Clay-Crosslinked Superabsorbent Polymers via Spray Polymerization
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Solution Overview
Problem
Existing superabsorbent polymers in absorbent articles face challenges with high gel strength leading to gel blocking, reduced absorption speed, and inefficient hydrolysis processes, which hinder their commercial scalability and effectiveness in absorbent applications.
Innovation Solution
The development of clay-crosslinked superabsorbent polymers formed through a spraying process where nano-sized or individual clay particles crosslink polymerizable compounds during polymerization, creating a uniform distribution and avoiding aggregation, thus enhancing absorption capacity and speed while bypassing the need for energy-intensive hydrolysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If internal crosslinking or surface crosslinking is increased to improve gel strength, then resistance against deformation improves, but absorbent capacity is reduced
Solution Approach 1:
The patent applies local quality by creating surface crosslinking through clay particle interaction at the particle surface, while maintaining different crosslinking density in the core region. This allows the surface to provide mechanical strength and resistance against deformation, while the interior maintains higher porosity and absorbent capacity. The clay particles preferentially crosslink at the surface, creating a gradient structure that resolves the contradiction between strength and capacity.
Solution Approach 2:
The patent uses composite materials by combining superabsorbent polymer with nano-sized clay particles to form a hybrid crosslinked structure. The clay particles serve as crosslinking agents that provide both mechanical reinforcement and controlled porosity. This composite approach allows simultaneous achievement of high gel strength through clay-polymer interactions and high absorbent capacity through maintained internal pore structure.
2Strength
If clay is added after polymerization to improve crosslinking, then gel strength improves, but clay aggregation occurs and uniform distribution is lost
Solution Approach 1:
The patent applies preliminary action by incorporating clay particles into the polymerization process itself, rather than adding them after polymerization. The clay particles are present during polymerization and become integrated into the forming polymer network, ensuring uniform distribution at the molecular level. This prevents aggregation that would occur with post-polymerization addition, while still achieving the desired crosslinking and gel strength.
Solution Approach 2:
The patent uses segmentation by utilizing nano-sized clay particles with dimensions in the nanometer range. This fine segmentation allows the clay particles to disperse uniformly throughout the polymer matrix during polymerization, preventing aggregation. The small size enables individual particles to be distributed evenly, creating consistent crosslinking throughout the material without forming large aggregates.
3Ease of manufacture
If hydrolysis process is used to convert polyacrylic esters to polyacrylates, then desired polymer form is achieved, but process time increases and energy consumption increases
Solution Approach 1:
The patent applies parameter changes by directly synthesizing the desired polyacrylate polymer form through polymerization, rather than converting from polyacrylic esters via hydrolysis. By changing the polymerization parameters (monomer selection, initiator type, reaction conditions) to directly produce polyacrylates, the process eliminates the time-consuming hydrolysis step while achieving the target polymer form. This direct synthesis approach maintains manufacturing feasibility while dramatically reducing process time.
4Speed
If absorption speed is increased to improve fluid uptake rate, then fluid distribution improves, but gel strength may be compromised
Solution Approach 1:
The patent applies local quality by creating different structural characteristics in different regions of the polymer particle. The surface region has higher crosslinking density from clay particle interaction, providing mechanical strength, while the interior maintains higher porosity and lower crosslinking density, enabling rapid fluid absorption and distribution. This spatial differentiation of properties allows simultaneous achievement of high absorption speed and adequate gel strength.
Solution Approach 2:
The patent uses composite materials to resolve the speed-strength contradiction. The clay-polymer composite structure provides a dual-function network: clay particles at the surface and interfaces provide mechanical reinforcement for gel strength, while the polymer matrix maintains porous channels for rapid fluid transport. The synergistic combination of clay and polymer phases enables both fast absorption kinetics and sufficient mechanical integrity.
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
This approach results in superabsorbent polymers with improved absorption speed, reduced gel blocking, and enhanced scalability, achieving high sorption capacity and permeability, making them suitable for commercial production and effective in absorbent applications.
Implementation Method 1
whereby said clay particles crosslink said polymers during polymerization, forming individual clay particle crosslinks and/or nano-size clay crosslinks
Implementation Method 2
nano-sized or individual clay particles, which are all introduced into a vessel by a spraying step in the form of a said spray-stream thereof
Implementation Method 3
obtainable by polymerizing in a spray-stream, polymerizable compounds in the presence of a polymerization initiator system
Implementation Method 4
large amounts of bodily fluids, e.g. urine, can be absorbed by the article and locked away
Implementation Method 5
water-swellable polymers (also referred to as absorbent gelling material, AGM, or superabsorbent polymers, SAP's)
Implementation Method 6
gel strength relates to the tendency of the swollen polymer particles (i.e. gel) to resist deformation under an applied stress
Implementation Method 7
maintain a high wet-porosity and have a high resistance against deformation thus yielding high permeability for fluid transport through the swollen gel bed
Data Source
AI summary
Superabsorbent material, comprising clay-crosslinked superabsorbent polymers, obtainable by polymerizing in a spray-stream, polymerizable compounds in the presence of a polymerization initiator system, and nano-sized or individual clay particles, which are all introduced into a vessel by a spraying step in the form of a said spray-stream thereof, whereby said clay particles crosslink said polymers during polymerization. The invention also relates to such a process and absorbent articles comprising such superabsorbent material.