Method and apparatus for dispersing pigment in liquid medium

Abstract

The present invention provides an apparatus for dispersing pigment in a water-based or oil-based intermediate mixture for producing a coating composition comprising a mixer and a dispersing device, the mixer having a vacuum pump and capable of conducting a primary mixing of a pigment component and resin-containing liquid medium to form an intermediate mixture, the dispersing device capable of conducting the secondary mixing of the intermediate mixture, the mixer and the dispersing device being connected by pipes to form a circulation channel for the intermediate mixture, one of the pipes being provided with a seal-less pump, the intermediate mixture capable of circulating between the mixer and the dispersing device through the circulation channel.

1 . An apparatus for dispersing pigment in a water-based or oil-based intermediate mixture useful for producing a coating composition, the apparatus comprising: 
 a mixer configured to conduct a primary mixing of a pigment component and resin-containing liquid medium so as to form an intermediate mixture,    a dispersing device configured to conduct a secondary mixing of the intermediate mixture,    a pipe connecting the mixer and the dispersing device to form a circulation path for the intermediate mixture,    a pump connected to the pipe configured to circulate the mixture in the circulation path,    a vacuum pump configured to reduce the pressure in the mixer,    a condenser between the mixer and the vacuum pump configured to obtain a gas fraction of a portion of the intermediate mixture and a liquid fraction of a portion of the intermediate mixture,    a return pipe connected to the mixer configured to return the liquid fraction from the condenser to the mixer,    a storage tank configured to receive the liquid fraction from the condenser,    a directional control valve configured to conditionally direct the liquid fraction into the storage tank and to conditionally direct the liquid fraction to the mixer,    a pump configured to supply a quantity of liquid from the storage tank to the mixer so as to control the viscosity of the circulating intermediate mixture.    
     
     
         2 . The apparatus according to  claim 1 , wherein the mixer is a pebble mill or beads mill.  
     
     
         3 . The apparatus according to  claim 1 , wherein the pump is a magnet-type seal-less pump or canned motor-type seal-less pump.  
     
     
         4 . The apparatus according to  claim 1 , wherein the vacuum pump is configured to maintain a pressure in the mixer in the range of about −0.095 MPa to about −0.01 MPa.  
     
     
         5 . The apparatus according to  claim 1 , wherein at least one of the mixer and dispersing device is provided with a temperature regulator configured to control the temperature of liquid in the apparatus.