ROOFING UNDERLAYMENT

Abstract

A breathable synthetic roofing underlayment having a hydrophobic nonwoven layer on top to deflect water, a liquid water-resistant and vapour-permeable membrane layer in the middle, and a bottom nonwoven layer which is hydrophilic and has rapid and high liquid water absorbency. This accelerates the movement of liquid water from a roofing deck into the nonwoven bottom layer and increases the rate of transfer of water through the underlayment. The bottom layer comprises a carrier resin and a hydrophilic agent, which may be a polyamide such as polycaprolactam (Nylon 6) or poly(hexamethylene adipamide), a polysorbate or other composition. The underlayment is especially useful for application to wet roofing decks.

Claims

1. A roofing underlayment comprising: (a) a first layer that is nonwoven, vapour-permeable, has a hydrophobic surface and low liquid water absorptive capacity, comprising a polymer or mixture of polymers, the first layer being an outer layer for contact with an exterior roofing material; (b) a second layer that is water vapour-permeable and a liquid water barrier, comprising a carrier resin and a breathability agent, and (c) a third layer for contact with a roofing deck, the third layer being nonwoven, hydrophilic and liquid water absorptive, the second layer being between the third layer and the first layer.

2. A roofing underlayment according to claim 1, wherein the underlayment has a water absorbency of at least 9 g/m.sup.2 in 10 minutes, measured according to the method of Example 1.

3. A roofing underlayment according to claim 1, wherein the underlayment has a water absorbency of at least 20 g/m.sup.2 in 10 minutes, measured according to the method of Example 1.

4. A roofing underlayment according to claim 1, wherein the underlayment has a water absorbency of at least 40 g/m.sup.2 in 10 minutes, measured according to the method of Example 1.

5. A roofing underlayment according to claim 1, wherein the underlayment has a water absorbency of at least 9 g/m.sup.2 in 10 minutes, measured using 10 g of water in an inverted cup at 23±2° C.

6. A roofing underlayment according to claim 1, wherein the underlayment has a water absorbency of at least 20 g/m.sup.2 in 10 minutes, measured using 10 g of water in an inverted cup at 23±2° C.

7. A roofing underlayment according to claim 1, wherein the underlayment has a water absorbency of at least 40 g/m.sup.2 in 10 minutes, measured using 10 g of water in an inverted cup at 23±2° C.

8. A roofing underlayment according to claim 1, wherein the underlayment has a surface wettability on its bottom surface such that a contact angle between the bottom surface and water remains constant at less than 105°, measured in accordance with standard test method ASTM D724.

9. A roofing underlayment according to claim 1, wherein the underlayment has a surface wettability on its bottom surface such that a contact angle between the bottom surface and water decreases to 0° in less than 6 seconds, measured in accordance with standard test method ASTM D724.

10. A roofing underlayment according to claim 1, wherein the underlayment has a surface wettability on its bottom surface such that a contact angle between the bottom surface and water decreases to 0° in less than 2 seconds, measured in accordance with standard test method ASTM D724.

11. A roofing underlayment according to claim 1, wherein the underlayment has a breathability of at least 10 perms, measured in accordance with standard test method ASTM 96.

12. A roofing underlayment according to claim 1, wherein the underlayment has a breathability of at least 70 perms, measured in accordance with standard test method ASTM 96.

13. A roofing underlayment according claim 1, wherein the third layer comprises a carrier resin and a hydrophilic agent.

14. A roofing underlayment according to claim 13, wherein the hydrophilic agent comprises a polyamide.

15. A roofing underlayment according to claim 14, wherein the polyamide comprises polycaprolactam (Nylon 6).

16. A roofing underlayment according to claim 14, wherein the polyamide comprises poly(hexamethylene adipamide).

17. A roofing underlayment according to claim 13, wherein the hydrophilic agent comprises a polysorbate.

18. A roofing underlayment according to claim 17, wherein the polysorbate comprises polyoxyethylene (20) sorbitan monooleate (polysorbate 80).

19. A roofing underlayment according to claim 17, wherein the polysorbate comprises polyoxyethylene (20) sorbitan monolaurate (polysorbate 20).

20. A roofing underlayment according to claim 13, wherein the hydrophilic agent comprises a mixture of polyethylene, polypropylene, wax and polyacrylamide.

21. A roofing underlayment according to claim 13, wherein the hydrophilic agent comprises silica-alumina.

22. A roofing underlayment according to claim 13, wherein the hydrophilic agent comprises from 0.1 to 10 weight % of the third layer.

23. A roofing underlayment according to claim 13, wherein the hydrophilic agent comprises at least 4 weight % of the third layer.

24. A roofing underlayment according to claim 13, wherein the carrier resin of the third layer comprises a polyolefin.

25. A roofing underlayment according to claim 16, wherein the polyolefin comprises polyethylene, polypropylene, or both.

26. A roofing underlayment according to claim 1, wherein the third layer has a weight of more than 20 g/m.sup.2.

27. A roofing underlayment according to claim 13, wherein the carrier resin comprises from 90 to 99.9 weight percent of the third layer.

