Sorbate Ester Coalescent for Low VOC Hard Coatings
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Solution Overview
Problem
Current paint formulations face challenges in achieving low or no odor and low volatile organic chemicals (VOCs) while maintaining desired paint performance attributes, particularly in balancing VOCs with film hardness and durability, as low Tg polymers result in soft coatings and high Tg polymers require volatile coalescents that are undesirable.
Innovation Solution
A composition comprising a stable aqueous dispersion of polymer particles with imbibed sorbate ester or sorbamide coalescent and a radical mediator, which enhances film formation at or below room temperature without high VOC coalescents, providing excellent mechanical strength and reducing color bodies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high Tg polymer latex is used to achieve film hardness, then coating hardness is improved, but volatile coalescents are required which increase VOC content
Solution Approach 1:
The invention changes the chemical parameters of the coalescent by using sorbate esters and sorbamides with specific molecular structures (formula I and II) that have low volatility. These coalescents maintain the necessary film-forming capability at room temperature while significantly reducing VOC emissions compared to conventional volatile coalescents like Texanol
Solution Approach 2:
The invention replicates the film-forming function of volatile coalescents using non-volatile sorbate ester/sorbamide molecules that mimic the plasticizing and coalescing effects without the harmful volatility, thereby achieving the same technical effect without the harmful byproduct
2Temperature
If low Tg polymer latex is used to achieve low temperature film formation, then film formation at room temperature is improved, but coating hardness and durability deteriorate
Solution Approach 1:
The invention creates a composite system combining high Tg polymer particles with sorbate ester/sorbamide coalescents. The high Tg polymer provides the necessary hardness and durability, while the sorbate ester/sorbamide coalescent enables low-temperature film formation by plasticizing the polymer particles during the coalescence process
Solution Approach 2:
The sorbate ester/sorbamide acts as an intermediary substance that facilitates film formation at room temperature by temporarily plasticizing the high Tg polymer particles, enabling them to deform and coalesce without requiring the polymer itself to have low Tg. After film formation, the coalescent remains in the film providing continued flexibility
3Strength
If permanent coalescents are used to achieve film hardness, then coating hardness is improved, but film formation at low temperature deteriorates
Solution Approach 1:
The invention modifies the volatility parameter of permanent coalescents by selecting sorbate esters and sorbamides with specific boiling points and vapor pressures that allow them to remain in the film after application. These coalescents maintain plasticizing effects at room temperature while providing long-term stability and hardness
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 composition achieves hardening of coatings without volatile coalescents, offering excellent mechanical strength and low temperature film formation properties, while reducing undesirable color bodies and VOC content.
Implementation Method 1
a radical mediator to reduce color bodies in the composition
Implementation Method 2
The composition provides a way to enhance film formation of coatings at or even below room temperature, prepared using relatively high Tg latexes without the aid of high volatile organic content (VOC) coalescents
Data Source
AI summary
The present invention is a composition comprising a stable aqueous dispersion of polymer particles and a sorbate ester, which is a liquid at 20 °C and has a molecular weight in the range of 125 to 500 g/mol. The composition of the present invention provides a way to enhance film formation of coatings prepared using relatively high Tg latexes without the aid of high volatile organic content (VOC) coalescents.