Acrylic-based rheology modifiers for partial or total hydroxyethyl cellulose replacement

 
The rheology of a waterborne latex paint is the function of complex interactions between different ingredients such as rheology modifiers, binder particles, pigments, extenders, tinting colorants, and other additives including dispersants and surfactants. A typical waterborne architectural paint formulation contains two to three rheology modifiers targeting various rheology profiles to deliver the desired balance of application experience and final application properties. Hydroxyethyl cellulose (HEC) thickeners are widely used in high pigment volume concentration (PVC) waterborne architectural paints as a part of the thickener package that optimizes the rheological behavior of coatings and helps controlling paint properties and phenomena such as sedimentation, syneresis, sagging, leveling and application feel according to the targeted behavior of the final product. HEC products are typically available in powder form and have some drawbacks such as the tendency to release dust during processing, which means increased occupational safety measures. Additionally, they are more challenging to incorporate into coatings formulations and a longer incorporation time is required for a sufficient swelling rate to reach the targeted viscosity. That could often lead to additional processing times, or require special process steps, such as the pre-gel preparation. In addition, HEC thickened paints tend to have lower gloss, lower film build, poor flow/leveling, poor roller application with significant spattering compared to paints thickened by rheology modifiers of different chemical nature. Due to these issues, there's a growing demand for synthetic rheology modifiers that offer more formulation flexibility and predictable viscosity. The general expectation is that they can be easily incorporated into the formulation and reduce dependency on specific raw materials and grades. This has led to the development of alternative options such as anionic hydrophobically modified alkali soluble emulsion (HASE) rheology modifiers. These acrylic-based thickeners are acid-containing, high solids, low viscosity acrylic swellable emulsion copolymers that are effective enough to partially or completely replace existing HEC grades by providing the desired viscosity based on both volume exclusion and associative thickening mechanisms. They are designed to interact well with other formulations ingredients and to provide a greater flexibility for formulations and production processes with easy handling. In this study, these acrylic-based rheology modifiers were tested as a partial or complete replacement of different molecular weight HEC grades in high PVC paints. These paints were formulated in different binder systems such as acrylics and vinyl acetate ethylene (VAE) to achieve the desired paint performance and overall application properties. Advanced imaging analysis technique was developed to quantify the spatter resistance during roller application. The study identified formulation spaces where these acrylic-based rheology modifiers could effectively replace HEC while maintaining paint performance. The paper will cover study's insights and the impact of these modifiers on paint performance, application properties, and total formulation cost.