Emulsion polymer blend coating compositions and methods for increasing chalky substrate adhesion

Abstract

The present invention relates to a coating composition containing a polymer blend dispersion including: a first polymer having a relatively low molecular weight and a relatively low glass transition temperature and comprising a self-crosslinking monomer; and a second polymer having a relatively high molecular weight and a relatively high glass transition temperature. Latex paint compositions and architectural coatings containing the coating composition according to the invention are also described herein, as well as substrates coated therewith.

1 . A latex composition comprising a polymer blend of a first polymer and a second polymer, wherein: 
 the first polymer is made from first constituent monomers, has a number average molecular weight less than about 100,000 Daltons, has a glass transition temperature calculated according to the Fox equation from about −20° C. to about 60° C., and comprises a self-crosslinking monomer;    the second polymer is made from second constituent monomers, has a number average molecular weight greater than about 100,000 Daltons, and has a glass transition temperature, calculated according to the Fox equation, from about −20° C. to about 60° C.;    the glass transition temperature of the second polymer is at least 10° C. higher than the glass transition temperature of the first polymer; and    the relative proportion of the first polymer to the second polymer is from about 1:4 to 4:3 by weight.    
     
     
         2 . The latex composition of  claim 1 , wherein the self-crosslinking monomer comprises an acetoacetoxyalkyl acrylate, an acetoacetoxyalkyl alkacrylate, a dialkoxyalkyl vinyl silane, a trialkoxy vinyl silane, or a combination thereof.  
     
     
         3 . The latex composition of  claim 2 , wherein the amount of the self-crosslinking monomer is from about 0.1% to about 5% by weight of the constituent monomers of the first polymer, and wherein the self-crosslinking monomer is a trialkoxy vinyl silane.  
     
     
         4 . The latex composition of  claim 1 , wherein the relative proportion of first polymer to second polymer is from about 1:3 to about 5:4 by weight.  
     
     
         5 . The latex composition of  claim 4 , wherein the relative proportion of first polymer to second polymer is from about 3:7 to about 1:1 by weight  
     
     
         6 . The latex composition of  claim 1 , wherein the glass transition temperature of the first polymer is from about −5° C. to about 20° C., and wherein the glass transition temperature of the second polymer is from about 5° C. to about 25° C.  
     
     
         7 . The latex composition of  claim 1 , wherein the number average molecular weight of the first polymer is from about 7,000 Daltons to about 80,000 Daltons  
     
     
         8 . The latex composition of  claim 1 , wherein the number average molecular weight of the first polymer is from about 15,000 Daltons to about 60,000 Daltons.  
     
     
         9 . The latex composition of  claim 1 , wherein the number average molecular weight of the second polymer is from about 100,000 Daltons to about 1,500,000 Daltons.  
     
     
         10 . The latex composition of  claim 1 , wherein the number average molecular weight of the second polymer is from about 200,000 to about 1,000,000.  
     
     
         11 . The latex composition of  claim 1 , wherein the constituent monomers of the first polymer are substantially acrylic or the constituent monomers of the second polymer are substantially acrylic.  
     
     
         12 . The latex composition of  claim 1 , wherein the constituent monomers of both the first polymer and the second polymer are substantially acrylic.  
     
     
         13 . The latex composition of  claim 1 , wherein the polymer blend is substantially free from sequentially polymerized polymers.  
     
     
         14 . A coating composition comprising the latex composition of  claim 1 .  
     
     
         15 . A paint composition comprising the latex composition of  claim 13 .  
     
     
         16 . The paint composition of  claim 15 , having a volatile organic compound content less than about 100 g/L.  
     
     
         17 . A coated substrate comprising a substrate having at least one surface on which a coating of the paint composition of  claim 15  is disposed.  
     
     
         18 . The coated substrate of  claim 17 , wherein the coating exhibits less than about 25% peeling from the crosshatch adhesion test under ASTM D3359 Method B.  
     
     
         19 . The coated substrate of  claim 17 , wherein the substrate comprises wood, a metal, a ceramic, a transparent substrate, a translucent substrate, a polymer, a woven fabric, a non-woven fabric, a building material, a chalky substrate, or a combination thereof.  
     
     
         20 . The coated substrate of  claim 17 , wherein the constituent monomers of the first polymer of the polymer blend in the paint composition are substantially acrylic, the constituent monomers of the second polymer of the polymer blend in the paint composition are substantially acrylic, or both.  
     
     
         21 . A latex composition comprising a polymer blend of a first polymer and a second polymer, wherein: 
 the first polymer is made from first constituent monomers, has a number average molecular weight less than about 100,000 Daltons, has a glass transition temperature, calculated according to the Fox equation, from about −20° C to about 60° C., and comprises a self-crosslinking monomer;    the second polymer is made from second constituent monomers, has a number average molecular weight greater than about 100,000 Daltons, and has a glass transition temperature, calculated according to the Fox equation, from about −20° C. to about 60° C.;    the glass transition temperature of the second polymer is at least 10° C. higher than the glass transition temperature of the first polymer;    the polymer blend is substantially free from sequentially polymerized polymers; and    the first constituent monomers, the second constituent monomers, or both, are substantially free from phosphorus-containing pendant groups, from polyacid-containing pendant groups, or from both.