Water-Absorbing Polymer Beads Crosslinking Process
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Solution Overview
Problem
Current methods for producing water-absorbing polymer beads often compromise between high saline flow conductivity and centrifuge retention capacity, requiring additional postcrosslinking steps to achieve optimal performance.
Innovation Solution
A process involving polymerization of a monomer solution with at least 0.5% crosslinker by weight in a gas phase surrounding droplets, resulting in polymer beads with a mean diameter of at least 150 μm, which enhances both saline flow conductivity and centrifuge retention capacity without the need for additional postcrosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the degree of crosslinking is increased to improve gel strength, then the absorption capacity falls and centrifuge retention capacity decreases
Solution Approach 1:
The patent applies local quality by implementing different crosslinking degrees in different regions of the polymer bead. The surface region has a higher crosslinking degree (提供更多的结构强度和凝胶强度), while the core region has a lower crosslinking degree (保持更高的吸收能力). This spatial differentiation of crosslinking density allows the bead to simultaneously achieve both high gel strength and high absorption capacity, resolving the contradiction between these two properties.
2Ease of manufacture
If postcrosslinking is performed to improve saline flow conductivity, then additional process steps are required increasing complexity
Solution Approach 1:
The patent applies preliminary action by incorporating the crosslinking function directly into the polymerization process itself, rather than performing it as a subsequent postcrosslinking step. By using water-soluble crosslinking agents and conducting crosslinking during the polymerization reaction in the aqueous phase, the process achieves both polymer formation and crosslinking in one integrated operation, thereby improving saline flow conductivity without adding process complexity.
3Ease of manufacture
If polymerization is performed in homogeneous phase with high crosslinker content, then permeability improves but particle size control becomes more difficult
Solution Approach 1:
The patent applies parameter changes by systematically optimizing multiple process parameters to achieve both high permeability and controlled particle size. Key parameters include: crosslinker concentration (0.01-10% by weight), monomer concentration (10-50% by weight), polymerization temperature (50-100°C), and pH value (3-7). By carefully adjusting these parameters within specific ranges, the process achieves high permeability through adequate crosslinking while maintaining particle size control through optimized polymerization kinetics and phase behavior.
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 process produces polymer beads with significantly improved saline flow conductivity and centrifuge retention capacity, typically exceeding 200×10−7 cm3 s/g and 30 g/g respectively, while minimizing residual hydrophobic solvent and surfactant content, and maintaining high sphericity.
Implementation Method 1
at least one initiator, wherein the polymerization in the droplet takes place in homogeneous phase
Implementation Method 2
the monomer solution comprises at least 0.5% by weight of the crosslinker b), based on the monomer a)
Implementation Method 3
Being products which absorb aqueous solutions, water-absorbing polymers are used to produce diapers
Implementation Method 4
polymerizing droplets of a monomer solution in a gas phase surrounding the droplets
Data Source
AI summary
A process for preparing water-absorbing polymer beads with high permeability by polymerizing droplets of a monomer solution in a gas phase surrounding the droplets, wherein the monomer solution comprises at least 0.5% by weight of a crosslinker, based on the monomer, the polymerization in the droplet takes place in homogeneous phase, and the polymer beads have a mean diameter of at least 150 μm.