Wax emulsion for emulsion aggregation toner

Abstract

A wax emulsion comprised of polyethylene wax and one or more surfactants in an aqueous medium, wherein the polyethylene wax has a degree of crystallinity of from about 50% to about 80% by weight of the polyethylene wax, is provided. The wax emulsion is made by emulsifying the polyethylene wax, one or more surfactants and an aqueous medium in a vessel at a temperature at or above the melting point of the polyethylene wax to form an emulsified product, and subsequently cooling the emulsified product to ambient temperature at a cooling rate of at least 10° C. per minute. The wax emulsion is preferably incorporated into toner particles prepared by emulsion/aggregation/coalescing.

1 . A wax emulsion comprised of polyethylene wax and one or more surfactants in an aqueous medium, wherein the polyethylene wax has a degree of crystallinity of from about 50% to about 80% by weight of the polyethylene wax.  
   
   
       2 . The wax emulsion according to  claim 1 , wherein the polyethylene wax is a linear polyethylene wax.  
   
   
       3 . The wax emulsion according to  claim 1 , wherein the one or more surfactants are selected from the group consisting of anionic surfactants, cationic surfactants, nonionic surfactants and mixtures thereof.  
   
   
       4 . The wax emulsion according to  claim 1 , wherein the polyethylene wax has a degree of crystallinity of from about 50 to about 75% by weight of the polyethylene wax.  
   
   
       5 . The wax emulsion according to  claim 1 , wherein the wax emulsion contains the polyethylene wax in an amount of about 5 to about 50% by weight of the wax emulsion.  
   
   
       6 . A method of preparing a wax emulsion comprised of polyethylene wax and one or more surfactants in an aqueous medium, wherein the polyethylene wax has a degree of crystallinity of from about 50 to about 80% by weight of the polyethylene wax, comprising: 
 emulsifying at least the polyethylene wax, the one or more surfactants and the aqueous medium in a vessel at a temperature at or above the melting point of the polyethylene wax to form an emulsified product, and    subsequently cooling the emulsified product to ambient temperature at a cooling rate of at least 10° C. per minute.    
   
   
       7 . The method according to  claim 6 , wherein the vessel is a homogenizer.  
   
   
       8 . The method according to  claim 6 , wherein the cooling rate is at from about 15° C. to about 30° C. per minute.  
   
   
       9 . The method according to  claim 6 , wherein the cooling is effected at least in part by passing cold water through a jacket of the vessel.  
   
   
       10 . The method according to  claim 6 , wherein the cooling is effected at least in part by discharging the emulsified product from the vessel and through a heat exchanger.  
   
   
       11 . The method according to  claim 7 , wherein the method further comprises, prior to the emulsifying, pre-emulsifying the polyethylene wax, the one or more surfactants and the aqueous medium at a pressure that is lower than the elevated pressure in the emulsifying.  
   
   
       12 . The method according to  claim 7 , wherein in the emulsifying, the vessel is further under an elevated pressure of at least about 1,000 psi.  
   
   
       13 . The method according to  claim 12 , wherein the elevated pressure in the emulsifying is from about 3,000 to about 10,000 psi.  
   
   
       14 . The method according to  claim 11 , wherein the pressure in the pre-emulsifying is 1,000 psi or less.  
   
   
       15 . The method according to  claim 6 , wherein the method further comprises mixing the cooled emulsified product with at least a latex binder, a colorant, one or more additional surfactants and optional one or more coagulants to form a mixture, aggregating the mixture to form toner particles, subsequently coalescing the toner particles, and recovering the toner particles, thereby forming toner particles including the polyethylene wax.  
   
   
       16 . Toner particles prepared by the method of  claim 15 .  
   
   
       17 . A toner particle comprising at least a binder, a polyethylene wax and a colorant, the polyethylene wax having a degree of crystallinity of from about 50 to about 80% by weight of the polyethylene wax.  
   
   
       18 . The toner particle according to  claim 17 , wherein the colorant comprises one or more pigments, one or more dyes, or mixtures thereof.  
   
   
       19 . The toner particle according to  claim 17 , wherein the toner particle comprises the colorant in an amount of from about 1 to about 30% by weight of the toner particle and the polyethylene wax in an amount of from about 1 to about 30% by weight of the toner particle.