CA1169749A - Self-adhesive roofing laminate having self-edge sealing properties - Google Patents

Abstract

Abstract of the Disclosure Improved flexible waterproofing membranes of the pre-formed pressure-sensitive or self-adhesive bituminous type particularly useful in roofing are described. The membranes are in the form of factory-manufactured, flexible, sheet-like laminates employing (a) a lower layer of waterproofing self-adhesive bituminous composition such as rubberized asphalt non-removably adhered to (b) an upper support layer comprised of a laminate of separate, pre-formed flexible sheet materials having different coefficients of linear thermal expansion. The uppermost sheet material in the support layer (b) has the higher linear thermal expansion coefficient in order that the edges of the applied laminate when exposed to, e.g., solar heating and subsequent cooling, turn downward towards the substrate to be waterproofed resulting in improved sealability. Additionally, further layers of e.g. protective films and coatings may be applied to the laminates.

Description

7~3 Background Of The Invention This inYention relates to laminates containing bituminous water-proofing layers adapted for waterprooing and sealing structures. More par~icularly, this invention relates to improved pre-formed flexible sheet like laminates of the pressure-sensitive or "self-adhesive" type for use in, e.g., roofing applieations as waterproofing membranes, which laminates employ layers of bituminous waterproofing compositions combined with support layers therefore comprised of laminated sheet materials having differing coefficients of thermal expansion.
Flexible sheet-like laminates of support films and self~sdhesive bituminous waterproofing layers pre-formed in the factory have been successfully employed in roofing applications as substitutes for the more conventional water-proofing membranes which are constructed at the job site by plying together one or more layers of bitumen-saturated paper or felt and bituminous adhesives. The pre-formed, self-adhesive laminate-membranes offer many advantages including factory controlled preparation, avoidance of heating equipment and handling of hot materials at the job site, as ~ell as many performance advantages.
Flexible pre-formed laminates of ~he aforementioned type and their use to form waterproofing layers in various kinds of building structures are described for example in United States Patent No.s 3,741,856; 3,853,682; and 3,900,102 to John Hurst. Such patents describe in particular the preparation of flexible laminates containing a support material, for example a layer of a polymeric or metallic film, and a layer of self-adhesive~ or pressure-sensitive adhesive, bitumen-elastomer waterproofing composition. As discussed in particular in United States Patent 3,900,102, such laminates may ldeally be constructed in the plant in the form of a roll with a protective sheet, for example siliconized paper applied against the self-adhesive bituminous water-proofing layer, transported to the ~ob site, and thereafter applied to a 7~

substrate adhesive side down, each successiVe laminate strip ~eing made to overlap the edge of the previously-applied strip of laminate to insure a continuous waterproofing seal.
In Canadian Patent No. 1,008,738 to Everett R. Davis, improved water-proofing laminates of the type described in the aforementioned United States patents are described which utilize as the support material for such laminates, cross-laminated or biaxially oriented polymeric films. As discussed in the Canadian patent, such support films were found to provide laminates which exhibit reduced wrinkling following adhesion to a substrate and subsequent exposure to heat, for example, exposure to the sun. In recent years, flexible preformed laminates utilizing cross-lamin~*ed high density polyethylene films as the support layers for self-adhesive waterproofing layers of asphalt-rubber composition have been successfully applied in the form of overlapping strips to the rooftops of a variety of types of buildings to form long-lasting protective membranes against the passage of water and moisture. Protective coatings containing for example inert aggregates, pigments, metal flakes, etc., have been applied to the exposed surfaces of the overlapped laminates which significantly increase the life of the waterproofing laminate-membrane. How~
ever, there is a continuing need in the art for improved flexible laminates for use as waterprooing membranes for roofs of buildings and the like.
Brief Summary Of The Invention The present invention concerns improved pre-formed laminates having particular utility in constructing waterproofing layers upon roofs of buildings and the like~ and to such roofs having such layers. The inventive laminates are constructed of a layer of waterproofing pressure-sensitive or self-adhesive bituminous composition non-releasably adhered to an upper and preferably thinner flexible support layer comprised of materials of differing coefficient of linear thermal expansion arranged to give a desired self-sealing ability to 7'~

