Cool roof covering and adhesive therefor

1. A heat-reflecting adhesive for use in forming a cool roof covering, the adhesive consisting essentially of a storage-stable, VOC-compliant mixture containing at least 10 wt. % of an organic resin component dissolved in an organic solvent, the organic resin component comprising at least one thermoplastic elastomer in the form of a block copolymer formed from at least one hard block and at least one elastomeric block such the block copolymer as a whole exhibits two distinct glass transition temperatures,

wherein the adhesive has a viscosity of 15,000 cps or less at 77° F. (25° C.), and

further wherein the adhesive when applied to a substrate and dried exhibits a lap shear strength of at least about 17 lbf/in and a solar reflectance of at least 50%.

2. The adhesive of claim 1 , wherein the adhesive has a viscosity of 12,500 cps or less at 77° F. (25° C.), and exhibits a lap shear strength when dried of at least about 50 lbf/in.

3. The adhesive of claim 2 , wherein the adhesive contains at least about 15 wt. % dissolved organic resin.

4. The adhesive of claim 1 , wherein the two distinct glass transition temperatures include a higher glass transition temperature of 50° C. or more and a lower glass transition temperature of −20° C. or less.

5. The adhesive of claim 4 , wherein the block copolymer exhibits a higher glass transition temperature of 75° C. or more while simultaneously exhibiting a lower glass transition temperature of −35° C. or less.

6. The adhesive of claim 4 , wherein the block copolymer is formed from a single elastomeric block in the center of the copolymer molecule with a single hard block on one or both ends.

7. The adhesive of claim 6 , wherein the adhesive contains a mixture of a diblock copolymer and a triblock copolymer, or a mixture of two diblock copolymers or a mixture of two triblock copolymers.

8. The adhesive of claim 7 , wherein the hard block or blocks is formed from styrene, while the elastomeric block is formed from ethylene, propylene, butylene, other C 5 -C 12 monounsaturated alkenes, polyunsaturated alkenes, or combinations thereof.

9. The adhesive of claim 8 , wherein the hard block or blocks are formed from styrene while the elastomeric block is formed from ethylene, propylene, butylene, isoprene, 1,4-butadiene or mixtures thereof.

10. The adhesive of claim 8 , wherein the adhesive contains a mixture of a diblock copolymer and a triblock copolymer.

11. The adhesive of claim 1 , wherein the adhesive is white or light-colored as a result of containing about 0.5 wt. % to about 15 wt. % pigment, and further wherein the pigment is titanium dioxide.

12. The adhesive of claim 1 , wherein the adhesive consists of said storage-stable, VOC-compliant mixture.

13. The adhesive of claim 1 , wherein the adhesive is essentially asphalt-free.

14. A cool roof covering for covering the underlayment of a bituminous roofing system, the cool roof covering comprising multiple heat-reflecting cap-sheets arranged in an adjacent, overlapping edge fashion and a layer of heat-reflecting cap-sheet adhesive applied to one or more lateral edges of each cap-sheet for securing these cap-sheets to one another as well as the underlayment,

wherein the heat-reflecting cap-sheets exhibit a solar reflectance of at least 60% and a thermal emittance of at least 65, and further

wherein the heat-reflecting cap-sheet adhesive consists essentially of a storage-stable, VOC-compliant mixture containing at least 10 wt. % of an organic resin component dissolved in an organic solvent, the organic resin component including at least one thermoplastic elastomer in the form of a block copolymer formed from at least one hard block and at least one elastomeric block such the block copolymer as a whole exhibits two distinct glass transition temperatures,

wherein the adhesive has a viscosity of 15,000 cps or less at 77° F. (25° C.), the adhesive when applied to a substrate and dried exhibiting a lap shear strength of at least about 17 lbf/in and a solar reflectance of at least 50%.

15. The cool roof covering of claim 14 , wherein the adhesive contains at least one thermoplastic elastomer in the form of a block copolymer exhibiting two distinct glass transition temperatures, a high glass transition temperature of 50° C. or more and a low glass transition temperature of −20° C. or less.

16. The cool roof covering of claim 15 , wherein the thermoplastic elastomer is formed from at least one hard block or blocks made from styrene and at least one elastomeric block made from ethylene, propylene, butylene, other C5-C12 monounsaturated alkenes, polyunsaturated alkenes, or combinations thereof.

17. The cool roof covering of claim 16 , wherein the block copolymer is formed from a single elastomeric block in the center of the copolymer molecule and a single hard block on one or both ends of the elastomeric block.

18. The cool roof covering of claim 17 , wherein the hard block or blocks are formed from styrene while the elastomeric block is formed from ethylene, propylene, butylene, isoprene, 1,4-butadiene or mixtures thereof.

19. The cool roof covering of claim 14 , wherein the adhesive is white or light-colored as a result of containing about 0.5 wt. % to about 15 wt. % pigment, and further wherein the pigment is titanium dioxide.

20. The cool roof covering of claim 14 , wherein the adhesive consists of said storage-stable, VOC-compliant mixture.

21. The cool roof covering of claim 14 , wherein the adhesive is essentially asphalt-free.