Composite Superabsorbent Particles via Dual Surface Crosslinking
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Solution Overview
Problem
Current superabsorbent polymers (SAPs) derived from polyacrylate are not biodegradable and rely on non-renewable petroleum resources, and their polysaccharide alternatives, such as carboxymethyl starch (CMS) particles, face challenges in achieving high Free Swell Capacity (FSC), Centrifuge Retention Capacity (CRC), Absorbance Under Load (AUL), and Saline Flow Rate (SFR) comparable to polyacrylate SAPs.
Innovation Solution
A composite superabsorbent material comprising a blend of carboxyalklated polysaccharides and synthetic polycarboxylate polymers, dual-surface crosslinked via ester linkages with C2-C4 polyols and trivalent metal salts, specifically aluminum sulfate, to enhance FSC, CRC, AUL, and SFR, with a weight ratio of 55:45 to 80:20 for the polycarboxylate polymer to carboxymethyl starch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If polysaccharide alternatives like carboxymethyl starch (CMS) are used to replace polyacrylate SAPs, then biodegradability and ecological sustainability are improved, but FSC, CRC, AUL, and SFR properties deteriorate
Solution Approach 1:
The patent creates composite superabsorbent particles by combining carboxymethyl starch (biodegradable polysaccharide) with polyacrylate polymer (synthetic polymer). This composite structure allows the material to benefit from both the biodegradability of starch and the high absorbency of polyacrylate, resolving the contradiction between ecological sustainability and performance reliability
Solution Approach 2:
The patent applies surface crosslinking treatment specifically to the surface of the composite particles using polyols and trivalent metal salts. This localized modification enhances the surface properties to improve FSC, CRC, AUL, and SFR performance without altering the bulk biodegradable starch structure, thus maintaining both ecological benefits and absorbency performance
2Reliability
If polyacrylate SAPs are used to achieve high absorbency, then FSC, CRC, and AUL properties are improved, but biodegradability and ecological sustainability worsen
Solution Approach 1:
The patent formulates composite particles where biodegradable carboxymethyl starch serves as the base matrix and polyacrylate polymer is incorporated as a functional component. This composite approach maintains the biodegradable nature of the starch while introducing high-performance absorbency characteristics from the polyacrylate, reversing the traditional composition hierarchy
Solution Approach 2:
Surface crosslinking with polyols and trivalent metal salts is applied locally to enhance the absorbency performance of the composite particles. This surface treatment improves FSC, CRC, and AUL properties without compromising the bulk biodegradability of the starch matrix, allowing high performance with ecological sustainability
3Object-affected harmful factors
If carboxymethyl starch particles are used as substitutes for polyacrylate SAPs, then ecological sustainability is improved, but Saline Flow Rate (SFR) property deteriorates
Solution Approach 1:
The patent applies surface crosslinking treatment specifically to the surface of carboxymethyl starch particles using polyols and trivalent metal salts. This localized surface modification enhances the SFR property by controlling the gel structure and pore formation at the particle surface, allowing rapid saline flow while maintaining the bulk biodegradable starch structure
Solution Approach 2:
The patent modifies the physical and chemical parameters of the carboxymethyl starch surface through crosslinking with polyols and trivalent metal salts. This parameter change in surface structure and composition improves the SFR property, enabling carboxymethyl starch to achieve saline flow rates comparable to conventional polyacrylate SAPs
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 composite particles exhibit improved FSC, CRC, AUL, and SFR values, with FSC of at least 40 g/g, CRC of at least 25 g/g, AUL of at least 15 g/g under 0.7 psi, and SFR of at least 50 ml/min with 0.9% saline, making them suitable substitutes for conventional polyacrylate SAPs in absorbent products.
Implementation Method 1
dual-surface crosslinked via formation of esters through a C 2 -C 4 polyol
Implementation Method 2
dual-surface crosslinked via formation of esters through a C 2 -C 4 polyol and with a trivalent metal salt
Implementation Method 3
Free Swell Capacity (FSC), which is a measure of the grams of a standardized solution that can absorbed per gram of particles
Implementation Method 4
Saline Flow Rate (SFR) is used to measure the flow of 0.9% saline in a standardized apparatus filled with test SAPs
Data Source
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AI summary
A dual-surface treated composite superabsorbent particle comprising a polycarboxylate polymer (e.g., saponified polyacrylamide) and a carboxylated starch polymer is disclosed. The surface of the particle is cross linked through esterification with a C2-C4 polyol exemplified with glycerol. In addition, the surface region is crosslinked through ionic bonds with a trivalent metal ion exemplified with aluminum. In a critical method of making, the acidification of the surface with the polyol occurs prior to treatment with the trivalent metal ion, which results is a hybrid particle that can include up to about 40% of carboxymethyl starch yet exhibit a FSC of at least 47 g/g, a CRC of at least 27 g/g, an AUL of at least 18 g/g under a load of 0.7 psi, and a SFR of at least 180 ml/min. Also disclosed is a method of making that includes a surface esterification prior to aluminum treatment.