Device for producing stabilized organic pigment particles

Abstract

A method of producing self dispersible organic pigment particles stabilized by the method. The method includes modifying organic pigment particles and then contacting the surface modified particles with an aqueous vapor entrained in a carrier gas to produce the stabilized organic pigment particles. Typically the pigment particles are modified by exposing their surfaces to ozone or a plasma-activated process gas. The surface stabilizing method prevents the violent exothermic reaction, which occurs when surface modified pigment particles are exposed to ambient air. The method is accomplished in a device, which includes a reactor, means for introducing in the reactor aqueous vapor entrained in a carrier gas and an agitator assembly for deagglomerating during surface modification the pigment particles placed in the reactor. The stabilized particles of the present invention are also well suited for use in ink jet inks, pigmented waterborne and solvent borne coating compositions, and pigmented powder coating compositions.

What is claimed is:  
     
         1 . A method of producing stabilized organic pigment particles, said method comprising: 
 surface modifying organic pigment particles;    contacting said surface modified particles with an aqueous vapor entrained in a carrier gas to produce said stabilized organic pigment particles.    
     
     
         2 . The method of  claim 1  wherein stabilized organic pigment particles have a surface oxygen to carbon ratio of about 0.05 to 1.  
     
     
         3 . The method of  claim 1  wherein said carrier gas is argon, nitrogen, helium, neon, carbon dioxide, air or a mixture thereof.  
     
     
         4 . The method of  claim 1 ,  2  or  3  wherein weight of said aqueous vapor entrained in said carrier gas ranges from 10 to 500 micrograms per square meter of pigment surface area.  
     
     
         5 . The method of  claim 1  wherein said contacting step is accompanied by deagglomeration of said surface modified particles to increase exposure of said surface modified particles to said aqueous vapor.  
     
     
         6 . The method of  claim 1 ,  2 ,  3  or  5  wherein surface pH of said stabilized particles is 0.1 to 8.  
     
     
         7 . The method of  claim 1  wherein said particles are surface modified by exposing surfaces of said particles to a plasma-activated process gas.  
     
     
         8 . The process of  claim 6  wherein said process gas is selected from the group consisting of oxygen, nitrogen, water vapor, hydrogen peroxide, carbon dioxide, ammonia, ozone, carbon monoxide, trimethylsilane, tetraetoxysilane, hexamethyidisiloxane, ethylene diamine, maleic anhydride, arylamine, acetylene, methane, ethylene oxide, hydrogen, styrene, air, sulfur dioxide, sulfonyl precursors, phosphonyl precursors, alcohols, and a mixture thereof.  
     
     
         9 . The method of  claim 1  wherein said particles are surface modified by exposing surfaces of said particles to ozone.  
     
     
         10 . The method of  claim 1  wherein said organic particles comprise carbon black, diketo-pyrrolopyrrole red pigment, perylene maroon pigment, polybutadiene, polychloroprene, polyethylene, polypropylene, polyacrylonitirle, polymethacrylic acid, polyvinyl acetate, polyvinyl chloride, cellulose, copper phthalocyanine blue pigment 15:2,3,4, polychloro copper phthalocyanine, C.I. pigment green 7, quinacridone red pigment, quinacridone violet, copper phthalocyanine blue, C.I. Pigment Yellow-17, C.I Pigment Yellow-74, C.I. Pigment Yellow-83, C.I. Pigment Yellow-95, C.I. Pigment Yellow-128, C.I. Pigment Yellow-151 or C.I. Pigment Yellow-154.  
     
     
         11 . Stabilized organic pigment particles produced in accordance with the method of  claim 1 .  
     
     
         12 . Ink jet ink composition comprising stabilized organic pigment particles produced in accordance with the method of  claim 1 .  
     
     
         13 . A coating composition comprising stabilized organic pigment particles produced in accordance with the method of  claim 1 .  
     
     
         14 . A device for producing stabilized organic pigment particles comprising: 
 a reactor,    means for introducing in said reactor aqueous vapor entrained in a carrier gas; and    an agitator assembly for deagglomerating said pigment particles placed in said reactor.    
     
     
         15 . The device of  claim 14  further comprises means for supplying ozone to said reactor.  
     
     
         16 . The device of  claim 14  or  15  wherein said agitator assembly comprises: 
 a plurality of vanes mounted on a flange rotatably positioned in said reactor, each said vane having a coil affixed thereto such that said coils physically contact an inner wall of said reactor.  
 
     
     
         17 . The device of  claim 14  or  15  wherein said means for introducing in said reactor aqueous vapor entrained in a carrier gas comprise a lance having an opening positioned distally from an exhaust end of said reactor to increase dwell time of aqueous vapor inside said reactor.