Gypsum wallboard
View Patent ↗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 latex composition, for use in making gypsum wall board, including a polymer having a styrene block and comprising:
about 4 to 70 wt. % butadiene;
about 20 to about 95 wt. % styrene; and
at least 0.25 wt. % of an ionic monomer comprised of 2-acrylamido-2-methyl propanesulfonic acid salt;
wherein said 2-acrylamido-2-methyl propanesulfonic acid salt is present predominantly within the styrene block of said polymer.
2. The latex according to claim 1 , wherein the latex is substantially stable against divalent ions.
3. The latex according to claim 1 , wherein the latex is substantially free of surfactants that impart stability against divalent ions.
4. The latex according to claim 1 , wherein the ratio of styrene to butadiene in the polymer is in the range of from about 10:1 to 1:1.
5. The latex according to claim 1 , wherein the 2-acrylamido-2-methyl propanesulfonic acid salt is sodium 2-acrylamido-2-methyl propanesulfonic acid.
6. The latex according to claim 1 , wherein said 2-acrylamido-2-methyl propanesulfonic acid salt is present only within the styrene block of said polymer.