Multi-layer co-extruded roofing membrane

Abstract

A multi-layer roofing membrane is provided including a top sheet including a co-extruded cap and inner layer and a bottom sheet. The use of a co-extrusion die allows for multi-layer sheets that reduce the need for expensive fillers in all but a cap layer of the membrane. A scrim reinforcement layer is optionally embedded in the membrane. When installed on a roof substrate, the membrane can be sealed by heat welding the seams of the membrane sheets or by other means.

Description

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-section of a prior art roofing membrane.

FIG. 2 is a cross-section of a 3-layer roofing membrane made in accordance with the present embodiments.

FIG. 3 is a cross-section of a 4-layer roofing membrane made in accordance with the present embodiments.

FIG. 4A is a schematic diagram showing the set-up for co-extruding a roofing membrane according to a present embodiment.

FIG. 4B is a schematic diagram showing an alternate set-up for co-extruding a roofing membrane according to a present embodiment.

FIGS. 5A, 5B, and 5C show a cross-sections of an edge of a roofing membrane according to various present embodiments where the scrim is encapsulated by one or more of the polymeric layers of the membrane.

Claims

1. A structural membrane comprising a polymeric top sheet and bottom sheet, wherein said top sheet comprises a cap layer, and an upper inner layer, and wherein said cap layer and said upper inner layer have been co-extruded through a common die.

2. The membrane of claim 1, further comprising an intermediate scrim layer positioned between said top and bottom sheets.

3. The membrane of claim 1, wherein said bottom sheet comprises a lower inner layer and a core layer, and wherein said lower inner layer and said core layer have been co-extruded through a second die.

4. The membrane of claim 3, wherein said cap layer and said core layer comprise a thermoplastic olefin.

5. The membrane of claim 1, wherein said cap layer comprises fire retardant additives and said other layers are at least substantially free of such additives.

6. The membrane of claim 1, wherein said die is a dual cavity die.

7. The membrane of claim 1, wherein said cap layer comprises a fire retardant, and a UV stabilizer.

8. The membrane of claim 1, wherein at least one of said layers except said cap layer comprise a reinforcing filler that functions to improve the mechanical properties of said membrane.

9. The membrane of claim 8, where said reinforcing filler comprises wollastonite.

10. The membrane of claim 1, wherein said membrane comprises a nano-mineral or nano-clay.

11. The membrane of claim 1, wherein said membrane has superior tongue tear, puncture resistance, and bond strength as compared to a two layer TPO membrane.

12. The membrane of claim 1, wherein said upper inner layer comprises linear low density polyethylene (LLDPE).

13. The membrane of claim 12, wherein said inner layer comprises a LLDPE/PP blend.

14. The membrane of claim 1, wherein said cap layer comprises a pigment and wherein said other layers are substantially free of pigment.

15. The membrane of claim 1, wherein said membrane comprises an extruded adhesive on the edges of said membrane.

16. The membrane of claim 1, wherein said cap layer comprises at least one of liquid crystal polymer, a fluoropolymer, or nano-mineral oxide/hydroxide.

17. The membrane of claim 3, wherein each of said cap layer, upper inner layer, lower inner layer and core layer has a thickness of from about 5-23 mils (0.13-0.58 mm).

18. The membrane of claim 17, where said cap layer has a thickness of about 21 mils (0.53 mm), said upper inner layer has a thickness of about 6 mils (0.15 mm), said lower inner layer has a thickness of about 6 mils (0.15 mm), and said core layer has a thickness of about 21 mils (0.53 mm).

19. The membrane of claim 2, wherein said scrim comprises polypropylene, polyethylene terephthalate, and/or polyester.

20. The membrane of claim 1, wherein at least one of said layers comprise a blend of a plastomer, low density polyethylene, and a propylene based polymer.

21. The membrane of claim 1, wherein said roofing membrane is characterized by having a flexural modulus of from 10,000 to 30,000 psi (69-207 MPa).

22. The membrane of claim 20, where the low-density polyethylene includes linear low density polyethylene.

23. The membrane of claim 22, where the linear low density polyethylene includes an ethylene-a-olefin copolymer including from about 2.5 to about 13 mole percent mer units deriving from a-olefins.

24. The membrane of claim 23, where the linear low density polyethylene is characterized by a density of from about 0.885 g/cc to about 0.930 g/cc per ASTM D-792.

25. The membrane of claim 20, where the propylene-based polymer comprises a propylene homopolymer or copolymer comprising propylene and a comonomer, and where the copolymer includes, on a mole basis, a majority of mer units derived from propylene.

26. The membrane of claim 25, where the propylene-based copolymers include from about 2 to about 6 mole percent mer units deriving from comonomer, with the balance including mer units deriving from propylene.

27. The membrane of claim 20, further comprising a flame retardant selected from the group consisting of halogenated flame retardants, non-halogenated flame retardants, and mixtures thereof.

28. The membrane of claim 27, where the halogenated flame retardants include halogenated hydrocarbons, where the halogenated hydrocarbons include hexabromocyclododecane, N,N′-ethylene-bis-(tetrabromophthalimide), and mixtures thereof, and where the non-halogenated flame retardants include magnesium hydroxide, aluminum trihydrate, zinc borate, ammonium polyphosphate, melamine polyphosphate, and mixtures thereof.

29. The membrane of claim 28, where the magnesium hydroxide includes a treated magnesium hydroxide or a functionalized magnesium hydroxide.

30. The membrane of claim 29, where the magnesium hydroxide includes magnesium oxide treated with or reacted with a carboxylic acid, or where the magnesium hydroxide includes that treated or reacted with stearic acid, or where the magnesium hydroxide includes that treated or reacted with silicon-containing compounds selected from the group including silanes, and polysiloxanes, or where the magnesium hydroxide includes magnesium hydroxide treated with titanates.

