The invention relates to an aqueous coating composition comprising a film-forming first polymer and a second polymer for improving the open time, the wet edge time, adhesion and/or hardness of the resulting coating. The invention further relates to said novel second polymer, its use in coating compositions for improving the open time and coalescence. The water soluble second polymer is an addition polymer comprising 25-95 wt % specific non-ionic hydrophilic monomers A and 5-75 wt % of hydrophobic monomers B which second polymer is sparingly water soluble and a solution of only said second polymer in water has a substantially Newtonian flow behavior in a wide solid contents range.