The present invention provides rheology modifiers, which are water-soluble polymers having a weight average molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and wherein the water-soluble polymers are in the form of solid particles. It also provides mixtures of rheology modifiers comprising a first rheology modifier, which is a water-soluble polymer having a weight average molecular weight (Mw) of at least 1,000,000 g/mol and an intrinsic viscosity of at least 2.5 dl/g, both as determined by size exclusion chromatography, and a second rheology modifier, which has a weight average molecular weight of from 2,000 g/mol to 800,000 g/mol. It also provides coating composition containing the rheology modifiers, respectively, mixtures of rheology modifiers, a process for their preparation, a process for coating a substrate using these coating compositions and substrates coated with these coating compositions.