Toner processes

• US 6,617,092 B1
• Filed: 03/25/2002
• Issued: 09/09/2003
• Est. Priority Date: 03/25/2002
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Patel, Raj D., Hopper, Michael A.
• Primary Examiner(s): Goodrow, John
• Application Number:
  US10/106,519
• Publication Number:
  US 20030180651A1
• Time in Patent Office: 533 Days
• Field of Search: 430/137.14, 430/106.2, 523/335
• US Class Current: 430/137.14
• CPC Class Codes: G03G 9/0804 whereby the components are brought together in a liquid dispersing medium
• CPC Class Codes: G03G 9/0833 Oxides
• CPC Class Codes: G03G 9/08782 Waxes
• CPC Class Codes: G03G 9/08795 characterised by their chemical properties, e.g. acidity, molecular weight, sensitivity to reactants
• CPC Class Codes: G03G 9/08797 characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature
• CPC Class Codes: G03G 9/0904 Carbon black

Abstract

An emulsion aggregation process for the preparation of a magnetite toner, and where the magnetite can function as a coagulant.

Claims

1. A process for the preparation of a magnetic toner comprising heating a colorant acicular magnetite dispersion, a carbon black dispersion, a latex emulsion, and a wax dispersion.

2. A process in accordance with claim 1 wherein said magnetite dispersion contains an anionic surfactant and a nonionic surfactant when said dispersion possesses a pH of from about 6.5 to about 6.8.

3. A process in accordance with claim 1 wherein said carbon black comprises particles dispersed in water and an anionic surfactant, and which dispersion possesses a pH of about 6.3 to about 6.8.

4. A process in accordance with claim 1 wherein said acicular magnetite is present in an amount of from about 20 to about 35 percent by weight of toner, and wherein in the presence of an acidic anionic latex said magnetite is charged thereby facilitating aggregation.

5. A process in accordance with claim 1 wherein said acicular magnetite is present in an amount of from about 23 to about 32 percent by weight of toner, and wherein in the presence of an acidic anionic latex functions as positively charged particles thereby facilitating aggregation.

6. A process in accordance with claim 1 wherein said acicular magnetite utilized exhibits a coercivity of from about 250 to about 700 Oe.

7. A process in accordance with claim 1 wherein said acicular magnetite has a particle size of about 0.6 micron in length by 0.1 micron in diameter, and is comprised of about 21 percent FeO and about 79 percent Fe₂O₃.

8. A process in accordance with claim 1 wherein said toner exhibits a magnetic signal of from about 115 to about 150 percent of the nominal signal.

9. A process in accordance with claim 1 wherein said toner possesses a minimum fix temperature (MFT) of about 170°

C. to about 195°

C.

10. A process in accordance with claim 9 wherein the toner hot offset temperature (HOT) is in excess of about 210°

C.

11. A process in accordance with claim 1 wherein the magnetite dispersion is obtained by a ball milling, attrition, polytroning or media milling resulting in magnetite particles dispersed in water containing an anionic surfactant.

12. A process in accordance with claim 1 wherein the carbon black dispersion is present in an amount of about 4 to about 8 percent by weight of toner.

13. A process in accordance with claim 1 wherein the latex resin particles are from about 0.15 to about 0.3 micron in volume average diameter.

14. A process in accordance with claim 1 wherein said magnetite is of a size of about 0.6 micron to about 0.1 micron, and said carbon black is of a size of about 0.01 to about 0.2 micron in average volume diameter.

15. A process in accordance with claim 1 wherein the said acid is selected from the group consisting of nitric, sulfuric, hydrochloric, citric and acetic acid.

16. A process in accordance with claim 1 wherein said base is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

17. A process in accordance with claim 1 wherein there is added to the formed toner aggregates a second latex comprised of submicron resin particles suspended in an aqueous phase containing an anionic surfactant, and wherein said second latex is selected in an amount of from about 10 to about 40 percent by weight of the initial latex to form a shell thereover on said formed aggregates, and which shell is of a thickness of about 0.2 to about 0.8 micron.

18. A process in accordance with claim 17 wherein the added latex contains the same resin as the initial latex of (i), or wherein said added latex contains a dissimilar resin than that of the initial latex.

19. A process in accordance with claim 1 (v) wherein the pH of the mixture resulting in (vi) is increased from about 2 to about 2.6 to about 6.5 to about 7.2, and wherein said base functions primarily as a stabilizer for the aggregates during coalescence (vii), and no or minimal toner particle size or GSD increases result.

20. A process in accordance with claim 1 wherein the temperature at which toner sized aggregates are formed controls the size of the aggregates, and wherein the final toner size is from about 5 to about 12 microns in volume average diameter.

21. A process in accordance with claim 1 wherein the aggregation (iv) temperature is from about 45°

C. to about 60°

C., and wherein the coalescence or fusion temperature of (vii) and (viii) is from about 85°

C. to about 95°

C.

