Superabsorbent Polymer Surface Crosslinking for Permeability
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Solution Overview
Problem
Existing superabsorbent polymers used in hygienic products like diapers face limitations in permeability under pressure, which affects their rewet property and leakage inhibition, despite advancements in product design and increased polymer content.
Innovation Solution
A superabsorbent polymer with a surface crosslink layer formed using a polymer-type surface crosslinking agent of 300 or more molecular weight, featuring hydroxy or epoxy groups, is developed, enhancing permeability without compromising internal crosslinking density or absorption performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If the molecular weight of the surface crosslinking agent is increased to 300 or more, then permeability under pressure is improved, but crosslinking density may be reduced
Solution Approach 1:
The patent applies local quality by using a surface crosslinking agent with molecular weight of 300 or more that selectively crosslinks only on the surface of the superabsorbent polymer particles, forming a porous surface layer with different properties from the dense internal structure. This local differentiation allows the surface to have high permeability while the interior maintains high crosslinking density for structural stability and absorption capacity.
Solution Approach 2:
The patent creates a porous surface structure through controlled surface crosslinking using high molecular weight crosslinking agents. The porous surface layer formed by this crosslinking provides channels for urine diffusion and improves permeability under pressure, while the bulk material maintains its integrity and absorption properties.
2Reliability
If surface crosslinking is enhanced to improve permeability, then rewet property improves, but absorption performance may be compromised
Solution Approach 1:
The patent segments the superabsorbent polymer structure into two distinct regions: a surface crosslinked layer and an internal non-crosslinked or lightly crosslinked core. This segmentation allows the surface to provide rapid urine uptake and diffusion (improving rewet property), while the internal core maintains high absorption capacity through its gel structure and crosslinked network.
Solution Approach 2:
Different functional properties are assigned to different regions: the surface layer is crosslinked to provide hydrophilicity, porosity, and rapid urine wicking, while the interior maintains a different structure optimized for bulk absorption. This local quality differentiation resolves the contradiction between surface permeability and bulk absorption performance.
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 enhanced permeability under pressure improves rewet property and leakage inhibition of hygienic products while maintaining excellent absorption performance, as demonstrated by increased centrifuge retention capacity and absorbency under pressure.
Implementation Method 1
a surface crosslink layer on the base resin powder, comprising second crosslinked polymer formed by additional crosslinking of the first crosslinked polymer by a surface crosslinking agent
Implementation Method 2
Super absorbent polymer (SAP) is synthetic polymer material that can absorb moisture of 500 to 1000 times of self-weight
Implementation Method 3
it is required to exhibit high absorption power to moisture
Implementation Method 4
the superabsorbent polymer should diffuse urine, and the like as wide as possible, even under pressure by the weight of a user
Data Source
AI summary
The invention relates to superabsorbent polymer that not only has excellent basic absorption performance, but also exhibits more improved permeability under pressure, and thus, can improve rewet property and leak inhibition property of hygienic products such as a diaper, and the like, and a method for preparing the same. The superabsorbent polymer comprises base resin powder comprising first crosslinked polymer of water soluble ethylenically unsaturated monomers having acid groups of which at least a part are neutralized; and a surface crosslink layer on the base resin powder, comprising second crosslinked polymer formed by additional crosslinking of the first crosslinked polymer by a surface crosslinking agent, wherein the surface crosslinking agent comprises a polymer type first surface crosslinking agent having number average molecular weight of 300 or more, and having plural hydroxy groups or epoxy groups.