Microperforated polymeric film for sound absorption and sound absorber using same

• US 6,977,109 B1
• Filed: 03/28/2000
• Issued: 12/20/2005
• Est. Priority Date: 07/24/1998
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wood, Kenneth Brian
• Primary Examiner(s): Morris, Terrel
• Assistant Examiner(s): Chang, Victor
• Application Number:
  US09/537,243
• Time in Patent Office: 2,093 Days
• Field of Search: 428/131, 181/292, 181/293, 181/284
• US Class Current: 428/131
• CPC Class Codes: G10K 11/16 Methods or devices for protecting against, or for damping, noise or other acoustic waves in general G10K11/36 takes precedence
• CPC Class Codes: Y10S 264/70 Processes for forming screens or perforating articles
• CPC Class Codes: Y10S 425/037 Perforate
• CPC Class Codes: Y10T 428/24273 including aperture

Abstract

Microperforated polymeric films and sound absorbers using such films are provided. The microperforated polymeric films may be relatively thin and flexible and may further include holes having a narrowest diameter less than the film thickness and a widest diameter greater than the narrowest diameter. The microperforated polymeric films of a sound absorber may also have relatively large free span portions, which, in certain embodiments, may vibrate in response to incident sound waves.

Claims

1. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter;

wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

2. The microperforated film of claim 1, wherein the narrowest diameter is about 50% or less of the film thickness.

3. The microperforated film of claim 1, wherein the widest diameter is about 200% to 300% of the narrowest diameter.

4. The microperforated film of claim 1, wherein the perforations have a hole density of about 356 to 4,000 perforations/square inch.

5. The microperforated film of claim 1, wherein the film has a bending stiffness of 10⁷ dyne-cm or less.

6. The microperforated film of claim 1, wherein the film has a bending stiffness of 10⁶ dyne-cm or less.

7. The microperforated film of claim 1, wherein the film has a bending stiffness of 10⁵ dyne-cm or less.

8. The microperforated film of claim 7, wherein the film has a surface density of 0.025 g/cm² or more.

9. The microperforated film of claim 1, wherein the narrowest diameter is about 20 mils or less.

10. The microperforated film of claim 9, wherein the film thickness is substantially uniform over the entire film.

11. The microperforated film of claim 1, wherein the narrowest diameter is about 10 mils or less.

12. The microperforated film of claim 1, wherein the film thickness is 80 mils or less.

13. The microperforated film of claim 1, wherein the film thickness is 40 mils or less.

14. A sound absorber, comprising:

a microperforated polymeric film having a thickness and defining a plurality of microperforations each having a narrowest diameter less than the film thickness and widest diameter greater than narrowest diameter, wherein the widest diameter is about 125% or more of the narrowest diameter; and

a surface, the microperforated film being disposed near the surface such that the film and the surface define a cavity therebetween, the cavity having a depth of at least about 0.25 inch and not greater than about 6 inches, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

15. The sound absorber of claim 14, wherein the narrowest diameter is about 50% or less of the film thickness.

16. The sound absorber of claim 14, wherein the film has a bending stiffness of 10⁷ dyne-cm or less.

17. The sound absorber of claim 14, wherein the film has a bending stiffness of 10⁶ dyne-cm or less.

18. The sound absorber of claim 14, wherein the film has a bending stiffness of 10⁵ dynes or less.

19. The sound absorber of claim 14, wherein the microperforations each include a lip defining the narrowest diameter.

20. The sound absorber of claim 14, wherein the film thickness is 80 mils or less.

21. The sound absorber of claim 14, wherein the film thickness is 40 mils or less.

22. The sound absorber of claim 14 wherein the cavity depth is about 0.4 inch to about 3.2 inches.

23. A sound absorber, comprising:

a microperforated polymeric film having a thickness and defining a plurality of microperforations each having a narrowest diameter less than the film thickness and widest diameter greater than narrowest diameter, wherein the widest diameter is about 125% or more of the narrowest diameter; and

a surface, the microperforated film being disposed near the surface such that the film and the surface define a cavity therebetween, the cavity having a depth of at least about 0.25 inch, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

24. A sound absorber, comprising:

a microperforated polymeric film having a thickness and defining a plurality of microperforations each having a narrowest diameter less than the film thickness and widest diameter greater than narrowest diameter, wherein the widest diameter is about 125% or more of the narrowest diameter; and

a surface, the microperforated film being disposed near the surface such that the film and the surface define a cavity therebetween, the cavity having a depth of at least about 0.25 inch, wherein the perforations have a hole density of about 356 to 4,000 perforations/square inch, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

