Superabsorbent Polymer Residual Monomer Reduction via Metal Salt
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Solution Overview
Problem
Conventional methods for preparing superabsorbent polymers often result in high concentrations of residual monomer (RM), which can compromise the absorption capacity and stability of these polymers, particularly when used in hygiene applications.
Innovation Solution
A method involving the use of a water-soluble metal salt, such as sodium sulfate, potassium sulfate, or lithium sulfate, is integrated into the polymerization process of superabsorbent polymers, utilizing a combination of ethylenic unsaturated monomers, photoinitiators, crosslinking agents, and thermal polymerization initiators to reduce RM concentrations through radical polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymerization methods are used to prepare superabsorbent polymers, then the polymerization process is simple and fast, but the concentration of residual monomer is high which compromises absorption capacity and stability
Solution Approach 1:
A water-soluble metal salt (sodium sulfate, potassium sulfate, or lithium sulfate) is introduced as an intermediary substance during the polymerization process. This metal salt acts as a mediator that interacts with the polymerization system to reduce residual monomer concentration, thereby improving absorption capacity and stability without fundamentally changing the polymerization methodology
Solution Approach 2:
The invention changes the chemical composition parameters of the polymerization system by adding water-soluble metal salts at specific concentrations (0.01-10 wt% based on monomer weight). This parameter modification affects the polymerization dynamics and final product quality, reducing harmful residual monomers while maintaining acceptable production efficiency
2Object-generated harmful factors
If acrylic acid with low dimer concentration is used to lower residual monomer concentration, then residual monomer concentration decreases, but other properties of the superabsorbent polymer may deteriorate or additional processing becomes complicated
Solution Approach 1:
Instead of changing the monomer properties or adding complex processing steps, a water-soluble metal salt is introduced as a simple intermediary that directly addresses the residual monomer issue during the existing polymerization process, avoiding complications with monomer selection and additional processing
Solution Approach 2:
The invention modifies the polymerization system by adding water-soluble metal salts at controlled concentrations, changing the chemical environment to favor complete polymerization and reduce residual monomers, without requiring changes to monomer selection or process complexity
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 method effectively lowers the concentration of residual monomers in superabsorbent polymers, enhancing their absorption capacity and stability, as demonstrated by the addition of metal sulfates which significantly decrease RM levels, especially when used in appropriate amounts.
Implementation Method 1
reacting a water-soluble ethylenic unsaturated monomer, a photoinitiator, a crosslinking agent, and a thermal polymerization initiator, in the presence of a water-soluble metal salt
Implementation Method 2
adding the mixture obtained in c) with the thermal polymerization initiator, and then performing a radical polymerization reaction using thermal polymerization or photopolymerization
Implementation Method 3
the addition of a water-soluble metal salt in the polymerization process of a superabsorbent polymer is very effective at decreasing the concentration of residual monomer (RM)
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3
AI summary
Disclosed are a superabsorbent polymer including a water-soluble salt and a method of preparing the same, wherein the addition of a water-soluble metal salt in the polymerization process of a superabsorbent polymer is very effective at decreasing the concentration of residual monomer.