Preparation of magnetic carrier particles

• US 5,272,039 A
• Filed: 05/04/1992
• Issued: 12/21/1993
• Est. Priority Date: 05/04/1992
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Yoerger, William E.
• Primary Examiner(s): GOODROW, JOHN L
• Application Number:
  US07/877,921
• Time in Patent Office: 596 Days
• Field of Search: 430/108, 430/109, 430/137
• US Class Current: 430/111.34
• CPC Class Codes: G03G 9/1075 Structural characteristics of the carrier particles, e.g. shape or crystallographic structure
• CPC Class Codes: G03G 9/1087 Specified elemental magnetic metal or alloy, e.g. alnico comprising iron, nickel, cobalt, and aluminum, or permalloy comprising iron and nickel
• CPC Class Codes: G03G 9/1131 Coating methods; Structure of coatings

Abstract

Electrostatographic carrier particles with improved conductivity and stability are prepared from magnetic stainless steel particles. The particles are treated by submersion in an aqueous oxalic acid solution. The passivated stainless steel carrier particles, preferably after being first coated with a resin, may then be mixed with toner powder for electrographic dry development.

Claims

1. A process for preparing carrier particles for use in the dry development of electrostatic charge patterns, comprising:

contacting stainless steel particles with an aqueous solution of oxalic acid;

removing said stainless steel particles from said solution; and

rinsing the oxalic acid from said stainless steel particles.

2. The process as described in claim 1, wherein said oxalic acid solution is at room temperature.

3. The process as described in claim 1, wherein the particles are rinsed with water.

4. The process as described in claim 1, wherein the particles are rinsed with water followed by rinsing with a water miscible solvent.

5. The process as described in claim 1, wherein said aqueous solution of oxalic acid comprises between 1 and 15% oxalic acid.

6. The process as described in claim 1, wherein said aqueous solution of oxalic acid comprises between 1 and 5% oxalic acid.

7. A process for preparing resin-coated carrier particles for use in the dry development of electrostatic charge patterns, comprising:

contacting stainless steel particles with an aqueous solution of oxalic acid;

removing said stainless steel particles from said solution;

rinsing the oxalic acid from said stainless steel particles;

mixing said stainless steel particles with an amount of powdered resin; and

heating said mixture to fuse the resin to said stainless steel particles.

8. The process as described in claim 17, wherein said amount of resin is between 0.05 and 0.30 weight percent resin.