Superabsorbent Polymer Copolymers for Load Absorbency
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Solution Overview
Problem
Current superabsorbent polymers face challenges such as low absorbency under load, salt sensitivity, and gel blockage, which limit their effectiveness in various applications, particularly in hygienic products like diapers and feminine napkins, due to their mechanical weakness and sensitivity to electrolyte solutions.
Innovation Solution
The development of copolymers comprising a major portion of charged monomers and a minor portion of alkyl or aryl end-capped neutral and hydrophilic monomers, lacking free hydroxyl groups, which enhance absorbency under load and reduce salt sensitivity, thereby improving the performance of superabsorbent polymers in a broad range of conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ionic monomers (acrylic acid or methacrylic acid) are used to prepare SAPs, then water absorbing and swelling properties are improved, but salt sensitivity increases and absorbency under load decreases
Solution Approach 1:
The patent uses composite materials by combining ionic monomers (acrylic acid or methacrylic acid) with nonionic hydrophilic monomers (such as polyethylene glycol derivatives) to create copolymer SAPs. This composite approach allows the ionic component to provide water absorption capacity while the nonionic component reduces salt sensitivity, resolving the contradiction between these two properties.
Solution Approach 2:
The patent changes the chemical composition parameters of the SAP by incorporating nonionic hydrophilic monomers with specific molecular weights and hydrophilic groups. This parameter change modifies the polymer's interaction with salt solutions, reducing counterion condensation and maintaining absorbency under load while preserving water absorption capacity.
2Quantity of substance
If charged monomers are used to enhance swelling response, then water absorption is improved, but absorbency under load decreases due to counterion condensation
Solution Approach 1:
The patent creates composite copolymers combining charged monomers with nonionic hydrophilic monomers. The nonionic component provides additional water binding through hydrogen bonding without introducing counterions, thereby maintaining swelling capacity while improving absorbency under load by preventing counterion condensation on the charged groups.
Solution Approach 2:
The nonionic hydrophilic monomers act as intermediaries that provide alternative water binding mechanisms. These monomers with hydroxyl, ether, or carboxyl groups form hydrogen bonds with water molecules, reducing the reliance on electrostatic repulsion and counterion effects, thereby improving mechanical strength and absorbency under load while maintaining swelling 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 proposed solution significantly improves absorbency under load and reduces salt sensitivity, leading to enhanced performance and broader applicability of superabsorbent polymers in consumer products without increasing costs or introducing additional processing steps.
Implementation Method 1
alkyl or aryl end-capped neutral and hydrophilic monomers
Implementation Method 2
Superabsorbent polymers (SAPs) are three-dimensional networks that can absorb and retain water
Implementation Method 3
the counterions such as sodium ions (Na+) present in physiological fluids can effectively screen the polymer backbone charges, resulting in counterion condensation with polymer-bound charged groups and, consequently, reduced counterion entropy and direct chain-chain repulsion forces available to drive a swelling response
Implementation Method 4
SAPs are three-dimensional networks that can absorb and retain water (or other aqueous media) and physiological fluids such as urine and blood more than hundreds times of their own dry weight, typically depending on the ionic concentration of the aqueous solution
Data Source
AI summary
Described herein are superabsorbent polymers that are made of copolymers of charged monomer and neutral monomers, where the neutral monomers are alkyl or aryl end-capped neutral and hydrophilic monomers that lack free hydroxyl groups and have a water solubility of at least 200 mg/mL. The copolymer-based superabsorbent polymers have significantly improved absorbency under load. The compositions and methods described herein are useful in a variety of absorbent products.