Heat weldable roofing membrane

1. A heat weldable roofing membrane comprising:

a substrate layer comprising a thermoplastic vulcanizate (TPV); and

a film layer adhered to at least one surface of said substrate layer, said film layer comprising a thermoplastic olefin (TPO).

2. The roofing membrane of claim 1 , wherein said TPV comprises polyethylene thermoplastic blended with an at least partially crosslinked ethylene copolymer rubber.

3. The roofing membrane of claim 2 , wherein said polyethylene thermoplastic is a metallocene catalyzed polyethylene.

4. The roofing membrane of claim 2 , wherein said ethylene copolymer rubber is a copolymer of ethylene and a carbonyl containing monomer.

5. The roofing membrane of claim 4 , wherein said ethylene copolymer rubber is an ethylene/vinyl acetate copolymer.

6. The roofing membrane of claim 2 , wherein said TPV further comprises a polypropylene polymer.

7. The roofing membrane of claim 6 , wherein said polypropylene polymer comprises an ethylene-propylene random copolymer.

8. The roofing membrane of claim 1 , wherein said TPO comprises polypropylene blended with an uncrosslinked olefinic elastomer.

9. The roofing membrane of claim 1 , wherein said substrate layer further comprises a scrim reinforcing layer embedded in said substrate layer.

10. The roofing membrane of claim 9 , wherein said scrim reinforcing layer comprises polypropylene.

11. The roofing membrane of claim 1 , wherein said film layer has a thickness of from about 2 mils to about 20 mils.

12. The roofing membrane of claim 1 , wherein said total thickness of said membrane is about 30 to about 50 mils.

13. The roofing membrane of claim 1 , wherein said film layer is adhered to both surfaces of said substrate layer.

14. The roofing membrane of claim 1 , wherein said film layer is adhered to at least one surface of said substrate layer by extrusion or melt bonding of said TPO onto said substrate layer.

15. The roofing membrane of claim 1 , wherein said TPV further comprises at least one of the following: a UV stabilizer, a filler, a flame retardant, a processing oil, a pigment and an antioxidant.

16. The roofing membrane of claim 1 , further comprising chopped polyester fibers embedded in said membrane.

17. A heat weldable roofing membrane comprising:

a substrate layer comprising TPV, said TPV comprising metallocene-catalyzed polyethylene, a polyethylene polymer and an at least partially crosslinked copolymer of ethylene and a carbonyl containing monomer; and

a film layer adhered to at least one surface of said substrate layer and comprising TPO.

18. The roofing membrane of claim 17 , wherein said at least partially crosslinked copolymer of ethylene and carbonyl containing monomer is an ethylene/vinyl acetate copolymer.

19. The roofing membrane of claim 17 , wherein said film layer is adhered to both surfaces of said substrate layer.

20. A heat weldable roofing membrane comprising:

a substrate layer comprising TPV, said TPV comprising from about 20 to 80 weight percent of metallocene-catalyzed polyethylene, a propylene polymer, about 5 to 50 weight percent fire retardant, and about 1 to 30 weight percent of an at least partially crosslinked copolymer of ethylene and a carbonyl containing monomer; and

a film layer adhered to at least one surface of the substrate layer and comprising TPO, wherein said membrane has a thickness of about 30 to about 50 mils.

21. The roofing membrane of claim 20 , wherein said propylene polymer comprises a random polypropylene copolymer.

22. The roofing membrane of claim 20 , wherein said copolymer of ethylene and carbonyl containing monomer is an ethylene/vinyl acetate copolymer.