TRANSFER ASSISTED SCREEN PRINTING METHOD OF MAKING SHAPED ABRASIVE PARTICLES AND THE RESULTING SHAPED ABRASIVE PARTICLES

• US 20110146509A1
• Filed: 06/30/2010
• Published: 06/23/2011
• Est. Priority Date: 12/22/2009
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Erickson, Dwight D., Boden, John T., Welygan, Dennis G.
• Granted Patent: US 8,480,772 B2
• Time in Patent Office: Days
• US Class Current: 101/129
• CPC Class Codes: B01J 2/006 Coating of the granules without description of the process or the device by which the granules are obtained to prevent the granules sticking together B01J2/30
• CPC Class Codes: B01J 2/20 by expressing the material, e.g. through sieves and fragmenting the extruded length
• CPC Class Codes: B01J 2/26 on endless conveyor belts
• CPC Class Codes: B41M 1/12 Stencil printing; Silk-screen printing
• CPC Class Codes: C04B 35/10 based on aluminium oxide
• CPC Class Codes: C09K 3/1409 Abrasive particles per se preparation of diamond C01B32/25
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

Shaped ceramic articles can be obtained by screen printing the desired shapes from a dispersion of a precursor of the ceramic onto a receiving surface using a transfer assisted technique that applies a differential pressure, at least partially drying the screen printed shapes, and firing them to generate the shaped ceramic articles. Shaped abrasive particles made using lower viscosity sol gels that tended to flow or creep after the screen printing formation were found to have higher grinding performance over screen printed shaped abrasive particles made with higher viscosity sol gels.

Claims

11. A process for the production of shaped abrasive particles comprising alpha alumina, the process comprising screen printing shapes of a boehmite alumina sol gel onto a receiving surface to form a plurality of screen printed shapes, removing the screen printed shapes from a printing screen while applying a differential pressure between a first side of the screen printed shapes and a second side of the screen printed shapes that are in contact with the receiving surface, at least partially drying the screen printed shapes and firing the screen printed shapes at a temperature sufficient to convert the alumina to the alpha phase.

12. The process according to claim 11 wherein the printing screen comprises apertures having dimensions to produce screen printed shapes with an aspect ratio of between about 2:

1 to about 50;

1.

13. The process according to claim 11 wherein the printing screen comprises a plurality of generally triangular apertures.

14. The process according to claim 11 wherein the applying a differential pressure comprises applying a positive pressure to the first side of the screen printed shapes.

15. The process according to claim 14 wherein a pressure transfer roll is used to apply the positive pressure.

16. The process according to claim 11 where the applying a differential pressure comprises applying a negative pressure to the second side of the screen printed shapes.

17. The process according to claim 16 wherein the receiving surface is air permeable and a vacuum box or vacuum roll is positioned adjacent to the receiving surface opposite the second side of the screen printed shapes on the receiving surface.

18. The process according to claim 14 where the applying a differential pressure comprises applying a negative pressure to the second side of the screen printed shapes.

19. A process for the production of shaped abrasive particles comprising alpha alumina, the process comprising screen printing shapes of a boehmite alumina sol gel onto an air permeable receiving surface, the air permeable receiving surface located adjacent to a vacuum box or vacuum roll while filling apertures in a printing screen with the sol gel to form a plurality of screen printed shapes, removing the screen printed shapes from the printing screen, at least partially drying the screen printed shapes, and firing the screen printed shapes at a temperature sufficient to convert the alumina to the alpha phase.

20. The process of claim 19 wherein removing the screen printed shapes from the printing screen comprises applying a differential pressure between a first side of the screen printed shapes and a second side of the screen printed shapes that are in contact with the receiving surface.

21. The process according to claim 20 wherein the applying a differential pressure comprises applying a positive pressure to the first side of the screen printed shapes.

22. The process according to claim 21 wherein a pressure transfer roll is used to apply the positive pressure.

23. The process according to claim 20 where the applying a differential pressure comprises applying a negative pressure to the second side of the screen printed shapes.

24. The process according to claim 23 wherein a vacuum box or vacuum roll is positioned adjacent to the air permeable receiving surface opposite the second side of the screen printed shapes on the receiving surface.

25. Shaped abrasive particles comprising a post-formation flowed surface.

1. A process for the production of shaped ceramic articles by a screen printing process which comprises applying a dispersion of a ceramic precursor to a receiving surface through a printing screen comprising a plurality of apertures, removing the printing screen from the receiving surface to form a plurality of screen printed shapes while applying a differential pressure between a first side of the screen printed shape and a second side of the screen printed shape that is in contact with the receiving surface, at least partially drying the screen printed shapes remaining on the receiving surface and firing the screen printed shapes to form sintered shaped ceramic articles.