the laminate. The laminates are pre~erably prepared with a further layer of protective material adjacent the adhesive layer which is easily removable from the adhesive layer ~ithout damage thereto prior to application of the laminate to the substrate to be waterproofed. The laminate may additionally have protective coatings and/or films applied to the upper support layer before or after installation upon the substrate to be waterproofed.
Thus in its broadest aspect this invention provides in a waterproof`ed construction comprised o~ a substrate and a continuous waterproofing layer adhered thereto, the improvement which comprises utilizing as said waterproofing layer a plurality of pre-formed, flexible pressure-sensitive adhesive waterproofing laminates, said pre-formed laminates being comprised, prior to application to said substrate, of an upper support layer (a) laminated to a lower layer (b) of waterproofing, pressure-sensitive, thermoplastic bituminous adhesive composition, said adhesive layer of said laminates being adjacent said substrate, said support layer (a) being comprised of first and second layers of flexible sheet material laminated together, said second layer of sheet material being positioned between said first layer of sheet material and said lower layer (b) of adhesive composition, said first layer of flexible sheet material having a higher coefficient of linear thermal expansion than said second layer of sheet material, said upper supprt layer (a) having relatively good thermal dimensional stability and exhibiting substantially "lay-flat" appearance prior to lamination to said adhesive layer (b), whereby the edges of said laminates because of said differing coefficients of thermal expansion are caused to curl downward towards said substrate after application of ..~."

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said laminates to said substrate and exposu~e to elevated temperature.
In a second aspect this invention provides a preformed, flexible pressure-sensitive adhesive roofing laminate ~or forming a continuous waterproofing layer on roofs, said laminate being in the form of a continuous strip having a length greater than its width and being comprised o~ an upper support layer (a) having a thickness of ~rom about 0.002 to about 0.025 inches laminated to a lower layer (b) of waterproofing, pressure-sensitive, thermoplastic bituminous adhesive composition having a thickness of at least about 0.010 inches, said adhesive layer (b) being provided with means to protect its sur~ace remote from said upper suppork layer (a) prior to application to said roof, said support layer (a) being comprised of first and second layers of flexible sheet material laminated together, said second layer of sheet material being positioned between said first layer of sheet material and said lower layer (b) of adhesive composition, said first layer of flexible sheet material having a higher coefficient of linear thermal expansion than said second layer of sheet material, said upper support layer (a) having relatively good thermal dimensional stability and exhibiting substantially "lay-flat7' appearance prior to lamination to said adhesive layer (b) 7 whereby the edges of said roofing laminate because of said differing coefficients of thermal expansion are caused to curl downward towards said roof after application of said laminate to said roof and exposure to elevated temperature.
D cription Of The Drawings ~igure 1. is a perspective cross-sectional view of a -3a-, .