31. The membrane of claim 20, where the at least one layer comprises i) from about 5 to about 50% by weight plastomer, ii) from about 10 to about 90% by weight low density polyethylene, and iii) from about 5 to about 50% by weight propylene-based polymer based upon the total weight of the plastomer, low density polyethylene, and propylene-based polymer, and also includes iv) from about 10 to about 50% by weight magnesium hydroxide, based upon the total weight of the at least one layer.

32. The membrane of claim 31, where the at least one layer includes i) from about 10 to about 45% by weight plastomer, ii) from about 15 to about 85% by weight low density polyethylene, and iii) from about 10 to about 45% by weight propylene-based polymer based upon the total weight of the plastomer, low density polyethylene, and propylene-based polymer, and also includes iv) from about 15 to about 45% by weight magnesium hydroxide, based upon the total weight of the at least one layer.

33. The membrane of claim 20, where the at least one layer includes at least 31% by weight low density polyethylene based upon the total weight of the plastomer, low density polyethylene, and propylene-based polymer.

34. The membrane of claim 33, where the at least one layer includes at least 35% by weight low density polyethylene.

35. The membrane of claim 1, wherein at least one of said top and bottom sheets comprises at least three distinct layers.

36. The membrane of claim 1, wherein said membrane comprises a roofing membrane.

37. The membrane of claim 1, wherein said membrane comprises a geo membrane.

38. A structural membrane comprising a polymeric top sheet and bottom sheet and a scrim positioned therebetween, wherein said top sheet comprises a cap layer, and an upper inner layer, wherein said bottom sheet comprises a lower inner layer and a core layer, wherein said cap layer and said upper inner layer have been co-extruded through a first die, and wherein said lower inner layer and said core layer have been co-extruded through a second die.

39. The membrane of claim 38, wherein said cap layer and said core layer comprise a thermoplastic olefin.

40. The membrane of claim 39, wherein said cap layer comprises fire retardant additives and said other layers are at least substantially free of such additives.

41. The membrane of claim 38, wherein at least one of said first or second dies is a dual cavity die.

42. The membrane of claim 38, wherein said cap layer comprises a fire retardant, and a UV stabilizer.

43. The membrane of claim 38, wherein at least one of said layers except said cap layer comprise a reinforcing filler that functions to improve the mechanical properties of said membrane.

44. The membrane of claim 43, where said reinforcing filler comprises wollastonite.

45. The membrane of claim 38, wherein said membrane comprises a nano-mineral or nano-clay.

46. The membrane of claim 38, wherein said membrane has superior tongue tear, puncture resistance, and bond strength as compared to a two layer TPO membrane.

47. The membrane of claim 38, wherein said upper inner layer comprises linear low density polyethylene (LLDPE).

48. The membrane of claim 47, wherein said inner layer comprises a LLDPE/PP blend.

49. The membrane of claim 38, wherein said cap layer comprises a pigment and wherein said other layers are substantially free of pigment.

50. The membrane of claim 38, wherein said membrane comprises an extruded adhesive on the edges of said membrane.

51. The membrane of claim 38, wherein said cap layer comprises at least one of liquid crystal polymer, a fluoropolymer, or nano-mineral oxide/hydroxide.

52. The membrane of claim 38, wherein each of said cap layer, upper inner layer, lower inner layer and core layer has a thickness of from about 5-23 mils (0.13-0.58 mm).

53. The membrane of claim 38, where said cap layer has a thickness of about 21 mils (0.53 mm), said upper inner layer has a thickness of about 6 mils (0.15 mm), said lower inner layer has a thickness of about 6 mils (0.15 mm), and said core layer has a thickness of about 21 mils (0.53 mm).

54. The membrane of claim 38, wherein said scrim comprises polypropylene, polyethylene terephthalate, and/or polyester.

55. The membrane of claim 38, wherein at least one of said layers comprise a blend of a plastomer, low density polyethylene, and a propylene based polymer.

56. The membrane of claim 38, wherein at one of said cap layer and upper inner layer of said first sheet and at least one of said lower inner layer and core layer of said second sheet has a greater width than a width of said scrim, such that said scrim is completely surrounded by said layers on the sides of the membrane.

57. The membrane of claim 56, wherein each of said cap layer, upper inner layer, lower inner layer, and core layer all have a greater width than a width of said scrim.

58. The membrane of claim 56, wherein only said cap layer and said core layer have a greater width than a width of said scrim.

59. The membrane of claim 56, wherein only said upper and lower inner layers have a greater width than a width of said scrim.

60. The membrane of claim 38, wherein said roofing membrane is characterized by having a flexural modulus of from 10,000 to 30,000 psi (69-207 MPa).

61. The membrane of claim 38, wherein at least one of said top and bottom sheets comprises at least three distinct layers.

62. The membrane of claim 38, wherein said membrane comprises a roofing membrane.

63. The membrane of claim 38, wherein said membrane comprises a geo membrane.

64. A structural membrane comprising a polymeric cap layer, a polymeric inner layer, a scrim, and a polymeric core layer, wherein at least one of said layers comprises a TPO.

65. The structural membrane according to claim 64, further comprising a second polymeric inner layer.

66. A structural membrane comprising polymeric top and bottom sheets and an intermediate scrim positioned therebetween, wherein said top and bottom sheets have a greater width than a width of said scrim, such that said scrim is completely surrounded by said sheets on the sides of the membrane.

67. A roof deck having a roofing membrane adhered thereto, said roofing membrane comprising at least a top and bottom sheet bonded together, said top sheet comprising a co-extruded cap layer and upper inner layer.