Patent ID: 7034067

Claim:
A process for the production of an aqueous two-component polyurethane coating emulsion comprising pumping a mixture of at least one polyisocyanate and an aqueous binder dispersion under a pressure of 1 to 30 MPa through a disperser, said disperser comprising: a) a ceramic sleeve having bores or slots in the wall thereof, with said bores or slots communicating with one end of a pipe, said pipe having an open end remote from said end communicating with said bores or slots, a1) said ceramic sleeve having an open end, a2) said ceramic sleeve further having a moveable solid ceramic piston located opposite said open end, a2i) with the movement of said moveable ceramic piston being such that flow through said bores or slots can be enabled or completely closed, and a2ii) with said movement being caused either via a pneumatic drive or an electric step motor, wherein the ceramic sleeve and the ceramic piston are ground in to fit accurately in order to avoid leakage between the piston and the sleeve, and wherein said mixture is pumped into the open end of said ceramic sleeve, through said bores or slots, and through said pipe.