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roofing laminate according to the invention;
Figure 2 is a cross-sectlonal view of a preferred laminate construction of the invention exhibiting a "built-in" edge sealing ability; and Figure 3 is a view in cross-section of two overlapped laminates of the invention exhibiting a "built-in" edge sealing ability; and Figure 4 is a perspective, cross-sectional view of a roof waterproofed according to the invention.
Detailed Description Of The Invention In the attached Figure 1, the inventive roofing laminate is shown as comprised of a comparatively thick layer of self-adhesive bituminous water-proofing composition 1, adhered to a comparatively thinner support layer 7 which is made up of lamina-tions 2 and 3 of separate, different, flexible sheet materials, for example, a sheet of thin metal foil 2 and polymeric film 3, or two, different synthetic polymeric films. The layers 1, 2 and 3 are well-bonded to one another, that is, are not separable from one another normally without physical damage resulting to one or more of the layers. While not shown in the drawing, layers 2 and 3 are adhered to one another by a thin layer of adhesive the sole function of which is to adhere the two layers together. The self-adhesive bituminous waterproofing layer 1 will normally have sufficient adhesive properties that additional adhesive to bond it thoroughly to the -3b-~L 3~ 3 7 ~ 3 support layer 7 will not be necessary. To pro~ect the sur~ace of the bitu-minous adhesive layer remote from layer 7, a removable pr~tective sheet 4, of, e.g. siliconized paper is applied thereto. The sheet ~ adheres su~icient-ly to the bituminous adhesive to keep it in place during handling of the lami-nate, but is easily removable therefrom without physical damage to the layer 1.
The roofing laminate shown in Figure 2 has a width ~"w"), e g. 36 inches, less ~han its length t"l"~, e.g. 60 feet, and can conveniently be packaged in ~he form of a roll which is simply unrolled at the job si~e, there-after the protective sheet 4 removed and the exposed surface of ~he bituminous adhesive layer 1 placed adjacent the substrate (5 in Figures 2, 3, and ~ to be waterproofed. Another like strip of waterproo~ing laminate (Figure 3) is then placed adjacent to the laminate, care being taken to overlap the edges of each laminate a short distance in the manner shown for example in Figures 3 and 4 of United States 3,900,102 to Hurst. An additional continuous protective coating 6 in Figure 3, may then be applied to the exposed surfaces o~ the over-lapped laminates.
The self-adhesive or pressure-sensitive bituminous waterproofing layer 1 useful herein is preferably of the type described in the aforementioned patents. The adhesive composition comprises a mixture of ta) a bituminous material and ~b) natural or synthetic polymer preferably a rubber or other elastomer polymer. The amount of polymer employed in such compositions is typically from about 1 to 100, preferably about 20 to 50, percent by weight of the bituminous material. The term "bituminous material" as used herein includes compositions containing asphalt, tar such as coal tar, or pitch. The bituminous adhesive may be reinforced with fibers and/or particulate fillers.
The adhesive composition may also contain a conventional extender component such as mineral oil. Suitable polymers include thermoplastic polymers such as polyethylene and the like. As aforementioned, the preferred polymer component 7~

is rubber which may be a virgin rubber or reclaimed rubber which is blended in-to the bitumen and preferably an extender oil component preferably at elevated temperature to form a smooth mix. Generally, suitable adhesive compositions have softening points (measured by the Ring and Ball method) of 10 to 120C., preferably 70 to 100C., and penetration values of 50 to ~00, preferably 50 to 100 dmm. at 25C (150 g/5-ASTM D217), and are thermoplastic in nature.
As mentioned in the aforementioned patents, in order to give optimum sealing and waterproofing performance the adhesive layer should be at least 0.010 inch thick and preferably in the range of about 0.025 to about 0.200 inch thick. The adhesive layer can be comprised of one or more layers of the afore-mentioned bituminous adhesive, not necessarily of the same composition, to give an adhesive layer within the overallaforementioned thickness range. Further, the adhesive layer can have a reinforcement such as an open weave fabric, gauze,scrim or the like located therein to strengthen it. The adhesive layer 1, at least at its surface remote from support sheet 3 is pressure-sensitive and tackyat normal ambient temperature in order that it be self-adhesive to the sub-strate. The bituminous adhesive layer serves to form a continuous waterproofing covering which is elastic and self-sealing against punctures at high and low temperature.
The support layer 7 is comprised of a laminate which has been bonded to the layer 1 of adhesive. The support layer 7 serves as a strength imparting and supporting member in the laminate and also as a barrier to prevent moisture vapor transmission through the laminate. Thus while of less thickness than that of the bituminous waterproofing layer 1, the support layer 7 should be of suffic-ient thickness to impart e.g. tear and puncture resistance to the laminate. The support layer 7 suitably has a thickness in the range of from about 0.002 to about 0.025 inches, preferably from about 0.004 to about 0.010 inches.
The preferred sheet materials for use in the layer 7 are films of 7~

