Multiple layer interlayer having improved optical and sound insulation properties

Abstract

Multilayered interlayers having good acoustic properties comprising a stiff skin layer(s) and a soft core layer(s) are disclosed. The multilayered interlayers comprise: a first polymer layer (skin layer) comprising plasticized poly(vinyl acetal) resin; a second polymer layer (core layer) comprising plasticized poly(vinyl acetal) resin; wherein at least one plasticizer is a high refractive index plasticizer. The multilayered interlayers have low mottle and resist mottle formation.

What is claimed is: 
     
         1 . A polymer interlayer comprising:
 a soft layer having a first refractive index, the soft layer comprising a first poly(vinyl acetal) resin having a first residual hydroxyl content and a first residual acetate content, and a first plasticizer;   a first stiffer layer having a second refractive index, the stiffer layer comprising a second poly(vinyl acetal) resin having a second residual hydroxyl content and a second residual acetate content, and a second plasticizer;   a second stiffer layer having a third refractive index, the second stiffer layer comprising a third poly(vinyl acetal) resin having a third residual hydroxyl content and a third residual acetate content, and a third plasticizer;   wherein at least one of the first, second and third plasticizers is a high refractive index plasticizer having a refractive index of at least about 1.460;   wherein the absolute value of the difference between the first refractive index and the second refractive index and the first refractive index and the third refractive index (delta RI) are each less than about 0.010;   wherein the difference between at least one of the first residual hydroxyl content and the second residual hydroxyl content and the second residual hydroxyl content and the third residual hydroxyl content is at least 2.0 weight percent; and   wherein the polymer interlayer has a damping loss factor (η) (as measured by ISO 16940) of at least about 0.15 at 20° C. and a sound transmission loss (STL) (as measured by ASTM E90 (2009) at 20° C.) of at least 37 decibels.   
     
     
         2 . The polymer interlayer of  claim 1 , wherein the soft layer of the polymer interlayer has a glass transition temperature (T g ) less than 20° C. 
     
     
         3 . The polymer interlayer of  claim 1 , wherein the high refractive index plasticizer is selected from adipates, epoxides, phthalates, terephthalates, iso-phthalates, benzoates, substituted phenols, and other specialty plasticizers and mixtures thereof. 
     
     
         4 . The polymer interlayer of  claim 1 , wherein the high refractive index plasticizer comprises an unsaturated aromatic moiety. 
     
     
         5 . The polymer interlayer of  claim 1 , wherein the difference between at least one of the first residual acetate content and the second residual acetate content and the second residual acetate content and the third residual acetate content is less than 2.0 weight percent. 
     
     
         6 . The polymer interlayer of  claim 1 , wherein at least one of the first poly(vinyl acetal) resin, the second poly(vinyl acetal) resin and the third poly(vinyl acetal) resin has a residual acetate content of at least about 4 wt. %. 
     
     
         7 . The polymer interlayer of  claim 1 , wherein at least one of the first plasticizer and the third plasticizer comprises a high refractive index plasticizer having a refractive index of at least 1.460. 
     
     
         8 . The polymer interlayer of  claim 1 , wherein at least one plasticizer further comprises a plasticizer having a refractive index of less than about 1.450. 
     
     
         9 . The polymer interlayer of  claim 1 , wherein the soft layer further comprises a fourth poly(vinyl acetal) resin having a fourth residual hydroxyl content and a fourth residual acetate content, and wherein the difference between the first residual acetate content and the fourth residual acetate content is at least 2.0 weight percent or the difference between the first residual hydroxyl content and the fourth residual hydroxyl content is at least 2.0 weight percent, or the difference between the first residual acetate content and the fourth residual acetate content is at least 2.0 weight percent and the difference between the first residual hydroxyl content and the fourth residual hydroxyl content is at least 2.0 weight percent. 
     
