Self repairing roof membrane

Abstract

A self repairing roof membrane includes a water impervious layer such as EPDM covering a layer including a water swellable polymer. Preferably, the water swellable polymer is bound to a nonwoven web. If a tear is formed through the membrane, water that passes through the tear will be absorbed by the water swellable polymer, which will form a hydrogel and plug the tear.

1 . A roof structure comprising a roof surface covered with a water impervious membrane said membrane having an exposed waterproof layer and an inner layer including a water swellable polymer. 
   
   
       2 . The roof structure claimed in  claim 1  wherein said inner layer comprises a web impregnated with said water swellable polymer. 
   
   
       3 . The roof structure claimed in  claim 1  wherein said inner layer is adjacent said roof surface. 
   
   
       4 . The roof structure claimed in  claim 1  wherein said inner layer is located between upper and lower waterproof membrane layers. 
   
   
       5 . The roof structure claimed in  claim 4  wherein said upper waterproof membrane layer comprises a thin layer of a polymer selected from the group consisting of polyethylene and polypropylene, polyvinyl chloride and modified bitumen. 
   
   
       6 . The roof structure claimed in  claim 4  wherein said waterproof membrane layers comprise ethylene propylene diene monomer rubber. 
   
   
       7 . The roof structure claimed in  claim 1  wherein said inner layer is adhered to a bottom surface of said waterproof layer. 
   
   
       8 . The roof structure claimed in  claim 1  wherein said waterproof layer is selected from the group consisting of ethylene propylene diene rubber, polyvinyl chloride, thermoplastic olefin and modified bitumen. 
   
   
       9 . A water impervious composite roofing membrane having an upper water impervious layer and an inner layer comprising a water swellable polymer layer. 
   
   
       10 . The roofing membrane claimed in  claim 9  wherein said water swellable polymer layer includes a nonwoven web impregnated with a water swellable polymer. 
   
   
       11 . The roofing membrane claimed in  claim 10  wherein said water swellable polymer layer is adhered to a bottom surface of said waterproof membrane. 
   
   
       12 . A built up roof structure having at least one layer of roofing felt and an outer water impervious coating
 and further including a water swellable polymer layer between a roof deck and said water impervious coat.   
   
   
       13 . The built up roof claimed in  claim 12  wherein said water swellable polymer layer comprises water swellable polymer bound to a nonwoven web.