synthetic organic polymers such as polyethylene, polypropylene OT other polyolefin; polyamide, polycster, e.g. polyethylene terephthalate, polyure thane, polyvinyl chloride, a copolymer of vinyl chloride and vinylidene chloride, synthetic rubber such as polychloroprene or butyl rubber, and metal films or foils such as aluminum, copper, zinc, etc. It is desirable that the upper sheet of film 3 have optimum weatherability characteristics. Thus polymeric films, e.g., may be rendered opaque, for example by the incorporation therein of a material such as carbon black to render the film non-translucent.
Protective coatings and films such as thin pigmented coatings and films can be applied in the factory to the surfaces of the sheet 3 to be exposed to the weather.
Cross-laminated polymeric films and biaxially-oriented polymeric films are desirable synthetic polymer films for use in the layer 7. As discussed in the aforementioned Canadian patent, such films are more dimension-ally stable when laminated to bituminous adhesive of the type employed herein, adhered to a roof substrate, and exposed to heat from, e.g. the sun. Any film-forming synthe~ic polymer or copolymer which can be oriented (biaxially or cross-laminated) is useful. Biaxially oriented films of such polymers as polyolefins, e.g. high and low density polyethylene, vinylidene chloride, poly-styrene, polyvinyl chloride, rubber hydrochloride, polyethylene terephthalate, etc., are commercially available. Especially useful films are biaxially oriented polyolefin and cross-laminated polyolefins. Preferred polymeric films for use in the support layer 7 are cross-laminated high density polyeth~lene films and biaxially oriented polyesters such as polyethylene terephthalate, desirably containing a filler such as carbon black to render the film opaque.
Metal films or foils may also be used as sheet materials in the support layer 7, having, e.g., a thickness of about 0.00025 to about 0.004 inches.
The layer of sheet material 2 positioned beneath layer 1 is selected .

to have a coefficient of linear thermal expansion less than that of the upper sheet material 3 leading to self-adhesive waterproofing laminates exhibiting a "built-in" edge sealing ability. After adherence to the roof substrate of such laminates, the edges of the laminate will bend to curl do~mwardly towards the substrate in a "self-sealing" fashion after a period of time has elapsed. This is because in actual practice the adhered laminates are exposed to repeated periods of heating and cooling due to changes in atmospheric temperature. Since the upper flexible sheet layer 3 in the support has a thermal expansion coefficient greater than the underlying sheet layer 2 in the support and the two layers are intimately bonded to one another, the edges of the laminate tend to curl downwardly, effecting an enhanced water-proofing seal at its edges. This downward curl becomes irreversible because the thermoplastic bituminous adhesive retains the laminate in the downwardly curled position. The sheet materials 2 and 3 of differing linear thermal expansion coefficient employed in the support layer should be materials having (a) a substantially "lay-flat" appearance and ~b) a relatively good thermal dimensional stability per seO By "substantially lay-flat appearance" is meant, that, when laid flat and non-adhered onto a flat, horizontal surface, the upper and lower surfaces of the sheet materials will be substantially parallel to such horizontal surface and exhibit substantially no curling upwardly or downwardly. By "good thermal dimensional stability" is meant that the sheet materials when exposed to elevated temperature exhibit substantially no shrinkage or at least do not shrink to an extent which would interfere with the desired "self-sealing" effect of the laminate described above. Should one or both of the sheet materials 2 or 3 employed in the support layer 7 for example ha~e a substantial degree of curl before application of adhesive layer 1, or shrink substantially when heated, the inherent curl or shrlnkability of the 7'~
material could interfere with the aforedescribed desired "self-sealing" ability of the laminate occasioned by use of the layers of difEering linear thermal expansion coefficient. The lower layer 2 of sheet material is preferably of lesser thickness than the upper layer 3 of sheet material in the support layer 7.
One example of a construction according to this invention to exhibit the above described "built-in" edge sealing ability after adhesion to a roof substrate is the laminate shown in the attached drawings and described in my copending Canadian application Serial No. 379,752 (filed June 15, 1981) employing for example a layer of high density polyethylene having substantially "lay-flat"
characteristics and good thermal stability as described above as the first layer 3 of sheet material, and aluminum foil as the second layer 2 (which also has such "lay-flat" and "dimensional stability" properties). Since the polyethylene film has a linear thermal coefficient approximately 5 times as great as that of the aluminum film (Table I), the edges of the adhered laminate will bend or curl downwardly towards the adhesive layer as shown in Figures 2 and 3, in a "self-sealing" fashion after exposure to fluctuation in atmospheric temperature.
The self-sealing downward edge-curling shown in Figures 2 and 3 can be promoted by adhering to the face of sheet material 2 remote from film 3 an additional layer (not shown) of a lay-flat sheet, for example a film of good dimension stability as described above and of lesser thickness than sheet 3 and having a thermal expansion coefficient lower than sheet 3. Similarly, the degree of downward edge-curling shown in Figures 2 and 3 can be offset or controlled to a desired extent by using as such additional sheet or film adhered to the face of metal 2 remote from sheet 3, a film having a linear thermal expansion coefficient greater than sheet 2.

