Superabsorbent Polymer Epoxy Crosslinking Rewetting
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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 method of preparing a superabsorbent polymer involving the crosslinking of acrylic acid-based monomers with a combination of first and second epoxy crosslinking agents, followed by surface modification, to enhance absorption properties and prevent rewetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a superabsorbent polymer absorbs liquid, then absorption capacity is improved, but rewetting phenomenon occurs under pressure
Solution Approach 1:
The patent changes the chemical parameters of the polymer by using specific epoxy equivalent weights (100-130 g/eq for first crosslinking agent, 130 g/eq or more for second crosslinking agent) and controlling the degree of neutralization of acrylic acid groups. These parameter changes create a polymer network that maintains absorption capacity while preventing rewetting under pressure.
Solution Approach 2:
The patent creates a composite crosslinking system combining two different epoxy crosslinking agents with distinct molecular weight characteristics. This composite approach generates a dual-network structure that simultaneously provides high absorption capacity and resistance to pressure-induced rewetting, resolving the contradiction between these two properties.
2Object-generated harmful factors
If crosslinking density is increased to suppress rewetting, then rewetting resistance is improved, but liquid permeability deteriorates
Solution Approach 1:
The patent applies local quality by creating regions with different crosslinking densities through the use of two epoxy crosslinking agents with different molecular weights. The first crosslinking agent (100-130 g/eq) creates local networks that maintain permeability, while the second crosslinking agent (130 g/eq or more) creates regions that provide rewetting resistance, achieving both properties simultaneously.
3Quantity of substance
If polymer volume is expanded by absorbing water, then absorption capacity is improved, but shape retention deteriorates
Solution Approach 1:
The patent performs preliminary crosslinking action before the polymer absorbs water and expands. By pre-establishing a robust crosslinked network structure using the two epoxy agents, the polymer is prepared to maintain its shape even when volume expands during water absorption, preventing collapse or deformation.
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
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
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
A superabsorbent polymer (SAP) is a synthetic polymeric material capable of absorbing moisture from 500 to 1000 times its own weight
Implementation Method 6
superabsorbent polymers are required to exhibit high absorbency with respect to water, etc., and not to release the absorbed water even under an external pressure
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; 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. A superabsorbent polymer having improved rewetting property liquid permeability is also provided.