Superabsorbent Polymer Surface Crosslinking for Rewetting Resistance
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Solution Overview
Problem
Superabsorbent polymers used in hygiene products face issues with rewetting and urine leakage phenomena due to pressure, which existing methods have not effectively addressed.
Innovation Solution
A superabsorbent polymer is developed by crosslinking an acrylic acid-based monomer with a sodium polycarboxylate surfactant and epoxy crosslinking agents of different equivalent weights, followed by surface modification, to enhance absorption properties and prevent rewetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional superabsorbent polymers are used to achieve high absorbency, then water absorption capacity is improved, but rewetting and urine leakage phenomena occur under pressure
Solution Approach 1:
The patent applies local quality by creating a surface crosslinked layer on the superabsorbent polymer particles. This surface layer has different properties (higher crosslinking density, lower water solubility) compared to the interior, providing pressure resistance and preventing rewetting while maintaining high absorption capacity in the core region.
Solution Approach 2:
The patent uses composite materials by combining the base superabsorbent polymer (acrylic acid-based) with epoxy crosslinking agents and surfactants. The resulting composite structure integrates the high absorption capability of the polymer with the mechanical strength and pressure resistance of the crosslinked network.
2Reliability
If the superabsorbent polymer is highly crosslinked to suppress rewetting, then reliability under pressure is improved, but liquid permeability deteriorates
Solution Approach 1:
The surface crosslinked layer provides the necessary crosslinking density for rewetting resistance, while the interior maintains appropriate porosity and crosslinking for liquid permeability. This spatial differentiation of properties resolves the contradiction between reliability and permeability.
Solution Approach 2:
The patent utilizes porous materials by maintaining a porous internal structure with controlled crosslinking density. The pores allow liquid penetration and absorption while the surface crosslinked layer prevents excessive water release under pressure, balancing permeability and rewetting resistance.
3Quantity of substance
If the superabsorbent polymer absorbs large amounts of liquid, then water retention capacity is improved, but urine leakage occurs under user weight pressure
Solution Approach 1:
The surface crosslinked layer acts as a protective barrier prepared in advance to prevent urine leakage. This pre-formed protective layer resists the compressive force of user weight, preventing the absorbed urine from leaking out, thus cushioning against the harmful effect before it occurs.
Solution Approach 2:
The composite structure of the crosslinked superabsorbent polymer with epoxy agents and surfactants creates a material that simultaneously achieves high water retention and pressure resistance, preventing urine leakage while maintaining absorption capacity.
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 resulting superabsorbent polymer exhibits improved water retention, liquid permeability, and reduced rewetting and urine leakage, maintaining a dry state even under pressure.
Implementation Method 1
an acrylic acid-based monomer having acidic groups which are at least partially neutralized and an internal crosslinking agent are crosslinked
Implementation Method 2
A superabsorbent polymer (SAP) is a synthetic polymeric material capable of absorbing moisture from 500 to 1000 times its own weight
Implementation Method 3
heating the base resin in the presence of a surface crosslinking agent to carry out surface modification of the base resin
Implementation Method 4
heating the base resin in the presence of a surface crosslinking agent
Implementation Method 5
an acrylic acid-based monomer having acidic groups which are at least partially neutralized and an internal crosslinking agent are crosslinked in the presence of a sodium polycarboxylate surfactant
Data Source
AI summary
A method of preparing a superabsorbent polymer includes preparing a base resin in which an acrylic acid-based monomer having acidic groups which are at least partially neutralized and an internal crosslinking agent are crosslinked in the presence of a sodium polycarboxylate surfactant; and heating the base resin in the presence of a surface crosslinking agent to carry out surface modification of the base resin, wherein the internal crosslinking agent includes a first epoxy crosslinking agent having an epoxy equivalent weight of 100 g/eq or more to less than 130 g/eq, and a second epoxy crosslinking agent having an epoxy equivalent weight of 130 g/eq or more. The superabsorbent polymer provides improved rewetting property and liquid permeability.