Voided Core-Shell Opacifiers for Organic Solvent Resistance
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Solution Overview
Problem
Current polymeric hollow latex particles used as opacifiers in non-water-based coating compositions, such as alkyd paints, lack resistance to organic solvents, causing them to collapse and lose their hiding power, resulting in a short shelf life.
Innovation Solution
Development of voided polymeric core-shell particles with a hollow interior, an interior shell, an intermediate shell, and an outer shell composed of methyl methacrylate, which maintains structural integrity in organic solvents for extended periods, using a multi-stage emulsion polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polymeric hollow latex particles are used as opacifiers in organic-based coating compositions, then cost-effectiveness and reduced weight are achieved, but the particles collapse and lose hiding power due to lack of resistance to organic solvents
Solution Approach 1:
The patent applies composite materials by creating a multi-layered particle structure combining different polymer materials with complementary properties. The core-shell architecture uses a hydrophilic polymer core (providing swelling capability) encapsulated by a hydrophobic polymer shell (providing solvent resistance), forming a composite that achieves both opacifying performance and chemical stability in organic media.
Solution Approach 2:
The patent applies local quality by assigning different functional properties to different regions of the particle. The core region provides swelling capability for opacity formation, while the shell region provides solvent resistance to maintain structural integrity. This spatial differentiation of material properties allows the particle to simultaneously achieve both hiding power and durability in organic coatings.
2Reliability
If the outer shell is made of poly(methyl methacrylate) to provide solvent resistance, then long-term stability in organic solvents is achieved, but the particle may be too rigid and less compatible with typical latex emulsion processes
Solution Approach 1:
The patent applies parameter changes by carefully controlling the glass transition temperature (Tg) of the poly(methyl methacrylate) shell to fall within the range of 60-100°C. This parameter adjustment ensures the shell maintains sufficient solvent resistance while remaining compatible with typical emulsion polymerization conditions and latex processing temperatures, balancing performance with manufacturability.
3Ease of manufacture
If the particle structure is simplified to ease manufacturing, then production cost and complexity are reduced, but the particle may lack sufficient resistance to organic solvents
Solution Approach 1:
The patent applies segmentation by dividing the particle into distinct functional regions: a hydrophilic polymer core and a hydrophobic polymer shell. This segmentation allows each region to be optimized for its specific function while maintaining overall structural integrity. The clear division between core and shell enables straightforward emulsion polymerization processes while achieving superior solvent resistance through the hydrophobic outer layer.
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 particles retain their opacity and structural integrity in organic solvents for at least 30 days, maintaining over 75% of their initial Y Reflectance value, even after storage for 30 days at 25°C, making them suitable for long-term use in alkyd coating compositions.
Implementation Method 1
The invention also relates to emulsion polymerization processes for forming these particles
Implementation Method 2
one or more free radical polymerizable hydrophilic monoethylenically unsaturated monomers and one or more free radical polymerizable non-ionic monoethylenically unsaturated monomers
Implementation Method 3
These particles are effective opacifiers due to their light-scattering property, which comes from the difference in refractive index between the air contained in their interior hollow core and their outer shell
Implementation Method 4
light-scattering property, which comes from the difference in refractive index between the air contained in their interior hollow core and their outer shell
Implementation Method 5
an interior shell comprised of a first polymer, wherein the first polymer is hydrophilic and swellable with an aqueous swelling solution
Implementation Method 6
have long-term resistance to common organic solvents that can be used in non-water-based coating compositions
Data Source
AI summary
Disclosed are voided latex particles, useful as opacifying agents for coating compositions containing organic solvents. The particles have a hollow interior, which substantially maintains its integrity after the particles are placed in contact with an organic solvent at 25° C. for 30 days. The particles also have a hydrophilic polymeric interior shell surrounding the hollow interior that is swellable with an aqueous swelling solution. The particles have first and second polymeric intermediate shells, surrounding the interior shell, formed from polymers that are different from each other and different from the interior shell polymer. Finally, the particles have an outer polymeric shell, surrounding the interior shells, which is formed from up to 100% by weight, as polymerized units, of methyl methacrylate. The interior shells and the outer shell each have a Tg greater than 60° C. Also disclosed is a multi-stage emulsion process for making the particles.