Stable Polymer Dispersion with Colloidal Silica via pH Control
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Solution Overview
Problem
Polymer dispersions comprising colloidal silica particles are not stable enough for long-term storage, limiting their application in the coating industry due to gel formation.
Innovation Solution
A method involving contacting an aqueous dispersion of de-ionized acidic colloidal silica particles with a first mixture of monomers, polymerizing at a specific pH range, and adding a second mixture of monomers at a controlled rate to complete polymerization, using ethylenically unsaturated nonionic monomers, to create a stable polymer dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If colloidal silica particles are added to polymer dispersions to improve performance, then dirt pick up resistance, hardness, and stain blocking performances are improved, but the dispersion stability deteriorates and gel formation occurs
Solution Approach 1:
The patent applies parameter changes by controlling the pH level during polymerization (maintaining pH between 2-7, preferably 3-5) and using de-ionized acidic colloidal silica particles. These parameter changes prevent gel formation while maintaining dispersion stability and improving hardness, directly resolving the technical contradiction between strength enhancement and stability maintenance.
2Object-affected harmful factors
If colloidal silica particles are added to polymer dispersions to improve performance, then dirt pick up resistance, hardness, and stain blocking performances are improved, but the dispersion becomes unstable for long-term storage
Solution Approach 1:
The patent uses parameter changes by controlling pH levels (2-7) and using de-ionized acidic colloidal silica particles to prevent gel formation during storage. This enables long-term storage stability while maintaining improved dirt pick up resistance, resolving the contradiction between performance enhancement and storage duration.
3Object-affected harmful factors
If colloidal silica particles are added to polymer dispersions, then stain blocking performance is improved, but gel formation occurs limiting application
Solution Approach 1:
The patent applies parameter changes by maintaining specific pH levels (2-7) and using de-ionized acidic colloidal silica particles to prevent gel formation. This ensures both improved stain blocking performance and reliable application suitability, resolving the technical contradiction between performance and reliability.
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 method results in a stable polymer dispersion suitable for long-term storage, with improved in-process and coating stability, as demonstrated by reduced gel formation and viscosity changes over time.
Implementation Method 1
polymerizing such combination at an initial pH of from 2 to 5 to at least 90% in completion; and (iii) adding a second mixture of monomers at a rate equal to the rate of consumption of such second mixture of monomers to continue and complete the polymerization
Data Source
AI summary
A method of preparing a polymer dispersion comprising (i) contacting an aqueous dispersion of de-ionized acidic colloidal silica particles with a first mixture of monomers to form a combination；(ii) polymerizing such combination at an initial pH of from 2 to 5 to at least 90％ in completion；and (iii) adding a second mixture of monomers at a rate substantially equal to the rate of consumption of such second mixture of monomers to continue and complete the polymerization. The present invention further provides a polymer dispersion made from the above method.