28. A roofing underlayment according to claim 1, wherein the polymer of the first layer comprises a polyolefin.

29. A roofing underlayment according to claim 28, wherein the polyolefin of the first layer comprises polyethylene, polypropylene or both.

30. A roofing underlayment according to claim 1, wherein the first layer comprises from 35% to 40% of the underlayment weight.

31. A roofing underlayment according to claim 1, wherein the breathability agent of the second layer comprises polyether block amide.

32. A roofing underlayment according to claim 1, wherein the breathability agent of the second layer is a polyolefin with calcium carbonate filler.

33. A roofing underlayment according to claim 1, wherein the carrier resin of the second layer comprises a polyolefin.

34. A roofing underlayment according to claim 33, wherein the polyolefin of the second layer comprises polyethylene, polypropylene, or both.

35. A roofing underlayment according to claim 1, wherein the carrier resin of the second layer comprises from 20 to 70 weight % of the second layer.

36. A roofing underlayment according to claim 1, wherein the breathability agent of the second layer comprises from 30 to 75 weight % of the second layer.

37. A roofing underlayment according to claim 1, wherein the second layer comprises from 10 to 15% of the underlayment weight.

38. A roofing underlayment according to claim 1, wherein the second layer bonds the first layer to the third layer.

39. A roofing underlayment according to claim 1, wherein the underlayment has a thickness in the range of 10-30 mils.

40. A roofing underlayment according to claim 1, wherein the underlayment has a weight in the range of 100-300 g per square meter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a schematic cross-sectional view of an embodiment of the roofing underlayment of the invention on a roofing deck.

[0012] FIG. 2 is a graph of surface wettability measurements for two embodiments of the invention, as described in Example 4.

DETAILED DESCRIPTION

[0013] Referring to FIG. 1, the underlayment 10 is a fabric having three layers, namely, a top layer 12, a middle layer 14, and a bottom layer 16. In use, the bottom layer 16 is in contact with the roofing deck 18, and the top layer 12 is opposite to the roofing deck 18 and would have roofing shingles or other exterior roofing material applied directly to it.

[0014] The top layer 12 is a hydrophobic, non-woven, thermoplastic polyolefin sheet. It comprises 35 to 40 percent of the product weight. Suitable polyolefin resins include polyethylene and polypropylene. Mixtures of such resins may also be used.

[0015] The middle layer 14 is a, breathable, thermoplastic, liquid water-resistant film. It laminates the top and bottom layers to each other. The middle layer comprises from 25 to 70 weight percent of a carrier resin, and from 30 to 75 weight percent of a breathability agent. The carrier resin is a polyolefin, for example, polyethylene or polypropylene. The breathability agent may be polyether block amide (PEBA), for example PEBAX (marketed by Arkema). In some embodiments, the breathability agent is a polyolefin with calcium carbonate filler. The middle layer comprises 10 to 15 percent of the product weight.

[0016] The bottom layer 16 is a hydrophilic, non-woven sheet made from fibers formed from a blend of thermoplastic resin and a hydrophilic agent, resulting in rapid and high liquid water absorbency characteristics for the bottom layer. The bottom layer fibers comprise from 90 to 99.9 weight percent of a carrier resin, and from 0.1 to 10 weight percent of a hydrophilic agent, alternatively from 1.0 to 10 weight percent of hydrophilic agent. The carrier resin is a polyolefin, for example, polyethylene or polypropylene. The hydrophilic agent may be a resin that comprises a polyamide, for example polycaprolactam (Nylon 6) and poly(hexamethylene adipamide). Examples of suitable hydrophilic agents include polysorbates, such as polyoxyethylene (20) sorbitan monooleate (polysorbate 80), polyoxyethylene (20) sorbitan monolaurate (polysorbate 20). In some embodiments, the hydrophilic agent of the bottom layer may be one or more hydrophilic agents sold under the trade names SH-04, HYDROSOFT-2036, HYDROSOFT-HPES, HYDROSOFT-PA, POLYFINISH-PU, POLYFINISH-8702, and LEDIGAL-BKS. In some embodiments, the hydrophilic resin comprises a mixture of polypropylene (10 wt. % to 38 wt. %), polyethylene wax (8 wt. % to 25 wt. %) and polyacrylamide (10 wt. % to 45 wt. %), said mixture being marketed under the trade name SH-04. In other embodiments, the hydrophilic agent comprises silica-alumina. The use of fibers formed from a blend of hydrophilic resin and thermoplastic resin in the bottom layer provides higher durability than using a topically applied hydrophilic coating, since a coating is susceptible to being washed off.