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The desired self-sealing downward edge curl shown in Figures 2 and 3 is obtained by preferably employing as the upper layer 3, lay-flat polymeric films of good dimensional stability and having linear thermal expansion coefficients at least about twice as great as tha~ o layer 2. Pre-ferred synthetic polymer films 3 for use in achieving the desired "self-sealing" properties of the laminates of the invention are those films which possess a linear thermal expansion coefficient greater than 30 x 10 6 per inch per degree Fahrenheit (in/in/deg. F). The linear thermal expansion coefficient of several films and foils are listed in Table I below TABLE I

Approximately Linear Thermal Coefficient FILM (FOIL) (in./in./F. X 10-6) Polyester 10 Aluminum 12 Polyvinyl fluoride 28 Nylon (polyamide) 55 Polycarbonate 36 Polymethyl methacrylate 39 Polyethylene 66 The "life" of waterproofing membrane layers formed using the waterproofing roofing laminates of the invention can be increased by the application of protective coatings, 6 in Figure ~, thereover at the job site following installation of the laminates upon the roof substrate. Such "field-applied" coatings are now in conventional use in connection with waterproofing laminates of the type described in the aforementioned patents and have been found to add significantly to the endurance of the laminate-membranes. The coatings further protect the exposed synthetic polymer support 37~

films from harmful ultra-violet radiation and weather damage. Conventional "field-applied~ coatings for this purpose are generally bitumen-, e.g. asphalt, based composition, containing plasticizers, fillers, antioxidants, pigments, etc. Reflective particles in such coatings, such as particles or flakes of metal such as aluminum, reduce the temperature of the laminate~membrane layer.
The protective coatings are typically applied to the surfaces of the installed laminate-membrane layer in thickness of from about 0.002 to a~out 0.070 inches.
The invention is further illustrated by the following examples.
Example I
Three sample laminates useful for waterproofing purposes were con-structed and tested for tendencies to curl at their edge after exposure to high and low temperaturesO The construction of each laminate ~Nos. 1 to 3) is shown in Table II.
TABLE II
Laminate Construction (LAYERS - TOP TO BOTTOM) NO. 1 NO. 2 NO. 3 _ . _ . , . . _. . _ Protective Coating Protective Coating Protective Coating Polymer Film "Al' Aluminum Foil Polymer Film "A"
Waterproofing Adhesive Polymer Film "A" Aluminum Foil Waterproofing Adhesive Polymer Film "B"

