Superabsorbent Polymer Surface Crosslinking Rewet Prevention
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Solution Overview
Problem
Superabsorbent polymers face challenges in simultaneously improving centrifuge retention capacity and absorption under pressure, while also preventing rewet phenomenon and urine leakage in hygienic products like diapers and sanitary pads, due to conflicting properties and limitations in crosslinking density.
Innovation Solution
A superabsorbent polymer composition is developed with a base resin of acrylic acid-based monomers and internal cross-linking agents, featuring a surface modification layer formed using an epoxy-based surface cross-linking agent and an inorganic filler, along with a hydrophobic material with specific melting and solubility characteristics, to enhance absorption properties and prevent rewet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the whole crosslinking density of superabsorbent polymer is controlled low, then centrifuge retention capacity becomes relatively high, but the crosslink structure becomes loose and gel strength decreases, thus deteriorating absorption under pressure
Solution Approach 1:
The patent applies local quality by introducing a surface crosslinked layer with different crosslinking density than the core. The surface layer has higher crosslinking density to provide strength and prevent rewet, while the core maintains lower crosslinking density for high centrifuge retention capacity. This spatial differentiation of crosslinking density resolves the contradiction between centrifuge retention capacity and gel strength.
Solution Approach 2:
The patent segments the superabsorbent polymer into two distinct regions: a core region with lower crosslinking density for absorption and a surface crosslinked layer with higher crosslinking density for strength and rewet prevention. This segmentation allows each region to optimize for its specific function, simultaneously achieving high centrifuge retention capacity and gel strength.
2Strength
If the crosslinking density is controlled high to improve absorption under pressure, then absorption under pressure improves, but it becomes difficult to absorb moisture between the dense crosslink structures, thus deteriorating centrifuge retention capacity
Solution Approach 1:
The patent applies local quality by creating a surface crosslinked layer with high crosslinking density to provide absorption under pressure, while the core maintains low crosslinking density to preserve centrifuge retention capacity. This spatial differentiation allows the surface layer to handle pressure absorption while the core maintains moisture absorption capability.
Solution Approach 2:
The patent segments the polymer structure into a core and surface layer with different crosslinking densities. The surface layer with high crosslinking density provides absorption under pressure, while the core with low crosslinking density maintains centrifuge retention capacity, resolving the contradiction between these two properties.
3Quantity of substance
If superabsorbent polymer absorbs liquid and then pressure is applied by the weight of a user, then absorption capacity is tested, but rewet phenomenon occurs wherein a part of the liquid absorbed in the superabsorbent polymer exudes again, and urine leakage may be generated
Solution Approach 1:
The patent applies preliminary action by pre-forming a surface crosslinked layer before the polymer absorbs liquid and undergoes swelling. This surface layer is prepared in advance with high crosslinking density to prevent rewet, so when liquid absorption occurs and pressure is applied during use, the pre-formed surface layer immediately prevents liquid exusion without requiring any additional action.
Solution Approach 2:
The patent applies local quality by concentrating the crosslinking density at the surface layer to provide rewet prevention, while the core maintains low crosslinking density for high absorption capacity. This spatial differentiation allows the surface to handle rewet prevention while the core maintains absorption capability.
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 effectively inhibits rewet and urine leakage, while maintaining excellent centrifuge retention capacity and absorption under pressure, demonstrating improved absorption performance and permeability.
Implementation Method 1
the surface modification layer includes hydrophobic material having a melting temperature(Tm) of 40 to 80°C, and water solubility at 25°C of 70 mg/L or less
Implementation Method 2
a surface modification layer formed on the surface of the base resin particles, in which the cross-linked polymer is additionally cross-linked by an epoxy-based surface cross-linking agent
Data Source
AI summary
The present invention relates to superabsorbent polymer and a method for preparing the same. According to the superabsorbent polymer and preparation method for the same of the present invention, superabsorbent polymer having improved rewet property and vortex time can be provided.