles are made thinner to increase wearing comfort, then ease of operation is improved, but fluid transportation capability deteriorates
Solution Approach 1:
The patent changes the physical and chemical parameters of the polymer particles through surface crosslinking, creating a crosslinked shell that prevents particle deformation. This maintains capillary void spaces and fluid transport pathways even in thinner absorbent structures, enabling thin articles to maintain adequate fluid transportation capability while improving wearing comfort.
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 coated water-absorbing material demonstrates improved fixed height absorption, free swell rate, and core shell saline flow conductivity, ensuring effective fluid transportation and absorption, even in thin absorbent articles, thereby addressing the challenges of gel blocking and enhancing wearing comfort.
Implementation Method 1
water-absorbing polymers, typically hydrogel-forming water-absorbing polymers, also referred to as absorbent gelling material, AGM, or super-absorbent polymers, SAPs. This polymer material ensures that large amounts of bodily fluids, e.g. urine, can be absorbed by the article
Implementation Method 2
hydrogel-forming water-absorbing polymers
Implementation Method 3
the coating is applied in a specific weight ratio and heat-treated to enhance the material's properties
Implementation Method 4
coated with a film-forming polyurethane
Data Source
AI summary
Absorbent structures, and absorbent articles with such structures, comprising water-absorbing polymer having a coating of film-forming polyurethane and therein incorporated a hydrophilic silica.