Waterproofing Adhesive The polymer film "A" used in the laminates of Table II was a cross-laminated, high-density polyethylene composite film (four, 2-mil thick films pre-laminated together) having a total thickness of 0.008 inch (8 mils).
The aluminum foil layer had a thickness of 0.35 mils, The waterproofing 7~
adhesive layer was 60 mils thick and comprised a self-adhesive, normally tacky mixture of asphalt, styrene-butadiene rubber and mineral oil. The water-proofing adhesive layer was applied to the laminates last. The polymer film "B" was a 1 mil thick layer of ionomer resin film. The protective coating applied to the top of each laminate comprised a 7 mil thick layer of a pro-prietary "field-applied" coating composition containing asphalt, plasticizers, and aluminum flakes for heat reflectance.
Portions of each of the sample laminates Nos. 1 to 3 measuring 3 inches by6 inches were also again adhered to a substrate, adhesive side down, and the tendency of each to curl at its edge was observed at 70F after exposure to a temperature cycle ranging from 150F to minus 15F. Laminate No. 1 exhibited no edge curl. The edges of laminate No. 2 curled upwardly away from the substrate, while the edges of laminate No. 3 curled downwardly towards the substrate in the manner of Figure 2, ideally exhibiting a "built-in" edge sealing ability.
Example II
Several rolls of a self-adhesive waterproofing laminate strip measuring 3 feet wide by 60 feet long and having a sixty mil-thick layer of waterproofing bituminous adhesive as in the laminates of Table II, were applied to the roof of a department store in Long Island in ~arch of 1978.
The rolls were sold to a commercial roofing installer who applied them to the roof as part of the flashing used in the roof. The laminate was similar in construction to that of sample No. 2 in Table II (the metal foil above the polymer film "A"), the difference being that in place of the 7 mils-thick protective coating used in Table II, a thin, protective coating of "Surlyn" brand ionomer resin ~"Surlyn" is a trademark of DuPont de Nemours, E. I. ~ Co.) was factory applied to the surface of the aluminum foil remote from polymer film "A" to give it weather protection. Approximately one month 7~

later a visual observation made of the applied laminate strip showed the edges tending to curl upwardly away from the substrate.
While the inventive roofing laminate strip has been described in connection with its usage in the formation of a continuous waterproofing membrane upon a roof where for practi.cal reasons a laminate having a width of at least about 36 inches is desired, strips havi.ng narrower dimensions can be utilized in other roofing applications. For instance, strips of the inventive laminate having a width of about 4 inches can be used to cover the joints between, e.gO insulation boards in roofs. Also, for, e.g., use as flashing strips in roofing applications, the laminate strips of the invention may have a width of, e.g. 12 inches.

Claims (31)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a waterproofed construction comprised of a substrate and a continuous waterproofing layer adhered thereto, the improvement which comprises utilizing as said waterproofing layer a plurality of pre-formed, flexible pressure-sensitive adhesive waterproofing laminates, said pre-formed laminates being comprised, prior to application to said substrate, of an upper support layer (a) laminated to a lower layer (b) of waterproofing, pressure-sensitive, thermoplastic bituminous adhesive composition, said adhesive layer of said laminates being adjacent said substrate, said support layer (a) being comprised of first and second layers of flexible sheet material laminated together, said second layer of sheet material being positioned between said first layer of sheet material and said lower layer (b) of adhesive composition, said first layer of flexible sheet material having a higher coefficient of linear thermal expansion than said second layer of sheet material, said upper support layer (a) having relatively good thermal dimensional stability and exhibiting substantially "lay-flat"
appearance prior to lamination to said adhesive layer (b), whereby the edges of said laminates because of said differing coefficients of thermal expansion are caused to curl downward towards said substrate after application of said laminates to said substrate and exposure to elevated temperature.

2. The construction of Claim 1 wherein said adhesive composition comprises a mixture of a polymer and bitumen.

3. The construction of Claim 2 wherein said polymer is natural or synthetic rubber and said bitumen is asphalt.

4. The construction of Claim 3 wherein said adhesive composition additionally contains mineral oil.

5. The construction of Claim 1 wherein said upper support layer (a) has a thickness of from about 0.002 to about 0.025 inches, and said adhesive layer has a thickness of at least 0.010 inch.

6. The construction of Claim 1 wherein said upper support layer (a) contains a sheet of polymer film comprised of a polymer selected from the group consisting of polyolefin, polyamide, polyester, polyurethane, polyvinyl chloride, a copolymer of vinyl chloride and vinylidene chloride, and synthetic rubber.