[0017] In some embodiments, the three layers have the following minimum weights: the top layer 12 is more than 30 g/m.sup.2, the middle layer 14 is more than 15 g/m.sup.2 and the bottom layer 16 is more than 20 g/m.sup.2.

[0018] The underlayment 10 is made by forming each of the two nonwoven layers 12, 16 and laminating these two layers together with the water vapour-permeable and liquid water barrier middle layer 14.

[0019] The underlayment 10 has a liquid water absorbency of at least 9 grams of water in 1 m.sup.2 of sample in 10 min, measured according to the method described in Example 1 below, i.e., using a 10 gram sample in an inverted cup at 23±2° C. In some embodiments, the minimum water absorbency is 20 grams, or 40 grams.

[0020] The underlayment 10 has a minimum breathability of at least 10 perms measured according to standard test method ASTM E96. It has a minimum of 70 perms when in contact with water according to ASTM E96-Inverted Cup.

[0021] The breathability of the underlayment 10 is up to 30 times higher than the breathability of conventional felt paper and the currently available breathable roofing underlayments when they are in contact with water. This allows a roofing deck, which is typically plywood, to dry much faster.

[0022] The underlayment 10 has a surface wettability on its bottom surface consistent with its ability to absorb liquid water quickly. When measured according to standard test method ASTM D724, in some embodiments the contact angle between the surface and water remains constant at less than 105°. In other embodiments, the contact angle decreases to 0° in less than 6 seconds, or in less than 2 seconds.

[0023] The underlayment 10 is also suitable for use with metal roofing. If there is any water pond on the metal roofing, existing breathable roofing underlayments may cause rotting of the deck surface or migration of water to the lower level of the roof. In contrast, the present underlayment 10 absorbs all water from the surface of the roof and dries out the metal roof quickly.

Example 1

[0024] An underlayment was fabricated according to the invention having 4 wt. % hydrophilic resin (trade name SH-04) in the bottom layer. The absorbency of liquid water into the underlayment and into the prior art products Breathex (HAL Industries), felt paper and Deck-Armor (GAF) was measured after 10 minutes of exposure according to the following method: The test was performed at 23±2° C. The specimen underlayments were conditioned at said temperature for 2±0.1 hour. 10 grams of water was put into a 10 cm diameter cup. A circular sample of the underlayment was cut with a diameter of 10 cm and was weighed. The sample was placed and sealed on top of the cup. The cup was inverted for 10 min at 23° C. and 50% humidity. After 10 min, the sample was removed from the cup and held vertically for 1 min to lose any excess water. The sample was weighed and the weight compared with the initial weight. The amount of absorbed water per square meter was calculated. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Absorption of water per square Product meter of underlayment (grams) Underlayment of invention with 41.35 4 wt. % hydrophilic resin Breathex 2.35 Felt paper 5.87 Deck-Armor 3.52

Example 2

[0025] A further test of water absorbency was conducted on each of the four underlayments described in Example 1. Water absorbency was measured according to the following method. The test was conducted at 23±2° C. The specimens were conditioned at said temperature for 2±0.1 h. A circular sample was cut with a 10 cm diameter. 5 grams of water was placed on the sample. The time required for the sample to absorb all the water was measured. It took less than 1 minute for the water to be absorbed into the underlayment of the invention, and more than 24 hours to be absorbed by each of the other three products.

Example 3

[0026] The permeability of underlayments according to the invention and prior art underlayments was tested, using the inverted cup method at 25° C. according to standard test method ASTM E96. In addition to the four products described in Example 1, tests were done on underlayments according to the invention with 2 wt. % and 1 wt. % hydrophilic resin (trade name SH-04) in the bottom layer, and on the prior art underlayment Hydra (marketed by FT Synthetics Inc. of Surrey, Canada). The results are set out in Table 2 below. A graph of the measurements for the 2 wt. % and 4 wt. % hydrophilic resin compositions of the invention is shown in FIG. 2.

[0027] The surface wettability of the products described in Example 3 was measured. 4 μL of water was put on the back side of the samples and the contact angle between the fabric and water was measured in accordance with standard test method ASTM D724. The results are set out in Table 2 below.

TABLE-US-00002 TABLE 2 Permeability (perms) Contact angle over Product (Example 3) time (Example 4) Underlayment of 335 Decreased from 55° at invention with 4 wt. % time = 0 to 0° at time = hydrophilic resin 1.5 seconds Underlayment of 104 Decreased from 83° at invention with 2 wt. % time = 0 to 0° at time = hydrophilic resin 5.5 seconds Underlayment of 75 Constant at 103.4° invention with 1 wt. % over 1 hour hydrophilic resin Hydra 70 Constant at 125.8° over 1 hour Felt paper 18 Constant at 127.6° over 1 hour Deck-Armor 10 Constant at 128.6° over 1 hour Breathex 5 Constant at 132.2° over 1 hour

[0028] Throughout the foregoing description and the drawings, specific details have been set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

[0029] As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the following claims.