Emulsion aggregation toner formulation
View Patent ↗An emulsion aggregation toner formulation for electrophotography and a method for preparation thereof. The emulsion aggregation toner formulation includes a polyester resin emulsion formed using an extruded polyester binder resin having a broad molecular weight distribution. The extruded polyester binder resin is formed using a plurality of polyester binder resins. Further, the emulsion aggregation toner formulation comprises at least one colorant dispersion and a wax dispersion.
1. A method for preparing an emulsion aggregation toner formulation for electrophotography, the method comprising:
loading a plurality of pre-emulsified polyester binder resins into an extruder and extruding the plurality of pre-emulsified polyester binder resins together to form an extruded polyester binder resin having a broader molecular weight distribution than the pre-emulsified polyester binder resins;
after extruding the plurality of pre-emulsified polyester binder resins and forming the extruded polyester binder resin, mechanically grinding the extruded polyester binder resin;
after mechanically grinding the extruded polyester binder resin, preparing a polyester resin emulsion using the extruded and ground polyester binder resin; and
combining and agglomerating the prepared polyester resin emulsion with at least one colorant dispersion and a wax dispersion to form the emulsion aggregation toner formulation.
2. The method of claim 1 wherein the extruder is a twin-screw extruder.
3. The method of claim 1 wherein the extruded polyester binder resin is characterized by a cross-linked gel content of less than or equal to about 5 percent by weight of the extruded polyester binder resin.
4. The method of claim 1 wherein each of the plurality of polyester binder resins has an acid value of less than or equal to about 40 milligrams of KOH per gram.
5. The method of claim 1 wherein each of the plurality of polyester binder resins has a glass transition temperature of about 40 to about 75 degrees Celsius.
6. The method of claim 1 wherein each of the plurality of polyester binder resins has a softening temperature of about 80 to about 150 degrees Celsius.
7. The method of claim 1 wherein each of the plurality of polyester binder resins is selected from the group consisting of a semi-crystalline polyester binder resin, a crystalline polyester binder resin, an amorphous polyester binder resin and a polyester copolymer binder resin.
8. The method of claim 1 wherein the at least one colorant dispersion comprises a self-dispersing colorant selected from the group consisting of dyes, pigments and combinations thereof.
9. The method of claim 1 wherein the at least one colorant dispersion comprises:
a colorant, the colorant selected from the group consisting of dyes, pigments and combinations thereof; and
a dispersant, the dispersant selected from the group consisting of a surfactant, a polymeric dispersant and a combination thereof.
10. The method of claim 1 wherein the wax dispersion comprises wax having a melting point of about 60 to about 135 degrees Celsius.
11. The method of claim 1 further comprising adding one or more charge control agents prior to agglomerating the prepared polyester resin emulsion with the at least one colorant dispersion and the wax dispersion.