A New Rheology Modifier for Waterborne Industrial Coatings: Formulations and Performance
Formulation of waterborne industrial coatings requires skillful balancing of the various formulation components to achieve the desired balance of film properties, application characteristics, package stability and substrate protection. Coatings formulators often attempt to minimize the use of water-soluble materials such as rheology modifiers. It is generally believed that water-soluble ingredients cause water sensitivity, which reduces the durability of the coating. This article examines HMHEC 100, a low-molecular-weight hydrophobically modified hydroxyethylcellulose.
Hydroxyethylcellulose (HEC) is a versatile, water-soluble polysaccharide widely used for thickening many types of flat to semi-gloss architectural latex paints. HEC is commercially available in a range of viscosity grades.1 Paint thickened with HEC exhibits excellent colorant compatibility and excellent storage stability. Paint properties dependent on the HEC molecular weight include thickening efficiency, flow and leveling, spatter resistance, film build, and sag resistance. HEC and other non-associative water-soluble polymers thicken the aqueous phase of paint, and the viscosity achieved is related to the hydrodynamic volume of the water-soluble polymer (WSP) and the degree of chain entanglement of these polymers in solution.2
Hydrophobically modified hydroxyethylcellulose (HMHEC) polymers were commercially introduced in 1984. HMHEC polymers thicken the aqueous phase of paint and also thicken by association of the hydrophobes. HMHEC polymers associate with other thickener molecules and other paint ingredients, such as dispersants, surfactants, and coalescing solvents.3