The invention describes a homogenising nozzle 100 comprising a casing 10, a piston 11 arranged displaceably along the longitudinal axis of the casing 10, a first inlet 14 for a first component, a second inlet 15 for a second component and an outlet 16 for a homogenised mixture of the first and second components, wherein the first inlet 14 and the outlet 16 are arranged along the longitudinal axis of the casing 10 in such a manner that, by displacing the piston 11, the free cross-section of the first inlet 14 and the free cross-section of the outlet 16 may be varied. A process is furthermore described for the production of an aqueous two-component polyurethane coating emulsion by mixing at least one aqueous binder dispersion comprising isocyanate-reactive groups and a polyisocyanate using the described homogenising nozzle.