Alkali Swellable Polymer Particles for Low VOC Coating Open Time
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Solution Overview
Problem
Waterborne coating formulations typically have a short open time, limiting the period during which a freshly applied paint film can be reworked without leaving brush marks, while maintaining other essential paint properties like film adhesive and cohesive strength, which is compromised compared to solvent-borne systems.
Innovation Solution
A process involving an aqueous dispersion of alkali swellable polymer particles with a shell having a Tg of not greater than 25° C and an acid functionalized core, combined with a rheology modifier and binder, to form a coatings composition with a VOC of less than 50 g/L, increasing the open time without degrading other paint properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If waterborne formulations are used to reduce VOC, then environmental compliance is improved, but open time is reduced from 30-45 min to 3-5 min
Solution Approach 1:
The patent introduces an intermediary substance (polymer additive with specific core-shell structure) that mediates between the waterborne formulation and the paint film properties. The additive contains a core with carboxylic acid functional groups and a shell with specific Tg, creating an intermediate layer that extends open time without requiring VOC
Solution Approach 2:
The patent changes physical parameters of the polymer additive (core-to-shell ratio from -1:3.2 to -1:6, shell Tg not greater than 25°C, coating composition 1-20% by weight of swelled polymer particles) to optimize open time extension while maintaining other paint properties in VOC-free formulations
2Duration of action of moving object
If open time is extended in waterborne formulations, then reworkability is improved, but film adhesive and cohesive strength is degraded
Solution Approach 1:
The patent applies local quality by creating a polymer additive with distinct functional zones: an acid functionalized core that interacts with binders to maintain strength, and a shell with low Tg (≤25°C) that provides flexibility and extends open time. This localized functional differentiation allows simultaneous improvement of open time and preservation of film strength
3Duration of action of moving object
If open time is extended in waterborne formulations, then other paint properties such as hardness, block resistance, and scrub resistance are degraded
Solution Approach 1:
The patent segments the polymer additive into distinct functional components: the core containing carboxylic acid groups that contribute to film cohesion and durability, and the shell with specific glass transition temperature that controls open time. This segmentation allows each component to independently optimize for its specific function without compromising overall paint performance
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 resulting coatings composition exhibits a significantly higher open time compared to formulations without alkali swellable particles, while maintaining or improving other paint properties such as film adhesive and cohesive strength.
Implementation Method 1
contacting an aqueous dispersion of alkali swellable polymer particles with a base to form an aqueous dispersion of swelled polymer particles
Data Source
AI summary
The present invention relates to a process comprising the step of contacting an aqueous dispersion of swelled polymer particles with a rheology modifier and a binder to form a coatings composition with a VOC of less than 50 g/L. The swelled polymer particles arise from neutralization of alkali swellable polymer particles having a high acid core content and a low Tg shell. The composition arising from the process of the present invention is useful for improving open time, especially for low VOC coatings applications.