Gypsum wallboard

Abstract

Gypsum wallboard can be made lighter and less dense, without sacrificing strength, by adding to the gypsum slurry used in making the board a styrene butadiene polymer latex substantially stable against divalent ions in which the styrene butadiene polymer includes at least 0.25 wt. % of an ionic monomer.

1 . A composition for making gypsum products comprising 
 water,    calcium sulfate hemihydrate, and    a styrene butadiene polymer latex substantially stable against divalent ions in which the styrene butadiene polymer includes at least 0.25 wt. % of an ionic monomer.    
     
     
         2 - 22 . (Cancelled)  
     
     
         23 . A styrene butadiene polymer latex comprising: 
 about 4 to 70 wt. % butadiene;    about 20 to 95 wt. % styrene; and    at least 0.25 wt. % of an ionic monomer comprised of 2-acrylamido-2-methyl propanesulfonic acid salt,    wherein said polymer is substantially free of surfactants that impart stability against divalent ions.    
     
     
         24 . The styrene butadiene polymer latex of  claim 23 , wherein the latex is substantially stable against divalent ions.  
     
     
         25 . The styrene butadiene polymer latex of  claim 23 , further comprising a hydrophilic adjunct comonomer selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, acrylonitrile, methacrylocitrile, acrylamide, methacrylamide, and mixtures thereof.  
     
     
         26 . The styrene butadiene polymer latex of  claim 25 , wherein the hydrophilic adjunct comonomer is hydroxyethyl acrylate.  
     
     
         27 . The styrene butadiene polymer latex of  claim 23 , wherein the ratio of styrene to butadiene is in the range of 10:1 to 1:1.  
     
     
         28 . The styrene butadiene latex of  claim 23 , wherein the 2-acrylamido-2-methyl propanesulfonic acid salt is sodium 2-acrylamido-2-methyl propanesulfonic acid.  
     
     
         29 . A styrene butadiene polymer latex that is substantially stable against divalent ions, said latex comprising: 
 about 7 to 40 wt. % butadiene;    about 45 to 90 wt. % styrene;    about 0.25 to 20 wt. % of an ionic monomer comprised of 2-acrylamido-2-methyl propanesulfonic acid salt;    wherein the ratio of styrene to butadiene is in a range of 7:1 to 1.5:1.    
     
     
         30 . The styrene butadiene polymer latex of  claim 29 , wherein said 2-acrylamido-2-methyl propanesulfonic acid salt is sodium 2-acrylamido-2-methyl propanesulfonic acid.  
     
     
         31 . The styrene butadiene polymer latex of  claim 29 , further comprising a hydrophilic adjunct comonomer selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and mixtures thereof.  
     
     
         32 . The styrene butadiene polymer latex of  claim 31 , wherein the hydrophilic adjunct comonomer is present in an amount of about 0.25 to 20 wt. % based on the weight of the polymer.  
     
     
         33 . The styrene butadiene polymer latex of  claim 31 , wherein the hydrophilic adjunct comonomer is hydroxyethyl acrylate.  
     
     
         34 . The styrene butadiene latex polymer of  claim 31 , wherein the polymer is substantially free of surfactants that impart stability against divalent ions.  
     
     
         35 . An aqueous styrene butadiene polymer latex comprising: 
 about 10 to 30 wt. % butadiene;    about 65 to 85 wt. % styrene;    about 0.5 to 10 wt. % of an ionic monomer comprised of 2-acrylamido-2-methyl propanesulfonic acid salt; and    a hydrophilic adjunct comonomer selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, acrylonitrile, methyacrylonitrile, acrylamide, methacrylamide and combinations thereof, wherein said polymer latex is substantially stable against divalent ions.    
     
     
         36 . The polymer latex of  claim 35 , wherein the hydrophilic adjunct comonomer is present in an amount of about 0.5 to 10 wt. %.  
     
     
         37 . The polymer latex of  claim 35 , wherein the hydrophilic adjunct comonomer is hydroxyethyl acrylate.  
     
     
         38 . The polymer latex of  claim 35 , wherein the hydrophilic adjunct comonomer is hydroxyethyl acrylate in an amount of about 0.5 to about 10 wt. %.  
     
     
         39 . The polymer latex of  claim 35 , wherein the weight ratio styrene to butadiene is 7:1 to 1.5:1.  
     
     
         40 . The polymer latex of  claim 35 , further comprising: 
 at least one monomer selected from the group consisting of isoprene, chloroprene, alpha-methylstyrene, 4-methylstyrene, 4-tert-butylstyrene, 4-ethylstyrene, divinylbenzene, vinylidene chloride, 2-vinylpyridene, 4-vinylpyridene, acrylic acid, methyacrylic acid, metal salts of acrylic acid and methyacrylic acid, ammonium salts of acrylic acid and methacrylic acid, substituted and unsubstituted amides of acrylic acid and methacrylic acid other than acrylamide and methacrylamide, nitriles of acrylic acid and methacrylic acid other than acrylonitrile and methacrylonitrile, and C 1  to C 12  esters of acrylic acid and methacrylic acid.    
     
     
         41 . The polymer latex of  claim 35 , wherein the ratio of styrene to butadiene is in a range of 6:1 to 2:1.  
     
     
         42 . The polymer latex of  claim 35 , wherein the hydrophilic adjunct is present in an amount of about 1 to about 4 wt. %.  
     
     
         43 . The polymer latex of  claim 35 , wherein the 2-acrylamido-2-methyl propanesulfonic acid salt is present in an amount of about 1 to 5 wt. %.  
     
     
         44 . The polymer latex of  claim 35 , wherein said polymer is substantially free of surfactants that impart stability against divalent ions.  
     
     
         45 . The polymer latex of  claim 35 , wherein said 2-acrylamido-2-methyl propanesulfonic acid salt is sodium 2-acrylamido-2-methyl propanesulfonic acid.