25. A sound absorber, comprising:

a microperforated polymeric film having a thickness and defining a plurality of microperforations each having a narrowest diameter less than the film thickness and widest diameter greater than narrowest diameter, wherein the widest diameter is about 125% or more of the narrowest diameter; and

a surface, the microperforated film being disposed near the surface such that the film and the surface define a cavity therebetween, the cavity having a depth of at least about 0.25 inch, wherein the film has a bending stiffness of 10⁵ dyne-cm or less, and wherein the film has a surface density of 0.025 g/cm² or more, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

26. A sound absorber, comprising:

a microperforated polymeric film having a thickness and defining a plurality of microperforations each having a narrowest diameter less than the film thickness and widest diameter greater than narrowest diameter, wherein the widest diameter is about 125% or more of the narrowest diameter; and

a surface, the microperforated film being disposed near the surface such that the film and the surface define a cavity therebetween, the cavity having a depth of at least about 0.25 inch, wherein the microperforations each include a lip defining the narrowest diameter, and wherein the lip has a thickness of about 1 mil to 4 mils.

27. A sound absorber, comprising:

a microperforated polymeric film having a thickness and defining a plurality of microperforations each having a narrowest diameter less than the film thickness and widest diameter greater than narrowest diameter, wherein the widest diameter is about 125% or more of the narrowest diameter; and

a surface, the microperforated film being disposed near the surface such that the film and the surface define a cavity therebetween, the cavity having a depth of at least about 0.25 inch, wherein the narrowest diameter is about 20 mils or less, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

28. The sound absorber of claim 27, wherein the film thickness is substantially uniform over the entire film.

29. The sound absorber of claim 27 wherein the narrowest diameter is about 10 mils or less.

30. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 200% to 300% of the narrowest diameter, wherein the film thickness is about 20 mils or less, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

31. The microperforated film of claim 30, wherein the narrowest diameter is about 50% or less of the film thickness.

32. The microperforated film of claim 30, wherein the film has a bending stiffness of 10⁷ dyne-cm or less.

33. The microperforated film of claim 30, wherein the film has a bending stiffness of 10⁶ dyne-cm or less.

34. The microperforated film of claim 30, wherein the film has a bending stiffness of 10⁵ dyne-cm or less.

35. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter, wherein the film thickness is about 20 mils or less, wherein the film has a bending stiffness of 10⁵ dyne-cm or less, and wherein the film has a surface density of 0.025 g/cm² or more, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

36. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter, wherein the film thickness is about 20 mils or less, wherein the microperforations each include a lip defining the narrowest diameter, and wherein the lip has a thickness of about 1 mil to 4 mils.

37. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter, wherein the film thickness is about 20 mils or less, and wherein the narrowest diameter is about 20 mils or less, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

38. The microperforated film of claim 37, wherein the film thickness is substantially uniform over the entire film.

39. The microperforated film of claim 37, wherein the narrowest diameter is about 10 mils or less.

40. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 200% to 300% of the narrowest diameter, wherein the narrowest diameter of the microperforations is about 4 mils to 20 mils, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

41. The microperforated film of claim 40, wherein the narrowest diameter is about 50% or less of the film thickness.

42. The microperforated film of claim 40, wherein the film has a bending stiffness of 10⁷ dyne-cm or less.

43. The microperforated film of claim 40, wherein the film has a bending stiffness of 10⁶ dyne-cm or less.

44. The microperforated film of claim 40, wherein the film has a bending stiffness of 10⁵ dyne-cm or less.

45. The microperforated film of claim 40, wherein the microperforations each include a lip defining the narrowest diameter.

46. The microperforated film of claim 40, wherein the film thickness is substantially uniform over the entire film.

47. The microperforated film of claim 40, wherein the film thickness is 80 mils or less.

48. The microperforated film of claim 40, wherein the film thickness is 40 mils or less.

49. The microperforated film of claim 40, wherein the density of the microperforations is less than about 4000 microperforations/square inch.

50. The microperforated film of claim 40, wherein the microperforated polymeric film has a sound absorption coefficient of 0.1 or greater at 1000 hertz.

51. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter, wherein the narrowest diameter of the microperforations is about 4 mils to 20 mils, wherein the film has a bending stiffness of 10⁵ or less, and wherein the film has a surface density of 0.025 g/cm² or more, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.

52. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter, wherein the narrowest diameter of the microperforations is about 4 mils to 20 mils, wherein the microperforations each include a lip defining a narrowest diameter, and wherein the lip has a thickness of about 1 mil to 4 mils.

53. A microperforated polymeric film for use in a sound absorber, comprising:

a polymeric film having a thickness; and

a plurality of microperforations defined in the polymeric film, the microperforations each having a narrowest diameter less than the film thickness and a widest diameter greater than narrowest diameter wherein the widest diameter is about 125% or more of the narrowest diameter, wherein the narrowest diameter of the microperforations is about 4 mils to 10 mils, wherein the microperforations each include a lip defining the narrowest diameter, wherein the thickness of the lip is about 1 mil to 4 mils.