An aqueous dispersion includes an associative thickener based on a hydrophobically modified poly(acetal- or ketal-polyether) (HM-PAPE) and at least one viscosity reducing agent selected from ethoxylated alcohols, ethoxylated acetyleneic diols, phosphate esters, dialkyl sulfosuccinates, and mixtures thereof. This aqueous dispersion improves the incorporation of the HM-PAPEs into aqueous based protective coatings. This dispersion also improves water-borne coating compositions that optionally contain latex.