Aqueous Coatings Using Polyalkoxylate Salts for Extended Open Time
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Solution Overview
Problem
Low volatile organic content (VOC) aqueous coating compositions face challenges in maintaining open time and wet edge time while ensuring film formation and adhesion properties, particularly with the transition to zero VOC binders and low glass-transition temperature coatings.
Innovation Solution
Incorporating an additive composition of phosphorus acid salts and polyalkoxylates with specific molecular weights and ethylene oxide content, combined with aqueous polymers, to enhance open time without compromising film formation and blocking resistance, while maintaining low VOC levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VOCs are used as coalescing agents in aqueous coating compositions, then film formation and open time are improved, but VOC emissions increase
Solution Approach 1:
The patent changes the chemical parameters of the coalescing agent by using polyalkoxylates with specific molecular weights (800-10,000) and ethylene oxide content (20-70 wt.%) instead of traditional VOC-based coalescing agents. This parameter change allows the composition to achieve film formation at lower temperatures while maintaining zero or low VOC content, directly resolving the contradiction between reliable film formation and reduced harmful emissions
Solution Approach 2:
The patent employs water as the primary continuous phase and uses polyalkoxylate salts as temporary coalescing agents that facilitate film formation during application but are designed to be non-volatile and environmentally benign, replacing the traditional approach of using volatile organic compounds that provide temporary benefits but create harmful emissions
2Adaptability or versatility
If the glass-transition temperature of emulsion polymers is reduced for low temperature film formation, then application temperature range is expanded, but open time decreases
Solution Approach 1:
The patent introduces polyalkoxylate salts as intermediary substances that mediate between the emulsion polymer particles during film formation. These intermediaries provide the necessary coalescing action at low temperatures without causing rapid film formation, thereby maintaining extended open time while enabling low temperature application
Solution Approach 2:
The patent changes the physical parameters of the coating composition by incorporating additives that modify the viscosity and coalescing behavior of the emulsion polymer. These parameter changes allow the system to maintain lower glass-transition temperatures for expanded application range while simultaneously preserving open time through controlled coalescing kinetics
3Duration of action of moving object
If polyalkoxylates with high ethylene oxide content are used to improve open time, then open time and wet edge time are extended, but viscosity increases
Solution Approach 1:
The patent optimizes the molecular weight parameter of the polyalkoxylate chains within the specific range of 800-10,000 and controls the ethylene oxide content at 20-70 wt.%. This precise parameter control allows the composition to achieve extended open time through increased polyalkoxylate content while managing viscosity through the selected molecular weight range, preventing excessive thickening
Solution Approach 2:
The patent uses a controlled amount of polyalkoxylate (0.1 to 5 wt.% as solids) which provides sufficient open time extension without requiring excessive quantities that would cause unacceptable viscosity increases. The partial action approach achieves the desired open time benefit while minimizing the adverse viscosity effect
Data Source
AI summary
The present invention provides aqueous compositions which have low or zero volatile organic content (VOC) comprising (i) an open time additive composition of one or more phosphorus acid salts, preferably a phosphoric acid salt, and one or more polyalkoxylates having from 2 to 15 polyalkoxylate chains and an ethylene oxide (EO) content ranging from 20 to 70 wt.%, based on the total weight of polyalkoxylate solids in the composition. The (i) additive compositions may have a solids content as high as 95 wt.%. Further, the compositions may comprise (ii) one or more aqueous polymer, such as for use in coatings or non-cementitious mortars.