Thermal Post-Treatment of Water-Absorbing Polymer Particles
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Solution Overview
Problem
Existing methods for removing residual monomers from water-absorbing polymer particles often lead to the formation of agglomerates at higher water contents, which is undesirable in the production of hygiene products and agricultural applications.
Innovation Solution
A thermal post-treatment process using rotating mixing tools at temperatures above 60°C with a water content of at least 8% by weight, in the presence of a surfactant with both polar and non-polar groups, where the surfactant's groups remain connected even under thermal conditions, to prevent agglomerate formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal post-treatment is performed with steam or water at high water content to remove residual monomers, then residual monomer removal is improved, but agglomerate formation increases
Solution Approach 1:
A surfactant is introduced as an intermediary substance during thermal post-treatment. The surfactant molecules adsorb at the interface between water and polymer particles, reducing surface tension and preventing agglomerate formation. This allows effective thermal treatment at high water content (at least 8 wt.%) to remove residual monomers while maintaining particle dispersion stability.
Solution Approach 2:
The invention changes the chemical parameters of the treatment system by selecting specific surfactant types (non-ionic, anionic, or cationic) with appropriate molecular structures. The surfactant's polar and non-polar groups remain connected under thermal conditions, creating a stable interfacial film that prevents agglomeration while allowing effective monomer removal through thermal treatment.
2Productivity
If thermal post-treatment temperature is increased to improve monomer removal efficiency, then processing speed increases, but energy consumption and risk of particle degradation increase
Solution Approach 1:
The invention optimizes the temperature parameter within a specific range (60-140°C) to achieve effective monomer removal without excessive energy consumption. The presence of surfactant allows the process to be conducted at moderate temperatures where the surfactant remains stable and effective, avoiding the need for high-temperature treatment that would increase energy consumption and risk particle degradation.
3Reliability
If conventional surfactants with carboxylic ester groups are used, then surface activity is achieved, but thermal stability during post-treatment deteriorates
Solution Approach 1:
The invention changes the chemical structure parameter of the surfactant by excluding compounds with hydrolysis-sensitive carboxylic ester groups. Instead, it employs surfactants where polar and non-polar groups remain connected under thermal conditions through stable bonds. This structural modification ensures thermal stability during post-treatment while maintaining surface activity and agglomeration prevention capabilities.
Data Source
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AI summary
The invention relates to a method for removing residual monomers from water-absorbing polymer particles, wherein the water-absorbing polymer particles are thermally post-treated in a mixer having rotating mixing tools at a temperature of at least 60°C in the presence of water and a tenside.