Water-absorbing polymer beads saline flow conductivity
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Solution Overview
Problem
Existing methods for producing water-absorbing polymer beads struggle to achieve high saline flow conductivity and centrifuge retention capacity simultaneously, often requiring additional postcrosslinking steps to enhance these properties.
Innovation Solution
A process involving polymerizing droplets of a monomer solution containing ethylenically unsaturated monomers with acid groups, polyvalent cations, and crosslinkers in a gas phase, 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 differentiating the crosslinking degree between the bead surface and interior. Postcrosslinking increases crosslinking density specifically at the bead surface (outer layer) while maintaining lower crosslinking in the bead interior. This spatial differentiation allows the surface to provide mechanical strength and the interior to maintain high absorption capacity, resolving the contradiction between gel strength and absorption capacity.
2Productivity
If postcrosslinking is performed to improve saline flow conductivity, then the degree of crosslinking at the bead surface increases, but this requires additional process steps
Solution Approach 1:
The patent merges the polymerization and crosslinking steps into a single integrated process. By incorporating crosslinkers (divalent or trivalent metal ions) into the monomer solution before polymerization, the crosslinking occurs simultaneously with polymer bead formation in the fluidized bed reactor. This eliminates the need for separate postcrosslinking steps while achieving the desired saline flow conductivity through controlled crosslinking during the main process.
3Reliability
If additional postcrosslinking steps are added to enhance saline flow conductivity and centrifuge retention capacity, then these properties improve, but the process complexity and time increase
Solution Approach 1:
The patent applies preliminary action by pre-incorporating crosslinkers into the monomer solution before polymerization begins. The crosslinking agents (divalent or trivalent metal ions) are mixed with monomers and initiators in advance, ensuring that crosslinking occurs during the polymerization process itself rather than requiring subsequent postcrosslinking steps. This preliminary preparation enables simultaneous achievement of high saline flow conductivity and centrifuge retention capacity while reducing total process time.
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 water-absorbing polymer beads with high saline flow conductivity (typically at least 5×10−7 cm3 s/g) and centrifuge retention capacity (typically at least 10 g/g), achieving the desired properties in a single step without the necessity for additional postcrosslinking.
Implementation Method 1
polymerizing droplets of a monomer solution comprising a) at least one ethylenically unsaturated monomer bearing acid groups, b) at least one crosslinker, c) at least one initiator, d) water, in a gas phase surrounding the droplets
Implementation Method 2
the monomer solution comprises polyvalent cations and the polymer beads have a mean diameter of at least 150 μm
Data Source
AI summary
A process for preparing water-absorbing polymer beads with high permeability by polymerizing droplets of a monomer solution, comprising monomers bearing acid groups, in a gas phase surrounding the droplets, wherein the monomer solution comprises polyvalent cations and the polymer beads have a mean diameter of at least 150 μm.