Method of attenuating sound, and acoustical insulation therefor

• US 5,841,081 A
• Filed: 06/21/1996
• Issued: 11/24/1998
• Est. Priority Date: 06/23/1995
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Knoll, Randall L., Thompson, Delton R.
• Primary Examiner(s): Dang, Khanh
• Application Number:
  US08/669,896
• Time in Patent Office: 886 Days
• Field of Search: 181/286, 181/290, 181/294, 181/296, 428/903, 428/297.1, 428/298.4
• US Class Current: 181/286
• CPC Class Codes: B29C 2043/025 forming a microstructure, i.e. fine patterning
• CPC Class Codes: B29C 2043/043 rotating on their own axis without linear displacement
• CPC Class Codes: B29C 2043/3433 using dispensing heads, e.g. extruders, placed over or apart from the moulds
• CPC Class Codes: B29C 2043/3455 for particles, powder, fibres, e.g. fluidized or sprayed
• CPC Class Codes: B29C 2043/461 the rollers having specific surface features
• CPC Class Codes: B29C 43/006 Pressing and sintering powders, granules or fibres
• CPC Class Codes: B29C 43/22 of articles of indefinite length
• CPC Class Codes: B29C 43/222 characterised by the shape of the surface
• CPC Class Codes: B29K 2105/06 containing reinforcements, fillers or inserts
• CPC Class Codes: B29L 2031/3041 Trim panels
• CPC Class Codes: B60R 11/0217 for loud-speakers
• CPC Class Codes: B60R 13/0815 Acoustic or thermal insulation of passenger compartments wall or roof liners integrating the insulating function B60R13/02; insulating floor mats or carpets B60N3/04
• CPC Class Codes: B60R 13/083 for fire walls or floors
• CPC Class Codes: B60R 13/0892 for humidity insulation sealing strips B60R13/06
• CPC Class Codes: B60R 2011/0021 Doors
• CPC Class Codes: D04H 1/54 by welding together the fibres, e.g. by partially melting or dissolving in combination with needling D04H1/485
• CPC Class Codes: D04H 1/558 in combination with mechanical or physical treatments other than embossing
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: G10K 11/162 Selection of materials
• CPC Class Codes: Y10S 428/903 Microfiber, less than 100 micron diameter
• CPC Class Codes: Y10T 428/249939 : Two or more layers
• CPC Class Codes: Y10T 428/249943 : Fiber is nonlinear [e.g., crimped, sinusoidal, etc.]

Abstract

Noise is attenuated through use of an acoustical insulation 10 that includes a molded, three-dimensional nonwoven web that contains organic microfibers 12 and heat activatable staple fibers 14 where the heat activatable staple fibers 14 are bonded to each other and to the microfibers 12 at various contact points. The web contains greater than 15 weight percent heat activatable staple fibers, has a thickness of about 0.5 centimeters or greater, and a density of less than 250 kilograms per cubic meter and preferably contains bulking staple fiber 16. The acoustical insulation is positioned between a source area and a receiving area such that a major face of the insulation intercepts and thereby significantly attenuates sound waves passing from the source area to the receiving area.

Claims

1. A method of attenuating sound, which method comprises:

(a) providing an acoustical insulation that includes a molded, three-dimensional nonwoven web that contains organic microfibers and 15 weight percent or greater heat activatable staple fibers, the heat activatable staple fibers being bonded to each other and to the microfibers at various contact points, and the nonwoven web having a thickness of 0.5 centimeters or greater and a density of less than 250 kilograms per cubic meter; and

(b) positioning the acoustical insulation between a source area and a receiving area such that a major face of the insulation intercepts and thereby significantly attenuates sound waves passing from the source area to the receiving area.

