Polyolefin Photovoltaic Backsheet Comprising a Stabilized Polypropylene Layer

Abstract

Polyolefin photovoltaic (PV) backsheets comprise a polypropylene layer stabilized with (A) at least one hindered amine with 2,2,6,6-tetraalkylpiperdine or 2,2,6,6-tetraakylpiperazinone, either or both in combination with a triazine moiety, (B) a thioester, and, optionally, (C) at least one hindered hydroxybenzoate, and/or (D) an ortho hydroxyl triazine compound. These PV backsheets exhibit a low flame spread index of <100 without the use of FR agents, and the polypropylene layer exhibits good weatherability while providing the required long term heat aging performance necessary for PV modules.

1 . A polyolefin PV backsheet comprising a polypropylene layer stabilized with (A) at least one hindered amine with 2,2,6,6-tetraalkylpiperdine or 2,2,6,6-tetraakylpiperazinone, either or both in combination with a triazine moiety, (B) a thioester, and, optionally, (C) at least one hindered hydroxybenzoate, and/or (D) an ortho hydroxyl triazine compound. 
     
     
         2 . The PV backsheet of  claim 1  further comprising at least one additional layer comprising a polyolefin other than polypropylene. 
     
     
         3 . The PV backsheet of  claim 1  in which the triazine moiety is oligomeric, polymeric or has a weight average molecular weight (Mw) of at least 500. 
     
     
         4 . The PV backsheet of  claim 3  in which the polypropylene layer further comprises at least one of an acid scavenger, metal deactivator, primary antioxidant, and a secondary antioxidant. 
     
     
         5 . The PV backsheet of  claim 4  comprising two outer layers joined by a tie layer in which at least one of the two outer layers is the polypropylene layer and the tie layer comprises the same stabilizers as the polypropylene layer. 
     
     
         6 . A PV module comprising the polyolefin PV backsheet of  claim 1 .