Electrostatographic toner and method for the preparation thereof

• US 5,283,150 A
• Filed: 05/28/1992
• Issued: 02/01/1994
• Est. Priority Date: 05/28/1992
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Tyagi, Dinesh, DiPrima, Donna A.
• Primary Examiner(s): GOODROW, JOHN L
• Application Number:
  US07/890,057
• Time in Patent Office: 614 Days
• Field of Search: 430/137, 430/105, 430/107, 430/110
• US Class Current: 430/137.11
• CPC Class Codes: G03G 9/0802 Preparation methods
• CPC Class Codes: G03G 9/08782 Waxes
• CPC Class Codes: G03G 9/09 Colouring agents for toner particles

Abstract

A method is described for the preparation of electrostatographic toner particles which involves the surface treatment of pigments using a low melting point highly reactive wax. The method involves preparing a melt dispersion comprising a pigment, a polymeric binder and a low melting point wax at elevated temperatures, the wax melting and coating the surface of the pigment. The melt dispersion is then used as a component of the organic phase in a limited coalescence process.

Claims

1. A method for the preparation of electrostatographic toner comprising the steps of:

(a) forming a melt dispersion by mixing a pigment, a low melting point hydrophobic wax and a first polymer material at a temperature above the melting point of the wax whereby the wax melts and forms an irregular coating on the surface of the pigment;

(b) mixing the melt dispersion with a solvent and optionally a second polymer material, and optionally a charge control agent to form an organic phase,

(c) dispersing the organic phase in an aqueous phase comprising a promoter and a particulate stabilizer and homogenizing the mixture, and

(d) evaporating the solvent and washing and drying the resultant product.

2. The method of claim 1 wherein the melt dispersion comprises up to 50%, by weight, pigment and up to 25%, by weight, low melting point reactive wax.

3. The method of claim 1 wherein the relationship between the aqueous phase and the organic phase, by volume, ranges from 1.5:

1 to 9;

1.

4. The method of claim 1 wherein the low melting point wax has a melting point within the range of 55°

-120°

C.

5. The method of claim 1 wherein the particulate stabilizer is selected from the group consisting of highly cross linked latex particles and SiO₂.

6. The method of claim 1 wherein the first and second polymer materials are the same.

7. The method of claim 1 wherein the pigment is a phthalocyanine pigment.

8. The method of with claim 1 wherein said melt dispersion comprises a copolymer of vinyl toluene and ethyl hexyl acrylate, a quinacridone magenta pigment and a reactive wax having a melting point of 83°

C.

9. The method of claim 8 wherein the second polymer comprises a butyl acrylate and styrene coploymer.

10. The method of claim 8 wherein the particulate stabilizer comprises latex particles.

11. Electrostatographic toner prepared in accordance with claim 1 including a matrix of toner resin comprising a wax coated pigment, the toner having a narrow distribution of charge from toner particle to toner particle.

12. In a method for preparing electrostatographic toner by dispersing an organic phase in an aqueous phase to yield a layer of particulate suspension stabilizer on the surface of a polymer, the improvement which comprises forming a melt dispersion comprising a pigment, a first polymer material and a low melting point wax and mixing the melt dispersion with a second polymer material, a charge agent and a solvent to form an organic phase.

13. Electrostatographic toner prepared in accordance with claim 12 including a matrix of toner resin comprising a wax coated pigment, the toner having a narrow distribution of charge from toner particle to toner particle.

14. The method of claim 12 wherein the low melting point wax has a melting point within the range of 55°

-120°

C.

15. The method of claim 12 wherein the pigment is Novaperm Yellow.

16. The method of claim 12 wherein the low melting point wax has a melting temperature of 83°

C.

17. The method of claim 12 wherein the solvent is dichloromethane.

18. The method of claim 12 wherein the solvent is ethyl acetate.