22. A process in accordance with claim 1 wherein the time of coalescence or fusion is from about 12 to about 20 hours, and wherein thereon are provided toner particles with a smooth morphology.

23. A process in accordance with claim 1 wherein the latex contains a resin or polymer selected from the group consisting of poly(styrene-alkyl acrylate), poly(styrene-1,3-diene), poly(styrene-alkyl methacrylate), poly(styrene-alkyl acrylate-acrylic acid), poly(styrene-1,3-diene-acrylic acid), poly(styrene-alkyl methacrylate-acrylic acid), poly(alkyl methacrylate-alkyl acrylate), poly(alkyl methacrylate-aryl acrylate), poly(aryl methacrylate-alkyl acrylate), poly(alkyl methacrylate-acrylic acid), poly(styrene-alkyl acrylate-acrylonitrile-acrylic acid), poly(styrene-1,3-diene-acrylonitrile-acrylic acid), and poly(alkyl acrylate-acrylonitrile-acrylic acid).

24. A process in accordance with claim 1 wherein the latex contains a resin selected from the group consisting of poly(styrene-butadiene), poly(methylstyrene-butadiene), poly(methyl methacrylate-butadiene), poly(ethyl methacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butyl methacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethyl acrylate-butadiene), poly(propyl acrylate-butadiene), poly(butyl acrylate-butadiene), poly(styrene-isoprene), poly(methylstyrene-isoprene), poly(methyl methacrylate-isoprene), poly(ethyl methacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butyl methacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethyl acrylate-isoprene), poly(propyl acrylate-isoprene), poly(butyl acrylate-isoprene);

poly(styrene-propyl acrylate), poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid), poly(styrene-butadiene-methacrylic acid), poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butyl acrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic. acid), poly(styrene-butyl acrylate-acrylononitrile), and poly(styrene-butyl acrylate-acrylononitrile-acrylic acid).

25. A process in accordance with claim 1 wherein said magnetite functions as a positively charged coagulant.

26. A process for the preparation of a magnetic toner comprising heating a colorant dispersion containing acicular magnetite, a carbon black dispersion, a latex emulsion, and a wax dispersion, and wherein said heating comprises a first heating at a temperature below the latex resin Tg, and a second heating above the latex resin Tg.

27. A process for the preparation of a magnetic toner comprising heating a colorant dispersion containing acicular magnetite, a carbon black dispersion, and a latex emulsion, and wherein said heating comprises a first heating at a temperature below the latex resin Tg, and a second heating above the latex resin Tg.

28. A process for the preparation of a magnetic toner comprising heating an acicular magnetite dispersion, a carbon black dispersion, a latex emulsion, and a wax dispersion, and wherein

(i) said acicular magnetite dispersion contains water and an anionic surfactant, or a nonionic surfactant, and said dispersion of carbon black contains water and an anionic surfactant, or a nonionic surfactant;

and wherein said carbon black dispersion possesses a pH of about 6.3 to about 6.8, and wherein said latex is an emulsion comprised of an anionic surfactant, water and resin, and which emulsion is at a pH of about 1.5 to about 2.5;

(ii) wherein said colorant dispersion is blended with said latex emulsion, and thereafter adding a wax dispersion comprised of submicron wax particles of from about 0.1 to about 0.5 micron in diameter by volume, and which wax is dispersed in an anionic surfactant;

(iii) wherein the resulting blend possesses a pH of about 2.2 to about 2.8 thereby inducing a positive charge on the magnetite particles to thereby initiate flocculation or aggregation of said resin latex, said colorant, and said wax;

(iv) heating the resulting mixture below about the glass transition temperature (Tg) of the latex resin to form toner sized aggregates;

(v) adding to the formed toner aggregates a second latex comprised of resin suspended in an aqueous phase containing an ionic surfactant and water, and stirring for a period of time to permit stabilization of aggregate particle size;

(vi) adding to the resulting mixture a base to thereby change the pH, which is initially from about 2 to about 2.8, to arrive at a pH of from about 6.9 to about 7.3 for the resulting toner aggregate mixture;

(vii) heating the resulting aggregate suspension of (vi) above about the Tg of the latex resin of (i), while maintaining the pH at a value of about 6.9 to about 7.3;

(viii) retaining the mixture temperature at from about 85°

C. to about 95°

C. for an optional period of about 10 to about 60 minutes, followed by a pH reduction with an acid to arrive at a pH of about 5.3 to about 5.8;

(ix) retaining the mixture temperature at from about 85°

C. to about 95°

C. for a period of about 7 to about 14 hours to assist in permitting the fusion or coalescence of the toner aggregates and to obtain smooth particles;

(x) washing the resulting toner slurry; and

(xi) isolating the toner.