Composite Particles for Opacifying Coatings
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Solution Overview
Problem
Existing formulations of opacifying coatings face challenges in achieving high opacity with minimal pigment usage, as polyacrylic acid and polymethacrylic acid homopolymers and copolymers do not effectively promote robust latex-pigment composite particle formation, leading to poor color acceptance and reduced opacity.
Innovation Solution
A stable aqueous dispersion is created using composite particles comprising pigment particles coated with a water-soluble polymer containing ethylenically unsaturated carboxylic acid and N-containing monomers, along with water-insoluble polymer particles, which enhances opacity and hiding efficiency in dry coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyacrylic acid and polymethacrylic acid homopolymers and copolymers are used as dispersants, then the coating formulation is simple and easy to manufacture, but composite particle formation is weak leading to poor opacity and color acceptance
Solution Approach 1:
The patent changes the chemical parameters of the dispersant by using copolymers containing both carboxylic acid groups and N-containing groups (such as amino or amido groups) with specific molecular weights and compositional ratios. This parameter change enables robust composite particle formation while maintaining ease of manufacture, resolving the contradiction between simple formulation and effective particle formation.
Solution Approach 2:
The patent employs composite polymer structures combining different functional monomers (carboxylic acid monomers and N-containing monomers) in specific ratios. This composite material approach creates dispersants with dual functionality: carboxylic acid groups for pigment interaction and N-containing groups for enhanced polymer-pigment binding, thereby improving composite particle formation without complicating the manufacturing process.
2Reliability
If more opacifying pigment is used to maximize hiding, then opacity is improved, but the amount of pigment increases leading to higher material cost and reduced efficiency
Solution Approach 1:
The patent segments the pigment dispersion into composite particles where multiple polymer-coated pigment particles associate together. This segmentation creates larger effective scattering units that provide enhanced opacity per unit of pigment, reducing the total pigment quantity needed while maintaining or improving hiding efficiency.
Solution Approach 2:
The patent introduces specially designed copolymer dispersants as intermediaries that mediate between pigment particles and the aqueous medium. These dispersants promote robust composite particle formation that enhances light scattering efficiency, allowing reduced pigment usage while achieving target opacity levels.
3Reliability
If robust latex-pigment composite particle formation is achieved, then opacity and hiding efficiency are improved, but the dispersion viscosity increases and stability decreases
Solution Approach 1:
The patent optimizes multiple parameters of the copolymer dispersant including molecular weight (1,000-25,000), compositional ratios (carboxylic acid 10-30%, N-containing 5-95%), and structural characteristics. These parameter changes enable the formation of stable composite particles with controlled size and distribution, achieving robust particle formation while maintaining dispersion stability and low viscosity.
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 solution provides a stable, low viscosity dispersion that effectively promotes composite particle formation, resulting in improved opacity and hiding efficiency in dry coatings, while minimizing the use of opacifying pigment.
Implementation Method 1
a pigment particle having disposed thereon a water-soluble polymer
Implementation Method 2
provide whiteness and opacity or 'hiding' to dry coatings
Data Source
AI summary
A stable aqueous dispersion including certain composite particles and a method for forming the stable aqueous dispersion is provided. The composite particles include a pigment particle, the pigment particle having disposed thereon a certain water-soluble polymer including copolymerized carboxylic acid monomer and N-containing monomer and the pigment particle bearing the water-soluble polymer having disposed on it a plurality of water-insoluble polymer particles. Also provided is a dry coating formed from the aqueous dispersion.