Aqueous Polymer Dispersion Microparticles
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Solution Overview
Problem
Current aqueous polymer dispersions for metal food and drink containers are limited by large particles, leading to uneven coatings and poor adhesion, and are often available only in organic solvents containing volatile organic compounds (VOCs), which are environmentally unfriendly.
Innovation Solution
A process involving a mixture of high viscosity polymers, where one polymer is immiscible in water and the other has dispersing groups, is melted under high shear in an extruder, reacted if possible, and then quenched to form a solid product that is broken down into smaller pieces and contacted with an aqueous medium, resulting in a dispersion of microparticles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight polymers are used to improve adhesion and flexibility, then coating performance is improved, but particle size becomes too large for thin film applications
Solution Approach 1:
The patent segments the high molecular weight polymer into microparticles of controlled size (0.01-10 μm) through a two-stage process: first forming a gel network in aqueous medium, then applying high shear force to break it into uniform microparticles. This segmentation enables thin film applications while preserving the adhesive properties of high molecular weight polymers.
Solution Approach 2:
The patent changes the physical state of the polymer from solid high viscosity material to aqueous gel dispersion, then to microparticle suspension. By controlling parameters such as water content (10-90 wt%), pH (2-12), and shear rate during processing, the patent achieves uniform microparticle sizes suitable for thin film coating while maintaining the performance benefits of high molecular weight polymers.
2Strength
If organic solvent dispersions are used to achieve good coating properties, then coating performance is improved, but volatile organic compounds (VOCs) are released which are environmentally unfriendly
Solution Approach 1:
The patent converts the traditionally harmful organic solvent system into a beneficial aqueous system. By using water as the dispersion medium instead of organic solvents, the patent eliminates VOC emissions while achieving comparable or superior coating performance through the controlled microparticle formulation and gel network structure.
Solution Approach 2:
The patent changes the dispersion medium from organic solvent to water, fundamentally altering the chemical composition to eliminate harmful VOCs. Additional parameter changes include adjusting pH (2-12) and ionic strength to stabilize the aqueous dispersion and control microparticle properties, achieving environmentally friendly coatings with maintained performance.
3Quantity of substance
If polymer dispersions with large particles are used, then high molecular weight polymers are available, but the coatings become uneven with poor adhesion and protective properties
Solution Approach 1:
The patent segments the polymer into uniformly sized microparticles (0.01-10 μm) through controlled gelation followed by high shear fragmentation. This segmentation maintains the high molecular weight benefits for adhesion and flexibility while achieving uniform distribution and smooth coating formation, eliminating the unevenness caused by large particle aggregates.
Solution Approach 2:
The patent introduces water as an intermediary medium that forms a gel network with the polymer, then uses this gel structure as a precursor to microparticles. The gelation process and subsequent high shear treatment act as intermediary steps that transform the polymer into a stable microparticle dispersion, ensuring uniform coating application while preserving high molecular weight properties.
4Volume of moving object
If very thin films (≤10 μm) are applied to reduce material usage, then coating thickness is reduced, but the coating must be free of particulate matter greater than this size
Solution Approach 1:
The patent segments the polymer into microparticles with maximum size of 10 μm, matching the minimum coating thickness requirement. This segmentation ensures that no particulate matter exceeds the film thickness, enabling application of very thin films (≤10 μm) without defects from large particles, while maintaining adequate material coverage for protective properties.
Solution Approach 2:
The patent controls particle size parameters through adjustment of water content (10-90 wt%), pH (2-12), and shear rate during processing. By optimizing these parameters, the patent produces microparticles sized 0.01-10 μm that are suitable for thin film applications, ensuring complete particle incorporation into the film without protruding defects.
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
This process produces stable aqueous dispersions with microparticles of high molecular weight polymers, achieving improved adhesion, flexibility, and chemical resistance while avoiding VOCs, suitable for thin film coatings on metal containers.
Implementation Method 1
causing the polymers to melt at a chosen temperature under conditions of high shear in an extruder to form an intimate mixture of the polymers
Implementation Method 2
quench cooling the molten mixture of step ii) or step iii) outside the extruder to form a solid product
Implementation Method 3
contacting the solid product with the aqueous medium wherein the aqueous medium dissolves the second polymer but not the first polymer to form a dispersion comprising microparticles of the first polymer in an aqueous solution of the second polymer
Data Source
AI summary
A process for the manufacture of an aqueous polymer dispersion comprising the steps of i)providing a mixture of a first and second polymer each having a viscosity greater than 30 Pa·s at 100s−1 when measured at 100° C., the mixture comprising a) from 1 to 60 parts by weight of a first polymer immiscible in aqueous medium and optionally comprising reactive moieties and b) from 40 to 99 parts by weight of a second polymer comprising dispersing 10 groups, the polymer being miscible in the aqueous medium and optionally further comprising moieties reactive with the moieties on the first polymer ii) causing the polymers to melt at a chosen temperature under conditions of high shear in an extruder to form an intimate mixture of the polymers iii)optionally causing the reactive moieties of the first and second polymer to 1 react with each other under conditions of high shear in an extruder, to form a reacted mixture iv) quench cooling the molten mixture of step ii) or step iii) outside the extruder to form a solid product v) optionally breaking up the solid product into smaller pieces 20 vi) contacting the solid product with the aqueous medium wherein the aqueous medium dissolves the second polymer but not the first polymer to form a dispersion comprising microparticles of the first polymer in an aqueous solution of the second polymer.