7. The construction of Claim 6 wherein said polymer film is comprised of a cross-laminated polymeric film or a biaxially-oriented polymeric film.

8. The construction of Claim 7 wherein said film is comprised of high density polyolefin or of polyethylene terephthalate.

9. The construction of any of Claims 6, 7 or 8 wherein said polymer film is employed as said first layer of sheet material in said laminates.

10. A construction according to Claim 1 wherein said laminates are in the form of a continuous strip having a width of at least about 36 inches and a length greater than said width.

11. The construction of Claim 1 wherein said laminates prior to application to said substrate have a protective coating or film applied to the surface of said upper support layer (a) remote from said adhesive layer (b).

12. The construction of Claim 11 wherein said protective coating or film is pigmented.

13. The construction of Claim 12 wherein said pigment is carbon black.

14. The construction of Claim 1 having a continuous protective coating over said waterproofing layer applied subsequent to the formation of said waterproofing layer on said substrate.

15. The construction of Claim 14 wherein said protective coating is a bitumen-containing composition.

16. The construction of Claim 14 or 15 wherein said protective coating contains metal particles.

17. A preformed, flexible pressure-sensitive adhesive roofing laminate for forming a continuous waterproofing layer on roofs, said laminate being in the form of a continuous strip having a length greater than its width and being comprised of an upper support layer (a) having a thickness of from about 0.002 to about 0.025 inches laminated to a lower layer (b) of waterproofing, pressure-sensitive, thermoplastic bituminous adhesive composition having a thickness of at least about 0.010 inches, said adhesive layer (b) being provided with means to protect its surface remote from said upper support layer (a) prior to application to said roof, said support layer (a) being comprised of first and second layers of flexible sheet material laminated together, said second layer of sheet material being positioned between said first layer of sheet material and said lower layer (b) of adhesive composition, said first layer of flexible sheet material having a higher coefficient of linear thermal expansion than said second layer of sheet material, said upper support layer (a) having relatively good thermal dimensional stability and exhibiting substantially "lay-flat"
appearance prior to lamination to said adhesive layer (b), whereby the edges of said roofing laminate because of said differing coefficients of thermal expansion are caused to curl downward towards said roof after application of said laminate to said roof and exposure to elevated temperature.

18. The laminate of Claim 17 wherein said means comprises a layer of sheet material removable from said adhesive without substantial damage thereto.

19. The laminate of Claim 17 wherein said adhesive composition comprises a mixture of a polymer and bitumen.

20. The laminate of Claim 17 wherein said polymer is natural or synthetic rubber and said bitumen is asphalt.

21. The laminate of Claim 20 wherein said adhesive composition additionally contains mineral oil.

22. A laminate according to Claim 17 wherein said width is at least about 36 inches.

23. The laminate of Claim 17 having a protective coating or film applied to said upper support layer (a) on its surface remote from said adhesive layer (b).

24. The laminate of Claim 23 wherein said protective coating or film is pigmented.

25. The laminate of Claim 24 wherein said pigment is carbon black.

26. The laminate of Claim 17 wherein said upper support layer (a) contains a sheet of polymer film comprised of a polymer selected from the group consisting of polyolefin, polyamide, polyester, polyurethane, polyvinyl chloride, a copolymer of vinyl chloride and vinylidene chloride, and synthetic rubber.

27. The laminate of Claim 26 wherein said polymer film is comprised of a cross-laminated polymeric film or a biaxially-oriented polymeric film.

28. The laminate of Claim 26 wherein said film is comprised of high density polyolefin or of polyethylene terephthalate.

29. The laminate of any of Claims 26, 27 or 28 wherein said polymer film is employed as said first layer of sheet material in said laminate.

30. The laminate of Claim 17 wherein said second layer of sheet material in said upper support layer (a) is of lesser thickness than said first layer of sheet material in said upper support layer (a).

31. The construction of Claim 1 wherein said second layer of sheet material in said upper support layer (a) is of lesser thickness than said first layer of sheet material in said upper support layer (a).