2. The method of claim 1, wherein the nonwoven web further comprises bulking staple fibers.

3. The method of claim 1, wherein the nonwoven web is 0.75 to 20 centimeters thick.

4. The method of claim 3, wherein the nonwoven web is 1 to 10 centimeters thick.

5. The method of claim 4, wherein the nonwoven is 2 to 5 centimeters thick.

6. The method of claim 1, wherein the nonwoven web has a density of about 6 to 200 kilograms per cubic meter.

7. The method of claim 6, wherein the density is about 10 to 100 kilograms per cubic meter.

8. The method of claim 7, wherein the density is 15 to 30 kilograms per cubic meter.

9. The method of claim 1, wherein the nonwoven web has a flexural strength of 1 to 40 pounds per square inch.

10. The method of claim 9, wherein the nonwoven web has a flexural strength of 5 to 20 pounds per square inch.

11. The method of claim 10, wherein the nonwoven web has a flexural strength of 10 to 15 pounds per square inch.

12. The method of claim 1, wherein the nonwoven web has a basis weight of 50 to 4,000 grams per square meter.

13. The method of claim 12, wherein the nonwoven web has a basis weight of 150 to 2,000 grams per square meter.

14. The method of claim 13, wherein the nonwoven web has a basis weight of 200 to 1,000 grams per square meter.

15. The method of claim 1, wherein the nonwoven web demonstrates an air pressure drop of 0.1 to 15 milimeters H₂ O.

16. The method of claim 1, wherein the nonwoven web demonstrates an air pressure drop greater than 0.2 milimeters H₂ O.

17. The method of claim 16, wherein the nonwoven web demonstrates a pressure drop greater than 0.3 milimeters H₂ O.

18. The method of claim 8, wherein the nonwoven web has a percent solidity of 0.5 to 4.

19. The method of claim 8, wherein the nonwoven web has a percent solidity of 1 to 3.

20. The method of claim 19, wherein the nonwoven web has a percent solidity of 1.5 to 2.5.

21. The method of claim 1, wherein the nonwoven web has an average effective fiber diameter of 2 to 20 micrometers.

22. The method of claim 21, wherein the nonwoven web has an average effective fiber diameter of 5 to 17 micrometers.

23. The method of claim 22, wherein the nonwoven web has an average effective fiber diameter of 7 to 16 micrometers.

24. The method of claim 1, wherein the nonwoven web contains 10 to 99 weight percent organic microfiber and 1 to 90 weight percent heat activatable staple fibers, based on the weight of the fibrous material in the web.

25. The method of claim 2, wherein the nonwoven web contains 15 to 98 weight percent organic microfiber, 20 to 70 weight percent heat activatable staple fibers, and 1 to 30 weight percent bulking staple fibers, based on the weight of the fibrous material in the web.

26. The method of claim 25, wherein the nonwoven web contains 20 to 70 weight percent organic microfiber, 30 to 50 weight percent heat activatable crimped staple fibers, and 3 to 6 weight percent crimped bulking staple fibers.

27. The nonwoven web of claim 1, wherein the organic microfibers are comprised of melt blown microfibers that are 1 to 25 micrometers in diameter.

28. The method of claim 27, wherein the melt blown microfibers are about 2 to 15 micrometers in diameter, and wherein the heat activatable staple fibers are crimped fibers having 1 to 10 crimps per centimeter.

29. The method of claim 2, wherein the heat activatable staple fibers have 3 to 5 crimps per centimeter, and wherein the bulking staple fibers are crimped and have 1 to 10 crimps per centimeter, have deniers of 3 to 75, and have an average length of 2 to 15 centimeters.

30. The method of claim 2, wherein the organic microfibers are polypropylene melt blown microfibers that are present in the web at about 55 weight percent, the heat activatable staple fibers are bicomponent fibers that have a copolyester sheath and a polyester core and are present in the nonwoven web at about 40.5 weight percent, and the bulking staple fibers are 50 denier polyester terephthalate crimped bulking staple fibers that are present in the nonwoven web at about 4.5 weight percent.

31. The method of claim 1, wherein the heat activatable staple fibers have a length of 15 to 75 milimeters.

32. Acoustical insulation that comprises a molded, three-dimensional nonwoven fibrous web that contains:

(a) organic microfiber; and

(b) 15 weight percent or greater heat activatable staple fibers that are bonded to each other and to the organic microfiber at various contact points.

33. The acoustical insulation of claim 32, wherein the nonwoven web is 0.75 to 20 centimeters thick, has a density of 6 to 200 kilograms per cubic meter, has a flexural strength of 1 to 40 pounds per square inch, has a basis weight of 50 to 4,000 grams per square meter, demonstrates an air pressure drop of 0.1 to 15 milimeters H₂ O, has a percent solidity of 0.5 to 4, and has an average effective fiber diameter of 2 to 20 micrometers.

34. The acoustical insulation of claim 33, wherein the nonwoven web is 1 to 10 centimeters thick, has a density of 10 to 100 kilograms per cubic meter, has a flexural strength of 5 to 20 pounds per square inch, has a basis weight of 150 to 2000 grams per, square meter, demonstrates an air pressure drop greater than 0.2 milimeters H₂ O, has a percent solidity of 1 to 3, and has an average effective fiber diameter of 5 to 17 micrometers.

35. The acoustical insulation of claim 32, wherein the nonwoven web contains 20 to 80 weight percent organic microfiber, 15 to 70 weight percent heat activatable staple fibers, and further contains 1 to 30 weight percent bulking staple fibers.

36. The acoustical insulation of claim 32, wherein the nonwoven web contains 20 to 80 weight percent organic microfiber, 30 to 50 weight percent heat activatable crimped staple fibers, and further contains 3 to 6 weight percent crimped bulking staple fibers.

37. The acoustical insulation of claim 32, wherein the organic microfibers are comprised of melt blown microfibers that are 1 to 25 micrometers in diameter.

38. The acoustical insulation of claim 32, wherein the melt blown microfibers are about 2 to 15 micrometers in diameter, and wherein the heat activatable staple fibers are crimped fibers having 1 to 10 crimps per centimeter.

39. The acoustical insulation of claim 35, wherein the heat activatable staple fibers have 3 to 5 crimps per centimeter, and wherein the bulking staple fibers are crimped and have 1 to 10 crimps per centimeter, have deniers of 3 to 75, and have an average length of 2 to 15 centimeters.

40. The acoustical insulation of claim 35, wherein the organic microfibers are polypropylene melt blown microfibers that are present in the web at about 55 weight percent, the heat activatable staple fibers are bicomponent fibers that have a copolyester sheath and a polyester core and are present in the nonwoven web at about 40.5 weight percent, and the bulking staple fibers are 50 denier polyester terephthalate crimped bulking staple fibers that are present in the nonwoven web at about 4.5 weight percent.