High impact polymer interlayers

Abstract

Multiple poly(vinyl butyral) layer interlayers that can be used in multiple layer glass panel type applications that require a high level of impact protection, for example in hurricane protection applications or in bullet proof glass applications. This effect is achieved by forming a poly(vinyl butyral) interlayer that has a relatively stiff poly(vinyl butyral) inner layer disposed between two relatively soft outer poly(vinyl butyral) layers, where the stiffness difference is achieved by a plasticizer differential that is achieved at least in substantial part by a residual hydroxyl content difference among the poly(vinyl butyral) layers.

1 . An interlayer comprising:
 a first polymer layer comprising a first poly(vinyl butyral) resin and at least one plasticizer, wherein the residual hydroxyl content of said first poly(vinyl butyral) resin is at least about 18.5 weight percent, wherein the plasticizer content of said first polymer layer is about 27 parts per hundred resin (phr) or less; and   a second polymer layer adjacent to and in contact with said first polymer layer, wherein said second polymer layer comprises a second poly(vinyl butyral) resin and at least one plasticizer,   wherein the residual hydroxyl content of said first poly(vinyl butyral) resin is at least 5 weight percent greater than the residual hydroxyl content of said second poly(vinyl butyral) resin, and wherein the plasticizer content of said second polymer layer is at least 2 phr greater than the plasticizer content of said first polymer layer.   
     
     
         2 . The interlayer of  claim 1 , further comprising, a third polymer layer, wherein said third polymer layer comprises a third poly(vinyl butyral) resin and at least one plasticizer, wherein said first polymer layer is disposed between and in contact with each of said second and said third polymer layers, and wherein the residual hydroxyl content of said first poly(vinyl butyral) resin is at least 5 weight percent greater than the residual hydroxyl content of said second poly(vinyl butyral) resin and the residual hydroxyl content of said third poly(vinyl butyral) resin. 
     
     
         3 . The interlayer of  claim 1 , wherein the residual hydroxyl content of said first poly(vinyl butyral) resin is at least 7.5 weight percent greater than the residual hydroxyl content of said second poly(vinyl butyral) resin. 
     
     
         4 . The interlayer of  claim 1 , wherein the residual hydroxyl content of said first poly(vinyl butyral) resin is less than about 30 weight percent. 
     
     
         5 . The interlayer of  claim 1 , wherein the residual acetate content of each of said first and said second poly(vinyl butyral) resins is less than 3 mole percent. 
     
     
         6 . The interlayer of  claim 1 , wherein said interlayer comprises at least four polymer layers. 
     
     
         7 . A multiple layer panel comprising a pair of substrates and said interlayer of  claim 1  disposed between and in contact with each of the substrates. 
     
     
         8 . An interlayer comprising:
 a first outer polymer layer comprising a first poly(vinyl butyral) resin and at least one plasticizer;   a second inner polymer layer comprising a second poly(vinyl butyral) resin and at least one plasticizer; and   a third outer polymer layer comprising a third poly(vinyl butyral) resin and at least one plasticizer,   wherein said second inner polymer layer is adjacent to and in contact with each of said first and said third outer polymer layers,   wherein the residual hydroxyl content of said second poly(vinyl butyral) resin is at least 5 weight percent greater than the residual hydroxyl content of at least one of said first and said third poly(vinyl butyral) resins, wherein the plasticizer content of said second inner polymer layer is about 27 phr or less and wherein the plasticizer content of each of said first and said third outer polymer layers is at least 2 phr greater than the plasticizer content of said second inner polymer layer.   
     
     
         9 . The interlayer of  claim 8 , wherein the plasticizer content of at least one of said first and said third outer polymer layers is in the range of from about 10 to about 80 phr. 
     
     
         10 . The interlayer of  claim 8 , wherein the plasticizer content of said second inner polymer layer is about 22 phr or less and/or wherein the plasticizer content of at least one of said first and said third outer polymer layers is about 50 phr or less. 
     
     
         11 . The interlayer of  claim 8 , wherein the residual hydroxyl content of said second poly(vinyl butyral) resin is at least 7.5 weight percent greater than the residual hydroxyl content of at least one of said first and said third poly(vinyl butyral) resins. 
     
     
         12 . The interlayer of  claim 8 , wherein the residual hydroxyl content of said second poly(vinyl butyral) resin is in the range of from about 18.5 to about 30 weight percent. 
     
     
         13 . The interlayer of  claim 8 , wherein the residual acetate content of each of said first, said second, and said third poly(vinyl butyral) resins is less than 3 mole percent. 
     
     
         14 . The interlayer of  claim 8 , wherein the difference between the plasticizer content of the first outer polymer layer and the plasticizer content of the second inner polymer layer is not the same as the difference between the plasticizer content of said third outer polymer layer and the plasticizer content of said second inner polymer layer. 
     
     
         15 . A multiple layer panel comprising a pair of substrates and said interlayer of  claim 8  disposed between and in contact with each of the substrates. 
     
     
         16 . An interlayer comprising:
 a first polymer layer comprising a first thermoplastic polymer selected from the group consisting of polyurethane, polyvinyl chloride, poly(ethylene vinyl acetate), and combinations thereof; and   a second polymer layer adjacent to and in contact with said first polymer layer, wherein said second polymer layer comprises a poly(vinyl butyral) resin and at least one plasticizer, wherein the residual hydroxyl content of said poly(vinyl butyral) resin is at least 20 weight percent and the plasticizer content of said second polymer layer is 27 phr or less.   
     
     
         17 . The interlayer of  claim 16 , further comprising a third polymer layer adjacent to and in contact with said second polymer layer such that said second polymer layer is disposed between and in contact with each of said first polymer layer and said third polymer layer, wherein said third polymer layer comprises another thermoplastic polymer selected from the group consisting of polyurethane, polyvinyl chloride, poly(ethylene vinyl acetate), and combinations thereof. 
     
     
         18 . The interlayer of  claim 16 , wherein each of said first and said third polymer layers comprises polyurethane or poly(ethylene vinyl acetate). 
     
     
         19 . The interlayer of  claim 16 , wherein the residual hydroxyl content of said second poly(vinyl butyral) resin is less than 30 weight percent. 
     
     
         20 . A multiple layer panel comprising a pair of substrates and said interlayer of  claim 16  disposed between and in contact with each of the substrates.