Claims
- 1. An erasable ink for use in a writing instrument, comprising:
a solvent, a shear-thinning additive, and a graphite flake pigment having an average thickness of less than about 0.25 microns dispersed in the solvent, wherein said ink has a shear-thinning index of between about 0.01 and 0.8.
- 2. The ink of claim 1, wherein said ink is substantially free of colorants other than said graphite flake pigment.
- 3. The ink of claim 1, wherein said ink exhibits an erasability of at least about 80%.
- 4. The ink of claim 1, wherein said ink has a shear-thinning index of between about 0.05 and about 0.60.
- 5. The ink of claim 1, wherein said ink has a shear-thinning index of between about 0.1 and about 0.3.
- 6. The ink of claim 1, wherein said ink has a viscosity between 2000 mPa·sec and 20,000 mPa·sec at a shear rate of about 1.0 sec−1, and a viscosity between 10 mPa·sec and 1000 mPa·sec at a shear rate of about 100 sec−1.
- 7. The ink of claim 1, wherein said solvent comprises an aqueous solvent system.
- 8. The ink of claim 7, wherein said aqueous solvent system comprises water and a water-soluble organic solvent.
- 9. The ink of claim 1, wherein said shear-thinning additive is selected from the group consisting of clays, organoclays, water-dispersible gums, and acrylic acid-based polymers.
- 10. The ink of claim 9, wherein said shear-thinning additive is a polysaccharide.
- 11. The ink of claim 1, wherein said graphite flake pigment has an average diameter from about 1 micron to about 25 microns.
- 12. The ink of claim 1, wherein said graphite flake pigment has an aspect ratio of between about 1 and about 8.
- 13. A writing instrument, comprising:
a reservoir containing an erasable ink comprising a solvent, a shear-thinning additive, and a graphite flake pigment having an average thickness of less than about 0.25 microns dispersed in the solvent, wherein said ink has a shear-thinning index of between about 0.01 and 0.8.
- 14. The writing instrument of claim 13, wherein said solvent comprises an aqueous solvent system.
- 15. The writing instrument of claim 14, wherein said aqueous solvent system comprises water and a water-soluble organic solvent.
- 16. The writing instrument of claim 13, wherein said shear-thinning additive is a polysaccharide.
- 17. The writing instrument of claim 13, wherein said graphite flake pigment has an aspect ratio of between about 1 and about 8.
- 18. A method of forming an erasable marking on a paper substrate, comprising:
making a marking on the substrate with a writing instrument containing an erasable ink comprising a solvent, a shear-thinning additive, and a graphite flake pigment having an average thickness of less than about 0.25 microns dispersed in the solvent, wherein said ink has a shear-thinning index of between about 0.01 and 0.8.
- 19. The method of claim 18, wherein said solvent comprises an aqueous solvent system.
- 20. The method of claim 19, wherein said aqueous solvent system comprises water and a water-soluble organic solvent.
- 21. The method of claim 18, wherein said shear-thinning additive is a polysaccharide.
- 22. The method of claim 18, wherein said graphite flake pigment has an aspect ratio of between about 1 and about 8.
Parent Case Info
[0001] This is a continuation-in-part of U.S. patent application Ser. No. 09/608,925, filed Jul. 03, 2000, the entire disclosure of which is herein incorporated by reference.
Continuations (1)
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Parent |
09898396 |
Jul 2001 |
US |
Child |
10867349 |
Jun 2004 |
US |
Continuation in Parts (1)
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09608925 |
Jul 2000 |
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09898396 |
Jul 2001 |
US |