     
         10 . The polymer interlayer of  claim 1 , wherein the polymer interlayer has at least two different glass transition temperatures (T g ) and the difference between two different glass transition temperatures (T g ) is at least 3° C. 
     
     
         11 . The polymer interlayer of  claim 1 , wherein the polymer interlayer has a mottle of less than 1. 
     
     
         12 . The polymer interlayer of  claim 1 , wherein the first poly(vinyl acetal) resin and the second poly(vinyl acetal) resin are the same. 
     
     
         13 . A polymer interlayer comprising:
 a soft layer having a first refractive index, the soft layer comprising a first poly(vinyl acetal) resin having a first residual hydroxyl content and a first residual acetate content, and a first plasticizer;   a first stiffer layer and a second stiffer layer, wherein each stiffer layer has a second refractive index, wherein each stiffer layer comprises a second poly(vinyl acetal) resin having a second residual hydroxyl content and a second residual acetate content, and a second plasticizer;   wherein at least one of the first and second plasticizers is a high refractive index plasticizer having a refractive index of at least about 1.460;   wherein the absolute value of the difference between the first refractive index and the second refractive index (delta RI) is less than about 0.010;   wherein the difference between the first residual acetate content and the second residual acetate content is at least 2.0 weight percent; and   wherein the polymer interlayer has a damping loss factor (η) (as measured by ISO 16940) of at least about 0.15 at 20° C. and a sound transmission loss (STL) (as measured by ASTM E90 (2009) at 20° C.) of at least 37 decibels.   
     
     
         14 . The polymer interlayer of  claim 13 , wherein the soft layer of the polymer interlayer has a glass transition temperature (T g ) less than 20° C., and wherein the polymer interlayer has at least two different glass transition temperatures (T g ) and the difference between two different glass transition temperatures (T g ) is at least 3° C. 
     
     
         15 . The polymer interlayer of  claim 13 , wherein the difference between the first residual hydroxyl content and the second residual hydroxyl content is less than 2.0 weight percent. 
     
     
         16 . The polymer interlayer of  claim 13 , wherein the difference between the first residual hydroxyl content and the second residual hydroxyl content is at least 2.0 weight percent. 
     
     
         17 . A polymer interlayer comprising:
 at least one soft layer having a first refractive index, the soft layer comprising a first poly(vinyl acetal) resin having a first residual hydroxyl content and a first residual acetate content, and a first plasticizer;   a first stiffer layer and a second stiffer layer, wherein each stiffer layer has a second refractive index, wherein each stiffer layer comprises a second poly(vinyl acetal) resin having a second residual hydroxyl content and a second residual acetate content, and a second plasticizer;   wherein at least one of the first and second plasticizers is a high refractive index plasticizer having a refractive index of at least about 1.460;   wherein the absolute value of the difference between the first refractive index and the second refractive index (delta RI) is less than about 0.010;   wherein the difference between the first residual hydroxyl content and the second residual hydroxyl content is at least 2.0 weight percent;   wherein the difference between the first residual acetate content and the second residual acetate content is at least 2.0 weight percent; and   wherein the polymer interlayer has a damping loss factor (η) (as measured by ISO 16940) of at least about 0.15 at 20° C. and a sound transmission loss (STL) (as measured by ASTM E90 (2009) at 20° C.) of at least 37 decibels.   
     
     
         18 . The polymer interlayer of  claim 17 , wherein the soft layer of the polymer interlayer has a glass transition temperature (T g ) less than 20° C., and wherein the polymer interlayer has at least two different glass transition temperatures (T g ) and the difference between two different glass transition temperatures (T g ) is at least 3° C. 
     
     
         19 . The polymer interlayer of  claim 17 , wherein at least one plasticizer further comprises a plasticizer having a refractive index of less than about 1.450. 
     
     
         20 . The polymer interlayer of  claim 17 , wherein the difference between the first residual hydroxyl content and the second residual hydroxyl content is at least 4.0 weight percent.