Water-absorbing polymer particles with cracked shell for high swell rate
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Solution Overview
Problem
Current methods for producing water-absorbing polymer particles do not effectively enhance the free swell rate while maintaining the necessary properties such as high saline flow conductivity and centrifuge retention capacity, often resulting in particle agglomeration and reduced mechanical stability.
Innovation Solution
A process involving polymerization, drying, grinding, classification, thermal surface postcrosslinking, and controlled remoisturization to increase the moisture content of the polymer particles, which enhances the free swell rate by forming cracks in the highly crosslinked shell without causing agglomeration, and subsequent dynamic drying to achieve optimal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-absorbing polymer particles are surface postcrosslinked to improve saline flow conductivity and absorption under pressure, then the crosslinking of the particle surface increases, but the free swell rate decreases
Solution Approach 1:
The patent applies surface erosion to create a porous or cracked shell structure on the polymer particles. This porous surface layer allows water to penetrate more rapidly into the particle interior, thereby increasing the free swell rate despite the high crosslinking density that improves saline flow conductivity. The controlled degradation of the shell creates pathways for faster water absorption.
Solution Approach 2:
The patent changes the physical and chemical parameters of the particle surface through controlled degradation processes. By modifying the shell structure (creating cracks or porous regions) while maintaining the crosslinked core, the surface properties are altered to enable faster water penetration without compromising the absorption capacity under pressure.
2Reliability
If the amount of crosslinker is increased to improve absorption under pressure, then the absorption under pressure increases, but the centrifuge retention capacity falls
Solution Approach 1:
The patent applies different crosslinking densities to different regions of the particle. The core maintains high crosslinking density for optimal absorption under pressure, while the shell has reduced crosslinking or is intentionally degraded to maintain porosity and water permeability. This spatial differentiation of properties allows both absorption capacity and retention capacity to be optimized simultaneously.
Solution Approach 2:
The particle structure is segmented into distinct functional zones: a highly crosslinked core for absorption under pressure and a degraded/porous shell for rapid water intake. This segmentation allows each region to perform its specific function optimally without interfering with the other property requirements.
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 significantly increases the free swell rate of water-absorbing polymer particles, improving their saline flow conductivity and centrifuge retention capacity while maintaining mechanical stability and preventing particle agglomeration, resulting in enhanced performance for applications like hygiene products and market gardening.
Implementation Method 1
the moisture content of the water-absorbing polymer particles after the thermal surface postcrosslinking is increased by 1 to 150% by weight
Implementation Method 2
polymerizing a monomer solution or suspension comprising a) at least one ethylenically unsaturated monomer which bears acid groups
Implementation Method 3
thermally surface postcrosslinking them
Implementation Method 4
by drying, grinding and classifying the polymer gel
Data Source
AI summary
The invention relates to a process for producing water-absorbing polymer particles with high free swell rate, comprising the steps of polymerization, drying, grinding, classification and thermal surface postcrosslinking, remoisturization and drying again.