Multiple layer polymer interlayers having a melt fractured surface

Abstract

The present invention provides multiple layer interlayers having a soft inner polymer layer and relatively stiff outer layers that can be laminated without unacceptable optical distortion and used in various multiple layer glass panel type applications. Multiple layer interlayers of the present invention have surface topography that is formed by controlling the melt fracture that occurs at the exposed surface of the interlayer, or individual layers of the multiple layer interlayer, during formation of the interlayer. By precisely controlling the surface topography of the interlayer, lamination of the interlayer with a rigid substrate does not lead to unacceptable optical distortion caused by the transfer of the surface topography through outer, stiffer layers into softer, internal layers of the interlayer.

1 . A polymer interlayer comprising:
 a first polymer layer comprising a plasticized thermoplastic polymer with a lower plasticizer content;   a second polymer layer comprising a plasticized thermoplastic polymer; and,   a third polymer layer comprising a plasticized thermoplastic polymer with a lower plasticizer content;   
       wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer; 
       wherein the lower plasticizer content of the a plasticized thermoplastic differ from the plasticizer content in the second a plasticized thermoplastic layer by at least 20 phr by weight in plasticizer content and, and 
       wherein both surfaces of said interlayer have an R Z  value of 20-60 and an R SM  value of less than 800. 
     
     
         2 . The interlayer of  claim 1 , wherein said first polymer layer, said second polymer layer, and said third polymer layer each comprise poly(vinyl butyral). 
     
     
         3 . The interlayer of  claim 1 , both surfaces of said interlayer have an R SM  value of less than 700. 
     
     
         4 . The interlayer of  claim 1 , wherein both surfaces of said interlayer have an R Z  value of 20-50. 
     
     
         5 . The interlayer of  claim 1  wherein said interlayer has no embossing. 
     
     
         6 . The interlayer of  claim 1  wherein the interlayer has a total thickness of 0.1 to 2.5 millimeters. 
     
     
         7 . The interlayer of  claim 1  wherein the lower plasticizer content of the a plasticized thermoplastic differ from the plasticizer content in the second a plasticized thermoplastic layer by at least 25 phr by weight in plasticizer content. 
     
     
         8 . The interlayer of  claim 1  wherein the high plasticizer content in the second poly(vinyl butyral) layer comprises 40 to 90 phr by weight plasticizer, wherein the lower plasticizer content poly(vinyl butyral) layers differ from the high plasticizer content poly(vinyl butyral) layer by at least 20 phr by weight in plasticizer content, wherein both surfaces of said interlayer have an R z  of 25-50 microns and an R sm  of less than 700 microns. 
     
     
         9 . The interlayer of  claim 1  wherein the high plasticizer content poly(vinyl butyral) layer comprises 50 to 80 phr by weight plasticizer, wherein the low plasticizer content poly(vinyl butyral) layers differ from the high plasticizer content poly(vinyl butyral) layer by at least 25 phr by weight in plasticizer content, wherein both surfaces of said interlayer have an R z  of 25-50 microns and an R sm  of less than 800 microns. 
     
     
         10 . The interlayer of  claim 1  wherein the sound transmission loss for the multiple layer glass panel is at least 2 dB greater than a comparable reference panel having a single layer interlayer with the same thickness as the multiple layer interlayer and being formed of same material used for the first low plasticizer content poly(vinyl butyral) layer. 
     
     
         11 . An interlayer interlayer comprising
 a first polymer layer comprising a plasticized thermoplastic polymer with a lower plasticizer content;   a second polymer layer comprising a plasticized thermoplastic polymer; and,   a third polymer layer comprising a plasticized thermoplastic polymer with a lower plasticizer content;   
       wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer; 
       wherein the lower plasticizer content of the a plasticized thermoplastic differ from the plasticizer content in the second a plasticized thermoplastic layer by at least 20 phr by weight in plasticizer content and, 
       wherein both surfaces of said interlayer have an R Z  value of 20-60 and an R SM  value of less than 800, 
       is produced by a process comprising the steps of:
 forming a first polymer melt, a second polymer melt, and a third polymer melt; and, 
 coextruding said first polymer melt, said second polymer melt, and said third polymer melt to form said interlayer; and 
 
       whereby both surfaces of said interlayer has a Rz value of 20-60 that is imparted by melt fracture during said coextruding and an R SM  of less than 800 that is imparted by melt fracture during said coextruding. 
     
     
         12 . The interlayer of  claim 11 , wherein the surface of said third polymer layer opposite said second polymer layer has an R Z  value of 20-50 that is imparted by melt fracture and an R SM  of less than 800 that is imparted by melt fracture. 
     
     
         13 . The interlayer of  claim 11 , wherein said first polymer layer, said second polymer layer, and said third polymer layer each comprise poly(vinyl butyral). 
     
     
         14 . The interlayer of  claim 11 , both surface of the interlayers have an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         15 . The interlayer of  claim 11 , wherein both surfaces have a R Z  value of 25-50 that is imparted by melt fracture. 
     
     
         16 . The interlayer of  claim 11 , wherein the step of controlling melt fracture is carried out using one or more of the following techniques—
 (i) controlling the composition of the first, and/or the third poly(vinyl butyral) melts, 
 (ii) controlling the temperature of the die lips or lands at the extrusion opening through which the interlayer is extruded, or 
 (iii) controlling the rate of cooling of the interlayer immediately after coextrusion. 
 
     
     
         17 . A multiple layer glass panel comprising:
 i) A top glass layer;   ii) An interlayer; and   iii) A bottom glass layer   
       wherein the interlayer comprises,
 a first polymer layer comprising a plasticized thermoplastic polymer with a lower plasticizer content; 
 a second polymer layer comprising a plasticized thermoplastic polymer; and, 
 a third polymer layer comprising a plasticized thermoplastic polymer with a lower plasticizer content; 
 
       wherein said second polymer layer is disposed between said first polymer layer and said third polymer layer; 
       wherein the lower plasticizer content of the a plasticized thermoplastic differ from the plasticizer content in the second a plasticized thermoplastic layer by at least 20 phr by weight in plasticizer content and, and 
       wherein both surfaces of said interlayer have an R Z  value of 20-60 and an R SM  value of less than 800. 
     
     
         18 . A multiple glass panel according to  claim 17  wherein the glass panel is prepared by a process comprising the steps of:
 providing a polymer interlayer, and 
 laminating said polymer interlayer between two glass substrates to form said multiple layer glass panel. 
 
     
     
         19 . The interlayer of  claim 18 , wherein both surfaces of the interlayer have a R Z  value of 20-60 that is imparted by melt fracture and an R SM  of less than 800 that is imparted by melt fracture. 
     
     
         20 . The interlayer of  claim 18 , wherein said first polymer layer, said second polymer layer, and said third polymer layer each comprise poly(vinyl butyral). 
     
     
         21 . The interlayer of  claim 18 , wherein both surfaces of the interlayer an R SM  value of less than 700 that is imparted by melt fracture. 
     
     
         22 . The interlayer of  claim 18 , wherein both surfaces of the interlayer have an R Z  value of 25-50 that is imparted by melt fracture.