Super Absorbent Polymer Surface Crosslinking Anti-Rewetting
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Solution Overview
Problem
Super absorbent polymers face challenges in simultaneously achieving high centrifuge retention capacity and absorbency under load, while also preventing rewetting phenomena, which affects their performance in hygiene products like diapers and sanitary napkins.
Innovation Solution
A super absorbent polymer is developed with a cross-linked structure formed using a water-soluble ethylenically unsaturated monomer and surface crosslinking agents, including epoxy-based and non-epoxy-based agents, to create a base polymer powder with specific gel bed permeability and absorbency under load properties, reducing the GBP change ratio to 0.90 or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the overall crosslinking density of the super absorbent polymer is controlled to be low, then the centrifuge retention capacity can be relatively high, but the crosslinking structure may be loose, the gel strength may be low and thus the absorbency under load may be lowered
Solution Approach 1:
The patent applies local quality by creating surface crosslinked layers with different crosslinking densities than the base polymer. The surface layers have higher crosslinking density to provide structural strength and prevent rewetting, while the base polymer maintains lower crosslinking density to ensure high centrifuge retention capacity. This spatial differentiation of properties resolves the contradiction between CRC and AUL.
Solution Approach 2:
The patent creates a composite structure consisting of a base polymer core and surface crosslinked layers. The base polymer provides high absorption capacity through low crosslinking density, while the surface layers provide mechanical strength and shape retention through high crosslinking density. This composite approach allows simultaneous optimization of both centrifuge retention capacity and absorbency under load.
2Strength
If controlling the crosslink density to a high level to improve the absorbency under load, then it becomes difficult for moisture to be absorbed between densely crosslinked structures, so that the basic centrifuge retention capacity may be lowered
Solution Approach 1:
The patent implements local quality by restricting high crosslinking density to only the surface layers while maintaining low crosslinking density in the base polymer core. This allows the surface to provide necessary mechanical strength for absorbency under load without compromising the internal structure's ability to absorb moisture and achieve high centrifuge retention capacity.
Solution Approach 2:
The patent segments the polymer structure into distinct functional zones: a base polymer core responsible for moisture absorption and a surface crosslinked layer responsible for structural integrity. This segmentation allows each zone to be optimized independently, with the core maintaining high porosity for CRC and the surface providing strength for AUL.
3Reliability
If various attempts have been made to improve the absorbency under load and the liquid permeability in order to suppress such rewetting phenomenon, then concrete methods capable of effectively suppressing the rewetting phenomenon have not been suggested
Solution Approach 1:
The patent applies preliminary action by pre-forming surface crosslinked layers on the base polymer particles before final product assembly. This preliminary surface treatment creates a protective shell that prevents rewetting during subsequent use, addressing the reliability issue while using conventional crosslinking chemistry that does not significantly complicate manufacturing.
Solution Approach 2:
The patent utilizes parameter changes by controlling the degree and location of crosslinking through selection of specific crosslinking agents and reaction conditions. By adjusting crosslinking density parameters in the surface layers versus the core, the patent achieves effective anti-rewetting properties while maintaining manufacturing feasibility through established polymer chemistry techniques.
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 polymer exhibits excellent absorbency and anti-rewetting effects, providing a smooth touch feeling and maintaining performance even when swollen, thus enhancing the functionality of hygiene products.
Implementation Method 1
a base polymer powder including a cross-linked polymer in which a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups is cross-linked in the presence of an internal crosslinking agent
Implementation Method 2
first and second surface cross-linked layers that are further cross-linked from the cross-linked polymer in the presence of a surface crosslinking agent and are formed on the base polymer powder
Implementation Method 3
Super absorbent polymer (SAP) is a synthetic polymer material capable of absorbing moisture from about 500 to about 1,000 times its own weight
Implementation Method 4
a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups
Implementation Method 5
it should well retain the shape even in a state where the volume is expanded (swelled) by absorbing water
Data Source
AI summary
A super absorbent polymer and a method for producing the same are disclosed herein. In some embodiments, the super absorbent polymer includes a base polymer powder including a cross-linked polymer, and first and second surface cross-linked layers formed on the base polymer powder. The first and second surface cross-linked layers are formed by further cross-linking the cross-linked polymer in the presence of a surface crosslinking agent, wherein the first and second surface cross-linked layers each include a cross-linked structure derived from epoxy-based and non-epoxy-based surface crosslinking agents. The super absorbent polymer can exhibit excellent absorbent properties even in a swollen state and thus exhibit excellent anti-rewetting effects. Accordingly, when the super absorbent polymer is used, it is possible to provide a sanitary material such as a diaper or a sanitary napkin which can give a smooth touch feeling even after the body fluid is discharged.