Low VOC Coating Additive for Extended Wet Edge and Open Time
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Solution Overview
Problem
Aqueous coatings have limited wet edge and open times due to high molecular weight polymers, leading to rapid viscosity increase and reduced repair time, while additives like alkylene glycols increase VOC content, necessitating a solution that prolongs these times without raising VOC levels.
Innovation Solution
A coating additive comprising a water-dispersible polymer with a glass transition temperature between 20° C and 160° C, a water-insoluble plasticizer with a molecular weight under 1000 g/mole, and cyclohexanedimethanol, which maintains low VOC content and improves drying characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aqueous coatings use high molecular weight polymers as binder material, then the coating provides adequate film formation and durability, but the wet edge time and open time are shortened due to rapid viscosity increase
Solution Approach 1:
The patent changes the molecular weight parameter of the polymer from high (conventional) to low (5,000-500,000 g/mol), which slows down the viscosity increase rate during drying while maintaining adequate film formation. This parameter change directly addresses the contradiction by allowing longer wet edge and open times without sacrificing film quality.
Solution Approach 2:
The patent creates a composite coating system combining low molecular weight polymer with specific additives (0.1-10% by weight) to achieve the desired performance. The composite approach allows the low MW polymer to provide extended open time while the additive system maintains film formation properties, resolving the contradiction between durability and working time.
2Duration of action of moving object
If alkylene glycols are added to aqueous coatings to prolong wet edge and open times, then the drying characteristics are improved, but the VOC content increases which violates regulations
Solution Approach 1:
The patent extracts and eliminates alkylene glycols (VOC-containing substances) from the coating formulation. Instead, it uses low molecular weight polymers and alternative additives that do not contribute to VOC content, thereby prolonging wet edge and open times without violating VOC regulations.
Solution Approach 2:
The patent replaces conventional high MW polymers with low MW polymers that serve as temporary viscosity modifiers during the drying process. These low MW polymers provide the necessary extended open time but are designed to be fully incorporated into the film without leaving harmful residues, effectively serving as temporary functional agents.
3Object-generated harmful factors
If the amount of alkylene glycols is reduced to comply with VOC regulations, then the VOC content decreases, but the wet edge and open times are reduced
Solution Approach 1:
The patent fundamentally changes the approach by using low molecular weight polymers (5,000-500,000 g/mol) instead of relying on alkylene glycol concentration adjustments. This parameter change in polymer molecular weight provides a VOC-free mechanism to control and extend wet edge and open times independently of VOC content.
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 additive extends wet edge and open times, enhances scrub resistance, and maintains low VOC content, addressing the limitations of aqueous coatings while ensuring coating performance.
Implementation Method 1
the dispersed polymer particles tend to coalesce in the edge region of an applied coating relatively soon after the coating has been applied. As a continuous film is formed, the viscosity of the coating increases rapidly
Implementation Method 2
a water-dispersible polymer having a glass transition temperature (Tg) of at least about 20° C. and a water-insoluble plasticizer having a molecular weight of less than 1000 g/mole
Data Source
AI summary
Disclosed is a low VOC coating additive employing a water-dispersible polymer, a water insoluble plasticizer, cyclohexanedimethanol, and optionally an amphiphilic component. The additive can be added to a coating to improve at least one performance characteristics of the coating, such as, wet-edge time, open time, scrub resistance, wet adhesion, and water resistance.