Toner processes

• US 20030180647A1
• Filed: 03/25/2002
• Published: 09/25/2003
• Est. Priority Date: 03/25/2002
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bartel, Joseph, Zwartz, Edward G., Patel, Raj D., Hopper, Michael A.
• Granted Patent: US 6,656,657 B2
• Time in Patent Office: Days
• 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 9/0812 Pretreatment of components
• CPC Class Codes: G03G 9/0815 Post-treatment
• CPC Class Codes: G03G 9/0839 Treatment of the magnetic components; Combination of the magnetic components with non-magnetic materials G03G9/0834 takes precedence

Abstract

A toner process comprising mixing an acidified dispersion of an acicular magnetite with an anionic latex, an anionic carbon black dispersion, and an anionic wax dispersion.

Claims

1. A toner process comprising heating an acidified dispersion of an acicular magnetite with an anionic latex, an anionic carbon black dispersion, and an anionic wax dispersion.

2. A process in accordance with claim 1 wherein

(i) said acicular comprises needle shape magnetite particles dispersed in water, and an anionic surfactant, which dispersion is acidified to a pH of about 2 to about 3 with an acid, subsequently adding said latex containing submicron resin particles, an anionic surfactant, and water, and which latex is at a pH of about 6.5 to about 7.5;

(ii) blending said magnetite and latex mixture of (i) with a colorant dispersion of carbon black particles dispersed in water and an anionic surfactant, followed by the addition of 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 thereby resulting in a mixture of magnetite, carbon black colorant, and wax particles with a pH of about 5 to about 5.5;

(iii) acidifying the blend of (ii) to a pH of about 2.2 to about 2.6 with an acid, thereby increasing the positive charge on the magnetite particles to about +30 to about +45 coulombs/cm² thereby initiating flocculation or aggregation of the resin latex, the magnetite, the carbon black, and the wax;

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

(v) optionally adding to the formed toner aggregates a second latex comprised of resin particles suspended in an aqueous phase containing an anionic surfactant and water, and acidifying said second latex to a pH of about 2.2 to about 2.6 with an acid, optionally followed by stirring for a sufficient period of time to permit stabilization of the aggregate particle size;

(vi) adding to the resulting mixture a base to thereby change the pH, which is initially from about 2.2 to about 2.6, to arrive at a pH of from about 6.8 to about 7.7 for the resulting toner aggregate mixture;

(vii) heating the resulting aggregate mixture of (vi) about above the Tg of the latex resin of (i), while maintaining the pH at a value of about 7.2 to about 7.7;

(viii) retaining the mixture temperature at from about 75°

C. to about 95°

C. optionally for a period of about 10 to about 60 minutes, followed by a pH reduction with an acid to arrive at a pH of about 5.8 to about 6.3;

(ix) optionally retaining the mixture temperature from about 80°

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 toner particles;

(x) optionally washing the resulting toner slurry; and

(xi) isolating the toner.

3. A process in accordance with claim 1 wherein said magnetite dispersion comprises said acicular magnetite particles dispersed in water, an anionic surfactant and a nonionic surfactant, and wherein when said dispersion possesses an initial pH of from about 6.5 to about 6.8 is acidified to a pH of about 2.2 to about 2.6.

4. A process in accordance with claim 1 wherein said latex comprises submicron resin particles suspended in water in the presence of anionic surfactant, and wherein said latex possesses a pH of about 6.5 to about 7.5, and when said latex is added to said acidified magnetite there results a mixture with a pH of about 5 to about 5.5.

5. A process in accordance with claim 4 wherein the resulting pH provides a positive charge on the magnetite particles of about +40 to about +10 coulombs/cm^2.

6. A process in accordance with claim 4 wherein there is added a dispersion of carbon black and a dispersion of wax particles, followed by adjusting with an acid the pH of said magnetite, latex, carbon black and wax blend to a pH of about 2.2 to about 2.6.

