Aqueous Polymer Dispersion Storage Stability via Core-Shell Design
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Solution Overview
Problem
Aqueous dispersions of core-stage polymer particles obtained through existing methods are not storage-stable, especially at elevated temperatures, and require substantial amounts of crosslinker to achieve desired properties.
Innovation Solution
A process for preparing aqueous dispersions of polymer particles by radical aqueous emulsion polymerization, involving specific monomer compositions and sequential polymerization steps to form a core-shell structure with an internal water content, which enhances storage stability and whiteness without relying on high crosslinker amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If substantial amounts of crosslinker are used to achieve desired properties of hollow organic particles, then the particle strength and structural integrity are improved, but the storage stability of the aqueous dispersion deteriorates, especially at elevated temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the core and shell polymers, specifically using polyalkylene oxide-containing substances in the core and carboxylic acid-containing monomers in the shell. This compositional parameter change enables the particles to achieve both strength and storage stability without requiring excessive crosslinker.
Solution Approach 2:
The patent creates a composite core-shell structure where the core contains polyalkylene oxide-containing polymer and the shell contains carboxylic acid-containing polymer. This composite material approach allows the different components to contribute their specific properties: the core provides structural integrity while the shell provides stability, eliminating the need for high crosslinker amounts.
2Illumination intensity
If hollow organic particles are used to enhance whiteness in cosmetic compositions and paper coatings, then the optical properties are improved, but the requirement for substantial crosslinker to maintain particle integrity increases
Solution Approach 1:
The patent modifies the monomer composition parameters to include specific ratios of polyalkylene oxide-containing substances (20-60 wt%) and carboxylic acid-containing monomers (5-30 wt%). This parameter optimization allows the particles to maintain their hollow structure and optical properties without requiring excessive crosslinker.
Solution Approach 2:
The patent incorporates stabilizing functional groups (carboxylic acid groups in the shell) during the polymerization process itself, before the particles are subjected to storage or application. This preliminary incorporation of stability-providing groups eliminates the need for additional crosslinker to be added later for stabilization purposes.
3Temperature
If the aqueous dispersion is stored at elevated temperatures for prolonged periods, then the processing flexibility is improved, but the storage stability deteriorates due to particle aggregation or degradation
Solution Approach 1:
The patent changes the chemical composition to include carboxylic acid-containing monomers in the shell (5-30 wt%), which provide thermal stability through hydrogen bonding and electrostatic repulsion between particles. This compositional parameter allows the dispersion to withstand elevated storage temperatures without aggregation.
Solution Approach 2:
The carboxylic acid groups in the shell provide a feedback mechanism where they form protective hydration shells around the particles and create electrostatic repulsion that prevents aggregation. This self-regulating mechanism automatically activates at elevated temperatures to prevent degradation, without requiring external stabilization.
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 results in storage-stable polymer particle dispersions with enhanced whiteness and controlled particle size, maintaining stability at elevated temperatures with reduced crosslinker usage.
Implementation Method 1
preparing an aqueous dispersion of polymer particles by radical aqueous emulsion polymerization
Implementation Method 2
the method which is preferred for environmental as well as economic reasons is that of osmotically swelling specific core-shell particles
Data Source
AI summary
The present invention relates to a process for preparing an aqueous dispersion of polymer particles by radical aqueous emulsion polymerization and also to the use thereof in paints, paper coatings, foams, crop protection compositions, cosmetic compositions, liquid inks, or thermoplastic molding compounds.