2. The process according to claim 1 wherein the precursor is a chemical precursor.

3. The process according to claim 1 wherein the dispersion comprises an alpha alumina precursor.

4. The process according to claim 3 wherein the dispersion is a boehmite alumina sol gel.

5. The process according to claim 4 wherein the sol gel has a solids content of between about 30% to about 60%.

6. The process according to claim 4 wherein the sol gel has a maximum yield stress and the maximum yield stress is between about 60,000 Pa·

Sec to about 5,000 Pa·

Sec.

7. The process according to claim 5 wherein the sol gel maximum yield stress is between about 15,000 Pa·

Sec to about 5,000 Pa·

Sec.

8. The process according to claim 1 wherein the applying a differential pressure comprises applying a positive pressure to the first side of the screen printed shapes.

9. The process according to claim 1 where the applying a differential pressure comprises applying a negative pressure to the second side of the screen printed shapes.

10. The process according to claim 8 where the applying a differential pressure comprises applying a negative pressure to the second side of the screen printed shapes.

26. The shaped abrasive particles of claim 25 comprising a first side, a second side, and a sidewall connecting the first side to the second side, and wherein the sidewall comprises the post-formation flowed surface.

27. The shaped abrasive particles of claim 26 wherein the sidewall is concave.

28. The shaped abrasive particles of claim 27 wherein the sidewall comprises a first portion intersecting the first side and a second portion intersecting the second side and the slope of the first portion is greater than the slope of the second portion.

29. The shaped abrasive particles of claim 28 wherein the length of the first portion is less than the length of the second portion.

30. The shaped abrasive particles of claim 28 comprising an angle between the second portion and the second side and wherein the angle is between about 10 degrees to about 60 degrees.

31. The shaped abrasive particles of claim 30 comprising an angle between the sidewall and the second side and wherein the angle is between about 10 degrees to about 60 degrees.

32. The shaped abrasive particles of claim 31 wherein the Second Side to First Side Area Ratio is between about 2.0 to about 3.5.

33. The shaped abrasive particles of claim 26 wherein the first side is concave.

34. The shaped abrasive particles of claim 33 wherein a Thickness Ratio, Tc/Ti, is between about 1.20 to about 5.00.

35. The shaped abrasive particles of claim 26 having an aspect ratio of from about 2:

1 to about 50;

1.

36. The shaped abrasive particles of claim 26 comprising a generally triangular shape.

37. The shaped abrasive particles of claim 26 wherein the second side is textured.

30-1. The shaped abrasive particles of claim 26 wherein a Second Side to First Side Area Ratio is between about 2.0 to about 10.0.

38. Shaped abrasive particles comprising a first side, a second side, and a sidewall connecting the first side to the second side;

the sidewall comprising a first portion intersecting the first surface and a second portion intersecting the second surface and the slope of the first portion is greater than the slope of the second portion.

39. The shaped abrasive particles of claim 38 wherein the length of the first portion is less than the length of the second portion.

40. The shaped abrasive particles of claim 39 comprising an angle between the second portion and the second surface and wherein the angle is between about 10 degrees to about 60 degrees.

41. The shaped abrasive particles of claim 38 wherein a Second Side to First Side Area Ratio is between about 1.5 to about 10.0

42. The shaped abrasive particles of claim 38 comprising an angle between the second portion and the second side and wherein the angle is between about 10 degrees to about 60 degrees.

43. The shaped abrasive particles of claim 42 wherein a Second Side to First Side Area Ratio is between about 1.5 to about 10.0.

44. The shaped abrasive particles of claim 38 wherein the first side is concave.

45. The shaped abrasive particles of claim 44 wherein a Thickness Ratio, Tc/Ti, is between about 1.20 to about 5.00.

46. The shaped abrasive particles of claim 38 having an aspect ratio of from about 2:

1 to about 50;

1.

47. The shaped abrasive particles of claim 38 comprising a generally triangular shape.

48. The shaped abrasive particles of claim 38 wherein the second side is textured.

49. The shaped abrasive particles of claim 38 wherein the sidewall comprises a post-formation flowed surface.

50. Shaped abrasive particles comprising a first side, a second side, and a sidewall connecting the first side to the second side;

and wherein the first side is concave and the sidewall is concave.

51. The shaped abrasive particles of claim 50 wherein the sidewall comprises a first portion intersecting the first side and a second portion intersecting the second side and the slope of the first portion is greater than the slope of the second portion.

52. The shaped abrasive particles of claim 51 wherein the length of the first portion is less than the length of the second portion.

53. The shaped abrasive particles of claim 50 wherein the second side is textured.

54. The shaped abrasive particles of claim 50 wherein a Thickness Ratio, Tc/Ti, is between about 1.20 to about 5.00.

55. The shaped abrasive particles of claim 50 wherein a Second Side to First Side Area Ratio is between about 1.5 to about 10.0.

56. The shaped abrasive particles of claim 50 having an aspect ratio of from about 2:

1 to about 50;

1.

57. The shaped abrasive particles of claim 50 comprising a generally triangular shape.