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

8. A process in accordance with claim 1 wherein said acidified dispersion contains acicular magnetite in an amount of from about 22 to about 35 percent by weight of toner, and wherein in the presence of said anionic latex said magnetite is positively charged.

9. 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 environment of about 1.8 to about 3.5 said magnetite possesses a positive charge of about +45 to about +25 coulombs/cm², and wherein said magnetite also functions as a positive charging coagulant.

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

11. A process in accordance with claim 1 wherein said acicular magnetite particles possess a particle size of about 0.6 micron in length by about 0.1 micron in diameter, and which magnetite is comprised of about 21 percent FeO and about 79 percent Fe₂O_3.

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

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

C. to about 195°

C.

14. A process in accordance with claim 12 wherein the toner hot offset temperature (HOT) is about 210°

C. to about 250°

C.

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

16. 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.

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

18. 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.

19. A process in accordance with claim 2 wherein said acid is selected from the group consisting of nitric, sulfuric, hydrochloric, citric and acetic acids.

20. A process in accordance with claim 2 wherein said base is selected from the group consisting of sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

21. A process in accordance with claim 2 wherein there is added to the formed toner aggregates said 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 (i) to form a shell thereover on said formed aggregates, and which shell is of an optional thickness of about 0.2 to about 0.8 micron.

22. A process in accordance with claim 21 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.

23. A process in accordance with claim 2 (v) wherein the pH of the mixture resulting in (vi) is increased from about 2 to about 2.6 to about 6.8 to about 7.7, and wherein said base functions primarily as a stabilizer for the aggregates during coalescence (vii), and no or minimal toner particle size increase results.

24. A process in accordance with claim 2 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 15 microns in volume average diameter.

25. A process in accordance with claim 2 wherein the aggregation (iv) temperature is from about 45°

C. to about 60°

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

C. to about 95°

C. resulting in coalescence of said carbon black, said magnetite, said wax, and said latex resin.

26. A process in accordance with claim 25 wherein the time of coalescence is from about 6 to about 15 hours, and wherein there are provided toner particles with a smooth morphology.

27. 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).

28. A process in accordance with claim 2 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).

29. A process in accordance with claim 1 wherein the magnetite dispersion comprises acicular magnetite pigment particles, water, and an anionic surfactant, and which dispersion functions as a coagulant.

30. A process in accordance with claim 1 wherein said latex contains from about 30 to about 45 percent solids, about 1 to about 2 percent anionic surfactant and water;

magnetite dispersion contains from about 25 to about 40 percent magnetite, about 1 to about 2 percent anionic surfactant and water; and

wherein said toner subsequent to heating contains about 25 to about 45 percent magnetite, about 4 to about 15 percent carbon black, about 7 to about 9 percent wax, and resin, and wherein the total of said components is about 100 percent.

31. A process in accordance with claim 30 wherein said resin is comprised of styrene-butylacrylate-beta CEA in the ratio of 73.5:

26.5;

3 pph, respectively.

32. A process in accordance with claim 1 wherein said mixture is first heated below about the glass transition temperature (Tg) of resin contained in said latex, followed by heating above said resin Tg.

33. A process in accordance with claim 32 wherein said acidified magnetite dispersion possesses a low pH of from about 1 to about 3;

said anionic latex is at a pH of from about 6 to about 8; and

said carbon black and said wax dispersion is at a pH of from about 6 to about 8.

34. A process in accordance with claim 1 wherein said magnetite dispersion is at a pH of about 2.

35. A process in accordance with claim 1 wherein said latex, carbon black and wax dispersion are of a pH of from about 6 to about 8.

36. A process in accordance with claim 35 wherein said pH is about 7, or a substantially neutral pH.

38. A toner obtained by the process of claim 1.

37. A toner process comprising heating a mixture of an acicular magnetite dispersion, a carbon black dispersion, and a latex dispersion, and wherein said magnetite dispersion possesses a low pH.

39. A toner process comprising heating an acidified dispersion of an acicular magnetite with an anionic latex, an anionic carbon dispersion, and optionally an anionic wax dispersion.