High impact polymer interlayers

Abstract

The present invention provides 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 . A multiple layer polymer interlayer comprising:
 a first polymer layer comprising poly(vinyl butyral);   a second polymer layer comprising poly(vinyl butyral);   a third polymer layer comprising poly(vinyl butyral);   wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer;   wherein the amount of plasticizer in said plasticized thermoplastic polymer of said first polymer layer is at least 2 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer;   wherein the amount of plasticizer in said plasticized thermoplastic polymer of said third polymer layer is at least 2 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer; and   wherein said second polymer layer has a residual hydroxyl content by weight that is at least 0.5% greater than the residual hydroxyl content by weight in each of said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer.   
     
     
         2 . (canceled) 
     
     
         3 . The polymer interlayer of  claim 1 , wherein said second polymer layer has a residual hydroxyl content by weight that is at least 2.0% greater than the residual hydroxyl content by weight in each of said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer. 
     
     
         4 . The polymer interlayer of  claim 1 , wherein the tensile break stress of said second polymer layer is greater than 180 kilograms per square centimeter, the tensile break stress of said first polymer layer and said third polymer layer is less than 230 kilograms per square centimeter, and wherein the tensile break stress of said second polymer layer is more than 15 kilograms per square centimeter greater than the tensile break stress of said first polymer layer and said third polymer layer. 
     
     
         5 . The polymer interlayer of  claim 1 , wherein the tensile break stress of said second polymer layer is more than 15 kilograms per square centimeter greater than the tensile break stress of said first polymer layer and said third polymer layer. 
     
     
         6 . The polymer interlayer of  claim 1 , wherein the amount of plasticizer in said plasticized thermoplastic polymer of said first polymer layer is at least 5 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer; and, wherein the amount of plasticizer in said plasticized thermoplastic polymer of said third polymer layer is at least 5 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer. 
     
     
         7 . A multiple layer glazing panel comprising:
 a rigid glazing substrate;   a multiple layer interlayer comprising:   a first polymer layer comprising poly(vinyl butyral);   a second polymer layer comprising poly(vinyl butyral);   a third polymer layer comprising poly(vinyl butyral);   wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer;   wherein the amount of plasticizer in said plasticized thermoplastic polymer of said first polymer layer is at least 2 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer;   wherein the amount of plasticizer in said plasticized thermoplastic polymer of said third polymer layer is at least 2 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer;   wherein said second polymer layer has a residual hydroxyl content by weight that is at least 0.5% greater than the residual hydroxyl content by weight in each of said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer: and,   wherein said interlayer is disposed in contact with said rigid glazing substrate.   
     
     
         8 . (canceled) 
     
     
         9 . The panel of  claim 7 , wherein said second polymer layer has a residual hydroxyl content by weight that is at least 2.0% greater than the residual hydroxyl content by weight in each of said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer. 
     
     
         10 . The panel of  claim 7 , wherein the tensile break stress of said second polymer layer is greater than 180 kilograms per square centimeter, the tensile break stress of said first polymer layer and said third polymer layer is less than 230 kilograms per square centimeter, and wherein the tensile break stress of said second polymer layer is more than 15 kilograms per square centimeter greater than the tensile break stress of said first polymer layer and said third polymer layer. 
     
     
         11 . The panel of  claim 7 , wherein the tensile break stress of said second polymer layer is more than 15 kilograms per square centimeter greater than the tensile break stress of said first polymer layer and said third polymer layer. 
     
     
         12 . The panel of  claim 7 , wherein the amount of plasticizer in said plasticized thermoplastic polymer of said first polymer layer is at least 5 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer; and, wherein the amount of plasticizer in said plasticized thermoplastic polymer of said third polymer layer is at least 5 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer. 
     
     
         13 . A method of making a multiple layer interlayer, comprising:
 forming a first polymer melt, a second polymer melt, and a third polymer melt, wherein the difference in phr of the plasticizer concentrations between any of said first polymer melt, said second polymer melt, and said third polymer melt is 2 phr or less;   coextruding said first polymer melt, said second polymer melt, and said third polymer melt to form said interlayer having a first polymer layer, a second polymer layer, and a third polymer layer, with said second polymer layer disposed between said first polymer layer and said third polymer layer, thereby causing a migration of plasticizer from said second polymer layer into both said first polymer layer and said third polymer layer;   wherein said second polymer layer has a residual hydroxyl content by weight that is at least 0.5% greater than the residual hydroxyl content by weight in said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer.   
     
     
         14 . The method of  claim 13 , wherein said second polymer layer has a residual hydroxyl content by weight that is at least 0.5% greater than the residual hydroxyl content by weight in each of said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer. 
     
     
         15 . The method of  claim 13 , wherein said second polymer layer has a residual hydroxyl content by weight that is at least 2.0% greater than the residual hydroxyl content by weight in each of said plasticized thermoplastic polymer of said first polymer layer and said plasticized thermoplastic polymer of said third polymer layer. 
     
     
         16 . The method of  claim 13 , wherein the tensile break stress of said second polymer layer is greater than 180 kilograms per square centimeter, the tensile break stress of said first polymer layer and said third polymer layer is less than 230 kilograms per square centimeter, and wherein the tensile break stress of said second polymer layer is more than 15 kilograms per square centimeter greater than the tensile break stress of said first polymer layer and said third polymer layer. 
     
     
         17 . The method of  claim 13 , wherein the tensile break stress of said second polymer layer is more than 15 kilograms per square centimeter greater than the tensile break stress of said first polymer layer and said third polymer layer. 
     
     
         18 . The method of  claim 13 , wherein the amount of plasticizer in said plasticized thermoplastic polymer of said first polymer layer is at least 5 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer; and, wherein the amount of plasticizer in said plasticized thermoplastic polymer of said third polymer layer is at least 5 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer. 
     
     
         19 . A method of making a multiple layer interlayer, comprising:
 forming a first polymer melt, a second polymer melt, and a third polymer melt;   coextruding said first polymer melt, said second polymer melt, and said third polymer melt to form said interlayer having a first polymer layer, a second polymer layer, and a third polymer layer, with said second polymer layer disposed between said first polymer layer and said third polymer layer;   wherein the amount of plasticizer in said plasticized thermoplastic polymer of said first polymer layer is at least 2 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer; and,   wherein the amount of plasticizer in said plasticized thermoplastic polymer of said third polymer layer is at least 2 phr greater than the amount of plasticizer in said plasticized thermoplastic polymer of said second polymer layer.